Determining the effects of Candida utilis-fermented pea starch vs. unfermented pea starch, alone or in whole diets, on palatability and glycemic response in dogs and cats

Current research suggests yeast fermentation has the potential to improve palatability of pea-based diets for both cats and dogs. However, to be useful, fermentation should not compromise other healthy attributes of peas such as a low glycemic response. Fermentation of uncooked pea starch with Candida utilis (ATCC 9950) appeared to increase crude protein, crude fiber content, inorganic compounds (phosphorus and iron) and phenols. Whole diets were designed with fermented and unfermented pea starch to assess palatability, food intake, and glycemic responses in unacclimated, mixed sex Beagle dogs and mixed breed cats (n = 8 and n = 7, respectively). For palatability testing, a control diet was formulated with 30% corn starch as well as test diets with 30% inclusion of fermented or unfermented pea starch (all lab-made), then compared to a commercial diet containing pea starch (Legacy/Horizon). Fermentation had little effect on rapidly digestible starch either in uncooked starch form or when incorporated into whole diets, but did decrease resistant starch by 15% and increase slowly digestible starch by 20%. Palatability tests using either two choices or four choices at a time revealed a significant preference for the fermented pea starch diet (p < 0.01) in both species. For the glycemic responses, a total of four different pea products were included: unfermented pea starch, fermented pea starch, and 30% inclusion of unfermented and fermented pea starch in whole formulated diets. There were no significant changes in glycemic responses with the fermented pea diet compared to the unfermented diet, demonstrating that healthful low glycemic properties of pea starch were retained after C. utilis fermentation. Overall, C. utilis-fermentation technique was successfully adapted to pea starch where it resulted in increased palatability and food intake in dogs and cats, with potential to positively contribute to overall health benefits for both species.

Examining the subchronic (28-day) effects of aqueous Cd-BaP co-exposure on detoxification capacity and cardiac function in adult zebrafish (Danio rerio)

The present study aimed to examine the effects of environmentally relevant concentrations of cadmium (Cd) and Benzo[a]Pyrene (BaP) in the adult zebrafish (Danio rerio). To this end, fish were exposed to either 1 or 10 μg/L Cd or 0.1 or 1 μg/L BaP in isolation, or a co-exposure containing a mixture of the two toxicants. Our results showed extensive modulation of the expression of key antioxidant genes (GPx, SOD1, catalase), detoxifying genes (MT1, MT2, CYP1A1) and a stress biomarker (HSP70) differing between control, single toxicant groups and co-exposure groups. We additionally carried out histopathological analysis of the gills, liver, and hearts of exposed animals, noting no differences in tissue necrosis or apoptosis. Finally, we carried out ultrasonographic analysis of cardiac function, noting a significant decrease of E-wave peak velocity and end diastolic volume in exposed fish. This in turn was accompanied by a decrease in stroke volume and ejection fraction, but not cardiac output in co-exposed fish. The present study is the first to demonstrate that a subchronic aqueous exposure to a Cd-BaP mixture can extensively modulate detoxification capacity and cardiac function in adult zebrafish in a tissue-specific manner.

Oligosaccharides and diet-related dilated cardiomyopathy in beagles

Introduction

In 2018 the US Food and Drug Administration reported a potential link between grain-free, legume-containing dog foods and the development of canine dilated cardiomyopathy in atypical breeds. One hypothesis was that high oligosaccharide content in legumes reduced bioavailability of taurine, an amino acid with some previous links to canine dilated cardiomyopathy.

Methods

To address this hypothesis, in the present study, 8 Beagle dogs consumed four diets: a husbandry commercial dental diet, and three test diets formulated with either 30% rice (control), 30% pea (grain-free) or 30% rice with the addition of 1% raffinose (the predominant oligosaccharide found in peas). The study was conducted in a randomized, crossover design with 5 week feeding periods. Measurement of basic health parameters (weight, body condition score, complete blood cell count, chemistry panel), plasma amino acids, cardiac biomarkers (plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac-specific troponin I), fecal bile acids and echocardiographic exams were completed pre-study after feeding the husbandry diet as well as after each test feeding period.

Results

Echocardiography showed 9-11% reduction in ejection fraction and 17- 20% greater left ventricular end systolic volume with the husbandry diet compared to both grain-containing test diets. Concentrations of plasma NT-proBNP were 1.3-2 times greater after the husbandry diet compared to the grain-based diet, with the oligosaccharide and pea-based diets showing intermediate levels. Plasma taurine levels were unchanged across diets, while plasma methionine levels were highest and cysteine/cystine levels were lowest after dogs ate the husbandry diet.

Discussion

Results indicate that raffinose in the diet is sufficient, but not required to see an increase NT-proBNP, but did not induce any changes in cardiac function after 5 weeks of feeding. Whether this could progress to reduction in cardiac function with longer term feeding is uncertain. A reduced cardiac function along with the greatest increase in NT-proBNP was observed after feeding the husbandry diet that contained the highest amount of insoluble fiber but did not contain legumes or oligosaccharide. Further research into the impact of insoluble fiber in the dental diet is needed to support these novel observations.

Solidified saturated fats coating subunit vaccines greatly extended vaccine booster release and contributed to a Th1/Th2 mixed immune response in mice

Delayed release of vaccine coupled with a soluble vaccine acts as a primer and a booster with only a single administration, which would be very beneficial to livestock producers. We developed a subdermal pellet consisting of solid-phase pure stearic acid (SA) or palmitic acid (PA) that was used to encapsulate a small volume liquid vaccine consisting of fluorescently labeled *Ovalbumin (Cy5-*OVA) formulated with Emulsigen-D +/- Poly I:C (EMP) adjuvants. Mice were also immunized via the subcutaneous route with Cy5-*OVA-EMP (soluble liquid). The vaccine leached out of the pellet with very little dissolution of the fat itself resulting in the sustained subdermal delivery of antigens and adjuvants. Cy5-*OVA was still visible 60 days post administration in mice immunized with stearic acid-coated or palmitic acid-coated pellets. In these mice, persistently high IgG1 and IgG2a antibody titres were detected as well as significant IFNγ production at least 60 days post-injection. These responses were significantly higher than those observed after a single subcutaneous injection of the vaccine. A repeat trial with the pellets alone +/- the soluble vaccine showed comparable immune responses after surgical implantation of the pellet, suggesting that pellet alone may be sufficient. The PA-coated vaccines led to dermal inflammation in the mice that would limit usefulness of this vehicle, but this was largely absent when SA was used to coat the pellets. These data suggest that the SA-coated adjuvanted vaccine prolonged the release of the vaccine and triggered a comparable immune response to the mice that received the two liquid injections, and a single pellet vaccine should be tested as a novel immunization method for livestock.

Effects of a 28-day feeding trial of grain-containing versus pulse-based diets on cardiac function, taurine levels and digestibility in domestic dogs

In 2018, the US Food and Drug Administration reported a link between canine dilated cardiomyopathy (DCM) and grain-free diets. Evidence to support a link has emerged, but the specific ingredients responsible and the role of taurine or other causative factors remain unclear. We hypothesized dogs fed pulse-based, grain-free diets for 28 days will show decreased macronutrient digestibility, increased fecal bile acid excretion, and reduced plasma cystine, cysteine, methionine and taurine, causing sub-clinical cardiac or blood changes indicative of early DCM. Three diets were formulated using white rice flour (grain), whole lentil (grain-free), or wrinkled pea (grain-free) and compared to the pre-trial phase on a commercial grain-based diet. After 28 days of feeding each diet, the wrinkled pea diet impaired stroke volume and cardiac output, increased end-systolic ventricular diameter and increased plasma N-Terminal Pro-B-type Natriuretic Peptide (NT-ProBNP), albeit in a sub-clinical manner. Digestibility of some macronutrients and sulphur-containing amino acids, excluding taurine, also decreased with pulse-based compared to grain-based diets, likely due to higher fiber levels. Plasma taurine levels were unchanged; however, plasma methionine was significantly lower after feeding all test diets compared to the commercial diet. Overall, DCM-like changes observed with the wrinkled pea diet, but not lentil diet, after only 4 weeks in a breed not known to be susceptible support a link between pea-based diets and canine nutritionally-mediated DCM.

Modulation of Cd and BaP uptake rate during acute aqueous co-exposure in adult zebrafish (Danio rerio)

Cadmium and Benzo[a]pyrene are two toxicants of great environmental importance given their frequency and ability to cause extensive toxicity in aquatic organisms including fish. There is evidence that fish can modulate their respective uptake rate during simultaneous exposures, albeit the mechanism behind this is poorly understood. The present study aimed to examine this interaction by exposing adult zebrafish to either 89.3 nM Cd, 4.25 nM BaP or a combination of the two for 72 hrs prior to examining the uptake rate of either toxicant via short-term exposures (3-6 hrs) to radiotracers (¹⁰⁹Cd and ¹⁴C-BaP). Our results showed that Cd uptake rate increased significantly in the gills when animals were pre-exposed to both toxicants simultaneously, resulting in an increased maximum uptake rate (Jmax). The increased Cd uptake rate did not correspond to increased expression of gill Cd transporters such as the epithelium calcium channel (ECaC) or the divalent metal transporter 1 (DMT1). Furthermore, BaP uptake rate increased significantly at the whole-body level when animals were exposed to both 5.03 nM ¹⁴C-BaP and 89.3 nM Cd concurrently. Additionally, we ran a time-course and observed BaP uptake rate is highest in the 6-12 hrs following the beginning of the exposure. Our results provide evidence that the increased bioaccumulation of Cd and BaP observed during co-exposures is at least in part due to an increase in uptake rate and is driven by separate mechanisms.

Low birth weight and reduced postnatal nutrition lead to cardiac dysfunction in piglets

Heart disease is the leading cause of death in humans and evidence suggests early life growth-restriction increases heart disease risk in adulthood. Therefore, this study sought to investigate the effects of low birth weight (LBW) and postnatal restricted nutrition (RN) on cardiac function in neonatal pigs. We hypothesized that LBW and RN would reduce cardiac function in pigs but this effect would be reversed with refeeding. To investigate this hypothesis, pigs born weighing <1.5 kg were assigned LBW, and pigs born >1.5 kg were assigned normal birth weight (NBW). Half the LBW and NBW pigs underwent ~25% total nutrient restriction via intermittent suckling (assigned RN) for the first 4 wk post-farrowing. The other half of piglets were allowed unrestricted suckling access to the sow (assigned NN). At 28 d of age (weaning), pigs were weaned and provided ad libitum access to a standard diet. Echocardiographic, vascular ultrasound, and blood pressure (BP) measurements were performed on day 28 and again on day 56 to assess cardiovascular structure and function. A full factorial three-way ANOVA (NN vs. RN, LBW vs. NBW, male vs. female) was performed. Key findings include reduced diastolic BP (P = 0.0401) and passive ventricular filling (P = 0.0062) in RN pigs at 28 d but this was reversed after refeeding. LBW piglets have reduced cardiac output index (P = 0.0037) and diastolic and systolic wall thickness (P = 0.0293 and P = 0.0472) at 56 d. Therefore, cardiac dysfunction from RN is recovered with adequate refeeding while LBW programs irreversible cardiac dysfunction despite proper refeeding in neonatal pigs.

Altered cerebrovascular regulation in low birthweight swine

Full-term low birthweight (LBW) offspring exhibit peripheral vascular dysfunction in the postnatal period; however, whether such impairments extend to the cerebrovasculature remains to be elucidated. We used a swine model to test the hypothesis that LBW offspring would exhibit cerebrovascular dysfunction at later stages of life. Offspring from 14 sows were identified as normal birthweight (NBW) or LBW and were assessed at 28 (similar to end of infancy) and 56 (similar to childhood) days of age. LBW swine had lower absolute brain mass, but demonstrated evidence of brain sparing (increased brain mass scaled to body mass) at 56 days of age. The cerebral pulsatility index, based on transcranial Doppler, was increased in LBW swine. Moreover, arterial myography of isolated cerebral arteries revealed impaired vasoreactivity to bradykinin and reduced contribution of nitric oxide (NO) to vasorelaxation in the LBW swine. Immunoblotting demonstrated a lower ratio of phosphorylated-to-total endothelial NO synthase in LBW offspring. This impairment in NO signaling was greater at 28 vs. 56 days of age. Vasomotor responses to sodium nitroprusside (NO-donor) were unaltered, while Leu³¹, Pro³⁴ neuropeptide Y-induced vasoconstriction was enhanced in LBW swine. Increases in total Y1 receptor protein content in the LBW group were not significant. In summary, LBW offspring displayed signs of cerebrovascular dysfunction at 28 and 56 days of age, evidenced by altered cerebral hemodynamics (reflective of increased impedance) coupled with endothelial dysfunction and altered vasomotor control. Overall, the data reveal that normal variance in birthweight of full-term offspring can influence cerebrovascular function later in life.

Assessing non-protein nitrogen sources in commercial dry dog foods

Protein is a macronutrient required by dogs for growth and maintenance metabolism. However, a portion of the crude protein listed on pet foods may actually arise from non-digestible organic nitrogen or potentially toxic inorganic non-protein nitrogen sources. Neither non-protein source is retained or used by the animal. However, these compounds may result in adverse effects such as methemoglobin formation and increased oxidative stress or potentially beneficial effects such as improved vascular distensibility and decreased inflammation. To analyze nitrogen retention and screen for non-protein nitrogen, four commercial, dry kibble dog foods and one laboratory-made diet were evaluated and then fed to beagles during two separate feeding trials. During the first trial, dogs were randomly assigned each diet (n = 4 dogs/diet) and fed chromium oxide-coated diets for 48 h, followed by total urine and marked fecal collection, as well as plasma collection for total nitrogen, nitrate, ammonia, and urea determination. The amount of nitrogen retained (93%–96%) did not differ among commercial diets. Protein total tract apparent digestibility (TTAD) ranged from 69% to 84%, with the high protein diets significantly higher than the laboratory-made and mid-ranged diets (1-way ANOVA: P < 0.05). The high protein diet also contained the highest concentration of nitrate with subsequent elevations in plasma nitrotyrosine levels (indicator of oxidative stress). During the second trial, eight dogs (n = 8) were fed the same diets for 6 d, after which echocardiography was completed with blood, urine, and feces collected. For health end-points, methemoblobin, plasma nitrotyrosine, and C-reactive protein (CRP; indicator of inflammation) levels were measured. Methemoglobin levels were significantly lower in the high protein diet (P > 0.05), possible due to the stimulation of methemoglobin reductase while nitrotyrosine was unchanged and CRP was undetectable. Furthermore, there was a positive relationship between crude protein, crude fat (simple linear regression: P = 0.02, r² > 0.6), price (P = 0.08, r² > 0.6), and caloric density (P = 0.11, r² > 0.6). There were no significant cardiovascular differences among any of the diets (P > 0.05). Ultimately, this study shows that in commercial diets, price does reflect protein content but that feeding dogs high protein diets for a long period of time may provide an excess in calories without a change in cardiovascular function or detectable increases in inflammation.

The Effects of Fermentation of Low or High Tannin Fava Bean-Based Diets on Glucose Response, Cardiovascular Function, and Fecal Bile Acid Excretion during a 28-Day Feeding Period in Dogs: Comparison with Commercial Diets with Normal vs. High Protein

We have shown that feeding dogs fava bean (FB)-based diets for 7 days is safe and FB flour fermentation with Candida utilis has the potential to decrease FB anti-nutritional factors. In the present study, the effects of 28-day feeding of 4 different FB-based test dog foods containing moderate protein (~27% dry matter (DM)) were compared with two commercial diets with normal protein (NP, grain-containing, ~31% DM protein) or high protein (HP, grain-free, ~41% DM protein). Health parameters were investigated in beagles fed the NP or HP diets or using a randomized, crossover, 2 × 2 Latin square design of the FB diets: unfermented high-tannin (UF-HT), fermented high-tannin (FM-HT), unfermented low-tannin (UF-LT), and fermented low-tannin (FM-LT). The results showed that fermentation increased glucose tolerance, increased red blood cell numbers and increased systolic blood pressure, but decreased flow-mediated vasodilation. Taken together, the overall effect of fermentation appears to be beneficial and improved FB nutritional value. Most interesting, even though the HP diet was grain-free, the diet did contain added taurine, and no adverse effects on cardiac function were observed, while glucose tolerance was impaired compared to NP-fed dogs. In summary, this study did not find evidence of adverse cardiac effects of pulses in ‘grain-free’ diets, at least not in the relatively resistant beagle breed over a 28-day period. More importantly, fermentation with C. utilis shows promise to enhance health benefits of pulses such as FB in dog food.

Nesfatin-1-like peptide is a negative regulator of cardiovascular functions in zebrafish and goldfish

Nucleobindins (NUCB1 and NUCB2) were originally identified as calcium and DNA binding proteins. Nesfatin-1 (NEFA/nucleobindin-2-Encoded Satiety and Fat-Influencing proteiN-1) is an 82 amino acid anorexigenic peptide encoded in the N-terminal region of NUCB2. We have shown that nesfatin-1 is a cardiosuppressor in zebrafish. Both NUCB1 and NUCB2 possess a -very highly conserved bioactive core. It was found that a nesfatin-1-like peptide (NLP) encoded in NUCB1 suppresses food intake in fish. In this research, we investigated whether NLP has nesfatin-1-like effects on cardiovascular functions. NUCB1/NLP-like immunoreactivity was found in the atrium and ventricle of the heart and skeletal muscle of zebrafish. Intraperitoneal injection (IP) of either zebrafish NLP or rat NLP suppressed cardiac functions in both zebrafish and goldfish. Irisin and RyR1b mRNA expression was downregulated by NLP in zebrafish cardiac and skeletal muscles. However, cardiac ATP2a2 mRNA expression was elevated after NLP injection. Administration of scrambled NLP did not affect irisin, RyR1b or ATP2a2 mRNA expression in zebrafish. Together, these results implicate NLP as a suppressor of cardiovascular physiology in zebrafish and goldfish.

The sympathetic/beta-adrenergic pathway mediates irisin regulation of cardiac functions in zebrafish

Irisin is a 23 kDa myokine encoded in its precursor, fibronectin type III domain containing 5 (FNDC5). The exercise-induced increase in the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α) promotes FNDC5 mRNA, followed by the proteolytic cleavage of FNDC5 to release irisin from the skeletal or cardiac muscle into the blood. Irisin is abundantly expressed in skeletal and cardiac muscle and plays an important role in feeding, modulates appetite regulatory peptides, and regulates cardiovascular functions in zebrafish. In order to determine the potential mechanisms of acute irisin effects, in this research, we explored whether adrenergic or muscarinic pathways mediate the cardiovascular effects of irisin. Propranolol (100 ng/g B·W) alone modulated cardiac functions, and when injected in combination with irisin (0.1 ng/g B·W) attenuated the effects of irisin in regulating cardiovascular functions in zebrafish at 15 min post-injection. Atropine (100 ng/g B·W) modulated cardiovascular physiology in the absence of irisin, while it was ineffective in influencing irisin-induced effects on cardiovascular functions in zebrafish. At 1 h post-injection, irisin downregulated PGC-1 alpha mRNA, myostatin-a and myostatin-b mRNA expression in zebrafish heart and skeletal muscle. Propranolol alone had no effect on the expression of these mRNAs in zebrafish and did not alter the irisin-induced changes in expression. At 1 h post-injection, irisin siRNA downregulated PGC-1 alpha, troponin C and troponin T2D mRNA expression, while upregulating myostatin a and b mRNA expression in zebrafish heart and skeletal muscle. Atropine alone had no effects on mRNA expression, and was unable to alter effects on mRNA expression of siRNA. Overall, this research identified a role for the sympathetic/beta-adrenergic pathway in regulating irisin effects on cardiovascular physiology and cardiac gene expression in zebrafish.

The Effect of Fermentation of High- or Low-Tannin Fava Bean on Glucose Tolerance, Body Weight, Cardiovascular Function, and Blood Parameters in Dogs After 7 Days of Feeding: Comparison With Commercial Diets With Normal vs. High Protein

Fava bean, which is available in high- and low-tannin varieties, is not an approved pet food ingredient and was not included in the “assumed to be safe” category based on its ability to cause favism and hemolytic anemia in susceptible humans. The effects of 7-day feeding of test canine diets containing moderate protein (~27%) were compared with two control commercial diets with normal (NP, grain-containing, ~25% protein) or high protein (HP, grain-free, ~41% protein). Fava bean diets were formulated either with or without Candida utilis fermentation processing to reduce antinutritional factors. Glucose tolerance, body weight, cardiovascular function, and blood parameters were investigated in beagles fed the NP or HP diets or a randomized, crossover, 2 × 2 Latin square design of the fava bean diets: unfermented high-tannin (UF-HT), fermented high-tannin (FM-HT), unfermented low-tannin (UF-LT), and fermented low-tannin (FM-LT). After 7 days, HP decreased red blood cells (RBC) (P < 0.05) compared with NP, while FM increased RBC compared with UF. HP increased blood bicarbonate, calcium, phosphorus, urea, cholesterol, and albumin:globulin ratio while decreasing bilirubin, liver enzymes, and total protein. Sodium:potassium ratio was increased in UF-HT, decreased in FM-HT, and intermediate in LT regardless of fermentation. Blood phosphorus was increased in HT. Blood amylase was increased in FM-HT and decreased in FM-LT, being intermediate in UF regardless of fava bean variety. Blood direct bilirubin was decreased in HT regardless of fermentation. Of note, left ventricular end-systolic volume and cardiac output were increased in NP compared with HP-fed dogs, but were normal and had no significant differences among the fava bean diets. As expected, plasma taurine, cystine, and cysteine levels were increased in HP- compared with NP-fed dogs. Plasma cysteine levels were increased in HT- compared with LT-fed dogs and in FM- compared with UF-fed dogs. Taken together, these results show that fava bean appears to be safe as a dog food ingredient at least in the short term, and its nutritional value appears improved by fermentation. Moreover, blood chemistry parameters and cardiovascular function were impacted by protein content which merits further investigation with longer term feeding trials.

The Effects of 7 Days of Feeding Pulse-Based Diets on Digestibility, Glycemic Response and Taurine Levels in Domestic Dogs

Grain-based carbohydrate sources such as rice comprise 30–50% of commercial pet foods. Some pet foods however have removed the use of grains and have instead incorporated pulses, such as peas and lentils, resulting in grain-free diets. The hypothesis was dog diets with higher levels of dietary fiber will produce a low glycemic response due to decreased rates of digestion and lowered bioavailability of all macronutrients and increased fecal bile salt excretion. This in turn was hypothesized to produce lower plasma concentrations of cysteine, methionine and taurine after 7 days of feeding each test diet in dogs. Six diets were formulated at an inclusion level of 20% available carbohydrate, using white rice flour (grain) or whole pulse flours from smooth pea, fava bean, red lentil or 2 different wrinkled pea varieties (CDC 4,140–4 or Amigold) and fed to beagles in a randomized, cross-over, blinded design. After 7 days feeding each diet, fasting blood glucose was the lowest in the lentil (3.5 ± 0.1 mmol/L) and wrinkled pea (4,140–4; 3.6 ± 0.1 mmol/L) diet periods, while peak glucose levels was lowest after feeding the lentil diet (4.4 ± 0.1 mmol/L) compared to the rice diet. Total tract apparent digestibility of all macronutrients as well as taurine differed among diets yet plasma taurine was not outside normal range. Decreased macronutrient and amino acid digestibility was associated with increasing amylose and dietary fiber content but the specific causative agent could not be determined from this study. Surprisingly, digestibility decreases were not due to increased bile salt loss in the feces since increasing dietary fiber content led to decreased fecal bile salt levels. In conclusion, although pulse-based canine diets have beneficial low glycemic properties, after only 7 days, these pulse-based diets decrease macronutrient and amino acid digestibility. This is likely related at least in part to the lower animal protein content, but on a long-term basis could put domestic dogs at risk for low taurine and dilated cardiomyopathy.

Glycemic, insulinemic and methylglyoxal postprandial responses to starches alone or in whole diets in dogs versus cats: Relating the concept of glycemic index to metabolic responses and gene expression

Species differences between domestic cats (Felis catus) and dogs (Canis familiaris) has led to differences in their ability to digest, absorb and metabolize carbohydrates through poorly characterized mechanisms. The current study aimed to first examine biopsied small intestine, pancreas, liver and skeletal muscle from laboratory beagles and domestic cats for mRNA expression of key enzymes involved in starch digestion (amylase), glucose transport (sodium-dependent SGLTs and -independent glucose transporters, GLUT) and glucose metabolism (hexokinase and glucokinase). Cats had lower mRNA expression of most genes examined in almost all tissues compared to dogs (p < 0.05). Next, postprandial glucose, insulin, methylglyoxal (a toxic glucose metabolite) and d-lactate (metabolite of methylglyoxal) after single feedings of different starch sources were tested in fasted dogs and cats. After feeding pure glucose, peak postprandial blood glucose and methylglyoxal were surprisingly similar between dogs and cats, except cats had a longer time to peak and a greater area under the curve consistent with lower glycolytic enzyme expression. After feeding starches or whole diets to dogs, postprandial glycemic response, glycemic index, insulin, methylglyoxal and d-lactate followed reported glycemic index trends in humans. In contrast, cats showed very low to negligible postprandial glycemic responses and low insulin after feeding different starch sources, but not whole diets, with no relationship to methylglyoxal or d-lactate. Thus, the concept of glycemic index appears valid in dogs, but not cats. Differences in amylase, glucose transporters, and glycolytic enzymes are consistent with species differences in starch and glucose handling between cats and dogs.

Interactive effects of cadmium and Benzo[a]pyrene in adult zebrafish (Danio rerio) during short-term aqueous co-exposure

Environmental water quality guidelines often work under the assumption that the toxicity of environmental pollutants is identical when present in isolation or in a complex chemical mixture. Thus, there is a crucial gap in our knowledge regarding how these toxicants interact and alter the toxicological effects in aquatic organisms. The present study examined the effects of acute (72-hr) aqueous exposures of Cadmium (Cd), a highly toxic non-essential trace metal, and Benzo[a]Pyrene (B[a]P), a prototypical polycyclic aromatic hydrocarbon (PAH) in adult zebrafish. Following a range-finding series of individual single-toxicant exposures, a second series was carried out using select concentrations in binary mixture exposures (using 5.8 or 22 μg/L for Cd; 0.44 or 1.07 μg/L for B[a]P). Our results demonstrated that tissue accumulation of both toxicants increased significantly in the presence of the second toxicant relative to single-toxicant exposures. Cd-only and B[a]P-only single toxicant exposures caused a significant downregulation of cytochrome p4501a (CYP1A1) and metallothionein-2 (MT2) mRNA in the gills, respectively, however binary co-exposures using both toxicants resulted in strong up-regulation of CYP1A1 and MT2. Additionally, co-exposures caused a strong induction of SOD1 and CAT mRNA transcript levels in the gill. The observed increase in body burden and transcript modulation did not translate into additive or more-than-additive toxic effects (oxidative stress) in zebrafish.

PSVI-32 The effects of varying amylose levels in different diets on digestibility and glycemic response in canines

This study was conducted to compare the digestibility of pulse-based diets to grain-based diets based on varying levels of amylose and study how changes in digestibility impacts glycemic response in dogs. To establish glycemic response, six diets were formulated at an inclusion level of 20% available starch with varying amylose content. A grain-based diet was formulated using rice, while pulse-based diets consisted of smooth pea, wrinkled pea (4140–4 and Amigold varieties), faba bean, or lentil. Beagles (n = 8, 4 females, 4 males) were fed the 6 different test diets for 7 days in a randomized, cross-over, blinded design. At the end of each feeding period, fecal samples were collected and beagles were fasted overnight and subjected to a glycemic test (1g/kg of diet or glucose fed). Data collected were statistically analyzed using SigmaPlot 12.0 and significance was declared at P ≤ 0.05. Amylose levels of diets varied from 4.64% to 14.82% on a dry basis. The rice-based diet had the lowest amylose content, while the wrinkled pea (Amigold variety) diet had the highest amylose content. Following the collection of glycemic response and fecal data, repeated-measures, 1-way ANOVA’s were conducted. There were significant differences observed between diets based on peak glucose levels (mmol/L, P = 0.01). The rice diet had the highest peak in glucose, while the lentil-based diet had the lowest glucose peak. Significant differences were also seen between diets based on their digestibility (P &lt; 0.001). Rice, lentil, faba bean and smooth pea-based diets had the highest levels of digestibility, while wrinkled pea varieties had decreased digestibility. Furthermore, varying amylose found in diets can be viewed as an impacting factor on glycemic response and digestibility. Incorporating pulses with higher amounts of amylose could be utilized in dog diets to promote a low glycemic response through decreased rates of digestibility.

Characterization of a Swine Model of Birth Weight and Neonatal Nutrient Restriction

Background

Evidence indicates that birth weight and neonatal nutrition have lifelong effects. Animal models are required to improve our understanding of these factors.

Objectives

We aimed to develop and validate a swine model of birth weight and neonatal undernutrition.

Methods

At birth, a total of 112 piglets were identified as low (LBW; 1.22 ± 0.28 kg SEM) or normal birth weight (NBW; 1.70 ± 0.27 kg). From day 3 to weaning (day 28), piglets received normal nutrition (NN) or restricted nutrition (RN) via intermittent suckling, where piglets were isolated from the sow for 6 h/d. After weaning, pigs were fed a common diet for 28 d. Body weight (BW) was determined for the duration of the study. On days 28 and 56, empty carcass, viscera, and individual organ weights were determined in 8 pigs/treatment.

Results

LBW pigs remained smaller than NBW pigs, regardless of nutrient restriction (P &lt; 0.05). Within birth weight category, RN reduced BW by day 7 after birth, which was maintained until weaning (P &lt; 0.05); however, at 7 d postweaning there was no difference in BW due to RN (P &gt; 0.05). At weaning, empty carcass, viscera, heart, liver, and lung weights were lower in LBW than in NBW pigs, whereas empty carcass, heart, small intestine, liver, kidneys, lung, and spleen weights were lower in RN than in NN pigs (P &lt; 0.05). Brain weight was highest in NBW-NN and lowest in NBW-RN, with LBW intermediate, regardless of nutrient restriction (P &lt; 0.05). Postweaning, LBW had lower empty carcass, viscera, heart, stomach, large intestine, liver, and kidney weights than NBW, whereas RN had a higher small intestine weight than NN (P &lt; 0.05).

Conclusions

Intermittent suckling is an effective means of inducing nutrient restriction in a swine model.

Comparison of intestinal glucose flux and electrogenic current demonstrates two absorptive pathways in pig and one in Nile tilapia and rainbow trout

The mucosal-to-serosal flux of ¹⁴C 3-O-methyl-d-glucose was compared against the electrogenic transport of d-glucose across ex vivo intestinal segments of Nile tilapia, rainbow trout, and pig in Ussing chambers. The difference in affinities (K_m "fingerprints") between pig flux and electrogenic transport of glucose, and the absence of this difference in tilapia and trout, suggest two absorptive pathways in the pig and one in the fish species examined. More specifically, the total mucosal-to-serosal flux revealed a super high-affinity, high-capacity (sHa/Hc) total glucose transport system in tilapia; a super high-affinity, low-capacity (sHa/Lc) total glucose transport system in trout and a low-affinity, low-capacity (La/Lc) total glucose transport system in pig. Comparatively, electrogenic glucose absorption revealed similar K_m in both fish species, with a super high-affinity, high capacity (sHa/Hc) system in tilapia; a super high-affinity/super low-capacity (sHa/sLc) system in trout; but a different K_m fingerprint in the pig, with a high-affinity, low-capacity (Ha/Lc) system. This was supported by different responses to inhibitors of sodium-dependent glucose transporters (SGLTs) and glucose transporter type 2 (GLUT2) administered on the apical side between species. More specifically, tilapia flux was inhibited by SGLT inhibitors, but not the GLUT2 inhibitor, whereas trout lacked response to inhibitors. In contrast, the pig responded to inhibition by both SGLT and GLUT2 inhibitors with a higher expression of GLUT2. Altogether, it would appear that two pathways are working together in the pig, allowing it to have continued absorption at high glucose concentrations, whereas this is not present in both tilapia and trout.

Echocardiography and electrocardiography reveal differences in cardiac hemodynamics, electrical characteristics, and thermal sensitivity between northern pike, rainbow trout, and white sturgeon

Doppler and B-mode ultrasonography and electrocardiography (ECG) were used to determine cardiac hemodynamics and electrical characteristics in 12°C-acclimated and metomidate-anesthetized northern pike, rainbow trout and white sturgeon (7-9 per species) at 12°C and 20°C, and at a comparable heart rate (f_H , ~60 beats/min). Despite similar relative ventricle masses and cardiac output (Q), interspecific differences were observed at 12°C in f_H , ventricular filling and ejection, stroke volume, the duration ECG intervals, and cardiac valve cross-sectional areas. Vis-a-fronte filling of the atrium due to ventricular contraction was observed in all species. However, biphasic ventricular filling (i.e., due to central venous pressure and then atrial contraction) was only observed in rainbow trout and white sturgeon. Changes in atrial and ventricular performance varied between the species as temperature increased from 12°C to 20°C. Rainbow trout had the highest thermal sensitivity for f_H (Q₁₀  = 3.73), which doubled Q, and the largest increase in transvalvular blood velocity during ventricular filling. Conversely, northern pike had the lowest Q₁₀ for f_H (1.58) and did not increase Q. At ~60 beats/min, the rainbow trout heart had the shortest period of electrical activity, which also resulted in the longest recovery period (TP interval) between successive beats. The QT interval at ~60 beats/min was also longer in the white sturgeon versus the other species. These results suggest that interspecific differences in fish cardiac hemodynamics may be related to cardiac morphology, the duration of electrical impulses through the heart, cardiac thermal sensitivity, and valve dimensions.

Intestinal electrogenic sodium-dependent glucose absorption in tilapia and trout reveal species differences in SLC5A-associated kinetic segmental segregation

Electrogenic sodium-dependent glucose transport along the length of the intestine was compared between the omnivorous Nile tilapia ( Oreochromis niloticus) and the carnivorous rainbow trout ( Oncorhynchus mykiss) in Ussing chambers. In tilapia, a high-affinity, high-capacity kinetic system accounted for the transport throughout the proximal intestine, midintestine, and hindgut segments. Similar dapagliflozin and phloridzin dihydrate inhibition across all segments support this homogenous high-affinity, high-capacity system throughout the tilapia intestine. Genomic and gene expression analysis supported findings by identifying 10 of the known 12 SLC5A family members, with homogeneous expression throughout the segments with dominant expression of sodium-glucose cotransporter 1 (SGLT1; SLC5A1) and sodium-myoinositol cotransporter 2 (SMIT2; SLC5A11). In contrast, trout's electrogenic sodium-dependent glucose absorption was 20-35 times lower and segregated into three significantly different kinetic systems found in different anatomical segments: a high-affinity, low-capacity system in the pyloric ceca; a super-high-affinity, low-capacity system in the midgut; and a low-affinity, low-capacity system in the hindgut. Genomic and gene expression analysis found 5 of the known 12 SLC5A family members with dominant expression of SGLT1 ( SLC5A1), sodium-glucose cotransporter 2 (SGLT2; SLC5A2), and SMIT2 ( SLC5A11) in the pyloric ceca, and only SGLT1 ( SLC5A1) in the midgut, accounting for differences in kinetics between the two. The hindgut presented a low-affinity, low-capacity system partially attributed to a decrease in SGLT1 ( SLC5A1). Overall, the omnivorous tilapia had a higher electrogenic glucose absorption than the carnivorous trout, represented with different kinetic systems and a greater expression and number of SLC5A orthologs. Fish differ from mammals, having hindgut electrogenic glucose absorption and segment specific transport kinetics.

Tissue-specific expression and circulating concentrations of nesfatin-1 in domestic animals

Nesfatin-1 is a naturally occurring 82-amino acid protein encoded in the precursor nucleobindin-2 (NUCB2) and has been implicated in multiple physiological functions, including food intake and blood glucose regulation. This study aimed to characterize nesfatin-1 in domestic species, especially cats (Felis catus), dogs (Canis lupus familiaris), and pigs (Sus scrofa). Our in silico analysis demonstrated that the NUCB2/nesfatin-1 amino acid sequence, especially the bioactive core region of the peptide, is very highly conserved (more than 90% identity) in domestic animals. Expression of mRNAs encoding NUCB2/nesfatin-1 was detected in the cat, dog, and pig stomach and pancreas. Immunohistochemistry revealed the presence of nesfatin-1 in the gastric mucosa of the stomach of dogs, cats, and pigs, and in the pancreatic islet β-cells of dogs and pigs. No nesfatin-1 immunoreactivity was found in the cat pancreas. Nesfatin-1 was detected in the serum of dog, cat, pig, bison, cow, horse, sheep, and chicken. Circulating nesfatin-1 in male and female dogs remained unchanged at 60 min after glucose administration, suggesting a lack of meal responsiveness in nesfatin-1 secretion in this species. The presence of nesfatin-1 in the gastric and endocrine pancreatic tissues suggests possible roles for this peptide in the metabolism of domestic animals. Future research should focus on elucidating the species-specific functions and mechanisms of action of nesfatin-1 in health and disease of domestic animals.

Cardiac and Metabolic Effects of Dietary Selenomethionine Exposure in Adult Zebrafish

Selenium (Se) is an essential micronutrient involved in important metabolic functions for all vertebrate species. As Se is reported to have a narrow margin between essentiality and toxicity, there is growing concern surrounding the adverse effects of elevated Se exposure caused by anthropogenic activities. Recent studies have reported that elevated dietary exposure of fish to selenomethionine (Se-Met) can alter aerobic metabolic capacity, energetics and swimming performance. This study aims to further investigate mechanisms of sublethal Se-Met toxicity, particularly potential underlying cardiovascular implications of chronic exposure to environmentally relevant concentrations of dietary Se-Met in adult zebrafish (Danio rerio). Adult zebrafish were fed either control food (1.1 μg Se/g dry mass [d.m.]) or Se-Met spiked food (10.3 or 28.8 μg Se/g d.m.) for 90 d at 5% body weight per day. Following exposure, ultrahigh resolution B-mode and Doppler ultrasound was used to characterize cardiac function. Chronic dietary exposure to elevated Se-Met significantly reduced ventricular contractile rate, stroke volume, and cardiac output. Exposure to Se-Met significantly decreased mRNA expression of methionine adenosyltransferase 1 alpha and glutathione-S-transferase pi class in liver, and a key cardiac remodelling enzyme, matrix metalloproteinase 2, in adult zebrafish heart. Se-Met significantly increased echodensity at the junction between atrium and ventricle, and these results combined with increased matrix metalloproteinase 2 expression are consistent with cardiac remodelling and fibrosis. The results of this study suggest that chronic exposure to dietary Se-Met can negatively impact cardiac function, and such physiological consequences could reduce the aerobic capacity and survivability of fish.

Cardiometabolic response of juvenile rainbow trout exposed to dietary selenomethionine

Selenium (Se) is considered an essential trace element, involved in important physiological and metabolic functions for all vertebrate species. Fish require dietary concentrations of 0.1-0.5 μg Se/g dry mass (d.m.) to maintain normal physiological and selenoprotein function, however concentrations exceeding 3 μg/g d.m. have been shown to cause toxicity. As Se is reported to have a narrow margin between essentiality and toxicity, there is growing concern surrounding the adverse effects of elevated Se exposure caused by anthropogenic activities. Previous studies have reported that elevated dietary exposure of fish to selenomethionine (Se-Met) can cause significant cardiotoxicity and alter aerobic metabolic capacity, energy homeostasis and swimming performance. The goal of this study aims to further investigate mechanisms of sublethal Se-Met toxicity, particularly potential underlying cardiovascular and metabolic implications of chronic exposure to environmentally relevant concentrations of dietary Se-Met in juvenile rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were fed either control food (1.3 μg Se/g d.m.) or Se-Met spiked food (6.4, 15.8 or 47.8 μg Se/g d.m.) for 60 d at 3% body weight per day. Following exposure, ultrahigh resolution B-mode and Doppler ultrasound was used to characterize cardiac function in vivo. Chronic dietary exposure to Se-Met significantly increased stroke volume, cardiac output, and ejection fraction. Fish fed with Se-Met spiked food had elevated liver glycogen and triglyceride stores, suggesting impaired energy homeostasis. Exposure to Se-Met significantly decreased mRNA abundance of citrate synthase (CS) in liver and serpin peptidase inhibitor, clad H1 (SERPINH) in heart, and increased mRNA abundance of sarcoplasmic reticulum calcium ATPase (SERCA) and key cardiac remodelling enzyme matrix metalloproteinase 9 (MMP9) in heart. Taken together, these responses are consistent with a compensatory cardiac response to increased susceptibility to oxidative stress, namely a decrease in ventricular stiffness and improved cardiac function. These cardiac alterations in trout hearts were linked to metabolic disruption in other major metabolic tissues (liver and skeletal muscle), impaired glucose tolerance with increased levels of the toxic glucose metabolite, methylglyoxal, increased lipid peroxidation in skeletal muscle, development of cataracts and prolonged feeding behaviour, indicative of visual impairment. Therefore, although juvenile rainbow trout hearts were apparently able to functionally compensate for adverse metabolic and anti-oxidant changes after chronic dietary exposure Se-Met, complications associated with hyperglycemia in mammalian species were evident and would threaten survival of juvenile and adult fish.

Irisin regulates cardiac physiology in zebrafish

Irisin is a myokine encoded in its precursor fibronectin type III domain containing 5 (FNDC5). It is abundantly expressed in cardiac and skeletal muscle, and is secreted upon the activation of peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1 alpha). We aimed to study the role of irisin on cardiac function and muscle protein regulation in zebrafish. Western blot analyses detected the presence of irisin protein (23 kDa) in zebrafish heart and skeletal muscle, and irisin immunoreactivity was detected in both tissues. Irisin siRNA treated samples did not show bands corresponding to irisin in zebrafish. In vitro studies found that treatment with irisin (0.1 nM) downregulated the expression of PGC-1 alpha, myostatin a, and b, while upregulating troponin C mRNA expression in zebrafish heart and skeletal muscle. Exogenous irisin (0.1 and 1 ng/g B.W) increased diastolic volume, heart rate and cardiac output, while knockdown of irisin (10 ng/g B.W) showed opposing effects on cardiovascular function. Irisin (1 and 10 ng/g B.W) downregulated PGC-1 alpha, myostatin a and b, and upregulated troponin C and troponin T2D mRNA expression. Meanwhile, knockdown of irisin showed opposing effects on troponin C, troponin T2D and myostatin a and b mRNAs in zebrafish heart and skeletal muscle. Collectively, these results identified muscle proteins as novel targets of irisin, and added irisin to the list of peptide modulators of cardiovascular physiology in zebrafish.

Exposure to a contextually neutral stressor potentiates fear conditioning in juvenile rainbow trout, Oncorhynchus mykiss

Organisms faced with stressors deploy a suite of adaptive responses in the form of behavioral, physiological and cognitive modifications to overcome the challenge. Interactive effects of these responses are known to influence learning and memory processes and facilitation is thought to be dependent, in part, upon contextual relevance of the stressor to the learning task. Predation is one such stressor for prey animals, and their ability to manage reliable information about predators is essential for adaptive antipredator strategies. Here, we investigated (i) the influence cortisol has on the ability of juvenile rainbow trout to learn and retain conditioned antipredator responses to predatory cues, and (ii) whether conditioned behavioral and physiological responses to predator cues are fixed or deployed in a threat-sensitive manner. Trout were fed cortisol-coated pellets minutes prior to a conditioning event where they were exposed to novel predator odor paired with chemical alarm cues (unconditioned stimulus). We tested for conditioned responses by exposing trout to predator cues after 2, 4 or 10days and subsequently documented physiological and behavioral responses. Both control and cortisol-fed trout learned the predator odor and responded 2 and 4days post conditioning. However, at 10days only cortisol-fed trout maintained strong behavioral responses to predator cues. Interestingly, we failed to find conditioned physiological responses to predator odor despite the presence of threat-sensitive cortisol responses to the unconditioned stimulus. Our findings suggest cortisol exposure prior to predator-learning may enhance retention of conditioned responses, even without a contextual link between stressor source and learning task.

Ultrasonography reveals in vivo dose-dependent inhibition of end systolic and diastolic volumes, heart rate and cardiac output by nesfatin-1 in zebrafish

Nesfatin-1 is an 82 amino acid peptide that inhibits food intake in rodents and fish. While endogenous nesfatin-1, and its role in the regulation of food intake and hormone secretion has been reported in fish, information on cardiovascular functions of nesfatin-1 in fish is in its infancy. We hypothesized that cardiac NUCB2 expression is meal responsive and nesfatin-1 is a cardioregulatory peptide in zebrafish. NUCB2/nesfatin-1 like immunoreactivity was detected in zebrafish cardiomyocytes. Real-time quantitative PCR analysis found that the cardiac expression of NUCB2A mRNA in unfed fish decreased at 1h post-regular feeding time. Food deprivation for 7days did not change NUCB2A mRNA expression. However, NUCB2B mRNA expression was increased in the heart of zebrafish after a 7-day food deprivation. Ultrasonography of zebrafish heart at 15min post-intraperitoneal injection of nesfatin-1 (250 and 500ng/g body weight) showed a dose-dependent inhibition of end diastolic and end systolic volumes. A dose dependent decrease in heart rate and cardiac output was observed in zebrafish that received nesfatin-1, but no changes in stroke volume were found. Nesfatin-1 treatment caused a significant increase in the expression of Atp2a2a mRNA encoding the calcium-handling pump, SERCA2a, while it had no effects on the expression of calcium handling protein RyR1b encoding mRNA. Our data support cardiosuppressive effects of nesfatin-1 in zebrafish, and reveals energy availability as one determinant of cardiac NUCB2 mRNA expression.

Comparison of the acute effects of benzo-a-pyrene on adult zebrafish (Danio rerio) cardiorespiratory function following intraperitoneal injection versus aqueous exposure

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants. PAH exposure causes developmental toxicity in multiple fish species, while acute adult fish toxicity is thought to be minimal. The literature increasingly suggests sublethal PAH effects may occur, but differences in exposure route may confound conclusions. We hypothesized that acute PAH exposure in adult fish will cause cardiorespiratory impairment that will not differ with exposure route. In order to investigate this hypothesis, adult zebrafish (Danio rerio) were injected intraperitoneal (i.p.) twice with increasing concentrations of the prototypical PAH, benzo-a-pyrene (BaP; 0.1, 10, and 1000μg/kg) or exposed aqueously (static, renewal at 24h; 16.2 and 162μg/L) for 48h and compared to corresponding dimethylsulfoxide controls. No mortalities or significant effects on weight of the fish were noted at any exposure concentration or route. At 48h, fish were subjected to swimming tests with concurrent oxygen consumption measurement (n=10 fish/treatment) or echocardiography (n=12 fish/treatment). Oxygen consumption (MO2) was increased at three swimming speeds in BaP-injected groups compared to control (p<0.01 in Fisher's LSD tests after two-way ANOVA). In contrast, aqueously BaP-exposed fish showed increased MO2 under only basal conditions. Despite increased oxygen demand, ventricular heart rate was significantly decreased in BaP-exposed fish, both injected and aqueously-exposed. Analysis of BaP body burdens in fish tissue allowed for identification of an overlapping dose group between exposure routes, through which comparisons of cardiorespiratory toxicity were then made. This comparison revealed most effects were similar between the two exposures routes, although minor differences were noted. At similar BaP body burdens, injected fish suffered from more severe bradycardia than aqueously exposed fish and had greater levels of increases in cytochrome P4501A (CYP1A) mRNA levels in liver and heart tissue compared to aqueous exposed fish. In conclusion, acute BaP exposure in adult zebrafish had negative effects on cardiorespiratory function. Differences in effect between exposure routes were attributed primarily to differences in bioavailability, since overall, similar effects were noted between the two exposure routes when similar BaP body burdens were achieved.

Effect of an extruded pea or rice diet on postprandial insulin and cardiovascular responses in dogs

Peas are increasing in popularity as a source of carbohydrate, protein and fibre in extruded canine diets. The aim of this study was to test the health effects of two canine diets with identical macronutrient profiles, but containing either yellow field peas or white rice as the carbohydrate source on metabolism, cardiovascular outcomes and adiposity. First, the acute glycemic, insulinemic and cardiovascular responses to the pea- or rice-based diets were determined in normal weight beagles (n = 7 dogs). The glycemic index did not differ between the pea diet (56 ± 12) and rice diet (63 ± 9). Next, obese beagles (n = 9) were fed the yellow field pea diet or white rice diet ad libitum for 12 weeks in a crossover study. Adiposity (measured using computed tomography), metabolic (oral glucose tolerance test, plasma leptin, adiponectin, C-reactive protein) and cardiovascular assessments (echocardiography and blood pressure) were performed before and after each crossover study period. After 12 weeks on each diet, peak insulin (p = 0.05) and area under the curve (AUC) for insulin after a 10 g oral glucose tolerance test (p = 0.05) were lower with the pea than the rice diet. Diet did not show a significant effect on body weight, fat distribution, cardiovascular variables, adiponectin or leptin. In conclusion, a diet containing yellow field peas reduced the postprandial insulin response after glucose challenge in dogs despite continued obesity, indicating improved metabolic health.

Acute effects of β-naphthoflavone on cardiorespiratory function and metabolism in adult zebrafish (Danio rerio)

Aryl hydrocarbon receptor (AhR) agonists are known to cause lethal cardiovascular deformities in fish after developmental exposure. Acute adult fish toxicity of AhR agonists is thought to be minimal, but limited evidence suggests sublethal effects may also involve the cardiac system in fish. In the present study, adult zebrafish (Danio rerio) were aqueously exposed to solvent control or three nominal concentrations of the commonly used model AhR agonist, β-naphthoflavone (BNF), for 48 h. Following exposure, fish were subjected to echocardiography to determine cardiac function or swimming tests with concurrent oxygen consumption measurement. Critical swimming speed and standard metabolic rate were not significantly changed, while active metabolic rate decreased with increasing BNF exposure, reaching statistical significance at the highest BNF exposure. Factorial aerobic scope was the most sensitive end-point and was decreased at even lower BNF concentrations, indicating a reduced aerobic capacity after acute AhR agonist exposure in adult fish. The highest BNF concentration caused a significant decrease in cardiac output, while increasing the ratio of atrial to ventricular heart rate (indicating atrioventricular conduction blockade). In conclusion, the effect of acute BNF exposure on zebrafish metabolic capacity and cardiac function is likely to be physiologically important given that fish have a critical need for adequate oxygen to fuel essential survival behaviors such as swimming, growth, and reproduction. Future studies should be directed at examining the effects of other polycyclic aromatic hydrocarbons on fish cardiorespiratory function to determine whether their effects and modes of action are similar to BNF.

Combined exposure to lead, inorganic mercury and methylmercury shows deviation from additivity for cardiovascular toxicity in rats

Environmental exposure to metal mixtures in the human population is common. Mixture risk assessments are often challenging because of a lack of suitable data on the relevant mixture. A growing number of studies show an association between lead or mercury exposure and cardiovascular effects. We investigated the cardiovascular effects of single metal exposure or co-exposure to methylmercury [MeHg(I)], inorganic mercury [Hg(II)] and lead [Pb(II)]. Male Wistar rats received four different metal mixtures for 28 days through the drinking water. The ratios of the metals were based on reference and environmental exposure values. Blood and pulse pressure, cardiac output and electrical activity of the heart were selected as end-points. While exposure to only MeHg(I) increased the systolic blood pressure and decreased cardiac output, the effects were reversed with combined exposures (antagonism). In contrast to these effects, combined exposures negatively affected the electrical activity of the heart (synergism). Thus, it appears that estimates of blood total Hg levels need to be paired with estimates of what species of mercury dominate exposure as well as whether lead co-exposure is present to link total blood Hg levels to cardiovascular effects. Based on current human exposure data and our results, there may be an increased risk of cardiac events as a result of combined exposures to Hg(II), MeHg(I) and Pb(II). This increased risk needs to be clarified by analyzing lead and Hg exposure data in relation to cardiac electrical activity in epidemiological studies.

Within and between population variation in epidermal club cell investment in a freshwater prey fish: a cautionary tale for evolutionary ecologists

Many prey fishes possess large club cells in their epidermis. The role of these cells has garnered considerable attention from evolutionary ecologists. These cells likely form part of the innate immune system of fishes, however, they also have an alarm function, releasing chemical cues that serve to warn nearby conspecifics of danger. Experiments aimed at understanding the selection pressures leading to the evolution of these cells have been hampered by a surprisingly large intraspecific variation in epidermal club cell (ECC) investment. The goal of our current work was to explore the magnitude and nature of this variation in ECC investment. In a field survey, we documented large differences in ECC investment both within and between several populations of minnows. We then tested whether we could experimentally reduce variation in mean ECC number by raising fish under standard laboratory conditions for 4 weeks. Fish from different populations responded very differently to being held under standard laboratory conditions; some populations showed an increase in ECC investment while others remained unchanged. More importantly, we found some evidence that we could reduce within population variation in ECC investment through time, but could not reduce among-population variation in mean ECC investment. Given the large variation we observed in wild fish and our limited ability to converge mean cell number by holding the fish under standard conditions, we caution that future studies may be hard pressed to find subtle effects of various experimental manipulations; this will make elucidating the selection pressures leading to the evolution of the cells challenging.

Postprandial impairment of flow-mediated dilation and elevated methylglyoxal after simple but not complex carbohydrate consumption in dogs

Hyperglycemia produces oxidative stress, which may impair endothelial function. Methylglyoxal, a reactive intermediate metabolite of glucose, is known to cause oxidative stress and is produced when excess carbohydrate is consumed in diabetic patients, but postprandial responses in healthy patients are unknown. We hypothesize that methylglyoxal levels will cause impaired endothelial function via increased oxidative stress after consuming a high glycemic index meal in healthy animals. Normal-weight laboratory beagles (n = 6) were used in a crossover study that tested postprandial responses of 4 complex carbohydrate sources (barley, corn, peas, rice) vs a simple carbohydrate (glucose). Blood samples were taken prefeeding and at timed intervals after feeding to measure serum glucose, insulin, nitrotyrosine, and methylglyoxal. Flow-mediated dilation (FMD), cardiac function (echocardiography), and blood pressure measurements were determined before and 60 minutes after feeding. The mean (±SEM) glycemic indices of the complex carbohydrate sources were 29 ± 5 for peas, 47 ± 10 for corn, 51 ± 7 for barley, and 55 ± 6 for rice. Postprandial FMD was lowest in the glucose group and significantly different from both the corn group and the FMD value for all complex carbohydrates combined. Methylglyoxal was significantly elevated at 60 minutes postprandial after glucose compared with the other carbohydrate sources. No significant effects of carbohydrate source were observed for blood pressure, nitrotyrosine, or echocardiographic variables. The novel finding of this study was that methylglyoxal levels increased after a single feeding of simple carbohydrate and may be linked to the observed postprandial decrease in endothelial function. Thus, consuming low-glycemic-index foods may protect the cardiovascular system by reducing oxidative stress.

Persistent effects on adult swim performance and energetics in zebrafish developmentally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) remains a potent and persistent toxicant in aquatic environments, causing lethal developmental deformities in fish. However, few studies have examined sublethal or persistent effects of developmental TCDD exposure and none have examined its effects on swimming capabilities in sub-adult fish. The objective of the current study was to examine whether effects of TCDD exposure during the critical period of cardiovascular development (2-4 days post fertilization) on swim performance, triglyceride stores and cardiovascular deformities would persist until adulthood in zebrafish. Zebrafish larvae were exposed between 48 and 96 h post fertilization to 1, 0.1, 0.01 ng/L TCDD or DMSO control (0.005%), then raised in clean water for 90 days. Despite having equal survivability, no significant increase in gross deformities and no change in cytochrome P450 1A (CYP1A) activity was observed, while critical swimming speed and dorsal aorta diameter were significantly decreased in TCDD-exposed fish at 90 days. Furthermore, whole body triglycerides were significantly elevated in TCDD-exposed fish both before and after swim testing. Therefore sublethal TCDD exposure during zebrafish development caused a persistent decrease in swim endurance. The cause of this persistent decrease in swim endurance is not known, but may be related to behavioral adaptations limiting swimming capabilities, failure to mobilize triglyceride stores, vascular deformities limiting blood flow to the periphery, or a combination of these factors.

Swim performance and energy homeostasis in spottail shiner (Notropis hudsonius) collected downstream of a uranium mill

The Key Lake uranium milling operation (Saskatchewan, Canada) releases complex effluent into the local watershed. The objective of the current study was to investigate whether fish from an effluent-receiving waterbody exhibited differences in swimming performance and energy homeostasis compared to fish from a local reference site. Juvenile spottail shiner (Notropis hudsonius) were collected from a lake downstream of the uranium mill, and compared to fish collected from a nearby reference lake. Critical swimming speed (U(crit); fatigue velocity), tail beat frequency, and tail amplitude did not differ significantly when comparing fish collected from the exposure lake and reference lake. Captured shiner used in swim tests were considered fatigued, and metabolic endpoints were compared between this group and non-fatigued fish, which were treated similarly but not subjected to swim tests. In both non-fatigued and fatigued shiner, liver glycogen was significantly greater in fish collected from the exposure lake compared to the reference lake. However, it is unclear if this effect, and others related to condition, were the result of contaminant exposure or other environmental factors. While there were no differences in plasma lactate, hematocrit or liver triglycerides in non-fatigued fish between sites, only fatigued reference fish had increased lactate and hematocrit and decreased triglycerides. In non-fatigued fish, plasma glucose did not significantly differ between sites, but significantly decreased after swimming only in fish from the exposure lake. In summary, shiner from the exposure site demonstrated similar swim endurance and possessed greater energy stores despite metabolic alterations compared to shiner from the reference site. Therefore, because fish collected downstream of the uranium mill operation had similar swimming ability as fish from the reference lake, U(crit) test results presented here may not reflect or be indicative of metabolic effects of complex effluent exposure.

Secondhand tobacco smoke, arterial stiffness, and altered circadian blood pressure patterns are associated with lung inflammation and oxidative stress in rats

Chronic smoking and secondhand tobacco smoke exposure are major risk factors for cardiovascular disease that are known to adversely alter the structural and mechanical properties of arteries. The objective of this study was to determine the effects of subchronic secondhand tobacco smoke exposure on circadian blood pressure patterns, arterial stiffness, and possible sources of oxidative stress in conscious, unsedated radiotelemetry-implanted rats. Pulse wave change in pressure over time (dP/dt) was used an indicator of arterial stiffness and was compared with both structural (wall thickness) and functional (nitric oxide production and bioactivity and endothelin-1 levels) features of the arterial wall. In addition, histology of lung, heart, and liver was examined as well as pulmonary and hepatic detoxifying enzyme activity (cytochrome P450, specifically CYP1A1). Subchronic secondhand tobacco smoke exposure altered the circadian pattern of heart rate and blood pressure, with a loss in the normal dipping pattern of blood pressure during sleep. Secondhand tobacco smoke exposure also increased pulse wave dP/dt in the absence of any structural modifications in the arterial wall. Furthermore, although nitric oxide production and endothelin-1 levels were not altered by secondhand tobacco smoke, there was increased inactivation of nitric oxide as indicated by peroxynitrite production. Increased lung neutrophils or pulmonary CYP1A1 may be responsible for the increase in oxidative stress in rats exposed to secondhand tobacco smoke. In turn, this may be related to the observed failure of blood pressure to dip during periods of sleep and a possible increase in arterial stiffness.

Swimming performance and energy homeostasis in juvenile laboratory raised fathead minnow (Pimephales promelas) exposed to uranium mill effluent

Research at the Key Lake uranium mill (Saskatchewan, Canada) suggests effluent discharged from the mill affects energy stores of resident fish, but the mechanisms by which energy homeostasis is affected and the subsequent effects on swimming performance are unknown. In the present study larvae were collected from laboratory raised adult fathead minnow (Pimephales promelas) exposed to 5% diluted uranium mill effluent or control (dechlorinated municipal) water, and reared in the same treatments to 60 days post hatch (dph). Critical swimming speed (U(crit)) was significantly lower in effluent exposed 60 dph fish compared to control fish. Fish used in tests were considered fatigued and compared to fish without swim testing (non-fatigued). There were no differences in whole body glycogen or triglyceride concentrations between effluent exposed versus control fish. However, fatigued fish from both treatments had significantly lower triglycerides, but not glycogen, compared to non-fatigued fish from the same treatment. Whole body β-hydroxyacyl coenzymeA dehydrogenase activity was similar in fish from both treatments, but citrate synthase activity was significantly lower in effluent exposed fish. Our results suggest uranium mill effluent exposure in the laboratory affects aerobic energy metabolism and swimming performance in juvenile fathead minnow, which could affect wild fish survivability.

Acute exposure to 2,4-dinitrophenol alters zebrafish swimming performance and whole body triglyceride levels

While swimming endurance (critical swimming speed or U(crit)) and lipid stores have both been reported to acutely decrease after exposure to a variety of toxicants, the relationship between these endpoints has not been clearly established. In order to examine these relationships, adult zebrafish (Danio rerio) were aqueously exposed to solvent control (ethanol) or two nominal concentrations of 2,4-dinitrophenol (DNP), a mitochondrial electron transport chain uncoupler, for a 24-h period. Following exposure, fish were placed in a swim tunnel in clean water for swimming testing or euthanized immediately without testing, followed by analysis of whole body triglyceride levels. U(crit) decreased in both the 6 mg/L and 12 mg/L DNP groups, with 12 mg/L approaching the LC₅₀. A decrease in tail beat frequency was observed without a significant change in tail beat amplitude. In contrast, triglyceride levels were elevated in a concentration-dependent manner in the DNP exposure groups, but only in fish subjected to swimming tests. This increase in triglyceride stores may be due to a direct interference of DNP on lipid catabolism as well as increased triglyceride production when zebrafish were subjected to the co-stressors of swimming and toxicant exposure. Future studies should be directed at determining how acute DNP exposure combines with swimming to cause alterations in triglyceride accumulation.

Blood glucose and liver function in dogs administered a xylitol drinking water additive at zero, one and five times dosage rates

A study was designed to determine the safety of a drinking water additive that reduces plaque and calculus in dogs, and contains xylitol as an active ingredient. The randomized, double-blind, placebo-controlled study was performed in 15 crossbred dogs that were randomly divided into three groups and had their drinking water treated for 14 days with either: i) a commercial health care product (BreathaLyser Plus) at the recommended dosage, ii) an experimental health care product (BreathaLyser Plus containing five times the amount of xylitol), or iii) a placebo of purified water with a colour additive. Results demonstrated that the continuous administration of a commercial, drinking water, oral health product containing xylitol, at one and five times the normal inclusion rate, does not cause hypoglycemia or alter liver function in dogs.<br />

Role of carbon monoxide in impaired endothelial function mediated by acute second-hand tobacco, incense, and candle smoke exposures

The aim of this study was to determine if carbon monoxide (CO) is responsible for acute adverse cardiovascular effects of different sources of smoke: second-hand tobacco smoke (SHS), incense and candle smoke. Endothelial function was tested using flow-mediated dilation (FMD) in pigs and was shown to be sensitive to nitric oxide synthase blockade. Subsequent experiments showed that FMD was significantly impaired compared to sham-exposed pigs at 30 min after a 30-min exposure to all three sources of smoke. In contrast, SHS significantly increased systolic, diastolic and pulse pressures compared to sham-exposure, while both incense and candle smoke exposure had no effect. The FMD impairment correlated well with CO levels in the exposure chamber, but not total particulates or venous CO-hemoglobin. Therefore, this study suggests a gas phase component of smoke that accompanies CO, but not CO itself, is responsible for acute endothelial dysfunction after SHS, incense or candle smoke exposure.

Resveratrol preserves cardiac function, but does not prevent endothelial dysfunction or pulmonary inflammation after environmental tobacco smoke exposure

The mechanisms by which environmental tobacco smoke (ETS) causes adverse cardiovascular effects remain unclear. Resveratrol is a natural polyphenol from red wine which may be beneficial to the cardiovascular system. Therefore, the ability of daily oral resveratrol (5mg/kg) to prevent adverse effects of a 14-day ETS exposure (1 h/day) on endothelial function (flow-mediated dilation), left ventricular function (echocardiography) and blood pressure (oscillometry) was assessed in juvenile male pigs (n=4 pigs/group). After a 14-day exposure to ETS, flow-mediated dilation was impaired while plasma nitrotyrosine was increased compared to sham-exposed pigs indicating impaired endothelial function. In ETS-exposed pigs, plasma C-reactive protein levels, lung cytochrome P4501A1 activity, bronchoalveolar lavage fluid total white blood cell count and leukocyte elastase activity were all significantly increased compared to sham-exposed pigs. Resveratrol treatment failed to prevent most ETS-mediated effects examined, but did increase left ventricular end-diastolic volume and ejection fraction in the presence of ETS exposure. In summary, ETS exposure impaired endothelial function and increased oxidative stress which was associated with pulmonary and systemic inflammation, but resveratrol failed to protect against these changes. More importantly, resveratrol exerted a positive effect on left ventricular function which may help explain the French paradox.

Using blood pressure telemetry to assess acute changes in arterial stiffness in rats after nitric oxide synthase inhibition or environmental tobacco smoke exposure

Although environmental tobacco smoke (ETS) exposure has been reported to acutely increase arterial stiffness in humans, understanding of the underlying mechanisms is unclear and few studies have measured these effects in experimental animals. One potential mechanism for the increased arterial stiffness is reduced nitric oxide (NO) bioactivity as a result of oxidative stress. Thus, the objective of this study was to determine whether acute changes in arterial stiffness could be detected using arterial pulse wave dP/dt in blood pressure telemetry implanted rats and to investigate the role of NO in regulating dP/dt. Intravenous injection of acetylcholine (0.91 ng/kg) decreased and norepinephrine (0.02 mg/kg) increased dP/dt compared to saline vehicle (0.5 mL/kg). Injection of the NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME; 30 mg/kg) decreased plasma nitrate/nitrite (NOx), but transiently increased dP/dt. ETS at low and high doses had no effect on dP/dt, but increased plasma NOx levels at high ETS exposure and increased plasma nitrotyrosine levels in both ETS groups. In conclusion, acute changes in NO production via acetylcholine or L-NAME alter the arterial pulse wave dP/dt consistently with the predicted changes in arterial stiffness. Although acute ETS appears to biologically inactivate NO, a concomitant increase in NO production at high ETS exposure may explain why dP/dt was not acutely altered by ETS in the current study.

Phenotypic anchoring of gene expression after developmental exposure to aryl hydrocarbon receptor ligands in zebrafish

The genes mediating developmental aryl hydrocarbon (AhR)-induced cardiovascular deformities remain unclear, with many cytochrome P450 monooxygenase (CYP)-1 isoforms known to be AhR-responsive and now a cyclo-oxygenase (COX) isoform suspected to contribute developmental toxicity. More importantly, no previous study has examined the role of these genes in producing deformities using low enough concentrations of AhR agonists to permit survival beyond early larval stages. Zebrafish (Danio rerio) eggs were aqueously exposed to a variety of agents that had multiple modes of action, but all of which are reported to be AhR ligands; benzo-a-pyrene (BaP) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alone and in combination with resveratrol or alpha-naphthoflavone (ANF). Whole larvae CYP (subtypes 1A, 1B1, 1C1, and 1C2) and COX (subtypes 1, 2a, and 2b) mRNA expression was quantified at 5 and 10 dpf and correlated with developmental phenotype. Both TCDD and BaP caused dose-dependent AhR-associated deformities and mortalities by 10 dpf, while BaP/ANF co-exposure exhibited the highest rate of deformities and mortalities at 5 dpf with all of these larvae having died at the highest rate by 10 dpf. Furthermore, BaP/ANF co-exposure caused the most marked alterations in cardiac and vascular morphology at 10 dpf at the concentrations used, namely decreased ventricular length and chamber width with increased ventricular wall thickness, as well as increased blood vessel luminal diameter. Exposure to TCDD, BaP and ANF alone all significantly increased CYP1A mRNA expression, while only TCDD consistently increased CYP1C1 expression. In contrast, TCDD transiently decreased CYP1C2 expression. BaP alone had no effect on CYP1C1 expression, but decreased COX2b expression when alone or in combination with ANF. In fact, ANF exhibited additive agonistic effects on expression of CYP1A and CYP1C1 with both BaP and TCDD, although additive or potentiating effects of ANF on CYP1C2 and COX2b were observed with only BaP. Correlation analyses revealed that gene expression at 5 dpf, but not 10 dpf, was strongly linked to abnormal cardiac and vascular phenotypes at 10 dpf. Principal components analysis suggests that cardiac deformities and blood vessel dilation were related positively to CYP1A and negatively to COX-2b gene expression. These relationships were separate from the one gene, CYP1C1, that was negatively associated with increased vascular wall thickness. However, further experiments are needed to confirm this difference and to determine whether the relationship is causative or merely associative.

Growth and energy storage in juvenile fathead minnows exposed to metal mine waste water in simulated winter and summer conditions

Juvenile fathead minnows (Pimephales promelas) were exposed from 10 to 100 days post-hatch (dph) to metal mining effluent under simulated summer (20 degrees C and 16/8 light/dark) or winter (4 degrees C and 8/16 light/dark) conditions in order to test the winter stress syndrome hypothesis. The condition factor of fish at 100 dph was similar between seasons, and was greater in the summer effluent exposure group compared to the summer control. Whole body triglycerides were lower in the effluent exposure group compared to control under winter conditions, but not summer. Whole body burdens of several trace metals, notably Cu, Rb and Se, were greater in the effluent exposed fish at 100 dph and displayed seasonal differences in bioaccumulation. Fathead minnows were also exposed from 10 to 100 dph to graded concentrations of ammonia (0.02-0.40 mg unionized NH(3)/L) under summer conditions in order to investigate potential effects of this component of the effluent. There was no effect of ammonia exposure on growth parameters, but an increase in whole body triglycerides was observed at the highest exposure. The seasonal differences in bioaccumulation and biological responses suggest that winter conditions may be an important modifying factor in aquatic toxicological studies.

Hepatic and vascular mRNA expression in adult zebrafish (Danio rerio) following exposure to benzo-a-pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin

Developmental exposure to aryl hydrocarbon receptor (AhR) agonists in fish causes severe defects in the cardiovascular system. However, the effects of acute AhR agonist exposure on the adult fish cardiovascular system are not clear. We hypothesized that AhR-mediated changes in adult vascular tissue gene expression would differ from that of hepatic tissue. Therefore, zebrafish (Danio rerio) were intraperitoneally injected with the AhR agonists benzo-a-pyrene (BaP; 1mg/kg) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 20microg/kg) alone and in combination with the AhR antagonists resveratrol (Res; 10mg/kg) or alpha-naphthoflavone (ANF; 50mg/kg). Hepatic and mesenteric artery cytochrome P450 enzyme (subtypes 1A, 1B1, 1C1, and 1C2) and cyclooxygenase enzyme (subtypes 1, 2a, and 2b) mRNA expression was quantified using real-time reverse transcriptase PCR. TCDD exposure significantly increased (p<or=0.05 in Tukey's posteriori test after 1-way ANOVA; n=4-6/group) CYP1A, CYP1C1, and COX-2b mRNA expression in hepatic tissue (105+/-21, 12+/-2, and 2+/-0.3 fold-increase, mean+/-SEM respectively). TCDD also increased CYP1A, CYP1B1, CYP1C1, CYP1C2, and COX-1 mRNA expression in mesenteric artery (121+/-23, 5+/-1, 28+/-6, 7+/-1, and 3+/-0.3, respectively). Importantly, while BaP exposure elicited no significant alterations in hepatic CYP mRNA expression, it increased COX-1 and COX-2b in liver tissues (3+/-1 and 2+/-0.1, respectively), as well as CYP1A, CYP1B1, CYP1C1, CYP1C2, and COX-1 expression in mesenteric artery (2+/-0.3, 4+/-0.3, 5+/-1, 5+/-1, and 2+/-0.3, respectively). Resveratrol was able to antagonize TCDD-induced CYP1C2 in mesenteric artery but was without effect in all other treatments in both liver and mesenteric artery. In contrast, ANF antagonized TCDD and BaP-induced COX-2b and TCDD-induced CYP1C1 expression increases, as well as reduced baseline CYP1B1 and COX-2a expression in liver, while failing to affect BaP and TCDD-induced hepatic CYP1A increases. However, in mesenteric artery, ANF alone acted instead as an agonist to increase expression of CYP1A, CYP1B1, CYP1C1, CYP1C2, COX-2a and COX-2b. Thus, there are important differences in response to both AhR agonists and antagonists between liver and mesenteric artery in adult zebrafish. The vascular-specific changes in gene expression will be linked to future studies examining alterations in cardiovascular function produced by acute AhR agonist exposure in adult fish.

Parturition induction two days prior to term decreases birth weight and lactational growth, but not piglet maturity, health or post-weaning growth

Premature parturition induction may adversely affect postnatal health and performance. The objective of this study was to evaluate the impact of cloprostenol induction 2 d prior to term on piglet maturity (liver glycogen), postnatal productivity (birth weight, growth rate), and health (morbidity, mortality, passive antibody, fecal Clostridium perfringens). Two hundred and sixteen pregnant sows and their progeny (2827 piglets) were assigned to the study. Induction decreased gestation length 2.1 d (P < 0.0001), birth weight 107.2 g pig-1 (P = 0.0004), lactational growth 10.1 g d-1 (P = 0.05), and day 16 weight 0.30 kg pig-1 (P < 0.05). Liver glycogen concentration was 71.2 µg g-1 higher in the stillborns of induced sows (P = 0.03), suggesting the pre-term sows were catabolic. No group differences in post-weaning growth rate, pre-weaning mortality or morbidity, passive antibody transfer or fecal Clostridium perfringens level were found. Reduced lactational growth appeared attributable to the reductions in gestation length and birth weight, rather than in piglet maturity. In spite of reducing lactational growth and body weight at 16 d of age, the administration of cloprostenol 2 d prior to term, under the conditions of this study, resulted in no measureable long-term health or performance consequences. Key words: Porcine, parturition-induction, cloprostenol, prostaglandin F2α, glycogen, Clostridium perfringens

Overwinter alterations in energy stores and growth in juvenile fishes inhabiting areas receiving metal mining and municipal wastewater effluents

The winter stress syndrome hypothesis proposes that the combination of winter conditions and contaminant exposure reduces overwinter survival in juvenile fishes, mainly due to increased depletion of stored energy (lipids). To test this hypothesis in the field, juvenile fathead minnows (Pimephales promelas), creek chub (Semotilus atromaculatus), and white sucker (Catostomus commersoni) were collected from three exposure sites along Junction Creek, Sudbury, Ontario, Canada, representing cumulative inputs from metal mining and municipal wastewater. Overwinter survival potential was determined through measurements of growth (length, weight, muscle RNA/DNA ratio, muscle proteins) and energy stores (whole body triglycerides) in fish collected just prior to and following the overwinter period. We hypothesized that fish collected from exposure sites would exhibit reduced growth and energy storage compared to reference fish in both fall and spring, and that fish from all sites would exhibit reduced energy storage in spring compared to the previous fall. Whole body Se concentrations were elevated (11-42 microg/g dry wt) in juvenile fathead minnows and white sucker collected at two exposure sites in comparison to fish collected from the reference site (3-6 microg/g dry wt). In contrast to our hypothesis, fathead minnows were larger with greater triglyceride stores at exposure sites compared to the reference site. White suckers were smaller at exposure sites but did not differ in triglycerides among sites. Overall, the results in these fish species exposed to metal mining and municipal wastewaters do not support the winter stress syndrome hypothesis. It is recommended that future studies focus on relating growth and energy storage with other environmental factors such as habitat and food availability in addition to anthropogenic contamination.