The Effects of Multiple Micronutrient Fortified Beverage and Responsive Caregiving Interventions on Early Childhood Development, Hemoglobin, and Ferritin among Infants in Rural Guatemala

Undernutrition and a lack of learning opportunities can jeopardize long-term growth and development among infants in low- and middle-income countries. We conducted a 6-month 2 × 2 cluster-randomized trial to assess the effects of multiple micronutrient-fortified beverages and responsive caregiving interventions among infants 6-18 months in 72 community sectors in southwest Guatemala. We administered baseline and endline assessments of childhood development (Bayley Scales of Infant and Toddler Development) and socioemotional development (Brief Infant Toddler Socio-Emotional Assessment) and measured ferritin and hemoglobin on a subsample. The trial was analyzed using linear mixed models. At the baseline, the mean age (SD) was 13.0 (4.6) months, including 49% males, 32% who were stunted, 55% who were anemic, and 58% who were iron deficient. At the endline (n = 328/386, 85% retention), there was no synergistic effect on the fortified beverage and responsive caregiving intervention. Compared to the non-fortified beverage group, socioemotional development improved in the fortified beverage group. There were no intervention effects on other measures of child development, hemoglobin, or ferritin. In a setting with high rates of anemia and iron deficiency, a multiple micronutrient-fortified beverage improved infants' socioemotional development.

Altered fecal microbiota, IgA, and fermentative end-products in adult dogs fed prebiotics and a nonviable Lactobacillus acidophilus

A study investigating the use of a nonviable Lactobacillus acidophilus (NVL: Culbac; TransAgra, Storm Lake, IA) and a mixed prebiotic (MP) blend (beet pulp, fructooligosaccharide (FOS), mannanoligosaccharide (MOS), inulin, and kelp) was done to evaluate changes in fecal microbiota, fermentative end products, and gut immune health in healthy female and male adult Beagle dogs (n = 24; 5.74 ± 2.18 yr; 9.30 ± 1.32 kg). The study protocol was first approved by the facility's Institutional Animal Care and Use Committee (Summit Ridge Farms; Susquehanna, PA) and followed throughout. Each of four test diets (control, NVL, MP, and MP + NVL [formulated to crude protein 25%, crude fat 14%, crude fiber 10% as-fed]) was fed once daily to maintain body weight for 21 d in a randomized-crossover design (four treatment periods and four washout periods). Fecal samples were collected on days 0 and 21 only for immunoglobulin A (IgA) and microbiota evaluation (16S rRNA V4 region and qPCR for Escherichia coli and Bifidobacterium), and fecal fermentative end-products and fecal pH were assessed only on day 21. Over the test periods, apparent total tract nutrient digestibility and stool quality were assessed. Data were analyzed by ANOVA (SAS v9.4, Cary, NC) or Kruskal-Wallis for between-diet effects, and paired t-test or Wilcoxon for time effects. Statistical significance was set at P ≤ 0.05. Apparent total tract nutrient digestibility revealed feeding MP-containing diets resulted in lower (P < 0.05) crude protein and fat digestibility vs. control and NVL diets. When dogs were fed MP, they had lower (P < 0.05) fecal pH compared with control and NVL diets, whereas fecal pH was lower in (P < 0.05) MP + NVL- vs. NVL-fed dogs. Fecal E. coli was (P < 0.05) lower at day 21 vs. day 0 when dogs were fed MP. Fecal Fusobacterium spp. was lower (P < 0.05) in both MP diets vs. control. Fecal Lactobacillus spp. increased (P < 0.05) from baseline with MP. Both diets with MP elicited greater (P < 0.05) fecal acetate and propionate concentration vs. control diet. At day 21, fecal IgA was greater (P < 0.05) in MP and MP + NVL compared with NVL diet. Only when dogs were fed MP did they have increased (P < 0.05) fecal IgA from day 21 vs. day 0. The MP + NVL diet decreased (P < 0.05) fecal isovalerate, isobutyrate, phenol, and indole vs. control. Overall, the MP elicited the most changes on microbiota, fermentative end-products, and IgA. Further investigation into NVL's gut health benefits is warranted.

Zinc deficiency associated with anaemia among young children in rural Guatemala

One in four children younger than age five in Guatemala experiences anaemia (haemoglobin <11.0 g/dl). This study characterized the factors and micronutrient deficiencies associated with anaemia in a baseline cross‐sectional sample of 182 Guatemalan infants/toddlers and 207 preschoolers, using generalized linear mixed models. Associations between anaemia and maternal, child and household variables, and biomarkers (soluble transferrin receptor, ferritin, zinc, folate, vitamin B12, C‐reactive protein, and α1‐acid glycoprotein) were explored. Rates of anaemia were 56% among infants/toddlers and 12.1% among preschoolers. In children with anaemia, rates of iron deficiency (low ferritin based on inflammation status, and/or high soluble transferrin receptor, ≥1.97 mg/L) and zinc deficiency (serum zinc <65 μg/dl) were 81.1% and 53.7%, respectively. Folate deficiency (either plasma folate <3 ng/ml or erythrocyte folate <100 ng/ml) was 3.3%. Vitamin B12 deficiency (plasma vitamin B12 <148 pmol/L) was 7.5%. For infants and toddlers (<24 months), the odds ratio of anaemia was lower when higher number of adults lived in the household (OR = 0.69; 95% CI [0.53, 0.90]), and higher when children were zinc deficient (OR = 3.40; 95% CI [1.54, 7.47]). For preschoolers (36–60 months), the odds ratio of anaemia was lower for every additional month of age (OR = 0.90; 95% CI [0.81, 1.00]). Findings suggest that micronutrient deficiencies coexist in Guatemalan rural children, and zinc deficiency is associated with anaemia in children <24 months, highlighting the need of continued multidisciplinary interventions with multiple micronutrients. Further research examining how household composition, feeding practices, and accessibility to micronutrient supplements and to animal source foods is needed to incorporate strategies to improve the nutritional status of Guatemalan children.

Mechanisms linking height to early child development among infants and preschoolers in rural India

Stunting has been negatively associated with children's development. We examined the range of height by testing hypotheses: (a) height is positively associated with children's development, with associations moderated by inflammation and (b) home environments characterized by nurturance and early learning opportunities is positively associated with children's development over time and attenuate associations with height. Data included 513 infants (mean age 8.6 months) and 316 preschoolers (mean age 36.6 months) in rural India from a randomized controlled trial of multiple micronutrient powders (MNPs). Measures included height (height-for-age z-scores based on WHO standards), inflammation (C-reactive protein concentration >5 mg/L), nurturance (HOME Inventory), child development (Mullens Scales of Early Learning), and inhibitory control (preschoolers). Linear mixed effects models accounting for repeated measures, clustering, and confounders were used to assess associations between height and child development over time (infants: enrollment, 6 and 12 months; preschoolers: enrollment and 8 months). Moderating effects of inflammation and nurturance were tested with interaction terms. Among infants and preschoolers, height and nurturance were positively associated with all domains of child development over time, with the exception of inhibitory control. Among preschoolers, in the presence of inflammation, height was not associated with child development. Among infants, but not preschoolers, a nurturant home environment attenuated significant associations between height with fine motor and receptive language development. The mechanisms associated with children's development over time are multifactorial and include direct and indirect associations among nutrition, health, and the home environment, as supported by the Nurturing Care Framework.

Comparison of two forms of daily preventive zinc supplementation versus therapeutic zinc supplementation for diarrhea on young children's physical growth and risk of infection: study design and rationale for a randomized controlled trial

Background

Zinc is an essential nutrient that is required for children’s normal growth and resistance to infections, including diarrhea and pneumonia, two major causes of child mortality. Daily or weekly preventive zinc supplementation has been shown to improve growth and reduce the risk of infection, while therapeutic zinc supplementation for 10–14 days is recommended for the treatment of diarrhea. The overall objective of the present study is to compare several regimens for delivering zinc to young children, both for the prevention of zinc deficiency and the treatment of diarrhea.

Methods

The present study is a community-based, randomized controlled trial in the Lao People’s Democratic Republic (PDR). Three thousand, four hundred children 6–23 months of age will be randomized to one of four intervention groups (daily preventive zinc dispersible tablet, daily preventive multiple micronutrient powder, therapeutic zinc dispersible tablet for diarrhea, or placebo control); interventions will be delivered for 9 months and outcomes measured at pre-determined intervals. Primary outcomes include physical growth (length and weight), diarrhea incidence, hemoglobin and micronutrient status, and innate and adaptive immune function. Secondary outcomes include mid-upper-arm circumference, neuro-behavioral development, hair cortisol concentrations, markers of intestinal inflammation and parasite burden. Incidence of adverse events and the modifying effects of inherited hemoglobin disorders and iron status on the response to the intervention will also be examined. We will estimate unadjusted effects and effects adjusted for selected baseline covariates using ANCOVA.

Discussion

Many countries are now rolling out large-scale programs to include therapeutic zinc supplementation in the treatment of childhood diarrhea, but few have established programs demonstrated to be effective in the prevention of zinc deficiency. This study will address how best to deliver supplemental zinc to prevent zinc deficiency and reduce the severity of diarrhea-related health complications.

Trial registration

Trial registration identifier (NCT02428647) ; Date of registration: April 29, 2015.

Consumption of a Double-Fortified Salt Affects Perceptual, Attentional, and Mnemonic Functioning in Women in a Randomized Controlled Trial in India

Background: Iron deficiency and iron deficiency anemia have been shown to have negative effects on aspects of perception, attention, and memory.Objective: The purpose of this investigation was to assess the extent to which increases in dietary iron consumption are related to improvements in behavioral measures of perceptual, attentional, and mnemonic function.Methods: Women were selected from a randomized, double-blind, controlled food-fortification trial involving ad libitum consumption of either a double-fortified salt (DFS) containing 47 mg potassium iodate/kg and 3.3 mg microencapsulated ferrous fumarate/g (1.1 mg elemental Fe/g) or a control iodized salt. Participants' blood iron status (primary outcomes) and cognitive functioning (secondary outcomes) were assessed at baseline and after 10 mo at endline. The study was performed on a tea plantation in the Darjeeling district of India. Participants (n = 126; 66% iron deficient and 49% anemic at baseline) were otherwise healthy women of reproductive age, 18-55 y.Results: Significant improvements were documented for iron status and for perceptual, attentional, and mnemonic function in the DFS group (percentage of variance accounted for: 16.5%) compared with the control group. In addition, the amount of change in perceptual and cognitive performance was significantly (P < 0.05) related to the amount of change in blood iron markers (mean percentage of variance accounted for: 16.0%) and baseline concentrations of blood iron markers (mean percentage of variance accounted for: 25.0%). Overall, there was evidence that the strongest effects of change in iron status were obtained for perceptual and low-level attentional function.Conclusion: DFS produced measurable and significant improvements in the perceptual, attentional, and mnemonic performance of Indian female tea pickers of reproductive age. This trial was registered at clinicaltrials.gov as NCT01032005.

Impact of preconceptional micronutrient supplementation on maternal mental health during pregnancy and postpartum: results from a randomized controlled trial in Vietnam

BACKGROUND

Micronutrient malnutrition has been associated with maternal depressive symptoms (MDS), but little is known about the effects of preconceptional micronutrient supplementation. This paper examined the effects of preconceptional micronutrient supplementation on MDS during pregnancy and postpartum.

METHODS

We used data from a double-blind controlled trial (PRECONCEPT) in which 5011 Vietnamese women were randomized to receive weekly supplements containing either a) multiple micronutrients (MM) b) iron and folic acid (IFA) or c) folic acid (FA) until conception (n = 1813). Maternal mental health was assessed using the Center for Epidemiologic Studies Depression Scale (CES-D) at baseline (preconception), and the Edinburgh Postnatal Depression Scale (EPDS) during pregnancy and 3 months postpartum. Elevated MDS was defined as EPDS score ≥ 4. All group comparisons were done using ANOVA or chi-square tests of proportions intention to treat and per protocol analyses (women consumed supplements ≥26 weeks before conception). We also conducted stratified analyses by preconception CES-D scores, underweight, or anemia status using generalized linear models.

RESULTS

Baseline CES-D scores were similar across treatment groups. The proportion of women experiencing elevated MDS was 11.3, 8.1 and 4.9% at first, second and third trimesters of pregnancy, respectively, and 3.6% at 3 mo postpartum. Mean EPDS scores at first (1.5 ± 2.7), second (1.1 ± 2.4), and third trimester of pregnancy (0.7 ± 2.0) and early postpartum (0.6 ± 1.8) were low and did not differ by treatment group. However, among women in the highest tertile of CES-D scores at preconception, mean EPDS scores in the first and second trimesters of pregnancy were lower in the MM and IFA groups compared to FA only (P < 0.05).

CONCLUSIONS

Weekly preconceptional micronutrient supplements containing iron did not improve depression measures relative to folic acid alone among all women, but may have benefitted women who were at risk for depression.

TRIAL REGISTRATION

The trial was registered retrospectively at ClinicalTrials.Gov as NCT01665378 on August 13, 2012.

Neither Preconceptional Weekly Multiple Micronutrient nor Iron-Folic Acid Supplements Affect Birth Size and Gestational Age Compared with a Folic Acid Supplement Alone in Rural Vietnamese Women: A Randomized Controlled Trial

BACKGROUND

Maternal nutritional status before and during early pregnancy plays a critical role in fetal growth and development. The benefits of periconception folic acid (FA) supplementation in the prevention of neural tube defects is well recognized, but the evidence for preconception micronutrient interventions for improving pregnancy outcomes is limited.

OBJECTIVE

This study aimed to evaluate whether preconception supplementation with weekly iron and folic acid (IFA) or multiple micronutrients (MMs) improves birth outcomes compared with FA alone.

METHODS

We recruited 5011 women of reproductive age in a double-blind, randomized controlled trial in Vietnam and provided weekly supplements containing either 2800 μg FA, 60 mg Fe and 2800 μg FA (IFA), or the same amount of FA and iron plus other MMs until they conceived (n = 1813). All pregnant women received daily IFA through delivery, and were followed up for birth outcomes, including birth weight, gestational age, preterm delivery and small for gestational age (SGA). Group comparisons were done with the use of ANOVA or chi-square tests for both intention-to-treat (n = 1599) and per-protocol analyses (women consumed supplements ≥26 wk before conception; n = 824). Effect modification by baseline underweight or anemia status was tested with the use of generalized linear models.

RESULTS

The mean age of the women was 26 y, 30% were underweight, and <10% were nulliparous. The groups were similar for most baseline characteristics. The mean ± SD duration of the preconception intervention was 33 ± 25 wk and compliance was high (>90%). Infants born to the 3 groups of women did not differ (P ≥ 0.05) on mean ± SD birth weight (3076.8 ± 444.5 g) or gestational age (39.2 ± 2.0 wk), or prevalence of SGA (12%), low birth weight (5%) and preterm delivery (10%). There were no significant differences in women who consumed supplements ≥26 wk before conception or by baseline underweight or anemia.

CONCLUSION

Weekly supplementation with MMs or IFA before conception did not affect birth outcomes compared with FA in rural Vietnamese women. The trial was registered at clinicaltrials.gov as NCT01665378.

Double-fortified salt is efficacious in improving indicators of iron deficiency in female Indian tea pickers

Poor iron status affects 50% of Indian women and compromises work productivity, cognitive performance, and reproduction. Among the many strategies to reduce iron deficiency is the commercial fortification of iodized table salt with iron to produce a double-fortified salt (DFS). The objective of this study was to test the efficacy of DFS in reducing iron deficiency in rural women of reproductive age from northern West Bengal, India. The participants were 212 women between 18 and 55 y of age who worked as full-time tea pickers on a large tea estate. Participants in the randomized, controlled, double-blind study were assigned to use either DFS or a control iodized salt for 7.5 to 9 mo. The DFS was fortified with 3.3-mg ferrous fumarate (1.1-mg elemental iron) per kg of iodized salt, whereas the control salt contained only iodine (47 mg/kg potassium iodate), and both salt varieties were distributed gratis to the families of participants at 0.5 kg/mo for each 2 household members. At baseline, 53% of participants were anemic (hemoglobin <120 g/L), 25% were iron deficient (serum ferritin <12 μg/L), and 23% were iron-deficient anemic. Also, 22% had a transferrin receptor concentration >8.6 mg/L and 22% had negative (<0.0 mg/kg) body iron stores. After 9 mo the participants receiving DFS showed significant improvements compared with controls in hemoglobin (+2.4 g/L), ferritin (+0.13 log10 μg/L), soluble transferrin receptor (-0.59 mg/L), and body iron (+1.43 mg/kg), with change in status analyzed by general linear models controlling for baseline values. This study demonstrated that DFS is an efficacious approach to improving iron status and should be further evaluated for effectiveness in the general population. This trial was registered at clinicaltrials.gov as NCT01032005.

Effect of supplementation with a lipid-based nutrient supplement on the micronutrient status of children aged 6-18 months living in the rural region of Intibucá, Honduras

BACKGROUND

Lipid-based nutrient supplements (LNS) have been effective in the treatment of acute malnutrition among children. We evaluated the use of LNS supplementation for improving the micronutrient status of young children.

METHODS

A 12-month randomised controlled trial was conducted among children aged 6-18 months living in Intibucá, Honduras. Communities (n = 18) were randomised into clusters matched by poverty indicators (9 intervention, n = 160 and 9 controls, n = 140). Intervention participants received LNS. All children received food vouchers and nutrition education. Primary outcomes included measures of micronutrient status: at baseline, 6 and 12 months' blood were collected for assessment of folate, iron, zinc, riboflavin, and vitamin B12 status; haemoglobin was measured every 3 months; and dietary and anthropometry collected monthly. Longitudinal analyses were based on intent to treat and LNS adherence. Generalised estimating equations were used in the estimation of generalised linear regression models specified for the data.

RESULTS

At 6-month follow-up, children in the intervention group had a lower proportion classified as deficient for B12 (43.6%) compared with the control (67.7%; P = 0.03). The intervention group had a higher mean concentration for folate at 6 months (P = 0.06), and improvements continued through 12 months for folate (P = 0.002) and vitamin A deficiency (P = 0.03). This pattern of results, with improved significance, remained in subanalysis based on LNS adherence.

CONCLUSION

These data demonstrate that LNS improved select micronutrient status in young non-malnourished Honduran children.

Rationale, design, methodology and sample characteristics for the Vietnam pre-conceptual micronutrient supplementation trial (PRECONCEPT): a randomized controlled study

BACKGROUND

Low birth weight and maternal anemia remain intractable problems in many developing countries. The adequacy of the current strategy of providing iron-folic acid (IFA) supplements only during pregnancy has been questioned given many women enter pregnancy with poor iron stores, the substantial micronutrient demand by maternal and fetal tissues, and programmatic issues related to timing and coverage of prenatal care. Weekly IFA supplementation for women of reproductive age (WRA) improves iron status and reduces the burden of anemia in the short term, but few studies have evaluated subsequent pregnancy and birth outcomes.The Preconcept trial aims to determine whether pre-pregnancy weekly IFA or multiple micronutrient (MM) supplementation will improve birth outcomes and maternal and infant iron status compared to the current practice of prenatal IFA supplementation only. This paper provides an overview of study design, methodology and sample characteristics from baseline survey data and key lessons learned.

METHODS/DESIGN

We have recruited 5011 WRA in a double-blind stratified randomized controlled trial in rural Vietnam and randomly assigned them to receive weekly supplements containing either: 1) 2800 μg folic acid 2) 60 mg iron and 2800 μg folic acid or 3) MM. Women who become pregnant receive daily IFA, and are being followed through pregnancy, delivery, and up to three months post-partum. Study outcomes include birth outcomes and maternal and infant iron status. Data are being collected on household characteristics, maternal diet and mental health, anthropometry, infant feeding practices, morbidity and compliance.

DISCUSSION

The study is timely and responds to the WHO Global Expert Consultation which identified the need to evaluate the long term benefits of weekly IFA and MM supplementation in WRA. Findings will generate new information to help guide policy and programs designed to reduce the burden of anemia in women and children and improve maternal and child health outcomes in resource poor settings.

TRIAL REGISTRATION

NCT01665378.

Astaxanthin modulates age-associated mitochondrial dysfunction in healthy dogs

Young (2.97±0.01 yr; 8.16±0.15 kg BW) and geriatric (10.71±0.01 yr; 9.46±0.18 kg BW) healthy female Beagle dogs (n=14/age group) were fed 0 or 20 mg astaxanthin daily for 16 wk to examine modulation of mitochondrial function. Fasted blood was sampled on wk 0, 8, and 16. Mitochondria membrane permeability, ATP production, cytochrome c oxidase/reductase, and number were assessed in leukocytes whereas astaxanthin uptake, glutathione, superoxide dismutase, nitric oxide, 8-hydroxy-2'-deoxyguanosine, 8-isoprostane, and protein carbonyl were measured in plasma. Aging increased (P<0.05) complex III cytochrome c oxidoreductase but decreased (P<0.05) 8-hydroxy-2'-deoxyguanosine and protein carbonyl. Mitochondrial function improved in both young and geriatric dogs by increasing (P<0.05) ATP production, mitochondria mass, and cytochrome c oxidoreductase activity, especially in geriatric dogs compared with young dogs. Astaxanthin feeding also increased (P<0.05) the reduced glutathione to oxidized glutathione ratio in young dogs and decreased (P<0.05) nitric oxide in both young and geriatric dogs. Dietary astaxanthin improved mitochondrial function in blood leukocytes, most likely by alleviating oxidative damage to cellular DNA and protein.

Fatty acid status in early life in low-income countries--overview of the situation, policy and research priorities

Fat intake may be low in low-income countries and little information is available on its composition in terms of (n-3) and (n-6) fatty acids (FA). As a result, long chain poly-unsaturated fatty acid (LCPUFA) status is a concern, especially in settings where fish intake is low and/or common sources of fat have a low alpha-linolenic acid (ALA) and high linoleic acid (LA) content. High LA levels, as found for instance in sunflower, safflower, corn, peanut and soy oils, may inhibit the conversion of ALA into its LC-PUFA derivatives. Other factors that affect LA and ALA conversion into LC-PUFA, including genetic factors, are little known and should also be investigated in different populations. Different interventions that could feasibly improve LC-PUFA status in low-income countries should be tested and their effects on functional outcomes assessed, preferably starting from pregnancy. Identifying affordable sources of ALA or LC-PUFA that could be made locally available and easily introduced in the diet early in life is also a priority.

Effect of bradykinin metabolism inhibitors on evoked hypotension in rats: rank efficacy of enzymes associated with bradykinin-mediated angioedema

BACKGROUND AND PURPOSE

Inhibition of bradykinin metabolizing enzymes (BMEs) can cause acute angioedema, as demonstrated in a recent clinical trial in patients administered the antihypertensive, omapatrilat. However, the relative contribution of specific BMEs to this effect is unclear and confounded by the lack of a predictive pre-clinical model of angioedema.

EXPERIMENTAL APPROACH

Rats were instrumented to record blood pressure and heart rate; inhibitors were infused for 35 min and bradykinin was infused during the last 5 min to elicit hypotension, as a functional marker of circulating bradykinin and relative angioedema risk.

KEY RESULTS

In the presence of omapatrilat bradykinin produced dose-dependent hypotension, an effect abolished by B(2) blockade. In the presence of lisinopril (ACE inhibitor), but not candoxatril (NEP inhibitor) or apstatin (APP inhibitor), bradykinin also elicited hypotension. Lisinopril-mediated hypotension was unchanged with concomitant blockade of NEP or NEP/DPPIV (candoxatril+A-899301). However, hypotension was enhanced upon concomitant blockade of APP and further intensified in the presence of NEP inhibition to values not different from omapatrilat alone.

CONCLUSIONS AND IMPLICATIONS

We demonstrated that bradykinin is degraded in vivo with an enzyme rank-efficacy of ACE>APP>>NEP or DPPIV. These results suggest the effects of omapatrilat are mediated by inhibition of three BMEs, ACE/APP/NEP. However, dual inhibition of ACE/NEP or ACE/NEP/DPPIV elicits no increased risk of angioedema compared to ACE inhibition alone. Thus, novel BME inhibitors must display no activity against APP to avoid angioedema risk due to high prevalence of ACE inhibitor therapy in patients with diabetes and cardiovascular disease.

Bcl-2 family proteins are essential for platelet survival

Platelets are relatively short-lived, anucleated cells that are essential for proper hemostasis. The regulation of platelet survival in the circulation remains poorly understood. The process of platelet activation and senescence in vivo is associated with processes similar to those observed during apoptosis in nucleated cells, including loss of mitochondrial membrane potential, caspase activation, phosphatidylserine (PS) externalization, and cell shrinkage. ABT-737, a potent antagonist of Bcl-2, Bcl-X(L), and Bcl-w, induces apoptosis in nucleated cells dependent on these proteins for survival. In vivo, ABT-737 induces a reduction of circulating platelets that is maintained during drug therapy, followed by recovery to normal levels within several days after treatment cessation. Whole body scintography utilizing ([111])Indium-labeled platelets in dogs shows that ABT-737-induced platelet clearance is primarily mediated by the liver. In vitro, ABT-737 treatment leads to activation of key apoptotic processes including cytochrome c release, caspase-3 activation, and PS externalization in isolated platelets. Despite these changes, ABT-737 is ineffective in promoting platelet activation as measured by granule release markers and platelet aggregation. Taken together, these data suggest that ABT-737 induces an apoptosis-like response in platelets that is distinct from platelet activation and results in enhanced clearance in vivo by the reticuloendothelial system.

Effects of post-exercise supplements on glycogen repletion in skeletal muscle

Post-exercise carbohydrate supplementation has been routinely used to enhance glycogen concentrations in skeletal muscle, particularly during multiple-day athletic events. Consumption of protein hydrolysates mixed with carbohydrate supplements during the post-exercise period may increase insulin response and cause glycogen repletion in skeletal muscle. A group of Alaskan sled dogs were selected to examine post-exercise supplementation in a paired crossover study design. The dogs were subjected to the same exercise regimen and provided one of three treatments-water, glucose polymers, or glucose polymers with protein hydrolysates-over a 2-month period. Parameters tested at various post-exercise time points included plasma insulin, glucagon and glucose concentrations, and skeletal muscle glycogen content to gain a better understanding of glucose metabolism and glycogen repletion. The results showed an enhanced insulin, glucose, and glucagon response immediately after supplementation and significantly increased glycogen concentrations in skeletal muscle within 24 hours when dogs received either of the glucose-containing supplements compared with water alone. There were no differences in the plasma parameters or skeletal muscle glycogen stores in dogs provided the glucose polymers alone or the glucose polymers plus protein hydrolysates. Thus, post-exercise carbohydrate supplementation increased muscle glycogen repletion, but inclusion of protein hydrolysates in the supplements provided no additional benefits.

Influence of dietary calcium and phosphorus content in a fixed ratio on growth and development in Great Danes

OBJECTIVE

To study the musculoskeletal development of Great Dane puppies fed various dietary concentrations of calcium (Ca) and phosphorus (P) in fixed ratio by use of dual energy x-ray absorptiometry (DEXA), determination of serum insulin-like growth factor 1 and parathyroid hormone concentrations, radiography, and blood chemistry analysis results.

ANIMALS

32 purebred Great Dane puppies from 4 litters.

PROCEDURE

At weaning, puppies were assigned randomly to 1 of 3 diets. Blood was collected for biochemical analyses and hormone assays, and radiography and DEXA were performed through 18 months of age. Changes in body weight, bone mineral content, fat tissue weight, lean mass, result of serum biochemical analyses, hormonal concentrations, and radius lengths were analyzed through 18 months of age.

RESULTS

Bone mineral content of puppies correlated positively with Ca and P content of the diets fed. Significant differences between groups in bone mineral content, lean mass, and body fat were apparent early. The disparity among groups increased until 6 months of age and then declined until body composition was no longer different at 12 months of age. Accretion rates for skeletal mineral content, fat, and lean tissue differed from each other and by diet group.

CONCLUSIONS AND CLINICAL RELEVANCE

Ca and P concentrations in the diet of young Great Dane puppies are rapidly reflected in the bone mineral content of the puppies until 5 to 6 months of age, after which hormonal regulation adjusts absorption and excretion of these minerals. Appropriate Ca and P concentrations in diets are important in young puppies < 6 months of age.

Standardized flow cytometry gating in veterinary medicine

Gating in flow cytometry is used to select subpopulations of cells for analysis. The technique is critical for subsequent analysis in order to select the population, free of debris and unrelated cells. Accurately quantifying subpopulations in clinical cases is necessary for correct diagnosis. Human lymphocytes are selected by backgating on populations of CD45+high CD14- cells. These reagents are not available widely across species. In veterinary medicine, markers to identify lymphocytes are usually limited to T-lymphocyte, CD4, CD8, and B-lymphocyte surface antigens. A standardized gating technique using a T-lymphocyte antibody is described and is applicable across species where limited phenotype markers are available.

Models of renal insufficiency: the anti-thy-1.1 model of acute proliferative glomerulonephritis

This unit describes the rat anti-Thy-1.1 model of acute proliferative glomerulonephritis for the study of chronic renal insufficiency. A procedure is detailed for the induction of glomerulonephritis in rats as well as measurement of daily urinary excretion of protein, which is a convenient, primary screening tool. The unit also provides methods for assessment of glomerular filtration rate and effective renal plasma flow in anesthetized rats with anti-Thy-1.1-induced renal insufficiency.

Association between vitamin E and enhanced athletic performance in sled dogs

PURPOSE

To determine the association between prerace plasma vitamin E concentration and performance in sled dogs competing in the 1998 Iditarod Race.

METHODS

Prerace blood samples were collected from 670 dogs. Samples were analyzed for plasma vitamin E concentration while controlling for selected hematological and biochemical variables and signalment. Starting in teams of 16, exercise consisted of running up to 1159 miles pulling a laden sled and musher via checkpoints. The records of dogs that were withdrawn from the race for health reasons, fatigue, or strategic or technical reasons, and those of dogs that finished the race were analyzed. Multiple logistic regression and Cox proportional hazards analysis were used to determine factors associated with endurance. Multiple linear regression analysis was used to determine factors associated with team speed.

RESULTS

A total of 323 dogs (48%) were withdrawn from racing at various distances from the start. Median time to finish for 39 teams was 11.5 d and the winning time was 9.2 d. Dogs with prerace plasma vitamin E concentrations > 40.7 microg.mL-1 were 1.9 times more likely to finish (P = 0.0006) and had 1.8 times less of a risk of being withdrawn for every mile ran (P = 0.03) than were dogs with plasma vitamin E concentrations between 16.3 and 40.7 microg.mL-1. Neither a team's mean prerace vitamin E concentration, nor the proportion of dogs within a team with high (> 40.7 microg.mL-1) vitamin E concentration was associated with team speed.

CONCLUSIONS

Dogs with higher plasma vitamin E concentrations have enhanced endurance compared with dogs with lower plasma vitamin E concentrations, but the plasma vitamin E status of a team is not associated with team speed.

Vitamin E and exertional rhabdomyolysis during endurance sled dog racing

Exertional rhabdomyolysis (ER) is common in sled dogs, animals with high energy expenditures that consume high fat (60% of ingested calories) diets. Associations between pre-race plasma [vitamin E] and total antioxidant status (TAS) and risk of developing ER were examined in dogs competing in the 1998 Iditarod race. Pre-race blood samples were collected from 750 dogs and a second sample was collected from 158 dogs withdrawn from the race at various times. Plasma creatine kinase activity was used to identify withdrawn dogs with ER. There was no association between pre-race plasma [vitamin E] and risk of development of ER. Dogs that developed ER started the race with higher TAS, but when withdrawn, had lower TAS than unaffected dogs and had similar pre-race [vitamin E] but higher [vitamin E] at time of withdrawal. Hence, the risk of ER in sled dogs is not affected by plasma [vitamin E] before the race.

Comparison of fermentation of selected fructooligosaccharides and other fiber substrates by canine colonic microflora

OBJECTIVE

To compare fermentation characteristics of fructooligosaccharides (FOS) and other fiber substrates that are commonly found in canine diets.

SAMPLE POPULATION

Fecal samples from 3 adult dogs.

PROCEDURE

The ability of fiber substrates to be used in microbial fermentation reactions was assessed by use of an in vitro fermentation system. Dogs were fed a commercially available food, and feces were collected for use as the microbial inoculum. Substrates used were beet pulp, cellulose, soy fiber, mannanoligosaccharides (MOS), FOS, and 4 inulin products (inulin 1, 2, 3, and 4). Each substrate was incubated anaerobically with fecal inoculum and growth media for 6, 12, and 24 hours, and production of short-chain fatty acids (SCFA) was measured.

RESULTS

Total production of SCFA was higher for fermentation of the 4 inulin products and FOS, whereas fermentation of beet pulp, MOS, and soy fiber resulted in moderate concentrations of SCFA. Fermentation of cellulose produced the lowest concentrations of total SCFA without detection of butyrate or lactate. Butyrate production was greatest for fermentation of the 4 inulin products and FOS. Total lactate production was greatest for FOS and inulin 4. As expected, production of SCFA increased for all substrates as fermentation time increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Canine fecal microflora ferment FOS-containing substrates in a similar manner, with little fermentation of cellulose-based carbohydrates. Furthermore, results of an in vitro fermentation system indicate that fiber type affects the metabolic activity of microorganisms, thus influencing the amount and nature of the end products of fermentation.

Effect of dietary supplements containing antioxidants on attenuation of muscle damage in exercising sled dogs

OBJECTIVE

To determine whether dietary antioxidants would attenuate exercise-induced increases in plasma creatine kinase (CK) activity in sled dogs.

ANIMALS

41 trained adult sled dogs.

PROCEDURE

Dogs, randomly assigned to 2 groups, received the same base diet throughout the study. After 8 weeks on that diet, 1 group (21 dogs) received a daily supplement containing vitamins E (457 U) and C (706 mg) and beta-carotene (5.1 mg), and a control group (20 dogs) received a supplement containing minimal amounts of antioxidants. After 3 weeks, both groups performed identical endurance exercise on each of 3 days. Blood samples were collected before and 3 weeks after addition of supplements and after each day of exercise. Plasma was analyzed for vitamins E and C, retinol, uric acid, triglyceride, and cholesterol concentrations, total antioxidant status (TAS), and CK activity.

RESULTS

Feeding supplements containing antioxidants caused a significant increase in vitamin E concentration but did not change retinol or vitamin C concentrations orTAS. Exercise caused significantly higher CK activity, but did not cause a significant difference in CK activity between groups. Exercise was associated with significantly lower vitamin E, retinol, and cholesterol concentrations and TAS but significantly higher vitamin C, triglyceride, and uric acid concentrations in both groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of supplements containing the doses of antioxidants used here failed to attenuate exercise-induced increases in CK activity. Muscle damage in sled dogs, as measured by plasma CK activity, may be caused by a mechanism other than oxidant stress.

Endothelin and ET(A) receptors in long-term arterial pressure homeostasis in conscious nonhuman primates

This study was designed to quantify the long-term contribution of endogenous endothelin-1 (ET-1) and ET(A) receptors to the regulation of arterial pressure under normal conditions in nonhuman primates. Therefore, mean arterial pressure (MAP) and heart rate were measured 24 h/day with the use of telemetry techniques in conscious cynomolgus monkeys under control conditions, during administration of an ET(A) selective receptor antagonist (ABT-627; 5 mg/kg, 2 times a day by mouth, 4 days), and a 6-day posttreatment period. Systemic ET(A) blockade reduced MAP (24 h) from 89 +/- 3 to 82 +/- 2 and 79 +/- 2 mmHg on days 1 and 4, respectively. Subsequently, MAP remained suppressed for 3 days posttreatment. Heart rate increased from 111 +/- 5 to 122 +/- 4 and 128 +/- 6 beats/min on days 1 and 4 of ABT-627, respectively, and remained above control for 3 days posttreatment. Plasma ET-1 concentration increased from 1.0 +/- 0.3 to 1.9 +/- 0.4 pg/ml in response to ABT-627 (day 4) but decreased to control values 4 days posttreatment. These data demonstrate a physiologically important role for endogenous ET-1 and ET(A) receptors in the long-term regulation of arterial pressure and plasma ET-1 levels in the conscious nonhuman primate.

Dietary beta-carotene absorption by blood plasma and leukocytes in domestic cats

Three experiments were conducted to study the uptake of oral beta-carotene by blood plasma and leukocytes in domestic cats. In Experiment 1, mature female Tabby cats (12 mo old) were given once orally 0, 10, 20 or 50 mg of beta-carotene and blood taken at 0, 12, 24, 30, 36, 42, 48 and 72 h after dosing. Concentrations of plasma beta-carotene increased in a dose-dependent manner. Peak concentrations were observed at 12-24 h and declined gradually thereafter. The half-life of plasma beta-carotene was 12-30 h. In Experiment 2, cats were dosed daily for six consecutive days with 0, 1, 2, 5 or 10 mg beta-carotene. Blood was sampled once daily at 12 h after each feeding. Daily dosing of cats with beta-carotene for 6 d resulted in a dose-dependent increase in circulating beta-carotene. Experiment 3 was designed to study the uptake of beta-carotene by blood leukocytes. Cats were fed 0, 5 or 10 mg of beta-carotene daily for 14 d. Blood leukocytes were obtained on d 7 and 14 to determine beta-carotene content in whole lymphocytes and in subcellular fractions. Blood lymphocytes took up large amounts of beta-carotene by d 7 of feeding. Furthermore, beta-carotene accumulated mainly in the mitochondria (40-52%), with lower amounts accumulating in the microsomes (20-35%), cytosol (15-34%), and nuclei (1.5-6%). Therefore, domestic cats readily absorb beta-carotene across the intestinal mucosa and transfer the beta-carotene into peripheral blood leukocytes and their subcellular organelles. beta-Carotene uptake kinetics show that some aspects of beta-carotene absorption and metabolism in cats are similar to those of humans.

Dietary beta-carotene stimulates cell-mediated and humoral immune response in dogs

The role of beta-carotene on immune response in domestic dogs is not known. Female Beagle dogs were fed 0, 2, 20 or 50 mg beta-carotene/d; blood was sampled at wk 0, 1, 2, 4 and 8 for analysis of the following: lymphoproliferation, leukocyte subpopulations and concentrations of interleukin-2 (IL-2), immunoglobulin (Ig)G and IgM. Delayed-type hypersensitivity (DTH) response was assessed at wk 0, 3 and 7. beta-Carotene supplementation increased plasma beta-carotene concentrations in a dose-dependent manner. Compared with unsupplemented dogs, those fed 20 or 50 mg of beta-carotene had higher CD4+ cell numbers and CD4:CD8 ratio. However, there was no treatment difference in CD8+, CD21+ and major histocompatability complex (MHC) class II+ cells. Plasma IgG, but not IgM concentration was higher in dogs fed beta-carotene throughout the study period. The DTH response to phytohemagglutinin (PHA) and vaccine was heightened in beta-carotene-supplemented dogs. beta-Carotene feeding did not influence mitogen-induced lymphocyte proliferation or IL-2 production. Immune response was impaired in dogs classified as low beta-carotene absorbers compared with similar dogs fed the same amount of beta-carotene. Therefore, dietary beta-carotene heightened cell-mediated and humoral immune responses in dogs.

Effects of dietary antioxidant supplementation on oxidative damage and resistance to oxidative damage during prolonged exercise in sled dogs

OBJECTIVES

To determine effects of dietary antioxidant supplementation on plasma concentrations of antioxidants, exercise-induced oxidative damage, and resistance to oxidative damage during exercise in Alaskan sled dogs.

ANIMALS

62 Alaskan sled dogs.

PROCEDURE

Dogs were matched for age, sex, and ability and assigned to 1 of 3 groups: sedentary and nonsupplemented (control [C]; n = 21), exercised and supplemented (S; 22), and exercised and nonsupplemented (N; 19). Dogs in group S were given 400 units of alpha-tocopherol acetate, 3 mg of beta-carotene, and 20 mg of lutein orally per day for 1 month, then dogs in groups S and N completed 3 days of exercise. Blood samples were collected before and after 1 and 3 days of exercise and after 3 days of rest. Plasma antioxidant concentrations were determined, and oxidative damage to DNA (plasma 7,8 dihydro-8-oxo-2'deoxyguanosine [8-oxodG] concentration) and membrane lipids (plasma hydroperoxide concentration) and resistance of plasma lipoproteins to oxidation were assessed.

RESULTS

Supplementation increased plasma concentrations of alpha-tocopherol, beta-carotene, and lutein. Plasma concentration of alpha-tocopherol increased and concentration of lutein decreased in group S with exercise. Concentration of 8-oxodG decreased in group S but increased in group N during and after exercise. Lag time of in vitro oxidation of lipoprotein particles increased with exercise in group S only.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary supplementation with antioxidants resulted in increased plasma concentrations of antioxidants. Moreover, supplementation decreased DNA oxidation and increased resistance of lipoprotein particles to in vitro oxidation. Antioxidant supplementation of sled dogs may attenuate exercise-induced oxidative damage.

Dietary beta-carotene is taken up by blood plasma and leukocytes in dogs

beta-Carotene uptake by blood plasma and leukocytes was studied in mature beagle dogs. In expt. 1, dogs were fed once orally with 0, 50, 100 or 200 mg of beta-carotene and their blood was sampled at 0, 1. 5, 3, 6, 10, 18 and 24 h. Plasma beta-carotene concentrations increased dose-dependently to peak at 6 h postfeeding. Concentrations decreased rapidly thereafter, showing a half-life of 3 to 4 h. In expt. 2, dogs were given daily doses for seven consecutive days with 0, 12.5, 25, 50 or 100 mg beta-carotene. Plasma beta-carotene concentrations increased dose-dependently; concentrations after the last dose were two- to fourfold higher than after the first dose. In expt. 3, dogs were fed 0, 50 or 100 mg beta-carotene daily for 30 d. beta-Carotene was elevated in lymphocytes and neutrophils in supplemented dogs. Furthermore, beta-carotene was taken up by the cytosol, mitochondria, microsomes (lymphocytes and neutrophils) and nuclei (lymphocytes only), proving that dogs can absorb beta-carotene. beta-Carotene is taken up by subcellular organelles of blood lymphocytes and neutrophils and in the plasma and leukocytes beta-carotene may have physiological importance as it relates to immunity in dogs. Uptake kinetics indicated that dogs are not an appropriate animal model for studying beta-carotene absorption and metabolism in humans.

Dietary lutein stimulates immune response in the canine

The possible immuno-modulatory action of dietary lutein in dogs is not known. Female Beagle dogs (17-18-month old; 11.4+/-0.4kg body weight) were supplemented daily with 0, 5, 10 or 20mg lutein for 12 weeks. Delayed-type hypersensitivity (DTH) response to saline, phytohemagglutinin (PHA) and a polyvalent vaccine was assessed on Weeks 0, 6 and 12. Blood was sampled on Weeks 0, 2, 4, 8 and 12 to assess (1) lymphocyte proliferative response to PHA, concanavalin A (Con A), and pokeweed mitogen (PWM), (2) changes in peripheral blood mononuclear cell (PBMC) populations, (3) interleukin-2 (IL-2) production and (4) IgG and IgM production. After the completion of 12-week study, we continued to collect the blood weekly up to 17 weeks to evaluate the changes in immunoglobulin production upon first and second antigenic challenges on Weeks 13 and 15. Plasma lutein+zeaxanthin was undetectable in unsupplemented dogs but concentrations increased (P<0.05) rapidly on Week 2 in lutein-supplemented dogs. Thereafter, concentrations generally continued to increase in dose-dependent manner, albeit at a much slower rate. Dogs fed lutein had heightened DTH response to PHA and vaccine by Week 6. Dietary lutein increased (P<0.05) lymphocyte proliferative response to all three mitogens and increased the percentages of cells expressing CD5, CD4, CD8 and major histocompatibility complex class II (MHC II) molecules. The production of IgG increased (P<0.05) in lutein-fed dogs after the second antigenic challenge. Lutein did not influence the expression of CD21 lymphocyte marker, plasma IgM or IL-2 production. Therefore, dietary lutein stimulated both cell-mediated and humoral immune responses in the domestic canine.

Oxidant stress in sled dogs subjected to repetitive endurance exercise

OBJECTIVE

To determine whether repetitive endurance exercise in sled dogs was associated with substantial lipid peroxidation, decreases in antioxidant capacity of the serum, and skeletal muscle damage.

ANIMALS

24 lightly trained sled dogs.

PROCEDURE

16 dogs completed a 58-km run on each of 3 consecutive days; the other 8 dogs (control) did not exercise during the study. Blood samples were collected before the first exercise run and after the first and third exercise runs. Plasma isoprostane and serum vitamin E concentrations, total antioxidant status of plasma, and serum creatine kinase activity were measured.

RESULTS

Plasma isoprostane concentrations in dogs in the exercise group were significantly increased after the first exercise run and further significantly increased after the third exercise run. Serum vitamin E concentration was significantly decreased after the first exercise run in dogs in the exercise group, and this change persisted after the third exercise run. There was a significant linear relationship between plasma isoprostane concentration and the logarithm of serum creatine kinase activity (adjusted ? = 0.84).

CONCLUSIONS AND CLINICAL RELEVANCE

Results demonstrate that repetitive endurance exercise in dogs is associated with lipid peroxidation and a reduction in plasma antioxidant concentrations. We interpret these results as indicating that the antioxidant mechanisms of minimally trained dogs may, in some instances, be inadequate to meet the antioxidant requirements of repetitive endurance exercise.

Modulation of humoral and cell-mediated immune responses by dietary lutein in cats

The immuno-modulatory role of dietary lutein in domestic cats is unknown. Female Tabby cats (10-month old; n=56) were supplemented daily for 12 weeks with 0, 1, 5 or 10mg lutein. Blood was collected on Weeks 0, 2, 4, 8 and 12 to assess the following: (1) mitogen-induced peripheral blood mononuclear cells (PBMCs) proliferation, (2) changes in PBMC subpopulations, (3) interleukin-2 (IL-2) production and (4) plasma immunoglobulin (Ig)G production. In addition, delayed-type hypersensitivity (DTH) response to concanavalin A (Con A) or a polyvalent vaccine was performed on Weeks 0, 6 and 12. Dietary lutein increased plasma lutein concentrations in a dose-dependent manner (p<0.001) and concentrations had not reached steady state after 12 weeks of feeding in cats given 5 or 10mg lutein. Concentrations of plasma retinol and alpha-tocopherol were not influenced by diet. The DTH response to vaccine but not to Con A increased (p<0.05) in a dose-dependent manner on Week 6. Compared to control, cats fed lutein also showed enhanced Con A- and pokeweed mitogen-stimulated PBMCs proliferation. Dietary lutein also increased the percentages of CD4+ and CD21+ lymphocytes on Week 12 but had no significant effect on pan T, CD8 and MHC class II markers. Plasma IgG was higher (p<0.05) in cats fed 10mg lutein on Weeks 8 and 12. These results support the immuno-modulatory action of lutein in domestic cats.

A standardized gating technique for the generation of flow cytometry data for normal canine and normal feline blood lymphocytes

Flow cytometry is becoming a commonly used technique to characterize a variety of cells. It provides a powerful application to rapidly determine the relative percentages of T-lymphocyte subsets and B-lymphocytes. The effectiveness of its application, however, is dependent on standardization, especially in a clinical setting. Application of flow cytometry to veterinary diagnostics has been limited by the unavailability of reagents and by the unstandardized characterization of normal values using antibodies not commercially available, but typically provided through the generosity of other researchers. This paper presents a standardized gating protocol, and average values and ranges observed for normal canine and feline blood lymphocytes using commercially available antibodies to cell surface markers for CD5, CD3, CD4, CD8, MHC II, and B lymphocytes. The averages for these markers on gated lymphocytes were as follows: Canine CD5 83.3%, Canine CD4 45.0%, Canine CD8 28.8%, Canine MHC II 98.0%, Canine B Cell 12.9%, Canine CD4/CD8 ratio 1.87, Feline T lymphocytes 77.3%, Feline CD4 44.5%, Feline CD8 25.7%, Feline B Cell 24.1%, Feline CD4/CD8 Ratio 1.75. Normal values were also established for a mixed breed group of dogs, and old versus young dogs. This information will provide researchers and clinicians with a standardized protocol for gating, which establishes a basis for comparison between techniques, and a measure of phenotypic percentages for flow cytometry in normal dogs and cats based on this standardization and commercially available antibodies.

Influence of angiotensin on the early progression of heart failure

The purpose of this study was to elucidate the role of circulating ANG II in mediating changes in systemic and renal hemodynamics, salt and water balance, and neurohormonal activation during the early progression of heart failure. This objective was achieved by subjecting six dogs to 14 days of rapid ventricular pacing (240 beats/min) while fixing plasma ANG II concentration (by infusion of captopril + ANG II) either at approximately normal (days 1-8, 13-14) or at high physiological (days 9-12) levels. Salt and water retention occurred during the initial days of pacing before sodium and fluid balance was achieved by day 8. At this time, cardiac output and mean arterial pressure were reduced to approximately 55 and 75% of control, respectively; compared with cardiac output, reductions in renal blood flow were less pronounced. Although plasma ANG II concentration was maintained at approximately normal levels, there were sustained elevations in total peripheral resistance (to approximately 135% of control), filtration fraction (to approximately 118% of control), and plasma norepinephrine concentration (to 2-3 times control). During the subsequent high rate of ANG II infusion on days 9-12, there were no additional sustained long-term changes in either systemic or renal hemodynamics other than a further rise in right atrial pressure. However, high plasma levels of ANG II induced sustained antinatriuretic, sympathoexcitatory, and dipsogenic responses. Because these same long-term changes occur in association with activation of the renin-angiotensin system during the natural evolution of this disease, these results suggest that increased plasma levels of ANG II play a critical role in the spontaneous transition from compensated to decompensated heart failure.

Effect of age, breed and dietary omega-6 (n-6): omega-3 (n-3) fatty acid ratio on immune function, eicosanoid production, and lipid peroxidation in young and aged dogs

The focus of this study was to examine the influence of age and diet on various parameters of immune function in young and old Fox Terriers and Labrador Retrievers. Eighteen young and old dogs were utilized for this study. Young and old dogs were fed a basal diet containing an (n-6):(n-3) ratio of 25:1 for sixty days (Phase I). Half of the dogs were then switched to a diet with an (n-6):(n-3) ratio of 5:1, and all were maintained on their respective diets for an additional sixty days (Phase II). Results from these studies revealed an age-associated decline in several immune parameters measured. Both these breeds demonstrated a reduction in sheep red blood cell titers, as well as in their ability to respond to different mitogens. Interestingly, this decline was greater in Fox Terriers, suggesting a decrease in cellular proliferative capacity in lymphocytes isolated from the larger breed. Neither cytokine production or DTH response was affected by age. Diet and breed interactions resulted in a significant increase in T- and B-cell mitogen responsiveness. In contrast, supplementation with n-3 fatty acids did not affect IL-1, IL-6 or TNF-alpha production. Supplementation with n-3 fatty acids resulted in increased PGE3 production from peritoneal macrophages but had no effect on PGE2 production from peripheral blood mononuclear cells or peritoneal macrophages. The n-3 fatty acid supplementation did not influence alpha-tocopherol status although older dogs had significantly lower serum alpha-tocopherol concentrations. Oxidative status of these dogs was assessed by serum levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Feeding an n-3-enriched diet did not affect 4-HNE levels but significantly decreased MDA levels in old dogs. In summary, this study indicates that feeding a diet containing an (n-6):(n-3) fatty acid ratio of 5:1 had a positive, rather than a negative, effect on the immune response of young or geriatric dogs.

Evaluation of selected high-starch flours as ingredients in canine diets

Cereal grains represent 30 to 60% of the DM of many companion animal diets. Once incorporated into a diet, the starch component of these grains can provide an excellent source of ME. However, crystallinity and form of starch are variable and can cause incomplete digestion within the gastrointestinal tract. Diets fed in this experiment included one of six high-starch flours as the main source of carbohydrate. The flours originated from barley, corn, potato, rice, sorghum, and wheat. The diets were extruded and kibbled. Starch fraction concentrations of flours consisted of nearly 100% rapidly digestible starch (RDS) and slowly digestible starch (SDS) combined. Starch fraction concentrations of diets paralleled concentrations in flours. Flours varied widely in concentrations of CP, fat, starch, and total dietary fiber. Ileal OM and CP digestibilities were lowest for the potato flour treatment (74 and 64%, respectively). Ileal and total tract starch digestibilities were different (P<.05) among treatments; however, the starch component of all diets was nearly completely digested (>99%). Total tract digestibility of DM and OM was lowest for sorghum (80 and 84%, respectively) compared to all other diets. Crude protein digestibility was highest for corn (87%). Wet fecal weights tended (P<.08) to be greatest for dogs fed the barley treatment (175 g/d). However, dry fecal weights (dried at 55 degrees C) were greatest for dogs consuming the sorghum diet (51 g/d). Fecal scores were consistently greater (i.e., looser stools) for the barley treatment. Any of these flours could be used without negative effects on digestion at either the ileum or in the total tract. Fecal consistency data for dogs consuming the barley treatment indicate that diets containing large amounts (>50%) of barley may not be advantageous for dog owners who house their animals indoors for most of the day.

Effect of protein intake during training on biochemical and performance variables in sled dogs

OBJECTIVE

To determine effects of protein intake on blood variables, plasma volume, and maximal oxygen uptake (VO2max) in sled dogs undergoing rigorous training.

ANIMALS

32 Alaskan sled dogs, between 2 and 6 years old.

PROCEDURE

Dogs were assigned to 1 of 4 groups on the basis of age, sex, and ability. Isocaloric diets containing 18% (diet A), 23% (diet B), 29% (diet C), or 35% (diet D) of energy as protein were assigned randomly to each group and fed 1 month before and during a 12-week training period. Maximal oxygen uptake was measured at 0 (before training) and 12 weeks. Body weight, protein and energy intake, plasma volume, PCV, hemoglobin concentration, and serum biochemical variables were measured at 0, 8, and 12 weeks.

RESULTS

Serum biochemical variables, PCV, and hemoglobin concentration remained within reference ranges for all dogs. Dogs fed diet A had a decrease in VO2max and a greater rate of soft tissue injury throughout training, compared with dogs fed the other diets. At 12 weeks, dogs fed diets C and D had greater serum sodium concentration and hemoglobin concentration than did dogs fed diet A. Dogs fed diet D also had more plasma volume at 12 weeks than did dogs of any other group.

CONCLUSIONS AND CLINICAL RELEVANCE

Consumption of a diet with 18% dietary protein on an energy basis (3.0 g of protein/kg of body weight) is insufficient to meet the metabolic requirements of sled dogs in training. For intense interval work, a diet with 35% dietary protein as energy (6.0 g of protein/kg) may provide a performance advantage by promoting an increase in plasma volume.

Renal denervation supersensitivity revisited

To determine whether the chronically denervated kidney is supersensitive to either physiological or pathophysiological plasma levels of norepinephrine (NE), studies were conducted in conscious dogs subjected to unilateral renal denervation and surgical division of the urinary bladder into hemibladders to allow separate 24-h urine collection from denervated and innervated kidneys. Plasma NE concentration was increased by chronic infusion of NE (4-5 days) at rates of 25, 100, and 200 ng . kg-1 . min-1. Twenty-four-hour control values for mean arterial pressure (MAP), plasma NE concentration, and ratios for urinary sodium and potassium excretion from denervated and innervated kidneys (Den/Inn) were 94 +/- 4 mmHg, 145 +/- 24 pg/ml, 1.05 +/- 0.05, and 0.97 +/- 0.07, respectively. With infusions of NE producing plasma levels of NE of up to approximately 3,000 pg/ml or plasma concentrations of NE at least threefold greater than present under most pathophysiological conditions and during acute activation of the sympathetic nervous system, there were no significant long-term changes in MAP or relative excretion rates of sodium and potassium from denervated and innervated kidneys. In marked contrast, pharmacological plasma levels of NE ( approximately 7,000 pg/ml) produced chronic increases in MAP (to 116 +/- 2% of control) and sustained reductions in Den/Inn for urinary sodium and potassium excretion to 57 +/- 4 and 68 +/- 5% of control, respectively, indicating a lower excretion rate of these electrolytes from denervated vs. innervated kidneys. We conclude that the chronically denervated kidney does not exhibit an exaggerated antinatriuretic response to either physiological or pathophysiological levels of circulating NE. It is therefore unlikely that renal denervation supersensitivity is a confounding issue in studies employing chronic renal denervation to elucidate the role of the renal nerves in the regulation of sodium excretion.

Evaluation of the effects of omega-3 fatty acid-containing diets on the inflammatory stage of wound healing in dogs

OBJECTIVES

To ascertain the effects of dietary omega-3 (n-3) fatty acids on biochemical and histopathologic components of the inflammatory stage of wound healing.

ANIMALS

30 purpose-bred Beagles.

PROCEDURE

Dogs were allotted to 5 groups of 6. Each group was fed a unique dietary fatty acid ratio of omega-6 to n-3--diet A, 5.3:1; diet B, 10.4:1; diet C, 24.1:1; diet D, 51.6:1; and diet E, 95.8:1. Dogs were fed once daily for 12 weeks, then biopsy specimens were taken from 4-day-old wounds of each dog and analyzed by gas chromatography-mass spectrometry for: prostaglandin E2 (PGE2) metabolites, and ratios of omega-6 to n-3 fatty acids, arachidonic acid (AA) to eicosapentaenoic acid (EPA), adrenic acid to docosahexaenoic acid, and PGE2 to prostaglandin E3 (PGE3) metabolites.

RESULTS

Qualitative analysis was carried out on AA, EPA, adrenic acid, docosahexaenoic acid, and the major metabolite from the PGE2 and PGE3 pathway. These molecules were further quantified with respect to diet to determine significant differences. By analysis of the AA-to-EPA ratio, diet A was different from diets D and E and diets B and C were different from diet E (P < 0.05). By analysis of the PGE2-to-PGE3 metabolite ratio, diet A was different from diet E (P < 0.05). Though biochemical analysis indicated dietary dependence, histopathologic data indicated no significant difference with respect to diet groups.

CONCLUSION

The biochemical component of the inflammatory stage of wound healing can be manipulated by diet.

CLINICAL RELEVANCE

Omega-3 fatty acid-enriched diets can be used to control inflammation associated with dermatologic conditions.

Reduced cardiac contractile responsiveness to isoproterenol in obese rabbits

Although obesity is characterized by increased sympathetic nervous system activity, there is often a paradoxical reduction in cardiovascular end-organ response to sympathetic stimulation. Mechanisms involved in reduced sympathetic responsiveness in obesity have not been well characterized. Therefore, we determined cardiac contractile responsiveness to beta-stimulation in the obese rabbit model using both isolated heart (IH) and isolated papillary muscle (IPM) preparations. Female New Zealand White rabbits were fed control (IH: n=9; IPM: n=6) or 10% fat diets (IH: n=9; IPM: n=7) for 12 weeks. Contractile responsiveness in the IH was determined using a modified Langendorff preparation to evaluate the dose-response relationship between isoproterenol and 1) peak developed pressure/g of left ventricular wet weight and 2) maximal rate of pressure development (+dP/dt/P). Contractile responsiveness in the IPM was determined using right ventricular papillary muscles to evaluate the dose-response relationship between isoproterenol and (1) peak developed tension (T)/mm2 cross-sectional area (CSA) and (2) maximal rate of tension development (dT/dt/CSA). In the IH, baseline and maximum developed pressure/g were reduced in obese rabbits by 37% and 31%, respectively (P< or =.05). In the IPM, baseline and maximum T/CSA responses were reduced in obese rabbits by 59% and 33%, respectively (P< or =.05). Potency of isoproterenol as reflected by the EC50 did not differ between lean and obese animals in either preparation. These results demonstrate that left ventricular contractility in obesity is reduced at baseline and in response to stimulation with isoproterenol and suggest that decreased responsiveness to beta-stimulation may be a factor in the obesity-related systolic dysfunction.