Effects of obesity and diabesity on heart rhythm in the Zucker rat

Obesity and type 2 diabetes mellitus are risk factors for hypertension, coronary heart disease, cardiac arrhythmias including atrial fibrillation, heart failure and sudden cardiac death. The effects of obesity and diabesity on heart rhythm were investigated in the Zucker diabetic fatty (ZDF) and Zucker fatty (ZF) compared to the Zucker lean (ZL) control rat. In vivo biotelemetry techniques were used to assess the electrocardiogram and other cardiac and metabolic parameters. ZDF rats were characterized by age-dependent elevations in fasting and non-fasting blood glucose, glucose intolerance and weight gain and ZF rats were characterized by smaller elevations in fasting and non-fasting blood glucose and greater weight gain compared to ZL rats. Heart rate (HR) was progressively reduced in ZDF, ZF and ZL rats. At 195 days (6.5 months) of age there were significant differences in HR between ZDF (265 ± 8 bpm, n = 10), ZF (336 ± 9 bpm, n = 10) and ZL (336 ± 10 bpm, n = 10) rats and significant differences in HRV between ZDF (22 ± 1 bpm, n = 10), ZF (27 ± 1 bpm, n = 10) and ZL (31 ± 1 bpm, n = 10) rats. Power spectral analysis revealed no significant (P > 0.05) differences in HRV at low frequencies, reduced HRV at high frequencies and increased sympathovagal balance in ZDF compared to ZF and ZL rats. HR was reduced by ageing and additionally reduced by diabesity in the absence of changes in physical activity and body temperature. Reductions in HRV associated with altered sympathovagal drive might partly underlie disturbed HR in the ZDF rat. Possible explanations for reduced HR and future mechanistic studies are discussed.

Ameliorative effects of supplemental folinic acid on Lamotrigine-induced fetal malformations in the mouse

Data from our previous work indicate that Lamotrigine (LTG) is teratogenic in the mouse. In the present study, we attempted to determine the possible protective effects of exogenous folate on LTG-induced fetal anomalies in TO mouse. Experiment I entailed administering 4 mg/kg of folinic acid (FA) and (25 mg/kg) of LTG intraperitoneally three times on gestation day (GD) 8 to a group of mice; other groups were a group that received similar volumes of saline, a group that received LTG and Saline, a group that received FA and saline. Experiment 2 involved administering groups of mice with daily 3 doses FA (or proportionate volume of saline) on GD 5 through 10 and either 3 doses of saline on GD8, or 3 doses of LTG on GD8. Maternal plasma concentrations of FA, vitamin B12 and homocysteine were determined an hour after the last injection from one-half of all animals. The other half were allowed to go to term (GD18) when they were euthanized and their fetuses were examined for visceral and skeletal malformations. A high incidence of resorption, abortion, embryolethality, congenital malformations, and intrauterine growth restriction (IUGR), was observed in the LTG-treated group. Folic acid and B12 levels were decreased and homocysteine concentration increased significantly in LTG groups. Mice receiving LTG with FA had normal levels of folate, Vitamin B12 and homocysteine levels, and the fetuses had fewer birth defects similar to the controls which were given saline only. Supplemental FA ameliorated to a great extent the LTG-induced embryonic resorption and malformations and restored the FA status.

Anticonvulsant and reproductive toxicological studies of the imidazole-based histamine H3R antagonist in mice

The imidazole-based H3R antagonist 2-18 with high in vitro H3R antagonist affinity, excellent in vitro selectivity profile, and high in vivo H3R antagonist potency was tested for its anticonvulsant effect in maximal electroshock (MES)-induced convulsions in mice having valproic acid (VPA) as a reference antiepileptic drug (AED). Additionally, H3R antagonist 2-18 was evaluated for its reproductive toxicity in the same animal species. The results show that acute systemic administration (intraperitoneal; i.p.) of H3R antagonist 2-18 (7.5, 15, 30, and 60 mg/kg, i.p.) significantly and dose dependently protected male as well as female mice against MES-induced convulsion. The protective action observed for H3R antagonist 2-18 in both mice sexes was comparable to that of VPA and was reversed when mice were pretreated with the selective H3R agonist (R)-alpha-methylhistamine (RAMH, 10 mg/kg, i.p.). Moreover, the results show that acute systemic administration of single (7.5, 15, 30, or 60 mg/kg, i.p.) or multiple doses (15×3 mg/kg, i.p.) of H3R antagonist 2-18 on gestation day (GD) 8 or 13 did not affect the maternal body weight of mice when compared with the control group. Furthermore, no significant differences were observed in the average number of implantations and resorptions between the control and H3R antagonist 2-18-treated group at the early stages of gestation and the organogenesis period. However, oral treatment with H3R antagonist 2-18 (15 mg/kg) on GD 8 induced a reduced number of live embryos when compared with the i.p.-treated mice. In addition, no significant changes in the fetal body and placental weights were observed after injection of H3R antagonist 2-18 with all selected doses. However, three dose groups of i.p. and oral 15 mg/kg on GD 13 significantly affected the placental weight when compared with control group. Notably, the treatment of pregnant female with the H3R antagonist 2-18 did not produce significant malformation in the fetus in both groups. In conclusion, the novel H3R antagonist 2-18 proves to be a very safe compound and displays a low incidence of malformations, demonstrating that H3R antagonist 2-18 may have a potential future therapeutic value in epilepsy.

Terbufos-sulfone exacerbates cardiac lesions in diabetic rats: a sub-acute toxicity study

Organophosphorus compounds (OPCs) have a wide range of applications, from agriculture to warfare. Exposure to these brings forward a varied kind of health issues globally. Terbufos is one of the leading OPCs used worldwide. The present study investigates the cardiac effect of no observable dose of a metabolite of terbufos, terbufos-sulfone (TS), under non-diabetic and streptozotocin-induced diabetic condition. One hundred nanomoles per rat (1/20 of LD50) was administered intraperitoneally to adult male Wister rats daily for fifteen days. The left ventricle was collected for ultrastructural changes by transmission electron microscopy. The blood samples were collected for biochemical tests including RBC acetylcholinesterase, creatinine kinase (CK), lactate dehydrogenase (LDH), cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), triglycerides, ALT, AST, and GGT. The study revealed about 10 % inhibition of RBC-AChE in two weeks of TS treatment in non-diabetic rats whereas RBC-AChE activity was significantly decreased in diabetic TS treated rats. CK, LDH, and triglycerides were significantly higher in diabetic TS treated rats. Electron microscopy of the heart showed derangement and lesions of the mitochondria of cardiomyocytes in the TS treated groups. The present study concludes that a non-lethal dose of TS causes cardiac lesions which exacerbate under diabetic condition. Biochemical tests confirmed the ultrastructural changes. It is concluded that a non-lethal dose of TS may be a risk factor for a cardiovascular disease, which may be fatal under diabetic condition.

Anticonvulsant and procognitive properties of the non-imidazole histamine H3 receptor antagonist DL77 in male adult rats

It has become clear that histamine H3 receptors (H3Rs) are implicated in modulating epilepsy and memory in laboratory animals. The new non-imidazole H3R antagonist DL77 has excellent selectivity profile and shows high in-vivo potency as well as in-vitro antagonist affinity with ED50 values of 2.1 ± 0.2 mg/kg and 8.4 ± 1.3 [nM], respectively. In the present study, the anticonvulsant effects of DL77 on maximal electroshock (MES)-, pentylenetetrazole (PTZ)-, and strychnine (STR)-induced seizure models were investigated. Moreover, the procognitive properties of DL77 were tested on acquisition, consolidation and retrieval processes in a one-trial inhibitory avoidance task in male Wistar rats. The results indicate that DL77 (5, 10, and 15 mg/kg, i.p.) significantly and dose-dependently reduced MES-induced seizure duration, whereas no protection was observed in PTZ- or STR-induced seizures. Importantly, the protective action observed for DL77 in MES-induced seizure was comparable to that of the reference antiepileptic drug (AED) phenytoin (PHT), and was also reversed when rats were pretreated with the CNS penetrant pyrilamine (PYR) (10 mg/kg, i.p.), or with the selective H3R agonist R-(α)-methyl-histamine (RAMH) (10 mg/kg, i.p.). Furthermore, the procognitive studies indicate that acute pre-training systemic administration of DL77 (2.5 mg/kg, i.p.) facilitated acquisition, whereas pre-testing acute administration of DL77 (5 and 10 mg/kg, i.p.) improved retrieval. Interestingly, the procognitive effect of DL77 on retrieval was completely abrogated when rats were pretreated with the centrally-acting H2R antagonist zolantidine (ZOL) but not the centrally acting H1R antagonist PYR, indicating that histaminergic pathways through activation of H2Rs appear to be participating in neuronal circuits involved in retrieval processes. Taken together, our results show that DL77 demonstrates anticonvulsant properties in the MES-induced seizure model and improves cognitive performance through actions on different memory stages. Therefore, H3Rs may have implications for the treatment of degenerative disorders associated with impaired memory function and may represent a novel therapeutic pharmacological target to tackle cognitive problems associated with the chronic use of antiepileptic drugs. This article is part of the Special Issue entitled 'Histamine Receptors'.

Thromboembolic injury and systemic toxicity induced by nicotine in mice

Nicotine is involved in the pathogenesis of hematological and cardiopulmonary diseases. The understanding of the pathophysiological mechanisms underlying these undesirable effects is however unclear. Cigarette smoking, nicotine gums and patches are common sources for nicotine ingestion. We have investigated the nicotine's effect on cerebral microvessel thrombosis and systemic toxicity. Mice received either nicotine (1 mg/kg, i.p.) or saline (control), once a day for 21 days. Briefly, after bolus intravenous fluorescein injection, a photo insult of cerebral microvessel was done. The platelet aggregation in microvessels was video recorded and analyzed. In conjunction, the plasma levels of superoxide dismutase (SOD), lactate dehydrogenase (LDH), liver enzymes, creatinine and blood urea nitrogen (BUN); and histopathological studies were carried out. Our results revealed a significant prothrombotic effect following nicotine exposure. Significant decrease in SOD indicates the occurrence of oxidative stress involved in the tissue damages and increase in the LDH emphasize the systemic toxicity. Substantial rise in the liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were observed. Lungs histology showed intra-vascular hemorrhagic infarction with necrosis, macrophage and neutrophils infiltration. Liver histology showed intravascular thrombosis and portal inflammation. We conclude that the sub-acute nicotine exposure causes an increase in thrombosis in cerebral microvessels and systemic, hepatic and pulmonary toxicity.

Acetylcholinesterase inhibitors as pretreatment before acute exposure to organophosphates: assessment using methyl-paraoxon

Prophylactic administration of reversible acetylcholinesterase (AChE) inhibitors can protect against the lethal effects of organophosphorus compounds (OPCs). The usefulness of pyridostigmine, the only compound approved by the Food and Drug Administration (FDA) for such pretreatment, has been questioned. In search for more efficacious alternatives, we have examined in vivo the efficacy of a group of ten compounds with known anti-AChE activity (pyridostigmine, metoclopramide, tiapride, ranitidine, physostigmine, tacrine, amiloride, methylene blue, 7- methoxytacrine and K-27) to reduce mortality induced by the OPC methyl-paraoxon. AChE inhibitors were given intraperitoneally in equitoxic dosage (25% of LD₀₁) 30 min before OPC exposure. Protection was quantified in rats by determining the relative risk of death (RR) by Cox analysis, with RR=1 for animals given only methyl-paraoxon, but no pretreatment. Only physostigmine (RR=0.39), K-27 (RR=0.40) and tacrine (RR=0.48) significantly (p≤ 0.05) reduced methylparaoxon- induced mortality, when given prophylactically. Pretreatment with pyridostigmine, ranitidine, tiapride, amiloride, metoclopramide and methylene blue did not significantly protect against the lethal effects of methyl-paraoxon. 7-methoxytacrine (7-MEOTA) significantly (p≤ 0.05) increased the relative risk of methyl-paraoxon-induced death (RR=1.31). These results indicate that pretreatment with pyridostigmine cannot be considered a broad-spectrum approach against OPC exposure. K-27 may be a suitable alternative if passage into the brain is contraindicated.

Anticonvulsant properties of histamine H3 receptor ligands belonging to N-substituted carbamates of imidazopropanol

Ligands targeting central histamine H3 receptors (H3Rs) for epilepsy might be a promising therapeutic approach. Therefore, the previously described and structurally strongly related imidazole-based derivatives belonging to carbamate class with high H3R in vitro affinity, in-vivo antagonist potency, and H3R selectivity profile were investigated on their anticonvulsant activity in maximal electroshock (MES)-induced and pentylenetetrazole (PTZ)-kindled seizure models in Wistar rats. The effects of systemic injection of H3R ligands 1-13 on MES-induced and PTZ-kindled seizures were screened and evaluated against the reference antiepileptic drug (AED) Phenytoin (PHT) and the standard histamine H3R inverse agonist/antagonist Thioperamide (THP) to determine their potential as new antiepileptic drugs. Following administration of the H3R ligands 1-13 (5, 10 and 15 mg/kg, ip) there was a significant dose dependent reduction in MES-induced seizure duration. The protective action observed for the pentenyl carbamate derivative 4, the most protective H3R ligand among 1-13, was significantly higher (P <0.05) than that of standard H3R antagonist THP, and was reversed when rats were pretreated with the selective H3R agonist R-(α)-methyl-histamine (RAMH) (10mg/kg), or with the CNS penetrant H1R antagonist Pyrilamine (PYR) (10mg/kg). In addition, subeffective dose of H3R ligand 4 (5mg/kg, ip) significantly potentiated the protective action in rats pretreated with PHT (5mg/kg, ip), a dose without appreciable protective effect when given alone. In contrast, pretreatment with H3R ligand 4 (10mg/kg ip) failed to modify PTZ-kindled convulsion, whereas the reference drug PHT was found to fully protect PTZ-induced seizure. These results indicate that some of the investigated imidazole-based H3R ligands 1-13 may be of future therapeutic value in epilepsy.

Vitamin E ameliorates the decremental effect of paraquat on cardiomyocyte contractility in rats

Background

Exposure to pesticides and industrial toxins are implicated in cardiovascular disease. Paraquat (PAR) is a toxic chemical widely used as an herbicide in developing countries and described as a major suicide agent. The hypothesis tested here is that PAR induced myocardial dysfunction may be attributed to altered mechanisms of Ca²⁺ transport which are in turn possibly linked to oxidative stress. The mechanisms of PAR induced myocardial dysfunction and the impact of antioxidant protection was investigated in rat ventricular myocytes.

Methodology

Forty adult male Wistar rats were divided into 4 groups receiving the following daily intraperitoneal injections for 3 weeks: Group 1 PAR (10 mg/kg), Control Group 2 saline, Group 3 vitamin E (100 mg/kg) and Group 4 PAR (10 mg/kg) and vitamin E (100 mg/kg). Ventricular action potentials were measured in isolated perfused heart, shortening and intracellular Ca²⁺ in electrically stimulated ventricular myocytes by video edge detection and fluorescence photometry techniques, and superoxide dismutase (SOD) and catalase (CAT) levels in heart tissue.

Principal Findings

Spontaneous heart rate, resting cell length, time to peak (TPK) and time to half (THALF) relaxation of myocyte shortening were unaltered. Amplitude of shortening was significantly reduced in PAR treated rats (4.99±0.26%) and was normalized by vitamin E (7.46±0.44%) compared to controls (7.87±0.52%). PAR significantly increased myocytes resting intracellular Ca²⁺ whilst TPK and THALF decay and amplitude of the Ca²⁺ transient were unaltered. The fura-2–cell length trajectory during the relaxation of the twitch contraction was significantly altered in myocytes from PAR treated rats compared to controls suggesting altered myofilament sensitivity to Ca²⁺ as it was normalized by vitamin E treatment. A significant increase in SOD and CAT activities was observed in both PAR and vitamin E plus PAR groups.

Conclusions

PAR exposure compromised rats heart function and ameliorated by vitamin E treatment.

Sub-chronic exposure to paraoxon neither induces nor exacerbates diabetes mellitus in Wistar rat

There is an increasing belief that organophosphorus compounds (OPCs) impair glucose homeostasis and cause hyperglycemia and diabetes mellitus. The present study was undertaken to investigate the putative diabetogenic effect of sub-lethal and sub-chronic exposure to paraoxon (POX), an extremely hazardous OPC used in pesticides. The effect of paraoxon on streptozotocin-induced diabetic rats was also examined. Each rat was injected with 100 nmol of POX 5 days per week for 6 weeks. Blood glucose levels and red blood cell acetylcholinesterase activity were measured weekly. Biochemical analysis and morphological studies were performed at the end of the experiment. The results revealed that POX neither induces nor exacerbates diabetes mellitus in experimental rats. Liver and kidney/body weight ratios revealed statistically insignificant differences when compared with controls. Biochemical analysis of urine samples showed a small but not significant increase in protein level in all groups. Urine bilirubin was significantly higher in the diabetes + POX group when compared with the control group. The number of blood cells in urine was significantly higher in the POX-treated group compared with the control group. Hyperglycemia was noted in the diabetes and diabetes + POX groups, but neither in the saline control nor in POX-treated normal rats. Electron microscopy of POX-treated pancreas did not show any morphological changes in beta cells. These results suggest that POX does not cause diabetes mellitus at sub-lethal sub-chronic exposure.

Usefulness of administration of non-organophosphate cholinesterase inhibitors before acute exposure to organophosphates: assessment using paraoxon

Reversible acetylcholinesterase (AChE) inhibitors can protect against the lethal effects of irreversible organophosphorus AChE inhibitors (OPCs), when administered before OPC exposure. We have assessed in vivo the mortality-reducing efficacy of a group of known AChE inhibitors, when given in equitoxic dosage before exposure to the OPC paraoxon. Protection was quantified in rats by determining the relative risk (RR) of death. Best in vivo protection from paraoxon-induced mortality was observed after prophylactic administration of physostigmine (RR = 0.30) or the oxime K-27 (RR = 0.34); both treatments were significantly superior to the pre-treatment with all other tested compounds, including the established substance pyridostigmine. Tacrine (RR = 0.67), ranitidine (RR = 0.72), pyridostigmine (RR = 0.76), tiapride (RR = 0.80) and 7-MEOTA (RR = 0.86) also significantly reduced the relative risk of paraoxon-induced death, but to a lesser degree. Methylene blue, amiloride and metoclopramide had an unfavorable effect (RR ≥ 1), significantly increasing mortality. When CNS penetration by prophylactic is undesirable K-27 is a promising alternative to pyridostigmine.

Acute cadmium exposure causes systemic and thromboembolic events in mice

Cadmium (Cd), an environmental and industrial pollutant, poses a potential threat and affects many systems in human and animals. Although several reports on Cd toxicity were presented, the acute effect of Cd on systemic and thrombotic events was not reported so far. Cd (2.284 mg/kg) or saline (control) was injected intraperitoneally (ip), and the systemic parameters were assessed in mice. Compared to control group, acute intraperitoneal injection of Cd, in mice showed significant quickening of platelet aggregation (P<0.001) leading to pial cerebral thrombosis. Likewise, Cd exposure caused a significant increase in white blood cell numbers (P<0.05) indicating the occurrence of systemic inflammation. Also, alanine aminotransferase (ALT) (P<0.05) and creatinine (P<0.01) levels were both significantly increased. Interestingly, the superoxide dismutase activity was significantly decreased in Cd treated group compared to control group (P<0.001), suggesting the occurrence of oxidative stress. We conclude that the Cd exposure in mice causes acute thromboembolic events, oxidative stress and alter liver and kidney functions.

Heart rhythm disturbances in the neonatal alloxan-induced diabetic rat

Diabetic patients show a higher incidence of cardiac arrhythmias, including ventricular fibrillation and sudden death. Their electrocardiograms may show several alterations from normal patterns, many of them related to the QT. Various diastolic and systolic abnormalities are frequently reported in diabetic patients, and the severity of the abnormalities depend on the patients' age and the duration of diabetes. The aim of this experimental study has been to clarify the progressive effects on heart rhythm in neonatal alloxan (ALX) (induced at 5 days of age) diabetic male rats. Cardiac biopotential data were acquired in vivo with a biotelemetry system. After an overnight fast blood glucose in diabetic rats, compared to age-matched controls, was elevated before and at 60, 120 and 180min after a glucose challenge at 2 and 8 months of age. Heart rate and heart rate variability were modestly reduced and QT interval modestly prolonged in diabetic rats, compared to controls, at 2, 6 and 8 months of age. There was also an age-dependent decline in heart rate and prolongation in QT interval. At 8 months heart rate was 296±8bpm in diabetic compared to 311±10bpm in controls and heart rate variability was 27±3bpm in diabetic rats compared to 32±4bpm in controls. Physical activity was significantly reduced in diabetic rats, compared to controls, at 6 and 8 months of age. Body temperature was modestly reduced in diabetic rats, compared to controls, at 2, 6 and 8 months. In conclusion, the neonatal ALX-induced diabetes mellitus was associated with disturbances in heart rate, heart rate variability, QT interval which in turn may be associated with changes in physical activity and body temperature.

Pretreatment for acute exposure to diisopropylfluorophosphate: in vivo efficacy of various acetylcholinesterase inhibitors

Prophylactic administration of reversible acetylcholinesterase (AChE) inhibitors before exposure to organophosphorus compounds (OPCs) can reduce OPC-induced mortality. Pyridostigmine is the only FDA-approved substance for such use. The AChE-inhibitory activity of known AChE inhibitors was quantified in vitro and their in vivo mortality-reducing efficacy was compared, when given prophylactically before the exposure to the OPC diisopropylfluorophosphate (DFP). The IC50 was measured in vitro for the known AChE inhibitors pyridostigmine, physostigmine, ranitidine, tiapride, tacrine, 7-methoxytacrine, amiloride, metoclopramide, methylene blue and the experimental oxime K-27. Their in vivo efficacy, when given as pretreatment, to protect rats from DFP-induced mortality was quantified by determining the relative risk of death (RR) by Cox analysis, with RR = 1 for animals given only DFP, but no pretreatment. Physostigmine was the strongest in vitro AChE-inhibitor (IC50 = 0.012 µ m), followed by 7-methoxytacrine, tacrine, pyridostigmine and methylene blue. Ranitidine (IC50 = 2.5 µ m), metoclopramide and amiloride were in the mid-range. Tiapride (IC50 = 256 µ m) and K-27 (IC50 = 414 µ m) only weakly inhibited RBC AChE activity. Best in vivo protection from DFP-induced mortality was achieved when physostigmine (RR = 0.02) or tacrine (RR = 0.05) was given before DFP exposure, which was significantly superior to the pretreatment with all other tested compounds, except K-27 (RR = 0.18). The mortality-reducing effect of pyridostigmine, ranitidine and 7-methoxytacrine was inferior, but still significant. Tiapride, methylene blue, metoclopramide and amiloride did not significantly improve DFP-induced mortality. K-27 may be a more efficacious alternative to pyridostigmine, when passage into the brain precludes administration of physostigmine or tacrine.

Heart rate, body temperature and physical activity are variously affected during insulin treatment in alloxan-induced type 1 diabetic rat

Diabetes mellitus is associated with a variety of cardiovascular complications including impaired cardiac muscle function. The effects of insulin treatment on heart rate, body temperature and physical activity in the alloxan (ALX)-induced diabetic rat were investigated using in vivo biotelemetry techniques. The electrocardiogram, physical activity and body temperature were recorded in vivo with a biotelemetry system for 10 days before ALX treatment, for 20 days following administration of ALX (120 mg/kg) and thereafter, for 15 days whilst rats received daily insulin. Heart rate declined rapidly after administration of ALX. Pre-ALX heart rate was 321+/-9 beats per minute, falling to 285+/-12 beats per minute 15-20 days after ALX and recovering to 331+/-10 beats per minute 5-10 days after commencement of insulin. Heart rate variability declined and PQ, QRS and QT intervals were prolonged after administration of ALX. Physical activity and body temperature declined after administration of ALX. Pre-ALX body temperature was 37.6+/-0.1 °C, falling to 37.3+/-0.1 °C 15-20 days after ALX and recovering to 37.8+/-0.1 °C 5-10 days after commencement insulin. ALX-induced diabetes is associated with disturbances in heart rhythm, physical activity and body temperature that are variously affected during insulin treatment.

Toxicokinetics of aflatoxin in pregnant mice

Our objective was to study the toxicokinetics of aflatoxin (AF) in pregnant mice. Aflatoxin B1 (AFB1) was administered intraperitoneally (IP) to groups of pregnant mice in single doses of 20 mg/kg on gestation day (GD) 13 and orally at the same gestational age. Controls received (IP and oral) a proportionate volume of solvent only. Maternal blood was collected at 15, 30, 45, 60, 90, 120, and 150 minutes posttreatment. Their AFB1 contents were determined. Aflatoxin B1 concentrations following maternal exposure to AFB1 were highly correlated with time after exposure. The serum concentrations were predictable and the highest serum levels were seen immediately at 15 minutes in mice given AFs IP and at 30 minutes in those given it orally. The absorption was 5.0 microg/min and elimination was 3.0 microg/min. The toxicokinetics of AFB1 have been delineated. Aflatoxins are easily and rapidly absorbed both from the gastrointestinal tract (GI) tract and through the peritoneum.

Vigabatrin (VGB) administered during late gestation lowers maternal folate concentration and causes pregnancy loss, fetal growth restriction and skeletal hypoplasia in the mouse

Vigabatrin (VGB) has several therapeutic advantages over older antiepileptic drugs (AED), but there is a lack of information about its potential reproductive toxicologic effects. Our aim was to evaluate the consequences of VGB administered during late gestation on fetal growth and development in the mouse. Based on the results of our previous study, we administered groups of mice a single dose of 450 mg/kg VGB on one of gestation days (GD) 15, 16 or 17. Fetuses were collected on GD 18. VGB groups had a significant incidence of fetal death, abortion, intrauterine growth restriction (IUGR), and hypoplasia of the axial skeleton, metacarpals, metatarsal and phalanges. Abortion was characterized by visible hemorrhagic expulsion of the embryos with their membranes. Maternal plasma folate (FA) and vitamin B12 concentrations were found to be markedly reduced within 12h of VGB treatment. Mice were supplemented with FA from GD 12 through GD 17 with or without a single dose of VGB on GD 15. This group had no abortions. Their fetuses had better body weight and lower frequency of IUGR than those of the non-supplemented VGB group. These data suggest that reductions in maternal FA and vitamin B12 concentrations play an important role in fetal loss, IUGR and skeletal hypoplasia induced by VGB during late gestation in the mouse. In view of the finding that a significant maternal toxicity is associated with this dose regimen, additional groups of mice were treated with 350 mg/kg VGB during embryogenesis and late gestation. This treatment was found to be maternally nontoxic. However, this low dose also resulted in significant fetal loss and IUGR when treatment occurred during late gestation. These data support the hypothesis that late gestation is particularly susceptible to VGB-induced fetal loss and IUGR in the mouse.

Long-term effects of type 2 diabetes mellitus on heart rhythm in the Goto-Kakizaki rat

In vivo biotelemetry studies have demonstrated a variety of heart rhythm disturbances in type 1 diabetes mellitus. In the streptozotocin (STZ)-induced diabetic rat, these disturbances have included reductions in heart rate (HR) and heart rate variability (HRV) and an electrocardiogram that displays prolonged QRS duration and Q-T interval. The aim of this study was to investigate the chronic effects of type 2 diabetes mellitus on heart rhythm in the Goto-Kakizaki (GK) rat. Transmitter devices were surgically implanted in the peritoneal cavity of young male GK and age-matched Wistar control rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. Electrocardiogram, physical activity and body temperature data were recorded in rats from age 2 to 15 months. Data were acquired for 2 weeks each month. Non-fasting blood glucose, glucose tolerance and body weight were measured periodically. In GK rats, growth rate and maximal attained body weight were significantly reduced and non-fasting blood glucose was progressively increased compared with age-matched Wistar control animals. Heart rate was significantly lower in GK compared with control rats at 2, 7 and 15 months of age. At 2 months of age, HR was 316 +/- 6 beats min(-1) in GK rats compared with 370 +/- 7 beats min(-1) in Wistar control animals. There was a progressive age-dependent decline in HRV in Wistar control rats; however, HRV in GK rats did not alter significantly with age. Heart rate variability was significantly reduced in GK compared with Wistar control rats at 2 and 7 months. At 2 months of age, HRV was 28 +/- 2 beats min(-1) in GK rats compared with 38 +/- 3 beats min(-1) in Wistar control rats. Reduced HR in GK rats may be an inherited characteristic. The absence of age-dependent reductions in HRV in GK rats may be a consequence of an underlying impairment of autonomic control which manifests at early age.

Five oximes (K-27, K-48, obidoxime, HI-6 and trimedoxime) in comparison with pralidoxime: survival in rats exposed to methyl-paraoxon

There is a clear need for broad-spectrum cholinesterase reactivators (active against a multitude of organophosphorus ester enzyme inhibitors) with a higher efficacy than pralidoxime. The purpose of the study was to quantify in vivo the extent of oxime-conferred protection, using methyl-paraoxon [dimethyl p-nitrophenyl phosphate; (methyl-POX)] as a cholinesterase inhibitor. There were seven groups of six rats in each cycle of the experiment. Group 1 (G1) received 2 micromol methyl-POX ( approximately LD(50)), the other groups (G2-7) received 2 micromol methyl-POX + one of the six reactivators. The animals were monitored for 48 h and the time of mortality was recorded. The procedure was repeated six times. All substances were applied i.p. The experiments were repeated using 3 and 5 micromol methyl-POX. Mortality data were compared and hazards ratios (relative risks) ranked using the Cox proportional hazards model with methyl-POX dose and group (reactivator) as time-independent covariables. The relative risk of death estimated by Cox analysis (95% CI) in oxime-treated animals when compared with untreated animals, adjusted for methyl-POX dose (high/low) was K-27, 0.58 (0.42-0.80); K-48, 0.60 (0.43-0.83); trimedoxime, 0.76 (0.55-1.04); pralidoxime, 0.88 (0.65-1.20); obidoxime, 0.93 (0.68-1.26); HI-6, 0.96 (0.71-1.31). Only K-27 and K-48 provided statistically significant protection in rats exposed to methyl-POX. Despite the lower inhibitory potency (higher IC(50)) of methyl-POX compared with POX (ratio 4:1), the ability of oxime reactivators to protect from methyl-POX induced mortality was reduced compared with protection from POX (ethyl-analog).

Chronic effects of type 2 diabetes mellitus on cardiac muscle contraction in the Goto-Kakizaki rat

Type 2 diabetes mellitus accounts for more than 90% of all cases of diabetes mellitus, and cardiovascular complications are the major cause of mortality and death in diabetic patients. The chronic effects of type 2 diabetes mellitus on heart function have been investigated in the Goto-Kakizaki (GK) rat. Experiments were performed in GK rats and age-matched Wistar control rats at 18 months of age. The progressive effects of diabetes on glucose metabolism were monitored periodically by application of the glucose tolerance test. Ventricular action potentials were measured in isolated, perfused heart. Shortening and intracellular Ca(2+) were measured in electrically stimulated ventricular myocytes. The GK rats displayed mild fasting hyperglycaemia and progressively worsening glucose tolerance. At 18 months of age and 180 min after intraperitoneal injection of glucose (2 g (kg body weight)(-1)), blood glucose was 436 +/- 47 mg dl(-1) in GK rats compared with 153 +/- 18 mg dl(-1) in control animals. Heart weight to body weight ratio was significantly increased in GK rats (4.10 +/- 0.09 mg g(-1), n = 5) compared with control animals (3.36 +/- 0.22 mg g(-1), n = 4). Spontaneous heart rate was slightly reduced in GK rats compared with control rats. Although the amplitude of shortening was not altered, the amplitude of the Ca(2+) transient was significantly increased in myocytes from GK rats (0.78 +/- 0.11 ratio units) compared with control rats (0.50 +/- 0.06 ratio units). Despite progressively worsening glucose metabolism, at 18 months of age the contractile function of the heart appears to be well preserved.

The Protective Effect of Tribulus terrestris in Diabetes

Tribulus terrestris L (TT) is used in the Arabic folk medicine to treat various diseases. The aim of this article was to investigate the protective effects of TT in diabetes mellitus (DM). Diabetes is known to increase reactive oxygen species (ROS) level that subsequently contributes to the pathogenesis of diabetes. Rats were divided into six groups and treated with either saline, glibenclamide (Glib), or TT for 30 days. Rats in group 1 were given saline after the onset of streptozotocin (STZ)-induced diabetes; the second diabetic group was administered Glib (10 mg/kg body weight). The third diabetic group was treated with the TT extract (2 g/kg body weight), while the first, second, and third nondiabetic groups were treated with saline solution, Glib, and TT extract, respectively. At the end of the experiment, serum and liver samples were collected for biochemical and morphological analysis. Levels of serum alanine aminotransferase (ALT) and creatinine were estimated. In addition, levels of malondialdehyde (MDA) and reduced glutathione (GSH) were assayed in the liver. The tested TT extract significantly decreased the levels of ALT and creatinine in the serum (P < 0.05) in diabetic groups and lowered the MDA level in liver (P < 0.05) in diabetic and (P < 0.01) nondiabetic groups. On the other hand, levels of reduced GSH in liver were significantly increased (P < 0.01) in diabetic rats treated with TT. Histopathological examination revealed significant recovery of liver in herb-treated rats. This investigation suggests that the protective effect of TT for STZ-induced diabetic rats may be mediated by inhibiting oxidative stress.

Ranitidine in Acute High-Dose Organophosphate Exposure in Rats: Effect of the Time-Point of Administration and Comparison with Pyridostigmine

Weak and reversible inhibitors of cholinesterase, when co-administered in large doses, can act in a protective manner against more potent inhibitors such as organophosphates. The clinically widely used histamine type 2 (H2) receptor blocker ranitidine is among H2 blockers the most potent inhibitor of acetylcholinesterase but roughly three to four orders of magnitude less potent than paraoxon (an irreversible organophosphate esterase inhibitor) or pyridostigmine (a reversible carbamate esterase inhibitor). We have previously shown that in vitro ranitidine confers some protection against inhibition of cholinesterases by paraoxon and that in vivo it both increases the number of rats surviving an acute paraoxon exposure and also protects to some degree the cholinesterases from organophosphate inhibition. The purpose of the study was to compare in a prospective non-blinded study, in a rat model of acute high-dose paraoxon exposure, ranitidine with pyridostigmine either administered simultaneously or 30 min. before exposure. There were 36 rats in each of the 5 groups. All substances were applied intraperitoneally. Additional analysis included data from a similar experiment carried out in 2005, in which 54 rats were exposed to paraoxon only (G1) and 54 to paraoxon+ranitidine simultaneously (G2). All groups (except controls; G6 & G7) received 1 micro Mol paraoxon (approximately LD75); groups 2-5 received in addition to paraoxon: G2: 50 micro Mol ranitidine within 1 min. of paraoxon, G3: 1 micro Mol pyridostigmine within 1 min. of paraoxon, G4: 50 micro Mol ranitidine 30 min. before paraoxon, G5: 1 micro Mol pyridostigmine 30 min. before paraoxon. Groups 6 & 7 received only ranitidine and pyridostigmine respectively, group G1 received only paraoxon. Mortality was recorded at 30 min., 1, 2, 3, 4, 24 and 48 hr. Mortality data were compared using Kaplan-Meier plots and logrank tests. No Bonferroni correction for multiple comparisons was applied and an alpha < or = 0.05 was considered significant. All statistical analysis was performed by using SPSS 12.0 statistical software (SPSS Inc., Chicago, IL, USA). Simultaneous administration of ranitidine or pyridostigmine with paraoxon does not significantly affect mortality. Pretreatment (30 min. before) with both ranitidine or pyridostigmine statistically and significantly reduced mortality. When administered before paraoxon, pyridostigmine is statistically significantly superior to ranitidine. Both ranitidine and pyridostigmine are protective against acute paraoxon toxicity provided they are administered before paraoxon. Pyridostigmine results are statistically significantly superior to ranitidine (< or =0.05).

Mitochondrial dysmorphology in the neuroepithelium of rat embryos following a single dose of maternal hyperthermia during gestation

Hyperthermia is teratogenic to human and animal embryos and induces mainly anomalies of the nervous system. However, the teratogenic mechanism is poorly understood. Mammalian embryos are known to switch from anaerobic to aerobic metabolism around the time of neural tube closure. This critical event might be sensitive to hyperthermia. The objective of the present study was to evaluate the ultrastructural changes of the mitochondria of the neuroepithelium (NE) of rat embryos following maternal exposure to hyperthermia. Pregnant rats were heat stressed for an hour on gestation day (GD) 9 and embryos were examined by electron microscopy on GD 10. NE presented extensive apoptosis. Intercellular junctions were weakened and copious cellular debris projected into the ventricle. The mitochondria were of diverse size and shape. Most of them were swollen and had short cristae and electron dense matrix. Hydropic changes were also observed in numerous mitochondria. Lipid-laden mitochondria were found in the apical portions of neuroblasts. The mesenchyme (ME) of heat-treated embryos showed paucity of cells and only as frequent apoptosis as the controls. Their mitochondria also showed changes similar to those of the NE. Additionally extensive lipid accumulation was observed in and in the vicinity of mitochondria, often surrounded by short strands of endoplasmic reticulum. Whereas mitochondrial pathology was associated with profound apoptosis in the NE, growth restriction and lipid accumulation accompanied mitochondrial changes in the ME. The results of this study indicate that the embryonic response to maternal heat shock is tissue-specific and morphologically distinct in this species.

Effects of insulin treatment on heart rhythm, body temperature and physical activity in streptozotocin-induced diabetic rat

1. Streptozotocin (STZ)-induced diabetic cardiomyopathy is frequently associated with depressed diastolic/systolic function and altered heart rhythm. 2. The effects of insulin treatment on heart rhythm, body temperature and physical activity in STZ-induced diabetic rats were investigated using biotelemetry techniques. 3. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar - Lead II configuration. Electrocardiogram, physical activity and body temperature data were recorded with a telemetry system for 10 days before STZ treatment, for 20 days following administration of STZ (60 mg/kg) and thereafter, for 30 days while rats received daily insulin. 4. Heart rate, physical activity and body temperature declined rapidly 3-5 days after administration of STZ. Pre-STZ heart rate was 362 +/- 7 b.p.m., falling to 266 +/- 12 b.p.m. 5-15 days after STZ with significant recovery to 303 +/- 14 b.p.m. 10-20 days after commencement of insulin. Pre-STZ body temperature was 37.5 +/- 0.1C, falling to 37.2 +/- 0.2C 5-15 days after STZ with significant recovery to 37.5 +/- 0.1C 10-20 days after commencement of insulin. Physical activity and heart rate variability were also reduced after STZ but there was no significant recovery during insulin replacement. 5. Defective autonomic regulation and/or mechanisms of control that are intrinsic to the heart may underlie disturbances in heart rhythm in the STZ-induced diabetic rat.

Effect of maternal exposure to homocystine on sodium valproate-induced neural tube defects in the mouse embryos

BACKGROUND

Neural tube defects (NTD) are mainly of multifactorial origin. Maternal treatment with valproic acid (VPA) during pregnancy induces NTD in susceptible fetuses. Elevated levels of homocysteine are observed in pregnancies with NTD. The mechanism by which homocysteine might cause NTD is unknown.

AIM OF THE STUDY

The aim of this study was to determine if homocystine would augment VPA-induced exencephaly in an experimental model.

METHODS

Groups of mice were injected (IP) on gestational day 8 (GD) with a single dose of 75 mg/kg of L: -Homocystine (HC) or a proportionate volume of saline, followed by a single dose of 600 mg/kg of VPA or an equal volume of saline. In a second experiment, mice were treated with a daily dose of 75 mg/kg of HC or an equal volume of saline (IP) from GD 5 and continued through GD 10. These animals had a single exposure to 600 mg/kg of VPA or saline (IP) on GD 8. All animals were killed by cervical dislocation on GD 18. Plasma homocysteine, folate and vitamin B12 were determined on GD 8 and GD 10 from single and multiple dose groups of mice, respectively, from additional experiments.

RESULTS

The VPA and HC+VPA induced significantly higher rates of embryonic resorption and intrauterine growth retardation (IUGR) than HC or saline alone. HC + VPA groups had significantly more numerous fetuses with severe IUGR than HC alone or VPA alone groups. Both single and multiple doses of HC augmented VPA-induced reduction in fetal body weight. Successive doses of HC did not augment the rate of IUGR more significantly than a single dose of HC. Incidence of exencephaly was significantly enhanced in the HC + VPA groups compared to that in the HC or VPA alone groups. HC alone was not teratogenic. Plasma homocysteine levels increased several fold both in HC and HC + VPA groups and the increase was not particularly more marked in multiple dose groups than in the single dose groups. VPA did not elevate homocysteine concentration. Both FA and vitamin B12 concentrations were reduced by VPA, HC and HC + VPA, but HC and VPA when combined did not produce an additive effect on vitamin levels.

CONCLUSION

These data indicate that HC and VPA interact in neurulation stage embryos, affect fundamental processes of closure of the neural tube and lead to enhanced incidence of NTD.

Tiapride pre-treatment in acute exposure to paraoxon: Comparison of effects of administration at different points-in-time in rats

INTRODUCTION

Accidental and suicidal exposures to organophosphorus compounds (OPC) are frequent. The inhibition of esterases by OPC leads to an endogenous ACh poisoning. Recently, the FDA approved, based on animal experiments, for military combat medical use oral pyridostigmine (PSTG) for pre-exposure treatment of soman; the concept is to block the cholinesterase reversibly using the carbamate pyridostigmine in order to deny access to the active site of the enzyme to the irreversible inhibitor (OPC) on subsequent exposure. We have shown previously that tiapride (TIA) is in vitro a weak inhibitor of AChE. We also have shown recently that in rats coadministration of TIA with the organophosphate paraoxon significantly decreases mortality without having an impact on red blood cell cholinesterase (RBC-AChE) activity.

PURPOSE OF THE STUDY

To establish in a prospective, non-blinded study in a rat model of acute high dose OPC (paraoxon; POX) exposure the ideal point in time for TIA pre-treatment administration and to correlate it with measured TIA plasma levels.

MATERIAL AND METHODS

There were six groups of rats in each cycle of the experiment and each group contained six rats. The procedure was repeated twelve times (cycles) (n = 72 for each arm; half male and half female). All substances were applied ip. All groups (1-6) received 1 microMol POX ( approximately LD(75)); groups 1-5 also received 50 microMol TIA at different points in time. Group 1 (G(1)): TIA 120 min before POX Group 2 (G(2)): TIA 90 min before POX, Group 3 (G(3)): TIA 60 min before POX, Group 4 (G(4)): TIA 30 min before POX, Group 5 (G(5)): TIA & POX simultaneously, Group 6 (G(6)): POX only. The animals were monitored for 48 hours and mortality/survival times were recorded at 30 min, 1, 2, 3, 4, 24 and 48 h. AChE activities were determined at 30 min, 24 and 48 h in surviving animals. Statistical analysis was performed on the mortality data, cumulative survival times and enzyme activity data. Mortality data was compared using Kaplan-Meier plots. Cumulative survival times and enzyme activites were compared using the Mann-Whitney rank order test. No Bonferroni correction for multiple comparisons was applied and an alpha < or= 0.05 was considered significant.

RESULTS

Mortality is statistically significantly reduced by TIA pre-treatment at all points-in-time. Highest protection is achieved if TIA is given 90 to 0 min before OPC exposure. The reduction in mortality is not correlated to TIA plasma levels (C (max) approximately 120 min post ip-administration). TIA pre-treatment is not affecting AChE activity regardless of the timing of administration.

CONCLUSION

The lack of correlation between TIA plasma levels and degree of mortality reduction as well as the lack of protective effect on enzyme activity seem to indicate that the site of action of TIA is not the blood. While our hypothesis that TIA would protect AChE in a pyridostigmine-like manner (via protection of the enzyme) could not be confirmed, the reduction in mortality with TIA pre-treatment is nevertheless of potential interest.

Estrogen and ghrelin increase number of submucosal urethral and anal canal blood vessels in ovariectomized rats

OBJECTIVES

Urinary and fecal control deteriorates after menopause, but it is not clear whether this is age or hormone related. This study investigates whether administration of estrogen and/or the anti-aging growth hormone-releasing peptide, ghrelin, improves the adverse effects of menopause/aging on urethral and anal canal submucosal blood vessel counts in middle-age rats.

METHODS

Female Wistar rats (13 months old) underwent ovariectomy, followed 1 month later by intraperitoneal once-daily administration of 17-beta estradiol (10 microg/kg), ghrelin (2 microg/kg), both hormones, or vehicle (n = 6 in each of four groups) for 42 days. An age-matched sham group (n = 6) received no intervention. Submucosal blood vessels were counted by light microscopy in five randomly selected fields from five nonconsecutive sections (5 microm thick) per rat of formalin-fixed and paraffin-embedded tissue blocks of the urethra and anal canal stained with hematoxylin-eosin. The results are expressed as the mean vessel number per high power field (x400).

RESULTS

Ovariectomy significantly reduced submucosal urethral and anal vascular counts below the sham values (7.41 +/- 0.98 versus 5.46 +/- 0.82, P = 0.003 and 7.16 +/- 1.11 versus 4.92 +/- 0.65, P = 0.0009, respectively). Estrogen restored the urethral counts (7.76 +/- 0.88, P = 0.5) and ghrelin or combined estrogen and ghrelin administration significantly increased the counts to greater than the sham counts (8.68 +/- 0.99, P = 0.04 and 9.72 +/- 1.21, P = 0.004, respectively). Estrogen, ghrelin, and combined estrogen and ghrelin administration also restored the anal counts to sham levels (7.26 +/- 0.97, P = 0.8; 6.56 +/- 0.78, P = 0.3; and 7.76 +/- 0.88, P = 0.3, respectively).

CONCLUSIONS

Combined or individual replacement of estrogen and ghrelin produces a beneficial effect by reversing the ovariectomy-induced decrease in urethral and anal canal submucosal vessel numbers in middle-age rats.

Long-term effects of streptozotocin-induced diabetes on the electrocardiogram, physical activity and body temperature in rats

In vivo biotelemetry studies have demonstrated that short-term streptozotocin (STZ)-induced diabetes is associated with a reduction in heart rate (HR) and heart rate variability (HRV) and prolongation of QT and QRS intervals. This study investigates the long-term effects of STZ-induced diabetes on the electrocardiogram (ECG), physical activity and body temperature. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. ECG, physical activity and body temperature data were continuously recorded with a telemetry system before and following the administration of STZ (60 mg kg(-1)) for a period of 22 weeks. HR, physical activity and body temperature declined rapidly 3-5 days after the administration of STZ. The effects became conspicuous with time reaching a new steady state approximately 1-2 weeks after STZ treatment. HR at 4 weeks was 268 +/- 5 beats min(-1) in diabetic rats compared to 347 +/- 12 beats min(-1) in age-matched controls. HRV at 4 weeks was also significantly reduced after STZ treatment (18 +/- 3 beats min(-1)) compared to controls (33 +/- 3 beats min(-1)). HR and HRV were not additionally altered in either diabetic rats (266 +/- 5 and 20 +/- 4 beats min(-1)) or age-matched controls (316 +/- 6 and 25 +/- 4 beats min(-1)) at 22 weeks. Reduced physical activity and/or body temperature may partly underlie the reductions in HR and HRV. In addition, the increased power spectral low frequency/high frequency ratio from 4 weeks after STZ treatment may indicate an accompanying disturbance in sympathovagal balance.

Ultra-structural morphological abnormalities of the urinary bladder in streptozotocin-induced diabetic female rats

The objective of this study was to evaluate the ultra-structural changes in the urinary bladder of diabetic rats in relation to disease duration since the morphological bases of diabetes-induced bladder dysfunction are poorly understood. Urinary bladders were examined chronologically by electron microscopy in a female Wistar-rat model of streptozotocin-induced diabetes mellitus and compared to control samples. Numerous dark mitochondria with swollen cristae and electron lucent, large, calcified and degenerated mitochondria were observed first in the urothelium. Intraepithelial capillaries surrounded by thick collagen were also present. Gap junctions between myocytes were interrupted or extensively widened with reduced mitochondria and caveolae. Collagen accumulation, degenerated nerve fibres and myelin bodies were seen between myocytes with increased collagen content and frequent mast cells, phagocytes and lymphocyte aggregates in the stroma. All ultra-structural lesions became augmented with longer duration of diabetes. Diabetes induces time-dependent pathologic changes in the urinary bladder of rats that might account for bladder dysfunction.

Effect of maternal administration of vigabatrin during late gestation on fetoplacental amino acid profile in the mouse

The objectives were to determine if vigabatrin in late gestation affects fetal growth and causes alterations in amino acid concentrations in the mouse. A single dose of 450 mg/kg VGB in saline or a proportionate volume of saline was administered intraperitoneally (IP) to Theiler outbred (TO) mice on gestation day 15 and maternal plasma, placentae and fetuses were collected at different time intervals after treatment. VGB attained peak concentration in the maternal plasma and the fetus at 2 h after treatment and in the placenta at 4 h. At 12 h significantly lower concentrations of several amino acid including methionine were found in the placentae and fetuses in the treated group. After 24 h, no difference was seen in the plasma amino acid concentrations but in the placentae and fetuses a significant decrease occurred in some amino acids in the treated group. At 48 and 72 h, a generalized increase in most amino acid levels occurred in the fetus and placenta but not in maternal plasma of the treated group although the fetal and placental weights were significantly reduced. VGB during late gestation causes fetal growth retardation accompanied by an initial disruption of amino acid supply followed by an increase in amino acid concentrations for the next 2 days. This increase did not help restore growth suggesting that early fetal period is particularly vulnerable to VGB-induced intrauterine growth retardation in the mouse.

Effect of maternal diabetes and ethanol interactions on embryo development in the mouse

The aim of this study was to determine the possible fetal effects of interaction between maternal diabetes and acute doses of alcohol. Pregnant TO mice were made diabetic by a single injection of streptozotocin (STZ) on gestation day (GD) 2. Single dose of 0.003 or 0.03 ml/g body weight of fresh ethanol (25% v/v of absolute alcohol in normal saline) was injected into groups of diabetic and nondiabetic animals on GD 7 or 8. One group of diabetic animals had a daily dose of 6-8 IU of insulin subcutaneously. Fetuses were collected on GD 18. There was a significant increase in the incidence of implantation failure in the diabetes plus ethanol groups and insulin control group. Ethanol injection on GD 7 accentuated diabetes-related embryonic resorption and intrauterine growth retardation (IUGR). This effect was less marked in the diabetic group treated with ethanol on GD 8. Diabetes alone produced a greater incidence of IUGR than ethanol alone. Midfacial hypoplasia and minor anomalies were found more frequently in the combination treatment groups. Holoprosencephaly and thymus hypoplasia observed in diabetic groups were found to be reduced in frequency in the diabetes plus ethanol groups, suggesting an antagonistic type of ethanol-diabetes interaction, stage-dependently. Since severely malformed embryos are known to be resorbed/killed in utero in mice, this reduction might reflect the magnitude of early death of severely malformed embryos. These data suggest that the interaction effects are possibly related to alterations in fundamental developmental processes of early embryos.

Experimental studies on reproductive toxicologic effects of lamotrigine in mice

BACKGROUND

Virtually all antiepileptic drugs (AED) tested so far have been found to be teratogenic. The second generation AED possess a number of therapeutic advantages over the older ones. There are, however, very little data on their effects on embryonic development. A recent report suggests that lamotrigine (LTG) can be teratogenic to human fetuses. With only a few cases of prenatal exposure to LTG in the record, however, it has not been possible to establish a recognizable pattern of malformations in the infants of LTG-treated mothers.

OBJECTIVES

The objectives of the present study were to evaluate the reproductive toxic effects of LTG .

RESULTS

Single (50-200 mg/kg) or multiple doses (25, 50, 75 mg/kg) of LTG were administered by intraperitoneal (i.p.) injection (note that the therapeutic administration is oral) to groups of TO mice on gestation day (GD) 7 or 8. Fetuses were collected on GD 18. Maternal toxic effects including a dose-related mortality, a high incidence of abortion, embryo lethality, congenital malformations and intrauterine growth retardation (IUGR) were observed in the LTG-treated group. Administration of LTG in multiple low doses resulted in a better maternal survival and increased incidence of embryonic resorption and malformations with increasing dose; IUGR was significant but not dose-dependent. The malformations characteristic of the LTG multiple low dose group fetuses included maxillary-mandibular hypoplasia, exencephaly, cleft palate, median facial cleft, urogenital anomalies and varying degrees of caudal regression. Skeletal malformations and developmental delay of the skeleton were observed both in single and multiple dose groups.

CONCLUSIONS

The results of this study indicate that LTG administered i.p. at high doses can induce intrauterine growth retardation and at low multiple doses causes a dose-dependent increase in embryonic resorption, craniofacial and caudal malformations as well as maternal toxicity in the mouse. Previous studies in other laboratories have used oral route of exposure and concluded that there are no teratogenic effects of LTG at dose levels that are not maternally toxic.

Effects of ovariectomy and hormone replacement on collagen and blood vessels of the urethral submucosa of rats

Collagen and blood vessels of the urethral submucosa of ovariectomized rats were studied following 28 daily subcutaneous injections of 17-beta estradiol (n=6, group 1), medroxy-progesterone acetate (n=6, group 2), both drugs (n=6, group 3) or vehicle (n= 6, control) and after sham surgery without castration or injection (n=6). Investigations included the immunohistochemistry of estrogen and progesterone receptors and collagen fibres, Western blot analysis of collagen types I and III and counting periurethral vessels by light microscopy. Our results showed positive immunostaining with estrogen, progesterone and collagen types I and III in all samples. Collagen type I and III levels were lower in the controls than in the sham group. The other groups showed increases (2>3>1) over the controls with a relatively higher increase in type III. The type I/III collagen ratio progressively decreased (control>1>2>3) below sham levels. The mean vessel count was significantly lower in control than in sham animals (P<0.00001). However, only estrogen treatment significantly increased the vessel number compared to controls (P=0.04). Our results indicate that estrogen and progesterone, alone or in combination, have an effect on collagen types I and III, and that estrogen has an effect on blood vessels of the urethral submucosa in female rats.

Intrauterine growth retardation in experimental diabetes: possible role of the placenta

Fetal growth disorders are common in pregnancy complicated by diabetes. Whereas macrosomia often occurs in infants of diabetic women, growth retardation is almost a rule in spontaneous and experimental diabetes in animals. However, it is not clear when during development growth inhibition starts and how placental pathology might affect fetal growth in maternal diabetes. In this study pregnant Wistar rats were injected (ip) with a single dose of 50 mg/kg of streptozotocin (STZ) on gestation day (GD) 2 and a blood glucose level of 200 mg/dl or more determined 24 hrs later indicated diabetes. The controls were non-treated, buffer treated or, following confirmation of diabetes, injected with a single dose of 2--6 IU of insulin (Novo Ultralente) once daily. Fetuses and placentae were collected from GD 14--20. Intrauterine growth retardation (IUGR) in STZ group was significant as early as GD 15 and persisted to GD 20. Insulin produced a significant recovery in fetal weight gain. The placentas of STZ-treated group were significantly heavier than those of the control groups. The reduction in cord length of the STZ group became apparent on GD 16 and remained so to term. The placenta of GD 14 STZ group had a thicker decidua basalis and dilated maternal sinusoids. By GD 16, the decidua basalis contained glycogen-containing decidual cells and scattered glycogen cells confirmed by Best's carmine with or without diastase. The glycogen cells of the basal zone were more abundant, and had degenerated in some sites leaving behind cysts with eosinophilic mass. The giant cells had proliferated enormously. The labyrinthine zone appeared spongy with persistent fetal mesenchyme, peri-vascular fibrosis, and enhanced placental barrier. The trophoblasts of the labyrinths also contained traces of glycogen unlike the controls. By GD 18, the decidua basalis of the STZ group was thinner than that of the controls and contained necrotic giant cells and lymphocytic aggregations. In the basal zone, the giant cells had proliferated further; more glycogen cells had degenerated. Perivascular fibrosis was still extensive in the labyrinthine zone. Bloodless maternal sinusoids, extensive vacuolization, degeneration of glycogen islands and formation of cysts characterized the labyrinthine zone. These changes varied in intensity from one area to another in the same placenta and between placentas of the same and of different litters. The development of the upper and lower jaws, elevation and fusion of palatal shelves, reduction of physiological umbilical hernia, descent of the testes, fusion of the urethral folds and separation of digits of the paws were significantly delayed in the STZ group. The consistent association of placental pathology with fetal growth retardation is suggestive of an alteration in placental function possibly contributing to IUGR in STZ-induced diabetes in rats.