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.

Melatonin increases intracellular calcium in the liver, muscle, white adipose tissues and pancreas of diabetic obese rats.

Melatonin, a widespread substance with antioxidant and anti-inflammatory properties, has been found to act as an antidiabetic agent in animal models, regulating the release and action of insulin. However, the molecular bases of this antidiabetic action are unknown, limiting its application in humans. Several studies have recently shown that melatonin can modify calcium (Ca(2+)) in diabetic animals, and Ca(2+) has been reported to be involved in glucose homeostasis. The objective of the present study was to assess whether the antidiabetic effect of chronic melatonin at pharmacological doses is established via Ca(2+) regulation in different tissues in an animal model of obesity-related type 2 diabetes, using Zücker diabetic fatty (ZDF) rats and their lean littermates, Zücker lean (ZL) rats. After the treatments, flame atomic absorption spectrometry was used to determine Ca(2+) levels in the liver, muscle, main types of internal white adipose tissue, subcutaneous lumbar fat, pancreas, brain, and plasma. This study reports for the first time that chronic melatonin administration (10 mg per kg body weight per day for 6 weeks) increases Ca(2+) levels in muscle, liver, different adipose tissues, and pancreas in ZDF rats, although there were no significant changes in their brain or plasma Ca(2+) levels. We propose that this additional peripheral dual action mechanism underlies the improvement in insulin sensitivity and secretion previously documented in samples from the same animals. According to these results, indoleamine may be a potential candidate for the treatment of type 2 diabetes mellitus associated with obesity.

Attenuation of stress-induced gastric lesions by lansoprazole, PD-136450 and ranitidine in rats.

Combining restraint with cold temperature (4°C) consistently induces gastric ulceration in rats after 3.5 h. The cold restraint-stress (CRS) method provides a suitable model for acute ulcer investigations. This study compares the antiulcer activities of lansoprazole (a proton pump inhibitor), PD-136450 (CCK(2)/gastrin receptor antagonist) and ranitidine (histamine H(2) receptor antagonist) on CRS-induced gastric ulcers in rats. The results have shown that lansoprazole, which is a potent anti-secretory agent, provides complete protection in this model of ulcer formation. The use of indomethacin pretreatment to inhibit the prostaglandin (PG) synthesis and N(G)-nitro L-arginine methyl ester (L-NAME) pretreatment to inhibit nitric oxide synthase did not alter the lansoprazole-induced inhibition of ulcer index obtained in the untreated Wistar rats indicating that these two systems were not involved in the activation of lansoprazole. PD-136450, an effective anti-secretory agent against gastrin- but not dimaprit-induced stimulation, evoked a dose-dependent inhibition of CRS-induced gastric ulcers. The results show that both PG and nitric oxide pathways can influence the inhibitory effect of PD-136450 against CRS-induced gastric ulcer. The antiulcer activities of both lansoprazole and PD-136450 were compared to that of ranitidine. The results showed that ranitidine was more potent than lansoprazole and PD-136450 in inhibiting CRS-induced gastric ulcers and its effect was shown to be influenced by PG as well as nitric oxide synthase. The results of this study have demonstrated that although lansoprazole, PD-136450 and ranitidine were protective against CRS-induced gastric ulcers, the antiulcer activities of PD-136450 and ranitidine involved both PG and nitric oxide pathways, while lansoprazole acted independently of these two systems during CRS.

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.

PD-136,450: a CCK2 (gastrin) receptor antagonist with antisecretory, anxiolytic and antiulcer activity.

This study investigated the effects of PD-136,450 (PD), a highly selective ligand for the CCK2 receptor, on gastric acid and pancreatic secretions, gastric cytoprotection and anxious behaviour in the rat and rabbit. PD inhibited gastrin (but not dimaprit) stimulated acid secretion in anaesthetized and conscious rats (IC50 of 1 mg kg(-1) sc) and inhibited 14C-aminopyrine uptake in isolated gastric glands from rabbits. In addition, PD decreased dose-dependently gastric haemorrhagic lesions in rats treated orally with acidified ethanol. Both, the antisecretory effects on gastric acid secretion and the gastric cytoprotective effects were less potent compared with the proton pump inhibitor omeprazole. PD strongly increased pancreatic secretion, which was substantially inhibited by the CCK1 antagonist L-364,718 (but not by the CCK2 antagonist L-365,260). PD also showed significant anxiolytic activity as assessed by a black and white box two-compartment activity assay. Both, time spent in the dark compartment and latency for movement from the light to the dark compartment was increased by PD (similarly with 5 mg kg(-1) diazepam). In conclusion, PD inhibited gastrin-stimulated gastric acid secretion, decreased ethanol-induced damage to the gastric mucosa, stimulated pancreatic secretion (via CCK1 receptors) and displayed anxiolytic activity. Thus, PD may have utility as an adjunct therapy in peptic ulcer disease by countering the actions of gastrin and increasing acid neutralization and mucosal protection.

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.

Comparison of the antisecretory and antiulcer activity of epidermal growth factor, urogastrone and transforming growth factor alpha and its derivative in rodents in vivo.

This study investigates the effects of epidermal growth factor (EGF), urogastrone (UG) and transforming growth factor-alpha (TGFalpha) and its derivative on dimaprit- and pentagastrin-induced gastric acid secretion and on acidified ethanol (AE)-evoked ulcer formation in anaesthetized rats. EGF, TGFalpha and UG administered subcutaneously (s.c.) 30 min before dimaprit inhibited gastric acid secretion. Against pentagastrin-stimulated secretion, TGFalpha inhibited, while EGF and UG potentiated, acid secretion dose-dependently. Intraduodenal (i.d.) administration of TGFalpha and UG had no effect, while EGF potentiated, both secretagogue-induced acid secretion in the same dosage schedule. Administration of either EGF, UG or TGFalpha i.v. bolus, in response to continuous infusion of dimaprit resulted in a significant (p < 0.05-p < 0.001) inhibition of acid secretion which was transient and returned to normal within 30-45 min for UG while it slowly returned to normal for EGF and TGFalpha. The truncated form of TGFa (amino acids 34-43) did not show any antisecretory effect when administered parenterally. Acidified ethanol produced gastric haemorrhagic lesions in the rat 1 h after oral administration. The gastric mucosal protective effects of TGFalpha, EGF and UG administered either orally or s.c. 30 min before the administration of AE were dose-dependent against this model of ulcer induction. Indomethacin (Indo), administered 15 min before AE to inhibit prostanoids biosynthesis, significantly (p < 0.001) reduced the cytoprotective effects of TGFalpha, EGF and UG and aggravated the ulcer index when administered s.c. The results show that PGs may be involved in mediating the protective effects of the three growth factors. Administration of NG-nitro-L argininemethylester (L-NAME) 15 min prior to TGFa, EGF and UG s.c. or orally, significantly (p < 0.001) decreased the degree of ulcer indices and was able to reduce the protective effects of TGFalpha, EGF and UG, thus including the role of NO in mediating the protective effects of these growth factors. In conclusion, these results have demonstrated that EGF, UG and TGFalpha have a short and reversible inhibitory effect on dimaprit-stimulated gastric acid secretion and each is effective parenterally but not orally. UG and EGF potentiated, while, TGFa inhibited pentagastrin-stimulated acid secretion. In addition, TGFalpha seems to lose its activity when it is truncated from the C terminus. The present study also suggests that EGF, UG and TGFalpha are equally effective against AE-induced gastric ulcer and bring about their cytoprotective action through their reduction of acid secretion and through PG and NO pathways.

An improved method to evaluate secretory activity of isolated gastric glands and cells.

The accumulation of [14C]aminopyrine (AP) is a valuable and widely used method to probe acid secretion of gastric glands and parietal cells. Usually, the dry weight of glands is used to normalize the AP accumulation ratio, and since the nonhomogeneity of the suspension makes it impossible to evenly distribute glands by simple pipetting, it is necessary to scrupulously dry and weigh each and every experimental sample. Thus, massive, time-consuming procedures of tube drying and weighing are involved. Moreover, the weighing of approximately 1 mg dried gland samples in a 1-g Eppendorf tube introduces considerable sample variance. Here, we present a modified protocol to simplify the AP accumulation method by introducing a generic 3H labeling of protein for normalization. Freshly isolated glands were treated with high specific activity 3H-labeled succinimidyl propionate (3H-succ, 60 Ci/mmol) for 10 min at room temperature during the normal isolation/washing procedure. This reagent reacts with primary amines, and even at normal cell pH the efficiency of reaction (25-30%) is more than adequate. The 3H-labeled glands are then processed normally with simultaneous monitoring of 3H (representing gland amount) and AP (representing the extent of acid accumulation) in separate energy windows of a liquid scintillation counter. Dose- and time-dependent efficiency of 3H labeling were evaluated. The relations between labeling and gland protein and dry weight were linear. No detrimental effects of reagent were noted in the useful range of 1-3 nM 3H-succ. Although some limited sample weighing or protein determination must be made for each batch of 3H-labeled glands, this method avoids massive tube weighings and provides the convenience of double label counting with a highly reproducible method for normalizing data.

A comparative study on the activity of lansoprazole, omeprazole and PD-136450 on acidified ethanol- and indomethacin-induced gastric lesions in the rat.

1. The proton pump inhibitors lansoprazole (LP) and omeprazole (OP) and the cholecystokinin (CCK)-receptor antagonist PD-136450 (PD) provide a broad spectrum of activities in their ability to inhibit gastric acid secretion and protect the stomach against ulcerogens. In the present study, we investigated the protective effects of these compounds against gastric ulcers induced by acidified ethanol (AE) and indomethacin. 2. Both AE (60% ethanol in 150 mmol/L HCl, 1 mL/rat) and indomethacin (30 mg/kg) produced gastric haemorrhagic lesions in the rat 1 and 6 h after oral administration, respectively. 3. The gastric mucosal protective effects of LP (1-20 mg/kg), OP (0.5-10 mg/kg) and PD (1-20 mg/kg), administered either orally or subcutaneously (s.c.) 30 min before the administration of AE or indomethacin, were dose dependent against both models of ulcer induction. 4. To determine whether the cytoprotective effect of LP, OP and PD (each 10 mg/kg) was mediated by endogenous prostaglandins (PG), indomethacin (10 mg/kg, s.c.) was administered 15 min before AE to inhibit prostanoids biosynthesis. Indomethacin reduced the cytoprotective effects of OP, but not LP, administered either orally or s.c. Indomethacin reduced the cytoprotective effect of PD administered orally, although the effect was much less significant than when PD was administered s.c. The results exclude the role of PG in mediating the protective effects of LP, whereas the possibility exists for PG to have a role in mediating the protective effects of OP and PD. 5. To investigate the possible involvement of endogenous nitric oxide (NO) in the cytoprotective action of LP, OP and PD, we treated rats with a selective inhibitor of NO synthesis, namely NG-nitro-L-arginine methyl ester (L-NAME; 25 mg/kg, s.c.). Administration of L-NAME 15 min prior to LP, OP or PD (each 10 mg/kg) orally or s.c. and challenge with AE or indomethacin did not significantly increase the degree of the ulcer index and L-NAME was not able to antagonize the protective effects of LP, OP and PD, thus excluding the role of NO in mediating the protective effects of these drugs. However, the effects of PD in reducing the indomethacin-induced ulcer index were less significant in the presence than the absence of L-NAME (P < 0.05 vs P < 0.001, respectively), suggesting a role for NO. 6. In conclusion, the results of the present study suggest that LP and OP are equally effective against AE- as well as indomethacin-induced gastric ulcers and were more potent than PD in protecting the stomach against ulcer formation. Lansoprazole, OP and PD bring about their cytoprotective action through the reduction of acid secretion and some other unknown mechanisms. However, OP and PD may exert their cytoprotective action through PG and NO pathways.

Placental transfer of vigabatrin (gamma-vinyl GABA) and its effect on concentration of amino acids in the embryo of TO mice.

BACKGROUND: The mechanism of the teratogenicity of vigabatrin (VGB) is unknown. The objectives of this study were to determine the placental transfer of VGB and to evaluate the effect of VGB on maternal, placental, and fetal concentrations of amino acids. METHODS: A single dose of 400 mg/kg VGB in physiological saline was administered intraperitoneally to a group of Theiler outbred (TO) mice on gestational day (GD) 10. The controls received a proportionate volume of saline. Maternal blood samples, embryos, and placentas were collected at 3.5, 6.0, and 9.0 hr after treatment and their total amino acid concentrations determined in an ion-exchange amino acid analyzer. RESULTS: At 3.5 hr, there was a decrease in concentrations of some amino acids in the blood, placenta, and embryos of VGB-treated mice, but the decrease in methionine was most marked. gamma-aminobutyric acid (GABA) was significantly higher in the VGB group in both the embryos and the placentas at 3.5 hr but at 6.0 and 9.0 hr the differences were not significant. Vigabatrin levels were higher in the placenta than in the embryo at 3.5 hr, but at 6.0 hr there was an overlap of the VGB peak with that of tryptophan with very much lower levels than at 3.5 hr. At 9.0 hr, there was no vigabatrin peak in either the placenta or the embryo. CONCLUSIONS: Maternal exposure to VGB results in peak levels of the drug after 3.5 hr in the placenta and embryo. Methionine concentration is most severely affected in VGB-treated mothers, placentas, and fetuses. We speculate that this deficiency could be a possible mechanism for the teratogenic effects of vigabatrin.

Effect of alpha-tocopherol supplementation on the ultrastructural abnormalities of peripheral nerves in experimental diabetes.

Ultrastructural observations were made on myelinated fibers in the tibial nerves in order to investigate the beneficial effects of alpha-tocopherol administration in streptozotocin-diabetic rats. Male Wistar rats, aged 12 weeks and weighing between 250 g to 300 g were studied. Six onset control rats were used to obtain the baseline parameters for this strain and age. Further 3 groups--untreated diabetic animals, diabetic animals treated with alpha-tocopherol, and age-matched controls--were studied over a 3-month period. In the diabetic animal, administration of alpha-tocopherol resulted in a significant increase (p < 0.05) in total plasma vitamin E levels when compared with other groups. Myelinated fiber cross-sectional area (p < 0.05), axonal area (p < 0.01) and myelin sheath area (p < 0.05) were significantly less in the tibial nerve of diabetic animals than in age-matched controls, but not different from those of onset controls. In the alpha-tocopherol treated diabetic animals, the values for these parameters were intermediate without showing significant difference when compared with age-matched controls and untreated diabetics. The "g" ratio (axon to fiber area) did not differ between any experimental groups. The number of large myelinated fibers were less in the untreated diabetic animals, but in the alpha-tocopherol-treated diabetics, the values were significantly higher (p < 0.05) than with untreated diabetics and were similar to those of age-matched controls. In conclusion, this ultrastructural study reiterated the fact that structural abnormalities of myelinated fibers occur in experimental diabetes and that alpha-tocopherol administration may be useful in preventing the development of these abnormalities.

Comparison of five antisecretory agents acting via gastric H+/K+-ATPase.

Lansoprazole(L), pantoprazole (P), rabeprazole and RO-18-5364 (RO) are new benzimidazole derivatives which rival omeprazole (O) as proton pump inhibitors (PPIs) for treatment of ulcer disease. In this study, we compared the effects of these compounds on acid secretion and determined their relative potencies in relation to their effect on [14C]-aminopyrine (AP) accumulation in isolated gastric glands. Inhibition of AP (1.2 microCi x mL(-1)) accumulation was measured in rabbit isolated gastric glands. dbcAMP (1 mmol; stimulant of acid secretion) and Ro 20-1724 (0.1 mmol; a phosphodiasterase inhibitor) were added to the Eppendorf tubes containing the PPIs and AP and dose-response curves were done for each drug after incubating for 5, 10 and 20 min at 37 degrees C and AP accumulation was determined using a scintillation counter. All the PPIs significantly (P < 0.001) inhibited acid secretion as demonstrated by the inhibition of AP accumulation in the isolated gastric glands. Minimum inhibition occurred at a concentration of 0.001 micromol for lansoprazole and omeprazole, 0.01 micromol for rabeprazole and RO 18-5364 and 0.02 micromol for pantoprazole. No differences were observed between PPIs with regards to the maximum inhibition they produce. When expressed as a percentage inhibition of control at 10-min incubation and at concentrations of 1 micromol, L showed 85.6 +/- 0.5, O 87 +/- 0.5, P 83.2 +/- 1.1, R 86.4 +/- 1.1 and RO 87.8 +/- 1.9 inhibition respectively. When comparing the IC50 values, their relative potencies were different. Maximum potency was shown by L (0.007 micromol) > O (0.012 micromol) > R (0.018 micromol) > RO (0.034 micromol) > P (0.050 micromol). All the new PPIs showed different potencies as inhibitors of acid secretion as evident from their IC50s. Extensive ulcer healing trials demonstrated comparable efficacy with a number of studies indicating that symptoms relief are more rapid with P and L, while in this study L appeared to be the most potent in inhibiting AP accumulation in the isolated gastric glands.

Pathogenesis of nonsteroidal anti-inflammatory drug gastropathy: clues to preventative therapy.

Gastric ulceration and bleeding are major impediments to the chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs). The development of effective therapies for prevention of these adverse effects requires better understanding of their pathogenesis. Several features of NSAIDs contribute to the development of damage in the stomach, including the topical irritant effects of these drugs on the epithelium, impairment of the barrier properties of the mucosa, suppression of gastric prostaglandin synthesis, reduction of gastric mucosal blood flow and interference with the repair of superficial injury. The presence of acid in the lumen of the stomach also contributes to the pathogenesis of NSAID-induced ulcers and bleeding in a number of ways. Acid impairs the restitution process, interferes with hemostasis and can inactivate several growth factors that are important in mucosal integrity and repair. Profound suppression of gastric acid secretion has been shown to be effective in preventing NSAID-induced ulceration. There is a strong possibility that new NSAIDs entering the market will have greatly reduced toxicity in the gastrointestinal tract.

Diversity in expression of glucose-6-phosphate dehydrogenase deficiency in females.

The aims of this study were to determine the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in the United Arab Emirates (UAE), to describe the different mutations in the population, to determine its prevalence, and to study inheritance patterns in families of G6PD-deficient individuals. All infants born at Tawam Hospital, Al-Ain, UAE from January 1994 to September 1996 were screened at birth for their G6PD status. In addition, those attending well-baby clinics during the period were also screened for the disorder. Families of 40 known G6PD-deficient individuals, selected randomly from the records of three hospitals in the country, were assessed for G6PD deficiency. Where appropriate, this was followed by definition of G6PD mutations. Of 8198 infants, 746 (9.1%), comprising 15% of males and 5% of females tested, were found to be G6PD deficient. A total of 27 families were further assessed: of these, all but one family had the nt563 Mediterranean mutation. In one family, two individuals had the nt202 African mutation. The high manifestation of G6PD deficiency in women may be due to the preferential expression of the G6PD-deficient gene and X-inactivation of the normal gene, and/or to the presence of an 'enhancer' gene that makes the expression of the G6PD deficiency more likely. The high level of consanguinity which, theoretically, should result in a high proportion of homozygotes and consequently a higher proportion of females with the deficiency, was not found to be a significant factor.

Teratogenic effects of vigabatrin in TO mouse fetuses.

Vigabatrin (VGB) is a relatively recently introduced antiepileptic drug that enhances the brain levels of gamma aminobutyric acid (GABA). Few data on its teratogenic effects appear to have been reported. Our objective was to determine if VGB was teratogenic in the TO mouse. Single doses of 300-600 mg/kg of VGB dissolved in saline were administered intraperitoneally (IP) to groups of TO mice on one of gestation days (GD) 7-12. The controls were saline treated or untreated. No maternal toxic effects were observed in the 300 or 450 mg/kg groups, and the 600 mg/kg dose was totally lethal to the mothers. Fetuses were collected on GD 18. Both 300 and 450 mg/kg doses induced a consistently significant intrauterine growth retardation irrespective of the developmental stage at administration. VGB did not augment the spontaneous incidence of neural tube defects characteristic of this strain, but accelerated destruction of the brain in spontaneous exencephalic embryos. Mandibular and maxillary hypoplasia, arched palate, cleft palate (two cases), limb defects (one case), and exomphalos were observed in the malformed fetuses. The high incidence of exomphalos appears to be a unique result of VGB treatment. Alizarin red-S/alcian blue-stained, skeletons revealed hypoplasia of mid facial bones, stage-dependent increase in the frequency of cervical and lumbar ribs, rib fusion, and sternal and vertebral malformations in the drug-treated fetuses. Middle and distal phalanges of the forepaw and mid phalanges and tarsals of the hindpaw failed to ossify in a significant number of experimental fetuses. Homeotic shift in terms of presacral vertebral number and a high incidence of lumbar and cervical ribs in the treated group are suggestive of treatment-related alterations in gene expression. In view of the paucity of human and animal data on the reproductive toxicologic effects of VGB, the results of the present study assume particular importance and suggest that VGB should be used in pregnancy with extreme caution.

Polymorphic N-acetyltransferase (NAT2) genotyping of Emiratis.

Polymorphic N-acetyltransferase (NAT2) genotypes were determined in 106 unrelated Emiratis by PCR-RFLP analysis to obtain estimates of allele frequencies. Thirteen different genotypes were found, four associated with the rapid acetylator phenotype and nine with the slow acetylator phenotype. Among 67 phenotypically slow acetylators, there was 100% concordance between phenotype and genotype. Among 39 phenotypically rapid acetylators, 37 possessed at least one wild type allele; a 95% concordance with genotype. Seven different NAT2 alleles associated with slow acetylation were found. The commonest was a NAT2*5 type (C481T) allele which occurred with a frequency of 0.53, a significantly higher frequency than has been reported for other ethnic groups. A second slow allele, a NAT2*6 type (G590A), occurred with a frequency of 0.21. The most common genotypes found were NAT2*5/*5 homozygotes, NAT2*5/*6 heterozygotes and NAT2*4/*5 heterozygotes with frequencies of 0.25, 0.25 and 0.22 respectively. The high overall prevalence of alleles associated with slow acetylation (173/212; 81.6%) among Emiratis is consistent with previously reported high frequency of the slow acetylator phenotype in Arabs. Two apparently new slow alleles were identified but have not yet been fully characterized. One appears to be a NAT2*5 variant allele. The other uncharacterized allele appears likely to contain an entirely new mutation associated with slow acetylation.

Effects of anaesthetics and trauma on stimulated gastric acid secretion in chronic fistula dogs.

1. The present study was undertaken to determine whether various anaesthetic agents affect canine gastric acid secretion independently of other experimental variables. 2. Acid secretory output was determined in dogs with chronic fistulae, by administering sedating doses of anaesthetics commonly used for studying gastric secretory mechanisms in laboratory animals. 3. The anaesthetic agents inhibited gastric acid secretion. As the inhibitory effect of the mixture of anaesthetics was pronounced, an attempt was made to study the effect of each individual anaesthetic agent separately. 4. Acetopromazine was given to sedate dogs. Although it has a long duration of action, it only had a transient inhibitory action on gastric acid secretion of 15-30 min duration. Moreover the drug reduced pentagastrin-stimulated secretion, but had no effect on histamine-stimulated secretion. 5. Thiopentone sodium given with acetopromazine produced a mild inhibitory effect on histamine-stimulated secretion for 45 min, but produced a more pronounced and sustained inhibitory effect on pentagastrin-stimulated secretion. 6. Trilene significantly inhibited both histamine- and pentagastrin-stimulated secretion. The effect on the latter was more pronounced and sustained. 7. Trauma had no significant effect on histamine-stimulated secretion, but showed a slight inhibitory effect on pentagastrin-stimulated secretion. 8. Experiments to study gastric secretory mechanisms and antisecretory drugs should take account of the potential inhibitory effects of anaesthetics. Where possible, studies in conscious dogs with gastric fistulae are preferable to experiments on anaesthetized animals.

Effects of anaesthetic agents on basal and histamine-stimulated acid secretion in the fistula rat.

OBJECTIVES: Anaesthetized rats or surgically modified preparations such as the Shay rat are widely used to study upper gastrointestinal function in the laboratory. Despite the existence of reports demonstrating that agents such as barbiturates can influence acid output, a systematic study of the effects of anaesthetics on gastric secretion has not been undertaken. METHODS: Basal and histamine-stimulated acid output were measured in chronic fistula rats after administration of injectable and volatile anaesthetics frequently used in studies of gastric secretion in anaesthetized animals. With the exception of ether, for which recovery is very rapid, sedating rather than full anaesthetic doses were used. RESULTS: Chloralose (40 mg/kg) had no significant effect on gastric secretion. Pentobarbitone (25 mg/kg) inhibited basal and histamine-stimulated acid output, but the effect was relatively short-lived and secretion returned to control levels after 2 h. Urethane (750 mg/kg) markedly inhibited basal acid output and abolished the secretory response to histamine given 15 to 60 min later. The effects of urethane on acid secretion persisted for the entire 3 h duration of experiments, during which time basal acid output declined to levels observed in fully anaesthetized rats given 1.5 g/kg. Full anaesthesia with ether for 60 min also caused profound inhibition of basal secretion and, like urethane, abolished the effect of histamine despite the fact that the animals recovered consciousness within 5 min. CONCLUSIONS: The differential activity of anaesthetics and profound antisecretory activity of ether and urethane should be taken into account when studying gastrointestinal function and mucosal ulceration in anaesthetized animals.