Species-dependent features of Dogiel type II neurones in the mammalian enteric nervous system.

Although autonomic gastrointestinal reflex movements, which occur in all mammalian species, have been described almost a century ago, little was known on the mechanisms underlying this behaviour. Recently, however, intrinsic primary afferent neurones, functioning as the first relay in the reflex arches embedded in the intestinal wall, have been identified in the guinea pig ileum. In guinea pig, such neurones display a Dogiel type II morphology and behave electrophysiologically as slow AHP neurones. In other gastrointestinal regions, in both guinea pig and rat, Dogiel type II cells are also encountered, but the strong correlation with slow AHP neuronal features seems less strict. In large mammals, a correlation of the cellular morphology with intracellular el ectrophysiological recordings has only been obtained in the pig small intestine. Surprisingly, in these experiments aberrant electrophysiological behaviour of Dogiel type II neurones is even more striking since the majority of these cells display electrophysiological features considered typical of S neurones. Furthermore, in those rare cases in which a slow afterhyperpolarization (AHP) could be recorded in porcine Dogiel type II cells, its amplitudes were negligible. This has led us to the conclusion that the differences in electrophysiological behaviour of neurones with comparable morphology in different species are most probably due to the modulating influence of the neurotransmitter substances present. This seems to be the most likely hypothesis in view of the considerable differences in neurotransmitter content of neurones with comparable functions throughout the species.     

Comparison of the teratogenic properties manifested in BALB c mice, by diphenylhydantoin and deuterated diphenylhydantoin

The aim of this study was to investigate the role of an arene oxide pathway in the teratogenicity displayed by DPH, a highly effective antiepileptic agent. This approach was carried out by comparing the teratogene potential of DPH and of p2-H-DPH administrated at days 8, 9 and 12 of gestation. The present findings support the hypothesis that substitution of protium by deuterium at the para position of one of the phenyl rings, which favours an arene oxide pathway, causes an increase in some to the teratogenic effects of DPH.     

Mutagenicity of some heterocyclic amines in Salmonella typhimurium with metabolic activation by human red blood cell cytosol.

Purified human red blood cell cytosol was used to activate the heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) into mutagenic intermediate(s) in the Salmonella test. The liquid preincubation method in the presence of strain TA98 was utilized. In order to understand the mechanism involved in this metabolic activation, some modulators were incorporated in the medium. The results suggest that an oxygenated hemoprotein, probably oxyhemoglobin, is involved in the activation into genotoxic intermediate(s).     

Positioning and maintenance of embryonic body wall muscle attachments in C. elegans requires the mup-1 gene

As part of a general study of genes specifying a pattern of muscle attachments, we identified and genetically characterised mutants in the mup-1 gene. The body wall muscles of early stage mup-1 embryos have a wild-type myofilament pattern but may extend ectopic processes. Later in embryogenesis, some body wall muscles detach from the hypodermis. Genetic analysis suggests that mup-1 has both a maternal and a zygotic component and is not required for postembryonic muscle growth and attachment. mup-1 mutants are suppressed by mutations in several genes that encode extracellular matrix components. We propose that mup-1 may encode a cell surface/extracellular matrix molecule required both for the positioning of body wall muscle attachments in early embryogenesis and the subsequent maintenance of these attachments to the hypodermis until after cuticle synthesis.     

Absence of a prostaglandinic mediator in the lateral hypothalamic cardio-vascular inhibition.

The cardio-vascular inhibition elicited by electrical stimulation of the paraventricular nucleus in the lateral hypothalamus of anaesthesized and desafferentiated dogs is not linked with a mediator release like PGE. The effect of this biological agent is not registered in the isolated femoral artery of a receiver, after deviation by a cruised circulation of the arterial blood of a hypothalamic stimulated donor dog. Antipyretics, which are also prostaglandin-synthetase inhibitors, enhance the lateral hypothalamic reactions. As the thermoregulation centre is localized in the same region as the cardio-vascular inhibition centre and because lowering of temperature depends upon vasodilation and decrease in the general cellular metabolism, both functions of the paraventricular nucleus activity, a hypothesis is proposed that thermoregulation and cardio-vascular inhibition centres are a functional and anatomical unity.