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Biomedical subjects

H Daniel

Publications and source records attributed to H Daniel.

At least 127 records · Page 7Linked to original sources
PubMed1988

The effect of Escherichia coli STa enterotoxin and other secretagogues on mucosal surface pH of rat small intestine in vivo.

The mucosal surface pH of rat small intestine was measured in vivo. The surface pH in the normal jejunum was 6.20 +/- 0.02 (67) and 7.00 +/- 0.05 (5) in the ileum. Escherichia coli STa toxin induced a rapid and reversible alkalinization of both jejunal and ileal mucosae to a pH of 6.91 +/- 0.08 (10) and 7.67 +/- 0.06 (5) respectively. The synthetic ST analogue, STh-(6-19), had an effect identical to native STa toxin on jejunal surface pH. Theophylline (20 mM) maintained the STa-elevated jejunal surface pH after toxin removal but had no effect on untreated tissue. 8-Bromo cyclic GMP resembled STa by causing similar mucosal alkalinization in the jejunum; 8-bromo cyclic AMP, forskolin and cholera toxin individually had considerably smaller effects on surface pH, although combining forskolin or cholera toxin with theophylline resulted in alkalinization of the jejunal mucosa to a pH of 6.92 +/- 0.03 (5) and 6.76 +/- 0.04 (4). These results indicate that cyclic-GMP-dependent secretory processes are more capable of inducing surface pH changes than those dependent on cyclic AMP. The ability of STa to alter mucosal surface pH makes it a useful tool to investigate the microclimate hypothesis for weak electrolyte absorption.

Animals↗
PubMed1988

Persistent reduction of Purkinje cell inhibition on neurones of the cerebellar nuclei after climbing fibre deafferentation.

The long lasting effects of inferior olive (IO) destruction were studied in rats treated with 3-acetylpyridine two years before. The activities of the Purkinje cells (PCs) and of their target neurones in the cerebellar nuclei (ECNs), were investigated and compared to those of a group of non-treated rats. Our results show that long-term deafferented PCs recovered a mean firing frequency similar to that of the controls while the ECNs discharge is enhanced. Furthermore, the cryodestruction of the cerebellar cortex produces a significant release of the ECNs firing in the control rats but not in the poisoned animals. Thus, it appears that IO destruction induces a permanent impairment of the inhibitory control exerted by the PCs on the activity of their target neurones.

Afferent Pathways↗
PubMed1987

Release of cerebellar inhibitory activity by partial destruction of the inferior olive with kainic acid in rat.

Partial destruction of the neurones of the inferior olive was obtained by local ionophoretic injection of kainic acid. Complex spike discharges of the Purkinje cells are suppressed 2-3 h after application of the drug. The metabolic activity increases in the region of the cerebellar nuclei within 2 h and persists for 3 days following the kainic acid injection. The increase is only observed in those parts of the cerebellar nuclei receiving terminals from the Purkinje cells deafferented of the climbing fibres. No changes were detected when the injection affected only the underlying reticular formation.

Action Potentials↗
PubMed1987

[Intestinal liberation and resorption of monosaccharides from carbohydrates of different degrees of polymerization. I. Relation between intestinal hydrolysis of carbohydrates and resorption of monosaccharides].

The study was designed to compare the intestinal absorption of monosaccharides from carbohydrates of different chain length. Furthermore, a correlation between the efficiency of hydrolysis of the polymers and the efficiency of the intestinal absorption was expected to be established. Glucose, the disaccharides maltose and sucrose and the polysaccharides maltodextrin DE 20 , maltodextrin DE 5 and starch were employed as substrates. The whole small intestines of anaesthetized rats were perfused in situ for 60 min with 0.5% solutions of these substrates in an open perfusion system. Initially 3-minute fractions of the perfusion medium, later 10-minute fractions were collected. The parameters determined were: secretion of pancreatic alpha-amylase activity, substrate hydrolysis (by alpha-amylase and by disaccharidases of the brush border membrane), intestinal absorption of the monosaccharides. alpha-amylase activity was significantly higher when the perfusion was carried out with starch solution. The possibility is discussed that this high-polymer substrate might stimulate the pancreas to an elevated alpha-amylase secretion. The highest rate of hydrolysis (45 mumol glucose/min) was determined from maltose as a substrate. The cleavage of the high-polymer substrates was less intensive. The hydrolysis of starch was limited by the capacity of the alpha-amylase, that of the sucrose by low activity of the saccharose. Absorption of glucose was more effective from the maltose solution than from the glucose solution. To understand this phenomenon, an additional "hydrolases-related transport system" could be taken into consideration. Glucose absorption from maltodextrin DE 20 was less effective than might have been expected from the rate of hydrolysis. This fact might possibly be explained by an inhibitory effect of oligosaccharides of chain length 4-10, contained in relatively high amounts in maltodextrin DE 20.

Animals↗
PubMed1987

The interposito-rubrospinal system. Anatomical tracing of a motor control pathway in the rat.

The cerebello-rubromotor pathway, impinging on both spinal and facial motor nuclei, has been traced in the rat, using the bidirectional transport of horseradish peroxidase-wheat germ agglutinin conjugate. After injection of the tracer in the red nucleus (NR), retrograde labelling shows a topical arrangement of the cerebellorubral connection. The nucleus lateralis projects to the parvocellular NR (NRp) and the nucleus interpositus to the magnocellular NR (NRm). The nucleus interpositus anterior (NIA) reaches the entire NRm and this projection is topographically arranged: the medial NIA sends fibres ventrally, the lateral NIA dorsally. The medial two-thirds of the nucleus interpositus posterior (NIP) project only to the medial aspect of the NRm, with no apparent organization. No connection has been found between the lateral third of NIP and the NRm. After injection of the tracer in the spinal cord or the nucleus of the facial nerve, retrograde labelling is observed almost throughout the entire caudorostral extent of the NR, although labelling is more scant in NRp than in NRm. Rubrospinal and rubrofacial projections are somatotopically arranged in the dorsoventral direction: ventrolateral regions of NR reach the lumbar cord, medioventral regions the lower cervical levels, intermediary regions the upper cervical levels and finally the dorsalmost part of the NR projects to the nucleus of the facial nerve. After injection of the tracer in the cerebellar nuclei, anterograde labelling in the NR shows that interpositorubral connections determine two subregions in the NR: a lateral one under the exclusive control of the NIA, and a medial one under the control of both NIA-NIP afferents. It confirms in addition the topography of the NIA-NRm projection and shows the preponderant participation of the NIA afferents to the interpositorubral connection. Thus, it appears from our results that the cerebellorubral arrangement matches, to a great extent, the "rubromotor" efferent organization.

Animals↗
PubMed1987

Comparison of hydrolases, peroxidase and protease inhibitors in bronchoalveolar fluid from Macacus cynomolgus and human controls.

1. Serial bronchoalveolar lavages were performed on a subhuman primate (Macacus cynomolgus) in order to give an experimental model for silicosis. 2. We have measured glycosidases, proteases, peroxidase and antiproteases of the BAL fluids from seven normal monkeys. 3. The results obtained were similar to those found in human control BAL fluids. 4. For monkeys, the repetition of the bronchoalveolar procedure does not seem to have an important influence on the values obtained. 5. The present results will now permit sequential follow up studies during the course of experimental silicosis.

Animals↗
PubMed1986

The cerebellorubral projection in the rat: retrograde anatomical study.

The cerebellorubral projections have been studied in the rat using the retrograde transport of horseradish peroxidase-wheat germ agglutinin conjugate. The lateral cerebellar nucleus projects to the parvocellular red nucleus (RN), the anterior (NIA) and posterior (NIP) interposed nuclei project to the magnocellular RN. Whereas the projections from the NIP are limited to the medial aspect of the RN, those from the NIA extend throughout the magnocellular RN. NIA-RN projections are topographically arranged: the medial NIA projects ventrally, the lateral NIA projects dorsally. Functionally, this differential distribution seems to fit the hindlimb-forelimb areas of origin of the rubrospinal tract.

Animals↗
PubMed1986

Long term modification of rubral activity after inferior olive destruction.

The long term effects of the inferior olive degeneration on red nucleus activity were studied in the rat. The animals were injected with 3-acetylpyridine to produce a pharmacological destruction of the inferior olive and were then used for acute experiments at 1-2, 5-7, 14-18, 29-37, 81-110 and 236-255 days later. After degeneration of the inferior olive, there was an 'initial period' lasting for a few days, characterized by a low discharge frequency of the red nucleus neurones. A 'period of adaptation' followed during the first month, characterized by a slow recovery towards the control firing rates of the rubral units. Nevertheless, the temporal distribution of the discharges was not recovered since the firing became organized in a bursting activity. From 1 up to 8 months, the normal unit activity was not restored. The hypothesis is advanced that the suppression of the inferior olive which increases the cerebellar inhibition, produces a consequent disfacilitation of red nucleus activity which persists for a few days. Then at increasing survival times, a progressive compensation takes place without a real restoration of the initial rubral activity.

Action Potentials↗
PubMed1986

[Mechanisms of intestinal absorption of nutrients].

The nutrient uptake from the intestinal lumen into the distributing blood circulation is mediated by the epithelial cell of the small intestine. The transfer process through this distinctly polar cell consists of three partial events: entrance of substances through the brush-border membrane, traversal of a metabolic active intracellular space and exit through the baso-lateral membrane. The fundamental transfer mechanisms--simple diffusion, facilitated diffusion, antiport and symport systems, electroneutral and electrogenic processes--are described. The significance of nutrient metabolization for transport processes is discussed: proton secretion by the epithelial cell coupled to the glucose and lactate metabolization is quoted as an illustration. The "acid microclimate" resulting from this proton secretion on the mucosal surface has a significant influence on weak-electrolyte absorption. This effect was clearly demonstrated for in vitro uptake of nicotinic acid into the intestinal tissue. It can be assumed that--similar to the role of a Na+-gradient--the proton gradient on the surface of absorptive epithelia is highly significant as a driving force of nutrient absorption.

Animals↗