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Biomedical subjects

C Bernard

Publications and source records attributed to C Bernard.

At least 19 recordsLinked to original sources
PubMed1992

Viral co-infections in human papillomavirus-associated anogenital lesions according to the serostatus for the human immunodeficiency virus.

In HIV-infected men, human papillomavirus (HPV) infection is strongly linked with the development of anogenital lesions but is not a sufficient factor to explain the neoplastic transformation of such lesions. We investigated the association between HPV and herpesvirus infections in penile and anal lesions from 54 HIV-seronegative and 54 HIV-seropositive men by means of colposcopy, histopathology and in situ hybridization. Our patients showed condyloma acuminata (39%), papular warts (35%) and macular warts (26%). High-grade lesions were predominant in the HIV+ men, whereas low-grade lesions were more frequent in the HIV- men. In the HIV+ group, potential oncogenic HPV were the most frequently detected (83.4%) whereas the "low-risk" HPV were found chiefly in HIV- men (62.1%). The CD4 number was lower in patients showing "high-risk" HPV than in men showing lesions without HPV or with non-oncogenic HPV. HPV types 6/11 were found mainly associated with koilocytosis or with AIN(PIN)I. Oncogenic HPV were more often detected in AIN(PIN)II-III. The herpesviruses DNA detection revealed a higher prevalence of HSVI and -2 than CMV and EBV in the studied biopsies. The frequency of HSV and CMV detection was higher in the HIV+ than in the HIV- men. A link was found between the "high-risk" HPV and the CMV detection whatever the population considered. The detection in HPV lesions of other sexually transmitted viral agents could therefore represent an important means of preventing progression of the anogenital disease, especially in immunosuppressed patients.

Anus Diseases↗
PubMed1992

Characterization of the genes encoding phycoerythrin in the red alga Rhodella violacea: evidence for a splitting of the rpeB gene by an intron.

The phycobilisome of the eukaryotic unicellular red alga Rhodella violacea presents in some respects an organization that is intermediate between those of the homologous counterparts found in cyanobacteria (the putative chloroplast progenitor) and more advanced, pluricellular red algae. This suggests evolutionary relationships that we investigated at the genome level. The present work describes the sequences of two rhodophytan phycobilisome genes, rpeA and rpeB. These chloroplast genes encode the alpha and beta subunits of phycoerythrin, the major component of the light-harvesting antennae and one of the most abundant cellular proteins in these algae. The amino acid sequences deduced from both rpeA and rpeB present strong homologies with those previously reported for phycoerythrin subunits of cyanobacteria, rhodophyta, and cryptomonads. The main difference with the corresponding cyanobacterial genes was the unexpected occurrence of an intervening sequence that split rpeB into two exons. This intervening sequence presents characteristics of group II introns but lacks several structural domains. Transcriptional analyses showed that the two rpe genes are cotranscribed and that the major RNA species detected corresponds to a mature mRNA lacking the intron. As the phycobiliproteins form a group of closely related polypeptides in cyanobacteria and rhodophyta, the molecular events affecting the corresponding genes, such as the rpeB intron, may be a clue to elucidate some aspects of the molecular processes involved in the evolution of plastid genes.

Amino Acid Sequence↗
PubMed1992

Cooperative effects of bombesin, substance P and methacholine on the release of intestinal neurotensin in rats.

The secretion of ileal neurotensin (NT) results from events occurring at the apical and basal side of the N-cells. The hypothesis of a functional relationship between cholinergic and peptidergic neurones with the N-cell was investigated in the present study utilizing the isolated vascularly perfused rat ileum. Intraarterial methacholine (MC, 10(-4) M) evoked a prompt and well sustained release of NT in the portal effluent (plateau value at 500% of basal). This effect was dose-dependent over the range of 10(-6) M to 10(-4) M. Bombesin (B) provoked a dose-dependent peak secretion of NT (800% of basal at 10(-7) M) followed by a rapid return to almost basal levels. The B-induced NT release remained unaltered upon 10(-6) M tetrodotoxin (TTX) or 10(-5) M atropine infusion. Substance P (SP) potently stimulated the release of NT. The maximal response, consisting of a sustained secretion, was observed at a concentration of 10(-7) M (350% of basal) while 10(-6) M SP induced a transient release. TTX or atropine did not reduce significantly the SP-induced secretion of NT. Neurokinin A and B did not increase NT concentrations in the portal effluent. B synergistically increased the secretion of NT induced by SP. Atropine or TTX did not modify the effect of combined SP and B infusion. MC potentiated the release of NT induced by B but not that evoked by SP. Combined infusion of SP, B and MC produced the largest output of NT. In conclusion, B, SP and MC are strong stimulants of NT release in rats. In addition, the cooperative effects of these transmitters argue in favor of a complex functional relationship between the intramural nervous network and the intestinal N-cells in rats.

Animals↗
PubMed1992

Activity distribution of seven digestive enzymes along small intestine in calves during development and weaning.

Ten groups of calves were used to study the changes in activity levels and distribution of seven hydrolases in the intestinal mucosa during development and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity of lactase and an increase in that of aminopeptidase N, maltase, and isomaltase. The distribution of all these enzymes along the small intestine was slightly influenced by age but not at all by weaning.

Animals↗
PubMed1992

Early-life patterns of plasma gut regulatory peptide levels in calves. Effects of age, weaning and feeding.

1. The effects of age, weaning and feeding on the release of seven gut regulatory peptides [gastrin, cholecystokinin (CCK), secretin, vasoactive intestinal peptide (VIP), pancreatic polypeptide (PP), motilin and somatostatin] were studied in calves either exclusively milk-fed between birth and 91 days (P group) or weaned between 22-56 days of age (R group). 2. During the first 3 weeks, the basal plasma immunoreactive levels increased with age for secretin, CCK and PP, decreased for gastrin, motilin and somatostatin and were unaffected for VIP. The changes were particularly rapid for somatostatin and gastrin. After 3 weeks, no significant trend was observed with age in the P group. 3. Weaning resulted in an increase of basal gastrin, CCK, PP and VIP and in a decrease of basal secretin and somatostatin. 4. In the P group, the morning meal was followed 1 hr later by an increase of gastrin and CCK, and by a fall of secretin, PP, motilin and somatostatin, but no significant effect was observed in VIP. Weaning resulted in a reduction of the differences between the fasting and the post-feeding values. 5. These changes suggest a large involvement of endocrine cells in the adaptation of gut tissues, secretions and motility at birth, during the maintenance at the pre-ruminant stage and at weaning.

Aging↗
PubMed1992

Plasma and tissue levels of digestive regulatory peptides during postnatal development and weaning in the calf.

Changes in the concentrations of cholecystokinin, gastric inhibitory peptide, gastrin, motilin, pancreatic polypeptide, secretin, somatostatin, and vasoactive intestinal peptide in calf plasma and antral, duodenal and/or pancreatic tissues were assessed by radioimmunoassay during postnatal development and after weaning in 50 male Holstein-Friesian calves (randomly distributed into 10 groups of 5 animals each). The calves in the first group were killed at birth while those in 6 other groups were colostrum-fed for 2 days and then milk-fed until 7, 28, 56, 70 or 119 days of age. Those in the remaining 3 groups were given the same diets until day 28, were then weaned between day 29-56, and slaughtered on days 56, 70 or 119. In milk-fed animals, changes in plasma and tissue concentrations of almost all digestive regulatory peptides were observed during the 1st month of postnatal life, especially at day 2. Weaning was accompanied by variations in the plasma concentrations of somatostatin, secretin, gastrin, pancreatic polypeptide and gastric inhibitory peptide but not by any apparent change in peptide tissue concentrations (except VIP in the duodenum). Thus, the variations in tissue concentrations are primarily age-related, while plasma concentrations were modified by age and weaning.

Aging↗
PubMed1992

Secretion of endolymph by the isolated frog semicircular canal.

Secretion of endolymph is localized in some structures of the inner ear, namely the stria vascularis in the cochlea and the dark cells in the vestibule and in the lower vertebrate inner ear. In isolated semicircular canal it is possible to study separately the endolymphatic composition in the ampulla, which contains the dark cells, and in its non-ampullar part, which is devoid of these cells. Further, in vitro preparation of the semicircular canal provides access to both faces of the epithelium so that different agents can be applied separately to the apical or to the basolateral membranes of the epithelium. In this structure, the following results were obtained: i) in vitro, the semicircular canal secreted a K-rich, positively polarized fluid; ii) this fluid was secreted only in the ampulla of the semicircular canal; iii) the secretion of endolymph was dependent on basolateral Na+, K(+)-ATPase, inhibited by ouabain, and basolateral Na-K-Cl co-transporter, inhibited by bumetanide; iv) approximately 60% of luminal Na absorption occurred across a luminal Na channel inhibited by amiloride; v) the permeability of the paracellular pathway of the semicircular canal epithelium was 7.10(-7) cm/s. These results indicate that endolymph secretion involves basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter. An Na channel has been shown at the apical membrane.

Animals↗
PubMed1992

Role of cyclic nucleotides and calcium in the nutrient-induced release of cholecystokinin-like immunoreactivity in rats.

1. This study was undertaken with an isolated vascularly perfused rat duodenojejunal preparation to investigate the mechanisms of the release of cholecystokinin measured by immunoassay (cholecystokinin-like immunoreactivity, CCK-LI). 2. Intra-arterial infusion of forskolin (2-20 microM) evoked a prompt and well-sustained secretion of CCK-LI which was increased to a mean value of 600% of basal with the highest dose tested. 3-Isobutyl-1-methylxanthine (IBMX) (10(-6)-10(-4) M) stimulated the secretion of CCK-LI (maximal increase of 400% of basal at 10(-4) M). 3. Intra-arterial infusion of beta-phorbol 12-myristate 13-acetate (5 x 10(-7)-5 x 10(-6) M) and calcium ionophore A23187 (10(-6)-10(-5) M) alone or in combination provoked only a transient increase in the release of CCK-LI. 4. Luminal infusion of a 5% ovalbumin hydrolysate solution produced an immediate release of CCK-LI followed by a well-sustained secretion at 580% of basal. Intra-arterial infusion of IBMX (10(-5) or 10(-4) M) in combination with luminal peptone induced a release of CCK-LI which was equal to the sum of the CCK responses evoked by IBMX and peptone given separately. 5. Intra-arterial infusion of EGTA (2 mM) abolished the forskolin- and peptone-induced CCK secretion while luminal EGTA (2 mM) had no inhibitory effect. Verapamil (5 x 10(-5)-10(-4) M) or nifedipine (10(-5)-5 x 10(-5) M) inhibited the peptone-evoked CCK secretion. A high concentration of trifluoperazine (10(-4) M) strongly reduced the release of CCK-LI induced by intraluminal peptone while 10(-5) M was ineffective. 6. It is concluded that the peptone-induced secretion of CCK-LI involves a cyclic AMP-dependent mechanism and the activation of calcium channels possibly located at the basolateral side of the CCK cell.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Early-life patterns of plasma gut regulatory peptide levels in calves: effects of the first meals.

The effects of the first meals on the release of seven gut regulatory peptides were studied in newborn calves fed colostrum either at serial intervals during the first day of life or at 28 h only. Fasted animals showed no significant variation of plasma peptides until the first feed, except for somatostatin, which peaked at 4-5 h and declined thereafter. As assessed before and 1 h after feeding, the first meal tended to induce rises in plasma gastrin, cholecystokinin and pancreatic polypeptide, while the other peptides were unaffected. Repeated colostrum feeds induced marked increases in plasma gastrin, cholecystokinin, secretin and vasoactive intestinal peptide from 10 h on. Pancreatic polypeptide was transiently increased from 4 to 16 h. Feeding was followed by a transitory reduction of plasma somatostatin and by a prolonged decrease of plasma motilin. We conclude that colostrum feeding potently modulates the release of several regulatory peptides shortly after birth in calves. These responses may be important for the adaptation of gut growth, secretions and motility to food ingestion in the neonatal period.

Animals↗
PubMed1992

Activated macrophages depress the contractility of rabbit carotids via an L-arginine/nitric oxide-dependent effector mechanism. Connection with amplified cytokine release.

Inflammatory mediators released by macrophages (M phi) are believed to be involved in septic vasoplegia. To investigate the effect of M phi on vascular reactivity, excised rabbit carotids were exposed intraluminally either to peritoneal rabbit M phi, activated by 18 h of incubation with 1 microgram/ml lipopolysaccharide, or to the supernatants (SPN) derived from them. The contractile responses to phenylephrine (PE, 10(-6) M) were determined by measuring changes in diameter using an ultrasonic microdimensiometer 1, 2, and 3 h after the first control contraction. In control arteries (n = 12), PE-induced contractions were, respectively, 102.9 +/- 3.3%, 95.2 +/- 4.1%, and 89.7 +/- 3.8% of the first contraction, after 1, 2, and 3 h. Activated M phi significantly reduced PE-stimulated contractions after as little as 1 h of carotid exposure (percentage of controls at 1, 2, or 3 h: 74.1 +/- 5.6, 57.2 +/- 5.2, and 34.2 +/- 5.6, n = 10, P less than 0.001). The activated macrophage-derived SPN took longer to diminish carotid contractility than the M phi themselves, and became significant only after 2 h. The greater effect of M phi might be due to cooperation between M phi and vascular cells, as suggested by the amplified interleukin-1 release observed after M phi infusion. The presence of the endothelium partially protected carotid contractility from depression by activated M phi. Extraluminal addition of NG-monomethyl-L-arginine, an inhibitor of nitric oxide synthesis prevented this depression in arteries with or without endothelium. No products of the oxidative pathway of L-arginine were detected in rabbit activated M phi. These results suggest that activation of this pathway in smooth muscle cells seems to be involved in vascular hypocontractility.

Animals↗
PubMed1992

[Study by in situ hybridization of the prevalence of herpes virus as cofactors of the tumoral development of papillomatous lesions of the anogenital region in seropositive and seronegative men against HIV].

Infection with specific types of HPV has emerged as necessary but not sufficient factor in the neoplastic transformation of anogenital condylomas. Some viruses (HIV, Herpes viridae: HSV, CMV, EBV) might act as cofactors in the neoplastic changes and cancer. To study the prevalence of these viral pathogens in anogenital lesions, biopsies were obtained from HIV seropositive or seronegative men and tested using in situ hybridization technique. Infection by "high risk" HPV, HSV and CMV are facilitated in patients immunocompromised by HIV. Presence of CMV is more frequent in high risk HPV-induced lesions than in low risk HPV lesions.

Anus Neoplasms↗
PubMed1992

[Medulloblastoma in children. Prognostic incidence of vascular hyperplasia, coagulation necrosis and postoperative clinical state on survival].

Fifty consecutive children with cerebellar medulloblastoma were operated on May, 1971 to December, 1988. At 5 and 10-years, actuarial survival rates were respectively 46% & 42%. To determine prognostic factors, various clinical and histological features were analysed: multivariate analysis showed that increased vascularity, coagulative necrosis, and postoperative clinical status have a significant influence survival. When necrosis and/or increased vascularity were present (H+), the 5-year survival rate was 17%, whereas it was 70% when absent (H-) (p less than 0.0001). Postoperative clinical status was described as poor when neurological symptoms such as vigilance or vegetative disorders, akinesia, hypotonia, apragmatism, mutism and emaciation were associated; the 5-year survival rate was 10% in the presence of such deficits (C+) and 55% in their absence (C-) (p = 0.0002). From these results, 2 distinct groups were identified: Group 1: 23 patients without pejorative factors (H- and C-); 5 and 10-year survival rates were 80%. Group 2: 27 patients with one or two pejorative factors (H+ and/or C+); 5 and 10-year survival rates were respectively 18% and 12% (p. less than 0.0001). From our experience, it appears that histology and postoperative clinical status can be early predictors of patient outcome, since neurosurgical and radiation therapy techniques have been largely optimized. These factors could be the basis for developing adapted treatment protocols.

Actuarial Analysis↗
PubMed1991

Propagation of parallel fiber volleys in the cerebellar cortex: a computer simulation.

We have studied the dynamic changes occurring during the propagation of active volleys through the parallel fiber (PF) tract in a portion of molecular layer of the cerebellar cortex, by means of a realistic computer simulation of the fibers (random distribution of PF origin; correlation between length and conduction velocity throughout depth). Surface electrical stimulations as well as mossy fiber stimulations of the PFs were mimicked. From a quantitative analysis of the propagation of the different types of volleys it appears that the constraints enforced by the morphological and functional characteristics of the PFs lead to an important spatial and temporal dispersion of the action potentials during their displacement along the folium. In particular, the time relationship between activity in the deep and superficial fibers as well as the number and location of active fibers at a given time (i.e. locus) will considerably vary during propagation. Moreover, in the case of a mossy fiber stimulation, there exists a striking asymmetry of the volleys travelling on each side of the site of stimulation. Therefore any information coded by the conjunctive activation of more than a few parallel fibers will be spatially and temporally dispersed in such a manner that successive postsynaptic Purkinje cells will receive very different combinations of inputs. This seems in favor of the hypothesis that these neurons function as coincidence detectors.

Action Potentials↗
PubMed1991

Release of ileal neurotensin in the rat by neurotransmitters and neuropeptides.

To investigate the functional relationship between the enteric nervous system and the intestinal neurotensin (N) cells, the release of neurotensin (NT) was measured upon vascular 8-min infusion periods of various neurotransmitters and neuropeptides in an isolated vascularly perfused rat jejunoileum. NT-like immunoreactivity (NT-LI) was measured with an antiserum that specifically recognizes intact NT. The cholinergic agonists methacholine and carbachol produced a strong release of NT-LI (250% and 700% of basal, respectively at 10(-5) M). The infusion of a lower dose (10(-7) M) was less effective in both cases. The nicotinic receptor agonist DMPP (10(-4) M) had no significant effect on NT-LI release. Norepinephrine (10(-6) M) produced a moderate and well-sustained secretion of NT (200% of basal). Infusion of higher doses of these neurotransmitters dramatically increased the arterial pressure. G-amino-n-butyric acid (GABA), histamine, serotonin and dopamine administered at final concentrations up to 10(-5) M had no effect on NT-LI release. In contrast, gastrin-releasing peptide and bombesin induced a dose-dependent transient increase of portal NT-LI (maximal value at 10(-7) M: 1000% of basal) followed by a rapid return to near basal values. Substance P (10(-7) M) evoked a prompt release of NT-LI with a peak at 600% of basal followed by a decline to 200% of basal at the end of the session. Leu-enkephalin and calcitonin-gene-related-peptide (CGRP, 10(-7) M) produced a small rise in portal NT-LI, while Met-enkephalin, dynorphin, vasoactive intestinal peptide (VIP), galanin, neuropeptide Y (NPY), peptide histidine isoleucine (PHI), neuromedin U and thyrotropin releasing hormone (TRH) had no stimulatory effect. Our results indicate that additionally to the secretion of NT induced by cholinergic agents and bombesin, substance P and to a lesser extent Leu-enkephalin are capable of stimulating NT release in the rat.

Animals↗
PubMed1991

Antidiuretic hormone stimulation of adenylate cyclase in semicircular canal epithelium.

Basal adenosine 3',5'-cyclic monophosphate (cAMP) content and the modulation of its production were studied in the frog's semicircular canal epithelium. This epithelium secretes endolymph, a K(+)-rich, positively polarized fluid. The basal cAMP content measured by microradioimmunoassay was 244 +/- 14.2 fmol/structure per 5 min (n = 30). This content was increased about 8 times by 10(-5) M forskolin. Vasotocin, the frog antidiuretic hormone, increased the cAMP production by factors of 1.3 and 3.3 at concentrations of 10(-8) M and 10(-7) M, respectively. This stimulatory effect of vasotocin was blunted by the addition of alpha 2-adrenergic agonists, such as 10(-8) M-10(-5) M norepinephrine, in the presence of 10(-5) M propranolol, or 10(-5) M clonidine. Prostaglandin E2 at a concentration of 10(-8) M, which did not affect the cAMP production, did not modify the response to vasotocin. Glucagon (10(-6) M), calcitonin (10(-6) M), and parathyroid hormone (10 units/ml) did not affect the cAMP content. Prostaglandin E2 (10(-7) M) and the beta-adrenergic agonist isoproterenol (10(-6) M) stimulated the cAMP production by a factor of 1.6. These results indicate that the frog semicircular canal is a target of both vasotocin and catecholamines and that catecholamines through alpha 2-receptors modulate vasotocin-induced cAMP generation. Further, this interaction might be of physiological relevance in the modulation of ion transport in this structure.

Adenylyl Cyclases↗
PubMed1991

Characterization of two insertion sequences, IS701 and IS702, from the cyanobacterium Calothrix species PCC 7601.

We describe the characterization of two insertion elements, IS701 and IS702, isolated from Calothrix species PCC 7601. These insertion elements were cloned from spontaneous pigmentation mutants. Both show the characteristics of typical bacterial insertion sequences, i.e. they present long terminal inverted repeats and they duplicate target DNA upon insertion. These elements share no homology with the only other cyanobacterial insertion sequence described so far, IS891. At least 15 copies of IS701 and 9 copies of IS702 were detected by hybridization experiments in the Calothrix 7601 genome. Their occurrence in several cyanobacterial strains is also reported.

Amino Acid Sequence↗
PubMed1991

Bombesin potentiates taurocholic acid-induced neurotensin release in rats.

The hypothesis of synergistic effects between luminal stimulants and the intramural neural network in the control of intestinal neurotensin (NT) release was investigated with an isolated vascularly perfused rat jejuno-ileum. Luminal administration of low doses of taurocholic acid (TC; 1, 5, and 10 mM) provoked only a small increase in NT-like immunoreactivity (NT-LI) in the portal effluent (50%, 100%, and 130%, respectively, above basal). Increasing the concentration of TC to 20 mM induced a strong and sustained release of NT-LI (700% above basal). The arterial infusion of bombesin (BOM; 10(-9) M) induced only a transient rise in NT-LI levels (200% above basal), with a rapid return to basal values. In contrast, 10(-9) M BOM synergistically enhanced NT-LI responses induced by 10 mM TC; the integrated response of NT-LI release was 3.2-fold higher than the sum of responses to 10(-9) M BOM and 10 mM TC alone. These cooperative effects were apparent with 10(-10) M BOM and TC concentrations over the physiological range 1-10 mM. Neither tetrodotoxin (10(-6) M) nor atropine (10(-5) M) was able to modify this synergy. Substance-P and methacholine, two other NT secretagogues, did not potentiate the TC-induced NT responses. In conclusion, BOM potentiated the release of NT induced by TC, thus suggesting that bombesinergic neurons, among other stimulatory neurons of the enteric nervous system, may modulate the sensitivity of N-cells to luminal stimulants.

Animals↗