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G Bertrand

Publications and source records attributed to G Bertrand.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for a direct stimulatory effect of cibenzoline on insulin secretion in rats.

The effect of cibenzoline succinate, a new antiarrhythmic agent, was studied on insulin secretion in rats. Experiments were performed both in vivo and in vitro using two preparations: the isolated perfused pancreas and isolated islets. In anaesthetized rats, cibenzoline was able to increase plasma insulin levels and to reduce glycaemia. These effects were observed at 1 mg/kg i.v. in fed rats and at 3 mg/kg i.v. in fasted rats. In the isolated pancreas perfused in the presence of a slightly stimulating glucose concentration (8.3 mM), cibenzoline (2 and 6 microM) elicited a progressive and sustained insulin response in a concentration-dependent manner. In the presence of a non-stimulating glucose concentration (4.2 mM), cibenzoline was ineffective at 2 microM and slightly increased basal insulin release at 6 microM. In isolated islets incubated with 8.3 mM glucose, cibenzoline (6 and 20 microM) caused a concentration-dependent stimulation of insulin release. It is concluded that cibenzoline stimulates insulin secretion by a direct action on pancreatic B cells in rats.

Animals↗
PubMed1992

Evidence for a direct inhibitory effect of PYY on insulin secretion in rats.

Peptide YY (PYY) has been shown to inhibit stimulated insulin secretion under in vivo conditions in the mouse, the rat, and the dog. In the present study, we investigated the effects of PYY on insulin secretion from the isolated perfused rat pancreas and isolated rat islets. In isolated pancreas perfused in presence of 8.3 mM glucose, PYY at 10(-10) and 10(-9) M, but not at 10(-8) M, inhibited insulin secretion. In the presence of 5.5 mM glucose, PYY (10(-9) M) did not modify basal insulin release but reduced the biphasic insulin response to arginine (10 mM). PYY also markedly reduced the pancreatic vascular flow rate; this effect was observed at all three concentrations tested in a dose-dependent manner. In isolated islets, glucose (15 mM)-stimulated insulin secretion was inhibited by PYY at 10(-7) M. We conclude that in the perfused rat pancreas, PYY inhibits insulin secretion and induces vasoconstriction without a causal relationship. In addition, our results on isolated islets suggest that the inhibitory action of PYY on insulin secretion is exerted through a direct islet action.

Animals↗
PubMed1992

Evidence for a glutamate receptor of the AMPA subtype which mediates insulin release from rat perfused pancreas.

1. The effect of L-glutamate has been studied on insulin secretion by the isolated perfused pancreas of the rat. The glutamate receptor subtype involved has been characterized. 2. In the presence of a slightly stimulating glucose concentration (8.3 mM), L-glutamate (5 x 10(-5)-4 x 10(-3) M) induced an immediate, transient and concentration-dependent insulin response. On the other hand, in the presence of a non stimulating glucose concentration (2.8 mM), L-glutamate (10(-3) M) did not modify the basal insulin secretion. 3. The three non-NMDA receptor agonists, kainate (10(-4)-10(-3) M), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA, 5 x 10(-5)-10(-4) M) and quisqualate (5 x 10(-6)-5 x 10(-5) M) all provoked a transient and concentration-dependent insulin response from pancreas perfused with 8.3 mM glucose. Compared with glutamate, kainate exhibited a similar efficacy, whereas AMPA and quisqualate elicited only a 3 fold lower maximal insulin response. In contrast, NMDA (10(-4)-10(-3) M) was ineffective. 4. An antagonist of non-NMDA receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 5 x 10(-5) M) totally prevented the stimulatory effect of L-glutamate (4 x 10(-4) M) and kainate (2 x 10(-4) M). In contrast, the NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine ((+) MK801) was without effect. 5. The insulin secretory effect of glutamate (4 x 10(-4) M) was not affected by atropine (3 x 10(-7) M) or tetrodotoxin (3 x 10(-6) M). 6. Quisqualate at a high maximally effective concentration (4 x 10(-4) M) inhibited glutamate (10(-3) M) or kainate (4 x 10(-4) M)-induced insulin release. 7. This study shows that L-glutamate stimulates insulin secretion in rat pancreas, by acting on an excitatory amino acid receptor of the AMPA subtype.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

Spontaneous spinal epidural hematoma causing paraplegia: resolution and recovery without surgical decompression.

Spontaneous spinal epidural hematomas are well-recognized but rare entities. The standard treatment for these hematomas has been prompt surgical evacuation. The authors report a case of a 76-year-old man who precipitously became paraplegic secondary to a spontaneous spinal epidural hematoma and then experienced the complete resolution of his neurological deficit and the hematoma. We conclude that conservative (nonoperative) management of spontaneous spinal epidural hematomas may be appropriate in those instances in which there is early and sustained neurological recovery confirmed by radiological resolution of the lesion.

Aged↗
PubMed1992

[A simplified terminology for abnormalities of the lumbar disks].

The terminology for abnormalities of the lumbar disk has always been a source of confusion. Recent advances in pathological studies have inspired the authors to propose a simple classification of common disk anomalies suitable not only for diagnostic radiologists but also for referring clinicians. Although the diagnosis of a few pathological entities will only be possible with specific imaging techniques, the proposed classification is appropriate for reporting observations from plain films, conventional tomograms, myelograms, discograms, computed tomography scans and magnetic resonance images. All lumbar disks can thus be classified into one or more of the following categories: normal, aging, scarred, ruptured and herniated. A disk herniation is defined as a localized exit of disk material beyond the limits of the original intervertebral space.

Adult↗
PubMed1992

[Bellini duct carcinoma or kidney collecting duct carcinoma].

The authors report a case of renal collecting duct carcinoma or Bellini duct carcinoma. This rare variety of renal carcinoma, which usually has a poor prognosis, is situated in the renal medulla and pyramid. It is composed of large cells similar to collecting duct cells and can be seen at a distance from the tumor. These cells are arranged in highly suggestive tubular, microcystic and papillary structures. These morphological data are compared with those reported in the literature.

Aged↗
PubMed1991

Adenosine-5'-O-(2-thiodiphosphate) is a potent agonist at P2 purinoceptors mediating insulin secretion from perfused rat pancreas.

1. The effects of a P2 purinoceptor agonist, adenosine 5'-O-(2-thiodiphosphate) (ADP-beta-S) have been studied on insulin secretion and flow rate of the isolated perfused pancreas of the rat. 2. In the presence of a moderately stimulating glucose concentration (8.3 mM), ADP-beta-S (4.95-495 nM) evoked a biphasic insulin response in a concentration-dependent manner. A comparison of relative potency between ADP-beta-S and adenosine 5'-triphosphate (ATP) showed that ADP-beta-S was 100 times more potent than ATP. On the other hand, in the presence of a non stimulatory glucose concentration (4.2 mM), ADP-beta-S (165 nM) did not modify the basal insulin secretion. 3. ADP-beta-S, at concentrations effective on insulin secretion and also at higher concentrations (1.65 and 16.5 microM), provoked an increase of the pancreatic flow rate in a concentration-dependent manner. 4. Our results show that ADP-beta-S is a potent insulin secretory P2 purinoceptor agonist. As it is resistant to hydrolysis it might be useful in studying the effect of activation of the P2 purinoceptor of beta cells on insulin secretion in vivo.

Adenosine Diphosphate↗
PubMed1991

The influence of gamma-aminobutyric acid on hormone release by the mouse and rat endocrine pancreas.

The present study was aimed at localizing gamma-aminobutyric acid (GABA) and its enzyme of synthesis, glutamic acid decarboxylase (GAD), in the mouse pancreas by immunocytochemical methods. The influence of GABA on hormone release was also studied with normal mouse and rat islets and the isolated perfused rat pancreas. Particular attention was paid to glucagon release to test a recent hypothesis suggesting that GABA mediates the still unexplained glucose-induced inhibition of glucagon release. GABA and GAD were identified only in islet cells and never in the exocrine tissue. Exogenous GABA, baclofen (agonist of GABAB receptors), muscimol (agonist of GABAA receptors), or bicuculline (antagonist of GABAA receptors) did not affect insulin and somatostatin release by isolated mouse or rat islets. GABA was also without effect on glucose-induced electrical activity in mouse B-cells. Glucagon secretion by mouse islets was only slightly inhibited (approximately 20%) by GABA. Since muscimol had a similar effect, and baclofen was ineffective, the inhibition by GABA probably involves GABAA receptor activation. Bicuculline, however, did not antagonize the inhibitory effects of GABA and muscimol, probably because the antagonist alone also decreased glucagon secretion. In contrast to GABA, low (3 mM) and high (20 mM) concentrations of glucose strongly inhibited (approximately 50-65%) glucagon release; this inhibition was not prevented by bicuculline. Similar results were obtained with the perfused rat pancreas; muscimol slightly inhibited glucagon release under various conditions, and bicuculline did not reverse the strong inhibition produced by 16.7 mM glucose. In conclusion, GABA does not affect insulin and somatostatin secretion, but inhibits A-cells, probably by acting on GABAA receptors. It is unlikely, however, that this small inhibitory effect can account for the inhibition of glucagon release produced by glucose.

Animals↗
PubMed1991

A simplified terminology for abnormalities of the lumbar disk.

The terminology for abnormalities of the lumbar disk has always been a source of confusion. Recent advances in pathological studies have inspired the authors to propose a simple classification of common disk anomalies suitable not only for diagnostic radiologists but also for referring clinicians. Although the diagnosis of a few pathological entities will only be possible with specific imaging techniques, the proposed classification is appropriate for reporting observations from plain films, conventional tomograms, myelograms, diskograms, computed tomography scans and magnetic resonance images. All lumbar disks can thus be classified into one or more of the following categories: normal, aging, scarred, ruptured and herniated. A disk herniation is defined as a localized exit of disk material beyond the limits of the original intervertebral space.

Aging↗
PubMed1990

P2 purinoceptor agonists stimulate somatostatin secretion from dog pancreas.

The effects of ATP and ADP structural analogues (2-methylthio ATP; alpha,beta-methylene ADP) on somatostatin secretion were tested in dogs. Insulin and glucagon secretion was also evaluated. Our experiments were performed in vivo and in vitro. In vivo, 2-methylthio ATP was infused directly into the pancreaticoduodenal artery of anesthetized dogs and blood was sampled from the pancreaticoduodenal vein. This ATP analogue (approximately 15 microM) immediately induced stimulation of both somatostatin and insulin secretion, which was accompanied by a slight reduction of glycemia. A delayed increase in glucagon output was observed. In vitro, using the isolated perfused dog pancreas uncinate process, alpha,beta-methylene ADP, a stable ADP analogue (16.5 microM), was infused in the presence of a substimulating glucose concentration (4.2 mM). Under these conditions, alpha,beta-methylene ADP immediately induced the stimulation of somatostatin secretion without affecting basal insulin and glucagon secretion. In conclusion our results suggest the presence of P2 purinoceptors on pancreatic somatostatin secreting cells.

Adenosine Diphosphate↗
PubMed1990

The influence of sodium omission on alpha 2-adrenergic inhibition of insulin release by mouse islets.

The mechanisms by which activation of alpha 2-adrenoceptors inhibits insulin release are still incompletely understood. This study, performed with isolated mouse islets, identifies a possible role of Na+ in this inhibition. Regardless of the stimulus used to induce insulin release, the inhibitory effect of low concentrations of clonidine (0.01-0.1 microM) was markedly smaller in the absence of Na+ (with choline or lithium as substitute) than in its presence. The effectiveness of a high concentration of clonidine (1 microM) was, however, not affected by Na+ omission. The results indicate either that Na+ omission indirectly counteracts an effect of clonidine (e.g. on a membrane permeability or on Ca2+ handling), or that Na+ is directly involved in a cellular process (e.g. a Na+ current or the Na+/H+ exchange) controlled by alpha 2-adrenoceptors.

Adrenergic alpha-Antagonists↗
PubMed1990

Spinal synovial cyst: case report using magnetic resonance imaging.

The case of a 65-year-old woman who developed a spinal synovial cyst at the L4-5 disk space is reported. Her clinical signs and symptoms are presented. A comparison among her preoperative myelogram, computed tomography scan, and magnetic resonance imaging showed magnetic resonance imaging to be more accurate in detailing both the intraoperative and pathological findings.

Aged↗
PubMed1979

Studies on the cytodynamics of human endometrial regeneration. III. In vitro short-term incubation historadioautography.

The proliferation kinetics of endometrial regeneration were assessed by tracing nucleoprotein precursor, radiothymidine. Increased isotope uptake occurred by cycle day 3 and was confined to the gland cells of denuded stratum basale (basal layer) and persistent uterine lining, bordering peripheral areas of denudation. This increase resulted in the formation of flattened surface epithelial cells, which initially were devoid of significant deoxyribonucleic acid synthesis. Such alterations are consistent with changes in cells involved in ameboid migration. Maturation of migrating cells was accompanied by a significant rise in labeling indices and replication at cycle days 3 and 4. By cycle day 5, endometrial repair was complete. The findings indicate that, following physiologic loss of stratum functionale, endometrial healing involves both migration and replication of surface cells, which originate from the gland stumps of the residual basal layer and the persistent surface epithelium adjacent to the periphery of denuded endometrium.

Adult↗
PubMed1979

Proliferation kinetics of human endometrium during the normal menstrual cycle.

A radioautographic analysis of the number and distribution of labeled nuclei after in vitro incorporation of radiothymidine was carried out in human endometrium during the normal menstrual cycle. The highest rates of proliferation were recorded on cycle days 8 to 10 in the upper one third of the functionalis layer. Coinciding with intraglandular secretory activity on cycle day 19, the rate of proliferation of gland cells decreased near zero levels and remained unchanged thereafter. Midsecretory phase arteriolar coiling and stromal predecidualization were associated with increased isotope incorporation. DNA synthesis in premenstrual endometrium was limited to the surface epithelium, predecidua, and vascular endothelium. The endometrium of the isthmus and cornual regions and of the basalis zone demonstrated relatively constant and comparatively lower rates of proliferation throughout the cycle. Regional and cellular variations in nucleic acid synthesis in cyclic endometrium are likely to reflect differences in physiologic functions in target cells in response to cyclic hormonal stimuli.

Adult↗
PubMed1979

Divorce and remarriage in a 65-year-old male following transphenoidal surgery and bromocriptine of hyperprolactinemic impotence: a dilemma.

Hyperprolactinemia, hypogonadotropinism, and subnormal plasma testosterone were found in a 65-year-old patient who had an enlarged sella turcica, complained of fatigue, and addmitted to decreased sexual interest and potency. Selective nontotal tumorectomy followed by bromocriptine therapy resulted in normoprolactinemia, increased plasma testosterone, and "rejuvenation difficult to follow" according to his wife. This patient described his sexual status as comparable to that of age 24 when he fathered his only child. Both wife and husband attributed the changes to bromocriptine and requested discontinuation (wife) and continuation (husband) of the treatment; because of the clinical indications, treatment was continued. Legally, a medical certification of a normal state of health was required before divorce--and subsequent marriage to a young woman--were permitted.

Bromocriptine↗
PubMed1979

The position and organization of motor fibers in the internal capsule found during stereotactic surgery.

Data gathered from exploratory stimulation of the diencephalon in 130 stereotactic operative procedures have been studied, with the aid of a computer graphic technique, to show the position and topography of motor responses in the internal capsule. The results obtained indicate that pyramidal fibers are organized into a rostral-caudal face-arm-leg sequence and occupy a short compact band in the caudal third of the posterior limb of the internal capsule. This is in contrast to previous concepts of the position of these fibers in the capsule.

Adolescent↗