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Biomedical subjects

G Bertrand

Publications and source records attributed to G Bertrand.

At least 55 records · Page 3Linked to original sources
PubMed1996

Agmatine is not a good candidate as endogenous ligand for imidazoline sites of pancreatic B cells and vascular bed.

In order to determine whether agmatine could be a putative endogenous ligand for imidazoline receptors mediating insulin secretion and vasoconstriction, we compared its effects with those of the imidazoline, efaroxan. Agmatine exhibited a much lower potency and efficacy than efaroxan on insulin secretion from rat pancreas perfused with 8.3 mM glucose. On the other hand, in contrast to efaroxan (100 microM), agmatine (3 mM) did not increase arginine-induced insulin release. In addition, agmatine failed to reproduce the vasoconstrictor effect of efaroxan on pancreatic vessels. These results show that agmatine does not behave like efaroxan, an agonist for the imidazoline receptors mediating insulin secretion or vasoconstriction in the pancreas.

Agmatine↗
PubMed1996

Migration of metal and polyethylene particles from articular prostheses may generate lymphadenopathy with histiocytosis.

Wear particles released from hip or knee prostheses are known to be involved in the fibrohistiocytic membrane interposed between bone and implant. During surgical treatment for pelvic carcinoma (5 cases) and for isolated pseudomalignant lymphadenopathy (4 cases) lymph nodes in 9 patients who had had lower limb articular replacement were harvested. Light microscopy and image analysis of the nodes showed florid endosinusal histiocytosis, predominant in the cortical area. Using Oil Red O staining and polarized light, metal particles and polyethylene particles were detected in the large histiocytes. Scanning electron microscopy with electron backscattering allowed us to localize metal particles and perform elemental microanalysis. Iron, cobalt, chromium, nickel, zirconium, and barium, known to be used in prosthetic and cementing materials, were identified as component of these particles. Large amounts of polyethylene particles appeared in all cases while metal particles were found to be abundant in only 2 cases. Thus, migration of polyethylene debris from the prosthetic site seems to be the major factor in development of the histiocytes induced in satellite lymph nodes.

Aged↗
PubMed1996

Low-grade pure and mixed cerebral astrocytomas treated in the CT scan era.

From 1974 to 1992, 63 patients diagnosed with low-grade pure or mixed oligo-astrocytoma were seen and treated at our institution. All patients underwent CT scan pre-operatively. There were 20 female and 43 males ranging in age from 12 to 73 years (median age of 33 years). 15 patients had a stereotactic biopsy as the only surgical procedure. 34 had a partial tumor resection and 14 a gross total tumor resection. 43 patients were treated with post-operative radiotherapy whereas 20 patients underwent surgery only as part of the initial management. 50 to 60 Gy (median 59.4 Gy) were given with daily fractions of 1.8 to 2 GY. Tumor volume ranged from 3.4 to 441 cm3. Median tumor volume was larger for radiotherapy treated patients. Median follow-up was 54 months (range of 4 to 240 months). The overall 10 and 15 actuarial survival rates were 37% and 25% respectively. The 5 years survival rate for patients treated at initial diagnosis with surgery alone was 66% and it was 67.3% for patients treated with radiation therapy (P = NS). Prognostic factors having independent significant impact on survival were: extent of surgery, age gender and tumor volume. As well, survival for patients with low-grade astrocytoma in the CT scan era appears to be improved compared to historical controls in the literature.

Adolescent↗
PubMed1996

Pancreastatin modulates glucose-stimulated insulin secretion from the perfused rat pancreas.

Pancreastatin is known to be produced in islet B cells and to inhibit insulin secretion. In this study, we examined whether the peptide affects insulin secretion from the perfused rat pancreas during raising or lowering the glucose concentration within the physiological range. We found that synthetic porcine pancreastatin (15 nmol L-1) significantly inhibited the first phase (5 min) of insulin release induced by raising the glucose concentration from 4.2 to 8.3 mmol L-1 (P < 0.05) without affecting the second phase. Furthermore, the fall in insulin secretion induced by lowering the glucose concentration from 8.3 to 5.5 mmol L-1 was significantly exaggerated in presence of pancreastatin during the first 5 min (P < 0.05). In contrast, pancreastatin did not affect the inhibition of insulin secretion induced by either the alpha 2-adrenoceptor agonist, clonidine (2 nmol L-1), or the P1-purinoceptor (A1-subtype) agonist, N6 (+)-phenylisopropyladenosine (D-PIA) (1.65 mumol L-1). In conclusion, our results show that pancreastatin is a modulator of the early changes in insulin secretion after increase or decrease of the glucose concentration within the physiological range. This suggests that pancreastatin is a modulator of glucose-stimulated insulin secretion.

Adrenergic alpha-Agonists↗
PubMed1996

Differential nitric oxide (NO) production by macrophages from mice and guinea pigs infected with virulent and avirulent Legionella pneumophila serogroup 1.

L-arginine-dependent reactive nitrogen intermediates have been identified as macrophage cytotoxic effector molecules against intracellular pathogens. To determine its role, ex vivo production of NO by peritoneal macrophages of C3H/HeN mice and Dunkin-Hartley guinea pigs infected intraperitoneally with a virulent and isogenic avirulent Legionella pneumophila serogroup 1 strain was compared with bacterial clearance from the lungs. While the virulent strain was cleared from mice lungs, the guinea pigs died within 96 h. In vivo infection with both strains resulted in the production of NO by mouse peritoneal macrophages ex vivo. In contrast, guinea pig macrophages did not produce detectable NO. In addition, infection by the avirulent strain led to the production of significantly more NO by mouse macrophages than the virulent parent strain, irrespective of stimulation with lipopolysaccharide (LP) and/or interferon-gamma (ifn-gamma). These results suggest that resistance to Leg. pneumophila infection may depend on the production of NO by host macrophages.

Animals↗
PubMed1996

Comparative effects of PACAP and VIP on pancreatic endocrine secretions and vascular resistance in rat.

1. The effects of pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP) and secretin on pancreatic endocrine secretions and vascular resistance were investigated and compared in the isolated perfused pancreas of the rat. The PACAP/VIP receptor types involved have been characterized. 2. On insulin secretion, in the range 10(-11) to 10(-8) M, PACAP and VIP elicited a concentration-dependent biphasic response from pancreas perfused with 8.3 mM glucose; the peptides were equipotent. In contrast, secretin was ineffective in the range 10(-11) to 10(-9) M; at 10(-8) and 10(-7) M, it induced only low and transient insulin responses. On the other hand, the peptides did not modify the basal insulin release in the presence of a non stimulating glucose concentration (2.8 mM). 3. On glucagon secretion, PACAP and VIP (10(-11) to 10(-8) M) but also secretin (10(-9) to 10(-7) M) caused a concentration-dependent peak shaped response from pancreas perfused with 2.8 mM glucose; PACAP and VIP were equipotent and 20 times more potent then secretin. On the other hand, the peptides did not affect the glucagon release in the presence of 8.3 mM glucose. 4. On pancreatic vessels, in the range 10(-11) to 10(-9) M, the three peptides were equipotent in inducing a concentration-dependent sustained increase in pancreatic flow rate. On the other hand, at the high concentration of 10(-7) M PACAP but not VIP provoked a transient decrease of flow rate. 5. This study provides evidence for PACAP/VIP type II receptors mediating insulin and glucagon secretion as well as vasodilatation in rat pancreas. In addition, the different efficacies of secretin suggest that these effects are mediated by different PACAP/VIP type II receptor subtypes.

Animals↗
PubMed1996

[Granulomatous mastitis and corynebacteria infection. Two case reports].

Diagnosis of granulomatous mastitis must be based on a multidisciplinary approach. First, it's necessary to eliminate carcinomatous mastitis. Usually, the diagnosis is unknown except for tuberculous and sarcoidosis granulomatous mastitis. On observations in two cases of Corynebacterium granulomatous mastitis, we discussed the diagnosis and therapeutic approach. When there is a clinical suspicion of granulomatous mastitis, surgical biopsy with immediate histological analysis and bacteriological culture of mammary tissue should be performed. This multidisiplinary approach should reduce the number of idiopathic granulomatous mastitis observed. Antibiotic treatment is required after biopsy or surgical excision of granuloma.

Adult↗
PubMed1995

Evidence for two different imidazoline sites on pancreatic B cells and vascular bed in rat.

The relative potencies of imidazoline compounds to induce insulin secretion and vascular resistance were compared in the isolated perfused rat pancreas. On insulin secretion, only the two imidazolines, antazoline and efaroxan, induced a concentration-dependent response, antazoline being 10 times more potent than efaroxan. In contrast, idazoxan, a blocker of imidazoline I1 sites, at concentrations up to 30 microM, antagonized the insulin response to 10 microM efaroxan (IC50 approximately equal to 14 +/- 2 microM) without affecting that to 3 microM tolbutamide. On pancreatic vessels, not only antazoline and efaroxan but also idazoxan induced a concentration-dependent vasoconstriction; the rank order of agonist potency was antazoline > efaroxan > idazoxan. In addition, cimetidine, an imidazole known to bind imidazoline I1 sites, ineffective per se, partially reversed the insulin stimulatory effect of efaroxan without affecting its vasoconstrictor effect. This study demonstrates that the insulin secretory and vasoconstrictor actions of imidazolines involve different imidazoline sites in rat pancreas. The results provide evidence for an I1 type mediating insulin secretion on B cells and an I2 type mediating vasoconstriction in vessels.

Adrenergic alpha-Antagonists↗
PubMed1995

Activities of roxithromycin against Mycobacterium avium infections in human macrophages and C57BL/6 mice.

The activity of roxithromycin against three clinical isolates of Mycobacterium avium was compared with that of clarithromycin both in a model of infection of human monocyte-derived macrophages and in a model of established infection of C57BL/6 mice. In the cell culture model, roxithromycin and clarithromycin were bactericidal for strains MO-1 and N-92159 and bacteriostatic for strain N-93043. For the three strains, the differences between the intracellular activities of roxithromycin and clarithromycin were not singificant after 7 days of treatment. Mice were infected with the MO-1 strain. Drugs were given by gavage at a dosage of 200 mg/kg of body weight 6 days per week for 16 weeks starting 5 weeks after infection. At the end of treatment, clarithromycin was more effective than roxithromycin in lungs; roxithromycin was as effective as clarithromycin in spleens. Thus, the activity of roxithromycin was comparable to that of clarithromycin both in vitro and in vivo.

Animals↗
PubMed1995

Glutamate stimulates insulin secretion and improves glucose tolerance in rats.

We previously showed in vitro that glutamate stimulates insulin release via an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. Here we address a more physiological question concerning the in vivo effect of intravenously or orally administered glutamate on insulinemia and glycemia in fed and fasted rats. In anesthetized fed rats, the intravenous administration of glutamate at 9 and 30 mg/kg transiently increased insulinemia in a dose-dependent manner. The insulin-secretory effect of glutamate (9 mg/kg) was blocked by an antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. In anesthetized fasted rats, glutamate at 9 mg/kg was ineffective, but during an intravenous glucose tolerance test (0.5 g/kg), glutamate markedly potentiated insulin release and increased the glucose disappearance rate. In conscious rats, the intragastric administration of glutamate at 200 mg/kg elicited a transient insulin response in fed animals and had no effect in fasted animals but, during an oral glucose tolerance test (1 g/kg), enhanced insulin secretion and reduced the hyperglycemia. Glutamate was effective at plasma concentrations of 200-300 microM. In conclusion, intravenously and orally administered glutamate stimulates insulin secretion in vivo via an excitatory amino acid receptor and improves glucose tolerance.

Administration, Oral↗
PubMed1995

[Prostate cancer: anatomo-pathological correlation and MRI].

In our study, 50 patients had a prostatic carcinoma stade B. Before the radical prostatectomy we have realised a MRImaging of the prostate. After a precise histopathologic correlation we tried to appreciate the MRI performance for the detection of neoplasic nodes in the peripheral zone and for the loco-regional staging of the carcinoma. In detection of the pathologic nodes, MRImaging is more sensitive from the apex (22.5%) to the base of the prostate (91%), but it is at the same time specificless (apex: 90%, base: 40%). The accurate diagnostic for loco-regional staging in our study is 70%. Extracapsular extension is often underestimated because of the very small size of the invasion. On the other hand the specificity of MRI in seminal vesicles extension is satisfactory (87.5%).

Aged↗
PubMed1995

[Breast micro-opacities of lead origin mimicking microcalcifications].

After a surgical excision of focal mammary "microcalcification" we noticed that in fact they represented fine lead deposits (mean diameter: 100 microns) resulting from an attempted suicide (22 long rifle) 10 years previously. The leaded nature of these foreign microbodies was demonstrated by a micro-analysis by energy dispersion on histological slides.

Breast↗
PubMed1994

Effects of imidazolines and derivatives on insulin secretion and vascular resistance in perfused rat pancreas.

The effects of imidazolines and derivatives were studied on insulin secretion and vascular resistance in the isolated perfused rat pancreas. On insulin secretion, two imidazoline alpha 2-adrenoceptor antagonists, efaroxan (1-100 microM) and RX821002 (10 microM), had a stimulating response; however, idazoxan, like the non-imidazoline alpha 2-adrenoceptor antagonist yohimbine, was ineffective at 10 microM. The oxazoline rilmenidine with alpha 2-adrenergic activity at 10 microM), an imidazoline devoid of alpha 2-adrenergic activity, also had an insulin-releasing effect. On pancreatic vessels, all imidazolines tested (efaroxan, RX821002, antazoline and idazoxan), in contrast to yohimbine, induced vasoconstriction. Rilmenidine did not have a vasoconstrictor effect after blockade of alpha 2-adrenoceptors. Furthermore, the efaroxan-induced insulin release or vasoconstriction was not affected by the blockade of alpha 2- and alpha 1-adrenoceptors. This study shows that imidazolines and derivatives are able to stimulate insulin release and induce vasoconstriction in the rat pancreas. These effects cannot be ascribed to an interaction with alpha-adrenoceptors but may involve different types of imidazoline sites.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1994

Purinergic receptors on insulin-secreting cells.

The insulin secreting B cell is fitted with the two types of purinergic receptors: P2 (for ATP and/or ADP) and P1 (for adenosine). The activation of P2 purinoceptors by ATP or ADP evokes a biphasic stimulation of insulin secretion from isolated perfused rat pancreas; this stimulation is dose-dependent between 10(-6) and 10(-4) M. Non hydrolysable structural analogues are also effective, and the relative potency of various agonists (2-methylthio ATP >> ATP = ADP = alpha, beta-methylene ATP >> AMP) gave evidence for a P2y purinoceptor subtype. Proposed mechanisms include both an increased Ca2+ uptake and an increased intracellular Ca2+ mobilization via the hydrolysis of polyphosphoinositides. ATP (or ADP) potentiates physiological insulin-secreting agents (glucose and acetylcholine) and P2 purinoceptors could play a physiological role in the stimulation of insulin secretion. The activation of P1 purinoceptors (adenosine receptors) decreases insulin secretion. Using structural analogues of adenosine, the receptor was characterized as an A1 subtype; it is coupled to a pertussis toxin sensitive G protein and it inhibits adenylate cyclase. It is of physiological relevance that the B cell has the two types of purinoceptors with opposite effects. Recently, a metabolically stable structural analogue of ADP, adenosine-5'-0-(2-thiodiphosphate) or ADP beta S, has been described as a potent secretory agent, effective at nanomolar concentrations on isolated perfused rat pancreas. In vivo, this substance is able to increase insulin secretion and to improve glucose tolerance after IV administration in rats and oral administration in dogs. Furthermore in streptozotocin-induced diabetes. ADP beta S retains its insulin secreting effects. These results suggest that P2y purinoceptors could be a new target for antidiabetic drugs.

Adenine Nucleotides↗
PubMed1994

[Malignant Leydig cell tumor].

A case of malignant Leydig cell tumor is reported. The best feature of malignancy of this rare tumor is the presence of vascular invasion. An immunohistochemical study is presented and the differential diagnosis is discussed.

Adult↗