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Biomedical subjects

S Delpech

Publications and source records attributed to S Delpech.

9 recordsLinked to original sources
PubMed2001

Conformational stability and in vitro bioactivity of porcine luteinizing hormone.

Temperature-dependent dissociation of porcine luteinizing hormone (pLH) and of two of its glycoforms was studied by a combination of SDS-PAGE and micro-scale size-exclusion HPLC in parallel with the study of co-operative folding by high-sensitivity differential scanning calorimetry (HS-DSC). The transition temperature of dissociation of pLH at pH 7.0 as quantified by SDS-PAGE, HPLC and residual activity in radioreceptor assay was found to match exactly the transition temperature of its unfolding as measured by HS-DSC. Free alpha- and beta-subunits did not exhibit any unfolding transition in the same conditions. The microcalorimetric data for two pLH isoforms exhibiting different glycosylations were identical to those of a preparation of non-separated isoforms. It is concluded that: (a) free subunits exhibit no co-operative folding (i.e. no stable three-dimensional structure) and co-operative folding occurs only in alphabeta heterodimers; (b) the co-operative folding is responsible for the stability of the association of subunits; and (c) the heterogeneity of carbohydrate chains does not affect the stability of folding and association of subunits. The fastening of the "seat-belt" of the beta-subunit embracing the alpha-subunit by the Cysbeta26-beta110 disulfide bridge had been postulated to play a role in the preservation of the dimeric structure of gonadotropins. The present work shows that dissociation of subunits is directly related to their loss of common co-operative folding.

Animals↗
PubMed1988

Differential localization of glycoconjugates having affinity for concanavalin A on the surface of the sperm head in the testis, the epididymis, and the ejaculate of the ram.

The localization of Con A receptors on the surface of the head of ram spermatozoa originating from the rete testis, from three regions of the epididymis, or from the ejaculate was investigated using a gold-Con A labelling technique. Electron microscopic observation revealed three major localizations, each being characteristic of the origin of the spermatozoa: periacrosomal in the rete testis, postacrosomal in the epididymis, on the entire surface of the sperm head in the ejaculate.

Animals↗
PubMed1988

[An in vitro study, in the human, of the relation between epididymal spermatozoa and the zona pellucida].

The ability of non capacitated human spermatozoa recovered from the caput, corpus and cauda epididymis, to bind the isologous or heterologous (rat) zona pellucida has been investigated. Experiments were performed with cold immobilized spermatozoa to avoid differences resulting from motility into the epididymis. Comparison with similar investigations in the ram (works and review of Fournier-Delpech and Courot, 1987) lead to conclude that human spermatozoa are: 1) able to bind to the human zona in the proximal epididymis; 2) unable to recognize heterologous zona at any level of the epididymis. From this, a strict species-specificity of the sperm-zona interactions exists in the proximal epididymis, in the human. By contrast, in the ram, sperm-zona binding develops in the epididymis iso- or hetero-specifically. Restricted species specificity appears in the ejaculate only. Data are in agreement with species specificity of gametes interactions in the human (Bedford, 1977). Such results could contribute to explain in vitro or in vivo fertilization with sperm originating from the middle epididymis (Temple-Smith et al., 1985; Soychsman and Bedford, 1986).

Adolescent↗
PubMed1987

[Complement activation in extracorporeal circulation. Comparison of nylon versus polyester bubble oxygenators].

Complement activation during cardiopulmonary bypass is well known and may influence postoperative morbidity. As nylon can particularly induce complement activation, its influence was assessed by measuring total haemolytic complement and B, C3 and C4 factors, during cardiopulmonary bypass with bubble oxygenators for coronary surgery, comparing "nylon" circuits (20 patients, Bentley BOS 10) versus "polyester" circuits (19 patients, Shiley S 100 A). Complement activation began with induction of anaesthesia and surgical procedures, B, C3 and C4 levels falling significantly (respectively 15, 17 and 20% from baseline values). The alternative pathway was activated before the classical pathway. Complement activation continued during cardiopulmonary bypass, with no more consumption of complement factors (slight variations of about 0 to 3% of the levels found after anaesthetic induction and surgical procedures). No statistically significant difference appeared between the two groups. This suggested that nylon did not significantly increase complement activation during cardiopulmonary bypass. The bubble oxygenator material cannot therefore be considered as a criterion for choosing the type of equipment.

Complement Activation↗
PubMed1985

[Bleeding after extracorporeal circulation and epsilon-aminocaproic acid].

In order to assess the efficacy of epsilon aminocaproic acid in reducing bleeding after extracorporeal circulation for aorto-coronary bypass grafting, a double blind study was carried out in 57 patients. The efficiency of epsilon aminocaproic acid was assessed by the fibrinolytic activity as measured by a Von Kaulla test one hour after injection of protamine, by the amount of blood transfusions required and by the measurement of blood losses between the end of the injection of protamine and transfer of the patient to the intensive care unit, and then during the first 24 h following operation. No significant difference (p less than 0.05) between the group of treated patients and the group with placebo could be found concerning the postoperative bleeding, the amount of blood transfusions necessary and the occurrence of fibrinolysis. It was therefore concluded that there was no reason to routinely use epsilon aminocaproic acid after aorto-coronary bypass grafting.

Aged↗
PubMed1985

[Hemolysis in patients with heart valve prostheses. Comparison between Björk-Shiley and Saint-Jude Medical valves].

The problem of haemolysis was studied in 244 patients with one or two prosthetic heart valves: 232 of these patients had normal valve function as assessed by clinical examination, radioscopy and echocardiography; 112 patients had a Bjork-Shiley (BS) prosthesis, 25 in the aortic position (BSA), 71 in the mitral position (BSM) and 16 in both aortic and mitral positions (BSA + M). These patients were operated between July 1979 and January 1981. One hundred and twenty other patients had Saint Jude medical (SJM) prostheses; 48 in the aortic position (SJMA), 44 in the mitral position (SJMM) and 28 in both aortic and mitral positions (SJMM + A). These patients were operated between January 1982 and July 1983. Twelve patients (operated between 1977 and 1984) had prosthetic valve dysfunction confirmed by angiography or anatomically (SJM = 7); BS = 5). The plasma haemoglobin concentration (pHb) was used as the reference: it was measured by spectrophotometry with a sensitivity of 0.5 mg/100 ml. There was no significant difference the SJM and BS groups at surgery (BS: 4.62 mg/100 ml; SJM: 4.31 mg/100 ml). In the absence of prosthetic valve dysfunction, haemolysis was significantly greater (p less than 0.001) in the SJM (8.28 mg/100 ml) than in the BS (3.08 mg/100 ml). No statistical correlation was observed with the severity of cardiac disease, the aortic or mitral position of the prostheses or with the number of prostheses. Haemolysis was subclinical in all cases. When haemodynamically significant prosthetic valve dysfunction was present, haemolysis was inconstant in BS prostheses (2 out of 5 cases) despite major haemodynamic disturbances in all cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Cytochemical studies of nuclear basic proteins in control and vitamin B12 starved Euglena.

In avitaminosis B12, Euglena gracilis Z is blocked in the cell cycle in the S/G2 phase. In these blocked cells, transcription and traduction go on and the amount of DNA is less than doubled and remains constant during the blockage. Chromatin clumps observed in situ with classical electron microscopic methods are always condensed in control cells but are not visualized in B12 starved cells. Two cytochemical reactions, ethanolic phosphotungstic acid and ammoniacal silver reaction, specific for lysine- or arginine-rich residues, are performed to reveal basic nuclear proteins of chromatin. With these two methods, control chromatin in situ always shows a condensed aspect, whereas the starved chromatin appears dispersed. These cytochemical differences might be considered to result from a different supramolecular organization of the two kinds of chromatin.

Animals↗