Search PubMed⌕ Search

Biomedical subjects

P Lefebvre

Publications and source records attributed to P Lefebvre.

At least 217 records · Page 12Linked to original sources
PubMed1982

Circadian variability of kinetics in a transplantable islet-cell tumor of the golden hamster.

The kinetics of a transplantable islet-cell tumor known to secrete paranormal hormonal compounds without any influence of usual regulatory mechanisms was studied in the golden hamster. It was found that during the 42nd diurnal period of growth, labelling and mitotic indices (peaks at midday), mean grain counts (lower at 4 a.m. and 8 a.m.), and PLM data (shift between G1 and S phase durations) varied significantly. The results are discussed in view of the discrepancy between hormonal release (unaffected by normal triggering factors) and circadian kinetics indicating the persistence of tumoral sensitivity to some control mechanisms. The theoretical importance of the diurnal variability for the correct interpretation of the internal kinetics of tumors is recalled.

Adenoma, Islet Cell↗
PubMed1982

Transcriptional control of gene expression during development of Dictyostelium discoideum.

During development of the cellular slime mold Dictyostelium discoideum, approximately 2,000 to 3,000 regulated mRNAs are induced when amoebae enter multicellular aggregates. We used in vitro transcription in isolated nuclei to follow the synthesis of individual mRNA precursors during development; these were quantitated by hybridization to cloned cDNAs or genomic DNAs. Those RNAs that are present at all stages of development--the common RNAs--were transcribed by nuclei from cells at all stages of development. By contrast, those RNAs that are present only after cells begin to aggregate--here called aggregation stage RNAs--were transcribed only by nuclei from cells at the aggregation and postaggregation stages of development. The temporal pattern of in vitro transcription correlated well with the time course of accumulation of different aggregation stage mRNAs. Continued expression of aggregation stage genes normally depends upon cell-to-cell contact or cyclic AMP (cAMP); when cells are disaggregated, the regulated mRNAs are rapidly and specifically degraded. When cAMP is subsequently added to the disaggregated cells, most of the mRNAs reaccumulate. We show here that disaggregation reduced 2- to 10-fold the relative transcription of several aggregation stage RNAs, whereas addition of cAMP to disaggregated cells reinduced the level of regulated gene transcription to values approximating those found in normal postaggregation cells. These results indicate that a representative set of Dictyostelium aggregation stage genes are under transcriptional control; both the transcription and the stability of these mRNAs require either continued cell-to-cell interactions or cAMP.

Cell Nucleus↗
PubMed1982

[Not Available].

Explore the source record for details and available documents.

France↗
PubMed1981

Glucagon immunoreactivity and antidiabetic action of somatostatin in the totally duodeno-pancreatectomized and gastrectomized human.

Ten patients who had been totally duodeno-pancreatectomized and totally (N = 1) or partially gastrectomized (N = 9) for chronic pancreatitis (N = 9) or pancreatic carcinoma (N = 1) were investigated. None had a measurable basal level of either plasma C-peptide or a C-peptide response to i.v. glucagon. Immunoreactive glucagon (IRG) was present in all patients, and the mean level (69 +/- 8 pg/ml) was not significantly different from the mean observed in normal subjects (81 +/- 16 pg/ml). Plasma IRG was unequivocally stimulated by arginine in 2 of the 10 subjects. The effect of somatostatin on plasma glucose and IRG during an oral glucose tolerance test was studied in 5 of the 10 patients. The effects of somatostatin on spontaneous hyperglycemia, plasma growth hormone, and IRG after withdrawal of insulin treatment was studied in 4 patients. Somatostatin blunted both the hyperglycemic and paradoxical IRG responses to the glucose challenge, and reduced the spontaneous rise of blood glucose that occurred after insulin withdrawal. This latter effect was not related to clear-cut changes in plasma growth hormone or in IRG. These data confirm the existence of circulating IRG in pancreatectomized patients and demonstrate the presence of circulating IRG in a completely gastrectomized and pancreatectomized patient. The somatostatin-induced improvement in glucose tolerance in the oral glucose tolerance test seems to be related to a reduction of the paradoxical IRG response. In contrast, the inhibition by somatostatin of the rise in blood glucose which occurs after insulin withdrawal does not seem to be mediated through IRG or growth hormone.

Adult↗
PubMed1980

The "one day at a time" syndrome in post-transplant evolution: the regressive megalomanic model versus the progressive hypomanic model.

After kidney transplantation patients experience an initial period of euphoria which is usually followed by a phase of disillusionment and depression. At this point the "one day at a time syndrome" appears as an attitude of adaptation and defense. It is proposed that there are two dynamically and prognostically different varieties of this syndrome: A first type represents a regressive megalomanic defense whereby depressive anxiety concerning the rejection of the part-self represented by the graft is conscious but depressive anxiety concerning the eventual death of the whole self is omnipotently denied. This variety of the syndrome is related to a more negative prognosis both psychologically and somatically. The second type of the "one day at a time syndrome" is a progressive hypomanic defense whereby depressive anxiety concerning the rejection of the part-self represented by the graft is present and conscious but relative and does not preclude the conscious depressive anxiety concerning the eventual death of the whole self, which once acknowledged can gradually be mastered, permitting the pursuit of as pleasurable a life as possible. This variety of the syndrome is prognostically more favourable both physically and psychologically.

Adaptation, Psychological↗
PubMed1980

Furosemide intravenous infusion in normal man: electrolytic, metabolic and hormonal effects. Lack of changes in basal insulin and glucagon plasma levels.

Eight overnight fasted healthy young volunteers received an intravenous infusion of 0.5 mg furosemide per kg body weight administered in 60 min. This period was preceded and followed by two control periods of one hour each during which physiological saline (o.154 mol/l) was administered at a rate of 1 ml/min. Furosemide markedly increased the diuresis and natriuresis which reached 1260 +/- 198 ml and 138.4 +/- 20.9 mmol per hour respectively. This was associated with a significant three fold increase in urinary total catecholamines excretion. Blood glucose, plasma free fatty acids, insulin and glucagon concentrations did not exhibit any significant change during and after furosemide infusion, compared to pre-infusion values. These results demonstrate that, in normal man, doses of furosemide capable of exerting plasma concentrations. It is concluded that the stimulation of insulin and glucagon secretion observed in vitro with high furosemide concentrations (5 mmol/l) are not observed under usual therapeutic conditions.

Adult↗