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Biomedical subjects

M Samson

Publications and source records attributed to M Samson.

At least 109 records · Page 6Linked to original sources
PubMed1982

Plasma membrane vesicles from isolated hepatocytes retain the increase of amino acid transport induced by dibutyryl cyclic AMP in intact cells.

We have investigated the effect of cyclic AMP on hepatic amino acid transport by measuring the uptake of L-alanine in plasma membrane vesicles purified from hepatocytes incubated without or with dibutyryl cyclic AMP. The application of an Na+ gradient to vesicles from hepatocytes exposed to dibutyryl cyclic AMP, compared to control, resulted in a greater transient accumulation of L-alanine, whereas in the presence of a K+ gradient a similar slow equilibration of L-alanine was observed. Kinetic analysis of L-alanine influx revealed that the increased uptake resulted from an increased capacity (Vmax) with no change in the affinity (Km) of the carriers for L-alanine. These results strongly suggest that dibutyryl cyclic AMP induces stable changes at the membrane level probably by increasing the number of amino acid carrier molecules.

Alanine↗
PubMed1982

Insulin and glucagon binding and stimulation of amino acid transport in isolated hepatocytes from streptozotocin diabetic rats.

The binding of insulin and glucagon and the effects of these hormones on amino acid transport were examined in isolated rat hepatocytes from streptozotocin diabetic rats. Hepatocytes from diabetic rats bound more insulin than cells from control animals. These changes were accounted for by a 50%-60% increase in the number of insulin receptors per cell. Glucagon binding did not significantly differ in hepatocytes from both groups. Following a 2 hr incubation of the cells in vitro, the basal rate of alpha-aminoisobutyric acid (AIB) influx was enhanced in diabetic rat hepatocytes compared to controls. This alteration was accounted for by an increase in the Vmax of both a low affinity and a high affinity component of transport. The ability of diabetic rat hepatocytes to respond to maximally stimulating concentrations of insulin or glucagon by enhancing further the rate of AIB influx was markedly diminished. Hormone responsiveness was restored to normal in hepatocytes from insulin-treated diabetic animals. The data suggest that in diabetic rat hepatocytes the diminished insulin and glucagon responsiveness with regard to the stimulation of amino acid transport stems from postreceptor alteration(s).

Aminoisobutyric Acids↗
PubMed1981

The effect of amiloride on hormonal regulation of amino acid transport in isolated and cultured adult rat hepatocytes.

Insulin and glucagon stimulate amino acid transport in isolated rat hepatocytes. Amiloride, a specific Na+-influx inhibitor, completely inhibited the hormonal (glucagon or insulin) stimulation of alpha-aminoisobutyric acid influx by preventing the emergence of a high-affinity transport component. The drug also inhibited [14C]valine incorporation into hepatocyte protein. The half-maximal concentration of amiloride for inhibition of protein synthesis was similar to that required for inhibition of hormone-stimulated amino acid transport (approx. 0.1 mM). In primary cultured rat hepatocytes, amiloride markedly depressed the stimulation of alpha-aminoisobutyric acid transport by glucagon, or a mixture of glucagon, insulin and epidermal growth factor. These results suggest that amiloride inhibits the hormonal stimulation of hepatocyte amino acid transport by preventing the synthesis of high-affinity transport proteins. They also suggest that the hormonal stimulation of hepatocyte amino acid transport is dependent, at least partly, on Na+ influx.

Amiloride↗
PubMed1980

Combination chemotherapy, radiotherapy, and BCG immunotherapy in extensive (metastatic) small cell carcinoma of the lung. A Southwest Oncology Group study.

From November 1976 to November 1978, the Southwest Oncology Group treated 254 patients with extensive (metastatic) small cell carcinoma of the lung with combination chemotherapy and radiotherapy with and without BCG immunotherapy. Patients receiving BCG achieved a response rate of 50% versus those patients not receiving BCG of 46% (P = .704). Response duration was 20 weeks for the BCG arms and 23 weeks for the no-BCG arms; survival was 28 weeks for the BCG arms versus 29 weeks for the no-BCG arms. An adverse effect in patients surviving more than one year was detected; those continuing to receive BCG had significantly shorter survival, 60 weeks versus 85 weeks (P = .019). Toxicities of the programs were not affected by the addition of BCG immunotherapy. It appears that BCG immunotherapy has no beneficial effect on response rate or duration of response in programs using chemotherapy and radiotherapy for control of metastatic small cell carcinoma of the lung. In addition, because of the adverse effect on long-term survival, we do not recommend the addition of BCG immunotherapy as a treatment modality in this tumor type.

Antineoplastic Agents↗
PubMed1980

Amino acid transport in isolated hepatocytes from streptozotocin-diabetic rats.

The enhanced ability of liver to extract glucogenic precursors from plasma in insulinopenic diabetes was investigated at the cellular level by measuring amino acid transport in isolated hepatocytes from streptozotocin-diabetes rats. The concentrative Na+-dependent uptake of alpha-amino[1-14C]isobutyric acid (AIB), a non-metabolizable analog of alanine, was increased in hepatocytes from diabetic rats compared with controls. This increase was observed both at a low (0.1 mM) and high (30 mM) extracellular concentration of the amino acid. Analysis of the relationship between AIB influx and AIB concentration revealed that the increased uptake in diabetic rat hepatocytes was due to an enhanced capacity (i.e., a twofold increase in the Vmax) of the transport system whereas the apparent affinity (Km) for AIB was unaltered. The increased amino acid transport activity in diabetic rat hepatocytes was due mainly to an increased transport through system A (alanine-preferring) and, to a much lesser extent, through system ASC (alanine, serine, cysteine). System L (leucine-preferring) and AIB entry through simple diffusion were not affected in diabetic rat hepatocytes compared with controls. Increased AIB transport of diabetic rat hepatocytes was returned to normal by insulin treatment.

Adenosine Triphosphate↗
PubMed1980

[Non-edematous spontaneously resolving cerebellar softening. Diagnostic possibilities and value (author's transl)].

Non edematous cerebellar softenings are usually unrecognized even though their relatively high frequency of occurrence is proved by systematic anatomical studies. They should be suspected when an acute late-onset vestibular syndrome is noted, in which there is a particular type of homolateral disequilibrium and nystagmus, good vestibular reactivity, and possible association with a cerebellar syndrome. Softening can usually be confirmed after several days by the complementary examinations presently available: computer tomography of the posterior fossa and scintigraphy with labelled bleomycin. Non-edematous forms are spontaneously resolving disorders but surveillance during the first few days is necessary together with anti-edematous therapy as early signs are common to those of edematous softening, responsible for rapid involvement of the brain stem and blocking of fluid pathways.

Aged↗
PubMed1980

[Application of correlation factors to the study of visual evoked potentials in multiple sclerosis (author's transl)].

A comparison is made between cerebral evoked potentials through the left and right eye by studying the correlation functions between the two visual responses obtained. Two values were retained: the correlation coefficient CO which shows the degree of similarity between the two curves, and the phase displacement D which indicates the duration for which a curve has to be shifted in relation to the other in order to resemble it as closely as possible. An original representation, in the form of a correlation/phase displacement diagram, is drawn for each subject, and enables easy separation of normal subjects from those with pathological conditions. This technique was applied to 20 normal subjects acting as controls and 40 patients with suspected or confirmed multiple sclerosis. In the latter group, anomalies were found in 67 p. cent whereas retrobulbar optic neuritis had been diagnosed in only 35 p. cent of cases. By reducing the sample to include only known or probable cases of MS, anomalies were found in 88 p. cent with retrobulbar optic neuritis known in only 51 p. cent. These results are comparable with those obtained by using previously described methods, but have the advantage of automatic readings which are completely objective.

Brain↗
PubMed1979

[Acute cerebellitis in infectious mononucleosis. One case (author's transl)].

A nineteen year old man present an original clinical case of acute cerebellitis in infectious mononucleosis. Eighteen months after the acute phase of the illness, there persisted a large deficit in the circulating B lymphocytes. A short review of pertinent litterature is presented and current physiopathological hypothesis are discussed. Briefly, delayed immunity and personal predisposition appear to play important etiological roles.

Adolescent↗
PubMed1979

Isocyanate asthma: respiratory symptoms due to 1,5-naphthylene di-isocyanate.

Occupationally related asthma developing in three patients due specifically to exposure to 1,5-naphthylene di-isocyanate (NDI), a hot curing agent used in manufacturing rubber, has been confirmed for the first time using bronchial provocation testing. This substance has been thought to be safer than toluene di-isocyanate (TDI) and diphenylmethane di-isocyanate (MDI) because of its relatively high melting point (120 degrees C). Each patient worked in the same factory and the circumstances of exposure were similar. Provocation testing was also performed with TDI in concentrations up to 0.018 parts per million (ppm) and MDI in concentrations up to 0.02 ppm, to which the patients had been exposed in the past, but no reactions were elicited. None of the patients had increased bronchial reactivity judged by histamine lability and exercise testing. Each patient was advised to give up his job, but two of the three could not find alternative employment and remained exposed. Three-year follow-up shows that airways narrowing has persisted in those who have remained exposed.

Adult↗