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Biomedical subjects

G Girard

Publications and source records attributed to G Girard.

At least 19 recordsLinked to original sources
PubMed2001

[Humus functioning types in evergreen coniferous forests of the French Inner Alps].

Three humus forms that are widespread in the Inner Alps, a dysmull below Pinus sylvestris, an oligomull below Abies alba and a mor below Pinus cembra, were studied by following mineral nitrogen production and uptake and by a characterization of the pedofauna. Due to the production and uptake of nitrogen, mainly as nitrates and also due to the dominance of Lumbricids versus Arthropods, the oligomull was the sole humus form that functioned as a mull. Nevertheless relatively weak mineral nitrogen production and the dominance of endogeic soil-dwelling earthworms versus anecic earthworms demonstrated the moderate activity of this mull, which is representative of humus forms of old growth forests and cold climates. There was a discrepancy between the very low biological activity of the dysmull and its status of mull, while an observed bifunctioning between the different layers of this humus also differentiated it from the mor.

Animals↗
PubMed2001

Translational control by delayed RNA folding: identification of the kinetic trap.

The maturation or A-protein gene of single-stranded RNA phage MS2 is preceded by a 130-nt long untranslated leader. When MS2 RNA folding is at equilibrium, the gene is untranslatable because the leader adopts a well-defined cloverleaf structure in which the Shine-Dalgarno (SD) sequence of the maturation gene is taken up in long-distance base pairing with an upstream complementary sequence (UCS). Synthesis of the A-protein takes place transiently while the RNA is synthesized from the minus strand. This requires that formation of the inhibitory cloverleaf is slow. In vitro, the folding delay was on the order of minutes. Here, we present evidence that this postponed folding is caused by the formation of a metastable intermediate. This intermediate is a small local hairpin that contains the UCS in its loop, thereby preventing or slowing down its pairing with the SD sequence. Mutants in which the small hairpin could not be formed made no detectable amounts of A-protein and were barely viable. Apparently, here the cloverleaf formed quicker than ribosomes could bind. On the other hand, mutants in which the small intermediary hairpin was stabilized produced more A-protein than wild type and were viable. One hardly growing mutant that could not form the metastable hairpin and did not make detectable amounts of A-protein was evolved. The emerging pseudo-revertant had selected two second site repressor mutations that allowed reconstruction of a variant of the metastable intermediate. The pseudo-revertant had also regained the capacity to produce the A-protein.

5' Untranslated Regions↗
PubMed1995

[Early detection of residents in trouble].

Early detection of residents' learning difficulties helps teachers offer appropriate help. During a series of educational workshops, a variety of behaviours associated with learning difficulties were described and four behavioural categories were established: limited cognitive response, disturbed affective response, deviant moral response, and diminished self-motivation.

Affect↗
PubMed1993

Region-selective reductions in activities of glutamine synthetase in rat brain following portacaval anastomosis.

Portacaval anastomosis in the rat results in liver atrophy, sustained hyperammonemia and mild encephalopathy. Previous studies have demonstrated region-selective alterations of glutamine and other ammonia-related amino acids in brain following portacaval anastomosis. Ammonia removal by brain relies on glutamine synthesis and the enzyme responsible, glutamine synthetase, has an almost exclusively astrocytic localization. Glutamine synthetase activities were measured using a radioenzymatic assay in homogenates of seven brain regions of rats four weeks after end-to-side portacaval anastomosis. Enzyme activities were significantly reduced in hippocampus (by 25%, p < 0.01), in cerebellum (by 29%, p < 0.01) and in cerebral cortex (by 14%, p < 0.05). Enzyme activities in other brain regions were within normal limits. Region-selective reductions of glutamine synthetase following portacaval anastomosis could result in disruption of neuron-glial metabolic interactions and in a deficit of glutamatergic synaptic regulation. Similar mechanisms could be implicated in the pathogenesis of hepatic encephalopathy accompanying chronic liver disease in humans.

Ammonia↗
PubMed1992

Effect of portacaval anastomosis on glutamine synthetase activities in liver, brain, and skeletal muscle.

Glutamine synthetase is responsible for the ATP-dependent amidation of glutamate to glutamine. In liver the enzyme is highly localized in perivenous hepatocytes; in brain the enzyme is localized in astrocytes. Portacaval anastomosis resulted in liver atrophy, hyperammonemia, and up to 90% loss of glutamine synthetase activity in liver homogenates. This effect, which appears to be irreversible, probably reflects the selective loss of perivenous hepatocytes following portacaval anastomosis. Glutamine synthetase activities in brain were unaffected by portacaval anastomosis of up to 12 weeks' duration. Enzyme activities in homogenates of skeletal muscle, on the other hand, were significantly increased at one and four weeks after shunt surgery. These effects were not the result of decreased food intake in shunted animals. These findings suggest fundamentally different regulatory mechanisms for glutamine synthetase in these tissues. Skeletal muscle may thus provide an important alternative site for ammonia detoxification after portal-systemic shunting.

Ammonia↗
PubMed1992

Autosomal inheritance of "senile" retinitis pigmentosa. A report of a family with consanguinity.

We describe two sisters affected with retinitis pigmentosa of late onset. Night blindness and progressive visual field loss occurred after 50 years of age in both cases. The parents of affected individuals were first cousins and there was no known history of other similar cases in previous generations. Autosomal recessive inheritance is suggested for such senile retinitis pigmentosa.

Aged↗
PubMed1989

Idiopathic constipation by colonic dysfunction. Relationship with personality and anxiety.

The personality of two groups of constipated women (by delayed colonic transit or by colonic inertia) was compared to that of two control groups of arthritic patients (rheumatoid or degenerative disease) with the Minnesota Multiphasic Personality Inventory (MMPI). All subjects suffered from chronic pain. Constipated women were found to have significantly higher scores on the hypochondria, hysteria, control, and low back pain scales and a lower score on the masculinity-femininity scale. Discriminant analysis permitted us to sort out constipated from arthritic patients in 83% of the cases, on the basis of only the personality data. In women with constipation by delayed colonic transit, multiple regression analysis demonstrated a close link (r = 0.90; P less than 0.001) between transit time in the ascending colon and levels of anxiety. It is concluded that women with constipation of colonic origin have a different pattern of personality than arthritic women and that severe constipation may play the role of a defense mechanism, where psychophysiologic responses to life stresses replace normal emotional reactions.

Adolescent↗
PubMed1989

Hospital practices and breastfeeding duration: a meta-analysis of controlled trials.

Controlled clinical trials studying the influence of hospital practices on breastfeeding duration were combined using meta-analysis. Nine studies were selected. Supplementation demonstrated a negative clinical effect on breastfeeding duration that was not significant. Nursing support demonstrated a positive clinical effect on breastfeeding duration that was not statistically significant if there was no telephone follow-up, but was significant if there was telephone follow-up. Early contact revealed a positive clinical effect that was significant. We conclude that early contact and nursing support with telephone follow-up appear as enhancing factors of breastfeeding duration.

Aftercare↗
PubMed1989

[Hospital practices and duration of breast feeding: meta-analysis].

Clinical trials studying the influence of hospital practices on breast-feeding duration were combined in a meta-analysis. Nine studies were selected. The global quality score was poor, and varied between 11.6 and 71.5 (Chalmers' scale). The results of each study were pooled using Peto's method and showed the following findings. Supplementation demonstrated a negative clinical effect on breast-feeding duration which was not significant (OR: 0.77, 95% CI[0.59, 1.02] p greater than 0.05). Nursing support demonstrated a positive clinical effect on breast-feeding duration which was not statistically significant if there was no telephone follow-up (OR : 2.29, 95% CI [0.87, 6.02] p greater than 0.05), but was significant if there was telephone follow-up (OR : 2.01, 95% CI [1.37, 2.94] p less than 0.05). Early contact revealed a positive clinical effect which was significant (OR : 2.96, 95% CI [1.6, 5.22] p less than 0.05). In conclusion, early contact and nursing support with telephone follow-up appear as enhancing factors of breast-feeding duration.

Adult↗
PubMed1988

Regional differences in the capacity for ammonia removal by brain following portocaval anastomosis.

Portocaval anastomosis (PCA) in the rat leads, within 4 weeks, to severe liver atrophy, sustained hyperammonemia, and increased brain ammonia. Because brain is not equipped with an effective urea cycle, removal of ammonia involves glutamine synthesis and PCA results in significantly increased brain glutamine. Glutamine synthetase activities, however, are decreased by 15% in cerebral cortex and are unchanged in brainstem of shunted rats. Administration of ammonium acetate to rats following PCA results in severe encephalopathy (loss of righting reflex and, ultimately, coma). Glutamine concentrations in brainstem of comatose rats are increased a further two-fold, whereas those of cerebral cortex are unchanged. Consequently, ammonia levels in cerebral cortex reach disproportionately high levels (of the order of 5 mM). These findings suggest a limitation in the capacity of cerebral cortex to remove additional blood-borne ammonia by glutamine formation following PCA. Such mechanisms may explain the hypersensitivity of rats with PCA and of patients with portal-systemic shunting to small increases of blood ammonia. Disproportionately high levels of brain ammonia in certain regions, such as cerebral cortex, may then result in alterations of inhibitory neurotransmission and, ultimately, loss of cellular (astrocytic) integrity.

Ammonia↗
PubMed1981

Distribution of amylase and chymotrypsin in four regions of the rat pancreas.

Recent observations have confirmed the existence of more than one pool of secretory proteins in the rat pancreatic tissue. To determine if these different pools could be located in the different regions of the rat pancreas, the amylase and chymotrypsin contents have been measured in the biliary, duodenal, gastric, and splenic regions. On a tissue DNA content, protein content, or a fresh weight basis, the proportions of these two enzymes are comparable in the four regions. It is therefore postulated that heterogeneity of enzyme composition exists either within these regions or within the acinar cell itself.

Amylases↗
PubMed1980

The action of leukotriene B4 (LTB4) on the lung.

The actions of leukotriene B4 (LTB4), a member of a newly discovered pathway of metabolism of arachidonic acid, were investigated both on the guinea-pig perfused lung preparation and on the parenchymal strip and compared to histamine and Slow Reacting Substance of Anaphylaxis (SRS-A). LTB was prepared from human polymorphonuclear leukocytes, extracted and purified by chromatography (Silicic acid and HPLC) and its purity was determined by gas chromatography and mass spectrometry. LTB4 is three times more potent than histamine (molar concentration) to contract the parenchymal strips and the contraction to LTB4 as well as to SRS-A lasted longer. The contraction to LTB4 is blocked by indomethacin (20 micrograms/ml), reduced by polyphloretin phosphate (50 micrograms/ml) and unaffected by FPL-55712 (1 micrograms/ml). Following its injection in the pulmonary artery of a perfused lung, LTB4 (1 microgram) induced the release of RCS (Rabbit Aorta Contracting Substance: a mixture of prostaglandins and thromboxanes) which can be abolished by indomethacin (1 microgram/ml). These findings suggest (a) that in the lung, LTB4 is a myotropic agent three times more powerful than histamine (b) that LTB4 stimulated a receptor which is different of histamine of SRS-A receptors, and (c) that its contractile action in the lung is mediated by prostaglandins and thromboxanes.

Animals↗