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P Richard

Publications and source records attributed to P Richard.

At least 163 records · Page 9Linked to original sources
PubMed1994

[Pathology of the human apolipoprotein E gene].

Apolipoprotein E (apo E) is a polymorphic glycoprotein that plays an essential part in the binding to receptors for the uptake of chylomicrons and VLDL remnants and of LDL. The three major isoforms are E3 (Cys112/Arg158), E4 (Arg112/Arg158) and E2 (Cys112/Cys158). The apo E genetic variation has a great impact. In most of type III familial hyperlipoproteinemias (HLP), E2 is implicated at the homozygote status. In other cases, rare alleles are directly responsible for dominant type III HLP. Apo E polymorphism is an essential determinant in the interindividual variations of lipids in healthy subjects in various populations. Its influence can be significant on the efficacy of nutritional or therapeutic interventions. The allele epsilon 4 appears to be associated with an increased risk of premature atherosclerosis. Recently, epsilon 4 was demonstrated to be associated with an early Alzheimer's disease onset. Apo E polymorphism contributes to the lipid disorders in diabetes and obesity. The analysis of apo E polymorphism can be carried out with two conceptually different approaches. The first one is based on the separation of plasma isoforms of the protein by isoelectric focusing or bidimensional electrophoresis. The other one consists in the application of molecular biology techniques (PCR and endonuclease restriction profiles) for a detection of the common alleles and of several rare alleles, avoiding the possible errors of the phenotyping technique of the apo E protein. The application of genetic engineering allows a better understanding of the role played by apo E towards its receptors and in other molecular interactions which are not well known up to now.

Amino Acid Sequence↗
PubMed1994

Common and rare genotypes of human apolipoprotein E determined by specific restriction profiles of polymerase chain reaction-amplified DNA.

The three common isoforms of human apolipoprotein E (apo E) differ at positions 112 and 158 and are named E3, E4, and E2 according to phenotyping by isoelectric focusing (IEF). The polymerase chain reaction (PCR) method allows the detection of common and several rare allelic apo E variants not detected by IEF. We propose a genotyping procedure for apo E that characterizes a given allele on the basis of amplification of specific sequences of the gene followed by the action of restriction endonucleases. When the nucleotide change does not lead to a restriction site, PCR-directed mutagenesis creates the discriminant site, and the differentiation of the three common alleles and five rare variants is possible. We present here profiles of common alleles and of three rare alleles, Weisgraber [Cys112/Asp127/Cys158], Christchurch [Cys112/Ser136/Arg158], and a new rare variant [Cys112/Leu142/Cys158].

Alleles↗
PubMed1993

Around the growth phase transition S. cerevisiae's make-up favours sustained oscillations of intracellular metabolites.

Under a limited set of hitherto incompletely defined conditions, inhibition of respiration has been shown to cause transient oscillations in NAD(P)H fluorescence of yeast cells. In this paper, we apply a new method [1992, Anal. Biochem. 204, 118-132] for extraction of intracellular metabolites. This method involves spraying the cells into -40 degrees C methanol; the neutral pH allows extraction of nearly all intracellular metabolites, including NADH. Close to the shift from glucose to ethanol as a growth substrate, the cells acquire a make-up amenable to sustained oscillations in intracellular concentrations of NADH and glycolytic intermediates such as glucose-6-phosphate. NADH was found to oscillate between 200 microM and 400 microM intracellular concentration. The cellular make-up determining the tendency to oscillate is 'remembered' by the cells after three hours of starvation.

Glycolysis↗
PubMed1993

Control and regulation of metabolic fluxes in microbes by substrates and enzymes.

The control of enzymes and substrates on the flux through microbial metabolic pathways can be quantified in terms of flux control coefficients. In pathways involving group transfer, the summation theorem for flux control by the enzymes has to be modified: the sum of control by all enzymes is between 1 and 2. The phosphoenolpyruvate:glucose phosphotransferase system is such a pathway. Experimental determination of the control by the enzymes in this pathway is under way. The control of the enzymes on the glycolytic flux in yeast is low, with the possible exception of the uptake step. In Klebsiella pneumoniae potassium and ammonium ions can simultaneously be 'limiting', (i.e. have significant control on growth) at pH6, but not at pH8. This may be due to the fact that at pH8 the high-affinity potassium uptake system is absent.

Ammonia↗
PubMed1993

Frequencies of HPRT- lymphocytes and glycophorin A variants erythrocytes in Fanconi anemia patients, their parents and control donors.

The mutant frequency of 6-thioguanine resistance (HPRT locus) in circulating T lymphocytes from 23 Fanconi anemia (FA) patients has been determined. The glycophorin A (GPA) in vivo cell mutants assay, which detects allele loss variant phenotypes arising from mutations in erythroid progenitor cells of GPA heterozygous MN individuals, has been applied in parallel to FA patients. No significant difference in frequency of HPRT- mutants was observed in FA compared to age matched healthy donors. In contrast, the mean frequency of GPA variant cells was elevated 31-fold for hemizygous NO variants and 8-fold for homozygous NN variants in FA patients over normal controls. In heterozygous FA parents, HPRT- mutant frequencies and GPA variant frequencies were within the normal range. Molecular analysis of HPRT- mutants has previously shown that FA cells have a high tendency to form deletions. Knowing that the cellular events allowing the detection of mutations at the HPRT and the GPA locus differ, our results emphasize the possible correlation between events of spontaneous loss of heterozygosity and genetic predisposition to cancer as observed in FA.

Adolescent↗
PubMed1993

Action of endogenous oxytocin within the paraventricular or supraoptic nuclei: a powerful link in the regulation of the bursting pattern of oxytocin neurons during the milk-ejection reflex in rats.

During suckling, the periodic and synchronous bursting activity of oxytocin neurons has been shown to be facilitated by oxytocin itself, acting via several target sites, including the magnocellular nuclei. To investigate the role of the endogenous oxytocin released within the magnocellular nuclei during the milk-ejection reflex in the rat, an oxytocin antagonist (50 microM solution of [d(CH2)5, Tyr(Me)2,Orn8]-vasotocin was pressure-injected into either one paraventricular or one supraoptic nucleus while recording the bursting pattern of oxytocin neurons within the injected nucleus and within a contralateral nucleus. The oxytocin antagonist was injected either during an ongoing milk-ejection reflex or during its facilitation induced by oxytocin (1 microliter of 1 microM solution injected into the third ventricle, i.e. 1 ng). During an ongoing milk-ejection reflex, injections of the oxytocin antagonist (10 nl of 50 microM solution, i.e. 50 ng) into the paraventricular or supraoptic nucleus decreased (more than 20% change) the burst amplitude (total number of spikes/burst) of neurons within the injected nucleus in 100% of tests, and simultaneously of contralateral neurons in 68% of tests. Burst periodicity of the entire population was also decreased in 50% of tests whatever the nucleus injected, but burst desynchronization was never observed. Successive injections of minute volumes of oxytocin (10 nl of 10 microM solution, i.e. 0.1 ng) into the paraventricular or supraoptic nucleus (which will progressively affect a greater number of neurons) first increased burst amplitude of oxytocin neurons within the injected nucleus and then increased simultaneously burst amplitude of contralateral neurons and burst frequency of the whole oxytocin neuron population. All these results suggest that the recruitment of a critical number of oxytocin neurons within one nucleus induces changes in the bursting activity of the oxytocin neurons in the four magnocellular nuclei. Within the minute following an intracerebroventricular oxytocin injection, the oxytocin antagonist injected into the supraoptic nucleus not only prevented the oxytocin-induced facilitation but also completely interrupted the milk-ejection reflex. When injected into the paraventricular nucleus, the oxytocin antagonist was less efficient: it decreased the oxytocin-induced facilitation but the reflex was not blocked. Similar partial inhibitory effect (decrease in burst amplitude and burst frequency) was also observed when the oxytocin antagonist was injected into the supraoptic nucleus after facilitation of the milk-ejection reflex by intracerebroventricular oxytocin injection. In conclusion, endogenous oxytocin released within the magnocellular nuclei during suckling represents a necessary link of the neuronal network regulating the bursting activity of oxytocin neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Electrical activity of neurons in the ventrolateral septum and bed nuclei of the stria terminalis in suckled rats: statistical analysis gives evidence for sensitivity to oxytocin and for relation to the milk-ejection reflex.

Our previous results obtained by lesioning or stimulating the ventrolateral part of the lateral septum and the bed nuclei of the stria terminalis suggested that this area is involved in the control of milk ejection pattern in rats. The present study was undertaken with the aim of testing ventrolateral part of the lateral septum-bed nuclei of the stria terminalis neurons as a putative link of the neuronal network controlling the bursting activity of oxytocin neurons in suckled lactating rats (anaesthetized with urethane). Ventrolateral part of the lateral septum-bed nuclei of the stria terminalis neurons were recorded simultaneously with hypothalamic oxytocin neurons in either the paraventricular or supraoptic nucleus in rats with (n = 26) or without (n = 29) periodic milk ejections. Analysis of their firing pattern enabled differentiation of two subgroups: type I, characterized by numerous high frequency spikes, often grouped in clusters; and type II with very few or no high frequency clusters of spikes. The probability density function of the interspike intervals of both patterns could be modelled using a mixture of two log-normal distributions, the parameters of which differed significantly. The presence of absence of milk ejections did not influence the overall mean level of activity (2.0 +/- 0.5 and 1.9 +/- 0.4 spikes/s, respectively). However, the characteristics of the type I firing pattern were affected by the presence of the milk-ejection reflex. The average level of activity was not always constant and 16/55 ventrolateral part of the lateral septum-bed nuclei of the stria terminalis neurons displayed cyclical activity (from 0.6 +/- 0.2 to 4.0 +/- 0.5 spikes/s) both in the presence (n = 8) and absence (n = 8) of the milk-ejection reflex. In five of eight neurons recorded during milk-ejection reflex, the cycles in firing were clearly correlated with the bursting of oxytocin neurons. These five neurons exhibited the type I firing pattern. The three remaining neurons and the eight neurons recorded in the absence of milk-ejection reflex displayed the type II firing pattern. Oxytocin (1-2 ng = 0.45-0.9 mU) was injected into the third ventricle (i.c.v.) in order to examine the possible involvement of ventrolateral part of the lateral septum-bed nuclei of the stria terminalis neurons in the facilitatory effect of oxytocin on the reflex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Long-term bone marrow culture in Fanconi's anaemia.

Fanconi's anaemia (FA) is the most common of the constitutional aplastic anaemias; the mechanisms leading to aplasia in this disease are poorly understood. A number of mechanisms have been implicated in the pathogenesis of acquired aplastic anaemia (AA), including a stem cell defect, an immune reaction against haematopoietic cells or defective function of the marrow microenvironment. To investigate the pathophysiology of this disorder we have performed bone marrow colony forming unit-granulocyte macrophage (CFU-GM) assays and long-term bone marrow culture (LTC) in 22 cases of FA compared with 17 cases of acquired AA. Defective in vitro haematopoiesis was observed in all patients with FA, including several cases with normal peripheral blood counts. The mean CFU-GM value for the FA group was approximately 15 times lower than for the normal group. A correlation was seen between CFU-GM and the severity of neutropenia in FA. In LTC an adherent layer formed in all cases of FA; despite this fact CFU-GM were either not generated or rapidly fell to zero in all patients. LTC is a sensitive method for the detection of impaired granulopoiesis in FA and reveals defects in all patients with this disease.

Adolescent↗
PubMed1993

Pharmacokinetics of apomorphine in parkinsonian patients.

Apomorphine, a dopamine agonist, has been used efficiently in parkinsonian patients to treat severe levodopa-induced on-off phenomenon. Motor improvement has been obtained both with continuous subcutaneous (SC) infusions, and multiple SC injections. So as to assist in the understanding of the clinical results, we studied the peripheral pharmacokinetics of apomorphine in 20 patients after intravenous (IV) or SC injections in the anterior abdominal wall and in the thigh at various doses, or SC infusion. Plasma apomorphine levels were measured by high-performance liquid chromatography with electrochemical detection. After an SC injection in the abdominal wall, the Tmax was brief (16 +/- 11 min) the drug was rapidly cleared from the plasma and had a short plasma half-life (69.7 +/- 25.8 min). The AUC was similar following SC and IV injections, suggesting that apomorphine was completely absorbed from subcutaneous tissue. Inter-subject variability in drug absorption was large. We noticed a trend towards a more complete absorption following injection in the abdominal wall rather than in the thigh. In patients chronically treated by continuous SC infusion, the apparent plasma half-life was five times longer than that following SC or IV injections. These pharmacokinetic data may explain the rapid onset and brief duration of clinical effects, and the usefulness of individual titration for intermittent SC apomorphine injections, and the smoother motor response obtained with continuous SC infusions.

Abdomen↗
PubMed1993

The Colorado Tobacco-Free Schools and Communities Project.

This article defends the appropriateness of tobacco-free school policies as an effective tool toward ensuring young people develop into healthy and intellectually strong adults, and demonstrates how such a policy can be introduced into a school district. Health education efforts to eliminate tobacco use are widely considered more effective when carried out in concert with school policies and adult role models offering the consistent message that tobacco use is unhealthy and unacceptable. Studies indicate students who attend schools with strict smoking policies are less likely to begin smoking than students who attend schools without such policies. Through research, support, and guidance, the Colorado Tobacco-Free Schools and Communities Project successfully has assisted almost half the 176 school districts in Colorado to adopt such policies.

Adolescent↗
PubMed1993

[Regressive leukoencephalopathy induced by an overdose of cyclosporine A].

We report a case of leucoencephalopathy with tremor and generalized motor seizures a few days after introduction of cyclosporin A (Cy A) in a kidney recipient. There was a relationship between acute neurological symptoms and high and sudden blood level of Cy A (1 260 ng/ml; therapeutic range: 120-275 ng/ml). White-matter hypodensities at CT scanning and severe slow-waves abnormalities at EEG were present. All neurological symptoms were reversible after Cy A level was lowered. Three months later, a blood Cy A level at 217 ng/ml due to nicardipine co-administration resulted in severe tremor and was reversed by decreasing blood Cy A level to 126 ng/ml.

Cyclosporine↗