Biomedical subjects

M Valentin

Publications and source records attributed to M Valentin.

At least 19 recordsLinked to original sources

PubMed2000

The transport modifier RS1 is localized at the inner side of the plasma membrane and changes membrane capacitance.

Previously we cloned membrane associated (M(r) 62000-67000) polypeptides from pig (pRS1), rabbit (rbRS1) and man (hRS1) which modified transport activities that were expressed in Xenopus laevis oocytes by the Na(+)-D-glucose cotransporter SGLT1 and/or the organic cation transporter OCT2. These effects were dependent on the species of RS1 and on the target transporters. hRS1 and rbRS1 were shown to be intronless single copy genes which are expressed in various tissues and cell types. Earlier immunohistochemical data with a monoclonal IgM antibody suggested an extracellular membrane association of RS1. In the present paper antibodies against recombinant pRS1 were raised and the distribution and membrane localization of RS1 reevaluated. After subcellular fractionation of renal cortex RS1 was found associated with brush border membranes and an about 1:200 relation between RS1 and SGLT1 protein was estimated. Also after overexpression in X. laevis oocytes RS1 was associated with the plasma membrane, however, at variance to the kidney it was also observed in the cytosol. Labeling experiments with covalently binding lipid-permeable and lipid-impermeable biotin analogues showed that RS1 is localized at the inner side of the plasma membrane. Western blots with plasma membranes from Xenopus oocytes revealed that SGLT1 protein in the plasma membrane was reduced when hRS1 was coexpressed with human SGLT1 which leads to a reduction in V(max) of expressed glucose transport. Measurements of membrane capacitance and electron microscopic inspection showed that the expression of hRS1 leads to a reduction of the oocyte plasma membrane surface. The data suggest that RS1 is an intracellular regulatory protein that associates with the plasma membrane. Overexpression of RS1 may effect the incorporation and/or retrieval of transporters into the plasma membrane.

Animals↗

PubMed2000

Progressive inactivation of the haploid expressed gene for the sperm-specific endozepine-like peptide (ELP) through primate evolution.

The endozepine-like peptide (ELP) is a novel intracellular molecule which is expressed in high amounts at both mRNA and protein levels very specifically in late haploid male germ cells. It is closely related to the ubiquitous acyl-CoA binding protein, is highly conserved, shares a similar ability to bind mid-long chain acyl-CoA, and is thus likely to be involved in mature sperm metabolism. While it has been characterized from diverse mammals, it has so far not been possible to identify an equivalent molecule in the primate testis. Using a PCR approach, combined with cDNA cloning and Northern hybridization, testicular transcripts and/or genomic DNA were analysed for different primate species, including human. In the marmoset and cynomolgus macaque normally structured transcripts appear to be expressed, though at a low level. In the human testis, two rare transcripts were characterized, hELP1 and hELP2, the products of independent duplicated genes. Both transcripts were longer than in non-mammalian species, included frame-shift mutations and substantial sequence insertions, preventing the translation of a sensible protein. Genomic PCR analysis of three anthropoid species, chimpanzee, gorilla and orangutan, showed the presence of a similarly mutated hELP1 gene. Only in the gorilla was a hELP2 gene identified, apparently lacking the frame-shift mutation, and thus potentially able to give rise to a functional ELP protein. Taken together, these results show that during primate evolution there has been a progressive inactivation of the ELP gene, initially with a down-regulation in lower primates, and subsequently with inactivating mutations in the open reading frame. At some time during simian evolution prior to these mutations there has been a gene duplication, though this second gene has also become inactivated in humans. In its pattern of evolution the ELP gene shows similarities with the MDC/fertilin family, whose members are also considered essential components of haploid sperm in non-primates, but which are progressively inactivated in anthropoids and humans. We should like to speculate that the established subfertility of the human male may not be a recent event, but the consequence of a longer evolutionary process whereby primates have traded off absolute fertility against social or sexual advantages.

Amino Acid Sequence↗

PubMed2000

Structure and expression of the mouse gene encoding the endozepine-like peptide from haploid male germ cells.

The endozepine-like peptide (ELP) represents a testis-specific isoform of the ubiquitous acyl-CoA binding protein (ACBP) and is highly expressed in late haploid stages of male germ cell development. The genomic sequence of the functional ELP gene as well as that of a pseudogene were analysed from independent bacteriophage clones of a 129sv mouse genomic library. Unlike the ACBP gene, which comprises four exons, the ELP gene has only a single intron within the region of the 5' untranslated region, suggesting that, like some other haploid expressed genes, the ELP gene might have evolved by retroposon-mediated gene duplication. Primer extension analysis was used to define the start site for transcription and hence the 5' promoter region. Electrophoretic mobility shift analysis was carried out on this region comparing nuclear extracts from adult mouse testis with those from mouse liver. Several testis-specific DNA-protein complexes were observed throughout 700 bp upstream of the transcription start site. One of these could be identified as corresponding to a steroidogenic factor-1 (SF-1) binding element. Further analysis using pure transcription factors showed that this element at position -340 was able to bind specifically to both SF-1 and to the germ cell nuclear factor (GCNF). Immunohistochemical analysis using an ELP-specific antibody showed that expression was very restricted within the testis to the postmeiotic germ cells, and in the ovary to interstitial/luteal cells, cell-types known to express GCNF and SF-1, respectively. Testes of CREM-tau knockout mice, lacking all spermatogenic stages later than round spermatids, were devoid of ELP immunoreactivity, whereas in RAD6 knockout mice the few remaining elongated spermatids were clearly defined by this excellent late haploid marker product. The ELP gene and its product thus offer an ideal system with which to investigate the differentiation of late haploid stages of spermatogenesis.

Animals↗

PubMed1996

[Lavoisier, forerunner of ergonomics].

Marcelin Berthelot has written that Lavoisier's physiological revolution has been nearly as important as his chemical one. Moreover he went beyond theoretical researches by a continual approach of labour and human environment, making himself a real precursor of ergonomics. Thus indeed can be considered his works on lighting, room aeration, hospitals reorganization, improvement of jails, transfer of slaughter-houses, watering and water-course, cesspools. Finally and chiefly his experimentation with Seguin on respiration and perspiration, as well as the wording of the program of the Prizes of Insalubrious Arts realize a genius' prospect of labour physiology and medicine already enclosed in what will later be ergonomics.

Environment↗

PubMed1995

[From simple past to future tense. The essential role of medical history, an example: saturnism].

Too frequently seen as an underknowledge, History of Sciences and Medicine may be quite on the contrary see understood as anmatter exemplary matter of instruction for students and practicians. This paper shows how it is possible to interpret difficult cases by a good knowledge of very old medical and historical stories, and the example of past diseases owing to saturnism (lead poisoning) may be very eloquent.

Education, Medical↗

PubMed1995

[The Royal Society of Medicine, harbinger of occupational medicine and ergonomics].

During her short life (1776-1793), the Royal Society of Medicine of Paris brought forth which will become Occupational Medicine. It was indeed at the meetings of the Royal Society that Fourcroy presented in 1776 the french translation of "De morbis artificum diatriba" from Ramazzini (1701), with introduction and notes showing evolution of knowledge. Then, from 1779 to 1793, corresponding fellows physicians, manufacturers, inspectors, showed professional diseases, prevention's means, learning's methods and diffusion's possibilities. Those impulses, too early stopped, will be born again during the XIX th. century and will arrive with Devoto in 1901 to the first using of a specific expression which will be in italian "Medicina del Lavoro".

Ergonomics↗

PubMed1994

[Vigilance and quality of sleep in night nurses].

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Adult↗

PubMed1993

Preparation of active recombinant TIMP-1 from Escherichia coli inclusion bodies and complex formation with the recombinant catalytic domain of PMNL-collagenase.

TIMP-1 is a member of the family of tissue inhibitors of metalloproteinases involved in regulating the activity of extracellular matrix degrading metalloproteinases. The TIMP-1 cDNA was obtained by reverse transcription-polymerase chain reaction (RT-PCR) amplification of the corresponding mRNA from human fibroblasts. Cloning and expression of the TIMP-1 cDNA were performed in Escherichia coli. In the host vector system chosen, rTIMP-1 is stored intracellularly in its denatured, insoluble form in inclusion bodies. We report a new method for the purification and renaturation of rTIMP-1 from E. coli inclusion bodies to an active inhibitor of matrix metalloproteinases (80% yield), presumably containing the correct assignment of the six disulfide bonds. A resin with the covalently bound recombinant catalytic domain of the PMNL-collagenase as the affinity ligand provided an effective means for the separation of correctly folded, active rTIMP-1 from inactive forms with mismatched disulfides. TIMP-1 and TIMP-2, the two most extensively examined members of the family of tissue inhibitors of metalloproteinases, are known to form a complex with the activated forms of most matrix metalloproteinases and the latent forms of the 92-kDa and 72-kDa gelatinases, respectively. In this study, we report on the complex formation of the recombinant catalytic domain of the PMNL-collagenase with TIMP-1, nonglycosylated recombinant TIMP-1, and recombinant TIMP-2. The Ki values for the different inhibitors were determined in a kinetic assay using a fluorogenic substrate peptide. In this assay, rTIMP-2 had a more effective inhibitory capability against the recombinant catalytic domain of the PMNL-collagenase than TIMP-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1993