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Biomedical subjects

I Vidal

Publications and source records attributed to I Vidal.

17 recordsLinked to original sources
PubMed1999

Transforming growth factor beta isoforms in human optic nerve heads.

AIM: To determine if the isoforms of transforming growth factor beta (TGF-beta) are present in fetal, normal adult, and glaucomatous optic nerve heads. METHODS: To localise cells synthesising TGF-beta, optic nerve heads were stained using antibodies to TGF-beta 1, TGF-beta 2, and TGF-beta 3. To demonstrate synthesis, human optic nerve heads from fetal, glaucomatous, and normal age matched subjects were explanted, cultured overnight, and the culture supernatant was assayed for the presence of TGF-beta 1 and TGF-beta 2 by bioassay. In addition, semiquantitative RT-PCR was performed to determine the gene expression pattern of TGF-beta 2. RESULTS: Immunohistochemistry of glaucomatous samples revealed the presence of intense staining for TGF-beta 2 primarily in astrocytes, whereas TGF-beta 1 was localised to blood vessels. No TGF-beta 3 immunoreactivity was observed. There was little or no expression of TGF-beta in normal optic nerve heads. Optic nerve heads from glaucomatous eyes released 70-100-fold more TGF-beta 2 than normal age matched optic nerve heads. Fetal optic nerve heads released 90-100-fold more TGF-beta 2 than normal adult optic nerve heads. TGF-beta 1 was undetectable by bioassay in all samples tested. There was no apparent increase in TGF-beta 2 gene expression in glaucomatous and fetal eyes, suggesting post-transcriptional regulatory mechanisms. CONCLUSIONS: These results demonstrate that TGF-beta 2 is produced in high levels in the fetal and glaucomatous optic nerve heads, perhaps by a mechanism of post-transcriptional regulation. TGF-beta may be important during development of the optic nerve head and, in glaucoma, TGF-beta 2 may be a mediator of astrocyte reactivation and extracellular matrix remodelling in the lamina cribrosa.

Aged↗
PubMed1999

[Is the a connection between prolonged carriage and clonal hospital-to-hospital clonal spread of multiresistant Pseudomonas aeruginosa of the O12 serotype? Are the specific habits of the hospitals involved the cause?].

Results obtained using our expert computer program (SIR, 12A, Montpellier, France) over the last seven years (1991-1998) suggest that the increased incidence of superficial pus infection or colonization with O12 Pseudomonas aeruginosa, together with the significantly longer carriage duration for this organism as compared to non O12. P. aeruginosa, may contribute to the current endemic clonal spread of O12 P. aeruginosa in a general hospital in Rodez, France, and in neighboring extended-care facilities. This ecological observation may reflect poor compliance with basic hygiene procedures in the Rodez hospital and in neighboring hospitals. The O12 P. aeruginosa clone in the Rodez hospital is indistinguishable from the one that has disseminated throughout Europe, suggesting that the ecological observation and hypothesis described herein may deserve to be investigated in other institutions that are also the site of endemic clonal O12 P. aeruginosa dissemination.

Disease Outbreaks↗
PubMed1998

Elastosis of the lamina cribrosa in glaucomatous optic neuropathy.

The purpose of this study was to determine whether elastotic degeneration of the elastin component of the lamina cribrosa occurs in optic neuropathy associated with different types of glaucoma. Human optic nerve heads with primary open-angle, neovascular, chronic angle closure and pseudoexfoliation glaucoma, and with varying duration of disease were compared with age-matched normal eyes, using electron microscopy and immunogold labeling of elastin. The percent area occupied by immunogold-labeled elastin material was determined using a digital image analysis system. In all eyes with a history of glaucoma, elastosis was found in the lamina cribrosa and there was a significantly greater percentage of area occupied by elastin compared with age-matched control eyes (P<0.0001). Among the glaucomatous eyes, pseudoexfoliation glaucoma had the largest area of elastosis, followed by primary open-angle and secondary glaucoma (neovascular and chronic angle closure). In all glaucoma samples, large, confluent elastin aggregates of irregular and varied shapes (elastosis) were observed in the lamina cribrosa and insertion region. These results demonstrate that glaucomatous optic neuropathy is associated with elastosis of the lamina cribrosa, which may contribute to the changes in compliance of the optic nerve heads of glaucomatous eyes.

Aged↗
PubMed1998

[Evaluation of aa tracking system for labile blood products in the Midi-Pyrenes region].

At the request of the regional authority, the system of traceability of blood products in the Midi-Pyrenees area in France was assessed using available documentation, visits and interviews of participants. We studied the time needed to obtain traceability data in the Blood Banks and the reactivity of the system defined as the time needed to carry out a simulated descending transfusional survey. This information allowed us to assess usefulness and cost of the system, its applicability and the timeliness of information, according to the criteria of the Centers for Disease Control. The system is based on a standardized nominative form for the delivery of blood products and specific feedback. For the participants, traceability makes transfusional surveys easier and improves transfusions safety. In two of the 130 hospitals, the system is linked to the "program of medicalization of information systems". In the 2nd semester of 1996, the traceability proportion was 97%. For a given date of distribution, 75% of blood products were traced in 14 days and 83% in a month. The study of reactivity showed that all donations coming from two randomly chosen blood collection sites could be traced in about 2 hours. This first evaluation of a regional system of traceability showed its feasibility and acceptability, based on evaluation criteria of a public health surveillance system. A continuous evaluation process would be necessary to assess the good functioning of the system and to detect and prevent possible deficiencies.

Blood Banks↗
PubMed1997

Expression of neural cell adhesion molecule (NCAM) characterizes a subpopulation of type 1 astrocytes in human optic nerve head.

The human optic nerve contains a heterogeneous population of astrocytes. In situ, a specialized subpopulation of astrocytes was distinguished in the adult optic nerve head by expression of neural cell adhesion molecule (NCAM). To further study the biology of astrocytes, we have developed and characterized cells grown from explanted optic nerve heads and myelinated optic nerves as in vitro model systems. Second or third passage cells were processed for immunocytochemistry using antibodies against glial fibrillary acidic protein (GFAP) and cell surface epitopes: CD56/NCAM, HNK-1/NCAM, A2B5, and O4. Synthesis and gene expression of NCAM were characterized by Western blot analysis and RNase protection assay. Cells grown from myelinated optic nerves expressing GFAP, but not NCAM or A2B5, were identified as type 1A astrocytes, and cells expressing GFAP and A2B5, but not NCAM, were identified as type 2 astrocytes. Cells grown from explanted optic nerve head expressing GFAP, NCAM, and O4 were identified as type 1B astrocytes. Expression of NCAM by type 1B astrocytes may provide these cells with adhesion properties that allow them specialized responses in their microenvironment. Astrocytes from the lamina cribrosa may form a functional barrier to prevent myelination of the retina. In glaucoma, these astrocytes may be exposed to stresses due to fluctuation in intraocular pressure and therefore participate in the optic nerve changes associated with glaucomatous optic neuropathy.

Adult↗
PubMed1997

Distribution of lutein and zeaxanthin stereoisomers in the human retina.

The distribution of macular pigment stereoisomers in the human retina has been mapped and a pathway to account for the presence of the non-dietary carotenoid, meso-zeaxanthin, is proposed. Adult neural retinas were cut into three concentric areas centered on the fovea, and the extracted carotenoids were analysed and purified by high-performance liquid chromatography. The dicarbamate or dibenzoate derivatives of the collected zeaxanthin fractions for each tissue sample were further analysed by HPLC to determine their stereoisomer composition. Whole retinas from infant eyes were similarly analysed. The results show that, relative to zeaxanthin, the concentration of lutein in the adult neural retina increases with radial distance from the fovea while that of meso-zeaxanthin decreases. Infant retinas were found to have more lutein and less meso-zeaxanthin, relative to zeaxanthin, than adult retinas. Small quantities of (3S, 3'S)-zeaxanthin were also found in the adult retina, particularly in the macula. It is proposed that lutein and zeaxanthin are transported into an individual's retina in the same proportions found in his or her blood serum. Some of the lutein is then converted into meso-zeaxanthin, primarily in the macula, by a mechanism which is less developed in infants than adults.

Age Factors↗
PubMed1988

Purification and characterization of diacetyl-reducing enzymes from Staphylococcus aureus.

A method was developed to purify diacetyl-reducing enzymes from Staphylococcus aureus. Two enzymes capable of catalysing diacetyl reduction were isolated, neither of which turned out to be a specific diacetyl reductase. One of them is a lactate dehydrogenase similar to the one from Staphylococcus epidermidis, which accepts diacetyl, although poorly. The other one uses as coenzyme beta-NAD and reduces uncharged alpha-dicarbonyls with more than three carbon atoms (especially the alpha-diketones diacetyl and pentane-2,3-dione), producing the L(+) form of the corresponding alpha-hydroxycarbonyls. This enzyme has an Mr of 68,000 and is, most probably, a monomer. Its optimum pH is 6.0. Its shows a high affinity for NADH and a rather low one for diacetyl, which, at least in vitro, does not seem to be as good a substrate as pentane-2,3-dione. We propose for it the systematic name L-alpha-hydroxyketone:NAD+ oxidoreductase and the recommended name of alpha-diketone reductase (NAD). We also suggest that the diacetyl reductase entry in the I.U.B. classification be suppressed.

Acetoin Dehydrogenase↗
PubMed1988

Kinetics of the diacetyl and 2,3-pentanedione reduction by diacetyl reductase (alpha-diketone reductase (NAD)) from Staphylococcus aureus.

The kinetic mechanism of diacetyl and 2,3-pentanedione reduction by diacetyl reductase from Staphylococcus aureus was investigated. The shape of the primary double reciprocal plots, the product inhibition pattern, and the features of the inhibition by a substrate analogue (acetone) show that diacetyl is reduced via an Ordered Bi-Bi mechanism, and 2,3-pentanedione by an Ordered Bi-Bi or Theorell-Chance mechanism. NADH is the leading substrate in both reactions. Affinity constants for the coenzyme and the substrates and inhibition constants for NAD, acetoin, and acetone were also calculated. This enzyme has a high affinity for NADH; Km (31-50 microM) and Ks (20-27 microM) for this compound are around one-tenth of the NADH intracellular concentration. Therefore, it must operate in vivo saturated with the coenzyme. This condition is not adequate to play the role, formerly proposed for diacetyl reductases, of regulating the equilibrium between oxidized and reduced forms of pyridine-nucleotides.

Acetoin Dehydrogenase↗
PubMed1985

Kinetics and thermodynamics of diacetyl reduction with NADPH by alpha-dicarbonyl reductase from pigeon liver.

alpha-dicarbonyl reductase from pigeon liver catalyzes diacetyl reduction with NADPH via an ordered Bi-Bi mechanism in which the coenzyme is the leading substrate, as deduced from the inhibition pattern by products and by acetone. The activation energy of the reaction has been calculated as 16.6 kcal/mol, delta H and delta F as 15.6 and 15.3 kcal/mol, respectively, and delta S as 1 cal/mol per k. Kinetic constants obtained for substrates (KmNADPH = 15 microM, KsNADPH = 10 microM; Kmdiacetyl = 0.5 mM, Ksdiacetyl = 0.35 mM) and products (KiNADP 50 microM; Kiacetoin = 100 mM) are about 10 times lower than those reported for this enzyme in the reduction of diacetyl with NADH. This confirms that NADPH is its physiological coenzyme.

Alcohol Oxidoreductases↗