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Biomedical subjects

G Thomas

Publications and source records attributed to G Thomas.

At least 685 records · Page 38Linked to original sources
PubMed1988

[Genes of hereditary diseases that predispose to tumors].

Ten genes responsible for the increase of specific tumor incidence in affected families have been localized on the human genetic map. This knowledge not only provides the mean of a precise genetic counselling but also opens a way for further investigating the genetic mechanisms of these disorders. Usually, it is admitted that dominantly inherited familial predisposition to tumors is due to a defective tumor suppressor gene. This hypothesis is almost certain for familial retinoblastoma, highly probable for hereditary nephroblastoma and possible for neurofibromatosis type II. In contrast, the gene for familial polyposis coli shows some characteristics of activated oncogenes.

Chromosome Deletion↗
PubMed1988

[Pulsatile administration of GnRH: from the future to the present].

Since the first clinical reports of the successful induction of ovulations and pregnancies using pulsatile administration of the neuropeptide GnRH by G. Leyendecker and L. Wildt's group in 1979, the role of the hypothalamic generator, as demonstrated in primates by E. Knobil, is widely accepted in human reproduction. During this time, an increasing number of group has experienced these therapies and there continues to be some controversies about the route of administration, the indications, the need for adjuvant therapies. A correct evaluation of these therapies needs multicentric studies and more accurate criteria: the MINITEL network provides a fast, inexpensive way to collect data from different groups and to perform studies with larger sample sizes. The Life table analysis method represents the more suitable method for evaluating and for comparing various therapy regimens. LH plasma pulsatility studies have been performed in humans in order to classify various "supra-pituitary" reproductive disorders. These studies are exposed to several methodological drawbacks and must be cautiously interpreted. Modelling is one of the new methodological issues which can give access to more physiological parameters.

Female↗
PubMed1988

[Rapid acquired tolerance to cow's milk by oral route in a case of severe childhood food allergy].

An attempt to desensitize to cow's milk a 5 year-old girl who had been forced to follow a strict egg and milk-free diet with concomitant impossibility of attendance at school, posed major practical problems. In a hospital environment, under cover of treatment with Nalcron and Solemedrol, the re-introduction of milk was started with 10(-10) ml of milk. After a severe episode on the 1st day, the child was able to take 100 ml on the 10th day and thereafter. Today, the child continues with Nalcron treatment, but she no longer has a diet and she leads a normal lifestyle.

Administration, Oral↗
PubMed1987

A neural net model for the release of prolactin during pseudopregnancy in the rat.

A theoretical probabilistic neural net model is proposed here based on the interaction between two subsystems, the connections of which are made up by means of chemical markers. The activity of such a system at t = n tau is exclusively dependent on the firing record of the system at t = (n-1) tau, on the level of spontaneous activity and on an external inhibitory influence which we have found that may play an important role in the prolactin release level during pseudopregnancy in rats. We explore some of the implications of this model on the possible role of the hippocampus in the phenomenon.

Animals↗
PubMed1987

[Development and effectiveness of struma prevention in East Germany].

For the control of iodine deficiency disorders in man and animal since 1985/1986 measures have been introduced which were interdisciplinary attuned: 84% of the paketed salt are iodized (32 mg KIO3/kg) and iodized mixtures of mineral substances are used in the animal production of agricultural useful animals. The effectiveness of the iodine prevention becomes visible by an increase of the renal iodine excretion, regression of the frequency of connatal goitre and iodine deficiency disorders in the animal production. Increased manifestations of cases of hyperthyroidism as sequelae are of transient importance.

Goiter, Endemic↗
PubMed1987

Xanthine oxidase and endothelium dependent relaxation.

Superoxide anion (O2-) generated from xanthine oxidase/xanthine has been used to decrease the half life of endothelium derived relaxing factor (EDRF). However, by itself, xanthine oxidase causes endothelium dependent relaxation. This relaxation is unrelated to the oxidative property of the enzyme since it is not inhibited by allopurinol. In addition, the relaxation is not inhibited by the cyclooxygenase inhibitor, indomethacin, or the phospholipase A2 inhibitor, p-bromophenacyl bromide. On the other hand the relaxation is inhibited by the trypsin inhibitor (TI) from chicken egg white. A similar endothelium dependent relaxation elicited by pancreatin and trypsin is also inhibited by TI. Pancreatin used in the preparation of xanthine oxidase contains trypsin, chymotrypsin and carboxypeptidase. When compared to trypsin both chymotrypsin and carboxypeptidase elicit little relaxation. Thus the endothelium dependent relaxation elicited by xanthine oxidase is likely due to contamination with trypsin. Our results emphasize that when the superoxide generating system, xanthine oxidase/xanthine is used to study the effect of oxygen radicals on EDRF, it is advantageous to ensure that only purified preparations of xanthine oxidase are used.

Animals↗
PubMed1987

Microcrystals of tryptophan synthase alpha 2 beta 2 complex from Salmonella typhimurium are catalytically active.

An improved and efficient method has been developed for the purification of the tryptophan synthase alpha 2 beta 2 complex (EC 4.2.1.20) from Salmonella typhimurium containing a multicopy plasmid. Microcrystals prepared in 12% poly(ethylene glycol) 8000 containing 2.5 mM spermine are shown by scanning electron microscopy to have the same crystal habit as the larger crystals that are being used for structural analysis by X-ray crystallography. The average dimensions of the crystals are 33 microns (length) X 9 microns (width) X 3 microns (maximum thickness). Our finding that suspensions of microcrystals are active in several reactions catalyzed by the active sites of the alpha and beta 2 subunits demonstrates that both active sites are functional in the crystal and accessible to substrates. Thus the larger crystals being used for X-ray crystallographic studies should form complexes with substrates and analogues at both active sites and should yield functionally relevant structural information. A comparison of the reaction rates of suspensions of microcrystals with those of the soluble enzyme shows that the maximum rate of the crystalline enzyme is 0.8 that of the soluble enzyme in the cleavage of indole-3-glycerol phosphate (alpha reaction), 0.3 that of the soluble enzyme in the synthesis of L-tryptophan by the beta reaction or the coupled alpha beta reaction, and 2.7 that of the soluble enzyme in the serine deaminase reaction. These small differences in rates probably reflect functional differences between the crystalline and soluble enzymes since the reaction rates of the microcrystals are calculated to be virtually free of diffusional limitation under these reaction conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, Ion Exchange↗
PubMed1987

Use of vaccinia virus to express biopharmaceutical products.

Recent technological advancements have fostered the continued development of vaccinia virus as an efficient eukaryotic cloning and expression vector system. Genetically engineered vaccinia virus strains have been constructed for use (i) as recombinant vaccines for the prophylaxis of infectious disease, (ii) in producing significant quantities of biologically active polypeptide factors or enzymes, and (iii) as basic research tools with which to investigate primary structure-function relationships between proteins and their catalytic activities. This review examines the basic vaccinia vector system, its advantages and limitations, and current areas of research. As a specific example of the power and utility of this approach, attention is focused on the application of this technology to the field of neurobiology, specifically the use of recombinant vaccinia to study the expression, processing, and transport of cellular neuropeptides.

Cloning, Molecular↗
PubMed1987

Essential fatty acid deficiency during pregnancy in the rat: influence of dietary carbohydrates.

We investigated the role of gestation in the development of essential fatty acids (EFA) deficiency by comparing four groups of nonpregnant rats and four groups of pregnant rats fed either glucose or sucrose as carbohydrate source (61.5% kJ) and either corn oil (EFA) or hydrogenated coconut oil [saturated fat (SF)] as fat source (5% kJ). Pregnancy was a crucial period for the onset of EFA deficiency in sucrose-fed rats. The arachidonic acid content of plasma lipids and liver microsomes was lower in SF-sucrose pregnant rats than in SF-sucrose nonpregnant rats. The liver microsome delta 6- and delta 5-desaturase activities were higher in sucrose pregnant rats than in sucrose nonpregnant rats. In glucose-fed rats the EFA deficiency was less severe. delta 6- and delta 5-desaturase activities were higher in SF-glucose rats than in EFA-glucose rats, except for delta 5-desaturase of the pregnant rats, in which activity was high in both glucose-fed groups. This might explain the effect of glucose in preventing the onset of EFA-deficiency in pregnant rats fed an SF diet.

Animals↗
PubMed1987

Present results of the treatment of myelodysplastic syndromes with low-dose cytosine arabinoside. Preliminary results of a cooperative protocol (38 patients) and review of the literature.

In vitro differentiating agents causing little bone marrow aplasia have been proposed as a specific therapy of myelodysplastic syndromes with excess of blasts. A critical review of the published data is presented. The preliminary results of a cooperative protocol using very low dosage of cytosine arabinoside (3mg/m2/twice daily) with or without androgens are given.

Aged↗