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Biomedical subjects

A Nicolas

Publications and source records attributed to A Nicolas.

At least 145 records · Page 8Linked to original sources
PubMed1983

[Case of mucolipidosis type I with a primary alpha-D-neuraminidase deficiency].

The authors describe a case of mucolipidosis I, the 9th reported in the world literature. The diagnosis was suspected in a 5 year old boy, from the appearance of hurler-like facial features. Lumbar kyphosis, dysostosis multiplex, cherry-red macular spot and foam cells in the bone marrow and it was confirmed by the characteristic oligosacchariduria (on thin layer chromatography) and excess sialic acid in cultured fibroblasts which also showed profoundly diminished activity of alpha D Neuraminidase (on two substrates - N-acetyl-Neuramin Lactose and 4 Methyl umbelliferyl N-acetyl-Neuraminide). The parents had intermediate enzyme activities, suggesting heterozygotism. After a review of the literature, the authors attempt to define the place of mucolipidosis I in the sialidoses.

Acetylglucosaminidase↗
PubMed1983

[Astrocytoma of the cerebellum in children. Apropos of 57 cases].

57 children with a cerebellar astrocytoma have been operated on between 1964-1982. Since 1977, CT Scan has led to safer and earlier diagnosis. CT Scan has documented three macroscopical types of cerebellar astrocytomas; a cystic form with a mural nodule enhanced and the wall of the cyst non enhanced, a cystic form with a nodule and the wall of the cyst enhanced, and a massive form. 6 patients were submitted to a ventricular-atrial shunt before direct surgery. All the patients underwent posterior fossa surgery in the sitting position. Removal of the tumor was macroscopically total in 48 patients. Removal is limited to the nodule for cystic form with the wall non enhanced. Removal is extended to the wall of the cyst when it is enhanced. In 9 patients, the CSF pathway was restored at the end of the procedure by cannulation of the Aqueduct with silastic tube. 3 patients died postoperatively (5.2%), 2 others later on (4 and 8 years). 3 patients had a recurrency. In 6 patients, radiation therapy was used after surgery.

Adolescent↗
PubMed1980

Heterotransplantability testing in nude mice of candidate cell for vaccine production.

Regulations for vaccine production require that candidate cells of human origin must be controlled for the absence of tumourigenic activities by heterotransplantability in animals. Usually, the test was done in the cheek-pouch of three week old hamsters, but this method presents disadvantages; long observation period (3 months) and a high rate of intercurrent diseases. The authors describe their experience using nude mice pretreated with antithymocyte serum of rabbit origin; the observation period is reduced to three weeks, the test is easy to perform and to read.

Animals↗
PubMed1979

Variation of gene conversion and intragenic recombination frequencies in the genome of Ascobolus immersus.

Eighty mutants in 17 ascospore character genes were studied for their conversion patterns. The correlation between conversion pattern and mutagenic origin, previously found in genes b1 and b2 was extended to all the genes studied. Aberrant 4:4 asci were found in most genes irrespective of their conversion frequency. From gene to gene, the conversion frequency showed an almost 100 times variation. The frequency of intragenic recombination also showed sharp variation from gene to gene. The mean conversion frequency and the maximal intragenic recombination frequency were shown to be highly correlated in 5 genes for which these 2 values are known. This correlation was extended to 12 other genes in other Ascomycetes: Saccharomyces cerevisiae, Schizosaccharomyces pombe, Neurospora, and Sordaria. From this study it is concluded that, 1) the probability of hybrid DNA formation undergoes considerable changes according to the region of the genome; 2) the intragenic recombination frequency primarily reflects the frequency of hybrid DNA formation rather than the physical length of the gene; 3) for a given physical distance on the DNA, a similar fraction of the gene conversion events lead to recombination in the 5 Ascomycetes.

Ascomycota↗
PubMed1979

Analytical study of ionized or ionizable groups of platelet membrane.

The knowledge of the molecular surface groups of the human blood platelets present a particular interest especially in some thrombotic processes or thrombocytopathies. The aim of this study was to approach quantitatively ionized or ionizable groups of the platelet membrane using liquid phase electrophoresis or physicochemical and analytical methods with specific reagents. A mean repartition of the principal groups (carboxyl, SH, amino and phosphate) on the membrane is obtained by cell electrophoresis.

Blood Platelets↗
PubMed1978

Study of amino groups of the human platelet membrane.

The authors attempted to evaluate different reagents in order to quantify the amino groups of the platelet membrane. The study was carried out by the action of different aldehydes and acid anhydrides. The use of 2,4,6-trinitrobenzenesulfonic acid made possible an approach by electrophoresis and chemical assay. The results showed an increase in the surface charge corresponding to a mean number of amino groups varying from 1.86.10(5) groups with citraconic acid to 3.94.10(5) groups with acetaldehyde.

Aldehydes↗
PubMed1978

Combination of attenuated measles vaccine (Schwarz) with meningococcus A and A + C vaccine.

There is an obvious interest in a combined meningococcus-measles vaccine since the two diseases are widespread and serious in Third World countries among children under five years of age. The purpose of our study was to show the safety and effectiveness of such a combined preparation. The study covered 110 children between 8 months and 4 years of age who were followed systematically in a maternal child health center in the Paris area. Only 93 of them were checked before and after the immunization. The serologic titrations by the hemagglutination assay (IHA) for measles, and by radioimmunological assay (RIA) for meningococcus A and C showed that the Schwarz strain measles vaccine combined with meningococcus A or the association A+C does not interfere with the increase of A or C titers. 100% of the children showed a seroconversion equal to or less than 2 micrograms per ml, in the case of meningococcus A, as well as for C, regardless of age. Furthermore, 88% of the subjects showed a titer greater than or equal to 4 micrograms for the meningococcus A and 79% for C. On the other hand, meningococcus A or the association A+C seem to depress measles vaccine activity. Nevertheless, more than 80% of the children tested showed seroconversion when the measles vaccine was combined with meningococcus A, and only 69% when combined with meningococcus A and C.

Age Factors↗
PubMed1978

Killed poliovirus antigen titration in humans.

To establish the antigen content of a killed poliovirus vaccine sufficiently potent to induce immunity with one or two doses and to establish a reference standard vaccine which has been tested under field conditions, a titration was carried out in infants to determine the amount of each of the three antigenic types of poliovirus vaccine required to induce seroconversion with a single dose. It has been observed that over a critical range of antigen concentration there is an essentially linear relationship between antibody response and quantity of antigen administered. More than 90 percent of the groups studied had detectable antibody after receiving single injections of 80, 8 and 64 D-antigen units of Types I, II and III, respectively. Four-fold less antigen for each of the three types was less effective. The implications of these findings for an efficient immunization procedure are discussed.

Antibodies, Viral↗
PubMed1977

Study of carboxyl groups on the human blood platelet membrane.

The authors have studied the whole carboxyl groups of the platelet membrane using liquid phase electrophoresis and an initial step of activation of the acid group by a water soluble carbodiimide (ethyl-l-diméthyl-aminopropyl-3-carbodiimide), followed by the action of a nucleophilic molecule. The calculation based on the theory of Gouy-Chapman have shown the existence of 24, 7.10(5) groups per cell. That is a number about 2.5 fold superior to the carboxyl groups of sialic acid as determined by the action of neuraminidase.

Blood Platelets↗
PubMed1975

[Physicochemical study of platelet aggregation by 3 polylysines].

The action of polylysines of various molecular weight on platelet behaviour is studied with the help of 3 techniques: photometric test, screen filtration pressure on PRP and electrophoretic mobility. Polylysines, which are polybasic substances, produce a platelet aggregation studied by photometry after a short period of latency. Aggregation, depending on the doses of poly-lysine and chiefly on the optic density, shows a "plateau" with the dose of 100 gamma/ml for poly-lysine L, of molecular weight 17000. The screen filtration pressure increases continuously in the presence of the polylysines studies. Finally, the platelet charge decreases. The results depend on the concentration of poly-lysine, and the optimal concentration which involves the more marked alterations is inversely proportional to the molecular weight of the polylysine studied.

Blood Platelets↗