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Biomedical subjects

V Thomas

Publications and source records attributed to V Thomas.

At least 127 records · Page 7Linked to original sources
PubMed1983

Further analysis of the effect of ultra-violet irradiation on the formation of the germ line in Xenopus laevis.

Ultra-violet (u.v.) irradiation of the vegetal pole of newly fertilized eggs has three documented effects: reduction of primordial germ cells (PGCs), cytological damage to the vegetal hemisphere and disruption of the normal mechanism by which the vegetal yolk mass induces the formation of the dorsal axis of the embryo. In this study, we find that 90 degrees rotation of the egg for various periods after irradiation rescues the dorsal axial structures but does not restore the number of PGCs found in the dorsal mesentery of the gut; neither is there any correlation between reduced numbers of PGCs and disruption of cleavage at the vegetal pole. We therefore conclude that the effect on the germ line is separate from the other two phenomena. Secondly, 90 degrees rotation of non-irradiated eggs was found to significantly reduce germ cell numbers migrating in the dorsal mesentery of the gut.

Animals↗
PubMed1982

Giardiasis.

Explore the source record for details and available documents.

Giardiasis↗
PubMed1981

Primordial germ cells of Xenopus embryos: the role of fibronectin in their adhesion during migration.

Primordial germ cells (PGCs) of Xenopus laevis are highly migratory. The last section of their migratory pathway is through the dorsal mesentery of the tadpole gut. This in vivo pathway is rich in fibronectin, a glycoprotein that promotes cell adhesion and migration in vitro. Isolated PGCs are associated with cells from the mesentery and with fibronectin. Treatment with trypsin removes both the mesentery cells and the fibronectin. The PGCs do not appear to resynthesize detectable fibronectin in vitro. In contrast, cultured adult mesentery epithelial cells synthesize large amounts of fibronectin and lay it down in subcellular fibrils that align with intracellular microfilament bundles. PGCs plated on cultured mesentery cell layers adhere to them, elongate and align with the microfilament bundles of the mesentery cells. PGCs adherent to mesentery cell layers are closely associated with fibronectin; moreover, F(ab)2 fragments of anti-Xenopus fibronectin IgG inhibit the adhesion and spreading of PGCs on the mesentery. These results indicate that PGCs can adhere to mesentery cells via fibronectin produced by the latter cells and suggest that fibronectin may be involved in the migration of PGCs in vivo.

Animals↗
PubMed1981

Seroepidemiology of malaria: age-specific pattern of Plasmodium falciparum antibody, parasite and spleen rates among children in an endemic area in peninsular Malaysia.

A seroepidemiological study was carried out on Orang Asli (Aborigines) children who lead a semi-nomadic life in the deep jungles of Ulu Kelantan, Malaysia. Out of a total of about 190 children below 14 years, 143 were studied. Blood was collected from finger pricks on standard "strip type" filter papers for indirect fluorescent antibody (IFA) tests with Plasmodium falciparum antigen. A positive reaction at 1:10 dilution in infants and young children was considered positive and the reasons are given. The P. falciparum antibody prevalence rate was 84.6% compared to 81.8% spleen and 43.4% parasite rates. Both P. Falciparum and P. vivax were present in children. The age-specific patterns of antibody, spleen and parasite rates were those of a hyperendemic community. There was a positive correlation between antibody and spleen rates up to the age of 9 years. In older children, the antibody rates increased while the spleen and the parasite rates dropped.

Adolescent↗
PubMed1981

Assessment of the sensitivity, specificity, and reproducibility of the indirect immunofluorescent technique for the diagnosis of amebiasis.

The indirect immunofluorescence (IIF) test was used to study antibody titers to Entamoeba histolytica in various manifestations of clinical amebiasis by comparing the results with parasitological and clinical data from confirmed cases. The sensitivity, specificity, and reproducibility of this test for diagnosis were also studied. A high degree of correlation was found between reactivity in the IIF test and confirmed cases of amebic liver abscess. A positivity rate of 96% in sera of confirmed cases of amebic liver abscess in the present study compares favorably with the results of other workers. The IIF test is very useful in the diagnosis of hepatic amebiasis but is less sensitive for amebic dysentery. The test could not be used to differentiate between hepatic amebiasis and amebic dysentery. The IIF test was insensitive for amebic colitis and of no diagnostic value. Specificity and reproducibility of the test were good, as shown by results obtained with sera from patients with parasitic infections other than amebiasis.

Amebiasis↗
PubMed1981

Prevalence of antibodies to parasitic infections in Nigerian children.

Sixty-six sera from Nigerian children who attended a paediatric clinic at University College Hospital, Ibadan were tested with Plasmodium falciparum, P. brazilianum, Entamoeba histolytica, Toxoplasma gondii and Schistosoma mansoni antigens using indirect fluorescent antibody technique. These sera were tested using ELISA technique for Schistosoma antibodies. Sera from all proven cases of infections gave positive results. Highest antibody prevalence rate was for P. falciparum (69.6%), followed by P. malariae (63.6%) and E. histolytica (42.4%) infections. About 17% and 16% were reactive with Toxoplasma and Schistosoma antigens respectively. Only nine (13.6%) children were negative with all antigens. Forty-four (66.6%) children were positive to two or more parasitic antibodies indicating exposure to those diseases. The significance of these antibodies in children is discussed.

Antibodies↗
PubMed1980

A case of congenital malaria in Malaysia with IgM malaria antibodies.

Congenital malaria from Malaysia is reported here for the first time. It occurred in a baby boy born to a 16-year-old primigravida who contracted Plasmodium falciparum infection during pregnancy. She suffered malaria during the later stages of pregnancy and at parturition. The placenta was heavily infested with various asexual stages of P. falciparum. Gametocytes were not seen. Extensive search did not show other species. Cord blood showed very light infection with young trophozoites of P. falciparum. Serological studies using IFA technique showed specific IgG and IgM antibodies to P. falciparum in maternal cord and two early neonatal sera. These serum samples showed lower levels of IgG antibodies against P. vivax and P. malariae, but there were no specific IgM antibodies against these species. The value of specific IgM antibody in the diagnosis of congenital malaria is discussed.

Adolescent↗
PubMed1980

Seroepidemiology of malaria in Peninsular Malaysia: Plasmodium falciparum antibody profile of adults in four states.

In 1973, 2610 sera were collected from adults living in 22 localities in four states in Peninsular Malaysia and tested by IFAT for Plasmodium falciparum antibodies. A larger number of thin films were examined. The attack phase of the Malaria Eradication Programme (MEP) in these areas was started between 1968 and 1973. The results showed that the highest prevalence rates and geometrical mean reciprocal titres (CMRT) were among adults from Kelantan where the antibody prevalence varied greatly among the adults and there was active transmission in at least three areas. The values were lowest for Kedah. The P. falciparum antibody prevalence rates were higher than the parasite rates as revealed in single thin film examinations but a number of the positive sera were reactive only at low titres. The low concentration probably indicated the residual antibody from cured cases or past infections and cross reactions to P. vivax and P. malariae infections. The strong reactions probably indicated current P. falciparum transmission as shown by positive thin films. The present study showed that the antibody profile of adults, as shown by IFAT, is of considerable value in assessing the malaria situation in a given area and that it would be useful as a malariometric tool in epidemiological studies to evaluate the progress of malaria eradication/control programmes.

Adult↗
PubMed1980

Biochemical and electron microscopic studies of the replication and composition of milker's node virus.

Replication of milker's node virus (MNV) DNA begins 4 to 8 h postinfection, continues to 30 to 36 h postinfection in the cytoplasm of infected, primary bovine embryonic kidney cells, and is accompanied by an inhibition of host nuclear DNA synthesis. Between 20 and 24 h postinfection, newly replicated genomes are incorporated into particles which cosediment with purified MNV. These biochemical measurements could be correlated with the development of MN virions as revealed by electron microscopic analysis of thin sections prepared from infected cells. Analysis of the DNA in purified MNV showed that the virions contained a double-stranded DNA molecule with a molecular weight of 85 x 10(6) to 87 x 10(6) and a guanine-plus-cytosine content of about 63%. After denaturation and sedimentation analysis of MNV DNA in alkaline sucrose gradients, three major DNA species were resolved. These species appeared to represent intact, terminally cross-linked genomes (approximately 75 to 80S); genomes bearing one nick (or with one cross-link removed) (60 to 65S); and complementary, denatured DNA strands released from cross-linked genomes bearing two nicks (or with both cross-links removed) (52 to 55S). Forty [35S]methionine-labeled polypeptides, ranging from approximately 200,000 daltons to 10,000 to 15,000 daltons, were detected by radioautography after polyacrylamide gel electrophoresis of the proteins present in detergent-solubilized MNV preparations. Treatment of MN virions with Nonidet P-40, beta-mercaptoethanol, and sonication released 10 polypeptides, which were apparently located on the surface of virions. Further fractionation of these released polypeptides, followed by electron microscopy and polyacrylamide gel electrophoresis, indicated that a 42,000- to 45,000-dalton polypeptide is a major component of the threadlike tubule structure present on the surface of MN virions.

Animals↗
PubMed1980

Experimental bacterial infection of the biliary tract.

The bacterial species commonly found in the human obstructed biliary tract were studied in an animal model of acute hepato-cholangitis. A rank order of their virulence and persistence in the bile and liver was shown which corresponded well to the clinical effects in the animals and also to the prevalence of bile bacteria in the benign bile duct stricture of man. Anaerobic organisms were found to be of low pathogenicity.

Animals↗
PubMed1980

Prevalence of antibodies including IgM to Toxoplasma gondii in Malaysians.

A total of 736 sera collected from cord blood babies, children and adults of both sexes and of different age groups in Malaysia were tested using indirect fluorescent antibody technique for Toxoplasma antibodies. The RH strain of Toxoplasma gondii zoites were used as antigen. One hundred and twenty five sera which were reactive at 1:64 or high titres were tested with IgM specific conjugate. Results of the present studies showed that the prevalence of Toxoplasma antibody was highest among the Malays and lowest among children than among adults. The significance of Toxoplasma specific IgM was discussed.

Adolescent↗
PubMed1979

Schistosomiasis: assessment of the sensitivity, specificity and reproducibility of serological methods for the diagnosis of schistosomiasis in Nigeria.

Three groups of sera were tested by indirect fluorescent antibody (IFA), complement fixation (CF) and counter-current immunoelectrophoresis (CCIE) techniques; 56 (10.1%) of 554 sera from Nigerians were anticomplementary and so could not be tested by the CF. Crude antigen extract of adult Schistosoma mansoni was used in the CF and CCIE tests and cercarial antigen in the IFA test. IFA was the most sensitive test and CF the most specific. The reproducibility of both these tests was good. The CCIE was the least sensitive and specific, and its reproducibility was poor. The IFA test was the most suitable for Nigerian conditions. Cross-reactions to S. haematobium antibodies were consistently present in all three tests and it was not possible to differentiate serologically S. mansoni from S. haemotobium. The interpretations of the results presented some difficulties because of the frequency of cross-reactions and false-positives, but the data fell within the infection prevalence rate of 50% reported earlier from south-western Nigeria. The IFA test was more specific and is considered ideal for serodiagnosis.

Adolescent↗