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Biomedical subjects

S R Rao

Publications and source records attributed to S R Rao.

At least 19 recordsLinked to original sources
PubMed1992

An environmental survey in chrysotile asbestos milling processes in India.

Environmental monitoring to determine airborne asbestos fiber levels has been carried out in four different mills processing chrysotile asbestos in the Cuddapah District (Andhra Pradesh) of India. The "membrane filter method" comprising standard asbestos sampling techniques, acetone-triacetin method for sample preparation, fiber counting, and sizing using the phase contrast optical microscope were adopted in the study. Fiber concentrations both with respect to personal exposures and processing areas were found in most of the cases to be much higher than the prescribed Threshold Limit Value (TLVs) of the developed and developing countries for chrysotile asbestos. By optical microscopy, fiber length distribution showed 70% of fibers in the milling processes were in size range > 5-10 microns, whereas in > 10-20 and > 20 microns, 20% and 8%, respectively. Fiber identification for major elemental content, also done by using scanning electron microscope equipped with an energy dispersive X-ray analyzer, indicated the presence of tremolite along with chrysotile. The study stresses the urgent need to adopt suitable engineering controls at the dust generating sources to reduce the fiber level in the mill environment below the threshold limit.

Air Pollutants, Occupational↗
PubMed1992

Assignment of 6-phosphogluconate dehydrogenase and malate dehydrogenase to chromosome 3 of Anopheles stephensi.

Genetics and linkage analysis of 6-phosphogluconate dehydrogenase (6-PGD) and malate dehydrogenase (MDH) have been investigated in Anopheles stephensi. Both these markers were found to be autosomal and linked and have been assigned to linkage group III. Two mutant markers, Black larva (Bl) and golden-yellow larva (gy), were used to establish the map distances, and the current sequence of loci on chromosome 3 is as follows: Bl (3.75)-gy (14.53)-Mdh-2 (49.83)-6-pgd.

Animals↗
PubMed1992

Insect sex chromosomes, XI. 3H-TdR induces random aberrations in the X chromosome(s) of Gryllotalpa fossor (Orthoptera).

The pattern of titrated thymidine (3H-TdR), a direct precursor of DNA, induced aberrations on the X chromosome of Gryllotalpa fossor was examined. 3H-TdR produced aberrations randomly distributed over the entire length of the X chromosome; breaks were observed in both the eu- and the heterochromatic arms of the X chromosome in both the sexes. Since the eu- and the heterochromatic arms cannot be distinguished cytologically in this insect, the presence of aberrations on both arms of the same X chromosome in the male and damage to both X chromosomes in the female indicate that both euchromatic and heterochromatic regions (facultative or constitutive) are equally liable to aberrations induced by H-TdR. This is in contrast to the non-random induction of aberrations by 3H-UdR, which causes chromosome damage due to the proximity of the labeled RNA to the DNA template during transcription.

Animals↗
PubMed1992

Aniridia--Wilms' tumour association--a case with 11p 13-14.1 deletion and ventricular septal defect.

A two year old female child with bilateral wilms tumor (WT) along with multiple congenital anomalies like bilateral aniridia with congenital cataracts and nystagmus, microcephaly, mental retardation and ventricular septal defect has been described. The karyotype analysis revealed 46 xx, del 11p 13-14.1. Association of ventricular septal defect with the classical features of 'Aniridia-Wilms' tumor association' is an unusual feature in this case.

Aniridia↗
PubMed1991

Random/nonrandom X-chromosome inactivation in Nesokia indica: possible influence of heterochromatin.

Five types of X chromosomes with different amounts of heterochromatin have been observed in Nesokia indica, the Indian mole rat. They have been found in both mosaic and nonmosaic individuals. The influence, if any, of heterochromatin on the kinetics of X-chromosome DNA replication was evaluated in bone marrow cells and peripheral blood lymphocytes of Nesokia females with variant X chromosomes. In bone marrow cells of nonmosaic females a random X-chromosome inactivation (XCI) pattern was observed, except when there was a total loss of heterochromatin from the variant X chromosome, resulting in predominantly early replication. A nonrandom pattern was observed, however, in blood and bone marrow cells of all individuals with mosaic genotypes. In these females the X chromosome with the lesser amount of heterochromatin was predominantly the active one. The amount of heterochromatin per se or, more likely, specific sequences contained in the heterochromatic region seem to influence the XCI pattern in a cis-acting manner. The observations also seem to support a process of cell selection in individuals with variant X chromosomes.

Animals↗
PubMed1991

Replication status of the fragile X chromosome and its implications for reproductive performance in the Indian mole rat (Nesokia indica).

In all fertile females the fragile X chromosome was almost always late replicating (inactive) in an average 82% of cells whereas in infertile females, it was early replicating (active) in about the same percentage of cells. These observations strongly suggest a correlation between the replication (activity) status of the fragile X chromosome and reproductive performance.

Animals↗
PubMed1991

Cerebrospinal dehydrogenases in central nervous system infections.

Cerebrospinal fluid (CSF) dehydrogenases were studied in 42 controls, 23 children with pyogenic meningitis, 22 with tuberculous meningitis and 19 with encephalitis to assess their usefulness in differentiating between the different central nervous system infections. CSF-LDH and ICD activity was increased in CNS infections (p less than 0.0001), LDH being significantly higher (p less than 0.001) in pyogenic meningitis than in tuberculous meningitis or encephalitis. However, ICD activity was significantly different in each of these conditions (p less than 0.001). The dehydrogenase activity declined with subsequent clinical improvement, in all children with meningitis. A significant direct relationship was found between the enzyme activity and CSF protein content as well as total cell count. The 95% confidence interval confirms the utility of assaying CSF dehydrogenase activity to differentiate various CNS infections, thus improving the diagnostic ability.

Acute Disease↗
PubMed1991

Fanconi's anemia: a clinico-hematological and cytogenetic study.

Eleven patients with typical features of Fanconi's anemia with cytogenetic studies were evaluated. Cytogenetic abnormalities was seen in all but one patient. Two patients had acute non-lymphoblastic leukemia (ANLL) and nine had Fanconi's anemia (FA). All patients with FA responded to oxymetholone and are well with a median follow up of 38.6 months. Both patients with ANLL died. This study stresses the need of an accurate cytogenetic analysis in FA patients along with a clinicohematological correlation.

Abnormalities, Multiple↗
PubMed1991

Unusual splenic metastasis from oesophageal cancer.

The most common visceral metastasis from oesophageal carcinomas are lungs and liver. A case of splenic metastasis from a squamous carcinoma of oesophagus is reported. To our knowledge, splenic metastasis without any nodal disease has not been described previously. The pattern of reported metastasis is summarised.

Carcinoma, Squamous Cell↗
PubMed1979

Insect sex chromosomes. IV DNA replication in the chromosomes of Gryllotalpa fossor.

In Gryllotalpa the cell cycle duration in the hepatic caecae in vivo is about 12.5 h and of various phases are, G2 + P about 10 h, S about 2.5--3.5 h, and G1 appears negligible or absent. These estimates of the cell cycle are the only ones available in Gryllotalpidae. In the female Gryllotalpa, as in mammals, there is asynchronous DNA replication between the two euchromatic arms of the two X chromosomes. The other arm is constitutively heterochromatized and as expected is late replicating. Thus, a regulatory mechanism for dosage compensation by X chromosome inactivation appears to be operating in Gryllotalpa. This we believe, is the first cytogenetic demonstration of such a mechanism outside mammals.

Animals↗