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Biomedical subjects

P Chandra

Publications and source records attributed to P Chandra.

At least 145 records · Page 8Linked to original sources
PubMed1977

Inappropriate erythropoietin secretion in polycythemia vera.

A patient with classical polycythemia vera (PV) was found to have an inappropriately elevated serum erythropoietin (Ep) level. Investigations did not reveal any lesion or blood abnormality known to be associated with excessive Ep production and erythrocytosis. Sudden withdrawal of blood to reduce the Hb and Hct from 18.5 gm% and 56% to 13.6 gm% and 41.5%, respectively, resulted in an increment of serum Ep to abnormal level. With iron treatment there was a brisk return of Hb and Hct to prebleeding levels which was associated with reduction in the serum Ep. The inverse relationship between the Ep and Hb or Hct is inconsistent with the presence of excessive Ep-producing lesion. These results suggested that the threshold for Ep secretion from normal Ep-secreting tissue to Hb and Hct levels is set at an abnormal level. This patient's marrow cells when cultured in vitro in the absence of Ep, unlike other PV patients' (except one) marrow cells, did not grow erythroid colonies. In the presence of Ep, however, the colonies comparable to those formed from normal marrow cultures were obtained. These results suggested that his marrow erythropoietic cells were neither Ep independent nor Ep-hyperresponsive, as has been suggested by some investigators for erythropoiesis in PV. This patient presents phenomena that hitherto have not been reported.

Animals↗
PubMed1976

A nutrition rehabilitation centre for children with xerophthalmia.

A nutrition rehabilitation centre for treatment of children with xerophthalmia was established in Madurai, India. Treatment was based on provision of locally available food, rich in protein and beta-carotene and cheap enough for the families concerned to buy at home. This diet alone, with general medical treatment for other diseases, was sufficient to reverse conjunctival xerophthalmia and corneal xerosis. Children with more severe xerophthalmia received additional vitamin A. The records of 296 children followed up for between two months and three years were analysed. The results of treatment at the centre seemed as good as those produced by more expensive, and usually unobtainable, hospital treatment. Participation of the mother in buying, cooking, and sharing the food given to her child was of some educational value.

Body Weight↗
PubMed1976

90 day dermal toxicity of DDVP in male rats.

Exposure of male rats to DDVP (21.4 mg/kg/day) through dermal painting for a period of 90 days did not produce any changes in skin or testis. None of the animals showed any clinical symptoms of DDVP poisoning or mortality during experimentation. Rapid degradation of DDVP and further its detoification in in liver of rats and other species of mammals seems to be the prime reason for the non-toxic effect of the insecticide.

Animals↗
PubMed1975

Structural specificity in the lethal and mutagenic activity of furocoumarins in yeast cells.

Using monofunctional (Angelicin) and bifunctional furocoumarins (Psoralen and 8 Methoxypsoralen) plus 365 nm light it is shown that both damages, the induced monoadducts and/or crosslinks in DNA, provoke lethal and mutgenic effects in haploid and diploid cells of Saccharomyces cerevisiae. Bifunctional furocoumarins are about 20 times more effective in cell killing than Angelicin. Diploid cells are always more resistant than haploid cells. Dark repair (agar haolding) increases survival. This effect can be at least in part correlated to the release of bound material from DNA in dark repair conditions. Bifunctional psoralens (10 mug/ml) are at least 10-fold more effective in inducing nuclear gene black mutations (his- to HIS+) than Angelicin (10 mug/ml) plus 365 nm light or 254 nm ultraviolet light. In contrast cytoplasmic "petite" (delta-) mutations are about as frequently induced by Angelicin plus 365 nm light as by 254 nm UV light. Bifunctional furocoumarins are less effective. The frequency of cytoplasmic "petite" mutations per survivors decreases during dark repair conditions more efficiently after Angelicin than after Psoralen plus 365 nm light treatment.

Cell Survival↗
PubMed1975

Polynucleotides containing 5-mercapto-substituted pyrimidines: inhibition of viral DNA polymerases and the biological implication.

Partially thiolated polycytidylic acids MPC I-III, containing 1.7%, 3.5% and 8.6% 5-mercaptocytidylate units, respectively) inhibited the DNA polymerase of Friend leukemia virus (FLV) in the endogenic reaction as well as in the presence of poly(A)-(dT)14 or poly[d(a-T)] templates; the inhibitory activities were directly related to the percent of thiolation. Various partially thiolated RNA and DNA isolates from Ehrlich ascites cells (containing one 5-mercaptopyrimidine nucleotide/50-100 nucleotide units) also inhibited the DNA polymerases of FLV in the endogenic reaction, and also in the presence of the synthetic templates. The thiolated DNA was the most active, but the thiolated tRNA also showed substantial inhibitory effects, while the thiolated ribosomal RNA was less effective. In a bacterial DNA polymerase (E. coli-K12, using denatured DNA as template), MPC I-III showed no activity. By contrast, MPC III and several partially thiolated nucleic acid isolates significantly inhibited a regenerating rat liver DNA polymerase (I) system; among those tested, the thiolated DNA from Ehrlich ascites cells showed the highest activity. Kinetic analysis of the inhibitory action of this thiolated DNA in the rat liver enzyme system, using as template the corresponding unmodified DNA, demonstrated that the thiolated DNA acts as a competitive inhibitor of the template, with a Ki/Km ratio of 0.5.

Animals↗
PubMed1975

[Inhibition of viral reverse transcriptase and leukemogenesis by modified nucleic acids (author's transl)].

Inhibition of DNA polymerase from oncorna viruses by a new class of macromolecular inhibitors is reported. The macromolecule, designated as mercaptopolycytidylic acid (MPC), is a chemically modified polycytidylic acid containing 5-SH cytidylic bases in the polymerase. Partially thiolated polycytidylic acids (MPC I-III, containing 1.7%, 3.5%, and 8.6% 5-mercaptocytidylate units, respectively) inhibited the DNA-polymerase of Friend leukemia virus (FVL) in the endogenic reaction as well as in the presence of poly rA-(dT)14 or poly (dA-dT) templates; the inhibitory activities were directly related to the percent of tholation. In a bacterial DNA polymerase (E coli-K12 with denatured calf thymus DNA as template) MPCI-III showed no activity. Biological experiments showed that MPC III inhibits the leukemogenic potential of cell-free spleen extracts from FVL-infected mice to about 60%, measured on the basis of spleen weight. The enzymatic and animal experiments have led us to carry out preliminary clinical trials in some cases of Children leukemia. These cases, resistent to the known therapeutic regimes (combination chemotherapy), responded well when treated with MPC along, or in combination with poly I. The experiments indicate that the development of modified polynucleotids with structural similarities to functional templates may be of potential use in the future chemotherapy of leukemia.

Animals↗