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Biomedical subjects

K Manoharan

Publications and source records attributed to K Manoharan.

13 recordsLinked to original sources
PubMed2003

HLA-DRB1*, -DQB1* in Piramalai Kallars and Yadhavas, two Dravidian-speaking castes of Tamil Nadu, South India.

Two Dravidian-speaking castes of Tamil Nadu, Piramalai Kallars (PKs, n = 205) and Yadhavas (YDs, n = 239) and a random panel (84) were studied for HLA-DRB1* and -DQB1* polymorphisms by DNA-SSOP typing methods. XI and XII International Histocompatibility primers and non-radioactive-labelled oligo probes were employed to identify the alleles. Results revealed that PKs possessed >0.1 allele frequencies of HLA-DRB1*15011, 0301, -DQB1*0201, 0501 and 0601; YDs, HLA-DRB1*0301, 0401, 07 and -DQB1*0601; and the random panel, DRB1*15021, 0401, 07, -DQB1 0201, 0301, 0302 and 0501. The highest frequency of DRB1*1501 in the world (GF = 0.225) was found in PKs. The most frequent two-locus haplotype (>500/10,000) in all the study samples was DRB1*10-DQB1*0501, while 1501-0601 was frequent in PKs and YDs. Comparison of the HLA-DRB1* data with Eastern European and South-East Asian populations suggested migration as the prime cause of the observed diversity in DRB1* allele frequencies. Nonetheless, the heterozygocity test and Watterson's homozygosity test indicated that balancing selection still operates on HLA-DRB1* locus, in this endemic region of various infectious diseases. This and spatial autocorrelation analysis support the view that selection may be a cause of "generating" new variants and allelic diversity in different ancient settlements. The study suggested that South Indian, inbred, endogamous, sympatrically isolated castes or similar well-defined breeding isolates around the world, living under the same milieu-epidemiology, may be ideal models to test the immunogenetic basis of disease susceptibility.

Adult↗
PubMed2000

Synthesis of phosphatidylserine in carrot cells cultured under carbon-source starvation.

When carrot suspension cells were cultured on medium containing no carbon source (starvation), the levels of phosphatidylserine (PS) increased transiently 3-4 d after the initiation of starvation while levels of most other phospholipid (PL) species decreased. We previously reported that fatty acids of these PLs served as an alternative carbon source during starvation. The present study showed that cells possess two different biosynthetic pathways involving phosphatidylcholine (PC)/phosphatidylethanolamine (PE) exchange enzymes and PS synthase to synthesize PS. These activities peaked similarly 4 d after the initiation of starvation and coincided with the peak of PS level. The synthesis of serine was also significantly activated during starvation. The activity of phosphoserine aminotransferase (PSAT) which is involved in serine synthesis increased with a time course similar to that of the increase in the PS level. These observations suggest that the increase in PS level plays an important role in membranes which are degraded during starvation.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1993

Scurvy--a forgotten disease.

A four-year-old male child was reported with sudden inability to stand walk of 10 days duration. Acute paralytic poliomyelitis was diagnosed in the presence of fever, respiratory infection, muscle tenderness, and weakness in lower extremity in an unimmunized child. Reevaluation after a week showed swelling, thickening, and tenderness of left femur. Plain x-ray of the left thigh was advised to exclude underlying osteomyelitis of the femur. X-ray showed features of scurvy. The child responded well to parenteral vitamin C therapy and resumed normal walking with in two weeks. Scurvy can present as pseudoparalysis of acute onset without any other signs even in older children. It emphasized the need for an index of suspicion of scurvy in a case of suspected paralysis. Dramatic response to vitamin C therapy can be used to confirm the diagnosis in the absence of laboratory support. Health education can be accelerated to prevent a disease like scurvy.

Ascorbic Acid↗
PubMed1987

DMBA induced DNA damage and repair in mammary epithelial cells in vitro measured by a nick translation assay.

A new E. coli DNA polymerase I directed nick translation assay was used for measuring 7,12-dimethylbenz[a]anthracene-induced in situ DNA damage and repair in mouse mammary epithelial cells in monolayer culture. The nick translation assay was capable of detecting a DMBA-dose dependent significant increase of DNA damage, and the same assay also allowed monitoring of the DNA repair activity provoked by DMBA treatment of the epithelial cells. This relatively simple method thus provides a rapid assay for carcinogen-induced in situ DNA damage and repair in an epithelial cell tumorigenic system.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

Measurements of chemical carcinogen-induced sister-chromatid exchanges in a whole organ in vitro.

Sister-chromatid exchange (SCE) was measured in epithelial cells of mammary organs exposed to 3 different carcinogens in vitro. 7,12-Dimethylbenz[alpha]anthracene (DMBA), N-nitrosodiethylamine (DENA) and N-methyl-N-nitrosourea (MNU) are capable of inducing a significant enhancement of SCE over the basal level in the mammary cells. Analysis of SCE caused by the mutagenic and/or carcinogenic agents in the organ culture presents the advantages that: (1) the culture procedure does not require enzymatic dissociation of the tissue and (2) the medium does not need to be supplemented with serum or exogenous mitogenic agents thereby minimizing the basal level of SCE. Moreover, the assay does not require utilization of exogenous microsomal enzymes needed for activation of certain carcinogenic chemicals. SCE measurements in the organ culture system also should provide clues about the mechanism of action of the chemopreventive agents, particularly the antioxidants, which are under investigation for their possible influence on the processes of neoplastic transformation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

beta-Carotene reduces sister chromatid exchanges induced by chemical carcinogens in mouse mammary cells in organ culture.

Present studies in the mammary epithelial cell transformation model in organ culture showed that presence of beta-carotene during the 24 hr treatment (initiation stage) of the glands with the carcinogens, 7,12-dimethylbenz[a]anthracene (DMBA), N-nitrosodiethylamine (DENA) and N-methylnitrosourea (MNU), caused a highly significant (P less than 0.001-0.01) reduction of SCE induced by the same carcinogens. In contrast, 4-hydroxyphenyl retinamide (4-HPR) which is known to act at the promotional stage of carcinogenesis did not show any significant reduction of SCE. Thus findings suggest that beta-carotene can modify the DNA damaging effect of the carcinogens and thereby may also prevent the initiation of the carcinogenic process.

9,10-Dimethyl-1,2-benzanthracene↗