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Biomedical subjects

R S Seshadri

Publications and source records attributed to R S Seshadri.

At least 19 recordsLinked to original sources
PubMed2001

Swallowing problems in post irradiated NPC patients.

We present three patients with Nasopharyngeal Carcinoma (NPC) developing swallowing problems after radiotherapy as the primary modality of treatment. All patients had advanced stage NPC presenting with enlarged neck nodes and underwent radical external beam radiotherapy. All three patients had both CN X and CN XII palsies and had difficulty in both the oral and pharyngeal phases of swallowing. None of them has any clinical or radiological evidence of local recurrence in the post nasal space and neck or metastasis to the skull base. One patient underwent cricopharyngeal myotomy with epiglottopexy and hyoid suspension which failed and subsequently underwent laryngectomy. Another patient had medialisation thyroplasty and the third underwent a percutaneous endoscopic gastrostomy (PEG).

Adult↗
PubMed1985

Methods for study of mutations and mutagenesis in human lymphocytes.

Detailed methods are presented for measurement and study of in vivo mutations and in vitro mutagenesis in human lymphocytes. The methods described include preparation of conditioned medium containing interleukin-2, enumeration of mutant clones, in vitro mutagenesis, and expansion of mutant clones for further study.

Clone Cells↗
PubMed1985

Increased mutation frequency following treatment with cancer chemotherapy.

The relationship between somatic mutation and cancer was studied by measuring in vivo mutation frequency and in vitro mutability using lymphocytes from 28 untreated adult patients with solid tumors, 14 untreated patients with lymphoma, and 27 patients with solid tumors or lymphoma who had been treated with chemotherapy and/or radiotherapy. In vivo mutation frequency in untreated patients did not differ from that of controls, except perhaps in patients with lymphoma, who showed a slight increase. Lymphocytes from untreated patients with solid tumors or lymphoma did not show a greater increase in mutations induced after X-radiation or UV radiation than did lymphocytes from controls. For all the untreated patients, the geometric mean mutation frequency was 6.72 X 10(-6), and it was significantly increased to 19.57 X 10(-6) following chemotherapy and 34.40 X 10(-6) following chemotherapy and radiotherapy. The results suggest that excessive systemic exposure to mutagens or inherent susceptibility to mutagenesis are not important etiological factors in at least the majority of patients with cancer. The mutations produced by treatment may be related to the late side effects of therapy such as second neoplasms.

Adult↗
PubMed1984

The cells of origin of lymphocyte clones grown by limiting dilution.

A high proportion of the mononuclear cells separated from peripheral blood by Ficoll-Hypaque centrifugation show extensive proliferation when cloned at limiting dilution. The nature of clone-forming cells ( CFCs ) and the cells generated during clone formation were studied by cytotoxicity with antibody and complement and by immunofluorescence. Cytotoxicity prior to cloning with OKT3 plus OKT11 eliminated 99.34% of clones, indicating that virtually all CFCs are T-lymphocytes, and cytotoxicity with OKT4 or OKT8 indicated that helper and suppressor subclasses each contribute approximately half of the CFCs . Immunofluorescence of cells proliferating in clones confirmed that all clones were T-lymphocytes and showed that 47% were OKT4 positive and 47% were OKT8 positive; 6% were negative with both OKT4 and OKT8. The results indicate that in the nearly optimal conditions for proliferation provided by limiting dilution, clones arise entirely from T-lymphocytes and clone formation is a property of a variety of lymphocyte subclasses.

Antibodies, Monoclonal↗
PubMed1983

Detection of the carrier state for an X-linked disorder, the Lesch-Nyhan syndrome, by the use of lymphocyte cloning.

Using a limiting dilution technique, we found that the frequency of thioguanine resistant (TGR) lymphocyte clones was less than 5.0 X 10(-5) in 14 normal individuals, between 9.0 X 10(-3) and 8.9 X 10(-2) in seven heterozygotes for Lesch-Nyhan syndrome, and 0.88 and 0.87 in two hemizygotes. TGR clones from heterozygotes were expanded and had the hemizygote phenotype as evidenced by low hypoxanthine incorporation and severely deficient hypoxanthine-guanine-phosphoribosyl-transferase activity. Enumeration of TGR lymphocyte clones provides a simple technique for detection of heterozygosity for Lesch-Nyhan syndrome. A similar approach using lymphocyte cloning may be suitable for detection of the carrier state for other X-linked disorders.

Clone Cells↗
PubMed1983

Cloning of human lymphocytes using limiting dilution.

A simple technique for cloning lymphocytes at limiting dilution in microwells has been developed using phytohaemagglutinin, irradiated cells and conditioned medium containing interleukin-2. For freshly isolated peripheral blood lymphocytes, the mean frequency of clone forming cells (CFC) was 29.4% and for continuously cultured lymphocytes it was 25.5%. Quantitative considerations, mixing experiments involving HLA-A2 positive and negative cells and replating experiments indicated that growth in most of the positive microwells originated from a single cell which had a very high self-renewal capacity and underwent approximately 15 divisions during the 14 days of culture. The high plating efficiency and sustained growth observed with this technique suggests that it is the method of choice for enumerating clone forming cells or for isolating clones.

Cells, Cultured↗
PubMed1982

Radiation sensitivity of human lymphocytes.

A simple and rapid in vitro technique to assess the sensitivity of human lymphocytes to X- and UV-radiation is described. Peripheral blood lymphocytes are cloned in agar and colony survival is used as the end point. Survival down to a fraction of approx. 0.02 can be measured accurately. The D10 for X-radiation is approx. 165 rad and the initial portion of the survival curve is linear with no evidence of a threshold. The D10 for UV-radiation is approx. 50 erg/mm2. The technique should be of value both for general radiobiological studies and for detecting individuals having abnormalities of DNA repair.

Cell Survival↗
PubMed1982

Reduced lymphocyte colony formation with age.

The lymphocyte colony forming ability of 83 normal healthy individuals aged 17-89 was studied. The total lymphocyte count did not alter with age, but there was a decline in the colony forming ability of cells from people with increasing age (r = -0.68, P less than 0.001). This age related defect was further investigated in 11 mixing experiments using paired young and old individuals. It was found that the defect in aged individuals was due primarily to a defect in the number and/or proliferative ability of the colony forming cell.

Adolescent↗
PubMed1981

Age-related variations in human lymphocyte DNA.

The molecular weight of DNA from human peripheral lymphocytes has been measured on alkaline sucrose density gradients. The number average molecular weight (MN) of DNA is found to decrease as the age of the donor increases. This result is discussed with reference to lesions in DNA, both repairable and non-repairable, which may accumulate with age.

Adolescent↗
PubMed1981

Lymphocyte DNA in aplastic anaemia.

Using ultracentrifugation on alkaline sucrose density gradients the DNA of lymphocytes from 14 patients with aplastic anaemia and 23 controls was studied before and after exposure to bleomycin, an agent known to cause strand breaks in DNA. Before exposure to bleomycin the DNA from aplastic patients had more strand breaks than the DNA from the controls of similar ages. Following exposure to bleomycin an abnormal number of DNA strand breaks was produced in 10 of 14 patients and this molecular evidence of drug sensitivity correlated well with the sensitivity of the proliferating lymphocytes to bleomycin in tissue culture. Furthermore, two relatives of patients with aplastic anaemia showed similar abnormality of DNA before and after exposure to bleomycin and increased sensitivity to bleomycin in tissue culture. These results suggest that an abnormality of DNA structure and/or repair may be present in some patients with aplastic anaemia.

Adult↗
PubMed1981

An improved method for the growth of human lymphocyte colonies.

An improved method has been developed for growth of human lymphocyte colonies in agar. The method is a single-step assay involving the addition of irradiated lymphocytes which do not themselves form colonies but which stimulate a small number of non-irradiated cells to do so. Over the range 0 to 1 x 10(5) target lymphocytes, there is a linear relationship between number of lymphocytes cultured and number of colonies produced. Technical factors which influence colony growth include osmolality of the medium, foetal calf serum concentration, agar concentration, PHA type and concentration, and 2-mercaptoethanol. Colony formation is not affected by using homologous irradiated cells from an individual of the same age. For normal individuals aged 11 to 45, colonies of 20-200 cells were grown to a plating efficiency of 2.18%, with a range 1.28-4.00%. The advantages of the method are its simplicity, the linear relationship between cells plated and colonies formed, which enables the method to be used as a quantitative assay, and the ability to determine whether an observed abnormality is due to an abnormality of colony forming cells or of irradiated stimulating cells.

Adolescent↗
PubMed1980

A proliferative defect of marrow cells in experimental chronic hypoplastic marrow failure (aplastic anaemia).

Marrow cells from control mice and mice with chronic hypoplastic marrow failure (CHMF, aplastic anaemia) were grown in tissue culture and growth was assessed by measuring the number of cells/colony and uptake of 3H-thymidine/colony. Cells from mice with CHMF showed impaired proliferation in response to colony stimulating factor. Mixing experiments suggested that the impairment of proliferation was not dut to alteration in suppressor or helper cells but to an intrinsic lesion of the marrow cells themselves.

Anemia, Aplastic↗
PubMed1979

Effective use of blood in elective surgical procedures.

The preoperative requests for crossmatching of blood in elective surgical procedures were studied at the Flinders Medical Centre, South Australia. The study revealed that surgeons order crossmatched blood on the basis of habit. This led to considerable time-expiry of blood, and to unnecessary use of laboratory personnel's time and reagents. The statistical information collected during the study was used to educate the surgeons to change their blood-ordering practice. In procedures where excessive blood loss is unlikely to occur, as a stand-by, a "group-and-screen" procedure was substituted for crossmatching. A firm recommendation for maximum blood order in elective surgical procedures was also made. It is estimated that this approach would save approximately $80,000 per year per 350-bed general hospital in Australia.

Australia↗