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Biomedical subjects

A Bhushan

Publications and source records attributed to A Bhushan.

39 records · Page 3Linked to original sources

Changes in the composition of free amino acids and sugars of leaf sheath and culm of wheat during uredospore and teleutospore formation of Puccinia graminis tritici.

There were altogether fourteen amino acids in leaf sheath and culm of wheat infected with Puccinia graminis tritici, especially in and around uredial and telial pustules. Valine, tyrosine, and proline, due to their exclusive presence in uredial pustules on leaf sheath and culm of wheat, were involved in the eruption of uredospores of P. graminis tritici. Glutamic acid and dl-threonine were, however, involved in a different manner during uredospore differentiation; their amounts diminishesd parallel to sporulation. The other amino compounds, detected in and around uredial and telial pustules on leaf sheaths and culms, were l-leucine/isoleucine, beta-phenylalanine, beta-alanine, glycine, serine, aspartic acid, homoserine, and glutamine. The amounts of these amino acids either remained the same or were lowered during uredo- and teluto-spores formation, except for serine which increased in its amount. The depletion of these amino compounds indicated their metabolic activity and utilization for uredo- and teleuto-spores differentiation of P. graminis tritici. Sucrose, glucose, and fructose, among sugars, were also utilized as their amounts diminished, for uredo- and teleuto-spores formation.

Amino Acids↗

Modulation of methotrexate resistance by genistein in murine leukemia L1210 cells.

We have previously shown that methotrexate (MTX) transport is impaired in murine L1210 cells selected for cisplatin (DDP) resistance (L1210/DDP) and that the decreased MTX uptake may be due to an altered 66 kDa membrane protein. We have further hypothesized that tyrosine phosphorylation is necessary for the function of this protein. To determine the importance of tyrosine phosphorylation we studied the effect of genistein, a tyrosine kinase inhibitor, on methotrexate sensitivity, uptake and tyrosine phosphorylation of the 66 kDa protein in L1210/0 cells. After 5 h of treatment with 50 microM genistein, methotrexate uptake was decreased by nearly 50% and the cells were protected from methotrexate cytotoxicity. Immunoblotting of whole cell lysates with a phosphotyrosine monoclonal antibody demonstrated that genistein treatment decreased phosphorylation of the 66 kDa membrane protein. We concluded that phosphorylation of a 66 kDa protein may be critical for methotrexate transport and that genistein protects L1210/0 cells from methotrexate toxicity.

Animals↗

Inhibition of glioma invasion of fetal brain aggregates.

Glioblastoma multiforme is a malignant primary brain tumor associated with short patient survival in part because of the ability of individual cells to migrate significant distances into brain tissue. Invasion is a difficult process to model, because many such human tumors do not invade immunologically competent animal tissue, tumors grown in animals do not invade human tissue, and relevant human tissue substrates are not easily reproduced. We discuss models for examining invasion in vitro, and in particular review work using the tumor spheroid--fetal rat brain aggregate co-culture model, assessed with confocal microscopy and four-dimensional imaging. Quantitation of invasion in this model is discussed, as well as the invasion-inhibitory properties of tyrosine kinase (TK) inhibitors. The effects of receptor-specific tyrphostins strongly support a dominant role for Epidermal Growth Factor Receptor activation in this process and show that invasion can be effectively inhibited at much lower concentrations of TK inhibitors than is necessary for growth suppression. Inhibition of activation of the purported growth factor receptor second messenger phospholipase C- gamma 1, by pharmacological means and gene transfection, also profoundly inhibits the invasive properties of human glioblastoma and rat C6 glioma cells. We have assessed invasiveness in several human tumor specimens, which may provide information relative to prognosis and recurrence risk. Our data supports the concept of differential control of invasion and proliferation, and points to possible strategies for anti-invasive therapy for glioblastoma multiforme.

Animals↗