Biomedical subjects

M Raizada

Publications and source records attributed to M Raizada.

5 recordsLinked to original sources

PubMed1990

Effect of four heavy metals on the biology of Nostoc muscorum.

This study presents the effects of Cr, Pb, Ni and Ag on growth, pigments, protein, DNA, RNA, heterocyst frequency, uptake of NH4+ and NO3-, loss of electrolytes (Na+ and K+), nitrate reductase and glutamine synthetase activities of Nostoc muscorum. The statistical tests revealed a direct positive correlation between the metal concentration and inhibition of different processes. Ni was found to be more toxic against growth, pigments and heterocyst differentiation compared to the other metals. Inhibition of pigment showed the following trend: chlorophyll greater than phycocyanin greater than carotenoid. No generalized trend for inhibition of macromolecules was observed. The loss of K+ and Na+ as affected by Cr, Ni and Pb was similar but more pronounced for K+ than Na+. The inhibition of physiological variables depicted the following trend: Na+ loss greater than K+ loss greater than glutamine synthetase greater than NH4+ uptake greater than growth greater than NO3- uptake greater than nitrate reductase greater than heterocyst frequency. This study therefore suggests that loss of electrolytes can be used as a first signal of metal toxicity in cyanobacteria. However, further study is needed to confirm whether the abnormality induced by nickel (branch formation) is a physiological or genetic phenomenon.

Ammonia↗

PubMed1989

Effect of bimetallic combinations of Ni, Cr, and Pb on growth, uptake of nitrate and ammonia, 14CO2 fixation, and nitrogenase activity of Nostoc muscorum.

The toxicity of Cr, Ni, and Pb individually as well as in combination (Cr + Ni, Cr + Pb, Ni + Pb) on growth, final yield, uptake of NO3- and NH4+, photosynthesis, and nitrogenase activity of Nostoc muscorum has been studied. All test metals, when used individually, depicted toxicity against the above-mentioned processes of test cyanobacterium. However, their interactive effect was found to be mostly of antagonistic type. Antagonism was more prevalent in those combinations containing nickel. In an attempt to measure the toxic potential of Cr, Ni, and Pb with respect to time, photosynthetic carbon fixation was found to be the more sensitive parameter followed by N2ase, NH4+ uptake, and NO3- uptake. Contrary to this, NH4+ uptake followed by carbon fixation, nitrate uptake, and N2ase appeared to be a preferred hierarchy sequence for measuring the toxicity of Cr, Ni, and Pb individually without any consideration of time. The toxicity potentials of metal combinations are generally less significant than those of individual metals. N2ase seems to be a more critical process followed by NH4+ uptake, photosynthesis, and NO3- uptake in measuring metal combination effects with respect to time. However, if time is not given any consideration, NH4+ uptake remains the most sensitive process for measuring metal combination effects. These results suggest that exposure time and treatment types are very important factors in evaluation of heavy metal toxicity.

Ammonia↗

PubMed1988

Dexamethasone reduces steady state insulin-like growth factor I messenger ribonucleic acid levels in rat neuronal and glial cells in primary culture.

Insulin-like growth factor I (IGF-I) mRNA was demonstrated in primary cultures of neuronal and glial cells from rat brain. On Northern blots, a rat IGF-I cDNA probe hybridized to RNA species of 7.5, 1.7, and 0.8-1.2 kilobases in total and poly(A)+ RNA from both cell types. Solution hybridization/RNase protection assays were performed using an antisense riboprobe complementary to the 5'-untranslated region as well as part of the coding region of rat IGF-I mRNA. These studies indicated that two of the previously described three possible alternative 5'-untranslated splicing variants (classes A and C) were expressed in neuronal and glial cells, with class C transcripts predominating. Neuronal cells also possessed extremely low levels of class B transcripts. Treatment of neuronal cell cultures with the synthetic glucocorticoid dexamethasone reduced IGF-I mRNA levels by 60%. Glial cell IGF-I mRNA levels were reduced by dexamethasone by up to 40%. These results suggest that glucocorticoid-induced reductions in IGF-I production could occur at the level of transcription and may underlie some of the actions of glucocorticoids in causing growth retardation and inhibition of cell proliferation.

Animals↗

PubMed1988

Alpha 1-adrenergic receptor stimulated responses.

alpha 1 Receptors have been investigated using a variety of experimental approaches. alpha 1-Receptor stimulation of phosphoinositide (PI) hydrolysis shows differences in agonist efficacy. The potency series and antagonists clearly suggest that alpha 1 receptors are coupled to phosphoinositide hydrolysis. This coupling appears to be mediated by a guanine nucleotide protein coupling the agonist-receptor complex to the phosphoinositide phosphodiesterase. However, certain alpha 1-agonists stimulate phosphoinositide hydrolysis only at very high concentrations that are not sensitive to prazosin antagonism. Other studies on alpha 1-receptor desensitization note discrepancies in coupling to phosphoinositide hydrolysis that are also found when comparing hypertensive (SHR) and normotensive (WKY) rats. Furthermore, molecular studies indicate that the apparent molecular weight of the alpha 1 receptors varies among tissues. These studies suggest heterogeneity in alpha 1 receptors and alpha 1-receptor-mediated responses. This heterogeneity is supported by studies on alpha 1-adrenergic-receptor-mediated decreases in angiotensin II receptors. The response to alpha 1 stimulation is opposite to that found with phorbol esters, which mimic the second messenger response to PI hydrolysis. Thus, these studies suggest that alpha 1-adrenergic receptors are coupled to multiple second messenger responses, one of which is phosphoinositide hydrolysis.

Animals↗

PubMed1979

Decrease in insulin receptors during Friend erythroleukemia cell differentiation.

The Friend erythroleukemia cell has an insulin receptor with all the properties of mammalian insulin receptors: rapid, reversible, and saturable binding of insulin; specific for insulin and insulin analogs; inversely proportional to temperatures; sharply pH dependent (optimum = 8.0); and demonstrated ligand-induced accelerated dissociation consistent with negative cooperativity. There were 17,200 sites per cell. After induction by dimethylsulfoxide, 80% of the cells became benzidine positive (i.e., contained hemoglobin). The receptor concentration dropped to 4300 sites per cell, while the remaining receptors retained all the initial binding characteristics. This loss of receptors could not be attributed directly to either dimethylsulfoxide or changes in cell size. Thus, during the process of differentiation, the concentration of insulin receptors in the Friend erythroleukemia cell decreases.

Animals↗