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Biomedical subjects

N B Reddy

Publications and source records attributed to N B Reddy.

At least 19 recordsLinked to original sources
PubMed2003

Pyroclastic fluoride in ground waters in some parts of Tadpatri Taluk, Anantapur district, Andhra Pradesh.

Fluorosis is a disease affecting the teeth and bones and caused by excessive ingestion of fluoride through drinking water. Fluoride concentration in ground water samples of the study area varies from 1.2 to 2.1 ppm., which is much above the permissible limit. The probable source of fluoride in ground water is fluoride bearing minerals like apatite, micas and clay minerals etc., present in the country rocks like shales and pyroclastic materials of the study area. The sample survey is carried out to know the incidence of fluorosis in this area which reveals that more than 43% of the inhabitants are affected by dental fluorosis and 0.4% by skeletal fluorosis.

Environmental Monitoring↗
PubMed1992

Myofibrillar and membrane-bound enzymes in skeletal muscle from myodystrophic mice.

1. Experiments were carried out to examine the biochemical changes, such as contractile protein biochemistry and membrane bound enzyme alterations associated with skeletal muscles of myd/myd. 2. Our studies demonstrate that there was a progressive decline in myofibrillar ATPase activity, and this decrease is greatest in 30 weeks old animals of myd/myd as compared to controls. 3. The proteolytic activity of myofibrils isolated from myd/myd was significantly higher than controls. 4. There was no significant difference in Ca2+ ATPase activity of myosin and actin-activated myosin ATPase activity of myd/myd and their controls. 5. Mg2+ ATPase and Na(+)+K(+)-ATPase of myodystrophic SL showed significant increase compared to controls. 6. Isoproterenol stimulated adenylate cyclase activity was significantly lower in the SL of dystrophic mice compared to controls. 7. GTP+isoproterenol stimulate adenylate cyclase was significantly higher in control SL and SR when compared to SL and SR isolated from myd/myd. 8. Guanylate cyclase activity was greater in myodystrophic mice both in the absence and presence of Triton X-100. cGMP and cAMP phosphodiesterase activities were greater in dystrophic mice as compared to controls. 9. These observations suggest that there are significant changes in myofibrillar ATPase, myofibrillar protease and membrane bound enzymes of myd/myd compared to control.

Adenosine Triphosphatases↗
PubMed1990

HLA-DQ molecules and the control of Mycobacterium leprae-specific T cell nonresponsiveness in lepromatous leprosy patients.

The major histocompatibility complex (MHC) controls of the outcome of the immune response to T cell-dependent antigens by dictating whether T cell responsiveness will result (MHC-immune response [Ir]genes) or alternatively T cell nonresponsiveness will occur, possibly through the activation of suppressor cells (MHC-immune suppression [Is] genes). In mice, I-A molecules typically restrict antigen-specific helper T cells. In contrast, H-2 I-E molecules have been reported to control nonresponsiveness to a variety of antigens through antigen-specific suppressor cells. In analogy, HLA-DR molecules are the dominant restriction elements for helper T cells in man. This forces the question whether DQ molecules may be involved in controlling nonresponsiveness in man, e.g. through suppression. In one system, T cell nonresponsiveness to Schistosoma japonicum, evidence has been presented supporting this notion. We have now used a second system, Mycobacterium leprae-specific T cell nonresponsiveness, that is typically found in lepromatous leprosy patients. We find positive but limited evidence for a role for HLA-DQ molecules in controlling T cell nonresponsiveness to M. leprae of the 22 nonresponder patients tested, 4 showed a proliferative T cell response to M. leprae after the addition of DQ- but not DR-specific mAb to the cell cultures. In one of the four BCG nonresponders, anti-DQ mAb had a similar effect.

Adolescent↗
PubMed1985

Autosomal dominant syndrome of lipid neuromyopathy with normal carnitine: successful treatment with long-chain fatty-acid-free diet.

A family (mother and two sons) have had lifelong muscle weakness and intolerance to fatty food. Histochemistry of muscle biopsies of all three patients demonstrated increased lipids in type I muscle fibers and type II muscle fiber atrophy and paucity. Electronmicroscopy of muscle revealed increased lipids, abnormal mitochondria, and increased lipofuscin granules. Electronmicroscopy of sural nerve showed inclusions in most of the Schwann cell cytoplasm, with lipid droplets, zebra bodies, lipofuscin granules, and abnormal mitochondria. Carnitine and CPT I and II levels were normal in serum and muscle. Treatment with long-chain fatty-acid-free diet resulted in remarkable clinical improvement and in decrease of lipid droplets in the muscle. This dietary program may be useful in other forms of lipid myopathy.

Adolescent↗
PubMed1982

Biochemical and morphological effects of 20,25-diazacholesterol on cultured muscle cells.

Effects of 20,25-diazacholesterol (DAC), a myotonia-inducing drug, were evaluated on certain biochemical and morphological properties of embryonic rat muscle cells grown in tissue culture. During DAC treatment, muscle fibers exhibited spontaneous contractions that changed from coarse twitches to finer fibrillation movements, The ultrastructural alterations produced by DAC were smeared Z-lines, disorganized myofibrils, occasional honeycomb appearance of membranes and large vacuoles connected to zipper-like structures. Biochemically, a microsomal fraction prepared from DAC-treated cells (compared to that of normal cells) showed a 30-45 per cent decrease in the isoproterenol-enhanced and the NaF-enhanced adenylate cyclase activity. however, the beta-adrenergic receptors, through which isoproterenol activates the enzyme, showed no change in density or affinity as judged by the binding of [125I]iodohydroxybenzylpindolol. That indicated that DAC treatment caused an uncoupling of beta-receptor-adenylate cyclase interaction. Guanylate cyclase and cyclic GMP-phosphodiesterase were both markedly increased in DAC-treated cells, indicating a greater turnover of cyclic GMP. Binding of [3H]concanavalin A to DAC-treated muscle membranes was decreased 20-40 per cent. The data indicate that DAC exert a direct influence on muscle fibers, affecting their functional, biochemical and morphological properties.

Animals↗
PubMed1982

Demonstration of 2',3'-cyclic nucleotide 3'-phosphohydrolase in cultured human Schwann cells.

Schwann cell cultures were established from adult human sural nerve biopsies. 2'3'-Cyclic nucleotide 3'-phosphohydrolase (CNPase) activity was estimated in the homogenates of those cells by a sensitive isotope assay using [3H]2',3'-cyclic AMP as substrate. A high level of CNPase activity was observed in cultured Schwann cells, whereas cultured human muscle and skin fibroblasts contained negligible levels of CNPase activity. CNPase of human Schwann cells followed typical enzyme-substrate kinetics, with an apparent Km of 1.6 mM for 2',3'-cyclic AMP, and the enzyme was stimulated by detergents such as Triton X-100 and deoxycholate. It was inhibited by p-chloromercuricbenzoate and 2'-AMP. These properties are typical of CNPase isolated from adult brain and spinal cord. CNPase can serve as a new biochemical marker of normal cultured human Schwann cells and can be useful in analyzing the properties of cultured Schwann cells from patients with dysschwannian neuropathies.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1979

In vitro characterization of skeletal muscle beta-adrenergic receptors coupled to adenylate cyclase.

[3H]Dihydroalprenolol, a potent beta-adrenergic antagonist, was used to identify the adenylate cyclase-coupled beta-adrenoceptors in isolated membranes of rat skeletal muscle. The receptor sites, as revealed by [3H]dihydroalprenolol binding, were predominantly localized in plasmalemmal fraction. That skeletal muscle fraction may also contain the plasmalemma of other intramuscular cells, especially that of blood vessels. Hence, the [3H]dihydroalprenolol binding observed in that fraction may be due partly to its binding to the plasmalemma of blood vessels. Small but consistent binding was also observed in sarcoplasmic reticulum and mitochondria. The level of [3H]dihydroalprenolol binding in different subcellular fractions closely correlated with the level of adenylate cyclase present in those fractions. The binding of [3H]dihydroalprenolol to plasmalemma exhibited saturation kinetics. The binding was rapid, reaching equilibrium within 5 min, and it was readily dissociable. From the kinetics of binding, association (K1) and dissociation (K2) rate constants of 2.21 . 10(7) M-1 . min-1 and 3.21 . 10(-1) min-1, respectively, were obtained. The dissociation constant (Kd) of 15 mM for [3H]dihydroalprenolol obtained from saturation binding data closely agreed with the Kd derived from the ratio of dissociation and association rate constants (K2/K1). Several beta-adrenergic agents known to be active on intact skeletal muscle also competed for [3H]dihydroalprenolol binding sites in isolated plasmalemma with essentially similar selectivity and stereospecificity. Catecholamines competed for [3H]dihydroalprenolol binding sites with a potency of isoproterenol greater than epinephrine greater than norepinephrine. A similar order of potency was noted for catecholamines in the activation of adenylate cyclase. Effects of catecholamines were stereospecific, (-)-isomers being more potent than (+)-isomers. Phenylephrine, an alpha-adrenergic agonist, showed no effect either on [3H]dihydroalprenolol binding or on adenylate cyclase. Known beta-adrenergic antagonists, propranolol and alprenolol, stereospecifically inhibited the [3H]dihydroalprenolol binding and the isoproterenol-stimulated adenylate cyclase. The Ki values for the antagonists determined from inhibition of [3H]dihydroalprenolol binding agreed closely with the Ki values obtained from the inhibition of adenylate cyclase. The data suggest that the binding of [3H]dihydroalprenolol in skeletal muscle membranes possess the characteristics of a substance binding to the beta-adrenergic receptor.

Adenylyl Cyclases↗
PubMed1979

X-linked recessive congenital muscle fiber hypotrophy with central nuclei: abnormalities of growth and adenylate cyclase in muscle tissue cultures.

Muscle cells in cultures established from biopsy specimens of two children with an infantile-fatal form of X-linked recessive muscle fiber smallness with central nuclei showed an unusual ability to proliferate through numerous passages. Ultrastructurally, the cultured muscle fibers appeared very immature even after several weeks. The nuclei were large, the number of ribosomes was greatly increased, the myofibrils remained unstriated, and glycogen was accumulated in large lakes. The plasmalemma bound concanavalin A, alpha-bungarotoxin, and ruthenium red normally, but with tannic acid it did not show the dark binding of mature fibers. Biochemically, in the cultured muscle fibers, beta-adrenergic receptors were quantitatively normal. The level of adenylate cyclase in membranes was less than in cultured normal muscle; this defect could be responsible for impaired control mechanisms resulting in the other abnormalities observed.

Adenylyl Cyclases↗
PubMed1979

Autoradiographic visualization of beta-adrenergic receptors in normal and denervated skeletal muscle.

Autoradiographic localization of beta-adrenergic receptors in rat skeletal muscle in vivo was achieved utilizing [125I]-iodohydroxybenzylpindolol, a potent beta-adrenergic blocker with high affinity and specificity for those receptors. In normal muscle the beta-adrenergic receptors were localized mainly to blood vessels, arterioles greater than venules, with much less concentration of grains over the fascicles of muscle fibers. One week after denervation there was an increase in binding both to blood vessels and muscle fibers, more so in soleus and gactrocnemius than in extensor digitorum longus. While these results parallel in vitro biochemical studies, they dictate caution when inferring cellular localization of beta-adrenergic receptors (and other molecules) solely on the basis of biochemical techniques applied to subcellular fractions of whole-organ homogenates.

Animals↗
PubMed1977

In vitro studies of skeletal muscle membranes. Adenylate cyclase of fast and slow twitch muscle and the effects of denervation.

Sarcolemmal membranes were prepared from slow-twitch (red) and fast-twitch (white) skeletal muscle of the rat. A sensitive adenylate cyclase assay was used and basal, fluoride- and catecholamine-stimulated activities measured. The greater in vivo sensitivity of red muscle to the effects of catecholamines correlates, in the present study, with approximately a twofold stimulation of its sarcolemmal adenylate cyclase with isoproterenol (10 micronm). The white muscle enzyme, on the other hand, is only minimally stimulated (20%) at the same concentration of beta-adrenergic agonist. Fast-twitch muscle is known to be physiologically insensitive to catecholamine in vivo. A course of sciatic nerve denervation was followed to further distinguish these two metabolic types of skeletal muscle and their respective adenylate cyclases. The slow-twitch muscle enzyme activities were completely and permanently lost on denervation. The white muscle enzyme, however, recovered almost completely after an initial reduction in specific activity the first week. Interestingly, the NaF-stimulated activity lagged behind both the basal and hormone-stimulated activities of the white muscle enzyme, in returning to control levels. The activities of cyclic nucleotide phosphodiesterase were evaluated in homogenates of the two muscle types in innervated rats and following denervation, in order to further define the neural influence on skeletal muscle cyclic nucleotide metabolism. The results suggest that the motor nerve may regulate some of the metabolic properties of slow-twitch muscle (which may involve cyclic AMP) by controlling the responsiveness of its sarcolemmal-bound adenylate cyclase system.

Adenylyl Cyclases↗