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Biomedical subjects

U Narayanan

Publications and source records attributed to U Narayanan.

9 recordsLinked to original sources
PubMed2000

An index for quantifying deviations from normal gait.

A method is derived to calculate the amount by which a subject's gait deviates from an average normal profile, and to represent this deviation as a single number. The method uses principal component analysis to derive a set of 16 independent variables from 16 selected gait variables. The sum of the square of these 16 independent variables is interpreted as the deviation of the subject's gait from normal. Statistical tests of the method's validity and an initial demonstration of its clinical utility are included. It is found that using this index, increasing clinical involvement corresponds to increasing index score.

Adolescent↗
PubMed2000

Effect of AMPA on cerebral cortical oxygen balance of ischemic rat brain.

We tested the hypothesis that the excitatory neurotransmitter receptor agonist, alpha amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), would worsen cerebral cortical oxygen supply/consumption balance during focal ischemia. In this study, we compared regional cerebral blood flow, arterial and venous O2 saturation, O2 extraction and oxygen consumption of ischemic and AMPA treated ischemic and control regions of rat brain. Ischemia was induced by middle cerebral artery (MCA) occlusion in isoflurane (1.4%) anesthetized Wistar rats. Twenty minutes after MCA occlusion, 10(-5) M AMPA was applied to the ischemic cortex (IC) for a period of 40 min; the fluid was changed every 10 min. After 1 hr of ischemia, animals were sacrificed and regional cerebral blood flow (rCBF) was determined using the C14-iodoantipyrine autoradiographic technique. Regional arterial and venous oxygen saturation were determined microspectrophotometrically. In control, the cerebral blood flow and oxygen consumption of the IC were significantly lower than the contralateral cortex (rCBF: 46 +/- 20 vs. 81 +/- 39 ml/min/100g, O2 consumption: 2.8 +/- 1.4 vs. 3.6 +/- 1.4 ml O2/min/100g). 10(-5) M AMPA did not significantly alter regional cerebral blood flow and oxygen consumption of the IC, but did decrease the average venous O2 saturation of the IC from 50.2 +/- 3.9% to 46.7 +/- 1.6%. AMPA also significantly increased the frequency of small veins with less than 45% O2 saturation in the IC (8 out of 56 veins in IC vs. 18 out of 56 veins in AMPA treated IC). Thus, topical application of 10(-5) M AMPA to the ischemic area worsens cerebral O2 balance and suggests that excitatory amino acids contribute to the degree of cerebral ischemia.

Animals↗
PubMed1994

Laboratory evaluation of interception and translocation of 131I in fenugreek and okra plants.

The work reported here deals with the study of interception and translocation of airborne 131I in fenugreek (Trigonella foenum-graecum) and okra (Hibiscus esculentus), two very common vegetables in India. Activity was injected into the experimental chamber in the form of iodide aerosols having a size distribution of 0.3 to 5.0 microns (AMAD). Samples of plants were collected over a period of a few days at different time intervals after injection of the aerosols. Evaluation of interception with deposition and translocation of 131I was done from the activity measured in air and in plant parts. For the deposition factor, the values are 1.22 m3 kg-1 for fenugreek leaves, and 1.49 m3 kg-1 for the plant as a whole. For okra plants these values are 0.02 and 0.16 m3 kg-1 in edible okra and leaves, respectively. For the okra plant as a whole, the value is 0.19 m3 kg-1. The translocation factors vary from 0.62 to 0.86 and 0.47 to 0.87 for leaves and stem, respectively, in the case of fenugreek plants. For okra plants, the translocation factor varies from 0.21 to 0.82, 0.53 to 0.93, and 0.42 to 0.81 in edible okra, leaves, and stems, respectively.

Aerosols↗
PubMed1992

Effects of diabetes and insulin on phosphoinositide metabolism in R3230AC mammary tumors.

The effects of diabetes and insulin administration on certain aspects of phosphoinositide metabolism in R3230AC mammary tumors were studied in vivo. Three weeks after diabetes was induced by streptozotocin, [3H]myoinositol incorporation into PI, PIP and PIP2 was increased in R3230AC tumors, whereas the formation of [3H]IP, [3H]IP2 and [3H]IP3 was decreased. Administration of protamine zinc insulin (3IU, twice daily, for 3 days) to diabetic rats decreased [3H]myoinositol incorporation into phosphoinositides and inositol phosphates in these mammary tumors. The R3230AC tumor from insulin-treated diabetic hosts had lower levels of unmetabolized [3H]-myoinositol compared to tumors from diabetic animals. Enzymatically-dissociated tumor cells from insulin-treated animals displayed decreased myoinositol transport in vitro. These findings suggest that the insulin-induced decrease in the turnover of inositol lipids in vivo in R3230AC mammary tumors could have resulted from the decreased level of [3H]myoinositol in these cells.

Adenocarcinoma↗
PubMed1988

Membrane-associated phosphatidylinositol kinase of R3230AC mammary tumors and normal mammary glands and effects of insulin on tumor enzyme activity.

Phosphatidylinositol (PI) kinase was characterized, its activity was measured in plasma membrane-enriched fractions of R3230AC rat mammary tumors, and these results were compared to enzyme activity in normal mammary glands at various stages of differentiation. PI kinase activity was found to be highest in mammary adenocarcinomas, whereas the mammary gland displayed the following order of decreasing activity: late lactation greater than early lactation greater than late pregnancy. Although diabetes only slightly increased tumor membrane PI kinase activity, insulin treatment of tumor-bearing diabetic rats, which reduced R3230AC tumor growth, caused a significant reduction (30 to 40%) in PI kinase activity. These results imply that PI kinase activity may be correlatable with normal mammary gland differentiation and with mammary tumor growth behavior. Formation of phosphatidylinositol-4-phosphate in tumor membranes was inhibited by low concentrations of calcium (microM range), suggesting the presence of calcium-sensitive polyphosphoinositide metabolism in the R3230AC carcinoma.

1-Phosphatidylinositol 4-Kinase↗
PubMed1986

Relationship of mitochondrial function and cellular adenosine triphosphate levels to hematoporphyrin derivative-induced photosensitization in R3230AC mammary tumors.

The effects of hematoporphyrin derivative-induced photosensitization on the levels of adenosine triphosphate (ATP) in R3230AC mammary adenocarcinomas were studied. Enzymatically dissociated tumor cells were exposed to various doses of hematoporphyrin derivative (HPD) in vitro plus photoradiation. A drug and light dose-dependent decrease in cellular ATP levels was observed; ATP levels were reduced by 60% after treatment with 7.0 micrograms HPD per ml plus 0.72 J total energy density per cm2. Cell viability, assessed by exclusion of trypan blue, displayed an apparently coordinate behavior to ATP levels. The effects of hematoporphyrin derivative plus photoradiation were examined in the presence of oligomycin, an inhibitor of mitochondrial oxidative phosphorylation, or iodoacetate, an inhibitor of glycolysis, experiments designed to elucidate the site of action leading to reduced ATP levels. The results indicated that HPD-induced photosensitization had little additive effects to oligomycin-sensitive ATP production, whereas significant further reduction in ATP levels was obtained by HPD-induced photosensitization in the presence of iodoacetate. Taken together, along with earlier studies of selected mitochondrial enzymes, we conclude that HPD plus photoradiation inhibits mitochondrial function leading to reduction in cellular ATP levels and loss of viability.

Adenosine Triphosphate↗
PubMed1985

Effects of streptozotocin-induced diabetes and insulin on phospholipid content of R3230AC mammary tumor cells.

The influence of diabetes and insulin treatment on the phospholipid content of R3230AC mammary tumors, a hormonally responsive neoplasm, was studied. Diabetes was induced by administration of streptozotocin 3 days prior to tumor implantation. Protamine zinc insulin, 3 IU/rat twice daily, was administered to tumor-bearing rats for 3 days. Enzymatically dissociated tumor cells from diabetic animals showed significant increases in phosphatidyl choline, lysophosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, and phosphatidic acid, compared to controls. Diabetic animals treated with insulin displayed reductions in phosphatidyl choline, lysophosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, and phosphatidic acid to levels approximating those found in intact (control) animals. However, neither diabetes nor insulin treatment altered sphingomyelin levels. Mammary tumor cells from diabetic animals showed a 21% increase in DNA content compared to that in intact controls and treatment of diabetic animals with insulin lowered DNA level significantly. The responsiveness of both phospholipids and DNA content to changes in the insulin milieu of the host suggest that phospholipids may play an important role in mediating the effects of insulin on growth of R3230AC tumors.

Adenocarcinoma↗
PubMed1983

Effect of iodobenzene therapy on mitochondrial activity in 2-thiouracil-induced hypothyroidism in weanling rats.

Hypothyroidism was produced in weanling albino rats by the oral administration of 2-thiouracil (TU) for 110 days. These animals recorded nearly 50 per cent reduction in mitochondrial oxidation of succinate, protein content and the activity of inner mitochondrial membrane-bound beta-hydroxybutyrate dehydrogenase. Administration of iodobenzene (IB; 0.1 microgram/rat/day) and L-thyroxine (T4; 0.6 microgram/rat/day) to two sets of hypothyroid rats restored the reduced oxidation rate, enzyme activity and protein content to near normal values. IB was comparable to T4 and may act as a thyroid stimulant.

Animals↗