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Biomedical subjects

N Bansal

Publications and source records attributed to N Bansal.

53 records · Page 3Linked to original sources
PubMed1987

Effect of vasectomy on humoral and cell-mediated immunity in monkeys with experimentally induced atherosclerosis.

The development of humoral and cell-mediated immune responses and circulating immune complexes following vasectomy were studied in rhesus monkeys fed a high cholesterol (atherogenic) diet. Four groups of monkeys were studied: (i) sham-vasectomized males fed a normal stock diet, (ii) sham-vasectomized males fed an atherogenic diet, (iii) vasectomized males fed a normal stock diet, and (iv) vasectomized males fed an atherogenic diet. Monkeys were observed for a period of 1.5 years. Sperm agglutinins and immobilizins in serum were detected in 100 and 60%, respectively, of vasectomized monkeys fed stock diet. In contrast, 60% of vasectomized monkeys fed an atherogenic diet showed agglutinins in their sera and only 20% exhibited immobilizins. The sensitization of lymphocytes by seminal plasma antigens was of a lower order in vasectomized monkeys fed an atherogenic diet as compared to those maintained on a stock diet. Circulating immune complexes (CIC) were present in both the groups of vasectomized monkeys but the level was higher in animals fed an atherogenic diet. The aortic atherosclerosis score was increased significantly in vasectomized monkeys fed an atherogenic diet, whereas the coronary atherosclerosis score was increased both in vasectomized males and in animals fed an atherogenic diet.

Animals↗
PubMed1986

Long term effects of vasectomy on experimental atherosclerosis in rhesus monkeys.

Five groups of male rhesus monkeys, Gp. I--sham-vasectomized stock diet-fed (SVS), Gp. II--vasectomized stock diet-fed (VS), Gp. III--sham-vasectomized atherogenic diet-fed (SVA), Gp. IV--vasectomized atherogenic diet-fed (VA) and Gp. V--atherogenic diet-fed vasectomized monkeys (AV) were observed for a period of 1 1/2 years. Vasectomy per se had no effect on the level of serum or tissue lipids either alone or in combination with atherogenic diet feeding. Following vasectomy the involvement of aorta by fatty lesions was significantly increased and this occurred in animals of all four experimental groups when compared with the control animals. The maximum increase was noted in group IV. Again, there was a significant increase in the frequency of aortic plaques in groups II, III and IV while it was increased in coronary arteries of all the experimental animals (Gps. II, III, IV and V). Group IV monkeys showed higher frequency of plaques as compared to group V animals. Although the plaque height was increased in all the vessels of the experimental animals, significant differences were observed only in the coronary arteries of group II monkeys and in intra-cranial cerebral vessels of group III animals. This study shows that vasectomy per se tends to increase atherosclerosis in rhesus monkeys.

Animals↗
PubMed1986

Small vessel disease in vasectomized diabetic monkeys: light microscopic study.

The following four groups of rhesus monkeys were studied for small vessel pathology of the heart, kidney and retina: sham-vasectomized, vasectomized, sham-vasectomized diabetic and vasectomized diabetic. A significant increase was observed in the frequency of pathological changes in small vessels (less than 60 micron diameter), of the heart muscle of nondiabetic vasectomized monkeys, and in sham-vasectomized and vasectomized diabetic monkeys. Further, the thickness of the glomerular capillary basement membrane was also significantly increased in the three experimental groups. In vasectomized diabetic monkeys, the vascular lesions were much greater than in the other two groups. Moreover, in this group one animal had a microaneurysm of a retinal vessel and another had distortion of retinal veins. The monkeys subjected to vasectomy or diabetes alone did not develop these changes. However, the ratio of mural to endothelial cells in retinal vessels was markedly altered in vasectomized and nonvasectomized diabetic monkeys.

Animals↗
PubMed1985

Aggravation of experimental atherosclerosis in vasectomized, cholesterol-fed rabbits.

Rabbits were fed a stock or atherogenic diet for a period of fourteen months. Half of each group of rabbits was bilaterally vasectomized while the other half underwent sham vasectomy. The level of plasma cholesterol was significantly elevated following vasectomy in stock diet-fed rabbits. Atherogenic diet feeding caused marked elevation of plasma cholesterol in both vasectomized as well as sham-vasectomized animals. At the termination of the experiments, aortic cholesterol in stock diet-fed vasectomized rabbits remained unchanged, but this was increased in both vasectomized and sham-vasectomized atherogenic diet-fed animals. Aortic sudanophilia, atherosclerotic plaque size and coronary atherosclerosis index were significantly increased in vasectomized atherogenic diet-fed rabbits as compared to their controls. In stock diet-fed vasectomized rabbits no macroscopic or microscopic lesions were seen even in the presence of mild hypercholesterolaemia.

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PubMedDate not supplied

In vivo Na-23 MR imaging and spectroscopy of rat brain during TmDOTP5- infusion.

In vivo sodium-23 and hydrogen-1 magnetic resonance (MR) imaging and spectroscopy of the rat brain during infusion of the shift reagent thulium DOTP5- (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra[methylene phosphonate] was performed to assign the various peaks observed during infusion and to evaluate the shift reagent in discriminating tissue compartments. Na-23 spectra collected during the infusion showed two shifted peaks that were assigned to intravascular Na+ and extracellular muscle Na+, respectively, and one unshifted peak assigned to intra- and extracellular brain Na+ and cerebrospinal fluid Na+. These assignments were validated with H-1 and Na-23 MR imaging and Na-23 chemical shift imaging (CSI). The H-1 and Na-23 images showed that a surface coil placed on a rat head can detect a substantial amount of signal from muscle surrounding the skull. Na-23 CSI spectra from successive 1-mm-thick coronal sections indicated that the shift reagent did not cross the blood-brain barrier. The study also showed that bulk susceptibility shifts are quite small with Tm-DOTP5-. This reagent may be useful in determining compartmental Na+ concentrations and blood flow kinetics in brain and in examining the integrity of the blood-brain barrier.

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PubMedDate not supplied

Oxygen tension mapping with F-19 echo-planar MR imaging of sequestered perfluorocarbon.

The authors used fluorine-19 inversion-recovery (IR) echo-planar imaging (EPI) to map oxygen tension on the basis of the spin-lattice relaxation rate (R1) of sequestered perfluorocarbon. R1 measured with IR-EPI varied as a linear function of oxygen tension and temperature, and the relationship agreed well with earlier spectroscopic findings. Oxygen tension maps of a mouse that had received a dose of perflubron emulsion were acquired before, during, and after the mouse breathed pure oxygen. Results showed low liver oxygen tension during air breathing, which increased during breathing of pure oxygen, with distinct regional heterogeneity, to 8-17% atm (60-130 torr [8.0-17.3 kPa]).

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PubMedDate not supplied

Three-dimensional triple quantum-filtered 23Na imaging of rabbit kidney with weighted signal averaging.

Low signal-to-noise ratio (SNR) has been the main obstacle to multiple quantum-filtered 23Na imaging becoming an important technique for biologic and clinical applications. Through computer simulations and phantom experiments, we show that the SNR in 23Na imaging can be substantially improved by weighted signal averaging. Three-dimensional single quantum and triple quantum (TQ)-filtered 23Na images of an externalized rabbit kidney were collected with this technique. The TQ-filtered image did not show any signal when the animal was alive. However, upon sacrificing the animal, the renal cortex became clearly visible without any significant increase in signal from the medullary region. This increase in TQ-filtered signal in the renal cortex may be caused by an increased concentration of intracellular Na+ in the large intracellular space present herein, compared with the medulla. To our knowledge, this study represents the first example of three-dimensional TQ-filtered 23Na image of a biological sample.

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PubMedDate not supplied

Three-dimensional triple-quantum-filtered 23Na imaging of the dog head in vivo.

Multiple-quantum (MQ) -filtered 23Na NMR has been proposed as a means to partially discriminate between intracellular and extracellular sodium. However, low signal-to-noise ratio (SNR) has been a major obstacle to MQ-filtered 23Na imaging becoming an important technique for biological and clinical applications. We compared the various MQ-filtered 23Na imaging pulse sequences to select the optimum sequence that provides the best SNR. The results of phantom experiments show that the gradient-echo MQ-filtered 23Na imaging sequence produces the best SNR. We also report, for the first time, three-dimensional single-quantum (SQ) and triple-quantum (TQ) -filtered 23Na images of the live dog brain and demonstrate the sensitivity of these images to ischemia produced by euthanizing the animal. The SQ images showed a 10% to 15% decrease in signal intensity from the brain post-mortem, whereas the TQ-filtered images showed a 40% to 50% increase. These changes in signal intensities are consistent with the influx of Na+ into the cells upon death. The feasibility of obtaining TQ-filtered 23Na images of in situ dog brain encourages us to apply this technique to humans.

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PubMedDate not supplied

Non-invasive magnetic resonance thermometry using thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA(-)).

Non-invasive thermometry is pivotal to the future advances of regional hyperthermia as a cancer treatment modality. Current magnetic resonance (MR) thermometry methods suffer from poor thermal resolution due to relatively weak dependence of chemical shift of the (1)H water signal on temperature. This study evaluated the feasibility of using thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA(-)) for MR thermometry. TmDOTA(-) is non-toxic and the gadolinium complex of DOTA(4-) is widely used as a MR contrast agent. The results demonstrate that the temperature dependence of the TmDOTA(-) proton shifts are about two orders of magnitudes higher than the water proton and, thus, provide excellent accuracy and resolution. In addition, TmDOTA(-) proton shifts are insensitive to the paramagnetic complex concentration, pH, Ca(2+) or presence of plasma macromolecules and ions. Because hyperthermia is known to produce changes in tissue pH and other physiological parameters, these properties of TmDOTA(-) greatly simplify the procedures for using the lanthanide complex for MR thermometry. Application of TmDOTA(-) for measurement of temperature in a subcutaneously implanted human melanoma xenograft is demonstrated. Finally, the feasibility of imaging one of the (1)H resonances of the lanthanide complex is demonstrated in phantom experiments. Overall, TmDOTA(-) appears to be a promising probe for MR thermometry in vivo.

Animals↗
PubMedDate not supplied

Effects of compound RU38486 on growth and lipid biosynthesis in glucocorticoid sensitive human leukemia line CEM-C7.

Glucocorticoid sensitive human lymphoblastoid cells CEM-C7 were examined for the effects of antiglucocorticoid RU38486 on the prevention of early dexamethasone-induced changes, including reduced cell growth, cell shrinkage and fragmentation, decrease in cell plating efficiency and incorporation of acetate into cellular lipids. When RU38486 was added no later than 24 hours after the addition of dexamethasone, it prevented the inhibition of [14C]acetate incorporation into nonsaponifiable lipids, partly reversed the decrease in plating efficiency and reduced cell fragmentation. In addition, the accumulation of dolichols in the nuclei of dexamethasone-treated cells was abolished by RU38486. These results indicate that glucocorticoid-induced changes in cellular lipids are receptor dependent and may be linked to the initiation of the apoptotic cascade.

Cell Division↗
PubMedDate not supplied

Role of circulating immune complexes and platelet aggregation in the development of experimentally induced atherosclerosis in monkeys with normal intact vas deferens and following vasectomy.

The study was undertaken in normal and vasectomized monkeys to elucidate the relationship of circulating immune complexes and platelet aggregability with experimental aortic and coronary atherosclerosis. Four groups of animals, viz. sham-vasectomized stock diet fed, vasectomized stock diet fed, sham-vasectomized atherogenic diet fed, were studied for a period of 1 year. An increased incidence of atherosclerosis was noted with high levels of circulating immune complexes in vasectomized monkeys. Platelets obtained from atherogenic diet fed monkeys had a clear tendency of increased aggregation and agglutination in the presence of ADP, epinephrine and ristocetin respectively. Vasectomy produced a significant enhancement in platelet aggregation response with ADP and epinephrine in atherogenic diet fed animals. The aortic and coronary atherosclerosis was also significantly increased in atherogenic diet fed groups both with and without vasectomy.

Animals↗
PubMedDate not supplied

Frequency and size of atherosclerotic plaques in vasectomized diabetic monkeys.

Male rhesus monkeys were used to elucidate the combined effect of vasectomy and diabetes on frequency and size of atherosclerotic plaques. Four groups were made: in two, bilateral vasectomy was performed, and the other two were subjected to sham vasectomy. Half of the vasectomized and sham-vasectomized monkeys were made diabetic by intravenous injection of alloxan. The animals were observed for a period of one year. Clinical examination revealed bilateral cataract in 40% of the diabetic animals. Marked hyperglycemia along with significant increase of serum triglycerides and free fatty acids was noted in diabetic monkeys. Vasectomy per se did not alter serum lipid levels and overall atherosclerotic plaque score in nondiabetic monkeys. However, the combination of vasectomy with diabetic state led to significant increase of overall atherosclerotic plaque score in coronary and renal arteries.

Agglutination↗