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Biomedical subjects

A Singh

Publications and source records attributed to A Singh.

At least 595 records · Page 33Linked to original sources
PubMed1989

Haemorrhage in cerebral toxoplasmosis. A report on a patient with the acquired immunodeficiency syndrome.

A patient with the acquired immunodeficiency syndrome (AIDS) presented to hospital with a haemorrhagic cerebral lesion. The lesion was biopsied and electron microscopy confirmed a diagnosis of toxoplasmosis. Although known in congenital cases, haemorrhagic infarction is unknown in adults suffering from cerebral toxoplasmosis. Severe vasculitis with subsequent thrombosis and extensive fibrinoid necrosis of the vessel wall or direct parasitism of endothelial cells with subsequent destruction and seepage of blood appear to be the possible mechanisms in a situation where the T-cell immune mechanism and tissue cell response are compromised. Other intracerebral haemorrhagic lesions in AIDS were reviewed.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Cyclic nucleotides augment the phasic action of tetraethylammonium on guinea-pig trachealis.

It is known that after exposure to (3 mM) tetraethylammonium (TEA), guinea-pig isolated trachealis generates tonic spasm followed by phasic tension changes. We found that 8-Br-cAMP or 8-Br-cGMP (10(-6)-5 x 10(-4) M) suppressed tonic spasm secondary to TEA and induced rapid mechanical oscillations. NaN3, forskolin, aminophylline, and isoprenaline had effects similar to those of the cyclic nucleotides. Tetrodotoxin, atropine, diphenhydramine, and cimetidine were without effect on the rapid oscillations. KCl (16 mM) stimulated the oscillations in tissue treated with TEA or TEA plus 8-Br-cGMP. Diltiazem abolished all rhythmic activity in TEA plus 8-Br-cGMP-treated tissues. We conclude: (A) The rapid oscillations are a result of increased cytoplasmic calcium flux with K+ affecting the contractile arm by increasing Ca2+ entry and cyclic nucleotides affecting the relaxant arm by reducing cytosolic free Ca2+. (B) The cyclic nucleotide effect is direct. (C) Cyclic nucleotides may enhance the rate of contraction and relaxation in the presence of some forms of phasic activity.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Effects of in vitro prepared immune complexes on rat adipose tissue lipoprotein lipase.

The possibility that circulating immune complexes (IC) could modify lipoprotein lipase (LPL) activity or release was explored in in vitro systems. IC were precipitated at antibody-Ag equivalence by using specific rabbit antisera and Ag from inactivated rubella virus and hemagglutinins from purified whole virions from three prototype strains of influenza (A/Brazil, A/Bangkok, and B/Singapore) as well as from a combined diphtheria and tetanus toxoid adsorbed with inactivated pertussis. After resolubilization, these IC were exposed to delipidated homogenates of rat epididymal fat pads before assay for LPL activity. LPL activity was stimulated two- to three-fold by the presence of 20 to 40 micrograms IC protein. This effect is not caused by the individual components of the IC because neither the specific Ag nor the individual antisera had any significant effect on LPL activity. With the rubella IC, a greater stimulatory effect was seen with increase in IC protein. With the influenza and diphtheria, pertussis, tetanus (DPT) IC, however, inhibition occurred when IC protein exceeded the amount of protein used for the LPL assay. C did not appear to be involved because IC prepared with heated antisera had similar effects. When intact rat epididymal fat pads were exposed to the rubella, influenza, or DPT IC, LPL activity recovered in the suspension medium was increased in each instance compared with pads exposed to a comparable amount of albumin. These findings may have implications for specific lipid changes that may occur during the immediate post-infectious period following rubella, influenza, or infections with the several bacteria whose Ag were present in the DPT IC used in these studies.

Adipose Tissue↗
PubMed1989

Effect of exercise on left ventricular systolic function and reserve in morbid obesity.

To assess the effect of exercise on left ventricular (LV) systolic function and reserve in morbid obesity, radionuclide left ventriculography was performed before and during supine, symptom-limited bicycle exercise in 23 patients whose body weight was greater than or equal to twice their ideal body weight. Echocardiography was performed before exercise. Resting LV ejection fraction was depressed in 13 patients and LV mass was increased in 10 patients. Exercise produced nonsignificant increases (of similar magnitude) in mean LV ejection fraction in the subgroups with normal and depressed resting LV ejection fraction. Exercise produced a significant increase in LV ejection fraction from 54 +/- 8 to 65 +/- 12% (p less than 0.005) in the subgroup with normal LV mass, but produced no significant change in LV ejection fraction in the subgroup with increased LV mass (53 +/- 10 at rest, 50 +/- 12% during exercise). Moreover, the LV exercise response (change in LV ejection fraction during exercise) in the subgroup with normal LV mass was significantly different from that in the subgroup with increased LV mass (p less than 0.005). There was a strong positive correlation between LV mass and the percent over ideal body weight (r = 0.912, p = 0.01) and a strong negative correlation between LV mass and LV exercise response (r = 0.829, p = 0.01). The results suggest that increased LV mass predisposes morbidly obese patients to impairment of LV systolic function during exercise.

Adult↗
PubMed1989

Percutaneous transluminal coronary angioplasty in patients with reduced left ventricular ejection fraction: effects on myocardial perfusion and left ventricular response to exercise.

Many patients with coronary artery disease treated by percutaneous transluminal coronary angioplasty (PTCA) have a history of previous myocardial injury resulting in a reduced left ventricular ejection fraction (EF). The effects of successful PTCA on myocardial perfusion and left ventricular function in these patients were compared to treatment in patients with normal left ventricular EF. There were 21 patients with a normal EF (mean EF 59 +/- 2%) (Group I) and 15 patients with reduced EF (mean EF 43 +/- 1%) (Group II). Before PTCA a similar degree of reversible myocardial ischemia was present on thallium scintigraphy. At peak exercise left ventricular EF in the Group I patients decreased by 4 +/- 1% compared to 8 +/- 1% in Group II. At one month following successful PTCA there was resolution of reversible myocardial ischemia in both groups. No changes in EF at rest were observed. At the same level of exercise as before PTCA the mean EF was 5 +/- 1% higher than the pretreatment value in Group I and 10 +/- 1% higher in Group II. Thus in this study reversible myocardial ischemia was associated with severe compromise in the left ventricular response to exercise which was substantially improved by PTCA.

Angioplasty, Balloon↗
PubMed1989

Atypical total anomalous pulmonary venous connection: two channels leading to infracardiac terminations.

Reported is a rare case of total anomalous pulmonary venous connection (TAPVC) where veins from each lung joined a homolateral confluence. From each confluence, a vein descended into the abdomen, the vein from the right lung joining the ductus venosus, while the vein from the left joined the portal vein. In TAPVC to systemic veins, multiple connections are rare. Multiple connections are most common at supracardiac and cardiac levels, less common at supra- and infracardiac levels, and rare at cardiac and infracardiac levels. From the literature, it is evident that multiple connections at one body level, as in our case, are rare.

Female↗
PubMed1989

Evaluation of alkali treatment for biodegradation of corn cobs by Aspergillus niger.

Effect of NaOH pretreatment on the biodegradation of corn cobs for the production of cellulase and protein was studied using Aspergillus niger. Delignification of cobs with NaOH remarkably increased the production of cellulase and protein. Treatment of cobs with 2% NaOH was found to be the best with respect to their susceptibility to biodegradation for maximum production of cellulose 1,4-beta-cellobiosidase, cellulase, beta-glucosidase soluble protein and crude protein; this also led to the highest protein recovery, maximum cellulose utilization and also for the maximum degradation of substrate.

Biodegradation, Environmental↗
PubMed1989

The effect of medroxyprogesterone acetate on aromatase and DNA polymerase alpha activities in breast tumours.

The effect of treatment with the progestogen medroxyprogesterone acetate (MPA) on the peripheral conversion of androstenedione to oestrone and tumour aromatase activity has been examined in post-menopausal women with advanced breast cancer. In addition to being a potent progestational compound, MPA also possesses glucocorticoid properties and glucocorticoids have been shown to stimulate in vitro aromatase activity. While some evidence was obtained of an increase in aromatase activity in tumour tissue after treatment with MPA, peripheral conversion of androstenedione to oestrone was similar when measured before (2.12 +/- 0.67%) and after (1.89 +/- 0.16%) treatment. DNA polymerase alpha activity, measured as a marker of cellular proliferation, decreased from 331 +/- 145 to 156 +/- 93 pmol thymidine triphosphate (TTP)/mg protein per h (P less than 0.02) in tumour samples examined before and after treatment. It is concluded that treatment with high doses of MPA has no effect on the peripheral conversion of androstenedione to oestrone but results in a significant reduction in tumour DNA polymerase alpha activity.

Aged↗
PubMed1989

Rapid enumeration of viable bacteria by image analysis.

A direct viable counting method for enumerating viable bacteria was modified and made compatible with image analysis. A comparison was made between viable cell counts determined by the spread plate method and direct viable counts obtained using epifluorescence microscopy either manually or by automatic image analysis. Cultures of Escherichia coli, Salmonella typhimurium, Vibrio cholerae, Yersinia enterocolitica and Pseudomonas aeruginosa were incubated at 35 degrees C in a dilute nutrient medium containing nalidixic acid. Filtered samples were stained for epifluorescence microscopy and analysed manually as well as by image analysis. Cells enlarged after incubation were considered viable. The viable cell counts determined using image analysis were higher than those obtained by either the direct manual count of viable cells or spread plate methods. The volume of sample filtered or the number of cells in the original sample did not influence the efficiency of the method. However, the optimal concentration of nalidixic acid (2.5-20 micrograms ml-1) and length of incubation (4-8 h) varied with the culture tested. The results of this study showed that under optimal conditions, the modification of the direct viable count method in combination with image analysis microscopy provided an efficient and quantitative technique for counting viable bacteria in a short time.

Colony Count, Microbial↗
PubMed1989

The effect of breast tumour and normal breast tissue cytosols on oestradiol 17 beta-hydroxysteroid dehydrogenase activity.

We have prepared cytosols of normal breast tissue and breast tumour tissue and examined their effect on 17 beta-oestradiol dehydrogenase (E2DH) activity in cultured normal breast fibroblasts and on the MCF-7 breast cancer cell line. Tumour cytosol increased the activity of E2DH in the reductive (E1----E2) direction in both MCF-7 cells and normal breast fibroblasts. E2DH activity in the oxidative (E2----E1) direction did not change. Increasing the amount of tumour cytosol progressively raised E2DH activity in the E1----E2 direction in MCF-7 cells, whereas equivalent amounts of cytosol from normal tissue had no effect. No change was seen in the oxidative direction. These findings suggest that a factor present in breast tumours may influence E2DH activity and consequently, the hormonal environment and growth of tumours.

17-Hydroxysteroid Dehydrogenases↗
PubMed1989

Efficacy of ivermectin against mange and gastrointestinal nematodes of buffalo (Bubalus bubalis).

The incidence of mange in dairy buffalo in India has increased significantly in recent years. The authors record an outbreak of mange affecting a dairy herd stocking about 30,000 buffalo and 1000 cows. The mange mites were either Sarcoptes scabiei or Psoroptes ovis, or a mixed infestation of both. The morbidity rate was 5-30% varying from group to group, with 100% in a severely affected group. Signs noticed were progressive dermatitis, alopecia, keratinization, skin thickened and wrinkled, intense itching and marked loss of condition often ending in death. Great losses of young animals from mange and gastrointestinal nematodes are very common in dairy herds in India. In view of their economic importance, the activity of ivermectin against naturally occurring mange and parasitic infections of adult buffalo and buffalo calves was determined. Ivermectin was administered by subcutaneous injection (IVOMEC 1% w/v - MSD AGVET) at a dose of 200 mcg kg-1 body weight. The efficacy was ascertained from the disappearance of mites from skin scrapings and the reduction in numbers of worm eggs in the faeces. The results of the treatment were dramatic: the mites disappeared within 2 weeks of the drug being administered in the majority of animals, with marked improvement in skin lesions. Four buffalo which had their entire body surface affected with mange needed a second dose on Day 28 for complete recovery. The effect on the nematodes was equally spectacular, with infections of Neoascaris vitulorum, Trichostrongylidae, Oesophagostomum spp. and Bunostomum being eliminated within 1 week of treatment.

Animals↗
PubMed1989

Effects of vitamin B6 deficiency and repletion on the uptake of steroid hormones into uterus slices and isolated liver cells of rats.

1. In vitro, pyridoxal phosphate extracts steroid-hormone receptors from tight nuclear binding (Cidlowski & Thanassi, 1981); in vitamin B6-deficient rats there is increased and prolonged nuclear accumulation of oestradiol in the uterus and testosterone in the prostate, associated with enhanced biological responsiveness of these target tissues to steroid hormone action (Symes et al. 1984; Bowden et al. 1986). 2. Slices of uterus from vitamin B6-deficient rats accumulated more [3H]oestradiol than did tissue from repleted animals. Acute repletion with vitamin B6 (0.5-1 h before killing) further increased the uptake of the steroid. 3. Isolated hepatocytes from vitamin B6-deficient rats accumulated more [3H]dexamethasone than did cells from repleted animals. Pre-incubation of the hepatocytes with pyridoxal phosphate resulted in a further increase in the uptake of the steroid. 4. The results suggest that in addition to the putative role of pyridoxal phosphate in releasing steroid-hormone-receptor complexes from tight nuclear binding (Cidlowski & Thanassi, 1981), vitamin B6 deficiency may also increase the concentration of steroid-hormone receptors or enzymes and other steroid-binding proteins in target tissues.

Animals↗
PubMed1989

Isolation and biological activity of corticostatic peptides (anti-ACTH).

Corticostatins (CS's) are a family of low molecular weight peptides, rich in arginine and cysteine with the ability to inhibit ACTH stimulated adrenocortical steroidogenesis. They show a high degree of specificity in that they do not inhibit the action of angiotensin II in the adrenal cortex. Four corticostatins have been isolated from rabbit lung extracts and peritoneal neutrophil extracts and one from human neutrophils. Among them corticostatin I, CSI, is the most potent with an I.D.50 of 25 nM. Corticostatin activity is different from other published inhibitory factors such as TGF-B and ANF, which inhibit basal and angiotensin II stimulated steroidogenesis. Other factors such as macrophage secreted products, and septic shock plasma factors which have not been fully characterized also have suppressive activity on ACTH induced adrenocortical steroidogenesis in vitro. It is not yet clear whether there is any relationship between corticostatins and these macrophage products and shock plasma factor. Corticostatins do not inhibit dbcAMP induced steroidogenesis, however they do inhibit the accumulation of cAMP in response to ACTH in rat adrenal cell suspensions. Binding studies show that CSI is a competitive inhibitor of ACTH, probably acting by blocking, the address recognition site of the receptor. There is wide variation in the potency of the corticostatins ranging from an ID50 of 100 ng/ml for CSI to a completely inactive analog, HP1. In this paper we will describe the purification of the corticostatins and some recent results obtained on their mechanism of action.

Adrenal Glands↗