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Biomedical subjects

S Krishnan

Publications and source records attributed to S Krishnan.

At least 91 records · Page 5Linked to original sources
PubMed1995

Administration of subtoxic doses of t-butyl alcohol and trichloroacetic acid to male Wistar rats to study the interactive toxicity.

Tertiary butyl alcohol and trichloroacetic acid (TCA) are known to be contaminants in drinking water. In order to evaluate the interactive toxicity of t-butyl alcohol (TBA) with TCA, young male Wistar rats were dosed through water at a dose level of TBA (0.5% v/v), 25 ppm TCA and a combined dose of TBA+TCA (0.5% v/v TBA, 25 ppm TCA) for a period of 10 weeks ad libitum and were maintained on normal diet. The control animals received plain water and normal diet. There was remarkable loss of body weight and significantly decreased liver triglycerides in the treatment groups in the order of TBA+TCA, TCA, TBA and increased liver weights were observed. Serum succinate dehydrogenase (SDH) levels were significantly increased in TCA- and TBA+TCA-treated groups. There was no significant change in serum alanine (GPT), aspartate (GOT) aminotransferase, serum alkaline (ALP) and acid (ACP) phosphatase levels as well as liver glutathione (GSH) and liver and serum cholesterol levels in the treated groups. But serum triglycerides, liver glycogen, serum glucose (only in TBA- and TCA-treated animals) were significantly high in the treated groups. Lipid peroxidation measured by diene conjugation was significant in TBA+TCA-treated group and kidney GSH levels were significantly low in the treated groups. These results show that interaction of TBA+TCA does bring about alteration in biochemical parameters which may play a pivotal role in toxic responses on long-term exposure.

Alanine Transaminase↗
PubMed1995

Cadmium accumulation in follicular fluid of women in in vitro fertilization-embryo transfer is higher in smokers.

OBJECTIVE: To assess cadmium, a heavy metal in cigarette tobacco, in follicular fluid (FF) of women in IVF-ET, who smoke. DESIGN: Controlled clinical study. SETTING: Infertile patients in a hospital IVF-ET program. PATIENTS: Fifty-one women selected in groups according to smoking habits: nonsmokers (n = 10), passive smokers (n = 17), light smokers (< 15 cigarettes per day, n = 19), and heavy smokers (> or = 15 cigarettes per day, n = 5). INTERVENTIONS: Ovarian hyperstimulation with GnRH agonist. RESULTS: The mean +/- SEM level of FF cadmium was higher in smokers (7.93 +/- 0.16 ng/mL) than in nonsmokers (6.73 +/- 0.31 ng/mL), and with a dose-effect of smoking. The individual levels in passive, light, and heavy smoking women also were higher than in nonsmoking women. CONCLUSIONS: Despite lack of vascularization of the follicle, cadmium accumulation was detectable in FF. Cadmium also could accumulate in oocytes of smokers; it does so, in a dose-dependent manner, in oocytes of cadmium-treated rats. Access to cadmium and other contaminants of cigarette smoke in FF may compromise the quality of oocytes, becoming a risk factor.

Adult↗
PubMed1995

Quantifying the Carhart effect in otosclerosis.

The Carhart effect consists of a depression in bone conduction thresholds in the presence of a conductive hearing loss. However, the mathematical relationship between the degree of conductive hearing loss and the degree of depression of bone conduction has not before been described. We have reviewed pre- and post-operative pure-tone audiograms performed on 102 consecutive patients having stapedectomy in an attempt to identify relationships between changes in bone conduction and air conduction and air-bone gap closure. Significant linear relationships were found between bone conduction and air conduction at 0.5. 1, 2 & kHz. Bone conduction was linearly related to air bone gap closure at 2 kHz.

Adolescent↗
PubMed1995

Internalization of Sucrose by Methanococcus thermolithotrophicus.

When sucrose is present in the external medium, it is internalized by Methanococcus thermolithotrophicus. Sucrose internalization, as determined by both natural abundance (sup13)C nuclear magnetic resonance spectroscopy and [(sup14)C]sucrose uptake, is directly proportional to external sucrose levels. The uptake is energy independent and exhibits kinetic behavior consistent with a simple passive diffusion process. In the presence of 0.2 M sucrose, methanogenesis is inhibited as the NaCl concentration in the external medium is increased. Growth, as determined by protein content, is inhibited by 0.2 M sucrose when the external NaCl concentration is 1.4 M. These results are important because they show that (i) sucrose cannot be used as a noncharged solute to replace NaCl in experiments to evaluate how external osmotic strength affects the internal solute composition of M. thermolithotrophicus, and (ii) sucrose cannot be used as an impermeable marker for the extracellular volume in experiments to measure the intracellular volume of M. thermolithotrophicus.

Journal Article↗
PubMed1994

Demonstration of herpes simplex type 2 in the cerebrospinal fluid of two patients with recurrent lymphocytic meningitis.

AIMS: To investigate the aetiology of recurrent lymphocytic meningitis in two patients with a past history of recurrent genital herpes simplex infection. METHODS: Cerebrospinal fluid (CSF) obtained from two patients during an acute recurrent episode of lymphocytic meningitis was analysed by polymerase chain reaction for the presence of herpes simplex DNA. RESULTS: In both patients, the acute CSF was positive for herpes simplex type 2 DNA. A second CSF obtained 2 weeks later from one patient was negative for HSV DNA: CONCLUSIONS: Herpes simplex type 2 may be an important cause of recurrent lymphocytic meningitis. Available evidence suggests that viral DNA is cleared from the CSF between episodes and supports active viral replication as the pathological mechanism. The recurrences of meningitis need not coincide with clinical recurrences of genital herpes.

Adult↗
PubMed1994

A study on children's condition thalassemia using neutron activation analysis and other techniques.

In this study, 50 thalassemia patients were tested using dual-energy X-ray absorptiometry (DEXA) and in vivo neutron activation analysis (IVNAA) to determine their bone mineral status. Both techniques were suitable for this purpose. Lower age was found to correspond to lower liver iron content and higher bone mineral content in the normal range. Patients undergoing treatment with transfusion had higher bone mineral content. Osteopenic patients had higher hepatic iron content than those with normal bone status. In the case of DEXA, bone mineral content (BMC) divided by height cubed was found to be a better indicator of bone mineral status than the BMD usually given. Liver density as determined by DEXA correlates well with hepatic iron.

Absorptiometry, Photon↗
PubMed1994

Effects of coronary artery occlusion and reperfusion on the idioventricular rate in anesthetized dogs.

OBJECTIVES: We evaluated the effects of alpha 1- and beta-adrenergic receptor blockade on the changes in idioventricular rate induced by occlusion and reperfusion of the left anterior descending coronary artery in anesthetized dogs. BACKGROUND: Because sinus rate usually exceeds idioventricular rate, the experimental induction of complete atrioventricular (AV) block may improve the definition of the effects of coronary occlusion and reperfusion on idioventricular pacemaker mechanisms. METHODS: We injected formaldehyde into the AV node to induce complete AV block in 35 chloralose-anesthetized dogs. Animals were assigned to untreated (n = 22), prazosin-treated (n = 6) and propranolol-treated (n = 7) groups. We paced the hearts at 120 beats/min during a 20- to 60-min period of complete coronary occlusion, but we did not pace the heart during reperfusion. RESULTS: In the untreated group, the idioventricular rate did not change significantly during coronary artery occlusions of 20 or 40 min, but it did increase significantly during the last 20 min of a 60-min occlusion. Prazosin and propranolol each attenuated but did not abolish this rate increase. The idioventricular rate increased markedly but transiently soon after reperfusion in all untreated animals. This tachycardia was virtually abolished by either prazosin or propranolol. CONCLUSIONS: The increase in idioventricular rate that develops during the last 20 min of a 60-min coronary occlusion is modulated but probably not mediated by adrenergic mechanisms. The pronounced ventricular tachycardia after reperfusion is virtually abolished by either alpha 1- or beta-adrenergic antagonists. Hence, this tachycardia requires the simultaneous activation of alpha 1- and beta-adrenergic mechanisms in dogs.

Analysis of Variance↗
PubMed1994

Halotolerance of Methanobacterium thermoautotrophicum delta H and Marburg.

Methanobacterium thermoautotrophicum delta H and Marburg were adapted to grow in medium containing up to 0.65 M NaCl. From 0.01 to 0.5 M NaCl, there was a lag before cell growth which increased with increasing external NaCl. The effect of NaCl on methane production was not significant once the cells began to grow. Intracellular solutes were monitored by nuclear magnetic resonance (NMR) spectroscopy as a function of osmotic stress. In the delta H strain, the major intracellular small organic solutes, cyclic-2,3-diphosphoglycerate and glutamate, increased at most twofold between 0.01 and 0.4 M NaCl and decreased when the external NaCl was 0.5 M. M. thermoautotrophicum Marburg similarly showed a decrease in solute (cyclic-2,3-diphosphoglycerate, 1,3,4,6-tetracarboxyhexane, and L-alpha-glutamate) concentrations for cells grown in medium containing > 0.5 M NaCl. At 0.65 M NaCl, a new organic solute, which was visible in only trace amounts at the lower NaCl concentrations, became the dominant solute. Intracellular potassium in the delta H strain, detected by atomic absorption and 39K NMR, was roughly constant between 0.01 and 0.4 M and then decreased as the external NaCl increased further. The high intracellular K+ was balanced by the negative charges of the organic osmolytes. At the higher external salt concentrations, it is suggested that Na+ and possibly Cl- ions are internalized to provide osmotic balance. A striking difference of strain Marburg from strain delta H was that yeast extract facilitated growth in high-NaCl-containing medium. The yeast extract supplied only trace NMR-detectable solutes (e.g., betaine) but had a large effect on endogenous glutamate levels, which were significantly decreased. Exogenous choline and glycine, instead of yeast extract, also aided growth in NaCl-containing media. Both solutes were internalized with the choline converted to betaine; the contribution to osmotic balance of these species was 20 to 25% of the total small-molecule pool. These results indicate that M. thermoautotrophicum shows little changes in its internal solutes over a wide range of external NaCl. Furthermore, they illustrate the considerable differences in physiology in the delta H and Marburg strains of this organism.

2,3-Diphosphoglycerate↗
PubMed1994

Is determination of creatine kinase-2 after electrophoretic separation accurate?

Since 1991, the Ontario Laboratory Proficiency Testing Program has assessed the analytical performance of creatine kinase (CK; EC 2.7.3.2) isoenzyme-2, using fresh human serum supplemented with purified human CK isoenzymes. In Ontario, the 142 laboratories licensed to analyze CK-2 use a variety of methods: electrophoresis-based, immunoinhibition, and mass assays. During a 1992 survey, duplicate CK-2 samples with different total CK activities showed poorer precision when analyzed after electrophoretic separation than by any other method. A 1993 survey designed to validate these observations conclusively showed that electrophoresis-based assays are subject to a bias proportional to the total CK activity. These survey results were confirmed by studies with selected patients' specimens. We therefore conclude that electrophoresis-based assays may not warrant their reputation as the gold standard for CK isoenzyme measurement.

Creatine Kinase↗
PubMed1993

Induction of virus-specific cytotoxic T lymphocytes in vivo by liposome-entrapped mRNA.

The induction of anti-influenza cytotoxic T lymphocytes (CTL) in vivo by immunizing mice with liposomes containing messenger RNA (mRNA) encoding the influenza virus nucleoprotein (NP) is described. NP mRNA, obtained by in vitro transcription, was encapsulated into simple cholesterol/phosphatidylcholine/phosphatidylserine liposomes by the detergent removal technique. The dependence of the route of mRNA-liposomes delivery on CTL induction was studied. The CTL induced were identical to those obtained in vivo with infectious virus in terms of specificity, lysing both peptide-sensitized and virus-infected targets. Furthermore, with the same mRNA-liposome preparation, virus-specific CTL responses could be also elicited in mice of three different haplotypes each of them known to present a distinct NP peptide in an MHC-restricted fashion. The relevance of these results in the context of vaccine development is discussed.

Animals↗
PubMed1992

Changes in plasma atrial natriuretic peptide concentration during heart transplantation.

Examination of changes in plasma atrial natriuretic peptide (ANP) concentrations during heart transplantation may provide important information about factors influencing plasma ANP in patients with severe heart failure. Serial changes in plasma ANP during heart transplantation, and atrial content of ANP in native and donor atria, were measured in 12 patients. Preoperative plasma ANP was elevated in all patients (387 +/- 77 pg/mL), whereas atrial content of ANP in native atria was reduced (0.36 +/- 0.082 micrograms/mg protein). Preoperative plasma ANP did not correlate with hemodynamics, but was negatively correlated with creatinine clearance (r = -0.76, P < .01). Intraoperative plasma ANP prior to transplantation was strongly correlated with intraoperative plasma ANP after transplantation (r = 0.84, P < .001). Although postoperative plasma ANP was reduced from preoperative plasma ANP by 75%, these two measurements were also significantly correlated (r = 0.70, P < .02). Postoperative plasma ANP was not correlated with hemodynamics, but was negatively correlated with both creatinine clearance (r = -0.65, P < .05) and content of ANP in the native atria (r = -0.75, P < .01). Multiple linear regression analysis suggested that up to 85% of the variability of early postoperative plasma ANP could be accounted for by the variability in these latter two parameters. The decrease in native atrial ANP content, in the context of elevated plasma ANP concentration, is consistent with prior animal studies suggesting that severe heart failure induces cellular adaptations favoring accelerated ANP synthesis and secretion (with resultant reduction in tissue content).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗