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Biomedical subjects

M Kumar

Publications and source records attributed to M Kumar.

At least 199 records · Page 11Linked to original sources
PubMed1995

Characterization of lymphocyte beta-adrenoceptor activity and Gs-protein in patients with rheumatic heart valvular disease.

In order to test whether the beta-adrenoceptor activity in rheumatic heart valvular disease depends on the ventricular load conditions, we determined their density and binding affinity to [125I]-iodocyanopindolol in lymphocytes, as well as plasma catecholamine and cAMP levels in 69 patients with regurgitant and stenotic lesions of the aortic and mitral valves. The patients were classified as having left ventricular pressure overload (LVP), left ventricular volume overload (LVV), mixed lesions (MOL) or right ventricular pressure overload (RVP). The beta-adrenoceptor activity was determined by radioligand binding methods, catecholamines by high performance liquid chromatography using an electrochemical detector and cAMP by radioimmunoassay. The mean beta-adrenoceptor density (Bmax) of the control group was 60.1 +/- 9.5 fmol (n = 29) per 10(6) lymphocytes. In the study population, the density was decreased by 83% in LVP, 78% in LVV, 87% in MOL and 86% in RVP. Plasma norepinephrine was elevated by 89% in LVP and 60% in MOL, epinephrine by 43% in LVP, 50% in VOL, 115% in MOL and 20% in RVP, while dopamine was not significantly changed, and cAMP was slightly elevated in all four groups. Screening for activating mutational changes in the Gs alpha-protein gave negative results, possibly dissociating the elevation in plasma cAMP from stimulatory effects of such abnormalities in the Gs-protein signaling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Comparison of fresh and glutaraldehyde-treated autologous stented pericardium as pulmonary valve replacement.

The use of fresh autologous pericardium in valve surgery has shown poor results in the past mainly due to thickening and retraction. Recently, it has been suggested that a short treatment with glutaraldehyde might radically change its behavior. In an attempt to determine whether this disparity in results is due to the glutaraldehyde treatment or to a better present-day surgical technique, fresh and glutaraldehyde-treated autologous pericardium was mounted in a frame and implanted in the pulmonary position of adult sheep. Six survivors obtained in each group were sacrificed between 2 and 8 months in the "fresh" group and between 2 and 6 months in the "glutaraldehyde-treated" group. Macroscopically, the fresh pericardium became thickened and retracted in all specimens, eventually resulting in severe regurgitation, while the glutaraldehyde-treated, although slightly thickened, retained its pliability without significant retraction. Microscopically, viability of the central core of the collagen was more often preserved in the fresh pericardium. Endothelialization was irregular. In conclusion, short glutaraldehyde treatment seems to improve the results of autologous pericardium mounted on a valve stent. Its effect on calcification remains to be ascertained.

Animals↗
PubMed1995

Select dietary fatty acids attenuate cardiopulmonary dysfunction during acute lung injury in pigs.

We examined the effect of substituting linoleic acid (LA) with eicosapentaenoic acid (EPA) and gamma-linolenic acid (gamma-LA), precursors of trienoic and monoenoic eicosanoids, respectively, on acute lung injury (ALI). Three groups (n = 8/group) of pigs were fed enteral diets containing LA (diet A), EPA (diet B), or EPA+gamma-LA (diet C) for 8 days. ALI was then induced with a 0.1 mg/kg bolus of Escherichia coli endotoxin followed by a continuous infusion for 4 h (0.075 mg.kg-1.h-1). Pulmonary arterial and capillary wedge pressures, cardiac index (CI), arterial blood gases, arterial O2 content, and plasma thromboxane B2 (TxB2) were measured. Arterial PO2 decreased at 20 min in animals fed diet A. This change was attenuated with diets B and C. The EPA- and EPA + gamma-LA-enriched diets attenuated the fall in O2 delivery at 20 min, an improvement that was sustained throughout the 4-h study period with the EPA+gamma-LA-enriched diet only. This improvement in O2 delivery was due not only to the improved arterial PO2, but also to the maintenance of CI at 20 min in animals fed diets B and C and throughout the 4-h study period in animals fed diet C. At 4 h, TxB2 increased 10-fold over baseline in animals fed diet A, whereas in animals fed diets B and C the increase was only 3-fold. These decreased TxB2 levels in animals fed diets B and C correlate with an attenuation in the increase in pulmonary vascular resistance that was observed at 20 min after endotoxin infusion in animals fed diet A. These data suggest that specialized enteral diets enriched in EPA+gamma-LA improve gas exchange and O2 delivery, presumably in part through a modification of TxB2 production with a decrease in pulmonary vascular resistance and an increase in CI, during ALI.

6-Ketoprostaglandin F1 alpha↗
PubMed1995

Peripheral serotonin in Alzheimer's disease.

The platelet has been suggested to be a peripheral model of the central serotonergic neuron. This investigation was carried out in order to test the hypothesis that levels of serotonin (5-HT) in the platelet will be decreased in Alzheimer's disease (AD) since neurochemical studies suggest that levels of 5-HT are decreased in the brain of AD patients. We investigated platelet and plasma 5-HT in a group of AD patients (n = 22) as well as in age-matched normal control subjects (n = 20). The results show that the platelet level of 5-HT was significantly reduced in AD (65.7 +/- 28.41 ng/10(8) platelets in AD vs. 112.9 +/- 35.11 ng/10(8) platelets in controls; p = 0.0001). There was no effect on the levels of its metabolite 5-hydroxyindoleacetic acid. These findings suggest that the peripheral serotonergic system in AD is adversely affected.

Aged↗
PubMed1995

A revised terminology for recording surgical findings of the mitral valve.

The existing terminology for the various structures of the mitral valve are diverse and numerous. With the resurgence of interest in reparative procedures for mitral valve disease, it becomes imperative to have a unified terminology which would convey precise connotations in recording the pathology as well as the corrective procedures applied. In an effort to suggest a commonly acceptable nomenclature, we reviewed the available terminology and propose a simple system which will fulfil the needs of recording the intraoperative observations of the pathology of each valve and the manouveres carried out to correct them by the surgeon. This involves designating all structures anterior to the intercommissural line as "anterior" or "A" and those posterior as "posterior" or "P". The structures, as observed by the surgeon through a standard left atriotomy, to the left of the line dropped perpendicular to the middle of the aortic curtain will be designated by the numeral "1" and those to the right "2". The chords will be termed in groups based on their point of insertion, irrespective of whether they are inserted to the free edge or the ventricular surface of the leaflet. The anterior leaflet chords will further be subdivided based on their relation to the stay chords. We hope that this system of naming the structures would provide a unified method of reporting intraoperative findings of mitral valve disease.

Heart Valve Diseases↗
PubMed1994

Binding of carbon disulfide to the site of acetyl-CoA synthesis by the nickel-iron-sulfur protein, carbon monoxide dehydrogenase, from Clostridium thermoaceticum.

Carbon monoxide dehydrogenase (CODH) is a key enzyme in the pathway of carbon monoxide and carbon dioxide fixation by anaerobic bacteria. It performs the oxidation of CO to CO2, the reduction of CO2 to CO, and the synthesis of acetyl-CoA from a methylated corrinoid/iron-sulfur protein, CO, and CoA. These reactions occur at metal centers on CODH and involve metal-carbon bond formation and transformation. There are three iron-containing centers that play distinct roles in CODH: Centers A, B, and C. Center A is the site of synthesis of acetyl-CoA and catalyzes an exchange reaction between CO and acetyl-CoA. Center C is the site of CO oxidation and CO2 reduction. In the work described here, inhibition of CODH by carbon disulfide was studied. CS2 was found to serve as a probe of the interaction of CODH with CO at Center A. EPR spectroscopic and steady-state kinetic studies demonstrated that CS2 mimics the binding of CO to the nickel/iron-sulfur cluster at Center A; however, CS2 itself does not undergo oxidation-reduction and does not appear to bind to Center C as does CO. In the isotope exchange reaction between acetyl-CoA and CO, CS2 was found to be a competitive inhibitor with respect to CO (Ki = 0.47 mM) and a mixed inhibitor with respect to acetyl-CoA (Ki1 = 0.30 and Ki2 = 1.1 mM). The reaction of dithionite-reduced CODH with CS2 resulted in an EPR spectrum with g values of 2,200, 2,087, and 2,017.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗
PubMed1994

Nature's carbonylation catalyst: Raman spectroscopic evidence that carbon monoxide binds to iron, not nickel, in CO dehydrogenase.

Carbon monoxide dehydrogenase catalyzes the synthesis of acetyl-coenzyme A from coenzyme A, a methyl group, and carbon monoxide. The carbon monoxide binds to a mixed metal center of the enzyme, which contains nickel bridged to an iron-sulfur cluster. Resonance Raman spectroscopy has been used to identify both C-O stretching and metal-CO stretching vibrations of the carbon monoxide adduct of the enzyme. This adduct was shown by isotopic exchange to be on the pathway for acetyl-coenzyme A synthesis. The metal to which carbon monoxide is bound was established to be iron, not nickel, by preparation of enzyme from bacteria grown on iron-54 and nickel-64. The Fe-CO frequency is low, 360 wave numbers, implying a weak bond, probably because of electron donation from sulfide and thiolate ligands of the iron. A bimetallic mechanism is proposed, in which carbon monoxide binds to an iron atom and is subsequently attacked by a methyl group on a nearby nickel atom, forming an acetyl ligand, which is then transferred to coenzyme A.

Acetyl Coenzyme A↗
PubMed1994

Congenital coagulopathies and pregnancy: report of four pregnancies in a factor X-deficient woman.

Pregnancy in women with congenital coagulation factor deficiencies has been associated with adverse fetal outcomes. Recurrent spontaneous abortions, placental abruptions, and premature births are reported, the exact reasons for which are not clear, and management of such patients continues to be a challenge. We reviewed the outcome of four pregnancies in a patient with factor X deficiency, and looked at the effect of factor replacement therapy on pregnancy. Her first two pregnancies resulted in the birth of extremely premature babies at 21 and 25 weeks of gestation, both of which died in the neonatal period. The patient was treated with fresh frozen plasma for acute bleeding episodes during these pregnancies. In addition during her second conception she was given factor IX complex [Konyne] prophylactically, but only in the latter half of her pregnancy. During her next two pregnancies she was treated early on during pregnancy, with prophylactic replacement of factor X. She delivered healthy babies at 34 and 32 weeks of gestation, and they are both doing well. We therefore suggest possible mechanisms by which aggressive prophylactic factor support in a female with severe congenital coagulopathy, may improve on fetal outcome.

Adult↗
PubMed1994

Changes in cognitive coping strategies predict EBV-antibody titre change following a stressor disclosure induction.

Previous research has shown that emotional disclosure of traumatic or stressful events is associated with facilitating insight into the experience, improving mood, and modulating some aspects of the immune system. The current study examined how cognitive changes and experiential involvement during an emotional disclosure induction protocol relate to immune functioning, as measured by IgG antibody titres to the Epstein-Barr virus viral capsid antigen (EBV-VCA). Seventy-six college undergraduates were randomly assigned to either a disclosure induction or an assessment-only control condition. Experimental subjects met with an experimenter for three weekly 20-min individual sessions during which time they were asked to discuss a stressful or traumatic topic which they had previously discussed only minimally with others. Blood was drawn a week prior to the first session and at one week following the third session. Subjects completed the Impact of Event Scale (IES) after session 1 and at followup, and the extent of experiential involvement in disclosure during each session was assessed by means of the Experiencing Scale. Mood was assessed before and after each disclosure using the Nowlis Mood Adjective Checklist. Although the disclosure induction did not directly affect EBV-VCA antibody titres, individual differences in subjects' ability to involve themselves in the disclosure process and abandon their avoidance of the stressful tropic during the course of the 3-wk period were predictive of antibody decrements. These associations were more pronounced for individuals who disclosed older and more troublesome events.

Adaptation, Psychological↗
PubMed1994

Monitoring intrathecal temperature: does core temperature reflect intrathecal temperature during aortic surgery?

Paraplegia secondary to spinal cord ischemia is a common occurrence following proximal aortic surgery. Recent research has suggested that modest reductions in neuronal temperature (ie, a 2 to 5 degrees C reduction) may protect the central nervous system from ischemic injury, and several medical centers are now using modest whole body hypothermia in an attempt to protect the spinal cord during aortic surgery. However, to date, there are no reports to validate that reductions in core temperature will reduce intrathecal temperature during aortic surgery. In the present study, the correlation between core temperature, assessed with a pulmonary artery thermistor, and intrathecal temperature, assessed with a lumbar intrathecal thermocouple, were evaluated. Both devices were corrected for bias using a mercury thermometer standard. It was found that there was excellent correlation between pulmonary artery temperature and intrathecal temperature during all portions of the surgery (r = 0.948; P < 0.001). The regression line for the relationship was defined by the formula: intrathecal temperature = 0.98 x pulmonary artery temperature + 0.65. Furthermore, there was excellent correlation between bias-corrected intrathecal temperature and the temperature measured by commercially available, bias-uncorrected thermistors placed in the esophagus (r = 0.869; P < or = 0.001), urinary bladder (r = 0.873; P < 0.001), and pulmonary artery (r = 0.929; P < 0.001). Based on these data, it is concluded that there is a close correlation between intrathecal temperature and core temperatures during proximal aortic surgery, and commercially available thermistors provide sufficient accuracy to assess spinal cord cooling during attempts to protect the spinal cord from ischemic injury.

Aortic Aneurysm, Abdominal↗
PubMed1994

Cerebrospinal fluid dopamine in HIV-1 infection.

BACKGROUND: Increasing evidence suggests significant involvement of the basal ganglia in patients with HIV-1 infection. OBJECTIVE: To study the effect of HIV-1 infection on cerebrospinal fluid (CSF) dopamine levels. DESIGN: CSF dopamine levels were measured by high-performance liquid chromatography. SETTING: A university-based outpatient clinic in south Florida involved in clinical AIDS research. SUBJECTS: Twenty-two subjects were enrolled in a prospective, longitudinal study of the neurological complications of AIDS. Five subjects were HIV-seronegative, but at risk for HIV-1 infection, 11 were HIV-1-seropositive without neurological disease and six had HIV-1-related neurological disease. RESULTS: The CSF dopamine mean values were significantly lower in the HIV-1-seropositive group with (P < 0.0001) or without (P < 0.0001) neurological disease than in the HIV-seronegative group. There was a very strong correlation between CD4 lymphocyte counts and CSF dopamine levels (P = 0.004) in the neurologically symptomatic group (P = 0.0008), but not in the other two groups. CONCLUSION: HIV-1 infection appears to have an effect on the central nervous system dopaminergic systems, as reflected in levels of CSF dopamine.

Adult↗
PubMed1994

A hypercellulolytic mutant of Fusarium oxysporum.

Multiple mutagenesis of Fusarium oxysporum DSM 841 resulted in enhanced yields of cellulases. The hypercellulolytic mutant (NTG-19) secretes high levels of extracellular cellulases on different cellulosic substrates. Addition of surfactant, Tween-80, further increased enzyme secretion by about 30%. The results on hydrolysis of wheat straw by parent strain, DSM 841 and mutant NTG-19 cellulases also revealed a significant improvement in the hydrolytic potential of the cellulolytic enzymes from the mutant NTG-19.

Cellulase↗
PubMed1994

Diagnostic and prognostic significance of lactate dehydrogenase in cerebrospinal fluid in patients of meningitis.

Activity of lactate dehydrogenase was measured in cerebrospinal fluid in 60 cases of meningitis (35 pyogenic, 18 tuberculous and 7 viral). Thirty age and sex matched healthy controls were taken to find out its diagnostic and prognostic significance in meningitis. The cerebrospinal fluid lactate dehydrogenase activity was significantly higher (p < 0.001) in cases of pyogenic meningitis and tuberculous meningitis as compared to the control group. The maximum elevation was seen on the 1st day in all types of meningitis but the activity declined significantly thereafter in patients of pyogenic meningitis who recovered without complications. However, in 2 cases of pyogenic meningitis and 5 cases of tuberculous meningitis who survived with complications, the lactate dehydrogenase activity on subsequent estimations increased serially. Further, the basal lactate dehydrogenase activity in 9 cases of pyogenic meningitis (who expired) was higher than those who survived without complications. The basal lactate dehydrogenase activity in pyogenic meningitis was significantly higher (p < 0.05) as compared to tuberculous meningitis and viral meningitis patients (p < 0.02) in this study.

Adolescent↗