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Biomedical subjects

K Kumar

Publications and source records attributed to K Kumar.

At least 19 recordsLinked to original sources
PubMed1992

Fixation of fractures by twisted plates. A new concept of osteosynthesis.

A new twisted plate has been designed for biplane fixation of diaphyseal fractures of long bones. Comparative mechanical testing of the new twisted plate and conventional flat plates showed that the twisted plate was 40% stronger when a bending moment was applied and 132% stronger to a twisting moment. The overall improvement in strength was 90.5%. Clinical trials have been carried out and this paper describes the use of the new plate.

Bone Plates↗
PubMed1992

The penetration of drugs into the lesions of spinal tuberculosis.

The concentration of antituberculous drugs in blood and pus from tuberculous spinal lesions was measured initially, and again after 3 to 5 months of treatment in 4 cases. The pre- and post-chemotherapy drug concentrations were almost the same. This indicated that healing does not interfere with the penetration of the drugs into the lesion.

Adolescent↗
PubMed1992

Expression of protein kinase C in postischemic brain: an in situ hybridization study.

Cerebral ischemia leads to a number of biochemical and molecular changes which include increase in intracellular calcium, arachidonic acid, and diacylglycerol, all of which are capable of activating protein kinase C (PKC). To investigate how the expression of PKC is affected in postischemic brain, ischemia was produced in gerbils by bilateral common carotid artery occlusion for 10 min followed by reperfusion for 15 min, 6 h, and 24 h. The brains of postischemic and normal control animals were removed, forebrains dissected, fresh frozen, and processed for in situ hybridization. The mRNA expression of PKC was analyzed by using oligonucleotide probes based on the sequences of PKC alpha and epsilon isozymes in this preliminary study. There was no change observed in the expression of PKC alpha in any region of the brain in any of the postischemic groups examined. There was, however, a qualitative increase in the transcription for PKC epsilon in two out of three brains of 15 min postischemic group which continued through 24 h of reperfusion. Since the protein itself was not examined, it can not be said how these observations regarding transcription relate to the synthesis of the protein and whether there are any changes in the subcellular distribution of PKC following ischemia. However, since there was no decrease in transcription demonstrated in our study, it appears that the reported decrease in PKC activity following ischemia is not due to decreased mRNA expression.

Animals↗
PubMed1992

Dissociation of gadolinium chelates in mice: relationship to chemical characteristics.

Tissue distributions of seven 153Gd-labeled Gd chelates were determined at five residence intervals (5 min to 14 days) following intravenous administration of 0.4 mmol/kg to mice. Relationships were sought among physicochemical parameters: thermodynamic and conditional (pH 7.4) equilibrium stability constants (log K and log K'), acid dissociation rate constants (k(obs)), lipophilicity (log P), overall charge, and size (molecular weight). Size and lipophilicity did not correlate with tissue distributions. There were possible correlations between anionic charge and rapid, early renal excretion and between stability constants and long-term residual Gd deposition. Strong correlations (r greater than 0.99) were found between acid dissociation rates and long-term deposition of Gd in the whole body, liver, and femur. This is attributed to dissociation of Gd from the chelates in vivo. Acid dissociation rates may be useful in predicting dissociation of Gd from chelates in vivo.

Animals↗
PubMed1992

Quantitative dependence of MR signal intensity on tissue concentration of Gd(HP-DO3A) in the nephrectomized rat.

Cardiac-gated SE 20/224 +/- 20 MR images were obtained from nephrectomized rats before and after intravenously administering 153Gd-Gd(HP-DO3A). The concentration of Gd, [Gd], was linear in dose in myocardium, skeletal muscle, and blood. Under steady-state conditions, where d[Gd]/dt = 0, image intensities (IIN) in regions of interest were compared with the measured [Gd]. IIN was linear in myocardium at less than or equal to 0.61 mumol/g-myocardium (less than or equal to 0.5 mmol/kg dose) and in skeletal muscle at less than or equal to 0.63 mumol/g-muscle (less than or equal to 0.75 mmol/kg). Above 0.6 mumol Gd/g-tissue, IIN did not increase further. The in vivo data were consistent with measured ex vivo and in vivo relaxivities. A 29% greater slope for IIN versus [Gd] in myocardium [14,439 +/- 4350 IIN (mumol/g)] than in muscle [10,258 +/- 5,296 IIN/(mumol/g)] was attributed to a significant difference in blood content: 25% versus 2% weight blood in myocardium and skeletal muscle, respectively. Two components were apparent from plots of ex vivo 1/T1 versus [Gd] in myocardium and muscle, and only one for blood.

Animals↗
PubMed1992

Post kala-azar dermal leishmaniasis: a neglected aspect of kala-azar control programmes.

Post kala-azar dermal leishmaniasis (PKDL) was studied in relation to the kala-azar epidemic in Bihar, India. Between 1970 and 1989, 530 individuals, 302 males and 228 females, were admitted to the hospital of Patna Medical College with PKDL, the number of cases steadily rising from two in 1970 to 59 in 1989. The age of the patients varied from four to 70 years, with 33% aged 11-20 years and 16% 0-10 years. The prevalence of kala-azar in India also increased in the same period, mostly as the result of an epidemic of the disease in Bihar. There were no cases of this disease admitted to Patna Medical College from 1958-1970, it having become rare in India in the 1950s, possibly as a result of the DDT sprayed during the National Malaria Eradication Programme. In the period 1977-1990, however, there were 301,076 cases of kala-azar reported in Bihar alone, with a mortality rate over 2% (compared with 31,074 cases and a mortality rate below 0.4% for the rest of India). It seems possible that, once DDT spraying stopped, the re-establishment of large sandfly population and infection of these vectors, largely as a result of them feeding on cases of PKDL, provoked the resurgence of kala-azar. The study emphasizes the need to search for cases of PKDL, even in young children, and to monitor and effectively treat them as part of kala-azar control programmes. All patients could be cured if treated with the right dosage for the right period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

A correlative study of serum zinc and in vivo cell mediated immune status in rheumatic heart disease.

This study was conducted to determine the zinc status and assess relationship between serum zinc and in vivo cell mediated immunity (CMI) in patients with rheumatic heart disease (RHD). The study comprised 22 patients with active rheumatic heart disease (ARHD), 15 patients with chronic rheumatic heart disease without activity (CRHD) (selection based on Jone's Criteria--Revised), and 15 age and sex matched healthy control. Zinc estimation was done by atomic absorption spectrophotometer. To assess CMI in vivo, phytohaemagglutinin skin test and skin window test were done. Serum zinc and in vivo CMI in patients with ARHD and CRHD compared with controls. Mean serum zinc was significantly decreased in patients with ARHD and CRHD, more pronounced in the former (P less than 0.001); and mean 24 h urinary zinc was significantly increased in patients with ARHD (P less than 0.001) as compared to controls. A significant depression in CMI in vivo was observed in patients with ARHD and CRHD (P less than 0.001). A significant positive correlation was seen among serum zinc and markers of in vivo CMI (P less than 0.001). In conclusion, depletion of zinc, observed in RHD, probably causes immune alterations and suggest role of zinc in immunopathogenesis of RHD. Zinc supplementation may alter the course of rheumatic fever and RHD.

Adolescent↗
PubMed1991

Electrophysiologic effects of oral diltiazem before and after beta blockade.

We conducted electrophysiologic (EP) studies and estimated the sinus node function and atrioventricular (AV) conduction in 10 patients with suspected coronary arterial disease (age range 35-55 years) before and during diltiazem therapy (60 mg thrice daily for 5-7 days). The effect of beta blockade (0.1 mg/kg of intravenous propranolol) was evaluated in both EP studies. The mean spontaneous sinus cycle length (SCL) and the AV nodal Wenckebach cycle lengths (AVWB) were significantly higher (p less than 0.05) after propranolol alone (913 +/- 131 and 504 +/- 197 ms, respectively) compared with baseline values (SCL: 827 +/- 149 ms, AVWB: 439 +/- 173 ms). Diltiazem alone failed to influence the SCL and AVWB significantly. Following the combination (diltiazem + propranolol), SCL (945 +/- 147 ms) and AVWB (533 +/- 148 ms) were significantly higher (p less than 0.05) than baseline and post diltiazem values (SCL: 840 +/- 150 ms; AVWB 457 +/- 103 ms). None of the other parameters (sinoatrial conduction time, corrected sinus node recovery time, AH and HV intervals, AV nodal and atrial effective refractory periods) were significantly influenced by propranolol, diltiazem, or the combination. No patient developed AV block, sinus arrest/sinoatrial exit block, or symptomatic sinus bradycardia following beta blockade after diltiazem administration. Oral diltiazem therapy alone and after beta blockade does not appear to adversely influence the sinus node function and AV conduction in patients below the age of 55 years. The combination of diltiazem and beta blocker thus appears safe in selected patients with coronary arterial disease.

Administration, Oral↗
PubMed1991

Cardiac involvement in nonspecific aortoarteritis (Takayasu's arteritis).

Fifty-four patients (18 males and 36 females, ages 2 to 37 years) with nonspecific aortoarteritis (NSAA) were studied. Evaluation revealed hypertension in 35, congestive heart failure (CHF) in 24, mild to moderate mitral regurgitation in six, and mild aortic regurgitation in two. Erythrocyte sedimentation rate was raised (greater than 35 mm in the first hour) in 38 patients. The arterial lesions included type I in seven, type II in eight, and type III in 34. Pulmonary artery involvement was present in 4 (type IV) of the 20 patients in whom it was studied. Selective coronary angiography was done in 11 patients and revealed 90% left main stenosis in one patient. Hemodynamic data revealed raised (greater than 7 mm Hg) mean right atrial pressure in nine, raised mean pulmonary artery pressure (greater than 20 mm Hg) in 29, and raised left ventricular filling pressure (greater than 12 mm Hg) in 27 patients. Radionuclide ventriculography revealed reduced (less than 45%) left ventricular ejection fraction (LVEF) in 27 patients. The myocardial morphology as evaluated on right ventricular endomyocardial biopsy revealed normal histology in nine, features of inflammatory myocarditis in 24, and nonspecific changes suggestive of dilated cardiomyopathy in six patients. Marked right ventricular endocardial thickening was present in three. All patients with CHF had some histologic abnormality. We emphasize that myocardial involvement including myocarditis is common in NSAA and may precipitate CHF in these patients.

Adolescent↗
PubMed1991

Comparison of vascular perfusion in ischemia-sensitive and ischemia-resistant regions of gerbil brain by an automated laser cytometric device: a preliminary study.

Reduced blood supply in the hippocampus has been considered to be a factor contributory to this region's selective susceptibility to ischemia. To determine if there are differences in vascularization of vulnerable and resistant regions of the brain, a quantitative morphometric assessment of vascular filling was performed in the gerbil brain by using a relatively new and highly sensitive automated laser cytometric device, ACAS (Adherent Cell Analysis and Sorting). Evan's blue, an intravital vascular tracer, was injected intracardiac in 5 Mongolian gerbils to identify perfused blood vessels in the cortex and CA1 region of hippocampus. Exactly 3 min later, the animal was decapitated, the brain removed and sections prepared for fluorescent quantitative morphometric analysis of blood vessels. The perfused vessels appeared as fluorescent structures due to the autofluorescent property of Evan's blue. Several fields in each of the two specified regions were studied and integrated numbers of blood vessels/mm2 obtained for statistical comparisons. Control brains perfused with normal saline (vehicle for Evan's blue) were used to determine the background fluorescence. The number of perfused blood vessels of all sizes was found to be lower in the CA1 sector of hippocampus than that in the cerebral cortex. The number of capillary size vessels was also lower in the CA1 region but the difference was not significant. Since it is the capillaries that are of prime importance in the diffusion system, and we found no significant regional difference in the density of capillary size vessels, it appears unlikely that the peculiarities of patterns of vascularization contribute significantly to vulnerability to ischemia.

Animals↗
PubMed1991

Probe angioplasty through an intracoronary probing catheter in lesions which are difficult to cross.

The clinical records of the first 17 consecutive patients (20 lesions) in whom percutaneous transluminal coronary angioplasty was done using the ultra-low profile "balloon-on-wire probe" passed through an intracoronary probing catheter were reviewed. All patients had high-grade "difficult" lesions. In 15 lesions (12 patients) other balloon systems (over-the-wire low profile balloons (n = 9), and balloon-on-wire used alone, (n = 6)) had failed to cross the lesion. Acute ischemia due to complete occlusion at the site of the lesion during attempts to cross was seen in 3 of these patients. The intracoronary probing catheter was used to deliver the probe across the lesion in all these cases. Successful dilatation was achieved in 14 lesions (93%). In 5 lesions (5 patients) this combination was used as the initial strategy. Three of these had chronic total occlusions. Successful dilatation was achieved in 3 lesions (60%) using this combination and in 1 lesion over-the-wire balloon finally succeeded. There was 1 failure. The intracoronary probing catheter in combination with probe balloon wire offers a promising method to increase the success rate in patients with high grade "difficult" lesions. This combination is especially useful in situations where other balloon systems fail to cross the lesion.

Angioplasty, Balloon, Coronary↗
PubMed1991

Reaction of gadolinium chelates with endogenously available ions.

The extent of reaction of 153Gd-radiolabeled Gd(L) chelates with 25 mM CO23- (25 mF), PO34-, Zn2+ and Cu2+ at pH 7 was determined for L = EDTA, DTPA, DOTA, HP-DO3A, and DO3A. Gd(EDTA)- and Gd(DTPA)2- reacted (greater than 20% in 10 min) with Cu2+ and Zn2+ in the presence of PO34-. These double replacement reactions yielded precipitated GdPO4 and chelated Cu(L). Gd(HP-DO3A), Gd(DO3A) and Gd(DOTA)- were inert to reaction with all four ions at room temperature (less than or equal to 1% reaction detected). The thermodynamic binding constants of the ligands for Gd3+ and Cu2+ were found to be equal (10(20) M-1) for DO3A, while DOTA and HP-DO3A favored Gd3+ over Cu2+ by greater than or equal to 10(2) M-1. The low order of reactivity of Gd(DOTA)- and Gd(HP-DO3A) was anticipated by the binding constants, but the lack of reactivity of Gd(DO3A) is attributed to kinetic inertia. This latter property, desirable in MRI contrast agents, is promoted by the conformational stability of the tetraazacyclododecane macrocycle, which forms the backbone of the ligand. It is concluded that this class of chelates is exceptionally inert in solutions of endogenously available ions, and that thermodynamics alone is an insufficient predictor of the reactivity of the highly inert Gd complexes based on the tetraazamacrocycle.

Contrast Media↗
PubMed1991

Tone-dependent waterfall behavior during venous pressure elevation in isolated canine hearts.

We examined the "vascular waterfall" hypothesis, which proposes that coronary flow is unaffected by elevations in outflow pressure until the latter reaches a critical threshold level, in 29 isolated canine hearts. In fibrillating hearts vasodilated with adenosine or carbocromen, coronary flow and the coronary pressure-flow relation were not affected by changes in great cardiac vein pressure (PGCV) below a threshold value of 11 +/- 0.9 (mean +/- SEM) mm Hg. Further elevations of PGCV reduced flow and shifted the pressure-flow relation to the right, increasing its pressure-axis intercept (Pf=0). When vasomotor tone was augmented with vasopressin, threshold PGCV increased to 25 +/- 2.7 mm Hg (p less than 0.001). Once again, the pressure-flow relation was unaffected by changes in PGCV below the threshold value and shifted to the right when this value was exceeded. The amount by which spontaneous values of Pf=0 exceeded threshold values of PGCV was greater when vasomotor tone was augmented than during vasodilation. Pf=0 continued to exceed PGCV when the latter was raised above the threshold level. Both Pf=0 and threshold values of PGCV were less during a long diastole than during ventricular fibrillation. We reached the following conclusions. 1) During changes in PGCV below a threshold value, the coronary circulation exhibits traditional waterfall behavior. 2) The threshold pressure for altering waterfall behavior is affected by vascular tone and mechanical activity. 3) Pf=0 remains above PGCV when the latter is increased above the threshold value needed to alter flow.

Animals↗