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Biomedical subjects

A Kumar

Publications and source records attributed to A Kumar.

At least 433 records · Page 24Linked to original sources
PubMed2000

Cardiovascular Dysfunction in Sepsis and Septic Shock.

The optimal therapy for the treatment of sepsis and septic shock remains controversial. Many protocols are followed, using different strategies for initial resuscitation, cardiovascular monitoring, hemodynamic intervention, and eradication of infection. Overall, an aggressive approach to the management of cardiovascular dysfunction in septic shock is warranted. Initially, large volume fluid resuscitation is instituted. Our first choice of resuscitation fluid is 0.9% normal saline. Invasive hemodynamic monitoring using a flotation pulmonary artery catheter as well as invasive arterial blood pressure monitoring is a necessity in the hemodynamic management of septic shock. If the patient remains hypotensive (mean arterial pressure < 65 mm Hg) after adequate volume resuscitation has been established (pulmonary capillary wedge pressure 12 to 15 mm Hg), then vasopressor agents must be instituted. Our first choice is usually dopamine. In patients who remain hypotensive after maximal doses of dopamine are reached, norepinephrine is added. If these agents generate excessive tachycardia or if tachyarrhythmias develop, phenylephrine can be substituted or added. Inotropic agents are useful if the patient demonstrates hypotension with a low cardiac output state. Dobutamine is the agent of choice. We initiate broad-spectrum empiric antibiotics at presentation, modifying the exact regimen based on 1) site of infection; 2) prevailing organisms and antibiotic resistance patterns in the patient's environment; and 3) other specific risk factors (immunosuppression, chronic disease, exposure and vaccination history, invasive medical devices). When appropriate, aggressive surgical debridement is pursued. Currently, there are no clinical data to support the use of antagonists for sepsis mediators, although various clinical trials remain underway. Steroids are contraindicated except for adrenal replacement therapy.

Journal Article↗
PubMed2000

Development of an ergonomic evaluation facility for Indian tractors.

The design of tractors manufactured in low-income countries like India has not changed much in the past two decades, especially from an ergonomic point of view. Moreover, in these countries tractors are used for transportation purposes in addition to farming operations. Therefore, the design criteria for these tractors need to be different from those in high-income countries. This paper describes the development of an ergonomic facility for improvement of tractor design. An ergonomic evaluation facility has been developed consisting of a work place envelope for the Indian population, a layout measuring device and an ergonomic rig. This facility can be used for comparative evaluation of the display and control layouts of different tractors in order to develop an optimum layout. The ergonomic rig has the facility to simulate the improved layout for subjective evaluation.

Agriculture↗
PubMed2000

Management of distal femoral fractures in elderly patients using retrograde titanium supracondylar nails.

We present our experience with a retrograde supracondylar nail used for the management of fractures of the distal femur in elderly patients. Eighteen fractures of the distal femur in 18 patients were treated with AIM titanium supracondylar nails. Sixteen patients with a median age of 83 years (62-100 years) were finally available for review. All 16 fractures were classified as extra-articular type A according to the AO classification. The average operative time was 58 min. Follow up ranged between 4 and 35 months (average 20.4 months). Fifteen fractures (93.7%) united in an average duration of 3.6 months. The average range of motion achieved at the knee was 100. 6 degrees. There were no implant failures, knee sepsis or wound healing problems. One non-union and two stress fractures of the femur above the nail were the main complications in this series. We concluded that the AIM titanium supracondylar nail is a useful alternative implant for the management of the osteoporotic fractures of the distal femur particularly the extra-articular AO type A fracture in the elderly population.

Aged↗
PubMed2000

Glomus faciale, glomus jugulare, glomus tympanicum, glomus vagale, carotid body tumors, and simulating lesions. Role of MR imaging.

In summary, MR imaging characteristics of a case of paraganglioma of the facial nerve are reported. The relationship of paragangliomas and the chromaffin system have been discussed. There are many reports of cases of synchronous paragangliomas and pheochromocytomas. These reports, along with simultaneous involvement in familial MEN syndromes, and the common embrylogic origin (neural crest) and similar histopathologic relationships between paragangliomas and pheochromocytoma, all support the fact that they are part of the chromaffin system.

Adrenal Gland Neoplasms↗
PubMed2000

Control of hepatocyte function on collagen foams: sizing matrix pores toward selective induction of 2-D and 3-D cellular morphogenesis.

While microporous biopolymer matrices are being widely tested as cell culture substrates in hepatic tissue engineering, the microstructural basis for their control of cell differentiation is not well understood. In this paper, we studied the role of void size of collagen foams in directing the induction of liver-specific differentiated morphology and secretory activities of cultured rat hepatocytes. Hepatocytes cultured on collagen foams with subcellular sized pore diameters of 10 microm assumed a compact, cuboidal cell morphology, rapidly achieving monolayer coverage, and secreted albumin at the rate of 40 +/- 8 pg/cell/d. Increasing the pore size to 18 microm elicited a distinctly spread cellular phenotype, with discontinuous surface coverage, and albumin secretion rates declined precipitiously to 3.6 +/- 0.8 pg/cell/d. However, when collagen foams with an even higher average void size of 82 microm were used, hepatocytes exhibited high degree of spreading within an extensive three-dimensional cellular network, and exhibited high albumin secretory activity (26 +/- 0.6 pg/cell/d). The effect of void geometry on cellular ultrastructral polarity was further analyzed for the three void size configurations employed. The distribution of the cell-cell adhesion protein, E-cadherin, was primarily restricted to cell-cell contacts on the 10 microm foams, but was found to be depolarized to all membrane regions in cells cultured on the 18 and 82 microm foams. Vinculin-enriched focal adhesions were found to be peripherally clustered on cells cultured on 10 microm foams, but were found to redistribute to the entire ventral surface of cells cultured on the 18 and 82 microm foams. Overall, we demonstrate the significance of designing pore sizes of highly adhesive substrates like collagen toward selective cell morphogenesis in 2-D or 3-D. Subcellular and supercellular ranges of pore size promote hepatocellular differentiation by limiting 2-D cell spreading or effecting 3-D intercellular contacts, while intermediate range of pore sizes repress differentiation by promoting 2-D cell spreading.

Actins↗
PubMed2000

Band-shaped and whorled microcystic dystrophy of the corneal epithelium.

OBJECTIVE: To report the clinical, histopathologic, and electron microscopic features of band-shaped and whorled microcystic corneal epithelial dystrophy. DESIGN: Two interventional case reports. PARTICIPANTS: Two patients, two eyes. INTERVENTION: The involved area of corneal epithelium was scraped from each cornea. RESULTS: Histopathologic examination showed microscopic vacuoles in the epithelial cytoplasm in both cases. Electron microscopic examination revealed mainly empty cytoplasmic vacuoles with scant nonspecific osmophilic material. The process recurred clinically in one patient. Changes in corneal topography are documented in one patient. CONCLUSION: Clinical findings and pathologic studies seem nearly identical to those in the original report. No pattern of systemic disorder or medication use was found. The cause of this condition remains unknown.

Aged↗
PubMed2000

Myocardial dysfunction in septic shock.

Over the last decade, it has become clear that myocardial depression, like vascular dysfunction, is typical of human septic shock. Human septic myocardial depression is characterized by reversible biventricular dilatation, decreased ejection fraction, and decreased response to fluid resuscitation and catecholamine stimulation (in the presence of overall hyperdynamic circulation). A circulating myocardial depressant substance, not myocardial hypoperfusion, is responsible for this phenomenon. This substance has been shown to represent low concentrations of TNF-alpha and IL-1 beta acting in synergy on the myocardium through mechanisms that include NO and cGMP generation. Despite major advances in our understanding of the hemodynamics and pathogenesis of cardiac dysfunction in sepsis, successful attempts to modulate these mechanisms to improve clinical outcomes in human trials have not been demonstrated to date. For the moment, the therapeutic approach to the patient with cardiac dysfunction in distributive or septic shock must be primarily aimed at reestablishing adequate organ perfusion and oxygen delivery by vigorous fluid resuscitation and vasopressor or inotropic support. In the long term, however, only continued research regarding the cellular mechanisms of organ dysfunction, including septic myocardial depression, will lead to successful therapeutic strategies. These strategies will likely involve direct manipulation of intracellular signaling processes that lead to organ dysfunction as manifested by septic myocardial dysfunction and septic shock.

Animals↗
PubMed2000

Phaco-chop versus stop-and-chop nucleotomy for phacoemulsification.

PURPOSE: To perform a comparative evaluation of phaco-chop versus stop-and-chop nucleotomy techniques of phacoemulsification. SETTING: Dr. Rajendra Prasad Center for Ophthalmic Sciences, New Delhi, India. METHODS: Forty eyes of 40 patients with immature senile cataract were included in the study. Twenty eyes each were randomly assigned to have phaco-chop (Group 1) or stop-and-chop (Group 2) nucleotomy during phacoemulsification. The main parameters were corneal endothelial count, effective phaco time, volume of infusion fluid used, central corneal pachymetry, best corrected visual acuity (BCVA), and intraoperative complications during nucleotomy. Follow-up visits were scheduled at 1, 4, and 12 weeks. RESULTS: The mean effective phaco time was 27 seconds +/- 18 (SD) in Group 1 and 28 +/- 16 seconds in Group 2. The mean corneal endothelial cell loss was 6.89% and 7.17%, respectively, at the end of 12 weeks. The difference between groups was not significant. An anterior capsule tear occurred in 3 eyes in Group 1 and 1 eye in Group 2. All eyes achieved a BCVA of 20/20 at the end of 4 weeks. There were no significant between-group differences in any intraoperative or postoperative parameter. CONCLUSIONS: The phaco-chop and the stop-and-chop nucleotomy techniques were equally efficacious for nuclear management during phacoemulsification.

Cell Count↗
PubMed2000

Atrophy and high intensity lesions: complementary neurobiological mechanisms in late-life major depression.

The primary objective of our study was to examine the role of atrophy, high intensity lesions and medical comorbidity in the pathophysiology of major depressive disorder in the elderly (late-life MDD). Our sample was comprised of 51 patients with late-life MDD and 30 non-depressed controls. All subjects were scanned on 1.5 tesla magnetic resonance imaging scanner (MRI) and absolute and normalized measures of brain and lesion volumes were obtained and used for comparison between groups. Patients with MDD had significantly smaller frontal lobe volumes, together with larger whole brain lesion volumes when compared with controls (p < .05). Whole brain lesion volumes correlated significantly (r = 0.41, p = .006) with overall medical comorbidity. The odds ratio (OR) for existing MDD increases significantly with a decrease in frontal lobe volume and an increase in whole brain lesion volumes (p < .05). Our findings suggest that atrophy and high intensity lesions represent relatively independent pathways to late-life MDD. While medical disorders lead to neuropathological changes that are captured on MR imaging as high intensity signals, atrophy may represent a relatively autonomous phenomenon. These findings have broad implications for the pathophysiology of mood disorders and suggest that complementary neurobiological processes may lead to cumulative neuronal injury thereby predisposing to clinical depression.

Age of Onset↗
PubMed2000

Genome-wide mutant collections: toolboxes for functional genomics.

The sequencing of entire genomes has led to the identification of many genes. A future challenge will be to determine the function of all of the genes of an organism. One of the best ways to ascertain function is to disrupt genes and determine the phenotype of the resulting organism. Novel large-scale approaches for generating gene disruptions and analyzing the resulting phenotype are underway in the budding yeast Saccharomyces cerevisiae and other organisms including flies, Mycoplasma, worms, plants and mice. These approaches and mutant collections will be extremely valuable to the scientific community and will dramatically alter the manner in which science is performed in the future.

Animals↗
PubMed2000

Temperature dependent luminescence characteristics of Sm3+-doped silicate glass.

We report here on the optical characterisation of Sm3+ (5 wt%): SiO2 + Al2O3 + Li2O + Na2O + MgO glass from the measurements of optical absorption spectra (at 300 K), total luminescence spectra (10-300 K) and fluorescence lifetimes (10-300 K) of the prominent emission transitions of the Sm3+ ions. Besides its spectral properties, physical and nonlinearity characterising property parameters have also been computed to understand the optical dispersive power of this glass. By the application of Judd-Ofelt parameters (omega(lambda)) of the measured absorption spectrum, the radiative transition probability factors (A) and stimulated emission cross-section (sigma(p)E) of the observed fluorescent levels have been analysed. Both emission intensity and measured lifetimes of the prominent luminescent transition (4G(5/2) --> 6H(7/2)) concerning Sm3+-glass has been showing a descending trend with the rise in temperature with N2-laser (337.1 nm) as the source of excitation.

Glass↗
PubMed2000

Candida antartica lipase B catalyzed polycaprolactone synthesis: effects of organic media and temperature.

Engineering of the reaction medium and study of an expanded range of reaction temperatures were carried out in an effort to positively influence the outcome of Novozyme-435 (immobilized Lipase B from Candida antarctica) catalyzed epsilon-CL polymerizations. A series of solvents including acetonitrile, dioxane, tetrahydrofuran, chloroform, butyl ether, isopropyl ether, isooctane, and toluene (log P from -1.1 to 4.5) were evaluated at 70 degrees C. Statistically (ANOVA), two significant regions were observed. Solvents having log P values from -1.1 to 0.49 showed low propagation rates (< or = 30% epsilon-CL conversion in 4 h) and gave products of short chain length (Mn < or = 5200 g/mol). In contrast, solvents with log P values from 1.9 to 4.5 showed enhanced propagation rates and afforded polymers of higher molecular weight (Mn = 11,500-17,000 g/mol). Toluene, a preferred solvent for this work, was studied at epsilon-CL to toluene (wt/vol) ratios from 1:1 to 10:1. The ratio 1:2 was selected since, for polymerizations at 70 degrees C, 0.3 mL of epsilon-CL and 4 h, gave high monomer conversions and Mn values (approximately 85% and approximately 17,000 g/mol, respectively). Increasing the scale of the reaction from 0.3 to 10 mL of CL resulted in a similar isolated product yield, but the Mn increased from 17,200 to 44,800 g/mol. Toluene appeared to help stabilize Novozyme-435 so that lipase-catalyzed polymerizations could be conducted effectively at 90 degrees C. For example, within only 2 h at 90 degrees C (toluene-d8 to epsilon-CL, 5:1, approximately 1% protein), the % monomer conversion reached approximately 90%. Also, the controlled character of these polymerizations as a function of reaction temperature was evaluated.

Candida↗
PubMed2000

Simulation of robotic courier deliveries in hospital distribution services.

Flexible automation in the form of robotic couriers holds the potential for decreasing operating costs while improving delivery performance in hospital delivery systems. This paper discusses the use of simulation modeling to analyze the costs, benefits, and performance tradeoffs related to the installation and use of a fleet of robotic couriers within hospital facilities. The results of this study enable a better understanding of the delivery and transportation requirements of hospitals. Specifically, we examine how a fleet of robotic couriers can meet the performance requirements of the system while maintaining cost efficiency. We show that for clinical laboratory and pharmaceutical deliveries a fleet of six robotic couriers can achieve significant performance gains in terms of turn-around time and delivery variability over the current system of three human couriers per shift or 13 FTEs. Specifically, the simulation results indicate that using robotic couriers to perform both clinical laboratory and pharmaceutical deliveries would result in a 34% decrease in turn-around time, and a 38% decrease in delivery variability. In addition, a break-even analysis indicated that a positive net present value occurs if nine or more FTEs are eliminated with a resulting ROI of 12%. This analysis demonstrates that simulation can be a valuable tool for examining health care distribution services and indicates that a robotic courier system may yield significant benefits over a traditional courier system in this application.

Computer Simulation↗
PubMed2000

Comparative evaluation of early vs. deferred vitrectomy in Eales' disease.

METHODS: 40 cases of vitreous haemorrhage secondary to Eales' disease were taken up for vitrectomy. Depending upon duration of vitreous haemorrhage patients were divided into two groups: Group I (20 eyes) - early vitrectomy group with duration between 3-6 months; Group II (20 eyes) - deferred vitrectomy group with duration of more than 6 months. All patients were followed up for a minimum period of 3 months following vitrectomy. RESULTS: Eyes in Group I showing a preoperative ultrasonic picture of complete posterior vitreous detachment, less mobility of organised vitreous haemorrhage and mid vitreous organisation on kinetic echography achieved a final visual acuity of 6/9 or better in 13 (65%) eyes as compared to 4 (20%) eyes in Group II (p<0.01). Poor visual outcome in the deferred group was secondary to cystoid macular oedema, macular scar, macular pucker formation and macular degeneration. CONCLUSION: Improved visual outcome in the early vitrectomy group was probably because the haemorrhagic blood and its toxic products had less time to damage the macula, a lesser incidence of macular traction and cystoid macular oedema.

Humans↗