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Biomedical subjects

D Kumar

Publications and source records attributed to D Kumar.

At least 199 records · Page 11Linked to original sources
PubMed1997

Central noradrenergic & dopaminergic modulation of brewer's yeast-induced inflammation & nociception in rats.

The possibility of central noradrenergic and dopaminergic modulation of Brewer's yeast-induced peripheral inflammation was investigated in rats. Centrally administered noradrenaline (NA), amphetamine, which liberates NA and dopamine in the central nervous system and L-dopa, the precursor of dopamine significantly suppressed paw oedema. Conversely, the beta-adrenoceptor blocker, propranolol, catecholaminergic neuron degenerator, 6-hydroxydopamine (6-OHDA), dopaminergic antagonist, haloperidol and dopamine synthesis inhibitor, alpha-methyl para tyrosine (AMPT) augmented paw oedema. In addition, 6-OHDA and haloperidol produced significant reduction in pain threshold. The results of this study indicate that central NA and dopamine exert inhibitory effects on Brewer's yeast-induced peripheral inflammation.

Amphetamine↗
PubMed1997

Cardiovascular effects of an organophosphate toxin isolated from Ptychodiscus brevis.

The dose-dependent hypotensive and bradycardic effects induced by an ichthyotoxic organophosphate compound isolated from the marine dinoflagellate Ptychodiscus brevis were studied. These effects were not antagonized by atropine, but potentiated by alpha-adrenoceptor blocker and hexamethonium. The toxin abolished the vasopressor effect elicited by phenylephrine, indicating an alpha-adrenergic blocking activity. The cardiovascular depressor responses were antagonized by tetraethylammonium while blockade of cholinergic and histaminergic receptors or inhibition of prostaglandin synthesis failed to modify these effects. The results indicate that the cardiovascular depressor effects of the toxin are probably mediated through alpha-adrenergic and ganglionic blockade accompanied by modulation of potassium channel activity.

Adrenergic alpha-Antagonists↗
PubMed1997

Role of the interstitial cells of Cajal in the control of gut motility.

BACKGROUND: The interstitial cells of Cajal (ICCs) are a population of cells in the gastrointestinal tract which have a role in the control of gut motility. METHOD: A comprehensive review of the scientific literature was undertaken to assess current understanding of the morphology, structure, identification, distribution, development and function of these cells. RESULTS AND CONCLUSIONS: ICCs have an important role in the control of gut motility. Experimental evidence from animal studies suggests roles as pacemakers and coordinators of gut motor activity, and as intermediaries in the neural control of motility. With an increasing understanding of the distribution and behaviour of these cells in the healthy or diseased human gastrointestinal tract, there is the potential to develop novel therapeutic approaches to diseases that have gut dysmotility as a contributory factor.

Digestive System↗
PubMed1997

Platelet aggregation and lipid profile in offsprings of young ischemics.

OBJECTIVE: To study the platelet aggregation and lipid profile in offsprings of young ischemic parents. DESIGN: Cross sectional. SETTING: Hospital based. METHODS: 40 adults under 45 years of age with proven CHD and their 50 offsprings comprised the study group. In the control group, 40 age matched adults with normal maximal treadmill test and their 50 off springs were included. All were screened for lipid profile and platelet aggregation. RESULTS: Platelet aggregation was significantly elevated in adults with CHD (44.0 +/- 15.5%) compared to controls (32.22 +/- 9.1%). Children of CHD adults also had significantly elevated aggregation (34.9 +/- 12.5%) compared to control offsprings (27.8 +/- 9.9%). Adult CHD subjects had significantly elevated serum cholesterol, LDL-cholesterol (LDL-C) and atherogenic index compared to control adults. The children in both groups had similar lipid profiles. CONCLUSION: Platelet aggregation is enhanced in offsprings of young ischemics. The potential of this index as a marker for early development of CHD needs to be explored.

Adolescent↗
PubMed1997

Mechanism of cardiotoxicity induced by a marine toxin isolated from Ptychodiscus brevis.

An organophosphate toxin of marine origin isolated from red tide dinoflagellate P. brevis produced a dose-dependent dual effect on rat atria, i.e. positive inotropic effect at low concentrations (2.8 x 10(-8) to 8.4 x 10(-7) M) and negative inotropic and chronotropic responses at an elevated dose (4.8 x 10(-6) to 7.2 x 10(-4) M). The negative chronotropic and inotropic responses of the toxin were potentiated with physostigmine and ouabain whereas antagonized by atropine and hemicholinium-3 pretreatments and those effects remained unaltered by isoproterenol, phenylephrine and ouabain pretreatments. The results indicate that the toxin induced negative inotropic and chronotropic effects are mediated through release of acetylcholine from the nerve endings and consequent activation of muscarinic receptor. In atria exposed to guanethidine, bretylium, propranolol and tyramine tachyphylaxis, the positive inotropic response of the toxin was not modified. However, the response was antagonized by EGTA, nifedipine, ryanodine, calcium-free ringer and potentiated with caffeine and amiloride pretreatments. The results suggest that the positive inotropic effect of the toxin is mediated through Ca2+ influx and impairment of Na+/Ca2+ exchange process.

Animals↗
PubMed1997

Adriamycin depresses in vivo and in vitro phosphatidylethanolamine N-methylation in rat heart sarcolemma.

Adriamycin, an effective anticancer chemotherapeutic agent, causes an insidious and delayed cardiotoxicity. Different subcellular abnormalities including calcium transport changes in the sarcolemma (SL) as well as downregulation of the adrenergic system have been shown to be associated with the development of this cardiomyopathy. Since both of these activities are influenced by phospholipid methylation, effects of adriamycin on the three catalytic sites of SL phosphatidylethanolamine N-methyltransferase were examined. Rats were administered with a cumulative dose of adriamycin (15 mg/kg) over 2 weeks and examined after 3 weeks. Vehicle injected animals served as controls. Dyspnea, high mortality rate, ascites and decrease in aortic and left ventricular systolic pressure, as well as increase in left ventricular end diastolic pressure were seen in the adriamycin group. Myocardial cell damage typical of adriamycin cardiomyopathy, i.e. sarcotubular swelling, vacuolization and myofibrillar drop-out, was also apparent. Total methyl group incorporation into SL phosphatidylethanolamine using radiolabeled S-adenosyl-L-methionine as the donor was significantly depressed in the 3 week group at catalytic sites II and III. Decreased production of methylated intermediates, phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine as well as phosphatidylcholine (PC) was seen. Depression of phosphatidylethanolamine N-methylation was also noticed when SL, isolated from untreated hearts, was exposed in vitro to different concentrations (10, 100 and 1000 microM) of adriamycin. Inhibition of phosphatidylethanolamine N-methylation appears to be mediated by adriamycin-induced increase in the oxidative stress and may contribute in the pathogenesis of subcellular changes associated with this cardiomyopathy.

Analysis of Variance↗
PubMed1997

Neural networks for signal processing applications: ECG classification.

QRS complexes were classified using a Multi Layer Perceptron (MLP) using a modified version of the original Backpropagation (BP) algorithm. The input to the network were bitmaps of the QRS complexes represented in the form of a 20 x 20 matrix. A number of hidden layers (and neurons in each hidden layer) were experimented upon to observe the rate at which the network converged. Larger Networks were observed to find the minimum on the error curve with ease. Increasing the network size beyond a certain size did not improve the performance rate, rather it decreased the performance rate. It is evident that there exists an optimal neural network architecture for every given problem. The weights change rules in Backpropagation algorithm were modified to include a variation of the relationship between momentum and learning rate to observe any increase in network's performance rate. A learning rate adaptation factor was introduced into the learning algorithm to decrease the network's chances of missing a minimum on the error curve. The network was found to perform extremely well with the modified version of the algorithm. The network converged after only 9000 learning cycles when compared to 14,000 cycles with the original algorithm.

Algorithms↗
PubMed1997

Conjunctival impression cytology in xerophthalmia among rural children.

The advent of Conjunctival Impression Cytology (CIC) has opened a new chapter in the detection of Vitamin A deficiency as it is a simplified field technique. The need for such a technique was of paramount importance in India where as estimated 5 to 7 percent children suffer from eye signs of Vitamin A deficiency. In the present study the results of clinical evaluation of apparently healthy children and those having clinical sings and symptoms of Vitamin A deficiency have been compared with CIC results. Serum Vitamin A levels have also been estimated wherever possible. The findings indicate that CIC results are superior to the clinical assessment and it is suggested that CIC can be used as screening tool for children of school going age (and earlier) for early detection and correction of Vitamin A deficiency.

Child↗
PubMed1996

A 43 kDa DNA binding protein from the pea chloroplast interacts with and stimulates the cognate DNA polymerase.

A DNA binding protein with DNA polymerase 'accessory activity' has been identified and purified to apparent homogeneity from pea chloroplasts. This protein consists of a single subunit of 43 kDa and binds to DNA regardless of its base sequence and topology. It increases cognate DNA polymerase-primase activity in a dose dependent manner. Using solid phase protein-protein interaction trapping and co-immunoprecipitation techniques, the purified protein was found to associate with the chloroplast DNA polymerase. The chloroplast DNA polymerase also binds directly to the radioiodinated 43 kDa protein. The specific interaction between 43 kDa protein and chloroplast DNA polymerase results in the synthesis of longer DNA chains. The 43 kDa protein, present abundantly in the pea chloroplast, appears to increase processivity of the chloroplast DNA polymerase and may play an important role in the replication of pea chloroplast DNA.

Antibodies↗
PubMed1996

Audit of sphincter repair. Factors associated with poor outcome.

PURPOSE: This study was designed to critically analyze the outcome of sphincter repair and, if possible, to identify high-risk factors. METHODS: Clinical and physiologic assessment was made of all sphincter repairs (42 patients) performed in one unit by two surgeons during five years. RESULTS: Forty-two patients (10 men, 32 women) underwent sphincter repair. Only three of five men with anterior defects of the anorectum from perineal trauma were rendered continent. Only three of five men with defects from fistula operations became continent, but one improved by later graciloplasty. All six women with fistula-related injuries eventually achieved continence, but two required repeat sphincter repairs because of early breakdown from sepsis. The worst results were in 26 women with third-degree obstetric injuries, of whom 11 remain incontinent; poor results in this group were associated with gross perineal descent, obesity, and age older than 50 years; two or more of these factors indicated a poor outcome. Preoperative anorectal physiology did not identify a poor-risk group. CONCLUSIONS: Poor results were identified in women with anterior defects from obstetric trauma, especially if they were obese, older than 50 years of age, and had perineal descent.

Adult↗
PubMed1996

Pediatric AIDS and advanced directives: a three-year prospective study in New York State.

Most HIV-infected families currently receive their care in an ambulatory setting. Ambulatory care provides greater means of medical care, and planning for the infected family members. Advanced Directives (AD) and Do Not Resuscitate (DNR) for adults are now discussed in an ambulatory setting rather than under the duress of a hospital admission. We felt it is important to examine the practice of discussing AD/DNR with the families of pediatric AIDS patients in an out patient setting. Twenty-one and 26 AIDS-designated centers in New York State and five major hospitals in New York City were contacted through a telephone survey in 1991 and 1994, respectively. Questions were designed to obtain demographics of the hospital, pediatric AIDS population, and their DNR/AD policies. In 1991 and 1994, the survey was conducted with the pediatric unit of hospitals with pediatric AIDS. In 1991, only 12 (75%) hospitals had an existing policy on pediatric DNR. No hospital had admitted a patient with AD/DNR obtained as an outpatient, nor were there guidelines at any hospital to approach the issue in an outpatient setting. In 1994, 20 (95%) hospitals had a DNR policy for pediatric patients. We found that even though six patients were admitted with AD obtained as outpatients, no outpatient guidelines existed for AD/DNR for pediatrics. The number of cases of pediatric AIDS in New York State increased by 29.7% for the 1991-1994 period. While pediatric DNR existed in 1991/1994, we found there were presently no guidelines for obtaining AD/DNR for pediatric AIDS patients in an ambulatory setting. Families infected with HIV should have a caring atmosphere to help them address pediatric AD/DNR with their primary care providers. However, we believe that guidelines should be developed to address this issue.

Acquired Immunodeficiency Syndrome↗
PubMed1996

bc1-1 rearrangement and cyclin D1 protein expression in multiple lymphomatous polyposis.

Multiple lymphomatous polyposis (MLP), characterized by multiple polyps involving long segments of the gastrointestinal (GI) tract, is believed to represent GI involvement by mantle cell lymphoma (MCL), primarily based on its histologic and immunophenotypic similarities with MCL. However, rearrangement of the bcl-1 locus, the molecular lesion characteristic of MCL, has not been investigated in this group of patients. The authors evaluated the morphologic, immunophenotypic, and molecular features of 18 cases of MLP and 8 B-cell lymphomas involving the GI tract (including 6 MALT lymphomas). All MLP cases presented with GI disease, and were histologically similar to MCL. DNA extracted from formalin-fixed, paraffin-embedded tissue was analyzed for evidence of bcl-1 rearrangement by PCR, using chromosome 11 specific and consensus JH primers. Amplifiable DNA was obtained in 24 of 26 cases (16 of 18 MLP cases and 8 of 8 controls). bcl-1 rearrangement was detected in 6 of 16 cases (38%), subsequently confirmed by sequencing of the breakpoint region, and in 0 of 8 controls. Immunostaining for cyclin D1 was positive in 14 of 18 MLPs, including the 6 bcl-1 rearranged cases and negative in 6 of 6 evaluable controls. The detection of bcl-1 rearrangement and cyclin D1 expression in cases of MLP supports the view that MLP represents primary MCL, of the GI tract. These techniques may also be helpful in differentiating MLP from other GI lymphomas, particularly low grade lymphomas of MALT, when only small routinely fixed endoscopic biopsies are available.

Adult↗
PubMed1996

Effect of hyperbaric oxygenation on existing oral mucosal carcinoma.

Hyperbaric oxygen therapy (HBO) is used to treat some complications of head and neck carcinoma treatment. Several patients treated with HBO have had rapid growth of a clinically cured squamous cell carcinoma. Prior studies have produced conflicting evidence about the effect of HBO on tumor growth. This study was undertaken to determine the effects of HBO on established squamous cell carcinoma. Forty Golden Syrian hamster cheek-pouch carcinomas were induced with the established chemical carcinogen 9,10-dimethyl-1,2-benzanthracene. Twenty hamsters underwent 30 HBO dives for 60 minutes each to 2.81 atm, while 20 served as controls. At necropsy, animals receiving HBO therapy had significantly smaller tumors (P < .05) and showed a trend toward fewer cervical metastases (P < .06). HBO therapy with coexistent carcinoma inhibited the established tumor's growth.

Animals↗
PubMed1996

Rapid cyclic changes in density and accessibility of endometrial ligands for Escherichia coli Dr fimbriae.

The mechanisms of developing infection in young, noncompromised individuals are well understood. Colonization is prerequisite for the development of infection. In human, ligands serving bacterial colonization belong to common antigens. Consequently, a majority of individuals should be sensitive to infection at all times. We hypothesize that the temporal patterns of some infections and sensitivity to them are associated with sudden changes in the density and accessibility of common receptors. Endometrial samples from women having normal menstrual cycles were examined for histological location, receptor density, and in situ hybridization of Dr (decaying-accelerating factor) ligands for Escherichia coli Dr fimbriae. Significant up-regulation and luminal expression of Dr ligands occurred during the secretory phase, whereas receptors were expressed in the basement membrane and in smaller quantities during the proliferative phase. This observation agrees with our hypotheses that some ligands recognized by bacterial adhesins change their compartmentalization and, most importantly, that they up-regulate expression at specific times.

Adult↗
PubMed1996

Identification of a 25-kilodalton protein of Mycobacterium bovis BCG to distinguish BCG strains from Mycobacterium tuberculosis.

Mycobacterium bovis BCG vaccine strains were compared with Mycobacterium tuberculosis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 25-kDa protein observed in the BCG strains was absent in M. tuberculosis. Rabbit antibodies specific to the 25-kDa protein uniquely identified this protein in BCG strains but not in M. tuberculosis. It is suggested that the 25-kDa protein and polyclonal antibodies directed against this antigen can be exploited to distinguish BCG strains from M. tuberculosis.

Antibodies, Bacterial↗