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Biomedical subjects

N Kumar

Publications and source records attributed to N Kumar.

At least 73 records · Page 4Linked to original sources
PubMed1999

Oral plasmablastic lymphoma in previously undiagnosed HIV disease.

Non-Hodgkin's lymphoma is the second most common HIV-associated malignancy. This report details a case of the recently described entity plasmablastic lymphoma of the mouth in a patient who was later found to have severe HIV disease. The tumor manifested as a large ulcerated mass of the left maxillary alveolus, causing bony destruction and tooth mobility. Histologic examination of lesional tissue revealed a lymphoid tumor with a high proliferation rate containing lymphoplasmacytoid cells that were reactive to the plasma cell marker VS38c but not to CD20 or CD79a; these are features of the recently reported non-Hodgkin's lymphoma termed plasmablastic lymphoma. This is only the second report of an unusual tumor that has a predilection for the orofacial tissues.

Adult↗
PubMed1999

Disruption of the Pfg27 locus by homologous recombination leads to loss of the sexual phenotype in P. falciparum.

Transmission of malaria depends upon the differentiation and development of the sexual stages of the parasite. In Plasmodium falciparum, it is a complex, multistage process, involving the expression of a large number of sexual stage-specific proteins. Pfg27 is one such protein, abundantly expressed at the onset of gametocytogenesis. We report successful disruption of the Pfg27 locus using homologous recombination and show that it is essential for the maintenance of the sexual phenotype. Transfectants lacking Pfg27 abort early in sexual development, resulting in vacuolated, highly disarranged, and disintegrating parasites. This suggests a critical role for Pfg27 in the sexual development of the parasite.

Animals↗
PubMed1999

A large simple randomized trial of rocuronium versus succinylcholine in rapid-sequence induction of anaesthesia along with propofol.

BACKGROUND: Rocuronium has an onset of action more rapid than other non-depolarizing neuromuscular blocking agents, but it is unclear whether it and succinylcholine give equivalent intubating conditions during rapid-sequence induction of anaesthesia. We performed this study to answer the question--are there clinically relevant differences between the use of rocuronium and succinylcholine to secure acceptable intubating conditions during rapid-sequence induction of anaesthesia with propofol? METHODS: Anaesthesia was induced using propofol 2.5 mg/kg in 349 ASA physical status grade I-IV patients who were undergoing either elective or emergency surgery. Propofol was followed immediately by either rocuronium 0.6 or 1 mg/kg or succinylcholine 1.0 mg/kg (randomly selected). Fifty seconds after the end of muscle relaxant injection laryngoscopy was performed and intubating conditions were graded by an experienced anaesthetist blind to the muscle relaxant allocation. This study design was selected so that a 10% difference in clinically acceptable intubating conditions between drugs would be detectable. RESULTS: In this setting rocuronium 1.0 mg/kg provided superior intubating conditions compared with rocuronium 0.6 mg/kg. The incidence of clinically acceptable intubating conditions with rocuronium 1.0 mg/kg and succinylcholine 1.0 mg/kg was 93.2% and 97.1% respectively, the difference being -3.9% (95% C.I. -9.7% to 1.9%). CONCLUSION: Rocuronium 1.0 mg/kg given along with propofol in a rapid-sequence induction of anaesthesia is clinically equivalent to succinylcholine 1.0 mg/kg.

Adolescent↗
PubMed1999

Quorum-sensing cross talk: isolation and chemical characterization of cyclic dipeptides from Pseudomonas aeruginosa and other gram-negative bacteria.

In cell-free Pseudomonas aeruginosa culture supernatants, we identified two compounds capable of activating an N-acylhomoserine lactone (AHL) biosensor. Mass spectrometry and NMR spectroscopy revealed that these compounds were not AHLs but the diketopiperazines (DKPs), cyclo(DeltaAla-L-Val) and cyclo(L-Pro-L-Tyr) respectively. These compounds were also found in cell-free supernatants from Proteus mirabilis, Citrobacter freundii and Enterobacter agglomerans [cyclo(DeltaAla-L-Val) only]. Although both DKPs were absent from Pseudomonas fluorescens and Pseudomonas alcaligenes, we isolated, from both pseudomonads, a third DKP, which was chemically characterized as cyclo(L-Phe-L-Pro). Dose-response curves using a LuxR-based AHL biosensor indicated that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) activate the biosensor in a concentration-dependent manner, albeit at much higher concentrations than the natural activator N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). Competition studies showed that cyclo(DeltaAla-L-Val), cyclo(L-Pro-L-Tyr) and cyclo(L-Phe-L-Pro) antagonize the 3-oxo-C6-HSL-mediated induction of bioluminescence, suggesting that these DKPs may compete for the same LuxR-binding site. Similarly, DKPs were found to be capable of activating or antagonizing other LuxR-based quorum-sensing systems, such as the N-butanoylhomoserine lactone-dependent swarming motility of Serratia liquefaciens. Although the physiological role of these DKPs has yet to be established, their activity suggests the existence of cross talk among bacterial signalling systems.

4-Butyrolactone↗
PubMed1999

Male partners of substance-abusing women in treatment: an exploratory study.

Despite evidence for the importance of significant others in the recovery process, little is known about male partners of female substance abusers. This paper presents a qualitative exploratory study conducted to learn more about male partners of crack/cocaine-addicted women and specifically examines the men's influence on the treatment and recovery process of their female partners. Subjects were found to have an extensive history of substance abuse and some experience with treatment; three-quarters were active crack/cocaine users. Although their attitude toward women's substance abuse was negative and their opinion of treatment for women positive, men's behavioral support for their partners was usually passive and inconsistent. Reasons are discussed why male partners of female drug users in treatment generally were resistant to active participation in family-oriented treatment: the men's active drug use, their desire to maintain the status quo in the relationship, possible focus on their own recovery, divergent views about treatment goals, and the desire to minimize stigma by association.

Adult↗
PubMed1999

Periodontopathic bacteria in English HIV-seropositive persons.

Selected periodontopathic bacteria were sought in 20 HIV-infected English patients and eight noninfected control subjects with similar periodontal status, using highly specific DNA probes. Actinobacillus actinomycetemcomitans (A. a), Porphyromonas gingivalis, Campylobacter rectus, Prevotella intermedia, and Fusobacterium nucleatum were more frequently detected and were found at higher levels in HIV-infected individuals than in controls. Significantly increased levels of Treponema denticola but, in contrast, lower levels of Eikenella corrodens were found in nonbleeding sites of HIV-infected patients compared with controls. The results of the present investigation on English patients suggest a periodontopathogenic role for A. a, P. gingivalis and C. rectus, and possibly P. intermedia and are in general accord with most previously reported data from the United States. Longitudinal studies are now required to determine more precisely the association between periodontopathic microflora, immune competence and periodontal health and disease in HIV-infected persons.

AIDS-Related Opportunistic Infections↗
PubMed1999

Piritramide.

Explore the source record for details and available documents.

Analgesics, Opioid↗
PubMed1999

Neither nociceptin nor its receptor are present in human synovial fluid or tissue.

Our aim was to identify the nociceptin receptor and its endogenous ligand, nociceptin, in human peripheral tissue. Synovial tissue was obtained from 11 patients (ASA I-III, 66-84 yr) undergoing elective total knee replacement. Synovial fluid was obtained from another 10 patients (ASA I-III, 57-81 yr). Fluid was mixed with trifluoroacetic acid and the tissue with isopentone before freezing at -70 degrees C. Nociceptin receptor identification was performed using a [3H]nociceptin binding assay and nociceptin detection by radioimmunoassay. There was no specific [3H]nociceptin binding to knee synovial tissue and radioimmunoassay did not detect nociceptin. Neither the nociceptin receptor nor nociceptin was found in human synovial tissue or fluid.

Aged↗
PubMed1999

Murine gamma delta T lymphocytes elicited during Plasmodium yoelii infection respond to Plasmodium heat shock proteins.

gamma delta T cells accumulate during Plasmodium infections in both murine and human malarias. The biological role of these cells and the antigens that they recognize are not clearly understood, although recent findings indicate that gamma delta T cells in general influence both innate and antigen-specific adaptive host responses. We examined the accumulation of gamma delta T cells elicited during infection with virulent and avirulent Plasmodium yoelii parasites in relatively susceptible and resistant strains of mice. Our results indicated that in nonlethal malaria infections, gamma delta T cells comprise a larger proportion of splenic T cells than in lethal infections and that only a live infection is capable of inducing an increase in the percentage of gamma delta T cells in vivo. Furthermore, we demonstrate that gamma delta T cells elicited during a P. yoelii infection respond by proliferation in vitro to P. falciparum heat shock proteins (HSPs) of 60 and 70 kDa, suggesting a possible immunological involvement of parasite HSPs in this arm of the cellular immune response during malarial infection in mice.

Animals↗
PubMed1999

Immunization of mice with DNA-based Pfs25 elicits potent malaria transmission-blocking antibodies.

Immunological intervention, in addition to vector control and malaria chemotherapy, will be needed to stop the resurgence of malaria, a disease with a devastating impact on the health of 300 to 500 million people annually. We have pursued a vaccination strategy, based on DNA immunization in mice with genes encoding two antigens present on the sexual stages of Plasmodium falciparum, Pfs25 and Pfg27, to induce biologically important antibodies that can block development of the parasite in the Anopheles mosquito and thus transmission of the disease. DNA encoding Pfs25 when administered by the intramuscular route, either alone or with DNA encoding Pfg27, had the most potent transmission-blocking effects, resulting in up to a 97% decrease in oocyst numbers in mosquito midguts and a 75% decrease in rate of infection. Immunization with DNA encoding a Pfg27-Pfs25 fusion protein was less effective and DNA encoding Pfg27 elicited antibodies in sera that had only modest effects on the infectivity of the parasite. These results show for the first time that DNA vaccination can result in potent transmission-blocking antibodies in mice and suggest that the Pfs25 gene should be included as part of a multicomponent DNA vaccine.

Animals↗
PubMed1999

Prophylactic activity of atovaquone against Plasmodium falciparum in humans.

The prophylactic antimalarial activity of atovaquone was determined in a randomized, double-blind, placebo-controlled study of healthy volunteers who were challenged by the bite of Plasmodium falciparum-infected Anopheles stephensi. Subjects were randomly assigned to one of three groups: six received seven daily doses of 750 mg of atovaquone, starting the day before challenge; six received a single dose of 250 mg of atovaquone the day before challenge; and four received placebo. Polymerase chain reaction- and culture-confirmed parasitemia developed in all four placebo recipients, but in none of the drug recipients, indicating that either of the atovaquone regimens provides effective prophylaxis (P = 0.005). However, in low-dose recipients, the drug levels by day 6.5 were profoundly subtherapeutic, indicating that parasites were eliminated prior to the establishment of erythrocytic infection. Atovaquone thus protects non-immune subjects against mosquito-transmitted falciparum malaria, and has causal prophylactic activity.

Adolescent↗
PubMed1999

Effect of 'Mentat' on the pharmacokinetics of single and multiple doses o phenytoin in rabbits.

The effect of 'Mentat', a herbal preparation, was studied on pharmacokinetics of single and multiple doses of phenytoin in rabbits. No significant effect was found after single oral dose of 'Mentat' on single dose kinetics of phenytoin. However, 'Mentat' administration for 7 days increased the steady state kinetic parameters. Peak plasma phenytoin concentration, area under the implasma concentration and elimination half life were significantly increased and t-max was significantly reduced, indicating the suppression of phenytoin metabolism by 'Mentat'.

Animals↗