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Biomedical subjects

K Prabhakaran

Publications and source records attributed to K Prabhakaran.

At least 19 recordsLinked to original sources
PubMed1997

Infections in paediatric renal transplant recipients.

A retrospective study of all children who had undergone renal transplantation at the National University Hospital was undertaken in order to investigate the types and frequency of infections in paediatric renal transplant recipients. A total of 13 children ranging in age from 3 to 17 years were transplanted over a 7-year period from 1989 to 1996. The mean follow-up period was 40.5 months. Ten patients (77%) had at least one episode of infection post-transplant, 70% of which occurred within the first 6 months post-transplant. These infections included urinary infections (8), disseminated cytomegalovirus (CMV) disease (4), Pneumocystis carinii pneumonia (1) and mycoplasma pneumonia (1). Urinary tract infections were significantly associated with the presence of ureteral stents. CMV disease was significantly associated with the use of mycophenolic acid in the early post-transplant period. Infection therefore continues to be a major cause of morbidity in paediatric renal transplant recipients.

Adolescent↗
PubMed1997

Suppression of the growth of six potentially-pathogenic mycobacteria by beta-lactam/beta-lactamase-inhibitors.

Drug-resistant tuberculosis and opportunistic infections by mycobacteria in immunocompromised subjects are not readily controlled with the antimycobacterial drugs now available. beta-Lactam antibiotics, the most widely used antibacterial agents, are ineffective against mycobacteria since they synthesize beta-lactamases. The beta-lactam/beta-lactamase-inhibitor combinations are used at present to treat infections caused by other beta-lactamase-positive organisms. Six potentially-pathogenic mycobacteria: Mycobacterium avium, M. chelonei, M. haemophilum, M. microti, M. scrofulaceum and M. simiae, were cultured in 7H9 medium (containing Tween 80 and albumin, dextrose, catalase) at 37 degrees C for 10-14 days, with or without various concentrations (2-100 micrograms/ml) of ampicillin/sulbactam, amoxicillin/clavulanate and piperacillin/tazobactam. More than 50-80% inhibition of the mycobacterial growth was observed at drug levels of 40-100 micrograms/ml in the medium; the drugs were active even when the detergent (Tween 80) was omitted. Against four of the mycobacteria, ampicillin/sulbactam proved to be the most active. The beta-lactam/beta-lactamase-inhibitor combinations may be of use as rational therapeutic agents against mycobacterial infections.

Anti-Bacterial Agents↗
PubMed1996

Age- and sex-related changes in lymphocyte subpopulations of healthy Asian subjects: from birth to adulthood.

Flow cytometric analysis of lymphocyte subsets were evaluated in 391 healthy Asian subjects ranging in age from birth to 40 years. Lymphocyte subsets were analysed using specific monoclonal antibodies: CD20 (B cells), CD3 and CD2 (T cells), CD16 and CD56+ (NK cells), CD4/CD3+ (helper-inducer T cells), CD8/ CD3+ (suppressor/cytotoxic T cells), HLA-DR expression on CD3 and CD25 (Tac) on CD3. The total white cell count, absolute lymphocyte counts, and B cell percentages peaked in infancy and declined steadily with age. Absolute counts of each subset, which were derived from absolute lymphocyte counts, also followed this trend. Increases with age were seen in the NK, T cell (CD2, CD3), and CD8 percentages. Males tended to have higher NK and CD8 percentages than females, and, conversely, females had higher CD3 and CD4 percentages than males. Comparison of our results with studies involving Caucasian subjects indicated higher NK percentages in our Asian population and lower CD4 absolute counts in the males of our population. These results indicate the presence of age, sex, and probable racial differences in lymphocyte subset expression. Our results may serve as reference standards for the Asian population.

Adolescent↗
PubMed1996

Properties of lysophospholipase in Mycobacterium leprae.

Lysophospholipids are key intermediates in the metabolism of phospholipids. Cytoplasmic membranes of both eukaryotes and prokaryotes are made of phospholipid bilayers. Phospholipases are activated during phagocytosis. Lysophospholipids generated by phospholipase A2 or A1 degrade cell membranes and can cause cell lysis. An active lysophospholipase, that hydrolyzes lysophospholipids, was detected by the radioisotope technique in Mycobacterium leprae. About two-thirds of the enzyme was particulate and one-third cytoplasmic. Optimum activity was at 37 degrees C, and at pH 6.0. Temperatures above 70 degrees C completely inactivated the enzyme. The compound AACOCF3, a trifluromethylketone analog of arachiodonic acid, inhibited the activity; the inhibition appeared to be of the uncompetetive type. The K(m) of the enzyme was 2.5 x 10(-4)M, suggesting a fairly strong affinity for the substrate. Lysophospholipids have been shown to be microbicidal to invading organisms. Possession of lysophospholipase by M. leprae is apparently one of the methods by which the bacilli overcome the defense mechanisms of the host.

Arachidonic Acids↗
PubMed1995

beta-Lactamase activity in mycobacteria including Mycobacterium avium and suppression of their growth by a beta-lactamase-stable antibiotic.

beta-Lactamase has been reported from only a few mycobacteria. It is widely assumed that Mycobacterium avium strains do not contain the enzyme, but earlier assays were done using insensitive methods. Thus the beta-lactamase activity in cell-free extracts of ten selected strains of mycobacteria, including four strains of M. avium, was determined using a highly sensitive spectrophotometric method. The results showed that all the mycobacteria tested possess the enzyme, which explains their resistance to beta-lactam antibiotics. However, some of the bacteria differed from others in the action of the inhibitors, clavulanate, sulbactam and tazobactam against their beta-lactamases. Growth of the mycobacteria was suppressed by novel combinations of the beta-lactam/beta-lactamase-inhibitors, and by a new beta-lactamase-stable cephalosporin, Cefepime (aminothiazolyl methoxyimino cephalosporin). The results presented, as well as reports of previous studies in vivo, suggest that the intracellular growth of the bacilli or the high partition coefficient of a beta-lactamase inhibitor such as sulbactam does not impede the antimycobacterial action of these compounds.

Anti-Bacterial Agents↗
PubMed1993

Modulation of non-specific immunity by hippocampal stimulation.

Rats subjected to electrical stimulation of hippocampus (30 min/day for 4 days) showed an increase in the neutrophils in the peripheral blood when compared to sham (P < 0.01) and controls (P < 0.001). They also showed a significant decrease in lymphocytes, when compared to control rats (P < 0.001). Both sham and stimulated animals showed a significant decrease in total white blood cell count when compared to controls (P < 0.001). The phagocytic index of stimulated animals showed a significant increase from control (P < 0.001) and sham (P < 0.001). In addition, the stimulated animals showed a significant (P < 0.001) decrease in plasma corticosterone level when compared to sham and controls.

Animals↗
PubMed1993

Use of beta-lactam/beta-lactamase-inhibitor combinations as antimycobacterial agents.

Mycobacterium tuberculosis and Mycobacterium leprae develop resistance against the drugs used to treat tuberculosis and leprosy, respectively. Now multidrug-resistant tuberculosis is spreading in many countries, especially with the emergence of AIDS. Multidrug treatment is being promoted at present to eradicate leprosy. Since M. leprae may also become multidrug-resistant, new approaches have to be adopted for controlling mycobacterial diseases. Mycobacteria usually synthesize beta-lactamase and are insensitive to beta-lactam antibiotics. M. tuberculosis contains a constitutive beta-lactamase; de-repression of beta-lactamase has been reported in M. leprae. Three different beta-lactam/beta-lactamase-inhibitor combinations (ampicillin/sulbactam, amoxicillin/clavulanate and piperacillin/tazobactam) were used to suppress the growth of several strains of mycobacteria (including M. tuberculosis H37Rv) in vitro. Ampicillin/sulbactam is a potent bactericidal agent against M. leprae multiplying in mouse foot pads. In the present work, ampicillin/sulbactam showed higher activity than the other drug combinations. The beta-lactam/beta-lactamase inhibitors are likely to be effective as rational therapeutic agents against mycobacterial infections.

Amoxicillin↗
PubMed1993

Management of fetal sacroccocygeal teratoma.

With the advent of antenatal ultrasound, the focus on sacroccocygeal teratoma has shifted from management at birth to management in the antenatal period. Multidisciplinary approach involving the obstetrician, neonatologist and paediatric surgeon is necessary to achieve good results. Two cases of antenatally detected sacrococcygeal teratomas are reported, one at 24 weeks and the other at 26 weeks of gestation. The tumour was benign in both cases and in both cases, delivery was done at full term. In one case, it was a normal vaginal delivery and in the other, an elective lower segment caesarean section was performed. Close ultrasound follow-up during pregnancy had excluded cardiac failure, hydropic changes and other congenital anomalies which could have altered the management of the pregnancy. Accurate diagnosis of such tumours during antenatal periods may in future allow intrauterine fetal interventional surgery for a premature fetus. The tumour was surgically dealt with successfully in each case on the third day after birth with good clinical results at the end of one year and eight months respectively.

Adult↗
PubMed1992

Reversal of drug resistance in Mycobacterium leprae by ampicillin/sulbactam.

The multiplication of Mycobacterium leprae in foot pads of experimentally-infected mice was suppressed by intramuscular administration of ampicillin combined with sulbactam or YTR-830H, two potent inhibitors of beta-lactamase in the bacteria. The antibiotic or the inhibitors by themselves were inactive. Ampicillin/sulbactam also inhibited the growth of drug-resistant M. leprae which grew in the presence of rifampin or dapsone. The finding provides a new approach to treat leprosy and to overcome drug resistance of the mycobacteria.

Ampicillin↗
PubMed1992

A unique type of GABA binding by Mycobacterium leprae.

Neurotropism is one of the unusual properties of Mycobacterium leprae. The organism contains glutamic acid decarboxylase that generates gamma-amino-butyric acid (GABA) which is an inhibitory neurotransmitter. The binding of GABA by M. leprae in vitro was studied by using 3H-GABA as substrate. The bacteria had high-affinity binding sites for the amino acid. The uptake was a specific saturable process with a Km of 66.7 pM, pH optimum of 7.3 and a temperature optimum of 37 degrees C. The binding did not seem to be time-dependent, being complete in about 5 min. None of the known antagonists and agonists of GABA uptake by neurons, showed any significant effect on M. leprae; the receptors in the bacteria are apparently of a non-neuronal type, and different from those reported in spermatozoa and Pseudomonas.

Animals↗
PubMed1991

Combined resection of hepatoblastoma and intracaval right atrial extension with profound hypothermia and circulatory arrest.

Hepatoblastoma is an uncommon liver neoplasm in children but its intraatrial extension through the inferior vena cava is extremely rare. The case described is a 3-year-old boy in whom profound hypothermia and circulatory arrest were used to resect a hepatoblastoma and its extension to the right atrium. This technique allows maximal resection and relief of venous obstruction from atrial extension of hepatoblastoma.

Carcinoma, Hepatocellular↗
PubMed1991

Cystic duplication of the caecum mimicking intussusception.

Diagnosis of gut duplications are often only made intraoperatively as they are uncommon and do not feature strongly in the differential diagnoses. A case of caecal cystic duplication mimicking intussusception is discussed with the aim of improving diagnostic accuracy in future cases. A 7 month old boy presented with the classical triad of abdominal pain, bleeding per rectum and a palpable mass. Barium enema revealed a mass in the caecum suggestive of an intussusceptum. Repeated attempts at hydrostatic reduction were unsuccessful as the mass was immobile. Laparotomy revealed cystic duplication of the caecum without intussusception. The bleeding per rectum was due to an ulcer in the colonic epithelium overlying the cyst.

Cecal Diseases↗