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Biomedical subjects

M Kumar

Publications and source records attributed to M Kumar.

At least 145 records · Page 8Linked to original sources
PubMed1999

Electrodeposition of brushite coatings and their transformation to hydroxyapatite in aqueous solutions.

In this study we examine the potential for using brushite (dicalcium phosphate dihydrate) as a coating for orthopedic implants. It was found that brushite is transformed into a more stable calcium phosphate (hydroxyapatite), regardless of the aqueous transforming media utilized. The transformation was carried out at room temperature in deionized water, deionized water with added calcium ions, and modified Hank's type solution without calcium and magnesium ions, modified Hank's type solution with calcium and magnesium ions, and modified Hank's type solution with added calcium ions. In several of the transformation systems it was noted that brushite provided an increased amount of calcium ions to the transforming media through solubility. The process was monitored using X-ray diffraction, X-ray photoelectron spectroscopy, and dissolution studies. Scanning electron microscopy and energy dispersive spectroscopy were also utilized for characterization. The brushite coatings can be easily achieved electrolytically on conducting substrates. The process is non line of sight, simple, and inexpensive; and when using an electrolyte that can sustain currents of approximately 100 mA/cm2, the necessary coating can be completed in about 3 min.

Calcium Phosphates↗
PubMed1999

Comparison of endoscopic ligation and propranolol for the primary prevention of variceal bleeding.

BACKGROUND AND METHODS: We compared propranolol therapy and endoscopic ligation for the primary prevention of bleeding from esophageal varices. This prospective, controlled trial included consecutive eligible patients who had large varices (>5 mm in diameter) that were at high risk for bleeding. The patients were assigned to either propranolol therapy, at a dose sufficient to decrease the base-line heart rate by 25 percent, or variceal ligation, to be performed weekly until the varices were obliterated or so reduced in size that it was not possible to continue treatment. RESULTS: Of the 89 patients, 82 of whom had cirrhosis of the liver, 44 received propranolol and 45 underwent variceal ligation. The mean (+/-SD) duration of follow-up in each group was 14+/-9 and 13+/-10 months, respectively. The mean time required to achieve an adequate reduction in the heart rate was 2.5+/-1.7 days; the mean number of sessions needed to complete variceal ligation was 3.2+/-1.1. After 18 months, the actuarial probability of bleeding was 43 percent in the propranolol group and 15 percent in the ligation group (P=0.04). Twelve patients in the propranolol group and four in the ligation group had bleeding. Three of the four in the ligation group had bleeding before their varices had been obliterated. Nine patients in the ligation group had recurrent varices, a mean of 3.7 months after the initial treatment. Five patients in each group died; bleeding from the varices was the cause of death of four patients in the propranolol group and of three in the ligation group. There were no serious complications of variceal ligation; in the propranolol group, treatment was stopped in two patients because of side effects. CONCLUSIONS: In patients with high-risk esophageal varices, endoscopic ligation of the varices is safe and more effective than propranolol for the primary prevention of variceal bleeding.

Adrenergic beta-Antagonists↗
PubMed1999

Purification, crystallisation and preliminary X-ray diffraction study of ribosome inactivating protein: saporin.

We report here the crysallisation and molecular replacement results on the structure determination of S-9 isoform of the ribosome inactivating protein saporin. The protein was purified to homogeneity by a simple and efficient protocol. The crystals belong to the space group I4l with a = b = 91.47 A, c = 150.66 A and contain two molecules in the asymmetric unit.

Chromatography, High Pressure Liquid↗
PubMed1999

Modulation of lead toxicity by Spirulina fusiformis.

The modulatory effects of lead toxicity by Spirulina fusiformis (Oscillatoreaceae) were observed on the testes of Swiss albino mice at a dose of 800 mg/kg body weight. The Spirulina fusiformis was non-toxic at the dose given. A significant enhancement in the survival time was observed in the pre- and post-treated Spirulina group compared with the control (lead treated) group. Lead induced toxicity was also reduced in terms of testes weight, animal weight, tubular diameter in the pre Spirulina treated group. The modulatory effects of Spirulina may be attributed to the presence of the antioxidants, beta-carotene and SOD enzyme.

Animals↗
PubMed1999

Transformation of modified brushite to hydroxyapatite in aqueous solution: effects of potassium substitution.

Brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4 x 2H2O) was deposited electrolytically from calcium dihydrogen phosphate solution with and without potassium chloride (KCl) as a supporting electrolyte. The kinetics of brushite transformation to hydroxyapatite (HA, Ca5(PO4)3OH) in the presence of calcium and protein free, aqueous body fluid (Hank's balanced salt solution, HBSS) was investigated. We present evidence that the deposition of brushite in a KCl-supported electrochemical bath yields a modified brushite where some of the calcium is substituted by potassium. Transformation of both normal (i.e. potassium free) and modified brushite to hydroxyapatite upon exposure to calcium and protein-free aqueous fluid (HBSS) was followed by reflectance Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. Changes in the morphology of the coatings were studied using scanning electron microscopy (SEM). Results indicate that modified brushite undergoes faster transformation to hydroxyapatite in HBSS in comparison to normal brushite. Our results show that the presence of potassium ions in the brushite not only favors the formation of different intermediate phases but also alters transformation rates to HA.

Calcium Phosphates↗
PubMed1999

Scleral-fixated intraocular lens implantation in unilateral aphakic children.

OBJECTIVE: To assess the feasibility of scleral-fixated intraocular lens (IOL) implantation as an alternative form of optical correction in aphakic children intolerant of contact lenses and whose anterior segments lack capsular support. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: A total of 11 eyes of 11 unilateral aphakic children in the age group 4 to 9 years (mean, 6.45 years) were included in the study. INTERVENTION: Secondary scleral-fixated IOL implantation was performed in all cases. The patients underwent anterior vitrectomy at the time of IOL implantation. Amblyopia therapy in the form of patching was given post-IOL surgery. The follow-up ranged from 4 to 18 months (mean, 10.90 months). MAIN OUTCOME MEASURES: Postoperative best-corrected visual acuity (BCVA) in comparison to preoperative visual status and complications from the procedure were analyzed. RESULTS: Postoperative BCVA remained within 1 Snellen line of the preoperative visual status in six eyes, or 54.5% of patients; it improved by more than 1 Snellen line in three eyes, or 27.2% of patients, and decreased by more than 1 Snellen line in two eyes, or 18.1% of patients. The complications encountered were suture erosion through the conjunctiva in two eyes (18.18%), marked postoperative anterior chamber reaction in two eyes (18.18%), IOL decentration in one eye (9.09%), glaucoma in one eye (9.09%), and cystoid macular edema in one eye (9.09%). CONCLUSION: Secondary scleral-fixated IOL implantation was successful in achieving BCVA comparable to preoperative BCVA. However, a longer follow-up is required to document any further complications.

Aphakia, Postcataract↗
PubMed1999

Cognitive-behavioral stress management buffers decreases in dehydroepiandrosterone sulfate (DHEA-S) and increases in the cortisol/DHEA-S ratio and reduces mood disturbance and perceived stress among HIV-seropositive men.

This study examined the effects of a 10-week cognitive-behavioral stress management (CBSM) intervention on dehydroepiandrosterone sulfate (DHEA-S) levels and the ratio of cortisol to DHEA-S (cortisol/DHEA-S), potential surrogate adrenal markers of HIV disease progression, in relation to alterations in mood and distress. HIV-seropositive men were randomized to either a group-based CBSM intervention (n = 43) or to a wait-list control group (n = 24), with both hormonal and distress measures assessed just prior to and immediately following the 10-week period. Results showed that CBSM buffers decreases in DHEA-S and increases in the cortisol/DHEA-S ratio. Further examination also revealed that changes in the cortisol/DHEA-S ratio were significantly and positively related to changes in total mood disturbance and perceived stress over time. These findings demonstrate that a short-term CBSM intervention can buffer against decrements in DHEA-S and increments in the cortisol/DHEA-S ratio among symptomatic, HIV-positive men, and that alterations in the cortisol/DHEA-S ratio move in concert with changes in mood and distress observed during CBSM.

Adolescent↗
PubMed1999

Characterization of Lhx9, a novel LIM/homeobox gene expressed by the pioneer neurons in the mouse cerebral cortex.

In order to explain the phenotype observed in Lhx2 mutant embryos, we previously proposed that an Lhx2 related gene might exist. We now have cloned a new LIM/homeobox gene called Lhx9. Lhx9 is closely related to Lhx2 and is expressed in the developing central nervous system (CNS). Lhx9 and Lhx2 have expression patterns that overlap in some areas but are distinct in others. Thus, in some developmental domains these two highly related proteins may be functionally redundant. Lhx9 is expressed in the pioneer neurons of the cerebral cortex, while Lhx2 is expressed throughout the cortical layers. Postnatally, Lhx9 is expressed in the inner nuclei of the cerebellum, while Lhx2 is in the granular layer. In the developing limbs, both genes are highly expressed in a similar pattern. Based on the expression pattern and the developmental regulation of Lhx9, we propose that Lhx9 may be involved in the specification or function of the pioneer neurons of the cerebral cortex. We show that both Lhx9 and Lhx2 bind the LIM domain binding protein Ldb1/Nli1/Clim2.

Age Factors↗
PubMed1999

Reversible antispermatogenic effect of gossypol in langur monkeys (Presbytis entellus entellus).

The present investigation reports the antispermatogenic effect of the orally active highly purified gossypol acetic acid at 7.5 mg and 10 mg/day for 180 days in langur monkeys. The results revealed a dose-dependent response in semen analysis as well as testicular morphology. Uniform severe oligospermia was observed in the lower dose (7.5 mg) group, while azoospermia was observed in 2 out of 5 animals in the higher dose (10 mg) group and the remaining animals showed severe oligospermia. Scanning electron microscopy of spermatozoa revealed deleterious abnormalities in the head and midpiece. Testicular morphology revealed a decrease in the seminiferous tubule diameter and arrest of spermatogenesis. The lower dose group had a germ cell population up to primary spermatocytes while the higher dose group had only Sertoli cells and spermatogonia. Withdrawal of treatment for 180 days led to the recovery of all the parameters studied, to normalcy.

Animals↗
PubMed1999

Expression, purification and characterization of peanut (Arachis hypogaea) agglutinin (PNA) from baculovirus infected insect cells.

Peanut (Arachis hypogaea) seed lectin, PNA is widely used to identify tumor specific antigen (T-antigen), Galbeta1-3GalNAc on the eukaryotic cell surface. The functional amino acid coding region of a cDNA clone, pBSH-PN was PCR amplified and cloned downstream of the polyhedrin promoter in the Autographa californica nucleopolyhedrovirus (AcNPV) based transfer vector pVL1393. Co-transfection of Spodoptera frugiperda cells (Sf9) with the transfer vector, pAcPNA and AcRP6 (a recombinant AcNPV having B-gal downstream of the polyhedrin promoter) DNAs produced a recombinant virus, AcPNA which expresses PNA. Infection of suspension culture of Sf9 cells with plaque purified AcPNA produced as much as 9.8 mg PNA per liter (2.0 x 10(6) cells/ml) of serum-free medium. Intracellularly expressed protein (re-PNA) was purified to apparent homogeneity by affinity chromatography using ECD-Sepharose. Polyclonal antibodies against natural PNA (n-PNA) cross-reacted with re-PNA. The subunit molecular weight (30 kDa), hemagglutination activity, and carbohydrate specificity of re-PNA were found to be identical to that of n-PNA, thus confirming the abundant production of a functionally active protein in the baculovirus expression system.

Animals↗
PubMed1999

Pregnancy in bone marrow failure syndromes: Diamond-Blackfan anaemia and Shwachman-Diamond syndrome.

Pregnancy in bone marrow failure syndromes has risk to mother and fetus. There are fewer than 30 reports of cases with Diamond-Blackfan anaemia (DBA), and none with Shwachman-Diamond syndrome (SD). We report two DBA and one SD cases. One DBA mother received transfusions intra-partum, and the other only post-partum. Both required caesarean sections (C-sections) for failure of labour to progress and severe pre-eclampsia respectively. Both subsequently resumed pre-pregnancy steroid-induced control of anaemia. approximately 40% of DBA pregnancies required maternal transfusions; 25% delivered by C-section. The SD patient also had Ehlers-Danlos (ED) syndrome and urticaria pigmentosa (UP). Her blood counts were adequate until week 38, when the platelet count dropped and a C-section was performed. Pregnancy management in marrow failure disorders requires obstetricians with expertise in high-risk pregnancies, and haematologists with experience with marrow failure syndromes.

Adult↗
PubMed1999

A recombinant BCG vaccine generates a Th1-like response and inhibits IgE synthesis in BALB/c mice.

The tubercle vaccine, bacille Calmette-Guérin (BCG), is a strong inducer of T-helper type 1 (Th1) responsiveness, and it has been suggested that recombinant BCG (rBCG), which produces and secretes antigens, may be used to prevent allergic diseases. The effects of rBCG vaccination on allergic responses in a murine model were examined in this study. A BCG-Escherichia coli shuttle vector was developed with the promoter and signal sequence of the alpha-antigen of Mycobacterium bovis, and the vector was tested using E. coli beta-galactosidase as the model antigen and allergen. This vector enabled the expression of the E. coli beta-galactosidase gene in BCG, which was detected in its protein extract by immunoblotting analysis. Vaccination of mice with a single dose of 106 recombinant BCG generated a beta-galactosidase-specific antibody response. The splenocytes of vaccinated mice compared with controls produced significantly higher amounts of interferon-gamma (IFN-gamma) (P<0. 01) and interleukin-2 (IL-2) (P<0.05) and lower amounts of IL-5 (P<0. 01). Mice vaccinated with rBCG had significantly less (P<0.01) serum IgE compared with controls. These results together demonstrate that rBCG secreting antigens or allergens may be utilized for the induction of a Th1-like response and the down-regulation of IgE antibody response.

Animals↗
PubMed1999

Surprisingly little polymorphism in the merozoite-surface-protein-2 (MSP-2) gene of Indian Plasmodium falciparum.

The polymorphism in the merozoite-surface-protein-2 (MSP-2) gene of six Indian Plasmodium falciparum isolates was studied by PCR amplification, cloning and sequencing. One of the isolates showed a deletion of 63 bp and all showed point mutations, although some of these mutations were silent. All the isolates also exhibited 5' and 3' conserved regions, with the two 32-mer amino-acid repeats characteristic of the FC27 family, and none belonged to the IC-1/3D7 family. Although the MSP-2 genes of these isolates represent new allelic sequences, they belong to the FC27 family and show remarkably little variation.

Amino Acid Sequence↗
PubMed1999

A single step purification process for cyclodextrin glucanotransferase from a Bacillus sp. isolated from soil.

Cyclodextrin glucanotransferase (CGTase) is a commercially important enzyme which catalyses the formation of cyclodextrins (CDs) from starch. A CGTase producing bacterium was isolated from soil which gave a fairly high enzyme activity of 7.5 U mL(-1) after 24 h of growth which was further increased to 22 U mL(-1) by proper media design. The enzyme was purified to homogeneity by a novel single affinity precipitation step which resulted in a very high recovery of more than 90%. The molecular weight, as determined by SDS-PAGE, was found to be 68 kDa. The pH optimum was found to be 6.6 while a temperature optimum of 65 degrees C was observed. The enzyme exhibited a fairly high degree of functional stability with little loss of activity, even after 8 h of incubation at 65 degrees C. Ca++ had little effect on the activity of the enzyme while urea at 10 mM concentration increased the activity of the enzyme by more than 200%, suggesting that it is a unique enzyme.

Bacillus↗
PubMed1999

Retroperitoneoscopic nephrolympholysis and ureterolysis for management of intractable filarial chyluria.

PURPOSE: To evaluate the feasibility of retroperitoneoscopic lymphatic disconnection in patients with intractable filarial chyluria with the aim of reducing the morbidity of the surgery. PATIENTS AND METHODS: Two patients presented to us with intractable chyluria. They did not respond to conservative measures and endoscopic sclerotherapy. In view of the severe lipid and protein loss associated with recurrent bouts of chyluria, they merited surgical correction by lymphatic disconnection. Because this operation requires extensive mobilization within the retroperitoneum over a large area, it necessitates a large flank or midline incision. In order to reduce the incision-related morbidity, it was decided to undertake the procedure laparoscopically. The retroperitoneal route was chosen for its obvious advantages. RESULTS: Surgery was carried out uneventfully in both patients, with a mean operating time of 2 hours. The patients stayed in the hospital for an average of 2.5 days. Chyluria resolved in the immediate postoperative period, and they have been asymptomatic over a follow-up of 30 and 18 months. One patient had drainage of lymph for 5 days, which resolved spontaneously. CONCLUSIONS: The objectives of open surgery can be achieved by the minimally invasive approach of retroperitoneoscopy. The new approach significantly reduces the incision-related morbidity without compromising the principles of open surgery. We propose five important steps necessary to avoid recurrence and reduce postoperative morbidity.

Adult↗
PubMed1999

Fluorine-18 fluorodeoxyglucose splenic uptake from extramedullary hematopoiesis after granulocyte colony-stimulating factor stimulation.

Two patients with sarcoma, one with recurrent osteosarcoma of the spine and the other with metastatic synovial cell sarcoma, were treated with high-dose chemotherapy that produced severe leukopenia. The patients received granulocyte colony-stimulating factor (G-CSF) to stimulate the bone marrow (480 mg given subcutaneously twice daily for 5 to 7 days); their responses were seen as a marked increase in peripheral leukocyte count with no change in the erythrocyte or platelet counts. The patients had fluorine-18 fluorodeoxyglucose (F-18 FDG) imaging 24 hours after the end of G-CSF treatment. Diffusely increased uptake of F-18 FDG was seen in the bone marrow in both patients. In addition, markedly increased uptake in the spleen was noted in both, indicating that the spleen was the site of extramedullary hematopoiesis. The patients had no evidence of splenic metastases. The first patient had a history of irradiation to the dorsal spine, which was less responsive to G-CSF administration than was the nonirradiated lumbar spine.

Adult↗