Biomedical subjects

K Mani

Publications and source records attributed to K Mani.

At least 19 recordsLinked to original sources

PubMed2001

Modulations of glypican-1 heparan sulfate structure by inhibition of endogenous polyamine synthesis. Mapping of spermine-binding sites and heparanase, heparin lyase, and nitric oxide/nitrite cleavage sites.

Cell surface heparan sulfate proteoglycans facilitate uptake of growth-promoting polyamines (Belting, M., Persson, S., and Fransson, L.-A. (1999) Biochem. J. 338, 317-323; Belting, M., Borsig, L., Fuster, M. M., Brown, J. R., Persson, L., Fransson, L.-A., and Esko, J. D. (2001) Proc. Natl. Acad. Sci. U. S. A., in press). Here, we have analyzed the effect of polyamine deprivation on the structure and polyamine affinity of the heparan sulfate chains in various glypican-1 glycoforms synthesized by a transformed cell line (ECV 304). Heparan sulfate chains of glypican-1 were either cleaved with heparanase at sites embracing the highly modified regions or with nitrite at N-unsubstituted glucosamine residues. The products were separated and further degraded by heparin lyase to identify sulfated iduronic acid. Polyamine affinity was assessed by chromatography on agarose substituted with the polyamine spermine. In heparan sulfate made by cells with undisturbed endogenous polyamine synthesis, free amino groups were restricted to the unmodified, unsulfated segments, especially near the core protein. Spermine high affinity binding sites were located to the modified and highly sulfated segments that were released by heparanase. In cells with up-regulated polyamine uptake, heparan sulfate contained an increased number of clustered N-unsubstituted glucosamines and sulfated iduronic acid residues. This resulted in a greater number of NO/nitrite-sensitive cleavage sites near the potential spermine-binding sites. Endogenous degradation by heparanase and NO-derived nitrite in polyamine-deprived cells generated a separate pool of heparan sulfate oligosaccharides with an exceptionally high affinity for spermine. Spermine uptake in polyamine-deprived cells was reduced when NO/nitrite-generated degradation of heparan sulfate was inhibited. The results suggest a functional interplay between glypican recycling, NO/nitrite-generated heparan sulfate degradation, and polyamine uptake.

Animals↗

PubMed2000

N-unsubstituted glucosamine in heparan sulfate of recycling glypican-1 from suramin-treated and nitrite-deprived endothelial cells. mapping of nitric oxide/nitrite-susceptible glucosamine residues to clustered sites near the core protein.

We have analyzed the content of N-unsubstituted glucosamine in heparan sulfate from glypican-1 synthesized by endothelial cells during inhibition of (a) intracellular progression by brefeldin A, (b) heparan sulfate degradation by suramin, and/or (c) endogenous nitrite formation. Glypican-1 from brefeldin A-treated cells carried heparan sulfate chains that were extensively degraded by nitrous acid at pH 3.9, indicating the presence of glucosamines with free amino groups. Chains with such residues were rare in glypican-1 isolated from unperturbed cells and from cells treated with suramin and, surprisingly, when nitrite-deprived. However, when nitrite-deprived cells were simultaneously treated with suramin, such glucosamine residues were more prevalent. To locate these residues, chains were first cleaved at linkages to sulfated l-iduronic acid by heparin lyase and released fragments were separated from core protein carrying heparan sulfate stubs. These stubs were then cleaved off at sites linking N-substituted glucosamines to d-glucuronic acid. These fragments were extensively degraded by nitrous acid at pH 3.9. When purified proteoglycan isolated from brefeldin A-treated cells was incubated with intact cells, endoheparanase-catalyzed degradation generated a core protein with heparan sulfate stubs that were similarly sensitive to nitrous acid. We conclude that there is a concentration of N-unsubstituted glucosamines to the reducing side of the endoheparanase cleavage site in the transition region between unmodified and modified chain segments near the linkage region to the protein. Both sites as well as the heparin lyase-sensitive sites seem to be in close proximity to one another.

Cell Line↗

PubMed2000

Biosynthesis of decorin and glypican.

Decorin and glypican are two examples of exclusively chondroitin/dermatan sulfate and heparan sulfate-substituted proteoglycans, respectively. Decorin is a secretory product, whereas glypican is linked to membrane lipids via a glycosyl-phosphatidyl-inositol (GPI) anchor. The nascent decorin protein enters the lumen of the ER, whereas that of glypican is transferred to the preformed GPI-anchors. Both types of glycosaminoglycuronans are initiated on Ser residues located in special consensus sequences, and the first glycosylation steps constitute a common pathway: the generation of the linkage region GlcA-Gal-Gal-Xyl-Ser<. The nature of the enzymes involved will be reviewed with special emphasis on the recently discovered transient 2-phosphorylation of xylose. The initiation enzymes (betaGalNAc-T1 and alphaGlcNAc-T1) then use these tetrasaccharide primers for either chondroitin or heparan sulfate assembly. The selection mechanism is not yet fully understood. The transferases that form the linkage-region and add the first hexosamine, as well as the uronosyl C-5 epimerases, appear to be products of single genes, but many isoforms of the copolymerases and sulfotransferases forming the repetitive part of the glycan chains are currently being discovered. When these enzymes work together, the fine structure of the glycosaminoglycuronans appears to be generated through the selective expression of isoforms that only operate in certain structural contexts. During heparan sulfate assembly, generation of GlcNH(2) as a permanent feature is now well recognised. Studies on glypican-1 glycoforms that recycle suggest that heparan sulfate chains are degraded by endoheparanase at or near GlcNH(2) residues, followed by deaminative cleavage catalysed by NO-derived nitrite. Chain-truncated glypican-1 can serve as a precursor for the reformation of a proteoglycan with full-size chains. Regulation of biosynthesis can be exercised at several levels, such as expression of the core protein, selection for chondroitin or heparan sulfate assembly, expression of modifying enzymes, and degradation and remodelling. Cytokines, growth factors, NO and polyamines may have regulatory roles.

Animals↗

PubMed2000

A novel role for nitric oxide in the endogenous degradation of heparan sulfate during recycling of glypican-1 in vascular endothelial cells.

We show here that the endothelial cell-line ECV 304 expresses the heparan sulfate proteoglycan glypican-1. The predominant cellular glycoform carries truncated side-chains and is accompanied by heparan sulfate oligosaccharides. Treatment with brefeldin A results in accumulation of a glypican proteoglycan with full-size side-chains while the oligosaccharides disappear. During chase the glypican proteoglycan is converted to partially degraded heparan sulfate chains and chain-truncated proteoglycan, both of which can be captured by treatment with suramin. The heparan sulfate chains in the intact proteoglycan can be depolymerized by nitrite-dependent cleavage at internally located N-unsubstituted glucosamine moieties. Inhibition of NO-synthase or nitrite-deprivation prevents regeneration of intact proteoglycan from truncated precursors as well as formation of oligosaccharides. In nitrite-deprived cells, formation of glypican proteoglycan is restored when NO-donor is supplied. We propose that, in recycling glypican-1, heparan sulfate chains are cleaved at or near glucosamines with unsubstituted amino groups. NO-derived nitrite is then required for the removal of short, nonreducing terminal saccharides containing these N-unsubstituted glucosamine residues from the core protein stubs, facilitating re-synthesis of heparan sulfate chains.

Brefeldin A↗

PubMed1999

Recent advances on the pathogenesis of Huntington's disease.

We review recent advances regarding the pathogenesis of Huntington's disease (HD). This genetic neurodegenerative disorder is caused by an expanded CAG repeat in a gene coding for a protein, with unknown function, called huntingtin. There is selective death of striatal and cortical neurons. Both in patients and a transgenic mouse model of the disease, neuronal intranuclear inclusions, immunoreactive for huntingtin and ubiquitin, develop. Huntingtin interacts with the proteins GAPDH, HAP-1, HIP1, HIP2, and calmodulin, and a mutant huntingtin is specifically cleaved by the proapoptotic enzyme caspase 3. The pathogenetic mechanism is not known, but it is presumed that there is a toxic gain of function of the mutant huntingtin. Circumstantial evidence suggests that excitotoxicity, oxidative stress, impaired energy metabolism, and apoptosis play a role.

Animals↗

PubMed1999

Homozygosity mapping to the USH2A locus in two isolated populations.

Usher syndrome is a group of autosomal recessive disorders characterised by progressive visual loss from retinitis pigmentosa and moderate to severe sensorineural hearing loss. Usher syndrome is estimated to account for 6-10% of all congenital sensorineural hearing loss. A gene locus in Usher type II (USH2) families has been assigned to a small region on chromosome 1q41 called the UHS2A locus. We have investigated two families with Usher syndrome from different isolated populations. One family is a Norwegian Saami family and the second family is from the Cayman Islands. They both come from relatively isolated populations and are inbred families suitable for linkage analysis. A lod score of 3.09 and 7.65 at zero recombination was reached respectively in the two families with two point linkage analysis to the USH2A locus on 1q41. Additional homozygosity mapping of the affected subjects concluded with a candidate region of 6.1 Mb. This region spans the previously published candidate region in USH2A. Our study emphasises that the mapped gene for USH2 is also involved in patients from other populations and will have implications for future mutation analysis once the USH2A gene is cloned.

Chromosomes, Human, Pair 1↗

PubMed1998

Heparan/chondroitin/dermatan sulfate primer 2-(6-hydroxynaphthyl)-O-beta-D-xylopyranoside preferentially inhibits growth of transformed cells.

Xylose forms the direct carbohydrate-protein link in extra- or pericellular proteoglycans (PGs) that are substituted with either chondroitin sulfate (CS)/dermatan sulfate (DS) and/or heparan sulfate (HS). Cell surface PGs carrying HS are important regulators of cell growth. Xylose coupled to an aromatic compound can enter cells and initiate either CS/DS synthesis or both HS and CS/DS synthesis, depending on the nature of the aromatic adduct. Here, we show that 2-(6-hydroxynaphthyl)-O-beta-D-xylopyranoside, which can prime both types of glycan chains, inhibits growth of a set of normal and transformed cells. Transformed cells are preferentially inhibited, and at a concentration of 0.15-0.20 mM xyloside, transformed cells are totally growth arrested, whereas normal cells are only < or = 50% inhibited. No inhibition of growth is observed with the stereoisomeric 2-(6-hydroxynaphthyl)-O-beta-L-xylopyranoside, which does not prime glycosaminoglycan synthesis at all; with the nonhydroxylated 2-naphthyl-O-beta-D-xylopyranoside, which only primes CS/DS synthesis under these conditions; or with p-nitrophenyl-O-beta-D-xylopyranoside, which is known to prime only CS/DS synthesis. We conclude that growth inhibition is due to priming of HS and/or CS/DS synthesis, which may either lead to the formation of specific antiproliferative glycans or glycan fragments or to interference with endogenous PG synthesis and turnover.

3T3 Cells↗

PubMed1997

Osteosarcoma of the jaw bones.

Osteosarcoma of the jaw bone is comparatively rare and accounts for about 6.5% of all osteosarcomas. We treated eight cases of osteosarcoma of the jaw bone involving the mandible and maxilla in equal proportions between 1986-1992. The median age was 31 years and male: female ratio was 5:3. Swelling and bony expansion were the most common presentations. Radiologically six patients had lytic lesions, and histopathologically they were osteoblastic (n = 4), chondroblastic (n = 3) and fibroblastic (n = 1). Three patients, two with mandibular and one with maxillary osteosarcoma underwent radical surgery and six courses of cisplatinum-based chemotherapy. All were alive and disease free 24, 30, and 54 months after treatment. Histologically all three were chondroblastic. Five patients had incomplete or palliative treatment. All patients died of progressive or locally recurrent disease within 2 years.

Adult↗

PubMed1997

Left ventricular morphology in chronic renal failure by echocardiography.

M-mode, two-dimensional, and Doppler echocardiography were performed in 38 chronic renal failure (CRD) patients on conservative management, 35 patients on hemodialysis, and 36 matched controls. The controls were matched for age, sex, and comorbidities. The incidence of hypertension, left ventricular (LV) end diastolic volume, LV end systolic volume, and LV mass index were significantly higher in patients on hemodialysis compared to the controls. The LV parameters in the predialysis patients were not significantly different from the controls, except the LV end systolic internal dimensions were significantly higher in the CRF patients. Multiple regression analysis underscored the strong association between increase in LV mass index (LVMI) and hypertension. The diabetic patients with renal failure had large LV internal diameter and end diastolic volume compared to non-diabetics. Systolic function was well preserved even in hypertensive and diabetic patients with uremia. The incidence of diastolic dysfunction and asymmetrical septal hypertrophy were not significantly different in the three groups of patients.

Diabetic Nephropathies↗

PubMed1997

Expression of the SIL gene is correlated with growth induction and cellular proliferation.

The SIL gene was discovered at the site of a cancer-associated interstitial deletion in which its promoter assumed the regulation of a second gene, SCL. The human SIL gene encodes a 1287-amino acid cytosolic protein that has been found to be highly conserved in the mouse. SIL is expressed in proliferating cells and is down-regulated when cellular proliferation ceases because of serum starvation, contact inhibition, or induction of terminal differentiation. SIL is induced within 1 h of stimulation by 20% serum in growth-arrested 3T3 cells. This induction is independent of protein synthesis because "superinduction" is observed in the presence of the protein synthesis inhibitor cyclohexamide. Thus, SIL is an immediate-early gene. Upon release from serum starvation of 3T3 fibroblasts, SIL mRNA and protein levels display a biphasic pattern during the first cell cycle. In contrast, in exponentially growing EL4 lymphoblasts, SIL mRNA is stable throughout the cell cycle, whereas SIL protein accumulates into G2 phase and then falls precipitously at the completion of the cell cycle. This pattern of cell cycle expression suggests that SIL may play an important role in cellular growth and proliferation.

Animals↗

PubMed1996

Magliant melanoma of the oral cavity: report of 14 cases from a regional cancer centre.

Fourteen patients with oral mucosal malignant melanomas seen at a regional cancer centre over a 10-year period were analysed. All the patients presented with symptoms of short duration, with extensive local disease at initial evaluation in 11 patients. The palate was the commonest site involved. Ten patients had regional nodal disease and of these four also had distant metastases to the liver and/or the lung. Coincidental melanosis was identified clinically in three patients and histologically confirmed in two patients. Only four patients underwent radical surgery. Of the five patients who received DTIC-based chemotherapy, only one achieved a complete response. No significant correlation between stage of the disease at presentation, histological features or type of treatment and survival could be seen as the number of cases is small.

Adult↗

PubMed1996

Quenching the thirst in dialysis patients.

In a double-blind cross-over trial, 22 stable end-stage renal failure patients on maintenance haemodialysis were subjected to conventional dialysis with dialysate containing 137 mEq/l sodium and constant ultrafiltration (UF) and to a different dialysis therapy, in which, by linear sodium modelling, the dialysate sodium was reduced from 137 to 128 mEq/l. A computerized UF program was used to gradually reduce the UF to a minimum towards the end of the session. Severity of thirst, interdialytic weight gain and intradialytic complications were less with low sodium dialysate. It allowed adequate UF with absolute hemodynamic stability. The reduced incidence of complication with low sodium dialysate therapy was probably because they required less UF.

Adult↗

PubMed1996

Valvular dysfunction in uraemia.

Regurgitation of the pulmonary, mitral, tricuspid and aortic valves have been observed frequently in chronic renal failure (CRF) and dialysis patients. Two dimensional, M mode and doppler echocardiography were performed on 35 CRF patients and 37 end stage renal failure (ESRD) patients on maintenance haemodialysis. Though structurally normal, valvular dysfunction was noted in 50 per cent of the patients with renal failure. Mitral regurgitation was the commonest abnormality, occurring in 36.1 per cent of the patients. Calcification of the valve was observed in only 5.6 and 16.7 per cent of CRF and dialysis patients respectively. Multiple regression analysis underscored the large contribution of diabetic status in the development of valvular dysfunction. Though end systolic volume was higher in patients with valvular abnormalities, the ejection fraction was well preserved. However, follow up studies are required to assess the significance of the functional valvular regurgitation on the cardiac function of the patients.

Female↗

PubMed1996

Optimal cyclosporine therapy--an Indian experience.

Thirty consecutive adult patients who underwent renal transplantation were prospectively studied. The immunosuppression consisted of cyclosporine, azathioprine and prednisolone. Oral Cyclosporine CyA was initiated at a dose of 7 mg/kg/Day and reduced by 1 mg/kg/month. Blood level of CyA was monitored by monoclonal RIA (Cyclo-Trac-NS) method on 3rd, 10th, 30th, 60th, 90th and 180th days. The dose was titrated according to the blood level and the renal function. In spite of progressive reduction in the dose of CyA, the blood level did not show any significant change, probably because of increased absorption or decreased metabolism. Though the percentage change in CyA dose was significant, the CyA level and serum creatinine remained relatively stable during the follow up period. Our patients required relatively lesser dose to achieve optimum blood level. Though the blood level of CyA ranged between 387 and 2120 ng/dL. There was no evidence of rejection or irreversible nephrotoxicity.

Absorption↗

PubMed1992

Blood pressure levels in south Indian adolescents.

The present study was undertaken to develop normative data for the blood pressure (BP) levels in adolescent boys and girls aged 10-17 years residing the rural and urban areas of North Arcot Ambedkar District, Tamil Nadu State. Blood pressures were evaluated as part of an ongoing study on growth and development in adolescents. A total of 7028 BP measurements collected cross-sectionally were subjected to statistical analysis. The mean systolic (SBP) and diastolic (DBP) blood pressure levels were elevated in rural children as compared to that in urban children of respective sexes during 10 and 15 years of age. The mean BP levels were higher in both the rural and urban girls as compared to their male counterparts till the age of 15, after which the trend was reversed. While the mean SBP and DBP levels for rural children of either sex were stable over the age range considered, those for urban children exhibited consistent increase with age. In urban boys, the yearly mean increments in SBP and DBP were 2.5 mm Hg and 2.0 mm Hg and that in urban girls 2.4 mm Hg and 1.7 mm Hg, respectively. It is suggested that perhaps stress factors are responsible for the elevated mean BP levels among the rural adolescents as they are generally engaged in activities that exert considerable physical and psychological stress.

Adolescent↗

PubMed1991

The relationship of microbial pathogens to acute infectious diarrhoea of childhood.

Bacterial, viral and parasitic enteric pathogens were detected in 692 of 916 children below 36 months of age with acute diarrhoea and in 289 of 587 matched controls. The rates of identification of only four groups of pathogens, rotavirus, Shigellae, Salmonella typhimurium and enterotoxigenic E. coli, were significantly higher in the patients. The prevalence of a variety of other enteric pathogens was similar in controls of patients. Shigellosis had a characteristic clinical profile but none of the other agents could be suspected on clinical grounds. The high prevalence of pathogens in controls suggested that the population may be partially protected against a variety of enteric pathogens and that final common pathways leading to diarrhoea may be activated by changes in the microbial ecology of the gut lumen.

Acute Disease↗

PubMed1989

Impact of MDT on incidence rates of leprosy among household contacts. Part 1. Baseline data.

This preliminary study from Gudiyatham Taluk, the leprosy control area of the Schieffelin Leprosy Research & Training Centre, investigated the incidence rates of leprosy among household contacts during the period 1970-1985. The incidence rates of leprosy among the household contacts prior to and during the initiation of multi-drug therapy are presented here. The overall incidence rate among the household contacts was 4 per 1000 person-years at risk. Contacts of multibacillary and paucibacillary cases had a relative risk of 3-6 times and 2-4 times the risk of leprosy in the general population, respectively. The incidence rates among children were higher than adults; the peak age-specific incidence rate was between 5-9 years, and nearly one third of the primary cases were children. These findings are presented and the methodological issues discussed.

Age Factors↗

PubMed1987

Effect of safe concentrations of some pesticides on testicular recrudescence in the freshwater murrel, Channa punctatus (Bl): a morphological study.

The effects of safe concentrations of fenitrothion 50% E.C., an organophosphate, and carbofuran 3% G, a carbamate, on testicular recrudescence of Channa punctatus during the maturing, prespawning, and spawning phases (15th April through 12th August, 1980) of the annual reproductive cycle have been studied. The results reveal that compared to the carbofuran treatment, the fenitrothion treatment was more effective in lowering testicular weights. Furthermore, the carbofuran treatment delayed the formation of spermatids and sperm, since their occurrence in the testes was observed at 90 days of exposure, but at 60 days of exposure in the control fish. The fenitrothion treatment not only delayed the formation of spermatids, but also arrested the formation of sperm, since most of the spermatids had undergone necrosis. The exposure for 120 days to safe concentrations of carbofuran/fenitrothion also resulted in the necrosis of spermatogonia and spermatocytes, which led to their gradual loss. As such, the lobules completely devoid of the spermatogenetic stages were observed in the testes of the treated fish. The occurrence of such empty lobules, however, was relatively greater in the fenitrothion-treated fish. The formation of the collagenous capsules around the necrotic germ cells was also observed in the treated fish testes. The interstitial (Leydig) cells were in the involuted condition in the treated fish testes, but active in the control fish.

Animals↗