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Biomedical subjects

M M Islam

Publications and source records attributed to M M Islam.

At least 19 recordsLinked to original sources
PubMed2000

The substrate activation process in the catalytic reaction of Escherichia coli aromatic amino acid aminotransferase.

Aromatic amino acid aminotransferase is active toward both aromatic and dicarboxylic amino acids, and the mechanism for this dual substrate recognition has been an issue in the enzymology of this enzyme. Here we show that, in the reactions with aromatic and dicarboxylic ligands, the pK(a) of the Schiff base formed between the coenzyme pyridoxal 5'-phosphate and Lys258 or the substrate increases successively from 6.6 in the unliganded enzyme to approximately 8.8 in the Michaelis complex and to >10.5 in the external Schiff base complex. Mutations of Arg292 and Arg386 to Leu, which mimic neutralization of the positive charges of the two arginine residues by the ligand carboxylate groups, increased the Schiff base pK(a) by 0.1 and 0.7 unit, respectively. In contrast to these moderate effects of the Arg mutations, the cleavage of the Lys258 side chain of the Schiff base, which was brought about by preparing a mutant enzyme in which Lys258 was changed to Ala and the Schiff base was reconstituted with methylamine, produced the Schiff base pK(a) value of 10.2, that being 3.6 units higher than that of the wild-type enzyme. The observation indicates that the Schiff base pK(a) in the enzyme is lowered by the torsion around the C4-C4' axis of the Schiff base and suggests that the pK(a) is mainly controlled by changing the torsion angle during the course of catalysis. This mechanism, first observed for the reaction of aspartate aminotransferase with aspartate [Hayashi, H., Mizuguchi, H., and Kagamiyama, H. (1998) Biochemistry 37, 15076-15085], does not require the electrostatic contribution from the omega-carboxylate group of the substrate, and can explain why in aromatic amino acid aminotransferase the aromatic substrates can increase the Schiff base pK(a) during catalysis to the same extent as the dicarboxylic substrates. This is the first example in which the torsion pK(a) coupling of the pyridoxal 5'-phosphate Schiff base has been demonstrated in pyridoxal enzymes other than aspartate aminotransferase, and suggests the generality of the mechanism in the catalysis of aminotransferases related to aspartate aminotransferase.

Bacterial Proteins↗
PubMed2000

Preferential amplification is minimised in long-PCR systems.

The advent of long PCR (XL-PCR) has proven to be a major advance in PCR technology and is currently being utilised to investigate numerous biological systems. The analysis of mixed DNA populations is a particularly useful application for XL-PCR. For example, XL-PCR has been used to investigate the occurrence of heterogeneous mitochondrial DNA (mtDNA) rearrangement mutations. With XL-PCR it became possible to amplify the entire length of the mtDNA chromosome and detect any mtDNA deletion or insertion mutations based on a measurable change in overall sequence length. In the present communication, XL-PCR and conventional short-length PCR were used to amplify mitochondrial DNA sequences from several human vastus lateralis skeletal muscle samples. The experiments demonstrated that there was minimal preferential amplification of shorter DNA sequences with XL-PCR and was significantly less than the preferential amplification of shorter sequences observed with conventional PCR. Also, XL-PCR amplification of the complete mtDNA sequence from control DNA containing a single mtDNA template (leucocyte extracts) showed that the generation of PCR artefacts was not a predisposed failing of the system but was dependant on the standard rules that govern the set up and optimisation of any PCR reaction. In optimised systems, XL-PCR artefacts were not generated and a single PCR product was always recovered.

Aging↗
PubMed2000

Contraceptive failure: levels, trends and determinants in Matlab, Bangladesh.

This study investigated the levels, trends and determinants of contraceptive use-failure in Matlab, Bangladesh, using a set of prospective data on 25,960 women of reproductive age. The data were extracted from the Record Keeping System (RKS) of Matlab for the period 1978-94. If there was any live birth during the use or within 7 months after the discontinuation of use, it was considered as a failure. The life table technique and hazard model were used as analytical tools. The results suggest that use-failure for pills, IUDs (TCu 200) and injectables and other temporary methods increased from 1978 to 1988, but began to decline after 1988. The cumulative probability of first-method failure within 1 year of method acceptance of the cohort of 1990-94 acceptors was 12.9% for pills, 2.0% for IUDs, 0.5% for injectables, 22.0% for condoms and 13.4% for 'other' methods (sampoon, foam, jelly and traditional methods). For pills, condoms and 'other' methods, the likelihood of failure declined with the duration of use; by contrast, the probability of an IUD failure increased over time, peaking at 3 years of use. The injectables maintained a low likelihood of failure regardless of the duration of use. The quality of Community Health Workers' (CHWs) performance was associated with the risk of failure of all temporary methods except condoms; women's background characteristics associated with failure varied by method. The effect of the quality of the CHWs' performance and the background variables on failure did not change much over time. It is felt that contraceptive failure deserves the serious attention of programme managers and policy makers to make the Bangladesh national family planning programme more successful.

Adult↗
PubMed2000

Mass media exposure and its impact on family planning in Bangladesh.

This paper analyses mass media exposure and its effect on family planning in Bangladesh using data from the Bangladesh Demographic and Health Survey (BDHS) 1993-94. The findings indicate that radio and television are two important mass media for disseminating family planning information in Bangladesh. However, access to them and exposure to family planning through them are still limited. Slightly more than 40% (42.1%) of respondents reported that they had heard family planning messages via radio, while 17.2% said television, 8.4% said poster and 5.4% said billboard. Respondent's place of residence, education, economic status, geographical region and number of living children appeared to be the most important variable determining mass media exposure to family planning. Multivariate analysis shows that both radio and TV exposure to family planning messages and ownership of a radio and TV have a significant effect on current use of family planning methods. These factors remain significant determinants of contraceptive use, even after controlling socioeconomic and demographic factors. The study reveals that both socioeconomic development policies and family planning programmes with a special emphasis on mass media, especially radio, may have a significant effect on contraceptive use in Bangladesh. The principal policy challenge is to design communications strategies that will reach the less privileged, rural and illiterate people who are by far the majority in Bangladesh.

Adolescent↗
PubMed2000

Tissue mitochondrial DNA changes. A stochastic system.

Several lines of evidence support the view that the bioenergetic function of the mitochondria in postmitotic tissue deteriorates during normal aging. Skeletal muscle is one such tissue that undergoes age-related fiber loss and atrophy and an age-associated rise in the number of cytochrome c oxidase (COX) deficient fibers. With such metabolic pressure placed on skeletal muscle it would be an obvious advantage to supplement the cellular requirement for energy by up-regulating glycolysis, and alternative pathway for energy synthesis. Analysis of rat skeletal muscle utilizing antibodies directed against key enzymes involved in glycolysis has provided evidence of an age-associated increase in the enzymes involved in glycolysis. Fructose-6-phosphate kinase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase protein levels appeared to increase in the soleus, gracilis, and quadriceps muscle from aged rats. The increase in the level of these proteins appeared to correlate to a corresponding decrease in the amount of cytochrome c oxidase protein measured in the same tissue. Together these results are interpreted to represent a general upregulation of glycolysis that occurs in response to the age-associated decrease in mitochondrial energy capacity. Mitochondrial DNA (mtDNA) damage and mutations may accumulate with advancing age until they reach a threshold level were they impinge on the bioenergy capacity of the cell or tissue. Evidence indicates that mtDNA from the skeletal muscle of both aged rats and humans not only undergoes changes at the nucleotide sequence level (mutations and DNA damage), but also undergoes modifications at the tertiary level to generate unique age-related conformational mtDNA species. One particular age-related conformational form was only detected in aged rat tissues with high demands on respiration, specifically in heart, kidney, soleus muscle, and, to a lesser extent, the quadriceps muscle. The age-related form was not detected in gracilis muscle which is predominantly dependent upon glycolysis with regard to its energy requirements. Finally, a comprehensive hypothesis is presented that features the stochastic nature of the mitochondrial system. The basis of the hypothesis is that a dynamic relationship exists between endogenous mutagen production, DNA repair, mtDNA turnover, and nuclear control of mtDNA copy number and that age-associated changes in the dynamics of this relationship lead to a loss of functional full-length mtDNA that eventually leads to bioenergy decline.

Aging↗
PubMed1999

Current trend in prevalence of diabetes mellitus in Japan, 1964-1992.

Prevalence of diabetes mellitus in Japan was investigated through studying the published reports from 1964 to 1992 by searching the electronic data base and some leading Japanese journals following certain inclusion criteria. Out of total 74 retrieved reports, 14 were found eligible for review, some containing data of multiple community and/or periods and were converted into total of 40 reports following a predetermined criteria. Review analysis of only the prevalence of diabetes was done paying much attention to age range, survey methodology and response rate. Oral glucose tolerance test (OGTT) was done in 19 (47.5%) with and in 21 (52.5%) reports without initial urine and/or blood sugar screening. OGTT was done using 75, 50, or 100 grams glucose following either Japan Diabetes Society or WHO criteria. The recent prevalence was estimated ranging from 9.6-11.9% in both sexes of 40 years or over, 4.2-13.1% in men and 2.6-12.9% in women. The higher prevalences were found in and around 1990 and the lower values in and around 1970. Regression analysis shows the upward trend of the prevalence of diabetes 2.2% in men (p < 0.01), 1.6% in women (p < 0.01) by 10 years.

Adult↗
PubMed1999

Comparative analysis of HPLC profile of cytosolic thymidine kinase activity between hepatoma and regenerating liver in rat with reference to phosphorylation.

Thymidine kinase (TK) activity in rat hepatoma JB1 and AH136B was mainly due to cytosolic TK and was much higher than that in rat regenerating liver. Two forms of cytosolic TK, designated as TK-I and TK-II, were revealed in addition to mitochondrial TK in anion-exchange high performance liquid chromatography (HPLC) of the enzyme extract from hepatoma JB1. During incubation of the enzyme extract at 20 degrees C in the presence of phosphatase inhibitor NaF, TK-II activity remained while TK-I activity almost disappeared. Thus, TK-II appeared to be more stable than TK-I. In Western blot analysis, TK-II was much more phosphorylated and exhibiting higher specific activity than TK-I. Meanwhile, regenerating liver derived from the rat 24 h after partial hepatectomy showed only TK-I activity, which completely disappeared after incubation at 20 degrees C even in the presence of NaF. Consequently, the presence of TK-II might account for the higher TK activity in hepatomas than in regenerating liver.

Animals↗
PubMed1999

An update on the prevalence of HIV/AIDS in Bangladesh.

The National AIDS Committee was formed in 1985 to develop and support policies that prevent transmission of human immunodeficiency virus (HIV). In 1990, the Institute of Epidemiology, Disease Control and Research in the Ministry of Health began sero-surveillance for AIDS/HIV infection. Convenience sampling was conducted among prisoners, sailors, truckers, antenatal attendees, repatriated Bangladeshi workers, and brothel-based prostitutes in Dhaka. In 1994, commercial sex workers in other high-risk areas were included in surveillance activities. Among over 75,700 HIV tests through 1998, 119 have been confirmed positive for HIV. While the cumulative HIV prevalence rate was only 1.5/1,000 tests, it was significantly higher among men (p < 0.0001) than among women. The rates among men were as high as 28/1,000 tests in 1996 and 21/1,000 tests in 1997. Almost 50% of the reported HIV cases are from cities on the border of India and Myanmar. It is anticipated that HIV transmission will increase further given the high prevalence of risk behaviors, core high-risk groups, and extreme poverty.

Acquired Immunodeficiency Syndrome↗
PubMed1998

The age-associated decrease in the amount of amplifiable full-length mitochondrial DNA in human skeletal muscle.

There has been a continuous evolution in our concept [1] that mtDNA undergoes a range of mutations with age and that such alterations lead to a decline in mitochondrial bioenergy capacity. Here we report that a wide range of deletion mutations accumulate with age and the amount of full-length mtDNA (FLmtDNA) amplifiable by extra-long PCR (XL-PCR) markedly decreases with age. An analysis of single human quadriceps muscle fibres reveals a close correlation between the decrease in FLmtDNA and the decline in cytochrome c oxidase activity, an exemplifier of mitochondrial bioenergy. However, Southern blotting analysis of unamplified genomic DNA shows that there is little decrease in FLmtDNA in aged quadriceps. The results are interpreted to indicate that while there is little change in the total mtDNA with age, nonetheless a significant proportion of this mtDNA is extensively damaged such that it cannot be amplified by XL-PCR. The amplifiable FLmtDNA, which putatively represents the functional component of the mtDNA, decreases markedly with age.

Adolescent↗
PubMed1998

Increased hepatic nicotinamide N-methyltransferase activity as a marker of cancer cachexia in mice bearing colon 26 adenocarcinoma.

When a cachexigenic subclone (clone 20) of murine colon 26 adenocarcinoma was transplanted into female BALB/c mice, hepatic NNMT activity continued to increase until death in proportion to progressive carcass weight loss, a marker of cancer cachexia. On the other hand, noncachexigenic subclone (clone 5)-transplanted mice showed neither increase of NNMT activity nor carcass weight loss. Among cytostatic fluorinated pyrimidines, 5'-dFUrd could inhibit the increase of NNMT activity and prevent weight loss in mice bearing clone 20. On the other hand, 2'-dFUrd did not show these effects. 5-FUra and Tegafur inhibited the increase of NNMT activity at higher concentrations. These findings suggest that the levels of hepatic NNMT activity are closely associated with the degree of weight loss, and they appear to be a useful marker of cancer cachexia.

Adenocarcinoma↗
PubMed1997

Promotion of proliferation of murine BALB/C3T3 fibroblasts mediated by nitric oxide at lower concentrations.

This study showed that nitric oxide (NO)-generating S-nitrosothiols, S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO), increased proliferation of BALB/c 3T3 (clone A31-1-1) fibroblasts in vitro. Treatment with SNAP at a relatively low concentration (0.005-0.02 mM) induced an increase in cell number compared to control. SNAP (0.005-0.02 mM) and GSNO (0.025-0.05 mM) both showed an increase of [3H]thymidine incorporation in exponentially growing cells in a dose-dependent manner. The maximal effect was observed at about 40 and 90% above control at 0.02 mM and 0.05 mM, respectively. The increase induced by 0.02 mM SNAP was abolished by the addition of 0.01 mM oxyhemoglobin, a scavenger of NO. [3H]Thymidine incorporation in stationary cells was also increased by SNAP. In addition, 0.02 mM SNAP produced a 1.8-3.2-fold increase of thymidine kinase activity in exponentially growing cells.

3T3 Cells↗
PubMed1997

Primary structure of the smallest (6.4-kDa) subunit of human and bovine ubiquinol-cytochrome c reductase deduced from cDNA sequences.

Amino acid sequences of the smallest subunit of human and bovine ubiquinol-cytochrome c reductase were deduced from nucleotide sequence of recombinant cDNA clones isolated by screening the corresponding cDNA libraries. Both proteins were composed of 56 amino acids. They were 84% homologous to each other in the coding nucleotide sequences and 88% homologous in the amino acid sequences. Southern blot analysis with human DNA suggested the presence of a single gene coding for the protein. Northern blot of human mRNAs from different tissues confirmed the existence of a single species of transcript among the tissues but the human gene is highly expressed in bioenergetically active tissues like heart and skeletal muscle.

Amino Acid Sequence↗
PubMed1997

Resistance to mineralocorticoids in Wistar-Furth rats.

Wistar-Furth rats (WF) do not develop hypertension when treated with salt and mineralocorticoids and therefore may be useful for investigating the mechanisms of mineralocorticoid action and hypertension. In the present studies, we determined vascular and renal responses of WF to mineralocorticoids. Control Wistar rats (W) developed deoxycorticosterone acetate (DOCA)-NaCl and dexamethasone hypertension, whereas WF rats developed dexamethasone hypertension only. Aldosterone treatment of vascular smooth muscle cells cultured from WF resulted in 82% less upregulation of angiotensin II radioligand binding, 50% less induction of angiotensin II AT1a receptor mRNA, and 76% less potentiation of angiotensin II-stimulated inositol phosphates than did aldosterone treatment of cells from W. Similarly, DOCA-NaCl potentiated angiotensin II- and phenylephrine-stimulated contractions in aortic rings from W but not from WF. Although DOCA-NaCl treatment affected hypokalemia to an equal degree in WF and W, increases in renal citrate synthase activity (a specific renal mineralocorticoid response) were greater in W than in WF. WF manifest a partial defect in mineralocorticoid responsiveness in vascular smooth muscle and, possibly, in the kidney.

Aldosterone↗
PubMed1996

Users of traditional methods of contraception in Bangladesh: 1981-91.

This paper examines the changing patterns of knowledge, attitude and use of traditional methods of contraception, compared to modern methods, over the last five contraceptive prevalence surveys in Bangladesh (1981-91). The results show that knowledge of at least one method of family planning is universal in Bangladesh and usage is higher at all ages for women who are using modern methods than for those who are using traditional methods. Educated women and those in employment are more likely to use modern contraceptive methods.

Adolescent↗
PubMed1995

Adolescent contraceptive use and its determinants in Bangladesh: evidence from Bangladesh Fertility Survey 1989.

This study is concerned with contraceptive use among the currently married adolescents in Bangladesh utilizing the 1989 Bangladesh Fertility Survey (BFS) data. The study analyzes the factors affecting the current use of contraception among the adolescents through bivariate and multivariate logistic regression analysis. The results indicate that although adolescents have almost universal knowledge about contraceptive methods, only 15 percent are currently using any method of contraception. The corresponding figures for the adults and for the nation as a whole are 34.4 percent and 31.4 percent, respectively. Among the individual methods currently used by the adolescents, the pill appears as the most popular method, followed by safe period. A substantial proportion of the adolescents were found to rely on the traditional methods of contraception. Among the socio-economic variables (as revealed by the logistic regression analysis), respondents' education, participation in the family planning decision, visit by family planning workers, region of residence, husband's occupation and possession of electricity in the household appear as the most significant factors determining the current use of contraception among the adolescents.

Adolescent↗
PubMed1994

Pathology of shigellosis and its complications.

One hundred and thirty-three colonic biopsies of proven cases of Shigella colitis were examined and post-mortem examinations were carried out on 29 fatal cases at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) hospital between 1988 and 1992. The distribution of pathological lesions and the spectrum of histopathological changes in the intestinal tract of these patients, and the features of intestinal and extra-intestinal complications of shigellosis are presented. Septicaemia, hyponatraemia, hypokalaemia and hypoglycaemia were present in a high percentage of these cases. All but two patients were malnorished at the time of autopsy. Shigellosis patients rapidly became hypoproteinaemic and were susceptible to other infections including opportunistic infections. Mortality amongst shigellosis patients admitted to our hospital continues to be high in spite of adequate antibiotic and supportive therapy.

Adult↗