Biomedical subjects

Rashidul Haque

Publications and source records attributed to Rashidul Haque.

At least 19 recordsLinked to original sources

PubMed2006

Diagnosis of amebiasis in Bangladesh.

Diagnosis of amebiasis by microscopic identification of the parasite in stool and liver abscess pus is insensitive and unable to distinguish the invasive parasite E. histolytica from the commensal parasites such as E. dispar and E. moshkovskii. New approaches to the detection of E. histolytica are based on detection of E. histolytica-specific antigen and DNA in stool and other clinical samples. Several molecular diagnostic tests for diagnosis of amebiasis have been developed and used to diagnose E. histolytica in Bangladesh. We have compared the TechLab E. histolytica-specific antigen detection test with PCR assays and with isoenzyme analysis of cultured amebas. The PCR assays are based on amplification of the multi-copy small subunit ribosomal RNA gene of E. histolytica and E. dispar. PCR assays and antigen detection test had comparable sensitivities when performed directly on fresh stool specimens. The correlation of antigen detection with PCR assays for identification of E. histolytica was excellent. TechLab's E. histolytica- specific antigen detection test was both rapid and simple to perform, making it appropriate for use in the developing world, where amebiasis is most prevalent.

Animals↗

PubMed2005

Giardia assemblage A infection and diarrhea in Bangladesh.

Giardia lamblia is the most prevalent human intestinal protozoan worldwide, but only a minority of infections result in diarrhea. We tested here whether the 2 major G. lamblia genotypes, assemblages A and B, differ in their propensity to cause disease. To determine whether an association exists between infection with assemblage A or B and diarrhea, 2534 Bangladeshi patients were enrolled in a case-control study. A total of 322 Giardia infections were identified and assayed for genotype by real-time polymerase chain reaction. Higher odds ratios for diarrhea were observed for assemblage A and A2 infections, whereas higher parasite DNA loads and a higher overall prevalence were observed for assemblage B infections. Our findings indicate that genotypic differences in virulence and fecundity may help to explain why not every Giardia infection results in disease, but they need to be confirmed in other urban populations of the developing world.

Animals↗

PubMed2005

Circadian clocks, clock networks, arylalkylamine N-acetyltransferase, and melatonin in the retina.

Circadian clocks are self-sustaining genetically based molecular machines that impose approximately 24h rhythmicity on physiology and behavior that synchronize these functions with the solar day-night cycle. Circadian clocks in the vertebrate retina optimize retinal function by driving rhythms in gene expression, photoreceptor outer segment membrane turnover, and visual sensitivity. This review focuses on recent progress in understanding how clocks and light control arylalkylamine N-acetyltransferase (AANAT), which is thought to drive the daily rhythm in melatonin production in those retinas that synthesize the neurohormone; AANAT is also thought to detoxify arylalkylamines through N-acetylation. The review will cover evidence that cAMP is a major output of the circadian clock in photoreceptor cells; and recent advances indicating that clocks and clock networks occur in multiple cell types of the retina.

Animals↗

PubMed2005

Ascariasis is a zoonosis in denmark.

A preliminary epidemiological survey indicated an association between Ascaris infections in Danish patients and contact with pigs or pig manure. In the present study, we compared Ascaris worms collected from humans and Ascaris worms collected from pigs by amplified fragment length polymorphism (AFLP) analysis, a technique for whole-genome fingerprinting, and by PCR-linked restricted fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer region of nuclear rDNA. The AFLP data were analyzed by distance- and model-based clustering methods. These results assigned Ascaris worms from Danish patients to a cluster different from that for worms from humans in other geographic areas. In contrast, worms from humans and pigs in Denmark were assigned to the same cluster. These results were supported by the PCR-RFLP results. Thus, all of the examined Danish patients had acquired Ascaris infections from domestic pigs; ascariasis may therefore be considered a zoonotic disease in Denmark.

Animals↗

PubMed2005

Multiplex real-time PCR assay using Scorpion probes and DNA capture for genotype-specific detection of Giardia lamblia on fecal samples.

Two major genotypic assemblages of Giardia lamblia infect humans; the epidemiologic significance of this phenomenon is poorly understood. We developed a single-vessel multiplex real-time PCR (qPCR) assay that genotypes Giardia infections into assemblages A and/or B directly from fecal samples. The assay utilized Scorpion probes that combined genotype-specific primers and probes for the 18S rRNA gene into the same molecule. The protocol was capable of detecting as few as 20 trophozoites per PCR on fecal DNA isolated using a commercial method or 1.25 trophozoites per PCR on fecal DNA isolated using a G. lamblia-specific oligonucleotide capture technique. The assay was specific for fecal specimens, with no amplification of the discordant genotype with the opposite Scorpion probe. When 97 clinical specimens from Bangladesh were used, the multiplex PCR assay detected 95% (21 of 22) of Giardia microscopy-positive specimens and 18% (13 of 74) of microscopy-negative specimens. Microscopy-negative and qPCR-positive specimens had higher average cycle threshold values than microscopy-positive and qPCR-positive specimens, suggesting that they represented true low-burden infections. Most (32 of 35) infections were assemblage B infections. This single-reaction multiplex qPCR assay distinguishes assemblage A Giardia infections from assemblage B infections directly on fecal samples and may aid epidemiologic investigation.

Animals↗

PubMed2005

Real-time-PCR assay for diagnosis of Entamoeba histolytica infection.

We developed a real-time-PCR assay utilizing a molecular-beacon probe for the detection of Entamoeba histolytica and compared its sensitivity to stool antigen detection and traditional PCR. A total of 205 stool and liver abscess pus specimens from patients and controls were used for this purpose, 101 (49%) of which were positive by the TechLab E. histolytica-specific antigen detection test, while the other 104 (51%) stool and liver abscess pus specimens were negative by the antigen detection test. DNA was extracted from the stool and liver abscess pus specimens by the QIAGEN method and the small-subunit rRNA gene of E. histolytica and then amplified by traditional and real-time PCR. Out of these 205 stool and liver abscess pus specimens, 124 were positive by the real-time-PCR assay and 90 were positive by the traditional-PCR test. Compared to the real-time-PCR assay, the antigen detection test was 79% sensitive and 96% specific. When the traditional-PCR test results were compared to the real-time-PCR assay, the sensitivity of traditional PCR was 72% and the specificity was 99%. In conclusion, all three methods for the detection of E. histolytica were highly specific, with real-time PCR being the most sensitive.

Animals↗

PubMed2005

Coding and noncoding genomic regions of Entamoeba histolytica have significantly different rates of sequence polymorphisms: implications for epidemiological studies.

To evaluate genetic variability among Entamoeba histolytica strains, we sequenced 9,077 bp from each of 14 isolates. The polymorphism rates from coding and noncoding regions were significantly different (0.07% and 0.37%, respectively), indicating that these regions are subject to different selection pressures. Additionally, single nucleotide polymorphisms (SNPs) potentially associated with specific clinical outcomes were identified.

Animals↗

PubMed2005

Risk factors for kala-azar in Bangladesh.

Since 1990, South Asia has experienced a resurgence of kala-azar (visceral leishmaniasis). To determine risk factors for kala-azar, we performed cross-sectional surveys over a 3-year period in a Bangladeshi community. By history, active case detection, and serologic screening, 155 of 2,356 residents had kala-azar with onset from 2000 to 2003. Risk was highest for persons 3-45 years of age, and no significant difference by sex was seen. In age-adjusted multivariable models, 3 factors were identified: proximity to a previous kala-azar patient (odds ratio [OR] 25.4, 95% confidence interval [CI] 15-44 within household; OR 3.2 95% CI 1.7-6.1 within 50 m), bed net use in summer (OR 0.7, 95% CI 0.53-0.93), and cattle per 1,000 m2 (OR 0.8, 95% CI 0.70-0.94]). No difference was seen by income, education, or occupation; land ownership or other assets; housing materials and condition; or keeping goats or chickens inside bedrooms. Our data confirm strong clustering and suggest that insecticide-treated nets could be effective in preventing kala-azar.

Adolescent↗

PubMed2004

Influence of human leukocyte antigen class II alleles on susceptibility to Entamoeba histolytica infection in Bangladeshi children.

BACKGROUND: The association of antibody responses with both innate and acquired immunity to amebiasis indicate that CD4+ T cells play a role in protection against Entamoeba histolytica infection. To test this hypothesis, we compared the genotype frequencies of human leukocyte antigen (HLA) class II alleles in a cohort of Bangladeshi children intensively monitored for E. histolytica infection for a 3-year period. METHODS: Using logistic regression, we calculated the odds of disease by genotype and by haplotype. RESULTS: The DQB1*0601 heterozygous and homozygous genotypes were found in 55% of E. histolytica-negative children but in only 34% of E. histolytica-positive children (overall odds ratio, 2.39; 95% confidence interval [CI], 1.26-4.54). Children who were heterozygous for the DQB1*0601/DRB1*1501 haplotype were 10.1 times (95% CI, 2.02-50.6) more likely to be both E. histolytica negative and serum anti-lectin immunoglobulin G negative at baseline. Other DQB1 and DRB1 alleles (DQB1*0202, DQB1*0301, and DRB1*0701) were not associated with any of the clinical outcomes related to amebiasis. CONCLUSION: A potential protective association was observed with the HLA class II allele DQB1*0601 and the heterozygous haplotype DQB1*0601/DRB1*1501. This association may explain why amebiasis does not occur in some children who are exposed to the parasite and implicates HLA class II-restricted immune responses in protection against E. histolytica infection.

Alleles↗

PubMed2004

Visceral leishmaniasis: consequences to women in a Bangladeshi community.

Visceral leishmaniasis (VL) or kala-azar (KA) affects the rural poor, causing significant morbidity and mortality. We examined the epidemiological and social impact of KA in an affected village in Bangladesh. A population-based survey of the village residents showed a case fatality rate of 14.7% among females and 5.3% among males. Before initiation of the study, female patients were ill longer than males before they received treatment. Future work needs to focus on understanding the implications of KA on women and to develop sustainable strategies for appropriate and timely access to treatment.

Adolescent↗

PubMed2003

Polymerase chain reaction-based genotype classification among human Blastocystis hominis populations isolated from different countries.

Since the genotype of human Blastocystis hominis isolates is highly polymorphic, PCR-based genotype classification using known sequenced-tagged site (STS) primers would allow the identification or classification of different genotypes. Five populations of human B. hominis isolates obtained from Japan, Pakistan, Bangladesh, Germany, and Thailand were subjected to genotype analysis by using seven kinds of STS primers. Ninety-nine out of 102 isolates were identified as one of the known genotypes, while one isolate from Thailand showed two distinct genotypes and two isolates from Japan were negative with all the STS primers. The most dominant genotype among four populations, except for all four isolates from Thailand, was subtype 3 and it varied from 41.7% to 92.3%. The second most common genotype among four populations was either subtype 1 (7.7-25.0%) or subtype 4 (10.0-22.9%). Subtype 2, subtype 5, and/or subtype 7 were only rarely detected among the isolates from Japan and Germany, while subtype 6 was not detected. The phylogenetic position of the two isolates which were negative with all STS primers, was inferred from the small subunit rRNA (SSU rRNA) genes with the known sequence data of 20 Blastocystis isolates. Since the two isolates were positioned in an additional clade in the phylogenetic tree, this suggested they were a new genotype. These results demonstrated that PCR-based genotype classification is a powerful tool with which to analyse genotypes of Blastocystis isolates obtained from clinical samples. In addition, two groups of the isolates from 15 symptomatic and 11 asymptomatic patients in Bangladesh were compared with the PCR-based subtype classification. Since both groups were only classified into two distinct genotypes of subtype 1 or subtype 3 and no statistically significant difference was observed between the two groups, in this study it could not be shown that the specific genotype correlated with the pathogenic potential of B. hominis.

Animals↗

PubMed2003

Amebiasis.

Explore the source record for details and available documents.

Amebicides↗

PubMed2003

Diurnal regulation of arylalkylamine N-acetyltransferase activity in chicken retinal cells in vitro: analysis of culture conditions.

PURPOSE: Arylalkylamine N-acetyltransferase (AANAT) is a key regulatory enzyme in the synthesis of melatonin, which displays daily fluctuations in chicken retinal photoreceptors in vivo. The purpose of the present study was to determine if cultures of embryonic neural retina cells express diurnal rhythms of AANAT activity. METHODS: Cell cultures were prepared from chick embryonic day 6 neural retina and incubated for 4 to 8 days in vitro (DIV). Cells were incubated under a daily light-dark (LD) cycle and were harvested day and night. Culture conditions were modified to test the effects of cell density, serum concentration, incubation temperature, S-(4-nitrobenzyl)-6-thioinosine (NBTI), and taurine on AANAT activity. AANAT activity was assayed in cell homogenates by measuring the catalytic formation of N-acetyltryptamine from tryptamine and acetyl coenzyme A. RESULTS: Cells cultured in medium containing 10% fetal bovine serum (FBS) failed to show any diurnal fluctuation in AANAT activity on DIV 5 and 6. However, if the culture medium was replaced on DIV 4 with one containing 1% FBS, and 5 microM NBTI or 5 mM taurine, the cells expressed significant diurnal rhythms of enzyme activity. NBTI was more potent and effective than taurine. Culture conditions were optimized with respect to cell density, serum concentration, incubation temperature, and NBTI concentration. Under optimized conditions, overall cell survival and the density of photoreceptor cells were increased relative to that with the other culture conditions tested. CONCLUSIONS: The results indicate that diurnal rhythms of AANAT activity are expressed in embryonic retinal cells incubated under particular culture conditions. The results show that the mechanisms regulating melatonin synthesis in chicken retinal cells are established during early embryonic life. This culture preparation will be useful in elucidating the photic control mechanisms involved in regulation of melatonin biosynthesis in photoreceptor cells.

Animals↗

PubMed2003

Temporal-spatial characterization of chicken clock genes: circadian expression in retina, pineal gland, and peripheral tissues.

The molecular core of the vertebrate circadian clock is a set of clock genes, whose products interact to control circadian changes in physiology. These clock genes are expressed in all tissues known to possess an endogenous self-sustaining clock, and many are also found in peripheral tissues. In the present study, the expression patterns of two clock genes, cBmal1 and cMOP4, were examined in the chicken, a useful model for analysis of the avian circadian system. In two tissues which contain endogenous clocks--the pineal gland and retina--circadian fluctuations of both cBmal1 and cMOP4 mRNAs were observed to be synchronous; highest levels occurred at Zeitgeber time 12. Expression of these genes is also rhythmic in several peripheral tissues; however, the phases of these rhythms differ from those in the pineal gland and retina: in the liver the peaks of cMOP4 and cBmal1 mRNAs are delayed 4-8 h and in the heart they are advanced by 4 h, relative to those in the pineal gland and retina. These results provide the first temporal characterization of cBmal1 and cMOP4 mRNAs in avian tissues: their presence in avian peripheral tissues indicates they may influence temporal features of daily rhythms in biochemical, physiological, and behavioral functions at these sites.

ARNTL Transcription Factors↗

PubMed2003

Entamoeba moshkovskii infections in children, Bangladesh.

Entamoeba moshkovskii cysts are morphologically indistinguishable from those of the disease-causing species E. histolytica and the nonpathogenic E. dispar. Although sporadic cases of human infection with E. moshkovskii have been reported, the organism is considered primarily a free-living amoeba. No simple molecular detection tool is available for diagnosing E. moshkovskii infections. We used polymerase chain reaction (PCR) to detect E. moshkovskii directly in stool. We tested 109 stool specimens from preschool children in Bangladesh by PCR; 17 were positive for E. histolytica (15.6%) and 39 were positive for E. dispar (35.8%). In addition, we found that 23 (21.1%) were positive for E. moshkovskii infection, and 17 (73.9%) of these also carried E. histolytica or E. dispar. The high association of E. moshkovskii with E. histolytica and E. dispar may have obscured its identification in previous studies. The high prevalence found in this study suggests that humans may be a true host for this amoeba.

Animals↗

PubMed2003

Epidemiologic and clinical characteristics of acute diarrhea with emphasis on Entamoeba histolytica infections in preschool children in an urban slum of Dhaka, Bangladesh.

The epidemiology, clinical features, nutritional status, and causative agents of diarrhea were studied in 289 Bangladeshi children (147 boys and 142 girls) 2-5 years old. The use of improved diagnostic tests for amebiasis enabled for the first time analysis of the contribution of Entamoeba histolytica to total diarrheal illness in this community setting. The average incidence rate of diarrhea was 1.8/child-year, and the average number of diarrheal days was 3.7 days/child-year over an average observation period of 2.8 years/child. Seventy-five percent of the diarrheal episodes were < or = 2 days in duration. Persistent diarrhea was relatively uncommon (0.2% of the children) and chronic diarrhea was observed in only one episode. Compared with malnourished and/or stunted children, better-nourished children experienced significantly fewer diarrheal episodes. The diarrheal incidence rate for children with blood group A was significantly less that that of the children with blood groups O and AB. The most frequent bacterial enteropathogens isolated from diarrheal stool specimens were enterotoxigenic Escherichia coli (9%) and Aeromonas species (9%), followed by Plesimonas shigelloides (4%) and Shigella flexneri (3.8%). Rotavirus was the most common viral agent isolated from diarrheal stool samples (5%). Giardia lamblia, Cryptosporidium parvum, and E. histolytica were identified in 11%, 8.4%, and 8%, respectively, of the diarrheal stool specimens. Dysentery was observed in 7.7% of all diarrheal episodes. The most common pathogens isolated from dysenteric stool were S. flexneri (11.6%), Aeromonas sp. (10%), E. histolytica (8.7%), Campylobacter jejunii (5.8%), P. shigelloides (4.3%), and A. caviae (4.3%). The overall incidence rate of E. histolytica-associated diarrhea was 0.08/child-year. Visible blood and hemoccult test-detected blood loss was found in 7% and 25%, respectively, of cases of E. histolytica-associated diarrhea. Children who had recovered from a diarrheal episode with E. histolytica, but not E. dispar, had half the chance of developing subsequent E. histolytica-associated diarrhea, consistent with the development of species-specific acquired immunity. In conclusion, the use of modern diagnostic tests demonstrated that E. histolytica contributed to overall morbidity from diarrheal illness. Understanding the etiology, frequency, and consequences of acute diarrhea in children from a developing country should aid in the design of interventions to improve child health.

Age Distribution↗

PubMed2003

Visceral leishmaniasis: consequences of a neglected disease in a Bangladeshi community.

Visceral leishmaniasis, or kala azar (KA), affects the rural poor, causing significant morbidity and mortality. We examined the epidemiologic, social, and economic impact of KA in a village in Bangladesh. A population-based survey among 2,348 people demonstrated a KA incidence of 2% per year from 2000 to 2002, with a case-fatality rate of 19% among adult women, compared with 6-8% among other demographic groups. Kala azar cases were geographically clustered in certain sections of the village. Anti-leishmanial drug shortages and the high cost of diagnosis and treatment caused substantial emotional and economic hardship for affected families. Communities wanted to learn more about KA, and were willing to take collective action to confront the problems it causes. To decrease the KA burden in endemic areas, community efforts should be supplemented with effective treatment programs to ensure access to appropriate and affordable diagnosis and case management.

Adolescent↗

PubMed2002

Dual regulation of cryptochrome 1 mRNA expression in chicken retina by light and circadian oscillators.

The localization and regulation of chicken cryptochrome 1 (cCry1) mRNA expression in retina was investigated by laser capture microdissection and quantitative real-time RT-PCR. Laser capture microdissection (LCM) of retinal cell layers showed the highest level of cCry1 expression in the ganglion cell and photoreceptor layers. In both layers, expression was high during the daytime and low at night in subjects exposed to a 12:12 h light:dark cycle. Robust circadian oscillations of cCry1 mRNA levels were observed in constant (24 h day) light, but not in constant darkness, with the highest expression during daytime at zeitgeber time (ZT) 8. Unlike cCry1, circadian rhythms of the melatonin-synthesizing enzyme, arylalkylamine N-acetyltransferase, persisted in constant darkness, suggesting that rhythmic cCry1 expression is not essential for circadian clock function or output. On the second day of constant darkness, when cCry1 expression is arrhythmic, light exposure for 2 h significantly increased retinal cCry1 mRNA levels at ZT 4 and 8, times that cCry1 expression is induced in LD and LL. Similar light exposure ending at ZT 20 had no significant effect. Thus, expression of cCry1 mRNA is regulated dually by light and circadian clocks.

Adaptation, Ocular↗