Biomedical subjects

Rashidul Haque

Publications and source records attributed to Rashidul Haque.

At least 19 recordsLinked to original sources

PubMed2006

Evidence for a link between parasite genotype and outcome of infection with Entamoeba histolytica.

The factors determining whether a person infected with Entamoeba histolytica develops disease remain obscure. To investigate whether the parasite genome contributes to the outcome, we have investigated the distribution of parasite genotypes among E. histolytica-infected individuals in Bangladesh. Samples were obtained from individuals who either were asymptomatic, had diarrhea/dysentery, or had developed a liver abscess. Genotypes were determined by using six tRNA-linked polymorphic markers, and their distributions among the three sample groups were evaluated. A significant population differentiation in the genotype distribution was found for four of the six individual markers as well as for the combined genotypes, suggesting that the parasite genome does contribute in some way to the outcome of infection with E. histolytica. The markers themselves do not indicate the nature of the underlying genetic differences, but they may be linked to loci that do have an impact on the outcome of infection.

Animals↗

PubMed2006

Evaluation of Entamoeba histolytica antigen and antibody point-of-care tests for the rapid diagnosis of amebiasis.

The bedside diagnosis of amebiasis could improve patient care. In Bangladesh and Vietnam, a novel and simple-to-use Entamoeba histolytica rapid antigen test had 97% sensitivity and 100% specificity compared to the results of a standard enzyme-linked immunosorbent assay antigen detection method, and a rapid antibody test had 89 to 100% sensitivity and 89 to 95% specificity.

Animals↗

PubMed2006

Temporal coupling of cyclic AMP and Ca/calmodulin-stimulated adenylyl cyclase to the circadian clock in chick retinal photoreceptor cells.

cAMP signaling pathways play crucial roles in photoreceptor cells and other retinal cell types. Previous studies demonstrated a circadian rhythm of cAMP level in chick photoreceptor cell cultures that drives the rhythm of activity of the melatonin synthesizing enzyme arylalkylamine N-acetyltransferase and the rhythm of affinity of the cyclic nucleotide-gated channel for cGMP. Here, we report that the photoreceptor circadian clock generates a rhythm in Ca(2+)/calmodulin-stimulated adenylyl cyclase activity, which accounts for the temporal changes in the cAMP levels in the photoreceptors. The circadian rhythm of cAMP in photoreceptor cell cultures is abolished by treatment with the l-type Ca(2+) channel antagonist nitrendipine, while the Ca(2+) channel agonist, Bay K 8644, increased cAMP levels with continued circadian rhythmicity in constant darkness. These results indicate that the circadian rhythm of cAMP is dependent, in part, on Ca(2+) influx. Photoreceptor cell cultures exhibit a circadian rhythm in Ca(2+)/calmodulin-stimulated adenylyl cyclase enzyme activity with high levels at night and low levels during the day, correlating with the temporal changes of cAMP in these cells. Transcripts encoding two of the Ca(2+)/calmodulin-stimulated adenylyl cyclases, type 1 and type 8 (Adcy1 and Adcy8), displayed significant daily rhythms of mRNA expression under a light-dark cycle, but only the Adcy1 transcript rhythm persisted in constant darkness. Similar rhythms of Adcy1 mRNA level and Ca(2+)/calmodulin-stimulated adenylyl cyclase activity were observed in retinas of 2-week-old chickens. These results indicate that a circadian clock controls the expression of Adcy1 mRNA and Ca(2+)/calmodulin-stimulated adenylyl cyclase activity; and calcium influx into these cells gates the circadian rhythm of cAMP, a key component in the regulation of photoreceptor function.

Adenylyl Cyclases↗

PubMed2006

Photic regulation of arylalkylamine N-acetyltransferase binding to 14-3-3 proteins in retinal photoreceptor cells.

14-3-3 proteins are a ubiquitous, highly conserved family of chaperone proteins involved in signal transduction, regulation of cell cycle, intracellular trafficking/targeting, cytoskeletal structure, and transcription. Although 14-3-3 proteins are among the most abundant proteins in the CNS, very little is known about their functional roles in the vertebrate retina. In the present study, we demonstrated that photoreceptors express 14-3-3 protein(s) and identified a 14-3-3 binding partner in photoreceptor cells, the melatonin-synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT). Importantly, our data demonstrate that the binding of 14-3-3 to AANAT is regulated by light, with dramatic functional consequences. During the night in darkness, retinal AANAT is phosphorylated and forms a complex with 14-3-3 proteins with an apparent molecular weight of approximately 90 kDa. Phosphorylation of AANAT facilitates the binding of enzyme to 14-3-3 proteins. Within the complex, AANAT is catalytically activated and protected from dephosphorylation and degradation. Light disrupts the AANAT/14-3-3 complex, leading to catalytic inactivation, dephosphorylation, and proteolytic degradation of the enzyme. In the presence of the proteasome inhibitor, lactacystin, light results in the formation of a high molecular weight complex (>150 kDa), which may represent an intermediate in the AANAT degradation process. These findings provide new insight into the roles of 14-3-3 proteins in photoreceptor cells and to the mechanisms controlling melatonin synthesis in the vertebrate retina.

14-3-3 Proteins↗

PubMed2006

Entamoeba histolytica-associated diarrheal illness is negatively associated with the growth of preschool children: evidence from a prospective study.

The enteric protozoa, Cryptosporidium, Giardia and Entamoeba histolytica, cause diarrhea in children. We investigated the association of enteric protozoan-associated diarrheal illness with the nutritional status and growth of preschool children in Dhaka, Bangladesh. The subjects were 221 children aged 2-5 years who were followed prospectively for diarrheal illness for 3 years. The weight and height of the children were measured at entry and at 4-month intervals. Cryptosporidium and E. histolytica were diagnosed with commercially available stool antigen detection kits. Giardia was diagnosed by conventional microscopy. Cryptosporidium- and Giardia-associated diarrheal illness was not associated with the growth of the children. Children with E. histolytica-associated diarrheal illness had lower weight for age Z-score changes (-0.103+/-0.120 vs. 0.176+/-0.052, P=0.038). Similarly, the change in height for age Z-score was lower in children with E. histolytica-associated diarrheal illness (-0.348+/-0.186 vs. 0.142+/-0.08, P=0.018). Children with E. histolytica-associated diarrheal illness were 2.93 times (95% CI 1.01-8.52, P=0.047) more likely to be malnourished and 4.69 times (95% CI 1.55-14.18, P=0.006) more prone to be stunted. Entamoeba histolytica-associated diarrheal illness was negatively associated with the growth of preschool children.

Age Factors↗

PubMed2006

Circadian clockwork machinery in neural retina: evidence for the presence of functional clock components in photoreceptor-enriched chick retinal cell cultures.

PURPOSE: Circadian clocks in retinas regulate a variety of biochemical and physiological processes. Retinal neurons, particularly photoreceptor cells, are thought to contain autonomous circadian clocks that control iodopsin expression, cFos expression, cAMP levels, and melatonin synthesis. Photoreceptor-enriched cell cultures prepared from chick embryo retina and entrained to a daily light-dark (LD) cycle exhibit circadian rhythms of cAMP levels and the activity of arylalkylamine N-acetyltransferase (AANAT), a key regulatory enzyme in melatonin synthesis. The present study was conducted to investigate the expression of circadian clockwork machinery comprised of clock genes; a clock-controlled gene, Aanat; and a clock output, melatonin, in the photoreceptor-enriched cultured retinal cells. METHODS: Photoreceptor-enriched cell cultures were prepared from E6 neural retinas and incubated under 14 h:10 h light-dark cycle (LD) of illumination for 8 days and then transferred to constant (24 h/day) darkness (DD). Cells were collected every 4 h in LD and DD, and RNA was isolated. cDNA was prepared from each sample and transcripts of clock genes and Aanat were measured using real-time polymerase chain reaction (PCR). Melatonin release into the culture medium was assayed by HPLC with fluorescence detection at intervals of 3 h in LD and DD. RESULTS: Cultured neural retina cells exposed to a light-dark cycle showed rhythmic expression of clock genes. Bmal1 and Npas2 (also known as Mop4) peaked late in the day in LD and in DD. Clock mRNA was high at night in LD, but arrhythmic in DD. Cry1 and Per2 transcripts increased rapidly in the early morning and were low at night. The rhythm of Per2 was reduced in amplitude in constant darkness (DD). Levels of Cry1 and Per2 transcripts were stimulated by light exposure at night. Melatonin release and Aanat mRNA were low during the day and high at night. Rhythmic expression of clock genes and Aanat was not observed in cultures not exposed to a LD cycle but treated otherwise identically to cultures described above. CONCLUSIONS: Photoreceptor-enriched cell cultures derived from chick embryo neural retina contain a complete circadian clockwork system that is entrained by the light-dark cycle, and has a core timekeeping mechanism and circadian output in the form of melatonin synthesis.

ARNTL Transcription Factors↗

PubMed2006

Multiplex analysis of circulating cytokines in the sera of patients with different clinical forms of visceral leishmaniasis.

BACKGROUND: The clinical spectrum of visceral leishmaniasis (VL), a chronic intracellular parasitic disease, ranges from a subclinical, asymptomatic infection to severe clinical disease (kala-azar). In experimental leishmaniasis, mice that have a Th1 response to infection tend to have limited disease while a Th2 response is associated with disease progression. Humans with VL most often have mixed rather than polarized responses. However, most clinical studies have used methods that require a relatively large sample volume, thus limiting their scope. Measuring multiple cytokine levels in blood samples using a multiplexed microsphere assay (MMA) may be useful to further evaluate the Th1/Th2 paradigm in humans. METHODS: Bangladeshi individuals (n=120) living in an area endemic for VL were categorized into one of the five clinical categories. Sera from these individuals were measured for levels of IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-gamma, and TNF-alpha by multiplexed microsphere cytokine immunoassay. RESULTS: Circulating IL-8, IL-10, and IL-12 differed significantly among the clinical groups. Persons with kala-azar demonstrated the highest median levels of IL-8 and IL-10 but lower median levels of IL-12. CONCLUSIONS: The MMA for cytokines is an extremely time-and sample-efficient method for characterizing circulating cytokine levels in visceral leishmaniasis patients.

Adult↗

PubMed2006

[In vitro antimalarial drug resistance in Southeastern Bangladesh].

Particularly in Southeast Asia drug resistance has become a major constraint in the treatment of falciparum malaria. So far relatively little is known about the current status of drug resistance in Bangladesh. The aim of this study was therefore to determine the in vitro drug susceptibility of Plasmodium falciparum in south-eastern Bangladesh. In the HRP2 in vitro drug sensitivity assay the tested isolates demonstrated a relatively high sensitivity to dihydroartemisinine (IC50 = 1.33 nM; 95% CI: 1.08-1.63; IC90 = 2.65 nM; 95% CI: 2.13-3.29), mefloquine (IC50 = 11.26 nM, 95% CI: 9.75-13.0; IC90 = 19.55 nM, 95% CI: 15.73-24.29) and quinine (IC50 = 73.24 nM, 95% CI: 65.26-82.21; IC90 = 157.75 nM, (95% CI: 134.16-185.5) thus being significantly more sensitive to mefloquine and quinine than isolates from Thailand. Chloroquine (IC50 = 93.06 nM, 95% CI: 80.38-107.76; IC90 = 214.76 nM, 95% CI: 175.64-262.62) sensitivity was highly compromised with inhibitory concentrations reaching levels comparable to Thailand. Therefore this drug should not be used in the treatment of falciparum malaria in this region. Despite compromised in vitro drug sensitivity to sulfadoxine/pyrimethamine, in clinical studies the combination of sulfadoxine (IC50 = 40.46 microM, 95% CI: 31.15-51.97; IC90 = 173.48 microM, 95% CI: 120.78-249.17) and pyrimethamine (IC50 = 1.7 microM, 95% CI: 1.25-2.3; IC90 = 4.83 microM, 95% CI: 3.17-7.37) with quinine proved to be an interesting option for treating uncomplicated falciparum malaria in Bangladesh.

Adolescent↗

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↗

PubMed2006

Real-time PCR detection and speciation of Cryptosporidium infection using Scorpion probes.

At least eight species of Cryptosporidium can cause human infection and disease. A real-time PCR (qPCR) assay based on the 18S rRNA gene and utilizing a Scorpion probe was developed to detect all human-pathogenic Cryptosporidium without the usual need for nested amplification. Sensitivity of detection in stool samples was highest using a glass bead-based DNA extraction method (under 10(3) oocysts per stool sample). The assay was validated against 123 human stool specimens from Bangladesh and Tanzania, exhibited a sensitivity and specificity of >91% versus microscopy, and detected an additional eight microscopy-negative infections. Cryptosporidium parvum-specific and Cryptosporidium meleagridis-specific Scorpion qPCR assays that provided 100% accurate speciation compared with VspI RFLP analysis and sequencing were developed subsequently. These Scorpion probe qPCR assays are simpler to perform than existing nested PCR and RFLP methods for diagnosis and epidemiological investigation of cryptosporidiosis.

Animals↗

PubMed2006

The economic impact of visceral leishmaniasis on households in Bangladesh.

OBJECTIVES: To explore current patterns of diagnosis and treatment, quantify household economic impact and identify household strategies to cover the costs of visceral leishmaniasis (VL) care in rural Bangladesh. METHOD: Structured interviews with 113 VL patients from 87 households documenting all provider visits and expenditures for health care for VL, and the ways in which the expenditures were covered. RESULTS: Patients paid a median of 7 visits to six different providers before beginning VL treatment. All visited the subdistrict government hospital at least once. While health care, including antileishmanial drug therapy, is officially available free of charge at government facilities, 79% of patients reported making informal payments for provider access, diagnostics and drug administration; only 14% of patients received their full drug course from this source. For the 58% of patients who purchased the full treatment course, drug cost constituted 34% of direct expenditure. Median direct expenditure for one VL patient was US$87 and median income lost was $40; median total expenditure was 1.2 times annual per capita income of our study population. Households employed multiple coping strategies to cover expenditures, most commonly sale or rental of assets (62%) and taking out loans (64%). CONCLUSIONS: Visceral leishmaniasis treatment causes a major economic burden in affected families. Control strategies for VL should facilitate timely, affordable diagnosis and treatment of patients to decrease the infection reservoir and to alleviate the economic burden of VL on households.

Adaptation, Psychological↗

PubMed2006

Entamoeba histolytica infection in children and protection from subsequent amebiasis.

The contribution of amebiasis to the burden of diarrheal disease in children and the degree to which immunity is acquired from natural infection were assessed in a 4-year prospective observational study of 289 preschool children in an urban slum in Dhaka, Bangladesh. Entamoeba histolytica infection was detected at least once in 80%, and repeat infection in 53%, of the children who completed 4 years of observation. Annually there were 0.09 episodes/child of E. histolytica-associated diarrhea and 0.03 episodes/child of E. histolytica-associated dysentery. Fecal immunoglobulin A (IgA) anti-parasite Gal/GalNAc lectin carbohydrate recognition domain (anti-CRD) was detected in 91% (183/202) of the children at least once and was associated with a lower incidence of infection and disease. We concluded that amebiasis was a substantial burden on the overall health of the cohort children. Protection from amebiasis was associated with a stool anti-CRD IgA response. The challenge of producing an effective vaccine will be to improve upon naturally acquired immunity, which does not provide absolute protection from reinfection.

Animals↗

PubMed2006

Cognitive effects of diarrhea, malnutrition, and Entamoeba histolytica infection on school age children in Dhaka, Bangladesh.

Cognitive function was assessed in 191 Bangladeshi children 6-9 years of age using verbal and nonverbal tests. These scores were added to a health surveillance database that was compiled over the four previous years that includes incidence of diarrhea and Entamoeba histolytica infection and nutritional status. The associations of diarrhea, malnutrition, and social factors with cognitive scores were analyzed statistically, and associations between diarrhea and test scores were controlled for the influence of social factors. Cognitive scores were negatively associated with stunting during school age, as well as the height-for-age and weight-for-age scores at study enrollment. Incidence of diarrhea was associated with nonverbal test scores before, but not after, controlling for socioeconomic factors. Generally E. histolytica infection was not found to independently influence scores, except that E. histolytica-associated dysentery was associated with lower test scores while dysentery of any etiology was not. Thus, malnutrition during the school age years, but not diarrhea or E. histolytica infection, was associated with a lower level of cognitive functioning. This suggested that intervention during school age years may be able to mitigate the cognitive deficiencies associated with malnutrition.

Animals↗

PubMed2006

Aetiology of diarrhoea in a birth cohort of children aged 0-2 year(s) in rural Mirzapur, Bangladesh.

The incidence of aetiology-specific diarrhoea and the pathogenicity of infectious agents in a birth cohort (n=252) in rural Bangladesh were determined. Stool specimens or rectal swabs were collected from diarrhoeal cases over two years and routinely on a monthly basis. Stool samples from children with diarrhoea were compared with stool samples from children without diarrhoea to calculate rates of isolation and pathogenicity of agents. In total, 1750 stool specimens from diarrhoea patients and 5679 stool specimens from children without diarrhoea were tested. An infectious agent was identified in 58% of the stool specimens from diarrhoea patients and 21.6% of the stool specimens from children without diarrhoea. The most commonly-isolated pathogens from all specimens were enterotoxigenic Escherichia coli (ETEC), enteroadherent E. coli, Shigella, Campylobacter jejuni, Giardia, and rotavirus. ETEC (ST and LT-ST toxin), enterotoxigenic Bacteroides fragilis, Shigella, and rotavirus were associated more with disease than with asymptomatic infections. Aetiology-specific infections were associated with acute episodes. The isolated enteropathogens were essentially the same as those found in other tropical rural settings. Enterotoxigenic B. fragilis was also identified as a pathogen. Ongoing vaccine efforts focusing on Shigella, rotavirus, and ETEC would be useful.

Bacterial Infections↗

PubMed2006

Therapeutic efficacy of quinine plus sulfadoxine-pyremethamine for the treatment of uncomplicated falciparum malaria in Bangladesh.

In terms of drug resistance Bangladesh acts as an important gateway to the Indian Subcontinent. However, little is known about the current status of drug resistance in this country. The aim of this study was therefore to determine the therapeutic efficacy as well as in vitro drug sensitivity of quinine for 3 days plus a single dose of sulfadoxine/pyrimethamine (Q3F), an affordable alternative to the previously used chloroquine, for the treatment of uncomplicated falciparum malaria. Sixty-three patients were enrolled in the study; the overall cure rate in a 42-day follow-up after PCR adjustment was 87.3% (95% CI: 77.6-94.1). One patient was classified as early treatment failure (1.7%, 95% CI: 0.0-8.9%); 6 patients (10%; 95% CI: 3.8-20.5%) had late treatment failures within a median time of 27 days. HRP2 in vitro drug sensitivity tests were performed on all samples. Significantly higher (P = 0.008) in vitro IC(50)s for pyrimethamine in treatment failures reflect the somewhat compromised drug sensitivity to this drug. These data suggest that the combination of 3 days of quinine with a single dose of sulfadoxine/pyrimethamine is an interesting and affordable alternative as long as or whenever ACT is not available.

Adolescent↗

PubMed2006

Loss of leishmanin skin test antigen sensitivity and potency in a longitudinal study of visceral leishmaniasis in Bangladesh.

Annual leishmanin skin test (LST) surveys were conducted in a visceral leishmaniasis-endemic Bangladeshi community from 2002 through 2004, using Leishmania infantum antigen from the same manufacturer and batch. In 2002, 530 (35%) of 1,532 had positive LST results; the prevalence increased with increasing age. The LST result was positive in 24 (51%) of 47, 18 (72%) of 25, and 11 (85%) of 13 kala-azar patients treated in the previous 1-11, 12-23, and 24-35 months. A positive LST result in 2002 was associated with protection against subsequent kala-azar (P < 0.0001). In 2003-2004, decreased antigen sensitivity was observed. Among 686 participants, 34% were LST-positive in 2002, 29% in 2003, and 19% in 2004. Of 63 cured kala-azar patients, 70% were positive in 2002, 53% in 2003, and only 30% in 2004. Among 171 participants tested with both antigens, L. infantum study antigen sensitivity was 70% compared with L. amazonensis antigen. Our data underscore the need for better production, standardization, and documentation of sensitivity, potency, and stability of leishmanin antigens.

Adolescent↗

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↗