Biomedical subjects

Aminul Islam

Publications and source records attributed to Aminul Islam.

15 recordsLinked to original sources

PubMed2006

Angiogenic switch in Barrett's adenocarcinoma: the role of vascular endothelial growth factor.

The development of cancerous cells from the normal cells is the consequence of multiple genetic and epigenetic abuses. Activation of "Angiogenic switch" or formation of new blood vessels is one of the upshots of these abuses. Multiple factors are associated with the activation of angiogenic switch. Vascular endothelial growth factor (VEGF) and its down stream signaling molecules is important troupe of this event. In this article, we reviewed the role this troupe in the development of Barrett's adenocarcinoma and also discussed the possible remedies, which have the impact on blocking the function of this troupe.

Adenocarcinoma↗

PubMed2006

Absolute quantification using real-time polymerase chain reaction of Marek's disease virus serotype 2 in field dust samples, feather tips and spleens.

Methods for Taqman quantitative real-time PCR (qPCR) assays to detect the three serotypes of Marek's disease virus (MDV) are available, and absolute quantification has been developed for MDV serotype 1 and serotype 3. The development of a method for absolute quantification of Marek's disease virus serotype 2 (MDV2) is described in this paper. Using plasmid DNA, the lower detection limit of the MDV2 assay was determined to be 10 copies. Three independent assay runs showed highly reproducible Ct values and calculated copy numbers, with mean intra- and inter-assay coefficients of variation of less than 3% for Ct and less than 21.5% for calculated copy number. Absolute quantification of MDV2 was performed successfully on dust samples collected from poultry farms across Australia, material from infectious spleens and feather tips from chickens vaccinated with an attenuated strain of MDV2. Thus, it is now possible to use qPCR assays for absolute quantification of all three serotypes of MDV in a sample.

Animals↗

PubMed2006

Effect of protein kinase A on accumulation of brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) in HepG2 cell nuclei.

Brefeldin A-inhibited guanine nucleotide-exchange proteins, BIG1 and BIG2, are activators of ADP-ribosylation factor GTPases that are essential for regulating vesicular traffic among intracellular organelles. Biochemical analyses and immunofluorescence microscopy demonstrated BIG1 in nuclei as well as membranes and cytosol of serum-starved HepG2 cells. Within 20 min after addition of 8-Br-cAMP, BIG1 accumulated in nuclei, and this effect was blocked by protein kinase A (PKA) inhibitors H-89 and PKI, suggesting a dependence on PKA-catalyzed phosphorylation. BIG2 localization was not altered by cAMP, nor did BIG2 small interfering RNA influence nuclear accumulation of BIG1 induced by cAMP. Mutant BIG1 (S883A) in which Ala replaced Ser-883, a putative PKA phosphorylation site, did not move to the nucleus with cAMP addition, whereas replacement with Asp (S883D) resulted in nuclear accumulation of BIG1 without or with cAMP exposure, consistent with the mechanistic importance of a negative charge at that site. Mutation (712KPK714) of the nuclear localization signal inhibited BIG1 accumulation in nuclei, and PKA-catalyzed phosphorylation of S883, although necessary, was not sufficient for nuclear accumulation, as shown by the double mutation S883D/nuclear localization signal. A role for microtubules in cAMP-induced translocation of BIG1 is inferred from its inhibition by nocodazole. Thus, two more critical elements of BIG1 molecular structure were identified, as well as the potential function of microtubules in a novel PKA effect on BIG1 translocation.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2006

Extracellular TNFR1 release requires the calcium-dependent formation of a nucleobindin 2-ARTS-1 complex.

Extracellular tumor necrosis factor (TNF) receptors function as TNF-binding proteins that modulate TNF activity. In human vascular endothelial cells (HUVEC), extracellular TNFR1 (type I TNF receptor, TNFRSF1A) is generated by two mechanisms, proteolytic cleavage of soluble TNFR1 ectodomains and the release of full-length 55-kDa TNFR1 in the membranes of exosome-like vesicles. TNFR1 release from HUVEC is known to involve the association between ARTS-1 (aminopeptidase regulator of TNFR1 shedding), an integral membrane aminopeptidase, and TNFR1. The goal of this study was to identify ARTS-1 binding partners that modulate TNFR1 release to the extracellular space. A yeast two-hybrid screen of a human placenta cDNA library showed that NUCB2 (nucleobindin 2), via its helix-loop-helix domains, binds the ARTS-1 extracellular domain. The association between endogenous ARTS-1 and NUCB2 in HUVEC was demonstrated by co-immunoprecipitation experiments, which showed the formation of a calcium-dependent NUCB2.ARTS-1 complex that associated with a subset of total cellular TNFR1. Confocal microscopy experiments demonstrated that this association involved a distinct population of NUCB2-containing intracytoplasmic vesicles. RNA interference was utilized to specifically knock down NUCB2 and ARTS-1 expression, which demonstrated that both are required for the constitutive release of a full-length 55-kDa TNFR1 within exosome-like vesicles as well as the inducible proteolytic cleavage of soluble TNFR1 ectodomains. We propose that calcium-dependent NUCB2.ARTS-1 complexes, which associate with TNFR1 prior to its commitment to pathways that result in either the constitutive release of TNFR1 exosome-like vesicles or the inducible proteolytic cleavage of TNFR1 ectodomains, play an important role in mediating TNFR1 release to the extracellular compartment.

Aminopeptidases↗

PubMed2006

Relationship between Marek's disease virus load in peripheral blood lymphocytes at various stages of infection and clinical Marek's disease in broiler chickens.

Vaccination with herpesvirus of turkey (HVT) vaccine provides protection against clinical Marek's disease (MD) but does not preclude infection with wild-type MD virus (MDV). The quantity of MDV detected in circulating lymphocytes during the early period after infection may be a useful predictor of subsequent clinical MD later in the life. A study was designed to quantify MDV and HVT copy number in peripheral blood lymphocytes (PBL) using real-time polymerase chain reaction between days 5 and 35 post-challenge and to relate this to subsequent development of gross MD lesions. Female commercial broiler chickens were vaccinated with HVT or were sham-vaccinated at hatch, then challenged with MDV strain MPF-57 at day 2 post-vaccination and reared in positive-pressure isolators up to 56 days post-challenge, when all survivors were euthanized. All dead and euthanized chickens were examined post mortem for gross MD lesions. Birds were scored for MD lesions and mortality. MDV and HVT genome copy numbers were determined for each PBL sample. There was an increase in HVT load in PBL between days 7 and 37 post-vaccination, with marked increases between days 7 and 16 and again between days 30 and 37. There was a steady increase in MDV load to 35 days post-challenge. The mean MDV copy number (log(10)) was greater in chickens subsequently exhibiting gross MD lesions (5.05 +/- 0.21) than in those that did not (2.88 +/- 0.223), with the largest difference at 14 and 21 days post-challenge (P < 0.001). Quantification of MDV during early infection is therefore a potential tool for monitoring MD in broiler flocks.

Animals↗

PubMed2005

Absolute quantitation of Marek's disease virus and Herpesvirus of turkeys in chicken lymphocyte, feather tip and dust samples using real-time PCR.

The further development of Taqman quantitative real-time PCR (qPCR) assays for the absolute quantitation of Marek's disease virus serotype 1 (MDV1) and Herpesvirus of turkeys (HVT) viruses is described and the sensitivity and reproducibility of each assay reported. Using plasmid DNA copies, the lower limit of detection was determined to be 5 copies for the MDV1 assay and 75 copies for the HVT assay. Both assays were found to be highly reproducible for Ct values and calculated copy numbers with mean intra- and inter-assay coefficients of variation being less than 5% for Ct and 20% for calculated copy number. The genome copy number of MDV1 and HVT viruses was quantified in PBL and feather tips from experimentally infected chickens, and field poultry dust samples. Parallelism was demonstrated between the plasmid-based standard curves, and standard curves derived from infected spleen material containing both viral and host DNA, allowing the latter to be used for absolute quantification. These methods should prove useful for the reliable differentiation and absolute quantitation of MDV1 and HVT viruses in a wide range of samples.

Analysis of Variance↗

PubMed2005

A stability indicating LC method for zolmitriptan.

A gradient, reversed-phase liquid chromatographic (RP-LC) assay method was developed for the quantitative determination of zolmitriptan, used to treat severe migraine headaches. The developed method is also applicable for the related substances determination in bulk drugs. The chromatographic separation was achieved on a Waters X Terra RP18, 250 mm x 4.6 mm, 5 microm column. The gradient LC method employs solutions A and B as mobile phase. The solution A contains a mixture of phosphate buffer pH 9.85:methanol:acetonitrile (70:20:10, v/v/v) and solution B contains a mixture of phosphate buffer, pH 9.85:acetonitrile (30:70). The flow rate was 1.0 ml/min and the detection wavelength was 225 nm. In the developed HPLC method, the resolution between zolmitriptan and its potential impurities, namely Imp-1, Imp-2 and Imp-3 was found to be greater than 3. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in alkaline medium and oxidative stress conditions. Degradation product formed during base hydrolysis was found to be Imp-3. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.5%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.

Acetonitriles↗

PubMed2005

Proteasome inhibition induces TNFR1 shedding from human airway epithelial (NCI-H292) cells.

The type 1 55-kDa TNF receptor (TNFR1) is an important modulator of lung inflammation. Here, we hypothesized that the proteasome might regulate TNFR1 shedding from human airway epithelial cells. Treatment of NCI-H292 human airway epithelial cells for 2 h with the specific proteasome inhibitor clasto-lactacystin beta-lactone induced the shedding of proteolytically cleaved TNFR1 ectodomains. Clasto-lactacystin beta-lactone also induced soluble TNFR1 (sTNFR1) release from the A549 pulmonary epithelial cell line, as well as from primary cultures of human small airway epithelial cells and human umbilical vein endothelial cells. Furthermore, sTNFR1 release induced by clasto-lactacystin beta-lactone was not a consequence of apoptosis or the extracellular release of TNFR1 exosome-like vesicles. The clasto-lactacystin beta-lactone-induced increase in TNFR1 shedding was associated with reductions in cell surface receptors and intracytoplasmic TNFR1 stores that were primarily localized to vesicular structures. As expected, the broad-spectrum zinc metalloprotease inhibitor TNF-alpha protease inhibitor 2 (TAPI-2) attenuated clasto-lactacystin beta-lactone-mediated TNFR1 shedding, which is consistent with its ability to inhibit the zinc metalloprotease-catalyzed cleavage of TNFR1 ectodomains. TAPI-2 also reduced TNFR1 on the cell surface and attenuated the clasto-lactacystin beta-lactone-induced reduction of intracytoplasmic TNFR1 vesicles. This suggests that TNFR1 shedding induced by clasto-lactacystin beta-lactone involves the zinc metalloprotease-dependent trafficking of intracytoplasmic TNFR1 vesicles to the cell surface. Together, these data are consistent with the conclusion that proteasomal activity negatively regulates TNFR1 shedding from human airway epithelial cells, thus identifying previously unrecognized roles for the proteasome and zinc metalloproteases in modulating the generation of sTNFRs.

Adenocarcinoma↗

PubMed2005

Aminonaphthalic anhydrides as red-emitting materials: electroluminescence, crystal structure, and photophysical properties.

The red and orange emitters (ANA-1-3) consisting of a 4-amino-1,8-naphthalic anhydride group were synthesized. The lowest absorption band of these ANA molecules centered at approximately 450 nm is assigned to be a charge-transfer transition with emission at 514-536 nm in nonpolar solvents such as n-hexane and at approximately 590-640 nm in polar solvents such as THF and CH(2)Cl(2) and in the solid states. Emission lifetimes are measured with time-correlated single photon counting. Shorter lifetimes are observed for the ANA molecules when dissolved in polar solvents compared with those in nonpolar solvents. Strong dipole-dipole interaction of ANA molecules with solvents is indicated. At high concentrations the measured emission lifetimes, generally shortened from self-quenching, are found to remain about the same order of magnitude in ANAs. This implies that the exciton states of aggregates are formed and they exhibit a relatively long lifetime. Crystallographic data of 4-(phenyl antracen-9-yl) (ANA-2) and 4-(phenyl-2-naphthyl) amino-1,8-naphthalic anhydrides (ANA-3) show that the molecules exist as dimeric structures with antiparallel head-to-tail stacking of naphthalic anhydride planes in addition to other pi-pi stacking. The strong dipole-dipole interactions and the pi-pi stacking account for the observed red-shifted emissions of ANAs in the powders. For films prepared from vacuum sublimation, a structure similar to that in the crystal but with less crystalline order is expected based on the emission wavelength. Several electroluminescent devices based on these ANAs are reported here; they emit orange-red light at 602-628 nm with high brightness and steady external quantum efficiency.

Journal Article↗

PubMed2005

Column chromatographic separation of metal ions on 1-(2-pyridylazo)-2-napthol modified amberlite IR-120 resin.

Cation exchange resin, Amberlite IR-120, has been modified by the sorption of 1-(2-pyridylazo)-2-napthol (PAN) at pH 6.0. The optimum conditions for the sorption of PAN on the resin have been established. The maximum sorption of PAN was found to be 8.70 micromol/g. In order to explore the separation possibilities of the material, distribution coefficients of a number of metal ions were determined in various solvent systems. A number of binary separations of metal ions of analytical interest have been carried out using columns packed with this material. In order to demonstrate the practical utility of this material, Zn2+ and Hg2+ have been selectively separated from synthetic mixtures of metal ions and assay of Zn2+ and Fe2+ in commercially available pharmaceutical tablets; namely Fesofor-Z and FE-Z, was carried out.

Journal Article↗

PubMed2005

Evaluation of stool antigen test for Helicobacter pylori infection in asymptomatic children from a developing country using 13C-urea breath test as a standard.

OBJECTIVE: Prevalence of asymptomatic Helicobacter pylori infection is very high in infants and children in developing countries. C urea breath test (UBT) is a reliable non-invasive diagnostic test for H. pylori infection in children that avoids invasive endoscopy. We compared a newly introduced H. pylori stool antigen test (with a high sensitivity and specificity in symptomatic children) with UBT in asymptomatic children mostly 1-5 years old, from a population with a high prevalence of infection. METHOD: Eighty six asymptomatic children (42 boys and 44 girls) were tested for H. pylori infection using the UBT and a stool antigen test (HpSA) based on a sandwich enzyme immunoassay for antigen detection. RESULTS: Forty five of the eighty-six (52.3%) children tested positive for H. pylori using the breath test. In 34 of these forty-five children, H. pylori antigen was detected in stool (sensitivity = 75.6%, 95% CI = 63 to 88%). Of the 50 of 86 (58%) children positive by HpSA test, 34 were positive for breath test. Of the 41 children with negative UBT test 25 were negative for stool antigen test (specificity = 61%, 95% CI = 46 to 76%). CONCLUSION: The sensitivity and specificity of the new stool antigen test are lower in asymptomatic children with high H. pylori prevalence rate compared to those reported for children with gastrointestinal symptoms. Its usefulness is limited for diagnosis in an asymptomatic child with H. pylori infection.

Antigens, Bacterial↗

PubMed2004

A validated chiral LC method for the determination of zolmitriptan and its potential impurities.

A new, accurate and reliable chiral HPLC method was developed for the determination of Zolmitriptan, (4S)-4-[[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl] methyl]-2-oxazolidinone an antimigraine agent and its potential impurities namely (4R)-4-[[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl] methyl]-2-oxazolidinone [(R)-enantiomer] and (4S)-4-(4-aminobenzyl)-2-oxazolidinone (Imp-1) in pharmaceutical formulations and in bulk drugs. HPLC separation was carried out by normal phase chromatography with a mobile phase composed of hexane:isopropanol:methanol:diethylamine in the ratio (75:10:15:0.1, v/v/v/v) pumped at a flow rate of 1.0 ml/min on a Chiralpak AD-H column. Zolmitriptan and its potential impurities were baseline resolved in the optimized method. The presence of diethylamine in the mobile phase has played a key role in achieving chromatographic resolution between the enantiomers and also in enhancing chromatographic efficiency. The developed method was also found to be selective under exposed conditions UV light and 60 degrees C. The developed method was completely validated and proved to be robust. The values of the limit of detection (LOD) and limit of quantification (LOQ) of (R)-enantiomer and Imp-1 were 100, 250 ng/ml and 30, 1000 ng/ml, respectively, for 10 microl injection volume. The validated method yielded good results regarding selectivity, linearity, precision, accuracy and ruggedness. Zolmitriptan sample solution and mobile phase are found to be stable for at least 24 h. The proposed method was found to be suitable and accurate for the quantitative determination of Zolmitriptan and its impurities namely (R)-enantiomer and Imp-1 in bulk drugs and commercial formulations.

Chromatography, Liquid↗

PubMed2004

Increased 5-HT2A receptor expression and function following central glucocorticoid receptor knockdown in vivo.

Central glucocorticoid receptor function may be reduced in depression. In vivo modelling of glucocorticoid receptor underfunctionality would assist in understanding its role in depressive illness. The role of glucocorticoid receptors in modulating 5-HT(2A) receptor expression and function in the central nervous system (CNS) is presently unclear, but 5-HT(2A) receptor function also appears altered in depression. With the aid of RNAse H accessibility mapping, we have developed a 21-mer antisense oligodeoxynucleotide (5'-TAAAAACAGGCTTCTGATCCT-3', termed GRAS-5) that showed 56% reduction in glucocorticoid receptor mRNA and 80% down-regulation in glucocorticoid receptor protein in rat C6 glioma cells. Sustained delivery to rat cerebral ventricles in slow release biodegradable polymer microspheres produced a marked decrease in glucocorticoid receptor mRNA and protein in hypothalamus (by 39% and 80%, respectively) and frontal cortex (by 26% and 67%, respectively) 5 days after a single injection, with parallel significant up-regulation of 5-HT(2A) receptor mRNA expression (13%) and binding (21%) in frontal cortex. 5-HT(2A) receptor function, determined by DOI-head-shakes, showed a 55% increase. These findings suggest that central 5-HT(2A) receptors are, directly or indirectly, under tonic inhibitory control by glucocorticoid receptor.

Animals↗

PubMed2004

Differential amplification and quantitation of Marek's disease viruses using real-time polymerase chain reaction.

Quantitative real-time PCR (qPCR) assays for the three serotypes of Marek's disease virus (MDV) have been developed. An internal control qPCR assay that detects chicken alpha2 (VI) collagen gene was also developed to allow quantitation of MDV. To reduce costs and time, the assays for MDV1 and the internal control were combined into a duplex assay. The sensitivity, specificity, precision, and reproducibility of each assay are reported. The MDV qPCR assays were specific to their target gene when compared using Australian field and vaccine strains of MDV and 10-100-fold more sensitive than standard PCR. Using DNA from infected spleen tissue, the lower limit of detection of total DNA (viral and host combined) was 0.025 ng for the MDV1 and collagen assays, and 0.25 ng for the HVT and MDV2 assays. All assays were found to be highly reproducible for Ct values, but less so for calculated concentrations. MDV1 and HVT were quantitated in spleen tissue of twenty experimentally infected chickens 7-35 days after infection. The relative abundance of MDV1 exhibited a clear peak at day 14 post-infection, whereas HVT displayed an increasing trend over the 35 days post-infection. The duplex assay was optimized such that it was able to accurately quantitate MDV1 in samples of very high, medium, and very low relative abundance of MDV1. These qPCR assays will be useful for reliable differentiation and quantitation of MDV for a range of research and industry applications.

Animals↗

PubMed2003

Novel acid-catalyzed rearrangement of methanofullerenes bearing an alpha-ylidic ester to cyclopentanofullerenes: a vinyl cyclopropane-type ring expansion.

A novel acid-catalyzed ring expansion of methanofullerenes bearing an alpha-ylidic ester has been investigated. Treatment of dialkyl acetylenedicarboxylate and tricycloalkylphosphine with C(60) led to the isolation of a methanofullerene ylide after passing the reaction mixtures through a basic alumina column. If the reaction mixture was passed through a silica gel column, a cyclopentanofullerene was isolated instead. These new cyclopentanofullerenes consisted of a fused cyclopentanone ring bearing an alpha-hydroxy ester and a phosphonium ylide and were confirmed by their NMR, mass, and X-ray diffraction data. The cyclopentanofullerenes were formed by the ring expansion of the corresponding methanofullerenes in the presence of silica gel. The ring expansion also proceeded by treating methanofullerene with acetic acid in chloroform. On the other hand, the methanofullerenes from RO(2)CCCCO(2)R, PAr(3), and C(60) were stable in silica gel. However, upon heating with acetic acid at 50 degrees C, they underwent ring expansion and dephosphination to give cyclopentenofullerenes. An implicit vinyl cyclopropane ring expansion mechanism was proposed to account for this novel acid-catalyzed rearrangement.

Journal Article↗