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Biomedical subjects

A Mirza

Publications and source records attributed to A Mirza.

At least 19 recordsLinked to original sources
PubMed2003

Requirement for the PI3K/Akt pathway in MEK1-mediated growth and prevention of apoptosis: identification of an Achilles heel in leukemia.

The Raf/MEK/ERK kinase cascade plays a critical role in transducing growth signals from activated cell surface receptors. Using DeltaMEK1:ER, a conditionally active form of MEK1 which responds to either beta-estradiol or the estrogen receptor antagonist 4 hydroxy-tamoxifen (4HT), we previously documented the ability of this dual specificity protein kinase to abrogate the cytokine-dependency of human (TF-1) and murine (FDC-P1 and FL5.12) hematopoietic cells lines. Here we demonstrate the ability of DeltaMEK1:ER to activate the phosphatidylinositol 3-kinase (PI3K)/Akt/p70 ribosomal S6 kinase (p70(S6K)) pathway and the importance of this pathway in MEK1-mediated prevention of apoptosis. MEK1-responsive cells can be maintained long term in the presence of beta-estradiol, 4HT or IL-3. Removal of hormone led to the rapid cessation of cell proliferation and the induction of apoptosis in a manner similar to cytokine deprivation of the parental cells. Stimulation of DeltaMEK1:ER by 4HT resulted in ERK, PI3K, Akt and p70(S6K) activation. Treatment with PI3K, Akt and p70(S6K) inhibitors prevented MEK-responsive growth. Furthermore, the apoptotic effects of PI3K/Akt/p70(S6K) inhibitors could be enhanced by cotreatment with MEK inhibitors. Use of a PI3K inhibitor and a constitutively active form of Akt, [DeltaAkt(Myr(+))], indicated that activation of PI3K was necessary for MEK1-responsive growth and survival as activation of Akt alone was unable to compensate for the loss of PI3K activity. Cells transduced by MEK or MEK+Akt displayed different sensitivities to signal transduction inhibitors, which targeted these pathways. These results indicate a requirement for the activation of the PI3K pathway during MEK-mediated transformation of certain hematopoietic cells. These experiments provide important clues as to why the identification of mutant signaling pathways may be the Achilles heel of leukemic cell growth. Leukemia treatment targeting multiple signal transduction pathways may be more efficacious than therapy aimed at inhibiting a single pathway.

Animals↗
PubMed2003

Prevalence of pulmonary tuberculosis in Karachi juvenile jail, Pakistan.

Jail inmates may be at increased risk of contracting tuberculosis (TB). We studied 386 detainees (mean age 17.7 years) in Karachi juvenile jail to determine the prevalence of TB and possible risk factors for contracting TB. We found a 3.9% prevalence of TB among the inmates, significantly higher than the estimated 1.1% prevalence in the general population of Pakistan. Positive family history of TB was a significant risk factor for TB. Poor adherence of previously diagnosed patients to anti-TB treatment was found. Our study highlights the vulnerability of inmates to TB owing to the presence of highly infectious cases, along with environmental conditions such as overcrowding and poor ventilation. This study strongly indicates the need for an effective treatment programme in the jails as well in the general community.

Adolescent↗
PubMed2001

Analyses of p53 target genes in the human genome by bioinformatic and microarray approaches.

The completion of the human genome sequence (International Human Genome Sequence Consortium (2001) Nature 409, 860-921; Venter, J. C., et al. (2001) Science 291, 1304-1351) allows for new ways to analyze global cellular regulatory mechanisms. Here we present a strategy to identify genes regulated by specific transcription factors in the human genome, and apply it to p53. We first collected promoters or introns of all genes available using two methods: GenBank(TM) annotation and a computationally derived transcript map. 4,852 genes analyzed in this way contained at least one p53 consensus binding sequence. Of 13 genes randomly selected for mRNA analysis, 11 were shown to respond to p53 expression. Five promoters were analyzed by chromatin immunoprecipitation, which revealed that all were bound by p53 in vivo. We then analyzed 33,615 unique human genes on cDNA microarrays, identifying 1,501 genes that respond to p53 expression. A parameter was derived that demonstrates that in silico prediction greatly enriches for genes that are activated and repressed by p53 and assists us to suggest other signaling pathways that may be connected to p53. The methods shown here illustrate a novel approach to analysis of global gene regulatory network through the integration of human genomic sequence information and genome-wide gene expression analysis.

Computational Biology↗
PubMed2001

Jun, Fos and Krox in the hippocampus after noxious stimulation: simultaneous-input-dependent expression and nuclear speckling.

Stimulation of sensory C-fibres produces extensive expression of the Fos, Jun and Krox families of inducible transcription factors (ITFs) in many nociceptive CNS areas [28]. In the hippocampus, however, c-Fos is only weakly induced by such stimulation, and expression of the other ITFs has not been studied. Here we examine the effects of single, repeated and simultaneous C-fibre inputs on ITF expressions in the rat hippocampus. A brief, strong electrical stimulation of sciatic nerve C-fibres induced little or no expression of c-Fos or Krox-20. In contrast, FosB was induced and continued to rise in all areas, whereas the basal expressions of c-Jun and Krox-24 were initially reduced but then returned during the subsequent 36 h. A weak noxious cutaneous stimulus applied to one hindpaw induced only weak expressions of the ITFs. However, if the sciatic stimulation was applied contralaterally and 6 h beforehand, this weak stimulus strongly induced Krox-24, but not other ITFs, i.e. there was a potentiation of Krox-24 expression. When these two stimuli were applied simultaneously a few c-Fos labelled cells did appear, and there was and an increased Krox-24 expression. There was also a strong potentiation of FosB and a strong reduction in c-Jun expression. This simultaneous stimulation was the only type of stimulation to induce expression of Krox-20. Also after simultaneous stimulation the majority of the nuclear labelling for FosB, but not of the other ITFs, had a speckled appearance. MK-801 blocked these changes in ITF expressions, but it could also cause the C-fibre stimulations to induce c-Fos and c-Jun in specific areas of the hippocampus. Thus C-fibre stimulation does affect transcription factor activity in the hippocampus; and the strong responses of some ITFs to simultaneous inputs points to their having a role as 'genetic coincidence detectors' in the hippocampus.

Animals↗
PubMed1999

Macrophage inflammatory protein-3 beta enhances IL-10 production by activated human peripheral blood monocytes and T cells.

We report that the addition of human macrophage inflammatory protein-3 beta (MIP-3 beta) to cultures of human PBMCs that have been activated with LPS or PHA results in a significant enhancement of IL-10 production. This effect was concentration-dependent, with optimal MIP-3 beta concentrations inducing more than a 5-fold induction of IL-10 from LPS-stimulated PBMCs and a 2- to 3-fold induction of IL-10 from PHA-stimulated PBMCs. In contrast, no significant effect on IL-10 production was observed when 6Ckine, the other reported ligand for human CCR7, or other CC chemokines such as monocyte chemoattractant protein-1, RANTES, MIP-1 alpha, and MIP-1 beta were added to LPS- or PHA-stimulated PBMCs. Similar results were observed using activated purified human peripheral blood monocytes or T cells. Addition of MIP-3 beta to nonactivated PBMCs had no effect on cytokine production. Enhancement of IL-10 production by MIP-3beta correlated with the inhibition of IL-12 p40 and TNF-alpha production by monocytes and with the impairment of IFN-gamma production by T cells, which was reversed by addition of anti-IL-10 Abs to the cultures. The ability of MIP-3 beta to augment IL-10 production correlated with CCR7 mRNA expression and stimulation of intracellular calcium mobilization in both monocytes and T cells. These data indicate that MIP-3 beta acts directly on human monocytes and T cells and suggest that this chemokine is unique among ligands binding to CC receptors due to its ability to modulate inflammatory activity via the enhanced production of the anti-inflammatory cytokine IL-10.

Adjuvants, Immunologic↗
PubMed1999

Mutations in the Newcastle disease virus hemagglutinin-neuraminidase protein that interfere with its ability to interact with the homologous F protein in the promotion of fusion.

Recent evidence suggests that the attachment (HN) and fusion (F) glycoproteins of Newcastle disease virus interact at the cell surface in a virus-specific manner to promote syncytium formation. Consistent with the existence of such an interaction, we have shown that it is possible to coimmunoprecipitate (co-IP) the two proteins from the surface of transiently expressing cells using a monoclonal antibody to either protein. Further, we show that a point mutation in the globular domain of HN that abolishes its receptor recognition and neuraminidase (NA) and fusion activities also abolishes its ability to interact with F in the co-IP assay. The mechanism by which this mutation might interfere with the interaction between the two proteins is discussed in terms of the postulate that recognition by HN of cellular receptors triggers its interaction with F and the apparently conflicting evidence for an interaction between the two proteins in the endoplasmic reticulum. Also, characterization of a set of chimeric HN proteins, having short overlapping sequences from a heterologous HN protein in the F-specific domain in the protein stalk, reveals that a weakened interaction between HN and F is still sufficient to trigger fusion.

Amino Acid Sequence↗
PubMed1999

Rapid development of genotypic resistance to lamivudine when combined with zidovudine in pregnancy.

The prevention of mother to child transmission of HIV-1 by zidovudine monotherapy is well known, but increasingly combination anti-retroviral therapy is prescribed during pregnancy. In this prospective study, 19 pregnant women with human immunodeficiency virus-1 (HIV-1) infection who elected to take anti-retroviral therapy during the second and third trimesters were treated with zidovudine or zidovudine plus lamivudine. Fourteen women treated with zidovudine monotherapy had a mean 0.3 log(10) reduction in viral load and a mean 52 x 10(6)/L (17%) increase in CD4+ lymphocytes at delivery compared with pre-treatment samples. Genotypic mutations associated with decreased susceptibility to zidovudine were detected in 2 of 10 women at delivery. Five women with more advanced HIV-1 infection were treated with zidovudine plus lamivudine and a mean 1.5 log(10) reduction in viral load together with a mean 30 x 10(6)/L (33%) increase in CD4+ lymphocytes was observed in this group. However, four of five women in the dual therapy arm had the M184V mutation in the reverse transcriptase gene associated with decreased susceptibility to lamivudine at delivery. We conclude that zidovudine plus lamivudine reduced HIV-1 plasma viraemia to low levels in pregnant women with advanced HIV-1 disease but the rapid development of genotypic resistance to lamivudine indicates that additional therapy is required both for the long-term benefit of the mothers and to prevent the development of resistant virus that may be transmitted to the infant.

Adult↗
PubMed1999

New approaches to mucosal immunization.

Every year more than 17 million deaths worldwide are caused by infectious diseases. The great majority of these deaths occur in underdeveloped countries and are attributed to diseases preventable by existing vaccines, or diseases that could potentially be prevented with new vaccines. The fact that most human and veterinary pathogens establish infection in the host by initiating contact at a mucosal surface, provide the rationale for the development of mucosal vaccines. An increasing number of strategies have been proposed to facilitate mucosal immunization. Among the most widely investigated strategies are the use of attenuated microorganisms; the inclusion of immunizing antigens in lipid-based carriers, the genetic creation of transgenic plants and the use of mucosal adjuvants derived from bacterial toxins. This review provides a brief summary of the most recent advances in the field of mucosal immunization with an special emphasis on a promising genetically detoxified mucosal adjuvant, LT(R192G), derived from the heat-labile toxin of enterotoxigenic E. coli. We present evidence regarding the safety, immunogenicity, and efficacy of LT(R192G) for the development of a new generation of mucosal vaccines.

Adenosine Diphosphate Ribose↗
PubMed1999

Helicobacter pylori infection and insulin requirement among children with type 1 diabetes mellitus.

OBJECTIVE: Helicobacter pylori induces gastric inflammation and the the production of cytokines in infected individuals. Theoretically, this increased production of cytokines could be deleterious for the control of the glycemia of patients with diabetes. This study aimed to describe the insulin requirement among patients with type 1 diabetes and H pylori infection compared with uninfected counterparts. METHODS: Cross-sectional design. Demographic information (age, gender, race, annual family income, and number of individuals per room in the household) and clinical information (age at diagnosis of diabetes, duration of illness, weight, height, compliance with clinical appointments, daily insulin units per kilogram of body weight [IU/kg/d], and glycosylated hemoglobin A level) was obtained from children and adolescents with diagnosis of type 1 diabetes mellitus who were seen at Children's Hospital in New Orleans. A total of 2 mL of blood was also collected and sera were tested for H pylori-specific immunoglobulin G antibodies using an enzyme immunoassay. The daily insulin requirement among infected and uninfected children was compared, and the effect of other variables was evaluated with multiple linear regression. RESULTS: Of the 71 subjects who were evaluated (median age: 11 years), 11 (15.5%) were found to be infected. H pylori infection was more frequent among subjects who were older, who had a lower family income, and who were black. Infected children were found to require more insulin (1.2 vs 0.9 IU/Kg/d) and their glycosylated hemoglobin A level was higher (14.9 vs 11.8) than the level found in uninfected subjects. Multiple linear regression analysis identified H pylori infection duration of illness, race (black), body mass index, and gender (female), to be associated independently with increased daily insulin requirement (IU/kg/d). CONCLUSION: n our study population, children with type 1 diabetes and H pylori infection had an increased daily insulin requirement compared with the requirement of their uninfected peers. The reason for this association requires additional investigation.

Adolescent↗
PubMed1999

Identification of the Escherichia coli enzyme I binding site in histidine-containing protein, HPr, by the effects of mutagenesis.

The structure of the N-terminal domain of enzyme I complexed with histidine-containing protein (HPr) has been described by multi-dimensional NMR. Residues in HPr involved in binding were identified by intermolecular nuclear Overhauser effects (Garrett et al. 1999). Most of these residues have been mutated, and the effect of these changes on binding has been assessed by enzyme I kinetic measurement. Changes to Thr16, Arg17, Lys24, Lys27, Ser46, Leu47, Lys49, Gln51, and Thr56 result in increases to the HPr Km of enzyme I, which would be compatible with changes in binding. Except for mutations to His15 and Arg17, very little or no change in Vmax was found. Alanine replacements for Gln21, Thr52, and Leu55 have no effect. The mutation Lys40Ala also affects HPr Km of enzyme I; residue 40 is contiguous with the enzyme I binding site in HPr and was not identified by NMR. The mutations leading to a reduction in the size of the side chain (Thr16Ala, Arg17Gly, Lys24Ala, Lys27Ala, and Lys49Gly) caused relatively large increases in Km (>5-fold) indicating these residues have more significant roles in binding to enzyme I. Acidic replacement at Ser46 caused very large increases (>100-fold), while Gln51Glu gave a 3-fold increase in Km. While these results essentially concur with the identification of residues by the NMR experiments, the apparent importance of individual residues as determined by mutation and kinetic measurement does not necessarily correspond with the number of contacts derived from observed intermolecular nuclear Overhauser effects.

Bacterial Proteins↗
PubMed1998

Generation or large numbers of immature and mature dendritic cells from rat bone marrow cultures.

We have defined conditions for generating large numbers of dendritic cells (DC) in marrow cultures from 10-12-week-old ACI or WF rats. The combination of granulocyte-macrophage colony-stimulating factor (GM-CSF) and TNF-alpha, known to induce DC from human CD34+ progenitors, was not effective with rat. In contrast, GM-CSF plus IL-4 generated DC in high yield, corresponding to 30-40% of the initial number of plated marrow cells. The DC proliferated in distinctive aggregates, in which most cells had an immature phenotype marked by undetectable surface B7 and high levels of MHC class II products within intracellular lysosomes. When dislodged and dispersed, the aggregates gave rise to mature stellate DC with abundant surface MHC class II and B7, sparse MHC class II- lysosomes, and strong T cell-stimulating capacity. Therefore, rat marrow progenitors can generate large numbers of immature DC, with abundant intracellular MHC class II compartments, and potent, stimulatory, mature DC.

Animals↗
PubMed1998

Colonization with enteroadherent, enterotoxigenic and enterohemorrhagic Escherichia coli among day-care center attendees in New Orleans, Louisiana.

BACKGROUND: E. coli strains producing specific virulence factors are frequently cited as causes of pediatric diarrhea in developing areas, although many well children from the same areas are colonized with these organisms. The role of these Escherichia coli in day-care center (DCC)-associated diarrhea in the United States has not been evaluated. METHODS: A cohort of 112 DCC attendees from 5 DCC in urban New Orleans were followed longitudinally with demographic data, biweekly routine stool samples and additional stool samples with episodes of diarrhea. E. coli isolates were routinely saved; diarrhea stool samples were tested to detect enterotoxigenic, enterohemorrhagic and enteroadherent strains; and the prevalence of these E. coli in children with and without diarrhea was investigated. RESULTS: During 225 child months of observation 21 episodes of diarrhea were documented and microbiologic data were available for 18. HEp-2 cell enteroadherent E. coli [mostly enteroaggregative (EAggEC) pattern] were identified in 6 of 18 (33.3%) diarrhea cases vs. 6 of 36 (16.6%) age-matched controls. However, the prevalence of EAggEC was very DCC-specific, with EAggEC found in 12 of 22 routine specimens from a DCC with recent EAggEC-related diarrhea vs. 0 of 11 routine specimens from age-matched children in another DCC without EAggEC-related diarrhea (P=0.002). Enterotoxigenic E. coli were uncommon in both ill and well children, and no enterohemorrhagic E. coli were detected. CONCLUSION: EAggEC were commonly isolated from children with and without diarrhea in certain DCC settings, although we cannot determine whether these strains caused diarrhea. Diarrhea-producing E. coli were not associated with diarrhea in this DCC population.

Adhesins, Escherichia coli↗
PubMed1997

Developmental regulation of MHC class II transport in mouse dendritic cells.

Dendritic cells (DCs) have the unique capacity to initiate primary and secondary immune responses. They acquire antigens in peripheral tissues and migrate to lymphoid organs where they present processed peptides to T cells. DCs must therefore exist in distinct functional states, an idea that is supported by observations that they downregulate endocytosis and upregulate surface molecules of the class II major histocompatibility complex (MHC) upon maturation. Here we investigate the features of DC maturation by reconstituting the terminal differentiation of mouse DCs in vitro and in situ. We find that early DCs, corresponding to those found in peripheral tissues, exhibit a phenotype in which most class II molecules are intracellular and localized to lysosomes. Upon maturation, these cells give rise to a new intermediate phenotype in which intracellular class II molecules are found in peripheral non-lysosomal vesicles, similar to the specialized CIIV population seen in B cells. The intermediate cells then differentiate into late DCs which express almost all of their class II molecules on the plasma membrane. These variations in class II compartmentalization are accompanied by dramatic alterations in the intracellular transport of the new class II molecules and in antigen presentation. We found that although early DCs could not present antigen immediately after uptake, efficient presentation of the previously internalized antigen occurred after maturation, 24-48 hours later. By regulating class II transport and compartmentalization, DCs are able to delay antigen display, a property crucial to their role in immune surveillance.

Amino Acid Sequence↗
PubMed1997

A role for tissue transglutaminase in hepatic injury and fibrogenesis, and its regulation by NF-kappaB.

This study was undertaken to delineate a possible role for tissue transglutaminase (tTG), an enzyme that catalyzes protein cross-linking, in hepatic fibrogenesis. Rats were treated with CCl4 solution and then killed at different stages of liver injury and fibrogenesis. Liver tTG mRNA levels were markedly increased as early as 6 h after the first injection, peaked at 4 days and 1 wk, and remained increased for 8 wk. The enzymatic activity of tTG was increased in livers of rats treated with CCl4, in a fashion that paralleled the Northern blot results. Cell isolation experiments indicated that all hepatic cell types synthesize tTG mRNA. Increased binding to the nuclear factor-kappaB (NF-kappaB) motif of the tTG promoter was found in the nuclear extracts prepared from CCl4-treated samples. These data demonstrate an increase in tTG gene expression during hepatic injury and fibrosis, suggesting a possible role for this enzyme in stabilizing the fibrotic bands during hepatic fibrogenesis. Moreover, increased NF-kappaB binding to the tTG promoter may represent one of the mechanisms by which cell injury induces tTG transcription and thus potentiates the process of fibrogenesis.

Animals↗
PubMed1997

A double-blind taste comparison of pediatric antibiotic suspensions.

This study examined the palatability of 22 antimicrobial suspensions by using five independent categories for scoring: appearance, smell, texture, taste, and aftertaste. The likely overall influence on patient compliance was also evaluated. Drugs were compared within their respective classes. The only antibiotics judged to be so unpalatable as to potentially jeopardize compliance were dicloxacillin, oxacillin, erythromycin/sulfisoxazole, and cefpodoxime. Among the penicillins, amoxicillin and ampicillin were preferred. Azithromycin was slightly superior to erythromycin and clarithromycin within the macrolide class. Many cephalosporins were ranked quite high, the best being loracarbef, cefadroxyl, cefprozil, and cefixime.

Adult↗
PubMed1995

DEC-205, a 205-kDa protein abundant on mouse dendritic cells and thymic epithelium that is detected by the monoclonal antibody NLDC-145: purification, characterization, and N-terminal amino acid sequence.

The monoclonal antibody NLDC-145 detects an antigen expressed at high levels by mouse dendritic cells (DCs) and thymic epithelial cells. Here we report on the purification and biochemical characterization of this antigen. The antigen detected by the NLDC-145 mAb is an integral membrane glycoprotein, with an apparent molecular mass of 205 kDa by immunoprecipitation and Western blotting. The isoelectric point is pH 7.5, and carbohydrates comprise about 7 kDa of the total mass. Lectin blotting and FACE analysis revealed heterogeneous biantennary N-linked glycans. O-linked glycans were not detected. N-terminal sequence analysis revealed that the antigen is a novel protein. Polyclonal antibodies prepared either to a synthetic N-terminal peptide or to whole purified protein bind the same 205-kDa protein recognized by NLDC-145. We refer to the protein as DEC-205, in view of its abundant expression by dendritic and thymic epithelial cells, and the revised molecular mass.

Amino Acid Sequence↗