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Biomedical subjects

A M Hussain

Publications and source records attributed to A M Hussain.

At least 19 recordsLinked to original sources
PubMed2001

Measuring the impact of needle exchange programs among injecting drug users through the National Behavioural Surveillance in Bangladesh.

Bangladesh is a low HIV prevalence country, with buprenorphine injectors having the highest prevalence of HIV at 2.5% as of 1999. Using National HIV Behavioral Surveillance data, the impact of a needle exchange program (NEP) on sharing behavior among injecting drug users in two cities was measured. Results showed positive changes that varied with the different settings. Those who reported utilizing the NEP were compared with those who did not. Differences in Dhaka were significant for the average proportion of needles shared but not for the proportion of men who ever shared in the last week. In Rajshahi, where professional injectors were the norm, the impact of an NEP was greater and affected both the proportion of needles shared as well as the proportion of men never sharing. Behavioral surveillance methods have the potential to measure intervention impact through comparative analysis in certain settings.

Adolescent↗
PubMed2000

Modulation of CD157 expression in multi-lineage myeloid differentiation of promyelocytic cell lines.

CD157/BST-1 is expressed on mature myeloid cells but not on their precursors in vivo. Also CD38, a homologous gene to CD157, is upregulated in promyelocytic HL-60 cells by the monocyte and granulocyte differentiation-inducing 1alpha,25dihydroxyvitamin D3 (VD3) and all-trans retinoic acid (ATRA), respectively. We have examined whether CD157 expression is upregulated when the promyeloid HL-60 and/or U937 cells are induced to differentiate into mature phenotypes in vitro. VD3 treatment irreversibly upregulated the expression of CD157 in HL-60 cells but not in U937 cells in a time- and concentration-dependent manner when analyzed by flow cytometry, immunoblotting and/or RT-PCR. Different monocyte and granulocyte lineage inducers induced CD157 expression to varying extents while the macrophage differentiation-inducing phorbol 12-myristate 13-acetate (PMA) induced its down-regulation. Time-kinetics of VD3 treatment of HL-60 cells showed that the appearance of CD157 and CD11b (a differentiation marker) antigens were not substantial up to 24 hours but increased subsequently although the appearance of CD38 became significant within 6 hours. Two-color staining of VD3-treated HL-60 cells displayed an apparently linear correlation between CD157 and CD11b expression. Dibutyryl cAMP (cAMP agonist) and forskolin (cAMP-increasing agent) augmented the VD3-dependent induction of CD157 and CD11b expression while PGE1 (cAMP-decreasing agent) inhibited it, suggesting the involvement of a cAMP-dependent mechanism in VD3-induced CD157 upregulation. Co-treatment of HL-60 cells with VD3 plus TNF-alpha or ara-C produced an additive effect on CD157 upregulation. The upregulated CD157 in the VD3-differentiated HL-60 cells was able to activate CD157-dependent tyrosine kinase signal when cross-linked with anti-CD157 antibody.

ADP-ribosyl Cyclase↗
PubMed2000

Effect of aging on tryptophan hydroxylase in rat brain: implications on serotonin level.

Tryptophan hydroxylase (TrpH) catalyzes a rate-limiting step in the biogenesis of serotonin. The main objective of this study is to investigate the effect of aging on the activity of TrpH in serotonergic-enriched brain regions such as midbrain, pons, and medulla. TrpH activity was monitored by incubating various concentrations of tryptophan in a fixed amount of brain homogenate from midbrain, pons, and medulla of 2-month (young), 12-month (mature), and 24-month (old) rats (pH 7.4, 37 degrees C). The product 5-hydroxytryptophan was quantitated using a reversed phase HPLC equipped with an electrochemical detection system. Michaelis-Menton constants, K(m) and V(max), were calculated using the Lineweaver-Burk plot. The affinity (K(m)) of the enzyme significantly declined in midbrain and pons of old rats (141.1 +/- 2. 6, 126.0 +/- 10.8 microM) relative to mature rats (22.4 +/- 7.7, 38. 2 +/- 4.7 microM). However, no change was observed in medulla of old rats. The V(max) of TrpH in pons of all three age group rats was fairly constant. However, the V(max) of midbrain was significantly elevated, whereas that of medulla was reduced in old rats relative to mature rats. Clearance formation, a ratio of V(max) to K(m), of 5-hydroxytryptophan declined significantly in midbrain, pons, and medulla of old rats relative to mature rats. A combined effect of inefficient phosphorylation and oxidative damage of TrpH enzyme may be responsible for lower TrpH activity in aging brain. Such alterations in TrpH activity may reduce the level of serotonin in brain, which may be linked to late-life depression and other brain disorders, such as Alzheimer and Parkinson diseases.

Aging↗
PubMed1999

Novel kinetics, behaviour and cell-type specificity of CD157-mediated tyrosine kinase signalling.

CD157, a recently characterized leukocyte surface antigen, has recently been shown to induce tyrosine phosphorylation of a 130-kDa protein (p130) when cross-linked with its antibody (ligand). We have further investigated the detailed kinetics, behaviour and cell-type specificity of this CD157-stimulated p130 phosphorylation. We demonstrate that CD157-mediated p130 phosphorylation is ligand independent in recombinant CD157-expressing CHO, MCA102 and COS-7 cells but is ligand dependent in HL-60-differentiated monocytes (mHL-60) having enhanced CD157 expression. This p130 phosphorylation is activated only at lower temperatures (0-4 degrees C) in MCA102, COS-7 and mHL-60 cells but is temperature insensitive in CHO cells. We further demonstrate that the CHO/CD157 cell clones have approximately 22-28% slower rates of proliferation than that of a CHO/mock clone. But the MCA102 cell proliferation remains unaffected by CD157 expression. We postulate that the difference in the temperature sensitivity of p130 phosphorylation can be responsible for the discrepancy in the rates of MCA102/CD157 and CHO/CD157 cell proliferation.

ADP-ribosyl Cyclase↗
PubMed1998

Functional expression of secreted mouse BST-1 in yeast.

BST-1, a bone marrow stromal cell surface antigen, is a glycosyl phosphotidylinositol-anchored protein that stimulates pre-B-cell growth and has adenosine diphosphate (ADP)-ribosyl cyclase and cyclic ADP-ribose (cADPR) hydrolase activity. The two enzymatic activities are responsible for the synthesis and hydrolysis of cADPR, a novel second messenger of calcium release from intracellular calcium stores. The expression and characterization of human BST-1 in certain mammalian cell lines have been reported. We have expressed the murine BST-1 in yeast as a 6 x His-tagged secreted protein. The recombinant protein has been purified and subjected to structural and functional characterization. It has an apparent molecular mass of 38.5 kDa on SDS-PAGE gel stained with Coomassie blue and is recognized on Western blots by a rabbit polyclonal antibody against BST-1. Deglycosylation of the protein with N-glycanase produces a ladder of bands with molecular sizes ranging from 32 to 39 kDa. The protein possesses the ADP-ribosyl cyclase activity as measured using nicotinamide guanine dinucleotide as substrate.

ADP-ribosyl Cyclase↗
PubMed1997

Relationships among calving season, heat load, energy balance and postpartum ovulation of dairy cows in a subtropical environment.

The study was designed to examine the relationships among calving season, energy balance, temperature humidity index (THI), and postpartum ovulation in high producing cows in a subtropical environment. Holstein cows calving in a feedlot dairy in southeast Queensland during winter (n = 23) and summer (n = 21) were monitored during the first 9 weeks of lactation. Cows were weighed and blood samples collected twice weekly: plasma progesterone, plasma metabolites related to energy and mineral balance, and haematological measurements were performed. Milk production was measured, body condition score was estimated, and trans-rectal ultrasound examinations of the ovaries were each undertaken once a week. The interval between calving and first ovulation was significantly longer in cows calving in summer (22.8 vs. 17.6 days, P < 0.05). Interval from calving to the first postpartum ovulation (FOVL) was inversely related to the mean plasma glucose concentration for the first 9 weeks after calving (GLU): FOVL = 80.0-17.9GLU, (R2 = 0.25, P < 0.001). Plasma progesterone concentration during the life of the second corpus luteum after calving was negatively correlated with THI during the first 2 weeks after calving (r = 0.55, P < 0.001). Plasma glucose concentration (GLU) was negatively correlated with milk yield (MYD) and rectal temperature (RT), and positively correlated with plasma calcium concentration (Ca) according to the following regression equation. GLU = 33.1 - 0.02MYD + 0.91Ca - 0.48RT, (R2 = 0.58, P = 0.0001).

3-Hydroxybutyric Acid↗
PubMed1992

Effects of intrauterine infusion of Escherichia coli endotoxin in normal cows and in cows with endometritis induced by experimental infection with Streptococcus agalactiae.

Two experiments were carried out to describe the effects of intrauterine infusion of Escherichia coli endotoxin on some aspects of nonspecific uterine defense mechanisms in healthy cyclic cows (Experiment 1) and in cows with induced endometritis by experimental infection with Streptococcus agalactiae (Experiment 2). In Experiments 1 and 2, the mean log(e) total white cell counts (>95% neutrophils) in the uterine flushing fluid of the endotoxin-treated group were significantly increased (P<0.01 and P<0.05, respectively). Streptococcus agalactiae was detected by the Latex Agglutination Test (LAT) in 47% of the samples from uteri experimentally infected with this organism; 12.5% were positive on culture, and only 10% were positive on both tests. With one exception, all the samples with a positive culture were positive to the LAT, but not all samples submitted to the LAT had positive culture. There was a significant (P<0.05) association between endotoxin treatment and the presence of infection detected by the LAT but not with that detected by culture (P>0.05) at 3 to 12 days post infection. Similar results were found at 8 to 16 days post infection. The infection disappeared from the endotoxin-treated group but not from the non-treated group 12 days after the induction of infection. It is concluded that intrauterine E. coli endotoxin infusion might provide an alternative treatment for those cows with endometritis that is refractory to conventional antimicrobial and hormonal therapy. It is also concluded that the LAT is an easier, quicker and more reliable method than bacterial culture for the detection of endometritis caused by Strep. agalactiae , and, possibly, such immunodiagnostic tests may be useful for the detection of other uterine infections.

Journal Article↗
PubMed1992

The bactericidal effect of N-acetyl-beta-D-glucosaminidase on bacteria.

The bactericidal activity of N-acetyl-beta-D-glucosaminidase (NAGase) on some of the potential bacterial pathogens of the cow was determined. NAGase treatment significantly decreased the mean log10 number of Actinomyces pyogenes (P less than 0.01) and Staphylococcus aureus (P less than 0.05) after 2 and 4 hours of incubation at 37 degrees C. Similarly NAGase treatment significantly (P less than 0.05) reduced the mean log10 number of Streptococcus agalactiae and Pseudomonas aeruginosa after 4 hours incubation at 37 degrees C. NAGase did not reduce the numbers of Escherichia coli or Enterobacter aerogenes after either 2 or 4 hours incubation. Since NAGase and presumably other lysosomal enzymes are free on normal mucosal surfaces such as the uterus it is suggested that this direct bactericidal activity may be an important component of the normal defense mechanisms.

Acetylglucosaminidase↗
PubMed1992

N-acetyl- beta -D-glucosaminidase activity in the endometrial epithelium of the cow's uterus during the oestrous cycle and pregnancy.

The levels of N-acetyl-beta-D-glucosaminidase (NAGase) were measured in the endometrial epithelial tissue of the bovine uterus during the oestrous cycle and during pregnancy. NAGase levels were significantly (P<0.001) higher in the epithelial tissue of the cow's uterus during the luteal phase of the cycle and during pregnancy than during the non-luteal phase. There were significantly (P<0.001) higher mean NAGase values in the epithelial than the subepithelial layers of the uterus in the two cycle phases and in pregnancy. Leucocyte numbers were significantly (P<0.05 and P<0.001) higher in the cows' uteri during the non-luteal phase than during the luteal phase and pregnancy, respectively. It is concluded that the endometrial epithelial layer is significantly active in terms of NAGase release and that this may be related to increased progesterone concentrations. In addition, the epithelial tissue (not leucocytes) appears to be the main contributor to the total NAGase activity in uterine tissue.

Journal Article↗
PubMed1991

Bovine endometritis: current and future alternative therapy.

Abnormal parturition can be followed by a persistent endometritis which can have deleterious effects on the cow's subsequent reproductive performance. Normal and active uterine defense mechanisms have been reported to be very important for the exclusion of bacterial infection from the uterus and recovery from endometritis developing after parturition. Despite the widespread use of local or systemic antibiotics, antiseptics, sulfonamides and hormones, rates of recovery from endometritis and the cow's subsequent fertility have not increased appreciably. Furthermore, the cost of any treatment, the frequency of its administration and the milk disposal after treatment make their use uneconomic. Alternative therapies which stimulate the natural uterine defense mechanisms have been suggested as treatments of bovine endometritis. These include: (I) Endotoxins such as lipopolysaccharide of E. coli, (II) serum, plasma or hyperimmune serum, (III) polymorphonuclear leucocyte (PMN) extracts and components and (IV) granulocyte-macrophage colony stimulating factors (G-M CSF).

Animals↗
PubMed1991

Nuclear magnetic resonance imaging (MRI).

This article discusses the basic concepts of Magnetic Resonance Imaging (MRI) with the intention to introduce the subject to uninitiated. The MRI technique is a powerful noninvasive probe of the body's internal anatomy. In MRI, the images are produced not by X-rays, but through the use of non-ionizing radiowaves that stimulate transitions between spin states of nuclei in a magnetic field when passed through the body. The time required for the nucleus to return to equilibrium gives information about the environment of that nucleus. In this way tissue abnormalities can be determined in vivo. This article covers the basis of MRI phenomena, the concept of magnetic moment of the sample, NMR exalation and emission and the equipment necessary to observe these NMR properties. The primary agents used to increase tissue contrast in MRI are also mentioned. Finally the importance and prospects of this technique in Pakistan have been discussed.

Humans↗
PubMed1990

Postpartum uterine flora following normal and abnormal puerperium in cows.

Uterine swabs were taken from the uteri of three groups of cows (n = 5 each) on Days 1 and 2 and then at 3-d intervals up to 32 d post partum. Group I cows had a normal delivery, Group II cows had dexamethasone-induced parturition, and Group III cows were subjected to a Caesarean section. All cows in Group III and two cows in Group II retained their fetal membranes. A total of 230 bacterial isolates were made, and the most frequently isolated bacteria were Escherichia coli, streptococci, Proteus spp., and clostridia. The highest number of bacterial isolates and the longest mean time to complete uterine involution were in the Group III cows.

Journal Article↗
PubMed1989

N-acetyl-beta-D-glucosaminidase activity in bovine uterine fluid and blood serum during the postpartum period.

Uterine fluid and serum N-acetyl-beta-D-glucosaminidase (NAGase) was determined in cows during the first 32 d post partum following normal and abnormal parturitions. Both uterine fluid and serum NAGase activities were elevated after calving and then started to decline gradually toward the 32nd day after calving, when they reached their lowest concentrations. No significant differences were found between the mean NAGase concentrations in uterine fluid of the two groups, although significant differences were found between the mean values of the combined groups between days. With serum NAGase concentrations, significant differences (P<0.01) were found between the mean values of the normal and abnormal puerperium groups. The major part of the enzyme detected in postpartum uterine fluid is probably contributed by epithelial cells present in the fluid. Uterine leucocytes and endometrial cell damage caused by bacterial infection may also contribute to the total NAGase activity in uterine fluid.

Journal Article↗
PubMed1989

Bovine uterine defense mechanisms: a review.

Bovine uterine defense mechanisms during physiological and pathological conditions have been reviewed in this article. The initial uterine defense against bacterial infection is phagocytosis by uterine leucocytes (mainly neutrophils). The reported literature showed that very little work has been done on immunoglobulins and their role in the bovine uterine defense mechanisms; however, some investigators have found a positive correlation between gamma-globulin and the development of uterine infection after calving. Many explanations exist for the difference in susceptibility of the uterus to infection during the different phases of estrous cycle; however, most of the reports agreed that the uterine defense mechanism is inadequate during diestrus. The abnormal puerperium effects uterine defense mechanisms adversely and prolongs the time to complete uterine involution. Future treatment may utilise natural antimicrobial substances such as proteins or peptides derived from PMN, chemoattractant substances such as E. coli lipopolysaccharide or a bacteria-free filtrate of streptococci. Specific hyperimmunserum could also be used as opsonin for refractory cases of uterine bacterial infections.

Animals↗
PubMed1989

Cytotoxicity due to a reaction between polystyrene and constituents of stool.

Cell monolayers grown in polystyrene culture plates and in glass tubes are routinely used in virology laboratories around the world for virus isolation and identification. Monolayers of different types of cells grown in polystyrene culture plates were found to show a strange cytotoxicity when inoculated with stool samples from healthy children from Bangladesh. When inoculated with 0.2 ml of a 10% stool sample 100% (80/80) of the cell monolayers established in polystyrene plates showed cytopathy by 4 days and 60% (48/80) within first 2 hours of sample inoculation. In contrast only 4% (4/90) of samples inoculated in the same type of cell monolayers but established in glass cell culture tubes showed cytopathy by 4 days; out of these 4 only 2 (2%) showed cytopathy in the first 2 hours. Cytotoxicity could be reduced to half when the amount of inoculated stool sample was reduced by half in cases where polystyrene was used as the substrate. This difference of cytopathy under two different circumstances (polystyrene substrate versus glass substrate) was statistically significant (P less than 0.001).

Cell Survival↗
PubMed1985

Mycotoxins as carcinogens.

Fungi which contaminate food and feed products produce toxic metabolites under favourable conditions, thus posing a serious health problem. A variety of mycotoxins are produced by different fungi, but aflatoxins have been investigated more extensively. Varied reports are available on the production of aflatoxins by different species of Aspergillus and Penicillium; however, A. flavus and A. parasiticus have the greatest capacity and appear to be the primary sources of aflatoxins. Preformed mycotoxins are ingested by man through the consumption of vegetable and animal products (milk, meat, etc.). Factors affecting toxicity include species, age, sex, and nutrition. Evidence from animal experiments provides enough information to indicate that most of the mycotoxins are carcinogens.

Aflatoxins↗