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Biomedical subjects

A Hussain

Publications and source records attributed to A Hussain.

At least 91 records · Page 5Linked to original sources
PubMed1999

Soil compaction. A role for ethylene in regulating leaf expansion and shoot growth in tomato?

The role of ethylene in regulating growth in tomato (Lycopersicon esculentum Mill.) during compaction stress was examined using wild-type (cv Ailsa Craig) and transgenic (ACO1(AS)) genotypes; the latter has a reduced capacity to produce ethylene. Ethephon or silver ions were applied to increase ethylene production or block its action. Shoot growth in both genotypes was comparable in uncompacted (1.1 g cm(-3)) and uniformly compacted soil (1.5 g cm(-3)). However, a 1.1/1.5-g cm(-3) split-pot treatment invoked marked genotypic differences: growth was reduced in cv Ailsa Craig but was comparable to uncompacted control plants in ACO1(AS). As xylem sap abscisic acid levels were similar, abscisic acid was not responsible for inhibiting growth in cv Ailsa Craig. These genotypic differences in growth were accompanied by increased ethylene evolution in cv Ailsa Craig, suggesting that the ability of ACO1(AS) to maintain growth in the split-pot treatment reflected its lower ethylene levels, a view supported by the observation that excising the roots in the compacted compartment reduced ethylene evolution and restored shoot growth in cv Ailsa Craig. Treatment with silver restored shoot growth in cv Ailsa Craig, whereas treatment with ethephon reduced growth in ACO1(AS). Thus, ethylene apparently has a key role in determining growth when tomato plants encounter differential soil compaction.

Journal Article↗
PubMed1999

Organizational barriers and ethnicity in the Scottish NHS.

The NHS faces a crisis in terms of staffing and recruitment. Many of the ethnic minority GPs in inner city areas throughout the UK are coming up to retirement age, and there is an insufficient supply of trainees to fill estimated vacancies. Over 2,000 nursing vacancies exist across the UK, and recruitment to the profession and retention within the profession are poor. Nurses have been recruited from overseas for the past 40 years, and are currently being recruited from Finland, Malaysia, and the West Indies, whilst doctors are being sought in India, Pakistan and Africa. Overseas recruitment is not a new phenomenon, and numerous studies have been carried out to examine equal opportunities and racial discrimination within the NHS. The aim of this paper was to examine ethnicity and equal opportunities within the Scottish NHS and record the levels of organisational awareness of ethnicity and equal opportunities' issues. The paper also examines the link between health service delivery to ethnic minorities and internal cultural attitudes to staff.

Career Mobility↗
PubMed1999

Speech-intelligibility improvements using a binaural adaptive-scheme based conceptually on human auditory processing.

A speech enhancement scheme is presented using diverse processing in sub-bands spaced according to a human-cochlear describing function. The binaural adaptive scheme decomposes the wide-band input signals into a number of band-limited signals, superficially similar to the treatment the human ears perform on incoming signals. The results of a series of intelligibility and formal listening tests are presented in which acoustic speech signals corrupted with recorded automobile noise were presented to 15 normal hearing volunteer subjects. For the experimental cases considered, the proposed binaural adaptive sub-band processing scheme delivers a statistically significant improvement in terms of both speech-intelligibility and perceived quality when compared with both the conventional wide-band processed and the noisy unprocessed case. The scheme is capable of extension to a potentially more flexible sub-band processing method based on a constrained artificial neural network (ANN).

Acoustic Stimulation↗
PubMed1999

Multi-sensor neural-network processing of noisy speech.

In this paper, a novel Artificial Neural-Network (ANN) based multi-sensor multi-band adaptive signal-processing scheme is described for enhancing acoustic-speech corrupted by real noise and reverberation. Numerically robust adaptation-algorithms are employed for the ANN based sub-band filters; and, new simulation experiments are reported using real-reverberant automobile data which demonstrate that the proposed speech-enhancement system is capable of outperforming conventional linear filtering-based wide-band and multi-band noise-cancellation schemes.

Acoustic Stimulation↗
PubMed1999

Increased regional and transmyocardial dispersion of ventricular repolarization in end-stage renal disease.

BACKGROUND: Approximately half of patients with end-stage renal disease die because of cardiac disease, and ventricular arrhythmias are the common terminal events. Increased dispersion of the repolarization phase of the myocardial action potential can predispose patients to ventricular tachycardia and fibrillation causing cardiac death. OBJECTIVE: To determine the existence of increased regional and transmyocardial dispersion of ventricular repolarization in end-stage renal disease. STUDY DESIGN: Case-control prospective study. PATIENTS AND METHODS: The QT dispersion and the interval between the peak of the T wave (Tp) and the end of the T wave (Te) on a surface electrocardiogram represent regional and transmyocardial dispersion in ventricular repolarization, respectively. The prehemodialysis QT dispersions and Tp-Te intervals of 94 consecutive patients with end-stage renal disease were determined and compared with those of age- and sex-matched healthy controls. RESULTS: Both the QT and the QTc dispersion were significantly higher in the end-stage renal disease group than in the control group (QT dispersion 46 +/- 17 ms [mean +/- SD] versus 26 +/- 16 ms, P < 0.001; QTc dispersion 51 +/- 20 ms versus 30 +/- 20 ms, P < 0.001). Similarly, both the corrected average Tp-Te and the corrected maximum Tp-Te intervals were significantly higher in the end-stage renal disease group than in the control group (corrected average Tp-Te interval 99 +/- 19 ms versus 87 +/- 19 ms, P = 0.023; corrected maximum Tp-Te interval 114 +/- 23 ms versus 103 +/- 23 ms, P = 0.023). CONCLUSIONS: Increased regional and transmyocardial dispersion of ventricular repolarization in end-stage renal disease was demonstrated. This increased dispersion may be a contributory factor in the high cardiac mortality in patients with end-stage renal disease.

Aged↗
PubMed1999

Verapamil prolongs atrial fibrillation by evoking an intense sympathetic neurohumoral effect.

BACKGROUND: Verapamil is an effective drug to slow ventricular rate in atrial fibrillation (AF). Clinically, however, i.v. verapamil enhances AF despite experimental evidence suggesting favorable effects of the drug on AF-induced electrical remodeling of the atria. METHODS AND RESULTS: To clarify this controversy, i.v. verapamil's effects were determined in 41 anesthetized dogs, including 6 after beta-blockade. Intravenous verapamil (0.20 mg/kg, bolus, and 0.20 mg/kg/h, infusion) increased the duration of AF (induced by a single extrastimulus), from 19 +/- 6 to 130 +/- 24 s, P < 0.001, and slowed its ventricular response, from 246 +/- 25 to 110 +/- 15 min-1, P < 0.001. Mean aortic pressure, P = 0.002, and systemic vascular resistance, P < 0.035, decreased, and mean right atrial pressure increased, P < 0.001. Plasma norepinephrine concentration increased by 502 +/- 83 pg/mL, P < 0.001, plasma epinephrine concentration by 804 +/- 206 pg/mL, P = 0.002, and plasma total catecholamine concentration by 1606 +/- 366 pg/mL, P = 0.001. Prolongation of AF was related to an increase in mean right atrial pressure, R = 0.49, P = 0.014, right atrial wall tension, R = 0.45, P = 0.044, and plasma norepinephrine concentration, R = 0.83, P < 0.001, with plasma norepinephrine concentration remaining as an independent predictor of AF lengthening on multivariable analysis. In the presence of beta-blockade, verapamil produced comparable or more exaggerated hemodynamic effects, but it did not promote AF. CONCLUSION: The prolongation of AF by verapamil can be related directly to the intense sympathetic neurohumoral effect that occurs following the drug's administration.

Animals↗
PubMed1998

Gene amplification and transcriptional upregulation of the sarco/endoplasmic reticulum Ca2+ transport ATPase in thapsigargin-resistant hamster smooth muscle cells.

We have selected a series of cell lines from the parental Syrian hamster smooth muscle cell line DDT1-MF2that are resistant to thapsigargin (TG), a specific inhibitor of the sarcoplasmic/endoplasmic reticulum Ca2+transport ATPases (SERCAs). Cells were selected for resistance to TG in the presence or absence of cyclosporin (CSA), which is a competitive inhibitor of the multidrug transporter p-glycoprotein (pgp). Since TG is a known substrate for pgp, selection for TG resistance was carried out in the presence of CSA in an attempt to minimize the contribution of pgp, and to identify the potential range of adaptive responses of the SERCA pump itself, during the development of the TG-resistant phenotype. Irrespective of whether the selection is carried out in the presence or absence of CSA, pgp is overexpressed in the TG-resistant DDT1-MF2cells. SERCA protein is also overproduced in the TG-resistant cell lines, which occurs through one of several mechanisms. Included among these, is amplification of the SERCA gene and enhanced transcription of the gene. Enhanced transcription is observed only upon long-term selection and occurs through the SERCA gene proximal promoter elements. Although SERCA transcription in wild-type cells is dependent upon the -284 to -72 bp region of the SERCA promoter, the TG-resistant cells utilize both the -284 to -72 bp and the -72 to +80 bp promoter regions for enhanced SERCA transcription. That is, additional elements within the -72 to +80 bp region are recruited in the TG-resistant cells to allow for increased SERCA expression. A post-transcriptional step may also be recruited by the TG-resistant cells in their overall strategy to produce increased amounts of the SERCA protein. These studies demonstrate that the DDT1-MF2cells can utilize different mechanisms which lead to increased levels of SERCA protein as the cells adapt to inhibition of the ATPase by TG.

Animals↗
PubMed1998

Specific substitutions at amino acid 256 of the sarcoplasmic/endoplasmic reticulum Ca2+ transport ATPase mediate resistance to thapsigargin in thapsigargin-resistant hamster cells.

High levels of resistance to thapsigargin (TG), a specific inhibitor of intracellular Ca2+ transport ATPases (SERCAs), can be developed in culture by stepwise exposure of mammalian cells to increasing concentrations of TG. We have identified, in two independently selected TG-resistant hamster cell lines of different lineages, mutant forms of SERCA. In the TG-resistant Chinese hamster lung fibroblast cell line DC-3F/TG, a T --> C change at nucleotide 766 introduces a Phe256 --> Leu alteration within the first cytosolic loop of the SERCA. In contrast, in the TG-resistant Syrian hamster smooth muscle cell line DDT/TG 4 microM, a T --> C change at nucleotide 767 introduces a Phe256 --> Ser mutation at that position. When these specific mutations are introduced into a wild-type full-length avian SERCA1 cDNA, transfection experiments reveal that Ca2+ transport function and ATP hydrolytic activity are not altered by such mutations. However, a 4-5-fold resistance to TG inhibition of Ca2+ transport function occurs upon the introduction of either the Phe256 --> Leu or the Phe256 --> Ser mutation into wild-type SERCA1. These specific mutations also render the hydrolytic activity of the ATPase resistant to inhibition by TG. Our results not only implicate amino acid 256 in TG-SERCA interactions, but also demonstrate that specific mutations within SERCA can mediate resistance to TG.

Amino Acids↗
PubMed1998

Analysis of nanomolar S-nitrosothiol concentrations in physiological media.

S-Nitrosothiols occur endogenously and are thought to function as storage forms and/or stable carriers of nitric oxide. Moreover, the S-nitrosothiols have been postulated to function as neurotransmitters and mediate the vasodilator action of glyceryl trinitrate. Because of the increasing pharmacological and physiological interest in S-nitrosothiols, a sensitive method for analysis of these substances is required. We describe a sensitive method based on adsorptive stripping voltammetry for measurement of two S-nitrosothiols, namely, S-nitroso-N-acetyl-D-penicillamine (SNAP) and S-nitrosoglutathione (SNOG), in Krebs' solution. The method is based on the irreversible electrochemical reduction of SNAP and SNOG at the hanging mercury drop electrode (HMDE). The analytes were adsorbed at the HMDE for 60 s at -0.100 V, then exposed to a cathodic linear potential scan of 100 mV s(-10) which resulted in the reduction of SNAP at -0.470 V and SNOG at -0.530 V. Under these conditions, 4 nM SNAP and 11 nM SNOG were readily quantified. Using the above method, we were able to confirm the rapid degradation of SNAP under UV irradiation. Reproducibility of the method as applied to the analysis of these S-nitrosothiols in Krebs' solution was demonstrated by the within-day and day-to-day coefficients of variation of 1.5% and 2.0%, respectively.

Adsorption↗
PubMed1998

Frontal sinolith.

We report on a case of an endogenous frontal sinolith and a literature review of classification and use of the terms rhinolith, and sinolith.

Calcinosis↗
PubMed1998

Development and internal validation of an in vitro-in vivo correlation for a hydrophilic metoprolol tartrate extended release tablet formulation.

PURPOSE: To develop and validate internally an in vitro-in vivo correlation (IVIVC) for a hydrophilic matrix extended release metoprolol tablet. METHODS: In vitro dissolution of the metoprolol tablets was examined using the following methods: Apparatus II, pH 1.2 & 6.8 at 50 rpm and Apparatus I, pH 6.8, at 100 and 150 rpm. Seven healthy subjects received three metoprolol formulations (100 mg): slow, moderate, fast releasing and an oral solution (50 mg). Serial blood samples were collected over 48 hours and analyzed by a validated HPLC assay using fluorescence detection. The f2 metric (similarity factor) was used to analyze the dissolution data. Correlation models were developed using pooled fraction dissolved (FRD) and fraction absorbed (FRA) data from various combinations of the formulations. Predicted metoprolol concentrations were obtained by convolution of the in vivo dissolution rates. Prediction errors were estimated for Cmax and AUC to determine the validity of the correlation. RESULTS: Apparatus I operated at 150 rpm, and pH of 6.8 was found to be the most discriminating dissolution method. There was a significant linear relationship between FRD and FRA when using either two or three of the formulations. An average percent prediction error for Cmax and AUC for all formulations of less than 10% was found for all IVIVC models. CONCLUSIONS: The relatively low prediction errors for Cmax and AUC observed strongly suggest that the metoprolol IVIVC models are valid. The average percent prediction error of less than 10% indicates that the correlation is predictive and allows the associated dissolution data to be used as a surrogate for bioavailability studies.

Adrenergic beta-Antagonists↗
PubMed1998

Specificity of cardiac troponin I and creatine kinase-MB isoenzyme in asymptomatic long-term hemodialysis patients and effect of hemodialysis on these cardiac markers.

OBJECTIVES: The objectives of this study were: (1) to evaluate the specificity of cardiac troponin I and creatine kinase-MB isoenzyme in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis, and (2) to evaluate the effect of hemodialysis on the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme. METHODS: One hundred and forty-four consecutive ambulatory asymptomatic chronic renal failure patients on hemodialysis for a minimum of 1 year were evaluated clinically. Serum cardiac troponin I and creatine kinase-MB isoenzyme levels were measured with specific monoclonal antibodies before and after dialysis using ACCESS Troponin I and ACCESS CK-MB assays. RESULTS: The specificity of serum cardiac troponin I was 83% with a cutoff level of 0.03 ng/ml, which is an expected level for healthy population, but it rose to 100% with a cutoff level of 0.15 ng/ml, which is a reference level for patients with acute myocardial infarction. Twenty-four (17%) patients had borderline elevation in cardiac troponin I (>0.03 to <0.15 ng/ml). A history of angina pectoris was more common in the borderline-elevated cardiac troponin I subgroup. In 28% of the patients, serum creatine kinase-MB isoenzyme levels were increased with a specificity of 72% at a cutoff level of 4 ng/ml, which is the upper limit of normal, but the specificity rose to 98% by increasing the cutoff level value to 10 ng/ml. There were no statistically significant differences in serum levels of cardiac troponin I and creatine kinase-MB isoenzyme before and after dialysis. CONCLUSIONS: Cardiac troponin I is highly specific in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis; borderline elevations in cardiac troponin I may represent microinjury to the myocardium. A serum level of creatine kinase-MB isoenzyme >2.5 times of the normal upper limit may be highly specific in this patient population. Hemodialysis per se does not significantly change the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme.

Angina Pectoris↗
PubMed1998

Gastrostomy complications in infants and children.

Thirty children have had percutaneous endoscopic gastrostomy (PEG) inserted for feeding purposes. During a follow-up period of 5-45 months (mean 24 months), complications were recorded in 13 patients. Some patients had more than one complication. Complications included colocutaneous fistula, gastro-oesophageal reflux, wound infection, granulation tissue formation, tube leakage, tube blockage and bleeding. The authors present a retrospective review of the results and discuss the management of these complications.

Adolescent↗
PubMed1997

Transcriptional repression of the cyclin-dependent kinase inhibitor p21WAF1/CIP1 gene mediated by cis elements present in the 3'-untranslated region.

The cyclin-dependent kinase inhibitor p21WAF1/CIP1 plays a major role in the induction of G1 cell cycle arrest following DNA damage and is known to be regulated by p53-dependent and -independent pathways. Here, we show that p21WAF1/CIP1 transcription is also regulated, independently of p53, by the cis elements that are located downstream of the transcription start site. A cDNA fragment of approximately 180 bp, located 260 bases 3' to the translation termination codon of p21WAF1/CIP1 cDNA, was cloned in both the sense and antisense orientations downstream of the CMV promoter, upstream of the SV40 promoter, and both upstream and downstream of the p21WAF1/CIP1 promoter in the plasmids carrying the luciferase reporter gene. The constructs were transiently transfected in human breast carcinoma cells MCF-7 and MDA-MB-468 and a Syrian hamster smooth muscle cell line DDT1MF2 and were found to elicit 2-3-fold or higher repression of luciferase activities. By using overlapping deletions of the above 180-bp fragment, we identified a 48-bp subfragment that contains putative cis element(s) that participate in the transcriptional repression of the p21WAF1/CIP1 gene. The overlapping subfragments bind, in vitro, to specific proteins present in the nuclear extracts of MDA-MB-468 and DDT1MF2 cells. We, therefore, propose that additional mechanism(s) exist that regulate expression of the cellular p21WAF1/CIP1 and may contribute to p21WAF1/CIP1-dependent control of the cell cycle.

Animals↗
PubMed1997

2-Phenylaminoadenosine stimulates dopamine synthesis in rat forebrain in vitro and in vivo via adenosine A2 receptors.

The adenosine agonist 2-phenylaminoadenosine (PAD) stimulated tyrosine hydroxylase activity in rat striatum in vitro. This effect was selectively blocked by the A2 antagonist 8-chlorostyrylcaffeine (CSC), suggesting an A2 receptor-mediated mechanism. PAD also produced a corresponding increase in striatal adenylyl cyclase activity. Using an in vivo model that measures presynaptic effects of drugs at dopamine nerve terminals, intracerebroventricular administration of PAD to rats stimulated tyrosine hydroxylase activity in striatum in a manner that was selectively blocked by CSC. These results suggest that PAD stimulates adenylyl cyclase and tyrosine hydroxylase activity, with a corresponding increase in dopamine synthesis, by activation of presynaptic A2-type receptors in mammalian forebrain.

Adenosine↗
PubMed1997

Effect of aprotinin on plasma fibronectin levels during cardiopulmonary bypass.

BACKGROUND: Acute depletion of plasma fibronectin levels has been reported during and after cardiopulmonary bypass; degradation of fibronectin by proteolytic enzymes has been suggested as one of the causes. This study was designed to assess the possible preservation of fibronectin levels by aprotinin during cardiopulmonary bypass. METHODS: Plasma fibronectin levels were evaluated in 19 patients undergoing either elective coronary artery bypass grafting or a valvular heart operation. The study was conducted prospectively in a controlled, randomized, double-blinded manner. Nine test patients (group A) received intraoperative, intravenous administration of aprotinin; 10 control patients (group B) received equivalent volume of normal saline solution. Fibronectin levels were measured immediately after induction of anesthesia (as the baseline for the study) and at the following times: after 5 minutes on bypass, after 30 minutes on bypass, immediately before the start of rewarming, and after being off bypass for 5 minutes, but before protamine administration. RESULTS: Both groups' basic characteristics were very similar. Group A patients were found to have significantly greater fibronectin levels than group B during and immediately after cardiopulmonary bypass (p < 0.002). CONCLUSIONS: Administration of aprotinin intraoperatively appears to result in better preservation of fibronectin levels during cardiopulmonary bypass. Although the mechanism of action of aprotinin as a proteolytic inhibitor remains unclear, it has been suggested that it exerts an inhibiting effect on proteolytic enzymes by forming an aprotinin-proteinase complex. The clinical implications of the greater level of fibronectin achieved by the intraoperative use of aprotinin during cardiopulmonary bypass need further evaluation.

Aprotinin↗
PubMed1997

Modified tragal cartilage--temporoparietal and deep temporal fascia sandwich graft technique for repair of nasal septal perforations.

Fifteen cases of nasal septal perforation were repaired with a tragal cartilage--temporoparietal and deep temporal fascia sandwich technique using a modification of the approach previously described (Hussain and Kay, 1992). Successful closure was achieved in 14 patients (100 per cent) after an observation time of up to two years. The operative technique and advantages of the modified approach are described.

Adult↗