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Biomedical subjects

A Malik

Publications and source records attributed to A Malik.

At least 37 records · Page 2Linked to original sources
PubMed2003

Experimental model for cartilage tissue engineering to regenerate the zonal organization of articular cartilage.

OBJECTIVE: Regeneration of the zonal organization of articular cartilage may be an important advancement for cartilage tissue engineering. The first goal of this study was to validate our surgical technique as a method to selectively isolate chondrocytes from different zones of bovine articular cartilage. The second goal was to confirm that chondrocytes from different zones would have different proliferative and metabolic activities in two-dimensional (2-D) and 3-D cultures. Finally, to regenerate the zonal organization, we sought to make multi-layered constructs by encapsulating chondrocytes from different zones of articular cartilage. DESIGN: Cartilage slices were removed from three (upper, middle, and lower) zones of articular cartilage of young bovine legs. Histology and biochemical composition of the cartilage slices were analyzed to confirm that they had been obtained from the proper zone. Growth kinetics and gene expression in monolayer culture and matrix formation in photopolymerizing hydrogels were evaluated. Multi-layered photopolymerizing hydrogels were constructed with chondrocytes from each zone of native cartilage encapsulated. Cell viability and maintenance of the cells in the respective layer were evaluated using the Live/Dead Viability kit and cell tracking protocols, respectively. After 3 weeks, the multi-layered constructs were harvested for histologic examination including immunohistochemistry for type II collagen. RESULTS: Analysis of histology and biochemical composition confirmed that the cartilage slices had been obtained from the specific zone. Chondrocytes from different zones differed in growth kinetics and gene expression in monolayer and in matrix synthesis in 3-D culture. Cells encapsulated in each of the three layers of the hydrogel remained viable and remained in the respective layer in which they were encapsulated. After 3-week culture, each zone of multi-layered constructs had similar histologic findings to that of native articular cartilage. CONCLUSION: We present this as an experimental model to regenerate zonal organization of articular cartilage by encapsulating chondrocytes from different layers in multi-layered photopolymerizing gels.

Animals↗
PubMed2003

Synthesis and antimicrobial activities of some isocoumarin and dihydroisocoumarin derivatives.

A new series of the isocoumarin derivatives of ibuprofen, fluribiprofen, naproxen, valproic acid and 1-naphthoic acid have been synthesized via condensation of homophthalic acid with their respective acid chlorides. The conversion of the latter two isocoumarins into (dl)-3,4-dihydroisocoumarins has also been achieved. Most of the synthesized compounds showed antifungal and antibacterial activities.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2003

Tuberculosis diagnosis and treatment practices of private physicians in Karachi, Pakistan.

In a densely populated urban area of Karachi, Pakistan, a questionnaire survey was made of the knowledge and practices of 120 private general practitioners about the diagnosis and treatment of tuberculosis (TB). The majority knew that cough, fever and weight loss were the main symptoms of TB, but less than half knew that blood in sputum, poor appetite and chest pain were associated with the disease. Only 58.3% of physicians used sputum microscopy for diagnosing TB and 35.0% used it as a follow-up test. Only 41.7% treated TB patients themselves, the remaining referring their patients to specialists. Around 73.3% of the doctors were aware of the 4 first-line anti-TB drugs. Efforts to improve the knowledge of private practitioners, and strategies to enhance public-private collaboration forTB control in urban areas are urgently required.

Anorexia↗
PubMed2002

Serotonin-Cu(II)-mediated DNA cleavage: mechanism of copper binding by serotonin.

It has been proposed that considerable DNA damage may be caused by endogenous metabolites produced during the body's normal metabolic processes. 5-hydroxytryptamine (serotonin) is an important neurotransmitter in brain and spinal cord. We have previously shown that serotonin induces oxidative cleavage of DNA strands in the presence of copper ions. In the present paper we have examined the mechanism of copper binding by serotonin using absorption spectroscopy, Cu(II)-mediated lipid peroxidation and by determining the oxidation of the serotonin molecule. Addition of increasing concentrations of Cu(II) to serotonin leads to a progressive enhancement in the absorption band and is accompanied by a shift towards a lower wavelength indicative of the formation of an oxidised species of serotonin. Studies with the structurally related molecules tryptophan and melatonin showed that only serotonin is able to reduce Cu(II) to Cu(I). Similarly, only serotonin was found to be able to abolish the copper-mediated peroxidation of mitochondria. These results suggested the involvement of the phenolic group in copper binding. Further, it was also shown that the binding of copper to serotonin leads to the formation of a quinone in the absence of molecular oxygen. Based on these results, a model has been proposed in which serotonin reduces two molar equivalents of Cu(II) to Cu(I) through a reaction involving two electron oxidation of the phenolic ring to a quinone methide.

Animals↗
PubMed2002

Sociocultural aspects of areca nut use.

This paper aims to describe the sociocultural context of areca nut use through exploring people's norms and values and the meaning underlying a wide range of different practices. A historical review is followed by an examination of more recent evidence, including quantitative and qualitative research conducted in the United Kingdom. It is concluded that some reports involving the various uses of areca nut and the conclusions drawn are confusing and that future studies need to be more explicit. While a sound scientific background is required, important sociocultural and religious issues around areca nut use must also be understood if health promotion initiatives are to be considered.

Africa↗
PubMed2002

Abnormalities of conduction after total correction of Fallot's tetralogy: a prospective study.

OBJECTIVE: To determine the frequency of post-operative conduction abnormalities in Pakistani patients undergoing total correction for Fallot's Tetralogy. PATIENTS AND METHODS: One hundred and fifteen patients of Fallot's Tetralogy underwent definitive repair between January, 1999 and April, 2000. Their mean age was 12.89 years (range 3-30 years). One hundred nine patients (94.78%) had severe cyanosis and 6 patients (5.21%) were moderately cyanotic due to mild right ventricular outflow tract (RVOT) obstruction. Thirty percent patients required frequent hospital admissions within 6 months before the time of operation due to -hyper-cyanotic spells. The mean haematocrit was 50.83 (range 28-71). The majority of patients were in NYHA class-III (57%) and 45% had previous palliative shunt procedures done. Surgical access was through the RVOT in 90% cases and trans-atrial in 10%. RVOT patch was used in 55.9%, Pulmonary artery patch in 13.5% and trans-annular patch in 17.1% of cases. RESULTS: The mean bypass time was 79.15 min and the mean cross clamp time 51.23 min. Average stay in the intensive care unit was 4.48 days. Twenty-three patients required re-exploration for bleeding. Sixty-nine patients required inotropic support. Fifteen patients had transient heart blocks and two had complete heart block requiring permanent pace-maker. Nineteen patients had various transient arrhythmias which were managed medically. Univariate analysis showed that higher age at operation, low preoperative heart rate, prolonged bypass time, prolonged cross clamp time and presence of patch on pulmonary artery were more common in patients who developed various heart blocks. However, none of these factors had statistical significance or definitive cause-effect relationship with heart blocks. CONCLUSION: With careful surgical technique, total correction of Fallot's tetralogy can be conducted in children and young adults, with a very low risk of conduction abnormalities.

Adolescent↗
PubMed2002

Predictors of inpatient mortality in 190 adult patients with tuberculous meningitis.

INTRODUCTION: Tuberculous meningitis (TBM), a tuberculous infection of the leptomeninges, carries significant morbidity and mortality. To date, little literature is available regarding TBM in Pakistan. METHODS: All adult patients with TBM admitted to a tertiary care teaching hospital in Karachi, were reviewed retrospectively. AIMS: To describe the demographic profile, clinical features, laboratory and radiological picture of these patients and to identify predictors of mortality. RESULTS: Among the 190 patients analyzed, majority (28%) were between 21-30 years of age. Fever (90%), impaired consciousness (63%) and nausea/vomiting (50%) were the most common presenting symptoms. Thirty four percent were categorized as clinical stage III. CSF cultures were positive in only 5%. Thirty seven percent had an associated lung pathology on a chest X-ray. Neuroimaging revealed meningeal enhancement in 27% and hydrocephalus in 23%. All patients were treated with antituberculous therapy; 79% received concomitant steroid therapy. Neurosurgical intervention was required in 13% and mechanical ventilation support in 12%. Overall mortality was 20% and neurological sequelae were seen in 42% of the survivors. Univariate analysis showed age greater than sixty years, clinical stage III and mechanical ventilation as predictors of mortality. The logistic regression model, however, revealed that stage III presentation was not an independent predictor. CONCLUSION: We continue to see late presentations of TBM in our setting. The current study has shown that age greater than sixty years and the need for mechanical ventilation are significant independent predictors of mortality.

Adolescent↗
PubMed2001

Sol-gel open tubular ODS columns with reversed electroosmotic flow for capillary electrochromatography.

Sol-gel chemistry was successfully used for the fabrication of open tubular columns with surface-bonded octadecylsilane (ODS) stationary-phase coating for capillary electrochromatography (OT-CEC). Following column preparations, a series of experiments were performed to investigate the performance of the sol-gel coated ODS columns in OT-CEC. The incorporation of N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride as one of the sol-gel precursors played an important role in the electrochromatographic performance of the prepared columns. This chemical reagent possesses a chromatographically favorable, bonded ODS moiety, in conjunction with three methoxy groups allowing for sol-gel reactivity. In addition, a positively charged nitrogen atom is present in the molecular structure of this reagent and provides a positively charged capillary surface responsible for the reversed electroosmotic flow (EOF) in the columns during CEC operation. Comparative studies involving the EOF within such sol-gel ODS coated and uncoated capillaries were performed using acetonitrile and methanol as the organic modifiers in the mobile phase. The use of a deactivating reagent, phenyldimethylsilane, in the sol-gel solution was evaluated. Efficiency values of over 400,000 theoretical plates per meter were achieved in CEC on a 64 cm x 25 microm i.d. sol-gel ODS open tubular column. Test mixtures of polycyclic aromatic hydrocarbons, benzene derivatives, and aromatic aldehydes and ketones were used to evaluate the CEC performances of both nondeactivated and deactivated open tubular sol-gel columns. The effects of mobile-phase organic modifier contents and pH on EOF in such columns were evaluated. The prepared sol-gel ODS columns are characterized by switchable electroosmotic flow. A pH value of approximately 8.5 was found correspond to the isoelectric point for the prepared sol-gel ODS coatings.

Journal Article↗
PubMed2001

Biodesulphurization of coal: effect of pulse feeding and leachate recycle.

Biodesulphurization of coal was carried out under four modes of operation namely: conventional batch, constant volume pulse feeding (CVPF), increasing volume pulse feeding (IVPF) and leachate recycle. The effects of different pulse feeding strategies and leachate (product) recycle on biological performance were studied and compared with a conventional batch process. The sulphur removal rates for each of the four processes were 0.04 g/day (batch), 0.09 g/day (CVPF), 0.19 g/day (IVPF) and 0.05 g/day (leachate recycle). The values of iron solubilization rate (batch-83 µg/ml/day; CVPF-136 µg/ml/day; IVPF-198 µg/ml/day; leachate recycle-133 µg/ml/day) also followed the same trend. The percentage sulphur removal on the 30th day using batch, CVPF, IVPF and leachate recycle processes was 72%, 93%, 97% and 90%, respectively. IVPF was found to be the best operational strategy for biodesulphurization process at enhanced rates for longer duration.

Journal Article↗
PubMed2001

Impact of endovascular repair for abdominal aortic aneurysms in octogenarians.

A total of 50 consecutive patients (86% male; median age, 82 years) underwent endovascular repair of abdominal aortic aneurysms (AAAs) ranging from 4.0 to 9.0 cm (median, 5.2 cm). Efficacy of aneurysm exclusion was assessed by angiography, duplex scan, and/or contrast-enhanced computed tomography (CT). Acute technical success was 82%. Access failed in one patient, and immediate conversion to open operation was required in two patients. Improper deployment of the endoluminal graft (ELG) across the renal arteries occurred in one patient. The median operation time, estimated blood loss, packed red blood cells received, contrast volume, and length of intensive care and hospital stay were 128 min, 200 mL, 0.1 unit, 297 mL, 0.9 days, and 3 days, respectively. ELG limb thrombosis was seen in one patient. There were 4 (8%) early endoleaks, and 2 endoleaks were discovered in other patients at 3 and 6 months. Local/vascular and remote/systemic postoperative complications were seen in 13 (26%) and 9 (18%) patients, respectively. At a median follow-up of 11 months (range 2 to 36 months), clinical success was 78%. The aneurysm sac diameter (n = 49) decreased from a preoperative median of 5.2 to 4.7 cm (p = 0.0001). Technical success was high, and results at 11 months were satisfactory. Long-term outcomes require further study.

Aged↗
PubMed2001

Trianthenol: an antifungal tetraterpenoid from Trianthema portulacastrum (Aizoaceae).

An antifungal tetraterpenoid named trianthenol 1 has been isolated from the chloroform extract of Trianthema portulacastrum. Its structure was established as 15-hydroxymethyl-2,6,10,18,22,26,30-heptamethyl-14-methylene- 17-hentriacontene on the basis of spectroscopic data including high resolution mass and two-dimensional NMR techniques. A benzaldehyde derivative 2, a pentacyclic triterpenoid 3 and benzoic acid derivatives 4-5 are also reported for the first time from Trianthema portulacastrum.

Antifungal Agents↗
PubMed2001

Ursene type nortriterpene from Debregeasia salicifolia.

A new triterpene, 3beta-19alpha-dihydroxy-30-norurs-12-ene (1), has been isolated from the methanolic extract of Debregeasia salicifolia stems. Its structure has been elucidated with the help of one- and two-dimensional NMR and NOE studies. Lupeol, beta-sitosterol, stigmasterol and oleanolic acid are also reported for the first time from this species.

Humans↗
PubMed2001

CRB1 mutations may result in retinitis pigmentosa without para-arteriolar RPE preservation.

PURPOSE: To report a new phenotype in retinitis pigmentosa (RP) patients with CRB1 mutations at the RP12 locus. PATIENTS: Thirty-seven patients from two Pakistani families with severe retinitis pigmentosa. METHODS: Samples were screened with single-strand conformation polymorphism analysis followed by DNA sequencing of the coding sequence of the CRB1 gene. RESULTS: Two novel CRB1 mutations were discovered. No patients had evidence of preservation of the para-arteriolar retinal pigment epithelium (PPRPE) that has been previously reported in all cases of RP associated with CRB1 mutations. CONCLUSIONS: Patients with severe autosomal recessive (or simplex) RP who lack the finding of PPRPE should not be excluded from molecular analysis of CRB1 purely because they lack the clinical feature of PPRPE. This report illustrates that RP at the RP12 locus is not clinically uniform. The absence of PPRPE cannot be used to exclude CRB1 as a potential molecular explanation for RP.

Adolescent↗
PubMed2001

Triterpenes from Mimusops elengi.

Pentacyclic triterpenes (1) and (2) have been isolated from Mimusops elengi and assigned structures 3beta,6beta,19alpha,23-tetrahydroxy-urs-12-ene and 1beta-hydroxy-3beta-hexanoyllup-20 (29)-ene-23, 28-dioic acid, respectively, on the basis of spectroscopic studies including 2D-NMR. The compound 1 showed moderate inhibiting activity against beta-glucuronidase enzyme

Animals↗