Biomedical subjects

Shahid Mahmood

Publications and source records attributed to Shahid Mahmood.

11 recordsLinked to original sources

PubMed2007

Detection of tumour thrombus by 18F-FDG-PET/CT imaging.

Tumour thrombus is a rare complication of many solid cancers including renal cell carcinoma, Wilms' tumour, testicular tumour, adrenal cortical carcinoma, lymphoma, pancreatic cancer, osteosarcoma and Ewing's sarcoma. We describe six patients who harboured occult tumour thrombus detected by fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography (PET)/X-ray computerized tomography (CT) imaging as part of the staging investigations. Recognition of this rare complication by PET/CT can change the management plan and prevent unnecessary long-term anti-coagulation treatment because of wrong diagnosis of cancer-related venous thrombus.

Adult↗

PubMed2006

Effects of management regime and plant species on the enzyme activity and genetic structure of N-fixing, denitrifying and nitrifying bacterial communities in grassland soils.

Management by combined grazing and mowing events is commonly used in grasslands, which influences the activity and composition of soil bacterial communities. Whether observed effects are mediated by management-induced disturbances, or indirectly by changes in the identity of major plant species, is still unknown. To address this issue, we quantified substrate-induced respiration (SIR), and the nitrification, denitrification and free-living N(2)-fixation enzyme activities below grass tufts of three major plant species (Holcus lanatus, Arrhenatherum elatius and Dactylis glomerata) in extensively or intensively managed grasslands. The genetic structures of eubacterial, ammonia oxidizing, nitrate reducing, and free-living N(2)-fixing communities were also characterized by ribosomal intergenic spacer analysis, and denaturing gradient gel electrophoresis (DGGE) or restriction fragment length polymorphism (RFLP) targeting group-specific genes. SIR was not influenced by management and plant species, whereas denitrification enzyme activity was influenced only by plant species, and management-plant species interactions were observed for fixation and nitrification enzyme activities. Changes in nitrification enzyme activity were likely largely explained by the observed changes in ammonium concentration, whereas N availability was not a major factor explaining changes in denitrification and fixation enzyme activities. The structures of eubacterial and free-living N(2)-fixing communities were essentially controlled by management, whereas the diversity of nitrate reducers and ammonia oxidizers depended on both management and plant species. For each functional group, changes in enzyme activity were not correlated or were weakly correlated to overall changes in genetic structure, but around 60% of activity variance was correlated to changes in five RFLP or DGGE bands. Although our conclusions should be tested for other ecosystems and seasons, these results show that predicting microbial changes induced by management in grasslands requires consideration of management-plant species interactions.

Agriculture↗

PubMed2006

The influence of synthetic sheep urine on ammonia oxidizing bacterial communities in grassland soil.

In grazed, grassland soils, sheep urine generates heterogeneity in ammonia concentrations, with potential impact on ammonia oxidizer community structure and soil N cycling. The influence of different levels of synthetic sheep urine on ammonia oxidizers was studied in grassland soil microcosms. 'Total' and active ammonia oxidizers were distinguished by comparing denaturing gradient gel electrophoresis (DGGE) profiles following PCR and RT-PCR amplification of 16S rRNA gene fragments, targeting DNA and RNA, respectively. The RNA-based approach indicated earlier, more reproducible and finer scale qualitative shifts in ammonia oxidizing communities than DNA-based analysis, but led to amplification of a small number of nonammonia oxidizer sequences. Qualitative changes in RNA-derived DGGE profiles were related to changes in nitrate accumulation. Sequence analysis of excised DGGE bands revealed that ammonia oxidizing communities in synthetic sheep urine-treated soils consisted mainly of Nitrosospira clusters 2, 3 and 4. Nitrosospira cluster 2 increased in relative abundance in microcosms treated with all levels of synthetic sheep urine. Low levels additionally led to increased relative abundance of Nitrosospira cluster 4 and medium and high levels increased relative abundance of cluster 3. Synthetic sheep urine is therefore likely to influence the spatial distribution and composition of ammonia oxidizer communities, with consequent effects on nitrate accumulation.

Ammonia↗

PubMed2006

Comparison of PCR primer-based strategies for characterization of ammonia oxidizer communities in environmental samples.

PCR-based techniques are commonly used to characterize microbial communities, but are subject to bias that is difficult to assess. This study aimed to evaluate bias of several PCR primer-based strategies used to study diversity of autotrophic ammonia oxidizers. 16S rRNA genes from soil- or sediment-DNA were amplified using primers considered either selective or specific for betaproteobacterial ammonia oxidizers. Five approaches were assessed: (a) amplification with primers betaAMO143f-betaAMO1315r; (b) amplification with primers CTO189f-CTO654r; (c) nested amplification with betaAMO143f-betaAMO1315r followed by CTO189f-CTO654r primers; (d) nested amplification with betaAMO143f-betaAMO1315r and CTO189f-Pf1053r primers; (e) nested amplification with 27f-1492r and CTO189f-CTO654r primers. Amplification products were characterized by denaturing gradient gel electrophoresis (DGGE) analysis after further amplification with 357f-GC-518r primers. DGGE profiles of soil communities were heterogeneous and depended on the approach followed. Ammonia oxidizer diversity was higher using approaches (b), (c) and (e) than using (a) and (d), where sequences of the most prominent bands showed similarities to nonammonia oxidizers. Profiles from marine sediments were more consistent, regardless of the approach adopted, and sequence analysis of excised bands indicated that these consisted of ammonia oxidizers only. The study demonstrates the importance of choice of primer, of screening for sequences of nontarget organisms and use of several approaches when characterizing microbial communities in natural environments.

Ammonia↗

PubMed2005

Lipomatous hypertrophy of the interatrial septum.

Lipomatous hypertrophy of the interatrial septum is a rare condition and it does not require any specific treatment. We present the transoesophageal echocardiogram findings of a 70-year-old lady demonstrating the appearances that were typical of lipomatous hypertrophy of the interatrial septum.

Aged↗

PubMed2005

Cultivation-independent in situ molecular analysis of bacteria involved in degradation of pentachlorophenol in soil.

The central aim of this study was to determine which components of an indigenous bacterial community in pristine grassland soil were capable of degrading pentachlorophenol (PCP) using two cultivation-independent, in situ, molecular techniques. The first involved polymerase chain reaction (PCR) and reverse transcription polymerase chain reaction (RT-PCR) amplification of 16S rRNA genes from DNA and RNA, respectively, extracted from PCP-amended soil. The second involved stable isotope probing (SIP), with incubation of soil with 13C-PCP and molecular analysis of 13C-labelled RNA, derived from cells incorporating PCP or its breakdown products, after separation from 12C-RNA by ultracentrifugation. Bacterial communities were characterized by denaturing gradient gel electrophoresis (DGGE) analysis of amplification products. PCP was degraded at an approximate rate of 1.18+/-0.25 (SEM) mg kg-1 day-1 and 39% of the measurable PCP fraction was degraded after incubation for 63 days. PCP degradation was associated with significant changes in bacterial community structure, leading to the appearance of seven bands in both DNA- and RNA-based DGGE profiles, the latter providing clearer evidence of qualitative shifts in community structure. The majority of novel bands increased in relative intensity during the first 35 days and subsequently decreased in relative intensity as incubation continued. Sequence and phylogenetic analysis of six of these bands indicated most to have closest database relatives that were uncultured bacteria with sequence homologies to reported hydrocarbon degraders. No band could be detected in RNA-SIP-DGGE profiles derived from 13C-RNA fractions at day 0 but several faint bands appeared in these fractions after incubation of soil for 4 days, indicating assimilation of PCP or its degradation products. These bands increased in intensity during subsequent incubation for 21 days and decreased with further incubation. With one exception, RNA-SIP-DGGE and RNA-DGGE profiles were similar, indicating that RNA-targeted DGGE, in this case, provided a good indication of the metabolically active microbial community.

Base Sequence↗

PubMed2004

Diclofenac residues as the cause of vulture population decline in Pakistan.

The Oriental white-backed vulture (OWBV; Gyps bengalensis) was once one of the most common raptors in the Indian subcontinent. A population decline of >95%, starting in the 1990s, was first noted at Keoladeo National Park, India. Since then, catastrophic declines, also involving Gyps indicus and Gyps tenuirostris, have continued to be reported across the subcontinent. Consequently these vultures are now listed as critically endangered by BirdLife International. In 2000, the Peregrine Fund initiated its Asian Vulture Crisis Project with the Ornithological Society of Pakistan, establishing study sites at 16 OWBV colonies in the Kasur, Khanewal and Muzaffargarh-Layyah Districts of Pakistan to measure mortality at over 2,400 active nest sites. Between 2000 and 2003, high annual adult and subadult mortality (5-86%) and resulting population declines (34-95%) (ref. 5 and M.G., manuscript in preparation) were associated with renal failure and visceral gout. Here, we provide results that directly correlate residues of the anti-inflammatory drug diclofenac with renal failure. Diclofenac residues and renal disease were reproduced experimentally in OWBVs by direct oral exposure and through feeding vultures diclofenac-treated livestock. We propose that residues of veterinary diclofenac are responsible for the OWBV decline.

Animals↗

PubMed2003

Colonisation of spruce roots by two interacting ectomycorrhizal fungi in wood ash amended substrates.

Interactions between two ectomycorrhizal fungal species, Piloderma croceum Erikss. and Hjortst. and Piloderma sp. 1 (found to colonise spruce roots and wood ash granules in the field), were investigated in wood ash amended substrates. The comparative ability of these fungi to colonise roots of non-mycorrhizal spruce (Picea abies (L.) Karst.) seedlings was studied in relation to factorial combinations of wood ash and N fertilisation. Non-mycorrhizal spruce seedlings (bait seedlings) were planted together with spruce seedlings colonised by P. croceum or Piloderma sp. 1. The growth substrate was a sand-peat mixture with wood ash or no ash and supplied with two levels of N, so that four substrate combinations were obtained. Piloderma sp. 1 mycelia colonised around 60% of the fine roots of bait seedlings in ash treatments regardless of N level and around 20-26% in treatments without ash. P. croceum only colonised 8% of the root tips in the presence of ash but 56% of the root tips in the low-N treatment without ash. However, in the high-N treatment without ash the colonisation level was reduced to around 30%. Total numbers of root tips per seedling did not vary significantly between the treatments. Possible reasons for the competitive advantage of Piloderma sp. 1 in wood ash fertilised substrate are discussed.

Basidiomycota↗

PubMed2003

Enhanced external counterpulsation.

Enhanced external counterpulsation is a noninvasive technique designed to increase myocardial perfusion and reduce cardiac workload in patients with coronary artery disease. Recent trials have documented beneficial hemodynamic effects. Stress testing and radionuclide imaging have demonstrated improvements in functional capacity and myocardial perfusion. This procedure may be the therapeutic choice for patients with severe diffuse disease or in whom repeat revascularization is not possible. The relatively low cost of the technique makes it feasible for patients in developing countries.

Coronary Artery Disease↗

PubMedDate not supplied

Geographical variation in the epidemiology of esophageal cancer in Pakistan.

STUDY OBJECTIVES: To evaluate whether factors such as the geographic area of residence, sex, and anatomic subsite of esophagus can prognosticate the histologic subtype of esophagus cancer. DESIGN: To study the major histologic subtypes of esophagus cancer stratified by various factors through multivariate analyses using morphology as the dependent factor and gender, province, and subsite of esophagus as independent factors. SETTING: A tertiary care cancer hospital situated in the city of Lahore in Pakistan. PATIENTS: Three hundred and thirty five patients diagnosed either with esophageal squamous cell carcinoma or adenocarcinoma, from December 1994 to April 2004, were included. Subjects were residents of either Punjab or the Northwest Frontier Province in Pakistan. MAIN RESULTS: An excessive likelihood of development of squamous cell carcinoma versus adenocarcinoma was established for the Northwest Frontier Province as compared to Punjab (odds ratio 2.7, 95 percent confidence interval: 1.2, 6.2, p = 0.02), and in the upper-third of the esophagus relative to the lower-third of the organ (odds ratio 8.8, 95 percent confidence interval: 2.8, 28.3, p < 0.001). CONCLUSIONS: This histologic variation may be explained by environmental and lifestyle factors peculiar to geographical regions.

Adenocarcinoma↗

PubMedDate not supplied

Characteristics of lung cancer patients--the Shaukat Khanum Memorial experience.

OBJECTIVES: The aims of this descriptive study were to characterize lung cancer patients by age at diagnosis, smoking status, and histology and, also to explore the histologic sub-type according to cigarette smoking, in a tertiary care setting. PATIENTS AND METHODS: A retrospective review of 830 patients for whom smoking status was available in the records was carried out at a comprehensive cancer care facility, the Shaukat Khanum Memorial Cancer Hospital and Research Center, situated in Lahore, Pakistan. RESULTS: The mean age at presentation of the 830 evaluable cases was 59.8 years (standard deviation 11.8, range 18-90). Stratifying by gender, statistically significant differences were found in the average age at diagnosis between males (60.1 years) and females (57.5 years) and, in the distributions of non-smokers, current smokers, and ex-smokers, but none for histology. CONCLUSIONS: Similar to other populations, the age of disease onset amongst females was lower than that seen in males. The proportion of smokers was higher amongst males versus females. The reversal of smoker to non-smoker ratio when stratified by gender, may highlight the importance of exploring alternate pathways implicated in the etiology of lung cancer in our population.

Adolescent↗