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Biomedical subjects

S M Khan

Publications and source records attributed to S M Khan.

At least 55 records · Page 3Linked to original sources
PubMed1982

Air monitoring network program in Saudi Arabia.

The Kingdom of Saudi Arabia has initiated a program to install air quality network stations throughout the country in order to measure concentration of the ambient air pollutants. The site selection of these stations is an important objective to be accomplished and must be done based on scientific and rational work. To accomplish this objective, a modified version of atmospheric transport and dispersion model, known as air resources laboratories - atmospheric transport and dispersion (ARL- ATAD) model, is used to evaluate long range transport and diffusion of air pollutants from major pollution causing sources such as refineries, open-air burning of associated gases of oil fields and major industries. Hourly meteorological data for a period of three years (from 1977 to 1979) on wind speed, wind direction, pressure, and temperature from 20 synoptic stations in Saudi Arabia is processed and used as model input. In addition to these, meteorological data from three upper air stations is also processed in order to determine base and top of critical inversion heights. Various pollution causing sources are identified within the study area. Air trajectories are drawn with sources as the origins of the trajectories and the dispersion characteristics is studied with distance and time. Based on long term meteorological records, the adversely affected zones are statistically identified for potential station sites.

Air Pollution↗
PubMed1981

The effect of electron carriers and other ligands on oxygen stability of clostridial hydrogenase.

The effects of various electron carriers, a substrate (H2) and a reversible inhibitor (CO) on the rate of irreversible oxygen inactivation of clostridial hydrogenase (ferredoxin: H+ oxidoreductase, EC 1.18.3.1) have been studied kinetically. Some electron carriers (e.g., clostridial ferredoxin and methyl viologen) greatly stabilize the enzyme, some (FAD, FMN) drastically reduce its stability, while others (benzyl viologen and methylene blue) only slightly alter the stability. Competitive experiments indicate that stabilizers and destabilizers do not compete with each other for binding with the active center of hydrogenase. Hydrogen and CO do not affect the rate of the oxygen inactivation. On the basis of the results obtained herein and kinetic data on hydrogenase catalysis from the literature, it is concluded that the active center of this hydrogenase comprises at least three different independent subsites. The first one (presumably an iron atom of the iron-sulfur cluster) binds H2 and CO and does not contribute to the oxygen stability. The second one binds stabilizers like methyl viologen while the third one binds destabilizers like FMN and FAD.

Benzyl Viologen↗
PubMed1980

Tyrosine fluorescence as a measure of denaturation in thermolysin.

The heat and guanidine hydrochloride denaturation of thermolysin has been followed by fluorescence techniques. The native enzyme has a single emission peak which is decreased in intensity and which splits into two clearly resolved peaks upon denaturation. These data are interpreted to indicate that energy transfer from tyrosine to tryptophan occurs in the native enzyme which is lost upon denaturation. Even though zinc is fully bound to thermolysin at 90 degrees C or in the presence of 6 M guanidine hydrochloride, removal of zinc from the denatured enzyme has no effect on the emission spectrum. Removal of Ca2+ from the denatured enzyme. These data indicate that even though the metal ions are bound to the denatured protein, they provide little structural integrity to the protein as measured by energy transfer between tyrosine and tryptophan.

Energy Transfer↗
PubMed1977

Prevalence of intestinal helminths among patients admitted to the Balik Pulau district hospital on Penang island.

Faecal samples from patients admitted to the District Hospital in Balik, Pulau, Penang revealed high infection rates for Ascaris lumbricoides, Trichuris trichiura and hookworms. The prevalence rates were Trichuris trichiura 51.7%, Ascaris lumbricoides 31.9% and hookworm 37.2%. The overall highest infection is among the Malays (79%), the least being among the Chinese (61.1%). The prevalence of Ascaris lumbricoides was highest in the 11-20 age group. The prevalence of Trichura was highest in the 51-60 age group, Ascaris and Trichuris infections is higher among the males but hookworm infection is higher among the females. 72.6% of the patients were infected with at least one type of helminth and 32.9% of the patients were infected with at least 2 types of helminths.

Adolescent↗
PubMedDate not supplied

The management of ureteric calculi without extracorporeal shock-wave lithotripsy.

BACKGROUND: Extracorporeal shock-wave lithotripsy (ESWL) is a relatively new technological adjunct in the treatment of renal calculi, but availability is limited. AIM: The aim of this study was to assess the outcome of ureteroscopic procedures in a unit without on-site ESWL facility. METHODS: A retrospective study of all cases of ureteric calculi presenting to this hospital during the period 1991 to 1997 was performed. RESULTS: One hundred and thirty five patients with a mean age of 46.8 years were evaluated. Ninety-four (69.5%) had their stone successfully manipulated and/or extracted at ureteroscopy. Using strict criteria, 41 patients (30.5%) had failed ureteroscopies. Fourteen (10.4%) suffered complications related to their ureteroscopy, thirteen had their complications treated conservatively and three (2.3%) needed open procedures. CONCLUSION: Ureteroscopy has a high success rate and low morbidity. We continue to advocate ureteroscopy in the initial management of ureteric calculi.

Humans↗
PubMedDate not supplied

Pediatric tumors in north west Pakistan and Afghan refugees.

All patients referred to the Institute of Radiotherapy and Nuclear Medicine in Peshawar (IRNUM) during 1990 to 1994 were analyzed. There were 1655 children with biopsy-proven cancers; 1290 were from the North West Frontier Province (NWFP), and the remaining 365 were Afghan refugees. Male children from the NWFP were 67% and females were 33%. Among Afghan children, 69% were males and 31% were females. Patients whose histopathologies were doubtful or not available were excluded from the study. The most common tumors in children in the NWFP were lymphoid leukemia, lymphoma, myeloid leukemia, Wilms tumor, tumors of the central nervous system (CNS), soft tissue sarcoma, bone tumors, retinoblastoma, neuroblastoma, and testicular tumors. Among Afghan children the most common cancers were lymphoma, lymphoid leukemia, myeloid leukemia, Wilms tumor, retinoblastoma, tumors of soft tissue, bone tumors, CNS tumors, testicular tumors, and neuroblastoma.

Afghanistan↗