Biomedical subjects
Publications and source records attributed to A R Khan.
BF3OEt2-catalysed glycosidation of phenolic compounds 3 and 6 with the mannofuranosyl glycosyl donor 2 separately gave the corresponding alpha-mannofuranosyl derivatives 4 and 7 in good yield, and the latter on selective deacetonation (hydrolysis) with 2% aqueous HCl afforded 5 and 8 respectively. Compounds 4 and 7 inhibited rat intestinal alpha-glucosidase more effectively than a standard drug acarbose.
The incidence of Hirschsprung's disease (HD) was determined in children who presented with constipation to a specialist paediatric surgical unit. During a 5-year period, 355 rectal biopsies were performed on 182 neonates, infants and children presenting with chronic constipation or intestinal obstruction: 25 (14%) were diagnosed HD. One hundred and four patients had suction and 78 had full-thickness rectal biopsies. Haematoxylin-eosin (HE) staining and acetylcholinesterase (AChE) histochemistry was used. In 13 cases (8%) of suction and 2 cases (2.5%) of full thickness rectal biopsies, specimens were inadequate to diagnose HD. The mean age of all patients was 2.9 years and that of patients diagnosed with HD was 3.64 months. Nineteen patients with HD were diagnosed in the first month, 5 in 1-12 months and 1 at 4 years of age (Fig. 1). The authors found that along with onset of constipation convincing indications for rectal biopsy to exclude HD were as follows: those infants and children who do not pass meconium within 48 hours, have low intestinal obstruction of unknown cause, severe constipation, chronic abdominal distension and failure to thrive. A diagnostic accuracy of 94% was achieved with AChE histochemistry for suction rectal biopsy. After this review, referring paediatricians were advised that screening of other common organic causes of constipation with the least invasive investigations, including laboratory, dietary and paediatric gastroenterology advice, should be undertaken to avoid unnecessary rectal biopsy to exclude HD and related disorders.
PURPOSE: To reduce the incidence of nephrectomy or hydronephrosis in children. MATERIALS AND METHODS: From September 1998 to October 2000, we treated 58 patients with hydronephrosis; their ages ranged from 35 days to 11 years (mean age 4 years 7 months). All patients were subjected to a DTPA renogram with split function. In 12 patients (study group), kidney function was less than 10 % (range 0 - 10 %). Initially, nephrostomy was carried out in all 12 patients followed by Anderson-Hyne's pyeloplasty after 4 - 6 weeks. Postoperatively renal USG, urine r/m/e & c/s (routine and microscopic examination and culture and sensitivity test), blood urea, serum creatinine were assessed and DMSA scan and DTPA renogram with split functions were carried out in all patients. RESULTS: In the study group, all 12 patients showed improvement of renal function (more than 10 %) after nephrostomy and in all of them pyeloplasty was subsequently carried out within 4 - 6 weeks. There were no significant pre-, peri- or postoperative complications. CONCLUSIONS: Contrary to common practice we do not recommend nephrectomy for hydronephrotic kidneys which show < 10 % of renal function on renogram. The renal functional status improves significantly after a preliminary nephrostomy, thus avoiding the need for a straightforward nephrectomy in children along with all the possible long-term effects of a single kidney.
Laboratory scale batch experiments were conducted at 20 degrees C to investigate the acidogenic fermentation for the conversion of wasted sludge into short chain fatty acids (SCFA) to be utilized as a carbon source in the denitrification process. Hydraulic retention time (HRT), volatile solid (VS) loading rate and pH were studied as these are the important parameters governing the production of volatile fatty acids (VFA). Four different phases were investigated by varying these parameters. HRT was varied from 2.7 to 8.2 days whereas VS loading rate was varied from 1.2 to 3.6 g d(-1). VFA production decreased with the increase in HRT above 2.7 days. 538.37+/-19.39 mg VFA(produced) x d(-1) (0.176+/-0.010 mg VFA(produced) mg(-1) VS(feed) was found as the maximum value of VFA at 2.7 days. The present results based on wasted sludge showed that almost 0.0483+/-0.0016 mg VFA (as COD mg(-1) initial COD) and about 5% of soluble COD production were achieved, which are slightly less than the results reported for primary sludges. The rates of VFA production increased with the increase in VS, however, opposite results were obtained when pH was increased in the reactor. SCFA/FA ratios during fermentation were found in the range of 67-73%. The specific denitrification rates (SDNR) of methanol (2.20+/-0.44 mg NO3-N g(-1) MLVSS x h(-1)) and the fermenter supernatant (2.00+/-0.45 mg NO3-N g(-1) MLVSS x h(-1)) were found to be comparable. Fermenter supernatant, therefore, has the potential to be utilized as a carbon source. However, the results need to be investigated further on a larger scale to ascertain their validity.
The present investigation deals with the effects of Bacillus thuringiensis ssp. kurstaki on various biological parameters of gamma-irradiated Cadra cautella. The pathogen, irradiation, and their combinations significantly affected the insects by increasing their mortality and developmental periods, reducing the pupal and adult survival (%), and the adult longevity and reproductive potential were also significantly reduced. It was observed that irradiation-pathogen combinations produced additive to synergistic effects on C. cautella.
A number of 3-O-[2'-hydroxy-3'-N,N-aminopropan-1'-yl]-alpha-D-glucofuranoses were synthesised by regioselective oxirane ring opening in compound 2 with different secondary amines followed by selective deacetalisation. All the compounds were tested for their immunomodulatory potential in vitro; seven of them expressed significant immunostimulant activity.
OBJECTIVE: To determine the prevalence and correlates of cigarette smoking among adults in high mountain rural areas of northern Pakistan. DESIGN: Cross sectional survey. PARTICIPANTS: A sample of 4203 adults (aged 18 years and over) were selected by stratified random sampling from 16 villages. MAIN OUTCOME MEASURE: Self reported smoking prevalence; age of smoking initiation; daily cigarette consumption and association between current smoking and sociodemographic variables, use of snuff, wine, body mass index, blood pressure, family history of stroke, and hypertension. RESULTS: 614/1406 men (43.7%) and 154/2797 (5.5%) women reported smoking cigarettes. The age standardised prevalence of smoking was 40.5% for men and 6.3% for women. Men were more likely (odds ratio (OR) 6.5, 95% confidence interval (CI) 4.75 to 8.79) to be smokers. Smokers were more likely to use snuff (OR 1.39, 95% CI 1.12 to 1.73), drink wine (OR 3.47, 95% CI 2.81 to 4.29), and were more likely to work as farmers (OR 1.55, 95% CI 1.05 to 2.29) or shopkeepers (OR 2.63, 95% CI 1.67 to 4.14). Individuals with college level education and with desirable body mass index were less likely to smoke (OR 0.55, 95% CI 0.35 to 0.87; OR 0.74, 95% CI 0.57 to 0.96). CONCLUSION: Cigarette smoking is a major public health problem in this high mountain community of Pakistan, particularly among the male population, the majority of whom begin to smoke quite early in life. A comprehensive tobacco control effort incorporated into the existing community based health infrastructure is needed.
OBJECTIVE: The objective of this study is to report, for the first time, the histopathologic pattern of Schistosomiasis from the Asir Region and to compare it to patterns reported from other regions of the Kingdom of Saudi Arabia. Several studies have reported the patterns of Schistosomiasis in other regions of the Kingdom of Saudi Arabia and other countries where Schistosomiasis is endemic. Schistosomiasis is endemic in certain areas of Asir region, however no data is available concerning the clinicopathological pattern of Schistosomiasis in the Asir Region. METHODS: This is a retrospective analysis of 217 cases of Schistosomiasis from surgical and biopsy files of Asir Central Hospital during a period from January 1990 to October 1999. RESULTS: Our study revealed that Schistosomiasis was more common among the expatriate population of Asir Region than Saudi nationals residing in this area. The urinary tract was most commonly involved, and then in descending frequency came the vermiform appendix, liver and large bowel. CONCLUSION: These findings are somewhat different from those observed in the Riyadh Region where the vermiform appendix was the most commonly affected organ. Based on the histopathologic pattern, our study describes the pattern of Schistosomiasis in the Asir Region and may serve as a base-line for future research work.
The crystal structure of the human class I MHC molecule HLA-A2 complexed with of an octameric peptide, Tax8 (LFGYPVYV), from human T cell lymphotrophic virus-1 (HTLV-1) has been determined. This structure is compared with a newly refined, higher resolution (1.8 A) structure of HLA-A2 complexed with the nonameric Tax9 peptide (LLFGYPVYV) with one more N-terminal residue. Despite the absence of a peptide residue (P1) bound in the conserved N-terminal peptide-binding pocket of the Tax8/HLA-A2 complex, the structures of the two complexes are essentially identical. Water molecules in the Tax8 complex replace the terminal amino group of the Tax9 peptide and mediate a network of hydrogen bonds among the secondary structural elements at that end of the peptide-binding groove. Thermal denaturation measurements indicate that the Tax8 complex is much less stable, DeltaTm = 16 degrees C, than the Tax9 complex, but both can sensitize target cells for lysis by some Tax-specific CTL from HTLV-1 infected individuals. The absence of a P1 peptide residue is thus not enough to prevent formation of a "closed conformation" of the peptide-binding site. TCR affinity measurements and cytotoxic T cell assays indicate that the Tax8/HLA-A2 complex does not functionally cross-react with the A6-TCR-bearing T cell clone specific for Tax9/HLA-A2 complexes.
Circumumbilical pyloromyotomy has been used widely to offer an optimum cosmetic approach. On occasion, there are difficulties in delivering the large pyloric tumour through a relatively small incision. The authors prospectively collected a series of 39 consecutive pyloromyotomies performed over a period of 3 years in three teaching hospitals. Patients were aged 13 to 90 days (average 35) and the male-female ratio was 5:1. The initial operative approach was a right upper quadrant (RUQ) incision (n = 6) and later a circumumbilical incision (CUI), with or without lateral extension, combined with transverse division of the linea alba and part of both rectus muscles (n = 33). Two infants (1 RUQ and 1 CUI) developed wound infections, which were treated with antibiotics. There were no other peri- or postoperative complications. It was necessary to extend the incision in one-third of CUI cases (n = 12) in order to facilitate the delivery of a large pyloric tumour through the incision. Both omega-shaped (n = 3) and a new modified extension (n = 9) have been used with good cosmetic results.
A method has been developed for the simultaneous determination of oxfendazole and oxyclozanide in a pharmaceutical preparation. The method involves reversed phase chromatography with isocratic elution of the mobile phase and detection at 300 nm. The range of quantification for oxfendazole and oxyclozanide was found to be 2-7 microg ml(-1) and 3-10 microg ml(-1), respectively. The validity of the method was evaluated in terms of linear regression analysis, precision, specificity and accuracy.
Alterations in trace elements and mineral homeostasis have been documented both in insulin-dependent diabetes mellitus and non-insulin dependent diabetes mellitus. No data are available about trace elements in fibrocalculous pancreatic diabetes, a unique form of secondary diabetes mellitus. This study evaluated the plasma concentrations of copper, zinc and magnesium in this form of diabetes. Twenty-five patients (9 men and 16 women) with fibrocalculous pancreatic diabetes and 25 healthy non-diabetic subjects (16 men and 9 women) were studied. Patients with overt nephropathy were excluded. Plasma copper, zinc, and magnesium levels were analyzed using a GBC 902 double beam absorption spectrophotometer. The effect of glycemic control, microalbuminuria, sex and modality of treatment received on the plasma levels of copper, zinc and magnesium was assessed. Results of the study revealed that plasma copper, zinc, and magnesium levels were comparable between patients with fibrocalculous pancreatic diabetes and control subjects. Plasma copper levels were significantly higher in patients with controlled diabetes (16.15 +/- 0.67 micromol L(-1)) as compared to those with uncontrolled diabetes (13.75 +/- 0.61 micromol L(-1)) and healthy controls (13.91 +/- 0.55 micromol L(-1)). This merits further investigation. Microalbuminuria, modality of treatment received and sex did not influence the levels of these elements in fibrocalculous pancreatic diabetes.
Small concentrations, approximately 2-10 parts per million (ppm), of injected sulfur trioxide (SO3) have improved particulate collection efficiencies of electrostatic precipitators burning lower-sulfur coal. However, the addition of extra SO3 not only incurs costs but also presents negative environmental effects. This work explored a method that could be applied to existing coal-fired power plants to convert the sulfur dioxide (SO2) already present in the flue gas to sufficient levels of SO3 for fly ash conditioning as an alternative to adding SO3 by burning elemental sulfur. During this research, a pre-mixed natural gas flame was used to promote the conversion of SO2 to SO3 in a drop-tube furnace with average non-flame, free stream gas temperatures of 450 and 1000 K. SO3 concentrations measured by wet chemistry and confirmed using elemental balances of other sulfur species measured by gas chromatography revealed that as much as 7% of SO2 was homogeneously transformed to SO3. The results also showed that at low temperatures, the rate at which SO3 is converted back to SO2 decreased, thus extending the time period during which SO3 concentrations would be sufficient for ash conditioning. An additional benefit of this technique is speculated to result from increased flue gas humidity.
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An audit of 3374 appendectomy specimens in 2578 Saudi and 796 non-Saudi nationals revealed a diagnosis rate of 74.7% of inflamed appendix, a normal appendix range of 7.8% to 22.5% with the higher rate of normal appendix found among females. The finding of high incidence of schistosomal appendicitis among Egyptian males is not surprising given the high incidence of schistosomiasis among Egyptians in general. The alternate diagnoses, which include such conditions as neoplasm, mucocele, other inflammatory conditions such as periappendicitis, and parasitic infestations, are not different from findings in the reported literature.
OBJECTIVE: The study was undertaken to compare the frequencies of the various types of malignant neoplasms affecting females in the Asir Region of Saudi Arabia during the years 1996-1998, to the experience of a previous report (1987 to 1989) in the same population with rapid advancing health care services. METHODS: A retrospective descriptive approach was adopted. Histopathological records of Asir Central Hospital were reviewed to extract data on female malignant neoplasms seen in the years January 1996-December 1998. The cancer from various sites were ranked based on their percentage (crude relative) frequencies, and compared with the previous report (1987-1989). RESULTS: Of the 274 cases of histologically confirmed female malignant diseases, the breast (22%), skin (9%) and thyroid (7%) were the leading sites. This ranking contrasts with the previous finding (1987-1989) which involved the skin, breast and non-Hodgkin's lymphoma, in descending order of frequencies. The frequency of gynecological malignancies was relatively higher than in the previous report. CONCLUSION: There may be a need to review the pattern of malignancies in the female population in this region from time to time in order to concurrently update planning on preventive and treatment measures.
The three-dimensional structures of the inactive protein precursors (zymogens) of the serine, cysteine, aspartic, and metalloprotease classes of proteolytic enzymes are known. Comparisons of these structures with those of the mature, active proteases reveal that, in general, the preformed, active conformations of the residues involved in catalysis are rendered sterically inaccessible to substrates by the residues of the zymogens' N-terminal extensions or prosegments. The prosegments interact in nonsubstrate-like fashions with the residues of the active sites in most of the cases. The gastric aspartic proteases have a well-characterized zymogen conversion pathway. Structures of human progastricsin, the inactive intermediate 2, and active human pepsin are known and have been used to define the conversion pathway. The structure of the zymogen precursor of plasmepsin II, the malarial aspartic protease, shows a new twist on the mode of inactivation used by the gastric zymogens. The prosegment of proplasmepsin disrupts the active conformation of the two catalytic aspartic acid residues by inducing a major reorientation of the two domains of the mature protease. The picornaviral 2A and 3C proteases have a chymotrypsin-like tertiary structure but with a cysteine nucleophile. These enzymes cleave themselves from the viral polyprotein in cis (intramolecular cleavage) and carry out trans cleavages of other scissile peptides important for the virus life cycle. Although the structure of the precursor viral polyprotein is unknown, it probably resembles the organization of the proenzymes of the bacterial serine proteases, subtilisin, and alpha-lytic protease. Cleavage of the prosegment is known to occur in cis for these precursor molecules.
A number of alpha-cyano-beta-substituted ethyl propenoates were synthesised by condensation of appropriate aldehydes with ethyl cyanoacetate in basic medium. These compounds have been studied for their antileishmanial activities in vivo in hamsters. Two compounds exhibited 70-77% activities both by intramuscular and oral routes.