Search PubMed⌕ Search

Biomedical subjects

S Ahmed

Publications and source records attributed to S Ahmed.

At least 271 records · Page 15Linked to original sources
PubMed1998

Corticotropin-releasing factor receptor blockade enhances conditioned aversive properties of cocaine in rats.

The behavioral profile of corticotropin-releasing factor (CRF) in mediating anxiogenic-like and aversive responses to stressors may be particularly relevant for dependence and withdrawal in drug-experienced organisms. Moreover, stressful aspects of drug exposure in the drug naive organism may also induce CRF system activation. In the present studies, the dependence of aversive properties of cocaine on activation of endogenous CRF systems has been evaluated in rats using taste conditioning and runway self-administration paradigms. Systemic cocaine administration (20 mg/kg i.p.) produced a conditioned saccharin aversion which was dose-dependently potentiated by central administration of the CRF receptor antagonist, D-phe CRF (12 41). In addition, i.v. cocaine administration (0.75 mg/kg per injection i.v.) produced runway goal-box avoidance and conditioned place avoidance responses which were significantly accelerated by CRF antagonist treatment. In contrast, CRF receptor stimulation using CRF itself abolished cocaine-induced increases in goal latency in the runway paradigm. This generalized involvement of CRF systems in cocaine-related motivational/associative states is consistent with the comprehensive role of CRF in mediating emotional responses to non-drug stressors.

Animals↗
PubMed1998

Results of Wilms' tumour management in two tertiary-care hospitals in Asia.

In the period 1985-1995, 87 children underwent surgery for Wilms' tumour; 16 were lost to follow-up. Of the remaining children, 27 presented with stage I disease, 11 with stage II, 12 with stage III, 14 with stage IV, and 6 with stage V. One child was not staged. The histology was favourable Wilms' tumour in 44, anaplastic in 12, unclassified in 8, clear-cell sarcoma in 4, and rhabdoid tumour in 3. Although a total nephrectomy was generally performed, partial renal surgery was performed for 6 bilateral and 4 unilateral tumours, the latter including 2 fused kidneys. Preoperative chemotherapy was employed with benefit in massive tumours, tumour in fused kidneys, bilateral tumours, and preoperatively diagnosed inferior vena caval tumour thrombi. Postoperative chemotherapy, employed in all cases, consisted of actinomycin D and vincristine with the addition of adriamycin in anaplastic and advanced-stage tumours. Ten children underwent second-line chemotherapy for disease unresponsive to the above management, but only 1 of these is currently free of disease. Postoperative tumour-bed radiotherapy, used in selected cases, prevented local recurrence in stage I and II disease. However, 20% of stage I and II patients not receiving radiotherapy developed tumour-bed recurrence. Twenty-three children have died and 5 with advanced disease and incomplete follow-up are presumed to be dead. Nine children are currently on treatment; 34 have successfully completed treatment, the disease-free survival in stages I-V being 81%, 75%, 42%, 14%, and 50%, respectively. Overall disease-free survival was 69% for Wilms' tumour of favourable histology and 50% for anaplastic tumours. The 3 patients with rhabdoid tumours and 3 of 4 with clear-cell sarcomas have died. Wilms' tumour management in the developing world is compromised by cases lost to follow-up and late presentation with massive tumours and advanced stage. Preoperative chemotherapy is advantageous in a number of cases, and postoperative radiotherapy should be deployed more frequently.

Adolescent↗
PubMed1998

Surgical management of complete ureteric duplication abnormalities.

In 2 decades (1974-1993), the senior author (S.A.) managed 148 patients with various abnormalities associated with complete ureteric duplication. Included were 72 patients with primary vesicoureteric reflux, 50 with ureteroceles, and 26 with upper-pole ectopic ureters. The majority of the patients were female, and the common clinical presentations included urinary tract infection (UTI), UTI with septicemia, and urinary incontinence. Ten cases were diagnosed after recognition of a renal abnormality on prenatal ultrasonography, an avenue that has provided new challenges, new opportunities, and new dilemmas. This review article is based on the authors' experience together with an analysis of current emphasis on early diagnosis, minimal surgery, and maximum preservation of renal function.

Female↗
PubMed1998

Comparison of proteolytic enzyme activities in adults of insecticide resistant and susceptible strains of the housefly M. domestica L.

Intracellular proteolytic activity in a DDT-resistant and a susceptible strain of M. domestica was determined by assaying a comprehensive range of cytoplasmic and lysosomal enzymes. The resistant strain showed significantly higher protease activities in whole body, head, thorax, abdomen and gut homogenates compared to the susceptible strain. The activity of alanyl- and arginyl aminopeptidase from both strains increased substantially after topical treatment with DDT at 1, 2 and 3 h, suggesting an involvement of proteolytic enzymes in the induction of detoxifying enzymes, thus indicating a possible role of the intracellular proteolytic activities in the resistance mechanism.

Aminopeptidases↗
PubMed1998

Tetrahymena mutants with short telomeres.

Telomere length is dynamic in many organisms. Genetic screens that identify mutants with altered telomere lengths are essential if we are to understand how telomere length is regulated in vivo. In Tetrahymena thermophila, telomeres become long at 30 degrees, and growth rate slows. A slow-growing culture with long telomeres is often overgrown by a variant cell type with short telomeres and a rapid-doubling rate. Here we show that this variant cell type with short telomeres is in fact a mutant with a genetic defect in telomere length regulation. One of these telomere growth inhibited forever (tgi) mutants was heterozygous for a telomerase RNA mutation, and this mutant telomerase RNA caused telomere shortening when overexpressed in wild-type cells. Several other tgi mutants were also likely to be heterozygous at their mutant loci, since they reverted to wild type when selective pressure for short telomeres was removed. These results illustrate that telomere length can regulate growth rate in Tetrahymena and that this phenomenon can be exploited to identify genes involved in telomere length regulation.

Animals↗
PubMed1998

The Mitrofanoff procedure in paediatric urinary tract reconstruction.

BACKGROUND: Urinary tract reconstruction is required in many congenital and some acquired urological conditions in childhood. The majority are managed by clean intermittent catheterization (CIC), for which purpose the appendix or other tubular structure may be used to provide a continent catheterizable abdominal stoma. METHODS: Between 1991 and 1996, 23 children underwent urinary tract reconstruction of varying complexity together with a continent diversion according to the Mitrofanoff principle. The appendix was used in 14 patients and the ureter in seven. Two patients had previously had an appendicectomy and the ureters were not suitable. One had a catheterizable channel made from an isolated segment of colon and the other had a detrusor tube constructed. RESULTS: Twelve patients with an appendix conduit, six with a ureteric conduit, and one with a colonic tube are continent, although the latter has had some problems with stomal stenosis. All manage CIC with comfort, the older children doing the procedure themselves. One appendix conduit has stomal incontinence and another was inadvertently divided during renal transplantation. The detrusor tube strictured and was removed. CONCLUSIONS: A continent abdominal stoma using the Mitrofanoff principle gives reliable results in children and is well tolerated. It should be considered in the management of children undergoing urinary tract reconstruction when CIC is necessary. The appendix is eminently suitable for this purpose but the ureter provides a satisfactory alternative in selected cases. When neither is available, alternative techniques for constructing a catheterizable continent channel may be considered.

Adolescent↗
PubMed1998

Tandem ureterocystoplasty.

BACKGROUND: Bladder augmentation may be undertaken by using various gastrointestinal segments but their use is associated with a multitude of well-recognized complications. The mega-ureter has proven to be a satisfactory alternative; in patients with bilateral mega-ureters, both ureters may be used for this purpose. METHODS: Seventeen patients had augmentation ureterocystoplasty, including three in whom both distal ureters were used in tandem. The latter included two patients with neurogenic bladder and one with bladder exstrophy. RESULTS: Satisfactory augmentation was achieved in all patients undergoing tandem ureterocystoplasty. The neurogenic bladder patients are managed by urethral clean intermittent catheterization (CIC) and the exstrophy patient is managed by CIC of an appendicovesicostomy (Mitrofanoff). All are continent. CONCLUSIONS: The mega-ureter provides an excellent source of augmentation material in patients with small non-compliant bladders. In those with bilateral mega-ureters, consideration should be given to using both ureters in tandem to achieve the maximum possible bladder capacity.

Bladder Exstrophy↗
PubMed1998

Construction of continent catheterizable urinary conduit from an isolated segment of colon.

BACKGROUND: Continent urinary diversion may be necessary in a range of urological abnormalities. In circumstances where the standard techniques are not possible, alternative innovative techniques may be used. METHODS: In a female patient with bladder exstrophy, a continent diversion was recommended. The appendix was not available, the ureters were not suitable and a continent stoma was fashioned from an isolated segment of colon. RESULTS: The stoma proved to be continent, although it was somewhat stenotic. However, clean intermittent catheterization maintained its patency. CONCLUSIONS: A continent catheterizable stoma may be constructed from a segment of colon. The technique may be considered when other well recognized methods are not feasible.

Bladder Exstrophy↗
PubMed1998

Pelviureteric obstruction in children: conventional pyeloplasty is superior to endo-urology.

BACKGROUND: Hydronephrosis secondary to pelviureteric junction (PUJ) obstruction is common in infancy and childhood. Pyeloplasty has until recently been the accepted method of management, but alternative endo-urological techniques have evolved in the last decade. METHODS: Published results of conventional pyeloplasty for primary PUJ obstruction in children were compared with published results of endo-urological procedures. RESULTS: Sixty-six pyeloplasties were performed in 61 children in a 6-year period. During a similar period, 63 primary endo-urological procedures were reported in the literature. The success rate after pyeloplasty was 95.5% compared with 65% after endo-urology. CONCLUSIONS: Conventional pyeloplasty is superior to endo-urology and should remain the gold standard for the treatment of primary PUJ obstruction in children.

Catheterization↗