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Biomedical subjects

I Ahmed

Publications and source records attributed to I Ahmed.

At least 163 records · Page 9Linked to original sources
PubMed1992

Intracerebroventricular injection of insulin or glucose alters insulin-like growth factor II (IGF-II) concentrations in specific hypothalamic nuclei.

Peripherally administered insulin has been shown to alter content and gene expression of hypothalamic insulin-like growth factor II (IGF-II) in a region specific manner (Lauterio, TJ. et al., Endocrinology, 126 (1990) 392-398. The objective of this experiment was to determine whether central administration of insulin can modulate hypothalamic IGF-II peptide content. Male Sprague-Dawley rats were implanted with lateral ventricular cannulae and allowed to recover from surgery one week prior to injection. At that point animals were remotely injected with one of the following: (1) synthetic cerebral spinal fluid vehicle (sCSF); (2) 2 mIU porcine insulin (I); (3) glucose (100 mg%) only. Animals were decapitated 30 min after injections and brains were quickly removed, frozen and dissected into specific hypothalamic regions for IGF-II analysis by RIA. Insulin increased IGF-II content in the ventromedial hypothalamic region by 80% (P < 0.001) and paraventricular nucleus by 30% (P < 0.01) compared to sCSF or glucose treatment. Arcuate nucleus and neurointermediary lobe pituitary IGF-II content was decreased with insulin treatment compared to controls (P < 0.01). Insulin had no effect on IGF-II concentrations in the dorsomedial or lateral hypothalamic regions or in the supraoptic and suprachiasmatic nuclei. Peripheral concentrations of glucose, insulin and IGF-II were unaffected by any treatment. Results show that insulin which reaches the brain can alter IGF-II levels in specific regions of the hypothalamus and suggests a possible role for IGF-II in insulin mediated changes in metabolism or hypothalamic hormone secretion.

Animals↗
PubMed1992

The non-equivalence of binding sites of coenzyme quinone and rotenone in mitochondrial NADH-CoQ reductase.

The fluorescent probe erythrosine 5'-iodoacetamide (ER) binds to mitochondrial NADH-CoQ reductase (Complex-I) accompanied by an enhancement of the fluorescence intensity. The binding of the CoQ analogue, 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB), decreased the fluorescence intensity of the ER:Complex-I system. The 'site 1' inhibitor rotenone did not decrease the fluorescence intensity showing the non-identical nature of the binding sites of DB and rotenone. Also, the reduced form of DB did not decrease the fluorescence intensity. The decrease of the fluorescence intensity by DB was shown to be due to the removal of bound ER by DB. The rapid kinetics of ER binding was studied by temperature-jump relaxation. While DB caused complete elimination of the relaxation process in the ER:Complex-I system, rotenone caused only a decrease in the relaxation rate, suggesting conformational change. The relaxation rate showed a pH dependence with a maximum around pH 7.5.

Binding Sites↗
PubMed1992

Immuno-electron microscopical localization of vimentin and glial fibrillary acidic protein in mouse astrocytes and their precursor cells in culture.

Immuno-electron microscopy was used to localize the distribution of vimentin and glial fibrillary acidic protein (GFAP) in mouse astrocytes and their precursor cells in primary cultures. In astroblasts and astrocytes, vimentin and GFAP form intermediate filaments (IF), which are heteropolymers, as previously observed in gliomas. Astrocytes and their precursor cells may have IF composed of GFAP-vimentin heteropolymer or vimentin alone, but IF composed of GFAP only were not seen. It seems that the formation of IF that are GFAP-vimentin heteropolymers is a feature of normal astroglia development and that the ratio of GFAP to vimentin in these IF reflects the degree of differentiation and functional state of the cell.

Animals↗
PubMed1992

Influence of exercise intensity on the presence, distribution, and size of thallium-201 defects.

The effects of two levels of exercise intensity on the size and location of thallium-201 defects were compared in 22 patients with known ischemic coronary artery disease. A symptom-limited incremental exercise test was performed followed (greater than 48 hours) by submaximal steady-state exercise at 70% of the peak heart rate achieved during the incremental test. Planar thallium-201 myocardial scans obtained after each protocol were analyzed by means of both visual qualitative and computerized quantitative methods. After incremental exercise all patients exhibited reversible thallium-201 defects, and submaximal exercise still resulted in reversible defects in 20 (91%) patients. However, the size of the ischemic area and the degree of ischemia were significantly reduced by both qualitative and quantitative criteria after submaximal exercise. Therefore interpretation of thallium-201 scans with regard to severity of disease and prognosis should take into account exercise intensity.

Blood Pressure↗
PubMed1992

Depression and neurological disease. Their distinction and association.

Depression and neurological disease often coexist but sometimes are difficult to distinguish. By analyzing eight patients, all seen by psychiatrists and the same neurologist, and by reviewing the pertinent literature, we will explore the complex differential features, coexistence, and interaction between depression and neurological disease. Neurological disease may lead to changes in mood and behavior, and these patients may present to psychiatrists with depression. In addition, depression may present with or exaggerate neurological signs and symptoms. Awareness of these interactions can lead to appropriate evaluation and treatment of both these disorders.

Adult↗
PubMed1992

Can somatosensory evoked potentials predict outcome from coma?

Long-term somatosensory evoked potential (SEP) recordings for a period of 2 1/2 years are reported for a patient rendered comatose from hypoxic encephalopathy. Findings are compared with previously published reports on poor outcome associated with bilaterally absent cortical responses. In the present case, the patient was admitted with poor neurological status but has preserved cortical responses bilaterally throughout his course until his final recovery and return to previous employment. Somatosensory cortical responses when bilaterally absent are universally associated with poor outcome; however, when persistently present they can indicate hope of recovery despite poor clinical status on admission.

Adult↗
PubMed1991

Comparison of chest pain, electrocardiographic changes and thallium-201 scintigraphy during varying exercise intensities in men with stable angina pectoris.

This study was performed to evaluate the presence of angina pectoris, electrocardiographic changes and reversible thallium-201 defects resulting from 2 different levels of exercise in 19 patients with known coronary artery disease and evidence of exercise-induced ischemia. The exercise protocols consisted of a symptom-limited incremental exercise test (Bruce protocol) followed within 3 to 14 days by a submaximal, steady-state exercise test performed at 70% of the maximal heart rate achieved during the Bruce protocol. The presence and time of onset of angina and electrocardiographic changes (greater than or equal to 0.1 mV ST-segment depression) as well as oxygen uptake, exercise duration and pressure-rate product were recorded. Thallium-201 (2.5 to 3.0 mCi) was injected during the last minute of exercise during both protocols, and the images were analyzed using both computer-assisted quantitation and visual interpretations. Incremental exercise resulted in anginal symptoms in 84% of patients, and electrocardiographic changes and reversible thallium-201 defects in all patients. In contrast, submaximal exercise produced anginal symptoms in only 26% (p less than 0.01) and electrocardiographic changes in only 47% (p less than 0.05), but resulted in thallium-201 defects in 89% of patients (p = not significant). The locations of the thallium-201 defects, when present, were not different between the 2 exercise protocols. These findings confirm the sequence of the ischemic cascade using 2 levels of exercise and demonstrate that the cascade theory is applicable during varying ischemic intensities in the same patient.

Angina Pectoris↗
PubMed1991

The antiproliferative effects of enzymatic deglycosylation and metabolic undersulfation of proteoglycans from the cell surface.

Enzymatic deglycosylation of plasma membrane proteoglycans and metabolic inhibition of glycosaminoglycan sulfation were employed as complementary methods to evaluate the effects of reduced cell surface content of functionally intact proteoglycans on the proliferative potential of cells. A Flavobacter heparinum extract, possessing multiple glycosaminoglycan substrate specificities, markedly inhibited the time-dependent expansion of BALB/c 3T3 fibroblast and human squamous cell carcinoma monolayers in culture and concurrently reduced the proportion of subconfluent cell populations in S-cell cycle phase by DNA flow-cytometry analysis. This antiproliferative effect was partially reproduced by lyases with heparan sulfate or chondroitin sulfate monospecificity, alone and in combination. The observed lability of heparan sulfate lyases I and II in serum-containing medium possibly hampered full reproduction of the effects of the multifunctional reagent. Growth inhibition of comparable magnitude was observed when glycosaminoglycan sulfation was metabolically blocked with sodium chlorate. The chlorate anion had its expected effect of substantially reducing sulfated glycosaminoglycan synthesis by the cells. Following release from serum deprivation, analysis of the progression of synchronized cell populations past the G1 restriction point suggested that in situ digestion with the glycosaminoglycan lyases limited, but did not delay, the numbers of cells entering S phase. These data support the hypothesis that plasma membrane proteoglycans mediate some of the cell-growth-promoting effects of serum factors via their glycosaminoglycan side chains.

Animals↗
PubMed1991

HMB-45 staining of dysplastic melanocytic nevi in melanoma risk groups.

To evaluate the hypothesis that reactivity of the intradermal component of melanocytic nevi to the monoclonal antibody HMB-45 correlates with melanoma risk, dysplastic compound melanocytic nevi were examined for expression of the HMB-45 epitope in three subject groups differing in epidemiological risk for melanoma. The study groups consisted of 10 subjects with dysplastic nevi and a personal history of melanoma, 25 subjects with dysplastic nevi and a history of melanoma in one or more first degree relatives, and 15 population control subjects with sporadic dysplastic nevi. For each case, sections from one lesion, immunohistochemically processed for HMB-45 binding, were evaluated by two pathologists without knowledge of the clinical data. Of all dysplastic nevi, 98% showed diffusely positive cytoplasmic staining of the junctional nevomelanocytes and 90% had such positive staining of those cells within the superficial dermis. Nevus cells within the deeper dermis did not stain positively in any case. Furthermore, the data showed no differences in frequency, pattern, or intensity of HMB-45 reactivity between the subject groups. These observations indicate that evaluation of dysplastic nevi with the monoclonal antibody HMB-45, an apparent marker of proliferative or otherwise stimulated melanocytes, has no discriminating value for identifying subjects at increased historical risk for melanoma. The data, however, support the concept that so-called dysplasia within nevi, as defined by histologic criteria, actually represents the active or proliferative phase of melanocytic nevi.

Antibodies, Monoclonal↗
PubMed1991

Psychosocial adjustment after renal transplantation.

Renal Transplantation is fairly new in our country and is expected to be the only satisfactory long-term treatment for patients with End Stage Renal Disease. Such treatment offers them a chance for near normal life. Seventeen patients who underwent kidney transplant during 1987-88 at the department of Nephrourology of J.P.M.C. Karachi, were reviewed. The result of ten patients who were assessed for their psychosocial adaptation is presented.

Adaptation, Psychological↗
PubMed1991

Local preparation, standardization and quality control of technetium labelled macroaggregated albumin for lung perfusion studies.

Lung perfusion study is an important investigation in various pulmonary diseases. The radiopharmaceutical commonly used now-a- days is imported macroaggregated human albumin (in kit form), which is labelled with technetium (Tc99m-MAA). Due to its high cost the technique could not be fully exploited. We have tried to locally prepare freeze dried MAA particles. Various parameters like concentration of protein, pH value, temperature, quality and quantity of reducing agents were studied to find out the optimum conditions for radiolabelling and the desired particle size. More than 98% of the added radioactivity was found tagged to the MAA particles in the final preparation (confirmed by paper chromatography). Labelled agent was found to be radiochemically stable for up to 6 hours. Initial animal and later human studies showed an ideal spectrum of particle size.

Chemistry, Pharmaceutical↗
PubMed1991

Methylphenidate in depressed medically ill patients.

BACKGROUND: The purpose of the authors' study was to evaluate the efficacy of methylphenidate in the medically ill depressed patients and to examine the factors that appear to affect therapeutic response and side effects. METHOD: Hospital charts were reviewed for 29 patients who received trials of methylphenidate for treatment of depressive disorders while admitted to a medical/surgical unit. RESULTS: Of the 29 patients, 16 (55%) had moderate or marked improvement, all within 2 days of commencing treatment with the maximal dose. Of the 25 nondelirious patients, 16 (64%) had moderate or marked improvement, and the presence of delirium was significantly associated with decreased response. Therapeutic response was significantly correlated with maximum methylphenidate dose. Side effects were noted in 8 (28%) patients; most side effects were mild (tachycardia or agitation), and all reversed after the medication was discontinued. CONCLUSIONS: Methylphenidate provides a safe and effective alternative to tricyclic antidepressants in medically ill populations but appears to be less effective in the presence of delirium.

Adjustment Disorders↗