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Biomedical subjects

A Mohamed

Publications and source records attributed to A Mohamed.

At least 19 recordsLinked to original sources
PubMed2000

Evidence of cingulate motor representation in humans.

A 44-year-old man with a right frontal lobe tumor and intractable seizures underwent subdural grid evaluation before resection. The electrode locations were identified on a three-dimensional surface-reconstructed image of the brain after subdural grid placement. Electrical stimulation of electrodes placed over the right cingulate gyrus revealed evidence of tonic posturing of the left forearm and wrist and tonic extension of the left leg. This finding provides further evidence of a motor area in the cingulate gyrus in humans.

Adult↗
PubMed2000

Epileptogenicity correlated with increased N-methyl-D-aspartate receptor subunit NR2A/B in human focal cortical dysplasia.

PURPOSE: Human cortical dysplasia (CD) is a frequent cause of medically intractable focal epilepsy. The neurotransmitter mechanisms of epileptogenicity in these lesions have been attributed to changes in various glutamate receptor subtypes. Increased N-methyl-D-aspartate (NMDA) receptor (NR) 2A/B coassembled with NR1 subunits has been shown in focal epileptic CD. The purpose of this study is to correlate in situ CD epileptogenicity and the expression of various glutamate receptor subtypes. METHODS: The histopathological, morphological, and immunocytochemical findings in cortical tissue resected from five patients with medically intractable epilepsy and CD were correlated with electroencephalographic data recorded from subdural grids. The NMDA antibodies identified subunits NR1 (splicing variants 1a, 1b, 2a, and 2b) and NR2A/B. RESULTS: Epileptogenic specimens displayed the following common features: (a) widespread histological abnormalities of horizontal and columnar dyslamination, neurons with inverted polarity, and more extensive dendritic changes; (b) significantly higher NR2A/B immunoreactivity in both the dysplastic somata and all their dendritic processes; and (c) no statistically significant change in NR1 subunit expression but a more pronounced staining of the apical dendrites in highly epileptogenic cortex. These abnormalities were either absent or minimal in resected specimens that did not show evidence of severe in vivo epileptogenicity. CONCLUSION: These studies provide direct evidence for a major contribution of the NR2A/B subunit in CD-induced epileptogenicity.

Adolescent↗
PubMed2000

Magnetic resonance imaging in temporal lobe epilepsy: usefulness for the etiological diagnosis of temporal lobe epilepsy.

With improvement in magnetic resonance (MR) imaging techniques, the ability to identify lesions responsible for temporal lobe epilepsy has increased. MR imaging has also enabled the in vivo diagnosis of hippocampal sclerosis. Brain tumors are responsible for 2-4% of epilepsies in adult population and 10-20% of medically intractable epilepsy. The sensitivity of MR imaging in the diagnosis of tumors and other lesions of the temporal lobe (vascular malformations, etc.) is around 90%. Both hippocampal sclerosis and other temporal lobe lesions are amenable to surgical therapy with excellent postsurgical seizure outcome. In this article, we characterize and underline distinguishing features of the different pathological entities. We also suggest an approach to reviewing the MR images of an epileptic patient.

Brain↗
PubMed1999

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Journal Article↗
PubMed1999

Myocardial protection with monophosphoryl lipid-A against aortic cross clamping-induced global stunning.

BACKGROUND: Monophosphoryl lipid-A (MLA) has a late window (24 hours) of cardioprotection against acute myocardial infarction. It is not known whether MLA, administered, 24 hours before surgery, attenuates intraoperative ventricular dysfunction "stunning" associated with aortic cross-clamping and reperfusion during elective cardiac surgery. We determined the dose-response relationship between MLA and ventricular function in a canine model of global myocardial stunning in the absence of necrosis. The role of expression of inducible heat shock protein 70 (HSP 70i) was also investigated. METHODS: Mongrel dogs (n = 32) were intravenously injected with either a vehicle solution or 3, 5, 10, 35 ug/kg MLA. Twenty four hours later, dogs were anesthetized and instrumented, in situ, to monitor the left ventricular performance (the slope of regression between stroke-work and end diastolic length). Tissue samples were obtained to determine HSP70i using immunoblot analysis. After a period of equilibration on cardiopulmonary bypass, the aortic cross-clamp was applied at normothermia for 30 minutes followed by 60 minutes of reperfusion. ATP and catabolites were determined in transmural myocardial biopsies. Triphenyl-tetrazolium chloride (TTC) staining was used to determine myocardial necrosis. RESULTS: MLA treatment did not alter myocardial contractility or ATP metabolism. Global ischemia resulted in about 50% depletion of ATP and remained depressed during reperfusion in all groups. MLA-treated hearts had improved functional recovery in a dose dependent-manner. Significant recovery was observed at the highest dose (35 ug/kg) compared to the control group. Immunoblot analysis demonstrated significant increase in HSP 70i in the MLA-treated hearts. CONCLUSIONS: MLA exhibits a delayed (24 hours) window of protection against myocardial stunning associated with aortic cross-clamping. HSP70i expression may play a role in MLA-mediated cardioprotection.

Adjuvants, Immunologic↗
PubMed1999

Interictal epileptiform discharges in temporal lobe epilepsy due to hippocampal sclerosis versus medial temporal lobe tumors.

PURPOSE: It remains controversial whether a specific pattern of interictal epileptiform activity exists that may help to differentiate temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) from other forms of TLE. In this study, we characterized the distribution of interictal epileptiform discharges in TLE due to HS as compared with those in patients with tumors restricted to the medial temporal lobe structures. METHODS: The study included 21 adult patients with unilateral HS who remained seizure free (>1 year) after anterior temporal lobectomy with amygdalohippocampectomy. Patients with "dual pathology" were excluded. The comparison group consisted of nine patients with tumors restricted to the amygdala and hippocampus. All patients underwent video-EEG monitoring preoperatively by using 39 scalp electrodes (including the 10-10 system over both temporal regions) and bilateral sphenoidal electrodes. RESULTS: The HS patient group showed a significantly higher percentage of ipsilateral epileptiform discharges maximal at anterior temporal electrodes (median, 97.0%; sphenoidal electrode alone, 88.1%), as compared with the tumor group (median, 72.1%; p<0.001; sphenoidal electrode alone, 24.8%; p<0.001). The HS group had significantly fewer extratemporal spikes/sharp waves (median, 0.0), as compared with the tumor group (10.0%; p<0.001). At least 90% of the interictal discharges were located in the anterior temporal region in 20 (95.2%) of 21 HS patients, but in none of the tumor patients (p<0.001). Bilateral temporal discharges were found in nine (42.9%) of 21 patients with HS and in two (22.2%) of nine tumor patients (p = 0.42). CONCLUSIONS: We conclude that ipsilateral interictal epileptiform discharges outside the anterior temporal region are rare (<10%) in adults with intractable TLE due to unilateral HS. Frequent posterior or extratemporal sharp waves may detract from the certainty of this diagnosis in complicated cases. These restricted epileptiform discharges suggest a smaller irritative zone in HS as compared with medial tumors, or a more organized activity associated with intrinsic hippocampal disease. Bilateral epileptiform discharges were not uncommon in both groups.

Adolescent↗
PubMed1999

Periictal diffusion-weighted imaging in a case of lesional epilepsy.

PURPOSE: Diffusion-weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period. METHODS: A periictal DWI study was performed on a 35-year-old patient during focal status epilepticus with repetitive prolonged focal motor seizures originating from a lesion in the right frontal lobe. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps. RESULTS: On DWI, a single area of signal increase (decrease in ADC) was found in the region of focal electrocorticographic seizures that was mapped intraoperatively. CONCLUSIONS: Ictal/postictal DWI may be a useful technique for seizure localization in patients with lesional epilepsy.

Adult↗
PubMed1999

Hippocampal chemical anatomy in pediatric and adolescent patients with hippocampal or extrahippocampal epilepsy.

We determined whether age or seizure types were associated with hippocampal neuron loss, mossy fiber (MF) and GABAergic synaptic reorganizations or postsynaptic receptor densities. Children and adolescents were grouped into: (1) nonhippocampal sclerosis (non-HS; n = 11) and (2) hippocampal sclerosis (HS; n = 11). The most important results showed that: (1) regardless of the etiology of the seizures, there were greater cell losses in Ammon's horn with older ages in years; in the non-HS group, cell losses were greater with the older ages or with longer epilepsy durations; however, in the HS patients, the cell losses were not related to the patients' ages or epilepsy durations; (2) in both HS and non-HS, CA1 had greater cell losses than CA4; (3) in HS, CA1 and CA4 had greater cell losses than those in non-HS; (4) in non-HS, MF sprouting was greater with ages or with longer epilepsy durations; by contrast, in HS, MF sprouting was not related to the patients' age or epilepsy duration; (5) densities for AMPA GluR1, GABA-Abeta and for GABA axonal terminals were positively increased with age. These findings support the hypothesis that hippocampal cell losses and aberrant synaptic reorganizations are greater in the hippocampi of adolescents than in children, even for non-HS pathologies.

Adolescent↗
PubMed1999

Prevalence of chronic inflammatory demyelinating polyneuropathy in New South Wales, Australia.

A prevalence study of chronic inflammatory demyelinating polyneuropathy (CIDP) was performed in New South Wales (NSW), Australia, with a prevalence day of August 6, 1996, which coincided with a national census. The population of NSW was 5,995,544, and the crude prevalence of CIDP was 1.9 per 100,000 population. It was higher in male patients than in female patients, and the age-specific prevalence reached a maximum of 6.7 per 100,000 population in the 70- to 79-year-old age group. The prevalence in the city of Newcastle, with a population of 448,663, was 2.0 per 100,000 population and is representative of the whole of NSW. The estimated crude annual incidence was 0.15 per 100,000 population. The mean age of onset was 47.6 years (median, 53.5 years), 51% of patients had a relapsing-remitting course, the mean duration on prevalence day was 7.1 years (median, 5 years), and 87% of patients were able to walk without walking aids or other assistance.

Adolescent↗
PubMed1998

Conduction block in vasculitic neuropathy.

Vasculitis involving peripheral nerves usually presents as an acute asymmetrical axonal neuropathy. We report a 67-year-old man with a symmetrical subacute neuropathy in which nerve conduction studies showed prominent conduction block, a finding indicative of demyelination. Sural nerve biopsy showed a vasculitic neuropathy with invasion of blood vessel walls by inflammatory cells and a mixture of nerve fiber loss and demyelination. The demyelination in this case was presumably a consequence of subinfarctive nerve ischemia.

Action Potentials↗
PubMed1997

Growth of human nondiploid primary prostate tumor epithelial cells in vitro.

Research into molecular and cellular defects underlying prostate cancer would be advanced by in vitro models of prostate tumor cells representing patient tumors. We have propagated, in serum-free medium, epithelial cell cultures derived from nondiploid prostate tumors and normal human prostate. The serial passage tumor cells exhibited nondiploid karyotype and transformed phenotypes of focus formation and anchorage-independent growth. In contrast, the normal prostate cells showed diploid karyotype and lacked transformed phenotypes. Both the tumor and normal cells were positive for prostate-specific antigen and cytokeratins 18 and 19 and negative for keratin 15. These results demonstrate that the nondiploid prostate tumors and normal prostate epithelial cell cultures retained their respective in vivo properties and should allow studies to elucidate molecular alterations involved in human prostate cancer.

Biomarkers↗
PubMed1997

Functional expression and apical localization of the cystic fibrosis transmembrane conductance regulator in MDCK I cells.

The gene product affected in cystic fibrosis, the cystic fibrosis transmembrane conductance regulator (CFTR), is a chlorideselective ion channel that is regulated by cAMP-dependent protein kinase-mediated phosphorylation, ATP binding and ATP hydrolysis. Mutations in the CFTR gene may result in cystic fibrosis characterized by severe pathology (e.g. recurrent pulmonary infection, male infertility and pancreatic insufficiency) involving organs expressing the CFTR. Interestingly, in the kidney, where expression of the CFTR has been reported, impaired ion transport in patients suffering from cystic fibrosis could not be observed. To understand the role of the CFTR in chloride transport in the kidney, we attempted to identify an epithelial cell line that can serve as a model. We demonstrate that the CFTR is expressed constitutively in Madine-Darby canine kidney (MDCK) type I cells, which are thought to have originated from the distal tubule of the dog nephron. We show expression at the mRNA level, using reverse transcriptase-PCR, and at the protein level, using Western blot analysis with three different monoclonal antibodies. Iodide efflux measurements indicate that CFTR expression confers a plasma membrane anion conductance that is responsive to stimulation by cAMP. The cAMP-stimulated iodide release is sensitive to glybenclamide, diphenylamine carboxylic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid, but not to 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid, an inhibitor profile characteristic of the CFTR chloride channel. Finally, the polarized localization of the CFTR to the apical plasma membrane was established by iodide efflux measurements and cell-surface biotinylation on MDCK I monolayers. Interestingly, MDCK type II cells, which are thought to have originated from the proximal tubule of the kidney, lack CFTR protein expression and cAMP-stimulated chloride conductance. In conclusion, we propose that MDCK type I and II cells can serve as convenient model systems to study the physiological role and differential expression of CFTR in the distal and proximal tubule respectively.

Animals↗
PubMed1997

Accumulation of phytate in vegetable-type soybean genotypes harvested at four developmental stages.

A total of 17 vegetable-type soybean (Glycine max [L.] Merr) genotypes were planted in four-row plots arranged in a randomized complete block design in 1988 and 1989 at Petersburg, Virginia. Each genotype was harvested at four developmental stages and evaluated for phytate content. Highly significant differences for phytate content were observed among the stages of harvest and genotypes, and there was an interaction between genotype x stage of harvest. The significant differences observed for phytate content among genotypes indicated that genetic variation exists among the tested genotypes for selection and improvement through hybridization. Among the genotypes, 'Kingston' and PI 423852 had the highest phytate content in most stages of harvest while PI 416771, 'Emperor', and PI 416982 had the lowest phytate values. A heritability estimate of 81 percent was observed for phytate content. This high heritability value indicates that selecting genotypes for lower phytate content would be effective. Significant correlations were observed for phytate content among genotypes harvested at R6, R7, R8, and overall. The magnitude of association of R6 with the overall phytate mean was especially high. These results illustrate that determining the phytate content of genotypes at the R6 growth stage would be a good predictor of the overall genotypic performance.

Food Analysis↗
PubMed1997

Registration bone scan in the evaluation of wrist pain.

We assessed the value of bone scintigraphy combined with X-ray registration for the diagnosis and management of wrist pain in 65 patients. Studies were reported independently by two observers before and after registration. Registration improved localization of scan abnormalities in 53% (observer 1) and 61% (observer 2). In these patients, the bone scan contributed to the diagnosis independently of the X-ray in 37% and the management was altered in 31%. The value of the bone scan in the early diagnosis and management of wrist pain is increased when it is registered with X-rays.

Adult↗
PubMed1997

Cytological aspects of uterine cervical adenocarcinoma, adenosquamous carcinoma and combined adenocarcinoma-squamous carcinoma: appraisal of diagnostic criteria for in situ versus invasive lesions.

This paper reports the cytological findings based on air-dried smears in a retrospective series of 143 cases of endocervical adenocarcinoma, combined adenocarcinoma-squamous carcinoma and adenosquamous carcinoma drawn from the files of the BC Cancer Registry. Cervical cytology smears were available before biopsy in 131 patients, but in 18 cases the cytology showed no abnormality. Malignant changes or high-grade atypia of glandular and/or squamous cells (defined as moderate or severe dyskaryosis) were detected in 103 cases. In 46 cases, only a high-grade squamous abnormality was detected. Low-grade glandular and/or squamous lesions were detected in nine cases and one showed atypical endometrial-type glands. The cervical smears of 64 cases were reviewed in detail to determine the important cytomorphological criteria of in situ and invasive adenocarcinoma in air-dried smears, the technique used for preparing PAP smears in British Columbia. Endocervical cells were absent in four cases. Numerous (> 10) groups of glandular cells were present in 51 cases. Important clues to the diagnosis of adenocarcinoma included crowding of nuclei, stratification of nuclei, loss of polarity, syncytial balls and papillary groups of glandular cells, nuclear enlargement, nuclear pleomorphism, and the presence of free-lying atypical glandular cells. Nuclear hyperchromatism, chromatin pattern, nuclear borders, nuclear membranes, and numbers and morphology of nucleoli were not helpful criteria in our material. Criteria enabling reliable distinction between in situ and invasive adenocarcinoma and/or mixed adenocarcinoma-squamous carcinoma could not be established.

Adenocarcinoma↗
PubMed1997

Establishment of a sandwich enzyme linked immunosorbent assay for canine interleukin-8.

To estimate canine interleukin-8 (cIL-8) levels in blood plasma samples, a sandwich enzyme linked immunosorbent assay (ELISA) was established. For the development of the sandwich ELISA, polyclonal anti-cIL-8 (capturing), biotinylated anti-cIL-8 (developing) antibodies and glutathione-S-transferase/cIL-8 (GST/cIL-8) fusion protein as an antigen were used. cIL-8 in the fusion protein of GST/cIL-8 was detected in a dose dependent manner. The lowest limit of GST/cIL-8 detectable by this method was 2 ng/ml of GST/cIL-8 (containing; 0.470 ng/ml of cIL-8). IL-8 levels in the plasma samples from apparently healthy dogs were less than 0.470 ng/ ml. Higher levels of IL-8 were detected in the plasma samples of dogs with cystitis, dermatitis, and gastric cancer. These results suggest that the determination of cIL-8 by the sandwich ELISA is useful in diagnosis of inflammatory diseases in dogs.

Animals↗
PubMed1997

Evaluation of MYC and chromosome 8 copy number in breast carcinoma by interphase cytogenetics.

We used fluorescence in situ hybridization (FISH) to determine MYC and chromosome 8 copy number on whole nuclear imprint preparations of 24 breast carcinomas, seven benign breast samples, and two phyllodes tumors. None of the benign tissues and neither of the phyllodes tumors demonstrated an increased copy number for MYC or chromosome 8, which was defined as greater than two signals in > 10% of nuclei. In contrast, 22 of 24 carcinomas demonstrated an increased MYC copy number. The modal numbers of MYC copies/nucleus were 0-2 in seven cases (29%), 3-5 in seven cases (29%), 6-9 in five cases (21%), and > 9 in five cases (21%). An increased chromosome 8 copy number was observed in 21 of 22 carcinomas with MYC gain, and the modal number of signals/nucleus was either identical to (n = 14; 64%) or less than (n = 8; 36%) the number of MYC copies. The number of MYC copies correlated with cellular DNA content, as determined by using flow cytometry. In peridiploid tumors (DNA index 0.9-1.2; n = 7), the MYC copy numbers/nucleus were 0-2 in five cases and 3-5 in two cases. In contrast, the modal MYC copy numbers/nucleus among the 11 hyperdiploid tumors (DNA index 1.3-1.9) were 0-2 in one case, 3-5 in four cases, 6-9 in five cases, and > 9 in one case. All three tetraploid/hypertetraploid carcinomas exhibited > 9 MYC copies/nucleus. We conclude that an increased MYC copy number, as detected by using interphase cytogenetics, is extremely frequent in human breast carcinomas. However, in most cases, MYC gene duplication is probably secondary to polysomy of chromosome 8 and/or genomic endoreduplication (i.e., DNA aneuploidy).

Aneuploidy↗