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Muhammad Ashraf

Publications and source records attributed to Muhammad Ashraf.

41 records · Page 3Linked to original sources
PubMedDate not supplied

Morphological recovery in the reattached retina of the toad Bufo marinus: a new experimental model of retinal detachment.

BACKGROUND: The retinal pigment epithelium (RPE) of the toad (Bufo marinus) has been used in many studies as a model for understanding its role and interaction with the neural retina. The toad's retina has been used to establish a new in vitro model of experimental retinal detachment (RD) and replacement . It has been shown that the electrophysiological measures of retinal function recovered following complete RD. The toad was chosen because its RPE is similar to the mammalian RPE . In this report, light microscopy was used to characterize the morphologic changes that occur in the RPE and neural retina following RD/replacement and to correlate these findings with recovery of electrophysiologic function. METHODS: Retinas from Bufo marinus were studied in vitro. The neural retina completely detached from the RPE and then replaced. At various times after replacement, neural retina-RPE tissues were processed for light microscopy. RESULTS: At 30 min after replacement, the subretinal space was greatly expanded, and the apical processes that normally ensheath the rod outer segments were short and no longer contacted the rod outer segments. The RPE was swollen, contained many vacuoles and the apical surface was rounded. By 2 h after replacement, the subretinal space was significantly resorbed and contained many shredded rod outer segments; RPE cells were still swollen, although less. During the next 5-10 h, the number of phagosomes in the RPE cytoplasm increased and the number of shredded rod outer segments in the subretinal space decreased. RPE cells regained their normal size and interdigitation of apical processes and rod outer segments were observed. CONCLUSIONS: These results demonstrate the re-establishment of morphological interactions between the RPE and neural retina within hours following RD/replacement. Morphological recovery coincides with recovery of electrophysiologic parameters. This is a good model to investigate the retinal pigment epithelium (RPE) and neural retina mechanisms involved in retinal adhesion and recovery from retinal detachment.

Animals↗
PubMedDate not supplied

Increased DNA methyltransferase 1 (DNMT1) gene expression in human lymphomas by fluorescent in situ hybridization.

BACKGROUND: The DNA Methyltransferase 1 (DNMTI) gene is among the better known 'epigenetic' systems that can regulate normal and abnormal gene expression as well as create 'hot spots' for DNA mutations. Its role has been studied in a number of malignancies with important implications for involvement in early events of malignant transformation. The present study describes the findings with respect to expression of this gene in human lymphomas studied by Fluorescent In Situ Hybridization (FISH). METHOD: The study was undertaken on randomly selected archival human lymph nodes comprising 50 specimens of normal or reactive lymph nodes and 50 specimens of lymphoma lymph nodes. These were subjected to FISH using oligonucleotide Antisense probes for the DNMT1 mRNA according to standard FISH protocols. Percent cells stained, mean 'dots' stained per cell and staining signal intensity were taken as the criteria for comparing control and lymphoma lymph nodes. Quantitation of probe signals was done both by manual visualisation of the fluorescent signals and computer based image analysis. RESULTS: Data indicated a significantly increased expression of the DNMT1 mRNA in lymphoma cases as compared to controls (p<0.001). CONCLUSION: This implies a possible role of the DNMT1 gene in transformation / oncogenesis in human lymphomas.

Base Sequence↗
PubMedDate not supplied

Dna methyltransferase 1 (DNMT1) gene activity in human lymphomas correlates with aberrant p53 gene expression.

BACKGROUND: The DNA Methyltransferase 1 (DNMT1) gene has been implicated as a mutagen for tumor suppressor genes by causing hypermethylation and subsequent TA mutations of CpG islands located in the promoter regions of these genes. The present study was undertaken to determine if increased DNMT1 gene activity correlated with increased aberrant p53 gene expression in human lymphomas. METHODS: The study was undertaken on randomly selected archival human lymph nodes comprising 50 normal or reactive lymph nodes and 50 lymphoma lymph nodes. These were subjected to Fluorescent In Situ Hybridization (FISH) using oligonucleotide Antisense probes for the DNMT1 and the p53 mRNA according to standard FISH protocols. Percent cells stained, mean 'dots' stained per cell and staining signal intensity were taken as the criteria for comparing control and lymphoma lymph nodes. Quantitation of probe signals was done both by manual visualization of fluorescent signals and computer based image analysis. Correlation analysis was performed by calculation of Pearson's correlation coefficient. RESULTS: Data indicated significantly increased expression of the DNMT1 and the p53 mRNA in lymphoma cases as compared to controls (p < 0.001). Moreover significant correlation was obtained for the expressions of these two genes in lymphomas (p < 0.001), but not in control lymph nodes. CONCLUSION: Increased DNMT1 gene activity may contribute to increased p53 gene expression in human lymphomas, supporting a mutagenic role for the DNMT1 gene.

Case-Control Studies↗
PubMedDate not supplied

Intracranial extra-skeletal mesenchymal chondrosarcoma.

Intracranial Mesenchymal Chondrosarcoma is a very rare and uncommon entity that affects young adults. We came across one such patient who presented with severe headache and intermittent nausea and vomiting. The clinical, radiological preoperative diagnosis was a meningioma, on histological examination it turned out to be mesenchymal chondrosarcoma of tentorial region in posterior fossa, uncommon site for this entity.

Adult↗