Biomedical subjects

Muhammad Tariq

Publications and source records attributed to Muhammad Tariq.

4 recordsLinked to original sources

PubMed2003

Erasure of CpG methylation in Arabidopsis alters patterns of histone H3 methylation in heterochromatin.

In mammals and plants, formation of heterochromatin is associated with hypermethylation of DNA at CpG sites and histone H3 methylation at lysine 9. Previous studies have revealed that maintenance of DNA methylation in Neurospora and Arabidopsis requires histone H3 methylation. A feedback loop from DNA methylation to histone methylation, however, is less understood. Its recent examination in Arabidopsis with a partial loss of function in DNA methyltransferase 1 (responsible for maintenance of CpG methylation) yielded conflicting results. Here we report that complete removal of CpG methylation in an Arabidopsis mutant null for DNA maintenance methyltransferase results in a clear loss of histone H3 methylation at lysine 9 in heterochromatin and also at heterochromatic loci that remain transcriptionally silent. Surprisingly, these dramatic alterations are not reflected in heterochromatin relaxation.

Arabidopsis↗

PubMed2003

Validaty of Siriraj Stroke Scoring.

OBJECTIVE: To study the sensitivity and specificity of Siriraj Stroke Scoring (SSS) and to validate the accuracy of SSS in acute supratentorial stroke syndromes. DESIGN: Noninterventional descriptive study. PLACE AND DURATION OF STUDY: Department of Neurology, Pakistan Institute Of Medical Sciences, Islamabad, and Department of Medicine, Federal Government Services Hospital, Islamabad, from July to December 2000 and February to July 2002, respectively. SUBJECTS AND METHODS: One hundred (100) consecutive cases of acute supratentorial strokes were studied in accordance with SSS and sensitivity and specificity of SSS for supratentorial infarction and haemorrhage was tested against the computerised brain scanning (CT) as a gold standard. Siriraj Stroke Scoring was applied. Patients with subarachnoid haemorrhage and transient ischemic attacks were excluded from the study. The findings were recorded, compared and statistically analyzed. RESULTS: Out of 100 patients 45 were male and 55 female with mean age of 59 years. Sixty-two patients had hypertension, 36 patients had one or more atheroma markers (diabetes, coronary artery disease and claudication). Mean diastolic blood pressure was 98 mmHg with range of 60-140 mmHg and mean systolic blood pressure of 163 mmHg with the range of 90-240 mmHg. Forty-eight patients had cerebral infarction, 36 had cerebral hemorrhage while 16 were borderline cases on the basis of Siriraj stroke scoring. CT brain showed 56 and 39 patients had cerebral infarction and haemorrhage respectively while 5 of CT scans were normal. The sensitivity and specificity of SSS for cerebral infarction was 71 and 85 respectively and for intracerebral haemorrhage, it was 73 and 90 respectively. The positive predictive values of SSS for cerebral infarction and haemorrhage were 87% and 83 respectively. CONCLUSION: The siriraj stroke scoring system is a valid and specific scoring system for the diagnosis of acute supratentorial stroke and intracerebral haemorrhage.

Adult↗

PubMed2003

Pulmonic valve endocarditis.

Pulmonic valve endocarditis is an extremely rare infection that shares epidemiologic, clinical, radiologic, microbiologic, and prognostic features with tricuspid valve endocarditis. We report a case of pulmonic valve infection on a structurally normal heart and review the English-language literature on this subject.

Echocardiography, Transesophageal↗

PubMed2002

Depletion of MOM1 in non-dividing cells of Arabidopsis plants releases transcriptional gene silencing.

Mitotic and meiotic inheritance of epigenetic information is coupled to the reproduction of chromatin conformation and DNA methylation patterns. This implies that the S phase of the cell cycle provides a window of opportunity for changes in epigenetic determination. Recent studies, however, have suggested that chromatin structure is also rather dynamic in quiescent cells of multicellular eukaryotes and that silent heterochromatic regions can become accessible to transcription. Such epigenetic flexibility in differentiated tissues could be of physiological importance. The mechanisms and molecular components involved are of great interest but as yet unknown. We examined MOM1 (Morpheus' Molecule 1), a regulator of transcriptional gene silencing (TGS) that acts independently of DNA methylation, for its role in the maintenance of TGS in non-dividing, differentiated cells. The results provide evidence that TGS maintenance mediated by MOM1 is a dynamic process that can be modified in non-dividing cells of mature plant organs by depletion of MOM1.

ATPases Associated with Diverse Cellular Activitie↗