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Biomedical subjects

R Raman

Publications and source records attributed to R Raman.

At least 73 records · Page 4Linked to original sources
PubMed1999

Opinion of New Zealand physicians on management of acute ischaemic stroke: results of a national survey.

BACKGROUND: Randomised trials have evaluated various treatments for acute ischaemic stroke, but it is unclear how the results of these studies are used in everyday practice. AIMS: To obtain the opinions of physicians on the management of acute ischaemic stroke. METHODS: A questionnaire was sent to 368 New Zealand Fellows of the Royal Australasian College of Physicians. The survey included questions about the availability of hospital services for stroke patients, management of acute ischaemic stroke and opinion on the efficacy of treatments used in acute ischaemic stroke. RESULTS: Of the 293 physicians who responded to the questionnaire, 171 managed patients in the first week after stroke. Forty-seven per cent of these physicians were general physicians. Ninety-five per cent usually managed these patients in a general medical ward. Only five physicians admitted patients to an acute stroke unit and only 57% considered acute stroke units were beneficial. Aspirin was usually or sometimes used for patients with acute ischaemic stroke by 92% of physicians, intravenous heparin by 43%, low-dose subcutaneous heparin by 41%, low-molecular-weight heparin by 25% and tissue-plasminogen activator (t-PA) by 3%. Two thirds considered that aspirin was definitely beneficial, but most were uncertain about the efficacy of intravenous heparin, low-dose subcutaneous heparin, low-molecular-weight heparin and t-PA. Sixty-two per cent were prepared to begin aspirin and 21% subcutaneous heparin before computerised tomography (CT). Twenty-three per cent used anti-hypertensive treatment in the first few hours after an ischaemic stroke. CONCLUSIONS: Several common deficiencies in the management of acute ischaemic stroke were identified. The widespread lack of stroke units, use of aspirin and heparin before CT, and lowering of blood pressure after an acute ischaemic stroke differed from accepted guidelines. Many physicians used heparin despite lack of evidence from randomised trials that it is beneficial. The development of stroke units and the appointment of physicians with a special interest in the management of stroke may improve the management of patients with acute stroke.

Anticoagulants↗
PubMed1999

Tissue-specific characterisation of DNA methylation in the gonad-specific proto-oncogene, c-mos, in the male laboratory mouse.

The proto-oncogene, c-mos, which is expressed only in the germ cells of both testis and ovary, plays an important role in meiotic maturation of these cells. In this research, the methylation status of several CpG sites, present both upstream and within the coding region of the c-mos gene, has been studied. The HpaII and HhaI sites examined in the 5' half of the coding region were unmethylated in both the c-mos expressing and non-expressing tissues. A HhaI site, h3, present 380bp downstream of the transcription start site, was unmethylated in germ cells, but was partially methylated in the somatic tissues, inversely correlating with the expression status of the gene. In contrast to these tissues, in the mouse fibroblast cell line L929, all the analysed sites were completely methylated.

Age Factors↗
PubMed1999

Characterisation of developmentally regulated chromatin structure in the coding region of the proto-oncogene, c-fos, in the male laboratory mouse.

In mouse, tissue-specific developmental de novo methylation of the proto-oncogene c-fos, which is abundantly expressed during embryonic stages, occurs perinatally (between the day of birth to 20 dpp) and is maintained in the adult. In liver, where c-fos is only active up to the day of birth, the gene has more sites methylated than in brain, where it is expressed until about day 5 post-partum. We have studied chromatin organisation of c-fos and compared thisto DNA methylation in the fetal and adult brain and liver. Purified nuclei of these tissues from fetus as well as adult were digested with the restriction enzyme Mspl. DNA was extracted from the Mspl digested chromatin and probed with two DNA segments covering the major part of the body of the gene (from distal part of second exon to major part of fourth exon). Southern hybridisation studies revealed that in the fetus, in both liver and brain, the chromatin in the coding region was sensitive to Mspl digestion and the extent of sensitivity was nearly the same between the two. In the adult tissues, however, chromatin from brain was almost as sensitive as in the fetus, but in the liver it was highly resistant to Mspl. We suggest that a shift from the undermethylated state in the fetus to the heavy methylated state in the adult causes a corresponding change in the organisation of chromatin of c-fos in the coding region. Furthermore, the difference in the tissue-specificity in the methylation induced chromatin compaction could be due to differences in the transcription levels of c-fos and de novo methylation during early neonatal development.

Animals↗
PubMed1998

Cerebral processes related to visuomotor imagery and generation of simple finger movements studied with positron emission tomography.

Positron emission tomography was used to compare the functional anatomy of visual imagination and generation of movement. Subjects were asked to generate visual images of their finger movement in response to a preparatory signal. Four conditions were tested: in two, no actual movement was required; in the other two, a second signal prompted the subjects to execute the imagined movement. Which movement to imagine was either specified by the preparatory stimulus or freely selected by the subjects. Compared with a rest condition, tasks involving only imagination activated several cortical regions (inferoparietal cortex, presupplementary motor area, anterior cingulate cortex, premotor cortex, dorsolateral prefrontal cortex) contralateral to the imagined movement. Tasks involving both imagination and movement additionally increased activity in the ipsilateral cerebellum, thalamus, contralateral anteroparietal, and motor cortex and decreased activity in the inferior frontal cortex. These results support the hypothesis that distinct functional systems are involved in visuomotor imagination and generation of simple finger movements: associative parietofrontal areas are primarily related to visuomotor imagination, with inferior frontal cortex likely engaged in active motor suppression, and primary motor structures contribute mainly to movement execution.

Adult↗
PubMed1998

A zinc finger domain gene in the lizard, Calotes versicolor, shows extensive homology with the mammalian ZFX and is expressed embryonically.

A 590-bp long zinc finger domain DNA fragment has been isolated by polymerase chain reaction from the lizard, Calotes versicolor, employing the primers used for amplifying the zinc finger domain of the human Y-chromosomal gene, ZFY. Cloned in pUC18, the fragment, called CvZfa, was sequenced and its expression during development was studied. At the nucleotide and amino acid level CvZfa shows respectively 83% and 90% identity with the human ZFY, but its extent of homology is greater with the ZFX of human (86% at nucleotide and 92% at amino acid level) and the ZFY-like genes of turtle and chick. Similarly its homology with the mouse Zfx and Zfa is much greater than that with Zfy-1 and Zfy-2. It appears that the mammalian ZFX (Zfx) evolved from reptilian ancestors with a considerable degree of conservation, but the ZFX to ZFY divergence within the class mammalia was more rapid. The CvZfa transcripts were seen in all the embryonic stages from which RNA was analysed. The whole mount in situ hybridization with the posteriorly placed mesonephros and the gonadal primordia of 10 to 25 day old embryos showed signal selectively in mesonephros of the 20 and 25 day embryos. There was no signal in the genital ridge. Thus CvZfa may not have a direct role in gonadogenesis of C. versicolor, but the possibility of its inductive role in the formation of adreno-gonadal axis through mesonephros cannot be discounted.

Amino Acid Sequence↗
PubMed1998

Vital signs services for secure telemedicine applications.

Telemedicine using teleconference provides only a part of the picture. The remote patient's electronic medical record and vital signs may often be essential for proper diagnosis and treatment. While there are commercial solutions for telemonitoring, they do not address issues such as security and interoperability leveraging the growing public communications infrastructure. On the other hand there are performance considerations due to the quality of service over available communications media that can hinder real-time operation. The objective of this research effort is to develop secure tele-monitoring facilities that enable healthcare providers to collaborate over public communication networks; to securely convey their patient's vital signs to a remote specialist; and to enable "near real-time" examination of those vital sign data. It is our belief that such applications can help overcome barriers to quality healthcare in the scattered populations of rural areas enabling telemedicine to be a part of the practice of medicine. The authors, who are developing secure telemedicine applications, describe their approach in developing secure vital signs services.

Blood Pressure↗
PubMed1997

CvSox-4, the lizard homologue of the human SOX4 gene, shows remarkable conservation among the amniotes.

SOX family genes share a high sequence similarity with the HMG box region of the human Y chromosomal gene, SRY. We have cloned and sequenced the HMG box motif of a Sox gene of the lizard, Calotes versicolor. A database search for the cloned sequence, CvSox-4, revealed 100% identity with the SOX4 gene of the human and its homologue in a bird. The result strongly suggests that SOX4 evolved prior to the diversification of amniotes and is highly conserved.

Amino Acid Sequence↗
PubMed1997

De novo methylation of the proto-oncogene, c-fos, during development occurs step-wise and directionally in the laboratory mouse.

We have analyzed the ontogenic initiation and maintenance of methylation of certain Hpall (m), Hhal (H), Hincll (Hc), and Sall (SI)-specific CpG sites in the coding region of the proto-oncogene, c-fos, through testicular cells, sperm, and fetal, neonatal, and adult somatic tissues. The results show that 1) sperm-derived methylated sites get demethylated in early development. However, unlike other studied genes, they remain so at least up to day 13.5 post coitum (pc); 2) de novo methylation proceeds unidirectionally in a step-wise, site-specific manner between m5-m3 sites; 3) the mature, tissue-specific, adult methylation pattern is established between day 0 and day 20 of neonatal development; 4) the Hc and SI sites (CGTCGAC), occurring at an interval of one nucleotide, are only partially methylated in all the tissues; and 5) m3 and H1 sites, which occur close to an Sp1 motif, escape methylation in most of the tissues. The present study on the embryonic gene, c-fos, thus provides a novel pattern of de novo methylation in development. Also, it suggests that close proximity of CpGs may prevent methylation.

Animals↗
PubMed1997

Giant cell arteritis: validity and reliability of various diagnostic criteria.

PURPOSE: To ascertain the validity, reliability, sensitivity, and specificity of various signs and symptoms of and diagnostic tests for early diagnosis of giant cell arteritis. METHODS: From 1973 to 1994, we studied 363 patients who had temporal artery biopsy for suspected giant cell arteritis. All patients underwent detailed clinical evaluation and had erythrocyte sedimentation rates determined; since 1985, 223 patients had their C-reactive protein values estimated. Erythrocyte sedimentation rate and C-reactive protein levels were also estimated in 749 and 138 control subjects, respectively. Signs and symptoms of giant cell arteritis, erythrocyte sedimentation rate, and C-reactive protein levels among patients with positive and negative biopsies were compared. RESULTS: Of the 363 patients, temporal artery biopsy was positive in 106 and negative in 257. The odds of a positive biopsy were 9.0 times greater with jaw claudication (P < .0001), 3.4 times greater with neck pain (P = .0085), 2.0 times greater with an erythrocyte sedimentation rate of 47 to 107 mm/hour (P = .0454), 3.2 times greater with C-reactive protein above 2.45 mg/dl (P = .0208), and 2.0 times greater for age 75 years or more (P = .0105). CONCLUSIONS: Clinical criteria most strongly suggestive of giant cell arteritis include jaw claudication, C-reactive protein above 2.45 mg/dl, neck pain, and an erythrocyte sedimentation rate of 47 mm/hour or more, in that order. C-reactive protein was more sensitive (100%) than erythrocyte sedimentation rate (92%) for detection of giant cell arteritis; erythrocyte sedimentation rate combined with C-reactive protein gave the best specificity (97%).

Adult↗
PubMed1997

Male-biased distribution of the human Y chromosomal genes SRY and ZFY in the lizard Calotes versicolor, which lacks sex chromosomes and temperature-dependent sex determination.

In the present investigation on the lizard Calotes versicolor, which lacks temperature-dependent sex determination, all the conventional cytological techniques used failed to resolve a distinguishable pair of sex chromosomes. However, probing of the genome with the human Y-linked genes SRY and ZFY showed sex-specific bias in their distribution. While the SRY probe hybridized to all the males, more than half of the females examined did not show any hybridization. ZFY hybridized to both the sexes, giving two bands; one was common to all the individuals of both sexes, but the other, of the lower molecular length, occurred in all the males but in less than 50% of females. This predominantly male-specific band is named AMF. The SRY-positive females were also positive for the AMF of ZFY. As positive as well as negative females were fertile and none of the males lacked SRY, it appears that SRY is essential for males only and that both the genes are syntenic in this species. This report raises interesting possibilities on the differentiation of the sex chromosomes in C. versicolor and evolution of SRY/ZFY on the Y chromosome of eutherian mammals through the ancestral group(s) that harbour sex-independent SRY- and ZFY-related genes.

Animals↗
PubMed1997

Increased choline signal coinciding with malignant degeneration of cerebral gliomas: a serial proton magnetic resonance spectroscopy imaging study.

The authors tested the hypothesis that proton magnetic resonance spectroscopy (1H-MRS) imaging can be used as a supportive diagnostic tool to differentiate clinically stable brain tumors from those progressing as a result of low- to high-grade malignant transformation or posttherapeutic recurrence. Twenty-seven patients with cerebral gliomas verified on histological examination were studied repeatedly with 1H-MRS imaging over a period of 3.5 years. At the time of each 1H-MRS imaging study, clinical examination, MR imaging, positron emission tomography with 18F-fluorodeoxyglucose, and biopsy findings (when available) were used to categorize each patient as having either stable or progressive disease. Measures of the percentage changes in the choline (Cho) 1H-MRS imaging signal intensity between studies, which were obtained without knowledge of the clinical categorization, allowed the investigators to segregate the groups with a high degree of statistical significance. All progressive cases showed a Cho signal increase between studies of more than 45%, whereas all stable cases showed an elevation of less than 35%, no change, or even a decreased signal. The authors conclude that increased Cho levels coincide with malignant degeneration of cerebral gliomas and therefore may possibly be used as a supportive indicator of progression of these neoplasms.

Adult↗