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Biomedical subjects

R Perera

Publications and source records attributed to R Perera.

At least 37 records · Page 2Linked to original sources
PubMed2000

Photobiological properties of positively charged methylene violet analogs.

O-Methyl methylene violet (OMeMV), O-methyl bromomethylene violet (OMeBrMV) and O-methyl iodomethylene violet (OMeIMV) have been prepared in order to test their potential utility as anti-viral and anti-tumor phototoxic dyes. Rates of photosensitized toxicity of KB cells with 633 nm irradiation are (x 10(-19) photon-1): 2.4, 2.2, 1.9 and 0.17 for OMeIMV, OMeBrMV, methylene violet (MV) and OMeMV, respectively. Rates of photosensitized inactivation of Sindbis virus in phosphate-buffered saline with 633 nm irradiation are (x 10(-18) photon-1): 3.3, 1.8, 0.99, 0.15 for MV, OMeIMV, OMeBrMV and OMeMV, respectively. Quantum efficiencies for singlet oxygen formation were determined as OMeIMV, 0.64; OMeBrMV, 0.40; OMeMV, 0.054. Titration of the dyes with double-stranded (ds)DNA resulted in bathochromic shifts and hypochromic effects in the visible absorption spectra. Association constants for interaction of the methylated dyes with dsDNA of approximately 1 x 10(5) M-1 were determined by Scatchard analysis of equilibrium dialysis and UV absorption titration data. Photolysis of the halogenated dyes with DNA under argon led to covalent bond formation with the nucleic acid; there was no evidence of covalent binding in the dark.

Antiviral Agents↗
PubMed1999

Fine needle aspiration cytology in the UK breast screening programme: a national audit of results.

The National Breast Screening Service in the UK depends upon triple assessment, with or without core biopsy, to determine the need for diagnostic biopsy or treatment for screen-detected lesions. To determine the efficacy of cytology in this process a nationwide survey of sensitivity and specificity of the technique was instituted by the National Coordinating Committees for both Radiology and Pathology. Although some units were performing to the national recommended standards, a significant number of units were shown to have problems with a high false negative rate and high inadequate rates from lesions which were eventually diagnosed as cancer. This suggests problems in localizing lesions adequately at aspiration. Generally, indicators of pathology diagnostic performance (e.g. positive predictive values) were good. The figures suggest that some units are not benefiting from an optimal cytological service. Consequently training programmes targeted at aspiration technique may be beneficial.

Journal Article↗
PubMed1999

International reference reagents: antihuman globulin. An ISBT/ICSH joint working party report. International Society of Blood Transfusion. International Committee for Standardization in Haematology.

An international working party has conducted a study designed to select a suitable reference reagent for antihuman globulin, to replace those first made available in 1987. The chosen preparation contains levels of anti-IgG and anti-C3 (anti-C3c and anti-C3d) potency that are considered suitable to serve for reference when evaluating either polyspecific antihuman globulin reagents or those containing their separate monospecific components. The reference material is available in 2-ml freeze-dried aliquots from seven assigned distribution centres.

Coombs Test↗
PubMed1998

Left atrial function is unchanged by implantable defibrillator shocks on hearts in sinus rhythm.

Sixteen patients in sinus rhythm at baseline undergoing implantable cardioverter-defibrillator implantation were monitored with transesophageal echocardiography both before and after direct current cardioversion with currents of 15 to 20 J, for any direct current induced atrial dysfunction. We found no change in the indexes of atrial function or appearance of spontaneous echo contrast in the immediate postshock period by intraoperative transesophageal echocardiography.

Atrial Function, Left↗
PubMed1998

A double-blind, dose-response study of midodrine in neurogenic orthostatic hypotension.

OBJECTIVE: To determine the best therapeutic strategy for the use of midodrine in patients with neurogenic orthostatic hypotension (NOH). BACKGROUND: Midodrine is a peripherally acting alpha-adrenergic agonist useful in the treatment of NOH. However, neither the most effective dosage of midodrine nor the required frequency of administration is established. DESIGN/METHODS: Midodrine dose-blood pressure response, pharmacokinetics, and duration of action were examined in a double-blind, placebo-controlled, four-way crossover trial. Twenty-five patients with NOH were randomized to receive on successive days placebo or midodrine 2.5, 10, or 20 mg. Blood pressures of patients in the supine and standing positions were measured sequentially. A global assessment of the patient's overall symptom improvement after each leg of the study was performed. Blood levels of midodrine and its active metabolite, desglymidodrine, were assayed. RESULTS: Midodrine significantly increased standing systolic blood pressure, with the increase peaking at 1 hour. There was a significant linear relation between midodrine dosage and mean systolic blood pressure. The mean score for global improvement of symptoms was significantly higher for midodrine (10 and 20 mg) compared with placebo. The half-life of desglymidodrine was approximately 4 hours. CONCLUSION: A 10-mg dose of midodrine prescribed two to three times daily is effective in increasing orthostatic blood pressure and ameliorating symptoms in patients with NOH.

Adrenergic alpha-Agonists↗
PubMed1998

User satisfaction with child psychiatry outpatient care: implications for practice.

INTRODUCTION: Satisfaction with outpatient care is determined by the extent to which the expectations of users are met. Obtaining the opinion of users is considered a reliable method of assessing the quality of service. The objective of our study was to assess the degree of satisfaction expressed by users of a child psychiatry outpatient service and to match degree of satisfaction with the dropout rate. METHOD: A questionnaire was used to assess the users' expectation of the service and degree of satisfaction. Dropout rate was determined from the clinical records. RESULTS: 165 new referrals to the outpatient service were recruited for the study. 41.2% expected a cure for the child's mental health problem. 65.5% expressed satisfaction with the treatment intervention and time provided at the first consultation. Positive free text comments supported this opinion, but were incongruent with the 32.8% dropout rate after the first and second visits to the clinic. Behaviour problems in children and serious social problems in the families increased the risk of dropout from treatment. CONCLUSIONS: Initial expression of satisfaction with the service by the users does not guarantee continued co-operation with follow up care. Sensitivity in the approach to treatment is needed where there is a higher risk of dropout.

Ambulatory Care Facilities↗
PubMed1997

Prolonged QT interval and cocaine use.

Cardiovascular consequences of cocaine use are well known, and surveillance for them is common practice in the routine care of cocaine abusers. However, the cardiac electrical abnormalities that arise, although studied in animal experiments, lack correlation with human reports. The case of a 17-year-old girl, who was admitted after a cocaine binge is reported. She was cardiologically asymptomatic, but an admission electrocardiogram was abnormal, with QT interval prolongation. This returned to normal within 24 hours of observation. The literature on the electrophysiologic effects of cocaine on the heart is reviewed.

Adolescent↗
PubMed1997

Syncope: the diagnostic value of head-up tilt testing.

To determine the usefulness of prolonged head-up tilt in the diagnosis of neurally mediated syncope, 201 patients with history of syncope of unknown cause and 102 age and gender matched control subjects underwent a 40 minute 60 degrees head-up tilt test. Head-up tilt elicited syncope (i.e., was positive) in 74 of the 201 patients (37%) with a history of unexplained syncope and in only 6 of the 102 controls (6%). The specificity of the test was 100% in patients 60 years of age and older. Symptoms during tilt-induced syncope were identified by the patients as similar to those they had suffered during their spontaneous episodes. All 80 subjects who had tilt-induced syncope recovered without sequelae. The positive predictive value of a positive responses to head-up tilt was 93% and the negative predictive value was 43%. The results indicate that the prolonged head-up tilt test is a very specific procedure of high diagnostic value in patients with a history of unexplained syncope. It is particularly useful in the elderly age groups who have a high incidence of syncope.

Female↗
PubMed1996

Enhancement of somatic intrachromosomal homologous recombination in Arabidopsis by the HO endonuclease.

The HO endonuclease promotes gene conversion between mating-type alleles in yeast by a DNA double-strand break at the site of conversion (the MAT-Y/Z site). As a first step toward understanding the molecular basis of homologous recombination in higher plants, we demonstrate that expression of HO in Arabidopsis enhances intrachromosomal recombination between inverted repeats of two defective beta-glucuronidase (gus) genes (GUS- test construct). One of these genes has the Y/Z site. The two genes share 2.5 kb of DNA sequence homology around the HO cut site. Somatic recombination between the two repeats was determined by using a histochemical assay of GUS activity. The frequency of Gus+ sectors in leaves of F1 plants from a cross between parents homozygous for the GUS- test construct and HO, respectively, was 10-fold higher than in F1 plants from a cross between the same plant containing the GUS- test construct and a wild-type parent. Polymerase chain reaction analysis showed restoration of the 5' end of the GUS gene in recombinant sectors. The induction of intrachromosomal gene conversion in Arabidopsis by HO reveals the general utility of site-specific DNA endonucleases in producing targeted homologous recombination in plant genomes.

Arabidopsis↗
PubMed1995

Effect of recombinant erythropoietin on anemia and orthostatic hypotension in primary autonomic failure.

Anemia is a common complication of autonomic failure and reduced red blood cell mass may contribute to the orthostatic hypotension of these patients. We investigated whether treatment with recombinant erythropoietin improves anemia and increases blood pressure in patients with primary autonomic failure. Three patients with multiple system atrophy and autonomic failure and one with pure autonomic failure were studied. All patients had normocytic normochromic anemia and low (n = 2) or normal (n = 2) serum levels of erythropoietin. Treatment with erythropoietin, 4000 U subcutaneously biweekly for 6 weeks, increased hematocrit and blood pressure in all patients. Hematocrit increased from 33.9 +/- 0.7 to 44.3 +/- 1.4%, blood pressure in supine position increased from 150 +/- 8/87 +/- 8 (systolic/diastolic; mean +/- SD) to 166 +/- 25/92 +/- 12 mmHg, and after 3 min in the head-up tilt position from 86 +/- 21/47 +/- 15 to 102 +/- 23/63 +/- 12 mmHg, (p < 0.05). All patients reported improvement in orthostatic symptoms and increased tolerance to standing. The study shows that treatment with erythropoietin improves anemia, increases blood pressure and ameliorates orthostatic hypotension in patients with primary autonomic failure.

Aged↗
PubMed1995

Emergence of penicillin resistant pneumococci in Sri Lanka.

Two strains of penicillin resistant (PR) pneumococci were isolated recently from cerebrospinal fluid of two children with meningitis. Penicillin resistance was detected by using a lug disc of oxacillin in the Stokes disc diffusion method. The strains were tested quantitatively for sensitivity to penicillin by an agar dilution technique. The minimum inhibitory concentration (MIC) to penicillin of these strains were 2 micrograms/ml and 0.12 microgram/ml, indicating that respectively they were of frank and intermediate resistance to penicillin. However these strains were sensitive to other antibiotics tested, namely, erythromycin, tetracycline, chloramphenicol, amoxycillin, cephalexin and cefotaxime. Penicillin resistant pneumococci are here in Sri Lanka. Though one strain was of intermediate resistance, therapeutic failure during treatment with penicillin was evident in this case.

Humans↗
PubMed1985

[Restriction map of the genetic transfer factor pAP42].

Based on the calculated molecular weights of EcoR1, HindIII, and SalI fragments of the genetic transfer factor pAP42 the restriction map of this plasmid was designed. Sites recognizing restrictases are mostly located in the plasmid fragment with a molecular weight of 5.7 MD.

Attachment Sites, Microbiological↗