PubMed Health⌕ Search

Biomedical subjects

N Prasad

Publications and source records attributed to N Prasad.

At least 19 recordsLinked to original sources
PubMed1995

Capsulotomy for phacoemulsification in hypermature cataracts.

We describe a modified surgical technique of anterior capsulotomy and phacoemulsification for use in hypermature cataracts. Surgical steps included inferior linear capsulotomy with aspiration of milky cortex, inflation of the capsular sac with viscoelastic, a reverse triangular anterior capsulotomy with Vannas scissors, and in-the-bag bimanual sculpting of the nucleus. An oval 5 mm x 6 mm posterior chamber intraocular lens was used with single horizontal or no-stitch wound closure. The technique was used successfully in 20 cases of hypermature cataract. The mean time required to perform phacoemulsification was 3.46 minutes (range 1.2 to 6.3 minutes), with a standard deviation of 1.29. Visual acuity on the first postoperative day ranged from 20/20 to 20/60 (median 20/40). At one week, the mean astigmatism was 1.01 diopters (range 0.25 to 2.75 diopters). The mean endothelial cell loss was 13% (range 3.6% to 26.0%). Based on our results, the modified phacoemulsification technique merits consideration for use in hypermature cataracts.

Adult↗
PubMed1995

Cloning and characterization of the Bacillus subtilis birA gene encoding a repressor of the biotin operon.

The Bacillus subtilis birA gene, which regulates biotin biosynthesis, has been cloned and characterized. The birA gene maps at 202 degrees on the B. subtilis chromosome and encodes a 36,200-Da protein that is 27% identical to Escherichia coli BirA protein. Three independent mutations in birA that lead to deregulation of biotin synthesis alter single amino acids in the amino-terminal end of the protein. The amino-terminal region that is affected by these three birA mutations shows sequence similarity to the helix-turn-helix DNA binding motif previously identified in E. coli BirA protein. B. subtilis BirA protein also possesses biotin-protein ligase activity, as judged by its ability to complement a conditional lethal birA mutant of E. coli.

Amino Acid Sequence↗
PubMed1995

Elevated blood pressure during the first two hours of ambulatory blood pressure monitoring: a study comparing consecutive twenty-four-hour monitoring periods.

OBJECTIVE AND DESIGN: Ambulatory blood pressure monitoring is being used increasingly in clinical practice and hypertension research. We have noted elevated blood pressure during the initial hours of monitoring. The objective of the present study was to examine the consistency, magnitude and duration of this elevation, and to determine whether this effect causes significant differences in the mean ambulatory blood pressure monitoring values comparing the first (day 1) and second (day 2) consecutive 24-h periods of monitoring. METHODS: Fifty patients who were hypertensive based on repeated clinic readings were studied prospectively. Each underwent continuous 48-h ambulatory blood pressure monitoring with a SpaceLabs 90207 monitor. The device recorded blood pressure at 15-min intervals during the daytime (0600-2159 h) and at 30-min intervals at night-time (2200-0559 h). From these readings hourly means were calculated. Repeated-measures analysis of variance was performed to compare the hourly means of days 1 and 2. RESULTS: Repeated-measures analysis of variance indicated that a significant difference existed for both systolic and diastolic blood pressure between day 1 and day 2. Paired Student's t-test revealed that this difference occurred during the first 2 h of monitoring. The daytime blood pressure was higher on day 1 as a result of the initial elevation of blood pressure at the onset of monitoring. The initial elevation of blood pressure was present both in white-coat hypertensives and in essential hypertensives. CONCLUSION: The first 2 h of ambulatory blood pressure monitoring are associated with elevated blood pressure both in white-coat hypertensives and in essential hypertensives. This has a minor effect on mean daytime and 24-h ambulatory blood pressures. We propose that improved ambulatory blood pressure monitoring recordings would be obtained in clinical practice, and more particularly in research applications, if 26-h ambulatory blood pressure monitoring was carried out, excluding the first 2 h from the summary analyses.

Adult↗
PubMed1995

A double-blind comparison of bisoprolol and atenolol in patients with essential hypertension.

We compared the beta 1-selective adrenoceptor antagonists bisoprolol and atenolol in a double-blind, randomized crossover study. After 4 weeks placebo phase, 59 patients with essential hypertension received either 10 mg bisoprolol or 50 mg atenolol once daily for 8 weeks, increased if necessary (target BP < or = 150/90 mmHg) to 20 and 100 mg, respectively, after 4 weeks. After a second placebo phase, crossover occurred to the alternative drug. We measured resting systolic and diastolic blood pressures and heart rate at 24 h post-dose baseline and after 4 and 8 weeks treatment. Both drugs significantly lowered systolic and diastolic blood pressures and heart rate at 8 weeks compared to baseline (all p < 0.05). Bisoprolol reduced heart rate significantly more than atenolol (p < 0.01), but systolic and diastolic blood pressure changes were not different between the two drugs. There was no difference in patient acceptability of the drugs as assessed by visual analogue scale. Despite theoretical and circumstantial evidence to suggest superiority of bisoprolol over atenolol, no significant difference between the two was found except for greater heart rate reduction with bisoprolol.

Atenolol↗
PubMed1994

Left ventricular hypertrophy in hypertension--general and local trends in diagnosis and therapy.

LVH is a frequent echocardiographic finding in the general population but it should be regarded as an ominous predictor of future cardiovascular events rather than an innocent compensatory phenomenon. Echocardiography is the most sensitive and specific method for its detection but the ECG should not be regarded as superfluous since additional prognostic information and information about coexisting myocardial damage is present. The decreasing prevalence of LVH suggests that LVH can be prevented by control of hypertension and prevention of weight gain. Once LVH is present then antihypertensive drugs, weight reduction or salt restriction may promote its reversal, with early studies demonstrating associated improvement in mortality and morbidity.

Adult↗
PubMed1994

The relationship between blood pressure and left ventricular mass in essential hypertension is observed only in the presence of the angiotensin-converting enzyme gene deletion allele.

An insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) gene accounts for approximately 50% of the variance in plasma ACE concentration: deletion homozygotes (DD) have the highest, and insertion homozygotes (II) the lowest ACE concentrations. ACE is responsible for the generation of angiotensin II, which is implicated in the development of left ventricular hypertrophy, an independent risk factor for morbidity and mortality in hypertension. The aim of this study was to investigate the contribution of ACE genotype to the development of left ventricular hypertrophy in patients with essential hypertension. Eighty-five patients with essential hypertension underwent echocardiographic assessment of left ventricular mass index (LVMI) and determination of ACE genotype from leukocyte DNA by polymerase chain reaction. There was no significant difference in LVMI among the genotypes (II, ID, DD). Analysis of covariance modelled for LVMI showed a significant interaction with systolic blood pressure (p = 0.036) but not diastolic blood pressure (p = 0.453). The relationship between LVMI and systolic blood pressure was strongest in the deletion homozygotes (p = 0.002, R2 = 0.47), and also present in the heterozygotes (p = 0.013, R2 = 0.40). No relationship was seen in the insertion homozygotes (p = 0.914, R2 = 0.23). These findings suggest that the effect of blood pressure on LVMI in essential hypertension is expressed only in the presence of the ACE gene deletion allele.

Alleles↗
PubMed1993

Effect of calcium channel blockers on serum levels of thyroid hormones.

One month oral therapy with calcium channel blockers caused significant (P < 0.001) decrease in serum levels of triiodothyronine and thyroxine and significant increase in serum levels of thyroid stimulating hormone in rabbits. Most probable mechanism of action was block in the synthesis and/or release of thyroid hormones.

Animals↗
PubMed1992

Mechanical behavior of three maxillofacial prosthetic adhesive systems: a pilot project.

The use of maxillofacial prosthetic adhesives remains controversial. A new machine for mechanical testing of adhesives was developed. This machine was used for in vivo testing of three adhesive systems to determine the adhesive joint strength of bonding silicone facial prosthetic elastomer to facial skin. Tensile, torsion, and combined tensile-torsion tests were carried out on two human subjects. The three adhesives tested were PSA1, Pros-Aide, and Dow Corning 355. All adhesives were applied according to the manufacturers' instructions. A 900 gm bonding load was applied for 20 seconds. The experimental design made use of two subjects, and the entire experiment was repeated on each subject. One test site on the cheek was used. Adhesive types were compared by means of the Student-Newman-Keuls method. Within the limitations of the design of this pilot study, the results showed that Dow Corning 355 adhesive was statistically significantly stronger than the other two adhesives evaluated by means of tensile and combined tensile-torsional tests. Although the results of the present pilot project are of interest, extrapolation to definitive conclusions of a clinical nature should be avoided.

Adhesives↗
PubMed1990

Very-low-calorie diets. Safe treatment for moderate and morbid obesity.

Very-low-calorie diets are a tedious but effective treatment for moderate and morbid obesity. An exercise program, nutrition counseling, and behavior modification are essential elements in the total program. Careful supervision by a knowledgeable physician and commitment by both the patient and the physician are essential. Although some side effects are inevitable with drastic weight reduction, current formulas are safer than those used in the past.

Behavior Therapy↗
PubMed1990

Safety of 4-T MR imaging: study of effects on developing frog embryos.

Fertilized eggs of Rana pipiens (leopard frogs) were exposed to 0.15- or 4.5-T magnetic resonance (MR) imaging and were compared with unexposed fertilized eggs with respect to the percentage of embryos cleaving and percentage of tail buds forming normally. Similarly exposed or unexposed sperm were used to fertilize unexposed eggs, and the same parameters were observed. There was no evidence that MR imaging exposure at 0.15 or 4.5 T had any effect on cleaving embryos or tail bud formation. Since embryogenesis in amphibians is very sensitive to foreign insult, the authors conclude that exposure to a magnetic field of up to 4.5 T has no adverse effect on early development.

Animals↗