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Biomedical subjects

R Ramakrishnan

Publications and source records attributed to R Ramakrishnan.

At least 145 records · Page 8Linked to original sources
PubMed1980

Prediction of the parameters of whole body cholesterol metabolism in humans.

Total body turnover of cholesterol was studied in 54 subjects by fitting a three-pool mathematical model to plasma decay curves of 32--49 weeks duration following [14C]cholesterol injection. Fifteen subjects were normal, 10 hypercholesterolemic, 21 hypertriglyceridemic, and 8 had both hypercholesterolemia and hypertriglyceridemia; 21 had a familial form of hyperlipidemia. In every subject in this heterogeneous population, the three-pool model gave the best fit for the data. An extensive search was conducted for relationships between model parameters and physiological variables (body size, serum lipid levels, age, and sex). Both linear and nonlinear relationships, and those involving interactions between pairs of variables, were explored. Fifty different forms of the model parameters and 53 forms of the physiological variables were examined. To guard against declaring statistical significance when none was present, subjects were first randomly divided into two matched groups. In the first (hypothesis-generating) group of 36 subjects, more than 100,000 regression equations were considered for each form of the model parameters. Twenty-one highly significant equations were found that were then tested in the second group (hypothesis-testing, 18 subjects). Eighteen of the 21 equations were found to be significant; of these, 6 were selected that accounted for a large part of the observed variation in the four model parameters for which equations were found (production rate (PR), and the sizes of pool 1, pool 3, and total exchangeable body cholesterol). The major determinant of cholesterol PR was body weight alone (r = 0.80). No function of serum lipid levels significantly influenced PR. Both body weight and serum cholesterol level entered into the equations for cholesterol mass. Age influenced the size of pool 3. Serum triglyceride level only had an effect on the size of pool 1. Since these equations were generated in one group of subjects and tested in another, they can be considered a confirmed set of predictive equations.

Adult↗
PubMedDate not supplied

Effects of protein-calorie malnutrition on transplacental kinetics of aminoisobutyric acid in rats.

In order to find out if inefficient transport of amino acids contributes to a decrease in fetal weight during maternal malnutrition, we injected [14C]- and [3H]-labelled aminoisobutyric acid (AIB), respectively, in the mother and its fetuses and determined its transplacental kinetics on day 20 of gestation in rats fed a 21 per cent (control) or a low (5 per cent) protein diet. Rats fed a low protein diet consumed significantly less food than did the rats fed a control diet and thus suffered from protein-calorie malnutrition. A low protein diet led to a significant (P less than 0.05) decrease in maternal and fetal volume of distribution of AIB, a decrease in the clearance of AIB from the mother to the fetus and an increase in the time required for the fetal plasma AIB concentration following maternal injection to exceed the maternal plasma AIB concentration. The clearance of AIB from the fetus into the mother or to outside (e.g. amniotic fluid) was not altered by protein deficiency. It is concluded that a decrease in the efficiency of the placenta to deliver amino acids to the fetus may be a contributing factor in fetal growth retardation during maternal protein malnutrition.

Aminoisobutyric Acids↗
PubMedDate not supplied

The use and evaluation of 2 + 2 photoaddition in immobilization of oligonucleotides on a three dimensional hydrogel matrix.

Photochemical attachment of synthetic oligonucleotides on the three dimensional surface of a polyacrylamide based hydrogel was used in the specific detection of target oligonucleotides. Covalent attachment of the oligonucleotide to the hydrogel was mediated by the incorporation of a 2 + 2 photo-attachable functional group in both the hydrogel and the oligonucleotide probe. Expression and SNP assays were used to evaluate this platform.

Acrylic Resins↗
PubMedDate not supplied

Blood clearance and tissue uptake of intravenous lipid emulsions containing long-chain and medium-chain triglycerides and fish oil in a mouse model.

BACKGROUND: Increasing interest in using different triglycerides (TGs) for specific clinical applications raised the question as to how the emulsion TG composition would affect blood clearance and emulsion delivery to hepatic and extrahepatic tissues. METHODS: Emulsions used were long-chain soy oil TG (long-chain triglyceride [LCT]), LCT/ medium-chain triglyceride (MCT; 1:1, wt/wt), LCT/MCT/C/omega-3 (5:4:1, wt/wt) and pure fish oil (omega-3 TG) labeled with non-degradable 3H-cholesteryl oleoyl ether (3H-CE) as a particle marker. Mice (C57BL/6J) were injected with four different commercial emulsions at a nonsaturating dose of 0.4 mg TG/20 to 25 g per mouse to obtain 1st order kinetics. Blood was sampled at 0.5, 2, 5, 10, 15, and 25 minutes, and the fractional catabolic rate was determined by fitting a straight line to the logarithm of the blood 3H-CE radioactivity. Retention of 3H-CE for each tissue at 25 minutes reflected organ uptake of the emulsion. RESULTS: Blood clearance of pure omega-3 TG (10.40% +/- 0.54% pools/h; mean +/- SE) was significantly slower than that of LCT, LCT/MCT, and LCT/MCT/omega-3 emulsion (18.9 +/- 0.6 pools/h, 17.0 +/- 0.96 pools/h, 16.5 +/- 1.08 pools/h, respectively) (p < .01). Based on 3H-CE uptake, LCT, LCT/MCT, and omega-3 TG emulsions showed similar delivery to liver (39% +/- 3.9%, 46% +/- 3.6%, 34% +/- 3.2%). Liver uptake of LCT/MCT/omega-3, (23% +/- 2.2%) was less than LCT/MCT (46% +/-3.6%, p < .0001) and LCT (39% +/- 3.9%, p = .002). CONCLUSIONS: Results indicate slow blood clearance of pure omega-3 TG emulsion from the blood compared with emulsion in which omega-3 TG was mixed with LCT and MCT. Earlier data showed that omega-3 TG are poorly hydrolyzed in extracellular media and therefore are delivered to tissues as part of the core of emulsion remnants. Thus, our data suggest that the incorporation of omega-3 TG with LCT/MCT will result in greater delivery of omega-3 fatty acids to extrahepatic tissue, which could be important in modulating immune and other responses.

Animals↗
PubMedDate not supplied

An experimental analysis of the catecholamines in hyperglycemia and acidosis induced rat brain.

Hyperglycemia and acidosis are the hallmark of diabetes. Since these factors play an important role in the diabetic complications, we have studied the brain catecholamine levels in hyperglycemic and acidotic conditions per se. Experimentally induced hyperglycemia and acidosis are accompanied by significant alterations in the catecholamine levels in discrete areas of the brain. We and others have shown that chronic or acute diabetes in animals as well as in human results in altered neurotransmitter levels. In the present study, hyperglycemia maintained by daily external administration of glucose for thirty days showed increased level of dopamine in striatum and hippocampus, elevation of norepinephrine in hippocampus, and increased level of epinephrine in hypothalamus, midbrain and pons medulla. The ammonium chloride induced acidosis demonstrated significant elevation of dopamine in midbrain and significant increase of norepinephrine in hypothalamus and midbrain, and increased level of epinephrine in hypothalamus, pons medulla and cerebral cortex. On the other hand, sodium acetoacetate induced acidosis did not show any significant change in the level of catecholamines in any of the areas studied. In conclusion, the changes in catecholamine levels observed in experimentally induced hyperglycemic as well as in acidotic conditions are closely related to the changes observed in spontaneous or alloxan or streptozotocin diabetic animals, thereby suggesting that these conditions may be responsible for the changes observed in diabetic animals.

Acidosis↗
PubMedDate not supplied

A study of the spectrum of Acanthamoeba keratitis: a three-year study at a tertiary eye care referral center in South India.

PURPOSE: To determine the epidemiological and clinical characteristics of Acanthamoeba keratitis and also to determine the sensitivity and specificity of smears in the detection of Acanthamoeba. MATERIALS AND METHODS: A retrospective review of all culture-positive cases of Acanthamoeba keratitis seen between October 1999 and August 2002 was performed. Corneal scrapes were subjected to culture and microscopy using standard protocols. RESULTS: Out of 3183 consecutive patients with clinically diagnosed corneal ulcers evaluated, 33 (1.04%) were found to be due to Acanthamoeba. Twenty-four out of 33 (72.72%) were less than 51 years of age (P<0.001). All patients were from rural areas (P<0.001) and 26 (78.79%) of them were agricultural workers (P=0.031). All 33 had history of corneal injury (P<0.001) and 28 (84.85%) patients had injury with mud (P<0.001). All 33 (100%) patients had previous medical treatment (P=0.009) and 10 (30.3%) had used traditional eye medicines (P=0.183). A clinical pattern of ring infiltrate was characteristic in 15 (45.45%) patients. The diameter of the corneal ulcer was more than 6 mm in 27 (81.82%) eyes (P<0.001). Twenty-six (78.79%) patients had visual acuity of perception of light on initial presentation (P<0.001) and 24 (72.73%) had the same as their final visual outcome. The sensitivity of 10% potassium hydroxide (KOH) preparation was found to be higher (P<0.001) in the detection of Acanthamoeba cysts. CONCLUSION: The incidence of Acanthamoeba keratitis amongst the corneal ulcer patients was 1% in this setting and it was mainly due to corneal injury by mud. The KOH preparation is a sensitive diagnostic tool for the detection of Acanthamoeba. Delayed diagnosis or misdiagnosis and inappropriate antimicrobial therapy results in poor visual outcome.

Acanthamoeba Keratitis↗
PubMedDate not supplied

Ulcerative keratitis associated with contact lens wear.

To review the microbiological profile of ulcerative keratitis associated with contact lens (CL)-wear, 35 patients with culture-proven CL-associated microbial keratitis were studied between September 1999 and September 2002. Corneal scrapes and CL-care products were collected and were subjected to microbiological evaluation. Gram-negative bacilli alone were recovered from the corneal scrapes of all 35 (100%) patients, all 70 (100%) CL storage case wells and also from CL-care solution of six (17.14%) of the 35 patients. There was a significantly higher number of Pseudomonas aeruginosa (71.43%) isolated from eyes with CL-related keratitis than other bacterial isolates (28.57%) (P<0.001). Microbial contamination of CL storage cases was a great risk for gram-negative bacterial infection among soft CL-wearers.

Adolescent↗
PubMedDate not supplied

Influence of recall period on estimates of diarrhoea morbidity in infants in rural Tamil Nadu.

Data collected on 689 infants, in a study to assess the incidence of diarrhoea during infancy, is used here to quantify the extent of under-reporting in diarrhoea morbidity surveys. The study area consisted of two contiguous primary health centres in Villupuram health unit district in Tamil Nadu, south India. Each day of infancy was assigned a recall period and proportion of diarrhoeal days for various recall period computed. The proportion of diarrhoea was 11.3%, 12.0% and 11.2% for zero, one and two days of recall period, respectively, (mean 11.5%) after which the proportion decreased. The under-reporting of diarrhoea was approximately 15%, 26% and 45% with three, six and 7-13 days of recall period, respectively compared to mean. As there is considerable under-reporting of diarrhoea morbidity when recall period exceeds three days, it would be better to collect information on diarrhoea twice a week in diarrhoeal morbidity surveys.

Community Health Centers↗
PubMedDate not supplied

Influence of recall period on estimates of diarrhoea morbidity in infants in rural Tamilnadu.

Data collected on 689 infants, in a study to assess the incidence of diarrhoea and acute respiratory infections during infancy, is used here to quantify the extent of under-reporting in diarrhoea morbidity surveys. The study area consisted of two contiguous primary health centres in Villupuram health unit district in Tamil Nadu, South India. Each day of infancy was assigned a recal period and proportion of diarrhoeal days for various recall period computed. The proportion of diarrhoea was 11.3%, 12.0% and 11.2% for zero, one and two days of recall period, respectively, after which the proportion decreased. The under-reporting of diarrhoea was approximately 15%, 26% and 45% with three, six and 7-13 days of recall period, respectively. As there is considerable under-reporting of diarrhoea morbidity when recall period exceeds three days, it would be best to collect information on diarrhoea at least twice a week in diarrhoeal morbidity surveys.

Bias↗
PubMedDate not supplied

Lot quality assurance sampling (LQAS) for monitoring leprosy elimination in an endemic district in Tamilnadu.

This paper examines whether the health administration can use lot quality assurance sampling (LQAS) for identifying high prevalence areas for leprosy for initiating necessary corrective measures. The null hypothesis was that leprosy prevalence in the district was at or above ten per 10,000 and the alternative hypothesis was that it was at or below five per 10,000. A total of 25,500 individuals were to be examined with 17 as an acceptable maximum number of cases (critical value). Two-stage cluster sample design was adopted. The sample size need not be escalated as the estimated design effect was 1. During the first phase, the survey covered a population of 4,837 individuals out of whom 4,329 (89.5%) were examined. Thirty-five cases were detected and this number far exceeded the critical value. It was concluded that leprosy prevalence in the district should be regarded as having prevalence of more than ten per 10,000 and further examination of the population in the sample was discontinued. LQAS may be used as a tool by which one can identify high prevalence districts and target them for necessary strengthening of the programme. It may also be considered for certifying elimination achievement for a given area.

Cluster Analysis↗
PubMedDate not supplied

Gangrenous Richter's hernia with intrasac abscess.

A 43 year old female was admitted with features of intestinal obstruction. On laparotomy, a strangulated Richter's hernia with an abscess within an incisional hernial sac through a previous lower segment caesarean section scar was diagnosed. Resection and anastomosis was performed. Strangulated Richter's hernia is a rare entity making up 8.3% of all strangulated hernias. There have been reports of Richter's hernia with strangulation in inguinal hernia, femoral hernia and port hernia after laparoscopic surgery but none so far in an incisional hernia.

Adult↗