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Biomedical subjects

G Rao

Publications and source records attributed to G Rao.

196 records · Page 11Linked to original sources
PubMedDate not supplied

Green fluorescent protein as a real time quantitative reporter of heterologous protein production.

Since its cloning and commercial availability, applications of green fluorescent protein (GFP) as a reporter gene have become prevalent in many aspects of science. The attributes of GFP could also be applied to the area of heterologous protein production. The work described here represents the first experiments to use GFP as a generic tool to monitor protein production in bioprocess development. We have constructed a plasmid containing an operon fusion of the two reporter genes GFP and chloramphenicol acetyl transferase (CAT). CAT served as a "model" recombinant protein product to demonstrate the in situ quantifiable reporting mechanism of GFP. Our results indicate there is a direct correlation between the fluorescence intensity of GFP and the functional activity of the downstream CAT protein. In addition, there is a quantitative relationship between the level of CAT protein concentration and GFP fluorescence. These experiments provide the groundwork for using GFP as an in situ reporter gene for scale-up and process optimization of recombinant protein production.

Chloramphenicol O-Acetyltransferase↗
PubMedDate not supplied

Modeling the response time of an in vivo glucose affinity sensor.

A mathematical model was developed to describe the dose-response relationship of an optical glucose sensor. The basis for glucose detection is the reversible competitive displacement of a ligand from a receptor protein with specific binding sites for certain carbohydrates. Detection of glucose is based on measurements of the change in fluorescent lifetime of the donor-labeled protein, as it binds to the acceptor-labeled ligand. The sensor was modeled as a hollow fiber membrane, permeable to glucose, which encapsulates a solution of the receptor protein and competing ligand. Model equations that describe the diffusion of glucose through the fiber membrane and the subsequent displacement reactions within the fiber lumen were solved numerically to predict the response time of the sensor following a step change in bulk glucose concentration. The incorporation of an external mass transfer boundary layer was found to increase the response time by a factor of 3.7 over the well-stirred case. On the basis of the results of a parametric study, the response time of the sensor was found to be most sensitive to the diffusion coefficient of glucose in the membrane. When compared to experimental response times for an intensity-based affinity sensor using Concanavalin A as the receptor protein and dextran as the competing ligand, the model predictions were found to be significantly shorter than those observed. The effect of the in vivo environment on the performance of the sensor was also investigated through the incorporation of a fibrotic capsule layer. The additional diffusional resistance offered by the capsular tissue resulted in a 5-fold increase in the response time of the sensor.

Animals↗
PubMedDate not supplied

Functional integrity of NMDA-dependent LTP induction mechanisms across the lifespan of F-344 rats.

Previous studies have reported a lack of an age effect in the induction of long-term potentiation (LTP) at CA1 synapses, using robust (supramaximal) stimulation parameters, but an apparent age effect on the induction threshold of LTP using less robust stimulation, in the perithreshold region. These findings have led to the suggestion that old animals may experience an alteration either in the efficacy of activation of N-methyl-D-aspartate (NMDA) receptors or in the metabolic processes subsequent to NMDA receptor activation that lead to LTP expression. An alternative explanation for the apparent threshold change in old animals is that, because of the known reduction of the intracellularly recorded, compound EPSP magnitude in old rats, equivalent electrical stimulation results in a smaller effective depolarization of the postsynaptic cells and a consequently less effective activation of NMDA receptors, which are otherwise functionally normal. To distinguish between these two hypotheses, weak orthodromic stimulation was paired with intracellularly applied current pulses, thus holding constant the degree of postsynaptic depolarization. No differences in LTP induction threshold or magnitude were observed in a large sample of rats from three age groups. It is concluded that the NMDA receptor mechanisms and associated biochemical processes leading to LTP induction are not altered in aged F-344 rats. The reduced compound EPSP in old animals was reconfirmed in the present study, and a significant correlation was found in old rats between the magnitude of the EPSP at a fixed stimulus level and their performance on a spatial memory task.

Animals↗
PubMedDate not supplied

Probability of causation for cancers potentially induced by ionizing radiation.

Prompted by increasing litigation claiming cancer induction from exposure to radiation from nuclear weapons tests, the United States Congress enacted an amendment to the Orphan Drug Act (Public Law 97-414, January 4, 1983), through which the National Institutes of Health was directed to and did produce Probability of Causation (PC) Tables. This review defines PC and discusses the data, limitations, and uses of the concept.

Breast Neoplasms↗
PubMedDate not supplied

Multifaceted therapy after global brain ischemia in monkeys.

UNLABELLED: The pathophysiology of postischemic encephalopathy is complex, and includes tissue acidosis, edema, hypoperfusion, membrane dysfunction, impaired energy production, and possibly hypermetabolism. We tested the hypothesis that this multifactorial clinical problem must be approached with multifaceted therapy, with specific treatment aimed at each of the above postischemic changes. Eighteen minutes of complete global brain ischemia was produced with a higher pressure neck cuff in pigtailed monkeys. Control treatment postischemia (n = 9): 1) Normotension (MAP greater than or equal to 80 mmHg) restored within 2 min postischemia, 2) controlled ventilation for 24 hours with PaCO2 = 25 mmHg, 3) normothermia, and 4) phenytoin seizure prophylaxis from 20 hours postischemia. Experimental treatment (n = 10): Control treatment plus the following modifications: 1) Hemodilution to hematocrit 25% at 1-4 min postischemia, 2) brief hypertension (MAP 130 mmHg for 5 min) after accomplished hemodilution, 3) hypothermia for 6 hours, 4) pentobarbital 30 mg/kg i.v., 5) dexamethasone 4 mg/kg i.v. Outcome was evaluated at 96 hours postischemia by overall performance categories (OPC) (OPC I = normal, OPC V = brain death), neurologic deficit (ND) scores (100% ND = brain death, 0% ND = normal), and histologic damage scores of the brains. RESULTS: Brain death developed in 1/9 control and 0/10 treated animals. The number of awake monkeys (OPC I and II) at 96 hours postischemia was significantly higher in the treated group (7/10) than in the control group (2/9) (p = 0.05). The median ND scores for the two groups were 16 and 35% respectively (p greater than 0.05). The results strongly suggest that postischemic treatment may be beneficial and that a multifaceted therapeutic approach is worth pursuing.

Animals↗
PubMedDate not supplied

Incidence and prevention of pulmonary embolism after coronary artery surgery.

Pulmonary embolism is one of the common complications of aortocoronary artery graft surgery. During one year period, 22 patients had documented evidence of pulmonary embolism out of 231 patients who were operated. There were four deaths and all confirmed by autopsy. Clinical signs of phlebitis were absent in many cases of pulmonary embolism. Elastic stockings were not effective to prevent phlebitis. Heparin did not prevent deaths in all four patients. Heparin therapy and aggressive caval interruption by Modin-Uddin umbrella has eliminated deaths in the last 450 cases.

Adult↗
PubMedDate not supplied

Aorto-coronary graft for dissected coronary artery.

A 46-year-old woman while undergoing selective coronary cine angiogram dissected her coronary artery. She was managed by heparin therapy followed by urgent aorto-coronary artery saphenous vein graft with no consequences.

Cineangiography↗
PubMedDate not supplied

The effects of methylprednisolone on the complications of coronary artery surgery.

Complications of coronary artery surgery were analyzed in a prospective controlled study of 150 patients, one group receiving methylprednisolone before temporary cardiopulmonary bypass. The patient population was comparable in both the groups. The number of deaths were the same in both the groups, myocardial infarction and cardiac arrhythmias were definitely lower in the Solu-Medrol group. Cerebral vascular accidents were higher in the control group and there were none in the drug treated group. Incidences of pulmonary embolism was reduced by the drug. Oxygen consumption by the tissues was higher in the Solu-Medrol treated group. There were no known complications of the drug, such as stress ulcer and infection. One patient did receive prophylactic antibiotics. Solu-Medrol was deliberately given in patients who were known to have uncomplicated duodenal ulcer. Post-operative bleeding in patients with duodenal ulcer was not noted. This could be explained due to the short acting nature of Solu-Medrol. We feel that Solu-Medrol does minimize serious sequelae of heart-lung machine in coronary artery surgery.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Long-term experience with the Mobin-Uddin umbrella.

Umbrella filters have been inserted in 56 patients over the last seven years. Indications varied from shock to a huge clot in the major veins. Most of the patients were in Greenfield's Class IV. All were treated with heparin before and after caval filter insertion. There were no deaths, but there were a few complications. the cava were patent during the follow-up period in patients who were on Coumadin therapy. Minimal residual venous stasis was noticed in the legs. The Mobin-Uddin umbrella in a simple and effective means of prevention of pulmonary emboli.

Adolescent↗
PubMedDate not supplied

Hemodynamic advantages of temperature sensing rate adaptive pacemaker.

During activity, the increase in body temperature triggers the pacemaker to adjust by increasing the rate. To assess the hemodynamic advantages twelve patients were studied. Heart function was measured by a noninvasive bioimpedance method. Heart functions were measured first at rest and then at the end of the exercise. Exercise was done in temperature mode and then later at a fixed heart rate. Cardiac output increased by 64% in temp mode compared to the fixed heart rate during the exercise. Stroke Volume increased by 38%. The Thoracic Fluid Index, Ventricular Ejection Time, Ejection Velocity Index and Ejection Fraction were unchanged. Hemodynamics are better in temp sensing rate responsive pacing during activity compared to fixed rate pacing. Clinically, the patients are doing well.

Aged↗
PubMedDate not supplied

New clinical signs.

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Humans↗