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Biomedical subjects

O Prakash

Publications and source records attributed to O Prakash.

At least 73 records · Page 4Linked to original sources
PubMed1991

Topographical requirements for delta-selective opioid peptides.

The conformational possibilities of three different delta-selective opioid peptides, which are DPDPE (Tyr-D-Pen-Gly-Phe-D-Pen), DCFPE (Tyr-D-Cys-Phe-D-Pen), and DRE (Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2, dermenkephalin), were explored using energy calculations. Sets of low-energy conformers were obtained for each of these peptides. The sets consisted of 61 structures for DPDPE, 32 for DCFPE, and 38 for DRE, including various types of rotamers of the Tyr and Phe side-chain groups. Comparison of the geometrical shapes of the conformers was performed for these sets using topographical considerations, i.e., examination of the mutual spatial arrangement of the N-terminal alpha-amino group, and of the Tyr and Phe side-chain groups. The results obtained suggest a model for the delta-receptor-bound conformer(s) for opioid peptides. The model suggests the placement of the Phe side chain in a definite position in space corresponding to the g- rotamer of Phe for peptides containing Phe4 and to the t rotamer for peptides containing Phe. The position of the Tyr1 side chain cannot be specified so precisely. The proposed model is in a good agreement with the results of biological testing of beta-Me-Phe4-substituted DPDPE analogues that were not considered in the process of model construction.

Amino Acid Sequence↗
PubMed1991

c-myc and K-ras-2 oncogenes in B-cell chronic lymphocytic leukemia with del(12)(p13).

Molecular and cytogenetic analyses were performed on chronic B-lymphocytic cell leukemia (CLL) from a 57-year-old male patient with del(12)(p13) anomaly. The deletion did not remove the K-ras-2 gene. However, c-myc gene amplification correlated with high-level expression, suggesting the involvement of this gene in the induction of neoplasia in this patient.

Chromosome Deletion↗
PubMed1991

Immediate hypersensitivity to Parthenium hysterophorus. II. Clinical studies on the prevalence of Parthenium rhinitis.

The airborne pollen of the South American weed, Parthenium hysterophorus (American feverfew), accidentally introduced into India was found to be responsible for severe allergic rhinitis. A random clinical survey conducted on 2035 residents of Bangalore city with the aid of questionnaires and skin tests revealed that 7.1% of the study population was suffering from allergic rhinitis due to exposure to Parthenium pollen. Skin-prick tests performed on 1294 clinic patients suffering from nasobronchial allergy during the past 4 years have also shown that 42.5% were sensitive to Parthenium pollen. IgE and IgG antibodies specific for Parthenium pollen allergens were demonstrable in the sera of Parthenium-sensitive rhinitis patients. The specificity of these antibodies to Parthenium allergens was established by ELISA. A 7- to 11-fold higher stimulation was observed when lymphocytes from two Parthenium-sensitive rhinitis patients were treated in vitro with Parthenium pollen extract. To our knowledge, nowhere in the world has such a high incidence of allergic rhinitis due to a single pollen ever been reported.

Adolescent↗
PubMed1991

Transactivation of human immunodeficiency virus type 1 long terminal repeats by cell surface tumor necrosis factor alpha.

Tumor necrosis factor alpha (TNF-alpha) is expressed in secreted and cell surface (csTNF-alpha) forms by activated monocytic and T cells. In this report, we demonstrate that csTNF-alpha may predominantly regulate the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) activation in the promonocytic cell line U937 and in the Epstein-Barr virus-transformed B-cell line BH1. Anti-TNF-alpha antibody suppressed both the constitutive expression of the HIV-1 LTR in BH1 cells and the expression induced by phorbol 12-myristate 13-acetate in U937 cells. This suppression was found to be mediated via csTNF-alpha. No correlation between the HIV-1 LTR activation and the secretion of TNF-alpha was evident in these cell lines. Suppression of TNF-alpha secretion by cyclosporin A or by a serine protease inhibitor did not suppress the HIV-1 LTR activation. These observations suggest a novel biological role for csTNF-alpha in the immunopathogenesis of AIDS.

Cell Line↗
PubMed1991

Angiotensin-converting enzyme inhibition reduces neuroblastoma cell growth rate.

Because of the known capacity of angiotensin II to serve as a growth factor in multiple tissues, we elected to study the effects of renin-angiotensin system inhibition on the growth of human SH-SY5Y neuroblastoma cells. Cells were treated with captopril (0.05-5 mg/ml), enalapril, or enalaprilat (0.02-5 mg/ml) or saralasin (0.1-0.25 mg/ml). In all cases, statistically significant reductions in cell growth were seen over 5 days of culture. In additional experiments, captopril and enalaprilat significantly decreased thymidine incorporation into DNA in these cells. The administration of angiotensin II in the presence of captopril partially offset these suppressive effects.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

Immunocytochemical localization of chloramphenicol acetyltransferase as a single-cell marker of transfected and transgenic cells.

A technique is described for immunocytochemical localization of the bacterial gene product chloramphenicol acetyltransferase, which is a commonly used reporter gene in transfected and transgenic cells. The described procedure is capable of localizing the enzyme in individual cells, providing a means of determining the cell type(s) expressing a foreign construct in complex cultures or in tissue sections of transgenic mice.

Animals↗
PubMed1990

Development of software for pulse oximeter and investigation of its realtime response in clinical environment.

We developed a pulse oximeter software at Thorax Centre, Erasmus University as a joint project with an industry and evaluated it in the clinical environment of thorax anaesthesia using a computerized protocol for realtime data collection during routine clinical procedures. This paper gives an account of the results we obtained from the development project and the clinical study. The paper consists of two parts. First part describes different components of the software module and their influence on different aspects of the clinical behaviour of the oximeter. The second part describes the results of realtime response investigation. The investigation was carried out using a personal computer to collect the data continuously during anaesthesia, surgery and post-operative periods. Two other industry standard oximeters, Nellcor and Ohmeda were also included in our study. We collected data on more than fifty patients on an average of eight hours per patient over a period of four months with major emphasis on low-saturation occurrences. The interpretation of the data was focused more on the realtime response anomalies on random cases than on ensemble statistical data evaluation. We found, that there are few factors in clinical environment which often influences the measurement of a pulse oximeter very strongly. Most often the anomalies were found during low saturation measurement. The main objective of this paper is to make the results available to practising clinicians so that it may be useful to identify these occurrences during routine clinical usage.

Evaluation Studies as Topic↗
PubMed1990

Breath detection algorithm in digital computers.

An algorithm for the detection and delineation of breaths is described. The proposed algorithm takes into account the different, common modes of ventilation like the pressure controlled, volume controlled and patient triggered modes of ventilation. Airway flow curve is used as the basic delineator and the airway pressure and the Co2 concentration curves are used to confirm the delineation. A flow chart is also included to explain the algorithm. The detailed explanation and modifications, for additional confirmation and for the selections of constants, to check for the rise or fall of the pressure and Co2 curves, are also included.

Algorithms↗
PubMed1990

Measurement of arterial pressure after cardiopulmonary bypass with long radial artery catheters.

Radial arterial pressure can significantly underestimate central aortic pressure in the postcardiopulmonary bypass (post-CPB) period. At the study institution, routine monitoring of perioperative arterial pressure in adult patients undergoing cardiac surgery is performed with a long radial artery catheter with the distal end positioned in the subclavian artery. In 68 patients presenting for elective cardiac surgery, both a conventional short radial artery catheter and a contralateral long radial artery catheter were placed. Analysis of radial and subclavian arterial pressures post-CPB in the first 47 patients showed average maximum differences of 7 mm Hg systolic and 4 mm Hg mean. In 15% of patients, the differences were clinically significant (greater than 20 mm Hg systolic and/or greater than 14 mm Hg mean). In 28 patients, central aortic pressure was measured post-CPB, and subclavian artery pressure was found to be an excellent estimator of central aortic pressure. There were no significant complications related to using long radial artery catheters in the 68 patients who were followed prospectively. Monitoring subclavian arterial pressure by percutaneous insertion of a long radial artery catheter provides a reliable estimation of central aortic pressure, even in patients with significant radial artery-to-central aortic pressure gradients post-CPB.

Adult↗
PubMed1990

Morphine-induced transactivation of HIV-1 LTR in human neuroblastoma cells.

Infection by human immunodeficiency virus (HIV) is followed in many cases by a clinically quiescent or latent phase that appears to continue as long as host antiviral defense is intact. This has raised the possibility that certain host susceptibility factors (i.e., environmental cofactors) might influence the progression of the disease. In this study we demonstrate that morphine can function to activate HIV/LTR-CAT fusion gene (HIV-long terminal repeat-chloramphenicol acetyltransferase) when transfected into undifferentiated human SH-SY5Y neuroblastoma cells. The stimulatory effect of morphine is amplified in SH-SY5Y cells that have been induced to differentiate first with phorbol 12-myristate 13-acetate (PMA) and is much less in cells differentiated with retinoic acid (RA). Morphine does not appreciably activate HIV/LTR-CAT expression in human MOLT-3 and other T cells. Morphine activation of HIV/LTR-CAT in the SH-SY5Y cells is not reversible by naltrexone and appears to involve a Fos/Jun signaling system. Our results suggest that narcotics such as morphine may lead to activation of latent HIV infection. This may be particularly important in tissues, such as brain, which can host latent HIV infection and which is uniquely damaged in patients with acquired immunodeficiency syndrome (AIDS) as evidenced by neuronal degeneration and dementia. We also predict that these findings may have important implications for the pathogenesis of AIDS, particularly in opiate drug abusers.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Immediate hypersensitivity to Parthenium hysterophorus. I. Association of HLA antigens and Parthenium rhinitis.

Lymphocytes collected from rhinitis subjects with strong positive skin reactions to the pollen allergens of Parthenium hysterophorus (American feverfew) having moderate to high titres of Parthenium-specific serum IgE were analysed for association of HLA-antigens covering 13 specificities of HLA-A, 17 specificities of HLA-B and eight specificities of HLA-DR loci by the NIH two-stage microlymphocytotoxicity assay. Comparison of the phenotypic frequencies of HLA-A and B antigens between Parthenium rhinitis subjects (n = 22) and control subjects (n = 137) did not suggest any significant association when tested for these antigen specificities. A significant correlation in the association of HLA-DR3 antigen with a relative risk of 11.33, however, was observed in Parthenium rhinitis subjects (n = 30) when compared to controls (n = 50).

Cross Reactions↗
PubMed1990

Do changes in pulmonary capillary wedge pressure adequately reflect myocardial ischemia during anesthesia? A correlative preoperative hemodynamic, electrocardiographic, and transesophageal echocardiographic study.

Pulmonary capillary wedge pressure (PCWP) is monitored during anesthesia in an attempt to detect changes in myocardial function in patients at risk of preoperative cardiac complications. Because the sensitivity with which preoperative PCWP monitoring indicates myocardial ischemia is uncertain, we monitored PCWP, 12-lead electrocardiogram, and left ventricular wall motion abnormalities as defined by transesophageal echocardiography (TEE) in 98 anesthetized patients before coronary artery bypass grafting. Measurements were made five times in each patient, before and after induction of anesthesia. Myocardial ischemia was identified by TEE in 14 patients; in 10 of these, it was associated with concomitant ST segment depression of at least 1 mm. The onset of ischemia, as defined by TEE, was accompanied by a mean increase in PCWP of 3.5 +/- 4.8 mm Hg, as compared with a mean change of 0 +/- 2.2 mm Hg between observations not associated with the onset of ischemia (p less than 0.01). An increase in PCWP of at least 3 mm Hg, tested as an indicator of ischemia, had a sensitivity of 25% and a positive predictive value of 15%; after correction for background changes associated with anesthetic induction, the sensitivity of this indicator was 33%, and its positive predictive value was 16%. These figures were not improved by selecting cutoff points higher or lower than 3 mm Hg. In this study, the onset of myocardial ischemia was associated with a small yet significant increase in mean PCWP at group level.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1990

S35 and derived parameters during extracorporeal circulation together with hemodilution and hypothermia in humans.

A new concept in monitoring systemic oxygenation that includes the effect of changes in oxyhemoglobin dissociation curve (ODC) has been introduced. Using the S35 (saturation of hemoglobin at PO2 = 35 mmHg), real arterial available oxygen content (CavlO2) can be calculated being the maximum amount of oxygen that can be extracted from hemoglobin before oxygen diffusion into tissue becomes compromised and oxygen uptake (VO2) may decrease. The relation between VO2 and CavlO2 expressed by the extraction ratio of the arterial available oxygen content (ERav) gives a realistic indices of oxygen supply in relation to oxygen consumption. In the present study, during extracorporeal circulation (ECC), a severe shift to the left of the ODC could be observed. THe classic parameters for monitoring systemic oxygenation as mixed venous saturation (Sv-O2) and extraction ratio (ER) did not change. The S35 increased because of the shift to the left of the ODC with consequent decrease in CavlO2. The ERav reached critical values during ECC together with hemodilution and hypothermia. A severe decrease in mixed venous PO2 (Pv-O2) was also observed. The authors conclude that besides Pv-O2, the S35, the CavlO2 and especially the ERav are of value in monitoring the systemic oxygenation during hypothermic ECC.

Arteries↗