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Biomedical subjects

A Joshi

Publications and source records attributed to A Joshi.

At least 199 records · Page 11Linked to original sources
PubMed1990

Metabolic dynamics in the human red cell. Part III--Metabolic reaction rates.

The kinetics of the enzymatic reaction and transport rates that constitute the main metabolic pathways of the red cell metabolism are described. The red cell metabolic model consists of 33 dynamic mass balances that contain 41 enzymatic reaction rate laws and transmembrane processes. Our goal here is two-fold: the development of rate expressions for the individual biochemical reactions of the integrated red cell metabolism, and order of magnitudes estimates to gauge their dynamic properties in terms of response times and action scales of substrates, products and regulators.

Adenosine Monophosphate↗
PubMed1990

Metabolic dynamics in the human red cell. Part IV--Data prediction and some model computations.

The biochemical information on the basic cellular determinants of the human red cell has been compiled into a comprehensive model of the red cell metabolic machinery. This model gives a consistent interpretation--both qualitative and quantitative--of the experimental findings. The predicted steady states and the dynamic states of the model are compared with the experimental findings, and the utility of this model is demonstrated.

2,3-Diphosphoglycerate↗
PubMed1989

Metabolic dynamics in the human red cell. Part I--A comprehensive kinetic model.

The experimental investigation of the red cell over the last three decades has accumulated extensive biochemical data on its enzymes and metabolites. The goal of this work is to provide a unified theoretical framework for the integration and consistent interpretation of these data by means of a comprehensive mathematical metabolic model of the red cell. This model is described in four parts. Here, we describe the general conception, scope and the biological assumptions of the model. The model is comprised of dynamic mass balances based on stoichiometry and enzyme kinetics with the imposed physico-chemical constraints of osmotic balance and electroneutrality.

Erythrocytes↗
PubMed1989

Metabolic dynamics in the human red cell. Part II--Interactions with the environment.

The maintenance of human red cell volume under multitude of trying physiological conditions is a self regulated dynamic process. Theoretical and experimental studies on red cell osmotic states have been primarily focussed on three different interdependent areas: the permeative properties of the red cell membrane, the kinetic studies of transmembrane fluxes of various ionic and nonionic chemical constituents of the red cell and plasma, and the ideal and non-ideal thermodynamic formulation of the osmotic states. The primary objective of this work is to provide a general model that converges the above mentioned components of the red cell and its environment under one umbrella. Such a model facilitates the simultaneous interpretation and prediction of quantitative changes in the red cell volume, pH, Donnan ratios, osmotic effects, plasma volume, transmembrane fluxes, and permeable and impermeable solute concentration.

Erythrocytes↗
PubMed1989

Brugia malayi: status of host during different stages of infection.

The status of glycogen, protein, lipid components, lipid peroxides and a few enzymes of energy metabolism was studied in liver of Mastomys natalensis during the development of Brugia malayi infection. Glycogen and lipid contents were decreased during the patent phase of infection while total protein was slightly altered in latent animals. Phospholipid and triglyceride contents declined at prepatent and patent phase of infection. The levels of lactate and malate dehydrogenases, as well as of adenosine triphosphatases (Na+K+, Mg2+, Ca2+), were significantly elevated and monoamine oxidase activity was decreased at patent phase of infection, while succinic dehydrogenase remained unaltered. The lipid peroxide formation was enhanced in liver during the development of filarial infection.

Adenosine Triphosphatases↗
PubMed1989

Effects of chloral hydrate on nitrous oxide sedation of children.

This study was conducted to examine the effects of chloral hydrate on nitrous oxide sedation of young children for dental treatment. Nineteen children, ranging in age from 19 to 41 months (mean 30 months), participated in this double-blind study. The subjects were assigned randomly to receive either a placebo or chloral hydrate (50 mg/kg) for the first visit with the alternate regimen administered during the second appointment. In addition, all subjects received inhalation nitrous oxide/oxygen at a concentration of 50%, and were restrained in a Papoose board (Olympic Medical Group; Seattle, WA) with head restraint. Seventy-four per cent of sedations were classified as very good or excellent when chloral hydrate was administered with nitrous oxide compared with only 26% when the placebo was administered.

Anesthesia, Dental↗
PubMed1987

A simple test to monitor aromatic amine clearance in occupational workers.

A simple, quick and sensitive procedure is described to monitor urinary clearance of aromatic amines in industrial workers. Estimation is based on the measurement of coloured Schiff's bases developed with 4-dimethylaminocinnamaldehyde-organic acid reagent. Extraction of amines in water saturated butanol ensured 89-97% recovery from biological samples with a coefficient of variation of less than 8%. Regression analyses of the absorbance-concentration curves with different aromatic amines showed excellent correlation coefficient and a high molar absorptivity with the lowest detection limits ranging between 0.05-0.12 microgram ml-1. The proposed reagent has additional use as a spray reagent to detect amine spots on chromatograms. Low final acidity ensures estimates of free amines without causing hydrolysis of conjugated amines.

Amines↗
PubMed1987

Reducing complexity in metabolic networks: making metabolic meshes manageable.

The dynamics of complex systems can be effectively analyzed by judicious use of intrinsic time constants. Order of magnitude estimation based on time constants has been used successfully to examine the dynamic behavior of complicated processes. The main goal of this paper is to introduce this approach to the analysis of complex metabolic systems. Time constants and dynamic modes of motion are defined within the context of well-established linear algebra. The order of magnitude estimation is then introduced into the systemic framework. The main goals of the analysis are: to provide improved understanding of biochemical dynamics and their physiological significance, and to yield reduced dynamic models that are physiologically realistic but tractable for practical use.

Animals↗
PubMed1987

Blood transfusion effect on the respiratory pattern of preterm infants.

Anemia may increase the risk of tissue hypoxia in preterm infants. This could lead to respiratory center depression and an increased risk for apnea. Heart rate and breathing pattern were recorded in 30 preterm infants (gestational age 30.0 +/- 2.3 weeks, postnatal age 46.6 +/- 20.8 days, and weight 1,438 +/- 266 g) before and after a transfusion of 10 mL/kg of packed RBCs. All infants were stable clinically, breathing room air, and free of prolonged apneic episodes. After transfusion, hematocrit levels increased from 27.0% +/- 2.5% to 35.8% +/- 4.7%. Heart rate decreased from 157.2 +/- 13.6 beats per minute to 148.4 +/- 13.9 beats per minute. There was no change in respiratory rate or BP. The duration of periodic breathing decreased significantly, as did the duration of the longest periodic breathing episode (P less than .01). The number of respiratory pauses lasting 5 to 10 seconds and the number of pauses lasting 11 to 20 seconds also decreased significantly (P less than .05). The total duration of respiratory pauses, excluding pauses during periodic breathing, were significantly lower after transfusion (P less than .05), as was the number of episodes of bradycardia. These results indicate that preterm infants have a more irregular breathing pattern while anemic than after correction of the anemia. The irregular breathing pattern is probably caused by mild hypoxic respiratory center depression.

Anemia↗
PubMed1983

Use of a heat detection paste on dairy cattle in France.

The aim of the present study was to evaluate the merits of a coloured paste applied to cows as an aid to heat detection in a dairy herd. It was performed on 110 French Friesian cows under a loose housing system over one year. For comparison, the results of the previous year, with no paste application, were also computed. Results of heat detection by the herdsman and by paste removal were compared to expected ovulations assessed by regular rectal palpation and, or, plasma or milk progesterone patterns. The paste system improved the percentages of oestrus detection of post partum and post inseminated cyclic cows by 26 and 22 per cent respectively, compared to the previous year. Overall missed heat incidence was 15 per cent and over estimation was negligible (less than 5 per cent). The mean durability period of the paste in the absence of mounting was 13 days. This suggests that to achieve the above mentioned results, application of paste should be performed at least every two weeks when no previous heat has been recorded, or only once, two weeks after service to check for non-pregnancy.

Animals↗
PubMed1983

The effect of head position on intracranial pressure in the neonate.

Elevation and maintenance of the head in an elevated, midline position reduces cerebral venous and intracranial pressure (ICP) in adult neurosurgical patients. To determine the possible effect of head position on ICP in the neonate, we studied 26 neonates less than 2500 g at birth and less than or equal to 10 days of age. ICP was measured in each of 4 different head positions: head turned to the right and bed horizontal (R-0 degrees); head turned to the right and head of the bed elevated 30 degrees (R-30 degrees); head in the midline and bed horizontal (M-0 degrees); and head in the midline and head of the bed elevated 30 degrees (M-30 degrees). ICP results were as follows: R-0 degrees, 10.0 +/- 1.2 (mean +/- SEM), cm H2O; R-30 degrees, 8.6 +/- 1.3 cm H2O; M-0 degrees, 6.9 +/- 1.2 cm H2O, and M-30 degrees, 5.3 +/- 1.0 cm H2O. ICP was significantly lower in the M-0 degrees and M-30 degrees positions when compared to either R-0 degrees and R-30 degrees. When the effect of elevating the head of the bed 30 degrees was evaluated for infants whose ICP was greater than or equal to 7 cm H2O in the R-0 degrees and M-0 degrees positions, it was noted that there was a significant drop in ICP in the elevated positions. These data suggest that head position influences ICP significantly in the neonate probably due to venous congestion caused when the neck is turned, and hydrostatic pressure changes when the head of the bed is elevated. ICP fluctuations due to changes in head position may be deleterious to the infant at risk for intracranial hemorrhage (ICH) or cerebral edema.

Head↗