Biomedical subjects

G F King

Publications and source records attributed to G F King.

59 records · Page 4Linked to original sources

PubMed1984

A proton n.m.r. study of iminodipeptide transport and hydrolysis in the human erythrocyte. Possible physiological roles for the coupled system.

The first description of a saturable iminodipeptide transport system present in human erythrocytes is given. The 1H-n.m.r. spectra of glycyl-L-proline and those of free glycine and L-proline are significantly different. This enabled the non-invasive monitoring by 1H-n.m.r. spectroscopy of the hydrolysis of the dipeptide in human erythrocytes and their lysates. The concentration-dependence of the rate of glycyl-L-proline hydrolysis by haemolysates was described by the Michaelis-Menten expression with Km = 14.1 +/- 2.4 mmol/litre and Vmax. = 130 +/- 10 mmol/h per litre of cell water. At concentrations of the dipeptide that saturated prolidase, hydrolysis of glycyl-L-proline by whole cells was approximately 130 times slower than by lysates. This rate difference indicated that transport is the rate-determining step in peptide hydrolysis by whole cells, and thus the concentration-dependence of the transport rate was determined. The membrane transport system was found to be saturable and could be described by the Michaelis-Menten expression with Kt = 4.7 +/- 0.4 mmol/litre and Vmax. = 0.997 +/- 0.026 mmol/h per litre of cell water. Numerical integration of a consistent set of differential rate equations that described a minimal model of the coupled transport-hydrolysis system successfully described prolonged time courses of peptide hydrolysis by whole cells. The simulations showed very low steady-state levels of dipeptide in the erythrocyte and very small lag periods (less than 5 min) in the progress curve describing the appearance of free amino acid inside the cells. The rates of transport of glycyl-L-proline into erythrocytes and kidney proximal-tubular epithelium were compared and the possible importance of erythrocyte prolidase in whole-body prolyl-peptide turnover is discussed.

Biological Transport↗

PubMed1984

Studies of rat brain metabolism using proton nuclear magnetic resonance: spectral assignments and monitoring of prolidase, acetylcholinesterase, and glutaminase.

The first application of inversion-recovery spin-echo proton nuclear magnetic resonance spectroscopy to the monitoring of reactions in rat brain preparations is presented. The initial report of the assignment of proton spin-echo nuclear magnetic resonance spectra from rabbit brain homogenates (C. R. Middlehurst et al., J. Neurochem. 42, 878-879, 1984) was used to assist in the assignment of spectra acquired from rat brain homogenates that were obtained from animals killed by cervical fracture or focussed microwave irradiation. Microwave-irradiated brains were divided into four major anatomical regions. Differences in metabolite levels were detected when spectra from fresh tissue and from various regions were compared. The in situ steady-state kinetics of prolidase in whole brain homogenate was determined. The procedure relies on the spectral differences between enzyme substrates and reaction products. The concentration dependence of the rate of hydrolysis of glycyl-L-proline was discribable by the Michaelis-Menten expression with a Michaelis constant of 1.90 mmol L-1 and a maximal velocity of 9.30 mumol min-1 mg-1 protein. The reactions catalysed by glutaminase and acetylcholinesterase in the brain were also monitored.

Acetylcholine↗

PubMed1984

Monitoring metabolic reactions in erythrocytes using NMR spectroscopy.

The kinetics of several metabolic reactions in intact human erythrocytes and in lysates were studied using 1H spin-echo and 13C nuclear magnetic resonance spectroscopy (NMR). The reactions monitored involved the following enzymes: (1) arginase, (2) glutathione reductase, (3) glutathione synthetase, (4) gamma-glutamyl cyclotransferase, (5) di- and tripeptidase, and (6) NAD-glycohydrolase; the first six enzymes are cytosolic whilst the latter is membrane associated. Detailed kinetics of the arginase reaction are given together with the rate of arginine transport into the cells.

Arginase↗

PubMed1983

Proton NMR spectroscopic studies of dipeptidase in human erythrocytes.

In studies on human erythrocyte metabolism in situ, high resolution (400 MHz) 1H spin-echo NMR spectroscopy was used to follow the time dependence of hydrolysis of glycylglycine and L-cysteinylglycine in intact cells and their lysates. The concentration dependence of the hydrolysis of L-cysteinylglycine was described by a rectangular hyperbola with Km, 3.5 +/- 0.6 mmol/l lysate and Vmax, 64.2 +/- 3.2 mmol/l lysate/h. We demonstrated that glycylglycine readily enters the erythrocyte and we introduce a means of analysing the data from the coupled reaction sequence; the sequence consists of transport followed by enzyme catalysed hydrolysis.

Dipeptidases↗

PubMedDate not supplied

Case studies of children presenting with a history of ritualistic abuse.

TOPIC: Ritualistic child abuse is an alarming and controversial problem. Child psychiatric nurses need to increase their awareness of the clinical picture associated with this specific form of abuse. PURPOSE: This article reviews the literature to date on ritualistic child abuse and addresses the controversy surrounding the phenomena. SOURCES: A small research project using historical data collection methods reviewed hospital records of children with a documented history of ritualistic abuse. Results are organized into clusters of linked interrelated characteristics. CONCLUSION: The symptom characteristics of these children revealed medical/somatic symptoms, distortion of self-oncept and world view, and a variety of emotional disturbances. The findings of this study are presented with implications for nurses who care for clients with a history of ritualistic abuse.

Child↗