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E Proctor

Publications and source records attributed to E Proctor.

At least 37 records · Page 2Linked to original sources
PubMed1990

Restoration of energy metabolism and resolution of oedema following profound ischaemia.

Cerebral ischaemia was produced in 2 groups of gerbils by occlusion of the common carotid arteries for 30 minutes, resulting in cerebral oedema. In group 1 cerebral oedema was measured by specific gravity microgravimetry, and in group 2 brain metabolism and blood flow were measured by 31P and 1H NMR spectroscopy and hydrogen clearance respectively. In group 1 the brain water content did not return to control levels by 180 minutes of reperfusion. Energy metabolism, determined by 31P NMR spectroscopy returned to control by 12 minutes, intracellular pH (pHi) by 20 minutes, and lactate, determined by 1H NMR spectroscopy, by 50 minutes. There was a lag of about 10 minutes before lactate began to be cleared from the brain. We suggest that while pHi is low, Na+/H+ exchange will negate the Na+ extrusion driven by the Na+/K+ ATPase. When pHi approaches normal there will be a net extrusion of Na+, taking osmotic water with it, and presumably with passive washout of lactate. This may be the cause of the initial delay in lactate clearance.

Animals↗
PubMed1989

Biochemical consequences of reflushing hypothermically-stored liver with fresh cold perfusate. Studies on rat liver using 31P NMR spectroscopy.

The metabolic response of the rat liver to flushing and reflushing with Marshall's solution at pH 7.2 or pH 7.8 has been studied by 31P nuclear magnetic resonance spectroscopy. The changes in intracellular pH, inorganic phosphate, ATP and phosphomonoesters have been determined from the 31P spectra. We show that the intracellular pH at any stage of the flushing protocol is largely independent of the pH of the medium when using these solutions. However, we demonstrate that there are differences between the efficiency of the two solutions in respect of the rates of hydrolysis of ATP and accumulation of phosphomonoesters. There were also differences in the response of the livers upon reflushing--those livers reflushed at pH 7.2 resynthesized ATP from a lower initial concentration to achieve ATP concentrations similar to those restored in livers reflushed at pH 7.8. These trends were mirrored in the responses of the phosphomonoester peaks (which contain a contribution from AMP). We conclude that short-term control of liver metabolism during hypothermia is possible by use of solutions of different pH, but that for longer-term storage, other approaches may be necessary to maintain metabolic integrity.

Animals↗
PubMed1989

The response of liver to lactobionate/raffinose (University of Wisconsin--UW) solution during hypothermic preservation: a study using 31phosphorus nuclear magnetic resonance.

31P nuclear magnetic resonance spectroscopy has been used to study rat livers following flushing with the University of Wisconsin (UW) lactobionate/raffinose solution (N. Jamieson, R. Sundberg, S. Lindell, J. Southard, and F.O. Belzer, Cryobiology 24, 573-574, 1987; M. Kalayoglu, H. Sollinger, R. Stratta, A. D'Alessandro, R. Hoffman, J. Pirsch, and F. O. Belzer, Lancet 1, 617-619, 1988). These studies have revealed that despite the improved storage properties that have been reported for this solution, hepatic ATP and ADP declined at a rate similar to that seen in the more commonly used Marshall's or Collins' solutions. However, there was a significant inhibition of the developing acidosis, such that by 5 hr postflush, the intracellular pH was 7.17 +/- 0.06 (mean +/- SD, n = 5) compared to 6.90 +/- 0.06 for Marshall's solution (4 hr postflush) and 6.94 +/- 0.04 for Collins' solution (4 hr postflush). This did not appear to be due to a buffering effect of the solution, as this was found to be relatively low, but was probably due to a modification of hepatic metabolism caused by the solution itself.

Animals↗
PubMed1989

Studies on cryoprotectant equilibration in the intact rat liver using nuclear magnetic resonance spectroscopy: a noninvasive method to assess distribution of dimethyl sulfoxide in tissues.

Nuclear magnetic resonance (NMR) spectroscopy was used in the study of rat livers following flushing with a clinically used preservation solution containing either 12 or 30% (v/v) Me2SO. The extent of equilibration of Me2SO in the tissue after 10-15 min of perfusion with Me2SO and again after subsequent washout with Me2SO-free medium was assessed by 1H NMR spectroscopy. 31P NMR spectroscopy was used to follow the changes in ATP, ADP, inorganic phosphate, and tissue pH. The data show that 1H NMR spectroscopy can be used as a sensitive and rapid method of assessing the equilibration and concentration of compounds such as Me2SO, since these compounds are likely to be present at concentrations greatly in excess of other constituents of the medium and will therefore give rise to strong, easily detected signals. At the same time, 31P NMR spectroscopy can be used to monitor the metabolic status of the tissue reflected in the levels of ATP, ADP, and inorganic phosphate, as well as being a noninvasive monitor of intracellular pH. The possibility of determining the tissue pH in the presence of solutes such as Me2SO is discussed.

Animals↗
PubMed1989

31P nuclear magnetic resonance of rat pancreatic grafts.

This study investigates whether phosphate metabolite concentrations and intracellular pH alter in early acute rejection of rat pancreatic allografts. In vitro biochemical assays, in vitro 31P nuclear magnetic resonance spectroscopy, and in vivo 31P NMR spectroscopy of the grafts were compared. Duct-ligated, vascularized rat pancreatic isografts and allografts were transplanted onto the infrarenal aorta of the recipients with inferior vena cava venous drainage. In order to obtain reproducible acute rejection, allografting was performed across a major histocompatibility barrier. For the in vitro experiments freeze-clamped graft extracts were prepared and analyzed for adenosine triphosphate concentration by fluorimetry, then placed in an 8.5 Tesla vertical bore magnet. 31P NMR spectra were recorded using a Bruker AM 360 spectrometer operating at 145.7 MHz for 31P. Spectra were acquired from nontransplanted controls; 3-day, 5-day, and 1-month posttransplant isografts, and 3-day and 5-day posttransplant allografts. All grafts examined were functioning satisfactorily. The ATP content of the extracts was significantly lower in the 3- and 5-day allografts than the respective isografts. Invasive in vivo 31P NMR spectra were recorded using surface coils adjacent to the grafts from functioning 5-day posttransplant isografts and allografts (i.e., 3 days prior to an expected elevation in blood sugar from acute rejection in the allografts). The ATP/inorganic phosphate ratios and pH from the in vivo spectra were significantly lower in the allografts than in the isografts. It is concluded that changes in intracellular metabolism occur early in the process of acute rejection and that 31P NMR spectroscopy may provide a means of diagnosing this before current methods.

Adenosine Triphosphate↗
PubMed1988

Quantitative estimation of lactate in the brain by 1H NMR.

1H NMR was used to detect lactate accumulation in the intact gerbil brain postmortem. The lactate concentration was estimated from the spectra by comparison to signals from N-acetylaspartate, creatine + phosphocreatine, and water. The effects of T2, phase modulation, and solvent suppression were taken into account. The estimated concentrations were compared to determinations performed on the same brains after extraction. The lactate concentration estimated from the intact brain spectra was between 70 and 90% of the values determined in vitro, on the extracts, depending on the concentration standard used. If N-acetylaspartate was used as the standard then the proportion of detected lactate (92%) was not significantly different from 100%.

Animals↗
PubMed1988

A 31P nuclear magnetic resonance study in vivo of metabolic abnormalities in rats with acute liver failure.

31P NMR spectroscopy was used in conjunction with conventional biochemical techniques to study metabolic abnormalities in normal rats, in rats with CCl4-induced acute liver failure and in rats with paracetamol-induced acute liver failure. Studies were carried out before and after a metabolic challenge in the form of a fructose infusion. Prior to fructose infusion the ATP levels in the groups with acute liver failure were significantly lower than in control rats, despite their having a similar ATP/Pi ratio. Following a fructose infusion in control animals, the changes in phosphomonoesters, ATP and inorganic phosphate were consistent with previously reported findings. However, in both test groups the percentage changes in phosphomonoesters and ATP were significantly smaller. Intracellular pH declined in control animals, but did not change significantly in the animals with acute liver failure. Fructose clearance from the blood in control animals was not significantly different from that in animals with CCl4-induced acute liver failure. Metabolic changes measured using a horizontal magnet were very similar to those obtained with a vertical magnet.

Acetaminophen↗
PubMed1988

Acute cerebral ischaemia: concurrent changes in cerebral blood flow, energy metabolites, pH, and lactate measured with hydrogen clearance and 31P and 1H nuclear magnetic resonance spectroscopy. III. Changes following ischaemia.

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anaesthesia. At the same time, intracellular pH and the concentrations of lactate and high-energy phosphates were measured in the brain using 1H and 31P nuclear magnetic resonance spectroscopy. Flow and metabolism have been followed during either a 15- or a 30-min ischaemic period (induced by bilateral carotid occlusion) and for up to 1 h of recovery. There was no significant difference between the flow characteristics of the two experimental groups. High-energy phosphate levels and pH returned to control within approximately 20 min of the end of the ischaemic period. Lactate clearance, following a 30-min occlusion, was slower than the recovery of pH. The concentration of free ADP, calculated from the creatine kinase equilibrium, was lower during the recovery phase than under control conditions.

Animals↗
PubMed1987

Acute cerebral ischaemia: concurrent changes in cerebral blood flow, energy metabolites, pH, and lactate measured with hydrogen clearance and 31P and 1H nuclear magnetic resonance spectroscopy. I. Methodology.

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anaesthesia. This has been correlated with changes in local pH, tissue lactate, and phosphorus energy metabolites measured in the same animals with 1H and 31P nuclear magnetic resonance (NMR) spectroscopy. The NMR measurements were made with two surface coils, one on each hemisphere. This article describes the experimental details and shows that in acute unilateral or bilateral forebrain ischaemia metabolic changes can be monitored by NMR with no significant interhemispheric cross talk. The metabolic effects of reperfusion are also shown. The model allows the definition of the time course of the metabolic consequences of regional ischaemia and reperfusion in individual laboratory animals.

Acute Disease↗
PubMed1987

Acute cerebral ischaemia: concurrent changes in cerebral blood flow, energy metabolites, pH, and lactate measured with hydrogen clearance and 31P and 1H nuclear magnetic resonance spectroscopy. II. Changes during ischaemia.

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anesthesia. This has been correlated with changes in local pH, tissue lactate, and phosphorus energy metabolites measured in the same animals with 1H and 31P nuclear magnetic resonance spectroscopy. We demonstrate a threshold flow value for the metabolic changes associated with energy failure at a level similar to the values previously reported for electrical failure and tissue water accumulation, but higher than that associated with breakdown of extracellular potassium homeostasis.

Animals↗
PubMed1987

Intracellular metabolites in rat muscle following trauma: a 31P and 1H nuclear magnetic resonance study.

Hind limb skeletal muscle was studied in vivo in a rat trauma model using nuclear magnetic resonance (NMR) spectroscopy. The model used was a 25% body surface area, full-thickness burn administered under anaesthesia. Two groups of six rats were studied. Weight loss was observed in the experimental group whilst the control group continued to gain weight. Concentration ratios involving intramyocellular phosphocreatine (PCr), creatine (Cr), adenosine triphosphate (ATP), inorganic phosphate (Pi), anserine (Ans) and taurine (Tau) were measured. No change in the ratios of PCr/Pi, PCr/ATP, Ans/PCr + Cr and Tau/PCr + Cr were seen between the two groups. Intracellular pH was the same in the two groups. NMR spectroscopy in vivo gives values of Pi and PCr that differ from those obtained by conventional techniques. NMR values are probably more accurate as no degradation occurs during measurement, the measurements being repeatable and noninvasive.

Adenosine Triphosphate↗