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Biomedical subjects

K M Welch

Publications and source records attributed to K M Welch.

At least 199 records · Page 11Linked to original sources
PubMed1985

A magnetic shield for large-bore, high field magnets.

An effective shield for the dc fringing fields produced by a large-bore, high field magnet intended for imaging and in vivo spectroscopy is presented. While limiting the extent of fringe fields, the shield has little effect on the homogeneity of the central field of the magnet. The effect of institutional safety policies as well as the exigencies of patient access in a hospital environment are emphasized as influences on the planning of an in vivo NMR installation.

Costs and Cost Analysis↗
PubMed1985

Biochemical effects of cerebral ischemia: relevance to migraine.

Although decreased CBF has now been reported during the prodrome of migraine, the cause of the decreased flow is still unknown. It is particularly unclear whether these phenomena are related to vasospasm and "steal" between the extracranial and intracranial circulation or to the spreading depression of Leao and the accompanying metabolic depression. In the present paper, metabolic changes in the brain during ischemia and reperfusion are reviewed and compared with CNS biochemical changes during migraine attack. In addition, the technique of Topical Magnetic Resonance (TMR) as applied to the in vivo study of energy phosphate metabolism in extracranial tissues and brain is described and the potential of this technique to evaluate shifts in energy metabolism and pH in stroke and migraine is discussed.

5-Hydroxytryptophan↗
PubMed1985

Successful migraine prophylaxis with naproxen sodium.

Naproxen sodium, a potent inhibitor of prostaglandin biosynthesis and platelet aggregation, was studied for efficacy in migraine prophylaxis in a randomized, double-blind, placebo-controlled, crossover trial. On naproxen treatment, 52% of the patients had no severe headaches, whereas 19% had no severe headaches during placebo. Naproxen sodium was much better than placebo when patients' diaries were reviewed for severity of attacks, nausea, vomiting, activity reduction, duration of headache, and decreased use of therapeutic medication. The degree of platelet inhibition did not correlate with efficacy in preventing headache. Naproxen sodium can be recommended as a drug of first choice for migraine prevention.

Adult↗
PubMed1984

Anoxia followed by hyperoxia: in vivo 31-P NMR of cat brain.

In vivo 31P NMR spectroscopy was performed on a cat brain subjected to an extended period of anoxia followed by restoration of oxygen. High energy phosphate spectra were continuously obtained and pH measured. Following the onset of anoxia, phosphocreatine and ATP peaks decreased with a concomitant increase in inorganic phosphate. Following 34 min ventilation on 100% N2, the animal was ventilated on 100% O2. The spectral content progressively changed, inorganic phosphate decreased and ATP increased with the spectrum closely resembling that of control. Our results suggest that the absence of NMR detectable ATP signal cannot be interpreted as an irreversable change in cellular metabolic function.

Adenosine Triphosphate↗
PubMed1984

The role of estrogen in migraine: a review and hypothesis.

The epidemiological, clinical and basic science evidence for a role of estrogen in migraine is reviewed. The hypothesis is put forward that estrogen exerts its influence by modulating sympathetic control of the cerebral vasculature.

Cerebrovascular Circulation↗
PubMed1980

Cerebral microvessel 2-deoxy-D-glucose uptake during ischemia-induced seizures.

Microvessels were isolated by albumin flotation and glass bead filtration from cerebral cortices of gerbils decapitated during pentylenetetrazol (PTZ)-induced seizures and ischemia-induced seizures. The uptake of 2-deoxy-D-glucose (2-DG) into these microvessels was studied in vitro. This uptake was increased during PTZ-induced seizures, in keeping with mechanisms whereby glucose transport into brain is increased to keep pace with the augmented tissue glycolysis provoked by enhanced neuronal activity. Uptake of 2-DG was decreased in microvessels isolated from animals that were decapitated while undergoing a seizure during ischemia and 90 to 120 minutes after ischemia. In contrast to results obtained when seizures are due to other causes, these results suggest that brain glucose transport is decreased during a seizure if the microvasculature has been previously subjected to ischemia. The results are discussed in relation to clinical stroke and Todd's postepileptic paralysis.

Animals↗
PubMed1979

Abnormal protein patterns in multiple sclerosis.

Sera from patients with multiple sclerosis (MS) and those obtained from normal subjects are indistinguishable by regular 5% or 7% polyacrylamide gel electrophoresis. However, 11 out of 15 MS sera examined by gradient polyacrylamide gel electrophoresis showed three distinct protein bands. None of the sera obtained from 10 normal subjects showed the characteristic protein patterns when they were examined by gradient gel electrophoresis. Similar results were obtained with de-albumin serum samples or with serum proteins precipitable at 50% ammonium sulfate saturation. These three proteins have now been purified to homogeneity by preparative gradient gel electrophoresis. Molecular weights of these proteins were estimated from gradient gel electrophoresis as 398,000, 363,000 and 302,000 daltons, respectively.

Blood Protein Electrophoresis↗
PubMed1979

Influence of cerebral embolism on brain monoamines.

In baboons the right cerebral hemisphere was embolised by a shower of microemboli, immediately followed by one large embolus designed to occlude the middle cerebral artery (MCA). One hour after embolism a significant, though small, reduction in blood flow and oxygen consumption of the embolised hemisphere was recorded, at which time the animals were killed and brain monoamines measured. Dopamine was reduced in the ipsilateral caudate nucleus, the reported site of maximal ischaemic damage in this model. Dopamine levels were increased in frontal and occipital grey matter sampled from areas surrounding the occluded MCA territory and in similar brain areas of the opposite non-embolised hemisphere. Noradrenaline was increased in grey matter from both cerebral hemispheres, as well as subcortical structures bilaterally. Brain 5-hydroxytryptamine levels were unaltered, but increased 5-hydroxyindoleacetic acid in cisternal cerebrospinal fluid suggested transient alteration in 5-hydroxytryptamine metabolism after embolism. The effects of cerebral embolism on brain monoamine metabolism appear to be different from the effects of permanent surgical occlusion of major cerebral vessels. The bilaterality of effects after unilateral hemispheric embolism might be related to diaschisis. The mechanisms of the observed changes, as well as their relevance to the progression of cerebral ischaemia and the complications associated with cerebral embolism, still require to be established.

Animals↗
PubMed1978

Ischemia-induced seizures and cortical monoamine levels.

Seizure activity as a component of the ischemic process possibly responsible for monoamine changes described in the gerbil stroke model was the subject of this study. Abnormal motor activity suggestive of seizures developed one to three hours after unilateral ligation of the common carotid artery in approximately 50% of gerbils that exhibited signs of stroke. Reduction of cortical levels of dopamine and norepinephrine was observed only when seizures occurred in association with stroke. The levels of 5-hydroxytryptamine were reduced bilaterally in animals with and without signs of stroke and were reduced further in animals with stroke plus seizures. Further study is needed to establish whether the catecholamine changes associated with ischemia-induced seizures are primary and causative or secondary to seizure activity itself. In the ischemic brain, 5-hydroxytryptamine metabolism appears disordered independent of seizure activity. Seizure activity must be taken into account when the mechanisms of disordered monoamine metabolism are being examined in the gerbil stroke model.

Animals↗