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Biomedical subjects

A P Dick

Publications and source records attributed to A P Dick.

At least 19 recordsLinked to original sources
PubMed1989

Immediate neurological effects of diving to a depth of 360 metres.

Eighteen divers performed a simulated dive to a depth of 360 metres of seawater breathing a mixture of helium and oxygen. Clinical neurological examinations and neurophysiological tests were performed before and after the dives. Two divers had mild ataxic signs and changed electronystagmography after the dive, and one had impaired vibration sense in one lower extremity. Abnormal EEGs with slow waves and sharp potentials, seen primarily in the temporal regions, occurred in 2 divers. No changes were found in the magnetic resonance imaging brain scans. The divers with evidence of previous central nervous system injury, or a history of unconsciousness or previous decompression sickness seemed more likely to develop neurological signs after these deep dives. This study shows that deep diving may induce immediate neurological changes. We recommend that future deep divers have a neurological examination and 2 separate EEGs included in their medical examinations.

Adult↗
PubMed1986

Distribution of the glucose transporter in the mammalian brain.

We used [3H]cytochalasin B as a specific ligand to study the glucose transporter of the following tissue preparations: (a) microvessels derived from the cerebral cortex and cerebellum of the rat and pig, (b) particulate fractions of the cerebral cortex and cerebellum of the rat and pig, (c) lateral, third, and fourth ventricular choroid plexus of the pig, and (d) synaptosomes from the pig cerebral cortex. Specific, D-glucose-displaceable binding of [3H]cytochalasin B was present in all the preparations studied. This binding was saturable and displayed the kinetics of a single class of binding sites, similar to the glucose transporter found in other mammalian tissues. The density of the glucose transporter was much higher in cerebral and cerebellar microvessels and choroid plexus than either in crude particulate fractions of the cerebrum and cerebellum or in cerebral synaptosomes. These findings agree with the physiologic function of brain microvessels that transport glucose, not only for their own use, but also for the much greater mass of the entire brain. In the pig, the density of the glucose transporter in cerebral microvessels was significantly higher than in cerebellar microvessels. Irreversible photoaffinity labeling of the glucose transporter of synaptosomal membranes with [3H]cytochalasin B followed by solubilization and polyacrylamide gel electrophoresis demonstrated a single region of radioactivity that corresponded to a molecular mass of 60,000-64,000 daltons.

Affinity Labels↗
PubMed1985

Specific ouabain binding to brain microvessels and choroid plexus.

The energy-dependent transport of ions across the blood-brain barrier and the blood-cerebrospinal fluid barrier by Na+, K+-ATPase is credited with an important role in brain homeostasis. In this study, we have assessed the relative enrichment of Na+, K+-ATPase in regional brain capillary preparations and in the choroid plexus by the quantitative determination of the cardiac glycoside binding sites in these preparations using [3H]ouabain as a ligand. We find that ouabain binds specifically to brain microvessels of the rat and the pig and to the choroid plexus of the pig in a saturable manner. The maximum density of ouabain binding sites in brain microvessels of both species is about one-fourth that of the crude membranes of the cerebrum and cerebellum. The density of ouabain binding sites in the pig choroid plexus is intermediate between that of the brain and brain microvessels. We do not find regional differences in ouabain binding to membrane fractions of the cerebrum and cerebellum, nor any significant differences in ouabain binding to cerebral and cerebellar microvessels. These findings provide quantitative estimates of Na+, K+-ATPase in brain capillaries and choroid plexus.

Animals↗
PubMed1985

Neurologic presentation of decompression sickness and air embolism in sport divers.

In a retrospective study of scuba divers with neurologic injuries, we found that mild symptoms were common. Seventy divers had decompression sickness, most often with paresthesias or numbness, rarely with paresis. Thirty-nine divers had air embolism that often caused unconsciousness or mild symptoms of cerebral injury. Many divers with neurologic decompression sickness gave histories of dives that were within conventional limits, and many with air embolism gave no history of breath-holding during ascent. Mild symptoms sometimes regressed spontaneously. Recompression delays were responsible for poor responses to therapy.

Adolescent↗
PubMed1984

Identification and characterization of the glucose transporter of the blood-brain barrier by cytochalasin B binding and immunological reactivity.

[3H]Cytochalasin B was used as a ligand to identify and characterize the glucose transporter in cerebral microvessels of the rat and the pig. Specific cytochalasin B binding, defined as that fraction of the total binding that is stereospecifically displaced by excess (500 mM) D-glucose, is saturable. Kinetic studies of this specific binding to cerebral microvessel preparations showed a dissociation constant (Kd) of 0.65-0.88 microM and a maximal binding (Bmax) of 60-80 pmol/mg of protein. In comparison, the Bmax of particulate fractions of the cerebral cortex was about one-tenth that of cerebral microvessels. The ability of various hexoses to displace specific cytochalasin B binding to cerebral microvessels in vitro correlated well with the capability of these hexoses to cross the blood-brain barrier in vivo. Irreversible photoaffinity labeling of the glucose transporter of cerebral microvessels with cytochalasin B followed by solubilization and polyacrylamide gel electrophoresis labeled a polypeptide(s) with a molecular weight of about 53,000. Antibodies prepared against the glucose transporter of human erythrocytes also reacted with a polypeptide(s) with a molecular weight of about 53,000 on electrophoresed preparations of cerebral microvessels. These results indicate that cerebral microvessels are richly endowed with a glucose transporter moiety of similar molecular weight and antigenic characteristics as the glucose transporter of human erythrocytes and other mammalian tissues.

Animals↗
PubMed1984

Decompression induced nitrogen elimination.

A method for measuring nitrogen elimination after air diving has been developed in which a subject breathes air instead of oxygen or helium-oxygen. Accuracy is improved with this method because only nitrogen absorbed during the dive is eliminated. Nitrogen stored in the lungs and tissues at sea level is unaffected. Measurements were made with a closed-circuit breathing apparatus using a spirometer as a counterlung. The oxygen partial pressure in the apparatus was controlled at 0.209 +/- 0.003 atm. The spirometer volume was recorded periodically with the subject holding his breath at functional residual capacity. Increases in spirometer volume were used to define a nitrogen elimination curve. Elimination measurements were made after resting and exercising dives to 60, 100, and 130 fsw (2.8, 4.0, and 4.9 atm) at the U.S. Navy no-decompression exposure limits. Exercise during a dive increased the volume of nitrogen eliminated after the dive, but results for both resting and exercising divers were variable. Possible causes of this variability include bubble formation and changes in blood flow.

Adult↗
PubMed1979

Double-blind controlled trial of cimetidine in the healing of gastric ulcer.

Sixty patients with gastric ulcers were treated for four weeks with either 1 g cimetidine per day or with identical tablets containing lactose. The healing rate, assessed by endoscopy, was 23 out of 35 (66%) in the patients given cimetidine and 13 out of 25 (52%) in those given placebo. The difference between the groups is not significant. During each of the four weeks of the study the cimetidine group experienced significantly fewer attacks of pain and consumed less antacids than the placebo treated patients.

Aged↗
PubMed1979

Cimetidine in the prevention of gastric ulcer relapse.

Twenty-five patients with healed gastric ulcers completed an 11-month double-blind controlled trial comparing cimetidine 1 g daily with placebo in the prevention of ulcer relapse. Ulcers recurred in 14 patients, 12 on placebo, 2 on cimetidine. In 11 patients, 9 on cimetidine, 2 on placebo, the ulcers remained healed at the end of the trial (P less than 0.002). Cimetidine 1 g daily significantly reduces the relapse rate in gastric ulceration.

Aged↗
PubMed1978

Prolyl hydroxylase activity in serum and rectal mucosa in inflammatory bowel disease.

Prolyl hydroxylase activity in rectal mucosa was found to be significantly greater in 11 patients with Crohn's disease than in 11 control subjects with the irritable bowel syndrome and 16 patients with ulcerative colitis (P less than 0.005). Seven of the patients with Crohn's disease had a histologically normal rectum. This abnormality in apparently normal mucosa supports the concept that Crohn's disease is a 'continuous' disease of the gastrointestinal tract. Although there was no significant difference in prolyl hydroxylase activity between control subjects and patients with ulcerative colitis, those patients with quiescent disease tended to have lower values than those with active mucosal inflammation. Prolyl hydroxylase activity could not, however, be detected in the sera of either healthy control subjects or patients with inflammatory bowel disease.

Adult↗
PubMed1978

Pseudopolyposis in Crohn's disease.

Eight cases of pseudopolyposis occurring in Crohn's colitis are described. Emphasis is placed on the variability of the lesions. Four of the cases demonstrate localized giant pseudopolyposis which has until recently been regarded mainly as a complication of ulcerative colitis.

Adult↗
PubMed1976

Effect of Crohn's disease on colonic diverticula.

Fifteen cases in which the same part of the colon has been affected by both diverticular disease and Crohn's disease have been studied. When Crohn's disease affects an area of colon where diverticula are present, radiological examination may show a diminution in number or disappearance of the diverticula with progress of the Crohn's disease. With improvement in the Crohn's disease diverticula may appear.

Aged↗