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Biomedical subjects

P Harris

Publications and source records attributed to P Harris.

At least 253 records · Page 14Linked to original sources

Acute spinal cord injury patients--who cares?

Pertinent aspects of the remarkable advances instituted and developed for the management of patients who have sustained serious spinal injuries are discussed in this communication, and the responsibilities of medical doctors and others who care for such patients is taken up in relation to some of the recent advances in our knowledge, both experimental, and clinical. There are new challenges in investigations and therapy to be considered, some of which are being somewhat precipitiously put into practice. In particular, early spinal operations, where certain closed or open reduction procedures are followed by some of the newer forms of vertebral column fixation, may cause complications. Also the apparent benefits from such techniques may not be achieved and a plea is made for careful well documented accounts to be assembled and where possible set out, using modern statistical methods, to be made by doctors treating such patients. The significance of a full understanding of the importance of modern rehabilitation techniques for spinal cord injury patients is stressed; and finally, the practical realisation of insurance claims and of possible medical litigation is mentioned.

Emergency Medical Services↗

Inhibition of rabbit cardiac adenylate cyclase by theophylline.

Theophylline inhibits basal adenylate cyclase activity as well as cyclase stimulated by sodium chloride, sodium fluoride, GTP or 5'-guanylimidodiphosphate. This inhibition, is dose-dependent and shows non-competitive inhibition, with respect to MgATP. The presence of adenosine deaminase does not alter the effect of theophylline. The inhibition produced by theophylline is not additive with that due to 2'-deoxyadenosine 3'-monophosphate (a P-site agonist). It is suggested that theophylline may act at the P-site to reduce adenylate cyclase activity.

Adenosine Deaminase↗

Time-dependent effects of hippocampo-entorhinal atropine on passive avoidance learning in the young rat.

Young rats 20 and 16 days of age received bilateral micro-injections of saline or atropine (115 micrograms/kg) into the posteroventral hippocampo-subiculo-entorhinal area, and were trained on a cool-draft-stimulus passive avoidance task thereafter. The delay between injection and training was variable: 17 min, 4 h and 6 h at 20 days; 17 min, 6 h and 12 h at 16 days. Atropine-induced learning deficits were observed after the short and intermediate intervals, but not after the longer ones, indicating that the action of atropine injected intracerebrally lasted for several hours (at least 4 h at 20 days, and 6 h at 16 days) and was over after 6 h and 12 h respectively.

Animals↗

The mode of action of chloride on rabbit heart adenylate cyclase.

The mechanism by which chloride stimulates adenylate cyclase was investigated. Depletion of GDP increased basal adenylate cyclase activity and reduced the stimulation by isoprenaline. Restoration of bound GDP partially reversed these effects. Chloride stimulated cyclase activity by the same proportion in control, GDP-depleted and GDP-restored preparations, as did Gpp(NH)p. Fluoride increased adenylate cyclase activity to the same final level in both GDP-depleted and GDP-restored membranes; addition of Gpp(NH)p as well as fluoride had no further effect. Solubilisation of adenylate cyclase reduced the stimulatory effect of Gpp(NH)p only slightly, but greatly attenuated the activation by chloride. We conclude that chloride does not stimulate cyclase activity by an action on GDP exchange. Activation by chloride may be due to a disrupting or chaotropic effect on membrane/protein interactions.

Adenylyl Cyclases↗

The effect of anions and cations on cardiac adenylate cyclase: interactions with isoprenaline and GTP.

Anions stimulated rabbit heart adenylate cyclase in the order chloride greater than phosphate greater than acetate, while the cations sodium and potassium had little effect. Activation by KCI was multiplicative with that of fluoride. Isoprenaline (10(-4) M) and GTP(10(-4) M) stimulated the cyclase independently, and their combined effects were multiplicative. GTP stimulated less than chloride but more than acetate. Activation by chloride or acetate was more than additive with that by GTP. The effect of isoprenaline was reduced in the presence of chloride or acetate, and this reduction was not modified by sodium or potassium. It was concluded that ionic influence may be biologically important in modifying cyclase activity and the extent of beta-receptor stimulation.

Acetates↗

Intermediate filaments, microtubules and microfilaments in epidermis of sea urchin tube foot.

Tube foot epidermal cells of the sea urchin Strongylocentrotus purpuratus were examined by transmission electron microscopy and fluorescence microscopy to identify the chemical nature of prominent bundles of cytoplasmic filaments. Cross sections revealed filaments of roughly 7-8 nm in diameter closely packed into dense bundles. These bundles, in turn, were each surrounded by a loose sheath of microtubules. The filament size and negative reaction with the fluorescent F-actin binding drug NBD-phallacidin indicated that they were not actin. Indirect immunofluorescence microscopy of whole tissues and frozen sections revealed a strong reaction of the filaments with a monoclonal antibody prepared against porcine stomach desmin. In SDS-polyacrylamide gels of whole tube foot protein, a band of apparent molecular weight around 50 000 daltons reacted with the anti-desmin monoclonal antibody. The combined data provide evidence that the epidermal filament bundles are related to vertebrate intermediate filaments, but further biochemical studies will be necessary to assign them to a particular class of filament proteins.

Actins↗

Effect of streptozotocin-induced diabetes in neonatal rat on bile acid pool changes in adult life: selective sensitivity in females.

The effect of streptozotocin-induced diabetes in neonatal rat on the bile acid pool and composition during adult life was investigated. Unlike the effect of diabetes in adult rats (where bile acid pool increases markedly), neonatal diabetes caused a reduction in bile acid pool in adult life in females (but not in males) with significant reduction in both cholic and chenodeoxycholic acids. Upon challenge with dietary cholesterol, only the female diabetic rat responded with a further reduction in total bile acid pool. These studies demonstrate a selective sensitivity in the female diabetic rat with regard to diabetes-induced changes in bile acid pool.

Aging↗

A comparison of the short-term incorporation of erucic acid and oleic acid in the perfused guinea-pig heart.

A comparison was made of the incorporation of radioactive erucic acid and oleic acid in the isolated perfused guinea pig heart, 2, 15 and 30 min after a radioactive pulse. The complementary techniques of (a) freeze-clamping followed by lipid extraction and thin layer chromatography and (b) electron microscope autoradiography were used. The incorporation of 3H-erucic acid into esterified lipids was much slower than that of 3H-oleic acid. Less radioactive CO2 was produced by hearts perfused with 14C erucic acid then by hearts perfused with 14C oleic acid. There was no significant effect of erucic acid on the relative areas of subcellular organelles in the autoradiographs and, in particular, there was no increase in the volume of lipid droplets. However, the incorporation of radioactivity into lipid droplets was much greater with 3H-oleic acid than with 3H-erucic acid, consistent with the higher incorporation into tissue triacylglycerol. Although oxidized less than oleic acid, erucic acid was readily transported to the mitochondria. High levels of radioactivity in free fatty acid in the hearts perfused with erucic acid suggest that a low rate of activation of the fatty acid to acyl-CoA limits both oxidation and the formation of triacylglycerol. Electron microscopy of the hearts perfused with erucic acid revealed a widespread, and quantitatively demonstrable general movement of lipid droplets towards the surface of the cell. This was occasionally accompanied by a local rupturing of the sarcolemma, possibly prior to expulsion of the lipid droplet from the cell.

Animals↗

Incorporation and distribution of 3H oleic acid in the isolated, perfused guinea-pig heart made hypoxic.

Improved methods of autoradiography and lipid extraction have been used to study the influence of hypoxia on the fate of radioactive fatty acids in the isolated guinea pig heart. Evidence is provided that hypoxia causes a shift of the rate-limiting step from transport into the cell to oxidation in the mitochondria. This leads to an increased radioactivity in myocardial free fatty acid and in the cytosol. Radioactivity in the mitochondria is decreased and disappears more slowly. At the same time, there is an increased radioactivity in lipid droplets and in triacylglycerol. There is no evidence of a specific location of radioactivity in the sacroplasmic reticulum.

Animals↗

The relevance of socio-demographic and resource factors in the use of acute psychiatric in-patient care in the Atlantic Provinces of Canada.

This study assessed the inter-relations of socio-demographic, resource and policy factors with standardized measures of short-term psychiatric bed-use in 42 counties of Atlantic Canada. The policy factor made up two-thirds of the total variability (61%) accounted for among males, and nearly one-half of the 47% accounted for among females. An accurate assessment of in-patient resource needs is seen as resulting from intertwining morbidity surveys with utilization studies.

Bed Occupancy↗

Factors affecting the apparent regrowth of Pseudomonas aeruginosa following exposure to bactericidal concentrations of carbenicillin.

Factors have been identified which are responsible for the phenomenon already reported in which regrowth of Pseudomonas aeruginosa was found to occur in broth cultures containing bactericidal concentrations of carbenicillin. In cultures incubated under stationary conditions, in a water bath, the factor primarily responsible for this phenomenon of regrowth appears to be the formation of condensate on the inside of the culture vessel. In such condensate, viable cells of P. aeruginosa were found in numbers equal or higher than those in the culture broth. As a result of coalescing, and running down the vessel wall, the condensate provides a continuous reintroduction of bacteria into the culture medium, and, notwithstanding a bactericidal concentration of antibiotic in the medium, this process of continual reinoculation leads to the formation of visible growth and an increase in the viable count in the culture medium after an initial bactericidal effect. In silicone-treated flasks, incubated in a water bath, regrowth did not occur. Under such conditions, condensate again formed, but only as discrete droplets on a non-wetting surface, and in such condensate the bacterial count was found to be low. In flasks incubated in an air incubator, condensate did not form, and under these conditions the phenomenon of regrowth was not observed.

Carbenicillin↗

Open trial of S-adenosylmethionine for treatment of depression.

Nine depressed inpatients completed trials with S-adenosylmethionine. Seven showed improvement or remission of their symptoms. As in European studies, no side effects were seen except the apparent induction of mania in two patients with bipolar disorder.

Adult↗

Isolation of a series of HLA class I clones from a human chromosome 6 genomic library.

Human metaphase chromosomes were fractionated by a fluorescent-activated cell sorter (FACS II) and the chromosome 6 fraction was sorted. A genomic library was constructed in lambda gtWES cloning arms using a partial EcoRI digest of the chromosomal DNA. We estimate that at least 60% of our library represents chromosome 6 material, and as 1.2 x 10(5) recombinants were obtained, this indicates that the majority of clonable chromosome 6 sequences are represented. The library was screened with a mouse H-2 class I clone and 18 HLA class I recombinants were isolated from 4 x 10(4) plaques.

Cell Fractionation↗

Caffeine-induced monaster cycling in fertilized eggs of the sea urchin Strongylocentrotus purpuratus.

Caffeine has several highly visible effects on mitosis in eggs of the sea urchin Strongylocentrotus purpuratus. It increases the cell cycle length in a dose-dependent manner and at a concentration between 5 and 10 mM it prevents the normal separation and function of the mitotic centers, resulting in periodic monaster formation rather than division. If fertilized eggs are placed in seawater containing 10 mM caffeine at prometaphase, the spindle rapidly shrinks, moving the mitotic centers to the middle of the metaphase plate in less than 10 min. Within 30 min the eggs recover their ability to polymerize microtubules to form a large monaster, and from this time on they continue to cycle monasters in the presence of caffeine, with a period of about 150 min, where the normal second division time is 55 min. Other cell cycle functions, such as chromosome condensation, nuclear membrane breakdown and reformation, attempted furrowing and surface membrane addition continue for at least several cycles, but at the slower rate. Although the evidence strongly suggests that the rapid breakdown of the prometaphase spindle results from a calcium release induced by caffeine, these experiments do not rule out other physiological effects of caffeine on the longer-term changes in cycle length, centriole function, and ultimately on cell survival.

Animals↗

Vasomotor responses recorded using the in situ perfusion of a portion of the rat cerebral circulation.

A simple method whereby an area of the rat cerebral circulation can be perfused in situ in the dead animal has been developed. A modified Krebs/Henseleit perfusate was passed at a constant flow rate through one internal carotid artery and recovered from the transverse sinus following ligature of the arterial system of the opposite side and all venous returns to the heart. Rubber latex injections indicated that the main perfusion pathway was unilateral via the middle, anterior, and posterior cerebral arteries. The basilar and cerebellar arteries were not involved. Vasoconstrictor substances, such as 5-hydroxytryptamine (5HT), noradrenaline, and related catecholamines, gave reproducible, dose-related responses, when tested over experimental periods of 4-5 hrs. Although the preparation had no intrinsic vascular tone, vasodilator substances, such as acetylcholine, isoprenaline, histamine, or the purines, adenosine, ATP, ADP, and AMP, could be tested against various levels of tone induced by the addition of 5HT to the perfusate. On the basis of these preliminary results, the preparation appears suitable for qualitative and quantitative investigations of the responses of the rat cerebral circulation to a wide range of vasoactive substances.

Animals↗