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Biomedical subjects

N Harrison

Publications and source records attributed to N Harrison.

At least 37 records · Page 2Linked to original sources
PubMed1995

A 31P NMR investigation into the effects of repeated vascular occlusion on uterine metabolites, intracellular pH and force, in vivo.

Little is known about the metabolic effects of ischaemia on high energy phosphates in vivo in smooth muscle. We have developed a method for reversibly occluding the uterine artery, which allows simultaneous measurement of uterine metabolites using 31P NMR spectroscopy, and intra-uterine pressure, in vivo during ischaemia. We have investigated the effects of repeated ischaemia on metabolites, intracellular pH and contractions in anaesthetized rats. Occlusion produced an immediate drop in uterine blood flow and decreased contractions. Although contractions recovered upon reperfusion after both occlusions, the contractile activity was less after the second period of occlusion, suggesting less resistance after a prior ischaemic period. Significant falls in [ATP] and [phosphocreatine] and an increase in [P(i)] occurred during both occlusions. These were all reversed within 30 min of reperfusion. There was a large drop in intracellular pH produced by occlusion, which was rapidly reversed upon reperfusion. The changes in metabolites and intracellular pH were similar during the repeated ischaemic period, to those occurring during the first ischaemic period suggesting no alteration in energy production or utilization had occurred, with prior exposure to ischaemia. The significance of these results to the functioning of the uterus in labour is briefly discussed.

Adenosine Triphosphate↗
PubMed1995

Using humour as an educational technique.

Humour can be constructive or destructive, so needs to be used selectively and sensitively. Teachers require training to acquire the appropriate level of self-awareness, knowledge and skills. Educational humour needs monitoring and evaluation.

Education, Nursing↗
PubMed1994

An in vivo study of the effects of ischaemia on uterine contraction, intracellular pH and metabolites in the rat.

There are no data concerning the functional or metabolic effects of hypoxia in vivo in smooth muscle. We have therefore used 31P-NMR spectroscopy and intra-uterine pressure measurements to examine simultaneously, in vivo, the effect of ischaemia on uterine metabolites, intracellular pH (pHi) and force. A 1-2 cm portion of uterus from day 1 postpartum anaesthetized rats was exteriorized and an NMR surface coil placed on it. A balloon catheter in the uterine lumen recorded intra-uterine pressure changes from the same area. Reversible occluders were placed around the uterine artery. Occlusion produced a decrease and then abolition of contractions, within 10 min. In four of five animals contraction was abolished within 2 min. Upon reperfusion force was rapidly restored (1 min), in all preparations. The mean level of force was significantly above control (pre-occlusion) 20-30 min after reperfusion. The NMR data showed a significant fall in [ATP] (28%) and [phosphocreatine] (34%) during occlusion. Inorganic phosphate doubled in concentration during this period. Metabolites recovered slowly upon reperfusion, taking 20-30 min to return to pre-occlusion levels. The mean pHi fell from 7.32 to 7.00 upon occlusion and was rapidly reversed upon reperfusion. The changes in pHi closely correlated with the changes in uterine force. Decreases of pHi of a similar magnitude in vitro have previously been shown to abolish contractions; thus it is suggested that during ischaemia in vivo the depression of contraction is caused by the large fall in pHi.

Animals↗
PubMed1994

Seasonal variation in heavy metal levels in tissues of common guillemots, Uria aalge from northwest Scotland.

Mercury, cadmium, zinc, and copper concentrations were analyzed in three samples of common guillemot (in April, June, and November). Levels measured were uniformly low, and not enough to have any toxic effects. Adult guillemots had significantly more cadmium in their livers and kidneys than juveniles, with juvenile levels ranging from 25% to 89% of adult levels. Mercury concentrations in liver and kidney were also higher in adults. Juvenile levels represented from 80% to 94% of adults, but there were no age differences in feather and muscle mercury. Mercury levels declined throughout the year in internal tissues from April through June to November. There was a strong seasonal fluctuation in cadmium levels in liver and kidney, rising significantly between April and June and declining in both adult and juvenile birds. The influences of seasonal processes (namely breeding and moult) and seasonal dietary differences as causative factors in the changes in metal burdens are discussed. These findings have implications for the use of seabirds as monitors of heavy metals in the marine environment.

Animals↗
PubMed1994

Phylogenetic relationships among members of the class Mollicutes deduced from rps3 gene sequences.

A gene for a ribosomal protein, rps3, was amplified by PCR and sequenced from representatives of the class Mollicutes. Alignments of the deduced amino acid sequences allowed the construction of a phylogeny that is consistent with the phylogenetic trees created from 5S and 16S rRNA comparisons, including the position of the former Acholeplasma florum on the Mycoplasma branch, rather than with the classical Acholeplasmataceae. Additional confirmation of the phylogeny comes from the deduction that the UGA triplet encodes tryptophan in the rps3 gene from Mesoplasma florum, as it does in the mycoplasmas and spiroplasmas. The sequence data from Acholeplasma axanthum 743 and Acholeplasma sp. strain J233 allow refinements to the phylogenetic tree within the Acholeplasmataceae, providing evidence that the sterol requirement of Anaeroplasma abactoclasticum (order Anaeroplasmatales) is a derived trait. It was also evident that the nonhelical plant-pathogenic members of the class Mollicutes, referred to as mycoplasma-like organisms or phytoplasmas, are more closely related to the true acholeplasmas (Acholeplasma laidlawii and strain J233) than to other members of the Mollicutes.

Amino Acid Sequence↗
PubMed1993

Chronic antagonist treatment does not alter the mode of interaction of dopamine with rat striatal dopamine receptors.

Chronic treatment with the D1 and D2 dopamine receptor antagonists SCH 23390 (0.5 mg/kg) and haloperidol decanoate (25 mg/kg) caused an up-regulation in D1 and D2 receptor densities, respectively, with no change in KD. Dopamine (20 microM) interacted with both receptor subtypes in a mixed competitive/non-competitive manner, causing a reduction in ligand binding affinity and an apparent decrease in receptor density. In the presence of dopamine, both vehicle-treated and SCH 23390-treated striatal preparations showed a significant loss in affinity for 3H-SCH 23390 binding to D1 receptors and a decrease in D1 receptor density of approximately 26%. Similarly, dopamine caused a substantial loss in 3H-spiperone binding affinity to D2 receptors and a 46% decrease in Bmax in both vehicle-treated and haloperidol-treated membranes. Thus, receptor up-regulation does not appear to alter the mode of interaction of dopamine with rat striatal dopamine receptors.

Animals↗
PubMed1993

Comparison of the quality of patient data collected by hospital and departmental computer systems.

The quality of patient data routinely collected in hospitals is rarely assessed, though by repute it may often be incomplete and inaccurate. To explore their completeness and accuracy, patient data separately collected by a hospital Patient Administration System (PAS) and by a departmental Clinical Information System (CIS) used by clinicians were compared. The results indicate that, although both systems appear to record reliably demographic and administrative data, PAS data are more complete than CIS data. Moreover clinicians and medical records staff seem to use classifications of diagnoses and procedures in profoundly different ways. More attention should be paid to the need to assess and improve data quality. The development of a shared database, used and validated by medical records staff and clinicians alike, may be the best way to achieve this.

Abstracting and Indexing↗
PubMed1992

Appropriate use of local anaesthetic for venous cannulation.

A departmental survey indicated that the large majority of anaesthetists believed that injection of local anaesthetic before insertion of an intravenous cannula was unnecessary if a cannula of 18 gauge or smaller was used, because injection of local anaesthetic would be more painful than insertion of the cannula. A study was undertaken to test this hypothesis. The results showed that intravenous cannulation with a cannula of 18, 20 or 22 gauge was significantly (p less than 0.006) more painful than a subcutaneous injection of 1% lignocaine. We recommend that subcutaneous injection of local anaesthetic should be considered before insertion of any size of intravenous cannula.

Adult↗
PubMed1991

Mandible reconstruction with vascularized bone grafts. A histologic evaluation.

To our knowledge, a histologic evaluation of bone healing after mandible reconstruction with vascularized human bone grafts has not been previously reported. Serial sections through both the decalcified graft and the junction between mandible and graft were evaluated in four patients who required surgical removal of their reconstructed mandibles. A failed scapular bone graft that had been wrapped within a pectoralis major myocutaneous flap for salvage following pedicle thrombosis showed markedly resorbed but viable bone with a fibrous union to the native mandible. Viable vascularized grafts without evidence of ongoing resorption characterized an iliac osteocutaneous bone graft and two scapula osteocutaneous grafts that healed with continuity of healthy bone between graft and mandible. Observations from the evaluation of these specimens are made regarding bone circulation, bone union, and bone graft survival as they occur clinically. Implications regarding the techniques of bone plating and indications for use of vascularized bone in mandible reconstruction are discussed.

Bone Transplantation↗
PubMed1990

Cardiopulmonary effects of a brief exposure to cigarette smoke in the guinea pig.

To investigate whether the acute inflammatory response produced by acute cigarette smoke exposure is associated with alterations in pulmonary and cardiovascular function, using a respirator we exposed 8 guinea pigs to 350 ml of cigarette smoke diluted in 2,000 ml room air for 10 min. Lung volumes, pressure volume curves and flow volume curves were performed. Measurements of pulmonary artery pressure, systemic pressure, heart rate and cardiac output were taken at baseline, immediately after the smoke exposure, and 1.5 h after smoke exposure. Aliquots of peripheral blood for total white cell count and differential count were obtained. After animal sacrifice, the right lung was lavaged and white cell count and differential count performed. We found that acute exposure to cigarette smoke produced a peripheral blood neutrophilia which rose progressively from a baseline of 36.3 +/- 8% to a maximum of 72.2 +/- 7.7% at 1.5 h after exposure. There was pulmonary neutrophilia with 24.6 +/- 6.3% neutrophils in the lavage fluid of the smoke-exposed animals compared to 8.4 +/- 4.3% in the control animals. Immediately after smoke exposure, there was acute airflow obstruction with a decrease in the peak flow and forced expiratory flow between 25-75% vital capacity. This was associated with airtrapping, as shown by a transient increase in residual volume. There was a slight decrease in systemic blood pressure in the smoke-exposed animals associated with a nonsignificant decrease in the heart rate, and the cardiac output remained stable.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗