Search PubMed⌕ Search

Biomedical subjects

G J Cooper

Publications and source records attributed to G J Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1995

Changes in gastric tissue oxygenation during mobilisation for oesophageal replacement.

We have measured changes in gastric tissue oxygen tension (PtO2, mmHg), with a modified Clark oxygen electrode, in eight patients (median age 59 years, range 52 to 74) undergoing oesophagectomy for carcinoma. Operations were performed with a cervical anastomosis and the stomach mobilised on the right gastric and gastroepiploic arteries. Tissue oxygen tension was measured in the gastric fundus at 4 points: (1) before mobilisation, (2) after mobilisation with the stomach in the abdomen, (3) with the fundus lifted to the neck and (4) after anastomosis. From a mean of 77 mmHg before mobilisation, PtO2 was halved to 36 mmHg after mobilisation with no further fall after transposition to the neck or anastomosis. Arterial oxygen concentration (PaO2), mean arterial pressure (MAP) and oxygen delivery (DO2) were similar at each point. Tissue oxygen tension was correlated with PAO2 at points 1 and 4 but MAP only at point 1 and DO2 not at all. These findings document the relationship of gastric PtO2 to mobilisation of the stomach and demonstrate the important influence of PaO2 on PtO2.

Aged↗
PubMed1995

A right ventricular hemopump restores right ventricular function with pulmonary artery banding.

We investigated the ability of the Hemopump to support the right ventricle during acute, partial, pulmonary artery obstruction. In 6 pigs, a 14 Fr size Hemopump was placed through the pulmonary artery into the right ventricle. Control measurements were made. A band around the pulmonary artery proximal to the outflow port of the Hemopump was tightened, and measurements were repeated with the Hemopump at minimum and then maximum speed. With banding, right ventricular stroke volume and output decreased (43 [SD, 7] to 28 [SD, 8] ml, p < 0.001; 4.9 [SD, 0.8] to 3.7 [SD, 1.0] L/min, p < 0.01 respectively), but they were restored with the Hemopump (38 [SD, 5] ml and 4.5 [SD, 0.6] L/min; both p = NS vs control). Increases in right ventricular peak systolic (28 [SD, 10] to 42 [SD, 17] mm Hg; p < 0.01) and end-diastolic pressure (2 [SD, 1] to 12 [SD, 6] mm Hg; p < 0.02) were reversed by the Hemopump (29 [SD, 8] and 4 [SD, 2] mm Hg; both p = NS vs control). Right ventricular pressure rate product almost doubled with banding (3,199 [SD, 1,252] to 5,962 [SD, 2,796] mm Hg; p < 0.01), but it decreased with the Hemopump (3,368 [SD, 767] mm Hg; p = NS vs control). With acute partial pulmonary artery banding, a right ventricular Hemopump restores output from and offloads the right ventricle.

Animals↗
PubMed1995

Right ventricular failure in patients requiring left ventricular assistance.

Right ventricular failure may complicate isolated left ventricular assistance. In a series of 8 patients undergoing left ventricular assistance in postcardiotomy cardiogenic shock, right ventricular failure developed in 5, directly contributing to death in all cases despite initially satisfactory support. Difficulty in grafting a dominant right coronary artery was a common factor in all cases. Early consideration should be given to biventricular support under these circumstances.

Aged↗
PubMed1995

The cerebral function monitor (CFM) is a useful addition to a bilateral carotid artery, vein graft model.

Following human coronary artery bypass surgery, vein graft occlusion is a major cause of morbidity and mortality. An agent is required which will reduce the incidence of early graft thrombosis without causing systemic bleeding. To assess the efficacy of such agents a suitable experimental vein-graft model is required. A porcine, unilateral saphenous vein-carotid artery bypass graft model has been described previously, although to assess the effect of locally applied anticoagulant drugs, insertion of grafts bilaterally would be advantageous, allowing treated and control grafts to be implanted in the same animal which would then act as its own control. Pigs are reported as having an excellent collateral cerebral circulation and hence in theory, would be suitable animals to use as a bilateral carotid vein-graft model. This paper describes the occurrence of serious neurological complications during the development of such a model and suggests that by using a cerebral function monitor, detection of critical reductions in cerebral perfusion can be made early and remedial action take.

Animals↗
PubMed1995

Management of small fragment wounds in war: current research.

The majority of war wounds are caused by antipersonnel fragments from munitions such as mortars and bomblets. Modern munitions aim to incapacitate soldiers with multiple wounds from very small fragments of low available kinetic energy. Many of these fragments may be stopped by helmets and body armour and this has led to a predominance of multiple wounds to limbs in those casualties requiring surgery. The development of an appropriate management strategy for these multiple wounds requires knowledge of the contamination and extent of soft tissue injury; conservative management may be appropriate. The extent of skin and muscle damage associated with a small fragment wound, the way in which these wounds may progress without intervention and their colonisation by bacteria has been determined in an experimental animal model. Results from 12 animals are presented. There was a very small (approximately 1 mm) margin of nonviable skin around the entrance wound. The amount of devitalised muscle in the wound tract was a few hundred milligrams. Some muscles peripheral to the wound track also showed signs of damage 1 h after wounding, but this improved over 24 h; the proportion of fragmented muscle fibres in the tissue around the track decreased as time went on. There was no clinical sign or bacteriological evidence of the track becoming infected up to 24 h after wounding. This preliminary work suggests that, in the absence of infection, the amount of muscle damage caused by small fragment wounds begins to resolve in the first 24 h after injury, even without surgical intervention.

Animals↗
PubMed1994

Na(+)-H+ exchange in frog early distal tubule: effect of aldosterone on the set-point.

1. Intracellular pH (pHi) regulation was investigated in frog early distal tubule. Single tubules were dissected and perfused, such that the compositions of apical and basolateral solutions could be varied independently. pHi was measured using the fluorescent probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF). 2. Brief exposure to NH4+ on the basolateral aspect of the tubules elicited an intracellular acidification, followed by an active recovery. The recovery was inhibited by amiloride and its analogue 5-(N-ethyl-N-isopropyl) amiloride (EIPA) when added to the basolateral, but not the apical, solution. Omission of Na+ from the basolateral solution alone completely inhibited pHi recovery. Thus the Na(+)-H+ exchangers appear to be located on the basolateral membrane. 3. Neither amiloride nor EIPA had any effect on pHi under control conditions, suggesting that the activity of the Na(+)-H+ exchangers at the resting pHi is low. However, removal of basolateral Na+ caused an acidification that was blocked by amiloride, indicating that the Na(+)-H+ exchangers can be activated from the resting state. 4. Intrinsic buffering power (beta i) was determined by stepwise removal of ammonium from the cells in Na(+)-free conditions, to prevent pH regulation, and in the presence of Ba2+ and furosemide (frusemide), to inhibit ammonium transport. beta i was a function of pHi, increasing as pHi decreased. 5. Proton efflux was calculated during the recovery from an acid load in tubules from normal and K(+)-loaded frogs and in tubules which had been incubated for 30 min with aldosterone. Potassium loading produces a chronic increase in plasma aldosterone. Both acute and chronic aldosterone treatment caused an intracellular alkalinization. This was due to an alkaline shift in the set-point of the basolateral Na(+)-H+ exchanger, with no change in the density and/or turnover rate.

Aldosterone↗
PubMed1994

Experimental experience with a temporary intraluminal heparin-bonded polyurethane arterial shunt.

After vascular injury, intraluminal arterial shunting may be employed if definitive surgery must be delayed. This paper describes use of a heparin-bonded polyurethane shunt to restore distal circulation after ligation of the femoral artery in sheep. In studies to determine tissue viability for 12 h after insertion into the femoral artery, five of seven shunts remained patent. In another series of experiments to study tissue viability after limb ischaemia, the femoral artery was ligated and a tight Esmarch bandage applied to the limb for 6 h before shunt insertion. The shunt remained patent for 12 h in five of six cases. Nearly all shunt failures occurred shortly after placement and were attributable to intimal damage arising from difficulties during insertion.

Anastomosis, Surgical↗
PubMed1994

Pattern of injury in those dying from traumatic amputation caused by bomb blast.

Traumatic amputation of limbs caused by bomb blast carries a high risk of mortality. This paper describes 73 amputations in 34 deaths from bomb blast in Northern Ireland. The principal aim was to determine the sites of traumatic amputation to provide a biophysical basis for the development of protective measures. Few amputations were through joints; nearly all were through the bone shafts. The most common site in the tibia was the upper third. The distribution of femoral sites resulting from car bombs differed from that characterizing other types of explosion. For car bombs the principal site of amputation was the upper third; for other types of device it was the lower third. It is concluded that flailing is not a notable contributor to limb avulsion. The pattern of amputation is consistent with direct local pressure loads leading to bone fracture; the amputation itself is a secondary event arising from the flow of combustion products.

Amputation, Traumatic↗
PubMed1994

The surgical management in war of penetrating wounds contaminated with chemical warfare agents.

Military surgeons in a future conflict may face the problem of wounds contaminated with chemical warfare (CW) agents. No useful guidelines for this eventuality exist-nor any assessment of the specific CW risk to such casualties or to the surgical teams operating on them. The principal hazard to surgeons is direct contact with contaminated clothing in the wound. Practices are recommended to reduce this threat significantly. Thorough wound excision augmented by lavage with a specific proprietary hypochlorite solution will provide effective wound decontamination without producing unacceptable tissue damage. The vapour hazard at surgery is very low-respirators are unnecessary but goggles or glasses should be worn to prevent conjunctival splashes of potentially contaminated body fluids.

Chemical Warfare Agents↗
PubMed1994

Right heart function during left ventricular assistance in an open-chest porcine model of acute right heart failure.

Changes in the right ventricular function measured with a thermodilution ejection fraction catheter have been recorded in open-chest normal pigs and pigs with acute right heart failure (RVF) undergoing left ventricular assistance with a pneumatic-sac-type device (LVAD). To produce acute right heart failure, 5 pigs underwent ligation of the right ventricular free wall coronary arteries. Compared with normal pigs, cardiac output in ligated pigs fell by 21% (7.5 +/- 0.5 vs 9.5 +/- 1.2 L/min; p < 0.05) and the right ventricular end diastolic pressure rose (11.4 +/- 2.6 vs 5.7 +/- 3.6 vs mmHg: p < 0.05). With the left ventricular assist device connected, the right atrial pressure was increased to 3, 5, 7, 10 and 12 mmHg by volume loading while maintaining the haematocrit at 35 +/- 6%. The right ventricular stroke work index (RVSWI) increased with volume loading in normal pigs. In RVF pigs, RVSWI increased significantly with the LVAD (59.2 +/- 5.8 vs 23.5 +/- 7.8 mmHg ml/min/kg, p < 0.01), approaching that of normal pigs (62.3 +/- 4.8 mmHg ml/min/kg). Similar changes were observed in the cardiac output and right ventricular stroke volume. These results show that, in this model of open-chest, mild, acute right heart failure, left ventricular assistance allows right ventricular function to return to normal, despite volume overloading, by decreasing right ventricular after load and increasing right ventricular compliance.

Acute Disease↗
PubMed1993

Response to intravenous injections of amylin and glucagon in fasted, fed, and hypoglycemic rats.

The actions of intravenous glucagon and amylin, a newly discovered hyperglycemic pancreatic islet hormone, have been compared in 20-h fasted and fed, lightly anesthetized rats, and in rats made hypoglycemic with an insulin infusion. In fasted animals, amylin (75 nmol/kg) was more effective than glucagon (90 nmol/kg) in increasing plasma glucose (glucose increment 4.55 vs. 1.71 mM, P < 0.001). Amylin elicited a marked increase in plasma lactate, as previously reported, whereas glucagon did not alter plasma lactate. In fed animals, glucagon elicited twice as much increase in plasma glucose as did amylin; amylin again elicited a marked lactate increase that was greater (increment 1.45 vs. 0.97 mM, P < 0.05) and more prolonged than in the fasted state, whereas glucagon was without effect on lactate levels. These findings are consistent with glucagon's known action to promote hyperglycemia from hepatic glycogenolysis and amylin's demonstrated action to promote muscle glycogenolysis and increase lactate supply to the liver. Infusions of sodium lactate that produced plasma lactate increments similar to those evoked by 75 nmol/kg amylin evoked patterns of glucose response in fasted and fed rats similar to those evoked by amylin. Thus increased lactate supply to the liver may account for amylin's hyperglycemic effects. Amylin and glucagon could each restore plasma glucose to control levels in fasted animals made hypoglycemic by insulin infusion (plasma glucose reduced to 3.3 mM). A bolus of 75 nmol/kg amylin was more effective than 180 nmol/kg glucagon, restoring basal glucose levels for > 3 h, whereas glucagon restored it for < 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid↗
PubMed1993

Circulating insulin levels are related to bone density in normal postmenopausal women.

We recently established that the dependence of bone mineral density (BMD) on body weight in women is mainly attributable to a close relationship between total body fat mass and BMD. The present study assesses whether this latter relationship might be contributed to by the hormones insulin or amylin, both of which may influence fat mass and calcium metabolism. Fifty-three normal postmenopausal women underwent a 75-g glucose tolerance test with measurement of plasma insulin and amylin concentrations every 30 min for 2 h. Body composition and BMD/height (to provide a quantity with the dimensions of volumetric density that is independent of body size) were measured by dual-energy X-ray absorptiometry, and volumetric density of the third lumbar vertebral body was calculated. Circulating insulin concentrations correlated with BMD/height and volumetric density of the third lumbar vertebral body (r = 0.28-0.52). They also were related to body weight (r = 0.34-0.56) and fat mass (r = 0.38-0.56) but were not independently related to lean mass on multiple regression. There were no consistent relationships between amylin levels and these variables. Multiple-regression analyses with fat mass and insulin levels as independent variables indicated that BMD/height of total body and femoral trochanter were primarily related to fat mass, whereas, in femoral neck, the significant relationship was with insulin. Volumetric density of the third lumbar vertebral body was related to insulin levels alone on this analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

The ultrastructure of rat lung following acute primary blast injury.

While a number of workers have described the effects of blast waves upon the lung at both the macroscopic and light microscopic level, studies involving the use of the electron microscope have not been reported. In the experiments reported here the ultrastructural changes seen in lungs from rats exposed to a blast wave impacting on the right side of the chest are described. Considerable damage to the right lower lobe was observed which took the form of tearing of the inter-alveolar septa with capillary rupture and intra-alveolar haemorrhage. Changes to the alveolar epithelium and type II pneumocytes were also noted. Lesions were also identified in the left lung; these included intra-alveolar oedema with a minimal amount of interstitial oedema together with increased pinocytosis and isolated rupture of the alveolar epithelium. 'Ballooning' of the endothelium into the lumen of the capillary was also observed. There was an indication that lesions noted in the left lung at the electron microscopic level may be progressive in the first 24 hours following injury.

Animals↗
PubMed1992

Nucleotide sequence of a cDNA for canine amylin.

Canine amylin cDNA was cloned and sequenced from a dog pancreas library using oligonucleotide probes corresponding to portions of human amylin. The sequence reported here is significantly different from an incomplete sequence previously reported. The non-amyloidogenic canine mature peptide is 89% and 95% identical to its amyloidogenic human and cat homologues, respectively. Both the dog and cat peptides are identical over the proposed amyloidogenic region, amino acids 20-29. Hydropathy plots comparing these three peptides are nearly identical suggesting that the primary sequence of amylin is in itself insufficient to explain pancreatic amyloid formation.

Amino Acid Sequence↗