Development of an evidence-based swimming representative military task to assess swimming competency in the British Army.

BACKGROUND: There is a requirement for British Army personnel to operate in/around water. Assessing role-related swimming/water competence will support personnel to conduct their job-roles safely and effectively. OBJECTIVE: To undertake a Job-Task Analysis (JTA) of British Army personnel when working in/around water and use this information to develop a Swimming Representative Military Task (RMT) to assess swimming/water competence. METHODS: Workshops, surveys, and observations were used to conduct a JTA, which identified and described job-tasks conducted by British Army personnel in/around water. Ergonomic analysis of these job-tasks identified seven water-based physical actions, which were considered fundamental for all personnel to be competent in performing. These seven actions guided design of a Swimming RMT, which was subsequently conducted twice by 103 serving personnel (89 men, 11 women) and once by 65 recruits (49 men, 16 women). RESULTS: The RMT comprised of entering the water in combat fatigues and webbing, removing webbing, swimming 50 m, and staying afloat for up to 10 minutes. During RMT trials, in trial 1, 85% of serving personnel and 74% of recruits successfully completed the RMT, which increased to 93% in serving personnel for trial 2. Across trials 1 and 2, all three timed RMT elements showed moderate-high correlational reliability (ICC range: 0.462-0.791). On average, serving personnel were quicker to complete the 50 m swim phase compared to recruits (91±24 s vs. 100±26 s; U = 2575.0, rb = -0.192, p = 0.039). CONCLUSIONS: The JTA-informed Swimming RMT provides an assessment of the minimum role-related swimming/water competence standard for British Army personnel.

Iatrogenic Phenol Injury Causing Facial Paralysis With Tympanic Membrane and Ossicular Necrosis.

OBJECTIVE: To describe a serious iatrogenic injury and propose means of reducing the risk of its reoccurrence. PATIENTS: A 21-year-old man who suffered facial paralysis, complete necrosis of the tympanic membrane, and ossicular discontinuity because of chemical burn from accidental application of copious amounts of topical anesthetic phenol into the ear. INTERVENTIONS: Conservative management of facial paralysis and delayed reconstruction of the tympanic membrane and ossicular chain. MAIN OUTCOME MEASURES: Gradual recovery to grade 1/6 facial function, successful repair of the tympanic membrane, but persistent 30-dB conductive hearing loss after partial ossicular replacement prosthesis presumably because of scarring. CONCLUSION: Phenol is a highly toxic chemical, topically to both skin and eyes. Absorbed through the skin it can have lethal cardiotoxicity. It is also potent neurotoxin at concentrations much lower (4-7%) than used for tympanic membrane anesthesia (89%) and has long been used therapeutically to destroy nerves in patients of contractions or intractable pain. Otologists need to have a healthy respect for the dangers of using phenol. As only a minute quantity is needed for tympanic anesthesia, commercially available prepackaged applicators are preferred. Storage of stock bottles of 89% phenol solutions in clinical settings risks injury to both patients and practitioners.

Hyperammonaemia reduces intracellular 22Na (sodium) ion and extracellular 86Rb ion concentrations in the blood-brain barrier of the rat.

Ammonia may be the major cerebral intoxicant responsible for the increased general or passive permeability of the blood-brain barrier (BBB) leading to the cerebral edema associated with acute liver failure. The present study investigated the effects of ammonia, as NH4+, on Na+ (22Na), K+ (86Rb), and 14C-mannitol uptake in the BBB. An in situ isolated perfused rat brain preparation was used to study the action of 1 mM ammonium acetate in Krebs'-Ringer perfusate. Passive water transport in the brain was studied by 14C-labeled mannitol uptake, a usually nondiffusible marker and active water transport by 22Na and 86Rb uptake. NH4+ significantly reduced 14C-mannitol uptake into the choroid plexus (P < 0.001) and increased it in the CSF (P < 0.05). Decreased 86Rb was measured in whole brain (P < 0.01) and CSF. However, no effect was observed in brain parenchyma, endothelium or choroid plexus thereby suggesting an increased efflux of 86Rb to the interstitial fluid. NH+ increased Na+ uptake into all areas of the brain studied. NH4+ does not increase the passive permeability into the BBB and was decreased in the choroid plexus. The increased 22Na+ uptake was substantiated by the observed decreases in 86Rb uptake in whole brain and CSF. This suggested NH4+ stimulates the Na+/K+ pump and increases extracellular Na+ concentrations and possibly intracellular concentrations with a concomitant decrease in K+ concentrations. These observations may provide a basis for the explanation of NH+ toxicity during hepatic encephalopathy and liver failure-induced cerebral edema.

Hepato-cardiovascular response and its regulation.

AIM: To determine the possible existence of a hepato-cardiovascular response and its regulatory mechanism in normal rats. METHODS: Systemic hemodynamic changes following intraportal injection of latex microspheres were studied in two modified rat models of hepatic circulation, in which the extrahepatic splanchnic circulation was excluded by evisceration and the liver was perfused by systemic blood via either the portal vein (model 1) or hepatic artery (model 2) in vivo. RESULTS: In model 1, intraportal injection of two sized microspheres (15-mum and 80-mum) induced a similar decrease in mean arterial pressure, while extrahepatic portal venous occlusion induced an immediate increase in mean arterial pressure. In model 2, microsphere injection again induced a significant reduction in mean arterial pressure, aortic blood flow and aortic resistance. There were no significant differences in these parameters between liver-innervated rats and liver-denervated rats. The degrees of microsphere-induced reduction in mean arterial pressure (-38.1+/-1.9% in liver-innervated rats and -35.4+/-2.1% in liver-denervated rats, respectively) were similar to those obtained by withdrawal of 2.0 mL of blood via the jugular vein (-33.3+/-2.1%) (P>0.05). Injection of 2.0 mL Haemaccel in microsphere-treated rats, to compensate for the reduced effective circulating blood volume, led to a hyperdynamic state which, as compared with basal values and unlike control rats, was characterised by increased aortic blood flow (+21.6+/-3.3%), decreased aortic resistance (-38.1+/-3.5%) and reduced mean arterial pressure (-9.7+/-2.8%). CONCLUSION: A hepato-cardiovascular response exists in normal rats. It acts through a humoral mechanism leading to systemic vasodilatation, and may be involved in the hemodynamic disturbances associated with acute and chronic liver diseases.

Development of bladder urothelial hyperplasia and carcinoma in portacaval shunted rats is not dependent upon urolithiasis.

The pathogenesis of bladder tumors is poorly understood, possibly due to the lack of a suitable experimental model that is drug-free. The aim of the present study was to determine whether bladder tumors could be reproduced reliably in portacaval anastomosis (PCS) rats and whether induction is due to urolithiasis from the development of bladder stones. Eighteen male Sprague-Dawley rats were anaesthetised with isoflurane. Twelve were subjected to portacaval anastomosis and allowed to recover for 38 weeks and the remaining 6 underwent sham control procedures. They were then re-anaesthetised, the anastomosis checked for patency and the bladders and livers excised, fixed, block-mounted, sectioned and stained with haematoxylin and eosin staining for histological examination. None of the control rats developed bladder wall abnormalities of any recognisable nature. However, 5 (42%) of the PCS group had urothelial lesions and bladder stones present and a further 5 (42%) had urothelial lesions alone with no recognisable evidence of bladder stone formation. One PCS rat had bladder stones alone and the remaining PCS rat had an apparently normal bladder epithelium and no stones. Thus, 10 (83%) of the 12 PCS rats developed epithelial lesions and half of these did not display evidence of bladder stone formation. This represented a highly significant difference between the development of bladder stones and the occurrence of urothelial lesions in PCS rats (P > 1.0, chi(2) analysis). Urothelial lesions, therefore, can be reproduced in PCS rats. Their occurrence appears independent of bladder stone formation.

The effect of anticoagulation with subcutaneously delivered polyethylene glycol conjugated hirudin and recombinant tissue plasminogen activator on recurrent stenosis in the rabbit double-balloon injury model.

Myointimal hyperplasia is the condition usually responsible for recurrent stenosis (restenosis) after endarterectomy, bypass grafting and angioplasty. Its cause is still not known. The present study examined whether inhibition of thrombin by tissue plasminogen activator (r-TPA) or polyethylene glycol recombinant hirudin (PEG-hirudin) could reduce restenosis in an animal model. Restenosis was induced in 20 cholesterol-fed rabbits. The right carotid artery underwent a double-balloon injury while left carotid artery acted as a control. Recombinant tissue plasminogen activator (1 mg kg(-1) s.c.) and PEG-hirudin (0.7 mg kg(-1) s.c.) were given subcutaneously with normal saline acting as a control. Blood levels of PEG-hirudin were measured by both ELISA and an Ecarin (activity) assay. Vessel dimensions were measured in histological sections, obtained from perfusion-fixed tissue, using computerised planimetry. The model reproduced many of the histological changes found in human restenosis, such as intramural thrombus, rupture of the elastic lamina, macrophage infiltration and smooth muscle migration. Reinjury caused an almost three-fold reduction in the area of the lumen (median 0.25 mm(2)) compared with uninjured vessels (median 0.72 mm(2)). The mean plasma levels of PEG-hirudin and r-tPA achieved were 291 ng/ml (S.E.M. 28 ng/ml) and 34 IU/ml (S.E.M. 12 IU/ml), respectively. PEG-hirudin significantly inhibited the effect of balloon injury on luminal area compared with saline-treated controls (0.21 versus 0.44 mm(2), respectively, P<0.05). Recombinant tPA also had a similar inhibitory affect, but this did not reach statistical significance (0.16 versus 0.44 mm(2), respectively, P>0.05). The magnitude of luminal narrowing was significantly reduced by subcutaneous injection of PEG-hirudin. Further studies are required to determine whether this effect can be enhanced by other antithrombins or improved methods of delivery.

The role of ATP and adenosine in the control of hepatic blood flow in the rabbit liver in vivo.

BACKGROUND: The role of adenosine and ATP in the regulation of hepatic arterial blood flow in the "buffer response" was studied in vitro and in a new in vivo model in the rabbit. The model achieves portal-systemic diversion by insertion of a silicone rubber prosthesis between the portal vein and inferior vena cava and avoids alterations in systemic haemodynamics. RESULTS: Hepatic arterial (HA) blood flow increased in response to reduced portal venous (PV) blood flow, the "buffer response", from 19.4 (3.3) ml min-1 100 g-1 to 25.6 (4.3) ml min-1 100 g-1 (mean (SE), p < 0.05, Student's paired t-test). This represented a buffering capacity of 18.7 (5.2) %. Intra-portal injections of ATP or adenosine (1 micrograms kg-1-0.5 mg kg-1) elicited immediate increases in HA blood flow to give -log ED50 values of 2.0 and 1.7 mg kg-1 for ATP and adenosine respectively. Injection of ATP and adenosine had no measurable effect on PV flow. In vitro, using an isolated dual-perfused rabbit liver preparation, the addition of 8-phenyltheophylline (10 MicroMolar) to the HA and PV perfusate significantly inhibited the HA response to intra-arterial adenosine and to mid-range doses of intra-portal or intra-arterial ATP (p < 0.001). CONCLUSIONS: It is suggested that HA vasodilatation elicited by ATP may be partially mediated through activation of P1-purinoceptors following catabolism of ATP to adenosine.

The role of nitric oxide in systemic and hepatic haemodynamics in the rat in vivo.

The physiological role of nitric oxide (NO) in portal venous and hepatic arterial haemodynamics in the rat in vivo during healthy and diseased conditions remains unclear. The present study determined the physiological role of nitric oxide in hepatic haemodynamics in the rat in vivo during healthy conditions as a basis for future pharmacological work. Male Wistar rats (300-350 g) were anaesthetised with fentany/fluanisone (0.3 mg/kg s.c.) and midazolam (0.3 mg/kg s.c.) and heparinised (30 U/100 g i.v.) via a cannulated left carotid artery for measurement of heart rate, mean arterial pressure, and the difference between systolic and diastolic blood pressures (P(S-D)). Following laparotomy, two distal ileocolic veins were cannulated, one catheter introduced to a distance of 1 cm and used for intraportal drug injections and the other to the main trunk of the portal vein for continuous measurement of portal venous pressure. The portal venous trunk and hepatic artery were carefully isolated and electromagnetic probes placed around each of them for measurement of portal venous flow and hepatic arterial flow. Augmentation of NO production was achieved by intraportal injection of 0.2, 0.4, 0.6 and 0.8 g/kg L-arginine and the NO donor, 3-morpholinosydnonimine (SIN-1), was injected intraportally at 0.2, 0.4, 0.6 and 0.8 mg/kg. L-NAME, the non-selective NOS inhibitor, was injected intraportally in increasing doses of 5, 10, 15 and 20 mg/kg in the absence or presence of L-arginine in doses of 0.2 and 0.5 g/kg. L-arginine increased portal blood flow by 25% without significant changes in systemic haemodynamics. SIN-1 decreased mean arterial pressure by 33% with no effect on portal blood flow. Both L-arginine and SIN-1 reduced portal venous pressure by 25% in a dose-dependent manner. L-NAME had no effect on portal haemodynamics despite a significant increase in systemic arterial pressure of 60% that was reduced dose-dependently by L-arginine. Hepatic arterial flow increased by 88% and 49% at the second and third doses of L-arginine and by 68% and 27% at the first two doses of L-NAME. No significant changes in hepatic arterial flow were found when L-NAME and L-arginine were given together. It is concluded that augmented endogenous NO production increased portal flow. Inhibition of endogenous NO had no effect on portal haemodynamics. Endogenous NO may not play a major role in regulation of portal haemodynamics in the rat in vivo.

The action of nitric oxide on hepatic haemodynamics during secondary biliary cirrhosis in the rat.

The role of nitric oxide (NO) in portal hypertension is poorly understood. The role of NO upon hepatic arterial and portal venous vasoconstrictor responses to noradrenaline and ATP in rats with secondary biliary cirrhosis was evaluated. Cirrhosis was induced by bile duct ligation after which livers were excised and dual-perfused in vitro. Concentration-dependent dose-response curves were then constructed to hepatic arterial and portal venous noradrenaline and ATP. Hepatic arterial responses to noradrenaline and ATP were significantly attenuated in cirrhotic rats. 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME) restored attenuated hepatic arterial responses to noradrenaline and ATP in cirrhotic rats. Portal venous responses to noradrenaline in cirrhotic rats were significantly increased compared to controls and were not affected by L-NAME. However, portal venous responses to ATP were significantly attenuated in cirrhotic rats and were also not restored by L-NAME. Hepatic arterial or portal venous responses to noradrenaline did not change after infusion of L-NAME. Hepatic arterial responses to noradrenaline and ATP were significantly attenuated in cirrhotic rats, possibly due to increased production of NO. However, portal venous responses in cirrhotic rats were increased to noradrenaline and attenuated to ATP, and were not related to increased NO production.

Cold storage of rabbit thoracic aorta in University of Wisconsin solution attenuates P2Y(2) purine receptors.

Post-transplantation thrombosis may occur in donor segments of iliac arteries and livers following surgical removal and storage in University of Wisconsin (UW) solution for transplantation. We have previously suggested that purine receptors are vulnerable to denaturation after UW storage. The aims of the present study were to determine what particular subtypes of purine P2Y receptors in rabbit thoracic aorta deteriorate after 8 days of UW storage by studying vascular reactivity to acetylcholine, ATP, 2MeSATP and UTP. Ring segments of aortae from male New Zealand White rabbits were mounted upon fine-wire myographs and vasodilatation to the above agents tested on fresh tissue, and after 8 days of UW storage. Vasodilatation to ATP was attenuated by 100 microM L-NAME in fresh tissue suggesting that the relaxant response was, in part, due to nitric oxide (NO). P2Y-mediated relaxation to ATP was significantly attenuated by UW storage and cholinergic responses were not. This attenuated relaxation to ATP was not further attenuated by L-NAME, suggesting a loss of the NO-dependent mechanism. De-endothelialisation indicated that UTP-mediated vasorelaxation, via P2Y(2) receptors, was endothelium-dependent. Any residual endothelium-independent relaxation to UTP was abolished by UW storage and endothelium-dependent UTP relaxation was reduced to the same level as that seen in fresh, de-endothelialised tissue. In contrast responses to 2MeSATP, via P2Y(1) receptors, were predominantly endothelium-independent and were only partially attenuated by UW storage. Responses to pyridoxalphosphate-6-azophenyl-2('),4(')-disulphonic acid (PPADS) and L-NAME suggested that vasorelaxation to 2MeSATP and UTP was mediated by P2Y(1) and P2Y(2) receptors, respectively. It is therefore concluded that UW storage predominantly decreases P2Y(2) receptor-mediated vascular reactivity.

Hepatic arterial perfusion decreases intrahepatic shunting and maintains glucose uptake in the rat liver.

Intrahepatic shunts have an important function in the regulation of portal venous pressure in the normal rat liver. The present study determined their location, the region of confluence between the hepatic arterial and portal venous vasculatures, regions within the liver that are bypassed and the effects of hepatic arterial perfusion upon the intrahepatic redistribution of portal venous flow. Livers of male Sprague-Dawley rats were excised and perfused in vitro. Hepatic bromosulphthalein (BSP) and glucose uptake were measured in hepatic venous samples. Diversion of the hepatic arterial supply into the portal venous vasculature opened the portal venous intrahepatic shunts and resulted in a 50% reduction in portal venous glucose uptake from 29.6+/-1.6% to 14.9+/-0.9% ( P<0.0001 Student's paired t-test). Portal venous injection of 15-microm-diameter microspheres also opened the intrahepatic shunts and reduced portal venous glucose uptake to 10% from 29.0+/-1.6% to 7.8+/-0.9% ( P<0.0001 Student's paired t-test). No significant reductions in portal venous BSP uptake (43.0+/-6.9 to 48.0+/-4.8%) or hepatic arterial glucose uptake, from an average value of 94.0%, occurred. Therefore, cessation of hepatic arterial perfusion or portal venous injection of microspheres reduced portal venous glucose uptake without affecting BSP uptake. It is concluded that intrahepatic shunts divert perfusate away from the perivenous, sinusoidal (zone III) regions and into the hepatic venous vasculature, distal to zone III. The microsphere data indicate that confluence between the hepatic arterial and portal venous vasculatures occurs mainly in sinusoidal zone II.

Reproducible production of thioacetamide-induced macronodular cirrhosis in the rat with no mortality.

BACKGROUND/AIMS: Hepatotoxin-induced rat models of liver cirrhosis are limited by the wide heterogeneity of cirrhosis produced. The present study developed a modified, reliable, and reproducible technique by which hepatic and systemic responses to thioacetamide during induction of cirrhosis were monitored by weekly weight changes. METHODS: Male Wistar rats (200-230 g) were divided into three groups. Group 1 (n=20) received continuous administration of 0.03% (w/v) thioacetamide in the drinking water for 12 weeks. Group 2 (n=20) received the same concentration of 0.03% thioacetamide as an initial concentration that was modified according to weekly weight changes in response to thioacetamide during the induction of cirrhosis. Group 3 (n=6) received normal water and served as controls. RESULTS: Mortality of Group 1 was 30% and the production of cirrhosis was only 45%. In contrast, there were no deaths in Group 2 and well-developed macronodular cirrhosis was found in 90% of the rats which was associated with significant portal hypertension, as indicated by increased portal venous pressure (13.6+/-0.4 vs. 9.1+/-0.3 mmHg, cirrhotic vs. control, respectively, P<0.01, Student's unpaired t-test). CONCLUSIONS: Variations in responses to thioacetamide can be easily monitored by weekly weight changes to reduce mortality to zero and simultaneously increase the production and quality of cirrhosis induced in rats.