Injury in rugby league

It was the purpose of this review to document the range, incidence, location and mechanism of injury occurring in the sport of rugby league. Rugby league is a collision sport played in Europe and the Pacific regions including Australia. The sport is well established and has competitions ranging from junior to elite professional. Due to the contact nature of the game, injury is relatively common. The most common injuries are musculotendinous in nature and afflict the lower limb more frequently than elsewhere. Despite the high incidence of minor (sprains/strains) to moderate musculoskeletal injury (fracture, ligament and joint injury) and minor head injuries such as lacerations, nasal fractures and concussions, rare more serious spinal cord and other injuries causing death have also been recorded. The literature on rugby league injury is small but growing and suffers from a lack of consistent definition of what an injury is, thereby causing variability in the nature and incidence/prevalence of injury. Information is lacking on the injury profiles of different age groups. Importantly, there has been little attempt to establish a coordinated injury surveillance program in rugby league in the junior or professional levels. The implementation of such programs would require a universal definition of injury and a focus on important events and competitions. The implementation could provide important information in the identification and prevention of risk factors for injury.

Synthesis and biological evaluation of new beta,beta'-disubstituted 6,7,8,9-tetrahydropyrido[1,2-a]indol-10-yl ethylamido melatoninergic ligands

Tricyclic analogs of melatonin with alkyl and cycloalkyl moieties in the beta position of the ethylamido chain have been prepared and tested for their ability to activate pigment granule aggregation in Xenopus laevis melanophores. The introduction of two methyl groups in the beta position of the side-chain of the methoxyl-substituted ligands induces a synergistic effect in agonist potency, which, importantly, is maintained after the methoxyl substituent is removed. The presence of more bulky beta-substituents, regardless of the size of the R group, seems to lead to antagonism.

Interactive effects of characteristics of defendant and mock juror on U.S. participants' judgment and sentencing recommendations

The authors examined the effects of interactions (a) between defendant attractiveness and juror gender and (b) between defendant race and juror race on judgment and sentencing among 207 Black, Hispanic, and White participants in the United States. After reading a vehicular-homicide vignette in which the defendant's attractiveness and race varied, the participants rated guilt and recommended sentences. The women treated the unattractive female defendant more harshly than they treated the attractive female defendant; the men showed an opposite tendency. The Black participants showed greater leniency when the defendant was described as Black rather than White. The Hispanic participants showed an opposite trend, and the White participants showed no race-based leniency. The findings on racial effects were consistent (a) with in-group favorability bias among the Black participants and (b) with attribution effects unrelated to race among the White participants.

Synergistic effects of feeding and dexamethasone on serum leptin levels

The objectives of this study were to determine the time course of the stimulatory effect of dexamethasone on serum leptin and whether it depends on food intake. Dexamethasone (4mg) was administered I.V. over 1 minute to healthy human volunteers (n=8) under fasting and feeding conditions (2000 kcal given at three meals over 7 hours). At 10 hours, serum leptin levels were increased only in the fed subjects (delta leptin 10.6+/-1.6 vs -2.4+/-1.9 ng/ml, p=0.01, n=8). To assess the interactive effect of food and dexamethasone on serum leptin, a subgroup (n=4) was studied under 4 conditions: 1) dexamethasone/fast; 2) dexamethasone/food; 3) saline/fast; 4) saline/food. Serum leptin declined from baseline under the fasting conditions, with or without dexamethasone. Feeding prevented the drop in serum leptin. In the dexamethasone/food condition, leptin levels rose from baseline after 7 hours and doubled after 10 hours (p<0.05). The rise in serum leptin was significantly greater in the food/dexamethasone condition compared to all other conditions (p<0.05). In summary, dexamethasone has no independent effect on serum leptin in the absence of food intake. Rather, dexamethasone appears to potentiate the food-induced increase in serum leptin. This synergism may be mediated by insulin and/or other factors associated with food ingestion.

Effect of intermittent exposure and drug-free intervals on the in vitro vascular tolerance to nitroglycerin

Recent reports suggest that intermittent nitroglycerin (NTG) treatment, incorporating a daily nitrate-free interval, can avoid the tolerance associated with continuous NTG therapy. This study has investigated whether an in vitro model of NTG tolerance could be used to examine the mechanisms of tolerance avoidance (by intermittent NTG exposure) and tolerance reversal. Isolated rat abdominal aortic rings were exposed to 55 microM NTG at varying intervals over a 60 min period, and the concentration-relaxation curves to NTG were subsequently determined. Intermittent NTG exposure (either 12 x 0.5 min or 3 x 2 min) significantly reduced NTG tolerance compared to continuous exposure over the same period of time (60 min). The diminished tolerance was apparently due to the reduced total exposure time, since the NTG responsiveness of aortic rings exposed to NTG intermittently or continuously for 6 min of the incubation period was not significantly different. Under the present conditions, in vitro NTG tolerance could be reversed if sufficient washout time was allowed. Thus, aortic rings exposed to NTG for the initial, but not the final, 6 min of incubation were not tolerant to NTG. In addition, rings exposed to NTG for 3 min exhibited near-maximal tolerance after 5 min washout, but no tolerance after 60 or 120 min washout. It appears, therefore, that the isolated vessel retains the "repair" mechanism responsible for tolerance reversal under the present conditions. This study suggests that the in vitro model of NTG tolerance may be useful for investigating the characteristics and mechanisms of tolerance avoidance and reversal, as well as tolerance induction.

Mechanisms for the pharmacologic interaction of organic nitrates with thiols. Existence of an extracellular pathway for the reversal of nitrate vascular tolerance by N-acetylcysteine

Recent reports have shown that the coadministration of N-acetylcysteine (NAC) potentiated the hemodynamic actions of i.v. nitroglycerin (NTG) and reversed NTG tolerance in humans. This study has investigated the feasibility of various pharmacokinetic and biochemical mechanisms for the thiol-organic nitrate interaction, using the rat as an animal model. In order to establish that the potentiating interaction between NAC and NTG can be reproduced in the rat, NTG dose-blood pressure response curves were determined before and during concurrent thiol infusion. The hypotensive effect of NTG was enhanced significantly by NAC and glutathione, but not by N-acetylserine, showing clearly that the potentiating effect of NAC was due specifically to its thiol functional group. The systemic clearance of NTG was not affected significantly by NAC coinfusion. In addition, the intracellular metabolism of NTG in thoracic aorta segments from rats infused previously with NAC or N-acetylserine was similar, both with respect to total production of metabolites and their distribution. Thus, the enhancement of NTG action could not be attributed apparently to an effect of NAC on NTG systemic pharmacokinetics or vascular metabolism of NTG. Because glutathione, which does not enter cells readily, also potentiated the effects of NTG, the possibility of an extracellular pathway for the thiol-organic nitrate interaction was examined. In vitro degradation of NTG in plasma and blood was accelerated in the presence of NAC (or glutathione). NAC also promoted the formation of S-nitroso-N-acetylcysteine from NTG in rat and human plasma and human blood.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential stimulation of synaptosomal norepinephrine uptake by high salt diet in Dahl rats

We have studied the norepinephrine (NE) uptake processes directly in synaptosomes isolated from the hypothalamus of both Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats. Both DS and DR rats were divided into two dietary groups, one high salt diet group and one low salt diet group. NE uptake was highly sodium dependent (averaging 80%) and ouabain sensitive (averaging 55%). The initial 3H-NE uptake by the hypothalamic synaptosomal fraction of DR and DS rats on a low salt diet during the first 10-min incubation period averaged 1.19 +/- 0.083 and 1.50 +/- 0.138 pmol/mg protein respectively while those of DR and DS on a high salt diet were 1.69 +/- 0.124 and 1.64 +/- 0.092 pmol/mg protein respectively. Baseline values of NE uptake on low salt diet were relatively high in DS compared to that in DR controls. High salt diet had a stimulatory effect on the net uptake of 3H-NE by hypothalamic synaptosomes of both strains of rats, DS showed an overall enhancement of 9% as compared to DR (42% increase, P = 0.003). This differential enhancement by the high salt diet was apparently contributed to by the sodium-mediated and ouabain sensitive amine uptake process and possibly resulted from a defective inducibility of (Na+-K+)-ATPase in DS rats.

Preparation of a covalently linked adduct between plastocyanin and cytochrome f

Plastocyanin can be covalently cross-linked to the monomeric cytochrome f from turnip by incubation in the presence of a water-soluble carbodiimide. The adduct between the two proteins has a molecular weight of approximately 43,000 suggesting a 1:1 stoichiometry between the two proteins of the adduct. This stoichiometry has been verified by spectral characterization of the adduct. The efficiency of the cross-linking reaction is pH dependent with a higher degree of cross-linking being observed at pH 6.5 than at pH 7.0.