Ca2⁺ and Na⁺ transport by chromaffin granules of the adrenal medulla

Chromaffin granules, the secretory organelles of the adrenal medulla, store and secrete catecholamines, proteins and nucleotides. Their very high internal catecholamine concentrations are achieved by a chemiosmotic coupling between an inwardly directed, electrogenic H+-translocating adenosine triphosphatase (H+- ATPase) and a separate catecholamine/H+ exchanger. Ca2+ is also a major component of the granule matrix, its nominal concentration being 20-30mM. The mechanism of Ca2+ uptake has hitherto only been partially characterised. Ca2+ uptake via electroneutral Ca2+/Na+ exchange has been demonstrated in resealed membrane "ghosts" and intact granules (Phillips (1981), Biochem. J. 200: 99-107; Krieger-Brauer & Gratzl (1982), Biochem. Biophys. Acta. 691: 61-70). To sustain Ca2+ uptake it is therefore necessary for granules to have an independent mechanism of Na+ uptake.In this thesis I show that chromaffin granules possess a novel amiloridesensitive Na+/H+ antiporter in their membranes. This explains why Na+ is mildly inhibitory to catecholamine transport (which is driven principally by the transmembrane pH difference generated by the ATPase). Na+/H+ antiport activity has been assayed using a variety of techniques: direct assay of 22Na+ accumulation in response to a transmembrane pH difference (ApH) generated by a rapid increase in external pH, or by ATP hydrolysis; generation of a ApH (measured with a fluorescent probe) in response to an imposed Na+ gradient; loss of a pH gradient due to Na+ uptake; and Na+/Na+ exchange. The antiporter has a relatively high Michaelis constant (Km) for extragranular Na+ (4.7mM at pH 7.0 determined from fluorescence experiments) and is inhibited competitively by the diuretic drug amiloride, a well known inhibitor of plasma membrane Na+/H+ antiporters, with an apparent inhibition constant (K|) of 0.26mMI have also measured the total and free concentrations of the inorganic cations Na+ and K+ inside the granule matrix. The total concentrations were found to vary depending on the ionic composition of the isolation buffer used to prepare the granules, with the lowest values being obtained with nominally Na+ and K+-free buffered sucrose solutions. The activity coefficients of both ions were found to be about 0.8, indicating that most of the Na+ and K+ is free within the matrix. The free concentration of Ca2+, however, was found to be approximately 5^M, a value markedly lower than the previously measured total concentration of 20mM (Phillips et al., (1977), Neuroscience, 2: 147-152). In other words, its free concentration is only 0.03% of the total.Because monovalent ion redistribution occurs during granule isolation, the concentrations of Na+, K+ and Ca2+ measured in vitro cannot be extrapolated to the intact cell in situ.Using Na+-loaded resealed membrane "ghosts", and using Ca2+ buffers to achieve various extravesicular free Ca2+ concentrations, I have determined that the apparent Km for Ca2+ uptake during Ca2+/Na+ exchange is about 1|iM, with maximal rates of Ca2+ uptake of the order of 1-2nmoles.mg"1.sec"1. In "ghosts", the activity of the Na+/H+ antiporter described above can be used to couple Ca2+ uptake via Ca2+/Na+ exchange to electrogenic proton translocation via the granule membrane ATPase. Therefore, Ca2+ uptake can be indirectly linked to the proton pump.However, under conditions designed to mimic the environment of a granule in the cytosol of a chromaffin cell, only very low amounts of Na+ could be accumulated within the granule matrix. Consequently, measured rates of Ca2+ accumulation are also low. Under such circumstances, the granules seem unlikely to play a major role in calcium homeostasis in the intact cell

Season-long increases in perceived muscle soreness in professional rugby league players: role of player position, match characteristics and playing surface

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Sports Sciences on 14/09/2015, available online: DOI: 10.1080/02640414.2015.1088166Rugby League (RL) is a high-impact collision sport characterised by repeated sprints and numerous high-speed impacts and consequently players often report immediate and prolonged muscle soreness in the days after a match. We examined muscle soreness after matches during a full season to understand the extent to which match characteristics influence soreness. Thirty-one elite Super League players provided daily measures of muscle soreness after each of the 26 competitive fixtures of the 2012 season. Playing position, phase of the season, playing surface and match characteristics were recorded from each match. Muscle soreness peaked at day 1 and was still apparent at day 4 post-game with no attenuation in the magnitude of muscle soreness over the course of the season. Neither playing position, phase of season or playing surface had any effects on the extent of muscle soreness. Playing time and total number of collisions were significantly correlated with higher ratings of muscle soreness, especially in the forwards. These data indicate the absence of a repeated bout effect or ‘contact adaptations’ in elite rugby players with soreness present throughout the entire season. Strategies must now be implemented to deal with the physical and psychological consequences of prolonged feeling of pai

Muscle glycogen utilisation during Rugby match play: Effects of pre-game carbohydrate

Objectives: Although the physical demands of Rugby League (RL) match-play are well-known, the fuel sources supporting energy-production are poorly understood. We therefore assessed muscle glycogen utilisation and plasma metabolite responses to RL match-play after a relatively high (HCHO) or relatively low CHO (LCHO) diet. Design: Sixteen (mean ± SD age; 18 ± 1 years, body-mass; 88 ± 12 kg, height 180 ± 8 cm) professional players completed a RL match after 36-h consuming a non-isocaloric high carbohydrate (n = 8; 6 g kg day−1) or low carbohydrate (n = 8; 3 g kg day−1) diet. Methods: Muscle biopsies and blood samples were obtained pre- and post-match, alongside external and internal loads quantified using Global Positioning System technology and heart rate, respectively. Data were analysed using effects sizes ±90% CI and magnitude-based inferences. Results: Differences in pre-match muscle glycogen between high and low carbohydrate conditions (449 ± 51 and 444 ± 81 mmol kg−1 d.w.) were unclear. High (243 ± 43 mmol kg−1 d.w.) and low carbohydrate groups (298 ± 130 mmol kg−1 d.w.) were most and very likely reduced post-match, respectively. For both groups, differences in pre-match NEFA and glycerol were unclear, with a most likely increase in NEFA and glycerol post-match. NEFA was likely lower in the high compared with low carbohydrate group post-match (0.95 ± 0.39 mmol l−1 and 1.45 ± 0.51 mmol l−1, respectively), whereas differences between the 2 groups for glycerol were unclear (98.1 ± 33.6 mmol l−1 and 123.1 ± 39.6 mmol l−1) in the high and low carbohydrate groups, respectively. Conclusions: Professional RL players can utilise ∼40% of their muscle glycogen during a competitive match regardless of their carbohydrate consumption in the preceding 36-h

Funny walking : the rise, fall and rise of the Anglo-American comic eccentric dancer

This article will attempt to reposition comic eccentric dance as a metamorphic form that still, surprisingly, exists, and is to be found with reasonable ubiquity, in renewed incarna-tions within twenty first century media. Tracing the origins of comic eccentric dance through examples of earlier comedy performance, and drawing from Bergson’s comic theory of body misalliance, this article will dis-cuss this particularly ludic fusion of music and comedy. Further changes to the form affected by modernist preoccupations during the new Jazz Age at the turn of the twentieth century will be suggested. Finally, ways in which the formulation lives on in twenty-first century in-carnations in the comedy work of, for instance, Jimmy Fallon and Ricky Gervase, and in popular television shows such as Strictly Come Dancing (BBC 2004 - ) and Britain’s Got Talent (ITV 2006 - ) will be posited

Contraindications of sentinel lymph node biopsy: Áre there any really?

BACKGROUND: One of the most exciting and talked about new surgical techniques in breast cancer surgery is the sentinel lymph node biopsy. It is an alternative procedure to standard axillary lymph node dissection, which makes possible less invasive surgery and side effects for patients with early breast cancer that wouldn't benefit further from axillary lymph node clearance. Sentinel lymph node biopsy helps to accurately evaluate the status of the axilla and the extent of disease, but also determines appropriate adjuvant treatment and long-term follow-up. However, like all surgical procedures, the sentinel lymph node biopsy is not appropriate for each and every patient. METHODS: In this article we review the absolute and relative contraindications of the procedure in respect to clinically positive axilla, neoadjuvant therapy, tumor size, multicentric and multifocal disease, in situ carcinoma, pregnancy, age, body-mass index, allergies to dye and/or radio colloid and prior breast and/or axillary surgery. RESULTS: Certain conditions involving host factors and tumor biologic characteristics may have a negative impact on the success rate and accuracy of the procedure. The overall fraction of patients unsuitable or with multiple risk factors that may compromise the success of the sentinel lymph node biopsy, is very small. Nevertheless, these patients need to be successfully identified, appropriately advised and cautioned, and so do the surgeons that perform the procedure. CONCLUSION: When performed by an experienced multi-disciplinary team, the SLNB is a highly effective and accurate alternative to standard level I and II axillary clearance in the vast majority of patients with early breast cancer

Comprehensive Axillary Evaluation in Neoadjuvant Chemotherapy Patients With Ultrasonography and Sentinel Lymph Node Biopsy

There is ongoing debate regarding the optimal sequence of sentinel lymph node (SLN) biopsy and neoadjuvant chemotherapy (CTX) for breast cancer. We report the accuracy of comprehensive pre–neoadjuvant CTX and post–neoadjuvant CTX axillary staging via ultrasound imaging, fine-needle aspiration (FNA) biopsy, and SLN biopsy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41405/1/10434_2005_Article_6534.pd

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700