Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production.

PURPOSE: This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. METHODS: Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. RESULTS: Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques (P < 0.05), and shortened contraction and relaxation rates (P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days (P < 0.05), and increased sweating rate after 5 and 10 days (P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions. CONCLUSION: HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.

Outpatient grip strength measurement predicts survival, perioperative adverse events, and nonhome discharge among patients with vascular disease.

OBJECTIVES: Frailty is associated with adverse outcomes among patients with vascular disease. Grip strength measurement is a comparatively simple, quick, and inexpensive screening test for weakness (a component of frailty) that is potentially applicable to clinical practice. We hypothesized that grip strength and categorical weakness are associated with clinical outcomes among patients with vascular disease. To test this hypothesis, we conducted a longitudinal cohort study evaluating associations between grip strength measured during outpatient clinic visits for vascular disease and clinical outcomes, including survival and perioperative outcomes. METHODS: Adult patients recruited from outpatient vascular surgery and/or vascular medicine clinics underwent dominant hand grip strength measurement using a hand dynamometer. Participants were categorized as weak based on grip strength, sex, and body mass index. Multivariable logistic models were used to evaluate perioperative outcomes. Mortality was evaluated using Cox proportional hazards models adjusted for sex, age, and operative intervention during follow-up. RESULTS: We enrolled 321 participants. The mean patients age was 69.0 ± 9.4 years, and 33% were women. Mean grip strength was 32.0 ± 12.1 kg, and 92 participants (29%) were categorized as weak. The median follow-up was 24.0 months. Adverse perioperative events occurred in 32 of 84 patients undergoing procedures. Grip strength was associated with decreased risk of perioperative adverse events (hazard ratio [HR], 0.41 per 12.7 kg increase; 95% confidence interval [CI], 0.20-0.85; P = .0171) in a model adjusted for open versus endovascular procedure (HR, 12.75 for open; 95% CI, 2.54-63.90; P = .0020) and sex (HR, 3.05 for male; 95% CI, 0.75-12.4; P = .120). Grip strength was also associated with a lower risk of nonhome discharge (HR, 0.34 per 12.7 kg increase; 95% CI, 0.14-0.82; P = .016) adjusted for sex (HR, 2.14 for male; 95% CI, 0.48-9.50; P = .31) and open versus endovascular procedure (HR, 10.36 for open; 95% CI, 1.20-89.47; P = .034). No associations between grip strength and length of stay were observed. Mortality occurred in 48 participants (14.9%) during follow-up. Grip strength was inversely associated with mortality (HR, 0.46 per 12.5 kg increase; 95% CI, 0.29-0.73; P = .0009) in a model adjusted for sex (HR, 5.08 for male; 95% CI, 2.1-12.3; P = .0003), age (HR, 1.04 per year; 95% CI, 1.01-1.08), and operative intervention during follow-up (HR, 1.23; 95% CI, 0.71-2.52). Categorical weakness was also associated with mortality (HR, 1.81 vs nonfrail; P = .048) in a model adjusted for age (HR, 1.06 per year; P = .002) and surgical intervention (HR, 1.36; 95% CI, 1.02-0.09; P = .331). CONCLUSIONS: Grip strength is associated with all-cause mortality, perioperative adverse events, and nonhome discharge among patients with vascular disease. These observations support the usefulness of grip strength as a simple and inexpensive risk screening tool for patients with vascular disease.

Short-term isothermic heat acclimation elicits beneficial adaptations but medium-term elicits a more complete adaptation.

PURPOSE: To investigate the effects of 60 min daily, short-term (STHA) and medium-term (MTHA) isothermic heat acclimation (HA) on the physiological and perceptual responses to exercise heat stress. METHODS: Sixteen, ultra-endurance runners (female = 3) visited the laboratory on 13 occasions. A 45 min sub-maximal (40% Wmax) cycling heat stress test (HST) was completed in the heat (40 °C, 50% relative humidity) on the first (HSTPRE), seventh (HSTSTHA) and thirteenth (HSTMTHA) visit. Participants completed 5 consecutive days of a 60 min isothermic HA protocol (target Tre 38.5 °C) between HSTPRE and HSTSTHA and 5 more between HSTSTHA and HSTMTHA. Heart rate (HR), rectal (Tre), skin (Tsk) and mean body temperature (Tbody), perceived exertion (RPE), thermal comfort (TC) and sensation (TS) were recorded every 5 min. During HSTs, cortisol was measured pre and post and expired air was collected at 15, 30 and 45 min. RESULTS: At rest, Tre and Tbody were lower in HSTSTHA and HSTMTHA compared to HSTPRE, but resting HR was not different between trials. Mean exercising Tre, Tsk, Tbody, and HR were lower in both HSTSTHA and HSTMTHA compared to HSTPRE. There were no differences between HSTSTHA and HSTMTHA. Perceptual measurements were lowered by HA and further reduced during HSTMTHA. CONCLUSION: A 60 min a day isothermic STHA was successful at reducing physiological and perceptual strain experienced when exercising in the heat; however, MTHA offered a more complete adaptation.

Grip strength measurement for frailty assessment in patients with vascular disease and associations with comorbidity, cardiac risk, and sarcopenia.

OBJECTIVE: Frailty is associated with adverse events, length of stay, and nonhome discharge after vascular surgery. Frailty measures based on walking-based tests may be impractical or invalid for patients with walking impairment from symptoms or sequelae of vascular disease. We hypothesized that grip strength is associated with frailty, comorbidity, and cardiac risk among patients with vascular disease. METHODS: Dominant hand grip strength was measured during ambulatory clinic visits among patients with vascular disease (abdominal aortic aneurysm [AAA], carotid stenosis, and peripheral artery disease [PAD]). Frailty prevalence was defined on the basis of the 20th percentile of community-dwelling population estimates adjusted for age, gender, and body mass index. Associations between grip strength, Charlson Comorbidity Index (CCI), Revised Cardiac Risk Index (RCRI), and sarcopenia (based on total psoas area for patients with cross-sectional abdominal imaging) were evaluated using linear and logistic regression. RESULTS: Grip strength was measured in 311 participants; all had sufficient data for CCI calculation, 217 (69.8%) had sufficient data for RCRI, and 88 (28.3%) had cross-sectional imaging permitting psoas measurement. Eighty-six participants (27.7%) were categorized as frail on the basis of grip strength. Frailty was associated with CCI (odds ratio, 1.86; 95% confidence interval, 1.34-2.57; P = .0002) in the multivariable model. Frail participants also had a higher average number of RCRI components vs nonfrail patients (mean ± standard deviation, 1.8 ± 0.8 for frail vs 1.5 ± 0.7 for nonfrail; P = .018); frailty was also associated with RCRI in the adjusted multivariable model (odds ratio, 1.75; 95% confidence interval, 1.16-2.64; P = .008). Total psoas area was lower among patients categorized as frail vs nonfrail on the basis of grip strength (21.0 ± 6.6 vs 25.4 ± 7.4; P = .010). Each 10 cm2 increase in psoas area was associated with a 5.7 kg increase in grip strength in a multivariable model adjusting for age and gender (P < .0001). Adjusted least squares mean psoas diameter estimates were 25.5 ± 1.1 cm2 for participants with AAA, 26.7 ± 2.0 cm2 for participants with carotid stenosis, and 22.7 ± 0.8 cm2 for participants with PAD (P = .053 for PAD vs AAA; P = .057 for PAD vs carotid stenosis; and P = .564 for AAA vs carotid stenosis). CONCLUSIONS: Grip strength is useful for identifying frailty among patients with vascular disease. Frail status based on grip strength is associated with comorbidity, cardiac risk, and sarcopenia in this population. These findings suggest that grip strength may have utility as a simple and inexpensive risk screening tool that is easily implemented in ambulatory clinics, avoids the need for imaging, and overcomes possible limitations of walking-based measures. Lower mean psoas diameters among patients with PAD vs other diagnoses may warrant consideration of specific approaches to morphomic analysis.

Endovascular Treatment of Chronic Mesenteric Ischemia in the Setting of Occlusive Superior Mesenteric Artery Lesions.

BACKGROUND: Endovascular intervention is considered the first-line treatment for chronic mesenteric ischemia (CMI) when feasible. Two-vessel revascularization is most definitive when celiac (CA) and superior mesenteric arteries (SMA) are diseased, but single-vessel intervention may be performed in patients with 2-vessel disease due to anatomic/technical factors. We evaluated anatomic predictors of clinical outcomes associated with endovascular treatment of CMI among patients with occlusive SMA lesions. METHODS: Patients with CMI treated with endovascular revascularization over 10 years were identified. Patients with SMA occlusions were selected for analysis. Between-group comparisons based on inclusion of an SMA revascularization were evaluated using t-test and chi-squared test. Freedom from symptomatic recurrence or repeat intervention was analyzed using proportional hazards regression. RESULTS: Fifty-four patients with CMI were analyzed. Sixteen (29.6%) patients had CA-only intervention, and 38 (70.4%) patients had SMA revascularization with or without CA intervention. No significant differences in demographics or comorbidity were identified between groups. In the CA-only intervention group, 8 of the 16 (50%) patients developed symptomatic recurrence compared with 8 of the 31 (21.1%) patients whose intervention included the SMA. Patients treated without SMA intervention also had decreased freedom from both symptomatic recurrence (hazard ratio [HR] 3.2, 95% confidence interval [CI] 1.2-8.6, P = 0.016) and repeat intervention (HR 5.5, 95% CI 1.8-16.3, P = 0.001). CONCLUSIONS: Among patients with CMI and occlusive SMA lesions, SMA revascularization appears to be the key determinant for symptomatic outcomes and repeat intervention. Patient counseling should include potential future need for surgical revascularization if endovascular SMA treatment cannot be accomplished.

The ß-lactamase gene regulator AmpR is a tetramer that recognizes and binds the D-Ala-D-Ala motif of its repressor UDP-N-acetylmuramic acid (MurNAc)-pentapeptide.

Inducible expression of chromosomal AmpC ß-lactamase is a major cause of ß-lactam antibiotic resistance in the Gram-negative bacteria Pseudomonas aeruginosa and Enterobacteriaceae. AmpC expression is induced by the LysR-type transcriptional regulator (LTTR) AmpR, which activates ampC expression in response to changes in peptidoglycan (PG) metabolite levels that occur during exposure to ß-lactams. Under normal conditions, AmpR represses ampC transcription by binding the PG precursor UDP-N-acetylmuramic acid (MurNAc)-pentapeptide. When exposed to ß-lactams, however, PG catabolites (1,6-anhydroMurNAc-peptides) accumulate in the cytosol, which have been proposed to competitively displace UDP-MurNAc-pentapeptide from AmpR and convert it into an activator of ampC transcription. Here we describe the molecular interactions between AmpR (from Citrobacter freundii), its DNA operator, and repressor UDP-MurNAc-pentapeptide. Non-denaturing mass spectrometry revealed AmpR to be a homotetramer that is stabilized by DNA containing the T-N11-A LTTR binding motif and revealed that it can bind four repressor molecules in an apparently stepwise manner. A crystal structure of the AmpR effector-binding domain bound to UDP-MurNAc-pentapeptide revealed that the terminal D-Ala-D-Ala motif of the repressor forms the primary contacts with the protein. This observation suggests that 1,6-anhydroMurNAc-pentapeptide may convert AmpR into an activator of ampC transcription more effectively than 1,6-anhydroMurNAc-tripeptide (which lacks the D-Ala-D-Ala motif). Finally, small angle x-ray scattering demonstrates that the AmpR·DNA complex adopts a flat conformation similar to the LTTR protein AphB and undergoes only a slight conformational change when binding UDP-MurNAc-pentapeptide. Modeling the AmpR·DNA tetramer bound to UDP-MurNAc-pentapeptide predicts that the UDP-MurNAc moiety of the repressor participates in modulating AmpR function.

AmpG inactivation restores susceptibility of pan-beta-lactam-resistant Pseudomonas aeruginosa clinical strains.

Constitutive AmpC hyperproduction is the most frequent mechanism of resistance to the weak AmpC inducers antipseudomonal penicillins and cephalosporins. Previously, we demonstrated that inhibition of the ß-N-acetylglucosaminidase NagZ prevents and reverts this mechanism of resistance, which is caused by ampD and/or dacB (PBP4) mutations in Pseudomonas aeruginosa. In this work, we compared NagZ with a second candidate target, the AmpG permease for GlcNAc-1,6-anhydromuropeptides, for their ability to block AmpC expression pathways. Inactivation of nagZ or ampG fully restored the susceptibility and basal ampC expression of ampD or dacB laboratory mutants and impaired the emergence of one-step ceftazidime-resistant mutants in population analysis experiments. Nevertheless, only ampG inactivation fully blocked ampC induction, reducing the MICs of the potent AmpC inducer imipenem from 2 to 0.38 µg/ml. Moreover, through population analysis and characterization of laboratory mutants, we showed that ampG inactivation minimized the impact on resistance of the carbapenem porin OprD, reducing the MIC of imipenem for a PAO1 OprD mutant from >32 to 0.5 µg/ml. AmpG and NagZ targets were additionally evaluated in three clinical isolates that are pan-ß-lactam resistant due to AmpC hyperproduction, OprD inactivation, and overexpression of several efflux pumps. A marked increase in susceptibility to ceftazidime and piperacillin-tazobactam was observed in both cases, while only ampG inactivation fully restored wild-type imipenem susceptibility. Susceptibility to meropenem, cefepime, and aztreonam was also enhanced, although to a lower extent due to the high impact of efflux pumps on the activity of these antibiotics. Thus, our results suggest that development of small-molecule inhibitors of AmpG could provide an excellent strategy to overcome the relevant mechanisms of resistance (OprD inactivation plus AmpC induction) to imipenem, the only currently available ß-lactam not significantly affected by P. aeruginosa major efflux pumps.

NagZ inactivation prevents and reverts beta-lactam resistance, driven by AmpD and PBP 4 mutations, in Pseudomonas aeruginosa.

AmpC hyperproduction is the most frequent mechanism of resistance to penicillins and cephalosporins in Pseudomonas aeruginosa and is driven by ampD mutations or the recently described inactivation of dacB, which encodes the nonessential penicillin-binding protein (PBP) PBP 4. Recent work showed that nagZ inactivation attenuates beta-lactam resistance in ampD mutants. Here we explored whether the same could be true for the dacB mutants with dacB mutations alone or in combination with ampD mutations. The inactivation of nagZ restored the wild-type beta-lactam MICs and ampC expression of PAO1 dacB and ampD mutants and dramatically reduced the MICs (for example, the MIC for ceftazidime dropped from 96 to 4 microg/ml) and the level of ampC expression (from ca. 1,000-fold to ca. 50-fold higher than that for PAO1) in the dacB-ampD double mutant. On the other hand, nagZ inactivation had little effect on the inducibility of AmpC. The NagZ inhibitor O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate attenuated the beta-lactam resistance of the AmpC-hyperproducing strains, showing a greater effect on the dacB mutant (reducing the ceftazidime MICs from 24 to 6 microg/ml) than the ampD mutant (reducing the MICs from 8 to 4 microg/ml). Additionally, nagZ inactivation in the dacB mutant blocked the overexpression of creD (blrD), which is a marker of the activation of the CreBC (BlrAB) regulator involved in the resistance phenotype. Finally, through population analysis, we show that the inactivation of nagZ dramatically reduces the capacity of P. aeruginosa to develop ceftazidime resistance, since spontaneous mutants were not obtained at concentrations > or = 8 microg/ml (the susceptibility breakpoint) for the nagZ mutant but were obtained with wild-type PAO1. Therefore, NagZ is envisaged to be a candidate target for preventing and reverting beta-lactam resistance in P. aeruginosa.

Impairment of Cycling Capacity in the Heat in Well-Trained Endurance Athletes After High-Intensity Short-Term Heat Acclimation.

PURPOSE: To investigate the effects of short-term, high-intensity interval-training (HIIT) heat acclimation (HA). METHODS: Male cyclists/triathletes were assigned into either an HA (n = 13) or a comparison (COMP, n = 10) group. HA completed 3 cycling heat stress tests (HSTs) to exhaustion (60% Wmax; HST1, pre-HA; HST2, post-HA; HST3, 7 d post-HA). HA consisted of 30-min bouts of HIIT cycling (6 min at 50% Wmax, then 12 × 1-min 100%-Wmax bouts with 1-min rests between bouts) on 5 consecutive days. COMP completed HST1 and HST2 only. HST and HA trials were conducted in 35°C/50% relative humidity. Cycling capacity and physiological and perceptual data were recorded. RESULTS: Cycling capacity was impaired after HIIT HA (77.2 [34.2] min vs 56.2 [24.4] min, P = .03) and did not return to baseline after 7 d of no HA (59.2 [37.4] min). Capacity in HST1 and HST2 was similar in COMP (43.5 [8.3] min vs 46.8 [15.7] min, P = .54). HIIT HA lowered resting rectal (37.0°C [0.3°C] vs 36.8°C [0.2°C], P = .05) and body temperature (36.0°C [0.3°C] vs 35.8°C [0.3°C], P = .03) in HST2 compared with HST1 and lowered mean skin temperature (35.4°C [0.5°C] vs 35.1°C [0.3°C], P = .02) and perceived strain on day 5 compared with day 1 of HA. All other data were unaffected. CONCLUSIONS: Cycling capacity was impaired in the heat after 5 d of consecutive HIIT HA despite some heat adaptation. Based on data, this approach is not recommended for athletes preparing to compete in the heat; however, it is possible that it may be beneficial if a state of overreaching is avoided.

A Glucose Sensing System Based on Transmission Measurements at Millimetre Waves using Micro strip Patch Antennas.

We present a sensing system operating at millimetre (mm) waves in transmission mode that can measure glucose level changes based on the complex permittivity changes across the signal path. The permittivity of a sample can change significantly as the concentration of one of its substances varies: for example, blood permittivity depends on the blood glucose levels. The proposed sensing system uses two facing microstrip patch antennas operating at 60 GHz, which are placed across interrogated samples. The measured transmission coefficient depends on the permittivity change along the signal path, which can be correlated to the change in concentration of a substance. Along with theoretical estimations, we experimentally demonstrate the sensing performance of the system using controlled laboratory samples, such as water-based glucose-loaded liquid samples. We also present results of successful glucose spike detection in humans during an in-vivo Intravenous Glucose Tolerance Test (IVGTT). The system could eventually be developed into a non-invasive glucose monitor for continuous monitoring of glucose levels for people living with diabetes, as it can detect as small as 1.33 mmol/l (0.025 wt%) glucose concentrations in the controlled water-based samples satisfactorily, which is well below the typical human glucose levels of 4 mmol/l.

Parathyroidectomy for tertiary hyperparathyroidism associated with X-linked dominant hypophosphatemic rickets.

BACKGROUND: X-linked dominant hypophosphatemic rickets (XLHR) is a hereditary metabolic bone syndrome that is only beginning to be understood and is rarely associated with progression to irreversible tertiary hyperparathyroidism. We report our surgical experience with 6 patients with XLHR who underwent parathyroidectomy for associated autonomous parathyroid hyperfunction. HYPOTHESIS: Parathyroidectomy can successfully treat tertiary hyperparathyroidism in the setting of XLHR, although an understanding of expected operative findings and postoperative complications is essential. DESIGN: The study group comprised 6 patients with XLHR identified from our endocrine surgery database. Presentation, surgical procedure, parathyroid pathologic findings, and subsequent outcome are outlined. RESULTS: There were 4 women and 2 men. All were exposed to long-term vitamin D and phosphate supplementation therapy. All had persistently elevated preoperative levels of parathyroid hormone and serum calcium. The patients were treated as follows: 3 had total parathyroidectomy, 2 had 3 parathyroid glands identified and resected, and 1 had 2 abnormal parathyroid glands resected with 2 normal-appearing parathyroid glands left in situ. One patient subsequently required completion parathyroidectomy for recurrent disease. Pathologic examination results revealed hyperplasia of all resected parathyroid glands in 4 of 6 patients. One patient had a single adenoma with 3-gland hyperplasia, and 1 patient had a double adenoma. The principal complication of this procedure was profound symptomatic hypocalcemia requiring intravenous calcium infusion. Hungry bone syndrome was also observed in most subjects. Long-term, all patients achieved normocalcemia. CONCLUSION: Tertiary hyperparathyroidism is a rare but recognized complication of XLHR. Parathyroidectomy effectively treats this complication caused by autonomous parathyroid hyperfunction, but profound postoperative hypocalcemia necessitates careful management.

Changing pattern of adrenalectomy at a tertiary referral centre 1970-2000.

BACKGROUND: In 1987, a report from this unit described the changing indications for open adrenalectomy over a 15-year period. The indications for adrenalectomy had switched from it being the principal therapeutic procedure used in advanced breast cancer in the early 1970s, to being predominately performed for Cushing's disease or incidental, asymptomatic, adrenal masses by the early 1980s. The aim of the present study was to evaluate the changes in the presentation and management of adrenal disease in the last 15 years and to compare these findings with our previously published results. METHODS: Information was gathered from a prospective database of all patients undergoing adrenalectomy in the University of Sydney Endocrine Surgical Unit at Royal North Shore Hospital from 1 January 1987 to 31 December 2000. Information was obtained on patient presentation, diagnostic investigations, indications for surgery, procedure performed and surgical outcomes. Prior to 1987, information was gathered by retrospective review of case notes of patients who had undergone adrenalectomy at Royal North Shore Hospital. During the period from 1 January 1970 to 31 December 2000, 236 patients underwent adrenalectomy. Excluding the 68 adrenalectomies performed for breast cancer, left 168 patients who underwent adrenalectomy for functional or non--functional masses. There were 97 (58%) women and 71 (42%) men, with a mean age of 48 years. RESULTS: Of the 168 patients, the principal indications for surgery were hyperaldosteronism (32%), phaeochromocytoma (20%), hypercortisolism (20%), incidentaloma (16%), carcinoma (6%) and other reasons (6%). Examination of the number of cases in each pathological group for the periods 1970-1986 and 1987-2000, revealed an 8-fold increase in the number of operations for hyper-aldosteronism, and a 3-fold increase in cases of phaeochromocytoma. The number of operations for the other pathological groups remained steady. The annual incidence of adrenalectomy in the hospital has steadily risen since 1990, with a linear increase in the adrenalectomy rate since the introduction of laparoscopic adrenalectomy in 1995. There were fewer complications in either the open or laparoscopic group since 1987 compared with the pre-1987 cohort. CONCLUSIONS: In the past 5 years, there has been a linear increase in the number of adrenalectomies performed in this unit for hyperaldosteronism and to a lesser extent phaeochromocytoma. This is a reflection of increased clinical awareness, improved diagnostic modalities and the advent of laparoscopic adrenalectomy.

Crystal structure of the AmpR effector binding domain provides insight into the molecular regulation of inducible ampc beta-lactamase.

Hyperproduction of AmpC beta-lactamase (AmpC) is a formidable mechanism of resistance to penicillins and cephalosporins in Gram-negative bacteria such as Pseudomonas aeruginosa and Enterobacteriaceae. AmpC expression is regulated by the LysR-type transcriptional regulator AmpR. ampR and ampC genes form a divergent operon with overlapping promoters to which AmpR binds and regulates the transcription of both genes. AmpR induces ampC by binding to one member of the family of 1,6-anhydro-N-acetylmuramyl peptides, which are cytosolic catabolites of peptidoglycan that accumulate during beta-lactam challenge. To gain structural insights into AmpR regulation, we determined the crystal structure of the effector binding domain (EBD) of AmpR from Citrobacter freundii up to 1.83 A resolution. The AmpR EBD is dimeric and each monomer comprises two subdomains that adopt alpha/beta Rossmann-like folds. Located between the monomer subdomains is a pocket that was found to bind the crystallization buffer molecule 2-(N-morpholino)ethanesulfonic acid. The pocket, together with a groove along the surface of subdomain I, forms a putative effector binding site into which a molecule of 1,6-anhydro-N-acetylmuramyl pentapeptide could be modeled. Amino acid substitutions at the base of the interdomain pocket either were found to render AmpR incapable of inducing ampC (Thr103Val, Ser221Ala and Tyr264Phe) or resulted in constitutive ampC expression (Gly102Glu). While the substitutions that prevented ampC induction did not alter the overall AmpR EBD structure, circular dichroism spectroscopy revealed that the nonconservative Gly102Glu mutation affected EBD secondary structure, confirming previous work suggesting that Gly102Glu induces a conformational change to result in constitutive AmpC production.

The University of Sydney Endocrine Surgery Database: 50 years of data accrual.

Surgical databases are now a fundamental part of clinical practice and research but have only been commonplace in the past decade or so. The University of Sydney Endocrine Surgery Database has now been in existence for more than 50 years since it was started by Tom Reeve in 1957. It includes comprehensive documentation of every aspect of every thyroid, parathyroid and adrenal procedure carried out by its surgeons while they were active members of the unit. During those 50 years, 17,466 such procedures have been documented. In the first year of data collection, only 20 thyroid procedures carried out by one surgeon in one hospital were entered, whereas in the most recent year, 1092 major endocrine procedures carried out by three surgeons in 10 separate hospitals required entry. As well as providing for surgical audit, the database has been integral to the writing of 130 published articles and articles in press on the topic of thyroid, parathyroid and adrenal surgery. The database has been instrumental to significant changes in the practice of endocrine surgery, including introduction of total thyroidectomy for benign bilateral multinodular goitre by this unit two decades ago, leading to changed practice in most countries around the globe. Data acquisition has also allowed documentation of the safety and efficacy of new minimally invasive endocrine procedures such as minimally invasive parathyroidectomy and minimally invasive thyroid surgery. Audit-based research with accumulation of data based on surgical outcomes, that is, evidence-based surgery, remains the fundamental basis of sound surgical practice with the potential to lead important changes in clinical practice.