GRD-1/PTR-11, the C. elegans hedgehog/patched-like morphogen-receptor pair, modulates developmental rate.

Both hedgehog (Hh) and target of rapamycin complex 2 (TORC2) are central, evolutionarily conserved signaling pathways that regulate development and metabolism. In C. elegans, loss of the essential TORC2 component RICTOR (rict-1) causes delayed development, shortened lifespan, reduced brood, small size and increased fat. Here, we report that knockdown of both the hedgehog-related morphogen grd-1 and its patched-related receptor ptr-11 rescues delayed development in TORC2 loss-of-function mutants, and grd-1 and ptr-11 overexpression delays wild-type development to a similar level to that in TORC2 loss-of-function animals. These findings potentially indicate an unexpected role for grd-1 and ptr-11 in slowing developmental rate downstream of a nutrient-sensing pathway. Furthermore, we implicate the chronic stress transcription factor pqm-1 as a key transcriptional effector in this slowing of whole-organism growth by grd-1 and ptr-11. We propose that TORC2, grd-1 and ptr-11 may act linearly or converge on pqm-1 to delay organismal development.

Analysis of styles of play according to season and end of season rank in the National Rugby League.

OBJECTIVES: This study aimed to identify styles of play in the National Rugby League (NRL) relative to season and end of season rank (position on the NRL ladder) across the 2015-2019 seasons. DESIGN: Retrospective, longitudinal analysis of performance indicators. METHODS: Forty-eight performance indicators (e.g. runs, tackles) from all NRL teams and matches during the 2015-2019 seasons (n=2010) were quantified. Principal component analysis (PCA) was then used to identify styles of play based on dimensions (Factors) of performance indicators. Multivariate analysis of covariance (MANCOVA) was then used to explain these emergent styles of play relative to 'season' and 'end of season rank'. RESULTS: The PCA revealed nine Factors (six attacking, two defensive and one contested style) accounting for ∼51% of seasonal team performance variance. These nine Factors differed across 'seasons', with four showing an effect against 'end of season rank'. From these four, two Factors (ball possession and player efforts) impacted upon the combined effects of 'season' and 'end of season rank'. CONCLUSIONS: The PCA identified nine Factors reflecting a spread of attacking, defensive and contested styles of play within the NRL. These styles differed relative to season and a team's end of season ranking. These results may assist practitioners with the recognition of more contemporary styles of play in the NRL, enabling the development of strategies to exploit competition trends.

Examining the evolution and classification of player position using performance indicators in the National Rugby League during the 2015-2019 seasons.

OBJECTIVES: This study aimed to: 1) examine recent seasonal changes in performance indicators for different National Rugby League (NRL) playing positions; and 2) determine the accuracy of performance indicators to classify and discriminate positional groups in the NRL. DESIGN: Retrospective, longitudinal analysis of individual performance metrics. METHODS: 48 performance indicators (e.g. passes, tackles) from all NRL games during the 2015-2019 seasons were collated for each player´s match-related performance. The following analyses were conducted with all data: (i) one-way ANOVA to identify seasonal changes in performance indicators; (ii) principal component analysis (PCA) to group performance indicators into factors; (iii) two-step cluster analysis to classify playing positions using the identified factors; and (iv) discriminant analysis to discriminate the identified playing positions. RESULTS: ANOVA showed significant differences in performance indicators across seasons (F=2.3-687.7; p=0-0.05; partial η2=0.00-0.075). PCA pooled all performance indicators and identified 14 factors that were included in the two-step cluster analysis (average silhouette=0.5) that identified six positional groups: forwards, 26.7%, adjustables, 17.2%, interchange, 23.2%, backs, 20.9%, interchange forwards, 5.5% and utility backs, 6.5%. Lastly, discriminant analysis revealed five discriminant functions that differentiated playing positions. CONCLUSIONS: Results indicated that player's performance demands across different playing positions did significantly change over recent seasons (2015-2019). Cluster analysis yielded a high-level of accuracy relative to playing position, identifying six clusters that best discriminated positional groups. Unsupervised analytical approaches may provide sports scientists and coaches with meaningful tools to evaluate player performance and future positional suitability in RL.

A consensus-based practical and daily guide for the treatment of acne patients.

BACKGROUND: Many current guidelines provide detailed evidence-based recommendations for acne treatment. OBJECTIVE: To create consensus-based, simple, easy-to-use algorithms for clinical acne treatment in daily office-based practice and to provide checklists to assist in determining why a patient may not have responded to treatment and what action to take. METHODS: Existing treatment guidelines and consensus papers were reviewed. The information in them was extracted and simplified according to daily clinical practice needs using a consensus-based approach and based on the authors' clinical expertise. RESULTS: As outcomes, separate simple algorithms are presented for the treatment of predominant comedonal, predominant papulopustular and nodular/conglobate acne. Patients with predominant comedonal acne should initially be treated with a topical retinoid, azelaic acid or salicylic acid. Fixed combination topicals are recommended for patients with predominant papulopustular acne with treatment tailored according to the severity of disease. Treatment recommendations for nodular/conglobate acne include oral isotretinoin or fixed combinations plus oral antibiotics in men, and these options may be supplemented with oral anti-androgenic hormonal therapy in women. Further decisions regarding treatment responses should be evaluated 8 weeks after treatment initiation in patients with predominant comedonal or papulopustular acne and 12 weeks after in those with nodular/conglobate acne. Maintenance therapy with a topical retinoid or azelaic acid should be commenced once a patient is clear or almost clear of their acne to prevent the disease from recurring. The principal explanations for lack of treatment response fall into 5 main categories: disease progression, non-drug-related reasons, drug-related reasons, poor adherence, and adverse events. CONCLUSION: This practical guide provides dermatologists with treatment algorithms adapted to different clinical features of acne which are simple and easy to use in daily clinical practice. The checklists to establish the causes for a lack of treatment response and subsequent action to take will facilitate successful acne management.

Aetiopathogenesis of atopic dermatitis.

The aetiopathogenesis of atopic dermatitis (AD) is complex and during recent years much has been learnt regarding the genetic predisposition to the development of this condition and how its interaction with the environment influences clinical manifestations. AD is not a simple condition. An inherited stratum corneum barrier defect, transepidermal water loss, early antigen exposure through the skin and over-hygienic care of the young child seem to be the major drivers in the manifestation of the disease. Many other, more specific, environmental factors may influence the clinical picture in individual patients; some of these have an allergic basis, while others do not. In this article, the terminology used in this issue of CME is explained, the evidence for the different aetiopathological factors is presented and the factors that worsen or improve AD are listed.

Effect of a training week on heart rate variability in elite youth rugby league players.

The aim of this study was to examine the influence of weekly training including a competitive game on heart rate (HR) variability (HRV). Youth players (n=9, age 17-20 years) were monitored during daily supine rest (10 min) and standing (8 min), 5 times over 8 days. Heart rate recordings were analysed for time domain, frequency (e. g. low frequency [LF], high frequency [HF]) domain and non-linear measures of HRV and compared using ANOVA or Friedman's tests. Relationships between HRV and training workloads were examined via Spearman rank rho (ρ) correlation coefficients. Prior to a game, mean HR was significantly increased and remained elevated until 2 days post-game while parasympathetic modulations (HF) were significantly reduced (p<0.05). The supine to standing change in HRV was significantly reduced for up to 4 days post-game (LF/HF ratio, - 1.0±2.9 vs. - 3.0±1.9, p<0.05). These results confirm that prior to a game, players exhibited reduced parasympathetic and/or predominant sympathetic modulation with the game significantly reducing autonomic responses to standing for up to the following 4 days. Identification of day to day fluctuations in HRV may provide a helpful tool for monitoring player workload to maximise training and game performance.

Photonic wire biosensor microarray chip and instrumentation with application to serotyping of Escherichia coli isolates.

A complete photonic wire molecular biosensor microarray chip architecture and supporting instrumentation is described. Chip layouts with 16 and 128 independent sensors have been fabricated and tested, where each sensor can provide an independent molecular binding curve. Each sensor is 50 µm in diameter, and consists of a millimeter long silicon photonic wire waveguide folded into a spiral ring resonator. An array of 128 sensors occupies a 2 × 2 mm2 area on a 6 × 9 mm2 chip. Microfluidic sample delivery channels are fabricated monolithically on the chip. The size and layout of the sensor array is fully compatible with commercial spotting tools designed to independently functionalize fluorescence based biochips. The sensor chips are interrogated using an instrument that delivers sample fluid to the chip and is capable of acquiring up to 128 optical sensor outputs simultaneously and in real time. Coupling light from the sensor chip is accomplished through arrays of sub-wavelength surface grating couplers, and the signals are collected by a fixed two-dimensional detector array. The chip and instrument are designed so that connection of the fluid delivery system and optical alignment are automated, and can be completed in a few seconds with no active user input. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria using serospecific polyclonal antibody probe molecules.

Influence of cycle ergometer type and sex on assessment of 30-second anaerobic capacity and power.

This study examined the influence of cycle ergometer type and sex on assessment of 30-s anaerobic capacity and power. 41 healthy adults performed a 30-s anaerobic cycle test using a mechanically- (ME) and air-braked (AE) ergometer in a randomised order, approximately 7 days apart. Peak heart rate (HR) and rating of perceived exertion were similar between tests with peak HR greater for females compared to males (187.0 ± 9.1 vs. 180.8 ± 9.9 bpm, p<0.05). Peak power (1 100 ± 330 vs. 802 ± 225 W), mean power (793 ± 223 vs. 587 ± 156 W) and total work (23.8 ± 6.7 vs. 17.6 ± 4.7 kJ) were greater for AE compared to ME (p<0.001) and greater for males compared to females (p<0.001). The mean difference for anaerobic capacity and power between AE and ME were similar for males and females (37-41% vs. 33-35%, p>0.05). Peak lactate was greater for AE compared to ME (16.1 ± 3.4 vs. 14.8 ± 2.9 mmol·L (-1); p<0.05) and greater for males compared to females (16.2 ± 3.5 vs. 14.6 ± 2.7 mmol·L (-1); p<0.05). The current study demonstrated that anaerobic power and capacity were substantially greater when assessed using AE compared to the traditional ME with the difference between ergometer types unaffected by sex. Ergometer type should be considered when comparing anaerobic results across populations and/or studies.

Guideline on the management of psoriasis in South Africa.

UNLABELLED: BACKGROUND; Psoriasis vulgaris is a chronic, relapsing, immune-mediated, potentially devastating disease, influenced by genetic and environmental factors, that can cause substantial morbidity and psychological stress and have a profound negative impact on patient quality of life. OBJECTIVE: These guidelines for the management of psoriasis have been developed in an attempt to improve the outcomes of treatment of this condition in South Africa. Psoriasis has a major impact on the quality of life of sufferers, and it is expected that these guidelines, if implemented, will play a role in achieving improved outcome. SCOPE: These guidelines were developed to address the diagnosis and treatment of psoriasis, of differing degrees of severity and in patients of all ages, by all health care professionals involved with its management. RECOMMENDATIONS: All health care workers involved in the management of psoriasis should take note of these guidelines and try to implement them in clinical practice as far as possible. All treatment methods and procedures not substantiated by evidence from the literature should be discontinued and avoided to decrease the financial burden of psoriasis treatment. VALIDATION: These guidelines were developed through general consensus by a group of 8 South African dermatologists (the 'Working Group') sanctioned by the Dermatological Society of South Africa (DSSA), by adaptation for the South African situation of the current guidelines used in the USA, the UK, Germany, Canada and Finland. Draft documents were made available for comment to the dermatological community as a whole via the official website of the DSSA, and the guidelines were presented and discussed at the annual congress of the DSSA in 2008. All input from these sources, where appropriate, were then incorporated into these guidelines. GUIDELINES SPONSOR: Schering-Plough initiated the project and sponsored the meetings of the working group and all costs generated by these meetings. PLANS FOR GUIDELINE REVISION: The field of biologicals and cytokine modulators is in a rapid phase of development, and revision of the scope and content of these guidelines will be ongoing as longer-term data emerge.

Silicon-on-insulator guided mode resonant grating for evanescent field molecular sensing.

We present experimental and theoretical results of label-free molecular sensing using the transverse magnetic mode of a 0.22 mum thick silicon slab waveguide with a surface grating implemented in a guided mode resonance configuration. Due to the strong overlap of the evanescent field of the waveguide mode with a molecular layer attached to the surface, these sensors exhibit high sensitivity, while their fabrication and packaging requirements are modest. Experimentally, we demonstrate a resonance wavelength shift of approximately 1 nm when a monolayer of the protein streptavidin is attached to the surface, in good agreement with calculations based on rigorous coupled wave analysis. In our current optical setup this shift corresponds to an estimated limit of detection of 0.2% of a monolayer of streptavidin.

The reliability of VO2(peak) determination in healthy females during an incremental arm ergometry test.

This study examined the reliability of an incremental arm ergometry (AE) protocol during peak aerobic power (VO2(peak)) determination in healthy females. Fifteen females completed two incremental AE tests to exhaustion, seven to eleven days apart, using a mechanically braked arm ergometer. The initial work rate was 16W and increased by 16W every two minutes until exhaustion. Significant differences between tests were determined by repeated measures ANOVA, and paired t-tests or Wilcoxon signed-rank tests, where appropriate. Reliability was determined by intraclass correlation coefficients (ICC), typical error, coefficient of variation (CV) and measurement bias/ratio and 95% limits of agreement (LOA). Peak cardio-respiratory responses were similar between tests, except for tidal volume (1.95 +/-0.47 vs. 1.81 +/- 0.41 L, P<0.05). Reliability for peak variables was moderate to high (ICC=0.659-0.941; CV< or =10%) while LOA were considerable for most variables including VO2(peak) (LOA=0.57 L.min(-1)). Similar peak cardio-respiratory responses, low CV and moderate-high ICC confirmed the reliability of the current incremental AE protocol to be similar to that of prior reported protocols for VO2(peak) determination. Substantial within-participant variability (LOA) for respiratory rate and tidal volume was common during the AE protocol and possibly reflects the influence of respiratory entrainment on reliability that requires further investigation.

A community change in the algal endosymbionts of a scleractinian coral following a natural bleaching event: field evidence of acclimatization.

The symbiosis between reef-building corals and their algal endosymbionts (zooxanthellae of the genus Symbiodinium) is highly sensitive to temperature stress, which makes coral reefs vulnerable to climate change. Thermal tolerance in corals is known to be substantially linked to the type of zooxanthellae they harbour and, when multiple types are present, the relative abundance of types can be experimentally manipulated to increase the thermal limits of individual corals. Although the potential exists for this to translate into substantial thermal acclimatization of coral communities, to date there is no evidence to show that this takes place under natural conditions. In this study, we show field evidence of a dramatic change in the symbiont community of Acropora millepora, a common and widespread Indo-Pacific hard coral species, after a natural bleaching event in early 2006 in the Keppel Islands (Great Barrier Reef). Before bleaching, 93.5% (n=460) of the randomly sampled and tagged colonies predominantly harboured the thermally sensitive Symbiodinium type C2, while the remainder harboured a tolerant Symbiodinium type belonging to clade D or mixtures of C2 and D. After bleaching, 71% of the surviving tagged colonies that were initially C2 predominant changed to D or C1 predominance. Colonies that were originally C2 predominant suffered high mortality (37%) compared with D-predominant colonies (8%). We estimate that just over 18% of the original A. millepora population survived unchanged leaving 29% of the population C2 and 71% D or C1 predominant six months after the bleaching event. This change in the symbiont community structure, while it persists, is likely to have substantially increased the thermal tolerance of this coral population. Understanding the processes that underpin the temporal changes in symbiont communities is key to assessing the acclimatization potential of reef corals.

Predictors of 1000-m outrigger canoeing performance.

UNLABELLED: This study examined the relationships between body composition, peak oxygen consumption and 1000-m time trial performance of female outrigger canoeists. PROCEDURES: Female outrigger canoeists (n = 17) completed anthropometric profiling and a 1000-m outrigger ergometer time trial, during which expired air was measured continuously and analysed at 15-s intervals for determination of peak oxygen consumption. Heart rate, stroke rate and power output were also recorded at 15-s intervals. Blood lactate was measured immediately and at 3-, 5- and 7-min post-exercise. Mean power output, peak power output and progressive split times were highly correlated (r > 0.80) to 1000-m performance. Arm girths, humerus breadth, mesomorphy, peak oxygen consumption, ventilation, mean heart rate and peak lactate were moderately correlated (r > 0.50) to 1000-m performance. Stepwise multiple regression analysis verified that mean power output and to a lesser extent flexed arm girth, humerus breadth, waist girth and sitting height can predict 1000-m performance. Enhanced 1000-m performance of female outrigger canoeists appears to be achieved through a combination of greater power production and maintenance, a muscular stature and to a lesser extent, a higher aerobic capacity. These characteristics should be considered when selecting crews.

High resolution electronic spectra of anisole and anisole-water in the gas phase: hydrogen bond switching in the S1 state.

Rotationally resolved S(1)<--S(0) electronic spectra of anisole and its hydrogen bonded complex containing one water molecule have been obtained. The results provide evidence for an "in-plane" complex in which the water molecule is attached via two hydrogen bonds to the anisole molecule, a donor O-H- - -O(CH(3)) bond and an acceptor H-O- - -H(ring) bond. Analysis of the subbands that appear in the spectrum of the complex suggests that hydrogen bond "switching" occurs when the complex absorbs light. The former O-H- - -O(CH(3)) bond is stronger in the ground (S(0)) state, whereas the latter H-O- - -H(ring) bond is stronger in the excited (S(1)) state. Dynamical consequences of this phenomenon are discussed.

Ethanol, errors, and the speed-accuracy trade-off.

Ethanol has been shown to have a relatively greater effect on error rates in speeded tasks than temazepam, and this may be due to a differential effect on the speed-accuracy trade-off (SATO). This study used different instruction sets to influence the SATO. Forty-nine healthy volunteers (24 males, aged 18-41 years) were allocated at random to one of three instruction conditions--emphasising accuracy, neutral, and emphasising speed. After familiarisation, they took part in two sessions spaced at least 4 days apart in which they received either ethanol (0.8 g/kg, max 60 g males, 50 g females) or placebo in randomised order. Tests were administered starting at 30 and 75 min postdrug. Instructions significantly affected performance. In two maze tasks, one on paper, the other on a pen computer, the pattern of instruction effects was as expected. A significant increase in errors with ethanol was seen for both maze tasks, and there was a tendency to speed up with ethanol (significant only for the pen computer task). Responses to fixed stimulus sequences on the Four-Choice Reaction Test also showed a tendency to speed up and an increase in errors with ethanol, while all other tests showed both slowing and increases in errors with ethanol compared to placebo. Error scores are consistently increased by ethanol in all test situations, while the effects of ethanol on speed are variable across tests.

Validity and sensitivity of a pen computer battery of performance tests.

This study compared administration of performance tests and visual analogue scales (VAS) using a newly developed pen computer (PenC) battery with established tests using either pencil-and-paper (PP) or conventional computer. The performance of 47 subjects (23 male, age 18-45 years, weight 51-112 kg) was compared on the two systems after a dose of ethanol (0.8 g/kg up to a maximum of 60 g for males, 50 g for females) or placebo in a double-blind two-period randomized crossover study. Mean (SD) blood ethanol concentrations (breathalyser) were 94.5 mg/100 ml (21.9) at the start of the test battery (30 min post-drink) and 80.2 (13.0) at the end of the battery (75 min post-drink). Ethanol effects were found in all tests, with most outcome measures showing significant slowing or loss of accuracy. Results from the Rapid Visual Information Processing, Sentence Verification and Continuous Attention tasks show that the ethanol-placebo difference and the statistical significance of this difference are in close correspondence for the two modes of administration. The pen computer versions of these tasks may therefore be used as direct replacements for the previous versions. Digit-Symbol and maze tasks did not correspond so closely both showing differences in the speed-accuracy trade-off between the two modes. These tests, however, are sensitive to the effects of ethanol, and may be useful in their own right. Principal component analysis suggested that VAS may be grouped into two factors: (1) 'functional integrity', including measures of alertness and perceived proficiency, and (2) 'mood', including happiness and sociability. Factor 1 showed substantial effects of ethanol, while factor 2 was unchanged. There was close agreement between the results from PP and PenC for both factors as well as for the Sober-Drunk scale, which showed the expected effects of ethanol. Thus pen computer VAS perform in a similar way to the PP versions.

Risks of fatal cancer from inhalation of 239,240plutonium by humans: a combined four-method approach with uncertainty evaluation.

The risk per unit dose to the four primary cancer sites for plutonium inhalation exposure (lung, liver, bone, bone marrow) is estimated by combining the risk estimates that are derived from four independent approaches. Each approach represents a fundamentally different source of data from which plutonium risk estimates can be derived. These are: (1) epidemiologic studies of workers exposed to plutonium; (2) epidemiologic studies of persons exposed to low-LET radiation combined with a factor for the relative biological effectiveness (RBE) of plutonium alpha particles appropriate for each cancer site of concern; (3) epidemiologic studies of persons exposed to alpha-emitting radionuclides other than plutonium; and (4) controlled studies of animals exposed to plutonium and other alpha-emitting radionuclides extrapolated to humans. This procedure yielded the following organ-specific estimates of the distribution of mortality risk per unit dose from exposure to plutonium expressed as the median estimate with the 5th to 95th percentiles of the distribution in parentheses: lung 0.13 Gy(-1) (0.022-0.53 Gy(-1)); liver 0.057 Gy(-1) (0.011-0.47 Gy(-1)); bone 0.0013 Gy(-1) (0.000060-0.025 Gy(-1)); bone marrow (leukemia), 0.013 Gy(-1) (0.00061-0.05 Gy(-1)). Because the different tissues do not receive the same dose following an inhalation exposure, the mortality risk per unit intake of activity via inhalation of a 1-microm AMAD plutonium aerosol also was determined. To do this, inhalation dose coefficients based on the most recent ICRP models and accounting for input parameter uncertainties were combined with the risk coefficients described above. The following estimates of the distribution of mortality risk per unit intake were determined for a 1-microm AMAD plutonium aerosol with a geometric standard deviation of 2.5: lung 5.3 x 10(-7) Bq(-1) (0.65-35 x 10(-7) Bq(-1)), liver 1.2 x 10(-7) Bq(-1) (0.091-20 x 10(-7) Bq(-1)), bone 0.11 x 10(-7) Bq(-1) (0.0030-4.3 x 10(-7) Bq(-1)), bone marrow (leukemia) 0.049 x 10(-7) Bq(-1) (0.0017-0.59 x 10(-7) Bq(-1)). The cancer mortality risk for all sites was estimated to be 10 x 10(-7) Bq(-1) (2.1-55 x 10(-7) Bq(-1))--a result that agrees very well with other recent estimates. The large uncertainties in the risks per unit intake of activity reflect the combined uncertainty in the dose and risk coefficients.

Elm Yellows Phytoplasma Lethal to Dutch Elm Disease-Resistant Ulmus americana Cultivars.

Ulmus americana (American elm) clonal cultivars Independence, New Harmony, and Valley Forge, together with the triploid putative hybrid cultivar Jefferson, were tested for reaction to the elm yellows (EY) phytoplasma. These cultivars all possess resistance to the fungal pathogen Ophiostoma novo-ulmi (1,4) but had not been screened for EY resistance or tolerance. Procedures and conditions of the test were similar to those used previously for assessing EY tolerance of Eurasian elm cultivars (3). In brief, 9 to 15 saplings of each cultivar and of U. americana raised from seed (susceptible controls), growing in a field plot at Ithaca, NY, were challenged by grafting their mainstems with bark patches from U. americana naturally affected by EY. Six to nine additional trees of each clone and of the seedling group were left untreated as controls. Inoculations were performed in July 1999, and trees were evaluated for symptoms in early September 2000. Multiple individuals in every inoculated group developed the syndrome typical of EY in U. americana: epinasty, foliar yellowing, yellow discoloration and necrosis of root and stem phloem, odor of methyl salicylate from moist discolored phloem on first exposure to air, defoliation or sudden permanent wilting, and death (2). The numbers of trees with these symptoms, of those inoculated, were: 9 of 9 Independence, 7 of 11 New Harmony, 10 of 14 Valley Forge, 3 of 13 Jefferson, and 12 of 15 trees grown from seed. Untreated controls remained asymptomatic, except for one tree of Valley Forge and two trees grown from seed that became infected naturally and had symptoms like those in the grafted trees. Based on these results, the elm cultivars named above are typical of U. americana in susceptibility to, and intolerance of, EY phytoplasmal infection. Effective EY resistance or tolerance in this species, although once thought to occur in rare individuals (2), remains undocumented. References: (1) J. L. Sherald et al. Can. J. For. Res. 24:647, 1994. (2) W. A. Sinclair. 2000. Page 121 in: The Elms. C. P. Dunn, ed. Kluwer Academic Publishers, Norwell, MA. (3) W. A. Sinclair et al. Plant Dis. 84:1266-1270, 2000. (4) A. M. Townsend. 2000. Page 271 in: The Elms. C. P. Dunn, ed. Kluwer Academic Publishers, Norwell, MA.

Dose limits for astronauts.

Radiation exposures to individuals in space can greatly exceed natural radiation exposure on Earth and possibly normal occupational radiation exposures as well. Consequently, procedures limiting exposures would be necessary. Limitations were proposed by the Radiobiological Advisory Panel of the National Academy of Sciences/National Research Council in 1970. This panel recommended short-term limits to avoid deterministic effects and a single career limit (of 4 Sv) based on a doubling of the cancer risk in men aged 35 to 55. Later, when risk estimates for cancer had increased and were recognized to be age and sex dependent, the NCRP, in Report No. 98 in 1989, recommended a range of career limits based on age and sex from 1 to 4 Sv. NCRP is again in the process of revising recommendations for astronaut exposure, partly because risk estimates have increased further and partly to recognize trends in limiting radiation exposure occupationally on the ground. The result of these considerations is likely to be similar short-term limits for deterministic effects but modified career limits.