George Hall

Surgical stress response

Recent advances in molecular medicine have allowed the characterization and quantification of inflammatory cascades following surgery and trauma. Activation of immune cells is followed by the release of various cytokines as well as by migration of leukocytes into inflamed tissues. Various methods have been developed in order to modulate the immune-inflammatory system and at the same time to prevent overreaction and unexpected complications. In this context, the magnitude of surgical stress exerted on the patient is of paramount importance. Several factors, either controllable or not, are known to contribute to the development and amplification of the surgical stress response. Therefore, they should be taken into consideration by both surgical practitioners and other medical specialties involved in the management of the traumatised patient.

The time course of the human growth hormone response to a 6 s and a 30 s cycle ergometer sprint.

Exercise is a potent stimulus for the release of human growth hormone (hGH), but the time course of the hGH response to sprint exercise has not been studied. The aim of the present study was to determine the time course of the hGH response to a 6 s and a 30 s maximal sprint on a cycle ergometer. Nine males completed two trials, on one occasion performing a single 6 s sprint and on another a single 30 s sprint. They then rested on a couch for 4 h while blood samples were obtained. Three of the participants completed a further control trial involving no exercise. Metabolic responses were greater after the 30 s sprint than after the 6 s sprint. The highest measured mean serum hGH concentrations after the 30 s sprint were more than 450% greater than after the 6 s sprint (18.5 - 3.1 vs 4.0 - 1.5 w g·l -1 , P ≪ 0.05). Serum hGH also remained elevated for 90-120 min after the 30 s sprint compared with ~ 60 min after the 6 s sprint. There was a large inter-individual variation in the hGH response to the 30 s sprint. In the control trial, serum hGH concentrations were not elevated above baseline at any time. It would appear that the duration of a bout of maximal sprint exercise determines the magnitude of the hGH response, although the mechanism for this is still unclear.

Different responses of selected hormones to three types of exercise in young men

Exercise is a potent stimulus for release of growth hormone (GH), cortisol, testosterone and prolactin, and prolonged exercise inhibits insulin secretion. These responses seem to be specific to the type of exercise but this has been poorly characterised primarily because they have not been compared during exercise performed by the same individuals. We investigated hormone responses to resistance, sprint and endurance exercise in young men using a repeated measures design in which each subject served as their own control. Eight healthy non-obese young adults (18–25xa0years) were studied on four occasions in random order: 30-s cycle ergometer sprint (Sprint), 30-min resistance exercise bout (Resistance), 30-min cycle at 70xa0% VO2max (Endurance), and seated rest in the laboratory (Rest). Cortisol, GH, testosterone, prolactin, insulin and glucose concentrations were measured for 60xa0min after the four different interventions. Endurance and sprint exercise significantly increased GH, cortisol, prolactin and testosterone. Sprint exercise also increased insulin concentrations, whereas this decreased in response to endurance exercise. Resistance exercise significantly increased only testosterone and glucose. Sprint exercise elicited the largest response per unit of work, but the smallest response relative to mean work rate in all hormones. In conclusion, the nature and magnitude of the hormone response were influenced by exercise type, perhaps reflecting the roles of these hormones in regulating metabolism during and after resistance, sprint and endurance exercise.

Growth hormone responses to 3 different exercise bouts in 18- to 25- and 40- to 50-year-old men

Exercise is a potent stimulus for growth hormone (GH) release, although aging appears to attenuate this response. The aim of this study was to investigate GH responses to different exercise stimuli in young and early middle-aged men. Eight men aged 18-25 y and 8 men aged 40-50 y completed 3 trials, at least 7 days apart, in a random order: 30 s cycle-ergometer sprint (sprint), 30 min resistance exercise bout (resistance), 30 min cycle at 70% maximal oxygen consumption (endurance). Blood samples were taken pre-, during, and post-exercise, and area under the GH vs. time curve was calculated for a total of 120 min. Mean blood lactate concentrations and percentage heart rate maximum at which the participants were working were not different between groups in any of the trials. In both groups, blood lactate concentrations were significantly lower in the endurance trial than in the sprint and resistance trials. There were no significant differences in resting GH concentration between groups or trials. GH AUC was significantly greater in the young group than the early middle-aged group, in both sprint (531 (+/-347) vs. 81 (+/-54) microg.L-1 per 120 min, p = 0.003) and endurance trials (842 (+/-616) vs. 177 (+/-137) microg.L-1 per 120 min, p = 0.010). Endurance exercise elicits a greater GH response than sprint and resistance exercise; however, aging per se, factors associated with aging, or an inability to achieve a sufficient absolute exercise intensity results in a smaller GH response to an exercise stimulus in early middle-aged men.

Age is an important determinant of the growth hormone response to sprint exercise in non-obese young men

Background:The factors that regulate the growth hormone (GH) response to physiological stimuli, such as exercise, are not fully understood. The aim of the present study is to determine whether age, body composition, measures of sprint performance or the metabolic response to a sprint are predictors of the GH response to sprint exercise in non-obese young men. Methods:Twenty-seven healthy, non-obese males aged 18–32 years performed an all-out 30-second sprint on a cycle ergometer. Univariate linear regression analysis was employed to evaluate age-, BMI-, performance- and metabolic-dependent changes from pre-exercise to peak GH and integrated GH for 60 min after the sprint. Results:GH was elevated following the sprint (change in GH: 17.0 ± 14.2 µg l–1; integrated GH: 662 ± 582 min µg l–1). Performance characteristics, the metabolic response to exercise and BMI were not significant predictors of the GH response to exercise. However, age emerged as a significant predictor of both integrated GH (β = –0.547, p = 0.003) and change in GH (β = –0.448, p = 0.019) after the sprint. Conclusion:In non-obese young men, age is a more important predictor of GH following sprint exercise than BMI, sprint performance or the metabolic response to sprint exercise.

Preface to the Fifth Edition

We were honoured to be asked by Springer, New York to prepare a fifth edition of Structure Determination by X-ray Crystallography. First published in 1977 under the Plenum imprint, this book has received wide acclaim in both teaching and research in X-ray crystallography because of its extensive and detailed coverage of all aspects of the subject. As we prepare this new edition, we are entering the centenary of the discovery of X-ray diffraction in 1912, the beginning of X-ray crystallography as a science in its own right. Today, X-ray crystallography and the complementary technique of neutron diffraction together provide the most powerful tools for the investigation and elucidation of crystal and molecular structures. X-ray and neutron crystallography may be described as the science of the structure of materials, in the widest sense of the phrase, and their ramifications are evident across a broad spectrum of scientific endeavour. The power of computers and available software has unleashed an unprecedented ability to carry out with speed the complicated calculations involved in crystal structure determination on a desktop PC. This is paralleled by the availability of powerful X-ray and neutron sources and low temperature devices for facilitating measurements at liquid nitrogen temperature or lower, which provide ever higher precision in the determination of crystal structures. However, a detailed knowledge of the theory underlying the process of crystal structure determination is still required in order both to ensure that the literature contains correct well-determined structures and to understand the complexities introduced by features such as disorder and twinning in crystals. There are many pitfalls in crystal structure determination to trap the unwary. In this new edition, we have continued the approach that has been well reviewed in its earlier editions. We have always kept in mind that students meeting X-ray crystallography for the first time are encountering a new discipline, and not merely extending the range of a subject already studied. In consequence, we have chosen, for example, to discuss the geometry and symmetry of crystals in rather more detail than is found in other books on this subject, for it is our experience that some of the difficulties that students meet in introductory X-ray crystallography lie in their unfamiliarity with a threedimensional concept, whether they be final-year undergraduate or post-graduate students in chemistry, biochemistry, materials science, geology, bioinformatics, information technology, or physics. Both low molecular weight (small molecules) and macromolecular methods (proteins) are covered in detail.