Effects of heat and intermittent exercise on leukocyte and sub-population cell counts

This study examined the combined effects of heat stress and intermittent exercise on circulating leukocyte and sub-population cell counts. Using a randomized-block design, 11 healthy male subjects [mean (SD) age = 29.1 (3.0) years maximal oxygen consumption ( ) = 47.6 (6.1) ml/(kg-min)] were assigned to four conditions. Each subject exercised on a cycle ergometer at 50% (two 30-min bouts, with 45 min rest between), or acted as his own control by sitting at 23°C, or at 40°C, 30% relative humidity, for 3 h. Blood samples taken prior to, during, and after each rest and exercise bout, and at corresponding times when sitting were used for Coulter cell counter and flow cytometric analysis. Sitting conditions did not produce any significant immunological changes. Intermittent exercise induced a biphasic response of granulocytosis, monocytosis and lymphocytosis, with a return to baseline between exercise bouts. One hour following the second exercise bout, samples showed a consistent granulocytosis, monocytosis and lymphocytosis (CD3⁺, CD4⁺, CD8⁺ and CD19⁺ cell counts). The second exercise bout produced a larger response than the first, further exacerbated when exercising at 40°C. We conclude there is a synergism between heat and exercise exposure. An increase in core temperature and exercise stress recruit leukocytes into the peripheral circulation, with potentiation of the response during a second bout of exercise. However, while the increase of core temperature remains moderate, the disturbance of immune function does not appear to have great clinical significance.     

Dietary fumonisin exposure in a rural population of South Africa

A validated culturally specific dietary assessment method was used to determine the habitual maize intakes of black Xhosa-speaking Africans living in the Centane region of the Eastern Cape Province to assess their exposure to the carcinogenic fumonisin mycotoxins. The mean total dry weight maize intakes of home-grown, commercial or combined (both maize sources) were 474, 344, 462 g day^?1, respectively. When considering the total mean levels of fumonisin in home-grown maize (1142 μg kg^?1) and commercial maize (222 μg kg^?1), the probable daily intakes (PDI’s), expressed as μg kg^?1 body weight day^?1 were 12.1 (95%CI: 0.3–4926.5) and 1.3 (95%CI: 1.0–1.8) for men and 6.7 (95%CI: 1.0–457.8) and 1.1 (95%CI: 0.9–1.3) for women, consuming home-grown and commercial maize, respectively. Based on the different maize-based beer drinking frequencies the PDI’s varied between 6.9 and 12.0 μg kg^?1/drinking event. Depending on the maize intake patterns an exposure “window” exists where fumonisin exposure is below the recommended group provisional maximum tolerable daily intake (PMTDI) for fumonisins of 2 μg kg^?1 bw day^?1. The assessment of fumonisin exposure and development of preventative strategies depend, not only the accurate determination of total fumonisin levels in maize, but also on the distinct dietary patterns of a specific population.     

Low-level echogenicity in intraventricular hemorrhage versus ventriculitis

Serial cranial sonograms of 55 neonates with large perinatal intraventricular/intraparenchymal hemorrhages and moderate-to-severe posthemorrhagic hydrocephalus were reviewed. In all 55 patients, the ventricles were initially enlarged and filled with anechoic cerebrospinal fluid, which contained discrete hyperechoic fragments of hematoma. Between 7 and 25 days after the initial hemorrhagic episode, however, diffuse, low-level echogenicity appeared in the ventricles of 34 patients. The low-level echogenicity was transient and persisted for 7-59 days (average, 18 days). In 32 patients, low-level echogenicity was a benign finding associated with prior intraventricular hemorrhage. In two patients, the low-level echogenicity was associated with ventriculitis. Low-level echogenicity appeared, increased, then cleared, but reappeared with the onset of ventriculitis in these two patients. Thickening of the ependyma and abnormal periventricular echogenicity, signs of inflammation, were also present. Although low-level echogenicity may commonly be a benign finding, the possibility of ventriculitis should not be ignored.     

Carbohydrate and fluid needs of the soccer player

Soccer is a game that demands a combination of repeated maximal sprinting wit with 10 to 11km of moderate running, sometimes performed under extremely warm conditions. Over the course of a match, there is partial to near complete depletion of glycogen reserves in the leg muscles (depending on the extent of initial reserves and the level of competition), with a resultant decrease in physical performance. Blood glucose levels also fall, sometimes to values likely to cause a deterioration of both tactical thinking and cooperation between players (3.0 to 3.8 mmol/L), while in tropical climates, fluid losses can amount to 4 to 5kg of bodyweight. The effectiveness of glucose solutions in correcting these problems is limited for 2 main reasons: concentrations greater than 2.5% slow the rate of gastric emptying and thus fluid absorption, while provoking a secretion of insulin with a resultant hypoglycaemia. Fructose solutions are less liable to increase insulin secretion, but they have an equal propensity for slowing gastric emptying; moreover, the ingested fructose is largely metabolised in the liver, without boosting blood glucose. However, glucose polymer preparations have a low osmotic pressure per unit content of glucose equivalent, so that substantial amounts of carbohydrate can be administered in this fashion before gastric emptying is inhibited. If polymers are given before and during a soccer game, they sustain blood glucose, sparing muscle glycogen stores and increasing game performance. If the concentration of polymer is too high, one possible complication is a movement of water from the plasma into the gut; nevertheless, with an appropriate choice of concentration (for example, 7% polycose, 360 mOsm/L, plasma volume is increased rather than decreased relative to that seen with administration of water. Probably because the intergame interval for competitive soccer players is short, replenishment of glycogen reserves proceeds quite slowly. Moreover, this process does not seem to be helped by ingestion of either glucose polymers or a high carbohydrate diet.     

Science and medicine of canoeing and kayaking

Canoeing and kayaking are upper-body sports that make varying demands on the body, depending on the type of contest and the distance covered. The shorter events (500 m) are primarily anaerobic (2 minutes of exercise), calling for powerful shoulder muscles with a high proportion of fast-twitch fibres. In contrast, 10,000 m events call for aerobic work to be performed by the arms. Such contestants need a high proportion of slow-twitch fibres, and an ability to develop close to 100% of their leg maximum oxygen intake when paddling. In slalom and whitewater contests, the value of physiological testing is somewhat limited, since performance is strongly influenced by experience and the ability to make precisely judged rapid paddling efforts under considerable emotional stress. Paddlers face dangers from their hostile cold water environment; causes of fatalities (drowning, cardiac arrest, ventricular fibrillation and hypothermia) are briefly reviewed. Medical problems include provision of adequate nutrition and a clean water supply, effects of repeated immersion (softening of the skin, blistering, paronychial infections, sinusitis, otitis), varicose veins (secondary to thoracic fixation) and hazards of exposure to fibreglass and polystyrene in the home workshop. Surgical problems include muscle sprains and mechanical injuries (haemotomas, lacerations, contusions, concussion, and fractures).     

Heart rate overshoot in running events.

The phenomenon of heart rate overshoot has been examined in 6 high-school athletes aged 15-16 years and in 8 university athletes aged 19-20 years. The incidence was 100% over distances of 50, 100 and 200 metres, and only one subject failed to show an overshoot following a 400 metre run. However, the overshoot was relatively larger and more long-lived following the shorter runs. While an accumulation of anaerobic metabolites seems the most likely explanation of the phenomenon over the longer distances, in the 50 metre event the Valsalva manoeuvre may also make some contribution.     

Exercise and employee-wellness initiatives

The present article reviews exercise-centred employee-wellnessinitiatives from the viewpoints of cost-effectiveness and cost-benefitanalysis. Emphasis is placed upon limitations of the availabledata, and the need for more definitive experiments. Programmecosts vary widely with the scale of facilities offered, andit is unclear how far expensive facilities contribute to aneffective programme. The main factor limiting health impactis a low employee participation rate; there remains a need formore effective methods of recruiting workers and sustainingtheir enthusiasm for the exercise programme. Possible benefitsfrom the programme include an improvement of overall corporateimage, the recruitment of premium employees, greater workersatisfaction with resultant gains of productivity, lesser absenteeismand employee turnover, lower healthcare costs and a reducedincidence of industrial injuries, with a likelihood of lowerfuture medical costs due to an improved personal lifestyle.Current evidence suggests that in economic terms, such gainsmore than offset likely programme costs. However, there remainsa need to broaden work-site fitness initiatives to address otherforms of risk-taking behaviour, and to extend programme availabilitybeyond the white-collar segment of the labour force who areemployed at corporate headquarters.     

Realized kernels in practice: trades and quotes

Summary Realized kernels use high‐frequency data to estimate daily volatility of individual stock prices. They can be applied to either trade or quote data. Here we provide the details of how we suggest implementing them in practice. We compare the estimates based on trade and quote data for the same stock and find a remarkable level of agreement. We identify some features of the high‐frequency data, which are challenging for realized kernels. They are when there are local trends in the data, over periods of around 10 minutes, where the prices and quotes are driven up or down. These can be associated with high volumes. One explanation for this is that they are due to non‐trivial liquidity effects.