Foot forces during exercise on the International Space Station

Long-duration exposure to microgravity has been shown to have detrimental effects on the human musculoskeletal system. To date, exercise countermeasures have been the primary approach to maintain bone and muscle mass and they have not been successful. Up until 2008, the three exercise countermeasure devices available on the International Space Station (ISS) were the treadmill with vibration isolation and stabilization (TVIS), the cycle ergometer with vibration isolation and stabilization (CEVIS), and the interim resistance exercise device (iRED). This article examines the available envelope of mechanical loads to the lower extremity that these exercise devices can generate based on direct in-shoe force measurements performed on the ISS. Four male crewmembers who flew on long-duration ISS missions participated in this study. In-shoe forces were recorded during activities designed to elicit maximum loads from the various exercise devices. Data from typical exercise sessions on Earth and on-orbit were also available for comparison. Maximum on-orbit single-leg loads from TVIS were 1.77 body weight (BW) while running at 8mph. The largest single-leg forces during resistance exercise were 0.72 BW during single-leg heel raises and 0.68 BW during double-leg squats. Forces during CEVIS exercise were small, approaching only 0.19 BW at 210W and 95RPM. We conclude that the three exercise devices studied were not able to elicit loads comparable to exercise on Earth, with the exception of CEVIS at its maximal setting. The decrements were, on average, 77% for walking, 75% for running, and 65% for squats when each device was at its maximum setting. Future developments must include an improved harness to apply higher gravity replacement loads during locomotor exercise and the provision of greater resistance exercise capability. The present data set provides a benchmark that will enable future researchers to judge whether or not the new generation of exercise countermeasures recently added to the ISS will address the need for greater loading.

Not all pain in the left iliac fossa is diverticular disease: A case study of a psoas myxoma and review

Intramuscular myxomas are rare, benign, mesenchymal tumours that may present to a wide variety of specialties. We present a case study of an intramuscular myxoma in the psoas muscle, followed by a review of the literature regarding the diagnosis and treatment of intramuscular myxomas

Acute weight loss followed by an aggressive nutritional recovery strategy has little impact on on-water rowing performance

OBJECTIVES

To assess the influence of moderate, acute weight loss on on-water rowing performance when aggressive nutritional recovery strategies were used in the two hours between weigh in and racing.

METHODS

Competitive rowers (n = 17) undertook three on-water 1800 m time trials under cool conditions (mean (SD) temperature 8.4 (2.0) degrees C), each separated by 48 hours. No weight limit was imposed for the first time trial--that is, unrestricted body mass (UNR1). However, one of the remaining two trials followed a 4% loss in body mass in the previous 24 hours (WT(-4%)). No weight limit was imposed for the other trial (UNR2). Aggressive nutritional recovery strategies (WT(-4%), 2.3 g/kg carbohydrate, 34 mg/kg Na+, and 28.4 ml/kg fluid; UNR, ad libitum) were used in the first 90 minutes of the two hours between weigh in and performance trials.

RESULTS

WT(-4%) had only a small and statistically non-significant effect on the on-water time trial performance (mean 1.0 second, 95% confidence interval (CI) -0.9 to 2.8; p = 0.29) compared with UNR. This was despite a significant decrease in plasma volume at the time of weigh in for WT(-4%) compared with UNR (-9.2%, 95% CI -12.8% to -5.6%; p<0.001).

CONCLUSIONS

Acute weight loss of up to 4% over 24 hours, when combined with aggressive nutritional recovery strategies, can be undertaken with minimal impact on on-water rowing performance, at least in cool conditions.

Physique traits of lightweight rowers and their relationship to competitive success

OBJECTIVES

Physique traits and their relationship to competitive success were assessed amongst lightweight rowers competing at the 2003 Australian Rowing Championships.

METHODS

Full anthropometric profiles were collected from 107 lightweight rowers (n = 65 males, n = 45 females) competing in the Under 23 and Open age categories. Performance assessments were obtained for 66 of these rowers based on results in the single sculls events. The relationship between physique traits and competitive success was then determined.

RESULTS

Lower body fat (heat time estimate -8.4 s kg(-1), p<0.01), greater total body mass (heat time estimate -4.4 s kg(-1), p = 0.03), and muscle mass (heat time estimate -10.2 s kg(-1), p<0.01) were associated with faster 2000 m heat times.

CONCLUSIONS

The more successful lightweight rowers were those who had lower body fat and greater total muscle mass.

Thrombospondin 1 protein expression relates to good prognostic indices in ductal carcinoma in situ of the breast

AIM

Angiogenesis plays an important role in tumour growth and has been shown to occur around both in situ and invasive tumours. The degree of angiogenesis within tumours depends on the balance of pro-angiogenic and anti-angiogenic factors. One such anti-angiogenic factor is thrombospondin 1 (TSP-1). This study investigates the pattern of expression of TSP-1 in ductal carcinoma in situ (DCIS) of the breast and its relation to the surrounding microvessel pattern and density.

MATERIALS/METHODS

The expression of TSP-1 was studied in formalin fixed, paraffin wax embedded sections from 58 cases of pure DCIS, using a monoclonal antibody against TSP-1 and the avidin-biotin-diaminobenzidine immunoperoxidase detection system. Vessels were stained with a monoclonal antibody to the endothelial cell marker CD31. Stromal microvessel density was assessed by counting "hot spots" within 500 micro m of the basement membrane of involved ducts using a 25 point Chalkey graticule.

RESULTS

TSP-1 staining of the basement membrane around duct spaces with DCIS was seen in 69% of cases. In addition, staining of the stroma between involved duct spaces was seen in 31% of cases, with a fibrillary pattern identical to that seen in invasive breast carcinomas. In 12% of cases no staining for TSP-1 was seen. Two patterns of vascularity were identified. A cuff of vessels immediately adjacent to the basement membrane of ducts with DCIS was seen in 71% of cases. The presence of stromal TSP-1 was significantly associated with DCIS showing no/little necrosis (p = 0.01) and no/little periductal inflammation (p = 0.04). There was a trend between the presence of stromal TSP-1 and tumour cell negativity for p53 (p = 0.087). The stromal microvessel Chalkey point count ranged between 3.33 and 16. An increased stromal microvessel count was associated with high histological grade (p = 0.02), extensive necrosis (p = 0.047), and pronounced periductal inflammation (p = 0.049). There was no association between the presence of stromal TSP-1 and stromal microvessel density.

CONCLUSIONS

TSP-1 is expressed in the stroma around DCIS and in the immediately adjacent basement membrane. Expression of stromal TSP-1 is lost in DCIS with more aggressive histological features. The absence of a relation with microvessel density suggests that other angiogenic factors may play an important role in DCIS.

Tachykinin-induced bronchoconstriction in sheep is NK-1 receptor mediated and exhibits tachyphylaxis

OBJECTIVE

Tachykinins are mediators of airway hyper-reactivity and inflammation. There is in vitro evidence that ovine responses to tachykinins correlate closely to human responses. This study was designed to characterize the effect of intravenously administered tachykinins on sheep lung resistance in vivo to determine the effect of dose timing on reproducibility of responses and the induction of tachyphylaxis. We then used this information to help further characterize the response with several pharmacological agents.

METHODOLOGY

Substance P (SP) was administered by infusion to conscious merino ewes and lung resistance (RL) was measured. Infusions were given at 30, 60, 120 min and 24 h intervals. The effect of various agents on the response to SP was then assessed.

RESULTS

Substance P led to a transient increase in RL, mean (+/- SEM) 754.8 (+/- 139)% of baseline, with marked tachyphylaxis at 30, 60 and 120 min. Phosphoramidon increased the peak response to 1151.5 +/- 196%. Atropine and CP 96 345 abolished the response to SP, while indomethacin, sodium cromoglycate and pyrilamine had no significant effect. Substance P had a greater effect on RL than did neurokinin A.

CONCLUSIONS

Substance P increases RL in sheep via a cholinergic mechanism which is mediated by NK-1 receptors, and is subject to tachyphylaxis. These findings have implications for the design of studies using the ovine model in the evaluation of tachykinin antagonists as potential therapeutic agents.

Arterial hypoxaemia in endurance athletes is greater during running than cycling

The effect of both training discipline and exercise modality on exercise-induced hypoxaemia (EIH) was examined in seven runners and six cyclists during 5 min high intensity treadmill and cycle exercise. There were no significant interactions between training discipline, exercise modality and arterial P(O(2)) (Pa(O(2))) when subject groups were considered separately but when pooled there were significant differences between exercise modalities. After min 2 of exercise arterial hydrogen ion concentration, minute ventilation, alveolar P(O(2)) (PA(O(2))) and Pa(O(2)) were all lower with treadmill running with the largest differential for the latter occurring at min 5 (treadmill, 80.8+/-1.8; cycle, 90.2+/-2.5, mmHg, N=13, P< or = 0.05). At every min of exercise, the differences in Pa(O(2)) between the ergometers were strongly associated with similar differences in PA(O(2)) and alveolar to arterial P(O(2)) (PA(O(2))-Pa(O(2))). It is concluded that the greater EIH with treadmill running is a consequence of the combined effect of a reduced lactic acidosis-induced hyperventilation and greater ventilation-perfusion inequality with this exercise mode.

Pulmonary gas exchange during exercise in highly trained cyclists with arterial hypoxemia

The causes of exercise-induced hypoxemia (EIH) remain unclear. We studied the mechanisms of EIH in highly trained cyclists. Five subjects had no significant change from resting arterial PO(2) (Pa(O(2)); 92.1 +/- 2.6 Torr) during maximal exercise (C), and seven subjects (E) had a >10-Torr reduction in Pa(O(2)) (81.7 +/- 4.5 Torr). Later, they were studied at rest and during various exercise intensities by using the multiple inert gas elimination technique in normoxia and hypoxia (13.2% O(2)). During normoxia at 90% peak O(2) consumption, Pa(O(2)) was lower in E compared with C (87 +/- 4 vs. 97 +/- 6 Torr, P < 0.001) and alveolar-to-arterial O(2) tension difference (A-aDO(2)) was greater (33 +/- 4 vs. 23 +/- 1 Torr, P < 0. 001). Diffusion limitation accounted for 23 (E) and 13 Torr (C) of the A-aDO(2) (P < 0.01). There were no significant differences between groups in arterial PCO(2) (Pa(CO(2))) or ventilation-perfusion (VA/Q) inequality as measured by the log SD of the perfusion distribution (logSD(Q)). Stepwise multiple linear regression revealed that lung O(2) diffusing capacity (DL(O(2))), logSD(Q), and Pa(CO(2)) each accounted for approximately 30% of the variance in Pa(O(2)) (r = 0.95, P < 0.001). These data suggest that EIH has a multifactorial etiology related to DL(O(2)), VA/Q inequality, and ventilation.

Measurement of cardiac output during exercise by open-circuit acetylene uptake

Noninvasive measurement of cardiac output (QT) is problematic during heavy exercise. We report a new approach that avoids unpleasant rebreathing and resultant changes in alveolar PO(2) or PCO(2) by measuring short-term acetylene (C(2)H(2)) uptake by an open-circuit technique, with application of mass balance for the calculation of QT. The method assumes that alveolar and arterial C(2)H(2) pressures are the same, and we account for C(2)H(2) recirculation by extrapolating end-tidal C(2)H(2) back to breath 1 of the maneuver. We correct for incomplete gas mixing by using He in the inspired mixture. The maneuver involves switching the subject to air containing trace amounts of C(2)H(2) and He; ventilation and pressures of He, C(2)H(2), and CO(2) are measured continuously (the latter by mass spectrometer) for 20-25 breaths. Data from three subjects for whom multiple Fick O(2) measurements of QT were available showed that measurement of QT by the Fick method and by the C(2)H(2) technique was statistically similar from rest to 90% of maximal O(2) consumption (VO(2 max)). Data from 12 active women and 12 elite male athletes at rest and 90% of VO(2 max) fell on a single linear relationship, with O(2) consumption (VO(2)) predicting QT values of 9.13, 15.9, 22.6, and 29.4 l/min at VO(2) of 1, 2, 3, and 4 l/min. Mixed venous PO(2) predicted from C(2)H(2)-determined QT, measured VO(2), and arterial O(2) concentration was approximately 20-25 Torr at 90% of VO(2 max) during air breathing and 10-15 Torr during 13% O(2) breathing. This modification of previous gas uptake methods, to avoid rebreathing, produces reasonable data from rest to heavy exercise in normal subjects.

Exercise-induced hypoxaemia in highly trained cyclists at 40% peak oxygen uptake

A group of 15 competitive male cyclists [mean peak oxygen uptake, VO2peak 68.5 (SEM 1.5 ml x kg(-1) x min(-1))] exercised on a cycle ergometer in a protocol which began at an intensity of 150 W and was increased by 25 W every 2 min until the subject was exhausted. Blood samples were taken from the radial artery at the end of each exercise intensity to determine the partial pressures of blood gases and oxyhaemoglobin saturation (SaO2), with all values corrected for rectal temperature. The SaO2 was also monitored continuously by ear oximetry. A significant decrease in the partial pressure of oxygen in arterial blood (PaO2) was seen at the first exercise intensity (150 W, about 40% VO2peak). A further significant decrease in PaO2 occurred at 200 W, whereafter it remained stable but still significantly below the values at rest, with the lowest value being measured at 350 W [87.0 (SEM 1.9) mmHg]. The partial pressure of carbon dioxide in arterial blood (PaCO2) was unchanged up to an exercise intensity of 250 W whereafter it exhibited a significant downward trend to reach its lowest value at an exercise intensity of 375 W [34.5 (SEM 0.5) mmHg]. During both the first (150 W) and final exercise intensities (VO2peak) PaO2 was correlated significantly with both partial pressure of oxygen in alveolar gas (P(A)O2, r = 0.81 and r = 0.70, respectively) and alveolar-arterial difference in oxygen partial pressure (P(A-a)O2, r = 0.63 and r = 0.86, respectively) but not with PaCO2. At VO2peak PaO2 was significantly correlated with the ventilatory equivalents for both oxygen uptake and carbon dioxide output (r = 0.58 and r = 0.53, respectively). When both P(A)O2 and P(A-a)O2 were combined in a multiple linear regression model, at least 95% of the variance in PaO2 could be explained at both 150 W and VO2peak. A significant downward trend in SaO2 was seen with increasing exercise intensity with the lowest value at 375 W [94.6 (SEM 0.3)%]. Oximetry estimates of SaO2 were significantly higher than blood measurements at all times throughout exercise and no significant decrease from rest was seen until 350 W. The significant correlations between PaO2 and P(A)O2 with the first exercise intensity and at VO2peak led to the conclusion that inadequate hyperventilation is a major contributor to exercise-induced hypoxaemia.

Loss of bcl-2 expression in ductal carcinoma in situ of the breast relates to poor histological differentiation and to expression of p53 and c-erbB-2 proteins

AIM

This study (1) investigates the incidence of bcl-2 protein expression in a series of 108 cases of ductal carcinoma in situ (DCIS), including 25 with early invasive carcinoma, and (2) evaluates the relationship of bcl-2 expression to the histological grade of DCIS and to the expression of oestrogen receptor (ER), c-erbB-2 and p53 proteins.

METHODS AND RESULTS

The expression of bcl-2, oestrogen receptor (ER), c-erbB-2 and p53 proteins was determined immunohistochemically. Cases were regarded as positive for individual antibodies when at least 10% of the DCIS cells showed positive staining. DCIS was graded histologically as well (n = 9), intermediately (n = 24), or poorly differentiated (n = 75). bcl-2 expression was documented in 57 cases (53%) and was strongly associated with the histological grade of DCIS (P < 0.0001). All cases of well-differentiated DCIS were bcl-2 positive and loss of bcl-2 expression was almost exclusively confined to poorly differentiated DCIS lesions. bcl-2 expression was also closely associated with positive ER status (P < 0.0001). Forty-seven of 57 (82%) bcl-2 positive cases were ER positive while 49/51 (96%) bcl-2 negative cases were ER negative. There was a significant inverse correlation between bcl-2 expression and both p53 protein expression (P = 0.0004) and c-erbB-2 expression (P < 0.0001). Nineteen of 24 (79%) p53 positive cases and 38/45 (84%) c-erbB-2 positive cases showed loss of bcl-2.

CONCLUSIONS

Loss of bcl-2 expression occurs in poorly differentiated DCIS and is related to negative ER status and to positive p53 and c-erbB-2 status. This pattern of bcl-2 expression and its association with other biological markers in DCIS is similar to that reported in invasive breast carcinoma.

Tachykinins contribute to the acute airways response to allergen in sheep actively sensitized to Ascaris suum

Tachykinins, found in sensory nerves, have effects in the airways which suggest that they may contribute to the pathogenesis of asthma. We aimed to find evidence for tachykinin involvement in the immediate airway response to allergen in a sheep model of experimental asthma. Twenty-four sheep were actively sensitized to Ascaris suum, then challenged with nebulized Ascaris extract in a dose-response fashion. Change in lung resistance (RL) in response to challenge was measured. Responder sheep (those with an increase in RL of > or = 100% over baseline) that had reproducible responses over three challenges were identified (n = 4 sheep) and a PC100 (number of breaths of extract required to induce a 100% increase in RL) was determined. The effect of the neutral endopeptidase inhibitor phosphoramidon, the NK-1 receptor-specific antagonist CP 96, 345 and capsaicin desensitization on the RL response to Ascaris challenge was then assessed. Administration of phosphoramidon before Ascaris decreased the PC100 to 31 +/- 7% of the PC100 seen with Ascaris alone (P < 0.05), whereas CP 96,345 and capsaicin desensitization increased the PC100 to 285 +/- 41% and 555 +/- 93% respectively (P < 0.05 for both). These findings suggest that endogenous tachykinins are released in response to allergen challenge and that they contribute to the immediate increase in RL.

Dental health of recent immigrant children in the Newcomer schools, San Francisco

Dental screenings of 1,012 recent immigrant elementary school children in San Francisco showed 77 per cent of children needed dental treatment on first screening, compared to 25 per cent in the 1979-80 National Institute of Dental Research (NIDR) survey for the western United States. The prevalence of dental caries in primary teeth of the immigrant six and seven year-olds was twice that of their US counterparts. Non-refugee immigrants had more serious dental needs but used dental services less often than children with refugee status.