Bone mineral density and lean mass asymmetries are greater in cyclists than non-cyclists.

Cyclists may be at greater risk of developing asymmetrical force and motion patterns than other ground-based athletes. However, functional asymmetries during cycling tend to be highly variable, making them difficult to assess. Dual-energy x-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD) and lean mass (LM) in the lower limbs may be a more sensitive and consistent method to identify asymmetries in cyclists. The goal of this study was to determine if competitive cyclists have greater levels of asymmetries in the lower body compared to non-cyclists using DXA. A secondary aim was to determine if aBMD and LM asymmetries change over the road cycling season. 17 competitive cyclists and 21 non-cyclist, healthy controls underwent DXA scans. Lower-body asymmetries were greater in cyclists compared to non-cyclists in aBMD and LM for all lower limb segments. However, these asymmetries did not tend to consistently favour a particular side, except for the pelvis having more LM on the dominant side. The were no longitudinal changes in aBMD or LM in the cyclists. Asymmetry analysis via DXA provides evidence that although functional asymmetries during cycling are variable, cyclists have increased lower body LM and aBMD asymmetries compared to non-cyclists.

Effect of temperature on race times on a synthetic surface.

REASONS FOR PERFORMING STUDY: Differences in racing times have been noted on synthetic track surfaces that appear to depend on the temperature of the track. No published study to date has considered this effect in a systematic manner. OBJECTIVES: To investigate the relationship between temperature of track and speed of horses racing on a synthetic surface. Potential changes in the wax component of the synthetic track were investigated as one possible cause of changes in the track speed at the temperatures observed. METHODS: At Del Mar racetrack (California, USA), the air, surface and subsurface temperatures at 4 depths in the synthetic race surface were measured periodically throughout the day over a 42 day period. The 6 furlong (1.2 km) race (afternoon) and fast training 'work' (morning) times were also compiled. Samples of the track were obtained and the wax separated using a solvent separation technique. Differential scanning calorimetry was used to determine the range of temperatures at which the wax from the track underwent softening and other material changes. Transformation temperatures were compared to temperatures acquired from the track to evaluate the likelihood of changes in the wax properties during racing. RESULTS: Average air, surface and subsurface temperatures changed significantly throughout the day. Temperatures were higher during the afternoon race sessions and race times were significantly slower compared to morning work times. Temperatures at which some of the components of the wax began to soften were found to be within the range of temperature measured during track operation. CONCLUSIONS: A correlation was found between temperature of the synthetic track and speed of horse. Wax separated from the track showed that the temperatures experienced in the surface during normal operation exceed the temperatures at which the wax begins to experience thermal transformation. It is therefore hypothesised that the wax may be a cause of the observed changes in the track performance. POTENTIAL RELEVANCE: Future work should include a study of components of the synthetic track responsible for the change and epidemiological association of risk of injury.

Cycling on rollers: Kreitler fan resistance at submaximal levels of effort.

The goal of this investigation was to characterize the commercially available fan unit for the KreitlerAlloy rollers at submaximal levels of effort (< or = 500 W). A single cyclist rode six times at each of three fan inlet settings (closed, half, and full open) and five fan speeds (900, 1800, 2700, 3600, and 4500 rpm). Fan power requirements were isolated by subtracting roller resistance from separate trials. Power requirements relative to fan inlet and fan speed possessed a significant interaction with the main effects for each also significant (all p < 0.001). Power increased to the cube of fan speed, regardless of inlet opening (r2 > or = 0.997). Fan resistance was virtually non existent at 900 rpm. Fan resistance then significantly increased with increasing fan speed and inlet opening. At 4500 rpm power requirements of the fan reached 269 +/- 6, 352 +/- 7, and 406 +/- 9 W with the inlet closed, half, and fully open, respectively (p < 0.001). The rear wheel-roller interaction supplied an additional 19 +/- 2 W on up to 104 +/- 4 W at the highest speed. Therefore, the fan unit increases the functionality of the rollers for a variety of training and testing environments.

Inertial effects on mechanically braked Wingate power calculations.

PURPOSE: The standard procedure for determining subject power output from a 30-s Wingate test on a mechanically braked (friction-loaded) ergometer includes only the braking resistance and flywheel velocity in the computations. However, the inertial effects associated with accelerating and decelerating the crank and flywheel also require energy and, therefore, represent a component of the subject's power output. The present study was designed to determine the effects of drive-system inertia on power output calculations. METHODS: Twenty-eight male recreational cyclists completed Wingate tests on a Monark 324E mechanically braked ergometer (resistance: 8.5% body mass (BM), starting cadence: 60 rpm). Power outputs were then compared using both standard (without inertial contribution) and corrected methods (with inertial contribution) of calculating power output. RESULTS: Relative 5-s peak power and 30-s average power for the corrected method (14.8 +/- 1.2 W x kg(-1) BM; 9.9 +/- 0.7 W x kg(-1) BM) were 20.3% and 3.1% greater than that of the standard method (12.3 +/- 0.7 W x kg(-1) BM; 9.6 +/- 0.7 W x kg(-1) BM), respectively. Relative 5-s minimum power for the corrected method (6.8 +/- 0.7 W x kg(-1) BM) was 6.8% less than that of the standard method (7.3 +/- 0.8 W x kg(-1) BM). The combined differences in the peak power and minimum power produced a fatigue index for the corrected method (54 +/- 5%) that was 31.7% greater than that of the standard method (41 +/- 6%). All parameter differences were significant (P < 0.01). The inertial contribution to power output was dominated by the flywheel; however, the contribution from the crank was evident. CONCLUSIONS: These results indicate that the inertial components of the ergometer drive system influence the power output characteristics, requiring care when computing, interpreting, and comparing Wingate results, particularly among different ergometer designs and test protocols.

Staphylococcus aureus isolates from patients with Kawasaki disease express high levels of protein A.

Kawasaki disease (KD) is an acute vasculitis of young children that can be complicated by coronary artery abnormalities. Recent findings suggest that a superantigen(s) may play an important role in stimulating the immune activation associated with the disease, although the origin of this superantigen(s) is unclear. Staphylococcus aureus, isolated from the rectum or pharynx of patients with KD, secretes toxic shock syndrome toxin 1 (TSST-1). The KD isolates express low levels of other exoproteins compared to isolates from patients with toxic shock syndrome (TSS). Thus, it was previously suggested that the KD isolates may be defective in the global regulatory locus agr (for accessory gene regulator), which positively regulates these factors (D. Y. M. Leung et al., Lancet 342:1385-1388, 1993). Here we describe another characteristic of KD isolates. When considered collectively, the KD isolates were found to express higher levels of staphylococcal protein A than the TSS isolates, another characteristic of an agr-defective phenotype. This correlated with a higher level of spa mRNA in these isolates. In contrast, the KD and TSS isolates expressed comparable levels of TSST-1, consistent with previous findings (D. Y. M. Leung et al., Lancet 342:1385-1388, 1993). Analysis of RNAIII transcript levels and nucleotide sequence analysis of the RNAIII-coding region suggested that the KD isolates are not defective in RNAIII, the effector molecule of the agr regulatory system. However, induction of RNAIII transcription in the KD isolates did not result in a dramatic decrease in the amount of spa mRNA, as has been reported for other strains (F. Vandenesch, J. Kornblum, and R. P. Novick, J. Bacteriol. 173:6313-6320, 1991).

Presence of IgE antibodies to staphylococcal exotoxins on the skin of patients with atopic dermatitis. Evidence for a new group of allergens.

In the current study, we investigated whether Staphylococcus aureus grown from affected skin of atopic dermatitis (AD) patients secreted identifiable toxins that could act as allergens to induce IgE-mediated basophil histamine release. The secreted toxins of S. aureus grown from AD patients were identified by ELISA using antibodies specific for staphylococcal enterotoxin (SE) exfoliative toxin (ET), or toxic shock syndrome toxin (TSST-1). S. aureus isolates from 24 of 42 AD patients secreted identifiable toxins with SEA, SEB, and TSST accounting for 92% of the isolates. 32 of 56 AD sera (57%) tested contained significant levels of IgE primarily to SEA, SEB, and/or TSST. In contrast, although SEA, SEB, or TSST secreting S. aureus could be recovered from the skin of psoriasis patients, their sera did not contain IgE antitoxins. Freshly isolated basophils from 10 AD patients released 5-59% of total histamine in response to SEA, SEB, or TSST-1 but only with toxins to which patients had specific IgE. Basophils from eight other AD patients and six normal controls who had no IgE antitoxin failed to demonstrate toxin-induced basophil histamine release. Stripped basophils sensitized with three AD sera containing IgE to toxin released 15-41% of total basophil histamine only when exposed to the relevant toxin, but not to other toxins. Sensitization of basophils with AD sera lacking IgE antitoxin did not result in release of histamine to any of the toxins tested. These data indicate that a subset of patients with AD mount an IgE response to SEs that can be grown from their skin. These toxins may exacerbate AD by activating mast cells, basophils, and/or other Fc epsilon-receptor bearing cells armed with the relevant IgE antitoxin.

Production of enterotoxins and toxic shock syndrome toxin by bovine mammary isolates of Staphylococcus aureus.

The production of staphylococcal enterotoxin A (SEA), SEB, SEC, SED, and SEE and toxic shock syndrome toxin 1 by bovine mammary isolates of Staphylococcus aureus was evaluated. Enterotoxin secretion was detected by immunodiffusion using specific polyclonal antisera. Of 262 isolates examined, 75 (28.6%) produced one or more toxins. The most common pattern was secretion of both SEC and SED and toxic shock syndrome toxin 1. No isolates secreted SEE, one produced SEA, and seven secreted SEB.

Reaction of toxic shock syndrome toxin 1 with endothelium of human umbilical cord vein.

The binding of toxic shock syndrome toxin 1 (TSST-1) to the endothelium of human umbilical cord veins and arteries was studied. Radiolabeled TSST-1, perfused through a segment of human umbilical cord vein, bound to the vessel at 4 degrees C, with a dissociation constant (Kd) of 6.5 X 10(-10) M. A pre-embedding electron-microscopic immunogold technique revealed that TSST-1 was located in the veins and arteries on the surface of endothelial cells and in the area of cell contacts. Umbilical cord vein segments filled with TSST-1 were incubated for 30 minutes at 37 degrees C, fixed by perfusion and embedded in hydrophilic resin (Lowicryl K4M). Postembedding immunogold staining of ultrathin sections showed TSST-1 in the vesicles crossing the cytoplasm of the veins' endothelial cells and entering underlying elastic and collagen layers.

Effects of blood and different media on the production of toxic shock syndrome toxin 1 by Staphylococcus aureus in the tampon sac method.

The use of three different agar concentrations in the tampon sac method resulted in slightly higher fluid uptake by the tampons when a 0.5% agar concentration was used. However, there was essentially no difference in the total amount of toxin produced. The largest amount of toxic shock syndrome toxin 1 was produced with brain heart infusion agar, followed closely by 3% NZ-amine NAK-1% yeast extract medium. The addition of plasma and serum to the inoculum resulted in increases (62 and 73%, respectively) in toxin production. The addition of whole blood to the inoculum had a variable effect on toxin production, with an increase in the amount of toxin produced with some tampons and not with others. Over fivefold differences in the amount of toxin produced were obtained when duplicate experiments were done on successive days, whereas the differences were less than twofold for experiments done on the same day. This was related to the effect of small changes in the parameters on toxic shock syndrome toxin 1 production.

Chromatofocusing in the purification of staphylococcal enterotoxin D.

A chromatofocusing procedure for the purification of staphylococcal enterotoxin D was developed. The purification included the removal of the toxic protein from culture supernatant fluids of Staphylococcus aureus 1151m by batch adsorption with CG-50 resin, chromatofocusing on Polybuffer Exchanger 94, and gel permeation chromatography on Sephacryl S-200. The purity of the staphylococcal enterotoxin D obtained was approximately 98%.

Low incidence of toxic shock syndrome in children with staphylococcal infection.

Children have frequent staphylococcal infections, and many lack antibody to TSST-1, a toxin associated with the toxic shock syndrome (TSS). To determine why there have been no nonmenstrual cases of TSS reported in children in Utah, the authors tested S. aureus isolated from children for TSST-1 by radial immunodiffusion and sera from other hospitalized children by radioimmunoassay for antibody to TSST-1. TSST-1 was produced by 25% of S. aureus. Fifty-two children had infections with toxin producing strains. None had TSS. The prevalence of presumably protective levels of antibody (greater than or equal to 1:100) was high in newborns (80%), declined until age 2 years and then gradually increased with age. Therefore, there may have been about 20 children with toxigenic infection who lacked protective antibody but did not show the usual features of TSS. We conclude that the rarity of TSS in children is not caused by misdiagnosis, underreporting, or the absence of toxigenic strains or susceptible patients. Additional factors, such as local conditions or duration of carriage, may influence the clinical presentation of infection with TSST-1 producing staphylococci.

Production of toxic shock syndrome toxin 1 by Staphylococcus aureus as determined by tampon disk-membrane-agar method.

The influence of 17 commercially available tampons on production of toxic shock syndrome toxin 1 (TSST-1) by Staphylococcus aureus was investigated by using a tampon disk method. Filter membranes overlaying agar medium (with or without blood) in small petri dishes were spread inoculated with a TSST-1-producing strain of S. aureus. Disks cut from unrolled tampons were pressed and laid on the inoculated membranes; incubation was for 19 h at 37 degrees C with 5% CO2 in air. CFU on the membranes and in the disks were enumerated, and the presence of TSST-1 in the disks and in the agar layers was determined. Tampons made of different materials supported characteristic levels of cell growth and toxin production in the tampon. Colonization of the interface surface of the tampon disks was heavy. The number of CFU extracted from the tampon disks ranged from 5 X 10(10) to 82 X 10(10). There was little variation in the CFU recovered from the membranes ([1.9 +/- 0.4] X 10(11)). Sixty to 170 micrograms of TSST-1 was recoverable from the agar, with an additional 10 to 90 micrograms recoverable from tampon disks, depending on the type of tampon disk. The amount of toxin in the agar layer from the various tampon disks was relatively constant and indicated an important contribution of toxin from vaginal S. aureus cells not growing in the tampon. The main role of tampons in toxic shock syndrome may be that of providing a fibrous surface for heavy colonization and sufficient air for TSST-1 production.

Production of toxic shock syndrome toxin 1 by Staphylococcus aureus restricted to endogenous air in tampons.

All types of four brands of tampons were tested in triplicate by a tampon sac method for their effect on production of toxic shock syndrome toxin 1 (TSST-1). In this method the available air is limited to that which is in the tampon sac. Tampons were weighed and inserted into dialysis sacs inoculated with a TSST-1-producing Staphylococcus aureus strain; the sacs were submerged into brain heart infusion agar, which was allowed to harden around the sacs, and were incubated for 18 h at 37 degrees C. The tampons were removed, weighed, and extracted; the CFU of staphylococci and the amount of toxin present in the extracts were determined. Glass wool was used in place of the tampons as one control, and inoculated empty sacs were used as a second control. The total CFU were consistently greater than 2 X 10(11) for the tampons and glass wool and less than or equal to 10(11) for the empty sac control. Total toxin production for all tampons tested and the glass wool was 2 to 10 times higher than the toxin produced with the empty sac control. These results indicate that tampons provide increased surface area for the staphylococci to grow and adequate oxygen for toxin production. No significant inhibition of growth of the staphylococci or TSST-1 production by any of the tampons tested was noted.

Production of human and murine interleukin-2 by toxic shock syndrome toxin-1.

Toxic shock syndrome toxin-1 (TSST-1), isolated from Staphylococcus aureus strains associated with toxic shock syndrome (TSS), is known as a potent mitogen and interleukin-1 inducer. The potential of TSST-1 as an interleukin-2 (IL-2) inducer was tested on human peripheral blood lymphocytes (HPBL) and murine spleen lymphocytes (MSL). These cells were incubated with TSST-1 and the supernatants analysed for IL-2 production. Preincubation of IL-2-dependent indicator cells (IC) with a monoclonal antibody specific for murine IL-2 receptors inhibited their proliferation by supernatants of TSST-1-treated MSL, thus strongly suggesting that they contain IL-2. The concentrations of TSST-1 required for HPBL or MSL to produce IL-2 ranged between 10(-1) and 10(-4) micrograms/ml. The amount of IL-2 units/ml varied little from one experiment to another. In contrast, IL-2 production by PHA-stimulated HPBL or Con A-stimulated MSL showed great variability and dependence on mitogen concentration. T-cell depleted MSL exposed to TSST-1 produced less IL-2. Experiments with germ-free mice and TSST-1-primed mice demonstrated that IL-2 production is not related to TSST-1 antigenicity.

Toxic shock syndrome--the role of the toxin.

From isolates of Staphylococcus aureus derived from patients suffering from toxic shock syndrome a toxin was identified by tests in monkeys and was found to be distinct from the enterotoxin responsible for staphylococcal food poisoning. When purified, this TSS toxin (TSST-1) was characterised and used to generate antibodies in rabbits. Only a small proportion of routine staphylococcal isolates produce TSST-1, though it is clear that this toxin has existed for some years. At the same time, TSST-1 producing staphylococci have been isolated in every continent, yet very few cases of toxic shock syndrome have been recognised in developing countries. Using the purified TSST-1, human sera have been examined for the presence of antibodies. Patients with the disease had either no antibodies, or low titres.

Analysis of the mitogenic effects of toxic shock toxin on human peripheral blood mononuclear cells in vitro.

It has been shown previously that the staphylococcal enterotoxins A and B are T-cell mitogens and also cause inhibition of murine plaque-forming cells generated in vitro. Similarly, toxic shock toxin, a 24,000-MW protein produced by toxic shock-associated strains of Staphylococcus aureus, is mitogenic and inhibits the generation of both murine and rabbit plaque-forming cells. In this study, an analysis of the T-cell response to toxic shock toxin was performed. Human peripheral blood mononuclear cells responded to toxic shock toxin over a broad dosage range (1 ng/ml to 5 micrograms/ml) with maximum proliferation at day 4 (96 hr) of culture. Heat treatment (100 degrees C for 60 min) of toxic shock toxin attenuated its mitogenic effects by only a small amount, and this attenuation could be reversed with increasing concentration of the toxin. By cytofluorography, both untreated and toxic shock toxin-treated small lymphocytes manifested normal percentages of OKT3+, OKT11+, OKT4+, OKT8+, HLA/DR+, and Leu-7+ cells. However, toxic shock toxin-induced blasts were 99% OKT11+ and expressed the receptor for interleukin 2 (89%-100% TAC+). Approximately 85% of the blasts were OKT4+, and 25% of the blasts were OKT8+. Proliferation of purified, double-rosetted T cells was enhanced monotonically by the addition of irradiated "non-T" cells. Irradiated, monocyte-enriched non-T cells were 2.5 times more potent than unfractionated non-T cells in producing quantitatively similar proliferation by toxic shock toxin-stimulated, autologous T cells. In addition, preincubation of non-T cells for 24 hr with toxic shock toxin, followed by extensive washing and irradiation, induced substantial proliferation by unexposed, autologous T cells. These data show that toxic shock toxin is mitogenic for T cells and requires accessory cells for maximal activity. Further, this substance appears to induce both a subset of OKT4+ (Class II MHC-restricted) and OKT8+ (Class I MHC-restricted) blasts.

Identification, purification, and some physicochemical properties of staphylococcal enterotoxin C3.

A third staphylococcal enterotoxin C (C3) has been identified, purified, and characterized. Staphylococcal enterotoxin C3 was identified from a Staphylococcus aureus isolated received from England. The purified toxin was determined by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be a simple protein with a molecular weight of 26,900. The isoelectric point of the major band was determined by isoelectric focusing in polyacrylamide gels to be 8.15. The reaction of enterotoxin C3 with its specific antibody was not affected by tryptic digestion at pH 8.0 or peptic digestion at pH 4.5. The enterotoxin C3 consisted of 236 amino acid residues. Serine was shown to be the NH2-terminal amino acid residue by end group analysis. The protein was highly emetic in cynomolgus monkeys both per os and intravenously.

Effect of Staphylococcus aureus enterotoxin F on human neutrophil oxidative metabolism.

Epidemiologic and animal challenge studies have suggested that SEF may play a critical role in toxic-shock syndrome [1]. However, the pathogenic mechanism of SEF activity is not known. One means by which this toxin could elicit the widespread organ dysfunction observed in toxic-shock syndrome would be by directly promoting PMN production of toxic oxygen species and the resultant secondary endothelial cell damage [2]. To evaluate this possibility, we assayed the effect of SEF on PMN oxidative metabolism. SEF at 0.01-100 ng/ml did not stimulate O2- release or O2 consumption by inactive PMNs. Similarly, incubation of PMNs with 10 ng of SEF/ml for 1 hr neither potentiated nor inhibited cellular O2 consumption stimulated by optimal (10 mg/ml) or suboptimal (0.1 mg/ml) concentrations of opsonized zymosan. Finally, SEF had no effect on O2- release by PMNs stimulated by PMA. PMN viability, as assessed by trypan blue exclusion, was unaffected by SEF. This study did not address the possibility that SEF might indirectly activate PMN oxidative metabolism by promoting leukocytic pyrogen production by monocytes and macrophages [3]. SEF neither directly activated PMN oxidative activity nor potentiated the cellular oxidative response to particulate or soluble stimuli. Consequently, direct stimulation of PMN-derived, O2- mediated damage to endothelial cells is not a tenable hypothesis to explain the mechanism of SEF toxicity.

Purification and some physicochemical properties of toxic-shock toxin.

A procedure for the purification of a protein marker for the staphylococci isolated from toxic-shock syndrome patients has been developed. The purification procedure involves the removal of the toxic protein from culture supernatant fluids of toxic-shock syndrome associated Staphylococcus aureus strains FRI-1169 and FRI-1183 by batch absorption with CG-50 resin, ion-exchange chromatography on CM-Sepharose CL-6B, and gel permeation chromatography on Sephacryl S-200. The purified toxin is a simple protein with a molecular weight of 24 000 +/- 500 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point of the major band is 7.0 as determined by isoelectric focusing in polyacrylamide gels. The TS-toxin's reactivity with its specific antibody is not affected by tryptic digestion at pH 8.0 but is slowly reduced by treatment with pepsin at pH 4.5. The TS-toxin consists of 188 amino acid residues. Serine was shown to be the NH2-terminal amino acid residue by end-group analysis. Initial studies indicated the protein was emetic; thus tentatively it was called staphylococcal enterotoxin F. In this paper it is called TS-toxin because the emetic action in monkeys has not been confirmed.