When does the influence of maturation on anthropometric and physical fitness characteristics increase and subside?

The relationships between maturation and anthropometric and physical performance characteristics are dynamic and often asynchronous; confounding the capability to accurately evaluate performance during adolescence. This study aimed to (i) examine the influence of chronological age (CA) and somatic maturation (YPHV) upon anthropometric and physical performance parameters, and (ii) identify the transition/change time points in these relationships using segmental regression. N = 969 soccer players (8-18 years of age) completed anthropometric and physical test assessments, including a countermovement jump (CMJ), agility T test, 10 and 20 m sprints, and multistage fitness test (MSFT). When modeled against CA and YPHV, results identified time point phases with increased rates of stature (CA-7.5, YPHV-8.6 cm/y at 10.7-15.2 years or -3.2 to +0.8 YPHV) and body mass gain (CA-7.1, YPHV-7.5 kg/y at 11.9-16.1 years or -1.6 to +4.0 YPHV), followed by gain reductions. Increased rates of sprint performance development (31%-43% gains) occurred at 11.8-15.8 CA or -1.8 to +1.2 YPHV, with gains subsiding thereafter. CMJ, T test, and MSFT gains appeared relatively linear with no change in developmental rate apparent. Developmental tempos did again, however, subside at circa (CMJ and T test) to post-PHV (MSFT). Based on our sample and analysis, periods of increased developmental rates (stature, mass, sprint) were apparent alongside progressive gains for other physical measures, before all subsided at particular age and maturation time points. Findings highlight dynamic asynchronous development of players, physical attributes, and the need to account for the influence of maturation on athletic performance until post-PHV.

Individualisation of time-motion analysis: a method comparison and case report series

This study compared the intensity distribution of time-motion analysis data, when speed zones were categorized by different methods. 12 U18 players undertook a routine battery of laboratory- and field-based assessments to determine their running speed corresponding to the respiratory compensation threshold (RCT), maximal aerobic speed (MAS), maximal oxygen consumption (vV˙O2max) and maximal sprint speed (MSS). Players match-demands were tracked using 5 Hz GPS units in 22 fixtures (50 eligible match observations). The percentage of total distance covered running at high-speed (%HSR), very-high speed (%VHSR) and sprinting were determined using the following speed thresholds: (1) arbitrary; (2) individualised (IND) using RCT, vV˙O2max and MSS; (3) individualised via MAS per se; (4) individualised via MSS per se; and (5) individualised using MAS and MSS as measures of locomotor capacities (LOCO). Using MSS in isolation resulted in 61% and 39% of player's % HSR and % VHSR, respectively, being incorrectly interpreted, when compared to the IND technique. Estimating the RCT from fractional values of MAS resulted in erroneous interpretations of % HSR in 50% of cases. The present results suggest that practitioners and researchers should avoid using singular fitness characteristics to individualise the intensity distribution of time-motion analysis data. A combination of players' anaerobic threshold, MAS, and MSS characteristics are recommended to individualise player-tracking data.

Post-transplant T cell chimerism predicts graft versus host disease but not disease relapse in patients undergoing an alemtuzumab based reduced intensity conditioned allogeneic transplant

In this multicentre retrospective study we have studied the impact of T cell chimerism on the outcome of 133 patients undergoing an alemtuzumab based reduced intensity conditioning allograft (RIC). The median age of the patients was 50 years (range 42-55 years). 77 patients were transplanted using an HLA identical sibling donor while 56 patients received a fully matched volunteer unrelated donor graft. 64 patients had a lymphoid malignancy and 69 were transplanted for a myeloid malignancy. 38 patients (29%) relapsed with no significant difference in risk of relapse between patients developing full donor and mixed donor chimerism in the T-cell compartment on D+90 and D+180 post transplant. Day 90 full donor T cell chimerism correlated with an increased incidence of acute GVHD according to NIH criteria (p=0.0004) and the subsequent development of chronic GVHD. Consistent with previous observations, our results confirmed a correlation between the establishment of T cell full donor chimerism and acute GVHD in T deplete RIC allografts. However our study failed to identify any correlation between T cell chimerism and relapse risk and challenge the use of pre-emptive donor lymphocyte infusions (DLI) in patients with mixed T cell chimerism transplanted using an alemtuzumab based RIC regimen.

Effects of different half-time strategies on second half soccer-specific speed, power and dynamic strength

This study compared the effects of whole body vibration (WBV) and a field-based re-warm-up during half-time (HT) on subsequent physical performance measures during a simulated soccer game. Ten semi-professional male soccer players performed 90-min fixed-intensity soccer simulations (SAFT(90)), using a multi-directional course. During the HT period players either remained seated (CON), or performed intermittent agility exercise (IAE), or WBV. At regular intervals during SAFT(90), vastus lateralis temperature (T(m)) was recorded, and players also performed maximal counter-movement jumps (CMJ), 10-m sprints, and knee flexion and extension contractions. At the start of the second half, sprint and CMJ performance and eccentric hamstring peak torque were significantly reduced compared with the end of the first half in CON (P≤0.05). There was no significant change in these parameters over the HT period in the WBV and IAE interventions (P>0.05). The decrease in T(m) over the HT period was significantly greater for CON and WBV compared with IAE (P≤0.01). A passive HT interval reduced sprint, jump and dynamic strength performance. Alternatively, IAE and WBV at HT attenuated these performance decrements, with limited performance differences between interventions.

The time-profile of the PBMC HSP70 response to in vitro heat shock appears temperature-dependent

Heat shock proteins (HSPs) are synthesised by cells subsequent to a stress exposure and are known to confer protection to the cell in response to a second challenge. HSP induction and decay are correlated to thermotolerance and may therefore be used as a biomarker of thermal history. The current study tested the temperature-dependent nature of the heat shock response and characterised its time profile of induction. Whole blood from 6 healthy males (Age: 26 +/- (SD) 2 yrs; Body mass 74.2 +/- 3.8 kgs; VO(2max): 49.1 +/- 4.0 ml.kg(-1).min(-1)) were isolated and exposed to in vitro heat shock (HS) at 37, 38, 39, 40, and 41 degrees C for a period of 90 min. After HS the temperature was returned to 37 degrees C and intracellular HSP70 was quantified from the leukocytes at 0, 2, 4, and 6 h after heat treatment. The concentration of HSP70 was not different between temperatures (P > 0.05), but the time-profile of HSP70 synthesis appeared temperature-dependent. At control (37 degrees C) and lower temperatures (38-39 degrees C) the mean HSP70 concentration increased up to 4 h post HS (P < 0.05) and then returned towards baseline values by 6 h post HS. With in vitro hyperthermic conditions (40-41 degrees C), the time-profile was characterised by a sharp rise in HSP70 levels immediately after treatment (P < 0.05 for 40 degrees C at 0 h), followed by a progressive decline over time. The results suggest a temperature-dependent time-profile of HSP70 synthesis. In addition, the temperature at which HSP70 is inducted might be lower than 37 degrees C.

Identification of non-B human immunodeficiency virus type 1 subtypes in rural Georgia

As part of an ongoing molecular epidemiological investigation of human immunodeficiency virus type 1 (HIV-1) in rural Georgia, the 5' half of reverse transcriptase (RT) genotypes from 30 patients was sequenced and phylogenetically analyzed. Two patients, GA132 and GA169, were infected with pol sequences of non-B subtype origin that were found to cluster phylogenetically with subtype A-E of Thai origin. Sliding window bootstrap analysis of GA169 showed clear evidence of A/B recombination within the pol gene segment, whereas in the other patient, GA132, no break point within RT could be identified. Interestingly, pairwise comparisons between these 2 patients' C2-V3 env region revealed a 13.5% divergence. However, similar comparisons within the non-B pol segments yielded a 1.23% nucleotide divergence, which suggests a complex phylogenetic and epidemiological history of the subtype A pol genotype in this region. These data demonstrate an increasing diversity of HIV-1 subtypes and the potential emergence of previously unidentified HIV-1 A-E/B recombinants in the rural United States.

Epidemiology of HIV-1 infection in rural Georgia: demographic trends and analysis at the Medical College of Georgia

We have conducted a retrospective study of 100 HIV-infected patients enrolled in an AZT monotherapy clinical study at the Medical College of Georgia (MCG) in Augusta, Georgia. When compared to the national trends, our results confirm previous studies that describe an overall increase in the burden of HIV infections among blacks, and, in particular, black women in the rural Southeast. In our cohort, infections due to homosexual contact accounted for approximately 40% of all cases while heterosexual contact and intravenous drug use (IDU) comprised 33% and 13%, respectively. Infections attributable to all other risk factors accounted for the remaining 14%. Relative to national surveillance data, we observed an increase in the prevalence of HIV infections among blacks, and heterosexually acquired infections, particularly among black women. Our analysis illustrates the dynamic nature of the current U.S. epidemic which appears to be shifting both in terms of its demographic and epidemiological profile. These data may indicate that national surveillance data may not reflect the dynamic nature of current demographic trends in HIV incidence, particularly as evidenced in the rural Southeast. This suggests that hospital or laboratory based cross-sectional studies, like ours, that analyze demographic variables of HIV-infected clinic attendees may be necessary to more accurately assess the leading edge of the HIV epidemic in rural, non-metropolitan areas.

Vaginal delivery after Caesarean section: factors influencing success rates

In a retrospective review of 333 pregnancies in women who had 1 previous Caesarean section, 244 (73.3%) underwent a trial of scar, and 89 (26.7%) had an elective Caesarean section. In the trial of scar group 197 (80.7%) had a vaginal delivery and 47 (19.3%) required an emergency Caesarean section. The success of the trial was favourably influenced by a nonrecurring indication for the original Caesarean section, a previous vaginal delivery, and a smaller baby. Maternal morbidity was greater in the groups requiring a Caesarean section, whether elective or emergency. Those patients delivered vaginally spent significantly less time in hospital. In 2 of the 244 patients (0.8%) who underwent a trial of scar the previous lower segment scar was found at Caesarean section to have dehisced or ruptured.

The ability of steroid-free bovine follicular fluid to suppress FSH secretion and delay ovulation persists in heifers actively immunized against inhibin

Previous reports indicate that administration of steroid-free bovine follicular fluid (bFF) to intact heifers suppresses plasma FSH levels and delays the timing of ovulation. In addition, cessation of bFF treatment is associated with a rebound hypersecretion of FSH. To test the hypothesis that these effects of bFF are mediated by inhibin, we have compared the responses to bFF treatment in heifers actively immunized against the N-terminal sequence of inhibin alpha subunit (bI alpha(1-29)Tyr30-ovalbumin) with those in ovalbumin-immunized controls. Oestrous cycles were synchronized, and inhibin-immune (n = 10) and control (n = 10) heifers were subdivided into two groups which received either 5 ml bFF (n = 5) or 5 ml bovine serum (n = 5) every 4 h for a 60 h period starting 8 h before prostaglandin (PG)-induced luteolysis. Blood was withdrawn every 4 h for 10 days starting 30 h before luteolysis and ovaries were examined daily by ultrasonography. Overall, mean ovulation rate in bI alpha(1-29)Tyr30-immunized heifers was 44% higher (P < 0.02) than in controls. Inhibin antibody titres tested in bI alpha(1-29)Tyr30-immunized heifers before (19 +/- 3%), during (19 +/- 3%) and after (20 +/- 3%) bFF treatment did not differ. In the pretreatment period (i.e. mid-luteal phase), plasma FSH levels were 32% (P < 0.05) higher in inhibin-immunized than in control heifers. During administration of bFF to control heifers, plasma FSH was suppressed to a level 40% lower than in serum-treated heifers (P < 0.02). Unexpectedly, bFF suppressed FSH to a similar extent in inhibin-immunized heifers (37% lower than in the serum-treated group; P < 0.025). Similarly, a post-bFF rebound hypersecretion of FSH was observed in both control (P < 0.05) and inhibin-immunized (P < 0.05) heifers, although the FSH rebound lasted about 24 h longer in the latter group (P < 0.001). The timing of the preovulatory LH surge in control (86 +/- 7 h post-PG) and immunized (81 +/- 6 h post-PG) groups treated with serum was similar as was the timing of the preovulatory rise in plasma oestradiol and the subsequent rise in plasma progesterone. However, bFF treatment delayed (P < 0.001) the preovulatory surges of LH and oestradiol and the subsequent rise in plasma progesterone to a similar extent (> 4 days) in both control and inhibin-immunized groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroid activity in relation to growth rate and body composition in four breeds of sheep

Four breeds of sheep, Hampshire, Southdown, Cheviot and Scottish Blackface, which differ in mature body size and body composition were intensively reared under an ad libitum or a restricted feeding regime. Thyroid activity was assessed at 13 weeks of age by the 131I uptake method. Slaughter at 24 weeks (ad lib) or 32 weeks (restricted) was followed by carcass dissection. The anticipated differences in body type represented by the 4 breeds was confirmed in terms of size and fatness. The Hampshires had the highest growth rate (liveweight for age) and the lowest thyroid uptake, and the breed differences in thyroid activity were shown to be independent of liveweight. Thyroid activity was positively related to growth rate in the Hampshires and negatively related to growth rate in the 3 other breeds. No association could be found however between the thyroid activity and the proportionate growth of body fat or lean. None of these conclusions were affected by a mild restriction in fed intake.

Effect of dantrolene on leg metabolism in porcine malignant hyperthermia

The effect of the intravenous administration of dantrolene 3.5 mg/kg body weight on leg metabolism during porcine malignant hyperthermia (MH) was investigated in six Pietrain pigs. Arterial pH improved only slowly after dantrolene and was associated with the continuing efflux of lactate from the leg. Oxygen uptake by the leg had returned to control values 30 minutes after dantrolene. Glucose production by the leg was observed during malignant hyperthermia but this was rapidly abolished by dantrolene. It is concluded that the most useful indices for assessing the adequacy of the treatment of MH are those which reflect changes in oxidative muscle metabolism.

Porcine malignant hyperthermia. VII: Hepatic metabolism

Hepatic metabolism during porcine malignant hyperthermia (MH) was investigated in seven Pietrain pigs. The estimated hepatic blood flow decreased during MH, but an increase in oxygen extraction enabled the splanchnic oxygen uptake to be maintained. There was a large release of glucose and potassium from the liver in MH which made an important contribution to the hyperglycaemia and hyperkalaemia. Measurement of hepatic uptake of the precursors of gluconeogenesis, lactate, glycerol and alanine, showed that glucose efflux from liver was derived mainly from glycogenolysis. Lactate uptake by the liver increased during MH, and there was no evidence of hepatic lactate production during the profound acidosis as suggested by in vitro studies with the isolated liver. There was no evidence of major abnormality of hepatic function during porcine MH.

Porcine malignant hyperthermia. VI: the effects of bilateral adrenalectomy and pretreatment with bretylium on the halothane-induced response

The effects of bilateral adrenalectomy, together with the i.v. administration of bretylium tosylate 20 mg kg-1 on halothane-induced malignant hyperthermia (MH), were investigated in six Pietrain pigs. All six animals survived the halothane challenge, and failed to show any signs of increased muscle metabolism. Bilateral adrenalectomy alone prevented halothane-induced MH in three out of four Pietrain pigs, whereas the i.v. administration of bretylium alone protected only one pig out of an additional four animals studied. The results show that complete adrenergic blockade inhibits the susceptibility of Pietrain skeletal muscle to halothane and that the adrenal medulla makes an important contribution to this response.