Mechanisms for activation and antagonism of an AMPA-sensitive glutamate receptor: crystal structures of the GluR2 ligand binding core

Crystal structures of the GluR2 ligand binding core (S1S2) have been determined in the apo state and in the presence of the antagonist DNQX, the partial agonist kainate, and the full agonists AMPA and glutamate. The domains of the S1S2 ligand binding core are expanded in the apo state and contract upon ligand binding with the extent of domain separation decreasing in the order of apo > DNQX > kainate > glutamate approximately equal to AMPA. These results suggest that agonist-induced domain closure gates the transmembrane channel and the extent of receptor activation depends upon the degree of domain closure. AMPA and glutamate also promote a 180 degrees flip of a trans peptide bond in the ligand binding site. The crystal packing of the ligand binding cores suggests modes for subunit-subunit contact in the intact receptor and mechanisms by which allosteric effectors modulate receptor activity.

Magnetic, microplate-format plasmid isolation protocol for high-yield, sequencing-grade DNA

We have developed a rapid, microplate-format plasmid isolation procedure to purify sequencing-grade DNA templates for high-throughput DNA sequencing operations. A modified lysozyme/boiling method is used to produce a plasmid-containing supernatant that is then purified by iron bead capture. After binding, the beads are pelleted in a magnetic field, washed and the DNA eluted in water. The method yields up to 10 micrograms plasmid DNA from a 1-mL overnight culture in a deep-well microplate. The procedure is suitable for large-scale experiments, amenable to automation and does not require expensive reagents or equipment. The entire protocol can be completed in as little as 2 h, and one technician with a 96-well pipetting station can process up to 48 plates per day. This protocol is ideal for any high-throughput operation in which template quantity, quality and reproducibility are of primary importance.

Longitudinal changes in 11-13-year-olds' physical activity

The influence of age, sex, maturity, body mass and body fatness on the physical activity (PA) of 11-13-y-olds was examined longitudinally. Body mass, triceps and subscapular skinfold thickness and pubic hair were recorded and 3-d continuous heart rate (HR) monitoring was used to estimate PA on each annual measurement occasion. At the onset, subjects were 11.0 (0.4)-y-old and data were available on 202, 143 and 160 subjects in years 1 to 3, respectively with an almost equal sex distribution. Multilevel regression modelling examined age-, sex- and maturity-related changes in time spent with HR above 139 (moderate activity) and 159 (vigorous activity) bpm. Sustained (10 or 20 min) periods of moderate or vigorous activity were not characteristic of PA patterns. Both PA measures declined with age, with a consistent sex difference reflecting the lower PA levels of girls. Body mass and fatness were not significant explanatory variables, but an additional decrement in activity was evident in late maturity.

CONCLUSION

Few children experience extended bouts of PA, and from 11-13 y, PA decreases, with more girls than boys becoming inactive. The data emphasize the importance of promoting active lifestyles during youth.

Longitudinal changes in young people's short-term power output

PURPOSE

The influences of age, body size, skin-fold thickness, gender, and maturation on the short-term power output of young people were examined using multilevel modelling.

METHODS

Subjects were 97 boys and 100 girls, aged 12.2 +/- 0.4 yr at the onset of the study. Sexual maturity was classified according to Tanner's indices of pubic hair. Peak power (PP) and mean power (MP) were determined on two occasions 1 yr apart using the Wingate Anaerobic Test (WAnT). The data were analyzed using multilevel regression modelling.

RESULTS

Initial models identified body mass and stature as significant explanatory variables with an additional positive effect of age, which was smaller for girls' MP. A significant gender difference was apparent for both power indices with girls achieving lower values than boys. A significant incremental effect of later maturity (stages 4 and 5 for pubic hair development) was identified for MP only. Subsequent incorporation of sum of two skin-fold thicknesses into the model yielded significant negative parameter estimates for PP and MP and negated both the stature effects and the maturation influence upon MP.

CONCLUSION

There are gender differences in the longitudinal growth of performance on the WanT. Regardless of gender differences, body mass and skin-fold thicknesses appear to be the best anthropometric predictors of WAnT determined PP and MP in young people.

Aerobic responses of prepubertal boys to two modes of training

OBJECTIVE

To investigate the effects of two contrasting eight week training programmes on the aerobic performance of 39 prepubescent boys (mean age 10.1 years).

METHODS

All boys were volunteer subjects from three city schools and the schools were matched by a health related behaviour questionnaire. All of the boys were assessed as Tanner stage one for genitalia and pubic hair development. Criterion laboratory tests included peak VO2 as assessed by an incremental discontinuous treadmill test to voluntary exhaustion. Submaximal measurements of heart rate, minute ventilation (VE) and VO2 were also recorded during the treadmill test. One of the schools provided the control group (n = 14), and boys from the other schools followed two contrasting training programmes. The first was a sprint interval running programme (n = 12) comprising 10 second and 30 second sprints, and the second a continuous cycle ergometer programme (n = 13) maintaining a heart rate in the range 80-85% of maximum for 20 minutes on a Monark cycle ergometer. After eight weeks training three times a week, the three groups were retested.

RESULTS

There were no significant differences in peak VO2 (p>0.05) with training in either of the groups. Neither were there significant changes in any of the submaximal variables VO2, VE, or heart rate (p>0.05).

CONCLUSION

The findings of this study indicate that neither eight week sprint interval running nor continuous cycle ergometer training programmes significantly improve maximal or submaximal indicators of the aerobic performance of prepubertal boys.

Longitudinal changes in submaximal oxygen uptake in 11- to 13-year-olds

The aim of this study was to monitor longitudinal changes in young people's submaximal oxygen uptake (VO2) responses during horizontal treadmill running at 8 km x h(-1). The 236 participants (118 boys, 118 girls) were aged 11.2+/-0.4 years (mean +/- s) at the onset of the study. Submaximal VO2, peak VO2 and anthropometry were recorded annually for three consecutive years. The data were analysed using multi-level regression modelling within a multiplicative, allometric framework. The initial model examined sex, age and maturity-related changes in submaximal VO2 relative to body mass as the sole anthropometric covariate. Our results demonstrate that the conventional ratio standard ml x kg(-1) x min(-1) does not adequately describe the true relationship between body mass and submaximal VO2 during this period of growth. The effects of maturity and age were non-significant, but girls consumed significantly less VO2 than boys running at 8 km x h(-1). In subsequent models, stature was shown to be a significant explanatory variable, but this effect became non-significant when the sum of two skinfolds was added. Thus, within this population, submaximal VO2 responses were explained predominantly by changes in body mass and skinfold thicknesses, with no additional maturity-related increments. When differences in body mass and skinfolds were controlled for, there was still a difference between the sexes in submaximal VO2, with girls becoming increasingly more economical with age.

Modeling growth and maturation changes in peak oxygen uptake in 11-13 yr olds

The influence of gender, growth, and maturation on peak O(2) consumption (VO(2 peak)) in 11-13 yr olds were examined by using multilevel regression modeling. Subjects were 119 boys and 115 girls, aged 11.2 +/- 0.4 (SD) yr at the onset of the study. Sexual maturation was classified according to Tanner's indexes of pubic hair. VO(2 peak) was determined annually for 3 yr. The initial model identified body mass and stature as significant explanatory variables, with an additional positive effect for age and incremental effects for stage of maturation. A significant gender difference was apparent with lower values for girls, and an age-by-gender interaction indicated a progressive divergence in boys' and girls' VO(2 peak). Subsequent incorporation of the sum of two skinfold thicknesses into the model negated stature effects, reduced the gender term, and explained much of the observed maturity effects. The body mass exponent almost doubled, but the age-by-gender interaction term was consistent with the initial model.

A maximum entropy method for determining column-length distributions from size-broadened X-ray diffraction profiles

We present a novel application of the maximum entropy (MaxEnt) method for solving the double-inverse problems of removing instrument broadening from X-ray diffraction profiles and calculating the column-length distribution of the crystallites. The MaxEnt approach is shown to have compelling advantages over the conventional methods it replaces: it is stable and robust, incorporates noise anda prioriinformation into the solution, preserves positivity of the solution, and can be applied successively. We also show how uncertainties in the derived profiles and column distributions can be determined and used in subsequent calculations, including integral breadth, Fourier coefficients, column-length distributions and apparent particle sizes. Calculations are performed on simulated X-ray diffraction profiles for a range of particle sizes, with a detailed study of the sensitivity of the results to background-level estimates and the use of an incorrect instrument response function.

Breath-to-breath "noise" in the ventilatory and gas exchange responses of children to exercise

The purposes of this investigation were to quantify the noise component of child breath-by-breath data, investigate the major determinants of the breath-to-breath noise, and to characterise the noise statistically. Twenty-four healthy children (12 males and 12 females) of mean (SD) age 13.1 (0.3) years completed 25 min of steady-state cycle ergometry at an exercise intensity of 50 W. Ventilatory and gas exchange variables were computed breath-by-breath. The mean (SD) oxygen consumption (VO2) ranged from 0.72 (0.16) to 0.92 (0.26) l x min(-1); mean (SD) carbon dioxide production (VCO2) ranged from 0.67 (0.20) l x min(-1) to 0.85 (0.16) l x min(-1); and mean (SD) minute ventilation ranged from 17.81 (3.54) l x min(-1) to 24.97 (5.63) l x min(-1). The majority of the breath-to-breath noise distributions differed significantly from Gaussian distributions with equivalent mean and SD parameters. The values of the normalised autocorrelation functions indicated a negligible breath-to-breath correlation. Tidal volume accounted for the majority of the VO2 (43%) and VCO2 (49%) variance. The breath-to-breath noise can be explained in terms of variations in the breathing pattern, although the large noise magnitude, together with the relatively small attainable response amplitudes in children reduces the certainty with which ventilatory and gas exchange kinetics can be measured.

A new protein folding screen: application to the ligand binding domains of a glutamate and kainate receptor and to lysozyme and carbonic anhydrase

Production of folded and biologically active protein from Escherichia coli derived inclusion bodies can only be accomplished if a scheme exists for in vitro naturation. Motivated by the need for a rapid and statistically meaningful method of determining and evaluating protein folding conditions, we have designed a new fractional factorial protein folding screen. The screen includes 12 factors shown by previous experiments to enhance protein folding and it incorporates the 12 factors into 16 different folding conditions. By examining a 1/256th fraction of the full factorial, multiple folding conditions were determined for the ligand binding domains from glutamate and kainate receptors, and for lysozyme and carbonic anhydrase B. The impact of each factor on the formation of biologically active material was estimated by calculating factor main effects. Factors and corresponding levels such as pH (8.5) and L-arginine (0.5 M) consistently had a positive effect on protein folding, whereas detergent (0.3 mM lauryl maltoside) and nonpolar additive (0.4 M sucrose) were detrimental to the folding of these four proteins. One of the 16 conditions yielded the most folded material for three out of the four proteins. Our results suggest that this protein folding screen will be generally useful in determining whether other proteins will fold in vitro and, if so, what factors are important. Furthermore, fractional factorial folding screens are well suited to the evaluation of previously untested factors on protein folding.

Submaximal exercise and maturation in 12-year-olds

The aim of this study was to examine the maturation responses of young people to submaximal treadmill exercise. Body mass was controlled using both the conventional ratio standard and allometric modelling. Ninety-seven boys and 97 girls with a mean age of 12.2 years completed a discontinuous, incremental exercise test to voluntary exhaustion. We measured peak oxygen uptake (VO2peak) and VO2 when running at 8, 9 and 10 km x h(-1). Sexual maturation was assessed visually using Tanner's indices of pubic hair. Peak VO2 was significantly higher in boys (P<0.001); this was still the case when the influence of body mass was covaried out. During submaximal exercise, no significant differences in absolute VO2 were observed between the sexes (P>0.05); however, values of VO2, expressed both in ratio with body mass and adjusted for body mass using allometry, were significantly greater in boys than in girls (P<0.001). For absolute VO2, significant main effects (P<0.05) were seen for maturity at each exercise stage. With the influence of body mass controlled using either the ratio standard or allometry, no significant main effects (P>0.05) for maturity were observed. Our results indicate that boys are less economical than girls while running at 8-10 km x h(-1) and that, independently of body mass, maturation does not influence the VO2 response to submaximal exercise.

Fungal sacral osteomyelitis as the initial presentation of Crohn's disease of the small bowel: report of a case

We report a unique case of Candida albicans sacral osteomyelitis in a 48 year-old female with previously undiagnosed Crohn's disease. The patient was ill for one year with fatigue, weakness, and a 60-lb weight loss. At the time of presentation, she developed chills, fever, right lower quadrant abdominal pain, and right knee pain. Physical examination was significant for a palpable right lower quadrant abdominal mass. A computed tomographic scan of the abdomen and pelvis identified a large right-sided retroperitoneal mass, severe right hydronephrosis, and air within the right sacrum. Findings at laparotomy included small-bowel changes consistent with Crohn's disease, a multiloculated retroperitoneal abscess, and evidence of sacral osteomyelitis. A right hemicolectomy with sacral debridement and placement of presacral drains was performed. Bone cultures from the sacrum demonstrated a predominance of C. albicans, in addition to coliforms and enterococcus. The patient was placed on amphotericin B and intravenous antibiotics. Because serial computed tomographic scans of her pelvis demonstrated progression of her pelvic osteomyelitis to include the sacrum, right ilium, right acetabulum, and right femoral head, a repeat debridement with resection of the right femoral head was performed. After 12 months of follow-up, she was doing well without medications and had no constitutional symptoms or radiographic evidence of disease progression. This report illustrates a unique case of Crohn's disease presenting as sacral osteomyelitis secondary to small-bowel fistulization. Aggressive multidisciplinary surgical and medical management were the key to the successful management of this difficult case.

Structure of a glutamate-receptor ligand-binding core in complex with kainate

Ionotropic glutamate receptors (iGluRs) mediate excitatory synaptic transmission in vertebrates and invertebrates through ligand-induced opening of transmembrane ion channels. iGluRs are segregated into three subtypes according to their sensitivity to the agonists AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid), kainate (a structural analogue of glutamate) or NMDA (N-methyl-D-aspartate). iGluRs are important in the development and function of the nervous system, are essential in memory and learning, and are either implicated in or have causal roles in dysfunctions ranging from Alzheimer's, Parkinson's and Huntington's diseases, schizophrenia, epilepsy and Rasmussen's encephalitis to stroke. Development of iGluR agonists and antagonists has been hampered by a lack of high-resolution structural information. Here we describe the crystal structure of an iGluR ligand-binding region in a complex with the neurotoxin (agonist) kainate. The bilobed structure shows the determinants of receptor-agonist interactions and how ligand-binding specificity and affinity are altered by remote residues and the redox state of the conserved disulphide bond. The structure indicates mechanisms for allosteric effector action and for ligand-induced channel gating. The information provided by this structure will be essential in designing new ligands.

Primate renal transplants using immunotoxin

BACKGROUND

T-lymphocyte depletion 7 days before transplantation with immunotoxin FN 18-CRM9 has resulted in tolerance to subsequent renal allografts. We tested the effect of giving immunotoxin on the day of the transplantation and evaluated its effect on rhesus monkey and allograft survival, on antibody production, and on T-cell recovery.

METHODS

Major histocompatibility complex mismatched renal allografts were performed in rhesus monkeys. Immunotoxin was given starting on the day of transplantation, with and without prednisone and mycophenolate mofetil for 3 days. T-cell subsets and alloantibody levels were measured by flow cytometry. The ability of treated monkeys to develop antibody to tetanus, diphtheria, and xenoantibody was measured. Histology of renal transplants was read in a blinded manner.

RESULTS

Immunotoxin started on the day of transplantation resulted in prolonged allograft survival in all treatment groups. Graft loss between days 50 and 135 was most often due to interstitial nephritis. Later graft loss was due to chronic rejection. Monkeys had intact antibody responses to alloantigen, tetanus, diphtheria, and xenoantibody. Their CD4 cells recovered gradually over 6 months.

CONCLUSIONS

Immunotoxin reliably prolongs renal allograft survival when started on the day of transplantation, but interstitial nephritis and chronic rejection limit the development of long-term tolerance. T-cell-dependent B-cell responses remain intact after treatment.

Analysis of primate renal allografts after T-cell depletion with anti-CD3-CRM9

BACKGROUND

FN18-CRM9 is a CD3-specific immunotoxin that is capable of depleting CD3+ T cells. Pretreatment of rhesus monkeys with this agent before transplantation can induce donor-specific tolerance and "split tolerance" to renal allografts.

METHODS

Heterotopic renal transplants were performed on monkeys that received posttransplant FN18-CRM9. Histological and immunohistological staining, as well as analysis of the intragraft cytokine profile by reverse transcriptase polymerase chain reaction, was performed on percutaneous allograft biopsies.

RESULTS

Experimental monkeys had significant prolongation of allograft survival. Although an interstitial, mononuclear cell infiltrate was seen in all of the renal transplants, there was minimal evidence of acute cellular rejection. Histological evidence of alloantibody-mediated damage was detected 3 to 5 months after transplantation in the monkeys treated with FN18-CRM9. Immunohistology demonstrated the reappearance of CD3+ and CD4+ T cells, as well as CD20+ B cells, in the grafts. Cytokine analysis demonstrated expression of interferon-gamma. An intact anti-donor IgG response was seen.

CONCLUSION

Treatment of monkeys with FN18-CRM9 immediately after transplantation significantly prolongs renal allograft survival. Allograft biopsies demonstrate a lack of acute cellular rejection; however, alloantibody-mediated graft damage and rejection occur, with an intact anti-donor IgG response. The intragraft expression of the interferon-gamma may reflect this ongoing humoral rejection. These data suggest that even a brief period of T-cell allosensitization may lead to humorally mediated allograft damage. Efforts to achieve tolerance with posttransplant FN18-CRM9 will require modification of the protocol to deplete T cells before allosensitization exposure or to supplement the posttransplant immunomodification strategy.

Choosing reconstruction after mastectomy: a qualitative analysis

PURPOSE/OBJECTIVES

To describe women's perspectives on factors that influenced their decision to have reconstructive surgery after a breast cancer diagnosis.

DESIGN

Exploratory, descriptive, qualitative study.

SETTING

A comprehensive cancer center in an urban setting.

SAMPLE

Eleven women who underwent mastectomy and reconstruction. Six participants had autologous transverse rectus abdominis musculocutaneous-flap reconstruction, four had saline implants, and one had a silicone implant. All but one reconstruction was performed at the time of mastectomy.

METHODS

Open-ended, face-to-face interviews using an interview guide were conducted within one month of reconstruction. One to two follow-up interviews were conducted approximately six months later.

MAIN RESEARCH VARIABLES

Decision making about reconstruction, perceptions of information needs and sources, sources of support, and factors important to decision making.

FINDINGS

The main theme identified was Getting My Life Back. The participants described this in terms of the themes of Information Seeking, Talking It Over, and Seeking Normality. The interactive skills of the healthcare provider played an important role in the women's decision making.

CONCLUSIONS

Reconstruction minimized the negative consequences of breast cancer and its treatment for the women in the study. The decision-making process was aimed at getting the person's life back as close to what it was before the diagnosis as possible or improving it. The three themes of decision making are interactive in nature, with participants returning to information Seeking and Talking It Over as necessary to increasing their understanding and clarifying their "normality goals."

IMPLICATIONS FOR NURSING PRACTICE

Healthcare professionals should determine how a woman wants to participate in decision making as well as the kind, amount, and sources of information the individual with breast cancer wants to have to make her decisions. Healthcare providers are key sources of information about treatment options, and they are critical to patient satisfaction with the decision-making process and with the final results of the surgical procedure. Family members, friends, and other women with breast cancer play a crucial role in talking it over.

Computed tomographic angiography with three-dimensional reconstruction in patients with complex diverticular disease and portal hypertension: report of a case

We report a case of a patient with portal hypertension secondary to alcoholic cirrhosis (Child's Class C) who initially presented with a colovaginal fistula secondary to acute sigmoid diverticulitis. The patient had a prior history of hepatic cirrhosis with ascites, coagulopathy, and portal hypertension. Computed tomography of the abdomen and pelvis demonstrated a large diverticular phlegmon and ascites. Computed tomographic angiography demonstrated a large left anterior abdominal wall varix in the region of the anticipated sigmoid resection. Three-dimensional reconstruction of the computed tomographic angiography further delineated the path of this large varix, confirming the increased risk from surgical intervention. Following initial conservative treatment with intravenous antibiotics, parenteral nutrition, and percutaneous abscess drainage, a transjugular intrahepatic portosystemic shunt procedure was performed to decompress the portal system varices. A repeat computed tomographic scan with three-dimensional reconstruction confirmed decompression of the varix. A successful sigmoid resection was subsequently performed. Preoperative computed tomographic angiography with three-dimensional reconstruction is a useful adjunct in planning the operative strategy in patients with complex intraabdominal pathology and collateral portovenous flow secondary to portal hypertension.

Peak oxygen uptake and maturation in 12-yr olds

The influences of gender and sexual maturation on the peak VO2 of 12-yr olds were examined. Subjects were 106 boys and 106 girls, ages 12.2 +/- 0.4 yr. The sexual maturity of 93 boys and 83 girls was classified according to Tanner's indices of pubic hair. No significant gender differences (P > 0.05) were detected in age, stature, or hemoglobin concentration. Peak VO2 was determined on a treadmill and boys' peak VO2 was significantly higher (P < 0.01) than girls' whether expressed in L x min(-1) (2.10 +/- 0.34 vs 1.92 +/- 0.28) or mL x kg(-1) x min(-1) (52 +/- 6 vs 44 +/- 5). With body mass controlled for using log-linear ANCOVA, the gender difference decreased from 18.2 to 17.1% but remained significant (P < 0.01). For peak VO2 (L x min[-1]) ANOVA revealed no significant interaction (P > 0.05) but significant (P < 0.01) main effects for both gender and maturation. For peak VO2 in ratio with body mass (mL x kg(-1) x min[-1]), ANOVA detected no significant interaction (P > 0.05) or significant main effect (P > 0.05) for maturation although the main effect for gender was significant (P < 0.01). Analysis of peak VO2 with body mass controlled for using log-linear ANCOVA revealed no significant interaction (P > 0.05) but main effects (P < 0.01) for both gender and maturation. Thus, gender differences, which are not simply explained by differences in body size or hemoglobin concentration, have been demonstrated in the peak VO2 of 12-yr olds. A log-linear scaling model has identified in both boys and girls a significant influence of maturation on peak VO2 independent of body mass. This effect may have been masked in previous studies by the inappropriate use of peak VO2 in ratio with body mass.

Prepubescents' ventilatory responses to exercise with reference to sex and body size

STUDY OBJECTIVES

To examine the ventilatory responses of prepubescent children to submaximal and peak exercise using appropriate allometric modeling to control for differences in body size.

DESIGN

Cross-sectional study of a representative sample of children.

SETTING

Middle schools (8 to 11 years) in Exeter, UK.

PARTICIPANTS

We studied 101 boys and 76 girls aged 11.1 (0.4) years and classified Tanner stage 1 for pubic hair (no true pubic hair).

MEASUREMENTS

At rest: stature, mass, sum of skinfolds, hemoglobin concentration, FVC, and FEV1. During treadmill exercise at 7, 8, 9, and 10 km/h, and at peak exercise: oxygen uptake (VO2), minute ventilation (VE), tidal volume (VT), and respiratory frequency (Rf).

RESULTS

At peak exercise, boys' VO2, VE, and VT were significantly (p<0.01) higher than girls' values and remained so even when the influence of body size was controlled using allometric principles. There were no significant (p>0.05) sex differences in Rf or the ratios VT/FVC or VE/VO2. When data were compared at the same relative exercise intensity (ie, 70 to 75% or 80 to 85% peak VO2), no significant (p>0.05) sex differences in Rf, VT/FVC, or VE/VO2 were detected. Boys' higher (p<0.001) VO2 values were reflected by their higher VE which remained higher than values for girls at both submaximal levels even when the influence of body size was covaried out.

CONCLUSIONS

Prepubescent boys demonstrate higher peak VO2 than girls and this is supported by a higher VE and VT, even when the influence of body size is accounted for using allometry. Other ventilatory responses to both peak exercise and exercise at the same relative intensity are remarkably similar in both boys and girls.

Expression of naked plasmid DNA injected into the afferent and efferent vessels of rodent and dog livers

A variety of reporter genes within plasmid constructs were injected into the afferent and efferent vessels of the liver in mice, rats, and dogs. Efficient plasmid expression was obtained following delivery via the portal vein, the hepatic vein, and the bile duct. The use of hyperosmotic injection solutions and occlusion of the blood outflow from the liver substantially increased the expression levels. Combining these surgical approaches with improved plasmid vectors enabled uncommonly high levels of foreign gene expression in which over 15 microg of luciferase protein/liver was produced in mice and over 50 microg in rats. Equally high levels of beta-galactosidase (beta-Gal) expression were obtained, in that over 5% of the hepatocytes had intense blue staining. Expression of luciferase or beta-Gal was evenly distributed in hepatocytes throughout the entire liver when either of the three routes were injected. Peri-acinar hepatocytes were preferentially transfected when the portal vein was injected in rats. These levels of foreign gene expression are among the highest levels obtained with nonviral vectors. Repetitive plasmid administration through the bile duct led to successive events of foreign gene expression. The integration of these findings into laboratory and clinical protocols is discussed.

Responses of young girls to two modes of aerobic training

OBJECTIVES

To investigate the physiological effects of two different three times a week, eight week training programmes on the aerobic fitness of nine to ten year old girls.

METHODS

Treadmill determined peak VO2, submaximal heart rates, and submaximal blood lactate were the criterion measures. Seventeen girls completed a programme of "aerobics" training where sessions lasted 20-25 minutes. Eighteen girls followed a cycle ergometer training programme which involved pedalling continuously for 20 minutes with the heart rate maintained between 160 and 170 beats/minute. A control group of 16 girls completed the criterion tests but did not train. In the cycle ergometer group and eight control subjects plasma total cholesterol and high density lipoprotein cholesterol were determined before and after training.

RESULTS

Peak VO2 did not change significantly with training in either training group, neither were there any significant changes in submaximal heart rates. Blood lactate declined significantly at the two lowest submaximal exercise intensities in the cycle ergometer training group (from 2.3 (1.1) to 1.4 (0.06) mmol/l at stage 1 and from 2.1 (1.2) to 1.6 (0.06) mmol/l at stage 2; means (SD); P < 0.01). Total cholesterol and high density lipoprotein cholesterol remained unchanged with training.

CONCLUSIONS

These findings suggest that an eight week structured exercise programme produces minimal changes in either the aerobic fitness or blood lipids of young girls. It may be more beneficial for long term health to promote enjoyment in activity and positive attitudes to exercise rather than attempting to enhance aerobic fitness through strenuous exercise programmes.

Effect of training on the aerobic power and anaerobic performance of prepubertal girls

The purpose of this study was to investigate the effects of two, three times a week, 8-week training programmes on the aerobic power and anaerobic performance of 30 prepubescent girls, with a mean age of 9.6 y. Peak oxygen uptake assessed by an incremental discontinuous treadmill test, and peak power in 5 s and mean power over 30 s estimated from a Wingate anaerobic test were used as the criterion measures. Twelve girls trained using a continuous cycle ergometer programme, 11 girls followed a sprint running programme and the control group consisted of 7 girls. Both training groups significantly (p < 0.05) increased their peak oxygen uptake and peak power in 5 s. However, the increase reported here are lower than those generally observed in adolescents following training. The control group demonstrated no significant (p > 0.05) change in either variable. No significant (p > 0.05) changes in mean power over 30 s were observed in any group.

Short-range cell-cell signals control ectodermal patterning in the oral region of the sea urchin embryo

The ectoderm of the sea urchin embryo has been a useful system for understanding how regions of a simple epithelium are specified during early development, as well as how pattern formation leads to the correct localization of mesenchyme cells during morphogenesis. This study examines cell-cell signals that regulate precise patterning of ectoderm within the oral region of embryos of the sea urchin, Lytechinus variegatus. The oral ectoderm contains at least two types of patterned tissues: (1) the ectoderm that forms the stomodeum and (2) ectoderm expressing pattern information required for formation of parallel oral skeletal rods by primary mesenchyme cells (PMCs). Using microsurgical isolations and cell transplantation, we show (1) that cell-cell signaling is capable of producing new oral ectodermal structures until immediately prior to the gastrula stage, (2) that the presumptive oral ectoderm is not committed to produce oral structures until the early gastrula stage, (3) that oral ectodermal patterning cues for PMCs are highly local in character, and (4) that interactions between the tip of the archenteron and the presumptive oral ectoderm are not required for the differentiation of cells within either tissue. These studies suggest that short-range cell-cell signals within the ectoderm are involved in specifying regionalized oral ectodermal tissues immediately prior to gastrulation, and that this patterned ectoderm then influences the localization of skeletogenic mesenchyme cells in the oral region.

Exercise performance and magnetic resonance imaging-determined thigh muscle volume in children

This study examined the relationships between thigh muscle volume (TMV) and aerobic and anaerobic performance in children. A total of 32 children, 16 boys and 16 girls, aged 9.9 (0.3) years completed a treadmill running test to exhaustion for the determination of peak oxygen uptake (peak VO2) and a Wingate Anaerobic Test (WAnT) for the determination of peak power (PP) and mean power (MP). The volume of the right thigh muscle was determined using magnetic resonance imaging. TMV was not significantly different in boys and girls [2.39 (0.29) l vs 2.18 (0.38) l, P > 0.05]. Peak VO2 and MP were significantly higher in boys than girls (P < 0.01) whether expressed in absolute, mass-related or allometrically scaled terms. Absolute PP was not significantly different in boys and girls but mass-related and allometrically scaled values were higher in boys (P < 0.01). TMV was correlated with absolute peak VO2, PP and MP in both sexes (r = 0.52-0.89, P < 0.01). In boys, mass-related PP was correlated with TMV (r = 0.53, P < 0.01), and in girls mass-related peak VO2 was correlated with TMV (r = -0.61, P < 0.01). However, in neither sex were allometrically scaled peak VO2, PP or MP correlated with TMV (P > 0.05). There were no significant differences between boys and girls in terms of peak VO2, PP or MP when expressed in a ratio to TMV or allometrically scaled TMV. In conclusion, this study has demonstrated that, when body size is appropriately accounted for using allometric scaling, TMV is unrelated to indices of aerobic and anaerobic power in 10-year-old children. Furthermore, there appear to be no qualitative differences in the muscle function of boys and girls in respect of aerobic and anaerobic function.

Is peak VO2 a maximal index of children's aerobic fitness?

A levelling of oxygen uptake (VO2 plateau) at high exercise intensities is conventionally used as the criterion for establishing VO2max during progressive, incremental exercise testing. Only a minority of children, however, demonstrate a VO2 plateau during exercise to voluntary exhaustion. This study was therefore designed to investigate whether a VO2 plateau is required before peak VO2 can be considered a maximal index of children's aerobic fitness. Eighteen girls and 17 boys (age 9.9 +/- 0.4 yrs) carried out three treadmill tests to exhaustion one week apart. The first test comprised a discontinuous, incremental protocol to voluntary exhaustion. In test two each child warmed up and then ran to exhaustion at the same belt speed but on a gradient 2.5% greater than that which had produced an exhaustive effort on the first test. The third test was conducted similarly but the treadmill gradient was raised to 5% greater than that which had produced an exhaustive effort on the first test. Seven girls and 6 boys demonstrated a VO2 plateau (< or = 2 ml.kg-1.min-7) on the first test but no significant differences in either anthropometrical or peak physiological data were detected between those who demonstrated a plateau and those who did not. Mean peak VO2 values during tests two and three (supramaximal tests) did not increase significantly above that achieved on test one although indicators of an increased anaerobic contribution were significantly higher in both supramaximal tests. These findings indicate that peak VO2 in test one was a maximal value despite the absence of a VO2 plateau. The requirement of a VO2 plateau before peak VO2 can be regarded as a maximal index of young children's aerobic fitness is therefore untenable.

Scaling peak VO2 for differences in body size

This paper examined the influence of different statistical modeling techniques on the interpretation of peak VO2 data in groups of prepubertal, circumpubertal, and adult males (group 1M, N = 29; group 2M, N = 26; group 3M, N = 8) and females (group 1F, N = 33; group 2F, N = 34; group 3F, N = 16). Conventional comparisons of the simple per-body-mass ratio (ml.kg-1.min-1) revealed no significant differences between the three male groups (P < 0.05). In females, a decline in VO2 between group 2F and 3F was observed (P < 0.05). Both linear and log-linear (allometric) models revealed significant increases across all three male groups for peak VO2 adjusted for body mass (P < 0.05). In females these scaling models identified a significantly lower peak VO2 in group 1F versus groups 2F and 3F (P < 0.05). Based upon the common mass exponent identified (b = 0.80, SE = 0.04), power function ratios (y.mass0.80) were generated and the logarithms of these compared. Again, results indicated a progressive increase in peak VO2 across groups 1M to 3M (P < 0.05) and an increase between groups 1F and 2F (P < 0.05). Incorporating stature into the allometric equation reduced the mass exponent to 0.71 (SE = 0.06) with the contribution of the stature exponent shown to be 0.44 (SE = 0.20). These results indicate that conventional ratio standards do not adequately account for body size differences when investigating functional changes in peak VO2.

Peak oxygen uptake of 12-18-year-old boys living in a densely populated urban environment

The purposes of this study were to provide data on the peak VO2 of 12-18-year-old boys from Hong Kong, a densely populated urban environment; to compare these data with those for other similarly aged populations; and to examine the correlations between peak VO2 and various anthropometric parameters of this group. A stratified, random sample of 86 ethnic Chinese boys had their peak VO2 determined using an on-line gas analysis system during incremental, treadmill running. The mean peak VO2 of the boys was 2.7 SD 0.44 l.min-1 or, when expressed in relation to body mass, 52.0 SD 5.8 ml.kg-1.min-1. Peak VO2 (l.min-1) was significantly correlated with body mass (r = 0.72, p < 0.001, age (r = 0.49, p < 0.001) and height (r = 0.71, p = 0.001). Peak VO2 (ml.kg-1.min-1) showed no correlation with age or height. These data suggest that this population group has peak VO2 values very similar to those observed in boys from most other population groups.

Aerobic fitness of prepubescent children

This study was designed to enhance understanding of the assessment and interpretation of the aerobic fitness of prepubertal children. Written informed consent to participate was obtained from 70% of the children in year six of the 15 state schools in the city of Exeter. Twenty-five per cent of the eligible children in each school were randomly selected from those who volunteered. The data reported here are those obtained from the 111 boys (11.1 SD 0.4 years) and 53 girls (10.9 SD 0.3 years) classified as Tanner stage 1 in both pubic hair rating and either genitalia rating (boys) or breast rating (girls). Peak oxygen uptake (peak VO2) was determined using a discontinuous, incremental protocol on a treadmill. Only a minority of children demonstrated a levelling-off or plateau in VO2 despite an increase in exercise intensity. There was no evidence to suggest that the children who demonstrated a VO2 plateau had significantly (p < 0.05) higher peak VO2, peak heart rate, peak respiratory exchange ratio or peak blood lactate than those children who did not demonstrate a plateau in VO2. These findings indicate that a VO2 plateau should not be used as a requirement for defining a maximal exercise test with prepubertal children. Boys had a significantly (p < 0.01) higher peak VO2 than girls, whether expressed in 1.min-1 (1.78 vs 1.46) or in relation to body mass (51 vs 45 ml.kg-1.min-1). The results compare favourably with those of similarly aged children from other countries, but why prepubescent boys have significantly higher (13.3%) mass-related peak VO2 than prepubescent girls is not readily apparent. Although conventional, the expression of peak VO2 as per body mass ratio may not adequately partition out body-size differences. The influence of body mass was therefore removed using a linear adjustment scaling model and a log-linear model, but the boys' peak VO2 remained significantly (p < 0.01) higher than the girls' peak VO2 with the difference now being 16.0% and 16.2%, respectively.

Child-adult differences in whole blood lactate responses to incremental treadmill exercise

The aim of this study was to evaluate whether fixed blood lactate reference values of 2.5 and 4.0 mmol.1(-1) corresponded to the equivalent intensity of exercise in prepubertal and teenage boys, and men. Twenty six prepubertal boys (mean(sd) age) 11.1(0.4) years), 26 teenage boys (mean(sd) age 14.1(0.3) years), and 23 men (mean(sd) age 22.4(2.7) years) gave informed consent to participate in the study. Oxygen consumption (VO2) and heart rates (HR) corresponding to the 2.5 and 4.0 mmol.1(-1) fixed blood lactate reference values were used as the criterion measures during incremental treadmill exercise. At the 2.5 mmol.1(-1) level there were no significant differences (P > 0.05) in % peak VO2 between groups. For both prepubertal and teenage boys the 4.0 mmol.1(-1) lactate level represented a higher mean % peak. VO2 than for the mean (P < 0.05). The prepubertal and teenage values were again not significantly different (P > 0.05). Factors other than maturation during puberty influence blood lactate responses to exercise.

High and low exercisers among 14- and 15-year-old children

To investigate ways in which young people's attitudes about, and motivation for, exercise vary with the levels of exercise they take, a self-completed questionnaire was given to 382 children aged 14-15 in two secondary schools in Devon. It was found that the high exercisers (defined by those in the highest quartile) had attitudes to exercise which were more favourable, received more encouragement to exercise and encouraged others to exercise more. The majority of low exercisers had positive beliefs about the value of exercise although approximately half in boys and one-third in girls were satisfied with the amount and kind of exercise they undertook. Low-exercising boys and girls at all exercise levels preferred their exercise to be noncompetitive. The majority of both sexes accepted that their future health depended on their current behaviour and, in girls, strength of this belief was directly related to exercise level. It may be concluded that advice to young people and physical education programmes in schools should take account of the attitudes and beliefs about exercise held by pupils of all physical abilities.

Children's task and ego goal profiles in sport

The purpose of this study was to examine the combined effects of task and ego goal orientations on children's sport motivation. Participants were 115 boys and 116 girls (mean age = 11.12 yrs). Unlike previous research, where the correlates of the two orientations have been examined separately, this study examined the motivational consequences of different task and ego combinations. Four groups were created based on mean splits on the task and ego scales of the Task and Ego Orientation in Sport Questionnaire. These were low task/low ego, low task/high ego, high task/low ego, and high task/high ego. The hi/hi group emerged as the most motivated and the lo/lo group least motivated in measures of sport enjoyment and perceived sport competence. The lo/lo group, made up primarily of girls, appear to be at high risk for non-participation in sport. Children dominated by a task orientation were more motivated than those dominated by an ego orientation. A similar pattern emerged whether children were in the lower or upper third of the perceived sport competence distribution. A high task orientation appears to provide the vital element for sport motivation. The addition of ego involvement to task involvement may enhance sport enjoyment and does not appear to be motivationally detrimental. Task and ego profile analysis seems to offer important insight into the achievement motivation of children of this age.

Skeletal pattern is specified autonomously by the primary mesenchyme cells in sea urchin embryos

In the sea urchin embryo the primary mesenchyme cells (PMCs) produce a CaCO3 skeleton in a pattern that is species specific. To establish whether skeletal pattern is specified autonomously by the PMCs or through instructive interactions with the ectoderm, we have taken advantage of improvements in cell transplantation techniques to produce PMC/ectoderm chimeras between two species. It was found that the pattern of the skeletons produced in these chimeric embryos depended upon the source of the PMCs. Thus, skeletal pattern appears to be specified autonomously by the PMCs. In comparing this data with other information known about skeletogenesis, it is proposed that the ectoderm provides spatial and temporal information for the correct placement and timing of skeletogenesis, and that the PMCs then synthesize the skeleton according to an endogenous program. The ability of PMCs from one species to produce an appropriately patterned skeleton in the ectoderm of another indicates that the cues provided by the ectoderm are largely conserved between species.

Cell-cell interactions regulate skeleton formation in the sea urchin embryo

In the sea urchin embryo, the primary mesenchyme cells (PMCs) make extensive contact with the ectoderm of the blastula wall. This contact is shown to influence production of the larval skeleton by the PMCs. A previous observation showed that treatment of embryos with NiCl2 can alter spicule number and skeletal pattern (Hardin et al. (1992) Development, 116, 671–685). Here, to explore the tissue sensitivity to NiCl2, experiments recombined normal or NiCl2-treated PMCs with either normal or NiCl2-treated PMC-less host embryos. We find that NiCl2 alters skeleton production by influencing the ectoderm of the blastula wall with which the PMCs interact. The ectoderm is responsible for specifying the number of spicules made by the PMCs. In addition, experiments examining skeleton production in vitro and in half- and quarter-sized embryos shows that cell interactions also influence skeleton size. PMCs grown in vitro away from interactions with the rest of the embryo, can produce larger spicules than in vivo. Thus, the epithelium of the blastula wall appears to provide spatial and scalar information that regulates skeleton production by the PMCs.

Promoting physical activity in schools

Neil Armstrong, director of the Coronary Prevention in Children Project, argues for a comprehensive programme for promoting children's physical activity. The project's survey of adult coronary risk factors in British children revealed a worryingly low level of physical activity among British schoolchildren. Schools are ideally placed to encourage children to take physical exercise, he writes, but parental role models also play an important part.

Abdominal fat deposition in 11-year-old children

Although the metabolic complications accompanying visceral deposition of fat are well-established, the onset and extent of such fat patterning in children has not been fully documented. This has been due to the problem of computerized tomography exposing children to a prohibitive radiation risk. Nuclear magnetic resonance imaging (MRI) has provided a feasible alternative. Specifically, the purposes of this study were to use MRI (i) to assess the extent of intra-abdominal (IA) and subcutaneous abdominal (SA) fat deposition in 11-year-old boys and girls, and (ii) to identify the most useful anthropometric indicators of IA adiposity in children. Twenty-five boys and 25 girls were selected to represent, by quintiles, the body mass index range for their age. IA fat, SA fat, and total cross-sectional areas were measured from an MRI scan at the umbilicus. Body density was assessed by hydrostatic weighing, and skinfold thicknesses, circumferences and related ratios, and stage of sexual maturity were measured. Results showed that a wide variation in IA fat deposition was present with amounts ranging from 6 to 58 cm2 (mean = 17.8 +/- 10.0) for boys and 15 to 50 cm2 (mean = 24.8 +/- 8.8) for girls. Percentage of cross-sectional area taken up by visceral fat appears to be less than in normal weight adults. Fourteen children had intra-abdominal/subcutaneous abdominal fat ratios that have been associated with higher health risk in obese adults. Waist-hip circumference ratio (WHR), which is widely used as an indicator of IA deposition in adults, was not a useful predictor in these children.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro preactivated human T cells engraft in SCID mice and migrate to murine lymphoid tissues

Mice with severe combined immunodeficiency (SCID) accept grafts of human T and B lymphocytes derived from resting peripheral blood mononuclear cells (PBMC). We wished to determine whether activated human T cells engraft and migrate into lymphoid tissues in SCID mice. PBMC (50 x 10(6)) activated in vitro in a 4-day mixed lymphocyte culture (MLC) were injected into the peritoneum of 12 SCID mice. In 11 of 12 animals killed at 3 or 4 weeks after injection, human cells were detected in cells pooled from lymphoid organs by flow cytometry and by immunohistochemical staining of frozen tissue sections. The percentage of CD45+ cells in the 11 mice ranged from 2% to 45% and the absolute numbers of CD45+ cells recovered from lymphoid organs ranged from 4 x 10(6) to 90 x 10(6). Up to 93% of the human cells expressed the CD3 antigen together with either CD4 or CD8. Human T cells were localized in periarteriolar areas in murine spleens, whereas in the lymph nodes and gut mucosa, the T cells did not show the pattern for T-dependent areas found in human lymphoid tissue. Numerous human plasma cells were detected in the spleen and gut mucosal crypts of engrafted SCID mice. Human IgG was detected in the serum of all 11 engrafted SCID mice. The functional activity of human T cells recovered from murine splenic tissue was very low 3-4 weeks after engraftment.

Daily physical activity and blood lactate indices of aerobic fitness in children

This study examined the relationship between daily physical activity and aerobic fitness in 11-16-year-olds. Habitual physical activity was assessed in 28 boys (mean(s.d.) age 13.6(1.3) years) and 45 girls (mean(s.d) age 13.7(1.3) years) from minute-by-minute heart rate monitoring during 3 school days. Aerobic fitness was assessed by determining the percentage peak VO2 at blood lactate reference values of 2.5 and 4.0 mmol l-1 during incremental treadmill running. The 4.0 mmol l-1 level occurred at a mean(s.d.) value of 89(7)% peak VO2 in both boys and girls and mean(s.d.) values at the 2.5 mmol l-1 level were 82(9)% peak VO2 in girls. Mean(s.d.) percentage time with heart rates at or above 140 beats min-1 was 6(3)% in boys and 5(3)% in girls. Corresponding values for percentage time at or above 160 beats min-1 were 3(2) for boys and 2(1) for girls. The number of 10- and 20-min periods of activity with the heart rate sustained above the 140 and 160 beats min-1 thresholds were also totalled over the 3 days. No significant relationships were identified between percentage peak VO2 at the 2.5 or 4.0 mmol l-1 blood lactate reference levels and either percentage time or number of 10- or 20-min periods above 140 or 160 beats min-1 (P > 0.05). These results support the hypothesis that daily physical activity levels in 11-16-year-old children do not stress aerobic metabolism sufficiently to influence aerobic fitness.

Antilymphoma activity of human gamma delta T-cells in mice with severe combined immune deficiency

Human Burkitt lymphoma (Daudi) cells grow as disseminated tumors in mice with severe combined immune deficiency (SCID) after either i.v. or i.p. injection. These cells are lysed in vitro by human V gamma 9/V delta 2 T-cells that recognize the groEL homologue on the Daudi cell surface. We report that both Daudi cell-stimulated peripheral blood mononuclear cells (Daudi-PBMC) containing 41-95% of V gamma 9/V delta 2 T-cells and V gamma 9/V delta 2 T-cell clones prolong the survival of SCID mice given inoculations of a lethal dose of Daudi cells. Groups of 6-8-week-old SCID mice were given inoculations i.v. or i.p. of 10(5) Daudi cells followed (through different injection sites) by: (a) 10(7) Daudi-PBMC; or (b) 10(7) unstimulated PBMC; or (c) 0.9% saline solution. All animals in groups (b) and (c) died of disseminated lymphoma, and their survival was significantly shorter than that of mice in group (a) (P < 0.001 for both i.v. and i.p. routes). Significant antitumor effects were also detected when Daudi-PBMC were injected 4 days before or 4 days after Daudi cells (P < 0.05). In vivo depletion of murine natural killer cells by anti-asialo GM-1 rabbit antiserum did not affect survival, suggesting that these cells did not contribute to lymphoma killing. Daudi-PBMC did not exert in vivo antitumor activity against the control Raji lymphoma. Mice receiving i.p. injections of Daudi cells followed by cytotoxic V gamma 9/V delta 2 T-cell clones also survived significantly longer (P < 0.05 for 3 different clones) than animals given Daudi cells alone or Daudi cells followed by noncytotoxic gamma delta T-cell clones. Our results indicate that this model system can be used for studies of human antilymphoma T-cell responses in vivo.

Serum lipids and blood pressure in relation to age and sexual maturity

This study was designed to examine serum lipid profile and blood pressure in relation to age and sexual maturity. Written informed consent to participate was obtained from 42% of the eligible population of two Devon communities. The blood pressure of 343 boys and 336 girls, aged 11-16 years, was recorded and sufficient blood for analysis was obtained from 320 boys and 301 girls. Of these, sexual maturity of 221 boys and 209 girls was visually assessed using the indices developed by Tanner. In girls there was a significant (p less than 0.05) correlation between age and serum triglyceride level (r = 0.16) and in boys both serum cholesterol and HDL-cholesterol were significantly (p less than 0.01) and negatively correlated with age (r = -0.25 and -0.18 respectively). Girls had significantly higher (p less than 0.05) levels of HDL-cholesterol than boys but neither sex demonstrated significant changes (p greater than 0.05) in serum lipids or lipoproteins with sexual maturity. No significant differences (p greater than 0.05) were detected between the mean diastolic blood pressures of boys and girls but older boys had significantly higher (p less than 0.05) systolic blood pressures than similarly aged girls. Age was positively and significantly correlated (p less than 0.01) with blood pressure in both boys (systolic, r = 0.49; diastolic, r = 0.30) and girls (systolic, r = 0.28; diastolic, r = 0.29). More mature children were demonstrated to have both higher systolic and diastolic blood pressures than less mature children (p less than 0.05) but when allowance was made for school year group through analysis of co-variance the relationship for diastolic blood pressure in boys no longer remained significant. Blood pressures observed in this study do not raise general cause for concern but the data indicate that unfavourable serum lipid and lipoprotein profiles are common.

The influence of the site of sampling and assay medium upon the measurement and interpretation of blood lactate responses to exercise

This paper reports the findings of two investigations into methodological problems associated with the interpretation of blood lactate (BLa) in the sports sciences. In Experiment 1, brachial artery (A), antecubital venous (V) and fingertip capillary (C) blood samples were drawn simultaneously from nine subjects (mean age 21.1 +/- 1.3 years) during an incremental treadmill protocol and immediately assayed for BLa concentration. Experiment 2 investigated the extent of lactate concentration differences in whole blood (WB), lysed blood (LB) and plasma (P) measured using a YSI 23 AM analyser. In Experiment 1, a comparison of the mean BLa concentrations obtained from the three sites revealed no significant differences (P greater than 0.05). Correlations between BLa samples from different sites were very high, with r values ranging from 0.858 to 0.983. In Experiment 2, the mean lactate concentrations were: WB, 4.7 +/- 2.7 mM; LB, 5.0 +/- 3.0 mM; P, 7.0 +/- 3.8 mM. Plasma (P) values were significantly higher than WB and LB. Values from all sites were highly correlated with coefficients ranging from 0.963 to 0.987.

IN CONCLUSION

(1) Significant arterial and venous BLa concentration differences do not exist during incremental treadmill exercise. (2) As capillary BLa concentrations reflect arterial values, their use in laboratory and field settings is recommended. (3) Lactate concentration differences in whole blood, lysed blood and plasma will influence the assessment of performance at fixed lactate reference values. (4) If the inter-laboratory test procedures are to be standardized and results compared, precise reporting of lactate sampling and assay techniques is critical.

Children's physical activity: an exploratory study of psychological correlates

Data are now accumulating that show that some children have apparently low levels of habitual physical activity, as measured by heart rate telemetry. However, relatively little is known about the likely correlates or determinants of such activity patterns. The purpose of this study, therefore, was to explore the extent to which activity levels were related to selected psychological factors. The heart rates of 11/12-year old boys and girls (N = 72) were monitored continuously for 12 hr on each of three school days. The same subjects completed psychological inventories assessing physical self-perceptions and motivation. Intrinsic motivation towards physical education and sport was significantly correlated with activity levels for boys. Motivational orientations also predicted activity, but differently for boys and girls. Evidence was found for a discrimination between 'active' and 'less active' girls on the basis of their physical self-perception and motivation scores.