The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents

Longitudinal paediatric population studies have provided evidence that the risk factor theory may be extended to children and adolescents. These studies could assist in identifying individuals at increased coronary risk. Numerous studies have focused on the effects of regular exercise on the paediatric lipoprotein profile, a recognised primary risk factor, with equivocal results. Cross-sectional comparisons of dichotomised groups provide the strongest evidence of an exercise effect. 'Trained' or 'active' children and adolescents demonstrate 'favourable' levels of high density lipoprotein-cholesterol (HDL-C), triacylglycerol, total cholesterol (TC)/HDL-C and low density lipoprotein-cholesterol (LDL-C)/HDL-C, whilst TC is generally unaffected. The evidence regarding LDL-C in these studies is equivocal. A possible self-selection bias means that a cause-effect relationship between exercise and the lipoprotein profile cannot be readily established from this design. Correlational studies are difficult to interpret because of differences in participant characteristics, methods employed to assess peak oxygen uptake and habitual physical activity (HPA), and the statistical techniques used to analyse multivariate data. Directly measured cardiorespiratory fitness does not appear to be related to lipoprotein profiles in the children and adolescents studied to date, although there are data to the contrary. The relationship with HPA is more difficult to decipher. The evidence suggests that a 'favourable' lipoprotein profile may be related to higher levels of HPA, although differences in assessment methods preclude a definitive answer. While few prospective studies exist, the majority of these longitudinal investigations suggest that imposed regular exercise has little, if any, influence on the lipoprotein levels of children and adolescents. However, most prospective studies have several serious methodological design weaknesses, including low sample size, inadequate exercise training volume and a lack of control individuals. Recent studies have suggested that increases in HDL-C and reductions in LDL-C may be possible with regular exercise. The identification of a dose-response relationship between exercise training and the lipoprotein profile during the paediatric years remains elusive.

Influence of muscle fibre type and fitness on the oxygen uptake/power output slope during incremental exercise in humans

We recently reported that a higher percentage of type I fibres in vastus lateralis and a greater peak oxygen uptake (O2) were associated with a greater initial rise in O2 (O2 /W, where W is work rate) following the onset of heavy constant power output exercise (above the lactate threshold, LT). It was unclear if these results were true only for heavy exercise, or if the association between fibre type and/or fitness and O2 /W would also be seen for moderate (< LT) exercise. The purpose of the present study was to compare the relationships between fibre type or peak O2 and O2 /W determined for moderate (< LT) and heavy (> LT) exercise intensities during incremental exercise. Nine healthy subjects performed an incremental ramp test on a cycle ergometer. The O2 /Wslope was calculated for the domain of power outputs up to the LT (S1), from the LT towards peak O2 (S2), and over the entire linear portion of the O2 /W response (ST), and compared to fibre type distribution determined from biopsy of the vastus lateralis, and to peak O2 (as ml kg-1 min-1). Significant correlations between O2 /W and the proportion of type I fibres were found for each exercise domain (r is 0.69, 0.71 and 0.84 for S1, S2 and ST, respectively, P < 0.05). S1 ranged between about 9 ml min-1 W-1 for a low proportion of type I fibres and 11 ml min-1 W-1 for a high proportion of type I fibres. Similar correlations were also found between S2 (r = 0.70) and ST (r = 0.76) and peak O2. These results are consistent with our previous findings during > LT constant power output exercise, and suggest that the proportion of type I fibres, and possibly fitness as indicated by peak O2, is associated with greater O2 /W during the initial adjustment to < LT as well as > LT exercise. These results do not appear to be explained by classical descriptions of the kinetics of adjustment of O2 following the onset of ramp or constant power output exercise. They might reflect enhanced motor unit recruitment in subjects with a greater percentage of type I fibres, and/or who are more aerobically fit. However, the underlying mechanism for these findings must await further study.

Immunogenetics: changing the face of immunodeficiency

Tables 1 and 2 highlight the enormous advances that have been made in the definition of the molecular defects underlying primary immunodeficiencies in the past decade. The identification of SAP as the gene defective in XLP now completes the molecular bases of all the recognised X linked syndromes. Of the autosomally inherited syndromes, only the genes for DiGeorge syndrome, hyper-IgE, and perhaps most importantly, common variable immunodeficiency remain to be elucidated. The major clinical benefits of this information have primarily been in offering more accurate and rapid molecular diagnoses. The ability to make a molecular diagnosis also increases the options for earlier definitive treatments such as bone marrow transplantation and somatic gene therapy. Finally, as illustrated by the studies on the functions of WASP and the gamma c/JAK-3 pathway, identification of the gene defect is the first step to understanding the molecular pathogenesis of the immunological abnormalities.

The long-term effect of quetiapine (Seroquel TM ) monotherapy on weight in patients with schizophrenia

INTRODUCTION

Quetiapine (Seroquel TM ) is an atypical antipsychoticdrug with demonstrated efficacy and tolerability. In particular, placebo-level extrapyramidal symptoms (EPS) across the entire dose range and a low propensity to cause sexual dysfunction suggest it may be associated with greater patient acceptability than alternative treatments. However, other side-effects, such as weight gain, may also have a significant impact on treatment acceptability.

METHOD

We report the long-term weight changes observed in a cohort of 427 patients with schizophrenia from controlled and open-label extension (OLE) trials, in which quetiapine (mean dose 475 mg/day after 1 year) was the only antipsychotic medication during the OLE period.

RESULTS

In these patients, there was no overall effect on weight across the body mass index (BMI) spectrum. There were no dose-related effects on weight, and only one patient withdrew from treatment due to an adverse event of weight gain. Quetiapine appeared to have a weightneutral or 'normalizing' effect, with a tendency towards favourable shifts in bodyweight in underweight patients (BMI<18.5 kg/m 2 ) and severely obese patients (BMI>35 kg/m 2 ).

CONCLUSION

These results indicate that long-term weight changes with quetiapine monotherapy are minimal and potentially beneficial, and do not appear to raise the medical concerns associated with some other atypical agents.

Effect of 6 weeks of endurance training on the lactate minimum speed

The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s: age 23+/-4 years; body mass 69.7+/-9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23+/-4 years; body mass 72.7+/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO2max, running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol x l(-1); and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO2max, running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol x l(-1) or the lactate minimum speed. In the training group, there was a significant increase in VO2max (from 47.9+/-8.4 to 52.2+/-2.7 ml x kg(-1) x min(-1)), running speed at the maximal lactate steady state (from 13.3+/-1.7 to 13.9+/-1.6 km x h(-1)), running speed at the lactate threshold (from 11.2+/-1.8 to 11.9+/-1.8 km x h(-1)) and running speed at a blood lactate concentration of 3 mmol x l(-1) (from 12.5+/-2.2 to 13.2+/-2.1 km x h(-1)) (all P < 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0+/-0.7 to 10.9+/-1.7 km x h(-1)). The results demonstrate that the lactate minimum speed, when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity.

Cloning of the murine unconventional myosin gene Myo9b and identification of alternative splicing

We report the cloning of a cDNA for the mouse unconventional myosin Myo9b, the orthologue of the rat myr5 and human MYOIXb genes. A full-length spleen cDNA of 7087bp encoding a protein of 1961 amino acids was isolated. By RT-PCR, we show that Myo9b is expressed in a wide range of tissues, including heart, brain, muscle and inner ear. In addition, we have identified two alternatively spliced exons. Equivalent exons have not been previously reported for either the human or rat homologues. These exons are located in the Myo9b specific actin-binding site insert of the head domain and in the tail region. A third splice form utilizing an alternative reading frame within the 3'UTR is also described. Several polymorphisms within the coding region were identified; of interest is an in-frame 33bp imperfect duplication within the tail region that was observed only in the C57Bl/6 strain. Myo9b has been previously mapped to mouse chromosome 8 and is a candidate for the mouse mutations myodystrophy and quinky.

Selected predictor variables and the lipid-lipoprotein profile of prepubertal girls and boys

PURPOSE

It is still unclear how habitual physical activity (HPA), peak VO2, percent body fat (%BF), and dietary composition are related to the lipid-lipoprotein profile in children. The purpose of this study was to identify independent contributions from these selected predictor variables to prepubertal children's lipid-lipoprotein profile.

METHODS

Peak VO2, HPA from continuous heart rate monitoring, %BF, 7-d dietary analysis, total cholesterol (TC), total triacylglycerol (TG), high density lipoprotein (HDL) cholesterol (HDL-C), low density lipoprotein (LDL) cholesterol (LDL-C), TC/HDL-C, and LDL-C/HDL-C were determined in 33 prepubertal girls and 38 prepubertal boys (mean +/- SD age, 10.6 +/- 0.7 yr).

RESULTS

Bivariate correlation analyses revealed that peak VO2, %BF, and HPA were related to the lipid-lipoprotein profile in girls (P < 0.05). For the boys, HPA was only related to TC/HDL-C (P < 0.05) and LDL-C/HDL-C (P < 0.05), whereas daily energy intake (kJ x d(-1)) was associated with TC and LDL-C (P < 0.05). Multiple linear regression analyses indicated that peak VO2, %BF and HPA were the main predictor variables for the girls. Peak VO2 accounted for 22.7%, 24.8%, 22.5%, and 24.2% of the unique variance (sr(i)2) in TG, HDL-C, LDL-C/HDL-C, and TC/HDL-C, respectively. For TC and LDL-C in girls, sr(i)2 were 18.0% and 22.6%, respectively, from HPA. In contrast, only daily energy intake had a significant unique contribution to the variance of TC (15.4%) and LDL-C (22.0%) for the boys.

SUMMARY

The main findings from this study were that the predictor variables are lipid-lipoprotein specific and depend on gender. These results would support the growing evidence that it is important to nurture an active lifestyle in children from an early age and that an awareness of fitness and body fatness is required.

Oral creatine supplementation improves multiple sprint performance in elite ice-hockey players

BACKGROUND

The purpose of this study was to assess the effect of oral creatine monohydrate supplementation on multiple sprint cycle and skating performance in ice-hockey players.

METHODS

PARTICIPANTS

sixteen elite ice-hockey players were selected as subjects.

EXPERIMENTAL DESIGN

subjects were randomly assigned to either a creatine (Cr) (n = 8) or a placebo (P) group (n = 8) in a double blind design. After familiarization and baseline tests, subjects loaded with 5 g of creatine monohydrate or placebo (glucose) four times per day for 5 days, after which a maintenance dose of 5 g per day for 10 weeks was administered. At baseline, and after 10 days and 10 weeks of supplementation, subjects performed i) a cycle test involving 5 all-out sprints of 15 sec duration separated by 15 sec recovery with the resistance set at 0.075 body mass (kg), and ii) 6 timed 80-m skating sprints with the sprints initiated every 30 sec and a split time taken at 47 m.

RESULTS

A two-way ANOVA demonstrated no significant change in any of the variables in the P group over the period of study. However, in the Cr group, average mean power output over the 5 sprints was significantly higher at 10 days (1074 +/- 241 W) and 10 weeks (1025 +/- 216 W) than at baseline (890 +/- 172 W), (p < 0.01). Average peak power output over the 5 sprints improved significantly from baseline (1294 +/- 311 W) to 10 days (1572 +/- 463 W), (p < 0.01). Average on-ice sprint performance to 47 m was significantly faster at 10 days (6.88 +/- 0.21 sec) and 10 weeks (6.96 +/- 0.19 sec) than at baseline (7.17 +/- 0.27 sec), (p < 0.005).

CONCLUSIONS

This study demonstrates that creatine supplementation has an ergogenic effect in elite ice-hockey players.

A disproportionate increase in VO2 coincident with lactate threshold during treadmill exercise

PURPOSE

The purpose of this study was to assess the relationship between pulmonary VO2 and running speed over a range of exercise intensities. During constant-load cycle exercise above the lactate threshold (Tlac), it has been shown that VO2 does not attain a steady state within 3 min but continues to rise until either a delayed but elevated steady-state VO2 is attained or exhaustion occurs. Since this greater oxygen cost of exercise (V02 slow component) has only been demonstrated at discrete exercise intensities above Tlac, it was hypothesised that the onset of the VO2 slow component would coincide with Tlac during an incremental test if the stage durations were of sufficient length.

METHODS

Five male subjects (mean +/- SD age 31 +/- 2 yr: VO2peak 60.1 +/- 5.8 mL x kg(-1) x min(-1)) performed four identical treadmill tests within an 8-d period. The tests involved the completion of six stages of 7-min duration. Running speed was increased by 0.5 km x h(-1) between stages. In the first test, fingertip capillary blood was sampled at the end of each stage for determination of Tlac. For all tests expired air was collected into Douglas bags from 3.0 to 3.75 min and from 6.0 to 6.75 min of each stage to determine any increase in V02 (deltaVO2) over the duration of the stage.

RESULTS

The mean deltaVO2 for each stage over the four tests was determined for each subject. Repeated measures ANOVA with post-hoc Tukey tests revealed a significant increase in deltaVO2 at running speeds above, but not below, Tlac.

CONCLUSIONS

The results of this study confirm the close association between the VO2 slow component and the onset of lactic acidosis and demonstrate alinearity in the VO2-exercise intensity relationship above Tlac for incremental treadmill exercise.

Effect of exercise modality on oxygen uptake kinetics during heavy exercise

The mechanisms responsible for the oxygen uptake (VO2) slow component during high-intensity exercise have yet to be established. In order to explore the possibility that the VO2 slow component is related to the muscle contraction regimen used, we examined the pulmonary VO2 kinetics during constant-load treadmill and cycle exercise at an exercise intensity that produced the same level of lactacidaemia for both exercise modes. Eight healthy subjects, aged 22-37 years, completed incremental exercise tests to exhaustion on both a cycle ergometer and a treadmill for the determination of the ventilatory threshold (defined as the lactate threshold, Th1a) and maximum VO2 (VO2max). Subsequently, the subjects completed two "square-wave" transitions from rest to a running speed or power output that required a VO2 that was halfway between the mode-specific Th1a and VO2max. Arterialised blood lactate concentration was determined immediately before and after each transition. The VO2 responses to the two transitions for each exercise mode were time-aligned and averaged. The increase in blood lactate concentration produced by the transitions was not significantly different between cycling [mean (SD) 5.9 (1.5) mM] and running [5.5 (1.6) mM]. The increase in VO2 between 3 and 6 min of exercise; (i.e. the slow component) was significantly greater in cycling than in running, both in absolute terms [290 (102) vs 200 (45) ml x min(-1); P<0.05] and as a proportion of the total VO2 response above baseline [10 (3)% vs 6 (1)%; P < 0.05]. These data indicate that: (a) a VO2 slow component does exist for high-intensity treadmill running, and (b) the magnitude of the slow component is less for running than for cycling at equivalent levels of lactacidaemia. The greater slow component observed in cycling compared to running may be related to differences in the muscle contraction regimen that is required for the two exercise modes.

Does perinatal phenobarbital exposure affect developmental outcome at age 2?

The objective of this paper is to determine if phenobarbital exposure during pregnancy affects developmental outcome at age 2 years. Between 1991 and 1994, 401 pregnant patients at risk for delivery prior to 34 weeks' gestation were invited to participate; 48 mothers declined entry. Before delivery, pharmacy randomized the pregnant women to receive phenobarbital and vitamin K or identically appearing placebo in a blinded fashion. Developmental follow-up at age 2 years was performed. Children from the treatment group scored significantly lower on the Bayley Mental Developmental Index (mean MDI +/- 1 SD) than children whose mothers were randomized to the placebo group [104 +/- 21 (n = 59) vs. 113 +/- 22 (n = 62), p = 0.023]. Of 36 independent variables, randomization group was one of five that individually contributed to the prediction of the Bayley MDI score (p < 0.05). It was concluded that perinatal phenobarbital therapy may impair developmental outcome.

Effect of incremental test protocol on the lactate minimum speed

PURPOSE

The purpose of this study was to investigate the effect of altering the initial running speed (RS) in the incremental portion of the lactate minimum test on the lactate minimum speed (LMS).

METHODS

Eight well-trained endurance runners (mean +/- SD age 29.0 +/- 5.4 yr, body mass 72.0 +/- 5.6 kg, VO2max 63.1 +/- 3.8 mL x kg(-1) min(-1)) completed a standard incremental treadmill test for the assessment of the lactate threshold (LT) and VO2max, and eight lactate minimum tests. Following a period of supramaximal exercise, subjects were allowed 8 min of recovery to allow blood [lactate] to peak. Subjects then undertook eight randomly-assigned incremental treadmill tests from different initial running speeds (3.0, 2.5, 2.0, 1.5, 1.0, and 0.5 km x h(-1) below the predetermined RS-LT, at the RS-LT, and at 1.0 km x h(-1) above the RS-LT) with RS increased by 1.0 km x h(-1) every 5 min until volitional fatigue. Blood samples for the determination of blood [lactate] were taken at the end of each stage and the LMS was determined by fitting a spline function to the data.

RESULTS

No LMS could be determined for the two highest initial RS conditions. For the other conditions, the LMS was significantly affected by the initial RS used in the incremental test and varied from 13.8 +/- 0.7 km x h(-1) with an initial RS of 3.0 km x h(-1) below the RS-LT, to 15.8 +/- 0.8 km x h(-1) with an initial RS of 0.5 km x h(-1) below the RS-LT. The LMS was significantly different from the RS-LT (15.4 +/- 0.8 km x h(-1)) (P < 0.05), except when the incremental test started at 1.0 or 1.5 km x h(-1) below the RS-LT.

CONCLUSIONS

These results suggest that the LMS test is not a valid method for estimation of the LT since it is profoundly influenced by the starting speed selected for the incremental portion of the test.

Intra-individual variation of plasma lipids and lipoproteins in prepubescent children

Estimates of the average intra-individual biological variability for plasma lipids and lipoproteins differs substantially among published studies. Moreover, this topic does not appear to have received consideration in exercise and health literature with normal, healthy children as subjects. The purpose of this study was, therefore, to determine the short-term, day-to-day variability of the lipid-lipoprotein profile from 19 children [mean (SD), 11.5 (0.8) years] from 3 separate venous blood samples. Intra-individual standard deviations, variances and coefficients of variance were determined for total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein-cholesterol (HDL-C), HDL-C sub-fractions HDL2 and HDL3, and low-density lipoprotein-cholesterol (LDL-C). The intra-individual variation for TC and LDL-C was used to calculate the 95% confidence intervals (CIs) around the National Cholesterol Education Programme (NCEP 1991) cut-off points. The main finding was that all of the measured blood analytes including TC, TG, HDL-C, HDL2, HDL3, and LDL-C varied considerably from day-to-day. Coefficients of total variation ranged from 3.5% for HDL3 to 25.4% for TG. Classification of individuals using NCEP guidelines was difficult based on only one or two blood samples. The magnitude of variation for LDL-C meant that a 95% CI could not be constructed around the NCEP borderline-high classification from either one or two samples. However, averaging three TC and LDL-C measurements increased the likelihood of classification within the 95% CI. The results indicate that when using the NCEP guidelines for children and adolescents, true concentrations for TC and LDL-C should be based on the mean of multiple samples.

Health knowledge and smoking among South African women

While several studies of developed countries have attempted to understand individual smoking using economic models, no such studies have been conducted in South Africa. The purpose of this paper is to identify which factors influence individual South African women's choice to smoke cigarettes and their knowledge of the health risks of smoking. To allow for the implied correlation between the unobservable components of the reduced form equations for these health inputs the model is estimated as a bivariate probit. In order to identify those women who are most at risk of becoming smokers and those who are most likely to benefit from health education, the results show how the probability of being an uninformed non-smoker or an uninformed smoker vary across different socio-economic groups.

Tracheary element differentiation uses a novel mechanism coordinating programmed cell death and secondary cell wall synthesis

Tracheary element differentiation requires strict coordination of secondary cell wall synthesis and programmed cell death (PCD) to produce a functional cell corpse. The execution of cell death involves an influx of Ca2+ into the cell and is manifested by rapid collapse of the large hydrolytic vacuole and cessation of cytoplasmic streaming. This precise means of effecting cell death is a prerequisite for postmortem developmental events, including autolysis and chromatin degradation. A 40-kD serine protease is secreted during secondary cell wall synthesis, which may be the coordinating factor between secondary cell wall synthesis and PCD. Specific proteolysis of the extracellular matrix is necessary and sufficient to trigger Ca2+ influx, vacuole collapse, cell death, and chromatin degradation, suggesting that extracellular proteolysis plays a key regulatory role during PCD. We propose a model in which secondary cell wall synthesis and cell death are coordinated by the concomitant secretion of the 40-kD protease and secondary cell wall precursors. Subsequent cell death is triggered by a critical activity of protease or the arrival of substrate signal precursor corresponding with the completion of a functional secondary cell wall.

Auxin-dependent cell expansion mediated by overexpressed auxin-binding protein 1

To test the hypothesis that auxin-binding protein 1 (ABP1) is a receptor controlling auxin-mediated plant cell expansion, ABP1 complementary DNAs were expressed in a controllable fashion in tobacco plants and constitutively in maize cell lines. Induction of Arabidopsis ABP1 expression in tobacco leaf strips resulted in an increased capacity for auxin-mediated cell expansion, whereas induction of ABP1 in intact plants resulted in leaves with a normal morphology, but larger cells. Similarly, constitutive expression of maize ABP1 in maize cell lines conferred on them the capacity to respond to auxin by increasing cell size. These results support a role of ABP1 as an auxin receptor controlling plant growth.

Mosaic supernumerary ring chromosome 19 identified by comparative genomic hybridisation

We report the use of comparative genomic hybridisation (CGH) to define the origin of a supernumerary ring chromosome which conventional cytogenetic banding and fluorescence in situ hybridisation (FISH) methods had failed to identify. Targeted FISH using whole chromosome 19 library arm and site specific probes then confirmed the CGH results. This study shows the feasibility of using CGH for the identification of supernumerary marker chromosomes, even in fewer than 50% of cells, where no clinical or cytogenetic clues are present.

The validity of the lactate minimum test for determination of the maximal lactate steady state

PURPOSE

The purpose of this study was to investigate the validity of the lactate minimum test ([Lac-]BMIN) in the determination of the velocity at the maximal lactate steady state (V-MLSS), and to identify those physiological factors most closely associated with 8-km running performance.

METHODS

Thirteen trained male runners (VO2max range 53-67 mL.kg-1.min-1) took part in an 8-km simulated race on flat roads and completed a comprehensive battery of laboratory tests.

RESULTS

Performance velocity was most strongly correlated with the estimated running velocity at VO2max (r = 0.93) and with V-MLSS (r = 0.92) and velocity at lactate threshold (V-Tlac) (r= 0.93). The running velocity at the ventilatory threshold (V-Tvent) (r = 0.81) and the [Lac-]BMIN (r = 0.83) also produced good correlations with performance velocity. Performance running velocity (mean +/- SEM 16.0 +/- 0.3 km.h-1) was not significantly different from V-MLSS (15.7 +/- 0.3 km.h-1). The running velocity at [Lac-]BMIN (14.9 +/- 0.2 km.h-1) was not significantly different from the V-Tlac (15.1 +/- 0.3 km.h-1) or V-Tvent (14.9 +/- 0.2 km.h-1) was not significantly different from the V-Tlac (15.1 +/- 0.3 km.h-1) or V-Tvent (14.9 +/- 0.3 km.h-1) but was significantly lower than the V-MLSS (P < 0.05). The [Lac-]BMIN provided the lowest correlation with V-MLSS (r = 0.61) and the worst estimate of V-MLSS (SEE = 0.75 km.h-1) compared with the other measures of lactate accumulation. The V-Tlac was not significantly different from V-MLSS and provided the highest correlation (r = 0.94) and a close estimate (SEE = 0.33 km.h-1) of the V-MLSS.

CONCLUSIONS

It is concluded that of the measures studied relating to blood lactate accumulation during submaximal exercise, V-Tlac provides the best estimate of the V-MLSS and the V-Tlac had equal predictive power for 8-km race performance.

Epithelial p53 gene expression and mutational analysis, combined with growth fraction assessment, in oral lichen planus

The immunohistochemical detection of epithelial p53 protein expression in oral lichen planus (OLP) biopsies was supplemented with molecular analysis for mutations of the p53 gene using the polymerase chain reaction - single stranded conformational polymorphism (PCR-SSCP) technique. p53 protein expression, in the basal epithelial cell layer, as detected by the DO7 and 1801 antibodies, was significantly more frequent in OLP compared with other oral keratoses and normal mucosa, as was the growth fraction. The 10 OLP biopsies that had the most frequent p53 staining (plus a case of OLP found in continuity with a SCC) were screened by the PCR-SSCP technique, but no mutations were detected in the p53 gene (exons 5 9). The p53 overexpression in the OLP samples may be a physiological response to the hyper-proliferative state, as revealed by the growth fraction determination. This may usefully serve to protect against mutagenesis, and so be a factor in the low incidence of carcinoma associated with OLP.

Absence of expression of the Wiskott-Aldrich syndrome protein in peripheral blood cells of Wiskott-Aldrich syndrome patients

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency that is usually associated with thrombocytopenia and eczema. The very variable phenotype of WAS results from defects in the WAS protein (WASP), the function of which is not well understood. In many cases causative mutations have now been identified in the WAS gene. Attempts have been made to correlate the nature of the mutations with the severity of the disease. In this study we investigated mutations in 13 patients with WAS and analyzed the expression of WASP in patient blood samples by immunoblot analysis. We found that despite extensive variation in the nature of the mutations in patients with severe WAS symptoms, none express the protein. However, in 1 patient with a mild clinical phenotype WASP expression was detected. Such an analysis could be used as an initial screening procedure for the diagnosis of WAS prior to genotypic analysis.

Dim-red-light-induced increase in polar auxin transport in cucumber seedlings. I. Development Of altered capacity, velocity, and response to inhibitors

We have developed and characterized a system to analyze light effects on auxin transport independent of photosynthetic effects. Polar transport of [3H]indole-3-acetic acid through hypocotyl segments from etiolated cucumber (Cucumis sativus L.) seedlings was increased in seedlings grown in dim-red light (DRL) (0.5 &mgr;mol m-2 s-1) relative to seedlings grown in darkness. Both transport velocity and transport intensity (export rate) were increased by at least a factor of 2. Tissue formed in DRL completely acquired the higher transport capacity within 50 h, but tissue already differentiated in darkness acquired only a partial increase in transport capacity within 50 h of DRL, indicating a developmental window for light induction of commitment to changes in auxin transport. This light-induced change probably manifests itself by alteration of function of the auxin efflux carrier, as revealed using specific transport inhibitors. Relative to dark controls, DRL-grown seedlings were differentially less sensitive to two inhibitors of polar auxin transport, N-(naphth-1-yl) phthalamic acid and 2,3,5-triiodobenzoic acid. On the basis of these data, we propose that the auxin efflux carrier is a key target of light regulation during photomorphogenesis.

A five year physiological case study of an Olympic runner

OBJECTIVE

To study physiological changes caused by long term endurance training in a world class female distance runner, and to compare these changes with alterations in 3000 m running performance.

METHODS

The subject underwent regular physiological assessment during the period 1991-1995. Physiological measures made included body composition, maximal oxygen uptake (VO2MAX), running economy, and lactate threshold. In addition, the running speed at VO2MAX was estimated. Test protocols, laboratory equipment, and laboratory techniques used were the same for each test session.

RESULTS

The 3000 m race performance improved by 8% from 1991 to 1993 after which it stabilised. In contrast, VO2MAX fell from 1991 (73 ml/kg/min) to 1993 (66 ml/kg/min). Submaximal physiological variables such as lactate threshold (from 15.0 to 18.0 km/h) and running economy (from 53 ml/kg/min to 48 ml/kg/min at 16.0 km/h) improved over the course of the study. Despite no increase in VO2MAX, the reduction in the oxygen cost of submaximal running caused the estimated running speed at VO2MAX to increase from 19.0 km/h in 1991 to 20.4 km/h in 1995.

CONCLUSIONS

Improvement in 3000 m running performance was not caused by an increase in VO2MAX. Rather, the extensive training programme adopted, together perhaps with physical maturation, resulted in improvements in submaximal fitness factors such as running economy and lactate threshold. These adaptations improved the running speed estimated to be associated with VO2MAX, and resulted in improved 3000 m running performance.

Something in the air: endotoxins and glucans as environmental troublemakers

This review provides a clear explanation of the current status of two common airborne contaminants, lipopolysaccharide and (1-->3)-beta-D-glucan, in the induction of indoor air-related disease. A full description of the origin of these two products is given together with information of their structure and function. Details of the biochemical mechanisms by which they interact with human cells and the physiological consequences of these interactions are outlined. Both compounds play a key role in the induction of airway inflammation and this paper highlights the environmental importance in the work place and home of these inhaled agents in terms of respiratory disease.