Recording the cardiac interbeat interval distribution.

A compact device is described, which picks up the R wave of the ECG, calculates the duration of successive interbeat intervals, classifies them in eight classes and stores the receptive counts in an integrated-circuit register. The distribution of intervals counted over the experimental period is retrieved through a separate numerical readout device.     

Feedback and incentive effects on the decrease of interbeat interval

Johnston and Lethem (1981) have hypothesized that when subjects attempt to decrease their interbeat interval (i.e., increase their heart rate) maximally, then interbeat interval feedback has a purely motivational role, but when they attempt to decrease their interbeat interval by a precise amount, such feedback has a primarily informational role. This was tested by comparing the performance of 16 subjects on both types of task. It was predicted that additional monetary incentives would reduce the difference between feedback and no-feedback conditions when subjects were attempting to reduce interbeat interval maximally but not when attempting to reduce it by a specific amount. This prediction was not supported. Incentive was found to aid performance on the maximal interbeat interval decrease task, but this was independent of the effects of feedback. Only feedback effects were detected on the specific interbeat interval decrease task.     

Changes in plasma and IgG N-glycome during childhood and adolescence

Despite the importance of protein glycosylation in all physiological and pathological processes and their potential as diagnostic markers and drug targets, the glycome of children is still unexplored. We analyzed N-linked plasma and IgG glycomes in 170 children and adolescents between 6 and 18 years of age. The results showed large biological variability at the population level as well as a large number of associations between different glycans and age. The plasma N-glycome of younger children was found to contain a larger proportion of large complex glycan structures (r = -0.71 for tetrasialylated glycans; r = -0.41 for trisialylated glycans) as well as an increase in disialylated biantennary structures (r = 0.55) with age. Core fucosylation and the level of agalactosylated plasma and IgG glycans decreased while digalactosylated glycans increased with age. This pattern of age-dependent changes in children differs from changes reported in adult population in both, direction and the intensity of changes. Also, sex differences are much smaller in children than in adults and are present mainly during puberty. These important observations should be accounted for when glycan-based diagnostic tests or therapeutics are being developed or evaluated.     

The role of estrogen in bone growth and maturation during childhood and adolescence

Twenty years ago it was believed that pubertal growth was stimulated by testicular androgen in boys and by adrenal androgen in girls. Estrogen, which was used to inhibit growth in excessively tall girls, was not thought to have growth-promoting effects. We hypothesized that estrogen has a biphasic effect on epiphyseal growth, with maximal stimulation at low levels. We showed that the administration of low doses of estrogen, corresponding to a serum estradiol level of about 4 pg/ml (15 pmol/l) caused more than a 60% increase over the prepubertal growth rate in both boys and girls. To test the hypothesis that estrogen is the principal mediator of the pubertal growth spurt in boys, we administered the aromatase inhibitor, testolactone, to boys with familial male-limited precocious puberty. Testolactone produced near normalization of both growth velocity and bone maturation, despite levels of serum testosterone that remained within the adult male range. The observation that low levels of estrogen stimulate growth and bone maturation suggested that estrogen might explain the more rapid epiphyseal maturation of prepubertal girls compared to boys. To determine whether prepubertal girls have higher estrogen levels than prepubertal boys, we developed an ultrasensitive recombinant cell bioassay for estrogen with a sensitivity of 0.02 pg/ml (0.07 pmol/l) estradiol equivalents. Prepubertal girls had approximately eight-fold higher levels of serum estradiol than did prepubertal boys (0.6 ± 0.6 pg/ml (SD) (2.2 ± 2.2 pmol/l) vs 0.08 ± 0.2 pg/ml (0.29 ± 0.73 pmol/l), P < 0.05). We concluded that the pubertal growth spurt of both sexes is driven primarily by estrogen, and that the more rapid epiphyseal maturation of prepubertal girls (vs boys) may be explained by their higher estradiol levels.     

The control of pulse transit time independently of interbeat interval by providing feedback from both

Sixteen subjects took part in a two-stage cardiovascular biofeedback experiment. For five sessions all subjects attempted to control their pulse wave transit time(TT), using TT feedback. The eight subjects who achieved control were given a further five sessions, during which they attempted to control their transit time without altering their interbeat interval(IBI) when provided with TT and IBI feedback. No evidence was found for complete dissociation of TT and IBI. When the single TT contingency was in operation, all subjects who had significant control of TT also showed significant changes in IBI in the same direction. When the dual contingency was introduced, subjects either controlled TT but failed to keep IBI stable or kept IBI stable but failed to control TT.     

Biocultural aspects of gender differences in body composition and obesity during childhood and adolescence

Gender differences in body composition, the prevalence in overweight and obesity as well as in physical activity patterns were tested among 3003 children and adolescents aging between 6 and 18 years (x = 12.1 +/- 3.6) in Vienna and rural parts of Eastern Austria. As to be expected, the absolute and relative amount of body fat was significantly higher among girls of nearly all age groups, while boys exhibited a significantly higher amount of lean or fat free body mass. The prevalence of overweight and obesity was markedly higher among prepubertal girls, however significantly lower among younger and older adolescent girls aging 11 years and older in comparison to their male counterparts. This was however only true of adolescents originating from Austria. Considering adolescents with a background of migration originating from Turkey or the Near East, a significantly higher amount of overweight and/or obesity was found among girls. Therefore, biocultural factors have to be considered to explain gender differences in obesity during childhood and adolescence.     

Fluctuations in interbeat interval in rhythmic heart-cell clusters. Role of membrane voltage noise.

Small clusters of ventricular cells prepared from 7-d chick heart maintain spontaneous, stationary, rhythmic beating in culture for many hours. For clusters containing I-125 cells, mean interbeat interval (IBI) is 0.45 +/- 0.08 s and is independent of cell number (N), whereas, the coefficient of variation of IBI (C) is proportional to N-1/2. Because membrane voltage noise in such clusters would also be expected to vary as N-1/2, we propose a model relating fluctuation in IBI (sigma IBI) to voltage noise (sigma v). A simplified model consisting of random voltage fluctuations superimposed upon a linear pacemaker depolarization of slope a is used to analyze the N-dependent shape of the IBI histogram. Values of sigma v derived from the relation sigma IBI = sigma v/a, or calculated from the skewness of the measured IBI histograms, both agree well with those extrapolated from steady-state noise recorded from resting heart-cell aggregates.     

Suicide and depression in childhood and adolescence

Suicide and depression in children and adolescents are reviewed. The true incidence of suicide in the pediatric population is not known because of under-reporting; suicide is, however, considered as a leading cause of death in this age group. Suicide in young children often reflects an immature comprehension of the state of death, combined with a wish to alter an intolerable living situation or to punish individuals significant in his environment. At age 14 the incidence of suicide increases markedly. These acts of self-destruction reflect a developmental process that follows puberty. During this period the youth experiences an impoverishment of values and controls, as well as an intensification of emotions and needs, resulting in extreme disequilibrium. In the late adolescent, as in the adult, suicide occurs commonly in response to real or imagined loss. Specific guidelines are set out for the assessment and management of the depressed and suicidal youth. Community and medical measures of a prophylactic nature are recommended in the belief that the rising incidence of suicide can be halted through an intensification of efforts on the part of the medical profession.     

Somatomedin-C/insulin-like growth factor-I as a modulator of growth during childhood and adolescence

Normal growth during childhood and adolescence is a complex process which requires the participation of a number of hormones and growth factors. Sm-C/IGF-I plays a central role in this process, with variations in both its serum concentration and the cellular responsiveness to it being important mechanisms regulating growth.     

Granulysin-expressing CD4+ T cells as candidate immune marker for tuberculosis during childhood and adolescence

Background

Granulysin produced by cytolytic T cells directly contributes to immune defense against tuberculosis (TB). We investigated granulysin as a candidate immune marker for childhood and adolescent TB.

Methods

Peripheral blood mononuclear cells (PBMC) from children and adolescents (1–17 years) with active TB, latent TB infection (LTBI), nontuberculous mycobacteria (NTM) infection and from uninfected controls were isolated and restimulated in a 7-day restimulation assay. Intracellular staining was then performed to analyze antigen-specific induction of activation markers and cytotoxic proteins, notably, granulysin in CD4⁺ CD45RO⁺ memory T cells.

Results

CD4⁺ CD45RO⁺ T cells co-expressing granulysin with specificity for Mycobacterium tuberculosis (Mtb) were present in high frequency in TB-experienced children and adolescents. Proliferating memory T cells (CFSE_lowCD4⁺CD45RO⁺) were identified as main source of granulysin and these cells expressed both central and effector memory phenotype. PBMC from study participants after TB drug therapy revealed that granulysin-expressing CD4⁺ T cells are long-lived, and express several activation and cytotoxicity markers with a proportion of cells being interferon-gamma-positive. In addition, granulysin-expressing T cell lines showed cytolytic activity against Mtb-infected target cells.

Conclusions

Our data suggest granulysin expression by CD4⁺ memory T cells as candidate immune marker for TB infection, notably, in childhood and adolescence.     

Biomechanical maturation of joint dynamics during early childhood: Updated conclusions

Dynamic parameters have been commonly explored to characterize the biomechanical maturation of children's gaits, i.e., age-revealing joint moment and power patterns similar to adult patterns. However, the literature revealed a large disparity of conclusions about maturation depending on the study, which was most likely due to an inappropriate scaling strategy and uncontrolled walking speed. With the first years of independent walking, a large growth in height and a large variability of dimensionless walking speed are observed. Moreover, the dynamic parameters were not well studied during early childhood.     

Contractile properties of human skeletal muscle in childhood and adolescence

Using a combination of single maximal stimuli and maximum voluntary contractions, a comparison has been made of muscle properties in pre- and post-pubertal male subjects. In the dorsiflexor and plantarflexor muscles of the ankle, the twitch and maximum voluntary torques were approximately twice as large in the older subjects; the mean height and mean weight increased by factors of 1.20 and 1.86 respectively. The only other muscle parameter that changed, as a function of age, was the contraction time of the ankle dorsiflexors; the mean value was significantly longer in the older subjects. In the younger subjects, there were already clear differences between the dorsiflexor and plantarflexor muscles, the former developing smaller torques and having shorter contraction and half-relaxation times, greater post-activation potentiation and more susceptibility to fatigue. Even in the youngest subject, motor unit activation was complete in the ankle dorsiflexors; although this was not always true of the plantarflexors, the difference between the two subject groups was not significant.     

Ovarian dynamics, serum estradiol and progesterone concentrations during the interovulatory interval in goats

Ovarian changes determined by daily transrectal ultrasonic scanning, and its correlation with serum progesterone (P4) and estradiol (E2) concentrations were studied in seven cyclic Saanen goats. Estrous cycles were synchronized with 2 injections of a PGF2 alpha analogue 9 d apart. All follicles > or = 2 mm in diameter and CL were measured each day. One goat showed a longer interestrous interval, associated with development of a cystic-luteinized structure. The mean interovulatory interval for the other 6 goats was 20.8 +/- 0.4 d. The incidence of goats with 4, 3, and 2 follicular waves was 3, 1 and 2 respectively; follicular waves emerged on Days 0.5 +/- 0.6, 7.2 +/- 0.7, 10.7 +/- 0.5 and 13.7 +/- 0.8 for Wave 1, 2, 3 and the Ovulatory wave, respectively. The largest follicle of Wave 2 was smaller (4.9 +/- 0.1 mm) than the largest follicles of Wave 3 (6.2 +/- 0.1 mm; P < or = 0.01) and of the Ovulatory wave (7.0 +/- 0.5 mm; P < or = 0.01), and tended to be smaller than the largest follicle of Wave 1 (6.3 +/- 0.6 mm; P < or = 0.09). Interval between emergence of Wave 1 and Wave 2 was longer than interval between emergence of Wave 2 and Wave 3 (7.3 +/- 0.9 d vs 4.0 +/- 0.4 d; P < or = 0.01), and between Wave 3 and the Ovulatory wave (3.8 +/- 1.1 d; P < or = 0.05). Two days before ovulation, the diameter of the ovulatory follicle was larger (P < or = 0.01) than the first subordinate follicle. Serum E2 concentrations increased from the day of ovulation (2.7 +/- 0.3 pg/mL) to Day 2 (7.6 +/- 0.9 pg/mL; P < or = 0.01), associated with the early-mid growing phase of the largest follicle of Wave 1, and then decreased to basal levels on Day 5 (P < or = 0.01) and peaked again (16.5 +/- 2.4 pg/mL) 2 d before ovulation. The CL were detected ultrasonically on Day 3 post ovulation and attained a mean maximum diameter of 13.5 +/- 0.8 mm between Days 8 and 14. The following characteristics were observed: 1) ovarian follicular development in goats is wave-like; 2) increased P4 concentrations may be promoting follicular wave turnover; 3) it is suggested that the presence of follicular dominance and the production of E2 are different among waves. While in Wave 1 and in the Ovulatory wave, follicular dominance is present and production of E2 is consistent, no changes in serum E2 concentrations were found in other stages of the interovulatory interval. In the intervening waves, no indicators of follicular dominance could be firmly documented.     

The growth of lung volumes affected by physical performance capacity in boys and girls during childhood and adolescence

The paper concerns a longitudinal study of the relationship between growth in lung functions in terms of forced vital capacity and forced expiratory volume in 1 s, and the development of maximal aerobic power during the age span from 8-18 years of age. The growth curves of anatomical dimensions for boys and girls were similar to those previously established for Northern European children. The growth in lung volume ended later than the growth in body height. It was found that the growth in lung volume was entirely due to growth in body dimensions, with no additional effect of changes in the development of physical performance capacity.