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Biomedical subjects

Dan Nemet

Publications and source records attributed to Dan Nemet.

33 records · Page 2Linked to original sources
PubMed2003

Catecholamine response to exercise in children with attention deficit hyperactivity disorder.

The objective of this study was to examine differences in catecholamine (CA) response to exercise between children who had received a diagnosis of attention-deficit/hyperactivity disorder (ADHD) and age- and gender-matched controls. On the basis of the notion of a CA dysfunction in ADHD, we reasoned that the normal robust increase in circulating CA seen in response to exercise would be blunted in children with ADHD. To test this, we recruited 10 treatment-naïve children with newly diagnosed ADHD and 8 age-matched controls (all male) and measured CA response to an exercise test in which the work was scaled to each subject's physical capability. After exercise, epinephrine and norepinephrine increased in both control and ADHD subjects (p = 0.006 and p = 0.002, respectively), but the responses were substantially blunted in the ADHD group (p = 0.018) even though the work performed did not differ from controls. Circulating dopamine increased significantly in the control subjects (p < 0.016), but no increase was noted in the subjects with ADHD. Finally, a significant attenuation in the lactate response to exercise was found in ADHD (between groups, p < 0.005). Our data suggest that CA excretion after exercise challenges in children with ADHD is deficient. This deficiency can be detected using a minimally invasive, nonpharmacologic challenge.

Attention Deficit Disorder with Hyperactivity↗
PubMed2003

Neuromotor noise limits motor performance, but not motor adaptation, in children.

Children do not typically appear to move with the same skill and dexterity as adults, although they can still improve their motor performance in specific tasks with practice. One possible explanation is that their motor performance is limited by an inherently higher level of movement variability, but that their motor adaptive ability is robust to this variability. To test this hypothesis, we examined motor adaptation of 43 children (ages 6-17) and 12 adults as they reached while holding the tip of a lightweight robot. The robot applied either a predictable, velocity-dependent field (the "mean field") or a similar field that incorporated stochastic variation (the "noise field"), thereby further enhancing the variability of the subjects' movements. We found that children exhibited greater initial trial-to-trial variability in their unperturbed movements but were still able to adapt comparably to adults in both the mean and noise fields. Furthermore, the youngest children (ages 6-8) were able to reduce their variability with practice to levels comparable to the remaining children groups although not as low as adults. These results indicate that children as young as age 6 possess adult-like neural systems for motor adaptation and internal model formation that allow them to adapt to novel dynamic environments as well as adults on average despite increased neuromotor or environmental noise. Performance after adaptation is still more variable than adults, however, indicating that movement inconsistency, not motor adaptation inability, ultimately limits motor performance by children and may thus account for their appearance of incoordination and more frequent motor accidents (e.g., spilling, tripping). The results of this study also suggest that movement variability in young children may arise from two sources--a relatively constant, intrinsic source related to fundamental physiological constraints of the developing motor system and a more rapidly modifiable source that is modulated depending on the current motor context.

Adaptation, Physiological↗
PubMed2003

Adipocytokines, body composition, and fitness in children.

Recent evidence suggests a role for adipose derived cytokines (adipocytokines) such as tumor necrosis factor-alpha (TNF-alpha), IL-6, and the recently discovered adiponectin in the mechanism of impaired glucose regulation and atherosclerosis in adults. However, the relationship between adipocytokines and body composition, fasting insulin, and fitness is virtually unknown children. Fasting blood sampling was performed in 30 healthy, predominately Hispanic- and Asian-American children (16 boys, mean age 12.7 +/- 0.1 y old) from a lower socioeconomic area in Los Angeles. Adiposity was measured by dual x-ray absorptiometry (DEXA); and peak oxygen uptake using cycle ergometry. Adiponectin (mean 10.8 +/- 0.8 micro g/mL) was inversely correlated with body mass index (BMI, as percentile by age) (r = -0.48, p = 0.011) and fat mass (r = -0.43, p = 0.03). In contrast, TNF-alpha and IL-6 were both positively correlated with BMI and fat mass. Adiponectin was inversely correlated with fasting insulin (r = -0.52, p = 0.006), but no correlations were found for insulin and either TNF-alpha or IL-6. Adiponectin was correlated with HDL (r = 0.448, p = 0.019). Paradoxically, peak oxygen consumption (an indicator of fitness) was negatively correlated with adiponectin levels (r = -0.471, p = 0.013) and positively correlated with TNF-alpha (r = 0.560, p = 0.002). In children, adipocytokines are correlated with fat mass, insulin sensitivity, and cardiovascular risk factors in a manner that is qualitatively similar to relationships recently observed in adults. In more obese children, the mass of fat tissue may attenuate potentially positive effects of fitness on circulating levels of adiponectin and TNF-alpha. The novel data on adiponectin suggest that deleterious dysregulation of adipocytokines associated with obesity may occur relatively early in life.

Absorptiometry, Photon↗
PubMed2003

Effect of water polo practice on cytokines, growth mediators, and leukocytes in girls.

PURPOSE: The effects of exercise on growth and development are mediated through a complex interaction between the endocrine, immune, and nervous systems. Very little is known about how these systems respond to exercise in children or adolescents. Moreover, there are few studies that have examined growth factors, inflammatory cytokines, and leukocyte responses to "real-life" or field exercise solely in girls. Thus, the goal of the present study was to determine the acute exercise-induced alterations in the growth hormone --> insulin-like growth factor-I axis, inflammatory cytokines, and certain aspects of immune function in a group of adolescent girls after a typical water polo practice. METHODS: Ten, healthy, high-school female subjects, 14-16 yr old, performed a single, typical, 1.5-h water polo practice session. Blood was sampled before and after the session. RESULTS: The exercise resulted in an increase in HR (from 82 +/- 2 to 161 +/- 5 beats.min(-1) at 30 min, P < 1.4.10(-6) ), as well as in circulating lactate levels (375 +/- 66%, P < 0.0005). Significant increases where noted in circulating IL-6 (396 +/- 162%, P < 0.005) and IL-1ra (71 +/- 20%, P < 0.015). A substantial increase in the level of IGFBP-1 (1344 +/- 344%, P < 0.001) was also observed. Interestingly, TNF-alpha levels decreased after the exercise (-10.4 +/- 3.8%, P < 0.04) as did insulin (55 +/- 12%, P < 0.005). The exercise led to significant increases in granulocytes, monocytes, and lymphocytes. The exercise significantly influenced adhesion molecules (such as CD62L and CD54), which has not been previously studied in adolescent girls. CONCLUSIONS: These data demonstrate that an intense "real-life" exercise bout in adolescent females leads to profound increases in inflammatory cytokines and reductions in anabolic mediators with substantial alterations in white blood cell subpopulations and adhesion molecules. The role of these frequent, almost daily immune and cytokine changes on growth and development have yet to be determined.

Adolescent↗
PubMed2003

The effect of neonatal sepsis on bone turnover in very-low birth weight premature infants.

Neonatal sepsis is very common in preterm infants, and severe morbidity during the neonatal period is a major cause of osteopenia of prematurity. We examined the effect of neonatal sepsis on bone turnover markers in premature infants. Twenty-four premature infants participated in the study. Ten of the premature infants developed sepsis during their hospitalization in the neonatal intensive care unit (mean gestational age [GA] 27.3 +/- 0.4 weeks; mean birth weight [BW] 898 +/- 82 g). Fourteen infants who did not develop sepsis served as controls (GA: 26.8 +/- 0.8 weeks, BW: 892 +/- 66 g). Blood samples for bone turnover markers were collected during the initial sepsis workup, and at the end of the first week of treatment, and were compared to the corresponding weekly changes in bone markers in the controls. In addition, samples were collected at the end of the 10th week of life to determine long-term effects of sepsis on bone turnover. Bone osteoblastic activity was assessed by measurements of circulating osteocalcin, bone-specific alkaline phosphatase (BSAP) and the C-terminal procollagen peptide (PICP) levels. Bone resorption was assessed by measurements of circulating carboxy terminal cross-links telopeptide of type I collagen (ICTP). There were no significant differences in the weekly changes of all bone turnover markers in premature infants who developed or did not develop sepsis. No significant differences were found in bone turnover markers at the age of 10 weeks between the groups. Neonatal sepsis in premature infants was not associated with biochemical evidence of reduced bone turnover.

Alkaline Phosphatase↗
PubMed2002

The effect of a combined intervention on body mass index and fitness in obese children and adolescents - a clinical experience.

UNLABELLED: We assessed the effect of a weight management programme on body weight, body mass index (BMI), and fitness in obese children and adolescents. The study was designed as a longitudinal, non-randomised, clinical experience of a 3 and 6 month combined dietary-behavioural-exercise intervention. A total of 177 obese children (age 6-16 years) participated in the 3 month programme, of whom 65 completed the 6 month intervention. A group of 25 age- and maturity-matched obese children who did not participate in the structured programme served as controls. Body weight, BMI, and fitness were evaluated at baseline, and after the 3 and 6 months intervention. Body weight and BMI were significantly reduced ( P<0.05), and endurance time significantly increased ( P<0.0005) following the 3 months intervention. Obese children who continued the programme for 6 months maintained the decrease in BMI and further improved endurance time. In contrast, obese children who did not participate in the structured programme gained weight, increased their BMI, and improved fitness less significantly. Gender, pubertal status, and the degree of obesity had no influence on BMI changes. Children without parental overweight had significantly greater decreases in BMI compared to children of obese parents. CONCLUSION: a combined, structured multidisciplinary intervention for childhood obesity results in decreased body weight, decreased body mass index and improved fitness.

Adolescent↗
PubMed2002

Spontaneous activity in premature infants affects bone strength.

OBJECTIVE: Determination of bone strength of lower extremities in very low birth weight (VLBW) premature infants with central nervous system pathology resulting in reduced unilateral spontaneous leg movements. STUDY DESIGN: Quantitative ultrasound (QUS) measurements of speed of sound (SOS) of the tibiae of both legs in three VLBW premature infants with brain insult and unilateral reduced spontaneous activity. Results were compared to QUS measurements of both legs in healthy premature infants. Measurements were performed by the same investigator who was blinded to the clinical course of the participants. RESULTS: Reduced spontaneous activity of one leg due to brain pathology resulted in decreased tibial SOS in the affected side. There was no difference in bone SOS between the legs of the healthy controls. CONCLUSION: Spontaneous movements (mainly antigravity flexion and extension) are important for bone structure and mineralization in VLBW premature infants. QUS may become an important diagnostic modality for the evaluation, treatment, and follow-up of bone strength and osteopenia in this unique population.

Central Nervous System Diseases↗
PubMed2002

Systemic vs. local cytokine and leukocyte responses to unilateral wrist flexion exercise.

We hypothesized that brief exercise of a small muscle group would lead to local rather than systemic alterations in cytokines, peripheral blood mononuclear cells, and mediators of angiogenesis. Fifteen men and eight women (age range 22-36 yr old) performed 10 min of unilateral wrist flexion exercise. Blood was sampled from venous catheters in the resting and exercising arm at baseline, at the end of exercise, and at 10, 30, 60, and 120 min after exercise. Lactate was significantly elevated in the exercising arm (+276 +/- 35%; P < 0.0005) with no change in the resting arm. In contrast, increases in both arms were observed for interleukin-6 (+139 +/- 51%; P < 0.0005), growth hormone (+1,104 +/- 284%; P < 0.003), natural killer cells (+81 +/- 9%; P < 0.0005), and lymphocytes expressing CD62L, CD11a, and CD54. There were no significant differences in these increases between the resting and exercising arm. Catecholamines increased in both arms [epinephrine peak increase, +226 +/- 36% (P < 0.001); norepinephrine peak increase, +90 +/- 15% (P < 0.01)]. Fibroblast growth factor-2 initially decreased with exercise in both arms, and this was followed by a rebound increase. Vascular endothelial growth factor demonstrated a small but significant increase in both arms (+124 +/- 31%; P < 0.05). Brief, low-intensity exercise leads to a systemic rather than local response of mediators that could be involved in inflammation, repair, or angiogenic adaptation to physical activity.

Adult↗
PubMed2002

The effect of endurance-type exercise training on growth mediators and inflammatory cytokines in pre-pubertal and early pubertal males.

Recent studies demonstrate an unexpected reduction in circulating levels of IGF-I after 5 wk of endurance-type exercise training in adolescent boys and girls and prepubertal girls. We hypothesized that the reduction in IGF-I would be accompanied by a training-associated stimulation of proinflammatory cytokines IL-1beta, IL-6, or tumor necrosis factor-alpha (TNF-alpha), each of which can inhibit the GH-->IGF-I axis. Healthy boys (age range 9-11 y old, mean Tanner 1.7) volunteered for the study and were randomized to control (n = 14) and training groups (n = 12) for 5 wk. After the intervention, significant increase in fitness was observed in the training group but not control group. Although IGF-I was correlated at baseline to peak oxygen consumption in all subjects, there was a significant decrease in IGF-I and IGF binding protein-3 in the training subjects (-12.8 +/- 7.3% and -17.5 +/- 7%, respectively, p < 0.05). In contrast, IGF binding protein-2, known to inhibit anabolic effects of IGF-I, increased in the training subjects (27.8 +/- 11%, p < 0.02) as did IL-1beta and TNF-alpha (51.5 +/- 30.22%, p < 0.02, and 44.5 +/- 23.2%, p < 0.02, respectively). Finally, we also found that GHBP was inversely correlated with fitness, suggesting altered GH function in more-sedentary boys. Thus, these data support the hypothesis that a sustained increase in physical activity can stimulate proinflammatory cytokines, which may contribute to suppression of the GH-->IGF-I axis. Physical activity can influence growth and development through its influence on anabolic and catabolic mediators.

Body Constitution↗
PubMed2002

Exercise, diet, and childhood obesity: the GH-IGF-I connection.

The recent "obesity epidemic" among children and adolescents is a major public health concern. The mechanisms responsible for the increased incidence of childhood obesity are not yet well understood. The absence of a clear mechanism makes treating the obese child or adolescent a difficult task, and standardized therapeutic approaches simply do not yet exist. Metabolic derangements associated with obesity may contribute to the difficulty in treatment. Observed abnormalities in the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis in obese adults and the impact of exercise on the GH-IGF-I system are of particular relevance to the growing obese child. In this review, we focus on the interacting mechanisms of diet and exercise through specific hormonal mediators and their contribution to the current obesity epidemic. An improved understanding of these mechanisms may be helpful in creating effective treatment programs for children with obesity.

Adipose Tissue↗
PubMed2002

Effect of intense exercise on inflammatory cytokines and growth mediators in adolescent boys.

OBJECTIVE: Exercise can enhance growth and development in children, but recent investigations have revealed an intriguing paradox. Namely, the early (4-5 weeks) response to training programs in children lead to a catabolic, growth hormone (GH)-resistant state rather than the expected anabolic activation of the GH-->insulin-like growth factor-I (IGF-I) axis. This paradox led us to hypothesize that single bouts of exercise in children could stimulate proinflammatory cytokines known to inhibit directly anabolic activity of the GH-->IGF-1 axis (interleukin [IL]-6, IL-1beta, and tumor necrosis factor-alpha [TNF-alpha]). METHODS: Eleven healthy high school-age boys, age 14 to 18.5 years, performed a single, typical, 1.5-hour wrestling practice session. Blood was sampled before and after the session. RESULTS: We found significant decreases in anabolic mediators: total IGF-I (-11.2 +/- 2.3%), bound IGF-I (-11.2 +/- 2.4%), and insulin (-42 +/- 10%. However, there was no change in unbound IGF-I. Remarkable increases were found in proinflammatory cytokines IL-6 (795 +/- 156%), TNF-alpha (30 +/- 12%), and IL-1beta (286 +/- 129%) and in IGF-binding protein-1 (835 +/- 234%), which itself is stimulated by inflammatory cytokines and is known to inhibit IGF-I. Evidence for compensatory mechanisms to counter the antianabolic inflammatory response to acute exercise were also noted: IL-1ra increased (80 +/- 20%) and IGF-binding protein-3 proteolysis (which can maintain unbound, biologically active IGF-I despite losses in total IGF-I) increased significantly (101 +/- 39%) as well. CONCLUSIONS: These data demonstrate that an intense exercise bout in male adolescents leads to reductions in anabolic mediators and profound increases in inflammatory cytokines. This might explain the development of what seems to be a paradoxical catabolic state in the initial phases of exercise training programs.

Adolescent↗
PubMed2002

[Acute acquired non-traumatic torticollis in hospitalized children].

BACKGROUND: The inflammatory process in torticollis involves the cervical muscles, nerves, and/or the vertebral synovia causing painful and abnormal head position. Most cases of acute acquired non-traumatic torticollis are of benign etiology, but some patients may suffer from a serious disease requiring thorough investigation and hospitalization. OBJECTIVES: To describe the epidemiology, clinical features and the etiology of acute acquired non-traumatic torticollis in our center. METHODS: A retrospective chart review of 45 hospitalized children in the Sapir Medical Center over a 10 year period. RESULTS: We studied 45 children; 23 girls and 22 boys. Their mean age was 6 years (range 6 months to 16 years). All patients reported marked neck pain as their main complaint. Local infection was the most frequent etiology, and 33 (73%) patients were hospitalized during the fall-winter season. Twenty six patients underwent x-ray imaging, and of these, ten (38%) had pathology. The main findings were some degree of atlanto-axial subluxation, and widening of the prevertebral space. Treatment included analgesic and antibiotics for suspected bacterial infections. Two patients required surgical drainage. Cervical neck traction was performed on 15 patients. Mean admission time was 4.1 days and was shorter in the pediatric department compared to the ENT and orthopedic departments. CONCLUSIONS: Careful clinical and radiological evaluation for the wide spectrum of clinical entities should be done. Local infections of the respiratory tract are the most common etiology. Conservative treatment usually leads to complete resolution in a short time.

Acute Disease↗
PubMedDate not supplied

The effects of exercise on body weight and circulating leptin in premature infants.

OBJECTIVE: To assess the effect of daily movements on weight gain, serum leptin, and insulin-like growth factor I (IGF-I) in premature infants. STUDY DESIGN: Twenty very-low-birth-weight premature infants were matched and randomized to a daily movement (n = 10) and control groups (n = 10). Daily movement consisted of passive range of motion with gentle compression of both the upper and lower extremities 5 days per week for 4 weeks. RESULTS: Daily movements led to a significant increase in weight gain (784 +/- 51 vs 608 +/- 26 g in movements and controls, respectively, p < 0.02), and to a significant increase in leptin (0.60 +/- 0.19 vs 0.13 +/- 0.06 ng/ml in movements and controls, respectively 18.8 +/- 4.1 vs 9.2 +/- 4.1 ng/ml in movements and controls, respectively); however, this increase was not statistically significant. CONCLUSION: A relatively brief range of motion daily movement intervention was associated with greater weight gain and increased leptin levels in very-low-birth-weight premature infants. This may suggest that at least part of the daily movements associated with increase in body weight resulted from an increase in adipose tissue.

Bone Density↗
PubMedDate not supplied

Obesity and lipid profiles in children and adolescents.

Childhood obesity is associated with unfavorable lipid profile, suggesting that obese children should be screened for hypercholesterolemia. However, the prevalence of hypercholesterolemia in childhood obesity, and the effect of the degree of obesity on lipid profile, are unknown. Eighty-nine obese children and adolescents (BMI >85%, mean age 10.4 +/- 2.5 years) and 53 non-obese control children matched for age, gender and pubertal stage participated in the study. Early morning blood samples for serum lipids were collected in all children after a 12-h fast. Mean serum cholesterol and triglycerides (TG) levels were significantly higher (p <0.05) among the obese children (cholesterol: 175.2 +/- 31.4 vs 143.3 +/- 24.3 mg/dl; TG: 122.8 +/- 69.7 vs 94.3 +/- 37.8 mg/dl in obese and control children, respectively). Among the obese children, 52% had elevated serum cholesterol levels (>170 mg/dl) compared to 16% in the controls. The degree of obesity (BMI 85-95% vs BMI >95%) had no effect on serum lipids. Unfavorable lipid levels were relatively common among obese children, suggesting that obesity should be considered a risk factor for hypercholesterolemia, and that screening obese children for hypercholesterolemia should be considered.

Adolescent↗