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Biomedical subjects

C Springer

Publications and source records attributed to C Springer.

At least 73 records · Page 4Linked to original sources
PubMed1992

Screening for five mutations detects 97% of cystic fibrosis (CF) chromosomes and predicts a carrier frequency of 1:29 in the Jewish Ashkenazi population.

To determine the distribution and frequency of cystic fibrosis (CF) mutations in the Israeli population, we have screened 96 patients for 11 relatively common mutations. Five mutations--delta F508, G542X, W1282X, N1303K, and 3849 + 10kb C-->T--were found to account for 97% of the CF alleles in the Ashkenazi Jews. In contrast, of the 11 mutations tested, only delta F508 was detected in Jewish patients of Sephardic or Oriental origin, accounting for 43% of the CF alleles. Four mutations--delta F508, G542X, W1282X, and N1303K--accounted for 55% of the CF alleles in Arab patients. In a pilot screening study, a random sample of 424 Ashkenazi individuals was analyzed for three mutations--delta F508, W1282X, and G542X. Thirteen individuals were detected as heterozygotes (six for delta F508 and seven for W1282X), predicting a heterozygote frequency of 1:29. This is similar to the frequency of carriers in the Caucasian population of northern European ancestry. On the basis of these data, the Ashkenazi population is considered to be a candidate for CF heterozygote screening.

Base Sequence↗
PubMed1991

Bronchial provocation determined by breath sounds compared with lung function.

Bronchial provocation testing with methacholine was undertaken in 15 children aged 5 to 8 years with obstructive lung disease, mostly asthma (13/15). The methacholine was inhaled during two minutes of tidal breathing in increasing concentrations. After each inhalation, lung function was measured and clinical signs recorded independently by two observers unaware of each other's results. The logarithm of the concentration of methacholine which caused wheezing over the trachea correlated closely with the logarithm of the concentration of methacholine causing a 20% fall in the forced expiratory volume in one second (FEV1) but was 52% greater on average. At the end of the test there was a mean (SD) fall in FEV1 of 33.3 (7.4)% and a fall in oxygen saturation of 5.2 (3.1)%. Bronchial provocation testing by listening for wheeze over the trachea is a safe technique, which correlates with objective measures of lung function in young children.

Bronchi↗
PubMed1991

Exercise but not methacholine differentiates asthma from chronic lung disease in children.

Bronchial provocation challenges with exercise and methacholine were performed on the same day or within a short interval in 52 children with asthma, 22 with other types of chronic lung disease (including cystic fibrosis), and 19 control subjects with no evidence of chronic lung disease. There were no significant differences in the baseline lung function before the two types of challenge in the individual groups and differences between the patients with asthma and with chronic lung disease were minor. When the mean -2 SD of the methacholine response of the control group was taken as the lower limit of normal, 49/52 (94%) patients with asthma and 18/22 (82%) with chronic lung disease responded abnormally. In contrast, with the mean +2 SD of the exercise response of the control group as the upper limit of normal, 41/52 (79%) asthmatic patients responded but none of those with chronic lung disease. Thus the response to the two types of challenge helps to distinguish asthma from other types of chronic lung disease in children.

Adolescent↗
PubMed1991

Nonspecific bronchial reactivity in asthmatic children depends on severity but not on age.

Bronchial reactivity to inhaled methacholine was measured by the steady-state tidal breathing method in asthmatic children aged 1 to 17 yr. The children were divided into three clinical groups according to their minimal therapeutic requirements: mild asthma, children requiring infrequent treatment with inhaled beta-agonists (81 patients); moderate asthma, children requiring daily preventive treatment with either cromolyn sodium or slow-release theophylline (67 patients); and severe asthma, children requiring daily preventive treatment with oral or inhaled steroids (34 patients). They were also divided into three age groups: from 1 to 6 yr, tested by using bronchial provocation with tracheal auscultation (BPTA) to determine the methacholine concentration causing wheezing (PCW); and from 7 to 11 yr and 12 to 17 yr, using lung function testing to determine the concentration causing a 20% fall in FEV1 (PC20). For the whole group the mean level of bronchial reactivity to methacholine correlated inversely with the severity of bronchial asthma according to the minimal drug requirements (p less than 0.0001) and was similar over the whole age range (p less than 0.9965) for each severity grouping. In the older children the difference between moderate and severe asthma was not significant, but this may have been a result of the effect of corticosteroids in the severe group. We concluded that age has no significant effect on the methacholine response in asthmatic children over a wide age range.

Adolescent↗
PubMed1991

Oxygen uptake and heart rate responses during hypoxic exercise in children and adults.

Control of ventilation and heart rate during exercise appears to undergo maturation, while aerobic metabolism (VO2) may not. Since we had previously found that hypoxia during exercise produced different ventilatory responses in children (C) compared to adults (A), we hypothesized that VO2 and heart rate kinetics during exercise would show similar maturational responses to hypoxia. To test this hypothesis, we examined the responses during progressive (ramp) and constant work rate tests in children and adults breathing either room air or hypoxic gas (FiO2 = 0.15). When corrected for body weight, children and adults had similar values for lactic acidosis threshold (LAT) (C: 29.1 +/- 5.0 ml.min-1.kg-1; A: 27.9 +/- 4.3) and VO2max (C: 40.7 +/- 8.6 ml.min-1.kg-1; A: 45.2 +/- 6.7) during normoxia. Hypoxia significantly lowered LAT (C: 27.5 +/- 5.4 ml.min-1.kg-1; A: 23.2 +/- 3.8; both P less than 0.05) and VO2max (C: 37.7 +/- 8.3 ml.min-1.kg-1; A: 40.1 +/- 5.3; both P less than 0.05) in both children and adults. Metabolic efficiency (delta VO2/delta work rate) and the VO2-heart rate relationship (delta VO2/delta HR/kg) were similar in the two groups and unaffected by hypoxia. During the constant work rate exercise, VO2 kinetics (time constant during phase 2 of the response (pi 1) and the O2 deficit) were similar between children and adults and were significantly slowed by hypoxia, consistent with current understanding of the control of oxidative metabolism. Finally, heart rate was increased at rest and during exercise with hypoxia, while the time to reach 75% of the end-exercise response was delayed significantly, in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Corticosteroids do not affect the clinical or physiological status of infants with bronchiolitis.

The treatment of infants aged 1.5-11.0 months suffering from acute bronchiolitis with a combination of inhaled albuterol and systemic corticosteroids or inhaled albuterol and placebo was compared in 50 infants in a double blind study. The mean initial clinical score and the rate of improvement was similar in the two groups. The mean +/- SD hospital stay was 5.0 +/- 1.2 days for the steroid group and 5.2 +/- 1.7 days for the placebo group. Lung function was measured in 14 infants (7 from each group) and showed evidence of increased lung volumes and severe airway obstruction in the acute stage (the mean values for the steroid group were: TGV, 31 mL/kg; SGaw, 0.104 L/s.cmH2O; VmaxFRC, 12.9 mL/s/kg; for the placebo group: TGV, 35 mL/kg; SGaw, 0.104 L/s.cmH2O; VmaxFRC, 8.5 mL/s/kg) which had improved 2-4 weeks later (steroid group: TGV, 25 mL/kg; SGaw, 0.168 L/s.cmH2O; VmaxFRC, 21.6 mL/s/kg; -placebo group: TGV, 24 mL/kg, SGaw, 0.198 L/s.cmH2O, VmaxFRC, 17.5 mL/s/kg). There were no significant differences of thoracic gas volume, specific airway conductance, and forced expiratory flow at resting lung volume between the two groups, either in the acute or convalescent stages. We conclude that corticosteroids do not change the rate of clinical improvement in acute bronchiolitis, nor do they effect lung function 2-4 weeks later.

Administration, Inhalation↗
PubMed1990

Are obese children truly unfit? Minimizing the confounding effect of body size on the exercise response.

To test the hypothesis that obese children are unfit (i.e., have abnormal responses to exercise testing consistent with reduced levels of habitual physical activity), we used new analytic strategies in studies of 18 obese children performing cycle ergometry. The subject's weight (mean +/- SD) was 168 +/- 24% that predicted by height, and the age range was 9 to 17 years. Size-independent measures of exercise (e.g., the ratio of oxygen uptake (VO2) to work rate during progressive exercise and the temporal response of VO2, carbon dioxide output (VCO2), and minute ventilation (VE) at the onset of exercise) were used. The ability to perform external mechanical work was corrected for VO2 at unloaded pedaling (change in maximum oxygen uptake (delta VO2max) and in anaerobic threshold (delta AT). On average, obese children's responses were in the normal range: delta VO2max, 104 +/- 41% (+/- SD) predicted (by age); delta AT, 85 +/- 51%; ratio of change in VE to change in VCO2, 111 +/- 21% and ratio of change in VO2 to change in work rate, 100 +/- 24%, but six of the obese children had values of delta VO2max or delta AT that were more than 2 SD below normal. In addition, obese children did not have increased delta VO2max or delta AT with age as observed in nonobese children. Although the response time of VO2 was normal (99 +/- 32% of predicted), those for both VCO2 and VE were prolonged. We conclude that the finding of obesity in a child is not a reliable indicator of poor fitness but that testing cardiorespiratory responses to exercise can be used to identify subjects with serious impairment and to individualize therapy.

Adolescent↗
PubMed1990

Oral [13C]bicarbonate measurement of CO2 stores and dynamics in children and adults.

During exercise, less additional CO2 is stored per kilogram body weight in children than in adults, suggesting that children have a smaller capacity to store metabolically produced CO2. To examine this, tracer doses of [13C]bicarbonate were administered orally to 10 children (8-12 yr) and 12 adults (25-40 yr) at rest. Washout of 13CO2 in breath was analyzed to estimate recovery of tracer, mean residence time (MRT), and size of CO2 stores. CO2 production (VCO2) was also measured breath by breath using gas exchange techniques. Recovery did not differ significantly between children [73 +/- 13% (SD)] and adults (71 +/- 9%). MRT was shorter in children (42 +/- 7 min) compared with adults (66 +/- 15 min, P less than 0.001). VCO2 per kilogram was higher in the children (5.4 +/- 0.9 ml.min-1.kg-1) compared with adults (3.1 +/- 0.5, P less than 0.0001). Tracer estimate of CO2 production was correlated to VCO2 (r = 0.86, P less than 0.0001) and when corrected for mean recovery accurately predicted the VCO2 to within 3 +/- 14%. There was no difference in the estimate of resting CO2 stores between children (222 +/- 52 ml CO2/kg) and adults (203 +/- 42 ml CO2/kg). We conclude that orally administered [13C]bicarbonate can be used to assess CO2 transport dynamics. The data do not support the hypothesis of lower CO2 stores under resting conditions in children.

Adult↗
PubMed1989

Effect of hypoxia on ventilatory control during exercise in children and adults.

Little is known about maturation of peripheral chemoreceptor tone (PCT) during growth. We recently demonstrated that the increase in PCT was 49% greater during hypoxic (15% O2) exercise in children compared to adults. As the PCT is a major determinant of ventilatory (VE) response at the onset of exercise (measured by the time constant tau), we hypothesized that hypoxia would affect tau VE (and tau VCO2) to a greater extent in children. Nine healthy children (6-10 y old) and nine healthy adults (18-40 y old) performed multiple transitions from rest to constant work rate on the cycle ergometer. Studies were done breathing 21% O2 and 15% O2. Hypoxic breathing quickened the VE responses in all of the adults and children, but the magnitude of the hypoxic effect did not differ between the two groups (in children, tau VE was 50.9 +/- 9.9 s during 21% O2 breathing and 32.6 +/- 6.9 s during hypoxia; in adults, tau VE was 69.4 +/- 17.6 s, which fell to 50.9 +/- 18.4 s during hypoxia). The hypothesized greater ventilatory response to hypoxia in children compared to adults during exercise was not observed. During 21% O2 breathing, the data demonstrated that children stored relatively less CO2 (by 49%) than did adults in the transition between rest and exercise, possibly explaining the faster ventilatory kinetics. We speculate that there must be additional respiratory control differences between adults and children such that for a given increase in PCT-induced by hypoxia, the VE response at the onset of exercise is less in children than in adults.

Adolescent↗
PubMed1988

Evidence that maturation of the peripheral chemoreceptors is not complete in childhood.

We examined the hypothesis that the peripheral chemoreceptors contribute a different degree of tone to respiration during exercise in normal young children as compared to adults. To improve resolution of the peripheral chemoreceptor contribution, the studies were conducted during controlled levels of exercise. Peripheral chemoreceptor function was assessed by the hyperoxic (FIO2 = 0.80) switch technique during steady-state, sub-anaerobic threshold exercise during air (FIO2 = 0.21) and midly hypoxic gas (FIO2 = 0.15) breathing in 9 healthy children (mean +/- 1 SD age (years) = 8.2 +/- 1.4) and 10 healthy adults (28.2 +/- 6.5). Ventilation during exercise was significantly greater under hypoxic conditions in both children and adults. During air breathing exercise the mean ventilatory decrease in response to the hyperoxic switch was similar in the two groups (27.9 +/- 10.7% in children and 23.3 +/- 6.3% in adults). In contrast, during hypoxic gas breathing exercise the children demonstrated a much greater decrease in ventilation following the hyperoxic switch (57.9 +/- 3.6%) compared to adults (38.9 +/- 5.5%) (P less than 0.0001). Thus, the peripheral chemoreceptors have a greater role in the exercise hyperpnea during hypoxic exercise in young children as compared to adults, suggesting attenuation of peripheral chemoreceptor function during maturation.

Adult↗
PubMed1987

Lung resection for bronchiectasis in children.

Twenty children with bronchiectasis underwent pulmonary resections during an 8-year period. All patients suffered from significant symptoms that did not respond to medical treatment and had localised disease. In 7 patients bronchiectasis developed following foreign body aspiration and in two the aetiology was cystic fibrosis and immune deficiency, respectively. The lower lobes were most commonly involved. Atelectasis of the remaining ipsilateral lung was the most common postoperative complication occurring in four patients. One patient required reoperation for recurrent symptoms. Fifteen out of 18 patients who underwent curative resections were asymptomatic in the longterm follow-up. It is concluded that for children with significant symptoms due to localised bronchiectasis that fails to respond to medical treatment, resection of the affected lobes is indicated.

Adolescent↗
PubMed1987

Nuclear magnetic resonance assessment of adenosine triphosphate (ATP) dynamics in ischemic mouse livers perfused with adenine and ribose.

Hepatic energy stores are essential to liver viability. We used a mouse liver perfusion model and MR spectroscopy to study the effect of adding two precursors of ATP (adenine and ribose) on ATP dynamics during ischemia and reperfusion. Using Krebs-Henseleit buffer with or without added adenine and ribose made little difference in the ATP decay rate during ischemia, but the recovery of ATP during reperfusion was more complete when adenine and ribose were added to the buffer. These findings suggest that the addition of the precursors of ATP, adenine and ribose, to perfusate after ischemia can accelerate and enhance ATP recovery.

Adenine↗
PubMed1987

Chloroquine treatment in desquamative interstitial pneumonia.

An infant presented with failure to thrive, tachypnoea, and hypoxia reversed by oxygen. Lung function showed decreased pulmonary compliance; lung biopsy showed desquamative interstitial pneumonitis. Chloroquine 10 mg/kg/day resulted in improvement and relapse when temporarily stopped. The patient was completely asymptomatic during four years' treatment and six months after stopping treatment.

Chloroquine↗
PubMed1987

Comparison of budesonide and beclomethasone dipropionate for treatment of asthma.

Beclomethasone dipropionate (BDP) and budesonide (BUD) were each given in a dose of 200 micrograms twice daily by metered dose inhaler to 10 asthmatic children already dependent on treatment with steroids. In a double blind randomised crossover study each course lasted one month. No clinically important differences were found between the two treatments when symptom scores, symptom free days, additional use of salbutamol, and results of lung function tests were considered. Metyrapone mildly reduced the plasma concentration of 11-deoxycortisol in two patients during treatment with budesonide, and in four during treatment with beclomethasone. It is concluded that although they are usually safe, both drugs may cause mild adrenal suppression when given in a dose of 200 micrograms twice daily.

Administration, Inhalation↗
PubMed1987

Expiratory volume clamping: a new method to assess respiratory mechanics in sedated infants.

During breathing under sedation via a two-way valve, airflow (V), volume (delta V), and airway pressure (P) were recorded in eight normal (N) infants, seven with reversible obstructive airway disease (ROAD), and seven with chronic lung disease (CLD). Intermittently, expiratory volume clamping (EVC) was applied, involving selective occlusion of the expiratory valve for three to five breaths. The latter produced cumulative increases in delta V that, due to progressive recruitment of the Hering-Breuer reflex, were accompanied by increasing expiratory plateaus in P (i.e., apneas). The resultant passive inflation delta V-P relationships were closely approximated by the expression: delta V = aP2 + bP + c, wherein a represented the pressure-related changes in chord compliance (Crs), b the Crs at P = 0, and c the difference between the dynamic end-expiratory and relaxation volumes of the respiratory system. Relative to N, the ROAD and CLD infants had significantly reduced weight-specific values of a/kg, their b/kg values were increased, whereas the c/kg measurements did not significantly vary. Moreover, for each subject we determined the net Crs/kg obtaining at P = 20 cmH2O (i.e., Crs20/kg), an estimate of the net deflation compliance; the passive respiratory time constant (tau rs) based on the slope of the expired delta V/V relationship; and the respiratory system conductance (Grs/kg). Relative to N, the mean Crs20/kg was significantly reduced only in the infants with CLD and, due to increases in tau rs, both patient groups depicted significantly diminished values of Grs/kg, suggesting the presence of airways obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗