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Biomedical subjects

J P Zock

Publications and source records attributed to J P Zock.

16 recordsLinked to original sources
PubMed1995

House dust mite allergen levels in dust from schools with smooth and carpeted classroom floors.

A study was conducted to investigate the levels of house dust mite allergen Der p I in classroom floor dust from 49 schools with smooth (n = 18) or carpeted (n = 31) floors. Schools were located in the city of Rotterdam (n = 29) and in a number of small communities in the Province of Gelderland (n = 20). Data on building characteristics of the schools were obtained. Dust samples were analysed for Der p I content, the major allergen of the house dust mite Dermatophagoides pteronyssinus. The results showed that in schools with carpeted classroom floors, larger amounts of settled dust and higher Der p I levels either expressed as concentrations (in ng/g) or loadings (in ng/m2) were found than in schools with smooth classroom floors. However, the levels of Der p I were considerably lower than in dust collected from floors in homes. Although the Der p I levels were low, effects of several building characteristics on the levels were found. Age of the floor cover, the number of classrooms in the school and the presence of damp spots in the building were related to Der p I concentrations and loadings mainly on carpeted floors. Remarkably, schools in the rural area contained significantly more dust and Der p I than schools in the urban area. We conclude that dust from carpeted classroom floors contains more house dust mite allergen than dust from smooth classroom floors, but much less than dust from floors in homes.

Adolescent↗
PubMed1994

Methods for measurement of energy expenditure and substrate concentrations in swimming rats.

A measuring system is described for the determination of oxygen consumption (Vo2) and carbon dioxide production (Vco2) in swimming rats. Vo2 and Vco2 were measured by means of an O2-analyzer (Ametek S3A) and a mass spectrometer (Balzers QMG 511), respectively, combined with a gas flow meter. The measurements were made in a 5-1 metabolic chamber on top of a swimming pool in which a water flow of 0.22 m/s was maintained. The rats were fitted with an indwelling catheter with its tip at the entrance of the right atrium for the repeated determination of energy substrate and hormone concentrations, before, during, and after swimming. The inaccuracy of the Vo2 and Vco2 measurements was 0.18% and 0.31% of the reading, respectively; the imprecision was 2.15% and 2.59%. This high accuracy and precision of the system was attained by measuring room air for 20 s after each 100 s of measuring air from the metabolic chamber, and by using demineralized water in the swimming pool. Vo2 during steady-state swimming was 1.89 +/- 0.06 mmol/kg.min (ca. 60% Vo2max), indicating moderate exercise. Respiratory quotient (RQ), during steady-state exercise, was 0.80 +/- 0.01. Vo2 and RQ resulted in rates for carbohydrate and fat utilization of 15.6 +/- 0.8 and 15.1 +/- 0.7 mg/kg.min, respectively.

Animals↗
PubMed1994

Peak-flow variability in asthmatic children is not related to wall-to-wall carpeting on classroom floors.

The hypothesis was tested that wall-to-wall carpets on school classroom floors have a negative effect on the respiratory health of asthmatic children. Asthmatic patients (n = 98) were selected from the records of the Sophia Children's Hospital in Rotterdam. The patients were between 5 and 11 years old. All children had peak-flow measurements three times a day for a 1-month period. The parents of the children completed a diary in which respiratory symptoms and medication use were recorded daily for the same period. Dust samples were taken from classroom floors, living-room and bedroom floors, and mattresses of the children. The dust samples were analyzed for Der p I content, the major allergen of the house-dust mite Dermatophagoides pteronyssinus. The results of the study showed that there was no significant difference between children visiting schools with or without carpeted classroom floors in peak-flow variability, acute respiratory symptoms, or medication use. The Der p I content of dust collected from classroom floors was much lower than of dust collected from homes. There was a significant correlation between peak-flow variability and mattress dust Der p I content in asthmatic children sensitized to dust mites, but not between peak-flow variability and classroom floor dust Der p I content. We concluded that carpeted classroom floors do not contribute to asthma symptom severity, possibly because of the low levels of Der p I on them.

Allergens↗
PubMed1994

House dust mite allergen in bedroom floor dust and respiratory health of children with asthmatic symptoms.

The purpose of this study was to investigate the effects of house dust mite allergen in bedroom floor dust on respiratory health of children with asthmatic symptoms. Two hundred and twenty eight school children with reported attacks of shortness of breath with wheezing in the past year and/or with doctor-diagnosed asthma, were included in the study. Data on home characteristics, both past and present, were obtained. These included data on allergen avoidance measures because of the child's respiratory health. Dust samples were taken from the child's bedroom floor, and the allergen Der p I of the house dust mite Dermatophagoides pteronyssionus was measured. Health diaries were kept over 4 weeks. Acute respiratory symptoms and medication usage were recorded daily. Peak expiratory flow (PEF) was measured using Mini-Wright peak flow meters three times daily. Levels of Der p I in dust from carpeted floors were significantly higher than in dust from smooth floors. We found a positive relationship of Der p I levels, in floor dust collected from carpeted floors, with PEF-variability and also with the prevalence of wheeze, shortness of breath, and attacks of shortness of breath with wheezing during the observation period. The effects on peak flow variability was larger in children allergic to house dust than in children not allergic to house dust. Peak flow variability was significantly increased at exposure levels well below 10,000 ng Der p I.g-1 dust, which has been suggested to be a "threshold" for increased risk symptoms among sensitized asthmatics.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1992

Effects of local nerve cooling on conduction in vagal fibres shed light upon respiratory reflexes in the rabbit.

In ten vagus nerves the effect of local cooling on the compound action potential was studied in the temperature range of 34 to 0 degrees C in spontaneously breathing, anaesthetized rabbits. The mean temperature at which the myelinated (A) fibres were completely blocked, was 10.2 +/- 2.4 degrees C (mean +/- S.D.). In nine nerves, local vagus cooling to 0 degrees C failed to block all non-myelinated (C) fibres. In one nerve, total blocking occurred at 2.0 degrees C. We conclude that in the rabbit, the earlier found increase in tonic activity of the diaphragm following lung inflation or deflation during bilateral local vagus cooling to a temperature between 8 and 0 degrees C is due to afferent impulses in vagal C fibres.

Action Potentials↗
PubMed1992

Measurement of total bodywater volume with deuterated water in newborn infants.

D2O and H2(18)O are often used as tracers for the determination of total body water (TBW). For newborn infants, the commonly used noninvasive method has not been validated. In this study TBW was calculated from D2O concentrations in blood and compared with TBW calculated from D2O concentrations in urine. TBW calculated from all urine portions voided at least 6 h after D2O administration on average was 1.0% lower. TBW calculated from only three urine portions voided 6, 12, and 24 h after D2O administration was 0.6% (mean) lower compared to TBW calculated from D2O concentrations in blood. This study indicates that the noninvasive method to measure TBW can be considered a reliable method when used in newborn infants.

Body Water↗
PubMed1990

Carbon monoxide binding in a model of hemoglobin differs between the T and the R conformation.

The ratio between carbon monoxide affinity and oxygen affinity (M) is usually assumed to have a fixed value (Haldane's law), which is about 200. However, this ratio is not a constant but depends on the level of saturation (Roughton, 1970) as well as on pH (Joels and Pugh, 1958). This means that simple procedures cannot be used to calculate the combined effects of simultaneous oxygen and carbon monoxide binding. Application of our mathematical model of hemoglobin (Zock, 1987) shows that this model can account for the above-mentioned phenomena in a straightforward way. Within the context of this mathematical model of human hemoglobin the differences in shape between oxygen equilibrium curve and carbon monoxide equilibrium curve of human hemoglobin could be readily explained by assuming that the ratio between oxygen affinity and carbon monoxide affinity differs between the T and the R conformation.

Binding Sites↗
PubMed1990

The effect of epinephrine on oxygen consumption, overall energy metabolism, and substrate utilization in rats.

In this study the influence of epinephrine (E) on oxygen consumption, overall energy metabolism, and substrate utilization in rats has been investigated. Therefore E was infused at rates of 20, 35, and 50 ng/min for 40 min. Infusion of the solvent, saline, served as control experiment. Before, during, and after the infusion, VO2, as parameter for total metabolism, and RQ, as parameter for substrate utilization, were determined using an open circuit. In addition blood samples were taken for determination of blood glucose, plasma free fatty acids (EFA) and plasma insulin concentrations. The results show a rise in VO2 and blood glucose during infusion of E. Plasma FFA concentrations were elevated during infusion of E and of saline. Plasma insulin decreased when E was administered. RQ values were increased when E was infused at rates of 35 and 50 ng/min. The results suggest that E can influence the ratio in which glucose and FFA are utilized. This influence seems to be excerpted indirectly by influencing the availability of the substrates, rather than directly, by influencing utilization.

Animals↗
PubMed1987

Influence of changes in cardiac output on the acid-base status of arterial and mixed venous blood.

While maintaining the arterial CO2 tension constant near the normal level of the dog (4.3 kPa), we studied the influence of decreasing cardiac output on both the arterial and mixed-venous blood acid-base status in anaesthetized, artificially ventilated dogs. Cardiac output was manipulated by applying positive end-expiratory pressure (PEEP), and by beta-adrenergic blockade to suppress a compensatory heart rate response. The systemic vascular response was attenuated by alpha-adrenergic blockade. Metabolic rate remained virtually unchanged when cardiac output decreased. Under these conditions a fall in cardiac output led to a shift of the arterial acid-base status in the direction of a metabolic acidosis. The changes occurring in the mixed-venous blood resembled those of an in-vivo CO2 bufferline, with the shift being such as if a respiratory acidosis was developing.

Acid-Base Imbalance↗
PubMed1981

Linearity and frequency response of Fleisch type pneumotachometers.

Some aspects of the linearity and the frequency response of flow measurement with Fleisch type pneumotachometers are considered. The transition from a uniform velocity distribution at the entrance of the capillary tubes of the transducer to a fully developed flow profile is discussed as one of the phenomena influencing the linearity of the set-up. Besides, an expression is derived for the frequency response of the Fleisch pneumotachometer. The frequency responses as derived from measurements show good agreement with theory. In the range of the lower frequencies the frequency response of the flow measuring set-up is proved to be largely determined by the frequency response of the pressure transducer with the connecting tubes. A simple way is indicated to measure the latter. This, in combination with the calculated frequency response of the flow transducer, makes it fairly easy to determine the frequency response characteristics of a flow measuring set-up containing a Fleisch type pneumotachometer.

Air Pressure↗
PubMed1981

Calculated changes in pH and pCO2 in arterial blood plasma assuming absence of ion and water exchange between plasma and erythrocytes during their equilibration with alveolar gas.

As a contribution to solving the problem of pH disequilibrium in arterial blood, the results of two modes of gas exchange in the lung have been calculated using an equilibrium state model of the blood. In both cases the HCO3-/Cl-exchange was assumed to occur after the gas exchange in the pulmonary capillaries. When the gas exchange was assumed to be dependent on intra-erythrocytic carbonic anhydrase, the plasma pH in the arterial blood increased. When plasma erythrocytes were assumed to equilibrate separately with the alveolar gas due to pressure of extra-erythrocytic carbonic anhydrase, plasma pH in the arterial blood decreased. In each case there was a slight increase in pCO2 after the blood had left the pulmonary capillaries.

Animals↗
PubMed1980

Intra-aortic decrease in blood plasma pH.

Using glass electrode catheters, a decrease in blood plasma pH was found in four dogs when the electrode at the tip of the catheter was passed from central to more peripheral sites of the arterial system. This findings can at least in part be explained by assuming that in the lung capillaries erythrocytes and plasma equilibrate separately with alveolar gas.

Animals↗