Biomedical subjects

R J Does

Publications and source records attributed to R J Does.

10 recordsLinked to original sources

PubMed1992

An interactive computer program for randomization analysis of response curves with facilities for multiple comparisons.

An interactive Fortran program, MUCRA, is presented. The program can perform randomization analysis of a completely randomized or randomized-blocks design extended to growth and response curves. A single-step Scheffé-type procedure as well as the Peritz's closed step-down procedure have been implemented which control the familywise type I error-rate. In general, MUCRA is suitable as a computer tool for a distribution-free analysis of variance with repeated measures. The use of MUCRA is demonstrated by analyzing the effects oxprenolol and atenolol have on exercise heart rate. Oxprenolol is a non-selective beta-blocker with moderate intrinsic sympathomimetic activity (ISA), given by the Oros delivery system. Atenolol is a beta 1-selective blocker without ISA. A randomized placebo-controlled crossover design was used to compare the effects of the beta 1-blockers on heart rate during a progressive maximal exercise test on a bicycle ergometer. Application of the Scheffé-type procedure showed that the two drugs significantly (alpha = .05) reduce the heart rate during the exercise test at the three prechosen times (2, 5, and 24 hr) after intake. The reduction from atenolol is more pronounced than from oxprenolol Oros at 2 and 5 hr.

Adult↗

PubMed1990

Design methods for some dose-response models.

A recently described design method for one-parameter biomedical models such as limiting or serial dilution assays is generalized to two-parameter models for which the dose-response relationship can be expressed as a linear regression model with parameters alpha (intercept) and beta (slope). Design formulae are proposed for three different cases in which prior information about the unknown regression parameters alpha and beta is available (alpha known, beta known and neither known, respectively). A suitable transformation of the two-parameter model enables the direct application of the one-parameter design method to the first two cases, while the third needs more advanced considerations. Two experimental designs, taken from the literature, are reproduced as closely as possible using the methods described, thus showing under which circumstances these designs are suitable.

Animals↗

PubMed1989

Statistical methods used in the marathon study.

In this note an outline is given of the statistical methods which were used in the marathon study. The techniques are: box-and-whisker plots, several nonparametric tests, and methods for assessing the intraindividual variations and critical differences.

Adaptation, Physiological↗

PubMed1989

Effects of endurance training and competition on exercise tests in relatively untrained people.

One hundred fourteen subjects (34 +/- 8 years) without any competition background took part in an endurance training study to be completed after 1.5 years with running a marathon. Ultimately, 60 males and 18 females achieved that goal. The training program, carefully supervised, was divided into three phases with a maximum of 45, 70, and 110 km/week training volume and concluded with a performance race of 15, 25, and 42.195 km, respectively. Three days before and 3 and 5 days after each race, 35 subjects were selected to perform a progressive treadmill test and the remaining subjects participated in performing field tests of running 400 and 1000 m. The maximal velocity achieved in the treadmill test was 4.75 +/- 0.36 m.s-1 for males and 4.18 +/- 0.28 m.s-1 for females; it remained constant throughout the study. However, the running velocity at 4 mmol.1(-1) plasma lactate concentration increased about 10% from phase 1 to 3. In the females this rise already appeared to be completed in phase 2. Heart rate showed a tendency to increase at both submaximal and maximal exercise from training phase 1 to 2 and 3, whereas plasma lactate concentration showed a decreasing tendency. Three days after the 25 km and the marathon race the maximal running velocity in the exercise test was 2%-4% lower compared with the pre-race test (P less than 0.05). Five days after the race this difference again faded away. This small decline in running performance was not reflected in changes of physiologic responses such as heart rate or plasma lactate concentration.

Adult↗

PubMed1989

Effect of training and 15-, 25-, and 42-km contests on the skeletal muscle content of adenine and guanine nucleotides, creatine phosphate, and glycogen.

Thirty-four nonathletic volunteers (23 males and 11 females) were subjected to a training program aimed at completing a marathon run within 18-20 months after the onset of training. During the course of the training the content of ATP, creatine phosphate, GTP, GDP, NAD+, purine bases, and glycogen in biopsyspecimens of m. vastus lateralis increased. No major gender differences were observed. The tissue content of adenine and guanine nucleotides such as ATP, ADP, AMP, GTP, and GDP did not change when measured within 6 h after a 15-, 25-, or 42-km contest. During 9 days after the 42-km contest the muscle content of the adenine nucleotides showed a slight, but significant decrease. Glycogen levels were found to be decreased to 90%, 60%, and 62% of their pre-contest values after the 15-, 25-, and 42-km contests, respectively. Nine days after the expenditures supranormal levels were only measured following the 15-km contest. The tissue content of glycogen returned to pre-contest levels after the 25- and 42-km races. The present findings indicate that, from a biochemical point of view, expenditures such as 15-, 25-, and 42-km contests are very well tolerated by the m. vastus lateralis in recreative runners subjected to a training with a maximal duration of 18-20 months.

Adenine Nucleotides↗

PubMed1989

Plasma activity of muscle enzymes: quantification of skeletal muscle damage and relationship with metabolic variables.

One hundred fourteen sedentary volunteers (34 +/- 8 years) took part in an endurance training study to be completed after 18-20 months with a marathon. Ultimately, 60 males and 18 females achieved that goal. The training program, carefully supervised, was divided into three periods with a maximum of 45-, 70-, and 110-km week training volume and concluded with a performance race of 15, 25, and 42.2 km, respectively. Three days before and 3 and 5 days after each race, 35 subjects were selected to perform a progressive treadmill test and the remaining subjects participated in field tests of 400 and 1000 m. A significant decrease in half-life time of CK enzyme plasma activity after running long distances in the course of the study from 20 h to 13 h was observed. Based on plasma enzyme activity and supposing that the total enzyme content left the muscle fiber, the estimated amount of muscle damage was found to be small. A gender difference in plasma enzyme activity increase (females demonstrated a lower increase) occurred only after the marathon.

Adaptation, Physiological↗

PubMed1989

White cell system changes associated with a training period of 18-20 months: a transverse and a longitudinal approach.

In the present study 60 males and 18 females were monitored during an 18- to 20-month training period, during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third periods were concluded with a 15-, 25-, and 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. The effect of training was investigated for the number of leukocytes, number of the subpopulations, and the percentage of white cells with a higher peroxidase activity (HPX cells). The measuring points were the start of the study (used as a reference value) and 1 week before and 1 week after three contests (15, 25, and 42 km). The results of all measuring points were compared transversely and longitudinally. Transversely the leukocytes hardly changed in the course of the study both in males and females, except a decrease of HPX cells. Longitudinally it appeared that Nvar and CVp90 of the numbers of leukocytes could not be calculated in males or in females. These findings suggest that a homogeneous population of leukocytes developed with respect to number and age.

Adaptation, Biological↗

PubMed1988

Computer aided design and evaluation of limiting and serial dilution experiments.

Two computer programs are presented which can be used for the determination of the design and the statistical evaluation of data in the context of limiting and serial dilution analysis. The first program (DESIGN) gives the experimenter the opportunity to set up different designs, to improve a design according to several suggestions, to make a picture of a design and to evaluate the results of artificial data, obtained from a random experiment corresponding with the chosen design, until (s)he is convinced of having a suitable design for a particular experiment. The second program (EVALUATE) evaluates the experimental data. The design method and the statistical methods used in the programs have been chosen on practical and theoretical grounds.

Colony Count, Microbial↗

PubMed1988

Using jackknife methods for estimating the parameter in dilution series.

Dilution assays are quantal dose-response assays that detect a positive or negative response in each individual culture within groups of replicate cultures that vary in the dose of cells/organisms tested. We propose three jackknife versions of the maximum likelihood estimator of the unknown parameter, i.e., the frequency of a well-defined cell within the context of limiting dilution assays or the density of organisms within the context of serial dilution assays. The methods have been evaluated with artificial data from extensive Monte Carlo experiments. As a result of these experiments and theoretical considerations, the jackknife version based on deleting one individual culture at a time is proposed as the statistical procedure of choice. The next best method is the jackknife version based on leaving out the same replicate from each of the culture groups at a time.

Biometry↗

PubMed1987

Limiting dilution assays. Experimental design and statistical analysis.

Two issues in limiting dilution analysis are considered. The first concerns the experimental design: a mathematical algorithm has been developed which calculates the number of replicate culture groups, and the (mean) number of cells per well to be used on the basis of the experimenter's a priori information about the unknown frequency. The procedure guarantees useful data if the a priori interval estimate of the frequency to be determined is correct and the cells are willing to grow. The second issue concerns the statistical method to be used for estimation of the unknown frequency. Several methods (minimum chi-square, maximum likelihood and the jackknife version of the maximum likelihood method) have been evaluated with artificial data from extensive Monte Carlo experiments. All three methods were useful in the statistical analysis of data. As a result of these experiments and theoretical considerations the jackknife version of the maximum likelihood estimation procedure is proposed as the statistical procedure of choice. The next best method is the maximum likelihood procedure.

Algorithms↗