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Biomedical subjects

G M Janssen

Publications and source records attributed to G M Janssen.

At least 37 records · Page 2Linked to original sources
PubMed1991

The effect of a 5-month endurance-training programme on physical activity: evidence for a sex-difference in the metabolic response to exercise.

The effect of a 5-month endurance training programme on physical activity and average daily metabolic rate (ADMR) was studied. Subjects were 16 males and 16 females preparing for a half marathon. Total physical activity, measured using an accelerometer, had increased by 62% and 63% after 20 weeks in males and females, respectively. Physical activity during the non-exercise part of the day did not change although in males it tended to increase (15%, NS). The ADMR had increased significantly in males after 8 and 20 weeks (+2.3 and +3.3 MJ.day-1, respectively, P less than 0.05) and exceeded the net energy expenditure for endurance-training three to four times. In females no significant increase in ADMR was found (+1.5 and +1.3 MJ.day-1, after 8 and 20 weeks, respectively). In females the change in ADMR could be largely attributed to the net cost of running itself and a small increase (10%) in resting metabolic rate during the time of day they were awake. In males a discrepancy was observed between the increase of ADMR and the expenditure due to exercise and non-exercise activities. We suggest exercise stimulates habitual physical activity and diet-induced thermogenesis in males but not in females.

Adult↗
PubMed1991

Body composition and sleeping metabolic rate in response to a 5-month endurance-training programme in adults.

This study examined the effect of exercise training on body composition and sleeping metabolic rate (SMR) in 15 men and 13 women who participated in a 20-week training programme aimed at running a half marathon. Body mass (BM) was measured after waking up, fasted and with an empty bladder. Body composition was assessed using densitometry. The SMR was measured from 0300-0600 hours during an overnight sleep in a respiration chamber. Assessment of SMR was at least 36 h after the last period of exercise training. After 20 weeks of endurance training no change in BM was observed. However, body composition changed significantly. On average men lost 2.4 kg body fat (P less than 0.01) and gained 1.7 kg fat free mass (FFM) (P less than 0.01). In women fat loss averaged 0.9 kg after 20 weeks (P less than 0.01), while FFM increased by 1.0 kg (P less than 0.05). Loss of fat mass was significantly larger in males (P less than 0.05). No changes in SMR were found, either in absolute terms, or when normalised for BM or FFM. Therefore, we have concluded that exercise training has no chronic, long-term effect on SMR. A possible explanation for this outcome in view of the different findings in similar studies is discussed.

Adult↗
PubMed1991

In vivo DNA synthesis is not uniformly increased in arterial smooth muscle of young spontaneously hypertensive rats.

We compared the distribution of DNA synthesis over the arterial tree of young normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) with marginally elevated blood pressure. Six-week-old male SHR and WKY rats were therefore infused with 5-bromo-2'-deoxyuridine (BrdUrd) for 2 days and the nuclear incorporation of the thymidine analogue in the media of various arteries was determined by immunohistochemistry. In WKY rats, 2.5% of the arterial smooth muscle nuclei in elastic, muscular and resistance arteries incorporated BrdUrd. In SHR, DNA synthesis was more marked in large arteries than in resistance arteries. It was in addition significantly larger in the aorta, superior mesenteric, renal and femoral arteries of the SHR than in those of the WKY rats. However, nuclear incorporation of BrdUrd in vivo did not differ between SHR and WKY rats in aortic endothelium, carotid arterial smooth muscle, nor in mesenteric or renal resistance arteries. Between 6 and 20 weeks of age, the number of nuclear profiles per media cross-section did not increase in large arteries of WKY rats and SHR. During this period of time, however, carotid artery and thoracic aorta weight and DNA content increased. SHR large arteries gained more DNA than those of WKY rats. These data indicate that DNA synthesis is uniformly distributed over the arterial system in young WKY rats and that DNA synthesis is elevated in the smooth muscle of large arteries of 6-week-old SHR but not in their resistance arteries.

Animals↗
PubMed1991

DNA synthesis in isolated arteries. Kinetics and structural consequences.

We evaluated changes in DNA synthesis, structure, and mechanical activity in isolated arteries during exposure to growth factors. Renal arteries were isolated from rats, sympathectomized, denuded of endothelium, and maintained in tissue culture. Up to 4 days of culture did not affect maximal contractile responses to depolarization. From the results of nuclear incorporation of the thymidine analogue 5-bromo-2-deoxyuridine (BrdUrd), culture stimulated DNA synthesis. In the media, incorporation of BrdUrd was maximal after 3 days but fell precipitously thereafter. Culture of arterial segments did not, however, increase the cross-sectional area of the media, the ploidy of the arterial nuclei, or the number of medial cells. In contrast, new layers of cells, part of which displayed smooth musclelike properties, developed at the border of the segments. The outermost edge of this newly formed layer continued to incorporate BrdUrd for at least 2 wk. These data demonstrate that stimulation of DNA synthesis by continuous exposure of the arterial wall to exogenous growth factors is 1) transient in the media; 2) does not, at least initially, compromise contractile reactivity; 3) does not alter gross medial structure; but 4) leads to proliferation of smooth musclelike cells outside the media. These findings suggest that the number of smooth muscle cells in the arterial media is maintained constant in the presence of even strong mitogenic stimuli.

Animals↗
PubMed1990

Elongation factor 1 beta of artemia: localization of functional sites and homology to elongation factor 1 delta.

Elongation factor (EF)-1 beta, a 26 kDa protein, is the eukaryotic equivalent of bacterial EF-Ts, the nucleotide exchange factor in protein synthesis. EF-1 beta catalyzes the exchange of guanine nucleotides bound to EF-1 alpha; the latter protein is the eukaryotic equivalent of bacterial EF-Tu. Limited proteolytic cleavage studies on EF-1 beta lead to the following picture: the protein is composed of two domains, an aminoterminal and a carboxyterminal domain, connected to each other by a stretch of hydrophilic, charged amino acids situated in the middle of the molecule. The carboxyterminal domain supplies the catalytic site for the nucleotide exchange reaction, whereas the aminoterminal domain interacts with EF-1 gamma, the third component of elongation factor 1. The regulatory, serine phosphate residue, Ser-89, localized in the hydrophilic stretch of EF-1 beta, does not appear to be necessary for the basic exchange reaction. The fourth component of the high molecular weight elongation factor complex (EF-1H), named EF-1 delta or 28 K protein, is homologous to EF-1 beta and contains regions very similar to the carboxyterminal part. EF-1 delta was found to be active in the nucleotide exchange reaction.

Amino Acid Sequence↗
PubMed1990

Transfer RNAs for primordial amino acids contain remnants of a primitive code at position 3 to 5.

Analysis of the nucleotide sequence of 1,400 transfer RNAs has revealed the imprint of a prototypic genetic code in position 3-4-5 of the acceptor stem. It appears only in the transfer RNAs for the primordial amino acids ie those found by chemical condensation of a nitrogen-methane-water-ammonia mixture. The model for primitive protein synthesis as mentioned by Crick assumes a direct interaction between the amino acid and a prototypic adaptor oligonucleotide. This has hitherto appeared irreconcilable with the large spatial separation between the aminoacylation site and the anticodon in present day transfer RNAs. The observations reported here show how this paradox can be resolved by a process of duplication and cleavage of a prototypic adaptor.

Amino Acid Sequence↗
PubMed1989

Food intake and body composition in novice athletes during a training period to run a marathon.

The change in diet and body composition was studied in a group of 9 female and 18 male subjects, starting a training program for 18 months with the ultimate goal of running the marathon. Mean daily intakes from 7-day dietary records for macro- and micronutrients were calculated at the start, after 1 year of training, and just before running the marathon. Anthropometric measurements were taken on the same occasions. In males the body fat mass decreased 2.4 kg, while in females no change in body composition was observed over the 18-month training period. Energy intake increased significantly in males from 131 to 159 kJ/kg/day. In women no significant change was recorded (141 to 147 kJ/kg/day). However, in both sexes CHO intake was significantly higher after 18 months (males 63.7-81.7 kJ/kg, females 68.0-81.9 kJ/kg). Also En% CHO increased significantly in males from 48 to 52 EN% and in females from 47 to 55 En%. This extra energy intake of CHO in women was covered at the expense of dietary fat. These changes in food habits in both groups are favorable in relation to the nutritional guidelines for better cardiovascular health. Whether the sex difference found in economizing energy exchange as a response to an intensive training program is based on an increased food efficiency will require further investigation.

Adult↗
PubMed1989

Fluid intake and gastrointestinal problems in runners competing in a 25-km race and a marathon.

A group of 114 previously untrained subjects, 31 females and 83 males, was followed for 18 months while training for a marathon. Forty-four of the subjects completed a survey regarding fluid intakes and gastrointestinal (GI) disturbances during competition for both their first 25-km race (run after 1 year of training) and their first marathon. GI problems were common. Among the individuals surveyed, 25% had GI complaints in the 25-km race. In the marathon, 52% complained of GI distress. In general, fluid consumption was low (25 km means = 109 ml; marathon w = 577 ml). Body weight losses in the marathon were substantial (w = 3.2%, BW; range 1.5%-6.2%) indicating sweat losses greater than fluid replacement. These losses were greater in men than in women (men w = 3.4% BW; women w = 2.6% BW). GI complaints were not associated with larger drink intakes. In contrast, dehydration above a certain limit appears to increase the frequency of GI disorders. In the marathon, 80% of the runners who lost greater than 4% BW had GI problems. It is possible that reduced blood flow to the GI region is compromised via the exercise itself as well as by a reduced blood volume, which may disrupt normal secretion/absorption of the digestive tract. It may also be that a rising core body temperature, associated with decreased sweating at high levels of dehydration, may be related to GI dysfunction.

Adult↗
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

Plasma urea, creatinine, uric acid, albumin, and total protein concentrations before and after 15-, 25-, and 42-km contests.

One hundred fourteen 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 contests of 15, 25, and 42.2 km, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. 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. Before and after three contests of 15, 25, and 42.195 km the plasma concentration of urea, creatinine, uric acid, albumin, and total protein were determined. Both sexes demonstrated an increase of the plasma concentrations of urea, creatinine, and uric acid after the contests. Plasma albumin concentration decreased 2 days after the contests and total protein did not change. In females the decrease of the elevated plasma urea concentration after the marathon from the 1st day to the 3rd day post-exercise was faster than in males. The increase of plasma creatinine and uric acid concentrations were hardly dependent on the contest's distance.

Adult↗
PubMed1989

Changes in basal plasma testosterone, cortisol, and dehydroepiandrosterone sulfate in previously untrained males and females preparing for a marathon.

In the present study 25 males and 11 females were monitored for 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 period 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. Before and after three contests of 15, 25, and 42.195 km, the plasma concentration of testosterone, cortisol, and dehydroepiandrosterone sulfate (DHEAS) were determined. The decrease of plasma testosterone concentration in males was dependent on the distance of the contests. Moreover, the plasma testosterone concentration was increased in males during the course of the training period. In females no clear relation between plasma testosterone levels and the contests could be observed, and no changes in basal levels were found in the course of the training period. DHEAS seems to be a more useful stress marker than the plasma cortisol concentration. The plasma levels of this hormone remained elevated both in males and females for 1-2 days after the contests. The amplitude of DHEAS increments, however, was greater after the marathon.

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

Muscle carnitine level in endurance training and running a marathon.

Twenty sedentary volunteers (13 men and 7 women) who were subjected to an 18- to 20-month training program aimed at completing a marathon after the onset of training participated in this study. In the course of the training and after running a marathon, the content of total carnitine in the m. vastus lateralis did not change. The content of muscle total carnitine was not sex related. However, significant correlations were demonstrated between muscle total carnitine content and plasma urea and creatinine concentrations. Also a negative significant correlation was found between the content of muscle total carnitine and the plasma activity of CK before running a marathon.

Adaptation, Physiological↗
PubMed1989

Structural and ultrastructural changes in skeletal muscle associated with long-distance training and running.

The histological and ultrastructural features of 21 males and 8 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-, 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Percutaneous biopsies were taken from the vastus lateralis muscle 5 days before each contest as well as 0.5-6 h post-contest and 8-9 days post-contest. No shift in fiber type was observed during the training period from the 15-km contest until the 42-km contest nor were any changes in fiber diameter observed. Histological examination demonstrated a gradual increase in degenerative changes during the training period, which occurred in type I as well as in type II fibers. Ultrastructural examination revealed irregular Z-lines and hypercontraction immediately after exercise. No damage to the sarcolemma was detected. The number of degenerative changes after each contest was not higher than before each race. It is concluded that long-distance running is associated with transient minor pathological changes in skeletal muscle, which are related to the total distance covered per week rather than the intensity of the exercise.

Adaptation, Physiological↗
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

Effect of training on red blood cell parameters and plasma ferritin: 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 erythrocyte count, hematocrit (Ht), hemoglobin (Hb), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cellular hemoglobin content (MCHC), the red cell distribution width (RDW), and ferritin content. The measuring points were the start of the study (used as a reference value) and 1 week before and 1 week after the three contests (15, 25, and 42 km). The results of all measuring points were compared transversely and longitudinally. We found a significant decrease of plasma ferritin content in the first period of the study which further remained constant. Also, other red cell parameters were decreased but remained within the normal range. During the whole training period larger intraindividual variations for most of the red cell parameters were observed compared with non-endurance-trained people.

Adaptation, Physiological↗