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Biomedical subjects

H Kuipers

Publications and source records attributed to H Kuipers.

At least 37 records · Page 2Linked to original sources
PubMed2003

Effect of testosterone and endurance training on glycogen metabolism in skeletal muscle of chronic hyperglycaemic female rats.

OBJECTIVES: To investigate in glycolytic and oxidative muscles of trained (nine weeks) and untrained hyperglycaemic female rats the effect of hyperandrogenicity and/or endurance training on energy metabolic properties. METHODS: Glycogen content and activity of muscle enzymes with regulatory functions in glycogen synthesis were examined. RESULTS: Testosterone treatment increased glycogen content of extensor digitorum longus (EDL) and soleus muscles of hyperglycaemic sedentary (18% and 84% respectively) and hyperglycaemic trained (7% and 16% respectively) rats. In both types of muscle of the hyperglycaemic testosterone treated exercised subgroup, less depletion of glycogen was found than in the untreated group (38% and 87% for EDL and soleus respectively). CONCLUSIONS: The mechanisms by which training and/or hyperandrogenism alone or in combination elicits their specific effects are complex. Differences in sex, surgery, levels of hormones administered, and exercise model used may be the main reasons for the observed discrepancies. Conclusions from the results: (a) hyperandrogenism is not a primary cause of the development of insulin resistance; (b) glycogen content of slow and fast twitch muscle is increased by training through increased glycogen synthase activity. The most plausible explanation for differences between different muscle fibre types is the different levels of expression of androgen receptors in these fibres. Hyperandrogenicity therefore acts on energy metabolic variables of hyperglycaemic animals by different mechanisms in glycolytic and oxidative muscle fibres.

Animals↗
PubMed2002

Misuse of androgenic-anabolic steroids and human deltoid muscle fibers: differences between polydrug regimens and single drug administration.

The objective of this investigation was to study the effects of androgenic-anabolic steroid (AAS) misuse on deltoid muscle fiber characteristics in experienced, male strength-trained athletes. In a double-blind study, 15 volunteers were administered nandrolone decanoate (ND) for 8 weeks (200 mg/week, intramuscularly). In an additional study, 12 subjects self-administered various AASs at supratherapeutic dosages (AAS group), while 7 non-users served as controls. In all subjects, a percutaneous needle biopsy sample of the deltoid muscle was obtained at baseline and after 8 weeks. Muscle sections were pre-incubated at pH 4.4, stained with adenosine triphosphatase and analyzed morphometrically. In each biopsy sample, at least 150 fibers were classified for "gray level" and "lesser fiber diameter" to determine the mean fiber size, the sizes of type I and type II fibers, and the fiber type distribution. ND administration did not seem to affect any of those parameters. In the AAS group, mean muscle fiber size (+ 12.6%), and the size of type I (+ 10.8%) and type II (+ 14.6%) muscle fibers increased. The fiber type distribution remained unaltered. We conclude that polydrug regimens of AAS misuse at supratherapeutic dosages increased the size of deltoid muscle fibers (especially type II fibers) in experienced strength-trained athletes, while ND at a therapeutic intramuscular dose of 200 mg did not exert any effect.

Adult↗
PubMed2002

The effects of acute exercise and high lactate levels on 35% CO2 challenge in healthy volunteers.

OBJECTIVE: To test the possible antipanic effects of acute exercise in healthy volunteers exposed to an inhalation of 35% CO2 challenge. METHOD: Twenty healthy subjects in a randomized separate group design, performed exercise in a bicycle ergometer reaching >6 mm of blood lactate and a control condition of minimal activity in the same fashion with no lactate elevation. Immediately afterwards an inhalation of a vital capacity using a mixture of 35% CO2/65% O2 through a mask was given on both conditions. RESULTS: Subjects under the exercise condition reported less panic symptoms than controls after a CO2 challenge on the diagnostic statistical manual-IV (DSM-IV) Panic Symptom List but no difference on the Visual Analogue Anxiety Scale. CONCLUSION: Subjects under the exertion condition had lactate levels comparable with those of lactate infusions but an inhibitory rather than accumulative effect was seen when combined with a CO2 challenge.

Adult↗
PubMed2002

Red blood cell profile of elite olympic distance triathletes. A three-year follow-up.

The purpose of this study was to monitor general and individual changes in hematological variables during long-term endurance training, detraining and altitude training in elite Olympic distance triathletes. Over a period of three years, a total of 102 blood samples were collected in eleven (7-male and 4 female) elite Olympic distance triathletes (mean +/- SD; age = 26.4 +/- 5.1 yr; VO(2) max = 67.9 +/- 6.6 ml/min/kg) for determination of hemoglobin (Hb), hematocrit (Hct), red blood cell count (RBC), Mean corpuscular hemoglobin (MCH), Mean corpuscular hemoglobin content (MCHC), Mean corpuscular volume (MCV) and plasma ferritin. The data were pooled and divided into three periods; off-season, training season and race season. Blood samples obtained before and after altitude training were analyzed separately. Of all measured variables only RBC showed a significant decrease (p < 0.05) during the race season compared to the training season. Hematological values below the lower limit of the normal range were found in 46 % of the athletes during the off-season. This percentage increased from 55 % during the training season to 72 % of the athletes during the race season. Hemoglobin and ferritin values were most frequently below the normal range. There was a weak correlation between Hb levels and VO(2) max obtained during maximal cycling (r = 0.084) and running (r = 0.137) tests. Unlike training at 1500 m and 1850 m, training at an altitude of 2600 m for three weeks showed significant increases in Hb (+ 10 %; p < 0.05), Hct (+ 11 %; p < 0.05) and MCV (+ 5 %; p < 0.05). Long-term endurance training does not largely alter hematological status. However, regular screening of hematological variables is desirable as many athletes have values near or below the lower limit of the normal range. The data obtained from altitude training suggest that a minimum altitude (>2000 m) is necessary to alter hematological status.

Adaptation, Physiological↗
PubMed2001

Effects of CCR5-Delta32, CCR2-64I, and SDF-1 3'A alleles on HIV-1 disease progression: An international meta-analysis of individual-patient data.

BACKGROUND: Studies relating certain chemokine and chemokine receptor gene alleles with the outcome of HIV-1 infection have yielded inconsistent results. OBJECTIVE: To examine postulated associations of genetic alleles with HIV-1 disease progression. DESIGN: Meta-analysis of individual-patient data. SETTING: 19 prospective cohort studies and case-control studies from the United States, Europe, and Australia. PATIENTS: Patients with HIV-1 infection who were of European or African descent. MEASUREMENTS: Time to AIDS, death, and death after AIDS and HIV-1 RNA level at study entry or soon after seroconversion. Data were combined with fixed-effects and random-effects models. RESULTS: Both the CCR5-Delta32 and CCR2-64I alleles were associated with a decreased risk for progression to AIDS (relative hazard among seroconverters, 0.74 and 0.76, respectively; P = 0.01 for both), a decreased risk for death (relative hazard among seroconverters, 0.64 and 0.74; P < 0.05 for both), and lower HIV-1 RNA levels after seroconversion (difference, -0.18 log(10) copies/mL and -0.14 log(10) copies/mL; P < 0.05 for both). Having the CCR5-Delta32 or CCR2-64I allele had no clear protective effect on the risk for death after development of AIDS. The results were consistent between seroconverters and seroprevalent patients. In contrast, SDF-1 3'A homozygotes showed no decreased risk for AIDS (relative hazard for seroconverters and seroprevalent patients, 0.99 and 1.03, respectively), death (relative hazard, 0.97 and 1.00), or death after development of AIDS (relative hazard, 0.81 and 0.97; P > 0.5 for all). CONCLUSIONS: The CCR5-Delta32 and CCR2-64I alleles had a strong protective effect on progression of HIV-1 infection, but SDF-1 3'A homozygosity carried no such protection.

Acquired Immunodeficiency Syndrome↗
PubMed2001

[Long-term intensive athletic training; few adverse effects on later physical health].

In general, physical activity benefits health. However, long-term intensive physical training may have detrimental effects on the health of some individuals. In cyclists, changes in the femoral arteries may occur leading to stenoses that are manifested in claudication type symptoms. Some endurance athletes may experience atrial fibrillations that are possibly related to long-term physical training. Older athletes only have an increased risk of osteoarthritis in joints that have suffered injuries. Menstrual disturbances and premature osteoporosis may occur in women as a consequence of intensive physical training. However, the risk for these adverse consequences of long-term physical training is small.

Amenorrhea↗
PubMed2001

Quantification and localisation of damage in rat muscles after controlled loading; a new approach to study the aetiology of pressure sores.

To obtain more insight in the aetiology of deep pressure sores, an animal model was developed to relate controlled external loading to local muscle damage. The tibialis anterior muscle (TA) and overlying skin of a rat were compressed between indentor and tibia. Loads of 10, 70 and 250kPa at skin surface were applied for 2 or 6h. During half of the 10 and 250kPa experiments interstitial fluid pressure (IFP) in the TA was measured. The TAs were excised 24h after load application. Both amount and location of damage were assessed by histological examination using a semi-automated image-processing program. In six of eleven loaded muscles damage was found. The damage was located from superficial to deep muscle tissue in a zone never exceeding the diameter of the indentor. The IFP measurements interfered with the occurrence of damage; application of 10 and 70kPa loads only caused damage when combined with IFP measurements, whereas IFP measurements increased damage at 250kPa loads. The results showed that the developed animal model can be used to provoke local damage by applying a controlled load and that the amount and location of damage can be assessed using the newly developed techniques.

Animals↗
PubMed2001

Validation of a computerized metabolic measurement system (Oxycon-Pro) during low and high intensity exercise.

The aim of the study was to validate a new, fast metabolic measurement system (the Oxycon-Pro) during low and high exercise intensities against the Douglas bag method. For this purpose twelve highly trained subjects performed an incremental cycle ergometer test. In the third minute of each exercise step simultaneous measurements of the Douglas bag and the Oxycon-Pro were performed. No significant differences between the Oxycon-Pro and the Douglas bag measurements for minute ventilation (VE), oxygen uptake (VO2) and carbon dioxide expiration (VCO2) were found. Bland and Altman analysis of validity demonstrated minimal bias and low standard deviations. In conclusion, the results show that the Oxycon-Pro is a valid apparatus for determination of minute ventilation (VE), oxygen uptake (VO2) and carbon dioxide expiration (VCO2) during low as well as during maximal exercise intensities. Unlike with the Douglas bag method, this fast metabolic measurement system can be used for accurate and quick determination of ventilatory variables during exercise.

Adult↗
PubMed2001

Body composition and anthropometry in bodybuilders: regional changes due to nandrolone decanoate administration.

The purpose of the present study was to investigate regional changes in body composition and anthropometric variables induced by nandrolone decanoate in bodybuilders. In a randomized, double blind, placebo controlled design 16 subjects received weekly intramuscular injections containing 200 mg nandrolone decanoate (ND) or placebo. Composition of total body and body parts were assessed using dual energy X-ray absorptiometry (DEXA), skinfolds and circumferences. Measurements were performed at baseline, after 8 weeks ND administration period and 6 weeks after drug withdrawal. DEXA revealed that total body mass (from 76.16 +/- 2.70 to 78.73 +/- 4.07 kg, p<0.5) and bone-free lean mass (from 59.54 +/- 2.36 to 63.06 +/- 2.99 kg, p < 0.025) increased significantly during ND administration whereas bone mineral mass remained unchanged. Six weeks after drug cessation bone-free lean mass was still increased compared to baseline levels. During ND administration significant increments of bone-free lean mass of the trunk (+ 2.03 kg) and legs (+ 1.08 kg) could be observed. Percentage fat of the legs decreased during the drug intervention period (-1.9%) and remained lowered six weeks after drug withdrawal. No alteration in any variable of the arms was observed. Skinfolds did not change during the entire study period in both groups. After 8 weeks ND administration circumference of the neck was increased (+0.9 cm) significantly although all circumferences underwent non-significant gains. In conclusion, the intramuscular administration of nandrolone decanoate (200 mg per week) during eight weeks induced an increase of body weight and bone-free lean body mass in bodybuilders that was mainly situated in the trunk and legs as determined by DEXA. The changes in the trunk were reflected in the circumferences but not the alterations in the legs. Skinfolds were not able to detect changes of fat mass of body parts. DEXA revealed that total fat mass and total percentage fat remained unaffected by drug administration while percentage fat of the legs decreased and remained lowered after drug cessation. These data indicate that changes of the composition of body parts induced by ND are elucidated less accurately by circumferences or skinfolds rather than by DEXA.

Absorptiometry, Photon↗
PubMed2001

A primary care walking exercise program for patients with intermittent claudication.

PURPOSE: In a pilot study, the hypothesis was tested that a home-based walking exercise program with structured coaching would improve walking performance and adherence in patients with intermittent claudication (IC). METHODS: Thirty-one IC patients with a rest ankle-brachial pressure index < 0.90 started a 24-wk walking program in the home environment. They were coached according to the Health Counseling Model (HCM). Patients were instructed to walk at least 9 bouts.wk-1 and to walk through the pain. The main effect measures were pain-free (initial claudication distance (ICD)) and maximum walking distance (absolute claudication distance (ACD)) measured with a graded treadmill test, a corridor exercise test, a walking-diary, and the score on the Walking Impairment Questionnaire (WIQ). RESULTS: Twenty-four participants completed the program. The reported walking frequency was 7.4 times.wk-1. The average ICD improved from 289 m (95% CI, 209-369) to 347 m (95% CI, 244-449) (P < 0.05) and from 241 m (95% CI, 171-310) to 373 m (95% CI, 273-472) on the treadmill and the corridor test, respectively. The average ACD improved from 490 m (95% CI, 397-583) to 544 m (95% CI, 438-650) and from 564 m (95% CI, 412-717) to 726 m (95% CI, 546-906) (P < 0.01) on the treadmill and the corridor test, respectively. The average maximum distance reported in the walking-diary improved from 957 m (95% CI, 291-1623) to 1294 m (95% CI, 646-1941). The score of the walking distance on the WIQ improved from 57% (95% CI, 42-71%) to 60% (95% CI, 46-74%). CONCLUSION: IC patients improved their average ICD and ACD. The walking exercise program in the home environment with coaching according to the HCM seems a promising intervention to be tested in a randomized controlled trial.

Adult↗
PubMed2001

A reduction in training volume and intensity for 21 days does not impair performance in cyclists.

OBJECTIVES: (a) To investigate the effects of reduced training on physical condition and performance in well trained cyclists; (b) to study whether an intermittent exercise programme would maintain physiological training adaptations more effectively than a continuous exercise programme during a period of reduced training. METHODS: Twelve male cyclists participated in a 21 day training programme and were divided into two training groups. One group (age 25.3 (7) years; weight 73.3 (5.7) kg; VO(2)MAX 58.6 (4.5) ml/kg/min; means (SD)) underwent a continuous endurance exercise training programme (CT) whereas the second group (age 22.8 (3.5) years; weight 74.1 (7.0) kg; VO(2)MAX 59.7 (6.7) ml/kg/min) followed an intermittent endurance exercise training programme (IT). During this reduced training period, both groups trained for two hours a day, three days a week. RESULTS: Neither group showed changes in maximal workload (WMAX) (4.6 (0.5) v 4.8 (0.5) W/kg and 4.6 (0.5) v 4.7 (0.6) W/kg for the CT and IT group respectively) and VO(2)MAX (58.6 (4.5) v 60.1 (5.8) ml/kg/min and 59.7 (6.7) v 58.8 (7.5) ml/kg/min for the CT and IT group respectively). During the submaximal steady state exercise test, substrate use and heart rate remained unchanged after reduced training. CONCLUSIONS: These results indicate that well trained cyclists who reduce training intensity and volume for 21 days can maintain physiological adaptations, as measured during submaximal and maximal exercise. An intermittent training regimen has no advantage over a continuous training regimen during a detraining period.

Adaptation, Physiological↗
PubMed2000

HLA and other host factors in transfusion-acquired HIV-1 infection.

The host and viral factors that underlie infection with HIV-1 vary considerably with some individuals progressing to AIDS within 3 to 5 years after infection, whereas others remain clinically asymptomatic for over 10 years. Host factors that may contribute to disease progression include HLA and allelic variants of the chemokine receptors CCR5 and CCR2, which have been shown to influence both long-term survival and rapid progression. In this study, we have examined the contribution of HLA and polymorphisms in CCR5 and CCR2 to long-term survival in transfusion-acquired HIV-1-infected individuals. We have found a higher number of HLA-A32 and -A25 alleles but a lower number of the HLA-B8 allele in the study group compared with the frequencies seen in the HIV-1-negative Australian caucasian population. However, there was no apparent contribution by allelic variants of CCR5 and CCR2 to long-term survival and the combined influence of HLA and CCR polymorphisms could not be evaluated in this relatively small (n = 20) group of study subjects. The results of this work support a role for HLA in long-term nonprogression though the presence in the Sydney Blood bank Cohort of nef-defective HIV-1 may confound associations between certain HLA alleles and long-term survival in the face of infection with HIV-1.

Adult↗
PubMed2000

Controlled lengthening or shortening contraction-induced damage is followed by fiber hypertrophy in rat skeletal muscle.

To study the hypothesis that more severe damage, caused by controlled lengthening (L) contractions, results in greater myofiber hypertrophy compared to increase in fiber size followed shortening (S) contractions, tibialis anterior muscles of anesthesized male Wistar rats were subjected to 240 either L or S contractions. The highest increase in muscle beta-glucuronidase activity, an indicator of muscle damage, was observed in L (7.1-fold) 4 days and in S (2.6-fold) 8 days postexercise. Dystrophin- and desmin-negative as well as fibronectin-positive fibers (signs of the early phase of damage) were observed immediately after exercise in the L group. At 4 days, massive myofiber injury was visible, and internally localized nuclei were present at 15-80 days after exercise in the L group. The shift towards more glycolytic fiber types (p<0.05 in L and S) and an increased mean cross-sectional area of type IIX/B fibers (p < 0.001 in L and S) at 80 days were observed in both groups. The observed minor damage with unchanged myofiber structures following S induced, however, an increase in myofiber cross-sectional area of nearly the same magnitude as that following L, which was more damaging. The results do not support the hypothesis that fiber hypertrophy depends on the extent of the myofiber damage upon the exercised muscles.

Animals↗
PubMed1999

Pre-exercise ingestion of carbohydrate and transient hypoglycemia during exercise.

To study the occurrence and contributing factors of transient hypoglycemia after pre-exercise ingestion of glucose after a 4-hour fast, 19 well-trained cyclists ingested 50 grams of glucose dissolved in water around noon after having a normal breakfast. The ingestion of the glucose solution was followed by 30 minutes rest after which the subjects cycled for 40 minutes at 60% of the predetermined maximal power output. Every 10 minutes blood was sampled for determination of glucose, catecholamines, and insulin concentrations. In 6 subjects (hypo-group) plasma glucose levels dropped transiently below 3.0 mmol/l, while in the other 13 subjects (non-hypo group) plasma glucose level remained above this level. Although at the onset of exercise the plasma glucose levels were lower in the hypo-group, insulin levels were similar in both groups, suggesting a higher insulin sensitivity in the hypo-group. During exercise, norepinephrine was lower in the hypo-group, indicating a lower sympathetic activity in the hypo-group. The lowest plasma glucose levels in both groups were observed after 20 minutes of exercise, after which plasma glucose concentration returned to normal levels. It is concluded that pre-exercise carbohydrate ingestion after a 4-hour fast is sufficient to induce a transient hypoglycemia. The data suggest that the occurrence of hypoglycemia is determined by a combination of a high insulin sensitivity, a small amount of ingested glucose, and a low sympathetic activity.

Adult↗
PubMed1998

The disruption of myofibre structures in rat skeletal muscle after forced lengthening contractions.

Specific antibodies against structural proteins (actin, desmin, dystrophin, fibronectin) of muscle fibres were used to study the effect of forced lengthening contractions on muscle microarchitecture. Tibialis anterior (TA) muscle of male Wistar rats were subjected to 240 forced lengthening contractions. At consecutive time points (0, and 6 h, 2, 4, and 7 days) after stimulation, the TA muscle was excised for biochemical and histological assays. Beta-Glucuronidase activity, a quantitative indicator of muscle damage, showed increased values 2-7 days after the lengthening, peaking on day 4 (11.7-fold increase). A typical course of histopathological changes (myofibre swelling, necrosis and regeneration) was observed. In immunohistochemistry, the earliest abnormality observed was discontinuous dystrophin staining in some swollen fibres immediately after commencement of exercise, while at the same time no alterations occurred in the staining of the other antibodies studied. Six hours later, all the swollen fibres were uniformly desmin as well as dystrophin negative. The great majority, but not all, of the swollen fibres showed disorganized actin staining and intramyocellular localization of fibronectin. The early phase disruption of myofibre structures as measured in this study provides evidence of their central role following damage in skeletal muscle. These results suggest that the sequence of structural changes in the route to muscle fibre necrosis in injury induced by forced lengthening contraction originates in the disruption of the plasma membrane and the intermediate filament, which leads to disturbances in the myofibrillar system.

Actins↗