Biomedical subjects

H Claassen

Publications and source records attributed to H Claassen.

At least 37 records · Page 2Linked to original sources

PubMed1995

mRNAs of enzymes involved in energy metabolism and mtDNA are increased in endurance-trained athletes.

Improvements in endurance capacity by training are associated with structural and biochemical adaptations of working muscles that affect the mitochondrial compartment. We investigated whether the 1.8-fold higher mitochondrial volume density in a group of endurance-trained athletes compared with untrained subjects was reflected by higher steady-state levels of mRNAs coding for components of the oxidative phosphorylation pathway using a quantitative polymerase chain reaction approach. We found that mitochondrially encoded RNAs (cytochrome-c oxidase subunit I, NADH reductase subunit 6, 16S rRNA), as well as nuclear-encoded RNAs (cytochrome-c oxidase subunit IV, succinate dehydrogenase, fumarase) are all increased coordinately in the athletes (1.54- to 1.94-fold). In addition, mitochondrial (mt) DNA concentration was also 1.55-fold higher in the trained athletes, whereas genomic DNA was not changed. Our findings thus show similar RNA expression of mitochondrially encoded genes in sedentary and endurance-trained subjects, whereas pretranslational control mechanisms account for higher levels of nuclear-encoded RNAs in the athletes.

Adult↗

PubMed1995

[Morphologic studies of the beginning of vascularization and ossification in human thyroid cartilage].

In contrast to the cartilaginous preformed bones of the skeleton, ossification of human thyroid cartilage begins at the end of the second decade of life. The process continues until an advanced age and shows sex differences. An in-growth of blood vessels by cartilage canals is a prerequisite for ossification. The aim of the study was to investigate the temporal and spatial appearance of cartilage canals in thyroid cartilage. Extracellular matrices of cells in cartilage canals were characterized immunohistochemically. Corrosion casts indicated that the cricothyroid branch of the superior thyroid artery was involved in vascularization of the thyroid cartilage. The first cartilage canals were detectable at the end of puberty, always lying at certain distances to almost ossified areas of the thyroid cartilage. The extracellular matrix localized at the border of the cartilage canals reacted with antibodies against type I collagen and type III procollagen, as well as with antibodies against type II collagen. This finding suggests that these cells are intermediate between fibroblasts and chondrocytes.

Adolescent↗

PubMed1994

Temporal and spatial localization of type I and II collagens in human thyroid cartilage.

Thyroid cartilages of various ages were investigated by immunofluorescence staining for localization of the fibrillar collagen types I and II in order to understand the tissue remodeling occurring during the mineralization and ossification of thyroid cartilage. In fetal and juvenile thyroid cartilages, type I collagen was restricted to the inner and outer perichondrium, while type II collagen was localized in the matrix of hyaline cartilage. However, in advanced ages, type I collagen was also localized in the pericellular and in the interterritorial matrix of intermediate and central chondrocytes of thyroid cartilage. The matrix of peripheral chondrocytes was negative for type I collagen. This suggest that some chondrocytes in thyroid cartilage undergo a differentiation to type I collagen-producing chondrocytes. At the beginning of ossification, bone-related type I collagen was chiefly detected in the central cartilage layer, but was never deposited first from the perichondrium in the direction to the subperichondrial cartilage. This observation confirmed previous findings showing that osteogenesis mainly follows an endochondral ossification pattern. Interterritorial matrix failed to react with the type II collagen antibody in men from the beginning of the third decade, and later still in women, even after treatment with hyaluronidase. These observations indicate that major matrix changes occur faster in male than in female thyroid cartilage.

Adolescent↗

PubMed1994

Immunolocalization of type X collagen before and after mineralization of human thyroid cartilage.

In this study the distribution of type X collagen in thyroid cartilages of various ages is described. Fetal and juvenile thyroid cartilage was negative for type X collagen, but showed a strong staining reaction for type II collagen. Type X collagen and calcium deposition were first detected in thyroid cartilage of 18-to 21-year-old adults. Type X collagen was restricted to large chondrocytes near or in mineralized cartilage, confirming the notion that type X collagen precedes mineralization. From these observations it was concluded that chondrocytes in thyroid cartilage undergo differentiation steps that are similar, but much slower, compared to cells in growth plate and sternal cartilage. Some type X collagen-positive areas also showed staining for type I collagen, suggesting that there is a further differentiation of chondrocytes to cells which are characterized by the simultaneous synthesis of type X and I collagen. However, a dedifferentiation process during aging of thyroid cartilage where cells switch from synthesis of type II to type I collagen cannot be excluded.

Adolescent↗

PubMed1994

Cardiopulmonary adaptations to pneumonectomy in dogs. III. Ventilatory power requirements and muscle structure.

Static and dynamic mechanical characteristics of the respiratory system were measured in five adult foxhounds 6-15 mo after right pneumonectomy (R-PNX) and in five matched foxhounds that underwent right thoracotomy without pneumonectomy (Sham). In R-PNX dogs, elastic recoil was lower than that in the left lung of Sham dogs. On exercise, absolute ventilatory power requirements of the lung and its components were measured, i.e., power requirements to overcome elastic and viscous resistances of the lung as well as power requirements during inspiration and expiration. All components were higher for a given minute ventilation in R-PNX dogs than in both lungs of Sham dogs. Ventilatory power requirements after R-PNX were also higher than in three adult foxhounds after left PNX studied previously by the same techniques. After R-PNX, the mass of the right costal diaphragm and total mass of inspiratory muscles were greater than in Sham dogs. There were no significant differences in ultrastructural features of the costal diaphragm. The unilateral increase in muscle mass is likely the result of chronic elevation and stretch of the right costal diaphragm after R-PNX.

Air Pressure↗

PubMed1993

Effects of training in normoxia and normobaric hypoxia on human muscle ultrastructure.

The adaptive response of skeletal muscle to training in normoxia and in severe normobaric hypoxia was studied. The first group of five male subjects trained for 3 weeks on a bicycle (2 h/day, 6 days/week) in normoxia (Control training, Con T). A second group of five subjects trained in an ambient FIO2 decreasing progressively from 12.7% to a final level of 10.0% (hypoxic training, Hyp T). Fourteen months later, these subjects trained in normoxia at the same absolute power (normoxic training, Nor T). Peak oxygen consumption (VO2 max) was measured in normoxic and hypoxic conditions. Biopsies from the vastus lateralis muscle were analysed for fibre size, capillary and ultrastructural composition. Nor T had no effect on muscle tissue or VO2 max. Con T increased volume density of total mitochondria and lipids by 36 and 135% respectively (P < 0.05). Hyp T induced a 10% increase (P < 0.05) in peak VO2 max measured in hypoxia. Mean fibre cross-sectional area, interfibrillar mitochondrial volume density and capillary-to-fibre ratio were increased (P < 0.05) by 10, 42 and 13% respectively in the Hyp T group. These results suggest that training at the same relative workload in normoxia and hypoxia have similar, but not identical, effects on muscle tissue. If training in normoxia is carried out at the same absolute workload as in severe hypoxia, no significant effects are observed.

Adult↗

PubMed1992

Fiber differentiation of the human laryngeal muscles using the inhibition reactivation myofibrillar ATPase technique.

The aim of the present study was to further subdivide the type II fibers of the human thyroarytenoid and posterior cricoarytenoid muscles by means of a modified myosin ATPase reaction. In order to understand the functioning of these highly strained muscles better, it is important to know the respective percentage of fatigue-resistant type IIA fibers and fatigable type IIB fibers. The material comprised the larynges of seven laryngectomized males aged between 45 and 70 years and four laryngectomized females aged between 39 and 72 years. After having been frozen in nitrogen, 10-microns-thick sections were cut from the laryngeal muscles in a cryostat. The pH-lability of the enzyme that can be utilized in a classical myosin ATPase reaction permits a differentiation between fiber types I, IIA and IIB. Evidently, this is not possible with every human muscle. The fiber types IIA and IIB of the thyroarytenoid and the posterior cricoarytenoid muscles could be clearly distinguished by means of the inhibition reactivation myofibrillar ATPase technique. Using this method, the myosin ATPase enzyme was initially inhibited by hydroxymercuribenzoate and subsequently reactivated by cysteine. Regarding the incidence of type I and IIA fibers, there was a statistically significant difference between the thyroarytenoid and the posterior cricoarytenoid muscles. The type IIA fiber content was statistically significantly higher in the arytenoid muscle than in the posterior cricoarytenoid muscle. The percentage of type IIB fibers was low, not only in the thyroarytenoid muscle and the posterior cricoarytenoid muscle but also in the other laryngeal muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗

PubMed1992

Preparation of four-color arterial corrosion casts of the laryngeal arteries.

The supply areas of the superior and inferior laryngeal arteries were studied in order to plan tissue-sparing laryngeal surgery. Arterial corrosion casts with and without preservation of the laryngeal skeleton were prepared and the supply areas of the superior and inferior laryngeal arteries were distinguished from each other by injecting differently colored methacrylates. The ramifications of the laryngeal arteries could be classified clearly in the macerated specimens which preserved the laryngeal skeleton.

Aged↗

PubMed1991

Muscle structure and performance capacity of Himalayan Sherpas.

The ultrastructure of the vastus lateralis muscle of Sherpas from Nepal [5 males; age 28 +/- 2.8 (SD) yr, indirect maximal O2 consumption 48.5 +/- 5.4 ml.kg(-1).min(-1)] was assessed and compared with those of sedentary lowlanders and of Caucasian climbers before and after high-altitude exposure. The mean cross-sectional area of the fibers was 3,186 +/- 521 microns2, i.e., similar to those of Caucasian elite high-altitude climbers (3,108 +/- 303 microns2) and a group of climbers after a 6- to 8-wk sojourn at 5,000-8,600 m (3,360 +/- 580 microns2) but significantly (P less than 0.05) smaller than that of unacclimatized climbers (4,170 +/- 710 microns2) and slightly, although not significantly, lower than that of sedentary lowlanders (3,640 +/- 260 microns2). The number of capillaries per square millimeter of muscle cross section was 467 +/- 22, not significantly smaller than those of climbers on return from a Himalayan expedition (538 +/- 89) and elite high-altitude climbers (542 +/- 127) but significantly (P less than 0.05) greater than that of sedentary lowlanders (387 +/- 25). The volume density of mitochondria was 3.96 +/- 0.54%, significantly (P less than 0.05) less than the values found for any other investigated group, including sedentary subjects at sea level (4.74 +/- 0.30%). It is concluded that Sherpas, like acclimatized Caucasian climbers, are characterized by 1) facilitated convective and diffusive muscle O2 flow conditions and 2) a higher maximal O2 consumption-to-mitochondrial volume ratio than lowlanders despite a reduced mitochondrial volume density.

Acclimatization↗

PubMed1991

[Neanderthal markers of the frontal bone--a conspicuous Hallstatt cranium of the burial field Dietfurt/Oberpfalz].

Between the skulls from early Iron Age cemeteries of the Hallstatt period (Beilngries, Dietfurt, Schirndorf and some other localities) in the Upper Palatinate (Bavaria) the skull Dietfurt 13/1 attracted attention because of its archaic traits at the viscerocranium and because of its extraordinarily large cranial capacity (1654 cm3). Such large cranial capacities were well known from Neandertals. Therefore this skull was examined for other neandertaloid traits: It was shown that the values for the angle of inclination and the vault-angle of the frontal bone fell into the neandertaloid range. With regard to the traits of the frontal bone Dietfurt 13/1 takes a more intermediate position between Homo sapiens sapiens and the Neandertals than the frontal bone from Hahnöfersand, which is dated about 36.300 +/- 600 years B.P. (Bräuer 1980). It is discussed, whether the specific traits of the frontal bone of Dietfurt 13/1 could fall within the variability of the subfossil Homo sapiens sapiens without postulating a phase of hybridization between Neandertals and anatomically modern man. Consequently, in the compilation of prehistorical skeleton-series more attention should be given to measures of the frontal bone.

Adult↗

PubMed1991

[Paleopathologic findings in Hallstatt Period humans of Oberpfalz. Conclusions concerning the environment].

Pathological findings from early Iron Age inhumation burials from three cemeteries of the Hallstatt Period (Beilngries, Dietfurt and Schirndorf) in the Upper Palatinate (Bavaria) were compiled. Particular stress was laid upon possible conclusions concerning environmental conditions. The infrequency of cribra orbitalia demonstrates that the studied groups did not suffer from a deficiency of iron. The uncommon fractures of the extremity bones and lesions of the skull give at present the image of a peaceful era during the Hallstatt period in the Upper Palatinate. Caries could be ascertained by 5.4% of the adults from Dietfurt, by 4.9% of those from Schirndorf. In the Dürrnberg the percentage of such cases was lower (2.2%). This can be explained on the one side by the earlier death-rate climax on the Dürrnberg and on the other by differing nutritional habits. The teeth of the adult population from Dietfurt show enamel hypoplasia in only 14.9% of all cases. This low percentage gives cause to suppose that sufficient Vitamin A, C and D were present in the nutrition of the studied populations.

Bone and Bones↗

PubMed1990

Morphological adaptations of human skeletal muscle to chronic hypoxia.

Muscle structural changes during typical mountaineering expeditions to the Himalayas were assessed by taking muscle biopsies from 14 mountaineers before and after their sojourn at high altitude (greater than 5000 m for over 8 weeks). M. vastus lateralis samples were analyzed morphometrically from electron micrographs. A significant reduction (-10%) of muscle cross-sectional area was found on CT scans of the thigh. Morphologically this loss in muscle mass appeared as a decrease in muscle fiber size mainly due to a loss of myofibrillar proteins. A loss of muscle oxidative capacity was also evident, as indicated by a decrease in the volume of muscle mitochondria (-25%). In contrast, the capillary network was mostly spared from catabolism. It is therefore concluded that oxygen availability to muscle mitochondria after prolonged high-altitude exposure in humans is improved due to an unchanged capillary network, supplying a reduced muscle oxidative capacity.

Acclimatization↗

PubMed1989

Total muscle mitochondrial volume in relation to aerobic capacity of horses and steers.

The relationship between maximal oxygen consumption rate (VO2max) and mitochondrial content of skeletal muscles was examined in horses and steers (n = 3 each). Samples of the heart left ventricle, diaphragm, m. vastus medialis, m. semitendinosus, m. cutaneous thoracicus and m. masseter, as well as samples of muscles collected in a whole-body sampling procedure, were analyzed by electron microscopy. VO2max per kilogram body mass was 2.7 x greater in horses than steers. This higher VO2max was in proportion to the higher total volume of mitochondria in horse versus steer muscle when analyzed from the whole-body samples and from the locomotor muscle samples. In non-locomotor muscles, total mitochondrial volume was greater in horses than steers, but not in proportion to their differences in VO2max. The VO2max of the mitochondria was estimated to be close to 4.5 ml O2.ml-1 mitochondria in both species. It is concluded that in a comparison of a highly aerobic to a less aerobic mammalian species of similar body size, a higher oxidative potential may be found in all muscles of the more aerobic species. This greater oxidative potential is achieved by a greater total volume of skeletal muscle mitochondria.

Animals↗

PubMed1989

[The injured and the immobilized muscle cell: ultrastructural observations].

Muscle soreness is a common feature among athletes and untrained individuals who engage in unusual, especially intense eccentric exercise. Various biochemical markers as for example elevated CK demonstrate a damage of muscle cells. The most prominent structural finding is a varying degree of disruption of the contractile material up to cell degeneration. These morphological findings reach their maximum 2 or 3 days after exercise. Signs of regeneration, however, are seen even weeks after exercise. In a prospective study we investigated the structures of the quadriceps muscle in 41 patients with chronic symptomatic instability of the anterior cruciate ligament before, 9 and 26 weeks after operation using the needle biopsy technique. The immobilized muscle showed a rapid and large atrophy which markedly reduced aerobic capacity as well as maximal strength. Preoperative values weren't attained 26 weeks postoperative despite intense physiotherapeutic exercise. The control leg showed an atrophy as well, but only aerobic capacity was reduced, maximal strength remained about the same.

Biopsy, Needle↗

PubMed1989

Muscle filament spacing and short-term heavy-resistance exercise in humans.

1. Six weeks of a dynamic heavy-resistance training of the quadriceps muscle in healthy young men resulted in a continuous increase in muscle strength, in an increase in muscle cross-sectional area (significant only in the second half of the training period) and in an increase in radiological density of the muscle tissue of 3.1% (2P less than 0.001) in the first three weeks and 1.6% (2P less than 0.01) in the second three weeks. 2. The linear distance between myosin filaments (38.7 +/- 0.3 nm before, 38.7 +/- 0.4 nm after training; mean +/- S.E.M.) as well as the ratio of actin to myosin filaments (3.94 +/- 0.03 before, 3.86 +/- 0.06 after training) did not change with training. 3. These results refute the concept that the increases in muscle strength or radiological density during short-term heavy-resistance training are caused by changes in myofilament spacing.

Adolescent↗

PubMed1986

Acute effects of endurance exercise on mitochondrial distribution and skeletal muscle morphology.

Biopsies of vastus lateralis from seven well-trained males were studied 1 month before and 15-30 min after a 100-km race. The distribution of interfibrillar mitochondria was analyzed to determine whether a long bout of exercise induced a redistribution of mitochondria. Capillary densities and mean fiber areas were also estimated. Capillary density and mean interfibrillar mitochondrial volume density were found to be significantly correlated with running time in the race. An earlier study on these biopsies found that the mean volume densities of interfibrillar and subsarcolemmal mitochondria did not change after a race, but the volume densities of lipid droplets and interfibrillar glycogen decreased significantly. In the present study, volume density of interfibrillar mitochondria [Vv(mi,fim)] before the race was highest with a value of 0.098 +/- 0.007 near the fiber border, and decreased progressively with distance to 0.045 +/- 0.004 at the fiber center. After the race, Vv(mi,fim) was unchanged at the fiber border, but was significantly higher (0.062 +/- 0.005) in the center of the fiber. This increase in mitochondrial volume density was attributable to the shrinkage of the fibers from consumption of energy stores, which was relatively greater for interfibrillar glycogen than for subsarcolemmal glycogen. Thus the primary effect of this extended bout of endurance exercise on vastus lateralis was the nearly complete depletion of the interfibrillar glycogen and lipids, but there was no evidence of an acute redistribution of mitochondria.

Adult↗

PubMed1986

Mitochondrial distribution in relation to changes in muscle metabolism in rat soleus.

Rats were subjected to exercise programs of either brief running once weekly or endurance running daily on a laddermill for 6 weeks. Both groups of exercised rats showed significant hypertrophy of the soleus. This muscle was analyzed morphometrically to determine if these running programs induced significant differences in the distribution of interfibrillar mitochondria. Interfibrillar mitochondrial volume density in the endurance-trained and control groups was highest near the fiber border and decreased with distance toward the fiber center, whereas in the weekly-run rats interfibrillar mitochondrial volume density was not correlated with distance within the fiber. Absolute interfibrillar mitochondrial volume (Vmi) was approximately 50% higher in endurance-trained rats than in controls at all locations sampled, but Vmi was nearly 80% higher in the weekly-run animals only in the fiber center. Thus the distribution of mitochondria was significantly different in weekly-run versus endurance-trained animals which may reflect differences in substrate source or high-energy phosphate flux in these fibers.

Animals↗

PubMed1986

Altered skeletal muscle ultrastructure in renal transplant patients on prednisone.

Treatment with glucocorticoids causes wasting of proximal skeletal muscles. The purpose of the present investigation was to quantify in the thigh muscle the areas of the different fiber types determined by histochemical methods, and the muscle ultrastructure by means of electron microscopy, in normal subjects (N = 41) and in renal transplant patients treated with prednisone (N = 12). The cross-sectional area of all three fiber types was reduced in renal transplant patients treated with prednisone (10.6 +/- 4.3 mg/day), the fast glycolytic fibers being most affected (slow oxidative fibers: 2642 +/- 625 vs. 3677 +/- 970 micron2, P less than 0.001; fast oxidative fibers: 3275 +/- 735 vs. 4443 +/- 1343 micron2, P less than 0.01; fast glycolytic fibers: 2305 +/- 802 vs. 3920 +/- 1522 micron2, P less than 0.001). This was mostly due to a decrease in the volume of myofibrils per unit volume of muscle fiber (-30%). The intracellular lipid content and the volume density of subsarcolemmal mitochondria were increased by more than 70% in prednisone treated patients. In conclusion, the decreased myofibril areas might account for the muscle weakness in renal transplant patients treated with prednisone, and the decrease in myofibrils is in part functionally compensated by an increase in subsarcolemmal mitochondria and intracellular lipid content.

Adult↗