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Biomedical subjects

H Howald

Publications and source records attributed to H Howald.

At least 55 records · Page 3Linked to original sources
PubMed1987

Exercise training induces transitions of myosin isoform subunits within histochemically typed human muscle fibres.

Fibre type composition based on histochemical myosin ATPase reaction was studied in cross sections of biopsies from the vastus lateralis muscle of men. In addition, protein composition as well as peptide patterns of isolated myosin heavy chains were examined in batches of individually classified fibres from the same biopsies. High intensity endurance training during 8 weeks induces significant decreases by 31-70% of the type IIB fibre population in 3 of 4 subjects (in one case no change was observed). These decreases were offset by corresponding increases in either type I or type IIA fibres with the type IIC fibres remaining always below 3%. A total of 13 professional cyclists with training periods over several years have a 20 times lower content of type IIB fibres than 4 sedentary controls and a concomitant high content of 80% of type I fibres. The content of type I and type IIB fibres of 8 sprinter athletes did almost not differ from that of controls. Thus the type IIB fibres respond most sensitively with a decrease to aerobic endurance training. Since both type IIA and IIB fibres were identical in protein composition containing the same fast variety of myosin light chains and heavy chains as well as troponin-I, their interconversion could not be seen at the molecular level. However, the slow variety of myosin light chains and of troponin-I started accumulating after 8 weeks of training in type IIA fibres. Furthermore, the myosin heavy chain isoform started shifting by producing new peptide patterns that resemble the digestion pattern of slow myosin heavy chains in fibres which still classified as type IIA. These changes on the molecular level in type IIA fibres mark the beginning of their transition over the intermediate and variable type IIC fibres, towards the slow type I fibre.

Adult↗
PubMed1987

Fetal sex and distribution of peri-intraventricular hemorrhage in preterm infants.

Peri-intraventricular hemorrhage (PIVH) is an important complication of the brain in immature newborn infants. In a real-time ultrasound study with frequent scanning of 78 preterm infants (50 with birth-weight less than 1,500 g and 28 weighing more than 1,500 g), we examined the influence of sex on the occurrence of PIVH. A significant difference between sexes was only found in the group with birth-weight below 1,500 g. PIVH occurred in 72% of male infants and in 28% of females (p less than 0.001). This effect is probably due to a difference in the timing of cerebral vascular maturation in males leading to a difference in the risk of developing PIVH between the sexes before 34 weeks of gestation.

Cerebral Hemorrhage↗
PubMed1987

Impact of physical training on the ultrastructure of midthigh muscle in normal subjects and in patients treated with glucocorticoids.

Exercise-training might be a logical method to reverse muscle atrophy and weakness in patients treated with glucocorticoids. The purpose of the present investigation was to establish whether a treatment with low dose prednisone (10 +/- 2.9 mg/d) modulates the effect of a moderate strength type isokinetic training during 7 wk (21 sessions of 20 min) on "muscle efficiency" (power output/muscle mass) and on concomitant changes in ultrastructure of the thigh muscle measured by quantitative electron-microscopic morphometry. Training caused a similar increase in "muscle efficiency" in patients on prednisone (n = 9) as in normal volunteers (n = 9). In normal subjects the increase in muscle efficiency was associated with an increase in sarcoplasm, whereas in patients on prednisone the functional improvement was associated with an increase in sarcoplasm, capillaries, and mitochondria content. Thus, a therapy with low dose prednisone does not abrogate training-induced improvement of muscle efficiency but modulates the ultrastructural response of the muscle to the training.

Exercise Therapy↗
PubMed1987

Incidence of peri-intraventricular hemorrhage in premature neonates weighing more than 1500 g.

With the advent of modern methods of neonatal care, intracranial hemorrhage probably has become the most common neurological complication in premature infants weighing less than 1500 g at birth. This paper is a prospective study of 75 preterm infants of 34 weeks gestation or more and birth weight above 1500 g (range 1500 g to 2500 g). All neonates were screened by cranial ultra-sonography for evidence of peri-intraventricular hemorrhage (PIVH). Perinatal risk factors, incidence of PIVH and neurological outcome were studied. Sonographic abnormalities were detected in 16 (21.3%) of our patients. Intracranial hemorrhage was frequently associated with a low Apgar score, need of resuscitation and/or assisted ventilation immediately after birth (P less than 0.005). This study suggests, that ultrasound screening should be reserved to those large premature infants (greater than 1500 g) with high risk of hypoxic-ischemic injury.

Birth Weight↗
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

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↗
PubMed1986

Structural changes in skeletal muscle tissue with heavy-resistance exercise.

Muscle strength, muscle cross-sectional area, fiber size, fiber type distribution, capillarity, and mitochondrial volume were estimated before and after 6 weeks of heavy-resistance exercise. Isokinetic torque production of the knee extensor muscles increased by a total of 17.6%, mainly during the first half of the training period. The cross-sectional area of the vastus lateralis muscle increased by 8.4%, mainly during the second half of the training period. Morphometrically determined fiber size, fiber type distribution, and capillarity from biopsies of vastus lateralis did not change significantly with training. Likewise, the surface densities of inner and outer mitochondrial membranes as well as the volume density of myofibrils remained unchanged. In contrast, the volume density of mitochondria decreased by 9.6%. However, due to the increase in total muscle volume, the calculated absolute volume of mitochondria remained constant, whereas the absolute volume of myofibrils increased by 10%. It is concluded that strength training of short duration in previously untrained young male subjects does not change the ultrastructural composition of mitochondria and that the apparent dilution of mitochondria can quantitatively be accounted for by the increase in myofibrillar volume.

Adenosine Triphosphatases↗
PubMed1986

Correlation of raised cord-blood CK-BB and the development of peri-intraventricular hemorrhage in preterm infants.

This study concerns the prognostic value of total cord-blood CK-BB activity measured with a new method in preterm infants at risk of PIVH. Twenty-six patients with gestational age less than 36 weeks were studied. The presence of PIVH was proved by either ultrasound scans or autopsy. Total CK-BB values in cord-blood of infants who developed PIVH were significantly higher than those of patients without cerebral bleeding (P less than 0.001).

Cerebral Hemorrhage↗
PubMed1986

Physiological profile of world-class high-altitude climbers.

The functional characteristics of six world-class high-altitude mountaineers were assessed 2-12 mo after the last high-altitude climb. Each climber on one or several occasions had reached altitudes of 8,500 m or above without supplementary O2. Static and dynamic lung volumes and right and left echocardiographic measurements were found to be within normal limits of sedentary controls (SC). Muscle fiber distribution was 70% type I, 22% type IIa, and 7% type IIb. Mean muscle fiber cross-sectional area was significantly smaller than that of SC (-15%) and of long-distance runners (LDR, -51%). The number of capillaries per unit cross-sectional area was significantly greater than that of SC (+ 40%). Total mitochondrial volume was not significantly different from that of SC, but its subsarcolemmal component was equal to that of LDR. Average maximal O2 consumption was 60 +/- 6 ml X kg-1 X min-1, which is between the values of SC and LDR. Average maximal anaerobic power was 28 +/- 2.5 W X kg-1, which is equal to that of SC and 40% lower that that of competitive high jumpers. All subjects were characterized by resting hyperventilation both in normoxia and in moderate (inspired O2 partial pressure = 77 Torr) hypoxia resulting in higher oxyhemoglobin saturation levels in hypoxia. The ventilatory response to four tidal volumes of pure O2 was similar to that of SC. It is concluded that elite high-altitude climbers do not have physiological adaptations to high altitude that justify their unique performance.

Adaptation, Physiological↗
PubMed1986

Specificity of leg power changes to velocities used in bicycle endurance training.

Increases in leg power production resulting from 8 wk of bicycle endurance training (30 min/day, 5 times/wk) were studied using an isokinetic dynamometer. In addition, biopsies of vastus lateralis were analyzed to characterize muscle ultrastructural changes. Performance increased on the dynamometer specifically near the estimated average knee angular velocity used during the bicycle training (200 degrees/s). Power measurements were made during the first 5 contractions (maximal power: Pmax) and last 5 contractions (final power: Pend) of 25 and 50 consecutive contractions (at 60 and 240 degrees/s, respectively). Pmax and Pend increased only at 240 degrees/s but not at 60 degrees/s. These increases in Pmax (86 W) and Pend (78 W) resulted primarily from longer torque maintenance but also from increased peak torque during each contraction and were close to the increase in mechanical power output maintained on the bicycle (Pb; 78 W) during the training sessions. The specificity of these changes to the angular velocities used in the bicycle training indicates a neural basis to these adaptations. We suggest that these neural adaptations, coupled with the observed enhancement of muscle mitochondrial and capillary density (+41 and +15%, respectively) underlie the increased ability to maintain power production on a bicycle after endurance training.

Adult↗
PubMed1986

Neurological prognosis of high-risk preterm infants with peri-intraventricular hemorrhage and ventricular dilatation.

Fifty-eight preterm neonates evaluated by real-time sonographic scanning of the head were prospectively studied. They were divided into three groups: 13 with peri-intraventricular hemorrhage (PIVH) alone, 19 with subsequent ventricular dilatation and 26 control infants without ultrasound evidence of PIVH. At 12 months of age detailed neurological follow-up assessment was carried out. Five (8.6%) patients had major handicaps, 34 minor neurological abnormalities. The severity of the PIVH correlated with the neurologic outcome (p less than 0.02). The incidence of major handicaps was significantly greater in the group with ventricular dilatation (p less than 0.03). Among the infants with PIVH, major handicaps were only present if associated with grade III and IV. Severe posthemorrhagic ventricular dilatation increased the risk for major handicaps. Adverse neurological sequelae at follow-up appeared to be attributable to the extent of PIVH and aggravated by severe ventricular enlargement.

Brain Diseases↗
PubMed1986

Fetal ventriculomegaly, agenesis of the corpus callosum and chromosomal translocation--case report.

Real-time ultrasound was used to evaluate intracranial anatomy and ventricular size in a child with fetal ventriculomegaly. It was associated with agenesis of the corpus callosum and chromosomal translocation. Serial measurements of cerebral ventricular dilatation at various gestational age may improve perinatal management of the newborn with fetal ventricular enlargement.

Agenesis of Corpus Callosum↗
PubMed1986

Obstructive ventriculomegaly.

Intracranial Hemorrhage (ICH) occurs primarily in premature infants, and post-hemorrhagic ventricular dilatation is a well-known complication in this age-group. Blood clots within the ventricle are diagnostic of ICH but not usually seen. In our case Real-Time Ultrasonography has proved to be very helpful to identify intraventricular hematomas and to control obstructive ventriculomegaly without therapeutic intervention.

Cerebral Hemorrhage↗