Biomedical subjects

A de Haan

Publications and source records attributed to A de Haan.

100 records · Page 6Linked to original sources

PubMed1988

Influence of muscle dimensions on economy of isometric exercise in rat medial gastrocnemius muscles in situ.

The effect of muscle dimensions on economy (force-time integral divided by the amount of energy utilized) was investigated in male rats (body mass range 95-490 g), anaesthetized with pentobarbital. The medial gastrocnemius muscle in situ performed 6 maximal isometric contractions of 350 ms duration (1.s-1) at twitch optimum length at 35 degrees C. The areas under the 6 time-force curves were added to obtain force-time integral of the experiment. Differences of concentrations of ATP, phosphocreatine and lactate between experimental and contralateral (resting) muscles were used to calculate high-energy phosphate consumption due to stimulation. Muscle mass and cross-sectional area increased (approximately +400% and +300%, respectively) over the rat body mass range studied. Muscle length and length of the most distal fibre bundle increased by approximately 17 mm and 4 mm, respectively. Force-time integral (N.s) increased proportional to cross-sectional area whereas high-energy phosphate consumption (mumoles) increased proportional to muscle mass. The relative fraction of the total energy consumption utilized for force-independent processes was independent of rat body mass. The economy of the actomyosin system was unaffected during growth, whereas economy of the whole muscle decreased during growth by approximately 30% (p less than 0.001). The effect of muscle dimensions on economy is discussed with respect to human endurance capacity measured by voluntary isometric contractions.

Animals↗

PubMed1988

Comparison of force-velocity characteristics obtained using twitches and tetani from in situ rat skeletal muscles.

Force-velocity and power-velocity characteristics of three different rat skeletal muscle-tendon complexes (soleus, extensor digitorum longus and medial gastrocnemius) were obtained using twitch and tetanic contractions. No differences were found between twitches and tetani with respect to the shape of the force-velocity curves, or to the velocity at which the highest power output occurs. The results indicate that twitch contractions can be used to standardize muscle preparations in experiments aimed to study muscle energetics during dynamic contractions.

Animals↗

PubMed1988

Microbial production and metabolism of epoxides.

Epoxides are intermediates in the metabolism of many alkenes and aromatic compounds in higher organisms and in microorganisms. In microbial formation of epoxides, and further metabolism or excretion of these reactive compounds, many different enzymes are involved. Bacteria and fungi sometimes form optically active epoxides or are able to degrade epoxides enantioselectively, allowing the biotechnological production of these chiral building blocks in organic synthesis.

Bacteria↗

PubMed1987

A multipurpose muscle ergometer.

A fast (0.1 mm steps within 2 ms), strong (40 N continuously) and accurate (resolution 0.002 N and 1.0 micron) muscle ergometer was developed to test dynamic and static properties of mammalian muscle. Both for twitches and for tetani isometric, isokinetic and isotonic contractions can be measured accurately. Force-velocity data and time to peak-force data of four EDL muscles, as well as force-extension data of their serial tendinous structures are shown to demonstrate the machine.

Animals↗

PubMed1987

Protein C levels in infancy and early childhood. Influence of breast feeding.

Protein C antigen levels were measured in the plasma of healthy full term infants by electroimmunoassay. During the first three months of life (on day four, at one month, two months and three months of age) protein C antigen levels were compared in breast-fed and bottle-fed infants. None of the two groups of infants received vitamin K at birth. Only at the age of three months there was a significant difference between the groups. Unexpectedly infants, who were breast-fed, had a higher protein C level at three months of age. Levels were also measured in 15 healthy children between one and three years of age. The antigen levels increase with age to reach adult values at about three years of age.

Breast Feeding↗

PubMed1986

Muscle economy of isometric contractions as a function of stimulation time and relative muscle length.

For rat medial gastrocnemius muscle economy (i.e. the ratio of time integral of force and total energy-rich phosphate consumption) was calculated. Muscles in situ at 35 degrees C were stimulated to perform either one continuous or several repetitive isometric contractions at one muscle length in the range from 70% to 130% of optimum muscle length for force generation. Whereas during one continuous contraction economy increased, no differences in economy were found between 6, 12 or 18 successive contractions. Economy during intermittent exercise was always lower than during continuous exercise. The difference in economy is a result of different rates of metabolism, whereas no difference was found for force generation. Economy was highest at optimum muscle length for force generation and decreased at muscle lengths smaller as well as greater than optimum muscle length. Force-dependent energy consumption was calculated by subtracting the force-independent part (obtained by extrapolation) from total energy consumption. The calculated force produced per mumol force-dependent energy-rich phosphate consumption was similar in muscles stretched beyond optimum length. In contrast, a decreasing amount of force per mumol force-dependent energy-rich phosphate consumption was observed at lengths smaller than optimum length.

Animals↗

PubMed1985

Effects of potassium + magnesium aspartate on muscle metabolism and force development during short intensive static exercise.

Improvement of muscle performance by 20%-50% in man at a submaximal work load after administration of potassium and magnesium salts of aspartic acid (K + Mg Asp) has been reported in the literature. Administration of K + Mg Asp has been reported to affect force production and energy metabolism in short-term activities of electrical stimulated animal muscles. The present study examined the possible effects of K + Mg Asp on: energy metabolism and force production of electrically stimulated rat quadriceps muscle and endurance time of a submaximal static force of voluntary contracting human muscles. In rat muscles metabolic parameters such as ATP, phosphocreatine, lactate, and L-aspartate were not influenced by oral administration of K + Mg Asp. Force parameters of rat quadriceps muscles were not enhanced after administration of K + Mg Asp. In human volunteers neither the exerted force nor the endurance time increased after oral administration of K + Mg Asp. An effect of K + Mg Asp on muscle metabolism by stimulation of the purine nucleotide cycle was not found. Improvement of muscle performance by 20%-50%, as reported for long-term activity, was not observed for short-term intensive activity.

Adult↗

PubMed1985

The effect of intensive interval training on the anaerobic power of the rat quadriceps muscle.

The effect of intensive interval training on the maximal anaerobic power of the rat quadriceps muscle was investigated. The anaerobic energy production was estimated from the changes in the concentrations of phosphocreatine, adenine nucleotides, inosine monophosphate and lactate in freeze-clamped muscle tissue after electrical stimulation for 2-30 s. The results showed that the maximal running speed of rats tested increased by 24%, the maximal force exerted increased by 13%, and the succinate dehydrogenase activity by 48%, while the adenylate kinase activity was the same before and after training. No difference could be observed between the maximal anaerobic power of the quadriceps muscles of trained and sedentary animals. It seems that trained muscles may be able to work with a higher degree of economy than untrained muscles.

Anaerobiosis↗

PubMedDate not supplied

Parental origin of the fra(X) gene is a major determinant of the cytogenetic expression and the CGG repeat length in female carriers.

The fragile X [fra(X)] syndrome is the most frequent form of inherited mental retardation, and co-segregates with a fragile site at Xq27.3 as well as with insertion of a variable number of trinucleotide repeats in the 5'-end of the FMR-1 gene. As the fra(X) gene is transmitted by females as well as males, we have investigated whether the parental origin of the fra(X) gene has an effect upon the cytogenetic expression and CGG repeat length. An increased fragment length of 0.2-0.6 kb appeared to be associated with a very low expression or even complete absence of the fragile site as well as with a normal phenotype, and was seen mostly in cases of paternal inheritance. However, in most female carriers with the maternally inherited fra(X) gene we found dispersed fragments ranging from 1.4-6.5 kb or even complete absence of a hybridization signal. Within the group of female carriers with the maternally inherited fra(X) gene we found a statistically significant correlation between the level of the cytogenetic expression and the PstI restriction fragment length encompassing the CGG repeat. These data can be taken as indirect evidence that CGG repeat length and cytogenetic expression are causally related.

Cytogenetics↗

PubMedDate not supplied

Bone adaptation to altered loading after spinal cord injury: a study of bone and muscle strength.

Bone loss from the paralysed limbs after spinal cord injury (SCI) is well documented. Under physiological conditions, bones are adapted to forces which mainly emerge from muscle pull. After spinal cord injury (SCI), muscles can no longer contract voluntarily and are merely activated during spasms. Based on the Ashworth scale, previous research has suggested that these spasms may mitigate bone losses. We therefore wished to assess muscle forces after SCI with a more direct measure and compare it to measures of bone strength. We hypothesized that the bones in SCI patients would be in relation to the loss of muscle forces. Six male patients with SCI 6.4 (SD 4.3) years earlier and 6 age-matched, able-bodied control subjects were investigated. Bone scans from the right knee were obtained by pQCT. The knee extensor muscles were electrically stimulated via the femoral nerve, isometric knee extension torque was measured and patellar tendon force was estimated. Tendon force upon electrical stimulation in the SCI group was 75% lower than in the control subjects (p<0.01). Volumetric bone mineral density of the patella and of the proximal tibia epiphysis were 50% lower in the SCI group than in the control subjects (p<0.01). Cortical area was lower by 43% in the SCI patients at the proximal tibia metaphysis, and by 33% at the distal femur metaphysis. No group differences were found in volumetric cortical density. Close curvilinear relationships were found between stress and volumetric density for the tibia epiphysis (r(2)=0.90) and for the patella (r(2)=0.91). A weaker correlation with the tendon force was found for the cortical area of the proximal tibia metaphysis (r(2)=0.63), and none for the distal femur metaphysis. These data suggest that, under steady state conditions after SCI, epiphyseal bones are well adapted to the muscular forces. For the metaphysis of the long bones, such an adaptation appears to be less evident. The reason for this remains unclear.

Adult↗