Estimating transit time for capillary blood in selected muscles of exercising animals.

The mean minimal capillary transit time was estimated in muscles of various animals using a combination of physiological and morphometric methods. Radioactive microspheres were injected intravascularly in various animals running on a treadmill at maximum oxygen consumption rate (VO2,max) to label blood flow to individual muscles. The muscles were then removed and preserved by standard methods for electron microscopy.

Characterization of 4-hydroxyphenylpyruvate dioxygenase. Primary structure of the Pseudomonas enzyme.

The primary structure of Pseudomonas 4-hydroxyphenylpyruvate dioxygenase was determined. Sequence degradation of the intact protein and of peptides from three different digests of the carboxymethylated protein established a 357-residue polypeptide chain with a free alpha-amino group. Hydroxylamine cleavage at a single Asn-Gly sequence was useful.

Running energetics in the pronghorn antelope.

The pronghorn antelope (Antilocapra americana) has an alleged top speed of 100 km h-1, second only to the cheetah (Acionyx jubatus) among land vertebrates, a possible response to predation in the exposed habitat of the North American prairie. Unlike cheetahs, however, pronghorn antelope are distance runners rather than sprinters, and can run 11 km in 10 min, an average speed of 65 km h-1. We measured maximum oxygen uptake in pronghorn antelope to distinguish between two potential explanations for this ability: either they have evolved a uniquely high muscular efficiency (low cost of transport) or they can supply oxygen to the muscles at unusually high levels.

Serum cobalamins in the elderly: a longitudinal study of a representative population sample from age 70 to 81.

In a representative population sample (n = 973) born 1901-1902 and examined at the ages of 70, 75, 79, and 81, the change in serum cobalamins with increasing age was studied by trend analysis using values obtained in single individuals at all four examinations. In subsamples without definable disorders, the mean annual decline was: among men 3.4 pmol/l (p less than 0.

Carnitine deficiency induced by pivampicillin and pivmecillinam therapy.

Short-term administration of pivampicillin and pivmecillinam resulted in a reduction of serum carnitine concentration and an increase in excretion of acylcarnitine in urine. These changes persisted for more than ten days after cessation of therapy. In seven girls on long-term treatment with a mixture of pivampicillin and pivmecillinam the mean total serum carnitine concentration fell to 15% (7-27%) of pretreatment values.

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.

The population study of women in Gothenburg 1980-81--the third phase of a longitudinal study. Comparison between participants and non-participants.

A representative population sample comprising 1,462 women was studied in Gothenburg, Sweden in 1968-69, and a third follow-up study was carried out in 1980-81. The participation rates in the baseline study and during the follow-up studies were high. In 1980-81 women in two new age strata, aged 26 and 38, were added.

Transport of carnitine into cells in hereditary carnitine deficiency.

Carnitine uptake has been studied in fibroblasts from a case of hereditary carnitine deficiency and in relatives. There was no evidence for carrier-dependent uptake in cells from the patient. The mother and probably the healthy sister had an impaired uptake.

Hydroxylation of aspartic acid in domains homologous to the epidermal growth factor precursor is catalyzed by a 2-oxoglutarate-dependent dioxygenase.

3-Hydroxyaspartic acid and 3-hydroxyasparagine are two rare amino acids that are present in domains homologous to the epidermal growth factor precursor in vitamin K-dependent plasma proteins as well as in proteins that do not require vitamin K for normal biosynthesis. They are formed by posttranslational hydroxylation of aspartic acid and asparagine, respectively. The first epidermal growth factor-like domain in factor IX (residues 45-87) was synthesized with aspartic acid in position 64, replacing 3-hydroxyaspartic acid.

Limitations to aerobic performance in mammals: interaction of structure and demand.

In this paper we have explored the linked series of structures that collectively comprise the respiratory system. In examining each of these structural resistors, some seem to be primarily fixed, for example, the trachea, while others must be primarily variable or adaptable, for example, the cardiovascular system. Those structures that are truly variable will not be maintained with structural capacity in excess of their functional demand.

Skeletal muscle mitochondria: the aerobic gate?

At an animal's maximum aerobic capacity (VO2max), the O2 flowing through the respiratory system is consumed by a functionally exclusive sink, skeletal muscle mitochondria. Thus, O2 consumption will never exceed the muscles O2 demand. If the system is ideally designed, structures upstream to the skeletal muscle O2 sink must be built to insure adequate O2 delivery to the working muscle.

4-Hydroxyphenylpyruvate dioxygenase is an iron-tyrosinate protein.

A resonance Raman investigation into the blue chromophore of 4-hydroxyphenylpyruvate dioxygenase, a non-heme iron enzyme from Pseudomonas P. J. 874, reveals the presence of enhanced vibrations characteristic of tyrosinate coordination to the iron center.

Estimate of muscle-shortening rate during locomotion.

All skeletal muscle can produce roughly the same maximal cross-sectional force; however, the power (energy X time-1) required to develop and maintain that force increases with increasing contraction velocity. Thus the rate of muscle tension development may be of primary importance in setting the energy demand of contracting muscle. We have estimated the rate of muscle shortening during terrestrial locomotion in mammals as a function of body mass.

Endurance training in humans: aerobic capacity and structure of skeletal muscle.

The adaptation of muscle structure, power output, and mass-specific rate of maximal O2 consumption (VO2max/Mb) with endurance training on bicycle ergometers was studied for five male and five female subjects. Biopsies of vastus lateralis muscle and VO2max determinations were made at the start and end of 6 wk of training. The power output maintained on the ergometer daily for 30 min was adjusted to achieve a heart rate exceeding 85% of the maximum for two-thirds of the training session.

Malleability of skeletal muscle in overcoming limitations: structural elements.

The quantitative structural composition of skeletal muscle tissue shows a wide range of variability among different species of animals and in any one species among muscles with a different function. Moreover, experimental manipulations such as exercise training or chronic electrical stimulation can dramatically change the ultrastructural appearance of the muscles involved. Both in endurance exercise and in chronic electrical stimulation the volume density of mitochondria can be increased greatly (by more than three-fold in the stimulation experiments).

Multiple forms of gamma-butyrobetaine hydroxylase (EC 1.14.11.1).

gamma-Butyrobetaine hydroxylase [4-trimethylaminobutyrate, 2-oxoglutarate:oxygen oxidoreductase (3-hydroxylating), EC 1.14.11.

Uncoupling and isotope effects in gamma-butyrobetaine hydroxylation.

Replacement of unlabeled gamma-butyrobetaine with gamma-[2,3,4-2H6]butyrobetaine has a profound effect on the stoichiometry between decarboxylation of 2-oxoglutarate and hydroxylation in the reaction catalyzed by human gamma-butyrobetaine hydroxylase. The ratios between decarboxylation and hydroxylation are 1.16 with unlabeled and 7.