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PubMed1977

The Salop Skate.

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Adolescent↗
PubMedDate not supplied

[Magnesium-activated adenosine triphosphate of the ampullae of Lorenzini of the skate Dasyatis pastinaca].

Studies have been made on Mg2+-activated ATPase of electroreceptor structures of the lateral line organin the ray D. pastinaca. It was shown that the enzyme is activated by magnesium ions (2.5 mM), maximum activation being observed at pH 8.0-8.5. The enzyme exhibits substrate specificity to adenyl nucleotides. Walls of ampullar canals also contain Mg2+-ATPase, however the level of the enzymatic activity in these walls is significantly lower.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Effect of ergotoxin on gastric motility in the skate, frog and turtle].

DG-erotoxine (SPOFA)--200 mg/kh b. w. has no effect to the motor activity in scates. The dose of 500 mkg/kh produces 20-30 min. after injection the excitation of contraction followed by the inhibition. In frogs the dose of 25 mkg/kg produces the excitation of stomach contractions. The dose of 100 mkg/kg initially stimulates motor activity, later on--inhibits it. In the tortoise the dose of 25 mkg/kg increases the contraction of the stomach the dose of 2000 mkg/kg inhibits it.

Animals↗
PubMedDate not supplied

[Perception of chemical and temperature stimuli by the ampullae of Lorenzini in in skates].

Recording impulse activity in single nervous fibers, studies have been made on the effect of chemical and thermal stimuli on the activity of Lorenzini ampullae in the rays Dasyatis pastinaca and Raja clavata. Application of the diluted sea water to the opening of ampullary canal increases the discharge rate of the receptors resulting into subsequent adaptation, whereas the increase in water salinity causes opposite changes. Threshold changes in the salinity of sea water amount 1--2%. Thermal transient in the sea water at the vicinity of the opening of ampullary canal did not affect the activity of the receptors. A decrease in temperature at the vicinity of receptor cells resulted in a transient rise of the firing rate of the receptors, while the increase of temperature decreased the activity of the receptors.

Adaptation, Physiological↗
PubMedDate not supplied

Amino acids and cell regulation.

Free amino play an important role in regulating cell volume in fishes. Four tissues/cells (skeletal muscle, RBC, brain, and myocardium) of the little skate, Raja erinacea, were selected for detailed study because of their special importance or unique advantage as experimental models. Three particular amino acids, beta-alanine, taurine, and sarcosine play a predominant role in all four tissues. As in higher vertebrates, amino acid uptake in skate brain, heart, and RBC is mediated via a Na+-dependent process. Amino acids leave the skate brain rapidly in response to a sudden decrease in plasma osmolality and/or to a simultaneous drop in extracellular Na+ concentration. However, although amino acids are important for volume regulation in normal brain cells, they do not appear to be likely candidates for the unidentified "idiogenic" osmolytes in mammalian brain cells. The high concentration of taurine in skate myocardium is of special interest because of the special role of this amino acid in myocardial contractility. Thus, unlike beta-alanine and sarcosine, taurine may play a dual role in regulating both cell volume and contractility of myocardial cells. The isolated skate atrium is well suited for in vitro studies of these two processes.

Amino Acids↗
PubMed1979

A longitudinal study of ice hockey in boys aged 8--12.

A group of fifteen boys (experimental or competitive) were studied over a five year period of competitive ice hockey beginning at age 8. The subjects were members of a team which averaged 66 games per year, ranging from 50 at age 8 to 78 at age 12. In addition, they practiced twice a week with heavy stress on skating and individual puck handling skills. A second group of eleven boys (control or less competitive) were studied from age 10 to 12. The latter subjects played an average of 25 games per year and practiced once a week. All subjects were measured each year on skating and puck control skills, fitness-performance tests, grip strength, physical work capacity as well as height and weight. The results demonstrate learning curves for skating and puck control tests which, while typical in nature, show extremely high levels of achievement. Fitness-Performance, grip strength and physical work capacity levels of the competitive group are extremely high in comparison with data from other countries.

Body Height↗
PubMed1979

Comparsions among VO2 max values for hockey players and runners.

This study was designed to investigate the specificity of the VO2 max response of runners and hockey players for multistage tests done on the treadmill (RUN) or on the ice, skating a shuttle 20m course with (20m+) or without equipment (20m-) and a 140m oval course (140m-). Hockey players VO2 max in ml.kg-1.min-1 (n=10) were similar for the 4 tests (RUN: X +/- SD = 61.4 +/- 6.3; 140m-: 62.1 +/- 9.4; 20m-: 58.6 +/- 6.4; and 20m+: 59.9 +/- 7.4). VO2 max of runners (n = 10) were superior on the treadmill (68.6 +/- 4.5) as compared to the ice (140m-: 65.6 +/- 5.4). Hockey players as compared to runners, were 15% more efficient on the ice and 7.9% less efficient on the treadmill. The equipment increased the energy cost of skating by 4.8% and decreased the multistage test time by 20.3%. The low temperature arena as compared to the standard temperature laboratory, yielded lower heart rate response with multistage tests. Blood lactates (mg%) were similar for all tests done with hockey players (RUN: 128.3 +/- 19.3; 140m-: 126.8 +/- 14.7; 20m-: 133.0 +/- 17.5; and 20m+: 131.4 +/- 18.5), but lower on the ice (140m-: 87.7 +/- 15.9) as compared to the treadmill (127.2 +/- 26.4) for the runners. Maximal skating speed disclosed a relatively homogenous group of hockey players but their VO2 max scores were more widely distributed.

Adult↗
PubMed1978

Comparative aspects of brain barrier systems for nonelectrolytes.

Blood-brain and blood-CSF barriers to inulin were compared in 11 vertebrate species. Twenty hours after systemic administration, [14C]inulin penetrated into the central nervous system to an equivalent extent in mudpuppy, salamander (adult and larval), red sculpin, big skate, little skate, southern stingray, and Atlantic stingray with values for RB (dpm/g brain divided by dpm/ml plasma) in the range 0.01- 0.04 and for RCSF (dpm/ml CSF divided by dpm/ml plasma) from 0.02 to 0.04. These values are similar to those reported for mammals. For dogfish, nurse shark, and lemon shark, RB ranged from 0.04 to 0.09 and RCSF from 0.08 to 0.29 and for hagfish RB=0.12, indicating that barrier systems to inulin are poorly developed in sharks and possibly absent in hagfish. Analyses of radiolabeled urea and sucrose penetration into brain and CSF revealed further differences in shark barrier function. Brain barriers to insulin in dogfish and little skate developed with age; in nurse shark there was no detectable change in the inulin ratios over the weight range, 0.2-110 kg.

Aging↗
PubMed1978

Cupular movement and nerve impulse response in the isolated semicircular canal.

The aim of the study was to record nerve impulse responses to controlled displacements of the cupula and relate these to observations of cupular motion. The preparation was the skate semicircular canal, isolated and maintained in a chamber. The canal was cut and tied tightly to an oil-filled tube driven by a 1 microliter syringe. In some experiments dye was used to make the face of the cupula visible. Small volume displacements (0.02 microliter) caused a billowing of the central portion of the cupula, whereas for repeated large displacements (0.1 microliter) the top of the cupula moved along the roof of the ampulla. Displacements of the latter amount were close to saturation in the characteristic functions (spike rate versus volume displacement) of nerve firing. It seems that the discharge rate of tonically responding units in the skate crista ampullaris rather faithfully record the force acting on the cupula. The motion of the base of the cupula rather than its tip appears to be the relevant parameter in setting the level of excitation in the sensory cells within the physiological range of stimulation. Such a mode of operation would ensure the highest sensitivity of the sense organ.

Animals↗
PubMed1978

Phylogenetic distribution of aromatase and other androgen-converting enzymes in the central nervous system.

Metabolism of [3H]androstenedione was studied in brain tissue homogenates of opossum, bird, snake, sea turtle, urodele amphibian, teleost, shark, skate, hagfish, and lobster. Estrone, 17 beta-estradiol, or 17 alpha-estradiol was formed by central neural tissues of all species, with the exception of the opossum, hagfish, and lobster. Aromatase activity was concentrated in the forebrain, although some estrogen was synthesized by mid- or hindbrain homogenates of two lower vertebrates (teleost and skate) and the newly hatched chick. 5 alpha-Androstanedione (5 alpha-androstane-3,17-dione) or 5 alpha-dihydrotestosterone were products of metabolism in several nonmammalian vertebrates and in the invertebrate central nervous system also. 5 alpha-Reductase was found in all major brain divisions. These and previously reported comparative studies indicate that the ability to aromatize and otherwise transform androgen substrates is a primitive characteristic of the brain that has been widely conserved phylogenetically.

Androstenedione↗
PubMed1979

[Winter sport injuries in childhood (author's transl)].

3374 accidents occurring on the field of sport during the years 1975--1977 accounted for 19% of all accidents dealt with at the Institute of Kinderchirurgie in Graz. 51% of the accidents were caused by the typical winter sports: skiing, tobogganing, ice-skating and ski-jumping with skiing accounting for 75% of the accidents. The fracture localization typical of the different kinds of winter sport is dealt with in detail. The correct size and safety of the equipment were found to be particularly important in the prevention of such accidents in childhood.

Adolescent↗