SEARCH · PubMed Health

Results for “Skating”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1976

Comparison of the temperature sensitivity of protein synthesis by cell-free systems from liver of rat and skate (Raja ocellata).

Studies were undertaken to determine the component(s) responsible for the temperature optimum characteristic of the protein-synthesizing system from skate and rat. 1. The macromolecular constituents of rat and skate liver ribosomes are compared. The number of ribosomal proteins is similar in the two species, although most proteins display different electrophoretic mobilities on polyacrylamide gels. The RNAs from the small subunit of skate and rat have similar sedimentation coefficients; however, the RNA from the large subunit of skate ribosomes appeared to be slight smaller than the comparable RNA from the rat. 2. Ribosomes from either rat or skate were capable of supporting poly(U)dependent polyphenylalanine synthesis with soluble factors from either species. 3. Maximal leucine incorporation directed by endogenous mRNA occurred at 35--40 degrees C with post-mitochondrial supernatant from the rat liver and at 20--30 degrees C with that from skate liver. 4. The characteristic temperature sensitivity of protein synthesis was dependent upon the source of cell sap and independent of the source of ribosomes. 5. Elongation factor 1 from both the rat and skate exhibited maximum activity at approx. 30 degrees C. 6. Phenylalanyl-tRNA synthetase from skate liver showed maximum activity at 30 degrees C while that from rat was maximally active at 37 degrees C. The rat enzyme, however, was active at 0--10 degrees C, at which temperature protein synthesis in the reconstructed rat system is virtually absent. 7. The protein-synthesizing capacity of the reconstituted system at various temperatures was closely correlated with the activity of Elongation factor 2 (translocase). Elongation factor 2 from rat liver displayed an optimum at 30 degrees C and lost all activity below 10 degrees C, while this same factor from skate liver showed an optimum at 20 degrees C and significant activity below 10 degrees C. At this low temperature the reconstituted skate liver system continued to exhibit the ability to synthesize protein. These studies suggest that Elongation factor 2 is the component responsible for determining the temperature at which the protein-synthesizing system displays its characteristic maximum activity.

Animals↗

PubMed1977

Free amino acids in tissues of the skate Raja erinacea and the stingray Dasyatis sabina: effects of environmental dilution.

Concentrations of individual free amino acids were determined in various tissues of the skate (Raja erinacea) and the stingray (Dasyatis sabina), and the relationship of cellular free amino acid concentrations to intracellular osmoregulation was investigated by adapting these elasmobranchs to half-strength seawater. Each tissue characteristically had high levels of certain specific amino acids. Skate sing muscle contained high concentrations of sarcosine and beta-alanine, skate heart had high concentrations of taurine, and skate erythrocytes had high levels of taurine and beta-alanine. Amino acid levels in skate plasma were very low. High concentrations of aturine and glutamate were found in stingray brain. Adaptation of skates and stingrays to half-strength seawater was accompanied by significant decreases in concentrations of the major free amino acids in skate wing muscle and erythrocytes and in stingray brain, but not in skate heart. The data suggest that in these elasmobranchs certain specific free amino acids are selectively involved in intracellular osmoregulatory mechanisms.

Adaptation, Physiological↗

PubMed2026

Developmental analysis of the cone photoreceptor-less little skate retina reveals distinct Onecut1 isoforms.

The retinal development of elasmobranchs, the subclass comprising sharks, skates, and rays, remains poorly understood. This group is diverse in retinal phenotype, with many sharks and rays possessing rods together with one or more cone types. In contrast, the little skate (Leucoraja erinacea) has only a single rod photoreceptor type, which has been reported to exhibit some physiological and anatomical properties associated with cones. To investigate how this unusual photoreceptor system develops, we first identified an embryonic stage of early photoreceptor formation based on otx2 expression. We then developed a retinal electroporation approach to test whether a onecut1-dependent cone-associated reporter could be activated in the embryonic skate retina. Activation of this reporter was not detected, indicating that the corresponding enhancer is not robustly active under the conditions tested. To assess developmental changes in gene expression, we generated bulk RNA-seq datasets from embryonic, hatchling, and adult retinas. These analyses showed strong embryonic expression of onecut1, increasing expression of rod-associated genes through development, and pseudogenization or loss of multiple cone-enriched genes. We further identified a developmentally regulated onecut1 splice isoform containing an additional 48 amino acid sequence between the CUT and homeodomain DNA-binding domains. This spacer-containing isoform, termed LSOC1X2, was most abundant in the embryonic retina. To test whether LSOC1X2 retained regulatory activity, we assayed it in a mouse retinal reporter system. Both skate Onecut1 isoforms activated the ThrbCRM1 reporter in this heterologous context. Together, these findings identify a novel, developmentally regulated retinal onecut1 isoform in the little skate and establish it as a candidate regulator for future studies of photoreceptor development in this species and its elasmobranch relatives.

Animals↗

PubMed1977

Bilirubin metabolism in the spiny dogfish, Squalus acanthias, and the small skate, Raja erinacea.

1. The main bilirubin conjugate in bile of spiny dogfish (Squalus Acanthias) and small skate (Raja Erinacea) is bilirubin monoglucuronide. 2. Microsomal preparations from dogfish and small skate liver have similar bilirubin UDPglucuronyltransferase (UDPGT) activity and catalyze the conjugation of bilirubin with glucose from UDPglucose. 3. The activity of bilirubin glucosidation (UDPGT) was 0.5 times UDPG1T activity in dogfish and 0.15 times in skate liver microsomes. 4. Sodium cholate increased UDPGT and UDPG1T activities in dogfish and skate liver microsomal preparations only minimally, but the detergent markedly increased thermolability of UDPGT in skate liver microsomes.

Animals↗

PubMedDate not supplied

Conditioning program for competitive figure skating.

To test the feasibility that traditional interval training methods could be adapted to the needs of competitive figure skaters, an interval skating program was conducted during a 3-month period for a group of skaters at diverse levels of proficiency. The program required only a small portion of the total ice time utilized by the skaters on a daily basis, i.e., 1/2 hr, three times a week. On alternate days, the skaters used the same amount of time in a strength training program. A flexibility-stretching facet was to be done by the skaters on a daily basis. Progress was evaluated by treadmill oxygen consumption determinations and ability to perform a 1/2-mile skate effort. Over the course of the 3-month period, the skaters in the program showed an average increase in oxygen consumption of 9% from 44.73 cc per kg per min to 55.51 cc per kg per min. This was accompanied by an average 10-sec reduction in the timed effort at the 1/2-mile skate. Subjectively, the skaters were less fatigued during their freestyle skating programs and were able to improve consistency at skilled maneuvers in the last minute of their performances. This initial effort to evaluate the efficacy of this type of a training program for competitive figure skating seems to have proven to be beneficial to the skaters. Currently, we are continuing our efforts to expand the program.

Adolescent↗

PubMed1978

Glycogen depletion patterns during continuous and intermittent ice skating.

The glycogen depletion patterns in the vastus lateralis muscle were studied during ice skating using eight hockey players. For each subject, exercise consisted of either repeated bouts (10) of high intensity work (120% Vo2 max) or continuous work (60 min) of low intensity (55% Vo2 max). During continuous skating, glycogen showed a 29% decline (p less than 0.05) over the 60 min. In the intermittent condition, there was a two fold greater depletion (p less than 0.05) with the most rapid loss occurring during the first five, one min work bouts. Histochemical analysis by fiber type indicated that the most pronounced glycogen loss was from the Type I fibers during continuous skating whereas during the intermittent condition, a preferential loss occurred in the Type II fibers, most notably the Type IIB fibers. Measurements of muscle metabolites during continuous skating indicated no change for ATP from the rest condition at 30 or 60 min, a reduction (p less than 0.05) in CP (4.1 mmoles.kg-1) at 60 min and an elevation (p less than 0.05) in lactate (0.85 mmoles.kg-1) at 60 min. In the intermittent condition, reductions (p less than 0.05) in ATP (0.47 mmoles.kg-1) and CP (8.7 mmoles.kg-1) and elevations (p less than 0.05) in lactate (21.7 mmoles.kg-1) were found following 5 work bouts. Thereafter, no significant changes were observed. It is concluded that the glycogen depletion patterns and alteration in muscle metabolites are similar to those seen during cycling at similar percentages of Vo2 max.

Adenosine Triphosphate↗

PubMed1979

Fatigue in ice skating: biomechanical considerations.

This paper attempts to describe how the mechanical patterns in ice skating are affected by muscular fatigue. It reviews several investigations dealing with the effects of muscular fatigue on standing broad jump performance and running. It concludes that fatigue studies dealing with ice skating can be expected to show that the mechanical patterns in ice skating deteriorate as a result of muscular fatigue.

Biomechanical Phenomena↗

PubMed1975

Histological changes associated with trichodinid infections in thorny skates, Raja radiata Donovan.

Histological changes in the wall of the copulatory sac of normal adult female thorny skates, Raja radiata, were compared with those naturally infected with Trichodina oviducti. The parasites were associated with extensive defoliation of the copulatory epithelium and in some instances had penetrated the submucosa resulting in petechiae. An excessive exudated that appeared at the vent was made up of mucus, sloughed cells and parasites. It is speculated that shedding of the copulatory epithelium may be due to a hyaluronidase-like enzyme. Furthermore, the restriction of T. oviducti to adult skates may be dependent on the presence of certain mucopolysaccharides that are very low or absent in immature skates.

Animals↗

PubMed1978

scyllo-inositol and myo-inositol levels in tissues of the skate Raja erinacea.

1. Many organs of the skate Raja erinacea have been found to contain scyllo-inositol levels that are much higher than myo-inositol, the opposite to that found in mammals. 2. Both inositols were found in all skate organs studied. 3. myo-Inosose-2 was found to accompany the inositols in many of these organs.

Animals↗

PubMed1976

Energy cost of speec skating and efficiency of work against air resistance.

The energy expenditure during speed ice skating (PB=650 mmHg; T=-5 degrees C) was measured on 13 athletes (speed range: 4-12 m/s) from VO2 and (for speeds greater than 10 m/s) from blood lactic acid concentration. The energy spent (O2 equivalents) per unit body wt and unit distance (Etot/V, ml/kg-min) increases with the speed (v, m/s): Etot/v=0.049 + 0.44 X 10(-3) V2. At 10 m/s, Vtot/v amounts then to 0.093 ml/kg-m: about half the value of running. The constant 0.049 ml/kg-m is interpreted as the energy spent against gravitational and inertial forces. The term 0.44 X 10(-3) v2 indicates the energy spent against the wind, the constant 0.44 X 10(-3) ml-s2-kg-1-m-3 being a measure of k/e, where k is the coefficient relating drag to v2, and e the efficiency of work against the wind. From a direct estimate of k in a wind tunnel, e was calculated as 0.11. In running, skating, and cycling k/e is similar (approximately 0.020 ml-s2-m-3 per m2 body area), hence at a given speed the energy spent against the wind is equal. On the contrary, the energy spent against other forces decreases in the above order: 0.19, 0.05, 0.018 ml-m-1 per kg body wt. This explains the different speeds attained in these exercises with the same power output.

Adult↗

PubMed1977

Renal tubule ion transport and collecting duct function in the elasmobranch little skate, Raja erinacea.

Renal micropuncture and microdissection techniques with ultramicro fluid analysis have been applied to evaluate single nephron function in the skate, Raja erinacea. We have divided the skate nephron into three proximal tubular segments (PTS I-III), three distal coilings (DC I-III), and a countercurrent loop system located between the proximal segments and the distal coilings. The collecting duct is the principal site of urinary dilution. Following exposure of the fish to 75% seawater for about 24 hours, the sodium concentration difference between the end collecting duct lumen and plasma is decreased sufficiently to account for the urinary dilution. The principal site for magnesium, phosphate and sulphate secretion appears to be PTS II. This segment is located on the ventral surface of the kidney. PTS II is also the main nephron site for reabsorption of sodium and chloride in excess of water.

Animals↗

PubMed1975

Retinal mechanisms of visual adaptation in the skate.

Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly iluminated background that had no measurable effect on the senitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and gaglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.

Animals↗

PubMed1977

Rhodopsin photoproducts and rod sensitivity in the skate retina.

The late photoproducts that result from the isomerization of rhodopsin have been identified in the isolated all-rod retina of the skate by means of rapid spectrophotometry. The sequence in which these intermediates form and decay could be described by a scheme that incorporates two pathways for the degradation of metarhodopsin II (MII) to retinol: one via metarhodopsin III (MIII) and the other (which bypasses MIII) through retinal. Computer simulation of the model yielded rate constants and spectral absorbance coefficients for the late photoproducts which fit experimental data obtained at temperatures ranging from 7 degrees C to 27 degrees C. Comparing the kinetics of the thermal reactions with the changes in rod threshold that occur during dark adaptation indicated that the decay of MII and the fall in receptor thresholds exhibit similarities with regard to their temperature dependence. However, the addition of 2 mM hydroxylamine to a perfusate bathing the retina greatly accelerated the photochemical reactions, but had no significant effect on the rate of recovery of rod sensitivity. It appears, therefore, that the late bleaching intermediates do not control the sensitivities of skate rods during dark adaptation.

Animals↗

PubMedDate not supplied

Cupula motion in the semicircular canal of the skate, Raja erinacea. An experimental investigation.

An upper bound on the magnitude of semicurcular canal cupula motion was experimentally determined in the isolated labyrinth of the skate, Raja erinacea. To visualize the cupula, a glass pipette was pushed through the ampullary wall, and local regions of the cupula were stained by slow infusion of small amounts of Alcian Blue dye. Caloric stimuli which produced large changes in single unit activity in the ampullary nerve and which often recruited several larger, previously silent units were found to produce on detectable cupula motion as seen through the ampulla wall. However when the cupula was first grossly displaced, motion was thereafter observed in response to identical caloric stimuli. Analysis of afferent responses indicates that the normal range of cupula motion in the skate is below the optical resolution of the method, conservatively estimated as 3--5 micrometers.

Animals↗

PubMed1975

Two new species of Echeneibothrium (Cestoda: Tetraphyllidea) from skates in the western North Atlantic.

Echeneibothrium bathyphilum sp. n. is described from the deep-sea skate, Raja bathyphila Holt and Byrne. Echeneibothrium sobrinum sp. n., a parasite in the spiral intestine of the skates Raja ocellata Mitchill and Raja erinacea Mitchill, is described from Vineyard Sound near Woods Hole, Massachusetts. Additional data are given for E. vernetae Euzet, 1956, from living and fixed specimens obtained from the type host in the type locality. Morphology of the strobilae and bothridia, testes numbers, and cirrus pouch dimensions clearly distinguish the new species from all others.

Animals↗

PubMed1978

Sensitizing activity of 9,13-dicis retinal in bleached photoreceptors of the skate.

9,13-dicis Retinal was externally applied to photoreceptors of isolated skate retina that previously had been desensitized by bleaching irradiation. This treatment led to a significant lowering of photoreceptor threshold and to the intracellular formation of isorhodopsin II, an artificial visual pigment containing 9,13-dicis retinal as its chromophore. These results suggest that isorhodopsin II can function in situ to promote an increase in the visual sensitivity of skate photoreceptors.

Animals↗

PubMed1979

A comparison of selected hockey skating starts.

The purpose of this study was to determine the effectiveness of three different methods of initiating forward movement (IFM). Six S's from four levels of Ice Hockey competition were instructed in the methods then were timed for 20 feet of forward skating from a standing start. Selected S's within each group were also analyzed biomechanically, via the cinema-computer process. Both statistical and biomechanical analysis showed a superiority of the rarely taught thrust and glide or "t" start over the two conventional techniques, the cross-over and normal standing start facing the direction of movement. Results indicate a need to include the thrust and glide in Ice Hockey instructional programs.

Biomechanical Phenomena↗

PubMed1978

Generation of b-wave currents in the skate retina.

Potassium kinetics within the skate retina were monitored extracellularly with K+-selective electrodes. Two sources of K+ efflux were detected in response to photic stimulation: one in the distal retina in the region of the outer plexiform layer, and the other at a more proximal location near the border between the inner nuclear and inner plexiform layers. The magnitude of the K+ efflux at these retinal depths was affected differently by spot and full-field illumination, suggesting that the two sources originate from different classes of neuron. There is evidence that both sources are associated with current sinks provided by the Müller cells, thereby establishing radial current paths along the lengths of these elements. We have proposed a model in which asymmetries in the magnitudes of these currents give rise to the b-wave of the electroretinogram. Extracellular field potentials recorded differentially at various retinal depths, and in response to changes in stimulus configuration, were consistent with predictions of the model.

Animals↗