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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↗
PubMed1992

Identification of vitellogenin in the little skate (Raja erinacea).

1. Vitellogenin was isolated from mature female skates by selective precipitation with MgCl2/EDTA followed by chromatography on DEAE-cellulose columns. 2. A single monomer of approximately 205 kDa was identified on 6.0% SDS-PAGE gels. 3. In addition, isolation of yolk proteins with ammonium sulfate yielded proteins of 94 and 38 kDa (putative phosvitins) and putative lipovitellins of ca 105, 91 and 67 kDa. 4. In vivo phosphate incorporation in female and male skates implanted with estradiol indicated that vitellogenin was phosphorylated. 5. Total protein phosphate incorporation was significantly higher in females than male skates. 6. In male skates treated with estradiol, phosphate incorporation increased from 2 days after implantation to a maximum at approximately 11 days after implantation. 7. Determination of the rate of disappearance of 32P-labeled protein suggests a half-life of ca 200 hr in normal female skate plasma.

Animals↗
PubMed2002

Injuries associated with inline skating in the European region.

OBJECTIVES: To gain greater awareness and understanding of the circumstances leading to injuries associated with inline skating and to provide indices for determining preventive measures. METHODS: Data on injuries during inline skating were collected from seven member states of the European Union (EU) through the European Home and Leisure Accident Surveillance System (EHLASS). RESULTS: The mean incidence rate for injuries while inline skating is 17 per 100,000 inhabitants. In the EU in 1996, about 65,000 people were treated at an Emergency Department for an inline skate injury (excluding traffic injuries). About 60% of the victims are male, while the age group most at risk is 10-14 years old. Most injuries are due to a fall and wrist injuries are most common. CONCLUSIONS: The results of the analysis give indications for possible preventive measures. Although the features of the injuries often differ per country, the countries can learn from each other in preventing these types of injuries. Educational campaigns should be targeted at young teenagers, use of protective equipment (like wrist protectors) and skating techniques. EHLASS has potential for intercountry comparisons, but its value will improve if selecting hospitals and coding agreements will be standardised.

Adolescent↗
PubMedDate not supplied

Gap-junctional properties of electrically coupled skate horizontal cells in culture.

Whole-cell voltage-clamp recordings were used to examine the unusual pharmacological properties of the electrical coupling between rod-driven horizontal cells in skate retina as revealed previously by receptive-field measurements (Qian & Ripps, 1992). The junctional resistance was measured in electrically coupled cell pairs that had been enzymatically isolated and maintained in culture; the typical value was about 19.92 M omega (n = 45), more than an order of magnitude lower than the nonjunctional membrane resistance. These data and the intercellular spread of the fluorescent dye Lucifer Yellow provide a good indication that skate horizontal cells are well coupled. The junctional conductance between cells was not modulated by the neurotransmitters dopamine (200 microM) or GABA (1 mM), nor was it affected by the membrane-permeable analogues of cAMP or cGMP, or the adenylate cyclase activator, forskolin. Although resistant to agents that have been reported to alter horizontal-cell coupling in cone-driven horizontal cells, the junctional conductance between paired horizontal cells of skate was greatly reduced by the application of 20 mM acetate, which is known to effectively reduce intracellular pH. Together with the results obtained in situ on the receptive-field properties of skate horizontal cells, these findings indicate that the gap-junctional properties of rod-driven horizontal cells of the skate are fundamentally different from those of cone-driven horizontal cells in other species. This raises the possibility that there is more than one class of electrical synapse on vertebrate horizontal cells.

Animals↗
PubMedDate not supplied

Cloning, immunolocalization, and functional expression of a GABA transporter from the retina of the skate.

Termination of GABA signals within the retina occurs through high-affinity reuptake of the released neurotransmitter by GABA transporters (GATs) present in neurons and glia surrounding the release site. In the present work, we have cloned a novel GAT from the retina of the skate (Raja erinacea). The clone codes for a 622 amino acid protein whose sequence has highest similarity to the GABA/beta-alanine transporter of the electric ray (Torpedo marmorata) (88% identity) and the GAT-3 isolated from rat brain (75% identity). The protein was expressed in Xenopus oocytes and characterized using the two-electrode voltage-clamp technique. Application of GABA induced a dose-dependent inward current, with 8 muM GABA producing a half-maximal response. The current required the presence of extracellular sodium and was unaffected by the GABA receptor blocker picrotoxin or the GAT-1 specific antagonist NO-711. The high homology between the cloned skate GABA transporter and the GAT-3 equivalents of other species, coupled with the strikingly similar pharmacological profile to GAT-3s of other species, lead us to conclude that we had cloned the GAT-3 homologue for the skate. Polyclonal antibodies specific to GAT-3 and the previously cloned skate GAT-1 transporter were used to examine the distribution of GAT-3 and GAT-1 immunoreactivity in the retina and in isolated cells of the skate. Antibodies for both transporters showed labeling in the outer and inner plexiform layers, and staining extended from the outer to inner limiting membranes.

Amino Acid Sequence↗
PubMed2000

A primitive ATP receptor from the little skate Raja erinacea.

P2Y ATP receptors are widely expressed in mammalian tissues and regulate a broad range of activities. Multiple subtypes of P2Y receptors have been identified and are distinguished both on a molecular basis and by pharmacologic substrate preference. Functional evidence suggests that hepatocytes from the little skate Raja erinacea express a primitive P2Y ATP receptor lacking pharmacologic selectivity, so we cloned and characterized this receptor. Skate hepatocyte cDNA was amplified with degenerate oligonucleotide probes designed to identify known P2Y subtypes. A single polymerase chain reaction product was found and used to screen a skate liver cDNA library. A 2314-base pair cDNA clone was generated that contained a 1074-base pair open reading frame encoding a 357-amino acid gene product with 61-64% similarity to P2Y(1) receptors and 21-37% similarity to other P2Y receptor subtypes. Pharmacology of the putative P2Y receptor was examined using the Xenopus oocyte expression system and revealed activation by a range of nucleotides. The receptor was expressed widely in skate tissue and was expressed to a similar extent in other primitive organisms. Phylogenetic analysis suggested that this receptor is closely related to a common ancestor of the P2Y subtypes found in mammals, avians, and amphibians. Thus, the skate liver P2Y receptor functions as a primitive P2Y ATP receptor with broad pharmacologic selectivity and is related to the evolutionary forerunner of P2Y(1) receptors of higher organisms. This novel receptor should provide an effective comparative model for P2Y receptor pharmacology and may improve our understanding of nucleotide specificity among the family of P2Y ATP receptors.

Amino Acid Sequence↗
PubMed1992

Receptive field properties of rod-driven horizontal cells in the skate retina.

The large receptive fields of retinal horizontal cells result primarily from extensive intercellular coupling via gap (electrical) junctions; thus, the extent of the receptive field provides an index of the degree to which the cells are electrically coupled. For rod-driven horizontal cells in the dark-adapted skate retina, a space constant of 1.18 +/- 0.15 mm (SD) was obtained from measurements with a moving slit stimulus, and a comparable value (1.43 +/- 0.55 mm) was obtained with variation in spot diameter. These values, and the extensive spread of a fluorescent dye (Lucifer Yellow) from the site of injection to neighboring cells, indicate that the horizontal cells of the all-rod retina of skate are well coupled electrically. Neither the receptive field properties nor the gap-junctional features of skate horizontal cells were influenced by the adaptive state of the retina: (a) the receptive field organization was unaffected by light adaptation, (b) similar dye coupling was seen in both dark- and light-adapted retinae, and (c) no significant differences were found in the gap-junctional particle densities measured in dark- and light-adapted retinas, i.e., 3,184 +/- 286/microns 2 (n = 8) and 3,073 +/- 494/microns 2 (n = 11), respectively. Moreover, the receptive fields of skate horizontal cells were not altered by either dopamine, glycine, GABA, or the GABAA receptor antagonists bicuculline and picrotoxin. We conclude that the rod-driven horizontal cells of the skate retina are tightly coupled to one another, and that the coupling is not affected by photic and pharmacological conditions that are known to modulate intercellular coupling between cone-driven horizontal cells in other species.

Animals↗
PubMed1999

Comparison between the physiological response to roller skiing and in-line skating in biathletes.

PURPOSE: Roller skiing is frequently used in Nordic disciplines during the off-season periods. Recently, in-line skating has become a potential alternative. In the present study, the responses of heart rate, oxygen uptake, respiratory exchange ratio, and lactic acid concentration to roller skiing and in-line skating were compared in competitive biathletes. METHODS: Eight male subjects performed three tests with both devices on a hilly outdoor track. They were requested to adjust their speed in such a way that the following criteria were met: intensity 1, lactate concentration about 2 mmol x L(-1); intensity 2, lactate concentration about 4 mmol x L(-1); AND intensity 3, maximal speed. RESULTS: Though the subjects were not experienced in-line skaters, all managed to adjust the required intensities. This was achieved through increased velocities during in-line skating. Independent of the exercise intensity the differences in speed ranged between 1.0 and 1.4 m x s(-1). The relationships between lactic acid concentration, oxygen uptake, respiratory exchange ratio, and heart rate were not influenced by the test device. The respiratory exchange ratio amounted to 0.88, 0.95, and 1.02 for intensities 1 to 3, respectively. CONCLUSIONS: These results show that in-line skating can be regarded as an alternative to roller skiing for off-seasonal training in Nordic disciplines. A potential advantage of in-line skating is that aerobic training intensities can be obtained at competitive velocities.

Adult↗
PubMed1988

Roller skating injuries in children.

Many children who roller skate sustain injuries. To determine the type and severity of these mishaps, the medical records of 76 children less than 16 years of age with roller skating injuries presenting to two pediatric emergency departments were reviewed. Seventy-five percent were girls, and 25% were boys. The upper extremity was the most common body part injured (74%) (P less than 0.0001). Lower extremity injuries occurred in 12%, head and face injuries in 10%, and chest injuries in 4%. The most common type of injury was a fracture (69%), with the wrist and forearm being most frequently fractured (53%). Hospitalization and long-term sequelae were infrequent. Younger children (less than or equal to 9) had an increased frequency of fracture injury (P less than 0.02). This is most likely because maturation of lower and upper extremity speed, strength, agility, coordination, balance, and reaction time and morphologically stronger bones combine to afford relative protection to the older child. Physicians and parents need to be aware of a child's skill level before the child is encouraged to roller skate. Measures which may decrease the likelihood of injury include protective gear, instruction in roller skating technique, learning to skate in an uncongested area on level, familiar terrain, and learning to fall properly.

Accident Prevention↗
PubMed2006

Nonparticipant injuries associated with skating activities.

OBJECTIVE: Children are at risk for injury even if they are not active recreational participants. This study describes the epidemiology of pediatric nonparticipant skating-related injuries treated in hospital emergency departments in the United States from 1993 to 2003. METHODS: Narratives of injuries identified by the US Consumer Product Safety Commission's National Electronic Injury Surveillance System consumer product codes as ice-skating, roller-skating, and in-line skating-related were reviewed. RESULTS: Fifty-eight children were treated for nonparticipant skating-related injuries in National Electronic Injury Surveillance System emergency departments. Mechanisms of injury included being stepped on (36.2%), dropped (34.5%), or kicked (12.1%) by skaters and collision with skaters (17.2%). The most common body regions injured were the lower extremities (41.4%), upper extremities (24.1%), and head (20.7%). Contusions/abrasions (32.8%), lacerations (20.7%), and fractures (19.0%) were the most common diagnoses. Children who were dropped sustained more head injuries than children injured by other mechanisms (relative risk [RR], 20.9; 95% confidence interval [CI], 2.9-150.5; P < 0.001) and were younger than those stepped on (RR, 1.5; 95% CI, 1.1-2.2; P = 0.02) or kicked (RR, 6.7; 95% CI, 1.1-40.9; P < 0.001). Children stepped on by skaters experienced more injuries to the extremities than children who were dropped by (RR, 3.3; 95% CI, 1.7-6.5; P < 0.001) or collided with skaters (RR, 1.7; 95% CI, 1.0-2.8; P < 0.01). CONCLUSIONS: Children are at risk for injury when they are around skaters. The risk of such injuries can be reduced if children are never carried by skaters, young children are closely supervised to avoid collisions, and skaters are cautioned against kicking or stepping on other children.

Adolescent↗
PubMed2000

ATP-dependent GSH and glutathione S-conjugate transport in skate liver: role of an Mrp functional homologue.

Multidrug resistance-associated proteins 1 and 2 (Mrp1 and Mrp2) are thought to mediate low-affinity ATP-dependent transport of reduced glutathione (GSH), but there is as yet no direct evidence for this hypothesis. The present study examined whether livers from the little skate (Raja erinacea) express an Mrp2 homologue and whether skate liver membrane vesicles exhibit ATP-dependent GSH transport activity. Antibodies directed against mammalian Mrp2-specific epitopes labeled a 180-kDa protein band in skate liver plasma membranes and stained canaliculi by immunofluorescence, indicating that skate livers express a homologous protein. Functional assays of Mrp transport activity were carried out using (3)H-labeled S-dinitrophenyl-glutathione (DNP-SG). DNP-SG was accumulated in skate liver membrane vesicles by both ATP-dependent and ATP-independent mechanisms. ATP-dependent DNP-SG uptake was of relatively high affinity [Michaelis-Menten constant (K(m)) = 32 +/- 9 microM] and was cis-inhibited by known substrates of Mrp2 and by GSH. Interestingly, ATP-dependent transport of (3)H-labeled S-ethylglutathione and (3)H-labeled GSH was also detected in the vesicles. ATP-dependent GSH transport was mediated by a low-affinity pathway (K(m) = 12 +/- 2 mM) that was cis-inhibited by substrates of the Mrp2 transporter but was not affected by membrane potential or pH gradient uncouplers. These results provide the first direct evidence for ATP-dependent transport of GSH in liver membrane vesicles and support the hypothesis that GSH efflux from mammalian cells is mediated by members of the Mrp family of proteins.

ATP-Binding Cassette Transporters↗
PubMed2003

Molecular characterization of the skate peripherin/rds gene: relationship to its orthologues and paralogues.

PURPOSE: A great deal of information about functionally significant domains of a protein may be obtained by comparison of primary sequences of gene homologues over a broad phylogenetic base. This study was designed to identify evolutionarily conserved domains of the photoreceptor disc membrane protein peripherin/rds by analysis of the homologue in a primitive vertebrate, the skate. METHODS: A skate retinal cDNA library was screened using a mouse peripherin/rds clone. The 5' and 3' untranslated regions of the skate peripherin/rds (srds) cDNA were isolated by the rapid amplification of cDNA ends (RACE) approach. The gene structure was characterized by PCR amplification and sequencing of genomic fragments. Northern and Western blot analyses were used to identify srds transcript and protein, respectively. RESULTS: A new homologue of peripherin/rds was identified from the skate retinal cDNA library. SRDS is a glycoprotein with a predicted molecular mass of 40.2 kDa. The srds gene consists of two exons and one small intron and transcribes into a single 6-kb message. Phylogenetic analysis places SRDS at the base of peripherin/rds family and near the division of that group and the branch leading to rds-like and rom-1 genes. SRDS protein is 54.5% identical with peripherin/rds across species. Identity is significantly higher (73%) in the intradiscal domains. Sequence comparison revealed the conservation of all residues that have been shown, on mutation, to associate with retinitis pigmentosa and showed conservation of most residues associated with macular dystrophies. Comparison with ROM-1 and other rds-like proteins revealed the presence of a highly conserved domain in the large intradiscal loop. CONCLUSIONS: Srds represents the skate orthologue of mammalian peripherin/rds genes. Conservation of most of the residues associated with human retinal diseases indicates that these residues serve important functional roles. The high degree of conservation of a short stretch within the large intradiscal loop also suggests an important function for this domain.

Amino Acid Sequence↗
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↗
PubMed1994

Electric organ discharge and electrosensory reafference in skates.

Skates possess bilateral electric organs that produce intermittent, weak discharges of relatively long duration compared to the discharges of other weakly electric fish. They, like all elasmobranchs, also have an electrosensory system capable of detecting weak, low-frequency electric fields. Several studies have suggested that the discharge is used in some type of social communication. This study measured the strength and nature of the response of the skate electrosensory system to electric organ discharge. Electric organ discharge (EOD) was elicited via electrical stimulation of the medullary command nucleus in two species of skates. The temporal structure and power spectra of the EODs demonstrated that they should be effective stimuli for the skate electrosensory system. The responses of electrosensory afferent fibers in the anterior lateral line nerve (ALLN) to EODs were variable depending upon the location and orientation of the receptor. The responses of most ALLN fibers were very weak compared to the strong reafference produced by the skate's ventilatory activity. Unlike the common-mode ventilatory reafference, EOD reafference was variable in terms of excitation or inhibition, depending upon receptor orientation. Despite the low signal-to-noise ratio observed in ALLN responses to EODs, it is likely that EODs serve as a communicative signal over moderate distances.

Action Potentials↗
PubMed2000

In-line skating: injuries and prevention.

BACKGROUND: Most reports on in-line skating injuries describe severe injuries admitted to injury clinics. Little is known about the overall rate of injury and the contribution of the different disciplines. METHODS: In a retrospective inquiry data on injuries were obtained of 105 in-line skaters of whose 69% were active in fitness skating, 59% in jumping/grinding and 51% in the halfpipe. Beside the nature, location and degree of the injury, information was given on where the injury happened and whether protectors were worn at the time of injury. RESULTS: Of 197 injuries 145 healed without medical treatment, 28 needed medical advice once, 22 several times and 2 needed hospitalisation. Injury location were 38% in the upper, 31% in the lower extremities, 21% in the hip/pelvis region and 10% on the head. The most frequent injuries pertained to concussions and skin lesions, 35% each, followed by ligament injuries with 10% and fractures with 5%. Simple injuries were 83% in fitness skating, 70% in jumping/grinding and 60% in the halfpipe. Several visits were necessary for 4% of fitness skaters, 10% of jumpers/grinders and 23% in halfpipe injured persons. All four protectors were worn at the time of injury by 5% in fitness skating, 18% in jumping/grinding and 55% in the halfpipe. No protectors were worn in 26% of the fitness injuries, in 9% jumping/grinding and in 6% in the halfpipe. CONCLUSIONS: The results reveal an apparent discipline specific degree of danger and that fitness in-line skating is less dangerous than the resulting benefits for preventive medicine.

Accidental Falls↗
PubMed1983

[Development, evaluation and application of a dynamometric system of skates].

The present paper accounts for the elaboration validation and application of a dynamometric system device for ice skates that allows measurements of the forces and the point of application of their resultant on the blade during ice skating. The dynamometric system was built using strain gauges fixed to the frame of the blade and mounted in a Wheatstone bridge network which enabled after proper calibration to record force measurements. The type of frame chosen for the blade and the various modifications that were brought to it appear essential for the applicability of the system. In order to conduct a dynamic study of the "stop" during skating the system was coupled with a cinematographic technique enabling measurements of tridimensional angles of the skates. Two male subjects completed five "stops" at three different determined speeds. Results indicated that dynamometric systems build with frames of modified metal blades were of an adequate precision for measuring forces. Moreover coupling of the system with the cinematographic technique allowing measurements of tridimensional angles provides a powerful and innovative tool for the dynamic study of ice skating.

Biomechanical Phenomena↗
PubMed1995

Physiological responses to in-line skating compared to treadmill running.

The physiologic responses to in-line skating were compared to those during treadmill running in 16 active males (18-37 yr). Each subject performed a VO2max test during in-line skating and treadmill running using speed-incremented, discontinuous protocols. Protocols were designed so that each subject completed 4-6 stages. Stages were 3 min in duration and separated by a 5-min rest period. It was found that absolute VO2max (4.19 vs 4.44 l.min-1, P = 0.045), relative VO2max (56.8 vs 59.9 ml.kg-1.min-1, P = 0.054), and HRmax (189 vs 194 b.min-1, P < 0.05) were lower for in-line skating compared to treadmill running. Regression analyses were used to determine the submaximal relationship between modalities. There were no significant (P > 0.05) differences in the slope and y-intercept of the HR/VO2 relationship, indicating a similar metabolic load at a given heart rate for both modes of exercise. Skating between 17.7-20.9 km.h-1 corresponded to 60-75% of VO2max or 75-90% of HRmax, which are common training intensities and within the guidelines recommended by the ACSM. Across the speeds investigated, caloric expenditure was 9.5-19.0 kcal.min-1. These results indicate that in-line skating elicits physiological responses comparable to treadmill running and thus would be another exercise alternative for improving aerobic capacity or maintaining body weight.

Adult↗
PubMed1994

Comparison of in-line skating injuries with rollerskating and skateboarding injuries.

OBJECTIVE: To describe the estimated relative frequency, types of injuries, and demographic features of people injured while in-line skating, rollerskating, and skateboarding in the United States. DESIGN: Case series. SETTING: Emergency department visits to hospitals participating in the National Electronic Injury Surveillance System. PARTICIPANTS: All persons treated for a product-related injury involving in-line skates, rollerskates, or a skateboard between July 1, 1992, and June 30, 1993. RESULTS: Approximately 30,863 persons (95% confidence interval, 23,073 to 38,653) were treated for in-line skating injuries during the study period. For every in-line skating injury, approximately 3.3 rollerskating and 1.2 skateboarding injuries occurred (P < .0001). The median age of those injured in these three sports was 15, 12, and 13 years, respectively (P < .0001). Sixty-three percent of injured in-line skaters had a musculoskeletal injury, including 37% with a wrist injury, of which two thirds were fractures and/or dislocations. Five percent of all injured in-line skaters had head injury and 3.5% of the injured in-line skaters required hospitalization. CONCLUSIONS: In-line skating and skateboarding injuries resulted in a similar number of emergency department visits, but fewer than that for rollerskating injuries. Because wrist fractures were the most common type of injury in all three sports, wrist protection is needed. Head protection by helmets is recommended.

Adolescent↗