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PubMed1984

Bicycle ergometry and speed skating performance.

A comparison between maximal power output during cycling and skating was made, and correlates of skating performance with bicycle performance and skating technique were investigated. Twenty-five well-trained speed skaters performed two bicycle tests and a 500-m and 1500-m ice skating race. The power (P) during skating is calculated from ice and air friction losses: at 500 m P500 = 344 +/- 60 W and at 1500 m P1500 = 283 +/- 65 W. Stroke frequency and pre-extension knee angle as principle determining factors of P were determined. The two bicycle tests (of 30" and 2'30" duration, maximal performance) yield P30C = 875 +/- 86 W and P2.30C = 420 +/- 52 W with VO2max = 4.76 +/- 0.45 l/min. The highest correlate of P500 as well as of P1500 appeared to be P30C, respectively, r = 0.78 and r = 0.85. Correlation coefficients between the power during skating and P2.30C or VO2max have a value of about 0.6. If the stroke frequency and P30C are correlated with the power during skating, then high multiple correlation coefficients are obtained: at 500 m R = 0.85 and at 1500 m R = 0.90. The correlation of P30C suggests that the interindividual differences of skating performance at 500-m and 1500-m distances can be attributed substantially to differences in anaerobic power. Yet, the predictive value of the bicycle test for speed skating performance is low. The difference observed between maximal power output during cycling and skating is discussed.

Adipose Tissue↗
PubMed1997

Skating technique for the straights, based on the optimization of a simulation model.

Although experimental data have been collected to determine the skating techniques of the fastest skaters in the world, the "ideal" skating technique has not been determined (i.e., stroke time, glide time, push-off velocity, and push-off direction). The purpose of this study was to determine the skating technique that results in the fastest steady-state speed on a straight-away using optimization of a simulation model. A dynamic model of a skater was developed that included anatomical and physiological constraints: leg length, instantaneous power, and average power of a skater. Results from the model demonstrate that a number of skating techniques can be used to achieve the same steady-state speed. Increasing the average power output of a skater raises the top skating speed and decreases the range of optimal skating techniques. Increasing instantaneous power output (i.e., increasing isometric strength) increases the range of techniques a skater may use for a given speed. In the future, this model can be applied to individual skaters to determine if changes in technique or if improvements in power production are necessary to improve their steady-state skating speed. This model may be adapted to skating sports, such as speed skating, in-line skating, hockey, and cross-country skiing.

Biomechanical Phenomena↗
PubMed1998

Comparison of injury patterns in elite hockey players using ice versus in-line skates.

PURPOSE: The purpose of this study was to assess the variation of injury patterns between hockey players who use in-line roller skates versus those who use ice skates. METHODS: Injury surveillance was undertaken on three professional hockey teams. Two performed on in-line skates and one performed on ice skates. Injury patterns including mechanism of injury, anatomic location, time-loss from sport, and injury type were evaluated with respect to the use of type of skate. The number of athletic exposures (AE) was calculated for each athlete to establish a relative risk. All athletes were elite professional athletes, and injuries were recorded and categorized by a certified athletic trainer or physician. RESULTS: Of the 215 games and 1122 athletic exposures evaluated, 142 injuries were recorded that required an evaluation by a physician and 46 of those required a time loss from sport. The total injury rate was similar between the two sports (in-line: 139 per 1000 AE; ice: 119 per 1000 AE) although injuries tended to be more severe in ice hockey (average time loss from sport: ice, 8.3 games; in-line, 6.5 games). CONCLUSIONS: Comparison of injury patterns by anatomic location, mechanism of injury, and injury type were similar between players using the two types of skates except that ice skates were associated with an increase in the number of lacerations, in-line skates were associated with an increased number of injuries secondary to checking and a decreased number of injuries relative to skate equipment, and ice hockey had an increased risk of head and neck injuries compared with hockey on in-line skates.

Female↗
PubMed1999

Evidence for restricted muscle blood flow during speed skating.

INTRODUCTION: We have previously hypothesized restricted muscle blood flow during speed skating, secondary to the high intramuscular forces intrinsic to the unique posture assumed by speed skaters and to the prolonged duty cycle of the skating stroke. METHODS: To test this hypothesis, we studied speed skaters (N = 10) during submaximal and maximal cycling and in-line skating, in both low (knee angle = 107 degrees) and high (knee angle = 112 degrees) skating positions (CE vs SkL vs SkH). Supportive experiments evaluated muscle desaturation and lactate accumulation during on-ice speed skating and muscle desaturation during static exercise at different joint positions. RESULTS: Consistent with the hypothesis were reductions during skating in VO2peak (4.28 vs 3.83 vs 4.26 L x min(-1)), the VO2 at 4 mmol x L(-1) blood lactate (3.38 vs 1.93 vs 3.31 L x min(-1)), and cardiac output during maximal exercise (33.2 vs 25.3 vs 25.6 L x min(-1)). The reduction in maximal cardiac output was not attributable to differences in HRmax (197 vs 192 vs 193 b x min(-1)) but to a reduction in SVmax (172 vs 135 vs 134 mL x beat(-1)). The reduction in SV appeared to be related to an increased calculated systemic vascular resistance (354 vs 483 vs 453 dynes x s(-1) x cm(-1)). During maximal skating there was also a greater % O2 desaturation of the vastus lateralis based on near infrared spectrophotometry (50.3 vs 74.9 vs 60.4% of maximal desaturation during cuff ischemia). The results were supported by greater desaturation with smaller knee angles during static exercise and by greater desaturation and accelerated blood lactate accumulation during on-ice speed skating in the low vs high position. The results of this study support the hypothesis that physiological responses during speed skating are dominated by restriction of blood flow, attributable either to high intramuscular forces, the long duty cycle of the skating stroke, or both.

Adult↗
PubMed1989

[A study on the effects of the physical load of instructors during ice skating camp].

The present study was conducted to estimate the effects of the physical load of instructors during ice skating camp. The subjects were 9 instructors aged from 20 to 24. To discover measures to relieve the physical load, we measured 1) urinary excretion of catecholamine (noradrenaline; NA, adrenaline; A), 17-OHCS, creatinine and nitrogen; N each day, 2) subjective symptoms of fatigue three time a day (morning, after skating, and at night), 3) nutrient intakes, 4) performed a time study and 5) measured the heart rate during skating instruction. The main results obtained were as follows: 1) The mean heart rate during skating instruction was 98.4-113.1 beats/min. 2) Urinary excretions of NA, A, and 17-OHCS were observed to have increased gradually during skating camp. The values of NA, A and 17-OHCS in the skating camp period were significantly higher than those of daily life. Subjective symptoms of fatigue were also increased gradually. The construction of symptom clusters was of the I-dominant type (I greater than III greater than II) at each point. 3) Intakes of energy, carbohydrate, protein and fat during the skating camp period were higher in comparison with those of daily life. 4) Urinary-N and creatinine levels during the skating camp period showed no changes. N-intake/urinary-N of the skating camp period tended to be higher than that of daily life. 5) In the time study, mean energy consumption was 3300-3400 kcal/day. The mean time of skating instruction was 218-227 min. The sleeping time was observed to have decreased gradually.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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↗
PubMed2003

Energy cost of different skating techniques in cross-country skiing.

The aims of this study were to compare the aerobic energy cost of four 'on-snow' skating techniques in cross-country skiing and to examine the relationships between performance and aerobic energy cost. Twelve male skiers from recreational to national standard performed four level skating trials of 6 min duration in random order, each at the same submaximal velocity but with a different skating technique: (1) 'offset' (V1), using a double asymmetrical and asynchronous pole plant as weight is transferred to one ski; (2) 'two-skate' (V2A), where the pole plant is symmetrical; (3) 'one-skate' (V2), where there is a pole plant as weight is transferred to each ski; and (4) 'conventional', without poles. Oxygen uptake (VO2), pulmonary ventilation, the respiratory exchange ratio and heart rate were measured using a K4(b2) portable gas analyser. The aerobic energy cost (VO2/mean speed) and heart rate were higher (P < 0.05) in the one-skate than in the offset condition. This may be explained by the greater and more efficient use of the upper body and the lower variation in centre of gravity velocity in the offset condition. The aerobic energy cost was 5-9% higher (P < 0.01) in the conventional than in the other techniques, probably because of the shorter duration of propulsive forces within a cycle in the conventional skating condition. Moreover, in ski skating, the mechanical efficiency (propulsive forces/total forces) was shown to be higher in the upper than in the lower limbs. The correlation coefficient between performance and aerobic energy cost was significant in the two-skate (r = 0.68, P = 0.02), one-skate (r = 0.72, P = 0.01) and conventional (r = 0.62, P = 0.04) conditions, but not in the offset condition (r = 0.50, P = 0.10). Our results stress the importance of the upper body component in cross-country skiing and that the aerobic energy cost discriminates between skiers of different standards.

Adult↗
PubMed2000

Physiological responses that account for the increased power output in speed skating using klapskates.

The present study investigates which physiological sources support the increase in mechanical power output (W out) that can be obtained using klapskates in speed skating. It was hypothesized that the increase in W out could be achieved through an increase in gross efficiency or an increase in aerobic power (W aer). Six speed skaters performed a submaximal and maximal 1,600-m skating test with both klapskates and conventional skates, to measure gross efficiency and maximal W aer during speed skating. The rate of oxygen uptake (VO2) and post-exercise blood lactate concentrations ([La]) were measured and video recordings were made. W aer was calculated from VO2. W out was derived from the power needed to overcome air and ice friction. Gross efficiency was calculated as the ratio of W out and W aer. In the maximal tests, the subjects skated faster with klapskates compared to conventional skates (10.0 vs 9.6 m x s(-1)). They sustained the resulting higher W out with klapskates with an equal VO2. [La] was, however, 1.7 mmol x l(-1) higher when klapskates were used, which might reflect an increase in anaerobic power. During the submaximal tests the skaters generated equal W out with both types of skate. Although not statistically significant, VO2 and W aer were, on average, lower when klapskates were used compared to conventional skates [mean (SD) 0.3 (0.43) l x min(-1), 105 (143) W]. Despite the lack of a statistically significant difference in W aer, gross efficiency was shown to be significantly higher with klapskates compared to conventional skates (16.3% vs 14.8%, P = 0.02). We conclude that the increase in W out when the subjects were using klapskates could be explained by an increase in gross efficiency rather than an increase in W aer.

Energy Metabolism↗
PubMed1992

In-line skating: physiological responses and comparison with roller skiing.

The use of in-line skates has become popular in recent years for recreational and conditioning purposes. This investigation evaluated the physiological responses of ten subjects during in-line skating on a flat track with three different in-line skating techniques. The double pole technique demonstrated the greatest economy with oxygen uptake requirements that were approximately 12% lower (p less than 0.05) than conventional skating (without poles) or the V1 skate technique. Across the investigated velocity spectrum of 14.6 to 18.0 km.h-1, individuals with an average fitness level of 40 ml.kg-1.min-1 will achieve exercise intensities of 68-90% of maximum oxygen uptake using the conventional skating and V1 skate techniques on flat terrain. These exercise intensities are appropriate for cardiorespiratory training. However, high fit individuals who are attempting to elicit a cardiorespiratory training effect using in-line skates with rolling resistances similar to those tested may need to perform uphill interval work or skate at higher velocities which may be technically difficult and may be unsafe in some training environments. Comparison of the present data with previously published data on roller skiing demonstrates that differences in physiological responses for the two modes of exercise are the result of differences in rolling resistances between the devices. Measurements of rolling resistance and comparison of the oxygen uptake requirements for double polling on both devices allow for the mechanical efficiency to be estimated at approximately 18% for this mode of locomotion.

Analysis of Variance↗
PubMed1998

Muscle activity in the slalom turn of alpine skiing and in-line skating.

The electromyographic (EMG) activity of seven muscles of the trunk and lower extremity in five male masters level ski racers during a slalom turn in both alpine skiing and in-line skating was recorded using a telemetry system. Measurements were made on separate testing days using slopes commonly used in each activity (24 slope alpine skiing, 5 in-line skating). Qualitative video recorded at 60 Hz was analyzed to partition the turning cycle in both slalom skiing and in-line skating into initiation and turning phases. The EMG data from each turning cycle were normalized to standard isometric contractions (SIC's) for each muscle in order to quantitatively compare the amplitude characteristics of each phase of the turning cycle in both slalom skiing and in-line skating. The turning phase of in-line skating was found to be significantly longer (55%) than in slalom skiing, most likely due to significantly lower subject velocities recorded during in-line skating (8.5 m/s vs 10.2 m/s). All muscles were active at moderate to high levels (48-172% of SIC) during each phase of the turning cycle in both slalom skiing and in-line skating. The EMG amplitude characteristics were similar for six of the muscles in both slalom skiing and in-line skating for each of the turning phases. Only the erector spinae displayed significantly higher average and peak amplitudes in slalom skiing for both phases. It is concluded that the muscle activity patterns associated with the slalom turn of in-line skating are similar but notably more quasi-static than in slalom skiing.

Adult↗
PubMed1987

Comparison of physiology and biomechanics of speed skating with cycling and with skateboard exercise.

Eight well-trained speed skaters performed three all-out tests during ice speed skating, board skating and cycling. Compared to speed skating, cycling produced significantly higher values of oxygen consumption (57.2 +/- 4.9 vs. 53.9 +/- 4.2 ml/(kg X min], ventilation (111.3 +/- 10.2 vs. 98.8 +/- 7.3 l/min) and respiratory exchange ratio (1.18 +/- 0.13 vs. 1.03 +/- 0.05). This seems to suggest a different demand on the aerobic metabolism during cycling compared to speed skating. Board skating resulted in a significantly higher value of the ventilation (110.0 +/- 8.6 l/min) only. Kinematic analysis showed that during both skating activities the time series of the hip and knee angles, angular velocities and angular accelerations were similar. High peak values, especially of the knee angular acceleration, occur in the short push-off phase. During cycling completely different curves were found. The possible significance of these differences for movement co-ordination and motor unit involvement is discussed. The results show that board skating is a more specific training exercise for speed skating than cycling, at least when training for skating performances lasting 8-10 minutes at most.

Adult↗
PubMed1999

Hepatic toxicity and persistence of ser/thr protein phosphatase inhibition by microcystin in the little skate Raja erinacea.

Microcystin-induced ser/thr protein phosphatase (PP) inhibition and toxicity were examined in the little skate (Raja erinacea), an evolutionarily primitive marine vertebrate. As in mammals, PP inhibition and toxicity were exclusively hepatocellular, but were much more persistent in the skate. A dose of 63 microg/kg given iv to adult male skates resulted in the near complete inhibition of hepatic PP activity at 24 h. PP activity was still 95% inhibited 7 days after dosing in skates given 125 microg/kg microcystin. Mortality occurred at doses of 500 microg/kg or more. Hepatic lesions were only seen in animals with fully inhibited PP activity in liver. The histological changes seen at 125 microg/kg were mild periportal inflammatory changes increasing in severity together with hepatocyte necrosis at higher doses of microcystin. Microcystin persisted and could be detected in plasma up to 7 days after dosing. This finding shows that, in the skate, as in mammals, the liver is the only organ capable of uptake of microcystin, since there was no significant inhibition of PP activity in the rectal gland and small decreases in PP activity of the kidney that were not time or dose dependent. In vitro microcystin caused dose-dependent inhibition of PP activity in isolated skate hepatocytes, while it was without effect in cultured rectal glands. Uptake of microcystin and the accompanying inhibition of PP activity in skate hepatocytes was prevented by the addition of a series of organic dyes and bile acids. The spectrum of inhibitors of microcystin uptake in skate is similar to that seen in the rat, indicating common features of the carrier(s) in these diverse species.

Animals↗
PubMed1996

Exercise responses to running and in-line skating at self-selected paces.

Exercise responses to running and in-line skating at self-selected paces. Med. Sci. Sports Exerc., Vol. 28, No. 2, pp. 247-250, 1996. The purpose of this investigation was to compare physiological responses to in-line skating and running at preferred levels of exertion. Ten males and ten females performed 15 min of in-line skating or running on two separate days. Subjects were instructed to exercise at an intensity that represented an effective cardiovascular workout. Heart rate (HR) and oxygen consumption (VO2) were monitored continuously using a portable, telemetric, open-circuit spirometry system. Subjects maintained steady rate VO2 over minutes 11-15 of in-line skating and running at speeds (mean +/- SD) of 21.7 +/- 2.4 and 12.2 +/- 2.3 km.h-1, respectively. A significantly higher (P = 0.03) VO2 (mean +/- SEM, 44.0 +/- 1.7 ml.kg-1.min-1) was observed during running compared with in-line skating (42.0 +/- 2.0 ml.kg-1.min-1), but there were no differences in ventilation, HR, or rating of perceived exertion. Consistent with the results of previous investigations, we conclude that in-line skating is an appropriate form of exercise for improving cardiorespiratory fitness. Future studies should compare the cardiovascular training effects of in-line skating and running in individuals of varying levels of fitness and skating ability.

Adult↗
PubMed1999

Preventing in-line skating injuries: how effective are the countermeasures?

There was a six-fold growth in participation in in-line skating in the US from 1989 to 1996 and a concomitant increase in injuries. Similar trends have been reported in Canada, the UK, Denmark and Australia. Falls, mostly from loss of balance, are a common cause of injury. Falling skaters typically put one or both hands out to break their fall and land on a hard surface with the upper limb sustaining the injury. Approximately one-quarter of all in-line skating injuries are wrist fractures. Hospital emergency department data shows that skaters aged 10 to 14 years are most at risk for injury. First-time skaters, inexperienced skaters and experienced skaters trying new tricks are also at risk for injury. In-line skating injuries can be severe, with several deaths reported. Measures to prevent in-line skating injury include: wearing personal protective equipment (wrist guards, helmets, knee and elbow pads); improving environmental conditions for skaters; providing lessons, particularly for novice skaters; certification for skating instructors; encouraging physical preparation; educating skaters about safety; improving equipment design and standards; and refining government policy and regulation in consultation with skating groups. Few of these measures have been formally proven to reduce injury. Controlled evaluations of the currently advocated methods are needed to establish their efficacy. More biomechanical and epidemiological research is needed, particularly in the area of wrist/forearm injury prevention. Given the rapid increase in popularity of in-line skating and the potential for a related epidemic of moderate to serious injuries, research into in-line skating injury prevention should be a priority.

Head Protective Devices↗
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↗
PubMed2005

Ski skating technique and physiological responses across slopes and speeds.

Appropriate technique choice may affect ski performance. V2 ski skating technique has in recent years become more widely applied on uphill terrain where V1 technique has typically been used. This investigation compared physiological responses of skiers using V1 and V2 techniques during uphill treadmill roller-skiing. Part 1: six skiers from B-level national ski teams participated in technique comparisons performed under six uphill conditions (3, 4, 5, 6, 7, and 8 degrees) with speeds selected so external work was approximately constant for each slope. The 12 trials of 5-min steady-state skating were randomly distributed across two test sessions of six trials each. Heart rate (HR), oxygen consumption (VO(2)), blood lactate concentration (La) and rating of perceived exertion (RPE) were measured. Part 2: 15 skiers from A-level and B-level national ski teams participated in V1-V2 technique comparison on constant slope (5 degrees) with five speeds ranging from 2.25 to 3.25 m s(-1). In two test sessions of V1 or V2 skating (randomly assigned for 2 days) similar characteristics as Part 1 were measured. Across all variables consistent responses were observed for both the experimental parts. As slope increased, V2 skating became increasingly costly compared to V1 skating. At constant slope across the range of speeds, V2 was more costly than V1 skating. This suggests that it may be disadvantageous for skiers to use V2 instead of V1 skating technique on moderate to steep uphill terrain. Doing so may result in elevated HR, La, and VO(2) compared to V1 skating at the same speed.

Adolescent↗
PubMed1997

Volume-activated osmolyte channel in skate erythrocytes: inhibition by pyridoxal derivatives.

Volume expansion of erythrocytes of little skate, Raja erinacea, triggers the opening of an osmolyte channel. We review this transport mechanism and further investigate the channel's physicochemical nature by probing the channel with a series of pyridoxine derivatives in skate RBC as well as in epithelial cells: MDCK and C6 glioma cells and in skate hepatocytes. The identity of the transport mechanism (band 3 vs. an anion channel) which mediates the swelling-activated efflux of osmolytes in fish RBC is controversial. Therefore, we compared taurine and Cl- effluxes in similar conditions. We found that there is significant Cl- loss from volume-expanded skate RBC. However, there was no effect of either hypotonicity or a number of taurine transport inhibitors on this loss. Utilizing changes in intracellular pH as a means of indirectly measuring H+/Cl- cotransport, we found that a rise in cell pH accompanied the loss of Cl-. This suggests that Cl- efflux could occur via a H+/Cl- cotransporter. To probe and compare the osmolyte channel (taurine efflux) of the skate RBC and three other cell types we used a family of pyridoxine inhibitors. The inhibitory patterns for the skate erythrocytes and hepatocytes differed from those for MDCK and C6 glioma cells and the two former cell types differed from each other. Therefore, the results show that the osmolyte channel in the skate differs from that in other epithelial cells with regard to pyridoxine derivative binding properties.

Animals↗
PubMed1990

The effects of colchicine on the ultrastructure of odontogenic cells in the common skate, Raja erinacae.

Ultrastructural alterations induced by colchicine were investigated to determine the secretory activities of odontogenic cells during formation of tooth enameloid matrix in skates. Treated skate inner dental epithelial (IDE) cells did not display dilated cisternae of the granular endoplasmic reticulum (GER) nor accumulate Golgi-associated secretory granules at any dose level or time interval examined. This response was markedly different from that observed in teleost IDE cells synthesizing the enameloid collagen matrix. Treated skate IDE cells did show increased accumulations of glycogen-containing vesicles and intercellular glycogen associated with amorphous material, compared to controls. Additionally, the aberrant occurrence of large intracellular glycogen pools and amorphous material suggested that carbohydrate processing was a major function of skate IDE cells. Treated odontoblasts associated with enameloid matrix formation sometimes showed dilated GER cisternae, but procollagen secretory granules were not observed. Instead, electron dense material was present within the Golgi cisternae, tubular granules, and large granules. Some electron-dense material appeared to be shunted to a resorptive pathway via multivesicular bodies in treated odontoblasts. The continuity of tubular granules with the enameloid matrix suggested that they contained precursors of the enameloid matrix, and possibly the periodic, 17.5-nm cross-striated, "giant" fibers. Treated odontoblasts associated with predentin collagen matrix deposition showed dilated GER cisternae and accumulations of procollagen secretory granules, features consistent with the function of active collagen synthesis and secretion. The findings indicate that (1) skate IDE cells do not synthesize enameloid collagen as found in bony fish tooth development; (2) skate IDE cells do process glycogen for secretion into the enameloid matrix; (3) collagen, although present, is not a major constituent of skate enameloid matrix; (4) enameloid "giant" fibers are unique to elasmobranchs; and (5) odontoblasts synthesize and secrete proteins other than collagen into the enameloid matrix.

Animals↗