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Biomedical subjects

M Spencer

Publications and source records attributed to M Spencer.

At least 19 recordsLinked to original sources

Reliability of a repeated-sprint test for field-hockey.

The purpose of this study was to assess the reliability of a repeated-sprint test, specifically designed for field-hockey, as it was based directly on the time-motion analysis of elite level competition. The test consisted of 6 x 30-m over-ground sprints departing on 25s, with an active recovery (approximately 3.1-3.3 ms(-1)) between sprints. Ten highly trained, male, field-hockey players (mean+/-S.D.: age, 23+/-3 years; body mass, 78.1+/-7.1 kg) participated in this study. Following familiarisation, the subjects performed the repeated-sprint test on two occasions, 7 days apart. The reliability of the test variables was assessed by the typical error of measurement (TE). The total sprint time was very reliable (T(1): 26.79+/-0.76 s versus T2: 26.83+/-0.74 s), as the TE was 0.7% (95% CL, 0.5-1.2%). However, the percent sprint decrement was less reliable (T1: 5.6+/-0.9% versus T2: 5.8+/-1.0%), with the TE being 14.9% (95% CL, 10.8-31.3%). In summary, it is suggested that this field-hockey-specific, repeated-sprint test is very reliable when the results are presented as the total sprint time.

Adult↗

Time-motion analysis of elite field hockey during several games in succession: a tournament scenario.

International field hockey tournaments may require teams to play three games within a period of four days. Therefore, there is potential for residual fatigue to affect the movement patterns of players during subsequent games. The purpose of this study was to document changes in time-motion analysis of 14 elite male field hockey players during three games within a period of four days during an international tournament. In addition, the nature of and any changes in repeated-sprint activity were investigated using a criteria of a minimum of three sprints with a mean recovery duration between sprints of < 21 s. The percent of total game time spent standing significantly increased across all three games (7.4+/-.2, 11.2+/-2.7 and 15.6+/-5.6%, respectively, P<0.05). Conversely, the percent time spent jogging significantly decreased from game 1 to game 2 and from game 1 to game 3 (40.5+/-7.3, 34.8+/-7.4 and 29.4+/-5.7%, respectively, P<0.05). Furthermore, the percent time in striding significantly increased from game 1 to game 3 and from game 2 to game 3 (4.1+/-1.3, 5.1+/-0.9 and 5.8+/-1.4%, respectively. P<0.05). Changes in mean motion frequency and duration were recorded across games for the motions of standing, striding and sprinting. The frequency of exercise bouts that met the criteria for 'repeated-sprint' decreased across the three games (17, 11 and 8, respectively). In summary, the results suggest that when elite field hockey players play three games within four days there are significant changes in time-motion analysis.

Adult↗

Expression of apoptotic and cell proliferation regulatory proteins in actinic cheilitis.

BACKGROUND: Actinic cheilitis (AC) is a pre-malignant lesion caused by ultraviolet (UV) radiation. The apoptotic proteins p53, bax, bcl-2, and the proliferation marker Ki-67, are known to play an important role in UV-exposed skin and carcinomas, therefore, these markers were assessed in AC and compared with normal lip and oral mucosa. METHODS: AC (n = 13), normal lip (n = 7) and oral mucosa (n = 6) biopsies were stained immunohistochemically for p53, bax, bcl-2 and Ki-67, to determine their expression and distribution. RESULTS: p53 was over-expressed in AC as compared with normal lip and oral mucosa (P < 0.003). Although bcl-2 expression was higher in AC than in oral mucosa (P < 0.002), it was significantly reduced as compared with normal lip (P < 0.04). Bax expression remained unchanged, and Ki-67 was significantly increased in AC and normal lip as compared with oral mucosa (P < 0.05). CONCLUSION: The results suggest that DNA-damaged cells by UV radiation in AC are eliminated by apoptosis.

Adult↗

Longitudinal assessment of the effects of field-hockey training on repeated sprint ability.

Repeated-sprint ability is thought to be an important fitness component of team sports. However, little is known about the effect sport-specific training has on this fitness component. Therefore, the purpose of this study was to investigate the effects of field-hockey specific training on repeated-sprint ability, plasma hypoxanthine (Hx) concentration and other blood parameters in 18 elite female field-hockey players. All subjects performed a repeated-sprint ability test on a cycle ergometer (5 x 6-sec maximal sprints every 30 secs) before and after seven weeks of training, designed to improve repeated-sprint ability. Following training, there was a significant (P< 0.05) increase in absolute total work (20.73+/-2.00 to 21.15+/-2.07 kJ, mean+/-SD). However, there was no significant change in total work when expressed per kg of body mass (341.3+/-16.4 to 345.5+/-18.8 J x kg(-1)). In addition, training resulted in a significant (P< 0.05) decrease in change values (peak-rest values) for Hx (8.2+/-3.8 to 5.5+/-2.7 micromol x L(-1)) and hydrogen ion concentration (22.8+/-5.2 to 19.1+/-5.1 nmol x L(-1)). The significant increase in absolute total work following seven weeks of field-hockey specific training was most likely due to an increase in lean muscle mass. The significant decrease in plasma Hx concentration (post-test minus rest values) following seven weeks of field hockey-specific training provides evidence that Hx production and/or efflux from the muscle are reduced. Therefore, one adaptation of sport-specific repeated-sprint training may be to conserve the purine nucleotide pool.

Adaptation, Physiological↗

Determinants of repeated-sprint ability in well-trained team-sport athletes and endurance-trained athletes.

AIM: To examine the importance of peak .VO(2) in determining repeated-sprint ability (RSA), we recruited 20 well-trained females (10 team-sport athletes and 10 endurance-trained runners; mean SD peak .VO(2): 3.3+/-0.2 L x min(-1)) who were homogenous with respect to peak .VO(2) (mean difference = 0.05 L x min(-1)). METHODS: Tests consisted of a RSA cycle test (5 x 6-s max sprints every 30 s) and a peak .VO(2) test. Venous and capillary blood was sampled immediately before and after the 5 x 6-s cycle test for the determination of hypoxanthine concentration ([Hx]), lactate concentration ([La-]) and pH; blood buffer capacity (beta(blood)) was also estimated. RESULTS: The team-sport athletes had significantly higher peak power for the 1(st) sprint (P(1); W x kg(-1)), total work for 5 x 6-s sprints (W(tot); J x kg(-1)) and power decrement across the 5 sprints (P(dec)), (p<0.05). There were also significant between-group differences for post-test values of [Hx], [La-] and pH (p<0.05). While there was no significant difference in beta(blood) between the 2 groups (p=0.10), there was a moderate effect (d=0.77). CONCLUSION: These results suggest that factors in addition to peak .VO(2) are likely to be important for RSA.

Adult↗

Predictors of repeated-sprint ability in elite female hockey players.

The ability to maintain maximal power over a series of sprints may depend, in part, on the resynthesis of PCr and the buffering of hydrogen ions (H+). As a result, repeated-sprint ability may be related to VO2peak and changes in plasma pH. Fourteen elite female field-hockey players (Mean +/- SD body mass: 61.1 +/- 5.9 kg and VO2pea: 55.7 +/- 3.2 mL x kg(-1) x min(-1)) participated in this investigation. Tests consisted of a repeated-sprint ability test (5 x 6-s all-out sprints every 30 s) and a VO2peak test. Capillary and venous blood was sampled before and after the 5 x 6-s cycle test for the determination of lactate concentration and pH. There were no significant correlations between VO2peak (mL x kg(-1) x min(-1)) and total work (J.kg(-1); r = 0.35), or power decrement (r = 0.30) during the repeated-sprint ability test. There was, however, a significant correlation between power decrement and change in plasma [H+] (r = 0.66; P < 0.05). The results of this study show that in a homogenous group of elite, team-sport athletes, VO2peak (mL x kg(-1) x min(-1)) is not a strong predictor of repeated-sprint ability. However, in this group, there is a significant correlation between change in plasma [H+] and repeated-sprint ability.

Adult↗

Fluoride release from a resin-modified glass-ionomer cement in a continuous-flow system. Effect of pH.

Fluoride is added to many dental restorative materials, including glass-ionomer cements, for the specific purpose of leaching fluoride into the surrounding tissues to provide secondary caries inhibition. During the caries process, an acidic environment attacks the dental tissues as well as the glass-ionomer cement. We hypothesized that pH significantly affects the rate of release of fluoride from the glass-ionomer cement. A continuous-flow fluoride-measuring system that monitors the amount of fluoride released over time was used to determine the release of fluoride from a resin-modified glass-ionomer cement (KetacFil). The results show that the release rate began with a fast burst of fluoride which quickly diminished to low levels in 3 days. Under neutral pH conditions, the rate of fluoride release at 72 hrs was significantly slower than at pH 4.

Cariostatic Agents↗

Detection of mitochondrial DNA mutations in primary breast cancer and fine-needle aspirates.

To determine the frequency and distribution of mitochondrial DNA mutations in breast cancer, 18 primary breast tumors were analyzed by direct sequencing. Twelve somatic mutations not present in matched lymphocytes and normal breast tissues were detected in 11 of the tumors screened (61%). Of these mutations, five (42%) were deletions or insertions in a homopolymeric C-stretch between nucleotides 303-315 (D310) within the D-loop. The remaining seven mutations (58%) were single-base substitutions in the coding (ND1, ND4, ND5, and cytochrome b genes) or noncoding regions (D-loop) of the mitochondrial genome. In three cases (25%), the mutations detected in coding regions led to amino acid substitutions in the protein sequence. We then screened an additional 46 primary breast tumors with a rapid PCR-based assay to identify poly-C alterations in D310, and we found seven more cancers with alterations. Using D310 mutations as clonal marker, we detected identical changes in five of five matched fine-needle aspirates and in four of four metastases-positive lymph nodes. The high frequency of D310 alterations in primary breast cancer combined with the high sensitivity of the PCR-based assays provides a new molecular tool for cancer detection.

Biopsy, Needle↗

A field-based population model for the sediment toxicity test organism Leptocheirus plumulosus: I. Model development.

We describe the development of a stage-structured population matrix model for the estuarine amphipod Leptocheirus plumulosus, a sediment toxicity test organism, based on regular sampling of a natural population for approximately 2 years. Annual population dynamics were characterized by abundance peaks in the spring and fall, and low densities in the summer and winter. We use a sequence of seasonal projection matrices to capture these qualitative patterns in population dynamics. We compare two methods for estimating transition probabilities: multiple regression and truncated singular value decomposition (SVD). Overall, SVD gave more realistic parameter estimates than regression, although fecundity estimation was problematic. There were predictable trends in growth, survival and fecundity within years. The SVD-derived model provides a framework for assessing the population-level effects of contaminants on Leptocheirus.

Animals↗

A field-based population model for the sediment toxicity test organism Leptocheirus plumulosus: II. Model application.

A stage-structured population model has been developed for the estuarine amphipod Leptocheirus plumulosus to provide interpretive guidance for sediment toxicity tests with this species. This time-varying, field-based model includes several matrices to reflect seasonal changes in demographics. In this paper, we conduct sensitivity analysis of the model to identify which life history parameters have the greatest potential impact on population growth rate (lambda). Results indicate seasonal variability in the relative demographic importance of vital rates. Over winter, annual population growth is most sensitive to the persistence of juveniles and adults and growth from the juvenile to the adult stage. In spring and fall, changes in fecundity are likely to have large effects on population dynamics. In addition, we demonstrate the applicability of the model by using it to interpret toxicological data from an assessment of sediment contamination in Baltimore Harbor, MD. The model was parameterized with survival data from acute toxicity tests with L. plumulosus to project effects on population growth rate (lambda). Results of these model simulations indicate that relatively small changes in survival can result in large changes in lambda, indicating high risk to benthic populations. Furthermore, population projections mirror observed abundances of L. plumulosus at the test sites. These analyses provide a first indication of the usefulness of the Leptocheirus population model as a tool for exploring ecological effects of sediment contamination.

Animals↗

Manuscript evolution.

Frequently, letters, words and sentences are used in undergraduate textbooks and the popular press as an analogy for the coding, transfer and corruption of information in DNA. We discuss here how the converse can be exploited, by using programs designed for biological analysis of sequence evolution to uncover the relationships between different manuscript versions of a text. We point out similarities between the evolution of DNA and the evolution of texts.

Evolution, Molecular↗

Manuscript evolution.

Frequently, letters, words and sentences are used in undergraduate textbooks and the popular press as an analogy for the coding, transfer and corruption of information in DNA. We discuss here how the converse can be exploited, by using programs designed for biological analysis of sequence evolution to uncover the relationships between different manuscript versions of a text. We point out similarities between the evolution of DNA and the evolution of texts.

DNA↗

The validity of a repeated sprint ability test.

Many team sports require participants to repeatedly produce maximal or near maximal sprints of short duration (1-7s) with brief recovery periods, over an extended period of time (60-90 min). Therefore, an important fitness component for these sports is what is often termed repeated sprint ability (RSA). A variety of tests have been devised to assess RSA. However, while the reliability of some of these tests has been reported, there has been no published attempt to assess the validity of RSA tests. The purpose of the present paper was to assess the validity of a popular RSA test--the 5 x 6 s cycle test. Ten moderately-trained males (Mean+/-SD age: 23.6+/-3.0 yrs, mass: 71.8+/-7.4 kg, peak VO2: 46.32+/-4.16 ml.kg(-1)min(-1)) participated in the investigation. Following familiarisation, subjects reported to the laboratory at the same time of day, on three occasions, each separated by at least 48 hours. Testing consisted of a 5 x 6 s cycle test (5 x 6 s maximal sprints every 30 s), a graded exercise test (GXT) and a simulated game (3 x 15 min periods separated by five min). The simulated game consisted of a 1-min circuit that was repeated 15 times in each period. The circuit replicated typical movement patterns observed during motion analysis of field hockey games. Each circuit commenced with a 15-m maximum sprint through timing gates. Time to run 5, 10 and 15 m was recorded. Oxygen consumption was measured during both the GXT and the simulated game with a portable gas analysis system (Cosmed K4 b2, Italy). Correlation coefficients between dependent variables were calculated using Pearson's Product Moment (r). There was a significant correlation between power decrement during the 5 x 6 s cycle test and decrement in 15-m time across the three periods (r = 0.76, P<0.05), but not decrement in 10-m time (r = 0.54) or 5-m time (r = 0.42). These results suggest that the 5 x 6 s cycle test is valid for assessing the decrement in 15-m time, but not the decrement in 5 or 10m time. Thus, one measure of RSA (sprint decrement) appears to be specific to the test protocol, rather than a general quality. The most likely explanation is that the energy requirements of the 5 x 6 s cycle test more closely match those required to repeatedly run 15 m (mean time = 2.74 s) than to repeatedly run 10 m (mean time = 1.97 s) or 5 m (mean time = 1.13 s). It is therefore suggested that, while the 5 x 6 s cycle test is often used to assess RSA ability in a wide range of sports, it may need to be modified to reflect the common sprint distances found in specific sports.

Adult↗

Nocturnal home hemodialysis in North America.

Nocturnal home hemodialysis (NHD) was made possible in the 1960s by fail-safe monitoring, the Scribner shunt, and low-resistant Kiil dialyzer allowing hemodialysis without a blood pump. In London, Sheldon was the first to use overnight home hemodialysis. The Lynchburg NHD program and Lisa Murphy, a dietician in Bender's NHD program in Kansas City, developed a questionnaire for short daily hemodialysis and NHD. The questionnaire was sent to all known daily hemodialysis programs in North America. Some advances in nocturnal home hemodialysis since 1994 include: improvement in teaching methods, preventing disconnects and air emboli, preventing catheter infections, and using arteriovenous fistulas and grafts for access. As of January 2001, there were 13 centers in North America performing daily nocturnal home hemodialysis caring for 115 patients. Since 1997, all programs performing NHD have validated Pierratos' reported results, showing improvement in quality of life, better blood pressure control with fewer medications, reduced Epogen usage, reduced hospitalizations, control of phosphorous without binders, and a greater sense of hope for patients. Even though this new modality is safe and better for selected patients with ESRD, dialysis providers in Canada and the United States cannot afford to offer NHD within the present reimbursement scheme.

Canada↗

Temporal variability and ignorance in Monte Carlo contaminant bioaccumulation models: a case study with selenium in Mytilus edulis.

Although the parameters for contaminant bioaccumulation models most likely vary over time, lack of data makes it impossible to quantify this variability. As a consequence, Monte Carlo models of contaminant bioaccumulation often treat all parameters as having fixed true values that are unknown. This can lead to biased distributions of predicted contaminant concentrations. This article demonstrates this phenomenon with a case study of selenium accumulation in the mussel Mytilus edulis in San Francisco Bay. "Ignorance-only" simulations (in which phytoplankton and bioavailable selenium concentrations are constant over time, but sampled from distributions of field measurements taken at different times), which an analyst might be forced to use due to lack of data, were compared with "variability and ignorance" simulations (sampling phytoplankton and bioavailable selenium concentrations each month). It was found that ignorance-only simulations may underestimate or overestimate the median predicted contaminant concentration at any time, relative to variability and ignorance simulations. However, over a long enough time period (such as the complete seasonal cycle in a seasonal model), treating temporal variability as if it were ignorance at least gave a range of predicted concentrations that enclosed the range predicted by explicit treatment of temporal variability. Comparing the temporal variability in field data with that predicted by simulations may indicate whether the right amount of temporal variability is being included in input variables. Sensitivity analysis combined with biological knowledge suggests which parameters might make important contributions to temporal variability. Temporal variability is potentially more complicated to deal with than other types of stochastic variability, because of the range of time scales over which parameters may vary.

Animals↗

Insulin lispro lowers postprandial glucose in prepubertal children with diabetes.

OBJECTIVE: This study compared the glucose-lowering effect of insulin lispro, given before or after meals, with regular human insulin given before meals in prepubertal children with diabetes. RESEARCH DESIGN AND METHODS: A 3-way crossover, open-label study involving 61 prepubertal children (ages 2.9-11.4 years) with type 1 diabetes. The children were randomly assigned to receive regular human insulin 30 to 45 minutes before meals, insulin lispro within 15 minutes before or immediately after meals, combined with basal insulin. Each treatment lasted 3 months. Hemoglobin A(1c) levels and home glucose monitoring profiles were measured at the end of each treatment period. RESULTS: Treatment with insulin lispro before breakfast resulted in lower 2-hour postprandial glucose values than regular human insulin (11.7 +/- 4.4 mmol/L vs 15.0 +/- 5.4 mmol/L). Similarly, insulin lispro given before dinner resulted in lower blood glucose values 2 hours postprandially (8.8 +/- 5.0 mmol/L vs 10.8 +/- 5.4 mmol/L) than regular human insulin. When insulin lispro was administered after meals, the 2-hour glucose levels were between those seen with either insulin lispro or regular human insulin given before meals. The number and types of adverse events, the rates of hypoglycemia, and the HbA(1c) levels did not differ among the 3 therapies. CONCLUSIONS: In prepubertal children, insulin lispro given before meals is safe and significantly lowers postprandial glucose levels after breakfast and dinner compared with regular human insulin, and insulin lispro given after the meal provides similar benefits as regular human insulin before the meal.

Age Factors↗