Effect of gender on mechanical power output during repeated bouts of maximal running in trained teenagers.

Seven high school boys (16.4 +/- 0.5 y, mean +/- SD) and 7 girls (16.4 +/- 0.5 y), who specialized in track and field events, performed ten 5-s maximal sprint runs with an interval of 10s between each sprint on a non-motorized running ergometer. In each sprint, the mean mechanical power (MP) from the start until the belt velocity of the ergometer (i. e., running velocity) peaked was calculated. The boys showed significantly higher MP than the girls in all sprints. However, when MP was expressed as the ratio to the total volume of muscles located in the right lower limb (MP x MV(-1)), estimated using a bioelectrical impedance analysis, significant gender effect was limited to the values at the 1 st and 2 nd sprints. The decline of MP over the ten sprints, expressed as a relative value to that at the 1 st sprint, was greater in boys (46.2 +/- 7.6 %) than in girls (33.9 +/- 8.6 %), and significantly correlated with MP x MV(-1) at the 1st sprint (r = 0.568, p < 0.05). However, no significant difference between the boys and girls was found in the relative difference between MP values at the 3rd and 10th sprints, where the gender difference in MP x MV(-1) at every sprint was insignificant. The findings here indicate that, for trained teenage boys and girls, (1) significant gender difference in mechanical power developed during repeated bouts of maximal running exists only in the initial phase of the task, when the difference in the volume of the lower limb muscles is normalized, and (2) it may be a reason for a greater decline of mechanical power developed during the bout in boys compared to girls.

Ergometry for estimation of mechanical power output in sprinting in humans using a newly developed self-driven treadmill.

An evaluation of mechanical power during walking and running in humans was undertaken after developing a specially designed running ergometer (RE) in which the subjects gripped the handlebar in front of them keeping both arms straight and in a horizontal position. Ten subjects participated in comparisons of the mean horizontal pushing force (MFam) on the handlebar with the mean horizontal ground reaction force (MFfp) recorded by force platform under the RE during five different constant speeds of walking or running and sprint running with maximal effort. Mechanical power developed during sprint running on the RE was compared with a 50 m sprint. Mean linear velocity (Mv) of the RE belt was recorded by the rotary encoder attached to the axis of the belt. Mean mechanical power calculated from the handlebar setting (MPam = MFam x Mv) was compared to that calculated from force platform recordings (MPfp = MFfp x Mv). A high test-retest reproducibility was observed for both MFfp (r = 0.889) and MFam (r = 0.783). Larger values for the coefficient of variation for MFam (11.3%-15.8%) were observed than for MFfp (3.3%-8.2%). The MPam, which were obtained from five different constant speeds of walking, running and sprint running were closely correlated to those of MPfp (y = 0.98x - 19.10, r = 0.982, P < 0.001). In sprint running, MPam was 521.7 W (7.67 W.kg-1) and was correlated to the 50 m sprint time (r = -0.683, P < 0.01). It is concluded that the newly developed RE was useful in the estimation of mechanical power output during human locomotion such as when walking, jogging and sprinting.

Suppression of a high-affinity transport system for manganese in cadmium-resistant metallothionein-null cells.

Cadmium is a hazardous heavy metal existing ubiquitously in the environment, but the mechanism of cadmium transport into mammalian cells has been poorly understood. Recently, we have established a cadmium-resistant cell line (Cd-rB5) from immortalized metallothionein-null mouse cells, and found that Cd-rB5 cells exhibited a marked decrease in cadmium uptake. To investigate the mechanism of altered uptake of cadmium in Cd-rB5 cells, incorporation of various metals was determined simultaneously using a multitracer technique. Cd-rB5 cells exhibited a marked decrease in manganese incorporation as well as that of cadmium. However, the reduced uptake of manganese was observed only at low concentrations, suggesting that a high-affinity component of the Mn(2+) transport system was suppressed in Cd-rB5 cells. Competition experiments and kinetic analyses revealed that low concentrations of Cd(2+) and Mn(2+) share the same high-affinity pathway for their entry into cells. The mutual competition of Cd(2+) and Mn(2+) uptake was also observed in HeLa, PC12, and Caco-2 cells. The highest uptake of Cd(2+) and Mn(2+) by parental cells occurred at neutral pH, suggesting that this pathway is different from a divalent metal transporter 1 that can transport various divalent metals including Cd(2+) and Mn(2+) under acidic conditions. These results suggest that a high-affinity Mn(2+) transport system is used for mammalian cellular cadmium uptake, and that the suppression of this pathway caused a marked decrease in cadmium accumulation in cadmium-resistant metallothionein-null cells.

Reduced uptake and enhanced release of cadmium in cadmium-resistant metallothionein null fibroblasts.

Metallothionein (MT) is known to play a predominant role in the protection of cells from cadmium (Cd) toxicity. To investigate other factors involved in Cd resistance, we established Cd-resistant cell lines from simian virus 40-transformed MT null fibroblasts. Cd-resistant MT null cells, Cd-rA7 and Cd-rB5, developed approximately 10-fold resistance to Cd compared to parental cells, but showed no cross-resistance to Zn, Cu, Hg, Ni, As, cisplatin or H2O2. Accumulation of Cd in the resistant cells was 13-18% of that of parental cells after treatment with Cd for 24 h. A short-term experiment revealed that the rate of Cd incorporation into the Cd-resistant cells was suppressed, and the rate of Cd release was enhanced in the resistant cells compared with that of parental cells. These results indicate that the altered transport of Cd, slow uptake and rapid release, may confer resistance to Cd on the Cd-resistant cells established from MT null fibroblasts.

Study on Chlamydia trachomatis infection among students and pregnant women in Japan: a step toward developing a reliable method for sexual behavior study.

2450 sera from students and 5215 sera from pregnant women were examined for the presence of Chlamydia trachomatis (CT) antibody. CT antibody positive rates were less than 5% with the students and 24.5% with the pregnant women suggesting the latter is significantly higher than former. The results provided a base for discussing possibility of using CT infection as a reliable method for studying sexual behavior.

Simian virus 40-transformed metallothionein null cells showed increased sensitivity to cadmium but not to zinc, copper, mercury or nickel.

Primary cultured embryonic cells derived from mice with disrupted metallothionein (MT) I and II genes and from control mice were transformed with a plasmid encoding the simian virus 40 (SV40) large T antigen. The resulting MT-/- and MT+/+ cell strains showed similar cell morphology, cell cycle and no significant differences in glutathione levels or in the activities of glutathione-related enzymes and antioxidant enzymes. The MT-/- cells were more sensitive to Cd than MT+/+ cells, though no increase in the sensitivity to Zn, Cu, Hg or Ni were observed in MT-/- cells. MT+/+ cells accumulated more Cd than MT-/- cells but showed less lesion, suggesting the role of MT induced by Cd in MT+/+ cells as a scavenger of toxic Cd ion. These results suggest a dominant protective role of MT against Cd compared with other metals. SV40-transformed MT-/- cells seem to be a useful tool for the investigation of cellular function of MT.

Effect of glutathione depletion on metallothionein synthesis induced by paraquat in mice.

The effect of Glutathione (GSH) depletion on the induction of metallothionein (MT) synthesis by paraquat (PQ) was examined in ICR mice. An increase in hepatic MT level in mice was observed after a single PQ administration. Pretreatment of mice with L-buthionine-SR-sulfoximine (BSO), an inhibitor of GSH synthesis, enhanced the induction of hepatic and renal MT synthesis by PQ depending on the decreased tissue GSH level. A similar result was obtained by pretreatment with diethylmaleate, a GSH depleting agent. The ratio of hepatic MT-I to MT-II induced by PQ was not changed by BSO pretreatment. An increase in the hepatic MT level in GSH depleted mice was observed from 3 hr to 24 hr after PQ administration. An increase in the hepatic MT-I mRNA level after treatment with PQ was observed prior to hepatic MT induction in BSO pretreated mice. Pretreatment with actinomycin D, an inhibitor of mRNA synthesis, inhibits the PQ-induced increase in hepatic MT and MT-I mRNA levels in BSO pretreated mice. Pretreatment with BSO did not affect the induction of MT synthesis by zinc, cadmium or dexamethasone. Pretreatment with dexamethasone, an anti-inflammatory agent, enhanced the hepatic MT induction by PQ treatment in GSH depleted mice, while dexamethasone reduced the MT induction by turpentine oil, which is known to induce inflammation and hepatic MT synthesis. These findings suggest that GSH depletion enhances the induction of MT synthesis by PQ because of an increase in the transcription rate, and this enhancement of MT synthesis is not due to an inflammatory response caused by PQ.

[Evaluation of hyperlipidemia in high school student--Part 1].

Recently the risk of ischemic heart disease (IHD) is increasing in young generations. Thus, we evaluated the degree of hyperlipidemia in the students of high school in Miyagi prefecture. At first, we examined the plasma level of total cholesterol in all students as screening. About 10% of all the students showed high level of total cholesterol over 200mg/dl. For second screening, we examined further indexes for hyperlipidemia including lipids, glucose and blood pressure at fasting state and got information about family history, diet and exercise. There was positive correlation between total cholesterol and LDL-cholesterol (LDL-C), but no relation was found among others. Lipoprotein (a) which was an independent factor of IHD showed a broad distribution as described before, and had no relation with other lipid levels. Early education and a familial consultation for protecting from IHD should be followed after the screening of lipids levels.

[An evaluation of tumor markers and risk factors in mass screening for various cancers].

The borderline values of tumor markers and the clarification of risk factors for cancer are problems to be solved in the development of mass screening tests for various cancers. A tiny abnormality may be overlooked in an evaluation based upon traditional reference standards obtained by surveying healthy subjects. Both negative and positive values are required in mass screening for various cancers. That is, cut-off values should minimize the incidence of false negatives and false positives in the screening test. A modified combination assay using tumor markers and risk factors was used to screen 967 healthy subjects over age 50 for nonspecific cancers and the results were analyzed. Positive rates based on ordinary cut-off values for each tumor marker were about 6 to 7% in CEA, CA19-9 and BFP, 2.7% in SPAN-1, 1.3% in PAP, and less than 1% in AFP, SCC, CA125 and NCC -ST-439. For pepsinogen, a risk factor of various cancers especially in the digestive tract, the cut-off value was determined as the mean-SD in 967 healthy subjects over 50 years old. That is, the cut-of value for pepsinogen I was 18.7 ng/ml. A lower value was found in 149 subjects (15.4%). The cut-off value for pepsinogen II was 7.4 ng/ml and a lower value was found in 227 subjects (23.5%). The cut-off value for the pepsinogen I/II ratio was 1.2 and 108 subjects showed lower values (11.2%). Positive cases were referred to specialists in various fields to detect the specific suspected cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

[Health examination in school age children].

Within recent years, various medical examinations have been performed on school age children. The purpose of the school examination is early detection of disease, but those with abnormal results should receive pertinent care (electrocardiogram, phonocardiogram, complete blood count, total cholesterol, and urinalysis). Therefore we analyzed the results obtained by questionnaire method on the management of the school age children with abnormal examination results.

A continuous and quantitative analysis of the uneven distribution of myocardial blood flow in dogs using a distribution function of the clearance time constant.

A continuous and quantitative analysis of the uneven distribution of coronary blood flow was accomplished in anesthetized open-chest dogs using the distribution function of the hydrogen (H2) clearance time constant. The distribution function was derived by analysing the H2 washout curves in the coronary sinus which were obtained by the H2 clearance method, using platinum electrodes placed in the coronary sinus. Twelve to seventeen platinum electrodes were employed to obtain simultaneous measurements of the regional myocardial flow before and after stenosis of the left anterior descending coronary artery. Theoretically, the H2 washout curves in the coronary sinus could be interpreted as a function with multi-exponential characteristics, represented by an equation similar to the Laplace transform of the distribution function of the H2 clearance time constant. Therefore, we assumed that such an equation would represent the uneven distribution of coronary blood. We obtained the distribution function by using an approximation method to solve the integral equation and we employed digital computation to increase the resolution. Before stenosis of the left anterior descending coronary artery, the log distribution function curves with respect to the H2 clearance time constant were roughly symmetrical in terms of the maximum peak in the time constant. After stenosis of the left anterior descending coronary artery, the log distribution function had two peaks and the range of distribution was much larger than that before coronary stenosis. Our findings may prove to be valuable as a technique to estimate continuously and quantitatively the heterogeneous distribution of myocardial blood flow.