Sex- and age-related differences in the rating of perceived exertion after high-intensity rowing exercise during childhood and adolescence

The present study aimed to evaluate the effects of age and sex on the rating of perceived exertion (RPE) during high-intensity exercise and determine whether mechanical and physiological parameters could be predictors of RPE during childhood and adolescence. Forty-three boys and 36 girls performed a 60-s all-out test on a rowing ergometer and were categorized by age group (10.0-11.9; 12.0-13.9; 14.0-15.9; 16.0-17.9 years) and sex. Ratings of perceived exertion were assessed using the 6-20 RPE and CR-10 scales and analyzed with respect to mechanical work rate (W_tot ), post-exercise peak blood lactate concentration ([La]_peak ), and peak minute ventilation (V̇E_peak ). Multilevel regression modeling revealed a significant influence of W_tot , [La]_peak and V̇E_peak on 6-20 RPE and CR-10 scores (r²  = .34 and .36, p < .001, respectively). However, while boys perceived high-intensity exercise as being subjectively more difficult than girls at all ages (p < .05) except 12.0-13.9 years, significant higher mechanical work rate and greater associated metabolic responses in boys than girls were only found from the age of 14 years (W_tot and V̇E_peak ) or 16 years ([La]_peak ), suggesting that the association between RPE and mechanical/physiological parameters could not be held before the age of 12 years. To conclude, RPE increased with increasing age, with boys exhibiting higher scores than girls at all ages except 12.0-13.9 years. This finding is probably explained by the higher W_tot and greater concomitant metabolic responses in boys at the time of puberty. However, other factors should be considered at least in children before the age of 12 years.

New evidence from exceptionally "well-preserved" specimens sheds light on the structure of the ammonite brachial crown

Ammonite soft body remains are rarely preserved. One of the biggest enigmas is the morphology of the ammonite brachial crown that has, up till now, never been recovered. Recently, mysterious hook-like structures have been reported in multiple specimens of Scaphitidae, a large family of heteromorph Late Cretaceous ammonites. A previous examination of these structures revealed that they belong to the ammonites. Their nature, however, remained elusive. Here, we exploit tomographic data to study their arrangement in space in order to clarify this matter. After using topological data analyses and comparing their morphology, number, and distribution to other known cephalopod structures, in both extant and extinct taxa, we conclude that these hook-like structures represent part of the brachial crown armature. Therefore, it appears that there are at least three independent evolutionary origins of hooks: in belemnoids, oegospids, and now in ammonites. Finally, we propose for the first time a hypothetical reconstruction of an ammonite brachial crown.

Importance of dimensional changes on glycolytic metabolism during growth

PURPOSE

The aim of the present study was to investigate (i) how glycolytic metabolism assessed by accumulated oxygen deficit (AOD_gly) and blood metabolic responses (lactate and pH) resulting from high-intensity exercise change during growth, and (ii) how lean body mass (LBM) influences AOD_gly and its relationship with blood markers.

METHODS

Thirty-six 11- to 17-year olds performed a 60-s all-out test on a rowing ergometer. Allometric modelling was used to investigate the influence of LBM and LBM + maturity offset (MO) on AOD_gly and its relationship with the extreme post-exercise blood values of lactate ([La]_max) and pH (pH_min) obtained during the recovery period.

RESULTS

AOD_gly and [La]_max increased while pH_min decreased linearly with LBM and MO (r² = 0.46 to 0.72, p < 0.001). Moreover, AOD_gly was positively correlated with [La]_max (r² = 0.75, p < 0.001) and negatively correlated with pH_min (r² = 0.77, p < 0.001). When AOD_gly was scaled for LBM, the coefficients of the relationships with blood markers drastically decreased by three to four times ([La]_max: r² = 0.24, p = 0.002; pH_min: r² = 0.30, p < 0.001). Furthermore, by scaling AOD_gly for LBM + MO, the correlation coefficients with blood markers became even lower ([La]_max: r² = 0.12, p = 0.037; pH_min: r² = 0.18, p = 0.009). However, MO-related additional changes accounted much less than LBM for the relationships between AOD_gly and blood markers.

CONCLUSION

The results challenge previous reports of maturation-related differences in glycolytic energy turnover and suggest that changes in lean body mass are a more powerful influence than maturity status on glycolytic metabolism during growth.

Matched wideband low-noise amplifiers for radio astronomy

Two packaged low noise amplifiers for the 0.3-4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300-4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<-10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range.

Impact of a joint labor-management ergonomics program on upper extremity musculoskeletal symptoms among garment workers

This study evaluated the effect of an ergonomics intervention program on the prevalence and intensity of symptoms of upper extremity work-related musculoskeletal disorders among 36 garment workers performing an operation called spooling. Adjustable chairs were introduced and workers were trained in their use. Symptom surveys were administered prior to and 6 months after introduction of adjustable chairs. Quantitative pre- and post-intervention measurement of joint position was performed utilizing videotapes among a subgroup of nineteen. Eighty nine percent of the cohort reported pain in either the neck or at least one upper extremity anatomic site prior to the adjustable chair intervention. Among subjects reporting pain at baseline, there were significantly decreased pain levels in 10 of 11 anatomic sites after the intervention. Among all subjects, the proportion reporting pain decreased for each anatomic site following the intervention, with statistically significant decreases in 3 sites. However, there were only modest declines in awkward posture among the videotaped subgroup. This study suggests that introduction of an ergonomics program focused on education and introduction of an adjustable chair may diminish musculoskeletal symptomatology in apparel manufacturing workers.

Exposure-response models based on extended follow-up of a cohort mortality study in the automobile industry

OBJECTIVE

This report describes the extended follow-up of a cohort of 46 399 automobile manufacturing workers with potential exposure to metalworking fluids (MWF). The outcomes of interest were cancers of the esophagus, stomach, colon, rectum, liver, pancreas, larynx, skin, prostate, and brain, as well as leukemia. Additional follow-up increased the power to detect modest elevations in mortality rates in association with specific types of MWF, including synthetic fluids not in widespread use until the 1970s.

METHODS

Standardized mortality ratios (SMR) were computed for the most recent 10 years of follow-up, as well as for the entire study period. Adjusted relative risks (RR) were estimated in Poisson regression models with categorical variables for cumulative exposure to each type of MWF and in proportional hazards models with continuous exposure variables.

RESULTS

Associations were found between straight MWF and esophageal, laryngeal and rectal cancer; soluble MWF and cancer of the esophagus, larynx, skin, and brain; synthetic MWF and cancer of the esophagus, liver, and prostate. The elevated RR values were modest in magnitude (1.5 to 2.0). SMR values were increased for stomach, liver, and pancreatic cancer and also for leukemia in the last 10 years of follow-up. The SMR values were also elevated for stomach and liver cancer among the persons recently hired.

CONCLUSIONS

The results provide further evidence that exposure to metalworking fluids causes cancer among workers in automobile manufacturing. Although airborne exposures declined over the study period, this study suggests that modest risk of several digestive cancers, as well as prostatic cancer and leukemia, may persist at current levels of exposure to water-based metalworking fluids.

Intrahepatic bile duct rupture following blunt abdominal trauma

The natural history of intrahepatic bile duct rupture secondary to blunt trauma is not known. A unique case of bilateral hepatic lobar duct rupture is presented to demonstrate the clinical features and potential complications of this injury. Operative intervention is not always indicated and treatment should be dictated by the specific lesion.

Synthesis and biological evaluation of fragmented derivatives of tetrahydroisoquinolines. 2. Trimetoquinol studies

The synthesis of N-(3',4',5'-trimethoxyphenylethyl)-3,4-dihydroxyphenylethylamine (2) and 1-(3,4,5-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (1) is presented. Comparative pharmacological effects of the optical isomers of 1 and compound 2 are reported in guinea pig atria, rat adipose tissue, guinea pig trachea, and guinea pig aortic strip preparations. In the beta-adrenoreceptor preparations, (-)-1 was shown to be more potent than (+)-1 or 2. Racemic 1 and 2 were shown to have equal alpha-antagonist properties in the inhibition of norepinephrine-induced contractions of guinea pig aorta.