Mechanical measures during maximal velocity knee extension exercise and their relation to fibre composition of the human vastus lateralis muscle

Summary A method for measuring the maximal velocity of knee extension exercise is described using a very light lever arm. Instrumentation of the lever arm with a potentiometer and accelerometer also allows for the measurement of peak acceleration, time to peak acceleration, the average rate of development of acceleration (jerk) and peak torque. With this apparatus and surface electromyography, electromechanical delay (EMD) was also determined. This apparatus was tested using 17 female and 10 male subjects, and the measures obtained were related to the percentage of fast twitch fibres (% FT) and the relative area of fast twitch fibres (% FTA) in the vastus lateralis determined from duplicate muscle biopsy samples. Peak velocity of unloaded knee extension averaged 12.1±1.2 and 12.2±1.7 rad · s^–1 for females and males, respectively, and were not significantly different. As well, peak acceleration, time to peak acceleration jerk and EMD values were not significantly different between the female and male subjects, but the mean peak torque for the female subjects (73.5±14.7 N · m) was significantly lower than that for the males (98.4±31.5 N · m). Peak acceleration was significantly correlated with %FT (r=0.40,P=0.04) for the total subject population. None of the other measures was significantly related to either %FT or %FTA for the male and female subjects or the combined population of subjects.     

A novel human leucocyte antigen-DRB1 genotyping method based on multiplex primer extension reactions

We have developed and validated a semi-automated fluorescent method of genotyping human leucocyte antigen (HLA)-DRB1 alleles, HLA-DRB1*01-16, by multiplex primer extension reactions. This method is based on the extension of a primer that anneals immediately adjacent to the single-nucleotide polymorphism with fluorescent dideoxynucleotide triphosphates (minisequencing), followed by analysis on an ABI Prism 3700 capillary electrophoresis instrument. The validity of the method was confirmed by genotyping 261 individuals using both this method and polymerase chain reaction with sequence-specific primer (PCR-SSP) or sequencing and by demonstrating Mendelian inheritance of HLA-DRB1 alleles in families. Our method provides a rapid means of performing high-throughput HLA-DRB1 genotyping using only two PCR reactions followed by four multiplex primer extension reactions and PCR-SSP for some allele groups. In this article, we describe the method and discuss its advantages and limitations.     

Rowing prevents muscle wasting in older men

We evaluated the effects of rowing on the morphology and function of the leg extensor muscle in old people. The area and the power of the leg extensor muscle were measured in 15 oarsmen – age [mean (SD)] 65 (3) years; height 171 (4) cm, body mass 68 (6) kg – and in 15 sedentary men – age 66 (4) years, height 170 (4) cm, body mass 67 (7) kg – who were matched on the basis of their body size. The leg extensor muscle area of the oarsmen was larger than that of the sedentary men [77.8 (5.4) vs 68.4 (5.1) cm², P<0.05]. Also the bilateral leg extension power of the oarsmen was larger than that of the sedentary men [1,624 (217) vs 1,296 (232) W, P<0.05]. Thus, the leg extension power per the leg extensor muscle area was not significantly different between two groups [20.9 (2.0) vs 19.9 (2.1) W·cm^–2) and leg extension power was correlated to the leg extensor muscle area (59–89 cm², r=0.74, P<0.001). Also the 2,000-m rowing ergometer time of the oarsmen [495 (14) s; range 479–520 s] was related to leg extensor muscle area (68–89 cm², r=0.63, P<0.01). The results suggest that rowing prevents age-related muscle wasting and weakness. Electronic Publication     

腰大肌作用力与脊柱伸展应力关系的生物力学实验研究

目的:探讨腰大肌作用力带动脊柱伸展应力的生物力学关系。方法:取家兔12只,分3组,每组4只,解剖后保留枢椎以下完整之脊柱及骨盆、髋关节、上段股骨,不损伤脊柱前、后纵韧带、椎间盘及所附着之腰大肌,保留脊柱背侧的竖脊肌、棘上韧带,置于生物力学拉伸测试仪(日本岛津制作所产AGS-J系列)。上端十字头分别夹枢椎(颈胸腰段)、第1胸椎(胸腰段)和第12胸椎(腰段),下端十字头夹股骨上部;分别作有腰大肌状态下和切断腰大肌状态下,股髋自屈曲位到过伸带动脊柱自屈曲位到过伸位拉伸试验,测定两种不同状态下脊柱各节段的伸展应力(N/mm2)。结果:有腰大肌状态和切断腰大肌状态下,股-髋-脊柱拉伸后脊柱伸展应力分别为:颈胸腰全段平均为306.6675N/mm2:78.7167N/mm2;胸腰段为680.8417N/mm2:373.0375N/mm2;腰段为1990.7944N/mm2:523.0608N/mm2;经统计学分析,具显著性差异,P<0.01。结论:腰大肌作用力对脊柱伸展应力影响显著,颈胸腰段占74.33%、胸腰段占45.21%,腰段占73.73%的伸展应力源自腰大肌。脊柱在腰大肌作用下产生腰椎向腹部的弯曲。     

Rapid detection of beta-globin gene (HBB) mutations coupling heteroduplex and primer-extension analysis by DHPLC

Beta-thalassemia is a common inherited disease, resulting from one or more of a total of more than 200 different mutations in the beta-globin gene (HBB). Efficient and reliable mutation-screening methods are essential in order to establish appropriate prevention programs for at-risk populations based upon a molecular diagnosis. We have developed a rapid and highly-specific mutation screening test for the diagnosis of beta-thalassemia by coupling heteroduplex and primer-extension analysis based on the denaturing high performance liquid chromatography (DHPLC) system. A total of 161 healthy heterozygous Taiwanese carriers featuring 10 different HBB mutations and 30 patients exhibiting 12 different compound heterozygous or homozygous HBB mutations were subjected to DHPLC. The elution profile for the heteroduplex analysis of DHPLC could be successfully used to identify the common disease-causing mutations of HBB. To further confirm the sequence variants, we developed a technique combining multiplex primer-extension analysis coupled with DHPLC for the genotyping of eight common disease-causing mutations in the HBB gene. Overall, by coupling heteroduplex and primer-extension analysis based upon DHPLC, we were able to unambiguously identify the most-common beta-thalassemia mutations corresponding to more than 99% of HBB alleles among the Taiwanese population. In conclusion, compared to classic approaches to mutation screening for this malady, we suggest that DHPLC is an excellent technique to be applied to the genetic screening of prenatal and postnatal individuals as a part of a diagnosis program for beta-thalassemia and provides a more-efficient, economic, and sensitive means to undertake such a screening program.     

Enhancing Behavior Change Skills in Health Extension Workers in Ethiopia: Evaluation of an Intervention to Improve Maternal and Infant Nutrition

Maternal and infant nutrition are problematic in areas of Ethiopia. Health extension workers (HEWs) work in Ethiopia’s primary health care system, increasing potential health service coverage, particularly for women and children, providing an opportunity for health improvement. Their roles include improving maternal and infant nutrition, disease prevention, and health education. Supporting HEWs’ practice with ‘non-clinical’ skills in behavior change and health communication can improve effectiveness. This intervention study adapted and delivered a UK-developed training intervention for Health Extension Workers (HEWs) working with the United Nations World Food Programme in Ethiopia. The intervention included communication and behavioral training adapted with local contextual information. Mixed methods evaluation focused on participants’ reaction to training, knowledge, behavior change, and skills use. Overall, 98 HEWs were trained. The intervention was positively received by HEWs. Pre-post evaluations of communication and behavior change skills found a positive impact on HEW skills, knowledge, and motivation to use skills (all p < 0.001) to change women’s nutritional behavior, also demonstrated in role-play scenarios. The study offered substantial learning about intervention delivery. Appropriate cultural adaptation and careful consideration of assessment of psychological constructs are crucial for future delivery.     

A Prophylactic Tibial Stem Reduces Rates of Early Aseptic Loosening in Patients with Severe Preoperative Varus Deformity in Primary Total Knee Arthroplasty

BackgroundPatients with a preoperative varus deformity >8 degrees are at increased risk of aseptic loosening after total knee arthroplasty. This study analyzes the effect of a tibial stem on the rate of aseptic loosening in patients with a severe preoperative varus deformity.MethodsPatients with a preoperative varus deformity of >8 degrees and 2-year minimum follow-up with a stemmed tibial component (n = 67) were matched 1:2 to patients with a similar preoperative varus deformity with a standard tibial component (n = 134). Radiolucent lines were measured on the tibia at 6 weeks, 1 year, and 2 years postoperatively using the Knee Society Radiographic Evaluation System. Failure was defined as revision due to aseptic loosening of the tibial component. Outcomes were evaluated using Student’s t-tests and log-rank tests.ResultsPatients with tibial stems had greater preoperative deformity (12.9 vs 11.3 degrees, P = .004). There was no difference in postoperative alignment (1.7 vs 2.1 degrees varus, P = .25) or tibial component angle (1.8 vs 2.1 degrees varus, P = .33). Patients with stems were more likely to have more constraint (44.8% vs 1.5%, P < .001). Progression of radiolucent lines >2 mm was observed in 17.6% (23/134) vs 5.97% (4/67) of patients in the stem group (P = .03). Rates of aseptic loosening were lower in the stem group (0% vs 5.15%, P = .05).ConclusionDespite worse preoperative deformity and higher utilization of constraint, tibial stem use in patients with severe preoperative varus deformity resulted in lower rates of aseptic loosening. Prophylactic use of stems in these patients may help increase implant survival.     

Influence of age and of desmotropic drugs on the step phenomenon observed in rat skin

Summary Comprehensive analysis of the mechanical properties of rat skin revealed the step phenomenon. This particular observation was made after constant strain rate (analysis of stress strain curves) as well as after constant load (creep experiments). Relative low extensions or low loads were necessary to provoke the steps. In most cases two, sometimes three steps were observed. The step phenomenon was found mainly in skin strips punched out perpendicularly to the body axis. Probably some bonds in the fibrous network are broken giving way to additional elongation whereafter stronger links take over the stress. Since earlier studies demonstrated a pronounced influence of age and of desmotropic drugs on mechanical properties at ultimate load, e.g., tensile strength, ultimate modulus of elasticity, and ultimate strain, also the step phenomenon was studied under these conditions. In stress-strain experiments most of the steps were found at the ages of 2 and 4 months. Total stress loss and total work loss due to the steps were the highest at the age of 4 months. If, however, these values were calculated as percentage of ultimate values, the highest figures were found in young animals. Elongation gain due to the steps also showed a maximum at time of maturation, e.g., 4 months. Similar findings were achieved in creep experiments at medium load (200 g). After treatment with prednisolone acetate more steps and after treatment with d-penicillamine fewer steps were observed. In stress-strain experiments total stress loss and total work loss due to steps were more than twice as high than controls after prednisolone treatment and only one half after d-penicillamine. If calculated as percentage of ultimate stress or percentage of work input, these changes disappeared because of similar changes at ultimate load. However, elongation gain due to steps, which was not significantly influenced by prednisolone acetate but significantly decreased by d-penicillamine, showed the same changes when calculated as percentage of ultimate strain. Under all conditions the step phenomenon mainly influenced the extension parameters. The data presented here confirm earlier observations that mechanical properties at low loads or low and medium extensions show at least to some extent a different pattern under the influence of maturation and age and after treatment with desmotropic drugs compared to the mechanical parameters at ultimate load.     

Life Extension Research: Health, Illness, and Death

Scientists, bioethicists, and policy makers are currently engaged in a contentious debate about the scientific prospects and morality of efforts to increase human longevity. Some demographers and geneticists suggest that there is little reason to think that it will be possible to significantly extend the human lifespan. Other biodemographers and geneticists argue that there might well be increases in both life expectancy and lifespan. Bioethicists and policy makers are currently addressing many of the ethical, social, and economic issues raised by life extension research. However, the emphasis on philosophical argument supporting or condemning efforts to increase human longevity means that much less attention is currently being given to the factors that might play a role in generating interest in efforts to increase human longevity. This analysis considers three factors that might play a role in heightening public interest in efforts to develop biomedical technologies capable of retarding or reversing aging processes. While discussions of life extension research can seem quite futuristic and impractical, there are some powerful existential factors that might well generate considerable public support for life extension strategies if effective biomedical interventions emerge. Rather than providing philosophical justifications supporting or condemning efforts to increase human longevity, this essay seeks to promote a better understanding of the factors generating contemporary interest in prolonging life and postponing death.     

Cooperative extension initiatives in marriage and couples education

Cooperative extension has a long‐term history of delivering family life education. Further, the organization has developed numerous research‐based resources and undertaken statewide initiatives in marriage and couples education. Most promising of all is the work of a group of extension specialists to create a practical, research‐based curriculum that may reach communities in the United States through the established network of extension educators and their collaborators. We review various family relationship models and describe how the design of the new couples' curriculum is based on those models.