The role of neural tension in hamstring flexibility.

Resistance to stretch, electromyographic (EMG) response to stretch, stretch discomfort and maximum range of motion (ROM) were measured during passive hamstring stretches performed in the slump test position (neural tension stretch) and in the upright position (neutral stretch) in eight healthy subjects. Stretches were performed on an isokinetic dynamometer at 5°/s with the test thigh flexed 40° above the horizontal, and the seat back at 90° to the horizontal. Surface EMG signals were recorded from the medial and lateral hamstrings during stretches. Knees were passively extended to maximum stretch tolerance with test order (neural tension vs neutral) alternated between legs. For neural tension stretches, the cervical and thoracic spine were manually flexed. Maximum ROM was 8° less for the neural tension stretch vs the neutral stretch (P<0.01). Resistance to stretch was 14-15% higher for the neural tension stretch vs the neutral stretch (P<0.001) at common joint angles in the final third of ROM. Stretch discomfort and EMG response were unaffected by neural tension. In conclusion, an increased passive resistance to stretch with the addition of neural tension during passive hamstring stretch despite no change in the EMG response indicates that passive extensibility of neural tissues can limit hamstring flexibility.

Sampling in seed health testing.

ABSTRACT Seed health tests are usually performed on a sample of a seed lot; therefore, it is crucial that the test sample be as homogeneous as possible and representative of the lot. Seed sampling procedures appropriate for seed health testing have been developed by seed testing organizations such as the International Seed Testing Association and the Association of Official Seed Analysts. Seed lot size is generally not a constraint when the distribution of contaminated/infected seed in the lot is relatively homogeneous; if the distribution is heterogeneous, increased sampling intensity is required. Sample size is determined by the damage threshold (intolerable infection level) for the pathogen and the probability of detection desired, commonly 95 or 99%. The probability of detection at a given damage threshold is greater as sample size increases, and this probability and the appropriate sample size can be determined by statistical methods. Most seed health tests utilize qualitative data based on the presence or absence of the pathogen in the test sample, with the lot being rejected if the pathogen is detected in the sample and accepted if the sample is negative.

Isolation and Characterization of a Carmo-like Virus from Calibrachoa Plants.

Spherical virus particles approximately 29 to 31 nm in diameter were isolated from Calibrachoa plants showing leaf mottling and chlorotic blotch symptoms. The virus was mechanically transmitted to Chenopodium amaranticolor, C. capitatum, C. quinoa, Nicotiana benthamiana, and N. clevelandii plants, but was not transmitted by green peach aphid (Myzus persicae), sweet potato whitefly (Bemisia tabaci), silverleaf whitefly (B. argentifolii), greenhouse whitefly (Trialeurodes vaporarium), or banded-wing whitefly (T. abutilonea). Virions contained a single species of single-stranded RNA of approximately 4.0 kb and a single capsid protein of approximately 41 kDa. The double-stranded (ds)RNA pattern consistently revealed one major band of about 4.0 kbp, and three minor dsRNA of approximately 3.1, 1.6, and 1.3 kbp. The virus-infected plants reacted with a homologous polyclonal antiserum in indirect enzyme-linked immunosorbent assay. The genome contained a sequence of a highly conserved motif of the RNA-dependent RNA-polymerase associated with the genus Carmovirus, and shared 94% identity with Carnation mottle virus (CarMV). However, the Calibrachoa virus and CarMV were distinct serologically and in host range. Based on the host ranges, particle morphology, dsRNA profile, properties of particles in sap, and features of the genome and protein, we concluded that the recently observed Calibrachoa disease is caused by a previously undescribed carmovirus on Calibrachoa plants. We propose to name this virus Calibrachoa mottle virus (CbMV).