Individual and cumulative measures of knee joint load associate with T2 relaxation times of knee cartilage in young, uninjured individuals: A pilot study.

BACKGROUND: Articular cartilage structure and chondrocyte health are sensitive and reliant on dynamic joint loading during activities. The purpose of this pilot study was to determine the association between measures of individual and cumulative knee joint loading with T2 relaxation times in the knee cartilage of young individuals without knee injury. METHODS: Twelve participants (17-30 years old) without history of knee injury or surgery completed MRI, physical activity (PA), and biomechanical gait testing. T2 relaxation times were calculated in the cartilage within the patella and lateral and medial compartments. Accelerometry was used to measure mean daily step counts, minutes of PA, and % sedentary time over 7 days. Vertical ground reaction force, external knee joint moments and peak knee flexion angle were measured during stance phase of gait using three-dimensional motion capture. Cumulative knee joint loading was calculated as daily step count by external knee joint moment impulse. The relationship between measures of knee joint loading and T2 relaxation times was assessed using Pearson correlations. RESULTS: Higher T2 relaxation times in the femoral and tibial cartilage were consistently correlated to greater body mass, daily step counts, moderate and vigorous PA, and peak knee joint moments (r = 0.10-0.84). Greater cumulative knee flexion and adduction loading was associated with higher T2 relaxation times in the femoral and tibial cartilage (r = 0.16-0.65). CONCLUSION: Preliminary findings suggest that individual loading factors and cumulative knee joint loading are associated with higher T2 relaxation times in the articular cartilage of young, healthy knees.

Histochemical and immunohistochemical evidence of a bacterium associated with lesions of epizootic bovine abortion.

Epizootic bovine abortion (EBA), a tick-transmitted disease of pregnant cattle grazing foothill pastures, is a major cause of reproductive failure in California and adjacent states. Affected fetuses develop a chronic disease, resulting in late-term abortion or premature calving. Despite investigations spanning 50 years, to the authors' knowledge, the etiologic agent of EBA has not yet been isolated from affected fetuses or the tick vector. The diagnosis of EBA is based on gross and microscopic lesions. Recently, documentation that the etiologic agent is susceptible to antibiotics and identification of a unique 16S deltaproteobacterial rDNA gene sequence in 90% of thymus tissues from aborted fetuses have supported the role of a bacterial infection as the cause of EBA. To determine whether bacteria could be detected in the tissues, histochemical staining and immunohistochemical procedures were used on formalin-fixed, paraffin-embedded tissues. Use of a modified Steiner silver stain revealed small numbers of intracytoplasmic bacterial rods in 37 of 42 thymic samples from EBA-affected fetuses. Improved detection was achieved by use of immunohistochemical staining with serum from EBA-affected fetuses that resulted in detection of numerous bacterial rods in the cytoplasm of histiocytic cells in the thymus from all 42 EBA-affected fetuses. Immunohistochemical examination of additional tissues from 21 field and experimental EBA cases revealed positively stained intracytoplasmic bacterial rods in many organs with inflammatory lesions. Use of the modified Steiner stain and immunohistochemical staining of tissues from negative-control fetuses failed to reveal organisms. To the authors' knowledge, this is the first report to document morphologic evidence of a bacterium associated with the lesions of EBA.

The influence of crumble and mash feed on oral lesions of white leghorn laying hens.

The effect of crumble and mash feed on oral lesions in laying hens was investigated. Each of two groups of white leghorn hens (group A, n = 120; group B, n = 120) was separated into crumble- and mash-fed treatments. At the start of the trial, group A chickens were free of oral lesions, whereas group B chickens had nearly 100% prevalence of oral lesions. The trials began at 17.4 and 22 wk of age and ended at 32 and 33 wk of age for groups A and B, respectively. Chickens were housed in cages indoors, fed free choice, and serologically monitored. Oral lesions were periodically evaluated by visual scoring. Lesion prevalence peaked in group A chickens at 23-25 wk of age, concurrently with an outbreak of respiratory disease, and decreased to a low level at the end of the trial. For most of the trial, crumble-fed chickens had significantly lower oral lesion prevalence than mash-fed chickens (P < 0.05). Lesion prevalence in group B chickens decreased after treatments began and maintained this trend to the end of the trial. Compared with mash-fed chickens, crumble-fed chickens in group B had significantly lower oral lesion prevalence throughout the trial (P < 0.001). Neither group had significant differences in oral lesion scores between treatments. Most lesions were on the lower palate, pinpoint to 2 mm in diameter, often multiple, and bilaterally symmetrical. Feed analyses for mycotoxins and heavy metals were within normal limits. The inciting etiology of oral lesions was not elucidated in this trial. However, this work demonstrated that once lesions were present, feed type had a strong effect on persistence of oral lesions.