GDF-8 propeptide binds to GDF-8 and antagonizes biological activity by inhibiting GDF-8 receptor binding

GDF-8 is a new member of the TGF-beta superfamily which appears to be a negative regulator of skeletal muscle mass. Factors which regulate the biological activity of GDF-8 have not yet been identified. However, the biological activities of TGF-beta superfamily members, TGF-beta1, -beta2 and -beta3, can be inhibited by noncovalent association with TGF-beta1, -beta2 and beta3 propeptides cleaved from the amino-termini of the TGF-beta precursor proteins. In contrast, the propeptides of other TGF-beta superfamily members do not appear to be inhibitory. In this investigation, we demonstrate that purified recombinant GDF-8 propeptide associates with purified recombinant GDF-8 to form a noncovalent complex, as evidenced by size exclusion chromatography and chemical crosslinking analysis. Furthermore, we show that GDF-8 propeptide inhibits the biological activity of GDF-8 assayed on A204 rhabdomyosarcoma cells transfected with a (CAGA)12 reporter construct. Finally, we demonstrate that GDF-8 propeptide inhibits specific GDF-8 binding to L6 myoblast cells. Collectively, these data identify the GDF-8 propeptide as an inhibitor of GDF-8 biological activity.     

Biomechanical characteristics of human trabecular bone

Objective. To evaluate the effect of strain rate (ġ3), apparent density (_a) and tissue density (_t) on Young's modulus (E), strength (σ_u) and ultimate strain (_u) on intervertebral bone from a Chinese population.

Methods. Testing was performed by uniaxial compression at five strain rates on 36 human trabecular bone specimens from three male T₁₂˜L₄ vertebrae.

Results. Apparent density ranged between 0.46 and 0.71 g/cm³. Tissue density ranged between 1.02 and 1.54 g/cm³. Non-linear regression analyses using strength, Young's modulus or ultimate strain as dependent variables (Y) and strain rate and apparent density or tissue density as independent variables were performed using the following equation: Y = a^bġ3^c. The exponent of apparent density and strain rate to Young's modulus were 1.88 and 0.07, separately (P = 0.0007). The variation of strength was explained only by apparent density with an exponent of 1.29 (P = 0.0107). The variation of Young's modulus was explained equally by the quadratic and cubic relationship to apparent density or tissue density (P < 0.01). Ultimate strain varied independently of apparent density or tissue density and strain rate.     

BMUS guidelines for the regular quality assurance testing of ultrasound scanners by sonographers

Quality Assurance of ultrasound systems is necessary to ensure the reliability of results and to check for deterioration in performance; a number of bodies have produced guidelines. Testing has traditionally been the responsibility of Medical Physics Departments but the important role of sonographers has been recognised and recent publications have included tests to be performed by ultrasound users. Since there are differences in approach between these publications the BMUS QA Working Party was established to provide a consistent set of guidelines specifically for sonographers. Three levels of testing are recommended, to include infection control and inspections for scanner and probe damage, basic display checks and further tests to assess drop-out, sensitivity and noise. These tests should form part of a programme that includes more comprehensive testing at longer intervals, perhaps by a Medical Physics Department.     

Sweet''s syndrome (acute febrile neutrophilic dermatosis) associated with adenocarcinoma of prostate and transitional cell carcinoma of urinary bladder

Association of Sweet's syndrome (SS) with solid tumours is found in about 15% of all malignancy-associated cases, but an association with two malignancies occurring in the same patient has been rarely reported. In the present report, we describe an 82-year-old male with SS in association with adenocarcinoma of the prostate and transitional cell carcinoma of the urinary bladder.