Vitamin A inhibits chondrogenesis but not myogenesis

Limb bud cells were isolated from HH stage 22–23 chick embryos and were grown as a ‘spot culture’ in in vitro conditions which support their differentiation into chondrocytes and myotubes. By day 4 of culture, numerous chondrocyte nodules developed and were scattered mainly in the very centre of the cell spot. In contrast, multinucleated myotubes formed at both the centre and the periphery of the cell spot. Treatment with vitamin A starting on day 1, inhibited chondrogenesis in these cultures, and by day 4–6 chondrocyte nodules could not be detected histologically. In contrast, no dose of vitamin A tested was effective in suppressing the development of multi-nucleated myotubes. These data show that vitamin A selectively inhibits chondrogenesis but not myogenesis in limb bud cell cultures.     

Autonomic neuropathy in Fabry disease: a prospective study using the Autonomic Symptom Profile and cardiovascular autonomic function tests

Background  

Fabry patients have symptoms and signs compatible with autonomic dysfunction. These symptoms and signs are considered to be due to impairment of the peripheral nervous system, but findings indicative of autonomic neuropathy in other diseases, such as orthostatic intolerance and male sexual dysfunction, are infrequently reported in Fabry disease. The aim of our study was to investigate autonomic symptoms and cardiovascular autonomic function in a large cohort of male and female Fabry patients.     

The high molecular weight Cat-301 chondroitin sulfate proteoglycan from brain is related to the large aggregating proteoglycan from cartilage, aggrecan.

Monoclonal antibodies Cat-301 and Cat-304 recognize a neuronal cell surface-associated chondroitin sulfate proteoglycan (CSPG), which is expressed during critical periods of postnatal development in the mammalian central nervous system (CNS). In the present study we show that the CNS CSPG identified by Cat-301/304 is similar to aggrecan, the high molecular weight CSPG from cartilage. By Western blot analysis, cartilaginous tissues, which are rich sources of aggrecan, have a high concentration of a high molecular weight CSPG which is immunoreactive with Cat-301 and 304. The Cat-301 and 304 epitopes, however, are partially masked by chondroitin sulfate glycosamino-glycan and are unmasked by digestion of the antigen with chondroitinase ABC. Although the antigen from both cartilage and CNS can be purified by CsCl buoyant density gradient centrifugation, a standard technique for purifying aggrecan, most of the antigen from the CNS has a lower buoyant density than that of cartilage. This may be due, in part, to the paucity of keratan sulfate substitution on the CNS antigen compared with that of the cartilage antigen. Both the CNS and cartilage antigens bind to hyaluronic acid, a feature characteristic of aggrecan. The physiochemical, biochemical, and functional properties of the Cat-301/304 antigen from cartilage are identical to aggrecan. The CNS antigen is similar, but not identical, to the cartilage antigen, and may thus represent another member of the family of high molecular weight CSPGs which bind to and aggregate with hyaluronic acid.     

Changes in protein and glycoprotein biosynthesis during differentiation of satellite cells in vitro

Satellite cells were isolated from leg skeletal muscles of adult mice and grown in culture. During the first few days in culture, satellite cells actively proliferated and starting on day 4 began to fuse into multinucleated myotubes. At various time points during the culture period, the biosynthesis of total cellular proteins and glycoproteins was analysed by pulse-labelling with radioactive leucine or sugars followed by electrophoretic analysis on two-dimensional gels. Our findings are: (1) Replicating mononucleated satellite cells on day 1 of culture did not synthesize detectable amounts of α and β tropomyosins, α-actin, and myosin light chains 1 and 2; (2) the synthesis of these polypeptides was readily detectable in multinucleated myotubes that formed by day 5–6 of culture; (3) other qualitative and quantitative differences in as yet unidentified proteins were observed in replicating cells as compared with multinucleated myotubes as well as to muscle fibroblasts; and (4) at least two distinct glucosamine-containing acidic glycoproteins of about 70 000 D and pI 5 were synthesized by myotubes, but not by replicating satellite cells.These data demonstrate that the biosynthetic programs for proteins and glycoproteins of cultured replicating satellite cells can be distinguished from those of multinucleated myotubes and from those of muscle fibroblasts. These data are interpreted to indicate that during muscle histogenesis in vivo, satellite cells become arrested prior to the expression of terminally differentiated traits.