A fine structural study of the development of the chick flexor digital tendon: a model for synovial sheathed tendon healing

The development of the synovial sheathed flexor digital tendon in the chick was studied by light and electron microscopy in 12-day embryos to 22-day post-hatched chickens. Areas of specialized connective tissue differentiation were identified in this complex structure consisting of a lubricated synovial sheath, elastic vincula and fibrocartilaginous adaptations on the surface of the tendon. The presence of some of these specialized adaptations may be related to the specific types of mechanical forces and stresses applied to the developing connective tissue system. This model system appears to be appropriate for the experimental study of tendon injuries related to the human hand.

Lymphokines in rheumatoid synovitis

In antigen-induced experimental arthritis of rabbits, a macrophage migration inhibitory factor was released from the inflamed synovial tissues. A migration inhibitory factor, blastogenic factor, and B-cell-stimulating factor were also found in human rheumatoid synovial fluids and culture supernatants of rheumatoid tissue explants. Joint fluids from patients with inflammatory conditions other than RA sometimes also displayed these activities. OA fluids were usually inactive. At present, little is known of the origin or role in vivo of the lymphokine-like activities observed in the joints of rheumatoid patients. In related experiments, injection of lymphokine-rich antigen-free lymphocyte supernatants into normal rabbit knee joints produced a synovitis characterized by lining layer hyperplasia and infiltration of the sublining layer by macrophages. The lymphocytic and plasmacytic components seen in active antigen-induced synovitis were absent. It seems likely that some of the changes observed in active chronic synovitis are mediated by soluble factors of the lymphokine variety.

[Electron-microscopic demonstration of virus-like structures in the synovial membrane in chronic progressive polyarthritis]

The recent demonstration of ultramicroscopic "virus-like" cell inclusions in various organs in patients with collagen and autoimmune diseases suggest that viruses may play an aetiological role in these diseases. This paper reports briefly on some of the evidence for such "virus-like" structures in different cells of the synovial membrane from two patients with rheumatoid arthritis. The inclusions were localised in the vaculoes of the endoplasmatic reticulum of endothelial cells, lymphocytes, macrophages, fibroblasts and perithelial cells. They appear as tubular bodies of approximately 250 A. diameter. The tubules join together so that they form a 3-dimensional network. The possible viral or non-viral nature of these inclusions is discussed. A ultramicroscopical resemblance to the RNA-containing paramyxo-viruses suggests their virus nature. However, the negative results in testing with serum antibodies and immunofluorescence techniques argue against this. The authors suggest that the demonstration of these inclusions in other than collagen diseases points more in the direction of the correlation of these inclusions with immune globulin synthesis rather than the presence of a virus.

Still's disease in an adult: A link between juvenile and adult rheumatoid arthritis

A 52-year-old man developed rheumatoid factor negative, chronic, symmetrical polyarthritis associated with high intermittent fever and morbilliform evanescent rash at the onset. A detailed investigation and follow-up for two years failed to reveal any secondary cause. The onset and course resemble Still's disease in children. The synovial membrane histology and electron microscopy were consistent with early rheumatoid arthritis. Adult onset Still's disease reported in the literature is reviewed and compared with Still's disease in children.

Molecular pathogenesis of systemic lupus erythematosus

The study of patients with systemic lupus erythematosus revealed the close association of the disease with measles--or a related virus. High titres of antibodies to measles virus were found in patients that correlated with the course of the disease. Immunofluorescence tests revealed measles virus or a related antigen in lupus-affected tissues. Inclusion bodies consisting of paramyxovirus-like ribonucleoprotein structures were regularly detected in both affected tissues and leukocytes. Molecular hybridization of measles virus RNA with DNA from the affected tissues showed that DNA transcripts of measles or a closely related virus are integrated in the cellular nuclear DNA. Possible pathogenetic mechanisms of the disease are discussed.

Ultrastructural study of the normal rabbit synovium

The major lining cells of normal rabbit synovium are morphologically classified into two types. One type resembling macrophages or histiocytes (M type) is characterized by dense peripheral nuclear chromatin, many cytoplasmic vacuoles, coated vesicles, poorly developed, rough-surfaced endoplasmic reticulum (RER) and numerous filopodia. Some of the superficially located M cells containing accumulated cytoplasmic filaments are small and less active than the lower M cells. The second type resembling fibroblasts (F type) possesses dispersed nuclear chromatin, distended RER, prominent Golgi apparatus and abundant smooth-surfaced pino-cytotic vesicles. Lysosomal inclusions are commonly seen in both types of cells. In view of the morphological and functional similarities of M cells and regular macrophages or histiocytes, respectively, it seems likely that they are derived from common precursors and these precursor cells differ from those of F cells.