Transforming growth factor-beta production by synovial tissues from rheumatoid patients and streptococcal cell wall arthritic rats. Studies on secretion by synovial fibroblast-like cells and immunohistologic localization

The growth of synovial fibroblast-like cells from patients with rheumatoid arthritis and rats with streptococcal cell wall (SCW)-induced arthritis in vitro under anchorage-independent conditions is inhibited by transforming growth factor-beta (TGF-beta). Because this growth factor is present in rheumatoid synovial fluids, we studied whether this cytokine might be secreted by cells in rheumatoid synovial tissue. We show that synovial tissues from patients with rheumatoid arthritis and osteoarthritis, and rats with SCW-induced arthritis, contain TGF-beta-1 mRNA. TGF-beta, predominantly type 1, was spontaneously secreted in vitro by synovial tissue explants and synovial fibroblast-like cells. In addition, TGF-beta could be detected immunohistochemically in cells throughout rheumatoid and SCW-induced arthritic rat synovial tissues. Finally, exogenous TGF-beta induced collagen and inhibited collagenase mRNA levels by cultured synoviocytes. These data support an autocrine role for TGF-beta in the regulation of synoviocytes in rheumatoid arthritis and, in light of its demonstrated effects on the immune system, suggest that TGF-beta might also have important paracrine effects on infiltrating inflammatory cells.     

Localization of the Escherichia coli rnt gene encoding RNase T by using a combination of physical and genetic mapping.

The rnt gene encoding RNase T was cloned on a 13-kilobase BamHI fragment. Restriction analysis of the fragment and comparison of it with the Escherichia coli restriction map localized rnt to kilobase coordinates 1733 to 1746, corresponding to about 36 min on the genetic map. The map location was confirmed by cotransduction with the nearby zdg-229::Tn10 and ksgB1 markers.     

Spatial arrangement and diet overlap between colonies of desert ants

Summary The spatial patterns and diets of three desert ant species were examined. The results indicate that food competition may account for the spatial arrangement of these species, and that only intraspecific interactions may be required. Each ant species was significantly overdispersed, and the average intraspecific nearest neighbor distances were greater than the interspecific nearest neighbor distances. A test of pairwise spatial arrangment showed that all three species pairs were aggregated interspecifically. The level of the interspecific aggregation was related to the diet similarity of the species. The two species pairs with the lowest diet overlaps were significantly aggregated, and the species pair with the most similar diets was not significantly aggregated. Pairwise dietary overlaps between colonies showed that average intraspecific overlaps were significantly greater than interspecific diet overlaps. Furthermore, the diet overlap was significantly positively correlated to the mean nearest neighbor distance for the three intraspecific and three interspecific comparisons. These data indicate competition for food, especially within species, may be regulating the intercolony distances of these ant species. A computer simulation tested whether only intraspecific territoriality is necessary to produce the observed nearest neighbor distances. A simulation that placed colonies randomly on a patch confirmed that these colonies are intraspecifically overdispersed. By adding intraspecific territoriality, the simulation nearest neighbor distances fit the empirical data reasonably well. Thus interspecific competitive interactions seem unnecessary to account for the spatial arrangement of these species.     

Additional fish recordsfrom the Judith River Formation (Campanian) of Montana

The recent recovery of additional fish remains from several fossil sites in Blaine County. Montana, allows us to add a new species of selachian and the occurrence of two genera of Chimaeriformes to the total vertebrate faunal assemblage of the Judith River Formation (Campanian).The new selachian genus is: Chiloscyllium missouriensis, a representative of the family: Orectolobidae.In association with the new orectolobid, there are representatives of the Chimaeroids: Ischyodus bifurcatusCase, and Elasmodus cf. greenoughiAgassiz.These new additions increase the total vertebratefaunnal assemblage of the Judith River Formation to twenty species.     

The role of introduced species in shaping the distribution and abundance of island reptiles

Summary Species interactions, as revealed by historical introductions of predators and competitors, affect population densities and sometimes result in extinctions of island reptiles. Mongoose introductions to Pacific islands have diminished the abundance of diurnal lizards and in some cases have led to extinctions. Through these population level effects, biogeographic patterns are produced, such as the reciprocal co-occurrence pattern seen with the tuatara and its predator, the Polynesian rat, and with the tropical gecko competitorsHemidactylus frenatus andLepidodactylus lugubris in urban habitats in the Pacific. Although competition has led to changes in abundance and has caused habitat displacement and reduced colonization success, extinctions of established reptile populations usually occur only as a result of predation.These introductions, along with many manipulative experiments, demonstrate that present day competition and predation are potent forces shaping community structure and geographic distributions. The human introduction of species to islands can be viewed as an acceleration of the natural processes of range expansion and colonization. The immediate biotic consequences of these natural processes should be of the same intensity as those of the human introductions. Coevolution may subsequently act to ameliorate these interactions and reduce the dynamical response of one species to the other. The role played by coevolution in mediating interactions between competitors and predator and prey is highlighted by the susceptibility of predator-naive endemic species to introduced predators and the invalidity of species-poor communities.