Production of a factor (CIF) from normal fibroblast cells inhibiting tumor necrosis factor/cachectin production

Murine embryonic fibroblast cells produce a factor designated cytotoxin-inhibiting factor (CIF) which inhibits tumor necrosis factor (TNF) and interleukin 1 production as well as tumoricidal activity by lipopolysaccharide-activated macrophages. This study determines the physiologic conditions of CIF production in serum-free medium. CIF production was largely dependent upon the presence of lipopolysaccharide. A quantitative correlation between fibroblast cell number, lipopolysaccharide concentration, and incubation time was established. Evidence is presented that CIF inhibited the production or release of TNF. CIF did not destroy TNF after production and release nor did it sequester secreted TNF. The supernatant fluids which inhibited TNF production did not suppress the capability of resting macrophages to phagocytize opsonized sheep erythrocytes, suggesting that only functions expressed in the activated state are inhibited.     

Glycosaminoglycans and a newly purified aortic chondroitin proteoglycan block polycationic modulation of protein phosphatase activity

Recently, we described a bovine aortic phosphatase which we called PCM-phosphatase (polycation modulable) because its activity in vitro can be modulated by polycations such as polylysine and histone-H1 (Di Salvo J, Gifford D, Kokkinakis A. Modulation of aortic protein phosphatase activity by polylysine. Proc Soc Exp Biol Med 177:24-32, 1984). We We suspected that polycationic modulation might be inhibited by polyanionic glycosaminoglycans. Accordingly, an aortic anionic substance was purified by sequential steps including (a) heating aortic extracts at 90 degrees C, (b) precipitation of protein with (NH4)2 SO4, and (c) anionic-exchange chromatography on a Mono Q HR 5/5 column using the Pharmacia fast protein liquid chromatography system. Electrophoresis (polyacrylamide-agarose) of the purified substance revealed one band which stained metachromatically with toluidine blue; however, no staining occurred with Coomassie blue. Electrophoretic mobility increased following proteolytic digestion of the substance with papain. The substance produced concentration-dependent reversal of polylysine-mediated inhibition of myosin light chain dephosphorylation, and it also reversed polylysine-mediated stimulation of phosphorylase phosphatase activity expressed by PCM-phosphatase. Its ability to inhibit or reverse polycationic modulation was abolished after incubation with either chondroitinase AC or chondroitinase ABC. Based on these properties the substance was identified as a chondroitin proteoglycan. Commercially available glycosaminoglycans (heparin and chondroitin sulfates) also reversed polycationic modulation. The results show that modulation of phosphatase activity may be significantly modified by naturally occurring glycosaminoglycans. These studies may also have an important bearing on the purported roles of phosphatase(s) and glycosaminoglycans in calcification of soft tissues.     

Limited capacity for acclimation of thermal physiology in a salamander, Desmognathus brimleyorum

Habitats vary in temperature both spatially and temporally. Variation in thermal habitat introduces challenges to organisms and may reduce fitness unless organisms can physiologically adjust to such changes. Theory predicts that thermal variability should influence the capacity for acclimation such that increased variation should favor a reduction in the thermal sensitivity of physiological traits. In this study, we investigated acclimation to constant and variable conditions in populations of the salamander Desmognathus brimleyorum from the Ouachita Mountains of Arkansas, USA. We exposed salamanders to constant and variable temperature regimes for 8 weeks in the laboratory. We then tested salamanders for acclimation of thermal tolerance, and the thermal sensitivities of swimming performance and standard metabolic rate. Our results indicate limited capacity for thermal acclimation to constant and variable conditions in D. brimleyorum. Instead, variation in physiological traits is dominated by differences among populations. Population differences do not appear to be correlated with observed variation in the thermal conditions of the streams, but are likely a consequence of structural and ecological differences. Due to the mixed support for theoretical predictions for acclimation to alternative environments, further consideration should be given to revising and expanding current theoretical models.     

LIGHT MICROSCOPE AND ULTRASTRUCTURAL STUDIES OF THE MALE GAMETOPHYTE IN GINKGO BILOBA: THE SPERMATOGENOUS CELL

A light microscope and ultrastructural study was made of the pollen tube of Ginkgo biloba, with special emphasis given to the spermatogenous cell that gives rise to two motile sperms. Just prior to the mitotic division that results in the formation of two sperms, the spermatogenous cell consists of a large nucleus, two blepharoplasts, two large osmiophilic globules, and a conspicuous lipo-protein body. Other organelles in the cytoplasm include numerous electron-dense proplastids (with some lamellar development), mitochondria, small vacuoles, and lipid bodies. Ribosomes are present in abundance, but endoplasmic reticulum and dictyosomes are sparse. The nucleus, prior to mitosis, is relatively Feulgen-negative, due undoubtedly to the diffuse distribution of DNA. Each blepharoplast, the main organelle of interest, is nearly spherical, measures 3.5–4.5 μm in diam, and supports about 1,000 probasal bodies. The interior of a blepharoplast consists of an electron-dense matrix and of less dense regions which appear to be infiltrated by a network of microtubules. Each probasal body is composed of a cylinder of nine separate tubules (singlets) at the basal or proximal end. The cylinder becomes elaborated distally into nine pairs of subtubules (doublets) and then into nine sets of subtubules (triplets). A central tubule is present the entire length of the probasal body. Some of the subtubules, as well as microtubules from the interior of the blepharoplast, extend into the cytoplasm and probably constitute the “astral rays” as seen with the light microscope. Comparisons are made with other published accounts of the organization of blepharoplasts in plants and of centrosomes and centrioles in animals.