Characterization of proteoglycans synthesized by rabbit articular chondrocytes in response to transforming growth factor-beta (TGF-beta)

The effect of transforming growth factor-beta (TGF-beta, 1 ng/ml) on proteoglycan synthesis by rabbit articular chondrocytes in culture was studied in the presence of fetal bovine serum. Exposure of confluent cells for 24 h to the factor resulted in a marked increase of 35S-labeled sulfate incorporation in the newly synthesized proteoglycans (PG), as estimated by glycosaminoglycan (GAG) radioactivity (+58%). The onset was observed 6 h after addition of the factor but was significant after 12 h. TGF-beta also enhanced the uptake of [35S]sulfate by chondrocytes, but had no effect on the release of PG by these cells. The effect of TGF-beta on the distribution of PG between the medium and the cell layer was shown to be dependent on the serum concentration in the medium: the relative proportion of cell-layer associated GAG of TGF-beta-treated cells decreased with increasing concentration of fetal bovine serum. The proportion of aggregated PG, the hydrodynamic size of PG monomers and GAG chains were not modified by TGF-beta, but the relative distribution of disaccharides 6- and 4-sulfate in GAG chains was altered by the factor: the proportion of chondroitin 6-sulfate (C6S) was decreased while that of chondroitin 4-sulfate (C4S) was augmented in presence of TGF-beta, leading to a decrease of the ratio C6S/C4S (-11 to -22%, P less than 0.01). The present study indicates that TGF-beta promotes the synthesis of a modified extracellular matrix in cultured articular chondrocytes. This mechanism could be relevant to some aspects of cartilage repair in osteoarticular diseases.     

Biochemical and autoradiographic investigations of the retrograde axonal transport of labeled material following [H]norepinephrine injection in the olfactory bulb

Biochemical and autoradiographic methods were used to investigate the retrograde transport of labeled material after injection of [³H]norepinephrine ([³H]NE) in the olfactory bulb (OB) of rat. Mechanical obstruction of the ventricular recess prevented intraventricular diffusion. At different time intervals following bilateral [³H]NE injections, total radioactivity was measured in the OB, locus caeruleus (LC), raphe dorsalis and periaqueductal gray. Preferential accumulation occurred in the LC, and an approximate rate of retrograde transport of 1–6 mm/h could be calculated. Previous administration of 6-hydroxydopamine in the OB reduced this accumulation by 60%. Sixteen hours after [³H]NE injection, the radioactivity in LC was equally distributed between an ethanol-soluble and -insoluble fraction. A small proportion of the soluble material was recovered as [³H]NE and/or [³H]normetanephrine. Following unilateral injections of [³H]NE, light microscopic autoradiograms demonstrated nerve cell body labeling mainly in the ipsilateral LC and of greater intensity after 16 than 4 and 8 h. These data lead to the conclusion that the movement of radioactive material was indeed representative of retrograde axonal transport rather than of other mechanisms such as diffusion. The observation of a preferential labeling of noradrenergic perikarya in LC supports the hypothesis of a process mediated by specific binding and/or uptake of [³H]NE into noradrenergic axon terminals.     

Disruption of imprinting by memory inhibitors

Several amnestic drugs were administered intracranially to day-old chicks at selected times around a 10-min exposure to an imprinting stimulus. The drugs used were monosodium glutamate, ouabain, cycloheximide and amino-iso-butyrate. The chicks were tested for 10 min in the same apparatus two days later, and the time spent following the stimulu was recorded., The index of memory retention was the difference between the time spent following on test and the time spent following on the initial exposure. When compared with saline-injected control, glutamate administered 5 min before the beginning of the initial exposure was effective in producing a reduction in following times and hence amnesia. Ouabian was effective when injeced before the beginning and immediately after the end of the initial exposure; while cycloheximide was effective when administered as late as 5 min after the initial exposure. The effective times of administration for the drugs to produce a reduction in following times were similar to that observed for amnesia in passive avoidance memory tasks. The increase in following shown by the control chicks was not a developmental effect due to the increae in age on test. Experiments involving a choice of stimuli on test support the invovement of a memoryrelated phenomenon in these experiments.     

Effect of lectins on the interactions between human peripheral blood lymphocytes and monocytes

Interactions between normal human peripheral blood T lymphocytes and monocytes were investigated by measuring the in vitro cellular adherence of these cells in the presence and in the absence of mitogens. Concanavalin A (Con A), lentil lectin (Lc), and phytohemagglutinin (PHA) in mitogenic doses increased 15 to 20 times the binding of T lymphocytes to monocytes. The lectin-induced binding was similar to that produced by neuraminidase-gal-actose-oxidase treatment. A good correlation was found between the early cellular adherence induced by these lectins and by neuraminidase-galactose-oxidase and the blastogenesis of the T lymphocytes measured after 3 days of culture by [³H]thymidine uptake. However, wheat germ agglutinin (WGA), a nonmitogenic lectin, also increased the binding of T lymphocytes to monocytes. Addition of specific carbohydrates completely inhibited the cellular interactions induced by lectins. Peanut agglutinin (PNA) induced adherence of lymphocytes only after treatment of these cells with neuraminidase. Striking differences were not found between the lectin-induced adherence observed with autologous and heterologous cells. Killing of monocytes abolished entirely the lectin-induced adherence of lymphocytes, however killed T lymphocytes were still able to interact weakly with live monocytes. Dexamethasone was found to be a potent inhibitor of mitogen-induced cellular interactions.     

Na movements and their oscillations during fertilization and the cell cycle in sea urchin eggs

We have analysed in detail the Na⁺ content and Na⁺ influx during fertilization and first divisions of the sea urchin egg (Paracentrotus lividus) using a filtration technique devised to eliminate rapidly contamination by the Na⁺ of external sea water. In the first 5 min following fertilization the egg fills up with Na⁺ (+ 30%). Thereafter Na⁺ is extruded and the Na⁺ content stabilizes at about 60% of the unfertilized egg level by the second cleavage (2 h). The initial increase in Na⁺ content is due to a large increase in Na⁺ influx already detected at 20 sec. The Na⁺ influx reaches its maximum at 1 min and its minimum at 5 min. H⁺ excretion follows the same kinetics. A second increase in Na⁺ influx is noted 5–10 min after fertilization; it reaches its maximum at prophase metaphase (30 min) and its minimum during cleavage (60 min). These oscillations in Na⁺ influx were observed for the first three divisions. Fertilization also immediately stimulates the Na⁺ efflux which remains elevated throughout the cell cycle and is responsible for the depletion of the Na⁺ content of the embryos. Activation of the eggs by weak amine bases (5 mM NH₄Cl) which bypasses the early cortical reaction produces only a depletion in the Na⁺ content of the egg similar to that produced by fertilization. NH₄Cl also increases the Na⁺ influx soon after fertilization, although no transient variations are noted.