The chemical composition of long-bone rudiments from the embryonic chick

Effect of TNF-alpha on the melatonin synthetic pathway in the rat pineal gland: basis for a 'feedback' of the immune response on circadian timing

A retino-hypothalamic-sympathetic pathway drives the nocturnal surge of pineal melatonin production that determines the synchronization of pineal function with the environmental light/dark cycle. In many studies, melatonin has been implicated in the modulation of the inflammatory response. However, scant information on the feedback action of molecules present in the blood on the pineal gland during the time course of an inflammatory response is available. Here we analyzed the effect of tumor necrosis factor-alpha (TNF-alpha) and corticosterone on the transcription of the Aa-nat, hiomt and 14-3-3 protein genes in denervated pineal glands of rats stimulated for 5 hr with norepinephrine, using real-time reverse transcription-polymerase chain reaction. The transcription of Aa-nat, a gene encoding the key enzyme in melatonin biosynthesis, together with the synthesis of the melatonin precursor N-acetylserotonin, was inhibited by TNF-alpha. This inhibition was transient, and a preincubation of TNF-alpha for more than 24 hr had no detectable effect. In fact, a protein(s) transcribed, later on, as shown by cycloheximide, was responsible for the reversal of the inhibition of Aa-nat transcription. In addition, corticosterone induced a potentiation of norepinephrine-induced Aa-nat transcription even after 48 hr of incubation. These data support the hypothesis that the nocturnal surge in melatonin is impaired at the beginning of an inflammatory response and restored either during the shutdown of an acute response or in a chronic inflammatory pathology. Here, we introduce a new molecular pathway involved in the feedback of an inflammatory response on pineal activity, and provide a molecular basis for understanding the expression of circadian timing in injured organisms.

The effect of chlorhexidine gluconate on the formation of experimental granulation tissue

The aim of the study was to investigate the effect of chlorhexidine gluconate on the connective tissue formation. Granulation tissue was produced with a method in which sponges were inserted beneath the back skin of rats. Dry sterilized sponges were impregnated either with 0.45% NaCl solution (control) or or 0.2% chlorhexidine solution [test]. The sponges were removed after 3, 5, 7, 10, 14, 19 and 23 days. The content of hydroxyproline, hexosamines, DNA and RNA was estimated from the sponges. The acid glycosaminoglycans were further purified and analyzed. The results of the study indicate that chlorhexidine had a clear delaying effect on the formation of granulation tissue.

Environmental control of macromolecular synthesis in cartilage and bone: morphogenetic response to hyaluronidase

Tibiae of 12-day embryonic chickens were grown in organ culture in synthetic medium for 48 h in the presence of various levels of hyaluronidase. This treatment: (1) removed between 49 and 86 % of hexosamine-containing material from the rudiments, and the level of hydroxyproline remained just below that in controls; (2) reduced the length and weight of the rudiments; (3) increased the total protein and DNA content in bone but reduced the amount gained in cartilage; (4) altered the fine-structure of the epiphysial chondroblasts; (5) failed to affect the rate of incorporation of isotopic uridine and leucine. When explants were subcultured in normal medium for a further 5-day period, the degree of recovery was dose-dependent; the final level of constituents in bone and cartilage of some rudiments exceeded those in controls. Hyaluronidase greatly enhanced the synthesis of hexosamine-containing materials during the period of treatment of the rudiments and a second, but generally smaller, wave of excess synthesis occurred during the recovery phase; initially, large amounts of polymer chains were released into the medium, but they were incorporated into the tissues rapidly towards the end of culture. Characterization of the glycosaminoglycans indicated, also, that an abnormal type of polymer chain was synthesized and rejected by the tissue. The rate of synthesis of both hydroxyproline, and hence collagen, and non-collageneous protein was also enhanced during the recovery period. The results showed that the cells could re-establish their normal environment following the initial loss of intercellular macromolecules, and that such changes in the concentration of constituents enhanced the synthetic responses of the cells.

Cellular control of macromolecular synthesis: rates of synthesis of extracellular macromolecules during and after depletion by papain

Papain was administered in doses of 1.6, 8.0 or 80.0 μ g/ml. of synthetic medium for 24 h to 11- to 12-day embryonic chicken tibiae grown in organ culture. This treatment caused: (1) a decrease in length and weight, (2) loss of cells and total protein, (3) little change in hydroxyproline content, and (4) release of large amounts of glycosaminoglycans. When subcultured and allowed to recover in normal medium for periods of up to 144 h the explants increased in length and weight and partially replaced the lost material. In response to the depletion of the glycosaminoglycans, primarily chondroitin sulphate and keratan sulphate, from the extracellular matrix the cells of the treated explants synthesized both precursor hexosamine and the requisite polymerized glycosaminoglycans more rapidly than control explants. This increased rate of synthesis occurred whether or not the glycosaminoglycans were incorporated into the matrix; indeed, during recovery after treatment with the 80 μ g/ml. dose the tissue was unable to accept the newly synthesized macromolecules even though the matrix was very deficient in these substances, and the glycosaminoglycans were released into the medium. Large amounts of the monomer precursors of hexosamine also were released into the medium before they could be assembled into the polymer glycosaminoglycans. The results showed that the cell compensates for its loss of extracellular material by increased synthesis of the depleted macromolecules; after treatment with 8.0 μ g/ml. the rate of production of hexosamine was over three times that of the control explants.