Summary Effects of graded intensity exercise on plasma lipids was studied in Standardbred and Finnish‐bred Trotters. The rate of lipolysis indicated by the elevated plasma concentrations of glycerol increased parallel with the intensity of the trot in the Standardbreds, but not as clearly in the Finnish‐bred trotters. During the exercise plasma triglyceride concentration increased significantly and the increase correlated with the intensity of the exercise as well as the activity of lipolysis. Together with the increase in plasma triglycerides, there was a parallel increase in the pre‐beta fraction of lipoproteins which suggests that the hepatic synthesis of triglycerides was increased. It was calculated that about one third of the nonesterified fatty acids released in lipolysis during the high‐intensity exercise is oxidized and the remainder is used for resynthesis of triglycerides. Since there were interstrain differences in the concentrations of triglycerides and glycerol after the high‐intensity exercise it is suggested that the differences may be of some value in the estimation of recovery after submaximal exercise. Zusammenfassung Durch Arbeit induzierte vorübergehende Hyperlipidämie beim Sportpferd Bei gewöhnlichen Trabern sowie bei finnischen Trabern wurde der Einfluß abgestufter Arbeit auf die Plasmalipide untersucht. Der die Lipolyserate widerspiegelnde Anstieg der Plasma‐Glycerin‐Konzentration nahm bei den gewöhnlichen Trabern mit der Intensität des Trabs zu. Bei den finnischen Trabern manifestierte sich dies weniger deutlich. Die Plasma‐Triglycerid‐Konzentration nahm während der Arbeit signifikant zu. Der Anstieg der Plasma‐Triglycerid‐Konzentration war dabei mit der Intensität des Trabs und der Lipolyseaktivität korreliert. Mit dem Plasmatriglyceriden nahm die prae‐beta‐Fraktion der Lipoproteine zu. Dies spricht für eine Steigerung der Triglyceridsyn‐these in der Leber. Rechnerisch wurde ermittelt, daß etwa ein Drittel der während intensiver Arbeit bei der Lipolyse freigesetzten Fettsäuren oxidiert werden und daß der Rest zu Triglyceriden resynthetisiert wird. Da sich nach intensiver Arbeit Rasseunterschiede in den Plasma‐Konzentrationen von Triglyceriden und Glycerin ergeben, könnten diese Unterschiede unter Umständen für die Beurteilung der Erholung nach submaximaler Belastung von Bedeutung sein.

Abstract. Wepreviously found that type V collagen repressed the attachment and spread of aortic smooth muscle cells. The present study was carried out to investigate the effects of type V collagen on the formation of fibronectin and F-actin filaments of human dermal fibroblasts in relation to cell attachment and spread, using an immunofluorescent technique and morphometry. The number and area of the cells attached to type V collagen at 1 and 3 hours after seeding were significantly lower than those of cells on other substrates, including collagen types I, III and IV, and bovine serum albumin. However, there was no significant difference in the attachment and spread amongthe cells on these substrates after 24 hours. Cultured fibroblasts exhibited two patterns of fibronectin; one was a clear, linear fibronectin localized mainly in the cellular margins, and the other was a granular or flocculent fibronectin found in the perinuclear areas. The former was stained in non-permeabilized cells, but not in trypsin-treated cells (cell surface fibronectin). In contrast, the latter was not detected in nonpermeabilized cells, but was found in trypsin-treated cells (perinuclear fibronectin). Most of the cells cultured on type V collagen did not form either linear cell surface fibronectin or F-actin filaments at 3 hours. In contrast, manycells on collagen types I, III, and IV developed both cell surface fibronectin and F-actin filaments, the distributions of which were partially coincident. Colocalization of linear cell surface fibronectin and F-actin filaments was found in cells on all of the substrates after 24 hours. Perinuclear fibronectin showedsimilar patterns, and was not colocalized with F-actin filaments on different substrates at 3 and 24 hours of culture. Solid-phase substrates induced a better cellular attachment at 3 hours than serum adhesive factors. The administration of monensin, which inhibits the secretion of protein products, decreased the intensity of the fluorescence of cell surface fibronectin in fibroblasts, which was observed in a clear line. These results suggest that the retardation of the initial attachment and spread of fibroblasts on type V collagen is related to an inhibition in the formation of the fibronexus, a close transmembranousassociation of individual fibronectin fibers and F-actin filaments.The interactions between cells and extracellular matrices have been shown to mediate the behaviors of cells, including their attachment, spread, proliferation and morphogenesis (8, 10, 28,39). Type V collagen has been shown to inhibit the adhesion of various types of cells, including human endothelial cells, fibroblasts and smooth muscle cells (6, ll, 29). Cell surface receptors for extracellular matrices, including collagens and basement membranes, have recently been shown to mediate the adhesion of cells to the extracellular matrix and to other cells (4,14,17, 27). However, the mechanism by whichtype V collagen suppresses cellular attachment and spread is poorly understood. It is well established that...