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A new method is described for observing and quantifying an aspect of contact inhibition of cell movement that is sometimes called "contact paralysis". Based on the scanning acoustic microscope (SAM), the method can detect changes in the mechanical properties of cells, as well as changes in their motility and may therefore be more sensitive to some dynamic changes than methods based on optical microscopy. With this method intracellular motility of normal and transformed cells of epithelial and fibroblastic origin was investigated. By subtraction of SAM images patterns of motility, domains were detected that changed in a characteristic way among various cell lines. Wave-like and nucleating domains could be distinguished; they were also used for the quantification of motility. Like migration intracellular motility is influenced by cell-cell contacts. In zones where a cell touches its neighbours motility domains change or disappear depending on the cell type. In immortalized epithelial cells (XTH-2 cells) large quiescent zones developed in the region where contact with neighbouring cells was established, whereas in fibroblastic (3T3) cells motility was reduced less and did not change in domain pattern. Epithelial and fibroblastic cells were less motile when in contact with other cells or in confluent cultures than when solitary, i.e. their motility was contact inhibited. Transformed (SV40 3T3) cells, however, did not reduce their motility when in contact to or enclosed by other cells. The molecular basis for motility domains remains to be investigated.

Some aspects of tissue damage as it may accompany shock are investigated in an in vitro model system. Some effects of cell debris obtained by sonication of BHK 21 cells on viable cultures of freshly dissociated cells of the same line are evaluated. After 24 h incubation on a coverglass, the area covered by cell nuclei per square millimeter was determined. Spreading of viable cells is inhibited by the cell debris. In this way, growth and viability are also impeded. After 24 h the mitotic index in controls and treated cell-cultures is the same. The inhibition is exhibited as well by the supernatant as the pellet of a centrifuged suspension of sonicated cells. The growth retardation is counteracted by the polyvalent protease inhibitor Trasylol (50 KIE/ml), when the whole suspension or its pellet are added to the culture, but not when the supernatant affects the cells. These results indicate that the injurious substance is not a protease. The protective action of Trasylol may be due to a stabilisation of lysosomes. Tissue injury is often accompanied by alterations in cellular adhesiveness to substrate and in growth rate. The system used here offers a simple model to study the influence of necrotic tissue on cell viability as well as its pharmacological susceptibility.

The physiological significance of the association of glycolytic enzymes with actin fibrils was investigated in cell culture. Cytochalasin D (CD) was used to induce the known actin-based sequence of events in a culture of an endothelial-cell line (XTH-2) derived from hearts from tadpoles of Xenopus laevis. 1 min following addition of CD, ruptures in the cortical fibrillar meshwork and in stress fibres are seen. At the same time the cellular ATP level decreases by ca. 25%. This and the following reactions resulting in a kind of arborization depend on a continuous supply with metabolic energy. As shown by measurements of oxygen consumption, cells with intact energy metabolism provide the ATP needed from glycolysis; ATP produced by oxidative phosphorylation is not utilized as long as lactate dehydrogenase (LDH) reoxidizes NADH2. After inhibition of LDH, respiration in XTH-2 cells doubles. CD treatment induces a transient increase in oxygen consumption, indicating an increased energy supply by respiration. From these results we conclude: The energy needed by the actomyosin system is - under normal metabolic conditions -supplied from ATP phosphorylated in glycolysis. The processes of energy metabolism seem to be highly compartmentalized; ATP is not a parameter that is kept constant in time intervals of minutes up to one hour.

Chloride cells are characterized by a great number of mitochondria and a uniquely proliferated agranular endoplasmic reticulum through which ions are transported to an apical pit for secretion to the environment. Chloride cells are extremely rare in the epidermis of the guppy, Poecilia reticulata Peters, adapted to fresh water. They are frequent in the epidermis of guppies adapted to sea water three weeks after adaptation, but have disappeared in fish that were kept in sea water for approximately one year. The fine structure of epidermal chloride cells and the influence of prolactin treatment on their number are described. The significance of these cells with respect to the possible roles of the epidermis and the pituitary hormone prolactin in teleost osmoregulation is discussed.

The dependence of the arrangement of fibrillar actin in cultured endothelial cells on metabolic conditions was investigated with cellular elements derived from the heart of Xenopus laevis tadpoles. Either primary culture or an established cell line (XTH-2) were used in these studies. The metabolic stage of the cells was influenced by inhibiting respiration and lactate production. The actin pattern was revealed either by indirect immunofluorescence or by tetramethylrhodaminyl (TRITC)-phalloidin fluorescence. Total block of energy supply causes in all cases a distinct loss of actin fibrils, while inhibition of respiration alone increases the variability of actin organization. In primary XTH cells but not in XTH-2 cells cyanide disintegrates most of the actin fibres during 3 h of treatment. This effect is independent of the inhibition of respiration, since actin gels prepared from skeletal muscle also undergo destruction in the presence of cyanide. It is concluded that the actin fibrils of the primary cells and the established line behave differently to changing metabolic conditions and to application of KCN.

The cytoskeleton of primary tissue-culture cells from the epidermis of Xenopus laevis tadpoles was investigated by phase-contrast, immunofluorescence, and electron microscopy. The connection between the arrangement of different types of filaments and the mechanical properties of the epidermis is discussed. The bilayered epidermis attains stability from thick bundles of tonofilaments interconnecting the basal desmosomes. Twisting of tonofilaments around each other can explain the occurrence of elastic filamentous curls forming a meshwork braced between rows of "small desmosomes" in the apical region of the epidermis. Actin is arranged as a diffuse meshwork and sometimes forms bundles intermingling with tonofilament bundles. Surface membranes and rows of "small desmosomes" are delineated by actin and contain alpha-actinin. Actin raises the tension for rounding and spreading of cells. Microtubules stabilize already well-developed lamellae.