Ultrastructural features of the aggregation stream and the center of the cellular slime mold D. discoideum were examined with special reference to the polarized movement of cells toward the center. The contact between stream cells and the substratum differed in proportion to their distance from the aggregation center. Cells in the aggregation stream located at a distance from the center were in close contact with the substratum, but cells closer to the center tended to be separated from the substratum. Although cells in the stream were generally loosely packed with large intracellular spaces, some areas of the cell surface were in close contact with other cells. Two conspicuous differences were evident in the intracellular structures of the anterior and posterior regions of stream cells. Cytoplasmic fibrils of about 60 Å in diameter were found more abundantly in the anterior region than in the posterior region, and a marked difference in the cell membrane structure was noted between the anterior and posterior ends. The biological significance of these differences was discussed in connection with the polarized movement and contact of cells.

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The Golgi apparatus and associated membrane structures (Novikoff's GERL) of rat anterior pituitary cells were examined by electron microscopy with cytochemical and three-dimensional techniques. The so-called Golgi lamellae were divided into an outer and inner part. The former showed a negative response to both acid phosphatase (AcPase) and thiamine pyrophosphatase (TPPase) activities, but strongly reduced osmium tetroxide. The inner part was characteristically positive in TPPase activity, but negative to AcPase reaction and osmification. GERL was a flat cisterna usually situated inside the Golgi lamellae, having a thicker membrane with bristle-like coating. GERL was positive to AcPase but not to TPPase reaction and osmification. Three dimensional observations indicated that GERL was sheet-like with a peripheral extension of tubular processes, whereas the inner part of Golgi lamellae was reticular in shape. Both the inner part of Golgi lamellae and GERL can produce secretory granules. The silver methenamine method for detection of polysaccharides and glycoproteins showed strong reaction in the secretory granules, lysosomes, rough ER, Golgi lamellae and GERL. As the contents of the inner part of Golgi lamellae and GERL were the same, they probably did not differ in function. GERL may thus belong to the Golgi apparatus.

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Tail tips of Xenopus laevis tadpoles were cultured in vitro and treated with triiodothyronine (T₃) to induce tail regression. Poly (A)-containing RNA [poly (A)-RNA] was isolated from regressing tail tips and characterized. The properties of poly (A)-RNA synthesis did not change throughout tail regression. The newly synthesized poly (A)-RNA was accumulated linearly for at least 24 h of labeling time, while the proportion of poly (A)-RNA to total labeled RNA remained approximately 3%. The major part of poly(A)-RNA labeled for 24 h showed a heterogeneous size distribution ranging from 0.5×10⁶ to 3.0×10⁶ daltons, with a broad peak around 2.0×10⁶ daltons, and the poly (A) segment consisted of 100-150 nucleotides of 3.3-5.0×10⁴ daltons. The results are discussed in relation to previous findings on RNA and protein synthesis in regressing tails.

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The electric surface charge of mouse melanoma B 16-C 2 W cells treated with various concentrations of Con A was determined by cell electrophoresis. At Con A concentrations higher than 5 μg/ml, the cellular electrophoretic mobility decreased significantly at 10 minutes incubation, but this effect was reversed by α-methyl-D-mannoside. At these higher Con A concentrations, more than 30% of Con A receptors were bound with lecitn. Pretreatment of cells with sulfhydryl blocking agents, 10^-5 M p-chloromercuribenzoic acid or 10^-5M N-ethylmaleimide, completely prevented the subsequent Con A-induced mobility reduction without changing the amount of Con A-binding to the cell surface. Similar effects were found with pretreatment with protein linkage agents, such as 2% glutaraldehyde and 10^-6M fluorescein mercuric acetate. The removal of chondroitin sulfate with the specific enzyme resulted in a 30% decrease in electrophoretic mobility of intact cells but produced no change in Con A-treated cells. These results suggest that Con A treatment may induce an alteration in chondroitin sulfate distributions at the cell surface and that sulfhydryl residues of membrane proteins may play an important role in this surface alteration.

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Changes in fluorescence intensity of the dye 3, 3'-dipropylthiodicarbocyanine iodide were monitored in guinea pig polymorphonuclear leukocytes (PMN) in the presence of reagents that modulate plasma membrane dynamics. Valinomycin, a specific K⁺ ionophore, increased fluorescence intensity as a function of log K⁺ concentration in incubation medium. The fluorescence was intensified by treating cells with concanavalin A, and 100μg/ml of the lectin was required for a half maximum change. The change was temperature dependent. It was inhibited by potent depressants of membrane fluidity, such as cholesterol ester and cepharanthine, or by colchicine which degrades microtubules. Cytochalasin B which degrades microfilament assembly stimulated fluorescence change. The change was also dependent on the ionic environment and energy state of PMN. These data suggest that the fluidity of the surface membrane and cytoskeletal system are closely related to changes in PMN membrane potential. The data further suggest that the changes might be involved in the concanavalin A-related transmembrane control mechanism.

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The protective effect of vitamin E was examined on inhibition by bisulfite of aggregations of dissociated embryonic quail liver cells in rotation-mediated cell culture. Bisulfite had a concentration-dependent inhibitory effect on the aggregation of cells. In the presence of 10^-2M bisulfite, the mean diameters of aggregates formed after 24 and 48 h were less than half of those of aggregates in control cultures. Addition of 10^-7M vitamin E significantly reduced the inhibitory effect of bisulfite on cell aggregation. A concentration of 10^-5M vitamin E had the most protective effect on aggregation of embryonic liver cells.

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The effect of vitamin E on the life span of human diploid cells was investigated. Ninety percent of vitamin E solubilized into growth medium was recovered from serum lipoprotein fractions in medium after removal of micelleous forms of vitamin E by Millipore filtration. Vitamin E in growth medium was found to be easily decomposed when the medium was placed in a dish in a CO₂-incubator but not in a culture bottle with a tight stopper. About 2_??_4% of vitamin E initially added to growth medium was incorporated into cells. The effect of vitamin E was investigated with parameters, such as cell attachment, cell proliferation rate and colony formation. Furthermore, in contrast to the findings by Packer and Smith, vitamin E had no effect on extending the life span of human fetal lung fibroblasts. Parallel cultures grown in the presence of 5 μg/ml hydrocortisone exhibited significant extensions in cell life span.

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A quantitative analysis of cell organelles was carried out by electron microscopy on synchronized populations of mouse leukemia L 5178 Y cells. The ratio of total mitochondrial volume-to-cytoplasmic volume (volume density of mitochondria) increased gradually from G1 to G2 through mid-S phase. The number of mitochondria per cell was nearly constant from G1 to mid-S phase but increased significantly from mid-S to G2 phase. The volume density of lysosomes increased by about 40% from mid-S to G2 phase, while no remarkable difference was detected in the volume density between G1 and mid-S phase. The surface area of rough-surfaced endoplasmic reticulum in unit volume of cytoplasm (surface density of rER) increased by about 140% from G1 to G2 phase. The volume density of Golgi apparatus increased by a small amount during interphase. The volume density of lipid bodies was the highest at mid-S phase, whereas their number per unit volume of the cytoplasm (numerical density of lipid bodies) decreased continuously from G1 to G2 phase through mid-S phase. The significance of these results is discussed with reference to mitochondria) proliferation, lysosomal activity and membrane turnover.

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Mating reactive cilia of complementary mating types of Paramecium caudatum were isolated, treated with heat and several kinds of enzymes and chemicals for the purpose of studying the chemical nature of the mating substances. Mating reactivity was lost by treatment with trypsin, chymotrypsin and thermolysin. The isolated cilia retained mating reactivity after treatment with non-proteolytic enzymes, such as neuraminidase, hyaluronidase, lysozyme, β-glucosidase, phospholipase C and snake venom phospholipase A. The mating reactivity of cilia was lost by treatment with extreme pH, heat, some organic solvents and some detergents. No effect was detected on the mating reactivity of isolated cilia with SH-group agents, such as p-chloro-mercuribenzoate, N-ethymaleimide, dithiothreitole and 2-mercaptoethanol. The results suggest that the mating substances in P. caudatum are integral proteins of ciliary membranes and that SH-groups have no essential role in the mating reaction.

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Protoplasts were enzymatically released from Spirogyra and Zygnema. The released protoplasts cultivated in liquid media regenerated a wall, grew in filamentous fashion and usually divided with an incomplete septum. When the media osmolarity was gradually reduced, the regenerated cells grew further. These regenerated cells appeared to be the same as the original cells.

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The movement of granules or materials composing the spindles of primary spermatocytes of grasshoppers was cinematographically recorded and photokymographically analyzed by tracing. These “markers” between chromosomes and spindle poles moved poleward during metaphase and anaphase at about the velocity of chromosomes during anaphase.

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A cross-linking agent (actinomycin D or mitomycin C) was administered to newborn rats with liver cells actively proliferating in diploid state, to test our recently proposed hypothesis that polyploidization and binucleate formation become manifest, under abortive cell proliferation, in nucleus with cross-links between double strands of DNA. The polyploidization of hepatocyte nuclei was analysed by Feulgen cytofluoromertric method with smear preparations, and binucleate formation was determined on section preparations. The number of polyploid and binuclear cells increased in rat liver treated with a cross-linking agent in comparison with the control. This finding supports our cross-linkage hypothesis.

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