Stimulating factor for calf thymus DNA polymerase β

A factor that stimulates purified DNA polymerase β about 2-fold was separated from DNA polymerase β activity on a DNA-cellulose column. During the early stage of purification, the factor may be associated with DNA polymerase β to form a complex that sediments at 3.9 S in sucrose gradients and behaved as a 52,000 dalton protein on a Sephadex G-100 column. The complex, which contains 40,000 and 12,500 dalton polypeptides, was insensible to the stimulator, and did not show any exonuclease activity.     

A contractile ring and cortical changes found in the dividing Tetrahymena pyriformis

A contractile ring consisting mainly of microfilaments was found in the fission zone of dividing Tetrahymena pyriformis. Diameters of the microfilaments were widely distributed from 2.5 to 15 nm. Ring-associated structures such as lateral stripes, linkers and beads with siender tails were recognized. Lateral stripes arranged at regular intervals of about 84 nm on some parts of microfilament bundles were found in both tangential and transverse sections, suggesting that they correspond to bands fastening the contractile ring microfilaments. Linkers that connect individual lateral stripes to the epiplasmic layer were present. Beads or beads with slender tails were found to be arranged on some microfilaments.The results of the present paper also indicate that drastic morphological changes occur in the cortex of the fission zone, especially in the epiplasmic layer, accompanying contraction of the division furrow. The epiplasmic layer which was proved to be a compact filamentous network in this study has been known to exist at the periphery of cytoplasm in immediate contact with one of the cell surface membranes, the inner alveolar membrane; however, in the fission zone of the dividing ceil, it was frequently separated from the membrane and subsided into the cytoplasm. The subsided epiplasmic layer was then loosened and dispersed. The subsidence of the epipiasmic layer appears to be caused by the force generated by the contraction of the contractile ring and transmitted with the linkers to the epiplasmic layer. The changes observed in the epiplasmic layer are presumably indispensable for the rigid cortical layer contraction involved in cytokinesis of Tetrahymena.     

An improved method based on the Porter-Silber reaction for determining 17-hydroxycorticosteroids in urine

This paper describes a highly specific method for determining urinary 17-hydroxycorticosteroids, which has been developed by (i) changing the composition of the Porter-Silber reagent and (ii) removing contaminants interfering with the color reaction by addition of sodium bisulfite to β-glucuronidase-hydrolyzed urine before extraction with solvent. For a reference method the Norymberski-Riondel (J. K. Norymberski and A. Riondel 1970, Biochem. J. 120, 493–498) gas chromatography (glc) was used: Correlation coefficient between the present method and GLC = 0.988, deviation from the theoretical regression LINE = 6.8%, and coefficient of SIMILARITY = 0.56. These results are much better than those obtained by I. Ernest, B. Håkansson, J. Lehmann, and B. Sjögren (1964, Acta Endocrinol. 46, 552–562) for the original Porter-Silber method in comparison with the chromatographic measurement of grouped and individual steroids.     

ADP-ribosylation of nuclear protein A24

Nuclear protein A24, which is composed of histone H2A and ubiquitin, a nonhistone protein, joined by an isopeptide linkage [Goldknopf and Busch (1977) $\text{Proc}$. $\text{Natl}$. $\text{Acad}$. $\text{Sci}$. $\text{USA}$$\text{74}$, 864–868], is found to be ADP-ribosylated in isolated rat liver nuclei.     

Long-day flowering of Lemna perpusilla 6746 in Mo-deficient medium

Lemna perpusilla 6746, a short-day duckweed, flowered undercontinuous illumination if some of the SH inhibitors, such ascyanide or tungstate were added to the M-sucrose medium. Theeffect of tungstate was not overcome by simultaneous applicationof molybdate, but deletion of the Mo from the medium was enoughto induce the long-day flowering. In vivo assay of nitrate reductaseactivity suggested that nitrate reduction was not inhibitedby tungstate, CuSO₄ or AgNO₃ which induced longday flowering.The possibility was suggested that suppression of some Mo-requiringprocess other than nitrate reduction brings about the long-dayflowering in this plant. (Received November 12, 1975; )     

Bioluminescence — the biochemistry of photogens and photagogika

The present trend emphasizes the definitive chemistry of photogens, such as specific luciferins, and of photagogika (the actual light-emitters) rather than indirect evidence concerning components of bioluminescent systems as has been practices for almost a century, resulting in many misleading hypotheses. Recent advances indicate that, contrary to earlier conclusions, chemically identical components characterize divers types of bioluminescent organisms and that the r route to light emission probably always involves a hydroperoxide that, at least in some instances, leads to formation of a dioxytenone ring before decomposition.     

Microendocytosis in eosinophilic leukocytes

Rat peritoneal eosinophils were examined after intraperitoneal infusion either of a mixture of phosphate-buffered saline (PBS) and colloidal gold or of fetal calf serum. These cells characteristically contained vesiculotubular structures, cuplike structures, and small granules during centrifugation. The cup-shaped structures and elaborate labyrinths of vacuole-like spaces increased markedly after injection of the PBS-colloidal gold mixture, presumably as features of heightened microendocytic activity. The vesiculotubular structures increased greatly after infusion of fetal calf serum. A few cyrstalloid granules exhibited fine-structural changes after the PBS-colloidal gold injection, and more numerous crystalloid granules appeared altered after fetal calf serum. Infrequent small granules contained a lucent, crystal-like silhouette after the fetal calf serum injection. Eosinophils evidenced microendocytic uptake of gold spherules into coated vesicles, the cup-shaped structures, and the small granules, but not into the vesiculotubular structures or crystalloid granules after intraperitoneal infusion of the PBS-gold mixture. Strong unmasked acid phosphatase activity in small granules contrasted with the general lack of activity in normal-appearing crystalloid granules and moderate activity in apparently altered crystalloid granules, presumably reflecting active and latent forms of enzyme in the different granules.     

Significant role of host sialylated glycans in the infection and spread of severe acute respiratory syndrome coronavirus 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been transmitted across all over the world, in contrast to the limited epidemic of genetically- and virologically-related SARS-CoV. However, the molecular basis explaining the difference in the virological characteristics among SARS-CoV-2 and SARS-CoV has been poorly defined. Here we identified that host sialoglycans play a significant role in the efficient spread of SARS-CoV-2 infection, while this was not the case with SARS-CoV. SARS-CoV-2 infection was significantly inhibited by α2-6-linked sialic acid-containing compounds, but not by α2–3 analog, in VeroE6/TMPRSS2 cells. The α2-6-linked compound bound to SARS-CoV-2 spike S1 subunit to competitively inhibit SARS-CoV-2 attachment to cells. Enzymatic removal of cell surface sialic acids impaired the interaction between SARS-CoV-2 spike and angiotensin-converting enzyme 2 (ACE2), and suppressed the efficient spread of SARS-CoV-2 infection over time, in contrast to its least effect on SARS-CoV spread. Our study provides a novel molecular basis of SARS-CoV-2 infection which illustrates the distinctive characteristics from SARS-CoV.