Rolling-Circle Plasmid pKYM Re-initiates DNA Replication

It is believed that rolling-circle plasmids are incapable ofre-initiation since they have to maintain their copy numberand this is one of the difierences between plasmids and phagesas phi-x174. To examine whether a rolling-circle plasmid pKYMis incapable of re-initiating DNA replication, we constructeda plasmid that carries both the pKYM origin (fragment 13, 173bp) and its truncated origin (fragment 32, 56 bp) in the sameorientation. This plasmid yielded two smaller plasmids in thepresence of RepK, an initiator protein. We showed that RepKcan bind to the fragment 13 but not to fragment 32 which lacksthe 3'-moiety of fragment 13. These results imply that RepKinitiates DNA replication from fragment 13 and terminates atfragment 32, then the same RepK is used for re-initiation ofreplication from the fragment 32 region. pKYM is likely to bea unique plasmid that re-initiates DNA replication like a phagephi-x174.     

Regulation of Tubulin Degradation in Isolated Zinnia Mesophyll Cells in Culture

Tubulin degradation in isolated Zinnia mesophyll cells in culturewas investigated by pulse-chase labeling with [³⁵S]-methionineand two-dimensional electrophoresis. Tubulin degradation changesdynamically during culture. Almost no tubulin degradation occursin the cells on the first day in culture. Treatment of thesecells with colchicine activates the degradation of tubulin,but not of proteins other than tubulin. In the presence of colchicine,the and ß-subunits of tubulin are degraded togetherand the half life of each subunit is approximately 6 h. After2 d in culture, there is active degradation of tubulin evenin the absence of colchicine. Colchicine did not inhibit new synthesis of tubulin in Zinniacells. This is very different from the results reported in culturedmammalian cells, whereby unpolymerized tubulin elevated by colchicine-treatmentdepresses its own synthesis. These and previous results dealing with changes in the leveland synthesis of tubulin in cultured Zinnia cells (Fukuda 1987),are discussed in relation to the regulation of tubulin metabolismin cultured Zinnia cells. ¹Present address: Biological Institute, Faculty of Science,Tohoku University, Aoba-yama, Sendai, 980 Japan. (Received September 5, 1988; Accepted December 20, 1988)     

A Change in Tubulin Synthesis in the Process of Tracheary Element Differentiation and Cell Division of Isolated Zinnia Mesophyll Cells

Changes in tubulin synthesis in the process of cytodifferentiationinto tracheary elements and cell division were investigatedusing a culture of single cells isolated from the mesophyllof Zinnia elegans. The tubulin content was measured by a sensitiveimmunoblotting method using a mouse monoclonal antibody to -or ß-tubulin as a probe and mung bean tubulin as astandard. Freshly isolated mesophyll cells had only small amountsof tubulin, but the content increased rapidly between 24 and48 h of culture before morphological differentiation and celldivision. The content rose more than sixfold during 48 h cultureand then decreased slightly. This pattern of increase closelyresembled that of the increase in cortical microtubules (MTs)estimated by electron microscopic analysis. The - and ß-tubulincontents in the cultured cells were almost the same and changedin coordination during culture. The activity of tubulin synthesis was determined by densitometricscanning of spots corresponding to tubulin subunits on an autoradiogramof a two-dimensional polyacrylamide gel of [³⁵S]-methionine-labeledproteins. Tubulin synthesis began as early as between 4 and8 h of culture and its rate increased similarly to the increasein the tubulin content, with the former always preceding thelatter, indicating that the increase in content resulted fromnew tubulin synthesis. (Received December 16, 1986; Accepted February 25, 1987)     

Inhibition of Cell Division and DNA Synthesis by Gibberellin in Isolated Zinnia Mesophyll Cells

A culture system of isolated mesophyll cells of Zinnia eleganswas used to examine the action of gibberellic acid (GA) on celldivision. Isolated Zinnia mesophyll cells cultured in a mediumcontaining auxin and cytokinin reinitiated cell division ina partly synchronized manner. When mesophyll cells isolatedfrom 21-day-old seedlings were used, GA added to the culturemedium at concentrations of 1 x 10^–6 M or higher suppressedthe initial rise in the number of divided cells. Tracer experimentswith [³H]-dThd revealed that GA treatment inhibited the incorporationof [³H]-dThd into DNA in the nucleus without inhibiting theuptake of [³H]-dThd into the cells, indicating that GA inhibitedDNA synthesis. GA applied at 48 h inhibited the incorporationof [³H]-dThd into DNA during the following 24 h, but GA appliedat 72 h did not inhibit the incorporation during the subsequent24 h. This suggests that GA affects the process of reinitiationof DNA synthesis, but does not affect DNA synthesis once cellshave become proliferative. (Received January 14, 1986; Accepted March 31, 1986)     

Clinical effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on various types of neutropenia including cyclic neutropenia

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was investigated for its clinical efficacy in the treatment of various types of neutropenia (3 cases with idiopathic neutropenia of suspected drug induction, 5 cases with idiopathic neutropenia of other origin, and 2 cases with cyclic neutropenia). Treatment with glycosylated rhG-CSF produced in the Chinese Hamster Ovary cells at dose levels of 2–5g/kg/day caused rapid increases of neutrophil counts associated with an improvement of the infection. In cyclic neutropenia patients, marked reduction in the duration of the neutropenic period was observed with rhG-CSF administration started before the period. Intercurrent stomatitis, which occurred in 1 patient, was markedly milder as compared to a previous episode which occurred during an untreated neutropenic period.The treatment of rhG-CSF was well tolerated and no adverse events were observed, nor was there any detectable anti-rhG-CSF antibody in any patients studied; hence the clinical use of rhG-CSF is considered to be safe.These results suggest beneficial effects of rhG-CSF on the recovery of neutrophil counts in cyclic and other types of idiopathic neutropenias, as well as for the treatment of neutropenia-associated infection.     

Patterns of nucleotide substitutions and implications for the immunological diversity of human immunodeficiency virus

Human immunodeficiency virus (HIV) exhibits immunological hypervariability, which has been an obstacle to successful production of effective anti-HIV vaccines. In this study, we estimated patterns of nucleotide and amino acid substitutions in the env gene of HIVs, with the aim of finding characteristics of the mechanism which generates the immunological diversity of the env protein of HIVs. We found that nucleotide changes between A and G are predominant compared to those between other nucleotides. Since this feature is consistent with the pattern of nucleotide substitutions of other retroviral genes but is quite different from those of most eukaryotic genes, a high rate of nucleotide substitution between A and G appears to be specific for retroviruses including HIVs. We discuss the biological relationship between this biased substitution and the mechanism generating hypervariability of epitopes on the env protein of HIVs.     

Sleep Apnea Syndrome (SAS) Clinical Practice Guidelines 2020

Sleep and Biological Rhythms - The prevalence of sleep-disordered breathing (SDB) is reportedly very high. Among SDBs, the incidence of obstructive sleep apnea (OSA) is higher than previously...     

Absence of contagious yawning in children with autism spectrum disorder

This study is the first to report the disturbance of contagious yawning in individuals with autism spectrum disorder (ASD). Twenty-four children with ASD as well as 25 age-matched typically developing (TD) children observed video clips of either yawning or control mouth movements. Yawning video clips elicited more yawns in TD children than in children with ASD, but the frequency of yawns did not differ between groups when they observed control video clips. Moreover, TD children yawned more during or after the yawn video clips than the control video clips, but the type of video clips did not affect the amount of yawning in children with ASD. Current results suggest that contagious yawning is impaired in ASD, which may relate to their impairment in empathy. It supports the claim that contagious yawning is based on the capacity for empathy.