Human newborn autologous mixed lymphocyte response: frequency and phenotype of responders and xenoantigen specificity

The response of human newborn lymphocytes in autologous mixed lymphocyte culture was examined for specificity (by restimulation), responder cell phenotype, and responder cell frequency. When the newborn T cells were separated from non-T cells by rosetting with sheep erythrocytes (E) in fetal calf serum (FCS), approximately 1:20,000 T cells proliferated. These responders had specificity for E + FCS, were T4+, and were self-restricted. Significant numbers of responder T cells were not found when newborn T and non-T cells were separated by nylon wool. Responses in parallel autologous cultures of adult T cells showed that 1) adults had a higher frequency than newborns of E + FCS specific responders, 2) evidence for self specificity was lacking in restimulated cultures, and 3) occasional responses to antigen on the surface of monocytes could not be excluded.     

Abortive Infection of L Cells by Influenza B Virus: Defect in Bud Formation

Host-dependent restriction of influenza B virus replication in L cells was analysed in comparison with productive infection in MDCK or 1–5C-4 cells. The synthesis and intracellular distribution of virus-specific proteins and the production of cytoplasmic ribonucleoproteins in nonpermissive L cells were similar to those in permissive MDCK cells. However, an electron microscopic study of infected L cells showed neither extracellular virions nor budding virus particles on the cell surface, in contrast to MDCK cells which produced numerous virus particles. PAGE analysis of the plasma membrane isolated from the cells demonstrated no significant difference in the composition of viral polypeptides between permissive 1-5C-4 and nonpermissive L cells. It was noted that the abortiveness of influenza B virus infection in L cells may be due to a defect in host cell function involved in the initiation of virus budding.     

Genotoxicity of ptaquiloside, a bracken carcinogen, in the hepatocyte primary culture/DNA-repair test

The genotoxicity of ptaquiloside (PT), recently isolated from bracken fern and shown to be carcinogenic, was examined by means of the hepatocyte primary culture/DNA-repair test. PT elicited clear unscheduled DNA synthesis with a dose-response effect. The result indicates that PT is a genotoxic carcinogen.     

The Effects of Ethylene on the Coordinated Synthesis of Multiple Proteins: Accumulation of an Acidic Chitinase and a Basic Glycoprotein Induced by Ethylene in Leaves of Azuki Bean, Vigna angularis

The ethylene-induced synthesis and accumulation of proteinswere studied in the primary leaves of azuki bean (Vigna angularis).Seven different proteins, designated AZ17, 23, 27, 32, 35, 36,42 according to their molecular masses, were synthesized andaccumulated in response to ethylene. AZ27 and AZ42 were purifiedto homogeneity and characterized. AZ27 was identified as anacidic chitinase and accumulated in the extracellular space.The sequence of the 40 N-terminal amino acids of AZ27 showedno similarity to that of a basic chitinase from bean and tobacco,but it was highly homologous to that of a chitinase from virus-infectedcucumber leaves. AZ42 was identified as a glycoprotein thataccumulated intracellularly. A search for proteins with sequenceshomologous to an internal sequence of 18 amino acids in AZ42was unsuccessful. Immunochemical examination revealed that auxinand abscisic acid enhanced the ethylene-induced accumulationof AZ27 but not of AZ42. In contrast, levels of AZ42 were notaffected by auxin or abscisic acid, but cytokinin suppressedthe accumulation of one of the doublet bands of AZ42. TranslatablemRNAs coding for AZ27 and AZ42 were not present in leaves thathad not been treated with ethylene, but levels of these mRNAsincreased after such treatment. (Received March 1, 1991; Accepted May 8, 1991)     

Conversion of Farnesol into Methyl dl-12-Homo-10-trans-juvenate,the 10-trans-lsomer of dl-C17-Cecropia Juvenile Hormone

Methyl dl-12-homo-10-trans-juvenate (III) was synthesized from farnesol (IV) in eight steps involving stereoselective conversion of the trans-terminal methyl group to an ethyl group. The product (III) was less active than dl-C₁₇-Cecropia juvenile hormone on both Tenebrio molitor and Galleria mellonella.     

Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges

When energetic particles irradiate matter, it becomes activated by nuclear reactions. Radioactivation induced cellular effects are not clearly understood, but it could be a part of bystander effects. This investigation is aimed at understanding the biological effects from radioactivation in solution induced by hadron radiation. Water or phosphate buffered saline was activated by being exposed to hadron radiation including protons, carbon- and iron-ions. 1 mL of radioactivated solution was transferred to flasks with Chinese hamster ovary (CHO) cells cultured in 5 mL of complete media. The induction of sister chromatid exchanges (SCE) was used to observe any increase in DNA damage responses. The energy spectrum and the half-lives of the radioactivation were analyzed by NaI scintillation detector in order to identify generated radionuclides. In the radioactivated solution, 511 keV gamma-rays were observed, and their half-lives were approximately 2 min, 10 min, and 20 min. They respectively correspond to the beta+ decay of ¹⁵O, ¹³N, and ¹¹C. The SCE frequencies in CHO cells increased depending on the amount of radioactivation in the solution. These were suppressed with a 2-hour delayed solution transfer or pretreatment with dimethyl sulfoxide (DMSO). Our results suggest that the SCE induction by radioactivated solution was mediated by free radicals produced by the annihilated gamma-rays. Since the SCE induction and DMSO modulation are also reported in radiation-induced bystander effects, our results imply that radioactivation of the solution may have some contribution to the bystander effects from hadron radiation. Further investigations are required to assess if radioactivation effects would attribute an additional level of cancer risk of the hadron radiation therapy itself.     

Mdm20 Modulates Actin Remodeling through the mTORC2 Pathway via Its Effect on Rictor Expression

NatB is an N-terminal acetyltransferase consisting of a catalytic Nat5 subunit and an auxiliary Mdm20 subunit. In yeast, NatB acetylates N-terminal methionines of proteins during de novo protein synthesis and also regulates actin remodeling through N-terminal acetylation of tropomyosin (Trpm), which stabilizes the actin cytoskeleton by interacting with actin. However, in mammalian cells, the biological functions of the Mdm20 and Nat5 subunits are not well understood. In the present study, we show for the first time that Mdm20-knockdown (KD), but not Nat5-KD, in HEK293 and HeLa cells suppresses not only cell growth, but also cellular motility. Although stress fibers were formed in Mdm20-KD cells, and not in control or Nat5-KD cells, the localization of Trpm did not coincide with the formation of stress fibers in Mdm20-KD cells. Notably, knockdown of Mdm20 reduced the expression of Rictor, an mTORC2 complex component, through post-translational regulation. Additionally, PKCα^S657 phosphorylation, which regulates the organization of the actin cytoskeleton, was also reduced in Mdm20-KD cells. Our data also suggest that FoxO1 phosphorylation is regulated by the Mdm20-mTORC2-Akt pathway in response to serum starvation and insulin stimulation. Taken together, the present findings suggest that Mdm20 acts as a novel regulator of Rictor, thereby controlling mTORC2 activity, and leading to the activation of PKCα^S657 and FoxO1.     

Ultrastructural changes of the midgut epithelial cells in feeding and moulting nymphs of the tick Haemaphysalis longicornis

The midgut epithelial cells in nymphs fed on laboratory rabbits were examined during feeding and after detachment. The midgut epithelium at the unfed stage consisted of digestive cells of lower activity, containing such nutritive substances as protein, lipid and glycogen. As feeding proceeded, the cells became active in intracellular digestion. At the middle of the feeding stage, the spent digestive cells derived from the active digestive cells began to be replaced by the new digestive cells of lower activity. After detachment, the pinocytotic activity of the above cells increased greatly, and the digestive activity increased to some extent. As a result, many large endosomes were formed by fusion of numerous pinosomes. Thereafter, endosomes decreased in size as digestion proceeded and there was an increase of haematin granules. On day 7 after detachment, the new digestive cells of lower activity, belonging to the 'nutritional reserve' type, appeared adjacent to the spent digestive cells which had almost exhausted all endosomes, and these new cells had completely replaced the spent cells by day 3 after moulting.