Different effects of cytochalasins on the growth and differentiation of<Emphasis Type="Italic"> Entamoeba invadens</Emphasis>

The effect of five different cytochalasins on the growth, encystation and excystation of Entamoeba invadens was examined. At 10 M, cytochalasins B, D, E and dihydrocytochalasin B markedly inhibited growth. Encystation was inhibited by cytochalasin D at 1 M but not by other cytochalasins at the same concentration, whereas it was inhibited by 10 M of cytochalasins B, E and dihydrocytochalasin B as well as cytochalasin D. Excystation, which was assessed by counting the number of metacystic amoebae after inducing excystation, was markedly enhanced by cytochalasin D as previously demonstrated, whereas the enhancing effect of cytochalasins A, B and dihydrocytochalasin B was weak. In contrast, cytochalasin E at 10 M inhibited excystation and metacystic development. These results indicate that there is a difference in the effect of different cytochalasins on the growth and differentiation of E. invadens, depending on differences in their chemical structure.     

Characteristics associated with empathic behavior in Japanese oncologists

Objective

Oncologists must have empathy when breaking bad news to patients who have incurable advanced cancer, and the level of empathy often depends on various individual characteristics. This study aimed to clarify the relationship between these characteristics and empathic behavior in Japanese oncologists.

Methods

We videotaped consultations in which oncologists conveyed news of incurable advanced cancer to simulated patients. Oncologists’ empathetic behaviors were coded, and regression analysis was performed to determine the existence of any relationships with factors such as age, sex, and specialism.

Results

Sixty oncologists participated. In a multivariate model, only age was related to the empathy score (r = 0.406, p = 0.033); younger oncologists scored higher than did older oncologists.

Conclusions

We found that empathic behaviors were more frequent in younger oncologists.

Practice implications

This information could be useful in determining the best approach for implementing future empathy and communication training programs for experienced oncologists in Japanese medical institutions.     

An improved mouse model that rapidly develops fibrosis in non‐alcoholic steatohepatitis

Non‐alcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. One of the most common models used in NASH research is a nutritional model where NASH is induced by feeding a diet deficient in both methionine and choline. However, the dietary methionine‐/choline‐deficient model in mice can cause severe weight loss and liver atrophy, which are not characteristics of NASH seen in human patients. Exclusive, long‐term feeding with a high‐fat diet (HFD) produced fatty liver and obesity in mice, but the HFD for several months did not affect fibrosis. We aimed to establish a mouse model of NASH with fibrosis by optimizing the methionine content in the HFD. Male mice were fed a choline‐deficient, L‐amino acid‐defined, high‐fat diet (CDAHFD) consisting of 60 kcal% fat and 0.1% methionine by weight. After 1–14 weeks of being fed CDAHFD, the mice were killed. C57BL/6J mice maintained or gained weight when fed CDAHFD, while A/J mice showed a steady decline in body weight (of up to 20% of initial weight). In both strains of mice, plasma levels of alanine aminotransferase increased from week 1, when hepatic steatosis was also observed. By week 6, C57BL/6J mice had developed enlarged fatty liver with fibrosis as assessed by Masson's trichrome staining and by hydroxyproline assay. Therefore, this improved CDAHFD model may be a mouse model of rapidly progressive liver fibrosis and be potentially useful for better understanding human NASH disease and in the development of efficient therapies for this condition.     

Effect of proteasome inhibitors on the growth,encystation, and excystation of <Emphasis Type="Italic">Entamoeba histolytica and Entamoeba invadens</Emphasis>

The effect of three proteasome inhibitors, lactacystin, clasto-lactacystin beta-lactone, and MG-132, on the growth, encystation, and excystation of Entamoeba histolytica and Entamoeba invadens was examined. All of these drugs blocked E. histolytica growth in a concentration-dependent manner; lactacystin was most potent for the inhibition and MG-132 showed the inhibitory effect only at higher concentrations. E. invadens was more resistant to these drugs than E. histolytica. Encystation of E. invadens was also inhibited and was more sensitive to the drugs than was growth. Beta-lactone was the most potent encystation inhibitor. The inhibitory effect of lactacystin and the beta-lactone on encystation was slightly and little abrogated by the removal of the drug, respectively. Multinucleation occurred in E. histolytica trophozoites treated with these drugs, being most marked with lactacystin. In contrast, no multinucleation was observed in E. invadens treated with the drugs. Electron microscopy revealed that the treatment of E. histolytica trophozoites with lactacystin led to an increase in the number of cells with many glycogen granules in the cytoplasm. Lactacystin, beta-lactone and MG-132 had no or little effect on the excystation and metacystic development of E. invadens. These results suggest that proteasome function plays an important role for Entamoeba growth and encystation, but has no obvious effect on excystation or metacystic development.     

Molecular cloning and characterization of the repetitive DNA sequences that comprise the constitutive heterochromatin of the W chromosomes of medaka fishes

Among the medaka fishes of the genus Oryzias, most species have homomorphic sex chromosomes, while some species, such as Oryzias hubbsi and Oryzias javanicus, have heteromorphic ZW sex chromosomes. In this study, a novel family of repetitive sequence was molecularly cloned from O. hubbsi and characterized by chromosome in situ and filter hybridization, respectively. This repetitive element, which we designated as a BstNI family element, localized at heterochromatin regions on the W chromosome, as well as on two pairs of autosomes. Homologous sequences to this element were found only in O. javanicus, which is a sister species of O. hubbsi, suggesting that this repeated element originated in the common ancestor of these two species. However, the intensity of the hybridization signals was lower in O. javanicus than in O. hubbsi, and the chromosomal location of this element in O. javanicus was confined to heterochromatin regions on one pair of autosomes. Thus, we hypothesize that this repetitive element was extensively amplified in the O. hubbsi lineage, especially on its W chromosome, after the separation of the O. javanicus lineage. In addition, we also found the W chromosomal location of the 18S–28S ribosomal RNA genes in both O. hubbsi and O. javanicus. Our previous studies showed no linkage homology of the sex chromosomes in these species, indicating that the RNA genes were shared between W chromosomes of different origins. This situation may be explained by a translocation of the sex-determining region with the ribosomal RNA genes in either species or an independent accumulation of the RNA genes as a convergent process during W chromosome degeneration.