A Brief Contact with Early Embryonic Cells Induces the Differentiation of Embryonal Carcinoma Cells

An assay system was developed to detect a switch of mouse embryonal carcinoma (EC) cells to the pathway for normal cell differentiation after a brief contact with normal embryonic cells. The system consisted of (1) the mixed aggregation of AT805 EC cells with 8-cell stage mouse embryos, (2) the stationary culture of the mixed aggregates into blastocysts and (3) the cell culture of inner cell masses isolated from chimeric blastocysts containing EC cells at 2, 3 and 4 days after the initiaion of chimeric aggregation. The number of foci of EC cells which appeared in the cultures of inner cell masses was decreased with a length of contact of EC cells with normal embryos as the mixed aggregates. After 4 days' contact, only fibroblastic and epithelial cells appeared in most cultures of inner cell masses. Examination of isozyme markers of GPI revealed that such cell cultures consisting of nonmalignant cells contained cells of tumor origin. Thus, it was concluded that a brief exposure to the environment of normal embryos can regulate the tumor cells to differentiate into non-malignant cells. This conclusion was substantiated by comparing the pattern of protein spots of the tumor cells with that of non-malignant cells of the tumor origin by two dimensional gel electrophoresis.     

Involvement of cyclic adenosine 3′,5′-monophosphate in methylation during 1-methyladenine production by starfish ovarian follicle cells

Summary

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). With respect to 1-MeAde production by follicle cells of the starfish, Asterina pectinifera, (1) the action of GSS is initiated by a receptor mediated activation of G-proteins, resulting in the activation of adenylate cyclase and cyclic AMP (cAMP) formation; (2) 1-MeAde produced under the influence of GSS is not prestored within the follicle cells but is newly synthesized from a 1-MeAde precursor; (3) AMP plays an important role in the process of methylation during 1-MeAde biosynthesis induced by GSS.     

Isolation and characterization of microsatellite loci from Quercus mongolica var. crispula

Microsatellites were isolated and characterized for the Japanese oak species, Quercus mongolica var. crispula, distributed in temperate deciduous forests of Japan. Eleven of the 48 primer pairs designed successfully amplified unambiguous and polymorphic single loci among 67 Q. mongolica var. crispula individuals within a plot in southwestern Japan. The observed and expected heterozygosities of the 11 microsatellite markers ranged from 0.522 to 0.896 and from 0.536 to 0.882, respectively. These polymorphic microsatellite markers are useful for estimating pollen‐mediated gene flow in Q. mongolica var. crispula.     

GROWTH OF THE CHICKEN EMBRYONIC LENS TRANSPLANTED ONTO THE CHORIO-ALLANTOIC MEMBRANE

The influence of neural retina on the growth of chicken embryonic lens was studied by comparing the growth pattern of the lens transplanted onto chorio-allantoic membrane (CAM) with that of the normal lens. The lens from 6-day embryo, transplanted onto CAM after labeled with ³H-thymidine, continued to grow in the absence of neural retina at least for 12 days of incubation, although its growth rate was reduced. In the transplanted lens, no ³H-labeled epithelial cell differentiated into fiber at least for 2 days of incubation and ³H-labeled nuclei first appeared in the fiber cells on the fourth day of incubation, while, in the normal lens of 6-day embryo labeled with ³H-thymidine in situ, ³H-labeled epithelial cells differentiated into fibers within 24 hours. On the other hand, the fiber cells differentiated before transplantation maintained the nearly normal growth rate on CAM. The neural retina transplanted onto CAM together with lens induced the new fibers from the lens epithelium. These observations suggest that the neural retina initiates and promotes the fiber differentiation in the chicken lens, but its continued influence is not always necessary for the successive differentiation of epithelial cell into fiber and especially for the growth of the differentiated fiber cells.     

DISPERSAL PATTERNS OF THE GIANT AFRICAN SNAIL, ACHATINA FULICA (FERUSSAC) (STYLOMMATOPHORA: ACHATINIDAE), EQUIPPED WITH A RADIO-TRANSMITTER

The dispersal pattern of the African giant snail, Achatina fulica(Férussac) was examined by radio-tracking for six months.They showed typically nocturnal locomotory activities. Theiractivities differed among three developmental stages; juvenile,young adult, and old adult. Juveniles dispersed for the longestdistances. The most active juvenile moved 500 m in 6 months.Young adults and old adults travelled only within a narrow area,although the dispersal range for young adults was greater thanthat of old adults. (Received 15 September 1992; accepted 11 December 1992)     

Biochemical studies on mitochondria formed during aging of sliced potato tuber tissue

Respiratory activities in mitochondria of potato tuber tissueincreased about 3-fold after aging sliced tissue for 1 day.Increased activity was insensitive to cyanide. The number ofmitochondrial particles also increased during aging. It seemslikely that newly formed mitochondria are heavier than pre-existingones and that respiration in the former is insensitive to cyanide. (Received January 26, 1970; )     

Detection of the Initial Step of Mesenchymal Differentiation of Teratocarcinoma Cells Using the Monoclonal Antibody Eccd-11

The monoclonal antibody ECCD-1 recognizes the Ca²⁺-dependent cell-cell adhesion molecule of teratocarcinoma stem cells (EC cells) and of a certain class of differentiated epithelial cells. It actively disrupts cell-cell adhesion when added to monolayer cultures of these cells, but does not affect adhesion of mesenchymal or neuronal cells. When ECCD-1 was added to clonal cultures of EC cells (PCC3/A/1 line), all the cells were initially sensitive to the antibody, but after 5 to 6 days of culture a fraction of the cells in certain colonies no longer reacted with the antibody although they expressed alkaline phosphatase activity, which is a marker of undifferentiated EC cells. We isolated these ECCD-1-resistant cells by recloning and examined their differentiation by clonal culture. Most of them differentiated into fibroblastic cells and a few into skeletal muscle-like cells, but none differentiated into any other cell types. From these observations, we suppose that the ECCD-1-resistant population of EC cells are committed to mesenchymal differentiation. The use of ECCD-1, thus, permitted us to detect EC cells at the initial stage of a particular differentiation pathway.     

In Vitro Induction of Starfish Oocyte Maturation by Cysteine Alkylesters

The effect of various disulfide-reducing agents including cysteine and its alkylesters on the induction of germinal vesicle breakdown (GVBD) in starfish ( Asterina pectinifera ) oocytes was investigated in vitro . Although cysteine did not induce GVBD, its alkylesters were effective. Cysteine alkylesters significantly mimicked the effect of 1-methyladenine (1-MeAde), the naturally occurring maturation-inducing hormone of starfish, on oocyte maturation. However, the effective concentrations and pH optimum for stimulation of oocyte maturation varied between 1-MeAde and the cysteine alkylesters. By comparing pKa values of the disulfide-reducing agents to pH of the medium, it is suggested that the redox potential of a disulfide-reducing agent is an important indicator its ability to induce oocyte maturation.
With the use of fluorescent probes for thiol groups, it was shown that the fluorescence in oocyte cortices increased within 5 min after administration of 1-MeAde. The fluorescence intensity in the cortices also increased after treatment with cysteine and its alkylesters, although the intensity was much stronger with the latter. Furthermore, both 1-MeAde and the disulfide-reducing agents were suggested to cause reduction of thiol groups within the plasma membrane as opposed to those on the external and internal surfaces. Thus, it is suggested that disulfide-reducing agents and 1-MeAde induce starfish oocyte maturation by changing the redox state of the thiol groups located within the oocyte plasma membrane.     

CELL ASSOCIATION PATTERN IN AGGREGATES CONTROLLED BY MULTIPLE CELL-CELL ADHESION MECHANISMS

We have previously assumed the presence of two mechanisms for the aggregation of Chinese hamster V79 cells, the Ca²⁺-dependent one and the Ca²⁺-independent one. In order to examine if each of these mechanisms contributed differently to the various aspects of cell aggregation, the morphology of V79 cell aggregates, pretreated so that they were provided with only one of the two adhesion mechanisms, was compared by light and electron microscopy. The adhesion among cells with only the Ca²⁺-dependent mechanism was very tight, with the formation of gap and intermediate junctions. Cells were arranged in a rod or dendric shape in aggregates. In aggregates of cells with only the Ca²⁺-independent mechanism, cells were loosely attached to each other without the formation of specialized junctions and the aggregates were of globular shape. In aggregates of cells with both mechanisms, both characteristics of the above two aggregates were found. Four clones of V79 cells, which formed colonies with different morphology when they were grown in soft agar, were isolated. It was found that such differences were due to the different activity of the Ca²⁺-independent mechanism among these clones. These results suggested that the two adhesion mechanisms play different roles in the cell arrangement in aggregates.