Syntheses of Alkaline Phosphatase in Embryonic Cells during Aggregate Formation

CELL interaction, an important process in morphogenesis, seems to regulate in some way the expression of genetic information, thereby giving rise to differentiation of the cell; but little is known about the mechanism of such regulation at the molecular level. Our results suggest that the synthesis of alkaline phosphatase is regulated at the translation level in embryonic cells.     

Morpho-Physiological Study of Ameboid Movement. 3. Invisible gel structures in the endoplasm of an ameba of the verrucosa type

SYNOPSIS. A small ameba of the verrucosa type has a flattened and fan-shaped body, at the broadest front of which there is formed a distinct hyaline zone. Along the lateral borders thereof there is a thin optically indistinct but rigid body wall, which can be determined by means of cine-micrographic analysis of the positions of granules in and near it, and their movements. Its caudal portion is well differentiated from the rest of the body and was identified as a region of complicated conditions, manifesting solating activity, contractility, ejection, formation of caudal pseudopods, and continuous shifting of its minute components. The tracks of moving endoplasmic granules were plotted to determine their individual irregularities in velocity and direction of movement. These tracks suggest the existence in the endoplasm of small to large motionless gel structures derived from the frontal hyaline zone, which is therefore postulated to be heterogeneously gelate as a whole. Judging from the fact that granules carried by the protoplasmic matrix passed through these so-called gel areas, it is proposed that the source of the motive force of ameboid movement may be in the advancing edge of the clear frontal zone where gelation is vigorously taking place.     

Meiosis of Primary Spermatocytes and Early Spermiogenesis in the Resultant Spermatids in Newt, Cynops pyrrhogaster in vitro

Dissociated spermatogenic cells were cultivated within the collagen matrix at low cell density. The largest cell type in the culture was identified as the primary spermatocytes by their size and the morphological characteristics revealed by ultra-thin sections. Chromosome analysis showed that about 90% of the cells examined were either in first or second meiosis. Within the collagen matrix, the fates of 282 single primary spermatocytes at meiotic stage in diakinesis or metaphase were followed. In a few days, most of them gave rise to four spermatids, passing through first and second meiotic divisions. About 80% of the spermatids formed motile flagella. They grew about 20–60 μm a day. The final state of the differentiation attained in our culture conditions was the spermatids with localized spherical nuclei and motile flagella, about 500 μm in length after 1-month's culture. Ultra-thin sections of the spermatids show that the rings, neck-pieces, and acrosomes developed in the cells.     

Mechanisms of reproductive isolation of interspecific hybridization between Trillium camschatcense and T. tschonoskii (Melanthiaceae)

Reproductive isolation plays a significant role in the prevention of gene flow between different plant species. Isolation factors can vary, acting either pre‐ or postzygotically. Trillium camschatcense and T. tschonoskii are herbaceous perennials which frequently grow together in Hokkaido, Japan. Natural hybrid formation, T. × hagae, between these species is common, and occurs asymmetrically with T. camschatcense as the maternal parent and T. tschonoskii as the paternal. Here, we examined the efficiency of each reproductive isolation factor to clarify which factor was responsible for the frequency and asymmetry of the hybridization. We found that prezygotic barriers, self fertilization and conspecific pollen precedence, are major isolation factors in both parental species, and that T. tschonoskii as a maternal parent has more effective prezygotic barriers than T. camschatcense. In addition, hybrids with T. tschonoskii as the maternal parent were not observed to reach the flowering stage. We concluded that prezygotic isolation factors in the both species act as main barriers to prevent natural hybridization, and that asymmetry of the isolating barriers between these species would promote T. camschatcense as the maternal parent of the hybrids.     

AN ANALYSIS OF DIFFERENTIATIVE CAPACITY OF PIGMENTED EPITHELIAL CELLS OF ADULT NEWT IRIS IN CLONAL CELL CULTURE

Singly dissociated cells from dorsal and ventral iris epithelia ( iris iridica ) of adult newts were cultured separately at clonal density to analyse their growth and differentiative capacity. Usually some attached cells began to proliferate on 12th day of culture, and grew with loss of melanosomes to form clonal cell colonies. Up to 30 days after inoculation, most of the clonal colonies formed typical epithelial monolayer sheets which consisted mostly of nonpigmented cells. Then, in some of those colonies, cells piled up together and form typical lens structures containing lens antigens. A month and a half after culturing, 30 to 40% of single iris cells, which had been previously marked, grew to form clonal colonies consisting of more than 100 cells. About 30% of these colonies expressed lens specificity and no significant differences in efficiency of colony formation and differentiation were detected between the dorsal cells and the ventral, suggesting that potent cells capable of transdifferentiating into lens cells are evenly distributed in all parts of the newt iris epithelium.     

Development of the Embryo Sac in Amitostigma kinoshitae (Makino) Schltr. (Orchidaceae)

The embryo sac of Amitostigma kinoshitae was studied. The ovuleis anatropous, bitegmic, and tenuinucellate. The inner integumentalone forms a micropyle. The megaspore of a tetrad nearest tothe chalaza develops into an eight-nucleate embryo sac of thetypical Polygonum-type. Double fertilization takes place normally.     

Ethnobotanical Studies in Gaoligong Mountains: II. The Dulong Ethnic Group

The traditional agro - ecosystem and indigenous botanical knowledge of the Dulong ethnic group in the Dulong Jiang (Dulong River) watershed of northern Gaoligong Mountains in western Yunnan, China are extensively investigated and studied through the approaches of human ecology and ethnobotany. Living in a very isolated environment, the Dulong people have established very close relationships with plants and the plant environment. The agro - ecosystem in the Dulong Jiang watershed is a typical montane swidden agro -ecosystem in which there are various traditional cultivars and local landraces of crops with potential value out-side of their area.     

Mitosis in Beating Cardiac Muscle Cells from Newt Embryos In Vitro

Cardiac muscle cells from newt embryos were cultured at relatively low cell density. Within 10 days in culture, 2 cell types (spindle and flat type) were distinguished both among beating and non-beating cells. Mitosis in single beating cells was frequently observed both in spindle and flat cells. Some cells maintained almost constant contractile activities throughout the mitotic stages, while the others transiently stopped beating during mitosis, which accords well to the case in chick embryos (1). Ultra-thin section shows the presence of myofibril's structure in a dividing cell, as shown in newborn rats (2, 3, 4), chick embryos (1, 5, 6, 7) and adult newts (8, 9). As a consequence of mitosis, 3 types (spindle, flat and mixed type) of beating colonies developed after 34 weeks in culture. Cell proliferation was accompanied with pulsation and could be directly pursued till the 4th division, suggesting that differentiated myocardiac cells with myofibrils proliferate by their mitoses in vivo , maintaining rhythmic contraction.     

A Reinvestigation of the Development of the Embryo Sac in Gastrodia elata Blume (Orchidaceae)

The embryo sac of Gastrodia elata was reinvestigated. The ovuleis anatropous, unitegmic and tenuinucellate. The chalazal megasporeof a triad develops into an embryo sac. Four nuclei are formedat the micropylar end but only two at the chalazal end. A typicalegg apparatus and a single polar nucleus are derived from themicropylar quartet, while the chalazal two disappear beforematuration of the embryo sac. Double fertilization takes placenormally.