Spermatogenesis in animals as revealed by electron microscopy. VI. Researches on the spermatozoon-dimorphism in a pond snail,Cipango-paludina malleata

This paper reports an electron microscope study of typical and atypical spermatogenesis in the pond snail, Cipangopaludina malteata. In the typical spermatid the nucleus undergoes profound changes as development proceeds, affecting both its form and internal fine structure. A large number of roughly parallel, dense filaments, arranged along the long axis of the nucleus, fuse with each other to form in the end the homogeneous helical body characteristic of the head of the adult spermatozoa. The nebenkern is apparently mitochondrial in nature and, in its early development, is similar to that of insects except that it appears as a double structure from the beginning. As differentiation proceeds, the mitochondria lose their membranes, and the residual, now denuded cristae, reorganize to give a parallel radial arrangement. In the last stages of development, the nebenkern derivations become applied to the sheath of the middle piece in a compact helical fashion. In the development of the atypical spermatozoa, the nucleus fails to differentiate and simply shrinks in volume until only a remnant, devoid of DNA, is left. The cytoplasm shows numerous vesicles containing small Feulgen-positive bodies, 80 to 130 mmicro in diameter. These vesicles plus contents increase in number as spermatogenesis proceeds. The "head" structure of the atypical spermatozoa consists of a bundle (7 to 17) of tail flagella, each with a centriole at its anterior end. The end-piece of the atypical form appears brush-like and is made up of the free ends of the several flagella.     

A Comparison Between Melanotic and Amelanotic Retinal Pigment Epithelial Cells In Vitro Concerning the Effects of L-Dopa and Oxygen on Cell Cycle

Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 μM and 250 μM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in the G₁ phase.     

Seasonal variation in embryonic diapause of the striped ground cricket, Allonemobius fasciatus

ABSTRACT. The incidence and intensity of embryonic diapause in the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), is influenced by the date of oviposition and the incubation temperature. At 20C, embryos develop normally until the end of the appendage-formation stage when diapause occurs. The intensity of 'winter' diapause at this stage is greatest in eggs laid early in the season. Incubation at higher temperature induces a different and earlier 'summer' diapause. The higher the temperature the earlier the stage at which this developmental suppression is imposed. At 27 and 30C, some individuals develop without any interruption and hatch within 20 days. The proportion of these fast-developing eggs is low in summer but increases towards the end of the laying season. In nature, this species is univoltine and precocious hatching before winter is unlikely.
When embryos diapausing at an early stage at 27C are transferred to low temperatures, they resume development and enter winter diapause. The time required to reach the winter-diapause stage after transfer is inversely related to the temperature (30-30C). At 30C, sunmer diapause is neither induced nor maintained.     

Change in Molecular Size of Cellulose during Regeneration of Cell Wall on Carrot Protoplasts

Protoplasts isolated from carrot cells were cultured in a chemically defined medium. The majority of them regenerated cell wall and underwent cell division. Cellulose synthesis started without a noticeable lag but the rate of deposition was very low during the initial stage. The degree of polymerization of cellulose was determined by viscosity measurement of the nitrated product. The cellulose formed in the early stage of the wall regeneration consisted mainly of low molecular weight glucan chains. Change in the average molecular weight of cellulose was found during the growth cycle of carrot cells in normal suspension culture.     

Fish Tumor Pigment Cells: Differentiation and Comparison to Their Normal Counterparts

The objectives of this paper are to describe 1) the developmentof new research systems for biochemical comparison of cellulartraits between normal and tumorous pigment cells of fish origin,2) the similarity and dissimilarity between these two categoriesof pigment cells with regard to growth, differentiation andpigment translocating activities and 3) the potentials of thesetumorous pigment cells to manifest multiple differentiation.The development of research systems has been achieved by theestablishment of 1) methods to obtain homogenous populationsof viable, cultivatable xanthophores (erythrophores) and melanophoresfrom goldfish skins, 2) permanent cell lines from goldfish erythrophoromas(tumors derived from erythrophores) and from Nibe croaker irido-melanophoromas(tumors composed of mixed populations of iridophore- and melanophore-likecells) and 3) procedures to induce differentiation in normaland tumorous stem cells (including the formation of pigmentsand ability to undergo pigment translocation in response tocAMP, to the neurotransmitter epinephrine and to the hormonesACTH and melatonin). Two kinds of tumorous pigment cell linesexamined herein have the ability to form, in addition to variouspigments, structures similar to dermal skeletons and lentoidbodies. These findings strongly suggest the possibility thatthese fish pigment cell tumors are neural crest stem cell tumorsin nature.     

Ecological association of birds and vegetation structure in wet tropical forests of Australia

Birds and environments of tropical rainforests were studied in 18 selected areas from sea level to 1520 m within the humid tropical region of northeastern Australia. A total of 122 sites (20 m × 20 m each) were established within the 18 areas, and bird data (observation and mist-netting) and environmental data (pro forma survey and foliage measurements) were collected at each site. The bird data were analysed numerically in two ways: abundance of 146 species in 18 areas and presence and absence of 108 species at 122 sites. Both classification and ordination analyses produced a major discontinuity between the tableland sites and the lowland sites, each divisible further into various types of vine forest and non-vine forest vegetation. The few rare species did not contribute to the general pattern. The environmental data were reduced to a set of those attributes that showed variation among the sites. They included topographic and edaphic features, physiognomic and structural features of vegetation, fruiting and defoliating habits of plants, foliage height diversity and evenness, and canopy cover. The primary pattern in the data set of 135 attributes by 122 sites was vine forest versus nonvine forest, and altitudinal divisions appeared as a secondary pattern, in both classification and ordination. Canonical correlation coefficients between bird vectors and environmental vectors were reasonably high for the first four canonical vectors, which correlated well with major Gower vectors of birds and environments. The back-correlation to the raw data produced bird species and matching environmental attributes with sites sharing them for both positive and negative ends of each canonical vector. In general, the analysis extracted elements of both fauna and environment that characterized the vine forest as opposed to the non-vine forest and the tableland sites as opposed to the lowland sites. Canonical correlation analysis is limited by the unverifiable nature of derived correlations. Such correlations may suggest certain associations to be tested by independent means (hypothesis-generating function), but may also formalize self-evident or fortuitous associations.     

Electrophoretic variants of serum transferrin in wild pig populations of Japan

Variants of serum transferrin in Japanese wild pig, Sus scrofa leucomystax, and Ryukyu wild pig, S.s. riukiuanus, of Japan were investigated by using starch gel electrophoresis. Five phenotypes, TfB, BC, C, CX and X, were observed, of which two, TfCX and X, are new variants. Comparison of gene frequency estimates which were calculated for each population showed remarkable geographic differences among several populations of these two subspecies.     

Consequences of forest fragmentation in an understory plant community: extensive range expansion of native dwarf bamboo

Understory bamboo species are important and influential components of temperate forests in at least several parts of the world. Here we report a study testing the effect of forest fragmentation on the dynamics of the dwarf bamboo Sasa chartacea and on forest herb communities in the Tokachi plain of Hokkaido, Japan. We studied 16 forest fragments of different sizes and small plots established in these fragments to examine the relationship between the abundance of S. chartacea, landscape and environmental conditions, and forest herb communities. Sasa chartacea was more abundant near forest edges and in smaller fragments, suggesting that the species has expanded its local range and increased its abundance in response to forest fragmentation. Edge‐related changes in light and soil moisture might have facilitated this range expansion. The species richness of forest herbs was strongly negatively related to the density of S. chartacea. Because much larger variation in species richness was explained by S. chartacea density than distance to the nearest forest edge, the expansion of S. chartacea has likely excluded other understory species by competition. In addition, the density of S. chartacea significantly explained variation in the species composition of forest herbs across plots. Taken together, our results emphasize the key roles of dwarf bamboos in changing plant communities following forest fragmentation.     

Novel Inducers and Inhibitors of Differentiation of Friend Erythroleukemia Cells: Application of an Opal Glass Transmission Method to Study of Erythroid Differentiation

The potencies of poly(ADP-ribosylation)-inhibitors in inducing erythroid differentiation of Friend erythroleukemia cells were surveyed. Picolinamide and m-aminobenzamide were newly found to be inducers, whereas compounds related caffeine did not induce differentiation. In other series of experiments some bile acids suspected of being tumor promoters were found to inhibit the differentiation like typical tumor promoters such as phorbol esters. These modifications of erythroid differentiation were detected by an opal glass transmission method. This method is simpler than any previously reported methods, and is sufficiently reliable to use in determining hemoglobin in living cells as a quantitative marker of erythroid differentiation.