Synergistic Effects of Adenosine and Compounds Related to Adenosine 3': 5'-cyclic Monophosphate on Dedifferentiating Iris Epithelial Cells in Culture

Addition of adenosine or 5' AMP to the primary culture of newt iris epithelial cells produces an extensive array of fine cytoplasmic processes in a fraction of the cell population. Dibutyryl cyclic AMP, monobutyryl cyclic AMP, cyclic AMP and theophylline have the same effect, but the minimum effective concentrations of the latter four compounds are higher than those of the former two. When the primary cultures are treated simultaneously with two effective compounds at various concentrations a synergis-tic effect is observed between dibutyryl cyclic AMP and theophylline; cyclic AMP and theophylline; adenosine and theophylline; adenosine and cyclic AMP. The results support the interpretation that an increase in cellular level of cyclic AMP, which is produced by exogenous adenosine or 5' AMP as well as by exogenous cyclic AMP, its derivatives or theophylline, is responsible for the formation of radial cytoplasmic processes. The morphogenetic response does not depend on the presence of serum in the culture medium. The possibility is discussed that the cellular level of cyclic AMP is involved as one link of the sequential events which control the dedifferentiation of iris epithelial cells in cell-type conversion.     

Local divergence in developmental traits within a trivoltine area of Hyphantria cunea Drury (Lepidoptera: Arctiidae)

To detect divergence of the introduced fall webworm, Hyphantria cunea, within its trivoltine area in Japan, developmental traits were determined in the Kobe (34°41′N) and Kumamoto (32°48′N) populations. The lower threshold temperature for development was not different between these two populations. The thermal constant for larval development was considerably smaller in the Kobe population than in the Kumamoto population. Two types of larva occurred in these populations, one with six instars and the other with seven. In the six‐instar type, the developmental period was not different between the populations in males, but the pupal weight was greater and the forewing was longer in both sexes in the Kumamoto population than in the Kobe population. In the Kumamoto population, the seven‐instar type had a longer developmental period, heavier pupa and longer forewing than the six‐instar type. The proportion of the seven‐ to the six‐instar type was greater in the Kumamoto population than in the Kobe population, resulting in the longer developmental time and greater body size of the former.     

Breakdown of middle lamella pectin by ●OH during rapid abscission in Azolla

Azolla, a small water fern, abscises its roots and branches within 30 min upon treatment with various stresses. This study was conducted to test whether, in the rapid abscission that occurs in Azolla, breakdown of wall components of abscission zone cells by ^●OH is involved. Experimentally generated ^●OH caused the rapid separation of abscission zone cells from detached roots and the rapid shedding of roots from whole plants. Electron microscopic observations revealed that ^●OH rapidly and selectively dissolved a well‐developed middle lamella between abscission zone cells and resultantly caused rapid cell separation and shedding. Treatment of abscission zones of Impatiens leaf petiole with ^●OH also accelerated the separation of abscission zone cells. However, compared with that of Azolla roots, accelerative effects in Impatiens were weak. A large amount of ^●OH was cytochemically detected in abscission zone cells both of Azolla roots and of Impatiens leaf petioles. These results suggest that ^●OH is involved in the cell separation process not only in the rapid abscission in Azolla but also in the abscission of Impatiens. However, for rapid abscission to occur, a well‐developed middle lamella, a unique structure, which is sensitive to the attack of ^●OH, might be needed.     

A NEW SPECIES OF DICERORHINUS (RHINOCEROTIDAE) FROM THE PLIO‐PLEISTOCENE OF MYANMAR

Abstract: A skull and mandible of the new species Dicerorhinus gwebinensis sp. nov. of Rhinocerotidae (Mammalia, Perissodactyla) is described. The material is collected from the upper part of the Irrawaddy sediments (Plio‐Pleistocene) in central Myanmar. D. gwebinensis sp. nov. is morphologically more similar to the extant species D. sumatrensis (Sumatran rhinoceros) than to other species of the genus but differs from D. sumatrensis in having the comparatively shorter nasal, the more concave dorsal profile of the skull, the more elevated occiput and presence of molar crista in M3/. This is the first discovery of Dicerorhinus in the upper Miocene to lower Pleistocene of the Indian subcontinent and Mainland Southeast Asia, and fills the chronological and geographical gap of this lineage in Asia. The Dicerorhinus clade probably migrated into Southeast Asia from East Asia by the Pliocene or early Pleistocene. This hypothesis is supported by the scarcity or absence of this clade in the Neogene mammalian fauna of the Indian Subcontinent.     

Fine structure of Bacillus subtilis. I. Fixation

The fine structure of Bacillus subtilis has been studied by observing sections fixed in KMnO(4), OsO(4), or a combination of both. The majority of examinations were made in samples fixed in 2.0 per cent KMnO(4) in tap water. Samples were embedded in butyl methacrylate for sectioning. In general, KMnO(4) fixation appeared to provide much better definition of the boundaries of various structures than did OsO(4). With either type of fixation, however, the surface structure of the cell appeared to consist of two components: cell wall and cytoplasmic membrane. Each of these, in turn, was observed to have a double aspect. The cell wall appeared to be composed of an outer part, broad and light, and an inner part, thin and dense. The cytoplasmic membrane appeared (at times, under KMnO(4) fixation) as two thin lines. In cells fixed first with OsO(4) solution, and then refixed with a mixture of KMnO(4) and OsO(4) solutions, the features revealed were more or less a mixture of those revealed by each fixation alone. A homogeneous, smooth structure, lacking a vacuole-like space, was identified as the nuclear structure in a form relatively free of artifacts. Two unidentified structures were observed in the cytoplasm when B. subtilis was fixed with KMnO(4). One a tortuous, fine filamentous element associated with a narrow light space, was often found near the ends of cells, or attached to one end of the pre-spore. The other showed a special inner structure somewhat similar to cristae mitochondriales.     

Distribution of greenhouse gases, nitrite, and δ13C of dissolved inorganic carbon in Lake Biwa: Implications for hypolimnetic metabolism

The vertical distribution of dissolved greenhouse gases (CH₄,CO₂ and N₂O), NO ,and ¹³C of CO₂ in Lake Biwa during a stagnantperiod was precisely determined. CO₂ as well as NO was accumulated in the hypolimnion, whereas NO and CH₄concen\-trations were generally higher in theepilimnion than in the hypolimnion. In August, NO andCH₄ were ephemerally accumulated at the thermocline. Theconcentration of CH₄ always exceeded equilibrium with respectto air/water exchange. N₂O was rather uniformly distributed inboth time and space, and remained near equilibrium with respect toair/water exchange. All of these observations are similar to otherstratified, oligotrophic lakes, in which the hypolimnia were welloxygenated. The ¹³C of CO₂ became morenegative with increasing depth, and showed a strong negativecorrelation with apparent oxygen utilization. From the data, the ¹³Cvalue of organic matter decomposed into CO₂ inthe hypolimnion was calculated by isotope mass-balance, and found tobe in a similar range to ¹³C of phytoplankton and benthic algaeand distinctively higher than ¹³C of both terrestrial andsedimentary organic matters. This suggests that autochthonous organicmatter was the major source of CO₂.