Synchronization of Mating Reactivity Rhythms in Populations of Paramecium bursaria

Cell populations of Paramecium bursaria show arhythmic mating reactivity after exposure to constant light (LL) for more than 2 wk. After this arhythmic population is exposed to darkness for 9 h, the mating reactivity rhythm of the cell population reappears. The phases of rhythms in individual cells are synchronized to each other. When the arhythmic population in constant light is exposed to dark pulses of various durations, the first peak of the recovered mating reactivity rhythm appears 6 h after the end of the dark pulse. Thus, in the case of dark pulses to cells in LL, the transition from dark to light sets the phase of the subsequent mating reactivity rhythm. When an arhythmic population in LL is transferred to constant darkness (DD), a rhythm of mating reactivity also appears and, in this case, the first peak of the rhythm occurs 18 h after the LL to DD transition. Therefore, arhythmic populations of cells in LL can be synchronized by either a dark pulse or by transition to continuous darkness. When the arhythmic populations in LL were transferred to various light/dark (LD) cycles, the mating reactivity rhythms entrained to LD cycles of 18 to 30 h in duration. Finally, mating rhythms can also be synchronized by treatment with puromycin (400 μg/ml for 6–18 h).     

BIOSYNTHESIS OF ECDYSONE IN THE ISOLATED ABDOMEN OF THE SILKWORM,BOMBYX MORI*

During pupal-adult development of the silkworm, Bombyx mori, the ecdysone titer changes, exhibiting two maxima in the females: one on the second day of pupal development and the other just before adult emergence. During the second maximum, ecdysone accumulates in the ovaries. It also accumulates in isolated abdomens, which were prepared just after pupal ecdysis and induced to initiate adult development by injection with β-ecdysone. Several lines of evidence suggest that ecdysone is synthesized in the ovary itself.     

POLYOL ACCUMULATION IN IN VITRO SYSTEMS OF BOMBYX EGGS

The mechanism of polyol accumulation in diapausing Bombyx eggs, conversion of [6-¹⁴C] glucose-6-phosphate into polyols and other neutral sugars was investigated in in vitro reaction systems. When a crude homogenate or a press juice of the eggs was incubated with [6-¹⁴C]glucose-6-P, the labelled trehalose, sorbitol and glycerol accumulated in the reaction mixture. In the press juice incubation system of developing eggs at day 1, ¹⁴C-sorbitol was detected in appreciable amounts, but it decreased rapidly with the development of the embryos. When the press juice was prepared from eggs in diapause, the formation of ¹⁴C-sorbitol was 3–5 times greater in eggs at early stages (day 2 to day 4) than in developing eggs.     

CYCLIC NUCLEOTIDE-DEPENDENT PROTEIN KINASES FROM SILKWORM EGGS: OCCURRENCE OF TWO CYCLIC NUCLEOTIDE-DEPENDENT PROTEIN KINASES, CHANGES IN THEIR ACTIVITIES AND LEVELS OF CYCLIC NUCLEOTIDES DURING DEVELOPMENT OF THE EGGS

Two cyclic nucleotide-dependent protein kinases, designated as protein kinase-I and -II, were obtained from the eggs of the silkworm, Bombyx mori . Protein kinase-I is highly dependent on cGMP, whereas protein kinase-II is dependent on cAMP. In developing non-diapause eggs, the level of cyclic nucleotide-dependent protein kinase activity is quite high but that in the diapause eggs is not. The developmental changes in the two protein kinases and the level of cyclic nucleotides were also studied during the development of the eggs.     

The status of donor cancer tissues affects the fate of patient-derived colorectal cancer xenografts in NOG mice

Patient-derived xenografts (PDXs) of tumors are increasingly becoming important tools for translational research in oncology. The NOD.Cg-Prkdc^scid Il2rg^tm1Sug/Jic (NOG) mouse is an efficient host for PDXs. Thus as a basis for future development of methods to obtain PDXs from various disease types, we have studied the factors that affect the outcome of transplantation of human colorectal cancer in NOG mice. Of the original donor cases examined, 73% had successful engraftment. The outcome of donor-matched tissues was consistent in most cases, and was thought to show that the condition of the host did not affect engraftment. Next we analyzed the tumor aggressiveness in terms of histology grade of the original tumor and found that they were related to engraftment. Detailed histopathological examination of the transplanted tissues strongly indicated that lymphocytes engrafted with the tumor cells affect engraftment. As a factor related to transplantation of lymphocytes, we studied the human IgG concentration in the serum of tumor-bearing mice, but there was no tendency for higher concentrations to result in unsuccessful engraftment. Finally, we studied the type, density and location of T cells in the original donor tissue to determine the immune contexture and found that the unsuccessful engraftment cases tended to have an adequate or coordinated immune contexture compared to successful engraftment cases. From these results, we concluded that the aggressiveness and the T cell infiltration of the original tumor affect the outcome of transplantation in the NOG mouse.     

Possible Involvement of ERK 1/2 in UVA‐Induced Melanogenesis in Cultured Normal Human Epidermal Melanocytes

UV‐induced melanogenesis is a well known physiological response of human skin exposed to solar radiation; however, the signaling molecules involved in the stimulation of melanogenesis in melanocytes following UV exposure remain unclear. In this study we induced melanogenesis in vitro in normal human epidermal melanocytes using a single irradiation with UVA at 1 kJ/m² and examined the potential involvement of mitogen‐activated protein kinases (MAPK) as UVA‐responsive signaling molecules in those cells. UVA irradiation did not affect the proliferation of melanocytes, but it did increase tyrosinase mRNA expression, which reached a maximum level 4 hr after UVA irradiation. The amount of tyrosinase protein, as quantitated by immunoblotting, was also increased at 24 hr following UVA irradiation. Among the MAPK examined, extracellular signal‐related kinase (ERK) 1/2 was phosphorylated within 15 min of UVA irradiation, but no such phosphorylation was observed for c‐Jun N‐terminal kinases (JNK) or p38. Accordingly, the activity of ERK1/2 was also increased shortly after UVA irradiation. These responses of ERK1/2 to UVA irradiation were markedly inhibited when cells were pre‐treated with N‐acetyl‐l ‐cysteine, an antioxidant, or with suramin, a tyrosine kinase receptor inhibitor. The formation of (6‐4)photoproducts or cyclobutane pyrimidine dimers was not detected in cellular DNA after UVA irradiation. These findings suggest that a single UVA irradiation‐induced melanogenesis is associated with the activation of ERK1/2 by upstream signals that originate from reactive oxygen species or from activated tyrosine kinase receptors, but not from damaged DNA.     

CARBOHYDRATE METABOLISM IN THE EGGS OF THE SILKWORM, BOMBYX MORI. I. ABSENCE OF PHOSPHOFRUCTOKINASE IN THE DIAPAUSING EGG

In the diapausing eggs of the silkworm, Bombyx mori , glycogen is rapidly converted to sorbitol and glycerol, and this conversion is reversed at termination of the diapause (C hino , 1958). To elucidate the pathway leading to this polyol formation and its regulatory mechanisms, enzymes concerning carbohydrate metabolism were surveyed in diapausing as well as in developing eggs of the silkworm.
Most of the enzyme activities concerning citric acid cycle are low at the beginning of the embryogenesis and during diapause, but increase at the later stages of the development. Making an exception, reduction rate of malate and fumarate was rather high from the onset of the embryonic development. Several glycolytic enzymes were also studied. Most remarkable fact is that phosphofructokinase activity could not be demonstrated in the diapausing and also in the early stages of the developing eggs. Other enzymes, viz. α-glycerophosphate dehydrogenase, aldolase, glyceraldehyde-3-phosphate dehydrogenase were detected from the beginning of the embryogenesis.
Absence of phosphofructokinase, together with the high activity in glucose-6-phosphate dehydrogenase, suggests that predominant pathway in carbohydrate metabolism in the early stages of embryogenesis and in the diapause period is by way of pentose phosphate pathway. This supposition is confirmed by the experiments using labeled glucose. Incorporation of the label into glycerol of the diapausing eggs was three to four fold when G-6-¹⁴C was injected into pupae as compared with the case of G-1-¹⁴C injection. The above experiments provide evidence supporting the theory that glycogen is converted into sorbitol and glycerol mostly by way of the pentose phosphate pathway in the diapausing eggs.     

Nestmate discrimination in the queenless ponerine ant Diacamma sp. from Japan

We examined the nestmate discrimination ability of Diacamma sp., an ant that reproduces by colony budding. We also tested for a relationship between internest distance and hostility. Hostility toward non‐nestmates was significantly stronger than that toward nestmates, suggesting that Diacamma sp. discriminates between nestmates and non‐nestmates. There was no significant correlation between internest hostility and internest distance, which indicates the absence of a “dear enemy” phenomenon in this species.     

EFFECT OF ECDYSONE ON THE OVARIAN DEVELOPMENT OF BOMBYX SILKWORM*

From the ligation experiments, it is indicated that the secretion from prothoracic glands during early pupal period induces the ovarian development in female pupa of the silkworm, Bombyx mori. The exogenous β-ecdysone injected into isolated pupal abdomen also induces the initiation of the ovarian development.     

Ion gradients in xylem exudate and guttation fluid related to tissue ion levels along primary leaves of barley

The concentration of ions in plant cells and tissues is an essential factor in determining physiological function. In the present study, we established that concentration gradients of mobile ions exist in both xylem exudates and tissues within a barley (Hordeum vulgare) primary leaf. For K⁺ and NO₃^?, ion concentrations generally decreased from the leaf base to the tip in both xylem exudates and tissues. Ion gradients were also found for Pi and Cl^? in the xylem. The hydathode strongly absorbed Pi and re‐translocated it to the rest of the plant, whereas Cl^? was extruded. The ion concentration gradients developed early during leaf growth, increased as the tissue aged and remained under both high and low transpiration conditions. Measurement of the expression profiles of Pi, K⁺ and NO₃^? transporters along the longitudinal axis of the leaf revealed that some transporters are more expressed at the hydathode, but for most transporters, there was no significant variation along the leaf. The mechanisms by which longitudinal ion gradients develop in leaves and their physiological functions are discussed.