Expression of epidermis-specific antigens during embryogenesis of the ascidian, Halocynthia roretzi

We have produced two monoclonal antibodies (Epi-1 and Epi-2) which specifically recognize epidermal cells and their derivative, the larval tunic, of developing embryos of the ascidian Halocynthia roretzi. The antigens, examined by indirect immunofluorescence staining, first appear at the early tailbud stage and are present until at least the swimming larval stage. There were distinct and separate puromycin and actinomycin D sensitivity periods for each antigen. Aphidicolin, a specific inhibitor of DNA synthesis, prevented the appearance of each antigen when embryos were exposed to the drug continuously from cleavage stages. These results suggest that the antigens are synthesized during embryogenesis by developing epidermal cells and that several rounds of DNA replication are required for the antigen expression. Early cleavage stage embryos, including fertilized but unsegmented eggs, in which cytokinesis had been blocked with cytochalasin B expressed the antigens, and blastomeres exhibiting the antigens were always of the epidermis lineage. In partial embryos produced by four separated blastomere pairs of the 8-cell embryos, the expression of antigens was seen only in those developed from the animal blastomere pairs, which are progenitors of epidermal cells. These observations indicate that differentiation of epidermal cells in ascidian embryos takes place in a typical "mosaic" fashion.     

Electrical stimulation of the suprachiasmatic nucleus of the hypothalamus causes hyperglycemia

We have presented evidence suggesting that the suprachiasmatic nucleus (SCN) is involved in central regulation of glucose homeostasis. To elucidate this role of the SCN, we examined the effects of its electrical stimulation on glucose metabolism in male Wistar rats. During and shortly after this stimulation, we observed hyperglycemia associated with enhanced hyperglucagonemia but no immediate hyperinsulinemia. In addition, we detected significant increase in liver glycogen phosphorylase alpha activity and significant decrease in the liver glycogen content. These findings suggest that the SCN is important in control of glucose homeostasis through effects on glucagon and insulin secretions and liver glycogen metabolism.     

A sensitive method for quantitative analysis of phospholipid molecular species by high-performance liquid chromatography

A simple and sensitive method was developed for quantitative analysis of phospholipid molecular species. Diacylglycerols were prepared from phospholipids by phospholipase C treatment and converted to the corresponding dinitrobenzoyl derivatives, which could be sensitively detected at 254 nm. The derivatives of 21 molecular species were resolved by high-performance liquid chromatography with an octadecylsilyl reversed-phase column. All the derivatives had the same peak area per mol, and peak areas were proportional to the amounts of the derivatives. Quantification was carried out at the picomole level.     

Diurnal changes in the vertical distribution of phytoplankton in hypertrophic Lake Kasumigaura,Japan

The daily vertical migration of five species;Microcystis aeruginosa (Kütz.) Trevis,Anabaena spiroides Klebahn f.crassa (L.) Elenkin,Aphanizomenon flos-aquae (L.) Ralfs,Melosira granulata (E). Ralfs, andCoscinodiscus lacustris Grun. was studied using a close-interval water sampler on a calm summer day in Lake Kasumigaura. Many colonies ofMicrocystis were observed at the middle of the water column (approx. 1.5 m depth) in the afternoon, and at the surface in the early morning.Anabaena occurred mostly in the upper layer whileAphanizomenon tended to be uniformly distributed. The difference in migration patterns suggests thatMicrocystis is superior toAnabaena andAphanizomenon in obtaining both light and nutrients from this lake. Among diatoms,Melosira remained at the bottom of the water column throughout day and night, but Coscinodiscus was uniformly distributed.     

Effects of Cu,Cd and Zn on photosynthesis of freshwater benthic algae

One hundred and eighteen algal isolates comprising seven classes were obtained from a range of sites from polluted rivers running through Cu or Zn mining regions, and from unpolluted rivers. All the isolates were tested for photosynthetic activity when exposed to Cu, Cd or Zn. The tolerance levels of Bacillariophyceae, Charophyceae, Cyanophyceae and Chlorophyceae to Cu showed significant positive correlations with Cu concentrations in the field. However the distribution of metal sensitivities of the algae from the sites with the same metal concentration was broad. Both Bacillariophyceae and Charophyceae had a number of strains whose sensitivity to Cu differed more widely in relation to Cu levels in the environment than Cyanophyceae and Chlorophyceae. Cyanophyceae were sensitive to all three metals, whether or not isolates were obtained from polluted sites, whereas Chlorophyceae tended to have high tolerance even in isolates from unpolluted sites. For Cd and Zn the correlation between tolerance levels and concentrations in the field was not so clear as for Cu. The occurrence of Cu tolerance was shown in 4 diatom species and one Charophyceae, whereas metal resistance occurred in some Chlorophyceae. Cu-tolerant isolates tended also to be Zn-tolerant in Bacillariophyceae, and Cd-resistant isolates tended also to be Zn-resistant in Chlorophyceae.     

Potential Distribution and Ionic Concentration at the Bean Root Surface of the Growing Tip and Lateral Root Emerging Points

The electrical potential distribution has been measured preciselyaround the root surface of the bean sprout Vigna mungo (L) Hepper.A large negative potential well was found at the growth portionof the root tip. Also, in the matured region of the root, wefound a negative potential well at an unspecified position inspite of the fact that nothing was detected on the smooth surface.A lateral root emerge was found to have initiated after 15–20hours just at the position corresponding to the potential well.With the expectation that these potentials can be elucidatedbased on the transport of ions which are released or absorbedby the root as a result of cell activity, we precisely measuredthe concentrations of major ion species (K⁺, H⁺, and Cl^–)around the root. The theoretical potential distribution curvesobtained by putting all the concentration data into the Henderson'sEquation for a liquid junction (diffusion) potential coincidedwell with the experimental curves. (Received October 24, 1994; Accepted March 24, 1995)     

Bioenergetics of Carbon Assimilation in Intact Chloroplasts: Coupling of Proton to Electron Transport at the Ratio H+/e=3 Is Incompatible with H+/ATP=3 in ATP Synthesis

During a transition from aerobic to largely anaerobic conditionslight-saturated carbon assimilation of intact chloroplasts wasnot decreased although both the transthylakoid proton gradientand ATP levels declined. After a dark period under anaerobiosis,illumination failed to initiate carbon assimilation. ATP increasedonly transiently in the light and then returned to the darklevel. Under such conditions, the addition of electron acceptorssuch as oxygen, oxalacetate or nitrite resulted in the increaseof ATP levels and carbon assimilation was initiated. Assimilationcontinued under anaerobiosis in the presence of reduced protongradients and reduced ATP levels after electron acceptors addedin addition to bicarbonate were reduced. Cyclic electron transport was inhibited when anaerobiosis didnot permit linear electron transport. It was induced in thissituation by micromolar concentrations of oxygen or when, underanaerobiosis, DCMU decreased PSII activity. Oxygen inhibitedcyclic electron transport by draining electrons from the cyclicpathway only when electron donation from PSII was weak. Theobservations give evidence of the delicate redox balance requiredfor cyclic electron transport. Since H⁺/e=3 in linear electron transport, the observationsof effective carbon reduction under a decreased transthylakoidproton gradient and decreased levels of ATP are incompatiblewith H⁺/ATP=2 or 3. They are compatible with H⁺/ATP=4. (Received May 1, 1995; Accepted October 3, 1995)     

Differential pulse polarographic determination of plasma menadione

A differential pulse polarographic assay for plasma vitamin K₃ (menadione) has been developed. Details of the assay are (i) lipid-soluble material is extracted from plasma into ether by the method of Bjornsson et al. [(1978) Thromb. Haemostas.2, 466–473]; (ii) ether is evaporated under nitrogen and the residue is dissolved in the supporting electrolyte, methanol: 0.2 m borate buffer (9:1), pH 6.8; (iii) current height is measured at ?0.32 V vs SCE on the differential pulse polarogram. The lower sensitivity limit of this technique after addition of standard vitamin K₃ to plasma is 0.3 μm; the calibration curve is linear from 0.6 through 10 μm. Two patients treated with a single dose of menadiol sodium diphosphate, 20 mg/M² i.m., achieved measurable plasma vitamin K₃ levels at 0.5 to 1.0 h ranging between 0.5 (0.08 μg/ml) and 2 μm (0.3 μg/ml).