Seasonal Variation in Serum Concentration of 5-S-Cysteinyldopa and 6-Hydroxy-5-Methoxyindole-2-Carboxylic Acid in Healthy Japanese

Serum concentrations of 5-S-cysteinyldopa (5-S-CD) and 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MI2C) have been used as biochemical markers of melanoma progression. We examined the effect of solar radiation on serum levels of 5-S-CD and 6H5MI2C in 10 healthy Japanese by measuring these markers every month during a period of 2 years. 5-S-CD levels were higher in early summer and lower in early winter. The difference in the average levels was approximately twofold, but among the 240 samples, no individual values exceeded the upper limit of normal value, 10 nmol/L. A significant correlation (P<0.02) was observed between 5-S-CD level and solar radiation. 6H5MI2C levels showed a smaller variation than 5-S-CD. No correlation was observed between 6H5MI2C level and solar radiation. This study showed that serum 5-S-CD and 6H5MI2C in healthy Japanese did not exceed the upper limit of normal values even in sunny season.     

Cytoplasmic Distribution of DNA in a Strain of Hartmannellid Amoeba1, 2

SYNOPSIS. The distribution of cytoplasmic DNA as determined by H³-thymidine incorporation in the Fernald strain of Hartmannella rhysodes was studied by electron microscope autoradiography. Of a total of 1,313 silver grains counted over the cytoplasm in thin sections, 488, 271, 202 and 230 were attributed to DNA in mitochondria, cytoplasmic matrix, plasmalemma and ectoplasm, respectively. On the basis of the ratio of grains associated with the relative area occupied by the various compartments, the plasmalemma accounted for 3 times more grains than the mitochondria and about 20 times that attributed to DNA in cytoplasmic matrix and ectoplasm. These findings are interpreted to indicate the presence of endosymbionts in this strain of soil amoeba. Since no definitive microorganism could be seen in this cell, the most likely endosymbiont is defective DNA virus(es) or episome-like genetic element(s).     

EFFECTS OF MEDIA OF DIFFERENT IONIC COMPOSITION ON THE ACTIVATION POTENTIAL OF ANURAN EGG CELLS

Activation potentials of the eggs of two anuran species, Bufo vulgaris formosus and Rana rugosa , were measured in media of different ionic composition, and the mechanism of their generation is discussed. The same trends of ionic effects upon the activation potential were consistently obtained in both species.
The membrane potential of the unactivated eggs was negative with respect to tap water, Ringer's solution, and the media described below except isotonic KCl and KNO₃, in which the potentials were nearly zero or sometimes slightly positive. Upon activation induced by pricking in tap water, isotonic Na₂SO₄, or 42 mM or 63 mM buffered sodium phosphate solution, depolarization followed by reversal of the membrane potential took place, associated with a decrease in the effective resistance. Then the potential gradually decreased and returned to the initial value.
On the other hand, in Ringer's solution, or in isotonic NaBr, NaNO₃, KCl or KNO₃, the activation potential occurred in a hyperpolarizing direction, associated with a decrease in the effective resistance.
These results suggest that the ooplasmic membrane of the anuran egg surface during activation is selectively permeable to NO₃⁻ and Br⁻ as well as Cl⁻, but not to SO₄⁻ and phosphate ions, or alternatively, that the activation potential is due to this selective permeability and to the concentration gradients of these monovalent anions across the ooplasmic membrane.     

INTER AND INTRATISSUE COMMUNICATION DURING AMPHIBIAN DEVELOPMENT*

The changes of electrical communication between various tissues of the newt (Cynops pyrrhogaster) embryo during development have been investigated by measuring electrotonic potentials at various interelectrode distances. In general, cells of the same tissue are electrically coupled from gastrulation up to closure of the neural tube. Notochordal cells, however, are an exception in that cell coupling decreases during stages 22–23 in comparison to earlier stages. Neuroectoderm cells are coupled to adjacent chorda-mesoderm cells during the initial stages of gastrulation (st. 12c). Subsequently coupling of these tissues diminishes (st. 15–16) and finally disappears (st. 22–23). The similar decrease of coupling was observed in inter-tissues of the chorda-mesoderm cells and the somitic mesoderm cells during the mesodermal differentiation. In contrast, coupling values of less than 0.1 recorded between somite cells and cells of the neural tube or epidermis still remain at st. 22–23. The neural plate cells remain coupled to the lateral ectoderm cells at st. 18 and then become insulated from the epidermis by st. 22–23, even though a coupling ratio of 0.1 remains between these tissues. These developmental patterns of coupling are discussed with respect to cellular movements of neuroectoderm and mesoderm during gastrulation, and with special reference to neural competence.     

FUNCTIONS OF CALCIUM IN THE CELL WALL OF RICE LEAVES

Rice plants were grown in nutrient solutions containing 0.5,20, and 500 ppm of calcium as CaO. Microscopic observation revealedthat the mesophyll structure in the leaves was disordered atthe lowest Ca level and became healthy with increasing supplyof calcium in the culture solution. The chemical constitutionof cell wall and the composition of sugar in each chemical constituentof wall differed little among the leaves grown with differentlevels of calcium. The calcium contents in the walls of calciumdeficient leaves were extremely low as compared with those ofnormal leaves. The amount of calcium extractable in the ligninfraction of Ca 0.5 leaves was only about one-sixth of that ofCa 500 leaves. Furthermore, calcium in the lignin fraction wasleached out by treating the wall previously with 2% acetic acidsolution. These results suggest a close association of calciumwith ligneous substances in combined forms of physiologicalimportance in the cell walls. (Received April 11, 1967; )     

Chemical Degradation of Melanins: Application to Identification of Dopamine-melanin

Melanocytes produce two chemically distinct types of melanin pigments, eumelanins and pheomelanins. These pigments can be quantitatively analyzed by acidic KMnO₄ oxidation or reductive hydrolysis with hydriodic acid (HI) to form pyrrole-2,3,5-tricarboxylic acid (PTCA) or aminohydroxyphenylalanine (AHP), respectively. Dark brown melanin-like pigments are also widespread in nature, for example, in the substantia nigra of humans and primates (neuromelanin), in butterfly wings and in the fungus Cryptococcus neoformans. To characterize such diverse types of melanins, we have improved the alkaline H₂O₂ oxidation method of Napolitano et al. (Tetrahedron, 51: 5913–5920, 1995) and re-examined the HI hydrolysis method of Wakamatsu et al. (Neurosci. Lett., 131: 57–60, 1991). The results obtained with H₂O₂ oxidation show that 1) pyrrole-2,3-dicarboxylic acid (PDCA), a specific marker of 5,6-dihydroxyindole units in melanins, is produced in yields ten times higher than by acidic KMnO₄ oxidation, and 2) PTCA is artificially produced from pheomelanins. The results with HI hydrolysis show that dopamine-melanin produces a 1:1 mixture of 3-amino and 4-amino isomers of aminohydroxyphenylethylamine, while the isomer ratio is about 0.2 in melanins prepared from dopamine and cysteine. These results indicate that alkaline H₂O₂ oxidation is useful in characterizing synthetic and natural eumelanins and that reductive hydrolysis with HI can be applied to analyzing oxidation products of dopamine such as neuromelanin.     

Inactivation of Nitrate Reductase of the Yeast, Rhodotorula glutinis

Nitrate reductase (NR) from the yeast, Rhodotorula glutinis var. salinaria was composed of two enzymatic components, diaphorase and terminal nitrate reducing moieties. The enzyme used NADPH as electron donor and FAD as cofactor. The synthesis of nitrate reductase was promoted specifically by nitrate and repressed by ammonium and amino acids. Nitrate reductase from this yeast had an inactive as well as an active form. Inactive enzyme was reactivated by oxidation with ferricyanide in vitro. Hydroxylamine promoted the formation of inactive enzyme in vivo. Ammonium could neither promote the inactivation nor reduce the total level of nitrate reductase activity. Nitrate could protect nitrate reductase from inactivation caused by nitrogen starvation or hydroxylamine.     

Effect of particle size distribution on filtration performance of cell culture medium

Cell culture media used in CHO-based biologic processes are typically sterile filtered to prevent microbial contamination prior to inoculation. In this study, the impact of common sterile filter throughput on a different, commercially available cell culture media was evaluated from the intermediate-adsorption fouling model of the filtration model. The key particle size range for optimum filter performance was discussed and identified by measuring the submicron order particle size distribution. It may be possible to predict the performance of filter capacity with size-exclusive separation by understanding the media particle counts and size distribution.