Sumiko Negishi

The effects of melanophore-stimulating hormone and cyclic nucleotides on teleost fish chromatophores

Abstract The effects of melanophore-stimulating hormone (MSH) and cyclic nucleotides on pigment translocation within the isolated scale chromatophores of the medaka, Oryzias latipes , were examined in relation to the second-messenger hypothesis. In leucophores, MSH, cyclic AMP, dibutyryl cyclic AMP (DBcAMP), and methylxanthines brought about a rapid pigment dispersal. β-Adrenergic blockers completely abolished methylxanthine-mediated dispersion without inhibiting the response induced by MSH or DBcAMP. In melanophores and xanthophores, MSH did not accelerate pigment dispersion. Dibutyryl cyclic GMP (DBcGMP) was more effective than cyclic AMP or DBcAMP in producing pigment dispersal. In the presence of DBcGMP, epinephrine was incapable of stimulating pigment aggregation in melanophores whereas the presence of DBcAMP did not interfere with the epinephrine-induced aggregation. The results implicate the involvement of the adenylate cyclase-cyclic AMP system in the regulation of leucophore response while in melanophores and xanthophores, cyclic GMP appears to mediate pigment displacement.

Epinephrine-induced changes in the cyclic nucleotide content of fish melanoma cells

Abstract Intracellular levels of adenosine 3′,5′-monophosphate (cyclic AMP) and guanosine 3′,5′-monophosphate (cyclic GMP) in melanoma tissues developed in platyfish and swordtail hybrids were determined by radioimmunoassay. The melanoma tissues were composed mostly of pigment cells, many of which responded to epinephrine with pigment aggregation. The aggregated melanosomes redispersed gradually by washing the cells with physiological saline, and rapidly by the perfusion with theophylline. Determination of intracellular levels of cyclic nucleotides revealed that epinephrine produced a small but significant decrease in cyclic AMP level, whereas theophylline elicited a remarkable increase in the intracellular concentration of cyclic AMP. On the other hand, the change in the levels of cyclic GMP was not significant among the tissues subjected to the different experimental conditions. The present results suggest that the centrifugal and centripetal translocations of melanosomes within melanophores are regulated directly by the intracellular concentration of cyclic AMP.

Dynein 1 from rainbow trout spermatozoa: Immunological similarity between trout and sea urchin dynein 1

Abstract This paper is the first biochemical presentation on dynein 1 from vertebrate spermatozoa. Axoneme of rainbow trout spermatozoon is surrounded by the functionally differentiated flagellar membrane, the undulating membrane. The long axis of the undulating membrane is perpendicular to the axonemal axis. Dynein 1 was obtained in the salt extract of axonemes and Fragment 1A was purified from the tryptic digest of salt-extracted dynein 1. Dynein 1 and Fragment 1A from trout were compared with those from sea urchin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis could not show the difference in the molecular weights of dynein 1, and subunit components and their molecular weights of Fragment 1A between two species. Anti-dynein 1 and anti-Fragment 1A sera raised against sea urchin antigens also reacted with trout dynein 1 and Fragment 1A, and inhibited their ATPase activities. Ouchterlonys double diffusion test indicated the pattern of “partial identity” between trout and sea urchin Fragment 1A. Immunoelectron microscopy using peroxidase-conjugated anti-IgG shows that the decoration was observed on the outer arms when the axonemes from the fresh spermatozoa were employed.

Larval arm resorption proceeds concomitantly with programmed cell death during metamorphosis of the sea urchin Hemicentrotus pulcherrimus

Sea urchins are excellent models to elucidate metamorphic phenomena of echinoderms. However, little attention has been paid to the way that their organ resorption is accomplished by programmed cell death (PCD) and related cellular processes. We have used cytohistochemistry and transmission electron microscopy to study arm resorption in competent larvae of metamorphosing sea urchins, Hemicentrotus pulcherrimus, induced to metamorphose by L-glutamine treatment. The results show that: (1) columnar epithelial cells, which are constituents of the ciliary band, undergo PCD in an overlapping fashion with apoptosis and autophagic cell death; (2) squamous epithelial cells, which are distributed between the two arrays of the ciliary band, display a type of PCD distinct from that of columnar epithelial cells, i.e., a cytoplasmic type of non-lysosomal vacuolated cell death; (3) epithelial integrity is preserved even when PCD occurs in constituent cells of the epithelium; (4) secondary mesenchyme cells, probably blastocoelar cells, contribute to the elimination of dying epithelial cells; (5) nerve cells have a delayed initiation of PCD. Taken together, our data indicate that arm resorption in sea urchins proceeds concomitantly with various types of PCD followed by heterophagic elimination, but that epithelial organization is preserved during metamorphosis.

Alterations in the integument of Armadillidium vulgare masculinized by implantation of androgenic glands

Summary Alterations in the integument of masculinized females of Armadillidium vulgare caused by the implantation of androgenic glands from normal males involve both pigment cells and epidermal cells with respect to the intracellular structure and the ommochrome content. Epidermal cells beneath the cuticle of masculinized females are thicker than those of normal females, having a number of small secretory granules and well developed rough endoplasmic reticulum in the cytoplasm. As a result of epidermal cell thickening, pigment cells are more widely separated from the cuticle in masculinized females than in normal females. The ommochrome content in the integument of masculinized females, which was initially the same as that of normal females, increased with each postoperative stage and coincided with that of male integument by the fourth postoperative stage. The observations suggest that the slate grey color characteristic of the male body, shown during masculinization of females after the implantation of ...

Properties and state of particulate tyrosinase of xanthic goldfish

Abstract 1. 1. The properties, subcellular distribution and status of particulate tyrosinase in xanthic goldfish skin were studied using fractionated materials. 2. 2. Tyrosinase occurred in two molecular forms that exhibited different electrophoretic mobilities in acrylamide-gel electrophoresis. 3. 3. Freshly prepared particulate or pterinosome suspension in an isotonic medium had no measurable tyrosinase activity. The enzyme activity was detected after mechanical or chemical breakage of the structural integrity of the particles. 4. 4. No endogenous tyrosinase inhibitor was found in the particulate fractions.

Novel structures in secreting the androgenic gland hormone.

Abstract The secretory granules in the androgenic gland of the terrestrial isopod Armadillidium vulgare, which have been indistinct for long time because of vulnerable structures, were revealed by using the rapid-freezing and freeze-substitution method. The fine struture of the androgenic gland is conspicuous by the distribution of numerous particular organelles in the cytoplasm consisting of the endoplasmic reticulum and the Golgi complex, and by having a number of highly organized structures developed between the androgenic gland cells. The structures connect to the intercellular space, which is seen as intercellular canaliculi for exporting the androgenic gland hormone. The plasma membranes near the particular structure of the intercellular canaliculi in the androgenic gland are often specialized to form cellular junctions. The secretory granules including the electron-dense materials, which are supposed to be peptides of androgenic gland hormone, are distributed beside the particular structure of the intercellular canaliculi. Some of the granules are seen to fuse with the plasma membranes. This observation suggests that, in the Armadillidium vulgare, the secretory granules containing androgenic gland hormone are transferred to the extracellular space through the intercellular canaliculi particularly developed for exporting the peptide hormone. This is the first evidence to show the secretory mechanism of the androgenic gland hormone in the Isopoda.

A sensitive bioassay for melanotropic hormones using isolated medaka melanophores

Melanophore-stimulating hormones (MSHs) from chum salmon cause pigment dispersion in isolated melanophores of medaka, a teleost. The in vitro medaka melanophore bioassay that responded to light with pigment dispersion and to the dark with pigment aggregation was utilized for measuring the activity of melanotropic hormones. alpha-MSH I was the most potent melanophore-dispersing agent tested. The minimal dose for the induction of pigment dispersion was 10(-15) M alpha-MSH I, 10(-13) M N-des-acetyl(Ac)-alpha-MSH, and 10(-11) M beta-MSH I, respectively. The melanosome-dispersing activity of beta-MSH I was enhanced about 40% by salmon N-acetyl-endorphin I (N-Ac-EP). The results suggest that N-Ac-EP may act as an enhancer for the activity of certain MSHs. The present bioassay provides a unique method for determining the biological activity of melanotropic peptides.

INVOLVEMENT OF TRYPTOPHAN METABOLISM IN THE BODY COLOR OF CRUSTACEA

The terrestrial isopod, Armadillidium vulgare is usually grey or black in color, however, red ones are occasionally found in the field. This is caused by the mutation of the ommochrome genesis in the integument. We focused our experiments on the mechanism of pigment genesis in which tryptophan metabolism had been expected to be different from the grey or black wild types. We obtained the result that 3-hydroxyanthranilic acid content was significantly higher in the red phenotype than in the wild type, and kynureninase activity was also higher in the red phenotype.

Ommochrome Genesis in an Albino Strain of a Terrestrial Isopod

The contents of tryptophan (Trp) metabolites and the activities of the enzymes involved in ommochrome biosynthesis were measured in an albino strain of a terrestrial isopod Armadillidium vulgare. There was little difference between the Trp content in the albino mutant and that in the wild type, although the contents of 3-hydroxykynurenine (3-OH-Kyn), 3-hydroxyanthranilic acid (3-OH-AA) and xanthommatin in the albino were significantly lower than those in the wild type. Tryptophan 2,3-dioxygenase (TDO) activity in the albino was extremely low, while the activities of Kyn-3-hydroxylase and kynureninase did not differ significantly between the two phenotypes. The extremely low activity of TDO is probably one of main reasons why almost no ommochrome pigment is produced in the albino mutant.