摘要:

AbstractIn this study, specific binding sites for [3H]‐LTC4on membrane preparations from American bullfrog (Rana catesbeiana) brain were characterized. Binding assays were done in the presence of serine (5mM) borate (10 mM) for 30 min at 23°C. Under these conditions, no metabolism of LTC4to LTD4occurred. Specific binding of [3H]‐LTC4reached steady state within 10 min, remained constant for 60 min, and was reversible with the addition of 1,000‐fold excess unlabelled LTC4. Scatchard analysis of the binding data indicated a single class of binding sites with an estimated Kdof 89.83 nM and Bmaxof 43.79 pmol/mg protein. Competition binding studies demonstrated that LTD4and LTE4were ineffective in displacing [3H]‐LTC4from its binding site. The Kifor LTC4was 51 nM. S‐decylglutathione, glutathione and hematin had Kivalues of 44, 312,602, and 25,576 nM, respectively. The mammalian cysteinyl leukotriene antagonist L‐660,711 inhibited specific binding of [3H]‐LTC4, with a Kiof 87,149 nM. Guanosine‐5′‐0‐3‐thiotriphosphate (GTPγS) did not affect specific binding of [3H]‐LTC4indicating that, like mammalian LTC4receptors, a Giprotein is not involved in the transduction mechanism. The LTC4binding site in bullfrog brain demonstrates both similarities and differences from its mammalian counterp

ISSN:0022-104X    

DOI:10.1002/jez.1402620102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAn electrophoretic characterization of histones from pyloric caeca, testes, and sperm ofAsterias vulgarisrevealed a sperm/testes‐specific variant of histone H1 significantly larger than its somatic counterpart from pyloric caeca. Additional proteins were observed in H1 regions of acetic acid‐urea polyacrylamide gels in testicular extracts. Sperm or testis‐specific variants of H2B observed in sea urchins were not found in the sea star. Evidence presented suggests that sperm‐ or testes‐specific H1 species of intermediate mobility may arise from a single, slow‐migrating H1 species (SpH1). Although an increase in nonspecific DNA binding by nuclear proteins must occur during the process of spermatogenesis, different organisms exhibit various patterns of sperm‐specific protein mediating differential binding during the process. Sperm‐specific variants of both H1 and H2B histones are observed in sea urchins, while the only variant observed in sea stars during spermatogenesis is SpH1. Sequencing of the N‐terminus of SpH1 from A.vulgarisrevealed a repeating tetrapeptide in residues 3–6 and 8–11 (Ser‐Pro‐Arg‐Lys and Ser‐Pro‐Lys‐Lys, respectively), homologous to repeats in the N‐termini of sperm‐specific H1s from sea urchins. Primary structure within critical, variable regions of molecules responsible for nonspecific DNA binding appear conserved in many organisms. The occurrence of repeating tetrapeptides in SpH1 and other DNA binding proteins suggests that such domains may function similarly in various chromatins undergoing regulated or reversible

ISSN:0022-104X    

DOI:10.1002/jez.1402620103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractEye pupil‐size changes, in response to repetitive ON‐OFF light stimulation, of 3 species of noctuid moths have been observed by infrared reflection photometry. For moderate ON stimulus intensities (2.5·109quanta·cm−2·s−1), eye reflectance changed exponentially with time, in both the ON and OFF phases. For low ON stimuli (2.5·108quanta·cm−2·s−1), however, the dark adaptation response in the OFF phase was composed of an initial exponential and a subsequent linear term. For repetitive low‐intensity ON‐OFF stimuli, the response amplitude changed in a diurnal way. The shape of the response to each ON‐OFF stimulus was, however, independent of diurnal time. Finally, in eyes that were spontaneously entering a light‐adapted state, pure exponential dark adaptation was elicited by intense light pulses. It is suggested that the substances controlling light and dark adaptation are interrelated. The substances constitute a chemical cycle running at constant speed, in the absence of light, and the substance causing pigment dispersion (light adaptation) is a photoproduct of the other substance. The concentration of the substance causing pigment contraction (dark adaptation) is controlled by the rate of the back reaction, which is composed of an exponential term, related to accumulation of the photoproduct during light stimulation, and a constant term, due to the speed of the cycle. The cycle speed is subject to diurnal change

ISSN:0022-104X    

DOI:10.1002/jez.1402620104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe sources of extracellular and intracellular 3,5,3′ ‐triiodo‐L‐thyronine (T3) binding to putative thyroid hormone receptors in liver, kidney, and gill nuclei were determined in vivo for immature rainbow trout at 12°C. Both [131I]T3and [125I]T4were injected intraperitoneally, the plasma and tissues were examined at isotopic equilibrium at 20 h, and the proportions of intracellular [125I]T3and extracellular [131I]T3saturably bound in the nucleus were determined. Comparable total amounts of T3were saturably bound in the nuclei of liver (7.2), kidney (8.0), and gill (9.7 moles × 10−13.mg DNA−1), but the percentage of nuclear T3generated within the target cell was greater for gill (76%) than for liver (50%) and kidney (28%). Both gill and liver possess a low Km T45′monodeiodinase which could be responsible for the high proportion of the nuclear T3generated within those tissues. © 1992

ISSN:0022-104X    

DOI:10.1002/jez.1402620105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe embryos of 2 larval morphs of the insect parasitoidCopidosoma floridanum(Ashmead) (Hymenoptera: Encyrtidae) were readily distinguished on the basis of temporal and morphological characters. Although larvae of the 2 morphs diftered in morphology and timing of hatch, both morphs derived a serosal membrane just prior to embryonic morphogenesis. Nuclei of the serosa increased in diameter and ploidy during development. Serosa polyploidy was similar in both morphs at identical stages of morphogenesis. Host endocrine perturbations that blockedC. floridanummorphogenesis also affected serosa development. Serosa ontogeny was blocked when the host was ligated at 7 h of the 4th stadium. Daily application of the juvenile hormone analogue methoprene starting at 20 h of the host's 3rd stadium resulted in serosal nuclei with greater diameters and ploidy values than those of untreated embryos. Treatment of the host with methoprene beginning at 20 h of the 3rd stadium followed by ligation at 7 h of the 4th stadium arrested serosa ontogeny and embryonic growth of the parasitoid. These data indicate that embryos of both morphs ofC. floridanumformed a serosa just prior to morphogenesis and that serosa ontogeny required host head factors. Furthermore, host juvenile hormone did not influence serosa ontogeny but stimulated polyploidy of membrane nuclei. © 1992 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402620106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe formation of the amphibian organizer is evidenced by the ability of cells of the dorsal marginal zone (DMZ) to self‐differentiate to form notochord and to induce the formation of other axial structures from neighboring regions of the embryo. We have attempted to determine when these abilities are acquired in the urodele,Ambystoma mexicanum(axolotl), and in the anuran,Xenopus laevis, by removing the mesodermalizing influence of the vegetal hemisphere at different stages of development and culturing the animal hemisphere isolate. This was possible, even at the 32 and 64‐cell stage, through the use of embryos with rare cleavage patterns. Cultured isolates were analyzed for morphological differentiation of mesodermal and neural structures, and for biochemical differentiation of the tissue‐specific enzyme, acetylcholinesterase (AChE). Large amounts of mesodermal and neural structures, and normal expression of AChE were found in isolates made as early as the 32‐cell stage in both species. Only a small increase in the percentage of isolates developing mesoderm was detected when isolations were made at later cleavage or blastula stages. The amount of mesoderm formed did not depend on the stage of isolation. Mesoderm differentiation was usually limited to the notocord and muscle. The isolates rarely formed pronephros, mesothelium, or mesenchyme, derivatives of ventral mesoderm, during normal development. The results indicate that the marginal zone of the cleavage‐stage embryo contains all of the information needed for the formation of the organizer. The formation of dorsal mesoderm does not require subsequent interaction with the cells of the vegetal hemisphere, although the presence of those cells is likely to play a role in normal pattern formation. © 1992 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402620107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractSecondary mesenchyme in sea urchin embryos is released into the blastocoel after primary mesenchyme, and although these cells have been recognized for some time, we lack knowledge about many fundamental aspects of their origin and fate. Here we documented the ontogeny of one of the principal, and least well‐known, types of cells derived from secondary mesenchyme. The blastocoelar cells arise from mesenchyme released from the tip of the archenteron following the initial phase of gastrulation. The cells migrate with their cell bodies suspended in the blastocoel, rather than being apposed to the basal lamina like primary mesenchyme. The cells extend numerous fine filopodia to form a network of cytoplasmic processes around the gut, along the skeletal rods, and within the larval arms. Once the network is formed, the cells maintain their positions, although they actively translocate vesicles and cytoplasm along their filopodia. Cell counts indicate there is an initial recruitment of cells during gastrulation, followed by a more gradual increase in cell number after the larva begins to feed. Lineage studies in which 16‐cell‐stage macromeres were injected with horseradish peroxidase indicate that almost all of the macromere‐derived mesenchyme forms pigment cells and blastocoelar cells. We propose that blastocoelar cells are a distinct subset of secondary mesenchyme that forms fibroblast‐like cells in the blastocoel of sea urchin embryos. © 1992 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402620108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThere are 5 tarsomeres in the normal cockroach leg, but this number is often reduced in regenerated legs. In order to examine this complicated situation, fore‐, mid‐, and hindlegs of German cockroaches were amputated at 11 different tarsal levels and at 18 different times during the last instar. When tarsi were amputated at or proximal to the 3rd tarsomere, 4‐segmented tarsi regenerated. When legs were amputated distal to the 3rd tarsomere, the regenerated tarsi had 5 segments. Three‐segmented tarsi rarely regenerated when legs were amputated proximal to the 3rd tarsomere and in the latter half of the instar period. The lengths of all tarsomeres of regenerated tarsi were measured together with those of unoperated contralateral tarsomeres, and the ratios of the former to the latter were calculated. The ratios ranged from 28 to 138% for the various tarsomeres and levels of amputation. From a comparison of the ratios and morphological observations, it was suggested that the 3rd tarsomere of the normal 5‐segmented tarsus has disappeared in the regenerated 4‐segmented tarsus. Pads and disto‐lateral spines of tarsomeres were observed on unoperated and regenerated tarsi. It was of interest that double spines were often found on the 4‐segmented tarsi, mostly on the 2nd tarsomere, just proximal to the position of the missing 3rd tarsomere. This observation supported the idea that the 3rd tarsomere has not simply disappeared, but has probably fused with the 2nd tarsomere. © 1992

ISSN:0022-104X    

DOI:10.1002/jez.1402620109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractRegulation of blastema cell proliferation during amphibian limb regeneration is poorly understood. One unexplained phenomenon is the relatively low level of active cell cycling in the adult newt blastema compared to that of larval axolotls. In the present study, we used ganglia implantation as a means of “superinnervating” normally innervated adult newt blastemas to test whether blastema cell subpopulations are responsive to nerve augmentation. The effectiveness of implanted ganglia to provide neurotrophic stimulation was demonstrated in denervated blastemas. Blastemas implanted with 2 dorsal root ganglia and simultaneously denervated 14 days after amputation exhibited control levels of cell cycle activity 6 days later, as measured by3H‐thymidine pulse labeling. Denervated blastemas that were sham‐operated or implanted with pituitary glands exhibited cell‐cycle declines similar to those of denervated blastemas without implanted ganglia. Thus, 2 implanted ganglia provide neurotrophic stimulation equivalent to that of the normal nerve supply. Dorsal root ganglia implanted into normally innervated blastemas, which should effectively double neurotrophic activity to the blastema, had no effect on cell‐cycle activity; innervated blastemas implanted with ganglia for 6 days exhibited pulse labeling indices similar to those of normally innervated blastemas. These data indicate that neurotrophic stimulation is not normally limiting in inner‐vated limbs, and that some other factor, whether extrinsic or intrinsic to blastema cells, accounts for the relatively low level of active cell cycling in the adult newt blastema. © 1992 W

ISSN:0022-104X    

DOI:10.1002/jez.1402620110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA highly repeated interspersed sequence (OLR1) was isolated from a genomic DNA library of the Medaka,Oryzias latipes.The OLR1 was about 160 base pairs (bp) in length. As judged from the results of colony hybridization experiments, OLR1 is one of the major repeated DNA sequences in the Medaka genome and is present in every 136 kb on average. Results of Southern and colony‐hybridization analyses indicate that OLR1 is a small interspersed repetitive element (SINE). OLR1‐related sequences were conserved in other three species (O. luzonensis, O. curvinotus, andO. mekongnensis) within the genusOryziasas a repetitive sequence. These results lend support at the DNA level to the hypothesis that these four species form one group in the genusOryzias, as has been suggested from an analysis of their karyotypes (Magtoon and Uwa, '85, Proc. Jpn. Acad., Ser. B,61:157–160). © 1992 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402620111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY