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Summary The protothyroid region in the endostyles of four species of tunicates was examined by means of autoradiography and cytochemistry, at both the light and electronmicroscopic levels. To reveal the primary binding site for iodine, autoradiography was carried out on endostylar tissue from animals that had been incubated with high activity 125I- over a short period of time. The specific iodine binding enzyme, a peroxidase, was traced by its reaction with DAB. In accordance with previous findings, the iodinebinding cells proved to be the same as those containing the peroxidase. There were also strong indications of a secondary uptake of iodinated compounds and subsequent release into the body fluid. Together with the ultrastructural features, the data provided strong evidence indicating that these cells constitute a protothyroid region, which partly functions as an endocrine organ, possibly homologous with the vertebrate thyroid gland. Since the number of zones varied between the species, the numeration of the protothyroid region also varied. However, in all the examined endostyles, the protothyroid region was seen to be situated dorsolaterally to the glandular regions of the endostyle concerned with food capture. 相似文献
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Dan -E. Nilsson Kurt Hamdorf Gunnar Höglund 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(2):217-226
Summary In the superposition eyes of the sphingid moth Deilephila and the neuropteran Ascalaphus, adjustment to different intensities is subserved by longitudinal migrations of screening pigment in specialized pigment cells. Using ophthalmoscopic techniques we have localized the light-sensitive trigger that controls pigment position.In both species, local illumination of a small spot anywhere within the eye glow of a dark-adapted eye evokes local light adaptation in the ommatidia whose facets receive the light. Details of the response pattern demonstrate that a distal light-sensitive trigger is located axially in the ommatidium, just beneath the crystalline cone, and extends with less sensitivity deep into the clear zone. The distal trigger in Deilephila was shown to be predominantly UV sensitive, and a UV-absorbing structure, presumably the distal trigger, was observed near the proximal tip of the crystalline cone.In Ascalaphus we also found another trigger located more proximally, which causes local pigment reaction in the ommatidia whose rhabdoms are illuminated (the centre of the eye glow). The light-sensitive trigger for this response appears to be the rhabdom itself. 相似文献
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Mutants with continuous microcycle conidiation in the filamentous fungus Fusarium solani f. sp. pisi
H. Gunnar Kølmark 《Molecular & general genetics : MGG》1984,198(1):12-18
Summary A method of repeated mutation induction and subsequent selection was used to obtain mutants with microcycle conidiation, mc, in Fusarium solani f. sp. pisi. Wild-type, wt, Fusarium has a filamentous (hyphal) growth in a three-stage, conidium—hypha—conidiophore (phialid) vegetative life cycle. The first major mutation induced (by means of the mutagen MNNG) changed the wild-type strain 1–3- from producing both macro- and microconidia to the mutant strain 19-P2-, producing only microconidia but preserving the three-stage life cycle. When strain 19-P2- was exposed to a similar mutagenic treatment mutants without the hyphal stage were obtained. In these mutants the microconidia germinate to form phialids directly, which in turn produce new conidia, thus accomplishing the life cycle as a two-stage, conidium-conidiophore, microcycle. The mc mutants were stabilized after reisolation through back-crossing to the wt of complementary mating type. Mc growth of the mutants is continuous under stable conditions, proceeding uninterrupted to the stationary stage in liquid as well as on solid medium. Mc colonies on solid medium are small and soft, well suited to replication by means of velvet or paper. Large numbers of mature, synchronized conidia are easily obtained from stationary-stage submerged cultures. Sequential mutations are of interest for studies of morphogenetic evolution. The ahyphal mutants make this group of eukaryotes well suited for genetic engineering and biotechnology. 相似文献
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Gunnar von Heijne 《Journal of molecular biology》1984,173(2):243-251
The specificity of the signal sequence cleavage reaction has been postulated to reside in a signal peptidase active site that can bind only to particular (i, i + 2) pairs of amino acids. In this paper, we present further patterns of non-random amino acid utilization in a region around in vivo cleavage sites, and show that they can be interpreted in terms of selection acting to reduce the number of potential competing sites in the vicinity of the correct one. 相似文献
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Gunnar Hoy 《Journal of Ornithology》1969,110(3):314-317
Zusammenfassung In dem großen Hochwaldgebiet, das sich am Fuße der Anden von Jujui bis Orán erstreckt, erbeutete der Verf. am 3. Januar 1969 ein junges Weibchen vonButeo albigula, erster Nach-weis dieser Art aus Argentinien. In dem gleichen Waldkomplex und in annähernd gleicher Höhenlage ist auchButeo brachyurus gesammelt worden. Daraus wird gefolgert, daß diese beiden Bussarde nicht subspezifisch verschieden sind (wieRand urteilte), sondern als zwei Spezies zu gelten haben.
Sinopsis Una hoven hembra deButeo albigula Philippi fué cazada en Orán del 3 de Energo 1969 por el autor. La especie es nueva para la fauna Argentina. Como la posición sistematica de esta forma era dudosa, el hallazgo es interesante, porque en la misma región ya es conocidaButeo brachyurus Vieillot. La región de las selvas del Noroeste, al pie de los Andes, incluye áreas grandes de bosque humedos, con alturas variables, desde la frontera con Bolivia hasta el sudeste de la provincia de Jujuy. Como ahora las dos formas,albigula y brachyurus son habitantes de la misma región, parecería que son especies y no subespecies.相似文献
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Gunnar D. Bloom 《The Journal of cell biology》1967,35(1):266-268