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  • 1
    ISSN: 1432-041X
    Keywords: Key words Ecdysteroid ; Nuclear condensation ; DNA fragmentation ; α-amanitin ; Cycloheximide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Silk gland is a larval specific tissue of lepidopteran insects and begins to degenerate shortly before pupation. Programmed cell death (PCD) of the anterior silk gland of Bombyx mori last instar larvae was studied in vivo and in vitro, focusing on the effects of 20- hydroxyecdysone (20E). The glands began to exhibit signs of PCD in vivo 2 days after gut purge and comp-leted PCD by 48 h. In vitro, 20E prematurely induced PCD, and its completion took 144 h (6 days). An oligo-nucleosomal ladder pattern was observed in DNA extracted at the end of PCD. Caspase 3 inhibitor inhibited attainment of full PCD, but it did not block chromatin condensation as revealed by acridine orange staining. α-Amanitin inhibited the PCD induced by 20E in vitro if added to the culture in the first 8 h. Similarly, cycloheximide and emetine completely blocked PCD when applied in the first 18 h of culture with 20E. These results indicate that 20E-stimulated transcription and protein synthesis for PCD are completed in 8 h and 18 h, respectively. Nevertheless, withdrawal of 20E from the medium at different times showed that 20E must be present in vitro for 42 h to elicit full PCD. Current results indicate that the effects of 20E on the progression of PCD are mediated by two distinct processes – one through nuclear hormone receptors, and the other independent from de novo gene expression.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 18 (1991), S. 13-36 
    ISSN: 0739-4462
    Keywords: isolated abdomen ; Lepidoptera ; pupal-adult development ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: When a pair of prothoracic glands (PGs) were removed from Manduca sexta pupae on the day of pupation, the hemolymph ecdysteroid titer remained at a low level. When a portion of the gland pair was extirpated from pupae after the critical period for prothoracicotropic hormone release, the maximum hemolymph ecdysteroid titer was reduced in proportion to the mass of the PGs removed. These findings clearly showed that the PGs in intact pupae are responsible for the elevated ecdysteroid titer required to elicit adult development on schedule. When brains were removed on the day of pupation, the initiation of adult development was delayed for weeks or months. In contrast, pupae whose PGs were removed on the day of pupation initiated development only 7 days late, indicating the existence of an additional source of pupal ecdysteroids. Further, abdomens of male M. sexta that were isolated on the day of pupation initiated adult development spontaneously within 70 days. The implantation of day 0 pupal brains into these isolated abdomens accelerated the initiation of adult development and elicited synchronous adult development. The hemolymph ecdysteroid titer of those isolated abdomens receiving implants of brains increased within 5 days and reached a maximum level of 1.5 μg/ml. The analysis of hemolymph ecdysteroids by reverse-phase HPLC revealed that ecdysone was the major moiety and that the ecdysteroid composition was similar to that of normal, intact pupae that had just initiated adult development. These results demonstrate that the PGs are not requisite for adult development. An increased hemolymph ecdysteroid titer was also observed in isolated abdomens from which the testes were removed and in abdomens devoid of their digestive tract. Indeed, in the latter case, the ecdysteroid titer attained much higher levels than those observed for abdomens with intact guts. Despite numerous attempts to identity the tissue(s) in the isolated abdomens responsible for the increase in ecdysteroid titer, its identity remains unknown.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 10 (1989), S. 179-197 
    ISSN: 0739-4462
    Keywords: insect molting ; tobacco hornworm ; dehydroecdysone ; ketoecdysteroid reductase ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The prothoracic glands of Manduca sexta synthesize dehydroecdysone, which is rapidly converted to ecdysone through the mediation of a hemolymph enzyme, a 3 β-forming-3-ketosteroid reductase. The hemolymph protein fraction (HPF) containing this enzyme was obtained from diapausing and non-diapausing pupae, isolated abdomens, surgically manipulated pupae, etc., and in all cases had the capacity to affect the conversion of dehydroecdysone to ecdysone. The enzyme is heat labile, is inactivated by trypsin, and has a molecular weight of between 20,000 and 30,000. The data indicate that the conversion of dehydroecdysone to ecdysone exhibits linear kinetics and may be dependent on both the enzyme concentration and the concentration of NADPH at the beginning of the reaction but may be limited by the absolute amount of reducing equivalents after 10 min, under the experimental conditions utilized. The capacity of the enzyme to reduce dehydroecdysone was titered in the hemolymph during the last larval instar and during prepupal and pupal life with maximum capacity exhibited at the beginning of the instar, on day 8 of larval life and at day 1 of pupal life. Even at its lowest point at day 5, 1 ml of hemolymph was able to convert 77 pmol (∼35 ng) dehydroecdysone to ecdysone in 1 min. These results require a new interpretation of the control of molting in the Lepidoptera.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 26 (1994), S. 111-122 
    ISSN: 0739-4462
    Keywords: braconid parasitoid ; polydnavirus ; venom ; ecdysone receptor ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The braconid endoparasitoid, Cotesia (=Apanteles) kariyai physiologically influences its host, Pseudaletia separata, through three factors: polydnavirus, venom, and teratocytes. Inhibiting testis development of the host seems to be one factor that is important for successful development of the parasitoid. CkPV (polydnavirus of Cotesia kariyai) plus venom depressed testis development. Testes from unparasitized day 0 last instar transplanted into isolated abdomens increased in volume after stimulation with 20-hydroxyecdysone (20HE). However, day 0 testis preincubated with CkPV plus venom for 6 h and then transplanted into an isolated abdomen did not respond to 20HE. Southern blot analysis indicated CkPV-DNA hybridized to testes-DNA from parasitized hosts, suggesting the possibility that CkPV is involved in suppression of testes growth. Binding assays using PNA indicated a 2-fold increase in ecdysteroid receptor binding activity during the late stage of parasitism. The increase in receptor activity might be related to the maintenance of a low ecdysteroid titer in parasitized hosts due to a feedback response. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 17 (1991), S. 39-51 
    ISSN: 0739-4462
    Keywords: hemagglutinin ; hemocyte ; ovary ; ecdysteroid ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: To identify the tissues which produce hemolymph lectin in larvae of Bombyx mori, ovary, testis, fat body, and hemocytes from 5th-instar larvae were cultured in vitro and the culture medium was partially purified and assayed for hemagglutinating activity. Among the tissues tested, hemocytes appeared to be a major source of the hemolymph lectins. Ovary produced lectins to about one-tenth of the amount observed for the hemocytes, whereas testis and fat body were not productive. To study the hormonal control of hemolymph lectin production by hemocytes, hemocytes from 4th-instar larvae were cultured in vitro. Hemagglutinating activity in the hemolymph of 4th-instar larvae was immunostainable with the monoclonal antibody raised against 350,000 dalton lectin found in the 5th-instar hemolymph, but their molecular sizes were larger than the 5th-instar hemolymph lectins. When 20-hydroxyecdysone was added into the medium, production of the lectin by the hemocytes was remarkably enhanced, depending upon the hormone concentration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 8 (1988), S. 219-228 
    ISSN: 0739-4462
    Keywords: methoprene ; PTTH ; brain ; prothoracic gland ; ecdysteroid ; larval diapause ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Injection of the juvenile hormone analog (JHA) methoprene into day 3, fifthinstar larvae of Bombyx mori induced developmental arrest. Feeding activity declined, and the larvae remained as larvae for more than 2 weeks, after which they died. After JHA injection, the hemolymph ecdysteroid titer was low, and the prothoracic glands were almost inactive for 7 days. During this period, prothoracic glands were stimulated by prothoracicotropic hormone (PTTH) in vitro, indicating that JHA did not inhibit the competence of the glands to respond to PTTH. When brain-corpora cardiaca-corpora allata complexes were removed from intact fifth-instar larvae on day 4, the prothoracic glands became autonomously active and produced enough ecdysone for pupation. When PTTH injections were given to larvae previously injected with JHA (7 days before), the larvae recovered feeding activity, purged their guts, and pupated. Injections of 20-hydroxyecdysone into larvae that had been injected with JHA 7 days earlier induced larval molting. These results suggest that JHA affects both the brain and the prothoracic gland.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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