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At least 397 records · Page 22Linked to original sources
PubMed1999

Toxic impact of organophosphorus insecticides on acetylcholinesterase activity in the silkworm, Bombyx mori L.

The effect of widely used commercial-grade organophosphorus insecticides, namely, fenitrothion and ethion, on acetylcholinesterase activity and acetylcholine levels in brain, fat body, and silk gland of Bombyx mori on Days 1, 3, and 5 and food intake of the fifth instar were studied. Acetylcholinesterase activity was found to be inhibited, followed by a concomitant increase in acetylcholine levels in the target tissues. These changes suggest an acceleration in energy metabolism of nerve cells, leading to death of the insects. Food consumption during the fifth instar underwent a significant decrease at lethal doses and an insignificant increase at sublethal doses of fenitrothion and ethion. The overall changes observed in acetylcholinestease, acetylcholine, and food intake due to fenitrothion and ethion were, insecticidewise, in the order fenitrothion<ethion; dosewise, in the order sublethal<lethal; and tissuewise, in the order fat body <silk gland <brain. Some characteristic behavioral changes were also observed in silkworms exposed to fenitrothion and ethion.

Acetylcholinesterase↗
PubMed1994

Neurosecretory cells expressing the gene for common precursor for diapause hormone and pheromone biosynthesis-activating neuropeptide in the suboesophageal ganglion of the silkworm, Bombyx mori.

Diapause hormone (DH) is a neurohormone which is secreted from suboesophageal ganglion (SG) and responsible for induction of embryonic diapause in the silkworm, Bombyx mori. DH is generated along with four other functionally different neuropeptides including pheromone biosynthesis-activating neuropeptide from the common polyprotein precursor, DH-PBAN (DHP), which is translated by a single species of mRNA. In this paper, the site of the gene expression was determined by reverse transcription-polymerase chain reaction and in situ hybridization using cDNA probe. The transcript of the DHP gene was found in SG of pupae and pharate adults, but no positive sign was detected in other tissues such as brain, thoracic ganglia, abdominal ganglia, and midgut. In situ hybridization with the cDNA clearly stained 12 cells near the ventral midline of SG which were aggregated into three clusters. The clusters were respectively localized in the mandibular, maximally, and labial neuromere of SG. The similar staining profile was observed in the SG cells at the larval, pupal, and adult stages, indicating that the DHP gene is expressed in the same set of cells throughout the postembryonic development.

Animals↗
PubMed1996

Effects of fenoxycarb on the secretory activity of the prothoracic glands in the fifth instar of the silkworm, Bombyx mori.

Effects of fenoxycarb on the secretory activity of the prothoracic glands (PGs) of the silkworm, Bombyx mori, were investigated. Fenoxycarb inhibited the secretory activity of PGs in vitro throughout the fifth instar. Incubation of PGs in the presence of 1 microgram of fenoxycarb resulted in a approximately 50% inhibition of their secretory activity. This inhibition of fenoxycarb was dose dependent. Stimulation of the PGs by recombinant prothoracicotropic hormone (rPTTH) reached a high activation ratio of 15.9. Simultaneous presence of fenoxycarb and 1 ng rPTTH significantly decreased the stimulatory effect of rPTTH on the PGs, and the activation ratio never exceeded 3.65. Early in the fifth instar, fenoxycarb strongly inhibited the secretory activity of the PGs and induced a developmental arrest as well. After the onset of pupal commitment, its action toward the PG secretory activity was inhibitory. However, fenoxycarb treatment was not able to induce a developmental arrest in intact animals after the pupal commitment although it could do so in head-ligated animals. On the contrary, application of fenoxycarb after the wandering behavior resulted in a significantly increased secretory activity by the PGs of both intact and head-ligated larvae.

Animals↗
PubMed1997

The role of 20-hydroxyecdysone in stimulating DNA synthesis in corpora allata of the silkworm, Bombyx mori.

Temporal changes in DNA synthesis were examined in the corpora allata of the silkworm Bombyx mori during the penultimate larval stadium. 5'-Bromo-2'-deoxyuridine (BrdU) labeling revealed that allatal DNA synthesis rose early in the stadium, peaking at about 2% of corpus allatum (CA) cells 24 hr after ecdysis. This corresponded to a rising phase of the ecdysteroid titer reported previously. DNA synthesis declined to a nearly undetectable level 1 day later. In larvae fed on leaves coated with 20-hydroxyecdysone (20E), the number of BrdU-labeled cells increased continuously after the normal peak and reached about 8% of CA cells at the end of the stadium. However, total count of CA cells from whole-mount monolayers and colchicine treatment indicated that, regardless of DNA content, CA cells did not divide. To determine if the rise in 20E was responsible for the onset of allatal DNA synthesis, we have established an organ culture system to support de novo DNA synthesis in vitro. The number of BrdU-labeled cells increased with increasing 20E concentration between 0.1 and 0.5 microg ml-1 in the medium, corresponding well to the rising 20E titer in the hemolymph. The level of DNA synthesis in culture was further elevated when 20% hemolymph was added together with 20E, suggesting that other direct stimulatory factors for allatal DNA synthesis may also exist in the hemolymph.

Animals↗
PubMed1999

Effect of octopamine on the activity of juvenile-hormone esterase in the silkworm Bombyx mori and the red flour beetle Tribolium freemani.

This study focuses on the effect of octopamine (OA) on metamorphosis of the silkworm Bombyx mori and the red flour beetle Tribolium freemani Hinton. Titers of OA and juvenile-hormone esterase (JHE) were measured at various larval and pupal stadia of both insects. Effects of OA, OA agonists, and antagonists on metamorphosis and JHE activity were also examined. At day 2, peaks of OA and JHE activity were observed in third instars, and at day 3, a sharp peak of OA was observed, followed by a large peak of JHE activity at day 4 in last instars of B. mori. However, no peaks of OA and JHE activity were observed in fourth instars. A high titer of OA appeared at days 2-4, followed by a peak of JHE activity at day 7 and the second OA peak at day 9 after the start of assay of T. freemani. At pupation, a small peak of OA and the highest activity of JHE were observed. The effects of OA on JHE activity were examined in vitro, because the relationship could be responsible for triggering pupation in B. mori and T. freemani larvae. Exogeneous OA (0.1-10 mM) stimulated the JHE activity of final instars (day 2) of B. mori in vitro. Similarly, the presence of OA (10 mM) activated the JHE activity of newly ecdysed T. freemani pupae in vitro. OA antagonists chlorpromazine and gramine delayed the start of spinning and reduced the JHE activity of B. mori, when applied in diet at 10-100 ppm. Some OA agonists stimulated the pupation and JHE activity of T. freemani larvae reared under crowded conditions, when topically applied. Thus, OA may contribute to activation of the events preparatory to a pupal molt, i.e., the secretion of OA increases JHE activity followed by stimulation of pupation.

Animals↗
PubMed2000

Glucose stimulates the release of bombyxin, an insulin-related peptide of the silkworm Bombyx mori.

The effects of starvation and feeding on the release of bombyxin, a peptide of insulin superfamily in insects, from the larval brain of the silkworm Bombyx mori were investigated. Following starvation, the bombyxin titer in the hemolymph of larvae decreased, whereas its content in the brain increased. On the other hand, refeeding of the starved larvae resulted in an increase in the hemolymph bombyxin titer and a rapid decrease in the hormone level in the brain. These results indicate that the release of bombyxin from the brain is suppressed by starvation and stimulated by feeding. The hemolymph glucose titer also changed sharply upon starvation and refeeding, and a close relationship was observed between the changes in glucose concentrations and bombyxin titers in the hemolymph. The injection of glucose into starved larvae could mimic the effect of refeeding on the release of bombyxin, suggesting that glucose serves as the signal for the "fed" state of the animal. It is likely that glucose is a common nutritional signal for inducing the release of mammalian and insect insulins.

Animals↗
PubMed2001

Induction of DNA synthesis by 20-hydroxyecdysone in the prothoracic gland cells of the silkworm Bombyx mori during the last larval instar.

DNA synthesis in the prothoracic gland cells of the silkworm Bombyx mori was studied immunocytochemically after in vivo labeling with 5-bromo-2'-deoxyuridine (BrdU), and its developmental changes during the last larval instar were examined. During the first 3 days of the last larval instar, no DNA-synthesizing cells were detected. On day 4, the number of DNA-synthesizing cells increased and peaked on day 7. When larvae were fed 20-hydroxyecdysone-supplemented mulberry leaves throughout the last larval instar, the number of DNA-synthesizing cells dramatically increased 2 days after 20-hydroxyecdysone treatment and reached a high level on day 5. The mechanism by which 20-hydroxyecdysone treatment induces DNA synthesis of prothoracic gland cells was further examined by using continuous in vitro BrdU labeling for a 2-day incubation. We conclude that 20-hydroxyecdysone may exert its growth-promoting action indirectly.

Animals↗
PubMed1995

Purification and partial characterization of an induced antibacterial protein in the silkworm, Bombyx mori.

Injection of live Escherichia coli into larvae of the silkworm, Bombyx mori, induces antibacterial activity in the hemolymph. The major induced antibacterial activity was purified in two steps by CM-Sephadex C-50 and Sephadex G-100 column chromatography. After trypsin treatment, the purified antibacterial protein lost its activity and the antibacterial activity was found to be partially heat labile. The purified protein was a single polypeptide chain of molecular weight 16 kDa. The 20 N-terminal amino acid sequence of the protein was determined and this sequence showed homology with the N-terminal amino acid sequence of lysozymes reported in other species. The purified protein was found to have comparable antibacterial activity against both E. coli and Micrococcus luteus. The purification of antibacterial protein and the antibacterial properties of the purified protein are discussed.

Amino Acid Sequence↗
PubMed1995

Developmental regulation of a silkworm gene encoding multiple GATA-type transcription factors by alternative splicing.

Gene BmGATA beta of the silkworm Bombyx mori was previously shown to encode factor BCFI, which regulates the expression of a class of chorion genes expressed during the late stages of choriogenesis. We now show that the expression of the BmGATA beta gene is spatially and temporally regulated by alternative splicing that generates two major (BmGATA beta 1 and BmGATA beta 2) and one minor (BmGATA beta 3) mRNA isoforms of non-identical tissue distribution. The three isoforms differ in the organization of the DNA-binding domains of the corresponding polypeptides. While all three isoforms are expressed in ovarian follicular cells and in testes, only one of them, BmGATA beta 1, is gonad-specific. BmGATA beta 2 is expressed in a variety of other larval and pupal tissues, while BmGATA beta 3 is detected in some pupal but none of the larval tissues. Analysis of RNA isolated from follicular cells of developing ovarian follicles has shown that the onset of ovarian transcription for all three mRNA isoforms occurs during late vitellogenesis, and that the level of accumulated mRNA declines significantly at the onset of choriogenesis. Coincident with the onset of late chorion gene expression, we have observed a significant change in the preference of splice site selection in favour of the one that results in the generation of BmGATA beta 1 mRNA. The transcriptional activation of the BmGATA beta gene in follicular cells during late vitellogenesis correlates with the previously demonstrated initial accumulation of factor BCFI in the cytoplasm of follicular cells and its appearance in follicular cell nuclei only during the late stages of choriogenesis. The relationship between factor BCFI and the different polypeptides encoded by the three BmGATA beta mRNA isoforms is discussed.

Alternative Splicing↗
PubMed1996

Expression of human growth hormone in silkworm larvae through recombinant Bombyx mori nuclear polyhedrosis virus.

We have generated a recombinant Bombyx mori nuclear polyhedrosis virus, vBmhGH, harboring the full length human growth hormone gene (2.4-kb genomic DNA, with four introns and the signal peptide sequences) under the control of the polyhedrin promoter. BmN cells in culture infected with the recombinant virus showed the presence of RNA corresponding to the authentic growth hormone mRNA as well as its incompletely processed precusor. Electrophoretic analysis and immunoprecipitation of proteins of recombinant virus-infected BmN cells revealed the presence of the growth hormone protein. Infection of silkworm larvae with vBmhGH led to the synthesis and efficient secretion of the protein into hemolymph. The recombinant human growth hormone was biologically active in a radioreceptor competition binding assay. The secreted protein was isolated and purified to homogeneity by a single step immunoaffinity chromatography, to a specific activity of 2.4 x 10(4) U/mg. The recombinant hGH retained the immunological and biological properties of the native peptide. We conclude that BmNPV vectors can be used successfully for expressing chromosomal genes harboring multiple introns.

Animals↗
PubMed1992

Immunocytochemical localization of beta-1,3-glucan recognition protein in the silkworm, Bombyx mori.

A monospecific antibody against beta-1,3-glucan recognition protein (a 62 kDa protein) of the larval silkworm prophenoloxidase activating system was used to study the localization of the protein. Among tissues from 5th instar larvae, only hemocytes and plasma were shown to contain a 62 kDa polypeptide immunoreactive with the antibody. Ultra-thin sections of the hemocytes were stained by an indirect immunogold staining method. Labelling occurred in the granules and cytoplasm of granulocytes and in the spherules and cytoplasm of spherulocytes. It was most conspicuous in granules of granulocytes and uniformly labelled spherules of spherulocyte, whereas no labelling was evident in prohemocytes, plasmatocytes and oenocytoids. The results are discussed in relation to the mode of recognition of fungi as non-self in insect hemocoel.

Animals↗
PubMed1994

A defective non-LTR retrotransposon is dispersed throughout the genome of the silkworm, Bombyx mori.

The presence of long repetitive sequences is demonstrated in the genome of the silkworm, Bombyx mori. Members of this BMC1 family reveal several features typical of the L1 (long interspersed sequence one) family of mammals, except for species specific elements. The number of BMC1 elements is estimated to be approximately 3500 per haploid genome. Elements containing the full length unit of 5.1 kb are dispersed throughout the genome and their restriction sites are conserved, although most members are preferentially truncated to varying extents at their 5' ends. DNA sequencing indicates that this element contains six tandem repeats of 15 bp CpG-rich sequence in the 5' proximal region. It terminates with a 3' oligo(A) stretch, and is flanked at both ends by a 7-10 bp target sequence duplication. In addition, there is significant evidence for amino acid sequence homology with reverse transcriptase domains of other L1 families, especially F, Doc and Jockey of Drosophila melanogaster. No large open reading frame is present. The BMC1 element is suggested to be dispersed in the genome by a transposition mechanism involving RNA intermediates.

Amino Acid Sequence↗
PubMed1992

Synthesis of bombyxin-IV, an insulin superfamily peptide from the silkworm, Bombyx mori, by stepwise and selective formation of three disulfide bridges.

We report the synthesis of bombyxin-IV, a disulfide-linked, heterodimeric, insulin superfamily peptide from the silkworm, Bombyx mori. The two chains (A- and B-chains) were synthesized separately by the solid-phase method using fluoren-9-ylmethoxycarbonyl (Fmoc) group as a protecting group for alpha-amino group. Three disulfide bonds were bridged step by step (A6-A11, A20-B22, and A7-B10) in a good yield. Synthetic bombyxin-IV was identical with natural one with regard to the retention time on a reversed-phase column and the molecular weight measured by mass spectrometry. Circular dichroism (CD) spectrum of the synthetic bombyxin-IV was very similar to that of the natural one. The specific activity of synthetic bombyxin-IV is equal to that of natural one (0.1 ng/Samia unit). These results suggest that the synthetic bombyxin-IV has the tertiary structure identical with the natural peptide. Our method developed for synthesis of bombyxin-IV would be generally applicable to the synthesis of insulin-like heterodimeric peptides.

Amino Acid Sequence↗
PubMed1992

Structural analysis on the single-stranded genomic DNAs of the virus newly isolated from silkworm: the DNA molecules share a common terminal sequence.

Recently, a parvo-like virus was newly isolated from silkworm larvae and the two viral DNAs (VD1 and VD2) with different electro-mobilities were identified. We cloned the viral DNAs in a plasmid pUC119 and demonstrated that these two DNAs were not a bimorphic molecules though they shared a common terminal sequence of 53 nucleotides. In addition, the sequence at the 5' terminus of each strand of the viral DNA was located in inverted form at its 3' terminus. On the other hand, the nucleotide sequences of VD1 and VD2 were different from that of the Bombyx densovirus (Ina isolate) DNA.

Animals↗
PubMed1995

Analysis of the genetic information of a DNA segment of a new virus from silkworm.

In 1983, a parvo-like virus (Yamanashi isolate) was newly isolated from silkworm. However, unlike parvovirus, two DNA molecules (VD1 and 2) were always extracted from purified virions. To investigate the structure and organization of the virus genomes, we determined the complete nucleotide sequence of VD2. The sequence consisted of 6031 nucleotides (nts) and contained a large open reading frame (ORF1) with 3513 nts. A smaller open reading frame (ORF2) with 702 nts was found in the complementary sequence. Computer analysis revealed that both ORFs did not code for the major structural proteins (VP1, 2, 3, and 4). These results suggest that VD2 has not enough information to produce progeny virions by itself. Further, the structural importance of the terminal sequence (CTS) common to both VD1 and VD2 was also predicted by a computer analysis.

Amino Acid Sequence↗
PubMed1992

Neuropeptides of the silkworm, Bombyx mori.

Six neuropeptides of the silkworm, Bombyx mori, have been isolated and chemically characterized during the past 10 years. They are bombyxin, prothoracicotropic hormone, pheromone-biosynthesis-activating neuropeptide/melanization-and-reddish-coloration hormone, diapause hormone, eclosion hormone, and adipokinetic hormone. Recent progress in research on these neuropeptides is described.

Amino Acid Sequence↗
PubMed2004

Effects of hypervitaminosis of vitamin B3 on silkworm biology.

A high-dose of vitamin B(3) in silkworm diet interrupts larval feeding and normal growth. High mortality of larvae occurs during molting and they cannot complete this process normally. Also the larvae exhibit nicotinamide hypervitaminosis symptoms such as immobility, dyspepsia, darkening of the skin, inability to excrete normally, exerting brownish fluid from anus and swelling of rectal muscles. Maximum larval weights in 1, 2 and 3 g/l treatments were 2.9, 1.6 and 1.2 g respectively, while maximum larval weight in the control was 5.6 g. Larval stage compared to control had increased 18, 26 and 31 days respectively. The concentration increase of uric acid in haemolymph demonstrates the hyperuricemia, while other measured biochemical compounds show significant decrease; sodium and potassium did not change significantly.

Animals↗