Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SILKWORMS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed1992

Isolation of cDNA clones coding for humoral lectin of silkworm, Bombyx mori, larvae.

In the hemolymph of the silkworm, Bombyx mori, lectin with hemagglutinating activity against sheep red blood cells increases at larval-larval ecdysis and at spinning stage (Suzuki and Natori, 1983) and is induced by infection with cytoplasmic polyhedrosis virus. A Bombyx lectin polypeptide with molecular weight approx 280K is responsible for hemagglutinating activity, since antiserum raised against this polypeptide inhibited hemagglutinating activity. The site of synthesis of Bombyx lectin was determined by primary tissue cultures of fat body and hemocytes. A hemagglutinating activity assay demonstrated that hemocyte is responsible for the release of hemagglutinin into the culture medium. Isolation of cDNA clones coding for Bombyx lectin was carried out on the cDNA library prepared in an expression vector lambda gt11 starting with poly(A)+ RNA from spinning larval hemocytes. As a result of immunoscreening, several positive clones were obtained, and the cDNA clones were characterized.

Animals↗
PubMed1991

Structures and organization of major plasma protein genes of the silkworm Bombyx mori.

In the silkworm, Bombyx mori, a group of structurally related proteins, termed 30K proteins, accumulate in the hemolymph of the last instar larvae. We have isolated and characterized three genes, each of which encodes a distinct 30K protein component. Each 30K protein gene is composed of a short first exon and a protein-coding second exon interspersed by a single intron. The transcription initiation site of the 30K protein mRNA was identified at the nucleotide level. A typical TATA box exists some 30 base-pairs upstream from the transcription initiation site. The 5'-flanking region of each gene also contains octamer-like sequences. Restriction mapping analyses revealed that the cloned 46 x 10(3) base-pair region of the chromosomal DNA bears three 30K protein genes. Several copies of highly reiterated retrotransposon-like sequences are present around the 30K protein genes. S1 nuclease protection analysis provided evidence that the biosynthesis of 30K protein is regulated in a stage-specific manner at the transcriptional level in the fat body.

Amino Acid Sequence↗
PubMed1981

Structural requirement of sterol side chain for the silkworm growth and development.

Several cholesterol analogs with modifications in the side chain were added to the artificial diet of the silkworm, and their effects on insect growth and development were determined. It was found that slight deviations of the cholesterol's side chain induced pronounced growth-retarding effects, suggesting an important functional role of the isooctane side chain of cholesterol.

Animals↗
PubMed1982

Structural requirement of sterol nucleus for the silkworm growth and development.

Several cholesterol analogs structurally modified in nuclear substitutions were tested for sustaining the growth of the silkworm Bombyx mori. 5 alpha-Cholest-7-en-3 beta-o1, 5,7-cholestadien-3 beta-o1 and cholesteryl acetate can replace cholesterol as sterol source for B. mori. Considerably good growth was also obtained with 5 alpha-cholest-14-en-3 beta-o1 and 5 alpha-cholesta-6,8(14)-dien-3 beta-o1. Other sterols tested were either partially effective or ineffective as nutrients.

Animals↗
PubMed1988

Regulation of gene expression in prediapausing embryos of the silkworm, Bombyx mori: pattern of protein synthesis.

Specific qualitative and quantitative changes in protein synthesis occur from the fertilization to the onset of diapause in the silkworm. We have used two-dimensional gel electrophoresis to analyse the patterns of proteins synthesized in prediapausing eggs of Bombyx. This analysis has been carried out with in vivo labelled polypeptides and with proteins synthesized in vitro by RNA isolated at different stages. The oocyte contains an abundant supply of diverse mRNA which are translatable in vitro. A set of proteins with molecular weight range of 68,000 to 74,000 and isoelectric points of 5.85-5.95 (hereafter referred to as No. 30) is specific of the germ-anlage stage. Transcripts encoding the No. 30 proteins are not detectable in oocytes, and inhibition of transcription by actinomycin D indicates that No. 30 mRNA are synthesized de novo. Treating eggs at the germ-anlage stage with 4 N HCl at 46 degrees C prevents diapause and is accompanied by overproduction of No. 30 protein. The induction of No. 30 synthesis is also the main event of the heat shock response. The implications of these findings in relation to early embryonic development and prevention of diapause are discussed.

Animals↗
PubMed1979

The primary transcription product of a silkworm alanine tRNA gene: identification of in vitro sites of initiation, termination and processing.

A 13.5 Kb fragment of Bombyx mori DNA containing a single tRNA2Ala gene has been cloned, and transcribed in vitro with Xenopus germinal vesicle extracts. The primary transcription product of the tRNA2Ala gene has been isolated and shown to possess an unprocessed triphosphorylated 5' terminus. Products resulting from processing of this transcript have also been isolated and characterized. Complete nucleotide sequence analysis of this cloned alanine tRNA gene and its primary transcript shows that transcription initiates three nucleotides away from the mature tRNA2Ala 5' end and terminates in a U cluster 22 nucleotides beyond the last encoded 3' nucleotide of the mature species. Sequence determination of the products of in vitro maturation shows that in contrast to the tRNA processing mechanism characteristic of procaryotes, the extra 3'-nucleotides in this silkworm tRNA precursor are removed by a single endonucleolytic cleavage.

Alanine↗
PubMedDate not supplied

Parallel induction of cecropin and lysozyme in larvae of the silkworm, Bombyx mori.

Lysozyme activity in the hemolymph of Bombyx mori increased in parallel with cecropin activity after injection of the larvae with soluble peptidoglycan or UV-killed bacteria. The lysozyme and cecropin A genes were expressed in parallel in the fat body after injection of peptidoglycan as detected by northern blot hybridization. The elicitor specificity for lysozyme induction was identical to that for cecropin, suggesting a common mechanism for recognition of bacteria and following signal transduction introducing to the simultaneous synthesis of cecropin and lysozyme. Bacterial cells killed by UV-irradiation were also effective as elicitor when added to the fat body culture, suggesting that phagocytosis of bacteria by hemocytes may not be an essential process for the induction of antibacterial protein synthesis in the silkworm.

Animals↗
PubMed1992

Isolation and nucleotide sequence of cecropin B cDNA clones from the silkworm, Bombyx mori.

Two cDNA clones encoding cecropin B, an antibacterial protein, were isolated from a fat body cDNA library of the silkworm, Bombyx mori. Amino acid sequences of these clones, deduced from nucleotide sequences, were identical, including signal peptide regions. However, the nucleotide sequences were different at 30 positions. Deduced amino acid sequences of Bombyx mori cecropin B showed higher homology with cecropins from Lepidoptera than with those from Diptera.

Amino Acid Sequence↗
PubMed1993

Purification, cDNA cloning and northern blot analysis of trehalase of pupal midgut of the silkworm, Bombyx mori.

Trehalase (alpha-glucoside-1-glucohydrolase, EC 3.2.1.28) was purified from silkworm pupal midgut to homogeneity by DEAE-Sepharose CL-6B and hydroxyapatite chromatography, and native gel electrophoresis. The enzyme had a molecular mass of 70 kDa. The N-terminal amino-acid sequence of the intact trehalase and its three fragments by V8 proteinase digestion was determined. Based on the amino-acid sequence, degenerate oligonucleotides were synthesized and used as primers in a polymerase chain reaction (PCR). Using a 0.8 kb PCR product as a hybridization probe, trehalase clones were isolated from the pupal midgut cDNA library. Sequence analysis revealed that the isolated trehalase cDNA contains 3103 nucleotides and comprises 579 amino acids, including a cleavable signal sequence and five potential N-glycosylation sites. Northern blot analysis clearly showed a 3.0 kb transcript in midgut, and Malpighian tubule, but not in fat body, silk gland, ovary, trachea, brain and suboesophageal ganglion.

Amino Acid Sequence↗
PubMed1994

Structure and developmental expression of a larval cuticle protein gene of the silkworm, Bombyx mori.

Structure and expression of the gene for a larval cuticle protein of the silkworm, Bombyx mori were studied. A major cuticle protein, termed 'LCP30' was purified from the urea extract of integuments of the fifth (final) instar larvae. Immunoblot analysis by use of the anti-LCP30 antibody revealed that LCP30 begins to accumulate in larvae as early as 10 h after hatch and is present throughout the larval stages. The LCP30 epitope is also detectable in the adult abdominal integument but is absent from pupal integument and adult wing. Screening of an epidermal cDNA expression library with the antibody probe yielded a cDNA clone for LCP30. Primary structure deduced from the cDNA sequence showed that LCP30 bears an arginine-glycine-aspartate (RGD) sequence. The region around this domain exhibits striking similarity with the amino acid sequences found in vertebrate collagens. The genomic DNA clone coding for LCP30 was isolated by screening a B. mori gene library with the LCP30 cDNA probe. The gene consists of five exons interspersed by four introns spanning over 2.7 kb region of chromosomal DNA. The LCP30 mRNA is detectable at high levels at larval intermolt stages, gradually declines after the fourth molt and totally disappears at mid-fifth larval instar, indicating that the expression of LCP30 gene is regulated in a stage-specific fashion in the epidermal cells. Topical application of a juvenile hormone analogue (methoprene) to the fifth instar larvae followed by RNA blot and S1 nuclease mapping analyses of the epidermal RNA proved that juvenile hormone activates transcription of the LCP30 gene.

Amino Acid Sequence↗
PubMedDate not supplied

Synthesis of bombyxin-IV, an insulin-like heterodimeric peptide from the silkworm, Bombyx mori.

Bombyxin-IV, a molecular species of bombyxin, which is a member of insulin-like heterodimeric peptides of the silkworm Bombyx mori with prothoracicotropic hormone activity, was synthesized. The A- and B-chains of bombyxin-IV containing four and two Cys residues, respectively, were first synthesized separately by solid phase chemistry using Boc protocol. Then they were coupled by stepwise removal of two different protecting groups at the cysteinyl thiols for semiselective formation of disulfide bridges to give bombyxin-IV in 8% yield. The synthetic bombyxin-IV was shown to have chromatographic and biological properties identical with those of natural bombyxin-IV.

Amino Acid Sequence↗
PubMed1994

The core and complementary sequence responsible for biological activity of the diapause hormone of the silkworm, Bombyx mori.

To evaluate the structure-function relationship of the diapause hormone of the silkworm, Bombyx mori, the entire molecule and selected fragment and deleted analogues were chemically synthesized to compare their biological activity. The C-terminal pentapeptide amide was the shortest fragment that elicited 11% diapause eggs at maximum, indicating that this sequence is the core-active structure required for a biological response. The full biological response of about 70% diapause eggs was expressed by the C-terminal hexapeptide amide. However, an ED50 value of this peptide amide was 1000-fold higher than that of the parent molecule. The serial elongation of peptide chain lengths toward the N-terminus brought about the sudden decrease in ED50 values at two positions between Arg9-Gly10 and Thr1-Asp2. The deletion of duplicated sequence(s) located in the middle part of the molecule or the truncation of N-terminal region of the parent molecule increased ED50 values but had no effects on response. Thus, N-terminal region and duplicated sequences act as the complementary structures for full potency of diapause hormone.

Amino Acid Sequence↗
PubMed1984

Uptake and metabolism of [3H]ecdysone in cultured ovaries of the silkworm, Bombyx mori.

Uptake of ecdysone by ovaries of the silkworm, Bombyx mori, was studied by organ culture. [3H]Ecdysone was transported almost linearly into the ovary for up to 3 h of the incubation. The uptake was proportional to the concentration of the labeled ecdysone, unsaturably, at concentrations ranging up to 10(-6) M. Ecdysone which had been transported into the ovary could usually be removed when the ovary was re-transferred to the ecdysone-free medium. Analysis of the transported compounds by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) revealed the marked conversion of ecdysone into 20-hydroxyecdysone, unknown metabolites and conjugated forms. Physiological significance of the metabolic activity of the ovary is discussed with respect to the accumulation of ecdysteroids in the ovary.

Animals↗
PubMed1990

Characterization of a basic polypeptide-activated protein kinase in the eggs of the silkworm, Bombyx mori.

A basic polypeptide-activated protein kinase (designated BA-kinase), which requires Mn2+ rather than Mg2+ for its activity, has been highly purified from a 1.5 M KCl extract of fertilized and unfertilized eggs of the silkworm, Bombyx mori. It was found that (i) the molecular weight of the purified protein kinase was approx. 260,000; (ii) the kinase phosphorylated vitellin, protamine and casein in a cAMP-, cGMP- and Ca2(+)-independent manner; (iii) the kinase phosphorylated only threonine residues when casein was used as a phosphate acceptor; (iv) protein phosphorylation by the kinase was remarkably stimulated by basic polypeptides, such as histone, polyArg and polyLys; and (v) the purified kinase had an affinity with DNA, but not with RNAs. Moreover, the observations that (a) the BA-kinase activity and phosphorylation of polypeptides by the kinase in the 1.5 M KCl egg extract greatly increased after fertilization, and (b) polypeptides, from this extract, of 16.5-21 kDa, which were highly phosphorylated by the kinase but not by A- or G-kinases, appeared within 4 h after fertilization, suggest that a basic polypeptide activated protein kinase (BA-kinase) may play an important role in the progression of embryogenesis through specific phosphorylation of yolk proteins by the kinase, in the presence of nucleic basic proteins.

Animals↗
PubMed1988

Small RNAs of the silkworm, Bombyx mori as revealed by in vitro capping and in vitro transcription.

1. We characterized several small RNAs in various tissues and strains of the silkworm, Bombyx mori by the in vitro capping and in vitro transcription. 2. Three subspecies of 7SL RNA, which is believed to be involved in protein secretion, were detected in the commercial strains. Structural differences among the three molecules were due to the nucleotide substitution at two positions or more. 3. A very AU-rich RNA, which is about 500 bases long, was always present in any tissue of Bombyx mori while 55 base RNA was only observed in a substantial amount in the fat body and culture cells. 4. These small RNAs were also observed among the in vitro transcripts of total Bombyx DNA in the cell-free extracts from the silkgland and fat body.

Animals↗
PubMed1988

Effect of diapause hormone on cyclic nucleotide metabolism in developing ovaries of the silkworm, Bombyx mori.

1. The content of cyclic AMP and cyclic GMP in ovaries of the silkworm, Bombyx mori, changed differently depending on development. 2. The extirpation of suboesophageal ganglion caused cyclic AMP to decrease and cyclic GMP to increase at different developmental stages. 3. The reversed changes in the cyclic nucleotides were brought about by implantation of the ganglion or by injection of the diapause hormone preparation. 4. No change in both cyclic nucleotides was induced in ovaries during the first 24 hr after an injection of the hormone, but the clear effects appeared after a lag phase of a few days.

Animals↗
PubMed1989

Comparison of the property of a novel isozyme E (formerly null mutant, O) with other isozymes of hemolymph acid phosphatase of the silkworm.

1. A novel acid phosphatase isozyme E (formerly null mutant 0) was partially purified by ammonium sulfate fractionation, DEAE-Sephacel and Sephacryl S-200 column chromatography, and its properties were compared with those of other isozymes of the silkworm hemolymph. 2. The isozyme E was extremely heat labile and showed lower pH-stability than those of others. 3. Three isozymes hydrolyzed p-nitrophenyl phosphate, alpha-naphthyl phosphate, alpha-naphthyl phosphate and glucose-1-phosphate strongly. The isozyme E showed about 50% hydrolyzing activity for alpha-naphthyl phosphate as compared to those of A and B. 4. Activities of three isozymes were inhibited by tartaric acid, sodium fluoride, ammonium molybdate and potassium diphosphate. Inhibitory effects of Cu(2+) and HG(2+) were most remarkable against E isozyme.

Acid Phosphatase↗
PubMed1990

Isolation and structure of cecropins, inducible antibacterial peptides, from the silkworm, Bombyx mori.

1. Cecropins, inducible antibacterial peptides, were purified by simple two step chromatography from immunized larval hemolymph of the silkworm, Bombyx mori. 2. The cecropins were further separated into four major and two minor forms by reverse-phase HPLC. 3. The four major cecropins were sequenced and divided into two types, A and B, whose structures were quite similar to cecropins A and B of Hyalophora cecropia. 4. Three of them contained an unusual amino acid, delta-hydroxylysine. 5. No remarkable difference in antibacterial activity against E. coli was detected among these cecropins.

Amino Acid Sequence↗