Influence of low temperature on the synthesis of some Galleria mellonella proteins.

In developing Galleria mellonella larvae (reared at 30 degrees C) three proteins of 74, 76 and 81/82 kDa were identified. They represent a group of storage proteins (LHP proteins). In Galleria larvae, the development of which is arrested by low temperature (18 degrees C), accumulation of the 74, 76 and 81/82 kDa proteins was detected in the hemolymph. The synthesis of 74 kDa and 76 kDa proteins started after 24 h, and that of about 80 kDa after 96 h following the transfer of larvae from 30 degrees C to 18 degrees C. 20-Hydroxyecdysone inhibited synthesis of the 74 and 76 kDa proteins in larvae exposed to low temperature. The arrest of development of Galleria larvae is associated with the synthesis and accumulation of storage proteins, and ecdysteroids are involved in these processes.

Brain factor from Galleria mellonella (Lepidoptera) stimulating silk gland activity.

Brain extracts from day 1-4 last instar larvae of Galleria mellonella (Lepidoptera) stimulate RNA synthesis in cultured silk glands from day 3 last instar larvae. When the fibroin-synthesizing posterior parts of silk glands were incubated for 3 h in vitro in the presence of brain extract (0.1 brain equivalent), [3H]-uridine incorporation into RNA was stimulated more than twofold. The stimulating effect of brain extract showed a dose response relationship. It is suggested that the heat-resistant and protease-sensitive brain factor is a peptide.

Transcription and polyadenylation processes during early development of quail embryo.

Transcription of tRNA and mRNA occurs in quail as early as during cleavage while rRNA transcription becomes measurable during blastulation. The polyadenylated fraction content is newly synthesized RNA amounting to 6% during cleavage and blastulation decreases to 3% during gastrulation. Up to 3/4 adenylic residues incorporated into RNA during cleavage are accumulated in the polyadenylated molecules mainly in the form of RNAse-resistant tracts.

The synthesis of RNA and silk protein in Galleria mellonella silk glands.

The silk protein synthesis in silk glands of Galleria mellonella is preceded by the increase of total RNA content. The levels of the main RNA classes: 28S and 18S rRNA, tRNA as well as poly(A) + RNA change proportionally to the total RNA pool of glands. The fibroin-like silk protein of molecular weight of about 240 000 is characterized by the high content of four amino acids: glycine, alanine, serine and leucine, which account for more than 70% of amino acid residues. This fibroin-like protein is present in the posterior, middle and anterior parts of silk gland of the last instar larvae.

Double-stranded structures in nuclear and cytoplasmic RNA of rat liver.

Double-stranded segments are found in poly(A)+hnRNA as well as in poly(A)-hnRNA, but in the second case they have partly intermolecular character and may originate from an interaction between primary transcripts and snRNA. Fragments of hnRNA containing double-stranded segments are preferentially removed from the nucleus. In cytoplasmic poly(A)+RNA double-stranded segments longer than 20 base pairs represent about 2%. In cytoplasmic poly(A)-RNA intermolecular double-stranded segments derived from rRNA prevail. Double-stranded fragments from nuclear RNP and free cytoplasmic mRNP exhibit similar affinity to hydroxyapatite but their base compositions are different: low content of adenine and high of guanosine in nuclear in contrast to nearly symmetrical base composition in cytoplasmic fragments.

Simple in vitro system for molecular studies of early avian development in the quail.

1. The development of quail embryos incubated in ovo and cultured in vitro was compared in terms of basic morphological and biochemical criteria. 2. Blastoderm culture in vitro may be a convenient system for investigation of molecular aspects of early development.

Oligo(A) and double-stranded segments in polyadenylated and non-polyadenylated RNA from cytoplasm and nuclei of chick embryo.

Chick embryonic RNA was fractionated by affinity chromatography on oligo(dT)-cellulose and poly(U)-Sepharose into three classes: poly(A)+RNA containing poly(A) segments of 100 and more residues, poly(A)-oligo(A)+RNA containing oligo(A) segments of about 25 residues, and poly(A)-oligo(A)-RNA which bound to neither of the beds used and which contained double-stranded segments of 300 and more base pairs. These three classes of RNA were found in cytoplasmic as well as in heterogeneous nuclear RNA. Double-stranded segments in hnRNA, unlike those in cytoplasmic RNA, were intermolecular in nature; this may explain the occurrence of "giant" molecules in hnRNA.

Precursors of cytoplasmic RNA in avian cell nucleus.

In nucleus of chick embryo four pre-rRNA of molecular weight of 3.43, 2.93, 2.36 and 1.87 X 10(6) were found in addition to the heterogeneous population of "giant" RNA molecules larger than 4.5 X 10(6) daltons, partially polyadenylated, with few methyl groups and numerous double-stranded regions.