Nasr Marei

Protein synthesis by ribosomes from fertilized and unfertilized eggs of houseflies, Musca domestica

Abstract The ribosomes from unfertilized and fertilized housefly eggs have been isolated and their ability to initiate protein synthesis in a cell-free system has been investigated. There is a greater proportion of polymeric forms in the ribosomes from fertilized eggs, and these have a greater capacity to initiate protein synthesis.

DNA-RNA hybrids from ovaries of normal and sterilized Musca domestica

Abstract DNA and C14-labelled RNA were isolated from normal and thiotepa-sterilized ovaries of houseflies (Musca domestica). The two forms of nucleic acid were obtained during different stages of oogenesis. RNA-DNA hybrids were prepared by hybridization of RNA with DNA immobilized on membrane filters. The degrees of hybridization of homologous and heterologous forms were determined by assaying the C14-labelled RNA incorporated into the RNA-DNA hybrids. The RNA from normal and sterilized fly ovaries hybridized with the homologous DNA to about the same degree. However, with heterologous hybrids, that is, RNA from one type of ovary and DNA from the other, there was a lesser degree of hybridization indicating that only a portion of the RNA was able to recognize complementary sites in the heterologous DNA.

Ribosomes from fig fruits: Physical properties and the occurrence of transient dimers

Abstract 1. Ribosomes isolated from fig fruits were fractionated on sucrose density gradients into subunits, monomers, dimers, and higher polymers. Sedimentation coefficients of these fractions were 39±1 and 60±2 S for the subunits, and 80±2, 120±3, and 146±2 S for the monomer, dimer and trimer fractions, respectively. The identity of each fraction was confirmed by electron microscopy. 2. The ribosomes were characterized according to ultraviolet absorption spectrum, sensitivity to deoxyribonuclease and ribonuclease, and hyperchromicity. 3. Ribosomes were isolated during all three phases of the double sigmoid growth curve characteristic of fig fruits. Two significant qualitative changes were observed: (a) the transient predominance of dimers at early stages of growth; and (b) a progressive decline in polysomes associated with senescence. 4. Identity of the dimer fraction was confirmed with the use of dual-labeled precursors, co-sedimentation with labeled Escherichia coli ribosomes and electron microscopy.

Characteristics of nucleic acids from ovaries of virgin and mated houseflies, Musca domestica

Abstract Ribosomal RNA (rRNA) from ovaries of virgin and mated houseflies is composed of 27·2s, 17·4s, and 4·0s particles. Purine-pyrimidine ratios of rRNA synthesis and DNA-rRNA hybridization studies indicate that there are no changes in nucleotide sequences in the newly synthesized rRNA or DNA.

Changes in soluble protein, dehydrogenases, and esterases of unfertilized and fertilized eggs of Musca domestica

Abstract The proteins, including dehydrogenases and esterases, of fertilized and unfertilized housefly eggs have been studied by acrylamide gel electrophoresis and their enzymatic activities measured. A considerable increase in the activity of lactic acid dehydrogenase (LDH) and acetylcholinesterase (AchE) was evident during embryonic development in the fertilized eggs. When the crude protein extract from the unfertilized eggs was purified by DEAE cellulose column chromatography, the activity of LDH increased but the activity of AchE remained relatively the same. The activities of malic acid dehydrogenase (MDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) were similar in fertilized and unfertilized eggs. At late embryogenesis, changes in protein patterns between fertilized and unfertilized eggs were barely detectable. During the period of development five LDH isoenzymes and six esterases were found in the fertilized eggs, whereas in the unfertilized eggs two LDH isoenzymes and four esterases were found. MDH and G-6-PDH isoenzyme bands were similar in both types of eggs with two distinct isoenzyme bands near the origin.

Amino acid incorporation by fig fruit ribosomes in a cell-free system☆

Abstract An amino acid-incorporating system from fig fruit tissue has been prepared and the requirements needed for such an activity were established. The pH 5 enzymes, prepared from the same tissue, successfully supported the incorporation of 14 C- l -phenylalanine by ribosomes. Puromycin and RNAse, but not DNAse, inhibited the protein synthesis activity. The addition of poly U increased the incorporation rate. A gradual increase in the rate of 14 C- l -phenylalanine incorporation began in the dimer (120 S) fraction and continued in the higher polysomal aggregates.

Effect of alkylating agents on transfer ribonucleic acid methylases of Musca domestica during oögenesis and embryogenesis

Abstract The transfer ribonucleic acid methylases ( t RNA) during the period of oogenesis and embrygenesis of Musca domestica , from normal and chemosterilized adult housefly has been studied. As shown by enzyme activity measurement, the rate of t RNA methylases activity was higher in normal tissues than it was in the chemosterilized one.