Cytological changes and DNA and protein synthesis in parthenogenetically activated sea urchin eggs

Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of³H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the³H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the³H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of¹⁴C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction.     

Synthesis and degradation of proteins during wheat endosperm development

Synthesis of proteins rich in lysine declines progressively with endosperm development and these proteins appear to be degraded preferentially at later stages. The proteolytic enzymes in extracts of endosperms at a late stage of development release considerably more lysine radioactivity from labelled endosperm proteins as compared with the enzymes in endosperms at an early stage.     

Photochemical Synthesis and Multiphoton Luminescence of Monodisperse Silver Nanocrystals

A rapid, photochemical solution-phase synthesis has been developed for the production of monodisperse, nanometer-sized silver particles. The stabilizer used in the synthesis can be used to control the average diameter of the particles over a range from 1 to 7 nm. The same reaction mixture can also be employed to deposit patterns of nanoparticles with a laser via multiphoton absorption. The particles exhibit strong multiphoton absorption-induced luminescence when irradiated with 800-nm light, allowing emission from single nanoparticles to be observed readily.     

A novel homozygous 10 nucleotide deletion in BBS10 causes Bardet–Biedl syndrome in a Pakistani family

Bardet–Biedl Syndrome is a multisystem autosomal recessive disorder characterized by central obesity, polydactyly, hypogonadism, learning difficulties, rod-cone dystrophy and renal dysplasia. Bardet–Biedl Syndrome has a prevalence rate ranging from 1 in 100,000 to 1 in 160,000 births although there are communities where Bardet–Biedl Syndrome is found at a higher frequency due to consanguinity. We report here a Pakistani consanguineous family with two affected sons with typical clinical features of Bardet–Biedl Syndrome, in addition to abnormal liver functioning and bilateral basal ganglia calcification, the latter feature being typical of Fahr's disease. Homozygous regions obtained from SNP array depicted three known genes BBS10, BBS14 and BBS2. Bidirectional sequencing of all coding exons by traditional sequencing of all these three genes showed a homozygous deletion of 10 nucleotides (c.1958_1967del), in BBS10 in both affected brothers. The segregation analysis revealed that the parents, paternal grandfather, maternal grandmother and an unaffected sister were heterozygous for the deletion. Such a large deletion in BBS10 has not been reported previously in any population and is likely to be contributing to the phenotype of Bardet–Biedl Syndrome in this family.     

Comparison of proteins synthesized in vivo and in vitro by mRNA from isolated protoplasts

Studies of proteins synthesized in vitro by messenger RNA (mRNA) extracted from tobacco protoplasts showed that the changes in protein synthesis and especially the lack of certain proteins observed previously in isolated protoplasts did not result from a failure of translation.     

Accumulation and conversion of sugars by developing wheat grains. 4. Effects of phosphate and potassium ions in endosperm slices

Abstract. Transverse slices through developing grains of Triticum aestivum cv. SUN 9E 16 d after anthesis were incubated in simple defined media with various radioactive labels. In some enzymic assays slices were pretreated with 2.5% Triton X-100 or with 5% butanol to remove cellular membranes and endogenous substrates.
Endogenous potassium leaked from endosperm slices into 30mol m⁻³ sucrose while sucrose was converted partly into starch. Exogenous alkali-ions, except Li⁺, stimulated conversion of sucrose to insoluble matter, specifically to starch with K⁺. Starch synthetase activity of Triton-pretreated slices was stimulated by K⁺ at both high and low substrate ADPG concentration, but was not affected by phosphate (25 mol m⁻³).
Phosphate in the medium had no effect on incorporation of sucrose or glucose into alcohol-insoluble material or starch in fresh slices (internal inorganic phosphate (P,) concentration was about 11 mol m⁻³). Three- to four-fold contrasts in internal P_i level, achieved by prolonged preincubations in different media, did not show an inhibition of starch synthesis by P_i. However, phosphate (25mol m⁻³) inhibited starch synthesis, that was mediated by ADPG pyrophosphorylase in butanol-pretreated endosperm slices by 15–18%.
It is concluded that starch synthesis in wheat endosperm is not regulated directly by apoplastic P_i; level.     

Effects of two chitin synthesis inhibitors on Thalassiosira fluviatilis and Cyclotella cryptica

Abstract The effects of two commercial chitin synthesis inhibitors, dimilin and polyoxin D, on chitin fiber formation and cell sedimentation for the diatoms Thalassiosira fluviatilis and Cyclotella cryptica (Bacillariophyceae) were investigated. Dimilin treatments for both diatom species were indistinguishable from controls in terms of chitin fiber productions, cell density and sedimentation. Polyoxin D-treated cells of both diatom species completely lacked the characteristic chitin fibers. Polyoxin D cultures were also characterized by a significant decrease in population density, increased sedimentation rates and a strong tendency to clump in comparison with control and dimilin treatments. It was concluded that (1) dimilin does not directly inhibit chitin synthesis in diatoms; (2) polyoxin-D inhibits β-chitin fibril formation, and (3) chitin fibers play an important role in cell separation and cell buoyancy.     

Repression of porin synthesis by salicylate in Escherichia coli, Klebsiella pneumoniae and Serratia marcescens

The synthesis of the OmpF porin in Escherichia coli K-12 was highly and reversibly inhibited by 5 mM salicylate in the bacterial growth medium, and salicylate also inhibited the OmpC porin synthesis, although only weakly. The full expression of the salicylate effect was presumed to require the ompB gene product on comparison between the wild type and ompB mutant strains. The salicylate effect was also observed for the porin protein synthesis in Klebsiella pneumoniae and Serratia marcescens, although an ompB-like gene remains to be identified in both species.     

Bacteriophage MB78 DNA synthesis is specifically inhibited by the chelating agent ethylene diamine tetraacetic acid

The growth of bacteriophage MB78, a virulent phage of Salmonella typhimurium is extremely sensitive to the chelating agent EDTA. Other chelating agents like EGTA, a specific chelator for Ca²⁺ and orthophenanthroline which chelates Zn²⁺ and Fe²⁺ have no effect. EDTA stops phage MB78 DNA synthesis while synthesis of host DNA and other Salmonella phage DNA are not affected in presence of such low concentrations of EDTA. The present report indicates that some early phage function(s) and most probably the phage DNA synthesis are sensitive to EDTA which is probably due to chelation of Mg²⁺.