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Biomedical subjects

J Weiser

Publications and source records attributed to J Weiser.

At least 55 records · Page 3Linked to original sources
PubMed1985

The efficacy of Bacillus thuringiensis var. israelensis against larvae of the blackfly Odagmia ornata (Meig.) (Simuliidae) at low temperatures.

The effect of the suspension of Bacillus thuringiensis var. israelensis spores on larvae of the blackfly Odagmia ornata was studied in the laboratory and under field conditions of a natural biotope in southern Bohemia. The preparation Moskitur was used and its effect was tested in laboratory at temperatures 0.1-2.9 degrees C and 17-19 degrees C. Although O. ornata larvae were able to filter feed on a lethal dose of the preparation even at a lower temperature than 2.9 degrees C, no marked manifestation of mortality was observed at low temperatures in comparison with a control sample.

Animals↗
PubMed1984

RNA and ribosomal protein patterns during aerial spore germination in Streptomyces granaticolor.

Disruption of the external sheath of Streptomyces granaticolor aerial spores and subsequent cultivation in a rich medium result in a synchronous germination. This method was used to analyze RNA and protein patterns during the germination. The germination process took place through a sequence of time-ordered events. RNA and protein synthesis started during the first 5 min and net DNA synthesis at 60-70 min of germination. Within the first 10 min of germination, synthesis of RNA was not sensitive to the inhibitory effect of rifamycin. During this period rRNA and other species including 4-5-S RNA were synthesized. Dormant spores contained populations of ribosomes or ribosomal precursors that were structurally and functionally defective. The ribosomal particles bound a sporulation pigment(s) of the melanine type. The ribosomal proteins complexed to the pigments formed insoluble aggregates which were easily removed from the ribosomes by one wash with 1 M NH4Cl. During the first 10 min of germination, pigment(s) were liberated from the complexes with the ribosomes and protein extracts of the washed ribosomes had essentially the same pattern as the extracts of ribosomes of vegetative cells. These structural alterations were accompanied by enhancement of the ribosome activities in polypeptide synthesis in vivo and in vitro. When the spores were incubated with a 14C-labelled amino acid mixture in the presence of rifamycin, only three proteins (GS1, GL1 and GS9) were identified to be radiolabelled in the extracts from the washed ribosomes. These experiments indicate that liberation of the sporulation pigment(s) from the complexes with ribosomal proteins and assembly of de novo synthesized proteins and proteins from a preexisting pool in the spore are involved in the reactivation of the ribosomes of dormant spores of S. granaticolor.

DNA Replication↗
PubMed1984

Formation of the ternary complex EF-Tu.GTP.Phe-tRNA in the translation system of Streptomyces aureofaciens.

The efficiency of formation of the ternary complex consisting of the elongation factor Tu and Phe-tRNA's from Escherichia coli and Streptomyces aureofaciens was tested to explain the lower activity of the in vitro poly(U) translation system from S. aureofaciens. Both factors were shown to be functionally interchangeable in the ternary complex formation with Phe-tRNA from either E. coli or S. aureofaciens. However, the efficiency of binding of S. aureofaciens Phe-tRNA to EF-Tu was much lower with both factors.

Guanosine Triphosphate↗
PubMed1984

Entomopathogenic spore-formers from soil samples of mosquito habitats in northern Nigeria.

Spore-forming bacteria, isolated from bottom soil samples of periodical mosquito-breeding places in Kaduna, N. Nigeria, were tested for mosquito pathogenicity. Culex pipiens autogenicus was used for this screening. Five strains, all of the Bacillus thuringiensis group, were active in 85 isolates from 32 samples. The isolates were from three different serotypes (H-14, H-5a5c, and H-8a8b). The activity, compared with the SIP standard, was in the known limits of B. thuringiensis israelensis.

Animals↗
PubMed1984

A mosquito-virulent Bacillus sphaericus in adult Simulium damnosum from northern Nigeria.

From newly emerged adult Simulium damnosum from Kaduna River, Northern Nigeria, a mosquito-virulent strain of Bacillus sphaericus was isolated. In another four cases non-virulent B. sphaericus were present. The isolate exerted a LC50 of 50 spores/ml for Culex pipiens L4-larvae and was less virulent for Anopheles stephensi (400 sp/ml) and Aedes aegypti (800 sp/ml).

Aedes↗
PubMed1983

Stimulatory effect of UTP on peptide chain initiation in Streptomyces aureofaciens.

The formation of the 30S and 70S initiation complex in Streptomyces aureofaciens differs from that in E.coli and B.stearothermophilus with respect to the requirement for nucleotide triphosphates for the maximum activity. In the presence of GTP and initiation factors from S.aureofaciens the codon specific binding of fMet-tRNA to ribosomes of S.aureofaciens was stimulated by ATP or UTP. UTP exhibited the most significant effect increasing the binding about 3.5 times, whereas CTP had no effect on the reaction. The stimulatory effect of UTP is GTP-dependent and was not observed in experiments with E.coli ribosomes.

Kinetics↗
PubMed1983

Susceptibility of ribosomes of the tetracycline-producing strain of Streptomyces aureofaciens to tetracyclines.

Ribosomes from cells of Streptomyces aureofaciens producing tetracycline antibiotics (Tc-ribosomes) differ in electrophoretic mobility of ribosomal proteins S2, S10 and L19 from those of the same strain, where the production of tetracyclines was suppressed by changed cultivation conditions (C-ribosomes). Purified tight vacant couples C- and Tc-ribosomes are equally active in the translation of poly(U). Both types of S. aureofaciens ribosomes are more sensitive to tetracycline and chlortetracycline than ribosomes of Escherichia coli in the Phe-tRNA binding and the translation of poly(U).

Escherichia coli↗
PubMed1982

Ribosomal proteins of Streptomyces aureofaciens producing tetracycline.

Three different two-dimensional polyacrylamide gel electrophoretic systems were employed for identification of individual ribosomal proteins of Streptomyces aureofaciens. Proteins of small subunits were resolved into 21 spots. Larger ribosomal subunits contained 35 proteins. The separated ribosomal proteins from 50 S subunits were transferred on nitrocellulose membranes for immunochemical estimations. Antibodies developed against 50 S proteins of S. aureofaciens and Escherichia coli were used for identification of structural homologies between 50 S proteins of the two species. Results of the experiments indicate that about one half of the 50 S proteins of S. aureofaciens share common immunochemical determinants with corresponding proteins of 50 S subunits of E. coli. Evidence is presented that acidic ribosomal protein SL5 of large ribosomal subunits of S. aureofaciens can be assembled to E. coli P0 cores lacking proteins L7/L12. Reconstitution of the P0 cores with proteins SL5 or L7/L12 led to restoration of 78% activity in polyphenylalanine synthesis.

Electrophoresis, Polyacrylamide Gel↗
PubMed1982

Isolation and characterization of Streptomyces aureofaciens protein-synthesis elongation factor Tu in an aggregated state.

The ability of EF-Tu to aggregate spontaneously was employed for the purification of homogeneous EF-Tu . GDP from Streptomyces aureofaciens. The formation of filamentous structures in the aggregated EF-Tu was demonstrated in a light microscope. The purified factor, with a specific activity of 19,100 +/- 1,000 units/mg in [3H]GDP exchange, was shown to be active in the translation of poly(U). Aggregated EF-Tu . GDP exhibited almost eight-times lower GDP-exchange capacity at 2 degrees C than at 30 degrees C. This suggests that GDP-binding sites are not freely accessible at lower temperatures in the aggregated factor, in contrast to Escherichia coli polymerized EF-Tu. Turbidimetric assays revealed that the solubilization of diluted aggregated S. aureofaciens EF-Tu is strongly dependent on temperature and causes an increase in the number of accessible GDP-binding sites.

Bacterial Proteins↗
PubMed1978

A new host, Simulium argyreatum Meig., for the cytoplasmic polyhedrosis virus of blackflies in Czechoslovakia.

The cytoplasmic polyhedrosis virus (CPV) from the midgut of blackfly larvae is recorded from a population of Simulium argyreatum in Czechoslovakia. A 7.7% infection of 2766 sampled larvae was manifested by white spots in their body. 85% of the white-spotted larvae were infected with CPV when sampled in June. In August 9% of 1377 larvae had white spots but only 10.6% of them were with CPV. Out of 823 collected pupae, only 3 imperfect pupae had the virus in apparent form. Other infections producing white spots in larvae were due to the microsporidia Plistophora multispora, P. simulii, P. debaisieuxi, Thelohania fibrata, the fungus Coelomycidium simulii and the mermithids.

Animals↗
PubMed1978

Natural infection of the tick Dermacentor reticulatus (Fabr.) with the microsporidian Nosema slovaca Weiser et Rehácek in Slovakia.

A total of 6,199 adult ticks (Haemaphysalis intermis, Dermacentor reticulatus, D. marginatus and Ixodes ricinus) collected in three localities in Slovakia were examined for microsporidian infection. The spores of Nosema slovaca were found in six D. reticulatus (0.097%). The microsporidian experimentally inoculated into the hemocele of half-engorged females of D. reticulatus caused acute infection and death of the host. The infection can be transmitted also to other tick species from the same region. The yield of spores from one tick ranges from 3 X 10(5) to 52 X 10(7) depending on the infection dose and tick species. Peroral infection of some butterfly larvae with the microsporidian pores was unsuccessful. The importance of Nosema infection in ticks in nature is discussed.

Animals↗
PubMed1977

Interaction of granaticin B with the transcription system of Bacillus subtilis.

The interaction of granaticin B, a quinone antibiotic produced by Streptomyces granaticolor, with some biologically important bivalent metal ions, DNA and ATP was demonstrated spectrophotometrically. The activity of isolated RNA polymerase was higher when the DNA of phage SP 50 served as template than with DNA isolated from Bacillus subtilis. Granaticin B inhibited in vitro RNA synthesis, similarly to certain other antibiotics (the inhibition was three times lower than that caused by actinomycin D or streptolydigin and slightly higher than that by epsilon-pyrromycinone). The inhibitory effect was higher when the Mg2+ concentration in the reaction mixture was decreased. The inhibition was then proportional to the concentration of the DNA template. DNA-dependent RNA synthesis is thus inhibited in vitro by granaticin B but this does not appear to be the only site of action of this antibiotic in vivo.

Adenosine Triphosphate↗