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Biomedical subjects

J Weiser

Publications and source records attributed to J Weiser.

At least 37 records · Page 2Linked to original sources
PubMed1991

Tolypocladium terricola sp. N., a new mosquito-killing species of the genus Tolypocladium Gams (Hyphomycetes).

A new entomopathogenic species of the genus Tolypocladium, T. terricola is described from a soil sample from Finalnd. From other known Tolypocladium species, T. terricola differs in morphology, production of secondary metabolites and possession of relatively strong mosquitocidal activity. The fungus is characterized by broad oval conidia (2.5 x 2 microns) with one pointed end which are produced in grape-like clusters, and are not firmly adherent. When treated with T. terricola, mosquito larvae show typical features of intoxication characterized by the concentration of larvae in the centre of cup, hanging by their siphons on the surface.

Animals↗
PubMed1991

Distinguishing benign and malignant melanocytic lesions with the AgNOR method.

A silver staining technique has recently been devised to aid in the differentiation between benign and malignant melanocytic lesions. This study showed a statistically significant difference between the staining of silver-nucleolar organizer regions (AgNORs) in melanocytic nevi and that of AgNORs in malignant melanomas.

Diagnosis, Differential↗
PubMed1991

Effect of ichthyomycin on the ultrastructure of tissues of Culex pipiens.

A new antibiotic ichthyomycin produced by Streptomyces sp. strain 1107 was tested for its toxicity and effect on the ultrastructure of tissues of larvae of Culex pipiens autogenicus. Concentrations used were 5 x 10(-7), 2.5 x 10(-7), 1.5 x 10(-7) and 1 x 10(-7) g ml-1. The mortality of larvae after 24 h exposure was 90, 30, 0 and 0%, and after 48 h was 100, 100, 87 and 0%, respectively. The effect of the antibiotic was most evident on mitochondria. They distended and ruptured with subsequent dissolution of their cristae. The microvilli of the brush border of the midgut cells and cell membranes were unchanged, and the peritrophic membrane remained coherent. Cisternae of the rough endoplasmic reticulum and microbodies filled the cytoplasm. Chromatin of the nuclei was aggregated into amorphous masses on the wall, but the nucleolus remained intact. Some cells showed large vacuoles in their cytoplasm from destroyed mitochondria. In muscle cells the mitochondria were in the process of dissolving and the sarcoplasmic reticulum formed elongate cisternae.

Animals↗
PubMed1990

How many EF-Tu molecules participate in aminoacyl-tRNA binding and peptide bond formation in Escherichia coli translation?

We have observed that two EF-Tu.GTP cycles are required to make one peptide bond during steady-state translation in an accurate and fast poly(U) translation system prepared from Escherichia coli. We have also found that there are two complexes of EF-Tu.GTP bound to one molecule of aminoacyl-tRNA under our experimental conditions. We suggest, on the basis of these data, that aminoacyl-tRNA enters the ribosomal A-site in a pentameric complex together with two EF-Tu and two GTP molecules. When the tRNA is delivered to the ribosome two GTP molecules are hydrolyzed. It is possible that the functional role of such an EF-Tu dimer is related to the function of the two L7/L12 dimers in the large ribosomal subunit.

Escherichia coli↗
PubMed1989

Content, distribution and stability of protein-synthesis elongation factor Tu in subcellular fractions of vegetative cells and spores of Streptomyces aureofaciens.

The protein synthesis elongation factor Tu (EF-Tu) was identified in dormant spores of Streptomyces aureofaciens and its content and distribution in vegetative cells and dormant spores were determined. Cell-free homogenates from spores were found to contain a EF-Tu cleaving membrane bound protease. The protease cleaved aggregated EF-Tu much less efficiently than non-aggregated factor in cell homogenates. The relative content of EF-Tu and ribosomes in dormant spores was very similar to that found in exponentially growing vegetative cells.

Cell Membrane↗
PubMed1989

Ultrastructural effects of macrotetrolides of Streptomyces griseus LKS-1 in tissues of Culex pipiens larvae.

The isolate of macrotetrolides produced by Streptomyces griseus strain LKS-1 was tested in its effect on the ultrastructure of larvae of Culex pipiens autogenicus. Changes were mainly in mitochondria where the cristae were destroyed and the outer membrane inflated. The endoplasmic reticulum was vacuolized and subsequently the nuclear membranes were seriously affected. Microvilli of the midgut epithelial cells and the surface membrane of these cells were unaltered and there were no changes in the arrangement of cells in the tissues. The effect of macrotetrolides on insect tissues is analogous to the effect of secondary metabolites of fungi such as beauvericin, destruxin E, cyclosporin or tolypin, and differs from the effects of bacterial endotoxins of Bacillus thuringiensis or B. sphaericus.

Animals↗
PubMed1989

Pathology of cyclosporin A in mosquito larvae.

Silica gel granules coated with cyclosporin A were used for intoxication of larvae of Culex pipiens. Pathological changes were evident in all tissues, characterized by the formation of minute vacuoles in the cytoplasm. Individual cells were affected to different degrees. The targets of cyclosporin A were mainly mitochondria which inflated their cristae, disintegrated and changed into vacuoles with ghosts of their structures remaining. Minor changes were evident in the endoplasmic reticulum and the Golgi apparatus. Microvilli, cell membranes and nuclear membranes were not affected, but were involved in the stages of degeneration of the killed cell.

Animals↗
PubMed1988

Molecular properties of elongation factor Tu from Streptomyces aureofaciens and Escherichia coli.

Some molecular properties of the elongation factor Tu of protein synthesis purified in an aggregated state from gram-positive Streptomyces aureofaciens were studied and compared with those of Tu from gram-negative Escherichia coli. Electrofocussing under reducing conditions showed that the molecule of EF-Tu from S. aureofaciens has an isoelectric point shifted more to the acidic side compared with EF-Tu from E. coli. A comparison of amino acid composition revealed minor differences in the content of several amino acids in the two factors and showed that EF-Tu from S. aureofaciens contains four half-cystines per molecule. Under denaturing conditions only two mercapto groups reacted with 5,5'-dithiobis(2-nitrobenzoic acid). Limited tryptic digestion of aggregated EF-Tu from S. aureofaciens yields six fragments: the four main fragments are of a similar size as those of the E. coli factor. All fragments detected after trypsin digestion of S. aureofaciens EF-Tu were immunologically cross-reactive with antibodies against E. coli EF-Tu. However, even after 2 h of the reaction there still remains a small part of streptomycete factor uncleaved, which documents high resistance of aggregated EF-Tu towards trypsin.

Amino Acids↗
PubMed1988

The effect of tolypin in Tolypocladium niveum crude extract against mosquito and blackfly larvae in the laboratory.

The efficacy of tolypin against mosquito and blackfly larvae was studied under laboratory conditions. It was tested against Culex molestus, Aedes aegypti, Anopheles maculipennis, Simulium noelleri and Odagmia ornata. A concentration 0.1 mg/ml caused 100% mortality in all species tested and a concentration 0.001 mg/ml caused 100% mortality only in the two species of blackflies used within 24 hours.

Aedes↗
PubMed1986

Rhabdovirus-like particles in the sporocyst of the trematode Brachylaimus fuscatus from terrestrial mollusc Ponsadenia duplocincta.

Rhabdovirus-like particles containing nucleoprotein in a helix with eight turns was demonstrated by transmission electron microscopy in subtegumental cells and syncytial layer of tegument in Brachylaimus fuscatus sporocyst. This is the first case of virus infection in trematodes. The possibility of transfer of the virus to intra-molluscan parasitic generations of the trematode is discussed with respect to the peculiarities of the life cycles of the family Brachylaimidae.

Animals↗
PubMed1985

[The activity of Bacillus thuringiensis var. israelensis against black fly larvae under field conditions in South Bohemia].

The effectiveness of Bacillus thuringiensis var. israelensis spore suspension against black fly larvae was tested in two regulated brooks in the Ceské Budĕjovice district, South Bohemia. The sites under study were small, regulated, paved brooks of trapezoidal profile, with vegetation of different density, and with stream flow rates ranging from 40 to 90 cm/sec. Lyophilized spores (produced by Roger Belon) at a final concentration of 1 X 10(5) spores per ml were used. The spore efficacy was determined in both natural and artificial substrates in the field and under laboratory conditions, on the larvae collected at the control sites. A 90-100% mortality of the larvae was recorded in all parts of the brooks examined both in the natural samples studied in laboratory and in those kept on artificial substrates. In the area of fading spore suspension action, a higher percentage of the last-instar larvae was found in larval population which may be ascribed, in agreement with other authors, to an increased susceptibility of younger larvae to the preparation. The results of the tests demonstrated that Bacillus thuringiensis var. israelensis is an effective agent to control the black fly species occurring in Central Europe and may be of value mainly in the control of some species of veterinary importance overpopulated in regulated brooks.

Animals↗
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↗