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Biomedical subjects

V Pokorný

Publications and source records attributed to V Pokorný.

At least 19 recordsLinked to original sources
PubMed1990

Modification of the Polaron sputter-coater unit for glow-discharge activation of carbon support films.

We describe a modification of the Polaron sputter-coater unit series 11 HD enabling activation of carbon support films for electron microscopy of macromolecules and macromolecular assemblies. The modification is simple and the device can be used in two modes, for sputter-coating of SEM samples and for glow-discharge activation of carbon support films. Examples of protein-free spreading of DNA and negative staining of bacteriophage particles on activated carbon support films are presented.

Bacteriophages↗
PubMed1989

[Our approach to the care of chronic instability of the knee joint].

Chronic instability of the knee joint is a serious problem for the affected patient and the attending physician. Diagnosis must reveal which structures of the soft knee are insufficient. We use as a basis in particular a detailed clinical examination which frequently must be made under short-term general anaesthesia. As to auxiliary examination methods, we recommend X-rays in forced positions, possibly arthroscopy. Defects of the cruciate ligaments can be evaluated well also by means of computed tomography. Operation should be indicated carefully. We consider the extent of the patient's complaints, the ability of dynamic compensation of the instability, the presence of exudates, haematomas, signs of arthritis, locomotor restrictions and, last not least, also the assumed ability of the patient to cooperate in rehabilitation. In surgical treatment of instabilities it is necessary to respect carefully biomechanical principles of the function of the knee joint. In prostheses of the cruciate ligaments we prefer direct reconstruction with an autologous graft to extraarticular operations. It seems that in older patients also reconstruction with synthetic ligaments will be feasible.

Adult↗
PubMed1979

A psychrophilic strain Actinoplanes sp. 220.

The strain designated Actinoplanes sp. 220 differed in its characteristics from other strains of the genus Actinoplanes listed in Bergey's Manual (1974). The strain belongs to psychrophilic culture growing within the range of 0-30 degrees C. The optimal temperature for growth on yeast--malt agar is 10-23 degrees C. Cultures transferred at 23 and 28 degrees C differed in morphological and physiological properties, enzyme activity and pigmentation in standard media. Submerged culture transferred at 28 degrees C inhibited growth of Bacillus subtilis ATCC 6633 and ATCC 9945. LL-2,6-Diaminopimelic acid was chromatographically detected in the submerged mycelium of this culture. This compound was not found in the mycelium of the original culture transferred at 23 degrees C. The cultures did not substantially differ in the composition of other amino acids contained in larger quantities in the mycelium.

Actinomycetales↗
PubMed1978

Microcycle sporulation in the Claviceps purpurea 244.

The mutant strain Claviceps purpurea 244 forming hyphae composed mainly from sclerotium-like cells was found to sporulate both in liquid and solid media, particularly in the form of terminal chlamydospores (4.0 x 6.5 micrometer). Chlamydospores produced during submerged cultivation germinated, new chlamydospores being formed directly from germ tubes, or, occasionally, conidia (the so-called microcycle) or new vegetative mycelium were formed. The ultrastructures of the chlamydospores and vegetative cells was identical. The cytoplasm was filled with ribosomes and contained lipid inclusions and vacuoles with membrane invaginations. Strain 244 cultivated under submerged conditions produced 150 microgram/ml clavins, with elymoclavin predominating (82%). The parent strain Claviceps pururea 129 only produced chlamydospores on the vegetative mycelium, whereas no microcycle was detected; under submerged conditions it produced mainly agroclavin (85%) at a concentration of 4 mg/ml.

Claviceps↗
PubMed1978

Development mutants of Streptomyces coeruleorubidus, a producer of anthracyclines: isolation and preliminary characterization.

The wild strain Streptomyces coeruleorubidus JA 10092 was found to segregate into two spontaneous morphological variants (spo-1 and bld-1) with a different ability to form aerial mycelium in media with glucose as the main carbon source. Six new types of developmental mutants were obtained from the bald variant bld-1 after treatment with mutagens (UV light, gamma radiation, nitrous acid) and after natural selection. Formation of the aerial mycelium was fully suppressed in the bld-2 type growing on media both with glucose and with starch. The other types were bald only on starch media, forming the aerial mycelium on media with glucose; types spo-2, spo-3, spo-4 and spo-5 differed in size, shape and surface structure of spores, the type whi formed asporogenous aerial hyphae.

Aminoglycosides↗
PubMed1978

Improved yields of daunomycinone glycosides in developmental mutants of Streptomyces coeruleorubidus.

When improving Streptomyces coeruleorubidus JA 10092, a producer of antibiotics of the daunomycinone complex, the most active variants were found among isolates of morphological types bld-1 (with a suppressed production of the aerial mycelium on organic media containing glucose) and whi (with an asporogenic aerial mycelium on glucose media and with the bald phenotype on media containing starch). Submerged cultures of the whi mutants produced increased quantities of daunomycinone glycosides in the antibiotic complex, the amount of free anthracyclinones being simultaneously decreased. The whi strains differed from the wild type also in higher demands for aeration, concentration of glucose and in an increased production capacity in starch media. The overall antibiotic activity increased more than 40 times after a six-step selection (application of UV light, gamma-radiation, nitrous acid and natural spreads) combined with an altered fermentation technology.

Culture Media↗
PubMed1978

Mutants of Streptomyces coeruleorubidus impaired in the biosynthesis of daunomycinone glycosides and related metabolites.

Mutants of Streptomyces coeruleorubidus, blocked in the biosynthesis of anthracycline antibiotics of the daunomycine complex, were isolated from the production strains after treatment with UV light, gamma-radiation, nitrous acid, and after natural selection; according to their different biosynthetic activity the mutants were divided into five phenotypic groups. Mutants of two of these groups produced compounds that had not yet been described in Streptomyces coeruleorubidus (aklavinone, 7-deoxyaklavinone, zeta-rhodomycinone and glycosides of epsilon-rhodomycinone). The mutants differed from the parent strains and also mutually in morphological characteristics but no direct correlation between these changes and the biosynthetic activity could be observed in most cases.

Anthraquinones↗
PubMed1977

Induction of DNA single-strand breaks in barley by sodium azide applied at pH 3.

Sodium azide (1 to 50 mM), adjusted to pH 3 and applied for 2 h to presoaked barley seeds, induced a dose-dependent frequency of single-strand breaks in DNA of non-germinating embryos. This was demonstrated by sedimentation analyses of isolated DNA samples in alkaline sucrose gradients and in neutral sucrose gradients with 80% formamide. The doses applied also inhibited dose dependently the root length, seed germination and partially the seedling height. Only the sub-lethal doses (10 and 12.5 mM) induced a low frequency of chromatid breaks and translocations in the root tip metaphases. The sedimentation rate (in alkaline sucrose gradients) of calf thymus DNA treated with sodium azide at pH 3, was similar to that of the control DNA treated with buffer (pH 3) alone.

Azides↗
PubMed1977

The relationship between conidiation and alkaloid production in saprophytic strains of Claviceps purpurea.

A direct relationship between alkaloid synthesis and conidia formation was observed in a series of mutants of the saprophytic fungus Claviceps purpurea 129 which produces high quantities of clavine alkaloids (4500 microgram-ml-1). Sclerotia-like mutants forming mostly arthrospores and only a low number of conidiospores were exceptional in that they were characterized by an inverse relationship between alkaloid synthesis and conidial formation. Conidiospores of the parent strain 129 differed both in their size and ultrastructure. They include oval microconidia (2 X 3.5 micrometer) and prolonged macroconidia (2 X 10.5 micrometer). Both conidial types originated on short lateral sporophores terminated by phialids. Most conidia were characterized by electron-dense cytoplasm with a number of lipidic inclusions; a minority of conidia contained granular cytoplasm and vacuoles with membrane invaginations. Bicellular conidia were only rarely observed.

Claviceps↗