PubMed Health⌕ Search

Biomedical subjects

B L Allakhverdov

Publications and source records attributed to B L Allakhverdov.

15 recordsLinked to original sources
PubMed1990

[The use of cryomethods for research on the sarcomere ultrastructure of rabbit skeletal muscles].

The ultrastructure of sarcomeres of glycerinated rabbit psoas muscle was studied using freeze-fracture-etching, freeze-drying and optical diffraction techniques in comparison with the investigation of this muscle by plastic sections and negative staining methods. In frozen and dried myofibrils isolated from the above muscle the stripes of minor proteins location in A- and I-disks were clearly seen. The pivot structure in thick filaments was revealed in longitudinal fractures of the muscle. The ordered arrangement of myosin heads (crossbridges) associated with actin filaments was preserved in frozen longitudinal fractures as evidenced by optical diffraction. Freeze etching technique allowed to revealed some details of Z-line structure: alpha-actinin bridges connecting the ends of actin filaments of neighbouring sarcomeres and to preserve the lateral struts between actin filaments in I-disks.

Animals↗
PubMed1990

[An analysis of the supramolecular organization of the olfactory neuroepithelium in the rat by freeze etching with rotary platinum-carbon shadow-casting].

The rat olfactory epithelium was analysed by freeze-deep etching and Pt/C rotary replication. Ultrathin sections and freeze-etching findings of proximal (dendrite) and distal (axon) parts of bipolar olfactory neurons are examined. The supramolecular organization of neuron membranes and intracellular cytoskeleton structure is studied. The role of the Schwann cells in formation of isolated axon bundles is discussed. Methods of the whole neuroepithelium preparation for freeze-etching and different easy approaches of obtaining the Pt/C rotary shadowing replicas with high resolution (15-20A) are presented.

Animals↗
PubMed1986

Ultracytochemical localization and microprobe quantitation of calcium stores in the insect oocyte.

Detection of calcium in the follicles of Galleria mellonella (Lepidoptera) was performed using two cytochemical methods. Calcium precipitation was obtained either with ammonium oxalate (AO) or with N,N-naphtaloylhydroxylamine (NHA). In both cases the X-ray "on line" analysis monitored the presence of calcium in the oocytes, which was correlated with the accumulation of yolk spheres. Concentration of calcium in oocytes filled with yolk and treated with AO amounted to 9 mmoles per 1,000 g tissue wet weight. This value is similar to that calculated previously for follicles untreated with any reagent and prepared for the analysis by the freeze-drying technique (Przeļecka et al. 1980). Examination of the ultrastructure of oocytes treated with NHA revealed calcium precipitate at the follicular epithelium/oocyte interface, in endocytotic canaliculi and vesicles formed by the oocyte plasma membrane, in ooplasm, and in yolk spheres. In oocytes treated with AO, the calcium-precipitate intermingled with the precipitate produced by the osmium alone. The presumed cause of this phenomenon is discussed.

Animals↗
PubMed1985

[Local x-ray spectral microanalysis in cell biology. The study of sections of hydrated biological tissues].

Rules required for fixation of tissues are considered aimed for a further localization of chemical elements in these tissue by means of local X-ray microanalysis. In addition, difficulties involved in fixation of diffusible elements, such as potassium or sodium, are mentioned. Physical bases of preparation of hydrated tissues for X-ray analysis are discussed.

Cytological Techniques↗
PubMed1982

[Method of computing the volumetric concentration of elements in thin tissue sections based on x-ray spectral microanalysis data].

For calculating the concentration of elements in terms of millimoles per litre according to the quantitative X-ray microprobe procedure (Warner, Coleman, 1973), the mass thickness is to be known. However, it can be omitted for thin tissue sections which may be considered as thin film. In the present work the limits of such thin sections are determined. In addition, the calculated corrections (Burovina, Pivovarova, 1978) are checked experimentally.

Electron Probe Microanalysis↗
PubMed1981

Some aspects of developing instruments for cryomethods.

Well-known advantages of specimen preparation by cryomethods are accompanied by some disadvantages resulting mainly from the inadequate level of the presently existing laboratory technology and instruments. For this reason prospects of cryomethod development are to a large extent determined by a possibility of creating effective instruments mostly suitable for cryomethods. We believe this problem can be solved by elaborating exchangeable plug-in units and module-vacuum equipment capable of performing a lot of operations without removing the specimen from the vacuum. Following these principles we have designed a vacuum cryotome which allows a simple insertion and removal of the specimen through the airlock, its reliable protection against heating and contamination, and to slice the object, etching of the specimen surface in a wide range of temperatures, casting the surface with carbon and metal shadow and to making replicas. Shadowing can be done at angles varying from 15 to 90 degrees including a rotating specimen. The specimen holder and the knife have a precise thermostabilization in a wide range of temperatures. When the object is rotating, thermostabilization is preserved. The cooled screen with a vast surface safely protects the specimen against thermal radiation of the chamber walls and against oil and water contamination. Unification of the fixation sites of all exchangeable instruments, application of the same airlocks to all inlet orifices of the vacuum chamber provide a wide variability and exchange of measuring and operating devices, in- and outlet of the specimen without dis- and reevacuation of the chamber.

Freezing↗
PubMedDate not supplied

[Coexistence of coacervate systems of different chemical composition].

Protein--nucleic acids--carbohydrate drops stabilized at pH 6.0 by the products of oxidative enzymes (polyphenol oxidase and peroxidase) were mixed with unstabilized ones. Using light, luminescent and electron microscopic techniques, a possibility was demonstrated of co-existence of coacervate drops with different chemical composition and formation of colonies from them. Coacervate drops are considered as a primitive form of cooperation of molecules in the course of the origin of the living matter. The results obtained will be used for obtaining more complex coacervate systems by imitation of a chain of catalytic reactions.

Biological Evolution↗