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Biomedical subjects

V Glushko

Publications and source records attributed to V Glushko.

13 recordsLinked to original sources
PubMed2004

Nonstoichiometric hydroxyapatite granules for orthopaedic applications.

A new method for the preparation of nonstoichiometric hydroxyapatite (HA) "dense" and porous granules, round in form and up to 8 mm in sizes designed for application in orthopaedic surgery has been developed. The "dense" granules' porosity was up to 32% and they only contained micropores. They differed from that kind of granules by increased values of compression strength (up to 48 MPa). The porous granules contained a system of interconnected micro- and macropores. The porosity value (up to 70%) and the porosity structure were similar to those in the mineral framework of a spongy bone. The compression strength of the porous granules (up to 25 MPa) was high enough for various kinds of application. Granules of both sorts were used in performing 42 operations on the locomotor system. Depending upon localization and supposed level of the injured area loading, "dense" or porous granules were used. The postoperative observations (up to four years in length) have attested to the high quality of the granules.

Adolescent↗
PubMed2001

Sintering peculiarities for hydroxyapatite with different degrees of crystallinity.

It has been shown that reduction of sintering temperature of hydroxyapatite is connected to the use of a powder, the particles of which consist of crystalline and amorphous-like constituents. Shrinkage of the pressings made of the powder starts at the middle temperatures (600-700 degrees C) and is realized by a mechanism of a mutual sliding of the particles. If the firing temperature of the pressings increases, the second stage, realized by a diffusion mechanism (over approximately 900 degrees C), begins. A shrinkage curve on the sliding stage has a stepped character. It is caused by a stopping effect on the shrinkage of the pressure of a gas, which is exuded as a result of crystallization of the amorphous-like constituent, and partly accumulates in closed cavities and pores. The contribution of the two mechanisms to the shrinkage process is determined by the degree of crystallinity of the powder (i.e. the ratio of the crystalline and the amorphous-like constituents). If a powder has a higher degree of crystallinity, higher temperatures result, and the stepped character of the shrinkage curve is smoothed. The sliding stage is practically lacking for pressings of crystalline powder, and a noticeable shrinkage starts at high temperatures (over approximately 900 degrees C) as diffusive processes develop.

Ceramics↗
PubMed1998

Inorganic phase composition of remineralisation in porous CaP ceramics.

The formation of bone tissue in pores, and around, a block made of partially dehydroxylated porous hydroxyapatite ceramic and implanted into a rat's femur using X-ray diffraction (XRD), infrared spectroscopy (IRS) and histological methods were investigated. Structural characteristics and composition of new bone tissue formed three months after implantation, in fact, do not differ from those of the normal femur. A model of osteogenesis based on dissolution-precipitation reactions is given, taking into account peculiarities of structure, deficiency and impurity composition for the material of the implant.

Animals↗
PubMed1986

Use of a reconstituted basement membrane to measure cell invasiveness and select for highly invasive tumor cells.

Malignant cells must traverse basement membranes during their migration to sites distant from the primary tumor. Since basement membranes are thought to be a critical barrier to the passage of tumor cells, we have constructed a model basement membrane-stromal matrix consisting of laminin and type IV collagen reconstituted onto a disk of type I collagen for use in an in vitro assay of invasiveness. Metastatic tumor cells and leukocytes are able to cross this barrier, whereas nonmetastatic tumor cells, fibroblasts, and epidermal cells cannot penetrate it. Those tumor cells that penetrate the barriers were found, when isolated and subcultured, to be more invasive and to produce more metastases than the parental population. This assay system should be useful for studying the invasiveness of tumor cells and for isolating highly invasive variants.

Animals↗
PubMed1985

Dermal wound repair: role of collagen matrix implants and synthetic polymer dressings.

The effects of two different polymeric wound dressings and a new collagen matrix (CM) implant on the healing and scarring of full-thickness excision wounds were studied in swine. The synthetic polymers comprised an occlusive O2-impermeable hydrocolloid dressing (HCD) and an occlusive O2-permeable polyurethane film (PUF). The CM implant consisted of an acellular collagen sponge fabricated from purified bovine tendon type I collagen. Wounds were evaluated for granulation tissue--production capacity by measuring 14C proline incorporation into collagenase-sensitive protein. Epidermal resurfacing and wound contraction were measured by computerized morphometric image analysis of wounds made on a tattooed grid. In comparison with air-exposed wounds, the relative collagen synthetic capacity was greater in the granulation tissue of wounds treated with HCD, PUF, or CM with occlusion. Both HCD and PUF accelerated by 40% the epidermal resurfacing over the granulating wound bed. Wound contraction was significantly reduced by CM but was not altered by the occlusive dressings.

Animals↗
PubMed1985

Collagen sponge as a topical hemostatic agent in mucogingival surgery.

Hemorrhage from palatal donor sites during periodontal mucogingival surgery was controlled by application of Collastat absorbable hemostatic sponges. The use of collagen sponges was evaluated in 20 free-graft cases. In contrast to microfibrillar collagen, which is normally delivered as clumps of material, a Collastat sponge was applied as a single piece that maintained structural integrity even when wet and was easy to maneuver into place. The highly porous sponges conformed to the wound, absorbed fluid and produced consistently reliable hemostasis with no secondary bleeding. By stemming the seepage of blood into the throat, patient safety and comfort were improved. The sponges were left on the wounds and removed at the 1-week postoperative visit, revealing well-formed granulation tissue. Healing proceeded normally with no evidence of infection, tissue reaction, or other adverse effects.

Collagen↗
PubMed1984

Abnormal membrane protein methylation and merocyanine 540 fluorescence in sickle erythrocyte membranes.

Sickle cell erythrocytes exhibit reduced carboxyl methylation of membrane proteins compared to normal erythrocytes. This altered methylation in sickle membrane proteins is also observable when extracted membranes, both intact and alkali treated, were used as substrates for the homologous protein methylase II (S-adenosylmethionine:protein-carboxyl O-methyltransferase, EC. 2.1.1.24). However, when glycophorin A, one of the major methyl acceptors in both membranes, was extracted by lithium diiodosalicylate and used as the methyl acceptor, the proteins from both membranes were methylated equally, suggesting an involvement of membrane structure in membrane-bound protein methylation. Merocyanine 540 (MC-540), a fluorescent probe, was used to determine if the membranes differed in organization. Incubation of both normal and sickle erythrocytes membranes with MC-540 produced a marked increase in extrinsic fluorescence, reflecting a relatively nonpolar environment for the dye bound to the membranes. The fluorescence from sickle cell ghosts was only 87% as intense as that from normal ghosts, while the actual amount of MC-540 associated with sickle cell membranes was only 62% of normal. These data suggest that differences exist in the distribution of surface charges on these plasma membranes. These results are consistent with the hypothesis that abnormal levels of membrane protein methylation observed in sickle erythrocytes may be a result of abnormal membrane organization characteristic to sickle cell anemia.

Anemia, Sickle Cell↗
PubMed1982

The fluorescence of bilirubin upon interaction with human erythrocyte ghosts.

Bilirubin fluorescence increased upon interaction with bovine serum albumin and human erythrocyte ghosts. When bound to albumin, the emission maximum occurred at 534 +/- 3 nm with maximum excitation at 462 +/- 3 nm. Upon interaction with human erythrocyte ghosts, bilirubin fluorescence increased in a biphasic manner. A rapid initial increase was followed by a slower process that required at least 40 min to reach maximum enhancement at 25 degrees C. At equilibrium, bilirubin fluorescence in erythrocyte ghosts was heterogeneous. With 470 nm excitation, maximum emission occurred in the range of 520 to 535 nm. However, decreasing the excitation to 450 nm or below, produced a red shift in the emission difference spectra. These results suggest that bilirubin exists in different states or sites when associated with plasma membranes.

Bilirubin↗
PubMed1979

A method for measuring membrane microviscosity using pyrene excimer formation. Application to human erythrocyte ghosts.

In order to determine the microviscosity of human erythrocyte membrane suspensions, a method has been developed which is based on pyrene excimer formation. First, measurements of partitioning of pyrene into membranes, in conjunction with known values for the volume of the lipid compartment of erythrocyte ghosts are used to determine the concentration of pyrene in the membrane lipid. Secondly, reported measurements of the diffusion constants of aromatic hydrocarbons similar in structure to pyrene, are used to derive an empirical equation relating solvent viscosity and the diffusion constant of pyrene. Then, measurements of pyrene excimer formation in a series of solvents ranging up to several poise in viscosity are used to determine that the interaction diameter of the excimer formation reaction is 3 +/- 1 A. Finally all these data are brought together in order to conclude that the viscosity of the lipid in the human erythrocyte ghost is 8.0, 4.0 and 1.6 P at 10, 25 and 40 degrees C, respectively.

Erythrocyte Membrane↗