Search PubMed⌕ Search

Biomedical subjects

G Picha

Publications and source records attributed to G Picha.

8 recordsLinked to original sources
PubMed1995

Histologic comparison of breast implant shells with smooth, foam, and pillar microstructuring in a rat model from 1 day to 6 months.

The purpose of this study was to determine the soft-tissue response to silicone breast implants with different surface morphologies and to correlate implant microtexturing with capsular formation. Using a rat model, we inserted breast implants having three types of shells: micropillared, silicone foam, and smooth silicone (control). We used 96 adult male Sprague-Dawley rats weighing between 250 and 300 gm. Thirty-two rats were assigned to each of the three shell groups. Within each shell group, 4 rats were implanted for 24 hours, 4 for 4 weeks, 4 for 8 weeks, 4 for 12 weeks, 4 for 16 weeks, 4 for 20 weeks, and 4 for 24 weeks. The rats were sacrificed at the end of each time interval, and periprosthetic tissue was obtained for histologic analysis. Our results show a stable soft-tissue response with some macrophages and fibroblasts for the smooth silicone shell group; capsule thicknesses were 10 to 12 cells with interwoven collagen. The silicone foam prolonged the active cellular response with regard to macrophages, fibroblasts, and multinucleated giant cells, along with random collagen deposition and alternating thin and thick capsular areas. The micropillar group had a more stable cellular response, with macrophages and fibroblasts, along with disruption of the long-range orientation of collagen fibers.

Animals↗
PubMed1988

Electrocatalytic glucose sensor.

High surface area platinum subjected to the appropriate electrical potential cycling regimes exhibits considerable electrocatalytic activity towards glucose oxidation. We have developed a special data processing method, the compensated net charge (CNC) method, to take advantage of the electrocatalytic activity of platinum. This method involves the determination of the net oxidation charge during one complete cycle of a cyclic voltammogram applied to the platinum electrode in a potentiodynamic mode. Under these conditions, the electrode response is very sensitive to glucose, completely insensitive to urea, and only moderately sensitive to amino acid concentration changes. Earlier work with other endogenous and exogenous potential co-reactants shows little interference. Data obtained in vitro and in vivo will be presented and discussed.

Animals↗
PubMed1977

Surface characteristics of the cardiac prostheses in vivo.

The pseudoneointima (PNI) deposited onto a cardiac prosthesis surface reflects many factors of biocompatibility, surface morphology, flow distribution, design, animal's physiological condition, and duration. In the evaluation of any prosthesis, the PNI is one of the prime considerations from both material and functional standpoints. Historically, Dacron fabric has been used as an internal lining for cardiac prostheses. However, we have observed cracks on the Dacron fibers, fiber fracture, fiber protrusion, and poor attachment to the diaphragm, which can cause potentially disastrous complications. In addition, there are basic differences in the PNI formation on aldehyde-treated pericardium and natural aortic valves as compared to the Dacron fabric. 1) Minimal degeneration takes place on the chemically treated natural tissue compared with the fabtic surface. Intact cells on the tissue suggest a greater compatibility. In later specimens (13 and 24 days), there is active cell infiltration onto the pericardium structure with capillary formation. 2) The deposits on natural tissue are mostly fibrin, with minimum cellular involvement and a trend toward reduction in thickness. 3) Fibroblast cells are found on the natural tissue as early as 7 days but were not observed on the Dacron fabrics. Based on these findings, the Dacron fabric-covered diaphragm studied was not favorable for use in long-term implantation of cardiac prostheses.

Adsorption↗
PubMed1976

The characterization of intima development in left ventricular assist device (LVAD) and total artificial heart (TAH).

1. The study of PNI development provides useful information in the design and improvement of the prosthetic devices. 2. Improved gelatin aldehyde impregnation on the dacron covered diaphragm of cardiac prostheses resulted in a reduced PNI thickness and minimized interfacial degeneration of PNI. 3. The PNI on the diaphragm's surface started with a platelet rich interface and ended with a striated fibrin and platelet matrix at the blood interface. 4. The PNI in the TAH's had a higher involvement of polymorphonuclear leukocytic cells at the PNI-housing or diaphragm interface than the LVAD's. 5. The aldehyde treated pericardial surface of cardiac prostheses generated a thin PNI that was fibrin-rich, a viable cell infiltration, no interfacial degeneration, and endothelial-like cells on its surface.

Aldehydes↗
PubMed1976

Application of aldehyde treatments to cardiovascular devices.

Biolized natural and synthetic materials represent a new class of materials. Aldehyde treatment of natural tissue creates cross-links in the collagen molecules while retaining mechanical strength and collagen structure. Synthetic polymers can also be biolized by the addition of protein and aldehyde treatment. Cross-linked materials such as these are resistant to degradation by proteolytic enzymes. The procedure for the aldehyde treatment of natural tissue and protein polymer composites has been established, and in vivo and in vitro studies have demonstrated an improved blood compatibility. Long-term survival with TAH and LVAD implanted animals has shown the successful application of these materials without the use of anticoagulants. Pseudoneointima growth occurs on these surfaces, and results to date indicate growth stabilization within 2 wks of impalntation. Studies are currently underway to fully characterize the pseudoneointima formed on the biolized surfaces of cardiac prostheses.

Aldehydes↗
PubMed1975

Biodegradable material for bladder reconstruction.

The objective of this study was to develop a biodegradable material for use in reconstructive surgery of the bladder to serve a temporary function until normal regrowth of the host's tissue is completed. The biodegradable material can serve as a base over which the new bladder can regenerate. At the conclusion of the regrowth of the new tissue, the temporary material could be consumed by the body and therefore not have to be removed. Material evaluation showed that 70% acetic anhydride treated bovine pericardium was digested and dissolved in 4 weeks when implanted subcutaneously in dogs. Based upon this, supplementation of the bladder using this material was performed on 5 dogs. One dog showed urinary leakage and was sacrificed after 1 week. In 3 dogs examined 4, 6, and 48 weeks after implantation, respectively, the implanted material had been dissolved. In one animal autopsied at 10.5 months, a small remnant of the material still remained. Post-operative observation of the animals, excretory pyelocystograms and cystometry confirmed that the material applied was useful for experimental urinary bladder supplementation.

Acetates↗