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Biomedical subjects

J Sauter

Publications and source records attributed to J Sauter.

13 recordsLinked to original sources
PubMed1997

Fluid dynamics of the CarboMedics kinetic bileaflet prosthetic heart valve.

OBJECTIVE: To compare hydrodynamic characteristics of a new bileaflet heart valve, the CarboMedics kinetic cardiac valve prosthesis, with those of a St. Jude Medical (SJM) heart valve. METHODS: Hydrodynamic characteristics were determined in the mitral and aortic positions of a Vivitro Systems pulse duplicator for size 23 Kinetic aortic values, size 23 SJM aortic valves, size 29 Kinetic mitral valves and size 29 SJM mitral valves. Test conditions were 72 beats per min with cardiac outputs of 2, 5 and 7 l/min. Values of forward flow pressure drop (delta P), regurgitant and energy loss were determined for each valve. The test results for the two valve designs were compared by valve size. RESULTS: The test results show that both the size 23 and size 29 Kinetic valves have 8-14% lower delta P values and 5-10% greater effective orifice area (EOA) values. The size 29 Kinetic mitral valve has a 1-2 ml lower regurgitant volume, while the size 23 Kinetic aortic valve has a 0.5 ml greater regurgitant volume than the corresponding SJM values. These factors combine to provide a 5-10% lower energy loss for size 23 Kinetic aortic valves and a 15-25% lower energy loss for size 29 Kinetic mitral valves over the cardiac cycle than for corresponding sizes of SJM valves. CONCLUSIONS: The Kinetic valve's fluid dynamics are superior to equivalent sizes of SJM valves. This is especially impressive considering that the tissue annulus diameters for Kinetic valves are approximately 0.5 mm less than equivalent size SJM valves. The primary reasons for the superior hydrodynamic performance of Kinetic valves are (1) the larger orifices which result in lower forward flow delta P values and (2) the opening angles, which have been customized for each valve size to minimize energy loss.

Aortic Valve↗
PubMed1997

Effects of near-lethal heat stress on bud break, heat-shock proteins and ubiquitin in dormant poplar (Populus nigra Charkowiensis x P. nigra incrassata).

We assessed the effects of near-lethal heat stress on bud break, heat-shock proteins (HSPs) and ubiquitin in hybrid poplar (Populus nigra (L.) Charkowiensis x P. nigra (L.) incrassata). Shoots, with 10-15 buds each, were collected from September to March and exposed to temperatures between 20 and 60 degrees C for 2 h. Shoots were then placed in a greenhouse at 18-22 degrees C with supplemental light and cumulative bud break was recorded over a 4-week period. Samples of bud tissues were collected during and up to 96 h after heat treatment for protein analysis. De novo synthesis of proteins was monitored by exposing excised buds to [(35)S]-methionine for 3 h before, during, or after heat treatment. Heat treatments of 40-45 degrees C resulted in both a release from endodormancy and a decrease in thermal units needed for bud break during ecodormancy. The response to near-lethal heat stress was complex and was affected by intrinsic thermal sensitivity. Heat treatments were least effective during August and became progressively more effective as endodormancy progressed. In the later stages of ecodormancy, a heat treatment of 45 degrees C either inhibited bud break or killed the buds. Although temperatures of 42.5 to 45 degrees C inhibited incorporation of [(35)S]-methionine into proteins for at least 48 h, several HSPs were synthesized in response to temperatures of 40-45 degrees C. Immunoblots indicated that one of the heat-induced proteins was immunologically related to HSP70. Increases in free and conjugated forms of ubiquitin were also observed in response to heat treatment. Production of HSPs and ubiquitin, however, was not consistently associated with the heat treatments that induced the highest percentage of bud break. The roles of heat-induced protein degradation, HSPs, and ubiquitin in overcoming dormancy by near-lethal heat stress are discussed.

Journal Article↗
PubMed1992

On the use of isofluorane as an anaesthetic for visual neurophysiology.

The use of the anaesthetic isofluorane (Forene, Deutsche Abbott) for unit cell recordings from the monkey striate cortex is considered. Two aspects are emphasised; the maintenance of sustained components of response and the stability of vegetative physiology under isofluorane anaesthesia. A comparison of the use of isofluorane with halothane is made. The similar physical constants of isofluorane and halothane allow the easy adaptation of conventional delivery systems to use with isofluorane, when allowance is made for differences in anaesthetic strength.

Anesthesia, General↗
PubMed1988

Prophylactic extradural blood patch is effective. A preliminary communication.

Ten obstetric patients received 17-20 ml of autologous blood through an extradural catheter after inadvertent dural puncture. The time interval from dural puncture to prophylactic extradural blood patch ranged from 90 to 660 min. One of the 10 patients developed a mild occipital headache, which required no further intervention.

Anesthesia, Epidural↗
PubMed1987

Quantitative determination of acyl chain composition of subnanomole amounts of cellular long-chain acyl-coenzyme A esters.

A procedure for the quantitative determination of the acyl chain composition of cellular long-chain acyl-CoA esters in subnanomole amounts is described. The abundant cellular lipids of samples are removed by extraction with organic solvents, and the proteins are precipitated from the aqueous phase by the addition of acetonitrile. The CoA thiolesters are adsorbed on neutral aluminum oxide and reduced with sodium borohydride to the corresponding alcohols that are then converted to t-butyldimethylsilyl ethers and analyzed quantitatively by gas chromatography. Saturated and unsaturated acyl chains behaved similarly throughout the procedure, and the common lipid esters do not interfere with the analysis of the CoA esters in the final assay procedure described. This simple and relatively rapid method is suitable for analyzing a large number of samples at a time.

Acyl Coenzyme A↗
PubMed1983

Oriented axon outgrowth from avian embryonic retinae in culture.

The neural retina of avian embryos was spread on a membrane filter and cut in any desired orientation. Strips cut across the retina of 4- to 7-day chick or 3- to 6-day quail embryos were explanted onto collagen gels. Vigorous neurite outgrowth was seen for about 3 days, by which time many neurites were 3 mm long. Horseradish peroxidase (HRP) labeling showed that the cells producing the neurites were large and formed a layer near the inner limiting membrane, indicating that the neurites in vitro were axons of retinal ganglion cells. The size of the neurite population and the regions from which neurites emerged varied with the donor age, while most neurites sprouted from the side of the explant formerly closest to the optic fissure. This pattern closely resembled that of axon growth in the normal retina, as revealed by SEM, silver staining, and HRP labeling. Mitotic inhibitors (Ara-C and FUdR) did not alter the neurite outgrowth. Pretreatment of retinae with trypsin or collagenase did not disorganize axons at the time of explanation, but tended to equalize neurite emergence on each side of the retinal strips. We suggest that microenvironmental factors, especially the enzyme-labile inner limiting membrane, are important for axon guidance in the retina.

Animals↗
PubMed1982

Ultrastructural and tissue-culture studies on the role of fibronectin, collagen and glycosaminoglycans in the migration of neural crest cells in the fowl embryo.

The initial migration of neural crest (NC) cells into cell-free space was studied by transmission electron microscopy at trunk levels of fowl embryos, some of which were fixed in the presence of ruthenium red. Migrating NC cells occurred in zones which contained fewer ruthenium-red stained 15-40nm diameter granules than other regions. The ruthenium-red stained granules were linked by similarly stained thin (greater than 3nm diameter) microfibrils. The granules resemble proteoglycan and the microfibrils may be hyaluronate. NC cells contacted thicker (greater than 10 nm diameter) fibrils and interstitial bodies, which did not require ruthenium red for visualization. Cytoplasmic microfilaments were sometimes aligned at the point of contact with the extracellular fibrils, which may be fibronectin and collagen. Phase-contrast time-lapse videotaping and scanning electron microscopy showed that NC cells of the fowl embryo in vitro migrated earlier and more extensively on glass coated with fibronectin-rich fibrous material and adsorbed fibronectin molecules than on glass coated with collagen type I (fibres and adsorbed molecules). NC cells became completely enmeshed in fibronectin-rich fibres, but generally remained on the surface of collagen-fibre gels. When given a choice, NC cells strongly preferred fibronectin coatings to plain glass, and plain glass to dried collagen gels. NC cells showed a slight preference for plain glass over glass to which collagen was adsorbed. Addition to the culture medium of hyaluronate (initial conc. 20 mg/ml), chondroitin (5 mg/ml) and fully sulphated chondroitin sulphate and dermatan sulphate (up to 10 mg/ml) did not drastically alter NC cell migration on fibronectin-rich fibrous substrates.

Animals↗
PubMed1978

Oxygen requirement for prostaglandin biosynthesis.

The formation of prostaglandins by vesicular gland cyclooxygenase can be regulated by O2 concentrations below 30 micron (20 mm Hg) with an apparent Km value of about 5 micron. This result suggests that most mammalian tissues might be expected normally to have sufficient O2 for some synthesis, and that only occasionally, would the level of oxygen available within some tissues become marginally inadequate to sustain a high rate of prostaglandin biosynthesis.

Animals↗