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Biomedical subjects

R Guggenheim

Publications and source records attributed to R Guggenheim.

46 records · Page 3Linked to original sources
PubMed1976

Changes in alveolar capillary configuration at different levels of lung inflation in the rat. An ultrastructural and morphometric study.

Changes in alveolar capillary configuration during positive pressure lung inflation were investigated by transmission and scanning electron microscopy as well as by morphometric methods. As the airway pressure was raised, an increasing number of alveoli expanded. However, in fully inflated or overinflated lungs, a few collapsed areas persisted. In such areas, the air-blood tissue barrier was folded into the capillary space, dividing it into intercommunicating chambers. In expanded alveoli, the capillaries appeared as a continuous space delimited at each side by a tissue leaflet. This space was crossed by tissue bridges consisting of the thick portion of air-blood barrier. In overinflated lungs, the capillary space was compressed between the alveoli and thus collapsed. Our findings suggest that the thin porne. The variations of the capillary configuration seem to be determined either by "passive" deformations or by compression of the alveolocapillary membrane, or as a result of contraction of interstitial cells which are located in the thick portion of the air-blood barrier and are attached to the basement membranes of two adjacent alveoli. The relationship between alveolar dynamics and capillary configuration is considered to be a basic factor in ventilation/perfusion auto-regulation.

Animals↗
PubMedDate not supplied

Demonstration of albumin receptors on isolated human hepatocytes by light and scanning electron microscopy.

The presence of albumin receptors on the plasma membrane of isolated human hepatocytes was investigated employing albumin-coupled latex minibeads. Hepatocyte-latex reaction was visualized by phase contrast and scanning electron microscopy. The experiments demonstrate that hepatocytes exhibit binding activity for polymeric and monomeric forms of glutaraldehyde-treated albumin. Additionally, the reaction was shown to be species-nonspecific. These findings support the hypothesis that polymerized albumin may act as a bridge between receptors on hepatitis B virus and human hepatocytes.

Cell Membrane↗
PubMedDate not supplied

Electron microscopy of isolated human hepatocytes. (Micromethods for scanning and transmission electron microscopy).

We have investigated, by scanning and transmission electron microscopy (SEM and TEM), the cell surface morphology of isolated human hepatocytes. For this purpose, liver cells were mechanically isolated from surgical or needle liver biopsies, fixed in 3% glutaraldehyde and post-fixed in 2% osmium tetroxide. In order to handle a low number of cells, a particular procedure for harvesting hepatocytes on coverslips has been developed for SEM and an in situ embedding procedure in polyethylene-embedding capsules was applied for TEM. A rough membrane exhibiting short, uniform microvilli and pores of 0.1 mu in diameter was the main feature of isolated liver cells. Furthermore, single hepatocytes showed no polarity and junctional or bile canaliculus remnants were rarely observed. However, differences in surface configuration were noted in relation to culture conditions, such as oxygen and temperature during isolation procedures. SEM, when controlled by TEM for intracellular preservation, is proposed as a reliable method for screening small quantities of hepatocyte suspensions, for intact cells and for the study of surface configuration under experimental conditions.

Cells, Cultured↗
PubMedDate not supplied

Evaluation of the interface between one-bottle bonding agents and dentin by cryopreparation and low-temperature scanning electron microscopy (LTSEM). A pilot study on perfused dentinal samples.

OBJECTIVES: Dentin bonding samples are generally observed in the high vacuum chamber of an electron microscope only after completion of the bonding procedure fixation, dehydration and drying of the specimens. The purpose of this study was to observe the effect of each step in the application of various one-bottle dentin bonding agents (DBA) using cryopreparation followed by low-temperature scanning electron microscopy (LTSEM). METHODS: Prime&Bond 2.1 (P&B 2.1), Coltène Experimental (Exp.) and Syntac Single Component (Syntac SC) were applied onto perfused dentin of extracted, human third permanent molar teeth. After acid-etching, rinsing and drying, and following the application of the respective resins, the teeth were fractured at random and plunge-frozen in liquid nitrogen before examination under LTSEM. As this method preserves the state of the treated surface at the moment when it is frozen, each step of the application of the DBA can be observed as if it were a 'real-time' procedure. RESULTS: Acid-etching the dentin resulted in the removal of the smear layer for all materials tested. Those one-bottle DBAs which recommend the application of two consecutive resin layers (P&B 2.1 and Syntac SC) showed incomplete saturation of the dentinal surface after application of the first layer. With Syntac SC the incomplete saturation was more pronounced than with P&B 2.1. The use of Exp. resulted in a much more homogeneous coverage of the dentin despite only one layer of resin having been applied. CONCLUSION: It is concluded that cryo-preparation followed by LTSEM appears to be a method which allows each stage of the application of DBA to be evaluated.

Acid Etching, Dental↗
PubMedDate not supplied

Marginal adaptation of titanium frameworks produced by CAD/CAM techniques.

This study evaluated the Digitizing Computer System (DCS Production) for computer-controlled fabrication of titanium copings. The three-dimensional shape of the crown preparations was acquired through micropalpation with a contact digitizer on the master cast. In this in vitro study the marginal fit of computer-machined titanium frameworks for veneered crowns was assessed using scanning electron microscopy. Measurement of the marginal gap between the framework and the tooth was performed along the entire length of the finish line. The evaluation was based on 1,475 individual measurements on 10 test specimens. The mean values of marginal fit for the individual crowns ranged from 21.2 +/- 14.6 microns to 81.6 +/- 25.1 microns. The mean value for all crowns was 47.0 +/- 31.5 microns.

Computer-Aided Design↗