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Biomedical subjects

Gregor Zünd

Publications and source records attributed to Gregor Zünd.

7 recordsLinked to original sources
PubMed2004

Validation of Intracoronary Shunt Flow Measurements for Off-Pump Coronary Artery Bypass Operations.

Abstract Introduction: Intracoronary shunting is a useful, easy and inexpensive technique to maintain blood flow during off-pump surgery to lessen myocardial ischemia. Intracoronary shunts should provide a minimal flow for adequate myocardial protection. Material and Methods: Two commercially available shunts were used to measure flow from a bulb-size diameter of 1.00 mm to 3.00 mm (n = 10) in an in vitro setup. Shunts were perfused with Glycerin 47% solution at 37 degrees C. Inlet pressure was raised continuously from 0 to 160 mmHg in all intracoronary shunts. Results: In both groups (recipients of either type A shunt or type B shunt), mean pressure of 40 mmHg was necessary in shunts with diameter of 3.0 mm to provide a flow of approximately 50 mL/min. At mean pressure of 100 mmHg, a maximum flow of 126 mL/min was measured. Shunt B of 2.5-mm and 3.0-mm diameter showed similar flow patterns: 50 versus 52 mL/min at 40 mmHg and 98 versus 108 mL/min at 100 mmHg. Shunt A at 2.5-mm diameter showed 37 mL/min at 40 mmHg and 80 mL/min at 100 mmHg ( P =.01). Shunt B at 1.5-mm diameter required 75 mmHg for approximately 40mL/min and showed maximum flow of 51 mL/min at 100 mmHg ( P <.001). Only minimal flow was measured in 1.0-mm shunts of both groups. Conclusions: There is a clear pressure/flow correlation in 2.0-mm to 3.0-mm shunts with maximum flow of 126 mL/min. Type B shunt of 1.5-mm and 2.5-mm diameter showed significant better flow rates. The possible value of 1.0-mm shunts is only in stenting and facilitating anastomosis and to obtain better visibility during anastomosis.

Journal Article↗
PubMed2003

Hypoxia and reoxygenation do not upregulate adhesion molecules and natural killer cell adhesion on human endothelial cells in vitro.

OBJECTIVES: Ischemia/reperfusion injury is characterized by endothelial cell activation leading to increased expression of adhesion molecules such as inter-cellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, endothelial- and platelet-selectin (E- and P-selectin), and to the subsequent recruitment of leukocytes. The aim of the present study was to investigate the respective effects of a proinflammatory cytokine (tumor necrosis factor alpha, TNF-alpha), hypoxia and/or reoxygenation on adhesion molecule expression and natural killer (NK) cell adhesion in an in vitro model of I/R. METHODS: Human aortic endothelial cells (HAEC) were stimulated in vitro for 8h with TNF-alpha (1000 U/ml) and exposed to hypoxia (1% O(2)), reoxygenation (21% O(2)) or different combinations thereof. Cell surface expression of ICAM-1, VCAM-1 and E-/P-selectin on HAEC was analyzed by flow cytometry, and culture supernatants were tested for soluble adhesion molecules by ELISA. Rolling adhesion of NK cells on HAEC was determined using a rotating assay. RESULTS: Untreated HAEC constitutively expressed ICAM-1 on their surface but neither expressed E-/P-selectin, VCAM-1, nor shedded soluble adhesion molecules. Exposure of HAEC to hypoxia or hypoxia and reoxygenation did not upregulate cell surface expression or shedding of adhesion molecules. In contrast, TNF-alpha significantly upregulated cell surface expression of ICAM-1, VCAM-1, and E-/P-selectin and led to the shedding of ICAM-1 and E-selectin. Combined treatment of HAEC with TNF-alpha, hypoxia and reoxygenation reduced E-/P-selectin surface expression and enhanced E-selectin shedding, but did not further influence ICAM-1 and VCAM-1. Soluble VCAM-1 was not detected. NK cell adhesion on HAEC increased 4-fold after TNF-alpha stimulation, but was not affected by hypoxia or hypoxia and reoxygenation. CONCLUSIONS: Both the expression of endothelial adhesion molecules and rolling NK cell adhesion was upregulated by TNF-alpha but not by hypoxia alone or hypoxia followed by reoxygenation supporting the view that anti-inflammatory treatment may reduce ischemia/reperfusion injury.

Aorta↗
PubMed2003

Tissue engineered cartilage generated from human trachea using DegraPol scaffold.

OBJECTIVE: To date numerous attempts have been undertaken to conquer the challenging problem of reconstructing long segmental tracheal defects, as yet without lasting success. Recently, employing concepts of tissue engineering in animals, cartilage-like constructs were transplanted in vivo. However, both the feasibility of fabricating tracheal replacements and the use of human tracheal chondrocytes (HTC) for tissue engineering are still under investigation. In this study, we optimized isolation and cultivation techniques for human tracheal cartilage, assessing the feasibility of seeding these cells onto a novel, three-dimensional (3-D) polyester-urethane polymer (DegraPol). METHODS: Human tracheal cartilage was harvested from the trachea of lung donors, digested in 0.3% collagenase II, and the condrocytes serially passaged every 7-9 days. Cells were also cultivated over agar plate during the total 6-8 weeks expansion phase. Thereafter, chondrocytes were seeded onto DegraPol (pore sizes 150-200 microm) with a seeding density of 2.4 x 10(7)/ml, and chondrocyte-polymer constructs maintained during in vitro static culture. RESULTS: HTC displayed stable proliferation kinetics in monolayer culture with positive expression of collagen type II. Following polymer seeding, both cellular proliferation and extracellular matrix (ECM) production, as measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and glycosaminoglycan assays, continued over extended culture. Active growth of HTC on DegraPol was further demonstrated by Alcian blue staining, with the histomorphological appearance of the construct resembling that of native cartilage. Scanning electron microscopy showed chondrocyte growth and ECM synthesis both on the surface and inside the porous scaffold, with a dense cell layer on the surface of the scaffold and a lower cell distribution in the scaffold's interior. CONCLUSIONS: The harvested chondrocytes from human trachea cartilage expand well in vitro and possess the ability to form new cartilage-like tissue when seeded onto DegraPol matrix. However, improved culture conditions are needed to permit cellular growth throughout cell-polymer constructs.

Absorbable Implants↗
PubMed2003

A single bicaval venous cannula used for optimization of endoscopic robotically assisted procedures of the heart.

Robotically assisted heart operation is one of the minimally invasive approaches that have revolutionized many surgical procedures. Robotic procedures on the heart, however, are by no means routine, and their optimization requires development of new instruments and techniques. Described here is the robotically assisted use in a sheep model of a new peripherally inserted bicaval venous cannula in the totally endoscopic closure of atrial septal defect. The exposure of the surgical target area was successful with no obstructions in the surgical view. The cannula shows sufficient flow characteristics for cardiopulmonary bypass. Subsequent suturing of the atrial septum defect was achieved without complications in the 4 experimental animals.

Animals↗
PubMedDate not supplied

Increased susceptibility of the left compared to the right ventricle to remote ischemia/reperfusion injury in human C1-inhibitor-overexpressing transgene mice.

Acute myocardial injury has been demonstrated as a remote sequela of severe lower torso ischemia-reperfusion (I/R) due to proinflammatory events. In a model of I/R injury, administration of C1 esterase inhibitor (C1-Inh) reduces myocardial necrosis. We investigated the susceptibility of the left (LV) versus right ventricle (RV) and the protective effect of transgenic C1-Inh-overexpressing mice. Two groups of mice (n = 6) underwent a 2-h lower torso ischemia followed by 3 h of reperfusion: transgenic and wild type with sham-operated controls. Animals were then injected with (125)I bovine albumin. Heart was removed and samples from right and left ventricular free wall were harvested, weighted, and radioactivity was determined. Permeability index for wild-type animals in the RV was 0.22 +/- 0.04, compared to 0.17 +/- 0.07 in controls (NS), and in the LV 0.36 +/- 0.08, compared to 0.21 +/- 0.05 in controls (p <.01). The LV showed a significantly higher value compared to the right (0.22 +/- 0.04 vs. 0.36 +/- 0.08, p <.01). No difference was seen in the RV between transgenic and wild-type mice; however, in the LV the values decreased significantly in transgenic animals (p <.015). Thus, remote myocardial injury after lower torso I/R is present in both ventricles; however, the LV seems to be more susceptible as assessed by albumin permeability. Inhibition of the classic complement cascade may be a promising therapeutic approach for myocardial protection in reperfusion injury.

Acute Disease↗
PubMedDate not supplied

A new approach to completely autologous cardiovascular tissue in humans.

In cardiovascular tissue engineering, synthetic or biologic scaffolds serve as templates for tissue development. Currently used scaffolds showing toxic degradation and immunogenic reactions are still far from ideal. We present a new alternative method to develop completely autologous human tissue without using any scaffold materials. Human vascular cells of arterial and venous origin were cultured to form cell sheets over a 4 week period under standard conditions. Thereafter, cell sheets of each origin were folded and cultured in a newly developed frame device for an additional 4 weeks. Controls remained under standard culture conditions. Tissue development was evaluated by morphology and biochemical assays. The formation of multilayered cell sheets and production of extracellular matrix were observed in all groups. Folded and framed neo-tissue showed a solid structure, with increased matrix formation and tissue organization when compared with the control groups. DNA content indicated significantly lower cell proliferation, and hydroxyproline assay indicated significantly higher collagen content in the framed cell sheets. We present a new approach to the engineering of cardiovascular tissue without the use of biodegradable scaffold material. Three-dimensional, completely autologous human tissue may be developed on the basis of this structure, thus avoiding scaffold induced toxic degradation or inflammatory reaction.

Blood Vessels↗