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H Fehrenbach

Publications and source records attributed to H Fehrenbach.

47 records · Page 3Linked to original sources
PubMed1995

Cellular distribution patterns of lanthanum and morphometry of rat hearts exposed to different degrees of ischemic stress.

BACKGROUND: The element lanthanum (La) can be used as a tracer for verification of membrane permeability. The aim of this study was to establish whether 1) distribution of La in the myocardium of rat hearts depends on the degree of ischemic stress and 2) morphometrically determined cell and mitochondrial swelling correlates with the La distribution. MATERIALS AND METHODS: Isolated beating rat hearts were arrested by coronary perfusion with the cardioplegic solution Custodiol (controls) or by aortic cross clamping followed by exposure to different degrees of ischemic stress. The solutions for perfusion-and postfixation as well as for rinsing contained 1.1% La(NO3)3. Cellular and mitochondrial swelling were determined morphometrically and myocytes exhibiting intracellular La were quantified and stated as percentage of test fields. RESULTS: Immediately after cardiac arrest La was present as precipitates only in a few myocytes adjacent to the outer mitochondrial membrane as seen by cTEM and ESI. In such cells La was also detected by EELS in mitochondrial matrix and myofibrils. Advanced ischemic stress led to an increase of the percentage of myocytes containing detectable intracellular La. After 45 min ischemia at 30 degrees C, myocytes and mitochondria showed a remarkable edema and different intracellular distribution patterns of La. After 90 min of ischemia at 20 degrees C interruptions of sarcolemma could only be detected in a few of the swollen myocytes. Roundish La granules were seen in the myofibrils. The percentage of myocytes containing intracellular La and the extent of cellular and mitochondrial swelling showed a significant correlation. CONCLUSIONS: Patterns of intracellular La distribution depend on the degree of ischemic stress and correspond to the degree of cellular as well as mitochondrial edema. These results point at a direct relation between alterations of membrane permeability and development of edema.

Animals↗
PubMed1995

Functional and fine structural changes in isolated rat lungs challenged with endotoxin ex vivo and in vitro.

The aim of this study was to relate changes in rat lung functions caused by the endotoxin lipopolysaccharide (LPS) to alterations in structure. The following four experimental groups were used: 1), control in vitro, perfusion for 150 minutes; 2), LPS in vitro, perfusion for 150 minutes and infusion of 5 mg of LPS after 40 minutes; 3), control ex vivo, perfusion for 10 minutes; and 4), LPS ex vivo, lungs perfused for 10 minutes from rats treated for 110 minutes with 20 mg/kg LPS intraperitoneally. Histologically, blood-derived leukocytes were detectable only in lungs from group 4, where neutrophils were found in capillaries, interstitium, and endothelial pouches. LPS treatment increased pulmonary resistance and decreased pulmonary compliance in group 4 (ex vivo), and, to a greater extent, in group 2 (in vitro). In these two groups, formation of giant lamellar bodies in the type II pneumocytes was observed. By histological examination, the bronchoconstriction induced by LPS in vitro was localized to the terminal bronchioles. At 2 hours after LPS treatment, no edema and no change in precapillary and postcapillary resistance, capillary pressure, vascular compliance, capillary permeability, and the wet/dry ratio was observed. Thus, our major findings are that LPS induced constriction of the terminal bronchioles in vitro, formation of giant lamellar bodies in type II pneumocytes ex vivo and in vitro, and trapping of neutrophils in endothelial pouches in vivo.

Animals↗
PubMed1994

Evaluation of lanthanide tracer methods in the study of mammalian pulmonary parenchyma and cardiac muscle by electron energy-loss spectroscopy.

Lanthanum (La) has widely been used as a tracer to study the integrity of plasma membranes. With conventional transmission electron microscopy (cTEM), the absence of electron scattering deposits from the cytoplasm has generally been assumed to reflect an intact cell membrane. However, the application of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS) reveals that electron scattering deposits may be present which do not contain La. However, La could be detected in regions of pulmonary parenchyma and cardiac muscle that were devoid of electron scattering deposits. Therefore, to exclude misinterpretations based on cTEM the application of microanalytical techniques is strongly recommended for the study of the integrity of plasma membranes by means of La tracers. In addition, ESI and EELS are shown to distinguish between different tracers in simultaneous applications of La and terbium (Tb) which were used at the different faces of the pulmonary air-blood barrier. The analysis of the distribution of both tracers which form electron scattering deposits, indistinguishable by cTEM, may help us to understand the different functional significances of cellular alterations of both cellular borders of the barrier. As was shown for La, however, strictly controlled conditions are mandatory during the fixation procedure because an increase in the incubation time to more than 1 h in samples of pulmonary parenchyma may result in the occurrence of La deposits within the cytoplasm. In the absence of electron scattering deposits, the presence of La in glycogen granules and ribosome-containing areas of various types of alveolar septal cells even after 15 min incubation indicates that the absence of deposits does not necessarily correspond to the absence of the tracer.

Animals↗
PubMed1994

Scanning and transmission electron microscopy of human donor lungs: fine structure of the pulmonary parenchyma following preservation and ischemia.

In six cases of clinical single-lung transplantation, the contralateral donor lungs were studied by means of scanning (SEM) and transmission (TEM) electron microscopy. SEM and TEM revealed an overall good to excellent preservation of the pulmonary parenchyma. Since the donor double lung blocks, which were preserved by means of pulmonary arterial perfusion with modified Euro-Collins solution, were separated immediately prior to transplantation, transplanted and contralateral lungs had been subjected to identical influences. Comparing the arterial oxygenation achieved in the recipient 6 h after transplantation with the structural data of the corresponding contralateral donor lung, the degree of epithelial alterations appeared to be most important in determining postoperative lung function. Concerning the assessment of the quality of the alveolar epithelium, gradings performed independently by means of SEM and TEM yielded largely corresponding scores, while a significant shortcoming of SEM was the very limited access to the endothelial surface. Taking into account the relevance of epithelial injury in determining postoperative lung function, SEM can provide clinically relevant data more quickly than TEM. To quantify the fine structural alterations of human donor lungs, however, TEM-based morphometry is required.

Adolescent↗
PubMed1994

Electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) of multilamellar bodies and multilamellar body-like structures in tannic acid-treated alveolar septal cells.

We used electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) to compare multilamellar bodies (MLB) of Type II alveolar epithelial cells with MLB-like structures that are present in various alveolar septal cells after fixation with tannic acid. Despite their structural similarity in conventional transmission electron microscopy, the phosphorus signal recorded by both ESI and EELS was considerably higher in multilamellar bodies than in MLB-like structures. This indicates that they are different in chemical composition.

Animals↗
PubMed1992

Electron spectroscopic study (ESI, EELS) of Nanoplast-embedded mammalian lung.

The potential of Nanoplast melamine resin embedding for the study of mammalian lung parenchyma was examined by means of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS). Samples were either fixed with glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid, or were directly transferred to the embedding medium without prior fixation. Organic dehydrants, as well as fixatives containing heavy metals and stains, were omitted. A very high level of ultrastructural detail of chromatin, ribosomes, mitochondria and plasma membranes was achieved by ESI from the Nanoplast-embedded samples. The most prominent gain in ultrastructural detail was achieved when moving from an energy loss just below the L2,3 edge of phosphorus at 132 eV to an energy loss just beyond this edge. This reflects the prominent P L2,3 edge observed by EELS of Nanoplast-embedded samples in comparison with conventionally processed samples. Thus, taking into account possible sectioning artefacts, excellent heterochromatin images which rely on the phosphorus distribution can be obtained from Nanoplast-embedded samples by computer-assisted analysis of electron spectroscopic images. In this respect glutaraldehyde-paraformaldehyde fixation is preferable to glutaraldehyde-tannic acid fixation because the presence of silicon, revealed by EELS, in tannic-acid-fixed samples may introduce artefacts in phosphorus distribution images obtained by the three-window method because of the close proximity of the L2,3 edges of silicon and phosphorus.

Animals↗
PubMed1991

Improved preservation of phospholipid-rich multilamellar bodies in conventionally embedded mammalian lung tissue--an electron spectroscopic study.

Different conventional methods of tissue processing were studied to determine the extent to which phospholipid-rich multilamellar bodies of pulmonary alveolar epithelial type II cells of the pig were preserved. Prolonged treatment with half-saturated aqueous uranyl acetate yielded excellent results on the stabilization of the multilamellar substructure, irrespective of whether glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid was used as a primary fixative. The lamellar periodicities were observed to be 5.5-6.1 nm. Differences in the phosphorus distribution among several types of lipid bodies of alveolar epithelial type II cells were studied by means of electron spectroscopic imaging and electron energy-loss spectroscopy. Multilamellar bodies gave phosphorus signals which were significantly higher than those obtained from granular regions of composite bodies, whereas homogeneous bodies gave phosphorus signals which were even lower than those obtained from mitochondria, endoplasmic reticulum membranes or ribosomes.

Animals↗
PubMedDate not supplied

Evaluation of pulmonary edema: stereological versus gravimetrical analysis.

Assessment of lung edema by gravimetrical analysis is a standard method to evaluate the severity of experimentally induced ischemia/reperfusion (IR) injury. The aim of this study was to compare gravimetrical assessment of pulmonary edema with a stereological approach which allows for qualitative and quantitative distinction between intravascular and edematous fluids by light microscopy. Eight experimental groups which differed in mode of preservation, ischemic storage and pharmacological treatments were studied in an extracorporeal rat lung model. Analysis of the pooled data showed that the wet/dry ratio values mainly reflected the amount of intra-alveolar edema (r(s) = 0.442; p = 0.0057) but only stereological assessment of edema formation revealed differences depending on the treatment used. Only stereological data correlated significantly with oxygen tension measured at the end of reperfusion (r(s) = -0.530; p = 0.0009). We conclude that gravimetry is of minor functional importance compared to assessment by stereological methods which prove to be a reliable and efficient tool for the evaluation of IR injury in the different experimental settings.

Animals↗
PubMedDate not supplied

Animal models of chronic obstructive pulmonary disease: some critical remarks.

A variety of animal models of chronic obstructive pulmonary disease (COPD) are available, comprising elastase instillation or inhalation of noxious agents and genetic models like mouse mutants, gene-targeted and transgenic mice. The present review discusses some critical aspects which should be taken into account when evaluating these animal models of human COPD. Critical aspects related to the human disease itself: (1) diagnosis is largely symptom based, and symptoms cannot be mimicked in animals; (2) COPD is not a well-defined entity, but comprises patients with variable contribution of chronic bronchitis, mucus hypersecretion and emphysema, and (3) various factors contribute to the development of COPD, indicating that different pathways may converge into a single endpoint. Critical aspects related to the animals used: (1) species-, strain- and gender-related differences in lung structure and function preclude mimicking some features of the human disease; (2) genetic models frequently present with air space enlargement as a result of the disturbance of early postnatal alveolization (conditionally controlled transgenic animals are recommended); (3) inhalation models frequently use young animals during lung growth, which may preclude distinguishing effects owing to growth retardation or to loss of existing alveolar walls; (4) inhalation of noxious agents may result in reduction of food intake and loss of body weight, which itself may result in emphysema, and (5) the presence of emphysema cannot be concluded based on measurement of air space enlargement alone, but should include the determination of total alveolar surface area.

Animals↗
PubMedDate not supplied

Euro-Collins flush perfusion in human lung preservation--ultrastructural studies of the preservation quality of the contralateral donor lung in clinical single lung transplantation.

The quality of pulmonary preservation after Euro-Collins flush perfusion was assessed by means of morphometric analysis based on transmission electron microscopy. In five patients undergoing single lung transplantation, the contralateral donor lung that could not be matched for another recipient was studied by means of light microscopy and transmission electron microscopy. While one of the donor lungs was transplanted, the contralateral lung was fixed by airway instillation at the same time and subsequently processed for microscopic examination. Although light microscopy showed an excellent quality of organ preservation, transmission electron microscopy revealed the presence of fine to medium alterations at the level of the air-blood-barrier. In the five contralateral donor lungs, different degrees of the cellular alterations were recorded by morphometric analysis, which correlated with differences observed in the early postoperative course of the patients receiving the other lung, respectively. Although in four of five patients the clinical course showed no complications and extubation was performed within 36 hours after the operation, one patient required artificial ventilation over a period of 10 days because of impaired oxygenation of the transplanted lung. In this patient, morphometric analysis of the air-blood-barrier showed a significantly (p < 0.02) smaller surface fraction of normal type 1 pneumocytes, a significantly (p < 0.05) smaller volume density of the capillary endothelial cells, and a significantly (p < 0.01) higher volume density of type 2 pneumocytes. The alterations of the alveolar epithelium have to be interpreted as a result of influences occurring during the donor's medical history rather than being an effect of preservation and/or ischemia.

Adolescent↗