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P Gehr

Publications and source records attributed to P Gehr.

At least 73 records · Page 4Linked to original sources
PubMed1981

Design of the mammalian respiratory system. V. Scaling morphometric pulmonary diffusing capacity to body mass: wild and domestic mammals.

This paper utilizes a comparative approach to establish the relationship between morphometric diffusing capacity for oxygen (DLo2) and maximal oxygen consumption (Vo2max). DLo2 and Vo2max were determined on the same 21 individuals in African mammals spanning a range in body mass from 0.4 to 240kg. We confirmed earlier findings that Dlo2 was proportional to Mb0.99 while Vo2max was proportional to Mb0.79. Thus, the ratio of Dlo2/Vo2 is approximately proportional to Mb0.20. We conclude that large animals require a larger pulmonary diffusing capacity to transfer oxygen at the same rate from air to blood.

Aerobiosis↗
PubMed1981

Design of the mammalian respiratory system. VII. Scaling mitochondrial volume in skeletal muscle to body mass.

Since O2 is mainly consumed in muscle mitochondria during heavy physical work, one would expect to find a relationship between the volume density of mitochondria in skeletal muscles and maximal O2 uptake. We analyzed the volume density of mitochondria, Vv(mt,f) in four muscles of a series of African mammals ranging in body mass from 0.4 to 251 kg. Vv(mt,f) scaled as Mb-0.231, Mb-0.163, Mb-0.139 and Mb-0.055 in Mm. semitendinosus, longissimus dorsi, vastus medialis and diaphragm, respectively. The mass or volume of diaphragm was found to scale as Mb0.865, whereas for Mm. semitendinosus and vastus medialis, muscle volume (Vmu) scaled as Mb1.030 and Mb0.956 respectively. Scaling the absolute volume of mitochondria Vmt, in these muscles (Vmt = Vv (mt,f) x Vmu) against Mb gives regression lines whose slopes closely parallel that obtained for Vo2max against body mass. Therefore the ratio of volume of mitochondria in these muscles to Vo2max is body mass independent.

Africa↗
PubMed1981

Design of the mammalian respiratory system. IX. Functional and structural limits for oxygen flow.

This paper presents the synthesis and interpretation of a series of correlated studies of the mammalian respiratory system--measurements of maximal rate of O2 consumption, the lung's diffusing capacity, the mitochondrial volume, and the capillary number and length in skeletal muscle. It discusses the results with respect to the principle of symmorphosis, i.e. of morphogenesis adapted to functional needs. We find that the accumulated evidence supports this principle at all organizational levels considered, although the models used for structure-function correlation need further refinement.

Aerobiosis↗
PubMed1981

Comparison of two subsampling methods for electron microscopic morphometry.

The purpose of the present paper is twofold. Firstly, to compare the accuracy per unit cost achieved by two different methods of subsampling micrographs from sections of a material for stereology when the sections cannot be analysed as a whole at the required magnification. Secondly, to illustrate, by means of real data, the application of some of the methods and formulae proposed in the companion paper (Cruz-Orive & Weibel, 1981) for estimating ratios at the electron microscopic level. The final estimates of a same ratio obtained by either subsampling method (namely systematic (SQ) and systematic area-weighted quadrats (SAWQ)) agreed in the mean and they were about equally precise. The former fact indicates that the new SAWQ method is at least as reliable as the SQ method as far as bias is concerned. The latter result is a consequence of the well-known fact that subsampling is relatively unimportant in two-stage sampling. Yet, SAWQ subsampling enjoys definite practical advantages over other subsampling methods in certain situations.

Anatomy↗
PubMed1980

The lung of shrews: morphometric estimation of diffusion capacity.

The lungs of 16 shrews from 8 species (Sorex minutus, Neomys fodiens, Suncus etruscus, Crocidura russula, C. juvenetae, C. poensis, C. flavescens, C. giffardi) ranging in body weight from 2.2 to 100 g were studied by morphometry in order to compare the structural diffusion capacity for oxygen. DL02, with the oxygen consumption, VO2, measured on the same animals. VO2 was determined by short term measurements using a respirometer. DLO2 was estimated morphometrically. Both parameters demonstrated good coincidence in their allometric behaviour, establishing further progress in structure-function relationship in the respiratory apparatus. Whereas VO2 as well as DLO2 of shrews with a body weight W greater than 5 g follow the same allometric function established for mammals in general, the values for shrews with W less than 5 g exhibit significantly higher values. It appears that the pulmonary gas exchange parenchyma of these smallest mammals is well suited to supply the organism with the comparatively high levels of O2 required by the high metabolic rates, exhibiting a structural adaptation of the lung to higher VO2.

Animals↗
PubMed1980

Morphometric estimation of pulmonary diffusion capacity in two horse lungs.

The lungs of two half-bred geldings were fixed in situ by instillation of a glutaraldehyde solution into the airways during deep anaesthesia. The body weight of both animals was 510 kg and their average lung volume about 38 l. Stratified random samples from 22 regions were morphometrically analysed from electron microscopic films. Eighty-six per cent of the total lung volume was gas exchange parenchyma. It contained 26.9 l air space and 5.6 l interalveolar septa which were composed of equal parts of capillaries and tissue. The average alveolar and capillary surface areas were 2457 m2 and 1663 m2, respectively. The arithmetic mean thickness of the air-blood tissue barrier was estimated at 1.37 micron; the harmonic mean thicknesses were 0.60 micron for the tissue barrier and 0.21 micron for the plasma barrier. From these morphometric data, total pulmonary diffusion capacity for oxygen was calculated. We obtained a maximal value of 3.55 l/min x mm Hg and a minimal value of 1.75 l/min x mm Hg. The above values are averages for the whole lung. However, there are considerable regional differences between the apical and diaphragmatic lobes and almost none between dorsal and ventral areas. The volume density of alveoli was 9% larger in the apical than in the diaphragmatic lobes. Conversely, the volume density of the capillaries was 54%, and the surface density of alveoli 16% smaller in the apical than in the diaphragmatic lobe.

Animals↗
PubMed1980

[Histologic investigations of PTFE-surface acting for direct tissue contact on implants (author's transl)].

Generally, implants give rise to toxic reactions and favour the formation and propagation of local infections. Adherance of the soft tissue to the implant prevents the development of fluid filled cavities, thus being of particular interest as a prophylactic measure in arresting spread of infections. Teflon cylinders with an etched surface have been investigated by optical and electron microskopic means following subcutane implantation in mice. We were able to demonstrate closed tissue contact. Signs of toxic tissue reactions were completely absent.

Animals↗
PubMed1979

Alterations of mechanical properties and morphology in excised rabbit lungs rinsed with a detergent.

To assess the influence of alterations of lung surfactant on the geometry of peripheral air spaces, the morphology of detergent-rinsed rabbit lungs was studied. In comparison to normal excised rabbit lungs, fixed in the same manner by vascular perfusion at different points on the deflation pressure-volume curve, the most important differences are as follows. 1) With decreasing lung volume there is a progressive collapse of alveoli; at low lung volume (40% of total lung capacity (TLC) (most alveoli are collapsed, and the air is contained in overextended ducts. 2) Accordingly, the alveolar surface area-to-volume ratio is considerably smaller in particular at medium and low lung volumes. 3) There is only a slight change of mean air-space curvature between 80 and 40% TLC. Hence, the results indicate that in detergent-rinsed lungs volume changes are brought about predominantly by recruitment and derecruitment of alveoli. It appears that both a normal surfactant and the mechanical interdependence within the fibrous continuum are required to maintain a normal respiratory surface area within the lung volume range of normal breathing.

Animals↗
PubMed1979

Alveolar volume-surface area relation in air- and saline-filled lungs fixed by vascular perfusion.

The influence of volume changes and interfacial forces on the geometry of peripheral air spaces was studied in excised rabbit lungs inflated with either air or saline and fixed by vascular perfusion at four points of the deflation limb of the pressure-volume curve corresponding to 100, 80, 60, and 40% of the total lung capacity (TLC). In air-filled lungs pleating and folding of alveolar septa were observed, especially in alveolar corners. However, the alveolar surfaces were smooth, except at low lung volumes where some surface crumpling occurred. In saline-filled lungs pleats were absent; the alveolar surface was irregular at all inflation levels due to undulating walls and bulging capillaries. Morphometry indicated that at all alveolar volumes (VA) the surface areas (SA) were larger in saline- than air-filled lungs. No simple mathematical function was found to characterize the relation between SA and VA over the entire volume range studied. Within the range of normal breaths (80 to 40% TLC) the best fit for n in the function SA = k.VnA was 0.58 for saline-filled lungs (r = 0.93) and 0.33 for air-filled lungs (r = 0.68), suggesting different and complex deflation patterns.

Animals↗
PubMed1978

Adaptation of the growing lung to increased Vo2: III. The effect of exposure to cold environment in rats.

This study was undertaken to further test the hypothesis that increased Vo2 operates as a stimulus for enhanced lung growth leading to a pulmonary diffusing capacity adapted to the body's O2 requirements. Vo2 was augmented by raising 4-week-old rats for 3 weeks at 11 degrees C ambient temperature, with controls kept at 24 degrees C; this led to an increase in Vo2 averaged over 24 h by 64%. In contrast to previous experiments with waltzing mice this regime did not affect body growth, as the final body weights were identical in both groups. In the cold-exposed rats the lung volume was larger by 24%, due to an increase by 26% in air volume (at about TLC), 13% in capillary blood volume and 19% in tissue volume. The alveolar and capillary surface areas were increased by 18%, and Dm and Dl by 17% and 21% respectively. It is concluded that the hypothesis of adaptation of pulmonary gas exchange capacity to increased Vo2 cannot be rejected. Whilst in previous experiments some doubts had to be retained as to the specificity of the stimulus, because of its rather marked effect on body weight, this reservation does not hold in this case. The structural modifications which lead to increased Dl in the various experimental models are discussed.

Adaptation, Physiological↗
PubMed1977

Adaptation of the growing lung to increased oxygen consumption. II. Morphometric analysis.

This paper is the second part of a study investigating the effect of increased O2 consumption on the lungs of growing animals. By means of injections of the drug IDPN (imino-betabeta'-dipropionitrile) hyperkinesia was permanently induced in white mice aged 3 weeks, thus increasing their Vo2 per gram body weight (= specific VO2) by 50%. 3 1/2 months later the lungs of these animals were fixed by standardized procedure, analysed by morphometric techniques and the results compared with those of control mice originating from the same litters. Whereas the specific weights (= weights per gram body weight) of various organs did not differ significantly in the two groups, the specific volume of the lungs fixed with standardized techniques was up by 23% in IDPN mice. The relative composotion of lung parenchyma was also altered: air space volume density was slightly but significantly reduced, whereas tissue and capillary volume densities were both increased by 15%. An analogous increase was detected in alveolar and capillary surface densities. These changes led to significantly higher specific capillary and tissue volumes, as well as higher specific gas exchange surface areas in DIPN mice. Therefore the morphometrically determined specific pulmonary diffusion capacity was increased by more than 40% in the IDPN-treated animals. The findings are compared with those hitherto reported, where a structural adaptation of the gas exchange apparatus to exercise or altered PO2 had been found. In view of our present knowledge of the postnatal lung growth the quantitative structural alterations found in this experiment indicate that the higher O2 requirements in IDPN mice induced an alteration in the septal morphology. This consisted in an augmentation of septal volume possibly due to a lengthening and corrugation of the intralveolar septa. This change is reflected by the increased alveolar surface area in IDPN mice and by the increase of the ratio Sa/Va estimating the air space surface complexity.

Adaptation, Physiological↗
PubMed1976

Adaptation of the growing lung to increased VO2. I. IDPN as inducer of hyperactivity.

This paper is the first part of a study aiming to further analyse the hypothesis that in growing animals an increased VO2 due to a high physical activity leads to a quantitative adaptation of the gas exchange apparatus. Trying to avoid the tedious treadmill exercises we tested the applicability of the drug IDPN (imino-beta,beta'-dipropionitrile) as an inducer of increased VO2. Three intraperitoneal injections of IDPN permanently transform normal white mice into 'waltzing mice'. In our experiments ten male mice were injected with IDPN at the age of 20, 21 and 23 days. A control group was simultaneously injected with saline. The typical 'IDPN' hyperkinetic syndrome' appeared within five days from the first injection. The treated mice lost weight and grew at a slower rate than the controls. Their physical activity, as measured by Animex activity meters, was about twice that of the controls and was accompanied by a 50% increase in specific VO2 (VO2/body weight). At the age of about 4 months all animals were killed, their lungs fixed by intratracheal instillation of glutaraldehyde for a complete morphometric analysis. The body weights and the weights of heart, liver, kidneys, viscera, skin and carcass as well as the skin surface area were determined. IDPN mice were significantly lighter than the controls (-16%). All the other parameters cited above were reduced in about the same proportions, so that, when related to body weight, no significant changes could be detected. Specific lung volumes (VL/body weight) of IDPN mice were however up by 23%. These findings confirm that IDPN treatment represents a suitable way to increase VO2 in mice and may therefore allow to avoid more cumbersome methods of enforced exercise. The complete morphometric analysis will be published in a following paper.

Animals↗
PubMedDate not supplied

Attachment of adult rat cardiomyocytes (ARC) on laminin and two laminin fragments.

Adult rat cardiomyocytes (ARC) were cultivated on five different substrates: gelatin, fibronectin, laminin-nidogen complex (laminin), the E8 laminin fragment, and the E1 laminin fragment. Comparative cell attachment assays have shown that ARC prefer adhesion to E8 laminin fragment and laminin. It were shown by video time-lapse (VTL) studies that, during the redifferentiation process of ARC in culture, the morphology of ARC grown on laminin, fibronectin, and gelatin is indistinguishable, whereas the size of ARC grown on the E8 fragment is larger, and when grown on the E1 fragment definitely smaller than ARC on the whole laminin protein. Immunostaining for vinculin combined with reflection contrast microscopy were used to visualize the focal contacts of ARC on these substrates. Quantitative measurements, done with the help of a test line system, show that the lengths of adhesion plaques/micron2 on gelatin, fibronectin, and laminin are about the same. On the E8 fragment more attachment sites/micron2 and on the E1 fragment fewer attachment sites/micron2 were counted than on whole laminin protein. This suggests that substrates influence the number of focal contacts. Correlating these results with the observations made in the VTL recording system, one can suggest that the length of adhesion sites/micron2 increases in very flat and large cells.

Animals↗
PubMedDate not supplied

Secondary lysosomes as an integral part of the cytoskeleton: a morphological study in rat Kupffer cells.

Rat Kupffer cells contain the three major cytoskeletal components: microfilaments (MF), microtubules (MT), and intermediate filaments (IF) of the vimentin type. Previous cytomagnetometric data obtained from alveolar macrophages and rat Kupffer cells in culture provided evidence that actin filaments contribute to the movements of lysosomes. The lysosomal transport in living cells was affected, when the MFs were selectively disturbed, whereas the depolymerization of the MTs had no effect on the lysosomal movement measured by cytomagnetometric means. Immunofluorescence and ultrastructural studies of isolated and cultured rat Kupffer cells, presented in this paper, will investigate the relationship between lysosomes and the cytoskeleton. The principal filamentous structure in the peripheral cytoplasm of Kupffer cells in a dense meshwork of actin filaments. The dimension of the meshes combined with the dimensions of lysosomes implies the necessity of either (i) disintegration of the actin filament cross-links, (ii) depolarymerization and redistribution of MF's, or (iii) a displacement of actin filaments by the lysosomes during the organelle transport. The presence of microtubules in cytoplasmic protrusions and their track from the periphery to the perinuclear region during interphase might play a role in the transport mechanism of lysosomes, the more so because microtubules could often be demonstrated in closest association with lysosomes even in the first phase of endocytosis. The distribution pattern of vimentin, found as a dense interconnected framework surrounding the lysosomes like a basket, could play a role in positioning the organelles. The dynamic functions of MF's and MT's and their multifunctionality led to an adaptive and flexible organization of these filaments which may both be involved in lysosomal motion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Magnetic particles in the liver: a probe for intracellular movement.

Previous studies have used magnetic particles to estimate the viscosity of cell cytoplasm in vitro 1-4. Here we describe how magnetic Fe2O3 particles can be used to estimate non-invasively the motion of organelles in hepatic macrophages in intact animals. We report that when these particles are injected intravenously (i.v.), most are phagocytosed by hepatic macrophages (Fig. 1)5. When an external magnetic field is applied to the rabbit, these particles become magnetized and aligned. After removal of the field, the particles collectively produce a remanent magnetic field which can be measured at the body surface. This field decreases with time due to particle rotation (relaxation) 6,7. As the particles are contained in phagosomes or secondary lysosomes, we conclude that motions of these organelles are responsible for the particle rotation and relaxation.

Animals↗