The acute inflammatory reaction in the rabbit ear chamber with particular reference to the phenomenon of leukocytic migration

Collagen-based cell migration models in vitro and in vivo

Fibrillar collagen is the most abundant extracellular matrix (ECM) constituent which maintains the structure of most interstitial tissues and organs, including skin, gut, and breast. Density and spatial alignments of the three-dimensional (3D) collagen architecture define mechanical tissue properties, i.e. stiffness and porosity, which guide or oppose cell migration and positioning in different contexts, such as morphogenesis, regeneration, immune response, and cancer progression. To reproduce interstitial cell movement in vitro with high in vivo fidelity, 3D collagen lattices are being reconstituted from extracted collagen monomers, resulting in the re-assembly of a fibrillar meshwork of defined porosity and stiffness. With a focus on tumor invasion studies, we here evaluate different in vitro collagen-based cell invasion models, employing either pepsinized or non-pepsinized collagen extracts, and compare their structure to connective tissue in vivo, including mouse dermis and mammary gland, chick chorioallantoic membrane (CAM), and human dermis. Using confocal reflection and two-photon-excited second harmonic generation (SHG) microscopy, we here show that, depending on the collagen source, in vitro models yield homogeneous fibrillar texture with a quite narrow range of pore size variation, whereas all in vivo scaffolds comprise a range from low- to high-density fibrillar networks and heterogeneous pore sizes within the same tissue. Future in-depth comparison of structure and physical properties between 3D ECM-based models in vitro and in vivo are mandatory to better understand the mechanisms and limits of interstitial cell movements in distinct tissue environments.

Visualization of Leukocyte Transendothelial and Interstitial Migration Using Reflected Light Oblique Transillumination in Intravital Video Microscopy

Dynamic visualization of the intravascular events leading to the extravasation of leukocytes into tissues by intravital microscopy has significantly expanded our understanding of the underlying molecular processes. In contrast, the detailed observation of leukocyte transendothelial and interstitial migration in vivo has been hampered by the poor image contrast of cells within turbid media that is obtainable by conventional brightfield microscopy. Here we present a microscopic method, termed reflected light oblique transillumination microscopy, that makes use of the optical interference phenomena generated by oblique transillumination to visualize subtle gradients of refractive indices within tissues for enhanced image contrast. Using the mouse cremaster muscle, we demonstrate that this technique makes possible the reliable quantification of extravasated leukocytes as well as the characterization of morphological phenomena of leukocyte transendothelial and interstitial migration.

Initiation of non-neoplastic late effects: the role of endothelium and connective tissue

While early radiation lesions might be a direct consequence of parenchymal cell loss, late-radiation injury most probably develops as a consequence of functional perturbations that may involve both parenchymal and nonparenchymal elements. Damage to blood vessels and consequent perturbations in blood flow and endothelial physiology play an important role in the development of late effects. The development of late-radiation damage has been studied in three different tissue systems: the skin, kidney and central nervous system. The results suggested that damage to vascular tissue played a major role in the development of radiation-induced late effects.

Morphology of irradiated microvasculature: a combined in vivo and electron-microscopic study

The purpose of this study was to establish a standardized experimental system to investigate the local effects of ionizing irradiation in the absence of systemic responses due to radiation. Twenty fully healed rabbit ear chambers in 13 rabbits were irradiated with single exposures of 7500 rads of beta-rays from a strontium-90 source. The irradiation resulted in an acute response, with cellular infiltration of the ear chambers, loss of vasomotion in arterioles, and vasodilatation. Over the weeks following irradiation, a gradual reduction in the number of blood and lymphatic vessels was noticed. A gradual reduction in the number of cells in the interstitium was also observed. Finally, only a few thin-walled blood vessels remained. Their endothelium contained no recognizable organelles and in places had disappeared completely, to expose the vascular basement membrane to the blood. These vessels were observed to be still flowing. No evidence either of capillary blockage due to swelling of endothelial cells or of platelet aggregation leading to thrombosis was obtained.

Leucocyte mobilization to skin lesions

Leucocyte mobilization to a chamber covering a skin lesion was studies in healthy volunteers. 111 Indium-labelled blood leucocytes accumulated in the chambers, indicating mobilization of leucocytes from the blood. The concentration of autologous serum in the chamber medium influenced the number of leucocytes mobilized, while heat inactivation of serum or the repeated use of the same serum had no effect on the counts. The use of zymosan-treated serum increased the mobilization by up to 53%. The kinetics for the mobilization of leucocytes to chambers containing autologous serum was followed in healthy subjects. The mobilization showed a uniform pattern, viz. a lag phase of 2--4 hours and maximal migration rates after 20--24 hours. The cumulated counts were 74 x 10(6) leucocytes/cm2/24 hours and 200 x 10(6) leucocytes/cm2/48 hours. Females and males exhibited the same kinetics and cumulated counts. Chamber leucocytes were predominantly neutrophil granulocytes (85--100%) with 2.9--3.6 nuclear segments. The chamber technique provides a simple method permitting quantitation of in vivo mobilization of leucocytes from the blood to an inflammatory lesion.

Pulmonary and systemic embolism after deliberate intravenous fluorocarbon administration

After intravenous injection of 0.1 ml Fluorocarbon (FC) into the caudal vein of rats clear droplets which are reminiscent of gas emboli appear in the pulmonary and cerebral arteries. These droplets cannot be stained with Azan, haematoxylin-eosin, Nile blue sulfate, Sudan black B, and Sudan III in Paraplast embedded or frozen sections. Gas chromatography of affected lung tissue reveals a high concentration of FC. The clear droplets are the histological correlates of FC emboli which lead to haemorrhagic lung infarction and ischaemic brain infarcts. After intralienal injection FC induces haemorrhagic infarcts of the spleen near the injection site and massive embolization of the intrahepatic portal veins with consequent liver cell necrosis. FC droplets are phagocytosed by hepatic sinusoidal lining cells. Due to the absence of a specific method for identifying FC embolization of renal vessels is difficult to assess.

Studies on the regulation of the neutrophil chemotactic response using a rapid and reliable method for measuring random migration and chemotaxis of neutrophil granulocytes

An economic and sensitive test system for measuring random and directional migration of human neutrophils is described. The technique, based on a modified Boyden chamber equipped with a two-filter system, permits a substantial reduction of both incubation time and sample volume. The influence of various technical factors such as the neutrophil concentration in the cell suspension, the incubation time of the chambers, the test concentration of activated plasma or serum, the presence of heparin, and the procedure for separating neutrophils from human peripheral blood, was investigated. Standardized procedures for measuring and reporting neutrophil chemotaxis are proposed. The method has been used to study the significance of factors regulating neutrophil migration such as cytotaxin inactivators and neutrophil immobilizing factors (NIF). Activity of cytotaxin inactivators as assessed in undiluted serum or plasma at pH 7.4, 6.0 or 4.0 was very low. In contrast, potent neutrophil immobilizing activity was found in human serum or diluted plasma. These factors which inhibit migration were accordingly termed neutrophil immobilizing factors of plasma (NIF-P) and neutrophil immobilizing factor of serum (NIF-S). These factors are heat-stable, non-dialysable and of high molecular weight.

Studies of intercellular invasion in vitro using rabbit peritoneal neutrophil granulocytes (PMNS). I. Role of contact inhibition of locomotion

Intercellular invasion is the active migration of cells on one type into the interiors of tissues composed of cells of dissimilar cell types. Contact paralysis of locomotion is the cessation of forward extension of the pseudopods of a cell as a result of its collision with another cell. One hypothesis to account for intercellular invasion proposes that a necessary condition for a cell type to be invasive to a given host tissue is that it lack contact paralysis of locomotion during collision with cells of that host tissue. The hypothesis has been tested using rabbit peritoneal neutrophil granulocytes (PMNs) as the invasive cell type and chick embryo fibroblasts as the host tissue. In organ culture, PMNs rapidly invade aggregates of fibroblasts. The behavior of the pseudopods of PMNs during collision with fibroblasts was analyzed for contact paralysis by a study of time-lapse films of cells in mixed monolayer culture. In monolayer culture, PMNs show little sign of paralysis of the pseudopods upon collision with fibroblasts and thus conform in their behavior to that predicted by the hypothesis.