Henry Z. Movat

Simple Method for Quantitation of Enhanced Vascular Permeability

Summary A simple physicochemical assay for the quantitation of enhanced vascular permeability in inflammation was described. It was shown that the assay is applicable to the study of inflammatory lesions induced with known chemical mediators, to the study of enhanced vessel permeability associated with the Arthus reaction, and that associated with thermal injury.

THE FINE STRUCTURE OF THE TERMINAL VASCULAR BED. IV. THE VENULES AND THEIR PERIVASCULAR CELLS (PERICYTES, ADVENTITIAL CELLS).

Abstract The fine structure of venules has been described. Venules are larger than capillaries. They are lined by a single layer of endothelium lying on a basement membrane and have an outer discontinuous coat of “perivascular” cells. The interlocking junctions between adjacent endothelial cells are often more complex than in capillaries. Lysosomes, which are not common in endothelium of the other portions of the terminal vascular bed, are common in venules. Pinocytic vesicles may attain a rather large size. The perivascular cells of venules (pericytes or adventitial cells) are similar to those of capillaries, though when stimulated by foreign protein, they show more signs of “activity.” They may become detached and probably can develop into macrophages or into plasma cells. Although continuous with smooth muscle cells in the more proximal and distal parts of the terminal vascular bed, perivascular cells do not have the structural characteristics of typical smooth muscle cells. Intercellularly, one encounters basement membrane , between endothelium and perivascular cells and around the latter. When perivascular cells become detached, the basement membrane around them is no longer demonstrable. Collagen and elastic elements may occur in the wall of venules. In the discussion the significance of venules in inflammation is pointed out, and the nature of the perivascular cells is discussed.

The fine structure of connective tissue: I. The fibroblast☆

Abstract The fine structure of fibroblasts of regenerating tendon, granulation tissue and various other tissues was studied by electron microscopy. The cells were identified as fibroblasts with the light microscope, and then ultrathin sections were prepared for electron microscopy. Fibrcblasts, particularly proliferating ones, are difficult to preserve adequately, swelling and disruption of mitochondria occurring frequently. The findings reported in this paper are based only on the study of adequately preserved material. Fibroblasts as seen by electron microscopy are elongated spindle-shaped or stellate cells, with a slightly indented nucleus. In the resting cell the cytoplasm may taper off into long slender processes. Both resting and proliferating cells contain ergastoplasm (rough-surfaced vesicles of the endoplasmic reticulum), but this is more abundant in proliferating cells. The ergastoplasm sometimes contains an electron dense substance and it may be distended. The periphery of the cell is free of ergastoplasm, but often contains fine filaments. A large Golgi apparatus was always seen in proliferating fibroblasts. Dense, osmiophilic, stellate bodies in the cytoplasm are typical of the fibroblast. Small granules or globules occur in the Golgi region, and somewhat larger ones are found in the periphery of the cytoplasm. Most of the granules resemble secretory granules. Others look like ingested material, or like structures described as lysosomes. A puzzling structure encountered in the Golgi area is a spindle-shaped body containing filamentous material, which stains intensely with phosphotungstic acid.

Platelet Aggregation and Release of ADP, Serotonin and Histamine Associated with Phagocytosis of Antigen-Antibody Complexes.∗

Summary and conclusions Aggregation of human and pig platelets by antigen-antibody complexes is probably induced by release of adenosine diphosphate (ADP) during phagocytosis of the complexes in vitro. The in vitro aggregation is associated with release of histamine, serotonin and ADP. The aggregation can be inhibited by iodoacetate, EDTA, adenosine monophosphate (AMP) and adenosine. During anaphylaxis in the rabbit induced by intravascular antigen-antibody interaction and precipitation, aggregated platelets in pulmonary vessels contain phagocytosed antigen-antibody complexes. During aggregation in vitro and in vivo the platelets become degranulated and probably release their lysosomal enzymes. This, together with degranulation of PMN-leukocytes, may be a significant pathogenetic mechanism in anaphylaxis and other hypersensitivity reactions.

Acute Inflammation and Microthrombosis Induced by Endotoxin, Interleukin-1, and Tumor Necrosis Factor and their Implication in Gram-Negative Infection

Acute inflammation constitutes the body’s principal mode of defense against infection and other harmful agents, and neutrophils are the primary effector cells in this process. When inflammation occurs in response to infection with pathogenic microorganisms, the damage that is often observed locally is a sacrifice aimed to prevent the spread of infectious agents throughout the body. Gram-negative microorganisms elicit a brisk inflammatory reaction which is largely induced by one of their cell wall constituents, endotoxin. The infiltrating neutrophils phagocytose and kill the bacteria. The inflammatory reaction is often associated with severe local microvascular injury and abscess formation. Besides eliciting inflammation, endotoxin can predispose the local microvasculature to thrombosis upon subsequent systemic endotoxemia or complement activation, as demonstrated by the local Shwartzman reaction. Both the inflammatory and the thrombotic phenomena induced by endotoxin are mediated by the local generation of cytokines.

THE FINE STRUCTURE OF THE LYMPHOID TISSUE DURING ANTIBODY FORMATION.

Abstract The histologic and ultrastructural changes which occur in spleen and lymph nodes of rabbits after primary or secondary antigenic stimulation are described. In the primary response, large pyroninophilic blast cells develop in the periarteriolar lymphcytic sheaths of the spleen. These blast cells migrate toward the periphery of the white pulp as they gradually develop into plasma cells. In lymph nodes, the process begins diffusely in the cortex, and migration occurs toward the medullary cords. Germinal center development lags behind these changes and reaches a peak when plasma cell development in the diffuse lymphoid tissue has been completed. Pyroninophilic blast cells develop in the centers but rarely mature into plasma cells. By using electron microscopy, the large pyroninophilic blast cells can be divided into two types. The cells developing first are characterized by large nuclei and nucleoli, and by numerous free ribosomes in the cytoplasm. These cells have been designated as immunoblasts . The immunoblast becomes a plasmablast by the development of a granular endoplasmic reticulum. By a decrease in the size and an increase in density of the nucleus, together with an enlargement of the Golgi area, the plasmablast becomes a plasma cell. Ultrastructural evidence is presented to show that the immunoblast develops from the lymphocyte, both in the diffuse lymphoid tissue of lymph nodes and periarteriolar lymphoid tissue of the spleen and in the germinal centers. Circumstantial evidence also supports this view.

The fine structure of the terminal vascular bed: II. The smallest arterial vessels: Terminal arterioles and metarterioles☆

Abstract The fine structure of the smallest arterial vessels (terminal arterioles and metarterioles) was described. These vessels have no internal elastic lamina. In these vessels, the number of cytoplasmic organelles varies from one endothelial cell to another. Interesting are the often complex interlocking junctions. The hyaloplasm of endothelial cells is often filamentous. The larger of the vessels without an internal elastic membrane (terminal arterioles) have a continuous media composed of well-differentiated smooth muscle cells with filaments, attachment bodies, and condensation of organelles in circumscribed areas. The smallest vessels (metarterioles) have a discontinuous coat of perivascular cells (pericytes). There are all gradations between these extremes. The intercellular elements between endothelium and the underlying cells, and between the smooth muscle or perivascular cells, consists mainly of basement membrane, with some collagen fibrils and very little elastic tissue. Downstream, there is a gradual transition into capillaries.

Isolation of two functionally different kininogens from human plasma—separation from proteinase inhibitors and interaction with plasma kallikrein☆

Abstract A high (HMW) and a low (LMW) molecular weight kininogen were isolated in highly purified form from human plasma, using QAE-Sephadex chromatography, followed by ammonium sulfate precipitation, gel filtration through Sephadex G-200, re-precipitation with ammonium sulfate, CM-Sephadex and SP-Sephadex chromatography. The initial preparative step was done at room temperature and the remaining procedures at 4°. In aqueous media, the apparent molecular size of the HMW-kininogen was about four times the size of the LMW-kininogen (200,000 vs 50,000). During the process of purification, proteinase inhibitors were separated from the two kininogens: α 1 -antitrypsin and α 2 -macroglobulin from the LMW-kininogen preparations: Cl-inactivator and inter-α-trypsin inhibitor from the HMW-kininogen preparations. There was a well defined functional difference between the two kininogens with respect to kinin generation by plasma kallikrein. This enzyme released kinin at a much faster rate from the HMW-kininogen than from the LMW-kininogen. When equipotent preparations of kininogens were incubated for 10 min with kallikrein, 60 times more enzyme was required to release the same amount of kinin from the LMW-kininogen as from the HMW-kininogen.

The fine structure of connective tissue: II. The plasma cell☆

Abstract The fine structure of plasma cells in lympho-reticular and connective tissue is described. When observed with the light microscope, mature plasma cells have a basophilic cytoplasm, a perinuclear clear area, and an eccentric dense nucleus. With the electron microscope, a well developed ergastoplasm and a large Golgi apparatus are characteristic of the cell. Immature plasma cells have well developed nucleoli, a relatively high nucleo-cytoplasmic ratio, and more abundant free RNP particles. In plasma cells, the ergastoplasmic sacs may be flat or dilated. When dilated they may contain a finely floccular substance, small dense bodies, large dense bodies (Russell bodies), or crystals. The Golgi area of plasma cells consists of small vesicles, flat or dilated tubules, round or irregular structures with a dense periphery and an obscured limiting membrane, and dense homogeneous globules. The latter are similar to, though much smaller than, the bodies or globules which occur occasionally in the rough surfaced vesicles (Russell bodies). Histochemical, in vitro , immuno-fluorescent studies and other evidence indicates that plasma cells produce antibody and other globulins. This theory is supported by the electron microscopic findings.

A permeability factor released from leukocytes after phagocytosis of immune complexes and its possible role in the Arthus reaction

Abstract Evidence is presented that a substance is released from leukocytes when they ingest Ag-Ab precipitates, which causes an increase in vascular permeability when injected intradermally into normal rabbits. It is postulated that this substance is released when leukocyte granules (lysosomes) enter the phagocytic vacuoles containing the immune precipitates (phagosomes), thus giving rise to a digestive vacuole. Isolated Leukocyte granules incubated with immune complexes also increases vascular permeability. Release of the postulated substance probably operates in vivo in the Arthus reaction. The possible nature of this substance is briefly discussed.