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Endothelial cells in growing tumors express activated Akt, which when modeled by transgenic endothelial expression of myrAkt1 was sufficient to recapitulate the abnormal structural and functional features of tumor blood vessels in nontumor tissues. Sustained endothelial Akt activation caused increased blood vessel size and generalized edema from chronic vascular permeability, while acute permeability in response to VEGF-A was unaffected. These changes were reversible, demonstrating an ongoing requirement for Akt signaling for the maintenance of these phenotypes. Furthermore, rapamycin inhibited endothelial Akt signaling, vascular changes from myrAkt1, tumor growth, and tumor vascular permeability. Akt signaling in the tumor vascular stroma was sensitive to rapamycin, suggesting that rapamycin may affect tumor growth in part by acting as a vascular Akt inhibitor.

Stimulation of platelets with strong agonists results in centralization of cytoplasmic organelles and secretion of granules. These observations have led to the supposition that cytoskeletal contraction facilitates granule release by promoting the interaction of granules with one another and with membranes of the open canalicular system. Yet, the influence of the actin cytoskeleton in controlling the membrane fusion events that mediate granule secretion remains largely unknown. To evaluate the role of the actin cytoskeleton in platelet granule secretion, we have assessed the effects of latrunculin A and cytochalasin E on granule secretion. Exposure of platelets to low concentrations of these reagents resulted in acceleration and augmentation of agonist-induced alpha-granule secretion with comparatively modest effects on dense granule secretion. In contrast, exposure of platelets to high concentrations of latrunculin A inhibited agonist-induced alpha-granule secretion but stimulated dense granule secretion. Incubation of permeabilized platelets with low concentrations of latrunculin A primed platelets for Ca(2+)- or guanosine triphosphate (GTP)-gamma-S-induced alpha-granule secretion. Latrunculin A-dependent alpha-granule secretion was inhibited by antibodies directed at vesicle-associated membrane protein (VAMP), demonstrating that latrunculin A supports soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein-dependent membrane fusion. These results indicate that the actin cytoskeleton interferes with platelet exocytosis and differentially regulates alpha-granule and dense granule secretion.

Mouse embryos genetically null for the alphav integrin subunit develop intracerebral hemorrhages at midgestation and die shortly after birth. A key question is whether the hemorrhage arises from primary defects in vascular endothelial cells or pericytes or from other causes. We have previously reported normal initiation of cerebral vessels comprising branched tubes of endothelial cells. Here we show that the onset of hemorrhage is not due to defects in pericyte recruitment. Additionally, most alphav-null vessels display ultrastructurally normal endothelium-pericyte associations and normal interendothelial cell junctions. Thus, endothelial cells and pericytes appear to establish their normal relationships in cerebral microvessels. However, by both light and electron microscopy, we detected defective associations between cerebral microvessels and the surrounding brain parenchyma, composed of neuroepithelial cells, glia, and neuronal precursors. These data suggest a novel role for alphav integrins in the association between cerebral microvessels and central nervous system parenchymal cells.

We performed an ultrastructural analysis of 10 skin biopsy specimens that had been obtained from three women who were undergoing daily subcutaneous dosing with recombinant methionyl-human stem cell factor (rhSCF) as part of a phase I clinical trial. The biopsy specimens were obtained at sites of subcutaneous administration of rhSCF, within approximately 1 to 2 hours of rhSCF injection, and, at the same time, at contralateral control sites that had not been directly injected with rhSCF. We previously reported that subcutaneous dosing with rhSCF in these subjects induced the local development of a wheal and flare response, which was associated with evidence of mast cell degranulation, as well as a systemic increase in numbers of cutaneous mast cells. The present electron microscopic analysis revealed that all biopsies of swollen, erythematous rhSCF-injected sites exhibited anaphylactic degranulation of both mature and immature mast cells, an acute inflammatory response characterized by the migration of neutrophils, basophils (some of which exhibited evidence of piecemeal degranulation), and eosinophils through blood vessel walls into the perivascular and extravascular spaces, and edema and fibrin deposition within the interstitium. By contrast, the control biopsies contained no evidence of mast cell degranulation or acute inflammation. However, both control and rhSCF-injected sites exhibited mast cells that were undergoing granule building and maturation. Thus at the doses tested in these subjects, subcutaneous injection of rhSCF induced anaphylactic-type degranulation of dermal mast cells at the injection site, with an acute inflammatory response that was associated with the recruitment of granulocytes. By contrast, mast cells at sites distant from those directly injected with rhSCF exhibited no evidence of enhanced secretion.

Stem cell factor (SCF) has a major role in hematopoiesis and in the regulation of mast cell development and function. For example, recombinant human SCF (rhSCF) can induce the development of human mast cells from precursor cells in vitro, stimulate mediator release from human skin mast cells in vitro, and promote both the development and functional activation of human skin mast cells in vivo. In the present study, we used a new ultrastructural enzyme-affinity method, employing diamine oxidase (DAO)-conjugated gold particles (DAO-gold), to detect histamine in skin biopsies obtained from patients with breast carcinomas who were receiving daily subcutaneous (SC) injections of rhSCF in a phase I study of this cytokine. We examined control biopsies obtained at sites remote from rhSCF injection as well as biopsies of rhSCF-injected skin that were obtained within 2 hours and 30 minutes of the SC injection of rhSCF at that site. The rhSCF-injected sites (which clinically exhibited a wheal-and-flare response), but not the control sites, contained mast cells undergoing regulated secretion by granule extrusion. The DAO-gold-affinity method detected histamine in electron-dense granules of mast cells in control and injected skin biopsies; however, the altered matrix of membrane-free, extruded mast cell granules was largely unreactive with DAO-gold. Notably, DAO-gold bound strongly to fibrin deposits and collagen fibers that were adjacent to degranulated mast cells. These findings represent the first morphologic evidence of histamine secretion by classical granule exocytosis in human mast cells in vivo.

We review a new technique--diamine oxidase (DAO)-gold ultrastructural enzyme-affinity labeling--which we developed to localize histamine in subcellular sites of mast cells. The DAO-gold method showed that isolated human lung mast cells contained abundant histamine in their cytoplasmic granules, a conclusion which was verified by a large number of specificity controls. We also studied mast-cell-rich eyelid lesions which developed in interleukin-4 transgenic mice. The DAO-gold method demonstrated histamine in the electron-dense granules of mast cells in these lesions, but little or no histamine was detected in the swollen, empty granules of mast cells undergoing piecemeal degranulation. This new enzyme-affinity-gold method has permitted the first ultrastructural localization of histamine in subcellular sites of routinely prepared electron microscopy samples. The method has also permitted the first morphological studies of histamine secretion in vivo and has demonstrated that such secretion can be associated with the ultrastructural changes of piecemeal degranulation.

Objective: Axonal necrosis was first described in samples of small intestine from patients with Crohn's disease (A.M. Dvorak et al. Hum Pathol 1980; 11:620-634). Clinically evident inflammation of continent ileal reservoirs (pouches) has clinical features that resemble Crohn's disease. Possible similarities in the pathogenesis of Crohn's disease and pouchitis were sought using ultrastructural and microbiologic tools to identify damaged enteric nerves and tissue bacteria., Methods: An encoded ultrastructural and microbiologic study of replicate biopsies from 114 samples of human intestine was done. Biopsies from ileum, colon, conventional ileostomy or continent pouch were obtained from patients with ulcerative colitis, Crohn's disease, or familial polyposis and grouped into three clinical study groups (control, normal pouch, pouchitis), based on clinical and endoscopic criteria. Biopsies were prepared for electron microscopy with standard methods; replicate biopsy samples were washed extensively before preparing cultures designed to identify aerobic as well as facultative and obligate anaerobic bacteria (Onderdonk et al. J Clin Microbiol 1992; 30:312-317). The ultrastructural diagnosis of damaged enteric nerves was based on previously published criteria for axonal necrosis (A.M. Dvorak and W. Silen. Ann Surg 1985; 201:53-63). Intergroup comparisons were tested for significance using Chi-square analysis., Results: The highest incidence of axonal necrosis was present in Crohn's disease control biopsies (53%), regardless of whether bacteria were present (or not) in cultures of replicate biopsies. Axonal necrosis also occurred in more ulcerative colitis and familial polyposis biopsies (regardless of biopsy site) that had positive bacterial cultures than in those that did not (p < 0.001). In addition, axonal necrosis was documented in 42% of the pouch biopsies from ulcerative colitis and familial polyposis patients, particularly in those pouches that were found to be inflamed by clinical criteria and that also had positive bacterial cultures of the biopsied tissues. Control biopsies from patients with ulcerative colitis and familial polyposis had significantly less nerve damage than pouch biopsies in the presence of positive cultures (p < 0.01). Among the clinically inflamed pouches biopsied in ulcerative colitis or familial polyposis patients, we found that none had damaged enteric nerves when bacterial cultures were negative (p < 0.005). If the presence of axonal necrosis alone was compared with the presence of undamaged enteric nerves in all biopsies from patients with ulcerative colitis, a highly significant number of ulcerative colitis biopsies with axonal necrosis occurred in pouches (72%) compared with controls (p < 0.001)., Conclusions: The ultrastructural finding of axonal necrosis in Crohn's disease confirms previous studies. The presence of damaged enteric nerves in patients with pouchitis provides ultrastructural support to the clinical impression of similarities between pouchitis and Crohn's disease. The association of damaged nerves and invasive bacteria in pouchitis suggests mechanistic similarities for the pathogenesis of Crohn's disease that requires further investigation.

Twenty-two percent of 117 biopsies of human intestinal tissues had ultrastructural images of classical regulated secretion from eosinophils in vivo i.e. eosinophil granule extrusion (EGE). Replicate intestinal biopsies that were positive for bacteria had EGE more often than not (p < 0.05); 77% of the isolates were Staphylococci. Some of the intestinal biopsies also had damaged nerves; all that had EGE and damaged enteric nerves also had positive bacterial cultures. The EGE that we observed could not account for all enteric nerve damage, suggesting multifactorial mechanisms for nerve damage in gut tissues. Among the possibilities are release of neurotoxic eosinophil granule proteins by an alternate secretory route, i.e., piecemeal degranulation, direct toxicity of tissue invasive bacteria and/or damaged nerves of unknown etiology such as those that are regularly present in uninvolved tissues of patients with Crohn's disease.

Tissue biopsy samples from patients with and without ileal pouches were examined by electron microscopic and microbiologic culture techniques to determine the numbers and types of microorganisms closely associated with or within the tissue biopsy samples. The disease status of each patient was determined by endoscopic and histopathologic methods. Of the 78 biopsy samples included in this study, 64 (82%) yielded obligately anaerobic and/or facultative bacteria when they were cultured. Fourteen of the 78 samples (17.9%) were negative by culture. Of the positive samples, 54 contained facultatively anaerobic bacterial species and 50 yielded obligately anaerobic species. The total counts for facultatively anaerobic bacteria for samples from patients with pouchitis were significantly greater than for samples from patients in control groups. In addition, the number of samples from patients with normal pouches that did not contain obligate anaerobes was significantly less than that from patients with pouchitis; 4 of 23 and 6 of 12 samples, respectively (P less than 0.043). For samples in which organisms were detected, there was agreement with electron microscopic detection of bacteria in 23 of 27 samples, for an overall sensitivity of electron microscopy compared with that of culture of 85%. The qualitative studies resulted in the characterization of 273 isolates comprising 77 different phenotypes. The specificity of these findings in patients with ileal pouchitis is discussed.

One hundred and seventeen coded intestinal biopsies were examined by electron microscopy and evaluated for morphological evidence of mast cell and basophil secretion in situ. Sixty percent of the biopsies had evidence of secretion. Mast cell secretion was evident in control biopsies, many of which were obtained from uninvolved tissues of patients with inflammatory bowel disease. Biopsies of inflamed continent pouches from ulcerative colitis (UC) patients showed more mast cell secretion than noninflamed UC pouch biopsies. This evidence of mast cell secretion supports recent work that documents high constitutive levels of histamine in jejunal fluids of Crohn's disease patients and suggests a proinflammatory role for mast cells in inflammation associated with pouchitis.

One hundred and seventeen coded intestinal biopsy specimens were examined by electron microscopy. All surgical biopsies were obtained from uninvolved sites of patients with two inflammatory bowel diseases (ulcerative colitis or Crohn's disease) and from patients with preneoplastic and neoplastic diseases (adenocarcinoma, rectal polyp, familial polyposis). Biopsy sites included normal ileum, colon, and rectum as well as conventional ileostomies and continent pouches constructed from the ileum. The data reported here describe the ultrastructural anatomy of human gastrointestinal tract mucosal mast cells in vivo and their anatomic associations with enteric nerves.

Lipid bodies are non-membrane-bound cytoplasmic inclusions that are prominent in leukocytes engaged in inflammatory responses. As demonstrated by electron microscopic autoradiography, lipid bodies can serve as intracellular sites of 3H-arachidonic acid localization in eosinophils and other cells. To evaluate the role of lipid bodies as stores of esterified arachidonate, subcellular fractionation of lipid-body-rich human eosinophils was used to isolate lipid bodies free of other organelles. In lipid bodies isolated from 3H-arachidonate-labeled eosinophils, 3H-arachidonate was esterified almost totally in glycerolipids, predominantly in classes of phospholipids, including phosphatidyl-inositol and phosphatidylcholine. Lipid bodies, especially in leukocytes participating in inflammation, could represent intracellular sources of esterified arachidonate available for eicosanoid formation.

We developed a simple technique that greatly facilitates the ultrastructural examination of cells growing in small, widely dispersed colonies in agar medium, and used the method to examine the development of morphologically mature mast cells and actively phagocytic macrophages in agar cultures of mouse bone marrow cells. The bone marrow cells of genetically mast cell-deficient WBB6F1-W/Wv or congenic normal (+/+) mice were cultured in semisolid agar medium supplemented with supernatants of concanavalin A-stimulated splenocytes. To prepare the colonies of hematopoietic cells for transmission electron microscopy, all the colonies within the agar-containing medium in a 96-well culture plate were removed with a Pasteur pipette and placed in a dilute, mixed aldehyde fixative. After fixation, the agar still enmeshing and separating individual colonies of cells was melted at 94 degrees C, rapidly mixed with molten 2% agar in a microfuge tube, centrifuged for 1 minute, and then the plastic tube was cooled in ice for 30 minutes. The plastic was removed with a razor blade, the agar block was hemisected from top to bottom, and then the blocks were processed for electron microscopy, embedded flat, and sectioned for light and electron microscopy. The culture conditions tested resulted in the development of morphologically mature mast cells and actively phagocytic macrophages, whether cultures were initiated with bone marrow cells from WBB6F1-W/Wv or congenic +/+ mice.

Electron microscopy, ultrastructural cytochemistry, and postembedding immunogold ultrastructural immunocytochemistry were used to study a papular cutaneous lesion from a patient with the hypereosinophilic syndrome. Peroxidase activity was detected cytochemically in 40-microns sections of skin utilizing the substrate diaminobenzidine; Charcot-Leyden crystal (CLC) protein was detected immunocytochemically in skin utilizing a postembedding immunogold technique; and a combined method was used where postembedding immunogold staining of CLC protein was performed on sections previously prepared to detect peroxidase activity. We describe a unique, eosinophil-rich inflammatory process in involved skin which contained extraordinary numbers of morphologically activated macrophages. Electron microscopy demonstrated (a) widespread eosinophil necrosis, (b) interstitial CLC formation, (c) macrophage activation, endocytosis, and phagocytosis, and (d) CLC formation in phagosomes of activated macrophages. Peroxidase activity was present as follows: (a) in the matrix of eosinophil specific granules in eosinophil cytoplasm, in membrane-bound specific granules released into interstitial tissues from dying eosinophils, being phagocytized by activated macrophages, and within macrophage phagosomes; (b) as amorphous interstitial debris; (c) in cytoplasm and nuclei of damaged eosinophils in the dermal tissues as well as in macrophage phagosomes; and (d) in endocytotic vesicles and vacuoles of macrophages and in CLC-containing phagosomes of macrophages. CLC protein was localized by immunocytochemistry to (a) eosinophil primary granules, (b) cytoplasm and nuclei of damaged eosinophils located in the interstitial tissues or within macrophage phagosomes, (c) CLC located in interstitial tissues adjacent to necrotic eosinophils and in macrophage phagosomes, and (d) aggregates of amorphous protein bound to macrophage surfaces; endocytotic vesicles and vacuoles of macrophages; amorphous protein aggregates in macrophage lysosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Lipid bodies are non-membrane bound intracellular organelles, which have been recognized morphologically in a diversity of mammalian and nonmammalian cells, but are of uncertain function. In mammalian cells, in addition to serving as a storage site of cholesterol and triglyceride, lipid bodies can be a repository of esterified arachidonic acid. Adult worms of the human filarial parasite Brugia malayi have been found to esterify exogenous [3H]arachidonic acid into parasite phospholipids and neutral lipids. Electron microscopic autoradiography demonstrated that [3H]arachidonate was preferentially incorporated into filarial lipid bodies. The dominant incorporation of arachidonate into lipid bodies of a nematode establishes that lipid bodies are a site of arachidonic acid accumulation in nonmammalian, as well as mammalian, cells.

We used ultrastructural autoradiographic and cytochemical methods to localize esterase activities in unstimulated guinea pig basophils and in basophils undergoing degranulation or recovery from degranulation. We used tritium-labeled diisopropylfluorophosphate (DFP) as a probe for serine enzymes and localized this probe by ultrastructural autoradiography to cytoplasmic granules of immature or mature unstimulated basophils, as well as to granules released by degranulating basophils. Ultrastructural cytochemistry using alpha naphthyl acetate (ANA) as substrate localized nonspecific esterase activity to extruded granules, either within the interiors of degranulation sacs or within granules completely separated from degranulating basophils. Extruded granules retained their esterase activity for as long as 24 hr after antigen-induced degranulation. The plasma membranes of unstimulated or degranulating basophils, as well as of basophils recovering from degranulation, displayed prominent cell surface ANA esterase ectoenzyme activity. Lipid bodies, organelles present in the cytoplasm of both control and recovering basophils, were also alpha naphthyl acetate esterase (ANAE)-positive. Thus, cytochemical and autoradiographic techniques localized esterase and/or [3H]-DFP-binding activities to cytoplasmic granules, lipid bodies, and cell surface of basophils, and these enzyme activities persisted during both degranulation and recovery from degranulation.

We studied the localization of nonspecific esterase activities in cloned guinea pig aortic endothelial cells using ultrastructural cytochemistry. Weibel-Palade bodies (WPB), which are known to contain von Willebrand protein, were positive for esterase, defining a heretofore unrecognized activity of these organelles. Esterase activity was also found localized to the external surface of the plasma membrane, to cytoplasmic lipid bodies, and to the outer (cytoplasm-facing) surface of certain membrane-bound cytoplasmic vacuoles. Localization of esterase activity to these four discrete sites probably reflects the presence of a number of endothelial cell enzymes capable of hydrolyzing alpha-naphthyl acetate or butyrate. The physiological substrate and biological function of these enzyme activities are not presently understood.

Ultrastructural and cytochemical studies of peripheral blood samples from a monkey continuously infused with recombinant human interleukin 3 were performed. Recombinant human interleukin 3 stimulated a delayed granulocytosis primarily characterized by numerous mature basophils and fewer eosinophils and neutrophils. Basophilic leukocytes were identified by ultrastructural analysis. They were found to be typical granulocytes with polylobed nuclei containing condensed chromatin and numerous cytoplasmic granules. Basophil secretory granules were filled with homogeneous dense contents and were larger than eosinophil and neutrophil secretory granules. Evidence of increased basophil production was accompanied by interleukin 3-associated activation morphologies. These included increased numbers of cytoplasmic and granule-associated vesicles, as are routinely present in a non-IgE-mediated basophil release reaction, termed piecemeal degranulation, and focal perigranular matrix swelling and granule membrane fusion which accompanies anaphylactic degranulation of basophils in other species. Monkey basophils were shown to have a different ultrastructural morphology than that published for monkey mast cells, but exhibited general morphologic criteria for the identification of circulating mature basophils in a number of species. Like human and guinea pig basophils, monkey basophils did not display endogenous peroxidase or peroxidatic activity in a cytochemical assay which simultaneously identified peroxidase-positive granules in neutrophils and eosinophils as well as in synthetic structures in eosinophils. In summary, these studies have identified monkey basophils in an in vivo recombinant human interleukin 3-stimulated model. Interleukin-3 induction of basophilia clearly allowed differentiation of activated mature basophils from eosinophils and neutrophils and mast cells in this species using ultrastructural morphologic criteria.