Porcine Salmonellosis

Renal vascular lesions associated with experimentally induced septicemic porcine salmonellosis consisted of fibrinoid necrosis of the vessel walls and fibrin thrombi within the lumina of interlobular arteries, afferent arterioles and glomerular capillary loops. Extrarenal vascular alterations were predominantly localized to the skin and the lungs. In these sites, too, mere fibrin thrombi were found in the capillaries, whereas mixed thrombi, consisting of fibrin, platelets, leucocytes and erythrocytes were present in larger vessels. The conclusion is drawn that the renal vascular injury is completely compatible to the generalized Shwartzman reaction, while the extrarenal vascular changes may only in part depend on this mechanism.     

Effect of epsilon toxin-GFP on MDCK cells and renal tubules in vivo.

Epsilon toxin (epsilon-toxin), produced by Clostridium perfringens types B and D, causes fatal enterotoxemia, also known as pulpy kidney disease, in livestock. Recombinant epsilon-toxin-green fluorescence protein (epsilon-toxin-GFP) and epsilon-prototoxin-GFP were successfully expressed in Escherichia coli. MTT assays on MDCK cells confirmed that recombinant epsilon-toxin-GFP retained the cytotoxicity of the native toxin. Direct fluorescence analysis of MDCK cells revealed a homogeneous peripheral pattern that was temperature sensitive and susceptible to detergent. epsilon-Toxin-GFP and epsilon-prototoxin-GFP bound to endothelia in various organs of injected mice, especially the brain. However, fluorescence mainly accumulated in kidneys. Mice injected with epsilon-toxin-GFP showed severe kidney alterations, including hemorrhagic medullae and selective degeneration of distal tubules. Moreover, experiments on kidney cryoslices demonstrated specific binding to distal tubule cells of a range of species. We demonstrate with new recombinant fluorescence tools that epsilon-toxin binds in vivo to endothelial cells and renal tubules, where it has a strong cytotoxic effect. Our binding experiments indicate that an epsilon-toxin receptor is expressed on renal distal tubules of mammalian species, including human.     

Occurrence of lymphomas and lupus erythematosus-like syndrome in the course of experimental Candida albicans infection in mice

Occurrence of four lymphomas was seen following injection of 1.4×10³ Candida albicans cells to the spleen of eighty non - inbred albine mice. These neoplastic changes occurred in three to seven months of the duration of the experiment. Extensive invasion of the subcutaneous tissue by the tumor was found in one animal. Two of the animals with lymphoma also had changes in the kidneys compatible with lupus erythematosus and presence of LE cells in the blood. In other animals most frequent and extensive pathological changes were found in the kidneys and in order of frequency were as follows: thickening of the basement membrane, fibrinoid degeneration, presence of hematoxylin bodies, wireloop formation. In total, the presence of positive LE cells in blood was found in seven instances and suggestive LE cells was observed in eight animals. Finding of perisplenitis, exudative pleuritis and pericarditis gave additional support to the resemblance of observed pathological changes with human lupus erythematosus. The fact that occurrence of lymphomas and lupus erythematosus together has been reported in humans provides additional interest to the results reported.Results presented here and previously suggest that there may be more extensive interrelationship among variety of pathological changes observed than is accepted until now. Better understanding of host — parasite relationship ofCandida albicans, and possible other fungi, could advance out knowledge of pathogenesis of these diseases.This work was supported partially byDora Kaplan, Joan Sloan, Memorial Funds and the Roon Foundation.     

Structuro-functional changes in the placenta as a result of exposure to atmospheric pollutants

Under the influence of atmospheric pollutions certain structural-functional changes take place in placenta: terminal villi per stipulated square unite, villi with desquamated epithelium, with dilated vessels, with deposition of fibrinoid masses, with plasmodial buds increase in number; section area occupied by epithelial layer decreases; RNA concentration and histoenzymatic activity change in the latter.     

Effects of tumor necrosis factor (TNF) on transplanted tumors induced by methylcholanthrene in mice. A histopathologic study

The effects of a highly purified tumor necrosis factor (TNF) on transplanted methylcholanthrene (Meth A)-induced murine tumors were compared with those of lipopolysaccharide (LPS). TNF caused immediate subepidermal edema and hyperemia followed 2 h later by fibrin thrombi in tumor blood vessels. Finally hemorrhagic necrosis with dispersal of tumor cells occurred. LPS produced similar hemorrhagic necrotizing changes. However, the necrotic action of LPS was delayed and complete tumor regression was not achieved with LPS. These findings suggest that tumor necrosis induced by TNF is due to circulatory disturbance associated with a microvascular injury in the tumor manifested by hyperemia and multiple fibrin thrombi.     

Local shwartzman phenomenon in animals with a complete absence and a reduction of the normal microflora]

Macro- and microscopic changes were studied in case of reproduction of the local Schwartzmann phenomenon in animals with various extent of bioisolation. It was revealed that the Schwartzmann phenomenon was positive in the usual animals and negative in the germ-free guinea pigs and in the animals with reduced enteric microbial flora given sterile diet. In the absence of microscopic changes in the germ-free animals there was revealed in their skin a neutrophilic-mononuclear infiltration of the derma, dilatation of the vessels, thrombosis of individual vessels. Apart from the same changes in guinea pigs with a reduced microbial flora, there were found focal extravasation and thrombosis of a somewhat greater number of vessels. There was no marked thromboses of small branches of the vessels, extensive hemorrhages or necroses which usually accompanied positive Schwartzmann phenomenon.     

Age-related characteristics of the organic angioarchitectonics of normal rats and in arterial hypertension

Architectonics of intraorganic arterial vessels in the cervical cortex, heart, kidneys and spleen have been investigated in 40 normotensive and spontaneously hypertensive rats, 6 months and 1 year old. In all the organs studied a direct dependence has been revealed between the degree of changes in the intraorganic arteries and relative content of the arterial vessels in the tissue organs. Functional changes of the arterial vessels in the organs studied observed during the hypertensive phase, transfer into the organic ones, as a result of prolonged adaptation, when the stage of a stable hypertension takes place.     

Spatial distribution of mast cells in chronic venous leg ulcers

Chronic venous leg ulcers (CVUs) show chronic inflammation but different pathological changes occur in different parts of the ulcer. There is a lack of re-epithelialisation and defective matrix deposition in the ulcer base but epidermal hyperproliferation and increased matrix deposition in the surrounding skin. The role of mast cells in wound healing, inflammation, fibrosis and epidermal hyperproliferation has been extensively studied but less is known about their role in CVUs. In the present study, we investigated the distribution of mast cells in CVUs with specific consideration of the differences between the ulcer base and the skin surrounding the ulcer. Both histochemical and immunohistological methods were used to detect the mast cell marker tryptase in frozen sections of CVU biopsies. Mast cells were counted in the dermis of normal skin, in the ulcer base and in the skin surrounding the ulcer. Double immunofluorescence staining was used to study the location of mast cells in relation to blood vessels. In normal skin few mast cells were seen in the dermis but none in the epidermis. However in CVUs there was a significant increase in intact and degranulated mast cells in the surrounding skin and ulcer edge (184 per field, p<0.003) of CVUs and a significant reduction in the ulcer base (20.5 per field p<0.05) in comparison to normal skin (61 per field). In CVUs mast cells showed a characteristic location near the epithelial basement membrane whilst mast cell granules and phantom cells (mast cells devoid of granules) were predominantly seen in the epidermis. In the dermis, mast cells were seen associated with blood vessels. The marked increase in mast cells in the surrounding skin of CVUs and depletion of mast cells in the ulcer base could implicate mast cell mediators in the pathological changes in CVUs particularly in the epidermal and vascular changes occurring in the surrounding skin.     

Mesentery capillary barrier in rats injected intravascularly with ascitic Zajdela hepatoma. III. Effect of serotonin and histamine on the extravasation of the tumor]

The addition of serotonin or of histamin with tumoral cells of ascitic Zajdela's hepatoma and their injection in aorta induce plain hemodynamic changes and increase the tumoral extravasation. So only cells blocked in thrombi are observed in blood vessels. Therefore, serotonin and histamin do facilitate tumoral cells extravasation, allowing so a better metastatic diffusion in this experimental pattern.     

The effect of blood flow velocity on the process of thrombus formation in microvessels

The growth rate constant of platelet thrombi as a function of mean blood flow velocity was studied using mesentery vessels of the white rat. An advanced mathematical model for the kinetics of platelet thrombi was developed. The dependence of platelet activation delay time upon the distance from the damaged vessel wall is pointed out as a result of theoretical and experimental data comparison.     

The pathogenesis of radiation nephropathy in the dog

Canine kidneys were biopsied at 2-week intervals from 3 to 13 weeks after a single 15-Gy dose of intraoperatively delivered 6 MeV electrons to determine the pathogenesis and dose-limiting tissue for radiation nephropathy. The data suggest that the dose and time after irradiation determine the dose-limiting tissue. The early functional survival of canine kidneys appeared to be dependent on parenchymal cell killing. Histologic changes in epithelial cells were seen as early as 3 weeks after irradiation. The parenchyma decreased to 50% of the preirradiation volume by 9 weeks but repopulated to near normal by 11 weeks. A second wave of depopulation, possibly due to perivascular fibrosis, was evident at 13 weeks. Previous investigators have demonstrated progressively extensive changes in renal vessels after irradiation. In this study, permanent vascular damage was seen at 3 weeks; however, most early changes in vessel walls proved to be temporary and probably resulted from atrophic vasoconstriction following parenchymal depopulation. Vessel dimensions returned to near normal as the parenchyma repopulated; however, a "histohematic barrier" created by progressively increasing perivascular fibrosis may cause a reduction in oxygen and nutrient support of the parenchyma and permanent loss of renal function.     

Epsilon toxin: a fascinating pore-forming toxin

Epsilon toxin (ETX) is produced by strains of Clostridium perfringens classified as type B or type D. ETX belongs to the heptameric β-pore-forming toxins including aerolysin and Clostridium septicum alpha toxin, which are characterized by the formation of a pore through the plasma membrane of eukaryotic cells consisting in a β-barrel of 14 amphipatic β strands. By contrast to aerolysin and C. septicum alpha toxin, ETX is a much more potent toxin and is responsible for enterotoxemia in animals, mainly sheep. ETX induces perivascular edema in various tissues and accumulates in particular in the kidneys and brain, where it causes edema and necrotic lesions. ETX is able to pass through the blood-brain barrier and stimulate the release of glutamate, which accounts for the symptoms of nervous excitation observed in animal enterotoxemia. At the cellular level, ETX causes rapid swelling followed by cell death involving necrosis. The precise mode of action of ETX remains to be determined. ETX is a powerful toxin, however, it also represents a unique tool with which to vehicle drugs into the central nervous system or target glutamatergic neurons.     

Histology of the adult mouse oviduct and endometrium following a single prenatal exposure to diethylstilbestrol

Light microscopy was used to examine the oviduct and endometrium of offspring from mice administered DES (10 micrograms/kg in 0.1 cc of corn oil, subcutaneously) or corn oil alone on Day 15 of gestation. Offspring were sacrificed at 5, 7 and 9 months of age. Oviduct changes in DES exposed offspring included numerous abnormal secretory cells which lined the mucosal folds of the isthmus. These cells contained a distinct granular cytoplasm which was eosinophilic and a nucleus displaced towards the apical surface. In addition both the ampulla and isthmus had mucosal folds which extended to the serosal surface and an accumulation of subepithelial fibrinoid material. Endometrial changes included squamous metaplasia of both the surface and glandular epithelial layer as well as extensive cystic glandular hyperplasia. In addition the endometrial connective tissue stroma exhibited fibrinoid accumulation. These changes may reflect an altered endocrine environment resulting from ovarian abnormalities during adulthood.     

Evaluation of different fluids for detection of Clostridium perfringens type D epsilon toxin in sheep with experimental enterotoxemia

Enterotoxemia caused by Clostridium perfringens type D is a highly lethal disease of sheep, goats and other ruminants. The diagnosis of this condition is usually confirmed by detection of epsilon toxin, a major exotoxin produced by C. perfringens types B and D, in the intestinal content of affected animals. It has been suggested that other body fluids can also be used for detection of epsilon toxin. This study was performed to evaluate the usefulness of intestinal content versus other body fluids in detecting epsilon toxin in cases of sheep enterotoxemia. Samples of duodenal, ileal and colon contents, pericardial and abdominal fluids, aqueous humor and urine from 15 sheep with experimentally induced enterotoxemia, were analysed for epsilon toxin using a capture ELISA. Epsilon toxin was detected in 92% of the samples of ileal content, 64% of the samples of duodenal content, 57% of the samples of colon content and in 7% of the samples of pericardial fluid and aqueous humor. No epsilon toxin was found in samples of abdominal fluid or urine from the animals with enterotoxemia or in any samples from six clinically healthy sheep used as negative controls. The results of this study indicate that with the diagnostic capture ELISA used, intestinal content (preferably ileum) should be used for C. perfringens type D epsilon toxin detection in suspected cases of sheep enterotoxemia.     

Bacterial endocarditis with obstruction of the right atrioventricular orifice and the pulmonary outflow trace in an African monkey (Cercopithecus aethiops).

A 7 to 8-year-old male African green monkey (Cercopithecus aethiops) was found moribund in his cage. Fluid and antibiotic therapy were administered, but the monkey dies 2 hours later. At necropsy, large septic mural thrombi obstructed the right atrioventricular orifice and the pulmonary outflow tract, and smaller septic thrombi were attached to the leaflets of the pulmonary and mitral valves. Staphylococci were isolated from the large thrombus occluding the atrioventricular orifice. Large abscesses were present in the upper and lower lobes of the right lung, and small, wedge shaped infarcts were present in the lungs and kidneys. The clinical and pathologic findings were consistent with a rapidly progressive form of bacterial endocarditis. This was the only case of vegetative bacterial endocarditis seen at this instituion in 700 necropsies of nonhuman primates.     

Ear tag induced Staphylococcus infection in mice

Mice used in a 2-year oral toxicity study developed a progressive, moist dermatitis. The initial lesions were seen around the ears in which metal identification tags had been placed and usually progressed to include the skin of the neck and shoulder. Clinically, the mice were pruritic, lost weight, had rough coats, and became moribund. The predominant finding at necropsy was pale brown kidneys with irregular granular surfaces. Histologically, there was inflammation and focal-to-diffuse necrosis in the visceral organs and affected skin. The predominant organism isolated from the skin, kidneys and heart blood was Staphylococcus aureus. This bacterium is a common inhabitant of the skin of conventionally housed mice and its isolation from the kidneys and blood suggested that the portal of entry was the wound caused by the insertion of the metal ear tag.     

Pathomorphism of experimental pancreatic necrosis after endolymphatic administration of contrical

Histological and electron microscopic studies of canine pancrease were conducted with biochemical control of pancreatic enzyme activity before and after treatment of experimental hemorrhagic pancreatonecrosis. 30-60 minutes after the disease induction microfocal pancreatonecrosis was revealed, while 6-8 hours later subtotal hemorrhagic pancreatonecrosis with changes in microcirculatory vessels of the pancreas manifested in erythrostasis, thrombosis and fibrinoid wall necrosis accompanied by the increase of pancreatic enzyme activity and decrease in blood, lymph and serum antienzyme activity developed. The treatment of experimental pancreatonecrosis with endolymphatic injection of contrical resulted in the morphologically confirmed attenuation of the necrosis intensity, limitation of necrotic zone size, blood circulation recovery in microcirculatory system, marked decrease of proteolytic enzyme activity and increase of blood serum and central lymph antienzyme activity.     

Mechanical mechanisms of thrombosis in intact bent microvessels of rat mesentery

The hypothesis that thrombus can be induced by localized shear stresses/rates, such as in the bent/stretched microvessels, was tested both experimentally and computationally. Our newly designed in vivo experiments were performed on the microvessels (post-capillary venules, 20-50mum diameter) of rat mesentery. These microvessels were bent/stretched with no/minimum injuries. In less than 60min after the microvessels were bent/stretched, thrombi were formed in 19 out of 61 bent locations (31.1%). Interestingly, thrombi were found to be initiated at the inner wall of the curvature in these bent/stretched vessels. To investigate the mechanical mechanisms of thrombus induction, we performed a 3-D computational simulation using commercial software, FLUENT. To simulate the bending and stretching, we considered the vessels with different curvatures (0 degrees , 90 degrees and 180 degrees ) as well as different shaped cross-sections (circular and elliptic). Computational results demonstrated that the highest shear stress/rate and shear stress/rate gradient are located at the inner wall of the curved circular-shaped vessels. They are located at the two apexes of the wall with shorter axis for the 0 degrees (straight) elliptic-shaped vessel and towards the inner side when the vessels are bent. The differences of the shear stresses/rates and of the shear stress/rate gradients between the inner and outer walls become larger in more bent and elliptic-shaped microvessels. Comparison of our experimental and numerical simulation results suggests that the higher shear stress/rate and the higher shear stress/rate gradient at the inner wall are responsible for initiating the thrombosis in bent post-capillary venules.     

Targeted ablation of the abcc6 gene results in ectopic mineralization of connective tissues

Pseudoxanthoma elasticum (PXE), characterized by connective tissue mineralization of the skin, eyes, and cardiovascular system, is caused by mutations in the ABCC6 gene. ABCC6 encodes multidrug resistance-associated protein 6 (MRP6), which is expressed primarily in the liver and kidneys. Mechanisms producing ectopic mineralization as a result of these mutations remain unclear. To elucidate this complex disease, a transgenic mouse was generated by targeted ablation of the mouse Abcc6 gene. Abcc6 null mice were negative for Mrp6 expression in the liver, and complete necropsies revealed profound mineralization of several tissues, including skin, arterial blood vessels, and retina, while heterozygous animals were indistinguishable from the wild-type mice. Particularly striking was the mineralization of vibrissae, as confirmed by von Kossa and alizarin red stains. Electron microscopy revealed mineralization affecting both elastic structures and collagen fibers. Mineralization of vibrissae was noted as early as 5 weeks of age and was progressive with age in Abcc6(-/-) mice but was not observed in Abcc6(+/-) or Abcc6(+/+) mice up to 2 years of age. A total body computerized tomography scan of Abcc6(-/-) mice revealed mineralization in skin and subcutaneous tissue as well as in the kidneys. These data demonstrate aberrant mineralization of soft tissues in PXE-affected organs, and, consequently, these mice recapitulate features of this complex disease.