Histopathology of experimental systemic candidosis in guinea-pigs

Unpretreated Albino guinea-pigs were infected intravenously with Candida albicans. Cutaneous candidosis with (pseudo-) hyphal outgrowth in the hair shafts and in the keratinized layers of the epidermis developed as a consequence of systemic dissemination. The spread of the infection was followed by cultures and by gross- and micropathological study of various organs of different animals during a follow-up period of 35 days. The possible relationship of organ invasion by C. albicans and skin candidosis is discussed.     

The role of the activation of lipid peroxidation in the pathogenesis of experimental peritonitis

Investigation was carried out for studying the role of lipid peroxidation (LP) in the genesis of destructive process in the abdominal cavity. The model of experimental peritonitis was made on the dogs. According to the concentration of fat acids conjugates with double couplings (diene conjugates--DC), malondialdehyde (MDA) the LP activity was discovered. Simultaneously the activity of ceruloplasmin (CP), superoxide dismutase activity of plasma, total proteolytic blood activity, summary indicators of antioxidants plasma status and the level of medium-mass molecules was indicated. It was established that LP activation began in the first hours of peritonitis development yet, concentration of LP metabolites (MDA and DC) in plasma increased during disease progressing. CP and superoxide dismutase activity of plasma decreased. Total proteolytic blood activity and level of medium-mass molecules increased after the growth of LP intensity.     

An experimental investigation of interactions in snail-macrophyte-epiphyte systems

Summary An experimental investigation under field conditions of enclosures containing freshwater pulmonate snails, the macrophyteCeratophyllum demersum and epiphytes, produced evidence of beneficial interactions.Ceratophyllum growth, measured in terms of stem length, numbers of leaf-nodes and growing tips and leaf survival was significantly enhanced in the presence of snails. This effect was attributed to the increased availability of plant nutrients of snail origin, such as phosphates and ammonia, as well as to the snails' action as “cleaning symbionts” in reducing the density of bacterial and algal epiphyton potentially deleterious to macrophytes. Principal component analysis revealed both seasonal and treatment effects of snail grazing on algal epiphyton. Small adnate algal species (e.g.Cocconeis placentula) survived grazing and benefited from the removal of larger, competitor, species. Snail densities increased in all treatments, despite high (86%) juvenile mortality. It is concluded that freshwater pulmonate snails are strong interactors in lentic habitats, enhancing the growth ofCeratophyllum and producing characterisic epiphyte communities. This benefits not only the snails, but also the plants and epiphytes that are associated with them. Thus the interactions between these component parts of the community can be considered as mutualistic.     

Oxalic acid production and its role in pathogenesis of Sclerotinia sclerotiorum

Abstract Sunflower plants were inoculated with a virulent isolate of Sclerotinia sclerotiorum and with the same isolate nutritionally conditioned to produce small amounts of oxalic acid. The preconditioned isolate behaved as hypovirulent. Tomato plants were inoculated with four S. sclerotiorum isolates of increasing virulence. A close correlation among disease severity, accumulation of oxalic acid, decrease in pH and inhibition of polyphenoloxidase in both infected host tissues was demonstrated. Oxalic acid production as an important factor of virulence in S. sclerotiorum is emphasized and its effect on the phenolic metabolism of the host via inhibition of polyphenoloxidase is suggested.     

The toxic role of alpha-haemolysin in the pathogenesis of experimental Escherichia coli infection in mice

Filtrates from strains of Escherichia coli possessing plasmid-cloned haemolysin (Hly) genes and from strains possessing 'wild' Hly plasmids were lethal for mice on intravenous inoculation; similar doses of preparations from derivatives of these strains in which the Hly genes had been rendered non-functional or which did not possess the 'wild' plasmids were not. Live cultures of both kinds of Hly+ strain usually had a lower lethal dose for mice on intraperitoneal inoculation than the corresponding Hly- forms. Mice that had been inoculated with Hly+ forms had shorter survival times and lower numbers of organisms in peritoneal washings, lungs and blood at point of death than mice that had been inoculated with the corresponding Hly- forms; this was also so for mice pre-treated with FeSO4, a procedure which rendered mice equally susceptible to the lethal effects of the Hly+ and Hly- forms of a strain. In FeSO4-treated mice the numbers of organisms in the tissues of those dying from infection with Hly+ organisms were no higher than they were at the same time after inoculation in others given the corresponding Hly- forms; before mice of the latter category died the numbers of organisms in their tissues increased greatly. The clinical and pathological signs exhibited by mice inoculated with Hly+ organisms, but not with Hly- organisms, resembled those exhibited by mice inoculated with bacteria-free haemolysin preparations. These results suggest that haemolysin played a significant role in the pathogenesis of the disease produced by the Hly+ organisms by having a direct toxic action on the host.     

The oral route in the pathogenesis of paracoccidioidomycosis: An experimental study in BALB/c mice infected with P. brasiliensis Conidia

Due to the high frequency of oral mucosal lesions observed in paracoccidioidomycosis patients, it was advocated that the infection was acquired by the traumatic implantation of the etiologic agent Paracoccidioides brasiliensis. Although at present this theory is considered invalid, it has not yet been excluded in experimental studies. In order to determine if intra-oral inoculation could explain the pathogenesis of paracoccidioidomycosis, 64 BALB/c mice were inoculated intra-orally with 850.000 viable P. brasiliensis conidia into the mandibular body. Animals were sacrificed at various time intervals up to 20 weeks and cultures were made from gingiva, lungs, spleen, and liver. Additionally, histopathological studies of the mandibular body were also performed. P. brasiliensis was isolated from all gingival tissues during the interval 24–72 h, indicating that the infection was active. During the 5–10 week period, the infection appeared to have been controlled at the inoculation site as cultures showed a significant reduction in colony forming units (CFU); however, at the 15–20 week period such control was lost and the fungus was recovered once more. Dissemination to other body sites was rare; thus, the lungs were involved in just one animal (2%), the liver in two (3%) and the spleen in seven (11%). The infection became established as proven by positive organ cultures, but the dissemination pattern did not correspond to the one observed in humans. Based on these findings, the intra-oral traumatic route does not appear to mimic the natural history of paracoccidioidomycosis. This revised version was published online in August 2006 with corrections to the Cover Date.     

A critical role for C5L2 in the pathogenesis of experimental allergic asthma

The complement fragment C5a plays dual roles in the development of experimental allergic asthma. It protects from pulmonary allergy by a regulatory effect on dendritic cells during allergen sensitization, but is proallergic during the effector phase. C5a can bind to two distinct receptors (i.e., C5a receptor and C5a receptor-like 2 [C5L2]). The functional role of C5L2 in vivo remains enigmatic. In this study, we show in two models of OVA- and house dust mite (HDM)-induced experimental allergic asthma that C5L2-deficient mice are protected from the development of airway hyperresponsiveness, Th2 cytokine production, eosinophilic airway inflammation, serum IgE, or mucus production. Surprisingly, HDM-induced experimental asthma in C5L2-deficient mice was associated with increased pulmonary IL-17A production and increased airway neutrophil numbers. To directly assess the role of C5L2 on myeloid dendritic cells (mDCs) during allergen sensitization, we performed single or repeated adoptive transfers of C5L2-deficient mDCs into wild-type mice. HDM-pulsed C5L2-deficient mDCs induced strong Th2 cytokine production, which was associated with marked IFN-γ and IL-17A production, decreased eosinophil numbers, and reduced IgE production as compared with HDM-pulsed mDCs from wild-type mice. HDM stimulation of C5L2(-/-) mDCs in vitro resulted in production of Th17-promoting cytokine IL-23, which was absent in wild-type mDCs. Our findings suggest that C5L2 acts at the mDC/T cell interface to control the development of Th1 and Th17 cells in response to airway HDM exposure. Furthermore, it drives Th2 immune responses independent of mDCs, suggesting a complex role for C5L2 in the development of experimental allergic asthma.     

An appraisal of the role of biliary phospholipases in the pathogenesis of gallstone disease

Human bile contains proteins that influence nucleation of cholesterol. Recently, it has been suggested that activity of phospholipases in bile may play a role in this process. To study the influence of phospholipase on nucleation we have determined the effect of phospholipases A2, C and D on the nucleation time of model bile. Phospholipase C decreased the nucleation time, whereas phospholipase A2 inhibited nucleation. The phospholipases were effective only at relatively high concentrations. Phospholipase D was strongly inhibited in model bile and probably only influenced the nucleation time by an aspecific protein effect. The cleavage products of the different phospholipases were determined in native bile samples of 14 cholesterol gallstone patients, 6 patients without stones and 4 patients with pigment stones. In all samples, choline, phosphorylcholine and free fatty acids (FFA) could be detected. However, there was no significant difference between the three groups of patients. The rate of production of choline, phosphorylcholine and FFA was measured in bile incubated at 37 degrees C. Again, there was no significant difference between the three groups of patients. We conclude that phospholipase activity in bile does not play an important role in the pathogenesis of gallstone disease.     

Topical treatment with eberconazole of the experimental guinea pig cutaneous candidosis.

Eberconazole is a new azole antifungal drug for topical treatment of superficial mycoses. The usefulness of this drug was evaluated in an experimental model of cutaneous candidosis in guinea pigs comparing with the classical clotrimazole in a single blind trial. Twenty-five animals were inoculated in two symmetrical areas of the back with Candida albicans developing skin infection. One group of 10 animals were treated once per day with clotrimazole 1% cream in one side and with excipient in the other. Other group of 10 guinea pigs received eberconazole 1% cream and excipient. Five animals did not receive any treatment and were used as controls. After five days of treatment most lesions cured or improved and cultures were negative when clotrimazole or eberconazole were applied. Seventy per cent of lesions treated with excipient were clinically improved and 10% cured, but 85% of cultures remained positive for C. albicans. The therapeutic efficacy of eberconazole 1% cream was similar to clotrimazole 1% cream in the guinea ping model of cutaneous candidosis. Tolerance of both drugs was excellent. These results suggest the usefulness of eberconazole in human cutaneous infections due to C. albicans.     

An investigation of the role of the copper in galactose oxidase.

Galactose oxidase is a metalloenzyme containing a single copper atom per molecule. The mechanism of action of galactose oxidase is studied in this paper by investigating substrate specificity and activation by peroxidase, and probing the copper site by electron spin resonance (ESR) spectroscopy. Line-shape simulation of ESR spectra are also reported and a comparison is made between observed and simulated spectra for galactose oxidase. A comparison is also reported for the enzyme from various commercial sources and enzyme isolated from a fungus in this laboratory. The results of this investigation suggest that the copper is in an environment of four in-plane nitrogens with axial symmetry.     

An investigation into the role of Bcl-2 in neuroendocrine differentiation

INTRODUCTION: In addition to its role in apoptosis suppression, Bcl-2 has been reported to be co-expressed with neuroendocrine markers in several tissues, leading to speculation that this oncoprotein may promote neuroendocrine differentiation. AIM: This study investigated whether Bcl-2 modulated neuroendocrine biopeptide expression. METHODS: Levels of chromogranin A, neurone specific enolase, protein gene peptide 9.5, pancreatic polypeptide, and the chromogranin-derived peptides, intervening peptide and vasostatin-1 were examined by immunocytochemistry in rat phaeochromocytoma (PC12) cell lines genetically engineered to over-express Bcl-2 and their mock-transfected controls. Intensity of fluorescence was graded using a semi-quantitative scale from (-) indicating negative expression to (+++) indicating intense positivity. RESULTS: Mann-Whitney U analysis indicated that no significant differences in expression existed between control and Bcl2 over-expressing cell lines for any of the six peptides examined. CONCLUSIONS: The results of this study do not support the hypothesis that Bcl-2 promotes the acquisition of a neuroendocrine phenotype.     

An investigation into the role of malonyl-coenzyme A in isoprenoid biosynthesis

1. [¹⁴C]Malonyl-CoA was incorporated into isoprenoids by cell-free yeast preparations, by preparations from pigeon and rat liver, and by Hevea brasiliensis latex. 2. In agreement with previous reports the incorporation of acetyl-CoA into isoprenoids was not inhibited by avidin and was not stimulated by HCO₃⁻. In a cell-free yeast preparation addition of HCO₃⁻ stimulated the formation of fatty acids from acetyl-CoA and decreased the incorporation into unsaponifiable lipids. 3. The labelling patterns of β-hydroxy-β-methylglutaryl-CoA formed from [2-¹⁴C]- and [1,3-¹⁴C]-malonyl-CoA in rat and pigeon liver preparations were those that would be expected if malonyl-CoA underwent decarboxylation to acetyl-CoA before incorporation. 4. The labelling pattern of ergosterol formed by cell-free yeast preparations from [2-¹⁴C]malonyl-CoA was also consistent with decarboxylation of malonyl-CoA before incorporation. 5. The incorporation of [2-¹⁴C]malonyl-CoA into mevalonate by rat liver preparations was related to the malonyl-CoA decarboxylase activity present in the preparation.     

Hemidesmosomal dimensions and frequency in experimental oral carcinogenesis: a stereological investigation

Connective tissue invasion by carcinomas results in a variety of morphological changes at the epithelial-connective tissue junction. In this report, hemidesmosomal size (-delta) and frequency (Ns) were quantified using established stereological methods. Following treatment of hamster cheek pouches with the chemical carcinogen DMBA, lesions defined as hyperplasias, dysplasias and carcinomas were evaluated using electron microscopical techniques. Untreated pouches served as controls. Stereological intersection counting procedures were used to quantify hemidesmosomes at the epithelial-connective tissue junction. During carcinogenesis, hemidesmosomal diameter decreased progressively, although the reductions were not statistically significant. Hemidesmosomal frequency also decreased progressively between control and carcinoma groups. Normal basal plasma membranes possessed approximately 8 hemidesmosomes/micron 2 whereas values were reduced to approximately 3/micron 2 in the carcinoma group. The reductions in hemidesmosomal frequency during carcinogenesis may reflect an increased motility of basal epithelial cells and a decreased adherence of basal cells to the adjacent lamina propria. The specificity of this alteration in the pathogenesis of malignancy can be readily determined by the application of stereological methods to various neoplastic and non-neoplastic lesions.