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M Schaller

Publications and source records attributed to M Schaller.

At least 55 records · Page 3Linked to original sources
PubMed1999

Secreted aspartic proteinase (Sap) activity contributes to tissue damage in a model of human oral candidosis.

Secreted aspartic proteinases (Saps) are important virulence factors during Candida albicans mucosal or disseminated infections. A differential expression of individual SAP genes has been shown previously in a model of oral candidosis based on reconstituted human epithelium (RHE), and in the oral cavity of patients. In this study, the ultrastructural localization of distinct groups of Sap isoenzymes expressed during RHE infection was shown by immunoelectron microscopy using specific polyclonal antibodies directed against the gene products of SAP1-3 and SAP4-6. Large amounts of Sap1-3 antigen were found within C. albicans yeast and hyphal cell walls, often predominantly in close contact with epithelial cells, whereas lower quantities of Sap4-6 were detected in hyphal cells. To elucidate the relevance of the expressed Saps during oral infections, we examined the effect of the aspartic proteinase inhibitor, pepstatin A, during infection of the RHE. The extent of lesions caused by the strain SC5314 was found to be strongly reduced by the inhibitor, indicating that proteinase activity contributes to tissue damage in this model. To clarify which of the SAP genes are important for tissue necrosis, the histology of RHE infection with Deltasap1, Deltasap2, Deltasap3, Deltasap4-6 and three Deltasap1/3 double mutants were examined. Although tissue damage was not blocked completely with these mutants, an attenuated phenotype was observed for each of the single sap null mutants, and was more strongly attenuated in the Deltasap1/3 double null mutants. In contrast, the lesions caused by the Deltasap4-6 triple mutant were at least as severe as those caused by SC5314. During infection with the mutants, we observed that the SAP gene expression pattern of the Deltasap1 and the Deltasap1/3 mutants was altered in comparison with the wild-type strain. Expression of SAP5 was observed only during infection with the Deltasap1/3 mutant, whereas upregulation of SAP2 and SAP8 transcripts was observed in the Deltasap1 and the Deltasap1/3 mutants. These results suggest that Sap1-3, but not Sap4-6, contribute to tissue damage in this model. Furthermore, C. albicans may compensate for the deletion of certain SAP genes by upregulation of alternative SAP genes.

Antigens, Fungal↗
PubMed1999

Cloning and expression of succinic semialdehyde reductase from human brain. Identity with aflatoxin B1 aldehyde reductase.

The neuromodulator gamma-hydroxybutyrate is synthesized in vivo from gamma-aminobutyrate by transamination to succinic semialdehyde and subsequent reduction of the aldehyde group. In human brain, succinic semialdehyde reductase is thought to be responsible for the conversion of succinic semialdehyde to gamma-hydroxybutyrate. In the present work, we cloned the cDNA coding for succinic semialdehyde reductase and expressed it in Escherichia coli. A data bank search indicated that the enzyme is identical with aflatoxin B1-aldehyde reductase, an enzyme implicated in the detoxification of xenobiotic carbonyl compounds. Structurally, succinic semialdehyde reductase thus belongs to the aldo-keto reductase superfamily. The recombinant protein was indistinguishable from native human brain succinic semialdehyde reductase by SDS/PAGE. In addition to succinic semialdehyde, it readily catalyzed the reduction 9,10-phenanthrene quinone, phenylglyoxal and 4-nitrobenzaldehyde, typical substrates of aflatoxin B1 aldehyde reductase. The results suggest multiple functions of succinic semialdehyde reductase/aflatoxin B1 aldehyde reductase in the biosynthesis of gamma-hydroxybutyrate and the detoxification of xenobiotic carbonyl compounds, respectively.

Aldehyde Reductase↗
PubMed1999

In vivo expression and localization of Candida albicans secreted aspartyl proteinases during oral candidiasis in HIV-infected patients.

Isoforms of aspartyl proteinase (Sap), which are encoded by at least nine related SAP genes, have been implicated to be a major virulence factor of the opportunistic yeast Candida albicans in experimental infections. Although it is generally assumed that proteinases are important for infections, detailed information on the pathogenetic role of Saps is still lacking. The same applies to the question whether the genes and corresponding isoforms of the enzyme are expressed during oral infection. For in vivo investigations, parts of the lesional oral epithelium were collected from three HIV-infected patients with oropharyngeal candidiasis. Immunoelectron microscopy was performed (pre- and post-embedding gold labeling with silver enhancement) using an anti-Sap murine monoclonal antibody directed against the gene products Sap1-3. It was possible to demonstrate expression of Sap antigens in each of the three samples of human oral candidiasis. This suggests that at least one of the genes SAP1-3 was expressed at the time of sample collection. Furthermore, a possible role of the enzymes during the interaction of yeast cells and mucosal cells is suggested: the majority of Sap antigens is secreted by those C. albicans cells that adhere directly to the epithelial surface. Sap immunoreactivity can be detected in particular at the site of close contact between C. albicans and epithelial cells, suggesting a pathogenetic role of the Saps in host-fungal interaction. Thus, inhibition of the enzyme might prove to be an important alternative in the prevention and treatment of candidiasis.

Adult↗
PubMed1999

Effects of the human immunodeficiency virus (HIV) proteinase inhibitors saquinavir and indinavir on in vitro activities of secreted aspartyl proteinases of Candida albicans isolates from HIV-infected patients.

The effects of therapeutically relevant concentrations of the human immunodeficiency virus (HIV) proteinase inhibitors saquinavir and indinavir on the in vitro proteinase activity of Candida albicans were investigated with isolates from HIV-infected and uninfected patients with oral candidiasis. After exposure to the HIV proteinase inhibitors, proteinase activity was significantly reduced in a dose-dependent manner. These inhibitory effects, which were similar to that of pepstatin A, and the reduced virulence phenotype in experimental candidiasis after application of saquinavir indicate the usefulness of these HIV proteinase inhibitors as potential anticandidal agents.

AIDS-Related Opportunistic Infections↗
PubMed1999

Light and electron microscopic findings in a model of human cutaneous candidosis based on reconstructed human epidermis following the topical application of different econazole formulations.

The effects of two commercially available econazole formulations (econazole nitrate cream, econazole liposome gel) on uninfected reconstructed human epidermis and on a model of human cutaneous candidosis were investigated. The morphological alterations of the reconstructed epidermis after infection and treatment were analysed with light and electron microscopy. The most important Candida albicans-specific alterations of the recently established in vitro model of human cutaneous candidosis were scaling, hyperkeratosis, parakeratosis, dyskeratosis and spongiosis. A single application of the cream to the uninfected reconstructed epidermis caused more epidermal barrier damage and irritative toxic effects than the liposome gel. Treatment of the modelled human cutaneous candidosis with the cream also resulted in increased toxic effects, e.g., enhancement of scaling with invasion of Candida albicans blastospores into the stratum corneum and intracellular vacuoles. After application of the liposomal preparation invasion of Candida albicans in the stratum corneum could not be detected and toxic effects were reduced. Some of the Candida albicans-specific alterations such as hyperkeratosis, focal thickening of the stratum corneum, dyskeratosis and parakeratosis were completely eliminated. The liposomal formulation increased slightly the morphological alterations of the blastospores. Remnants of the cream formulation could be detected only very rarely in the stratum corneum or the blastospores. The liposomal preparation showed a strong affinity for the Candida albicans cells and the stratum corneum. Intact liposomes could even be observed in the intercellular spaces of the upper stratum corneum. As successful treatment depends on the ability to target the liposomal agent to the wanted site of action, this might be useful for more effective treatment of cutaneous candidosis.

Antifungal Agents↗
PubMed1999

Parameters for determination of Candida albicans virulence in murine peritonitis.

Using intraperitoneal (i.p.) infection of mice with Candida albicans we determined which parameters might be useful for characterization of virulence in this model. Upon i.p. infection of mice with two reference strains striking differences in lethality were detected. These differences in virulence corresponded with invasion of the liver and pancreas by the virulent strain and with a lack of invasion by the avirulent strain. The virulent strain was able to release high amounts of the enzymes alanine aminotransferase (ALT) and alpha-amylase (AM) from liver and pancreas into the blood plasma. Most likely, these enzymes were released by penetration of hyphae into the cytoplasm which was shown with electron microscopy. When invasion slowed down, there was also a drop in the activities of ALT and AM measured in the blood of infected mice. As both strains disseminated to the heart, kidneys, and lungs, dissemination into these organs was no reliable parameter for virulence in this model. However, only the virulent strain was able to reach the brain and to germinate in the kidneys and brain. In contrast to invasion and enzyme activities, the fungal load in the peritoneal cavity and in the neighbouring organs appeared not to be related with virulence. This may be concluded from the fact that there were no differences in the absolute colony forming units (cfu) and the length of persistence of both strains when similar inocula were used. We conclude that the ability of a given strain of C. albicans to invade neighbouring organs, to reach the brain upon dissemination and germination in the brain and kidneys may be used for measurement of virulence in this model when virulence is defined as lethality.

Alanine Transaminase↗
PubMed1998

[Botulinum toxin A in dermatology].

Based on its unique botulinum toxin is referred to as the most poisonous poison. Its specific inhibition of the acetyl-cholin-dependent neuromuscular transmission is used by ophthalmologists and neurologists for the relaxation of spastic or dystonic muscles, preferably in muscle groups in the head and neck area. Analogously, it is being used by dermatologists to remove facial wrinkles by paralyzing mimic muscles which account for mechanically induced wrinkling. Apart from this purely cosmetic use, botulinum toxin has gained recent attention in dermatology as a potent treatment modality for circumscribed hyperhidrosis.

Botulinum Toxins, Type A↗
PubMed1998

[Axillary hyperhidrosis: successful treatment with botulinum toxin A].

Severe hyperhidrosis may present as a vexing condition for the patient and a therapeutic challenge for the physician. As botulinum toxin-A (BT-A) can potently block cholinergic sympathic innervation of sweat glands it was used in an open trial for controlling severe axillary hyperhidrosis. After visualization of hyperhidrosis using the iodine-starch-test BT-A (Dysport, 400 Units) was injected intradermally in one axilla. One week later gravimetric quantification of sweat secretion revealed a reduction of sweating to 4-9% of initial values. In order to rule out daily variations as well as other factors interfering with sweat production BT-A treatment was restricted to only one axilla in each individual clearly demonstrating extensive anhidrotic efficacy on the treated side only. The treatment was well tolerated without side-effects and was assessed as 'completely satisfying' by all patients. BT-A may offer a fast, safe and highly effective therapeutic option for severe hyperhidrosis.

Adolescent↗
PubMed1998

A model of human cutaneous candidosis based on reconstructed human epidermis for the light and electron microscopic study of pathogenesis and treatment.

The use of reconstructed human epidermis provided the basis for an in vitro model of human cutaneous candidosis. Candida albicans blastospores on the surface of reconstructed human epidermis provoked the following changes within 72 h: superficial keratin degradation, scaling, hyperkeratosis, parakeratosis, dyskeratosis representing hyperproliferative stress, spongiosis, and vesiculation. Great differences in the intensity of these reactions of intact reconstructed human epidermis or chemically or mechanically damaged reconstructed human epidermis illustrate the importance of the stratum corneum as a barrier. Uninfected reconstructed human epidermis showed prominent cell proliferation representing wound healing 72 h after mechanical or chemical pretreatment. These signs of repair were blocked in the presence of C. albicans and the blastospores were able to invade the stratum corneum. When desmosomes were accessible, a high affinity of C. albicans blastospores to these structures was observed. A single application of an econazole liposome dispersion decreased scaling, hyperkeratosis and dyskeratosis. Morphological alterations of C. albicans blastospores after treatment with the econazole liposome dispersion in the proposed ill vitro model were identical, as described in established animal models. This reconstructed human epidermis model of cutaneous disease may provide insight into the pathogenesis and treatment of cutaneous candidosis and may provide a substitute for animal models and investigations on humans.

Antifungal Agents↗
PubMed1998

Differential expression of secreted aspartyl proteinases in a model of human oral candidosis and in patient samples from the oral cavity.

Candida albicans, an opportunistic pathogen in humans, secretes secretory aspartyl proteinases (Saps), which have been correlated with virulence. We examined the temporal regulation of the mRNA expression of seven known members of the SAP gene family by reverse transcription polymerase chain reaction (RT-PCR) in (i) an in vitro model of oral candidosis based on reconstituted human epithelium (RHE); and (ii) clinical samples from patients with oral candidosis. SAP1 and SAP3 transcripts were first detected 42 h after inoculation of RHE, while at the same time, slight morphological alterations in the epithelium were documented by light microscopy. SAP6 expression occurred 6 h later concomitantly with germ tube formation of some infecting Candida cells and severe lesions of the epithelial tissue. SAP2 and SAP8 RT-PCR products were first detected 60 h after infection, while SAP4 and SAP5 transcripts were never discovered. Thus, a temporal progression of SAP expression in the order SAP1 and SAP3 > SAP6 > SAP2 and SAP8 was observed at the same time as increasing RHE damage occurred. At the protein level, Sap antigen was found within the C. albicans yeast cells and the epithelial cells by immunoelectron microscopy using an anti-Sap murine monoclonal antibody directed against the gene products Sap1-3. Expression of SAP1-3 and 6 was also detected by RT-PCR in samples from patients suffering from oral candidosis. Our results suggest that the pathogenesis of experimental and clinical oral candidosis is associated with the differential and temporal regulation of SAP gene expression.

Adult↗
PubMed1998

[What functions do six different genes for secretory proteinases have in Candida albicans?].

Secreted Aspartate Proteinases (Sap) are among those factors of the human pathogen Candida albicans, which promote infections in the immunocompromised host. Sap isoenzymes are encoded by at least nine different genes (SAP1-9), which are differentially regulated in vitro. RT-PCR analysis during experimental infections and from patient samples confirmed the expression of SAP genes in vivo. However, while Sap2 is the dominant isoenzyme under culture conditions, other SAP genes are also expressed during infections. In order to investigate the role of single isoenzymes during the pathogenesis of candidosis, mutants were produced which harbour deletions in SAP1, SAP2, SAP3 and SAP4-6. Although only SAP2 and SAP4-6 mutants showed a strong reduction of proteolytic activity in vitro, all SAP mutants were significantly attenuated in systemic infections. In addition, SAP2, SAP3 and SAP4-6 mutants were clearly more sensitive to neutrophilic leucocytes compared to the wild type SC5314. These investigations show that several proteinase isoenzymes are likely to be involved in the pathogenesis of candidosis.

Candida albicans↗
PubMed1998

[Investigations on the regulation of secreted aspartyl proteases in a model of oral candidiasis in vivo].

By means of RT-PCR and specific primers the expression of SAP1-6 and SAP8 was investigated with respect to the time course in an in vitro candidosis model based on reconstituted human mucosal epithelium. Corresponding morphological alterations of the epithelium were documented by light microscopy. The detection of Sap was performed immunoelectron microscopically using a monoclonal antibody. In the oral candidosis model SAP1 and SAP3 transcripts were detected 42 h after inoculation corresponding to first histopathological changes. Additional SAP6 expression was observed six hours later concomitantly with germ-tube formation. Later on SAP2 and SAP8 transcripts were found after 60 h. On protein level it was possible to demonstrate Sap antigens within Candida and markedly deteriorated epithelial cells. Initial experiments with proteinase mutants and proteinase inhibitors showed reduction of histological damage. In a clinical specimen obtained from a twenty nine-year-old female patient suffering from acute oral candidosis SAP1, 3 and 6 could be demonstrated corresponding to the findings in vitro after 48 h. Investigating a clinical specimen obtained from a lesion of chronic oral candidosis in an HIV-infected patient also showed SAP2 expression. On the basis of our results a relationship between the expression on of particular SAP genes and the turn up of lesions looks as probable as a relevant contribution to the in vivo infection.

Adult↗
PubMed1997

Integrin-mediated activation of MAP kinase is independent of FAK: evidence for dual integrin signaling pathways in fibroblasts.

Integrin-mediated cell adhesion causes activation of MAP kinases and increased tyrosine phosphorylation of focal adhesion kinase (FAK). Autophosphorylation of FAK leads to the binding of SH2-domain proteins including Src-family kinases and the Grb2-Sos complex. Since Grb2-Sos is a key regulator of the Ras signal transduction pathway, one plausible hypothesis has been that integrin-mediated tyrosine phosphorylation of FAK leads to activation of the Ras cascade and ultimately to mitogen activated protein (MAP) kinase activation. Thus, in this scenario FAK would serve as an upstream regulator of MAP kinase activity. However, in this report we present several lines of evidence showing that integrin-mediated MAP kinase activity in fibroblasts is independent of FAK. First, a beta1 integrin subunit deletion mutant affecting the putative FAK binding site supports activation of MAP kinase in adhering fibroblasts but not tyrosine phosphorylation of FAK. Second, fibroblast adhesion to bacterially expressed fragments of fibronectin demonstrates that robust activation of MAP kinase can precede tyrosine phosphorylation of FAK. Finally, we have used FRNK, the noncatalytic COOH-terminal domain of FAK, as a dominant negative inhibitor of FAK autophosphorylation and of tyrosine phosphorylation of focal contacts. Using retroviral infection, we demonstrate that levels of FRNK expression sufficient to completely block FAK tyrosine phosphorylation were without effect on integrin-mediated activation of MAP kinase. These results strongly suggest that integrin-mediated activation of MAP kinase is independent of FAK and indicate the probable existence of at least two distinct integrin signaling pathways in fibroblasts.

3T3 Cells↗
PubMed1997

[Generalized Mycobacterium avium-intracellulare infection due to immunosuppressive therapy of paraneoplastic dermatomyositis].

The ubiquitous Mycobacterium avium-intracellulare (MAI) is the most frequent cause of disseminated atypical mycobacteriosis in AIDS patients. MAI infections may develop in patients with other acquired immune defects, such as connective tissue disorders. In adults, the gastrointestinal and respiratory systems are most frequently affected. We report a patient with dermatomyositis receiving immunosuppressive therapy in whom only the skin and the skeletal system were affected by MAI. Because it presented with polymyositis-like symptoms, the infection was initially not identified and treated. The MAI was cultured from a periarticular joint effusion from the right upper arm and from venous blood, as well as identified histologically in lesional skin. Resistance to antibiotics developed most likely because the patient failed to take oral antibiotics regularly. Because of an acute exacerbation of the tumor-associated dermatomyositis, immunosuppressive therapy was initiated, while the tuberculostatic therapy was continued. Using these therapies both diseases markedly improved. In patients with connective tissue disorders receiving longterm immunosuppressive therapy, especially when changes in symptoms and signs are observed, opportunistic infections such as MAI should be considered and included in the differential diagnosis.

Adenocarcinoma↗
PubMed1997

[Juvenile hyaline fibromatosis].

Juvenile hyaline fibromatosis is a rare autosomal recessive connective tissue disease first described in 1873 by Murray. Major diagnostic criteria are multiple cutaneous tumors and gingival hypertrophy; minor criteria include contractures, osteolytic lesions and a positive family history. After a normal perinatal period at the age of 6 months our 24 year old patient developed gingival hypertrophy. During the first months of life several skin coloured nodules had been noticed on the neck and in the perianal area. At the age of 15 months, these nodules began to appear more rapidly, both spontaneously and posttraumatically. The patient showed normal development, but the lesions progressed. By the age of 15 years, the patient had extensive deformities and was unable to walk and move by himself. Both his sisters and the unrelated parents had no lesions. Essential for the diagnosis are the clinical picture and the histology. Electron microscopy is helpful to support the diagnosis. Defective connective tissue proteins such as chondroitin, collagen and mucopolysaccharides are probably the pathological defect. A therapy is so far unknown.

Adult↗