[Aggressive angiomyxoma in a male patient: a case report]

INTRODUCTION

Aggressive angiomyxoma (AA) is a rare mesenchymal tumour of the connective tissue of the pelvis, which was described mainly in women in their reproductive period of life. Until now 45 cases of AA in men are documented with predominantly inguinal, parafunicular or scrotal localisation. These tumours slowly infiltrate the adjacent tissue and since symptoms are noticed only later these tumours have reached a considerable size at the time of diagnosis. In contrast to their benign histological appearance and almost entire absence of metastasis AA tends to (multiple) relapse.

CASE REPORT

We report on a 46-year-old male with a large tumour in the perineum. After complete resection, histological analysis revealed an AA. 26 months after surgery there is no evidence of relapse.

CONCLUSION

AA has to be considered as a possible diagnosis for obscure tumours of the pelvis. Since these tumours tend to relapse, margin-negative resection is most important. Also in cases of relapse, secondary excision should be achieved within healthy tissue. Adjuvant hormonal chemotherapy or radiation can be considered in cases of multiple relapse. Because of the risk of local recurrence rather than metastasis, these patients need a long-term follow up.

The osteoprotegerin/receptor activator of nuclear factor kappaB/receptor activator of nuclear factor kappaB ligand system in cartilage

OBJECTIVE

The receptor activator of nuclear factor kappaB (RANK) is a member of the tumor necrosis factor receptor family. It is activated by the secreted or cell surface-bound RANK ligand (RANKL). Osteoprotegerin (OPG) is a soluble nonsignaling receptor for RANKL and interferes with RANK activation. This receptor-ligand system regulates the differentiation of osteoclasts and dendritic cells. The present study examined human articular cartilage for the expression of these molecules and the role of RANKL in the regulation of chondrocyte function.

METHODS

Normal and osteoarthritic (OA) human articular cartilage was used for explant tissue culture or for isolation of chondrocytes and cell culture. Expression of RANK, RANKL, and OPG was analyzed by immunohistochemistry, Western blotting, or reverse transcription-polymerase chain reaction. Recombinant RANKL was added to cartilage or chondrocyte cultures, and gene expression, collagenase and nitric oxide production, and NF-kappaB activation were determined.

RESULTS

RANK, RANKL, and OPG messenger RNA (mRNA) were expressed in normal cartilage. By immunohistochemistry, RANK, RANKL, and OPG were detected in the superficial zone of normal cartilage. OA cartilage contained increased levels of OPG mRNA, and expression of the 3 proteins extended into the midzone of OA cartilage. OPG was detected by Western blotting, and was increased in response to interleukin-1beta stimulation. OPG, RANK, and RANKL protein were also detected in cultured chondrocytes. Addition of exogenous RANKL did not activate NF-kappaB, induce expression of genes encoding proinflammatory mediators in chondrocytes, or stimulate the production of collagenase and nitric oxide.

CONCLUSION

These results demonstrate the expression of OPG, RANK, and RANKL in cartilage. However, RANKL does not activate human articular chondrocytes.

Photosynthetic water oxidation in cytochrome b(559) mutants containing a disrupted heme-binding pocket

The role of cytochrome b(559) in photosynthetic oxygen evolution has been investigated in three chloroplast mutants of Chlamydomonas reinhardtii, in which one of the two histidine axial ligands to the heme, provided by the alpha subunit, has been replaced by the residues methionine, tyrosine, and glutamine. Photosystem two complexes functional for oxygen evolution could be assembled in the methionine and tyrosine mutants up to approximately 15% of wild type levels, whereas no complexes with oxygen evolution activity could be detected in the glutamine mutant. PSII supercomplexes isolated from the tyrosine and methionine mutants were as active as wild type in terms of light-saturated rates of oxygen evolution but in contrast to wild type contained no bound heme despite the presence of the alpha subunit. Oxygen evolution in the tyrosine and methionine mutants was, however, more sensitive to photoinactivation than the WT. Overall, these data establish unambiguously that a redox role for the heme of cytochrome b(559) is not required for photosynthetic oxygen evolution. Instead, our data provide new evidence of a role for cytochrome b(559) in the protection of the photosystem two complex in vivo.

Regulation of CD95 (Fas/APO-1)-induced apoptosis in human chondrocytes

OBJECTIVE

To examine the role of nuclear factor kappaB (NF-kappaB) and caspases 3, 8, and 9 in CD95-mediated apoptosis of normal chondrocytes.

METHODS

First-passage chondrocytes from normal human knee cartilage were stimulated with CD95 antibody, and cell death was determined by annexin V binding and by an enzyme-linked immunosorbent assay. Activation of caspases 3, 8, and 9 was measured by Western blotting, and their role in death signaling was evaluated using caspase-specific small peptide inhibitors. The influence of NF-kappaB was determined by electrophoretic mobility shift assay (EMSA) and proteasome inhibition-dependent blocking of the degradation of inhibitor of NF-kappaB.

RESULTS

Low levels of NF-kappaB activity were detected by EMSA in unstimulated chondrocytes. NF-kappaB activity was increased in response to agonistic CD95 antibody. CD95 antibody-induced apoptosis was potentiated by the proteasome inhibitors MG-132 and PS1, and this was associated with a reduced nuclear translocation of NF-kappaB. Proteasome inhibitors also caused the induction of DNA fragmentation by tumor necrosis factor alpha. Procaspase 3 processing was enhanced by the proteasome inhibitor MG-132. Procaspase 8 was undetectable by immunoblotting in whole cell lysates of chondrocytes, but caspase 8 messenger RNA was detected by reverse transcription-polymerase chain reaction. Furthermore, apoptosis induced by CD95 stimulation and proteasome inhibitors was blocked by the caspase 8-specific inhibitor Ac-IETD-CHO. Processing of procaspase 9 was not observed, and inhibition of CD95-dependent cell death by the caspase 9 inhibitor Ac-LEHD-CHO was not significant.

CONCLUSION

These results suggest that CD95-dependent cell death is enhanced by NF-kappaB inhibition at and/or downstream of caspase 8 activation and that caspase 9 activation is not involved in CD95-mediated apoptosis in chondrocytes.

Parkin expression in the adult mouse brain

Mutations in a protein designated Parkin were shown to be involved in the pathogenesis of autosomal recessive juvenile parkinsonism. Nothing is known about its regional and subcellular distribution in the mouse. In order to elucidate the Parkin mRNA and protein distribution in the adult mouse, the mouse cDNA was cloned and polyclonal antisera were generated against the N-terminal part of mouse Parkin. The antibodies were shown to be specific using Western blot analysis, immunostaining of cells transfected with mouse Parkin and pre-absorption tests. The Parkin protein expression profile was studied using immunohistochemistry and Western blot analysis and was compared with that of the mRNA yielded by in situ hybridization and RT-PCR analysis. Parkin protein was widely distributed in all subdivisions of the mouse brain. Low levels were found in the telencephalon and diencephalon, while the brainstem contained a large number of cells heavily expressing Parkin. Ultrastructural analysis and double immunohistochemistry revealed that the majority of Parkin-expressing cells were neurons, while only single glial cells exhibited immunostaining. The protein was distributed nonhomogeneously throughout the entire cytoplasm. A subpopulation of Parkin-immunopositive cells displayed speckled immunodeposits in the nucleus. Dopaminergic cells of the substantia nigra pars compacta exhibited high levels of Parkin mRNA but no Parkin protein, while the striatum contained immunopositive profiles but no mRNA signals. Our data indicate that Parkin is neither restricted to a single functional system nor associated with a particular transmitter system. The speckled nuclear distribution of Parkin immunoreactivity strongly suggests a role for Parkin in gene expression.

The spatial orientation of the essential amino acid residues arginine and aspartate within the alpha1beta1 integrin recognition site of collagen IV has been resolved using fluorescence resonance energy transfer

The interaction of collagen IV with cells is mediated mainly by the integrin alpha1beta1. The recognition site has been located to a segment of the triple-helical domain 100 nm away from the N terminus of the collagen molecule. The three essential amino acid residues of the alpha1beta1 binding site, arginine alpha2(IV)461 and the two aspartate residues alpha1(IV)461, are all located on different chains. Since the spatial array of the three residues depends on the stagger of the chains within the triple helix, the stagger has been elucidated using fluorescence resonance energy transfer with phenylalanine alpha1(IV)473 and tryptophan alpha2(IV)479 as the fluorescent donor/acceptor pair. The distance R between phenylalanine and tryptophan was determined by analysis of the energy transfer efficiency, E, and the orientation factor, kappa(2). In parallel, distance R and orientation factor, kappa(2 )were also calculated from the coordinates of the triple helix. Comparison of the calculated and empirically determined values unequivocally showed the stagger to be alpha1'alpha1alpha2. This arrangement of the three alpha chains describes the conformation of the alpha1beta1 integrin recognition site, that is the distinct orientation of the side-chains of the essential residues aspartate and arginine in respect to the helix axis.

IL-1 beta protects human chondrocytes from CD95-induced apoptosis

This study addresses the effects of IL-1 beta on apoptosis induced by agonistic anti-CD95 (Fas) Ab. IL-1 beta inhibited anti-CD95 Ab-induced apoptosis in all preparations of normal human articular chondrocytes tested. Inhibitors of nitric oxide synthase or cyclooxygenase did not influence the protective effect of IL-1 beta, indicating that nitric oxide and PGs were not involved in the modulation of CD95-induced apoptosis. However, when the IL-1 beta-dependent induction of NF-kappa B was inhibited, the antiapoptotic effect of IL-1 beta was partially reversed, suggesting that NF-kappa B-mediated gene activation is part of the protective mechanism. In addition, IL-1 beta significantly increased the expression of Bcl-2. The protein tyrosine kinase inhibitor herbimycin A completely eliminated the protective effect of IL-1 beta on CD95-induced apoptosis. These findings suggest that IL-1 beta modulates the CD95 death cascade in chondrocytes by mechanisms that involve tyrosine phosphorylation events and NF-kappa B-dependent gene activation.

Cell density modulates apoptosis in human articular chondrocytes

This study addresses the effects of cell density and serum on CD95 (APO-1/Fas) and CD95L (Fas Ligand) expression and on the induction of CD95-dependent apoptosis in human articular chondrocytes from normal knees. Subsets of articular chondrocytes in first passage monolayer culture expressed CD95 and CD95L on the cell surface. The expression of both molecules was influenced by cell density: 22.3% of chondrocytes plated at subconfluent density expressed CD95L while expression in confluent cultures was reduced to 8.2%. CD95 expression was 32.1% under subconfluent and 12.2% under confluent conditions. Induction of specific apoptosis by agonistic antibody to CD95 was 15 times higher in confluent cultures than in subconfluent cultures despite higher levels of CD95 and CD95L expression in subconfluent cells, suggesting that protective antiapoptotic mechanisms were activated in low-density cultures. In subconfluent cultures, serum withdrawal had no effect on the sensitivity of the cells toward CD95 antibody-induced apoptosis. However, in confluent cultures, serum withdrawal led to a significant reduction of CD95-dependent apoptosis. Together, these findings demonstrate that cell density is an important modulator of CD95/CD95L expression and susceptibility to CD95-mediated apoptosis in cultured human chondrocytes.

Prevalence of verotoxin-producing Escherichia coli (VTEC) in bovine coli mastitis and their antibiotic resistance patterns

Between December 1996 and October 1997, milk samples from a total of 145 cows with coli mastitis were screened for the presence of verotoxin-producing E. coli (VTEC). VTEC were found in four (2.8%) out of the 145 samples. The four isolated strains proved to be verotoxin (VT) 1-, VT2- or VT1- and VT2-positive. However, no strain contained all three virulence factors tested. Further strain characterization was carried out by serotyping as well as by resistance pattern analysis.

Mechanisms of chondrocyte apoptosis

This study addresses the occurrence and significance of chondrocyte apoptosis in the pathogenesis of cartilage destruction. Chondrocyte apoptosis can be induced in vitro by nitric oxide donors, but not by pro-inflammatory cytokines, such as IL-1 or TNF. A subset of chondrocytes, located in the superficial zone of cartilage, expresses the Fas antigen. Activation of the Fas receptor triggers apoptosis in these cells. In human and experimental osteoarthritis (OA) induced in rabbits by anterior cruciate ligament transection increased numbers of chondrocytes were undergoing apoptosis. Cartilage areas that contained apoptotic cells showed proteoglycan depletion and the number of apoptotic cells was significantly correlated with the levels of nitric oxide production and with the severity of OA. Articular cartilage is not vascularized and does not contain mononuclear phagocytes. There is, thus, no apparent mechanism for the clearance of apoptotic bodies. Chondrocyte-derived apoptotic bodies produced pyrophosphate and precipitated calcium. These results suggest that chondrocyte-derived apoptotic bodies express functional properties that may contribute to the pathologic cartilage degradation and calcification. Inhibition of chondrocyte apoptosis may be of therapeutic value after cartilage injury and in arthritis.