Isopeptidase activity of human transglutaminase 2: disconnection from transamidation and characterization by kinetic parameters

Transglutaminase 2 (TG2) is a multifunctional protein with diverse catalytic activities and biological roles. Its best studied function is the Ca(2+)-dependent transamidase activity leading to formation of γ-glutamyl-ε-lysine isopeptide crosslinks between proteins and γ-glutamyl-amine derivatives. TG2 has a poorly studied isopeptidase activity cleaving these bonds. We have developed and characterised TG2 mutants which are significantly deficient in transamidase activity while have normal or increased isopeptidase activity (W332F) and vice versa (W278F). The W332F mutation led to significant changes of both the K m and the V max kinetic parameters of the isopeptidase reaction of TG2 while its calcium and GTP sensitivity was similar to the wild-type enzyme. The W278F mutation resulted in six times elevated amine incorporating transamidase activity demonstrating the regulatory significance of W278 and W332 in TG2 and that mutations can change opposed activities located at the same active site. The further application of our results in cellular systems may help to understand TG2-driven physiological and pathological processes better and lead to novel therapeutic approaches where an increased amount of crosslinked proteins correlates with the manifestation of degenerative disorders.

Synthesis and evaluation of phosphorus containing, specific CDK9/CycT1 inhibitors

Although there is a significant effort in the design of a selective CDK9/CycT1 inhibitor, no compound has been proven to be a specific inhibitor of this kinase so far. The aim of this research was to develop novel and selective phosphorus containing CDK9/CycT1 inhibitors. Molecules bearing phosphonamidate, phosphonate, and phosphinate moieties were synthesized. Prepared compounds were evaluated in an enzymatic CDK9/CycT1 assay. The most potent molecules were tested in cell-based toxicity and HIV proliferation assays. Selectivity of shortlisted compounds against CDKs and other kinases was tested. The best compound was shown to be a highly specific, ATP-competitive inhibitor of CDK9/CycT1 with antiviral activity.

[Pyrido[2,3-b]pyrazines inhibiting both erlotinib-sensitive and erlotinib-resistant cell lines, and their preparation via regioselective condensation reaction]

The EGFR inhibitor erlotinib possesses high anti-tumor effect but despite the good clinical responses in most of the cases recrudescence occures. This can be attributed to a secondary, acquired mutation causing resistance to tyrosine kinase inhibitors. In our work we were looking for small-molecule inhibitors, which simultaneously affect on the proliferation of erlotinib-sensitive PC9 cells and PC9-ER erlotinib-resistant cells. A set of molecules were selected from Vichem Chemie Research Ltd.'s kinase inhibitor compound library (Nested Chemical Library™). According to the results of medium throughput screening (MTS) of this set of compounds, novel structures with pyrido[2,3-b]pyrazine core were designed. These compounds were proved to be effective inhibitors of resistant cells in phenotypic screening. Based on these results structure-activity relationships were set up. The pyrido[2,3-b]pyrazine core was synthesized by a condensation reaction, which resulting two asymmetric products. In the reaction two regioisomer intermediates formed, and one of the products is the intermediate of the effective compounds. This condensation reaction was optimized, the regioisomers were identified by NMR analysis and X-ray crystallography. As a result of optimization we found that lower reaction temperature and replacement of dimethylformamide solvent with trifluoroacetic acid provided the undesired isomer in less than 2 % ratio.

[Malignant insulinoma]

Authors present the history of a 56-year-old man who was evaluated for recurrent epigastric pain. Clinical investigation revealed a 4-cm tumor in the head of the pancreas and a solitary liver metastasis. Pathological examination of the surgically excised pancreatic tumor indicated a moderately differentiated neuroendocrine carcinoma and Ki-67 labeling index revealed moderate proliferative activity. Despite short-term chemotherapy combined with interferon and somatostatin analogue administration, the metastatic disease rapidly progressed. Octreotide scintigraphy disclosed abundant expression of somatostatin receptors both on primary tumor and hepatic metastases. ⁹⁰Yttrium-DOTATOC treatment was performed in three sessions within 9 months (3 x 200 mCi) with a mixed therapeutic response. Endocrine symptoms were not observed during the first 33 months of the disease. 34 months after the initial diagnosis of the neoplastic disease, imaging studies and chromogranin A measurement revealed rapidly progressing disease and the patient developed frequent episodes of hypoglycemic attacks. Serum insulin and C-peptide measurements confirmed insulin oversecretion. Continuous administration of somatostatin analogue was supplemented with diazoxide, but the latter therapy was not tolerated because of severe water retention. The high dose oral carbohydrate intake was supplemented with continuous glucose infusion. As a rescue procedure, repeated liver chemoembolization was performed, which resulted only in a short-term effect. The autopsy and the immunohistochemical investigations confirmed the diagnosis of insulin-producing, metastatic neuroendocrine carcinoma.

Transglutaminase-mediated intramolecular cross-linking of membrane-bound alpha-synuclein promotes amyloid formation in Lewy bodies

The alpha-synuclein immunopositive and chaotrope-insoluble material from human brains with Lewy body pathology was analyzed by mass spectrometry. From the proteinase K-cleavable peripheral fraction of Lewy bodies, which was densely cross-linked by gamma-glutamyl-epsilon-lysine bonds between HspB1 and ubiquitin in a pattern similar to neurofibrillary tangles (Nemes, Z., Devreese, B., Steinert, P. M., Van Beeumen, J., and Fésüs, L. (2004) FASEB J. 18, 1135-1137), 53 proteins were identified. In the core of Lewy bodies only alpha-synuclein was found, and it contained a low amount of intramolecular cross-links between Gln-99 and Lys-58. In vitro cross-linking of alpha-synuclein by transglutaminases 1-3 and 5 produced a heterogeneous population of variably cross-linked alpha-synucleins in solution, which inhibited the aggregation of the protein into amyloid. However, in the presence of phosphatidylserine-rich membranes and micromolar calcium concentrations, the cross-linking by transglutaminases 1, 2, and 5 showed specificity toward the utilization of Gln-99 and Lys-58. As shown by thioflavin T fluorescence monitoring, the formation of this cross-link accelerated the aggregation of native alpha-synuclein. Chemical cross-linking of residues 58-99 triggered amyloid formation, whereas such bonding of residues 99 to 10 was inhibitory. Our findings reveal the pivotal role of membrane attachment and transglutaminase-mediated intermolecular cross-linking for the propagative misfolding and aggregation of alpha-synuclein.

Tissue response to iodine-125 interstitial brachytherapy of cerebral gliomas

The purpose of this study was to investigate histopathological changes and the role of the microglia/macrophage cell system in the therapeutic effect of iodine-125 (125I) interstitial brachytherapy on cerebral gliomas. Out of a series of 60 cases harboring cerebral astrocytomas and other brain tumors treated with 125I interstitial brachytherapy, autopsy material was available in 10 cases between 0.75 and 60 months after irradiation. The patients were treated with 60-Gy maximum doses at the tumor periphery. Besides the routine HE and Mallory's PTAH trichrome staining, immunohistochemical reactions were carried out for CD15, CD31, CD34, CD45, CD68 (PG-M1), CPM, HAM 56 and HLA-DR antigens to study immunological characteristics of the reactive cell population around gliomas after 125I treatment. The present immunohistochemical study demonstrated that the early lesions following 125I interstitial brachytherapy of gliomas are characterized by migrating macrophages apparently concerned with the removal of necrotic debris. The established phase of reactive zone around the necrotic center disclosed a narrow inner rim of microglial accumulation, and a broad outer area consisting of astrocytic gliosis, vascular proliferation, activated microglia and infiltration by macrophages. In the burned-out phase, the necrosis undergoes liquefaction, the microglial rim is replaced by end-stage macrophages, and the reactive zone is transformed into astrocytic gliosis, which can be considered as equivalent to scar tissue formed around necrosis outside of the central nervous system.

The role of microglia/macrophage system in the tissue response to I-125 interstitial brachytherapy of cerebral gliomas

OBJECTIVE

To study histopathologic changes and the role of the microglia/macrophage cell in the therapeutic effect of I-125 interstitial brachytherapy on the cerebral gliomas.

METHODS

Out of a series of 60 cases with cerebral astrocytomas and other brain tumors treated with I-125 interstitial brachytherapy, autopsy materials were available in ten cases 0.75 and 60 months after irradiation. The patients were treated with the maximum dosage (60 Gy) on the tumor periphery. Besides the routine hematoxylin-eosine and Mallory's PTAH trichrome staining, immunohistochemical reactions were carried out for CD15, CD31, CD34, CD45, CD68, CPM, HAM56 and HLR-DR antigens on paraffin sections to study immunologic phenotypic characteristics of the reaction cell population around gliomas after I-125 treatment.

RESULT

One month after irradiation, a necrotic zone developed around the I-125 seeds within the 72 Gy isodose curve. Histologically, there was a fresh coagulation necrosis in the center of the lesion. Reactive zone has not yet developed but scattered interstitial and perivascular CD68 positive macrophages were present in the surrounding brain tissues. Six months after the I-125 isotope treatment, a reactive zone developed: a microglial rim around the necrosis tissue, and a broad area of proliferating vessels and glial fibrillary acidic protein (GFAP) positive astroglial cells which contained CD68 positive activated microglial and macrophage cells. Fifty-four months after I-125 interstitial irradiation, the necrotic center became colliquative and cystic. The microglial rim was replaced by round end stage (HLR-DR and CD31 positive) macrophages. The reactive zone was characterized by astrocytic gliosis but vascular proliferation and macrophages were lacking.

CONCLUSION

Results of the present immunohistochemical study suggest that the early lesions are characterized by migrating macrophages apparently concerned with the removal of necrotic debris. The established phase of reactive zone around the necrotic center is characterized by a narrow inner rim of microglial accumulation and a broad outer area characterized by astrocytic gliosis, vascular proliferation, activated microglia and infiltration by macrophages. In the burned-out phases of I-125 interstitial brachytherapy of gliomas, the necrosis undergoes liquefaction and the microglial rim is replaced by astrocytic gliosis which can be considered as equivalent to the scar tissue formed around necrosis outside the central nervous system.

Clearance of dying autophagic cells of different origin by professional and non-professional phagocytes

MCF-7 cells undergo autophagic death upon tamoxifen treatment. Plated on non-adhesive substratum these cells died by anoikis while inducing autophagy as revealed by monodansylcadaverine staining, elevated light-chain-3 expression and electron microscopy. Both de novo and anoikis-derived autophagic dying cells were engulfed by human macrophages and MCF-7 cells. Inhibition of autophagy by 3-methyladenine abolished engulfment of cells dying through de novo autophagy, but not those dying through anoikis. Blocking exposure of phosphatidylserine (PS) on both dying cell types inhibited phagocytosis by MCF-7 but not by macrophages. Gene expression profiling showed that though both types of phagocytes expressed full repertoire of the PS recognition and signaling pathway, macrophages could evolve during engulfment of de novo autophagic cells the potential of calreticulin-mediated processes as well. Our data suggest that cells dying through autophagy and those committing anoikis with autophagy may engage in overlapping but distinct sets of clearance mechanisms in professional and non-professional phagocytes.

Expression of p16INK4A, p53, and Rb proteins are independent from the presence of human papillomavirus genes in oral squamous cell carcinoma

BACKGROUND

The overexpression of p16(INK4A) and suppression of p53 and Rb proteins are key features of oncogenic transformation by human papillomaviruses (HPV) in anogenital cancers. HPV genomes are often detected in cancers of the oral cavity, but it is unclear whether HPV has a specific oncogenic role there.

OBJECTIVES

The objectives of the study were to investigate the expression of p53, Rb, and p16(INK4A) proteins and identify HPV infection and viral integration into the host genome.

METHODS

Seventy-nine cases of oral squamous cell carcinoma (OSCC) were studied by immunohistochemistry. Polymerase chain reaction (PCR) was performed to identify HPV DNA from the samples. The results were correlated with clinical data.

RESULTS

Thirty-three cases were HPV positive for high-risk HPV (HR-HPV) types, of which 27 harbored HPV16. In 25 of 27 HPV16-positive tumors, the HPV16 genome was fully integrated into the host genome, as evidenced by the lack of PCR-amplifiable E2 gene sequences. Forty-five patients were p53 overexpressing, 20 with HR-HPV-positive and 25 with HR-HPV-negative tumors. p16(INK4A) protein was overexpressed in 4 of 31 HR-HPV-positive and 9of 45 HR-HPV-negative cases. Twenty-six of 32 HR-HPV-positive and 37 of 44 HR-HPV-negative samples exhibited pRb nuclear staining. These differences between HR-HPV-positive and -negative tumors were not statistically significant. No correlation was found between these biological factors and tumor location, stage, differentiation grade, or alcohol or tobacco abuse.

CONCLUSIONS

A tumor immunophenotype, similar to HPV-related anogenital cancers, is not present in OSCC and highly oncogenic HPV types are therefore unlikely to be specific or independent risk factors for oral cancer.

Effect of IBD sera on expression of inducible and endothelial nitric oxide synthase in human umbilical vein endothelial cells

AIM: To study the expression of endothelial and inducible nitric oxide synthases (eNOS and iNOS) and their role in inflammatory bowel disease (IBD).

METHODS: We examined the effect of sera obtained from patients with active Crohn’s disease (CD) and ulcerative colitis (UC) on the function and viability of human umbilical vein endothelial cells (HUVEC). HUVECs were cultured for 0-48 h in the presence of a medium containing pooled serum of healthy controls, or serum from patients with active CD or UC. Expression of eNOS and iNOS was visualized by immunofluorescence, and quantified by the densitometry of Western blots. Proliferation activity was assessed by computerized image analyses of Ki-67 immunoreactive cells, and also tested in the presence of the NOS inhibitor, 10^-4 mol/L L-NAME. Apoptosis and necrosis was examined by the annexin-V-biotin method and by propidium iodide staining, respectively.

RESULTS: In HUVEC immediately after exposure to UC, serum eNOS was markedly induced, reaching a peak at 12 h. In contrast, a decrease in eNOS was observed after incubation with CD sera and the eNOS level was minimal at 20 h compared to control (18% ± 16% vs 23% ± 15% P<0.01). UC or CD serum caused a significant increase in iNOS compared to control (UC: 300% ± 21%; CD: 275% ± 27% vs 108% ± 14%, P<0.01). Apoptosis/necrosis characteristics did not differ significantly in either experiment. Increased proliferation activity was detected in the presence of CD serum or after treatment with L-NAME. Cultures showed tube-like formations after 24 h treatment with CD serum.

CONCLUSION: IBD sera evoked changes in the ratio of eNOS/iNOS, whereas did not influence the viability of HUVEC. These involved down-regulation of eNOS and up-regulation of iNOS simultaneously, leading to increased proliferation activity and possibly a reduced anti-inflammatory protection of endothelial cells.

Pathology of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is one of the leading causes of death and morbidity worldwide. Despite intensive investigation, its pathology and pathophysiology are not well understood. The hallmarks of the disease are irreversible airflow limitation and chronic inflammation. Small airway obstruction due to progressive inflammation and fibrosis, and the loss of elastic recoil mediated by elastolysis and apoptosis equally contribute to pathologic changes. However, it is debated to what extent the obstruction of large airways leads to altered lung function. Three morphologic entities are described in the literature under one disease; chronic bronchitis, obstructive bronchiolitis and emphysema may appear in the same patient at the same time. The authors review pathologic changes observed in chronic obstructive pulmonary disease, including acute exacerbations and secondary pulmonary hypertension as severe but common complications of the disease. Furthermore, we detail recent scientific evidences for major cellular and molecular inflammatory pathway activation. These mechanisms result in accelerated apoptosis, remodeling and increased proinflammatory cytokine release. Targeting intracellular pathological changes may lead to the discovery of a new generation of drugs that could reduce chronic obstruction before airway irreversibility is established.

The effect of mineral composition on the sorption of cesium ions on geological formations

The sorption of cesium-137 on rock samples, mainly on clay rocks, is determined as a function of the mineral composition of the rocks. A relation between the mineral groups (tectosilicates, phyllosilicates, clay minerals, carbonates) and their cesium sorption properties is shown. A linear model is constructed by which the distribution coefficients of the different minerals can be calculated from the mineral composition and the net distribution coefficient of the rock. On the basis of the distribution coefficients of the minerals the cesium sorption properties of other rocks can be predicted.

Transformed dermatofibrosarcoma protuberans: a clinicopathological study of eight cases

BACKGROUND

Fibrosarcomatous (FS) or malignant fibrous histiocytomatous (MFH) transformation of dermatofibrosarcoma protuberans (DFSP) is a rare, but well known, entity. DFSPs with sarcomatous areas have questionable biological behaviour. Several studies suggest that they have a higher risk for local recurrence and distant metastases than ordinary DFSPs. One recent study described no difference in the behaviour of conventional and transformed DFSP.

AIMS

To investigate the biological behaviour of a series of transformed DFSPs.

METHODS

Eight transformed DFSPs were analysed clinicopathologically. Follow up ranged from four to 36 years.

RESULTS

The tumours involved the trunk (six cases) and lower extremity (two cases) and measured 3.5-8 cm (median, 4). Sarcomatous change presented de novo in all cases. The type of sarcomatous change was FS (five cases) and MFH (three cases). The estimated proportion of sarcomatous area in the tumour was 25-70% (median, 43.37%). Mitotic counts ranged from nine to 16 mitotic figures/10 high power fields in the FS and MFH areas (median, 12), and from one to three in the DFSP areas. Six patients were treated by wide local excision with histopathologically negative margins and two were treated by simple surgical excision with positive margins. Three patients developed recurrences and one developed metastasis during follow up. Of those treated by wide local excision, one developed recurrence. All tumours expressed CD34 in the DFSP component, but only three in the sarcomatous area.

CONCLUSIONS

Although DFSP containing sarcoma may be a more aggressive tumour, its behaviour can be influenced by surgical treatment.

[Association of Hodgkin lymphoma with Epstein-Barr virus in Hungary]

INTRODUCTION

The occurrence of Epstein-Barr virus associated Hodgkin's lymphoma shows considerable variation from continent to continent and from country to country but in Hungary no such investigations have been performed so far.

AIM

The authors analyse the presence of Epstein-Barr virus and the type of latency in histologic samples taken from Hodgkin's disease patients.

METHOD

They have analyzed the presence of virus using PCR, in situ hybridisation and immunohistochemistry.

RESULTS

Out of 109 cases, 61 patients (56%) showed virus positivity by PCR while latent membrane protein 1 positivity was found in 47 cases (43%). As regards to gender ratio, 53% female and 58% male patients were virus positive by PCR. Epstein-Barr virus association did not show any alteration in children (1-14 years) when compared to that of adults (out of the 10 children 6 were positive by PCR). As regards to the lifestyle of Epstein-Barr virus positive patients, the incidence of smoking and the ratio of poor social conditions were significantly higher. Mixed cell type was the most frequent (65%) in these patients and Epstein-Barr PCR virus positivity was highest in this type (60%), primarily in age groups 11-20 and over 51 years. Epstein-Barr virus PCR positivity was 52% in nodular sclerosis (negative cases cumulated in the age group 15-30 years), other histologic subtypes could not be evaluated due to the small number of cases. On examining Hodgkin's lymphoma and Epstein-Barr virus association disease models, they could not categorize their patients into any of them though characteristic patient groups could be more or less observed also in their material. This may be explained by the socioeconomic differences of the population living under different economic conditions.

CONCLUSION

These results indicate that Epstein-Barr infection may play an important role in the development of Hodgkin's lymphoma in Hungary, too.

Changes in the expression and distribution of the inducible and endothelial nitric oxide synthase in mucosal biopsy specimens of inflammatory bowel disease

OBJECTIVE

The role of nitric oxide (NO) in the pathophysiology of inflammatory bowel disease (IBD) is controversial. The aim of this study was to investigate the expression and localization of nitric oxide synthase isoforms (iNOS, eNOS) in IBD colonic mucosa.

MATERIAL AND METHODS

Forty-four patients with IBD (24 ulcerative colitis (UC), 20 Crohn's disease (CD) and 16 controls) were investigated by colonoscopy. iNOS and eNOS in tissue sections was demonstrated by histochemistry (NADPH-diaphorase reaction) and immunohistochemistry. Cell type analysis and quantitative assessment of the iNOS immunoreactive (IR) cells and densitometry of iNOS in immunoblots were also performed.

RESULTS

iNOS-IR cells were significantly numerous in inflamed mucosa of UC (64+/-4 cells/mm2) than in CD (4+/-2 cells/mm2). iNOS-IR/CD15-IR cells showed significant elevation in inflamed (i) versus uninflamed (u) UC mucosa (UCu 8+/-3%, UCi 85+/-10%) In CD, the percentage of iNOS-IR/CD68-IR cells was lower in inflamed sites (CDu 23+/-8%, CDi 4+/-3%). Immunoblot of biopsies revealed significant elevation of iNOS in active UC compared with uninflamed sites, whereas in CD no significant changes were detected. Differences were observed in eNOS and endothelial marker CD31 immunoreactivity. In patients with UC and in controls the ratios of eNOS/CD31-IR vessels were 82.3% and 92.0% respectively, whereas in CD the ratio was 8.3% with a concomitantly significant increase of CD31-IR vessels. The distribution and morphological characteristics of the NOS-IR inflammatory cells and endothelia were similar to those showing NADPH-diaphorase reactivity.

CONCLUSIONS

Differences observed in the expression and distribution of NOS isoforms in immune and endothelial cells may contribute to better understanding of the structural and physiological changes in UC and CD.

p21WAF1/CIP1 expression is a marker of poor prognosis in oral squamous cell carcinoma

BACKGROUND

Previous research on the prognostic relevance of p21(WAF1/CIP1) in oral squamous cell carcinomas (OSCC) yielded inconclusive and contradictory data.

OBJECTIVES

To investigate the prognostic significance of p21(WAF1/CIP1) expression, its relationship to p53 accumulation, proliferation-associated proteins Ki-67 and cyclin D1 in relation to survival and clinicopathological features in OSCC.

METHODS

Surgical specimens taken from 106 randomly selected patients were studied by immunohistochemistry. Expression of the protein of interest was correlated with clinical data.

RESULTS

p21(WAF1/CIP1) expression was found in 61.3% of OSCCs. Expression of p21(WAF1/CIP1) significantly correlated with tumor size (P = 0.005), lymph node involvement (P = 0.002), clinical stage (P < 0.001), and tumor site (P = 0.002). Patients with tumors showing p21(WAF1/CIP1) immunopositivity had decreased 2-year survival (P = 0.018). Expression of p21(WAF1/CIP1) was not related to age, gender, risk factors (tobacco, alcohol), dental status, or tumor differentiation grade. The p21(WAF1/CIP1) expression positively correlated with proliferation-related variables Ki-67 (P = 0.010) and cyclin D1 (P < 0.001), but not with p53 expression.

CONCLUSIONS

The expression of p21(WAF1/CIP1) was found to be associated with poorer prognosis and tumor aggressivity in OSCC.

Characterization of a new disease-causing mutation ofSH2D1Ain a family with X-linked lymphoproliferative disease

Males with an expressed mutation in the SH2D1A gene that encodes an SH2 domain protein named SH2D1A or SAP (NP_002342; signaling lymphocyte activating molecule [SLAM]-associated protein), have an X-linked syndrome characterized by an increased vulnerability to infection with Epstein-Barr virus (EBV). We evaluated two related male patients with fatal infectious mononucleosis (FIM) and mutation in the SH2D1A gene. Sequence analysis revealed a hemizygous c.47G>A mutation in one of the patients, and heterozygosity for this mutation in the genomic DNA from his mother and maternal grandmother. This mutation resulted in p.G16D amino acid change in the sequence of the SAP protein. To analyze the effect of this missense mutation on protein function cDNA was generated by site-directed mutagenesis and expressed in COS cells. We found that half-life of the p.G16D protein was comparable to that of wild type SAP. However, the mutant protein was defective in binding to its physiological ligands SLAM and 2B4. These results suggest that a defect in ligand binding contributes to the loss of function of the SAP protein in patients carrying p.G16D mutation.

TASK-3 immunoreactivity shows differential distribution in the human gastrointestinal tract

The presence and distribution of TASK-3 immunopositivity (a channel with potential oncogenic significance) was investigated in the human gastrointestinal system. The immunohistochemical reactions were performed with two commercially available polyclonal antibodies, targeting different epitopes of the channel protein. Experiments conducted on frozen and formalin-fixed samples indicated that the application of a suitable antigen retrieval (AR) technique was essential to produce consistent, strong and reproducible TASK-3-specific immunolabelling of the formalin-fixed tissue. The lack of or inappropriate selection of the AR resulted in false-negative reactions. As for the distribution of the TASK-3 channels, strong immunolabelling was observed in the gastric and large intestinal mucosa, with particularly prominent immunoreactivity of the epithelial cells. In contrast, the smooth-muscle layers demonstrated weak TASK-3 positivity. Intense TASK-3 expression was noted in both the exocrine and endocrine pancreas, but the islets of Langerhans exhibited more powerful reactions. The ductal apparatus of the submandibular gland and lymphocytes situated in pericolonic lymph nodes were also TASK-3 positive. Strong TASK-3 positivity could also be observed in malignant gastrointestinal tumours, with intense nuclear-perinuclear labelling of some of the tumour cells. The present findings suggest that TASK-3 channels may have roles in the gastrointestinal functions, including insular hormone secretion.

Cross-linking of ubiquitin, HSP27, parkin, and alpha-synuclein by gamma-glutamyl-epsilon-lysine bonds in Alzheimer's neurofibrillary tangles

The accumulation of misfolded proteins in intracellular inclusions is a generic feature of neurodegenerative disorders. Although heavily ubiquitylated, the aggregated proteins are not degraded by the proteasomes. A possible reason for this phenomenon may be a modification of deposited proteins by transglutaminases forming gamma-glutamyl-epsilon-lysine (GGEL) cross-links between distinct proteins. Here, we show that the frequency of GGEL cross-links is an order of magnitude higher in Alzheimer's brain cortex than in age-matched or younger controls. This difference is due to the accumulation of GGEL cross-links in ubiquitin-immunopositive protein particles present in both Alzheimer's brains and those from aged individuals. The highly cross-linked protein aggregates show immunoreactivity to antibodies against tau and neurofilament proteins, and partially also to alpha-synuclein, indicating that these structures are inherent in Alzheimer's neurofibrillary tangles and Lewy bodies. Using mass sequence analysis, we identified the same six pairs of peptide sequences cross-linked in both senile and Alzheimer's specimens: Gln31 and Gln190 of HSP27 protein are cross-linked with Lys29 and Lys48 of ubiquitin and HSP27 therefore may cross-link two (poly)ubiquitin chains. One lysine residue of parkin and one of alpha-synuclein were also found to be cross-linked. The data suggest that cross-linking of (poly)ubiquitin moieties via HSP27 may have a role in the stabilization of the intraneuronal protein aggregates by interference with the proteasomal elimination of unfolded proteins.

[Study of pathogenetic role of Epstein-Barr virus in Hungarian patients with B-cell non-Hodgkin lymphomas]

INTRODUCTION

The Epstein-Barr virus is a member of herpesvirus family. It plays an important role in the etiopathogenesis of Burkitt lymphoma, other B-cell non-Hodgkin lymphomas, nasopharyngeal carcinoma, X chromosome-linked lymphoproliferative disease, Hodgkin lymphomas and a part of T-cell lymphomas. It has been suggested that association of Epstein-Barr virus with lymphomas and its pathological significance in disease varies in different geographical areas. The aim of our study was to reveal the role of Epstein-Barr virus in B-cell non-Hodgkin lymphomas diagnosed in Hungary. The authors asked: A) What is the frequency of the presence of virus genome in the biopsy specimen from B-cell non-Hodgkin patients? B) Which types of virus latency can be observed?

PATIENTS AND METHODS

Genomic DNA and EBER-specific RNA of Epstein-Barr virus in paraffin-embedded specimens were detected by polymerase chain reaction and in situ hybridisation, respectively.

RESULTS

Out of 36 B-cell non-Hodgkin lymphoma cases, 16 (45%) were found to be positive for Epstein-Barr virus by the above methods. Expression of latency genes, nuclear antigene-2 and latent membrane protein-1 was studied by immunohistochemical technique. The 16 virus-positive non-Hodgkin lymphoma cases showed Epstein-Barr virus latency types II. (37%) or III. (63%).

CONCLUSIONS

The authors data suggest that Epstein-Barr virus may be associated with the development of B-cell non-Hodgkin lymphomas in Hungarian patients.

[Evaluation of survival in mixed connective tissue disease (MCTD)]

INTRODUCTION

179 patients with mixed connective tissue disease (MCTD) were follow-up, and the cause of death was analyzed in 12 died patients.

PATIENTS AND METHODS

The survival of 179 patients with MCTD was evaluated by using Kaplan-Meier's method. Clinically and immunological data of the patients were analyzed between 1 and 25 years follow-up period (mean: 13.1 +/- 5.5 years).

RESULTS

The five-year survival rate was 96.4%, 10-year survival rate was 93.9%, and the 15-year survival rate was 89.6%. The cause of death was pulmonary hypertension in 5 patients, thrombotic thrombocytopenic purpura/hemolytic uremic syndrome in 3 cases, infection in 3 cases (hepatitis C virus induced hepatic coma in 2 patients, Staphylococcus sepsis in one patient), and on one patient myocarditis. The pulmonary hypertension was the most serious prognostic factor.

CONCLUSION

In patients with MCTD the pulmonary hypertension with endothelial cells proliferation and microangiopathy developed very quickly, and there was progressive and therapy resistant statement. The secondary virus and bacterial infections may develop in the patients who were followed-up the long term period. Their survival rate was better than the data in the literature. This fact may cause genetic-demographic factors, and the sequential follow-up of the patients.

[Attention deficit hyperactivity disorder. Literature review for the pediatric dentist]

The purpose of this review was to give a complete summary of the ADHD (Attention Deficit Hyperactivity Disorder) for dentists, especially for those who deal with dental traumatology. Children with ADH disorder show symptoms of restlessness, hyperactivity, impulsive behaviour and inattention often resulting in serious dental accidents. The article summarizes the literary data concerning ADH-Syndrome, presents a typical case and also deals with the dental considerations.

N(epsilon)(gamma-glutamyl)lysine in cerebrospinal fluid marks Alzheimer type and vascular dementia

N(epsilon)(gamma-glutamyl)lysine isodipeptide is released from the breakdown of proteins cross-linked by transglutaminase enzymes. Transglutaminase activation is a marker of apoptosis and elevated isodipeptide concentrations in body fluids might correlate with the intensity of apoptotic cell turnover. The concentration of N(epsilon)(gamma-glutamyl)lysine was measured in the cerebrospinal fluid (CSF) of patients with probable Alzheimer's disease (n = 14) and vascular type dementia (n = 11) and compared with not demented surgical controls (n = 17). Baseline levels of 26-62 nM/l (mean 37.9 +/- 8.7 SD) free isodipeptide were detected in control patients. CSF isodipeptide levels showed significant elevation in vascular (mean 95.6 +/- 45.1 SD) as well as Alzheimer patients (176.6 +/- 77.1 SD). Isodipeptide concentrations above 120 nM/l were 72% specific and 77% sensitive to Alzheimer's dementia, although the difference between the two dementias was statistically insignificant (p > 0.05). Determination of CSF N(epsilon)(gamma-glutamyl)lysine isodipeptide concentration offers a novel method for measurement of neurodegeneration in primary and mixed dementias.

Crystallization and preliminary X-ray analysis of human transglutaminase 3 from zymogen to active form

Transglutaminases(TGases; protein-glutamine-glutamyl-transferases) are a large family of calcium-dependent acyl-transfer enzymes that catalyze the formation of covalent cross links in proteins. Of these, the "epidermal" or "hair follicle" TGase 3 isoform is critically involved in barrier formation in epithelia. It is a zymogen, requiring proteolytic activation to achieve maximal specific activity. In order to understand its structure and function, we have devised methods for the rapid large-scale expression of the TGase 3 zymogen in the baculovirus system, and here we describe the purification of the zymogen and activated forms. We describe methods for the formation of high-quality, well-diffracting crystals within 3-5 days, using both dioxane and beta-octylglucoside to overcome severe twinning problems. The crystal of the zymogen belongs to the triclinic space group P1 and diffracts to 2.2-A resolution, and the crystal of the active form belongs to the P2(1) space group at 2.7-A resolution.

Apoptosis-linked in vivo regulation of the tissue transglutaminase gene promoter

Tissue transglutaminase (tTG) is upregulated in various cells undergoing apoptosis. To investigate the transcriptional regulation of tTG a mouse strain carrying a beta-galactosidase reporter gene under the control of a 3.8 kilobase fragment of the tTG promoter was characterised. The transgene construct was shown to be expressed in the apoptotic regions of the mouse embryo. Here we report that the regulation of the transgene is also apoptosis-linked in adult animals. The transgene is induced in endocrine apoptosis involving mammary gland involution and corpus luteum regression. Induction of the reporter gene is detectable during in vivo but not in vitro apoptosis of thymocytes induced by the glucocorticoid receptor, the nur77, p53 and the retinoid receptor gamma mediated pathways. Additionally, the lacZ expression mimics the activation of the endogenous promoter in tissues characterised by high apoptotic turnover. These results suggest that the apoptosis-specific transcriptional regulation of tTG is mediated through elements of a 3.8 kb promoter and may require cosignals available only in tissue environment. Cell Death and Differentiation (2000) 7, 1225 - 1233.

Cholesterol 3-sulfate interferes with cornified envelope assembly by diverting transglutaminase 1 activity from the formation of cross-links and esters to the hydrolysis of glutamine

The loss of transglutaminase 1 enzyme (TGase 1) activity causes lamellar ichthyosis. Recessive X-linked ichthyosis (XI) results from accumulation of excess cholesterol 3-sulfate (CSO(4)) in the epidermis but the pathomechanism how elevated epidermal CSO(4) causes ichthyosis is largely unknown. Here we provide evidence that XI is also a consequence of TGase 1 dysfunction. TGase 1 is a key component of barrier formation in keratinocytes: it participates in the cross-linking of cell envelope (CE) structural proteins, and also forms the lipid bound envelope by esterification of long chain omega-hydroxyceramides onto CE proteins. Using involucrin and an epidermal omega-hydroxyceramide analog as substrates, kinetic analyses revealed that at membrane concentrations above 4 mol %, CSO(4) caused a marked and dose-dependent inhibitory effect on isopeptide and ester bond formation. Sequencing of tryptic peptides from TGase 1-reacted involucrin showed a large increase in deamidation of substrate glutamines. We hypothesize that supraphysiological levels of CSO(4) in keratinocyte membranes distort the structure of TGase 1 and facilitate the access of water into its active site causing hydrolysis of substrate glutamine residues. Our findings provide further evidence for the pivotal role of the TGase 1 enzyme in CE formation.

A novel function for transglutaminase 1: attachment of long-chain omega-hydroxyceramides to involucrin by ester bond formation

Transglutaminases (TGases) are defined as enzymes capable of forming isopeptide bonds by transfer of an amine onto glutaminyl residues of a protein. Here we show that the membrane-bound form of the TGase 1 enzyme can also form ester bonds between specific glutaminyl residues of human involucrin and a synthetic analog of epidermal specific omega-hydroxyceramides. The formation of a approximately 5-nm-thick lipid envelope on the surface of epidermal keratinocytes is an important component of normal barrier function. The lipid envelope consists of omega-hydroxyceramides covalently linked by ester bonds to cornified envelope proteins, most abundantly to involucrin. We synthesized an analog of natural omega-hydroxyceramides N-[16-(16-hydroxyhexadecyl)oxypalmitoyl]sphingosine (lipid Z). When recombinant human TGase 1 and involucrin were reacted on the surface of synthetic lipid vesicles containing lipid Z, lipid Z was attached to involucrin and formed saponifiable protein-lipid adducts. By mass spectroscopy and sequencing of tryptic lipopeptides, the ester linkage formation used involucrin glutamine residues 107, 118, 122, 133, and 496 by converting the gamma-carboxamido groups to lipid esters. Several of these residues have been found previously to be attached to ceramides in vivo. Mass spectrometric analysis after acetonide derivatization also revealed that ester formation involved primarily the omega-hydroxyl group of lipid Z. Our data reveal a dual role for TGase 1 in epidermal barrier formation and provide insights into the pathophysiology of lamellar ichthyosis resulting from defects of TGase 1 enzyme.

[Sweet syndrome following therapeutic use of granulocyte colony stimulating factor]

Sweet's syndrome is an acute febrile neutrophilic dermatosis. Classical form occurs after infection of the gastrointestinal or respiratory tract. This syndrome is often associated with myeloproliferative disorders and solid tumors. Some cases are reported in the literature in which usage of granulocyte colony-stimulating factor induced the symptoms of Sweet's syndrome. We report the case of an 53-year-old woman with hyperthyreosis. She wasn't euthyreoid in spite of medicaments since 1994, so her doctors planned operation. In the preoperative period her peripheral blood revealed agranulcytosis and she has got fever. 2 days after administration of granulocyte colony-stimulating factor erythematous plaques appeared on her face, neck and extremities. Biopsy from these plaques showed dermal neutrophilia, so a diagnosis of neutrophilic dermatosis was made. After the administration of corticosteroids, immunglobulin and antibiotics the skin lesions were resolved. She was examined because of suspicion of autoimmune diseases but we couldn't find any of them. Retrospectively, appearance of Sweet's syndrome was associated with granulocyte colony-stimulating factor. The case of this woman is important because usage of colony-stimulating factors is widespread and the Sweet's syndrome could be occurs as side effect of these drugs.

[Hairy cell leukemia: authors' own experience (1977-1998)]

Hairy cell leukaemia (HCL) is a rare, clinically and haematologically well characterised entity. The prognosis of patients with hairy cell leukaemia has significantly improved due to the new therapeutic approaches. Development of diagnostic and therapeutic methods, together with the analysis of their own hairy cell leukaemia patients, is reviewed by the authors. Between 1977 and 1998 twenty five patients (16 male, 9 female) were treated. The malignant cells were usually analysed by morphological and cytochemical methods and recently flow cytometric analysis could be performed in eight patients. Splenectomy with lethal outcome in six patients was performed in 21 cases. Approximately one third of patients received interferon, while 2-chlorodeoxyadenosine was given only to three patients. Favourable experiences obtained by splenectomy and efficacy of interferon treatment are emphasised, but according to the literature and their own results administration of purine analogues can be highly recommended in the future.

Involucrin cross-linking by transglutaminase 1. Binding to membranes directs residue specificity

The transglutaminase 1 (TGase 1) enzyme is essential for the assembly of the cell envelope barrier in stratified squamous epithelia. It is usually bound to membranes, but to date most studies with it have involved solution assays. Here we describe an in vitro model system for characterizing the function of TGase 1 on the surface of synthetic lipid vesicles (SLV) of composition similar to eukaryote plasma membranes. Recombinant baculovirus-expressed human TGase 1 readily binds to SLV and becomes active in cross-linking above 10 microM Ca2+, in comparison to above 100 microM in solution assays, suggesting that the membrane surface is important for enzyme function. Involucrin also binds to SLV containing 12-18% phosphatidylserine and at Ca2+ concentrations above 1 microM. In reactions of involucrin with TGase 1 enzyme in solution, 80 of its 150 glutamines serve as donor residues. However, on SLV carrying both involucrin and TGase 1, only five glutamines serve as donors, of which glutamine 496 was the most favored. As controls, there was no change in specificity toward the glutamines of other substrates used by free or SLV-bound TGase 1 enzyme. We propose a model in which involucrin and TGase 1 bind to membranes shortly after expression in differentiating keratinocytes, but cross-linking begins only later as intracellular Ca2+ levels increase. Furthermore, the data suggest that the membrane surface regulates the steric interaction of TGase 1 with substrates such as involucrin to permit specific cross-linking for initiation of cell envelope barrier formation.

Bricks and mortar of the epidermal barrier

A specialized tissue type, the keratinizing epithelium, protects terrestrial mammals from water loss and noxious physical, chemical and mechanical insults. This barrier between the body and the environment is constantly maintained by reproduction of inner living epidermal keratinocytes which undergo a process of terminal differentiation and then migrate to the surface as interlocking layers of dead stratum corneum cells. These cells provide the bulwark of mechanical and chemical protection, and together with their intercellular lipid surroundings, confer water-impermeability. Much of this barrier function is provided by the cornified cell envelope (CE), an extremely tough protein/lipid polymer structure formed just below the cytoplasmic membrane and subsequently resides on the exterior of the dead cornified cells. It consists of two parts: a protein envelope and a lipid envelope. The protein envelope is thought to contribute to the biomechanical properties of the CE as a result of cross-linking of specialized CE structural proteins by both disulfide bonds and N(epsilon)-(gamma-glutamyl)lysine isopeptide bonds formed by transglutaminases. Some of the structural proteins involved include involucrin, loricrin, small proline rich proteins, keratin intermediate filaments, elafin, cystatin A, and desmosomal proteins. The lipid envelope is located on the exterior of and covalently attached by ester bonds to the protein envelope and consists of a monomolecular layer of omega-hydroxyceramides. These not only serve of provide a Teflon-like coating to the cell, but also interdigitate with the intercellular lipid lamellae perhaps in a Velcro-like fashion. In fact the CE is a common feature of all stratified squamous epithelia, although its precise composition, structure and barrier function requirements vary widely between epithelia. Recent work has shown that a number of diseases which display defective epidermal barrier function, generically known as ichthyoses, are the result of genetic defects of the synthesis of either CE proteins, the transglutaminase 1 cross-linking enzyme, or defective metabolism of skin lipids.

Integrin expression on normal and neoplastic human breast epithelium

Integrin adhesion receptor expression of different benign and malignant breast tumours was examined by means of immunohistochemical techniques. A panel of seven different anti-alpha and two different anti-beta subunit antibodies was used. Normal breast epithelium displayed a well characterized and constant pattern of integrin expression consisting of strong alpha 1,2,3,6 and alpha v, and a relatively weaker beta 1 and beta 3 staining. No staining for alpha 4 or alpha 5 could be detected on the epithelial cells. Benign fibroadenomas did not show changes in their receptor expression compared to normal tissues. In the cases of different types of breast cancer, there was a significant downregulation of all subunits. The staining pattern was distinct if there could a basement membrane like structure be detected around the invading tumour nodules. When laminin and collagen type IV surrounded the tumour cells, those cells in contact with the extracellular matrix components still displayed strong positivity for the integrin subunits. Other cells inside the tumour cell nests or not surrounded by basement membrane did not express integrins. The positively staining cells might be more differentiated owing to the effect the basement membrane. Myoepithelial labeling of the integrin expressing cells gave negative results. The observed integrin expression heterogeneity renders the histologic picture difficult to interpret with regard to clinical behavior of the tumour.

Tissue transglutaminase-dependent posttranslational modification of the retinoblastoma gene product in promonocytic cells undergoing apoptosis

The retinoblastoma gene product (pRB) plays an important role in controlling both cell release from the G1 phase and apoptosis. We show here that in the early phases of apoptosis, pRB is posttranslationally modified by a tissue transglutaminase (tTG)-catalyzed reaction. In fact, by employing a novel haptenized lysis synthetic substrate which allows the isolation of glutaminyl-tTG substrates in vivo, we identified pRB as a potential tTG substrate in U937 cells undergoing apoptosis. In keeping with this finding, we showed that apoptosis of U937 cells is characterized by the rapid disappearance of the 105,000- to 110,000-molecular-weight pRB forms concomitantly with the appearance of a smear of immunoreactive products with a molecular weight of greater than 250,000. The shift in pRB molecular weight was reproduced by adding exogenous purified tTG to extracts obtained from viable U937 cells and was prevented by dansylcadaverine, a potent enzyme inhibitor. The effect of the pRB posttranslational modification during apoptosis was investigated by determining the E2F-1 levels and by isolating and characterizing pRB-null clones from U937 cells. Notably, the lack of pRB in these U937-derived clones renders these p53-null cells highly resistant to apoptosis induced by serum withdrawal, calphostin C, and ceramide. Taken together, these data suggest that tTG, acting on the pRB protein, might play an important role in the cell progression through the death program.

Identification of cytoplasmic actin as an abundant glutaminyl substrate for tissue transglutaminase in HL-60 and U937 cells undergoing apoptosis

A lysine derivative, 3-[Nalpha[Nepsilon-[2', 4'-dinitrophenyl]-amino-n-hexanoyl-L-lysylamido]-propane-1-ol, a novel amine substrate of transglutaminases, was synthesized and delivered into intact HL-60 and U937 human leukemia cells to probe the function of the intracellular enzyme. The novel substrate compound was covalently incorporated into intracellular proteins in these cells expressing high levels of tissue transglutaminase and undergoing apoptosis following the induction of their differentiation with dimethyl sulfoxide and retinoic acid. Immunoaffinity purification and microsequencing of labeled proteins identified cytoplasmic actin as the main endogenous glutaminyl substrate in these cells. As shown by confocal image analysis, cells revealed distinct labeling of the microfilament meshwork structures by the novel compound as the result of the intracellular action of transglutaminase.

Differential expression of tissue transglutaminase during in vivo apoptosis of thymocytes induced via distinct signalling pathways

A significant increase in the expression and activity of tissue transglutaminase (tTG), one of the effector elements of apoptosis, was observed during involution of thymus elicited by treatment with either anti-CD3 antibody or dexamethasone or by irradiation. The blood plasma concentration of epsilon(gamma-glutamyl)lysine isodipeptide, the end-product of the digestion of transglutaminase cross-linked proteins, was also elevated in each of these cases. tTG was localized in cells of the cortical layer of the thymus and immunofluorescence double staining revealed that the enzyme appeared in the apoptotic cells. None of these observations could be made when apoptosis was induced by fas-receptor stimulation. The lack of tTG activity in fas-stimulated cells was accompanied with a less organized apoptotic morphology. Our data suggest that distinct signalling pathways, which induce apoptosis within the same cell type, can differentially regulate the expression of tTG, and this enzyme may be involved in structural stabilization of the apoptotic cells.

Transglutaminase induction by various cell death and apoptosis pathways

Clarification of the molecular details of forms of natural cell death, including apoptosis, has become one of the most challenging issues of contemporary biomedical sciences. One of the effector elements of various cell death pathways is the covalent cross-linking of cellular proteins by transglutaminases. This review will discuss the accumulating data related to the induction and regulation of these enzymes, particularly of tissue type transglutaminase, in the molecular program of cell death. A wide range of signalling pathways can lead to the parallel induction of apoptosis and transglutaminase, providing a handle for better understanding the exact molecular interactions responsible for the mechanism of regulated cell death.

[Secondary lymphomatous polyposis of the gastrointestinal tract in patients with nodal lymphomas]

Multiplex lymphomatous polyposis is an uncommon disease characterized by polypoid accumulations of malignant lymphoid cells within the submucosa of long segments of the gastrointestinal tract. Primary gastrointestinal form of disease is referred as an extranodal variant of the entity knows as mantle zone lymphoma. Rarely, this typical lesion may appear as a secondary involvement of the alimentary tract in patients with primary nodal lymphomas. In present article, the clinical, histological features of our two cases of primary nodal lymphoma presenting with gastrointestinal symptoms and secondary involvement of the bowels are discussed. The nodal lymphomas of these patients were classified as a mantle zone and a follicle center cell origin lymphoma. The development of gastrointestinal symptoms occurred 29 and 41 months after the diagnosis. Our cases suggest that lymphomatous polyposis can manifest itself secondarily in patients with nodal lymphomas of not only the mantle cell type. The polypoid lesion might be mediated by lymphocyte homing receptors and the pattern of proliferation can be produced by more than one phenotypically different lymphoma.

Expression and activation of tissue transglutaminase in apoptotic cells of involuting rodent mammary tissue

Apoptosis is a form of cell death in which cellular integrity is maintained and neither cytoplasmic nor nuclear content is released. The Ca(2+)-dependent tissue transglutaminase (tTG) is an enzyme that forms protein cross-links between specific glutamyl and lysyl side-chains of intra- and extracellular proteins, therefore it may be responsible for the structural stabilization observed during the death process. In this study, the expression of tTG was investigated following the physiological process of forced weaning which results in an almost complete elimination of secretory epithelium by apoptosis and remodelling of the tissue structure. A dramatic induction of tTG was detected by immunoblotting of total mammary gland homogenates prepared from the involuting glands. The concentration of epsilon(gamma-glutamyl)-lysine crosslinks was also elevated in these samples, showing that the enzyme is activated during apoptosis. To determine the distribution of tTG and its relationship to apoptotic cells, paraffin-embedded specimens were studied by RNA in situ hybridization and immunohistochemical methods as well as using in situ labeling for nuclear fragmentation. All of these approaches indicated that mammary secretory epithelium expressed tissue transglutaminase coincident with the onset of apoptosis. The apoptotic and tTG-expressing cells were found to be identical as demonstrated by a histological double-labeling technique.

Hemangiopericytoma of the cerebello-pontine angle. Diagnostic pitfalls and the diagnostic value of the subunit A of factor XIII as a tumor marker

The authors report on a case that during its 9-year-long history has repeatedly been misdiagnosed due to the misleading clinical and histopathological findings. The patient has been treated, in chronological order, for cerebrovascular disease, acoustic Schwannoma, glomus tympanicum tumor (chemodectoma) and finally turned out to have an intracranial hemangiopericytoma that originated from the area of the glomus tympanicum and eventually widely metastatized within and outside the intracranial compartment. The proper diagnosis was reached with the help of detailed immunohistochemical analysis. The subunit A of Factor XIII (FXIIIa) can be demonstrated on formaldehyde-fixed paraffin embedded sections. It has recently been shown that FXIIIa reactivity is characteristic and hence diagnostic of a subpopulation of cells within systemic and intracranial (central) hemangiopericytomas (HPCs). Since it is consistently missing from all cell components of ordinary meningiomas, glomus tumors (chemodectomas) and a host of other soft tissue tumors, its presence or absence is a helpful sign in various differential diagnostic dilemmas.

Plexiform fibrohistiocytic tumour with novel phenotypic features

Plexiform fibrohistiocytic tumour is a recently described type of fibrohistiocytic tumour, the differentiation pattern of which is poorly understood. A case representing the predominantly fibrohistiocytic type of the tumour is reported. Immunohistochemical analysis supports the histiocytic origin of this entity. The expression of EBM/11 and tissue transglutaminase both in fibroblast-like and histiocyte-like cells indicate that a single cell line produces the dual morphological features. It is proposed that a non-phagocytic epithelioid pattern of histiocytic differentiation characterizes this tumour.

[Anaplastic transformation of papillary carcinoma of the thyroid]

Anaplastic transformation of well-differentiated carcinomas of the thyroid is not common. The authors present a case of a 61-year-old woman, on whom, 17 years earlier, a near-total thyroidectomy was performed with a unilateral selective lymphatic dissection of the neck because of a papillary carcinoma of the thyroid. The operations were followed by a course of external irradiation. For 17 years the patient had no complaints, then she was treated again for recurrence of tumor in the residual thyroid tissue. By biopsy next to papillary carcinoma the authors diagnosed an anaplastic tumor with giant cells, which led to the patient's death 6 months after the operation. Surveying the data in literature they draw attention to the role of external irradiation in anaplastic transformations after the first operation.

[Retrospective clinicopathological study of juvenile nasopharyngeal angiofibroma in a 20-year case load]

From the files of our institution 7 cases originally diagnosed as juvenile nasopharyngeal angiofibroma have been reviewed. Only 3 cases proved to be juvenile nasopharyngeal angiofibroma on revision, in one case inflammatory polyp, in two cases pyogenic granuloma and in one case richly vascular granulation tissue was the correct diagnosis. The clinical and histopathological aspects of the differential diagnosis of juvenile nasopharyngeal angiofibroma are discussed. All patients with true juvenile nasopharyngeal angiofibroma were males. The diagnostic usefulness of the recognition of morphological features suggesting erectile tissue are stressed.