Expression of selected microRNAs in pancreatic ductal adenocarcinoma: is there a relation to tumor morphology, progression and patient's outcome?

Pancreatic ductal adenocarcinoma (PDAC) remains a disease with extremely poor prognosis and limited effective available treatment. Differential expression of miRNAs isolated from tumor tissue has been proposed as a marker for tumor diagnosis, progression, and prognosis. Nevertheless, the prognostic value of miRNAs expression in PDACs for patient outcome still remains unclear. Expression of 7 selected miRNAs, isolated from FFPE samples of 54 PDAC patients, was quantified using RT-qPCR. The relationship of miRNA expression levels with tumor histology, clinicopathological characteristics, patient overall survival (OS), and progress-free survival (PFS), was subsequently evaluated. Overexpression of miR-21, miR-155, and miR-210 was observed in PDACs (up to 72.62, 232.36, and 181.38-fold, respectively), in comparison with non-neoplastic tissues. On the other hand, miR-96 and miR-217 were significantly downregulated in PDACs (up to one hundred times). No differences were, however, noticed between cancer and normal tissues for the expression levels of miR-148a and miR-196a. On the other hand, expression levels of all 7 miRNAs failed to demonstrate a significant correlation with parameters of tumor progression, such as tumor stage, grade, nodal involvement, perineural, and vascular invasion. The positive correlation of miR-210 levels was, however, observed with patient age (ρ=0.35). Additionally, miR-148a and miR-217 expressions have shown a positive association with tubular tumor growth pattern (ρ=0.39; ρ=0.28). The negative correlation of miR-148a values was also demonstrated with dissociative growth pattern and nuclear atypia (ρ=-0.30; ρ=-0.27). Finally, no statistically significant correlation could be demonstrated with the expression levels of all 7 tested miRNAs and PDAC patient survival; neither for OS nor for PFS (p>0.05). Our data have confirmed abnormal miRNAs expression in PDACs in comparison with adjacent non-neoplastic tissue. On the other hand, no correlation was discovered between miRNA expression and parameters of tumor progression. We have found a significant association between histologic tumor growth patterns and miRNA expression, making this work the first study, which analyses this aspect of PDAC. Finally, in our group of patients, no relationship of miRNA levels and patient prognosis could be demonstrated. Therefore, further investigation is required to evaluate the predictive and prognostic potential of miRNAs in a clinical setting.

Dilemmas in autoimmune pancreatitis. Surgical resection or not?

Surgical treatment is not commonly recommended in the management of autoimmune pancreatitis. The article describes a dilemma in diagnostics and treatment of a 68-year old man with the mass in the head of the pancreas that mimicked pancreatic cancer and that was diagnosed as a type 1 autoimmune pancreatitis (IgG4-related pancreatitis) after a surgical resection. Diagnosis of the autoimmune pancreatitis is a real clinical challenge, as in the current diagnostic criteria exists some degree of overlap in the findings between autoimmune pancreatitis and pancreatic cancer (indicated by the similarity in radiologic findings, elevation of IgG4, sampling errors in pancreatic biopsy, and the possibility of synchronous autoimmune pancreatitis and pancreatic cancer). Despite the generally accepted corticosteroids as the primary treatment modality in autoimmune pancreatitis, we believe that surgical resection remains necessary in a specific subgroup of patients with autoimmune pancreatitis (Fig. 4, Ref. 37).

[Extramammary Paget´s disease of the vulva - a case report]. / Extramamární Pagetova choroba vulvy - kazuistika.

OBJECTIVE: Analysis of one case of vulvar extramammary Paget´s disease (EMPD) and associated well differentiated endometrial adenocarcinoma.Desing: A case report. METHODS AND RESULTS: On this case report we present current theoretical knowledge about EMPD, difficulty of diagnostics, treatment and dispensarization the patients with this rare intraepithelial non-squamous neoplasia. We report a rare case of a 62 years old female patient with extramammary Paget´s disease of vulva and associated well differentiated endometrial adenocarcinoma. CONCLUSIONS: EMPD is a rare intraephitelial non-squamous neoplasia, which represents less then 1% vulvar tumors. Predominantly it affects white women between 60 and 80 years of age. EMPD occurs in cutaneous areas bearing apocrine glands - vulva, perineum, perianal area, axilla, penis, scrotum and rarely region of tights or buttocks. It is characterized microscopically by the presence of specific tumor cells called Paget´s cells - atypical large cells with pale clear cytoplasm and large round nuclei. KEYWORDS: extramammary Paget´s disease, EMPD, Paget´s cells, vulvectomy, imiquimod 5%, photodynamic therapy, imunotherapy, radiotherapy.

[Risk factors for recurrent disease in borderline ovarian tumors]. / Rizikové faktory pro vznik recidivy u borderline nádoru ovaria.

OBJECTIVE: To evaluate risk factors for development of recurrent disease in borderline ovarian tumors. DESIGN: Retrospective study of 10-years single institution population. SETTING: Dept. of Gynecology and Obstetrics, 3rd Medical Faculty of Charles University in Prague. METHOD: 59 consecutive cases of borderline ovarian tumors (BOT) were analyzed for age, histopathological type, DNA ploidy, stage, presence of invasive and non-invasive peritoneal implants, type of surgical procedure, residual disease, adjuvant therapy, recurrence and long-time prognosis of the patients. RESULTS: Median follow-up was 47 months (range 1-144). There were 5 (8.5%) patients with DNA aneuploid tumors in the study group; 4 of them were younger than 50 years, 4 of them were early stage serous BOT; no one recur so far. No death of disease was described in the whole study group; only 2 patients (3.4%) developed recurrent disease - both were young patients after conservative surgery for serous diploid stage I/II BOT. Conservative surgery was the only significant factor for recurrence in univariate analysis (p = 0.0159) in our setting. CONCLUSION: DNA ploidy was not proved to be prognostic factor in borderline ovarian tumors in our study group. The only significant risk factor for development of recurrent disease was conservative surgery, with no influence on overall survival.

[Guideline for treatment of gynaecological malignant tumours 2010---endometrial carcinoma]. / Guideline gynekologických zhoubných nádoru 2010. Primární chirurgická lécba zhoubných nádoru endometria.

OBJECTIVE: To develop guideline for primary surgical treatment of endometrial carcinoma. DESIGN: Review, consensus of expert group. SETTING: Dept. of Gynaecology and Obstetrics, 3rd Medical Faculty of Charles University in Prague. METHOD: A retrospective review of published data, analysis of statistic data from Czech Republic, consensus among proposers and opponents. RESULTS: The guideline recognizes endometrial carcinoma patients based on their risk and recommends type of surgical treatment for certain group. It emphasizes the importance of centralized oncogynaecological treatment. Surgical staging remains the basic principle for treatment of endometrial carcinoma patients. The aim of pre-operative diagnostics is to estimate the extent of the disease--"interim staging", that can be different from definitive histopathological staging. Based on risk factors patients are divided into low or high risk group. Standard procedure for low risk patients is hysterectomy and bilateral salpingoophorectomy. It is advisable to use peroperative biopsy in these patients that can shift the patient to high risk group. High risk patients are recommended for hysterectomy, bilateral salpingoophorectomy, and systematic aortopelvic lymphadenectomy. The guideline contains recommendation for young patients wishing to preserve their fertility, for cases of inadequate surgery and for follow-up. CONCLUSION: Guideline for treatment of endometrial carcinoma is recommendation for clinicians and other subjects who participate on the process of the diagnostics/treatment of endometrial carcinoma patients. All points of the guideline were discussed and voted about by all participants of expert group.

[Post-traumatic pseudocyst of the spleen]. / Poúrazová pseudocysta sleziny.

INTRODUCTION: Post-traumatic splenic pseudocysts are rare condition and comprise more than 75% of non-parasitic cysts. They result from subcapsular or intraparenchymatous hematoma, by its liquefaction and creation of the fibrous peripheral capsula. Splenic pseudocysts have no epithelial lining, its diameter could be more than 15 cm and are mostly symptomatic. CASE REPORT: A female, 53 years old, was admitted to the Clinic of surgery with blunt pains in the left hypochondrium after falling on the left side of body 6 months ago. Ultrasonography and CT scan reveal posttraumatic pseudocyst of the spleen, 156 x 135 x 148 mm in diameter. The splenic parenchyma was reduced to 15 mm dorso-caudal. Extirpation of the pseudocyst and splenectomy during laparotomy was performed with healing per primam. The patient was discharged 6 day after surgery. CONCLUSION: Posttraumatic splenic pseudocysts are good diagnosed in CT scan. Giant pseudocysts and psuedocysts in splenic hilus require surgical resection. Spleen parenchyma preserving operations, currently recommended in small cysts, reduce the risk of early and late septic complications, particularly overwhelming postsplenectomy sepsis. Partial splenectomy offers a definitive treatment of a splenic cyst while preserving splenic functions. Miniinvasive surgery as a percutaneous drainage and laparoscopic fenestration have an unacceptably high rate of failure.

Pharmacological stimulation of Wnt/beta-catenin signaling pathway attenuates the course of thioacetamide-induced acute liver failure.

Acute liver failure (ALF) is known for extremely high mortality rate, the result of widespread damage of hepatocytes. Orthotopic liver transplantation is the only effective therapy but its application is limited by the scarcity of donor organs. Given the importance in the liver biology of Wnt/beta-catenin signaling pathway, we hypothesized that its stimulation could enhance hepatocyte regeneration and attenuate the course of thioacetamide (TAA)-induced ALF in Lewis rats. Chronic treatment with Wnt agonist was started either immediately after hepatotoxic insult ("early treatment") or when signs of ALF had developed ("late treatment"). Only 23 % of untreated Lewis rats survived till the end of experiment. They showed marked increases in plasma alanine aminotransferase (ALT) activity and bilirubin and ammonia (NH3) levels; plasma albumin decreased significantly. "Early" and "late" Wnt agonist treatment raised the final survival rate to 69 % and 63 %, respectively, and normalized ALT, NH3, bilirubin and albumin levels. In conclusion, the results show that treatment with Wnt agonist attenuates the course of TAA-induced ALF in Lewis rats, both with treatment initiated immediately after hepatotoxic insult and in the phase when ALF has already developed. Thus, the pharmacological stimulation of Wnt/beta-catenin signaling pathway can present a new approach to ALF treatment.

End-organ damage in hypertensive transgenic Ren-2 rats: influence of early and late endothelin receptor blockade.

The rat strain transgenic for the murine Ren-2 renin gene (TGR) is defined as a monogenic model of angiotensin II-dependent hypertension with endogenous activation of the renin-angiotensin system. Homozygous males TGR develop malignant hypertension with a strong salt-sensitive component. These animals show severe hypertension, proteinuria and high mortality. Morphological changes of renal parenchyma correspond to chronic ischemic glomerular changes. Heterozygous TGR develop only mild hypertension and thus provide a more suitable model of hypertension regarding to clinical studies. Within the renal parenchyma, secondary focal segmental glomerulosclerosis (FSGS) predominates. High-salt diet in heterozygous animals induces transition from benign to malignant phase of hypertension. In this case, ischemic glomerular changes are superimposed on preexisting secondary FSGS. In the regression model of hypertension (late-onset treatment) the effect of salt intake is attenuated. In homozygous TGR, early selective ET(A) receptor blockade decreased blood pressure and ameliorated end-organ damage. Late selective ET(A) receptor blockade reduced podocyte injury despite final severe hypertension. Survival rate was markedly improved in both regimens with ET(A) selective blockade, while there was only partial improvement with early non-selective blockade. Both bosentan and atrasentan decreased ET-1 levels in both regimens. In heterozygous TGR, early and late ET(A) treatment substantially while ET(A)/ET(B) treatment partially improved survival rate. Significant effect on BP was found with early and late ET(A) blockade, while ET(A)/ET(B) blockade had no effect. Bosentan and atrasentan similarly decreased ET-1 levels on both regimens. In conclusion, selective ET(A) receptor blockade is superior to nonselective ET(A)/ET(B) receptor blockade in attenuating hypertension and end-organ damage. Its effect is more pronounced when applied early in the life.

Serum resistin levels in benign prostate hyperplasia and non-metastatic prostate cancer: possible role in cancer progression.

Resistin is a member of adipokine family involved in the regulation of inflammatory reactions and insulin sensitivity. In presented study its possible role in the development of benign prostate hyperplasia and prostate cancer was evaluated. Blood samples and prostate specimens were collected from 26 patients with benign prostate hyperplasia (BPH) and from 42 patients with prostate cancer (PCa) stage pT2 (n=18) and pT3 (n=24). Selected metabolic and biochemical parameters and serum resistin levels were measured and anthropometric measurements were performed as well as tissue immunohistochemistry for resistin. Serum resistin levels did not differ significantly between benign hyperplasia and prostate cancer but in cancer patients there was a trend towards decrease with higher cancer stage. Moreover, serum resistin levels were significantly lower in patients with seminal vesicle invasion in comparison to those without invasion. While in BPH serum resistin levels correlated with insulin resistance, inflammatory status and cortisol, in PCa positive correlation with F/T PSA ratio and cortisol was observed. Tissue immunohistochemistry did not show any differences in staining pattern between benign and neoplastic prostate tissue. We conclude that serum resistin levels do not significantly differ between patients with benign prostate hyperplasia and prostate cancer, but there is a trend towards decrease in resistin serum levels in advanced cancer cases.

Adiponectin as a potential marker of prostate cancer progression: studies in organ-confined and locally advanced prostate cancer.

Serum levels of adiponectin were measured in patients with benign prostatic hyperplasia and prostate cancer of pT2 and pT3 stage. Adiponectin ELISA assay, immunohistochemistry, and selected metabolic and biochemical parameters measurement was performed in 25 patients with benign prostatic hyperplasia and 43 with prostate cancer (17 patients with organ-confined and 26 patients with locally advanced disease). Serum adiponectin levels did not differ between prostate benign hyperplasia and cancer clinical stage T2, but was significantly higher in pT3 relative to pT2 group (14.51+/-4.92 vs. 21.41+/-8.12, P = 0.003). Tissue immunohistochemistry showed enhanced staining in neoplastic prostate glands and intraepithelial neoplasia relative to benign prostatic hyperplasia without distinction between disease grade and stage. Serum adiponectin levels are higher in locally advanced relative to organ-confined prostate cancer and may thus serve as an auxiliary marker providing further improvement for discrimination between pT2 and pT3 stages.

Renoprotective effects of ET(A) receptor antagonists therapy in experimental non-diabetic chronic kidney disease: Is there still hope for the future?

Chronic kidney disease (CKD) is a life-threatening disease arising as a frequent complication of diabetes, obesity and hypertension. Since it is typically undetected for long periods, it often progresses to end-stage renal disease. CKD is characterized by the development of progressive glomerulosclerosis, interstitial fibrosis and tubular atrophy along with a decreased glomerular filtration rate. This is associated with podocyte injury and a progressive rise in proteinuria. As endothelin-1 (ET-1) through the activation of endothelin receptor type A (ET(A)) promotes renal cell injury, inflammation, and fibrosis which finally lead to proteinuria, it is not surprising that ET(A) receptors antagonists have been proven to have beneficial renoprotective effects in both experimental and clinical studies in diabetic and non-diabetic CKD. Unfortunately, fluid retention encountered in large clinical trials in diabetic CKD led to the termination of these studies. Therefore, several advances, including the synthesis of new antagonists with enhanced pharmacological activity, the use of lower doses of ET antagonists, the addition of diuretics, plus simply searching for distinct pathological states to be treated, are promising targets for future experimental studies. In support of these approaches, our group demonstrated in adult subtotally nephrectomized Ren-2 transgenic rats that the addition of a diuretic on top of renin-angiotensin and ET(A) blockade led to a further decrease of proteinuria. This effect was independent of blood pressure which was normalized in all treated groups. Recent data in non-diabetic CKD, therefore, indicate a new potential for ET(A) antagonists, at least under certain pathological conditions.

Connexin 50 mutation lowers blood pressure in spontaneously hypertensive rat.

We assessed the effect of the previously uncovered gap junction protein alpha 8 (Gja8) mutation present in spontaneously hypertensive rat - dominant cataract (SHR-Dca) strain on blood pressure, metabolic profile, and heart and renal transcriptomes. Adult, standard chow-fed male rats of SHR and SHR-Dca strains were used. We found a significant, consistent 10-15 mmHg decrease in both systolic and diastolic blood pressures in SHR-Dca compared with SHR (P<0.01 and P<0.05, respectively; repeated measures analysis of variance (ANOVA)). With immunohistochemistry, we were able to localize Gja8 in heart, kidney, aorta, liver, and lungs, mostly in endothelium; with no differences in expression between strains. SHR-Dca rats showed decreased body weight, high-density lipoprotein cholesterol concentrations and basal insulin sensitivity in muscle. There were 21 transcripts common to the sets of 303 transcripts in kidney and 487 in heart showing >1.2-fold difference in expression between SHR and SHR-Dca. Tumor necrosis factor was the most significant upstream regulator and glial cell-derived neurotrophic factor family ligand-receptor interactions was the common enriched and downregulated canonical pathway both in heart and kidney of SHR-Dca. The connexin 50 mutation L7Q lowers blood pressure in the SHR-Dca strain, decreases high-density lipoprotein cholesterol, and leads to substantial transcriptome changes in heart and kidney.

Improvement of insulin sensitivity after peroxisome proliferator-activated receptor-alpha agonist treatment is accompanied by paradoxical increase of circulating resistin levels.

We studied the effect of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation on serum concentrations and tissue expression of resistin, adiponectin, and adiponectin receptor-1 and -2 (AdipoR1 and AdipoR2) mRNA in normal mice and mice with insulin resistance induced by lipogenic, simple-carbohydrate diet (LD). Sixteen weeks of LD feeding induced obesity with liver steatosis and increased insulin levels but did not significantly affect circulating adiponectin or resistin. Treatment with PPAR-alpha agonist fenofibrate decreased body weight and fat pad weight and ameliorated liver steatosis in LD-fed mice with concomitant reduction in blood glucose, free fatty acid, triglyceride, serum insulin levels, and homeostasis model assessment index values. Euglycemic-hyperinsulinemic clamp demonstrated the development of whole-body and liver insulin resistance in LD-fed mice, which were both normalized by fenofibrate. Fenofibrate treatment markedly increased circulating resistin levels on both diets and adiponectin levels in chow-fed mice only. Fat adiponectin mRNA expression was not affected by fenofibrate treatment. Resistin mRNA expression increased in subcutaneous but not gonadal fat after fenofibrate treatment. In addition to fat, a significant amount of adiponectin mRNA was also expressed in the muscle. This expression markedly increased after fenofibrate treatment in chow- but not in LD-fed mice. Adipose tissue expression of AdipoR1 mRNA was significantly reduced in LD-fed mice and increased after fenofibrate treatment. In conclusion, PPAR-alpha activation ameliorated the development of insulin resistance in LD-fed mice despite a major increase in serum resistin levels. This effect could be partially explained by increased AdipoR1 expression in adipose tissue after fenofibrate treatment.

Adipocytokines and cancer.

Adipose tissue-produced hormones significantly affect the metabolism of lipids and carbohydrates as well as numerous other processes in human body. It is generally accepted that endocrine dysfunction of adipose tissue may represent one of the causal links between obesity and insulin resistance/diabetes. Epidemiological studies underlined that obesity represents a significant risk factor for the development of cancer, although the exact mechanism of this relationship remains to be determined. Multiple recent studies have indicated that some of adipose tissue-derived hormones may significantly influence the growth and proliferation of tumorous stroma and malignant cells within. Here we review current knowledge about possible relationship of leptin and adiponectin to the etiopathogenesis of different malignant tumors. Most of the studies indicated that while leptin may potentiate the growth of cancer cells in vitro, adiponectin appears to have an opposite effect. Further studies are necessary to decide whether obesity-induced endocrine dysfunction of adipose tissue can directly influence carcinogenesis in different tissues and organs.

An unusual cause of renal amyloidosis secondary to gout: the first description of familial occurrence.

BACKGROUND: AA amyloidosis caused by the chronic inflammation accompanying gouty arthritis is extremely rare and familial occurrence has not been described so far. CASE REPORT: We present the case of two brothers (47 and 44 years old) with 7- and 10-year history of hyperuricaemia and chronic tophaceous gout with polyarticular involvement. The enzymatic assay performed in their erythrocytes proved the partial hypoxanthine-guanine phosphoribosyl transferase deficiency (Kelley-Seegmiller syndrome), the genetic defect of purine metabolism. Later on they developed proteinuria and chronic renal insufficiency /CRI/. Renal biopsy disclosed the combination of AA amyloidosis and gouty nephropathy in both the cases. Despite the standard treatment the older brother progressed to chronic renal failure. On the contrary, the younger one being longterm treated with oral colchicin have stabilized CRI. CONCLUSIONS: Only several cases of AA renal amyloidosis until recently, secondary to gout have been reported. Our case represents the first report of familial occurrence of this extremely rare disease.

Wilms tumor gene 1 (WT1), TP53, RAS/BRAF and KIT aberrations in testicular germ cell tumors.

PURPOSE: Wilms tumor gene 1 (WT1), a zinc-finger transcription factor essential for testis development and function, along with other genes, was investigated for their role in the pathogenesis of testicular germ cell tumors (TGCT). METHODS: In total, 284 TGCT and 100 control samples were investigated, including qPCR for WT1 expression and BRAF mutation, p53 immunohistochemistry detection, and massively parallel amplicon sequencing. RESULTS: WT1 was significantly (p < 0.0001) under-expressed in TGCT, with an increased ratio of exon 5-lacking isoforms, reaching low levels in chemo-naïve relapsed TGCT patients vs. high levels in chemotherapy-pretreated relapsed patients. BRAF V600E mutation was identified in 1% of patients only. p53 protein was lowly expressed in TGCT metastases compared to the matched primary tumors. Of 9 selected TGCT-linked genes, RAS/BRAF and WT1 mutations were frequent while significant TP53 and KIT variants were not detected (p = 0.0003). CONCLUSIONS: WT1 has been identified as a novel factor involved in TGCT pathogenesis, with a potential prognostic impact. Distinct biologic nature of the two types of relapses occurring in TGCT has been demonstrated. Differential mutation rate of the key TGCT-related genes has been documented.

Intrapulmonary activation of the angiotensin-converting enzyme type 2/angiotensin 1-7/G-protein-coupled Mas receptor axis attenuates pulmonary hypertension in Ren-2 transgenic rats exposed to chronic hypoxia.

The present study was performed to evaluate the role of intrapulmonary activity of the two axes of the renin-angiotensin system (RAS): vasoconstrictor angiotensin-converting enzyme (ACE)/angiotensin II (ANG II)/ANG II type 1 receptor (AT1) axis, and vasodilator ACE type 2 (ACE2)/angiotensin 1-7 (ANG 1-7)/Mas receptor axis, in the development of hypoxic pulmonary hypertension in Ren-2 transgenic rats (TGR). Transgene-negative Hannover Sprague-Dawley (HanSD) rats served as controls. Both TGR and HanSD rats responded to two weeks´ exposure to hypoxia with a significant increase in mean pulmonary arterial pressure (MPAP), however, the increase was much less pronounced in the former. The attenuation of hypoxic pulmonary hypertension in TGR as compared to HanSD rats was associated with inhibition of ACE gene expression and activity, inhibition of AT1receptor gene expression and suppression of ANG II levels in lung tissue. Simultaneously, there was an increase in lung ACE2 gene expression and activity and, in particular, ANG 1-7 concentrations and Mas receptor gene expression. We propose that a combination of suppression of ACE/ANG II/AT1receptor axis and activation of ACE2/ANG 1-7/Mas receptor axis of the RAS in the lung tissue is the main mechanism explaining attenuation of hypoxic pulmonary hypertension in TGR as compared with HanSD rats.

Retroviruses in foreign species and the problem of provirus silencing.

Retroviruses are known to integrate in the host cell genome as proviruses, and therefore they are prone to cell-mediated control at the transcriptional and posttranscriptional levels. This plays an important role especially after retrovirus heterotransmission to foreign species, but also to differentiated cells. In addition to host cell-mediated blocks in provirus expression, also so far undefined host specificities, deciding upon the pathogenic manifestation of retrovirus heterotransmission, are in play. In this respect, we discuss especially the occurrence of wasting disease and immunodeficiency syndrome, which we established also in avian species using avian leukosis virus subgroup C (ALV-C) inoculated in mid-embryogenesis in duck or chicken embryos. The problem of provirus downregulation in foreign species or in differentiated cells has been in the recent years approached experimentally. From a series of observations it became apparent that provirus downregulation is mediated by its methylation, especially in the region of proviral enhancer-promoter located in long terminal repeats (LTR). Several strategies have been devised in order to protect the provirus from methylation using LTR modification and/or introducing in the LTR sequence motifs acting as antimethylation tags. In such a way the expression of retroviruses and vectors in foreign species, as well as in differentiated cells, has been significantly improved. The complexity of the mechanisms involved in provirus downregulation and further possibilities to modulate it are discussed.

Amyloid A amyloidosis in non-infected and avian leukosis virus-C persistently infected inbred ducks.

The breeding history of the first inbred strain of Khaki Campbell ducks is presented. The genetic homogeneity of this strain was tested on the basis of serum amyloid A (SAA) polymorphism and it was established that it harbours only the SAA allele A, which is expressed in liver, lung and bursa of Fabricius tissues. Pathogenic changes in control and avian leukosis virus-C (ALV-C) persistently infected ducks were evaluated during the period spanning 1 to 10 months after hatching. In both groups, AA amyloidosis was revealed and characterized. In spite of the inbred nature of animals, the incidence of amyloid A deposition varied among experiments, suggesting that additional non-genetic factors are involved. Similar variation was found in ALV-C persistently infected ducks, where only in one out of three experiments was the incidence ofAA amyloidosis significantly higher than in controls.