Biomedical subjects

P Dvorák

Publications and source records attributed to P Dvorák.

At least 19 recordsLinked to original sources

PubMed2006

Temporary liver blood-outflow occlusion increases effectiveness of radiofrequency ablation: an experimental study on pigs.

AIM: To evaluate the feasibility of liver blood outflow (LBOF) occlusion and its impact on the effectiveness of radiofrequency ablation (RFA). METHODS: The experiment was performed on 10 pigs. The animals were divided into groups A and B according to RFA protocol. In group A (n=5) the RFA time was that taken to reach the target temperature of 105 degrees C, whereas group B (n=5) had a constant RFA temperature of 105 degrees C and constant time of 8min. The liver blood flow (LBF) was quantified using Doppler ultrasonography before LBOF occlusion and after that. RFA were performed using an expandable 3cm RF needle. Two liver ablations created in different liver lobes were compared; the first ablation was created before balloon inflation and the second one was created under LBOF occlusion. The time required for RFA procedure, liver ablation volumes, shape and microscopic changes of the thermoablated zones were recorded. RESULTS: The LBF dropped significantly in all liver vessels after balloon inflation. The volume of the ablated area was 8.2+/-2.2cm(3) and increased significantly after LBOF occlusion to 17.4+/-3.8cm(3) (p<0.001), in group A. A significant enlargement of the ablated area with occluded LBF was registered in group B, it was 6.7+/-2.8cm(3) versus 19.4+/-1.8cm(3) respectively (p<0.01). CONCLUSIONS: Temporary LBOF occlusion led to a significant reduction in liver blood flow, enlargement of the thermoablated area volume and homogeneity of the coagulated zones.

Animals↗

PubMed2006

A modified radiofrequency-assisted approach to right hemihepatectomy.

AIMS: To evaluate a modified radiofrequency-assisted approach to right hemihepatectomy. METHODS: Following a bilateral subcostal incision and intraoperative ultrasonography, the liver was mobilized in the standard manner, and a cholecystectomy was performed. The portal vein was isolated, encircled, and ligated. After demarcating the liver parenchyma, coagulation necrosis was achieved using a radiofrequency-assisted device along the line demarcated for transecting the liver parenchyma. The actual transection of the liver parenchyma and the right portal vein was done using a surgical scalpel along the radiofrequency-coagulated line. The right hepatic vein was coagulated using the radiofrequency sealer or by stitching in the resection plane. The hepatic artery was not dissected and was sealed together with the bile ducts in the resection plane using the radiofrequency instrument. The hepatic vein was not divided. RESULTS: Between July 2005 and July 2006, a total of 49 liver resections were performed in our unit. Of these, the radiofrequency-assisted technique was used in 33 cases with metastatic disease; 14 of these cases had right hemihepatectomies, including 2 repeat resections. The mean operation time was 180min (range, 120-240min), and the average blood transfusion was 0.14U (range, 0-2U). Postoperatively, there was no morbidity, such as bleeding, infection, or biliary fistula, related to the liver resection technique, and no patients died as a result of surgery. In 8 out of the 14 right hemihepatectomies, a right-sided pleural effusion was observed; 3 of them required evacuation. CONCLUSION: This paper describes a modified radiofrequency-assisted hemihepatectomy, which allows one to obtain control of the portal blood flow going into the resected part of liver. The modified approach appears to be simple and safe.

Catheter Ablation↗

PubMed2006

[Radiofrequency assisted liver resection in non-cirhotic liver. Initial clinical experience].

AIM OF THE STUDY: To evaluate the radiofrequency assisted liver resection using Habib sealer (RITA Medical System, Inc., Mountain View, CA). METHODS: The operation time, liver transection time, transfusion units used, and postoperative complications were recorded in a prospective way. RESULTS: 22 liver resections were performed between July 2005 and December 2005, 15 of them were done using radiofrequency technique. Twelve anatomical resections and three non-anatomical resections were performed in total. The mean operation time equalled 155 (120-240) minutes. An average of 0.6 (0-4) transfusion units was used. In 13 of the 15 operations, which represent 86% of the patients, no transfusions were used. Postoperatively, no major bleeding from the resection plane was noted and no biliary fistula was observed. CONCLUSIONS: Radiofrequncy assisted liver resection is a safe technique with the major benefit of minimal perioperative blood lost.

Catheter Ablation↗

PubMed2006

[Improved control of hypertension and its effect on graft function in children after renal transplantation].

BACKGROUND: Hypertension in patients after renal transplantation (RTx) is associated with impaired graft functions and graft survival. Control of hypertension in children after RTx is low--only 20-50 % of children have well controlled hypertension. The aim of this interventional study is to improve blood pressure control and to investigate whether the improved control will improve the graft survival. METHODS AND RESULTS: 36 children after RTx (mean age 13.9 +/- 4.4 years, time after RTx 2.7 +/- 2.4) fulfilled the inclusion criteria. Ambulatory blood pressure monitoring (ABPM) and graft function were examined. In children with uncontrolled hypertension, the dose and number of antihypertensive drugs were increased to reach BP <95th centile. ABPM was repeated after 12 months. After 12 months day-time and night-time BP dropped non-significantly, however prevalence of uncontrolled hypertension improved significantly from 42 % to 34 % (p<0.05). Number of antihypertensive drugs increased from 2.1 +/- 0.9 to 2.4 +/- 0.8 drugs per patient (p<0.05), namely that of ACE-inhibitors (from 19% to 27%, p<0.05). Graft function decreased by 3.6 ml/min/1.73m2/year (p<0.05). CONCLUSIONS: This 12 months interventional trial demonstrated that control of hypertension in children after RTx can be improved by increasing number of prescribed antihypertensive drugs. The decline of graft function was lower comparing with previous trials.

Adolescent↗

PubMed2005

Retinoic acid-induced neural differentiation of P19 embryonal carcinoma cells is potentiated by leukemia inhibitory factor.

Leukemia inhibitory factor (LIF) is a cytokine that exhibits proliferation, survival and differentiation in a wide range of cell types. Here we show that LIF potentiates retinoic acid-mediated neural induction in pluripotent P19 embryonal carcinoma cells. This activity of LIF was demonstrated by a profounded neural morphology followed by increased expression of neural-specific proteins (N-CAM, III beta-tubulin, and GAP-43), up-regulation of early neural lineage-specific gene Mash-1, and down-regulation of early endoderm-specific genes -fetoprotein and GATA-4. Moreover, LIF also slows growth and increases the level of apoptosis in differentiating cells.

Animals↗

PubMed2005

Proteinuria in children after renal transplantation.

Proteinuria is associated with poor long-term allograft as well as patient survival among adults after renal transplantation. In children, there are no studies focusing primarily on posttransplant proteinuria. The aim of this cross-sectional study was to investigate the prevalence of and possible risk factors associated with proteinuria. Thirty-three children (mean age of 13.7 +/- 4.3 years; mean time after renal transplantation = 2.3 +/- 2.2 years) were eligible for the study. There was an 82% prevalence of proteinuria (> or =96 mg/m2/d) with nephrotic range proteinuria (> or =960 mg/m2/d) in 12% of children. The mean urinary protein excretion was 256 +/- 299 mg/m2/d (range = 47 to 1264). Children with hypertension, as defined by ambulatory blood pressure monitoring, showed significantly higher proteinuria than normotensive children (382 +/- 435 vs 163 +/- 79 mg/m2/d, P < .05). Children with a history of a previous acute rejection episode showed significantly higher proteinuria than children who never had an episode (416 +/- 445 vs 165 +/- 91 mg/m2/d, P < .05). Children with proteinuria did not show statistically different graft function than children without proteinuria. No statistically significant correlation was observed between proteinuria and ambulatory blood pressure values or graft function. In conclusion, proteinuria is a frequent finding also in children after renal transplantation; it is associated with hypertension and a history of rejection episodes.

Adolescent↗

PubMed2005

Neural differentiation of pluripotent mouse embryonal carcinoma cells by retinoic acid: inhibitory effect of serum.

In both embryonal carcinoma (EC) and embryonic stem (ES) cells, the differentiation pathway entered after treatment with retinoic acid (RA) varies as it is based upon different conditions of culture. This study employs mouse EC cells P19 to investigate the effects of serum on RA-induced neural differentiation occurring in a simplified monolayer culture. Cell morphology and expression of lineage-specific molecular markers document that, while non-neural cell types arise after treatment with RA under serum-containing conditions, in chemically defined serum-free media RA induces massive neural differentiation in concentrations of 10(-9) M and higher. Moreover, not only neural (Mash-1) and neuroectodermal (Pax-6), but also endodermal (GATA-4, alpha-fetoprotein) genes are expressed at early stages of differentiation driven by RA under serum-free conditions. Furthermore, as determined by the luciferase reporter assay, the presence or absence of the serum does not affect the activity of the retinoic acid response element (RARE). Thus, mouse EC cells are able to produce neural cells upon exposure to RA even without culture in three-dimensional embryoid bodies (EBs). However, in contrast to standard EBs-involving protocol(s), neural differentiation in monolayer only takes place when complex signaling from serum factors is avoided. This simple and efficient strategy is proposed to serve as a basis for neurodifferentiation studies in vitro.

Animals↗

PubMed2005

Effects of sodium restriction and cyclooxygenase-2 inhibition on the course of hypertension, proteinuria and cardiac hypertrophy in Ren-2 transgenic rats.

The present study was performed to evaluate the effects of sodium intake and of chronic cyclooxygenase-2 (COX-2) inhibition on systolic blood pressure (SBP) in heterozygous male transgenic rats harboring the mouse Ren-2 renin gene (TGR) and in transgene-negative normotensive Hannover Sprague-Dawley (HanSD). Twenty-eight days old TGR and HanSD were randomly assigned to groups fed either normal salt (NS) or low sodium (LS) diets. COX-2 blockade was achieved with NS-398 (1 mg x kg(-1).day(-1) in drinking water). During an experimental period of 26 days, SBP was repeatedly measured by tail plethysmography in conscious animals. We found that the LS diet prevented the development of hypertension in TGR and did not change SBP in HanSD. Low sodium intake also prevented proteinuria and cardiac hypertrophy in TGR. On the other hand, irrespective of sodium intake chronic COX-2 inhibition did not alter the course of SBP in either TGR or HanSD. The present data indicate that TGR exhibit an important salt-sensitive component in the developmental phase of hypertension. They also suggest that systemic COX-2-derived prostaglandins do not act as vasodilatory counterregulatory agents in TGR in which an exaggerated vascular responsiveness to angiotensin II is assumed as the pathophysiological mechanism in the development of hypertension.

Animals↗

PubMed2004

Increased apoptosis in differentiating p27-deficient mouse embryonic stem cells.

In mouse embryonic stem (mES) cells, the expression of p27 is elevated when differentiation is induced. Using mES cells lacking p27 we tested the importance of p27 for the regulation of three critical cellular processes: proliferation, differentiation, and apoptosis. Although cell cycle distribution, DNA synthesis, and the activity of key G1/S-regulating cyclin-dependent kinases remained unaltered in p27-deficient ES cells during retinoic acid-induced differentiation, the amounts of cyclin D2 and D3 in such cells were much lower compared with normal mES cells. The onset of differentiation induces apoptosis in p27-deficient cells, the extent of which can be reduced by artificially increasing the level of cyclin D3. We suggest that the role of p27 in at least some differentiation pathways of mES cells is to prevent apoptosis, and that it is not involved in slowing cell cycle progression. We also propose that the pro-survival function of p27 is realized via regulation of metabolism of D-type cyclin(s).

Animals↗

PubMed2004

Chronic endothelin receptor blockade reduces end-organ damage independently of blood pressure effects in salt-loaded heterozygous Ren-2 transgenic rats.

The present study was performed to evaluate the role of an interaction between the endothelin (ET) and the renin-angiotensin systems (RAS) in the development and maintenance of hypertension and in hypertension-associated end-organ damage in heterozygous male and female transgenic rats harboring the mouse Ren-2 renin gene (TGR). Twenty-eight days old heterozygous TGR and age-matched transgene-negative normotensive Hannover Sprague-Dawley rats (HanSD) were randomly assigned to groups with normal-salt (NS) or high-salt (HS) intake. Nonselective ET(A)/ET(B) receptor blockade was achieved with bosentan (100 mg.kg(-1).day(-1)). All male and female HanSD as well as heterozygous TGR on NS exhibited 100 % survival rate until 180 days of age (end of experiment). HS diet in heterozygous TGR induced a transition from benign to malignant phase hypertension. The survival rates in male and in female heterozygous TGR on the HS diet were 46 % and 80 %, respectively, and were significantly improved by administration of bosentan to 76 % and 97 %, respectively. Treatment with bosentan did not influence either the course of hypertension (measured by plethysmography in conscious animals) or the final levels of blood pressure (measured by a direct method in anesthetized rats) in any of the experimental groups of HanSD or TGR. Administration of bosentan in heterozygous TGR fed the HS diet markedly reduced proteinuria, glomerulosclerosis and attenuated the development of cardiac hypertrophy compared with untreated TGR. Our data show that the ET receptor blockade markedly improves the survival rate and ameliorates end-organ damage in heterozygous TGR exposed to HS diet. These findings indicate that the interaction between the RAS and ET systems plays an important role in the development of hypertension-associated end-organ damage in TGR exposed to salt-loading.

Administration, Oral↗

PubMed2004

Renal concentrating capacity is linked to blood pressure in children with autosomal dominant polycystic kidney disease.

Impaired glomerular filtration rate (GFR) is a risk factor for the development of hypertension in patients with autosomal dominant polycystic kidney disease (ADPKD). However, markers of tubular function were not tested whether they are linked to hypertension or blood pressure (BP) level. The aim of our study was to investigate the relationship between renal concentrating capacity and BP in children with ADPKD. Fifty-three children (mean age 11.8+/-4.4 years) were investigated. Standardized renal concentrating capacity test was performed after nasal drop application of desmopressin, BP was measured by ambulatory BP monitoring (ABPM). Renal concentrating capacity was decreased in 58 % of children. The prevalence of hypertension was significantly higher in children with decreased renal concentrating capacity (35 %) than in children with normal renal concentrating capacity (5 %) (p<0.05). Significant negative correlations were found between renal concentrating capacity, ambulatory BP and number of renal cysts (r = -0.29 to -0.39, p<0.05 to p<0.01). In conclusion, the concentrating capacity is decreased in about half of the patients and is linked to BP. Decreased renal concentrating capacity should be considered.

Adolescent↗

PubMed2004

[Appendiceal mucocele].

Appendiceal mucocele is a rare condition encountered it only 0.07-0.4% of all appendectomies. The male to female ratio is 1:4 and an average age at the time of diagnosis is over 50 years. Mucocele of the appendix is defined as appendiceal obstruction leading to lumen distension with accumulation of mucoid material. The disease ranges from benign forms to malignant cystadenocarcinoma. The cause of the obstruction may be classified based on histology into four groups. These groups include simple mucocele, mucosal hyperplasia, cystadenoma, and cystadenocarcinoma. Abdominal ultrasound and CT scan may suggest the diagnosis. The authors discuss two cases of simple appendiceal mucocele. A 48-year-old man presented with acute right lower quadrant pain. Ultrasound examination was performed and the structure in the right iliac fossa was reported as an periappendiceal abscess. The patient underwent acute exploratory laparotomy, which revealed an appendiceal mucocele filled with gelatinous material. It was performed ileocoecal resection. A 65-year-old man presented with abdominal distension and discomfort of several week duration. At laparotomy, a smooth cystic tumor of the appendix was found. This patient underwent appendectomy alone. Pathology revealed an simple appendiceal mucocele.

Aged↗

PubMed2003

Temporal distribution of CDK4, CDK6, D-type cyclins, and p27 in developing mouse oocytes.

Various molecular interactions not operating in other cell types are most likely required for mammalian oocytes to develop into fully competent eggs. This study seeks to initiate analyses of the potential oocyte-specific functions of regulators of G1/S progression-CDK4, CDK6, D-type cyclins, and p27-by first determining their expression patterns in growing and maturing mouse oocytes and in mouse embryos early after fertilization. Western blot and immunofluorescence analyses on isolated oocytes were employed to evaluate both their levels and their localization. The data show that 1). mouse oocytes contain significant amounts of all studied regulators; 2). their amounts and localization undergo dramatic changes as the oocytes grow, meiotically mature, and transit into embryogenesis; and 3). some regulators (CDK4, CDK6, cyclin D2, and p27) appear in unusual, most likely posttranslationally modified, forms. These data distinguish G1/S regulators as the potential players in molecular processes that are important for oocytes to function normally.

Animals↗

PubMed2002

Medical application of 3-D polymer gel dosemeter evaluated by nuclear magnetic resonance.

A polymer-gel dosemeter, which can be evaluated by nuclear magnetic resonance (NMR), was prepared and then a few samples were homogeneously irradiated by a Leksell gamma knife using an 18 mm collimator (60Co gamma photons) to obtain a calibration curve (NMR 1/T2 response to absorbed dose). To measure dose distribution from the Leksell gamma knife, a testing flask tilled with the gel was fixed in the head phantom and then irradiated based on a calculated treatment plan. Evaluation of dosemeters was performed on a Siemens EXPERT 1T NMR scanner. Dose profiles in X, Y and Z coordinates through the ellipsoidal shape of the dose distribution were obtained to compare experimental results from the irradiated phantom with the treatment planning system calculations. The use of a polymer-gel dosemeter for a verification of stereotactic procedures has some unique advantages which can be summarised as follows: (1) the dosemeter itself is tissue equivalent, (2) three-dimensional dose distributions can be measured, (3) the dosemeter allows patient's procedures to be simulated without any limitations.

Calibration↗

PubMed2002

In vivo thermoluminescence dosimetry for total body irradiation.

An improvement in the clinical results obtained using total body irradiation (TBI) with photon beams requires precise TBI treatment planning, reproducible irradiation, precise in vivo dosimetry, accurate documentation and careful evaluation. In vivo dosimetry using LiF Harshaw TLD-100 chips was used during the TBI treatments performed in our department. The results of in vivo thermoluminescence dosimetry (TLD) show that using TLD measurements and interactive adjustment of some treatment parameters based on these measurements, like monitor unit calculations, lung shielding thickness and patient positioning, it is possible to achieve high precision in absorbed dose delivery (less than 0.5%) as well as in homogeneity of irradiation (less than 6%).

Calibration↗

PubMed2001

FGF-2 abnormalities in B cell chronic lymphocytic and chronic myeloid leukemias.

An elevated level of fibroblast growth factor-2 (FGF-2) in peripheral blood is considered to play a role in regulating the growth of leukemia cells. Here, we show that the level of plasma FGF-2 is increased in 54% of B cell chronic lymphocytic leukemias (B-CLL) and in 44% of chronic myeloid leukemias (CML). Notably, white blood cells (WBCs) from B-CLL patients contain 18, 22 and 24 kDa isoforms of FGF-2 whereas WBCs from CML patients contain only the 24 kDa isoform. Furthermore, as cultured B-CLL WBCs release 18 kDa FGF-2 into the medium, they constitute a potential source of FGF-2 in the blood. In a receptor binding assay, 125I-FGF-2 binds weakly to B-CLL WBCs, whereas the ligand binds more strongly to CML WBCs. Correspondingly, FGF-2 is unable to activate mitogen-activated protein kinase kinase (MEK) and its substrate, extracellular signal-regulated kinase (ERK), in B-CLL cells, whereas phosphorylation of both these cell growth-related kinases increases following treatment of CML WBCs. We conclude that B-CLL WBCs secrete FGF-2 with no apparent autocrine actions. In contrast, WBCs in CML bind FGF-2 provided by other FGF-2-hyperproducing cells and activate the MEK/ERK kinase cascade, possibly to modulate cell growth.

Adult↗

PubMed2001

Cytomegalovirus infection in immunocompetent and immunocompromised individuals--a review.

This review summarizes the state-of-the-art knowledge on diagnosis, pathogenesis, immune response to, clinical picture, treatment and prevention of cytomegalovirus (CMV) infection in humans. CMVs are ubiquitous betaherpesviruses that infect animals as well as humans. Primary infection with human cytomegalovirus (HCMV) is followed by persistence of the virus in a latent form. During life, the virus can reactivate, resulting in renewed shedding of the virus or development of disease. Redundant molecular mechanisms have been identified by which CMVs interfere with the host immune control, but finally, the infection is held in check by the host's immune response. As a consequence, CMV disease is restricted to the immunocompromised or immunologically immature host. HCMV is the leading cause of congenital infections, with an incidence of 1-2.4% of live births, with possible severe classic "cytomegalovirus inclusion disease" in 10% of them. Congenital CMV infection is the leading infectious cause of brain damage and hearing loss in children and also a relevant health issue to transplant recipients and human immunodeficiency virus (HIV)-infected patients. Significant progress has been made in the last few years in detecting CMV, but in the immunocompromised patients, establishing the diagnosis of CMV infection can still be problematic. The most sensitive molecular amplification methods such as polymerase chain reaction (PCR) should be used. The decision how to treat the infection depends mainly on the immune status of the host. In immunocompetent patients only symptomatic treatment is recommended, while in immunocompromised patients antiviral therapy and immunotherapy should be used. The most commonly used antivirotics are: ganciclovir, foscarnet, cidofovir, valganciclovir, valaciclovir.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Levels and interactions of p27, cyclin D3, and CDK4 during the formation and maintenance of the corpus luteum in mice.

The cyclin-dependent kinase (CDK) inhibitor p27, the regulator of the cell cycle, is required for proper functioning of luteinizing/luteinized cells in vivo. Since different members of the CDK family may be targeted by p27 during luteinization-associated cell cycle exit, this in vivo study further analyzed the organization of the network of cell cycle regulators that may underlie both the establishment and maintenance of the luteal phenotype. Most importantly, it shows that the luteinization process is associated with down-regulation of CDK2 and cyclin D1, and up-regulation of p27 and cyclin D3. Both p27 and cyclin D3 proteins not only accumulated during initial phases of luteinization, but they remained elevated until termination of the luteal function. Along with its accumulation, p27 lost physical contact with CDK2 and instead became associated with CDK4. In fully luteinized cells, all cyclin D3 was incorporated into complexes with p27, some complexes being p27/cyclin D3/CDK4 trimers. Despite the significant amounts of CDK4 and CDK6, only nonphosphorylated forms of retinoblastoma protein were detectable in fully luteinized cells. Together, our data indicate that while inhibition of proliferation is underlaid by the progressive loss of positive regulators of the cell cycle, including cyclins and CDK2, maintenance of the luteal phenotype is driven by up-regulated levels of p27 and cyclin D3, at least partially owing to formation of p27/cyclin D3/CDK4 trimers.

Animals↗