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Biomedical subjects

J Novotny

Publications and source records attributed to J Novotny.

At least 19 recordsLinked to original sources
PubMed2006

Role of single nucleotide polymorphisms and haplotypes in BRCA1 in breast cancer: Czech case-control study.

We aimed at determining whether any association exists between six single nucleotide polymorphisms in breast cancer associated gene (BRCA1) and the risk of breast cancer. We constructed haplotypes and analyzed their importance as well. Clinico-pathological characteristics of breast cancer patients were included in the study to evaluate the prognostic impact of BRCA1 polymorphisms and haplotypes. Polymerase chain reaction-restriction fragment length polymorphism-based genotyping assays were used to determine the frequency of polymorphisms in codons 356, 871, 1038, 1183, 1436, and 1613 of BRCA1 in a group of 306 incident breast cancer patients and 313 unaffected controls of Czech origin. Statistical analyses revealed that the BRCA1 Arg356 allele may play a protective role in breast cancer (age-adjusted OR = 0.61, CI = 0.39-0.94, p = 0.026). We also observed a significant correlation between polymorphism Gln356Arg and stage (p = 0.026) in premenopausal cases suggesting that carriers of the wild Gln356Gln allele are at significantly higher risk of advanced disease. The most common haplotypes of BRCA1 did not play a significant role in breast cancer either as risk factors or as prognostic factors. The study on rare BRCA1 haplotypes however should be repeated using larger groups. In conclusion, the BRCA1-Gln356 allele presents risk factor in the onset and progression of breast cancer in Czech population and its use as a possible screening tool should be considered.

Adult↗
PubMed2005

Comparative analysis of thymidylate synthase, thymidine phosphorylase and dihydropyrimidine dehydrogenase expression in colorectal cancer and surrounding normal tissue.

Thymidylate synthase [TS], thymidine phosphorylase [TP] and dihydropyrimidine dehydrogenase [DPD] play the essential role in the activation and catabolism of the fluoropyrimidines used in cancer therapy. Its expression may influence the antitumor activity or toxicity of these drugs. We studied the expression levels of selected enzymes in colorectal tumors and adjacent normal mucosa. The analysis of TS, TP and DPD gene expression was performed using quantitative Real time PCR technique (Roche) in 15 (TS), 64 (TP) and 12 (DPD) of 64 colorectal cancer patients. The mean gene expression of TS, TP and DPD was found to be 3.29; 3.79 and 8.24 in tumors and 1.88; 3.80 and 19.69 in normal mucosa. The corresponding median gene expression was 1.87; 2.32 and 4.50 for tumors and 2.14; 2.63 and 11.64 for normal tissue. We did not find any significant differences in TS, TP and DPD gene expression between colorectal tumor and surrounding mucosa.

Colorectal Neoplasms↗
PubMed2004

[Lymphadenopathy in the groin. Unusual etiology in a 65-year-old patient].

A 65 year old female patient was admitted to our hospital with unspecific symptoms and a lump in the right groin which raised suspicion of a malignant lymphoma. Histologically a follicular dendritic reticular cell tumor was found. Because there are aggressive forms of this tumor and no established standard therapy, we decided to treat her with surgery followed by a combined radio- and chemotherapy. Despite this treatment 16 months after the first diagnosis a relapse occurred with a metastasis of the follicular dendritic cell tumor in the lung. The metastasis was resected surgically. The optimal management of this kind of tumor is not known.

Aged↗
PubMed2004

A prospective, randomised, phase II study of horse antithymocyte globulin vs rabbit antithymocyte globulin as immune-modulating therapy in patients with low-risk myelodysplastic syndromes.

Immunosuppression has recently been proposed for low-risk myelodysplastic syndromes (MDS) to reverse bone marrow failure by inhibiting intramedullary secretion of proapoptotic cytokines. We treated 35 MDS patients (24 refractory anaemia (RA), 10 RA with excess blasts and one chronic myelomonocytic leukaemia) with either horse antithymocyte globulin 15 mg/kg/day or rabbit antithymocyte globulin 3.75 mg/kg/day, each for 5 days. Median age was 63 years (range: 41-75). After 1 to 34+ months of follow-up (mean: 15+), four patients experienced complete haematological responses (CR), six good responses (GR) and two minor responses. All CRs and GRs occurred in patients with RA, in whom both horse and rabbit ATG yielded five responses out of 12 (42%). Time to response varied between 1 and 10 (mean: 3) months. The median duration of response was 9+ (1-17+) months; five patients are in continuing response. In all, 23 patients suffered side effects > degrees II WHO (the degree of toxicity encountered according to the internationally accepted WHO toxicity grading); one patient died 2 weeks after rabbit ATG from rhinocerebral mucormycosis. Parameters that correlated with response were duration of disease and RA subgroup. In our experience, immune-modulating therapy with either horse or rabbit ATG is feasible in patients with RA and short duration of disease.

Adult↗
PubMed2004

Mammaglobin A, a novel marker of minimal residual disease in early stages breast cancer.

Mammaglobin A, in contrast to other factors, is a breast specific member of uteroglobin gene family. Expression is restricted to normal and neoplastic breast epithelium. A highly homologous mammaglobin B is not specific to breast tissue. In this pilot feasibility study we examined expression of both markers for minimal residual disease in the bone marrow of patients with breast cancer. We obtained bone marrow aspirates of 34 patients with stage I (41%), II (56%) and III (3%) breast cancer who underwent either immediate complete resection of the tumor or neoadjuvant therapy with subsequent curative surgery. mRNA was isolated using QIAamp RNA blood mini kit (Qiagen). Subsequently two-step nested RT-PCR for the expression of mammaglobin A and mammaglobin B was performed. Mammaglobin A was detected in samples from 4 (12%) out of 34 patients. None of the specimens was positive for mammaglobin B. With a median follow-up of 21 month we observed only 2 recurrences, one in patient with mammaglobin A positive bone marrow.RT-PCR assay for mammaglobin A may be a useful tool for detection of occult breast cancer cells in the bone marrow. Clinical and prognostic relevance of minimal residual disease should be further investigated.

Adult↗
PubMed2003

Measurement of the peripheral doses for linac stereotactic radiotherapy.

The purpose of this study was to establish peripheral doses during stereotactic treatments. The doses to different organs were measured by thermoluminescence dosemeters. A simple power function can describe the relationship between the measured peripheral dose and the distance from target. The dependence of measured peripheral dose at a particular point on the collimator size can also be described by a simple exponential function. Leakage radiation contributes very little to the dose, but becomes dominant at distances of more than 50 cm from the target. The arrangement of arcs as well as the collimator size influence the magnitude of the peripheral dose due to the contribution of exit dose and due to the increasing scattering volume of target. By changing the arc arrangement and using smaller collimators one can reduce the peripheral dose significantly and minimise the total body radiation burden.

Humans↗
PubMed2003

The evaluation of left ventricular function in childhood cancer survivors by pharmacological stress echocardiography.

Late cardiotoxicity after anthracycline chemotherapy for childhood cancer is well recognized sequelae. Many long-term survivors may have subclinical cardiac dysfunction undetectable at a baseline evaluation. Various tests have been utilized for the diagnosis of left ventricular impairment. Recently, low-dose dobutamine stress echocardiography has been proposed as a more sensitive screening test. We have applied low-dose dobutamine stress echocardiography (5-10 microg/kg/min) in 36 asymptomatic survivors (20 male/16 female aged 14.6+/-4.7 years) treated with a cumulative dose of 226+/-106 mg/m2 of doxorubicin. The median follow-up was 5 years. Control group consisted of 20 sex and age matched volunteers (12 male/8 female aged 12.6+/-4.9 years). We found significant differences in mean velocity of circumferential fibre shortening, myocardial performance index (Tei index), left ventricular posterior wall thickening and endsystolic wall stress at a baseline. The stress response was significantly blunted only in a patient group in the following parameters: endsystolic wall stress, isovolumic relaxation time and myocardial performance index. The threshold response was abnormal (0-5% improvement of a variable only) in 45% of subjects from a control group in one or two parameters. On the contrary, 63% of subjects from a patient group responded pathologically (the worsening of a variable) in one or more parameters. We have not found a good correlation between risk factors of late cardiotoxicity and stress changes of left ventricular function parameters. Low-dose dobutamine stress echocardiography is safe and feasible diagnostic tool in children and adolescents. Dobutamine significantly increases the differences in cardiac variables between healthy population and asymptomatic survivors for childhood cancer. In comparison to the controls, most asymptomatic patients revealed subclinical myocardial damage at test. The predictive value for the development of clinical symptoms and cardiac complications need to be assessed in a large prospective study.

Adolescent↗
PubMed2002

Hormone-induced subcellular redistribution of trimeric G proteins.

Trimeric guanine nucleotide-binding proteins (G proteins) function as the key regulatory elements in a number of transmembrane signaling cascades where they convey information from agonist-activated receptors to effector molecules. The subcellular localization of G proteins is directly related to their functional role, i.e., the dominant portion of the cellular pool of G proteins resides in the plasma membrane. An intimate association of G protein subunits with the plasma membrane has been well known for a long time. However, results of a number of independent studies published in the past decade have indicated clearly that exposure of intact target cells to agonists results in subcellular redistribution of the cognate G proteins from plasma membranes to the light-vesicular membrane fractions, in internalization from the cell surface into the cell interior and in transfer from the membrane to the soluble cell fraction (high-speed supernatant), i.e., solubilization. Solubilization of G protein a subunits as a consequence of stimulation of G protein-coupled receptors (GPCRs) with agonists has also been observed in isolated membrane preparations. The membrane-cytosol shift of G proteins was detected even after direct activation of these proteins by non-hydrolyzable analogues of GTP or by cholera toxin-induced ADP-ribosylation. In addition, prolonged stimulation of GPCRs with agonists has been shown to lead to down-regulation of the relevant G proteins. Together, these data suggest that G proteins might potentially participate in a highly complex set of events, which are generally termed desensitization of the hormone response. Internalization, subcellular redistribution, solubilization, and down-regulation of trimeric G proteins may thus provide an additional means (i.e., beside receptor-based mechanisms) to dampen the hormone or neurotransmitter response after sustained (long-term) exposure.

Animals↗
PubMed2002

Favourable response to antithymocyte or antilymphocyte globulin in low-risk myelodysplastic syndrome patients with a 'non-clonal' pattern of X-chromosome inactivation in bone marrow cells.

OBJECTIVE: Antithymocyte and antilymphocyte globulin (ATG/ALG) have a therapeutic effect in about 30% of patients with myelodysplastic syndromes (MDS). We were interested to know whether responding patients achieve clonal or polyclonal remissions. PATIENTS: Ten women with low-risk MDS received either ALG or ATG. Before treatment and 3, 6, and 12 months later, X-chromosome inactivation patterns of peripheral blood T lymphocytes were compared with those of peripheral blood granulocytes or bone marrow cells, using the human androgen receptor gene assay and the phosphoglycerate kinase-1 assay. RESULTS: Six women did not respond to therapy. Prior to treatment, four of them had a monoclonal, one had an oligoclonal, and one had a skewed X-chromosome inactivation pattern (XCIP). Four patients responded to ATG/ALG. Three of them were informative in our X-inactivation assays, and showed a non-clonal XCIP which did not change significantly after treatment with ATG/ALG. CONCLUSION: A non-clonal XCIP in the bone marrow was associated with a response to ATG/ALG. Non-clonal XCIPs do not necessarily imply that there is no pathological clone. By definition, they just indicate that there is no evidence of a clone contributing more than 50% of cells in a sample. Non-clonal XCIPs may therefore be attributable to incomplete clonal expansion. This, in turn, might be explained by a vigorous immune attack against the MDS clone, which simultaneously causes collateral damage in the remaining normal haemopoiesis. In such patients, ATG/ALG may improve normal haemopoiesis by relieving the immunological pressure on the innocent bystanders.

Aged↗
PubMed2001

Structure of the adenovirus E4 Orf6 protein predicted by fold recognition and comparative protein modeling.

To facilitate investigation of the molecular and biochemical functions of the adenovirus E4 Orf6 protein, we sought to derive three-dimensional structural information using computational methods, particularly threading and comparative protein modeling. The amino acid sequence of the protein was used for secondary structure and hidden Markov model (HMM) analyses, and for fold recognition by the ProCeryon program. Six alternative models were generated from the top-scoring folds identified by threading. These models were examined by 3D-1D analysis and evaluated in the light of available experimental evidence. The final model of the E4 protein derived from these and additional threading calculations was a chimera, with the tertiary structure of its C-terminal 226 residues derived from a TIM barrel template and a mainly alpha-nonbundle topology for its poorly conserved N-terminal 68 residues. To assess the accuracy of this model, additional threading calculations were performed with E4 Orf6 sequences altered as in previous experimental studies. The proposed structural model is consistent with the reported secondary structure of a functionally important C-terminal sequence and can account for the properties of proteins carrying alterations in functionally important sequences or of those that disrupt an unusual zinc-coordination motif.

Adenovirus E4 Proteins↗
PubMed2001

In silico structural and functional analysis of the human cytomegalovirus (HHV5) genome.

The open reading frames of human cytomegalovirus (human herpesvirus-5, HHV5) encode some 213 unique proteins with mostly unknown functions. Using the threading program, ProCeryon, we calculated possible matches between the amino acid sequences of these proteins and the Protein Data Bank library of three-dimensional structures. Thirty-six proteins were fully identified in terms of their structure and, often, function; 65 proteins were recognized as members of narrow structural/functional families (e.g. DNA-binding factors, cytokines, enzymes, signaling particles, cell surface receptors etc.); and 87 proteins were assigned to broad structural classes (e.g. all-beta, 3-layer-alphabetaalpha, multidomain, etc.). Genes encoding proteins with similar folds, or containing identical structural traits (extreme sequence length, runs of unstructured (Pro and/or Gly-rich) residues, transmembrane segments, etc.) often formed tandem clusters throughout the genome. In the course of this work, benchmarks on about 20 known folds were used to optimize adjustable parameters of threading calculations, i.e. gap penalty weights used in sequence/structure alignments; new scores obtained as simple combinations of existing scoring functions; and number of threading runs conducive to meaningful results. An introduction of summed, per-residue-normalized scores has been essential for discovery of subdomains (EGF-like, SH2, SH3) in longer protein sequences, such as the eight "open sandwich" cytokine domains, 60-70 amino acids long and having the 3beta1alpha fold with one or two disulfide bridges, present in otherwise unrelated proteins.

Amino Acid Sequence↗
PubMed2001

Non-alpha-helical elements modulate polytopic membrane protein architecture.

In "all alpha-fold" transmembrane proteins, including ion channels, G-protein-coupled receptors (GPCRs), bacterial rhodopsins and photosynthetic reaction centers, relatively long alpha-helices, straight, curved or kinked, pack into compact elliptical or circular domains. Using both existing and newly developed tools to analyze transmembrane segments of all available membrane protein three-dimensional structures, including that very recently elucidated for the GPCR, rhodopsin, we report here the finding of frequent non-alpha-helical components, i.e. 3(10)-helices ("tight turns"), pi-helices ("wide turns") and intrahelical kinks (often due to residues other than proline). Often, diverse helical types and kinks concatenate over long segments and produce complex inclinations of helical axis, and/or diverse frame shifts in the "canonical", alpha-helical side-chain pattern. Marked differences in transmembrane architecture exist even between seemingly structurally related proteins, such as bacteriorhodopsin and rhodopsin. Deconvolution of these non-canonical features into their composite elements is essential for understanding the pleiotropy of polytopic protein structure and function, and must be considered in developing valid macromolecular models.

Amino Acid Sequence↗
PubMed2001

Membrane-Bound and cytosolic forms of heterotrimeric G proteins in young and adult rat myocardium: influence of neonatal hypo- and hyperthyroidism.

Membrane and cytosolic fractions prepared from ventricular myocardium of young (21-day-old) hypo- or hyperthyroid rats and adult (84-day-old) previously hypo- or hyperthyroid rats were analyzed by immunoblotting with specific anti-G-protein antibodies for the relative content of Gs alpha, Gi alpha/Go alpha, Gq alpha/G11 alpha, and G beta. All tested G protein subunits were present not only in myocardial membranes but were at least partially distributed in the cytosol, except for Go alpha2, and G11 alpha. Cytosolic forms of the individual G proteins represented about 5-60% of total cellular amounts of these proteins. The long (Gs alpha-L) isoform of Gs alpha prevailed over the short (Gs alpha-S) isoform in both crude myocardial membranes and cytosol. The Gs alpha-L/Gs alpha-S ratio in membranes as well as in cytosol increased during maturation due to a substantial increase in Gs alpha-L. Interestingly, whereas the amount of membrane-bound Gi alpha/Go alpha and Gq alpha/G11 alpha proteins tend to lower during postnatal development, cytosolic forms of these G proteins mostly rise. Neonatal hypothyroidism reduced the amount of myocardial Gs alpha and increased that of Gi alpha/Go alpha proteins. By contrast, neonatal hyperthyroidism increased expression of Gs alpha and decreased that of Gi alpha and G11 alpha in young myocardium. Changes in G protein content induced by neonatal hypo- and hyperthyroidism in young rat myocardium were restored in adulthood. Alterations in the membrane-cytosol balance of G protein subunits associated with maturation or induced by altered thyroid status indicate physiological importance of cytosolic forms of these proteins in the rat myocardium.

Age Factors↗
PubMed2001

Geometric analysis of potential error in using femoral intramedullary guides in total knee arthroplasty.

Proper component orientation is necessary for the long-term success of a total knee arthroplasty. Femoral component placement has used jigging systems that are based on intramedullary and extramedullary guides. The intramedullary system has been shown to foster more accurate and reproducible placement of the femoral component. This study analyzed and quantified the potential error of the intramedullary guide system. Geometric data of the human femur were obtained from radiographs of 45 cadaver femora in the anteroposterior and lateral views. The correct entry point of the intramedullary rod in the distal femur is the midaxial line of the femoral canal on anteroposterior and lateral radiographs. The position of this point in relation to the mediolateral and anteroposterior dimensions of the distal femur was calculated as a ratio. The average calculated ratios were anteroposterior, 0.53 offset medially; lateral, 0.32 offset anterior. Mathematical models were constructed to quantify the potential varus valgus and flexion extension error of the guide rods. Variables investigated were entry point location, guide rod diameter, guide rod length, and rotation. The surgeon must be cognizant of these potential sources of error to maximize the accuracy of the femoral intramedullary jigging system.

Arthroplasty, Replacement, Knee↗
PubMed2001

Temperature dependence of polymer-gel dosimeter nuclear magnetic resonance response.

The purpose of this study was to find a physical-mathematical description capable to correct a polymer-gel dosimeter relaxation rate R2-dose response for different temperatures. Four different modifications of polymer-gel dosimeters were used in this study. Samples with polymer-gel dosimeter in glass test vessels were homogeneously irradiated by 60Co gamma photons. A multi-echo sequence with 16 equidistant echoes was used for evaluation of irradiated polymer-gel dosimeters. The sequence parameters were as follows: TR 2000 ms, TE 22.5-360.0 ms, slice thickness 5 mm, FOV 255 mm, one acquisition. The proposed description recommends to subtract R2 response of the nonirradiated dosimeter from the total R2-dose response. The relaxation rate for the irradiated dosimeter can be expressed as a function of temperature and dose. The temperature dependence has an exponential behavior in the measured range. The proposed description allows to correct the measured NMR R2-dose responses for different temperatures.

Dose-Response Relationship, Radiation↗
PubMed2001

Energy and dose rate dependence of BANG-2 polymer-gel dosimeter.

The purpose of this study was to evaluate dependence of BANG-2 polymer-gel dosimeter sensitivity on different photon and electron energies as well as on different mean dose rates expressed as repetition rates for a standard clinically used linear accelerator. The sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modality. A calibration curve (in the linear region) based on five dosimeters (four irradiated and one background) was obtained for each photon and electron energy and different repetition rates. Dosimeter sensitivity dependence on energy was studied for 4, 6, and 18 MV x-ray photons and for nominal electron energies 9, 12, 16, and 20 MeV. Dosimeter sensitivity dependence on mean dose rate was separately studied for electron and photon beams with the use of repetition rates 80, 160, 240, 320, and 400 MU min(-1). Evaluation of dosimeters was performed on Siemens MAGNETOM EXPERT 1T scanner in the head coil. A multiecho sequence with 16 equidistant echoes was used for the evaluation of irradiated polymer-gel dosimeters. The parameters of the sequence were as follows: TR 2000 ms, TE 22.5-360.0 ms, slice thickness 5 mm, FOV 255 mm, one acquisition. There was observed a trend in polymer-gel dosimeter sensitivity dependence on the quality index of high energy x-ray beams used and on mean electron energy absorbed in the center of the dosimeter. Polymer-gel dosimeter sensitivity was decreasing with increasing photon or electron energy. There was observed no trend in polymer-gel dosimeter sensitivity dependence on mean dose rate expressed as a repetition rate for both photon and electron beams.

Calibration↗
PubMed2001

Antibiotic use and development of resistance in blood culture isolates: 8 years of experience from a cancer referral center.

The consumption of antimicrobial agents in a Slovakian national cancer institute from 1989-1996 was compared with resistance rates in clinically significant blood culture isolates. We observed an increase in resistance of viridans streptococci to penicillin and of enterococci to ampicillin. Resistance to vancomycin and teicoplanin was stable over the entire period despite a 20-fold increase in vancomycin consumption. Nor did we observe increased resistance to ofloxacin despite a 10-fold increase in consumption. Consumption of aminoglycosides and resistance levels were both stable. A different situation was observed with third-generation cephalosporins, where resistance of Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter spp. to ceftazidime and cefotaxime increased with increasing consumption. Resistance of Enterobacteriaceae to cefotaxime and ceftazidime was stable. Resistance to imipenem did not change significantly. However, the number of Stenotrophomonas maltophilia bacteremias increased significantly after imipenem was introduced in 1991. Because of improved outcome in bacteremia, an increased incidence of both gram-negative and gram-positive bacteremia led to only a slight increase in associated mortality.

Anti-Bacterial Agents↗