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Biomedical subjects

J Gregor

Publications and source records attributed to J Gregor.

At least 19 recordsLinked to original sources
PubMed2006

Three-dimensional focus of attention for iterative cone-beam micro-CT reconstruction.

Three-dimensional iterative reconstruction of high-resolution, circular orbit cone-beam x-ray CT data is often considered impractical due to the demand for vast amounts of computer cycles and associated memory. In this paper, we show that the computational burden can be reduced by limiting the reconstruction to a small, well-defined portion of the image volume. We first discuss using the support region defined by the set of voxels covered by all of the projection views. We then present a data-driven preprocessing technique called focus of attention that heuristically separates both image and projection data into object and background before reconstruction, thereby further reducing the reconstruction region of interest. We present experimental results for both methods based on mouse data and a parallelized implementation of the SIRT algorithm. The computational savings associated with the support region are substantial. However, the results for focus of attention are even more impressive in that only about one quarter of the computer cycles and memory are needed compared with reconstruction of the entire image volume. The image quality is not compromised by either method.

Algorithms↗
PubMed2005

[Sleep and normality: usefulness for the practitioner].

About fifty percent of patients consulting their primary care physician complain of sleep disorders. Clinicians have to distinguish normal from abnormal sleep. For example, sleep normality is usually characterised by an apnea/hypopnea index < 5 h(-1) in absence of sleep symptoms. However such an index varies in relation with age, gender, body mass index, measurements methods In daily clinical practice, clinicians should look for sleep symptoms to define an abnormal sleep. More studies are needed to better define which patient will really benefit from a specific sleep therapy.

Adolescent↗
PubMed2005

Comparative study of Dutch and German emergency-management models for near border nuclear accidents.

Four institutes, all of which are involved in nuclear-emergency management in the Dutch-German border region, have compared their short-range dispersion and radiological dose models using scenarios consisting of single-station meteorology and two dispersed radionuclides. After adjustment of some of the parameters, the consequence of the differences in parameters on the effective dose was quantified at several stages from source to exposure. Results for the neutral stability class agreed within a factor of four. Variations in wet deposition of radioactive material, giving rise to external radiation from the ground, can cause significant variations to the effective dose. Furthermore, the way the different emergency-management tools model the atmospheric dispersion for a stable stability class in the horizontal plane can generate large differences. Finally, the methodology of calculating cloudshine is not comparable among the models, which causes the effective dose near the source to show large deviations for high emission sources.

Accidents↗
PubMed2005

[Contemporary view on the plasma natriuretic peptide assessment in the clinical practice].

Plasma natriuretic peptide assessment became a part of the routine clinical practice because of the laboratory methods development. After a brief historical overview of natriuretic peptides discovery, the article focuses on the brain natriuretic peptide (BNP). BNP plays an important role in the pathophysiology of many diseases of cardiovascular system due to its effects on the circulation (natriuresis, diuresis, inhibition of renin-angiotensin system, etc). The authors describe process of BNP synthesis, factors leading to its release into circulation. The main emphasis is done on the clinical significance of BNP and NT-proBNP assessment for the-diagnosis in cardiovascular diseases, risk stratification and monitoring of the treatment.

Biomarkers↗
PubMed2005

[Ischemia-modified albumin: new marker of myocardial ischemia?].

The Albumin Cobalt Binding Test is a quantitative in vitro diagnostic test used on human serum that detects ischemia-modified albumin by measuring the cobalt binding capacity of albumin in human serum. Ischemia modified albumin is intended for use in conjunction with ECG and cardiac troponin as an aid to short term risk stratification of patients presenting with chest pain suggestive of cardiac origin. Thus, in patients with chest pain or equivalent symptoms suggestive of cardiac origin, with non-diagnostic ECG and normal troponin, a negative IMA can be used as an aid to rule out acute coronary syndrome (ACS) in low risk patients.

Biomarkers↗
PubMed2005

[Acetylsalicylic acid (ASA) resistance in patients with ischemic heart disease (IHD) as bioindicator of the treatment strategy].

BACKGROUND: The interest in aspirin resistance has been increasing during the last few years, with researchers earnestly pursuing alternative anti-platelet therapies and devices for measuring platelet aggregation. The recent studies suggest that 5-45% of patients taking aspirin do not experience adequate anti-platelet effects. METHODS AND RESULTS: There is scant evidence proving that aspirin resistance has some clinical consequences. To assess the prevalence of aspirin resistance in patients with ischemic heart disease (IHD) two independent methods were used: platelet aggregation in platelet rich plasma (PRP) after induction by propylgallate (CPG), and assessment of platelet function by PFA 100 method. The study population consisted of 424 patients treated for IHD on the 2nd Dept. of Medicine, Teaching Hospital, Hradec Kralove. The age, gender, diagnosis and effect of therapy were characterized in this group of the patients. Daily ASA dose was 100 mg. We used two methods to monitor ASA treatment efficacy: a) thrombocyte aggregation after induction by CPG, b) the assessment of platelet function by PFA 100 method. a) Of the patients studied by CPG platelet aggregation, 51 (12.1%) pts were resistant to ASA dose 100 mg/day, and 32 (7.6%) pts remained resistant even after increasig the dose to 200 mg/day. In 80 (20%) pts, the daily ASA dose of less than 100 mg was sufficient to inhibit platelet function. b) Although the PFA-100 system is not able to detect the difference between low and high ASA dose, we found 53 (15.2%) patients aspirin resistant using this method. CONCLUSIONS: In the patients with IHD treated with 100 mg of ASA per day, our study has shown that the prevalence of aspirin resistance was 12.1% using CPG method, and 15.2% using PFA-100 method. Aspirin resistance was dose dependent. Prevalence of ASA resistance in patients treated with 200 mg of ASA per day was only 7.6% using the CPG method.

Adolescent↗
PubMed2004

Simulation of emission tomography using grid middleware for distributed computing.

SimSET is Monte Carlo simulation software for emission tomography. This paper describes a simple but effective scheme for parallel execution of SimSET using NetSolve, a client-server system for distributed computation. NetSolve (version 1.4.1) is "grid middleware" which enables a user (the client) to run specific computations remotely and simultaneously on a grid of networked computers (the servers). Since the servers do not have to be identical machines, computation may take place in a heterogeneous environment. To take advantage of diversity in machines and their workloads, a client-side scheduler was implemented for the Monte Carlo simulation. The scheduler partitions the total decay events by taking into account the inherent compute-speeds and recent average workloads, i.e., the scheduler assigns more decay events to processors expected to give faster service and fewer decay events to those expected to give slower service. When compute-speeds and sustained workloads are taken into account, the speed-up is essentially linear in the number of equivalent "maximum-service" processors. One modification in the SimSET code (version 2.6.2.3) was made to ensure that the total number of decay events specified by the user is maintained in the distributed simulation. No other modifications in the standard SimSET code were made. Each processor runs complete SimSET code for its assignment of decay events, independently of others running simultaneously. Empirical results are reported for simulation of a clinical-quality lung perfusion study.

Computer Communication Networks↗
PubMed2004

Freshwater phytoplankton quantification by chlorophyll a: a comparative study of in vitro, in vivo and in situ methods.

Standard ISO method for chlorophyll a quantification (extraction into ethanol, spectrophotometrical quantification at 665 and 750 nm), spectrofluorometry (reader for 96 wells, excitation 410 nm, emission 670 nm), and a submersible fluorescence probe for in situ phytoplankton quantification (excitation 410, 525, 570, 590, and 610 nm, emission 685 nm) were compared in different freshwater environments-reservoirs and rivers. The ISO method is accepted as a standard method but requires sample handling and transport to the laboratory. Spectrofluorometry is a sensitive method, even for natural phytoplankton populations. Nevertheless, it cannot be recommended for the quantification of cyanobacterial water blooms because colonial and filamentous species such as Microcystis, Anabaena, or Aphanizomenon display unacceptable variability (18-33%). The submersible probe featured high correlation with a standard ISO method (r=0.97, P<0.05). This probe can provide the selective measurement of technologically important phytoplankton groups like cyanobacteria, diatoms, green algae, and cryptophytes in lake vertical profiles of up to 100 m. The limitation of this instrument is the possible reabsorption of the light signal, e.g. in the presence of humic substances, or dense algal blooms. The use of submersible probes for in situ phytoplankton quantification can be recommended as a sensitive tool for water management, especially in the case of drinking water resources.

Chlorophyll↗
PubMed2004

[Syncope in ventricular tachycardia as a first clinical sign of patent ductus arteriosus in an adulthood].

The case-report describes a 48-year-old-female patient with the patent ductus arteriosus with the following structural changes leading to the malignant arrhythmias manifested as a syncope. The patient was treated by Amplatzer occluder and the implantation of the cardioverter-defibrillator. The authors discuss the patent ductus arteriosus, arrhythmias and sudden cardiac death in the patients with the congenital heart disease in an adulthood.

Ductus Arteriosus, Patent↗
PubMed2001

Genome sequence of enterohaemorrhagic Escherichia coli O157:H7.

The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.

Base Sequence↗
PubMed2001

Influence of the replacement of the oxo function with the thioxo group on the antimycobacterial activity of 3-aryl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones.

Series of 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithiones, 3-arylquinazoline-2,4(1H,3H)-diones and 3-arylquinazoline-2,4(1H,3H)-dithiones were synthesized, and the antimycobacterial activities of the derivatives evaluated in vitro. The compounds were active against Mycobacterium tuberculosis and conditionally pathogenic mycobacteria (Mycobacterium kansasii and Mycobacterium avium). The replacement of oxygen by sulfur in 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2.4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones gave rise to an increase of antimycobacterial activity. The most active compound was 3-(3-chlorophenyl)-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithione.

Antitubercular Agents↗
PubMed2001

Arsenic removal during conventional aluminium-based drinking-water treatment.

The changing forms and concentrations of arsenic through aluminium-based coagulation treatment processes were tracked for three drinking-water treatment plants. This has provided direct evidence of where and how arsenic is removed. In general, soluble As(V) is converted to particulate As(V) by adsorption during rapid mixing, and is removed along with naturally occurring particulate arsenic predominantly by clarification. Soluble As(III) tracks through the treatment processes and is converted to soluble As(V) during final chlorination. The ability of a water treatment process to achieve the maximum acceptable concentration for arsenic in drinking water is dependent on the concentration of As(III) in the source water.

Aluminum↗
PubMed2001

[Using ultrasound imaging in implantation].

Sonography represents one of the best methods of clinical investigation which might give information about the preimplantation prognosis by evaluation of the following parameters:--morphological parameters (with bidimensional sonography): thickness and structure of the endometrium;--functional parameters (with doppler): evaluation of uterine vascularisation. The prognostic value of the morphological parameters appears to be controversial:--thickness of endometrium: a linear correlation between endometrial thickness and implantationsuccess may not exist. However no pregnancy occurs without a minimum threshold value of 6 to 8 mm endometrial thickness;--structure of the endometrium: concerning the role of the endometrial structure, controversial studies are available. According to some authors, endometrial hyperechogenicity is incompatible with a pregnancy. However hypoechogenic endometrium with 5 well delimited layers is an excellent prognostic factor. The coloured pulsed Doppler allows a functional assessment of the uterus and represents a technical progress in sonography investigations since the early nineties. The evaluation of uterine vascularisation can take place at different levels of the uterine vessels.--The pregnancy rate is inversely proportional to the uterine pulsatility index (PI). There is a consensus concerning a threshold value of PI. With values above 3, the pregnancy rate drops significantly.--The presence of a protodiastolic notch and the absence of end diastolic blood flow have bad prognosis. The presence or not of a sub-endometrialen vascular flow may be the most important prognostic parameter. No pregnancy may occur by absence of these flows. The sonography gives not only important morphological informations about endometrium but also allows a study of the uterine vascularisation by coloured doppler. This allows a real assessment of endometrial potentials for implantation. Optimal conditions of implantation could be:--endometrium > 7 mm,--hypoechogenic endometrium with 5 well delimited layers,--uterine PI < 3,--presence of sub-endometrial vascular flow.

Embryo Implantation↗
PubMed2001

[Opinions and attitudes of patients visiting pharmacies].

The paper is devoted to the problems concerning the opinions and attitudes of customers of pharmacies, i.e. their opinions on and attitudes to the question of information needs and satisfaction with information and services provided in pharmacies in the Czech Republic. The article presents the results of a questionnaire survey answering the following questions: why the respondents come to pharmacies and what the reason of the present visit is, whom they prefer as the dispenser of the drug and why, how often they went to a pharmacy in the recent period, from where they get information concerning drugs, whether it is advantageous for them to obtain information in a pharmacy and what information they received during the present visit, who provided the information or advice, how many pieces of information they got and how they are satisfied with them, whether they required information in a pharmacy, or whether they came to a pharmacy for this purpose, why the respondents have purposefully selected a particular pharmacy, whether they take drugs daily and which ones, what their opinion on the amount the supplementary payment is, what OTC drugs they buy, what drugs they prefer, whether they concentrate on a certain preparation, or possibly which one, what is their opinion about the scale of the assortment of OTC drugs, whether they use homeopathic medicines, and what they miss in pharmacies.

Adult↗
PubMed2001

[Antimicrobial salicylanilides and 3-phenyl-2H-1,3-benzoxazine-2,4(3H)-diones].

Salicylanilides and 3-phenyl-2H-1,3-benzoxazine-2,4(3H)-diones are strong antimycobacterial substances which can be considered to be potential antituberculotics. In order to be able to verify the prognostics of the relationships between the structure and antimycobacterial activity, the series of previously evaluated substances was extended to include 4'-ethoxycarbonylsalicylanilide, 4'-trifluoromethylsalicylanilide, 4'-cyanidosalicylanilide, 4'-thiocarbamoylsalicylanilide, 3-(4-ethoxycarbonylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dione, 3-(4-trifluoromethylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dione, and 3-(4-cyanidophenyl)-2H-1,3-benzoxazine-2,4-(3H)-dione. The substances were evaluated against Mycobacterium tuberculosis, M. kansasii, and M. avium. In harmony with the previous study (see ref. 1), antimycobacterial activity increased with increasing lipophilicity and electron-acceptor properties of substituents. As the values of regression coefficients were not substantially changed after the complementation of the group, the present authors consider the problem under study to be solved.

Anti-Bacterial Agents↗
PubMed2001

[Recurrent pneumothorax in a child with Langerhans' cell histiocytosis].

We are presenting a 16 months old boy, who has been previously developing normally, physically very active, and who suddenly developed right-sided pneumothorax with infiltrations in both lungs, initially defined as inflammatory. After placing suction drainage of the pleural cavity and antibiotic administration the child's condition improved quickly. The infiltration changes still remained in lungs arousing a suspicion of fibrocystic changes. During an attempt at changing the drainage into a water one, the symptoms of pneumothorax with hypertension increased again. A minithoracotomy with an edge resection of segment 4 and pleurectomy were performed, relating to the histopathological test of the sample, Largenhans' cell histiocytosis was diagnosed. The symptoms of diabetes insipidus appeared. The treatment according to the program DAL-HX83/90 modified by the Polish Group for Leukaemia and Malignant Lymphoma was introduced. During the treatment inducing remission a pneumothorax occurred two more times.

Histiocytosis, Langerhans-Cell↗
PubMed2001

The effect of trimetazidine on C-reactive protein, cytokines and adhesion molecules in the course of acute myocardial infarction.

The aim of this randomised, double-blind, placebo controlled, parallel group study was to assess the effect of trimetazidine (TMZ), a potent antiischaemic drug, on plasma C-reactive protein (C-RP), cytokine and adhesion molecule levels. The study population consists of 18 patients (16 males, 2 females, average age 56.45 +/- 10.97 years) with acute myocardial infarction admitted within 6 hours after onset of symptoms and treated with streptokinase. Blood samples were taken at 3-hour intervals during the time of treatment. All patients were randomised blindly using a centralised randomisation process, between trimetazidine (40 mg bolus i.v. then 60 mg per day for 48 hours intravenously in glucose infusion) or placebo group. Plasma C-RP level was significantly lower in TMZ group (39.5 mg/ml +/- 9.7 mg/ml) as compared to placebo (75.7 +/- 29.4 mg/ml, p < or = 0.001) and peaked 28 hours later in TMZ group. Plasma interleukin 6 (IL 6) level showed a sharp peak 9 hours after the onset of the symptoms in TMZ group (116.9 +/- 180.2 pg/ml vs. 45.4 +/- 37.9 pg/ml) and was increased up to 30 hours after the onset of the symptoms. Plasma interleukin 1 beta (IL 1 beta) was also higher in TMZ group notably 21 hours after the onset of symptoms (26.4 +/- 9.3 pg/ml vs. 16.2 +/- 2.4 pg/ml). TMZ group showed lower plasma E-selectin levels. Plasma IL 8, TNF alpha and ICAM 1 levels were without statistical significant differences. The present study demonstrates a significant reduction of plasma C-reactive protein level in the course of acute myocardial infarction treated with streptokinase and intravenous trimetazidine infusion compared with the group of patients without trimetazidine treatment.

C-Reactive Protein↗