Search PubMed⌕ Search

Biomedical subjects

Z Lewandowski

Publications and source records attributed to Z Lewandowski.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of biofilm image thresholding methods.

To evaluate biomass distribution in heterogeneous biofilms from their microscope images, it is often necessary to perform image thresholding by converting the gray-scale images to binary images consisting of a foreground of biomass material and a background of interstitial space. The selection of the gray-scale intensity used for thresholding is arbitrary but under the control of the operator, which may produce unacceptable levels of variability among operators. The quality of numerical information extracted from the images is diminished by such variability, and it is desirable to find a method that improves the reproducibility of thresholding operations. Automatic methods of thresholding provide this reproducibility, but often at the expense of accuracy, as they consistently set thresholds that differ significantly from what human operators would choose. The performance of five automatic image thresholding algorithms was tested in this study: (1) local entropy; (2) joint entropy; (3) relative entropy; (4) Renyi's entropy; and (5) iterative selection. Only the iterative selection method was satisfactory in that it was consistently setting the threshold level near that set manually. The extraction of feature information from biofilm images benefits from automatic thresholding and can be extended to other fields, such as medical imaging.

Algorithms↗
PubMed2001

Growing reproducible biofilms with respect to structure and viable cell counts.

We have developed a new method of growing 4-day-old biofilms that are reproducible, with respect to viable cell number and biofilm structure. To demonstrate the utility of the method, we grew biofilms composed of Pseudomonas aeruginosa (ATCC#700829), P. fluorescens (ATCC#700830) and Klebsiella pneumoniae (ATCC#700831), 18 times in flat-plate reactors under well-defined conditions of: flow rate, nutrient concentration, temperature, inoculum and growth rate. The resulting 4-day-old biofilms were approximately 200-300 microm thick and exhibited a high degree of reproducibility. The number of viable cells that accumulated per unit surface area and the biofilm areal porosity were reproduced within 10% error. We have also quantified other parameters characterizing biofilm structure using biofilm-imaging techniques: fractal dimension, textural entropy and diffusion distance as auxiliary parameters characterizing the reproducibility of biofilm accumulation. As a result of analysis, we have introduced a new parameter to better quantify and characterize the number of viable cells in biofilms, "specific number of viable cells" (SNVC). This parameter is the viable cell number normalized with respect to the surface area covered by the biofilm and with respect to the biomass of the biofilm. This new descriptor represents the dynamics of biofilm accumulation better than the traditionally used colony-forming unit (CFU) per surface area covered by the biofilm because it accounts not only for the surface coverage but also for the biofilm thickness.

Bacteriological Techniques↗
PubMed2001

The future of chronic diseases.

Major chronic diseases continue to be the main health scourge of the most developed countries, have only recently been retreating in frequency in the fledgling market economies, and are becoming dominant in many populous areas of the developing world. The descriptive evidence from the developments of the near past strongly suggests that much of the control outcomes have already been achieved with the existent imperfect causative knowledge. The continuation of desirable trends in major chronic diseases in some places like Central & Eastern Europe, is uncertain within the intermediate time range without gaining more etiological clues, among which the role of medical care is worthy of reconsideration. Other factors can grow in importance, like obesity, which may be freed from the suppressive influence of cigarette smoking to trigger major mass pathologies, like type 2 diabetes mellitus, arterial hypertension, some cancers etc. The role of social underpriviledge seems recalcitrant, although the part played by social share of biological risk agents may diminish in response to educational persuasion. The remotest destinies of some chronic diseases may depend on the mixture of external and genetic influences ending as predispositions towards some ailments, antecedents of which might have protected their carriers from dangers of the past unfriendly environment, like obesity (or diabetes) against famine, or hypertension against inefficient defense reaction. The resulting medium-range prediction of well-being for inhabitants of more developed world may not be forbidding, since increasing life expectancy needs not be synonymous with disability, and attaining old age does not require excessive sacrifice, beyond reducing number smoked, or preserving decent respiratory volumes.

Chronic Disease↗
PubMed2001

[Granulosa cell tumor--the assessment of some clinical and therapeutic parameters as prognostic factors].

The results of the clinical and therapeutic factors in prognostic mean was presented. 48 cases of granulosa cell tumours treated from 1984 to 1994 in Oncology Centre in Warsaw were analysed. In investigated group 13 patients died, but only 8 because of relapse of the tumour. Among all analysed patients, 79% have reached 5 years free survival period. Tumour rupture, FIGO stage and incidence of irregular bleeding before recognition of the tumour had significant prognostic value. There were surprising that relative risk of relapse between patients stage I and II were similar (1.0 vs 1.01). The relative risk between I and III stage had strong prognostic difference. Additional operation after no radical surgery did not influence on better prognosis, but followed radiotherapy increase treatment results.

Adult↗
PubMed2000

Quantifying biofilm structure using image analysis.

We have developed and implemented methods of extracting morphological features from images of biofilms in order to quantify the characteristics of the inherent heterogeneity. This is a first step towards quantifying the relationship between biofilm heterogeneity and the underlying processes, such as mass-transport dynamics, substrate concentrations, and species variations. We have examined two categories of features, areal, which quantify the relative magnitude of the heterogeneity and textural, which quantify the microscale structure of the heterogeneous elements. The feature set is not exhaustive and has been restricted to two-dimensional images to this point. Included in this paper are the methods used to extract the structural information and the algorithms used to quantify the data. The features discussed are porosity, fractal dimension, diffusional length, angular second moment, inverse difference moment and textural entropy. We have found that some features are better predictors of biofilm behavior than others and we discuss possible future directions for research in this area.

Biofilms↗
PubMed2000

Effect of catalase on hydrogen peroxide penetration into Pseudomonas aeruginosa biofilms.

The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosa strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the katA gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.

Biofilms↗
PubMed2000

[Mortality from cardiovascular diseases in patients with type 2 diabetes].

In the period 1973/74-1995 a prospective observation was carried out on 4420 diabetic patients (1990 males and 2430 females) aged 30-68 years, with type 2 (non-insulin dependent diabetes) of 1-10 years duration. During the 22-year period nearly 80% of the initial cohort died. The risk of death was 2-times higher in diabetes than in the samples of general population observed at the same time. The death risk from cardiovascular diseases was over 3.0 times higher than in general population. The relevant risk ratio was found over 5-times higher for coronary heart disease, which was unlike to result from the differences in death ascertainment between diabetics and the city dwellers. The all-causes ratio of death and cardiovascular diseases was the same for women and men but it was selectively higher for females than males group for coronary heart disease and cerebrovascular diseases, and for males 50% higher for atherosclerosis and other heart diseases. The highest cumulation of risk factors was observed for deaths from cardiovascular diseases, and coronary heart disease. There were risk factors typical for cardiovascular disease and typical for poor metabolic control of diabetes (hyperglycaemia, glucosuria) and presence of complications of diabetes (nephropathy).

Adult↗
PubMed1999

Structural deformation of bacterial biofilms caused by short-term fluctuations in fluid shear: an in situ investigation of biofilm rheology.

The physical properties (rheology) of biofilms will determine the shape and mechanical stability of the biofilm structure and consequently affect both mass transfer and detachment processes. Biofilm viscoelasticity is also thought to increase fluid energy losses in pipelines. Yet there is very little information on the rheology of intact biofilms. This is due in part to the difficulty in using conventional testing techniques. The size and nature of biofilms makes them difficult to handle, while removal from a surface destroys the integrity of the sample. We have developed a method which allowed us to conduct simple stress-strain and creep experiments on mixed and pure culture biofilms in situ by observing the structural deformations caused by changes in hydrodynamic shear stress (tau(w)). The biofilms were grown under turbulent pipe flow (flow velocity (u) = 1 m/s, Reynolds number (Re) = 3600, tau(w) = 5. 09 N/m(2)) for between 12 and 23 days. The resulting biofilms were heterogeneous and consisted of filamentous streamers that were readily deformed by changes in tau(w). At tau(w) of 10.11 N/m(2) the streamers were flattened so that the thickness was reduced by 25%. We estimated that the shear modulus (G) of the mixed culture biofilm was 27 N/m(2) and the apparent elastic modulus (E(app)) of both biofilms was in the range of 17 to 40 N/m(2). The biofilms behaved like elastic and viscoelastic solids below the tau(w) at which they were grown but behaved like viscoelastic fluids at elevated tau(w). The implications of these results for fluid energy losses and the processes of mass transfer and detachment are discussed.

Bacteria↗
PubMed1999

The formation of migratory ripples in a mixed species bacterial biofilm growing in turbulent flow.

Mixed-species biofilms, consisting of Klebsiella pneumoniae, Pseudomonas aeruginosa, Pseudomonas fluorescens and Stenotrophomonas maltophilia, were grown in glass flow cells under either laminar or turbulent flow. The biofilms grown in laminar flow consisted of roughly circular-shaped microcolonies separated by water channels. In contrast, biofilm microcolonies grown in turbulent flow were elongated in the downstream direction, forming filamentous 'streamers'. Moreover, biofilms growing in turbulent flow developed extensive patches of ripple-like structures between 9 and 13 days of growth. Using time-lapse microscopic imaging, we discovered that the biofilm ripples migrated downstream. The morphology and the migration velocity of the ripples varied with short-term changes in the bulk liquid flow velocity. The ripples had a maximum migration velocity of 800 micromh(-1) (2.2 x 10(-7) m s(-1)) when the liquid flow velocity was 0.5 ms(-1) (Reynolds number=1,800). This work challenges the commonly held assumption that biofilm structures remain at the same location on a surface until they eventually detach.

Biofilms↗
PubMed1999

[Should sinus rhythm be restored in patients with chronic atrial fibrillation? Preliminary results from the Polish "Hot Cafe" study].

Atrial fibrillation (AF) is the most common arrhythmia occurring in clinical practice. It is the most frequent cause of hospitalization in cardiac rhythm disturbance. Despite comprehensive progress in the research into electrophysiological mechanisms leading to this loss of normal rhythm and new procedures dealing with it, the main problem being the conversion to and maintaining the normal sinus rhythm (SR) has not been solved. The polish study "Hot Cafe" is trying to evaluate the advantages and risks of the two procedures widely used in clinical practice in patients (pts) with chronic AF, i.e. conversion and maintaining SR vs leaving pts with the arrhythmia. Pts with non-valvular chronic AF fulfilling the criteria for including them into the sample are randomly assigned to two procedures: conversion to SR by means of direct current cardioversion and maintaining it or leaving pts with AF. Pts left with AF are treated by rate control and antithrombotic treatment. The project is of prospective kind and it will be carried out by many medical institutions. It is planned to include 200 pts. The observation period will last at least 12 months. Preliminary results after inclusion of the first 121 pts are shown.

Aged↗
PubMed1998

Microelectrode measurements of local mass transport rates in heterogeneous biofilms.

Microelectrodes were used to measure oxygen profiles and local mass transfer coefficient profiles in biofilm clusters and interstitial voids. Both profiles were measured at the same location in the biofilm. From the oxygen profile, the effective diffusive boundary layer thickness (DBL) was determined. The local mass transfer coefficient profiles provided information about the nature of mass transport near and within the biofilm. All profiles were measured at three different average flow velocities, 0.62, 1.53, and 2.60 cm sec-1, to determine the influence of flow velocity on mass transport. Convective mass transport was active near the biofilm/liquid interface and in the upper layers of the biofilm, independent of biofilm thickness and flow velocity. The DBL varied strongly between locations for the same flow velocities. Oxygen and local mass transfer coefficient profiles collected through a 70 micrometer thick cluster revealed that a cluster of that thickness did not present any significant mass transport resistance. In a 350 micrometer thick biofilm cluster, however, the local mass transfer coefficient decreased gradually to very low values near the substratum. This was hypothetically attributed to the decreasing effective diffusivity in deeper layers of biofilms. Interstitial voids between clusters did not seem to influence the local mass transfer coefficients significantly for flow velocities of 1.53 and 2.60 cm sec-1. At a flow velocity of 0.62 cm sec-1, interstitial voids visibly decreased the local mass transfer coefficient near the bottom.

Biofilms↗
PubMed1998

Resistance of biofilms to the catalase inhibitor 3-amino-1,2, 4-triazole.

Consortia of catalase positive bacteria consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae, in both the planktonic form and as biofilms, disproportionate hydrogen peroxide into oxygen and water. The biofilm, however, continued to disproportionate the hydrogen peroxide in the presence of the catalase inhibitor, 3-amino-1,2,4-triazole, while the planktonic organisms did not. While the bacterial catalase-peroxidase-dismutase system was probably responsible for the disproportionation of hydrogen peroxide in both cases, biofilms resisted inhibition of this enzyme system.

Amitrole↗
PubMed1998

Oscillation characteristics of biofilm streamers in turbulent flowing water as related to drag and pressure drop.

Mixed population biofilms consisting of Pseudomonas aeruginosa, P. fluorescens, and Klebsiella pneumoniae were grown in a flow cell under turbulent conditions with a water flow velocity of 18 cm/s (Reynolds number, Re, =1192). After 7 days the biofilms were patchy and consisted of cell clusters and streamers (filamentous structures attached to the downstream edge of the clusters) separated by interstitial channels. The cell clusters ranged in size from 25 to 750 microm in diameter. The largest clusters were approximately 85 microm thick. The streamers, which were up to 3 mm long, oscillated laterally in the flow. The motion of the streamers was recorded at various flow velocities up to 50.5 cm/s (Re 3351) using confocal scanning laser microscopy. The resulting time traces were evaluated by image analysis and fast Fourier transform analysis (FFT). The amplitude of the motion increased with flow velocity in a sigmoidal shaped curve, reaching a plateau at an average fluid flow velocity of approximately 25 cm/s (Re 1656). The motion of the streamers was possibly limited by the flexibility of the biofilm material. FFT indicated that the frequency of oscillation was directly proportional to the average flow velocity (u(ave)) below 9.5 cm/s (Re 629). At u(ave) greater than 9.5 cm/s, oscillation frequencies were above our measurable frequency range (0.12-6.7 Hz). The oscillation frequency was related to the flow velocity by the Strouhal relationship, suggesting that the oscillations were possibly caused by vortex shedding from the upstream biofilm clusters. A loss coefficient (k) was used to assess the influence of biofilm accumulation on pressure drop. The k across the flow cell colonized with biofilm was 2.2 times greater than the k across a clean flow cell.

Biofilms↗
PubMed1998

Electrochemical concepts and techniques in the study of stainless steel ennoblement.

Electrochemical theory and technique used to investigate microbially influenced corrosion is discussed with a focus on methods used to demonstrate the manganic-oxide mechanism of stainless steel Ennoblement. The concept of mixed potential and its relationship to the current-voltage behavior of stainless steel is developed. This concept is used to interpret microbially induced changes in corrosion potential, polarization behavior, surface-oxide abundance, and the redox environment at submerged metal surfaces. Microelectrode, capacitance, and coulometric methods are described that can be used to discriminate electrochemical effects caused by changes in solution properties from those caused by mineral deposition at the metal surface. The variety of electrochemical, wet-chemical, microbiological, and surface analytical techniques used to demonstrate the effect of biomineralized manganese dioxide on the electrochemical behavior of stainless steel are summarized.

Biodegradation, Environmental↗
PubMed1998

[Mortality of diabetic patients in Warsaw--22 year prospective observation (1973/74-1995). I. Mortality of diabetic patients with type 2 diabetes (non-insulin-dependent-diabetes)].

In the period 1973/74-1995 a prospective observation was carried out on 4420 diabetic patients (1990 males and 2430 females) aged 30-68 years, with type 2 (non-insulin dependent diabetes) of 1-10 years duration. During the 22-years period nearly 80% of initial cohort died. The risk of death were 2-times higher in diabetes than in the samples of general population observed at the same time. The death risk from cardiovascular disease were over 3-times higher than in general population. The relevant risk ratio has been found over 5-times higher for coronary heart disease, which were unlike to results from the differences in death ascertainment between diabetics and the city dwellers. The all-causes ratio of death and cardiovascular diseases were the same for women and men but it was selectively higher for females then males group for coronary heart disease and cerebrovascular diseases. Among diabetic cohort the risk of death was also higher for neoplasms, especially in women.

Adult↗
PubMed1998

[Mortality of diabetic patients in Warsaw--22 year prospective observation (1973/74-1995). II. Mortality of patients with type I diabetes (insulin-dependent-diabetes)].

During the follow-up 1973/74-1995 years 171 subjects with type 1 (insulin dependent diabetes) (105 males and 66 females) aged 18-30 years died 31.6% (32.4% males and 30.3% females). The relative risk of mortality for all causes in the compared to the general population was 5.0 (3.5 for men and 7.5 for women). Almost 30% deaths were from renal disease, 17% from ischemic heart disease, and 3 death in women from carcinoma of breast.

Adult↗