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Biomedical subjects

J Hübner

Publications and source records attributed to J Hübner.

At least 19 recordsLinked to original sources
PubMed2005

Ultrafast deflection of spatial solitons in AlxGa(1-x)As slab waveguides.

We demonstrate ultrafast all-optical deflection of spatial solitons in an AlxGa(1-x)As slab waveguide, using 190 fs, 1550 nm pulses to generate and deflect the spatial soliton. The steering beam is focused onto the top of the waveguide near the soliton pathway, and the soliton is steered by refractive-index changes induced by optical Kerr, or free-carrier (Drude), effects. Angular deflections up to 8 mrad are observed.

Journal Article↗
PubMed2003

Design and evaluation of novel blood incubation systems for in vitro hemocompatibility assessment of planar solid surfaces.

Success in the development of hemocompatible biomaterials depends on adequate equipment and procedures for standardized analysis of blood-materials interactions in vitro. In view of the limited standard of knowledge on that important aspect, two novel incubation systems were designed, built, and evaluated for the in vitro assessment of the hemocompatibility of planar solid surfaces: A screening setup was introduced for the comparison of up to 12 different samples. A perfusion setup was developed to model the directed blood flow in the vascular system during incubation by a recirculation circuit, allowing the variation of the wall shear rate at the sample surface. The incubation procedures utilized freshly drawn, heparinized whole human blood. Hemocompatibility in terms of selected aspects of coagulation, thrombogenicity, and immune responses was quantified through plasma levels of characteristic molecules (immunoassays), cell counting, and analysis of adherent cells and fibrin formation (scanning electron microscopy), respectively. Prevention of blood-air contact and mechanical stress, constant temperature and blood pH during incubation, and the suitable choice of reference materials were found to be crucial for reliable testing. Considering those requirements, screening and perfusion system both provided sensitive discrimination between a given set of planar solid surfaces. In conclusion, the suggested methods for an in vitro hemocompatibility assessment permit versatile, sensitive, and efficient analysis of important blood-material interactions despite the unavoidable variability of blood characteristics in different experiments.

Biocompatible Materials↗
PubMed2003

Direct observation of optically injected spin-polarized currents in semiconductors.

Quantum interference of one- and two-photon excitation of unbiased semiconductors yields ballistic currents of carriers. The magnitudes and directions of the currents and the spin orientations of the carriers are controlled by the polarization and relative phase of the exciting femtosecond laser fields. We provide direct experimental evidence for the spin polarization of the optically injected spin currents by detecting a phase-dependent spatial shift of the circularly polarized photoluminescence in cubic ZnSe.

Journal Article↗
PubMed2002

[The ocular form of larval toxocariasis in the Czech Republic].

The damage of the eye is one of the clinical syndromes of the Toxocara infection, caused by the migration activity of the Toxocara canis and Toxocara cati larvae. Ocular larva migrans (OLM) lesions mostly occur unilaterally and frequently are diagnosed as retinoblastoma. The typical symptoms of OLM are presented in our publication. The first signs of the ocular infection most often include diminished vision, leukocoria, red eye and strabismus. Inflammatory intraocular reaction, caused as a response to the antigens, released from dead or dying larvae is often diagnosed. The living larvae are observed very rarely. The reason and a way of the ocular invasion are still not sufficiently cleared. The supposition that the ocular syndrome is caused by migration of single larvae, when the immunological response is light, was not reliably verified. Sometimes if the infection size was heavy, the eye can be invaded with systemic complications as well. The most common laboratory findings include an elevation of the immunoglobulins in the serum of the patient and the presence of Toxocara specific antibodies response in the vitreous and/or aqueous humor. An analysis of the humor in cases of presumptive OLM was made only in 8 patients because not all oculists are ready to take this material, mainly in children. Highly sensitive assay--ELISA reaction with specific excretory-secretory antigen (TES) was used. For discrimination between chronic and recent infection the method of measuring IgG avidity was applied.

Adolescent↗
PubMed2001

Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices.

The fabrication and performance of an electrophoretic separation chip with integrated optical waveguides for absorption detection is presented. The device was fabricated on a silicon substrate by standard microfabrication techniques with the use of two photolithographic mask steps. The waveguides on the device were connected to optical fibers, which enabled alignment free operation due to the absence of free-space optics. A 750 microm long U-shaped detection cell was used to facilitate longitudinal absorption detection. To minimize geometrically induced band broadening at the turn in the U-cell, tapering of the separation channel from a width of 120 down to 30 microm was employed. Electrical insulation was achieved by a 13 microm thermally grown silicon dioxide between the silicon substrate and the channels. The breakdown voltage during operation of the chip was measured to 10.6 kV. A separation of 3.2 microM rhodamine 110, 8 microM 2,7-dichlorofluorescein, 10 microM fluorescein and 18 microM 5-carboxyfluorescein was demonstrated on the device using the detection cell for absorption measurements at 488 nm.

Electrophoresis, Capillary↗
PubMed2001

[Diagnosis of the early phase of larval toxocariasis using IgG avidity].

The term avidity used to express the strength of the bond between a serum specimen and a multivalent antigen. It is known that the avidity increases with time after antibody challenge and measurement of the avidity has been used diagnostically. Recently an assay measuring the IgG avidity of various virus infections and of toxoplasmosis was used to distinguish between acute and chronic infection. Our study was focused on the method to distinguish acute and chronic Toxocara infection, zoonosis caused by the larvae of dog and cat ascarids Toxocara canis and Toxocara cati known all over the world for the possibility of provoking the infestation of man, accompanied by visceral or ocular clinical manifestations. The infection is generally diagnosed by demonstration of specific immunoglobulins to Toxocara excretory-secretory antigens (TES) in sera of infected patients. Highly sensitive assays with specific antigens are necessary for detection of antibodies. The test that has been proved clinically useful is the ELISA reaction with TES antigens. This method detects the antibodies for months or even years after infection and this is the reason why the discrimination between chronic and recent infection is very difficult. For disrupting the hydrogen bond urea has been used. The index of avidity was calculated as the ratio of IgG values in sera treated with urea and the value of IgG in non-treated sera, multiplied by 100. An index up to 40 is considered as low avidity, that means freshly acquired infection (36 to 40 borderline) and more than 40 is high avidity. In the group of 1,376 patients only 5.09% low avidities were found. It means that predominantly patients in the chronic stage of infection attend examination.

Animals↗
PubMed1998

The ica locus of Staphylococcus epidermidis encodes production of the capsular polysaccharide/adhesin.

Clinical isolates of coagulase-negative staphylococci often elaborate a biofilm involved in adherence to medical devices and resistance to host defenses. The biofilm contains the capsular polysaccharide/adhesin (PS/A), which mediates cell adherence to biomaterials, and another antigen, termed polysaccharide intercellular adhesin (PIA), which is thought to mediate bacterial accumulation into cellular aggregates. PIA is a polymer of beta-1, 6-linked N-acetyl glucosamine residues with a molecular mass of <30, 000 kDa. We found that recombinant Staphylococcus carnosus and Staphylococcus aureus carrying a plasmid with genes of the ica locus, which was reported to encode the biosynthetic proteins for production of PIA, were also able to synthesize PS/A. PS/A and a chemically and immunologically identical polysaccharide isolated from S. carnosus carrying the ica genes on plasmid pCN27 were found to be high-molecular-mass (>250,000 kDa), acid-stable polymers of beta-1,6-linked glucosamine substituted on the amino group primarily with succinate, although some preparations also contained acetate. Moreover, all recombinant staphylococcal strains with the ica genes had the biologic properties previously attributed to PS/A. ica-positive strains readily formed an in vitro biofilm on plastic, adhered 3- to 10-fold more to catheters during a 30-min assay compared with control strains carrying only the cloning vector, adsorbed out antibodies to PS/A from immune serum, and elaborated a capsule visualized by immunoelectron microscopy with antisera to PS/A. These properties were also seen with PS/A-producing strains of Staphylococcus epidermidis, but not with transposon mutants lacking PS/A. An antiserum raised to PIA contained high-titer antibody to PS/A that was readily adsorbed out by PS/A-positive strains of S. epidermidis and recombinant strains of staphylococci carrying the ica genes. We conclude that the ica locus encodes production of PS/A and that the properties of S. epidermidis associated with initial bacterial adherence, biofilm formation, and intercellular adhesion can be correlated with elaboration of PS/A.

Adhesins, Bacterial↗
PubMed1998

Seroprevalence of Toxocara canis infection in Czech Republic.

An enzyme-linked immunosorbent assay (ELISA) with Toxocara canis excretion--secretion (TES) antigen was used for determination the seroprevalence of Toxocara canis infection in healthy population of several districts in Czech Republic. It was found that the seropositivity ranged from 5.8% to 36.0% in various districts. Valuation by sex, age, profession of the examined persons and different type of their habitation (urban or rural) was used. It is obvious that the percentage of seropositivity rise in dependence on the age of examined persons. This fact may be attributed to the longlasting serological positivity detected in ELISA reaction. Almost in all districts the positivity was higher in inhabitants with a rural type of habitation in comparison with urban residents. The geographical conditions in various districts play an important role in seropositivity of the population too.

Adolescent↗
PubMed1997

[Alveolar hydatidosis (alveococcosis) in the Czech Republic and its immunodiagnosis].

The frequent contemporary infections with the tapeworm Echinococcus multilocularis in foxes in some districts of the Czech Republic make it necessary to consider the probability of infection of man by the larval stage of this tapeworm in this country. So far there was in the Czech Republic a single case of alveolar hydatidosis (in 1977) in man with a lethal outcome. Foxes Vulpes vulpes increased in the Czech Republic considerably in numbers in recent years, and their infestations with E. multilocularis, in particular in the South Bohemian and North Bohemian regions is alarming. However so far it is not known whether the findings in foxes have a rising trend as compared with previous years as nobody was concerned with this particular problem in the past. The authors discuss also the epidemiology of alveococcosis and describe briefly its symptomatology.

Aged↗
PubMed1996

Immunological studies on human larval toxocarosis.

The aim of the study was to characterize the antiparasite humoral response in patients with the syndrome of visceral larval toxocarosis. Specific IgG, specific IgE and total IgE immunoglobulins against Toxocara canis excretory/secretory antigens (TES) were detected by using ELISA technique. Antibody response was studied in complete sera as well as in immunoglobulin fractions (IgG and IgE), isolation of which was performed on Protein A Sepharose. It was observed that removal of IgG from the serum samples resulted mostly in increasing levels of anti-Toxocara IgE antibodies what agrees with the theory of the blocking effect of IgG in the immune response. The results demonstrated a little correlation between slgG and slgE in the sera of symptomatic patients, examined in ELISA reaction.

Animals↗
PubMed1995

Cross infections due to coagulase-negative staphylococci in high-risk patients.

Until recently, infections due to coagulase-negative staphylococci (CNS) have been regarded as endogenous in origin. However, there are now increasingly reports in the literature on the endemic occurrence of distinct strains of CNS. Several outbreaks due to CNS are reported in cardiac surgery or in neonates. The latter seem to be high risk populations in regard to CNS infections because of certain risk factors (i.e. degree of immunosupression, routine use of central venous catheters and parenteral lipids as well as broad spectrum antibiotic therapy). On the other hand, these newborn babies have no physiological skin flora and are therefore easily colonized by multiresistent bacteria. The persistence of certain well-defined Staphylococcus epidermidis (SE) strains in neonatal intensive care units have been demonstrated over periods as long as a decade. Specific putative virulence factors (i.e. slime production and polysaccharide/adhesin PS/A) were more common in endemic strains as compared to single isolates. Pulsed-field gel electrophoresis (PFGE) proves to be a powerful tool in the study of the epidemiology of CNS while other modern typing techniques (ribotyping, plasmid typing) were also used in the literature to investigate outbreaks of CNS infections.

Coagulase↗
PubMed1993

Comparison of three typing methods in hospital outbreaks of Acinetobacter calcoaceticus infection.

During a period of 11 months Acinetobacter baumanii was isolated from 27 patients and 21 environmental samples in the Intensive Care Unit (ICU) and in one surgical unit of a University Hospital. The isolates were characterized by biotyping, antibiograms and plasmid profiles and compared with co-isolates. Plasmid fingerprinting distinguished three outbreaks, whereas other typing methods were less sensitive and discriminatory. Although plasmid profiles seem to be a simple and reproducible marker for epidemiological studies with acinetobacter strains, it might be useful to combine at least two typing methods since plasmids are unstable genetic structures, and not all strains possess plasmids.

Acinetobacter Infections↗
PubMed1993

Isolation and characterization of transposon mutants of Staphylococcus epidermidis deficient in capsular polysaccharide/adhesin and slime.

We used transposon (Tn) mutagenesis to study the role of capsular polysaccharide/adhesin (PS/A) and slime in adherence of Staphylococcus epidermidis to catheters. pLTV1, containing Tn917-LTV1, was transformed into S. epidermidis M187 by protoplast fusion with S. aureus RN4220(pLTV1), creating M187(pLTV1). Tn mutants were isolated following growth at 42 degrees C; mutants deficient in PS/A and slime production were selected. PS/A- and slime-deficient Tn mutants had a 10-fold decrease in vitro in the initial phase of adherence to catheters, comparable to levels of strains that do not produce PS/A. Introduction of Tn917-LTV1-interrupted DNA from PS/A-deficient mutant M187sn3 into the parental strain via transformation of protoplasts yielded recipients with inserts identical to those of the Tn mutant that were PS/A and slime deficient. Chromosomal DNA flanking the Tn in mutant M187sn3 was cloned into Escherichia coli. The cloned DNA was found to hybridize to approximately 5-kb EcoRI fragments from the parental strain and from control Tn mutants that express parental levels of PS/A and to either approximately 9- or approximately 14-kb EcoRI fragments from other highly adherent, PS/A-producing strains. Mapping studies demonstrated that in the eight PS/A-deficient mutants that have been isolated, the Tn insertions all occur within a region of approximately 11.6 kb that is defined by three EcoRI sites. These results support previous findings indicating that in S. epidermidis PS/A is involved with in vitro adherence to plastic biomaterials and elaboration of PS/A is closely associated with slime production.

Bacterial Adhesion↗
PubMed1992

[Isolation of Dirofilaria repens in vitreoretinal findings].

The authors present the case of a 18-year-old patient who reported deteriorated vision and mobile dark shadows on the left eye. Examination revealed in the vitreous body an extremely mobile filiform, worm-like formation, white in colour, of the size of an arteriole, about 9 mm long. In the course of hospitalization the formation was isolated by surgery of the pars plana vitrectomy and subjected to detailed helminthological examination. The worm was identified as Dirofilaria repens (Reillet et Henry 1911) and described in detail. The presented finding is the first finding of this parasite in this country and at the same time the first finding of this parasite in Czechoslovakia.

Adolescent↗
PubMed1991

[The effect of Federal Public Health Service guidelines on air, surface and floor germ count in a general surgery and an orthopedic operating room].

In a prospective study the environmental contamination in an old and a new operating theatre was investigated. The old operating rooms were constructed in 1936 whereas the new rooms were built in 1986. The study was conducted in surgical and orthopedic surgical operating rooms. There was a slight increase in floor as well as in surface contamination in the new operating rooms. On the other hand there was a slight decrease in the airborne microorganisms in the orthopedic surgery and nearly identical colony counts in the general surgery operating rooms. All the differences were statistically not significant. The spectrum of microorganisms and the occurrence of Staphylococcus aureus in the old and the new operating rooms showed no difference.

Air Microbiology↗
PubMed1989

[Simultaneous toxoplasmosis and larval toxocariasis infection in the Czechoslovak population].

The authors discuss the coexistence of infection with toxoplasmosis and larval toxocariasis in man. Both these zoonoses are the most widespread and most serious of all tissue parasitoses on the territory of the CSSR. Knowledge of the incidence and frequency of concurrent infections is important for the differential diagnosis and therapy. In the introduction the authors mention briefly the incidence of toxoplasmosis and toxocariasis in animal hosts on the territory of the CSSR, deals with the developmental stages of the two parasites, Toxoplasma gondii and Toxocara canis and Toxocara cati which are infectious also for man, and with the transmission of infection. In the world literature there are so far only two papers dealing with the parallel course of these two zoonoses and they present only one confirmed case of concurrent disease in man. In the diagnostic group investigated by the authors during examination of tissue helminthoses among almost 9000 examinations larval toxocarosis was diagnosed 798 times. These patients were examined repeatedly to investigate the dynamics of toxocaral antibodies and concurrently possible toxoplasmatic antibodies. In 45 instances concurrent toxoplasmosis was revealed. In the discussion the author deals with possibilities and interrelations of infection with the two parasitoses.

Czechoslovakia↗