Biomedical subjects

K Simek

Publications and source records attributed to K Simek.

At least 19 recordsLinked to original sources

PubMed2001

Predator-specific enrichment of actinobacteria from a cosmopolitan freshwater clade in mixed continuous culture.

We investigated whether individual populations of freshwater bacteria in mixed experimental communities may exhibit specific responses to the presence of different bacterivorous protists. In two successive experiments, a two-stage continuous cultivation system was inoculated with nonaxenic batch cultures of the cryptophyte Cryptomonas sp. Algal exudates provided the sole source of organic carbon for growth of the accompanying microflora. The dynamics of several 16S rRNA-defined bacterial populations were followed in the experimental communities. Although the composition and stability of the two microbial communities differed, numerous members of the first assemblage could again be detected during the second experiment. The introduction of a size-selectively feeding mixotrophic nanoflagellate (Ochromonas sp.) always resulted in an immediate bloom of a single phylotype population of members of the class Actinobacteria (Ac1). These bacteria were phylogenetically affiliated with an uncultured lineage of gram-positive bacteria that have been found in freshwater habitats only. The Ac1 cells were close to the average size of freshwater bacterioplankton and significantly smaller than any of the other experimental community members. In contrast, no increase of the Ac1 population was observed in vessels exposed to the bacterivorous ciliate Cyclidium glaucoma. However, when the Ochromonas sp. was added after the establishment of C. glaucoma, the proportion of population Ac1 within the microbial community rapidly increased. Populations of a beta proteobacterial phylotype related to an Aquabacterium sp. decreased relative to the total bacterial communities following the addition of either predator, albeit to different extents. The community structure of pelagic microbial assemblages can therefore be influenced by the taxonomic composition of the predator community.

Actinobacteria↗

PubMed2001

Changes in bacterial community composition and dynamics and viral mortality rates associated with enhanced flagellate grazing in a mesoeutrophic reservoir.

Bacterioplankton from a meso-eutrophic dam reservoir was size fractionated to reduce (<0.8-microm treatment) or enhance (<5-microm treatment) protistan grazing and then incubated in situ for 96 h in dialysis bags. Time course samples were taken from the bags and the reservoir to estimate bacterial abundance, mean cell volume, production, protistan grazing, viral abundance, and frequency of visibly infected cells. Shifts in bacterial community composition (BCC) were examined by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing of 16S rDNA genes from the different treatments, and fluorescence in situ hybridization (FISH) with previously employed and newly designed oligonucleotide probes. Changes in bacterioplankton characteristics were clearly linked to changes in mortality rates. In the reservoir, where bacterial production about equaled protist grazing and viral mortality, community characteristics were nearly invariant. In the "grazer-free" (0.8-microm-filtered) treatment, subject only to a relatively low mortality rate (approximately 17% day(-1)) from viral lysis, bacteria increased markedly in concentration. While the mean bacterial cell volume was invariant, DGGE indicated a shift in BCC and FISH revealed an increase in the proportion of one lineage within the beta proteobacteria. In the grazing-enhanced treatment (5-microm filtrate), grazing mortality was approximately 200% and viral lysis resulted in mortality of 30% of daily production. Cell concentrations declined, and grazing-resistant flocs and filaments eventually dominated the biomass, together accounting for >80% of the total bacteria by the end of the experiment. Once again, BCC changed strongly and a significant fraction of the large filaments was detected using a FISH probe targeted to members of the Flectobacillus lineage. Shifts of BCC were also reflected in DGGE patterns and in the increases in the relative importance of both beta proteobacteria and members of the Cytophaga-Flavobacterium cluster, which consistently formed different parts of the bacterial flocs. Viral concentrations and frequencies of infected cells were highly significantly correlated with grazing rates, suggesting that protistan grazing may stimulate viral activity.

Animals↗

PubMed2001

[Iatrogenic injuries of the colon during colonoscopy].

Endoscopic examinations of hollow organs, similarly as other invasive operations, are associated with a certain percentage of sometimes very serious complications. Iatrogenic perforations of the gut, in particular during the procedure belong to the most dramatic ones. During the period of 1990-2000 the authors had the opportunity to deal in collaboration with the medical department with five cases.

Aged↗

PubMed2000

[Prevention and therapy of dehiscent laparotomy wounds].

Dehiscence of laparotomic wounds is always unpleasant, starting with the resentment of the patient and the lack of confidence leading as far as complete negation of a favourable result of the operation. Due to lack of more suitable materials we elaborated ten years ago our own technique which we use nowadays for treatment but in particular for prevention. We feel that it could be a certain asset because it is simple and financially feasible.

Humans↗

PubMed2000

[Treatment of ingrown toenails].

Surgery of ingrowing toe nails are one of the most frequent operations in ambulatory practice. It is well known that a minor operation which relieves the patient of his complaints is appreciated more than the most complicated operation. Based on the article of Dr. Krticka we wish to present our own modification of an operation called Klapp's operation. We found that the results when using a modified vertical U stitch are better than when the classical technique is applied.

Hallux↗

PubMed1997

Morphological and compositional shifts in an experimental bacterial community influenced by protists with contrasting feeding modes.

In a two-stage continuous-flow system, we studied the impacts of different protozoan feeding modes on the morphology and taxonomic structure of mixed bacterial consortia, which were utilizing organic carbon released by a pure culture of a Rhodomonas sp. grown on inorganic medium in the first stage of the system. Two of three second stages operated in parallel were inoculated by a bacterivorous flagellate, Bodo saltans, and an algivorous ciliate, Urotricha furcata, respectively. The third vessel served as a control. In two experiments, where algal and bacterial populations grew at rates and densities typical for eutrophic waters, we compared community changes of bacteria, algae, and protozoa under quasi-steady-state conditions and during the transient stage after the protozoan inoculation. In situ hybridization with fluorescent oligonucleotide probes and cultivation-based approaches were used to tentatively analyze the bacterial community composition. Initially the cell size distribution and community structure of all cultivation vessels showed similar patterns, with a dominance of 1- to 2.5-(mu)m-long rods from the beta subdivision of the phylum Proteobacteria ((beta)-Proteobacteria). Inoculation with the ciliate increased bacterial growth in this substrate-controlled variant, seemingly via a recycling of nutrients and substrate released by grazing on algae, but without any detectable effect on the composition of bacterial assemblage. In contrast, an inoculation with the bacterivore, B. saltans, resulted in a decreased proportion of the (beta)-Proteobacteria. One part of the assemblage (<4% of total bacterial numbers), moreover, produced large grazing-resistant threadlike cells. As B. saltans ingested only cells of <3 (mu)m, this strategy yielded a refuge for (symbl)70% of total bacterial biomass from being grazed. Another consequence of the heavy predation in this variant was a shift to the numerical dominance of the (alpha)-Proteobacteria. The enhanced physiological status of the heavily grazed-upon segment of bacterial community resulted in a much higher proportion of CFU (mean, 88% of total bacterial counts) than with other variants, where CFU accounted for (symbl)30%. However, significant cultivation-dependent shifts of the bacterial community were observed toward (gamma)-Proteobacteria and members of the Cytophaga/Flavobacterium group, which demonstrated the rather poor agreement between cultivation-based approaches and oligonucleotide probing.

Journal Article↗

PubMed1997

Contrasting bacterial strategies to coexist with a flagellate predator in an experimental microbial assemblage.

We studied predator-induced changes within a slowly growing mixed microbial assemblage that was sustained by algal exudates in a continuous cultivation system. In situ hybridization with fluorescent monolabeled oligonucleotide probes was used for a tentative community analysis. This method also allowed us to quantify the proportions of predators with ingested bacteria of different taxonomic groups. In addition, we determined grazing rates on bacteria with fluorescently labelled prey. Bacteria belonging to the alpha and beta subdivisions of the phylum Proteobacteria ((alpha)- and (beta)-Proteobacteria, respectively) showed very different responses to the addition of a bacterivorous flagellate, Bodo saltans. Within one day, filamentous protist-inedible bacteria developed; these belonged to the (beta)-Proteobacteria and constituted between 8.7 and 34% of bacteria from this subgroup. Total abundance of (beta)-Proteobacteria decreased from 3.05 x 10(sup6) to 0.23 x 10(sup6) cells ml(sup-1), and estimated cell division rates were low. Other morphologically inconspicuous protist-edible bacteria belonging to the (alpha)-Proteobacteria were found to respond to predation by an increase in growth rate. Although these bacteria were heavily grazed upon, as on average >85% of flagellate cells had ingested (alpha)-Proteobacteria, they numerically dominated after the addition of B. saltans (mean, 1.35 x 10(sup6) cells ml(sup-1)). It was thus mainly those fast-dividing strains of (alpha)-Proteobacteria that supported the growth of the flagellate population. We conclude that bacteria in mixed assemblages can adopt at least two distinct strategies as a reaction to intense flagellate predation: to outgrow predation pressure or to develop inedible, inactive filaments. Since these strategies occurred within 24 h after the addition of the flagellate, we hypothesize that chemical stimuli released by the predator may have triggered bacterial responses.

Journal Article↗

PubMed1996

Evaluation of Extracellular, High-affinity beta-N-acetylglucosaminidase Measurements from Freshwater Lakes: An Enzyme Assay to Estimate Protistan Grazing on Bacteria and Picocyanobacteria

Protistan community grazing rates upon both bacterioplankton and autotrophic picoplankton were estimated using fluorescently-labeled prey and by measurement of extracellular hydrolysis of 4-methylumbelliferyl (MUF) beta-N-acetylglucosaminide in a eutrophic reservoir and an oligo-mesotrophic lake during phytoplankton blooms. In addition, enzyme methods were optimized in bacterivorous flagellate cultures by two enzyme assays, based on fluorometric detection of protistan digestive activity, which were compared and calibrated independently against flagellate bacterivory. Enzymatic hydrolyses of MUF beta-N,N',N''-triacetylchitotriose and MUF beta-N-acetylglucosaminide were measured in cell-free (sonicated) and whole-cell (unsonicated) samples. The hydrolysis of both substrates, using the whole-cell enzyme assay at in situ pH, was correlated significantly with total grazing rate of Bodo saltans. Thus the whole-cell enzyme assay with MUF beta-N-acetylglucosaminide was used for freshwater samples. High-affinity (Km < 1 μmol l-1) and low-affinity (Km > 100μmol l-1) enzymes were distinguished kinetically in most samples from both systems studied. Activities (Vmax) of the high-affinity enzyme varied from 0.24 to 1.43 nmol l-1 h-1. Protistan community grazing on bacterioplankton was in the range of 0.15-1.36 μg C l-1 h-1 both for lake and reservoir, the differences being observed in grazing on picocyanobacteria (lake, 0.03-0.22 μg C l-1 h-1; reservoir, 0.35-1.56 μg C l-1 h-1). The enzyme activities were correlated significantly with the protistan grazing both on bacterioplakton (rs=0.62, P<0.001) and total procaryotic picoplankton (the sum of organic carbon grazed from bacteria and picocyanobacteria, rs=0.73, P<0.001) in the eutrophic reservoir. Weaker relationships (rs=0.42) with a lower slope were found for the oligo-mesotrophic lake. Ingestion rate studies are time-consuming and the digestive enzyme assay with MUF beta-N-acetylglucosaminide presents a rapid alternative for estimating total protistan prokaryotic picoplanktivory in freshwaters.

Journal Article↗

PubMed1996

[Surgical wound closure with continuous sutures].

The author describes the technique of closure of surgical wounds by continuous suture. It is a vertical mattress suture, as described by Donatti-Mc Millen, which is made continuously along the whole wound. It may involve either one layer, depending on the depth of the wound, or it can be used after the usual treatment of the subcutaneous layer. For suture monophil fibre with atraumatic threading is optimal but any other material can be used for suture. The advantage is the simple and rapid character of the procedure, adequate haemostasis and perfect adaptation of the margins of the wound. A balanced tension of the fibre in the whole wound reduces the risk of ischaemisation of a single stitch. The stitch can be readily removed, and if properly done, the cosmetic effect is satisfactory. The economy of material is not negligible either. The authors have used it as a matter of routine since 1984.

Humans↗

PubMed1995

[Traumatic rupture of the greater pectoral muscle tendon].

The authors describe the case-history of a rare covered injury of the musculus pectoralis major, abruption of the attachment of its tendon on the humerus. In the world literature only three major groups were described, the majority of publications pertain only to individual observations. In the development of the injury always a very similar mechanism is involved, a considerable proportion are sports injuries. The injury is adequately defined from the diagnostic aspect, it may cause embarrassment because it is uncommon. As the loss of function is marked, surgical repair is considered the method of choice. The importance of early operation is emphasized. The described technique of reinsertion produced results satisfactory from the patient's point of view.

Humans↗

PubMed1994

[High ileus with a prolonged course].

The authors describe the atypical development of a so-called high ileus caused by a bulky phytobezoar made up of tropical fruit. it is of interest that the organism managed to cope for two months relatively well with a condition described in surgical practice as acute abdomen where urgent or at least acute intervention is essential. The authors draw attention to pitfalls of out-patient care which may involve risk of delay due to incomplete evaluation by the specialists involved. This risk is particularly great during the present period of restructuring of the health services "hunting for a"high point score".

Bezoars↗

PubMed1994

[An inveterate incarceration of an umbilical hernia treated by radical excision].

The authors describe the case-history of an elderly female patient with an inveterate incarcerated relapsing umbilical hernia. The patient's age, and obviously also associated diseases, were the cause of subjective underrating of the severity of the condition, late admission to hospital and surgical intervention. The syndrome of advanced ileus had already developed as well as local changes complicating or rather making classical surgical treatment impossible. The applied technique which can be described as "no touch" with regard to the hernia and its contents is considered as one of the dominating features of successful treatment. The second dominating feature is a satisfactory interdisciplinary collaboration in treating the condition which at first appeared infaust.

Aged↗

PubMed1993

4-Methylumbelliferyl-beta-N-Acetylglucosaminide Hydrolysis by a High-Affinity Enzyme, a Putative Marker of Protozoan Bacterivory.

Hydrolysis of an artificial fluorogenic substrate, 4-methylumbelliferyl-beta-N-acetylglucosaminide, has been studied in a monoculture predator-prey system with either a flagellate (Bodo saltans) or a ciliate (Cyclidium sp.) fed upon pure bacterial culture (Aeromonas hydrophila or Alcaligenes xylosoxidans). Aeromonas hydrophila produced a low-affinity beta-N-acetylglucosaminidase-like enzyme (K(m), >>100 mumol liter) but Alcaligenes xylosoxidans did not. Inoculation of both bacterial strains with bacterivorous protozoa induced the occurrence of another, high-affinity, beta-N-acetylglucosaminidase-like enzyme (K(m), <0.5 mumol liter). The latter enzyme showed significant, close correlations with total grazing rates of both B. saltans (r = 0.96) and Cyclidium sp. (r = 0.89) estimated by using uptake of fluorescently labelled bacteria. Further significant correlations between several protozoan parameters and kinetic parameters of this enzyme suggest its likely protozoan origin. If both types of enzyme occurred together, they could be satisfactorily distinguished by using kinetic data analysis. Hence, measurements of beta-N-acetylglucosaminidase-like activities might be promising to use to improve estimations of protozoan bacterivory.

Journal Article↗

PubMed1992

Direct and indirect evidence of size-selective grazing on pelagic bacteria by freshwater nanoflagellates.

Size-selective grazing of three heterotrophic nanoflagellates (with cell sizes of 21, 44, and 66 mum) isolated from Lake Arlington, Texas was examined by using a natural mixture of fluorescence labelled lake bacteria. Sizes of ingested bacteria in food vacuoles were directly measured. Larger bacterial cells were ingested at a frequency much higher than that at which they occurred in the assemblage, indicating preferential flagellate grazing on the larger size classes within the lake bacterioplankton. Water samples were collected biweekly from June through September, 1989, fractionated by filtration, and incubated for 40 h at in situ temperatures. The average bacterial size was always larger in water which was passed through 1-mum-pore-size filters (1-mum-filtered water) (which was predator free) than in 5-mum-filtered water (which contained flagellates only) or in unfiltered water (in which all bacterivores were present). The increase of bacterial-cell size in 1-mum-filtered water was caused by a shift in the size structure of the bacterioplankton population. Larger cells became more abundant in the absence of flagellate grazing.

Journal Article↗

PubMed1992

[Surgical treatment of atypical location of a clavus on the lower extremity].

Clavus is a very frequent condition of the toes which, despite the fact that it is usually underrated, can complicate the life of its carriers. The authors describe a surgical technique tested in a group of 12 female patients in the course of six years, which became a simple method of choice for the elimination of these complaints.

Adult↗

PubMed1991

[Surgical stabilization of injuries of the malleolar fork].

The author describes the technique of tibiofibular hemicerclage by a double loop of the binding wire which is a modification of Mlcoch's method. It achieves complete stability of the damaged malleolar fork in dislocating injuries of the upper talus without the necessity of additional fixation. It makes early rehabilitation of the complete extent of associated movements of the talus possible; contrary to clamps the dynamics of the lower tibiofibular joint are accepted. On actual examples the author demonstrates the firmness of the bond. He gives also an outline of the somewhat non-standard method of comprehensive therapeutic care. The method was tested in 61 patients in the course of 11 years.

Ankle Injuries↗

PubMed1990

[Modified traction cerclage in fractures of the outer ankle].

The authors describe two techniques of osteosynthesis which can be used as the method of choice in suitable types of fractures. Both were elaborated as the author's modification in 1978 and used in the course of 10 years in 24 instances. They can be applied without special instrumental equipment in any department. The authors consider them very stable without requiring additional plaster immobilization and the authors use early rehabilitation immediately after operation. The authors never observed usuration of the bone beneath the cerclage or slower healing, pseudoarthrosis or any other complications. They assume that the described methods may supplement the therapeutic range and be sometimes a good starting poit from a situation which would be otherwise, difficult to resolve.

Ankle Injuries↗

PubMed1984

Steady-state kinetics of horse-liver alcohol dehydrogenase with a covalently bound coenzyme analogue.

The steady-state kinetics of the enzyme modified by affinity labelling with NAD analogue, nicotinamide-N6-[N-(6-aminohexyl)carbamoylmethyl]-adenine dinucleotide, has been investigated using a recycling reaction with p-nitrosodimethylaniline and n-butanol as substrates and compared to the kinetics of native alcohol dehydrogenase. The modified enzyme obeys a ping-pong mechanism involving two inactive enzyme forms (enzyme-NAD and enzyme-NADH complexes in the 'open' conformations, the nicotinamide moieties of the coenzymes being out of the active center). The rate of p-nitrosodimethylaniline reduction in the reaction catalyzed by the modified enzyme is comparable to that observed in the presence of the native enzyme. On the other hand, the oxidation of butanol by the modified enzyme is essentially slower under our experimental conditions (pH 8.5). The measurements in the presence of specific alcohol dehydrogenase inhibitors competing with substrates and coenzymes (isobutyramide, pyrazole and AMP) revealed that the relative portion of the inactive 'open' form of the enzyme-NADH complex is negligible, whereas the 'open' form of the enzyme-NAD complex seems to represent a more significant portion (about 30%) under the conditions used.

Alcohol Dehydrogenase↗