Showing papers by "Academy of Sciences of the Czech Republic published in 1997"

The comet assay: what can it really tell us?

Abstract: A range of applications of the alkaline comet assay is covered, from investigations of the physicochemical behaviour of DNA, through studies of cellular responses to DNA damage, to biomonitoring of human populations. The underlying principles of this assay are discussed, and new evidence presented which supports the concept of relaxation of supercoiled loops, rather than alkaline unwinding, as the primary reason for comet tail formation. DNA-damaging agents that do not induce strand breaks directly can be detected when cellular repair processes convert lesions to transient strand breaks; an approach is outlined here which maximises this effect and thus widens the scope of the assay. Purified repair enzymes, applied to DNA during the course of the comet assay procedure, greatly increase the sensitivity and specificity of the assay; recent developments with formamidopyrimidine glycosylase (recognising 8-OH-gua and other damaged purines) and uvrABC (for bulky lesions) are presented. The kinetics of cellular repair after low doses of oxidative damage have been followed with this modified comet assay. Finally, the successful measurement of biomarkers of oxidative damage in human populations establishes the comet assay as a valuable tool in molecular epidemiology.

Hypoplastic model for cohesionless soils with elastic strain range

Abstract: SUMMARY In order to eliminate ratcheting a so-called intergranular strain has been added to a hypoplastic constitutive model. This additional state variable represents the deformation of the interface layer between the grains. The new concept is outlined and comparisons with and without intergranular strain are presented. Some comments on numerical implementation and determination of material constants are made. A discussion on the uniqueness of the solution and objectivity of the rate of intergranular strain is added. # 1997 John Wiley & Sons, Ltd. Mech. of Cohes.-Frict. Mater., 2, 279‐299 (1997)

Search for neutral heavy leptons produced in Z decays

Abstract: Weak isosinglet Neutral Heavy Leptons (m) have been searched for using data collected by the DELPHI detector corresponding to 3:3 106 hadronic Z0 decays at LEP1. Four separate searches have been performed, for short-lived m production giving monojet or acollinear jet topologies, and for long-lived m giving detectable secondary vertices or calorimeter clusters. No indication of the existence of these particles has been found, leading to an upper limit for the branching ratio BR(Z0 ! m) of about 1:310−6 at 95% confidence level for m masses between 3.5 and 50 GeV/c2. Outside this range the limit weakens rapidly with the m mass. The results are also interpreted in terms of limits for the single production of excited neutrinos.

The H1 detector at HERA

Abstract: General aspects of the H1 detector at the electron-proton storage ring HERA as well as technical descriptions of the magnet, luminosity system, trigger, slow-control, data acquisition and off-line data handling are given. The three major components of the detector, the tracking, calorimeter and muon detectors, will be described in a forthcoming article. The present paper describes the detector that was used from 1992 to the end of 1994. After this a major upgrade of some components was undertaken. Some performance figures from luminosity runs at HERA during 1993 and 1994 are given.

Performance of empirical potentials (AMBER, CFF95, CVFF, CHARMM, OPLS, POLTEV), semiempirical quantum chemical methods (AM1, MNDO/M, PM3), and ab initio Hartree–Fock method for interaction of DNA bases: Comparison with nonempirical beyond Hartree–Fock results

Abstract: Empirical energy functions (AMBER 4.1, CFF95, CHARMM23, OPLS, Poltev), semiempirical quantum chemical methods (AM1, MNDO/M, PM3), and the nonempirical ab initio self-consistent field (SCF) method utilizing a minimal basis set combined with the London dispersion energy (SCFD method) were used for calculation of stabilization energies of 26 H-bonded DNA base pairs, 10 stacked DNA base pairs (thymine was replaced by uracil), and the B-DNA decamer (only DNA bases were considered). These energies were compared with nonempirical ab initio beyond Hartree–Fock values [second-order Moller–Plesset (MP2)/6–31G*(0.25)]. The best performance was exhibited by AMBER 4.1 with the force field of Cornell et al. The SCFD method, tested for H-bonded pairs only, exhibited stabilization energies that were too large. Semiempirical quantum chemical methods gave poor agreement with MP2 values in the H-bonded systems and failed completely for stacked pairs. A similar failure was recently reported for density functional theory calculations on base stacking. It may be concluded that currently available force fields provide much better descriptions of interactions of nucleic acid bases than the semiempirical methods and low-level ab initio treatment. © 1997 John Wiley & Sons, Inc. J Comput Chem18: 1136–1150

Delayed early embryonic lethality following disruption of the murine cyclin A2 gene.

Abstract: In higher eukaryotes, cell cycle progression is controlled by cyclin dependent kinases (Cdks) complexed with cyclins. A-type cyclins are involved at both G1/S and G2/M transitions of the cell cycle. Cyclin A2 activates cdc2 (Cdk1) on passage into mitosis and Cdk2 at the G1/S transition. Antisense constructs, or antibodies directed against cyclin A2 block cultured mammalian cells at both of these transitions. In contrast, overexpression of cyclin A2 appears to advance S phase entry and confer anchorage-independent growth, and can lead to apoptosis. A second A-type cyclin, cyclin A1 has been described recently which, in the mouse, is expressed in germ cells but not somatic tissues. To address the possible redundancy between different cyclins in vivo and also the control of early embryonic cell cycles, we undertook the targeted deletion of the murine cyclin A2 gene. The homozygous null mutant is embryonically lethal, demonstrating that the cyclin A2 gene is essential. Surprisingly, homozygous null mutant embryos develop normally until post-implantation, around day 5.5 p.c. This observation may be explained by the persistence of a maternal pool of cyclin A2 protein until at least the blastocyst stage, or an unexpected role for cyclin A1 during early embryo development.

Identification of the MN/CA9 Protein As a Reliable Diagnostic Biomarker of Clear Cell Carcinoma of the Kidney

Abstract: The MN/CA9 protein is a tumor-associated antigen that has been shown to have diagnostic utility in identifying cervical dysplasia and carcinoma. MN/CA9 expression is limited to very few normal tissues. We have now extended those observations to further investigate expression of the MN/CA9 protein in histological sections and fine-needle aspiration biopsy smears of normal kidney, benign renal cell lesions, all categories of renal cell carcinomas (clear/granular/spindle cell, chromophilic cell, chromophobic cell, and collecting duct cell RCCs), metastatic RCCs, and non-renal cell clear cell adenocarcinomas. We have found that high levels of MN/CA9 expression is seen in all primary RCCs, cystic RCCs, and metastatic RCCs, with the exception of two cases of the chromophobe cell type, which were MN/CA9 negative. Identical MN/CA9 immunostaining was also observed in the aspiration cytological smears. In contrast, all benign lesions, including pyelonephritis, renal cysts, adenomas, oncocytomas, and normal kidney, did not express the MN/CA9 protein. Thus, we conclude that MN/CA9 protein expression could serve as a valuable adjunct to the cytological and histological diagnosis of benign renal cysts versus cystic RCC, adenoma versus RCC, and oncocytoma versus granular cell RCC. Diffuse membraneous staining of all RCCs (with the exception of chromophobic cell RCC) suggests that MN/CA9 protein expression might have an important clinical utility in the early detection and treatment of RCC. Absence of MN/CA9 expression in non-renal cell clear cell adenocarcinoma also indicates that MN/CA9 protein expression may be used as a differential diagnostic biomarker of metastatic clear cell RCC.

Initiation of growth of baboon primordial follicles in vitro.

Abstract: Factors that cause some primordial follicles to enter the growth phase while the others remain quiescent are unknown. The hypothesis was tested that primate primordial follicles can survive and initiate growth in vitro in serum-free medium. Superficial pieces of ovarian cortex, containing mostly primordial follicles, were obtained from baboon fetuses during late gestation and cultured for 0, 2, 4, 7, 10 or 20 days in Waymouth MB 752/1 medium supplemented with insulin, transferrin, selenium, linoleic acid, and bovine serum albumin (ITS +). Histological examination of cortical pieces revealed that after 2 and 4 days in culture, the total number of primordial follicles had decreased by 55 and 76% (P < 0.01) respectively, relative to day 0 of culture. This was associated with a sustained, 5- to 8-fold increase in total primary follicles (P < 0.01) beginning on day 2 of culture. There was also a gradual increase in the total number of early secondary and secondary follicles. The average diameter of follicles and oocytes increased gradually throughout culture for all follicular categories (P < 0.01), except secondary follicles and oocytes. Immunohistochemical localization of proliferating cell nuclear antigen (PCNA), a marker for cell proliferation and growth, showed that PCNA was generally absent in primordial follicles on day 0, but was observed after 2 or 4 days in culture in both granulosa cells and oocytes of most growing follicles. Comparison of cortical pieces cultured for 10 or 20 days with ITS + versus 10% fetal bovine serum (FBS) showed a more pronounced decrease in the numbers of primordial follicles and more primary, early secondary and secondary follicles in ITS + compared to FBS-treated cortical pieces (P < 0.01 at 20 days). These results show that primordial follicles from non-human primates can survive and develop to the secondary stage in vitro in serum-free conditions.

Transfer of molecular property tensors in cartesian coordinates: A new algorithm for simulation of vibrational spectra

Abstract: A direct transfer of Cartesian molecular force fields FF and electric property tensors is tested on model systems and compared to transfer in internal coordinates with an aim to improve simulation of vibrational spectra for larger molecules. This Cartesian transformation can be implemented easily and offers greater flexibility in practical computations. It can be also applied for transfer of anharmonic derivatives. The results for model calculations of the force field and vibrational frequencies for N-methylacetamide show that our method removes errors associated with numerical artifacts caused by nonlinearity of the otherwise required Cartesian to internal coordinate transformation. For determination of IR absorption and vibrational circular dichroism intensities, atomic polar and axial tensors were also transferred in the Cartesian representation. For the latter, which are dependent upon the magnetic dipole operator, a distributed origin gauge is used to avoid an origin dependence. Comparison of the results of transferring ab initio FF and intensity parameters from an amide dimer fragment onto a tripeptide with those from a conventionally determined tripeptide FF document some limitations of the transfer method and its possible applications in the vibrational spectroscopy. Finally, application to determination of the FF and spectra for helical heptapeptide are presented and compared to experimental results. Q 1997 by John Wiley & Sons, Inc.

Positive Cooperativity of Acetylcholine and Other Agonists with Allosteric Ligands on Muscarinic Acetylcholine Receptors

Abstract: It is well known that allosteric modulators of muscarinic acetylcholine receptors can both diminish and increase the affinity of receptors for their antagonists. We investigated whether the allosteric modulators can also increase the affinity of receptors for their agonists. Twelve agonists and five allosteric modulators were tested in experiments on membranes of CHO cells that had been stably transfected with genes for the M1-M4 receptor subtypes. Allosterically induced changes in the affinities for agonists were computed from changes in the ability of a fixed concentration of each agonist to compete with [3H]N-methylscopolamine for the binding to the receptors in the absence and the presence of varying concentrations of allosteric modulators. The effects of allosteric modulators varied greatly depending on the agonists and the subtypes of receptors. The affinity for acetylcholine was augmented by (-)-eburnamonine on the M2 and M4 receptors and by brucine on the M1 and M3 receptors. Brucine also enhanced the affinities for carbachol, bethanechol, furmethide, methylfurmethide, pilocarpine, 3-(3-pentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1- methylpyridine (pentylthio-TZTP), oxotremorine-M, and McN-A-343 on the M1, M3, and M4 receptors, for pentylthio-TZTP on the M2 receptors, and for arecoline on the M3 receptors. (-)-Eburnamonine enhanced the affinities for carbachol, bethanechol, furmethide, methylfurmethide, pentylthio-TZTP, pilocarpine, oxotremorine and oxotremorine-M on the M2 receptors and for pilocarpine on the M4 receptors. Vincamine, strychnine, and alcuronium displayed fewer positive allosteric interactions with the agonists, but each allosteric modulator displayed positive cooperativity with at least one agonist on at least one muscarinic receptor subtype. The highest degrees of positive cooperativity were observed between (-)-eburnamonine and pilocarpine and (-)-eburnamonine and oxotremorine-M on the M2 receptors (25- and 7-fold increases in affinity, respectively) and between brucine and pentylthio-TZTP on the M2 and brucine and carbachol on the M1 receptors (8-fold increases in affinity). The discovery that it is possible to increase the affinity of muscarinic receptors for their agonists by allosteric modulators offers a new way to subtype-specific pharmacological enhancement of transmission at cholinergic (muscarinic) synapses.

Mineral Nutrition of Carnivorous Plants: A Review.

Abstract: Plant carnivory is one of many possible adaptation strategies to unfavorable conditions, mostly low nutrient availability in wet, acid soils. The following issues concerning the mineral nutrition of carnivorous plants are reviewed: the relative importance of carnivory and root nutrition for growth; which nutrients (elements) from prey are of principal importance for growth; the relationship between mineral and organic nutrition based on carnivory; the interactions between carnivory and root mineral nutrition; and the importance of carnivory under natural conditions. Special attention is paid to aquatic carnivorous plants. Studies on mineral nutrition carried out in laboratory and/or greenhouse conditions are discussed separately from those carried out in field conditions. The emphasis of this review is on recapitulation of original data and conclusions of results from a variety of studies that approach carnivorous plants from an ecophysiological point of view.

Theory and simulation of crystal growth

Abstract: Crystal growth phenomena are discussed with special reference to growth from vapour. The basic concepts of crystal growth are recalled, including the different growth modes, the dependence of the growth rate on disequilibrium and temperature, and the atomic processes relevant for growth. The methods used in crystal growth simulations are reviewed, with special reference to kinetic Monte Carlo methods. The roughness of growing surfaces, and the roughness properties of the discrete and continuum growth models (the latter being described via stochastic differential equations) are discussed, together with the special phenomena occurring in the vicinity of the roughening temperature. A number of simulations based on the six-vertex model and on kinetic counterparts of the BCSOS model are reviewed. Finally, the instabilities arising during growth are considered, including a discussion of phenomena such as dendritic growth and ramified cluster growth and reviewing the recent, extensive studies concerning unstable MBE growth.

Ammonia mediates communication between yeast colonies

Abstract: Under certain growth conditions unicellular organisms behave as highly organized multicellular structures For example, the fruiting bodies of myxobacteria1 and of the slime mould Dictyostelium discoideum2 form structures composed of non-dividing motile cells Although non-motile, yeasts can create organized structures, colonies in which cells communicate and act in a coordinated fashion Colony morphologies are characteristic for different species and strains Here we describe that, in addition to short-range intracolony cell–cell communication, yeasts exhibit long-distance signals between neighbouring colonies The volatile alkaline compound ammonia, transmitted by yeast colonies in pulses, has been identified as a substance mediating the intercolony signal The first alkaline pulse produced by neighbouring colonies is non-directed and is followed by acidification of the medium The second pulse seems to be enhanced and is oriented towards the neighbour colony Ammonia signalling results in growth inhibition of the facing parts of both colonies This phenomenon is observed in different yeast genera The presence of amino acids in the medium is required for ammonia production Colonies derived from the yeast Saccharomyces cerevisiae shr3 mutant, defective in localization of amino-acid permeases3, do not produce detectable amounts of ammonia and do not exhibit asymmetric growth inhibition

The tracking calorimeter and muon detectors of the H1 experiment at Hera

Abstract: Technical aspects of the three major components of the H1 detector at the electron-proton storage ring HERA are described. This paper covers the detector status up to the end of 1994 when a major upgrading of some of its elements was undertaken. A description of the other elements of the detector and some performance figures from luminosity runs at HERA during 1993 and 1994 are given in a paper previously published in this journal.

Ergot alkaloids--sources, structures and analytical methods.

Abstract: Natural sources, i.e. fungal strains and species producing ergot alkaloids (EA), are surveyed together with the chemical structures of EA and a list of new natural EA discovered in the last three decades. Other topics include new efficient chromatographic methods (HPLC) for the separation and isolation of new natural EA and also immunological methods of EA detection.

Enhancement of optical gain of semiconductors embedded in three-dimensional photonic crystals

Abstract: The three-dimensional photonic crystals used in this study were synthetic opals, composed of submicron silica spheres, close-packed in a face-centered cubic structure with a period of 200 nm, that exhibit photonic stopbands around 600 nm. We present measurements of the optical gain of CdS quantum dots (QDs) embedded inside the interstitials between the silica spheres. Unlike the usual gain spectra of CdS QDs in glass matrices, which display maximum gain at energies of the first quantum-confined transitions, for QDs embedded in photonic crystals the gain maximum is shifted toward the high-frequency edge of the photonic stopband (2.2 eV) far below the absorption edge of the semiconductor (2.5 eV). Studies of temperature, intensity, and orientation dependencies of the gain spectra allow one to ascribe the observed effect to gain enhancement caused by multiple coherent Bragg scattering of light in the periodic photonic crystal.

The Extracellular Space in the CNS: Its Regulation, Volume and Geometry in Normal and Pathological Neuronal Function

Abstract: Changes in extracellular space (ECS) composition and geometry are a consequence of neuronal activity and of glial K+, pH, and amino acids homeostasis. They accompany the phenomena of repetitive neuronal activity and also occur as a result of seizures, anoxia, injury, and many other pathological states in the CNS, and they may significantly affect signal transmission in the CNS. Activity-related, or CNS damage-related ionic changes and release of amino acids result in fast, pulsatile, and long-term cellular (particularly glial) swelling. Cellular swelling is compensated for by ECS volume shrinkage and by a decrease in the apparent diffusion coefficients of neuroactive substances diffusing in the ECS. Movement of substances is hindered in the narrower clefts, but presumably also because of the crowding of molecules of the ECS matrix and/or by the swelling of the fine glial processes that form diffusional barriers. This can either increase efficacy of synaptic and nonsynaptic transmission by greater accumula...

Dynamic ideal free distribution: effects of optimal patch choice on predator-prey dynamics

Abstract: This study examines the influence of individual behavior on predator-prey dynamics in a two-patch environment. I assume that individuals behave to maximize their fitness measured by the instantaneous per capita growth rate. The population dynamics in each patch are de- scribed by the Lotka-Volterra continuous model. Two cases are studied in detail. The first case assumes only predators are free to move between patches, whereas the second assumes that both predators and prey move freely between patches. The study shows that the optimal behavior of animals leads to persistence of predator-prey systems and reduction of oscillations in population densities. In this article, I develop a dynamic framework for modeling the spatial distribu- tion of predator and prey populations, assuming animals behave optimally (i.e., they maximize their fitness). I follow the idea behind the ideal free distribution (Fretwell and Lucas 1970; Kacelnik et al. 1992), which describes the equilibrium distribution of a population of predators among several habitat patches. The Fret- well and Lucas model assumes that predators are free to settle in any patch, travel time between patches is zero, predators are omniscient, and resource densities in patches remain constant through time (Kacelnik et al. 1992). If each predator settles in the patch where its rate of resource acquisition is maximized, the model predicts that at equilibrium, predators in all patches will experience the same intake rate. The original Fretwell and Lucas model was modified in several direc- tions to include factors such as interference (Sutherland 1983), differences in competitive ability (Sutherland and Parker 1985; Parker and Sutherland 1986), perceptual constraints (Abrahams 1986), learning (Bernstein et al. 1988), and resource dynamics (Lessells 1995). However, the original Fretwell and Lucas model and these generalizations do not consider predator-prey dynamics that in turn will influence the distribution of predators and prey among patches. More- over, the optimality criterion based on maximization of energy intake should also be replaced by a more general criterion that includes the consequences of varia- tion in predator mortality rates among all patches. In natural communities, the richer habitat is often also the more dangerous one, owing to a higher predation

Regulation of cytokinin content in plant cells

Abstract: Cytokinin levels in plant cells are dependent on cytokinin biosynthesis and/or uptake from extracellular sources, metabolic interconversions, inactivation and degradation. Cytokinin conversion to compounds differing in polarity seems to be decisive for their entrapment within the cell and intracellular compartmentation, which affects their metabolic stability. Increase in cytokinin levels, resulting either from their uptake or intracellular biosynthesis, may promote further autoinductive accumulation of cytokinins which may function in the induction of cytokinin-initiated physiological processes. Accumulated cytokinins are capable of inducing cytokinin oxidase which consequently decreases cytokinin levels. This seems to be the mechanism of re-establish-ment and maintenance of cytokinin homeostasis required for further development of physiological events induced by transient cytokinin accumulation. Auxin may influence cytokinin levels by down regulation of cytokinin biosynthesis and/or by promotion of cytokinin degradation. A model of the regulation of cytokinin levels in plant cells based on these phenomena is presented and its physiological role(s) is discussed.

The H1 lead/scintillating-fibre calorimeter

Abstract: The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high-resolution lead/scintillating-fibre calorimeter. The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out-of-time background events at the first trigger level. It must be compact due to space restrictions. These requirements were fulfilled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic fibres embedded in a lead matrix. Its lead-to-fibre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter fibres with a lead-to-fibre ratio of 3.4:1. The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.

Quantitative trait loci for cellular defects in glucose and fatty acid metabolism in hypertensive rats.

Abstract: Coronary heart disease, hypertension, non-insulin-dependent diabetes and obesity are major causes of ill health in industrial societies. Disturbances of carbohydrate and lipid metabolism are a common feature of these disorders1–9. The bases for these disturbances and their roles in disease pathogenesis are poorly understood. The spontaneously hypertensive rat (SHR), a widely used animal model of essential hypertension10, has a global defect in insulin action on glucose metabolism and shows reduced catecholamine action on lipolysis in fat cells11–14. In our study we used cellular defects in carbohydrate and lipid metabolism to dissect the genetics of defective insulin and catecholamine action in the SHR strain. In a genome screen for loci linked to insulin and catecholamine action, we identified two quantitative trait loci (QTLs) for defective insulin action, on chromosomes 4 and 12. We found that the major (and perhaps only) genetic determinant of defective control of lipolysis in SHR maps to the same region of chromosome 4. These linkage results were ascertained in at least two independent crosses. As the SHR strain manifests many of the defining features of human metabolic Syndrome X, in which hypertension associates with insulin resistance, dyslipidaemia and abdominal obesity, the identification of genes for defective insulin and catecholamine action in SHR may facilitate gene identification in this syndrome and in related human conditions, such as type-2 diabetes and familial combined hyperlipidaemia.

Task-Dependent Representations in Rat Hippocampal Place Neurons

Abstract: Kobayashi, Tsuneyuki, Hisao Nishijo, Masaji Fukuda, Jan Bures, and Taketoshi Ono. Task-dependent representations in rat hippocampal place neurons. J. Neurophysiol. 78: 597–613, 1997. It is suggeste...

The Spread of an Advantageous Allele Across a Barrier: The Effects of Random Drift and Selection Against Heterozygotes

Abstract: A local barrier to gene flow will delay the spread of an advantageous allele. Exact calculations for the deterministic case show that an allele that is favorable when rare is delayed very little even by a strong barrier: its spread is slowed by a time proportional to log((B/sigma) square root of 2S)/S, where B is the barrier strength, sigma the dispersal range, and fitnesses are 1:1 + S:1 + 2S. However, when there is selection against heterozygotes, such that the allele cannot increase from low frequency, a barrier can cause a much greater delay. If gene flow is reduced below a critical value, spread is entirely prevented. Stochastic simulations show that with additive selection, random drift slows down the spread of the allele, below the deterministic speed of sigma square root of 2S. The delay to the advance of an advantageous allele caused by a strong barrier can be substantially increased by random drift and increases with B/(2S rho sigma 2) in a one-dimensional habitat of density rho. However, with selection against heterozygotes, drift can facilitate the spread and can free an allele that would otherwise be trapped indefinitely by a strong barrier. We discuss the implications of these results for the evolution of chromosome rearrangements.

Distribution of Borrelia burgdorferi sensu lato genomic groups in Europe, a review.

Abstract: The survey is based on a total of 1263 records (738 isolations and 525 molecular DNA detections) of five Borrelia burgdorferi s.l. genomic groups available from 26 European countries: B. burgdorferi sensu stricto, B. afzelii, B. garinii, B. valaisiana (= VS116) and B. lusitaniae (= PoTiB2). It shows the geographic distribution, the source (ixodid ticks 802 records, fleas 2 records, mosquitoes 2 records, wild mammals 66 records, human patients 391 records) and the association of the genomic groups with particular clinical manifestations of Lyme borreliosis in humans (B. afzelii significantly prevails in skin lesions whereas B. garinii is more often associated with neuroborreliosis). The most frequent genomic groups in Europe are B. garinii (501 records) and B. afzelii (469 records). They occur across the continent and islands, whereas the third frequent genomic group, B. burgdorferi s.s. (201 records), has only rarely been isolated in eastern Europe. The remaining genomic groups, i.e. B. valaisiana (85 records) and B. lusitaniae (7 records) have only been isolated from, or detected in, Ixodes ricinus ticks in a few European countries.