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M Labuda

Publications and source records attributed to M Labuda.

At least 37 records · Page 2Linked to original sources
PubMed1997

The Friedreich ataxia GAA triplet repeat: premutation and normal alleles.

The most common mutation causing Friedreich ataxia (FRDA), an autosomal recessive neurodegenerative disease, is the hyperexpansion of a polymorphic GAA triplet repeat localized within an Alu sequence (GAA-Alu) in the first intron of the frataxin (X25) gene. GAA-Alu belongs to the AluSx subfamily and contains several polymorphisms in strong linkage disequilibrium either with a subgroup of normal alleles, or with hyperexpanded FRDA-associated alleles. GAA repeat sizes in 300 normal chromosomes (97 from carriers and 203 from controls) were distributed in two separate groups: 83% of them contained between six and 10 triplets (small normal alleles), while the remaining 17% had more than 12 triplets, up to 36 (large normal alleles). Sequence analysis showed that no normal, stable allele contained more than 27 uninterrupted GAA triplets. All longer normal alleles were interrupted by a hexanucleotide repeat (GAGGAA). An allele containing an uninterrupted run of 34 GAA triplets was stably transmitted in four instances, but in one case underwent hyperexpansion to 650 triplets. Overall, our results suggest that the FRDA-associated expanded GAA repeats originate from normal alleles by recurrent expansions of alleles at risk.

Alleles↗
PubMed1997

Transmission of tick-borne bunyaviruses by cofeeding ixodid ticks.

Palma and Bhanja bunyaviruses replicated in Dermacentor marginatus, D. reticulatus, Rhipicephalus sanguineus, R. appendiculatus and Ixodes ricinus ticks after parenteral inoculation and appropriate incubation and feeding. Palma virus was transmitted to D. marginatus and D. reticulatus males, D. reticulatus and R. sanguineus females, and R. appendiculatus nymphs while cofeeding with infected ticks on laboratory mice. Bhanja virus was transmitted to D. marginatus males and R. appendiculatus nymphs. Laboratory mice developed low levels of viraemia detectable only by intracranial (i.c.) inoculation of newborne laboratory mice.

Animals↗
PubMed1996

Importance of localized skin infection in tick-borne encephalitis virus transmission.

Arboviruses are transmitted to vertebrates by the "bite" of infected arthropods. Events at the site of virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) virus transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus). Virus transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels > or = 2.0 log10 ic mouse LD50/0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE virus transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne virus transmission.

Animals↗
PubMed1996

[Treatment of choledocholithiasis in the era of laparoscopic cholecystectomy].

Laparoscopic cholecystectomy (L-CHE) is currently considered to be the optimal standard in the therapy of cholecystolithiasis. However, it is choledocholithiasis which is problematic, especially the timing of the solution in relation to L-CHE. In general, the opinion predominates that in preoperatively verified choledocholithiasis the ERCP with EPS and extraction of choleliths should be performed 24-28 hours prior to the elective L-CHE. Surgical removal of choleliths from the main biliary ducts indicated only in a small group of patients. The authors of the study reflect upon the current trends of the choledocholithiasis therapy in the era of laparoscopic cholecystectomy. They present their own set of patients and recommend the procedure of the choledocholithiasis therapy concommitted with cholecystolithiasis with the subjective of the full use of endoscopic methods in the therapy of this disease. (Ref. 14.).

Adult↗
PubMed1996

Linkage disequilibrium analysis in young populations: pseudo-vitamin D-deficiency rickets and the founder effect in French Canadians.

Pseudo-vitamin D-deficiency rickets (PDDR) was mapped close to D12S90 and between proximal D12S312 and distal (D12S305, D12S104) microsatellites that were subsequently found on a single YAC clone. Analysis of a complex haplotype in linkage disequilibrium (LD) with the disease discriminated among distinct founder effects in French Canadian populations in Acadia and in Charlevoix-Saguenay-Lac-Saint-Jean (Ch-SLSJ), as well as an earlier one in precolonial Europe. A simple demographic model suggested the historical age of the founder effect in Ch-SLSJ to be approximately 12 generations. The corresponding LD data are consistent with this figure when they are analyzed within the framework of Luria-Delbrück model, which takes into account the population growth. Population sampling due to a limited number of first settlers and the rapid demographic expansion appear to have played a major role in the founding of PDDR in Ch-SLSJ and, presumably, other genetic disorders endemic to French Canada. Similarly, the founder effect in Ashkenazim, coinciding with their early settlement in medieval Poland and subsequent expansion eastward, could explain the origin of frequent genetic diseases in this population.

Base Sequence↗
PubMed1995

Ixodid tick salivary gland extracts inhibit production of lipopolysaccharide-induced mRNA of several different human cytokines.

Extracts prepared from the salivary glands (SGE) of partially fed adult female Rhipicephalus appendiculatus ticks reduced the expression by human peripheral blood leukocytes 9PBLs) of lipopolysaccharide (LPS)-stimulated cytokine mRNA. Treatment with SGE had no obvious effect on cytokine mRNA production when compared with untreated PBLs. LPS treatment induced or increased mRNA production for IFN alpha, TNF-alpha, IL-1 alpha, IL-1 beta, IL-5, IL-6, IL-7 and IL-8. All the LPS-stimulated cytokine mRNAs were reduced when treated with a mixture of LPS and SGE. The results indicate the potential of ticks in modulating the cytokine network of their vertebrate hosts, possibly to facilitate blood feeding.

Animals↗
PubMed1995

Genetic characterization of a new hantavirus detected in Microtus arvalis from Slovakia.

A new hantavirus, called Malacky, has been identified in lung tissue specimens of a vole, Microtus arvalis, by the reverse transcriptase polymerase chain reaction (RT-PCR). The voles were trapped in a geographical area in Slovakia where hemorrhagic fever with renal syndrome (HFRS) is endemic in the human population. Sequence analysis of a major part of the S segment showed this virus to represent a new subtype within Tula, a new hantavirus genetic group defined very recently.

Amino Acid Sequence↗
PubMed1995

Mixed natural focus of tick-borne encephalitis, tularemia and haemorrhagic fever with renal syndrome in west Slovakia.

Total of 923 small mammals of 7 species were collected in locality Záhorská Ves, West Slovakia, in 1990-1992. Among examined small mammal species it was Clethrionomys glareolus (48.7% of total, 17.5% positive for tick-borne encephalitis (TBE) virus antibodies), Apodemus flavicollis (29.7% of total, 17.5% positive), A. sylvaticus (11.3% of total, 16.3% positive), and Microtus arvalis (6.2% of total, 10.5% positive). The most abundant tick species (larval and nymphal stages) on small mammals was Ixodes ricinus. The extensity of infestation was 35.1-50.7%, and the intensity of infestation ranged in average from 4.1 to 7.8 ticks per animal. Out of 884 small rodent serum samples 16.9% had neutralizing antibody to TBE virus. Eight TBE virus isolates were recovered, six from C. glareolus and one each from A. flavicollis and A. sylvaticus; seven isolates were from brain tissue and one was from a pool of lung and liver tissues. One strain of Francisella tularensis was isolated from a pool of spleens of four C. glareolus collected in August 1991. Hantavirus antigens were detected in lung tissues of four M. arvalis collected in July and November 1990-1992. Antibody to Hantaan virus was detected by ELISA in one serum sample of A. flavicollis (titer 1:256) and antibody to Puumala virus in one serum sample of C. glareolus (titer 1:16).

Animals↗
PubMed1995

[Splenectomy and sparing surgery of the spleen].

In 1958-1993 the authors made at the Second Surgical Clinic in Bratislava 357 splenectomies on account of haematological diseases and four conservative operations of the spleen. They consider it inevitable to seek accessory spleens and to drain the left subphrenic space. Analysis of long-term results revealed that clinical and laboratory remission was achieved in particular in lienal types of destruction. The authors draw attention to the possibility of preserving the spleen or its part in some lienal diseases such as pseudocysts and cysts of non-parasitic origin. In conservative operations of the spleen the use of the fibrin glue. Tissuecol, is of basic importance. It was shown that 25-30% of the original tissue suffices to preserve complete function of the spleen.

Adolescent↗
PubMed1995

Nucleotide sequence of the protein E gene of the tick-borne encephalitis virus strain 595 isolated in Slovakia.

Tick-borne encephalitis (TBE) virus, strain 595 was isolated from Ixodes ricinus ticks in southern Slovakia. A part of the protein E gene was sequenced and compared with the prototype strain Neudorfl. Seventeen silent mutations and two amino acid changes (Ile-->Val, residue 167; Asn-->Thr, residue 366) were found. The nucleotide homology in the sequenced part of protein E gene of the strain 595 and the prototype strain Neudorfl is 98.6%. These findings indicate that the strain 595 is closely related to the strain Neudorfl.

Amino Acid Sequence↗
PubMed1994

Change in phenotype of tick-borne encephalitis virus following passage in Ixodes ricinus ticks and associated amino acid substitution in the envelope protein.

Serial passage of an uncloned tick-borne encephalitis virus (strain 4387 isolated from the liver and lungs of a bank vole) in Ixodes ricinus ticks, was accompanied by gradual reduction in virulence of the virus, as indicated by transmission of virus by infected ticks feeding on laboratory mice. After the 7th serial passage in ticks (strain 4387/7), 95% of mice survived the bite of infected ticks. The surviving infected mice showed either no or only low viraemia although virus could be isolated from the brains of some mice 14 and 30 days after commencement of tick feeding, implying that the tick passaged virus might have established a persistent infection in the mice. Tests for haemagglutinating capacity were positive with TBE strain 4387 but strain 4387/7 exhibited no haemagglutinating activity over a wide pH range, suggesting that phenotypic changes, resulting from selection, had affected the site on the viral envelope protein that binds red blood cell receptors. Sequencing of the envelope protein gene of the virulent TBE strain 4387 showed 3 amino acid codon differences from western European TBE virus strain Neudorfl, which is also virulent for mice. The attenuated virus 4387/7, had an amino acid substitution that was different from 4387 and Neudorfl TBE virus (amino acid 84, E to K) and a second substitution different from 4387 but identical to Neudorfl virus (amino acid 319, I to T). Thus, the phenotypic change from virulence to attenuation was associated with a single amino acid codon change in the viral envelope gene of TBE virus. It is recognised, however, that amino acid substitutions in other parts of the viral genome have not been ruled out.

Amino Acid Sequence↗
PubMed1994

Adaptations of arboviruses to ticks.

Arboviruses differ from other viruses in their need to replicate in both vertebrate and invertebrate hosts. The invertebrate is a blood-sucking arthropod that is competent to transmit the virus between susceptible animals. Arboviruses transmitted by ticks must adapt to the peculiar physiological and behavioral characteristics of ticks, particularly with regard to blood feeding, bloodmeal digestion, and molting. Virus imbibed with the blood meal first infects cells of the midgut wall. During this phase the virus must contend with the heterophagic bloodmeal digestion of ticks (an intracellular process occurring within midgut cells) and overcome the as yet undefined "gut barrier" to infection. Genetic and molecular data for a number of tick-borne viruses indicate ways in which such viruses may have adapted to infecting ticks, but far more information is needed. After infection of midgut cells, tick-borne viruses pass to the salivary glands for transmission during the next blood-feeding episode. To do this, the virus must survive molting by establishing an infection in at least one cell type that does not undergo histolysis. Different tick-borne viruses have different strategies for surviving the molting period, targeting a variety of tick tissues. The infection can then persist for the life span of the tick with little evidence of any detrimental effects on the tick. Transmission to a vertebrate host during feeding most probably occurs via saliva that contains virus secreted from infected salivary gland cells. The virus then enters the skin site of feeding, which has been profoundly modified by the pharmacological effects of tick saliva. At least three tick-borne viruses exploit such tick-induced host changes. This phenomenon (saliva-activated transmission) is believed to underlie "nonviremic transmission," whereby a virus is transmitted from an infected to an uninfected cofeeding tick through a host that has an undetectable or very low viremia. Thus tick-borne viruses that have adapted to the feeding characteristics of their tick vectors may not need to induce a virulent infection (with high viremia) in their natural vertebrate hosts. Efficient transmission of tick-borne viruses between cofeeding ticks may be a means of amplifying virus infection prevalence in F1 generations infected by transovarial transmission.

Adaptation, Physiological↗
PubMed1994

Reverted virulence of attenuated tick-borne encephalitis virus mutant is not accompanied with the changes in deduced viral envelope protein amino acid sequence.

Serial passages of tick-borne encephalitis (TBE) virus strain 4387 isolated from the liver and lungs of the bank vole through the salivary glands of Ixodes ricinus ticks led to a reduction of its virulence for laboratory mice infected via peripheral route. When attenuated mutants were passaged through mouse brains, virulent phenotypes have appeared in the 3rd mouse passage. After 5 consecutive passages the virus was more pathogenic for mice after peripheral inoculation than the parental 4387 strain. The nucleotide sequence of the envelope proteins of the strain 4387 was studied after passaging through ticks salivary glands and subsequently through mice. The sequences coding for the envelope protein E of the virus from the first, third and fifth mouse passages were compared with those of parental virus and mutant attenuated in ticks. The attenuated mutant differing from the parental strain 4387 by the amino acid substitution from glutamic acid to lysine at position 84, and from isoleucine to threonine at amino acid position 319 revealed strongly reduced pathogenicity for adult laboratory mice after peripheral inoculation. The attenuated mutant regained its virulence after 3 - 5 mouse brain passages, but the two amino acid substitutions were still conserved.

Amino Acid Sequence↗
PubMed1994

[Familial epidemics of tick-borne encephalitis in central Povazie].

The authors describe two cases of tick-born encephalitis family epidemies in the natural focus of tick-born encephalitis (TbE) in the central part of Povazie in the district of Povazká Bystrica in the years 1989 and 1993. The infection took place due to consumption of raw goat milk. The best prevention against tick-born encephalitis is represented by vaccination. (Tab. 4, Ref. 6.)

Adult↗
PubMed1994

Salivary gland extracts of partially fed Dermacentor reticulatus ticks decrease natural killer cell activity in vitro.

The salivary glands and saliva of ticks (Arachnida, Acari, Ixodida) play a vital role in blood feeding, including manipulation of the host's immune response to tick infestation. Furthermore, a diverse number of tick-borne pathogens are transmitted to vertebrate hosts via tick saliva. A factor synthesized in the salivary glands of feeding ticks potentiates the transmission of certain tick-borne viruses. We show that salivary gland extracts (SGE) derived from Dermacentor reticulatus female ticks fed for 6 days on laboratory mice (SGED6) induced a decrease in the natural killer (NK) activity of effector cells obtained from 16 healthy blood donors. The decreased activity ranged from 14 to 69% of NK activity observed with the respective untreated effector cells. Such a decrease was not observed after treatment of effector cells with SGE from unfed ticks. Ten-fold dilution of SGED6 significantly reduced the capacity to decrease NK activity and a further 10-fold dilution almost eliminated the effect. After addition of IFN-alpha 2, the SGED6-induced decrease in NK activity was restored to activity levels approaching those of untreated cells. The apparent reversibility of the inhibition indicates that the effect of SGED6 on NK activity was not due to cytotoxicity. The results demonstrate the presence of a factor(s) in the salivary gland products of feeding D. reticulatus female ticks that influences human NK activity in vitro. These data suggest a possible mechanism by which tick SGE potentiates the transmission of some tick-borne viruses through suppression of NK activity.

Animals↗
PubMed1993

Non-viraemic transmission of tick-borne encephalitis virus: a mechanism for arbovirus survival in nature.

The vectors of arthropod-borne viruses (arboviruses) become infected by feeding on the viraemic blood of an infected animal. This theory is based on transmission studies involving artificial infection of vertebrate hosts by syringe inoculation. To reproduce natural conditions of virus transmission, infected and uninfected vectors (ticks) of tick-borne encephalitis virus, the most important arbovirus in Europe, were allowed to feed together on uninfected wild vertebrate hosts. The greatest numbers of infected ticks were obtained from susceptible host species that had undetectable or very low levels of viraemia. The results suggest that 'nonviremic transmission' is an important mechanism for the survival of certain arboviruses in nature.

Animals↗