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S Sommer

Publications and source records attributed to S Sommer.

At least 19 recordsLinked to original sources
PubMed2006

[Can preoperative fine-needle aspiration of parotid tumors pose problems for a definitive histological diagnosis?].

INTRODUCTION: Fine-needle aspiration cytology (FNAC) is a minimally invasive procedure that offers high specifity and acceptable sensitivity in the preoperative diagnosis of parotid tumors. FNAC provides information that can be particularly valuable in surgical planning and patient education. In some cases, it may even help prevent unnecessary surgery. After an FNA procedure, on rare occasions, morphological changes in the tumor may be observed and can make a definitive histological examination difficult or even impossible. METHODS: Histopathological changes in parotid tumors after preoperative FNAC are described on the basis of a case report and a survey of the literature. RESULTS: In rare cases, puncture-induced histopathological changes, such as hyalinization of the subepithelial stroma, necrosis and squamous metaplasia, so extensive that a definitive histological diagnosis is difficult, are observed. In the present case report, fine-needle aspiration of a 3 x 2 cm tumor, which had been classified as malignant on the basis of cytological findings, resulted in complete necrosis and made a definitive histological diagnosis impossible. Similar cases have been described by other authors in recent years. DISCUSSION: In rare cases, histological changes in the tumor tissue can occur after an FNA procedure, making a definitive histological examination difficult or even impossible. When a preoperative FNAC is performed, the pathologist in charge should be advised accordingly. In addition, patients should be informed about this infrequent risk before undergoing the procedure.

Aged↗
PubMed2005

Association between major histocompatibility complex class II DRB alleles and parasite load in the hairy-footed gerbil, Gerbillurus paeba, in the southern Kalahari.

We investigated the importance of the MHC-constitution (major histocompatibility complex-constitution) on the endoparasite load in free-range hairy-footed gerbils (Gerbillurus paeba) in the southern Kalahari Desert. While the number of alleles of the duplicated DRB exon 2 gene had no significant effects on the individual status of being 'not infected' or 'infected' and on the number of helminth morphotype infections per individual, it significantly affected the faecal egg count values. One allele (Gepa-DRB*15) was only found in uninfected mice. Our results support the hypotheses that MHC polymorphism in G. paeba is maintained by pathogen-driven selection. The present study is the first investigation on associations between duplicated DRB gene loci and the parasite load in mammals.

Animals↗
PubMed2005

MHC diversity and the association to nematode parasitism in the yellow-necked mouse (Apodemus flavicollis).

In vertebrates, the genes of the major histocompatibility complex (MHC) are among the most debated candidates accounting for co-evolutionary processes of host-parasite interaction at the molecular level. The exceptionally high allelic polymorphism found in MHC loci is believed to be maintained by pathogen-driven selection, mediated either through heterozygous advantage or rare allele advantage (= frequency dependent selection). While investigations under natural conditions are still very rare, studies on humans or mice under laboratory conditions revealed support for both hypotheses. We investigated nematode burden and allelic diversity of a functional important MHC class II gene (DRB exon2) in free-ranging yellow-necked mice (Apodemus flavicollis). Twenty-seven distinct Apfl-DRB alleles were detected in 146 individuals with high levels of amino acid sequence divergence, especially at the antigen binding sites (ABS), indicating selection processes acting on this locus. Heterozygosity had no influence on the infection status (being infected or not), the number of different nematode infections (NNI) or the intensity of infection, measured as the individual faecal egg count (FEC). However, significant associations of specific Apfl-DRB alleles to both nematode susceptibility and resistance were found, for all nematodes as well as in separate analyses of the two most common nematodes. Apodemus flavicollis individuals carrying the alleles Apfl-DRB*5 or Apfl-DRB*15 revealed significantly higher FEC than individuals with other alleles. In contrast, the allele Apfl-DRB*23 showed a significant association to low FEC of the most common nematode. Thus, our results provide evidence for pathogen-driven selection acting through rare allele advantage under natural conditions.

Alleles↗
PubMed2005

Parasite burden and constitution of major histocompatibility complex in the Malagasy mouse lemur, Microcebus murinus.

We investigated the importance of the major histocompatibility complex (MHC) constitution on the parasite burden of free-ranging mouse lemurs (Microcebus murinus) in four littoral forest fragments in southeastern Madagascar. Fourteen different MHC class II DRB-exon 2 alleles were found in 228 individuals with high levels of sequence divergence between alleles. More nonsynonymous than synonymous substitutions in the functional important antigen recognition and binding sites indicated selection processes maintaining MHC polymorphism. Animals from the four forest fragments differed in their infection status (being infected or not), in the number of different nematode morphotypes per individual (NNI) as well as in the fecal egg counts (FEC) values. Heterozygosity in general was uncorrelated with any of these measures of infection. However, a positive relationship was found between specific alleles and parasite load. Whereas the common allele Mimu-DRB*1 was more frequently found in infected individuals and in individuals with high NNI and FEC values (high parasite load), the rare alleles Mimu-DRB*6 and 10 were more prevalent in uninfected individuals and in individuals with low NNI and FEC values (low parasite load). These three alleles associated with parasite load had unique amino acid motifs in the antigen binding sites. This distinguished them from the remaining 11 Mimu-DRB alleles. Our results support the hypothesis that MHC polymorphism in M. murinus is maintained through pathogen-driven selection acting by frequency-dependent selection. This is the first study of the association of MHC variation and parasite burden in a free-ranging primate.

Analysis of Variance↗
PubMed2004

Mismatch repair ensures fidelity of replication and recombination in the radioresistant organism Deinococcus radiodurans.

We have characterized the mismatch repair system (MMR) of the highly radiation-resistant type strain of Deinococcus radiodurans, ATCC 13939. We show that the MMR system is functional in this organism, where it participates in ensuring the fidelity of DNA replication and recombination. The system relies on the activity of two key proteins, MutS1 and MutL, which constitute a conserved core involved in mismatch recognition. Inactivation of MutS1 or MutL resulted in a seven-fold increase in the frequency of spontaneous RifR mutagenesis and a ten-fold increase in the efficiency of integration of a donor point-mutation marker during bacterial transformation. Inactivation of the mismatch repair-associated UvrD helicase increased the level of spontaneous mutagenesis, but had no effect on marker integration--suggesting that binding of MutS1 and MutL proteins to a mismatched heteroduplex suffices to inhibit recombination between non identical (homeologous) DNAs. In contrast, inactivation of MutS2, encoded by the second mutS -related gene present in D. radiodurans, had no effect on mutagenesis or recombination. Cells devoid of MutS1 or MutL proteins were as resistant to gamma-rays, mitomycin C and UV-irradiation as wild-type bacteria, suggesting that the mismatch repair system is not essential for the reconstitution of a functional genome after DNA damage.

Amino Acid Sequence↗
PubMed2004

Systemic lupus erythematosus or infection with HIV, or both?

The features of both HIV infection and connective tissue disease are often nonspecific and may mimic other disorders as well as each other. We treated a patient with presumed systemic lupus erythematosus (SLE) for 4 years, who finally admitted to longstanding infection with HIV. The coexistence of SLE and HIV is unusual and has, although reported in the rheumatological journals, not often been discussed in the dermatological literature.

Adult↗
PubMed2004

Cytogenetic damage in lymphocytes for the purpose of dose reconstruction: a review of three recent radiation accidents.

The analysis of chromosomal aberrations in peripheral blood of radiation accident victims is an established method of biological dosimetry. The dose estimate on the basis of an in vitro calibration curve is straightforward when the radiation exposure is homogeneous and the analysis not delayed. In recent years three radiation accidents occurred, where the irradiation or sampling conditions precluded a simple estimation of the dose. During the Georgian accident soldiers carried in their pockets small sources of 137Cs leading to partial and protracted body exposures. During the Tokai-mura accident, three employees involved in the process of 235U enrichment were exposed to very high doses of gamma rays and neutrons. During the Bialystok accident, five patients with breast cancer undergoing radiotherapy were exposed to a single dose of electrons which reached about 100 Gy. In the present paper the approaches chosen to estimate, by cytogenetic methods, the doses absorbed by the people involved in the accidents are described.

Breast Neoplasms↗
PubMed2003

The ant's estimation of distance travelled: experiments with desert ants, Cataglyphis fortis.

Foraging desert ants, Cataglyphis fortis, monitor their position relative to the nest by path integration. They continually update the direction and distance to the nest by employing a celestial compass and an odometer. In the present account we addressed the question of how the precision of the ant's estimate of its homing distance depends on the distance travelled. We trained ants to forage at different distances in linear channels comprising a nest entrance and a feeder. For testing we caught ants at the feeder and released them in a parallel channel. The results show that ants tend to underestimate their distances travelled. This underestimation is the more pronounced, the larger the foraging distance gets. The quantitative relationship between training distance and the ant's estimate of this distance can be described by a logarithmic and an exponential model. The ant's odometric undershooting could be adaptive during natural foraging trips insofar as it leads the homing ant to concentrate the major part of its nest-search behaviour on the base of its individual foraging sector, i.e. on its familiar landmark corridor.

Animal Migration↗
PubMed2003

In situ experimental evidence of the fate of a phytodetritus pulse at the abyssal sea floor.

More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic communities, and a large fraction of the annual food load can arrive in pulses within a few days. Owing to logistical constraints, the available data concerning the fate of such a pulse are scattered and often contradictory, hampering global carbon modelling and anthropogenic impact assessments. We quantified (over a period of 2.5 to 23 days) the response of an abyssal benthic community to a phytodetritus pulse, on the basis of 11 in situ experiments. Here we report that, in contrast to previous hypotheses, the sediment community oxygen consumption doubled immediately, and that macrofauna were very important for initial carbon degradation. The retarded response of bacteria and Foraminifera, the restriction of microbial carbon degradation to the sediment surface, and the low total carbon turnover distinguish abyssal from continental-slope 'deep-sea' sediments.

Animals↗
PubMed2003

Efficacy of pulsed dye laser treatment of port wine stain malformations of the lower limb.

BACKGROUND: There is relatively little information about treatment of port wine stains (PWS) of the lower limb. Few studies have specifically addressed the efficacy of pulsed dye laser (PDL) treatment of a PWS on the lower limb and there is no information on the relative efficacy at different sites on the lower limb. It has been suggested that treatment is not as successful when compared with the face and postinflammatory hyperpigmentation has been reported to be a significant problem. OBJECTIVES: To review retrospectively patients who attended for PDL treatment of PWS affecting the lower limb and assess the efficacy and adverse effects with particular reference to skin site. METHODS: A retrospective review was carried out of patients attending the Leeds Dermatology Laser Centre for treatment of a PWS on the lower limb with a 585-nm PDL. RESULTS: A total of 52 sites in 39 patients were treated: 17 on the thigh, 31 on the lower leg and four on the foot. The mean number of sessions per patient was 14, with an excellent outcome in seven treatment sites (13.5%), good in 13 (25%), moderate in 21 (40.4%) and poor outcome in 11 (21.1%). Patients were generally pleased with their results with a mean improvement of 7 on a scale of 0-10. Perifollicular persistence of the PWS was observed in six sites (11.5%). Adverse effects occurred in 36 patients (92.3%), most commonly hyperpigmentation (87%). Six patients (15.4%) developed atrophic scarring and four (10.3%) hypopigmentation. Atrophie blanche-like changes were seen in four patients on the lower leg. Hypertrophic scarring was not seen. CONCLUSIONS: Although physician-assessed good or excellent responses of 38.5% are lower than frequently reported for other skin sites and adverse effects may be more frequent, patient satisfaction with treatment was generally high. Patients with PWS on the lower limb merit a trial of PDL treatment.

Adolescent↗
PubMed2003

Prediction of outcome in the treatment of onychomycosis.

Patients with toenail onychomycosis remain a therapeutic challenge despite the introduction of new systemic therapies. Around 20% of patients remain uncured even with optimal oral therapy, but the reasons for treatment failure are unclear. Thus far there are no data to suggest that treatment failures can be identified on the basis of their presenting features or progress during treatment. In a series of patients, we have attempted to identify clinical parameters that determine the patient response to 12 weeks of oral terbinafine for confirmed dermatophyte onychomycosis. As part of a dose-defining randomized multicentre study, 35 patients were followed for 48 weeks. The unaffected nail length, growth rate, hyperkeratosis, onycholysis and presence of a dermatophytoma were assessed prospectively. To confirm our findings, at the end of the study period we analysed retrospectively photographs that had been taken regularly throughout the trial. The average degree of hyperkeratosis was less severe in the group achieving a disease-free nail, meaning clinical and mycological cure. For mycological cure alone, no predictive factors could be identified.

Administration, Oral↗
PubMed2003

Effects of habitat fragmentation and changes of dispersal behaviour after a recent population decline on the genetic variability of noncoding and coding DNA of a monogamous Malagasy rodent.

While interactions among demography, behaviour and genetic structure are well-documented for neutral genetic markers, the role of these parameters and the effects of genetic drift and selection are considerably less well understood in functional genes, such as the major histocompatibility complex (MHC). In this study, the consequences of habitat fragmentation and the effects of a current population decline on noncoding (mitochondrial DNA) and two coding MHC loci (DQA, DRB) with different functional importance were investigated in the small remnant subdivided population of the endangered Malagasy giant jumping rat (Hypogeomys antimena). Both neutral and selective markers revealed a significant genetic differentiation between the two remnant subpopulations. The FST values were much lower in the MHC DQA and DRB genes than in the mitochondrial data. The MHC DRB loci display the effects of both balancing selection (high sequence diversity, four times higher nonsynonymous than synonymous substitutions in the functionally important antigen-binding site positions, twice the average heterozygosity of individual amino acids at the positions identified as part of the antigen-binding site (ABS) than those outside the ABS and nonselective forces including genetic drift. Simultaneously with a current population decline offspring reduced their dispersal distances. No substantial effects were detected within the first 6 years of reduced gene flow in either mitochondrial or MHC markers.

Animals↗
PubMed2002

Quantification of RecA protein in Deinococcus radiodurans reveals involvement of RecA, but not LexA, in its regulation.

RecA protein is essential for the very high level of resistance of Deinococcus radiodurans to DNA damage induced by ionizing radiation or other DNA-damaging agents. Since the mechanism(s) involved in the control of recA expression and the extent of RecA induction following DNA damage in this species are still unclear, we have performed a genetic analysis of the recA locus and quantified the basal and induced levels of RecA protein in wild type, recA, and lexA mutants. We found that the two genes upstream of recA in the predicted cinA ligT recA operon appear to have no role in the regulation of recA expression or function, despite the fact that the reading frames in the operon overlap. By using a translational fusion of recA to a lacZ reporter gene, we showed that induction began with no delay following exposure to gamma-radiation or treatment with mitomycin, and continued at a constant rate until it reached a plateau. The induction efficiency increased linearly with inducer dose, levelling off at a concentration fourfold above the background. The basal concentration of RecA protein measured by Western blotting corresponded to approximately 11,000 monomers per cell, and the induced concentration to around 44,000 monomers per cell. These levels remained unchanged upon disruption of the lexA gene, indicating that LexA does not plays a role in recA regulation. However, inactivation of lexA caused cells to aggregate, suggesting that LexA may control the activity or expression of as yet undefined membrane functions. Cells bearing the recA670 mutation showed an elevated constitutive expression of recA in the absence of DNA damage. This phenotype did not result from the defect in DNA repair associated with the RecA670 protein, since the increased basal level of recA expression was also found in recA670/ recA(+) diploid cells that are proficient in DNA repair. These results suggest that RecA may be involved in regulating its own expression, possibly by stimulating proteolytic modification of other regulatory proteins.

Bacterial Proteins↗
PubMed2002

Type IV hypersensitivity reactions to natural rubber latex: results of a multicentre study.

BACKGROUND: Positive patch test reactions to natural rubber latex (NRL) have been interpreted as allergic or irritant by different groups. Additives to the NRL test solution have also caused positive reactions in previous studies. OBJECTIVES: Five centres of the British Contact Dermatitis Group conducted a prospective study on the prevalence of type IV hypersensitivity to NRL, using ammonia-preserved NRL solution for testing. PATIENTS AND METHODS: A total of 2738 consecutive patients were patch tested. Where clinically indicated, specific IgE was measured or a prick test done. RESULTS: Twenty-seven patients (1%) had a positive patch test reaction to NRL, which was considered to be allergic and of current relevance in 19 (70%) patients. Fourteen of these also had a positive prick test or specific IgE. Thirteen patients (48%) were male, 19 (70%) atopic and 13 (48%) had eczema on their hands. CONCLUSIONS: We conclude that delayed-type hypersensitivity to NRL is a problem for a proportion of patients with eczema, particularly on their hands, and that patch testing with ammonia-preserved NRL can be recommended to identify these patients. Patients with a positive patch test should be investigated for contact urticaria to NRL.

Adult↗
PubMed2002

Eczema: quality of life by body site and the effect of patch testing.

BACKGROUND: Patients with dermatitis are known to have impaired quality of life. Whether this varies according to body site has not been evaluated. Patch tests have previously been shown to influence quality of life, although no previous studies have shown if this is dependent on the results of the patch tests. OBJECTIVES: To evaluate the impact of patch testing on quality of life according to the outcome of the investigations and to determine how quality of life varies according to eczema body site. METHODS: One hundred and sixty consecutive adult patients with active eczema were selected from a patch test clinic for inclusion into the study. Quality of life was determined using the Dermatology Life Quality Index (DLQI) and the SF-36, prior to patch testing and 2 months later. Perceived eczema severity at each time point was also noted, along with the outcome of patch testing. Baseline comparison of quality of life was performed between four body site groups (face, hand, generalized, other). RESULTS: Patients confirmed as having relevant positive contact allergens were shown to have a significant improvement in both perceived eczema severity (P = 0.0004) and DLQI score (P = 0.0015) at 2 months after patch testing. No significant changes were noted in the SF-36 score, other than a borderline improvement in the pain score (P = 0.048). The improvement in quality of life and eczema severity was not noted in patients with negative patch tests. Eighty-nine per cent of patients diagnosed as having contact allergy were able to comply with avoidance advice. No significant variation was noted in quality of life according to body site affected by eczema. There was a positive correlation between DLQI score and perceived eczema severity (P < 0.0001). CONCLUSIONS: Patients confirmed as having contact allergy show a subsequent improvement in eczema severity and an improvement in quality of life.

Adolescent↗
PubMed2002

Type-IV hypersensitivity to betamethasone valerate and clobetasol propionate: results of a multicentre study.

BACKGROUND: Most studies investigating steroid allergy have been performed with tixocortol pivalate, hydrocortisone butyrate and budesonide. Betnovate and Dermovate are widely prescribed in the U.K. but little is known about the frequency of sensitization to them. OBJECTIVES: To determine the optimum method to detect contact allergy to betamethasone valerate (BV) and clobetasol propionate (CP). METHODS: Seven centres tested consecutive patients attending for investigation of suspected allergic contact dermatitis to these steroids at a range of concentrations in different vehicles. RESULTS: Of 1562 patients tested, 16 (1%) reacted to either BV or CP. Ten patients (0.7%) reacted to BV and 13 (0.8%) to CP. Two patients of a further centre were included in analysis of dilutions and vehicles. Sixteen of a total of 25 reactions (64%) were identified with a 1% dilution in ethanol. CONCLUSIONS: Consideration should be given to adding BV and CP to a standard allergy series, given that both are frequently used in the treatment of eczema and that most patients sensitized to them are not identified with currently used markers of steroid allergy. If patch tests to BV and CP are initially negative, but an allergy is suspected, the patient should be further investigated. Further studies are required to identify the ideal patch test material.

Adult↗