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Biomedical subjects

C Scheidegger

Publications and source records attributed to C Scheidegger.

At least 19 recordsLinked to original sources
PubMed2004

Recombination and clonal propagation in different populations of the lichen Lobaria pulmonaria.

Propagation, dispersal, and establishment are fundamental population processes, and are critical stages in the life cycle of an organism. In symbiotic organisms such as lichens, consisting of a fungus and a population of photobionts, reproduction is a complex process. Although many lichens are able to reproduce both sexually and asexually, the extent of vegetative propagation within local populations is unknown. We used six polymorphic microsatellite loci to investigate whether recombination is common in natural populations, and to assess if and how clonal reproduction influences the spatial genetic structure within populations of the epiphytic lichen species Lobaria pulmonaria. High genetic diversity within all 12 investigated populations and evidence of recombination, from various tests, indicated that L. pulmonaria is a predominantly outcrossing species. Nevertheless, clonality occurred in all populations, but the presence of recurring multilocus genotypes influenced the spatial genetic structure only within low-density populations. This could be interpreted as indicative of genetic bottlenecks owing to increased habitat loss and disturbance. Consequently, for a predominantly outcrossing lichen species, exogenous factors might be substantially altering population processes and hence genetic structure.

DNA, Plant↗
PubMed2003

Regulation of cell expansion by the DISTORTED genes in Arabidopsis thaliana: actin controls the spatial organization of microtubules.

The control of the directionality of cell expansion was investigated using a class of eight genes, the so-called DISTORTED (DIS) genes, that are required for proper expansion of leaf trichomes in Arabidopsis thaliana. By tracing the separation of latex beads placed on the trichome surface, we demonstrate that trichomes grow by diffuse rather than tip growth, and that in dis mutants deviations from the normal orientation of growth can occur in all possible directions. We could not detect any differences in intracellular organization between wild-type and dis-group mutants by electron microscopy. The analysis of double mutants showed that although the expression of the dis phenotype is generally independent of branching and endoreduplication, dis mutations act synthetically in combination lesions in the ZWI gene, which encodes a kinesin motor protein. Using a MAP4:GFP marker line, we show that the organization of cortical microtubules is affected in dis-group mutants. The finding that most dis-group mutants have actin defects suggested to us that actin is involved in organizing the orientation of microtubules. By analyzing the microtubule organization in plants treated with drugs that bind to actin, we verified that actin is involved in the positioning of cortical microtubules and thereby in plant cell expansion.

Actins↗
PubMed2001

[Cold agglutinins of the IgM class in a patient with monoclonal gammopathy of the IgA class].

HISTORY AND CLINICAL PRESENTATION: A 61-year-old patient was examined in hospital because he had suffered from fatigue and weight loss for several years. History and physical examination showed no symptoms specific for a disease of a particular organ except a goitre. INVESTIGATIONS: Laboratory examination serum showed a decreased haptoglobin, a slightly elevated bilirubin, an acceleration of the blood sedimentation rate and a M-gradient in the protein electrophoresis. The immunofixation electrophoresis revealed a monoclonal gammopathy of the IgA-class. The cold agglutinin titre was clearly elevated (2048 at 4 degrees C), caused by an auto-anti-I of the IgM-class. No signs of an infection or a haematological neoplasm were found. TREATMENT AND COURSE: No specific therapy was given for the compensated haemolytic anaemia and the monoclonal gammopathy. There was no significant change in the course of the disease over 5 years. CONCLUSION: Between the specificity and the immunoglobulin class of cold agglutinins correlations exist that are also of significance for these autoantibodies. As shown by this case, an exact analysis of the specificity and the immunoglobulin class of cold agglutinins should be done in cases with unusual combinations of laboratory results to prevent misleading interpretations.

Agglutinins↗
PubMed2001

Species-specific detection of Lobaria pulmonaria (lichenized ascomycete) diaspores in litter samples trapped in snow cover.

The foliose lichen Lobaria pulmonaria has suffered a substantial decline in central and northern Europe during the twentieth century and is now considered to be critically endangered in many European lowland regions. Based on demographic studies, it has been proposed that under the present environmental conditions and forest management regimes, dispersal of diaspores and subsequent establishment of new thalli are insufficient to maintain the remnant small lowland populations. Chances of long-term survival may therefore be reduced. The data and analytical power of these demographic studies are limited. Since lichen diaspores show very few species-specific morphological characteristics, and are therefore almost indistinguishable, the accurate assessment of diaspore flux would be a fundamental first step in better understanding the life cycle of L. pulmonaria. Here we present a new molecular approach to investigate the dispersal of L. pulmonaria diaspores in its natural environment by specifically identifying small amounts of DNA in snow litter samples at varying distances from known sources. We used a species-specific polymerase chain reaction (PCR) primer pair to amplify the ribosomal internal transcribed spacer region (ITS rDNA) and a sensitive automated PCR product detection system using fluorescent labelled primers. We detected considerable amounts of naturally dispersed diaspores, deposited as far as 50 m away from the closest potential source. Diaspores were only found in the direction of the prevailing wind. Diaspore deposition varied from 1.2 diaspores per m(2) per day at 50 m distance from the source to 15 diaspores per m(2) per day at 1 m distance. The method described in this paper opens up perspectives for studies of population dynamics and dispersal ecology mainly in lichenized ascomycetes but also in other organisms with small, wind-dispersed diaspores.

Lichens↗
PubMed1999

Genetic variation within and among populations of the threatened lichen Lobaria pulmonaria in Switzerland and implications for its conservation.

The foliose epiphytic lichen Lobaria pulmonaria has suffered a significant decline in European lowlands during the last decades and therefore is considered as endangered throughout Europe. An assessment of the genetic variability is necessary to formulate biologically sound conservation recommendations for this species. We investigated the genetic diversity of the fungal symbiont of L. pulmonaria using 143 specimens sampled from six populations (two small, one medium, three large) in the lowland, the Jura Mountains, the pre-Alps and the Alps of Switzerland. Among all nuclear and mitochondrial regions sequenced for this study, variability was found only in the internal transcribed spacer (ITS I), with three polymorphic sites, and in the nuclear ribosomal large subunit (nrLSU), with four polymorphic sites. The variable sites in the nrLSU are all located within a putative spliceosomal intron. We sequenced these two regions for 81 specimens and detected six genotypes. Two genotypes were common, two were found only in the more diverse populations and two were found only in one population each. There was no correlation between population size and genetic diversity. The highest genetic diversity was found in populations where the fungal symbiont is reproducing sexually. Populations with low genetic diversity included only the two same common genotypes. Our study provides evidence suggesting that L. pulmonaria is self-incompatible and heterothallic. Based on our results we give populations with sexually reproducing individuals a higher rank in terms of conservation priority than strictly asexual populations. The remaining lowland populations are so small, that one single catastrophic event such as a windthrow might destroy the entire population. Hence we suggest augmenting such populations in size and genetic diversity using small thallus fragments or vegetative diaspores collected in other populations. As we did not detect any locally adapted genotypes, these transplants can be taken from any other genetically diverse population in Switzerland.

Base Sequence↗
PubMed1998

HIV-related non-Hodgkin's lymphoma: CHOP induction therapy and interferon-alpha-2b/zidovudine maintenance therapy.

In a prospective multicenter study 68 out of 158 patients with HIV infection and malignant lymphoma were assigned to a risk-adapted induction therapy using the following algorithm: High-risk patients fulfilled 2 of 3 criteria: T4 lymphocytes <50/microL; WHO activity index 3 or 4; pre-existing AIDS-defining opportunistic infection. Normal-risk patients received 4 to 6 cycles of CHOP chemotherapy; those that achieved complete remission (CR) received zidovudine (500 mg/d) and interferon-alpha maintenance therapy (5 million units three times a week) for one year. High-risk patients received low-dose CHOP or vincristine/prednisone chemotherapy. Supportive care was performed with pentamidine inhalation and G-CSF. Intrathecal (it) methotrexate was given for CNS prophylaxis. The median survival was 634 days for 38 patients of the normal-risk group and 129 days for 30 patients of the high-risk group. 18 high-risk patients treated with low-dose CHOP had better survival (156 days) than 12 patients treated with vincristine/prednisone (72 days p=0.044). 68% of the patients in the normal-risk group achieved complete remission. 5 out of 18 high-risk patients treated with low-dose CHOP achieved complete remission. Three normal-risk patients developed fatal opportunistic infections during chemotherapy. Immune parameters deteriorated after CHOP induction and partially recovered with maintenance treatment. We conclude that the normal-risk patients survived longer than reported in most published studies. Toxicity was low. Low-dose CHOP seems to be superior to vincristine/prednisone therapy in high-risk patients.

Adult↗
PubMed1996

Incidence and spectrum of severe medical complications among hospitalized HIV-seronegative and HIV-seropositive narcotic drug users.

OBJECTIVE: To examine differences in the incidence and spectrum of diseases, as well as duration of inpatient stay, between HIV-seronegative and HIV-seropositive narcotic drug, users (NDU). DESIGN: Retrospective analysis of 9 years of experience. Data collection by chart review using preset criteria for diagnoses. Estimation of hospital admission densities by assuming a dynamic but stable population of 2000 NDU (with a mean HIV-seroprevalence of 25%) throughout the study period. PATIENTS: Comprising 314 HIV-seronegative NDU. 217 HIV-seropositive NDU, and 10 NDU with admissions registered in either group (from a total of 1011 admissions). RESULTS: The overall admission incidence density was 35 and 120 per 1000 person-years among HIV-seronegative NDU and HIV-seropositive NDU, respectively [risk ratio (RR) 3.5, 95% confidence interval (CI) 3.2-3.7]. Compared with seronegative NDU, HIV-seropositive NDU were more frequently admitted for various non-opportunistic infections (RR 7.2, 95% CI 6.1-8.4), including pneumonia (RR 10.9, 95% CI 7.6-16.6), tuberculosis (RR 30.0, 95% CI 3.6-233.8), soft-tissue infections (RR 3.5, 95% CI 1.7-7.2), osteoarticular infections (RR 6.0, 95% CI 1.5-23.9), endocarditis (RR 5.3, 95% CI 1.5-17.9), and various other infections (RR 5.8, 95% CI 3.2-10.5). HIV-seropositive NDU were also more frequently admitted for non-infectious medical complications (RR 2.3, 95% CI 1.8-3.0). Seronegative NDU had a shorter median inpatient stay (2 versus 9 days, P < 0.00001). HIV infection accounted for an estimated excess burden of at least 2700 inpatient care days in 9 years among the 500 local HIV-seropositive NDU. CONCLUSIONS: Among NDU, HIV infection adds considerable excess burden in terms of severe complications needing inpatient care.

AIDS-Related Opportunistic Infections↗
PubMed1995

Effects of ozone fumigation on epiphytic macrolichens: ultrastructure, CO2 gas exchange and chlorophyll fluorescence.

The lichen species Anaptychia ciliaris, Collema nigrescens, Evernia prunastri, Hypogymnia bitteri, Lobaria pulmonaria, Pseudevernia furfuracea and Usnea rigida s.l. were fumigated with site-relevant concentrations (for Central Europe) of ozone over 80 days (180 microg m(-3) during daytime, 80 microg m(-3) during the night). Chlorophyll fluorescence measurements revealed a significant reduction of Fv/Fm after ozone fumigation in five of the species investigated, indicating severe stress on photosystem II due to ozone. The physiological impairment paralleled our fine structural investigations, revealing a significantly higher percentage of collapsed photobiont cells. This indicates that the effects of ambient ozone concentrations under experimental conditions included biophysical and physiological, as well as structural impairment in the lichens studied.

Journal Article↗
PubMed1991

[HIV-associated lymphomas].

Forty-one HIV-positive homosexual men (mean age 39.8 [23-72] years) with malignant lymphomas were examined with the object of exploring the clinical and pathological spectrum of HIV-associated lymphomas in Central Europe, and their therapeutic aspects. There were 33 patients with non-Hodgkin lymphoma of high malignancy and four with non-Hodgkin lymphoma of low malignancy; four further patients suffered from Hodgkin's disease. 27 patients died during the period of observation. The mean survival period after diagnosis was 5.5 months. It depended on the stage reached by the lymphoma at the time of diagnosis: 11.8 months in stage I, 10.6 months in stage II, 7 months in stage III, 3.3 months in stage IV and 1.3 months in patients with primary involvement of the central nervous system by the lymphoma. Eight out of nine patients with highly malignant non-Hodgkin lymphoma in stage I or II attained complete and lasting remissions after chemotherapy or irradiation. However, only minimal prolongation of life was achieved in the 16 patients with lymphomas in stages III or IV. The response rate among all patients treated (complete and partial remissions) was 75%; 45% achieved complete remission. Hodgkin's disease responded well to standard therapy, but the disease rapidly recurred in every case.

Adult↗
PubMed1991

Humoral immune response to pneumococcal antigen 23-F in an asplenic patient with recurrent fulminant pneumococcaemia.

Host defence mechanisms were analysed in a patient with three episodes of fulminant pneumococcaemia and one episode of bacteraemic epiglottitis with Haemophilus influenzae type b. The first episode took place 11 years after splenectomy for blunt abdominal trauma. Investigations revealed several host defence mechanisms to be impaired. In addition to the patient's asplenia, an inherited C2-deficiency was noted. Assessment of IgG subclasses repeatedly revealed markedly low IgG4 concentrations. These were not due to an increased turnover of IgG4, as could be shown following infusion of intravenous IgG. In addition, IgG2 concentrations were low in the patient who lacked G2M(23). Opsonic mediating antibodies against type 23-F pneumococci were in the range of those of non-immune volunteers 6 months after vaccination with a 23-valent pneumococcal vaccine. These antibodies did not increase after a septic episode with 23-F capsular-type pneumococci. Neutrophil function was apparently normal.

Adolescent↗
PubMed1982

[Survey of the recommendations given to travelers to tropical zones].

This inquiry, conducted with the collaboration of 250 doctors, 150 pharmacists and 76 travel agencies in the Canton de Vaud was set up to assess the prophylactic advice given against tropical diseases. Replies concerning major affections are discussed. It appears that in a high proportion of cases the recommendations available to travellers are inadequate, due in part to lack of precise, standardised and up to date information.

Cholera↗