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Biomedical subjects

C Keitel

Publications and source records attributed to C Keitel.

13 recordsLinked to original sources
PubMed2004

Water shortage affects the water and nitrogen balance in Central European beech forests.

Whilst forest policy promotes cultivation and regeneration of beech dominated forest ecosystems, beech itself is a highly drought sensitive tree species likely to suffer from the climatic conditions prognosticated for the current century. Taking advantage of model ecosystems with cool-moist and warm-dry local climate, the latter assumed to be representative for future climatic conditions, the effects of climate and silvicultural treatment (different thinning regimes) on water status, nitrogen balance and growth parameters of adult beech trees and beech regeneration in the understorey were assessed. In addition, validation experiments with beech seedlings were carried out under controlled conditions, mainly in order to assess the effect of drought on the competitive abilities of beech. As measures of water availability xylem flow, shoot water potential, stomatal conductance as well as delta (13)C and delta (18)O in different tissues (leaves, phloem, wood) were analysed. For the assessment of nitrogen balance we determined the uptake of inorganic nitrogen by the roots as well as total N content and soluble N compounds in different tissues of adult and young trees. Retrospective and current analysis of delta (13)C, growth and meteorological parameters revealed that beech growing under warm-dry climatic conditions were impaired in growth and water balance during periods with low rain-fall. Thinning affected water, N balance and growth mostly of young beech, but in a different way under different local climatic conditions. Under cool, moist conditions, representative for the current climatic and edaphic conditions in beech forests of Central Europe, thinning improves nutrient and water status consistent to published literature and long-term experience of forest practitioners. However, beech regeneration was impaired as a result of thinning at higher temperatures and under reduced water availability, as expected in future climate.

Carbon Isotopes↗
PubMed2004

Stable isotope composition of organic compounds transported in the phloem of European beech--evaluation of different methods of phloem sap collection and assessment of gradients in carbon isotope composition during leaf-to-stem transport.

The analysis of stable isotope composition (delta13C, delta15N, delta18O) of phloem-transported organic matter is a useful tool for assessing short-term carbon and water balance of trees. A major constraint of the general application of this method to trees at natural field sites is that the collection of phloem sap with the "phloem bleeding" technique is restricted to particular species and plant parts. To overcome this restriction, we compared the contents (amino compounds and sugars) and isotope signatures (delta13C, delta15N, delta18O) of phloem sap directly obtained from incisions in the bark (bleeding technique) with phloem exudates where bark pieces were incubated in aqueous solutions (phloem exudation technique with and without chelating agents [EDTA, polyphosphate] in the initial sampling solution, which prevent blocking of sieve tubes). A comparable spectrum of amino compounds and sugars was detected using the different techniques. O, C, or N compounds in the initial sampling solution originating from the chelating agents always decreased precision of determination of the respective isotopic signatures, as indicated by higher standard deviation, and/or led to a significant difference of mean delta as compared to the phloem bleeding technique. Hence, depending on the element from which the ratio of heavy to light isotope is determined, compounds lacking C, N, and/or O should be used as chelating agents in the exudation solution. In applying the different techniques, delta13C of organic compounds transported in the phloem of the twig (exudation technique with polyphosphate as chelating agent) were compared with those in the phloem of the main stem (phloem bleeding technique) in order to assess possible differences in carbon isotope composition of phloem carbohydrates along the tree axis. In July, organic compounds in the stem phloem were significantly enriched in 13C by > 1.3 per thousand as compared to the twig phloem, whereas this effect was not observed in September. Correlation analysis between delta13C and stomatal conductance (Gs) revealed the gradient from the twigs to the stem observed in July may be attributed to temporal differences rather than to spatial differences in carbon isotope composition of sugars. As various authors have produced conflicting results regarding the enrichment/depletion of 13C in organic compounds in the leaf-to-stem transition, the different techniques presented in this paper can be used to provide further insight into fractionation processes associated with transport of C compounds from leaves to branches and down the main stem.

Biological Transport↗
PubMed2003

[Outpatient geriatric rehabilitation: an evaluation of two models assessing trends of medical outcomes].

In Germany, complex and intensified outpatient geriatric rehabilitation is currently scarcely practised, mainly in model projects. The evaluation of these projects is exclusively conducted in uncontrolled studies. In our project "AMBRA", two different organisational models of geriatric rehabilitation are compared: a mobile rehabilitation team based at a geriatric hospital department and an outpatient rehabilitation centre run by GPs trained in geriatrics. Outcomes were assessed in terms of capability of self-care (Barthel-Index), mobility (Tinetti-Test, Timed "Up & Go"-Test, TUG), and depression (Geriatric Depression Scale, GDS). They were documented at three points in time (start of rehabilitation, end of rehabilitation, 6 months after end of rehabilitation) and analysed by multivariate analyses of variance (repeated measurements). 162 complete patients histories were taken in the first 18 months of the project. They show significant improvements in capability of self-care and mobility (both Tinetti-Test and TUG) between the beginning and the end of rehabilitation (adjusted for age, sex, cognitive function, diagnosis, rehabilitation model). On a medium-term basis, these results remained stable (TUG declined, however). Average GDS values did not change significantly. There were no significant sex- or age-related effects. The patients' cognitive function influenced changes in the results of the Barthel-Index and the Tinetti-Test. Patients with skeletal diseases showed less favourable trends in the Barthel-Index as did patients with cognitive impairments caused by vascular disease in the TUG, but these patients also benefited in the course of the model rehabilitation procedures. Differences in trends between patient groups of the two models were observed in the Barthel-Index. 96 % of patients previously living at home were still living there at the end of rehabilitation, 91 % were still living there 6 months after the end of rehabilitation. At the end of rehabilitation, 67 % of patients described an improvement of their personal situation associated with the rehabilitation procedure. Six months later, 82 % described an improvement or a stabilisation of their personal situation. Our results show positive medium-term rehabilitation trends concerning medical and subjective outcomes. In order to analyse effectiveness, we will have to wait for the results of a regional control group which is being recruited.

Activities of Daily Living↗
PubMed2002

[Outpatient geriatric rehabilitation - the structural and process quality of a geriatric mobile service team and a community-based outpatient center].

The trial "Outpatient Geriatric Rehabilitation (AMBRA)" has been launched to compare two outpatient rehabilitation models close to their place of residence or at home: a mobile rehabilitation team based at a geriatric hospital department and a community-based outpatient rehabilitation center run by GPs. Primary analyses concerning structural and process quality of the models are presented in this paper. They refer to medical features and factors associated with care which were assessed at the beginning of the rehabilitation procedures and during intervention. The models include 60 patients attended by the mobile rehabilitation team and 76 patients attended by the outpatient rehabilitation centre. The patients are suffering from multiple illnesses and are limited in their daily activities. Both teams co-ordinate interdisciplinary rehabilitation programs with an average of 50 therapeutic units per patient under medical supervision. The programs' focus is on physiotherapy and occupational therapy and, if indicated, on logotherapy. Psychosocial and health promotional offers are hardly integrated into the procedures. The mobile rehabilitation team on average cares for patients with better cognitive functions (Mini-Mental State Examination) but worse abilities to cope in daily life (Barthel index) than the outpatient rehabilitation team. These differences between rehabilitation groups remain significant after multivariate consideration of sociodemographic, morbidity and process factors. However, differences in mobility (Tinetti Test) can be explained by these variables. The future comparison of results of the rehabilitation programs must therefore consider the different baseline levels and determinants between both groups.

Aged↗
PubMed2001

The response regulator ARR2: a pollen-specific transcription factor involved in the expression of nuclear genes for components of mitochondrial complex I in Arabidopsis.

Two-component signal systems regulate a variety of cellular activities. They involve at least two common signalling molecules: a signal-sensing kinase and a response regulator that mediates the output response. Multistep systems also require proteins containing phosphotransfer domains. Here we report that the response regulator ARR2 from Arabidopsis is predominantly expressed in pollen and is localized in the nuclear compartment of the plant cell. Furthermore, ARR2 is transcriptionally active in yeast and binds to the promoters of nuclear genes for several components of mitochondrial respiratory chain complex I (nCI) from Arabidopsis. The nuclear nCI genes are up-regulated in pollen during spermatogenesis. The transcription factor functions of ARR2 are mediated by its C-terminal output domain. Our data identify ARR2 as the first eukaryotic response regulator which functions as a transcription factor at a known promoter sequence. Yeast two-hybrid analysis and in vitro interaction studies suggest that ARR2 very probably forms part of a multistep two-component signalling mechanism that includes HPt proteins like AHP1 or AHP2. These findings point to an as yet unidentified signal transduction system that may regulate aspects of floral and mitochondrial gene expression.

Arabidopsis↗
PubMed1995

Childhood immunization: one HMO's experience in benchmarking and improving plan performance.

In 1994, Health Net initiated a childhood immunization campaign and research project to improve health plan member immunization rates by motivating and educating parents of children 20-32 months old as to the importance of fully immunizing their child. The findings indicate that 88 percent of those parents with children who were not fully immunized believed their child had been fully immunized by age two. This lack of awareness may explain the unreliability of self-reported immunization status. Future immunization campaigns must include ongoing member reminder systems, educate members as to the immunization schedule, and must take into consideration the barriers, real and perceived, that block full immunization.

California↗
PubMed1990

Differential expression of the oncoproteins c-myc and c-myb in human lymphoproliferative disorders.

Altered regulation of oncogene expression has been described in a variety of hematopoietic malignancies. In this study we analyzed the protein level of c-myc and c-myb in 15 established cell lines derived from lymphopoietic disorders and in 45 samples from patients with acute or chronic lymphatic leukemias. Oncoproteins were assayed by radioimmuno-precipitation with polyclonal rabbit antibodies. In B-cell derived lines, such as Burkitt lymphoma and plasmocytoma lines, we found high amounts of c-myc and no or low amounts of c-myb. In contrast, all T-cell-derived lines revealed high levels of c-myb. In addition, T-lymphoma cell lines of low malignancy also exhibited high levels of c-myc, while T-cell lines of high malignancy (acute T-lymphoblastic leukemias) exhibited moderate levels of c-myc. Of the 45 patient samples analyzed, only three (one B-prolymphocytic and two acute T-lymphoblastic leukemias) contained detectable amounts of myc or myb protein. Corresponding to the results found in established cell lines, the B-cell sample revealed a high level of c-myc but no c-myb, while the T-cell samples revealed high levels of c-myb and no or low levels of c-myc. We therefore conclude that the predominance of c-myc or c-myb expression in malignant lymphoproliferative disorders may be associated to the B-cell or T-cell lineage, respectively. Further, regarding the T-cell lines, there is a possible correlation between cell maturation and the level of c-myc found together with a consistently elevated c-myb.

Cell Line↗