Biomedical subjects

W Brüggemann

Publications and source records attributed to W Brüggemann.

17 recordsLinked to original sources

PubMed2006

Forced and unforced ocean temperature changes in Atlantic and Pacific tropical cyclogenesis regions.

Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 degrees C to 0.67 degrees C over the 20th century. The 22 climate models examined here suggest that century-timescale SST changes of this magnitude cannot be explained solely by unforced variability of the climate system. We employ model simulations of natural internal variability to make probabilistic estimates of the contribution of external forcing to observed SST changes. For the period 1906-2005, we find an 84% chance that external forcing explains at least 67% of observed SST increases in the two tropical cyclogenesis regions. Model "20th-century" simulations, with external forcing by combined anthropogenic and natural factors, are generally capable of replicating observed SST increases. In experiments in which forcing factors are varied individually rather than jointly, human-caused changes in greenhouse gases are the main driver of the 20th-century SST increases in both tropical cyclogenesis regions.

Atlantic Ocean↗

PubMed2005

The inheritance of chilling tolerance in tomato (Lycopersicon spp.).

During the past 25 years, chilling tolerance of the cultivated (chilling-sensitive) tomato Lycopersicon esculentum and its wild, chilling-tolerant relatives L. peruvianum and L. hirsutum (and, less intensively studied, L. chilense) has been the object of several investigations. The final aim of these studies can be seen in the increase in chilling tolerance of the cultivated genotypes. In this review, we will focus on low-temperature effects on photosynthesis and the inheritance of these traits to the offspring of various breeding attempts. While crossing L. peruvianum (male symbol) to L. esculentum (female symbol) so far has brought the most detailed insight with respect to physiological questions, for practical purposes, e.g., the readily cross ability, crossing programmes with L. hirsutum as pollen donor at present seem to be a promising way to achieve higher chilling-tolerant genotypes of the cultivated tomato. This perspective is due to the progress that has been made with respect to the genetic basis of chilling tolerance of Lycopersicon spp. over the past five years.

Adaptation, Physiological↗

PubMed2003

Contributions of anthropogenic and natural forcing to recent tropopause height changes.

Observations indicate that the height of the tropopause-the boundary between the stratosphere and troposphere-has increased by several hundred meters since 1979. Comparable increases are evident in climate model experiments. The latter show that human-induced changes in ozone and well-mixed greenhouse gases account for approximately 80% of the simulated rise in tropopause height over 1979-1999. Their primary contributions are through cooling of the stratosphere (caused by ozone) and warming of the troposphere (caused by well-mixed greenhouse gases). A model-predicted fingerprint of tropopause height changes is statistically detectable in two different observational ("reanalysis") data sets. This positive detection result allows us to attribute overall tropopause height changes to a combination of anthropogenic and natural external forcings, with the anthropogenic component predominating.

Journal Article↗

PubMed2003

Influence of satellite data uncertainties on the detection of externally forced climate change.

Two independent analyses of the same satellite-based radiative emissions data yield tropospheric temperature trends that differ by 0.1 degrees C per decade over 1979 to 2001. The troposphere warms appreciably in one satellite data set, while the other data set shows little overall change. These satellite data uncertainties are important in studies seeking to identify human effects on climate. A model-predicted "fingerprint" of combined anthropogenic and natural effects is statistically detectable only in the satellite data set with a warming troposphere. Our findings show that claimed inconsistencies between model predictions and satellite tropospheric temperature data (and between the latter and surface data) may be an artifact of data uncertainties.

Journal Article↗

PubMed2002

Biochemical responses to iron deficiency in kiwifruit (Actinidia deliciosa).

A comparative study of two kiwifruit genotypes (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa) with different tolerance to iron (Fe) deficiency was conducted to identify biochemical features associated with tolerance to Fe deficiency. After 14 days of growth in hydroponic culture under Fe-deficient and Fe-sufficient conditions, leaf chlorophyll concentration, activities of ferric chelate reductase (FCR), phosphoenolpyruvate carboxylase (PEPC) and citrate synthase in root extracts, concentrations of organic acids in roots, leaves and xylem sap, and xylem sap pH were measured. In response to Fe deficiency, the tolerant genotype D1 showed: (i) higher FCR activity associated with a longer lasting induction of FCR; (ii) higher PEPC activity; (iii) higher concentrations of citric acid in roots; and (iv) lower xylem sap pH compared with the susceptible genotype Hayward. These findings imply that induction of FCR and PEPC activities in roots in response to Fe deficiency are important physiological adaptations enabling Fe-efficient kiwifruit plants to tolerate Fe deficiency.

Actinidia↗

PubMed1996

[Follow-up and immunologic findings in drug-induced myasthenia].

PATIENT AND METHOD: We report 5 patients, who developed myasthenia, four of them after treatment on D-penicillamine, one after treatment on chloroquine. 3 patients suffered from rheumatoid arthritis, one from a psoriatic arthritis and one from cirrhosis of the liver. Three patients developed an ocular myasthenia, one patient an oculopharyngeal and one patient has had generalized myasthenic syndrome. RESULTS: Four patients showed an improvement of clinical status within days up to 18 months following discontinuation of the therapy, whereas one patient deteriorated. The quickest improvement was observed in the patient with chloroquine induced myasthenia. Four patients had raised acetylcholine-receptor antibody titers. The patient with chloroquine induced myasthenia had had a normal acetylcholin-receptor antibody titer. The human leucocyte antigen type was compared with the results of literature. CONCLUSION: To what extent human leucocyte antigen type HLA DR 4 has a correlation with the development of myasthenia following treatment on chloroquine can not yet be answered with respect to the very small number of cases at the moment.

Aged↗

PubMed1995

Responses to iron deficiency in Arabidopsis thaliana: the Turbo iron reductase does not depend on the formation of root hairs and transfer cells.

Arabidopsis thaliana (L.) Heynh. Columbia wild type and a root hair-less mutant RM57 were grown on iron-containing and iron-deficient nutrient solutions. In both genotypes, ferric chelate reductase (FCR) of intact roots was induced upon iron deficiency and followed a Michaelis-Menten kinetic with a Km of 45 and 54 microM FeIII-EDTA and a Vmax of 42 and 33 nmol Fe2+.(g FW)-1.min-1 for the wild type and the mutant, respectively. The pH optimum for the reaction was around pH 5.5. The approximately four fold stimulation of FCR activity was independent of formation of root hairs and/or transfer cells induced by iron deficiency. Iron-deficiency-induced chlorosis and the development of a rigid root habit disappeared when ferric chelate was applied to the leaves, while FCR activity remained unchanged. The time course of the responses to iron deficiency showed that morphological and physiological responses were controlled separately.

Arabidopsis↗

PubMed1989

Ciliary neurotrophic factor supports target-deprived preganglionic sympathetic spinal cord neurons.

Spinal cord neurons in the intermediolateral column (IML) that innervate the adrenal medulla require target-derived factor(s) for their maintenance in vivo. Selective destruction of the adult rat adrenal medulla causes an approximate 25% loss of Nissl-stained IML neurons between spinal cord levels Th 4 weeks after surgery. We have previously suggested that basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF) or closely related molecules are present in adrenal chromaffin cells and granules. Basic FGF supplemented in gelfoams to the medullectomized adrenal gland fully prevented IML neuron losses. These results are now extended by demonstrating that (i) CNTF administered in vivo (7.2 micrograms/gelfoam) also rescues IML neurons, and (ii) the rescue effect is abolished by splanchnicotomy, i.e. interruption of axonal pathway from the spinal cord to the adrenal gland. These data would be consistent with CNTF being a retrograde trophic messenger to the spinal cord, but do not exclude the possibility that CNTF mimics or induces the formation of an endogenous trophic factor.

Adrenalectomy↗

PubMed1986

Structure of viroid replicative intermediates: physico-chemical studies on SP6 transcripts of cloned oligomeric potato spindle tuber viroid.

The structure and structural transitions of transcripts of cloned oligomeric viroid were studied in physico-chemical experiments and stability calculations. Transcripts of (+) and (-) polarity, from unit up to sixfold length, were synthesized from DNA clones of the potato spindle tuber viroid (PSTV) with the SP6 transcription system. Their structural properties were investigated by optical denaturation curves, high performance liquid chromatography (HPLC), electron microscopy, sedimentation-diffusion equilibrium and velocity sedimentation. Secondary structures of the RNAs and theoretical denaturation curves were calculated using an energy optimization program. The secondary structure of lowest free energy for unit length and oligomeric transcripts is a rod-like structure similar to that of the mature circular viroids. When this structure is used as a model for calculations, there is a large degree of agreement between the theoretical and the experimental denaturation curves. At high temperatures, however, (+) strand transcripts exhibited a transition which was more stable than expected from the calculations or than was known from curves of mature viroids. This transition arises from a rearrangement of the central conserved region of viroids to a helical region of 28 stable base pairs either intermolecularly leading to bimolecular complexes, or intramolecularly giving rise to a branched secondary structure. The rearrangement could be detected by electron microscopy, HPLC, and analytical ultracentrifugation. The helical region serves to divide up the oligomeric (+) strand into structural units which may be recognized by cleavage and ligation enzymes which process the oligomeric intermediates to circular mature viroids.

Microscopy, Electron↗

PubMed1983

Large-scale purification of viroid RNA using Cs2SO4 gradient centrifugation and high-performance liquid chromatography.

A procedure for the purification of viroid RNA from tomato plants is described which yields up to a milligram of viroid RNA of gel electrophoretic homogeneity within 2 days. This technique is at least three times as fast as previous methods and is generally applicable to other RNA species. Plant material was homogenized and phenol extracted. In a Cs2SO4 density gradient, viroid RNA together with low-molecular-weight RNA, was separated from large single-stranded RNA, DNA, polysaccharides, polyphenols, and other compounds. The separation is based on the differences in the buoyant density and on the selective precipitation of large single-stranded RNA in Cs2SO4. Further purification of viroid RNA was achieved by HPLC over a weak anion exchanger linked to silica gel of optimized pore size. The elution was carried out by a salt gradient with complete exclusion of divalent metal ions. The procedures were applied to whole plants, leaves, stems, roots, cells, and protoplasts. The yields of nucleic acids at the different steps of purification are given for leaves, stems, and roots.

Centrifugation, Density Gradient↗

PubMed1981