Publications by authors named "Isabel Keller"

Despite a high sucrose accumulation in its taproot vacuoles, sugar beet (Beta vulgaris subsp. vulgaris) is sensitive to freezing. Earlier, a taproot-specific accumulation of raffinose was shown to have beneficial effects on the freezing tolerance of the plant.

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Chloroplasts play a pivotal role in the metabolism of leaf mesophyll cells, functioning as a cellular hub that orchestrates molecular reactions in response to environmental stimuli. These organelles contain complex protein machinery for energy conversion and are indispensable for essential metabolic pathways. Proteins located within the chloroplast envelope membranes facilitate bidirectional communication with the cell and connect essential pathways, thereby influencing acclimation processes to challenging environmental conditions such as temperature fluctuations and light intensity changes.

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Sugar transport across membranes is critical for plant development and yield. However, an analysis of the role of intracellular sugar transporters in senescence is lacking. Here, we characterized the role of Senescence-Associated Sugar Transporter1 (SAST1) during senescence in Arabidopsis (Arabidopsis thaliana).

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Article Synopsis
  • Tumour innervation can worsen patient outcomes in cancers like breast cancer, and more aggressive tumours show higher levels of nerve growth, linked to the molecule SLIT2 in tumour blood vessels.
  • Breast cancer cells stimulate sensory neurons to release a neuropeptide called substance P (SP), which enhances tumour growth and spread, correlating with worse outcomes for patients with high SP levels in their tumours.
  • Targeting the interaction between SP and its receptors with the drug aprepitant, commonly used for nausea, has been shown to inhibit breast cancer growth and metastasis, suggesting a new therapeutic approach.
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Sugars Will Eventually be Exported Transporters (SWEETs) are the most recently discovered family of plant sugar transporters. By acting as uniporters, SWEETs facilitate the diffusion of sugars across cell membranes and play an important role in various physiological processes such as abiotic stress adaptation. AtSWEET17, a vacuolar fructose facilitator, was shown to be involved in the modulation of the root system during drought.

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Endogenous programs and constant interaction with the environment regulate the development of the plant organism and its individual organs. Sugars are necessary building blocks for plant and organ growth and at the same time act as critical integrators of the metabolic state into the developmental program. There is a growing recognition that the specific type of sugar and its subcellular or tissue distribution is sensed and translated to developmental responses.

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Regulation of intracellular sugar homeostasis is maintained by regulation of activities of sugar import and export proteins residing at the tonoplast. We show here that the EARLY RESPONSE TO DEHYDRATION6-LIKE4 (ERDL4) protein, a member of the monosaccharide transporter family, resides in the vacuolar membrane in Arabidopsis (Arabidopsis thaliana). Gene expression and subcellular fractionation studies indicated that ERDL4 participates in fructose allocation across the tonoplast.

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Nucleotide limitation and imbalance is a well-described phenomenon in animal research but understudied in the plant field. A peculiarity of pyrimidine de novo synthesis in plants is the complex subcellular organization. Here, we studied two organellar localized enzymes in the pathway, with chloroplast aspartate transcarbamoylase (ATC) and mitochondrial dihydroorotate dehydrogenase (DHODH).

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Intracellular sugar compartmentation is critical in plant development and acclimation to challenging environmental conditions. Sugar transport proteins are present in plasma membranes and in membranes of organelles such as vacuoles, the Golgi apparatus, and plastids. However, there may exist other transport proteins with uncharacterized roles in sugar compartmentation.

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Background: DNA methylation is thought to influence the expression of genes, especially in response to changing environmental conditions and developmental changes. Sugar beet (Beta vulgaris ssp. vulgaris), and other biennial or perennial plants are inevitably exposed to fluctuating temperatures throughout their lifecycle and might even require such stimulus to acquire floral competence.

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Sugar beet ( subsp. ) is the exclusive source of sugar in the form of sucrose in temperate climate zones. Sugar beet is grown there as an annual crop from spring to autumn because of the damaging effect of freezing temperatures to taproot tissue.

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Maltose, the major product of starch breakdown in Arabidopsis (Arabidopsis thaliana) leaves, exits the chloroplast via the maltose exporter1 MEX1. Consequently, mex1 loss-of-function plants exhibit substantial maltose accumulation, a starch-excess phenotype and a specific chlorotic phenotype during leaf development. Here, we investigated whether the introduction of an alternative metabolic route could suppress the marked developmental defects typical for mex1 loss-of-function mutants.

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Sugars are the main building blocks for carbohydrate storage, but also serve as signaling molecules and protective compounds during abiotic stress responses. Accordingly, sugar transport proteins fulfill multiple roles as they mediate long distance sugar allocation, but also shape the subcellular and tissue-specific carbohydrate profiles by balancing the levels of these molecules in various compartments. Accordingly, transporter activity represents a target by classical or directed breeding approaches, to either, directly increase phloem loading or to increase sink strength in crop species.

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Parental care elevates reproductive success by allocating resources into the upbringing of the offspring. However, it also imposes strong costs for the care-giving parent and can foster sexual dimorphism. Trade-offs between the reproductive system and the immune system may result in differential immunological capacities between the care-providing and the non-care-providing parent.

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During their first year of growth, overwintering biennial plants transport Suc through the phloem from photosynthetic source tissues to storage tissues. In their second year, they mobilize carbon from these storage tissues to fuel new growth and reproduction. However, both the mechanisms driving this shift and the link to reproductive growth remain unclear.

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The ability of plants to withstand cold temperatures relies on their photosynthetic activity. Thus, the chloroplast is of utmost importance for cold acclimation and acquisition of freezing tolerance. During cold acclimation, the properties of the chloroplast change markedly.

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Importance: Transferring patients with large-vessel occlusion (LVO) or intracranial hemorrhage (ICH) to hospitals not providing interventional treatment options is an unresolved medical problem.

Objective: To determine how optimized prehospital management (OPM) based on use of the Los Angeles Motor Scale (LAMS) compares with management in a Mobile Stroke Unit (MSU) in accurately triaging patients to the appropriate hospital with (comprehensive stroke center [CSC]) or without (primary stroke center [PSC]) interventional treatment.

Design, Setting, And Participants: In this randomized multicenter trial with 3-month follow-up, patients were assigned week-wise to one of the pathways between June 15, 2015, and November 15, 2017, in 2 regions of Saarland, Germany; 708 of 824 suspected stroke patients did not meet inclusion criteria, resulting in a study population of 116 adult patients.

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Sucrose (Suc) is one of the most important types of sugars in plants, serving inter alia as a long-distance transport molecule, a carbon and energy storage compound, an osmotically active solute, and fuel for many anabolic reactions. Suc biosynthesis and degradation pathways are well known; however, the regulation of Suc intracellular distribution is poorly understood. In particular, the cellular function of chloroplast Suc reserves and the transporters involved in accumulating these substantial Suc levels remain uncharacterized.

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Sexual dimorphism is founded upon a resource allocation trade-off between investments in reproduction versus other life-history traits including the immune system. In species with conventional parental care roles, theory predicts that males maximize their lifetime reproductive success by allocating resources toward sexual selection, while females achieve this through prolonging their lifespan. Here, we examine the interrelation between sexual dimorphism and parental care strategies in closely related maternal and biparental mouthbrooding cichlid fishes from East African Lake Tanganyika.

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Background: Parental care, while increasing parental fitness through offspring survival, also bears cost to the care-giving parent. Consequentially, trade offs between parental care and other vitally important traits, such as the immune system seem evident. In co-occurring phases of parental care and immunological challenges negative consequences through a resource allocation trade off on both the parental and the offspring conditions can be predicted.

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Background: An ambulance equipped with a computed tomography (CT) scanner, a point-of-care laboratory, and telemedicine capabilities (mobile stroke unit [MSU]) has been shown to enable the delivery of thrombolysis to stroke patients directly at the emergency site, thereby significantly decreasing time to treatment. However, work-up in an MSU that includes CT angiography (CTA) may also potentially facilitate triage of patients directly to the appropriate target hospital and specialized treatment, according to their individual vascular pathology.

Methods: Our institution manages a program investigating the prehospital management of patients with suspicion of acute stroke.

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Microparasites have a higher evolutionary potential than their hosts due to an increased mutation rate and a shorter generation time that usually results in parasites being locally adapted to their sympatric hosts. This pattern may not apply to generalist pathogens as adaptation to sympatric host genotypes is disadvantageous due to a narrowing of the host range, in particular under strong gene flow among host populations. Under this scenario, we predict that the immune defense of hosts reveals adaptation to locally common pathogen phylotypes.

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Background: Only 2-5% of patients who have a stroke receive thrombolytic treatment, mainly because of delay in reaching the hospital. We aimed to assess the efficacy of a new approach of diagnosis and treatment starting at the emergency site, rather than after hospital arrival, in reducing delay in stroke therapy.

Methods: We did a randomised single-centre controlled trial to compare the time from alarm (emergency call) to therapy decision between mobile stroke unit (MSU) and hospital intervention.

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Currently, stroke laboratory examinations are usually performed in the centralized hospital laboratory, but often planned thrombolysis is given before all results are available, to minimize delay. In this study, we examined the feasibility of gaining valuable time by transferring the complete stroke laboratory workup required by stroke guidelines to a point-of-care laboratory system, that is, placed at a stroke treatment room contiguous to the computed tomography, where the patients are admitted and where they obtain neurological, laboratory, and imaging examinations and treatment by the same dedicated team. Our results showed that reconfiguration of the entire stroke laboratory analysis to a point-of-care system was feasible for 200 consecutively admitted patients.

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Background: Fabry disease (FD) is a rare hereditary lysosomal storage disease that has been highlighted as a possible etiology of stroke at a young age. Enlarged basilar artery diameters (BADs) have been demonstrated in FD, and we hypothesize that they might be useful for the screening of FD in young stroke patients. The aim of this study was to compare BADs of young stroke patients without FD to those of FD patients and of healthy age-matched controls.

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