Magnetic resonance imaging of plants: plant water status and drought stress response

This Thesis presents an approach for the study of plant water balance during drought stress, using a combination of in vivo NMR experiments and computer simulations. The ultimate aim is the interpretation of the NMR parameters in terms of physiologically relevant characteristics, such as cell dimensions and membrane permeability. Especially the latter has raised a growing interest in plant science, and up to now the measurement of this parameter in vivo was limited to single cells and short experiment time spans.NMR microscopy of plants yields information on various levels of organisation. The NMR images provide clear anatomical details, which have been used to monitor the response of stem growth rates to osmotic stress. On the tissue and cell levels, the NMR parameters T 2 (transverse spin relaxation time) and D app (apparent diffusion coefficient) provide information on the physical and chemical properties. Correct quantitative values for T 2 and D app are crucial for a useful interpretation. Therefore, Chapter 2 evaluates the accuracy of different fitting procedures.The physical and chemical properties can vary considerably between and within different tissues, cells, and intracellular compartments, resulting in distinctly different relaxation and diffusion characteristics for these compartments. The interpretation of these parameters is not straightforward. A numerical model of restricted diffusion and relaxation behaviour was therefore developed, based on Fick's second law of diffusion (Chapter 3). This model expands previous one-dimensional models to a two-dimensional space, consisting of multiple concentric cylindrical compartments, separated by membranes. Numerical simulation experiments using this model demonstrate the importance of modelling two-dimensional diffusion in relation to the effects of spatial restrictions, and spin exchange between the different compartments.This model has been applied to investigate the effects of diffusive exchange on the transverse spin relaxation times, the apparent diffusion coefficients, and the NMR signal amplitudes of water in plant cells (Chapter 4). For different multi-compartment model systems a Pulsed Field Gradient Multiple Spin Echo (PFG-MSE) experiment was simulated, and intrinsic physiological parameters, i.e. the bulk diffusion constant, the cell radius and the membrane permeability were afterwards extracted using common theoretical models. The results justify the use of these models to interpret the in vivo experiments, since meaningful diffusion constants, cell radii and membrane permeabilities can be extracted for a large range of conditions. This is still true if not all conditions of the theory are known or met, e.g . for intact plants.Chapters 5 and 6 study the effect of mild osmotic stress on maize and pearl millet by in vivo1H NMR microscopy, and water uptake measurements. Single NMR parameter images of (i) the water content, (ii) the transverse relaxation time ( T 2 ) and (iii) the apparent diffusion coefficient ( D app ) were used to follow the water status of the stem apical region during osmotic stress. The results are interpreted using the multi-compartment model (Chapter 4), tailored to suit plant cells. For this particular case, an equation was derived to describe the relation between the observed T 2 , the cell dimensions, the bulk T 2 , and the membrane permeability, based on the Brownstein & Tarr theory. Experimentally determined T 2 values of non-stressed stem tissue are indeed correlated to the cell dimensions, which is in agreement with the derived equation. The T 2 of maize cells is higher than the T 2 of equally sized millet cells, implying that the membrane permeability of the latter is higher.The growth rate was strongly inhibited by mild stress in both species, even though the water uptake was only mildly affected. During stress, there are hardly any changes in water content or T 2 of the stem region of maize. In contrast, the apical tissue of pearl millet showed a ~30% decrease of T 2 within 48 hours of stress, whereas the water content and D app hardly changed. This decrease in T 2 can be caused by a decreasing cell radius, a decreasing bulk T 2 , and/or an increasing membrane permeability for water. To distinguish between these contributions, additional scanning electron microscopy was used, showing no apparent changes in cell size. Transverse spin relaxation measurements of a wide range of sugar solutions showed only very small effects of osmotic adjustment on the bulk T 2 . Together, these results point to an increase in membrane permeability during stress. This conclusion is confirmed by numerical simulations of the plant cell model, which showed that only an increasing membrane permeability yields a similar combination of water content, T 2 , and D app values during stress.Under severe osmotic stress, the effects on the plant water balance are naturally larger (Chapter 7). During stress, no significant changes occurred in the maize stem, though the leaves wilted, and the plant died after two days of stress. Pearl millet showed again changes in T 2 , especially in the secondary shoots, which were more pronounced than during mild stress. Furthermore, the stem tissue shrunk, implying that the cell dimensions changed; the secondary shoots showed far less decrease in water content, however. Despite these changes, the plants recovered once stress was relieved. In the framework of the plant cell model, the decreasing T 2 is interpreted as the result of a combination of decreasing cell size and increasing membrane permeability. The latter can result in a higher tissue conductance, thereby facilitating water re-allocation to young, expanding tissues to prevent irreparable damage.The combination of experimental data and simulations as presented in this Thesis has proven to be an effective tool to link NMR information to physiology (Chapter 8). This approach promises to be of great use to plant science, and to NMR microscopy in general

Drepanosticta hamalaineni spec. nov and Sulcosticta sierramadrensis spec. nov from the Northern Sierra Madre Natural Park, Luzon, the Philippines (Zygoptera: Platystictidae)

Conservation Biology - ol

The burden of parenting children with frontal lobe epilepsy

Objective: Caring for a child with a chronic illness adds stress to the typical parenting stress in healthy developing children. This stress can place a heavy burden on parents and may increase when a child displays problem behavior. In general, parenting and child's behavior problems are associated. Furthermore, externalizing (more outgoing) behavior is reported frequently in children with frontal lobe epilepsy (FLE). Therefore, in this study, we first investigated the burden of parents of children with FLE, and second, we investigated the relation between the experienced burden and reported behavioral problems. The validity of parents' reports on proxy measures as well as duration of epilepsy is taken into account. Methods: Thirty-one parents of children with FLE completed validated questionnaires about behavioral problems and burden of parenting. To examine if parents tend to be inconsistent or unusually negative, we used the two validity scales of the Behavioral Rating Inventory of Executive Function (BRIEF) (Negativity and Inconsistency). Results: Only parents of children with FLE who have had epilepsy for 5 years or longer report more problems on the Nijmeegse Vragenlijst voor de Opvoedingssituatie (NVOS) subscales 'Able to manage', 'Child is a burden', and 'Good Interaction' compared with the healthy controls. The subscale 'Child is a burden' significantly predicts scores in about 20% to 49% on the main scales of the Child Behavior Checklist (CBCL), the Global Executive Composite (GEC), and Behavioral Regulation Index (BRI) of the BRIEF. Only 6% of parents scored in the dinical range of the negativity scale of the BRIEF. For the inconsistency scale, this was 45%. Conclusion: Parents of children with FLE do not report excessive parental burden. Longer duration of epilepsy might be a risk factor in experiencing burden. The findings suggest a link between parental burden and behavioral problems in children with FLE. Externalizing behavioral problems are the most marked behavioral problems, which relate to the parental burden. Parents tend to be inconsistent in their ratings. (C) 2019 Elsevier Inc. All rights reserved

The burden of parenting children with frontal lobe epilepsy

Objective: Caring for a child with a chronic illness adds stress to the typical parenting stress in healthy developing children. This stress can place a heavy burden on parents and may increase when a child displays problem behavior. In general, parenting and child's behavior problems are associated. Furthermore, externalizing (more outgoing) behavior is reported frequently in children with frontal lobe epilepsy (FLE). Therefore, in this study, we first investigated the burden of parents of children with FLE, and second, we investigated the relation between the experienced burden and reported behavioral problems. The validity of parents' reports on proxy measures as well as duration of epilepsy is taken into account.Methods: Thirty-one parents of children with FLE completed validated questionnaires about behavioral problems and burden of parenting. To examine if parents tend to be inconsistent or unusually negative, we used the two validity scales of the Behavioral Rating Inventory of Executive Function (BRIEF) (Negativity and Inconsistency).Results: Only parents of children with FLE who have had epilepsy for 5 years or longer report more problems on the Nijmeegse Vragenlijst voor de Opvoedingssituatie (NVOS) subscales 'Able to manage', 'Child is a burden', and 'Good Interaction' compared with the healthy controls. The subscale 'Child is a burden' significantly predicts scores in about 20% to 49% on the main scales of the Child Behavior Checklist (CBCL), the Global Executive Composite (GEC), and Behavioral Regulation Index (BRI) of the BRIEF. Only 6% of parents scored in the dinical range of the negativity scale of the BRIEF. For the inconsistency scale, this was 45%.Conclusion: Parents of children with FLE do not report excessive parental burden. Longer duration of epilepsy might be a risk factor in experiencing burden. The findings suggest a link between parental burden and behavioral problems in children with FLE. Externalizing behavioral problems are the most marked behavioral problems, which relate to the parental burden. Parents tend to be inconsistent in their ratings. (C) 2019 Elsevier Inc. All rights reserved.</p

Diplopia as the First Sign of Gastric Carcinoma

Orbital metastasis may be the initial manifestation of a malignancy of unknown origin. The primary locations of orbital metastasis are usually the lung, prostate, gastrointestinal tract, skin, kidney, eye, or thyroid gland. Metastasis of gastric carcinoma to an extraocular eye muscle is extremely rare. A solitary thickening in an extraocular eye muscle with no inflammatory features is suspect for a tumor. Symptoms such as diplopia, proptosis, ptosis, vision loss, or pain may be associated with an orbital malignancy. Our patient, a 67-year-old man known with radically resected prostate cancer, presented with complaints of vertigo with a tendency to fall, headache, and diplopia when looking to the right. As a coincidental finding, swelling of the rectus lateralis muscle of the left eye was observed on imaging. Extensive additional investigations showed that a gastric carcinoma with intraorbital and leptomeningeal metastasis was the cause. In conclusion, a solitary thickened extraocular eye muscle should be recognized in time and examined further

Effects of Alzheimer's disease and formalin fixation on the different mineralised-iron forms in the human brain

Iron accumulation in the brain is a phenomenon common to many neurodegenerative diseases, perhaps most notably Alzheimer's disease (AD). We present here magnetic analyses of post-mortem brain tissue of patients who had severe Alzheimer's disease, and compare the results with those from healthy controls. Isothermal remanent magnetization experiments were performed to assess the extent to which different magnetic carriers are affected by AD pathology and formalin fixation. While Alzheimer's brain material did not show higher levels of magnetite/maghemite nanoparticles than corresponding controls, the ferrihydrite mineral, known to be found within the core of ferritin proteins and hemosiderin aggregates, almost doubled in concentration in patients with Alzheimer's pathology, strengthening the conclusions of our previous studies. As part of this study, we also investigated the effects of sample preparation, by performing experiments on frozen tissue as well as tissue which had been fixed in formalin for a period of 5 months. Our results showed that the two different preparations did not critically affect the concentration of magnetic carriers in brain tissue, as observable by SQUID magnetometry.Functional Genomics of Muscle, Nerve and Brain Disorder

Establishing freshwater protected areas to protect biodiversity and improve food security in the Philippines

This paper describes the efforts to establish a network of community-conserved areas in the municipality of San Mariano on Luzon, with the dual aim to protect the Philippine crocodile and to improve inland fisheries. The necessary steps to establish a community-conserved area are summarized, and their sustainability assessed. The importance of local leadership and democratic decision-making processes in the design of community-based conservation measures is highlighted, and it is argued that implicit cultural values, such as hospitality and respect, are often a more important motivation for rural communities to protect aquatic resources than explicit concerns about food security and livelihoods.Global Challenges (FSW)Environmental BiologyConservation Biolog

Quantitative MRI and laser ablation-inductively coupled plasma-mass spectrometry imaging of iron in the frontal cortex of healthy controls and Alzheimer's disease patients

Neuro Imaging Researc

MRI of intact plants

Nuclear magnetic resonance imaging (MRI) is a non-destructive and non-invasive technique that can be used to acquire two- or even three-dimensional images of intact plants. The information within the images can be manipulated and used to study the dynamics of plant water relations and water transport in the stem, e.g., as a function of environmental (stress) conditions. Non-spatially resolved portable NMR is becoming available to study leaf water content and distribution of water in different (sub-cellular) compartments. These parameters directly relate to stomatal water conductance, CO2 uptake, and photosynthesis. MRI applied on plants is not a straight forward extension of the methods discussed for (bio)medical MRI. This educational review explains the basic physical principles of plant MRI, with a focus on the spatial resolution, factors that determine the spatial resolution, and its unique information for applications in plant water relations that directly relate to plant photosynthetic activity

Natriuretic Peptides in Post-mortem Brain Tissue and Cerebrospinal Fluid of Non-demented Humans and Alzheimer's Disease Patients

Pathophysiology, epidemiology and therapy of agein