U Zimmermann's research while affiliated with University of Wuerzburg and other places

Publications (303)

Article
Further improvement on irrigation management requires continuous plant water status monitoring. The non-invasive ZIM-probe measures the pressure (Pp) transfer function through a patch of an intact leaf, which is inversely correlated with the turgor pressure. Data are sent wireless in real-Time by telemetry to an internet server via a mobile phone n...
Article
Full-text available
Stem sap flow (Q) and leaf turgor pressure (Pc) were measured simultaneously on 4-year-old, 2.4 m tall ‘Arbequina’ olive trees in a hedgerow orchard. Measurements were performed on well-watered control trees as well as on 60RDI and 30RDI trees (RDI = regulated deficit irrigation). The 60RDI trees received 59.2% of the crop water needs (ETc), and th...
Article
The non-invasive leaf patch clamp pressure (LPCP) probe measures the attenuated pressure of a leaf patch, P(p) , in response to an externally applied magnetic force. P(p) is inversely coupled with leaf turgor pressure, P(c) , i.e. at high P(c) values the P(p) values are small and at low P(c) values the P(p) values are high. This relationship betwee...
Article
Relative changes in cell turgor of leaves of well-watered tomato plants were evaluated using the leaf patch clamp pressure probe (LPCP) under dynamic greenhouse climate conditions. Leaf patch clamp pressure changes, a measure for relative changes in cell turgor, were monitored at three different heights of transpiring and non-transpiring leaves of...
Article
The need for sophisticated irrigation strategies in fruit tree orchards has led to an increasing interest in reliable and robust sensor technology that allows automatic and continuous recording of the water stress of trees under field conditions. In this work we have evaluated the potential of the leaf patch clamp pressure (LPCP) probe for monitori...
Article
Full-text available
Leaf turgor pressure provides a very sensitive indicator of plant water status. Diurnal changes in turgor pressure of olives were measured over several months with a novel leaf patch clamp pressure (LPCP) probe. The LPCP probe is user-friendly, non-invasive, online-monitoring, robust and versatile, and is characterised by high precision, low-cost a...
Article
Real-time monitoring of plant water status under field conditions remains difficult to quantify. Here we give evidence that the magnetic-based leaf patch clamp pressure (LPCP) probe is a non-invasive and online-measuring method that can elucidate short- and long-term temporal and spatial dynamics of leaf water status of trees with high precision in...
Article
Background and Aims: Effects of four irrigation treatments on leaf turgor pressure of grapevines were studied using the novel leaf patch clamp pressure (LPCP) probe. Data were correlated with yield and yield components. Methods and Results: The LPCP probe measures leaf water status by monitoring the attenuation of an external pressure applied magne...
Article
Turgor pressure provides a sensitive indicator for irrigation scheduling. Leaf turgor pressure of Musa acuminate was measured by using the so-called leaf patch clamp pressure probe, i.e. by application of an external, magnetically generated and constantly retained clamp pressure to a leaf patch and determination of the attenuated output pressure P(...
Chapter
Transplantation of immunoisolated endocrine tissue could improve the therapy of many diseases, especially the in industrial countries common diabetes mellitus, without use of immunosuppressive treatment. Many efforts have been taken to choose the proper capsule material, to make it biocompatible and to produce it in a standardized way but the capsu...
Chapter
Stem cells are at the centre of biomedical research: besides improving the basic understanding of human development and cellular differentiation processes, stem cells hold the unique potential for novel therapies of degenerative diseases. Future therapies, however, will have to build on a readily available, reliable and safe supply of high-quality...
Article
An advanced non-invasive, field-suitable and inexpensive leaf patch clamp pressure probe for online-monitoring of the water relations of intact leaves is described. The probe measures the attenuated output patch clamp pressure, P(p), of a clamped leaf in response to an externally applied input pressure, P(clamp). P(clamp) is generated magnetically....
Article
The continuity of the xylem water columns was studied on 17- to 23-m tall birch trees (trunk diameter about 23 cm; first branching above 10 m) all year round. Fifty-one trees were felled, and 5-cm thick slices or 2-m long boles were taken at regular, relatively short intervals over the entire height of the trees. The filling status of the vessels w...
Article
Cryopreservation of human tumour cells and tissue is a valuable tool for retrospective analysis and for the transport and handling of biopsy material. Tumour tissue consists of different cell types, which have different optimal freezing conditions, and extracellular matrix. A well-defined and authentic model system is required for developing new fr...
Article
Full-text available
Investigation of 67 gymnosperm and angiosperm species belonging to 25 orders shows that epistomatal mucilage plugs are a widespread phenomenon. Measurements of the leaf water status by using the leaf patch clamp pressure technique suggest that the mucilage plugs are involved in moisture uptake and buffering leaf cells against complete turgor pressu...
Article
Seasonal variations in osmolality and components of xylem sap in tall birch trees were determined using several techniques. Xylem sap was extracted from branch and trunk sections of 58 trees using the very rapid gas bubble-based jet-discharge method. The 5-cm long wood pieces were taken at short intervals over the entire tree height. The data show...
Article
Xylem probe measurements in the roots of intact plants of wheat and barley revealed that the xylem pressure decreased rapidly when the roots were subjected to osmotic stress (NaCl or sucrose). The magnitude of the xylem pressure response and, in turn, that of the radial reflection coefficients (σr) depended on the transpiration rate. Under very low...
Article
Full-text available
A high-precision pressure probe is described which allows non-invasive online-monitoring of the water relations of intact leaves. Real-time recording of the leaf water status occurred by data transfer to an Internet server. The leaf patch clamp pressure probe measures the attenuated pressure, Pp, of a leaf patch in response to a constant clamp pres...
Article
Replacing dysfunctional endocrine cells or tissues (e.g. islets, parathyroid tissue) by functional, foreign material without using immunosuppressives could soon become reality. Immunological reactions are avoided by encapsulating cells/tissues in hydrogel (e.g. alginate) microcapsules, preventing interaction of the enclosed material with the host’s...
Article
Cytosolic Ca2+ changes induced by electric field pulses of 50-μs duration and 200-800 V/cm strength were monitored by measuring chemiluminescence in aequorin-transformed BY-2 tobacco cells. In Ca2+-substituted media, electropulsing led to a very fast initial increase of the cytosolic Ca2+ concentration reaching a peak value within <100-200 ms. Peak...
Article
Full-text available
The water supply to leaves of 25 to 60 m tall trees (including high-salinity-tolerant ones) was studied. The filling status of the xylem vessels was determined by xylem sap extraction (using jet-discharge, gravity-discharge, and centrifugation) and by (1)H nuclear magnetic resonance imaging of wood pieces. Simultaneously, pressure bomb experiments...
Chapter
Full-text available
The ion-selective xylem probe is a new tool that allows for on-line recording of ion activities in the xylem sap when water is under tension. Ion-selective electrodes are combined with a xylem pressure probe additionally measuring the electrical potential in a vessel. Using a K+-selective probe, xylem K+ in maize roots was recorded simultaneously w...
Chapter
Herbaceous plants exhibit complex reaction patterns as a response to changes in environmental factors such as light intensity, relative humidity, temperature and root water-supply. The reactions of volume flows and hydrostatic pressures within the intact plant can only be described in an authentic way if minimal- and non-invasive methods are used f...
Article
Giant HEK293 cells of 30-65 microm in diameter were produced by three-dimensional multi-cell electrofusion in 75 mOsm sorbitol media. These strong hypotonic conditions facilitated fusion because of the spherical shape and smooth membrane surface of the swollen cells. A regulatory volume decrease (RVD), as observed at higher osmolalities, did not oc...
Article
Small organic solutes, including sugar derivatives, amino acids, etc., contribute significantly to the osmoregulation of mammalian cells. The present study explores the mechanisms of swelling-activated membrane permeability for electrolytes and neutral carbohydrates in Jurkat cells. Electrorotation was used to analyze the relationship between the h...
Article
Using an electric field pulse technique, we induced fusion between vacuoles and protoplasts of Kalanchoë daigremontiana, between protoplasts from etiolated and green leaf mesophyll, and between mesophyll protoplasts from plants of different physiological properties (Avena sativa: C3 mechanism of photosynthesis, Kalanchoë daigremontiana: crassulacea...
Article
Since its introduction in the late 19th century, the so-called cohesion theory has become widely accepted as explaining the mechanism of the ascent of sap. According to the cohesion theory, the minimum standing vertical xylem tension gradient should be 0·01 MPa m−1. When transpiration is occurring, frictional resistances are expected to make this g...
Article
The absolute pressure in conducting xylem vessels of roots of 2-week-old, slowly transpiring intact maize plants (bathed in nutrition medium) was determined to be +0·024 ± 0·044 MPa using the xylem pressure probe. When the roots were subjected to osmotic stress (NaCI, KCI or sucrose), the xylem pressure decreased immediately and became more negativ...
Article
We have already demonstrated that thermodynamic-stabilized Ba2+-alginate beads can be used to immunoisolate islets of Langerhans and thereby restore normoglycemia after intraperitoneal transplantation into immunocompetent streptozotocine-diabetic Balb/c-mice (Schneider et al., Diabetes 2005). But an effective long term graft function (normoglycemia...
Article
In the past, we have reported on significant improvements of the conventional cryo-technique resulting in increased islet viability after cryopreservation. However, even with these optimized protocols, the islet cell quality was still markedly impaired after thawing, making its use for clinical transplantation unlikely. Recently we tried to develop...
Article
Alginate-based microencapsulation is a promising method for long-term maintenance of cellular and membrane function of the cells and tissue fragments required for in vitro and in vivo biosensors, for tissue engineering and particularly for immunoisolation of non-autologous transplants. Microcapsules of high mechanical strength and optimum permeabil...
Article
Electrotransfection and electrofusion, both widely used in research and medical applications, still have to face a range of problems, including the existence of electroporation-resistant cell types, cell mortality and also great batch-to-batch variations of the transfection and fusion yields. In the present study, a systematic analysis of the param...
Article
Full-text available
The concept of encapsulated-cell therapy is very appealing, but in practice a great deal of technology and know-how is needed for the production of long-term functional transplants. Alginate is one of the most promising biomaterials for immunoisolation of allogeneic and xenogeneic cells and tissues (such as Langerhans islets). Although great advanc...
Article
Volume changes of human T-lymphocytes (Jurkat line) exposed to hypotonic carbohydrate-substituted solutions of different composition and osmolality were studied by videomicroscopy. In 200 mOsm media the cells first swelled within 1-2 min and then underwent regulatory volume decrease (RVD) to their original isotonic volume within 10-15 min. RVD also...
Article
A micro-Raman spectroscopy approach was used for the direct in situ characterization of lipid bodies in the water-conducting branch xylem of an African resurrection plant and three deciduous European tree species. Because of average diameters of at least 1 microm, the lipid bodies of all investigated species proved to be easily accessible by this t...
Article
The entrapment of enzymes, drugs, cells or tissue fragments in alginates cross-linked with Ca2+ or Ba2+ has great potential in basic research, biotechnology and medicine. The swelling properties and, in turn, the mechanical stability are key factors in designing an optimally cross-linked hydrogel matrix. These parameters depend critically on the cr...
Article
Among the hydrogels used for microencapsulation of cells and tissues, alginate has been and will continue to be one of the most important biomaterials. A mandatory requirement for clinical immunoisolated transplantations is the reproducible production of biocompatible alginate. As shown here for alginates extracted from freshly collected algal stip...
Article
A key engineering challenge in designing microcapsules made from biocompatible alginate is maintaining adequate exchange of nutrients and oxygen between the entrapped cells and the environment, while simultaneously avoiding swelling and subsequent failure of the microcapsule. Approval for the use of alginate in pharmaceutical and/or biomedical appl...
Article
The giant marine alga Valonia utricularis is capable of regulating its turgor pressure in response to changes in the osmotic pressure of the sea water. The turgor pressure response comprises two phases, a fast, exponential phase arising exclusively from water shifting between the vacuole and the external medium (time constant about 10 min) and a se...
Article
Summary • Lipids play a crucial role in the maintenance of the structural and functional integ- rity of the water-conducting elements and cells of the resurrection plant Myrotham- nus flabellifolia during complete dehydration. • Lipid composition, mobility and distribution within the internodal and nodal xylem regions (including short shoots and le...
Article
Cross-linked alginate microcapsules of sufficient mechanical strength can immunoisolate cells for the long-term treatment of hormone and other deficiency diseases in human beings. However, gelation of alginate by external Ba(2+) (or other divalent cations) produces non-homogeneous cross-linking of the polymeric mannuronic (M) and guluronic (G) acid...
Article
The pressure response of (plant) cells to osmotic challenges depends on the reflection coefficient, sigma, of osmotically active solutes; it is less than predicted by the van't Hoff equation if sigma < 1. In Valonia utricularis, sigma is significantly reduced by internal (and, to a lesser extent, by external) unstirred layers, protecting the cytopl...
Article
Full-text available
The electrical properties of protoplasts of the turgor pressure-regulating giant marine alga Valonia utricularis were investigated by using the patch-clamp technique. In the whole-cell configuration, large inward currents were elicited by negative-going voltage pulses. The time-dependent component was predominantly carried by Cl-, as revealed by 't...
Article
Full-text available
The ultrastructure of the several micrometers thick cytoplasmic layer of the giant marine alga Valonia utricularis displays characteristics which are apparently linked with the capability of this alga to regulate turgor pressure. Transmission and scanning electron microscopy of cells prefixed in different ways, including a protocol that allows pref...
Article
The disaccharide trehalose is increasingly being used as a very efficient stabilizer of cells, membranes and macromolecules during cryo- and lyoconservation. Although extracellular trehalose can reduce cryo- and lyodamage to mammalian cells, the sugar is required on both sides of the plasma membrane for maximum protection efficiency. In the present...
Article
The radial electrical potential difference between the root xylem and the bathing solution, i.e. the so-called trans-root potential, was measured in intact maize and wheat plants using a xylem pressure probe into which an Ag/AgCl electrode was incorporated. Besides other advantages (e.g. detection and removal of tip clogging; determination of the r...
Article
The resurrection plant Myrothamnus flabellifolia has the ability to recover from repeated prolonged and extreme desiccation cycles. During the dry state the inner walls of the xylem vessels seemed to be covered, at least partly, by a lipid film as shown by Sudan III and Nile Red staining. The lipid film apparently functioned as an ‘internal cuticle...
Article
Mouse myeloma cells were electropermeabilized by single square-wave electric pulses with amplitudes of up to approximately 150 kV/cm and durations of 10-100 nsec. The effects of the field intensity, pulse duration and medium conductivity on cell viability and field-induced uptake of molecules were analyzed by quantitative flow cytometry using the m...
Article
ABSTRACT A new method for simultaneously quantifying rates of flow in xylem and phloem using the FLASH imaging capabilities of nuclear magnetic resonance (NMR) spectrometry was applied in this study. The method has a time resolution of up to 4 min (for the xylem) and was used to measure the velocity of flows in phloem and xylem for periods of sever...
Chapter
Background: At least 1000 new patients per annum suffer from permanent hypoparathyroidism in Germany alone, generally caused by thyroid surgery. The need for transgenic transplantation of parathyroid tissue (PT) is undisputed. In this study it was tested whether perfluorocarbone (FC 43) increases as additive the oxygen supply and stability of micro...
Article
The axial and radial refilling with water of cut dry branches (up to 80 cm tall) of the resurrection plant Myrothamnus flabellifolia was studied in both acro- and basipetal directions by using 1H-NMR imaging. NMR measurements showed that the conducting elements were not filled simultaneously. Axial water ascent occurred initially only in a cluster...
Article
The acropetal water refilling kinetics of the dry xylem of branches (up to 80 cm tall) of the resurrection plant Myrothamnus flabellifolia were determined with high temporal resolution by observation of light refraction at the advancing water front and the associated recurving of the folded leaves. To study the effect of gravity on water rise, data...
Article
: Flow-sensitive NMR imaging and pressure probe techniques were used for measuring xylem water flow and its driving forces (i.e., xylem pressure as well as cell turgor and osmotic pressure gradients) in a tropical liana, Epipremnum aureum. Selection of tall specimens allowed continuous and simultaneous measurements of all parameters at various dist...
Article
Many diseases are closely tied to deficient or subnormal metabolic and secretory cell functions. Milder forms of these diseases can be managed by a variety of treatments. However, it is often extremely difficult or even impossible to imitate the moment-to-moment fine regulation and the complex roles of the hormone, factor or enzyme that is not suff...
Article
A simple procedure is described for the extraction and purification of alginate from the inner stipes of the kelp Laminaria pallida. Alginate yield was about 10-15% of the dry mass, with a 70:30 mannuronic/guluronic acid ratio. Analysis of the purified alginate revealed a low polyphenol content while proteins were below detection level. The purifie...
Article
Full-text available
The giant marine alga Valonia utricularis is a classical model system for studying the electrophysiology and water relations of plant cells by using microelectrode and pressure probe techniques. The recent finding that protoplasts can be prepared from the giant ``mother cells'' (Wang, J., Sukhorukov, V.L., Djuzenova, C.S., Zimmermann, U., Müller, T...
Article
Transplantation studies with immunoisolated foreign cells / tissues (encapsulated in Ba²⁺-cross-linked alginate) show that several obligatory requirements have to be met before this immunoisolation technique can be used for routine clinical trials. We present chemical procedures and technical developments which could address and solve the current p...