Detlef Kramer

Learn More
Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with(More)
Helianthus annuus L. responds to iron deficiency by forming a thickened cortex and abundant root hairs in a zone near the root apex that corresponds to the primary developmental stage. Cytological investigations revealed that within 24 to 48 h of iron deficiency most of the peripheral cells differentiate into transfer cells. The wall labyrinth is always(More)
The predominance of IgA antibodies in mucosal sites reflects a combination of high rate IgA isotype switching among precursor cells in induction sites, their selective localization in mucosal effector tissues and vigorous proliferation of these cells after extravasation. Each of these steps leading to IgA expression at the mucosa is under cytokine control.(More)
Infection of Chlorella NC64A cells by PBCV-1 produces a rapid depolarization of the host probably by incorporation of a viral-encoded K(+) channel (Kcv) into the host membrane. To examine the effect of an elevated conductance, we monitored the virus-stimulated efflux of K(+) from the chlorella cells. The results indicate that all 8 chlorella viruses tested(More)
Previous studies have established that chlorella viruses encode K(+) channels with different structural and functional properties. In the current study, we exploit the different sensitivities of these channels to Cs(+) to determine if the membrane depolarization observed during virus infection is caused by the activities of these channels. Infection of(More)
In the succulent leaves of Aloe arborescens Mill diurnal oscillations of the malic acid content, being indicative of Crassulacean Acid Metabolism (CAM), were exhibited only by the green mesophyll. In contrast, the malic acid level of the central chloroplast-free water-storing tissue remained constant throughout the day-night cycle. Apart from malate, the(More)
The structure of xylem parenchyma cells is examined in relation to transport of ions through the root. Measurement of uptake of 86Rb+ and its transport through the root at different distances from the apex show that this is a general activity along the length of the root and not confined to a limited region. Thus transport through the root is not stopped by(More)
The performance of crassulacean acid metabolism (CAM) by dicotyledonous trees of the genusClusia sampled at three sites in the state of Falcon in northern Venezuela is characterized.Clusia leaves have a somewhat succulent appearance. Unlike leaves of many other CAM plants, which are uniformly built up of very large isodiametric cells, there are distinct(More)
ATPase activity in xylem parenchyma cells of barley (Hordeum vulgare L.) roots was demonstrated cytochemically with a lead precipitation reaction. The methodical parameters of this cytochemical test were optimized for distinction between ATPase-specific and nonspecific precipitates. Optimum conditions were prefixation in 1% glutaraldehyde for 1 hour and(More)
A technique is described for X-ray microanalysis of unfixed, frozen, hydrated higher plant cells using a scanning electron microscope in conjunction with a cryostage. Freezing in liquid N2 is the only preparative step required. Using this method, ion distribution was compared in the roots of Zea mays L. (termed a salt excluder) and Hordeum vulgare L. (which(More)