Light-stimulated proton transport into the vacuoles of leaf mesophyll cells does not require energization by the tonoplast pyrophosphatase

Photosynthetic characteristics of transgenic tobacco (Nicotiana tabacum L.) plants with a soluble pyrophosphatase in the cytosol of their leaf cells were compared to those of wild-type plants. Although the development of the transgenic plants was somewhat retarded compared to the wild type, as shown by stunted growth and delayed flowering, photosynthetic responses were comparable in transgenic and wild-type leaves of similar physiological age. In particular, light-dependent proton transport into the vacuoles of leaf mesophyll cells was not decreased in leaves of the transgenic plants, which did not contain pyrophosphate in the cytosol owing to the presence of a soluble pyrophosphase. This shows that light-stimulated proton pumping did not require the pumping activity of the tonoplast pyrophosphatase. Apparently, light-stimulated proton pumping can be based solely on the activity of the tonoplast ATPase.Abbreviation CDCF 5-(and 6-)arboxy-2,7-dichlorofluorescein This work was supported within the Sonderforschungsbereiche 176 and 251 of the University of Würzburg.     

Specificity and function of monoclonal antibodies directed against Ewing sarcoma cells

A selection of 16 monoclonal antibodies has been produced against a fresh Ewing's sarcoma (ES) tumor mixed with a permanent ES cell line. The majority of antibodies identify an 80-kDa molecule, which is not detected on healthy tissues except on certain cultured monocytes. One antibody recognize the CD2 ligand MIC2 and 2 antibodies (numbers 13 and 16) define a higher-molecular-mass antigen. Antibody 16 is also expressed on mesenchymal fibroblasts of bone marrow or fetal origin. Tumorspecific antigen expression is potentially linked to the chromosome 22 abnormality decribed in Ewing's sarcoma.     

Orotidine-5′-monophosphate decarboxylase fromPseudomonas aeruginosa PAO1: Cloning,overexpression, and enzyme characterization

Orotidine-5-monophosphate decarboxylase (OMPdecase) catalyzes the final step in pyrimidine biosynthesis, the conversion of orotidine-5-monophosphate (OMP) to uridine-5-monophosphate. ThepyrF gene, encoding OMPdecase, was isolated from a chromosomal library ofPseudomonas aeruginosa PAO1 by screening for complementation of anEscherichia coli and aP. aeruginosa pyrF mutant. The nucleotide sequence of a 2510-bp chromosomal DNA fragment, complementing both strains, was determined (EMBL accession number X65613). On this a 696-bp open reading frame capable of encoding the 24 kDa OMPdecase was identified. Despite a generally good correspondence to other OMPdecase sequences, theP. aeruginosa gene was unique in that it did not constitute part of an operon. ThepyrF gene was amplified by polymerase chain reaction, overexpressed in the pT7-7/E. coli BL21(DE3) system and purified to near electrophoretic homogeneity by anion exchange chromatography. Characterization of the purified enzyme revealed the following data, aK _m value for OMP of 9.91 M and an isoelectric point of 6.65. No major decrease in enzyme activity was observed in a pH range between 7.8 and 10.2. Gel electrophoresis under nondenaturing conditions suggested that the native form of OMPdecase is the dimer.     

Resynchronization of the Circadian Corticosterone Rhythm After a Light/Dark Shift in Juvenile and Adult Mice

Most of the extensive literature concerning the resynchronization of circadian rhythms after a Zeitgeber shift is devoted to the dependence of resynchronization on the mode of the shift and the strength of the Zeitgeber, as well as on the circadian function investigated. Ontogenetic influences have rarely been investigated. Therefore, we studied the resynchronization of several circadian rhythms in juvenile and adult female laboratory mice. We present here the results concerning the corticosterone rhythm. The daily rhythms were determined as transverse profiles (2-h intervals) before as well as 3, 7, and 14 days after an 8-h phase delay of the light/dark cycle produced by a single prolongation of dark time. The corticosterone concentration in serum was determined radioimmunologically. In the control animals the daily patterns were bimodal, with main maxima at the end of the light time and secondary ones just after lights on. Ontogenetic differences were small. In adult mice the amplitude was slightly increased due to an increase in the maximum values, and the time of highest hormone concentrations was slightly phase advanced. In juvenile mice, a distinct daily pattern with a phase position in relation to the light/dark cycle corresponding to that of control animals was present on the 3rd day after the Zeitgeber shift. The daily mean as well as the minimum and maximum values increased initially and reached the values of control animals during the second week. In adult animals, a pronounced daily rhythm with the normal phase position was present only at the 7th postshift day. The amplitude, daily mean, and maximum values were decreased, and the minimum values were increased. The initial values were not reached even after 2 weeks. The results show that resynchronization was faster in juvenile mice compared with adult mice. As a possible cause for the observed age-related differences, a not yet stabilized phase-coupling between various circadian rhythms is supposed.     

The first decade of oligotrophication of Lake Constance

In Lake Constance, after several decades of cutrophication, a decrease in phosphorus loading over the last decade has lead to a partial recovery from eutrophication. Here we analyse the shift in the taxonomic composition of phytoplankton during the first decade of oligotrophication in Lake Constance. During the 1980s, spring total P concentrations decreased from ca. 130 to less than 50 ·l^–1. This decrease was reflected by an approximately proportional decrease in summer phytoplankton biomass while spring phytoplankton biomass seemed unresponsive. Major taxonomic changes occured during both growth seasons. In spring, the proportion of diatoms, green algae and Chrysophyta increased while the proportion of Cryptophyta decreased. The summer trend was very different: the relative importance of diatoms decreased and Cryptophyta and Chrysophyta increased, while Chlorophyta reached their peak around 1985. These trends are also analysed at the genus level. Comparison with taxonomic trends during the eutrophication period shows the expected reversals in most cases. Comparison with other lakes shows general similarities, with the notable exception that Planktothrix rubescens has never been important in Lake Constance. The increase of diatoms during spring is attributed to their improved competitive performance with increasing Si:P ratios. Their decrease during summer is explained by the increasing silicate removal from the epilimnion by increasing spring populations.     

Electron Flow to the Intersystem Chain from Stromal Components and Cyclic Electron Flow in Maize Chloroplasts, as Detected in Intact Leaves by Monitoring Redox Change of P700 and Chlorophyll Fluorescence

The functional pool size of electrons in the intersystem chainof the chloroplasts of maize was estimated to be about 25 perP700 by the redox change in P700 with single- and multiple-turnoverlights under far-red light in intact leaves. This is about twicethe pool size observed in C₃ plants. Furthermore, the stromalpool size of electrons that can be donated to P700⁺ after actinicillumination was larger in maize leaves than in leaves of C₃plants, giving a maximum value of 225 electrons per P700. Maizeleaves showed an increase in the yield of modulated Chl fluorescenceafter turning off of actinic light, which confirms the donationof electrons in the dark to the intersystem chain from the stromaldonors that accumulated during actinic illumination. We proposethat the mesophyll chloroplasts are responsible for a high levelof electron-donating activity to the intersystem chain fromstromal donors such as triose phosphates and malate with NADPHas an intermediate. The level of P700⁺ under strong far-redlight was decreased after actinic illumination, suggesting theoperation of an actinic light-triggered cyclic electron flowin chloroplasts of the bundle sheath cells. (Received August 14, 1992; Accepted October 13, 1992)     

HLA-DP/DR interaction in early onset pauciarticular juvenile chronic arthritis

We investigated the polymorphic second exon of the HLA-DPB1 and HLA-DRB1 genes, using in vitro DNA amplification by polymerase chain reaction (PCR) and oligonucleotide hybridization in 136 patients with early onset pauciarticular juvenile chronic arthritis (EOPA-JCA) and 199 healthy controls. The analysis of the HLA-DRB1 system revealed that most of the DRB1 alleles are not indifferent with respect to susceptibility to EOPA-JCA. There is a hierarchy of susceptible (DRB1*08, DR5), permissive (DRB1*01), moderately protective (DR2, DRB1*04), and protective (DRB1*07) alleles. In contrast, no hierarchy could be shown for the HLA-DPB1 system. DPB1*0201 was found to be susceptible. The relatively frequent alleles DPB1*0402 and DPB1*0401 seem to be indifferent. The associations with DPB1*0201, DR5, and DRB1*08 are independent of each other: that is to say they, are not brought about by linkage disequilibrium. The susceptible alleles DPB1*0201 and DR5 show evidence for interaction in the pathogenesis of EOPA-JCA. Interaction seems likely between DPB1*0201 and DRB1*08, DR5 and DRB1*08, or between DR6 and DRB1*08. The strongest interaction exists between DPB1*0201 and a common DQ factor associated with both DR5 and DRB1*08. Finally, we observed a hierarchy among the various marker combinations, where the risk of developing EOPA-JCA increases with the number of associated markers present in an individual.This work was supported by SFB217.The data presented here are part of the doctoral thesis of C. Paul.     

Effects of magnetic fields on mammary tumor development induced by 7, 12-dimethylbenz(a)anthracene in rats

A series of epidemiological studies have indicated associations between exposure to magnetic fields (MFs) and a variety of cancers, including breast cancer. In order to test the possibility that MF acts as a cancer promoter or copromoter, four separate experiments have been conducted in rats in which the effects of chronic exposure to MFs on the development of mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) were determined. Female rats were exposed in magnetic coils for 91 days (24 h/day) to either alternating current (AC; 50 Hz)-MF or direct current (DC)-MF. Magnetic flux density of the DC-MF was 15 mT. Two AC-MF exposures used a homogeneous field with a flux density of 30 mT (rms); one used a gradient field with flux density ranging from 0.3–1 μT. DMBA (5 mg) was administered orally at the onset of MF exposure and was repeated thrice at intervals of 1 week. In each experiment, 18–36 animals were exposed in 6 magnetic coils. The same number of rats were used as sham-exposed control. These control animals were treated with DMBA and were placed in dummy coils in the same room as the MF-exposed rats. Furthermore, groups of age-matched rats (reference controls) were treated with DMBA but housed in another room to exclude any MF exposure due to the magnetic stray field from the MF produced by coils. At the end of the exposure or sham-exposure period, tumor number and weight or size of tumors were determined at necropsy. Results were as follows: In sham-exposed animals or reference controls, the tumor incidence varied between 50 and 78% in the 4 experiments. The average number of mammary tumors per tumor-bearing animal varied between 1.6 and 2.9. In none of the experiments did MFs significantly alter tumor incidence, but in one of the experiments with AC-MF exposure at 30 mT, the number of tumors per tumor-bearing animal was significantly increased. Furthermore, exposure to a DC-MF at 15 mT significantly enhanced the tumor weight. Exposure to a gradient AC-MF at 0.3–1 μT exerted no significant effects. These experiments seem to indicate that MFs at high flux densities may act as a promoter or copromoter of breast cancer. However, this interpretation must be considered only a tentative conclusion because of the limitations of this study, particularly the small sample size used for MF exposure and the lack of repetition of data. © 1993 Wiley-Liss. Inc.     

Ultrastructure and Cytochemistry of Periostracum and Mantle Edge of Biomphalaria glabrata (Gastropoda,Basommatophora)

Abstract Three layers of different electron density can be distinguished in the periostracum. Periostracal units of up to 900 nm length are merged into the outer fibrous layer and binding of gold-labelled lectin-WGA indicates the presence of chitin because it is labile to chitinase treatment. The periostracum is formed by the epithelia of the groove and the belt at the mantle edge. The distal and basal epithelium of the groove consists mainly of type A cells with an extended Golgi apparatus and apical vesicles. The presence of peroxidase and phenol oxidase indicates a function in tanning of the periostracum. In the proximal epithelium of the groove, type B cells with protruding apices add more material for periostracum formation. Type C cells secrete single periostracal units which are formed within single vesicles or larger vacuoles. Type D cells secrete electron-dense vesicles which also contain WGA-positive material. The distal cells of the belt are characterized by predominating strands of the rER while subapical vacuoles, to some of which WGA binds, dominate in the cells of the central part. In the belt, phenol oxidase and peroxidase can be localized in cisternae of the rER and the Golgi apparatus. Numerous control incubations indicate that, indeed, two different enzymes are localized.     

mtDNA variation of aboriginal Siberians reveals distinct genetic affinities with Native Americans.

The mtDNA variation of 411 individuals from 10 aboriginal Siberian populations was analyzed in an effort to delineate the relationships between Siberian and Native American populations. All mtDNAs were characterized by PCR amplification and restriction analysis, and a subset of them was characterized by control region sequencing. The resulting data were then compiled with previous mtDNA data from Native Americans and Asians and were used for phylogenetic analyses and sequence divergence estimations. Aboriginal Siberian populations exhibited mtDNAs from three (A, C, and D) of the four haplogroups observed in Native Americans. However, none of the Siberian populations showed mtDNAs from the fourth haplogroup, group B. The presence of group B deletion haplotypes in East Asian and Native American populations but their absence in Siberians raises the possibility that haplogroup B could represent a migratory event distinct from the one(s) which brought group A, C, and D mtDNAs to the Americas. Our findings support the hypothesis that the first humans to move from Siberia to the Americas carried with them a limited number of founding mtDNAs and that the initial migration occurred between 17,000-34,000 years before present.