Maize Brittle Stalk2-Like3, encoding a COBRA protein, functions in cell wall formation and carbohydrate partitioning.

Carbohydrate partitioning from leaves to sink tissues is essential for plant growth and development. The maize (Zea mays) recessive carbohydrate partitioning defective28 (cpd28) and cpd47 mutants exhibit leaf chlorosis and accumulation of starch and soluble sugars. Transport studies with 14C-sucrose (Suc) found drastically decreased export from mature leaves in cpd28 and cpd47 mutants relative to wild-type siblings. Consistent with decreased Suc export, cpd28 mutants exhibited decreased phloem pressure in mature leaves, and altered phloem cell wall ultrastructure in immature and mature leaves. We identified the causative mutations in the Brittle Stalk2-Like3 (Bk2L3) gene, a member of the COBRA family, which is involved in cell wall development across angiosperms. None of the previously characterized COBRA genes are reported to affect carbohydrate export. Consistent with other characterized COBRA members, the BK2L3 protein localized to the plasma membrane, and the mutants condition a dwarf phenotype in dark-grown shoots and primary roots, as well as the loss of anisotropic cell elongation in the root elongation zone. Likewise, both mutants exhibit a significant cellulose deficiency in mature leaves. Therefore, Bk2L3 functions in tissue growth and cell wall development, and this work elucidates a unique connection between cellulose deposition in the phloem and whole-plant carbohydrate partitioning.

Effects of Long-Term Exposure of Intermediate Frequency Magnetic Fields (20 kHz, 360 µT) on the Development, Pathological Findings, and Behavior of Female Mice.

The use of magnetic fields in the intermediate-frequency (IF) range to wirelessly charge electric cars with power transfer in the kilowatt range has become increasingly widespread, leading to unavoidable stray fields in the microtesla range. Only a handful of studies have assessed the potential biological risks associated with exposure to such fields. We exposed female mice (n = 80 per group) to either 20 kHz, 360 µT (rms), or sham in Helmholtz coils to conduct a blind design study. Exposure started at 3 months of age (24 h/day). Body mass was recorded every 1-2 weeks. At 10 months of age, three behavioral tests were performed on 24 animals per group. Three months later, the mice were sacrificed and organs (brain, liver, kidney, spleen, and lung) were removed and prepared for microscopic analysis. Our findings demonstrate no differences in the development of body mass and survival rates (96% and 89%, respectively). Similarly, no significant differences were observed in tumor incidence rates. When it comes to behavioral tests, the 8-arm maze results revealed no significant differences. In contrast, the Rotarod data were significantly (P < 0.001) different with longer retention times seen in the exposed mice. In the open field, the number of supported rears was significantly lower (P < 0.01), whereas the other endpoints did not show any differences. Overall, our data reveal no adverse effects of exposure to 20 kHz, 360 µT on the development and tumor incidences, while the significant differences in the behavioral tests may indicate higher levels of alertness in mice.

Maize Carbohydrate Partitioning Defective33 Encodes an MCTP Protein and Functions in Sucrose Export from Leaves.

To sustain plant growth, development, and crop yield, sucrose must be transported from leaves to distant parts of the plant, such as seeds and roots. To identify genes that regulate sucrose accumulation and transport in maize (Zea mays), we isolated carbohydrate partitioning defective33 (cpd33), a recessive mutant that accumulated excess starch and soluble sugars in mature leaves. The cpd33 mutants also exhibited chlorosis in the leaf blades, greatly diminished plant growth, and reduced fertility. Cpd33 encodes a protein containing multiple C2 domains and transmembrane regions. Subcellular localization experiments showed the CPD33 protein localized to plasmodesmata (PD), the plasma membrane, and the endoplasmic reticulum. We also found that a loss-of-function mutant of the CPD33 homolog in Arabidopsis, QUIRKY, had a similar carbohydrate hyperaccumulation phenotype. Radioactively labeled sucrose transport assays showed that sucrose export was significantly lower in cpd33 mutant leaves relative to wild-type leaves. However, PD transport in the adaxial-abaxial direction was unaffected in cpd33 mutant leaves. Intriguingly, transmission electron microscopy revealed fewer PD at the companion cell-sieve element interface in mutant phloem tissue, providing a possible explanation for the reduced sucrose export in mutant leaves. Collectively, our results suggest that CPD33 functions to promote symplastic transport into sieve elements.

Tumor promotion by exposure to radiofrequency electromagnetic fields below exposure limits for humans.

The vast majority of in vitro and in vivo studies did not find cancerogenic effects of exposure to electromagnetic fields (RF-EMF), i.e. emitted by mobile phones and base stations. Previously published results from a pilot study with carcinogen-treated mice, however, suggested tumor-promoting effects of RF-EMF (Tillmann et al., 2010). We have performed a replication study using higher numbers of animals per group and including two additional exposure levels (0 (sham), 0.04, 0.4 and 2 W/kg SAR). We could confirm and extend the originally reported findings. Numbers of tumors of the lungs and livers in exposed animals were significantly higher than in sham-exposed controls. In addition, lymphomas were also found to be significantly elevated by exposure. A clear dose-response effect is absent. We hypothesize that these tumor-promoting effects may be caused by metabolic changes due to exposure. Since many of the tumor-promoting effects in our study were seen at low to moderate exposure levels (0.04 and 0.4 W/kg SAR), thus well below exposure limits for the users of mobile phones, further studies are warranted to investigate the underlying mechanisms. Our findings may help to understand the repeatedly reported increased incidences of brain tumors in heavy users of mobile phones.

Effects of early-onset radiofrequency electromagnetic field exposure (GSM 900 MHz) on behavior and memory in rats.

Female Wistar rats, from an age of 14 days to 19 months, were exposed in the head region for 2 h per day, 5 days per week, to a GSM-modulated 900 MHz radiofrequency electromagnetic field (RF-EMF). The average specific absorption rates (SAR) in the brain were 0 (sham), 0.7, 2.5 and 10 W/kg. To ensure a primary exposure of the head region, rats were fixed in restraining tubes of different sizes according to their increasing body weight. During the experiment, a set of 4 behavioral and learning tests (rotarod, Morris water maze, 8-arm radial maze, open field) were performed 3 times in juvenile, adult and presenile rats. In these tests, no profound differences could be identified between the groups. Only presenile rats of the cage control group showed a lower activity in two of these tests compared to the other groups presumably due to the lack of daily handling. The rotarod data revealed on some testing days significantly longer holding times for the sham-exposed rat vs. the exposed rat, but these findings were not consistent. During the first year, body weights of sham-exposed and exposed rats were not different from those of the cage controls, and thereafter only marginally lower, so that the effect of stress as confounder was probably negligible. The results of this study do not indicate harmful effects of long-term RF-EMF exposure even when begun at an early age on subsequent development, learning skills and behavior in rats, even at relatively high SAR values.

Noninvasive assessment of metabolic effects of exposure to 900 MHz electromagnetic fields on Djungarian Hamsters ( Phodopus sungorus ).

Sixteen male Djungarian hamsters, serving as their own controls, were individually exposed to RF-EMF (900 MHz, GSM modulation) at 0 (sham), 0.08, 0.4 or 4 W/kg specific absorption rate (SAR) in specially constructed rectangular waveguides. Exposure duration was one week per condition, followed by one week without exposure. Once per day, the temperatures of the hamsters' back fur (a surrogate for skin temperature) and the cornea of the eye (a surrogate for body temperature), were measured by infrared thermography. Oxygen, carbon dioxide and humidity were measured continuously in the ambient and exhaled air. Food and water consumption, as well as body weight were recorded once per week. Only at the highest SAR level were the following effects observed: fur temperatures were elevated by approximately 0.5°C (P < 0.001), while the temperatures of the eyes' surface were not affected; food consumption was lowered (P < 0.05), while water consumption and body weight were not affected; the production of carbon dioxide was lowered during the day (P < 0.01) and unaffected during the night, while oxygen consumption levels remained unaffected and finally the respiratory quotient (carbon dioxide production divided by oxygen consumption) was lower during the day (P < 0.05) and also somewhat lower during the night (not significant). The results demonstrate the usefulness of our methods for experiments dealing with metabolic effects of RF-EMF exposure in rodents. They also confirm the assumption that even though the metabolism is reduced at high SAR levels, the body core temperature is being kept constant by the energy uptake from the RF-EMF exposure which is able to physiologically compensate for the reduced metabolism.

Probing lymphoma infiltration in spleen of AKR/J mice chronically exposed to electromagnetic fields for risk assessment--toward noninvasive modeling.

Using the AKR/J mouse model, the potential of Raman spectroscopy for monitoring lymphoma in predisposed subjects is demonstrated by discriminating lymphoma infiltration in spleens; the relevance of different excitation profiles is shown. Under green excitation with optimal fluorescence bleaching, stronger DNA bands, intensity variations at amide-III and phenylalanine bands, and the behavior of the 1606/1639 cm(-1) doublet correlate with tumorigenesis. Under red excitation, Raman fingerprints with multivariate models help to discriminate AKR/J-mouse histological subtypes: Lymphoblastic lymphoma (LB) is found significantly distant from both separated lymphocytic lymphoma (LL) and healthy spleen; this agrees with histology since LB has well differentiated large lymphoma cells, while LL, with smaller cells similar to normal lymphocytes, usually cannot be discriminated from normal tissue without histoimmunoassays.

Temporal control of spermatogenesis is independent of the central circadian pacemaker in Djungarian hamsters (Phodopus sungorus).

In mammals, the duration of the cycle of the seminiferous epithelium (DCSE) largely differs between species, but is remarkably stable within a species, usually showing variations of 1%-3%. It is difficult to change the DCSE, e.g., by hormones or chemicals. Initial experiments, employing quantitative RT-PCR, aimed at investigating the diurnal profiles of the clock genes Arntl (previously called Bmal1) and Per1 in testes and kidneys of Djungarian hamsters (Phodopus sungorus). While the testicular levels of Arntl were almost constant, clear diurnal variations were identified for Per1. In order to clarify whether day length (T-cycle) is a factor for DSCE, adult male hamsters (n = 20 per group) were exposed to normal (T = 24 h), prolonged (T = 25 h), or shortened (T = 23 h) T-cycles, with cycles thus being longer or shorter by 4.2% compared to the normal condition. Exposure lasted for 43 days, during which the activity of the animals was recorded to confirm entrainment. DCSE was estimated by incorporation of bromodeoxyuridine in dividing cells and the immunohistochemical localization of labeled cells in stages I-XII of the seminiferous epithelium. Despite the low variability of the results and the close agreement with previously published data, no effects of prolonged or shortened T-cycles on DCSE could be identified (24 h: 7.98 ± 0.05 days; 23 h: 7.94 ± 0.04 days; 25 h: 7.91 ± 0.03 days; P > 0.05). The results strongly indicate that the high temporal precision of spermatogenesis is independent of the central circadian clock.

Effects of radiofrequency electromagnetic fields (UMTS) on reproduction and development of mice: a multi-generation study.

Male and female mice (C57BL) were chronically exposed (life-long, 24 h/day) to mobile phone communication electromagnetic fields at approximately 1966 MHz (UMTS). Their development and fertility were monitored over four generations by investigating histological, physiological, reproductive and behavioral functions. The mean whole-body SARs, calculated for adult animals at the time of mating, were 0 (sham), 0.08, 0.4 and 1.3 W/kg. Power densities were kept constant for each group (0, 1.35, 6.8 and 22 W/m(2)), resulting in varying SARs due to the different numbers of adults and pups over the course of the experiment. The experiment was done in a blind fashion. The results show no harmful effects of exposure on the fertility and development of the animals. The number and the development of pups were not affected by exposure. Some data, albeit without a clear dose-response relationship, indicate effects of exposure on food consumption that is in accordance with some data published previously. In summary, the results of this study do not indicate harmful effects of long-term exposure of mice to UMTS over several generations.

The role of CC chemokine receptor 2 in alveolar monocyte and neutrophil immigration in intact mice.

The CC chemokine ligand 2 (CCL2) (JE, monocyte chemotactic protein-1 [MCP-1]) and its CC chemokine receptor 2 (CCR2) are critical regulators of monocyte/macrophage trafficking. Recently, we demonstrated that application of exogenous CCL2 in the lungs of mice induced monocyte accumulation in the airspace, whereas combined bronchoalveolar instillation of CCL2 and Escherichia coli endotoxin provoked both enhanced monocyte accumulation and extensive neutrophil influx associated with loss of pulmonary endothelial/epithelial barrier function. In this study, we investigated the role of the CCL2 receptor CCR2 in alveolar leukocyte traffic. In CCR2 knockout mice or wild-type mice treated with the anti-CCR2-blocking monoclonal antibody MC21, monocyte accumulation in response to alveolar CCL2 or CCL2 plus endotoxin was inhibited by more than 90%. Unexpectedly, alveolar neutrophil accumulation in the CCL2/lipopolysaccharide (LPS) model was also drastically reduced by both approaches of CCR2 function interference. When wild-type mice treated with anti-Gr-1 monoclonal antibody to deplete neutrophils selectively or treated with antileukinate, a CXC receptor inhibitor, were challenged with alveolar CCL2 plus LPS, alveolar monocyte accumulation was markedly decreased. Wild-type mice treated with MC21 to block CCR2 function or with anti-Gr-1 to deplete neutrophils did not exhibit the vascular leakage that typically accompanies inflammation triggered by CCL2 and LPS in wild-type mice. These findings confirm a central role for CCR2 in the process of alveolar monocyte recruitment in response to CCL2 alone and combined CCL2 plus LPS and reveal a previously unobserved interdependence between monocyte and neutrophil trafficking that has important implications for the concomitant increase in vascular permeability.