Antigravitropic PIN polarization maintains non-vertical growth in lateral roots

Lateral roots are typically maintained at non-vertical angles with respect to gravity. These gravitropic setpoint angles are intriguing because their maintenance requires that roots are able to effect growth response both with and against the gravity vector, a phenomenon previously attributed to gravitropism acting against an antigravitropic offset mechanism. Here we show how the components mediating gravitropism in the vertical primary root-PINs and phosphatases acting upon them-are reconfigured in their regulation such that lateral root growth at a range of angles can be maintained. We show that the ability of Arabidopsis lateral roots to bend both downward and upward requires the generation of auxin asymmetries and is driven by angle-dependent variation in downward gravitropic auxin flux acting against angle-independent upward, antigravitropic flux. Further, we demonstrate a symmetry in auxin distribution in lateral roots at gravitropic setpoint angle that can be traced back to a net, balanced polarization of PIN3 and PIN7 auxin transporters in the columella. These auxin fluxes are shifted by altering PIN protein phosphoregulation in the columella, either by introducing PIN3 phosphovariant versions or via manipulation of levels of the phosphatase subunit PP2A/RCN1. Finally, we show that auxin, in addition to driving lateral root directional growth, acts within the lateral root columella to induce more vertical growth by increasing RCN1 levels, causing a downward shift in PIN3 localization, thereby diminishing the magnitude of the upward, antigravitropic auxin flux.

GSK3-mediated phosphorylation of DEK3 regulates chromatin accessibility and stress tolerance in Arabidopsis

Chromatin dynamics enable the precise control of transcriptional programmes. The balance between restricting and opening of regulatory sequences on the DNA needs to be adjusted to prevailing conditions and is fine-tuned by chromatin remodelling proteins. DEK is an evolutionarily conserved chromatin architectural protein regulating important chromatin-related processes. However, the molecular link between DEK-induced chromatin reconfigurations and upstream signalling events remains unknown. Here, we show that ASKβ/AtSK31 is a salt stress-activated glycogen synthase kinase 3 (GSK3) from Arabidopsis thaliana that phosphorylates DEK3. This specific phosphorylation alters nuclear DEK3 protein complex composition and affects nucleosome occupancy and chromatin accessibility that is translated into changes in gene expression, contributing to salt stress tolerance. These findings reveal that DEK3 phosphorylation is critical for chromatin function and cellular stress response and provide a mechanistic example of how GSK3-based signalling is directly linked to chromatin, facilitating a transcriptional response.

Application of light scattering tomography for Si(111) samples

The detection of bulk micro-defects in Czochralski-grown silicon (Si) 〈100〉 wafers has significant importance in wafer quality control. Light Scattering Tomography (LST) is an industry standard technique for this purpose. This optical non-contact metrology requires destructive sample preparation: Samples have to be cleaved into half. One particular feature of the method is a dark field detection arrangement, which is achieved by separating the light detection part (microscope unit) from the illumination. Illumination is applied to the front surface of the sample, and the light scattered off of the defects is collected via the cleaved surface. The technique requires the perpendicularity of the cleaved surface to the front surface, which is fulfilled for Si(100) wafers. However, the nominally cleaved surface for Si(111) wafers is not perpendicular to the front surface but has an angle of 70.5°. This significant difference in cleavage results in the fact that Si(111) wafers cannot be measured by standard LST systems. Fortunately, the standard LST system can be modified by tilting the detection part under a proper angle allowing the measurements of Si(111) samples. In this article, we present this new technique in detail, showing the design and measurement capability of the new system. The measurement results are validated by a direct comparison to standard LST measurements on the same samples after proper sample preparation.

Bulk micro-defect detection with low-angle illumination

The detection of oxygen precipitates, voids, and other defects is critical for semiconductor wafer makers. One of the industry standard techniques for detecting these Bulk Micro-Defects (BMDs) is Semilab's Light Scattering Tomograph (LST) system. In this measurement, unpatterned wafers are nominally cleaved in half. Illumination is applied to the front surface of the sample, and the light scattered off of the defects is collected via the cleaved surface. This technique had been limited to the measurement of unpatterned wafers, but device makers show significant interest in measuring BMD distributions on patterned wafers using scattering-based techniques. A pattern on the surface of the wafer can cause significant scattering, making the standard LST technique unsuitable for this task. We present a solution for patterned wafer BMD measurements by an addition of a low-angle illumination unit to the standard LST system. This new illumination unit focuses the light into the bulk of the wafer via the cleaved surface, which enables measurement on patterned samples. The new system is called "light scattering tomograph enhanced by low-angle illumination." Excellent correlation was found between the detected defect densities obtained by the low-angle and the standard LST illumination mode.

Differentiating sepsis from similar groups of symptoms at triage level in emergency care

OBJECTIVES

Conditions that have similar initial presentations as sepsis may make early recognition of sepsis in an emergency room (ER) difficult. We investigated whether selected physiologic and metabolic parameters can be reliably used in the emergency department to differentiate sepsis from other disease states that mimic it, such as dehydration and stroke.

METHODS

Loess regression on retrospective follow-up chart data of patients with sepsis-like symptoms (N = 664) aged 18+ in a large ER in Hungary was used to visualize/identify cutoff points for sepsis risk. A multivariate logistic regression model based on standard triage data was constructed with its corresponding receiver operating characteristic (ROC) curve and compared with another model constructed based on current sepsis guidelines.

RESULTS

Age, bicarbonate, HR, lactate, pH, and body temperature had U, V, W, or reverse U-shaped associations with identifiable inflexion points, but the cutoff values we identified were slightly different from guideline cutoff values. In contrast to the guidelines, no inflexion points could be observed for the association of sepsis with SBP, DPB, MAP, and RR and therefore were treated as continuous variables. Compared to the guidelines-based model, the triage data-driven final model contained additional variables (age, pH, bicarbonate) and did not include lactate. The data-driven model identified about 85% of sepsis cases correctly, while the guidelines-based model identified only about 70% of sepsis cases correctly.

CONCLUSION

Our findings contribute to the growing body of evidence for the necessity of finding improved tools to identify sepsis at early time points, such as in the ER.

AGC kinases and MAB4/MEL proteins maintain PIN polarity by limiting lateral diffusion in plant cells

Polar subcellular localization of the PIN exporters of the phytohormone auxin is a key determinant of directional, intercellular auxin transport and thus a central topic of both plant cell and developmental biology. Arabidopsis mutants lacking PID, a kinase that phosphorylates PINs, or the MAB4/MEL proteins of unknown molecular function display PIN polarity defects and phenocopy pin mutants, but mechanistic insights into how these factors convey PIN polarity are missing. Here, by combining protein biochemistry with quantitative live-cell imaging, we demonstrate that PINs, MAB4/MELs, and AGC kinases interact in the same complex at the plasma membrane. MAB4/MELs are recruited to the plasma membrane by the PINs and in concert with the AGC kinases maintain PIN polarity through limiting lateral diffusion-based escape of PINs from the polar domain. The PIN-MAB4/MEL-PID protein complex has self-reinforcing properties thanks to positive feedback between AGC kinase-mediated PIN phosphorylation and MAB4/MEL recruitment. We thus uncover the molecular mechanism by which AGC kinases and MAB4/MEL proteins regulate PIN localization and plant development.

•

MAB4/MEL proteins are recruited to the plasma membrane by PINs

•

PINs, MAB4/MELs, and AGC kinases directly interact in a multiprotein complex

•

PIN phosphorylation and MAB4/MEL recruitment form a positive feedback loop

•

MAB4/MELs and AGC kinases maintain PIN polarity by limiting PIN lateral diffusion

Receptor kinase module targets PIN-dependent auxin transport during canalization

Spontaneously arising channels that transport the phytohormone auxin provide positional cues for self-organizing aspects of plant development such as flexible vasculature regeneration or its patterning during leaf venation. The auxin canalization hypothesis proposes a feedback between auxin signaling and transport as the underlying mechanism, but molecular players await discovery. We identified part of the machinery that routes auxin transport. The auxin-regulated receptor CAMEL (Canalization-related Auxin-regulated Malectin-type RLK) together with CANAR (Canalization-related Receptor-like kinase) interact with and phosphorylate PIN auxin transporters. camel and canar mutants are impaired in PIN1 subcellular trafficking and auxin-mediated PIN polarization, which macroscopically manifests as defects in leaf venation and vasculature regeneration after wounding. The CAMEL-CANAR receptor complex is part of the auxin feedback that coordinates polarization of individual cells during auxin canalization.

Publisher Correction: The lipid code-dependent phosphoswitch PDK1-D6PK activates PIN-mediated auxin efflux in Arabidopsis

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The lipid code-dependent phosphoswitch PDK1-D6PK activates PIN-mediated auxin efflux in Arabidopsis

Directional intercellular transport of the phytohormone auxin mediated by PIN-FORMED (PIN) efflux carriers has essential roles in both coordinating patterning processes and integrating multiple external cues by rapidly redirecting auxin fluxes. PIN activity is therefore regulated by multiple internal and external cues, for which the underlying molecular mechanisms are not fully elucidated. Here, we demonstrate that 3'-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1 (PDK1), which is conserved in plants and mammals, functions as a molecular hub that perceives upstream lipid signalling and modulates downstream substrate activity through phosphorylation. Using genetic analysis, we show that the loss-of-function Arabidopsis pdk1.1 pdk1.2 mutant exhibits a plethora of abnormalities in organogenesis and growth due to defective polar auxin transport. Further cellular and biochemical analyses reveal that PDK1 phosphorylates D6 protein kinase, a well-known upstream activator of PIN proteins. We uncover a lipid-dependent phosphorylation cascade that connects membrane-composition-based cellular signalling with plant growth and patterning by regulating morphogenetic auxin fluxes.

Salicylic Acid Targets Protein Phosphatase 2A to Attenuate Growth in Plants

Plants, like other multicellular organisms, survive through a delicate balance between growth and defense against pathogens. Salicylic acid (SA) is a major defense signal in plants, and the perception mechanism as well as downstream signaling activating the immune response are known. Here, we identify a parallel SA signaling that mediates growth attenuation. SA directly binds to A subunits of protein phosphatase 2A (PP2A), inhibiting activity of this complex. Among PP2A targets, the PIN2 auxin transporter is hyperphosphorylated in response to SA, leading to changed activity of this important growth regulator. Accordingly, auxin transport and auxin-mediated root development, including growth, gravitropic response, and lateral root organogenesis, are inhibited. This study reveals how SA, besides activating immunity, concomitantly attenuates growth through crosstalk with the auxin distribution network. Further analysis of this dual role of SA and characterization of additional SA-regulated PP2A targets will provide further insights into mechanisms maintaining a balance between growth and defense.

•

SA modulates root development independently of NPR1-mediated canonical signaling

•

SA attenuates growth through crosstalk with the auxin transport network

•

SA upregulates the phosphorylation status of PIN auxin efflux carriers through PP2A

•

SA directly targets A subunits of PP2A, inhibiting the activity of the complex

Pressure-induced switching properties of the iron(iii) spin-transition complex [FeIII(3-OMeSalEen)2]PF6

The volume-dependent properties of a spin-crossover Fe(iii) prototypical compound revealed by combined magnetic, vibrational and structural investigations of the pressure effect.

Effect of composition and pressure on the shear strength of sodium silicate glasses: An atomic scale simulation study

The elastoplastic behavior of sodium silicate glasses is studied at different scales as a function of composition and pressure, with the help of quasistatic atomistic simulations. The samples are first compressed and then sheared at constant pressure to calculate yield strength and permanent plastic deformations. Changes occurring in the global response are then compared to the analysis of local plastic rearrangements and strain heterogeneities. It is shown that the plastic response results from the succession of well-identified localized irreversible deformations occurring in a nanometer-size area. The size and the number of these local rearrangements, as well as the amount of internal deviatoric and volumetric plastic deformation, are sensitive to the composition and to the pressure. In the early stages of the deformation, plastic rearrangements are driven by sodium mobility. Consequently, the elastic yield strength decreases when the sodium content increases, and the same when pressure increases. Finally, good correlation was found between global and local stress-strain relationships, reinforcing again the role of sodium ions as local initiators of the plastic behavior observed at larger scales.

Elastic coupling between spin-crossover particles and cellulose fibers

Composite materials made of cellulose fibers and spin crossover micro-particles investigated by dynamic mechanical analysis revealed an abrupt and reversible stiffening upon spin transition from the low spin to the high spin state.

Nanocrystals of Fe(phen)2(NCS)2 and the size-dependent spin-crossover characteristics

We describe the preparation of nano- and microcrystals of the Fe(phen)₂(NCS)₂ spin-crossover prototypical compound based on the solvent-assisted technique applied to an ionic and soluble precursor and analyze the size-dependent characteristics of the thermal spin-crossover.

Immunohistochemistry of cerebellar seizures: mossy fiber afferents play an important role in seizure spread and initiation in the rat

Clinical reports suggest the participation of the cerebellum in epilepsy. Mossy fibers are the main excitatory afferents of the cerebellar cortex; most of them use glutamate and strongly excite granule cells through NMDA and AMPA receptors. The role of the ponto-cerebellar mossy fibers in cerebellar neuronal hyperactivity was investigated in the present study in experimental adult Wistar rats. We detected neuronal hyperactivity through the expression of the glutamate-induced c-fos protein, by means of immunohistochemistry and immunoblotting in the vermis and in the hemispheres. Generalized seizures were induced by means of intraperitoneal 4-aminopyridine injections. Following the 4-aminopyridine seizures, the c-fos expression of cerebellar granule cells was significantly elevated at 1.5h in every lobule. Maximum c-fos expression was seen at 3h. The role of the ponto-cerebellar mossy fiber afferents in the induction of c-fos expression was examined after the transection of the middle cerebellar peduncle on the left side. Immunohistochemical analysis 14 days after the surgery revealed that the synapsin I immunoreactivity was significantly reduced in the cerebellar cortex on the operated side, compared to the sham-operated controls and to the non-operated cerebellar hemisphere of the operated animals, indicating the degeneration of mossy fiber terminals. Transection of the middle cerebellar peduncle suppressed cerebellar c-fos expression in the vermis and in the hemispheres significantly. These findings suggest the strong involvement of the middle cerebellar peduncle and the ponto-cerebellar mossy fibers in the pathophysiology of cerebellar epilepsy.

Enhanced luminescence stability with a Tb–spin crossover nanocomposite for spin state monitoring

Tb–spin crossover nanocomposite possessing high photoluminescence stability is shown to be very efficient for spin state monitoring via a reabsorption mechanism.

Formation of nanoparticles by ion beam irradiation of thin films

The possibility of fabricating nanoparticles by ion bombardment was investigated by the ion bombardment of indium films on oxide covered Si and Cr surfaces. The different masses of implanting specimen ensured the different energy transfer while the same Si substrate ensured the same thermal conductivity for the In and Cr layers. Chromium served as a reference for the effect of ion bombardment and as a substrate as well. The SRIM program was used to simulate the ion surface interaction process. The nanoparticles were detected by scanning electron microscopy (SEM). We found that the melting of the In layer results in the formation of nanoparticles of 50-300 nm diameter and 5-10 nm height. This method can be promising for nanoparticle formation of materials with low melting point.

[Transanal endoscopic microsurgery--our initial experience]

The aim of this study was to describe a single institution's experience with transanal endoscopic microsurgery (TEMS) in patients with benign and malignant rectal tumors.

MATERIAL AND METHOD

This was a prospective descriptive survey. Between January 2006 and January 2010, 14 patients underwent transanal endoscopic microsurgery excision of benign (8) or malignant (6) rectal tumors, located 4 to 15 cm from the dentate line. Median age was 59.7 years and the mean follow up was 29 months.

RESULTS

The average tumor size was 3.4 cm, median operating time was 40 min. Median length of hospital stay was 4.35 days. During the follow-up period, benign tumor recurrence was observed in one patient (7.14%), managed by repeated TEMS. Histologic staging of malignant tumors was T1 (2) and T2 (4). In two patients with inadequate resection margins open radical surgery was performed. One had recurrent disease, which was managed by radical surgery. No cancer-related deaths were observed during the follow-up period. There was no operative mortality. No major postoperative complications were recorded. Anal incontinence persisted for 3 weeks in one patient.

CONCLUSION

Transanal endoscopic microsurgery excision is a safe and precise technique and should become a procedure of choice for benign rectal tumors and selected early malignant neoplasms.

Circulatory consequences of reduced endogenous nitric oxide production during small-volume resuscitation

Hypertonic small-volume resuscitation transiently restores the cardiovascular function during various circulatory disturbances. Nitric oxide (NO) is an important mediator of flow-induced peripheral and central hemodynamic changes, and therefore, we hypothesized that a decreased endogenous NO production could influence the consequences and the effectiveness of hypertonic fluid therapy. The main goal of this study was to outline and compare the circulatory effects small volume hypertonic saline-dextran (HSD, 7.5% NaCl-10% dextran; 4 ml/kg iv) infusion with (n=7) or without (n=7) artificially diminished NO production in normovolemic anesthetized dogs. HSD administration significantly increased cardiac index (CI), coronary flow (CF) and myocardial contractility, and elevated plasma nitrite/nitrate (NOx) and endothelin-1 (ET-1) levels. However, the late (2 h) postinfusion period was characterized by significantly decreased myocardial NO synthase (NOS) and enhanced myeloperoxidase activities. Pre-treatment with the non-selective NOS inhibitor N-nitro-L-arginine (NNA, 4 mg/kg) immediately increased cardiac contractility, and the HSD-induced CI and CF elevations and the positive inotropy were absent. Additionally, plasma ET-1 levels increased and NOx levels were significantly decreased. In conclusion, our results demonstrate that HSD infusion leads to preponderant vasoconstriction when endogenous NO synthesis is diminished, and this could explain the loss of effectiveness of HSD resuscitation in NO-deficient states.

[Therapeutic approach for patients with positive resection line (R1) after gastrectomy for gastric cancer]

INTRODUCTION

The radical treatment of the gastric cancer consist in large gastric resections and lymphadenectomy. Resection line involvement at microscopic histopathological examination (R1) could change prognostic unfavorable.

MATERIAL AND METHODS

They were 135 patients with gastric cancer operated between 2006-2007, with radical gastric resections and lymphadenectomy. In 3 patients with early gastric cancer and 23 patients with different stages of cancers, histopathological examination showed resection line involvement. From this study were eliminated the patients with stage IV cancers in whom resections were palliative.

RESULTS

Incidence of positive resection line involvement was 19,25%. 88,46% of the tumors were staged pT2 and pT3 and the majority was poorly differentiated or undifferentiated (G3 and G4). Lymphatic involvement (pN1 or pN2) was demonstrated in 18 (69,23%0 patients with R1. Perioperative complications were encountered in 15,38% of this patients, with 7,69% mortality.

CONCLUSIONS

Presence of tumoral tissue at resection line level could decrease survival in this patients. Therapeutic protocol in patients with resection line involvement (re-laparotomy with re-resection or surveillance) must be establish in accordance with several factors: T and N category, risks of another surgical interventions, patients acceptance.

[The role of diagnostic laparoscopy in periampullary and pancreatic cancers. A study based on 27 cases]

BACKGROUND

Starting from the premise that abdominal tumours require very accurate assessment and staging, the study "DIASTAL" (laparoscopic diagnosis and staging of abdominal tumours) proposed to establish the effectiveness of laparoscopy in the diagnosis and resectability of these neoplasms. The aim of this study was to evaluate diagnostic laparoscopy for periampullary and pancreatic neoplasms.

METHODS

The clinical study was based on the analysis two different groups including 27 patients in total, in whom we used also diagnostic laparoscopy as a staging method.

RESULTS

The percentage of understaged patients after preoperative examinations was high in both groups range 59.09%-63.63%. Diagnostic laparoscopy reduced the number of unnecessary laparotomies.

CONCLUSIONS

Diagnostic laparoscopy could lead to more accurate assessment of periampullary and pancreatic cancers, not only as a staging method but also as a minimally invasive surgical technique for palliation.

Bioinspired artificial photonic nanoarchitecture using the elytron of the beetle Trigonophorus rothschildi varians as a 'blueprint'

An unusual, intercalated photonic nanoarchitecture was discovered in the elytra of Taiwanese Trigonophorus rothschildi varians beetles. It consists of a multilayer structure intercalated with a random distribution of cylindrical holes normal to the plane of the multilayer. The nanoarchitectures were characterized structurally by scanning electron microscopy and optically by normal incidence, integrated and goniometric reflectance measurements. They exhibit an unsaturated specular and saturated non-specular component of the reflected light. Bioinspired, artificial nanoarchitectures of similar structure and with similar properties were realized by drilling holes of submicron size in a multilayer structure, showing that such photonic nanoarchitectures of biological origin may constitute valuable blueprints for artificial photonic materials.

Modulation of cardiac contractility through endothelin-1 release and myocardial mast cell degranulation

The aim of this study was to outline the consequences of a hypertonic saline-dextran-40 (HSD) infusion-induced peripheral flow stimulus on the ventricular function in closed-chest, pentobarbital-anesthetized dogs. We hypothesized that HSD-induced elevation in endothelin-1 (ET-1) and nitric oxide (NO) release can have a role in myocardial contractile responses; and that cardiac mast cells (MC) degranulation may be involved in this process. The consequences of disodium cromoglycate (a MC stabilizer) or ETR-p1/fl peptide (an endothelin-A receptor antagonist) treatment were evaluated. A 4 ml/kg iv HSD40 infusion significantly increased cardiac index and myocardial contractility, and resulted in a decreased peripheral resistance. The postinfusion period was characterized by significant plasma NO and ET-1 elevations, these hemodynamic and biochemical changes being accompanied by a decreased myocardial ET-1 content, NO synthase activity and enhanced myocardial MC degranulation. Disodium cromoglycate treatment inhibited the HSD40-induced elevations in myocardial contractility and MC degranulation, and similar hemodynamic changes were noted after treatment with ETR-p1/fl peptide, together with a normalized myocardial myocardial ET-1 content, NO synthesis and a significant reduction in MC degranulation. These results indicate that peripheral NO and ET-1 release modulates the cardiac contractility through myocardial ET-A receptor activation and MC degranulation.

Formation of ge nanocrystals in SiO2 by electron beam evaporation

Ge nanocrystals were formed by electron beam evaporation on SiO2 covered Si substrates. The size and distribution of the nanocrystals were studied by atomic force microscopy, scanning electron microscopy and cross-sectional transmission electron microscopy. Dependencies of the nanocrystal size, of the nanocrystal surface coverage, and sheet resistance obtained by van der Pauw method of the Ge layer have been found on the evaporation time. The suggested growth mechanism for the formation of nanocrystals is the Volmer-Weber type. The sheet resistance exhibited a power dependence on the nanocrystal size.

Selective photoswitching of the binuclear spin crossover compound {[Fe(bt)(NCS)2]2(bpm)} into two distinct macroscopic phases

The low-spin (LS-LS, S = 0) diamagnetic form of the binuclear spin crossover complex {[Fe(bt)(NCS)(2)](2)(bpm)} was selectively photoconverted into two distinct macroscopic phases at different excitation wavelengths (1342 or 647.1 nm). These long-lived metastable phases have been identified, respectively, as the symmetry-broken paramagnetic form (HS-LS, S = 2) and the antiferromagnetically coupled (HS-HS, S = 0) high-spin form of the compound. The selectivity may be explained by the strong coupling of the primary excited states to the paramagnetic state.

Reliability and precision of neural spike timing: simulation of spectrally broadband synaptic inputs

Spectrally broadband stimulation of neurons has been an effective method for studying their dynamic responses to simulated synaptic inputs. Previous studies with such stimulation were mostly based upon the direct intracellular injection of noisy current waveforms. In the present study we analyze and compare the firing output of various identified molluscan neurons to aperiodic, broadband current signals using three types of stimulus paradigms: 1. direct injection in current clamp mode, 2. conductance injection using electrotonic coupling of the input waveform to the neuron, and 3. conductance injection using a simulated chemical excitatory connection. The current waveforms were presented in 15 successive trials and the trial-to-trial variations of the spike responses were analyzed using peri-stimulus spike density functions. Comparing the responses of the neurons to the same type of input waveforms, we found that conductance injection resulted in more reliable and precise spike responses than direct current injection. The statistical parameters of the response spike trains depended on the spectral distribution of the input. The reliability increased with increasing cutoff frequency, while the temporal jitter of spikes changed in the opposite direction. Neurons with endogenous bursting displayed lower reproducibility in their responses to noisy waveforms when injected directly; however, they fired far more reliably and precisely when receiving the same waveforms as conductance inputs. The results show that molluscan neurons are capable of accurately reproducing their responses to synaptic inputs. Conductance injection provides an enhanced experimental technique for assessing the neurons' spike timing reliability and it should be preferred over direct current injection of noisy waveforms.

Cadmium ions modulate GABA induced currents in molluscan neurons

The effect of Cd2+, as one of the most widespread toxic environmental pollutants, was studied on gamma-aminobutyric acid (GABA) evoked responses of identified neurons in the central nervous system of the pond snail, LYmnaea stagnalis L. (Gastropoda). In the experiments, the modulation of the action of GABA both on neuronal activity (current clamp recording) and on the a GABA activated membrane Cl- current (voltage clamp studies) has been shown. It was found that: 1. GABA could evoked three different various types of response in GABA sensitive neurons: i) hyperpolarization with strong inhibition of ongoing spike activity, ii) short depolarization with an increase of spike the activity, iii) biphasic respone with a short excitation followed by a more prolonged long inhibition. 2. In low-Cl- solution the inhibitory action of GABA was reduced or eliminated, but the excitatory one was not or only moderately affected. 3. CdCl2 inhibited the GABA evoked hyperpolarization, but left intact or only slightly reduced the excitation evoked by GABA. 4. The inward Cl- current evoked by GABA at a -75 mV holding potential was slightly augmented in the presence of I micromol/l Cd2+, but was reduced or blocked at higher cadmium concentrations. The effect of Cd2+ was concentration and time dependent. 5. Parallel with reducing the GABA evoked current, cadmium increased both the time to peak and the half inactivation time of the current. 6. CdCl2 alone, in 50 micromol/l concentration, induced a 1-2 nA inward current. The blocking effect of cadmium on GABA activated inhibitory processes can be an important component of the neuro-toxic effects of this heavy metal ion.

Rapid identification of Arabidopsis insertion mutants by non-radioactive detection of T-DNA tagged genes

To assist in the analysis of plant gene functions we have generated a new Arabidopsis insertion mutant collection of 90 000 lines that carry the T-DNA of Agrobacterium gene fusion vector pPCV6NFHyg. Segregation analysis indicates that the average frequency of insertion sites is 1.29 per line, predicting about 116 100 independent tagged loci in the collection. The average T-DNA copy number estimated by Southern DNA hybridization is 2.4, as over 50% of the insertion loci contain tandem T-DNA copies. The collection is pooled in two arrays providing 40 PCR templates, each containing DNA from either 4000 or 5000 individual plants. A rapid and sensitive PCR technique using high-quality template DNA accelerates the identification of T-DNA tagged genes without DNA hybridization. The PCR screening is performed by agarose gel electrophoresis followed by isolation and direct sequencing of DNA fragments of amplified T-DNA insert junctions. To estimate the mutation recovery rate, 39 700 lines have been screened for T-DNA tags in 154 genes yielding 87 confirmed mutations in 73 target genes. Screening the whole collection with both T-DNA border primers requires 170 PCR reactions that are expected to detect a mutation in a gene with at least twofold redundancy and an estimated probability of 77%. Using this technique, an M2 family segregating a characterized gene mutation can be identified within 4 weeks.

Regulation of transcript levels of the Arabidopsis cytochrome p450 genes involved in brassinosteroid biosynthesis

Cytochrome P450 enzymes of the closely related CYP90 and CYP85 families catalyze essential oxidative reactions in the biosynthesis of brassinosteroid (BR) hormones. Arabidopsis CYP90B1/DWF4 and CYP90A1/CPD are responsible for respective C-22 and C-23 hydroxylation of the steroid side chain and CYP85A1 catalyzes C-6 oxidation of 6-deoxo intermediates, whereas the functions of CYP90C1/ROT3, CYP90D1, and CYP85A2 are still unknown. Semiquantitative reverse transcriptase-polymerase chain reaction analyses show that transcript levels of CYP85 and CYP90 genes are down-regulated by brassinolide, the end product of the BR biosynthesis pathway. Feedback control of the CYP90C1, CYP90D1, and CYP85A2 genes by brassinolide suggests that the corresponding enzymes might also participate in BR synthesis. CYP85 and CYP90 mRNAs show strong and transient accumulation during the 1st week of seedling development, as well as characteristic organ-specific distribution. Transcripts of CYP90A1 and CYP85A2 are preferentially represented in shoots and CYP90C1, CYP90D1, and CYP85A1 mRNAs are more abundant in roots, whereas CYP90B1 is ubiquitously expressed. Remarkably, the spatial pattern of CYP90A1 expression is maintained in the BR-insensitive cbb2 mutant, indicating the independence of organ-specific and BR-dependent regulation. Quantitative gas chromatography-mass spectrometry analysis of endogenous BRs in shoots and roots of Arabidopsis, pea (Pisum sativum), and tomato (Lycopersicon esculentum) reveal similar partitioning patterns of BR intermediates in these species. Inverse correlation between CYP90A1/CPD transcript levels and the amounts of the CYP90A1 substrate 6-deoxocathasterone in shoots and roots suggests that transcriptional regulation plays an important role in controlling BR biosynthesis.

Characterisation of BRH1, a brassinosteroid-responsive RING-H2 gene from Arabidopsis thaliana

Although many important aspects of plant development are controlled by brassinosteroids (BRs), the early molecular events of their hormonal action are largely unknown. Using a differential-display RT-PCR screen designed to detect early response transcripts, those regulated by BR treatment in the absence of de novo protein synthesis, we identified an Arabidopsis thaliana (L.) Heynh. gene (designated BRH1) that encodes a novel RING finger protein. As deduced from a complete cDNA clone, the 170-amino-acid sequence of BRH1 forms an N-terminal hydrophobic domain and a C-terminal RING-H2 signature. In wild-type Arabidopsis, the level of the BRH1 transcript was rapidly down-regulated by brassinolide, but this effect was abolished in a BR-insensitive mutant deficient in the BRI1 receptor. BRH1 mRNA abundance was not influenced by other phytohormones, but the pathogen elicitor chitin induced a rapid and transient accumulation of the transcript. Antisense expression of BRH1 resulted in transgenic Arabidopsis plants with thicker inflorescence stems and altered leaf morphology, whereas in sense overexpression lines no phenotypic effect could be observed. Considering the potential of the RING proteins to participate in regulatory protein complexes, BR-dependent expression of BRH1 may suggest its involvement in later hormonal effects.

Influence of thermal quenching on the thermostimulated processes in alpha-Al2O3. Role of F and F+ centres

Anion deficient alpha-Al2O3 is highly sensitive to ionising radiations and is widely used as a thermoluminescence and optically stimulated luminescence dosemeter in environmental monitoring. Two types of alpha alumina were studied and it was observed that both were affected by thermal quenching of luminescence. This effect, which manifests itself by the decay of the TL response when the heating rate increases, can be described by the Mott-Seitz theory. It was observed that thermostimulated exoemission response increased when the heating rate increased, whereas thermostimulated conductivity remained constant. However, none of the available theories could explain the dependence of the F- centre emission on the heating rate. A model is proposed to describe simultaneously the various thermally stimulated processes.

A Ca(2+)-activated NADPH oxidase in testis, spleen, and lymph nodes

Superoxide and its derivatives are increasingly implicated in the regulation of physiological functions from oxygen sensing and blood pressure regulation to lymphocyte activation and sperm-oocyte fusion. Here we describe a novel superoxide-generating NADPH oxidase referred to as NADPH oxidase 5 (NOX5). NOX5 is distantly related to the gp91(phox) subunit of the phagocyte NADPH oxidase with conserved regions crucial for the electron transport (NADPH, FAD and heme binding sites). However, NOX5 has a unique N-terminal extension that contains three EF hand motifs. The mRNA of NOX5 is expressed in pachytene spermatocytes of testis and in B- and T-lymphocyte-rich areas of spleen and lymph nodes. When heterologously expressed, NOX5 was quiescent in unstimulated cells. However, in response to elevations of the cytosolic Ca(2+) concentration it generated large amounts of superoxide. Upon Ca(2+) activation, NOX5 also displayed a second function: it became a proton channel, presumably to compensate charge and pH alterations due to electron export. In summary, we have identified a novel NADPH oxidase that generates superoxide and functions as a H(+) channel in a Ca(2+)-dependent manner. NOX5 is likely to be involved in Ca(2+)-activated, redox-dependent processes of spermatozoa and lymphocytes such as sperm-oocyte fusion, cell proliferation, and cytokine secretion.