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PubMedDate not supplied

Benefit of against-the-rule astigmatism to uncorrected near acuity.

PURPOSE: To determine whether with-the-rule (WTR) or against-the-rule (ATR) astigmatism gives a better visual outcome after cataract and intraocular lens (IOL) implantation surgery by comparing the uncorrected distance and near visual acuities in eyes with low, simple, myopic residual astigmatism. SETTING: S. Geraldo Eye Hospital, Federal University of Minas Gerais, Belo Horizonte, Brazil. METHODS: Two groups of 10 eyes each, one with WTR and the other with ATR simple, myopic astigmatism, were studied after uneventful cataract and IOL implantation surgery. All patients had an uncorrected distance visual acuity of 20/40 or better. The negative cylinder ranged from 1.00 to 1.50 diopters (D). The uncorrected distance and near visual acuities of the two groups were compared. RESULTS: There was no statistically significant between-group difference in uncorrected distance visual acuity. However, for uncorrected near, the difference between groups was highly statistically significant (P < .001). Patients with ATR astigmatism had much better uncorrected near acuity than those with WTR astigmatism. CONCLUSION: In pseudophakia, low, simple, ATR myopic astigmatism is better than WTR astigmatism because it provides superior uncorrected near visual acuity.

Aged↗
PubMed2006

The radiomimetic enediyne C-1027 induces unusual DNA damage responses to double-strand breaks.

Cells lacking the protein kinase ataxia telangiectasia mutated (ATM) have defective responses to DNA double-strand breaks (DSBs), including an inability to activate damage response proteins such as p53. However, we previously showed that cells lacking ATM robustly activate p53 in response to DNA strand breaks induced by the radiomimetic enediyne C-1027. To gain insight into the nature of C-1027-induced ATM-independent damage responses to DNA DSBs, we further examined the molecular mechanisms underlying the cellular response to this unique radiomimetic agent. Like ionizing radiation (IR) and other radiomimetics, breaks induced by C-1027 efficiently activate ATM by phosphorylation at Ser1981, yet unlike other radiomimetics and IR, DNA breaks induced by C-1027 result in normal phosphorylation of p53 and the cell cycle checkpoint kinases (Chk1 and Chk2) in the absence of ATM. In the presence of ATM, but under ATM and Rad3-related kinase (ATR) deficient conditions, C-1027 treatment resulted in a decrease in the level of Chk1 phosphorylation but not in the level of p53 and Chk2 phosphorylation. Only when cells were deficient in both ATM and ATR was there a reduction in the level of phosphorylation of each of these DNA damage response proteins. This reduction was also accompanied by an increased level of cell death in comparison to that of wild-type cells or cells lacking either ATM or ATR. Our findings demonstrate a unique cellular response to C-1027-induced DNA DSBs in that DNA damage response proteins are unaffected by the absence of ATM, as long as ATR is present.

Amino Acids, Cyclic↗
PubMedDate not supplied

Blends of poly-(epsilon-caprolactone) and polysaccharides in tissue engineering applications.

Bioartificial blends of poly-(epsilon-caprolactone) (PCL) with a polysaccharide (starch, S; dextran, D; or gellan, G) (PCL/S, PCL/D, PCL/G 90.9/9.1 wt ratio) were prepared by a solution-precipitation technique and widely characterized by differential scanning calorimetry analysis (DSC), Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), optical microscopy (OM), wide-angle X-ray diffraction analysis (WAXD), and thermogravimetry (TGA). DSC showed that the polysaccharide reduced the crystallinity of PCL and had a nucleation effect, which was also confirmed by OM analysis. Hoffman-Weeks analysis was performed on PCL and blend samples allowing calculation of their equilibrium melting temperatures (). WAXD showed that the crystalline unit cell type was the same for PCL and blends. FTIR-ATR did not evidence interactions between blend components. Thermal stability was affected by the type of polysaccharide. Microparticles (<125 microm) were produced from blends by cryogenical milling and characterized by scanning electron microscopy analysis (SEM). Selective laser sintering (SLS), a new rapid prototyping technology for scaffold fabrication, was applied to sinter blend microparticles according to a PC-designed two-dimensional geometry (strips and 2 x 2 mm(2) square-meshed grids). The optimal experimental conditions for sintering were established and laser beam parameters (beam speed, BS, and power, P) were found for each blend composition. Morphology of sintered objects was analyzed by SEM and found to be dependent on the morphology of the sintered powders. Sintered samples were analyzed by chemical imaging (CI), FTIR-ATR, DSC, and contact angle analysis. No evidence of the occurrence of degradation phenomena was found by FTIR-ATR for sintered samples, whereas DSC parameters of PCL and blends showed changes which could be attributed to some molecular weight decrease of PCL during sintering. CI of sintered samples showed that the polysaccharide phase was homogeneously dispersed within the PCL matrix, with the only exception being the PCL/D blend. The contact angle analysis showed that all samples were hydrophilic. Fibroblasts were then seeded on scaffolds to evaluate the rate and the extent of cell adhesion and the effect of the polysaccharides (S, D, G) on the bioactivity of the PCL-based blends.

Animals↗
PubMed2005

Supercritical carbon dioxide: an inert solvent for catalytic hydrogenation?

Various surface species originating from the reaction between CO2 and H2 over Al2O3-supported Pt, Pd, Rh, and Ru model catalysts were investigated by attenuated total reflection infrared (ATR-IR) spectroscopy under high-pressure conditions. Two different spectroscopic cells were used: a variable-volume view cell equipped with ATR-crystal and transmission IR windows (batch reactor) and a continuous-flow cell also equipped with a reflection element for ATR-IR spectroscopy. The study corroborated that CO formation from dense CO2 in the presence of hydrogen occurs over all Pt-group metals commonly used in heterogeneous catalytic hydrogenations in supercritical CO2 (scCO2). In the batch reactor cell, formation of CO was detected on all metals at 50 and 90 degrees C, with the highest rate on Pt. Additional surface species were observed on Pt/Al2O3 at 150 bar under static conditions. It seems that further reaction of CO with hydrogen is facilitated by the higher surface concentration at higher pressure. In the continuous-flow cell, CO coverage on Pt/Al2O3 was less prominent than that in the batch reactor cell. A transient experiment in the continuous-flow cell additionally revealed CO formation on Pt/Al2O3 at 120 bar after switching the feed from a H2-ethane to a H2-CO2 mixture. The in situ ATR-IR measurements indicate that CO formation in CO2-H2 mixtures is normally a minor side reaction during hydrogenation reactions on Pt-group metal catalysts, and dense ("supercritical") CO2 may be considered as a relatively "inert" solvent in many practical applications. However, blocking of specific sites on the metal surface by CO and consecutive products can affect structure sensitive hydrogenation reactions and may be at the origin of unexpected shifts in the product distribution.

Journal Article↗
PubMed2006

Extending in situ attenuated-total-reflection surface-enhanced infrared absorption spectroscopy to ni electrodes.

Surface-enhanced infrared absorption spectroscopy (SEIRAS) in the attenuated-total-reflection configuration (ATR-SEIRAS) has been applied for the first time to Ni electrodes. SEIRA-active Ni electrodes were obtained through initial chemical deposition of a 60-nm-thick Au underlayer on the reflecting plane of an ATR Si prism followed by potentiostatic electrodeposition of a 40-nm-thick Ni overlayer in a modified Watt's electrolyte. The Ni nanoparticle film thus obtained exhibited exceptionally enhanced IR absorption for the surface probe molecule CO while maintaining unipolar and normally directed bands. With the advantages of ATR-SEIRAS, free H2O molecules coadsorbed with CO at the Ni electrode were revealed, and their role in the electrooxidation of the CO adlayer at the Ni electrode is discussed. In addition, the conversion of bridge to linearly bonded CO at Ni electrode in a neutral solution was clearly identified upon electrooxidation of the CO adlayer. ATR-SEIRAS was also used to characterize the adsorption configuration of a pyridine adlayer at the Ni electrode. Both A1 and B1 modes of adsorbed pyridine were detected with comparably large intensities, essentially maintaining the spectral feature of pyridine molecules rather than that of "alpha-pyridyl species", which strongly suggests an "edge-tilted pyridine" configuration present at the Ni electrode, a configuration intermediate between the "end-on pyridine" and "edge-on alpha-pyridyl" adsorption modes reported in the literature.

Journal Article↗
PubMed1996

The relative effect of Azone and Transcutol on permeant diffusivity and solubility in human stratum corneum.

PURPOSE: The purpose of this work was to analyse the mechanism of the enhancement of percutaneous penetration demonstrated by the known enhancers Azone and Transcutol. METHODS: Enhancer induced changes in the diffusivity and solubility of a model permeant (4-cyanophenol) in human stratum corneum were monitored (in-vitro) using Attenuated total reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy and compared to the gross effects of the enhancers on flux as measured using simple Franz-type diffusion cells. RESULTS: It has been shown by both the well-established Franz diffusion cell technique and the use of ATR-FTIR spectroscopy that the enhancers studied both increase the flux of cyanophenol across human skin in-vitro by a factor of approximately two. Furthermore, it has been demonstrated by ATR-FTIR that these enhancers are likely to exert their effects by different mechanisms. It is probable that Azone reduces the diffusional resistance of the stratum corneum and that Transcutol increases the solubility of the penetrant in this barrier. CONCLUSIONS: There is increasing interest in the apparently synergistic nature in which certain enhancers appear to work. The exact nature of these multiplicative and/or additive effects is not known although there are numerous suggestions in the current literature. The application of ATR-FTIR spectroscopy to such enhancing systems will allow the mechanisms of the observed enhancements to be probed in greater depth.

Analysis of Variance↗
PubMed1993

Validation of reflectance infrared spectroscopy as a quantitative method to measure percutaneous absorption in vivo.

Attenuated total-reflectance infrared (ATR-IR) spectroscopy has been used to follow the penetration of a model compound (4-cyanophenol; CP) across human stratum corneum (SC) in vivo, in man. CP was administered for periods of 1, 2, or 3 hr, either (a) as a 10% (w/v) solution in propylene glycol or (b) in an identical vehicle which also contained 5% (v/v) oleic (cis-9-octadecenoic) acid. At the end of the treatment periods, SC at the application site was progressively removed by adhesive tape-stripping. Prior to the removal of the first tape-strip, and after each subsequent tape-strip, an ATR-IR spectrum of the treated site was recorded. The presence of CP, as a function of position in the SC, was monitored spectroscopically via the intense C = N stretching absorbance at 2230 cm-1. The absolute amount of CP, as a function of SC depth, was determined by "spiking" the applied solutions with 14C-labeled compound and subsequent liquid scintillation counting of the removed tape-strips. The presence of oleic acid in the applied formulation significantly increased the rate and extent of CP delivery as evaluated by either spectroscopy or radiochemical analysis. Furthermore, the ATR-IR and direct 14C analysis of CP as a function of SC position were highly correlated. These data strongly support, therefore, the validation of ATR-IR as a quantitative tool to assess percutaneous penetration in vivo.

Administration, Cutaneous↗
PubMed2006

Small molecule-based reversible reprogramming of cellular lifespan.

Most somatic cells encounter an inevitable destiny, senescence. Little progress has been made in identifying small molecules that extend the finite lifespan of normal human cells. Here we show that the intrinsic 'senescence clock' can be reset in a reversible manner by selective modulation of the ataxia telangiectasia-mutated (ATM) protein and ATM- and Rad3-related (ATR) protein with a small molecule, CGK733. This compound was identified by a high-throughput phenotypic screen with automated imaging. Employing a magnetic nanoprobe technology, magnetism-based interaction capture (MAGIC), we identified ATM as the molecular target of CGK733 from a genome-wide screen. CGK733 inhibits ATM and ATR kinase activities and blocks their checkpoint signaling pathways with great selectivity. Consistently, siRNA-mediated knockdown of ATM and ATR induced the proliferation of senescent cells, although with lesser efficiency than CGK733. These results might reflect the specific targeting of the kinase activities of ATM and ATR by CGK733 without affecting any other domains required for cell proliferation.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2025

Nuclear rupture in confined cell migration triggers nuclear actin polymerization to limit chromatin leakage.

Upon cell migration in confined space, such as during cancer metastasis, mechanical forces from the extracellular matrix act onto the nucleus leading to nuclear envelope (NE) rupture, chromatin leakage and genomic instability. Here we found that during confined migration, NE rupture triggers dynamic nuclear F-actin formation dependent on the formins DIAPH1 and DIAPH3. We show that DIAPH3 dynamically and transiently relocates to the nucleus upon NE rupture. Interfering with DIAPH1/3 or with nuclear actin polymerization resulted in nuclear instability during confined migration. Notably, nuclear formin activity or actin assembly limit NE rupture-induced chromatin leakage. Similarly, silencing of Ataxia Telangiectasia and Rad3-related protein (ATR) reduced NE rupture-triggered nuclear F-actin assembly and increased chromatin leakage. Consistent with this, ATR promotes the phosphorylation of DIAPH3 at S1072 adjacent to its autoregulatory domain to promote nuclear actin polymerization. Using atomic force microscopy, we found that nuclear actin assembly or nuclear DIAPH3 activity promotes nuclear stiffness in an ATR-dependent manner. Thus, our study identifies an ATR-formin module that regulates nuclear mechanical properties through induction of intranuclear actin scaffolding.

Formins↗
PubMed1981

Metabolic insufficiency as a limiting factor in the dietetic treatment of obesity.

Previous observations that acute total fasting decreases serum T3 and increase rT3 has prompted the following study. 17 obese women were placed on a 1000 kcal/day weight-reducing diet, and body weight (BW), serum T4, RT3U, T3, rT3, TSH and the Achilles tendon reflex (ATR) were estimated before and after each month for 3 consecutive months of the diet. The results showed a consistent decrease in serum T3, and inconsistent increase in rT3, a consistent prolongation of the ATR and a levelling-off of the BW loss after the second month of the diet. At 3 months there was a negative correlation between the decrease in BW and the increase in ATR, i.e. the more abnormal the ATR became, the less weight the patient lost. It is concluded: 1) Even a moderate hypocaloric diet in ambulatory patients induces a disturbance in the peripheral conversion of T4 to T3 and a secondary state of metabolic insufficiency. 2). This insufficiency is probable related to the observed tendency of the BW loss to level off after two months. 3) A controlled trial of physiologic doses of T3, such as 40 mu g/day, seems indicated, as opposed to pharmacologic dosed of T3 used by previous investigators.

Achilles Tendon↗
PubMed2006

The FATC domains of PIKK proteins are functionally equivalent and participate in the Tip60-dependent activation of DNA-PKcs and ATM.

Members of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, including the ATM, DNA-PKcs, Atr, and Trrap proteins, function in signal transduction pathways that activate the DNA damage response. PIKK proteins contain a conserved C-terminal FAT/kinase domain/FATC domain structure. The FATC domain of ATM mediates the interaction between ATM and Tip60, a histone acetyltransferase that regulates activation of ATM. Here, we examined whether the FATC domains of DNA-PKcs, Atr, and Trrap were also able to interact with Tip60. Deletion of the FATC domain of ATM blocked the interaction between ATM and Tip60 and suppressed the activation of ATM kinase activity by DNA damage. Replacement of the FATC domain of ATM with the FATC domains of DNA-PKcs, Atr, or Trrap restored the activation of ATM and its association with Tip60. These results indicate that the FATC domains of DNA-PKcs, Atr, Trrap, and ATM are functionally equivalent. Immunoprecipitation experiments demonstrated that Tip60 is constitutively associated with DNA-PKcs and that the histone acetyltransferase activity associated with DNA-PKcs is up-regulated by DNA damage. When Tip60 expression was suppressed by small interfering RNA, the activation of DNA-PKcs (measured by autophosphorylation of DNA-PKcs at serine 2056 and threonine 2609) was inhibited, demonstrating a key role for Tip60 in the activation of DNA-PKcs by DNA damage. The conserved FATC domain of PIKK proteins may therefore function as a binding domain for the Tip60 histone acetyltransferase. Further, the ability of Tip60 to regulate the activation of both ATM and DNA-PKcs in response to DNA damage demonstrates that Tip60 is a key component of the DNA damage-signaling network.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2004

Exhaustive whole-genome tandem repeats search.

MOTIVATION: Approximate tandem repeats (ATR) occur frequently in the genomes of organisms, and are a source of polymorphisms observed in individuals, and thus are of interest to those studying genetic disorders. Though extensive work has been done in order to identify ATRs, there are inherent limitations with the current approaches in terms of the number of pattern sizes that can be searched or the size of the input length. RESULTS: This paper describes (1) a new algorithm which exhaustively finds all variable-length ATRs in a genomic sequence and (2) a precise description of, and an algorithm to significantly reduce, redundancy in the output. Our ATR definition is parameterized by a mismatch ratio p which allows for more mismatches in longer tandem repeats (and fewer in shorter). Furthermore, our algorithm is embarrassingly parallel and thus can attain near-linear speed-up on Beowulf clusters. We present results of our algorithm applied to sequences of widely differing lengths (from genes to chromosomes). AVAILABILITY: Source and binaries are available on request.

Algorithms↗
PubMed2000

Modulation of ventricular fibrillation in the isolated heart: the role of slow calcium channel activity under continuous perfusion.

The individual activities of sodium versus calcium channels in the initiation and maintenance of ventricular fibrillation (VF) have not been fully elucidated. Therefore we studied in isolated heart under nonischemic conditions (a) VF characteristics in untreated hearts, (b) initiation and maintenance of VF during attenuation and blockade of slow calcium channel activity by verapamil, (c) the effect of these interventions on the characteristics of the induced arrhythmia, and (d) the impact of heart weight on the observed results. Measurements were carried out in both ventricles of isolated feline hearts during ventricular pacing and 8 min of electrically induced tachyarrhythmias. Measurements during ventricular pacing included epicardial conduction time (CON), refractoriness (VRP), and all tissue resistivity (ATR; an indirect measure of changes in intercellular electrical coupling). Measurements during arrhythmia included ATR, peak frequency [PKF; a measure of the prevailing frequency based on Fast Fourier Transform (FFT) analysis], and normalized entropy (ENTROP; a measure of the degree of arrhythmia organization). Measurements during sinus rhythm and arrhythmia were repeated after blocking of calcium channel activity by verapamil at a high concentration (1.8x10(-4) M; n = 8) and at two low concentrations (1.5 and 3.0x10(-7) M; n = 8). In untreated hearts, mainly VF episodes were induced, exhibiting a low degree of organization with no significant change in this parameter throughout the arrhythmia (8 min). In the left ventricle (LV; and to a much smaller extent in the right ventricle; RV), a gradual increase in PKF was observed throughout the arrhythmia, with no significant change in ATR. Verapamil at a high concentration increased CON, but did not affect VRP. These findings were similar in both ventricles. In lower verapamil concentrations, CON was not affected, and VRP was slightly shortened. After treatment with a high verapamil concentration, VF could not be induced in small hearts but was always inducible in large hearts. Transient arrhythmia episodes appeared in 9% of untreated hearts, in 25% with "high" verapamil, and in 25-37% with "low" verapamil. With all verapamil concentrations, the induced arrhythmia was modulated from a predominantly VF to PVT or MVT type, manifested by a decrease in ENTROP. This effect was less pronounced with increasing heart weight. No significant change in PKF and in ATR was obtained with verapamil throughout the arrhythmia. It is suggested that verapamil modulation of arrhythmia organization is associated mainly with a direct blockade of calcium channel activity (perhaps by causing reduction in the safety factor for conduction), rather than with indirect modulation of electrophysiological parameters.

Animals↗
PubMed2001

Neurally mediated syncope and cardiac beta-adrenergic receptor function.

To evaluate the mechanism of neurally mediated syncope (NMS), we investigated basal autonomic nerve function using a conventional pharmacological method and [123I]-metaiodobenzyl-guanidine (MIBG) single photon emission computed tomography (SPECT). Nine patients with NMS, whose syncope was induced by head-up tilt test with or without isoproterenol, underwent [123I]-MIBG SPECT. Eight of nine NMS patients showed reduced myocardial uptake (two patients, diffuse; four patients, anteroseptal and inferior; one patient, anteroseptal; one patient, inferior). In the study of pharmacological autonomic nervous function test, atropine sulfate (atr.) (0.04 mg/kg), isoproterenol (isp.) (5 x 10(-3) microg/kg/min), propranolol (prop.) (0.2 mg/kg), phenylephrine (phenyl.) (0.4 microg/kg/min), and phentolamine (phent.) (0.2 mg/kg) were successively administered to patients with NMS (n = 5) and control subjects (n = 5). The heart rate (HR) after atr. and prop., and systolic blood pressure (SBP) after phent. were defined as intrinsic HR (IHR) and intrinsic SBP (ISBP). Parasympathetic activity (increase in HR by atr.), beta-sympathetic tone (HR after atr. minus IHR), beta-sensitivity (change in HR by 1 microg isp./kg/min), beta-secretion (beta-tone/beta-sensitivity), alpha-sympathetic tone (SBP before phenyl. minus ISBP), alpha-sensitivity (change in SBP by 1 microg phenyl./kg/min) and alpha-secretion (alpha-tone/alpha-sensitivity) were also calculated. The beta-secretion was decreased (0.0027+/-0.0008 versus 0.0060+/-0.0004 microg/kg/min/isp.; p < 0.05), while the beta-sensitivity was increased (5850+/-947 versus 3150+/-292 beats/microg/kg/min isp.; p < 0.05) in NMS compared with control subjects. In the other indexes, there were no significant differences between two groups. The results of the present study suggest that increased beta-sensitivity may contribute hypercontraction of left ventricles, which might partially explain the mechanism of NMS.

3-Iodobenzylguanidine↗
PubMed1996

The alpha-thalassemia/mental retardation syndromes.

The chromosome-16 and the X-chromosome forms of alpha-thalassemia--ATR-16 and ATR-X--exemplify 2 important causes of syndromal mental retardation. ATR-16 is a contiguous gene syndrome which arises from loss of DNA from the tip of chromosome 16p13.3 by truncation, interstitial deletion, or unbalanced translocation. It provided the first example of a chromosome translocation that could be detected by molecular analysis but not conventional cytogenetics. It also provided the first example of a telomeric truncation giving rise to a complex genetic syndrome. In contrast ATR-X appears to be due to mutations in a trans-acting factor that regulates gene expression. Mutations in transcription factors have recently been identified in a number of genetic diseases (for example, Denys-Drash syndrome, WT1 [19]; pituitary dwarfism, PIT1 [16]; Rubinstein-Taybi syndrome, CBP [20]. Not only is this mechanism proving to be an important cause of complex syndromes but it is providing new perspectives on certain developmental pathways. XH2 may not be a classical transcription factor but it is certainly involved in the regulation of gene expression, exerting its effects on several different genes. It seems likely that other mutations in this class of regulatory proteins will be found in patients with complex disorders including mental retardation. In broader terms the 2 mechanisms described here may prove to be responsible for a significant proportion of mental retardation. However, without a feature such as alpha-thalassemia to pinpoint the area of genome or pathways involved it may prove difficult to identify other, similarly affected genes underlying other forms of mental retardation. As the human genome project and rapid genome analysis evolve this problem should become less of an obstacle. In the meantime, it is very worthwhile to continue looking for unusual clinical associations that may point to critical genes underlying human genetic disorders.

Chromosome Aberrations↗
PubMed1993

Outcome of spinal screening.

Spinal screening using the Scoliometer was performed on one thousand high school students to determine the prevalence of spinal deformity and the appropriate degree of deformity to be used as a selection criterion. Eighty percent of students were found to have 3 degrees or more angle of trunk rotation (ATR). This new information predicts a referral rate of three percent if 7 degrees degrees ATR is used as referral criterion (12% referral if 5 degrees ATR is the criterion). A paradigm using the best available information on natural history and screening allows a comparison of the outcomes of screened versus non-screened school populations. Spinal screening appears to be effective in reducing the need for surgical treatment of scoliosis, but does not decrease the total cost of care for this problem. An appropriate referral criterion for spinal screening appears to be 7 degrees ATR at any level of the spine.

False Negative Reactions↗
PubMed2007

Arabidopsis WEE1 kinase controls cell cycle arrest in response to activation of the DNA integrity checkpoint.

Upon the incidence of DNA stress, the ataxia telangiectasia-mutated (ATM) and Rad3-related (ATR) signaling kinases activate a transient cell cycle arrest that allows cells to repair DNA before proceeding into mitosis. Although the ATM-ATR pathway is highly conserved over species, the mechanisms by which plant cells stop their cell cycle in response to the loss of genome integrity are unclear. We demonstrate that the cell cycle regulatory WEE1 kinase gene of Arabidopsis thaliana is transcriptionally activated upon the cessation of DNA replication or DNA damage in an ATR- or ATM-dependent manner, respectively. In accordance with a role for WEE1 in DNA stress signaling, WEE1-deficient plants showed no obvious cell division or endoreduplication phenotype when grown under nonstress conditions but were hypersensitive to agents that impair DNA replication. Induced WEE1 expression inhibited plant growth by arresting dividing cells in the G2-phase of the cell cycle. We conclude that the plant WEE1 gene is not rate-limiting for cycle progression under normal growth conditions but is a critical target of the ATR-ATM signaling cascades that inhibit the cell cycle upon activation of the DNA integrity checkpoints, coupling mitosis to DNA repair in cells that suffer DNA damage.

Aphidicolin↗
PubMed2005

Undistorted structural analysis of soluble proteins by attenuated total reflectance infrared spectroscopy.

Water from the solvent very strongly absorbs light in the frequency range of interest for studying protein structure by infrared (IR) spectroscopy. This renders handling of the observation cells painstaking and time consuming, and limits the reproducibility of the measurements when IR spectroscopy is applied to proteins in aqueous solutions. These difficulties are circumvented by the use of an Attenuated Total Reflectance (ATR) accessory. However, when protein solutions are studied, ATR spectroscopy suffers from several drawbacks, the most severe being nonproportionality of the observed absorbance with the protein concentration and spectral distortions that vary from protein to protein and from sample to sample. In this study, we show (1) that the nonproportionality is due to adsorption of the protein on the ATR crystal surface; (2) that the contribution of the crystal-adsorbed protein can easily be taken into account, rendering the corrected absorbance proportional to the protein concentration; (3) that the observed variable base line distortions, likely due to changes in the penetration depth of the light beam in solutions with the refractive index that depends on the protein concentration, can be easily eliminated; and (4) that ATR IR spectra thus corrected for protein adsorption and light penetration can be used to properly analyze the secondary structure of proteins in solution.

Muramidase↗