bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arabidopsis thaliana AtPOLK encodes a DinB‐like DNA polymerase that extends mispaired primer termini and is highly expressed in a variety of tissues
Authors: García‐Ortiz Maria Victoria , Ariza Rafael R. , Hoffman Peter D. , Hays John B. , Roldán‐Arjona Teresa 
Published: June 2004

SummaryCell survival after DNA damage depends on specialized DNA polymerases able to perform DNA synthesis on imperfect templates. Most of these enzymes belong to the recently discovered Y‐family of DNA polymerases, none of which has been previously described in plants. We report here the isolation, functional characterization and expression analysis of a plant representative of the Y‐family. This polymerase, which we have termed AtPolκ, is a homolog of Escherichia coli pol IV and human pol κ, and thus belongs to the DinB subfamily. We purified AtPolκ and found a template‐directed DNA polymerase, endowed with limited processivity that is able to extend primer–terminal mispairs. The activity and processivity of AtPolκ are enhanced markedly upon deletion of 193 amino acids (aa) from its carboxy (C)‐terminal domain. Loss of this region also affects the nucleotide selectivity of the enzyme, leading to the incorporation of both dCTP and dTTP opposite A in the template. We detected three cDNA forms, which result from the alternative splicing of AtPOLK mRNA and have distinct patterns of expression in different plant organs. Histochemical localization of β‐glucuronidase (GUS) activity in transgenic plants revealed that the AtPOLK promoter is active in endoreduplicating cells, suggesting a possible role during consecutive DNA replication cycles in the absence of mitosis.
The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinization of the columella cytoplasm and a persistent lateral auxin gradient
Authors: Hou Guichuan , Kramer Victoria L. , Wang Yuh‐Shuh , Chen Rujin , Perbal Gerald , Gilroy Simon , Blancaflor Elison B. 
Published: June 2004

SummaryThe actin cytoskeleton has been implicated in regulating plant gravitropism. However, its precise role in this process remains uncertain. We have shown previously that disruption of the actin cytoskeleton with Latrunculin B (Lat B) strongly promoted gravitropism in maize roots. These effects were most evident on a clinostat as curvature that would exceed 90° despite short periods of horizontal stimulation. To probe further the cellular mechanisms underlying these enhanced gravity responses, we extended our studies to roots of Arabidopsis. Similar to our observations in other plant species, Lat B enhanced the response of Arabidopsis roots to gravity. Lat B (100 nm) and a stimulation time of 5–10 min were sufficient to induce enhanced bending responses during clinorotation. Lat B (100 nm) disrupted the fine actin filament network in different regions of the root and altered the dynamics of amyloplasts in the columella but did not inhibit the gravity‐induced alkalinization of the columella cytoplasm. However, the duration of the alkalinization response during continuous gravistimulation was extended in Lat B‐treated roots. Indirect visualization of auxin redistribution using the DR5:β‐glucuronidase (DR5:GUS) auxin‐responsive reporter showed that the enhanced curvature of Lat B‐treated roots during clinorotation was accompanied by a persistent lateral auxin gradient. Blocking the gravity‐induced alkalinization of the columella cytoplasm with caged protons reduced Lat B‐induced curvature and the development of the lateral auxin gradient. Our data indicate that the actin cytoskeleton is unnecessary for the initial perception of gravity but likely acts to downregulate gravitropism by continuously resetting the gravitropic‐signaling system.
Interactions of tobacco microtubule‐associated protein MAP65‐1b with microtubules
Authors: Wicker‐Planquart Catherine , Stoppin‐Mellet Virginie , Blanchoin Laurent , Vantard Marylin 
Published: June 2004

SummaryTobacco microtubule associated protein (MAP65) (NtMAP65s) constitute a family of microtubule‐associated proteins with apparent molecular weight around 65 kDa that collectively induce microtubule bundling and promote microtubule assembly in vitro. They are associated with most of the tobacco microtubule arrays in situ. Recently, three NtMAP65s belonging to the NtMAP65‐1 subfamily have been cloned. Here we investigated in vitro the biochemical properties of one member of this family, the tobacco NtMAP65‐1b. We demonstrated that recombinant NtMAP65‐1b is a microtubule‐binding and a microtubule‐bundling protein. NtMAP65‐1b has no effect on microtubule polymerization rate and binds microtubules with an estimated equilibrium constant of dissociation (Kd) of 0.57 µm. Binding of NtMAP65‐1b to microtubules occurs through the carboxy‐terminus of tubulin, as NtMAP65‐1b was no longer able to bind subtilisin‐digested tubulin. In vitro, NtMAP65‐1b stabilizes microtubules against depolymerization induced by cold, but not against katanin‐induced destabilization. The biological implications of these results are discussed.
Feline corneal sequestra: a review of 64 cases (80 eyes) from 1993 to 2000
Authors: Featherstone Heidi J. , Sansom Jane 
Published: June 2004

AbstractFeline corneal sequestrum is a common condition of the feline cornea. The purpose of this study was to provide a detailed description of the clinical features of the condition including the response to different management options and to assess the rate of recurrence. The medical records of 64 cases (80 eyes) of feline corneal sequestra that presented to the Animal Health Trust from 1993 to 2000 were reviewed. Fifty‐two cases were reviewed retrospectively; 12 cases were assessed prospectively between April and September 2000 as part of a separate study. The Persian was the most frequently encountered breed and the mean age of affected cats was 5.6 years. At initial presentation, sequestra were unilateral in 58 cats and bilateral in 6 cats, 5 of which were Persians. Ocular discomfort and ocular discharge were common presenting signs, occurring in 42 and 36 eyes, respectively. Seventy‐four eyes were managed surgically with keratectomy only (n = 44) or keratectomy followed by a graft procedure (n = 30). Sequestra recurred in 16 eyes in the study. There was no significant difference in the rate of recurrence between eyes that received a graft procedure (n = 5) and eyes that did not (n = 11) (P = 0.56). Complications following transection of conjunctival pedicle grafts were observed. Brown to black discoloration of noncorneal tissue and therapeutic biomaterials was observed, including discoloration of both viable and apparently nonviable grafted conjunctival tissue, small intestinal submucosa graft material and bandage contact lenses.
Feline corneal sequestrum: laboratory analysis of ocular samples from 12 cats
Authors: Featherstone Heidi J. , Franklin Valerie J. , Sansom Jane 
Published: June 2004

AbstractFeline corneal sequestrum is a common ocular condition typified by brown to black discoloration of the cornea. The nature of the discoloration has not been identified. The purpose of this study was to perform a laboratory investigation of ocular samples from 12 clinical cases of feline corneal sequestrum in an attempt to characterize the nature of the discoloration. The 12 cases were referred to the Ophthalmology Unit at the Animal Health Trust between April and September 2000, and were also part of a clinical review of 64 cases of feline corneal sequestrum described separately. Five laboratory techniques that are routinely performed at the Biomaterials Unit, Aston University were employed for analysis of the ocular samples. Ocular material included corneal sequestrum, tear samples, meibomian gland secretions, and bandage contact lenses from the 12 clinical cases. High‐performance liquid chromatography data showed that total tear lipid in affected eyes was significantly lower than in control eyes (P = 0.016); total tear lipid in affected eyes was lower than in the unaffected, contralateral eyes of the same cat but the difference was not significant (P = 0.29). The presence of an unknown lipid class was observed in tears and meibomian secretions of affected, contralateral and control eyes. Scanning electron microscopy showed that the discoloration in affected corneas was not due to the presence of iron. Fluorescence spectroscopic analysis of sequestra, unaffected corneas and contact lenses (from affected and contralateral/unaffected eyes) showed that lipid and protein were present but did not play an important role in sequestra. Ultraviolet–visible light absorbance spectroscopy revealed a peak at 385 nm in unaffected corneas that was absent in sequestra and the difference was significant (P < 0.0001); this peak may be a characteristic feature of the normal feline cornea. The absorbance spectra displayed a peak at 280 nm in two sequestra suggesting that chromophore groups (e.g. melanin) were present. Optical microscopy performed on 10 sequestra revealed the presence of particles, which were consistent with the appearance of melanin particles, providing laboratory evidence that characterized the nature of the discoloration as melanin for the first time.
Tick‐borne encephalitis virus as a possible cause of optic neuritis in a dog
Authors: Stadtbäumer K. , Leschnik M. W. , Nell B. 
Published: June 2004

AbstractA 3‐year‐old spayed female Siberian Husky was presented due to acute vision loss. Examination revealed bilateral optic neuritis and lymphocytic meningoencephalitis. The serum (1:800) and cerebrospinal fluid (CSF; 1:200) immunoglobulin (Ig)G titers for tick‐borne encephalitis virus (TBEV) were elevated as were the serum IgG titer forAnaplasma phagocytophilum(1:640) and serum IgM titer forToxoplasma gondii(1:20). Intracytoplasmic inclusion bodies such as ehrlichial or anaplasmal morulae were not observed in the CSF or blood smear. The dog was treated with methylprednisone and doxycycline. The left eye regained vision; the right eye remained blind. Anti‐inflammatory therapy was stopped on day 18 after diagnosis. Four days later the dog showed evidence of hyperesthesia in the cervical region. Analysis of CSF showed no abnormalities and CSF IgG titers for TBEV andA. phagocytophilumwere negative. Funduscopic evidence of active papillitis was absent on day 22 in the left eye and on day 86 in the right eye. On day 243, the dog was presented again with lethargy, ataxia, disorientation and temporary head tilt. The IgG titer for TBEV was again elevated in the CSF (1:800) and in serum (1:400). After interpretation of all findings, we assume that meningoencephalitis and optic neuritis in this patient was caused by TBEV and associated immune‐mediated inflammation. In endemic areas, TBEV should be considered as cause of optic neuritis in dogs.
Secondary glaucomas in the dog in North America
Authors: Gelatt Kirk N. , MacKay Edward O. 
Published: June 2004

AbstractObjective To determine the prevalence of secondary glaucomas in dogs associated with cataract formation, lens luxation or displacement, cataract surgery, uveitis, hyphema and intraocular neoplasia.Methods Information was obtained from the Veterinary Medical Data Base (VMDB) from all veterinary medical teaching hospitals in North America from March 1964 to March 2003. Secondary glaucomas were diagnosed at the same examination or after the primary diagnosis was made, and included those associated with cataract formation, lens luxation, cataract surgery, uveitis of unknown cause, hyphema of unknown cause, and intraocular neoplasia. The data were evaluated by decade, breed, gender and age of presentation.Results A total of 1 592 831 dogs were presented, and 9695 canine secondary glaucomas. Secondary glaucoma associated with cataract formation represented 81% of all the canine secondary glaucomas. Breeds (n = 7890 dogs) predisposed to secondary glaucoma and cataracts had an overall prevalence of 0.5%, but nearly 20% of all the cataractous dogs developed secondary glaucoma in at least one eye. For the years 1994–2003, these breeds included the American Cocker Spaniel; Boston Terrier; Toy, Miniature and Standard Poodle; English Springer Spaniel; Bichon Frise; and Labrador Retriever. The other forms of secondary glaucoma occurred less frequently, and included those glaucomas with lens luxation or displacement (779 dogs; 12.0%), postcataract surgery (528 dogs; 5.1%), with uveitis from unknown cause (399 dogs; 7.1%), with hyphema from unknown cause (117 dogs; 7.3%), and with intraocular neoplasia (19 dogs; 3.5%). The risk of the secondary glaucomas from 1984 to 2002 was highest after the intracapsular lens extraction (ICLE), less in the extracapsular technique (ECLE), and lowest for the phacoemulsification/phacofragmentation method.Conclusion Prevalence of the canine secondary glaucomas ranges from 0.25% (1964–1973), 0.46% (1974–1983), 0.79% (1984–1993), to 0.80% (1994–2003) and are as frequent as the primary or breed‐related glaucomas during these same time periods.
Tono‐Pen XL®calibration curves for cats, cows and sheep
Authors: Passaglia Christopher L. , Guo Xiaoli , Chen Jie , Troy John B. 
Published: June 2004

AbstractThe objective of this study was to provide calibration curves for correcting intraocular pressure (IOP) measurements obtained using the Tono‐Pen XL®tonometer in cats, cows and sheep. Twelve eyes from 9 cats, 13 eyes from 7 cows, 10 eyes from 5 sheep were used. The anterior chamber of the eye was cannulatedin vivo,in situ(immediately post mortem) orex vivowith a fine needle and IOP was varied from 10 to 90 mmHg in steps of 10 mmHg by adjusting the height of a saline reservoir connected to the needle. For each pressure setting, several readings of IOP were made using the tonometer. The relationship between Tono‐Pen®reading and manometer setting was linear over the full range of measurement. However, the slope of the data regression line deviated significantly from 1 and indicated that the instrument systematically underestimated IOP. For cats the average slope was 0.62 and for cows and sheep it was 0.72 and 0.69, respectively. For the latter animals, the regression line also had a nonzero intercept of ≈ 4.5 mmHg. Similar results were obtained fromin vivoandex vivoeyes and with different Tono‐Pen XL®tonometers. Although developed for use on humans, the Tono‐Pen XL®can provide reproducible and accurate measurement of IOP in cats, cows and sheep when suitably calibrated by manometry. The calibration curves provided here, and by implication those reported for other animals using this tonometer, differ in slope from those measured with earlier models of the Tono‐Pen®. The reproducibility of the curves we obtained implies that they can be used to correct IOP readings from the Tono‐Pen XL®when manometry is not possible.
Evaluation of intraocular pressure in association with cardiovascular parameters in normocapnic dogs anesthetized with sevoflurane and desflurane
Authors: Almeida D. E. , Rezende M. L. , Nunes N. , Laus J. L. 
Published: June 2004

AbstractThe objective of this study was to determine intraocular pressure (IOP) and cardiac changes in normocapnic dogs maintained under controlled ventilation and anesthetized using sevoflurane or desflurane. Sixteen healthy adult mixed‐breed dogs, seven males and nine females, weighing 10–15 kg were used. The dogs were randomly assigned to one of two groups composed of eight animals anesthetized with sevoflurane (SEVO) or desflurane (DESF). In both groups, anesthesia was induced with propofol (10 mg/kg), and neuromuscular blockade was achieved with rocuronium (0.6 mg/kg/h IV). No premedication was given. Ventilation was adjusted to maintain end‐tidal carbon dioxide partial pressure at 35 mmHg. Anesthesia was maintained with 1.5 minimum alveolar concentration (MAC) of sevoflurane or desflurane. In both groups IOP was measured by applanation tonometry (Tono‐Pen) before induction of anesthesia. IOP, mean arterial pressure (MAP), heart rate (HR), cardiac index (CI) and central venous pressure (CVP) were also measured 45 min after the beginning of inhalant anesthesia and then every 20 min for 60 min. A one‐way repeated measures anova was used to compare data within the same group and Student's t‐test was used to assess differences between groups. P < 0.05 was considered statistically significant. Measurements showed normal IOP values in both groups, even though IOP increased significantly from baseline during the use of desflurane. IOP did not differ between groups. CI in the desflurane group was significantly greater than in the sevoflurane group. Sevoflurane and desflurane have no clinically significant effects on IOP, MAP, HR, CI or VCP in the dog.
Physics & reality
Authors: Einstein Albert 
Published: June 2004

Editor's Note: There is probably no modern scientist as famous as Albert Einstein. Born in Germany in 1879 and educated in physics and mathematics at the Swiss Federal Polytechnic School in Zurich, he was at first unable to find a teaching post, working instead as a technical assistant in the Swiss Patent Office from 1901 until 1908. Early in 1905, Einstein published “A New Determination of Molecular Dimensions,” a paper that earned him a Ph.D. from the University of Zurich. More papers followed, and Einstein returned to teaching, in Zurich, in Prague, and eventually in Berlin, where an appointment in 1914 to the Prussian Academy of Sciences allowed him to concentrate on research. In November of 1919, the Royal Society of London announced that a scientific expedition had photographed a solar eclipse and completed calculations that verified the predictions that Einstein had made in a paper published three years before on the general theory of relativity. Virtually overnight, Einstein was hailed as the world's greatest genius, instantly recognizable, thanks to “his great mane of crispy, frizzled and very black hair, sprinkled with gray and rising high from a lofty brow” (as Romain Rolland described in his diary). In the essay excerpted here, and first published in 1936, Einstein demonstrates his substantial interest in philosophy as well as science. He is pragmatic, in insisting that the only test of concepts is their usefulness in describing the physical world, yet also idealistic, in aiming for the minimum number of concepts to achieve that description. In 1933, Einstein renounced his German citizenship and moved to the United States, where he lived until his death in 1955. A recipient of the Nobel Prize in physics in 1921, he was elected a member of the American Academy of Arts & Sciences in 1924.
The BOLD Hemodynamic Response in Healthy Aging
Authors: Aizenstein Howard J. , Clark Kristi A. , Butters Meryl A. , Cochran Jennifer , Stenger V. Andrew , Meltzer Carolyn C. , Reynolds Charles F. , Carter Cameron S. 
Published: June 2004

Abstract
Several previous studies have compared the blood oxygen level-dependent (BOLD) hemodynamic response (HDR) in healthy elderly subjects to the HDR in young subjects. Some studies have found a relative decreased amplitude in the elderly in the visual cortex, whereas other studies have found the elderly HDR amplitude in the visual cortex to be nearly identical to that in young subjects. A possible explanation for the different findings is that the peak voxel HDR is similar between the groups, but that the HDR in the group-averaged region-of-interest (ROI) is “washed out” by the inclusion of less significant voxels (due to a smaller extent of activation in the elderly) or by the inclusion of negative-peaking voxels. We tested this hypothesis using event-related functional magnetic resonance imaging (fMRI). While undergoing fMRI, subjects performed a simple visual and motor task, pressing with their index fingers in response to visual presentation of the word tap. Data from 18 subjects, 8 young and 10 elderly, were analyzed. For each subject, a visual and a motor ROI was selected by choosing the most significant positive voxels within the anatomically defined ROI. This individual subject approach excluded both low-significance and negative-peaking voxels. Similar peaks were found for the elderly and the young subjects in both motor and visual regions and a more sustained BOLD response was found for the elderly in both regions. Additionally, as predicted, a greater percentage of voxels with a negative HDR was found for the elderly in the visual region; this finding was also replicated in our reanalysis of an independent fMRI and aging study from the fMRI Data Center. Functional neuroimaging observations of negative HDRs in visual areas have been interpreted as the effect of unconstrained processing during rest. Our results suggest that the elderly may have more unconstrained visual processing during the rest condition in the scanner. The observation that the group differences in the BOLD response are sensitive to voxel selection (e.g., inclusion of low-significance and/or negative voxels) underscores the importance of ROI selection criteria in the interpretation of fMRI studies using elderly populations.
Derivation and Analysis of Basic Computational Operations of Thalamocortical Circuits
Authors: Rodriguez A. , Whitson J. , Granger R. 
Published: June 2004

AbstractShared anatomical and physiological features of primary, secondary, tertiary, polysensory, and associational neocortical areas are used to formulate a novel extended hypothesis of thalamocortical circuit operation. A simplified anatomically based model of topographically and nontopographically projecting (“core” and “matrix”) thalamic nuclei, and their differential connections with superficial, middle, and deep neocortical laminae, is described. Synapses in the model are activated and potentiated according to physiologically based rules. Features incorporated into the models include differential time courses of excitatory versus inhibitory postsynaptic potentials, differential axonal arborization of pyramidal cells versus interneurons, and different laminar afferent and projection patterns. Observation of the model's responses to static and time-varying inputs indicates that topographic “core” circuits operate to organize stored memories into natural similarity-based hierarchies, whereas diffuse “matrix” circuits give rise to efficient storage of time-varying input into retrievable sequence chains. Examination of these operations shows their relationships with well-studied algorithms for related functions, including categorization via hierarchical clustering, and sequential storage via hash or scatter-storage. Analysis demonstrates that the derived thalamocortical algorithms exhibit desirable efficiency, scaling, and space and time cost characteristics. Implications of the hypotheses for central issues of perceptual reaction times and memory capacity are discussed. It is conjectured that the derived functions are fundamental building blocks recurrent throughout the neo cortex, which, through combination, gives rise to powerful perceptual, motor, and cognitive mechanisms.