bluuebunny/crossref_metadata_2025 huggingface dataset:
The underachieving child
Authors: Evans Bruce J. W.
Published: September 2002

Visual factors in specific learning difficulties (SpLD) are reviewed. People with SpLD fail to achieve at a level that is commensurate with their intelligence. The commonest SpLD is dyslexia, which usually results from phonological processing/decoding deficits. Additionally, there are several optometric correlates of SpLD which may, in some cases, contribute to the learning difficulty. These correlates include binocular instability and a low amplitude of accommodation. Some people with reading difficulties and perceptual distortions/eyestrain can be helped by individually prescribed coloured filters. A visual processing anomaly is also often present in the form of a deficit of the transient visual system. The role of the optometrist is discussed.
Methods of investigating a visual deficit in dyslexia
Authors: Greatrex J. C. , Drasdo N.
Published: September 2002

The evidence for a visual deficit in dyslexia is inconclusive. We have developed several tests to investigate the parallel pathways of the visual system which can be applied to dyslexic subjects. Using the techniques of electroretinography, visual evoked potentials, adaptometry and contrast sensitivity, special protocols have been designed to elicit responses from these parallel pathways. These techniques are also applicable in the investigation of many pathological conditions, and of interest for pure research.
An A B C of glaucoma: apoptosis, blood flow and confocal imaging
Authors: Hosking Sarah L.
Published: September 2002

A clear understanding and definition of the glaucomas continues to elude the clinician. Broadening awareness of the many risk factors in glaucoma, the wide variety of presentations of the disease and greater understanding of the pattern of progression will help to improve treatment protocols. In the meantime, the diagnosis and monitoring of the disease remains a huge clinical and financial burden. Modern imaging techniques permit quantitative stereometric assessment of the optic nerve head and nerve fibre layer, affording morphologic evaluation to complement clinical psychophysical investigation.
Non‐compliance in optometric practice
Authors: Claydon Bridget E. , Efron Nathan , Woods Craig
Published: September 2002

The purpose of this paper is to explore how some of the recent and future changes relating to the optometric profession could affect non‐compliant behaviour among patients. Non‐compliance has been widely documented and discussed in numerous health care fields and is understood to be the responsibility of both the practitioner and patient working in a health care partnership. At least one third of patients have been reported to be non‐compliant with health care recommendations which can result in the poor outcome of a treatment, secondary medical problems, dissatisfaction, frustration and the wasting of health resources. In recent years contact lens complications have been linked with non‐compliant behaviour with contact lens care and maintenance regimens which has led to several media scares over contact lens related hygiene risks and has heightened interest in the issue of non‐compliance in the field of optometry. Shared care schemes have already been adopted in some areas of the United Kingdom and if therapeutic pharmaceutical agents are introduced to the list of drugs permitted for use by optometrists in the future the issue of non‐compliance will become even more poignant. Every optometrist needs to be aware of the high probability of non‐compliant behaviour among patients, the consequences of this non‐compliance and the steps that can be taken to enhance compliance in different areas of eye‐care.
Scanning laser tomography: effect of change in keratometry values on retinal distance measures
Authors: Hosking Sarah , Flanagan John
Published: September 2002

Scanning laser tomography is an objective non‐invasive method for the three‐dimensional imaging of the eyein‐vivo. It has become a valuable tool in the diagnosis and monitoring of changes to the fundus and optic nerve head in diseases such as glaucoma. Optical errors should be eliminated where possible to improve accuracy and maximise the potential for the detection of subtle change due to disease progression. Alterations in the keratometry reading cause scaling changes in the (x,y) plane. This study demonstrated the importance of the keratometry value on retinal measurements. Accurate fundus measurements require input of the appropriate keratometry value for each subject, while for the detection of subtle change over time in longitudinal study, the keratometry reading should not be altered from baseline.
Glaucoma update: epidemiology and new approaches to medical management
Authors: Flanagan John G.
Published: September 2002

Glaucoma describes a group of ocular conditions which involve progressive optic nerve damage associated with loss of visual function and, frequently, with elevated intraocular pressure. Recent estimates of worldwide prevalence predict that 67 million people will suffer from glaucoma by the year 2000. Although the clinical features of glaucoma are reasonably well described, the pathogenesis of optic nerve damage remains unclear. Intraocular pressure (IOP) is accepted as an important risk factor; however, it is clear that other factors play a role in the pathogenesis of the disease, and such factors may interact with IOP to greatly enhance its harmful effects. Many of the new therapeutic approaches to the stabilisation and potential cure of glaucoma attempt to address these non‐IOP factors. The aim of the following paper is to consider the implications of new estimates of disease prevalence, discuss theories related to optic nerve damage and outline new and future approaches to the medical management of the disease.
Scattering properties of Bagolini lenses and their effects on spatial vision
Authors: Cheng Desmond , Woo George C. , Irving Elizabeth L. , Charman W. Neil , Murray Ian J.
Published: September 2002

The effect of a Bagolini lens on spatial vision was investigated by studying its far‐field diffraction pattern as produced by a coherent beam of laser light, and its effect on the contrast sensitivity function (CSF) in human subjects. For lenses of the main type studied, which were crossed by a series of slightly‐irregular striated bands, each consisting of fine, parallel, etched lines of various widths and separations, the diffraction pattern consisted of undiffracted light giving a bright central spot and wide‐angle, diffracted light giving a dim streak. The latter was due to the sum of the diffraction patterns associated by the irregular fine etched lines. The streak produced by a single striated band was modulated by a series of regular maxima and minima related to the width of the band. Analysis of this pattern gave the width of the band as 0.6 mm, in close agreement with direct microscopical measurements. When four bands were illuminated by a beam of about 3 mm diameter, similar to the diameter of the photopic pupil, the diffraction pattern showed no obvious maxima and minima, due to irregularity in the width and separation of the bands. The central spot contained more than 90% of the total light in the diffraction pattern. Thus the Bagolini lens, with its relatively weak far‐field diffraction pattern lacking regular maxima and minima when areas ≥3 mm in diameter were used, was expected to have only a small effect on the apparent contrast of the targets in CSF experiments. This was confirmed by the measurements: Bagolini lenses showed no significant effect on either the monocular or binocular CSF. Further similar measurements with lenses of slightly different design from another manufacturer confirmed these findings. Therefore Bagolini lenses do not disrupt vision when they are used to determine the presence of suppression and anomalous retinal correspondence.
New approximation for the whole profile of the human crystalline lens
Authors: Kasprzak Henryk T.
Published: September 2002

This paper presents a new approximation for the whole profile of the human crystalline lens by the use of only one analytical function for both unaccommodated lens and the lens on accommodation. Approximation of the anterior and posterior lens profile is composed of hyperbolic cosine functions and is given in polar coordinates. Each of the hyperbolic cosines is modulated by the function of hyperbolic tangent type. The curvature of the hyperbolic cosine in polar coordinates is discussed and some results concerning the stability of its central radius of curvature are shown. Fitting of the hyperbolic cosine type curve to various results of the lens curvature measurements is presented. Examples of profiles of the lens under accommodation are given. It is shown that this approximation can be used for the description of iso‐indical profiles inside the lens.
Glaucoma in optometric practice: a survey of optometrists
Authors: Willis C.E. , Rankin S.J.A. , Jackson A.J.
Published: September 2002

Aims/background: With the ageing population, numbers of glaucoma patients are an increasing problem in ophthalmic outpatient clinics. A postal questionnaire survey was carried out in Northern Ireland with the aim of finding out how well placed optometrists are to become involved in the monitoring of glaucoma.

Results: Of the 171 practices surveyed, 68% of the senior practitioners responded. One practice was without a tonometer and one practice was without visual field instrumentation. Age criteria were used by 95% of practitioners for measuring intraocular pressure (IOP) and 82% used appropriate selection criteria for visual field testing. An IOP of 25 or 26 mmHg was used by 45% of practitioners as the level for referral if there are no risk factors; 89% would refer at any level if a visual field defect and disc cupping were present.

Conclusion: The results confirm that the majority of optometrists are well equipped for the screening of glaucoma. However a significant investment in training and equipment would be required if any sort of shared care scheme were to be introduced.
The calibration of a 2.5× Galilean focusable telescope as an optometer for refraction
Authors: Cheng Desmond , Woo George C.
Published: September 2002

A 2.5× Selsi achromatic Galilean focusable telescope was calibrated for refraction at 6 m. In its calibration, minus power trial lens was placed at the objective of the telescope to simulate vergence of a target at a finite distance, before the back vertex power (BVP) of the telescope at each setting (telescope length) was measured by a focimeter. By using a graphical presentation of the results, the BVP of the telescope at each setting could be determined at different selected target distances. For a target vergence of −0.167 D or a distance of 6 m, the common testing distance in clinical practice, this calibrated telescope had a BVP or refraction measuring range of −7.27–+7.52 D. When this telescope was used to measure simulated manifest refractive errors at 6 m, it yielded a mean error of +0.13 D with a 95% confidence limit of agreement of −0.38–+0.64 D. These results indicated that the accuracy and precision of telescopic refraction were comparable to that of retinoscopy. Therefore, the calibrated telescope could be considered as a reliable and inexpensive instrument for determining spherical refractive errors. Telescopic refraction is applicable in refracting economically disadvantaged population in under‐served areas where modern equipment and electricity are not available. In addition, it provides an alternative subjective refraction method for low vision population because the magnification of this calibrated telescope has the advantage of allowing low vision patients to be refracted at the common 6 m testing distance in clinical practice.
An optometrist's role of co‐management in a hospital glaucoma clinic
Authors: Banes M. J. , Culham L. E. , Crowston J. G. , Bunce C. , Khaw P. T.
Published: September 2002

In recent years, optometrists have started to work in some clinical roles in hospital medical clinics. This paper outlines the current working practice in a typical glaucoma clinic at Moorfields Eye Hospital NHS Trust and goes on to establish the ability of an optometrist working with a team of ophthalmologists.

In this study, 54 patients(n=108 eyes) were recruited and clinically assessed by an optometrist. Subsequently, a research fellow (i.e. ophthalmologist) assessed the same patients independently. The results were compared in order to determine the accuracy of the optometrist's evaluation and proposed management.

This paper considers the costs of employing personnel by reviewing the salaries of optometrists and medical assistants. Although nurses have started to work alongside ophthalmologists, and orthoptists may be considering such work, it is not within the scope of this paper to consider either of these groups. If optometrists are to become an accepted part of a glaucoma clinical team, consideration needs to be given to the training and experience they receive.
The depth, contour and angle of the glazing grooves of spectacle frames: don't blame the glazer?
Authors: Walsh Glyn , Mitchell John W.C.
Published: September 2002

The groove of a spectacle frame is responsible for lens retention. It also tends to fill with unsightly dirt which cannot be readily removed by our patients. The results of this investigation would suggest that both loose spectacle lenses and dirt accumulation may often be due to poor quality control in the frame industry. The data also suggests that unwanted stress may be present in both frames and lenses due to non‐optimal groove shape.
Whole-genome comparative analysis of three phytopathogenic
Xylella fastidiosa
strains
Authors: Bhattacharyya Anamitra , Stilwagen Stephanie , Ivanova Natalia , D'Souza Mark , Bernal Axel , Lykidis Athanasios , Kapatral Vinayak , Anderson Iain , Larsen Niels , Los Tamara , Reznik Gary , Selkov Eugene , Walunas Theresa L. , Feil Helene , Feil William S. , Purcell Alexander , Lassez Jean-Louis , Hawkins Trevor L. , Haselkorn Robert , Overbeek Ross , Predki Paul F. , Kyrpides Nikos C.
Published: September 2002

Xylella fastidiosa
(
Xf
) causes wilt disease in plants and is responsible for major economic and crop losses globally. Owing to the public importance of this phytopathogen we embarked on a comparative analysis of the complete genome of
Xf pv citrus
and the partial genomes of two recently sequenced strains of this species:
Xf pv almond
and
Xf pv oleander
, which cause leaf scorch in almond and oleander plants, respectively. We report a reanalysis of the previously sequenced
Xf 9a5c
(CVC, citrus) strain and the two “gapped”
Xf
genomes revealing ORFs encoding critical functions in pathogenicity and conjugative transfer. Second, a detailed whole-genome functional comparison was based on the three sequenced
Xf
strains, identifying the unique genes present in each strain, in addition to those shared between strains. Third, an “
in silico
” cellular reconstruction of these organisms was made, based on a comparison of their core functional subsystems that led to a characterization of their conjugative transfer machinery, identification of potential differences in their adhesion mechanisms, and highlighting of the absence of a classical quorum-sensing mechanism. This study demonstrates the effectiveness of comparative analysis strategies in the interpretation of genomes that are closely related.
Nerve growth factor controls GAP-43 mRNA stability via the phosphoprotein ARPP-19
Authors: Irwin Nina , Chao Steven , Goritchenko Luda , Horiuchi Atsuko , Greengard Paul , Nairn Angus C. , Benowitz Larry I.
Published: September 2002

The membrane phosphoprotein GAP-43 is involved in axon growth and synaptic plasticity. In PC12 pheochromocytoma cells, induction of a neuronal phenotype by nerve growth factor (NGF) is accompanied by a marked increase in GAP-43 levels. NGF regulates GAP-43 expression by altering the half-life of its mRNA. We report here that the phosphoprotein ARPP-19 mediates this regulation. In an NGF-dependent manner, ARPP-19 bound to a region in the 3′ end of GAP-43 mRNA previously found to be important for regulating the half-life of the mRNA. Overexpression of wild-type ARPP-19 in PC12 cells increased the NGF-dependent expression of a reporter construct linked to the critical 3′ region of GAP-43 mRNA. Mutation of serine 104, the site of phosphorylation by protein kinase A in ARPP-19, to either alanine or aspartate abolished this regulation in PC12 cells. These findings demonstrate that ARPP-19 is an important link between NGF signaling and post-transcriptional control of neuronal gene expression.
Akt induces enhanced myocardial contractility and cell size
in vivo
in transgenic mice
Authors: Condorelli Gianluigi , Drusco Alessandra , Stassi Giorgio , Bellacosa Alfonso , Roncarati Roberta , Iaccarino Guido , Russo Matteo A. , Gu Yusu , Dalton Nancy , Chung Clarence , Latronico Michael V. G. , Napoli Claudio , Sadoshima Junichi , Croce Carlo M. , Ross John
Published: September 2002

The serine-threonine kinase Akt seems to be central in mediating stimuli from different classes of receptors. In fact, both IGF-1 and IL6-like cytokines induce hypertrophic and antiapoptotic signals in cardiomyocytes through PI3K-dependent Akt activation. More recently, it was shown that Akt is involved also in the hypertrophic and antiapoptotic effects of β-adrenergic stimulation. Thus, to determine the effects of Akt on cardiac function
in vivo
, we generated a model of cardiac-specific Akt overexpression in mice. Transgenic mice were generated by using the E40K, constitutively active mutant of Akt linked to the rat α-myosin heavy chain promoter. The effects of cardiac-selective Akt overexpression were studied by echocardiography, cardiac catheterization, histological and biochemical techniques. We found that Akt overexpression produced cardiac hypertrophy at the molecular and histological levels, with a significant increase in cardiomyocyte cell size and concentric LV hypertrophy. Akt-transgenic mice also showed a remarkable increase in cardiac contractility compared with wild-type controls as demonstrated by the analysis of left ventricular (dP/dt
max
) in an invasive hemodynamic study, although with graded dobutamine infusion, the maximum response was not different from that in controls. Diastolic function, evaluated by left ventricular dP/dt
min
, was not affected at rest but was impaired during graded dobutamine infusion. Isoproterenol-induced cAMP levels, β-adrenergic receptor (β-AR) density, and β-AR affinity were not altered compared with control mice. Moreover, studies on signaling pathway activation from myocardial extracts demonstrated that glycogen synthase kinase3-β is phosphorylated, whereas p42/44 mitogen-activated protein kinases is not, indicating that Akt induces hypertrophy
in vivo
by activating the glycogen synthase kinase3-β/GATA 4 pathway. In summary, our results not only demonstrate that Akt regulates cardiomyocyte cell size
in vivo
, but, importantly, show that Akt modulates cardiac contractility
in vivo
without directly affecting β-AR signaling capacity.
Friction traced to the single atom
Authors: Giessibl Franz J. , Herz Markus , Mannhart Jochen
Published: September 2002

Friction is caused by dissipative lateral forces that act between macroscopic objects. An improved understanding of friction is therefore expected from measurements of dissipative lateral forces acting between individual atoms. Here we establish atomic resolution of both conservative and dissipative forces by lateral force microscopy, presenting the resolution of atomic defects. The interaction between a single-tip atom that is oscillated parallel to an Si(111)-(7 × 7) surface is measured. A dissipation energy of up to 4 eV per oscillation cycle is found. The dissipation is explained by a “plucking action of one atom on to the other” as described by G. A. Tomlinson in 1929 [Tomlinson, G. A. (1929)Phil. Mag.7, 905–939].
Purification and electron microscopic visualization of functional human spliceosomes
Authors: Zhou Zhaolan , Sim Jeonggu , Griffith Jack , Reed Robin
Published: September 2002

Pre-mRNA splicing takes place in a large and highly dynamic complex known as the spliceosome. Here we report the optimization of a maltose-binding protein (MBP) affinity-purification method to isolate functional spliceosomes for electron microscopic analysis. Visualization of the spliceosome preparations revealed distinct 40–60 nm particles. Immunogold-conjugated antibodies to spliceosome components specifically label these particles, which are eliminated by treatment with either RNase or protease. Moreover, spliceosomes assembled on two different pre-mRNAs are indistinguishable. This first visualization of purified functional spliceosomes assembled
in vitro
reveals striking structural features, including one or more central cavities and multiple elongate lobes.
STAT4 serine phosphorylation is critical for IL-12-induced IFN-γ production but not for cell proliferation
Authors: Morinobu Akio , Gadina Massimo , Strober Warren , Visconti Roberta , Fornace Albert , Montagna Cristina , Feldman Gerald M. , Nishikomori Ryuta , O'Shea John J.
Published: September 2002

T helper 1 (TH1) differentiation and IFN-γ production are crucial in cell-mediated immune responses. IL-12 is an important regulator of this process and mediates its effects through signal transducer and activator of transcription 4 (STAT4). IFN-γ production is also regulated by the p38 mitogen-activated kinase pathway, although the mechanisms are ill-defined. We show here that GADD45-β and GADD45-γ can induce STAT4 S721 phosphorylation via the MKK6/p38 pathway. Thus, STAT4 could be a target that accounts for the defects in cell-mediated immunity associated with perturbations in the p38 pathway. To investigate the biological significance of STAT4 S721 phosphorylation, we reconstituted primary spleen cells from STAT4-deficient mice with wild-type and mutated STAT4, by using a retroviral gene transduction. We demonstrated that expression of wild-type STAT4, but not the S721A mutant, restored normal TH1 differentiation and IFN-γ synthesis. The inability of STAT4 S721 to restore IFN-γ production was not caused by decreased IL-12R expression because the STAT4 S721 mutant also failed to restore IFN-γ production in STAT4-deficient IL-12Rβ2 transgenic cells. Importantly, STAT4 S721A-transduced cells showed normal proliferative response to IL-12, illustrating that serine phosphorylation is not required for IL-12-induced proliferation. Additionally, the results imply the existence of STAT4 serine phosphorylation-dependent and -independent target genes. We conclude that phosphorylation of STAT4 on both tyrosine and serine residues is important in promoting normal TH1 differentiation and IFN-γ secretion.
Serotonin mediates food-odor associative learning in the nematode
Caenorhabditis
elegans
Authors: Nuttley William M. , Atkinson-Leadbeater Karen P. , van der Kooy Derek
Published: September 2002

We demonstrate that
Caenorhabditis elegans
is able to form an association between the presence of the odorant benzaldehyde and the food content of its environment. When exposed to 100% benzaldehyde for 1 h in the absence of food the naive attractive response is reduced, and we have found that this olfactory adaptation is attenuated by the presence of food. Contrary to nonassociative (single stimulus) learning theory, this response is not a function of the total time of exposure to benzaldehyde but rather an associative function of the ability of benzaldehyde to predict a nutrient-deficient environment. Genetic and pharmacological evidence revealed that the effects of food in this learning paradigm are mediated by serotonergic signaling.
Electrical and chemical synapses among parvalbumin fast-spiking GABAergic interneurons in adult mouse neocortex
Authors: Galarreta Mario , Hestrin Shaul
Published: September 2002

Networks of γ-aminobutyric acid (GABA)ergic interneurons connected via electrical and chemical synapses are thought to play an important role in detecting and promoting synchronous activity in the cerebral cortex. Although the properties of electrical and chemical synaptic interactions among inhibitory interneurons are critical for their function as a network, they have only been studied systematically in juvenile animals. Here, we have used transgenic mice expressing the enhanced green fluorescent protein in cells containing parvalbumin (PV) to study the synaptic connectivity among fast-spiking (FS) cells in slices from adult animals (2–7 months old). We have recorded from pairs of PV-FS cells and found that the majority of them were electrically coupled (61%, 14 of 23 pairs). In addition, 78% of the pairs were connected via GABAergic chemical synapses, often reciprocally. The average coupling coefficient for step injections was 1.5% (
n
= 14), a smaller value than that reported in juvenile animals. GABA-mediated inhibitory postsynaptic currents and potentials decayed with exponential time constants of 2.6 and 5.9 ms, respectively, and exhibited paired-pulse depression (50-ms interval). The inhibitory synaptic responses in the adult were faster than those observed in young animals. Our results indicate that PV-FS cells are highly interconnected in the adult cerebral cortex by both electrical and chemical synapses, establishing networks that can have important implications for coordinating activity in cortical circuits.
A functional polymorphism in the promoter of the progesterone receptor gene associated with endometrial cancer risk
Authors: De Vivo Immaculata , Huggins Gordon S. , Hankinson Susan E. , Lescault Pamela J. , Boezen Marike , Colditz Graham A. , Hunter David J.
Published: September 2002

Excessive estrogen stimulation unopposed by progesterone strongly predisposes to endometrial cancer. Because the antiproliferative effect of progesterone requires the progesterone receptor (PR), which exists in two isoforms, PR-A and -B, we reasoned that variants in the PR gene may predispose to endometrial cancer. We found six variable sites, including four polymorphisms in the
hPR
gene and five common haplotypes. One promoter region polymorphism, +331G/A, creates a unique transcription start site. Biochemical assays showed that the +331G/A polymorphism increases transcription of the
PR
gene, favoring production of hPR-B in an endometrial cancer cell line. Using a case-control study nested within the Nurses' Health Study cohort, we observed a statistically significant association between the +331G/A polymorphism and the risk of endometrial cancer, which was even greater in overweight women carriers. After including a second population of controls, these associations remained intact. Our findings suggest that the +331G/A
hPR
gene polymorphism may contribute to endometrial cancer risk by increasing expression of the hPR-B isoform.
Revisiting the kinetics of nitric oxide (NO) binding to soluble guanylate cyclase: The simple NO-binding model is incorrect
Authors: Ballou David P. , Zhao Yunde , Brandish Philip E. , Marletta Michael A.
Published: September 2002

Soluble guanylate cyclase (sGC) is a ferrous iron hemoprotein receptor for nitric oxide (NO). NO binding to the heme activates the enzyme 300-fold. sGC as isolated is five-coordinate, ferrous with histidine as the axial ligand. The NO-activated enzyme is a five-coordinate nitrosyl complex where the axial histidine bond is broken. Past studies using rapid-reaction kinetics demonstrated that both the formation of a six-coordinate intermediate and the conversion of the intermediate to the activated five-coordinate nitrosyl complex depended on the concentration of NO. A model invoking a second NO molecule as a catalyst for the conversion of the six-coordinate intermediate to the five-coordinate sGC–NO complex was proposed to explain the observed kinetic data. A recent study [Bellamy, T. C., Wood, J. & Garthwaite, J. (2002)
Proc. Natl. Acad. Sci. USA
99, 507–510] concluded that a simple two-step binding model explains the results. Here we show through further analysis and simulations of previous data that the simple two-step binding model cannot be used to describe our results. Instead we show that a slightly more complex two-step binding model, where NO is used as a ligand in the first step and a catalyst in the second step, can describe our results quite satisfactorily. These new simulations combined with the previous activation data lead to the conclusion that the intermediate six-coordinate sGC–NO complex has substantial activity. The model derived from our simulations also can account for the slow deactivation of sGC that has been observed
in vitro
.
Folate synthesis in plants: The first step of the pterin branch is mediated by a unique bimodular GTP cyclohydrolase I
Authors: Basset Gilles , Quinlivan Eoin P. , Ziemak Michael J. , Díaz de la Garza Rocío , Fischer Markus , Schiffmann Susi , Bacher Adelbert , Gregory Jesse F. , Hanson Andrew D.
Published: September 2002

GTP cyclohydrolase I (GCHI) mediates the first and committing step of the pterin branch of the folate-synthesis pathway. In microorganisms and mammals, GCHI is a homodecamer of ≈26-kDa subunits. Genomic approaches identified tomato and
Arabidopsis
cDNAs specifying ≈50-kDa proteins containing two GCHI-like domains in tandem and indicated that such bimodular proteins occur in other plants. Neither domain of these proteins has a full set of the residues involved in substrate binding and catalysis in other GCHIs. The tomato and
Arabidopsis
cDNAs nevertheless encode functional enzymes, as shown by complementation of a yeast
fol2
mutant and by assaying GCHI activity in extracts of complemented yeast cells. Neither domain expressed separately had GCHI activity. Recombinant tomato GCHI formed dihydroneopterin triphosphate as reaction product, as do other GCHIs, but unlike these enzymes it did not show cooperative behavior and was inhibited by its substrate. Denaturing gel electrophoresis verified that the bimodular GCHI polypeptide is not cleaved
in vivo
into its component domains, and size-exclusion chromatography indicated that the active enzyme is a dimer. The deduced tomato and
Arabidopsis
GCHI polypeptides lack overt targeting sequences and thus are presumably cytosolic, in contrast to other plant folate-synthesis enzymes, which are mitochondrial proteins with typical signal peptides. GCHI mRNA and protein are strongly in expressed unripe tomato fruits, implying that fruit folate is made
in situ
rather than imported. As ripening advances, GCHI expression declines sharply, and folate content drops, suggesting that folate synthesis fails to keep pace with turnover.
Engineering growing tissues
Authors: Alsberg Eben , Anderson Kenneth W. , Albeiruti Amru , Rowley Jon A. , Mooney David J.
Published: September 2002

Regenerating or engineering new tissues and organs may one day allow routine replacement of lost or failing tissues and organs. However, these engineered tissues must not only grow to fill a defect and integrate with the host tissue, but often they must also grow in concert with the changing needs of the body over time. We hypothesized that tissues capable of growing with time could be engineered by supplying growth stimulus signals to cells from the biomaterial used for cell transplantation. In this study, chondrocytes and osteoblasts were cotransplanted on hydrogels modified with an RGD-containing peptide sequence to promote cell multiplication. New bone tissue was formed that grew in mass and cellularity by endochondral ossification in a manner similar to normal long-bone growth. Transplanted cells organized into structures that morphologically and functionally resembled growth plates. These engineered tissues could find utility in treating diseases and injuries of the growth plate, testing the effect of experimental drugs on growth-plate function and development, and investigating the biology of long-bone growth. Furthermore, this concept of promoting the growth of engineered tissues could find great utility in engineering numerous tissue types by way of the transplantation of a small number of precursor cells.
Act locally and think globally: Intracerebral testosterone implants induce seasonal-like growth of adult avian song control circuits
Authors: Brenowitz Eliot A. , Lent Karin
Published: September 2002

There is pronounced seasonal plasticity in the morphology of the neural circuits that regulate song behavior in adult songbirds, primarily in response to changes in plasma testosterone (T) levels. Most song nuclei have androgen receptors. Afferent input from the telencephalic nucleus HVc (also known as the “high vocal center”) is necessary for seasonal growth of the direct efferent target nuclei RA and area X. We asked here whether T-stimulated growth of HVc is sufficient to induce growth of its efferent nuclei. Intracerebral T implants were placed unilaterally near HVc or RA in photosensitive adult male white-crowned sparrows for one month. The T implant near HVc produced significant growth of the ipsilateral (but not contralateral) HVc, RA, and area X, and increased neuronal number in the ipsilateral HVc. The T implant near RA did not produce selective growth of ipsilateral RA, HVc, or area X. Intracerebral T implants did not elevate plasma T levels, nor did they stimulate growth of two peripheral androgen sensitive targets, the syrinx and the cloacal protuberance. These results suggest that seasonal growth of the adult song circuits results from T acting directly on HVc, which then stimulates the growth of RA and area X transynaptically.
Transgenic cyclooxygenase-2 overexpression sensitizes mouse skin for carcinogenesis
Authors: Müller-Decker Karin , Neufang Gitta , Berger Irina , Neumann Melanie , Marks Friedrich , Fürstenberger Gerhard
Published: September 2002

Genetic and pharmacological evidence suggests that overexpression of cyclooxygenase-2 (COX-2) is critical for epithelial carcinogenesis and provides a major target for cancer chemoprevention by nonsteroidal antiinflammatory drugs. Transgenic mouse lines with keratin 5 promoter-driven COX-2 overexpression in basal epidermal cells exhibit a preneoplastic skin phenotype. As shown here, this phenotype depends on the level of COX-2 expression and COX-2-mediated prostaglandin accumulation. The transgenics did not develop skin tumors spontaneously but did so after a single application of an initiating dose of the carcinogen 7,12-dimethylbenz[
a
]anthracene (DMBA). Long-term treatment with the tumor promoter phorbol 12-myristate 13-acetate, as required for tumorigenesis in wild-type mice, was not necessary for transgenics. The ratios of squamous cell carcinomas to papillomas and of sebaceous gland adenomas to papillomas plus squamous cell carcinomas were increased markedly in transgenic mice treated with DMBA alone compared with DMBA/phorbol 12-myristate 13-acetate-treated transgenic and wild-type mice. Thus, COX-2 overexpression, which leads to high levels of epidermal prostaglandin E
2
, prostaglandin F
2α
, and 15-deoxy
Δ12,14
-PGJ
2
, is insufficient for tumor induction but transforms epidermis into an “autopromoted” state, i.e., dramatically sensitizes the tissue for genotoxic carcinogens.
Position of aromatic residues in the S6 domain, not inactivation, dictates cisapride sensitivity of HERG and eag potassium channels
Authors: Chen Jun , Seebohm Guiscard , Sanguinetti Michael C.
Published: September 2002

Unintended block of HERG K
+
channels is a side effect of many common medications and is the most common cause of acquired long QT syndrome associated with increased risk of life-threatening arrhythmias. The molecular mechanism of high-affinity HERG block by structurally diverse compounds has been attributed to π-stacking and cation-π interactions of a drug (e.g., cisapride) with specific aromatic amino acid residues (Tyr-652 and Phe-656) in the S6 α-helical domain that face the central cavity of the channel. It also has been proposed that strong C-type inactivation of HERG facilitates or is the primary determinant of high-affinity drug binding. The structurally related, but noninactivating eag channel is insensitive to HERG blockers unless inactivation is induced by specific amino acid mutations [Ficker, E., Jarolimek, W. & Brown, A. M. (2001)
Mol. Pharmacol.
60, 1343–1348]. Here we examine the relative importance of inactivation vs. positioning of S6 aromatic residues in determining sensitivity of HERG and eag channels to block by cisapride. The repositioning of Tyr-652 or Phe-656 along the S6 α-helical domain of HERG reduced sensitivity of channels to block by cisapride. Moreover, independent of inactivation, repositioning of the equivalent aromatic residues in
Drosophila
eag channels induced sensitivity to block by cisapride. These findings suggest that positioning of S6 aromatic residues relative to the central cavity of the channel, not inactivation
per se
determines drug block of HERG or eag channels.
Genomic profiles of clinical and environmental isolates of
Vibrio cholerae
O1 in cholera-endemic areas of Bangladesh
Authors: Zo Young-Gun , Rivera Irma N. G. , Russek-Cohen Estelle , Islam M. Sirajul , Siddique A. K. , Yunus M. , Sack R. Bradley , Huq Anwar , Colwell Rita R.
Published: September 2002

Diversity, relatedness, and ecological interactions of toxigenic
Vibrio cholerae
O1 populations in two distinctive habitats, the human intestine and the aquatic environment, were analyzed. Twenty environmental isolates and 42 clinical isolates were selected for study by matching serotype, geographic location of isolation in Bangladesh, and season of isolation. Genetic profiling was done by enterobacterial repetitive intergenic consensus sequence–PCR, optimized for profiling by using the fully sequenced
V. cholerae
El Tor N16961 genome. Five significant clonal clusters of haplotypes were found from 57 electrophoretic types. Isolates from different areas or habitats intermingled in two of the five significant clusters. Frequencies of haplotypes differed significantly only between the environmental populations (exact test;
P
< 0.05). Analysis of molecular variance yielded a population genetic structure reflecting the differentiating effects of geographic area, habitat, and sampling time. Although a parameter confounding the latter differences explained 9% of the total molecular variance in the entire population (
P
< 0.01), the net effect of habitat and time could not be separated because of the small number of environmental isolates included in the study. Five subpopulations from a single area were determined, and from these we were able to estimate a relative differentiating effect of habitat, which was small compared with the effect of temporal change. In conclusion, the resulting population structure supports the hypothesis that spatial and temporal fluctuations in the composition of toxigenic
V. cholerae
populations in the aquatic environment can cause shifts in the dynamics of the disease.
Identifying novel transcripts and novel genes in the human genome by using novel SAGE tags
Authors: Chen Jianjun , Sun Miao , Lee Sanggyu , Zhou Guolin , Rowley Janet D. , Wang San Ming
Published: September 2002

The number of genes in the human genome is still a controversial issue. Whereas most of the genes in the human genome are said to have been physically or computationally identified, many short cDNA sequences identified as tags by use of serial analysis of gene expression (SAGE) do not match these genes. By performing experimental verification of more than 1,000 SAGE tags and analyzing 4,285,923 SAGE tags of human origin in the current SAGE database, we examined the nature of the unmatched SAGE tags. Our study shows that most of the unmatched SAGE tags are truly novel SAGE tags that originated from novel transcripts not yet identified in the human genome, including alternatively spliced transcripts from known genes and potential novel genes. Our study indicates that by using novel SAGE tags as probes, we should be able to identify efficiently many novel transcripts/novel genes in the human genome that are difficult to identify by conventional methods.
A global pH sensor:Agrobacteriumsensor protein ChvG regulates acid-inducible genes on its two chromosomes and Ti plasmid
Authors: Li Luoping , Jia Yonghui , Hou Qingming , Charles Trevor C. , Nester Eugene W. , Pan Shen Q.
Published: September 2002

A sensor protein ChvG is part of a chromosomally encoded two-component regulatory system ChvG/ChvI that is important for the virulence ofAgrobacterium tumefaciens. However, it is not clear what genes ChvG regulates or what signal(s) it senses. In this communication, we demonstrate that ChvG is involved in the regulation of acid-inducible genes, includingaopBandkatA, residing on the circular and linear chromosomes, respectively, and the tumor-inducing (Ti)-plasmid-harboredvirgenes,virBandvirE. ChvG was absolutely required for the expression ofaopBand very important for the expression ofvirBandvirE. However, it was responsible only for the responsiveness ofkatAand, to a limited extent, thevirgenes to acidic pH. ChvG appears to play a role inkatAexpression by repressingkatAat neutral pH. ChvG had no effect on the expression of two genes that were not acid-inducible. Because ChvG regulates unlinked acid-inducible genes encoding different functions in different ways, we hypothesize that ChvG is a global sensor protein that can directly or indirectly sense extracellular acidity. We also analyzed the re-sequencedchvGand found that ChvG is more homologous to itsSinorhizobium meliloticounterpart ExoS than was previously thought. Full-length ChvG is conserved in members of the α-proteobacteria, whereas only the C-terminal kinase domain is conserved in other bacteria. Sensing acidity appears to enableAgrobacteriumto coordinate its coping with the environment of wounded plants to cause tumors.
The ribosome filter hypothesis
Authors: Mauro Vincent P. , Edelman Gerald M.
Published: September 2002

A variety of posttranscriptional mechanisms affects the processing, subcellular localization, and translation of messenger RNAs (mRNAs). Translational control appears to occur primarily at the initiation rather than the elongation stage. It has been suggested that translation is mediated largely by means of a cap-binding/scanning mechanism. On the basis of recent findings, we propose here that differential binding of particular mRNAs to eukaryotic 40S ribosomal subunits before translation may also selectively affect rates of polypeptide chain production. In this view, ribosomal subunits themselves are considered to be regulatory elements or filters that mediate interactions between particular mRNAs and components of the translation machinery. Differences in these interactions affect how efficiently individual mRNAs compete for ribosomal subunits. These competitive interactions would depend in part on the complementarity between sequences in mRNA and rRNA, as well as on structural differences among ribosomes in different cell types. By these means, translation may either be enhanced through increased recruitment of ribosomes or inhibited through strong interactions that sequester mRNAs. We propose that ribosomal filters may be important in cell differentiation and describe experimental tests for the filter hypothesis.
Somatic hypermutation of the AID transgene in B and non-B cells
Authors: Martin Alberto , Scharff Matthew D.
Published: September 2002

Somatic hypermutation (SHM) of the Ig genes is required for affinity maturation of the humoral response to foreign antigens. Activation-induced cytidine deaminase (AID), which is specifically expressed in germinal center centroblasts, is indispensable for this process. Expression of AID is sufficient to activate SHM in hybridomas, non-B cells, and
Escherichia coli
, suggesting that it initiates the mutational process by deaminating DNA. However, the cis-acting sequences that are responsible for targeting AID activity to the variable (V) region of Ig genes are unknown. Here we show that expression of AID in B cell lines (i.e., Burkitt's lymphoma Ramos and hybridoma P1–5) not only causes hypermutation of Ig sequences, but also of the AID transgene itself. Because it is possible that B cell-specific transacting factors bind to and recruit the “mutator” to the AID transgene, we tested whether the AID transgene can mutate in non-B cells. Indeed, we show that expression of AID in Chinese hamster ovary cells causes SHM of both the Ig and AID transgenes. These data suggest that high transcription rates alone may predispose any gene to mutation by AID but do not preclude that there are specific B cell factors that account for the extremely high rate of V mutation
in vivo
and its targeting to the V region.
Nerve growth factor and galantamine ameliorate early signs of neurodegeneration in anti-nerve growth factor mice
Authors: Capsoni Simona , Giannotta Sabina , Cattaneo Antonino
Published: September 2002

Phenotypic knockout of nerve growth factor (NGF) activity in transgenic anti-NGF mice (AD11 mice) results in a progressive neurodegenerative phenotype resembling Alzheimer's disease. In this article, we examine whether and how the progressive neurodegenerative phenotype of AD11 mice could be prevented or ameliorated by pharmacological treatments with NGF or the cholinergic agonist galantamine, at a relatively early phase of Alzheimer's disease-like neurodegeneration. We demonstrate that the neurodegeneration induced by the expression of anti-NGF antibodies in AD11 mice can be largely reversed by NGF delivery through an olfactory route.
Inhibition of Fe-S cluster biosynthesis decreases mitochondrial iron export: Evidence that Yfh1p affects Fe-S cluster synthesis
Authors: Chen Opal S. , Hemenway Shawn , Kaplan Jerry
Published: September 2002

Decreased expression of Yfh1p in the budding yeast,
Saccharomyces cerevisiae
, and the orthologous human gene frataxin results in respiratory deficiency and mitochondrial iron accumulation. The absence of Yfh1p decreases mitochondrial iron export. We demonstrate that decreased expression of Nfs1p, the yeast cysteine desulfurase that plays a central role in Fe-S cluster synthesis, also results in mitochondrial iron accumulation due to decreased export of mitochondrial iron. In the absence of Yfh1p, activity of Fe-S-containing enzymes (aconitase, succinate dehydrogenase) is decreased, whereas the activity of a non-Fe-S-containing enzyme (malate dehydrogenase) is unaffected. Aconitase protein was abundant even though the activity of aconitase was decreased in both aerobic and anaerobic conditions. These results demonstrate a direct role of Yfh1p in the formation of Fe-S clusters and indicate that mitochondrial iron export requires Fe-S cluster biosynthesis.
The structural basis for the transition from Ras-GTP to Ras-GDP
Authors: Hall Brian E. , Bar-Sagi Dafna , Nassar Nicolas
Published: September 2002

The conformational changes in Ras that accompany the hydrolysis of GTP are critical to its function as a molecular switch in signaling pathways. Understanding how GTP is hydrolyzed by revealing the sequence of intermediary structures in the reaction is essential for understanding Ras signaling. Until now, no structure of an intermediate in GTP hydrolysis has been experimentally determined for Ras alone. We have solved the crystal structure of the Ala-59 to Gly mutant of Ras, (RasA59G), bound to guanosine 5′-imidotriphosphate or GDP to 1.7-Å resolution. In the guanosine 5′-imidotriphosphate-bound form, this mutant adopts a conformation that is intermediate between the GTP- and GDP-bound forms of wild-type Ras and that is similar to what has been predicted by molecular dynamics simulation [Ma, J. P. & Karplus, M. (1997)
Proc. Natl. Acad. Sci. USA
94, 11905–11910]. This conformation is stabilized by direct and water-mediated interactions between the switch 1 and switch 2 regions and is characterized by an increase in the binding affinity for GTP. We propose that the structural changes promoted by the Ala-59 to Gly mutation exhibit a discrete conformational state assumed by wild-type Ras during GTP hydrolysis.