How Good are Patients at Determining which Side of the Nose is More Obstructed? A Study on the Limits of Discrimination of the Subjective Assessment of Unilateral Nasal Obstruction

Background

The subjective sensation of nasal obstruction is of great importance to the patient and surgeon because it is this symptom that causes the patient to present for investigation and treatment. Although there are several studies in the literature looking at the correlation (or lack of correlation) between objective and subjective measures of nasal obstruction, there is no information on the minimum objective change in obstruction measured as nasal airway resistance or flow, which can be detected by a patient. The aim of this study was to measure the minimum difference in unilateral airflow that can be reliably detected by a patient.

Methods

Sixty participants with a common cold were recruited. One hundred twenty unilateral measurements of objective and subjective nasal obstruction were obtained using the technique of posterior rhinomanometry and a 100-mm visual analog scale (VAS).

Results

Seventy-seven percent of the participants correctly discriminated between the high- and low-flow nasal passages using the VAS. Ninety-five percent of subjects correctly discriminated on the VAS between the high- and low-flow nasal passages when the difference in flow between the nasal passages was at least 100 cm3/s.

Conclusion

This study provides new knowledge about the limits of subjective sensation of nasal obstruction. At a level of 100 cm3/s difference in unilateral nasal flow, 95% of subjects with acute rhinitis can correctly identify the more obstructed nasal passage when using a VAS. With smaller differences in unilateral flow, the percentage of correct responses declines rapidly toward 50% as expected by chance alone.

Nonalcoholic Steatohepatitis Modulates Membrane Protein Retrieval and Insertion Processes

Interindividual variability in drug response in nonalcoholic steatohepatitis (NASH) can be mediated by altered regulation of drug metabolizing enzymes and transporters. Among these is the mislocalization of multidrug resistance-associated protein (MRP2)/Mrp2 away from the canalicular membrane, which results in decreased transport of MRP2/Mrp2 substrates. The exact mechanism of this mislocalization is unknown, although increased activation of membrane retrieval processes may be one possibility. The current study measures the activation status of various mediators implicated in the active membrane retrieval or insertion of membrane proteins to identify which processes may be important in rodent methionine and choline deficient diet-induced NASH. The mediators currently known to be associated with transporter mislocalization are stimulated by oxidative stressors and choleretic stimuli, which play a role in the pathogenesis of NASH. The activation of protein kinases PKA, PKCα, PKCδ, and PKCε and substrates radixin, myristoylated alanine-rich C-kinase substrate, and Rab11 were measured by comparing the expression, phosphorylation, and membrane translocation between control and NASH. Many of the mediators exhibited altered activation in NASH rats. Consistent with membrane retrieval of Mrp2, NASH rats exhibited a decreased phosphorylation of radixin and increased membrane localization of PKCδ and PKCε, thought to be mediators of radixin dephosphorylation. Altered activation of PKCδ, PKA, and PKCα may impair the Rab11-mediated active insertion of Mrp2. Overall, these data suggest alterations in membrane retrieval and insertion processes that may contribute to altered localization of membrane proteins in NASH.

Can early second-look tympanoplasty reduce the rate of conversion to modified radical mastoidectomy?

CONCLUSIONS

Combined approach tympanoplasty (CAT) allows for successful treatment of cholesteatoma with rates of recurrent and residual disease comparable to open mastoid surgery. Early timing of second-look procedures allows easier removal of any recurrent or residual disease, which reduces the conversion rate to open mastoidectomy.

OBJECTIVES

The aims of the study were to report the rates of recurrent and residual cholesteatoma following primary CAT surgery and to report the rate of conversion to a modified radical mastoidectomy.

METHODS

This was a retrospective review of a single surgeon series between 2006 and 2012.

RESULTS

In total 132 second-look operations were undertaken, with a mean interval between primary surgery and second-look procedures of 6 months. The rate of cholesteatoma at second-look surgery was 19.7%, which was split into residual disease (10.6%) and recurrent disease (9.09%). New tympanic membrane defects with cholesteatoma were considered as recurrent disease. Residual disease was defined as cholesteatoma present behind an intact tympanic membrane. The majority of recurrent and residual disease was easily removed at second look (73.1%). Only four cases were converted to a modified radical mastoidectomy (3%) and three cases required a third-look procedure.

An extensive phase space for the potential martian biosphere

We present a comprehensive model of martian pressure-temperature (P-T) phase space and compare it with that of Earth. Martian P-T conditions compatible with liquid water extend to a depth of ∼310 km. We use our phase space model of Mars and of terrestrial life to estimate the depths and extent of the water on Mars that is habitable for terrestrial life. We find an extensive overlap between inhabited terrestrial phase space and martian phase space. The lower martian surface temperatures and shallower martian geotherm suggest that, if there is a hot deep biosphere on Mars, it could extend 7 times deeper than the ∼5 km depth of the hot deep terrestrial biosphere in the crust inhabited by hyperthermophilic chemolithotrophs. This corresponds to ∼3.2% of the volume of present-day Mars being potentially habitable for terrestrial-like life.

Transverse tubules are a common feature in large mammalian atrial myocytes including human

Transverse (t) tubules are surface membrane invaginations that are present in all mammalian cardiac ventricular cells. The apposition of L-type Ca(2+) channels on t tubules with the sarcoplasmic reticulum (SR) constitutes a "calcium release unit" and allows close coupling of excitation to the rise in systolic Ca(2+). T tubules are virtually absent in the atria of small mammals, and therefore Ca(2+) release from the SR occurs initially at the periphery of the cell and then propagates into the interior. Recent work has, however, shown the occurrence of t tubules in atrial myocytes from sheep. As in the ventricle, Ca(2+) release in these cells occurs simultaneously in central and peripheral regions. T tubules in both the atria and the ventricle are lost in disease, contributing to cellular dysfunction. The aim of this study was to determine if the occurrence of t tubules in the atrium is restricted to sheep or is a more general property of larger mammals including humans. In atrial tissue sections from human, horse, cow, and sheep, membranes were labeled using wheat germ agglutinin. As previously shown in sheep, extensive t-tubule networks were present in horse, cow, and human atrial myocytes. Analysis shows half the volume of the cell lies within 0.64 ± 0.03, 0.77 ± 0.03, 0.84 ± 0.03, and 1.56 ± 0.19 μm of t-tubule membrane in horse, cow, sheep, and human atrial myocytes, respectively. The presence of t tubules in the human atria may play an important role in determining the spatio-temporal properties of the systolic Ca(2+) transient and how this is perturbed in disease.

Differential expression of IEG mRNA in rat brain following acute treatment with clozapine or haloperidol: a semi-quantitative RT-PCR study

Antipsychotic drugs have been shown to modulate immediate early gene (IEG) expression in rat brain regions that are associated with schizophrenia, which may be directly linked to their immediate therapeutic benefit. In this study, we analysed the expression profile of a series of IEGs (c-fos, c-jun, fra-1, Krox-20, Krox-24, arc, sgk-1, BDNF and NARP) in six rat brain regions (prefrontal cortex, hippocampus, striatum, nucleus accumbens, thalamus and cerebellum). Rats (n=5) were administered either clozapine (20 mg/kg i.p.), haloperidol (1 mg/kg i.p.) or the appropriate vehicle with pre-treatment times of 1, 6 and 24 h. IEG expression was analysed in these regions by Taqman RT-PCR. The spatial and temporal profile of IEG induction following antipsychotic drug treatment correlates with regions associated with the efficacy and side effect profile of each drug. In particular, sgk-1 expression levels after antipsychotic drug treatment may have predictive value when investigating the profile of a novel antipsychotic drug.

Maxillary frontal process fracture complicating acute dacryocystorhinostomy

A case of maxillary frontal process fracture complicating an acute endonasal dacryocystorhinostomy is presented. The management of this previously unrecorded complication and the corrective procedure that resulted in both patient and clinician satisfaction is described.

Expression of pcp4a in subpopulations of CNS neurons in zebrafish

The molecular organization of the zebrafish brain and its relation to neuroanatomical divisions are still largely unknown. In this study we have analyzed the expression of a small transcript encoding for the IQ containing polypeptide Pcp4a in developing and juvenile zebrafish. The transcript is exclusively expressed in neural structures with a pattern that is highly specific for restricted domains and cell populations throughout development, and it allows us to follow the development of these structures at different times. The expression of pcp4a characterizes the dorsocaudal telencephalon, dorsal habenula, pretectal nuclei, preglomerular complex, mammillary bodies, and deep layers of the optic tectum and is a hallmark of a subpopulation of reticulospinal neurons. In the telencephalon, comparison of the expression of pcp4a with other pallial markers showed a rostrocaudal gradient in the expression of these genes, which suggests that the dorsal telencephalon of zebrafish may be organized in distinct areas with different molecular natures. Pcp4 has been involved in modulating calcium signals and in binding to calmodulin, but its precise role in neuronal functions is not known. The analysis of pcp4a expression and localization in the zebrafish brain suggests that pcp4a may be a useful marker for sensory and some motor neuronal circuitries and for telencephalic areas processing sensory inputs.

How good are patients at determining which side of the nose is more obstructed? A study on the limits of discrimination of the subjective assessment of unilateral nasal obstruction

BACKGROUND

The subjective sensation of nasal obstruction is of great importance to the patient and surgeon because it is this symptom that causes the patient to present for investigation and treatment. Although there are several studies in the literature looking at the correlation (or lack of correlation) between objective and subjective measures of nasal obstruction, there is no information on the minimum objective change in obstruction measured as nasal airway resistance or flow, which can be detected by a patient. The aim of this study was to measure the minimum difference in unilateral airflow that can be reliably detected by a patient.

METHODS

Sixty participants with a common cold were recruited. One hundred twenty unilateral measurements of objective and subjective nasal obstruction were obtained using the technique of posterior rhinomanometry and a 100-mm visual analog scale (VAS).

RESULTS

Seventy-seven percent of the participants correctly discriminated between the high- and low-flow nasal passages using the VAS. Ninety-five percent of subjects correctly discriminated on the VAS between the high- and low-flow nasal passages when the difference inflow between the nasal passages was at least 100 cm3/s.

CONCLUSION

This study provides new knowledge about the limits of subjective sensation of nasal obstruction. At a level of 100 cm3/s difference in unilateral nasal flow, 95% of subjects with acute rhinitis can correctly identify the more obstructed nasal passage when using a VAS. With smaller differences in unilateral flow, the percentage of correct responses declines rapidly toward 50% as expected by chance alone.

Paradoxical sensation of nasal airflow in patients with common cold. Are we measuring the correct modality?

CONCLUSIONS

A paradoxical relationship between objective and subjective measures of nasal obstruction exists in participants not exposed to any treatment. The sensation of nasal obstruction may be due to the amalgamation of many different nasal sensations. Improved methods for measuring nasal sensations are required to further investigate the relationship between objective and subjective measures of nasal obstruction.

OBJECTIVES

In a recent study it was shown that the subjective sensation of nasal patency increased as the nasal passages became objectively more obstructed in patients who received a placebo compared to those who received an oral decongestant. This paradoxical response may be explained as a placebo effect, i.e. patients who received a placebo may have expected to feel less obstructed. The aim of the present study was to investigate this interesting paradox by determining objective and subjective measures of nasal obstruction over time in participants not exposed to any treatment.

MATERIAL AND METHODS

A total of 60 healthy participants with common cold were recruited. Objective and subjective measures of nasal obstruction were recorded at baseline and at 1 and 2 h using posterior rhinomanometry and a visual analogue scale.

RESULTS

Objective measures demonstrated an increase in nasal obstruction over time for both nasal passages considered together and for individual nasal passages. Subjective measures demonstrated a sensation of decreased nasal obstruction over time for both nasal passages considered together and for individual nasal passages.

Evidence for correlation of objective and subjective measures of nasal airflow in patients with common cold

OBJECTIVES

To utilize posterior rhinomanometry and conductance, as units of measurement, to further investigate the relationship between subjective and objective measures of nasal airflow.

DESIGN

A prospective, observational study.

SETTING

Common Cold Research Centre.

PARTICIPANTS

Sixty healthy volunteers from the staff and student population of Cardiff University with an upper respiratory tract infection.

MAIN OUTCOMES MEASURES

To determine correlations between visual analogue scores (VAS) and posterior rhinomanometry for total, unilateral, high and low conductance groups.

RESULTS

No correlation was found between total VAS and total conductance (r = 0.17, P = 0.10). A substantially significant correlation was found between unilateral VAS and unilateral conductance (rho = 0.50, P < 0.001). The unilateral VAS and conductance were highly correlated for the low total conductance group (rho = 0.61, P < 0.001).

CONCLUSIONS

Posterior rhinomanometry allows actual measurement of the combined and unilateral conductance of nasal passages. The units of conductance, as opposed to resistance, allow totally obstructed nasal passages to be included in analysis. Visual analogue scores and conductance correlate strongly in unilateral measures for participants with a low total nasal conductance. Posterior rhinomanometry and units of conductance are recommended for future studies investigating the relationship between objective and subjective measures of nasal airflow.

Post-transplant lymphoproliferative disorder presenting as epistaxis

An unusual case of epistaxis resulting from post-transplant lymphoproliferative disorder is described. A 30-year-old woman who had undergone renal transplantation 12 years previously presented with profuse, posterior, unilateral epistaxis. The initial findings, workup and treatment are presented. A post-nasal space (PNS) mass was detected and biopsy showed this to be an Epstein-Barr virus-positive polymorphous B-cell post-transplant lymphoproliferative disorder. Computed tomography findings showed a polypoid lesion protruding from the sphenoethmoidal recess and filling the left PNS. Post-transplant lymphoproliferative disorder is well known to involve tonsil tissue. Commonly, this is the first presentation of the disease in children. However, until now post-transplant lymphoproliferative disorder has not been described in the PNS or nasal cavity presenting as epistaxis. We conclude that all transplant patients presenting with epistaxis should be followed up for an accurate examination of the PNS and nasal cavity after the acute episode.

The extracellular ATP receptor, cP2Y(1), inhibits cartilage formation in micromass cultures of chick limb mesenchyme

We have investigated the function of the G protein-coupled receptor for extracellular ATP, chick P2Y(1) (cP2Y(1)) during development of the chick limb. cP2Y(1) is strongly expressed in undifferentiated limb mesenchyme cells but appears to be lost from cells as they differentiate, raising the possibility that the function of this receptor may be to inhibit cell differentiation. This pattern of expression was particularly striking surrounding areas of cartilage formation. We tested whether cP2Y(1) was able to regulate cartilage formation by using an in-vitro micromass model of chondrogenesis. Because limb cells in micromass culture lose expression of cP2Y(1), we have used a gain-of-function approach to demonstrate that cP2Y(1) expression can inhibit cartilage differentiation. We also demonstrate that early limb mesenchyme cells release ATP into the extracellular medium and have mechanisms to breakdown extracellular ATP. These results suggest that extracellular ATP, signaling through cP2Y(1), can modulate the differentiation of limb mesenchyme cells in vitro, and the expression pattern of cP2Y(1) suggests that this type of signaling could play a similar role in ovo.

A reciprocal relationship between cutaneous nerves and repairing skin wounds in the developing chick embryo

Various studies have suggested that the rate of adult skin healing may be in some way dependent on signals emanating from cutaneous nerves. Further, it appears that adult wounds become hyperinnervated by sensory nerves during the process of healing. In order to investigate this reciprocal relationship further, we have used a simple embryonic model to look at the effect of wounds on nerves, and conversely, the effect of nerves on wounds. We find that wounds made to the dorsum of the chick wing bud, at a stage prior to normal innervation (at E4), or soon after the normal establishment of cutaneous innervation (at E7), subtly alter the pattern of branching by perturbing developmental guidance cues, but do not cause hyperinnervation, whereas wounding at E14 does cause hyperinnervation. By creating chicks with nerveless wings, we show that from E7, wound healing in the absence of nerves is significantly impaired. These observations suggest that, from the earliest stages of skin innervation, the presence of nerves is beneficial to the healing process, but that, in contrast to neonatal and adult tissues, wound healing in the embryo and early foetus does not trigger hyperinnervation.

Activation of an EDS1-mediated R-gene pathway in the snc1 mutant leads to constitutive, NPR1-independent pathogen resistance

The Arabidopsis NPR1 protein is an essential regulatory component of systemic acquired resistance (SAR). Mutations in the NPR1 gene completely block the induction of SAR by signals such as salicylic acid (SA). An Arabidopsis mutant, snc1 (suppressor of npr1-1, constitutive 1), was isolated in a screen for suppressors of npr1-1. In the npr1-1 background, the snc1 mutation resulted in constitutive resistance to Pseudomonas syringae maculicola ES4326 and Peronospora parasitica Noco2. High levels of SA were detected in the mutant and shown to be required for manifestation of the snc1 phenotype. The snc1 mutation was mapped to the RPP5 resistance (R) gene cluster and the eds1 mutation that blocks RPP5-mediated resistance suppressed snc1. These data suggest that a RPP5-related resistance pathway is activated constitutively in snc1. This pathway does not employ NPR1 but requires the signal molecule SA and the function of EDS1. Moreover, in snc1, constitutive resistance is conferred in the absence of cell death, which is often associated with R-gene mediated resistance.

In vivo imaging indicates muscle fiber dedifferentiation is a major contributor to the regenerating tail blastema

During tail regeneration in urodele amphibians such as axolotls, all of the tissue types, including muscle, dermis, spinal cord, and cartilage, are regenerated. It is not known how this diversity of cell types is reformed with such precision. In particular, the number and variety of mature cell types in the remaining stump that contribute to the blastema is unclear. Using Nomarski imaging, we followed the process of regeneration in the larval axolotl tail. Combining this with in vivo fluorescent labeling of single muscle fibers, we show that mature muscle dedifferentiates. Muscle dedifferentiation occurs by the synchronous fragmentation of the multinucleate muscle fiber into mononucleate cells followed by rapid cell proliferation and the extension of cell processes. We further show that direct clipping of the muscle fiber and severe tissue damage around the fiber are both required to initiate dedifferentiation. Our observations also make it possible to estimate for the first time how many of the blastema cells arise specifically from muscle dedifferentiation. Calculations based on our data suggest that up to 29% of nondermal-derived cells in the blastema come from dedifferentiation of mature muscle fibers. Overall, these results show that endogenous multinucleate muscle fibers can dedifferentiate into mononucleate cells and contribute significantly to the blastema.

Constitutive salicylic acid-dependent signaling in cpr1 and cpr6 mutants requires PAD4

Salicylic acid (SA)-dependent signaling controls activation of a set of plant defense mechanisms that are important for resistance to a variety of microbial pathogens. Many Arabidopsis mutants that display altered SA-dependent signaling have been isolated. We used double mutant analysis to determine the relative positions of the pad4, cpr1, cpr5, cpr6, dnd1 and dnd2 mutations in the signal transduction network leading to SA-dependent activation of defense gene expression and disease resistance. The pad4 mutation causes failure of SA accumulation in response to infection by certain pathogens, while the other mutations cause constitutively high levels of SA, defense gene expression and resistance. The cpr1 pad4, cpr5 pad4, cpr6 pad4, dnd1 pad4 and dnd2 pad4 double mutants were constructed and assayed for stature, presence of spontaneous lesions, resistance to Pseudomonas syringae and Peronospora parasitica, SA levels, expression of PAD4, PR-1 and PDF1.2, and accumulation of camalexin. We found that the effects of the cpr1 and cpr6 mutations on SA-dependent gene expression are completely dependent on PAD4 function. In contrast, SA accumulation in the lesion-mimic mutant cpr5 is partially PAD4-independent, while in dnd1 and dnd2 mutants it is completely PAD4-independent. A model describing a possible arrangement of activities in the signal transduction network is presented.

Constitutive disease resistance requires EDS1 in the Arabidopsis mutants cpr1 and cpr6 and is partially EDS1-dependent in cpr5

The systemic acquired resistance (SAR) response in Arabidopsis is characterized by the accumulation of salicylic acid (SA), expression of the pathogenesis-related (PR) genes, and enhanced resistance to virulent bacterial and oomycete pathogens. The cpr (constitutive expressor of PR genes) mutants express all three SAR phenotypes. In addition, cpr5 and cpr6 induce expression of PDF1.2, a defense-related gene associated with activation of the jasmonate/ethylene-mediated resistance pathways. cpr5 also forms spontaneous lesions. In contrast, the eds1 (enhanced disease susceptibility) mutation abolishes race-specific resistance conferred by a major subclass of resistance (R) gene products in response to avirulent pathogens. eds1 plants also exhibit increased susceptibility to virulent pathogens. Epistasis experiments were designed to explore the relationship between the cpr- and EDS1-mediated resistance pathways. We found that a null eds1 mutation suppresses the disease resistance phenotypes of both cpr1 and cpr6. In contrast, eds1 only partially suppresses resistance in cpr5, leading us to conclude that cpr5 expresses both EDS1-dependent and EDS1-independent components of plant disease resistance. Although eds1 does not prevent lesion formation on cpr5 leaves, it alters their appearance and reduces their spread. This phenotypic difference is associated with increased pathogen colonization of cpr5 eds1 plants compared to cpr5. The data allow us to place EDS1 as a necessary downstream component of cpr1- and cpr6-mediated responses, but suggest a more complex relationship between EDS1 and cpr5 in plant defense.

Roles of salicylic acid, jasmonic acid, and ethylene in cpr-induced resistance in arabidopsis

Disease resistance in Arabidopsis is regulated by multiple signal transduction pathways in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) function as key signaling molecules. Epistasis analyses were performed between mutants that disrupt these pathways (npr1, eds5, ein2, and jar1) and mutants that constitutively activate these pathways (cpr1, cpr5, and cpr6), allowing exploration of the relationship between the SA- and JA/ET-mediated resistance responses. Two important findings were made. First, the constitutive disease resistance exhibited by cpr1, cpr5, and cpr6 is completely suppressed by the SA-deficient eds5 mutant but is only partially affected by the SA-insensitive npr1 mutant. Moreover, eds5 suppresses the SA-accumulating phenotype of the cpr mutants, whereas npr1 enhances it. These data indicate the existence of an SA-mediated, NPR1-independent resistance response. Second, the ET-insensitive mutation ein2 and the JA-insensitive mutation jar1 suppress the NPR1-independent resistance response exhibited by cpr5 and cpr6. Furthermore, ein2 potentiates SA accumulation in cpr5 and cpr5 npr1 while dampening SA accumulation in cpr6 and cpr6 npr1. These latter results indicate that cpr5 and cpr6 regulate resistance through distinct pathways and that SA-mediated, NPR1-independent resistance works in combination with components of the JA/ET-mediated response pathways.

Roles of salicylic acid, jasmonic acid, and ethylene in cpr-induced resistance in arabidopsis

Disease resistance in Arabidopsis is regulated by multiple signal transduction pathways in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) function as key signaling molecules. Epistasis analyses were performed between mutants that disrupt these pathways (npr1, eds5, ein2, and jar1) and mutants that constitutively activate these pathways (cpr1, cpr5, and cpr6), allowing exploration of the relationship between the SA- and JA/ET-mediated resistance responses. Two important findings were made. First, the constitutive disease resistance exhibited by cpr1, cpr5, and cpr6 is completely suppressed by the SA-deficient eds5 mutant but is only partially affected by the SA-insensitive npr1 mutant. Moreover, eds5 suppresses the SA-accumulating phenotype of the cpr mutants, whereas npr1 enhances it. These data indicate the existence of an SA-mediated, NPR1-independent resistance response. Second, the ET-insensitive mutation ein2 and the JA-insensitive mutation jar1 suppress the NPR1-independent resistance response exhibited by cpr5 and cpr6. Furthermore, ein2 potentiates SA accumulation in cpr5 and cpr5 npr1 while dampening SA accumulation in cpr6 and cpr6 npr1. These latter results indicate that cpr5 and cpr6 regulate resistance through distinct pathways and that SA-mediated, NPR1-independent resistance works in combination with components of the JA/ET-mediated response pathways.

FGF-2 Up-regulation and proliferation of neural progenitors in the regenerating amphibian spinal cord in vivo

Regeneration of the spinal cord occurs spontaneously in adult urodele amphibians. The key cells in this regenerative process appear to be the ependymal cells that following injury migrate and proliferate to form the ependymal tube from which the spinal cord regenerates. Very little is known about the signal(s) that initiates and maintains the proliferative response of these cells. Fibroblast growth factor 2 (FGF-2) has been shown to play a role in maintaining neural progenitor cell cycling in vitro and may be important for neuronal survival and axonal growth after injury. We have investigated its role in regeneration of the spinal cord in vivo following tail amputation in the adult salamander, Pleurodeles waltl. We show that only the low-molecular-weight form of FGF-2 is found in Pleurodeles and that in the normal cord it is expressed in a subset of neurons, but is hardly detectable in ependymal cells. Tail amputation results in induction of FGF-2 in the ependymal cells of the regenerating structure, and later in regeneration FGF-2 is up-regulated in some newborn neurons. FGF-2 pattern of expression in the ependymal tube parallels that of proliferation. Furthermore, exogenous FGF-2 significantly increases ependymal cell proliferation in vivo. Overall our results strongly support the view that one important role of FGF-2 during spinal cord regeneration in Pleurodeles is to induce proliferation of neural progenitor cells.

Identification and cloning of a negative regulator of systemic acquired resistance, SNI1, through a screen for suppressors of npr1-1

Systemic acquired resistance (SAR) is a plant immune response induced after a local infection by necrotizing pathogens. The Arabidopsis NPR1 gene is a positive regulator of SAR, essential for transducing the SAR signal salicylic acid (SA). Mutations in the NPR1 gene abolish the SA-induced expression of pathogenesis-related (PR) genes and resistance to pathogens. To identify additional regulators of SAR, we screened for suppressors of npr1-1. In the npr1-1 background, the sni1 (suppressor of npr1-1, inducible 1) mutant shows near wild-type levels of PR1 expression and resistance to pathogens after induction. Restoration of SAR in npr1-1 by the recessive sni1 mutation indicates that wild-type SNI1 may function as a negative regulator of SAR. We cloned the SNI1 gene and found that it encodes a leucine-rich nuclear protein.

Fate maps old and new

Fate mapping was once the province of classical experimental embryologists. Now a battery of new and sophisticated methods can be used to trace where cells go and what they do in embryos. Here we use examples from gastrulating fish and amphibian embryos and from the chick limb bud and central nervous system to show how this information has contributed to our understanding of developmental processes. This knowledge will become increasingly important in interpreting the complex patterns of gene expression that are being discovered during development, as well as in understanding the effects of genetic manipulations and in directing experimental interventions.

Requirement for the zebrafish mid-hindbrain boundary in midbrain polarisation, mapping and confinement of the retinotectal projection

The organizer at the midbrain-hindbrain boundary (MHB organizer) has been proposed to induce and polarize the midbrain during development. We investigate the requirement for the MHB organizer in acerebellar mutants, which lack a MHB and cerebellum, but retain a tectum, and are mutant for fgf8, a candidate inducer and polarizer. We examine the retinotectal projection in the mutants to assay polarity in the tectum. In mutant tecta, retinal ganglion cell (RGC) axons form overlapping termination fields, especially in the ventral tectum, and along both the anterior-posterior and dorsal-ventral axis of the tectum, consistent with a MHB requirement in generating midbrain polarity. However, polarity is not completely lost in the mutant tecta, in spite of the absence of the MHB. Moreover, graded expression of the ephrin family ligand Ephrin-A5b is eliminated, whereas Ephrin-A2 and Ephrin-A5a expression is leveled in acerebellar mutant tecta, showing that ephrins are differentially affected by the absence of the MHB. Some RGC axons overshoot beyond the mutant tectum, suggesting that the MHB also serves a barrier function for axonal growth. By transplanting whole eye primordia, we show that mapping defects and overshooting largely, but not exclusively, depend on tectal, but not retinal genotype, and thus demonstrate an independent function for Fgf8 in retinal development. The MHB organizer, possibly via Fgf8 itself, is thus required for midbrain polarisation and for restricting axonal growth, but other cell populations may also influence midbrain polarity.

Problem eating attitudes and behaviors in young children

OBJECTIVE

The factor structure of the Children's Eating Attitudes Test (ChEAT) and the predictors of problem eating were examined in young boys and girls.

METHODS

Two hundred and twenty eight children from Grades 2 and 4 completed questionnaires which examined problem eating attitudes and behaviors, body image, and self-concepts.

RESULTS

Four factors were found for girls and boys. The girls' four factors, Dieting, Food Preoccupation, Social Pressure to Eat, and Restricting and Purging, corresponded closely to previous studies with older girls and women. Four different factors were found for the boys, Global Problems, Dieting versus Purging, Dieting and Food Preoccupation, and Emotional Eating. However, dieting behaviors in both girls and boys were predicted by poorer body image and in boys emotional concerns about eating were predicted by poorer body image and lower self-concepts.

DISCUSSION

There is still relatively little research that has examined problem eating attitudes and behaviors of boys and men. As boys tend to report infrequent dieting, we may need to focus more on the emotional concerns about eating and becoming overweight as a potential indicator of eating problems in boys.

Selective expression of purinoceptor cP2Y1 suggests a role for nucleotide signalling in development of the chick embryo

Responses to extracellular nucleotides (e.g., ATP, ADP, etc.) have been demonstrated in a number of embryonic cell types suggesting they may be important signalling molecules during embryonic development. Here the authors describe for the first time the expression of a G-protein-coupled receptor for extracellular ATP, chick P2Y1 (cP2Y1), during embryonic development of the chick. During the first 10 days of embryonic development, cP2Y1 is expressed in a developmentally regulated manner in the limb buds, mesonephros, brain, somites, and facial primordia, suggesting that this receptor may have a role in the development of each of these systems.

Differential patterning of ventral midline cells by axial mesoderm is regulated by BMP7 and chordin

Ventral midline cells in the neural tube have distinct properties at different rostrocaudal levels, apparently in response to differential signalling by axial mesoderm. Floor plate cells are induced by sonic hedgehog (SHH) secreted from the notochord whereas ventral midline cells of the rostral diencephalon (RDVM cells) appear to be induced by the dual actions of SHH and bone morphogenetic protein 7 (BMP7) from prechordal mesoderm. We have examined the cellular and molecular events that govern the program of differentiation of RDVM cells under the influence of the axial mesoderm. By fate mapping, we show that prospective RDVM cells migrate rostrally within the neural plate, passing over rostral notochord before establishing register with prechordal mesoderm at stage 7. Despite the co-expression of SHH and BMP7 by rostral notochord, prospective RDVM cells appear to be specified initially as caudal ventral midline neurectodermal cells and to acquire RDVM properties only at stage 7. We provide evidence that the signalling properties of axial mesoderm over this period are regulated by the BMP antagonist, chordin. Chordin is expressed throughout the axial mesoderm as it extends, but is downregulated in prechordal mesoderm coincident with the onset of RDVM cell differentiation. Addition of chordin to conjugate explant cultures of prechordal mesoderm and neural tissue prevents the rostralization of ventral midline cells by prechordal mesoderm. Chordin may thus act to refine the patterning of the ventral midline along the rostrocaudal axis.

Progenitor dispersal and the origin of early neuronal phenotypes in the chick embryo spinal cord

Using DiI fluorescent dextrans, we have created fate maps of the neural plate and early neural tube describing the extent of progenitor cell dispersal and the spatial origin of morphologically distinct neuronal cell types along the dorsoventral axis of the developing chick spinal cord. Nonuniform dispersal and mixing of progenitors occur within the early neuroepithelium, with the degree of dispersal being determined by the initial position of the cells along the mediolateral axis of the neural plate. Dispersal is greatest in the midregions of the ventricular epithelium and decreases toward the dorsal and ventral midlines. Phenotypically diverse classes of neurons are born at specific dorsoventral locations in the neural tube. Motor neurons are the most ventral cell type generated followed, at progressively more dorsal positions, by distinct classes of interneurons. Several genes show dorsoventrally restricted patterns of expression within the neural tube and the fate maps were used to investigate the relationship between one of these genes, Pax3, and progenitor cell dispersal and fate. The results indicate that the dorsoventral pattern of Pax3 expression is not maintained by restrictions to cell mixing and are consistent with a role for this transcription factor in specifying the identity of neurons with contralateral descending axons.

Stability and plasticity of neural crest patterning and branchial arch Hox code after extensive cephalic crest rotation

The extent to which the spatial organisation of craniofacial development is due to intrinsic properties of the neural crest is at present unclear. There is some experimental evidence supporting the concept of a prepattern established within crest while contiguous with the neural plate. In experiments in which the neural tube and premigratory crest are relocated within the branchial region, crest cells retain patterns of gene expression appropriate for their position of origin after migration into the branchial arches, resulting in skeletal abnormalities. But in apparent conflict with these findings, when crest is rerouted by late deletion of adjacent crest, infilling crest alters its pattern of gene expression to match its new location, and a normal facial skeleton results. In order to reconcile these findings thus identify processes of relevance to the course of normal development, we have performed a series of neural tube and crest rotations producing a more extensive reorganisation of cephalic crest than has been previously described. Lineage analysis using DiI labelling of crest derived from the rotated hindbrain reveals that crest does not migrate into the branchial arch it would have colonised in normal development, rather it simply populates the nearest available branchial arches. We also find that crest adjacent to the grafted region contributes to a greater number of branchial arches than it would in normal development, resulting in branchial arches containing mixed cell populations not occurring in normal development. We find that after exchange of first and third arch crest by rotation of r1-7, crest alters its expression of hoxa-2 and hoxa-3 to match its new location within the embryo resulting in the reestablishment of the normal branchial arch Hox code. A facial skeleton in which all the normal components are present, with some additional ectopic first arch structures, is formed in this situation. In contrast, when second and third arch crest are exchanged by rotation of r3 to 7, ectopic Hox gene expression is stable, resulting in the persistence of an abnormal branchial arch Hox code and extensive defects in the hyoid skeleton. We suggest that the intrinsic properties of crest have an effect on the spatial organisation of structures derived from the branchial arches, but that exposure to increasingly novel environments within the branchial region or "community effects" within mixed populations of cells can result in alterations to crest Hox code and morphogenetic fate. In both classes of operation we find that there is a tight link between the resulting branchial arch Hox code and a particular skeletal morphology.

Fate map of the developing chick face: analysis of expansion of facial primordia and establishment of the primary palate

Developing facial primordia change shape substantially in stages leading up to primary palate formation. We investigated expansion of cell populations within each of the four facial primordia of chick embryos between HH-stages 20 and 28, by using DiI labelling. Populations of cells centred around the nasal pits in the upper face, the midline of the paired mandibular primordia in the lower face, and at sites of fusion contribute most to overall expansion. Abundant Msx-1 transcripts are found in regions of high expansion, and Fgf-8 transcripts are seen in ectoderm associated with some of these regions. Many cell populations display preferential expansion along one axis. Maxillary and mandibular primordia cell populations expand along the proximodistal axis, whereas at the distal tip of the frontonasal mass, cell populations expand mediolaterally. Thus outgrowth occurs at the tips of mandibular and maxillary primordia, but at the base of the frontonasal mass. At regions where adjacent primordia abut each other, we found bidirectional movement of cells between primordia, unidirectional movement or could detect no movement at all. Regions of highest expansion in each primordium have the highest percentage of S phase labelled cells. Cell death occurs in some regions of low expansion but it seems likely that cell rearrangements and intercalations also contribute to shaping. These rearrangements could be associated with stretching of the primordia by neighbouring tissues. Treatment of chick embryos with retinoic acid causes clefts of the primary palate (Tamarin et al. [1984] J. Embryol. Exp. Morphol. 84:105-123). We found a decrease in expansion of cell populations that normally contribute to primary palate formation but surprisingly little ectopic cell death. Expansion of other cell populations in the treated upper face was more even rather than directed. This further supports the idea that tension exerted by neighbouring tissues plays a major role in global shaping of the upper face.

Differential progenitor dispersal and the spatial origin of early neurons can explain the predominance of single-phenotype clones in the chick hindbrain

Clonal analysis of the chick embryo hindbrain has shown that during the first 48 hr of neurogenesis the large majority of neural progenitor cells generate clones of neurons of only a single major phenotype or of only closely related phenotypes. This is despite considerable spatial intermixing of diverse neuronal phenotypes at these stages of development and suggests that phenotype may be decided early in mitotic precursors and remembered through several subsequent rounds of division and dispersal (Lumsden et al. [1994] Development 120:1581-1589). Here we have used fate-mapping and clonal analysis to study neuroepithelial cell dispersal and mixing in the early hindbrain and discuss this data in relation to the generation of single phenotype neuronal clones. We find that dispersal is not uniform throughout the dorsoventral axis of the neural tube, but is highly dependent on position along that axis. Neuronal identity is related to the spatial origin and, hence, environment of the cell, and the spatial intermixing of diverse neuronal phenotypes at HH stage 20 is largely the result of circumferential neuronal migration as medially born branchial motor neurons migrate laterally while the more laterally born mlf neurons migrate medially. Constraints on the dispersal of clonally related progenitors, in particular those that lie adjacent to the floor plate, may serve to restrict the fate of these cells to the generation of only one major neuronal phenotype, i.e., motor neurons.

Characterization of a haemolysin from Mycobacterium tuberculosis with homology to a virulence factor of Serpulina hyodysenteriae

Scrutiny of sequence data from the Mycobacterium leprae genome sequencing project identified the presence of a gene encoding a 268-amino-acid polypeptide which is highly similar to a pore-forming haemolysin/cytotoxin virulence determinant, TlyA, from the swine pathogen Serpulina hyodysenteriae. Using degenerate oligonucleotide primers based on the TlyA sequences, the Mycobacterium tuberculosis homologue was amplified and this product was used to obtain the clone and sequence a 2.5 kb fragment containing the whole M. tuberculosis tlyA gene. tlyA encodes a 267-amino-acid protein with a predicted molecular mass of 28 kDa. TlyA homologues were identified by PCR in M. leprae, Mycobacterium avium and Mycobacterium bovis BCG, but appeared absent in Mycobacterium smegmatis, Mycobacterium vaccae, Mycobacterium kansasii, Mycobacterium chelonae and Mycobacterium phlei. The M. tuberculosis gene appeared to be the first gene in an operon containing at least two other genes. Introduction of the M. tuberculosis tlyA gene into M. smegmatis using a mycobacterial shuttle expression plasmid converted non-haemolytic cells into those exhibiting significant haemolytic activity. Similarly, inducible haemolytic activity was observed in sonicated bacteria when tlyA was expressed as a His6-tagged fusion protein in Escherichia coli. tlyA mRNA was detected in both M. tuberculosis and M. bovis BCG using RT-PCR, confirming that this gene is expressed in organisms cultured in vitro.

Uncoupling PR gene expression from NPR1 and bacterial resistance: characterization of the dominant Arabidopsis cpr6-1 mutant

In Arabidopsis, NPR1 mediates the salicylic acid (SA)-induced expression of pathogenesis-related (PR) genes and systemic acquired resistance (SAR). Here, we report the identification of another component, CPR 6, that may function with NPR1 in regulating PR gene expression. The dominant CPR 6-1 mutant expresses the SA/NPR1-regulated PR genes (PR-1, BGL 2, and PR-5) and displays enhanced resistance to Pseudomonas syringae pv maculicola ES4326 and Peronospora parasitica Noco2 in the absence of SAR induction. cpr 6-1-induced PR gene expression is not suppressed in the cpr 6-1 npr1-1 double mutant but is suppressed when SA is removed by salicylate hydroxylase. Thus, constitutive PR gene expression in cpr 6-1 requires SA but not NPR1. In addition, resistance to P. s. maculicola ES4326 is suppressed in the cpr 6-1 npr1-1 double mutant, despite expression of PR-1, BGL 2, and PR-5. Resistance to P. s. maculicola ES4326 must therefore be accomplished through unidentified antibacterial gene products that are regulated through NPR1. These results show that CPR 6 is an important regulator of multiple signal transduction pathways involved in plant defense.

Segmentation, crest prespecification and the control of facial form

The early development of the vertebrate head is dependent on the formation of two series of segmented structures, the rhombomeres of the hindbrain and the branchial arch series. The initial formation of these two systems is closely linked, as the principal source of branchial arch mesenchyme is the neural crest, which derives from the lateral edge of the neural plate at the time of rhombomere formation. The subsequent development of the two systems maintains a close level of integration, as specific spatial relationships between skeletal, muscle and neural elements arising from the same axial level are established. Given the level of conservation of these anatomical relationships in vertebrates, it is likely that they are a reflection of a key mechanism in early facial and pharyngeal development. One model, in part based on these findings, proposed that the neural crest acquires an axial-level specific combination of gene expression while part of the neural plate. This prepattern is then maintained throughout the crest's subsequent development. In the model, this combination of gene expression would then specify the form of the facial and pharyngeal structures that the crest would give rise to. In this review we evaluate recent evidence on whether early facial development involves a crest prespecification of this type, and conclude that it is not the case.

Dorso-ventral ectodermal compartments and origin of apical ectodermal ridge in developing chick limb

We wish to understand how limbs are positioned with respect to the dorso-ventral axis of the body in vertebrate embryos, and how different regions of limb bud ectoderm, i.e. dorsal ectoderm, apical ridge and ventral ectoderm, originate. Signals from dorsal and ventral ectoderm control dorso-ventral patterning while the apical ectodermal ridge (AER) controls bud outgrowth and patterning along the proximo-distal axis. We show, using cell-fate tracers, the existence of two distinct ectodermal compartments, dorsal versus ventral, in both presumptive limb and flank of early chick embryos. This organisation of limb ectoderm is the first direct evidence, in vertebrates, of compartments in non-neural ectoderm. Since the apical ridge appears to be confined to this compartment boundary, this positions the limb. The mesoderm, unlike the ectoderm, does not contain two separate dorsal and ventral cell lineages, suggesting that dorsal and ventral ectoderm compartments may be important to ensure appropriate control of mesodermal cell fate. Surprisingly, we also show that cells which form the apical ridge are initially scattered in a wide region of early ectoderm and that both dorsal and ventral ectoderm cells contribute to the apical ridge, intermingling to some extent within it.

Local origin of cells in FGF-4 - induced outgrowth of amputated chick wing bud stumps

Urodele amphibians are the only vertebrates that can regenerate amputated limbs, even as adults. However, we have previously shown that amputated chick wing bud stumps can be induced to ((regenerate)) and to form a complete set of correctly-patterned skeletal elements, following implantation of beads soaked in fibroblast growth factor-4 (FGF-4). We have now performed Dil injection experiments to determine which cells contribute to FGF-4-induced chick wing bud ((regenerates)). We show that the FGF-4-induced outgrowth of the regenerating wing bud stump is comprised of mesenchyme cells that originate from a region within 200 microm of the FGF-4 bead, and that cells proximal to the bead move distally.

The cpr5 mutant of Arabidopsis expresses both NPR1-dependent and NPR1-independent resistance

The cpr5 mutant was identified from a screen for constitutive expression of systemic acquired resistance (SAR). This single recessive mutation also leads to spontaneous expression of chlorotic lesions and reduced trichome development. The cpr5 plants were found to be constitutively resistant to two virulent pathogens, Pseudomonas syringae pv maculicola ES4326 and Peronospora parasitica Noco2; to have endogenous expression of the pathogenesis-related gene 1 (PR-1); and to have an elevated level of salicylic acid (SA). Lines homozygous for cpr5 and either the SA-degrading bacterial gene nahG or the SA-insensitive mutation npr1 do not express PR-1 or exhibit resistance to P. s. maculicola ES4326. Therefore, we conclude that cpr5 acts upstream of SA in inducing SAR. However, the cpr5 npr1 plants retained heightened resistance to P. parasitica Noco2 and elevated expression of the defensin gene PDF1.2, implying that NPR1-independent resistance signaling also occurs. We conclude that the cpr5 mutation leads to constitutive expression of both an NPR1-dependent and an NPR1-independent SAR pathway. Identification of this mutation indicates that these pathways are connected in early signal transduction steps and that they have overlapping functions in providing resistance.

The cpr5 mutant of Arabidopsis expresses both NPR1-dependent and NPR1-independent resistance

The cpr5 mutant was identified from a screen for constitutive expression of systemic acquired resistance (SAR). This single recessive mutation also leads to spontaneous expression of chlorotic lesions and reduced trichome development. The cpr5 plants were found to be constitutively resistant to two virulent pathogens, Pseudomonas syringae pv maculicola ES4326 and Peronospora parasitica Noco2; to have endogenous expression of the pathogenesis-related gene 1 (PR-1); and to have an elevated level of salicylic acid (SA). Lines homozygous for cpr5 and either the SA-degrading bacterial gene nahG or the SA-insensitive mutation npr1 do not express PR-1 or exhibit resistance to P. s. maculicola ES4326. Therefore, we conclude that cpr5 acts upstream of SA in inducing SAR. However, the cpr5 npr1 plants retained heightened resistance to P. parasitica Noco2 and elevated expression of the defensin gene PDF1.2, implying that NPR1-independent resistance signaling also occurs. We conclude that the cpr5 mutation leads to constitutive expression of both an NPR1-dependent and an NPR1-independent SAR pathway. Identification of this mutation indicates that these pathways are connected in early signal transduction steps and that they have overlapping functions in providing resistance.

Cell movements, neuronal organisation and gene expression in hindbrains lacking morphological boundaries

Rhombomeres are segmental units of the hindbrain that are separated from each other by a specialised zone of boundary cells. Retinoic acid application to a recently segmented hindbrain leads to disappearance of posterior rhombomere boundaries. Boundary loss is preceded by changes in segmental expression of Krox-20 and Cek-8 and followed by alterations in Hox gene expression. The characteristic morphology of boundary cells, their expression of follistatin and the periodic accumulation of axons normally associated with boundaries are all lost. In the absence of boundaries, we detect no change in anteroposterior dispersal of precursor cells and, in most cases, no substantial cell mixing between former rhombomeric units. This is consistent with the idea that lineage restriction can be maintained by processes other than a mechanical barrier composed of boundary cells. Much of the early organisation of the motor nuclei appears normal despite the loss of boundaries and altered Hox expression.

Cell fate in the chick limb bud and relationship to gene expression

We have produced detailed fate maps for mesenchyme and apical ridge of a stage 20 chick wing bud. The fate maps of the mesenchyme show that most of the wing arises from the posterior half of the bud. Subapical mesenchyme gives rise to digits. Cell populations beneath the ridge in the mid apical region fan out into the anterior tip of the handplate, while posterior cell populations extend right along the posterior margin. Subapical mesenchyme of the leg bud behaves similarly. The absence of anterior bending of posterior cell populations has implications when considering models of vertebrate limb evolution. The fatemaps of the apical ridge show that there is also a marked anterior expansion and cells that were in anterior apical ridge later become incorporated into non-ridge ectoderm along the margin of the bud. Mesenchyme and apical ridge do not expand in concert--the apical ridge extends more anteriorly. We used the fatemaps to investigate the relationship between cell lineage and elaboration of Hoxd-13 and Fgf-4 domains. Hoxd-13 and Fgf-4 are initially expressed posteriorly until about the mid-point of the early wing bud in mesenchyme and apical ridge respectively. Later in development, the genes come to be expressed throughout most of the handplate and apical ridge respectively. We found that at the proximal edge of the Hoxd-13 domain, cell populations stopped expressing the gene as development proceeded and found no evidence that the changes in extent of the domains were due to initiation of gene expression in anterior cells. Instead the changes in extent of expression fit with the fate maps and can be attributed to expansion and fanning out of cell populations initially expressing the genes.

Hox9 genes and vertebrate limb specification

Development of paired appendages at appropriate levels along the primary body axis is a hallmark of the body plan of jawed vertebrates. Hox genes are good candidates for encoding position in lateral plate mesoderm along the body axis and thus for determining where limbs are formed. Local application of fibroblast growth factors (FGFs) to the anterior prospective flank of a chick embryo induces development of an ectopic wing, and FGF applied to posterior flank induces an ectopic leg. If particular combinations of Hox gene expression determine where wings and legs develop, then formation of additional limbs from flank should involve changes in Hox gene expression that reflect the type of limb induced. Here we show that the same population of flank cells can be induced to form either a wing or a leg, and that induction of these ectopic limbs is accompanied by specific changes in expression of three Hox genes in lateral plate mesoderm. This then reproduces, in the flank, expression patterns found at normal limb levels. Hox gene expression is reprogrammed in lateral plate mesoderm, but is unaffected in paraxial mesoderm. Independent regulation of Hox gene expression in lateral plate mesoderm may have been a key step in the evolution of paired appendages.

The Arabidopsis NPR1 gene that controls systemic acquired resistance encodes a novel protein containing ankyrin repeats

The Arabidopsis NPR1 gene controls the onset of systemic acquired resistance (SAR), a plant immunity, to a broad spectrum of pathogens that is normally established after a primary exposure to avirulent pathogens. Mutants with defects in NPR1 fail to respond to various SAR-inducing treatments, displaying little expression of pathogenesis-related (PR) genes and exhibiting increased susceptibility to infections. NPR1 was cloned using a map-based approach and was found to encode a novel protein containing ankyrin repeats. The lesion in one npr1 mutant allele disrupted the ankyrin consensus sequence, suggesting that these repeats are important for NPR1 function. Furthermore, transformation of the cloned wild-type NPR1 gene into npr1 mutants not only complemented the mutations, restoring the responsiveness to SAR induction with respect to PR-gene expression and resistance to infections, but also rendered the transgenic plants more resistant to infection by P. syringae in the absence of SAR induction.

The Arabidopsis NPR1 gene that controls systemic acquired resistance encodes a novel protein containing ankyrin repeats

The Arabidopsis NPR1 gene controls the onset of systemic acquired resistance (SAR), a plant immunity, to a broad spectrum of pathogens that is normally established after a primary exposure to avirulent pathogens. Mutants with defects in NPR1 fail to respond to various SAR-inducing treatments, displaying little expression of pathogenesis-related (PR) genes and exhibiting increased susceptibility to infections. NPR1 was cloned using a map-based approach and was found to encode a novel protein containing ankyrin repeats. The lesion in one npr1 mutant allele disrupted the ankyrin consensus sequence, suggesting that these repeats are important for NPR1 function. Furthermore, transformation of the cloned wild-type NPR1 gene into npr1 mutants not only complemented the mutations, restoring the responsiveness to SAR induction with respect to PR-gene expression and resistance to infections, but also rendered the transgenic plants more resistant to infection by P. syringae in the absence of SAR induction.

Characteristics of skeletal muscle chloride channel C1C-1 and point mutant R304E expressed in Sf-9 insect cells

Using the baculovirus system, the skeletal muscle chloride channel, CIC-1 (rat), and a point mutant replacing arginine 304 with glutamic acid were expressed at high levels in cultured Sf-9 insect cells. Whole-cell patch-clamping revealed large inwardly rectifying currents with maxima up to 15 nA inward and 2.5 nA outward. Saturation was evident at voltage steps positive to +40 mV whilst steps negative to -60 mV produced inactivating currents made up of a steady state component and two exponentially decaying components with tau 1 = 6.14+/- 0.92 ms, tau 2 = 36.5+/- 3.29 ms (S.D) n = 7 for steps to -120 mV. Currents recorded in the outside-out patch configuration were often unexpectedly large and up to 5% of whole-cell currents obtained in the same cell, suggesting an uneven channel distribution in the plasmalemma of Sf-9 cells. The pharmacology of a number of chloride channel blockers, including anthracene-9-carboxylate (A9C), niflumate, and perrhenate, was investigated and showed for the first time that perrhenate is an effective blocker of C1C-1 and that it has a complex mechanism of action. Further, the potency of A9C was found to be dependent on external chloride concentration. As in studies on muscle cells themselves, blockade was rapidly effective and easily reversible, except when applying the indanyloxyacetate derivative, IAA94/95, which took up to 10 min to act, and, consistent with an intracellular site of action, was difficult to reverse by washing. Mutation of the highly conserved arginine at position 304 to a glutamic acid did not significantly alter the behaviour of the channel.

Ectopic expression of Hoxa-1 in the zebrafish alters the fate of the mandibular arch neural crest and phenocopies a retinoic acid-induced phenotype

Considerable evidence has demonstrated that retinoic acid influences the formation of the primary body axis in vertebrates and that this may occur through the regulation of Hox gene expression. In this study, we show that the phenotype induced by exogenous retinoic acid in the zebrafish can also be generated by the overexpression of Hoxa-1 following injection of synthetic RNA into the fertilised egg. The isolation, sequence and expression pattern of the zebrafish Hoxa-1 gene is described. We show that exogenously applied retinoic acid causes the ectopic accumulation of Hoxa-1 message during gastrulation in the hypoblast in the head region. Overexpression of Hoxa-1 following injection of RNA causes abnormal growth of the anterior hindbrain, duplication of Mauthner neurons in rhombomere (r) 2 and fate changes of r2 mesenchymal and neurogenic neural crest. These results are discussed in terms of the role of Hoxa-1 in controlling anterior hindbrain patterning and the relationship between expression of Hoxa-1 and retinoic acid.

Dystrophin expression in the hair cells of the cochlea

Dystrophin is normally expressed in a number of tissues including muscle, brain and the outer plexiform layer of the retina. In Duchenne and Becker muscular dystrophy abnormal or deficient dystrophin expression leads to muscle degeneration and has been implicated in mental retardation and a form of night blindness. We have examined the expression of dystrophin immunoreactivity in cochlear tissues of normal guinea-pig and mouse, and whether expression is perturbed in the cochlea of the dystrophic MDX mouse. A single band of approximately 427 kDa, corresponding to a full-length isoform of dystrophin was detected in guinea-pig and normal mouse but was absent from the MDX mouse. Cochleae from guinea-pig, normal and MDX mouse also showed a second dystrophin isoform of 116 kDa molecular weight with the C-terminal specific antibody. Immunostained guinea pig cochlear half turns were examined by laser scanning confocal microscopy. Dystrophin was localized in both inner and outer hair cells with staining patterns which were qualitatively similar with both antibodies. In the outer hair cells labelling of the lateral wall was especially distinctive. The synaptic region of both hair cell types was also strongly labelled.

Exogenous retinoic acid causes specific alterations in the development of the midbrain and hindbrain of the zebrafish embryo including positional respecification of the Mauthner neuron

Exogenously applied retinoic acid given at the early stages of gastrulation causes abnormal development of the caudal midbrain and anterior hindbrain in vertebrate embryos. We describe the limits of the brain regions that are affected using neuroanatomical criteria in the zebrafish embryo. Analysis of the reticulospinal complex shows that the Mauthner cell, which normally differentiates in rhombomere 4, is duplicated either in this rhombomere or in rhombomere 2. Using probes for zebrafish krx20 and pax2, it is demonstrated that retinoic acid affects the expression domains of these regulatory genes in a manner that is consistent with the neuroanatomical data. Expression of the goosecoid gene, which expressed in the prospective anterior mesoderm from the onset of gastrulation, is unaffected by the doses of retinoic acid used in this study, reflecting the normal development of the anterior end of the embryo.

Early phenotypic choices by neuronal precursors, revealed by clonal analysis of the chick embryo hindbrain

The mechanisms that generate diverse neuronal phenotypes within the central nervous system are thought to involve local cues or cell-cell interactions acting late in neurogenesis, perhaps as late as the last precursor cell division. We describe here a clonal analysis of neuronal development in the chick hindbrain, using an intracellular tracer to mark single precursor cells, that suggests the operation of an alternative strategy. The majority of clones, ranging from 1 to 46 cells, contained neurons of only one of several possible phenotypes. These single-phenotype clones were not positionally restricted within a rhombomere but were interspersed with other clones containing distinct phenotypes. The assignment of neuronal phenotype in this brain region may, therefore, be made in early precursors and remembered through several rounds of mitotic expansion and dispersal.