bluuebunny/crossref_metadata_2025 huggingface dataset:
Active hair-bundle motility harnesses noise to operate near an optimum of mechanosensitivity
Authors: Nadrowski Björn , Martin Pascal , Jülicher Frank
Published: August 2004

The ear relies on nonlinear amplification to enhance its sensitivity and frequency selectivity to oscillatory mechanical stimuli. It has been suggested that this active process results from the operation of dynamical systems that operate in the vicinity of an oscillatory instability, a Hopf bifurcation. In the bullfrog's sacculus, a hair cell can display spontaneous oscillations of its mechanosensory hair bundle. The behavior of an oscillatory hair bundle resembles that of a critical oscillator. We present here a theoretical description of the effects of intrinsic noise on active hair-bundle motility. An oscillatory instability can result from the interplay between a region of negative stiffness in the bundle's force-displacement relation and the Ca
2+
-regulated activity of molecular motors. We calculate a state diagram that describes the possible dynamical states of the hair bundle in the absence of fluctuations. Taking into account thermal fluctuations, the stochastic nature of transduction channels' gating, and of the forces generated by molecular motors, we discuss conditions that yield a response function and spontaneous noisy movements of the hair bundle in quantitative agreement with previously published experiments. We find that the magnitude of the fluctuations resulting from the active processes that mediate mechanical amplification remains just below that of thermal fluctuations. Fluctuations destroy the phase coherence of spontaneous oscillations and restrict the bundle's sensitivity as well as frequency selectivity to small oscillatory stimuli. We show, however, that a hair bundle studied experimentally operates near an optimum of mechanosensitivity in our state diagram.
Thermophilic ATP synthase has a decamer
c
-ring: Indication of noninteger 10:3 H
+
/ATP ratio and permissive elastic coupling
Authors: Mitome Noriyo , Suzuki Toshiharu , Hayashi Shigehiko , Yoshida Masasuke
Published: August 2004

In a rotary motor F
o
F
1
-ATP synthase that couples H
+
transport with ATP synthesis/hydrolysis, it is thought that an F
o
c
subunit oligomer ring (
c
-ring) in the membrane rotates as protons pass through F
o
and a 120° rotation produces one ATP at F
1
. Despite several structural studies, the copy number of F
o
c
subunits in the
c
-ring has not been determined for any functional F
o
F
1
. Here, we have generated and isolated thermophilic
Bacillus
F
o
F
1
, each containing genetically fused 2-mer–14-mer
c
(
c
2
–
c
14
). Among them, F
o
F
1
containing
c
2
,
c
5
, or
c
10
showed ATP-synthesis and other activities. When F
1
was removed, F
o
containing
c
10
worked as an H
+
channel but F
o
s containing
c
9
,
c
11
or
c
12
did not. Thus, the
c
-ring of functional F
o
F
1
of this organism is a decamer. The inevitable consequence of this finding is noninteger ratios of rotation step sizes of F
1
/F
o
(120°/36°) and of H
+
/ATP (10:3). This step-mismatch necessitates elastic twisting of the rotor shaft (and/or the side stalk) during rotation and permissive coupling between unit rotations by H
+
transport at F
o
and elementary events in catalysis at F
1
.
DNA targeting of rhinal cortex D2 receptor protein reversibly blocks learning of cues that predict reward
Authors: Liu Zheng , Richmond Barry J. , Murray Elisabeth A. , Saunders Richard C. , Steenrod Sara , Stubblefield Barbara K. , Montague Deidra M. , Ginns Edward I.
Published: August 2004

When schedules of several operant trials must be successfully completed to obtain a reward, monkeys quickly learn to adjust their behavioral performance by using visual cues that signal how many trials have been completed and how many remain in the current schedule. Bilateral rhinal (perirhinal and entorhinal) cortex ablations irreversibly prevent this learning. Here, we apply a recombinant DNA technique to investigate the role of dopamine D2 receptor in rhinal cortex for this type of learning. Rhinal cortex was injected with a DNA construct that significantly decreased D2 receptor ligand binding and temporarily produced the same profound learning deficit seen after ablation. However, unlike after ablation, the D2 receptor-targeted, DNA-treated monkeys recovered cue-related learning after 11–19 weeks. Injecting a DNA construct that decreased
N
-methyl-
d
-aspartate but not D2 receptor ligand binding did not interfere with learning associations between the cues and the schedules. A second D2 receptor-targeted DNA treatment administered after either recovery from a first D2 receptor-targeted DNA treatment (one monkey), after
N
-methyl-
d
-aspartate receptor-targeted DNA treatment (two monkeys), or after a vector control treatment (one monkey) also induced a learning deficit of similar duration. These results suggest that the D2 receptor in primate rhinal cortex is essential for learning to relate the visual cues to the schedules. The specificity of the receptor manipulation reported here suggests that this approach could be generalized in this or other brain pathways to relate molecular mechanisms to cognitive functions.
Sexual dichotomy of an interaction between early adversity and the serotonin transporter gene promoter variant in rhesus macaques
Authors: Barr Christina S. , Newman Timothy K. , Schwandt Melanie , Shannon Courtney , Dvoskin Rachel L. , Lindell Stephen G. , Taubman Julie , Thompson Bill , Champoux Maribeth , Lesch Klaus Peter , Goldman David , Suomi Stephen J. , Higley J. Dee
Published: August 2004

A polymorphism in the human serotonin transporter gene promoter (
5-HTT
LPR) is associated with anxiety and increased risk for developing depression in the face of adversity. Here, we report that among infant rhesus macaques, an orthologous polymorphism (rh
5-HTT
LPR) interacts with adversity in the form of peer rearing to influence adrenocorticotropic hormone (ACTH) response to stress and, further, that this interaction is sexually dichotomous. ACTH responses to separation are higher in
l
/
s
than in
l
/
l
males. In females, however, it is only among those with a history of adversity that the
s
allele is associated with increased ACTH responses to stress. Of interest, peer-reared animals, in particular females carrying the
s
allele, also exhibit lower cortisol responses to stress, a pattern that has been recognized in association with certain stress-related neuropsychiatric disorders. By extension, our findings suggest the intriguing possibility that human females carrying the
5-HTT
LPR
s
allele could be more vulnerable to the effects of early adversity. This interactive effect may underlie the increased incidence of certain stress-related disorders in women.
Quantifiable cytotoxic T lymphocyte responses and HLA-related risk of progression to AIDS
Authors: Scherer Almut , Frater John , Oxenius Annette , Agudelo Juliet , Price David A. , Günthard Huldrych F. , Barnardo Martin , Perrin Luc , Hirschel Bernard , Phillips Rodney E. , McLean Angela R. ,   The Swiss HIV Cohort Study∥∥
Published: August 2004

There are significant associations between possession of certain HLA class I alleles and rate of progression to AIDS. Immunological data provide an explanatory mechanism for this relationship. Patients with HLA types associated with rapid disease progression recognize a significantly smaller fraction of their known repertoire of viral epitopes than do patients with HLA types associated with slow progression. Population frequency of HLA types (or supertypes) and their capacity to elicit cytotoxic T lymphocyte responses are also negatively correlated. These data provide an immunological mechanism to explain HLA-related risk of progression to AIDS and emphasize the central role of viral evolution in the pathogenesis of HIV.
Neuregulin induces the expression of transcription factors and myosin heavy chains typical of muscle spindles in cultured human muscle
Authors: Jacobson Christian , Duggan David , Fischbach Gerald
Published: August 2004

Neuregulin (NRG) (also known as ARIA, GGF, and other names) is a heparin sulfate proteoglycan secreted into the neuromuscular junction by innervating motor and sensory neurons. An integral part of synapse formation, we have analyzed NRG-induced changes in gene expression over 48 h in primary human myotubes. We show that in addition to increasing the expression of acetylcholine receptors on the myotube surface, NRG treatment results in a transient increase of several members of the early growth response (Egr) family of transcription factors. Three Egrs, Egr1, -2, and -3, are induced within the first hour of NRG treatment, with Egr1 and -3 RNA levels showing the most significant increases of ≈9- and 16-fold, respectively. Also noted was a corresponding increase in protein levels for both of these transcription factors. Previous literature indicates that Egr3 expression is required for the formation of muscle spindle fibers, sensory organs that are distinct from skeletal muscle contractile fibers. At the molecular level, muscle spindle fibers express a unique subset of myosin heavy chains. Two isoforms of the myosin heavy chain, the slow development and neonatal, were found to be increased in our myotube cultures after 48 h of treatment with NRG. Taken together, these results indicate that not only can NRG induce the expression of a transcription factor key to spindle fiber development (Egr3), but that a portion of this developmental process can be replicated
in vitro
.
Hypoxia-regulated therapeutic gene as a preemptive treatment strategy against ischemia/reperfusion tissue injury
Authors: Pachori Alok S. , Melo Luis G. , Hart Melanie L. , Noiseux Nicholas , Zhang Lunan , Morello Fulvio , Solomon Scott D. , Stahl Gregory L. , Pratt Richard E. , Dzau Victor J.
Published: August 2004

Ischemia and reperfusion represent major mechanisms of tissue injury and organ failure. The timing of administration and the duration of action limit current treatment approaches using pharmacological agents. In this study, we have successfully developed a preemptive strategy for tissue protection using an adenoassociated vector system containing erythropoietin hypoxia response elements for ischemia-regulated expression of the therapeutic gene human heme-oxygenase-1 (hHO-1). We demonstrate that a single administration of this vector several weeks in advance of ischemia/reperfusion injury to multiple tissues such as heart, liver, and skeletal muscle yields rapid and timely induction of hHO-1 during ischemia that resulted in dramatic reduction in tissue damage. In addition, overexpression of therapeutic transgene prevented long-term pathological tissue remodeling and normalized tissue function. Application of this regulatable system using an endogenous physiological stimulus for expression of a therapeutic gene may be a feasible strategy for protecting tissues at risk of ischemia/reperfusion injury.
A vascular cell-restricted RhoGAP, p73RhoGAP, is a key regulator of angiogenesis
Authors: Su Zhi-Jian , Hahn Christopher N. , Goodall Gregory J. , Reck Niamh M. , Leske Annabell F. , Davy Ann , Kremmidiotis Gabriel , Vadas Mathew A. , Gamble Jennifer R.
Published: August 2004

Angiogenesis is a major therapeutic target. Ideal drug targets are genes expressed only in endothelial cells (ECs) or only during the angiogenic process. Here, we describe a gene, p73RhoGAP (p73), that has both of these properties. By using a PCR-based subtraction–hybridization approach to clone cDNAs from ECs undergoing capillary-tube formation, we identified a RhoGAP member, p73. p73 displays GTPase activity to Rho but not to Rac or Cdc42. Knockdown of p73 protein, achieved by adenovirus delivery of p73 antisense and by small interfering RNA into ECs, demonstrated the importance of this protein in EC function. Under such conditions, EC migration, proliferation, and capillary-tube formation were inhibited. Furthermore, angiogenesis
in vivo
was also inhibited by antisense p73. A mutant R82A alteration achieved a similar phenotype
in vitro
to the antisense, demonstrating the importance of the GTPase-activating protein activity to p73 function. Expression profiling of p73 shows that it is vascular cell-selective, being highly expressed in ECs and smooth-muscle cells but not in other cell types. Finally, we show that the mRNA of p73 is up-regulated in an angiogenic milieu with little or no regulation seen under nonangiogenic conditions. p73, a vascular cell-specific GTPase-activating protein, is an important modulator of angiogenesis and displays many of features that make it worthy of being a drug target.
Gender-selective patterns of aggressive behavior in
Drosophila melanogaster
Authors: Nilsen Steven P. , Chan Yick-Bun , Huber Robert , Kravitz Edward A.
Published: August 2004

Complex behaviors, such as aggression, are comprised of distinct stereospecific behavioral patterns (modules). How such patterns get wired into nervous systems remains unknown. Recently, we reported on a quantitative analysis of fighting behavior in male flies of the common Canton-S strain of
Drosophila melanogaster
. Here, we report a similar analysis of fighting behavior in females of the same species. Fights were carried out between pairs of virgin and pairs of mated females in competition for a yeast resource. Each fight was videotaped and analyzed by using transition matrices and Markov chain analyses. We observe only small difference in fighting intensity between virgin and mated females. In contrast to what is seen in male fights, however, no clear hierarchical relationship is formed in the female fights. A further comparison of the behavioral patterns making up male and female fights reveals that some modules are shared by both sexes, whereas others are highly selective. Within the shared components, transitions between the modules also show gender-selective differences. By using the powerful genetic methods available for examining behavior in fruit flies, it should be possible to use the gender-selective differences in fighting behavior to address the question of how these behavioral patterns get established in the brains of fruit flies.
Large-scale characterization of HeLa cell nuclear phosphoproteins
Authors: Beausoleil Sean A. , Jedrychowski Mark , Schwartz Daniel , Elias Joshua E. , Villén Judit , Li Jiaxu , Cohn Martin A. , Cantley Lewis C. , Gygi Steven P.
Published: August 2004

Determining the site of a regulatory phosphorylation event is often essential for elucidating specific kinase–substrate relationships, providing a handle for understanding essential signaling pathways and ultimately allowing insights into numerous disease pathologies. Despite intense research efforts to elucidate mechanisms of protein phosphorylation regulation, efficient, large-scale identification and characterization of phosphorylation sites remains an unsolved problem. In this report we describe an application of existing technology for the isolation and identification of phosphorylation sites. By using a strategy based on strong cation exchange chromatography, phosphopeptides were enriched from the nuclear fraction of HeLa cell lysate. From 967 proteins, 2,002 phosphorylation sites were determined by tandem MS. This unprecedented large collection of sites permitted a detailed accounting of known and unknown kinase motifs and substrates.
Subdomain organization of theAcanthamoebamyosin IC tail from cryo-electron microscopy
Authors: Ishikawa Takashi , Cheng Naiqian , Liu Xiong , Korn Edward D. , Steven Alasdair C.
Published: August 2004

Acanthamoebamyosin IC (AMIC) is a single-headed myosin comprised of one heavy chain (129 kDa) and one light chain (17 kDa). The heavy chain has head, neck (light chain-binding), and tail domains. The tail consists of four subdomains: a basic region (BR) (23 kDa) and two Gly/Pro/Ala-rich (GPA) regions, GPA1 (6 kDa) and GPA2 (15 kDa), flanking an Src homology 3 region (6 kDa). Although the AMIC head is similar in sequence, structure, and function (ATPase motor) to other myosin heads, the organization of the tail has been less clear as has its function beyond an assumed role in binding interaction partners, e.g., the BR has a membrane affinity and the GPA components bind F-actin in an ATP-independent manner. To investigate the spatial arrangement of subdomains in the tail, we have used cryo-electron microscopy and image reconstruction to compare actin filaments decorated with WT AMIC and tail-truncated mutants of various lengths. The BR forms an oval-shaped feature, ≈40 Å long, that diverges obliquely from the head, extending azimuthally around the actin filament and toward its barbed end. GPA2 and GPA1 are located together on the inner (actin-proximal) side of the tail, close enough to act in concert in binding the same or another actin filament. The outer face of the BR is strategically exposed for membrane or vesicle binding.
The membrane actions of estrogens can potentiate their lordosis behavior-facilitating genomic actions
Authors: Kow Lee-Ming , Pfaff Donald W.
Published: August 2004

The membrane actions of estrogens can facilitate their genomic actions. To determine whether this facilitation bears on CNS mechanisms for estrogen-dependent behaviors, ovariectomized rats were subjected to a two-pulse treatment of estrogen directly in the hypothalamic ventromedial nucleus. Two days later, each rat was given progesterone and then tested for lordosis behavior, the induction of which requires the genomic actions of estrogen. When estrogen was given in both pulses (15 min to 2 h duration, and 5 h apart) lordosis was induced. Based on results from studies on neuroblastoma cells, we hypothesized that the membrane actions of estrogen in the first pulse would potentiate the genomic actions of estrogen in the second. This hypothesis was confirmed with the use of a membrane-impermeable estrogen. However, surprisingly, the order of the pulses could be reversed and still achieve lordosis behavior induction. Finally, activators of protein kinase A or PKC were effective substitutes for the membrane-limited pulse of estrogen. Thus, estrogen-induced membrane actions in the hypothalamus can potentiate its lordosis-inducing genomic actions on behavior and may be mediated by signaling pathways involving the activation of protein kinase A and PKC.
Translation arrest of SecM is essential for the basal and regulated expression of SecA
Authors: Murakami Akiko , Nakatogawa Hitoshi , Ito Koreaki
Published: August 2004

The SecM protein of
Escherichia coli
contains an arrest sequence (F
150
XXXXWIXXXXGIRAGP
166
), which interacts with the ribosomal exit tunnel to halt translation elongation beyond Pro-166. This inhibition is reversed by active export of the nascent SecM chain. Here, we studied the physiological roles of SecM. Arrest-alleviating mutations in the arrest sequence reduced the expression of
secA
, a downstream gene on the same mRNA. Among such mutations, the arrest-abolishing P166A substitution mutation on the chromosomal
secM
gene proved lethal unless the mutant cells are complemented with excess SecA. Whereas secretion defect due either to azide addition, a
secY
mutation, or low temperature leads to up-regulated SecA biosynthesis, this regulation was lost by a
secM
mutation, which synergistically retarded growth of cells with lowered secretion activity. Finally, an arrest-alleviating rRNA mutation affecting the constricted part of the exit tunnel lowered the basal level of SecA as well as its secretion defect-induced up-regulation. Thus, the arrest sequence of SecM has at least two roles in SecA translation. First, the transient elongation arrest in normal cells is required for the synthesis of SecA at levels sufficient to support cell growth. Second, the prolonged SecM elongation arrest under conditions of unfavorable protein secretion is required for the enhanced expression of SecA to cope with such conditions.
Listeria monocytogenesregulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence
Authors: Gründling Angelika , Burrack Laura S. , Bouwer H. G. Archie , Higgins Darren E.
Published: August 2004

Previous studies have shown thatListeria monocytogenesflagellar motility genes, includingflaA, encoding flagellin, are transcriptionally down-regulated at 37°C. For someL. monocytogenesstrains, temperature-dependent motility gene expression is less stringent. By usingflaA-lacZtranscriptional fusions, we identified regions upstream of the –35/–10 promoter elements that are necessary for temperature-dependent expression offlaAinL. monocytogenesstrain EGDe. Whereas the sequence of theflaApromoter region was identical inL. monocytogenesstrain 10403S, transcriptional activity was only partially down-regulated at 37°C in 10403S. This finding suggested that a transacting regulatory protein with differential expression or activity in EGDe might be involved in temperature-dependent transcription offlaA. Indeed, a protein factor capable of specifically binding to theflaApromoter region was identified in cytoplasmic extracts of EGDe by using affinity purification and MS. Deletion of the factor-encoding gene (lmo0674) resulted in loss of temperature-dependentflaAexpression and an increase inflaApromoter activity. Expression of other motility genes was also deregulated in thelmo0674deletion. We have designatedlmo0674asmogR, indicating its role as a motility gene repressor. In tissue culture models, MogR repression offlaAduring intracellular infection was independent of temperature and a deletion ofmogRreduced the capacity for cell-to-cell spread. Duringin vivoinfection, a deletion ofmogRresulted in a 250-fold decrease in virulence. These studies indicate that regulation of flagellar motility gene expression and/or other genes controlled by MogR is required for full virulence ofL. monocytogenes.
Evolution of p53 in hypoxia-stressedSpalaxmimics human tumor mutation
Authors: Ashur-Fabian Osnat , Avivi Aaron , Trakhtenbrot Luba , Adamsky Konstantin , Cohen Meytal , Kajakaro Gadi , Joel Alma , Amariglio Ninette , Nevo Eviatar , Rechavi Gideon
Published: August 2004

The tumor suppressor genep53controls cellular response to a variety of stress conditions, including DNA damage and hypoxia, leading to growth arrest and/or apoptosis. Inactivation ofp53, found in 40–50% of human cancers, confers selective advantage under hypoxic microenvironment during tumor progression. The mole rat,Spalax, spends its entire life cycle underground at decidedly lower oxygen tensions than any other mammal studied. Because a wide range of respiratory adaptations to hypoxic stress evolved inSpalax, we speculated that it might also have developed hypoxia adaptation mechanisms analogous to the genetic/epigenetic alterations acquired during tumor progression. ComparingSpalaxwith human and mouse p53 revealed an arginine (R) to lysine (K) substitution inSpalax(Arg-174 in human) in the DNA-binding domain, identical to known tumor associated mutations. Multiple p53 sequence alignments with 41 additional species confirmed that Arg-174 is highly conserved. Reporter assays uncovered thatSpalaxp53 protein is unable to induce apoptosis-regulating target genes, resulting in no expression ofapaf1and partial expression ofpuma, pten, andnoxa. However, cell cycle arrest and p53 stabilization/homeostasis genes were overactivated bySpalaxp53. Lys-174 was found critical forapaf1expression inactivation. A DNA-free p53 structure model predicts that Arg-174 is important for dimerization, whereasSpalaxLys-174 prevents such interactions. Similar neighboring mutations found in human tumors favor growth arrest rather than apoptosis. We hypothesize that, in an analogy with human tumor progression,Spalaxunderwent remarkable adaptive p53 evolution during 40 million years of underground hypoxic life.
Life satisfaction among European American, African American, Chinese American, Mexican American, and Dominican American adolescents
Authors: Bradley Robert H. , Corwyn Robert F.
Published: August 2004

This study examined contextual and personality factors and their relation to perceived life satisfaction among adolescents in five sociocultural groups. Variations in the contribution of specific predictors were noted for the five groups, but no one factor accounted for a large amount of variance in any group. Among the most consistent predictors were marital status, self-efficacy beliefs, and adolescent health status. Somewhat surprisingly, neither the amount of family conflict, adolescent academic achievement, nor observed socioemotional support from parents was strongly correlated with life satisfaction. The effect of study variables on adolescent quality of life was dependent upon other variables in the analysis. For example, considerate behaviour on the part of the adolescent was suppressed by task-orientation.
Flanker effects on motor output and the late-level response activation hypothesis
Authors: Mattler Uwe
Published: August 2004

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli, the flankers produce a flanker compatibility effect on behavioural measures. Current accounts of the flanker compatibility effect assume that both target and flanker stimuli affect response activation. This idea is supported by electrophysiological studies, which show that irrelevant flanker stimuli can affect the motor system. The present experiments examined the characteristics of flanker effects on the motor system by analysing the details of the motor output with response force measures. A total of 60 participants responded in the flanker task to arrows (Experiment 1) or letters (Experiment 2). Reaction time as well as response force increased on incompatible trials. Analyses of the distribution of incorrect activation revealed that both response times and correct motor output increased with the amount of incorrect activity. However, the flanker compatibility effect was only marginally modulated by incorrect activity. Results suggest that the largest part of the flanker compatibility effect cannot be attributed to response activation and competition at late levels of the response system.
Country of origin, social support and the risk of small for gestational age birth
Authors: Dejin-Karlsson Elisabeth , Östergren Per-Olof
Published: August 2004

Aims: This study investigates the risk of small for gestational age (SGA) in relation to country of origin of the mother. The role of psychosocial resources, socioeconomic and lifestyle factors was examined in different causal models. Methods: Among all pregnant nulliparous women in the city of Malmö, Sweden, who gave birth in 1991 - 92, 872 (87.7%) women completed a questionnaire during their first antenatal visit. The study was carried out among women whose pregnancies resulted in a singleton live birth (n=826); 22% (n=182) of these women were foreign-born. Results: Fifty-five (6.7%) of the infants were classified as SGA, 37 (5.7%) of mothers of Swedish origin and 18 (9.7%) of foreign origin. SGA deliveries were much more prevalent among Middle East- and North Africa-born women (22%) and sub-Saharan-born women (15%). In all, women of foreign origin had increased odds for delivering SGA babies (OR=1.8, 95% CI=1.0,3.2). In a multivariate analysis psychosocial and socioeconomic factors explained 30% and 40%, respectively, of the increased SGA risk. Psychosocial factors seemed to be more prominent risk factors for SGA among mothers of foreign origin. A possible synergistic relation was demonstrated between foreign origin of the mother and low social anchorage. Conclusions: This study showed that psychosocial factors, most probably linked to a disadvantaged social situation, could be the theoretically most important focus for preventing SGA in immigrant women. This could also further support a hypothesis of a link between psychosocial stress and SGA in general. However, this should not exclude the need for intervention in the antenatal care system in terms of specially tailored support and education.
Parasuicide in a low-income country: results from three-year hospital surveillance in Nicaragua
Authors: Caldera Trinidad , Herrera Andrés , Renberg Ellinor Salander , Kullgren Gunnar
Published: August 2004

Aims: A study was undertaken to assess the incidence of parasuicide in Nicaragua, to identify groups at risk, and to describe the characteristics of parasuicides, such as methods used and seasonal and diurnal patterns. Method: All hospital-admitted parasuicide cases in the area of León, Nicaragua, were assessed over a three-year period using standardized instruments. Results: Two hundred and thirty-three parasuicide cases were identified in the catchment area giving a parasuicide rate of 66.3/100,000 inhabitants per year based on the population 10 years and older. Corresponding figure for 15 years and older was 71.3. A majority were females (68.8%), who were significantly younger than the males (mean 20.8 years vs. mean 24.6 years). The highest rates were found in the age group 15 - 19 years with a female rate three times higher than the male rate (302.9 vs. 98.9). Pesticides, a highly lethal substance, were used as method in 19.1% of the attempts. Consistent seasonal variation with peaks in May - June and September - October were found over the years. Among parasuicide cases, 46.5% had been in contact with the healthcare system within 6 months before attempting suicide. Conclusions: Parasuicides represent a significant health problem among young people in Nicaragua. Preventive efforts should be directed especially towards the life situation for young girls, limitation of availability of suicide means, increased awareness in schools concerning suicidal problems, as well as improved management of patients with mental health problems within primary healthcare.
DaPKC-dependent phosphorylation of Crumbs is required for epithelial cell polarity in Drosophila
Authors: Sotillos Sol , Díaz-Meco María Teresa , Caminero Eva , Moscat Jorge , Campuzano Sonsoles
Published: August 2004

Both in Drosophila and vertebrate epithelial cells, the establishment of apicobasal polarity requires the apically localized, membrane-associated Par-3–Par-6–aPKC protein complex. In Drosophila, this complex colocalizes with the Crumbs–Stardust (Sdt)–Pals1-associated TJ protein (Patj) complex. Genetic and molecular analyses suggest a functional relationship between them. We show, by overexpression of a kinase-dead Drosophila atypical PKC (DaPKC), the requirement for the kinase activity of DaPKC to maintain the position of apical determinants and to restrict the localization of basolateral ones. We demonstrate a novel physical interaction between the apical complexes, via direct binding of DaPKC to both Crb and Patj, and identify Crumbs as a phosphorylation target of DaPKC. This phosphorylation of Crumbs is functionally significant. Thus, a nonphosphorylatable Crumbs protein behaves in vivo as a dominant negative. Moreover, the phenotypic effect of overexpressing wild-type Crumbs is suppressed by reducing DaPKC activity. These results provide a mechanistic framework for the functional interaction between the Par-3–Par-6–aPKC and Crumbs–Sdt–Patj complexes based in the posttranslational modification of Crb by DaPKC.
Endocytotic elimination and domain-selective tethering constitute a potential mechanism of protein segregation at the axonal initial segment
Authors: Fache Marie-Pierre , Moussif Anissa , Fernandes Fanny , Giraud Pierre , Garrido Juan José , Dargent Bénédicte
Published: August 2004

The axonal initial segment is a unique subdomain of the neuron that maintains cellular polarization and contributes to electrogenesis. To obtain new insights into the mechanisms that determine protein segregation in this subdomain, we analyzed the trafficking of a reporter protein containing the cytoplasmic II–III linker sequence involved in sodium channel targeting and clustering (Garrido, J.J., P. Giraud, E. Carlier, F. Fernandes, A. Moussif, M.P. Fache, D. Debanne, and B. Dargent. 2003. Science. 300:2091–2094). Here, we show that this reporter protein is preferentially inserted in the somatodendritic domain and is trapped at the axonal initial segment by tethering to the cytoskeleton, before its insertion in the axonal tips. The nontethered population in dendrites, soma, and the distal part of axons is subsequently eliminated by endocytosis. We provide evidence for the involvement of two independent determinants in the II–III linker of sodium channels. These findings indicate that endocytotic elimination and domain-selective tethering constitute a potential mechanism of protein segregation at the axonal initial segment of hippocampal neurons.
Esophageal muscle physiology and morphogenesis require assembly of a collagen XIX–rich basement membrane zone
Authors: Sumiyoshi Hideaki , Mor Niv , Lee Sui Y. , Doty Stephen , Henderson Scott , Tanaka Shizuko , Yoshioka Hidekatsu , Rattan Satish , Ramirez Francesco
Published: August 2004

Collagen XIX is an extremely rare extracellular matrix component that localizes to basement membrane zones and is transiently expressed by differentiating muscle cells. Characterization of mice harboring null and structural mutations of the collagen XIX (Col19a1) gene has revealed the critical contribution of this matrix protein to muscle physiology and differentiation. The phenotype includes smooth muscle motor dysfunction and hypertensive sphincter resulting from impaired swallowing-induced, nitric oxide–dependent relaxation of the sphincteric muscle. Muscle dysfunction was correlated with a disorganized matrix and a normal complement of enteric neurons and interstitial cells of Cajal. Mice without collagen XIX exhibit an additional defect, namely impaired smooth-to-skeletal muscle cell conversion in the abdominal segment of the esophagus. This developmental abnormality was accounted for by failed activation of myogenic regulatory factors that normally drive esophageal muscle transdifferentiation. Therefore, these findings identify collagen XIX as the first structural determinant of sphincteric muscle function, and as the first extrinsic factor of skeletal myogenesis in the murine esophagus.
The KinI kinesin Kif2a is required for bipolar spindle assembly through a functional relationship with MCAK
Authors: Ganem Neil J. , Compton Duane A.
Published: August 2004

Although the microtubule-depolymerizing KinI motor Kif2a is abundantly expressed in neuronal cells, we now show it localizes to centrosomes and spindle poles during mitosis in cultured cells. RNAi-induced knockdown of Kif2a expression inhibited cell cycle progression because cells assembled monopolar spindles. Bipolar spindle assembly was restored in cells lacking Kif2a by treatments that altered microtubule assembly (nocodazole), eliminated kinetochore–microtubule attachment (loss of Nuf2), or stabilized microtubule plus ends at kinetochores (loss of MCAK). Thus, two KinI motors, MCAK and Kif2a, play distinct roles in mitosis, and MCAK activity at kinetochores must be balanced by Kif2a activity at poles for spindle bipolarity. These treatments failed to restore bipolarity to cells lacking the activity of the kinesin Eg5. Thus, two independent pathways contribute to spindle bipolarity, with the Eg5-dependent pathway using motor force to drive spindle bipolarity and the Kif2a-dependent pathway relying on microtubule polymer dynamics to generate force for spindle bipolarity.
Junctate is a key element in calcium entry induced by activation of InsP3 receptors and/or calcium store depletion
Authors: Treves Susan , Franzini-Armstrong Clara , Moccagatta Luca , Arnoult Christophe , Grasso Cristiano , Schrum Adam , Ducreux Sylvie , Zhu Michael X. , Mikoshiba Katsuhiko , Girard Thierry , Smida-Rezgui Sophia , Ronjat Michel , Zorzato Francesco
Published: August 2004

In many cell types agonist-receptor activation leads to a rapid and transient release of Ca2+ from intracellular stores via activation of inositol 1,4,5 trisphosphate (InsP3) receptors (InsP3Rs). Stimulated cells activate store- or receptor-operated calcium channels localized in the plasma membrane, allowing entry of extracellular calcium into the cytoplasm, and thus replenishment of intracellular calcium stores. Calcium entry must be finely regulated in order to prevent an excessive intracellular calcium increase. Junctate, an integral calcium binding protein of endo(sarco)plasmic reticulum membrane, (a) induces and/or stabilizes peripheral couplings between the ER and the plasma membrane, and (b) forms a supramolecular complex with the InsP3R and the canonical transient receptor potential protein (TRPC) 3 calcium entry channel. The full-length protein modulates both agonist-induced and store depletion–induced calcium entry, whereas its NH2 terminus affects receptor-activated calcium entry. RNA interference to deplete cells of endogenous junctate, knocked down both agonist-activated calcium release from intracellular stores and calcium entry via TRPC3. These results demonstrate that junctate is a new protein involved in calcium homeostasis in eukaryotic cells.
Thymic T Cell Development and Progenitor Localization Depend on CCR7
Authors: Misslitz Ana , Pabst Oliver , Hintzen Gabriele , Ohl Lars , Kremmer Elisabeth , Petrie Howard T. , Förster Reinhold
Published: August 2004

T cell differentiation in the adult thymus depends on sequential interactions between lymphoid progenitors and stromal cells found in distinct regions of the cortex and medulla. Therefore, migration of T cell progenitors through distinct stromal environments seems to be a crucial process regulating differentiation and homeostasis inside the thymus.

Here we show that CCR7-deficient mice are distinguished by a disturbed thymic architecture, impaired T cell development, and decreased numbers of the thymocytes. Analysis of developing double negative (CD4−CD8−) pool of wild-type thymus reveals that CCR7 expression is restricted to a CD25intCD44+ subpopulation. Correspondingly, CCR7 deficiency results in an accumulation of this population in mutant thymus. Furthermore, immunohistology shows that in CCR7-deficient mice CD25+CD44+ cells accumulate at the cortico-medullary junction, suggesting that CCR7 signaling regulates the migration of early progenitors toward the outer thymic cortex, thereby continuing differentiation. Results obtained from mixed bone marrow chimeras support this view, since the development of CCR7-deficient thymocytes is also disturbed in a morphologically intact thymus. Thus, our findings establish an essential role for CCR7 in intrathymic migration and proper T cell development.
Type I Interferon Production Enhances Susceptibility to Listeria monocytogenes Infection
Authors: O'Connell Ryan M. , Saha Supriya K. , Vaidya Sagar A. , Bruhn Kevin W. , Miranda Gustavo A. , Zarnegar Brian , Perry Andrea K. , Nguyen Bidong O. , Lane Timothy F. , Taniguchi Tadatsugu , Miller Jeff F. , Cheng Genhong
Published: August 2004

Numerous bacterial products such as lipopolysaccharide potently induce type I interferons (IFNs); however, the contribution of this innate response to host defense against bacterial infection remains unclear. Although mice deficient in either IFN regulatory factor (IRF)3 or the type I IFN receptor (IFNAR)1 are highly susceptible to viral infection, we show that these mice exhibit a profound resistance to infection caused by the Gram-positive intracellular bacterium Listeria monocytogenes compared with wild-type controls. Furthermore, this enhanced bacterial clearance is accompanied by a block in L. monocytogenes–induced splenic apoptosis in IRF3- and IFNAR1-deficient mice. Thus, our results highlight the disparate roles of type I IFNs during bacterial versus viral infections and stress the importance of proper IFN modulation in host defense.
Type I Interferon Sensitizes Lymphocytes to Apoptosis and Reduces Resistance to Listeria Infection
Authors: Carrero Javier A. , Calderon Boris , Unanue Emil R.
Published: August 2004

Infection with Listeria monocytogenes causes lymphocyte apoptosis that is mediated by the actions of the pore-forming virulence factor listeriolysin O (LLO). Previous work showed that activated lymphocytes were highly sensitive to LLO-induced apoptosis, whereas resting lymphocytes were less susceptible. We now show that mice deficient in the type I interferon (IFN) receptor were more resistant to Listeria infection and had less apoptotic lesions than wild-type counterparts. Furthermore, treatment of resting splenic lymphocytes with recombinant IFN-αA enhanced their susceptibility to LLO-induced apoptosis. Together, these data suggest that type I IFN signaling is detrimental to handling of a bacterial pathogen and may enhance the susceptibility of lymphocytes undergoing apoptosis in response to bacterial pore-forming toxins.
Mice Lacking the Type I Interferon Receptor Are Resistant to Listeria monocytogenes
Authors: Auerbuch Victoria , Brockstedt Dirk G. , Meyer-Morse Nicole , O'Riordan Mary , Portnoy Daniel A.
Published: August 2004

Listeria monocytogenes is a facultative intracellular pathogen that induces a cytosolic signaling cascade resulting in expression of interferon (IFN)-β. Although type I IFNs are critical in viral defense, their role in immunity to bacterial pathogens is much less clear. In this study, we addressed the role of type I IFNs by examining the infection of L. monocytogenes in BALB/c mice lacking the type I IFN receptor (IFN-α/βR−/−). During the first 24 h of infection in vivo, IFN-α/βR−/− and wild-type mice were similar in terms of L. monocytogenes survival. In addition, the intracellular fate of L. monocytogenes in macrophages cultured from IFN-α/βR−/− and wild-type mice was indistinguishable. However, by 72 h after inoculation in vivo, IFN-α/βR−/− mice were ∼1,000-fold more resistant to a high dose L. monocytogenes infection. Resistance was correlated with elevated levels of interleukin 12p70 in the blood and increased numbers of CD11b+ macrophages producing tumor necrosis factor α in the spleen of IFN-α/βR−/− mice. The results of this study suggest that L. monocytogenes might be exploiting an innate antiviral response to promote its pathogenesis.
Service failure recovery in China
Authors: Magnini Vincent P. , Ford John B.
Published: August 2004

In the hotel industry, exceptional service failure recovery is a key determinant of customer satisfaction and loyalty. Western‐based hotel corporations should adapt their failure recovery training programs for their properties in China. Adjustments are necessary because of differences in cognitive processing. Modifications are also required due to various Chinese cultural characteristics.
Industry‐specific and general environmental factors impacting on hotel employment
Authors: Wong Kevin K.F.
Published: August 2004

The demand for manpower resource by a hotel is derived from the public's demand for travel goods and services. In filling job vacancies, hotel managers are confronted with an array of internal constraints, industry‐specific drivers as well as external economy‐wide factors that influence the availability and cost of the labour input required. In this study a model incorporating relevant task and general environmental factors is used to measure their impact on hotel managers' decision to raise or lower the level of employment in hotels. Industry‐specific factors which were found to be statistically significant in influencing the demand for hotel staff included the number of hotel rooms, total revenue earned from room rentals and food and beverage sales and revenue obtained from the sale of these items. More broadly, general environmental factors of importance were the production index and the gross domestic product in impacting on the number of hotel employees hired by hotel management.
Creating economic value in the US airline industry: are we missing the flight?
Authors: Madanoglu Melih , Chang David Y. , Chu Yung‐Hui
Published: August 2004

Prolonged periods of ineffective capital allocation and mismanagement destroy massive amounts of wealth and damage the economic wellbeing of the service and manufacturing industries. The purpose of this paper is to outlay the facts and figures that can illustrate the value destruction in the US airline industry for the period of 1990‐1999. The EVA analysis for the last decade of the millennium demonstrated that even when the US economy was prosperous, the airline industry failed to benefit from this favorable environment.
Explaining the performance of a new public service visitor attraction shop
Authors: Wilson Lesley‐Ann , Boyle Emily
Published: August 2004

Because public service visitor attractions are increasingly under pressure to provide best value for money by generating revenue as well as offering a service their shops are becoming more important in their operations. This article therefore looks at the performance of the shop of one new purpose built public service visitor attraction W5 in Belfast, Northern Ireland in order to identify the impact of a number of key factors, both controllable and uncontrollable, on it. The factors concerned were the nature of the target customers, the attraction's location and other locational issues and the public image of the shop. Having considered the impact of these factors on the performance of the shop the article examines the actions and decisions of the visitor attraction's management in its efforts to optimise the shop's performance.
Destination image: to see or not to see?
Authors: White Christopher J.
Published: August 2004

A review of the tourism literature revealed that the conceptualisation and operationalision of destination image as a construct was fragmented and incomplete. Literatures relating to philosophy and cognitive psychology were reviewed and revealed that the concept of image has been the focus of much research and debate in those domains. The dominant themes that emerged from this work are summarised in this article and the implications for destination image management and research are discussed.
Employees' interference with the distribution of guest satisfaction questionnaires
Authors: Poria Yaniv
Published: August 2004

The literature claims that respondents who fill in guest satisfaction questionnaires do not form a truly representative sample of the hotel guests because they do so on a voluntary basis. This study explores the distribution of guest satisfaction questionnaires and the biases that employees bring to the process. Data were gathered via in‐depth, semi‐structured interviews. Individuals with different characteristics were selected in an attempt to reduce the risk of producing findings specific to a certain hotel settings. The results suggest that sampling procedures that were supposed to be carried out systematically are more often done at the convenience of hotel employees or for other, self‐presentational reasons. It is suggested that the employees' intervention is a factor that biases the data and renders it less than informative. Recommendations for hotel operators are provided.
What’s the board’s role in strategy development?: Engaging the board in corporate strategy
Authors: Nadler David A.
Published: August 2004

This article offers an action plan for CEOs who wish to constructively engage their boards in strategy development. In this approach, the board participates in the strategic thinking and strategic decision‐making processes, adding value but not infringing on the CEO’s and executive team’s fundamental responsibilities. More specifically, in value‐added engagement, the CEO and management lead and develop the strategic plan with directors’ input, and the board generally approves the strategy and the metrics to assess progress. The author details the five key elements critical to successful engagement of the board in strategy development: view strategy as a process, not an event; design parallel but lagged processes; inform and educate the board; collect and analyze director input; generate strategic alternatives. The recommended framework for engaging the board in strategy development is called the “strategic choice process”; it has six steps, with the CEO and his/her team leading the way.