bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex change in two Mediterranean species of Coralliophilidae (Mollusca: Gastropoda: Neogastropoda)
Authors: Richter Alexandra , Luque Ángel A.
Published: March 2004

Sex ratio and size–gender distribution of Coralliophila meyendorffii and Babelomurex cariniferus collected in the field was studied. While sex ratio did not depart from the expected Fisher 1:1 ratio for dioecious species, the size–frequency distributions showed clearly a sexual size dimorphism with males significantly smaller than females. Laboratory monitoring of penis reduction in both species, combined with an anatomical and histological study of the reproductive system of individuals reducing penis revealed the existence of transitional sexual stages, proving the existence of protandry. Penis monitoring also demonstrated a high plasticity in size at sex change, suggesting a socially controlled sex change. In C. meyendorffii, where penis monitoring followed an experimental design based on the assumption that protandry existed and that presence of females influenced sex change, results strongly supported a social control of sex change. Evidences for protandry in other coralliophilids are summarized and protandry as a widespread sexual strategy in Coralliophilidae is postulated.
Age and growth of the ommastrephid squid Todarodes sagittatus from the western Mediterranean Sea
Authors: Quetglas Antoni , Morales-Nin Beatriz
Published: March 2004

Age and growth of Todarodes sagittatus were estimated based on statolith analysis from individuals (N=352; 81–418 mm mantle length) caught by bottom trawlers during a year of sampling in the western Mediterranean. The daily nature of statolith increments was indirectly validated comparing the mean age of consecutive monthly modes (identified on the monthly length–frequency distributions) with the corresponding increase of 30 days. In agreement with other ommastrephids, results confirmed the following points: (1) lifespan lasts nearly a year; (2) growth rates decrease with age; (3) when adult, females have higher growth rates than males; and (4) females mature about a month later than males. Significant correlation was found between hatching (which occurred throughout the year but with a peak in November) and temperature at 50 m depth (where it is thought that hatchlings inhabit). Age and growth results were compared with those obtained in a similar work carried out in north-west Africa (Arkhipkin et al., 1999). Comparisons suggested that due to higher growth rates in juveniles, southern populations reach maturity and consequently decrease somatic growth at younger ages and smaller sizes than northern squid, which attain larger sizes as a result of maintaining fast growth and delaying maturation. Greater growth rates in juveniles from west Sahara could be explained by higher temperatures in this area than in the Mediterranean.
Diversity, relative density and structure of the cetacean community in summer months east of Great Abaco, Bahamas
Authors: MacLeod Colin D. , Hauser Nan , Peckham Hoyt
Published: March 2004

Little is known about cetacean communities in the tropical and sub-tropical Atlantic. This paper describes the cetacean community found east of Great Abaco in the northern Bahamas (26·5°N) during summer months between 1998 and 2001. Nine species of cetaceans were recorded, which could be divided into two distinct groupings: firstly, ‘permanent’ species, which had relative sightings rates between 0·026–0·084 sightings per hour and which were recorded on many occasions in all years and most months; secondly, ‘sporadic’ species, which had relative sightings rates an order of magnitude lower (0·004–0·008 sightings per hour) and which were recorded on very few occasions. The ‘permanent’ species were the Stenella frontalis (Atlantic spotted dolphin), Kogia simus (the dwarf sperm whale), Mesoplodon densirostris (Blainville's beaked whale) and Ziphius cavirostris (Cuvier's beaked whale). These four species differed significantly in the depth of grid squares utilized (χ=20·25, df=9, P<0·01) suggesting that these species occupied four separate niches. Stenella frontalis dominated the surface feeding niche, while the remaining three deep-diving species segregated into different depth ranges. Kogia simus was the dominant species in water depths of less than 200 m, M. densirostris in water depths of 200 to 1000 m and Z. cavirostris in water depths of greater than 1000 m. The overall relative density (2·533 individuals per hour of effort) and diversity of species in the study area was relatively low and may relate to low levels of local productivity. It is hypothesized that the four ‘permanent’ species may competitively exclude ecologically similar species, resulting in a reduced number of species and that ‘sporadic’ species may only enter the study area during times of higher than usual productivity when the ‘permanent’ species are no longer able to dominate their individual niches.
Cognitive test performance in relation to psychotic symptoms and paranoid ideation in non-demented 85-year-olds
Authors: ÖSTLING S. , JOHANSSON B. , SKOOG I.
Published: March 2004

Background. Clinical studies suggest that psychotic and paranoid states in late life are associated with cognitive dysfunction. However, it is not clear whether this finding would be observed in general population samples of non-demented elderly, particularly after adjustment for potential confounding factors.

Method. A representative sample of non-demented 85-year-olds living in the community or in institutions in Göteborg, Sweden (N=347) was examined using a psychiatric and physical examination (including a medical history), key-informant interview, psychometric testing and review of medical records. Individuals with psychotic symptoms and paranoid ideation were compared with the mentally healthy regarding tests of verbal ability, inductive logical reasoning, spatial ability, perceptual speed, basic arithmetic, primary memory and secondary memory.

Results. Non-demented 85-year-olds with psychotic symptoms or paranoid ideation performed specifically worse on tests measuring verbal ability, logical reasoning and two tests of spatial ability after adjustment for sex, education, hearing impairment, visual deficits, somatic disorders, depression, 3-year-mortality rate and incident dementia.

Conclusions. Psychotic symptoms and paranoid ideation were associated with lower performance on cognitive tests related to verbal ability, logical reasoning and spatial ability in non-demented 85-year-olds after adjustment for potential confounders.
The nosology of sub-acute and chronic fatigue syndromes that follow infectious mononucleosis
Authors: WHITE P. D. , THOMAS J. M. , SULLIVAN P. F. , BUCHWALD D.
Published: March 2004

Background. A previous principal components analysis of symptoms occurring after infectious mononucleosis suggested that a discrete fatigue syndrome occurs, which is independent of psychiatric disorder. This work has not been replicated and no latent class analysis of subjects has been published.

Method. We prospectively examined a cohort of 150 American primary care patients 2 and 6 months after the onset of corroborated infectious mononucleosis. A subset of 50 subjects was studied 4 years after onset. We performed principal components analyses of both psychological and somatic symptoms and latent class analyses of subjects.

Results. Principal components analyses consistently delineated two fatigue factors at 2 and 6 months and one fatigue factor at 4 years. These factors were separate from a mixed anxiety and depressive factor. A four-class solution for the latent class analyses consisted of most subjects with few symptoms, a few with many symptoms, a group with predominantly mood symptoms and some subjects with fatigue symptoms.

Conclusions. The symptoms of the principal factors with fatigue were similar to those previously described. Both the factors and classes were independent of an equally delineated mood factor and class. These results support the existence of two discrete chronic fatigue syndromes after infectious mononucleosis, one of which is still demonstrable 4 years after onset.
Gender differences in heritability of depressive symptoms in the elderly
Authors: JANSSON M. , GATZ M. , BERG S. , JOHANSSON B. , MALMBERG B. , McCLEARN G. E. , SCHALLING M. , PEDERSEN N. L.
Published: March 2004

Background. The present study aimed to investigate the relative importance of genetic and environmental influences on depressive symptoms in the elderly.

Methods. Depressive symptoms were assessed through the Center for Epidemiological Studies – Depression (CES-D) scale. The CES-D scale was administered to 959 twin pairs (123 female MZs, 90 male MZs, 207 same-sex female DZs, 109 same-sex male DZs and 430 opposite-sex DZs) aged 50 years or older (mean age 72 years). A dichotomous depressed state variable was constructed based on CES-D cut-offs and self-reported use of antidepressant medication. Structural equation models were fitted to the data to dissect genetic and environmental variance components.

Results. The sex-specific heritability estimates for depressive symptoms were 14% for males and 29% for females and 23% when constrained to be equal for men and women. The prevalence of clinically significant depressive symptoms was 16% for men and 24% for women. Heritability estimates for the dichotomous depressed state measure were 7% for males and 49% for females in the full model and 33% when constrained to be equal.

Conclusion. Our results suggest that depressive symptoms in the elderly are moderately heritable, with a higher heritability for women than men, although differences in heritability estimates were not statistically significant.
Histology and growth of the cetacean petro‐tympanic bone complex
Authors: de Buffrénil Vivian , Dabin Willy , Zylberberg Louise
Published: March 2004

The histological organization and the main growth trends of the periotic and tympanic bones are described in known‐aged common dolphins. The maximum sizes of these bones are already acquired in new‐born specimens, and their full mineralization (84.62% and 83.3%, respectively) is reached either at birth (tympanic) or within the first 6 months. Mass, compactness and density of the periotic and tympanic quickly rise during the first year of life, and remain stable afterwards. Mean values of compactness and density observed in adults are 94% and 2.65 g/cm3 for the periotic, and 98% and 2.66 g/cm3 for the tympanic. The periotic and tympanic are composed of a fibro‐lamellar tissue, initially deposited as a loose spongiosa with hypermineralized trabeculae. Before the end of the first year, this spongiosa is made compact by the perivascular formation of primary osteons. The vascular network of bone, originally very extensive, is obliterated rapidly by the osteons. The collagen matrix is composed of very thin collagen fibrils (diameter: 10 to 30 nm) arranged in a dramatically reduced network compared to normal bone. Hence, the room available for the mineral phase is considerably increased. Whatever the age of the animals, there is no inner (Haversian) remodelling in the periotic and tympanic. Since the compactness and density of these bones augment during the nursing period, it seems likely that the full hearing capacities of the dolphins are not reached before weaning.
Systematic error of microwave scatterometer wind related to the basin‐scale plankton bloom
Authors: Hashizume Hiroshi , Liu W. Timothy
Published: March 2004

Chlorophyll‐a concentration derived from satellite ocean color sensor are compared with coincident wind speed difference between microwave scatterometer QuikSCAT product and reanalysis product from the National Center for Environmental Prediction over global oceans. The objective is to explore if a natural surface film, which originates in biological productivity, causes the underestimation of surface wind in scatterometer measurement by damping the small capillary wave through the surface tension. The wind speed difference (Reanalysis wind – QuikSCAT wind) is found to correlate positively with chlorophyll‐a over the biologically highly productive areas, especially from intra‐seasonal to seasonal time scales, indicating the surface film effect. The wind speed difference increases from ∼−1 m s−1 to ∼0.5 m s−1 as chlorophyll‐a increases from ∼0.1 mg m−3 to ∼3 mg m−3, which is comparable with the results of previous laboratory experiments with artificial oil.
Chemical and dynamical response to the 11‐year variability of the solar irradiance simulated with a chemistry‐climate model
Authors: Egorova T. , Rozanov E. , Manzini E. , Haberreiter M. , Schmutz W. , Zubov V. , Peter T.
Published: March 2004

Atmospheric effects of the solar irradiance variations during 11‐year solar cycle are investigated using a chemistry‐climate model. The model is enhanced by a more detailed parameterization of the oxygen and ozone UV heating rates. The simulated ozone response to the imposed solar forcing shows a positive correlation in the tropical stratosphere and a negative correlation in the tropical mesosphere, in agreement with theoretical expectation. The model suggests an acceleration of the polar night jets in both hemispheres and a dipole structure in the temperature changes at high latitudes. The model results also show an alteration of the tropospheric circulation air resulting in a statistically significant warming of 1 K in the annual mean surface air temperature over North America and Siberia. This supports the idea of a solar‐climate connection.
In situ aerosol profiles over the Southern Great Plains cloud and radiation test bed site: 1. Aerosol optical properties
Authors: Andrews Elisabeth , Sheridan Patrick J. , Ogren John A. , Ferrare Richard
Published: March 2004

Aerosol optical properties were measured over the Southern Great Plains (SGP) cloud and radiation test bed site using a light aircraft (Cessna C‐172N). The aircraft flew level legs at altitudes between 500 m and 3500 m several times per week over the course of 2 years in order to obtain a statistically representative data set of in situ aerosol vertical profiles. Instrumentation on the aircraft was similar to that at the surface SGP site so that measurements at the surface and aloft could easily be compared. Measured parameters included total light scattering, backscattering, and absorption, while calculated parameters included single‐scattering albedo, backscatter fraction, and Ångström exponent. Statistical plots of aerosol optical properties and their variation in the lower column (0–4000 m) showed that over the course of the 2 years studied, albedo, backscatter fraction, and Ångström exponent were fairly invariant with altitude (at least up to 1800 m). Despite the vertical consistency the correlation between column average and surface values for single‐scattering albedo, backscatter fraction, and Ångström exponent tended to be quite low, with R2 ranging from 0.3 to 0.6 and linear regression slopes ranging from 0.2 to 0.6. These results suggest that long‐term surface aerosol measurements capture the column aerosol properties but may not be as representative of day‐to‐day variations in the column. Comparison of aerosol optical depth (AOD) calculated from the vertical profiles with other measurements of AOD made at SGP (i.e., by the Cimel Sun photometer and the multifilter rotating shadowband radiometer (MFRSR)) showed fair correlation (R2 ∼ 0.7 Cimel, R2 ∼ 0.8 MFRSR), although the aircraft AODs tend to have a consistent offset of −0.04, even after incorporating a correction for supermicrometer aerosol and stratospheric aerosol.
Observations of double‐peaked E region coherent spectra with the CUTLASS Finland HF radar
Authors: Danskin D. W. , Koustov A. V. , Makarevitch R. A. , Lester M.
Published: March 2004

Cooperative UK Twin Located Auroral Sounding System Finland HF radar observations of E region coherent spectra are presented for several events. The Burg spectrum method is applied to study microstructure of the spectra. It is discovered that many spectra are two‐peaked, and quite often there is a systematic pattern in their occurrence; the double‐peak echoes are typically observed at intermediate and far ranges of the E region echo band and at ranges farther than the power maximum in the range profile. The typical separation between the peaks is about 150 m/s and hardly changes with the azimuth of observations. Velocities of two components in a double‐peak spectrum are typically larger and smaller than the velocity of the unresolved spectrum and single‐peaked velocity of echoes at shorter ranges. It is hypothesized that the two components of the echoes occur because of signal reception from the top and bottom of the electrojet layer.
Dynamics of HIV-1 recombination in its natural target cells
Authors: Levy David N. , Aldrovandi Grace M. , Kutsch Olaf , Shaw George M.
Published: March 2004

Genetic recombination is believed to assist HIV-1 diversification and escape from host immunity and antiviral therapies, yet this process remains largely unexamined within the natural target-cell populations. We developed a method for measuring HIV-1 recombination directly that employs reporter viruses bearing functional enhanced yellow fluorescent protein (YFP) and enhanced cyan fluorescent protein (CFP) genes in which recombination produces a modified GFP gene and GFP fluorescence in the infected cells. These reporter viruses allow simultaneous quantification of the dynamics of HIV-1 infection, coinfection, and recombination in cell culture and in animal models by flow-cytometric analysis. Multiround infection assays revealed that productive cellular coinfection was subject to little functional inhibition. As a result, generation of recombinants proceeded according to the square of the infection rate during HIV-1 replication in T lymphocytes and within human thymic grafts in severe combined immunodeficient (SCID)-hu (Thy/Liv) mice. These results suggest that increases in viral load may confer a compounding risk of virus escape by means of recombinational diversification. A single round of replication in T lymphocytes in culture generated an average of nine recombination events per virus, and infection of macrophages led to ≈30 crossover events, making HIV-1 up to an order of magnitude more recombinogenic than recognized previously and demonstrating that the infected cell exerts a profound influence on the frequency of recombination.
Human papillomavirus (HPV) origin-binding protein associates with mitotic spindles to enable viral DNA partitioning
Authors: Van Tine Brian A. , Dao Luan D. , Wu Shwu-Yuan , Sonbuchner Timothy M. , Lin Biing Yuan , Zou Nianxiang , Chiang Cheng-Ming , Broker Thomas R. , Chow Louise T.
Published: March 2004

Human papillomaviruses (HPVs) establish long-term infections in patients. The mechanism for extrachromosomal HPV DNA persistence in cycling cells is unknown. We show that HPV origin-containing plasmids partition as minichromosomes, attributable to an association of the viral origin recognition protein E2 with mitotic spindles. α-, β-, and γ-tubulins were pulled down with a tagged E2. The N-terminal transacting and C-terminal protein dimerization/DNA binding domains independently associated with the spindles. We suggest that this E2 property enables these viruses to establish persistence. Its implication for HPV oncogenesis is presented.
MglA regulates transcription of virulence factors necessary for
Francisella tularensis
intraamoebae and intramacrophage survival
Authors: Lauriano Crystal M. , Barker Jeffrey R. , Yoon Sang-Sun , Nano Francis E. , Arulanandam Bernard P. , Hassett Daniel J. , Klose Karl E.
Published: March 2004

Francisella tularensis
is able to survive and grow within macrophages, a trait that contributes to pathogenesis. Several genes have been identified that are important for intramacrophage survival, including
mglA
and
iglC. F. tularensis
is also able to survive within amoebae. It is shown here that
F. tularensis mglA
and
iglC
mutant strains are not only defective for survival and replication within the macrophage-like cell line J774, but also within
Acanthamoebae castellanii
. Moreover, these strains are highly attenuated for virulence in mice, suggesting that a common mechanism underlies intramacrophage and intraamoebae survival and virulence. A 2D gel analysis of cell extracts of wild-type and
mglA
mutant strains revealed that at least seven prominent proteins were at low levels in the
mglA
mutant, and one MglA-regulated protein was identified as the IglC protein. RT-PCR analysis demonstrated reduced transcription of
iglC
and several other known and suspected virulence genes in the
mglA
mutant. Thus, MglA regulates the transcription of virulence factors of
F. tularensis
that contribute to intramacrophage and intraamoebae survival.
Analytic models for mechanotransduction: Gating a mechanosensitive channel
Authors: Wiggins Paul , Phillips Rob
Published: March 2004

Analytic estimates for the forces and free energy generated by bilayer deformation reveal a compelling and intuitive model for MscL channel gating analogous to the nucleation of a second phase. We argue that the competition between hydrophobic mismatch and tension results in a surprisingly rich story that can provide both a quantitative comparison with measurements of opening tension for MscL when reconstituted in bilayers of different thickness, and qualitative insights into the function of the MscL channel and other transmembrane proteins.
Insulin-like growth factor-binding protein 5
(
Igfbp5
) compromises survival, growth, muscle development, and fertility in mice
Authors: Salih Dervis A. M. , Tripathi Gyanendra , Holding Cathy , Szestak Tadge A. M. , Gonzalez M. Ivelisse , Carter Emma J. , Cobb Laura J. , Eisemann Joan E. , Pell Jennifer M.
Published: March 2004

The insulin-like growth factors (IGFs) are essential for development; bioavailable IGF is tightly regulated by six related IGF-binding proteins (IGFBPs).
Igfbp5
is the most conserved and is developmentally up-regulated in key lineages and pathologies;
in vitro
studies suggest that IGFBP-5 functions independently of IGF interaction. Genetic ablation of individual
Igfbps
has yielded limited phenotypes because of substantial compensation by remaining family members. Therefore, to reveal
Igfbp5
actions
in vivo
, we generated lines of transgenic mice that ubiquitously overexpressed
Igfbp5
from early development. Significantly increased neonatal mortality, reduced female fertility, whole-body growth inhibition, and retarded muscle development were observed in
Igfbp5
-overexpressing mice. The magnitude of the response in individual transgenic lines was positively correlated with
Igfbp5
expression. Circulating IGFBP-5 concentrations increased a maximum of only 4-fold, total and free IGF-I concentrations increased up to 2-fold, and IGFBP-5 was detected in high
M

r

complexes; however, no detectable decrease in the proportion of free IGF-I was observed. Thus, despite only modest changes in IGF and IGFBP concentrations, the
Igfbp5
-overexpressing mice displayed a phenotype more extreme than that observed for other
Igfbp
genetic models. Although growth retardation was obvious prenatally, maximal inhibition occurred postnatally before the onset of growth hormone-dependent growth, regardless of
Igfbp5
expression level, revealing a period of sensitivity to IGFBP-5 during this important stage of tissue programming.
Evaluation of the protective effects of α-tocopherol and retinol against ochratoxin A cytotoxicity
Authors: Baldi A. , Losio M. N. , Cheli F. , Rebucci R. , Sangalli L. , Fusi E. , Bertasi B. , Pavoni E. , Carli S. , Politis I.
Published: March 2004

Ochratoxin A (OTA), a mycotoxin frequently present in food and feedstuffs, produces a wide range of toxic effects, including cell death via lipid peroxidation. In one human and four animal cell lines we determined the half lethal concentration (LC50) of OTA, its effect on reactive oxygen species (ROS) production, and its ability to induce cytochrome p450 activity. We also examined the protective effect of α-tocopherol and all-trans-retinol in the most sensitive cell lines (i.e. bovine mammary epithelia, for which LC50was 0·8μg/ml (24h), and Madin Darby canine kidney, for which LC50was 4·3μg/ml (48h)). Pre-incubation for 3h with either antioxidant significantly (P<0·05) ameliorated the OTA-induced reduction in cell viability and significantly decreased (P<0·05) ROS production. These findings indicate that oxidative stress is an important factor in OTA cytotoxicity. Supplementation with antioxidant molecules may counteract the short-term toxicity of this mycotoxin.
Loss of negative priming following sleep deprivation
Authors: Harrison Yvonne , Espelid Erik
Published: March 2004

It has been argued that one night of sleep loss in young healthy adults produces changes similar to that associated with normal, healthy ageing—in particular, that young sleep-deprived adults perform similarly to 60-year-old sleep-satiated adults on some tasks of frontal lobe function. This proposition was examined using a protocol viewed by many to be a direct probe of nonvolitional attention mechanisms associated with frontal lobe function. A negative priming (NP) procedure was used to compare performance between non-sleep-deprived (NSD) and sleep-deprived (SD, 34 hr) young, healthy adults. This protocol allowed for exploration of two theories of the NP effect based on inhibitory or memorial processes. Under conditions believed to facilitate inhibitory processes a normal NP effect was found for NSD(16 ms) and SD (9 ms) participants. Under conditions believed to rely on memorial processes there was no NPeffect following SD, compared with a normal NP effect for NSD participants (11 ms). Distractor interference was also greater following SD. These findings do not suggest a similar pattern of change following sleep loss in healthy young adults to that of normal, healthy, non-sleep-deprived aged groups.
Parallel programming of exogenous and endogenous components in the antisaccade task
Authors: Massen Cristina
Published: March 2004

In the antisaccade task subjects are required to suppress the reflexive tendency to look at a peripherally presented stimulus and to perform a saccade in the opposite direction instead. The present studies aimed at investigating the inhibitory mechanisms responsible for successful performance in this task, testing a hypothesis of parallel programming of exogenous and endogenous components: A reflexive saccade to the stimulus is automatically programmed and competes with the concurrently established voluntary programme to look in the opposite direction. The experiments followed the logic of selectively manipulating the speed of processing of these components and testing the prediction that a selective slowing of the exogenous component should result in a reduced error rate in this task, while a selective slowing of the endogenous component should have the opposite effect. The results provide evidence for the hypothesis of parallel programming and are discussed in the context of alternative accounts of antisaccade performance.
A memory-based, Simon-like, spatial congruence effect: Evidence for persisting spatial codes
Authors: Zhang John X. , Johnson Marcia K.
Published: March 2004

The Simon effect refers to the finding that in a task where stimulus location is irrelevant, reaction time is faster when stimulus and response locations are congruent than when they are not. Dominant theories of the Simon effect have generally attributed this spatial congruence effect to a spatial code automatically generated upon stimulus presentation. A common assumption of these theories is that this spatial code decays in less than a few hundred milliseconds following stimulus onset. We report two working-memory experiments suggesting a reexamination of this assumption—a Simon-like spatial congruence effect persisted over a delay of as long as 2400 ms. We propose that, in addition to generating short-lived perceptual codes, spatial information may be coded in working memory as part of the context associated with stimulus events. When reactivated by cues from the original event, such information may influence response selection and produce spatial congruence effects (in this case, positive when participants made a “yes” response and negative when they made a “no” response).
Analogical transfer in the THOG task
Authors: Koenig Cynthia S. , Griggs Richard A.
Published: March 2004

The influences of surface and structural similarity on analogical transfer were examined with 318 undergraduate participants in four experiments using Needham and Amado's (1995) Pythagoras THOG problem as the source problem and Wason's standard abstract THOG task as the target problem. In Experiments 1–3, systematic changes in surface similarity between the source and target problems were introduced by changing the named exemplar, the dimensional values, and the dimensions, respectively, in the target problem. Significant transfer was obtained in all three experiments. In Experiment 4, we explored the basis of this transfer by examining three versions of the Pythagoras THOG problem, factorially combining its facilitating features as source problems. Results indicated that the inclusion of a hypothesis generation request was necessary for significant transfer. The implications of our findings for using transfer versus facilitation as the performance criterion for deductive reasoning are considered.
Experimental extinction in Pavlovian conditioning: Behavioural and neuroscience perspectives
Authors: Delamater Andrew R.
Published: March 2004

This paper reviews the behavioural and neuroscience literatures on extinction in Pavlovian conditioning with a view towards finding possible points of contact between these two often independent lines of investigation. Recent discoveries at the behavioural level indicate (1) that conditioned stimulus (CS)–unconditioned stimulus (US) associations specific in their sensory content are fully preserved during extinction, (2) that inhibitory stimulus-response associations appear to be learned during extinction, (3) that extinction is influenced by the level of activation of the US representation during nonreinforced trials, (4) that decreases in attention can influence conditioned performance during extinction, and (5) that contexts acquire an ability to modulate learning during both conditioning and extinction. Recent discoveries at the neural systems level suggest (1) that the hippocampus is important in context-specific learning during extinction, (2) that the prefrontal cortex is possibly important in long-term memory for extinction, (3) that the basolateral amygdala may be important in sustaining attention to a CS during extinction, (4) that NMDA receptors are important either in neural plasticity during extinction or by affecting the value of the US representation during extinction, and (5) that the GABAergic system may partially mediate inhibitory learning during extinction. It is concluded that both of these levels of analysis can benefit the other in the pursuit of a more comprehensive understanding of extinction.
Shaping of Strategic Behavior: Global Practices of Listing on the US NASDAQ Stock Exchange
Authors: Szyliowicz Dara , Nelson Teresa , Kennedy Kevin H.
Published: March 2004

This article suggests that by explicitly addressing issues of the macro environment, scholars will be better able to understand and predict strategic behavior. A wide range of macro-environmental forces affects firm behavior. Economic factors have been widely discussed in the literature but less attention has been paid to other critical exogenous forces. In particular, the role of wider systems of meaning (shared understandings by a variety of actors) in determining firm activity is largely ignored, although they have been discussed in the organizations literature in a variety of ways. Specifically, we examine the effects of national culture, legal system, political system, and colonial heritage level variables on the equity acquisition process by countries with firms listed on the United States NASDAQ stock exchange from 1991 to 2002. We find that combining perspectives and using variables from the macro-environment allows us to better predict and understand firm strategy.
Comparison of the Outcome of Conventional Osteosarcoma at Two Specialist International Orthopaedic Oncology Centres
Authors: Ford Samuel , Saithna Adnan , Grimer Robert J. , Picci Piero
Published: March 2004

Objective: To determine the prognostic value of patient and treatment parameters in osteosarcoma, and whether these are
equally important across international boundaries.

Design: Retrospective, cross‐sectional study of 428 patients diagnosed with around‐knee osteosarcoma, between 1990 and
1997 in Birmingham, UK, and Bologna, Italy. Disease‐free survival (DFS) and overall survival (OS) assessed by Kaplan–Meier, Fisher′s PLSD and Cox proportional hazard regression.

Results: Five‐year DFS and OS were 56 and 73% at Centre 1, compared to 43 and 60% at Centre 2 (P=0.0022 and P = 0.025, respectively). The most important bad prognostic factors for DFS and OS respectively were raised alkaline phosphatase at diagnosis (P=0.002 and P=0.003), tumour necrosis < 90% following chemotherapy (P=0.001 and P = 0.004) and volume > 150 cm3 at diagnosis (P=0.04 and P=0.006). The most significant combination of bad prognostic factors was alkaline phosphatase and tumour necrosis. A total of 73% of patients at Centre 1 had greater than 90% necrosis of the tumour following neoadjuvant chemotherapy compared with 29% at Centre 2.

Conclusions: Tumour‐based prognostic factors have similar significance across international boundaries. Chemotherapy effectiveness appears to be a major factor in explaining the survival difference between the two centres.
A Radiotherapy Technique to Improve Dose Homogeneity Around Bone Prostheses
Authors: Williams M. V. , Burnet N. G. , Sherwin E. , Kestelman R. , Geater A. R. , Thomas S. J. , Wilson C. B.
Published: March 2004

Purpose. Following limb conserving surgery for bone or soft tissue sarcoma, patients may require post‐operative radiotherapy
to minimise the risk of local recurrence. In such circumstances the metal prosthesis reduces the dose in its shadow by
approximately 10% when using opposed fields. We describe a technique to boost the underdosed area to overcome this
problem.

Patients or subjects. Seven sequential patients presenting between 1995 and 2001 had their treatment individualised because
they had metal prosthesis in the treatment volume.

Methods. To improve the target dose homogeneity we used a custom‐made keyhole cutout to boost the area in the shadow of
the prosthesis. The degree of attenuation caused by the metal prosthesis was estimated and a boost dose calculated. Exit
thermoluminescent dosimetry (TLD) was used to confirm the estimates made.

Results and discussion. Variation between patients was seen, demonstrating the need for exit TLD to individualise the
treatment plan. The use of a boost field provides a method to overcome under‐dosage in the shadow of a metal prosthesis. It
improves dose homogeneity throughout the target volume and ensures adequate dose intensity around the prosthesis, the site
most at risk of local recurrence.
Nerve-independent formation of a topologically complex postsynaptic apparatus
Authors: Kummer Terrance T. , Misgeld Thomas , Lichtman Jeff W. , Sanes Joshua R.
Published: March 2004

As the mammalian neuromuscular junction matures, its acetylcholine receptor (AChR)–rich postsynaptic apparatus is transformed from an oval plaque into a pretzel-shaped array of branches that precisely mirrors the branching pattern of the motor nerve terminal. Although the nerve has been believed to direct postsynaptic maturation, we report here that myotubes cultured aneurally on matrix-coated substrates form elaborately branched AChR-rich domains remarkably similar to those seen in vivo. These domains share several characteristics with the mature postsynaptic apparatus, including colocalization of multiple postsynaptic markers, clustering of subjacent myonuclei, and dependence on the muscle-specific kinase and rapsyn for their formation. Time-lapse imaging showed that branched structures arise from plaques by formation and fusion of AChR-poor perforations through a series of steps mirroring that seen in vivo. Multiple fluorophore imaging showed that growth occurs by circumferential, asymmetric addition of AChRs. Analysis in vivo revealed similar patterns of AChR addition during normal development. These results reveal the sequence of steps by which a topologically complex domain forms on a cell and suggest an unexpected nerve-independent role for the postsynaptic cell in generating this topological complexity.
Hepatitis C virus NS5A protein interacts with 2′,5′-oligoadenylate synthetase and inhibits antiviral activity of IFN in an IFN sensitivity-determining region-independent manner
Authors: Taguchi Takashi , Nagano-Fujii Motoko , Akutsu Masato , Kadoya Hiroyasu , Ohgimoto Shinji , Ishido Satoshi , Hotta Hak
Published: March 2004

The non-structural protein 5A (NS5A) of hepatitis C virus (HCV) has been implicated in inhibition of antiviral activity of IFN. While previous studies have suggested an interaction between NS5A and the double-stranded RNA-dependent protein kinase (PKR), the possibility still remains that interaction with another molecule(s) is involved in the NS5A-mediated inhibition of IFN. In the present study, we investigated a possible interaction between NS5A and 2′,5′-oligoadenylate synthetase (2-5AS), another key molecule in antiviral activity. We observed that NS5A physically interacted with 2-5AS in cultured cells, with an N-terminal portion of NS5A [aa 1–148; NS5A(1–148)] and two separate portions of 2-5AS (aa 52–104 and 184–275) being involved in the interaction. Single point mutations at residue 37 of NS5A affected the degree of the interaction with 2-5AS, with a Phe-to-Leu mutation (F37L) augmenting and a Phe-to-Asn mutation (F37N) diminishing it. Virus rescue assay revealed that the full-length NS5A (NS5A-F) and NS5A(1–148), the latter of which contains neither the IFN sensitivity-determining region (ISDR) nor the PKR-binding domain, significantly counteracted the antiviral activity of IFN. Introduction of a F37N mutation into NS5A(1–148) impaired the otherwise more significant IFN-inhibitory activity of NS5A(1–148). It was also found that the F37N mutation was highly disadvantageous for the replication of an HCV RNA replicon. Taken together, our results suggest the possibility that NS5A interacts with 2-5AS and inhibits the antiviral activity of IFN in an ISDR-independent manner.
Assembly of Marek's disease virus (MDV) capsids using recombinant baculoviruses expressing MDV capsid proteins
Authors: Kut E. , Rasschaert D.
Published: March 2004

The genes UL18, UL19, UL26, UL26.5, UL35 and UL38 of Marek's disease virus 1 (MDV-1) strain RB1B, encoding the homologues of herpes simplex virus type 1 (HSV-1) capsid proteins VP23, VP5, VP21–VP24, preVP22a, VP26 and VP19C, were identified and sequenced. Recombinant baculoviruses were used to express the six capsid genes in insect cells. Coexpression of the six genes or of UL18, UL19, UL26.5 and UL38 in insect cells resulted in the formation of capsids with a large core. In addition, electron microscopy of thin sections clearly revealed the presence of large numbers of small spherical particles. Experimental coinfection demonstrated that these small particles were associated with production of the preVP22a protein.
PPARγ signaling exacerbates mammary gland tumor development
Authors: Saez Enrique , Rosenfeld John , Livolsi Antonia , Olson Peter , Lombardo Eleuterio , Nelson Michael , Banayo Ester , Cardiff Robert D. , Izpisua-Belmonte Juan Carlos , Evans Ronald M.
Published: March 2004

Breast cancer cell lines that express the nuclear peroxisome proliferator-activated receptor γ (PPARγ) can be prompted to undergo growth arrest and differentiation when treated with synthetic PPARγ ligands. To evaluate the therapeutic potential of increased PPARγ signaling in vivo, we generated transgenic mice that express a constitutively active form of PPARγ in mammary gland. These mice are indistinguishable from their wild-type littermates. However, when bred to a transgenic strain prone to mammary gland cancer, bigenic animals develop tumors with greatly accelerated kinetics. Surprisingly, in spite of their more malignant nature, bigenic tumors are more secretory and differentiated. The molecular basis of this tumor-promoting effect may be an increase in Wnt signaling, as ligand activation of PPARγ potentiates Wnt function in an in vivo model of this pathway. These results suggest that once an initiating event has taken place, increased PPARγ signaling serves as a tumor promoter in the mammary gland.
Supervisory leadership and implementation phase
Authors: Pechlivanidis Pantelis , Katsimpra Angeliki
Published: March 2004

This study's aim is to explore the role of the manager‐leader when decisions are being implemented. Contingency theories of leadership served as a primary basis on this direction. The choice of a specific version of his/her supervisory style turned out an interplay of critical factors. The satisfaction of his/her subordinates in the phase of implementation remained a key for their acceptance/commitment to the goals. The fine tuning with the situation enhanced the prestige and reputation that he/she enjoyed among the corporate networks. More topics complemented the understanding of his/her role: the obstacles arising during a top‐down change program; the implementation dynamism behind the conflicts of the subordinates over decisions; and the subordinates’ daily contribution towards a participative culture.
A taxonomy of operations strategies of high performing small and medium enterprises in Singapore
Authors: Sum Chee‐Chuong , Shih‐Ju Kow Lynn , Chen Cheng‐Sheng
Published: March 2004

Small and medium enterprises (SMEs) are recognized as playing a pivotal role in the economic growth and technological progress of many countries, yet there is a dearth of research that examines the operational performance and strategies of these smaller enterprises, especially in the Asian context. Of particular interest is the operational posture in terms of the key operations priorities adopted by successful SMEs in carving out their own competitive niches. This study is the first to develop a taxonomy of operations strategies based on the operational performance of high performing SMEs in Singapore. As Singapore is one of the most competitive countries in the world and a highly successful newly industrializing nation in Asia, the use of Singapore data provides benchmarking and best practice information for international business communities and newly industrializing countries. Three strategic clusters were identified. Analysis showed significant differences in the operational posture, financial performance and the kinds of improvement programs undertaken by the three strategic clusters. The strategic role of operations in terms of its contribution to corporate strategic formulation and financial profitability was also investigated. Managerial implications of our findings are presented.
Survey on attitudes towards buildings in three Chinese cities: Hong Kong, Shanghai and Taipei
Authors: So Albert T.P. , Leung Andrew Y.T.
Published: March 2004

This paper presents the results of an attitudinal survey of residential and commercial building users from three Chinese cities – Hong Kong, Shanghai and Taipei. The results have been obtained from a much larger survey, primarily involving the living and working standards in the three cities. Apart from the descriptive statistics showing the preferences of the user, inferential statistics also showed significant differences among the attitudes of citizens living in the three cities. The results could give insights to designers and developers on the improvement of building standards.
Improved EDMC for the processes with high variations and/or sign changes in steady‐state gain
Authors: Haeri Mohammad
Published: March 2004

EDMC represents extended dynamic matrix control, which can be applied to nonlinear process control. In this method, control inputs are determined based on a linear model that approximates the process and is updated during each sampling interval. Since nonlinear relation still exists between the prediction error and the control input, numerical (iterative) methods are used to solve the optimization problem defined in the method. For nonlinear processes with high variation and/or sign changes in their steady‐state gain, iterative methods do not converge properly to an acceptable solution for some desired outputs or external disturbances. To eliminate the problem, we augment the process with its steady‐state gain inverse (or pseudo inverse whenever required) such that the steady‐state gain for the new augmented system is constant or contains slow variations. In the case of unstable processes, the method may be applied after stabilizing the process using a proper state or output feedback. Effectiveness of the method has been examined using computer simulations of some benchmark processes. Some of the obtained results are presented in this paper.
Analysis of non‐stationary signals in power systems
Authors: Leonowicz Zbigniew
Published: March 2004

Classical techniques to estimate the spectrum of the multi‐component signal are based on Fourier‐based transformations. The frequency estimates obtained from their spectral peaks are affected by the window length and phase of signal component, thus presenting a large variance even in the absence of noise. The spectrum of the signals is estimated with the help of the Wigner‐Ville distribution and its time‐frequency representation is obtained. For the same purpose, the min‐norm method (subspace method) is used. The accuracy of the tested methods was investigated and compared with the parameters of the frequency estimation via FFT. The proposed methods were also tested with non‐stationary multiple‐component signals occurring during the fault operation of inverter‐fed drives and transmission lines.
The computation of flow and heat transfer through square‐ended U‐bends, using low‐Reynolds‐number models
Authors: Nikas Konstantinos‐Stephen P. , Iacovides Hector
Published: March 2004

This study is concerned with the computation of turbulent flow and heat transfer in U‐bends of strong curvature. Following the earlier studies within the authors' group on flows through round‐ended U‐bends, here attention is turned to flows through square‐ended U‐bends. Flows at two Reynolds numbers have been computed, one at 100,000 and the other at 36,000. In the heat transfer analysis, the Prandtl number was either 0.72 (air) or, in a further departure from our earlier studies, 5.9 (water). The turbulence modelling approaches examined, include a two‐layer and a low‐Re k‐ε model, a two‐layer and a low‐Re version of the basic differential stress model (DSM) and a more recently developed, realisable version of the differential stress model that is free of wall‐parameters. For the low‐Re effective viscosity model (EVM) and DSMs, an alternative, recently proposed length‐scale correction term, independent of wall distance has also been tested. Even the simplest model employed – two‐layer EVM – reproduces the mean flow development with reasonable accuracy, suggesting that the mean flow development is mainly influenced by mean pressure rather than the turbulence field. The heat transfer parameters, on the other hand, show that only the low‐Re DSMs produce reliable Nusselt number predictions for both Prandtl numbers examined.