The canine distemper epidemic in Serengeti: are lions victims of a new highly virulent canine distemper virus strain,or is pathogen circulation stochasticity to blame?

In the year 1994, the Serengeti lion population was decimated by a canine distemper disease outbreak. Retrospective investigations showed that this host population had already been in contact with the pathogen in 1981 without any detected sign of disease. As an alternative to the virus mutation hypothesis to explain this difference in virulences observed in 1981 and 1994, we propose a novel mechanism of disease emergence based on variation in population immunity. We use a stochastic model to show that stochastic fluctuations in pathogen circulation, owing to a low probability of virus transmission from its reservoir to the target host and thereby resulting in variations in the global immunity level of the target host population, can explain the observations made in Serengeti. This mechanism may also be involved in other infectious disease emergences or re-emergences.     

Levels of cystathionine gamma lyase production by Geotrichum candidum in synthetic media and correlation with the presence of sulphur flavours in cheese

Geotrichum candidum is a cheese-ripening agent with the potential to produce sulphur flavour compounds in soft cheeses. We aimed to develop an alternative test for predicting the aromatic (sulphur flavours) potential of G. candidum strains in soft cheese. Twelve strains of G. candidum with different levels of demethiolase activity (determined by a chemical method) in YEL-met (yeast extract, lactate methionine) medium were studied. We investigated cgl (cystathionine gamma lyase) gene expression after culture in three media - YEL-met, casamino acid and curd media - and then carried out sensory analysis on a Camembert cheese matrix. We found no correlation between demethiolase activity in vitro and cgl gene expression. Sensory analysis (detection of sulphur flavours) identified different aromatic profiles linked to cgl expression, but not to demethiolase activity. The RT-PCR technique described here is potentially useful for predicting the tendency of a given strain of G. candidum to develop sulphur flavours in cheese matrix. This is the first demonstration that an in vitro molecular approach could be used as a predictive test for evaluating the potential of G. candidum strains to generate sulphur compounds in situ (Camembert cheese matrix).     

The Roles of Luteinizing Hormone,Follicle-Stimulating Hormone and Testosterone in Spermatogenesis and Folliculogenesis Revisited

Spermatogenesis and folliculogenesis involve cell–cell interactions and gene expression orchestrated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). FSH regulates the proliferation and maturation of germ cells independently and in combination with LH. In humans, the requirement for high intratesticular testosterone (T) concentration in spermatogenesis remains both a dogma and an enigma, as it greatly exceeds the requirement for androgen receptor (AR) activation. Several data have challenged this dogma. Here we report our findings on a man with mutant LH beta subunit (LHβ) that markedly reduced T production to 1–2% of normal., but despite this minimal LH stimulation, T production by scarce mature Leydig cells was sufficient to initiate and maintain complete spermatogenesis. Also, in the LH receptor (LHR) knockout (LuRKO) mice, low-dose T supplementation was able to maintain spermatogenesis. In addition, in antiandrogen-treated LuRKO mice, devoid of T action, the transgenic expression of a constitutively activating follicle stimulating hormone receptor (FSHR) mutant was able to rescue spermatogenesis and fertility. Based on rodent models, it is believed that gonadotropin-dependent follicular growth begins at the antral stage, but models of FSHR inactivation in women contradict this claim. The complete loss of FSHR function results in the complete early blockage of folliculogenesis at the primary stage, with a high density of follicles of the prepubertal type. These results should prompt the reassessment of the role of gonadotropins in spermatogenesis, folliculogenesis and therapeutic applications in human hypogonadism and infertility.     

Optimization of Extreme Load and Break-in Period in Plain ZDDP Oil with FeF3 Catalyst Using Design of Experiment and Fundamental Study under Different Speeds

The mechanism of tribofilm formation and breakdown was carefully followed and studied in 0.1 P% (percentage phosphorus content) plain zinc dialkyldithiophosphate (ZDDP) oil in the presence of iron fluoride (FeF₃) catalyst under extreme Hertzian contact pressure (3.0 GPa) and two different rotational speeds or variable speed with break in period (100 rpm for the first 5,000 revolutions and a 700 rpm until failure or 100,000 revolutions, whichever comes first). At the onset of large frictional fluctuations, the contact surface temperature increased significantly and reached 90°C ± 5°C. The present article describes an innovative method of reducing the surface temperature by using a break in period of 2 or 3 min and rerunning the test until failure. The two different rotational speeds or variable speed will be compared to a steady-state speed of 700 rpm.

Thermal decomposition of ZDDP is examined in the presence of powder and dispersed FeF₃ using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface analyses were carried out using scanning electron microscopy (SEM) coupled with X-ray of the wear tracks, transmission electron microscopy (TEM), and auger electron spectroscopy (AES). Results showed that submicrometer dispersed FeF₃ provided excellent wear protection when combined with ZDDP in the variable-speed test with break-in by forming a tribofilm that is amorphous in nature and rich in phosphorus, which was shown by the TEM and X-ray analyses.     

Effect of weathering and thickness on the superficial microhardness of acrylic resin and ocular button

Purpose

This study evaluated the effects of weathering (1008 h) and thickness (1 and 3.5 mm) on the superficial microhardness of the ocular button, using five colorless acrylic resins, and colorless buttons specific for ocular prosthesis.

Materials and methods

One-hundred-and-twenty specimens were made and distributed allocated to 12 groups. Microhardness analysis was carried out with a microdurometer (Shimadzu, Japan) before and after weathering for 1008 h. Data were then analyzed statistically by ANOVA and the Tukey Test at 1% significance.

Results

The data demonstrated that the ocular button and the QC 20 resin presented, respectively, the highest (22.9) and lowest (18.31) values of surface microhardness (Knoop), independently of the variable evaluated.

Conclusion

Thickness did not influence the property studied, and the specimens presented higher mean values of superficial microhardness after weathering for 1008 h.     

Size‐Dependent Cytotoxicity of Monodisperse Silica Nanoparticles in Human Endothelial Cells

The effect that monodisperse amorphous spherical silica particles of different sizes have on the viability of endothelial cells (EAHY926 cell line) is investigated. The results indicate that exposure to silica nanoparticles causes cytotoxic damage (as indicated by lactate dehydrogenase (LDH) release) and a decrease in cell survival (as determined by the tetrazolium reduction, MTT, assay) in the EAHY926 cell line in a dose‐related manner. Concentrations leading to a 50% reduction in cell viability (TC₅₀) for the smallest particles tested (14‐, 15‐, and 16‐nm diameter) ranging from 33 to 47 µg cm^?2 of cell culture differ significantly from values assessed for the bigger nanoparticles: 89 and 254 µg cm^?2 (diameter of 19 and 60 nm, respectively). Two fine silica particles with diameters of 104 and 335 nm show very low cytotoxic response compared to nanometer‐sized particles with TC₅₀ values of 1095 and 1087 µg cm^?2, respectively. The smaller particles also appear to affect the exposed cells faster with cell death (by necrosis) being observed within just a few hours. The surface area of the tested particles is an important parameter in determining the toxicity of monodisperse amorphous silica nanoparticles.     

Calorimetric study of milk fat/rapeseed oil blends and their interesterification products

Milk fat (MF) and rapeseed oil (RO) blends were analyzed by differential scanning calorimetry (DSC). It was shown that peak and onset temperatures can be used to determine the percentage of each fat in the blend and that the relative enthalpy of one peak assigned to low‐melting triacylglycerols (TAG) can also be used to determine the percentage of RO in the blend. A linear relation was also established between MF content of the blend and its dropping point (DP), indicating that DP can be linearly related with the above DSC data. A blend of MF/RO 70 : 30 (wt/wt) was then chosen as a model system for enzymatic interesterification (EIE). The applicability of DSC analyses to EIE products was checked and a correct correlation could be established between DSC values and the interesterification degree and DP. Among the data from the DSC profiles, the peak associated with low‐melting TAG was the best indicator of the reaction course. In the same way, a high‐melting MF stearin fraction was interesterified with RO. In that case, onset temperatures and peak “a” were better reaction indicators than for the interesterified MF/RO blend. We therefore suggest that values from DSC endotherms could be used to monitor EIE of fat blends.     

The Micro Gallery: an evaluation of the hypertext system in The National Gallery,London

Abstract

The paper reports on a user evaluation of the Micro Gallery hypertext system of Western European Paintings at The National Gallery in London. A combination of data collection methods was used, including questionnaires before and after the use of the system and direct observation with talk aloud, to examine the impact of the interface features on searching behaviour. The diagnostic analysis highlights difficulties encountered with starting off, access points, navigation, orientation and the touch screen interaction. Linear and non-linear approaches to searching arc compared for first time and experienced users and arc discussed in terms of the completeness of user mental models.     

Automaticité du traitement de l'information et évaluation du retard mental.

The goal of this study was to show the usefulness of data concerning reaction time (RT) and its variability on simple psychometric items in the context of intellectual assessment of mentally retarded individuals. Two experiments compared the response time data for 2 groups of normal 7- and 9-yr-old children with data for 2 groups of mentally retarded persons whose mental ages compared to that of the children. The joint analysis of response time and variability resulted in indications regarding not only the effectiveness of information processing but the development of skills as reflected in degree of automaticity. In fact, analysis of response time variability enables the distinction of cases in which a specific skill leads to the restructuring of information processing, i.e., automation, from those which do not have such restructuring. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the mechanical damage of a chemically degraded cement paste

Cement-based materials as concrete interact with their environment. In the presence of aqueous mediums, dissolutions and precipitations of solid species composing the cement paste induce a chemical damage, which may affect the structure integrity. This paper presents a mechanical characterization of the Young modulus evolution of chemically damaged cement paste, based on a microstructural approach coupled to a reactive-transport model. The method has been successfully applied to cement pastes leached by pure water. It is concluded that the capillary porosity and its spatial distribution within the material are the parameters, which mainly rule the stiffness evolution.