Dislocation dynamics in a Ni
3
(Al, Ta) single-crystal alloy have been studied by means of mechanical spectroscopy at intermediate temperatures, that is in the temperature range of the flow stress ...anomaly. The mechanical loss of specimens predeformed at 300 K was found to be strongly dependent on temperature, predeformation level and heating rate. Thermal cycling (heating-cooling) and ageing experiments were also performed, which provided additional information about the annealing time dependence of the mechanical loss, elastic modulus of the material and plastic deformation of the specimens. The obtained results can be explained by a combination of two phenomena simultaneously occurring as the temperature is increased from 300 to about 500 K: exhaustion of the mobile dislocation parts (superkinks) and pinning of the screw dislocation segments via cross-slip from the (111) onto the (010) planes.
Recently, attention has focussed on phenotypic and functional differences between classic myeloid dendritic cells (DC), and DC that reportedly develop from an early, committed lymphoid precursor. In ...mice, DC from these separate hemopoietic lineages differ by their surface expression of CD8 alpha . We undertook a comparative study of CD8 alpha super(+) (CD11b super(low); lymphoid-related) and CD8 alpha super(-) (CD11b super(high); myeloid) DC isolated from mouse liver. CD8 alpha super(+) and CD8 alpha super(-) DC each constituted less than or equal to 1.0% of the freshly isolated, normal nonparenchymal cells (NPC). Both populations were enriched 10-15% by overnight culture and metrizamide density centrifugation. Flt3 ligand (Flt3L) potently induced equal expansion of both subsets in vivo. Tissue-resident CD8 alpha super(+) DC, freshly isolated from Flt3L-treated mice, existed primarily as immature cells (CD11c super(+), CD11b super(low), CD40 super(-/low), CD80 super(low), CD86 super(low), MHC class II super(low)), consistent with previous observations regarding bulk DC freshly isolated from nonlymphoid tissues. Following over-night culture in GM-CSF, CD8 alpha super(+) DC underwent phenotypic and functional maturation equivalent to that observed for CD8 alpha super(-) DC. CD95 ligand (FasL) mRNA was detected in both immature and mature DC of each subset. In vitro analysis confirmed that flow-sorted, mature CD8 alpha super(+) and CD8 alpha super(-) DC were strong and equally efficient stimulators of allogeneic T cell proliferation in primary MLR. Both immunohistochemical and genomic DNA analysis revealed that in vivo, sorted CD8 alpha super(+) DC trafficked from s.c. sites to T cell areas of allogeneic lymphoid tissue and were equally efficient at priming naive T cells compared with CD8 alpha super(-) DC. This is the first comparative study of lymphoid-related DC isolated from nonlymphoid tissue.
Fluorescence emission spectra, recorded at different excitation wavelengths (λ
ex
), and synchronous-scan excitation spectra of Sep-Pak extractable marine organic matter (SPE-MOM) and its reverse ...phase HPLC fractions were used to describe the fluorescence characteristics of such naturally occurring organic compounds. Sep-Pak extractable soil fulvic acid (SPE-SFA) and its Chromatographic fractions were used as reference material. The results show a different distribution of fluorescent material with respect to the chromophoric one in the HPLC fractions of SPE-MOM with a higher concentration of the shortest wavelength emitting fluorophores in the most hydrophobic fraction. No apparent correlation with polarity was observed for the SPE-SFA sample. Synchronous-scan excitation spectra indicate a higher presence of the shorter λ
ex
fluorophores in SPE-MOM whereas SPE-SFA exhibits a remarkable presence of longer λ
ex
fluorophores. Hence, a younger formation of marine organic matter with a lower structural complexity was postulated.
The toxicity of mercury to marine organisms depends both on the concentration and on the physico-chemical forms in which the metal is present in the aquatic environment. From this point of view the ...knowledge of mercury levels and its chemical forms present particular interest. In this paper the distribution of mercury in waters and sediments along the coast of Tuscany (Italy) between the Arno and Cecina estuaries is reported. For the determination of "reactive" and "total" mercury, a method based on fluorescence spectrometry has been applied.
ITALIANO: La tossicita del mercurio sugli organismi marini dipende sia dalla concentrazione che dalle forme chimico-fisiche in cui questo metallo si distribuisce nell'ecosistema acquatico. Questa distribuzione e regolata sia dagli equilibri che si instaurano tra i componenti abiotici del sistema (aria-acqua-sedimenti), sia dalle trasformazioni del metallo indotte dagli organismi. La conoscenza dei livelli di mercurio e delle sue forme chimico-fisiche presenti nelle acque e quindi un anello importante per il chiarimento del complesso ciclo biogeochimico di questo metallo in relazione alla sua tossicita sugli organismi. In questa comunicazione sono riportati i risultati di una indagine sulla distribuzione del mercurio nelle acque e sedimenti di un tratto di costa della Toscana. Il mercurio "reattivo" e "totale" e stato determinato nelle acque con un metodo basato sulla spettrometria di fluorescenza.
Vascular disease is frequent in uremics and may contribute to tissue malnutrition and damage. The aim of this study was to detect whether uremic patients show also changes of microcirculation and to ...evaluate the effects induced by hemodialysis (HD) session. Eleven uremics on HD (7 males, 4 females, aged 25-65 years) were studied; 11 healthy subjects, age- and sex-matched, served as controls. Skin microcirculatory basal flow (BF), maximal postischemic flow (PIF-max) and flow motion index (FMI) were determined at the upper limb contralateral to arteriovenous fistula, by means of a laser Doppler flowmeter. The measurements were taken before, at 1 and 2 h after starting HD and 30 min after the end of HD. In uremics, FMI was lower than in controls (mean +/- SD: 15.2 +/- 13.6 vs. 29.1 +/- 7.4%; p < 0.005); just 1 h after the start of HD, a significant improvement (28.4 +/- 17.7%; p < 0.01) versus basal values was observed and it persisted throughout the HD session. No statistical correlation was observed between the changes of FMI and those of plasma levels of Na+, K+, HCO-3, urea, iPTH or rate of ultrafiltration. BF and PIF-max were similar in uremics and controls, and no changes were observed during HD. Our study shows that the physiological flow motion is reduced in the skin microcirculation of uremics on HD. This abnormality is rapidly corrected by HD.
Epidermal Langerhans cells (LCs) show extraordinary immunostimulatory capacity and play a key role in the initiation and regulation of immune responses. Studies of LC biology are currently the focus ...of efforts to engineer immune responses and to better understand the immunopathology of cutaneous diseases. Here we identified and characterized a population of LC precursors that were resident in human skin. These immediate precursors expressed CD14, langerin and functional CCR6. When cultured with transforming growth factor beta -1 alone, they had the potential to differentiate into epidermal LCs; when cultured in the presence of granulocyte macrophage-colony-stimulating factor and interleukin 4 they differentiated into functionally mature dendritic cells. Identification and characterization of these LC precursors provided insight into LC biology and the mechanism(s) through which LCs repopulate the epidermis.
High dietary protein intake, in the past recommended for nephrotic syndrome, does not improve hypoproteinemia and may accelerate progressive renal damage. In contrast, low-protein diets reduce ...proteinuria and preserve renal function in experimental renal models of nephrotic syndrome. In this study, 20 steroid-resistant, nephrotic patients were treated with a pure vegetarian, low-protein diet, supplemented with essential amino acids and ketoanalogues (supplemented vegan diet, SVD) for 4.6 +/- 3.1 months. Before the study, these patients followed an unrestricted protein, low-sodium diet (LSD). Proteinuria, daily urea nitrogen excretion and creatinine clearance decreased significantly on SVD. A similar lowering effect of SVD was observed on serum total cholesterol. Seven of the 20 patients changed from LSD to SVD and vice-versa on 3 occasions, and in all cases, we found an increase of proteinuria during the LSD period. Serum albumin, HDL cholesterol, triglycerides and anthropometric measurements did not change on SVD. Our data suggest that SVD exerts a favorable effect on proteinuria and hypercholesterolemia in nephrotic patients, without inducing clinical or laboratory signs of malnutrition.
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