Spatio-temporal dynamics and transition from asymptotic equilibrium to bounded oscillations in Chrysomya albiceps (Diptera, Calliphoridae)

The sensitivity of parameters that govern the stability of population size in Chrysomya albiceps and describe its spatial dynamics was evaluated in this study. The dynamics was modeled using a density-dependent model of population growth. Our simulations show that variation in fecundity and mainly in survival has marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations. C. albiceps exhibits a two-point limit cycle, but the introduction of diffusive dispersal induces an evident qualitative shift from two-point limit cycle to a one fixed-point dynamics. Population dynamics of C. albiceps is here compared to dynamics of Cochliomyia macellaria, C. megacephala and C. putoria.

Preferential transcription of Paracoccidioides brasiliensis genes: host niche and time-dependent expression

Paracoccidioides brasiliensis causes infection through inhalation by the host of airborne propagules from the mycelium phase of the fungus. This fungus reaches the lungs, differentiates into the yeast form and is then disseminated to virtually all parts of the body. Here we review the identification of differentially-expressed genes in host-interaction conditions. These genes were identified by analyzing expressed sequence tags (ESTs) from P. brasiliensis cDNA libraries. The P. brasiliensis was recovered from infected mouse liver as well as from fungal yeast cells incubated in human blood and plasma, mimicking fungal dissemination to organs and tissues and sites of infection with inflammation, respectively. In addition, ESTs from a cDNA library of P. brasiliensis mycelium undergoing the transition to yeast were previously analyzed. Together, these studies reveal significant changes in the expression of a number of genes of potential importance in the host-fungus interaction. In addition, the unique and divergent representation of transcripts when the cDNA libraries are compared suggests differential gene expression in response to specific niches in the host. This analysis of gene expression patterns provides details about host-pathogen interactions and peculiarities of sites within the host.

15d-PGJ2 modulates acute immune responses to Trypanosoma cruzi infection

The acute phase of Trypanosoma cruzi infection is associated with a strong inflammatory reaction in the heart characterised by a massive infiltration of immune cells that is dependent on the T. cruzi strain and the host response. 15d-PGJ2 belongs to a new class of anti-inflammatory compounds with possible clinical applications. We evaluated the effects of 15d-PGJ2 administered during the acute phase of T. cruzi infection in mice. Mice were infected with the Colombian strain of T. cruzi and subsequently treated with 15d-PGJ2 repeatedly for seven days. The inflammatory infiltrate was examined by histologic analysis. Slides were immunohistochemically stained to count the number and the relative size of parasite nests. Infection-induced changes in serum cytokine levels were measured by ELISA. The results demonstrated that treatment with 15d-PGJ2 reduced the inflammatory infiltrate in the skeletal muscle at the site of infection and decreased the number of lymphocytes and neutrophils in the blood. In addition, we found that 15d-PGJ2 led to a decrease in the relative volume density of amastigote nests in cardiac muscle. T. cruzi-infected animals treated with 15d-PGJ2 displayed a statistically significant increase in IL-10 levels with no change in IFN-γ levels. Taken together, we demonstrate that treatment with 15d-PGJ2 in the acute phase of Chagas disease led to a controlled immune response with decreased numbers of amastigote nests, as measured by the volume density.

Short-term therapy with simvastatin reduces inflammatory mediators and heart inflammation during the acute phase of experimental Chagas disease

Trypanosoma cruzi infection induces progressive cardiac inflammation that leads to fibrosis and modifications in the heart architecture and functionality. Statins, such as 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors, have been studied due to their pleiotropic roles in modulating the inflammatory response. Our goal was to evaluate the effects of simvastatin on the cardiac inflammatory process using a cardiotropic strain of T. cruzi in a murine model of Chagas cardiomyopathy. C57BL/6 mice were infected with 500 trypomastigotes of the Colombian strain of T. cruzi and treated with an oral dose of simvastatin (20 mg/Kg/day) for one month and inflammatory and morphometric parameters were subsequently evaluated in the serum and in the heart, respectively. Simvastatin reduced the total cholesterol and inflammatory mediators (interferon-gamma, tumour necrosis factor-alpha, CCL2 and CCL5) in the serum and in the heart tissue at 30 days post-infection. Additionally, a proportional reduction in heart weight and inflammatory infiltration was observed. Simvastatin also reduced epimastigote proliferation in a dose-dependent manner in vitro and was able to reduce blood trypomastigotes and heart amastigote nests during the acute phase of Chagas disease in vivo. Based on these data, we conclude that simvastatin exerts a modulatory effect on the inflammatory mediators that are elicited by the Colombian strain of T. cruzi and ameliorates the heart damage that is observed in a murine model of Chagas disease.

Mineralization of organic phosphorus in soil size fractions under different vegetation covers in the north of Rio de Janeiro

In unfertilized, highly weathered tropical soils, phosphorus (P) availability to plants is dependent on the mineralization of organic P (Po) compounds. The objective of this study was to estimate the mineralization of total and labile Po in soil size fractions of > 2.0, 2.0-0.25 and < 0.25 mm under leguminous forest tree species, pasture and "capoeira" (secondary forest) in the 0-10 cm layer of a Red-Yellow Latosol after 90 d of incubation. The type of vegetation cover, soil incubation time and soil size fractions had a significant effect on total P and labile P (Pi and Po) fraction contents. The total average Po content decreased in soil macroaggregates by 25 and 15 % in the > 2.0 and 2.0-0.25 mm fractions, respectively. In contrast, there was an average increase of 90 % of total Po in microaggregates of < 0.25 mm. Labile Po was significantly reduced by incubation in the > 2.0 (-50 %) and < 0.25 mm (-76 %) fractions, but labile Po increased by 35 % in the 2.0-0.25 mm fraction. The Po fraction relative to total extracted P and total labile P within the soil size fractions varied with the vegetation cover and incubation time. Therefore, the distribution of P fractions (Pi and Po) in the soil size fraction revealed the distinctive ability of the cover species to recycle soil P. Consequently, the potential of Po mineralization varied with the size fraction and vegetation cover. Because Po accounted for most of the total labile P, the P availability to plants was closely related to the mineralization of this P fraction.

KINETIC STUDY OF SELECTIVE GAS-PHASE OXIDATION OF ISOPROPANOL TO ACETONE USING MONOCLINIC ZRO2 AS A CATALYST

Zirconia was prepared by a precipitation method and calcined at 723 K, 1023 K, and 1253 K in order to obtain monoclinic zirconia. The prepared zirconia was characterized by XRD, SEM, EDX, surface area and pore size analyzer, and particle size analyzer. Monoclinic ZrO2 as a catalyst was used for the gas-phase oxidation of isopropanol to acetone in a Pyrex-glass-flow-type reactor with a temperature range of 443 K - 473 K. It was found that monoclinic ZrO2 shows remarkable catalytic activity (68%) and selectivity (100%) for the oxidation of isopropanol to acetone. This kinetic study reveals that the oxidation of isopropanol to acetone follows the L-H mechanism.

Is there correlation between the turbulent eddies size and mechanical hemolysis ?

Hemolytic profile of an artificial device chronically implanted in the cardiovascular system may represent the difference between the success and failure in its long-term performance. Last decades have witnessed efforts on the development of methods capable of predicting red blood cell damage in artificial organs. However, all of them have had limited success to predict hemolysis. The primary cause of this problem is that such models do not take into consideration structures of turbulent flow. The present paper demonstrates that microscopic measurable occurrences of the turbulent flow may be linked to red blood cell trauma. This study suggests that if the smallest turbulent eddies dimension is under 10 m m hemolysis is not dependent on the exposure time and the red blood cells damage depends only on the dissipation of the turbulent energy in the erythrocyte membrane. The analysis reported here opens the possibility of mapping the flow field in artificial assist devices based on the smallest eddy length scales. This is a promising new trend and should be considered in the designing requirements of the next generations of artificial organs.

Horizontal Slug Flow in a Large-Size Pipeline: Experimentation and Modeling

The knowledge of the slug flow characteristics is very important when designing pipelines and process equipment. When the intermittences typical in slug flow occurs, the fluctuations of the flow variables bring additional concern to the designer. Focusing on this subject the present work discloses the experimental data on slug flow characteristics occurring in a large-size, large-scale facility. The results were compared with data provided by mechanistic slug flow models in order to verify their reliability when modelling actual flow conditions. Experiments were done with natural gas and oil or water as the liquid phase. To compute the frequency and velocity of the slug cell and to calculate the length of the elongated bubble and liquid slug one used two pressure transducers measuring the pressure drop across the pipe diameter at different axial locations. A third pressure transducer measured the pressure drop between two axial location 200 m apart. The experimental data were compared with results of Camargo's1 algorithm (1991, 1993), which uses the basics of Dukler & Hubbard's (1975) slug flow model, and those calculated by the transient two-phase flow simulator OLGA.

Circadian time-dependent effects of fencamfamine on inhibition of dopamine uptake and release in rat striatal slices

Fencamfamine (FCF) is a central stimulant that facilitates central dopaminergic transmission through inhibition of dopamine uptake and enhanced release of the transmitter. We evaluated the changes in the inhibition of uptake and the release of striatal [3H]-dopamine at 9:00 and 21:00 h, times corresponding to maximal and minimal behavioral responses to FCF, respectively. Adult male Wistar rats (200-250 g) maintained on a 12-h light/12-h dark cycle (lights on at 7:00 h) were used. In the behavioral experiments the rats (N = 8 for each group) received FCF (3.5 mg/kg, ip) or saline at 9:00 or 21:00 h. Fifteen minutes after treatment the duration of activity (sniffing, rearing and locomotion) was recorded for 120 min. The basal motor activity was higher (28.6 ± 4.2 vs 8.4 ± 3.5 s) after saline administration at 21:00 h than at 9:00 h. FCF at a single dose significantly enhanced the basal motor activity (38.3 ± 4.5 vs 8.4 ± 3.5 s) and increased the duration of exploratory activity (38.3 ± 4.5 vs 32.1 ± 4.6 s) during the light, but not the dark phase. Two other groups of rats (N = 6 for each group) were decapitated at 9:00 and 21:00 h and striata were dissected for dopamine uptake and release assays. The inhibition of uptake and release of [3H]-dopamine were higher at 9:00 than at 21:00 h, suggesting that uptake inhibition and the release properties of FCF undergo daily variation. These data suggest that the circadian time-dependent effects of FCF might be related to a higher susceptibility of dopamine presynaptic terminals to the action of FCF during the light phase which corresponds to the rats' resting period

The carotid body of the spontaneous insulin-dependent diabetic rat

The carotid bodies from adult spontaneous insulin-dependent diabetic rats (strain BB/S) were perfusion-fixed at normal arterial blood pressure with 3% phosphate-buffered glutaraldehyde and compared with the organs from control rats (strain BB/Sc) prepared in the same way. Serial 5-µm sections were cut, stained, and using an interactive image analysis system, were analysed to determine the volumes of the carotid body and its vascular and extravascular compartments. There was no evidence of systemic arterial disease in the carotid stem arteries in either group of animals, and the microvasculature of the organs appeared normal by light microscopy. The volume of the carotid body was unchanged 3 months after the onset of diabetes but was increased at 6 months. The total vascular volume of the organ was unchanged, but the volume of the small vessels (5-12 µm) was increased. In the control group the small vessels comprised 5% of the total volume of the carotid body, or about 44% of the vascular compartment. The percentage of small vessels increased at 3 months in the diabetic group, but had returned to normal at 6 months. The extravascular volume followed the same pattern as the total carotid body volume and so did not change appreciably when expressed as a percentage of the total volume of the organ. The increase in size of the carotid body in diabetic rats is due, therefore, to an augmented extravascular volume. In one diabetic specimen the carotid sinus nerve showed signs of diabetic neuropathy, axonal swelling and intramyelinic oedema. The clinical implications of these results are discussed.

Nitric oxide, cholesterol oxides and endothelium-dependent vasodilation in plasma of patients with essential hypertension

The objective of the present study was to identify disturbances of nitric oxide radical (·NO) metabolism and the formation of cholesterol oxidation products in human essential hypertension. The concentrations of·NO derivatives (nitrite, nitrate, S-nitrosothiols and nitrotyrosine), water and lipid-soluble antioxidants and cholesterol oxides were measured in plasma of 11 patients with mild essential hypertension (H: 57.8 ± 9.7 years; blood pressure, 148.3 ± 24.8/90.8 ± 10.2 mmHg) and in 11 healthy subjects (N: 48.4 ± 7.0 years; blood pressure, 119.4 ± 9.4/75.0 ± 8.0 mmHg).Nitrite, nitrate and S-nitrosothiols were measured by chemiluminescence and nitrotyrosine was determined by ELISA. Antioxidants were determined by reverse-phase HPLC and cholesterol oxides by gas chromatography. Hypertensive patients had reduced endothelium-dependent vasodilation in response to reactive hyperemia (H: 9.3 and N: 15.1% increase of diameter 90 s after hyperemia), and lower levels of ascorbate (H: 29.2 ± 26.0, N: 54.2 ± 24.9 µM), urate (H: 108.5 ± 18.9, N: 156.4 ± 26.3 µM), ß-carotene (H: 1.1 ± 0.8, N: 2.5 ± 1.2 nmol/mg cholesterol), and lycopene (H: 0.4 ± 0.2, N: 0.7 ± 0.2 nmol/mg cholesterol), in plasma, compared to normotensive subjects. The content of 7-ketocholesterol, 5alpha-cholestane-3ß,5,6ß-triol and 5,6alpha-epoxy-5alpha-cholestan-3alpha-ol in LDL, and the concentration of endothelin-1 (H: 0.9 ± 0.2, N: 0.7 ± 0.1 ng/ml) in plasma were increased in hypertensive patients. No differences were found for ·NO derivatives between groups. These data suggest that an increase in cholesterol oxidation is associated with endothelium dysfunction in essential hypertension and oxidative stress, although ·NO metabolite levels in plasma are not modified in the presence of elevated cholesterol oxides.

The role of complement in the modulation by fluid-phase IgG of the production of reactive oxygen species by polymorphonuclear leukocytes stimulated with IgG immune complexes

The production of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMN) can be induced by immune complexes and is an important component of phagocytosis in the killing of microorganisms, but can also be involved in inflammatory reactions when immune complexes are deposited in tissues. We have observed that fluid-phase IgG can inhibit the generation of ROS by rabbit PMN stimulated with precipitated immune complexes of IgG (ICIgG) in a dose-dependent manner, acting as a modulatory factor in the range of physiological IgG concentrations. This inhibitory effect is compatible with the known affinity (Kd) of monomeric IgG for the receptors involved (FcRII and FcRIII). The presence of complement components in the immune complexes results in a higher stimulation of ROS production. In this case, however, there is no inhibition by fluid-phase IgG. The effect of complement is strongly dependent on the presence of divalent cations (Ca2+ or Mg2+) in the medium, whereas the stimulation of ICIgG (without complement) does not depend on these cations. We have obtained some evidence indicating that iC3b should be the component involved in the effect of complement through interaction with the CR3 receptor. The absence of the inhibitory effect of fluid-phase IgG in ROS production when complement is present in the immune complex shows that complement may be important in vivo not only in the production of chemotactic factors for PMN, but also in the next phase of the process, i.e., the generation of ROS.

Pressure-induced dissociation of casein micelles: size distribution and effect of temperature

Pressure-induced dissociation of a turbid solution of casein micelles was studied in situ in static and dynamic light scattering experiments. We show that at high pressure casein micelles decompose into small fragments comparable in size to casein monomers. At intermediate pressure we observe particles measuring 15 to 20 nm in diameter. The stability against pressure dissociation increased with temperature, suggesting enhanced hydrophobic contacts. The pressure transition curves are biphasic, compatible with a temperature (but not pressure)-dependent conformational equilibrium of two micelle species. Our thermodynamic model predicts an increase in structural entropy with temperature.

Differences in pressure and temperature transitions of proteins and polymer gels

Pressure-driven and temperature-driven transitions of two thermoresponsive polymers, poly(N-isopropylacrylamide) (pNIPAM) and poly(N-vinylisobutyramide) (pNVIBA)), in both a soluble linear polymer form and a cross-linked hydro-gel form, were examined by a dynamic light-scattering method and direct microscopic observation, respectively. Their behavior was compared with that of protein systems. Changes in some characteristic parameters in the time-intensity correlation functions of dynamic light-scattering measurement of aqueous solutions of pNIPAM at various pressures and temperatures showed no essential differences during temperature and pressure scanning and, as a whole, the motions of polymers in aqueous solutions were similar in two types of transitions until chain shrinkage occurred. The gels (cross-linked polymer gels) prepared from the thermoresponsive polymers also showed similar volume transitions responding to the pressure and temperature increase. In temperature transitions, however, gels showed drastic volume shrinkage with loss of transparency, while pressure-induced transition showed a slow recovery of transparency while keeping the size, after first transient drastic volume shrinkage with loss of transparency. At a temperature slightly higher than the transition under atmospheric temperature, so-called reentry of the volume change and recovery of the transparency were observed during the pressure-increasing process, which implies much smaller aggregation or non-aggregated collapsed polymer chains in the gel at higher pressures, indicating a certain mechanistic difference of the dehydration processes induced by temperature and pressure.

Are the beneficial cardiovascular effects of simvastatin and metformin also associated with a hormone-dependent mechanism improving insulin sensitivity?

In addition to lipid-lowering and cardiovascular protective actions, statins may have beneficial effects on insulin sensitivity. The objective of the present study was to evaluate the effect of simvastatin therapy on insulin resistance and on leptin, adiponectin, and C-reactive protein (CRP) levels, as compared to metformin, in overweight pre-diabetic subjects. Forty-one subjects with BMI >25 kg/m² and impaired fasting glucose or impaired glucose tolerance were randomized to take simvastatin, 20 mg/day (N = 20) or metformin, 1.7 g/day (N = 21) for 16 weeks. Blood samples for the determination of metabolic, hormonal, and inflammatory parameters were obtained at baseline and after each treatment. After metformin therapy, significant reductions in mean BMI and waist circumference were observed, and after simvastatin treatment LDL and triglyceride levels were significantly reduced. Insulin resistance determined by the homeostasis model assessment decreased only with metformin. Independently of the type of medication, a significant decrease in CRP levels was detected from baseline to the end of the study. CRP showed a mean reduction of 0.12 ± 0.04 mg/dL (P = 0.002) over time. No change in leptin or adiponectin levels was induced by any therapy. The data suggest that a low dose of simvastatin does not affect insulin resistance in overweight pre-diabetic subjects and has no effect on leptin or adiponectin levels. Further studies including a larger sample size, higher doses of statins, and a placebo control group are necessary to confirm the present data.