Mathematical simulation parameters for drying of cassava starch pellets

Based on experimental tests, it was obtained the equations for drying, equilibrium moisture content, latent heat of vaporization of water contained in the product and the equation of specific heat of cassava starch pellets, essential parameters for realizing modeling and mathematical simulation of mechanical drying of cassava starch for a new technique proposed, consisting of preformed by pelleting and subsequent artificial drying of starch pellets. Drying tests were conducted in an experimental chamber by varying the air temperature, relative humidity, air velocity and product load. The specific heat of starch was determined by differential scanning calorimetry. The generated equations were validated through regression analysis, finding an appropriate correlation of the data, which indicates that by using these equations, can accurately model and simulate the drying process of cassava starch pellets.

Influence of distal ileum exclusion on hepatic and renal functions in presence of extrahepatic cholestasis

OBJECTIVE: To verify whether the ileal exclusion interferes with liver and kidney functional changes secondary to extrahepatic cholestasis.METHODS: We studied 24 rats, divided into three groups with eight individuals each: Group 1 (control), Group 2 (ligation of the hepatic duct combined with internal biliary drainage), and Group 3 (bile duct ligation combined with internal biliary drainage and exclusion of the terminal ileum). Animals in Group 1 (control) underwent sham laparotomy. The animals of groups 2 and 3 underwent ligation and section of the hepatic duct and were kept in cholestasis for four weeks. Next, they underwent an internal biliary bypass. In Group 3, besides the biliary-enteric bypass, we associated the exclusion of the last ten centimeters of the terminal ileum and carried out an ileocolic anastomosis. After four weeks of monitoring, blood was collected from all animals of the three groups for liver and kidney biochemical evaluation (albumin, ALT, AST, direct and indirect bilirubin, alkaline phosphatase, cGT, creatinine and urea).RESULTS: there were increased values of ALT, AST, direct bilirubin, cGT, creatinine and urea in rats from Group 3 (p < 0.05).CONCLUSION: ileal exclusion worsened liver and kidney functions in the murine model of extrahepatic cholestasis, being disadvantageous as therapeutic procedure for cholestatic disorders.

Effects of fasting and refeeding on the metabolic functions of the turtle Kinosternon scorpioides (Linnaeus, 1766) raised in captivity

The metabolic responses of adult and young freshwater Kinosternon scorpioides turtles raised in captivity were evaluated. Two experiments were performed: a) blood metabolite changes caused by food deprivation, and b) liver and muscle glycogen and total lipid differences after fasting and refeeding. Blood glucose concentration of young animals was susceptible to food deprivation. In both groups this metabolite decreased after 30 days of fasting. Feeding for 15 days did not recover blood glucose. Total seric proteins were not affected by food deprivation. Fasting decreased blood urea nitrogen and the highest difference was found around 30 days. Uric acid increased in young animals after 60 days of fasting. Triacylglicerol decreased after 15 days of fasting and refeeding for 15 days recovered the pre-fasting levels. Free fatty acid plasma tended to increase around 15 days of fasting. Liver glycogen decreased at day 15 of fasting, being stable thereafter while muscle glycogen decreased at a slower rate. Total liver lipid stabilized after 30 days and then decreased 70% after 60 days of fasting. Muscle lipids remained stable throughout fasting. It could be concluded that fasting of Kinosternon scorpioides led to metabolic adaptations similar to the one reported from reptiles and fish.

Long term dietary deficiency in steers: vital functions and T3 and IGF-1 relationships

To evaluate the influence of diets with different degrees of energy deficiency on the hormonal profile and vital functions, 12 steers were randomly distributed into 3 groups of 4 animals. For 140 days, each group received (G1) a diet to promote a weight gain of 900gr/day (17.7 Mcal/d DE and 13% CP), (G2) 80% of the maintenance requirements (5.8 Mcal/d DE and 7% CP), or (G3) 60% of the maintenance requirements (4.7 Mcal/d DE and 5% CP). In G2 and G3, the energy deficit caused a marked decrease in the heart rate and respiratory rate and a reduction in the blood levels of Insulin like growth factor-1 (IGF-1) and triiodothyronine (T3). The decrease in heart rate, respiratory movement and, to a lesser extent, reduction of the rectal temperature, reflected the low status of energy and was negatively impacted by the low levels of T3. There was a strong correlation between the hormones T3 and IGF-1 (r=0.833). There were also strong correlations between T3 and HR (r=0.701), T3 and RR (r=0.632), IGF-1 and HR (r=0.731), and IGF-1 and RR (r=0.679). There were intermediate correlations between T3 and TºC (r=0.484), T3 and insulin (r=0.506), IGF-1 and insulin (r=0.517), and IGF-1 and TºC (r=0.548). This study showed the influence of a long period of providing an energy-deficient diet on animal performance, correlating hormonal status and vital functions in growing cattle. The results indicated that the evaluated parameters represent an important tool for the early detection of dietary deficiency.

Gas-solid two-phase flow in the riser of circulating fluidized beds: mathematical modelling and numerical simulation

A mathematical model is developed for gas-solids flows in circulating fluidized beds. An Eulerian formulation is followed based on the two-fluids model approach where both the fluid and the particulate phases are treated as a continuum. The physical modelling is discussed, including the formulation of boundary conditions and the description of the numerical methodology. Results of numerical simulation are presented and discussed. The model is validated through comparison to experiment, and simulation is performed to investigate the effects on the flow hydrodynamics of the solids viscosity.

Decreased spermatogenic and androgenic testicular functions in adult rats submitted to immobilization-induced stress from prepuberty

We investigated whether chronic stress applied from prepuberty to full sexual maturity interferes with spermatogenic and androgenic testicular functions. Male Wistar rats (40 days old) were immobilized 6 h a day for 60 days. Following immobilization, plasma concentrations of corticosterone and prolactin increased 135% and 48%, respectively, while plasma luteinizing hormone and testosterone presented a significant decrease of 29% and 37%, respectively. Plasma concentration of follicle-stimulating hormone was not altered in stressed rats. Chronic stress reduced the amount of mature spermatids in the testis by 16% and the spermatozoon concentration in the cauda epididymidis by 32%. A 17% reduction in weight and a 42% decrease in DNA content were observed in the seminal vesicle of immobilized rats but not in its fructose content. The growth and secretory activity of the ventral prostate were not altered by chronic stress.

Carbon monoxide: from toxin to endogenous modulator of cardiovascular functions

Carbon monoxide (CO) is a pollutant commonly recognized for its toxicological attributes, including CNS and cardiovascular effects. But CO is also formed endogenously in mammalian tissues. Endogenously formed CO normally arises from heme degradation in a reaction catalyzed by heme oxygenase. While inhibitors of endogenous CO production can raise arterial pressure, heme loading can enhance CO production and lead to vasodepression. Both central and peripheral tissues possess heme oxygenases and generate CO from heme, but the inability of heme substrate to cross the blood brain barrier suggests the CNS heme-heme oxygenase-CO system may be independent of the periphery. In the CNS, CO apparently acts in the nucleus tractus solitarii (NTS) promoting changes in glutamatergic neurotransmission and lowering blood pressure. At the periphery, the heme-heme oxygenase-CO system can affect cardiovascular functions in a two-fold manner; specifically: 1) heme-derived CO generated within vascular smooth muscle (VSM) can promote vasodilation, but 2) its actions on the endothelium apparently can promote vasoconstriction. Thus, it seems reasonable that the CNS-, VSM- and endothelial-dependent actions of the heme-heme oxygenase-CO system may all affect cardiac output and vascular resistance, and subsequently blood pressure.

Heparan sulfates and heparins: similar compounds performing the same functions in vertebrates and invertebrates?

The distribution and structure of heparan sulfate and heparin are briefly reviewed. Heparan sulfate is a ubiquitous compound of animal cells whose structure has been maintained throughout evolution, showing an enormous variability regarding the relative amounts of its disaccharide units. Heparin, on the other hand, is present only in a few tissues and species of the animal kingdom and in the form of granules inside organelles in the cytoplasm of special cells. Thus, the distribution as well as the main structural features of the molecule, including its main disaccharide unit, have been maintained through evolution. These and other studies led to the proposal that heparan sulfate may be involved in the cell-cell recognition phenomena and control of cell growth, whereas heparin may be involved in defense mechanisms against bacteria and other foreign materials. All indications obtained thus far suggest that these molecules perform the same functions in vertebrates and invertebrates.

Functions of the extracellular matrix and matrix degrading proteases during tumor progression

Cell interactions with extracellular matrices are important to pathological changes that occur during cell transformation and tumorigenesis. Several extracellular matrix proteins including fibronectin, thrombospondin-1, laminin, SPARC, and osteopontin have been suggested to modulate tumor phenotype by affecting cell migration, survival, or angiogenesis. Likewise, proteases including the matrix metalloproteinases (MMPs) are understood to not only facilitate migration of cells by degradation of matrices, but also to affect tumor formation and growth. We have recently demonstrated an in vivo role for the RGD-containing protein, osteopontin, during tumor progression, and found evidence for distinct functions in the host versus the tumor cells. Because of the compartmentalization and temporal regulation of MMP expression, it is likely that MMPs may also function dually in host stroma and the tumor cell. In addition, an important function of proteases appears to be not only degradation, but also cleavage of matrix proteins to generate functionally distinct fragments based on receptor binding, biological activity, or regulation of growth factors.

Alternative mitochondrial functions in cell physiopathology: beyond ATP production

It is well known that mitochondria are the main site for ATP generation within most tissues. However, mitochondria also participate in a surprising number of alternative activities, including intracellular Ca2+ regulation, thermogenesis and the control of apoptosis. In addition, mitochondria are the main cellular generators of reactive oxygen species, and may trigger necrotic cell death under conditions of oxidative stress. This review concentrates on these alternative mitochondrial functions, and their role in cell physiopathology.

A mathematical framework for group analysis of von Willebrand factor multimeric composition following luminography

The objective of the present study was to establish a method for quantitative analysis of von Willebrand factor (vWF) multimeric composition using a mathematical framework based on curve fitting. Plasma vWF multimers from 15 healthy subjects and 13 patients with advanced pulmonary vascular disease were analyzed by Western immunoblotting followed by luminography. Quantitative analysis of luminographs was carried out by calculating the relative densities of low, intermediate and high molecular weight fractions using laser densitometry. For each densitometric peak (representing a given fraction of vWF multimers) a mean area value was obtained using data from all group subjects (patients and normal individuals) and plotted against the distance between the peak and IgM (950 kDa). Curves were constructed for each group using nonlinear fitting. Results indicated that highly accurate curves could be obtained for healthy controls and patients, with respective coefficients of determination (r²) of 0.9898 and 0.9778. Differences were observed between patients and normal subjects regarding curve shape, coefficients and the region of highest protein concentration. We conclude that the method provides accurate quantitative information on the composition of vWF multimers and may be useful for comparisons between groups and possibly treatments.

A method for multiple sequential analyses of macrophage functions using a small single cell sample

Microbial pathogens such as bacillus Calmette-Guérin (BCG) induce the activation of macrophages. Activated macrophages can be characterized by the increased production of reactive oxygen and nitrogen metabolites, generated via NADPH oxidase and inducible nitric oxide synthase, respectively, and by the increased expression of major histocompatibility complex class II molecules (MHC II). Multiple microassays have been developed to measure these parameters. Usually each assay requires 2-5 x 10(5) cells per well. In some experimental conditions the number of cells is the limiting factor for the phenotypic characterization of macrophages. Here we describe a method whereby this limitation can be circumvented. Using a single 96-well microassay and a very small number of peritoneal cells obtained from C3H/HePas mice, containing as little as <=2 x 10(5) macrophages per well, we determined sequentially the oxidative burst (H2O2), nitric oxide production and MHC II (IAk) expression of BCG-activated macrophages. More specifically, with 100 µl of cell suspension it was possible to quantify H2O2 release and nitric oxide production after 1 and 48 h, respectively, and IAk expression after 48 h of cell culture. In addition, this microassay is easy to perform, highly reproducible and more economical.

High doses of riboflavin and the elimination of dietary red meat promote the recovery of some motor functions in Parkinson's disease patients

Abnormal riboflavin status in the absence of a dietary deficiency was detected in 31 consecutive outpatients with Parkinson's disease (PD), while the classical determinants of homocysteine levels (B6, folic acid, and B12) were usually within normal limits. In contrast, only 3 of 10 consecutive outpatients with dementia without previous stroke had abnormal riboflavin status. The data for 12 patients who did not complete 6 months of therapy or did not comply with the proposed treatment paradigm were excluded from analysis. Nineteen PD patients (8 males and 11 females, mean age ± SD = 66.2 ± 8.6 years; 3, 3, 2, 5, and 6 patients in Hoehn and Yahr stages I to V) received riboflavin orally (30 mg every 8 h) plus their usual symptomatic medications and all red meat was eliminated from their diet. After 1 month the riboflavin status of the patients was normalized from 106.4 ± 34.9 to 179.2 ± 23 ng/ml (N = 9). Motor capacity was measured by a modification of the scoring system of Hoehn and Yahr, which reports motor capacity as percent. All 19 patients who completed 6 months of treatment showed improved motor capacity during the first three months and most reached a plateau while 5/19 continued to improve in the 3- to 6-month interval. Their average motor capacity increased from 44 to 71% after 6 months, increasing significantly every month compared with their own pretreatment status (P < 0.001, Wilcoxon signed rank test). Discontinuation of riboflavin for several days did not impair motor capacity and yellowish urine was the only side effect observed. The data show that the proposed treatment improves the clinical condition of PD patients. Riboflavin-sensitive mechanisms involved in PD may include glutathione depletion, cumulative mitochondrial DNA mutations, disturbed mitochondrial protein complexes, and abnormal iron metabolism. More studies are required to identify the mechanisms involved.

Mathematical modeling of electro-rotation spectra of small particles in liquid solutions: Application to human erythrocyte aggregates

Electro-rotation can be used to determine the dielectric properties of cells, as well as to observe dynamic changes in both dielectric and morphological properties. Suspended biological cells and particles respond to alternating-field polarization by moving, deforming or rotating. While in linearly polarized alternating fields the particles are oriented along their axis of highest polarizability, in circularly polarized fields the axis of lowest polarizability aligns perpendicular to the plane of field rotation. Ellipsoidal models for cells are frequently applied, which include, beside sphere-shaped cells, also the limiting cases of rods and disks. Human erythrocyte cells, due to their particular shape, hardly resemble an ellipsoid. The additional effect of rouleaux formation with different numbers of aggregations suggests a model of circular cylinders of variable length. In the present study, the induced dipole moment of short cylinders was calculated and applied to rouleaux of human erythrocytes, which move freely in a suspending conductive medium under the effect of a rotating external field. Electro-rotation torque spectra are calculated for such aggregations of different length. Both the maximum rotation speeds and the peak frequencies of the torque are found to depend clearly on the size of the rouleaux. While the rotation speed grows with rouleaux length, the field frequency nup is lowest for the largest cell aggregations where the torque shows a maximum.