Effects of arterial oxygen tension and cardiac output on venous saturation: a mathematical modeling approach

OBJECTIVES: Hemodynamic support is aimed at providing adequate O-2 delivery to the tissues; most interventions target O-2 delivery increase. Mixed venous O-2 saturation is a frequently used parameter to evaluate the adequacy of O-2 delivery. METHODS: We describe a mathematical model to compare the effects of increasing O-2 delivery on venous oxygen saturation through increases in the inspired O-2 fraction versus increases in cardiac output. The model was created based on the lungs, which were divided into shunted and non-shunted areas, and on seven peripheral compartments, each with normal values of perfusion, optimal oxygen consumption, and critical O-2 extraction rate. O-2 delivery was increased by changing the inspired fraction of oxygen from 0.21 to 1.0 in steps of 0.1 under conditions of low (2.0 L.min(-1)) or normal (6.5 L.min(-1)) cardiac output. The same O-2 delivery values were also obtained by maintaining a fixed O-2 inspired fraction value of 0.21 while changing cardiac output. RESULTS: Venous oxygen saturation was higher when produced through increases in inspired O-2 fraction versus increases in cardiac output, even at the same O-2 delivery and consumption values. Specifically, at high inspired O-2 fractions, the measured O-2 saturation values failed to detect conditions of low oxygen supply. CONCLUSIONS: The mode of O-2 delivery optimization, specifically increases in the fraction of inspired oxygen versus increases in cardiac output, can compromise the capability of the "venous O-2 saturation" parameter to measure the adequacy of oxygen supply. Consequently, venous saturation at high inspired O-2 fractions should be interpreted with caution.

Anti-Atherogenic Effects of a Phenol-Rich Fraction from Brazilian Red Wine (Vitis labrusca L.) in Hypercholesterolemic Low-Density Lipoprotein Receptor Knockout Mice

Moderate wine intake (i.e., 1-2 glasses of wine a day) is associated with a reduced risk of morbidity and mortality from cardiovascular disease. The aim of this study was to evaluate the anti-atherosclerotic effects of a nonalcoholic ethyl acetate fraction (EAF) from a South Brazilian red wine obtained from Vitis labrusca grapes. Experiments were carried out on low-density lipoprotein (LDL) receptor knockout (LDLr-/-) mice, which were subjected to a hypercholesterolemic diet and treated with doses of EAF (3, 10, and 30 mg/kg) for 12 weeks. At the end of the treatment, the level of plasma lipids, the vascular reactivity, and the atherosclerotic lesions were evaluated. Our results demonstrated that the treatment with EAF at 3 mg/kg significantly decreased total cholesterol, triglycerides, and LDL plus very low-density lipoprotein levels compared with control hypercholesterolemic mice. The treatment of mice with EAF at 3 mg/kg also preserved the vasodilatation induced by acetylcholine on isolated thoracic aorta from hypercholesterolemic LDLr-/- mice. This result is in agreement with the degree of lipid deposit on arteries. Taken together, the results show for the first time that the lowest concentration of an EAF obtained from a red wine produced in southern Brazil significantly reduced the progression of atherosclerosis in mice.

Expression of soluble and functional full-length human matrix metalloproteinase-2 in Escherichia coli

Characterization of the matrix metalloproteinase-2 (MMP-2) substrates and understanding of its function remain difficult because up to date preparations containing minor amounts of other eukaryotic proteins that are co-purified with MMP-2 are still used. In this work, the expression of a soluble and functional full-length recombinant human MMP-2 (rhMMP-2) in the cytoplasm of Escherichia coli is reported, and the purification of this metalloproteinase is described. Culture of this bacterium at 18 degrees C culminated in maintenance of the soluble and functional rhMMP-2 in the soluble fraction of the E. coli lysate and its purification by affinity with gelatin-sepharose yielded approximately 0.12 mg/L of medium. Western Blotting and zymographic analysis revealed that the most abundant form was the 72-kDa MMP-2, but some gelatinolytic bands corresponding to proteins with lower molecular weight were also detected. The obtained rhMMP-2 was demonstrated to be functional in a gelatinolytic fluorimetric assay, suggesting that the purified rhMMP-2 was correctly folded. The method described here involves fewer steps, is less expensive, and is less prone to contamination with other proteinases and MMP inhibitors as compared to expression of rhMMP-2 in eukaryotic tissue culture. This protocol will facilitate the use of the full-length rhMMP-2 expressed in bacteria and will certainly help researchers to acquire new knowledge about the substrates and biological activities of this important proteinase. (C) 2011 Elsevier B.V. All rights reserved.

A multiple time scale survival model with a cure fraction

Many recent survival studies propose modeling data with a cure fraction, i.e., data in which part of the population is not susceptible to the event of interest. This event may occur more than once for the same individual (recurrent event). We then have a scenario of recurrent event data in the presence of a cure fraction, which may appear in various areas such as oncology, finance, industries, among others. This paper proposes a multiple time scale survival model to analyze recurrent events using a cure fraction. The objective is analyzing the efficiency of certain interventions so that the studied event will not happen again in terms of covariates and censoring. All estimates were obtained using a sampling-based approach, which allows information to be input beforehand with lower computational effort. Simulations were done based on a clinical scenario in order to observe some frequentist properties of the estimation procedure in the presence of small and moderate sample sizes. An application of a well-known set of real mammary tumor data is provided.

The polysaccharide fraction of Propionibacterium acnes modulates the development of experimental focal segmental glomerulosclerosis

The pathogenesis of focal segmental glomerulosclerosis (FSGS) appears to be associated with type-2 cytokines and podocyte dysfunction. In this study, we tested the hypothesis that immunization with the polysaccharide fraction of Propionibacterium acnes (PS), a pro-Th1 agonist, may subvert the type-2 profile and protect podocytes from adriamycin-induced glomerulosclerosis. Adriamycin injection resulted in albuminuria and increased serum creatinine in association with loss of glomerular podocin and podoplanin expression, which is consistent with podocyte dysfunction. Renal tissue analysis revealed the expression of transcripts for GATA3 and fibrogenic-related proteins, such as TGF-beta, tissue inhibitor of metalloproteinase-1 (TIMP-1) and metalloproteinase 9 (MMP9). In association with the expression of fibrogenic transcripts, we observed peri-glomerular expression of a-smooth muscle actin (alpha-SMA), indicating epithelial-to-mesenchymal transition, and increased expression of proliferating cell nuclear antigen (PCNA) in tubular cells, suggesting intense proliferative activity. Previous immunization with PS inhibited albuminuria and serum creatinine in association with the preservation of podocyte proteins and inhibition of fibrogenic transcripts and the expression of alpha-SMA and PCNA proteins. Tissue analysis also revealed that PS treatment induced expression of mRNA for GD3 synthase, which is a glycosiltransferase related to the synthesis of GD3, a ganglioside associated with podocyte physiology. In addition, PS treatment inhibited the influx of inflammatory CD8(pos) and CD11b(pos) cells to kidney tissue. Finally, PS treatment on day 4 post-ADM, a period when proteinuria was already established, was able to improve renal function. Thus, we demonstrate that the PS fraction of P. acnes can inhibit FSGS pathogenesis, suggesting that immunomodulation can represent an alternative approach for disease management. (C) 2011 Elsevier GmbH. All rights reserved.

Influence of low-level laser associated with osteogenic proteins recombinant human BMP-2 and Hevea brasiliensis on bone repair in Wistar rats

This study analyzed the newly formed bone tissue after application of recombinant human BMP-2 (rhBMP-2) and P-1 (extracted from Hevea brasiliensis) proteins, 2 weeks after the creation of a critical bone defect in male Wistar rats treated or not with a low-intensity laser (GaAlAs 780 nm, 60 mW of power, and energy density dose of 30 J/cm2). The animals were divided into two major groups: (1) bone defect plus low-intensity laser treatment and (2) bone defect without laser irradiation. The following subgroups were also analyzed: (a) 5 mu g of pure rhBMP-2; (b) 5 mu g of pure P-1 fraction; (c) 5 mu g of rhBMP-2/monoolein gel; (d) 5 mu g of P-1 fraction/monoolein gel; (e) pure monoolein gel. Comparisons of the groups receiving laser treatment with those that did not receive laser irradiation show differences in the areas of new bone tissue. The group treated with 5 mu g of rhBMP-2 and laser irradiation was not significantly different (P >0.05) than the nonirradiated group that received the same treatment. The irradiated, rhBMP-2/monoolein gel treatment group showed a lower area of bone formation than the nonirradiated, rhBMP-2/gel monoolein treatment group (P < 0.001). The area of new bone tissue in the other nonirradiated and irradiated groups was not significantly different (P > 0.05). Furthermore, the group that received the 5 mu g of rhBMP-2 application showed the greatest bone formation. We conclude that the laser treatment did not interfere with the area of new bone tissue growth and that the greatest stimulus for bone formation involved application of the rhBMP-2 protein. Microsc. Res. Tech. 2011. (c) 2011 Wiley Periodicals, Inc.

Bioassay guided purification of the antimicrobial fraction of a Brazilian propolis from Bahia state

Abstract Background Brazilian propolis type 6 (Atlantic forest, Bahia) is distinct from the other types of propolis especially due to absence of flavonoids and presence of other non-polar, long chain compounds, but presenting good in vitro and in vivo antimicrobial activity. Several authors have suggested that fatty acids found in this propolis might be responsible for its antimicrobial activity; however, so far no evidence concerning this finding has been reported in the literature. The goals of this study were to evaluate the antibacterial activity of the main pure fatty acids in the ethanolic extract and fractions and elucidate the chemical nature of the bioactive compounds isolated from Brazilian propolis type 6. Methods Brazilian propolis type 6 ethanolic extract (EEP), hexane fraction (H-Fr), major fatty acids, and isolated sub-fractions were analyzed using high performance liquid chromatography (HPLC), high resolution gas chromatography with flame ionization detection (HRGC-FID), and gas chromatography-mass spectrometry (GC-MS). Three sub-fractions of H-Fr were obtained through preparative HPLC. Antimicrobial activity of EEP, H-Fr, sub-fractions, and fatty acids were tested against Staphyloccus aureus ATCC 25923 and Streptococcus mutans Ingbritt 1600 using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results EEP and H-Fr inhibited the growth of the microorganisms tested; nevertheless, no antimicrobial activity was found for the major fatty acids. The three sub-fractions (1, 2, and 3) were isolated from H-Fr by preparative HPLC and only sub-fraction 1 showed antimicrobial activity. Conclusion a) The major fatty acids tested were not responsible for the antimicrobial activity of propolis type 6; b) Sub-fraction 1, belonging to the benzophenone class, was responsible for the antimicrobial activity observed in the present study. The identification of the bioactive compound will improve the development of more efficient uses of this natural product.