Effect of cholesterol content on some physical and functional properties of mitochondria isolated from adult rat liver,fetal liver,cholesterol-enriched liver and hepatomas AH-130, 3924A and 5123

The choleterol to phospholipid ratio in mitochodria from hepatomas AH-130, 3924A and 5123 is higher than in the particles isolated from adult or fetal rat livers. Nearly all the cholesterol of hepatoma mitochonda is located in membranes. As in liver mitochondria, in the particles isolated from hepatoma AH-130 there is more cholesterol in the outer than in the inner membrane.In mitochondria from cholesterol-enriched liver and hepatomas, there occur a decrease in extent of hypoosmotic and phosphate-induced sweeling and decrease of conformational linked energy states. The phenomenon is more marked in particles which exhibit higher cholesterol to phospholopid ratios. A statistically significant negative correlation exists between the cholesterol to phospholipid ratio and extent of volume or conformation changes. No significant modifications of these parameters were found in fetal liver mitochondria.Cholesterol content does not influence K⁺ uptake by cholesterol-enriched or hepatoma mitochondria. Nor does cholesterol content affect the respiratory increment related to this uptake. As a consequence of K⁺ uptake, total mitochodrial water exchangeable with tritiated water rises 20% while sucrose-impermeable water rises 42–48% in both adult rat liver and hepatoma AH-130 mitochondria. Absorbance changes linked to ion uptake do not correspond merely to variations in mitochobdrial water content. Water content. Water is apparently not influenced by the cholesterol to phospholipid ratio. However, the ratio is signifacantly correlated to both extent and initial rate of absorbance decrease of mitochondrial suspension during K⁺ uptake. The higher the ratio, the lower the extent and and initial rate of absorbance decrease.     

Effect of cholesterol content on some physical and functional properties of mitochondria isolated from adult rat liver, fetal liver, cholesterol-enriched liver and hepatomas AH-130, 3924A and 5123.

The cholesterol to phospholipid ratio in mitochondria from hepatomas AH-130, 3924A and 5123 is higher than in the particles isolated from adult or fetal rat livers. Nearly all the cholesterol of hepatoma mitochondria is located in membranes. As in liver mitochondria, in the particles isolated from hepatoma AH-130 there is more cholesterol in the outer than in the inner membrane. In mitochondria from cholesterol-enriched liver and hepatomas, there occurs a decrease in extent of hypoosmotic and phosphate-induced swelling and a decrease of conformational changes linked to energy states. The phenomenon is more marked in particles which exhibit higher cholesterol to phospholipid ratios. A statistically significant negative correlation exists between the cholesterol to phospholipid ratio and extent of volume or conformational changes. No significant modifications of these parameters were found in fetal liver mitochondria. Cholesterol content does not influence K+ uptake by cholesterol-enriched or hepatoma mitochondria. Nor does cholesterol content affect the respiratory increment related to this uptake. As a consequence of K+ uptake, total mitochondrial water exchangeable with tritiated water rises 20% while sucrose-impermeable water rises 42-48% in both adult rat liver and hepatoma AH-130 mitochondria. Absorbance changes linked to ion uptake do not correspond merely to variations in mitochondrial water content. Water content is apparently not influenced by the cholesterol to phospholipid ratio. However, the ratio is significantly correlated to both extent and initial rate of absorbance decrease of mitochondrial suspensions during K+ uptake. The higher the ratio, the lower the extent and initial rate of absorbance decrease.     

Morphological and Spatio‐Temporal Mismatches Shape a Neotropical Savanna Plant‐Hummingbird Network

Complex networks of species interactions might be determined by species traits but also by simple chance meetings governed by species abundances. Although the idea that species traits structure mutualistic networks is appealing, most studies have found abundance to be a major structuring mechanism underlying interaction frequencies. With a well‐resolved plant–hummingbird interaction network from the Neotropical savanna in Brazil, we asked whether species morphology, phenology, nectar availability and habitat occupancy and/or abundance best predicted the frequency of interactions. For this, we constructed interaction probability matrices and compared them to the observed plant‐hummingbird matrix through a likelihood approach. Furthermore, a recently proposed modularity algorithm for weighted bipartite networks was employed to evaluate whether these factors also scale‐up to the formation of modules in the network. Interaction frequencies were best predicted by species morphology, phenology and habitat occupancy, while species abundances and nectar availability performed poorly. The plant–hummingbird network was modular, and modules were associated to morphological specialization and habitat occupancy. Our findings highlight the importance of traits as determinants of interaction frequencies and network structure, corroborating the results of a previous study on a plant–hummingbird network from the Brazilian Atlantic Forest. Thus, we propose that traits matter more in tropical plant–hummingbird networks than in less specialized systems. To test the generality of this hypothesis, future research could employ geographic or taxonomic cross‐system comparisons contrasting networks with known differences in level of specialization.     

Antiproliferative effects of several compounds isolated from Amburana cearensis A. C. Smith

Amburana cearensis a common tree found in Northeastern Brazil is widely used in folk medicine. The present work evaluated the cytotoxicity of kaempferol, isokaempferide, amburoside A and protocatechuic acid isolated from the ethanol extract of the trunk bark of A. cearensis. The compounds were tested for their cytotoxicity on the sea urchin egg development, hemolysis assay and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay using tumor cell lines. Isokaempferide and kaempferol, but not amburoside A and protocatechuic acid, inhibited the sea urchin egg development as well as tumor cell lines, but in this assay isokaempferide was more potent than kaempferol. Protocatechuic acid was the only compound able to induce hemolysis of mouse erythrocytes, suggesting that the cytotoxicity of kaempferol and isokaempeferide was not related to membrane damage.     

Changes of CYP1A1, GST, and ALDH3 enzymes in hepatoma cell lines undergoing enhanced lipid peroxidation

Hepatoma cells show alterations in the response to oxidative stress (decreased lipid peroxidation) and in xenobiotic metabolism enzymes (decreased P450, increased GST and ALDH3). This study examined the effect of lipid peroxidation on the expression of the above enzymes in two rat hepatoma cell lines (MH(1)C(1) and 7777). To induce oxidative stress, cells were exposed to arachidonic acid (to increase lipid peroxidation substrate) and/or to beta-naphthoflavone (to increase CYP450), and treated with one dose of iron/histidine. The cells, that were still viable after the challenge, were refed with the culture medium and CYP1A1, GST, and ALDH3 enzymes monitored for 1, 6, 12, and 24 h. Treatments that increased markers indicative of lipid peroxidation are associated with a decrease in enzyme activities, which was permanent for CYP1A1 and transient for the other enzymes. We speculate from these data that aldehydic byproducts of lipid peroxidation may be responsible for these effects. Thus, restoration of lipid peroxidation in hepatoma cells seems to induce a rapid adaptation to oxidative stress, which is achieved by a simultaneous decrease of reactive oxygen species production and an increase in the two main enzymes involved in the removal of the aldehydic products of lipid peroxidation.     

The effect of 4-hydroxy-2, 3-trans-pent-en-1-al and maleylaldehyde on some mitochondrial functions

Low concentrations of HPE and MLA inhibited state 3 respiration of rat liver mitochondria in the presence of different NAD⁺-dependent substrates. MLA appeared to be more active than HPE. High aldehyde concentrations inhibited the state 3 respiration with succinate. The restraint of succinate oxidation by HPE and MLA and of glutamate plus malate oxidation by MLA correlated with the inhibition of succinate and glutamate dehydrogenase activites, respectively. HPE inhibited glutamate dehydrogenase at concentrations higher than those affecting glutamate oxidation. Malate dehydrogenase activity was slightly sensitive to HPE and MLA. Both aldehydes inhibited NADH oxidation by freeze-thawed mitochondria. These results suggest the existence of a site particularly sensitive to aldehydes in the electron transport chain between the specific NAD⁺-linked dehydrogenases and ubiquinone.     

HMG-CoA reductase and PPARα are involved in clofibrate-induced apoptosis in human keratinocytes

Contrasting data have been reported on the effects of clofibrate, a PPARα agonist and hypolipidemic drug. The carcinogenic and anti-apoptotic effects have been demonstrated especially in rodents in both “in vivo” and “in vitro” experiments. In contrast, in rat and human hepatoma cell lines, several reports have shown its concentration-dependent pro-apoptotic effect. No epidemiological data exist about its carcinogenetic effect in man. This study shows that clofibrate also induced apoptosis in a human non-tumour cell line, NCTC 2544, which shares the characteristic of proliferation with tumour cells. Both HMG-CoA reductase and PPARα were found to be involved in the signal transduction pathway inducing apoptosis, the former being the principal target: HMG-CoA reductase decreased and PPARα increased. Changes in HMG-CoA reductase expression caused activation of parameters leading to apoptosis via the mitochondria pathway. Clofibrate must be considered a pro-apoptotic molecule at concentrations of 0.25 mM and above: the effect is exercised not only on tumour cells but also on normal human proliferating cells. Clofibrate should thus be regarded as a potential drug to reduce the number of proliferating cells in pathological conditions.     

Impact of nightshift work on overweight and abdominal obesity among workers of a poultry processing plant in southern Brazil

The authors examined the associations of shiftwork with overweight and abdominal obesity through a cross-sectional study of 1206 employees 18 to 50 yrs of age who were working on a production line in a poultry processing plant. Night-shift workers (n = 800) were considered exposed, whereas day shiftworkers (n = 406) were considered nonexposed. Overweight was defined as a body mass index ≥ 25 kg/m(2) and abdominal obesity as a waist circumference ≥ 88 cm in women and ≥ 102 cm in men. The mean age of the workers was 30.5 yrs (standard deviation = 8.7 yrs), and 65.2% were women. Nightshift workers compared to dayshift workers showed higher prevalences of overweight (42.2% vs. 34.3%; p=?.020) and abdominal obesity (24.9% vs. 19.5%; p =?.037). After adjusting for sociodemographics, parental overweight status, behavioral characteristics, and sleep characteristics, including hours of sleep, the prevalence ratios for overweight and abdominal obesity were 1.27 (95% confidence interval [ CI]: 1.00-1.61) and 1.45 (95% CI: 1.10-1.92), respectively, for the nightshift workers compared to the dayshift workers. A consistent finding in our study was the independent contribution of night shiftwork to overweight and abdominal obesity among Brazilian workers. Further studies are needed to understand the biological mechanisms involved and the complex behavioral and social adaptations experienced by night-shift workers.     

Theoretical study of the NMR chemical shift of Xe in supercritical condition

In this work we investigate the level of theory necessary for reproducing the non-linear variation of the ¹²⁹Xe nuclear magnetic resonance (NMR) chemical shift with the density of Xe in supercritical conditions. In detail we study how the ¹²⁹Xe chemical shift depends under supercritical conditions on electron correlation, relativistic and many-body effects. The latter are included using a sequential-QM/MM methodology, in which a classical MD simulation is performed first and the chemical shift is then obtained as an average of quantum calculations of 250 MD snapshots conformations carried out for Xe _n clusters (n =?2 ? 8 depending on the density). The analysis of the relativistic effects is made at the level of 4-component Hartree-Fock calculations (4c-HF) and electron correlation effects are considered using second order Møller-Plesset perturbation theory (MP2). To simplify the calculations of the relativistic and electron correlation effects we adopted an additive scheme, where the calculations on the Xe _n clusters are carried out at the non-relativistic Hartree-Fock (HF) level, while electron correlation and relativistic corrections are added for all the pairs of Xe atoms in the clusters. Using this approach we obtain very good agreement with the experimental data, showing that the chemical shift of ¹²⁹Xe in supercritical conditions is very well described by cluster calculations at the HF level, with small contributions from relativistic and electron correlation effects.     

Importance of inverse correlation between ALDH3A1 and PPARγ in tumor cells and tissue regeneration

Aldehyde dehydrogenase (ALDH) enzymes are involved in maintaining cellular homeostasis by metabolizing both endogenous and exogenous reactive aldehydes. They modulate several cell functions including proliferation, differentiation, survival as well as cellular response to oxidative stress. We previously reported that ALDH3A1 expression is inversely correlated with the activation of PPARs (Peroxisome Proliferators-Activated Receptors), a category of orphan nuclear hormone receptors, in both rat and human cells. PPARγ is involved in cell proliferation. In this study, we have used PPARγ transfection and inhibition to examine the relationship between ALDH3A1 and PPARγ and their role as regulators of cell proliferation. Induction of PPARγ in A549 and NCTC 2544 cells by transfection caused a decrease in ALDH3A1 and inhibition of cell proliferation, a result we obtained previously using ligands that induce PPARγ. A reduction of PPARγ expression using siRNA increased ALDH3A1 expression and cell proliferation. In cells induced to proliferate in a model of tissue regeneration, ALDH3A1 expression increased during the period of proliferation, whereas PPARγ expression decreased. In conclusion, through modulation of PPARγ or ALDH3A1, it may be possible to reduce cell proliferation in tumor cells or stimulate cell proliferation in normal cells during tissue regeneration.