Sex-specific metabolic adaptations in transgenic mice overexpressing cytochrome b5 reductase-3

Cytochrome b5 reductase 3 (CYB5R3) activates respiratory metabolism in cellular systems and exerts a prolongevity action in transgenic mice overexpressing this enzyme, mimicking some of the beneficial effects of calorie restriction. The aim of our study was to investigate the role of sex on metabolic adaptations elicited by CYB5R3 overexpression, and how key markers related with mitochondrial function are modulated in skeletal muscle, one of the major contributors to resting energy expenditure. Young CYB5R3 transgenic mice did not exhibit the striking adaptations in carbon metabolism previously detected in older animals. CYB5R3 was efficiently overexpressed and targeted to mitochondria in skeletal muscle from transgenic mice regardless sex. Overexpression significantly elevated NADH in both sexes, although differences were not statistically significant for NAD+, and increased the abundance of cytochrome c and the fission protein DRP-1 in females but not in males. Moreover, while mitochondrial biogenesis and function markers (as TFAM, NRF-1 and cleaved SIRT3) were markedly upregulated by CYB5R3 overexpression in females, a downregulation was observed in males. Ultrastructural changes were also highlighted, with an increase in the number of mitochondria per surface unit, and in the size of intermyofibrillar mitochondria in transgenic females compared with their wild-type controls. Our results support that CYB5R3 overexpression upregulates markers consistent with enhanced mitochondrial biogenesis and function, and increases mitochondrial abundance in skeletal muscle, producing most of these potentially beneficial actions in females.

Mitochondrial dynamics maintain muscle stem cell regenerative competence throughout adult life by regulating metabolism and mitophagy

Skeletal muscle regeneration depends on the correct expansion of resident quiescent stem cells (satellite cells), a process that becomes less efficient with aging. Here, we show that mitochondrial dynamics are essential for the successful regenerative capacity of satellite cells. The loss of mitochondrial fission in satellite cells-due to aging or genetic impairment-deregulates the mitochondrial electron transport chain (ETC), leading to inefficient oxidative phosphorylation (OXPHOS) metabolism and mitophagy and increased oxidative stress. This state results in muscle regenerative failure, which is caused by the reduced proliferation and functional loss of satellite cells. Regenerative functions can be restored in fission-impaired or aged satellite cells by the re-establishment of mitochondrial dynamics (by activating fission or preventing fusion), OXPHOS, or mitophagy. Thus, mitochondrial shape and physical networking controls stem cell regenerative functions by regulating metabolism and proteostasis. As mitochondrial fission occurs less frequently in the satellite cells in older humans, our findings have implications for regeneration therapies in sarcopenia.

CYB5R3 overexpression preserves skeletal muscle mitochondria and autophagic signaling in aged transgenic mice

Cytochrome b₅ reductase 3 (CYB5R3) overexpression activates respiratory metabolism and exerts prolongevity effects in transgenic mice, mimicking some of the salutary effects of calorie restriction. The aim of our study was to understand how CYB5R3 overexpression targets key pathways that modulate the rate of aging in skeletal muscle, a postmitotic tissue with a greater contribution to resting energy expenditure. Mitochondrial function, autophagy and mitophagy markers were evaluated in mouse hind limb skeletal muscles from young-adult (7 months old) and old (24 months old) males of wild-type and CYB5R3-overexpressing genotypes. Ultrastructure of subsarcolemmal and intermyofibrillar mitochondria was studied by electron microscopy in red gastrocnemius. CYB5R3, which was efficiently overexpressed and targeted to skeletal muscle mitochondria regardless of age, increased the abundance of complexes I, II, and IV in old mice and prevented the age-related decrease of complexes I, III, IV, and V and the mitofusin MFN-2. ATP was significantly decreased by aging, which was prevented by CYB5R3 overexpression. Coenzyme Q and the mitochondrial biogenesis markers TFAM and NRF-1 were also significantly diminished by aging, but CYB5R3 overexpression did not protect against these declines. Both aging and CYB5R3 overexpression upregulated SIRT3 and the mitochondrial fission markers FIS1 and DRP-1, although with different outcomes on mitochondrial ultrastructure: old wild-type mice exhibited mitochondrial fragmentation whereas CYB5R3 overexpression increased mitochondrial size in old transgenic mice concomitant with an improvement of autophagic recycling. Interventions aimed at stimulating CYB5R3 could represent a valuable strategy to counteract the deleterious effects of aging in skeletal muscle.

Covalent Immobilization of Antibodies through Tetrazine-TCO Reaction to Improve Sensitivity of ELISA Technique

Enzyme-linked immunosorbent assay (ELISA) is routinely used to detect biomolecules related to several diseases facilitating diagnosis and monitoring of these, as well as the possibility of decreasing their mortality rate. Several methods have been carried out to improve the ELISA sensitivity through antibodies immobilization on the microtiter plates. Here, we have developed a strategy of antibodies immobilization to improve the ELISA sensitivity increasing the antibody density surface through the tetrazine (Tz)-trans-cyclooctene (TCO) reaction. For this, we prepared surfaces with tetrazine groups while the captured antibody was conjugated with TCO. The tetrazine surfaces were prepared in two different ways: (1) from aminated plates and (2) from Tz-BSA-coated plates. The surfaces were evaluated using two sandwich ELISA models, one of them using the low-affinity antibody anti-c-myc as a capture antibody to detect the c-myc-GST-IL8h recombinant protein, and the other one to detect the carcinoembryonic human protein (CEA). The sensitivity increased in both surfaces treated with tetrazine in comparison with the standard unmodified surface. The c-myc-GST-IL8h detection was around 10-fold more sensible on both tetrazine surfaces, while CEA ELISA detection increased 12-fold on surfaces coated with Tz-BSA. In conclusion, we show that it is possible to improve the ELISA sensitivity using this immobilization system, where capture antibodies bond covalently to surfaces.

A 1-Month Ketogenic Diet Increased Mitochondrial Mass in Red Gastrocnemius Muscle, but Not in the Brain or Liver of Middle-Aged Mice

Alterations in markers of mitochondrial content with ketogenic diets (KD) have been reported in tissues of rodents, but morphological quantification of mitochondrial mass using transmission electron microscopy (TEM), the gold standard for mitochondrial quantification, is needed to further validate these findings and look at specific regions of interest within a tissue. In this study, red gastrocnemius muscle, the prefrontal cortex, the hippocampus, and the liver left lobe were used to investigate the impact of a 1-month KD on mitochondrial content in healthy middle-aged mice. The results showed that in red gastrocnemius muscle, the fractional area of both subsarcolemmal (SSM) and intermyofibrillar (IMM) mitochondria was increased, and this was driven by an increase in the number of mitochondria. Mitochondrial fractional area or number was not altered in the liver, prefrontal cortex, or hippocampus following 1 month of a KD. These results demonstrate tissue-specific changes in mitochondrial mass with a short-term KD and highlight the need to study different muscle groups or tissue regions with TEM to thoroughly determine the effects of a KD on mitochondrial mass.

A ketogenic diet impacts markers of mitochondrial mass in a tissue specific manner in aged mice

Declines in mitochondrial mass are thought to be a hallmark of mammalian aging, and a ketogenic diet (KD) may prevent the age-related decreases in mitochondrial content. The objective of this study was to investigate the impact of a KD on markers of mitochondrial mass. Mice were fed an isocaloric control diet (CD) or KD from 12 months of age. Tissues were collected after 1 month and 14 months of intervention, and a panel of commonly used markers of mitochondrial mass (mitochondrial enzyme activities and levels, mitochondrial to nuclear DNA ratio, and cardiolipin content) were measured. Our results showed that a KD stimulated activities of marker mitochondrial enzymes including citrate synthase, Complex I, and Complex IV in hindlimb muscle in aged mice. KD also increased the activity of citrate synthase and prevented an age-related decrease in Complex IV activity in aged brain. No other markers were increased in these tissues. Furthermore, the impacts of a KD on liver and kidney were mixed with no pattern indicative of a change in mitochondrial mass. In conclusion, results of the present study suggest that a KD induces tissue-specific changes in mitochondrial enzyme activities, or structure, rather than global changes in mitochondrial mass across tissues.

Highly enhanced ELISA sensitivity using acetylated chitosan surfaces

Background

The enzyme-linked immunosorbent assay (ELISA), is the most widely used and reliable clinical routine method for the detection of important protein markers in healthcare. Improving ELISAs is crucial for detecting biomolecules relates to health disorders and facilitating diagnosis at the early diseases stages. Several methods have been developed to improve the ELISA sensitivity through immobilization of antibodies on the microtiter plates. We have developed a highly sensitive ELISA strategy based on the preparation of acetylated chitosan surfaces in order to improve the antibodies orientation.

Results

Chitin surfaces were obtained by mixing small quantities of chitosan and acetic anhydride in each well of a microtiter plate. Anti-c-myc 9E10 low affinity antibody fused to ChBD was cloned and expressed in CHO cells obtaining the anti-c-myc-ChBD antibody. We found that anti c-myc-ChBD binds specifically to the chitin surfaces in comparison with anti-c-myc 9E10, which did not. Chitin surface was used to develop a sandwich ELISA to detect the chimeric human protein c-myc-GST-IL8 cloned and expressed in Escherichia coli. The ELISA assays developed on chitin surfaces were 6-fold more sensitive than those performed on standard surface with significant differences (p<0,0001).

Conclusions

As shown here, acetylated chitosan surfaces improve the antibody orientation on the substrate and constitute a suitable method to replace the standard surfaces given the stability over time and the low cost of its preparation.

Mitochondrial adaptations in liver and skeletal muscle to pro-longevity nutritional and genetic interventions: the crosstalk between calorie restriction and CYB5R3 overexpression in transgenic mice

Calorie restriction without malnutrition (CR) is considered as the most effective nongenetic nor pharmacological intervention that promotes healthy aging phenotypes and can extend lifespan in most model organisms. Lifelong CR leads to an increase of cytochrome b₅ reductase-3 (CYB5R3) expression and activity. Overexpression of CYB5R3 confers some of the salutary effects of CR, although the mechanisms involved might be independent because key aspects of energy metabolism and lipid profiles of tissues go in opposite ways. It is thus important to study if some of the metabolic adaptations induced by CR are affected by CYB5R3 overexpression. CYB5R3 overexpression greatly preserved body and liver weight in mice under CR conditions. In liver, CR did not modify mitochondrial abundance, but lead to increased expression of mitofusin Mfn2 and TFAM, a transcription factor involved in mitochondrial biogenesis. These changes were prevented by CYB5R3 overexpression but resulted in a decreased expression of a different mitochondrial biogenesis-related transcription factor, Nrf1. In skeletal muscle, CR strongly increased mitochondrial mass, mitofusin Mfn1, and Nrf1. However, CYB5R3 mice on CR did not show increase in muscle mitochondrial mass, regardless of a clear increase in expression of TFAM and mitochondrial complexes in this tissue. Our results support that CYB5R3 overexpression significantly modifies the metabolic adaptations of mice to CR.

The Impact of Aging, Calorie Restriction and Dietary Fat on Autophagy Markers and Mitochondrial Ultrastructure and Dynamics in Mouse Skeletal Muscle

Loss of skeletal muscle mass and function is a hallmark of aging. This phenomenon has been related to a dysregulation of mitochondrial function and proteostasis. Calorie restriction (CR) has been demonstrated to delay aging and preserve function until late in life, particularly in muscle. Recently, we reported the type of dietary fat plays an important role in determining life span extension with 40% CR in male mice. In these conditions, lard fed mice showed an increased longevity compared to mice fed soybean or fish oils. In this article, we analyze the effect of 40% CR on muscle mitochondrial mass, autophagy, and mitochondrial dynamics markers in mice fed these diets. In CR fed animals, lard preserved muscle fibers structure, mitochondrial ultrastructure, and fission/fusion dynamics and autophagy, not only compared to control animals, but also compared with CR mice fed soybean and fish oils as dietary fat. We focus our discussion on dietary fatty acid saturation degree as an essential predictor of life span extension in CR mice.

Conserved and species-specific molecular denominators in mammalian skeletal muscle aging

Aging is a complex phenomenon involving functional decline in multiple physiological systems. We undertook a comparative analysis of skeletal muscle from four different species, i.e. mice, rats, rhesus monkeys, and humans, at three different representative stages during their lifespan (young, middle, and old) to identify pathways that modulate function and healthspan. Gene expression profiling and computational analysis revealed that pathway complexity increases from mice to humans, and as mammals age, there is predominantly an upregulation of pathways in all species. Two downregulated pathways, the electron transport chain and oxidative phosphorylation, were common among all four species in response to aging. Quantitative PCR, biochemical analysis, mitochondrial DNA measurements, and electron microscopy revealed a conserved age-dependent decrease in mitochondrial content, and a reduction in oxidative phosphorylation complexes in monkeys and humans. Western blot analysis of key proteins in mitochondrial biogenesis discovered that (i) an imbalance toward mitochondrial fusion occurs in aged skeletal muscle and (ii) mitophagy is not overtly affected, presumably leading to the observed accumulation of abnormally large, damaged mitochondria with age. Select transcript expression analysis uncovered that the skeletal inflammatory profile differentially increases with age, but is most pronounced in humans, while increased oxidative stress (as assessed by protein carbonyl adducts and 4-hydroxynonenal) is common among all species. Expression studies also found that there is unique dysregulation of the nutrient sensing pathways among the different species with age. The identification of conserved pathways indicates common molecular mechanisms intrinsic to health and lifespan, whereas the recognition of species-specific pathways emphasizes the importance of human studies for devising optimal therapeutic modalities to slow the aging process.

Aging is a complex phenomenon involving functional declines in multiple physiological systems with the passage of time. Focusing on skeletal muscle, a group of international scientists identified pathways involved in healthspan and by determining global gene expression profiles across species they exposed common mechanisms fundamental to the aging process. Their experimental design involved comparative analysis of mice, rats, rhesus monkeys and humans, targeting three key time points during their respective lifespans. Pathways related to oxidative stress, inflammation and nutrient signaling, which function collectively to affect the quality and status of mitochondria, emerged across all species in an age-influenced manner. The identification of conserved pathways reveals molecular mechanisms intrinsic to health and survival, whereas the unveiling of species-specific pathways emphasizes the importance of human studies for devising optimal therapeutic modalities to slow the aging process.

Effects of Sex, Strain, and Energy Intake on Hallmarks of Aging in Mice

Calorie restriction (CR) is the most robust non-genetic intervention to delay aging. However, there are a number of emerging experimental variables that alter CR responses. We investigated the role of sex, strain, and level of CR on health and survival in mice. CR did not always correlate with lifespan extension, although it consistently improved health across strains and sexes. Transcriptional and metabolomics changes driven by CR in liver indicated anaplerotic filling of the Krebs cycle together with fatty acid fueling of mitochondria. CR prevented age-associated decline in the liver proteostasis network while increasing mitochondrial number, preserving mitochondrial ultrastructure and function with age. Abrogation of mitochondrial function negated life-prolonging effects of CR in yeast and worms. Our data illustrate the complexity of CR in the context of aging, with a clear separation of outcomes related to health and survival, highlighting complexities of translation of CR into human interventions.

Dietary fat composition influences glomerular and proximal convoluted tubule cell structure and autophagic processes in kidneys from calorie-restricted mice

Calorie restriction (CR) has been repeatedly shown to prevent cancer, diabetes, hypertension, and other age‐related diseases in a wide range of animals, including non‐human primates and humans. In rodents, CR also increases lifespan and is a powerful tool for studying the aging process. Recently, it has been reported in mice that dietary fat plays an important role in determining lifespan extension with 40% CR. In these conditions, animals fed lard as dietary fat showed an increased longevity compared with mice fed soybean or fish oils. In this paper, we study the effect of these dietary fats on structural and physiological parameters of kidney from mice maintained on 40% CR for 6 and 18 months. Analyses were performed using quantitative electron microcopy techniques and protein expression in Western blots. CR mitigated most of the analyzed age‐related parameters in kidney, such as glomerular basement membrane thickness, mitochondrial mass in convoluted proximal tubules and autophagic markers in renal homogenates. The lard group showed improved preservation of several renal structures with aging when compared to the other CR diet groups. These results indicate that dietary fat modulates renal structure and function in CR mice and plays an essential role in the determination of health span in rodents.

Mitochondrial permeabilization without caspase activation mediates the increase of basal apoptosis in cells lacking Nrf2

Nuclear factor E2-related factor-2 (Nrf2) is a cap'n'collar/basic leucine zipper (b-ZIP) transcription factor which acts as sensor of oxidative and electrophilic stress. Low levels of Nrf2 predispose cells to chemical carcinogenesis but a dark side of Nrf2 function also exists because its unrestrained activation may allow the survival of potentially dangerous damaged cells. Since Nrf2 inhibition may be of therapeutic interest in cancer, and a decrease of Nrf2 activity may be related with degenerative changes associated with aging, it is important to investigate how the lack of Nrf2 function activates molecular mechanisms mediating cell death. Murine Embryonic Fibroblasts (MEFs) bearing a Nrf2 deletion (Nrf2KO) displayed diminished cellular growth rate and shortened lifespan compared with wild-type MEFs. Basal rates of DNA fragmentation and histone H2A.X phosphorylation were higher in Nrf2KO MEFs, although steady-state levels of reactive oxygen species were not significantly increased. Enhanced rates of apoptotic DNA fragmentation were confirmed in liver and lung tissues from Nrf2KO mice. Apoptosis in Nrf2KO MEFs was associated with a decrease of Bcl-2 but not Bax levels, and with the release of the mitochondrial pro-apoptotic factors cytochrome c and AIF. Procaspase-9 and Apaf-1 were also increased in Nrf2KO MEFs but caspase-3 was not activated. Inhibition of XIAP increased death in Nrf2KO but not in wild-type MEFs. Mitochondrial ultrastructure was also altered in Nrf2KO MEFs. Our results support that Nrf2 deletion produces mitochondrial dysfunction associated with mitochondrial permeabilization, increasing basal apoptosis through a caspase-independent and AIF-dependent pathway.

Mitochondrial ultrastructure and markers of dynamics in hepatocytes from aged, calorie restricted mice fed with different dietary fats

In this paper we analyzed changes in hepatocyte mitochondrial mass and ultrastructure as well as in mitochondrial markers of fission/fusion and biogenesis in mice subjected to 40% calorie restriction (CR) for 18 months versus ad libitum-fed controls. Animals subjected to CR were separated into three groups with different dietary fats: soybean oil (also in controls), fish oil and lard. Therefore, the effect of the dietary fat under CR was studied as well. Our results show that CR induced changes in hepatocyte and mitochondrial size, in the volume fraction occupied by mitochondria, and in the number of mitochondria per hepatocyte. Also, mean number of mitochondrial cristae and lengths were significantly higher in all CR groups compared with controls. Finally, CR had no remarkable effects on the expression levels of fission and fusion protein markers. However, considerable differences in many of these parameters were found when comparing the CR groups, supporting the idea that dietary fat plays a relevant role in the modulation of CR effects in aged mice.

Alterations of ultrastructural and fission/fusion markers in hepatocyte mitochondria from mice following calorie restriction with different dietary fats

We analyzed ultrastructural changes and markers of fission/fusion in hepatocyte mitochondria from mice submitted to 40% calorie restriction (CR) for 6 months versus ad-libitum-fed controls. To study the effects of dietary fat under CR, animals were separated into three CR groups with soybean oil (also in controls), fish oil, and lard. CR induced differential changes in hepatocyte and mitochondrial size, in the volume fraction occupied by mitochondria, and in the number of mitochondria per hepatocyte. The number of cristae per mitochondrion was significantly higher in all CR groups compared with controls. Proteins related to mitochondrial fission (Fis1 and Drp1) increased with CR, but no changes were detected in proteins involved in mitochondrial fusion (Mfn1, Mfn2, and OPA1). Although many of these changes could be attributed to CR regardless of dietary fat, changing membrane lipid composition by different fat sources did modulate the effects of CR on hepatocyte mitochondria.

FaGAST2, a strawberry ripening-related gene, acts together with FaGAST1 to determine cell size of the fruit receptacle

Numerous GAST-like genes have been reported in higher plants, but only one GAST-like gene (FaGAST1) has been described in strawberry so far. Herein, we have identified a novel strawberry FaGAST gene (FaGAST2) whose expression showed an increase throughout fruit receptacle development and ripening, coinciding with those stages where a decrease in fruit expansion processes (G3-W and R-OR stages) occurs. FaGAST2 only shares 31% and 15.7% amino acid and nucleotide sequence homology, respectively, with the previously reported FaGAST1 gene, but both genes contain a signal peptide and a highly conserved GASA domain (cysteine-rich domain) in the C-terminal region. FaGAST2 expression is mainly confined to the fruit receptacle and is not regulated by auxins, GA(3) or ABA, but is regulated by ethephon, an intracellular generator of ethylene. In addition, the expression of the FaGAST2 gene also increased under oxidative stress conditions (H(2)O(2) or Colletotrichum acutatum infection), suggesting a direct role for FaGAST2 protein in reactive oxygen species scavenging during fruit growth and ripening and during fungal infection. On the other hand, the overexpression of the FaGAST2 gene in different transgenic lines analyzed caused a delay in the growth of strawberry plants and a reduction in the size of the transgenic fruits. The histological studies performed in these fruits showed that their parenchymal cells were smaller than those of the controls, supporting a relationship between FaGAST2 gene expression, strawberry fruit cell elongation and fruit size. However, transitory silencing of FaGAST2 gene expression through RNA interference approaches revealed an increase in FaGAST1 expression, but no changes in fruit cell size were observed. These results support the hypothesis that both genes must act synergistically to determine fruit cell size during fruit development and ripening.

Genetic deletion of Nrf2 promotes immortalization and decreases life span of murine embryonic fibroblasts

Nuclear factor E2-related factor-2 (Nrf2) transcription factor is one of the main regulators of intracellular redox balance and a sensor of oxidative and electrophilic stress. Low Nrf2 activity is usually associated with carcinogenesis, but Nrf2 is also considered as an oncogene because it increases survival of transformed cells. Because intracellular redox balance alterations are involved in both senescence and tumorigenesis, we investigated the impact of Nrf2 genetic deletion on cellular immortalization and life span of murine embryonic fibroblasts. We report that Nrf2 genetic deletion promotes immortalization due to an early loss of p53-dependent gene expression. However, compared with control cells, immortalized Nrf2-/- murine embryonic fibroblasts exhibited decreased growth, lower cyclin E levels, and impaired expression of NQO1 and cytochrome b₅ reductase. Moreover, SirT1 was also significantly reduced in immortalized Nrf2-/- murine embryonic fibroblasts, and these cells exhibited shorter life span. Our results underscore the dual role of Nrf2 in protection against carcinogenesis and in the delay of cellular aging.

A strawberry fruit-specific and ripening-related gene codes for a HyPRP protein involved in polyphenol anchoring

A strawberry (Fragaria x ananassa cv. Chandler) fruit cDNA (Fahyprp -cDNA) and its corresponding gene (Fahyprp) showing sequence homology to higher plant hyprp genes have been isolated. The cDNA contains an open reading frame encoding a 16 kDa protein with 156 amino acids. The peptide has an amino-terminal signal sequence, a repetitive proline-rich sequence, and a cysteine-rich carboxy-terminal region homologous to other HyPRP proteins. Northern blot and QRT-PCR analysis have shown that the strawberry transcript is specifically expressed in fruit, not being detected in other plant tissues. " In situ " hybridization and immunolocalization studies have indicated that the Fahyprp gene is strongly expressed in achene sclerenchyma cells, in the vascular and receptacle cells of immature green fruit and in the vascular cells of mature red fruits. The achenes removal from unripe green fruits induced the expression of this Fahyprp gene. This induction was reverted by treatment of deachened fruit with the auxin NAA, supporting the idea that Fahyprp gene expression is regulated by auxins. Furthermore, the HyPRP protein has been localized in parenchymatic cells of immature fruits associated to structures containing condensed tannins. The results are discussed supporting a putative role of this protein in the anchoring of polymeric polyphenols in the strawberry fruit during growth and ripening.

Redox-related peroxidative responses evoked by methyl-jasmonate in axenically cultured aeroponic sunflower (Helianthus annuus L.) seedling roots

Methyl-jasmonate (MeJA) has been proposed to be involved in the evocation of defense reactions, as the oxidative burst in plants, substituting the elicitors or enhancing their effect. 48 h dark- and sterilely cultured (axenic) aeroponic sunflower seedling roots excised and treated with different concentrations of MeJA showed a strong and quick depression of the H(+) efflux rate, 1.80 microM MeJA totally stopping it for approximately 90 min and then reinitiating it again at a lower rate than controls. These results were wholly similar to those obtained with nonsterilely cultured roots and have been interpreted as mainly based on H(+) consumption for O(2)(*-) dismutation to H(2)O(2). Also K(+) influx was strongly depressed by MeJA, even transitorily reverting to K(+) efflux. These results were consistent with those associated to the oxidative burst in plants. MeJA induced massive H(2)O(2) accumulation in the middle lamella and intercellular spaces of both the root cap cells and the inside tissues of the roots. The native acidic extracellular peroxidase activity of the intact (nonexcised) seedling roots showed a sudden enhancement (by about 52%) after 5 min of MeJA addition, maintained for approximately 15 min and then decaying again to control rates. O(2) uptake by roots gave similar results. These and other results for additions of H(2)O(2) or horseradish peroxidase, diphenylene iodonium, and sodium diethyldithiocarbamate trihydrate to the reaction mixture with roots were all consistent with the hypothesis that MeJA induced an oxidative burst, with the generation of H(2)O(2) being necessary for peroxidase activity. Results with peroxidase activity of the apoplastic fluid were in accordance with those of the whole root. Finally, MeJA enhanced NADH oxidation and inhibited hexacyanoferrate(III) reduction by axenic roots, and diphenylene iodonium cancelled out these effects. Redox activities by CN(-)- preincubated roots were also studied. All these results are consistent with the hypothesis that MeJA enhanced the NAD(P)H oxidase of a redox chain linked to the oxidative burst, so enhancing the generation of O(2)(*-) and H(2)O(2), O(2) uptake, and peroxidase activity by roots.

Effect of dietary coenzyme Q and fatty acids on the antioxidant status of rat tissues

Wistar rats were fed with different diets with or without supplement coenzyme Q(10) (CoQ(10)) and with oil of different sources (sunflower or virgin olive oil) for six or twelve months. Ubiquinone contents (CoQ(9) and CoQ(10)) were quantified in homogenates of livers and brains from rats fed with the four diets. In the brain, younger rats showed a 3-fold higher amount of ubiquinone than older ones for all diets. In the liver, however, CoQ(10) supplementation increased the amount of CoQ(9) and CoQ(10) in both total homogenates and plasma membranes. Rats fed with sunflower oil as fat source showed higher amounts of ubiquinone content than those fed with olive oil, in total liver homogenates, but the total ubiquinone content in plasma membranes was similar with both fat sources. Older rats showed a higher amount of ubiquinone after diets supplemented with CoQ(10). Two ubiquinone-dependent antioxidant enzyme activities were measured. NADH-ferricyanide reductase activity in hepatocyte plasma membranes was unaltered by ubiquinone accumulation, but this activity increased slightly with age. Both cytosolic and membrane-bound dicumarol-sensitive NAD(P)H:(quinone acceptor) oxidoreductase (DT-diaphorase, EC 1.6.99.2) activities were decreased by diets supplemented with CoQ(10). Animals fed with olive oil presented lower DT-diaphorase activity than those fed with sunflower oil, suggesting that the CoQ(10) antioxidant protection is strengthened by olive oil as fat source.

Cloning, expression and immunolocalization pattern of a cinnamyl alcohol dehydrogenase gene from strawberry (Fragaria x ananassa cv. Chandler)

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) catalyses the conversion of p-hydroxy-cinnamaldehydes to the corresponding alcohols and is considered a key enzyme in lignin biosynthesis. By a differential screening of a strawberry (Fragariax ananassa cv. Chandler) fruit specific subtractive cDNA library, a full-length clone corresponding to a cad gene was isolated (Fxacad1). Northern blot and quantitative real time PCR studies indicated that the strawberry Fxacad1 gene is expressed in fruits, runners, leaves, and flowers but not in roots. In addition, the gene presented a differential expression in fruits along the ripening process. Moreover, by screening of a strawberry genomic library a cad gene was isolated (Fxacad2). Similar to that found in other cad genes from higher plants, this strawberry cad gene is structured in five exons and four introns. Southern blot analyses suggest that, probably, a small cad gene family exists in strawberry. RT-PCR studies indicated that only the Fxacad1 gene was expressed in all the fruit ripening stages and vegetative tissues analysed. The Fxacad1 cDNA was expressed in E. coli cells and the corresponding protein was used to raise antibodies against the strawberry CAD polypeptide. The antibodies obtained were used for immunolocalization studies. The results showed that the CAD polypeptide was localized in lignifying cells of all the tissues examined (achenes, fruit receptacles, runners, leaves, pedicels, and flowers). Additionally, the cDNA was also expressed in yeast (Pichia pastoris) as an extracellular protein. The recombinant protein showed activity with the characteristic substrates of CAD enzymes from angiosperms, indicating that the gene cloned corresponds to a CAD protein.

Topography of the 27- and 31-kDa electron transport proteins in the onion root plasma membrane

Plasma membranes purified from onion roots contain two distinct NAD(P)H-dehydrogenases of 27 and 31 kDa that differ in their physicochemical properties, substrate specificities and inhibitors sensitivities. The 27-kDa enzyme used both NADH and NADPH as electron donors. The 31-kDa enzyme was fully specific for NADH and accounted for the bulk of NADH-ferricyanide oxidoreductase. We have used NADPH- and NADH-ferricyanide oxidoreductase activities as markers for investigating the orientation of the 27- and 31-kDa enzymes at the plasma membrane, respectively. These activities were assayed in right-side-out vesicles isolated by two-phase partition, inside-out vesicles obtained by treatment with the detergent Brij 58 and membranes permeabilized with Triton X-100. Upon addition of Brij 58 to right-side-out plasma membrane vesicles, both NADPH- and NADH-ferricyanide oxidoreductases were activated to the same degree as the plasma membrane H(+)-ATPase. Redox activities were similar when measured in the presence of either Brij 58 or Triton X-100. Our results demonstrate that both enzymes expose their catalytic sites toward the cytoplasmic side of the plasma membrane.

Ascorbate and plant cell growth

Ascorbate and related enzymes are involved in the control of several plant growth processes. Ascorbate modulates cell growth by controlling (i) the biosynthesis of hydroxyproline-rich proteins required for the progression of G1 and G2 phases of the cell cycle, (ii) the cross-linking of cell wall glycoproteins and other polymers, and (iii) redox reactions at the plasma membrane involved in elongation mechanisms. The effect of ascorbate on onion root elongation is reviewed here. The ascorbate free radical induces a high vacuolization responsible for elongation. This effect may be dependent on the activity of the redox system linked to the plasma membrane. Current data are discussed on the basis of the modulation of the plasma membrane energetic state derived from the ascorbate-induced hyperpolarization and the activity of an intrinsic transplasmalemma ascorbate-regenerating enzyme.

Two distinct NAD(P)H-dependent redox enzymes isolated from onion root plasma membranes

Plasma membranes purified by two-phase partition from onion roots catalyzed the NAD(P)H-dependent reduction of a variety of electron acceptor such as ferricyanide, quinones, dyes and ascorbate free radical. Among these, NAD(P)H-ferricyanide and -quinone oxidoreductase activities were effectively solubilized by Triton X-100. Both oxidoreductase activities were bound to an affinity column of Blue-Sepharose CL 6B. NADH eluted a redox enzyme showing more juglone than ferricyanide-dependent activity. Ulterior unspecific elution with salt allowed us to the partial purification of a different redox enzyme of about 31 kDa that reduced better ferricyanide than quinones and constituted the bulk of solubilized redox activity.

A quantitative ultrastructural and cytochemical study of TPA-induced differentiation in HL-60 cells

The effects of the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate on morphometric and stereological parameters have been studied using the HL-60 cell line as a differentiation model for the monocytic pathway. Evaluation of the differentiation was carried out by quantification of endoplasmic reticulum, Golgi apparatus, mitochondria and cytoplasmic granules. Changes in both nuclear and cytoplasmic volumes during TPA-induced differentiation led to a decrease of the nucleus-cytoplasmic ratio after 3 days of treatment. Plasma membrane glycoprotein pattern was also determined. The major change in cell surface was the presence of high amounts of glycoproteins containing N-acetyl glucosamine residues that make wheatgerm agglutinin lectin a valuable marker of the monocytic differentiation pathway in HL-60 cells.

Effects of hypothyroidism on the ultrastructure of rat pancreatic acinar cells: a stereological analysis

The morphological and stereological characteristics of the exocrine pancreas subcellular organelles from healthy and thyroidectomized rats have been studied. The acinar tissue from hypothyroid rats showed an interstitial edema and evidence of degenerative processes. Stereological parameters of zymogen granules were significantly reduced in thyroidectomized rats. The hypothyroidism induced degenerative changes in the pancreatic acinar cells as well as a decrease in the number and size of the zymogen granules. These modifications probably cause functional alterations.

Growth kinetics of the Golgi apparatus during the cell cycle in onion root meristems

In onion root meristems, the number of dictyosomes per cell shows a kinetics of growth strongly related to the cell cycle. During the interphase of steady-state proliferative cells, the volume density and numerical density of the Golgi apparatus decrease to reach minimum values in late-interphase cells, characterized by their greatest length. This pattern is also found in the total volume occupied by Golgi apparatus. Once in mitosis, the above-mentioned parameters begin to increase reaching maximum mean values in telophase. After the experimental uncoupling of chromosome and growth cycles by presynchronization with hydroxyurea, we found a similar behaviour pattern in the Golgi apparatus: decreasing values during interphase and a triggering of Golgi-apparatus growth in prophase independently of the bigger cell sizes reached in mitosis as an effect of pretreatment with hydroxyurea. These results indicate a cyclic kinetics of this subcellular component in higher-plant meristems, coupled with early mitotic events.