AN EXPERIMENTAL INVESTIGATION ON ISOTHERMAL FREE SWIRLING JET

This paper reports an experimental investigation on the dynamics of turbulent unconfined swirling flows. Isothermal free swirling jets with five different swirl numbers (S) and fixed Reynolds number (Re = 21800) are investigated to analyze the effect of swirl intensity on the recirculation, vortex breakdown and the occurrence of the precession vortex core (PVC) by means of 3C-2D Stereoscopic Particle image velocimetry (PIV). The contours and radial profiles of mean axial velocity confirmed the central recirculation zone (CRZ) for high swirl number. The importance of central recirculation zone is to ensure a good mixing of air/ fuel and combustion products and to generate a low velocity region for flame stabilization. Results shows that swirl intensity increases the backflow rate in the recirculation zone and jet spreads almost linearly with a higher spread rate as compared to non swirling flow. The frequency characteristics have been measured with a capacitive microphone. The frequency spectrum indicates the presence of periodic oscillation related to the existence of PVC. The Strouhal number associated with the frequency of the PVC vary almost linearly with swirl intensity

Morfología y protrusión-retracción de la cámara genital femenina de phyllophaga obsoleta (coleoptera: melolonthidae)

The females of Phyllophaga obsoleta (Blanchard) (Coleoptera: Melolonthidae) have a great agricultural importance in Mexico. They display a sexual calling behavior, that expose a bag-like structure on the abdominal tip, wich causes them to attract the males. The content of this structure has been extracted and confirmed his biological activity by wind tunnel and electroantenography bioessays. Nevertheless, their morphologic characteristics have not been studied yet. For that reason in the present study, the P. obsoleta abdominal terminalia were characterized morphologically and protrusion-retraction mechanism of bag-like structure was studied. Longitudinal dissections of the abdominal terminalia were analyzed with stereoscopic microscopy. The bag-like structure is the protractile genital chamber (PGC) of Melolonthidae females and its protrusion and retraction is related to the activity of lateral sterno-sacular muscles with ventral sterno-sacular muscles, as well as for intersegmental membranes VIII and IX. They should be involucrated in protrusion and retraction PGC mechanismsLas hembras de Phyllophaga obsoleta (Blanchard) (Coleoptera: Melolonthidae), una de las especies de mayor importancia agrícola en México, presentan un llamado sexual en el cual exponen una estructura en forma de bolsa del ápice abdominal y provocan la atracción de los machos. El contenido de esta estructura se ha extraído en estudios previos con diferentes disolventes y se ha confirmado su actividad biológica mediante bioensayos con túnel de viento y electroantenografía. Sin embargo, las características morfológicas de esta bolsa no han sido estudiadas. Por ello, en el presente trabajo se caracterizó morfológicamente los terminalia del abdomen femenino de P. obsoleta y se estudió el mecanismo de protrusión-retracción de la estructura en forma de bolsa. Se realizaron disecciones longitudinales de los terminalia del abdomen de hembras para su análisis con microscopía estereoscópica. Se encontró que la bolsa es la cámara genital protráctil (CGP), propia de las hembras de Melolonthidae y que se encuentra flanqueada por músculos esterno-saculares laterales y esternosaculares ventrales, así como de membranas intersegmentales VIII y IX. Músculos y membranas podrían estar involucrados en los procesos de protrusión y retracción de la CGP

Sym1, the yeast ortholog of the MPV17 human disease protein, is a stress-induced bioenergetic and morphogenetic mitochondrial modulator

A peculiar form of hepatocerebral mtDNA depletion syndrome is caused by mutations in the MPV17 gene, which encodes a small hydrophobic protein of unknown function located in the mitochondrial inner membrane. In order to define the molecular basis of MPV17 variants associated with the human disorder, we have previously taken advantage of S. cerevisiae as a model system thanks to the presence of an MPV17 ortholog gene, SYM1. We demonstrate here that the SYM1 gene product is essential to maintain OXPHOS, glycogen storage, mitochondrial morphology and mtDNA stability in stressing conditions such as high temperature and ethanol-dependent growth. To gain insight into the molecular basis of the Sym1-less phenotype, we identified and characterized multicopy suppressor genes and metabolic suppressor compounds. Our results suggest that (i) metabolic impairment and mtDNA instability occur independently from each other as a consequence of SYM1 ablation; (ii) ablation of Sym1 causes depletion of glycogen storage, possibly due to defective anaplerotic flux of tricarboxylic acid (TCA) cycle intermediates to the cytosol; (iii) flattening of mitochondrial cristae in Sym1-defective organelles suggests a role for Sym1 in the structural preservation of the inner mitochondrial membrane, which could in turn control mtDNA maintenance and stability

YEAST AS A MODEL SYSTEM TO SHED LIGHT ON THE ROLE OF THE HUMAN DISEASE PROTEIN MPV17

An intriguing gene necessary for the maintenance of mtDNA is human MPV17, mutation of which leads to a peculiar form of hepatocerebral mtDNA depletion syndrome (MDS). Even though Mpv17 mutations are one of the causes of MDS in humans and the discovery of this protein has been reported more than 20 years ago, its function is not yet understood. Originally considered as a peroxisomal membrane protein, it was later demonstrated that Mpv17 is localized to the inner mitochondrial membrane, as also previously demonstrated for the yeast orthologue Sym1, identified as a heat shock protein with a role in metabolism and/or tolerance to ethanol. With the aim of clarifying the role of MPV17 pathological alleles in MDS, we took advantage of S. cerevisiae as a model system. These studies in yeast have shed some light on the function of Sym1. The sym1 mutant mitochondria are morphologically abnormal, with flattened mitochondrial cristae and accumulation of electron-dense particles, suggesting a role for Sym1 in the structural preservation of the inner mitochondrial membrane. This defect is not a consequence of the mtDNA instability because it has been observed under cultural conditions where no defect of mtDNA was observed, indicating that the morphogenetic effects of Sym1 are likely to precede and possibly determine its effects on mtDNA stability. The phenotypes of double mutants (cit1 sym1, cit2 sym1) and the nature of multicopy suppressors (ODC1, YMC1) suggest for sym1 null mutant a defect in Krebs cycle confirmed by an enzymatic analysis that clearly indicates a heavy reduction of succinate dehydrogenase activity. Accordingly, sym1Δ displays a significant reduction in the amount of glycogen that is dependent on gluconeogenesis, which is in turn regulated by the anaplerotic flux of tricarboxylic acid intermediates from mitochondria to the cytosol. Interestingly, patients with Mpv17 mutations suffer from drastic, often fatal, hypoglycaemic crises, which are likely due to glycogen shortage in liver. Moreover blue-native gel electrophoresis immunovisualization clearly demonstrated that Sym1 is part of a high-molecular weight complex. While further work is necessary to identify the primary role of Sym1, including the molecular dissection and characterization of the Sym1-containing protein complex, these results indicate that Sym1 is involved in the structural and functional stability of the inner mitochondrial membrane, thus controlling crucial mechanisms related to this compartment, including respiratory chain complexes activity, mitochondria morphology and mtDNA maintenance

Sym1, the yeast ortholog of the MPV17 human disease protein, is a stress-induced bioenergetic and morphogenetic mitochondrial modulator

A peculiar form of hepatocerebral mtDNA depletion syndrome is caused by mutations in the MPV17 gene, which encodes a small hydrophobic protein of unknown function located in the mitochondrial inner membrane. In order to define the molecular basis of MPV17 variants associated with the human disorder, we have previously taken advantage of S. cerevisiae as a model system thanks to the presence of an MPV17 ortholog gene, SYM1. We demonstrate here that the SYM1 gene product is essential to maintain OXPHOS, glycogen storage, mitochondrial morphology and mtDNA stability in stressing conditions such as high temperature and ethanol-dependent growth. To gain insight into the molecular basis of the Sym1-less phenotype, we identified and characterized multicopy suppressor genes and metabolic suppressor compounds. Our results suggest that (i) metabolic impairment and mtDNA instability occur independently from each other as a consequence of SYM1 ablation; ( ii) ablation of Sym1 causes depletion of glycogen storage, possibly due to defective anaplerotic flux of tricarboxylic acid (TCA) cycle intermediates to the cytosol; (iii) flattening of mitochondrial cristae in Sym1-defective organelles suggests a role for Sym1 in the structural preservation of the inner mitochondrial membrane, which could in turn control mtDNA maintenance and stability