Alteration of mitochondrial function in a model of chronic ischemia in vivo in rat heart

The aim of this study was to investigate mitochondrial alterations in an animal model of chronic myocardial ischemia in rats obtained by surgical constriction of the left coronary artery. Resting coronary blood flow was measured using the fluorescent microsphere technique. Contractile function, defined by rate-pressure product, and myocardial oxygen consumption were measured in a Langendorff preparation. The mitochondrial function was evaluated on permeabilized skinned fibers. Three weeks after surgery, ischemic hearts showed a significant decrease in coronary blood flow compared with sham. Hemodynamic measurements showed a significant systolic and diastolic dysfunction. Alterations in mitochondrial function in ischemic hearts were mainly characterized by a significant decrease in the maximal velocity and apparent half-saturation constant for ADP, loss of the stimulatory effect of creatine, and a stimulatory effect of exogenous cytochrome c. These functional alterations were supported by structural alterations characterized by mitochondrial clustering and swelling associated with membrane rupture. We conclude that the alterations in systolic function after chronic ischemia are supported by severe modifications of mitochondrial structure and function.     

Comparison of the Schwartz and CKD-EPI Equations for Estimating Glomerular Filtration Rate in Children,Adolescents, and Adults: A Retrospective Cross-Sectional Study

Background

Estimating kidney glomerular filtration rate (GFR) is of utmost importance in many clinical conditions. However, very few studies have evaluated the performance of GFR estimating equations over all ages and degrees of kidney impairment. We evaluated the reliability of two major equations for GFR estimation, the CKD-EPI and Schwartz equations, with urinary clearance of inulin as gold standard.

Methods and Findings

The study included 10,610 participants referred to the Renal and Metabolic Function Exploration Unit of Edouard Herriot Hospital (Lyon, France). GFR was measured by urinary inulin clearance (only first measurement kept for analysis) then estimated with isotope dilution mass spectrometry (IDMS)–traceable CKD-EPI and Schwartz equations. The participants’ ages ranged from 3 to 90 y, and the measured GFRs from 3 to 160 ml/min/1.73 m². A linear mixed-effects model was used to model the bias (mean ratio of estimated GFR to measured GFR). Equation reliability was also assessed using precision (interquartile range [IQR] of the ratio) and accuracy (percentage of estimated GFRs within the 10% [P10] and 30% [P30] limits above and below the measured GFR). In the whole sample, the mean ratio with the CKD-EPI equation was significantly higher than that with the Schwartz equation (1.17 [95% CI 1.16; 1.18] versus 1.08 [95% CI 1.07; 1.09], p < 0.001, t-test). At GFR values of 60–89 ml/min/1.73 m², the mean ratios with the Schwartz equation were closer to 1 than the mean ratios with the CKD-EPI equation whatever the age class (1.02 [95% CI 1.01; 1.03] versus 1.15 [95% CI 1.13; 1.16], p < 0.001, t-test). In young adults (18–40 y), the Schwartz equation had a better precision and was also more accurate than the CKD-EPI equation at GFR values under 60 ml/min/1.73 m² (IQR: 0.32 [95% CI 0.28; 0.33] versus 0.40 [95% CI 0.36; 0.44]; P30: 81.4 [95% CI 78.1; 84.7] versus 63.8 [95% CI 59.7; 68.0]) and also at GFR values of 60–89 ml/min/1.73 m². In all patients aged ≥65 y, the CKD-EPI equation performed better than the Schwartz equation (IQR: 0.33 [95% CI 0.31; 0.34] versus 0.40 [95% CI 0.38; 0.41]; P30: 77.6 [95% CI 75.7; 79.5] versus 67.5 [95% CI 65.4; 69.7], respectively). In children and adolescents (2–17 y), the Schwartz equation was superior to the CKD-EPI equation (IQR: 0.23 [95% CI 0.21; 0.24] versus 0.33 [95% CI 0.31; 0.34]; P30: 88.6 [95% CI 86.7; 90.4] versus 29.4 [95% CI 26.8; 32.0]). This study is limited by its retrospective design, single-center setting with few non-white patients, and small number of patients with severe chronic kidney disease.

Conclusions

The results from this study suggest that the Schwartz equation may be more reliable than the CKD-EPI equation for estimating GFR in children and adolescents and in adults with mild to moderate kidney impairment up to age 40 y.     

Darwinism and Ethology The Role of Natural Selection in Animals and Humans

The role of behaviour in biological evolution is examined within the context of Darwinism. All Darwinian models are based on the distinction of two mechanisms: one that permits faithful transmission of a feature from one generation to another, and another that differentially regulates the degree of this transmission. Behaviour plays a minimal role as an agent of transmission in the greater part of the animal kingdom; by contrast, the forms it may assume strongly influence the mechanisms of selection regulating the different rates of transmission. We consider the decisive feature of the human species to be the existence of a phenotypical system of cultural coding characterized by precision and reliability which are the distinctive features of genetic coding in animals. We examine the consequences for the application of the Darwinian model to human history. This revised version was published online in June 2006 with corrections to the Cover Date.     

Characterization of photosystem II mutants of Chlamydomonas reinhardii lacking the psbA gene

Summary We have examined 78 chloroplast mutants of Chlamydomonas reinhardii lacking photosystem II activity. Most of them are unable to synthesize the 32 Kdalton protein. Analysis of 22 of these mutants reveals that they have deleted both copies of the psbA gene (which codes for the 32 Kdalton protein) in their chloroplast genome. Although these mutants are able to synthesize and to integrate the other photosystem II polypeptides in the thylakoid membranes, they are unable to assemble a stable functional photosystem II complex. The 32 Kprotein appears therefore to play an important role not only in photosystem II function, but also in stabilizing this complex.     

Assignment of the Ly-6--Ril-1--Sis--H-30--Pol-5/Xmmv-72--Ins-3--Krt-1--Int-1--Gdc-1 region to mouse chromosome 15

Previous work has demonstrated linkage between Ly-6, H-30, and a locus, Ril-1, that affects susceptibility to radiation-induced leukemia. Results of preliminary linkage analyses suggested further that the cluster might be linked to Ly-11 on the proximal portion of mouse chromosome 2. Using molecular probes to examine somatic cell lines and recombinant inbred and congenic strains of mice, we have re-evaluated these linkage relationships. A cloned genomic DNA fragment derived from a retroviral site has been used to define a novel locus, Pol-5, that is tightly linked to both H-30 and Ril-1 as shown by analysis of the B6.C-H-30 ^c congenic mouse strain. Following the segregation of the Pol-5 mouse-specific DNA fragment in a series of somatic cell hybrids carrying various combinations of mouse chromosomes on a rat or Chinese hamster background mapped Pol-5 to mouse chromosome 15. During the course of these studies, restriction fragment length polymorphisms were defined associated with several loci, including Pol-5, Ly-6, Sis, Ins-3, Krt-1, Int-1, and Gdc-1. Three of these loci, Sis, Int-1, and Gdc-1, have been previously mapped to chromosome 15 by others using somatic cell hybrids or isoenzyme analyses. Following the inheritance of these eight loci in recombinant inbred strains of mice allowed the definition of a linkage group on the chromosome with the order Ly-6-Ril-1--Sis--H-30--Pol-5--Ins-3--Krt-1--Int-1--Gdc-1. Analyses of alleles inherited as passengers in B6.C-H-30 ^c, C3H.B-Ly-6 ^b, and C57BL/6By-Eh/+ congenic mouse strains and in situ hybridization experiments support the above gene order and indicate further that the cluster is located on distal chromosome 15, with Ly-6 and Sis near Eh.Abbreviations A agouti - Abl cellular homolog of the Abelson leukemia virus oncogene - Ada adenosine deaminase - Ak-1 adenylate kinase-1 - AXB A/J × C57BL/6J recombinant inbred strain - B2m beta-2 microglobulin - BXA C57BL/6J × A/J recombinant inbred strain - BXD C57BL/6J × DBA/2J recombinant inbred strain - BXH C57BL/6J × C3H/HeJ recombinant inbred strain - CXB BALB/cBy × C57BL/6By recombinant inbred strain - DNA deoxyribonucleic acid - Eh hairy ears - Fpgs folypolyglutamyl synthetase - FXI fractionated x-irradiation - Gdc-1 glycerol phosphate dehydrogenase-1 - Il2r IL-2 receptor - Ins-3 a novel insulinlike gene - Int-1 mammary tumor integration site-1 - Itp inosine triphosphatase - Krt-1 the locus designated here includes a cluster of at least three keratin genes - LTR long terminal repeat - Ly lymphocyte - Lv-6 lymphocyte antigen-6 - Ly-11 lymphocyte antigen-11 - MIH minor histocompatibility - Myc cellular homolog of the Abelson leukemia virus oncogene; pa, pallid; - Pol-5 locus encoding retroviral polymerase-5 - RFLP restriction fragment length polymorphism - RI recombinant inbred mouse strains - Ril-1 radiation-induced leukemia susceptibility-1 locus - SDP strain distribution pattern - Sis cellular homolog of the simian sarcoma virus oncogene - SFFV spleen focus-forming virus - Tpi-1 triosephosphate isomerase-1 - Ve velvet     

A comparative study by electron microscopy of the structures of effective and ineffective nodules ofTrifolium subterraneum induced byRhizobium trifolii andRhizobium leguminosarum

Summary Bacteroid formation and haemoglobin pigment were observed 3 days after the appearance of nodules formed by the effectiveRhizobium trifolii strain TA1 onTrifolium subterraneum. Effective nodules were large and cylindrical and evidence of bacteroid degeneration did not appear until about 21 days. Electron microscopy of ineffective nodules formed byRhizobium trifolii strain 6 showed limited meristematic activity and vascular development, and infection threads were sparse. Degeneration of plant cells and bacteria was visible by 3 days and mostly complete by 14 days. Both types of nodules occurred randomly over the root system. In contrast, the ineffective nodules formed byRhizobium leguminosarum strains onTrifolium subterraneum, occurred mainly at lateral root junctions with vascular connections to either the primary or lateral root depending on strain. Infection thread development was widespread and most cells were invaded. The released bacteria became pleomorphic and rounded, the nodules became cylindrical, enlarged slightly but remained white. Degeneration was apparent at 5 days and complete by 14 days in nodules formed by strain 1020A, but nodules formed by strain 1013 degenerated more slowly and degenerate cells sometimes showed secondary invasion by vegetative rhizobia.

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Estudio comparativo mediante microscopia electronica de las estructuras de nodulos eficaces e ineficaces de Trifolium subterraneum inducidos por Rhizobium trifolii y Rhizobium leguminosarum

Resumen Se observó la formación de bacteroides y de (leg)hemoglobina tres días después de laapparación de nódulos formados por la cepaeficaz TA1 deRhizobium trifolii enTrifolium subterraneum. Los nódulos eficaces eran grandes y cilíndricos. No hubo evidencia de degeneración de bacteroides hasta pasados 21 dias. El estudió al microscopio electrónico de nódulos no eficaces formados por la cepa 6 deR. trifolii mostro una actividad meristemática reducida al igual que el desarrollo vascular, siendo escasas la lineas de infección. La degeneración de las células de la planta y de las bacterias era observable a los 3 días y practicamente completa a los 14. Los nódulos formados por ambas cepas se distribuyen al azar en todo el sistema radicular, en cambio, los nódulos ineficaces formados enT. subterraneum porR. leguminosarum se encuentran principalmente en conexiones vasculares laterales con raíces primarias o secundarias, dependiendo de la cepa. La línea de infección en este caso está ampliamente desarrollada y la mayoría de las células estan invadidas. Las bacterias que han sido liberadas se vuelven esféricas y pleomórficas, los nódulos se vuelven cilíndricos y aumentan ligeramente de tamaño pero permanecen blancos. La degeneración de los nódulos formados por la cepa 1020A era aparente a los 5 días y completa a los 14. Sin embargo, los nódulos formados por la cepa 1013 degeneraron más lentamente y las células degeneradas mostraron una invasión secundaria porRhizobium vegetativos.

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Etude comparative en microscopie électronique de la structure des nodules efficaces et inefficaces de Trifolium subterraneum induits par Rhizobium trifolii et Rhizobium leguminosarum

Résumé La formation de bactéroides et la production de leg-hémoglobine ont été observées 3 jours après l'apparition des nodules formés surTrifolium subterraneum par la souche efficace TA1 deRhizobium trifolii. Les nodules efficaces sont larges et cylindriques, et les signes de la dégénérescence en bactéroides n'apparaissent pas avant 21 jours. La microscopie électronique des nodules inefficaces formés par la souche 6 deR. trifolii montre une activité méristématique et un développement vasculaire faibles, et les filaments d'infection sont rares. La dégénérescence des cellules végétales et des bactéries est visible au bout de 3 jours et presque complète en 14 jours. Les deux types de nodules sont répartis au hasard sur le système racinaire. Par contre, les nodules inefficaces formés par les souches deR. leguminosarum surT. subterraneum sont répartis préférentiellement sur les jonctions racinaires latérales, les connections vasculaires étant, suivant la souche, dirigées vers la racine primaire ou vers la racine latérale. Le développement des filaments d'infection est très répandu et la plupart des cellulessont envahies. Les bactéries relâchées deviennent pléomorphes et arrondies; les nodules deviennent cylindriques et légèrement renflés, mais restent incolores La dégénérescence est apparente après 5 jours et complète en 14 jours dans les nodules formés par la souche 1020A, mais ceux formés par la souche 1013 dégénèrent plus lentement et les cellules dégénérées présentent parfois une invasion secondaire par des rhizobiums végétatifs.

     

The Nanomechanical Properties of Lactococcus lactis Pili Are Conditioned by the Polymerized Backbone Pilin

Pili produced by Lactococcus lactis subsp. lactis are putative linear structures consisting of repetitive subunits of the major pilin PilB that forms the backbone, pilin PilA situated at the distal end of the pilus, and an anchoring pilin PilC that tethers the pilus to the peptidoglycan. We determined the nanomechanical properties of pili using optical-tweezers force spectroscopy. Single pili were exposed to optical forces that yielded force-versus-extension spectra fitted using the Worm-Like Chain model. Native pili subjected to a force of 0–200 pN exhibit an inextensible, but highly flexible ultrastructure, reflected by their short persistence length. We tested a panel of derived strains to understand the functional role of the different pilins. First, we found that both the major pilin PilB and sortase C organize the backbone into a full-length organelle and dictate the nanomechanical properties of the pili. Second, we found that both PilA tip pilin and PilC anchoring pilin were not essential for the nanomechanical properties of pili. However, PilC maintains the pilus on the bacterial surface and may play a crucial role in the adhesion- and biofilm-forming properties of L. lactis.