Quality Of Mitochondria Research Articles

Dual roles of mitochondrial fusion gene FZO1 in yeast age asymmetry and in longevity mediated by a novel ATG32-dependent retrograde response.

The replicative lifespan of the yeast Saccharomyces cerevisiae models the aging of stem cells. Age asymmetry between the mother and daughter cells is established during each cell division, such that the daughter retains the capacity for self-renewal while this ability is diminished in the mother. The segregation of fully-functional mitochondria to daughter cells is one mechanism that underlies this age asymmetry. In this study, we have examined the role of mitochondrial dynamics in this phenomenon. Mitochondrial dynamics involve the processes of fission and fusion. Out of the three fusion and three fission genes tested, we have found that only FZO1 is required for the segregation of fully-functional mitochondria to daughter cells and in the maintenance of age asymmetry as manifested in the potential of daughters for a full replicative lifespan despite its deterioration in their mothers. The quality of mitochondria is determined by their turnover, and we have also discovered that deletion of FZO1 reduces mitophagy. Mitochondrial dysfunction elicits a compensatory retrograde response that extends replicative lifespan. Typically, the dysfunction that triggers this response encompasses energy production. The disruption of mitochondrial dynamics by deletion of FZO1 also activates the retrograde response to extend replicative lifespan. We call this novel pathway the mitochondrial dynamics-associated retrograde response (MDARR) because it is distinct in the signal proximal to the mitochondrion that initiates it. Furthermore, the MDARR engages the mitophagy receptor Atg32 on the mitochondrial surface, and we propose that this is due to the accumulation of Atg32-Atg11-Dnm1 complexes on the mitochondrion in the absence of Fzo1 activity. MDARR can be masked by the operation of the 'classic' retrograde response.

Metabolism as master of hematopoietic stem cell fate.

HSCs have a fate choice when they divide; they can self-renew, producing new HSCs, or produce daughter cells that will mature to become committed cells. Technical challenges, however, have long obscured the mechanics of these choices. Advances in flow-sorting have made possible the purification of HSC populations, but available HSC-enriched fractions still include substantial heterogeneity, and single HSCs have proven extremely difficult to track and observe. Advances in single-cell approaches, however, have led to the identification of a highly purified population of hematopoietic stem cells (HSCs) that make a critical contribution to hematopoietic homeostasis through a preference for self-renewing division. Metabolic cues are key regulators of this cell fate choice, and the importance of controlling the population and quality of mitochondria has recently been highlighted to maintain the equilibrium of HSC populations. Leukemic cells also demand tightly regulated metabolism, and shifting the division balance of leukemic cells toward commitment has been considered as a promising therapeutic strategy. A deeper understanding of precisely how specific modes of metabolism control HSC fate is, therefore, of great biological interest, and more importantly will be critical to the development of new therapeutic strategies that target HSC division balance for the treatment of hematological disease.

Mitophagy Receptor FUNDC1 Links Mitochondrial Quality Control to Muscle–Adipose Dialogue in Alleviating Dietary Obesity

The quality of mitochondria in skeletal muscle is essential for maintaining metabolic homeostasis during adaptive stress responses. However, the precise control mechanism of muscle mitochondrial quality and its physiological impacts remain unclear. Here, using two independent skeletal muscle-specific knockout mouse lines, we demonstrate that FUNDC1, a mediator of mitophagy, plays an essential role in controlling muscle mitochondrial quality as well as metabolic homeostasis. Mice with FUNDC1 deficiency in skeletal muscle (FUNDC1 mKO) showed decreased muscle fat utilization and endurance capacity (∼40%) compared to WT littermates during exercise. Analysis of biochemical markers of mitophagy revealed a marked decrease in mitochondrial localization of LC3-II and P62 protein levels, and this caused impaired mitochondrial respiration capacity. FUNDC1 loss-of-function studies in primary skeletal myocyte recapitulated defective mitophagy and impaired mitochondrial energetic as observed in FUNDC1 mKO muscle. Surprisingly, mice lacking muscle FUNDC1 were resistant to high fat diet (HFD) induced obesity despite reduced muscle mitochondrial energetics. Moreover, glucose and insulin tolerance tests demonstrated that HFD-fed FUNDC1 mKO mice were more tolerant to glucose challenge and more sensitive to insulin stimulation compared to HFD-fed WT controls. This seemingly paradoxical phenotype was due to enhanced fat burning in in adipose tissue. HFD-fed FUNDC1 mKO mice had markedly elevated expression of key thermogenic genes such as Ucp1 (17-fold), Cidea (13-fold), and Dio2 (9-fold) in white adipose. Mechanistically, FUNDC1 deficiency elicited a retrograde response in muscle that upregulated FGF-21 expression, thereby promoting the thermogenic remodeling of adipose tissue. Thus, these findings reveal a pivotal role of FUNDC1-dependent mitochondrial quality-control in mediating the muscle-adipose dialogue to regulate systemic metabolism. Disclosure T. Fu: None. Z. Xu: None. L. Liu: None. X. Liang: None. D. Zhou: None. Q. Guo: None. L. Xiao: None. Z. Gan: None.

Mitophagy Directs Muscle-Adipose Crosstalk to Alleviate Dietary Obesity

The quality of mitochondria in skeletal muscle is essential for maintaining metabolic homeostasis during adaptive stress responses. However, the precise control mechanism of muscle mitochondrial quality and its physiological impacts remain unclear. Here, we demonstrate that FUNDC1, a mediator of mitophagy, plays a critical role in controlling muscle mitochondrial quality as well as metabolic homeostasis. Skeletal-muscle-specific ablation of FUNDC1 in mice resulted in LC3-mediated mitophagy defect, leading to impaired mitochondrial energetics. This caused decreased muscle fat utilization and endurance capacity during exercise. Interestingly, mice lacking muscle FUNDC1 were protected against high-fat-diet-induced obesity with improved systemic insulin sensitivity and glucose tolerance despite reduced muscle mitochondrial energetics. Mechanistically, FUNDC1 deficiency elicited a retrograde response in muscle that upregulated FGF21 expression, thereby promoting the thermogenic remodeling of adipose tissue. Thus, these findings reveal a pivotal role of FUNDC1-dependent mitochondrial quality control in mediating the muscle-adipose dialog to regulate systemic metabolism.

Carbon black suppresses the osteogenesis of mesenchymal stem cells: the role of mitochondria

BackgroundThe rapid increase in carbon black poses threats to human health. We evaluated the effect of CB (Printex 90) on the osteogenesis of bone-marrow-derived mesenchymal stem cells (MSCs). Mitochondria play an important role in the osteogenesis of MSCs and are potential targets of nanomaterials, so we studied the role of mitochondria in the CB Printex 90-induced effects on osteogenesis.ResultsLow doses of Printex 90 (3 ng/mL and 30 ng/mL) that did not cause deleterious effects on MSCs’ viability significantly inhibited osteogenesis of MSCs. Printex 90 caused down-regulation of osteoblastic markers, reduced activity of alkaline phosphatase (ALP), and poor mineralization of osteogenically induced MSCs. Cellular ATP production was decreased, mitochondrial respiration was impaired with reduced expression of ATPase, and the mitochondrial membrane was depolarized. The quantity and quality of mitochondria are tightly controlled by mitochondrial biogenesis, mitochondrial dynamics and mitophagy. The transcriptional co-activator and transcription factors for mitochondrial biogenesis, PGC-1α, Nrf1 and TFAM, were suppressed by Printex 90 treatment, suggesting that decreased biogenesis was caused by Printex 90 treatment during osteogenesis. Mitochondrial fusion and fission were significantly inhibited by Printex 90 treatment. PINK1 accumulated in Printex 90-treated cells, and more Parkin was recruited to mitochondria, indicating that mitophagy increased to remove the damaged mitochondria.ConclusionsThis is the first report of the inhibitory effects of CB on the osteogenesis of MSCs and the involvement of mitochondria in CB Printex 90-induced suppression of MSC osteogenesis.

Mitophagy during Differentiation of Human Embryonic Stem Cells

Mitochondria are cellular organelles that are critical for energy production. They also serve as signalling hubs, integrating a variety of inputs related to metabolic demand, redox control, and apoptosis. The mass and quality of mitochondria within a cell are determined by a balance between mitochondrial biogenesis and mitochondrial turnover. In human embryonic stem cells (hESCs), mitochondrial quality control is especially critical, as this inner‐cell‐mass derived cells are pluripotent and can propagate indefinitely. Cultured hESCs accumulate mutations in the mitochondrial genome, a fact that may limit the use of hESCs (and their differentiated derivate) in regenerative medicine. Mitophagy is a selective form of autophagy in which a mitochondrion is sequestered within a vesicle, delivered to the lysosome, and degraded. Here we show that the number of mitophagic events increases during early stages of hESC differentiation, as indicated by elevated co‐localization between LC3‐GFP‐labeled autophagosomes and MitoTracker‐labeled mitochondria. Furthermore, we detect increased levels of mitophagy in hESCs treated with agents that perturb mitochondrial integrity (e.g., EtBr, which damages mitochondrial DNA, and CCCP, which depolarizes the mitochondrial membrane). Our data demonstrate for the occurrence of mitophagy within hESCs. Our findings further suggest that mitophagy may selectively remove damaged mitochondria as hESCs differentiate. A more thorough understanding of the molecular mechanisms controlling mitophagy in hESCs may eventually allow for manipulation of this process, a technology that could improve the mitochondrial quality of cultured hESCs and thus facilitate the therapeutic application of these cells in regenerative medicine.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Parkin functionally interacts with PGC-1α to preserve mitochondria and protect dopaminergic neurons.

To understand the cause of Parkinson's disease (PD), it is important to determine the functional interactions between factors linked to the disease. Parkin is associated with autosomal recessive early-onset PD, and controls the transcription of PGC-1α, a master regulator of mitochondrial biogenesis. These two factors functionally interact to regulate the turnover and quality of mitochondria, by increasing both mitophagic activity and mitochondria biogenesis. In cortical neurons, co-expressing PGC-1α and Parkin increases the number of mitochondria, enhances maximal respiration, and accelerates the recovery of the mitochondrial membrane potential following mitochondrial uncoupling. PGC-1α enhances Mfn2 transcription, but also leads to increased degradation of the Mfn2 protein, a key ubiquitylation target of Parkin on mitochondria. In vivo, Parkin has significant protective effects on the survival and function of nigral dopaminergic neurons in which the chronic expression of PGC-1α is induced. Ultrastructural analysis shows that these two factors together control the density of mitochondria and their interaction with the endoplasmic reticulum. These results highlight the combined effects of Parkin and PGC-1α in the maintenance of mitochondrial homeostasis in dopaminergic neurons. These two factors synergistically control the quality and function of mitochondria, which is important for the survival of neurons in Parkinson's disease.

MitoPho8Δ60 Assay as a Tool to Quantitatively Measure Mitophagy Activity.

Mitophagy, a selective type of macroautophagy (hereafter referred to as autophagy), specifically mediates the vacuole/lysosome-dependent degradation of damaged or surplus mitochondria. Because this process regulates the number and quality of mitochondria, it is vital for proper cellular homeostasis. Mitophagy also plays critical roles in the clearance of paternal mitochondria in C. elegans embryos, in erythroid cell maturation, and in the prevention of neurodegenerative disease and cancer. In order to study the molecular mechanism and regulation of mitophagy, sensitive assays are necessary to quantitatively measure mitophagy activity. In the budding yeast, Saccharomyces cerevisiae, a "mitoPho8Δ60" assay was developed to study mitophagy. In this assay, Pho8, a vacuolar phosphatase protein, is genetically engineered to be targeted to mitochondria. When mitophagy is induced, the phosphatase protein, along with mitochondria, is conveyed to the vacuole, where its C-terminal propeptide is removed and the phosphatase activity becomes activated; under growing conditions only a background level of delivery occurs. For this reason, the enzymatic activity of mitoPho8Δ60 is correlated with the amount of mitochondria delivered to the vacuole. Thus, this assay serves as a very convenient tool to quantitatively monitor mitophagy activity in yeast.

Proteasome Impairment Induces Recovery of Mitochondrial Membrane Potential and an Alternative Pathway of Mitochondrial Fusion.

Mitochondria are vital and highly dynamic organelles that continuously fuse and divide to maintain mitochondrial quality. Mitochondrial dysfunction impairs cellular integrity and is known to be associated with various human diseases. However, the mechanism by which the quality of mitochondria is maintained remains largely unexplored. Here we show that impaired proteasome function recovers the growth of yeast cells lacking Fzo1, a pivotal protein for mitochondrial fusion. Decreased proteasome activity increased the mitochondrial oxidoreductase protein Mia40 and the ratio of the short isoform of mitochondrial intermembrane protein Mgm1 (s-Mgm1) to the long isoform (l-Mgm1). The increase in Mia40 restored mitochondrial membrane potential, while the increase in the s-Mgm1/l-Mgm1 ratio promoted mitochondrial fusion in an Fzo1-independent manner. Our findings demonstrate a new pathway for mitochondrial quality control that is induced by proteasome impairment.

Biogenêse mitocondrial e exercício físico: hipótese do acoplamento elétrico-transcripcional

Resumo Uma das principais modificações ocorridas no organismo em decorrência do treinamento físico-esportivo envolvendo exercícios físicos de longa duração é o aumento na quantidade e qualidade funcional de mitocôndrias do tecido muscular esquelético. Não existe até o momento um mecanismo causal explicativo para esse fenômeno. A proposta a ser discutida neste ensaio é denominada por "hipótese do acoplamento elétrico-transcripcional". Segundo a mesma, modificações na atividade elétrica celular, principalmente de despolarização membranar, constituem-se em método de controle e regulação dos processos de biossíntese no organismo multicelular. Por exemplo, estudos que provocaram hiperpolarização artificial em células somáticas induziram diferenciação celular e supressão da proliferação, sendo que o contrário ocorreu com a despolarização. Ou seja, a despolarização celular durante o exercício físico devido a contração muscular intensa e constante pode ativar processos responsáveis por biossínteses e, possivelmente, duplicação de mitocôndria.

Abstract 207: Unc-51-like Kinase 1 (ULK1) Plays A Crucial Role In Mitophagy In Cardiomyocytes

The mitochondrion is an essential organelle that supplies ATP in cardiomyocytes (CMs). However, damaged mitochondria are harmful via the production of reactive oxygen species and induction of apoptosis in pathological conditions. Therefore, quality of mitochondria should be controlled tightly through various mitochondrial quality control mechanisms. Mitochondrial autophagy (mitophagy) is considered an integral part of this mechanism, and recent investigations uncovered the role of PINK1 and Parkin in mitophagy. However, these observations were made under artificial conditions, such as over-expression of Parkin or treatment with CCCP, and thus the precise mechanism has not been fully elucidated in more pathophysiologically relevant conditions. Recent evidence suggests that mitophagy can take place independently of ATG7, a molecule essential for the conventional form of autophagy, and that this form of autophagy is ULK1-dependent. We investigated the role of ULK1 and ATG7 in mediating mitophagy using mitochondria-targeted Keima (Mito-Keima) in cultured rat neonatal CMs. Keima has a bimodal excitation spectrum peaking at 440 and 560 nm, corresponding to the neutral and acidic pH, respectively. In CMs transfected with Mito-Keima, the fluorescent dots with a high 560nm/440nm ratio represent the mitochondria incorporated into autolysosomes which indicate mitophagy. Here we report that ULK1 plays a more predominant role in glucose deprivation (GD) -induced mitophagy than ATG7. Control CMs exhibited 8.7±1.0 % of the area of high-ratio dots per cells after GD. Knockdown of ULK1 significantly reduced the area to 2.3±0.9 % in CMs after GD (p<0.01, vs sh-Control). The reduction was significantly greater in CMs with knockdown of ULK1 than that of ATG7 (7.0±1.6 %, p<0.05, sh-ULK1 vs sh-ATG7). In addition, knockdown of Beclin1 and Drp1 also significantly decreased the area of high-ratio dots (about 1.0 % and 0.5 %, respectively). Overexpression of ULK1 was sufficient to induce mitophagy without starvation, whereas that of ATG7 was not. These results suggest that ULK1, Beclin1 and Drp1 play an essential role in mediating GD-induced mitophagy in CMs.

Drinking coffee burns hepatic fat by inducing lipophagy coupled with mitochondrial β-oxidation

Coffee is one of the most consumed and popular beverages in the world nowadays. According to the National Coffee Association, more than 60% of American adults drink coffee each day, and an average of 3.1 cups of coffee are consumed by each drinker per day. In spite of its popularity, it has been controversial whether drinking coffee is detrimental or beneficial for human health. While a large body of evidence suggests that drinking coffee may be beneficial for a variety of chronic health conditions including type 2 diabetes, stroke, cancer and all-cause mortality, some other studies suggest that drinking coffee may be a potential hazard for coronary heart disease and may increase mortality in younger drinkers less than 55 years old. 1,2 The reasons for the conflicting results from these large population-based studies could be very complex, but one possibility could be due to the remarkable variety of different types of coffee and the preparation and brewing methods around the world. In contrast to the controversy regarding the health effect of coffee on other organs and tissues, all the experimental and population-based studies support unanimous beneficial effects of drinking coffee on the liver.

Ginsenoside Rg3 improves cardiac mitochondrial population quality: Mimetic exercise training

Emerging evidence indicates exercise training could mediate mitochondrial quality control through the improvement of mitochondrial dynamics. Ginsenoside Rg3 (Rg3), one of the active ingredients in Panax ginseng, is well known in herbal medicine as a tonic and restorative agent. However, the molecular mechanism underlying the beneficial effects of Rg3 has been elusive. In the present study, we compared the effects of Rg3 administration with aerobic exercise on mitochondrial adaptation in cardiac muscle tissue of Sprague–Dawley (SD) rats. Three groups of SD rats were studied: (1) sedentary control, (2) Rg3-treated and (3) aerobic exercise trained. Both aerobic exercise training and Rg3 supplementation enhanced peroxisome proliferator-activated receptor coactivator 1 alpha (PGC-1α) and nuclear factor-E2-related factor 2 (Nrf2) protein levels in cardiac muscle. The activation of PGC-1α led to increased mRNA levels of mitochondrial transcription factor A (Tfam) and nuclear related factor 1(Nrf1), these changes were accompanied by increases in mitochondrial DNA copy number and complex protein levels, while activation of Nrf2 increased levels of phase II detoxifying enzymes, including nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1(NQO1), superoxide dismutase (MnSOD) and catalase. Aerobic exercise also enhanced mitochondrial autophagy pathway activity, including increased conversion of LC3-I to LC3-II and greater expression of beclin1 and autophagy-related protein 7 (ATG7), these effects of aerobic exercise are comparable to that of Rg3. These results demonstrate that Rg3 mimics improved cardiac adaptations to exercise by regulating mitochondria dynamic remodeling and enhancing the quantity and quality of mitochondria.

Oxidative stress-induced autophagy in plants: The role of mitochondria

The strictly regulated removal of oxidized structures is a universal stress response of eukaryotic cells that targets damaged or toxic components for vacuolar or lysosomal degradation. Autophagy stands at the crossroad between cell survival and death. It promotes survival by degrading proteins and organelles damaged during oxidative stress, but it is also activated as a part of death programs, when the damage cannot be overcome. Evidence is accumulating that the cellular sites of ROS production and signaling may be primary targets of autophagy. Therefore, autophagosomal targeting of mitochondria (mitophagy) is of particular importance. Mitophagy is a selective process that can specifically target dysfunctional mitochondria, but also mitophagy may play a role in controlling the number and quality of mitochondria during stress. Here we review the mechanisms of both non-specific autophagy and mitochondrial targeting in plants, drawing analogies and emphasizing differences with yeast and mammalian systems.

Abstract 482: High CD44/CD24 expressive cells presented cancer stem cell characteristics and undergo mitochondrial resetting and metabolic shift in nasopharyngeal carcinoma

Abstract Cancer stem cells (CSCs) are a rare subset cancer cells with self-renewal property and cause many difficulties in clinical treatment. CSCs have been found in different tumors by specific surface markers. However, the surface marker of CSC remains unknown in various cancer types, including in nasopharyngeal carcinoma (NPC). Here, we took advantage of CSC's properties, such as chemoresistance, radioresistance, and the ability to form tumor spheres, to isolate CSCs from NPC cell lines. Combining these three isolation methods, and surface marker screening, we identified that NPC CSCs had high level of CD44 and CD24 surface antigen expression. We then validated the CD44/CD24 high positive as NPC CSC surface marker. In cell proliferation assay by MTT test, tumorigenity assay in soft agar and in vivo xenotransplantation, and radioresistant assay, CD44/CD24 high positive cells expressed significant CSC properties compared with CD44/CD24 double negative and parental NPC cells. We further found that CSCs underwent mitochondria resetting, including the distribution, quantity, and quality of mitochondria. Metabolic shift that largely relied on glycolysis also occured in CSCs. They predominately ultilized glycolysis instead of mitochondrial respiration to meet energy demand. Inhibiting glycolysis or treating antioxidants suppresses the viability and malignant traits of CSCs which provides therapeutic implication in NPC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 482. doi:10.1158/1538-7445.AM2011-482

Mitochondrial concept of leukemogenesis: key role of oxygen-peroxide effects

Background and hypothesisThe high sensitivity of hematopoietic cells, especially stem cells, to radiation and to pro-oxidative and other leukemogenic agents is related to certain of their morphological and metabolic features. It is attributable to the low (minimal) number of active mitochondria and the consequently slow utilization of O2 entering the cell. This results in an increased intracellular partial pressure of O2 (pO2) and increased levels of reactive oxygen (ROS) and nitrogen (RNS) species, and a Δ(PO – AO) imbalance between the pro-oxidative (PO) and antioxidative (AO) constituents.Proposed mechanismBecause excessive O2 is toxic, we suggest that hematopoietic cells exist in a kind of unstable dynamic balance. This suggestion is based on the idea that mitochondria not only consume O2 in the process of ATP production but also constitute the main anti-oxygenic stage in the cell's protective antioxidative system. Variations in the mitochondrial base capacity (quantity and quality of mitochondria) constitute an important and highly efficient channel for regulating the oxidative stress level within a cell.The primary target for leukemogenic agents is the few mitochondria within the hematopoietic stem cell. Disturbance and weakening of their respiratory function further enhances the initial pro-oxidative state of the cell. This readily results in peroxygenation stress, creating the necessary condition for inducing leukemogenesis. We propose that this is the main cause of all related genetic and other disorders in the cell. ROS, RNS and peroxides act as signal molecules affecting redox-sensitive transcription factors, enzymes, oncogenes and other effectors. Thereby, they influence the expression and suppression of many genes, as well as the course and direction of proliferation, differentiation, leukemogenesis and apoptosis.Differentiation of leukemic cells is blocked at the precursor stage. While the transformation of non-hematopoietic cells into tumor cells starts during proliferation, hematopoietic cells become leukemic at one of the interim stages in differentiation, and differentiation does not continue beyond that point. Proliferation is switched to differentiation and back according to a trigger principle, again involving ROS and RNS. When the leukemogenic ΔL(PO – AO) imbalance decreases in an under-differentiated leukemia cell to the differentiation level ΔD(PO – AO), the cell may continue to differentiate to the terminal stage.ConclusionThe argument described in this article is used to explain the causes of congenital and children's leukemia, and the induction of leukemia by certain agents (vitamin K3, benzene, etc.). Specific research is required to validate the proposals made in this article. This will require accurate and accessible methods for measuring and assessing oxidative stress in different types of cells in general, and in hematopoietic cells in particular, in their different functional states.

EFFECT OF PREPARATION PROCEDURE ON THE FUNCTION AND MORPHOLOGY OF LIVER MITOCHONDRIA FROM CONTROL AND ENDOTOXIC RATS

Background: Endotoxic shock is a condition in which cells fail to extract oxygen adequately from blood. The mitochondria are responsible for oxygen extraction from the blood. It is important to determine adequately mitochondrial function during pathological states. The isolation of mitochondria can result in a loss of a mitochondrial population (e.g. pathologically changed mitochondria). Aim: We determined whether the preparation procedure can influence mitochondrial functions and morphology or not. Methods: Rats received LPS (8 mg/kg i.v.). Untreated rats were used as a control. After 16 hours the livers were extracted, homogenized, mitochondria were prepared and used in three experiments. A) Comparison of mitochondrial morphology in liver tissue and isolated mitochondria by means of electron microscopy. B) Comparison of mitochondrial respiratory parameters using the high-resolution respirometry. C), comparison of the quality of mitochondrial preparations by the analysis of respiratory chain markers (cyt b, cyt c1, cyt c and cyt a). Results: We found A) no difference in swelling of mitochondria, observed in liver slices during endotoxic shock and in isolated mitochondria (no swelling in isolated control mitochondria), B) no difference between mitochondrial inrespiratory parameters in homogenate and isolated mitochondria, C) no significant difference in the quality of mitochondria in homogenates or isolated. Conclusions: All these data together suggest that the used isolation procedure of rat liver mitochondria from control and LPS treated rats does not significantly influence mitochondrial morphology and function and represent the full mitochondrial pool in liver tissue.

Radiosensitivity and metabolic properties of two tumour-types indigenous to the same host. I. A correlation of cellular structure and radiosensitivity.

SummaryThe radiosensitivity and metabolic properties of two types of mouse mammary tumours, epithelial (DBAH) and spindle (DBAG), both indigenous to the same host, are under extensive study. The cytological response of these tumours to 500 r, 1000 r and 3000 r is described in this first report. The spindle-tumour cells (DBAG) proved to be more radiosensitive and produced unusually abnormal mitotic figures, unipolar and multipolar. Electro-micrographs of this tumour revealed a paucity of mitochondria and their inferior quality, thereby explaining their extremely low capacity to phosphorylate in comparison with the epithelial tumour (DBAH). It is postulated that the quantity and quality of mitochondria play a significant role in cellular radiosensitivity. Thus the chromosomal imbalance may not be the only factor in cell-death induced by irradiation. This postulate is supported by observations on the tumours herein reported.