Mitochondrial form and function relationships in vivo: their potential in toxicology and pathology

Mitochondrial morphology in the mouse adrenal cortex: Influence of chronic psychosocial stress

Mitochondria within the adrenal cortex play a key role in synthesizing steroid hormones. The adrenal cortex is organized in three functionally specialized zones (glomerulosa, fasciculata, and reticularis) that produce different classes of steroid hormones in response to various stimuli, including psychosocial stress. Given that the functions and morphology of mitochondria are dynamically related and respond to stress, we applied transmission electron microscopy (TEM) to examine potential differences in mitochondrial morphology under basal and chronic psychosocial stress conditions. We used the chronic subordinate colony housing (CSC) paradigm, a murine model of chronic psychosocial stress. Our findings quantitatively define how mitochondrial morphology differs among each of the three adrenal cortex zones under basal conditions, and show that chronic psychosocial stress mainly affected mitochondria in the zona glomerulosa, shifting their morphology towards the more typical glucocorticoid-producing zona fasciculata mitochondrial phenotype. Analysis of adrenocortical lipid droplets that provide cholesterol for steroidogenesis showed that chronic psychosocial stress altered lipid droplet diameter, without affecting droplet number or inter-organellar mitochondria-lipid droplet interactions. Together, our findings support the hypothesis that each adrenal cortex layer is characterized by morphologically distinct mitochondria and that this adrenal zone-specific mitochondrial morphology is sensitive to environmental stimuli, including chronic psychosocial stressors. Further research is needed to define the role of these stress-induced changes in mitochondrial morphology, particularly in the zona glomerulosa, on stress resilience and related behaviors.

Activity regulates a cell type-specific mitochondrial phenotype in zebrafish lateral line hair cells

Hair cells of the inner ear are particularly sensitive to changes in mitochondria, the subcellular organelles necessary for energy production in all eukaryotic cells. There are over 30 mitochondrial deafness genes, and mitochondria are implicated in hair cell death following noise exposure, aminoglycoside antibiotic exposure, as well as in age-related hearing loss. However, little is known about the basic aspects of hair cell mitochondrial biology. Using hair cells from the zebrafish lateral line as a model and serial block-face scanning electron microscopy, we have quantifiably characterized a unique hair cell mitochondrial phenotype that includes (1) a high mitochondrial volume and (2) specific mitochondrial architecture: multiple small mitochondria apically, and a reticular mitochondrial network basally. This phenotype develops gradually over the lifetime of the hair cell. Disrupting this mitochondrial phenotype with a mutation in opa1 impacts mitochondrial health and function. While hair cell activity is not required for the high mitochondrial volume, it shapes the mitochondrial architecture, with mechanotransduction necessary for all patterning, and synaptic transmission necessary for the development of mitochondrial networks. These results demonstrate the high degree to which hair cells regulate their mitochondria for optimal physiology and provide new insights into mitochondrial deafness.

Structural and functional diversity of mitochondria in vestibular/cochlear hair cells and vestibular calyx afferents

Mitochondria supply energy in the form of ATP to drive a plethora of cellular processes. In heart and liver cells, mitochondria occupy over 20% of the cellular volume and the major need for ATP is easily identifiable - i.e., to drive cross-bridge recycling in cardiac cells or biosynthetic machinery in liver cells. In vestibular and cochlear hair cells the overall cellular mitochondrial volume is much less, and mitochondria structure varies dramatically in different regions of the cell. The regional demands for ATP and cellular forces that govern mitochondrial structure and localization are not well understood. Below we review our current understanding of the heterogeneity of form and function in hair cell mitochondria. A particular focus of this review will be on regional specialization in vestibular hair cells, where large mitochondria are found beneath the cuticular plate in close association with the striated organelle. Recent findings on the role of mitochondria in hair cell death and aging are covered along with potential therapeutic approaches. Potential avenues for future research are discussed, including the need for integrated computational modeling of mitochondrial function in hair cells and the vestibular afferent calyx.

Isn't It Time for Establishing Mitochondrial Nomenclature Breaking Mitochondrial Paradigm?

In this work, we decided to initiate a discussion concerning heterogeneity of mitochondria, suggesting that it is time to build classification of mitochondria, like the one that exists for their progenitors, α-proteobacteria, proposing possible separation of mitochondrial strains and maybe species. We continue to adhere to the general line that mitochondria are friends and foes: on the one hand, they provide the cell and organism with the necessary energy and signaling molecules, and, on the other hand, participate in destruction of the cell and the organism. Current understanding that the activity of mitochondria is not only limited to energy production, but also that these alternative non-energetic functions are unique and irreplaceable in the cell, allowed us to speak about the strong subordination of the entire cellular metabolism to characteristic functional manifestations of mitochondria. Mitochondria are capable of producing not only ATP, but also iron-sulfur clusters, steroid hormones, heme, reactive oxygen and nitrogen species, participate in thermogenesis, regulate cell death, proliferation and differentiation, participate in detoxification, etc. They are a mandatory attribute of eukaryotic cells, and, so far, no eukaryotic cells performing a non-parasitic or non-symbiotic life style have been found that lack mitochondria. We believe that the structural-functional intracellular, intercellular, inter-organ, and interspecific diversity of mitochondria is large enough to provide grounds for creating a mitochondrial nomenclature. The arguments for this are given in this analytical work.

Mitodiversity

Here, in addition to the previously coined term "mitobiota", we introduce the term "mitodiversity" for various phenotypic and genetic heterogeneities of mitochondria within the same cell or organ. Based on data on the mitochondrial transmembrane potential determined both in situ and in vitro under normal conditions and after organ ischemia/reperfusion, such heterogeneity is most evident under pathologic conditions. Herein, a part of the mitochondrial population with transmembrane potential typical of the normal state is sustained even under a pathological condition that, perhaps, underlies the development of ways of reversing pathology back to the normal state. The membrane potentials of isolated mitochondria were shown to directly correlate with the magnitude of side-scattered light depicting internal structure of mitochondria. We analyzed possible interpretations of data on mitochondrial membrane potential obtained using fluorescent probes. We suggest a possible mechanism underlying retention of fluorescent probes inside the cells and mitochondria.

Calcium-induced alteration of mitochondrial morphology and mitochondrial-endoplasmic reticulum contacts in rat brown adipocytes

Mitochondria are key organelles maintaining cellular bioenergetics and integrity, and their regulation of [Ca²⁺]_i homeostasis has been investigated in many cell types. We investigated the short-term Ca-SANDOZ^® treatment on brown adipocyte mitochondria, using imaging and molecular biology techniques. Two-month-old male Wistar rats were divided into two groups: Ca-SANDOZ^® drinking or tap water (control) drinking for three days. Alizarin Red S staining showed increased Ca²⁺ level in the brown adipocytes of treated rats, and potassium pyroantimonate staining localized electron-dense regions in the cytoplasm, mitochondria and around lipid droplets. Ca-SANDOZ^® decreased mitochondrial number, but increased their size and mitochondrial cristae volume. Transmission electron microscopy revealed numerous enlarged and fusioned-like mitochondria in the Ca-SANDOZ^® treated group compared to the control, and megamitochondria in some brown adipocytes. The Ca²⁺ diet affected mitochondrial fusion as mitofusin 1 (MFN1) and mitofusin 2 (MFN2) were increased, and mitochondrial fission as dynamin related protein 1 (DRP1) was decreased. Confocal microscopy showed a higher colocalization rate between functional mitochondria and endoplasmic reticulum (ER). The level of uncoupling protein-1 (UCP1) was elevated, which was confirmed by immunohistochemistry and Western blot analysis. These results suggest that Ca-SANDOZ^® stimulates mitochondrial fusion, increases mitochondrial-ER contacts and the thermogenic capacity of brown adipocytes.

Gender dimorphism in rat liver mitochondrial oxidative metabolism and biogenesis

In the present study, we have investigated gender differences in rat liver mitochondrial oxidative metabolism. Total mitochondrial population (M) as well as the heavy (M1), medium (M3), and light (M8) mitochondrial fractions obtained by means of differential centrifugation steps at 1,000, 3,000, and 8,000 g, respectively, were isolated. Electron microscopic analysis was performed and mitochondrial protein content and cardiolipin levels, mitochondrial O(2) flux, ATP synthase activity, mitochondrial membrane potential, and mitochondrial transcription factor A (TFAM) protein levels were measured in each sample. Our results indicate that mitochondria from females have higher protein content and higher cardiolipin levels, greater respiratory and phosphorylative capacities, and more-energized mitochondria in respiratory state 3. Moreover, protein levels of TFAM were four times greater in females than in males. Gender differences in the aforementioned parameters were more patent in the isolated heavy M1 and M3 mitochondrial fractions. The present study demonstrates that gender-related differences in liver mitochondrial function are due mainly to a higher capacity and efficiency of substrate oxidation, likely related to greater mitochondrial machinery in females than in males, which is in accord with greater mitochondrial differentiation in females.

Gender-related differences in morphology and thermogenic capacity of brown adipose tissue mitochondrial subpopulations

To investigate the possible existence of a gender dimorphism in the morphology and functionality of brown adipose tissue (BAT) mitochondrial subpopulations, we obtained three mitochondrial fractions - heavy, medium and light - by differential centrifugation. Electron microscopic analysis was carried out and mitochondrial protein content, cytochrome c oxidase and ATP synthase activities, mitochondrial DNA content and UCP1 protein levels were measured in each mitochondrial fraction. Female rats showed a greater mitochondrial size than males, with a different distribution pattern of the subpopulations. These differences were accompanied by higher oxidative and thermogenic capacities and a higher protein content in female rat BAT. This tissue also showed a greater tendency to respiratory chain uncoupling, as well as a close coordination between the oxidative, phosphorylative and thermogenic processes. These differences were found in the heavy subpopulation but not in the light one. Our results demonstrate that female rat BAT shows a highly differentiated mitochondrial pool, with the heavy mitochondrial subpopulation as the main responsible for the greater thermogenic activity of this tissue. In addition, it seems that there is a differential regulation of the mitochondrial growth cycle between genders in BAT, which leads to enhanced thermogenic capacity in female rat mitochondria.

Chronic corticosterone affects brain weight, and mitochondrial, but not glial volume fraction in hippocampal area CA3

Corticosterone (CORT), the predominant glucocorticoid in rodents, is known to damage hippocampal area CA3. Here we investigate how that damage is represented at the cellular and ultrastructural level of analyses. Rats were injected with CORT (26.8 mg/kg, s.c.) or vehicle for 56 days. Cell counts were estimated with the physical disector method. Glial and mitochondrial volume fractions were obtained from electron micrographs. The effectiveness of the CORT dose used was demonstrated in two ways. First, CORT significantly inhibited body weight gain relative to vehicles. Second, CORT significantly reduced adrenal gland, heart and gastrocnemius muscle weight. Both the adrenal and gastrocnemius muscle weight to body weight ratios were also significantly reduced. Although absolute brain weight was reduced, the brain to body weight ratio was higher in the CORT group relative to vehicles, suggesting that the brain is more resistant to the effects of CORT than many peripheral organs and muscles. Consistent with that interpretation, CORT did not alter CA3 cell density, cell layer volume, or apical dendritic neuropil volume. Likewise, CORT did not significantly alter glial volume fraction, but did reduce mitochondrial volume fraction. These findings highlight the need for ultrastructural analyses in addition to cellular level analyses before conclusions can be drawn about the damaging effects of prolonged CORT elevations. The relative reduction in mitochondria may indicate a reduction in bioenergetic capacity that, in turn, could render CA3 vulnerable to metabolic challenges.

The many shapes of mitochondrial membranes

The roles of mitochondria in cell death and in aging have generated much excitement in recent years. At the same time, however, a quiet revolution in our thinking about mitochondrial ultrastructure has begun. This revolution started with the use of vital dyes and of green fluorescent protein fusion proteins, showing that mitochondria are very dynamic structures that constantly move, divide and fuse throughout the life of a cell. More recently, some of the first proteins contributing to these various processes have been discovered. Our view of the internal structures of mitochondria has also changed. Three-dimensional reconstructions obtained with high voltage electron microscopy show that cristae are often connected to the mitochondrial inner membrane by thin tubules. These new insights are brought to bear on the wealth of data collected by conventional electron microscopic analysis.

Experimental diabetes in rats causes hippocampal dendritic and synaptic reorganization and increased glucocorticoid reactivity to stress

We report that 9 d of uncontrolled experimental diabetes induced by streptozotocin (STZ) in rats is an endogenous chronic stressor that produces retraction and simplification of apical dendrites of hippocampal CA3 pyramidal neurons, an effect also observed in nondiabetic rats after 21 d of repeated restraint stress or chronic corticosterone (Cort) treatment. Diabetes also induces morphological changes in the presynaptic mossy fiber terminals (MFT) that form excitatory synaptic contacts with the proximal CA3 apical dendrites. One effect, synaptic vesicle depletion, occurs in diabetes as well as after repeated stress and Cort treatment. However, diabetes produced other MFT structural changes that differ qualitatively and quantitatively from other treatments. Furthermore, whereas 7 d of repeated stress was insufficient to produce dendritic or synaptic remodeling in nondiabetic rats, it potentiated both dendritic atrophy and MFT synaptic vesicle depletion in STZ rats. These changes occurred in concert with adrenal hypertrophy and elevated basal Cort release as well as hypersensitivity and defective shutoff of Cort secretion after stress. Thus, as an endogenous stressor, STZ diabetes not only accelerates the effects of exogenous stress to alter hippocampal morphology; it also produces structural changes that overlap only partially with those produced by stress and Cort in the nondiabetic state.

Chronic stress alters synaptic terminal structure in hippocampus

Repeated psychosocial or restraint stress causes atrophy of apical dendrites in CA3 pyramidal neurons of the hippocampus, accompanied by specific cognitive deficits in spatial learning and memory. Excitatory amino acids mediate this atrophy together with adrenal steroids and the neurotransmitter serotonin. Because the mossy fibers from dentate granule neurons provide a major excitatory input to the CA3 proximal apical dendrites, we measured ultrastructural parameters associated with the mossy fiber-CA3 synapses in control and 21-day restraint-stressed rats in an effort to find additional morphological consequences of stress that could help elucidate the underlying anatomical as well as cellular and molecular mechanisms. Although mossy fiber terminals of control rats were packed with small, clear synaptic vesicles, terminals from stressed animals showed a marked rearrangement of vesicles, with more densely packed clusters localized in the vicinity of active zones. Moreover, compared with controls, restraint stress increased the area of the mossy fiber terminal occupied by mitochondrial profiles and consequently, a larger, localized energy-generating capacity. A single stress session did not produce these changes either immediately after or the next day following the restraint session. These findings provide a morphological marker of the effects of chronic stress on the hippocampus that points to possible underlying neuroanatomical as well as cellular and molecular mechanisms for the ability of repeated stress to cause structural changes within the hippocampus.

The impact of heavy metals on the grey garden slug, Deroceras reticulatum (Müller): Metal storage, cellular effects and semi-quantitative evaluation of metal toxicity

Laboratory-reared grey garden slugs, Deroceras reticulatum, were exposed to soil and food treated with solutions of three metal salts (CdCl2, ZnCl2, PbCl2) in three environmentally relevant concentrations, each for 21 days. Metal concentrations were determined in the soil, food and slugs by atomic absorption spectrophotometry (AAS). Zinc was localized ultrastructurally in the hepatopancreatic cells by means of energy-filtering transmission electron microscopy (EFTEM). Zinc, and also high amounts of copper, could be detected by electron spectroscopical imaging (ESI) and electron energy loss spectroscopy (EELS) in spherites of the basophilic cells. Ultrastructural responses to metal impact were investigated in two cell types of the hepatopancreas (digestive and basophilic cells) and the cellular responses were found to be dose- and metal-dependent. In order to evaluate the toxicity of the respective metal concentrations to the slugs, the ultrastructural reactions were semi-quantified and summarized as complex reaction patterns of numerous organelles. This novel approach provides a basis for the use of data from standardized tests as a background for risk assessment studies in the field.

Mitochondrial biogenesis in striated muscle

Mitochondrial biogenesis (synthesis) has been observed to occur in skeletal muscle in response to chronic use. It also occurs in cardiac muscle during growth and hypertrophy, and it may be impaired during the aging process. This review summarizes the literature on the processes of mitochondrial biogenesis at the biochemical and molecular levels, with particular reference to striated muscles. Mitochondrial biogenesis involves the expression of nuclear and mitochondrial genes and the coordination of these two genomes, the synthesis of proteins and phospholipids and their import into the organelle, and the incorporation of these lipids and proteins into their appropriate locations within the matrix, inner or outer membranes. The emphasis is on the regulation of these events, with information derived in part from other cellular systems. Although descriptions of mitochondrial content changes in heart and skeletal muscle during altered physiological states are plentiful, much work is needed at the molecular level to investigate the regulatory processes involved. A knowledge of biochemical and molecular biology techniques is essential for continued progress in the field. This is a promising area, and potential new avenues for future research are suggested.

Schwann cell mitochondrial alterations in peripheral nerves of rabbits treated with 2',3'-dideoxycytidine

2',3'-Dideoxycytidine (ddC) is a nucleoside analogue and reverse-transcriptase inhibitor that is approved for treatment of AIDS patients. A rabbit model of ddC neurotoxicity was developed to help understand the dose-limiting clinical neurotoxicity of ddC. Rabbits with a myelinopathy resulting from treatment with ddC exhibited mitochondrial alterations in Schwann cells of sciatic and tibial nerves and dorsal root ganglia. These changes were initially evident after 16 weeks of oral treatment with 35 mg/kg per day of ddC and were positively correlated with myelin pathology in individual animals. Cup-shaped mitochondria were frequently observed; when these mitochondria occurred in multiple concentric arrays or at various angles to one another, different profiles were formed depending on the plane of section. An increased number of mitochondrial cristae assumed a tubular configuration. It is suggested that the complex aggregations of mitochondria seen in this experiment are an adaptive response to altered mitochondrial function caused by treatment with ddC.

Close correlations between mitochondrial swelling and ATP-content in the ischemic canine myocardium. A combined morphometric and biochemical study

This study investigates how far mitochondrial swelling in the ischemic heart is influenced by factors pertaining to anaerobic energy turnover. Canine hearts were arrested by aortic cross clamping or cardioplegically with St. Thomas or HTK solution and incubated at 25 degrees C in the solution used for cardiac arrest. Samples of the left ventricle were taken at the end of cardiac arrest and during ischemia for structural evaluation and biochemical analysis. The extracellular pH in the interventricular septum was measured. Mitochondrial swelling was determined with the surface to volume ratio, a parameter independent of the reference space. Values obtained for different swelling were related to defined metabolite concentrations and pHe values to establish possible correlations between structural and biochemical parameters in the ischemic heart. At the onset of ischemia and during the breakdown of creatine phosphate (CP) to 3 mumol/g wet weight mitochondrial volume depends on the method of cardiac arrest and does not increase significantly in any of the three groups. The degree of mitochondrial swelling after depletion of CP correlates with the decline in ATP independent of the form of cardiac arrest. Characteristic values of the surface to volume ratio ascertained at different times of ischemia for all groups correspond to determined ATP concentrations. Acid pHe values seem to intensify mitochondrial swelling. With increased lactate concentrations mitochondria swell, but first initially the degree of swelling differs significantly in the forms of cardiac arrest investigated. Thus, the surface to volume ratio is a powerful and valid ultrastructural parameter, which makes correlations between mitochondrial structure and metabolism possible and furthermore indicates a strong correlation between mitochondrial swelling and ATP-concentration in the ischemic heart.

Cytoplasmic changes in primary cultured adult mouse sensory neurons induced by ethanol and acetaldehyde treatments

Primary cultured sensory neurons prepared from adult mice were maintained for 8 days in vitro. Such cultures were exposed to either a range of ethanol concentrations (50-300 mM) or acetaldehyde (0.5-2 mM) in serum-free medium for up to 24 h. Treated neuronal cultures, together with untreated controls in both the presence and absence of serum, were prepared for transmission electron microscopy. Nuclear morphology was not changed following treatment with either substance at the doses studied. A number of changes were observed, however, in the cytoplasm of neurons, and these were intensified by an increase in concentration and the length of exposure. Acetaldehyde induced effects at a much lower concentration than was required to induce a response with ethanol. Myelin lamellae loosely wound around dense granular core material appeared in multivesicular bodies at low doses. The prevalence of these increased with concentrations of 100 mM ethanol and 1 mM acetaldehyde; the numbers of lamellae in each myelin figure also increased but the core material was less prominent. Electron-dense bodies were also evident at higher dosages together with evidence of vacuolation of the endoplasmic reticulum and Golgi complexes. Mitochondrial profiles similar to those in untreated neurons persisted throughout the exposure periods. The generation of these inclusions may reflect a mechanism of membrane turnover, both of internal systems and cell membrane cycling, as a response to alcohol and aldehyde treatment.

Cyclosporin A protects hepatocytes subjected to high Ca2+ and oxidative stress

Hepatocytes incubated with 0.8 mM t-butylhydroperoxide are protected by cyclosporin A when the medium Ca2+ concentration is 10 mM, but not when it is 2.5 mM. The highest Ca2+ level is associated with an inhibition of t-butylhydroperoxide-dependent malondialdehyde accumulation and with mitochondrial Ca2+ loading within the cells. These findings are new evidence that t-butylhydroperoxide can kill cells by peroxidation-dependent and -independent mechanisms, and suggest that the mitochondrial permeability transition and the resultant de-energization are components of the peroxidation-independent mechanism. Cyclosporin A may have considerable utility for the protection of cells subjected to oxidative stress.

Electron spectroscopic study (ESI, EELS) of Nanoplast-embedded mammalian lung

The potential of Nanoplast melamine resin embedding for the study of mammalian lung parenchyma was examined by means of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS). Samples were either fixed with glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid, or were directly transferred to the embedding medium without prior fixation. Organic dehydrants, as well as fixatives containing heavy metals and stains, were omitted. A very high level of ultrastructural detail of chromatin, ribosomes, mitochondria and plasma membranes was achieved by ESI from the Nanoplast-embedded samples. The most prominent gain in ultrastructural detail was achieved when moving from an energy loss just below the L2,3 edge of phosphorus at 132 eV to an energy loss just beyond this edge. This reflects the prominent P L2,3 edge observed by EELS of Nanoplast-embedded samples in comparison with conventionally processed samples. Thus, taking into account possible sectioning artefacts, excellent heterochromatin images which rely on the phosphorus distribution can be obtained from Nanoplast-embedded samples by computer-assisted analysis of electron spectroscopic images. In this respect glutaraldehyde-paraformaldehyde fixation is preferable to glutaraldehyde-tannic acid fixation because the presence of silicon, revealed by EELS, in tannic-acid-fixed samples may introduce artefacts in phosphorus distribution images obtained by the three-window method because of the close proximity of the L2,3 edges of silicon and phosphorus.

Capillary and mitochondrial support of neural plasticity in adult rat visual cortex

Young adult rats (60 days old) were placed in complex environments (EC) or kept in individual cages (IC) for 10, 30, or 60 days. Previously reported findings in these same animals of synaptogenesis, decreased neuronal density, and increased cortical thickness in the EC animals demonstrated that cortical volume substantially expanded after 30 days. Such expansion would have spread apart existing capillaries and mitochondria, thereby diluting metabolic support. However, capillary spacing and mitochondrial volume fraction were maintained in these EC animals after 30 days, suggesting that new capillaries and mitochondria had infiltrated the tissue. Furthermore, many small vessels appeared after 10 days of complex experience, followed by expansion in vessel size until vessels from rats in EC for 60 days were larger than those from rats in IC for 60 days. The findings of constant vessel spacing in the face of expanding tissue volume, along with a set of small vessels that subsequently increased in size, suggest that small-sized new vessels were introduced in EC cortex by 10 days but had not matured in size until after 30 days. The results indicate that young adult rats can generate new capillaries and mitochondria in response to increased metabolic demands, but in a less vigorous fashion than in previously described weanling animals.

Non-Warthin's tumor oncocytic lesions

Oncocytes differ from other epithelial cells of salivary tissues in their excessive proliferation of mitochondria, in turn leading to a hypertrophy and hyperplasia of the chondriome. Oncocytic transformation is not a degenerative process, but rather a redifferentiation of the cells as they attempt to increase their output of high-energy phosphate. As oncocytes divide, their pathologic metabolic activity and mitochondrial phenotype are passed on to their progeny, and these cells produce salivary lesions that range from focal oncocytic metaplasia and hyperplasias to benign and malignant neoplasms--oncocytomas and oncocytic carcinomas.

The abnormal-shaped mitochondria in thymus lymphocytes treated with inhibitors of mitochondrial energetics

The effects of uncouplers (DNP, FCCP), oligomycin, and rotenone on the energetics and mitochondrial ultrastructure in lymphocytes have been studied. We confirmed the previous observations done on Ehrlich ascites and cardiomyocyte culture cells that uncouplers and respiratory inhibitors cause the appearance of ringlike and dumbbell-like mitochondria. It is shown that this effect does not correlate with decrease in ATP concentration, changes in oxygen consumption, or condensation of the mitochondrial matrix. FCCP (2 microM) is more effective in the induction of abnormal-form mitochondria than 240 microM DNP, oligomycin, or rotenone. Combined treatment with DNP, oligomycin, and rotenone or with DNP and rotenone produces an effect as strong as 2 microns FCCP. DNP (240 microM) and FCCP (2 microM) have a similar effect on respiration and intracellular ATP, but only the latter induces condensation of the mitochondrial matrix.

The fate of intramitochondrial paracrystalline inclusion bodies in germ line cells of water frogs (Amphibia, Anura)

Numerous intramitochondrial paracrystalline inclusion bodies (ICIB) were observed in the germinal plasm of a mid-blastula, and in primordial germ cells (PGCs) after their migration to the germinal ridges, in Rana ridibunda, R. lessonae and R. esculenta. In oogonia the number of ICIB decreases rapidly. Single ICIB are observed in the germ cells up to the leptotene stage; they have never been observed in pachytene oocytes. In diplotene oocytes that have reached a diameter of about 100 microns ICIB are visible again, and their number increases concomitantly with oocyte growth.

Cadmium induced changes in cell organelles: an ultrastructural study using cadmium sensitive and resistant muntjac fibroblast cell lines

A detailed electron microscopy study of cadmium sensitive and resistant muntjac fibroblast cell lines has identified a wide range of intracellular damage following exposure to cadmium. Damaged organelles included cell membrane, mitochondria, Golgi cisternae and tubular network, chromatin, nucleoli, microfilaments and ribosomes. Although cell membrane damage was generally the earliest indication of adverse cadmium action, particularly with continuous cadmium exposures, cells could tolerate extensive membrane loss. Mitochondrial distortion and some damage to Golgi was also tolerated. The turning point at which cadmium became lethal was generally marked by a cascade of events which included damage to both nuclear and cytoplasmic components. These results for fibroblasts are discussed and compared with damage reported in other types of cells.

Clinico-pathological study on macular mutant mouse

The macular mutant mouse was clinically and pathologically examined. The hemizygotes began to show white fur color and curly whiskers around postnatal day 3, then seizures and ataxia around day 8, while the normal littermates did not. The hemizygotes also increased weight gradually from birth to day 9, but then showed weight loss and died around day 15 with severe emaciation. These clinical features resembled those in Menkes kinky hair disease. There were no pathological changes in the cerebral cortex in the hemizygotes on day 7. On day 10, two to three clear vacuoles began to appear in a few neurons in the cerebrum. These neurons with vacuoles increased gradually in number and degenerative neurons were also observed by day 14. Ultrastructurally, they corresponded to giant abnormal mitochondria with an electron-lucent matrix and short peripherally located cristae. Other abnormal mitochondria, which were characterized by an electron-dense matrix with tubular or vesicular cristae, were also observed in the cerebral cortical neurons.

Light and electron microscopic study on cerebellar cortex of macular mutant mouse as a model of Menkes kinky hair disease

The macular mouse is a mutant mouse, the hemizygotes of which show clinical and biochemical abnormalities similar to those in Menkes kinky hair disease (MKHD) in humans. The cerebellar cortex of this mutant suckling mouse was examined by light and electron microscopy. In hemizygotes, the Purkinje cells showed a delay in the maturation of dendrites and somatic spines. Somal sprouts, abnormal mitochondria, and filamentous cytoplasmic inclusions were observed on these cells on day 13. Axonal swellings, containing abnormal mitochondrias were also seen in the inner granular layer. These findings correspond with those of MKHD in humans and those of the brindled mouse, another model mouse of MKHD.

Inhibition of respiration in mitochondria and in digitonin-treated rat hepatocytes by podophyllotoxin

The effects of the microtubular inhibitor, podophyllotoxin, on mitochondrial respiration were determined using isolated, digitonin-permeabilized hepatocytes and isolated mitochondria. In hepatocytes, podophyllotoxin (1.5 mM) inhibited coupled and uncoupled respiration of both FAD and NAD-linked substrates. In mitochondria, podophyllotoxin inhibited State III respiration, prevented the return to State IV respiration, and inhibited uncoupled respiration. There was no inhibition of ascorbate/TMPD oxidation in either the hepatocytes or the mitochondria. Podophyllotoxin had no effect upon oligomycin inhibition of coupled respiration. Oligomycin had no effect on the podophyllotoxin-inhibition of uncoupled respiration in either hepatocytes or mitochondria. The results indicate that podophyllotoxin alters electron flow at a site early in the electron transport chain.

Effects of ethidium bromide, tetramethylethidium bromide and betaine B on the ultrastructure of HeLa cell mitochondria in situ. A comparative binding study

Several investigators have described the ultrastructural changes that occur in the mitochondria of cells in tissue cultures after treatment with the drug ethidium bromide (E). The mitochondria swell and the cristae become greatly altered and finally disappear; in the cristae-free region of the matrix electron-dense granules can be observed. It has been assumed that intercalation of E between the base pairs of the mitochondrial DNA induces the formation of the granular inclusions. To investigate whether intercalation is really the initial step in the generation of dense granules inside the matrix, we performed a comparative incubation study of HeLa-cell mitochondria in situ using three closely related dyes (D), i.e., E, tetramethylethidium bromide (TME) and betaine B (B). They strongly differ with regard to their affinity for DNA and their ability to cross membranes. E was used as a reference dye. TME does not intercalate, but is externally bound to DNA only weakly. The neutral B is not bound at all, but can cross membranes more easily than the cation E. Moreover, in aqueous solutions at pH approximately equal to 7.0, B is in equilibrium with its protonated cation BH. BH and E have almost equal affinities for DNA. Therefore B may quickly pass the inner mitochondrial membranes and the cristae, and should then be bound inside the matrix, thus forming a BH-DNA complex. On the assumption that intercalation is necessary for the generation of intramitochondrial electron-dense bodies, we predicted that BH/B should be more efficient than E, while TME should be relatively ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hydrophobic acridine dyes for fluorescent staining of mitochondria in living cells. 3. Specific accumulation of the fluorescent dye NAO on the mitochondrial membranes in HeLa cells by hydrophobic interaction. Depression of respiratory activity, changes in the ultrastructure of mitochondria due to NAO. Increase of fluorescence in vital stained mitochondria in situ by irradiation]

The hydrophobic fluorescence dye 10-n-nonyl-acridinium-orange-chloride, NAO, stains specifically the mitochondria of living HeLa-cells. A dye concentration of 1 X 10(-8) M is sufficient for vital staining and at 5 X 10(-7) M an incubation time less than 1 min is enough to generate the bright green fluorescence of the mitochondria. The retention of NAO by the mitochondria is longer than 7 days. The dye accumulation is not affected by the ionophores valinomycin, nigericin, gramicidin, the uncoupling agents DNP, CCCP or by ouabain. In contrast to Rh 123 the trans-membrane potential is not the driving force of the NAO accumulation. We assume that NAO is bound to the hydrophobic lipids and proteins in the mitochondrial membranes by hydrophobic interaction. With valinomycin, 500 ng/ml, 10 min, the mitochondria in HeLa-cells swell. Now it is possible to observe some details in the enlarged mitochondria by light microscopy. After vital staining with NAO, 5 X 10(-7) M, 10 min, the periphery of the swollen mitochondria shows an intense green fluorescence, the inner part is dark. Obviously the dye is bound to the membranes. By electron microscopy it can be shown that the valinomycin treated and NAO stained mitochondria have outer and inner membranes and cristae. They differ from untreated mitochondria mainly in the size. After incubation of the HeLa-cells with relatively high NAO concentrations, 5 X 10(-6) M, 10 min, the mitochondria show a weak orange fluorescence. It is generated by the dimers D of NAO. Therefore the dye concentration in the mitochondrial membranes is locally very high and causes dye dimerisation. The weak orange fluorescence is instable and disappears within a few seconds. Instead we observe a green fluorescence with growing intensity that is generated by the monomers M of NAO. The intensity has its maximum value after a few seconds. Using low NAO concentrations for incubation, 1 X 10(-7) M, 10 min, we observe only the green fluorescence with increasing intensity. In this case the orange fluorescence is too weak for observation (concentration quenching). It can be shown by experiments and quantum mechanics that the orange fluorescence is assigned to an optical forbidden, the green fluorescence to an allowed electronic transition of D or M respectively. Our results indicate a dissoziation of D in 2 M by irradiation of the mitochondria under the fluorescence microscope.(ABSTRACT TRUNCATED AT 400 WORDS)

An analysis of the contribution of the preparatory technique to the appearance of condensed and orthodox conformations of liver mitochondria

The structure and volume of isolated mitochondria embedded for electron microscopy during different respiratory states were analyzed in thin sections. Three different embedding methods were compared; osmium tetroxide fixation/acetone dehydration, glutaraldehyde fixation/acetone dehydration, and glutaraldehyde fixation-osmium tetroxide postfixation/acetone dehydration. Analysis of fresh mitochondria, isolated in a sucrose medium, revealed the presence of a homogeneous population with respect to structure when any of the three methods were applied. After fixation with osmium alone, or in combination with glutaraldehyde, nearly 100% of the mitochondria were in a "condensed" conformation. Mitochondria fixed with glutaraldehyde alone resulted in a population of mitochondria that had large spaces separating the two membranes of the cristae which corresponds to the condensed conformation as observed after osmium fixation. Transfer of the mitochondria to the incubation medium led to the appearance of two classes of mitochondria with respect to size. One class had a volume close to that observed when suspended in sucrose, and another class was present that was 30-45% larger. In osmium fixed or in double-fixed preparations, these small and large classes corresponded to "condensed" and "orthodox" forms of mitochondria respectively. When glutaraldehyde was used alone as the fixative, the two size classes were also present. However, the mitochondria were homogeneous with respect to structure. In these mitochondria, the width of the space that separated the cristae membranes had become reduced when compared to mitochondria suspended in sucrose. The two size classes were also present in samples of mitochondria prepared during both states 3 and 4. State 4 conditions did not lead to any significant increase of the number of condensed mitochondria. In state 3 preparations, 65-70% of the population were condensed. The condensed and orthodox forms could be related to normal and swollen forms of mitochondria. Conditions that led to a swelling also led to an increase in the number of orthodox mitochondria in osmium-fixed material. The different appearance of the mitochondria is explained by the different conditions for fixation of the mitochondria that exist when nonswollen and swollen mitochondria are fixed. This difference is particularly crucial in the case of osmium tetroxide due to the unique way this fixative, among generally used fixatives, denatures proteins.