CRYSTALLINE STRUCTURES IN THE MITOCHONDRIA OF NORMAL HUMAN LIVER PARENCHYMAL CELLS

Giant mitochondria in human liver disease

This thematic review aims to provide an overview of the current state of knowledge about the occurrence of giant mitochondria or megamitochondria in liver parenchymal cells. Their presence and accumulation are considered to be a major pathological hallmark of the health and fate of liver parenchymal cells that leads to overall tissue deterioration and eventually results in organ failure. The first description on giant mitochondria dates back to the 1960s, coinciding with the availability of the first generation of electron microscopes in clinical diagnostic laboratories. Detailed accounts on their ultrastructure have mostly been described in patients suffering from alcoholic liver disease, chronic hepatitis, hepatocellular carcinoma and non-alcoholic fatty liver disease. Interestingly, from this extensive literature survey, it became apparent that giant mitochondria or megamitochondria present themselves with or without highly organised crystal-like intramitochondrial inclusions. The origin, formation and potential role of giant mitochondria remain to-date largely unanswered. Likewise, the biochemical composition of the well-organised crystal-like inclusions and their possible impact on mitochondrial function is unclear. Herein, concepts about the possible mechanism of their formation and three-dimensional architecture will be approached. We will furthermore discuss their importance in diagnostics, including future research outlooks and potential therapeutic interventions to cure liver disease where giant mitochondria are implemented.

Aldehyde dehydrogenase, Ald4p, is a major component of mitochondrial fluorescent inclusion bodies in the yeast Saccharomyces cerevisiae

When Saccharomyces cerevisiae strain 3626 was cultured to the stationary phase in a medium that contained glucose, needle-like structures that emitted autofluorescence were observed in almost all cells by fluorescence microscopy under UV excitation. The needle-like structures completely overlapped with the profile of straight elongated mitochondria. Therefore, these structures were designated as mitochondrial fluorescent inclusion bodies (MFIBs). The MFIB-enriched mitochondrial fractions were successfully isolated and 2D-gel electrophoresis revealed that a protein of 54 kDa was only highly concentrated in the fractions. Determination of the N-terminal amino acid sequence of the 54-kDa protein identified it as a mitochondrial aldehyde dehydrogenase, Ald4p. Immunofluorescence microscopy showed that anti-Ald4p antibody specifically stained MFIBs. Freeze-substitution electron microscopy demonstrated that cells that retained MFIBs had electron-dense filamentous structures with a diameter of 10 nm in straight elongated mitochondria. Immunoelectron microscopy showed that Ald4p was localized to the electron-dense filamentous structures in mitochondria. These results together showed that a major component of MFIBs is Ald4p. In addition, we demonstrate that MFIBs are common features that appear in mitochondria of many species of yeast.

Multiple mitochondrial alterations in a case of myopathy

Mitochondrial alterations are the most common feature of human myopathies. A biopsy of quadriceps muscle from a 50-year-old woman exhibiting myopathic symptoms was examined by transmission electron microscopy. Biopsied fibers from quadriceps muscle displayed numerous subsarcolemmal mitochondria that contained crystalloids. Numbering 1-6 per organelle, these consisted of rows of punctuate densities measuring ∼0.34 nm; the parallel rows of these dots had a periodicity of ∼0.8 nm. The crystalloids were ensconced within cristae or in the outer compartment. Some mitochondria without crystalloids had circumferential cristae, leaving a membrane-free center that was filled with a farinaceous material. Other scattered fibrocyte defects included disruption of the contractile apparatus or its sporadic replacement by a finely punctuate material in some myofibers. Intramitochondrial crystalloids, although morphologically striking, do not impair organelle physiology to a significant degree, so the muscle weakness of the patient must originate elsewhere.

Megamitochondria formation - physiology and pathology

Mitochondria undergo structural changes simultaneously with their functional changes in both physiological and pathological conditions. These structural changes of mitochondria are classified into two categories: simple swelling and the formation of megamitochondria (MG). Data have been accumulated to indicate that free radicals play a crucial role in the mechanism of the MG formation induced by various experimental conditions which are apparently various. These include ethanol-, chloramphenicol- and hydrazine-induced MG formation. Involvement of free radicals in the mechanism of MG formation is showed by the fact that MG formation is successfully suppressed by free radical scavengers such as alpha-tocopherol, coenzyme Q(10), and 4-OH-TEMPO. Detailed mechanisms and pathophysiological meanings of MG formation still remain to be investigated. However, a body of evidence strongly suggests that enormous changes in physicochemical and biochemical properties of the mitochondrial membranes during MG formation take place and these changes are favorable for membrane fusion. A recent report showed that continous exposure of cells with MG to free radicals induces apoptosis, finding which suggests that MG formation is an adaptative process to unfavorable environments at the level of intracellular organelles. Mitochondria try to decrease intracellular reactive oxygen species (ROS) levels by decreasing the consume of oxygen via MG formation. If mitochondria succeed to suppress intracellular ROS levels, MG return to normal both structurally and functionally, and they restore the ability to actively synthesize ATP. If cells are additionally exposed to excess amounts of free radicals, MG become swollen, membrane potential of mitochondria (DeltaPsim) decreases, cytochrome c is released from mitochondria, leading to activation of caspases and apoptosis is induced.

Multifunctional proteins in Tetrahymena: 14-nm filament protein/citrate synthase and translation elongation factor-1 alpha

One gene encoding a protein has been shown to have two entirely different functions. Such a phenomenon, which has been called "gene sharing," was first known in crystallins. We found two multifunctional proteins in the ciliated protozoan Tetrahymena: 14-nm filament protein and protein translation elongation factor 1-alpha (EF-1 alpha). The 14-nm filament protein has dual functions as a citrate synthase in mitochondria and as a cytoskeletal protein in cytoplasm. In cytoplasm, the 14-nm filament protein was involved in oral morphogenesis and in pronuclear behavior during conjugation. The observation that Tetrahymena intramitochondrial filamentous inclusions contain the 14-nm filament protein and that the citrate synthase activity of the 14-nm filament protein is decreased by polymerization and increased by depolymerization, suggests a possible modulating mechanism of citrate synthase activity by monomer-polymer conversion in mitochondria in situ. The EF-1 alpha functions as an F-actin-bundling protein and a 14-nm filament-associated protein as well as an elongation factor in protein synthesis. The F-actin-bundling activity of EF-1 alpha was regulated by Ca2+ and calmodulin. Here we review the properties and functions of two multifunctional proteins in Tetrahymena.

Pathology of hepatic peroxisomes and mitochondria in patients with peroxisomal disorders

The morphology of hepatic peroxisomes in five patients with metabolic disorders believed to be due to inherited defects of peroxisomal function or biogenesis is described. Electron microscopy and cytochemical staining for catalase were used to identify peroxisomes in two boys with infantile Refsum's disease (IRD), a girl with autopsy confirmed neonatal adrenoleukodystrophy (NALD), and two boys with pseudo-Zellweger syndrome (PZS). In the patients with IRD and NALD hepatic peroxisomes were significantly reduced in size and number and contained electron dense centres. In the liver of the patients with PZS the peroxisomes were enlarged. Morphologically abnormal peroxisomes were also detected in autopsy tissue from one boy with PZS using electron microscopy. Lamellar-lipid inclusions and mitochondria with crystalline inclusions and/or abnormal cristae are also described in two patients, one with IRD, the other with NALD.

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.

Use of histological examination to assess ultrastructure of liver in patients with long standing jejuno-ileal bypass for morbid obesity

To assess the pattern and severity of liver disease in patients who had undergone jejuno-ileal bypass for the treatment of morbid obesity, 23 patients were biopsied, all of whom had had intact bypasses for more than 10 years. These were examined by light and electron microscopy. Previous biopsy specimens from each patient, including specimens taken before bypass, were reviewed. Similar biopsy specimens were obtained from six obese patients undergoing gastroplasty. There was no evidence of cirrhosis, and mild or moderate degrees of fibrosis were found in only a few patients. Steatosis tended to persist after bypass, albeit to a lesser degree. Giant mitochondria and intramitochondrial filamentous inclusions were present in four of six specimens taken before gastroplasty and in 15 of 23 specimens taken after jejuno-ileal bypass, being especially numerous in those specimens showing little or no steatosis. It is suggested that such features reflect ultrastructural evidence of adaptation to an abnormal metabolic environment both in the morbidly obese and even many years after jejuno-ileal bypass. Their prognostic importance is unclear.

Significance of megamitochondria in alcoholic liver disease

The significance of megamitochondria in the alcoholic liver injury of humans was investigated as part of a large Veterans Administration cooperative study of the natural history of alcoholic hepatitis. Two hundred twenty patients were clinically stratified into the following three groups according to disease severity using serum bilirubin and prothrombin time as indicators: Group 1 (mild disease), serum bilirubin levels less than 5 mg/dl and prothrombin time prolonged for less than 4 s; group 2 (moderate disease), serum bilirubin levels greater than 5 mg/dl but prothrombin time prolonged for less than 4 s; and group 3 (severe disease), serum bilirubin levels greater than 5 mg/dl and prothrombin time prolonged for greater than 4 s. Megamitochondria were observed in 20% of the patients (45 of 220). Of these, 43 patients were in groups 1 and 2 of severity and only 1 patient belonged in group 3. The association of megamitochondria with cirrhosis was infrequent (33%, 15 of 45 patients). The differences in severity correlated with the differences in mortality: in patients with megamitochondria, only 1 had died at 6 mo compared with 40 deaths in patients without megamitochondria. By 12 mo, there were two deaths in patients with megamitochondria versus 51 deaths in those patients without. No complications were present in 72% of patients with megamitochondria versus 39% for those without. Infection, gastrointestinal bleeding, pancreatitis, hyperglycemia, azotemia, delirium tremens, seizures, and hepatic encephalopathy were all more common in patients without megamitochondria. The patients with megamitochondria appear to represent a subcategory of alcoholic hepatitis with a milder degree of clinical severity, lower incidence of cirrhosis, fewer complications, and good long-term survival.

Ultrastructural study of the liver in argininosuccinase deficiency

The liver of a 19-year-old woman with argininosuccinase deficiency was studied ultrastructurally under conditions for excellent tissue fixation. Dilated smooth endoplasmic reticulum and mitochondrial crystalloids were the most prominent abnormalities found. These features were compared to fine-structural abnormalities found in other disorders of the Krebs-Henseleit pathway. No change was considered specific or related to subcellular enzyme localization.

Acute fatty liver of pregnancy: a clinicopathologic study of 35 cases

Acute fatty liver of pregnancy is a disease of the third trimester which is generally considered to be rare and to have a grave prognosis. This study found an optimistic outlook for patients with acute fatty liver of pregnancy due to early termination of the pregnancy as well as the recognition of milder cases. In prospectively followed women, a maternal mortality of 8% and a fetal mortality of 14% were observed. The disorder also appears to be more common than previously suspected and should be considered in all women with liver dysfunction in late pregnancy, even if they are anicteric. Histologically, the characteristic fine droplet steatosis usually produces distinct vacuolization in sections stained with hematoxylin-eosin. However, early in the course of the illness, liver cells have a ballooned appearance and the presence of lipid is masked. When accompanied by a significant necroinflammatory reaction, this stage may be difficult to distinguish from acute viral hepatitis. Whenever acute fatty liver of pregnancy is suspected, a small piece of the biopsy should be reserved for special stains to confirm the presence of lipid in frozen sections. Significant loss of hepatic parenchyma is a regular accompaniment of acute fatty liver of pregnancy and is due to hepatocytolysis, acidophilic degeneration and liver cell atrophy. Extramedullary hematopoiesis and giant mitochondria are often present; the latter change is probably an adaptive or degenerative response to an altered metabolic environment. Despite the frequent presence of signs and symptoms of toxemia in patients with acute fatty liver of pregnancy, no histologic overlap was observed, suggesting that they represent distinct etiologic entities.

Histopathological identification of hepatic intramitochondrial crystalloid inclusions (IMCI)

A 45-year-old female with systemic lupus erythematosus underwent liver biopsies twice during the period of cefazolin administration and a complication of cefazolin-induced toxic hepatitis was strongly suggested. Histologically, a small number of spindle-shaped, esoinophilic crystalloid bodies were faintly noticed in the cytoplasm of hepatocytes in hematoxylin and eosin-stained sections, while they showed strong positivity for strains inherent to mitochondria as well as specific to phospholipid and sharply showed a spindle or needle shaped configuration. Moreover, they greatly increased in number in these sections. They were distributed throughout the the parenchyma but were prominent in the degenerated hepatocytes with slight fatty metamorphosis. Electron microscopically, they proved to correspond to the intramitochondrial crystalloid inclusions (IMCI). Despite many ultrastructural descriptions of the IMCI, precise histopathological examination of the IMCI referring to the staining property on the deparaffinated sections has not yet been described since the first report of the IMCI by Napolitano (1958).

The pig yolk sac I. Fine structure of the posthaematopoietic organ

Yolk sacs from pig embryos ranging between 18 mm and 55 mm in length were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and histochemistry. The organ was no longer present in embryos of 70 mm length. The endoderm proliferates in embryos of about 20 mm length with gland-like endodermal cell columns and finally becomes stratified, representing over 90% of the yolk sac mass. The endodermal cells show a high activity of oxidoreductases and lysosomal enzymes; their luminal surface bears few absorptive specializations. The mesothelium is inert, as judged from its surface ultrastructure, organelle composition and enzyme content. TEM reveals the endodermal cells to be polarized even in stratified areas. They resemble liver parenchymal cells with respect to their basal villi, which are exposed to capillaries with discontinuous or fenestrated endothelium. Giant mitochondria with crystalline inclusions in the mature endodermal cytoplasm are outnumbered by large stacks of the rough ER, which can amount to 60% of the cytoplasm. This conspicuous RER is suspected to be the production site of serum proteins which are discharged into the vascular bed. Close to the time of the organ's regression, an unusual storage of material in terminal buds of the ER was found. Intercellular canaliculi and the endocytic apparatus of the endoderm are thought to serve regression.

Ultrastructural comparison of hepatoblastoma and hepatocellular carcinoma

The ultrastructural characteristics of fetal liver, two hepatoblastomas and two hepatocellular carcinomas were compared. Tumor cells of hepatoblastoma disclosed monotonous nuclei, poorly-developed cytoplasmic membrane system, abundant free ribosomes and prominent glycogen granules. Thos of hepatocellular carcinoma revealed comparatively pleomorphic nuclei, well-developed cytoplasmic membrane system, a few free ribosomes and numerous glycogen granules. Fetal liver showed monotonous nuclei, well-developed RER abundant free ribosomes and prominent glycogen granules. Young mesenchymal cells with well-developed RER and continuous basal lamina surrounding the epithelial cells were detected in both cases of hepatoblastoma but not in those of hepatocellular carcinoma. Tumor cells of hepatoblastoma in a case showed intramitochondrial crystalloids and thick bundles of fibrils in the cytoplasm.

Effects of anabolic steroids on liver cell ultrastructure in sheep

Castrated male sheep were sham inplanted or implanted with estradiol, trenbolone acetate or trenbolone acetate in combination with estradiol, and slaughtered after 56 days. Ultrastructural and morphometric examination of the livers of steroid-treated sheep showed an increase in the volume density of the cell occupied by rough endoplasmic reticulum and microbodies. In four of the eight sheep treated with trenbolone acetate, either alone or in combination with estradiol, enlarged mitochondria with crystalline inclusions were seen. The increase in hepatic rough endoplasmic reticulum may be of benefit to the sheep whereas the mitochondrial changes after anabolic steroid use indicate a cellular lesion of unknown significance for health.

The significance of ragged-red fibres in neuromuscular disease

The pathological significance of ragged-red fibres is uncertain. We have studied ragged-red fibres in the muscle biopsies of 3 adults; one with polymyositis and two with progressive external ophthalmoplegia. All the ragged-red fibres were Type 1 fibres. In two patients the mean diameter of the ragged-red fibres was significantly smaller than the unaffected Type 1 fibres. Some of these fibres showed features of regeneration, and others of degeneration. In the patient with polymyositis the mitochondria were proliferated and contained osmiophilic dense bodies; in the other two patients paracrystalline mitochondrial inclusions were prominent. These findings suggest that ragged-red fibres do not represent a single pathological process.

Corticosteroid-responsive skeletal muscle disease associated with partial carnitine deficiency: studies of liver and metabolic alterations

A patient with progressive skeletal muscle weakness had lipid-containing vacuoles in type I muscle fibers and partial carnitine deficiency of skeletal muscle. Results of certain liver function tests were abnormal, marked morphologic abnormalities of liver were detected, and a reduced cyclic adenosine 3',5'-monophosphate response to glucagon was present. After the oral administration of prednisone the patient exhibited gradual but striking clinical improvement, skeletal muscle fiber vacuoles could no longer be demonstrated, and the glucagon-provoked cyclic AMP response reverted to normal, but liver abnormalities persisted. At the same time utilization by skeletal muscle of long-chain fatty acids, pyruvate and beta-hydroxybutyrate was depressed. It is possible that the involvement of skeletal muscles was due to an inability of carnitine to attach to or to penetrate the sarcolemmal membrane. Some of the derangement, perhaps related to liver malfunction, was apparently corrected by the oral administration of prednisone although skeletal muscle metabolism remained impaired.

Abnormal liver function in chronic hypervitaminosis A

A case of chronic hypervitaminosis A is reported in a 57-year-old woman who took vitamin preparations for alopecia. Liver biopsy of the patient showed both an increase in the number and size of fat-storing cells on light microscopy and rapidly fading green autofluorescence of vitamin A. Electron microscopy confirmed the presence of engorged fat-storing cells in the space of Disse and minor toxic changes in hepatocytes. This case illustrates the early hepatic changes of chronic hypervitaminosis A and indicates a need for restriction of sales of vitamin preparations.

Hepatocyte giant mitochondria: an almost constant lesion in systemic scleroderma

Liver electron microscopic studies were performed in 14 patients with systemic scleroderma. In 13 of these patients, giant mitochondria were demonstrated in the hepatocytes. This ultrastructal abnormality was present whatever the type and duration of the disease and was also present even when the liver was histologically normal. The mechanism of formation of giant mitochondria in systemic scleroderma is unknown.

The general occurrence of intramitochondrial crystals in Hydra cells

Intramitochondrial crystals are found in normal Hydra as well as in animals undergoing various conditions (budding, regenerating, eserine-treated, and sexual). They appear in all regions of the animal, but seem to be more prevalent at or near the extremities: hypostome, tentacles and basal disk. They are found in all of the seven basic cell types: interstitial, cnidocyte, nerve, epithelio-muscular, gland, mucous and digestive cells. The chemical nature of the intramitochondrial crystals is unknown and their significance remains speculative.

Effects of levamisole on the ultrastructure of mitochondria in the liver of Beagle dogs

Purebred Beagle dogs were treated daily for 6 days with levamisole in oral doses of 10 mg/kg body weight. Liver biopsies taken before and after treatment showed no ultrastructural differences. Intramitochondrial paracrystalline inclusions before, as well as after, the drug administration were rare. Other minor abnormalities, in a few mitochondria, were as frequent before as after the drug treatment.

Fine structure of the medial nucleus of the trapezoid body of the bat with special reference to two types of synaptic endings

The medial nucleus of the trapezoid body has been studied electron microscopically in two species of bat, Miniopterus schreibersi fuliginosus and Vespertilio superans, which were perfused with three different kinds of fixatives, osmium tetroxide, glutaraldehyde, and formaldehyde. Two types of synaptic endings are observed in the nucleus: the abundant calyciferous endings and the less frequently occurring "small-vesicle endings." The former endings vary greatly in size, and contain extended extracellular spaces between pre- and post-synaptic membranes. The latter endings are always small, without the extended extracellular spaces, and tend to lie side by side. In all of the materials perfused with three different fixatives, synaptic vesicles in the calyciferous endings are round in shape and larger than those in the small-vesicle endings. The shape of vesicles in the small-vesicle endings varies according to the kinds of fixatives used; round in osmium tetroxide-fixed materials, flattened in formaldehyde-fixed materials, and somewhat round or flattened in glutaraldehyde-fixed materials. It is suggested that the calyciferous endings are excitatory in nature and that the small-vesicle endings are inhibitory.