Large Number Of Mitochondria Research Articles

Germline Transmission of Mitochondrial DNA in the Mouse.

In mammals, mitochondria and mitochondrial DNA (mtDNA) are transmitted through the female germline. Mature oocytes contain nearly 200,000 copies of mtDNA, organized at 1-2 copies per organelle. Despite the high genome copy number, mtDNA sequence variants are observed to segregate rapidly between generations, and this has led to the concept of a genetic bottleneck for the transmission of mtDNA. Here, we demonstrate that a subgroup of replicating genomes in the early post-natal ovary is responsible for the rapid segregation of mtDNA and show that the rate of segregation of mtDNA can be accelerated when mtDNA copy number is further reduced in heteroplasmic germline-specific knockout mouse models, yet very extreme reductions in germ cell mtDNA content seem to cause female-specific infertility. Low copy number embryos can be fertilized and proceed through preimplantation development yet fail to develop normally after implantation. Tracking the developmental outcome of embryos containing a range of mtDNAs points to a developmental threshold of about 50,000 copies of mtDNA in the oocyte Thus, we advance the hypothesis that the large number of mitochondria and mtDNAs present in the oocyte represent a genetic mechanism to ensure their distribution to the gametes and somatic cells of the next generation. If true, mtDNA copy number may be the most important determinant of oocyte quality not because of the effects on oocyte metabolism, but because too few would result in a maldistribution in the embryo. (platform)

Mimicking Mitochondrial Cristae Dynamics and the Amyloid - beta (1- 42) Induced Failure of Mitochondrial Cristae. A Study Involving Model Lipid Membranes

Number of studies showed, in the case of Alzheimer's disease, abnormalities in the oxidative metabolism of mitochondria, reduced ATP production, and, mitochondrial damage (broken cristae), which were related, amongst others, to the excessive presence of Amyloid-beta peptide in mitochondrial cristae. Surprisingly, the mechanisms relating the accumulation of Amyloid-beta in the cristae with the large number of mitochondria with broken cristae was even not evoked, never mind that it is widely recognized now that mitochondria function and morphology are coupled. In our previous work (Khalifat et al., 2008, Biophys J 95:4924), using giant unilamellar vesicles (GUVs) for modeling mitochondrial inner membrane, we offered some original insights into the factors that determine the dynamical tubular structures of the mitochondrial inner membrane cristae. Furthermore, we suggested a theoretical model (Fournier et al., 2009, Phys Rev Lett 102:018102) for elucidating the physical background of a particular membrane instability - membrane tubule formation, triggered by modulation of local pH. In the present work, using GUVs in a similar manner, we show directly (using video-microscopy) that Amyloid-beta might itself cause brutal rupturing of the model lipid membrane and make cristae-like morphology fail. Using large unilamellar vesicles we showed as well that the Amyloid-beta induces membrane dehydration and rise of membrane viscosity. Our hypothesis is: the failure of mitochondrial inner membrane morphology might be due to very basic and purely physical mechanism - the deterioration of mechanical (visco-elastic) properties of the lipid membrane. Thereby, the local strain created during cristae formation could provoke the inner membrane rupture. In other words, the Amyloid-beta (1-42) could induce the lipid bilayer incapacity to support the dynamics of shape changes underlying (and inherent to) mitochondrial inner membrane normal functioning.

Developmental changes and organelle biogenesis in the reproductive organs of thermogenic skunk cabbage (Symplocarpus renifolius).

Sex-dependent thermogenesis during reproductive organ development in the inflorescence is a characteristic feature of some of the protogynous arum species. One such plant, skunk cabbage (Symplocarpus renifolius), can produce massive heat during the female stage but not during the subsequent male stage in which the stamen completes development, the anthers dehisce, and pollen is released. Unlike other thermogenic species, skunk cabbage belongs to the bisexual flower group. Although recent studies have identified the spadix as the thermogenic organ, it remains unclear how individual tissues or intracellular structures are involved in thermogenesis. In this study, reproductive organ development and organelle biogenesis were examined during the transition from the female to the male stage. During the female stage, the stamens exhibit extensive structural changes including changes in organelle structure and density. They accumulate high levels of mitochondrial proteins, including possible thermogenic factors, alternative oxidase, and uncoupling protein. By contrast, the petals and pistils do not undergo extensive changes during the female stage. However, they contain a larger number of mitochondria than during the male stage in which they develop large cytoplasmic vacuoles. Comparison between female and male spadices suggests that mitochondrial number rather than their level of activity correlates with thermogenesis. Their spadices, even in the male, contain a larger amount of mitochondria that had greater oxygen consumption, compared with non-thermogenic plants. Taken together, our data suggest that the extensive maturation process in stamens produces massive heat through increased metabolic activities. The possible mechanisms by which petal and pistil metabolism may affect thermogenesis are also discussed.

Mitochondrial Dysfunction and Psychiatric Disorders

Mitochondrial oxidative phosphorylation is the major ATP-producing pathway, which supplies more than 95% of the total energy requirement in the cells. Damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of psychiatric disorders. Tissues with high energy demands, such as the brain, contain a large number of mitochondria, being therefore more susceptible to reduction of the aerobic metabolism. Mitochondrial dysfunction results from alterations in biochemical cascade and the damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of neuropsychiatric disorders, such as bipolar disorder, depression and schizophrenia. Bipolar disorder is a prevalent psychiatric disorder characterized by alternating episodes of mania and depression. Recent studies have demonstrated that important enzymes involved in brain energy are altered in bipolar disorder patients and after amphetamine administration, an animal model of mania. Depressive disorders, including major depression, are serious and disabling. However, the exact pathophysiology of depression is not clearly understood. Several works have demonstrated that metabolism is impaired in some animal models of depression, induced by chronic stress, especially the activities of the complexes of mitochondrial respiratory chain. Schizophrenia is a devastating mental disorder characterized by disturbed thoughts and perception, alongside cognitive and emotional decline associated with a severe reduction in occupational and social functioning, and in coping abilities. Alterations of mitochondrial oxidative phosphorylation in schizophrenia have been reported in several brain regions and also in platelets. Abnormal mitochondrial morphology, size and density have all been reported in the brains of schizophrenic individuals. Considering that several studies link energy impairment to neuronal death, neurodegeneration and disease, this review article discusses energy impairment as a mechanism underlying the pathophysiology of some psychiatric disorders, like bipolar disorder, depression and schizophrenia.

Role of mitochondria and reactive oxygen species in dendritic cell differentiation and functions

Dendritic cells (DC) are potent antigen-presenting cells capable of inducing T and B responses and immune tolerance. We have characterized some aspects of energy metabolism accompanying the differentiation process of human monocytes into DC. Compared to precursor monocytes, DC exhibited a much larger number of mitochondria and consistently (i) a higher endogenous respiratory activity and (ii) a more than sixfold increase in ATP content and an even larger increase in the activity of the mitochondrial marker enzyme citrate synthase. The presence in the culture medium of rotenone, an inhibitor of the respiratory chain Complex I, prevented the increase in mitochondrial number and ATP level, without affecting cell viability. Rotenone inhibited DC differentiation, as revealed by the observation that the expression of CD1a, which is a specific surface marker of DC differentiation, was strongly reduced. Cells cultured in the presence of rotenone displayed a lower content of growth factor-induced, mitochondrially generated, hydrogen peroxide. A similar drop in ROS was observed upon addition of catalase, which caused functional effects similar to those produced by rotenone treatment. These results suggest that ROS play a crucial role in DC differentiation and that mitochondria are an important source of ROS in this process.

Chronic administration of methylphenidate activates mitochondrial respiratory chain in brain of young rats

Methylphenidate is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. Psychostimulants can cause long-lasting neurochemical and behavioral adaptations. The exact mechanisms underlying its therapeutic and adverse effects are still not well understood. In this context, it was previously demonstrated that methylphenidate altered brain metabolic activity, evaluated by glucose consumption. Most cell energy is obtained through oxidative phosphorylation, in the mitochondrial respiratory chain. Tissues with high energy demands, such as the brain, contain a large number of mitochondria. In this work, our aim was to measure the activities of mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase in cerebellum, prefrontal cortex, hippocampus, striatum, and cerebral cortex of young rats (starting on 25th post-natal day and finishing on 53rd post-natal day) chronically treated with methylphenidate. Our results showed that mitochondrial respiratory chain enzymes activities were increased by chronic administration of this drug. Succinate dehydrogenase was activated in cerebellum, prefrontal cortex and striatum, but did not change in hippocampus and brain cortex. Complex II activity was increased in cerebellum and prefrontal cortex and was not affected in hippocampus, striatum and brain cortex. Finally, complex IV activity was increased in cerebellum, hippocampus, striatum and brain cortex, and was not affected in prefrontal cortex. These findings suggest that chronic exposure to methylphenidate in young rats increases mitochondrial enzymes involved in brain metabolism. Further research is being carried out in order to better understand the effects of this drug on developing nervous system and the potential consequences in adulthood resulting from early-life drug exposure.

Combined Leptin Actions on Adipose Tissue and Hypothalamus Are Required to Deplete Adipocyte Fat in Lean Rats: IMPLICATIONS FOR OBESITY TREATMENT

Intense hyperleptinemia completely depletes adipocyte fat of normal rats within 14 days. To determine the mechanism, epididymal fat pads from normal wild-type (+/+) and obese (fa/fa) Zucker Diabetic Fatty (ZDF) donor rats were transplanted into normal +/+ and fa/fa ZDF recipients. Hyperleptinemia induced by adenovirus-leptin administration depleted all fat from native fat pads and from fat transplants from +/+ donors but not from transplants from ZDF(fa/fa) donors with defective leptin receptors. In both native and transplanted +/+ fat pads, large numbers of mitochondria were apparent, and genes involved in fatty acid oxidation were up-regulated. However, +/+ fat pads transplanted into fa/fa recipients did not respond to hyperleptinemia, suggesting lack of an essential leptin-stimulated cohormone(s). In +/+ but not in fa/fa rats, plasma catecholamine levels rose, and both P-STAT3 and P-CREB increased in adipose tissue, suggesting that both direct and indirect (hypothalamic) leptin receptor-mediated actions of hyperleptinemia are involved in depletion of adipocyte fat.

Phylogenetic position of Karotomorpha and paraphyly of Proteromonadidae

The taxon Slopalinida (Patterson, 1985) comprises two families of anaerobic protists living as commensals in the intestine of vertebrates. The proteromonadids are small Xagellates (ca. 15 m) with one nucleus, a single large mitochondrion with tubular cristae, Golgi apparatus and a Wbrillar rhizoplast connecting the basal bodies and nucleus (Brugerolle and Mignot, 1989). The number of Xagella diVers between the two genera belonging to the family: Proteromonas, the commensal of urodelans, lizards, and rodents, has two Xagella, whereas Karotomorpha, the commensal of frogs and other amphibians, has four Xagella. The surface of the cell is folded, the folds are supported by single microtubules (Proteromonas) or by ribbons of several laterally interconnected microtubules (Karotomorpha). The transitional Xagellar region contains double transitional helix. The posterior part of Proteromonas cell is covered with Wne tubular hairs— the somatonemes (Brugerolle and Joyon, 1975). The representatives of the second family—Opalinidae— are quite diVerent from the proteromonadid Xagellates. They are multinucleated and multiciliated, often large (up to several mm). They are common commensals of frogs, some can inhabit the intestine of urodelans or Wsh. The family comprises three binucleated genera (Protoopalina, Protozelleriella, Zelleriella) and two genera with up to hundreds of nuclei (Cepedea, Opalina). Besides nuclei the cell contains a large number of mitochondria with tubular cristae, Golgi complexes and small digestive vacuoles (Delvinquier and Patterson, 1993). The cell surface is heavily folded, the folds are supported by ribbons of microtubules in a very similar way as in Karotomorpha. The ultrastructure of Xagellar transi-

Nasal Oncocytoma in a Domestic Shorthair Cat

An oncocytoma was diagnosed in the nasal cavity of a 12-year-old Domestic Shorthair cat who presented with periocular swelling and sneezing. Histologic examination from biopsy material revealed monomorphic sheets, anastomosing cords, tubules, and acini composed of large polygonal to oval cells that contained abundant finely granular eosinophilic cytoplasm. No vascular or lymphatic invasions were noted. Histochemical stains revealed positive staining of tumor cells with periodic acid-Schiff (PAS) (before and after diastase digestion) and phosphotungstic acid-hematoxylin. Immunohistochemical evaluation of the tumor cells demonstrated positive staining for cytokeratin and negative staining for vimentin, desmin, S-100, glial fibrillar acidic protein, and neuronal specific enolase. Ultrastructurally, the tumor cells contained large numbers of mitochondria within their cytoplasm, which confirmed a diagnosis of oncocytoma.

Medical Imaging

Medical Imaging

Structural and ultrastructural analysis of embryonic development ofProchilodus lineatus(Valenciennes, 1836) (Characiforme; Prochilodontidae)

This survey was performed to characterize the embryogenesis of Prochilodus lineatus. Seven stages of embryo development were identified--zygote, cleavage, blastula, gastrula, segmentation, larval and hatching--after a period of incubation of 22 h (24 degrees C) or 14 h (28 degrees C). The following cleavage pattern was identified: the first plane was vertical (2 blastomeres); the second was vertical and perpendicular to the first (4 blastomeres); the third was vertical and parallel to the first (4 x 2); the fourth cleavage was vertical and parallel to the second (4 x 4); the fifth was vertical and parallel to the first (4 x 8); and the sixth cleavage was horizontal (64 blastomeres). At the blastula stage (3.0-4.0 h (24 degrees C); 1.66-2.0 h (28 degrees C)) irregular spaces were detected and periblast structuring was initiated. At the gastrula stage (4.0-8.0 h (24 degrees C); 3.0-6.0 h (28 degrees C)) the epiboly, convergence and cell movements, as well as the formation of embryonic layers, had begun. The segmentation stage (10.0-15.0 h (24 degrees C); 7.0-10.0 h (28 degrees C)) was characterized by a rudimentary formation of organs and systems (somites, optic vesicle and intestinal delimitation). The embryo at the larval stage (16.0-21.0 h (24 degrees C); 11.0-13.0 h (28 degrees C)) showed a free tail, more than 25 somites, an optic vesicle and a ready-to-hatch larval shape. The blastomeres at cleavage stage had disorganized nuclei indicating high mitotic activity. At gastrula, the blastomeres and the periblast had euchromatic nuclei and a large number of mitochondria and vesicles. The yolk was organized into globose sacs, which were dispersed into small pieces prior to absorption.

Adverse Effects of Antiretroviral Drugs on HIV-1-Infected and -Uninfected Human Monocyte-Derived Macrophages

Antiretroviral drugs approved for treatment of HIV-1 infection include nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs). Use of these drugs in combinations (highly active antiretroviral therapy) has delayed disease progression. However, long-term therapy is associated with potentially serious adverse effects. NRTIs are thought to contribute to these adverse effects via depletion of mtDNA. Inasmuch as macrophages (major targets for HIV-1) are highly metabolically active with large numbers of mitochondria, we investigated the effects of NRTIs (didanosine, stavudine, lamivudine, and zidovudine) on the viability and function of HIV-1-infected and -uninfected human monocyte-derived macrophages (MDMs). We demonstrate that the combinations didanosine/stavudine and lamivudine/zidovudine decrease mtDNA content in MDMs, with HIV-1-infected MDMs displaying a greater reduction than uninfected cells. This decrease correlated with decreased complement-mediated phagocytosis (C'MP) by MDMs, a process dependent on mitochondrial function. Inasmuch as PIs have previously been reported to interact with cellular proteases and given that cellular proteases are involved in the phagocytic process, we investigated the effects of the PI indinavir on C'MP. We demonstrate that indinavir augments C'MP by uninfected MDMs, but not HIV-1-infected MDMs. This study provides additional understanding on the effects of commonly used antiretroviral drugs on cellular immune function.

Morphology of the prothoracic discs and associated sensilla of Acanthocnemus nigricans (Coleoptera, Acanthocnemidae)

The Australian ‘little ash beetle’ Acanthocnemus nigricans (Coleoptera, Cleroidea, Acanthocnemidae) is attracted by forest fires. A. nigricans has one pair of unique prothoracic sensory organs and it has been speculated that these organs may play a role in fire detection. Each organ consists of a cuticular disc, which is fixed over an air-filled cavity. On the outer surface of the disc, about 90 tiny cuticular sensilla are situated. The poreless outer peg of a sensillum is 3–5 μm long and is surrounded by a cuticular wall. One ciliary sensory cell innervates the peg. As a special feature, the outer dendritic segment is very short already terminating below the cuticle. A massive electron-dense cylindrical rod, which most probably represents the hypertrophied dendritic sheath, extends through the cuticular canal connecting the tip of the outer dendritic segment to the peg. The dendritic inner segment and the soma are fused indistinguishably. Thin, leaflike extensions of glial cells deeply extend into that conjoint and considerably enlarged compartment which also contains large numbers of mitochondria. In summary, the sensilla of the sensory disc of A. nigricans represent a new type of insect sensillum of hitherto unknown function. The possible role of the prothoracic sensory organ in fire detection is discussed.

Reverse Transcriptase Inhibitors Alter Uncoupling Protein-1 and Mitochondrial Biogenesis in Brown Adipocytes

Human adipose depots contain remnant brown adipocytes interspersed among white adipocytes, and disturbances of brown with respect to white adipocyte biology have been implicated in highly active antiretroviral therapy (HAART)-induced lipomatosis. Brown adipocytes express the uncoupling protein-1 (UCP1) and contain a large number of mitochondria, potential targets of HAART toxicity. The aim of this study was to evaluate the effects of reverse transcriptase inhibitors (RTIs) on primary brown adipocytes differentiated in culture. We analysed the effects of RTIs, nucleoside analogues (NRTIs: stavudine, zidovudine, didanosine and lamivudine) and non-nucleoside analogues (NNRTIs: nevirapine and efavirenz), on differentiation, mitochondrial biogenesis and gene expression in brown adipocytes. None of the NRTIs altered brown adipocyte differentiation whereas NNTRIs had differing effects. Efavirenz blocked lipid deposition and expression of adipose marker genes but nevirapine induced lipid accumulation and adipose gene expression, promoted mitochondrial biogenesis and increased UCP1. Stavudine, zidovudine and didanosine reduced mitochondrial DNA (mtDNA) content. However, mitochondrial genome expression was only impaired in didanosine-treated adipocytes. Stavudine, but not zidovudine, induced expression of the mitochondrial transcription factors and this may explain compensatory mechanisms for the depletion of mtDNA by up-regulating mtDNA transcription. Stavudine caused a specific induction of UCP1 gene expression through direct interaction with a retinoic acid-dependent pathway. Specific disturbances in brown adipocytes in adipose depots may contribute to HAART-induced lipomatosis. Mitochondrial depletion does not appear to be the only mechanism explaining adverse effects in brown adipocytes because there is evidence of compensatory mechanisms that maintain mtDNA expression, and the expression of the UCP1 gene is specifically altered.

Low-grade renal collecting duct carcinoma. A case report with histochemical, immunohistochemical, and ultrastructural study

We report a rare tumor called low-grade renal collecting duct carcinoma. Grossly, the tumor consisted of multiple cysts and solid white nodules, measuring 10 cm in diameter and occupying most of the renal parenchyma. Histologically, the tumor was characterized by well-differentiated tubules lined by eosinophilic cells without papillary projections, abundant predominantly extracellular mucin, minimal cellular atypia, no desmoplasia, and rare mitoses. This tumor occurs in collecting ducts and the tumor cells were positive for epithelial membrane antigen, high-molecular-weight keratin, CD15, and mitochondrial antibody and negative for CD10. Few cells stained weakly positive for ulex europaeus. Ultrastructural study showed a large number of mitochondria according to the eosinophilic cells seen in light microscopy.

311 ULTRASTRUCTURAL ANALYSIS OF OVINE PREANTRAL FOLLICLES CULTURED IN THE PRESENCE OF INDOLE ACETIC ACID, EGF, AND FSH

Previous studies from our team demonstrated that ovine primordial follicles are successfully activated in vitro after culturing in medium supplemented with 40 ng/mL indole acetic acid (IAA); besides that, the addition of IAA and epidermal growth factor (EGF) or EGF and follicle stimulating hormone (FSH) to the culture media were the most effective treatments to sustain the health and viability of activated ovine primordial follicles during in vitro culture. In this work, follicular quality was assessed only by histological studies; there is a great need to evaluate ultrastructural changes occurring in primordial follicles during activation in vitro. The aim of this study was to investigate the ultrastructural characteristics of preantral follicles after culturing of cortical slices in media containing IAA, EGF, and FSH, alone and in combination. Ovaries (n = 8) from adult merino ewes were collected at local slaughterhouses. Small pieces of ovarian fragments were removed for transmission electron microscopy (TEM). These pieces of ovarian cortex were cultured in culture dishes containing 1 mL aliquots of culture medium at 39�C with 5% CO2 in air. The media used were: (T1) Minimum essential medium (MEM) supplemented with ITS (insulin 6.25 �g/mL, transferrin 6.25 �g/mL and selenium 6.25 ng/mL), 0.23 mM pyruvate, 2 mM glutamine, 2 mM hypoxantine, 1.25 mg/mL bovine serum albumin (BSA), and antibiotics (100 ��g/mL penicillin and 100 ��g/mL streptomycim) (MEM+, control medium); (T2) MEM+IAA (40 ng/mL); (T3) MEM+IAA + epidermal growth factor (EGF) (100 ng/mL; Sigma, St. Louis, MO, USA); or (T4) MEM+EGF+FSH (100 ng/mL). After 6 days of culture of cortex tissue fragments in media, ultrastructural analysis was performed on preantral follicles (n = 3 in each treatment) included in a small cortical fragments. Preantral follicles were classified according to the stage of development as primordial follicles or as developing follicles. Preantral follicles cultured in supplemented media for 6 days were ultrastructurally normal. Their oocytes had an intact nucleus and cytoplasm that contained heterogeneous-sized lipid droplets, and numerous round or elongated mitochondria with intact parallel cristae were observed. Occasionally these organelles were associated with smooth endoplasmic reticulum (SER). Rough endoplasmic reticulum (RER) was rarely found. The cytoplasm of granulosa cells contained a large number of mitochondria and abundant RER. In contrast, follicles cultured in MEM+ (control) had a large number of vacuoles in the oocyte cytoplasm and excessive clustering of the chromatin material in the nucleus, suggesting an initial process of oocyte degeneration. In conclusion, the presence of IAA, EGF, FSH and their combinations helped to maintain ultrastructural integrity of ovine preantral follicles in cortical slices cultured in vitro.

Morphology of the Alimentary Canal of <I>Chrysoperla rufilabris</I> (Neuroptera: Chrysopidae) Adults in Relation to Microbial Symbionts

A study of the internal morphology of the alimentary canal of Chrysoperla rufilabris (Brumeister) adults in relation to yeast symbionts was conducted using light, scanning, and transmission electron and epifluorescence microscopy. The alimentary canal of field-collected adults possessed a single large (≈300–400 μm in length) diverticulum at the posterior end of the foregut. Although yeast cells (4.0–6.5 μm) were distributed throughout the alimentary canal, large numbers of blastically dividing cells (i.e., yeast) were observed within the diverticulum. The diverticulum interior was highly convoluted and folded transversely and longitudinally, and yeast cells were observed to accumulate within the folds. Large tracheal trunks were attached to the lateral side of the diverticulum, suggesting a high demand for gas exchange within this organ. The diverticulum was lined with cuticle, and the underlying tissues did not contain large amounts of endoplasmic reticulum, mitochondria, or Golgi complex, indicating that minimal absorption occurred within this gut region. This suggested that the high potential for gas exchange in the diverticulum by the tracheal trunks was primarily to support yeast metabolic activity. All size classes (i.e., 0.1, 4.0, and 10.0 μm) of fluorescence particles ingested by newly eclosed adults eventually ended up in the midgut and hindgut regions, indicating that the foregut and/or diverticulum do not possess an absolute mechanism for retaining particles based on size. However, all size classes of the fluorescent particles typically persisted within the diverticulum. The evident confluence between the diverticulum lumen and the gut lumen suggested a free exchange or flow of fluids between these regions. The proventriculus (proximal to the diverticulum) was pronounced and consisted of a series of long “hairs,” short “hairs,” and small spine-like structures projecting into the midgut. Large numbers of yeast cells were observed in association with the proventricular hairs, and these hairs may play a role in the retention of yeast cells. The midgut possessed typical absorptive structures (i.e., microvilli), and large numbers of mitochondria, rough endoplasmic reticulum, and Golgi complex were observed in midgut epithelial cells. Because evidence indicated no or minimal absorption of nutrients within the diverticulum, it was concluded that nutritional factors provided by the yeast must be transferred to the midgut where absorption occurs. Large numbers of yeast cells enclosed within a well-developed peritrophic matrix were observed in the midgut, suggesting that the yeast themselves may serve as a source of nutrients. Whereas the exact mechanism by which yeast contribute to the nutrition of C. rufilabris adults was not determined, morphological evidence obtained in this study supported the hypothesis that chrysopids form a mutualistic symbiosis with yeast and that the esophageal diverticulum was a specialized structure for housing them.

Ultrastructural cytochemistry of the sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae: Phlebotominae)

The sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae) were analyzed by cytochemical techniques. In adult males, the epithelium at the fourth abdominal tergite is modified into a glandular epithelium, with large columnar gland cells located side by side. The gland cell cytoplasm contains a large number of mitochondria and peroxisomes, the latter with positive (electron-dense) reaction for catalase, a typical peroxisomal enzyme marker. The gland cell cytoplasm also contains a central vacuolated area, with a large number of electron-lucent vacuoles, not limited by a unit membrane. In well-preserved preparations such vacuoles present a homogenous and slightly electron-dense content, typical of lipid droplets. Indeed, incubation of the tergites with imidazole-buffered osmium tetroxide (to detect lipids) resulted in positive reaction in these vacuoles, as well as in between the microvilli of the gland cells. Use of the osmium–potassium iodide (Os–KI) technique allowed to demonstrate the presence of several endoplasmic reticulum (ER) profiles, as expected in secretory cells. Our data suggest that ER, lipid droplets and peroxisomes are involved in the sand fly pheromone biosynthesis.

Demonstration of MyoD1 expression in oncocytic cardiomyopathy: report of two cases and review of the literature

Oncocytic cardiomyopathy is a rare arrhythmogenic disorder usually associated with female sex, difficult-to-control arrhythmias, or sudden death of infants and children. Morphologically, it is characterized by the presence of oncocytic cells, which are diffusely distributed or form the nodular structures within the myocardium, occasionally involving the valves, with a large number of mitochondria in cytoplasms. We present two cases of oncocytic cardiomyopathy. The first case had a fatal clinical outcome, and the other case was surgically treated. The nuclear expression of skeletal muscle transcription factor MyoD1 was demonstrated in the first case, supporting the theory that oncocytic cardiomyopathy is a conduction system developmental disorder. To confirm this hypothesis, it is necessary to further investigate myogenic transcription factor program in human cardiac conduction system cells.

In situ localization of manganese peroxidase production in mycelial pellets of Phanerochaete chrysosporium.

The ultrastructure of Phanerochaete chrysosporium hyphae from pellets in submerged liquid cultures was investigated in order to learn more about the interrelation between fungal architecture and manganese peroxidase (MnP) production. At day 2 of cultivation, some subapical regions of hyphae in the outer and middle zones of the pellet initiated differentiation into intercalary thick-walled chlamydospore-like cells of about 10 micro m diameter. At the periphery of the cytoplasm of these cells, a large number of mitochondria and Golgi-like vesicles were observed. The sites of MnP production were localized at different stages of cultivation by an immunolabelling procedure. The immunomarker of MnP was mainly concentrated in the chlamydospore-like cells and principally distributed in Golgi-like vesicles located at the periphery of the cytoplasm. The apices of hyphae in the outer layer of the pellets were apparently minor sites of MnP production. Maximal MnP release into the culture supernatant coincided with apparent autolysis of the chlamydospore-like cells. Production of extracellular autolytic chitinase and protease coincided with the disappearance of these structures from the pellets. The chlamydospore-like cells observed in the mycelial pellets of P. chrysosporium could be metabolically active entities operating as an enzyme reservoir, delivering their content into the surrounding medium possibly by an enzyme-mediated autolytic process.