Mitochondria of human Leydig cells as seen by high resolution scanning electron microscopy

Impacts of iron on ultrastructural features of NCI-H295R cell line related to steroidogenesis

The current study was intended to evaluate impacts of both iron (Fe) enrichment and overload (in the form of ferrous sulphate heptahydrate, FeSO4.7H2O) on ultrastructural characteristics of human adrenocarcinoma NCI-H295R cell line. Here, the NCI-H295R cells were treated with 0, 3.90, and 1000 µM FeSO4.7H2O, and consequently proceeded for purposes of ultrastructural studies. Micrographs taken under transmission electron microscope (TEM) were investigated from the qualitative and quantitative (unbiased stereological approaches) aspects, and obtained findings were compared among the three groups of the cells. The ultrastructural features related to the steroidogenic process were found to be similar between the untreated and both Fe-exposed cell populations, with conspicuous mitochondria with well-defined lamellar cristae (creating clusters of varying sizes in the regions of increased energy demands) and concentric whorls of smooth endoplasmic reticulum (SER) being the most noticeable characteristics. The precise estimates of the component (volume, surface) fractions of the nucleus, mitochondria, and lipid droplets (LDs), as well as of the nucleus/cytoplasm (N/C) ratio have revealed close similarities (P > 0.05) in all cell groups investigated. Nonetheless, the low concentration of FeSO4.7H2O exhibited beneficial action on ultrastructural organization of the NCI-H295R cells. In effect, these cells were distinguished by mitochondria with smoother surfaces and clearer outlines, higher density of thin, parallel lamellar cristae (deeply extending into the mitochondrial matrix), and more widespread distribution of fine SER tubules as compared to the control ones, all of them suggesting higher level of energy requirements and metabolic activity, and more intensive rate of steroidogenesis. Interestingly, no obvious ultrastructural modifications were observed in the NCI-H295R cells treated with high FeSO4.7H2O concentration. This finding can be linked to either an adaptive ultrastructural machinery of these cells to cope with the adverse effect of the element or to insufficient dose of FeSO4.7H2O (1000 µM) to induce ultrastructural signs of cytotoxicity. Purposefully, the results of the current study complement our previous paper dealing with impacts of FeSO4.7H2O on the NCI-H295R cell viability and steroidogenesis at the molecular level. Hence, they fill a knowledge gap considering structure-function coupling in this cellular model system upon the metal exposure. This integrated approach can enhance our understanding of the cellular responses to Fe enrichment and overload which can be helpful for individuals with reproductive health concerns.

STZ-diabetic rat heart maintains developed tension amplitude by increasing sarcomere length and crossbridge density

New Findings

What is the central question of this study?

In the papillary muscle from type I diabetic rats, does diabetes‐associated altered ventricular function result from changes of acto‐myosin interactions and are these modifications attributable to a possible sarcomere rearrangement?

What is the main finding and its importance?

For the first time, we showed that type‐I diabetes altered sarcomeric ultrastructure, as seen by transmission electron microscopy, consistent with physiological parameters. The diabetic condition induced slower timing parameters, which is compatible with a diastolic dysfunction. At the sarcomeric level, augmented β‐myosin heavy chain content and increased sarcomere length and crossbridges' number preserve myocardial stroke and could concur to maintain the ejection fraction.

Abstract

We investigated whether diabetes‐associated altered ventricular function, in a type I diabetes animal model, results from a modification of acto‐myosin interactions, through the in vitro recording of left papillary muscle mechanical parameters and examination of sarcomere morphology by transmission electron microscopy (TEM). Experiments were performed on streptozotocin‐induced diabetic and age‐matched control female Wistar rats. Mechanical isometric and isotonic indexes and timing parameters were determined. Using Huxley's equations, we calculated mechanics, kinetics and energetics of myosin crossbridges. Sarcomere length and A‐band length were measured on TEM images. Type I and III collagen and β‐myosin heavy chain (MHC) expression were determined by immunoblotting. No variation in resting and developed tension or maximum extent of shortening was evident between groups, but diabetic rats showed lower maximum shortening velocity and prolonged timing parameters. Compared to controls, diabetics also displayed a higher number of crossbridges with lower unitary force. Moreover, no change in type I and III collagen was associated to diabetes, but pathological rats showed a two‐fold enhancement of β‐MHC content and longer sarcomeres and A‐band, detected by ultrastructural morphometry. Overall, these data address whether a preserved systolic function accompanied by an altered diastolic phase results from a recruitment of super‐relaxed myosin heads or the phosphorylation of the regulatory light chain site in myosin. Although the early signs of diabetic cardiomyopathy were well expressed, the striking finding of our study was that, in diabetics, sarcomere modification may be a possible compensatory mechanism that preserves systolic function.

Reactivity of human labial glands in response to cevimeline treatment

Among the pathologies affecting the salivary glands, the Sjögren's syndrome (SS), an autoimmune disease, causes progressive destruction of the glandular tissue. The effect of SS is particularly evident on the labial glands and the morphological analysis of these minor glands is considered useful for diagnosis. Cevimeline hydrochloride (SNI), a selective muscarinic agonist drug, is one of the elective treatments for the hyposalivation due to SS, acting not only on major salivary glands, but also on labial glands since their secretion is primarily under parasympathetic control. Aim of this study is to describe the morphology of human labial glands treated with SNI by light, transmission, and high-resolution scanning electron microscopy. Moreover, a morphometric analysis was applied to the light and transmission electron microscopy micrographs to obtain data that were then compared with analogous data collected on control and carbachol-treated labial glands. Following SNI administration, the mucous tubules exhibited enlarged lumina, which were filled with a dense mucous secretion. Occasionally, small broken debris of the cells were retrieved into the lumen. In the mucous secretory cells, some mucous droplets fused to form a large vacuole-like structure. Similarly, the seromucous acini showed both dilated lumina and canaliculi. These above reported signs of secretion were confirmed through morphometric analysis and a milder action of SNI than carbachol on labial parenchyma was observed. This study confirmed that SNI also evoked secretion on labial glands and that its effect is more physiologic than that of the pan-muscarinic agonists.

Suitability of the thawed algae for transmission electron microscopy study: Ultrastructural investigation on Coccomyxa melkonianii SCCA 048

Morphological and ultrastructural investigations are crucial for the identification and characterization of species such as microalgae, microorganisms that greatly change their morphology and physiology during their life cycle. Transmission electron microscopy (TEM) is an excellent tool for the ultrastructural observation of cells and their components. To date, limited ultrastructural studies have been carried out on microalgae, due to the difficulties in sample preparation. The aim of this work is to establish an appropriate fixation method that allows to better preserve the algal ultrastructure and test the suitability of the thawed algae for TEM observation. Fresh and thawed algae (Coccomyxa melkonianii SCCA 048) were fixed with different TEM fixation methods (a mix of glutaraldehyde and paraformaldehyde for several incubation times, sometimes preceded by a prefixation in cold methanol). The ultrastructural images obtained from fresh algae were compared to those obtained from frozen biomass. The best morphological results were achieved by fixing fresh algae in 1% paraformaldehyde and 1.25% glutaraldehyde for 5 hr. Pretreating with frozen methyl alcohol reduced fixation time to 2 hr. Both fresh and frozen algae ultrastructure were rather well preserved also with 1% paraformaldehyde and 1.25% glutaraldehyde for 2 hr. Ultrastuctural morphological images of the thawed algae demonstrated that also frozen samples can be used in TEM research, widening specimen suitability by means of this technique.

Optimizing the reaction temperature to facilitate an efficient osmium maceration procedure

The osmium maceration method is a powerful technique for observing the three-dimensional ultrastructure of cellular organelles by scanning electron microscopy. In the conventional osmium maceration method, tissues are immersed in a diluted osmium tetroxide solution for several days at 20°C to remove soluble cytosolic proteins from the freeze-cracked surface of cells, and the optimal duration of this process is dependent on the cell type. To improve the efficiency of the osmium maceration procedure, we have examined systematically the relationship between the reaction temperature and time of the osmium maceration procedure. Treatment at temperatures higher than 20°C drastically shortened the time required to remove cytosolic proteins from the freeze-cracked surface of specimens with optimal durations for the osmium maceration of hepatocytes at 30, 40, 50 and 60°C being 30, 15, 5 and 1 h, respectively. Considering the stability and reproducibility of the macerated specimens, we concluded that the most appropriate temperature was 30 to 40°C. This rapid osmium maceration procedure was used successfully to observe the 3D ultrastructure of Purkinje cells in the cerebellum and proximal convoluted tubule cells in the kidney. This simple and reproducible rapid osmium maceration protocol should find wide appeal for the 3D analysis of cellular organelles in various cell types.

New insights on mitochondrial heterogeneity observed in prepared mitochondrial samples following a method for freeze-fracture and scanning electron microscopy

Mitochondria are dynamic intracellular organelles with diverse roles in tissue- and cell type-specific processes, extending beyond bioenergetics. In keeping with this array of functions, mitochondria are described as heterogeneous both between and within tissue types based on multiple parameters, including a broad spectrum of morphological features, and new research points toward a need for the evaluation of mitochondria as isolated organelles. Although transmission electron microscopy (TEM) is commonly used for the evaluation of mitochondria in tissues and renders mitochondrial structures in ultra-thin sections in two-dimensions, additional information regarding complex features within these organelles can be ascertained using scanning electron microscopy (SEM), which allows for analysis of phenotypic differences in three-dimensions. One challenge in producing mitochondrial images for evaluation of ultrastructure using SEM has been the ability to reliably visualize important intramitochondrial features, the inner membrane and cristae structures, on a large-scale (e.g. multiple mitochondria) within a sample preparation, as mitochondria are enclosed within a double membrane. This can be overcome using a 'freeze-fracture' technique in which mitochondrial preparations are snap-frozen followed by application of intense pressure to break open the organelles, revealing the intact components within. Previously published reports using freeze-fracture strategies for mitochondrial SEM have demonstrated feasibility in whole tissue specimens, but a detailed methodology for SEM analysis on isolated mitochondrial fractions has not been reported. By combining previously reported tissue freeze-fracture strategies, along with utilizing the depth of field created by SEM, herein we present a complete method reliant on the freeze-fracture of mitochondrial fractions prepared by differential centrifugation to produce a comprehensive and direct evaluation of three-dimensional mitochondrial ultrastructure by SEM. Image analysis of internal mitochondrial features demonstrates heterogeneity in mitochondrial ultrastructure from a single sample preparation.

The changes of stage distribution of seminiferous epithelium cycle and its correlations with Leydig cell stereological parameters in aging men

PURPOSE

To evaluate the changes of stage distribution of seminiferous epithelium cycle and its correlations with Leydig cell stereological parameters in aging men.

METHODS

Point counting method was used to analyze the stereological parameters of Leydig cells. The stage number of seminiferous epithelium cycle was calculated in the same testicular tissue samples which were used for Leydig cell stereological analysis.

RESULTS

The aging group had shown more severe pathological changes as well as higher pathologic scores than the young group. Compared with the control group, the volume density (VV) and surface density (NA) of Leydig cells in the aging group were increased significantly. The stage number of seminiferous epithelium cycle in the aging group was decreased coincidently compared to the young group. Leydig cell Vv in the young group has a positive relationship with stages I, II, III, V and VI of seminiferous epithelium cycle, and Leydig cell NA and numerical density (NV) were positively related to stage IV. However, only the correlation between NV and stage II was found in the aging group.

CONCLUSIONS

The stage number of seminiferous epithelium cycle was decreased in aging testes. Changes in the stage distribution in aging testes were related to the Leydig cell stereological parameters which presented as a sign of morphological changes.

Multiple muscle cell alterations in a case of encephalomyopathy

Skeletal muscle from an encephalomyopathy was examined by morphological and biochemical modalities. Mitochondria displayed variability in size, numbers per myocyte, and morphology. Certain organelles had stacks of dense cristae, others contained variable numbers of crystalloids or several lipid droplets. In isolated skeletal muscle mitochondria, oxidative phosphorylation was reduced, but activities of the electron transport chain components were unaffected. This is the second case of adult onset encephalomyopathy with a phenotype overlapping MERRF and Kearns-Sayre syndrome associated with a heteroplasmic mtDNA 3255G > A mutation in the tRNA(UUR(LEU)). This study emphasizes the desirability of a multidisciplinary approach in the diagnosis of complex myopathies.

A useful method for observing intracellular structures of free and cultured cells by scanning electron microscopy

Scanning electron microscopy (SEM) using osmium-maceration methods has been used for analyzing the three-dimensional structure of cell organelles in tissue samples, but it has been quite difficult to observe free and cultured cells with this technique. The present study was performed to develop a method that can be applied to free and cultured cells for SEM studies of intracellular structures after osmium maceration. The method was also applied to light microscopy (LM) and to transmission electron microscopy (TEM). HeLa cells and human leukocytes were fixed with a mixture of 0.5% paraformaldehyde and 0.5% glutaraldehyde followed by an additional fixation with 1% osmium tetroxide. These cells were embedded in low-melting-point agarose. A temperature-responsive dish was also used for collection of cultured cells before embedding. For LM and TEM, the cell-embedded agarose was further embedded in epoxy resin, and semi- and ultrathin sections were examined conventionally. For SEM, the agarose was freeze-fractured in 50% dimethyl sulfoxide, processed for osmium maceration and observed in a high-resolution SEM. Low-melting-point agarose was useful as an embedding medium for SEM, because it was well preserved during prolonged osmication for SEM. Thus, the fine structure of cell organelles was clearly analyzed by SEM after osmium-maceration treatment. These SEM images could also be compared with those of LM and TEM of the agarose-embedded tissues.