Pancreatic cancer, most frequently as ductal adenocarcinoma (PDAC), is the third leading cause of cancer death. Clear-cell primary adenocarcinoma of the pancreas (CCCP) is a rare, aggressive, still poorly characterized subtype of PDAC. We report here a case of a 65-year-old male presenting with pancreatic neoplasia. A histochemical examination of the tumor showed large cells with clear and abundant intracytoplasmic vacuoles. The clear-cell foamy appearance was not related to the hyperproduction of mucins. Ultrastructural characterization with transmission electron microscopy revealed the massive presence of mitochondria in the clear-cell cytoplasm. The mitochondria showed disordered cristae and various degrees of loss of structural integrity. Immunohistochemistry staining for NADH dehydrogenase [ubiquinone] 1 alpha subcomplex, 4-like 2 (NDUFA4L2) proved specifically negative for the clear-cell tumor. Our ultrastructural and molecular data indicate that the clear-cell nature in CCCP is linked to the accumulation of disrupted mitochondria. We propose that this may impact on the origin and progression of this PDAC subtype.

A 16-year-old female spayed domestic shorthaired cat was examined for lameness and a mass on the fourth digit of the right hindlimb. Cytologic examination of an aspirate of the mass revealed large discrete cells admixed with low numbers of well-granulated mast cells. The discrete cells contained single to many variably sized light pink to purple granules in their cytoplasm and had pleomorphic nuclei, with intranuclear cytoplasmic inclusions. Karyomegalic, binucleated and multinucleated cells were seen. Histologic examination of formalin-fixed sections of the excised mass showed a mildly infiltrative, unencapsulated, multinodular dermal mass that extended into the subcutis and consisted of similar discrete cells. On immunohistochemical staining, the tumor cells expressed ionized calcium-binding adapter molecule 1 (Iba1) and CD18. The tumor cells did not express CD3, CD20, CD117, pancytokeratin (AE1/AE3), melanoma antigen (Melan-A), multiple myeloma oncogene-1 (MUM1), melanoma-associated antigen (PNL-2), and S-100. Low numbers of tumor cells expressed CD204 and protein gene product 9.5 (PGP9.5). Granules were variably positive for Periodic-acid Schiff (PAS) and Alcian blue. On transmission electron microscopy, the cells contained filopodia, abundant endoplasmic reticulum, and moderate numbers of low-density membrane-bound granules. This case documents a previously undescribed granular variant of a histiocytic tumor in a cat.

Although infections with Cyclospora cayetanensis are prevalent worldwide, many aspects of this parasite\'s life cycle remain unknown. Humans are the only known hosts, existing information on its endogenous development has been derived from histological examination of only a few biopsy specimens. In histological sections, its stages are less than 10 μm, making definitive identification difficult. Here, confirmation of cyclosporiasis in a duodenal biopsy specimen from an 80-year-old man without any recognized immunodeficiency patient is reported. Asexual forms (schizonts) and sexual forms (gamonts) were located within enterocytes, including immature and mature schizonts, an immature male gamont and a female gamont. Merozoites were small (<5 μm × 1 μm) and contained two rhoptries, subterminal nucleus and numerous micronemes and amylopectin granules. These parasite stages were like those recently reported in the gallbladder of an immunocompromised patient, suggesting that the general life-cycle stages are not altered by immunosuppression.

OBJECTIVE: To examine corneal buttons with light and transmission electron microscopy (TEM) to visualize the interface area and highlight the ultrastructural corneal changes after deep anterior lamellar keratoplasty (DALK).
METHODS: Two patients underwent excimer laser-assisted penetrating repeat keratoplasty after predescemetic DALK. The corneal buttons were examined by light microscopy and TEM.
RESULTS: The light microscopic examination of the corneal buttons revealed fragments of a second Descemet\'s membrane in the central and midperipheral areas (Case 1). In both cases, visualization of the interface area was not possible by light microscopy. The donor and host stroma were tightly attached without dehiscence. TEM identified the interface area by irregularities in the collagen distribution between the donor and host stroma. The thickness of the remaining recipient corneal stroma measured approximately 30 µm (Case 1) and 100 µm (Case 2), respectively. In the host stroma, TEM revealed the absence or degeneration of keratocytes, accumulation of amorphous material between the collagen lamellae, and vacuolar inclusions dispersed in the stroma, forming a band-like zone anterior to Descemet\'s membrane.
CONCLUSIONS: The interface area after DALK has been mainly investigated by in vivo confocal microscopy. Light microscopy and TEM findings indicate remodeling processes after DALK that are associated with increased keratocyte degeneration and structural alterations of the extracellular matrix in the host stroma. The choice of surgical method may influence the postoperative morphological and functional outcome since these findings were primarily apparent in the remaining host stroma. Therefore, complete exposure of Descemet\'s membrane is an important prognostic factor for the postoperative visual outcome.
UNASSIGNED: Untersuchung von Hornhautexzisaten mit Licht- und Transmissionselektronenmikroskopie (TEM) zur Visualisierung des Interface-Bereichs und Hervorhebung der ultrastrukturellen Hornhautveränderungen nach tiefer anteriorer lamellärer Keratoplastik (DALK).
METHODS: Bei 2 Patienten wurde eine Excimerlaser-gestützte perforierende Keratoplastik nach einer prädescemetalen DALK durchgeführt. Die Hornhautexzisate wurden mittels Lichtmikroskopie und TEM untersucht.
UNASSIGNED: Die lichtmikroskopische Untersuchung der Hornhautexzisate zeigte Fragmente einer 2. Descemet-Membran im zentralen und mittleren peripheren Bereich (Fall 1). In beiden Fällen war die Visualisierung des Interface-Bereichs lichtmikroskopisch nicht möglich. Das Spender- und Wirtsstroma waren ohne Dehiszenz miteinander verbunden. In der TEM wurde der Interface-Bereich durch Unregelmäßigkeiten in der Kollagenverteilung zwischen Spender- und Wirtsstroma identifiziert. Die Dicke des verbliebenen Empfängerhornhautstromas betrug ca. 30 µm (Fall 1) bzw. 100 µm (Fall 2). Im Wirtsstroma zeigte die TEM fehlende oder degenerierte Keratozyten, Ansammlungen von amorphem Material zwischen den Kollagenlamellen und vakuoläre Einschlüsse, die im Stroma verstreut waren und eine bandartige Zone vor der Descemet-Membran bildeten.
UNASSIGNED: Bislang wurde der Interface-Bereich nach DALK hauptsächlich konfokalmikroskopisch untersucht. Die licht- und elektronenmikroskopischen Befunde deuten auf Umbauprozesse nach DALK hin, die mit einer verstärkten Keratozytendegeneration und strukturellen Veränderungen der extrazellulären Matrix im Wirtsstroma einhergehen. Die Wahl der Operationsmethode kann das postoperative morphologische und funktionelle Ergebnis beeinflussen, da diese Befunde vor allem im verbliebenen Wirtsstroma zu beobachten waren. Daher ist eine vollständige Freilegung der Descemet-Membran ein wichtiger prognostischer Faktor für das postoperative Visusergebnis.

McCune - Albright syndrome is a genetic disease with cutaneous mosaicism caused by post-zygotic activating mutations in GNAS locus, it has a triad of fibrous bone dysplasia, café-au-lait macules and precocious puberty. We examined a 22-year-old female patient with café au lait spot in right side of the abdomen, with a chessboard - like distribution, extending to right thigh with geographical contours, she has also an ovarian cyst, scoliosis and truncal obesity. Biopsies were taken from the hyperpigmented area and processed for light microscopy and for transmission electron microscopy. Light microscopy showed increased melanin pigment with HE staining. Immunohistochemistry with melanocytic markers (HMB-45 and Melan-A) revealed a normal number of melanocytes. Transmission electron microscopy demonstrated normal epidermal structures, such as desmosomes, cytokeratin filaments and hemidesmosomes. With high magnifications an irregular melanossomal contour was seen, with some indentations in their outline.

BACKGROUND: SARS-CoV-2 may produce intestinal symptoms that are generally mild, with a small percentage of patients developing more severe symptoms. The involvement of SARS-CoV-2 in the physiopathology of bowel damage is poorly known. Transmission electron microscopy (TEM) is a useful tool that provides an understanding of SARS-CoV-2 invasiveness, replication and dissemination in body cells but information outside the respiratory tract is very limited. We report two cases of severe intestinal complications (intestinal lymphoma and ischaemic colitis) in which the presence of SARS-CoV-2 in intestinal tissue was confirmed by TEM. These are the first two cases reported in the literature of persistence of SARS-CoV-2 demonstrated by TEM in intestinal tissue after COVID 19 recovery and SARS-CoV-2 nasopharyngeal clearance.
METHODS: During the first pandemic peak (1st March-30th April 2020) 932 patients were admitted in Hospital Universitari Mútua Terrassa due to COVID-19, 41 (4.4%) required cross-sectional imaging techniques to assess severe abdominal pain and six of them (0.64%) required surgical resection. SARS-CoV-2 in bowel tissue was demonstrated by TEM in two of these patients. The first case presented as an ileocaecal inflammatory mass which turned to be a B-cell lymphoma. Viral particles were found in the cytoplasm of endothelial cells of damaged mucosa. In situ hybridization was negative in tumour cells, thus ruling out an oncogenic role for the virus. SARS-CoV-2 remained in intestinal tissue 6 months after nasopharyngeal clearance, suggesting latent infection. The second patient had a severe ischaemic colitis with perforation and SARS-CoV-2 was also identified in endothelial cells.
CONCLUSIONS: Severe intestinal complications associated with COVID-19 are uncommon. SARS-CoV-2 was identified by TEM in two cases, suggesting a causal role in bowel damage.

Abnormal accumulation of inorganic trace elements in a human brain, such as iron, zinc and aluminum, oftentimes manifested as deposits and accompanied by a chemical valence change, is pathologically relevant to various neurodegenerative diseases. In particular, Fe2+ has been hypothesized to produce free radicals that induce oxidative damage and eventually cause Alzheimer\'s disease (AD). However, traditional biomedical techniques, e.g. histology staining, are limited in studying the chemical composition and valence states of these inorganic deposits. We apply commonly used physical (phys-) science methods such as X-ray energy dispersive spectroscopy (EDS), focused-ion beam (FIB) and electron energy loss spectroscopy (EELS) in transmission electron microscopy in conjunction with magnetic resonance imaging (MRI), histology and optical microscopy (OM) to study the valence states of iron deposits in AD patients. Ferrous ions are found in all deposits in brain tissues from three AD patients, constituting 0.22-0.50 of the whole iron content in each specimen. Such phys-techniques are rarely used in medical science and have great potential to provide unique insight into biomedical problems.

Modern morphological and structural studies are coming to a new level by incorporating the latest methods of three-dimensional electron microscopy (3D-EM). One of the key problems for the wide usage of these methods is posed by difficulties with sample preparation, since the methods work poorly with heterogeneous (consisting of tissues different in structure and in chemical composition) samples and require expensive equipment and usually much time. We have developed a simple protocol allows preparing heterogeneous biological samples suitable for 3D-EM in a laboratory that has a standard supply of equipment and reagents for electron microscopy. This protocol, combined with focused ion-beam scanning electron microscopy, makes it possible to study 3D ultrastructure of complex biological samples, e.g., whole insect heads, over their entire volume at the cellular and subcellular levels. The protocol provides new opportunities for many areas of study, including connectomics.

Autolysis is an internal phenomenon following the death of an organism that leads to the degradation of tissues. In order to explore the initial stages of autolysis and attempt to establish reference standards for tissue changes after death, we studied the rapidly autolyzing tissue of the crayfish hepatopancreas. Samples from the hepatopancreas of crayfish were examined 0, 5, 10, 30, 60, and 120 minutes after death. Histological and ultrapathological examinations and evaluations and apoptotic cell counts were conducted to determine the initiation time and degree of autolysis. The results showed that autolysis in the hepatopancreas of crayfish began within 5 minutes. Initially, autolysis manifested in the swelling of hepatic tubular cells and the widening of mesenchyme. Cells undergoing autolysis showed severe organelle necrolysis. Based on these observations, tissue samples should be collected and preserved within five minutes to avoid interfering with histopathological diagnoses.

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