Polarized Ends of Human Macula Densa Cells: Ultrastructural Investigation and Morphofunctional Correlations.

The morphology of the kidney macula densa (MD) has extensively been investigated in animals, whereas human studies are scanty. We studied the fine structure of human MD cells focusing on their apical and basal ends and correlating structure and function. The MD region was examined by transmission electron microscopy in six renal biopsies from patients with kidney disease. Ultrastructural analysis of MD cells was performed on serial sections. MD cells show two polarized ends. The apical portion is characterized by a single, immotile cilium associated with microvilli; apically, cells are joined by adhering junctions. In the basal portion, the cytoplasm contains small, dense granules and numerous, irregular cytoplasmic projections extending to the adjacent extraglomerular mesangium. The projections often contain small, dense granules. A reticulated basement membrane around MD cells separates them from the extraglomerular mesangium. Although the fact that tissue specimens came from patients with kidney disease mandates extreme caution, ultrastructural examination confirmed that MD cells have sensory features due to the presence of the primary cilium, that they are connected by apical adhering junctions forming a barrier that separates the tubular flow from the interstitium, and that they present numerous basal interdigitations surrounded by a reticulated basement membrane. Conceivably, the latter two features are related to the functional activity of the MD. The small, dense granules in the basal cytoplasm and in cytoplasmic projections are likely related to the paracrine function of MD cells. Anat Rec, 301:922-931, 2018. © 2017 Wiley Periodicals, Inc.

Giant mesenteric cyst of mesothelial origin in a haemodialysis patient with previous peritoneal dialysis therapy.

A 55-year-old female haemodialysis patient presented progressive abdominal liquid formation after having been excluded from peritoneal dialysis therapy because of recurrent peritonitis. Ultrasound was suspicious for ascites secondary to sclerosing peritonitis. Computed tomography revealed a thin-walled mesenteric cyst extending from the epigastric to the pelvic region. The cyst was excised incompletely as extensive adhesions were present. Histology was consistent with a mesothelial cyst of inflammatory origin. Three months after surgery, ultrasound detected a local recurrence at the descending colon. This case emphasizes the relation between mesenteric cyst, persistent inflammatory status and preceding peritoneal dialysis complicated by peritonitis.

Ribosome-lamella complexes in injured podocytes: description of a case and review of the literature.

Ribosome-lamella complexes (RLCs) are mainly observed in a variety of hematological disorders and occasionally in solid neoplasms and in nonneoplastic diseases. These intracytoplasmic organelles are held to arise from rough endoplasmic reticulum, but, in agreement with more recent literature data, their function is still unclear. Ultrastructural analysis of glomeruli from a patient with focal segmental glomerulosclerosis secondary to metabolic syndrome disclosed significant foot process loss and abundant cytoskeletal proteins in major podocyte processes; two of the latter also displayed RLCs. This is the second report of RLCs in human renal glomerulus. Their close association with cytoskeletal proteins and lysosomes suggests a relationship with abnormal protein biosynthesis.

Intermitochondrial cement (nuage) in a spermatocytic seminoma: comparison with classical seminoma and normal testis.

The nuage, an ultrastructural marker of normal human germ cells (spermatogonia type A and primary spermatocytes), may be found associated with mitochondria (intermitochondrial cement) and/or free in the cytoplasm. Eight specimens from germ cell-related tumours were reviewed to assess whether the nuage could have diagnostic significance in testicular neoplasms. The nuage of neoplastic cells from seven classical seminomas and one spermatocytic seminoma was compared with that from two normal testes. The ultrastructural study demonstrated that only spermatocytic seminoma cells contained both types of nuage and that significantly fewer spermatocytic seminoma cells (28%) contained intermitochondrial cement compared with control spermatogonia type A (81.1%) and primary spermatocytes (47.6%). The data indicate that (1) the detection of the nuage confirms that the phenotype of spermatocytic seminoma is more differentiated than that of classical seminoma; (2) the intermitochondrial cement is an additional example of how a distinctive organelle of a normal cell is preserved in its neoplastic counterpart and (3) if the intermitochondrial cement were found in other cases of spermatocytic seminoma, this organelle of the normal germ cell lineage could be considered as a new ultrastructural marker of the neoplasm.

Brush cells in the human duodenojejunal junction: an ultrastructural study.

Brush cells have been identified in the respiratory and gastrointestinal tract mucosa of many mammalian species. In humans they are found in the respiratory tract and the gastrointestinal apparatus, in both the stomach and the gallbladder. The function of brush cells is unknown, and most morphological data have been obtained in rodents. To extend our knowledge of human brush cells, we performed an ultrastructural investigation of human small intestine brush cells. Six brush cells identified in five out of more than 300 small intestine biopsies performed for gastrointestinal tract disorders were examined by transmission electron microscopy. Five brush cells were located on the surface epithelium and one in a crypt. The five surface brush cells were characterized by a narrow apical pole from which emerged microvilli that were longer and thicker than those of enterocytes. The filamentous core extended far into the cell body without forming the terminal web. Caveolae were abundant. Filaments were in the form of microfilaments and intermediate filaments. Cytoplasmic projections containing filaments were found on the basolateral surface of brush cells. In a single cell, axons containing vesicles and dense core granules were in close contact both with the basal and the lateral surface of the cell. The crypt brush cell appeared less mature. We concluded that human small intestine brush cells share a similar ultrastructural biology with those of other mammals. They are polarized and well-differentiated cells endowed with a distinctive cytoskeleton. The observation of nerve fibres closely associated with brush cells, never previously described in humans, lends support to the hypothesis of a receptor role for these cells.

Unusual ultrastructural features in microvillous inclusion disease: A report of two cases.

Microvillous Inclusion Disease (MID) is an inherited disorder characterized by intractable diarrhea in infancy. Ultrastructural detection of pathognomonic microvillous inclusions in the enterocytes is essential for diagnosis. The aim of this research is to contribute to the knowledge of MID studying enterocytes and goblet cells (gc). Samples of duodenal mucosa from two young infants with MID (aged 75 days and 3 months, respectively) were studied by light and electron microscopy. Detection in the intestinal villi of immature gc (with microvilli) in one of the cases led us to seek them in control samples. The total number of gc with microvilli (immature) and without microvilli (mature) were counted. In both MID specimens, light microscopy showed atrophy of villi and PAS-positive material in the enterocyte cytoplasm. The ultrastructure of villous enterocytes was characterized by brush-border abnormalities, microvillous inclusions, dense apical granules, and lysosomes. Intermediate structures between microvillous inclusions and lysosomes were also detected within a cell, as were rare microvilli on the lateral membrane of the enterocytes. In one MID specimen, immature gc were also identified in the absorptive compartment. Only mature gc were observed in the controls. The significance of the latter finding requires further studies.