A comparative study of the ultrastructure of microvilli in the epithelium of small and large intestine of mice.

A comparative analysis of the fine structure of the microvilli on jejunal and colonic epithelial cells of the mouse intestine has been made. The microvilli in these two locations demonstrate a remarkably similar fine structure with respect to the thickness of the plasma membrane, the extent of the filament-free zone, and the characteristics of the microfilaments situated within the microvillous core. Some of the core microfilaments appear to continue across the plasma membrane limiting the tip of the microvillus. The main difference between the microvilli of small intestine and colon is in the extent and organization of the surface coat. In the small intestine, in addition to the commonly observed thin surface "fuzz," occasional areas of the jejunal villus show a more conspicuous surface coat covering the tips of the microvilli. Evidence has been put forward which indicates that the surface coat is an integral part of the epithelial cells. In contrast to the jejunal epithelium, the colonic epithelium is endowed with a thicker surface coat. Variations in the organization of the surface coat at different levels of the colonic crypts have also been noted. The functional significance of these variations in the surface coat is discussed.

Demonstration of the fuzzy surface coat of rat intestinal microvilli by freeze-etching.

In freeze-etch replicas of epithelial cells of rat rectum, the fuzzy surface coat is composed of discrete filaments which are aligned in parallel with each other and with the long axes of the microvilli.

The ultrastructural identification of Auer body precursors in a case of acute promyelocytic leukemia using high-angle specimen tilt.

Auer body (AB) precursors were identified in a case of poorly differentiated acute promyelocytic leukemia (APL). They consist of azurophilic granules containing membraneous lamellae. In most granules the lamellae were seen only after high-angle specimen tilting. In small but more mature ABs, the periodic tubular structure also was visualized best by specimen tilting. An intermediate granule having both lamellae and tubules is described and discussed in relation to the fusion of azurophilic granules to form ABs. The early diagnosis of APL, in the absence of ABs and intravascular coagulation, is assisted by specimen tilting to resolve the lamellae in the azurophilic granules.

Identification of crystals deposited in brain and kidney after xylitol administration by biochemical, histochemical, and electron diffraction methods.

The positive identification of crystals of calcium oxalate occurring in brain and kidney after xylitol administration is described. Biochemical, histochemical, conventional light and electron microscopical methods, including selected area electron diffraction, were used to characterize the crystals.

C bodies and R bodies in the epithelial cells of normal and diseased human rectum.

Small spherical, extracellular bodies (C bodies) measuring 20 to 80 nm in diameter and enclosed by a trilaminar membrane 7 nm wide surrounded the microvilli of human rectal epithelial cells. Similar bodies were observed within membrane-bound vesicles (R bodies) in the apical cytoplasm. The C bodies associated with the mature epithelial cells of the luminal surface were more numerous than those associated with the immature cells of the crypts, where the R bodies predominated. A decreased number of C bodies was observed in ulcerative colitis. We concluded that the membrane-bound C bodies surrounding the microvilli were cellular in origin and arose from R bodies within the cytoplasm of the rectal epithelial cells.

Malignant mesothelioma: cytologic diagnosis with histologic, immunohistochemical, and ultrastructural correlation.

The differential diagnoses of malignant mesothelioma in serous effusions include adenocarcinoma and reactive mesothelial cells. While several cytologic features are of predictive value in separating these entities, immunostaining and ultrastructural examination are important adjuncts that increase the diagnostic yield. Many of the cytomorphologic features can be correlated with immunohistochemical and ultrastructural findings. Most important among these is the ultrastructural demonstration of long, often branching microvillous processes in malignant mesothelial cells. Corresponding microvilli can be visualized by immunostaining for epithelial membrane antigen in both cell block preparations from effusions and biopsy specimens, allowing the identification of malignant mesothelioma. In addition, the circumferential distribution of these immunostained microvilli in cells dispersed in stromal connective tissue identifies them as malignant mesothelial cells, corresponding to the ultrastructural appearance of aberrant microvilli, which project through deficiencies in the basal lamina. These microvilli show interdigitation with stromal collagen fibers, a phenomena not observed in adenocarcinoma.

Ultrastructural changes in cerebral blood vessels of sheep injected with tunicamycin.

Changes resembling those of annual ryegrass toxicity were produced in sheep by the subcutaneous injection of tunicamycin and the cerebellum was examined by electron microscopy. The results suggested vascular endothelial damage as the basis for the cerebral lesions in this condition.

Ultrastructural changes in the cerebellum of nursling rats given corynetoxin, the aetiological agent of annual ryegrass toxicity.

Nursling rats were given a lethal dose of corynetoxin and the sequential morphological alterations in the cerebellum were examined at daily intervals up to 3 days post-inoculation. Ultrastructural changes were those of cerebral vascular damage, which was usually focal in affected endothelial cells, and resulted in vascular stasis or thrombosis. These changes ultimately constituted a failure of perfusion in focal areas of brain parenchyma supplied by these vessels, resulting in necrosis.

Freeze-fracture study of intercellular junctions in benign and malignant mesothelial cells in effusions and a comparison with those seen in pleural mesotheliomas (solid tumour).

This study involves an analysis by thin section and freeze-fracture techniques of the intercellular junctions of exfoliated benign and malignant mesothelial cells obtained from 4 cases, two benign and two malignant effusions. Pleural biopsies (solid tumours) of two further cases of confirmed epithelial malignant mesotheliomas were also studied to compare the organization, distribution and characteristics of the tight junctions, gap junctions and desmosomes observed between the three groups of cases. The results showed that both tight and gap junctions varied greatly in their organization in the exfoliated benign and malignant mesothelial cells. However they were often large and very well developed. In contrast, the tight and gap junctions in the solid tumours were considerably reduced both in their size and frequency, a feature which is well recognized in the literature as consistent with the neoplastic process. Our observation of florid tight and gap junctions in the exfoliated benign and malignant mesothelial cells, raises some important aspects of behaviour of neoplastic cells in effusion fluid. It is our opinion that cells in the fluid are exposed to microenvironmental influences which are quite distinct from those in a 'solid' tumour. We suggest that alteration in the binding sites of the extracellular matrix molecules, their influence on the cytoskeleton and the consequent effect on the development of tight and gap junctions are important factors which need further elucidation. The most significant feature of this study is however the demonstration of essential differences in the cell junctional characteristics between neoplastic mesothelial cells in body cavity fluids and those in tissues thus emphasizing the importance of environmental influences in the development of a neoplasm and its spread.

Variation in intramembranous particle distribution in the cell membrane of the sperm head of the plains rat and western chestnut mouse (Pseudomys Spp.).

Freeze-fracture studies were used to investigate the size, density, and distribution of intramembranous particles (IMPs) in the plasma membrane of the sperm head of two species of Australian hydromyine rodents Pseudomys australis and P. nanus both of which are characterized by having, in addition to a dorsal hook, two long ventral hooks that extend from the antero-concave surface. It was found that on the P face of the plasma membrane over the dorsal hook of caput and upper corpus spermatozoa a paracrystalline arrangement of small, approximately 7nm, IMPs were interspersed with a few large, 9 to 12 nm, IMPs. In the cauda epididymidis the small particles became randomly arranged. On the P face of the plasma membrane over the ventral hooks of caput sperm, and in the postacrosomal region, a much higher density of large, 9 to 12 nm, IMPs was present. In the ventral hooks of cauda sperm the IMPs were increased even further and were arranged in short, variably orientated, ridges; this did not appear to be evident in the plasma membrane over the postacrosomal region. It suggests a change in distribution of the IMPs in the cell membrane over the ventral hooks, but not over the postacrosomal region, during epididymal transit of the spermatozoa. This may indicate that the plasma membrane of these two regions of the head of ejaculated spermatozoa has intrinsic differences in its structure and function.

Freeze-fracture study of the intercellular junctions in bronchiolo-alveolar carcinoma (Clara cell type).

Two bronchiolo-alveolar carcinomas of Clara cell type have been studied by thin section and freeze-fracture techniques. Thin sections of the tumour cells showed junctional complexes (tight junctions and intermediate junctions) at the luminal aspect of the lateral cell membranes and desmosomes below them. Freeze-fracture replicas showed well-developed tight junctions with strands arranged in parallel or polygonal patterns. The junctions were continuous 'zonula occludens' type, usually three or more strands deep, with focal proliferation in some areas. The granules in the tumour cells tended to be larger than those of normal human Clara cells, although they were morphologically similar. There was no evidence of secretion of granules from the tumour cells. The relationships between tumour differentiation and growth pattern, and junctional development are discussed.

Primitive neuroepithelial tumours of soft tissues and of bone: further ultrastructural and immunocytochemical clarification of 'Ewing's sarcoma', including freeze-fracture analysis.

The ultrastructural appearances of 7 primitive neuroepithelial tumours (PNETs) originating in soft tissues and bone are described. Three of the tumours represented primary soft tissue lesions, while locally recurrent tumour or pulmonary metastases were studied from the 4 skeletal tumours, all of which had been diagnosed previously as Ewing's sarcomas. Rosettes were present in one of the soft tissue lesions and although not seen in the primary skeletal neoplasms, they were identified by light microscopy (LM) in 2 of 3 pulmonary metastases, one of which had the morphology of a neuroepithelioma, with innumerable Homer Wright rosettes. Conventional TEM revealed cytoplasmic processes in all cases and rosettes in varying stages of development were also evident, but the appearances did not achieve the level of cellular organization seen in neuroblastoma: microtubules were few, while dense-core granules varied in number but were generally sparse and pleomorphic, resembling lysosomes. However, typical neurosecretory granules were found in one lung metastasis; the neoplastic cells comprising the same tumour also had epithelial markers in the form of well constructed desmosomes, while freeze-fracture analysis demonstrated elaborate tight junctions. In thin sections, junctions in the other tumours appeared rudimentary, but freeze-fracture of a further case revealed small collections of membrane particles suggesting extremely poorly developed desmosomes. Immunocytochemical study of 4 tumours (2 originating in soft tissue and 2 in bone) demonstrated weak to moderate immunostaining for neurone-specific enolase and with several monoclonal antibodies reactive with neuroblastomas, but there was no evidence of immunolabelling for tyrosine hydroxylase.(ABSTRACT TRUNCATED AT 400 WORDS)

Membrane changes associated with mucus production by intestinal goblet cells.

Changes in the structural organization of membranes of mucous bodies and the plasma membrane that occur during mucus production in goblet cells of rat rectum have been studied by thin-section and freeze-fracture techniques. Immature mucous bodies are bounded by a trilaminar membrane and fracture faces of the membrane have randomly distributed intramembrane particles. During maturation, mucous bodies become packed tightly together and changes in the structure of their membranes include (1) fusion of apposing membranes of adjacent bodies to form a pentalaminar structure, (2) a reduction in the density of particles on membrane fracture faces, and (3) exclusion of particles from regions of membrane apposition. Some trilaminar membranes of mucous bodies fuse with the lumenal plasma membrane to form a pentalaminar structure. Sites of apposition between mucous body membranes and the lumenal plasma membrane are seen as particle-cleared bulges on fracture faces of the plasma membrane. Our results indicate that membrane reorganization associated with mucous production in goblet cells includes a reduction and redistribution of some membrane proteins and that membrane fusion occurs between portions of membranes from which proteins have been displaced.

Electron microscopic localization of alpha toxin within the staphylococcal cell by ferritin-labeled antibody.

Highly purified staphylococcal alpha toxin has been used to produce monospecific anti-alpha antibody in rabbits. Gamma globulin prepared from the serum of these rabbits was coupled with ferritin by using toluene diisocyanate. Staphylococcal cells which had been disrupted by two passages through an LKB X-press were treated with this conjugate. Electron microscopic examination of this material showed alpha toxin or an antigenically mature precursor located on the cytoplasmic membrane. The possible function of alpha toxin in this situation is discussed.