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.

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)

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 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.

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.

Preparation of cytoplasmic bodies (cytospheres) from isolated hepatocytes and their biochemical properties.

The controlled centrifugation of isolated rat hepatocytes at 260 000 g results in the formation of membrane-bounded cell fragments that we have termed 'cytospheres'. A method is described for the isolation of these cytospheres. Cytospheres are spherical, have a mean diameter of 9.2 +/- 3.2 microns (SD) and a protein content of 225 +/- 12 mg/g wet wt. About 3% of the protein from the original isolated hepatocyte suspension is recoverable. Transmission electron microscopy (TEM) shows cytospheres to possess a trilaminar membrane, and a finely granular hyaloplasm generally devoid of organelles, filaments and microtubules. Freeze-fracture studies reveal a membrane structure typical of a plasma membrane. Ouabain and wheat germ agglutinin (WGA)-binding studies indicate that the original orientation of the plasma membrane is maintained throughout the formation of the cytospheres. The cytospheres have also been characterized biochemically. Cytospheres are enriched in the enzymes normally associated with the hyaloplasm, whereas the activities of enzymes localized in organelles are greatly diminished. Lipid analysis of the cytosphere membrane indicates that it is derived from the plasma membrane of the hepatocyte. Cytospheres are sensitive to changes in the osmolarity and ionic composition of their environment. Cytospheres should therefore prove a useful preparation for the study of hyaloplasm metabolism and of plasma membrane receptor and permeability properties.

The fine structure of the intramitochondrial crystalloids in mitochondrial myopathy.

The fine structure of the intramitochondrial crystalloids found in mitochondrial myopathies was investigated using high angle tilting of ultrathin sections and freeze fracture replicas. Observations show the crystalloids to be composed of 8 nm granules in a unique array. Analysis of the arrangement seen in three mutually perpendicular planes has permitted a model of the crystalloid and its relationship to the mitochondrial membranes to be proposed. The biochemical nature and pathophysiological significance of the crystalloids is still undetermined.

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.

Tomaculous neuropathy: hereditary predisposition to pressure palsies.

A family is described in which six members in three generations have been affected by a remittent and pressure-sensitive mononeuritis or mononeuritis multiplex. In addition, nerve conduction studies have demonstrated the presence of peripheral neuropathy in clinically unaffected as well as affected family members, thus providing evidence of an autosomal dominant inheritance pattern. A sural nerve biopsy from one of of an autosomal dominant inheritance pattern. A sural nerve biopsy from one of the clinically affected members of this family showed 'sausage-shaped' swellings of myelin sheaths characteristic of tomaculous neuropathy. This rare condition, which is briefly reviewed, appears to be a distinctive clinicopathological entity and usually follows a benign course.

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.

Clinical features of mitochondrial myopathy.

Five patients with mitochondrial myopathy are discussed. Two presented with progressive external ophthalmoplegia (CPEO), one with CPEO and retinitis pigmentosa, and two with Kearns-Sayre syndrome. Ragged red fibres and intra-mitochondrial paracrystalline inclusions were found in each case. The clinical heterogeneity of the mitochondrial myopathy syndrome in the presence of identical pathological changes in skeletal muscle is emphasised.

Intercellular junctions in hepatocellular carcinoma.

The freeze-fracture technique has been used to study the organization of intercellular junctions in two cases of hepatocellular carcinoma. A tumor free cirrhotic liver has been included for comparison. Tight junctions were disorganized in the tumor cells of hepatocellular carcinoma. The tight junction networks often were not orientated parallel to the canalicular lumen. In some areas tight junctions comprised 2 to 4 strands, while in other areas they were reduced to a single strand. Discontinuities and local proliferation of tight junctions were also seen. Some tight junctions were composed of intramembrane particles aligned to form a discontinuous network. Gap junctions between the tumor cells were small and infrequent. Gap junctions were found only on the lateral plasma membranes and were not seen within the tight junction networks. These findings have been interpreted to indicate changes in intercellular communication, and an alteration in the ability of hepatocytes to differentiate tight junctions in hepatocellular carcinoma.

Exocytosis of neurosecretory granules in small cell undifferentiated carcinoma.

The tumor cells in the pleural effusions of a case of small cell undifferentiated carcinoma have been studied by light microscopy and by thin section and freeze-fracture electron microscopy. Evidence of exocytosis of neurosecretory granules from the tumor cells is presented. The tumor cells form clumps, with the cells joined by focal tight junctions and small desmosomes. These findings are discussed with reference to the neuroendocrine origin of these tumors and the role of the junctional complexes in the formation of tumor cell aggregates.