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The ependymal lining of the diencephalic third ventricle is known to exhibit significant variation in zonal architecture and the relations of neurites to the ventricular surface in different regions remains obscure. The present study explores the fine structural organization of the ependymal region of the thalamic paraventricular nucleus. Methodology was developed for tracing neurites of cells retrogradely labelled with horseradish peroxidase based on our recent observation that paraventricular neurons projecting to the amygdaloid complex cluster near the ventricle and emit numerous dendrites extending toward the ependymal surface. A relatively uniform population of cuboidal 'pale' ependymocytes dominates the ventricular lining of the thalamic paraventricular nucleus, although a few 'dark' ependymocytes are interspersed. The subependymal region displays a variety of glial elements. Dendrites of thalamic paraventricular projection neurons terminate in proximity to the ependymal layer from which they are generally separated by thin cytoplasmic processes of putative astrocytes, and few indent the basal portion of ependymal cells. Thin 'terminal' (i.e., serially traced) horseradish peroxidase-labelled dendrites filled with lipid and lysosome-like dense bodies were often enveloped by astrocyte membrane whorls. This feature may constitute a reactive glial response in horseradish peroxidase-labelled dendritic terminals. A distinctive arrangement of tortuous astrocyte leaflets was insinuated between the basal portion of ependymocytes in a zone exhibiting numerous caveolae, apparently isolating neurites from direct contact with the cerebrospinal fluid. These findings indicate that the ependymal region of the thalamic paraventricular nucleus is not characterized by those features of the basal third ventricle suspected to confer neuroendocrine interaction between neurons and cerebrospinal fluid. The structural arrangement between ependymocytes and thalamic paraventricular projection cells indicate a specialized relation of these neurons with the ependymal interface, but apparently not directly with the overlying cerebrospinal fluid.

We report a case of benign multicystic mesothelial proliferation (the so-called multicystic peritoneal mesothelioma) arising multifocally in the abdomen of a 46-year-old white man. His anamnesis showed an 8-year history of intermittent pain in the right lower abdominal quadrant. Mucin stains, immunohistochemistry, and electron microscopy confirmed the mesothelial origin of the lesion. Review of the available literature allowed us to find another 85 reported cases of benign multicystic mesothelial proliferations of the peritoneum. Out of these cases, eighteen only occurred in men, the majority being reported in middle-aged women mostly with complaints of abdominal pain. Electron microscopy or immunohistochemistry are needed to make a differential diagnosis towards other multicystic lesions, such as peritoneal cystic lymphangioma. Although multicystic mesothelial proliferations of the peritoneum have often been regarded as benign neoplasms, the true nature--neoplastic or hyperplastic--of these lesions still remains greatly elusive. Therefore, we believe that the unbinding term benign multicystic mesothelial proliferation (first used with regard to the unique hitherto reported case arisen in the pleural cavity) should be considered at present more appropriate to indicate even these peritoneal lesions.

The distribution of lanthanum on the taste disc of the frog, Rana esculenta, after en bloc staining of the tongue with lanthanum nitrate was studied at the ultrastructural level by means of scanning electron microscopy (in the secondary electron mode or in the back scattered electron mode), energy-dispersive X-ray microanalysis, transmission electron microscopy and electron spectroscopic imaging. It was consistently found that lanthanum distribution on the surface of the taste disc is not homogeneous and that the surface of putative receptor cells is in contact with strongly lanthanum-positive material. Calcium co-localizes with lanthanum at that level. These results suggest that different microenvironments exist at the surface of the taste disc and that this could be relevant to the receptor function.

The ultrastructural study of a large series of samples of normal human thymic epithelial cells (TECs) in primary cultures is here presented. Cultured TECs are heterogeneous due to marked differences in their cytoplasmic organization. In particular, a spectrum of ultrastructural features have been observed, ranging from poorly-differentiated cells to secretory and epidermoid-like ones, as well as intermediate transitional forms and cells co-expressing both epidermoid-like and secretory features. Cells with peculiar secretory (neuroendocrine-like) characteristics have also been identified in the culture obtained from one of the donors. These data suggest the existence of a thymic epithelial cell type which may act as a dynamic unit, changing its cytoplasmic organization in response to microenvironmental signals. The types and interrelationships of cytoplasmic organelles observed in the secretory cells suggest that the production of thymic peptides involves the classical pathway of protein synthesis and secretion.

The authors report the results of their ultrastructural study on the rat brown adipose tissue using the freeze-fracturing techniques. It is well known from transmission electron microscopy that lipid vacuoles of the brown adipose tissue cells are bound by a dense line corresponding to a structure as yet totally unknown. The results of the study using freeze-fracturing technics show that the morphology of lipid vacuoles surface is different from that of the typical unit membrane. The possibility is discussed that the particular aspect of the surface is due to the lypolysis induced by tissue fixation.

Peritoneal macrophages from mice injected with aclacinomycin (ACM) (4 mg/kg, i.p.) showed increased functional activity, as assessed by increased antitumoral activity in vitro and in vivo and zymosan-triggered chemoluminescence. They also showed ultrastructural signs of activation (increased number of cytoplasmic organelles), and atypical alterations (giant vacuoles and giant lysosomes containing heterogenous myelinoid bodies, lipofuscine-like substance, cytoplasmic debris, and a fine granular material). As these atypical alterations could be due to the generation of superoxide following ACM injection, superoxide dismutase (SOD) was injected 1 h prior to ACM administration. Neither the morphological characteristics of activation, nor the enhanced metabolic and antitumoral activities induced by ACM were affected by SOD pretreatment, but the atypical alterations were inhibited in a dose-dependent manner. Heat-inactivated SOD did not prevent their appearance. The atypical alterations were not found in peritoneal macrophages from talc or lipopolysaccharide-injected mice, but they were present in Adriamycin-treated mice and were also prevented by SOD pretreatment, indicating that the alterations are due to anthracycline treatment. Finally, [125I]SOD was phagocytized by peritoneal macrophages in vitro and in vivo and not by L1210 tumoral cells, explaining why the atypical alterations induced by ACM were no longer seen after SOD pretreatment. The unchanged direct oncostatic activity of ACM following SOD pretreatment suggests that this combination may have some wider perhaps clinical, potential.

Periepidydimal fat pad of young rat shows, in the peripheral zone, areas with lobular aspect and areas with flattened aspect, surrounded by a mesothelial sheath. In adult rats the flattened areas are no longer observed. The ultrastructural study of the cells present in the flattened zones of the periepidydimal fat pad and the comparison with the same tissue of adult rats seems to indicate that the flattened areas in the peripheral zone of the periepidydimal fat pad of the young rat are a site where the adipocyte precursors can best be studied. Furthermore in the pericytes of the blood vessels wall, rare little lipid vacuoles can be seen: this is in accordance with the hypothesis proposed by other autøhors that the precursors of the adipocytes derive from pericytes.

The authors report the results of their ultrastructural study on the lactating mammary gland of the rat treated with bromocriptine. On the sixth day of treatment the mammary gland shows the same morphological features of the physiologically involuting mammary gland and the same morphological features of the mammary gland of the rat whose pups have been taken away. These results suggest that the pharmacologic treatment with bromocriptine induces a physiological involution of the lactating mammary gland in the rat and that the same drug abates the effect of the persisting suckling stimulus.

The unlabeled antibody peroxidase-antiperoxidase complex technique was used to stain for electron microscopy the secretory granules of a pituitary tumor that had been surgically removed from a woman with high serum prolactin levels. Granules were stained using anti-human prolactin serum. The diameter of the secretory granules was smaller than that measured for the granules of prolactin producing cells in normal human pituitary glands. A shortened storage phase would explain the diameter reduction.

The microcysts found in two adenohypophyses removed from patients with nonsecreting adenomas of this gland have been studied. In one case the cysts were completely surrounded by neoplastic tissue, whereas in the second they were located within the normal parenchyma. The cysts were surrounded by a basement membrane, and appeared to contain a finely granular weakly electron-dense substance. Their walls were lined by mostly cubic cells with microvilli, joined by junctional complexes. Intracytoplasmic microlumina could be seen in some of these cells. Cells showing cilia with a 9 + 2 fibrillar pattern and cells with mucosecretory differentiation were also present. Furthermore endocrine cells were also found in the cyst-lining epithelium. The ultrastructural aspects of the cyst cells lead to reject the hypothesis that these are derived from folliculostellate cells. Besides, intermediate aspects between cyst cells and tumor cells were never visible. Therefore it seems likely that a relationship between adenoma and cyst cells does not exist and that cyst cells originate from remnants of Rathke's pouch with a ciliate or mucosecretory differentiation. The presence of endocrine cells in the cyst-lining epithelium deserves further study, for it seems to indicate that an endocrine differentiation may occur in the adult, too. To our knowledge this is the first ultrastructural study of these structures in adult human pituitary gland.

The immunogold staining method has been recently introduced and proved to be of interest in immunoelectron microscopy as a tracer for detection of cell surface antigens defined by monoclonal antibodies in leukocytes. As variations in sample manipulations and different distribution patterns of gold particles in positive cells are reported, the authors described the experimental conditions which permit them to obtain a good and well interpretable labelling in peripheral blood lymphatic cells. In order to verify the sensitivity and the specificity of this labelling and the interpretation of positivity, a comparison between the percentages of positive cells obtained in electron microscopy and immunofluorescence has been reported. The correlation is acceptable and since the ultrastructural details are also well preserved, this method seems promising for the comparison of molecular phenotypic characteristics and submicroscopic appearance of lymphatic cells.

We have studied at the E.M. the adenohypophysis removed from a woman who had undergone bilateral ovariectomy 4 months earlier because of a disseminated breast cancer. Our study has focused on the submicroscopic aspects of follicular-stellate cells, whose function has not yet been fully ascertained, though it is known from studies carried out on laboratory animals, that these cells are activated under conditions of stimulus to hyperactivity of one or more of the cell types of the adenohypothysis. In our material we have observed numerous follicular structures with variable amounts of colloid-like substance. Follicular-stellate cells limiting colloid-filled cavities showed many cytoplasmic organules with hypertrophic Golgi complex, intracytoplasmic lumina, interdigitations of the cytoplasmic membranes. These aspects are consistent with a condition of hyperactivity of follicular-stellate cells due to bilateral ovariectomy.

The authors report the results of their ultrastructural study on the lactating mammary gland of the rat using Grimelius' silver stain, modified for electron microscopy. The granules of the gland proteic ésocrine secretion are positive to silver impregnation, both within the cytoplasm and in the alveolar lumen. These results are interesting since they suggest that Grimelius' stain positive structures, in the mammary gland, should not be necessarily interpreted as endocrine, at least in the rat.

Ultrastructural features of CD8+ and CD4+ peripheral T-cell lymphomas were studied and the results revealed distinct traits correlated with phenotype. CD8+ peripheral T-cell lymphomas were characterized by a rich organular pattern with a well-developed Golgi apparatus, dense granules, numerous and atypical giant mitochondria. CD4+ peripheral T-cell lymphomas were characterized by wide cytoplasmic areas devoid of organelles. Since similar ultrastructural features differentiated normal and pathological CD8+ and CD4+ peripheral T-lymphocytes, we conclude that under both normal and pathological conditions the expression on the part of the peripheral T-lymphocytes of CD8+ and CD4+ phenotypes is associated to morphological features which distinguish the two subsets.

Submicroscopic findings of T lymphocytic subpopulations of normal human peripheral blood defined by OKT monoclonal antibodies were studied using ultrastructural immunocytochemistry (immunogold staining). The results show that OKT4-and OKT8-positive lymphocytic subpopulations have a distinct morphological pattern, although some variations in the ultrastructural details of cells in each subset are evident. The most representative features of OKT8-positive cells are regular or slightly indented nucleus with condensed chromatin, abundant cytoplasm, prominent Golgi apparatus, several granules frequently localized in the Golgi area, and numerous mitochondria, often in cluster disposition. OKT4-positive cells show generally less condensed chromatin, scanty cytoplasm and poor organule pattern. Furthermore, positive lymphocytes with prominent nuclear irregularities are found in both lymphocytic subpopulations. Ultrastructural similarities between the T cell subsets phenotypically characterized by monoclonal antibodies and other immunological criteria are also discussed.

Bone-marrow cells from 11 cases of T- and 18 cases of B-lymphatic leukemia, at different maturation stages, were examined by scanning electron microscope (SEMI. All cases were extensively studied for the expression of surface markers by immunofluorescence. In addition six cases of T- and 10 cases of B-cell leukemia were labeled with a panel of monoclon;tl antibodies (including CD3, CD5, CD7, CD10, CD4, CD8, CD19, CD20 and CD22) and, after incubation with a colloidal gold conjugate, observed with SEM in the back-scattered electron imaging mode. Early stages of leukemic lymphoid B- and T-cell differentiation are characterized by prevalently smooth cell surfaces. Short stub-like microvilli constantly appear on more mature T cells, while complex surface features like small ruffles and pleomorphic microvilli are present in well-differentiated B-cell proliferations. Surface microvilli can be interpreted als structural features of lymphoid cells, progressively expressed with maturation and differentiation of leukemic as well as normal cells.

The thymus plays a central role in the differentiation of T-lymphocytes. During the past years several in vitro models have been developed for the elucidation of the functional role of different thymic stromal cells. After reviewing the literature, the authors discuss: a) the in vivo and in vitro data on the structural organization of the thymus microenvironment, with particular reference to the epithelial cells; b) the endocrine function of the thymus; c) the interaction between the thymic epithelium and T-cell precursors. The experimental approaches to these problems are also discussed. In particular, the authors examine in detail the experimental aspects which are at present under investigation in their laboratories.

In this report the authors show the main ultrastructural features of malignant non-Hodgkin's lymphomas and lymphoid leukemias, trying to outline the more important findings useful to diagnostic purpose. Since, from an immunologic point of view, lymphoid malignancies reflect the main steps of normal B and T ontogenesis, the various tumours are progressively presented in relation to their stage of phenotypic differentiation. An exact knowledge of the potential information from electron microscopy and its intrinsic limitations, including the high cost and the time expense, permit a correct use of this investigation in diagnostic procedure in lymphoid malignancies.

The authors report the results obtained from the application of electron microscopy techniques to the cytology of fine-needle-aspirated samples of neoplastic lesions from various body sites. These results show that the tissue structure, which is usually lost during the squashing necessary for light microscopy cytology, is preserved when the samples are processed for ultrastructural analysis. Electron microscopy also allows a highly detailed study of the cell's inner structures. Thus, when this technique is applied, fine needle-aspirated samples can be regarded as actual microbiopsies. However, because of the high cost of ultrastructural techniques, we suggest that actual analysis be performed only in selected cases, whereas fixation and inclusion for electron microscopy could be done routinely.

Bioptic specimens of 10 normal human parathyroid glands taken during thyroidectomies were studied both by light microscopy, using a histochemical technique, and electron microscopy. All the glands exhibited regions of different sizes in which follicles made up the tissue architecture. The follicles contained a homogeneous colloid-like substance. Our results seem to exclude the amyloid nature of the follicular content suggested by some Authors, though no further clarification as to its real make-up is provided. The cells lining the follicles belong to a type not as yet described in the normal human parathyroid. These cells appear to be large and clear and are also found in the non-follicular parenchyma. On the basis of their morphologic features we have classified the large clear cells as a particular, deviated stage of the actively secreting chief-cell. The origin and significance of the follicles are also discussed.

Golden hamsters were submitted, three times a week during 4 weeks, to i.p. administration of an antracenedione, mitoxantrone (MTX), and 12 different anthracyclines, adriamycin (ADM), detorubicin (DTR), daunorubicin (DNR), 4'-epi-adriamycin (e-ADM), rubidazone (RBZ), aclacinomycin (ACM), N-trifluoroacetyladriamycin-14-valerate (AD-32), tetrahydropyranyl-adriamycin (THP-ADM), N-L-leucyl-daunorubicin (l-DNR), carminomycin (CAM), rubicyclamin (RBC) and N-trifluoroacetyl-adriamycin-14-9-hemiadipate (AD-143), at doses equivalent to 3/4 those which are optimally oncostatic on murine L1210 leukemia. The electron microscopic (EM) study of the myocardium showed that all studied drugs are cardiotoxic, but with different degree of cardiotoxicity. The histopathological study of the skin detect degenerative lesions with different degree of alopecia. According to the degree of their cardiotoxicity, skin toxicity, and general toxicity or mortality, all drugs studied are classified into 3 groups: 1st group, ADM, DNR, 1-DNR and RBZ, causing very severe cardiac alterations and alopecia (grade 2-3), and very high mortality, 2nd group, e-ADM, DTR, CAM RBC and MTX, with less severe cardiac alterations, and alopecia (grade 1-2), and always high mortality, and 3rd group, ACM, THP-ADM, AD-32 and AD-143, causing less severe myocardial alterations (grade 1-2), without alopecia (grade 0), and extremely low mortality and general toxicity.

The ultrastructural features of normal human thymocytes were analyzed at various stages of immunologic differentiation as defined by a panel of OKT monoclonal antibodies visualized by colloidal gold labelled antimouse IgG. The study shows that first stage thymocytes (OKT10+, OKT9+) have a typical morphology not found in more mature stages and describes the critical ultrastructural change which they undergo in becoming second stage thymocytes (OKT10+, OKT6+, OKT8+, OKT4+). No change in thymocyte fine morphology has been found in the progression from second to third stage (OKT10+, OKT3+, OKT8+ or OKT10+, OKT3+, OKT4+). Cells with ultrastructural features intermediate between those of the first and second stage have been found to react with monoclonal antibodies characterizing the first and the second stage. Ultrastructural similarity and homogeneity found in OKT8+ and OKT4+ thymic subpopulations suggests the acquisition by T lymphocytes of morphologic structures correlate with immunologic features previously found in peripheral blood T cell subpopulations to be a post-thymic process.