Isolation and ultrastructural features of brown adipocytes in culture

Interscapular brown adipose tissue was removed from young rats, the cells isolated using collagenase, pelleted by centrifugation and cultured. Ultrastructural observations were made on these cells immediately after isolation and on Days 1, 2, 4, 10 and 14 of culture. The isolated cells show the typical submicroscopic features of cells in intact brown adipose tissue, i.e. a multivacuolar lipid depot and numerous typical mitochondria with dense cristae. However, as early as Day 1 of culture, the cells show degeneration of the typical mitochondria which are probably then extruded from the cells. Atypical mitochondria now begin to appear and become dominant on Day 4 of culture. By contrast, the typical multivacuolar shape of the lipid droplet does not change. Not even after prolonged periods of culture (2-4 weeks) is there any evidence of coalescence of the multivacuolar lipid depot. These findings are consistent with the possibility that the typical mitochondria of brown adipocytes depend on in vivo conditions, perhaps adrenergic innervation, while the multivacuolar characteristic of the lipid depot does not, and may be an intrinsic feature of the brown adipose cell.

An ultrastructural study of adipocyte precursors from epididymal fat pads of adult rats in culture

It has been demonstrated that cells with poor or no lipid content, isolated from epididymal fat pads of young rats, develop fully into mature adipocytes in vitro. The ultrastructural feature of these cells during such a development have been studied recently. In the present work the electron microscopic aspects of similarly obtained cells from adult rats have been investigated. It has been found that no morphological differences are present in the cells immediately after isolation between young and adult rats. During culture the cells from both adult and young rats show the same maturative process, but in adult rats this process is generally slower and not homogeneous, suggesting the presence of two populations of adipocyte precursors. The former accumulate lipids quickly and have electron microscopic features very similar to those observed for young rat precursors, however maturation is still faster in the latter cells. The latter have electron microscopic aspects of less differentiated cells (some fibroblast-like features) during the first days of culture; however they show a similar development when longer culture periods are studied. These data suggest that the fibroblast-like cells seen after a period of time in culture probably represent an early stage of adipocyte precursor differentiation. Thus it is suggested that in adult mammals, there may be a population of adipocyte precursors present within the adipose tissue which upon stimulation by as yet unknown factors would develop fully into adipocytes.

An ultrastructural morphometric analysis of the adenohypophysis of lactating rats

A morphometric analysis of the adenohypophysis (pars distalis) of lactating rats was carried out by a semi-automated method at the ultrastructural level. The cellular elements were identified by their ultrastructural morphology. The following values were considered for the morphometric study: numerical density of cells/mm3 of tissue and the percentage of parenchymal volume occupied by every cell type. Mammotropes (PRL cells) numbered 624 X 10(3)/mm3 and occupied 59.9% of the parenchymal volume (p.v.). Somatotropes (GH cells) numbered 206 X 10(3)/mm3 and occupied 15.0% of the p.v. Folliculo-stellate cells (FS cells) numbered 128 X 10(3)/mm3 and occupied 8.1% of the p.v. Gonadotropes (GN cells) numbered 47 X 10(3)/mm3 and occupied 6.0% of the p.v. Adrenocorticotropes (ACTH cells) numbered 45 X 10(3)/mm3 and occupied 3.8% of the p.v. Thyrotropes (TSH cells) numbered 36 X 10(3)/mm3 and occupied 3.4% of the p.v. PRL cells were characterized by aspects compatible with intense hormone production. GH cells did not show differences with those of nonlactating animals. Folliculo-stellate elements appeared hypertrophic with abundant cytoplasm, enlarged Golgi complex, and dilation of the follicular lumina. GN cells had abundant cytoplasm with a well-developed and dilated ergastoplasm, particularly in type II GN cells. ACTH cells did not show differences with those of nonlactating animals. TSH cells showed moderate nucleocytoplasmic activation. These fine structural morphometric findings are discussed in relation to other studies regarding nonlactating adenohypophysis and hormone changes during lactation.

Human brown adipose cells in culture

Brown adipose tissue (BAT), obtained from the axillary and perirenal regions of newborns 24-48 h after death, was digested with collagenase and the free cells were cultured. Only the cultures of cells from tissue obtained later than 24 h post mortem were successful. These cells grew slowly to reach confluence. Their typical mitochondria gradually disappeared, being replaced by untypical mitochondria. After confluence, the cells accumulated large amounts of lipid in non-coalescent multivacuolar depots. This model can be useful for the study of the metabolic and morphological features of human brown fat cells.

An ultrastructural study on muciparous microcysts of the human adenohypophysis

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.

Changes in the structure of somato-sensitive neurons in cat following retrograde uptake of HRP

Neurons of cat cerebral cortex, area S1, labelled by retrograde transport of HRP, have been studied by electron microscopy; the animals were sacrificed 48 h after HRP injection. The cells studied are those in which the enzyme is found both in granular and in diffused form in the cytoplasm (diffuse-granular HRP neurons, DGN), or in diffused form in the cytoplasm (Golgi-like labelled neurons, GLN). The observations have shown that the certain recognition of DGN through electron microscopy, requires a comparison with a semithin section adjacent to the ultrathin section since the labelling granules are light-scattering in dark field. Instead the GLN are not light-scattering in dark field but are directly and unmistakably identifiable even by electron microscopy. The DGN are well preserved on the whole in all their organelles; the GLN show a highly damaged aspect in relation to both the Golgi apparatus and the smooth reticulum, to the cytoplasmic organelles and to the nucleus. Our hypothesis is that the latter neurons take on this appearance because of the combined action of: a) the peripheral mechanical lesions caused by the needle and b) the enormous amount of HRP that the cell is forced to take up (through these pathways) because of its lost integrity and because of the large quantity of marker around the axons. In conclusion intracellular HRP is identifiable by electron microscopy only when it is found in diffused form in the cytoplasm.

A morphological study of the adipocyte precursor

In order to attempt to characterize the adipocyte precursor cell in situ in developing adipose tissues from young rats, the light and electron microscopic characteristics were determined of cells in situ in these tissues, as well as in suspensions from the same tissues of cells liberated with collagenase subsequently developing to adipocytes in culture. The functional characteristics of adipose precursor cells at different stages of development in culture is known from previous work, and could therefore be added in parallel to the morphological characteristics. In order to allow comparison with fibroblasts from a site where adipocyte formation does not occur, lung-fibroblasts were also studied in parallel cultures. In culture, a rapidly dividing cell confluenced and reached full expression to adipocytes. This cell had morphological characteristics developing at the same time as early lipid accumulation making it easily distinguishable from a lung fibroblast in culture. A similar cell was found in abundance in the peripheral, non-developed part of the intact epididymal fat pad, here often surrounded by collagen. However, the early preadipocyte (without lipid droplets) and the adipoblast cannot be morphologically distinguished in situ from the fibroblast; therefore it cannot be excluded that fibroblasts and adipoblasts are the same cells in adipose tissue, possibly deriving from the pericyte.

Ultrastructural aspects of nailfold capillaries in a case of eosinophilic fasciitis

An ultrastructural study was made on the nailfold capillaries in an 18-year-old female with eosinophilic fasciitis. Scleroderma-like capillaroscopic lesions were visible at the sites where biopsy was performed. Light microscopy revealed ectasic capillaries at the apex of dermal papillae. Aspects of thickening and duplication of the epidermal basement membrane as well as an activation of endothelial cells were visualized at the ultrastructural level. These cells contained many virus-like tubulo-reticular inclusions, associated with cisternae of endoplasmic reticulum. Aspects of degeneration of nerve fibres and Schwann cells were also present. Large, homogeneously electron-dense deposits could be seen in the basement membrane at the dermo-epidermal junction. This study not only confirms previous observations on the microangiopathy in eosinophilic fasciitis, but also documents two new aspects: electron-dense deposits at the dermo-epidermal junction and tubulo-reticular inclusions within endothelial cells.

Electron microscopy applied to fine-needle aspiration. A report of six cases from various sites

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.

Ultrastructural features of cultured mature adipocyte precursors from adipose tissue in multiple symmetric lipomatosis

The pathogenesis of multiple symmetric lipomatosis (MSL) is as yet unknown; however, some studies seem to indicate the neoplastic nature of this lesion. In this study we have examined the ultrastructural features of the adipocyte precursors of patients with MSL. The cells were isolated by collagenase, cultured, and then examined at the moment of their confluence in a monolayer. Their ultrastructural features were compared with those of cells of the abdominal subcutaneous adipose tissue taken from patients with nonsystemic, surgically treated illnesses. When examined immediately after isolation, the cells from normal tissue did not show significant differences from MSL cells. In culture, however, MSL grew more quickly into a monolayer and showed numerous nuclear pockets and cytoplasmic microfilaments, which were not seen in cells from normal tissue. These differences appear compatible with the neoplastic nature of the MSL adipocyte precursors.

The normal human parathyroid gland. A histochemical and ultrastructural study with particular reference to follicular structures

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.

[Submicroscopic study of brown adipose tissue in young rats by the freeze-fracturing method]

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.

[Ultrastructural study of the stellate cells of the adenohypophysis in an ovariectomized woman]

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.

[A new model for the in vivo study of adipocyte precursors in the rat]

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.

Eosinophilic fasciitis: a mast cell disorder?

The rarity of eosinophilic fasciitis has so far prevented systematic investigations. Its etiology is still unknown and its nosographical position to be defined. We report here a further case whose distinctive features were: a gradual onset simultaneous with allergic bronchial asthma; the absence of eosinophils and presence of a high number of degranulating mast cells and Sezary-like cells in the inflamed fascia. The follow-up and a second biopsy suggested that early steroid treatment is advisable in these patients.

[An ultrastructural immunocytochemical study of secretory granules of an adenohypophyseal tumor]

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.

[Ultrastructural changes in the mammary gland of the lactating rat induced by treatment with bromocriptine]

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.

[Ultrastructural histochemical study of the mammary gland of the lactating rat]

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.

RER-associated structure in parathyroid glands removed because of tertiary hyperparathyroidism

We have performed a submicroscopic analysis of the parathyroid glands removed from 2 patients with tertiary hyperparathyroidism. In both cases an RER-associated structure was found, which has never been described in normal or pathologic conditions in protein-secreting cells. This finding was present in only one of the glands of each patient. Their morphologic features are described. The significance of this structure is also discussed.

Human malignant diffuse mesothelioma: submicroscopic study on the epithelial component

A submicroscopic analysis of eight cases of malignant diffuse mesothelioma was performed. Unlike normal and hyperplastic mesothelium, well differentiated neoplastic cells were found to have a prominent RER and a conspicuous Golgi system. By using a postfixation in osmium ferrocyanide, an amorphous substance was observed in the extracellular space. These features may be related to the ability of malignant diffuse mesothelioma to produce large amounts of hyaluronic acid. The significance of groups of membrane bound dense bodies found in seven of eight cases examined is also discussed.