Scanning electron microscopic study of precancerous and cancerous pancreatic lesions induced by N-nitrosobis (2-oxopropyl) amine in Syrian golden hamsters

Sequential alteration of Syrian golden hamster pancreatic ducts and ductules was investigated by scanning electron microscope during and subsequent to 10 weekly subcutaneous injections of N-nitrosobis (2-oxopropyl) amine (BOP). By examining surface morphology of ductal cells and resin casts of the secretory branches arising from the common duct, a series of lesions ranging from slight derangement of the luminal dimensions and loss of cilia to marked projections of "finger-like" processes accompanied by pleomorphism at the cellular and microvilli levels and increase in numbers of goblet cells could be established. A ductal histogenesis is proposed on the basis of the present scanning electron microscopic and earlier light microscopic findings.     

Scanning electron microscopic observations on bone.

The maceration technique employed in the preparation of specimens of bone for museum purposes has also been found to be of use in the preparation of fresh specimens for study with the scanning electron microscope. The technique requires less technical supervision, permits a greater underprocessing to overprocessing margin, and allows comparability of recent biopsy material with previously macerated bone specimens with no less detail than that found by other authors using other techniques on biopsy material.     

Neurogenic stomach neoplasms induced by nitrosomethylures in Syrian hamsters]

In the experiment with inoculation of N-nitroso-N-methylurea (a maximum total dose of 7.5 mg) to Syrian hamsters, tumors developed in 20 out of 25 animals surviving the time of the occurrence of the first tumor (31 weeks). Out of 35 tumors 17 developed at the site of inoculation: in the left cheek pouch (of them 12 embryonal rhabdomyoblastomas), 11 in the stomach (of them 6 neurogenic), and 7 in other organs (skin, liver, adrenals, hemopoietic system). The paper describes the histological pattern of 6 neurogenic tumors of the stomach in which all the elements of the nervous system have been found: ganglionic cells, neuroglia, and nerve stems. On the basis of some signs the authors classify these tumors as malignant.     

Adrenocortical adenoma with Cushing's syndrome. Scanning electron microscopic observations

Adrenocortical adenomas with Cushing's syndrome (Cushing's adenoma) consisted of two different features, which intermingled in various proportions and were related with each other. The first feature showed long-columnar or trabecular arrangement and a vacuolar appearance which correspond to lipid droplets of clear-type cells. In the second feature, the sinusoid was well developed and meandering, and the perisinusoidal space was prominent and contained collagen fibrils, bleb-like structures, and granules. The collagen fibrils were entangled with the parenchymal cells. The sinusoid was lined by a sinusoidal wall with fenestrations or pores. Bleb-like structures and granules traversed them. Two different features were speculated to be consistent with areas of clear-type cells and compact-type cells, respectively, observed light and transmission electron microscopies.     

Multilocular renal cyst. Scanning and transmission electron microscopic observations

A multilocular renal cyst in a boy aged one year and four months is presented, with particular attention being paid to the nature of the epithelial lining cells. Light and transmission electron microscopy showed the cyst to be lined by a single layer of flattened or cuboidal epithelial cells of relatively uniform morphology. Neither embryonic elements nor nephroblastomatous foci were noted in the intervening stroma. The scanning electron microscopy showed hitherto undescribed surface morphological features of the epithelial lining cells: They were characterized by the presence of one or, occasionally two centrally positioned long cilia and by variably oriented microvilli. The observations presented here suggested that the lining cells of the cyst most closely resembled the principal cells of the collecting ducts, especially those located in the inner medulla of the kidney. An unexpected finding was the additional occurrence of a giant bullous lesion in the right lung of this patient.     

SV40 lymphomagenesis in Syrian golden hamsters

Simian virus 40 (SV40) isolates differ in oncogenic potential in Syrian golden hamsters following intraperitoneal inoculation. Here we describe the effect of intravenous exposure on tumor induction by SV40. Strains SVCPC (simple regulatory region) and VA45-54(2E) (complex regulatory region) were highly oncogenic following intravenous inoculation, producing a spectrum of tumor types. Three lymphoma cell lines were established; all expressed SV40 T-antigen, were immortalized for growth in culture, and were tumorigenic following transplantation in vivo. New monoclonal antibodies directed against hamster lymphocyte surface antigens are described. The cell lines expressed MHC class II and macrophage markers and were highly phagocytic, indicating a histiocytic origin. Many hamsters that remained tumor-free developed SV40 T-antigen antibodies, suggesting that viral replication occurred. This study shows that route of exposure influences the pathogenesis of SV40-mediated carcinogenesis, that SV40 strain VA45-54(2E) is lymphomagenic in hamsters, that hamster lymphoid cells of histiocytic origin can be transformed in vivo and established in culture, and that reagents to hamster leukocyte differentiation molecules are now available.     

Light and electron microscopic observations on hydrocortisone-induced cleft palate in hamsters

Palatal histogenesis in hydrocortisone-treated hamster fetuses was studied by both light and electron microscopy. At an early stage in the hydrocortisone-affected fetuses, when the palatal shelves hung vertically on either side of the tongue, necrotic changes could be seen in some of the basal epithelial cells which lay adjacent to the fragmented basal lamina. The normal looking cells lay on an intact basal lamina and were attached to the contiguous necrotic cells by desmosomes. With horizontal reorientation of the palatal shelves and their approach to the midline, cellular necrosis and fragmentation of the basal lamina increased. When compared with normal cells, the hydrocortisone-affected ones were seen to be lighter, to contain fewer ribosomes and no lysosomes. At a later stage, when midline palatal fusion was lacking, the epithelium underwent stratification and keratinization while the necrotic debris was removed by mesenchymal macrophages. It appears that the normal process of protein synthesis is inhibited following hydrocortisone administration and that this, in turn, during palatogenesis, disrupts normal cellular differentiation and the integrity of the basal lamina, which are associated with the production of a cleft palate.     

Fourth ventricular floor in human embryos: Scanning electron microscopic observations

The ultrastructural surface features of the normal fourth ventricular floor of seven human embryos ranging from Carnegie stage 14 to stage 19 (crown-rump length: 7.6–16.2 mm) were examined by using scanning electron microscopy (SEM). Low-power SEM views showed the median sulcus, sulcus limitans, and neuromeres, transient structures characteristic of the earlier embryonic period. High-power SEM observation revealed supraependymal cells (SE cells) and supraependymal fibers (SE fibers) which exhibited a characterisitc localization, as well as generalized surface-membrane modifications such as microvilli and cilia. SE cells could be classified into two major groups. The type 1 SE cells seem to possess neuronal functions, as deduced from morphological similarities to their counterparts in adults and the specialized distribution closely related to neuromeres. The type 2 SE cell morphologically resembled the phagocytic SE cell described in related literature. SE fibers ran a course either rostrocaudally in the median sulcus or mediolaterally on the neuromeres, most frequently near the interneuromeric cleft; they made contact with type 1 SE cells and ependymal surface modifications and then penetrated the ependymal layer.     

Scanning electron microscopic observations of the basement membranes with dithiothreitol separation

Scanning electron microscopic (SEM) studies of the interstitial surface of the lamina densa can be performed with dithiothreitol separation, which is the only method of exposing this surface. SEM observation revealed the three-dimensional structures of the meshwork in the lamina densa and anchoring fibrils in dithiothreitol-separated specimens. Detection of the components of the basement membrane can be performed by immunoscanning electron microscopy on this exposed surface by comparing the backscattered and the secondary electron images. SEM observation also revealed the fine structure of the lamina fibroreticularis using separated dermis or the lamina propria mucosae.     

Scanning electron microscopic observations of the development of the chicken caecum

The surface pattern of the caeca of the chicken was examined using the scanning electron microscope (SEM) in stages ranging from 11th day of foetal development to 60 days of post-natal life. During incubation the proximal region (basis) of the caecum presented a few irregular elevations, which were later regarded as villi and after hatching, gradually, became longer and wider. These structures were found to be similar to those of the small intestine. The middle (corpus) and distal (apex) regions of caecum presented ridges/folds with short and blunt villi that were even shorter in the apex. The ridges/folds were running longitudinally the inner surface of the corpus while those of the apex were not so well developed.     

Scanning electron microscopic observations of Anopheles albimanus (Diptera: Culicidae) eggs.

To investigate the existence of subspecies of Anopheles albimanus Wiedeman in southern Mexico, the egg morphology of specimens obtained from several field populations and from insectary-adapted colonies of uniform pupal phenotype was examined. Scanning electron microscopic observations have shown that the eggs of An. albimanus are polymorphic in respect to the size and shape of their floats, but not in their ornamentation. Four types of eggs were found. Differences in the proportion of the various morphological types were statistically significant, although proportions of egg types were variable among individuals within the same population. These observations are suggestive of distinctive populations and warrant further studies using more sensitive methods to investigate sibling species in An. albimanus sensu lato.     

Attachment and ingestion of mycoplasmas by mouse macrophages. II. Scanning electron microscopic observations.

Mycoplasmas adhere closely to the central region of the surface of mouse peritoneal macrophages in vitro. They do not appear connected to each other or the macrophage membrane, and they induce no change in the surface of the cell. After addition of antimycoplasma antibody, mycoplasmas show interconnections and the cell shows an increase occurrence of ruffled membrane and folding over the mycoplasmas. Large and small lacunae appear in the membrane at sites other than those taking in organisms, and the cell develops a diffusely granular appearance. These changes are associated with an increase in pinocytosis of horseradish peroxidase that is 85% above controls. Five minutes after addition of antibody, the macrophage appears contracted and engorged and has persistent membrane changes consisting of pits, openings, and membrane folds. Trypsin causes slow ingestion of surface mycoplasmas without the obvious membrane folding over organisms but with evidence of a predominantly invaginating process of phagocytosis. The macrophage surface has numerous microprojections, but is does not have the granular appearance seen after addition of antibody. Trypsin and Mycoplasma pulmonis antigen do not enhance macrophage pinocytic rates. (Am J Pathol 87:347-358, 1977).     

Development of intrapancreatic transplantable model of pancreatic duct adenocarcinoma in Syrian golden hamsters.

Intrapancreatic and subcutaneous (SC) inoculation of cultured pancreatic cancer cells, derived from an induced primary pancreatic cancer in a Syrian hamster, resulted in tumor take in all recipient hamsters. The intrapancreatic allografts grew rapidly, were invasive, and metastasized into the lymph nodes and liver in 2 of 9 cases. In comparison, SC tumors grew relatively slower and formed a large encapsulated mass without invasion and metastases. Histologically, tumors of both sites showed fairly well-differentiated adenocarcinomas of ductal/ductular type resembling the induced primary cancer. Similar to the primary induced pancreatic cancers, tumor cells of both allografts expressed blood-group-related antigens, including A, B, H, Le(b), Le(y), Le(x), and tumor-associated antigen TAG-72. The tumor cells did not express Le(a), CA 19-9, 17-1A, or DU-PAN-2. The expression of these antigens was retained in the metastases and presented the same patterns of reactivity as the allografts. Thus intrapancreatic transplantation provides a rapid model for production of pancreatic cancer with morphologic similarities to human pancreatic cancer.     

Scanning electron microscopic observations of normal and regenerating nerve roots in the cat

The surface morphology of normal and regenerated nerve roots was studied using correlated scanning and transmission electron microscopic methods. Nerve roots of the cauda equina were either cut and rejoined or crossed from a segment above to a segment below. Good regeneration was observed in both experimental procedures. The regenerated nerve root sheath had alterations in surface structure created by extensive growth of collagen. Despite this collagen formation, regenerated axons crossed the anastomotic site with relative ease. Surface features of the regenerated axons were similar in appearance to those of the normal axon. Schwann cells were easily recognized, as were the collagen fibers of the endoneurium, although the endoneurium was more prominent and occupied more of the interaxonal space. Macrophages were identified as round structures with a laminated surface or as a honeycomb structure. Internal features of the regenerating axons were more difficult to identify, but mitochondria and a fibrous network were observed. These studies have demonstrated the application of scanning electron microscopic methods to visualize surface structures and cells in regenerated nerve roots.     

Immunohistochemical demonstration of Clara cell antigen in lung tumors of bronchiolar origin induced by N-nitrosodiethylamine in Syrian golden hamsters.

Both alveolar type II cells and Clara cells have been suggested as cells of origin of human bronchioloalveolar lung carcinomas and other pulmonary neoplasms, based on the presence of cell specific markers identified by immunocytochemical methods. Alveolar type II cell origin of solid and papillary lung tumors of the mouse has been demonstrated, and Clara cells have been suggested as cell of origin for hamster pulmonary neoplasms. Therefore, chemically induced bronchiolar hyperplasias and pulmonary neoplasms of Syrian golden hamsters were analyzed by avidin-biotin immunohistochemistry to localize a hamster-specific Clara cell antigen (CCA) and keratin. The hamsters had been treated subcutaneously with multiple doses of N-nitrosodiethylamine (NDEA). Proliferative lesions of low cuboidal, tall columnar, or pleomorphic cells were present within bronchioles or adjacent to airways in the alveolar parenchyma. Frequently areas of squamous cell differentiation were present focally or diffusely that were immunoreactive for cytokeratin. Immunoreactivity for cytokeratin was also noted for hyperplastic bronchiolar neuroepithelial bodies. Cellular hyperplasias extending out into the alveolar parenchyma contained ciliated cells and frequently consisted of cells immunoreactive for CCA, showing them to be of bronchiolar Clara cell origin. Tumors developed from bronchiolar cell hyperplasias localized within bronchioles and from bronchiolar cells lining former alveolar walls. Neoplastic growth patterns were tubulo-papillary, forming loose networks or densely cellular areas. Immunoreactivity for cytoplasmic CCA was found in 50% of the tumors and was seen most frequently in small cuboidal cells and larger, vacuolated cells scattered throughout the neoplasms. In summary, evidence is presented that NDEA-induced pulmonary tumors of the Syrian golden hamster originated from cells lining bronchioles and from extrabronchiolar Clara cell hyperplasias of the terminal bronchioles. As the pulmonary tumors of the hamsters progressed towards a squamoid cell type, CCA was no longer detectable but cells became immunoreactive for keratin.     

Achondrogenesis type I in three sibling fetuses. Scanning and transmission electron microscopic studies.

Three spontaneously aborted fetuses with Type I achondrogenesis in a family with a first cousin marriage are described. Studies by light microscopy revealed abnormal cartilage, enchondral, and periosteal bone, and normal tooth development with abnormal alveolar bone. Electron microscopic studies of cultured skin fibroblasts manifested structurally normal cells. Scanning electron microscopy studies had shown deficient intercartilaginous septa in the metaphysis, with abnormally large calcifying globules. In the diaphysis, the orientation of bone trabeculae and collagen fibers within the trabeculae was disturbed. The numerous osteocytic lucunae were wide and irregular in arrangement and shape. Type 2 achondrogenesis, as studied in these fetuses, is probably a widespread mesenchymal defect, manifested by abnormal calcification and ossification of enchondral and periosteal bone.     

Scanning electron microscopic observations of the periodontal ligament fibers and cells in rat molar teeth.

The periodontal ligament of rat molar teeth was observed with scanning electron microscopy (SEM) using two different methods: NaOH maceration and KOH-collagenase treatments. Rat jaws with molar teeth were fixed, demineralized with 10% EDTA, and cut into several pieces. After maceration with 5% NaOH for 5 days at room temperature, the cellular elements were completely removed and the periodontal ligament fibers appeared as bundles of collagen fibrils. The fibers branched and anastomosed but did not spread fibrils randomly. In some regions near the alveolar bone, collagen fibrils circularly binding the fibers were found. When treated with 30% KOH for 7 to 10 minutes at 60 degrees C and with 0.1% collagenase, the periodontal ligament fibers were removed and the cells appeared as spindle and stellate shapes, and combined with the irregular cell processes of each other. Thus, the interaction between the periodontal ligament fibers and cells were three-dimensionally visualized by using the two different methods.