Ultrastructural and immunohistochemical characteristics of lipid-rich carcinoma of the breast

Summary Five cases of lipid-rich carcinomas of the breast were investigated ultrastructurally and immunohistochemically for alpha-lactalbumin (ALA), lactoferrin (Lfr) and human milk fat globule membrane antigen (HMFG-2). Staining for ALA and Lfr showed intensive reaction on nearly all of the tumour cells whereas immunoreaction for HMFG-2 revealed positivity in single cells. All tumours were negative for steroid receptor content. Ultrastructurally the tumour cells showed numerous intracytoplasmic non-membrane bound lipid droplets which were often found within autophagocytic vacuoles. Neither rough endoplasmic reticulum nor Golgi complexes showed any sign of lipid synthesis. Extrusion of lipid droplets and extracellular lipid deposition was not observed. In conclusion, our findings do not justify the consideration of lipid-rich carcinoma of the breast as a clearly defined group of tumours with specific secretory activity. Therefore, the term lipid-rich carcinoma should be used in preference to lipid-secreting, unless there is evidence of active lipid secretion.     

Ultrastructural observations on closure of the neural tube in the mouse

Summary The fusion of the neural walls in the cephalic part of mouse embryos varying in age from 9 to 20 somites was examined with the electron microscope. In the rhombencephalic region the rim of the neural wall was formed from outside inward by ectodermal surface cells, a row of flattened cells without surface projections and neuroepithelial cells. At the junction of the surface ectoderm and the flat cells were seen large projections containing a cytoplasmic matrix without organelles and previously referred to as ruffles. The initial contact between the walls was made by the large cytoplasmic arms and numerous finger-like projections interdigitating with similar projections from the opposite wall. The projections originated from the surface ectoderm and possibly neural crest cells. During further fusion the surface ectoderm cells formed dense membrane specializations, thus establishing a firm contact.The initial contact in the mesencephalon was formed by extensions from the surface ectoderm and was followed by the formation of specialized membrane junctions, as seen between the surface ectoderm in the rhombencephalon. The neuroepithelial cells facing the gap between the neural walls with their apical ends made contact with the cells from the opposing wall by numerous finger-like projections but membrane specializations failed to develop.The closing mechanism in the prosencephalon and anterior neuropore regions differed from the previous areas in that the initial contact was established by the neuroepithelial cells. Only after this contact had been formed did the surface ectoderm cells close the gap. In contrast with the other areas many phagocytosed particles were seen in the prosencephalon and in the region of the anterior neuropore. Many particles from degenerated cells were found inside healthy surrounding cells. Some of these particles contained nuclear material and cytoplasmic organelles.     

Ultrastructural observations on axonal swelling in the human gracile nucleus

Summary The morphology of the spheroids in human gracile nuclei was studied by light and electron microscopy. Various spheroids encountered in the present study could be classified into three types based on the internal structure: The first one was chiefly composed of many irregular homogeneous dense bodies, multivesicular bodies and mitochondria. The dense bodies seemed to deposit multicentrically in an axon in the early stage of balloon formation and coalesce to form larger ones. The second was characterized by a marked accumulation of closely approximated mitochondria and dense concentric bodies. In the third the most characteristic findings were neurofibrillary accumulation and aggregations of dense bodies. These findings showed some divergence from those of dystrophic axons and the last two mimic those of degenerative or regenerative axons, which suggested that axonal swelling (including dystrophic axon) is not characteristic reaction of specific disease but rather nonspecific one to a variety of noxious stimuli.With light microscope, it was difficult to distinguish balloons with different structures since they were quite diverse and manifold in their shape, size, appearance and stainability. Intra-axonal corpora amylacea were seen in most cases and their incidence appeared to be nonspecific for any diseases.     

Fine-needle aspiration cytology of pulmonary carcinosarcoma with immunocytochemical and ultrastructural observations

The cytologic, immunocytochemical, and ultrastructural features of a pulmonary carcinosarcoma diagnosed by fine-needle aspiration biopsy are presented. Both malignant epithelial groups and bizarre spindle-shaped cells arranged in loose groups, microtissue fragments and in a dissociate fashion showed dual immunoperoxidase staining with cytokeratins and vimentin. Although the immunocytochemical staining pattern is typical of this neoplasm, it does not allow differentiation in all cases from the more common primary large-cell undifferentiated carcinoma, which can also show dual staining for cytokeratin and vimentin. However, the presence of poorly differentiated epithelial groupings associated with a malignant mesenchymal component set in a myxoid stroma should suggest the correct diagnosis. Cytologically, differentiating carcinosarcoma, a poorly differentiated malignancy showing dual staining for cytokeratin and vimentin, from a large-cell carcinoma is important, since the former may pursue a more indolent clinical course.     

Ultrastructural and biochemical observations on the metanephros of normal and cultured chick embryos

Summary A comparative electron microscopical study was conducted on the metanephros from chick embryos differentiated either in shell-less culture or in ovo. Developmental characteristics were very similar in both cases. Up to stage 37 (Hamburger-Hamilton) the metanephros contained large numbers of immature nephrons; their renal corpuscles were crescent-shaped and consisted of an outer layer of flat cells and an inner one of cuboidal cells. In more advanced corpuscles also found at this stage the inner layer had formed numerous rudimentary pedicels and the tunica media of the glomerular arteriole contained juxta-glomerular cells with numerous, small, electron dense granules.In the metanephros from embryos at stage 38 or older, large numbers of nephrons had completed their differentiation; their rounded renal corpuscles had fully differentiated podocytes with thin interdigitating pedicels and the proximal convoluted tubules had numerous apical microvilli, vesicles, vacuoles and tubular invaginations indicating an active process of resorption. These results appear to indicate that both in culture and in ovo-developed embryos, the metanephri start to function around stage 38. In the case of normal embryos this conclusion agrees with previous physiological and biochemical determinations. The injection of 20 USP parathyroid hormone into 16-day old chick embryos produced an increase in the concentration of cyclic AMP in the metanephros. This favours the idea that the regulation of kidney function by the hormone begins during the embryonic period.     

Ultrastructural,immunohistochemical and biochemical studies on amylase and ACTH producing lung cancer

Summary Tumour tissue from a lung cancer patient who showed elevated serum amylase and adrenocorticotropin (ACTH) was studied ultrastructurally, immunohistochemically and biochemically. Histologically the tumour was a small cell carcinoma. On electron microscopic examination the tumour cells contained large zymogen-like granules within the cytoplasm. Furthermore, cells which possessed many small dense core granules of the endocrine type were also observed. It was of interest that the large zymogen-like granule-containing tumour cells had microvilli at the apical border, connected by desmosomes and forming lumina showing adenocarcinomatous differentiation. Electrophoretic analysis of the serum revealed that the major elevated amylase was of the salivary type with minor components. Immunostaining clearly demonstrated that most of the tumour cells possessed immunoreactive ACTH, whereas salivary amylase was only found in occasional clusters of the tumour cells. The results seem to indicate that the tumour showed both endocrine and exocrine characteristics - an amphicrine carcinoma, expressing amylase and ACTH simultaneously.     

Malignant myoepithelioma of the oral palate: Ultrastructural and immunohistochemical studies and survey of the literature

Malignant myoepithelioma arising in the palatal gland is extremely rare. The present study demonstrated ultrastructural and immunohistochemical features of malignant myoepithelioma transformed from long-standing benign myoepithelioma occurring in the palatal gland. Microscopically, the tumor mass was composed of plasmacytoid cells and epitheloid cells. The malignant feature was seen only at the area adjacent to the bone. Immunohistochemically, most of the cells were S-100 positive, whereas vimentin and keratin were only partially positive. Glial fibrillary acid protein (GFAP) was positive at the peripheral cells of the solid nests and epitheloid cells with myxoid stroma. Ultrastructurally, filament-rich cells, tonofilament-rich cells, and filament-poor cells were observed. At the area adjacent to the bone, the cells implying malignancy were filament-poor cells in which the luminal structures could be detected. From these findings, a scarcity of filaments in myoepitheliomatous components may imply a malignancy.     

Ultrastructural correlates of functional relationships between nigral dopaminergic or cortical afferent fibers and neuropeptide Y-containing neurons in the rat striatum

This study examines the ultrastructural relationships established by the nigrostriatal dopaminergic and the corticostriatal afferent fibers with neuropeptide Y (NPY)-containing neurons in the rat striatum. By means of dual immunolabeling procedures using peroxidase conjugated F(ab) fragments and ¹²⁵I-labeled protein A, direct appositions and morphologically defined synaptic contacts of the symmetrical type were visualized between tyrosine hydroxylase-labeled nerve terminals and NPY-labeled neurons. After deafferentation of the striatum from its cortical input direct appositions and asymmetrical synaptic contacts were evidenced between characteristic degenerative boutons and NPY-positive neurons in the striatum. These results suggest that striatal NPY interneurons undergo direct influence from both nigrostriatal dopaminergic and corticostriatal neuronal systems.     

Ultrastructural observations on the histogenesis of localized fibrous tumours of the pleura (benign mesothehoma)

Summary Five localized fibrous tumours of the pleura (benign mesothelioma) were studied ultrastructurally in order to elucidate their histogenesis. The histological subtypes of this benign fibrous lesion of the visceral pleura, i.e. the cellular, the collagenous, and the hyaline, were separately analysed.The tumours are composed of undifferentiated mesenchymal cells, intermediate and differentiated fibroblasts as well as collagenous interstitial tissue. The varying distribution of these cell elements account for the various histological subtypes. Morphological similarities between the mesenchymal tumour cells and the superficial mesothelial cells, which are always separated from the true tumour tissue by an intact basement membrane, were not observed.The different cellular elements can be regarded as parts of a continuous spectrum of cytodifferentiation, in which the mature fibroblasts are derived via intermediate forms from the undifferentiated cells. It is concluded that the localized fibrous tumours of the pleura arise from immature mesenchymal stem cells, which seems to be normally found in the submesothelial layer of the visceral pleura.     

Ultrastructural identification of somata and neural processes immunoreactive to antibodies against glutamic acid decarboxylase (GAD) in the dorsal lateral geniculate nucleus of the cat

Summary The cat dorsal lateral geniculate nucleus (LGN) was examined at the light- and electron-microscopic level after immunocytochemistry for GAD (the synthesizing enzyme of the inhibitory neurotransmitter GABA), to identify cells and processes with GAD-like immunoreactivity. GAD-positive perikarya were distributed throughout the A and C laminae, constituting a moderate proportion of cells in the LGN. Labeled cells were characterized by small size, scant cytoplasm, relatively large nuclei with common indentations, small mitochondria, few organelles and few strands of rough endoplasmic reticulum. Unlabeled cells were of large, medium and small size. GAD-positive terminals were identified as F1 and F2 types (Guillery's nomenclature) on the basis of their synaptic relations and ultrastructure. Labeled F2 terminals were postsynaptic to retinal (RLP) boutons and presynaptic to unlabeled dendrites in synaptic glomeruli. Labeled F1 terminals made synapses on unlabeled somata and dendrites, and on labeled dendrites and F2 terminals. Presumably, most labeled F1 terminals originate from GABAergic perigeniculate axons. Retinal (RLP) and cortico-geniculate (RSD) boutons remained unlabeled in the reative zone. These terminals made synapses with labeled and unlabeled dendrites and with labeled F2 boutons. In conjunction with previous studies on GAD-positive cells in the perigeniculate nucleus, these results provide immunocytochemical and morphological evidence suggesting that the GABAergic intrinsic and extrinsic (perigeniculate) interneurons mediate the different inhibitory phenomena which occur in relay cells of the cat LGN. The ultrastructural features and synaptic relations of GABAergic cells and processes in the cat LGN are similar to those of equivalent neural elements in the LGN of rat and monkey, suggesting general principles of organization and morphology for GABAergic neurons in the thalamus of different mammals.Supported in part by grants EY 02877 and HD 03352 from the National Institutes of Health     

Morphometric and autoradiographic studies on the growth of red and white axial muscle fibres in the shark Etmopterus spinax

Summary The axial muscle growth of the shark Etmopterus spinax has been studied by means of morphometry, slide histology and autoradiography from radioactive thymidine and amino acids. Comparisons have been made between the red and the white muscle fibres. While growing from 10 to 23 cm in length, the white muscle transverse sectional (ts) area increases 5.4 times, while the red area increases 3.7 times. The mean ts area of individual white fibres increases by 2.7, and the ts area of red fibres increases by 1.6. The number of white fibres does not increase significantly, while the red fibres increase slightly in number. Red fibres incorporate amino acids faster than the white fibres, and have a higher turnover rate. The myonuclei of the red fibres (satellite cell nuclei) incorporate thymidine more often than do those of white fibres, but the frequency of the satellite cells is simillar in the two fibre types. Mitoses are extremely rare in the myonuclei. The nucleocytoplasmic ratio is higher in the red than in the white fibres.     

Ultrastructural and immunohistochemical similarities of two distinct entities; multiple sclerosis and hereditary motor sensory neuropathy

In the present study, we present the ultrastructural and immunohistochemical properties of the sural nerves of two patients, one of whom was diagnosed as having multiple sclerosis with involvement of the peripheral nervous system (PNS), and the other as having hereditary motor sensory neuropathy type-I with involvement of the central nervous system (CNS). Expression of several extracellular matrix (ECM) proteins (fibronectin, laminin, and collagen type-IV), intermediate filaments (vimentin) and S-100 protein (marker for the axon-Schwann cell interface) was investigated by means of immunohistochemical methods. In addition, the tissue samples were evaluated ultrastructurally. Immunohistochemical staining revealed increased expression of the ECM molecules mentioned above in relation with the sural nerves of the patients. We hypothesize that this enhanced expression is due to Schwann cell-axon interactions. Vimentin expression was different in Schwann cells and S-100 immunostaining was decreased near the Schwann cell-axon interface. Myelin fragmentation, axon vacuolization, onion bulbs, tomoculous formation, axonal degeneration were found to occur. These results suggest that there is active ECM reorganization in the sural nerve of these patients, and some ultrastructural changes are similar in the damaged axonal organization and in Schwann cells although the changes are not completely the same in the two patients. In conclusion, our study demonstrates that there is an association between the demyelinization process in the CNS and the PNS even though they are affected by different mechanisms.     

Ultrastructural observations and growth of occluding crystals in carious dentine

The aim of the present study was to investigate the ultrastructural mechanisms involved in the formation of caries-induced intratubular dentine. Conventional, high resolution and scanning transmission electron microscopy, electron diffraction and energy-dispersive X-ray spectroscopy techniques were used to study the ultrastructure of the inorganic phase in the transparent zone of carious dentine. The results demonstrated that the bulk of the inorganic phase in caries-induced intratubular dentine had an apatite crystal structure with the presence of additional Mg-substituted beta-TCP (beta-tricalcium phosphate) phase in the carious region. Highly oriented apatite crystallites observed in intratubular dentine demonstrated a regulated biomineralization process during the formation of inorganic phase in this region, whereas Mg beta-TCP crystals were presumably formed purely via "dissolution/precipitation" mechanism. The study demonstrated the importance of "dissolution/precipitation" process and the growth kinetics of Mg-substituted beta-TCP crystals in understanding the process of formation of calcium-phosphate crystallites in carious intratubular dentine.     

Ultrastructural observations on cytotoxic effector cells infiltrating pancreatic islets of low-dose streptozocin treated mice

Summary The aim of this study was to observe the ultrastructural events, during the onset of diabetes mellitus in the low-dose streptozocin (LDS)-treated mouse model with emphasis on the infiltrating elements. Forty male C57 BL/6J mice were given 40 mg/streptozocin on 5 consecutive days and killed 5, 6, 7, 8, 9, 10, 15, and 18 days after the first injection. Results demonstrated that islet infiltration occurring in LDS-treated mice is characterized by a very early pre-infiltration state in which mononuclear phagocytes in islet capillary vessels were considerably increased in number. A new histopathological time sequence for the early insulitis is described, in which attraction of blood mononuclear phagocytes into the islet capillary lumen is the first step. During the successive stage, occurring on days 6–8 we observed that mononuclear phagocytes migrate through capillary and venule walls into the islet parenchyma, where they differentiate into tissue macrophages. It was only later (step 3) that these macrophages acquired novel properties, typical of their activated state and started to phagocytose islet beta-cell debris. These data suggest that during the pre-infiltration and early insulitis the mononuclear phagocyte system plays a key role in the onset of LDS diabetes.     

Ultrastructural studies and immunolocalization of enamel proteins in rodent secretory stage ameloblasts processed by various cryofixation methods

Background: Cryofixation rapidly immobilizes cell and tissue components in their native state, thereby resulting in an ultrastructural preservation very close to the living situation. We have applied this approach to examine the morphology of secretory stage ameloblasts and the distribution of enamel proteins in these cells. Methods: Molar and incisor tooth germs from newborn mice and/or rats were quickly dissected and divided into segments. The segments were then rapidly frozen using slam, plunge or pressure freezing, freeze-substituted and embedded in Epon. In addition, incisors from older rats were chemically fixed by vascular perfusion and also dehydrated by freeze-substitution. Results: Well-preserved ameloblasts were obtained with all four tissue processing methods. However, slam freezing often showed mechanical damage to the ameloblasts, particularly at the level of the distal portion of Tomes' processes which appeared severed or distorted. Plunging into liquid nitrogen-cooled liquid propane resulted in comparatively less tissue distortion. High pressure freezing gave a relatively higher yield of well-preserved specimens, although displacement of organelles in ameloblasts was sometimes observed, probably resulting from hydrostatic pressure. Minimal ice crystal and mechanical damage was observed in chemically fixed tooth samples processed by freeze-substitution since such specimens are cryoprotected and their examination is not restricted to a surface layer. With all of the above cryopreparation methods, the ultrastructure of well preserved ameloblasts was, in general, similar to that obtained following conventional chemical fixation, and immunocytochemistry with an anti-amelogenin antibody indicated no profound differences in the distribution of enamel proteins. Conclusions: These results indicate that, despite some limitations, it is possible to adequately cryofix tooth organs while preserving the architecture of ameloblasts and permitting immunolocalization of enamel proteins. Furthermore, they confirm the general morphology of secretory stage ameloblasts as currently derived from conventional chemical tissue processing. © 1994 Wiley-Liss, Inc.     

The process of granule exocytosis in non-stimulated atrial granular cells of the snail, Achatina achatina: An ultrastructural,histochemical and immunocytochemical study

Abundant secretory granular cells (GCs) in the Giant African land snail atrium harbor a range of bioactive substances and undergo rapid total degranulation in response to stimulation of the cardiac nerve or stressful influences. Here we have analyzed exocytotic events in the non-stimulated GCs. It was shown that the GCs contain three major distinct types of granules that differ histochemically, immunocytochemically and ultrastructurally, each performing specific functions. The type I granules characteristically filled with electron-lucent homogeneous materials exhibit intense immunoreactivity for bioactive proteins and therefore are considered to be storage granules. Histochemistry using vital staining with Acridine Orange and Gomori acid phosphatase technique has revealed lysosomal-related nature of the electron-dense type II granules. Digestion remnants appearing as fine filamentous materials fill the type III granules. Only the type III granules fuse together and with the plasma membrane form degranulation channels and surface pores, through which the debris is removed from the cell. The finding of granules exhibiting intermediate ultrastructural, histochemical and immunocytochemical features suggests that the major granule types represent most stable states along a granule empting continuum. Thus, under physiological conditions, the GCs continuously produce secretory proteins and so maintain readiness for stress-response, but use protein degradation machinery to prevent massive release of these bioactive substances into hemolymph.     

Intraepithelial lymphocytes and macrophages in the normal breast

Summary In this study the presence of intraepithelial cells within the normal breast parenchyma was investigated by electron microscopy and immunocytochemistry. Cells were observed which could be differentiated from the epithelial and myoepithelial cells by their cytoplasmic and nuclear morphology and the absence of cell junctions. Two cell types (lymphocytes and macrophages) were identified ultrastructurally and the bone marrow origin of the cells was confirmed by immunocytochemistry. The intraepithelial lymphocytes and macrophages were present in all samples irrespective of the physiological state. In the resting, pregnant, and lactating breast the majority of cells were lymphocytes while in the involuting breast there was a marked increase in the proportion of macrophages. The rarity of lymphoma of the breast may be related to the relatively small amount of lymphoid tissue present and the passive nature of the environment.     

Ultrastructural and immunohistochemical investigation on the gills of the teleost, Thalassoma pavo L., exposed to cadmium

An investigation was conducted to determine the effects of the heavy metal, cadmium (Cd), on the gills of the teleost fish, Thalassoma pavo Linnaeus, 1758. The fishes were exposed to several sublethal concentrations of cadmium (10, 40, 60 and 120 μM (mg/L)) for a period of 48, 96 and 192 h. The value of the LC50 after 96 h of cadmium exposure, determined using the System of Finney, was equal to 128.3 μM. The gills of the fishes were examined by light and electron microscopy. Toxic, apoptotic and cadmium effects were analyzed using some neuropeptides, metallothioneins (MT), caspase 3, PCNA and calmodulin, as bioindicators, respectively. The results showed that the alterations in the gills were proportional to the exposure periods and concentrations of the metal, which were found to be both dose and time dependent. The biological responses in the gills of the tested animals are discussed in relation to results obtained by analysis of the biomarkers. These data may be used for the planning of a model to determine biological risk in the marine environment and may be particularly useful to investigate organisms exposed to cadmium.     

Ultrastructural and immunohistochemical analysis of rat uroepithelial cell junctions after partial bladder outlet obstruction and selective COX-2 inhibitor treatment

The present study was undertaken to evaluate alterations in uroepithelial cell junctional complexes in partial bladder outlet obstruction (PBOO) of rat bladders using ultrastructural morphometry and immunohistochemistry, and to determine whether selective COX-2 inhibitors have any effects on these structures. A total of 18 male rats were separated into three groups of six rats each: (1) sham-operated animals served as controls; (2) a PBOO group, without further treatment (3) and a group that immediately after PBOO, received treatment for 4 weeks with oral Celecoxib, a selective COX-2 inhibitor. Uroepithelial cell junctions were evaluated using transmission electron microscopy combined with morphometry. Results were also assessed by E-cadherin and -catenin immunohistochemistry. Morphometrical analysis of ultrastructural evaluations revealed that 4 weeks of PBOO caused a significant reduction in the electron density of zonula adherens and zonula occludens junctional complexes. Moreover, some desmosomes located between the deeper cells of the uroepithelium showed signs of disintegration. Selective COX-2 inhibitor treatment during 4 weeks of PBOO showed protective effects on adherens and occludens junctions, as well as on desmosomes. Immunohistochemical analysis of E-cadherin confirmed that the decreased E-cadherin immunolabelling in 4 weeks of PBOO was prevented by selective COX-2 inhibitor treatment. Based on ultrastructural morphometrical analysis, we conclude that PBOO alone and in combination with selective COX-2 inhibitors can have considerable effects on uroepithelial cellular junctions. Our findings provide a novel area of investigation regarding the selective use of COX-2 inhibitors following PBOO.     

Differentiation of the epidermis in turtle: an immunocytochemical, autoradiographic and electrophoretic analysis

Proteins involved in the process of cornification of turtle epidermis are not well known. The present immunocytochemical, electrophoretic and autoradiographic study reports on the localization patterns and molecular weights of keratins, which are cornification proteins, and of tritiated histidine in turtle epidermis. Alpha-keratins with a molecular weight of 40-62 kDa are present in the epidermis. Beta-keratin is mainly detectable in the stratum corneum of the carapace and plastron, but is rarely present or even absent in the corneous layer of limb, tail and neck epidermis. After electrophoresis and immunoblotting with an antibody against chicken scale beta-keratin, bands at 15-17, 22-24, and 36-38 kDa appeared. This antibody recognized weaker bands at 38-40 and 58-60 kDa in the soft epidermis. After reduction and carboxymethylation of proteins extracted from carapace and plastron, but not of proteins from the soft epidermis, protein bands at 15-17 and 35-37 kDa were found when using the anti-beta 1-keratin antibody. Loricrin-, filaggrin-, sciellin-, and transglutaminase-like immunostaining was detectable only in the transitional and lowermost corneous layers of the soft epidermis. Vesicular bodies in the transitional layer were immunolabeled by the anti-loricrin antibody, and weakly by the anti-filaggrin and anti-transglutaminase antibodies. In immunoblots, the anti-loricrin antibody reacted with a major band at 50-54 kDa in both carapace-plastron and soft epidermis. The anti-sciellin antibody detected major bands at 38-40 and 50 kDa in hard epidermis, and at 50 and 54-56 kDa in soft epidermis. Filaggrin-like immunostained bands were observed at 50-55 and 62-64 kDa. This immunostaining was probably due to a common epitope in filaggrin and some keratins. Histidine was evenly incorporated in the epidermis, and the ultrastructural study showed random labeling, often associated with keratin bundles of alpha and beta-keratinocytes. Histidine-labeled protein bands were not found in the carapace-plastron. In the soft epidermis, weakly labeled bands at 15-20, 25, and 45-60 kDa were found occasionally. The latter bands probably represented neo-synthesized keratins as was also indicated by the ultrastructural autoradiographic analysis. In conclusion, our study suggests that proteins with epitopes that they have in common with cornification proteins of mammalian epidermis are also present in the epidermis of turtle.