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Luteal cell fine structure was studied in hysterectomized control and hysterectomized, prostaglandin-treated (1-5 days) guinea pigs. In hysterectomized control animals, luteal cells were hypertrophied and were characterized by an abundance of agranular endoplasmic reticulum (AER) suggesting steroidogenic activity. With one day of prostaglandin treatment, little change in the cytological appearance had occurred. After two, or three days of treatment, cells showed a decrease in size and an apparent increase in the number of lipid droplets. Following four days of prostaglandin treatment, luteal tissue was characterized by the presence of large amounts of collagen in the intercellular spaces and by the invasion of fibroblasts. Areas of degenerating luteal cells with numerous myelin figures and lipid droplets were observed. After five days of prostaglandin treatment, most of the luteal cells had undergone extensive luteolytic changes. Typically they contained coalescing lipid droplets, myelin figures and crystalloids, and were surrounded by collagen fibers. These observation suggest that prostaglandin F2alpha does effect structural luteolysis in this species in the absence of uterine tissue.
Anat Rec 1975 Oct
PMID:The effects of prostaglandin F2alpha on the fine structure of the corpus luteum of the hysterectomized guina pig. 120 Apr

Electron microscopy of the normal human thymus demonstrates a characteristic vascular-parenchymal relationship. The vascular lumen is always separated from the thymic parenchyma by: the endothelial cell cytoplasm, a muscular coat in arterioles and veins, the vascular basal lamina, a perivascular space containing collagen fibers and cells, the epithelial-reticular cell basal lamina and the epithelial-reticular cell cytoplasm. The width of this perivascular space is proportional to the size of the vessel it surrounds; it is wide around the vessels in the septa and at the cortical-medullary junction, but narrow around capillaries. While many cells are present in this space around larger vessels, only collagen is observed around the capillaries. Lymphocytes are the predominant cell type in the space; however, plasma cells, eosinophils, histiocytes, polymorphonuclear leukocytes, mast cells and unidentified granulated cells are also seen. The vascular complex described above may function as a blood-thymus barrier, as the initial site of exposure of the lymphocytes to circulating antigen and as the route of lymphocytes from the thymus.
Anat Rec 1975 Dec
PMID:The normal human thymic vasculature: an ultrastructural study. 120 Apr 6

The principal cell types associated with the humoral immune response (monocyte-macrophages, lymphocytes, and plasma cells) are numerous in the endometrial stroma of the uterus during the first four postpartum days in two types of mammals, the marsupial North America opossum and the eutherian albino rat. This transietn cellular differentiation coincides with the physiologic period of rapid uterine regression which includes massive reduction in the amount of extracellular stromal material. In addition, heterophils and eosinophils, cell types also known to be associated with phagocytic and immunologic activity, appear in the stroma during the first two postpartum days; their presence may, however, be associated more directly with the postpartum estrus that occurs on day 1 postpartum than with endometrial regression. Thus, the five cell types, which are known in pathologic conditions to be components present in the inflammatory response to a foreign antigen, are conspicuously present in the normal regressing endometrium. Furthermore, there is ample ultrastructural evidence of frequent macrophagic-lymphocytic interaction, transformation of lymphocytes, and active secretion by plasma cells during this early postpartum period. An hypothesis has been derived by uniting this new description of endometrial stromal cell differentiation with the existing literature on uterine collagenase activity, an important feature of postpartum regression (reviews of Gross, '74; Harris and Krane, '74). It is based on the assumption that during regression the extracellular action of neutral collagenase (and possibly other extracellular proteases) release new antigenic sites in proteins located in the ground substance. In the case of collagenase, these transient antigenic sites would arise at the locus of enzymic cleavage as well as from the subsequent denaturation of the fragments of the collagen molecule. This endogenous antigenic stimulus would be strong and temporary, and would lead to the cellular manifestations of the transient humoral immunologic response which are evident in the regressing stroma of these two mammals. This humoral immune reaction may be one of the regulatory mechanisms involved in the cyclic renewal of the extracellular compartment of the uterine stroma.
Anat Rec 1976 Jan
PMID:Cellular mechanisms involved in cyclic stroma renewal of the uterus. III. Cells of the immune response. 125 14

A crucial part of secondary palate morphogenesis is the movement of the palatal shelves from an initial vertical position on either side of the tongue to a final horizontal one above it to achieve palate closure. The immunocytochemical localization of extracellular matrix (ECM) molecules in the palatal shelf during this remodelling and reorientation revealed the existence of an ECM infrastructure within the mesenchyme. The major components of this infrastructure were collagen III, fibronectin, and hyaluronate (HA). With remodelling, HA's domain within the mesenchyme was expanded, whereas those of fibronectin and collagen III became more circumscribed. The expansion of an HA-rich matrix within the mesenchyme is thought to be crucial for palatal reorientation. The results of this study suggest that, as this expansion occurs, it is modulated by collagen and fibronectin components of the ECM infrastructure. Prior to shelf remodelling, this infrastructure may be anchored by a specialized region of the midoral epithelial-mesenchymal interface and the subjacent mesenchyme which is characterized by the unique distribution of collagen III, fibronectin, and tenascin. The midoral palatal epithelium also may play a role in directing shelf expansion. This epithelial region undergoes changes in cell packing and epithelial cell layering that correlate with shelf remodelling. These changes occur concomitantly with changes in the expression of collagen III, collagen IV, and laminin within the underlying basement membrane. The localization and patterning of tenascin within the developing palate suggests that it not only contributes to the postulated anchoring structure of the midoral epithelial-mesenchymal region, but also plays a role in the determining the fate of the medial edge epithelial cells during the final stage of palate closure.
Anat Rec 1992 Dec
PMID:An extracellular matrix infrastructure provides support for murine secondary palatal shelf remodelling. 128 Sep 22

The characteristics of the lymphatic vessel endothelial wall have been investigated in human normal and inflamed dental pulps. In normal pulps the endothelial wall is characterized by the presence of micropinocytotic vesicles and intraparietal channels. In the inflamed pulpal tissue, where an increase in interstitial fluid pressure occurs, the distended endothelial wall presents open junctions between endothelial cells and the openings of the intraparietal channels. Moreover the micropinocytotic vesicles disappear. The cytoplasm of the endothelial cells is characterized by the presence of numerous Weibel-Palade bodies, which increase in number in the dilated vessels. In the fibrillar apparatus surrounding the lymphatic vessel wall collagen fibrils are the prevalent component, while elastic fibers are not present. The different morphological properties of the lymphatic vessels are compared and discussed with regard to the variation of the functional conditions of the tissue.
Anat Rec 1992 Sep
PMID:Lymphatic vessels of the human dental pulp in different conditions. 141 95

Fibroblasts cultured within free-floating collagen gels can bind to and reorganize the surrounding collagen fibrils into a more dense and compact arrangement. Collagen gel contraction provides an in vitro model for studying fibroblast-collagen interactions important in wound healing, fibrosis, scar contraction, and connective tissue morphogenesis. We have assessed the role of fibronectin and its interaction with the alpha 5 beta 1 "high affinity" fibronectin-specific integrin receptor in collagen gel contraction. A variety of agents, which specifically inhibit fibronectin-alpha 5 beta 1 interactions, were tested for their abilities to inhibit fibroblast-mediated collagen gel contraction. These included anti-alpha 5 beta 1 monoclonal antibodies, the synthetic peptide GRGDSP, the cell adhesive fragment of fibronectin, and an antibody against the cell adhesive region of fibronectin. None of these agents inhibited collagen gel contraction. Therefore, it is concluded that fibronectin-alpha 5 beta 1 interactions are not necessary for collagen gel contraction. However, collagen gel contraction is dependent on a member or members of the beta 1 subfamily of integrin matrix receptors. A polyclonal antiserum and a monoclonal antibody, both directed against the beta 1 subunit of integrin matrix receptors, inhibited the spreading of fibroblasts in the collagen gel and inhibited collagen gel contraction. This study demonstrates that fibroblast-mediated collagen gel contraction is independent of fibronectin-alpha 5 beta 1 interactions but dependent on an interaction of beta 1 integrin matrix receptors with collagen fibers.
Anat Rec 1992 Oct
PMID:Fibroblast-mediated collagen gel contraction does not require fibronectin-alpha 5 beta 1 integrin interaction. 141 2

The submandibular salivary gland originates from the floor of the mouth whose mucosa contains elastic fibers. Therefore, such fibers were sought in the duct system of the derivative organ. In adult rats, light microscopy has indeed revealed fine, circumferential, elastic fibers near the basement membrane of the duct epithelium. In the larger extralobular ducts, they were separated from several layers of longitudinal elastic fibers by a capillary-rich zone sparse in elastic fibers except for fine angular ones. More peripherally, larger angular-appearing fibers were frequently present near the submandibular parasympathetic ganglia in the duct wall. As duct diameter decreased, elastic fiber size and number diminished. Intralobularly, the smaller striated ducts, granular and intercalated ducts, and acini generally lacked such fibers. Electron microscopy of the extraglandular portion of the main duct revealed fibrils extending from both fibroblasts and elastic fibers that were close to the epithelium. Microfibrils coursed from them toward the lamina densa. Anchoring filaments joined the lamina densa to the basal plasma membrane of the epithelium. Elastic fibers also appeared to connect to both capillaries and collagen via finer intermediate structures. These associations might permit dynamic interactions of fibroblasts, fibers, smaller fibrillar components, vasa, and the duct epithelium. This interplay could occur during feeding and grooming when tongue protrusion and neck extension stretch the submandibular duct and the gland itself. As a result, the tensile forces engendered could modify cell geometry and the calibers of the larger ducts' lumens and intercellular spaces, thus affecting the flow and composition of salivary secretion.
Anat Rec 1992 Nov
PMID:Elastic fibers in the duct system of the rat submandibular salivary gland. 144 62

The importance of the extracellular matrix (ECM) in epithelial-mesenchymal interactions in developing organisms is well established. Proteoglycans and interstitial collagens are required for the growth, morphogenesis, and differentiation of epithelial organs and the distribution of these molecules has been described. However, much less is known about other ECM macromolecules in developing epithelial organs. We used confocal microscopy to examine the distribution of laminin, heparan sulfate (BM-1) proteoglycan, fibronectin, and collagen types I, IV, and V, in mouse embryonic salivary glands. Organ rudiments were isolated from gestational day 13 mouse embryos and cultured for 24, 48, or 72 hours. Whole mounts were stained by indirect immunofluorescence and then examined using a Zeiss Laser Scan Microscope. We found that each ECM component examined had a distinct distribution and that the distribution of some molecules varied with culture time. Laminin was mainly restricted to the basement membrane. BM-1 proteoglycan was concentrated in the basement membrane and also formed a fine network throughout the mesenchyme. Type IV collagen was mainly located in the basement membrane of the epithelium, but it was also present throughout the mesenchyme. Type V collagen was distributed throughout the mesenchyme at 24 hours, but at 48 hours was principally located in the basement membrane. Type I collagen was distributed throughout the mesenchyme at all culture times, and accumulated in the clefts and particularly at the epithelial-mesenchymal interface as time in culture increased. Fibronectin was observed throughout the mesenchyme at all times.
Anat Rec 1992 Nov
PMID:Localization of extracellular matrix components in developing mouse salivary glands by confocal microscopy. 144 71

The ultrastructural distribution of two noncollagenous proteins, osteopontin (OPN) and osteocalcin (OC), originally extracted from bone matrix and proposed to play an important role in bone formation, was examined in the matrices of bone and cartilage from embryonic and postnatal chicken tibial growth plates by high-resolution immunocytochemistry using the colloidal gold technique. In bone, immunolabeling patterns using polyclonal antibodies against chicken OPN and OC were generally similar in that both showed an intense, but regionally variable, labeling of mineralized bone matrix and small mineralization loci dispersed throughout the osteoid and containing prominent condensed organic material. Unmineralized osteoid showed weak-to-moderate labeling. In the mineralized bone matrix proper, labeling was predominantly associated with amorphous, electron-dense patches of organic material among the collagen fibrils. In growth plate cartilage, both proteins first appeared related to calcified cartilage in the hypertrophic zone, although the labeling patterns were somewhat different. For OPN, gold particles were mostly associated with an organic lamina limitans-like density containing condensed, filamentous organic matrix at the periphery of small nodules and large masses of calcified cartilage, with additional moderate labeling throughout the interior of the calcified cartilage. For OC, labeling was observed over filamentous structures throughout the calcified cartilage matrix, with some, but less, labeling at the periphery. In the lowermost zones of the growth plate, the major reaction using both antibodies was found over a layer of dense, amorphous organic material at the periphery of the calcified cartilage at the future bone/calcified cartilage interface, a labeling pattern that persisted following bone deposition at these sites. OPN and to a lesser extent OC were also concentrated in cement (resting, reversal) lines. Throughout the bone and cartilage of the tibia, cells of both the osteoblastic and the osteoclastic lineages were found directly apposed to labeled surfaces and lamina limitans of organic matrix containing OPN and OC. In summary, it is concluded from the immunocytochemical data presented here that the association of OPN and OC with mineralized regions of the extracellular matrices of bone and cartilage and the accumulation of these proteins at tissue surfaces and interfaces are consistent with the hypotheses that they play a role in the extracellular mineralization process per se and/or that they may mediate cell adhesion and dynamics.
Anat Rec 1992 Dec
PMID:High-resolution immunolocalization of osteopontin and osteocalcin in bone and cartilage during endochondral ossification in the chicken tibia. 145 51

Three-dimensional alteration of fibrillar matrix in the rat mandibular condylar cartilage was investigated with a high-resolution scanning electron microscope (SEM) and it was determined whether alterations correlate with developing occlusion and advancing age. Two important SEM techniques of DMSO freeze-cracking and treatment with trypsin and hyaluronidase were employed to remove interfibrillar proteoglycans and disclose fibril arrangement. Our SEM investigation demonstrated that collagen fibrils in the fibrous zone covering hyaline-cartilaginous area in the condyle are thicker (50 to 80 nm in diameter) than the fibrils (30 to 50 nm in diameter) that predominantly constituted an interterritorial fibrillar matrix (IFM) in the area. While the thick fibrils had a distinct striation of about 55 nm periodicity, the thin fibrils had no distinguishable striation. The thick fibrils having a periodic striation of about 60 nm was found along with the thin fibrils, also in the IFM in the aged rats and in the deep IFM, but were considerably less than the thin fibrils. The fibrils in the fibrous zone and IFM were disorderly arranged at 19-day-insemination age. In 1-week-old rats whose incisors erupted, the fibrils constituting the fibrous zone altered from disordered to ordered arrangement. The IFM in these rats took the form of a network. Incorporation of small fibrillar bundles into the fibrillar network was seen in 2-week-old rats whose upper and lower first molars erupted. In 8-week-old rats whose molars had erupted completely, the IFM completely occupied by regularly oriented fibrils appeared additionally.(ABSTRACT TRUNCATED AT 250 WORDS)
Anat Rec 1992 Dec
PMID:Ultrastructural alteration of cartilaginous fibril arrangement in the rat mandibular condyle as revealed by high-resolution scanning electron microscopy. 145 52


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