Angioarchitecture of the rabbit extrahepatic bile ducts and gallbladder

The angioarchitecture of extrahepatic bile ducts and gallbladder of the miniature rabbit was studied by scanning electron microscopy (SEM) of vascular corrosion casts. Light microscopy of Masson-stained, paraffin-embedded transverse tissue sections served to attribute cast vascular structures to defined layers of bile ducts and gallbladder. In all segments of the bile tract, a mucosal and a subserosal vascular network was found. In glandular segments, the mucosal network was composed of a meshwork of subepithelial and circumglandular capillaries, which serve the mucosal functions. Differences in the angioarchitectonic patterns existed only in the subserosal networks as hepatic ducts own one supplying arteriole only, while the common bile duct owns a well-defined rete arteriosum subserosum. A well-developed dense subserosus venous plexus was present throughout the bile tract. Vascular patterns of the gallbladder body resembled those of the bile duct, whereby the dense subserous venous plexus was located close to the mucosal capillary network. The subserosal network in the neck of the gallbladder resembled that of the cystic duct. Spatial changes of the mucosal vascular network during volume changes of the gallbladder were documented. Measurements from tissue sections revealed bile tract diameters of 220-400 microm (extrahepatic ducts), 500-650 microm (cystic duct), and 4-6 mm (common bile duct). Data gained from high-powered SEM micrographs of vascular corrosion casts revealed vessel diameters of 200 microm (cystic artery), 90-110 microm (cystic vein), 30-40 microm (feeding arterioles), and 25-110 microm (subserosal venules). Crypt diameters in the filled gallbladder were 300-1,500 mum; those in the contracted organ were 100-600 microm.     

Serosal Tissue: Reactive Tissue as a Model for Understanding Mesotheliomas

Serosal tissues consist of a surface mesothelial layer and subsurface spindled connective tissue cells. Surface cells are decorated with antibodies to both low and high molecular weight cytokeratin whereas subserosal cells only express the intermediate filament vimentin. Serosal injury results in the proliferation of multipotential subserosal cells (MSC) which have the ultrastructural morphology of myofibroblasts and yet co-express low molecular weight cytokeratin and vimentin. These cells appear responsible for the re-establishment of surface mesothelium during which they acquire high molecular weight cytokeratin and loose vimentin. There are many parallels between reactive and neoplastic serosal tissues. Desmoplastic/sarcomatoid mesotheliomas resemble the MSC and co-express low molecular weight cytokeratin and vimentin and epithelial mesotheliomas resemble surface mesothelium and express both low and high molecular weight cytokeratin. The ability of normal serosal tissue to modulate its cell shape and intermediate filament expression helps understand the diversity of serosal tumors.     

Serosal tissue: reactive tissue as a model for understanding mesotheliomas

Serosal tissues consist of a surface mesothelial layer and subsurface spindled connective tissue cells. Surface cells are decorated with antibodies to both low and high molecular weight cytokeratin whereas subserosal cells only express the intermediate filament vimentin. Serosal injury results in the proliferation of multipotential subserosal cells (MSC) which have the ultrastructural morphology of myofibroblasts and yet co-express low molecular weight cytokeratin and vimentin. These cells appear responsible for the re-establishment of surface mesothelium during which they acquire high molecular weight cytokeratin and loose vimentin. There are many parallels between reactive and neoplastic serosal tissues. Desmoplastic/sarcomatoid mesotheliomas resemble the MSC and co-express low molecular weight cytokeratin and vimentin and epithelial mesotheliomas resemble surface mesothelium and express both low and high molecular weight cytokeratin. The ability of normal serosal tissue to modulate its cell shape and intermediate filament expression helps understand the diversity of serosal tumors.     

Tubuloreticular inclusions in equine connective tissue neoplasms

Abnormal irregularly branched and anastomosing tubules within cisternae of endoplasmic reticulum were observed by transmission electron microscopy in tumour cells comprising connective tissue neoplasms (sarcoids) from three horses and a mule. These tubuloreticular inclusions were also observed in cultured tumour cells from one of these horses examined, but were not detected in fibroblasts (fibrocytes), epidermis, or vascular endothelial cells in skin biopsy specimens from five clinically healthy horses, nor in one additional equine connective tissue neoplasm.     

CAM5.2-positive subserosal myofibroblasts in appendicitis

In this study, we examined the distribution and origin of myofibroblasts around the perforations of appendicitis. Stromal cells of 45 cases were studied by immunohistochemistry. In the normal appendix, myofibroblasts were restricted to the mucosa, and CD34-positive stromal cells were distributed in the submucosal and subserosal layers. Some mesothelial cells were positive for cytokeratin CAM5.2, cytokeratin 5, or mesothelial cells (HBME-1). In perforation of appendicitis with both abscess and granulation tissue, a small to moderate or a moderate to large number of myofibroblasts appeared in the subserosal area around the perforation, respectively, but CD34-positive stromal cells were completely absent there. In the subserosal area of the perforation of appendicitis with abscess, cytokeratin 5-positive stromal cells were absent. However, a small to moderate number of cytokeratin CAM5.2-positive stromal cells were observed there. Double immunostaining showed the coexpression of alpha-smooth muscle actin (ASMA) and cytokeratin CAM5.2 and the coexpression of cytokeratin 5 and cytokeratin CAM5.2 in many or some stellate-shaped or spindle-shaped stromal cells existing in the subserosal area with granulation tissue around the perforation of appendicitis, respectively. Finally, many myofibroblasts appearing in the subserosal area of the perforation of appendicitis may be derived from submesothelial cells or mesothelial cells.     

Absence of ganglionated plexus in bullfrog gallbladder.

We first carried out microscopic observation of the intramural nerves of a bullfrog gallbladder which were fixed and stained with a solution of OsO4 and ZnI2. We then investigated if the responses of isolated frog gallbladder evoked by electrical stimulation are mediated through the intramural nerves. The following results were obtained: 1. The nerve plexus and the perivascular nerves were observed in the subserosal layer of the wall of the gallbladder. These nerves do not have a ganglia. That is to say, no ganglionated plexus or ganglia were observed in the subserosal layer of the wall of the gallbladder. 2. Electrical stimulation caused the gallbladders to contraction with rectangular pulses (50 volt, 40 Hz) of durations of 0.5, 1, 2, 3, 4 and 5 msec for a period of 10 sec. Three blockers of nerve mediated responses, atropine (1 x 10(-6) M), guanethidine (1 x 10(-6) M) and tetrodotoxin (3 x 10(-7) M), had no effect on the gallbladder contractions induced by stimulation with pulses as short as 0.5 msec or as long as 5 msec. These results suggest that the bullfrog gallbladder may not contain nerves related to movement. Thus, the contraction of the bullfrog gallbladder induced by electrical stimulation does not seem to be modulated by extrinsic nerve terminals distributed in the gallbladder wall.     

Apolipoprotein localization in the human bile duct and gallbladder

Apolipoproteins AI, AII and B were identified in the normal and pathological human bile duct and the gallbladder epithelium using an avidin-biotin immunoperoxidase technique. Small intestine and stomach sections served as positive and negative controls respectively. Staining was focal for apolipoproteins AI and AII, and continuous for apolipoprotein B. In addition to homogenous and granular cytoplasmic staining, foamy cytoplasmic staining, particularly for apolipoproteins AI and AII, was observed around lipid droplets in cells containing much lipid. No correlation between a particular pathological condition of the gallbladder (acute cholecystitis, mucocele, chronic cholecystitis, cholesterolosis) and staining pattern or intensity of staining was found for any of the apolipoproteins, although both apolipoproteins AI and AII stained more intensely than apolipoprotein B in each group. Positive staining was also found for all apolipoproteins in epithelial cells which had invaded the underlying connective tissue (gallbladder carcinoma), suggesting that the epithelial cells are capable of synthesizing apolipoproteins de novo. In this latter case, apolipoprotein B stained more intensely than for either AI or AII, and significantly (p less than 0.05) more strongly than that found in the other pathological groups. The identification of apolipoproteins in the gallbladder epithelium raises the interesting question of their origin and functional role.     

Stromelysin, gelatinase A and TIMP-1 in prosthetic interface tissue: a role for macrophages in tissue remodelling

Aseptic loosening of prosthetic components is the most important long-term complication of total joint replacement. To investigate the underlying destructive mechanisms, periprosthetic tissues from both well-fixed and loosened sites from six patients, undergoing surgery for aseptic loosening of knee or hip prostheses, were analysed in detail by immunohistochemical methods for the presence, of matrix metalloproteinases and tissue inhibitor of metalloproteinases-1 (TIMP-1). The tissues contained small numbers of cells positive for either collagenase, stromelysin, gelatinase A or TIMP-1; these were randomly distributed, neither specifically next to the bone interface nor to wear particles, and the number of positive cells did not correlate with macroscopic observations at operation. Gelatinase A was co-localized in cells with prolyl-4-hydroxylase, an enzyme involved in collagen synthesis. The predominant cell type in these tissues was shown to be the macrophage by the use of cell marker antibodies. Dual localization was not technically possible but the results strongly suggest that monocyte/macrophages were the primary source of gelatinase A and TIMP-1. Stromelysin was immunolocalized on connective tissue matrix in four patients, and gelatinase A in one patient, and were also observed in tissues in which there was no evidence of cellular synthesis of these enzymes. This suggests that secretion had taken place previously, resulting in enzyme bound to matrix for some time. Taken together, these data indicate that localized focal connective tissue remodelling occurs in periprosthetic tissues from both well fixed and loosened sites.     

An Immunohistochemical Study of Matrix Components in Early‐Stage Vascular Canals Within Mandibular Condylar Cartilage in Midterm Human Fetuses

Matrix components of vascular canals (VCs) in human fetal mandibular condylar cartilage (15–16 weeks of gestation) were analyzed by immunohistochemistry. Prevascular canals (PVCs), consisting of spindle‐shaped cells without capillary invasion, were observed within the cartilage. Intense immunoreactivity for collagen type I, weak immunoreactivity for aggrecan and tenascin‐C, weak hyaluronan (HA) staining, and abundant argyrophilic fibers in PVCs indicated that they contain noncartilaginous fibrous connective tissues that was different from those in the perichondrium/periosteum. These structural and immunohistochemical features of PVCs are different from those of previously reported cartilage canals of the long bone. Capillaries entered the VCs from the periosteum and ascended through VCs. Following capillary invasion, loose connective tissue had formed in the lower part of VCs, and immunoreactivity for collagen types I and III, tenascin‐C, and HA staining was evident in the matrix of loose connective tissue. No chondroclasts or osteogenic cells were seen at the front of capillary invasion, although small, mononuclear tartrate‐resistant acid phosphatase (TRAP)‐positive cells were present. Meanwhile, TRAP‐positive, multinucleated chondroclasts and flattened, osteoblast‐like cells were observed in the loose connective tissue at the lower part of VCs. These results may indicate slow progress of endochondral ossification in human fetal mandibular condyle. Further, unique matrix components in PVCs/VCs, which were different from those in cartilage canals in long bone, may reflect the difference of speed of endochondral ossification in cartilage canals and human fetal mandibular condyles. Anat Rec, 298:1560–1571, 2015. © 2015 Wiley Periodicals, Inc.     

猴松果体分泌物释放入脑脊液主要途径的结构基础电镜研究

目的 探讨松果体分泌物直接释放入脑脊液途径的开矿学依据,方法 采用常规及ＮaＯＨ 消蚀法电镜样品制备技术,对成年日本猴松果体及其补囊进行了扫描和航向电镜观察。结果松果体囊同一层扁平上皮细胞和上皮下结缔组织构成。在面对蛛网膜下隙的囊上皮细胞和细胞间存在许多上皮孔;上上结缔组织什入要体形成小叶间隔,浆松果体分隔为许多实质小叶。松果体结缔组织的主要成分为胶原纤维;实质小叶由大量松果体细胞和少数胶质细胞组成     

Anatomical assessment of bile ducts of Luschka in human fetuses

Bile ducts of Luschka (also called subvesical or supravesicular ducts) can cause bile leakage during laparoscopic cholecystectomy, especially if surgery is carried out in ignorance of such variations. The aim of this study was to clarify the clinical anatomy of these ducts in human fetuses and frequency of the ducts locating near gallbladder fossa. Thirty-two fetal cadaver livers were dissected and the gallbladders were separated from the livers and ducts were investigated under a surgical microscope. All observed ducts were examined microscopically and connective tissue cords were excluded. Bile ducts of Luschka locating near cystic fossa were found in 7 of 32 fetuses (21.9%). Three of the seven ducts ran towards to liver segment 5 (S5); three ducts were found in the gallbladder fossa; and one duct ran towards to liver segment 4 (S4). Also it was found that three of the seven ducts drained into the subsegmental duct of S5, two ducts drained into the right hepatic duct, one duct drained into the right anterior branch bile duct, and one duct drained into the subsegmental duct of S4. Subvesical ducts running along the gallbladder fossa between the gallbladder and the liver parenchyma were found in a relatively high incidence in fetuses than adults. Awareness and knowledge about incidence of such ducts alerts the surgeon during laparoscopic cholecystectomy. Therefore morbidity due to bile leaks can be reduced.     

EVIDENCE FOR EXPRESSION OF Ly - 6.2 ON NON-BONE MARROW-DERIVED CELLS IN KIDNEY,SKIN AND CONNECTIVE TISSUES

Mouse alloantigen Ly-6.2 is detectable in various non-lymphoid tissues such as kidney, but it is not clear whether or not this expression is due to bone-marrow derived passenger leukocytes. To determine whether non-marrow derived cells express Ly-6.2, we examined the expression of this antigen in kidney and on isolated connective tissue and epidermal cells. Studies in radiation chimeras demonstrated that the kidney did not become Ly-6.2 positive when negative animals were reconstituted with positive marrow. Thus, passenger leukocytes cannot account for the renal expression of Ly-6.2, indicating that most of this antigen is on non-marrow-derived (parenchymal) cells in kidney. Various isolated cell types-fibroblasts, osteocytes, chondrocytes and skin epidermal cells-were found to be Ly-6.2 positive. Indeed, absorption and cytotoxicity results suggested that the amount of Ly-6.2 on fibroblasts exceeded the amount of an H-2 antigen on these cells. Comparison of fibroblast to lymphocytes indicated that fibroblastts had 13-60 times more Ly-6.2 than spleen cells and three times more than PHA blasts. The results indicate that the Ly-6.2 detected in non-lymphoid tissues is predominantly on the parenchymal or connective tissue elements of those tissues.     

结缔组织对人胎骨髓间充质干细胞向上皮分化的诱导作用

目的 探讨结缔组织诱导人胎儿骨髓间充质干细胞（BMSCs)分化为上皮细胞的机制。 方法 取20例孕16～20周因故引产胎儿,10例选择性剖宫产妇羊膜,酶联免疫吸附测定（ELISA）法检测去上皮羊膜和胎儿肠壁结缔组织中表皮生长因子(EGF)的含量;分离、培养、扩增胎儿BMSCs;将4,6-二脒基-2-苯基吲哚（DAPI）标记的第3代BMSCs（P3-BMSCs）种植于羊膜上,分别加入肠壁结缔组织上清液、羊膜上清液（均含EGF 30μg/L）、外源性EGF 30ug/L、30ng/L、完全培养基（1～5组）中。培养7d后,免疫组织化学和激光扫描共焦显微镜检测BMSCs表达的细胞角蛋白(CK)及CK20。 结果 每100mg肠壁结缔组织及羊膜中EGF含量分别为（320.22±0.257）pg、（299.20±0.994）pg。羊膜与肠壁结缔组织上清液或羊膜上清液联合诱导BMSCs后,其CK和 CK20阳性细胞率均明显强于羊膜与外源性EGF诱导组以及单纯羊膜诱导组,P＜0.01。羊膜与肠壁结缔组织上清液诱导后BMSCs表达CK20高于羊膜与羊膜上清液组,P＜0.05。羊膜诱导组与外源性EGF联合诱导组间的差异无统计学意义。 结论 直接接触可能是羊膜结缔组织诱导BMSCs向上皮细胞分化的机制之一。肠壁结缔组织上清液和羊膜上清液均能联合羊膜诱导BMSCs向上皮细胞及具有肠上皮细胞表型的细胞分化。     

An Asian variant of intravascular lymphoma: unique clinical and pathological manifestation in the gallbladder

We here present a rare case of intravascular lymphoma (IVL) in a Japanese man. 4 months after cholecystectomy due to cholecystitis, a diagnosis of intravascular lymphoma (IVL) was strongly suspected. Lymphoma cells were diffusely observed in the bone marrow parenchyma, but were absent in the vascular spaces. The patient died of respiratory failure and at autopsy a small number of lymphoma cells in the extravascular parenchyma of the adrenal gland and bone marrow were seen. Serial sections of the surgically resected gallbladder retrospectively confirmed the diagnosis of IVL. In addition, congestion and edema were observed in the connective tissue layer. It is possible that edema or ischemia in the gallbladder wall or at other anatomic sites due to the circulation disturbance induced by the intravascular obstruction of lymphoma cells may have caused the initial symptoms. In conclusion, clinicians and pathologists should keep in mind that the gallbladder may be initially involved in IVL.     

Elevated expression in situ of selectin and immunoglobulin superfamily type adhesion molecules in retroocular connective tissues from patients with Graves' ophthalmopathy.

Activation of certain adhesion molecules within vascular endothelium and the surrounding extravascular space is a critical event in the recruitment and targeting of an inflammatory response or autoimmune attack to a particular tissue site. We have recently demonstrated that the adhesion of lymphocytes to cultured retroocular fibroblasts obtained from patients with Graves' ophthalmopathy (GO) is mediated predominantly by the interaction of lymphocyte function-associated antigen-1 (LFA-1), expressed on lymphocytes, with intercellular adhesion molecule-1 (ICAM-1), expressed by these cells following exposure to interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), IL-1 alpha or purified thyroid-stimulating immunoglobulins. We now report the expression and localization in situ of several adhesion molecules, ICAM-1, endothelial leucocyte adhesion molecule-1 (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), and LFA-3 in retroocular tissues derived from patients with severe GO (n = 4) and normal individuals (n = 3). Serial cryostat sections of tissue specimens were processed for immunoperoxidase staining using various MoAbs against ICAM-1, ELAM-1, VCAM-1 and LFA-3. In addition, consecutive sections were stained with MoAbs against LFA-1, CD45RO (UCHL-1)DR-human leucocyte antigen (HLA-DR), CD11b/CD18 (Mac-1), and CD11c/CD18 (p150,95). In GO-retroocular tissues, strong immunoreactivity for ICAM-1 and LFA-3 was detected in blood vessels (> 90%), in perimysial fibroblasts surrounding extraocular muscle fibres, and in connective tissue distinct from extraocular muscle. No ICAM-1 or LFA-3 immunoreactivity was present in extraocular muscle cells themselves. ICAM-1 and LFA-3 immunoreactivity in normal tissues was minimal or absent both in connective and muscle tissues. Vascular endothelium was strongly positive for ELAM-1 and VCAM-1 in GO-retroocular tissues, while VCAM-1 immunoreactivity was minimal (< 5% of blood vessels) and ELAM-1 immunoreactivity was generally absent in normal retroocular tissue. LFA-1-expressing, activated mononuclear cells and memory T lymphocytes (CD3+/CD45RO+) were only detected in GO-retrocular tissues, and were mainly localized around blood vessels and in areas of ICAM-1-expressing connective and perimysial tissue. HLA-DR expression was restricted to GO-tissue specimens, with strong immunoreactivity detected in blood vessels, macrophages and connective tissue and perimysial fibroblasts. No HLA-DR was detectable in extraocular muscle cells. In conclusion, infiltration of the orbit in GO by mononuclear cells, and their targeting within the orbit, may depend upon the coordinate expression of certain adhesion and MHC molecules.(ABSTRACT TRUNCATED AT 400 WORDS)     

Laminin和survivin的表达与胆囊癌临床病理特征的关系

目的:研究laminin和survivin蛋白在原发性胆囊癌组织中的表达情况,及其与癌组织类型、病理分级和转移状况的关系。 方法:应用免疫组织化学方法检测49例原发性胆囊癌、21例胆囊腺瘤和13例慢性胆囊炎组织中laminin和survivin蛋白的表达。 结果:胆囊黏膜内癌或原位癌细胞基底膜laminin线性染色完整；NevinⅡ期胆囊癌组织表现为基底膜不完整,变薄,断裂,或缺损；临床NevinⅢ、Ⅳ、Ⅴ期胆囊癌，则无基底膜形成，在肿瘤组织周围，laminin表达类型呈碎片状或断线状和连续线状，部分癌组织内laminin染色消失和癌细胞浆内有laminin弱染色。胆囊癌组织中survivin阳性表达率明显高于胆囊腺瘤和慢性胆囊炎组织，但survivin的阳性表达与胆囊癌细胞分化程度、病理分级和转移无关(P>0.05)。且胆囊癌组织中laminin的连续线断裂或缺失,与胆囊癌组织中survivin的表达情况无相关性。 结论:胆囊癌基质中laminin的表达类型与胆囊癌的侵袭和转移有关，而survivin在胆囊癌中表达增加，但两者之间似乎无关联。      

Kinetics and staining properties of mast cells proliferating in rat small intestine tunica muscularis and subserosa following infection with Nippostrongylus brasiliensis

Mucosal mast-cell hyperplasia occurs in the rat small intestine mucosa after infection with Nippostrongylus brasiliensis. In the present study, the number of mast cells was found to increase in the muscularis and subserosa as well as in the mucosa of rat small intestines 2-3 weeks after infection with this nematode. Mast cells in the muscularis were stained blue by the alcian blue/safranin sequence and did not bind berberine sulfate. The staining was blocked when tissues were fixed in neutral formalin. The increase in mast cells was transient and gradually disappeared; the half-life was 40 days. After an intravenous administration of compound 48/80, mast cells in the muscularis did not discharge granules. The results indicate that these mast cells were of the mucosal type. The mast cell phenotype in the muscularis did not change even 12 weeks after infection. Mast cells in the subserosal tissue were first of the mucosal type as were those in muscularis. After 8-12 weeks, however, many subserosal mast cells became positive for berberine sulfate and safranin. These results show that mucosal-type mast cells do not undergo phenotypic changes during the period of observation when these cells appear in the muscularis but the phenotypic expression may change as the cells arise in subserosal tissue.     

Polysaccharides of metaplastic mucosa and carcinoma of the gallbladder.

The polysaccharide composition of the human gallbladder well was studied in carcinomas and metaplastic changes of various degrees, and the results obtained were compared with those for the normal material previously presented (Terho, T., and Laitio, M. Biochim. Biophys. Acta 338: 135, 1974). Elevated amounts of acid connective tissue polysaccharides (heparitin and dermatan sulfates as well as chondroitin 4- or 6-sulfate, or both, could be observed in carinomas. In histochemical stainings it was found that in carcinomas and in the two specimens classified as group III (containing the most extensive metaplastic changes at disposal), the intracellular mucin was mainly neutral or nonsulfated acidic. The amounts of sulfated mucin were relatively insignificant. This mucin polysaccharide material was isolated and its composition was determined. It was observed to be large polysaccharide material was isolated and its composition was determined. It was observed to be large molecular (approximate molecular sizes 1 to 2 times 10-6), and to be composed of fucose, galactose, glucosamine, and galactosamine as well as small amounts of sialic acid. The basic structure of these polysaccharides is thus similar to that of normal sulfated mucin. The almost total absence of acid groups, however, causes the polysaccharide material in question to stain in a manner identical with neutral mucin when investigated with histochemical methods. The carcinomas also contained some sulfomucin; its proportion, however, was small as compared with the amounts of nonsulfated acid and neutral mucin in biochemical characterization. A small molecular polysaccharide fraction, assumed to originate in membrane-bound glycoproteins, was isolated from the insoluble gallbladder tissue residue. The proportion of this fraction was larger in carcinomas than in normal material. This rise as well as the rise in the quantity of acid connective tissue polysaccharides is presumably due to the large number of cells in the carcinoma tissue as well as to fibrosis.     

Fibril diameters in the extracellular matrix of the periodontal connective tissues of the rat

The diameters of collagen fibrils were measured in three varieties of periodontal connective tissue in the rat mandible (incisor periodontal ligament, incisor enamel-related connective tissue and molar periodontal ligament). Despite structural and functional differences between the tissues, a similar range of collagen fibril diameters was seen in each (average 45 nm). Variation between animals and between adjacent fiber bundles in any given tissue was observed. Even within any single fiber bundle, the fibrils had a variety of diameters. Although it has been claimed that collagen fibrils have diameters which are multiples of 8 nm, such a relationship could not be discerned for periodontal collagen fibrils. It was estimated that about 65 per cent of a periodontal collagen fiber bundle or sheet is composed of ground substance. Despite reports of abundant oxytalan fibers in periodontal tissues at the light microscope level, only one fiber having characteristics of oxytalan was observed in this electron microscopic study. Some aspects of the functional significance of the findings are discussed.     

Ultrastructural changing of the rat parathyroid gland under various fixation methods

Ultrastructural features of the rat parathyroid (PT) glands have been studied under 3 different glutaraldehyde fixation methods. Cell differences caused by fixation or due to functional conditions were evaluated. The changes of organelles and relationship of plasma membranes of chief dark-light cells, as well the pericapillary and intercellular spaces were used for this evaluation. Light cells were observed in all PT glands studied. PT glands adequately perfused presented light chief cells as transitional secretory form. Incompletely-perfused and immersion-fixed glands presented most of light chief cells as a fixation artifact. The same interpretation was given to intercellular spaces which appeared only in glands fixed by immersion. In adequately perfused glands interdigitated and straight plasma membranes of neighbour chief cells were tightly continuous with frequent desmosomes. Distended mitochondria, RER and Golgi cisternae as well vacuolizations of chief cell cytoplasm and connective tissue were characteristics of unadequately perfused glands. The best fixation method for a homogeneous preservation of all components of rat PT glands, which decreased the possibility of a wrong interpretation of normal variations, was perfusion through the left ventricle. Fixative with pH and osmolarity carefully controlled were injected after saline washing of the vascular bed.