摘要:

AbstractCalbindin‐D 28 kDa (CaBP 28 kDa), a vitamin D‐dependent calcium‐binding protein, has been associated with calcium handling by cells. We have investigated the expression of this protein in the rat incisor enamel organ, an epithelium interposed between a mineralizing matrix and connective tissue rich in blood vessels, by radioimmunoassay (RIA), Western blotting, and quantitative protein A‐gold immunocytochemistry with antibodies to rat kidney CaBP 28 kDa. RIA of cytosolic extracts showed that enamel organs contained relatively high concentrations of CaBP 28 kDa (compared to kidney; see review by Christakos S., C. Gabrielides, and W.B. Rhoten 1989 Endocr. Rev.,10:3–25). Immunoblotting of proteins extracted from enamel organ strips revealed an intensely‐stained band near 28 kDa throughout amelogenesis following ameloblast differentiation. Immunocytochemically, CaBP 28 kDa was localized exclusively within ameloblasts. The density of labelling increased from the presecretory stage to the secretory stage and fluctuated across the maturation stage in relation to ameloblast modulation. Ruffle‐ended ameloblasts consistently showed the most intense immunoreaction. Gold particles were present throughout the cytoplasm and nuclei of ameloblasts but regions rich in rough endoplasmic reticulum or cell webs showed a higher immunolabelling. Some gold particles were also associated with the external face of the rough endoplasmic reticulum. Multivesicular bodies in maturation stage ameloblasts were occasionally immunoreactive. These data suggest that the intracellular concentration of CaBP 28 kDa is regulated throughout amelogenesis reflecting a stage‐specific control of calcium homeostasis

ISSN:0003-276X    

DOI:10.1002/ar.1092300202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractMicroridges produce a characteristic fingerprint‐like pattern on the surface of fish oral mucosa. The cytoskeleton in these microridges was examined by immunofluorescence microscopy and transmission electron microscopy after detergent extraction and decoration with myosin subfragment 1. The effect of cytochalasin B on microridges was probed with scanning electron microscopy. Immunofluorescence microscopy revealed that actin filaments were present throughout the periphery of the epithelial cells and were especially localized beneath the free surface of the epithelium. In thin sections treated with Triton X‐100, the majority of filaments in the microridges and their bases were found to be actin filaments and a plexus of keratin filaments that underlay the network of actin filaments. A part of the plexus of keratin filaments entered the microridges. After extraction with Triton X‐100 and decoration with myosin subfragment 1, decorated actin filaments were found in the microridge cores, connected to the keratin filaments. The keratin filaments aggregated in the pattern of microridges and a few of them protruded into the microridges. Treatment with cytochalasin B caused microridges to disappear or to become thinner and lower or to change short or microvillus‐like microridges. When most microridges disappeared, the surface of the superficial cells was prominently swollen, but the cell boundaries were fastened, and the microridges in the periphery were preserved. On the basis of these observations, the possible roles of actin and keratin filaments in the maintenance and the formation of microridges are di

ISSN:0003-276X    

DOI:10.1002/ar.1092300203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractWe present a rapid technique for determining cancellous bone mineral changes in small experimental animals. We used the distal centimeter of the right femur from ovariectomized (OX) (N = 30) and shamovariectomized (ShOX) (N = 28) rats, aged 90 days at surgery and killed at times from 125–540 days postsurgery. We used dual photon absorptiometry to scan the segment three times: intact, after parasagittal splitting, and after removing all cancellous bone. We equated the difference between the second and third scans to cancellous bone mineral content (Cn.BMC). To validate this, we compared it with histomorphometrically determined bone volume (BV/TV) of the proximal tibial metaphysis of the same rat. Parasagittally splitting the segment removed no detectable mineral. OX rats had 40% less Cn.BMC than ShOX rats. However, OX rats had 80% lower BV/TV than ShOX rats. The subtraction technique not only makes a rapid, reasonable assessment of cancellous bone loss in OX rats but permits a smaller sample size than histomorphometry. The histomorphometric technique finds a greater difference between OX and ShOX rats because it examines a region where cancellous bone loss is more marked than does the scanning technique. The current technique measures bone of not only the central secondary spongiosa but also the juxtacortical region and the primary spongiosa, where OX‐related differences are less prominent. The principles of this subtraction technique proved workable. However, for the future, we recommend a two‐scan technique using a dual energy X‐ray scanner. It is likely to take only 20–30 min per specimen to assess cancellous bon

ISSN:0003-276X    

DOI:10.1002/ar.1092300204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe fibronexus is a close transmembrane association between fibronectin filaments and actin microfilaments. It has been found at the surfaces of fibroblasts in tissue culture, as well as within contracting granulation tissue. This specialized connection has been proposed to play an important role in the adhesive properties of fibroblasts. The purpose of this study is to determine whether the fibronexus is present in other contracting tissues besides granulation tissue, specifically in Dupuytren's diseased tissue. Dupuytren's disease is a pathologic condition in which the palmar aponeurosis becomes shortened leading to irreversible flexion of the digits. Shortening of the aponeurosis is believed to be an active cellular process. Extracellular filaments and actin microfilaments form close transmembrane associations at the surfaces of actin‐rich fibroblasts in Dupuytren's disease. Extracellular filaments extend from the cell surface into the surrounding tissue connecting fibroblasts with collagen fibrils and adjacent cells. In this study we have used immunoelectron microscopy to demonstrate that the extracellular filaments that participate in these close transmembrane associations contain fibronectin. High voltage electron microscopy has been used to examine the three‐dimensional relationships between the cytoskeleton and fibronectin filaments in Dupuytren's diseased tissue. We propose that the fibronexus is a dominant adhesive structure at the surface of fibroblasts in Dupuytren's diseased tissue. The fibronexus, by mediating cell‐to‐cell and cell‐to‐matrix attachments, may serve to transmit contractile forces generated by actin microfilaments in these cells throughout the dise

ISSN:0003-276X    

DOI:10.1002/ar.1092300205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractMuscle spindles in the tenuissimus muscle of mature golden Syrian hamsters were examined by conventional and high‐resolution scanning electron microscopy (HRSEM). For conventional SEM, entire muscles were first fixed in 2.5% buffered glutaraldehyde. Spindles were then isolated with a dissecting microscope under darkfield illumination and postfixed in 1.0% OsO4. Some spindles were treated with 8 N HCl at 60°C to clearly expose intrafusal fiber surfaces once the outer capsular sheath was mechanically disrupted. Preparation for HRSEM included aldehyde/osmium fixation and freeze‐cleavage in liquid N2. The cytosol and certain cellular elements were also selectively extracted by immersion in 0.1% OsO4for varying time intervals. In these preparations, the capsular sleeve showed a multilayered pattern of vesicle‐laden cells with variant surface topography in different regions, including filopodia and small bristle‐like surface‐projections. An interlacing three‐dimensional network of collagen fibrils intervened between the capsular lamellae. Within the spindles, sensory and fusimotor nerve endings closely adhered to the outer surfaces of intrafusal fibers. Sensory nerve terminals were enveloped by a prominent external lamina, and those that were cleaved open contained a plethora of elongated mitochondria that ran parallel with the longitudinal axis, along with vesicles, axoplasmic filaments, and lysosomes. Multiple adhesion sites between the sensory nerve membrane and the underlying sarcolemma of the intrafusal fiber were also observed in select regions. Fusimotor nerve endings were covered externally by processes of Schwann cells and their axoplasm was filled with a multitude of cellular organelles and synaptic vesicles. Dilated cisternae of the sarcoplasmic reticulum and numerous mitochondria were, in addition, observed below the postjunctional sarcolemma at the neuromuscular interface. The methodology used in this study provides a novel view of the exquisite three‐dimensional architecture of this complex neuromus

ISSN:0003-276X    

DOI:10.1002/ar.1092300206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effect of tunicamycin (TM) on testicular cord organization in the fetal mouse was examined in vitro at light and electron microscopic levels, with special reference to the glycoprotein functions during Sertoli cell differentiation.In testicular explants treated with TM, testicular cord organization was inhibited. TM treatment affected basal lamina formation by Sertoli cells, resulting in a discontinuous basal lamina or none at all in certain areas. The disorganized Sertoli cells were amorphous in shape, exhibited poor epithelial polarity, and were irregularly arranged in the testicular parenchyma. Extracellular matrix and collagen fibers were often observed in the intercellular spaces between the disorganized Sertoli cells. Lectin histochemical observation revealed that the number of wheat germ agglutinin binding sites on the plasma membrane and basal lamina of disorganized Sertoli cells was significantly decreased by TM treatment. However, junctions were normally observed in the plasma membrane between disorganized Sertoli cells. Leydig cells showed a normal differentiation in the testicular parenchyma in the presence of TM.These observations suggest that basal lamina formation of Sertoli cells and/or the expression of their cell surface glycoconjugates may be crucial for the establishment of Sertoli cell polarity and/or the Sertoli‐Sertoli cell interactions required for proper testicular cord formation. Sertoli cell organization into testicular cords and Leydig cell differentiation may be controlled by different regulatory mechanism

ISSN:0003-276X    

DOI:10.1002/ar.1092300207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of actin in spermatogenic cells and epididymal spermatozoa of the opossum,Monodelphis domestica, was examined by immuno‐fluorescence microscopy to identify its potential function in the major structural events of sperm development. In spermatogenic cells actin was located at the site of initial interaction between the nucleus and acrosome and remained present through subsequent acrosome morphogenesis. Actin was also associated both with the posterior pole of the nucleus, at the site of flagellar attachment, and with the manchette. Thus actin may play a role in establishing the specific associations of spermatid organelles and in the streamlining of the cells' architecture. In epididymal spermatozoa two sites of actin localization are present. The first site is surrounding the connecting piece where it may participate in the characteristic 90° rotation of the head. The second site was a ring of actin surrounding the lateral boundary of the acrosome where it may play a role in the sperm pairing process which also occurs in the epididym

ISSN:0003-276X    

DOI:10.1002/ar.1092300208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe cytoplasmic distribution of poly(A)+mRNA and its relationship to annulate lamellae were examined in developingNecturus maculosusoocytes by in situ hybridization with [3H]poly(U). The specificity of [3H]poly(U) binding was tested by incubating control ovarian sections with either KOH or RNase A before in situ hybridization. In both experiments, the silver grain densities were markedly reduced. Poly(A)+RNA is uniformly distributed in the cytoplasm until the mid‐growth phase and then later in vitellogenesis becomes localized in the subcortical ooplasm. The silver grain density in the cytoplasm varied during oogenesis and was greatest in previtellogenic oocytes. Annulate lamellae commonly are observed with the light microscope in oocytes prior to vitellogenesis. In such oocytes, the labeled mRNA probe is observed over cytoplasmic regions of annulate lamellae. The results suggests that a differential localization of messenger RNA occurs during oogenesis inNecturus maculosus. Furthermore, poly(A)+RNA is present in cytoplasmic regions of annulate lamella

ISSN:0003-276X    

DOI:10.1002/ar.1092300209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractDevelopment of the fetal mouse esophageal epithelium was followed using light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and radioautography. At 15 days of gestation in the cervical (C), mediastinal (M), and abdominal (A) segments of the esophagus, the epithelium was two or three cells thick, and only cells located in the basal (germinal) layer incorporated tritiated thymidine. Ciliated cells were sparse in all three segments. At 17 days of gestation, longitudinal mesenchymal ridges became more differentiated in the distal segment. Labeling indices were lower than at preceding stages in each segment. Ciliated cells had increased in number and appeared to be evenly distributed along the whole esophagus. In periodic acid‐Schiff (PAS)‐stained sections, an increasing proximodistal distribution of glycogen stores was observed, with greatest concentrations found in segment A. At 18 days of gestation, labeling indices were comparable in segments C and M (11.7% ± 2.9% and 12.8% ± 1.9%, respectively) but remained higher in segment A (17.9% ± 2.0%). Ciliated cells were still present. At this stage, transverse circular furrows and ridges started to appear. They increased in number at 4 days after birth and were very closely distributed in the adult. In longitudinal sections, these ridges corresponded to projections of stratum granulosum and of the overlying stratum corneum. After birth, ciliated cells desquamated rapidly but some patches were still present at 4 days. At 8 days, the esophageal epithelium was not yet kerat

ISSN:0003-276X    

DOI:10.1002/ar.1092300210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe effect of acute alcohol exposure on the gastric mucosal basal lamina, and its major structural protein type IV collagen, was assessed by transmission electron microscopy (TEM) and immunogold (IG) labeling of this collagenous material. Fasted rats orally received either 50% or 100% ethanol. Five or 60 minutes later animals were sacrificed and mucosal samples were obtained from the glandular epithelium for TEM or IG localization of type IV collagen. For IG studies, the number of gold particles/area lamina densa was quantified in interfoveolar, pit, and gland regions as an index of the molecular integrity of type IV collagen. Both ethanol concentrations induced epithelial exfoliation with pleating of the denuded lamina densa. Absolute ethanol, and to a lesser extent 50% ethanol, caused frequent rupture of a thickened, precipitated lamina densa. Immunolabeling of type IV collagen varied with the experimental protocol. In control tissues exposed to oral saline, binding was greatest in the interfoveolar zone. Low binding occurred with 100% ethanol in all regions when compared with controls, but 50% ethanol evoked significantly higher binding in interfoveolar regions, in a similar fashion to controls. In additional studies in which 16,16 dimethyl prostaglandin E2(PGE2) (10 μg/kg) was injected subcutaneously prior to oral ethanol exposure, PGE2pretreatment prevented the large decrease in IG binding induced by absolute ethanol, but the level still remained significantly less than with corresponding controls. In contrast, pretreatment with PGE2prior to 50% ethanol exposure restored type IV collagen immunolabeling to control levels. These results indicate that ethanol induces a concentration‐dependent lowering of IG binding to type IV collagen which also effects its reversibility by PG

ISSN:0003-276X    

DOI:10.1002/ar.1092300211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY