摘要:

AbstractThe movement of proteins into and out of enamel was followed over time using a highly sensitive microprecipitation technique to quantify the amount of TCA‐insoluble radioactivity present within small pieces of freeze‐dried enamel and cells (enamel organ) dissected from the mandibular incisors of rats injected with L‐[35S]‐methionine. Conventional image processing techniques were also used to estimate the number of silver grains over enamel and cells in radioautographs of mandibular incisors from rats similarly injected with L‐[methyl3H]‐methionine. Data from both techniques indicated that the average half‐life for labeled proteins secreted into enamel was about 8.9 days. Typically, radioactive proteins accumulated in increasing amounts for 8 hours after which they were lost slowly up to 4 days and more rapidly thereafter when enamel formed during the secretory stage underwent maturation. The half‐life for radioactive proteins in cells was only about 20.7 hours. No significant accumulation of radioactivity could be detected in the TCA‐soluble or TCA‐insoluble fractions of cells as enamel development proceeded. Results from this study suggest that radioautographs provide an accurate estimate of changes occurring to proteins in enamel and cells except at early time intervals (less than 1 hour) when a high percentage of total radioactivity is present within the TCA‐solu

ISSN:0003-276X    

DOI:10.1002/ar.1092320102

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe periarterial lymphoid sheath (PALS) in the rat spleen was studied by light, transmission, and scanning electron microscopy. The PALS was divided into three regions: the central region, peripheral region, and marginal zone bridging channel. In the central region, lymphocytes were easily washed away by perfusion. Large spaces were found between flat reticular cells or in large meshworks of stellate reticular cells; these may be deep lymphatic vessels. True lymphatic vessels were found in the central region near the hilus. In the marginal zone bridging channel, flat reticular cells surrounded the central artery in a circumferential pattern and formed channel‐like spaces between the flat reticular cells. These spaces were connected with the meshwork of the red pulp reticular cells and may be a route for lymphocytes between the deep lymphatic vessels and the red pulp. In the peripheral region of the PALS, it was usually difficult to wash away free cells by perfusion, and free cells were found among the reticular cells. In places in the peripheral region, however, free cells were washed away. It is suggested that the lymph flow may start from the region surrounding the PALS, and that the peripheral region of the PALS may also be another route for lymphocyte migratio

ISSN:0003-276X    

DOI:10.1002/ar.1092320103

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn order to analyse, at the electron microscope level, the three‐dimensional configuration of the trans compartment of the Golgi apparatus rat dorsal root ganglia were treated to demonstrate cytidine monophosphatase (CMPase) activity. The localization of enzymatic activity in the Golgi apparatus varied according to cell types. In type A and C cell, CMPase was exclusively located in the transmost sacculotubular element, whereas in type B cells all the saccules of the stacks forming the Golgi ribbon and the trans‐Golgi networks were impregnated. Numerous dense bodies seen at proximity were also CMPase positive. In 3 μm thick sections of type A cells examined at low magnification, the impregnated element was scattered throughout the cytoplasm and never formed a continuous structure. In type B cells, the strongly reactive trans‐Golgi networks did not follow the entire length of the impregnated Golgi ribbon but were preferentially located in the concavity of its arched portions. At higher magnification and in all cell types some tubular portions of the trans‐Golgi networks took the apperance of spheroidal cage‐like structures, the CMPase positive anastomotic tubules forming the bars of the cage. Anastomotic tubules separated from the trans‐Golgi networks formed fenestrated spheres, while nearby CMPase‐reactive dense bodies exhibited a paler hilus. These observations were taken to indicate that in ganglion cells, some CMPase positive dense bodies, presumably lysosomes, formed by fragmentation of the trans

ISSN:0003-276X    

DOI:10.1002/ar.1092320104

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe presence of proteoglycans (PGs) was studied in compact lamellar rat and human bone at the electron microscopic level. With the cationic dye cuprolinic blue (CBI), PGs could be demonstrated in the mineralized bone matrix. The amounts of PGs appeared to be equal in the different lamellae and osteons. More CBI‐positive material was found in the outermost lamella of the cortex, in the perilacunar matrix around the osteocyte lacunae, and around the canaliculi. Enzyme digestion with chondroitinase ABC demonstrated that the CBI‐positive rods consisted of PGs. These observations amplify biochemical studies in which PGs have been isolated from the mineralized bone matrix. The presence of CBl‐positive rods in the mineralized matrix suggest that PGs do not have to be removed completely to make the matrix calcif

ISSN:0003-276X    

DOI:10.1002/ar.1092320105

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

年代:1992

数据来源: WILEY

摘要:

AbstractCollagen fibrils with a symmetric banding pattern, an as yet overlooked component of the extracellular matrix, were found in the reticular layer of the basement membrane of human sebaceous glands. In longitudinal sections this newly described banding pattern is D‐periodic (D = 67 nm) resembling the period length of native type collagen fibrils. In cross sections the symmetrically banded fibrils are irregularly outlined. The period length and the symmetric banding pattern led to the assumption that collagen molecules are staggered by the distance D, similar to native type collagen fibrils, but are arranged antiparallel. This hypothesis was tested by antiparallel superposing transparent photocopies of native type fibrils. In addition, schematic drawings of the cross striation pattern of native type fibrils were superposed in reverse directions by means of computerized image‐manipulation. A model of molecular alignment was evolved from these experiments, which is characterized by two features: (1) pairs of antiparallel collagen molecules are D‐staggered and (2) the two molecules of a pair are slightly shifted from precise register. The proposed model is the only one correlating with the data obtained from direct measurements on symmetrically cross striated fibrils. The fibrils described in the present study represent a supramolecular aggregate of collagen previously not observed in

ISSN:0003-276X    

DOI:10.1002/ar.1092320106

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

年代:1992

数据来源: WILEY

摘要:

AbstractVitamin A and its congeners, collectively called retinoids, are known to have teratogenic potential and have induced craniofacial and limb malformations in numerous animal species. More importantly, retinoids are recognized as teratogenic to fetuses of pregnant women who have taken such preparations for dermatologic disorders. Information gathered from the study of animal models suggests that retinoids interfere with cartilage differentiation. If chondrogenesis in limb development is disturbed it may contribute to limb reductions and malformations. In vitro studies using various animal systems have shown that cartilage matrix macromolecules are altered to resemble those secreted by mesenchymal cells. The response of human chondrocytes to retinoids in vitro is not known. Culture of human chondrocytes in agarose maintains the cartilage phenotype and therefore serves as a model system to evaluate the influence of retinoids directly on human chondrogenesis. The studies presented in this paper were done to determine if the expression of specific matrix macromolecules of human chondrocytes in agarose culture is altered by retinol treatment. Immunocytochemistry demonstrated enhanced labeling of type I collagen while type II collagen labeling was reduced in cultures treated with retinol. In addition, morphometric analyses indicated a decrease in the size and number of chondrogenic clusters and that individual cells synthesized less alcian blue matrix when compared to parallel control cultures. The size of the proteoglycan monomers, glycosaminoglycan side chains as well as the disaccharide composition were not affected. However, there was a reduction in the quantity of proteoglycan monomers produced.

ISSN:0003-276X    

DOI:10.1002/ar.1092320107

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

年代:1992

数据来源: WILEY

摘要:

AbstractImmunofluorescence and immunogold localization studies show that the two Ca2+‐dependent proteinases (μ‐calpain for the micromolar Ca2+‐requiring proteinase and m‐calpain for the millimolar Ca2+‐requiring proteinase) and their protein inhibitor (calpastatin) are located exclusively intracellularly in normal rat soleus muscle. Quantitative immunogold studies indicate that binding of antibodies to both calpains and to calpastatin is approximately two times greater at the Z‐disk of myofibrils than it is at the I‐band or A‐band regions. Mitochondria and nuclei in muscle cells contain both calpains and calpastatin at concentrations approximately one‐tenth and one‐fifth, respectively, of the concentration at the Z‐disk, as estimated by antibody binding. Very little calpain or calpastatin was seen in the cytoplasmic intermyofibrillar spaces, and most of the calpain and calpastatin in muscle cells is associated with intracellular structures. Immunofluorescence results suggest that concentration of m‐calpain but not μ‐calpain or calpastatin is, in some instances, slightly higher near the intracellular surface of the plasma membrane than elsewhere in the muscle cell. Most m‐calpain, however, is distributed throughout the interior of mature rat skeletal muscle cells. Denervation, or fasting and refeeding increases the concentration of the calpains and calpastatin in the muscle cell but does not change their distribution. Some μ‐and m‐calpain and calpastatin is found extracellularly in denervated soleus muscle or soleus muscle from fasting rats, but the extracellular calparns and calpastatin seem to originate from “leakage” of these proteins out of the cell because serum creatine kinase levels are much higher tha

ISSN:0003-276X    

DOI:10.1002/ar.1092320108

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis study deals with regional differences in the architectural design of the human masseter muscle. For a number of defined muscle regions the three‐dimensional corrdinates of origin and insertion points, and the lengths of the muscle fibers and the sarcomeres were determined in the closed jaw position. Measurements were made from cadavers and the data were used as input for a model predicting sarcomere length at other mandibular positions. At a closed jaw average muscle fiber length of the muscle regions ranged between 19.0–30.3 mm. The fibers appeared to be considerably longer (35%) anteriorly than posteriorly in the muscle, and deeply situated fibers were on average 5% shorter than superficially situated ones. Average sarcomere length of the regions ranged between 2.27–2.55 μm, indicating that at a closed jaw position sarcomeres are at suboptimum length and have different positions on the length‐tension curve. In the deep layer of the muscle sarcomeres were significantly shorter (6%) than in the superficial layer. Within the superficial layer sarcomere lengths did not differ significantly, but in the deep layer sarcomeres were shorter (8%) posteriorly than anteriorly in the muscle. The model shows that jaw displacement had a different effect on sarcomere length in the muscle regions. When the jaw was rotated about a transverse axis (open/close rotation) sarcomere excursions were relatively small in the posterior muscle regions and large in the anterior regions. The reverse was true when the jaw was rotated contralaterally about a vertical axis. It is concluded that, due to heterogeneity in fiber and sarcomere lengths, the distribution of maximal isometric tension across the muscle at full effort is not

ISSN:0003-276X    

DOI:10.1002/ar.1092320109

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe epididymis, a post‐testicular site required for maturation and storage of spermatozoa, is actively involved in exocytic and endocytic events, two phenomena likely to depend on the integrity of the lysosomal system. To study the lysosmal system of the epididymis, five monoclonal antibodies, previously characterized as recognizing five distinct lysosomal integral membrane proteins (LIMPs 1–5), were used as molecular probes of lysosome distribution in cells lining the epithelium. Immunocytochemical localization of LIMPs, using biotin‐streptavidin immunoperoxidase methodology, was performed on frozen sections of adult rat epididymides and in cell cultures prepared from either the caput or cauda epididymis. In frozen sections, a heterogeneous distribution of the different LIMPs along the length of the epididymis was observed. For example, the distribution of LIMP 1 (35–50 K) was detected in all cells of the caput and quite dramatically in clear cells of the distal caput, corpus, and cauda epididymis, but specifically not in the principal cells of the distal caput, corpus, and cauda. In contrast, LIMP 2 (64–71 K) was present in all cells of the epidiyms, except clear cells. LIMPs 4 and 5 (93 K and 93 K) were detected in all epididymal cells, including the clear cells. Finally, whereas the regional and cell type distribution of LIMP 3 (74 K) in the epididymis was identical to that of LIMPs 4 and 5, the nature of the vesicles immunostained was distinct. In cultured cells, the general immunostaining patterns observed in vivo were maintained during the duration of the primary cultures for all five LIMPs. Our results begin to address the molecular heterogeneity of the lysosomal system along the lenght of the epidiymis, and may suggest in part a basis for underlying structural and functional characteristics of the epididymis leading to the sequential maturation

ISSN:0003-276X    

DOI:10.1002/ar.1092320110

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

年代:1992

数据来源: WILEY

摘要:

AbstractA monoclonal antibody raised against an extract from theGanglionNodosum of the chick and designated GIN2 proves to bind specifically to a subpopulation of cardiomyocytes in the embryonic human heart. In the youngest stage examined (Carnegie stage 14, i. e., 4 1/2 weeks of development) these GIN2‐expressing cells are localized in the myocardium that surrounds the foramen between the embryonic left and right ventricle. In the lesser curvature of the cardiac loop this “primary” ring occupies the lower part of the wall of the atrioventricular canal. During subsequent development, GIN2‐expressing cells continue to identify the entrance to the right ventricle, but the shape of the ring changes as a result of the tissue remodelling that underlies cardiac septation. During the initial phases of this process the staining remains recognizable as a continuous band of cells in the myocardium that surrounds the developing right portion of the atrioventricular canal, subendocardially in the developing interventricular septum and around the junction of the embryonic left ventricle with the subaortic portion of the outflow tract. During the later stages of cardiac septation, the latter part of the ring discontinues to express GIN2, while upon the completion of septation, no GIN2‐expressing cardiomyocytes can be detected anymore. The topographic distribution pattern of GIN suggests that the definitive ventricular conduction system derives from a ring of cells that initially surrounds the “primary” interventricular foramen. The results indicate that the atrioventricular bundle and bundle branches develop from GIN2‐expressing myocytes in the interventricular septum, while the “compact” atrioventricular node develops at the junction of the band of GIN2‐positive cells in the right atrioventricular junction (the right atrioventricular ring bundle) and the (“pentrating”) atrioventricular bundle. A “dead‐end tract” represents remnants of conductive tissue in the anterior part of the top of the interventricular septum. The location of the various components of the avian conduction system is topographically homologous with that of the GIN2‐ring in the human embryonic heart, indicating a phylogentically conserved origin of the

ISSN:0003-276X    

DOI:10.1002/ar.1092320111

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

年代:1992

数据来源: WILEY