摘要:

AbstractAmelogenesis in the cat has been suggested to closely resemble enamel formation in human teeth. In order to further characterize the sequence of events leading to enamel formation in the cat, the expression and distribution of enamel proteins throughout amelogenisis were examined by postembedding immunocytochemistry using an antibody to mouse amelogenins and the high resolution protein A‐gold technique. Enamel proteins were first immunodetected in ameloblasts and in the extracellular matrix during the presecretory stage. Secretory stage ameloblasts showed the most intense cellular reactivity. In these cells, protein synthetic organelles, secretory granules, and large lysosome‐like structures were all intensely labeled. Extracellulary, numerous gold particles were observed over enamel and over patches of material found at the baso‐lateral surfaces of these ameloblasts. During the early maturation stage, the protein synthetic organelles and secretory granules of ameloblasts still showed some immunoreactivity, although the most conspicuous labeling at this later stage was found over enamel and over material present amoung the extensive apical membrane infoldings of ruffle‐ended ameloblasts. Qualitative analysis of lysosome‐like elements in ameloblasts suggested that their frequency and immunoreactivity in the maturation stage were relatively lower than in the secretory stage, where some groups of cells often showed numerous large labeled structures. The enamel matrix was intensely labeled at all stages; however, cervical‐occlusal and surface‐depth gradients were readily apparent by conventional staining and by quantitative analysis of immunolabeling in the late secretory and early maturation stages. These data suggest that the cellular and extracellular distribution of enamel proteins in the cat is generally similar to that reported in other species, although some particularities were observed, perhaps reflecting variation in the timing of developmental parameters. © 1992 W

ISSN:0003-276X    

DOI:10.1002/ar.1092330302

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

年代:1992

数据来源: WILEY

摘要:

AbstractLiterature referring to the conflicting results of investigations into the possible existence and composition of the lamina splendens is reviewed. Two hundred micrometer thick histological sections from 80 human cadaveric lower lumbar zygapophyseal joint articular cartilages were examined by ordinary light and darkfield microscopy. The findings illustrate what appears to be an acellular surface lamina on the opposing cartilaginous surfaces. No speculation is made regarding the possible physiological significance of the lamina based on this anatomical study. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092330303

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe present paper presents ultrastructural details of chondrogenesis of Meckel's cartilage and of ossification of its associated peri‐ and parachondral bones in a teleost fish, the cichlidHemichromis bimaculatus. We have distinguished four stages during chondrogenesis, each of which is characterized by specific cellular and matrix features: blastema, primordium, differentiated cartilage and cartilage surrounded by perichondral bone. The blastema is characterized by prechondroblasts and the lack of cartilage matrix; the primordium by chondroblasts and the onset of secretion of matrix of fibrillar and granular nature; differentiated cartilage is characterized by chondrocytes and larger amounts of typical hyaline cartilage matrix. Once perichondral bone is laid down, the chondrocytes show degenerative features but not true hypertrophy. Differentiation of the cartilage cells is attended with cytoplasmic changes indicative of an increasing secretory activity. There is a regional calcification of the cartilage matrix by fusion of calcospherites. Chondrogenesis of the symphyseal area is continuous with that of the rami but starts slightly later. Formation of perichondral bone at the cartilage surface is attended with the deposition of a transitional zone apparently containing a mixture of the two matrices. The role of the perichondral cells is discussed and it is proposed that they may contribute to the formation of the two matrices. The transitional zone may then result either from a diffusion process or from the simultaneous deposition of elements of the two matrices. Growth of the cartilage is argued to be largely the result of matrix secretion, except in the symphyseal area where appositional growth probably occurs until the region is completely covered by perichondral bone. This paper provides a basis for further studies on the developmental interactions between cartilage, bone and teeth during mandibular development in cichlids. © 1992 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092330304

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe studied soleus (SOL), plantaris (PLN), and gastrocnemius (GST) muscles to determine whether early cast removal minimizes muscle atrophy or permits recovery from atrophy after tendon repair. After right tendocalcaneus (Achilles tendon) was transected and repaired, rabbit right hindlimbs were immobilized with the ankle plantar flexed and the knee flexed to 90°, Rabbits were maintained in the cast and sacrificed at 5, 15, or 21 days postoperatively or the cast was removed on day 5 and the animals sacrificed at day 15 or 21. SOL, PLN, and GST muscles of both limbs were removed and weights, mean fiber cross‐sectional area, and percentage of Type I fibers and increased the percentage of Type IIc fibers. Ten days after cast removal (i. e., postoperative day 15), SOL muscle atrophy and fiber composition did not differ significantly from continuously immobilized controls. However, 16 days after cast removal (i. e., postoperative day 21), SOL muscle fiber cross‐sectional area and fiber composition were near normal, differing significantly from continuously casted controls. At each of the time intervals studied, PLN (containing many glycolytic fibers) did not atrophy as much as SOL (containing mainly oxidative fibers). Our results indicate that (1) early cast removal prevents atrophy of PLN glycolytic fibers, but not oxidative fibers in either PLN or SOL, and (2) early cast removal promotes recovery from atrophy of both oxidative and glycolytic fibers. In spite of the many differences between rabbits and humans, these findings suggest that, although early cast removal may not prevent oxidative muscle fiber atrophy after postoperative immobilization, it may facilitate recovery from atrophy. © 1992 Wiley‐Li

ISSN:0003-276X    

DOI:10.1002/ar.1092330305

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper reports adsorptive endocytosis of exogenous proteins by the trophotaenial absorptive cells (TACs) in the viviparous goodeid teleost,Ameca splendens. In vitro incubations were performed with gold conjugated to bovine serum albumin (Au‐BSA), human transferrin (Au‐HTf), fetuin (Au‐Fet), and asialofetuin (Au‐ASFet). Localization of gold label on the TAC surface was nearly exclusive to patches of an amorphous coat associated with part of the intermicrovillous plasma membrane. On addition of excess BSA, HTf, Fet, or ASFet to incubation media containing, respectively, Au‐BSA, Au‐HTf, Au‐Fet, or AuASFet, the density of gold particles adsorbed on the TAC surface decreased drastically. Moreover, attachment of the four protein‐gold complexes to the same plasma membrane sites was suggested by reciprocal inhibitory effects. Further proteins such as hemoglobin, myoglobin, and cytochrome c were as well potent inhibitors of Au‐BSA and Au‐HTf binding and uptake.Binding to TACs of native BSA or HTf was visualized by immunogold labeling. The interactions between proteins and binding sites required both the presence of Ca2+and appropriate pH>6.6. Analyses of the concentration‐dependent BSA and HTf binding curves, plotted from morphometric data, resulted in apparent dissociation constants, Kds, of approximately 5 × 10−7M and 4 × 10−7M, respectively.Following binding at the TAC surface and internalization via clathrin‐coated pits and vesicles the several ligands were routed along the lysosomal pathway with transit through the endosomal compartment. Prolonged incubation periods led to massive intracellular accumulation of tracer proteins. The effects of NH4Cl (10 mM) treatment on TACs included enormous cytoplasmic vacuolation, a reversible loss of protein binding sites on the plasma membrane, and a block in the transport of protein‐gold complexes to ly

ISSN:0003-276X    

DOI:10.1002/ar.1092330306

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe luminal surfaces of epithelial cells in the fimbriae, ampulla, isthmus, and utero‐tubal junction of the oviducts of the prolific Chinese Meishan pig at follicular and luteal phases of the estrous cycle were examined by scanning electron microscopy. Marked cyclic changes were observed on the surfaces of cells in the fimbriae and ampulla, but little change was found in the isthmus and at the utero‐tubal junction. The cells of the fimbrial epithelium in the follicular phase were densely ciliated, and the cilia partially concealed the bulbous processes of the secretory cells. In the luteal phase, the secretory cells predominated in the epithelium, and most of the ciliated cells were hidden by the processes of the secretory cells. The ampullar epithelium showed similar changes, but to a lesser extent. In the isthmus and at the utero‐tubal junction, the secretory cells had many microvilli on their bulbous processes at the follicular phase, but they were flat and the microvilli were fewer in number and shorter in length during the luteal phase. Conspicuous solitary cilia protruded from the surfaces of secretory cells in the fimbriae and ampulla during the luteal phase. These results demonstrate that there are regional variations in the cyclic changes associated with the oviductal epithelial cells of the Chinese Meishan pig. © 1992 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092330307

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe location of stem cells and the direction of colonocyte migration in the normal rat colonic crypt were investivageted using a serial bromodeoxyuridine (BrdU) and [3H]thymidine labeling protocol. The results demonstrate that in the distal colon the stem cells are located in the crypt base and that cells migrate up toward the luminal surface. In the proximal colon, however, the stem cells are located in the midcrypt, and the colonocytes migrate in two directions, up toward the luminal surface and down toward the crypt base. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092330308

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

年代:1992

数据来源: WILEY

摘要:

AbstractEffects of colony‐stimulating factors M‐CSF, GM‐CSF, G‐CSF, and IL‐3 were assessed on cells of macrophage lineage present in organ cultured 14‐day prenatal rat lungs. Treatment groups were compared between one another and against control lungs grown on standard medium containing 40% fetal bovine serum without added factors, where a monoculture of macrophages rapidly develops from precursors present at explantation, leading to appearance of a large mature population on the pleural surface outside the lungs. Studies were carried out in living cultures and by light and electron microscopy using peroxidase‐coupled isolectin B4ofGriffonia simplicifoliato identify macrophages and their precursors. In the first experiment, 14‐day prenatal lung explants (14+0 days) containingmacrophage precursorsbut not matured cells were exposed to individual CSFs for 7 days in an attempt to determine whether precursors are committed irrevocably to the macrophage line or can be altered by exposure to factors promoting significant granulocyte development. In succeeding experiments, 4‐ and 7‐day‐old cultures (14+4, 14+7 days) containingmatured macrophageswere targeted to see whether macrophage survival can be extended beyond expectations in controls and whether mitotic activity is stimulated. Recombinant CSFs were used at dosage levels known to promote colony formation in vitro (200–1,000 CFU/ml).Cultures exposed from prenatal day 14to M‐, GM‐, G‐CSF, or IL‐3 yielded a monoculture of macrophages without exception. Populations developed in the presence of M‐ or GM‐CSF were much larger than in controls or cultures grown with the other blood factors. GM‐CSF‐exposed cultures produced by far the largest macrophages, among them many multinucleate giant cells. Macrophages developed in the presence of G‐CSF were also significantly larger than controls.Growth of the mature macrophage populationwas greatly stimulated by exposure to M‐CSF or GM‐CSF but not by IL‐3 or G‐CSF. Mitotic figures were noted in the coronas of emerged cells surrounding stimulated cultures, compared to none in the controls. Ultrastructurally, macrophages stimulated by M‐CSF retained a mature appearance like macrophages in control, IL‐3, and G‐CSF treatment groups, whereas many in the GM‐CSF group became less differentiated. As tolong‐term survival, a single 14‐day explant was grown for 8 days on standard medium (the equivalent date for birth), then placed in a soft agar medium containing M‐CSF. Supplemented irregularly by M‐CSF and GM‐CSF, the culture remained viable until fixed on the 137th “postnatal” day and retained a small population of macrophages. Conclusions: (1) the macrophage lineage from embryonic rat lungs can be manipulated in culture; (2) macrophage precursors in these lungs seem committed to the macrophage line; (3) replication of both immature and mature macrophages is stimulated by M‐CSF and GM‐CSF; (4) with M‐CSF, however, retention of mature characteristics and longevity are favored, whereas with GM‐CSF maturity

ISSN:0003-276X    

DOI:10.1002/ar.1092330309

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

年代:1992

数据来源: WILEY

摘要:

AbstractCoronary artery anatomy was studied in 16 shark species belonging to 9 families of the orders Hexanchiformes, Squaliformes, and Carcharhiniformes. The study included 101 specimens and used an injection‐corrosion technique that obtained internal casts of the main trunks and coronary arterial branches.The results showed 2 main patterns of coronary arterial arrangement: the dorsoventral coronary trunk pattern, shared by lamnoid and advanced carcharhinoid sharks, and the lateral coronary trunk pattern, shown by hexanchoid and squaloid sharks.ScyliorhinusandGaleushad intermediate arrangements of their vessels. © 1992 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092330310

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe origin and morphological identity of hematopoietic progenitor cells, as well as their precursor, the pleuripotential hematopoietic stem cell (HSC), has not been established. Our studies of 2 μm sectioned undecalcified plastic‐embedded bone marrow (BM) from healthy human fetuses; normal adults; patients with acute myeloblastic leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic granulocytic leukemia (CGL) in various stages (chronic, accelerated, acute blastic phase, and after autografting); and patients recovering from therapy‐induced marrow hypoplasia suggest that proliferative hematopoietic zones exist near the endosteum (endosteal marrow) and the vascular endothelium (capillary and sinus‐lining endothelium) and a maturational zone distal to these regions. In some of these areas, morphologically recognizable hematopoietic cells were seen and interpreted as emerging and maturing in a sequential progression, suggesting an origin from the endosteal or endothelial progenitors. In other loci, early hematopoietic cells were seen in close contact with the endosteal or vascular endothelial (VE) cells. This latter relationship suggested that these areas of cellular contact were important and represented sites of cell to cell interaction that may be associated with the liberation of growth factors by endosteal and endothelial cells and their action on hematopoietic progenitor cells. Following treatmentinduced hypoplasia, the endosteal and VE cells were seen to modulate, transform, and migrate into the surrounding empty and edematous marrow space as fibroblasts. Later, as hemopoietic regeneration began, clusters of regenerating hematopoietic cells were seen adjacent to bone trabecule (BT) and near the vascular endothelium. We postulate that endosteal and VE cells are the equivalent of embryonal‐stage, undifferentiated mesenchyme and, under the appropriate regulatory influence, are capable of modulation and transformation (differentiation) into stromal (fibroblast‐like) cells and precursors of hematopoietic cells in normal (physiologic) and stressed (pathologic) conditions. Recently, human endothelial cells have been shown to express a large number of cell surface antigens in common with hematopoietic (myeloid and lymphoid) cells. It is also possible that, in some situations, the VE cells act to establish a microenvironment and liberate growth factor (s), enabling pleuripotential and progenitor cell differentiation into mature hematopoietic cells adjacent to the vascular endothelium. Indeed, vascular endothelium has been shown to elaborate growth factors that participate in normal hematopoiesis. © 1992 Wile

ISSN:0003-276X    

DOI:10.1002/ar.1092330311

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

年代:1992

数据来源: WILEY