摘要:

AbstractIn a recent study of the corpus epithelium in the mouse stomach, eleven cell types have been identified and enumerated (Karam and Leblond: Anat. Rec. 232:231–246, 1992). The dynamics of these cells will be examined in a series of five articles, of which this is the first. This article focuses on the proliferative ability of the cells, as measured by the labeling index in radioautographs from mice sacrificed 30 min after an intravenous injection of3H‐thymidine. Furthermore, the ultrastructure of the cells found to be proliferative was examined in the hope of finding features characteristic of stem cells.On the basis of their labeling index, the epithelial cells have been classified into four groups. The first includes three cell types which do not take up any label and accordingly are non‐dividing:parietalor oxyntic cells, cells namedpre‐parietalas they are immature cells suspected of being parietal cell precursors, and the rarecaveolatedor brush cells. The second group is composed of three cell types which are only rarely labeled and, therefore, divide only occasionally:zymogenicor chief cells,entero‐endocrinecells, and cells namedpre‐zymogeniccells as they are suspected of being zymogenic cell precursors. The third group includes two cell types which are always labeled at a low degree and, therefore, divide regularly, but at a low rate: surface mucous cells, herein calledpitcells, whose labeling index is 0.8%, and mucous neck cells, simply known asneckcells, 1.8%. The final group consists of three immature cell types with high labeling indices indicating a high rate of division:granule‐freecells, which are devoid of secretory granules and have the highest labeling index, 32.4%,prepitcells, which possess a few dense secretory granules similar to, but smaller than, those in pit cells, 24.6%, andpre‐neckcells, with a small number of secretory granules similar to, but smaller than, those in neck cells, 11.3%. These three cell types, as well as pre‐parietal cells, are rapidly renewed, with the turnover times estimated at 3.0 days for pre‐neck and pre‐parietal cells and less than 2.6 days for granule‐free and pre‐pit cells.Ultrastructural studies of granule‐free cells reveal that they may be sub‐divided into three subtypes according to their Golgi features: subtype I, which consists of undifferentiated cells in which the Golgi trans face exhibits no prosecretory vesicles; subtype II, namedpre‐pit cell precursorsbecause the Golgi trans face shows prosecretory vesicles similar to those in pre‐pit cells; and subtype III, namedpre‐neck cell precursors, whose prosecretory vesicles are similar to those in pre‐neck cells. On the other hand, pre‐parietal cells include three variants that could each arise from a different granule‐free subtype: variant I, which has no mucous secretory granules, could arise from the undifferentiated cells; variant II, which possesses dense mucous granules similar to those in pre‐pit cells, could come from pre‐pit cell precursors; and variant III, which has cored granules as in pre‐neck cells, could come from pre‐neck cell precursors.Only the undifferentiated granule‐free cells have the features expected from stem cells and, therefore, are considered to be the stem cells of the epithelium. A model based on the radioautographic and morphological data (Fig. 17) summarises the filiation of the other immature cell types as follows. The undifferentiated granule‐free cells as stem cells reproduce themselves and give rise to three other cell types: (1) the pre‐parietal cells lacking secretory granules (i.e., variant I); (2) the pre‐pit cell precursors, which mainly give rise to pre‐pit cells, but also yield the variant II pre‐parietal cells; (3) the pre‐neck cell precursors, which mainly give rise to pre‐neck cells, but also yield the variant III pre‐parietal cells. Further differentiation of these immature cell types into the other cells of the corpus epithe

ISSN:0003-276X    

DOI:10.1002/ar.1092360202

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe pit cells (or surface mucous cells) present along pit walls and gastric surface have been investigated by electron microscopy and radioautography after a pulse or continuous infusion of3H‐thymidine. For these studies, the pit region has been subdivided into four segments: three of equal length along the pit wall, respectively named low pit, mid pit and high pit, and a last one at the surface named pit top.The pit region includes an average of 37 pit cells, characterized by dense mucous granules accumulated along the apical membrane in an organelle‐free zone referred to as ectoplasm. Continuous3H‐thymidine infusion reveals that pit cells come from pre‐pit cells, which are believed to arise in the isthmus region from the undifferentiated granule‐free cells through a pre‐pit cell precursor stage. The pre‐pit cells, characterized by the presence of a few mucous secretory granules scattered in the cytoplasm, migrate outward (i.e., in the direction of the gastric lumen). When the secretory granules line up along the apical membrane in the ectoplasm, the pre‐pit cell becomes pit cell. It is estimated that 87% of pit cells differentiate from pre‐pit cells, while the remaining 13% come from their own mitoses.Observations at successive times after a3H‐thymidine pulse demonstrate that pit cells, like pre‐pit cells, migrate toward the gastric surface where they are eventually lost. The continuous3H‐thymidine infusion results indicate that this migration takes 3.1 days on the average. Cells spend almost a day in each pit wall segment. In the low pit segment, cells produce more and larger mucous secretory granules than do pre‐pit cells. In the mid and high pit segments, the number and size of the granules generally keeps on increasing, thus indicating that mucous differentiation is progressing.The secretory granules arising in the Golgi apparatus of pit wall cells are mostly spherical; they retain this shape during the few minutes taken to cross the cytoplasm and enter the apical ectoplasm. They spend about an hour in the ectoplasm, where they change to an ovoid shape as they approach the apical membrane to finally release their content by exocytosis. The mucous differentiation along the pit wall is associated with a progressive decline in the organelles: nucleoli and mitochondria decrease in size while the amount of free ribosomes diminishes.When pit cells reach the free surface, they produce fewer, smaller secretory granules and at a lower rate than in mid and high pit. Meanwhile, organelles decline further, while mitochondria tend to swell and disintegrate. Clearcut signs of degeneration appear in some of the cells. These cells find their way into the gastric lumen either by direct extrusion or indirectly after being phagocytosed by a neighbor cell which is itself eventually extruded.Thus a sequence of cells—the pit cell lineage—derived from the stationary undifferentiated granule‐free cells, includes pre‐pit cell precursors, pre‐pit cells, and pit cells, which all migrate in the direction of the gastric lumen, where pit cells are even

ISSN:0003-276X    

DOI:10.1002/ar.1092360203

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe neck cells (or mucous neck cells) present in the neck region and the zymogenic cells (or chief cells) present in the base region of the units in the mouse corpus were examined in the electron microscope (EM) and in radioautographs prepared after administration of3H‐thymidine by single or multiple injections or by continuous infusion for 1–52 days. For these studies, the neck region of the units has been subdivided into three equal segments, respectively named high neck, mid neck, and low neck, while the base region has been similarly subdivided into high base, mid base, and low base.The neck region includes an average of 12.6 neck cells, characterized in the EM by dark, mucous secretory granules that frequently exhibit a light, pepsinogenic core. Continuous3H‐thymidine infusion reveals that neck cells come from pre‐neck cells, which are believed to arise in the isthmus region from the undifferentiated granule‐free cells through a pre‐neck cell precursor stage. The pre‐neck cells, characterized by the presence of a few cored secretory granules, migrate inward (i.e., in the direction of the blind end of the units) and enter the neck region to become neck cells. It is estimated that 59% of the neck cells arise from differentiation of pre‐neck cells, whereas the other 41% are derived from their own mitoses. Neck cells migrate inward in 1–2 weeks from the high through the mid and low neck segments, while they keep on producing more and larger secretory granules and thus further differentiate as mucus‐producing cells.When neck cells reach the high base segment, they become pre‐zymogenic cells that produce secretory granules in which appear light, irregular, pepsinogenic patches which encroach on the dark mucous content. With time, the pre‐zymogenic cells, of which there are 5.0 per unit on the average, keep on producing new granules with larger and larger light patches, so that in the end the cells produce granules which are entirely filled by light, pepsinogenic material. At this stage, the cells are zymogenic cells.Zymogenic cells, which average 67.5 per unit, further migrate inward, while gradually enlarging and producing pepsinogenic granules of increasing size. In the low base segment, some zymogenic cells show signs of degeneration leading to death by either necrosis or apoptosis. While remnants of the necrotic cells appear to be released to the unit lumen, the apoptotic cells are phagocytosed by a neighboring zymogenic cell or by a connective tissue macrophage breaking through the basement membrane of the oxyntic unit.Briefly, the zymogenic cell lineage, a cell sequence initiated from the stationary undifferentiated granule‐free cells, includes pre‐neck cell pre‐cursors, pre‐neck cells, neck cells, pre‐zymogenic cells, and finally zymogenic cells, which all migrate in the direction of the unit's blind end, near which zymogenic cells

ISSN:0003-276X    

DOI:10.1002/ar.1092360204

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe life story of parietal cells has been investigated in the corpus of the mouse stomach using electron microscopy and3H‐thymidine radioautography. Parietal cells are scattered in the four regions of the unit. On the average 3.6 cells are in the pit, 6.2 in the isthmus, 5.6 in the neck, and 10.6 in the base. Parietal cells do not divide. They arise from partially differentiated pre‐parietal cells, which are believed to be derived in the isthmus from the three subtypes of granule‐free cells: undifferentiated cells, pre‐pit cell precursors, and pre‐neck cell precursors. Radioautography indicates that the transformation of granule‐free cells into pre‐parietal cells takes at least one day. The pre‐parietal cells, of which there are 0.6 per unit on the average, develop into parietal cells through three successive stages. Stage 1 is characterized by small immature cells that are identified by long apical microvilli. Stage 2 is characterized by larger cells, about one‐third the size of parietal cells, and by an incipient canaliculus and a few apical tubulovesicles. Stage 3 is characterized by the expansion of the canalicular and tubulovesicular systems as well as mitochondrial enlargement, which cause the pre‐parietal cell to gradually approach the size of, and eventually become, a parietal cell. This cell sequence mainly takes place in the isthmus, but may extend to the neck region.Continuous infusion of3H‐thymidine confirms that parietal cells originate in the isthmus and that they migrate in two directions: some go outward to the pit and the others migrate inward to the neck and eventually to the base. It has been estimated that for every six parietal cells produced per month in the isthmus, three migrate to the pit and three migrate to the neck to eventually reach the base.While almost all parietal cells in the isthmus and neck appear normal, a large proportion of those reaching the pit (21%) and base (23%) undergo gradual alteration and degeneration. After the ensuing death, parietal cells are eliminated in one of two major ways: (1) extrusion into the gastric lumen, if they appear necrotic, or (2) phagocytosis by a neighboring cell or even by an invading connective tissue macrophage, if they are apoptotic. The overall turnover time of parietal cells averages 54 days.Briefly, a sequence of cells—the parietal cell lineage—is initiated in the isthmus, where the three subtypes of granule‐free cells are presumed to give rise to pre‐parietal cells, which then differentiate into parietal cells. Half of the parietal cells migrate away in the direction of the gastric lumen and gradually degenerate as they approach the free surface, while the other half migrate in the other direction toward the unit's blind end, where they degenerate and are elimi

ISSN:0003-276X    

DOI:10.1002/ar.1092360205

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

年代:1993

数据来源: WILEY

摘要:

AbstractEntero‐endocrine cells and the rare cells named caveolated or brush cells have been examined in light microscopic radioautographs of the mouse corpus after various periods of continuous3H‐thymidine infusion. Moreover a search for immature forms and mitoses of these cells was undertaken in the electron microscope.Entero‐endocrine cells are present in the four regions of the epithelial units, but their number is low in the pit, intermediate in the isthmus and neck, and high in the base. The labeling pattern after continuous3H‐thymidine infusion indicates that these cells are produced in the isthmus from undifferentiated granule‐free cells presumed to be the stem cells of the epithelium, and may retain a limited ability to divide. A few of the newly formed entero‐endocrine cells migrate to the pit, but the majority goes to the neck and, from there, to the base where they are present in relatively high numbers.Little information is available on the dynamics of caveolated cells. Since immature forms are present in the isthmus and mature ones in the other regions, it is concluded that they arise in the isthmus and migrate away in both directions.Finally, concluding remarks are presented on the kinetics of each one of the cell lineages described in this and the four previous articles. © 1993 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092360206

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe pelvic flexure portion of the equine large colon is the proposed location of a pacemaker mechanism. This study was conducted to ascertain whether the distribution of certain putative neurotransmitters differs at the pelvic flexure compared to other sampling sites. Tissue samples were collected from the intestinal tracts of six horses. Serial sections from these samples were reacted with primary antisera specific for substance P, vasoactive intestinal polypeptide (VIP), methionine‐Enkephalin, and calcitonin gene‐related peptide (CGRP).The regional distribution of immunoreactive neuronal elements was uniform for each of the neuropeptides except VIP. Although neurons exhibiting VIP‐like immunoreactivity were abundant throughout the colon, they were somewhat more plentiful near the apex of the pelvic flexure and the left dorsal colon. These neurons may participate in the initiation and propagation of the propulsive/retropulsive contraction waves, which emanate from this location and are believed to lend a sphincter‐like capacity to the pelvic flexure. The submucosal plexus was replete with neurons with intense substance P and VIP‐like reactivity. Reactive fibers left submucosal ganglia to project to the intestinal mucosa, reflecting a possible secretogogic role for these neurons. This role may be especially important for the horse as a hindgut fermenter. There were abundant methionine‐Enkephalin and substance P‐like reactive varicosities throughout the myenteric plexus, many of which established a pericellular plexus of varicose fibers. The abundance of these varicosities, which may correlate with a high degree of neuronal integration, did not vary regionally. These data may enhance our understanding of both normal colonic peristalsis and motility disorders caused by a depletion of these neuropeptides. © 1993 W

ISSN:0003-276X    

DOI:10.1002/ar.1092360207

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe structure and function of two major joints, the humeroscapular and the squamoso‐mandibular joints in mice, are compared. The specific roles that these two joints fulfill during early postnatal period are reflected in a different cellular organization observed in them. Following maturation, when similar functional needs are stressed upon these two joints, similar homologous structures are detected in both of them. A possible conceptual explanation for these observations and their relatedness to the human equivalent joints are discussed. © 1993 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092360208

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

年代:1993

数据来源: WILEY

摘要:

AbstractChanges of lectin staining patterns in the Golgi stack during cell differentiation were examined in the ameloblasts of developing rat molar tooth germs, using HRP‐labeled lectins: Canavalia ensiformis (Con A), Griffonia simplicifolia I (GS‐I), Glycine max (SBA), Ulex europeus I (UEA‐I), Triticum vulgaris (WGA), and Arachis hypogaea (PNA). The Golgi stacks of the inner enamel epithelial cells and the presecretory ameloblasts were stained with the lectins, although the staining strength and pattern varied among the stacks with each lectin. In some cases, the reaction products for the lectins were observed in most or all saccules of the Golgi stack. In the secretory ameloblasts, however, discrete staining patterns of the Golgi stack were found for each lectin. The reaction products deposited in definite saccules of the Golgi stack of the secretory ameloblast, especially for UEA‐I and PNA which stained only the trans Golgi saccules of the stack. The reaction‐positive saccules distributed more extensively in the Golgi stack of the inner enamel epithelial cell and the presecretory ameloblast than in the secretory ameloblast. These findings suggest that the Golgi stack is not fully compartmentalized in the inner enamel epithelial cell and the presecretory ameloblast. It is proposed that, in the differentiating ameloblast, various glycosyltransferases may coexist in most saccules of the Golgi stack. © 1993 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092360209

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe trabecular bone of the secondary spongiosa of mature rats shows a coupling of bone formation to resorption. It has been clearly shown that in adult man the coupling of formation and resorption involves a site‐specific sequence of events, in which bone resorption is normally followed, at the same site, by bone formation. Whether the coupled processes of bone resorption and formation also occur at the same site in the rat is controversial. To elucidate the spatial relationship between bone formation and resorption in the rat, we compared the percentage of crenated and non‐crenated cement lines with the percentage of crenated and non‐crenated bone surfaces in the proximal tibia of adult rats aged 16 weeks to 2 years. A similar comparison was also made using bone from adult human iliac crest.We found that the trabecular bones of 16‐week‐old and 7‐month‐old rats exhibited a low percentage (7–11%) of crenated cement lines, which is opposite to the proportion (88%) we observed in human trabecular bone. In contrast, the surfaces of rat bone trabeculae showed a similar low proportion of crenated surface to human bone (rat 1.1–1.4% vs. 5% in humans). In older (2 years) rats, in which bones have ceased to grow in length, the percentage of cement lines that were crenated increased to 45%. These results imply that the major proportion of bone formation in the trabecular bone of growing rats occurs on non‐resorbed surfaces. Thus, although there is substantial evidence that bone formation is coupled to resorption in the rat, such that increased resorption is associated with increased formation, and suppression of resorption suppresses bone formation, bone formation does not necessarily occur on a previously resorbed site. This suggests that in the rat, the processes are not coupled by local release of cytokines or local cell interactions but by some other signal, such as mechanical stimulation. Since site‐specificity appears not to be crucial to the coupling of formation to resorption, the greater site‐specificity of coupling in man, and in older rats, may be attributable to a more static skeleton, which engenders a closer spatial correlation between bone formation and the resorption that induced it.

ISSN:0003-276X    

DOI:10.1002/ar.1092360210

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

年代:1993

数据来源: WILEY

摘要:

AbstractBone formation in vivo occurs via two major processes, one of which depends on pre‐existing cartilage, and the other does not. Bone morphogenetic proteins (BMPs) have been suggested to induce cartilage formation from non‐skeletogenic mesenchymal cell population, which results in osteogenesis through the endochondral sequence. In the present study we examined if BMPs could cause direct bone formation independent of pre‐existing cartilage using bovine fibrous collagen membrane (FCM) as a carrier for BMPs. Bovine metatarsal bone was extracted in 4 M guanidine HCl and BMPs were partially purified through the hydroxyapatite chromatography and the Heparin‐Sepharose CL6B chromatography. The carrier was loaded with BMPs and then implanted in Wistar rats subcutaneously. The implants were fixed together with surrounding tissue every week after implantation and processed for von Kossa stain, immunohistochemistry, and electron microscopy. The phenotypes of bone and cartilage were identified histologically and immunohistochemically using antibodies against type I and type II collagen. Cartilage and bone were independently induced by 2 weeks. The bone formed directly on the collagen substrate of FCM without pre‐existing cartilage. Calcification occurred in the carrier as well as the cartilage and bone matrix. The present study suggests that the BMPs induce osteogenesis in vivo independent of the endochondral sequence. © 1993 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092360211

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

年代:1993

数据来源: WILEY