摘要:

AbstractInformation regarding the presence of the glyoxylate cycle in chick liver was sought. This metabolic pathway has long been thought to be absent from vertebrate tissues. Previous studies in other tissues have shown that, when present, this pathway is sensitive to vitamin‐D. Thus, the effect of long‐term vitamin‐D deficiency and subsequent vitamin‐D replacement on liver structure was studied by light microscopy. In addition, specific biochemical assays for the presence of glyoxylate cycle enzymes were performed. Light microscopy of lipid extracted tissues, light microscopic histochemistry, and quantitative histochemistry showed that the hepatocytes from vitamin‐D‐deficient animals contained primarily lipid. Hepatocytes from normal and vitamin‐D‐replete livers contained primarily carbohydrate as judged by their staining with periodic acid‐Schiff (PAS). Also, malate synthase positive peroxisomes were seen in hepatocytes from normal and vitamin‐D‐treated chicks. Structures positive for this glyoxylate cycle enzyme were rarely seen in the hepatocytes from vitamin‐D‐deficient animals. Biochemical analyses showed the presence of the two unique glyoxylate cycle enzymes, isocitrate lyase and malate synthase, in chick hepatocytes. The activity of these enzymes was markedly increased in the vitamin‐D‐replete livers. In addition, chick hepatocytes demonstrated the capacity to oxidize fatty acid in the presence of cyanide. This activity, which is characteristic of peroxisomal B‐oxidation rather than mitochondrial, was stimulated by vitamin‐D treatment. Lastly, incubation of chick liver in the presence of a fatty acid substrate (palmitate) led to higher tissue glycogen content. The latter was further increased in liver from vitamin‐D‐replete animals. These data show the presence of glyoxylate cycle enzymes in a higher vertebrate and indicate that this tissue is endowed with the capa

ISSN:0003-276X    

DOI:10.1002/ar.1092270302

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

年代:1990

数据来源: WILEY

摘要:

AbstractIsolated rabbit ventricular cardiac myocytes adapt readily to primary culture. As the myocytes spread and flatten over the culture substratum, the myofibrillar apparatus retains a “rod‐like” orientation. Development of contractile activity is crucial in the maintenace of the integrity of the myofibrillar apparatus during prolonged culture. Myocytes that fail to beat display morphological indications of atrophy; conversely, myocytes that commence beating show no such morphological signs of myofibrillar disorganization. The subcellular organization of other elements of the contractile apparatus, including the transverse tubular system and the sarcoplasmic reticulum, retain their structural relationship with the myofibrils in beating myocytes but not in quiescent cells. Cultured adult myocytes represent an important model to investigate the influence of mechanical factors on the organization and maintenance of the adult cardiac phen

ISSN:0003-276X    

DOI:10.1002/ar.1092270303

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

年代:1990

数据来源: WILEY

摘要:

AbstractHuman trabecular bone that encloses the bone marrow (BM) is covered by a single layer of thin, sometimes inconspicuous, flat, elongated (spindle‐shaped) endothelium‐like cells with a round or oval nucleus. These “bone lining” cells, or endosteal cells (EC), form a continuous membrane (endosteum) over the trabecular bone surfaces. In most cases, the composition and thickness of these cells do not vary unless the cells are in intimate contact with hematopoietic tissue. In that instance, they are seen as a single layer adjacent to hematopoietic tissue or as a zone of tightly packed or loosely arranged mononuclear (hematopoietic) cells, some apparently originating from the endosteum. In a reparative process, such as following BM harvest, during which bony trabeculae (BT) are mechanically fratured, these cells are seen giving rise to osteoprogenitor (osteoblasts and osteoclasts) cells. Occassionally, the EC appear similar to BM stromal cells (morphologically and by their association with collagen/reticulin fibers) and are best seen at or near the BT that are cut tangentially. Short processes extending from the EC towards the underlying osteocytes have also been observed, suggesting that a channel of communication exists between them and osteocytes. Our observations, coupled with the experimental findings of others (i.e., that hematopoietic stem cells are concentrated near the endosteum, that cells responsible for BM and stroma regeneration are derived from the endosteal layer, and that high concentrations of hematopoietic colony‐stimulating factors are produced there), indicate that, in addition to functioning as a simple membranous covering layer for BT, the endosteum helps to support osteocytes and maintains mineral homestasis. In addition, these cells contribute to the hematopoietic microenvironment and thereby play a role in regulating hematopoiesis. We also believe that the EC are reminiscent of embryonal‐stage, undifferentiated mesenchyme, which under appropriate regulatory influence, can modulate and transform into cells with hematopoietic potential, stromal cells and osteoproge

ISSN:0003-276X    

DOI:10.1002/ar.1092270304

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

年代:1990

数据来源: WILEY

摘要:

AbstractType X collagen is a prominent component of the extracellular matrix in cartilage destined to mineralize during endochondral ossification, yet its role is only now being determined. As a prelude to determining what, if any, alterations occur in the distribution of type X collagen in growth plates of poultry with rickets or tibial dyschondroplasia, our objective in the current study was to determine the distribution of type X collagen in the proximal tibiotarsi of broiler chickens and turkeys from 1 day of age through physeal closure. Proximal tibiotarsi from five male broiler chickens, five female broiler chickens and five male turkeys were collected at 1, 7, 14, 28, 56, and 98 days of age and processed for immunohistochemistry; a monoclonal antibody for type X collagen was used to demonstrate type X collagen distribution.Our findings indicate that type X collagen is produced in the prehypertrophic and early hypertrophic zones of the avian growth plate and is incorporated into the extracellular matrix in these zones. Furthermore, intracellular type X collagen is markedly decreased in more mature areas of the growth plate, although type X collagen is markedly decreased in more mature areas of the growth plate, although type X collagen remains a prominent component of the extracellular matrix unitl the matrix is completely resorbed. In addition, the distribution of type X collagen is similar in the proximal tibiotarsi of broiler chickens and turkeys at comparable stages of endochondral ossification and distribution of type X collagen in the secondary center of ossification parallels that in the physis.

ISSN:0003-276X    

DOI:10.1002/ar.1092270305

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

年代:1990

数据来源: WILEY

摘要:

AbstractIntrafusal muscle fibers of the extraocular muscles (EOMs) of the sheep, cow, and pig were studied histochemically and immunohistochemically. In sheep and cow spindles, three intrafusal fiber types, namely the bag1, bag2, and chain fibers, were identified by a combination of standard histochemical methods and immunohistochemical staining with antibodies selective for slow‐tonic (antitonic ALD) and slow twitch (anti‐I BA‐D5) myosin. The bag1and bag2fibers appeared immunologically different on the basis of their differential reactivity with the two antisera. Anti‐tonic ALD preferentially stained the bag1fibers, whereas anti‐I BA‐D5 labeled the bag2fibers. Chain fibers did not react with either antisera. In the pig EOM spindles, in general, one bag and some chain intrafusal fibers were identified. The bag fiber was labeled by anti‐tonic ALD, but it did not react with the anti‐I BA‐D5. These findings point to the existence in pig EOM spindles of only one bag fiber antigenically similar to the bag1fiber of the other

ISSN:0003-276X    

DOI:10.1002/ar.1092270306

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

年代:1990

数据来源: WILEY

摘要:

AbstractUltrastructural and autoradiographic observations of cultured chick hepatocytes under the following conditins are described: Induction of glycogen synthesis with glucose alone and glucose plus insulin, and glucagon‐induced glucogen glucogen breakdown. Profiles of hepatocytes cultured in medium containig 10 mM glucose showed typical cellular organelles and occasionally a few glycogen granules. After incubation of hepatocytes with3H‐glucose, silver grains were found over these sparse glycogen granules, indicating a low level of glycogen synthesis by a few cells. After addition of 75 mM glucose for 1 hr about 3% of the profiles of cells showed glycogen, and by 24 hr half of the hepatocytes had glycogen. Addition ofinsulin plus glucose induced glycogen synthesis in 82% of the cells after 6 hr. and by 24 hr almost every cellular profile showed glyocgen particles. Morphologically, glycogen accumulation was similar whether the cells were stimulated by high glucose or by glucose plus insulin: glycogen granules appeared in restricted regions of the cytoplasm, which were rich in smooth endoplasmic reticulum (SER), and peroxisomes were found close to the newly deposited glycogen particles. At maximum glycogen accumulation the association of SER and peroxisomes with glycogen was less obvious. Glycogenolysis induced by incubation of glycogen‐rich hepatocytes with glucagon resulted in proliferation of SER in the glycogen regions of the cells. These observations are compatible with the concept of regions in the hepatocyte cytoplasm specialized for glycogen metabolism. Possible roles for SER and peroxisomes found near glycogen particles and other organelles in hepatic glycogen metabolism are disc

ISSN:0003-276X    

DOI:10.1002/ar.1092270307

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

年代:1990

数据来源: WILEY

摘要:

AbstractImmunoreactive follicle‐stimulating hormone (IR‐FSH) is detected in sections of formalin‐fixed and paraffin‐embedded gastric mucosal tissue of normal men, using the immunoperoxidase staining technique and specific antisera to hFSH (NIDDK, NIH). Positive staining for IR‐FSH was detected in the parietal cells lining the gastric glands of the intermediate zone. The staining was intracytoplasmic and distributed throughout the cytoplasm. IR‐FSH was also found to be present in the basal part of the foveolar epithelium. Stromal tissue and nuclei were devod of the stain. The zymogen cells in the deeper region of the mucosa did not show any detectable staining for IR‐FSH. The presence of IR‐FSH in gastric mucosa was also detected by radioimmunoassay.Gel chromatography of the gastric tissue extract showed a single peak of FSH immunoreactivity that coeluted with the125I‐labled highly purified FSH preparation (NIDDK, NIH). Furthermore, the FSH in the pituitary tissue extract had a chromatographic profile similar to that of IR‐FSH from gastric tissue, and125I‐FSH labeled highly purified FSH, indicating a close resemblance in their molecular sizes. These results demonstrate that IR‐FSH is present in the normal human gastric mucosa. The role of this regulatory petpide in gastric tissue, if any, n

ISSN:0003-276X    

DOI:10.1002/ar.1092270308

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

年代:1990

数据来源: WILEY

摘要:

AbstractAutoradiographs were prepared from lungs of a newborn Syrian golden hamster exposed continuously to3H‐thymidine for the final 4.5 days of a normal 16 day gestation. Silver grain were counted over nuclei of 1,298 smallgranule endocrine cells in 165 neuroepithelial bodies (NEBs) in the right upper lobe and along the left axial bronchus, wherenodalNEBs occured at branch points andinternodalNEBs in the airway between them. Nuclei of 1,005 nonendocrine airway epithelial cells were counted next to the NEBs. Label was distributed differently in the two populations: All nonendocrine cells were labeled, whereas many endocrine cells were not. In NEBs of the right upper lobe, total label (net grains/nuclear profile) averaged only 23% of that in nonendocrine cells. Along the left axial bronchus, mean label in nonendocrine cells and internodal NEBs rose 10‐fold between the hilum and the periphery. Increase for both populations were linear and parallel, but total label in the NEBs was consistently lower than that in the surrounding epithelium by 15 grains/nuclear profile. Nodal NEBs were more lightly labeled than those of the internodes, consistent with their earlier formation. A few very heavily labeled small‐granule cells (0.9%) occurred singly in the periphery of large, otherwise lightly labled NEBs. Statistically these belonged to the labeling distribution of nearby nonendocrine cells. In contrast to NEBs, neurons in 10 bronchial ganglia of the right lung were virtually unlabeled. These aris from vagal neural crest and seem to comprise an entirely distinct population. We conclude that NEBs belong intrinsically to pulmonary endoderm, not neural crest. During fetal life each develops from a cell or cells programmed to stop dividing well ahead of other elements in the epithelium. Their formation is linked closely to early proliferation of the bronchial tree and is an integral part of growth and differentiation of the airway lining. After a wave of initial formation has passed down the airway, small‐granule cells are added slowly to mature NEBs, probably through diffierentiation from adjoining airway epithelial cells—a potential mechanism for cell replacement in a

ISSN:0003-276X    

DOI:10.1002/ar.1092270309

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

年代:1990

数据来源: WILEY

摘要:

AbstractEndothelial cell division in the metaphyseal capillaries of growing rats was studied by serial sectioning and electron microscopic examination. The endothelium of these capillary sprouts forms a continuous attenuated saqmous lining. During endochodral bone formation these growing vessels possess a region of endothelial cell division which is located behind the sprout tip in an area where the microvascular wall consists of an endothelium and a discontinuous layer of perivascular cells. Examination of this region has shown the presence of junctional attachments between daughter cells even before cell separation is complete. Thus, the integrity of the vascular wall is not compromised during cell division. Junctional complexes with adjacent endothelial cells are also formed along the cleavage plane prior to the completion of cytokinesis. Numerous microvilli from both the daughter cells and adjacent endothelial cells often make contact and form junctions with the plasma membrane of the dividing cells. A model for endothelial junction formation between daughter cells during cytokinesis and the role that microvilli play in the process is proposed.

ISSN:0003-276X    

DOI:10.1002/ar.1092270310

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

年代:1990

数据来源: WILEY

摘要:

AbstractFemale mice bearing secondary oocytes or preimplantation embryos of various stages were injected with Hoechst 33342 (H 33342), either intravenously or intraperitoneally and sacrificed at various intervals afterward. The dye penetrated through the wall of oviduct and stained the nuclei of its cells as well as mitotic chromosomes of secondary oocytes, the pronuclei of one‐cell embryos, and nuclei of blastomeres and polar bodies. The nuclear fluorescene was observed in living cells flushed out of the oviduct as well as in those fixed in oviduct, embedded in paraffin, and sectioned. H 33342 injected in a dose of 10 μg/g of body weight failed to interfere with preimplantation development of stained embryos as indicated by the number of blastocysts per mouse and number of cells per blastocy

ISSN:0003-276X    

DOI:10.1002/ar.1092270311

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

年代:1990

数据来源: WILEY