摘要:

AbstractActin polymerization is an essential component of platelet activation. Since actin appears to polymerize at its membrane‐associated end, knowledge of the structural relationship of actin filaments to membrane is an important part of understanding that polymerization process. A membrane‐associated actincontaining cytoskeleton has been described in human platelets biochemically and is composed, at least in part, by an association between glycoprotein Ib and the actin‐binding protein originally isolated from macrophages. Many other actinassociated proteins with known sub‐membranous localization in other systems have been found in platelets, including alpha‐actinin, vinculin, and low levels of spectrin and the red cell protein Band 4.1. Because of the density of the platelet cytoplasm, the structure of the membrane‐skeleton has not yet been visualized. We have used quick freeze‐deep etch techniques to observe the sub‐membranous cytoplasm and report visualization of a periodic, submembranous filament system not before seen in the platelet. This filamentous system was more easily observed in thrombin‐stimulated platelets, but appeared to be present in resting, discoid cells as well. The filaments could also be readily observed when platelets are lysed after fixation, stained with tannic acid, and embedded for thin‐sectioning. This membrane cytoskeleton was composed of 9 nm thick filaments lying 15 nm apart, and 15 nm from the membrane. The filaments appeared to lie in parallel and to encircle the cell. Similar filaments could be seen associated with intracytoplasmic membrane systems

ISSN:0003-276X    

DOI:10.1002/ar.1092270102

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

年代:1990

数据来源: WILEY

摘要:

AbstractNine‐month‐old female rats were double‐labled with bone markers and subjected to right hindlimb immobilization or served as control for 0, 2, 10, 18, or 26 weeks. The right limb was immobilized against the abdomen, thus unloading it, while the left limb was overloaded during ambulation. Single photon absorptiometry and cancellous bone histomorphometry were performed on dissected intact femur and 20‐m̈m‐thick undecalcified specimens of the proximal tibial metaphysis. In the unloaded limb, immobilization‐induced muscle and cancellous bone loss occurred rapidly before 10 weeks and stabilized at 50% less bone mass after 18 weeks. Unloading caused a negative bone balance from a combination of elevated bone resorption and depressed bone formation. At 2, 10, and 18 weeks of immobilization, the ratios of bone resorption to bone formation surfaces were 1.6, 1.5, and 1.3, respectively; at 26 weeks, the ratio was 1. The bone loss was accompanied by poorer trabecular architecture (trabecular number decreased and trabecular separation increased), reaching the maximum at 18 weeks and stabilizing thereafter. These observations are in general agreement with Frost's postulate for mechanical effects on lamellar bone remodeling, and the findings on disuse osteoporosis in man. Therefore, the one‐legged immobilization model can be useful in studies of the mechanisms of structural adaptation to me

ISSN:0003-276X    

DOI:10.1002/ar.1092270103

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

年代:1990

数据来源: WILEY

摘要:

AbstractSheep extraocular muscles were prepared for light and electron microscopy and their proximal tendons searched for Golgi tendon organs (GTO). An extensive aponeurotic lamina on the orbital surfaces contained numerous GTO 250–1350 μm in length with characteristic terminal form and relationship with collagen. They differed from usual GTO structure in containing large fluid‐filled spaces dividing collagen into several well separated compartments and a muscle fiber entered and terminated in about one third of the receptors. The fibers, Felderstruktur in type, often penetrated deep within tendon organs, and in a few instances two or more fibers entered. This feature is shared by the rare GTO of monkey extraocular muscles.That the presence of GTO in the proximal tendons of extraocular muscles is previously unrecorded may be attributed to the practice of restricting attention to the long distal tendons. The possibility that receptors may be so placed in other species warrants further work especially in those purported to lack any rece

ISSN:0003-276X    

DOI:10.1002/ar.1092270104

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

年代:1990

数据来源: WILEY

摘要:

AbstractBasal and follicle‐stimulating hormone (FSH)‐stimulated cyclic AMP (cAMP) productions by seminiferous tubular segments from irradiated adult rats were investigated at defined stages of the epithelial cycle when specific spermatogenic cells were low in number.Seven days post‐irradiation, depletion of spermatogonia did not influence the basal cAMP production, but FSH response increased in stages II‐VIII. Seventeen days post‐irradiation when spermatocytes were low in number, there was a small increase in basal cAMP level in stages VII‐VIII and FSH‐stimulated cAMP production increased in stages VII‐XII and XIII‐I. At 38 days when pachytene spermatocytes and round spermatids (steps 1‐6) were low in number, a decreased basal cAMP production was measured in stages II‐VI and IX‐XII. FSH‐stimulated cAMP output increased in stages VII‐XII but decreased in stages II‐VI. At 52 days when all spermatids were low in number, basal cAMP levels decreased in all stages of the cycle, whereas FSH response was elevated only in stages VII‐XII.All spermatogenic cell types seem to have an effect on cAMP production by the seminiferous tubule in a stage‐specific fashion. Germ cells appear to regulate Sertoli cell FSH response in a paracrine way, and a part of cAMP may originate from spermatids stimulated by an unknown FSH‐dependent Sertoli cell factor. The FSH‐dependent fuctions may control such phenomena as spermatogonial proliferation, final maturatio

ISSN:0003-276X    

DOI:10.1002/ar.1092270105

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe testes of Lewis rats were studied at intervals from 2 weeks to 3 months after bilateral vasectomy, vasectomy followed 1 month later by vasovasostomy, or sham operations. Aims were to determine the nature of early alterations after vasectomy, and to determine whether vasovasostomy after 1 month would result in reversal of vasectomy‐induced changes. Approximately one‐fourth of the testes in the vasectomy and vasovasostomy groups displayed histological changes, which consisted mainly of depletion of germ cells. The extent of the depletion varied greatly in different seminiferous tubules. In tests altered in this way, no abnormal infiltrations of lymphocytes, macrophages, or other cells were observed in the seminiferous epithelium or in the interstitium. The rete testis and straight tubules were normal in testes with altered seminiferous epithelium. A few testes in the vasectomy and vasovasostomy groups had necrotic centers. The results suggest that depletion of germ cells occurred as a result of shedding from the seminiferous epithelium into the lumen of the tubules. A cellular immune response, such as occurs in experimental allergic orchitis in other species, did not appear to be responsible for the observed loss of germ cells. This suggests a possible role for humoral antibody in this model, since there is an association between testicular changes and serum antisperm antibodies at longer intervals after vasectomy. Testicular alterations were not reversed by performance of a vasovasostomy 1 month after vasect

ISSN:0003-276X    

DOI:10.1002/ar.1092270106

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

年代:1990

数据来源: WILEY

摘要:

AbstractVascular labelling with carbon suspension was used to identify endometrial vessels demonstrating macromolecular leakage at implantation sites in the rabbit. Extravasation was seen first in venous components of the deep endometrial stroma on the mesometrial aspect of implantation sites. Carbon labelling was apparent in such vessels at 7 d, 0 hr post coitum, (p.c.), and was attributed to gap formation between endothelial cells. Later in the implantation process, leakage was seen as microextravasations of carbon in the lateral and antimesometrial walls of implantation chambers. Here, penetration of vessels by trophoblast was apparent and membranous processes from the trophoblast projected into vessel lumina. Extravasated material (carbon, platelets) was localized to a labyrinthine system of membranes within the trophoblast, and a potential role for the labyrinth in handling of ingested plasma constituents is discussed. A similar process of trophoblastic penetration of vessels occurred on the mesometrial aspect of implantation sites several hours later. Systemic administration of the anti‐inflammatory agent indomethacin blocked vascular leakage due to endothelial gap formation but had little or no effect on trophoblast knob penetration of vessels. This observation may explain the results of previous studies in which treatment with anti‐inflammatory agents reduced, but could not inhibit completely, the vascular permeability changes at implantation si

ISSN:0003-276X    

DOI:10.1002/ar.1092270107

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe stage‐dependent action of follicle‐stimulating hormone (FSH) in the rat seminiferous epithelium was investigated in microdissected 1 mm tubule segments, where the precise stage of the cycle was identified by a rapid screening method of live cell squash preparations. For distinction of stages I and II and the substages of VII, new criteria were used. The step 16 spermatids with rapid assembly of outer dense fibers leading to marked increase of flagellar thickness were used for distinction of stages I and II. The form and density of the cytoplasmic lobes of step 19 spermatids was used for recognition of substages of VII.Highest basal production of cyclic AMP (cAMP, measured by radioimmunoassay) was found in stage II of the cycle and stages XIV‐I‐VI had higher values than did stages VII‐XIII. A decline occurred during stage VII and an increase at stage XIV. When stimulated with FSH, highest cAMP secretion was found in stage IV of the cycle; again, stages XIV‐I‐VI had higher values than did other stages. A small but significant (P<.01) stimulation was found at substage VIId. FSH‐stimulated and basal cAMP productions of different stages were compared, highest values were found at stages IV and XIII, and lowest, at stages VIIa‐c and IX of the cycle.Since the FSH‐dependent cAMP production is confined to Sertoli cells, and the number of these cells is constent per unit length of seminiferous tubules, the Sertoli cells are obviously under a stage‐specific paracrine control by the surrounding spermatogenic cells. Specific steps in cell differentiation, such as spermatogonial proliferation, final maturation of the spermatids (stages I‐VII), onset of meiosis (substage VIId), and completion of meiotic divisons (stage XIV) may be invol

ISSN:0003-276X    

DOI:10.1002/ar.1092270108

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn antibody to a protein produced by Clara cells in adult Syrian golden hamsters has been used to monitor the development and functional differentiation of secretory cells in the conducting airway epithelium of this species. Lungs from fetal and neonatal hamsters at gestational day 11 and at intervals up to and including 3.5 weeks of age (as well as adults) were studied. The earliest time this Clara cell protein could be identified by immunoperoxidase labeling in the fetal conducting airways was at gestational day 15. On this day, labeling was observed in a few secretory cells lining the trachea, in many lining the lobar bronchi, and in virtually all secretory cells lining the bronchioles. Ciliated cells and endocrine cells were not labeled. Granules first appeared within the apical cytoplasm of the secretory cells on gestational day 15 at all airway levels. To identify the exact subcellular location of this protein, an ultrastructural labeling procedure using protein A gold was employed. The gold particles labeled only electron‐dense granules within the secretory cells, indicating that they represent the specific site of this protein. Since secretory cells in the most distal conducting airways began to produce this protein on the same day in development as cells in the larger airways, including the trachea, this expression of functional maturation occurs simultaneously throughout the conducting respiratory tree rather than proceeding sequentially in a cranial to caudal direction. Consequently, secretory cells lining the smaller conducting airways mature more rapidly than those lining the larger airway

ISSN:0003-276X    

DOI:10.1002/ar.1092270109

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

年代:1990

数据来源: WILEY

摘要:

AbstractBy using an immunoperoxidase method with antiserotonin antiserum, the distribution of serotonin‐immunoreactive cells in the carotid body region was investigated in chickens. The thyroid gland, cranial and caudal parathyroid glands, carotid body, and ultimobranchial gland of chickens were located along the common carotid artery as a continuous series and were supplied with branches arising from the artery. Almost all chief cells of the chick carotid bodies were immunoreactive for serotonin. Furthermore, numerous serotonin‐immunoreactive cells were widely distributed in the adventitial connective tissue around those arteries that issued from the common carotid artery to supply each endocrine organ, i.e., the carotid body artery, the esophagotracheobronchial artery, the ascending esophageal artery, and the inferior thyroid artery. These arteries usually arose by one trunk from the lateral aspect of the middle portion of the common carotid artery. The serotonin cells were most numerous around the carotid body artery and were dispersed along the whole length of the artery. In addition, they were detected around the common trunk of each artery and the roots of the ascending esophageal artery, the inferior thyroid artery, and the esophagotracheobronchial artery. The serotonin cells were also distributed in the tunica media of the common carotid artery. In that place, they were concentrated around the origin of the common trunk of each artery and were scattered below the origin along the longitudinal axis and on the opposite side of the origin. The serotonin‐immunoreactive cells distributed around and in the arteries may be involved in the control of blood flow and may have chemoreceptive prope

ISSN:0003-276X    

DOI:10.1002/ar.1092270110

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe pituitary intermediate lobe, a source of pro‐opiomelanocortin (POMC) peptides, was examined with light and electron microscopic techniques in Sprague‐Dawley rats aged 5–18 months and Zucker rats aged 18 months. Cysts were common in the intermediate lobe in the Zucker animals, a finding also noted in human pituitary glands by other investigations. The nuclear envelopes were often indented in cells of aging rats, while those of young animals were generally smooth. Lipid droplets and lysosomes, rarely seen in tissue from young animals, were frequently observed in endocrine cells of older rats. Most cells had an abundance of secretory granules, suggestive of enhanced storage of peptides in the cytoplasm. Nerve terminals which were present among endocrine cells contained myelin figures in some of the old rats, and may indicate degenerative changes, while other terminals appeared normal. These morphologic findings suggest that the aging phenomena in intermediate lobe tissue have characteristics in common with nervous tissue, and may also reflect a diminished inhibitory neuroregul

ISSN:0003-276X    

DOI:10.1002/ar.1092270111

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

年代:1990

数据来源: WILEY