摘要:

AbstractWe have studied the shape and size distribution of membrane‐bound polysomes in somatotropes and mammotropes, which are the sources, respectively, of growth hormone and of prolactin in the rat pituitary. The observations were made in conventional electron micrographs of these cellsin situ, where occasional surface oren faceviews of the rough endoplasmic reticulum allow the polysomes to be seen as rows of ribosomes arranged in distinctive patterns on the membranes. It is possible by this means to characterize the shape and number of ribosomes for the total population of bound polysomes in the respective cell types.The great majority of membrane‐bound polysomes in these two cell types (81% in somatotropes, 78% in mammotropes) have an approximately circular shape and contain an average of 6.8 (somatotropes) or 6.5 (mammotropes) ribosomes, which is an appropriate size for translation of the polypeptide hormones produced by these cells. About 17% of the membrane‐bound polysomes in somatotropes and 20% in mammotropes have a spiral shape, resembling somewhat the letter “G,” and contain about eight to nine ribosomes in both cell types.The preponderance of circular polysomes on the rough endoplasmic reticulum of somatotropes and mammotropes suggests the possibility that ribosomes (or the 40S ribosomal subunit) may recycle on the polysome after the translation of growth hormone or of

ISSN:0002-9106    

DOI:10.1002/aja.1001780102

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

年代:1987

数据来源: WILEY

摘要:

AbstractSeveral glycoconjugates are thought to bind spermatozoa as they pass through reproductive ducts. Paraffin sections of testis, ductuli efferentes, epididymis, and vas deferens of male mice were stained with ten different lectin‐horseradish peroxidase conjugates to localize possible sites of synthesis and secretion of such glycoconjugates, based on the carbohydrate moieties in their constituent oligosaccharide side chains. Principal (columnar) cells lining the efferent ducts, germinal epithelium, and developing and maturing spermatozoa were examined with light microscopy. Staining of the Golgi and apical zones of cells was interpreted as evidence for synthesis and secretion of glycoconjugates. Principal cells synthesized and secreted glycoconjugates with sugar moieties as follows: sialic acid, all regions of the efferent ducts examined; the terminal disaccharide D‐galactose‐ (β1 → 3) ‐N‐acetyl‐D‐galactosamine, all regions of ducts except epididymis I; terminal α‐D‐galactosamine, some cells in epididymis III‐V; N‐acetyl‐D‐galactosamine, ductuli efferentes, epididymis I, II, and some cells in epididymis III‐V; α‐L‐fucose, ductuli efferentes, vas deferens, and all regions of the epididymis except IV; N‐glycosidic side chains, ductuli efferentes, vas deferens, and epididymis I, IV, and V. All of these sugar residues as well as N‐acetyl‐D‐glucosamine were associated with the acrosomes and tails of spermatozoa throughout the ducts except for α‐N‐acetyl‐D‐galactosamine in epididymis I, and all occurred during one or more stages of spermiogenesis. The synthesis and secretion of glycoconjugates that bind to spermatozoa appear to involve more regions of the primary

ISSN:0002-9106    

DOI:10.1002/aja.1001780103

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

年代:1987

数据来源: WILEY

摘要:

AbstractEfferent reproductive ducts of male mice, including ductuli efferentes, epididymis, and vas deferens, were fixed and embedded in paraffin, and sections were stained with a battery of lectin‐horseradish peroxidase conjugates to localize specific sugars or sugar sequences in glycoconjugates. Cilia and the apical surfaces of ciliated cells in the ductuli efferentes stained intensely with lectin specific for sialic acid and terminal α‐N‐acetyl‐D‐galactosamine. Flask cells and clear cells in the epididymis reacted positively and similarly with most lectins used, providing evidence that these cell types are related. In contrast, disparities in lectin staining suggest that flask cells and clear cells are a cell type distinct from principal cells. Basal cells were not present in the ductuli efferentes but formed a continuous layer in the epididymis and vas deferens. Basal cells contained oligosaccharides terminated by sialic acid and α‐D‐galactose and varying amounts of terminal β‐D‐galactose and α‐N‐acetyl‐D‐galactosamine. Basal cells also stained variably with lectins specific for the core region of complex type N‐glycosidic side chains. The basal cells varied structurally, having long spinous apical processes approaching or reaching the lumen in region I of the epididymis and being low cuboidal or squamoid and lacking apical processes in epididymal regions II–V and in the vas deferens. The contiguous nature of the basal cells and the presence of glycoconjugates bearing terminal α‐galactosyl residues in all basal cells suggest a possible role for these cells in a regulatory influence on transepithelial movement of fluid and/or ion

ISSN:0002-9106    

DOI:10.1002/aja.1001780104

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn this study, closely staged placental villi from rhesus monkeys between 19 and 60 days of gestation were used to examine (1) the origin of endothelial cells and the mechanism of angiogenesis in villi; (2) the origin of placental macrophages (Hofbauer cells), and (3) the origin of the reticular cells that compartmentalize the stroma. The results did not support the concept that early stromal cells in the villi were derived byin situdelamination from cytotrophoblast. The extraembryonic mesodermal (mesenchymal) cells at the earliest of ages examined contained considerable granular ER. These cells organized into groups and formed primitive intercellular junctions, thus giving rise to the early angioblastic masses. The angioblastic masses were cellular, not syncytial; and lumen formation was not the result of intracellular vacuolization, but rather was the result of the acquisition of junctionally defined spaces. The earliest capillaries lacked intravascular blood cells and a basal lamina. Later, blood cells were evident in the lumina. At about 45–50 days of gestation, fetal capillaries began to indent the basal surface of the trophoblast. The basal lamina of the fetal capillaries still had not developed by 60 days of gestation. Between 35 and 40 days of gestation, significant morphological changes took place in the villous stroma. Evidence was obtained that the mesenchymal cells differentiated into the reticular cells that subdivided the stroma into fibrilrich and fibril‐free compartments. At the same time, Hofbauer cells were observed for the first time; they occupied the fibril‐free regions of the stroma. We did not observe any clear indications of intermediate stages of differentiation between other stromal cell types and Hofbauer cells. It is suggested that placental macrophages may have an origin independent of other stromal types; one possibility is that they are derived from blood monocytes as in other tissues. It is further suggested that the activities of the macrophages and reticular cells may be important in remodeling the extracellular matrix and may be related to the process of branching morphogenesis in the

ISSN:0002-9106    

DOI:10.1002/aja.1001780105

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

年代:1987

数据来源: WILEY

摘要:

AbstractRat cerebral vasculature serves as a model for study of the pathophysiology of stroke in humans. Human thalamic anteries show a high incidence of stroke. The objective is to describe the thalamic arterial vascular pattern in normotensive male rats as the initial step for quantitative histochemical studies of enzyme activities in the walls of these vessels. Intracardiac injections of methyl methacrylate monomer provide detailed vascular endocasts. The thalamic vascular bed defined byin situdissection, serial reconstruction, and light and scanning electron microscopy of endocasts contained four groups of vessels: (1) ventral medial thalamic arteries, (2) thalamic branches from the posterior cerebral artery, and (3) ventral lateral and (4) ventral anterior thalamic arteries. Thalamic vessels are muscular arterioles that, after three to four bipinnate branches, feed into a continuous capillary bed (no loops). The parent vessels and their subsequent branches have been evaluated in terms of their mean internal diameters, mean interbranch intervals, and branch angles. The arterial patterns to rat and human thalami are very similar, with the exception of the anterior choroidal artery which is missing in the rat. The branches supplying the thalamus in both the rat and human are closely associated with the circle of Willis; however, the constituent parts of the circle in rat vary from the pattern in human brain. The rat thalamic arteries show morphological features similar to those seen in the stroke‐prone ganglionic arteries in the human basal gangli

ISSN:0002-9106    

DOI:10.1002/aja.1001780106

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

年代:1987

数据来源: WILEY

摘要:

AbstractDonor tissue containing Rathke's pouch (RP) with its associated mesenchyme and neural lobe was isolated from 15‐day fetal rats and stereotaxically transplanted either to hypothalamic hypophysiotropic sites or to cerebral cortex of adult females for 30 days. Hosts either were intact or had been hypophysectomized 2–4 weeks prior to transplantation of Rathke's pouch. Grafts in the hypothalamus of either intact or hypophysectomized hosts were pleomorphic and large, often as wide as 1–2 mm, and occasionally larger. Grafts in the cortex of either intact or hypophysectomized hosts were nodular and occasionally projected upward in association with the meninges (cortex/meninges grafts).Certain features were characteristic of the grafts in all experimental groups, i.e., development of histotypic pars distalis with cell cords and fenestrated capillaries. In all experimental groups gonadotrophs and somatotrophs, when present, were localized at the graft margin adjacent to the connective‐tissue interface; mammotrophs, when present, were distributed throughout the graft. Features specific to each experimental group also were apparent. Grafts in the hypothalamus of both intact and hypophysectomized hosts typically were encapsulated by a labyrinthine meshwork of cell processes, whereas cortex/meninges grafts directly abutted dense connective tissue or neural tissue. In hypothalamic grafts in intact hosts, moderately differentiated mammotrophs, gonadotrophs, and somatotrophs could be identified by their cytological features and immunopositivity for prolactin, luteinizing hormone, and growth hormone, respectively. In hypothalamic grafts in hypophysectomized hosts, mammotrophs were absent, and gonadotrophs and somatotrophs were poorly granulated and not abundant. Grafts in the cortex of intact hosts contained numerous, well‐differentiated mammotrophs, gonadotrophs, and somatotrophs. Many of the mammotrophs in these grafts were hypertrophied, and profiles of exocytosis were common. In grafts in the cortex of hypophysectomized hosts, mammotrophs were either absent or very few, whereas gonadotrophs and somatotrophs were numerous. Gonadotrophs in these grafts were dramatically hypertrophied, although exocytosis was rare.The results indicate that development of histotypic pars distalis may occur in hypophysiotropic and nonhypophysiotropic brain sites and that the hormonal state of the host as well as implantation site modulate cytodifferentiation of specific pars distalis c

ISSN:0002-9106    

DOI:10.1002/aja.1001780107

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe surface epithelium of the mouse pyloric antrum invaginates into blind‐ended tubules whose proliferative activity was investigated by using light microscopy and3H‐thymidine radioautography. Adult, male, CD1 mice were habituated to 12 hr of light (0600–1800hr) alternating with 12 hr of darkness. Groups of four were given an injection of 40 μCi of3H‐thymidine per animal and killed 1 hr later at 0600, 1200, 1800, and 2400 hr. The glands at the base of the tubules and the adjacent isthmi were serially cross‐sectioned, and 0.5‐μm‐thick sections were prepared for radioautography. By using morphological criteria, glands were divided into five levels from their base to the isthmus (which was considered as being a sixth level). Proliferative activity was estimated by measuring the proportion of cells incorporating3H‐thymidine (labeling index) and the proportion of cells undergoing mitosis (mitotic index).The labeling index was found to decrease gradually from a high value in the isthmus to a relatively low one in the gland base; and this was observed at four times of the day. Similar gradients were observed in the mitotic index. Moreover, significant circadian variation was disclosed at most levels by comparing either labeling or mitotic index at four different times of the day. The labeling index tended to peak at the transition from dark to light (0600 hr) and drop at the transition from light to dark (1800 hr). In contrast, mitoses usually reached a maximum at the end of the light cycle (1800 hr) and a minimum at 2400 hr.In summary, the rates of DNA synthesis and cell division showed a sharply decreasing gradient of cell proliferation from the immature cells of the isthmus (level 6) to the mature cells of the gland base (level 1). The existence of some degree of proliferation, even in mature cells, sets apart the renewal taking place in the isthmus‐gland system, since in other renewal sites, cells stop dividing before they reach maturity. Finally, circadian variation has been identified in the proliferative activity of isthmus and gland and appears to be closely related to t

ISSN:0002-9106    

DOI:10.1002/aja.1001780108

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn the transformation of a spermatid into a spermatozoon, cytoplasmic loss occurs, allowing the sperm to swim unhindered. Cytoplasmic loss takes place via elimination of theresidual bodyand through structures known astubulobulbar complexes. A determination of cytoplasmic loss in several species was undertaken by using high‐resolution electron microscopic morphometric techniques. During the period that tubulobulbar complexes are present, an average 53% cytoplasmic loss was recorded for five species (guinea pig, 48.8±6.2% (SEM); monkey, 60.3±4.3%; opossum, 54.5±4.4%; rabbit, 46.9±2.7%; and rat, 55.7±4.9%), whereas there was essentially no loss or gain in cytoplasm during the same period for round spermatids. Surprisingly, during spermatid elongation an approximate 36% loss of cytoplasm was also recorded for five species (guinea pig, 50.1±6.3%; monkey, 30.0±15.4%; opossom, 25.4±9.0%; rabbit, 42.4±8.6%; and rat, 34.9±11.9%), which is only partially (∼60%) accounted for by fluid pumping from the nucleus during nuclear condensation. A densification of the cytoplasm of elongate spermatids, as compared with round spermatids, suggests fluid is also pumped from the elongating spermatid cytoplasm. Fluid loss from germ cells may contribute to the seminiferous tubule fluid, a fluid previously thought to be solely of Sertol

ISSN:0002-9106    

DOI:10.1002/aja.1001780109

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

年代:1987

数据来源: WILEY

摘要:

AbstractAlpha‐melanocyte‐stimulating hormone (α‐MSH), one of several peptide hormones originating in the intermediate lobe of the pituitary as proopiomelanocortin, was discovered in bovine pituitary intraglandular colloid by using radioimmunoassay. The quantity of α‐MSH varied from 5 to 368 μg/mg protein in the three pools. The importance of this finding is discussed in light of the possibility that the colloid is a transport medium for α‐MSH and other intermediate

ISSN:0002-9106    

DOI:10.1002/aja.1001780110

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

年代:1987

数据来源: WILEY

摘要:

AbstractExocytosis is the release of intracellular vesicular contents directly to the cell exterior after fusion of the vesicular and plasma membranes. It is generally accepted as the process by which transmitters and hormones are released from neurons and neurosecretory cells. There is overwhelming biochemical evidence that exocytosis is the mechanism by which catecholamines are released from adrenal chromaffin cells. With the exception of the hamster, however, there is little ultrastructural evidence to support such a mechanism. We have used a modifiedin vitrotannicacid method to visualize exocytosis by transmission electron microscopy in intact and saponin‐permeabilized bovine chromaffin cells. When cells are exposed to tannic‐acid‐containing medium, the content of vesicles involved in exocytosis is coagulatedin situas the vesicle opens to the exterior. Numerous exocytotic profiles were observed. The exposed vesicle contents appeared more granular than those of vesicles in the cell interior. Tannic acid also made the plasma membrane more distinct. Small holes were apparent in the plasma membrane of saponin‐treated cells, with little disruption of underlying cytoplasmic structure. Furthermore, when these cells were stimulated with calcium, exocytosis was evident only at regions of intact plasma membrane, not at the holes. Parallel measurements of secretion showed no secretion in the presence of tannic acid. Pretreatment with tannic acid prevented subsequent secretion by intact cells and markedly reduced that of permeabilized cells, indicating a probable change in the nature of the plasma membrane. Our results provide the first ultrastructural demonstration of exocytosis in bovine chromaffin cells with the aid of transmission electron microscopy. It is also clear that exocytosis is the mechanism of release in both intact and permeabilize

ISSN:0002-9106    

DOI:10.1002/aja.1001780111

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

年代:1987

数据来源: WILEY