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  • 1
    Electronic Resource
    Electronic Resource
    Establishment of heterogeneity among blood vessels: Hormone-influenced appearance of hepatic lipase in specific subsets of the ovarian microvasculature (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 235 (1993), S. 487-500 
    Details
    ISSN: 0003-276X
    Keywords: Hepatic lipase ; Blood vessel heterogeneity ; Gonadotropin ; Ovary ; Rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We used biochemical and structural approaches to analyze the influence of gonadotropic hormones on the association of hepatic lipase with specific subsets of ovarian blood vessels. Western blotting was used to detect this enzyme in effluent collected from heparin-perfused ovaries of nonhormone-treated immature rats and those primed with pregnant mare's serum gonadotropin (PMSG) alone or in combination with human chorionic gonadotropin (hCG). The effects of these hormones on hepatic lipase distribution among oyarian blood vessels was assessed before and after hCG and/or PMSG treatment by immunofluorescence and immunogold cytochemistry. For the latter, immunoreagents and fixative were delivered directly to chilled, unfixed ovaries by in situ vascular perfusion. Data from biochemical and structural analyses indicated that hepatic lipase was absent from nonhormone-treated ovaries. As shown by Western blotting of ovarian effluent, the enzyme appeared following treatment with PMSG and PMSG-hCG; it increased in amount in a time-dependent manner, with a transient decline in the early hours after hCG injection. Enzyme levels paralleled growth and vascularization of follicles and corpora lutea; the fall tended to coincide with early events in luteal angiogenesis. Immunogold microscopy showed that hepatic lipase was abundant in thin-walled blood vessels of theca interna of follicles, corpora lutea, and interstitial cells but sparse in those of the stroma. Moreover, during neovascularization of differentiating corpora lutea, vascular sprouts arising from hepatic lipase-laden thecal vessels appeared to lose, then regain, the enzyme as development progressed. Our findings thus suggest (1) that hormones influence the establishment of endothelial cell heterogeneity within the microvasculature of a single organ and (2) that development of novel endothelial cell properties in specific subsets of blood vessels underlies compartmentalization of function within a tissue. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092350402
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  • 2
    Electronic Resource
    Electronic Resource
    Surface morphology of macrophages in the regressing corpus luteum, as revealed by scanning electron microscopyThis work was supported in part by Research Grant HD 09993 from the National Institute of Child Health and Human Development. Portions of this study have appeared in an abstract (Paavola, L. G., and C. O. Boyd, 1978, J. Cell Biol., 79 (2. part 2): 62a). (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 195 (1979), S. 659-681 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Activated macrophages phagocytize moribund luteal cells and thus play a central role in the postpartum regression of corpora lutea in guinea pigs (Paavola, '79). When viewed by transmission electron microscopy (TEM), these luteal macrophages exhibit many surface protrusions. To characterize more fully the nature and extent of these evaginations, as well as to gain further understanding of phagocytes in their natural surroundings, luteal macrophages were studied in situ by scanning electron microscopy of regressing corpora lutea. Correlated TEM was carried out to confirm the identity of the various cell types. Even in low power scanning electron micrographs, macrophages are conspicuous, and can be readily distinguished from luteal cells by their surface topography. Luteal cell surfaces bear low ridge-like folds and sparse microvilli. In contrast, macrophages characteristically exhibit highly developed surface projections, the most common of which are knob-like or clubbed processes of varying size and shape. Other distinctive surface modifications displayed by luteal macrophages include long, slender filopodia, and well developed pseudopodia. These processes generally have an uneven distribution over the cell; thus, luteal macrophages may appear polarized with regard to surface activity. Both filopodia and pseudopodia occur in close contact with luteal cell surfaces. In addition, occasional luteal macrophages have surfaces that are covered with large, crater-like depressions. The phagocytosis ofcells and cellular debris by macrophages was also observed. In summary, the highly pleomorphic surface activity of luteal macrophages appears to be correlated with their role in the removal of senescent luteal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091950407
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  • 3
    Electronic Resource
    Electronic Resource
    Cytoplasmic granules in luteal cells of pregnant and non-pregnant guinea pigs. A cytochemical study (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 201 (1981), S. 127-140 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Secretory granules, which are released by exocytosis and are speculated to contain progesterone, have been described in luteal cells of sheep and other large domestic animals. These granules are small and densely staining. Gemmell and Stacy ('79) suggested that luteal cells of guinea pigs also contain secretory granules, although they could not document exocytosis of granule content at the fine structural level. For the present study, quantitative methods were used to reexamine the possibility that luteal cells of guinea pigs possess secretory granules. Ovaries of guinea pigs were fixed in situ by vascular perfusion at the time of maximum progesterone secretion, when such granules would be most abundant, as well as at other stages. Two types of granules that might be confused with secretory granules are microperoxisomes and lysosomes. Therefore, slices of perfusion-fixed corpora lutea were incubated for the fine structural localization of a peroximomal enzyme, catalase, or for the lysosomal enzymes, acid phosphatase (ACPase) and arylsulfatase. Other tissue was prepared for conventional electron microscopy. Granule types were classified on the basis of size, morphology, and enzyme content. Quantitation of granule types was carried out on both cytochemically reacted and conventionally prepared luteal tissue. More than 5500 microperoxisomes, 2800 lysosomes, and 1100 multivesicular bodies (MVBs) were tabulated. The results indicate that luteal cells of guinea pigs have three main types of granules: (1) Microperoxisomes, about 0.2μm in diameter and containing catalase; (2) lysosomes, about 0.5μm in diameter and positive for ACPase and arylsulfatase; and (3) MVBs, about 0.4μm in diameter and containing small vesicles. At the time of peak steroid secretion during pregnancy and the estrous cycle, the granule population in luteal cells of guinea pigs consists of 73-80% microperoxisomes, 13-17% lysosomes, and 7-l9% MVBs. These proportions are similar in tissue reacted for cytochemistry and tissue prepared by conventional means. Greater than 99% of the small 0.2-0.3μm diameter granules in guinea pig luteal cells are catalase reactive. This finding eliminates from further consideration most of the prime candidates for secretory granules in these cells. Finally, neither a sequential appearance of granules nor exocytosis of secretory product was detected. Our data thus argue against the suggestion that luteal cells of guinea pigs have secretory granules of the type observed in corpora lutea of large domestic animals.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092010115
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  • 4
    Electronic Resource
    Electronic Resource
    Heterogeneity among ovarian blood vessels: Endogenous hepatic lipase is concentrated in blood vessels of rat corpora lutea (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 230 (1991), S. 291-306 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We used indirect immunofluorescence and immunogold light microscopy to examine the distribution of hepatic lipase, an enzyme involved in lipoprotein metabolism, in ovaries of gonadotropin-treated immature rats. Antibodies utilized were rabbit anti-rat hepatic lipase IgG, anti-rat von Willebrand factor (VWF, an endothelial cell marker), and goat anti-rabbit IgG conjugated to gold particles or rhodamine. Immunoreagents were applied to fresh frozen sections of unfixed ovary or liver (positive control) or were delivered to ovaries by vascular perfusion before fixation in situ and silver-enhancement of sections. Appropriate controls verified that the immunolocalizations were specific. Immunofluorescence implied that luteal but not stromal blood vessels of ovaries were positive for hepatic lipase, whereas luteal and stromal blood vessels bore VWF. The improved morphology gained by perfusing ovaries with antibodies allowed precise localization of the enzyme. Hepatic lipase was concentrated within thin-walled vessels of corpora lutea but not those of stroma in ovaries at the time of peak steroidogenic activity. Quantification of hepatic lipase-labeled vessels in stromal and luteal compartments confirmed our visual impression. Many images suggested that stromal vessels lacking hepatic lipase gained this enzyme upon contact with luteal tissue. Perfusion of ovaries with cationized ferritin labeled all ovarian vessels equally well, ruling out the possibility that the observed distribution of hepatic lipase was artifactual. These findings demonstrate that ovarian blood vessels are heterogeneous for hepatic lipase. Moreover, they imply that luteal tissue, perhaps luteal cells, may influence expression of hepatic lipase binding sites by endothelial cells.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092300302
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  • 5
    Electronic Resource
    Electronic Resource
    The corpus luteum of the guinea pig. Fine structure at the time of maximum progesterone secretion and during regressionThis work was supported in part by Research Grant HD 05897 from the N.I.H., by General Research Support Grant, RR 05417, from the N.I.H. to Temple University School of Medicine, and by a Grant-in-Aid of Research from Temple University. A preliminary report of this work was presented at the fifteenth annual meeting of the American Society for Cell Biology in Puerto Rico (Paavola, ′75). (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 150 (1977), S. 565-603 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This report describes the fine structure of guinea pig luteal cells during the period of maximum progesterone secretion and throughout involution, in ovaries that have been fixed by perfusion, a technique that provides optimal preservation of steroid-secreting tissues. Smooth endoplasmic reticulum (smooth ER), a prominent organelle in these cells, is particularly well preserved by this method of fixation. During the time of maximal progesterone secretion, luteal cells contain abundant tubules and cisternae of smooth ER, many mitochondria, a well-developed Golgi complex and some lipid droplets. This fine structural picture is consistent with active steroidogenesis.Autophagy plays an important role in the regression of luteal cells in the corpus luteum. The onset of luteolysis is marked by the appearance of structurally complex autophagic vacuoles, one of which has not been described previously in luteal cells. This autophagic vacuole seems to originate from GERL (Golgi-endoplasmic reticulum-lysosomes) as a cup-shaped structure, which subsequently increases in size and complexity. Regressing luteal cells also contain increased numbers of both dense bodies (lysosomes) and lipid droplets, and exhibit changes in nuclear and mitochondrial morphology. In contrast to previous reports in the literature, changes in the morphology of smooth ER were not observed as a characteristic feature of involution in corpora lutea of guinea pigs in the present study. Advanced regression of luteal cells is characterized by multiple fusion of lipid droplets and a decrease in the amount of smooth ER.Another mechanism active in the breakdown of the corpus luteum is the phagocytosis of luteal cells by macrophages. Although present at all stages, macrophages are most abundant in older corpora lutea, where they often surround dead or dying luteal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001500406
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  • 6
    Electronic Resource
    Electronic Resource
    The corpus luteum of the guinea pig. IV. Fine structure of macrophages during pregnancy and postpartum luteolysis, and the phagocytosis of luteal cellsThis work was supported by Research Grant HD 09993 and by Biomedical Research Support Grant RR 05417 from the National Institutes of Health. Portions of this study have appeared in a preliminary report presented at the ninetieth annual session of the American Association of Anatomists in Detroit, Michigan (Paavola, L. G., 1977, Anat. Rec., 187: 673, Abstract). (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 154 (1979), S. 337-363 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Little information is available on the ultrastructure of macrophages in the corpus luteum or their importance in the regression of luteal tissue. In the present study, the fine structure of activated luteal macrophages during pregnancy and the postpartum period was examined by electron microscopy of guinea pig ovaries fixed by vascular perfusion. In these corpora lutea, macrophages can readily be distinguished from luteal cells. Activated macrophages typically display three prominent inclusions in their cytoplasm: (1) heterophagic vacuoles, (2) distinctive large dense inclusions, and (3) large and small electron-lucent vacuoles. In addition, they contain numerous smaller lysosome-like dense bodies. Activated macrophages in corpora lutea also characteristically show many surface protrusions, such as processes, folds or pseudopodia, which often occur in close contact with nearby luteal cells. Generally, nuclei of macrophages are irregular in shape and display a dense border of heterochromatin, thus differing from those of luteal cells.Macrophages seem to be most abundant in regressing corpora lutea, where they commonly display heterophagic vacuoles containing recognizable luteal cell fragments, evidence that these phagocytes ingest senescent luteal cells. The digestion of luteal cell components in heterophagic vacuoles presumably gives rise to the distinctive large dense inclusions typically seen in macrophages. The findings of this study indicate that macrophages play a central role in luteolysis by phagocytizing luteal cells or their remnants. They therefore appear to bring about the reduction in volume of the corpus luteum that occurs as this tissue regresses. These results taken together with those previously published (Paavola, 1978) further indicate that breakdown of the corpus luteum during postpartum luteolysis in guinea pigs involves both autophagy and heterophagy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001540304
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