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  • 1
    Electronic Resource
    Electronic Resource
    Skeletal alterations in hypophysectomized rats: I. A histomorphometric study on tibial cancellous bone (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 241 (1995), S. 505-512 
    Details
    ISSN: 0003-276X
    Keywords: Bone formation ; Bone resorption ; Bone remodeling ; Hypophysectomy ; Cancellous bone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: Hypophysectomy (HX) results in a cessation of bone growth and a decrease in bone metabolism. The purpose of this study is to examine the effect of HX on the static and dynamic histomorphometry of cancellous bone in the secondary spongiosa of the proximal tibial metaphysis in rats.Methods: Female rats, at 2 or 3 months of age, were HX and sacrificed at 0, 5 days, 2 and 5 weeks after the surgery. Age-matched intact rats served as controls. Cancellous bone histomorphometry was performed on doublefluorescent labeled, 30-um-thick sections of the proximal tibia. Tartrateresistant acid phosphatase histomorphometry was performed at 5 days on HX and control rats to evaluate the resorption in the metaphyseal bone.Results: Although the intact rats gained in body weight, tibial length, tibial weight, and density after 5 weeks, these changes did not occur following HX. As compared to the basal group, HX resulted in a decrease in the density and dry weight of the metaphysis. The histomorphometric data showed that the cancellous bone volume and trabecular number of the secondary spongiosa were decreased and the separation was increased in the HX rats. The dynamic results showed that HX significantly decreased longitudinal growth rate and tissue-based bone formation and resorption. However, the bone surface-based eroded surface, labeled surface, the mineral apposition rate, and the bone formation rate did not differ between the intact and the HX rats at either the 2 or 5 weeks study. Five days after HX, the bone surface and tissue-based osteoclast surfaces were significantly lower in the HX than in the intact rats.Conclusions: Pituitary hormone deficiency results in cancellous bone loss. The bone loss is due primarily to the suppression of longitudinal growth-dependent bone gain and the inhibition of tissue-based bone turnover with a lower bone formation relative to bone resorption. The surfacebased bone turnover is not affected. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092410408
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  • 2
    Electronic Resource
    Electronic Resource
    Skeletal alterations in hypophysectomized rats: II. A histomorphometric study on tibial cortical bone (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 241 (1995), S. 513-518 
    Details
    ISSN: 0003-276X
    Keywords: Cortical bone ; Hypophysectomy ; Bone formation ; Bone resorption ; Histomorphometry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: Pituitary hormones play an important role in bone growth, modeling, and remodeling. The purpose of this study is to examine the effect of hypophysectomy (HX) on tibial cortical bone with histomorphometry.Methods: Forty-Five female Sprague-Dawiey rats, at 3 months of age, were hypophysectomized or served as intact controls. They were sacrificed at 0, 2, and 5 weeks after the surgery. Cortical bone histomorphometry was performed on double-fluorescent-labeled 30-mcm-thick sections of the tibial shaft.Results: The dry weight and density of tibial diaphysis and the cortical bone area of the tibial shaft in the HX rats were significantly lower (P〈0.05) than that of the age-matched intact rats, but did not differ between the HX and basal control rats. The dynamic data show that the bone formation parameters (labeled surface, mineral apposition rate, and bone formation rate) were profoundly decreased (P〈0.01) on both the periosteal and endocortical surfaces in the HX rats as compared with the age-matched intact rats at the 2 and 5 weeks. However, the decrease in the labeled surface was much less on the endocortical envelope than on the periosteal envelope in the HX rats. Although no significant change was detected in the medullar size between the HX and age-matched intact rats, the eroded surface on the endocortical surface was greater (P〈0.05) in the HX rats than in the intact rats at either time point.Conclusions: Hypophysectomy-suppressed, radial growth-dependent bone gain without a bone loss in the tibial shaft of the young rat. This is associated with decreased modeling-dependent bone formation. A greater eroded surface on the endosteum did not affect the marrow size at 5 weeks after hypophysectomy. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092410409
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  • 3
    Electronic Resource
    Electronic Resource
    Observations of hamster sperm-egg fusion in freeze-fracture replicas including the use of filipin as a sterol marker (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 351-365 
    Details
    ISSN: 1040-452X
    Keywords: Electron microscopy ; Sperm-egg interactions ; Polyspermic conditions ; Filipin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have extended the observations of previous transmission electron microscopy studies of sperm-egg fusion to include those of freeze-fracture replicas showing sperm-egg interactions before, during, and following sperm head fusion with the egg membrane. Hamster eggs were incubated with hamster sperm under polyspermic conditions and were observed after a period of 5-30 minutes. After fixation, the eggs and sperm were exposed to filipin, which binds β-OH-sterols to form visible complexes in freeze-fracture replicas. Filipin can act as a marker for egg plasma membrane wherein it is abundant, while filipin is relatively scarce in the acrosome-reacted hamster sperm membrane, found only in the plasma membrane of the equatorial segment. The earliest sperm-egg interactions are observed between the egg microvilli and the perforatorium and the equatorial segment of the sperm, and the initial fusion between egg and sperm occurs in the vicinity of the equatorial segment. At later stages of fusion involving the postacrosomal segment, a clear line of demarcation is observed between the filipin-rich egg membrane and the filipin-poor sperm postacrosomal segment, suggesting that filipin binding lipids from the egg intercalate into the sperm membrane following membrane fusion. The anterior segment of the sperm does not fuse with the egg but is instead incorporated into a cytoplasmic vesicle derived from both sperm and egg membranes. In this latter step, filipin-sterol complexes are not found in sperm-derived membranes suggesting that there may be barriers to the movement of filipin binding lipids from the egg into these sperm membranes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080270410
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  • 4
    Electronic Resource
    Electronic Resource
    Further observations on the phagocytosis of Candida albicans by Hamster and Human Oocytes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 28 (1991), S. 79-84 
    Details
    ISSN: 1040-452X
    Keywords: Yeast ; Ultrastructure ; Oocyte infection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Pathogenic yeast, Candida albicans, were incubated with hamster and human oocytes for up to 21 hours in order to determine the nature and time course of phagocytosis of these organisms. Aliquotes of the interacting cells were taken at various time intervals for electron microscopic examination. Some specimens had their zona pellucidae enzymatically removed prior to incubation with yeast, and these specimens showed the most extensive interaction and phagocytosis of Candida. The zona pellucida appears to be an effective barrier to yeast, at least over the time span studied. The observations are consistent with the hypothesis of an initial attachment of yeast via a surface component to oocyte microvilli followed by phagocytic uptake into an endosome. There is no compelling evidence of lysosomal degradation of the yeast over the time course of this study; however, the oocytes appear to undergo some degenerative changes at long incubation times.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080280113
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  • 5
    Electronic Resource
    Electronic Resource
    Spermophagy in semen in the red wolf, Canis rufus (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 457-461 
    Details
    ISSN: 1040-452X
    Keywords: Canine sperm ; Pyospermia ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The red wolf (Canis rufus) is an endangered species with 194 individuals remaining in the wild and in various captive facilities. Breeding efforts at the Graham, WA site (Point Defiance Zoo and Aquarium) have involved artificial insemination with fresh or frozen semen in an effort to increase population and maximize the genetic potential of the stock. Electron microscopic observations were made in semen specimens obtained by electroejaculation from mature males prior to their use in an effort to determine semen parameters that might be useful in guiding breeding procedures. Sperm samples were either fixed immediately or treated with capacitating media and fixed after 4 to 7 hr of incubation. Many of the specimens examined were pyospermic (white cell in semen) and showed evidence of spermophagy, primarily by neutrophils. Of the six animals surveyed, only one showed little evidence of spermophagy, and three had extensive pyospermia and spermophagy but this finding was not correlated with fertility. Samples fixed immediately as well as those incubated for several hours showed evidence of spermophagy, indicating that the phagocytosis was not the result of culture. Gene pool restriction and/or captive stress may be contributing factors of reduced semen quality. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370413
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  • 6
    Electronic Resource
    Electronic Resource
    Reglation of autocrine gastrin expression by the TGFα autocrine loop (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 162 (1995), S. 256-265 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Gastrin is transcriptionally responsive to EGF stimulation (Merchant et al., 1991, Mol. Cell. Biol., 11:2686-2696). Consequently, we hypothesized that previously recognized gastrin autocrine loops (Hoosein et al., 1990, Exp. Cell. Res., 186:15-21), might be controlled by autocrine TGFα in human colon carcinoma cells. Therefore, we examined the interaction between these two autocrine growth factors in two colon carcinoma cell lines which utlizie TGFα. The FET cell line requires exogenous TGFα/EGF for optimal growth and has a classical TGFα autocrine loop which is disrupted by TGFα or epidermal growth factor receptor (EGFr) antibodies. The HCT 116 cell line is not dependent on exogenous TGFα/EGF and exhibits a nonclassical TGFα autocrine loop which is not disrupted by neutralizing antibodies to either TGFα itself or the EGFr. Basal gastrin mRNA production is significantly higher in HCT 116 than FET as measured by RNase protection assay. In the FET cells, exogenous EGF stimulates gastrin mRNA production but not in HCT 116. When the TGFα autocrine loop in HCT 116 is disrupted by constitutive expression of antisense TGFα mRNA, the gastrin mRNA level is significantly repressed. In xenografts derived from these antisense clones, TGFα reverted to high expression, and the gastrin mRNA level was again increased. This interaction between the strong TGFα loop in HCT 116 and the gastrin autocrine loop may confer a growth advantage to these colon cells. Such interactions between growth factors may promote enhanced tumorigenicity to transformed cells with these strong, nonclassical autocrine loops. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041620211
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  • 7
    Electronic Resource
    Electronic Resource
    Significant induction of spermidine/spermine N1-acetyltransferase without cytotoxicity by the growth-supporting polyamine analogue 1,12-dimethylspermine (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 165 (1995), S. 71-76 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The superinduction of the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase (SSAT) has been implicated in the cell type-specific cytotoxic activity of some polyamine analogues. We now report that one polyamine analogue, 1, 12-dimethylspermine (DMSpm), produces a large induction of SSAT with no significant effects on growth in the human large cell lung carcinoma line, NCI H157. This cell line has been demonstrated to respond to other analogues with SSAT superinduction and cell death. Treatment of the lung cancer cell line with DMSpm produces a rapid increase in SSAT activity and a near complete depletion of the natural polyamines. Additionally, DMSpm supports cell growth in cells which have been depleted of their natural polyamines by the ornithine decarboxylase inhibitor, 2-difluoromethylornithine. The current results suggest that significant induction of SSAT can occur in the absence of cytotoxicity when the inducing polyamine analogue can support growth and that increased SSAT activity alone is not sufficient for cytotoxicity to occur. © 1995 Wiley-Liss Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041650109
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature-dependent sex determination in reptiles: Proximate mechanisms, ultimate outcomes, and practical applications (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 15 (1994), S. 297-312 
    Details
    ISSN: 0192-253X
    Keywords: Sex determination ; sexual differentiation ; reptiles ; temperature-dependent sex determination ; behavior ; steroidogenic enzymes ; aromatase ; reductase ; estrogen ; androgen ; steroid hormone receptors ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In many egg-laying reptiles, the incubation temperature of the egg determines the sex of the offspring, a process known as temperature-dependent sex determination (TSD). In TSD sex determination is an “all or none” process and intersexes are rarely formed. How is the external signal of temperature transduced into a genetic signal that determines gonadal sex and channels sexual development? Studies with the red-eared slider turtle have focused on the physiological, biochemical, and molecular cascades initiated by the temperature signal. Both male and female development are active processes - rather than the crganized/default system characteristic of vertebrates with genotypic sex determination - that require simultaneous activation and suppression of testis- and ovary-determining cascades for normal sex determination. It appears that temperature accomplishes this end by acting on genes encoaing for steroidogenic enzymes and steroid hormone receptors and modifying the endocrine microenvironment in the embryo. The temperature experienced in development also has long-term functional outcomes in addition to sex determination. Research with the leopard gecko indicates that incubation temperature as well as steroid hormones serve as organizers in shaping the adult phenotype, with temperature modulating sex hormone action in sexual differentiation. Finally, practical applications of this research have emerged for the conservation and restoration of endangered egg-laying reptiles as well as the embryonic development of reptiles as biomarkers to monitor the estrogenic effects of common environmental contaminants. © 1994 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020150310
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  • 9
    Electronic Resource
    Electronic Resource
    Comparisons of the low-resolution structures of ornithine decarboxylase by electron microscopy and X-ray crystallography: The utility of methylamine tungstate stain and butvar support film in the study of macromolecules by transmission electron microscopy (1991)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 18 (1991), S. 157-166 
    Details
    ISSN: 0741-0581
    Keywords: Proteins ; Molecular structure ; Negative-stain electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The structure of ornithine decarboxylase (Mr ≍ 1.04 × 106) from Lactobacillus 30a was investigated by electron microscopy and x-ray crystallography. Electron micrographs showed the structure to be well preserved in methylamine tungstate stain. The molecules interacted little with the Butvar support film, yielding three unique projections: a hexagonal ring (front view) and two rod-shaped projections (edge views). Stereo pairs revealed a novel feature of the Butvar film in that some molecules were suspended in the stain in random orientations. Consequently, the relatedness of the hexagonal ring and the rod-shaped particles could be demonstrated since some particle shapes interconverted when the stage was tilted ± 45°. The two edge views were related by a 30° rotation about the sixfold axis. Image averaging of the three primary views suggested a dodecamer (point group symmetry 622) composed of two hexameric rings, apparently in an eclipsed configuration. To investigate the structural organization of the complex, the dissociation of the enzyme was studied by electron microscopy. The dissociation process involved the initial breakage of the ring followed by separation of dimers from the ring (one subunit from each of the two hexamers). Thus, the dodecamer forms as a hexamer of dimers rather than a dimer of hexamers. These structural studies were confirmed and extended by x-ray crystallographic analysis. A 4.0-Å resolution electron density map revealed two hexameric rings, consisting of six closely associated dimers, tilted approximately 10° with respect to the molecular twofold axis. Electron density projections of the three primary views of the molecule derived from the x-ray data corresponded closely to those obtained from image averaging of the electron microscopy data, thereby establishing in a novel way the reliability of the electron microscopy studies. Methylamine tungstate stain and Butvar support film therefore offer unique advantages for investigating protein structures by electron microscopy.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060180210
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