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  • 1
    Electronic Resource
    Electronic Resource
    Maturation of pig and rat oocytes transplanted into surrogate pig follicles in vitro (1985)
    New York, NY : Wiley-Blackwell
    Gamete Research 11 (1985), S. 107-119 
    Details
    ISSN: 0148-7280
    Keywords: oocyte maturation ; follicular maturation ; cumulus maturation ; surrogate follicles ; xenogenous ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Pig oocytes obtained from slaughterhouse material and rat oocytes obtained from PMSG-treated immature females were incubated as isolated oocytes or injected into explanted pig follicles (5-8 mm). Free oocytes of both species, with or without their cumulus investment or gonadotropins during culture, matured at high rates after 30 hr or 9-10 hr of culture, respectively. Gonadotropic stimulation was necessary for maturation of both the native and injected cumulus-intact pig oocytes in follicle culture. Cumulus-free pig oocytes injected into follicle failed to mature in response to gonadotropic stimulation, suggesting an inability to perceive or respond to stimulation. Injected rat oocytes, however, matured irrespective of cumulus investment or gonadotropic stimulation. Their maturation was delayed and reduced at 9 hr. These results in the rat suggest that the pig follicular environment is incapable of regulating rat oocyte maturation but rather presents a permissive or supportive environment for their maturation. The explanted surrogate follicles from the pig or other species may provide a useful model for the study of oocyte-follicle interactions in oocyte maturation within or between species.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120110202
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  • 2
    Electronic Resource
    Electronic Resource
    Alteration of sperm thiol-disulfide status and capacitation in the guinea pig (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 13 (1986), S. 93-102 
    Details
    ISSN: 0148-7280
    Keywords: spermatozoa ; capacitation ; acrosome reaction ; thiol-disulfide status ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Epididymal spermatozoa of the guinea pig were incubated under conditions known to promote a rapid synchronous capacitation in a large proportion of the spermatozoa (Ca2+-free medium with lysophosphatidylcholine, LC) or in Ca 2+-free medium without LC. To study the effects of altered thiol-disulfide status and content, incubations were conducted with reagents that maintain and increase thiol groups (DTT, GSH), maintain and increase disulfide groups (diamide, GSSG), or which irreversibly block thiol groups by alkylation (NEM). The permeable DTT inhibited LC-induced capacitation and at high concentrations diminished the percentage of acrosome reactions in capacitated spermatozoa. The permeable diamide exhibited a stimulatory effect upon capacitation. The largely impermeable GSH and GSSG exhibited effects similar to their respective permeable counterparts but their effects were moderate and required extremely high concentrations. The DTT inhibition of LC-induced capacitation was reversible by washing and a further 1 hr incubation. In this final incubation after removal of DTT by washing, LC was absent too so its stimulatory effect must have been accomplished prior to washing and in the presence of DTT. NEM-alkylation of the existing thiol population did not affect LC-induced capacitation but alkylation of the increased thiol population after prior DTT treatment was inhibitory of capacitation. These results suggest that the maintenance and/or formation of disulfide groups on enzymes or structural proteins may be a component of the capacitation process. In contrast, the formation and maintenance by alkylation of increased thiol groups but not the maintenance of existing thiol groups, is inhibitory of capacitation. The relevance of these findings to a role for a thiol-sensitive proteinase in capacitation is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120130202
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  • 3
    Electronic Resource
    Electronic Resource
    Fertilizability of cryopreserved zona-free hamster ova (1979)
    New York, NY : Wiley-Blackwell
    Gamete Research 2 (1979), S. 357-366 
    Details
    ISSN: 0148-7280
    Keywords: ova ; spermatozoa ; cryopreservation ; fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Mature unfertilized ova from superovulated hamsters were freed from all investments and frozen at -50°C. They were cooled at about 1°C/min to 0°C then at 0.8° to 0.6°C/min to -50°C. At 0°C, dimethyl sulfoxide was added to a final concentration of 1.25 M. The ova were stored at -50°C for up to four months. Thawing was performed at 2-4°C/min and followed by several washes with insemination medium. Approximately 90% of the ova were normal in appearance after thawing. The frozen and thawed ova with normal appearance could be penetrated by hamster or human spermatozoa at a rate comparable to unfrozen controls. The ability of hamster ova to tolerate storage at a relatively convenient temperature (-50°C) for long periods (tested for up to four months) makes possible their shipment at low cost to institutions lacking this resource. There they can be used for basic biological studies of sperm-egg interaction or in the clinical assessment of human sperm quality.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120020408
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  • 4
    Electronic Resource
    Electronic Resource
    Lysophosphatidylserine inhibits completion of meiotic maturation of rat oocytes in vitro (1983)
    New York, NY : Wiley-Blackwell
    Gamete Research 8 (1983), S. 57-63 
    Details
    ISSN: 0148-7280
    Keywords: meiosis ; lysophosphatidylserine ; polar body ; oocyte ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Follicular oocytes collected prior to the expected time of the LH surge from PMSG-treated immature rats were incubated cummulus-intact (with or without LH) or cumulus-free (CF). Oocytes were incubated in the presence or absence of lysophosphatidlylserine (LS), a naturally occurring membrane phospholipid that has been previously shown to block sperm-related membrane fusion events. Fusion events occurring during oocyte maturation that might be affected by LS include maintenance of the intact germinal vesicle (GVI) and prevention of GV breakdown (GVBD) and first polar body formation (PBI). LS had only a slight effect upon GVI. The incidence of GVI was significantly increased in only one of the three oocyte culture conditions employed (CF). Exposure to LS from the outset of collection and washing did not increase the incidence of GVI, indicating the lack of effect by LS was not owing to the passage of a sensitive period during oocyte collection. In contrast, LS was not owing to the passage of a sensitive period during oocyte colection. In contrast, LS almost completely abolished PBI in all oocyte culture conditions at 100 μ in PBI and those sperm-related fusion processes previously found to be sensitive to LS. Finally, LS or similar agents may be responsible for the block to maturation (often at anaphase I) and even the retarded cleavage observed in vitro during oocyte maturation or embryo culture in some species.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120080107
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of various lipids on the acrosome reaction and fertilizing capacity of guinea pig spermatozoa with special reference to the possible involvement of lysophospholipids in the acrosome reaction (1981)
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 253-273 
    Details
    ISSN: 0148-7280
    Keywords: capacitation ; acrosome reaction ; fertilization ; lysophospholipids ; spermatozoa ; membrane fusion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of lipids on the survival, acrosome reaction, and fertilizing capacity of guinea pig spermatozoa were studied by incubating the spermatozoa in media containing various concentrations of the lipids. Lipids tested were: phosphatidyl-choline (PC), -ethanolamine (PE), -inositol (PI), -serine (PS), sphingomyelin (S), cholesterol (C), lysophosphatidyl-choline (LC), -ethanolamine (LE), -inositol (LI), -serine (LS), and glyceryl monooleate (M).When spermatozoa were incubated in a regular medium (containing 2 mM Ca2+) with M, the majority underwent the acrosome reaction within 1 hour. None of the other lipids were as effective as M, and some were totally ineffective under the same conditions. However, when spermatozoa were preincubated in Ca2+-free medium containing LC, LE, or LI, they gained the ability to undergo the acrosome reaction. One hour of preincubation in Ca2+-free medium with LC, LE, or LI was enough to render the vast majority of spermatozoa capable of undergoing the acrosome reaction in response to Ca2+. The optimum concentrations for LC, LE, and LI were approximately 85 μg/ml, 210 μg/ml, and 140 μg/ml, respectively. Spermatozoa that had undergone the acrosome reaction by pretreatment with LC, LE, or LI remained actively motile and were capable of fertilizing eggs. LS was totally ineffective in rendering the spermatozoa capable of undergoing the acrosome reaction, and in fact it inhibited the acrosome reaction by itself and also inhibited the LC-, LE-, or LI-mediated acrosome reaction. LS did not prevent acrosome-reacted spermatozoa from penetrating the zona pellucida, but did prevent sperm-egg fusion.Based on these findings, it is suggested that lysophospholipids are intricately involved in the sperm acrosome reaction and perhaps in sperm-egg fusion.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120040402
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  • 6
    Electronic Resource
    Electronic Resource
    Developmental capability of rat oocytes matured in vitro in defined medium (1985)
    New York, NY : Wiley-Blackwell
    Gamete Research 12 (1985), S. 255-263 
    Details
    ISSN: 0148-7280
    Keywords: oocyte ; maturation ; fertilization ; fetal development ; cumulus-free ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The normality of in vitro matured oocytes was compared to that of in vivo matured (ovulated) oocytes at the following stages of development: germinal-vesicle breakdown, first polar body formation, fertilization (two polar bodies and two pronuclei with a sperm tail or first cleavage), and fetal development (day 20 fetuses). At all points, the in vitro oocytes exhibited a reduced ability, with oocytes matured cumulus-free having the poorest. The exposure of oocytes to human chorionic gonadotropin (hCG) for 2 hr before collection or during incubation improved their rates of maturation and development to day 20 fetuses but not their ability to undergo fertilization. While beneficial, the exposure to gonadotropins before or during maturation was not essential, as evidenced by the production of two day 20 fetuses matured and fertilized in vitro without any gonadotropin (luteinizing hormone or hCG) treatment in vivo or in vitro. These data demonstrate that in the population of in vitro matured oocytes there exist individuals wholly competent of complete normal development, albeit in a reduced proportion in comparison to normally matured and ovulated oocytes. That the in vitro handling, treatment, and culture of the oocytes may be responsible for some of the reduced developmental ability observed is suggested by the developmental abilities of ovulated oocytes under different conditions. Ovulated oocytes fertilized in the donor had the highest rates of development (46%), followed by those fertilized after transfer into mated recipients' oviducts (20%). The lowest rate was achieved with in vitro fertilized oocytes (7%), which represented the group subject to the greatest degree of manipulation and distinction from the normal in vivo process.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120120304
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  • 7
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    Automatic detection of retinal anatomy to assist diabetic retinopathy screening (2006)
    Institute of Physics
    Details
    Publication Date: 2006-12-21
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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  • 8
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    Automated detection of exudates for diabetic retinopathy screening (2007)
    Institute of Physics
    Details
    Publication Date: 2007-12-05
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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