The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Lori Mathews - One of the best experts on this subject based on the ideXlab platform.
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sperm Nuclear Transformations in cytoplasmic extracts from surf clam spisula solidissima oocytes
Developmental Biology, 1994Co-Authors: Frank J Longo, Lori Mathews, Robert E PalazzoAbstract:Abstract Following their incorporation into oocytes, sperm nuclei (SN) of the surf clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female proNuclear development, respectively. To analyze possible changes occurring in SN at fertilization, surf clam oocyte extracts; prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in ∼90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only ∼30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact Nuclear envelope possessing Nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethylami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm Nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
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proNuclear formation in starfish eggs inseminated at different stages of meiotic maturation correlation of sperm Nuclear Transformations and activity of the maternal chromatin
Developmental Biology, 1991Co-Authors: Frank J Longo, Susan Wagner Cook, Lori MathewsAbstract:Changes in sperm nuclei incorporated into starfish, Asterina miniata, eggs inseminated at different stages of meiosis have been correlated with the progression of meiotic maturation. A single, uniform rate of sperm expansion characterized eggs inseminated at the completion of meiosis. In oocytes inseminated at metaphase I and II the sperm nucleus underwent an initial expansion at a rate comparable to that seen in eggs inseminated at the proNuclear stage. However, in oocytes inseminated at metaphase I, the sperm nucleus ceased expanding by meiosis II and condensed into chromosomes which persisted until the completion of meiotic maturation. Concomitant with the formation and expansion of the female pronucleus, sperm chromatin of oocytes inseminated at metaphase I enlarged and developed into male pronuclei. Condensation of the initially expanded sperm nucleus in oocytes inseminated at metaphase II was not observed. Instead, the enlarged sperm nucleus underwent a dramatic increase in expansion commensurate with that taking place with the maternal chromatin to form a female pronucleus. Fusion of the relatively large female pronucleus and a much smaller male pronucleus was observed in eggs fertilized at the completion of meiotic maturation. In oocytes inseminated at metaphase I and II, the male and female pronuclei, which were similar in size, migrated into juxtaposition, and as separate structures underwent prophase. The chromosomes in each pronucleus condensed, intermixed, and became aligned on the metaphase palate of the mitotic spindle in preparation for the first cleavage division. These observations demonstrate that the time of insemination with respect to the stage of meiotic maturation has a significant effect on sperm Nuclear Transformations and proNuclear morphogenesis.
Frank J Longo - One of the best experts on this subject based on the ideXlab platform.
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sperm Nuclear Transformations in cytoplasmic extracts from surf clam spisula solidissima oocytes
Developmental Biology, 1994Co-Authors: Frank J Longo, Lori Mathews, Robert E PalazzoAbstract:Abstract Following their incorporation into oocytes, sperm nuclei (SN) of the surf clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female proNuclear development, respectively. To analyze possible changes occurring in SN at fertilization, surf clam oocyte extracts; prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in ∼90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only ∼30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact Nuclear envelope possessing Nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethylami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm Nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
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proNuclear formation in starfish eggs inseminated at different stages of meiotic maturation correlation of sperm Nuclear Transformations and activity of the maternal chromatin
Developmental Biology, 1991Co-Authors: Frank J Longo, Susan Wagner Cook, Lori MathewsAbstract:Changes in sperm nuclei incorporated into starfish, Asterina miniata, eggs inseminated at different stages of meiosis have been correlated with the progression of meiotic maturation. A single, uniform rate of sperm expansion characterized eggs inseminated at the completion of meiosis. In oocytes inseminated at metaphase I and II the sperm nucleus underwent an initial expansion at a rate comparable to that seen in eggs inseminated at the proNuclear stage. However, in oocytes inseminated at metaphase I, the sperm nucleus ceased expanding by meiosis II and condensed into chromosomes which persisted until the completion of meiotic maturation. Concomitant with the formation and expansion of the female pronucleus, sperm chromatin of oocytes inseminated at metaphase I enlarged and developed into male pronuclei. Condensation of the initially expanded sperm nucleus in oocytes inseminated at metaphase II was not observed. Instead, the enlarged sperm nucleus underwent a dramatic increase in expansion commensurate with that taking place with the maternal chromatin to form a female pronucleus. Fusion of the relatively large female pronucleus and a much smaller male pronucleus was observed in eggs fertilized at the completion of meiotic maturation. In oocytes inseminated at metaphase I and II, the male and female pronuclei, which were similar in size, migrated into juxtaposition, and as separate structures underwent prophase. The chromosomes in each pronucleus condensed, intermixed, and became aligned on the metaphase palate of the mitotic spindle in preparation for the first cleavage division. These observations demonstrate that the time of insemination with respect to the stage of meiotic maturation has a significant effect on sperm Nuclear Transformations and proNuclear morphogenesis.
Frank Rösch - One of the best experts on this subject based on the ideXlab platform.
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the basics of Nuclear chemistry and radiochemistry an introduction to Nuclear Transformations and radioactive emissions
2019Co-Authors: Frank RöschAbstract:Radiopharmaceutical chemistry and Nuclear medicine make use of radioactive elements and compounds labeled with them. This chapter describes the fundamentals of radioactivity in the context of life sciences. It addresses principal questions such as: What is the composition of an atomic nucleus and what are the forces which hold nucleons bound within the nucleus? Even so, some nuclei are stable, and many others are not—why? The fate of unstable nuclei is transforming into more stable nucleon configurations—but what are the basic pathways to do so? What’s going on inside the nucleus? What are the energetics and velocities of these Transformations? And finally, the various changes inside the nucleus and in part also in the electron shell of the unstable nucleus are accompanied by individual emissions of electromagnetic and particular radiations: beta-electrons and positrons, electron neutrinos and anti-electron neutrinos, alpha particles, gamma-photons and X-rays, conversion electrons and Auger/Coster-Kronig electrons, and bremsstrahlung. What are those emissions in detail?
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Nuclear Transformations and radioactive emissions: Part II—secondary transitions and post-effects
ChemTexts, 2018Co-Authors: Frank RöschAbstract:The present chapter follows part I of a series of two articles, which characterized unstable nuclei and described primary transformation pathways to stabilize a nucleus in terms of its nucleon compositions. Part II focuses on follow-up phenomena of those “primary” Transformations. It first illustrates the class of secondary transitions, which all originate from an excited Nuclear level of a nucleus, formed in a primary transformation. Next it discusses post-effects, which appear when Nuclear Transformations and transitions affect the atom as a whole, i.e. also its electron shell. Third, there are several post-effect phenomena when particular or electromagnetic radiation emitted in the course of the above-mentioned processes interact with surrounding condensed matter. Consequently, there are many specific emissions which accompany those secondary and post-effect processes, and which are not directly related to the primary Transformations. A prominent example is γ-emissions as emitted in one of the three secondary transition pathways. These γ-rays, however, represent just one of the many emission which altogether are the essence of radioactivity.
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Nuclear Transformations and radioactive emissions: Part I—primary transformation pathways of unstable nuclei
ChemTexts, 2018Co-Authors: Frank RöschAbstract:To understand the origin and character of individual radioactive emissions accompanying Nuclear transformation processes, it is essential to understand what an unstable nucleus is, what its motivation is to transform, and how the nucleus selects the best way to transform. The following chapter represents part I of a series of two articles. It introduces the composition of stable atomic nuclei, the meaning of “isotopes”, the discrepancy between the mass of the nucleus and the sum of the mass of the nucleons it is composed of (the “mass defect”), and the parameter of “mean nucleon binding energy”. It is the fate of those unstable nuclei, that they transform to more stable ones. Part I will focus on the “primary” pathways of those Transformations, i.e., those, where the nucleon composition of an unstable nucleus is modified to gain mean nucleon binding energy. Those transformation processes are the origin of certain radioactive emissions, and part I will discuss those originating from the primary transformation pathways, i.e., mainly β- and α-emissions.
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Nuclear Transformations and radioactive emissions part i primary transformation pathways of unstable nuclei
ChemTexts, 2018Co-Authors: Frank RöschAbstract:To understand the origin and character of individual radioactive emissions accompanying Nuclear transformation processes, it is essential to understand what an unstable nucleus is, what its motivation is to transform, and how the nucleus selects the best way to transform. The following chapter represents part I of a series of two articles. It introduces the composition of stable atomic nuclei, the meaning of “isotopes”, the discrepancy between the mass of the nucleus and the sum of the mass of the nucleons it is composed of (the “mass defect”), and the parameter of “mean nucleon binding energy”. It is the fate of those unstable nuclei, that they transform to more stable ones. Part I will focus on the “primary” pathways of those Transformations, i.e., those, where the nucleon composition of an unstable nucleus is modified to gain mean nucleon binding energy. Those transformation processes are the origin of certain radioactive emissions, and part I will discuss those originating from the primary transformation pathways, i.e., mainly β- and α-emissions.
Robert E Palazzo - One of the best experts on this subject based on the ideXlab platform.
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sperm Nuclear Transformations in cytoplasmic extracts from surf clam spisula solidissima oocytes
Developmental Biology, 1994Co-Authors: Frank J Longo, Lori Mathews, Robert E PalazzoAbstract:Abstract Following their incorporation into oocytes, sperm nuclei (SN) of the surf clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female proNuclear development, respectively. To analyze possible changes occurring in SN at fertilization, surf clam oocyte extracts; prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in ∼90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only ∼30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact Nuclear envelope possessing Nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethylami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm Nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
Susan Wagner Cook - One of the best experts on this subject based on the ideXlab platform.
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proNuclear formation in starfish eggs inseminated at different stages of meiotic maturation correlation of sperm Nuclear Transformations and activity of the maternal chromatin
Developmental Biology, 1991Co-Authors: Frank J Longo, Susan Wagner Cook, Lori MathewsAbstract:Changes in sperm nuclei incorporated into starfish, Asterina miniata, eggs inseminated at different stages of meiosis have been correlated with the progression of meiotic maturation. A single, uniform rate of sperm expansion characterized eggs inseminated at the completion of meiosis. In oocytes inseminated at metaphase I and II the sperm nucleus underwent an initial expansion at a rate comparable to that seen in eggs inseminated at the proNuclear stage. However, in oocytes inseminated at metaphase I, the sperm nucleus ceased expanding by meiosis II and condensed into chromosomes which persisted until the completion of meiotic maturation. Concomitant with the formation and expansion of the female pronucleus, sperm chromatin of oocytes inseminated at metaphase I enlarged and developed into male pronuclei. Condensation of the initially expanded sperm nucleus in oocytes inseminated at metaphase II was not observed. Instead, the enlarged sperm nucleus underwent a dramatic increase in expansion commensurate with that taking place with the maternal chromatin to form a female pronucleus. Fusion of the relatively large female pronucleus and a much smaller male pronucleus was observed in eggs fertilized at the completion of meiotic maturation. In oocytes inseminated at metaphase I and II, the male and female pronuclei, which were similar in size, migrated into juxtaposition, and as separate structures underwent prophase. The chromosomes in each pronucleus condensed, intermixed, and became aligned on the metaphase palate of the mitotic spindle in preparation for the first cleavage division. These observations demonstrate that the time of insemination with respect to the stage of meiotic maturation has a significant effect on sperm Nuclear Transformations and proNuclear morphogenesis.
