Wiley
Công bố khoa học tiêu biểu
Sắp xếp:
Induction of nuclear breakdown and meiosis in <i>Spisula solidissima</i> oocytes by calcium ionophore Abstract Induction of germinal vesicle breakdown and reinitiation of the meiotic process resulted following exposure of immature Spisula solidissima oocytes to divalent ionophore A23187. Meiosis continued to completion in the presence of the ionophore; however, parthenogenetic development of the gametes did not occur. Incubation of oocytes in calcium deficient media (Ca++ free or Ca++ Mg++ free seawater) but not Mg++ free seawater inhibited ionophore induced maturation. Effects of calcium deficiency were reversible. The results suggest that nuclear disintegration and the meiotic process induced by sperm are mediated by ionic stimuli and that the establishment of meiotic arrest is linked to the availability of calcium with in the oocyte.
Wiley - Tập 191 Số 3 - Trang 433-440 - 1975
Uptake OF Ca<sup>2+</sup> is one of the earliest responses to fertilization of sea urchin eggs Abstract Sea urchin eggs take up Ca for 10 min following insemination (determined as uptake of 45 Ca from the SW (3)). Although 90% of this uptake occurs after the beginning of the cortical reaction and may represent external binding of Ca to the egg surface coats, there is a brief phase of uptake (0–30 sec) which precedes the cortical reaction; this may represent a Ca flux into the eggs.
Wiley - Tập 203 Số 1 - Trang 143-149 - 1978
The role of divalent cations in activation of the sea urchin egg. I. Effect of fertilization on divalent cation content Abstract The Ca and Mg content of unfertilized sea urchin eggs (3 and 21 μmole/ml eggs) remains remarkably constant over periods of hours, even when the eggs are suspended in Ca‐ or Mg‐free sea water. After fertilization the Ca content of eggs in regular sea water increases sharply by about 20%, followed by a decrease to the unfertilized level by 40 minutes. However, if the fertilized eggs are washed three minutes in Ca‐free sea water a sharp decrease in the Ca content occurs amounting to 30% of the total in the first 40 minutes, with little change thereafter. Suspension of the eggs in Ca‐free sea water results in an even greater loss of Ca amounting to about 43% of the total in the same time interval, followed by a continuing slow loss. It is concluded that fertilization initiates the intracellular release of Ca, which is then extruded. For unwashed eggs this change is masked by the simultaneous generation of new extracellular coats with high affinity for Ca. Changes in the Mg content of fertilized eggs follow the same general pattern except that absorption of this divalent cation to the extracellular coats is minimal.
Wiley - Tập 198 Số 1 - Trang 65-77 - 1976
The passerine bird song system as a model in neuroendocrine research
Wiley - Tập 256 Số S4 - Trang 22-30 - 1990
Calcium requirement and increased association with bovine sperm during capacitation by heparin Abstract The requirement for external Ca+2 during capacitation of ejaculated bovine sperm with heparin and changes in sperm‐associated 45 Ca+2 during capacitation were investigated in vitro. Sperm capacitation was evaluated by ability to undergo an acrosome reaction (AR) upon exposure to lysophosphatidylcholine. The percentage of sperm which were capacitated during a 4 h incubation with heparin increased exponentially with increased exposure time to 2 mM Ca+2 . When sperm were incubated with or without heparin in the presence of 45 CaCl2 , there was no difference in the amount of 45 Ca+2 associated with sperm initially or at 1 h of incubation. Incubation with heparin resulted in a greater amount of sperm‐associated 45 Ca+2 at 2, 3, and 4 h as compared to sperm incubated without heparin. The amount of 45 Ca+2 associated with sperm during capacitation was unaffected by washing with 2 mM EGTA‐5 mM LaCl3 . Glucose (5 mM) inhibited the effects of heparin on sperm‐associated 45 Ca+2 and on capacitation. The inhibitory effects of glucose could be overridden by 8‐bromo‐cAMP. The results suggest that the requirement for external Ca+2 during capacitation with heparin may be related to an increased association of external Ca+2 with sperm.
Wiley - Tập 252 Số 2 - Trang 174-182 - 1989
Detrimental effect of visible light on meiosis of mammalian eggs in vitro Abstract Short wavelength visible light (<470–480 nm) emmitted from ordinary light sources is detrimental to unfertilized hamster eggs in that prolonged exposure to the light disturbs the completion of normal meiosis after the eggs are penetrated by spermatozoa. The fluorescent light commonly used in modern laboratories is more harmful than the light from incandescent lamps. In experiments involving the handling of eggs in vitro, minimal exposure to the light or the use of appropriate filters (e.g., red cellophane sheets) is recommended.
Wiley - Tập 206 Số 3 - Trang 365-369 - 1978
Distal‐less and other homeobox genes in the development of the dentition Abstract The mammalian tooth develops through an interaction between two tissue layers of different embryologic origin. A number of transcription factors and as well as two members of the Msx class of homeobox genes have been shown to be involved in the histogenesis of the mammalian tooth. This raised the possibility that other homeobox genes might be involved in dental morphogenesis. We have amplified mouse tooth germ cDNA from three different gestational ages by the polymerase chain reaction with degenerate primers for 18 classes of homeobox genes. Members of several classes have been isolated, including the Msx genes, two Dlx genes, and the Dbx, MHox, Mox2A genes. One of the Dlx genes, Dlx‐7, had not previously been reported in mammals, and some details are presented of its cDNA sequence. This work plus that of other investigators has shown that at least six Dlx genes are expressed in developing teeth or in first branchial arches, suggesting the possibility that these genes are involved in specifying complexity within or between teeth. The screening approach with degenerate primers is a successful way to identify new as well as previously known regulatory genes expressed in developing tooth embryos. © Wiley‐Liss, Inc.
Wiley - Tập 270 Số 3 - Trang 273-284 - 1994
A comparison of aromatase, 5α‐, and 5β‐ reductase activities in the brain and pituitary of male and female quail <i>(C. c. japonica)</i> Abstract In numerous vertebrate species including Japanese quail (Co‐turnix coturnix japonica) , actions of testosterone (T) on neuroendocrine target tissues are mediated in part by conversion to estrogenic and androgenic metabolites. In order to assess which pathways were favored in each identified androgen target area in quail brain and whether there were discernible sex differences, we developed an assay for simultaneously quantifying aromatase, 5α‐, and 5β‐reductase. In addition, we made the first definitive identification of aromatase in quail pituitary and compared all three enzyme activities in the pituitary of males and females. Enzymes were measured in tissue homogenates by the conversion of [3 H]androstenedione to [3 H]estrone, [3 H]5α‐androstanedione, and 5β‐androstanedione. Aromatase activity was restricted to limbic tissues (anterior hypothalamus > posterior hypothalamus > septum > archistriatum containing nucleus taenia) while hyperstriatum, cerebellum, and midbrain containing nucleus intercollicularis were aromatase‐negative. Quail pituitary aromatized androgen at rates equivalent to anterior hypothalamus pre‐optic area (aHPOA). 5α‐ and 5β‐reductase were present in all tissues tested. Aromatase was significantly higher in aHPOA and pituitary of males, whereas 5α‐reductase was significantly higher in female pituitary. These data suggest that a complex of androgen‐metabolizing enzymes controls the neuroanatomic (spatial) distribution of active hormone in neuroendocrine tissues and that quantitative differences between males and females may account for sex differences in behavior.
Wiley - Tập 242 Số 2 - Trang 171-180 - 1987
Developmental expression of cytochrome P450 aromatase genes (CYP19a and CYP19b) in zebrafish fry (<i>Danio rerio</i>) Abstract Cytochrome P450 aromatase (CYP19) is the terminal enzyme in the steroidogenic pathway that converts androgens (e.g., testosterone) into estrogens (e.g., estradiol). Regulation of this gene dictates the ratio of androgens to estrogens; therefore, appropriate expression of this enzyme is critical for reproduction as well as being pivotal in sex differentiation for most vertebrates. It is assumed that most vertebrates have a single CYP19 gene that is regulated by multiple tissue‐specific promoter regions. However, the zebrafish (Danio rerio ) has two genes (CYP19a and CYP19b), each encoding a significantly different protein and possessing its own regulatory mechanism. The primary purpose of this study was to determine the pattern of expression of each of the CYP19 genes in the developing zebrafish. A fluorescent‐based method of real‐time, quantitative RT‐PCR provided the sensitivity and specificity to determine transcript abundance in single embryos/juveniles harvested at days 0 through 41 days post‐fertilization (dpf), which encompasses the developmental events of sex determination and gonadal differentiation. CYP19 transcripts could be detected as early as 3 or 4 dpf, (CYP19a and CYP19b, respectively) and peak abundance was detected on day five. In general, the CYP19 genes differed significantly in the ontogeny of their expression. In most cases, the gonadal form of CYP19 (CYP19a) was more abundant than the brain form (CYP19b); however, unlike CYP19a, the pattern of CYP19b expression could be clearly segregated into two populations, suggesting an association with sex differentiation. Pharmacological steroids (ethinylestradiol and 17α‐methyltestosterone) enhanced the expression of the CYP19b gene at all three days examined (4, 6, and 10 dpf). These data suggest that the timely and appropriate expression of CYP19 is important in development and that the expression of CYP19b (the “extra‐gonadal” form) may be associated with sexual differentiation if not sexual determination. J. Exp. Zool. 290:475–483, 2001 . © 2001 Wiley‐Liss, Inc.
Wiley - Tập 290 Số 5 - Trang 475-483 - 2001
Tổng số: 39
- 1
- 2
- 3
- 4