Wiley
0022-104X
1097-010X
Cơ quản chủ quản: N/A
Lĩnh vực:
Phân tích ảnh hưởng
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The passerine bird song system as a model in neuroendocrine research
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.
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.
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.
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.
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.
Tập 290 Số 5 - Trang 475-483 - 2001
A mechanism for the action of pregnant mare serum gonadotropin on aromatase activity in the ovarian follicle of the medaka, <i>Oryzias latipes</i> Abstract Our recent studies (Sakai et al., '88) have shown that there is a progressive increase in aromatase activity, assessed indirectly by the conversion of exogenous testosterone to estradiol‐17β, in medaka (Oryzias latipes ) vitellogenic follicles isolated between 28 and 20 hr before spawning. The present study was designed to determine if pregnant mare serum gonadotropin (PMS) and cAMP are able to induce aromatase activity in early vitellogenic follicles isolated at 32 hr before spawning. Both 100 IU/ml PMS and 100 ng/ml testosterone alone significantly stimulated estradiol‐17β production by follicles at this stage. PMS also enhanced testosterone‐induced estradiol‐17β production. This enhancing effect of PMS on aromatization of exogenous testosterone to estradiol‐17β was completely inhibited by 10 μg/ml actinomycin D and 10 μ/ml cycloheximide. Both 5 mM dibutyryl cAMP (dbcAMP) and 10 μM forskolin, an adenylate cyclase activator, alone significantly stimulated estradiol‐17β production. A 1 μg/ml dose of cyanoketone, a potent inhibitor of 3β‐hydroxysteroid dehydrogenase, completely suppressed PMS‐ and forskolin‐induced estradiol‐17β production in the absence of testosterone, but did not influence the enhancing effect of either PMS or forskolin on the conversion of exogenous testosterone to estradiol‐17β. These results indicate that PMS induces aromatase activity in medaka vitellogenic follicles via an adenylate cyclase‐cAMP system, and further suggest that this action of PMS is dependent upon both transcriptional and translational processes.
Tập 259 Số 1 - Trang 53-58 - 1991
Analysis of ciliary beat frequencies in hamster oviducal explants Abstract We have developed a simple direct method, requiring minimal manipulation, to measure beat frequencies of the cilia on the external surface of hamster oviducal infundibula in vitro. Two perfusion chambers (closed and open) were used; both can be hand‐made in a few minutes and discarded after use. Ciliary beat frequencies were determined by measuring variations in light intensity with time in a single pixel positioned over a video image of the beating cilia. Data files were collected using Image 1 software and later transferred to PSI Plot or Lotus 123 spreadsheets for analysis by counting the number of brightness peaks recorded per second or by subjecting the data to Fourier transformation with or without smoothing. These methods of analysis gave similar results. To verify that Image 1 data files contain accurate representations of CBF, videotapes of beating cilia were made and subjected to frame‐by‐frame analysis. Image 1 interfaced with a standard video camera was found to collect reliable data over a beat frequency range of 0‐‐15 cycles/sec. In some Fourier transforms, secondary peaks were observed and were shown to represent cilia beating at more than one frequency in a sampled region. Coefficients of variation for repeated measurements taken on the same region varied from 4.1% to 9.0%. Small but significant differences were found between beat frequencies at different regions of the same oviduct. When chambers were perfused discontinuously and measurements of beat frequency were made at least 5 min after each perfusion, no effect of perfusion on frequencies was observed. However, during continual perfusion of the open chamber, a slight but significant increase in beat frequency was observed after perfusion was initiated. Muscle contraction, which sometimes occurs in the open chamber, did not affect beat frequency measurements. Infundibula could be stored at 4°C overnight without any negative effect on beat frequencies. Cold storage also reduced muscle contraction. Placement of a small coverslip on infundibula in the open chambers was also found to reduce muscle contraction and facilitate beat frequency measurements. Coverslipping did not affect beat frequencies. This method of beat frequency analysis will be valuable for analyzing factors that regulate or influence cilia in mammalian oviducts. © 1995 Wiley‐Liss, Inc.
Tập 272 Số 2 - Trang 142-152 - 1995
The role of calcium in the acrosome reaction: An analysis using ionophore A23187 Abstract The role of Ca+2 in the acrosome reaction of echinoid and mammalian sperm was investigated using the Ca+2 transporting ionophore A23187. The ionophore induced morphologically normal acrosome reactions in both types of sperm (as assessed by electron microscopic observation of echinoid sperm and phase contrast microscopic observation of mammalian sperm). In echinoids, these reactions were immediate. In the guinea pig and hamster, ionophore significantly decreased the capacitation interval; early reactions were accompanied by activation of motility. Ionophore induced reactions were affected by sperm, ionophore and Ca+2 concentrations. Since both ionophore induced and natural reactions require extracellular Ca+2 , it is suggested that an influx of Ca+2 represents the initial step of the acrosome reaction. Under natural conditions, the permeability change which results in Ca+2 influx may be induced in echinoid sperm by egg jelly and may occur in mammalian sperm during capacitation. Ionophore A23187 should prove an experimentally useful drug for further study of the acrosome reaction since its effect on cells is understood, it induces synchronous reactions in a high percentage of sperm, and it conveniently reduces the capacitation interval in mammalian sperm.
Tập 198 Số 3 - Trang 383-392 - 1976