ISSN:0022-104X    

DOI:10.1002/jez.1402610202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe motility of the spermatozoa of freshwater fish is usually of short duration, but a precise description has rarely been provided. Motility requires a high dilution (more than 1,000‐fold) for initiation of synchronous motility in 100% of spermatozoa; a two‐step procedure is necessary, with an initial dilution of 1 to 100 in a medium that keeps the spermatozoa immotile and allows good mixing of the viscous semen. The second dilution (1 to 20) in the activating solution can be made directly under the microscope. Studies of carp sperm indicate that movement of live sperm is influenced by the ionic environment. The inhibition of motility in semen is mainly due to K+ions in trout and osmotic pressure in carp, but other ions such as Na+, H+, and Mg2+also interfere. Initiation of motility in trout requires external divalent cations. Immediately after dilution at 20°C, spermatozoa exhibit large circular trajectories (>400 μm in diameter), high beat frequencies (60 Hz), and velocities of 250 μm/sec. These values decrease rapidly. Within 20 sec after dilution, most spermatozoa stop moving, although some of them show some agitation with low beat frequency (<10 Hz) and with very limited displacement during the next few minutes. A similar pattern is observed in carp, with active motility lasting 40 sec. Under certain ionic conditions, intratesticular spermatozoa are motile and have some fertilizing ca

ISSN:0022-104X    

DOI:10.1002/jez.1402610203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractDue to a cystic mode of spermatogenesis and zonal testes, the spiny dogfish shark (Squalus acanthias) and salamander (Necturus maculosus) are advantageous for studying the relationship between steroidogenesis and germ cell development. Direct analysis of steroidogenic enzymes and steroid receptors in staged tissue samples, together with light and electron microscopic observation, suggests that androgens and estrogens produced by Sertoli cells or Leydig cells immediately before or after spermiation serve as intratesticular regulators of events specific to premeiotic stages of spermatogenesis. These correlative data are consistent with limited observations in mammalian testis and provide a conceptual framework for direct testing of functional interactions between spermatogenesis and steroidogenesis in future studies.

ISSN:0022-104X    

DOI:10.1002/jez.1402610204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn an attempt to discern general mechanisms by which specific hormones control certain aspects of fish spermatogenesis, we focus on a single fish species (Fundulus heteroclitus), and, by analogy, generalize to other fishes. At least three androgenic steroids (testosterone, 11‐ketotestosterone, 11β‐hydroxytestosterone) are present in the serum ofFundulus heteroclitus, but only testosterone appears to be associated with spermatogenesis in vitro as well as in vivo. 11‐Ketotestosterone appears to be associated with spermiation in vivo, but has not yet been tested for its ability to cause spermiation in vitro. The preponderant androgen present in the serum, 11β‐hydroxytestosterone, does not appear to be directly associated with spermatogenic process either in vitro or in vivo.InF. heteroclitus, in vivo studies indicate that at least two different gonadotropins are produced, on that primarily causes steroid production and a second that causes testicular growth. Indirect evidence suggests that production of these gonadotropins is seasonal in terms of both their amounts and their relative pr

ISSN:0022-104X    

DOI:10.1002/jez.1402610205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTestis structure in the chordates has been evaluated based upon relationships between primary spermatogonia, Sertoli cells, and the changes in the chronological secretion of the extracellular basement membrane. Prespermatocystic, polyspermatocystic, lobular, and tubular testicular types are described. In all chordates, germinal and interstitial compartments are separated by a basement membrane. The timing of the formation of this separation varies with the chordate class. Although primary spermatogonia are not initially separated from the interstitial tissue in agnathans and elasmobranchs, a basement membrane forms around secondary spermatogonia and associated Sertoli cells before meiosis. The spermatocyst so formed is a unit of testicular evolution. In fishes and amphibians, Sertoli cells, primary spermatogonia, and the subsequent stages of germ cell development reside in spermatocysts. They are always sequestered from interstitial tissues by a basement membrane. Sertoli cells rest upon the basement membrane and their processes form the borders of spermatocysts. I propose the Extracellular Matrix Hypothesis to explain how changes in the chronological formation of basement membranes resulted in the evolution of lobular and tubular testes from spermatocystic testes.

ISSN:0022-104X    

DOI:10.1002/jez.1402610206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAnnual variations of androgen secretion and Leydig cell number occur in seasonally breeding animals: herein we review comparative observations on two widely divergent species, the salamander and hamster. Based on our laboratory studies in the hamster, we conclude that Leydig cell numbers increase during testicular recrudescence through a combination of differentiation of mesenchymal cell precursors and Leydig cell division. Secretion of androstane‐3α, 17β‐diol, a 5α‐reduced androgen, occurs transiently during the seasonal cycle and may be a characteristic of differentiating Leyd

ISSN:0022-104X    

DOI:10.1002/jez.1402610207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this report, seasonal changes in testicular structure and spermatogenesis in several shark species are reviewed, and new information concerning the bonnethead shark,Sphyrna tiburo, is presented. Shark species are separated into four categories based on the relationship between testicular GSI and mating season: 1) species that have a defined seasonal cycle in GSI and a defined mating season, 2) species that have a defined seasonal cycle in GSI and that mate year‐round, 3) species that show no seasonal change in GSI but that have a defined mating season, and 4) species that show no seasonal change in GSI but that mate year‐round. The testis ofS. tiburodiffers from the few species that have been examined in that 1) not all spermatogenic stages are present at all times of the year, 2) an annual zone of degeneration that progresses through the testis is not present, and 3) there appears to be complete testicular regression and recrudesce

ISSN:0022-104X    

DOI:10.1002/jez.1402610208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractDue to the relative dearth of data regarding somatic cell‐germ cell interactions in the testes of non‐mammalian chordates, functional homologies between Sertoli cells from diverse organisms have been difficult to assess. However, recent developments in non‐mammalian testis cell and organ culture techniques have provided experimental approaches to compare Sertoli cell‐germ cell interactions in different vertebrates. Data from in vitro analyses of Sertoli cell‐germ cell interactions are presented to suggest that Sertoli cells from rodents and the frogXenopus laevishave similarities in supporting energy metabolism and glutathione metabolism in spermatogenic cells. Comparative in vitro analyses of Sertoli cell functions should provide further insights into the evolution of cell‐cell interactions in

ISSN:0022-104X    

DOI:10.1002/jez.1402610209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractSexual differentiation in eutherian mammals follows a simple governing paradigm: development proceeds in a female direction unless a masculinizing mechanism intervenes. Sexual development in fishes is much more plastic than in mammals. It permits the intervention of environmental factors and follows several different types of sequences that produce successive hermaphrodites and alternative pathways for the development of the same final sex. In spite of this plasticity, the primacy of female development is suggested by the initial ovarian phase in the development of gonads of both sexes in some gonochoristic fishes and by protogynous sex change. One barrier to the application of this principle to fishes generally is the existence of protandric hermaphrodites. Recent evidence suggests a reinterpretation of gonadal differentiation in a protandric anemonefish and a protandric sparid. In both cases, testicular development is both preceded and followed by ovarian development. These patterns are interpreted to mean that female development is primary and that male development is a temporary phase initiated by a masculinizing mechanism and terminated by its cessation.

ISSN:0022-104X    

DOI:10.1002/jez.1402610210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMale zebrafish,Brachydanio rerio, have paired testes and no additional reproduction glands. Incubation experiments with3H‐labeled steroid precursors showed the capacity of testes to synthesize seven steroid glucuronides. Enzyme histochemical studies demonstrated interstitial (Leydig) cells as steroid and steroid glucuronide producing sites. Male holding water, testis homogenates, and testis fractions containing steroid glucuronides were able to induce ovulation in female zebrafish. Deglucuronidation of these fractions led to a loss of ovulation inducing potency, indicating steroid glucuronides as ovulation inducers. The chemical substances are perceived by the recipients by means of olfaction, as anosmic females do not have an ovulatory response after administration of male holding water. In African catfish,Clarias gariepinus, the male reproductive organ system consists of two paired structures, the testis and the seminal vesicle. Histochemical enzyme investigations pointed to interstitial cells as sites of steroid and steroid glucuronide production both in testis and seminal vesicle. Glucuronidation of steroids may also take place in the epithelium lining and seminal vesicle tubules. Biochemical studies showed the seminal vesicle as the main source of steroid glucuronides. Eight conjugated steroids were identified. Electrophysiological studies demonstrated that these compounds, especially 5β‐pregnane‐3α, 17α‐diol‐20‐one‐glucuronide are olfactory stimulants in female conspecifics. Males with enlarged seminal vesicles, caused by compensatory growth after castration, were more attractive to ovulated female catfish in a two‐choice test, using a U‐shaped tank. Males lacking seminal vesicles were less attractive. The steroid glucuronide fraction of seminal vesicle fluid appeared to be responsible for the attraction effect. A synthetic mixture of steroid glucuronides resulted in a dose dependent attraction effect. The data are indicative of a pheromonal function for steroid glucuronides that are produced by the reproductive organ system of male zebrafish

ISSN:0022-104X    

DOI:10.1002/jez.1402610211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY