摘要:

AbstractThe loss in protein synthesis which the regenerating forelimb of the newt suffers after denervation can be recovered by infusing into it an extract of newt soluble brain protein. Moreover, the synthesis of basic protein shows a greater response to the active brain principle than does that of acidic protein. The active agent of the nervous tissue is destroyed by heat and trypsin digestion. Extracts of liver and spleen, similarly prepared, do not evoke recovery of lost protein synthesis. Synaptosomal extracts of the frog brain also cause recovery of protein synthesis in the denervated regenerate, demonstrating the likelihood that the active agent is not species‐specific within these amphibians, that it is a constituent of the neuronal fraction of nervous tissue, and that it is present in axonal terminals. Additional experiments showed that the nervous agent is likely a basic protein, and that the amount of protein infused is of the order of only 1.0% of the total regenerate protein. The significance of the findings is discussed in relation to the nature of the effect on protein synthesis and the nature of the active principl

ISSN:0022-104X    

DOI:10.1002/jez.1401960202

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe process of spermatogenesis inRana esculenta(living in the surroundings of Naples) resurges gradually in the spring months, proceeds actively through the summer and declines gradually in the winter months reaching an almost total “quiescence” for a short length of time. The repeating from year to year with a distinct regularity of spermatogenetic cycle suggests that environmental cues play a role in timing its various phases. Both temperature and photoperiod appear to be potential modifiers of spermatogenetic activity in this species. It is, however, probable that photoperiod acts only in a permissive way to facilitate the temperature response which seems to be the more direct modifier of the testicular activity.The proliferation of primary spermatogonia seems to be favoured by only low temperatures. The formation of secondary spermatogonia, and primary and secondary spermatocytes occurs when there occurs a gradual increase in the ambient temperature, day length and gonadotropin secretion. This period is characterized by very low plasma level of testosterone, that, through the reduced negative feedback to the hypothalamus, favours an increased secretion of FSH‐like gonadotropin. Spermatid formation is entirely androgen‐dependent as confirmed by the use of a specific antiandrogen, cyproterone acetate. In fact spermatid formation naturally occurs in a period when plasma level of testosterone is increasing and pituitary gonadotrops are declining in their secretory activity. In this period the ambient temperature and the photoperiod gradually decline.The importance of lateral eyes and the pineal gland in the mediation of influence of photic cues has been shown. It seems that without either the eyes or the pineal gland both light and temperature are completely ineffective in stimulating the early spermatogenesis, which shows the permissive role of light on temperature influence upon spermatogenesis.Hypophysectomy impairs spermatogenesis, which can be restored by a replacement therapy with homoplastic pituitary extract. Testosterone alone does not restore spermatogenesis except enhancing spermatid formation. Pituitary extract stimulates mitotic activity of spermatogonia and formation of primary and secondary spermatocytes. Testosterone is not involved because the stimulatory effects of pituitary extract are only marginally blocked by the antiandrogen. In fact spermatogonial multiplication is partially inhibited, while spermatid formation is totally blocked, indicating that ICSH‐like gonadotropin acts upon the formation of spermatids through the stimulation of testosterone production.Thus it has been found that there exists a complex interaction between the environmental factors and the “endogenous hormonal trigger” that subsequently steps into the regulation of sp

ISSN:0022-104X    

DOI:10.1002/jez.1401960203

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

年代:1976

数据来源: WILEY

摘要:

AbstractTo account for the differences between proters and opisthes with regard to extra cytoproct morphogenesis inParamecium tetraurelia, two hypotheses have been proposed and tested. (i) The differences may be a result of different actions of proter‐macronucleus and opisthe‐macronucleus. This hypothesis has been tested by cytoplasmically connecting the proter with the opisthe in the form of chains, some of which have only one macronucleus per chain. However, the connected proters and opisthes remain different in extra cytoproct morphogenesis, thus arguing against the hypothesis. (ii) The differences may be a result of differences between the proter and the opisthe with regard to the development of their posterior‐ventral cortex: proters have a newly‐developed posterior‐ventral cortex whereas opisthes receive the posterior‐ventral cortex from the pre‐fission mother animal. This hypothesis has been tested by surgically producing an opisthe with a newly‐regenerated posterior cortex. Such opisthes, however, remain different from proters in extra cytoproct morphogenesis. Thus no direct support for the second hypothesis is obtained. Also, proteropisthe difference in morphogenesis may be understood in terms of Wolpert's positional information hypothesis, by assuming that the anterior and posterior ends of a dividing animal serve as reference points for establishing a gradient and that positional information before separation of the two daughter animals leads to differences in extra cytoproct morphogenesis between them a

ISSN:0022-104X    

DOI:10.1002/jez.1401960204

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe inhibitory effect of dithiothreitol on meiotic maturation of mouse oocytes in vitro is a function of the intracellular dibutyryl cyclic AMP concentration. Inhibition of nuclear (germinal vesicle) breakdown by dibutyryl cyclic AMP is reversed upon transfer of oocytes to plain culture medium, where‐as, transfer to medium containing dithiothreitol results in continued inhibition. Dithiothreitol significantly enhances the effectiveness of dibutyryl cyclic AMP as an inhibitor of meiotic maturation. These results suggest that the reported effect of sulfhydryl reducing agents on membrane dissolution and reconstitution, in both meiotic and mitotic cells, may be attributed to their influence on intracellular levels of cyclic AM

ISSN:0022-104X    

DOI:10.1002/jez.1401960205

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

年代:1976

数据来源: WILEY

摘要:

AbstractCanine ovarian oocytes were cultured in a medium consisting of TC medium 199, fetal calf serum and antibiotics. Ninety‐nine percent of the apparently healthy oocytes were in the germinal vesicle (dictyate) stage when recovered from the ovaries; 25% of them reached metaphase I or II by 72 hours of culture. Washed ejaculated spermatozoa were added to BWW medium containing oocytes which had either been removed directly from the follicles or which had been cultured for 24‐72 hours. The earliest acrosome reaction and zona penetration by spermatozoa were seen at seven hours after insemination. Seventy‐four percent of the oocytes examined between 11 and 24 hours after insemination showed evidence of zona penetration by spermatozoa. Neither the condition of the oocyte vitellus nor the stage of nuclear maturation influenced the incidence of zona penetration. Decondensing sperm nuclei were found in the vitellus of 27% of the oocytes which had not been cultured and in the vitellus of 20% of those which had been cultured for 24–72 hours and were in various stages of maturation. These results indicate that (1) canine ovarian oocytes can be matured in vitro, (2) the spermatozoa require capacitation which takes approximately seven hours in vitro and (3) maturation of the oocytes is not required for sperm passage through the zona pellucida or entry into the vitellus nor for sperm nuclear deconde

ISSN:0022-104X    

DOI:10.1002/jez.1401960206

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn certain fish hybrids, malignant transformation of pigment cells is due to the presence of a tumor gene (Tu), the action of which is controlled by several regulatory elements. Absence of these controlling genes causes rapid proliferation of theTu‐transformed cells and ultimately results in melanoma formation. One of these genes has been identified as a differentiation gene (Diff), since it seems to control the differentiation of the transformed pigment cells. Light and electron microscopy ofTu‐transformed cells of fish differing in the dosage ofDiff, and the determination of tyrosinase activity in homogenates of the respective tissues revealed that the degree of cellular differentiation depends on the dosage ofDiffpresent in the genome. It is concluded that the geneDiffpromotes the differentiation of malignant melanoma cells into benign melanopho

ISSN:0022-104X    

DOI:10.1002/jez.1401960207

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

年代:1976

数据来源: WILEY

摘要:

AbstractA system for stagingA. maculatumduring growth and metamorphosis was devised, based on several parameters of body size; body length, tail length and tail width. Animals at various stages of metamorphosis were empolyed to study the relationship between specific biochemical and histological changes that occur in the tail of this urodele during metamorphosis. The specific and total activity of two hydrolytic enzymes, acid phosphatase and β‐N‐acetyl‐glucosaminidase, were measured in tail tissues at progressive stages of development. The activites of these enzymes increased in both the fins and muscular portion of the tail during metamorphosis. These activities can be correlated with resorption of the tail fins and the remodeling of tissues in the muscular portion of th

ISSN:0022-104X    

DOI:10.1002/jez.1401960208

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe recessivempgene in syngen 1 (Species 1) ofTetrahymena pyriformisresults in a characteristic set of abnormalities of the adoral membranelles, commonly including some extra membranellar segments (Kaczanowski, '75). The abnormal pattern is produced in about 10% of dividing cells, compared to 80% of cells undergoing oral replacement. Thus the percentage of abnormal cells increases during prolonged stationary phase. Abnormal oral replacement arises primarily from a separation of two kinetosomal fields: the field of kinety no. 1 (the K‐1 field), and the anterior field originating from the displaced undulating membrane. Both sites of proliferation appear also during wild type morphogenesis, but they fuse early to form one integrated field (Frankel, ′69). The prolonged separation of the subfields inmp/mpcells results in a separate assembly of adoral membranelles; however, the independently developing membranelles of the two subfields are united later to produce a single oral apparatus. A single gene‐dependent factor apparently alters some property of the cortical layer, which in turn is responsible for a reduced integrity of the oral replacement primo

ISSN:0022-104X    

DOI:10.1002/jez.1401960209

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

年代:1976

数据来源: WILEY

摘要:

AbstractMale red‐winged blackbirdsAgelaius phoeniceusin their first year normally do not establish territories or breed. To investigate the possibility that interactions with older males might inhibit reproductive development of young males, we compared the behavior of first‐year males in the presence and absence of older males. For three months during the first half of the breeding season, we studied mixed‐ and single‐age groups of three males in standardized outdoor aviaries: two groups of three first‐year males (FFF groups), two groups of one older and two first‐year males (AFF groups), and one group of three older males (AAA group). In all groups one male established clear dominance, invariably the older male in AFF groups. The dominant male in FFF groups displaced subordinates less frequently than did the dominant older male in AFF groups early in the season, but equally frequently later. In May the largest testis weights of males in FFF groups were significantly lower than those of dominant older males in AFF groups. First‐year males in the absence of direct interactions with older males can achieve levels of aggressive behavior comparable to those of a dominant older male in similar social environments but the seasonal development of their aggressive behavior occurs later and their testes in May are smaller than dominant adults'. This delay in the seasonal development of aggressive behavior in first‐year males, independent of the immediate social environment, suggests that the age‐dependent territoriality of males in this species is not strongly regulated by effects of older males on the development

ISSN:0022-104X    

DOI:10.1002/jez.1401960210

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe role of the thymus during the first three weeks of larval life in the maturation of humoral immunity in the amphibian,Xenopus laevis, is examined. Thymectomy throughout this period dramatically affects the heterologous red cell response of young adults. Sheep erythrocyte (SRBC) administration elicited haemolytic antibody production in the blood and in the spleen (measured by the appearance of plaque forming cells) of control animals, but failed to do so in all thymectomized toadlets. Moreover, use of the immunocytoadherence assay, which proved to be a sensitive test for SRBC reactivity in controlXenopus, indicated a complete absence of induced responsiveness to this antigen in the spleens of thymectomized toadlets, even in those animals thymectomized as late as 22 days of age.In contrast to allograft immunity inXenopus, which is suppressed only by thymic ablation during the first two weeks of larval life, the development of reactivity to heterologous erythrocytes therefore requires an additional period of thymic influence during ontogeny. These experiments support a concept of thymus‐dependent cell heterogeneity in amphibian

ISSN:0022-104X    

DOI:10.1002/jez.1401960211

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

年代:1976

数据来源: WILEY