摘要:

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of gonad-stimulating substance (GSS). It has also been reported that 1-MeAde induces follicular envelope breakdown (FEBD), releasing oocytes from the ovaries; i.e., spawning. This study was undertaken to determine whether the amount of 1-MeAde produced by follicle cells is enough to induce germinal vesicle breakdown (GVBD) and FEBD in the starfishAsterina pectinifera. After incubation of an ovary with GSS at concentrations of more than 0.05 mg/ml for about 20 min, spawning started. Almost the same period of time was required for spawning after treatment with 0.1 μM 1-MeAde. However, continuous treatment with GSS was not necessary, and about 5 min of GSS application was sufficient for induction of spawning. Each oocyte is surrounded by a follicular envelope consisting of about 50 cells. 1-MeAde production by isolated follicle cells started immediately upon GSS stimulation, and the amount of 1-MeAde produced in vitro was correlated with the number of follicle cells present. Thus, 50 follicle cells were shown to produce about 1.1 fmol 1-MeAde during 5 min of GSS treatment. These results confirm that the amount of 1-MeAde produced by follicle cells is sufficient for meiosis initiation and release of oocytes in starfish.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672357

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Concentrations of tributyltin (TBT) less than 5 ng/l were recorded in most coastal water samples taken from a series of sites in north-east England during autumn 1991. Levels in the industrialized Tyne estuary still exceeded the Environmental Quality Standard (EQS) in 1991 but had fallen from values recorded in 1989–90. Coastal dogwhelkNucella lapillus(L.) samples taken in 1991 had low concentrations of <0.01–0.03 μg TBT/g wet tissue. Dogwhelk populations were suffering from severe imposex when they were sampled in 1986, but there was clear evidence of recovery by 1991/92. Relative Penis Size Index scores declined between 1986 and 1991/92; two populations which were not breeding in 1986 (as evidenced by lack of juvenile recruitment) reproduced successfully in the years preceding 1991; and dogwhelk abundance on the shore increased over the study period.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672358

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672359

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672360

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672346

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor