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Regular Article |
a Department of Biochemistry and Molecular Biology, Division of Reproductive Biology, Johns Hopkins School of Public Health, Baltimore, Maryland 21205
b Department of Psychology,
c Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21218
ABSTRACT
To determine the extent to which testicular regression involves apoptotic cell death, photosensitive adult starlings were photostimulated for up to 9 wk by exposure to long-day (18 h of light) photoperiods. Apoptotic activity in recrudescing and regressing testes was assessed by in situ TUNEL labeling. Absolute testis mass in male starlings increased after 2 wk of photostimulation and subsequently decreased with continued long-day exposure. Seminiferous tubule diameter also increased after 1–3 wk of photostimulation, then decreased as photorefractoriness developed. Testosterone concentrations increased significantly by Week 2 of photostimulation and declined with further light exposure. TUNEL labeling was significantly elevated in germ cells with 4 wk of photostimulation. An approximate 7-fold increase in the degree of apoptotic cell death was observed over the course of gonadal regression. Incidences of TUNEL labeling in somatic Sertoli cells also increased. Light and electron microscopy examination confirmed that these somatic cells displayed morphological characteristics of apoptotic death. In rodents, Sertoli cells have not been previously reported to die during gonadal regression. These results suggest that seasonal testicular regression in European starlings is mediated by apoptosis.
First decision: 8 August 2000.
1 This research was supported by NIMH grant 57535 to R.J.N., NICHHD training grant T32-HD-07276 to K.A.Y., NSF grant IBN 9905401 to G.F.B., and NIH grant NS 35467 to G.F.B.
2 Correspondence and current address: Kelly A. Young, Oregon Regional Primate Center, Division of Reproductive Sciences, Oregon Health Sciences University, 505 NW 185th Ave., Beaverton, OR 97006. FAX: 503 690 5563; youngk{at}ohsu.edu
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