Spermiogenesis in the Nile tilapia Oreochromis niloticus with notes on a unique pattern of nuclear chromatin condensation

Spermiogenesis in the Nile tilapia, Oreochromis niloticus, was observed ultrastructurally. The process of spermatid differentiation can be divided into six distinct stages based mainly on changes in the nucleus of spermatids. During the latter half of the process, nuclear chromatin condenses progressively to form many dense globules, which ultimately adhere tightly to pack the head of mature spermatozoa. During chromatin condensation the nucleus diminishes in size, and part of the nuclear envelope and nucleoplasm forms a vesicular structure that is finally discarded from the cells together with an associated thin layer of cytoplasm. The spermatozoon comprises a roundish head, a relatively small midpiece, and a relatively short flagellum consisting of the usual 9+2 axoneme. No acrosomal structure is developed during spermiogenesis.     

TRH-Gly, a precursor of TRH, alters GH secretion in acromegaly

We explored effects of a precursor of thyrotropin (TSH)-releasing hormone (TRH), TRH-Gly, on growth hormone (GH) secretion in acromegaly. Intravenous injection of TRH-Gly produced a profound increase in GH secretion in eight, decrease in two, and no response in five out of a total fifteen patients. The magnitude of GH responsiveness to TRH-Gly was significantly correlated with that induced by TRH (r = 0.824, P less than 0.01). In contrast, TRH-Gly did not induce secretion of TSH or prolactin. The present data suggest that TRH-Gly may participate in regulating GH secretion in some patients with acromegaly and that TRH-Gly-induced GH secretion may be due at least in part to TRH-associated mechanisms underlying GH secretion.