S Wanichacheewa | PubMed Health

PubMed2001

Decrease in the number of sperm associated with decreased blood testosterone levels in male rats treated with extracts from seven plants consumed by natives of northern Thailand.

Natives of northern Thailand believe that certain plants preserved in alcohol provide sexual elevation although there is no scientific proof. To ascertain whether those plants have any biological effects on reproductive activity, we administered the extracts from seven kinds of plants to male rats. Treatments with these extracts resulted in a decrease in the number of sperm associated with decreased serum testosterone levels and an elevation of serum prolactin levels. The circulating levels of follicle stimulating hormone were only slightly affected by all extracts, although some extracts significantly decreased the luteinizing hormone levels. Thus, the extracts may contain a biologically active substance such as phytoestrogen and lead to a hormonal imbalance.

Journal Article↗

PubMedDate not supplied

Juvenile hormone-mediated termination of larval diapause in the bamboo borer, Omphisa fuscidentalis.

Larvae of the bamboo borer, Omphisa fuscidentalis are in diapause for more than nine months (Singtripop, T., Wanichaneewa, S., Tsuzuki, S., Sakurai, S. 1999. Larval growth and diapause in a tropical moth, Omphisa fuscidentalis Hampson. Zool. Sci. 16, 725-733). To examine the endocrine mechanisms underlying this larval diapause, we assayed the responsiveness of the diapausing larvae to 20-hydroxyecdysone (20E) and a juvenile hormone analogue (JHA: S-methoprene). 20E injection caused the larvae to halt movement, followed by deposition of a pupal cuticle. Topical application of JHA induced pupation in a dose-dependent manner. JHA also induced pupation of the larvae whose brains were removed before JHA application. In those larvae, the prothoracic glands became active and competent to respond to brain extracts within seven days after JHA treatment, and the hemolymph ecdysteroid concentration began to increase 12 days after JHA application. These results indicate that JHA stimulates the prothoracic glands of diapausing Omphisa larvae, terminating larval diapause, in contrast with previous findings that JH inhibits the brain-prothoracic gland axis and thus maintains the larval diapause. Current results therefore suggest a novel regulatory mechanism for larval diapause in this species.

Animals↗