Distribution and density of Lutraria rhynchaena Jonas, 1844 relate to sediment while reproduction shows multiple peaks per year in Cat Ba-Ha Long Bay, Vietnam.

Lutraria rhynchaena Jonas, 1844 is of great commercial interest, but its reserves have dramatically declined over recent decades. Therefore, there is an urgent need of scientific basis to propose effective fishery management measures and improve artificial aquaculture of the clam. In this study, we investigated the distribution and density of L. rhynchaena, sediment characteristics, and established the clam's reproductive cycle through monthly observations from August 2017 to July 2018. The study results showed that distribution and density of clams are related to sediment types, and the sediment type of medium sand is likely the best benthic substrate for the clams. The spawning of clams occurred throughout the year with three spawning peaks in January, April and September. For the sustainable management of the clam resource in Cat Ba-Ha Long Bay, the fishery authorities can issue a ban on harvest of the clam in spawning peak months in January, April and September.

One-pot synthesis of hollongdione from dipterocarpol.

A one-pot synthesis of a hybrid triterpenoid-steroid molecule, hollongdione (22,23,24,25,26,27-hexanordammar-3,20-dion), was achieved in a yield of 89%, based on the selective dehydration of dipterocarpol following ozonolysis. The structure of hollongdione was confirmed by X-ray analysis for the first time. Dammar-20(22),24(25)-dien inhibited the growth of Mycobacterium tuberculosis (strain H37Rv) in vitro with a MIC of 50 µg/mL.

Chrysosplenol C increases contraction in rat ventricular myocytes.

Chrysosplenol C (4',5,6-trihydroxy-3,3',7-trimethoxyflavone) is a flavone contained in several medicinal plants including Miliusa balansae and Pterocaulon sphacelatum. This compound is known to have an antiviral effect and show cytotoxic activity in several cell lines. In the present study, we explored the effect of chrysosplenol C on contractility in isolated adult rat ventricular myocytes. Chrysosplenol C was isolated from M. balansae, and cell shortenings were measured in field-stimulated single myocytes using a video edge detection method at room temperature. Chrysosplenol C was found to increase cell shortenings in a dose-dependent manner with a half-maximal effective concentration of 45 ± 7.8 µM. Maximal effect of chrysosplenol C, approximately 185% of control, was observed at ≥80 µM. The positive inotropic effect caused by chrysosplenol C was reversible. Time-to-peak contraction and time-to-relengthening were significantly increased by chrysosplenol C. The velocity of cell shortening was slightly accelerated, whereas that of relaxation was not altered by chrysosplenol C. The chrysosplenol C­induced positive inotropic effect was not inhibited by propranolol posttreatment or H-89 pretreatment, suggesting that chrysosplenol C increased contraction independently of ß-adrenergic receptor stimulation and protein kinase A. Our findings are the first to demonstrate that chrysosplenol C is a positive inotropic agent in cardiac myocytes.