Measurement of hemodialysis access recirculation: a two-needle method at the start of dialysis.

Conventional methods of measuring recirculation in hemodialysis access include a three site method performed during dialysis, and a two site technique conducted at the end of a hemodialysis treatment. This study describes a two site procedure performed at the beginning of a hemodialysis session. Blood samples are drawn from the arterial side of the hemodialysis access immediately prior to hemodialysis (AIPD), and from the same arterial line (A+5) and venous line (V+5) when maximal blood flows are reached 5 min after starting hemodialysis. Blood urea nitrogen (BUN) is measured in these samples, and the results entered into the formula AIPD - A+5/AIPD - V+5 X 100% to calculate the percent recirculation. Percent recirculation calculated by this method compared favorably with, and may hold several advantages over conventional techniques.

Variations during the gonotrophic cycle in the titer of the myotropic ovulation hormone and the response of the ovarian muscles in Rhodnius prolixus.

The response of the ovarian muscles to a standard preparation of the myotropic ovulation factor from identified neurosecretory cells in the brain of Rhodnius prolixus increases after feeding in both virgin and mated females. This increase is unaffected by removal of the neurosecretory cells and by increases imposed on the resting tension of the ovaries used in the bioassay. The hemolymph titer of the myotropic activity as determined by bioassay exhibits a peak after feeding in both mated and virgin females. A second peak, corresponding both with the principal bout of ovulation/oviposition and with a corresponding peak in ovarian motility previously observed in vivo, is observed only in mated females. It is concluded that the changes in ovarian motility associated with ovulation in Rhodnius are a consequence primarily of variations in the hemolymph titer of the myotropic ovulation hormone from neurosecretory cells in the brain.