Effect of fentanyl constant-rate infusions with or without medetomidine on the minimum infusion rate of propofol required to prevent motor movement in dogs

Propofol is a potential injectable anesthetic agent used in total intravenous anesthesia. However, the sparing effect of fentanyl and medetomidine on the required propofol dose in dogs remains unclear. We aimed to investigate the effect of fentanyl constant-rate infusion (CRI) with or without medetomidine on the minimum infusion rate of propofol required to prevent motor movement (MIRNM) in dogs. Six healthy purpose-bred dogs were anesthetized on three occasions with propofol alone (loading dose [LD], 8 mg/kg to effect; initial infusion rate [IR], 0.70 mg/kg/min); propofol (LD, 6 mg/kg to effect; IR, 0.35 mg/kg/min) and fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min); or propofol (LD, 4 mg/kg to effect; IR, 0.25 mg/kg/min), fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min), and medetomidine (LD, 2 µg/kg; IR, 0.5 µg/kg/hr) under controlled ventilation. The MIRNM was determined by observing the response to a noxious electrical stimulus. Heart rate, blood pressure, and blood gas analyses were performed at 1, 2, 3, and 4 hr after initiating CRI. The MIRNM (mean [range]) was significantly lower in the propofol-fentanyl-medetomidine group (0.16 [0.10-0.27] mg/kg/min) than that in the propofol-alone group (0.63 [0.47-0.82] mg/kg/min) (P=0.0004). Fentanyl combined with medetomidine did not significantly decrease the mean arterial pressure in dogs receiving propofol CRI 1-3 hr after initiating CRI compared with propofol CRI alone (P>0.9999, P=0.1536, and P=0.0596, respectively), despite inducing a significantly lower heart rate.

A cytochemical study of the sulfhydryl groups of sea urchin eggs during the first cleavage

In the eggs of four species of echinoderms, Mespilia globulus, Pseudocentrotus depressus, Hemicentrotus pulcherrimus and Clypeaster japonicus, changes in the distribution of protein-bound SH groups from fertilization to the 2 cell stage have been studied cytochemically by use of a mercaptide-forming azo dye. In the eggs of these species, the color intensity in the cytoplasm increased upon fertilization. The astral centers and spindle during mitosis were stained deeply. When the aster formation was suppressed by ether, hyaline spots appeared in the egg cytoplasm instead of well formed astral centers and these spots were stained by the SH-specific dye. Upon recovery of such eggs in pure sea water, and when cleavage ensued, such spots disappeared and two new astral centers were reorganized. The SH-protein occurring in the centrosphere is considered to be the precursor material for the asters and spindle, and this material is apparently derived from the cytoplasm.