A sustained release gel formulation of doramectin for control of lone star ticks (Acari: Ixodidae) and horn flies (Diptera: Muscidae) on cattle.

A gel formulation formed by incorporating technical doramectin into a 10% hydroxypropyl methylcellulose aqueous solution was used to subcutaneously inject steers at varying dosages. Doramectin serum concentration of steers receiving 600 microg (AI)/kg body weight declined from 21.9 ppb at 0.5 wk to below detectable at 8 wk postinjection. The 1,200 microg (AI)/kg injection resulted in serum concentrations of 29.1 ppb at 0.5 wk and declined to 0.5 ppb at 8 wk postinjection. Both the 600 and 1,200 microg (AI)/kg injections provided 100% inhibition of index of fecundity (IF) in adult lone star ticks, Amblyomma americanum L. (Acari: Ixodidae) through week 8, after which inhibition declined to 79.4 and 45.3%, respectively, during the 12th week posttreatment. For steers treated at 600 microg (AI)/kg, mortality of adult horn flies, Hematobia irritans L. (Diptera: Muscidae), declined from 16.9% during week 2 to 3.1% during week 7 postinjection. The blood from steers treated at 1,200 microg (AI)/kg resulted in a similar decline in mortality of blood fed adult horn flies from 29.4% during week 1 to 4.0% during week 7. The 600 microg (AI)/kg treatment provided complete control of larval horn flies in the manure for 9 wk, whereas the 1,200 microg (AI)/kg injection gave complete control for 14 wk posttreatment. The doramectin gel formulation provided long-lasting delivery of doramectin to cattle and extended control of lone star ticks and larval horn flies. Such a simple and inexpensive formulation could be useful in tick eradication programs by reducing the frequency of gathering cattle.

Connective tissue activation. XVIII. Stimulation of hyaluronic acid synthetase activity.

Human synovial fibroblasts synthesize hyaluronic acid, a process that can be stimulated by a number of agents. Several steps in the synthetic pathway could be the locus at which these stimulators act; the final step, promoted by hyaluronic acid synthetase, was selectd for study. Hyaluronic acid synthetase is an enzyme system that transfers monosaccharide units to nascent hyaluronic acid chains. Activities of the enzyme were determined in lysates of cultured synovial fibroblasts by measuring incorporation of 14C-UDP-glucuronic acid into hyaluronic acid. Rates of hyaluronic acid synthesis were increased by adding CTAP-I or CTAP-III, DbcAMP, or prostaglandin E2 to the cultures. In each instance, hyaluronic acid synthetase activity was enhanced in a manner comparable to that seen in hyaluronic acid synthesis. The changes in enzyme and product were observed as early as 6 hr after cultures were exposed to CTAP-III, and both indices declined when this stimulator was withdrawn for 24 hr. Although DbcAMP incrased the hyaluronic acid synthetase activity of intact fibroblasts, it had no effect on the enzyme in lysates of cells. In the cultured cells, cycloheximide reduced basal levels of synthetase activity and hyaluronic acid synthesis of hyaluronic acid may do so by inducing hyaluronic acid synthetase.