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Two main applications of term rewriting systems are equational reasoning in theorem provers and equational computation in programming languages. The present paper examines a number of term rewriting systems in terms of how rewriting is used in different implementations of theorem provers, the use of rewriting techniques in logic programming languages and the problem of efficiency. In addition a non-exhaustive catalogue of distributed implementations is presented

Progesterone binding was studied in the uterus of rabbits at two different hormonal stages; either after oestrogen priming or a short time before implantation of the blastocyst (162 h post coitum). Uterine cytosols were incubated with [3H]progesterone, or the labelled hormone was injected into the uterine lumen 1 h before killing the animals. Gel filtration, ion exchange chromatography, sucrose gradient centrifugation, isoelectric focusing and saturation analysis indicate that during the period prior to implantation, the uterine progesterone receptor disappears and progesterone binding is performed by uteroglobin. These findings support the hypothesis that the physiological role of uteroglobin in the reproductive process is connected with its hormone-binding ability.

The effects of a highly cytokinin-active urea derivative, N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (Thidiazuron), and zeatin on cytokinin-autonomous growth and the metabolism of N6-(Δ2-isopentenyl)[8-14C]adenosine ([14C]i6 Ado) were examined in callus tissues of two Phaseolus lunatus genotypes, cv Jackson Wonder and P.I. 260415. Tissues of cv Jackson Wonder maintained on any concentration of Thidiazuron became cytokinin autonomous, whereas only tissues exposed to suboptimal concentrations of zeatin displayed cytokinin-autonomous growth. Tissues of P.I. 260415 remained cytokinin dependent under all these conditions. The metabolism of [14C]i6 Ado was similar for the two genotypes, but differed with the medium used. [14C]i6 Ado was rapidly converted to N6-(Δ2-isopentenyl)[8-14C]adenosine 5′-P ([14C]i6 AMP) by tissues grown on zeatin-containing medium, whereas only traces of the nucleotide were formed in tissues grown on medium with Thidiazuron. Incubation with [14C] i6 AMP of tissues grown in the presence of Thidiazuron resulted in rapid conversion to [14C]i6 Ado, while [14C]i6 AMP persisted in tissues maintained on zeatin. Thus, Thidiazuron appears to stimulate enzyme activity converting the ribonucleotide to ribonucleoside. Although the cytokininactive phenylureas and adenine derivatives differ in their effects on cytokinin autonomy as well as nucleotide formation, the two types of effects do not seem to be related.