Codases: 50 years after

Aminoacyl-tRNA synthetases (codases) catalyze aminoacylation of a particular tRNA with the corresponding amino acid at the first step of protein biosynthesis. The review considers the universal structural and functional characteristics of this largest family of enzymes, partitioned into two classes. The modes of tRNA binding and recognition, as well as additional editing activity, which are responsible for the extremely high fidelity of aminoacyl-tRNA synthesis, are discussed. The available data suggest an unusual evolutionary history for the most important components of the mechanism that ensures the proper synthesis of proteins and the association of this mechanism with amino acid biosynthesis. In addition, the review considers the secondary functions of synthetases in various cell metabolic processes, including pathophysiological ones. Their investigation may help to develop new diagnostic techniques and therapies.     

Creosotebush vegetation after 50 years of lagomorph exclusion

In 1939, an experiment was established on the Jornada Experimental Range to evaluate the effects of shrub removal, rabbit exclusion, furrowing, and seeding in creosotebush [Larrea tridentata (DC.) Cov] vegetation. Sixteen plots (21.3×21.3 m) were laid out in four rows of four plots per row with a buffer zone of 7.6 m between plots and rows. A barbed wire fence excluded cattle and poultry wire fencing excluded lagomorphs. Treatments were factorially applied at two levels. Plant cover in the plots was sampled in 1938 (before treatment), 1947, 1956, 1960, 1967 and 1989 with randomly located, line-intercept transects. Data from all sampling dates were analyzed as a split plot in time and main effects for 1989 tested by analysis of variance for a 2×4 factorial experiment. There were significant (P<0.10) year x treatment interactions. Seeding and furrowing treatments were ineffective but lagomorph exclusion and shrub clearing treatments resulted in significant treatment differences for several species. In 1989, basal area of spike dropseed (Sporobolus contractus A.S. Hitchc.) was 30-fold greater on the lagomorph excluded than on the lagomorph unexcluded treatment. Canopy cover of honey mesquite (Prosopis glandulosa Torr. var. glandulosa), tarbush (Flourensia cernua DC.) and mariola (Parthenium incanum H.B.K.) were affected by lagomorph exclusion. None of the responses were viewed as successional in nature. They principally represented individual species sensitivities to either absence of a primary herbivore or removal of aboveground shrub biomass. Though the physical treatments could be regarded as relatively severe disturbances of the system, the impacts on community vegetation dynamics were relatively insignificant.     

Follow-up of 50 adolescent girls 2 years after abortion.

Thirty-eight adolescents who underwent an abortion were studied by questionnaire and interview with a psychiatrist and a social worker 2 years after the abortion. Most did not regret their abortion and considered it a positive experience. Most said they would not have another abortion, although adoption was unanimously rejected as a choice for the pregnant teenager. Relations with their parents were generally good and the families were supportive in the decision-making process and in the postabortion period. The girl''s father had been absent because of death or separation in 37% of instances. A lengthy relationship with the putative father before the abortion was common, but 37% of the relationships were not able to withstand the pregnancy-abortion crisis. The proportion using contraceptives before the abortion was 2%, and 2 years after the abortion, 84%.     

Some thoughts on taxonomic terminology

There are gaps and inconsistencies in current taxonomic vocabulary which might benefit from some attention. To address these issues, some terminological standards are proposed and explained herein. The validity of terminology derived from clear grammatical patterns is not necessarily precluded by an absence of previous use. It is still, however, a worthwhile exercise to include such potential terms in a body of text that can serve as a reference to anyone wishing to employ terminology of this nature, with the secondary benefit that it may encourage more widespread use of these terms for a more consistent use of taxonomic terminology.