Hypermethylation and higher stability of a plant (Eleusin coracana) tRNA

Total tRNA isolated from four-day-old ragi (Eleusin coracana) seedlings has been shown to be highly methylated. Each tRNA molecule on average contains two 2′-O-ribose methylated nucleosides. The high molar yields of 1-methyladenosine (1.6%) indicate that nearly a third of all the tRNA molecules contains more than one residue of 1-methyladenosine. Thermal denaturation studies with total tRNA show that the hypermethylated ragi tRNA melts slower that the yeast tRNA which is less methylated but otherwise has similar base composition. Ragi tRNA is also less susceptible to ribonucleases A, T₂ and T₂.     

THE DELIMITATION OF BIGNONIACEAE AND SCROPHULARIACEAE BASED ON FLORAL ANATOMY,AND THE PLACEMENT OF PROBLEM GENERA

The delimitation of Bignoniaceae and Scrophulariaceae has long been a taxonomic problem. Several genera, including Paulownia, Schlegelia, Gibsoniothamnus, and Synapsis, have been variously placed in one or the other family. Differences between these two families have been noted with regard to the presence of endosperm, embryo and seed morphology, and placentation; however, the lack of comprehensive data on the distribution of such characters within these two families left the delimitation problem unsolved. A comprehensive study of floral anatomy confirmed a basic difference in the placentation of these two families, as well as a basic difference in gynoecial vascularization. Paulownia has a floral anatomy, embryo morphology, and seed morphology consistent with placement in Scrophulariaceae. While reminiscent of Bignoniaceae, Paulownia is not an intermediate genus linking the two families. Schlegelia and Gibsoniothamnus have a floral anatomy consistent with placement in Scrophulariaceae. Schlegelia also has a scrophulariaceous seed morphology. Considered anomalous in the Bignoniaceae, the Schlegelieae similarly are distinct in the Scrophulariaceae.     

UNDERGROUND MORPHOLOGY AND HABITAT RELATIONSHIPS OF THREE PAIRS OF FOREST HERBS

To evaluate the ecological importance of differences in underground morphology, ten individuals per species were excavated for three species pairs in a coniferous forest in the Cascade Mountains of Oregon. The two species of each pair had similar aboveground morphologies, divergent underground morphologies, and different geographical ranges and habitat relationships. Erythronium montanum and Clintonia uniflora have one or two elliptic leaves per ramet but E. montanum has a short, segmented rhizome and only one ramet per genet, whereas C. uniflora spreads vegetatively via long rhizomes. Streptopus roseus and Smilacina stellata have similar, determinant aerial shoots and spread by long rhizomes, but S. stellata has a dimorphic root and rhizome system that allows it to occupy a wider range of habitats. Rubus pedatus and Rubus lasiococcus both spread via stolons, but R. lasiococcus has deeper roots and can occupy drier habitats than R. pedatus. The differences in underground morphology within the species pairs are consistent with the species’ geographical ranges and habitats occupied, and may be causal in determining distribution patterns.     

ANTAGONISTIC PLEIOTROPY: AN INTERSPECIFIC DROSOPHILA COMPARISON

Wild-type flies of 12 Drosophila species and semispecies were examined to determine whether correlation patterns between early- and late-life fitness characters predicted for individuals within a population by the antagonistic-pleiotropy hypothesis are reflected in comparisons of related species and semispecies that are known to differ in lifespan. Our goal was to determine whether the hypothesis is relevant to the evolution of life-history differences beyond the population level. Two fitness traits, egg production and percentage mating success, were observed at three ages: onset of reproductive age, one week later, and one month later. Age-dependent patterns of these traits do not consistently conform to predictions of the hypothesis. Species or semispecies that show reproductive vitality early in life need not be short-lived, and long lifespan need not be accompanied by a cost in early reproductive vitality, as measured by mating success and egg production. The two fitness traits can show different age-dependent patterns in the same species or semispecies. Potential explanations for the frequent inconsistency of the data with predictions of the hypothesis are discussed. Results support the idea that the hypothesis is only relevant to the evolution of life-history differences among individuals in the same breeding population confronted by the same environmental constraints.     

Ultrasonic cries from infant rats stimulate prolactin release in lactating mothers

Lactating female rats, separated from their litters for 6 hr, showed a dramatic elevation in plasma prolactin following a 15-min playback of ultrasonic vocalizations recorded from 7-day-old pups. Virgin females exhibited a smaller but still significant prolactin response to recorded pup calls. Control recordings of either background noise or adult ultrasonic vocalizations (22–26 kHz) had no effect on prolactin secretion even in lactating females. These results demonstrate that infant vocalizations can act as a stimulus for prolactin release and suggest that such communications may play a role in the maintenance of normal lactation.     

MARINE CRYPTOMONAD STARCH FROM AUTOLYSIS OF GLYCEROL-GROWN CHROOMONAS SALINA1

The extracellular starch released by autolysis of glycerol-grown Chroomonas salina (Wislouch) Butcher was purified and chemically characterized. It contained 99%D-glucose, formed a blue complex (λmax at 605 nm) with iodine, and showed an optical rotation value more positive than that of potato starch. Methylation analysis established the presence of 1,4- and 1,4,6-glucoside linkages in the proportion 15:1. These properties indicate the cryptomonad starch to be an iodophilic α-(1,4)-glucan, composed of ca. 30% amylose with amylopectin, and broadly resembling potato, Chilomonas and other unicellular algal starches.     

Actin and spectrin-like (Mr= 260–240 000) proteins in gregarines

In Gregarina blaberae a M_r = 47 000 and a M_r = 260–240 000 doublet polypeptides reacted in immunoblotting: i) with a polyclonal monospecific rabbit antibody to frog muscular actin, a monoclonal anti-actin antibody against chicken gizzard; and ii) with polyclonal and monoclonal antibodies to human erythrocyte β-spectrin, respectively. The M_r = 47 000 actin-like protein is associated with the ghost and a contractille cytoplasmic extract. The presence of an actin-like protein in Gregarina and Lecudina and its cellular distribution in the cortex indicated that the gliding movement might involve an actin-myosin system in contrast to previous studies. Immunofluorescence showed clear differences between the anterior part of Gregarina and Lecudina which illustrated the high cell polarity of these protozoa. The M_r = 260–240 000 doublet was detected in SDS-PAGE from G. blaberae trophozoite ghosts but not in the cytoplasmic extracts or in extracts from sexual stages, indicating that the presence of these spectrin-like proteins is stage-dependent. Visualization of the M_r = 260–240 000 by immunofluorescence showed clear species differences, with rings arranged perpendicular to the longitudinal narrow folds of G. blaberae, with longitudinal lines underlying the folds of L. pellucida and with lines separating the large folds of Selenidium pendula. The cellular distribution is consistent with a stabilizer function of the spectrin-like proteins in the scaffolding of the cortex of gregarines according to the high diversity of the cell-shape and the cell motility systems in gregarines. The presence of spectrin-like proteins in protozoa and particularly in parasites from primitive arthropods indicated that ancestral spectrin genes could the M_r = 260–240 000 form.