Localization of porphyrin fluorescence in planarians

Two species of planarians were studied by fluorescence microscopy. Red fluorescence of uroporphyrin was observed localized in the epidermal rhabdites and subepidermal rhabdite-containing gland cells. Fluorescence was observed in isolated rhabdites of homogenates, but was not seen in rhabdites of the living animal. The identity of rhabdites was established by their location, shape, size, and acid-ophilic staining properties.     

Fissioning in planarians: control by the brain

Reduced population densities lead to increased rates of fissioning in planarians whereas higher population densities suppress fissioning. This effect is not primarily due to mucus deposition or substances secreted into the water. Experiments are presented which show a system of population feedback control. In the presence of other planarians, the brain exerts an influence (probably neurohormonal) to suppress fissioning. This influence becomes attenuated with axial distance from the brain.     

Unconditioned response to electric shock: mechanism in planarians

Some implications of a mathematical theory relating neuronal geometry to the parameters of excitation in unconditioned response of planarians to electric shock are experimentally verified. The regions and patterns of primary neural excitation depend on the relation between the distribution of neural sizes and the wave form of the electric stimulus.     

Comment on "Positive selection of tyrosine loss in metazoan evolution"

Tan et al. (Reports, 25 September 2009, p. 1686) argued that loss of tyrosine residues from proteins in metazoans was driven by positive selection to remove potentially deleterious phosphorylation sites. We challenge this hypothesis, providing evidence that the high guanine-cytosine (GC) content of metazoan genomes was the primary driver in the loss of tyrosine residues.     

Effect of ribonuclease on retention of conditioned response in regenerated planarians

Conditioned planarians were transected and allowed to regenerate in a ribonuclease solution or in pond water. Heads which had regenerated in ribonuclease displayed a retention level equal to that of head and tail sections which had regenerated in pond water. However, tails regenerated in ribonuclease performed randomly although they could be retrained to criterion.     

人源中心体新基因E9730在大肠杆菌中的表达及其多克隆抗体的制备

E9730是从人胎肝cDNA文库中分离出来的一个中心体新基因,其在mRNA水平上经5’端选择性剪 切为两个剪切体E9730—A和E9730—B,它们分别编码99个和142个氨基酸残基的多肽链。试验成功实现了 E9730-A和E9730—B在大肠杆菌JM109中的高效表达,并制备了相应的多克隆抗体,后经Western blot检测 具有良好的特异性。     

Constraints in the evolution of sex ratio adjustment

When the relative fitness of male and female offspring varies with environmental conditions, evolutionary theory predicts that parents should adjust the sex of their offspring accordingly. Qualitative and even quantitative support for this prediction is striking in some taxa but much less convincing in others. Explaining such variation across taxa in the fit of sex ratio theory remains a major challenge. We use meta-analysis to test the role of two constraints in the evolution of sex ratios. Based on analysis of sex ratio skews in birds and wasps, we show that (i) mechanisms of sex determination do not necessarily constrain the evolution of sex ratio adjustment, and (ii) parental ability to predict their offsprings' environment influences the evolution of sex ratio patterns across taxa. More generally, our results show that multiple constraints may determine the precision of adaptation.     

Abiotic forcing of plankton evolution in the Cenozoic

We characterize the evolutionary radiation of planktic foraminifera by the test size distributions of entire assemblages in more than 500 Cenozoic marine sediment samples, including more than 1 million tests. Calibration of Holocene size patterns with environmental parameters and comparisons with Cenozoic paleoproxy data show a consistently positive correlation between test size and surface-water stratification intensity. We infer that the observed macroevolutionary increase in test size of planktic foraminifera through the Cenozoic was an adaptive response to intensifying surface-water stratification in low latitudes, which was driven by polar cooling.     

Farmland loss and concern in the Treasure Valley

Structural changes in the agriculture and food system have resulted in larger but fewer farms, while increasing populations in urban areas have pushed development into rural areas. Despite these changes, little research has examined the concern of individuals with regards to loss of farmland and how this may vary based on geography. Building on Bell’s argument that the rural–urban continuum still exists and remains an important part of rural residents’ identity, in this article we examine residents’ concern over loss of farmland as a result of urban growth. We pay particularly close attention to urban–rural differences over concern with loss of farmland. Utilizing survey data collected from over 400 households in the Treasure Valley, a region of the western United States, our results indicate that rural residents show greater levels of concern with farmland loss when compared to their urban counterparts.     

Universality in the evolution of orientation columns in the visual cortex

The brain's visual cortex processes information concerning form, pattern, and motion within functional maps that reflect the layout of neuronal circuits. We analyzed functional maps of orientation preference in the ferret, tree shrew, and galago--three species separated since the basal radiation of placental mammals more than 65 million years ago--and found a common organizing principle. A symmetry-based class of models for the self-organization of cortical networks predicts all essential features of the layout of these neuronal circuits, but only if suppressive long-range interactions dominate development. We show mathematically that orientation-selective long-range connectivity can mediate the required interactions. Our results suggest that self-organization has canalized the evolution of the neuronal circuitry underlying orientation preference maps into a single common design.     

Quantitative analysis of evolution of the brain in mammals

Empirical equations derived from brain size (E) and body size (P) of archaic-Eocene, Oligocene, and Recent mammals were all of the form, E = kP(2/3); k = 0.03 for the Eocene, 0.06 for the Oligocene, and 0.12 for the Recent groups. It is suggested that k, which has been used as an index of cephalization in contemporary mammals, may be an appropriate measure of brain evolution in the mammals as a class.