Phototropism in Dunaliella and its application in a harvesting device.

Summary The influence of wavelength, light intensity and algal concentration on the phototropism of Dunaliella sp. is described. A practical device for harvesting the alga, based in this effect is shown.     

Direct anabolic metabolism of three-carbon propionate to a six-carbon metabolite occurs in vivo across tissues and species

Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of ¹³C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate.     

THE HORMONAL INTEGRATION OF SEXUAL REPRODUCTION IN OEDOGONIUM

Rawitscher -Kunkel , Erika , and L. Machlis . (U. California, Berkeley.) The hormonal integration of sexual reproduction in Oedogonium. Amer. Jour. Bot. 49 (2) : 177–183. Illus. 1962.—Sexual reproduction in a heterothallic, nannandrous species of Oedogonium was investigated cytologically and physiologically. Several new observations are reported. Oogonial mother cells release a substance which attracts androspores to them. The androspores, when attached to the oogonial mother cells, grow in well-defined directions apparently in response to a hormone originating in the oogonial mother cells. An oogonial mother cell divides into an oogonium and a suffultory cell only after the attached androspores complete their development into dwarf males, each bearing an antheridium. Presumably the developing dwarf males provide a chemical stimulus for the division of the oogonial mother cell. During development, the oogonia become enveloped in a massive gel which also encases the antheridia cut off at the apical ends of the dwarf male plants. The gel appears to function as a sperm trap, preventing the dissemination of the sperm into the surrounding liquid. The sperm are attracted to the protoplasmic papilla which briefly protrudes through the oogonial pore indicating the operation of a second chemotactic agent.     

The Haitians, the Healers, and the Anthropologist. Two Case Studies

The Haitians, the Healers, and the Anthropologist. Two Case Studies. 1997. 100 minutes, color. video by Philip Singer. For more information contact Traditional Healing Productions, Philip Singer. Ph.D. 17280 Madison. Southfield, MI 48076.     

Single mitochondrial gene barcodes reliably identify sister-species in diverse clades of birds

Background  

DNA barcoding of life using a standardized COI sequence was proposed as a species identification system, and as a method for detecting putative new species. Previous tests in birds showed that individuals can be correctly assigned to species in ~94% of the cases and suggested a threshold of 10× mean intraspecific difference to detect potential new species. However, these tests were criticized because they were based on a single maternally inherited gene rather than multiple nuclear genes, did not compare phylogenetically identified sister species, and thus likely overestimated the efficacy of DNA barcodes in identifying species.     

Predicting species distributions in poorly-studied landscapes

Conservationists are increasingly relying on distribution models to predict where species are likely to occur, especially in poorly-surveyed but biodiverse areas. Modeling is challenging in these cases because locality data necessary for model formation are often scarce and spatially imprecise. To identify methods best suited to modeling in these conditions, we compared the success of three algorithms (Maxent, Mahalanobis Typicalities and Random Forests) at predicting distributions of eight bird and eight mammal species endemic to the eastern slopes of the central Andes. We selected study species to have a range of locality sample sizes representative of the data available for endemic species of this region and also that vary in their distribution characteristics. We found that for species that are known from moderate numbers (N = 38–94) of localities, the three methods performed similarly for species with restricted distributions but Maxent and Random Forests yielded better results for species with wider distributions. For species with small numbers of sample localities (N = 5–21), Maxent produced the most consistently successful results, followed by Random Forests and then Mahalanobis Typicalities. Because evaluation statistics for models derived from few localities can be suspect due to the poor spatial representation of the evaluation data, we corroborated these results with review by scientists familiar with the species in the field. Overall, Maxent appears to be the most capable method for modeling distributions of Andean bird and mammal species because of the consistency of results in varying conditions, although the other methods have strengths in certain situations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Climatic patterns in the establishment of wintering areas by North American migratory birds

Long‐distance migration in birds is relatively well studied in nature; however, one aspect of this phenomenon that remains poorly understood is the pattern of distribution presented by species during arrival to and establishment of wintering areas. Some studies suggest that the selection of areas in winter is somehow determined by climate, given its influence on both the distribution of bird species and their resources. We analyzed whether different migrant passerine species of North America present climatic preferences during arrival to and departure from their wintering areas. We used ecological niche modeling to generate monthly potential climatic distributions for 13 migratory bird species during the winter season by combining the locations recorded per month with four environmental layers. We calculated monthly coefficients of climate variation and then compared two GLM (generalized linear models), evaluated with the AIC (Akaike information criterion), to describe how these coefficients varied over the course of the season, as a measure of the patterns of establishment in the wintering areas. For 11 species, the sites show nonlinear patterns of variation in climatic preferences, with low coefficients of variation at the beginning and end of the season and higher values found in the intermediate months. The remaining two species analyzed showed a different climatic pattern of selective establishment of wintering areas, probably due to taxonomic discrepancy, which would affect their modeled winter distribution. Patterns of establishment of wintering areas in the species showed a climatic preference at the macroscale, suggesting that individuals of several species actively select wintering areas that meet specific climatic conditions. This probably gives them an advantage over the winter and during the return to breeding areas. As these areas become full of migrants, alternative suboptimal sites are occupied. Nonrandom winter area selection may also have consequences for the conservation of migratory bird species, particularly under a scenario of climate change.     

Mice Lacking Platelet-Derived Growth Factor D Display a Mild Vascular Phenotype

Platelet-derived growth factor D (PDGF-D) is the most recently discovered member of the PDGF family. PDGF-D signals through PDGF receptor β, but its biological role remains largely unknown. In contrast to other members of the PDGF family of growth factors, which have been extensively investigated using different knockout approaches in mice, PDGF-D has until now not been characterized by gene inactivation in mice. Here, we present the phenotype of a constitutive Pdgfd knockout mouse model (Pdgfd^-/-), carrying a LacZ reporter used to visualize Pdgfd promoter activity. Inactivation of the Pdgfd gene resulted in a mild phenotype in C57BL/6 mice, and the offspring was viable, fertile and generally in good health. We show that Pdgfd reporter gene activity was consistently localized to vascular structures in both postnatal and adult tissues. The expression was predominantly arterial, often localizing to vascular bifurcations. Endothelial cells appeared to be the dominating source for Pdgfd, but reporter gene activity was occasionally also found in subpopulations of mural cells. Tissue-specific analyses of vascular structures revealed that NG2-expressing pericytes of the cardiac vasculature were disorganized in Pdgfd^-/- mice. Furthermore, Pdgfd^-/- mice also had a slightly elevated blood pressure. In summary, the vascular expression pattern together with morphological changes in NG2-expressing cells, and the increase in blood pressure, support a function for PDGF-D in regulating systemic arterial blood pressure, and suggests a role in maintaining vascular homeostasis.