Capacity of neural crest cells from various axial levels to participate in thymic development

Summary In order to assess the capacity of neural crest from different sources to participate in thymic development, neural crest from selected axial levels was transplanted unilaterally from quail donors to the region in chick hosts from which neural crest cells normaly migrate to interact with the primordial thymus. The greatest representation of donor cells was observed after isotopic transplantation and when donor tissue was taken from the hyoid and mesencephalic regions of the neural crest. The capacity for transplants to contribute cells decreased both anteriorly and posteriorly, so that neural crest close to the usual origin of mesenchyme-producing cells contributed a larger number of donor cells around the developing thymus than neural crest from anterior and posterior regions. Cells from the transplant were inserted as an addition to the host chick cells. Thus, a special relationship and capacity for interaction in thymic development is expressed by neural crest at usual levels over a limited span of axial regions, but to some extent by all regions. This study has established that the capacity for neural crest cells from different axial levels to interact with developing organs is not uniform, but may vary, depending upon the nature of the interaction with a particular organ.This study was supported by Grant No. 2332, The Council for Tobacco Research, USA, Inc.     

A comparison of the effects of chromate,molybdate and cadmium oxide on respiration in the yeastSaccharomyces cerevisiae

Summary Growth ofSaccharomyces cerevisiae on non-fermentable medium was more sensitive to inhibition by chromate than growth on fermentable medium. Chromate was selectively toxic against oxygen uptake in cells grown in non-fermentable medium and also inducedpetite mutations. CdO demonstrated similar but lesser effects on growth and respiration. However, molybdate had little toxicity to yeast non-fermentable growth and stimulated oxygen uptake in cells grown in fermentable and non-fermentable media. These results suggest that chromate, a carcinogen, may act more directly against the mitochondria ofS. cerevisiae than related chemical species, CdO and molybdate.     

The effects of phosphate supply on growth of plants from the Brasilian Cerrado: experiments with seedlings of the annual weed,Bidens gardneri Baker (Compositeae) and the tree,Qualea grandiflora (Mart.) (Vochysiaceae)

Summary Plants of the cerrado tree species Qualea grandiflora and the annual herb Bidens gardneri were grown from seed in controlled environment rooms at 30/20° C and 12 hour photoperiod. Seedlings were grown in pots or small tubes containing sand and provided with various amounts of mineral solutions based on the formulation of Hoagland and Arnon but with the phosphate content modified in some cases. In a long-term experiment lasting 213 days, plants supplied with full strength Hoagland's solution all died but plants of Qualea given 1/10 strength solution survived, although they grew very slowly. Low relative growth rates (0.008–0.036 d^–1) were also a feature of other experiments with Qualea and calculated rates of net assimilation rate gave values of 3–7 mg CO₂ dm^–2 h^–1. Expansion of the photosynthetic surface proceeded slowly and the cotyledons were the main site of photosynthesis for more than 40 days. The low rates of growth occurred despite significant uptake of phosphorus by young plants and in shortterm experiments growth was independent of the amount of phosphate supplied and accumulated. In contrast, the values of R found for plants of Bidens reached 0.24 d^–1. Growth of young plants was dependent on the external supply of phosphorus, being reduced when this was low and also when it was very high. Growth of the photosynthetic surface was also much more rapid than for Qualea and also varied with supply of phosphorus. The results are discussed in the context of the occurrence of these species in the Cerrado.     

Sexual size dimorphism and growth plasticity in snakes: an experiment on the Western Diamond-backed Rattlesnake (Crotalus atrox)

We conducted an experiment to examine the effects of sex and food intake on growth, mass gain, and attainment of sexual maturity in Western Diamond-backed Rattlesnakes (Crotalus atrox). We also measured testosterone levels to determine whether testosterone might be involved in the male-biased sexual size dimorphism observed in this species. We collected neonate rattlesnakes and raised them in the laboratory for 2 years on either a high-intake diet (fed one mouse per week) or a low-intake diet (fed one mouse every 3 weeks). High-intake snakes grew and gained mass more rapidly than low-intake snakes, but males did not grow or gain mass more rapidly than females in either treatment group. High-intake snakes attained reproductive maturity earlier than low-intake snakes, indicating that size, not age, is the critical determinant of reproductive maturity. Males had higher levels of testosterone than females but did not grow more quickly, suggesting that testosterone may not affect growth in this species and may therefore not be the proximate determinant of sexual size dimorphism.     

Vitreous Carbon: A New Material for Making Microtome Knives

The quality of sections obtained by microtomy depends to a large extent on the quality and characteristics of the microtome knife itself. Despite the need for improved microtomy techniques, there have been few significant developments since the introduction of glass and diamond knives in the 1950's. The manufacture of microtome knives from vitreous carbon provides new possibilities for developing both improved methods and improved equipment for specimen sectioning. Vitreous carbon has unique physical properties that lend themselves to the generation of precision cutting edges. Such an edge can be obtained either by breaking a piece of vitreous carbon or by using lapidary techniques. The resultant edge seems well adapted to both thick and thin sectioning. The introduction of vitreous carbon as a sectioning tool offers a significant alternative to metal, glass and diamond knives.     

Energy, wealth, and human development: Why and how biomass pretreatment research must improve

A high level of human development is dependent on energy consumption (roughly 4 kW per person), and most developed countries that have reached this level have done so through the extensive use of fossil energy. However, given that fossil resources are finite, in order for developed countries to maintain their level of development and simultaneously allow developing countries to reach their potential, it is essential to develop viable renewable energy alternatives. Of particular importance are liquid fuel replacements for petroleum, the fossil resource that primarily drives commerce and economic growth. The intent of this article is to remind our fellow biofuel researchers, particularly those involved in lignocellulosic pretreatment, of these global issues and the serious nature of our work. We hope that this will inspire us to generate and report higher quality and more thorough data than has been done in the past. Only in this way can accurate comparisons and technoeconomic evaluations be made for the many different pretreatment technologies that are currently being researched. The data that primarily influence biorefinery economics can be subdivided into three main categories: yield, concentration, and rate. For these three categories we detail the specific data that should be reported for pretreatment research. In addition, there is other information that is needed to allow for a thorough comparison of pretreatment technologies. An overview of these criteria and our comparison of the current state of a number of pretreatment technologies with respect to these criteria are covered in the last section. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 893–898, 2012     

Synthesis and biological evaluation of prodigiosene conjugates of porphyrin,estrone and 4-hydroxytamoxifen

To generate the first series of prodigiosene conjugates, the tripyrrolic skeleton was appended to estrone, tamoxifen and porphyrin frameworks by way of ester linkers and various hydrocarbon chain lengths. The ability of the conjugates to inhibit various types of cancer cells was evaluated in vitro. The porphyrin conjugates did not exhibit significant activity. The estrone conjugates exhibited modest activity, for the most part. However, significantly greater growth inhibition activity against certain breast, colon, lung, leukemia, melanoma and prostate cell lines was noted. This unusual effect for this first generation model class of compound warrants further investigation and comparison to cases where estrogens are linked to prodigiosenes via connection points that do not feature in estrogen receptor binding. The 4-hydroxytamoxifen conjugates exhibit nanomolar range activity against the MCF-7 breast cancer cell line, paving the way to expand the scope and connectivity of prodigiosene–tamoxifen conjugates.     

Testing the impact of calibration on molecular divergence times using a fossil-rich group: the case of Nothofagus (Fagales)

Although temporal calibration is widely recognized as critical for obtaining accurate divergence-time estimates using molecular dating methods, few studies have evaluated the variation resulting from different calibration strategies. Depending on the information available, researchers have often used primary calibrations from the fossil record or secondary calibrations from previous molecular dating studies. In analyses of flowering plants, primary calibration data can be obtained from macro- and mesofossils (e.g., leaves, flowers, and fruits) or microfossils (e.g., pollen). Fossil data can vary substantially in accuracy and precision, presenting a difficult choice when selecting appropriate calibrations. Here, we test the impact of eight plausible calibration scenarios for Nothofagus (Nothofagaceae, Fagales), a plant genus with a particularly rich and well-studied fossil record. To do so, we reviewed the phylogenetic placement and geochronology of 38 fossil taxa of Nothofagus and other Fagales, and we identified minimum age constraints for up to 18 nodes of the phylogeny of Fagales. Molecular dating analyses were conducted for each scenario using maximum likelihood (RAxML + r8s) and Bayesian (BEAST) approaches on sequence data from six regions of the chloroplast and nuclear genomes. Using either ingroup or outgroup constraints, or both, led to similar age estimates, except near strongly influential calibration nodes. Using "early but risky" fossil constraints in addition to "safe but late" constraints, or using assumptions of vicariance instead of fossil constraints, led to older age estimates. In contrast, using secondary calibration points yielded drastically younger age estimates. This empirical study highlights the critical influence of calibration on molecular dating analyses. Even in a best-case situation, with many thoroughly vetted fossils available, substantial uncertainties can remain in the estimates of divergence times. For example, our estimates for the crown group age of Nothofagus varied from 13 to 113 Ma across our full range of calibration scenarios. We suggest that increased background research should be made at all stages of the calibration process to reduce errors wherever possible, from verifying the geochronological data on the fossils to critical reassessment of their phylogenetic position.