Barley domestication: the end of a central dogma?

Genomic analysis of barley paints a picture of diffuse origins of this crop, with different regional wild populations contributing putative adaptive variations.     

Reclassification of the serows and gorals: the end of a neverending story?

相似文献   

Endocytosis: A Positive or a Negative Influence on Wnt Signalling?

Endocytosis, with subsequent targeting to lysosomes for degradation, is traditionally seen as a way for cells to terminate signalling. However, in a few instances, endocytosis has been demonstrated to contribute positively to signalling. Here we review recent work on the role of endocytosis in Wnt signalling. Biochemical evidence suggests that the branch of Wnt signalling that controls planar cell polarity (PCP) does require endocytosis, although how endocytosis of Frizzled receptors is translated into PCP in vivo remains unknown. With respect to the main signalling branch (called the canonical or beta-catenin pathway), the literature is divided as to whether endocytosis is required. Results of in vivo experiments are inconclusive because of the toxic side-effects of blocking endocytosis. Some results with cultured cells suggest the need for endocytosis in canonical signalling; however, it remains unclear whether the ligand-receptor complex must enter the cell by clathrin-mediated or caveolae-mediated endocytosis in order to signal. Means of specifically altering Wnt trafficking as well as of tracking the internalization route in different cell types are needed.     

Prion hypothesis: the end of the controversy?

Forty-three years have passed since it was first proposed that a protein could be the sole component of the infectious agent responsible for the enigmatic prion diseases. Many discoveries have strongly supported the prion hypothesis, but only recently has this once heretical hypothesis been widely accepted by the scientific community. In the past 3 years, researchers have achieved the 'Holy Grail' demonstration that infectious material can be generated in vitro using completely defined components. These breakthroughs have proven that a misfolded protein is the active component of the infectious agent, and that propagation of the disease and its unique features depend on the self-replication of the infectious folding of the prion protein. In spite of these important discoveries, it remains unclear whether another molecule besides the misfolded prion protein might be an essential element of the infectious agent. Future research promises to reveal many more intriguing features about the rogue prions.     

Hexoses as phloem transport sugars: the end of a dogma?

According to most textbooks, only non-reducing carbohydrate species such as sucrose, sugar alcohols, and raffinose-family sugars function as phloem translocates. Occasional abundance of reducing sugar species (such as hexoses) in sieve-tube sap has been discarded as an experimental artefact. This study, however, discloses a widespread occurrence of hexoses in the sieve-tube sap. Phloem exudation facilitated by EDTA provided evidence that many of the members of two plant families (Ranunculaceae and Papaveraceae) investigated translocate >80% of carbohydrates in the form of hexoses. Representatives of other families also appear to translocate appreciable amounts of hexoses in the sieve tubes. Promoting effects of EDTA, activities of sucrose-degrading enzymes, and sugar uptake by micro-organisms on hexose contents of phloem exudates were checked. The rate of sucrose degradation is far too low to explain the large proportions of hexoses measured in phloem exudates; nor did other factors tested seem to stimulate the occurrence of hexoses. The validity of the approach is further supported by the virtual absence of hexoses in exudates from species that were known as exclusive sucrose transporters. This study urges a rethink of the existing views on carbohydrate transport species in the phloem stream. Hexose translocation is to be regarded as a normal mode of carbohydrate transfer by the phloem equivalent to that of sucrose, raffinose-family sugars, or sugar alcohols.     

Drosophila olfaction: the end of stereotypy?

Recent work has demonstrated substantial wiring and functional stereotypy in the fly olfactory system. In this issue of Neuron, Murthy et al. demonstrate that in the mushroom body, a site of olfactory associative learning, this initial peripheral stereotypy gives way to functionally nonstereotyped circuits.     

Influence of aluminium on the immune system – an experimental study on volunteers

The purpose of this study was to examine whether oral exposure to aluminum (Al) can affect the human immune system. Eighteen healthy volunteers (mean age 42, 28–57 yr) were divided into a test group (9 females, 4 males) and a referent group (3 females, 2 males). Over 6 weeks, the test subjects ingested 10 ml of antacid (aluminum hydroxide, 59 mg Al/ml) three times daily. Aluminum was analyzed in urine before and during the exposure period (ICP-MS). Blood samples were used for analysis of lymphocyte subpopulations, mitogen-induced lymphocyte proliferation and in vitro production and circulating plasma concentrations of immunoglobulin (Ig) A, IgG, IgM, interleukin (IL) -2 and IL-4. Urinary Al concentration in the test subjects was approximately 10- to 20-fold higher than in the referent group during exposure. This indicates that ingestion of an Al-containing antacid is associated with an Al absorption far above that originating from food and drinking water. In both referents and test subjects the lymphocyte subpopulations, lymphocyte proliferation and the in vitro Ig and IL production showed similar, time-dependent changes before as well as during the exposure period. No major differences were seen between the referent and test groups regarding the immune parameters, except for a slightly smaller CD8+CD45R0+ population (primed cytotoxic T-cells), in the exposed individuals as compared to the referents. The results also show that subjects on antacid therapy may constitute a suitable population for studying biological effects of high-dose oral exposure to Al.     

Impact of maternal age on birth outcomes: a population-based study of primiparous Brazilian women in the city of São Paulo

The aim of this study is to analyse the impact of maternal age at first birth on low birth weight, preterm birth and low Apgar scores at one minute and at five minutes among live births delivered to primiparous Brazilian women in the city of S?o Paulo. Analyses were based on 73,820 birth records from the 1998 birth cohort. Logistic regression was used to assess the association between maternal age and each outcome variable, controlling for the following risk factors: delivery mode, plurality, sex, maternal education, number of prior losses, prenatal care, race, parity and community development. Maternal ages below 20 and above 30 years were significantly associated with the risks of low birth weight and preterm birth, but no association was found between maternal ages and Apgar score, with the exception that ages 15-19 reduced the odds of a low one-minute score. Even though this result seems to be inconsistent, low birth weight, preterm birth and low Apgar scores measure different dimensions of newborn well-being, and the association of each measure with maternal age is expected to diverge.     

Influence of β-cyclodextrin on the Properties of Norfloxacin Form A

Cyclodextrins are able to form host–guest complexes with hydrophobic molecules to result in the formation of inclusion complexes. The complex formation between norfloxacin form A and β-cyclodextrin was studied by exploring its structure affinity relationship in an aqueous solution and in the solid state. Kneading, freeze-drying, and physical mixture methods were employed to prepare solid complexes of norfloxacin and β-cyclodextrin. The solubility of norfloxacin significantly increased upon complexation with β-cyclodextrin as demonstrated by a solubility isotherm of the A_L type along with the results of an intrinsic dissolution study. The complexes were also characterized in the solid stated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffractometry, scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance (ssNMR) spectrometry. The thermal analysis showed that the thermal stability of the drug is enhanced in the presence of β-cyclodextrin. Finally, the microbiological studies showed that the complexes have better potency when compared with pure drug.KEY WORDS: bioassay, complexation, intrinsic dissolution, norfloxacin, β-cyclodextrin     

Nitrotyrosine as a marker for peroxynitrite‐induced neurotoxicity: the beginning or the end of the end of dopamine neurons?

This review examines the involvement of nitrotyrosine as a marker for peroxynitrite-mediated damage in the dopamine neuronal system. We propose that the dopamine neuronal phenotype can influence the cytotoxic signature of peroxynitrite. Dopamine and tetrahydrobiopterin are concentrated in dopamine neurons, and both are essential for their proper neurochemical function. It is not well appreciated that dopamine and tetrahydrobiopterin are also powerful blockers of peroxynitrite-induced tyrosine nitration. What is more, the reaction of peroxynitrite with either dopamine or tetrahydrobiopterin forms chemical species (i.e. o-quinones and pterin radicals, respectively) whose cytotoxic effects may be manifested far earlier than nitrotyrosine formation in the course of dopamine neuronal damage. A better understanding of how the dopamine neuronal phenotype modulates the effects of reactive nitrogen species could reveal early steps in drug- and disease-induced damage to the dopamine neuron and form the basis for rational, protective therapies.     

DNA patenting: the end of an era?

Debates on patenting DNA must evolve to reflect the global decline in filings and regional disparities in patenting activity.