Smog nitrogen and the rapid acidification of forest soil, San Bernardino Mountains, southern California

We report the rapid acidification of forest soils in the San Bernardino Mountains of southern California. After 30 years, soil to a depth of 25 cm has decreased from a pH (measured in 0.01 M CaCl2) of 4.8 to 3.1. At the 50-cm depth, it has changed from a pH of 4.8 to 4.2. We attribute this rapid change in soil reactivity to very high rates of anthropogenic atmospheric nitrogen (N) added to the soil surface (72 kg ha(-1) year(-1)) from wet, dry, and fog deposition under a Mediterranean climate. Our research suggests that a soil textural discontinuity, related to a buried ancient landsurface, contributes to this rapid acidification by controlling the spatial and temporal movement of precipitation into the landsurface. As a result, the depth to which dissolved anthropogenic N as nitrate (NO3) is leached early in the winter wet season is limited to within the top approximately 130 cm of soil where it accumulates and increases soil acidity.     

Kluyveromyces lactis sexual pheromones. Gene structures and cellular responses to alpha-factor

The Kluyveromyces lactis genes for sexual pheromones have been analyzed. The alpha-factor gene encodes a predicted polypeptide of 187 amino acid residues containing four tridecapeptide repeats (WSWITLRPGQPIF). A nucleotide blast search of the entire K. lactis genome sequence allowed the identification of the nonannotated putative a-pheromone gene that encodes a predicted protein of 33 residues containing one copy of the dodecapeptide a-factor (WIIPGFVWVPQC). The role of the K. lactis structural genes KlMFalpha1 and KlMFA1 in mating has been investigated by the construction of disruption mutations that totally eliminate gene functions. Mutants of both alleles showed sex-dependent sterility, indicating that these are single-copy genes and essential for mating. MATalpha, Klsst2 mutants, which, by analogy to Saccharomyces cerevisiae, are defective in Galpha-GTPase activity, showed increased sensitivity to synthetic alpha-factor and increased capacity to mate. Additionally, Klbar1 mutants (putatively defective in alpha-pheromone proteolysis) showed delay in mating but sensitivity to alpha-pheromone. From these results, it can be deduced that the K. lactis MATa cell produces the homolog of the S. cerevisiaealpha-pheromone, whereas the MATalpha cell produces the a-pheromone.     

Research Participation Influences Willingness to Reduce Zoonotic Exposure in Uganda

EcoHealth - The majority of emerging and re-emerging infectious diseases in people are zoonotic. Despite substantial research in communities adjacent to protected areas with high levels of...     

The Implication of Early Chromatin Changes in X Chromosome Inactivation

1. Download high-res image (238KB)
2. Download full-size image

     

Inhibition of Na+-K+-2Cl- cotransport by mercury

Mercury alters thefunction of proteins by reacting with cysteinyl sulfhydryl(SH) groups. Theinorganic form (Hg²⁺) is toxicto epithelial tissues and interacts with various transport proteinsincluding the Na⁺ pump andCl channels. In this study,we determined whether theNa⁺-K⁺-Clcotransporter type 1 (NKCC1), a major ion pathway in secretory tissues,is also affected by mercurial substrates. To characterize theinteraction, we measured the effect ofHg²⁺ on ion transport by thesecretory shark and human cotransporters expressed in HEK-293 cells.Our studies show that Hg²⁺inhibitsNa⁺-K⁺-Clcotransport, with inhibitor constant(K_i) values of25 µM for the shark carrier (sNKCC1) and 43 µM for thehuman carrier. In further studies, we took advantage of speciesdifferences in Hg²⁺ affinity toidentify residues involved in the interaction. An analysis ofhuman-shark chimeras and of an sNKCC1 mutant(Cys-697Leu) reveals that transmembrane domain 11 plays an essential role in Hg²⁺binding. We also show that modification of additionalSH groups by thiol-reactingcompounds brings about inhibition and that the binding sites are notexposed on the extracellular face of the membrane.

     

Amphibians as a model system for the investigation of respiratory control development

Recent medical advances have made it possible for babies to survive premature birth at increasingly earlier developmental stages. This population requires costly and sophisticated medical care to address the problems associated with immaturity of the respiratory system. In addition to pulmonary complications, respiratory instability and apnea reflecting immaturity of the respiratory control system are major causes of hospitalization and morbidity in this highly vulnerable population. These medical concerns, combined with the curiosity of physiologists, have contributed to the expansion of research in respiratory neurobiology. While most researchers working in this field commonly use rodents as an animal model, recent research using in vitro brainstem preparation from bullfrogs (Rana catesbeiana) have revealed the technical advantages of this animal model, and shown that the basic principles underlying respiratory control and its ontogeny are very similar between these two groups of vertebrates. The present review highlights the recent advances in the area of research with a focus on intermittent (episodic) breathing and the role of serotonergic and GABAergic modulation of respiratory activity during development.     

Molecular tools for a molecular medicine: analyzing genes, transcripts and proteins using padlock and proximity probes

Procedures and reagents are needed to specifically detect all the macromolecules that are being identified in the course of genome projects. We discuss how this challenge may be met using a set of ligation-based reagents termed padlock probes and proximity ligation probes. These probes include elements with affinity for specific nucleic acid and protein molecules, respectively, along with unique identifier DNA sequence elements that encode the identity of the recognized target molecules. The information content of DNA strands that form in the detection reactions are recorded after amplification, allowing the recognized target molecules to be identified. The procedures permit highly specific solution-phase or localized analyses of large sets of target molecules as required in future molecular analyses.     

How the Chlorophyll-Proteins got their Names

This is the story of how we started studying the green bands seen on SDS-polyacrylamide gels of thylakoid membranes dissociated with the non-ionic detergent beta-octyl-D-glucopyranoside. We explain some of the complications we and other workers encountered along the pathway to untangling the chlorophyll-protein complexes of higher plants, and give a concise summary of the complexes, their polypeptides and their genes.     

Expression and characterization of melanin-concentrating hormone receptors on mammalian cell lines

The neuropeptide melanin-concentrating hormone (MCH) is expressed in central and peripheral tissues where it participates in the complex network regulating energy homeostasis as well as in other physiologically important functions. Two MCH receptor subtypes, MCH-R1 and MCH-R2, have been cloned which signal through activation of Gi/o/q proteins and hence regulate different intracellular signals, such as inhibition of cAMP formation, stimulation of IP3 production, increase in intracellular free Ca2+ and/or activation of MAP kinases. Most of the data were obtained with cell systems heterologously expressing either of the MCH receptors. Fewer reports exist on studies with cell lines which endogenously express MCH receptors. Here, we describe human and other mammalian cell lines with which MCH receptor activation can be studied under "natural" conditions and we summarize the characteristics and signaling pathways of the MCH receptors in the different cell systems.