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<jats:p> Few data exist on the environmental risks of biological control. The weevil <jats:italic>Rhinocyllus conicus</jats:italic> Froeh., introduced to control exotic thistles, has exhibited an increase in host range as well as continuing geographic expansion. Between 1992 and 1996, the frequency of weevil damage to native thistles consistently increased, reaching 16 to 77 percent of flowerheads per plant. Weevils significantly reduced the seed production of native thistle flowerheads. The density of native tephritid flies was significantly lower at high weevil density. Such ecological effects need to be better addressed in future evaluation and regulation of potential biological control agents. </jats:p>

<jats:p> Tuberculosis is the leading cause of death due to an infectious organism, killing an estimated 3 million people annually. <jats:italic>Mycobacterium tuberculosis</jats:italic> , the causative agent of tuberculosis, and other pathogenic mycobacteria require entry into host macrophages to initiate infection. An invasion mechanism was defined that was shared among pathogenic mycobacteria including <jats:italic>M. tuberculosis</jats:italic> , <jats:italic>M. leprae</jats:italic> , and <jats:italic>M. avium</jats:italic> but not by nonpathogenic mycobacteria or nonmycobacterial intramacrophage pathogens. This pathway required the association of the complement cleavage product C2a with mycobacteria resulting in the formation of a C3 convertase. The mycobacteria-associated C2a cleaved C3, resulting in C3b opsonization of the mycobacteria and recognition by macrophages. </jats:p>

<jats:p> Anandamide, an endogenous ligand for central cannabinoid receptors, is released from neurons on depolarization and rapidly inactivated. Anandamide inactivation is not completely understood, but it may occur by transport into cells or by enzymatic hydrolysis. The compound <jats:italic>N</jats:italic> -(4-hydroxyphenyl)arachidonylamide (AM404) was shown to inhibit high-affinity anandamide accumulation in rat neurons and astrocytes in vitro, an indication that this accumulation resulted from carrier-mediated transport. Although AM404 did not activate cannabinoid receptors or inhibit anandamide hydrolysis, it enhanced receptor-mediated anandamide responses in vitro and in vivo. The data indicate that carrier-mediated transport may be essential for termination of the biological effects of anandamide, and may represent a potential drug target. </jats:p>

<jats:p> Nerve growth factor (NGF) is a neurotrophic factor secreted by cells that are the targets of innervation of sympathetic and some sensory neurons. However, the mechanism by which the NGF signal is propagated from the axon terminal to the cell body, which can be more than 1 meter away, to influence biochemical events critical for growth and survival of neurons has remained unclear. An NGF-mediated signal transmitted from the terminals and distal axons of cultured rat sympathetic neurons to their nuclei regulated phosphorylation of the transcription factor CREB (cyclic adenosine monophosphate response element <jats:bold>–</jats:bold> binding protein). Internalization of NGF and its receptor tyrosine kinase TrkA, and their transport to the cell body, were required for transmission of this signal. The tyrosine kinase activity of TrkA was required to maintain it in an autophosphorylated state upon its arrival in the cell body and for propagation of the signal to CREB within neuronal nuclei. Thus, an NGF-TrkA complex is a messenger that delivers the NGF signal from axon terminals to cell bodies of sympathetic neurons. </jats:p>

<jats:p> Mutations in the <jats:italic>SUPERMAN</jats:italic> gene affect flower development in <jats:italic>Arabidopsis</jats:italic> . Seven heritable but unstable <jats:italic>sup</jats:italic> epi-alleles (the <jats:italic>clark kent</jats:italic> alleles) are associated with nearly identical patterns of excess cytosine methylation within the <jats:italic>SUP</jats:italic> gene and a decreased level of <jats:italic>SUP</jats:italic> RNA. Revertants of these alleles are largely demethylated at the <jats:italic>SUP</jats:italic> locus and have restored levels of <jats:italic>SUP</jats:italic> RNA. A transgenic <jats:italic>Arabidopsis</jats:italic> line carrying an antisense methyltransferase gene, which shows an overall decrease in genomic cytosine methylation, also contains a hypermethylated <jats:italic>sup</jats:italic> allele. Thus, disruption of methylation systems may yield more complex outcomes than expected and can result in methylation defects at known genes. The <jats:italic>clark kent</jats:italic> alleles differ from the antisense line because they do not show a general decrease in genomic methylation. </jats:p>

<jats:p> Signaling cascades triggered by receptor tyrosine kinases (RTKs) participate in diverse developmental processes. The active state of these signaling pathways was monitored by examination of the in situ distribution of the active, dual phosphorylated form of mitogen-activated protein kinase (ERK) with a specific monoclonal antibody. Detection of the active state of the <jats:italic>Drosophila</jats:italic> epidermal growth factor receptor (DER) pathway allowed the visualization of gradients and boundaries of receptor activation, assessment of the distribution of activating ligands, and analysis of interplay with the inhibitory ligand Argos. This in situ approach can be used to monitor other receptor-triggered pathways in a wide range of organisms. </jats:p>

<jats:p> Thermophilic (45° to 75°C) bacteria that reduce amorphous Fe(III)-oxyhydroxide to magnetic iron oxides have been discovered in two geologically and hydrologically isolated Cretaceous- and Triassic-age sedimentary basins in the deep (&gt;860 meters below land surface) terrestrial subsurface. Molecular analyses based on 16 <jats:italic>S</jats:italic> ribosomal RNA (rRNA) gene sequences revealed that some of these bacteria represent an unrecognized phylogenetic group of dissimilatory Fe(III)-reducing bacteria. This discovery adds another dimension to the study of microbial Fe(III) reduction and biogenic magnetism. It also provides examples for understanding the history of Fe(III)-reducing microorganisms and for assessing possible roles of such microorganisms on hot primitive planets. </jats:p>

<jats:p> The <jats:italic>PATCHED</jats:italic> ( <jats:italic>PTC</jats:italic> ) gene encodes a Sonic hedgehog (Shh) receptor and a tumor suppressor protein that is defective in basal cell nevus syndrome (BCNS). Functions of <jats:italic>PTC</jats:italic> were investigated by inactivating the mouse gene. Mice homozygous for the <jats:italic>ptc</jats:italic> mutation died during embryogenesis and were found to have open and overgrown neural tubes. Two Shh target genes, <jats:italic>ptc</jats:italic> itself and <jats:italic>Gli</jats:italic> , were derepressed in the ectoderm and mesoderm but not in the endoderm. Shh targets that are, under normal conditions, transcribed ventrally were aberrantly expressed in dorsal and lateral neural tube cells. Thus Ptc appears to be essential for repression of genes that are locally activated by Shh. Mice heterozygous for the <jats:italic>ptc</jats:italic> mutation were larger than normal, and a subset of them developed hindlimb defects or cerebellar medulloblastomas, abnormalities also seen in BCNS patients. </jats:p>

<jats:p> The roots of plants normally carry small hairs arranged in a regular pattern. Transfer DNA–tagged lines of <jats:italic>Arabidopsis thaliana</jats:italic> included a mutant with few, randomly distributed root hairs. The mutated gene <jats:italic>CAPRICE</jats:italic> ( <jats:italic>CPC</jats:italic> ) encoded a protein with a Myb-like DNA binding domain typical of transcription factors involved in animal and plant development. Analysis in combination with other root hair mutations showed that <jats:italic>CPC</jats:italic> may work together with the <jats:italic>TTG</jats:italic> gene and upstream of the <jats:italic>GL2</jats:italic> gene. Transgenic plants overexpressing <jats:italic>CPC</jats:italic> had more root hairs and fewer trichomes than normal. Thus, the <jats:italic>CPC</jats:italic> gene determines the fate of epidermal cell differentiation in <jats:italic>Arabidopsis</jats:italic> . </jats:p>