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Vertebrates and invertebrates are thought to employ common mechanisms to guide outgrowing cells to their final destinations. We have chosen the nematode Caenorhabditis elegans as a model system to study guidance processes because of its powerful genetics and transparency, which allows for individual cells to be viewed by microscopy. The excretory cell is an excellent growth cone to use in this type of analysis because the cell body is located in the anterior end of the animal and extends two short processes anteriorly and two long canals posteriorly along the length of the animal. This bidirectional and short vs long trajectory allows for the selection of mutations that specifically affect only certain aspects of longitudinal extension. We screened for mutations in the longitudinal outgrowth of the posterior excretory canals and identified two mutations (pm23 and pm24) which map to LG V. Both of these alleles have similar phenotypes; they are short with epidermal defects and possess very short canals that terminate at the anterior gonad suggesting that pm23 and pm24 may define a locus which is important in the general elongation of growth cones. One intriguing candidate gene which resides on LG V and has a similar phenotype to pm23 and pm24 is the sma-1 gene which encodes a unique [Beta]-spectrin, an important component of the apical cytoskeleton (C. McKeown, V. Praitis, and J. Austin, 1998, Development 125, 2087-2098). We have constructed a transgenic reporter strain that expresses GFP in the excretory canals to facilitate high-density screening for additional mutations in longitudinal path finding of this growth cone.

Transgenic strains of the nematode Caenorhabditis elegans, which carry stress-inducible lacZ reporter genes, are measurably stressed by exposure to heavy metals in aqueous solution. This stress response canbe quantified, using enzymatic assays for the reporter gene-product (Escherichia coli beta-galactosidase), or estimated approximately by in situ staining for beta-galactosidase in exposed worms. Stress responses to heavy metals have been demonstrated both in laboratory testsusing Cd{sup}2+{end} or Hg{sup}2+{end} and also in water samples taken from a metal-polluted river system in southwest England. The RiverCarnon flows through an area with an ancient mining history, principally for Sn, but also for Cu and other metals; As, Cd, Al, Mn, and Zn, as well as large amounts of Fe, are all present in these ore bodies. Four sites in the Carnon river basin were compared with respect to their macroinvertebrate diversity, physical and chemical characteristics (including the concentrations of As, Cd, Al, Cu, Mn, Zn, and Fe).Transgenic worms were exposed to water samples from these four sites, and also to a 0.33% (v/v) dilution of metal-laden minewater from the principal local mine (Wheal Jane). Transgene expression was inducedin all five cases, though markedly less so for the least polluted ofthe sites (which also supported a richer macroinvertebrate fauna). Two different transgenic strains were tested in this study; strain PC72 (using a homologous hsp16 promoter) is slightly more sensitive to most metal-containing water samples than strain CB4027 (using a heterologous Drosophila hsp70 promoter). Both transgenic strains and two different assay methods gave essentially similar results. These findings demonstrate that transgenic nematodes could provide a rapid and simple assessment of aquatic pollution, in that the transgene response is inducible by mixtures of dissolved metals at concentrations actually encountered in metal-polluted watercourses. [ABSTRACT FROM AUTHOR]

Social determinants of health are known to underly excessive burden from infectious diseases. However, it is unclear if social determinants are strong enough drivers to cause repeated infectious disease clusters in the same location. When infectious diseases are known to co-occur, such as in the co-occurrence of HIV and TB, it is also unknown how much social determinants of health can shift or intensify the co-occurrence. We collected available data on COVID-19, HIV, influenza, and TB by county in the United States from 2019-2022. We applied the Kulldorff scan statistic to examine the relative risk of each disease by year depending on the data available. Additional analyses using the percent of the county that is below the US poverty level as a covariate were conducted to examine how much clustering is associated with poverty levels. There were three counties identified at the centers of clusters in both the adjusted and unadjusted analysis. In the poverty-adjusted analysis, we found a general shift of infectious disease burden from urban to rural clusters., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Blake et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Human behavior lies somewhere between purely self-interested homo economicus and socially-motivated homo reciprocans. The factors that cause people to choose self-interest over costly cooperation can provide insights into human nature and are essential when designing institutions and policies that are meant to influence behavior. Alcohol consumption can shed light on the inflection point between selfish and selfless because it is commonly consumed and has global effects on the brain. The present study administered alcohol or placebo (N = 128), titrated to sex and weight, to examine its effect on cooperation in a standard task in experimental economics, the public goods game (PGG). Alcohol, compared to placebo, doubled the number of free-riders who contributed nothing to the public good and reduced average PGG contributions by 32% (p = .005). This generated 64% higher average profits in the PGG for those who consumed alcohol. The degree of intoxication, measured by blood alcohol concentration, linearly reduced PGG contributions (r = -0.18, p = .05). The reduction in cooperation was traced to a deterioration in mood and an increase in physiologic stress as measured by adrenocorticotropic hormone. Our findings indicate that moderate alcohol consumption inhibits the motivation to cooperate and that homo economicus is stressed and unhappy., Competing Interests: The authors have declared that no competing interests exist.

Cell migration and outgrowth are thought to be based on analogous mechanisms that require repeated cycles of process extension, reading and integration of multiple directional signals, followed by stabilisation in a preferred direction, and renewed extension. We have characterised a C. elegans gene, unc-53, that appears to act cell autonomously in the migration and outgrowth of muscles, axons and excretory canals. Abrogation of unc-53 function disrupts anteroposterior outgrowth in those cells that normally express the gene. Conversely, overexpression of unc-53 in bodywall muscles leads to exaggerated outgrowth. UNC-53 is a novel protein conserved in vertebrates that contains putative SH3- and actin-binding sites. unc-53 interacts genetically with sem-5 and we demonstrated a direct interaction in vitro between UNC-53 and the SH2-SH3 adaptor protein SEM-5/GRB2. Thus, unc-53 is involved in longitudinal navigation and might act by linking extracellular guidance cues to the intracellular cytoskeleton.

The Caenorhabditis elegans ubq-2 gene encodes a fusion of ubiquitin and a 52-amino-acid ribosomal protein. This single copy gene is both cis- and trans-spliced. It is expressed in all life stages of the worm and its transcript abundance is unaffected by heat stress. Transgenic analysis shows that expression of ubq-2 is regulated by an upstream promoter and a downstream element. The downstream element is required for ubq-2 promoter activity in embryos and in cells of the somatic gonad, including the distal tip cells, sheath cells, spermathecal cells, and cells of the uterus. The gonad-specific activity of the downstream regulator is transferable to a stress gene promoter such that heat-inducible expression of the transgene occurs in the somatic gonad. Stress-inducible beta-galactosidase expression in the gonad does not occur in all life stages, but is initiated late in the second or early in the third larval stage, when differentiation of gonadal tissues begins. Expression of a beta-galactosidase fusion protein from constructs containing the downstream ubq-2 regulator causes abnormalities of the gonad and embryonic lethality. Gonad abnormalities include arrested development and general disorganization. These abnormalities may be related to the overexpression of ubiquitin in the gonad.

Heat shock promoters have been employed to achieve tightly regulated expression of transformed genes in a wide variety of model systems including tissue culture cells, bacteria, yeast, Drosophila, and more recently Caenorhabditis elegans. Here we investigate the feasibility of using a laser microbeam to induce a sub-lethal heat shock response in individual cells of C. elegans. We demonstrate that in transgenic strains carrying heat shock promoter-lacZ fusions, single cell expression of beta-galactosidase in a variety of cell types of endodermal, mesodermal, or ectodermal origin can be achieved after pulsing with a laser. A tissue-general, inducible promoter can therefore be converted into one of single cell specificity which can be induced rapidly at any point in development, offering unique opportunities to study cell-cell interactions in C. elegans. This technique defines a new approach to generate mosaic animals and may be adaptable to other organisms or tissues.

The expression of the polyubiquitin-encoding gene (ubq-1) of Caenorhabditis elegans was analysed using transgenic nematode lines carrying translational ubq-1::lacZ fusions. Animals carrying a construct consisting of 938 bp of ubq-1 upstream sequences fused to lacZ (ubq938::lacZ) expressed beta Gal in embryos and in a tissue-general manner in 20% of L1 larvae. Somatic expression in later stages was usually confined to body muscle. Progressively larger deletions extending from the 5' end of ubq938::lacZ did not significantly alter the pattern of expression until 827 bp of sequence had been removed. Thus, sequences upstream from the transcription start point, including a G+C-rich block and a sequence resembling a TATA box (GAATAA), are not required to generate the expression pattern seen with ubq938::lacZ. Moreover, a basal level of expression was maintained in embryos when 903 bp were deleted. These results suggest that the promoter elements required for efficient expression of ubq-1 may reside within the transcribed region of the gene; alternatively, they must lie more than 1.7 kb upstream or 0.8 kb downstream from this region. Polymerase chain reaction analysis indicates that RNA molecules transcribed from the ubq938::lacZ and ubq delta 827::lacZ transgenes are trans-spliced to SL1, as is ubq-1 RNA.