A Diurnal zooplankton migration study in Lake Mead

The diurnal vertical movement of zooplankton was first recorded in freshwater lakes by Weismann (1877) in Lake Constance (Bodensee), although Cuvier was credited with observing the migration of Daphniae in 1817 (Gushing, 1955). The migration is best observed in deep oligotrophic lakes and migrations of 50 m per day are described (Worthington, 1931). In addition, two species of chaetognaths are reported to migrate 400 m a day in marine waters off of Lisbon (Waterman and Berry, 1967) while Birge (1895) found little evidence of the phenomenon at all in Lake Mendota, Wisconsin. Most zooplankton that migrate rise at night and sink during the day. Welch (1952) and Pennak (1944) point out that the most important factor involved in diurnal migration is light. It appears that the extent of the diurnal movements varies from lake to lake, among the sexes and among the age of a particular plankter. Crustaceae and some rotifers are the organisms that most often exhibit this phenomenon. Rare cases in which zooplankters show reversed migrations have been recorded (Worthington and Ricardo, 1936; Maloney and Tressler, 1942). Previous studies on Lake Mead have dealt primarily with the physical limnology of Lake Mead (Smith, et al., 1948; National Research Council, 1949) Anderson, 1950; Anderson and Pritchard, 1951; Harbeck, et al., 1958; and Bureau of Reclamation, 1965). Moffett (1943) did a preliminary report on the plankton and fish of the lake from samples collected in November, 1941. A study by Everett (1972) showed that the highest primary productivity rates in Lake Mead occurred in the Boulder Basin. The purpose of the present investigation is to find whether nocturnal migration patterns occur in the zooplanktonic fauna of Lake Mead during times of isothermy and to determine the extent of this possible migration

Seasonal variation of vitamin B12, B12 analogs, and phytoplankton in a Long Island estuary

Dissolved vitamin B12 concentrations in the Peconic Bay estuary, Long Island, were determined over a seasonal period by assay with the diatom Thalassiosira pseudonana clone 3H…

Phytoplankton distribution and water quality indices for Lake Mead (Colorado River)

Phytoplankton samples were collected in Lake Mend 6 times from September 1910 to June 1971 for 8 stations at depths of 0. 3, 5, 10, 20, and 30 m. These samples were processed through a Millipore filter apparatus and 79 planktonic algae were identified. Algal divisions represented were Bacillariophyta, 42 species; Chlorophyta, 18 ; Cyanophyta, 9; Chrysophyta, 3; Cryptophyta, 3; Pyrrophyta, 2; and Euglenophyta, 2. Blue-green algae were dominant in late summer and fall; green algae, diatoms, and, cryptomonads in winter; and green algae in spring. The early summer flora was best represented by the Chlorophyta, Cryptophyta, and Chrysophyta. Palmer\u27s pollution-tolerant algae indices and Nygaard\u27s indices were calculated from phytoplankton data. These indices suggest eutropic conditions in Lake Mead, especially for Boulder Basin

Inhibitor-bound complexes of dihydrofolate reductase-thymidylate synthase from Babesia bovis

Structural characterization of the bifunctional enzyme dihydrofolate reductase-thymidylate synthase from B. bovis in the apo state and complexed with antifolate inhibitors in both enzymatic active sites is reported

Leveraging structure determination with fragment screening for infectious disease drug targets: MECP synthase from Burkholderia pseudomallei

As part of the Seattle Structural Genomics Center for Infectious Disease, we seek to enhance structural genomics with ligand-bound structure data which can serve as a blueprint for structure-based drug design. We have adapted fragment-based screening methods to our structural genomics pipeline to generate multiple ligand-bound structures of high priority drug targets from pathogenic organisms. In this study, we report fragment screening methods and structure determination results for 2C-methyl-D-erythritol-2,4-cyclo-diphosphate (MECP) synthase from Burkholderia pseudomallei, the gram-negative bacterium which causes melioidosis. Screening by nuclear magnetic resonance spectroscopy as well as crystal soaking followed by X-ray diffraction led to the identification of several small molecules which bind this enzyme in a critical metabolic pathway. A series of complex structures obtained with screening hits reveal distinct binding pockets and a range of small molecules which form complexes with the target. Additional soaks with these compounds further demonstrate a subset of fragments to only bind the protein when present in specific combinations. This ensemble of fragment-bound complexes illuminates several characteristics of MECP synthase, including a previously unknown binding surface external to the catalytic active site. These ligand-bound structures now serve to guide medicinal chemists and structural biologists in rational design of novel inhibitors for this enzyme

SARS-CoV-2 innate effector associations and viral load in early nasopharyngeal infection

COVID-19 causes severe disease with poor outcomes. We tested the hypothesis that early SARS-CoV-2 viral infection disrupts innate immune responses. These changes may be important for understanding subsequent clinical outcomes. We obtained residual nasopharyngeal swab samples from individuals who requested COVID-19 testing for symptoms at drive-through COVID-19 clinical testing sites operated by the University of Utah. We applied multiplex immunoassays, real-time polymerase chain reaction assays and quantitative proteomics to 20 virus-positive and 20 virus-negative samples. ACE-2 transcripts increased with infection (OR =17.4, 95% CI [CI] =4.78-63.8) and increasing viral N1 protein transcript load (OR =1.16, CI =1.10-1.23). Transcripts for two interferons (IFN) were elevated, IFN-λ1 (OR =71, CI =7.07-713) and IFN-λ2 (OR =40.2, CI =3.86-419), and closely associated with viral N1 transcripts (OR =1.35, CI =1.23-1.49 and OR =1.33 CI =1.20-1.47, respectively). Only transcripts for IP-10 were increased among systemic inflammatory cytokines that we examined (OR =131, CI =1.01-2620). We found widespread discrepancies between transcription and translation. IFN proteins were unchanged or decreased in infected samples (IFN-γ OR =0.90 CI =0.33-0.79, IFN-λ2,3 OR =0.60 CI =0.48-0.74) suggesting viral-induced shut-off of host antiviral protein responses. However, proteins for IP-10 (OR =3.74 CI =2.07-6.77) and several interferon-stimulated genes (ISG) increased with viral load (BST-1 OR =25.1, CI =3.33-188; IFIT1 OR =19.5, CI =4.25-89.2; IFIT3 OR =245, CI =15-4020; MX-1 OR =3.33, CI =1.44-7.70). Older age was associated with substantial modifications of some effects. Ambulatory symptomatic patients had an innate immune response with SARS-CoV-2 infection characterized by elevated IFN, proinflammatory cytokine and ISG transcripts, but there is evidence of a viral-induced host shut-off of antiviral responses. Our findings may characterize the disrupted immune landscape common in patients with early disease