Pour-Plate Method for the Detection of Coagulase Production by Staphylococcus aureus

A pour-plate method is described for the detection of coagulase production by Staphylococcus aureus. Either Brain Heart Infusion agar or yeast extract-Trypticase soy agar containing swine plasma was the best medium for the detection of coagulase by this method. The advantages of this method and its potential utilization in the clinical laboratory, in food microbiology, and in specialized studies with S. aureus are discussed.     

External reflection FTIR of peptide monolayer films in situ at the air/water interface: experimental design, spectra-structure correlations, and effects of hydrogen-deuterium exchange.

A Fourier transform infrared spectrometer has been interfaced with a surface balance and a new external reflection infrared sampling accessory, which permits the acquisition of spectra from protein monolayers in situ at the air/water interface. The accessory, a sample shuttle that permits the collection of spectra in alternating fashion from sample and background troughs, reduces interference from water vapor rotation-vibration bands in the amide I and amide II regions of protein spectra (1520-1690 cm-1) by nearly an order of magnitude. Residual interference from water vapor absorbance ranges from 50 to 200 microabsorbance units. The performance of the device is demonstrated through spectra of synthetic peptides designed to adopt alpha-helical, antiparallel beta-sheet, mixed beta-sheet/beta-turn, and unordered conformations at the air/water interface. The extent of exchange on the surface can be monitored from the relative intensities of the amide II and amide I modes. Hydrogen-deuterium exchange may lower the amide I frequency by as much as 11-12 cm-1 for helical secondary structures. This shifts the vibrational mode into a region normally associated with unordered structures and leads to uncertainties in the application of algorithms commonly used for determination of secondary structure from amide I contours of proteins in D2O solution.     

Host Suitability of Selected Hybrids,Varieties and Inbreds of Corn to Populations of Meloidogyne spp.

Rates of reproduction of root-knot nematodes on corn varied with Meloidogyne species, with different populations of certain species, and with corn cultivars. M. arenaria, M. incognita and M. javanica reproduced at varying rates on all corn cultivars tested. None of the three selections of M. hapla reproduced on corn. Most of the Meloidogyne populations increased more rapidly on ''Coker'' and ''Pioneer'' hybrids than on ''McNair'' hybrids or on open-pollinated varieties or inbreds. Nematodes often reduced root growth, but the differences within given nematode-cultivar treatments were not usually significant. Root growth of ''Coker 911,'' which supported a high rate of reproduction, was affected less than ''Pioneer 309B'' which supported a low rate of nematode reproduction.     

Identification of glycoinositol phospholipid linked and truncated forms of the scrapie prion protein

Analysis of carboxy-terminal peptides derived from endoproteinase Lys-C digests of the scrapie isoform of the hamster prion protein revealed that the majority of the molecules are glycoinositol phospholipid linked through ethanolamine attached at serin-231. However, approximately 15% of PrPSc had a carboxy-terminal peptide that ends at glycine-228. It is intriguing that this glycine is part of the PrP sequence Gly-Arg-Arg, which is an established target sequence for the proteolysis and release of bioactive peptides from larger precursors. The mechanism of formation, as well as the role of the truncated carboxy terminus in the dissemination and neuropathology of scrapie, remains to be determined.     

Differential transmission of human immunodeficiency virus type 1 by distinct subsets of effector dendritic cells

Dendritic cells (DC) support human immunodeficiency virus type 1 (HIV-1) transmission by capture of the virus particle in the mucosa and subsequent transport to the draining lymph node, where HIV-1 is presented to CD4(+) Th cells. Virus transmission involves a high-affinity interaction between the DC-specific surface molecule DC-SIGN and the viral envelope glycoprotein gp120 and subsequent internalization of the virus, which remains infectious. The mechanism of viral transmission from DC to T cells is currently unknown. Sentinel immature DC (iDC) develop into Th1-promoting effector DC1 or Th2-promoting DC2, depending on the activation signals. We studied the ability of these effector DC subsets to support HIV-1 transmission in vitro. Compared with iDC, virus transmission is greatly upregulated for the DC1 subset, whereas DC2 cells are inactive. Increased transmission by DC1 correlates with increased expression of ICAM-1, and blocking studies confirm that ICAM-1 expression on DC is important for HIV transmission. The ICAM-1-LFA-1 interaction is known to be important for immunological cross talk between DC and T cells, and our results indicate that this cell-cell contact is exploited by HIV-1 for efficient transmission.     

Regulation of K+ current in human airway epithelial cells by exogenous and autocrine adenosine

The regulatory actions ofadenosine on ion channel function are mediated by four distinctmembrane receptors. The concentration of adenosine in the vicinity ofthese receptors is controlled, in part, by inwardly directed nucleosidetransport. The purpose of this study was to characterize the effects ofadenosine on ion channels in A549 cells and the role of nucleosidetransporters in this regulation. Ion replacement and pharmacologicalstudies showed that adenosine and an inhibitor of human equilibrative nucleoside transporter (hENT)-1, nitrobenzylthioinosine, activated K⁺ channels, most likely Ca²⁺-dependentintermediate-conductance K⁺ (I_K)channels. A₁ but not A₂ receptor antagonistsblocked the effects of adenosine. RT-PCR studies showed that A549 cellsexpressed mRNA for I_K-1 channels as well asA₁, A_2A, and A_2B but notA₃ receptors. Similarly, mRNA for equilibrative (hENT1 andhENT2) but not concentrative (hCNT1, hCNT2, and hCNT3) nucleosidetransporters was detected, a result confirmed in functional uptakestudies. These studies showed that adenosine controls the function ofK⁺ channels in A549 cells and that hENTs play a crucialrole in this process.