Identification of low-abundance differentially expressed transcripts using arrayed cDNA clones

Analysis of comparative gene expression by the use of DNA microarrays has become a widely used tool. However, this technique is only readily applied to organisms where sequence information is known. This paper describes the development of a low-cost method of gene discovery by enrichment of differentially expressed transcripts, which uses cDNA library arrays of bacterial clones on nylon membranes (macroarrays) coupled with a subtractive probe preparation method to discover differentially expressed genes. The method requires no prior knowledge of the organism's genome sequence and overcomes the inherent insensitivity of standard methods of macroarray hybridisation.

Robust and sensitive nylon hybridization membrane suitable for high-throughput robotic arraying applications

An important aspect of automated macroarraying is the suitability of the nylon membrane selected on which samples are to be arrayed. PerForma is a positively charged nylon membrane that has been developed specificallyfor automated macroarraying. Tests usingfluorescent hybridization detection methods have shown that immobilized DNA amounts as low as 0.25 pg can be detected and that positive signals are obtainable after 21 stripping cycles. This report describes the improved colony growth, improved handling characteristics, increased hybridization detection sensitivity, and increased stripping and reprobing capability obtained using PerForma.

Molecular analysis of the locus responsible for production of plantaricin S, a two-peptide bacteriocin produced by Lactobacillus plantarum LPCO10

A 4.5-kb region of chromosomal DNA carrying the locus responsible for the production of plantaricin S, a two-peptide bacteriocin produced by Lactobacillus plantarum LPCO10 (R. Jiménez-Díaz, J. L. Ruiz-Barba, D. P. Cathcart, H. Holo, I. F. Nes, K. H. Sletten, and P. J. Warner, Appl. Environ. Microbiol. 61:4459-4463, 1995), has been cloned, and the nucleotide sequence has been elucidated. Two genes, designated plsA and plsB and encoding peptides alpha and beta, respectively, of plantaricin S, plus an open reading frame (ORF), ORF2, were found to be organized in an operon. Northern blot analysis showed that these genes are cotranscribed, giving a ca. 0.7-kb mRNA, whose transcription start point was determined by primer extension. Nucleotide sequences of plsA and plsB revealed that both genes are translated as bacteriocin precursors which include N-terminal leader sequences of the double-glycine type. The role of ORF2 is unknown at the moment, although it might be expected to encode an immunity protein of the type described for other bacteriocin operons. In addition, several other potential ORFs have been found, including some which may be responsible for the regulation of bacteriocin production. Two of them, ORF8 and ORF14, show strong homology with histidine protein kinase and response regulator genes, respectively, which have been found to be involved in the regulation of the production of other bacteriocins from lactic acid bacteria. A third ORF, ORF5, shows homology with gene agrB from Staphylococcus aureus, which is involved in the mechanism of regulation of the virulence phenotype in this species. Thus, an agr-like regulatory system for the production of plantaricin S is postulated.

Ground-Based Near-Infrared Imaging Observations of Venus During the Galileo Encounter

Near-infrared images of Venus, obtained from a global network of ground-based observatories during January and February 1990, document the morphology and motions of the night-side near-infrared markings before, during, and after the Galileo Venus encounter. A dark cloud extended halfway around the planet at low latitudes (>+/-40 degrees ) and persisted throughout the observing program. It had a rotation period of 5.5 +/- 0.15 days. The remainder of this latitude band was characterized by small-scale (400 to 1000 kilometers) dark and bright markings with rotation periods of 7.4 +/- 1 days. The different rotation periods for the large dark cloud and the smaller markings suggests that they are produced at different altitudes. Mid-latitudes (+/-40 degrees to 60 degrees ) were usually occupied by bright east-west bands. The highest observable latitudes (+/-60 degrees to 70 degrees ) were always dark and featureless, indicating greater cloud opacity. Maps of the water vapor distribution show no evidence for large horizontal gradients in the lower atmosphere of Venus.

Where is the malpractice crisis taking us?

There have been several approaches taken to solve the malpractice insurance problem in this country. However, since the cost of malpractice insurance continues to climb, the changes so far have not solved the problem, and more changes seem inevitable. A major change could be the development of a patient insurance plan that would provide compensation for certain injuries related to medical care. The insurance coverage would be centered on hospital care. If certain requirements are met, the plan may not be more expensive than the current tort liability system, and would offer several advantages. In addition to the patient injury insurance, there could be federal assumption of liability for national immunization programs.