Lysosomal dysfunction produces distinct alterations in synaptic alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid and N-methyl-D-aspartate receptor currents in hippocampus

The early processes that lead to synaptic dysfunction during aging are not clearly understood. Dysregulation of alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors may cause age-related cognitive decline. Using hippocampal slice cultures exhibiting lysosomal dysfunction, an early marker of brain aging that is linked to protein accumulation, we identified alterations to AMPA and NMDA receptor-mediated synaptic currents. The miniature and spontaneous excitatory postsynaptic currents that were examined after 3, 6, and 9 days of lysosomal disruption showed progressive changes in amplitude, frequency, and rise and decay kinetics. To investigate whether modifications in specific channel properties of single synaptic receptors contributed to changes in the amplitude and time course of synaptic currents, we examined the single channel properties of synaptic AMPA and NMDA receptors. The channel open probability and the mean open times showed decreases in both receptor populations, whereas the closed times were increased without any change in the channel conductance. The Western blot analysis revealed a progressive decline in synaptic markers including glutamate receptor subunits. These results indicate that lysosomal dysfunction leads to progressive functional perturbation of AMPA and NMDA receptors in this slice model of protein accumulation, suggesting that age-related cognitive decline could result from altered glutamate receptor function before reductions in synaptic density.

Quantification of HCV RNA levels and detection of core antigen in donations before seroconversion

BACKGROUND

Detection of HCV during the window phase of infection before seroconversion is important in blood screening. HCV RNA levels were measured before seroconversion and compared with HCV core antigen and anti-HCV detection.

STUDY DESIGN AND METHODS

A total of 41 plasma samples from 17 US plasmapheresis donors and one English National Blood Service donor in the window phase before seroconversion of HCV infection were tested for the presence of anti-HCV, HCV RNA, and HCV core antigen.

RESULTS

HCV RNA levels between 5.4 x 10(2) and 3.4 x 10(7) IU per mL were measured. HCV core antigen was detected in 11 of 18 donors at the same time point as RNA was detected.

CONCLUSIONS

A wide range of HCV RNA levels can be detected during the seronegative window phase of HCV infection. HCV core antigen can be used to detect HCV infection during the window phase of infection.

Automated screening of blood donations for hepatitis C virus RNA using the Qiagen BioRobot 9604 and the Roche COBAS HCV Amplicor assay

BACKGROUND AND OBJECTIVES

In order to reduce the potential for transmission of hepatitis C virus (HCV) from an RNA-positive, anti-HCV-negative blood donation, the National Blood Service (NBS) introduced nucleic acid amplification technology (NAT) testing for HCV in England and Wales. The objective of this study was to develop an automated assay using commercial components for the detection of HCV RNA in blood donations for transfusion.

MATERIALS AND METHODS

The Qiagen QIAamp 96 'Viral RNA' and 'Virus' BioRobot kits for HCV RNA extraction, and the Roche COBAS HCV Amplicor v2.0 and AmpliScreen v2.0 assays for polymerase chain reaction (PCR) amplification and detection, were investigated.

RESULTS

QIAamp technology and the BioRobot 9604 allow automation of the viral RNA extraction process. By combining the automated silica-membrane based QIAamp 96 Virus extraction and automated reverse transcription-polymerase chain reaction (RT-PCR) set-up with COBAS HCV AmpliScreen v2.0 amplification and detection it is possible to achieve a 95% detection level for HCV of 12.8 IU/ml. Cross-contamination studies have shown that use of the BioRobot 9604 does not pose a detectable contamination risk. Between 1999 and 2001, approximately 6.8 x 106 donations were tested in England and Wales, of which only four were found to contain RNA without anti-HCV.

CONCLUSIONS

This combination of methods results in an assay with a high sample throughput, little 'hands-on' time and fast turnaround time that is also sufficiently sensitive to allow testing of pools of up to 96 samples at a time. These methods have been successfully introduced into routine use within the NBS for release of blood components with a shelf-life of longer than 24 h.

Effects of handling and storage of blood on the stability of hepatitis C virus RNA: implications for NAT testing in transfusion practice

BACKGROUND AND OBJECTIVES

To determine the stability of hepatitis C virus (HCV) RNA during transport and storage of blood samples from donors, prior to screening for HCV by nucleic acid amplification technology.

MATERIALS AND METHODS

Various blood and plasma sample types were stored for up to 120 h at different temperatures and the HCV RNA level was measured using an in house quantitative reverse transcription-polymerase chain reaction.

RESULTS

No decline in HCV RNA level was observed after 72 h of storage of whole blood at 4 degrees C in EDTA tubes (Greiner) and Plasma Preparation Tubes (PPT; Becton Dickinson), while insignificant declines of 0.2 log10 and 0. 25 log10 occurred at 25 degrees C after 72 h in the EDTA tubes and PPT tubes, respectively. When whole blood was stored with mixed anticoagulants CPDA-1 and EDTA for up to 120 h, no decline in HCV RNA level was observed at 4 degrees C and 25 degrees C, while a significant decline of 0.37 log10 occurred at 37 degrees C after 120 h. The temperature during transportation was investigated with a 12-hour period at 25 degrees C and 37 degrees C before storage at 4 degrees C for 108 h. Neither temperature resulted in any loss of HCV RNA in comparison with 120 h of storage at 4 degrees C.

CONCLUSION

Whole blood anticoagulated with EDTA or CPDA-1/EDTA may be stored at up to 25 degrees C (room temperature) for up to 5 days without any significant loss in plasma HCV RNA level.

SirR, a novel iron-dependent repressor in Staphylococcus epidermidis

In Staphylococcus epidermidis and Staphylococcus aureus, a number of cell wall- and cytoplasmic membrane-associated lipoproteins are induced in response to iron starvation. To gain insights into the molecular basis of iron-dependent gene regulation in the staphylococci, we sequenced the DNA upstream of the 3-kb S. epidermidis sitABC operon, which Northern blot analysis indicates is transcriptionally regulated by the growth medium iron content. We identified two DNA sequences which are homologous to elements of the Corynebacterium diphtheriae DtxR regulon, which controls, in response to iron stress, for example, production of diphtheria toxin, siderophore, and a heme oxygenase. Upstream of the sitABC operon and divergently transcribed lies a 645-bp open reading frame (ORF), which codes for a polypeptide of approximately 25 kDa with homology to the DtxR family of metal-dependent repressor proteins. This ORF has been designated SirR (staphylococcal iron regulator repressor). Within the sitABC promoter/operator region, we also located a region of dyad symmetry overlapping the transcriptional start of sitABC which shows high homology to the DtxR operator consensus sequence, suggesting that this region, termed the Sir box, is the SirR-binding site. The SirR protein was overexpressed, purified, and used in DNA mobility shift assays; SirR retarded the migration of a synthetic oligonucleotide based on the Sir box in a metal (Fe2+ or Mn2+)-dependent manner, providing confirmatory evidence that this motif is the SirR-binding site. Furthermore, Southern blot analysis of staphylococcal chromosomal DNA with the synthetic Sir box as a probe confirmed that there are at least five Sir boxes in the S. epidermidis genome and at least three in the genome of S. aureus, suggesting that SirR controls the expression of multiple target genes. Using a monospecific polyclonal antibody raised against SirR to probe Western blots of whole-cell lysates of S. aureus, S. carnosus, S. epidermidis, S. hominis, S. cohnii, S. lugdunensis, and S. haemolyticus, we identified an approximately 25-kDa cross-reactive protein in each of the staphylococcal species examined. Taken together, these data suggest that SirR functions as a divalent metal cation-dependent transcriptional repressor which is widespread among the staphylococci.

Engineering the luxCDABE genes from Photorhabdus luminescens to provide a bioluminescent reporter for constitutive and promoter probe plasmids and mini-Tn5 constructs

The luxCDABE operon of Photorhabdus luminescens has been cloned and engineered as an easily mobilisable cassette flanked by sites for commonly used restriction enzymes. Constitutive and promoter probe plasmids utilising the P. luminescens luxCDABE have been constructed using a number of compatible replicons and antibiotic markers. Complementary to these plasmids, a range of promoterless and constitutive luxCDABE mini-Tn5 derivatives has been constructed. The potential of coupling mini-Tn5 luxCDABE promoter probe transposons with automated luminometry and photometry to screen for mutants that exhibit growth phase variation in gene expression is demonstrated.

The numbers and distribution of ammonia-oxidizing bacteria in some Northern Territory and South Australian soils

Ammonia-oxidizing bacteria were detected in 75 soil samples from the Northern Territory and South Australia. Silica gel plates gave soil counts comparable with those obtained in liquid media. The counts varied from 20 to 8000 cells per gram of soil. Nitrosogloea merismoides was detected in 53 of the soils, Nitrosornonas europaea in 39 soils, and Nitrosococcus nitrosus in 14 soils. There was little difference between the numbers and types of nitrifying bacteria present in the desert soils compared with those from the more temperate areas, nor did the average annual rainfall have any appreciable effect.