Ultrasensitive human prion detection in cerebrospinal fluid by real-time quaking-induced conversion

The development of technologies for the in vitro amplification of abnormal conformations of prion protein (PrP(Sc)) has generated the potential for sensitive detection of prions. Here we developed a new PrP(Sc) amplification assay, called real-time quaking-induced conversion (RT-QUIC), which allows the detection of ≥1 fg of PrP(Sc) in diluted Creutzfeldt-Jakob disease (CJD) brain homogenate. Moreover, we assessed the technique first in a series of Japanese subjects and then in a blind study of 30 cerebrospinal fluid specimens from Australia, which achieved greater than 80% sensitivity and 100% specificity. These findings indicate the promising enhanced diagnostic capacity of RT-QUIC in the antemortem evaluation of suspected CJD.     

Not(ch) just development: Notch signalling in the adult brain

The Notch pathway is often regarded as a developmental pathway, but components of Notch signalling are expressed and active in the adult brain. With the advent of more sophisticated genetic manipulations, evidence has emerged that suggests both conserved and novel roles for Notch signalling in the adult brain. Not surprisingly, Notch is a key regulator of adult neural stem cells, but it is increasingly clear that Notch signalling also has roles in the regulation of migration, morphology, synaptic plasticity and survival of immature and mature neurons. Understanding the many functions of Notch signalling in the adult brain, and its dysfunction in neurodegenerative disease and malignancy, is crucial to the development of new therapeutics that are centred around this pathway.     

Separate People: Speaking of Creek Men and Women

Subjectivity, gender, and language are examined among contemporary Creek Indians of northeastern Oklahoma. Creek men are shown to define and shape social reproduction. Women's generality and unbounded "flow," such as that signified by menstruation, provide vitality and growth that force the separation of men from women and signal their definition as "separate(d) people." Creek language use is shown to be organized through these mutually interdependent principles of gendered subjectivity.     

Multicenter evaluation of mycobacteria identification by PCR restriction enzyme analysis in laboratories from Latin America and the Caribbean

The identification of mycobacterial species in clinical isolates is essential for making patient care decisions. Polymerase chain reaction (PCR) restriction enzyme analysis (PRA) is a simple and rapid identification method, based on amplification of 441 bp of the hsp65 gene and restriction with BstEII and HaeIII. As a contribution to the validation of PRA, a multicenter study was performed in eight laboratories located in Argentina, Brazil, Colombia, Chile, and Guadeloupe. Each laboratory received 18 coded isolates from the collection of the Institute of Tropical Medicine (Antwerp, Belgium), representing duplicates of nine laboratory strains: Mycobacterium terrae CIPT 140320001, Mycobacterium scrofulaceum CIPT 140220031, Mycobacterium flavescens ATCC 14474, Mycobacterium triviale ATCC 23292, Mycobacterium nonchromogenicum ATCC 19530, Mycobacterium chitae ATCC 19627, Mycobacterium abscessus ATCC 19977, Mycobacterium kansasii ATCC 12478, and Mycobacterium peregrinum ATCC 14467. A detailed protocol including amplification, enzymatic digestion, and gel preparation was provided to each laboratory. Two laboratories identified correctly all 18 (100%) isolates, one identified correctly 17 (94.5%), two identified 14 (77.7%), one identified 11 (61%), and two identified 8 (44.4%) isolates. Errors detected in laboratories with more than 77% accuracy were associated with electrophoresis running conditions and an unspecific amplicon produced by a single strain. Lower accuracy was mainly related to inappropriate use of DNA markers and insufficient training in interpretation of patterns. In conclusion, the PRA method was readily implemented in some Latin American and Caribbean laboratories of mycobacteria, but improvements in critical points, as gel running conditions and training in interpretiation of patterns, are needed in order to improve accuracy. In others, improvement in critical points is still necessary.     

Analysis of human immunodeficiency virus type 1 Gag dimerization-induced assembly

The nucleocapsid (NC) domains of retrovirus precursor Gag (PrGag) proteins play an essential role in virus assembly. Evidence suggests that NC binding to viral RNA promotes dimerization of PrGag capsid (CA) domains, which triggers assembly of CA N-terminal domains (NTDs) into hexamer rings that are interconnected by CA C-terminal domains. To examine the influence of dimerization on human immunodeficiency virus type 1 (HIV-1) Gag protein assembly in vitro, we analyzed the assembly properties of Gag proteins in which NC domains were replaced with cysteine residues that could be linked via chemical treatment. In accordance with the model that Gag protein pairing triggers assembly, we found that cysteine cross-linking or oxidation reagents induced the assembly of virus-like particles. However, efficient assembly also was observed to be temperature dependent or required the tethering of NTDs. Our results suggest a multistep pathway for HIV-1 Gag protein assembly. In the first step, Gag protein pairing through NC-RNA interactions or C-terminal cysteine linkage fosters dimerization. Next, a conformational change converts assembly-restricted dimers or small oligomers into assembly-competent ones. At the final stage, final particle assembly occurs, possibly through a set of larger intermediates.     

The Arg482His mutation in the beta-galactosidase gene is responsible for a high frequency of GM1 gangliosidosis carriers in a Cypriot village

GM1 gangliosidosis is a lysosomal storage disorder caused by deficiency of beta-galactosidase. It is mainly characterized by progressive neurodegeneration, and in its most severe infantile form, it leads to death before the age of 4. The GLB1 gene gives rise to two alternatively spliced mRNAs that encode the beta-galactosidase and the elastin binding protein (EBP). The diagnosis of two patients with the infantile form of GM1 gangliosidosis and 11 carriers in a small mountainous village in Cyprus prompted us to carry out a study in order to establish the frequency of carriers in the village and identify the mutations involved. Carrier detection was initially based on the measurement of beta-galactosidase activity in leucocytes. Among 85 random samples from the village, 10 were classified as carriers. Sequencing of the GLB1 gene in a Cypriot patient identified the missense mutation c.1445G>A (p.Arg482His) in the homozygous state. Seven of the 10 carriers identified using the enzyme assay were found to carry the same mutation by NspI restriction enzyme analysis. The three individuals who were negative for the c.1445G>A had borderline enzyme results and were probably wrongly classified as carriers. The frequency of GM1 gangliosidosis carriers in this village is approximately 8% (1:12). Western blot analysis showed a marked decrease of the 64-kDa mature form of the enzyme protein and a similar reduction of the 67-kDa EBP. Our results indicate that the c.1445G>A mutation, which appears to be responsible for all GM1 gangliosidosis alleles in this Cypriot village, affects protein conformation.     

Scaling up a microbore separation for semipreparative analysis: differential recoveries of radiolabeled amino acids

Application of a high-sensitivity microbore system designed to separate and quantify nonderivatized amino acids by anion exchange chromatography and amperometric detection for determination of amino acid-specific activities in biological samples requires high capacity to recover sufficient labeled material for adequate count statistics. Scale up from a low (25-1000 pmol) to a high (500-15,000 pmol) working range was achieved by use of a thick working electrode gasket to reduce sensitivity and eliminate peak splitting and tailing and by modification of the wash procedure to eliminate carryover. Analysis of recoveries of labeled amino acids revealed that specific amino acids are either selectively retained on the column or partially degraded during analysis and that assessment of purities of labeled compounds and metabolic labeling patterns requires careful analysis of recoveries of labeled compounds in the appropriate eluate fraction.     

INFgamma stimulates arginine transport through system y+L in human monocytes

Freshly isolated human monocytes transport L-arginine mostly through a sodium independent, NEM insensitive pathway inhibited by L-leucine in the presence, but not in the absence of sodium. Interferon-gamma (IFNgamma) stimulates this pathway, identifiable with system y+L, and markedly enhances the expression of SLC7A7, the gene that encodes for system y+L subunit y+LAT1, but not of SLC7A6, that codes for the alternative subunit y+LAT2. System y+ plays a minor role in arginine uptake by monocytes and the expression of system y+-related genes, SLC7A1 and SLC7A2, is not changed by IFNgamma. These results demonstrate that system y+L is sensitive to IFNgamma.