Impact of pooling on accuracy of hepatitis B virus surface antigen screening of blood donations.

Expenditure on screening blood donations in developing countries can be reduced by testing donations in pools. This study evaluated serological screening in pools for hepatitis B virus (HBV) at the Israeli national blood bank and a hospital blood bank in Gaza, the Palestinian Authority. The accuracy of HBV surface antigen (HBsAg) enzyme immunoassay performed on pools of 3-24 samples was compared with individual tests. Delay in detecting positive samples due to dilution in pools and the possibility of antibody-antigen neutralization were analyzed. The sensitivity of pooled testing for HBsAg was 93-99%, prolonging the window period by 5 days (8.3%). Neutralization of HBsAg by hepatitis B surface antibodies (anti-HBs) could be minimized by testing immediately after pooling. Serological testing for HBsAg in pools may be performed using manually created pools of up to six samples, with 5% loss in sensitivity and a risk of neutralization by anti-HBs present in the donor population. Pooling can therefore be considered as an option only in countries with a low prevalence of HBV.

The trithorax group gene moira encodes a brahma-associated putative chromatin-remodeling factor in Drosophila melanogaster.

The genes of the trithorax group (trxG) in Drosophila melanogaster are required to maintain the pattern of homeotic gene expression that is established early in embryogenesis by the transient expression of the segmentation genes. The precise role of each of the diverse trxG members and the functional relationships among them are not well understood. Here, we report on the isolation of the trxG gene moira (mor) and its molecular characterization. mor encodes a fruit fly homolog of the human and yeast chromatin-remodeling factors BAF170, BAF155, and SWI3. mor is widely expressed throughout development, and its 170-kDa protein product is present in many embryonic tissues. In vitro, MOR can bind to itself and it interacts with Brahma (BRM), an SWI2-SNF2 homolog, with which it is associated in embryonic nuclear extracts. The leucine zipper motif of MOR is likely to participate in self-oligomerization; the equally conserved SANT domain, for which no function is known, may be required for optimal binding to BRM. MOR thus joins BRM and Snf5-related 1 (SNR1), two known Drosophila SWI-SNF subunits that act as positive regulators of the homeotic genes. These observations provide a molecular explanation for the phenotypic and genetic relationships among several of the trxG genes by suggesting that they encode evolutionarily conserved components of a chromatin-remodeling complex.

Cellular pathways acting along the germband and in the amnioserosa may participate in germband retraction of the Drosophila melanogaster embryo.

Germband retraction in Drosophila melanogaster, like most embryonic morphogenetic events in this organism and in higher eukaryotes, is not well understood. We have taken several approaches to study the relationships between previously identified mutations (u-shaped, serpent, hindsight and tailup) that selectively cause germband retraction defects in homozygous embryos, and a more pleiotropically acting locus, DER/faint little ball. Our observations from genetic, immunohistochemical, and embryo culture experiments suggest that the former four loci are elements of at least two parallel and partially redundant cellular pathways that affect germband retraction by acting in amnioserosal development or maintenance. An additional discrete and unique pathway, represented by DER/faint little ball, is likely to function in the germband itself. While the role of the amnioserosa during germband retraction appears to be permissive, the action of DER in the germband may be mediated by the cytoskeleton.

The nature of the nucleotide at the 5' side of the tRNA Su9 anticodon affects UGA suppression in Escherichia coli.

In Escherichia coli a UGA codon can be efficiently suppressed by a suppressor tRNA(Trp) called Su9. Here, we show that the level of UGA suppression is determined by the nature of the nucleotide at the 5' side of the anticodon of the suppressor (position 33). UGA suppression occurs when a pyrimidine residue is located in position 33 of the tRNA, and suppression is more efficient with a U than with a C in this position. On the other hand, when a purine residue is located at this position UGA suppression is extremely low. These results show that in the case of tRNA Su9, the UGA codon context effect does not require base pairing between the nucleotide at the 3' side of the codon and the 5' side of the anticodon.

Donut-shaped chambers for analysis of biochemical processes at the cellular and subcellular levels.

In order to study cell-cell variation with respect to enzymatic activity, individual live cell analysis should be complemented by measurement of single cell content in a biomimetic environment on a cellular scale arrangement. This is a challenging endeavor due to the small volume of a single cell, the low number of target molecules and cell motility. Micro-arrayed donut-shaped chambers (DSCs) of femtoliter (fL), picoliter (pL), and nanoliter (nL) volumes have been developed and produced for the analysis of biochemical reaction at the molecular, cellular and multicellular levels, respectively. DSCs are micro-arrayed, miniature vessels, in which each chamber acts as an individual isolated reaction compartment. Individual live cells can settle in the pL and nL DSCs, share the same space and be monitored under the microscope in a noninvasive, time-resolved manner. Following cell lysis and chamber sealing, invasive kinetic measurement based on cell content is achieved for the same individual cells. The fL chambers are used for the analysis of the same enzyme reaction at the molecular level. The various DSCs were used in this proof-of-principle work to analyze the reaction of intracellular esterase in both primary and cell line immune cell populations. These unique DSC arrays are easy to manufacture and offer an inexpensive and simple operating system for biochemical reaction measurement of numerous single cells used in various practical applications.

Expanding the Mot1 subfamily: 89B helicase encodes a new Drosophila melanogaster SNF2-related protein which binds to multiple sites on polytene chromosomes.

Many proteins of the SNF2 family, which share a similar DNA-dependent ATPase/putative helicase domain, are involved in global transcriptional control and processing of DNA damage. We report here the partial cloning and characterization of 89B helicase, a gene encoding a new Drosophila melanogaster member of the SNF2 family. 89B Helicase protein shows a high degree of homology in its ATPase/helicase domain to the global transcriptional activators SNF2 and Brahma and to the DNA repair proteins ERCC6 and RAD54. It is, however, most strikingly similar to the Saccharomyces cerevisiae protein Mot1, a transcriptional repressor with many target genes for which no homologue has yet been described. 89B helicase is expressed throughout fly development and its large transcript encodes a >200 kDa protein. Staining with anti-89B Helicase antibodies reveals that the protein is present uniformly in early embryos and then becomes localized to the ventral nerve cord and brain. On the polytene chromosomes, 89B Helicase is bound to several hundred specific sites that are randomly distributed. The homology of 89B Helicase to Mot1, its widespread developmental expression and its large number of targets on the polytene chromosomes of larval salivary gland cells suggest that 89B Helicase may play a role in chromosomal metabolism, particularly global transcriptional regulation.