Three-dimensional structure of the major autoantigen in primary biliary cirrhosis

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by the presence of antimitochondrial autoantibodies in patients' serum. The major autoantigen, recognized by antibodies from > 95% of patients with PBC, has been identified as the E2 component (E2p) of the pyruvate dehydrogenase multienzyme complex. Immunodominant sites on E2p have been localized to the inner of the two lipoyl domains, where the essential cofactor lipoic acid is attached covalently. The aim of this study was to determine the three-dimensional structure of the inner lipoyl domain of human E2p.

METHODS

The domain was expressed in Escherichia coli; after purification, its structure was analyzed using nuclear magnetic resonance spectroscopy.

RESULTS

The structure of the lipoyl domain from human E2p was determined, and the implications of the structure for autoimmune recognition were assessed.

CONCLUSIONS

Knowledge of the structure further defines the major epitope and may help in the design of antigen-specific immunotherapy for treatment of PBC.

Development of LBP110 expression by neural crest-derived enteric precursors: migration and differentiation potential in ls/ls mutant mice

Neural crest-derived cells acquire a 110-kD laminin-binding protein (LBP110) when they colonize the murine bowel. Laminin stimulates LBP110-expressing cells to develop as neurons. We have followed the development of LBP110 by neural crest-derived cells as they enter the gut of control and ls/ls mutant mice. The expression of neurofilament and choline acetyltransferase was used as markers of a neuronal phenotype. Tyrosine hydroxylase was used as a marker for the mash-1-dependent lineage of enteric precursors, while calcitonin gene-related peptide was used as a marker for the mash-1-independent lineage of crest-derived cells. A subset of cells expressing LBP110 was located along the vagi at E10 at cervical and thoracic levels. At E12, cells expressing LBP110 extended from the foregut to the midgut. The expression of neurofilament protein lagged behind that of LBP110 by about 0.5 day and then became coincident with LBP110 immunoreactivity. By E15, cells doubly labeled with antibodies to LBP110 and neurofilament protein were located along the entire extent of the bowel up to but not including the terminal colon. By E16, both the proximal and terminal colon contained cells expressing LBP110 and neurofilaments. The pattern of immunoreactivity could not be distinguished between ls/ls and control animals prior to E16. By E16, when the terminal colon of control animals contained many cells expressing LBP110 and neurofilaments, the terminal colon of ls/ls animals lacked cells expressing these proteins; nevertheless, structures outside of the terminal colon were heavily endowed with cells expressing LBP110 and neurofilaments. These ectopically located cells derived from both mash-1-dependent and -independent lineages of crest-derived precursors.

Chick ciliary ganglion neurons contain transcripts coding for acetylcholine receptor-associated protein at synapses (rapsyn)

A peripheral membrane protein of approximately 43 kDa (rapsyn) clusters muscle nicotinic acetylcholine receptors (AChRs), but molecules relevant to clustering neuronal AChRs have not been identified. Here, we have detected rapsyn transcripts in the chick nervous system, localized rapsyn mRNA in ciliary ganglion (CG) neurons, which are known to cluster AChRs, and identified three rapsyn cDNAs derived from the ganglion. Our initial Northern blots, performed using a mouse probe, revealed rapsyn-like transcripts in chick muscle and brain. To develop species-specific probes, we prepared a chick rapsyn cDNA construct, Ch43K.1, that encodes a protein having extensive homology to mouse rapsyn. Using primers designed to anneal near the 5' and 3' boundaries of Ch43K.1, three prominent cDNAs were amplified from chick muscle templates by reverse transcriptase based-PCR. Products of similar size were also amplified using cDNA prepared from neuronal tissues expected to contain clustered AChRs (CG and brain), whereas none were detected using templates from tissues not displaying clustered AChRs (sensory ganglia and liver). In situ hybridization confirmed that rapsyn mRNA is expressed both in chick muscle fibers and in CG neurons. Sequencing the three cDNAs amplified from CG templates revealed the largest to be Ch43K.1, whereas the smaller two may represent splice variants. These findings suggest that multiple rapsyn-like molecules are involved in clustering the distinct AChRs expressed by muscle fibers and neurons.

Three-dimensional structure of the lipoyl domain from the dihydrolipoyl succinyltransferase component of the 2-oxoglutarate dehydrogenase multienzyme complex of Escherichia coli

A sub-gene encoding the lipoyl domain of the dihydrolipoyl succinyltransferase polypeptide chain of the 2-oxoglutarate dehydrogenase multienzyme complex of Escherichia coli was over-expressed and the protein was purified uniformly labelled with 15N. The three-dimensional structure of the domain was determined by means of nuclear magnetic resonance spectroscopy, based on 905 nuclear Overhauser effect inter-proton distance restraints, 42 phi torsion angle restraints and hydrogen bond restraints from 24 slowly exchanging amide protons. The structure of the 80-residue domain is that of a flattened beta-barrel surrounding a hydrophobic core in which Trp22 plays a central role in anchoring two four-stranded sheets together. The polypeptide backbone exhibits a 2-fold axis of quasi-symmetry, with the lipoylation site, Lys43, located at the tip of an exposed beta-turn in one beta-sheet and the N and C-terminal residues close together in space in the other beta-sheet. The atomic r.m.s. distribution about the mean coordinate is 0.46 A for the backbone atoms in the highly structured region and 0.88 A along the entire backbone (residues Ser1 to Asn80), including a less well-defined surface loop and the lipoyl-lysine beta-turn. The structure closely resembles that of the lipoyl domains from pyruvate dehydrogenase complexes, in accord with the existence of strongly conserved residues at critical positions in the domains. The structures of the lipoyl domains throw light on the requirements for the specificity of reductive acylation of their pendant lipoyl groups in the parent 2-oxo acid dehydrogenase complexes; an important aspect of the mechanisms underlying active site coupling and substrate channelling.

Immunopathogenesis and immunoregulation in schistosomiasis. Distinct chronic pathologic syndromes in CBA/J mice

Inbred CBA/J mice with chronic (20-week) Schistosoma mansoni infections demonstrate two distinct syndromes. Hypersplenomegaly syndrome (HSS), characterized by a massive spleen, liver fibrosis, ascites, and anemia, resembles hepatosplenic human schistosomiasis, complete with portal hypertension and shunting. Moderate splenomegaly (MSS) syndrome, with less severe pathology, parallels most chronic human infections. Phenotypic analyses of spleen cells for CD44, CD62L, CD45RB, Ia, and CD25 indicate that HSS mice have more activated and memory CD4+ T cells than do MSS mice. HSS animals also have more B cells that highly express B7-2. Anti-CD3 stimulated spleen cells from 8-week or chronically infected mice produce IL-4 and IL-10 in a manner that appears not to involve the CD28/B7-2 costimulation pathway. By contrast IFN-gamma production is augmented in the presence of anti-CD28 and decreased in the presence of anti-B7-2. Infected mice make very little IL-2 to anti-CD3, even with added anti-CD28. As cytokines affect resultant B-cell responses and HSS and MSS mice display distinctive isotypes, differential regulatory or anergy hypotheses may best explain MSS/HSS differences.

Increased expression of laminin-1 and collagen (IV) subunits in the aganglionic bowel of ls/ls, but not c-ret -/- mice

Extracellular matrix molecules, including laminin, affect the development of enteric neurons and accumulate in the aganglionic colon of ls/ls mice. Quantitative Northern analysis revealed that mRNAs encoding the beta 1 and gamma 1 subunits of laminin and collagens alpha 1(IV) and alpha 2(IV) are increased in the colons of ls/ls mice. Transcripts of laminin alpha 1 were evaluated quantitatively with reverse transcription and the competitive polymerase chain reaction (RT-cPCR). The abundance of laminin alpha 1 transcripts was developmentally regulated, but greater in the ls/ls than the wild-type colon at each age examined. In situ hybridization revealed that transcripts in the colon encoding laminin alpha 1 and beta 1 and collagen alpha 2(IV) were initially expressed in the endoderm, but by E15, expression shifted to cells of the colonic mesenchyme (ls/ls > wild type) where crest-derived cells migrate. The expression of laminin alpha 1 was examined in the totally aganglionic intestine of E15 and newborn c-ret -/- mice, to determine whether an increase occurs when neurogenesis fails independently of the ls/ls defect. RT-cPCR revealed no difference from control in mRNA encoding laminin alpha 1 in the c-ret -/- colon in either E15 or newborn animals. The accumulation of immunohistochemically demonstrable laminin that is prominent in the newborn ls/ls colon could not be detected in that of c-ret -/- animals. These observations suggest that transcripts encoding laminin-1 and collagen (IV) are increased in the colon and surrounding pelvic mesenchyme of ls/ls mice because of an intrinsic lesion, rather than a secondary consequence of aganglionosis. The data are compatible with the hypothesis that the increased expression of laminin-1 contributes to the failure of crest-derived cells to complete their colonization of the ls/ls colon.

Protective immune responses to the E and NS1 proteins of Murray Valley encephalitis virus in hybrids of flavivirus-resistant mice

The lack of an effective animal model has been a major obstacle in attempts to define the role of humoral and cellular immune responses in protection against flavivirus infection. We have used F1 hybrid mice (BALB/c x C3H/RV) that are heterozygous for the flavivirus resistance allele F1vr and show reduced virus replication in the brain after intracerebral inoculation. F1 hybrid mice challenged by intracerebral inoculation with Murray Valley encephalitis (MVE) virus developed encephalitis 2-3 days later than a genetically susceptible strain (BALB/c) but showed a similar mortality rate. This delay in the onset of disease provided more opportunity for virus clearance by primed immune responses. Using F1 hybrid mice we were able to demonstrate protective immunity induced by structural and non-structural proteins of MVE virus by immunization with pure NS1 protein or recombinant vaccinia viruses that expressed various regions of the MVE genome. These constructs included VV-STR (C-prM-E-NS1-NS2A), VV-delta C (prM-E-Ns1-NS2A) and VV-NS1 (NS1-NS2A). VV-delta C vaccinated mice were completely protected (100% survival)from challenge with 1000 infectious units of MVE virus, while mice inoculated with VV-STR, VV-NS1 or pure NS1 were partially protected (40%, 47% and 85% respectively). Analysis of prechallenge sera and in vivo depletion studies revealed that the solid protection induced by VV-delta C was mediated by neutralizing antibody to the E protein and did not require a CD8+ T cell response. The partial protection provided by VV-STR, VV-NS1 and pure NS1 occurred after induction of antibody to NS1. However, depletion of CD8+ cells prior to virus challenge ablated the protection provided by VV-NS1 indicating some requirement for class I restricted cytotoxic T cells.

Infectious disease emergencies in disasters

This article discusses the relationship between disasters and infections. Infections that are reviewed include those resulting from (1) a breakdown of the usual mechanisms of infection control, (2) the introduction or emergence of pathogens, and (3) the movement of populations into new areas. Components of infectious-disease surveillance and disaster teams are detailed.

Techniques for isolating thermotolerant and pathogenic freeliving amebae

Several conditions of isolation were evaluated to determine which yielded the greatest number of thermotolerant and pathogenic freeliving amebae. Swab samples, easier to obtain and process, produced more pathogenic amebae than water samples. If water samples are required, 50-ml volumes gave the greatest percentage of pathogenic isolates. An incubating temperature of 42 degrees C yielded the most thermotolerant amebae. A total of 11 pathogenic isolates were obtained from 762 environmental samples and were Acanthamoeba (55%), Naegleria fowleri Carter, 1970 (27%), and N. australiensis De Jonckheere, 1981 (18%).

Expression of nicotinic acetylcholine receptors and subunit mRNA transcripts in cultures of neural crest cells

The expression of neuronal phenotypic characteristics by neural crest-derived neurons is dependent upon both environmental cues and intrinsic properties. Neuronal nicotinic acetylcholine receptors (nAChRs) are expressed by most neural crest-derived peripheral neurons; nevertheless, the factors that influence and modulate the early expression of nAChRs on neuronal precursor cells are unknown. We used RT-PCR to analyze the temporal sequence of the appearance of transcripts encoding alpha 3, alpha 5, alpha 7, beta 2, and beta 4 nAChR subunits in cultures of quail neural crest cells. At 2 days in culture, mRNA encoding each of these nAChR subunits was detectable and, except for alpha 7, remained so through 12 days. The appearance of NAPA 73 immunoreactivity during neural crest cell migration suggested that some cells express neuronal characteristics early in development and that the expression of nAChR subunits may be cell autonomous for some neural crest-derived cells. Between 8 and 10 days in culture, a 2.0-kb transcript encoding alpha 3 subunit appears in addition to the expected 3.5-kb transcript that is present at 8 days. nAChR protein was detected immunocytochemically at 7 days and was observed in immunoblots by 9 days. Whole-cell patch clamp recordings demonstrated that functional nAChRs develop concurrently in a subset of neural crest-derived neurons. In addition, both neuronal and nonneuronal cells showed inward and delayed outward currents in response to step depolarization. The appearance of functional nAChRs on neural crest-derived cells, in vitro, occurs independently of innervation and of the components in growth medium. The data suggest that neural crest-derived cells express transcripts encoding nAChR subunits, possibly as an intrinsic property of some peripheral neurons, early in development.

Immunodominant epitopes on the NS1 protein of MVE and KUN viruses serve as targets for a blocking ELISA to detect virus-specific antibodies in sentinel animal serum

Two mosquito-borne flaviviruses, Murray Valley encephalitis (MVE) and Kunjin (KUN), are the aetiological agents of Australian encephalitis. MVE causes a severe and potentially fatal form of the disease while KUN is responsible for only a few relatively mild cases. Therefore it is important that serological tests used in flavivirus surveillance differentiate between infections with these two viruses. However, this has been hampered in the past by the close antigenic relationships between flaviviruses in traditional serological assays. An epitope blocking ELISA using MVE-specific and KUN-specific monoclonal antibodies (mAb) reacting to the non-structural protein NS1 of these viruses and a flavivirus group-specific mAb reacting to the envelope (E) protein was assessed for testing sentinel animals for seroconversion to specific flavivirus infections. Using these assays we were able to detect serum antibodies to a variety of flavivirus in laboratory infected rabbits, and naturally infected chickens and in the case of primary infections, differentiate those caused by KUN or MVE. These assays are now used routinely in our laboratory for testing chicken sera from sentinel flocks in the Kimberley and Pilbara regions of north Western Australia.

Glycosylation and antigenic variation among Kunjin virus isolates

Previous studies have found Kunjin (KUN) virus isolates from within Australia to be genetically homogenous and that the envelope protein of the type strain (MRM61C) was unglycosylated and lacked a potential glycosylation site. We investigated the extent of antigenic variation between KUN virus isolates from Australia and Sarawak using an immunoperoxidase assay and a panel of six monoclonal antibodies. The glycosylation status of the E protein of each virus was also determined by N glycosidase F (PNGase F) digestion and limited sequence analysis. The results showed that KUN viruses isolated within Australia oscillated between three antigenic types defined by two epitopes whose expression was influenced by passage history and host cell type. In contrast an isolate from Sarawak formed a stable antigenic type that was not influenced by passage history and was distinct from all Australian isolates. PNGase F digestions of KUN isolates indicated that 19 of the 33 viruses possessed a glycosylated E protein. Nucleotide sequence of the 5' third of the E gene of selected KUN isolates revealed that a single base change in PNGase F sensitive strains changed the tripeptide N-Y-F (amino acids 154-156 of the published sequence) to the potential glycosylation site N-Y-S. Further analysis revealed that passage history also had a significant influence on glycosylation.

A novel complex formed between the flavivirus E and NS1 proteins: analysis of its structure and function

We examined the structural features and functional significance of a novel complex which forms between the envelope (E) protein and nonstructural protein NS1 of Murray Valley encephalitis (MVE) virus. Western blot analysis of virus-infected C6/36 cell lysates revealed that the undenatured form of this E-NS1 complex was a heat-sensitive E-(NS1 dimer) complex. Furthermore, the E-NS1 complex was observed in cells infected with Kunjin, Japanese encephalitis, West-Nile and Kokobera viruses which indicates the complex is a common feature of flavivirus infection. E-NS1 complex which had been immunoaffinity purified from MVE-infected cell lysates or eluted from gel slices exhibited partial breakdown into the individual monomers, demonstrating that the complex arose from the association of E and NS1 proteins and was not a single polypeptide created from incomplete gene cleavage. Radioimmunoprecipitation and western blot analysis of MVE-infected cell lysates and culture fluid preparations collected at various times after infection revealed that the E-NS1 complex has a long half life, accumulates in the virus-infected cell with time and is not secreted into the extracellular fluid. We have postulated that the E-NS1 complex, or at least a major portion of the complex, is a non-specific aggregation with no functional significance in the viral life cycle.

Eye-extract factors promote the expression of acetylcholine sensitivity in chick dorsal root ganglion neurons

We have examined the development of acetylcholine (ACh) responses in chick sensory neurons and their regulation by growth factors. Between Embryonic Days E13 and E18 in vivo, the proportion of freshly dissociated dorsal root ganglion (DRG) neurons that were appreciably sensitive to 500 microM ACh increased from approximately 40 to > 90% and the size of the ACh response per unit membrane area increased nearly 10-fold. Nerve growth factor (NGF) supports the survival, growth, and differentiation of central, sympathetic, and sensory neurons. NGF also promotes ACh sensitivity in PC12 cells and nodose ganglion neurons grown in cell culture. When E13 chick DRG neurons were maintained in culture with NGF for 4-6 days, however, only approximately 50% had appreciable ACh sensitivity, and large responses comparable to those observed at E18 in vivo were rare. Chick-eye extract contains a 21.5-kDa trophic factor termed growth-promoting activity (GPA) that supports survival of sympathetic and DRG neurons for 24 hr in culture and an activity of approximately 50 kDa that promotes increases in choline acetyltransferase activity, ACh sensitivity, and ACh receptors (AChRs) in ciliary ganglion neurons (Nishi and Berg, 1981; Halvorsen et al., 1991). In the present study, whole-eye extract supported full survival of E13 DRG neurons for up to 6 days in culture and promoted ACh sensitivity in > 90% of the neurons tested. GPA-containing eye-extract fractions and NGF individually supported full DRG neuron survival for up to 6 days in culture, but neither promoted ACh sensitivity. Adding eye-extract fractions containing material of approximately 50 kDa for 4-6 days to either GPA- or NGF-supplemented media led to appreciable ACh sensitivity in approximately 90% of the DRG neurons tested. The levels of ACh sensitivity observed in DRG neurons maintained either in whole-eye extract or in fractions containing 50-kDa material were close to those observed at an equivalent developmental age in vivo. The results indicate that components in the 50-kDa eye-extract fraction promote the ACh sensitivity of DRG neurons in culture and suggest that similar factors may influence the appearance of AChRs on the neurons in vivo.

Detection of the 5-HT1A receptor and 5-HT1A receptor mRNA in the rat bowel and pancreas: comparison with 5-HT1P receptors

We tested the hypothesis that the rat bowel and pancreas contain 5-HT1A receptors. 3H-8-hydroxy-2-(di-n-propylamino)tetralin (3H-8-OH-DPAT) was used as a radioligand. Binding of 3H-8-OH-DPAT to membranes derived from the myenteric plexus and the pancreas was investigated by rapid filtration. Alternatively, radioautography was employed to locate 3H-8-OH-DPAT binding sites in frozen sections of unfixed bowel or pancreas. An excess of 5-HT (10 microM) was used to define nonspecific binding. Saturable, high affinity binding of 3H-8-OH-DPAT to enteric (Kd = 2.8 +/- 1.1 nM; Bmax = 83.8 +/- 4.3 fmol/mg protein) and pancreatic (Kd = 6.6 +/- 1.3 nM; Bmax = 44 +/- 2.2 fmol/mg protein) membranes was found. The binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was inhibited by 8-OH-DPAT, NAN-190, and spiperone. In contrast, the binding of 3H-8-OH-DPAT to enteric and pancreatic membranes was not inhibited by 5-carboxyamidotryptamine, or by a variety of compounds known to bind to other subtypes of 5-HT receptor. Digoxigenin-labeled oligonucleotides were found to detect mRNA encoding the 5-HT1A receptor in a subset of neurons in myenteric and submucosal ganglia. In contrast, 5-HT1A mRNA was not found in the pancreas. Radioautography revealed that the highest density of 3H-8-OH-DPAT binding sites was found in the stomach. These sites were especially numerous in the lamina propria adjacent to gastric glands, and in myenteric ganglia. Pancreatic 5-HT1A receptors were located on nerves, lymphoid tissue (especially the capsule of nodes), and on cells scattered in the pancreatic parenchyma. The concentration of 3H-8-OH-DPAT binding sites in the rat bowel and pancreas was less than that of 3H-5-HT binding sites; however, the distribution of 3H-8-OH-DPAT binding sites was similar to that of sites that bind 3H-5-HT. It is concluded that the rat gut and its extension in the pancreas contains 5-HT1A receptors. Many, if not all, of the nerve cells and processes that express 5-HT1A receptors express 5-HT1P receptors as well. The function of these receptors in the physiology of the entero-pancreatic innervation remains to be determined.

Role of growth factors in catecholaminergic expression by neural crest cells: in vitro effects of transforming growth factor beta 1

The differentiation of neural crest cells into catecholaminergic neurons is dependent upon both intrinsic properties and signals from the embryonic microenvironment. In tissue culture, the development of catecholaminergic traits is dependent upon factors present in chick embryo extract (CEE). This dependency suggests that soluble growth factors affect catecholaminergic differentiation in vivo. We have studied the role of CEE-derived factors and the potentially related influence of characterized growth factors on catecholaminergic phenotypic expression in avian neural crest cells. In this report, we show that CEE-derived factors and transforming growth factor beta1 (TGF-beta 1) differentially influence catecholaminergic phenotypic expression as well as melanogenesis. TGF-beta 1 substituted for CEE-derived factors and supported the in vitro differentiation of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) immunoreactivities, as well as catecholamine biosynthesis and storage. Differentiation of catecholaminergic cells was dependent on factors present in 10% CEE during the first 1-4 days in culture suggesting an initial critical period for exposure. One day of initial exposure to either CEE-derived factors or TGF-beta 1 was sufficient to support the subsequent expression of catecholaminergic phenotypic characteristics. The time course of responsiveness to TGF-beta 1 was different than for CEE-derived factors. Neural crest cells remain responsive to TGF-beta 1 for at least 5 days, which is past the critical period for CEE-derived factors. Bioassay of CEE shows that endogenous levels of TGF-beta are less than or equal to 0.5 ng/ml. Immunoprecipitation of TGF-beta from CEE or blockade by neutralizing antibodies did not result in a loss of catecholaminergic differentiation by neural crest cells. Although CEE supports melanogenesis under all of the growth conditions tested, TGF-beta 1 was found to be inhibitory.

Decreased beta 2-adrenergic receptor mRNA expression in receptor-deficient S49 lymphoma cells

Many variants of the S49 mouse lymphoma cell have been isolated along the pathway of cyclic AMP generation and response. Two such variants, beta p and beta d, were isolated by Johnson and colleagues and described in 1979 [Mol. Pharmacol. 15:16-27 (1979)]. The beta p and beta d variants express one half and one quarter, respectively, of the wild-type number of beta 2-adrenergic receptors. This observation has now been extended through the use of DNA-excess solution hybridization. Using this exquisitely sensitive technique for quantitation of gene and mRNA, we have been able to demonstrate that the beta 2-adrenergic receptor-deficient variant cells contain the same quantity of the beta 2-adrenergic receptor gene as the wild-type cells. In contrast, the beta 2-adrenergic receptor-deficient variant cells express reduced quantities of beta 2-adrenergic receptor-specific mRNA. The amount of beta 2-adrenergic receptor-specific mRNA correlates very well with the reduction in receptor expression in these cells. Both gene and mRNA in the wild-type and variant cells appear to be the same size, as judged by Southern and Northern analysis. Thus, the diminution of beta 2-adrenergic receptors in the beta p and beta d variants appears to reflect primarily the relative paucity of gene transcripts in the variant cells. These data imply that variations in cellular content of beta 2-adrenergic receptor mRNA, which may occur among closely related cells, is one explanation for differences in receptor number.

Detection of immobilised Murray Valley encephalitis virus RNA using oligonucleotide probes with varying degrees of mismatch

The design of oligonucleotides used for hybridisation studies often utilises available sequence information of the type strain of a particular virus. If hybridisation studies, using such oligonucleotides, are carried out with field isolates of the same virus, the problem of base pair mismatches and consequent difficulties in detection may arise. This study examined the effect of base pair mismatches on the hybridisation between membrane-bound Murray Valley encephalitis virus (MVE) RNA derived from various strains and deliberately mismatched oligonucleotide probes. Under conditions of very low stringency, probes containing up to 5 mismatches were able to detect MVE RNA, but not yeast RNA. Under washing conditions of increased stringency, hybridisation could be detected between MVE virus RNA and probes with only 3 to 4 mismatches. However, the extent of this interaction was dependent on the number and type of mismatches and their relative sequence position.

Direction of gaze during vibrotactile choice reaction time tasks

A vibrotactile choice reaction time (RT) task was used, with the hands in their own hemispace (arms uncrossed), and in their opposite hemispace (arms crossed). Gaze was directed at the stimulated and responding hand, away from it at the other (inactive) hand, or at a central fixation point (a neutral control). Responses were slower in the crossed than the uncrossed condition. Further, in the crossed condition, responses were faster when subjects looked at the stimulated and responding hand, rather than at the inactive hand or at the central fixation point. As RT in the latter two conditions did not differ, there is a benefit when subjects look at the stimulated and responding hand, rather than a cost when they look at the inactive hand. In the look at condition, visual or attentional factors may reduce the response coding conflict which occurs when arms are crossed.

Networks strengthen ties, status of rural hospitals

Rural hospitals are a integral part of the health care system in this country. But a lack of funds and a shrinking patient-base are leaving many of them without the resources to provide state-of-the-art care in their communities. In the following article, the authors discuss a network model that brings urban hospitals to the financial and service aid of rural facilities.