Functional and antigenic landscape of the Nipah virus receptor binding protein

Nipah virus recurrently spills over to humans, causing fatal infections. The viral receptor-binding protein (RBP or G) attaches to host receptors and is a major target of neutralizing antibodies. Here we use deep mutational scanning to measure how all amino-acid mutations to the RBP affect cell entry, receptor binding, and escape from neutralizing antibodies. We identify functionally constrained regions of the RBP, including sites involved in oligomerization, along with mutations that differentially modulate RBP binding to its two ephrin receptors. We map escape mutations for six anti-RBP antibodies, and find that few antigenic mutations are present in natural Nipah strains. Our findings offer insights into the potential for functional and antigenic evolution of the RBP that can inform the development of antibody therapies and vaccines.

Protein nanoparticle vaccines induce potent neutralizing antibody responses against MERS-CoV

Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic betacoronavirus that causes severe and often lethal respiratory illness in humans. The MERS-CoV spike (S) protein is the viral fusogen and the target of neutralizing antibodies, and has therefore been the focus of vaccine design efforts. Currently there are no licensed vaccines against MERS-CoV and only a few candidates have advanced to Phase I clinical trials. Here we developed MERS-CoV vaccines utilizing a computationally designed protein nanoparticle platform that has generated safe and immunogenic vaccines against various enveloped viruses, including a licensed vaccine for SARS-CoV-2. Two-component protein nanoparticles displaying MERS-CoV S-derived antigens induced robust neutralizing antibody responses and protected mice against challenge with mouse-adapted MERS-CoV. Electron microscopy polyclonal epitope mapping and serum competition assays revealed the specificities of the dominant antibody responses elicited by immunogens displaying the prefusion-stabilized S-2P trimer, receptor binding domain (RBD), or N-terminal domain (NTD). An RBD nanoparticle vaccine elicited antibodies targeting multiple non-overlapping epitopes in the RBD, whereas anti-NTD antibodies elicited by the S-2P- and NTD-based immunogens converged on a single antigenic site. Our findings demonstrate the potential of two-component nanoparticle vaccine candidates for MERS-CoV and suggest that this platform technology could be broadly applicable to betacoronavirus vaccine development.

SARS-CoV-2 spike conformation determines plasma neutralizing activity elicited by a wide panel of human vaccines

Numerous safe and effective coronavirus disease 2019 vaccines have been developed worldwide that use various delivery technologies and engineering strategies. We show here that vaccines containing prefusion-stabilizing S mutations elicit antibody responses in humans with enhanced recognition of S and the S1 subunit relative to postfusion S as compared with vaccines lacking these mutations or natural infection. Prefusion S and S1 antibody binding titers positively and equivalently correlated with neutralizing activity, and depletion of S1-directed antibodies completely abrogated plasma neutralizing activity. We show that neutralizing activity is almost entirely directed to the S1 subunit and that variant cross-neutralization is mediated solely by receptor binding domain-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants than current technologies.

Omicron spike function and neutralizing activity elicited by a comprehensive panel of vaccines

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant of concern comprises several sublineages, with BA.2 and BA.2.12.1 having replaced the previously dominant BA.1 and with BA.4 and BA.5 increasing in prevalence worldwide. We show that the large number of Omicron sublineage spike mutations leads to enhanced angiotensin-converting enzyme 2 (ACE2) binding, reduced fusogenicity, and severe dampening of plasma neutralizing activity elicited by infection or seven clinical vaccines relative to the ancestral virus. Administration of a homologous or heterologous booster based on the Wuhan-Hu-1 spike sequence markedly increased neutralizing antibody titers and breadth against BA.1, BA.2, BA.2.12.1, BA.4, and BA.5 across all vaccines evaluated. Our data suggest that although Omicron sublineages evade polyclonal neutralizing antibody responses elicited by primary vaccine series, vaccine boosters may provide sufficient protection against Omicron-induced severe disease.

Single dose, CYP2D6 genotype-stratified pharmacokinetic study of atomoxetine in children with ADHD

The effect of CYP2D6 genotype on the dose-exposure relationship for atomoxetine has not been well characterized in children. Children 6-17 years of age diagnosed with attention-deficit hyperactivity disorder (ADHD) were stratified by CYP2D6 genotype into groups with 0 (poor metabolizers [PMs], n = 4), 0.5 (intermediate metabolizers [IMs], n = 3), one (extensive metabolizer [EM]1, n = 8) or two (EM2, n = 8) functional alleles and administered a single 0.5 mg/kg oral dose of atomoxetine (ATX). Plasma and urine samples were collected for 24 (IM, EM1, and EM2) or 72 hours (PMs). Dose-corrected ATX systemic exposure (area under the curve [AUC]0-∞ ) varied 29.6-fold across the study cohort, ranging from 4.4 ± 2.7 μM*h in EM2s to 5.8 ± 1.7 μM*h, 16.3 ± 2.9 μM*h, and 50.2 ± 7.3 μM*h in EM1s, IMs, and PMs, respectively (P < 0.0001). Simulated steady state profiles at the maximum US Food and Drug Administration (FDA)-recommended dose suggest that most patients are unlikely to attain adequate ATX exposures. These data support the need for individualized dosing strategies for more effective use of the medication.

Hippocampal circuit dysfunction in the Tc1 mouse model of Down syndrome

Hippocampal pathology is likely to contribute to cognitive disability in Down syndrome, yet the neural network basis of this pathology and its contributions to different facets of cognitive impairment remain unclear. Here we report dysfunctional connectivity between dentate gyrus and CA3 networks in the transchromosomic Tc1 mouse model of Down syndrome, demonstrating that ultrastructural abnormalities and impaired short-term plasticity at dentate gyrus-CA3 excitatory synapses culminate in impaired coding of new spatial information in CA3 and CA1 and disrupted behavior in vivo. These results highlight the vulnerability of dentate gyrus-CA3 networks to aberrant human chromosome 21 gene expression and delineate hippocampal circuit abnormalities likely to contribute to distinct cognitive phenotypes in Down syndrome.

Characterization of altered intrinsic excitability in hippocampal CA1 pyramidal cells of the Aβ-overproducing PDAPP mouse

Transgenic mice that accumulate Aβ peptides in the CNS are commonly used to interrogate functional consequences of Alzheimer's disease-associated amyloidopathy. In addition to changes to synaptic function, there is also growing evidence that changes to intrinsic excitability of neurones can arise in these models of amyloidopathy. Furthermore, some of these alterations to intrinsic properties may occur relatively early within the age-related progression of experimental amyloidopathy. Here we report a detailed comparison between the intrinsic excitability properties of hippocampal CA1 pyramidal neurones in wild-type (WT) and PDAPP mice. The latter is a well-established model of Aβ accumulation which expresses human APP harbouring the Indiana (V717F) mutation. At the age employed in this study (9-10 months) CNS Abeta was elevated in PDAPP mice but significant plaque pathology was absent. PDAPP mice exhibited no differences in subthreshold intrinsic properties including resting potential, input resistance, membrane time constant and sag. When CA1 cells of PDAPP mice were given depolarizing stimuli of various amplitudes they initially fired at a higher frequency than WT cells. Commensurate with this, PDAPP cells exhibited a larger fast afterdepolarizing potential. PDAPP mice had narrower spikes but action potential threshold, rate of rise and peak were not different. Thus not all changes seen in our previous studies of amyloidopathy models were present in PDAPP mice; however, narrower spikes, larger ADPs and the propensity to fire at higher frequencies were consistent with our prior work and thus may represent robust, cross-model, indices of amyloidopathy. This article is part of a Special Issue entitled 'Neurodevelopment Disorder'.

In Vitro and In Vivo Recording of Local Field Potential Oscillations in Mouse Hippocampus

Oscillations in hippocampal local field potentials (LFP) reflect the coordinated, rhythmic activity of constituent interneuronal and principal cell populations. Quantifying changes in oscillatory patterns and power therefore provides a powerful metric through which to infer mechanisms and functions of hippocampal network activity at the mesoscopic level, bridging single-neuron studies to behavioral assays of hippocampal function. Here, complementary protocols that enable mechanistic analyses of oscillation generation in vitro (in slices and a whole hippocampal preparation) and functional analyses of hippocampal circuits in behaving mice are described. Used together, these protocols provide a comprehensive view of hippocampal phenotypes in mouse models, highlighting oscillatory biomarkers of hippocampal function and dysfunction. Curr. Protoc. Mouse Biol. 2:273-294 © 2012 by John Wiley & Sons, Inc.

Establishment of a standardized multiplex assay with the analytical performance required for quantitative measurement of BCR-ABL1 on the international reporting scale

Accurate and standardized methods for the quantitative measurement of BCR–ABL1 are a prerequisite for monitoring of treatment response in t(9;22)-positive leukemia. Here, we describe a novel multiplex assay system based on the proven TaqMan and Armored RNA technologies and optimized for sensitive detection of three BCR–ABL1 fusion transcripts and ABL1 in a single reaction. Analytical experiments confirmed the absence of significant competition between the simultaneous amplification reactions and established the sensitivity, linearity and precision of the assay. Comparative studies with 115 clinical specimens resulted in high qualitative and quantitative agreement with independent singleplex laboratory-developed tests routinely used in clinical testing. Direct comparison with a reference laboratory calibrated to the international scale (IS) demonstrated minimal analytical bias between methods and an overall accuracy and precision within the performance range required for quantitative measurement of BCR–ABL1 on the IS. We conclude that detection of e1a2, b2a2, b3a2 and ABL1 can be achieved in a multiplex assay format compatible with IS reporting. Further clinical validation of the assay could improve the operational efficiency of clinical laboratories, increase their adherence to current recommendations for b2a2/b3a2 reporting on the IS and provide for the first time an opportunity to standardize e1a2-monitoring results.

Voltage- and temperature-dependent gating of heterologously expressed channelrhodopsin-2

Channelrhodopsins are light-activated channels originally isolated from algae that are being used increasingly as tools to non-invasively stimulate neurones. Despite their widespread use some aspects of their biophysical properties have not been fully characterised. Here we report detailed investigation of the gating kinetics and voltage-dependence of ChR2 transiently expressed in HEK-293 cells. Currents were elicited using light pulses of defined duration and intensity generated by a blue LED. Datasets were gathered both at room temperature (RT, ∼22°C) and 37°C. Current responses to light rose rapidly to a peak and then desensitized to a steady state plateau. When illumination was terminated currents rapidly deactivated. Recovery from desensitization at -85 mV was slow with half-times of 1.4 and 3.1s at 37°C and ∼22°C, respectively. At both temperatures, the reversal potential of ChR2 responses was a few mV positive to 0 mV. Both the peak and plateau phases of ChR2 responses exhibited strong inward rectification with only small outward currents at positive membrane potentials. The rates of ChR2 activation, deactivation and desensitization were ∼2 times faster at 37°C than at ∼22°C. Both the activation and deactivation kinetics of ChR2 were significantly slowed by depolarization at both temperatures. Additionally, the degree of steady state desensitization was greater at more depolarized potentials. The macroscopic desensitization kinetics were not voltage-dependent, but recovery from desensitization was slowed by depolarization. These gating behaviour data provide an important basis for more detailed analysis of the properties and limitations of ChR2 use in more complex systems.

Paleozoic seeds with embryos

Seeds in a conifer cone from the Lower Permian of west Texas contain embryo tissue. These are the oldest plant embryos on record. Their development prior to seed dispersal shows that the sequence of embryo growth typical of most modern seed plants had evolved before the end of the Paleozoic Era.

The functional neurophysiology of the amyloid precursor protein (APP) processing pathway

Amyloid beta (Abeta) peptides derived from proteolytic cleavage of amyloid precursor protein (APP) are thought to be a pivotal toxic species in the pathogenesis of Alzheimer's disease (AD). Furthermore, evidence has been accumulating that components of APP processing pathway are involved in non-pathological normal function of the CNS. In this review we aim to cover the extensive body of research aimed at understanding how components of this pathway contribute to neurophysiological function of the CNS in health and disease. We briefly outline changes to clinical neurophysiology seen in AD patients before discussing functional changes in mouse models of AD which range from changes to basal synaptic transmission and synaptic plasticity through to abnormal synchronous network activity. We then describe the various neurophysiological actions that are produced by application of exogenous Abeta in various forms, and finally discuss a number or other neurophysiological aspects of the APP pathway, including functional activities of components of secretase complexes other than Abeta production.

Characterization of a CNS penetrant, selective M1 muscarinic receptor agonist, 77-LH-28-1

BACKGROUND AND PURPOSE

M1 muscarinic ACh receptors (mAChRs) represent an attractive drug target for the treatment of cognitive deficits associated with diseases such as Alzheimer's disease and schizophrenia. However, the discovery of subtype-selective mAChR agonists has been hampered by the high degree of conservation of the orthosteric ACh-binding site among mAChR subtypes. The advent of functional screening assays has enabled the identification of agonists such as AC-42 (4-n-butyl-1-[4-(2-methylphenyl)-4-oxo-1-butyl]-piperidine), which bind to an allosteric site and selectively activate the M(1) mAChR subtype. However, studies with this compound have been limited to recombinantly expressed mAChRs.

EXPERIMENTAL APPROACH

In this study, we have compared the pharmacological profile of AC-42 and a close structural analogue, 77-LH-28-1 (1-[3-(4-butyl-1-piperidinyl)propyl]-3,4-dihydro-2(1H)-quinolinone) at human recombinant, and rat native, mAChRs by calcium mobilization, inositol phosphate accumulation and both in vitro and in vivo electrophysiology.

KEY RESULTS

Calcium mobilization and inositol phosphate accumulation assays revealed that both AC-42 and 77-LH-28-1 display high selectivity to activate the M1 mAChR over other mAChR subtypes. Furthermore, 77-LH-28-1, but not AC-42, acted as an agonist at rat hippocampal M1 receptors, as demonstrated by its ability to increase cell firing and initiate gamma frequency network oscillations. Finally, 77-LH-28-1 stimulated cell firing in the rat hippocampus in vivo following subcutaneous administration.

CONCLUSIONS AND IMPLICATIONS

These data suggest that 77-LH-28-1 is a potent, selective, bioavailable and brain-penetrant agonist at the M1 mAChR and therefore that it represents a better tool than AC-42, with which to study the pharmacology of the M1 mAChR.

KCNQ/Kv7 channel regulation of hippocampal gamma-frequency firing in the absence of synaptic transmission

Synchronous neuronal firing can be induced in hippocampal slices in the absence of synaptic transmission by lowering extracellular Ca2+ and raising extracellular K+. However, the ionic mechanisms underlying this nonsynaptic synchronous firing are not well understood. In this study we have investigated the role of KCNQ/Kv7 channels in regulating this form of nonsynaptic bursting activity. Incubation of rat hippocampal slices in reduced (<0.2 mM) [Ca2+]o and increased (6.3 mM) [K+]o, blocked synaptic transmission, increased neuronal firing, and led to the development of spontaneous periodic nonsynaptic epileptiform activity. This activity was recorded extracellularly as large (4.7 +/- 1.9 mV) depolarizing envelopes with superimposed high-frequency synchronous population spikes. These intraburst population spikes initially occurred at a high frequency (about 120 Hz), which decayed throughout the burst stabilizing in the gamma-frequency band (30-80 Hz). Further increasing [K+]o resulted in an increase in the interburst frequency without altering the intraburst population spike frequency. Application of retigabine (10 microM), a Kv7 channel modulator, completely abolished the bursts, in an XE-991-sensitive manner. Furthermore, application of the Kv7 channel blockers, linopirdine (10 microM) or XE-991 (10 microM) alone, abolished the gamma frequency, but not the higher-frequency population spike firing observed during low Ca2+/high K+ bursts. These data suggest that Kv7 channels are likely to play a role in the regulation of synchronous population firing activity.

A pharmacological investigation of the role of GLUK5-containing receptors in kainate-driven hippocampal gamma band oscillations

Low concentrations of kainate can induce gamma frequency (25-80 Hz) oscillations in hippocampal slices as well as other brain structures in vitro. Little is known, however, about the kainate receptor (KAR) subtypes that underlie this type of rhythmic neuronal network activity. In this study, the role of GLU(K5) subunit-containing KARs in kainate-induced hippocampal gamma frequency oscillations was assessed using GLU(K5)-selective pharmacological ligands. Activation of GLU(K5)-containing subunits using the selective agonists (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propanoic acid (ATPA; 0.1-1 microM) or iodowillardiine (0.1-1 microM) failed to induce gamma frequency oscillations in area CA3 of the rat hippocampal slice. Likewise, preincubation with a selective GLU(K5) antagonist, (RS)-3-(2-carboxybenzyl)willardiine (UBP296), did not prevent the appearance of gamma oscillations induced by 150 nM kainate. However, addition of UBP296 (10 microM) to hippocampal slices in which kainate-driven gamma oscillations were pre-established resulted in an approximately 50% reduction in gamma frequency power. These effects occurred in the absence of any effect on AMPA receptor-mediated synaptic transmission. Furthermore, carbachol-induced gamma oscillations were also unaffected by application of UBP296. These results suggest that GLU(K5)-containing KARs are not alone sufficient to generate gamma frequency oscillations, but are involved in maintaining neuronal network activity induced by the actions of kainate at other KARs such as GLU(K6).

Modulation of hippocampal excitability by 5-HT4 receptor agonists persists in a transgenic model of Alzheimer's disease

5-HT(4) receptors are widely distributed in both peripheral and central nervous systems where they couple, via a G-protein, to the activation of adenylate cyclase. In the brain, the highest 5-HT(4) receptor densities are found in the limbic system, including the hippocampus and frontal cortex. It has been suggested that activation of these receptors may be of therapeutic benefit in diseases that produce cognitive deficits such as Alzheimer's disease (AD). Previous electrophysiological studies have shown that the 5-HT(4) agonist, Zacopride, can increase population spike amplitude recorded in region CA1 of rat hippocampal slices in a cyclic AMP (cAMP)/cAMP-dependent protein kinase A-dependent manner. We report here that the 5-HT(4) agonist, Prucalopride, and the 5-HT(4) partial agonist, SL65.0155, produce a similar effect in rat hippocampal slices and that the specific 5-HT(4) antagonist, GR113808, blocks these effects. To investigate the potential use of 5-HT(4) agonists in the treatment of AD, Prucalopride was applied to hippocampal slices from a transgenic mouse line that overexpresses the Abeta peptide. Despite the deficit in synaptic transmission present in these mice, the percentage increase of the CA1 population spike induced by Prucalopride was the same as that observed in wild-type mice. These data support 5-HT(4) receptors as a target for cognitive enhancement and suggest that a partial agonist would be sufficient to produce benefits, while reducing potential peripheral side effects. In addition, we show that 5-HT(4) receptors remain functional in the presence of excess Abeta peptide and may therefore be a useful target in AD.

LPA1 receptor-deficient mice have phenotypic changes observed in psychiatric disease

Several psychiatric diseases, including schizophrenia, are thought to have a developmental aetiology, but to date no clear link has been made between psychiatric disease and a specific developmental process. LPA(1) is a G(i)-coupled seven transmembrane receptor with high affinity for lysophosphatidic acid. Although LPA(1) is expressed in several peripheral tissues, in the nervous system it shows relatively restricted temporal expression to neuroepithelia during CNS development and to myelinating glia in the adult. We report the detailed neurological and behavioural analysis of mice homozygous for a targeted deletion at the lpa(1) locus. Our observations reveal a marked deficit in prepulse inhibition, widespread changes in the levels and turnover of the neurotransmitter 5-HT, a brain region-specific alteration in levels of amino acids, and a craniofacial dysmorphism in these mice. We suggest that the loss of LPA(1) receptor generates defects resembling those found in psychiatric disease.

Gabapentin is not a GABAB receptor agonist

Recent experiments have demonstrated that formation of functional type B gamma-aminobutyric acid (GABA(B)) receptors requires co-expression of two receptor subunits, GABA(B1) and GABA(B2). Despite the identification of these subunits and a number of associated splice variants, there has been little convincing evidence of pharmacological diversity between GABA(B) receptors comprising different subunit combinations. However, Ng et al. [Mol. Pharmacol., 59 (2000) 144] have recently suggested a novel and important pharmacological difference between GABA(B) receptor heterodimers expressing the GABA(B1a) and GABA(B1b) receptor subunits. This study suggested that the antiepileptic GABA analogue gabapentin (Neurontin) is an agonist at GABA(B) receptors expressing the GABA(B1a) but not the GABA(B1b) receptor subunit. The importance of this finding with respect to identifying novel GABA(B) receptor subunit specific agonists prompted us to repeat these experiments in our own [35S]-GTPgammaS binding and second messenger assay systems. Here we report that gabapentin was completely inactive at recombinant GABA(B) heterodimers expressing either GABA(B1a) or GABA(B1b) receptor subunits in combination with GABA(B2) receptor subunits. In addition, in both CA1 and CA3 pyramidal neurones from rodent hippocampal slices we were unable to demonstrate any agonist-like effects of gabapentin at either pre- or post-synaptic GABA(B) receptors. In contrast, gabapentin activated a GABA(A) receptor mediated chloride conductance. Our data suggest that gabapentin is not a GABA(B)-receptor agonist let alone a GABA(B) receptor subunit selective agonist.

A cis-acting element known to block 3' mRNA degradation enhances expression of polyA-minus mRNA in wild-type yeast cells and phenocopies a ski mutant

mRNA lacking a 3' polyA tail is not translated efficiently in wild-type eukaryotic cells, but is translated efficiently in yeast ski mutants. This enhanced expression could be due to altered translational specificity. However, as the SKI genes are required for 3' mRNA degradation, it could be a consequence of inhibition of 3' mRNA decay. Therefore, we asked if inhibition of 3' decay of a polyA-minus mRNA in cis would allow its efficient expression in wild-type cells. Capped in vitro reporter transcripts were prepared with or without a 3' cis-acting element known to inhibit 3' degradation (oligoG) and electroporated into yeast cells. The addition of oligoG to a polyA-minus mRNA enhanced expression 30-fold in wild-type cells. This level of expression was the same as that for an oligoG-minus, polyA-minus transcript in a ski mutant. The addition of oligoG did not significantly enhance the expression of polyA-minus mRNA in a ski mutant. The oligoG-dependent increase in expression was due to an increase in initial rate of translation and an increase in the functional half-life of the mRNA, similar to the effects observed in a ski mutant. The enhanced expression of the oligoG-containing RNA did not require Pab1p. We conclude that the enhanced translation of polyA-minus RNA in a ski mutant is due to inhibition of 3' mRNA degradation. Furthermore, a polyA-minus mRNA is expressed in wild-type cells when terminated in an element known to inhibit 3' decay in cis.

Inhibition of mRNA turnover in yeast by an xrn1 mutation enhances the requirement for eIF4E binding to eIF4G and for proper capping of transcripts by Ceg1p

Null mutants of XRN1, encoding the major cytoplasmic exoribonuclease in yeast, are viable but accumulate decapped, deadenylated transcripts. A screen for mutations synthetic lethal with xrn1Delta identified a mutation in CDC33, encoding eIF4E. This mutation (glutamate to glycine at position 72) affected a highly conserved residue involved in interaction with eIF4G. Synthetic lethality between xrn1 and cdc33 was not relieved by high-copy expression of eIF4G or by disruption of the yeast eIF4E binding protein Caf20p. High-copy expression of a mutant eIF4G defective for eIF4E binding resulted in a dominant negative phenotype in an xrn1 mutant, indicating the importance of this interaction in an xrn1 mutant. Another allele of CDC33, cdc33-1, along with mutations in CEG1, encoding the nuclear guanylyltransferase, were also synthetic lethal with xrn1Delta, whereas mutations in PRT1, encoding a subunit of eIF3, were not. Mutations in CDC33, CEG1, PRT1, PAB1, and TIF4631, encoding eIF4G1, have been shown to lead to destabilization of mRNAs. Although such destabilization in cdc33, ceg1, and pab1 mutants can be partially suppressed by an xrn1 mutation, we observed synthetic lethality between xrn1 and either cdc33 or ceg1 and no suppression of the inviability of a pab1 null mutation by xrn1Delta. Thus, the inhibition of mRNA turnover by blocking Xrn1p function does not suppress the lethality of defects upstream in the turnover pathway but it does enhance the requirement for (7)mG caps and for proper formation of the eIF4E/eIF4G cap recognition complex.

The yeast antiviral proteins Ski2p, Ski3p, and Ski8p exist as a complex in vivo

The yeast superkiller (SKI) genes were originally identified from mutations allowing increased production of killer toxin encoded by M "killer" virus, a satellite of the dsRNA virus L-A. XRN1 (SKI1) encodes a cytoplasmic 5'-exoribonuclease responsible for the majority of cytoplasmic RNA turnover, whereas SKI2, SKI3, and SKI8 are required for normal 3'-degradation of mRNA and for repression of translation of poly(A) minus RNA. Ski2p is a putative RNA helicase, Ski3p is a tetratricopeptide repeat (TPR) protein, and Ski8p contains five WD-40 (beta-transducin) repeats. An xrn1 mutation in combination with a ski2, ski3, or ski8 mutation is lethal, suggesting redundancy of function. Using functional epitope-tagged Ski2, Ski3, and Ski8 proteins, we show that Ski2p, Ski3p, and Ski8p can be coimmunoprecipitated as an apparent heterotrimeric complex. With epitope-tagged Ski2p, there was a 1:1:1 stoichiometry of the proteins in the complex. Ski2p did not associate with Ski3p in the absence of Ski8p, nor did Ski2p associate with Ski8p in the absence of Ski3p. However, the Ski3p/Ski8p interaction did not require Ski2p. In addition, ski6-2 or ski4-1 mutations or deletion of SKI7 did not affect complex formation. The identification of a complex composed of Ski2p, Ski3p, and Ski8p explains previous results showing phenotypic similarity between mutations in SKI2, SKI3, and SKI8. Indirect immunofluorescence of Ski3p and subcellular fractionation of Ski2p and Ski3p suggest that Ski2p and Ski3p are cytoplasmic. These data support the idea that Ski2p, Ski3p, and Ski8p function in the cytoplasm in a 3'-mRNA degradation pathway.

High resolution transmission soft X-ray microscopy of deterioration products developed in large concrete dams

In concrete structures, the reaction of certain siliceous aggregates with the highly alkaline concrete pore solution produces an alkali-silicate gel that can absorb water and expand. This reaction can lead to expansion, cracking, increased permeability, and decreased strength of the concrete. Massive concrete structures, such as dams, are particularly susceptible to the damage caused by the alkali-silica reaction because of the availability of water and because massive gravity dams usually do not contain steel reinforcement to restrain the expansion. Both the cement hydration products and alkali-silica reaction products are extremely sensitive to humidity. Consequently, characterization techniques that require high vacuum or drying, as many existing techniques do, are not particularly appropriate for the study of the alkali-silica reaction because artefacts are introduced. Environmental scanning electron micrographs and scanning electron micrographs with energy dispersive X-ray analysis results demonstrate the effect of drying on the morphology and chemical composition of the alkali-silicate reaction gel. Thus, the impetus for this research was the need to observe and characterize the alkali-silica reaction and its gel product on a microscopic level in a wet environment (i.e. without introducing artefacts due to drying). Only soft X-ray transmission microscopy provides the required high spatial resolution needed to observe the reaction process in situ. The alkali-silica reaction can be observed over time, in a wet condition, and at normal pressures, features unavailable with most other high resolution techniques. Soft X-rays also reveal information on the internal structure of the sample. The purpose of this paper is to present research, obtained using transmission soft X-ray microscopy, on the effect of concrete pore solution cations, namely sodium and calcium, on the product formed as a result of alkali attack. Alkali-silicate reaction (ASR) gel was obtained from the FURNAS Dam in Minas Gerais, Brazil. Images of the ASR gel in sodium hydroxide indicated dissolution and repolymerization of the silicate into a less dense form, demonstrating the expansive nature of the gel when exposed to alkalis. In the calcium hydroxide solution, ASR gel, silica fume, and chemical grade silica gel each reacted with the calcium ions in solution to produce a calcium silicate hydrate precursor with a lathlike, branching morphology. The distinctive spherulitic microstructure formed during this reaction was identified as the 'sheaf of wheat' morphology, previously described in the literature. In addition, the development of the sheaf of wheat morphology was documented over time. These results suggest that of the cations studied in this investigation, it is the alkalis in concrete pore solution that produce the expansive ASR gel, while reaction with calcium ions does not result in expansion or damage to the concrete structure. More broadly, these results demonstrate the advantage of transmission soft X-ray microscopy for the study of the alkali-silica reaction, indicating the value of this technique for further studies in concrete technology.

Imaging of humic substance macromolecular structures in water and soils

Humic substances (HSs) are the natural organic polyelectrolytes formed from the biochemical weathering of plant and animal remains. Their macromolecular structure and chemistry determine their role in biogeochemical processes. In situ spectromicroscopic evidence showed that the HS macromolecular structures (size and shape) vary as a function of HS origin (soil versus fluvial), solution chemistry, and the associated mineralogy. The HSs do not simply form coils in acidic or strong electrolyte solutions and elongated structures in dilute alkaline solutions. The macromolecular structural changes of HSs are likely to modify contaminant solubility, biotransformation, and the carbon cycle in soils and sediments.

X-ray microscopic visualization of specific labeling of adhesive molecule CD36 and cytoadherence by Plasmodium falciparum infected erythrocytes

We investigated the cytoadherence of Plasmodium falciparum infected erythrocytes to target cells that express CD36 by soft x-ray microscopy. Using immunogold beads enhanced with silver, we localized CD36 on the surface of intact melanoma cells and throughout Triton extracted melanoma cells. We examined the orientation of parasites within erythrocytes that bound to target cells, and the interactions between the red cell membrane and the target cell, and we confirmed that fibrillar structures on the surface of melanoma and endothelial cells can be involved in the association between infected erythrocytes and melanoma cells or endothelial cells.

Intracellular structures of normal and aberrant Plasmodium falciparum malaria parasites imaged by soft x-ray microscopy

Soft x-ray microscopy is a novel approach for investigation of intracellular organisms and subcellular structures with high spatial resolution. We used x-ray microscopy to investigate structural development of Plasmodium falciparum malaria parasites in normal and genetically abnormal erythrocytes and in infected erythrocytes treated with cysteine protease inhibitors. Investigations in normal red blood cells enabled us to recognize anomalies in parasite structures resulting from growth under unfavorable conditions. X-ray microscopy facilitated detection of newly elaborated structures in the cytosol of fixed, unstained, intact erythrocytes, redistribution of mass (carbon) in infected erythrocytes, and aberrant parasite morphology. In cysteine protease inhibitor-treated, infected erythrocytes, high concentrations of material were detected in abnormal digestive vacuoles and aggregated at the parasite plasma membrane. We have demonstrated that an abnormal host erythrocyte skeleton affects structural development of parasites and that this aberrant development can be detected in the following generation when parasites from protein 4.1-deficient red blood cells infect normal erythrocytes. This work extends our current understanding of the relationship between the host erythrocyte membrane and the intraerythrocytic malaria parasite by demonstrating for the first time that constituents of the erythrocyte membrane play a role in normal parasite structural development.

Characterization of the tumor invasion area in the rat intracerebral glioma

Tumor cell invasion surrounding intracerebrally implanted tumors in rats was studied by comparing the results of cerebral microangiography, fluorescence imaging of blood-brain barrier (BBB) disruption and histopathology. Each comparison was on subsequent sections taken from an initial 1 mm coronal slice of brain taken through the cell injection site containing tumor using the RT-2 glioma model. Tumor extension was assessed at 3, 5, 7 and 9 days after tumor implantation. Analysis of the brain adjacent to tumor shows that the actual tumor cell invasion area is greater than the area of BBB disruption at later stages of tumor growth and the extent of tumor vascularization lies well within the area defined by the extent of tumor cell invasion. Furthermore, this study found that the size of the area of tumor cell invasion remains relatively stable in proportion to the solid tumor mass at various stages of growth such that the area of tumor invaded brain was approximately 2.5 times greater than the area outlined by solid tumor mass. We conclude that measurement of the solid tumor mass, tumor vascular area and region of blood-brain barrier disruption due to tumor, grossly underestimate the total tumor volume. Therapies aimed at controlling glial tumor growth must, therefore, include normal appearing regions of brain peripheral to the abnormal region defined as tumor and tumor invaded brain as defined by radiographic and imaging studies.

Peroneal tenosynovitis following acute gonococcal infection

A 17-year-old adolescent girl presented with tenosynovitis of the peroneal tendons following diagnosis and treatment of an endocervical gonococcal infection. The need for careful history in any sexually active adolescent is emphasized. Acute peroneal tenosynovitis, although not previously cited in the literature, can occur and should be suspected.

Toxicity of photodynamic therapy with photofrin in the normal rat brain

The widespread acceptance of photodynamic therapy (PDT), a potential adjuvant brain tumor therapy under clinical evaluation since 1980, has been partially restrained by its potential toxicity toward normal brain tissue. This study examined PDT-produced injury of normal rat brain as a function of photosensitizer dose. Brain injury was characterized by correlating measurements of the area of cerebral edema using T2-weighted magnetic resonance images, measurement of brain water content at the lesion site, microscopic examination of histological sections through the PDT lesion, and by evaluation of the area of blood brain barrier (BBB) disruption using computerized morphometric analysis of the region of Evans blue (EB) dye-labelled albumin extravasation. Monochromatic red light (630 nm) was delivered intracerebrally using a 5-mm-long cylindrical, diffusion-tip optical fiber at a constant energy dose of 15 joules. A Photofrin dose of 2 mg/kg of body weight produced a transient breakdown in the blood brain barrier around the site of the implanted optical fiber demonstrated by magnetic resonance imaging (MRI), extravasation of EB dye and pallor on hematoxylin and eosin-stained microscopic tissue sections. A much larger area of BBB disruption was seen at a dose of 4 mg/kg of Photofrin, and this drug dose resulted in significant permanent brain injury. In this model, a Photofrin dose of 4 mg/kg body weight is not tolerated by the normal brain.

Physician-related barriers to breast cancer screening in older women

Despite evidence that annual mammographic screening in women 50 years and older reduces mortality, surveys of physicians and patients have repeatedly demonstrated that annual screening mammography is not performed. The fundamental question addressed in this chapter is: If the assumption is made that the scientific evidence supports the use of mammography, what, then, are physician-related barriers to mammographic screening of elderly women? Using a model that classifies barriers to implementing prevention protocols into three categories (predisposing, enabling, and reinforcing factors), literature is reviewed to help identify reasons for low mammographic screening rates, especially in elderly women. This article concludes with a discussion of strategies that may help overcome barriers to mammographic screening in elderly women.

The unit of analysis error in studies about physicians' patient care behavior

OBJECTIVE

To estimate the frequency with which patients are incorrectly used as the unit of analysis among statistical calculations in published studies of physicians' patient care behavior.

DESIGN

Retrospective review of studies published during 1980-1990. ARTICLES: 54 articles retrieved by a computerized search using medical subject headings for physicians and study characteristics. Article selection criteria included the requirement that the physician should have been the correct unit of analysis.

INTERVENTION

Presence of the error was determined by consensus using published criteria.

MAIN RESULTS

The error was present in 38 articles (70%). The number of study physicians was reported in 35 articles (65%). The error was found in 57% of articles that reported the number of study physicians and in 95% of those that did not. The error rate was not lower among articles published more recently nor among those published in journals with higher rates of article citations in the medical literature.

CONCLUSION

The unit of analysis error occurs frequently and can generate artificially low p values. Failure to report the number of study physicians can be a clue that this type of error has been made.

Improved survival from intracavitary photodynamic therapy of rat glioma

The effectiveness of intratumoral photoradiation in photodynamic therapy (PDT) using a polyporphyrin photosensitizer was studied in the RT-2 rat glioma model. One week after intracerebral implantation of RT-2 cells, experimental rats received a single i.p. injection of 2 mg/kg of Photofrin. After administration of the photosensitizer (48 h), the tumors were partially resected and the exposed cavity was irradiated with 15 J of laser light at a wavelength of 630 nm. Further treatment with a large craniectomy significantly enhanced rat survival. Control rats which received no photosensitizer but were treated with surgery, alone or in combination with laser irradiation, succumbed from early tumor recurrence. Photodynamic therapy without decompressive surgery resulted in hemorrhagic infarction of residual tumor and adjacent brain with focal cerebral edema which resulted in cerebral herniation and early death. Our results indicate that photodynamic therapy is effective in treating residual brain tumor but at the expense of brain tissue surrounding the tumor. Unless relieved, intracranial pressure from photodynamic therapy-associated cerebral edema in this animal model resulted in shortened survival.

Relation between polyporphyrin distribution and blood brain barrier changes in the rat glioma model

Photofrin (a polyporphyrin mixture) distribution in a rat glioma model was studied in relation to changes in the blood brain barrier (BBB). At selected intervals after intraperitoneal injection of Photofrin, the concentration of polyporphyrins (PP) and Evans Blue Dye, an indicator of BBB permeability, were determined for tumor, brain adjacent to tumor (BAT), and normal brain tissue. Contrary to earlier reports of maximal accumulation at 4-24 hours, tumor levels of PP increased throughout the 96 hour measurement period. During the early stages of tumor development, PP uptake by tumor appeared to be less correlated to BBB disruption. We conclude that passive diffusion through an incompetent BBB does not completely explain PP accumulation in tumor tissue.

Traumatic spondylolisthesis of the lower cervical spine: case report

A case of traumatic spondylolisthesis of C6 and C7 is presented. The mechanism of injury and the therapeutic implications are discussed.

Interstitial photoradiation injury of normal brain

The effect on normal brain of continuous interstitial laser irradiation at 630 nm through an implanted cylindrical-shape, diffusion-tipped optical fiber was studied in the rat. Brain water content in the laser irradiation area (LIA) and Evans blue (EB) dye content in selected areas of the brain were measured for different laser power outputs from 0 to 250 mW after 5 minutes of photoradiation. The degree and nature of tissue damage was examined histologically and correlated with the laser power level. There is significant brain damage, blood brain barrier (BBB) disruption, and brain edema in LIA for laser power outputs in excess of 100 mW from the diffusion tip (p less than 0.001). Brain edema in the LIA is strongly correlated with BBB disruption indicated by the presence of EB. Histologically, the cortical surface was more susceptible than deeper white matter regions to interstitial laser irradiation. Possible indirect mechanisms of brain injury from interstitial laser irradiation are discussed.

The Duke Minority Medical Student Summer Fellowship: one program's attempt to attract minority residents

Despite numerous Federal and private funding programs aimed at increasing the numbers of underrepresented minorities in medicine, the participation of minority groups in the medical profession remains low and shows little sign of improvement. With the goal of improving minority representation in our primary care residency program, the Minority Medical Student Summer Fellowship started in July 1990. The program's purpose is to give minority medical students positive exposure to primary care and attract them back for residency training. In this four-week elective, students participate in seminars with our primary care residents, see patients in a variety of clinics, and complete a project. Key implementation issues include support of the medicine chairman and dean, funding, and malpractice coverage for the students. Program evaluation from the first two students rated the clinic experiences higher than the seminar sessions and the independent project. Both students stated our fellowship made them more likely to train at this medical center should they enter a primary care program. Implications for other programs are listed.

Can physician education lower the cost of prescription drugs? A prospective, controlled trial

OBJECTIVE

To determine whether an educational program featuring a drug cost manual can assist physicians in reducing their patients' out-of-pocket prescription drug expenses.

DESIGN

Prospective controlled trial.

SETTING

A general internal medicine-teaching clinic in a university hospital.

PARTICIPANTS

Fifty-one medical interns.

INTERVENTION

Thirty-one interns received a manual of comparative drug prices annotated with prescribing advice, two feedback reports, and weekly cost-oriented prescribing reminders. A control group concurrently participated in a manual-based educational program on cholesterol management.

MEASUREMENTS

Copies of 3012 prescriptions written over 8 months were analyzed.

MAIN RESULTS

Intervention group physicians prescribed less expensive drugs within classes of drugs. The change in drug price score per prescription was -0.15 (95% Cl, -0.27 to -0.04; P = 0.01). A score of 3 was assigned to the most expensive, 2 was assigned to intermediate-priced, and 1 was assigned to the least expensive drug or drugs in the class. An increase of 0.74 months' (Cl, 0.49 to 0.98; P less than 0.001) supply of medication was dispensed per prescription, reducing dispensing fees. The program was well accepted by the physicians.

CONCLUSION

This relatively simple educational intervention can help physicians to reduce their patients' drug expenses and may serve as a model for incorporating cost information into the routine practice of medicine.

Quantitative analysis of the outpatient oral case presentation: piloting a method

OBJECTIVE

To measure the content of oral outpatient case presentations and to assess the correlation of objective assessments of this content with subjective ratings provided by the clinic attending physician.

DESIGN

Blinded assessment via audiotape of 36 oral case presentations of new patient evaluations by 23 medical residents.

SETTING

Outpatient general medical clinic.

PARTICIPANTS

Duke University Medical Center medical residents during their outpatient rotation.

MEASUREMENTS AND MAIN RESULTS

Important deficiencies were found in oral case presentation content. Specifically, psychosocial data were often missing (employment history) was mentioned in 28% of presentations; illicit drug use, in 17%; household social structure, in 11%; sexual history, in 6%). An assessment and a plan were mentioned only 56% and 69% of the time, respectively. No correlation was seen between an objective "content score" and the attending physician's subjective rating of the quality of the presentation (r = 0.09).

CONCLUSIONS

1) The outpatient care presentation can be quantitatively assessed in a simple, straightforward manner; 2) outpatient case presentations have important deficiencies in content; and 3) preceptors' evaluations of case presentations may be based upon factors other than content of the presentation.

Breast cancer screening in older women: practices and barriers reported by primary care physicians

Annual mammography, in combination with clinical breast examinations, can reduce mortality from breast cancer. However, surveys of both patients and physicians suggest that mammography is underutilized. This study examined whether physicians' reported breast cancer screening practices and barriers to mammography varied with patients' age. Data from 576 primary care physicians (internal medicine, family/general practice, and obstetrics/gynecology) who participated in a mailed statewide survey were analyzed. Physicians reported screening elderly women significantly less often than younger women, regardless of family history of breast cancer. With the exception of medical specialty, physicians' demographic and practice characteristics were not associated with reported screening practices. However, physicians' knowledge and beliefs about breast cancer in older women were associated with reported screening practices. When analyzing barriers to ordering mammography, cost to the patient was viewed as a barrier for women of all ages, and pain was viewed as a greater barrier for younger women; otherwise, physicians consistently believed that their elderly patients faced considerably more barriers compared with younger women. Further investigation is required to examine why primary care physicians report age-related differences in both breast screening and barriers to mammography.

Genetic suppression demonstrates interaction of TonB protein with outer membrane transport proteins in Escherichia coli

Energy-coupled reactions of the Escherichia coli outer membrane transport proteins BtuB and Cir require the tonB product. Some point mutations in a region of btuB and cir that is highly conserved in TonB-dependent transport proteins led to loss of TonB-coupled uptake of vitamin B12 and colicin Ia, whereas binding was unaffected. Most other point mutations in this region had no detectable effect on transport activity. Mutations in tonB that suppressed the transport defect phenotype of these btuB mutations were isolated. All carried changes of glutamine 165 to leucine, lysine, or proline. The various tonB mutations differed markedly in their suppression activities on different btuB or cir mutations. This allele specificity of suppression indicates that TonB interacts directly with the outer membrane transport proteins in a manner that recognizes the local conformation but not specific side chains within this conserved region. An effect of the context of the remainder of the protein was seen, since the same substitution (valine 10----glycine) in btuB and cir responded differently to the suppressors. This finding supports the proposal that TonB interacts with more of the transport proteins than the first conserved domain alone.

Conditional hyporecombination mutants of three REC genes of Saccharomyces cerevisiae

We have isolated and characterized three conditional hyporecombination mutants, rec1-1, rec3-1 and rec4-1, that define three REC genes of Saccharomyces cerevisiae required for spontaneous general mitotic interchromosomal recombination. Each MATa/MAT alpha rec/rec diploid is deficient in mitotic single site gene conversion, intragenic recombination, intergenic recombination and sporulation at the restrictive temperature (36 degrees C). The rec1-1 mutation also confers conditional enhanced sensitivity to the killing effects of X-rays. The rec1-1 and rec3-1 mutations have been mapped to chromosome VII. The rec1-1, rec3-1 and rec4-1 mutations exhibit complementation at 36 degrees C for both mitotic recombination and sporulation.

The initiation and maintenance of callus cultures

Plant tissues grown in vitro provide an ideal research tool for the study of a wide range of aspects of plant science. For example, they have been used in the investigation of both primary and secondary metabolism, cytodifferentiation, morphogenesis, plant tumor physiology, and the formation of plant hybrids via protoplast fusion techniques. Plant tissue culture is also being increasingly adopted for the commercial propagation of plants.

Organogenesis in callus culture

Plant cells can be totipotent, i.e., each cell may be capable of developing into an entire plant when provided with the correct environmental stimuli. Research during the last 30 yr has demonstrated that successful organogenesis in callus cultures can be achieved by the correct choice of medium components, selection of a suitable inoculum, and control of the physical environment (1). The manipulation of plant growth regulator concentration is probably the most widely used technique for the induction of organogenesis, and this methodology has formed the basis of the propagation of commercially important plants via tissue culture in recent years (2).

Functional outcome following spinal cord injury. A comparison of specialized spinal cord injury center vs general hospital short-term care

The functional outcomes of 185 patients with spinal cord injuries undergoing rehabilitation who were initially treated in a specialized short-term care unit (center patients) were compared with those of 153 patients initially treated in general hospitals (noncenter patients). After stabilization, all patients were admitted to the Rehabilitation Institute of Chicago (Ill) and received the same rehabilitation program. The groups were comparable in terms of demographic, injury, and medical characteristics at the time of rehabilitation center admission, but the duration from injury to rehabilitation was more than twice as long for noncenter patients. While center patients were discharged from the rehabilitation center at equivalent functional skill levels, their daily rate of functional gains during the rehabilitation center stay was significantly greater than that of noncenter patients although the length of stay at the rehabilitation center was comparable for the two groups. These results support the practice of specialized short-term spinal cord injury care as a means of enhancing rehabilitation outcome.

Photosensitization of human glioma cells by chalcogenapyrylium dyes

Chalcogenapyrylium (CP) dyes which are specifically activated by red and near infrared light (600-900 nm) were examined as potential photosensitizers for photochemotherapy of malignant gliomas. Eleven CP dyes of varying chemical structure and redox potential were evaluated for selective toxicity against glioma and normal skin fibroblast cell cultures both before and after light activation. Eight of eleven CP dyes exhibited differential toxicity to tumor over fibroblast cells at dye concentrations of 1.0 microM. Dose dependent toxicity was seen both in the dark and after laser light activation. The toxicity of two of the CP dyes was significantly enhanced by photoactivation with 800 nm light. The CP dyes that absorb light maximally between 775 and 850 nm, in the range of excellent light penetration through brain, appear to be promising candidates as photosensitizers for treating malignant brain tumors.

The effect of a chalcogenapyrylium dye with and without photolysis on mitochondrial function in normal and tumor cells

A chalcogenapyrylium dye 8b, which is under investigation for the photodynamic therapy of malignant gliomas (brain tumors), was evaluated for inhibition of mitochondrial function both before and after exposure to laser light of 800 nm. Neoplastic and normal cells forced to use mitochondrial substrates were killed by the light-activation of intracellular 8b as well as exposure to classic mitochondrial inhibitors, rotenone and sodium azide. Correspondingly, cells in glucose-rich media showed little decrease in viability due to the photolysis of intracellular 8b or the presence of mitochondrial toxins. The toxicity of 8b without light activation was found to be the same regardless of the cell's energy source. Measurement of cellular ATP generated during treatment also showed the photolysis of intracellular 8b to be more inhibitory towards mitochondrial function than the unactivated parent compound. We conclude that the chalcogenapyrylium dyes localize to the mitochondrion and that photoactivation results in mitochondrial injury.

Screening mammography in the elderly: a case-control study

This case-control study tested the hypothesis that elderly women with metastatic breast cancer were previously screened less than controls. Cases included women over 60 years old who had metastatic breast cancer; the tumor registry provided controls. Identical criteria yielded comparable groups (cases = 109, controls = 211) receiving primary care at this tertiary center. Radiology and medical records were examined for mammograms; these were blindly categorized "diagnostic," "screening," or "indeterminant." The major, unexpected finding was that less than 6% of controls had ever had screening mammography. The associations between screening and metastatic cancer (odds ratios) suggest a beneficial effect of screening: OR/0.73 for ever screened and OR/0.71 if screened within the year of cancer diagnosis. All confidence intervals include one; however, low screening participation leaves this study with little power. The major implication is that despite the current recommendations, the elderly are not being included in screening mammography programs.