Structure-based design and optimization of a new class of small molecule inhibitors targeting the P-stalk binding pocket of ricin

Ricin, a category-B agent for bioterrorism, and Shiga toxins (Stxs), which cause food poisoning bind to the ribosomal P-stalk to depurinate the sarcin/ricin loop. No effective therapy exists for ricin or Stx intoxication. Ribosome binding sites of the toxins have not been targeted by small molecules. We previously identified CC10501, which inhibits toxin activity by binding the P-stalk pocket of ricin toxin A subunit (RTA) remote from the catalytic site. Here, we developed a fluorescence polarization assay and identified a new class of compounds, which bind P-stalk pocket of RTA with higher affinity and inhibit catalytic activity with submicromolar potency. A lead compound, RU-NT-206, bound P-stalk pocket of RTA with similar affinity as a five-fold larger P-stalk peptide and protected cells against ricin and Stx2 holotoxins for the first time. These results validate the P-stalk binding site of RTA as a critical target for allosteric inhibition of the active site.

Structural Basis of Antibody-Mediated Inhibition of Ricin Toxin Attachment to Host Cells

Monoclonal antibodies, JB4 and SylH3, neutralize ricin toxin (RT) by inhibiting the galactose-specific lectin activity of the B subunit of the toxin (RTB), which is required for cell attachment and entry. It is not immediately apparent how the antibodies accomplish this feat, considering that RTB consists of two globular domains (D1, D2) each divided into three homologous subdomains (α, β, γ) with the two functional galactosyl-specific carbohydrate recognition domains (CRDs) situated on opposite poles (subdomains 1α and 2γ). Here, we report the X-ray crystal structures of JB4 and SylH3 Fab fragments bound to RTB in the context of RT. The structures revealed that neither Fab obstructed nor induced detectable conformational alterations in subdomains 1α or 2γ. Rather, JB4 and SylH3 Fabs recognize nearly identical epitopes within an ancillary carbohydrate recognition pocket located in subdomain 1β. Despite limited amino acid sequence similarity between SylH3 and JB4 Fabs, each paratope inserts a Phe side chain from the heavy (H) chain complementarity determining region (CDR3) into the 1β CRD pocket, resulting in local aromatic stacking interactions that potentially mimic a ligand interaction. Reconciling the fact that stoichiometric amounts of SylH3 and JB4 are sufficient to disarm RTB's lectin activity without evidence of allostery, we propose that subdomain 1β functions as a "coreceptor" required to stabilize glycan interactions principally mediated by subdomains 1α and 2γ. Further investigation into subdomain 1β will yield fundamental insights into the large family of R-type lectins and open novel avenues for countermeasures aimed at preventing toxin uptake into vulnerable tissues and cells.

Structure of a transmission blocking antibody in complex with Outer surface protein A from the Lyme disease spirochete, Borreliella burgdorferi

319-44 is a human monoclonal antibody capable of passively protecting mice against tick-mediated infection with Borreliella burgdorferi, the bacterial genospecies responsible for Lyme disease in North America. In vitro, 319-44 has complement-dependent borreliacidal activity and spirochete agglutinating properties. Here, we report the 2.2 Å-resolution crystal structure of 319-44 Fab fragments in complex with Outer surface protein A (OspA), the ~30 kDa lipoprotein that was the basis of the first-generation Lyme disease vaccine approved in the United States. The 319-44 epitope is focused on OspA β-strands 19, 20, and 21, and the loops between β-strands 16-17, 18-19, and 20-21. Contact with loop 20-21 explains competition with LA-2, the murine monoclonal antibody used to estimate serum borreliacidal activities in the first-generation Lyme disease vaccine clinical trials. A high-resolution B-cell epitope map of OspA will accelerate structure-based design of second generation OspA-based vaccines.

Structural Elucidation of a Protective B Cell Epitope on Outer Surface Protein C (OspC) of the Lyme Disease Spirochete, Borreliella burgdorferi

Outer surface protein C (OspC) plays a pivotal role in mediating tick-to-host transmission and infectivity of the Lyme disease spirochete, Borreliella burgdorferi. OspC is a helical-rich homodimer that interacts with tick salivary proteins, as well as components of the mammalian immune system. Several decades ago, it was shown that the OspC-specific monoclonal antibody, B5, was able to passively protect mice from experimental tick-transmitted infection by B. burgdorferi strain B31. However, B5's epitope has never been elucidated, despite widespread interest in OspC as a possible Lyme disease vaccine antigen. Here, we report the crystal structure of B5 antigen-binding fragments (Fabs) in complex with recombinant OspC type A (OspC_A). Each OspC monomer within the homodimer was bound by a single B5 Fab in a side-on orientation, with contact points along OspC's α-helix 1 and α-helix 6, as well as interactions with the loop between α-helices 5 and 6. In addition, B5's complementarity-determining region (CDR) H3 bridged the OspC-OspC' homodimer interface, revealing the quaternary nature of the protective epitope. To provide insight into the molecular basis of B5 serotype specificity, we solved the crystal structures of recombinant OspC types B and K and compared them to OspC_A. This study represents the first structure of a protective B cell epitope on OspC and will aid in the rational design of OspC-based vaccines and therapeutics for Lyme disease. IMPORTANCE The spirochete Borreliella burgdorferi is a causative agent of Lyme disease, the most common tickborne disease in the United States. The spirochete is transmitted to humans during the course of a tick taking a bloodmeal. After B. burgdorferi is deposited into the skin of a human host, it replicates locally and spreads systemically, often resulting in clinical manifestations involving the central nervous system, joints, and/or heart. Antibodies directed against B. burgdorferi's outer surface protein C (OspC) are known to block tick-to-host transmission, as well as dissemination of the spirochete within a mammalian host. In this report, we reveal the first atomic structure of one such antibody in complex with OspC. Our results have implications for the design of a Lyme disease vaccine capable of interfering with multiple stages in B. burgdorferi infection.

High prevalence of vertebral fractures in seizure patients with normal bone density receiving chronic anti-epileptic drugs

People with epilepsy who take certain medications are at risk for developing osteoporosis and fractures of the vertebrae that commonly go undiagnosed. By using technology available in a bone density scan, we observed at least one fracture in many subjects with bone density in the normal and osteopenic range.

PURPOSE/INTRODUCTION

Chronic use of antiepileptic drugs (AEDs), both enzyme-inducing (phenytoin, phenobarbital, carbamazepine, and primidone) and non-enzyme-inducing (i.e., valproate), is recognized as a cause of secondary osteoporosis. Vertebral compression fractures (VF) are the most common type of osteoporotic fractures and may confer an increased risk of future hip, wrist, and vertebral fractures. Vertebral compression fractures in the general population are frequently asymptomatic, and under-diagnosed. The purpose of this study is to describe the prevalence of VF in a cohort of male veterans with epilepsy on chronic AEDs.

METHODS

The cohort for this study consisted of 146 male veterans who carried a diagnosis of epilepsy and were chronic users of AEDs known to cause osteoporosis (phenobarbital, phenytoin, carbamazepine, primidone, and valproate). Chronic AED use was defined as receiving an AED for at least 2 years. Subjects were previously seen in the osteoporosis clinic and had been evaluated by a dual-energy X-Ray absormetry (DXA) instrument including morphometric studies following a standard vertebral fracture assessment (VFA) protocol during the same DXA imaging acquisition session.

RESULTS

The mean age was 63 years. Low bone mineral density defined as osteoporosis or osteopenia was observed in 29% and 43% respectively. We observed at least one VF in 41 % of the subjects who had normal BMD, 54% in the osteopenic range, and 75% in the osteoporotic range.

CONCLUSIONS

By performing a VFA in addition to standard bone densitometric studies, we disclosed a large prevalence of compression fractures in individuals with epilepsy chronically treated with AEDs who had BMDs in the normal and osteopenic ranges. The addition of VFA or other imaging methods to evaluate VF should be included in the evaluation of bone health in individuals with epilepsy receiving AEDs since it may modify treatment recommendations to prevent future osteoporotic fractures.

Structural Analysis of Toxin-Neutralizing, Single-Domain Antibodies that Bridge Ricin's A-B Subunit Interface

Ricin toxin kills mammalian cells with notorious efficiency. The toxin's B subunit (RTB) is a Gal/GalNAc-specific lectin that attaches to cell surfaces and promotes retrograde transport of ricin's A subunit (RTA) to the trans Golgi network (TGN) and endoplasmic reticulum (ER). RTA is liberated from RTB in the ER and translocated into the cell cytoplasm, where it functions as a ribosome-inactivating protein. While antibodies against ricin's individual subunits have been reported, we now describe seven alpaca-derived, single-domain antibodies (V_HHs) that span the RTA-RTB interface, including four Tier 1 V_HHs with IC₅₀ values <1 nM. Crystal structures of each V_HH bound to native ricin holotoxin revealed three different binding modes, based on contact with RTA's F-G loop (mode 1), RTB's subdomain 2γ (mode 2) or both (mode 3). V_HHs in modes 2 and 3 were highly effective at blocking ricin attachment to HeLa cells and immobilized asialofetuin, due to framework residues (FR3) that occupied the 2γ Gal/GalNAc-binding pocket and mimic ligand. The four Tier 1 V_HHs also interfered with intracellular functions of RTB, as they neutralized ricin in a post-attachment cytotoxicity assay (e.g., the toxin was bound to cell surfaces before antibody addition) and reduced the efficiency of toxin transport to the TGN. We conclude that the RTA-RTB interface is a target of potent toxin-neutralizing antibodies that interfere with both extracellular and intracellular events in ricin's cytotoxic pathway.

Blocking Borrelia burgdorferi transmission from infected ticks to nonhuman primates with a human monoclonal antibody

Disrupting transmission of Borrelia burgdorferi sensu lato complex (B. burgdorferi) from infected ticks to humans is one strategy to prevent the significant morbidity from Lyme disease. We have previously shown that an anti-OspA human mAb, 2217, prevents transmission of B. burgdorferi from infected ticks in animal models. Maintenance of a protective plasma concentration of a human mAb for tick season presents a significant challenge for a preexposure prophylaxis strategy. Here, we describe the optimization of mAb 2217 by amino acid substitutions (2217LS: M428L and N434S) in the Fc domain. The LS mutation led to a 2-fold increase in half-life in cynomolgus monkeys. In a rhesus macaque model, 2217LS protected animals from tick transmission of spirochetes at a dose of 3 mg/kg. Crystallographic analysis of Fab in complex with OspA revealed that 2217 bound an epitope that was highly conserved among the B. burgdorferi, B. garinii, and B. afzelii species. Unlike most vaccines that may require boosters to achieve protection, our work supports the development of 2217LS as an effective preexposure prophylaxis in Lyme-endemic regions, with a single dose at the beginning of tick season offering immediate protection that remains for the duration of exposure risk.

Structural basis for the interaction of Shiga toxin 2a with a C-terminal peptide of ribosomal P stalk proteins

The principal virulence factor of human pathogenic enterohemorrhagic Escherichia coli is Shiga toxin (Stx). Shiga toxin 2a (Stx2a) is the subtype most commonly associated with severe disease outcomes such as hemorrhagic colitis and hemolytic uremic syndrome. The catalytic A1 subunit (Stx2A1) binds to the conserved elongation factor binding C-terminal domain (CTD) of ribosomal P stalk proteins to inhibit translation. Stx2a holotoxin also binds to the CTD of P stalk proteins because the ribosome-binding site is exposed. We show here that Stx2a binds to an 11-mer peptide (P11) mimicking the CTD of P stalk proteins with low micromolar affinity. We cocrystallized Stx2a with P11 and defined their interactions by X-ray crystallography. We found that the last six residues of P11 inserted into a shallow pocket on Stx2A1 and interacted with Arg-172, Arg-176, and Arg-179, which were previously shown to be critical for binding of Stx2A1 to the ribosome. Stx2a formed a distinct P11-binding mode within a different surface pocket relative to ricin toxin A subunit and trichosanthin, suggesting different ribosome recognition mechanisms for each ribosome inactivating protein (RIP). The binding mode of Stx2a to P11 is also conserved among the different Stx subtypes. Furthermore, the P stalk protein CTD is flexible and adopts distinct orientations and interaction modes depending on the structural differences between the RIPs. Structural characterization of the Stx2a-ribosome complex is important for understanding the role of the stalk in toxin recruitment to the sarcin/ricin loop and may provide a new target for inhibitor discovery.

Nuclear Localization Is Not Required for Tip60 Tumor Suppressor Activity in Breast and Lung Cancer Cells

The Tip60 lysine acetyltransferase is a tumor suppressor in most cancers but an oncogene in prostate and gastric cancer. Tip60 is commonly found in the nucleus, where it acetylates proteins involved in transcription, DNA repair, and chromatin; however, it has also been shown to acetylate cytoplasmic targets. In this study, we investigated the relationship between Tip60 localization and breast and lung cancer. In cell fractionation experiments, cancer-derived cell lines showed a shift from nuclear to cytoplasmic endogenous Tip60 compared with cell lines derived from normal cells. With immunofluorescence, we observed four different localization patterns of overexpressed Tip60 and found that cancer cells had increased cytoplasmic localization of Tip60 compared with HEK-293 cells. The addition of a nuclear localization signal (NLS) increased the number of cells containing nuclear Tip60, whereas mutation of a putative endogenous NLS increased the number of cells with cytoplasmic Tip60. Overexpression of Tip60 increased cancer cell line sensitivity to paclitaxel regardless of changes in localization. These results suggest that dysregulation of Tip60 in breast and lung cancer is not limited to reduced expression but may also involve subcellular localization.

Intracellular Neutralization of Ricin Toxin by Single-domain Antibodies Targeting the Active Site

The extreme potency of the plant toxin, ricin, is due to its enzymatic subunit, RTA, which inactivates mammalian ribosomes with near-perfect efficiency. Here we characterized, at the functional and structural levels, seven alpaca single-domain antibodies (VHHs) previously reported to recognize epitopes in proximity to RTA's active site. Three of the VHHs, V2A11, V8E6, and V2G10, were potent inhibitors of RTA in vitro and protected Vero cells from ricin when expressed as intracellular antibodies ("intrabodies"). Crystal structure analysis revealed that the complementarity-determining region 3 (CDR3) elements of V2A11 and V8E6 penetrate RTA's active site and interact with key catalytic residues. V2G10, by contrast, sits atop the enzymatic pocket and occludes substrate accessibility. The other four VHHs also penetrated/occluded RTA's active site, but lacked sufficient binding affinities to outcompete RTA-ribosome interactions. Intracellular delivery of high-affinity, single-domain antibodies may offer a new avenue in the development of countermeasures against ricin toxin.toxin, antibody, structure, intracellular.

Contribution of an unusual CDR2 element of a single domain antibody in ricin toxin binding affinity and neutralizing activity

Ricin toxin's enzymatic subunit (RTA) has been subjected to intensive B cell epitope mapping studies using a combination of competition ELISAs, hydrogen exchange-mass spectrometry and X-ray crystallography. Those studies identified four spatially distinct clusters (I-IV) of toxin-neutralizing epitopes on the surface of RTA. Here we describe A9, a new single domain camelid antibody (VHH) that was proposed to recognize a novel epitope on RTA that straddles clusters I and III. The X-ray crystal structure of A9 bound to RTA (2.6 Å resolution) revealed extensive antibody contact with RTA's β-strand h (732 Å2 buried surface area; BSA), along with limited engagement with α-helix D (90 Å2) and α-helix C (138 Å2). Collectively, these contacts explain the overlap between epitope clusters I and III, as identified by competition ELISA. However, considerable binding affinity, and, consequently, toxin-neutralizing activity of A9 is mediated by an unusual CDR2 containing five consecutive Gly residues that interact with α-helix B (82 Å2), a known neutralizing hotspot on RTA. Removal of a single Gly residue from the penta-glycine stretch in CDR2 reduced A9's binding affinity by 10-fold and eliminated toxin-neutralizing activity. Computational modeling indicates that removal of a Gly from CDR2 does not perturb contact with RTA per se, but results in the loss of an intramolecular hydrogen bond network involved in stabilizing CDR2 in the unbound state. These results reveal a novel configuration of a CDR2 element involved in neutralizing ricin toxin.

Comparison between magnetic force microscopy and electron back-scatter diffraction for ferrite quantification in type 321 stainless steel

Several analytical techniques that are currently available can be used to determine the spatial distribution and amount of austenite, ferrite and precipitate phases in steels. The application of magnetic force microscopy, in particular, to study the local microstructure of stainless steels is beneficial due to the selectivity of this technique for detection of ferromagnetic phases. In the comparison of Magnetic Force Microscopy and Electron Back-Scatter Diffraction for the morphological mapping and quantification of ferrite, the degree of sub-surface measurement has been found to be critical. Through the use of surface shielding, it has been possible to show that Magnetic Force Microscopy has a measurement depth of 105-140 nm. A comparison of the two techniques together with the depth of measurement capabilities are discussed.

Mapping the distribution of the main host for plague in a complex landscape in Kazakhstan: An object-based approach using SPOT-5 XS, Landsat 7 ETM+, SRTM and multiple Random Forests

Plague is a zoonotic infectious disease present in great gerbil populations in Kazakhstan. Infectious disease dynamics are influenced by the spatial distribution of the carriers (hosts) of the disease. The great gerbil, the main host in our study area, lives in burrows, which can be recognized on high resolution satellite imagery. In this study, using earth observation data at various spatial scales, we map the spatial distribution of burrows in a semi-desert landscape.

The study area consists of various landscape types. To evaluate whether identification of burrows by classification is possible in these landscape types, the study area was subdivided into eight landscape units, on the basis of Landsat 7 ETM+ derived Tasselled Cap Greenness and Brightness, and SRTM derived standard deviation in elevation.

In the field, 904 burrows were mapped. Using two segmented 2.5 m resolution SPOT-5 XS satellite scenes, reference object sets were created. Random Forests were built for both SPOT scenes and used to classify the images. Additionally, a stratified classification was carried out, by building separate Random Forests per landscape unit.

Burrows were successfully classified in all landscape units. In the ‘steppe on floodplain’ areas, classification worked best: producer's and user's accuracy in those areas reached 88% and 100%, respectively. In the ‘floodplain’ areas with a more heterogeneous vegetation cover, classification worked least well; there, accuracies were 86 and 58% respectively. Stratified classification improved the results in all landscape units where comparison was possible (four), increasing kappa coefficients by 13, 10, 9 and 1%, respectively.

In this study, an innovative stratification method using high- and medium resolution imagery was applied in order to map host distribution on a large spatial scale. The burrow maps we developed will help to detect changes in the distribution of great gerbil populations and, moreover, serve as a unique empirical data set which can be used as input for epidemiological plague models. This is an important step in understanding the dynamics of plague.

Importance of bird-to-bird transmission for the establishment of West Nile virus

West Nile virus (WNV) is principally considered to be maintained in a mosquito-bird transmission cycle. Under experimental conditions, several other transmission routes have been observed, but the significance of these additional routes in nature is unknown. Here, we derive an expression for the basic reproduction number (R0) for WNV including all putative routes of transmission between birds and mosquitoes to gauge the relative importance of these routes for the establishment of WNV. Parameters were estimated from published experimental results. Sensitivity analysis reveals that R0 is sensitive to transmission between birds via close contact, but not to mosquito-to-mosquito transmission. In seasons or in areas where the mosquito-to-bird ratio is low, bird-to-bird transmission may be crucial in determining whether WNV can establish or not. We explain the use of R0 as a flexible tool to measure the risk of establishment of vector-borne diseases.

The basic reproduction number for complex disease systems: defining R(0) for tick-borne infections

Characterizing the basic reproduction number, R(0), for many wildlife disease systems can seem a complex problem because several species are involved, because there are different epidemiological reactions to the infectious agent at different life-history stages, or because there are multiple transmission routes. Tick-borne diseases are an important example where all these complexities are brought together as a result of the peculiarities of the tick life cycle and the multiple transmission routes that occur. We show here that one can overcome these complexities by separating the host population into epidemiologically different types of individuals and constructing a matrix of reproduction numbers, the so-called next-generation matrix. Each matrix element is an expected number of infectious individuals of one type produced by a single infectious individual of a second type. The largest eigenvalue of the matrix characterizes the initial exponential growth or decline in numbers of infected individuals. Values below 1 therefore imply that the infection cannot establish. The biological interpretation closely matches that of R(0) for disease systems with only one type of individual and where infection is directly transmitted. The parameters defining each matrix element have a clear biological meaning. We illustrate the usefulness and power of the approach with a detailed examination of tick-borne diseases, and we use field and experimental data to parameterize the next-generation matrix for Lyme disease and tick-borne encephalitis. Sensitivity and elasticity analyses of the matrices, at the element and individual parameter levels, allow direct comparison of the two etiological agents. This provides further support that transmission between cofeeding ticks is critically important for the establishment of tick-borne encephalitis.

Effects of (+/-)3,4-methylenedioxymethamphetamine, (+/-)3,4-methylenedioxyamphetamine and methamphetamine on temperature and activity in rhesus macaques

Severe and malignant hyperthermia is a frequently reported factor in emergency department (ED) visits and fatalities in which use of amphetamine drugs, such as (+/-)3,4-methylenedioxymethamphetamine (MDMA), (+/-)3,4-methylenedioxyamphetamine (MDA) and (+)methamphetamine (METH), is confirmed. Individuals who use "ecstasy" are also often exposed, intentionally or otherwise, to several of these structurally-related compounds alone or in combination. In animal studies the degree of (subcritical) hyperthermia is often related to the severity of amphetamine-induced neurotoxicity, suggesting health risks to the human user even when emergency medical services are not invoked. A clear distinction of thermoregulatory risks posed by different amphetamines is therefore critical to understand factors that may produce medical emergency related to hyperthermia. The objective of this study was therefore to determine the relative thermoregulatory disruption produced by recreational doses of MDMA, MDA and METH in nonhuman primates. Body temperature and spontaneous home cage activity were monitored continuously in six male rhesus monkeys via radiotelemetric devices. The subjects were challenged intramuscularly with 0.56-2.4 mg/kg MDMA, 0.56-2.4 mg/kg MDA and 0.1-1.0 mg/kg METH. All three amphetamines significantly elevated temperature; however the time course of effects differed. The acute effect of METH lasted hours longer than MDA or MDMA and a disruption of nighttime circadian cooling was observed as long as 18 h after 1.0 mg/kg METH and 1.78-2.4 mg/kg MDA, but not after MDMA. Activity levels were only reliably increased by 0.32 mg/kg METH. It is concluded that while all three substituted amphetamines produce hyperthermia in rhesus monkeys, the effects do not depend on elevated locomotor activity and exhibit differences between compounds. The results highlight physiological risks posed both by recreational use of the amphetamines and by current trials for clinical MDMA use.

Dependence of population response to fertility control on the survival of sterile animals and their role in regulation

The species for which fertility control is presently used, or for which it is being developed, range from small mammal pests, such as the house mouse (Mus domesticus), to large mammals, such as the African elephant (Loxodonta africana). However, the possibility of a population response other than a reduction in abundance proportional to the fraction of animals rendered infertile has been shown in field trials. For example, when intermediate levels of sterility were imposed on wild populations of European rabbits (Oryctolagus cuniculus), there was an increase in their abundance, on an annual basis, due to enhanced survival of juveniles and adult females. In this article, we relate intraspecific regulatory processes to the response of populations to fertility control using a set of density-dependent structured-population models. In each of the models, the population is exposed periodically to a fertility control agent that renders a fraction of fertile females sterile. Although our intention is not to predict the population response of any one particular species, the results of the models are illustrated using parameter values that are representative of populations of the European fox (Vulpes vulpes) in south-eastern Australia. When populations were regulated by density-dependent mechanisms in which sterile females did not participate, such as competition for resources among young animals or competition among fertile females for breeding sites or territories, then populations could increase in abundance for low and intermediate levels of imposed sterility. For other intraspecific regulatory mechanisms, such as competition for resources between all individuals, all levels of sterility were observed to reduce abundance. The population response was sensitive to (i) whether the survival of sterile adults was higher than that of fertile adults, (ii) whether animals could be sterilized before sexual maturity, and (iii) whether density dependence was modelled as a threshold process.

Minimizing false-positives in universal newborn hearing screening: a simple solution

BACKGROUND AND OBJECTIVES

The false-positive rates of previously reported universal newborn hearing screening (UNHS) programs range between 2.5% and 8%. Critics of UNHS programs have claimed that this rate is too high and might lead to a number of the negative effects produced by false-positive screening tests, namely emotional trauma, disease labeling, iatrogenesis from unnecessary testing, and increased expense in terms of time and money. We previously reported, based on some preliminary data, that as many as 80% of newborns who failed the initial hearing screen subsequently passed when they were retested the following day, before being discharged from the hospital. We now present the results of this intervention for our entire UNHS program during a 7-month period.

METHODS

We analyzed data from 3142 non-neonatal intensive care unit infants screened with an automated auditory brainstem response at the Women's Hospital of Greensboro from November 1, 1999 to May 31, 2000. A protocol was developed wherein all infants who failed the initial UNHS were rescreened with another automated auditory brainstem response before hospital discharge. Data collected included pass/fail rates during the inpatient stay as well as follow-up data and risk factors for congenital hearing loss.

RESULTS

Confirmed hearing loss occurred in 8 nonneonatal intensive care unit infants, a rate of 2.5/1000. Eighty percent of newborns who failed the initial hearing screen passed on rescreening before hospital discharge. This produced a false-positive rate of 0.8% and a corresponding positive predictive value of 24%. If inhospital rescreening had not occurred, our false-positive rate and positive predictive value would have been 3.9% and 6.1%, respectively.

CONCLUSIONS

Our simple intervention of rescreening all infants who failed their initial UNHS before hospital discharge reduced the false-positive rate of UNHS to 0.8%. We suggest that this simple, inexpensive intervention should be instituted for all similar UNHS programs.

Periodic triggering of an inducible gene for control of a wild population

A possible method of control for the management of wild populations consists of continual introgression of an inducible transgene by releasing transgenic individuals, with periodic exposure of the population to a trigger. Exposure to the trigger causes death or sterility in carriers of the transgene, but is otherwise benign. We investigate the effectiveness of various strategies for control. We show that suppression of the population density below any pre-specified level is possible using this technique. At the same time we show that too frequent or too efficient exposure to the trigger can select for non-transgenic genotypes at an intensity such that the population density will be largely unaffected by the trigger. Choices for management parameters can ensure that the latter scenario is avoided. We show that releasing individuals carrying the transgene at more than one locus facilitates density control.

The false-positive in universal newborn hearing screening

OBJECTIVES

Concern has been raised about the frequency and subsequent emotional effect of a false-positive result during universal newborn hearing screening (UNHS). This study describes: 1) the results of 1 UNHS program and a potential method to significantly reduce the false-positive rate, and 2) the effect a false-positive result has on lasting maternal anxiety toward their children as well as their views toward UNHS in general.

METHODS

A retrospective analysis was conducted using data from 5010 infants screened with an automated auditory brainstem response (ABR) at the Women's Hospital of Greensboro (WHOG) from July 6, 1998 to June 30, 1999. In addition, a structured telephone survey was given to mothers of infants who had failed the initial hearing screen (stage 1) and who had completed an outpatient rescreen (stage 2).

RESULTS

Confirmed hearing loss occurred in non-neonatal intensive care unit infants at a rate of 1.8/1000. A false-positive rate of 1.9% occurred during stage 1 of UNHS (screening before newborn discharge). We attribute this relatively low rate to rescreening of 51% of those newborns who failed the initial screen before hospital discharge. Eighty percent of these rescreened infants passed, thus needing no additional follow-up. If we had rescreened all infants before discharge, the false-positive rate would have approached.5%. Results of the survey were reassuring with regard to lasting emotional effects of false-positive tests. Only 9% of mothers said they "treated their child differently" before outpatient rescreening, and only 14% reported any lasting anxiety after their child passed the outpatient repeat screen. Although none reached statistical significance, potential risk factors for lasting anxiety include more educated mothers, lack of understanding of UNHS, and a false-positive result in both stage 1 and stage 2. Over 90% of all mothers believed that UNHS was a good idea.

CONCLUSIONS

By rescreening all infants before hospital discharge, the false-positive rate of UNHS performed using automated ABR can be reduced to <1%. However, for the false-positive results that do occur, any long-lasting and detrimental emotional impact between mother and infant seems to be small and could be reduced even more with improved understanding about UNHS.

Effects of mitomycin C and carboplatin pretreatment on multidrug resistance-associated P-glycoprotein expression and on subsequent suppression of tumor growth by doxorubicin and paclitaxel in human metastatic breast cancer xenografted nude mice

Overexpression of P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP), and several other proteins has been associated with development of multidrug resistance by cancer cells, which represents a significant obstacle to successful treatment by chemotherapy. We had previously demonstrated that a single noncytotoxic dose of mitomycin C (MMC), carboplatin, or one of several other DNA cross-linking agents suppressed mRNA expression of the mdr1 gene coding for Pgp, leading to a subsequent suppression of Pgp protein levels and a concomitant decrease in drug efflux. Pretreatment with MMC led to a 5- to 10-fold decrease in the ED50 for cell killing by a subsequent agent such as the Pgp substrate, doxorubicin, but did not affect killing by the non-Pgp substrate, cisplatin. In this study, we report that MMC and carboplatin each significantly suppressed Pgp protein levels in human MDA-MB-435 cells xenografted as solid tumors into the lateral mammary fat pads of female nude mice, with a similar time course as had previously been observed in cell culture. Pretreatment of mice with MMC or carboplatin 48-72 h prior to receiving either doxorubicin or paclitaxel caused a significantly greater reduction in tumor growth rate compared to either agent alone or the combination given simultaneously. These data suggest that a combination chemotherapy regimen consisting of a DNA cross-linking agent given to modulate the MDR phenotype, followed by a second cytotoxic agent, may be an effective treatment for human patients with de novo or late stage acquired multidrug-resistant malignancies.

In vitro susceptibility of Yersinia enterocolitica isolated from the oral cavity of swine

Antimicrobial susceptibility of 181 (107 ail-harboring isolates and 74 non-ail-harboring) Yersinia enterocolitica isolates obtained from the oral cavity of swine was determined against 24 antimicrobial agents. All Y. enterocolitica isolates were susceptible to sulfamethoxazole/trimethoprim, enrofloxacin, aminoglycosides, and nitrofurantoin. Susceptibility to tetracycline appeared to vary by lot of origin. Isolates were resistant to sulfonamides (other than sulfamethoxazole/trimethoprim), penicillin, ampicillin, ticarcillin, cephalothin, macrolides, and tiamulin.

The AB-180 circulatory support system: summary of development and plans for phase I clinical trial

BACKGROUND

The AB-180 circulatory support system is a small, durable, efficient centrifugal pump with low thrombogenic potential. The device was designed to provide a fully implantable, left ventricular assist system for short-term support to address the issues of systemic anticoagulation, thrombus formation, infection, and cost.

METHODS

Extensive bench and animal studies were performed to validate the mechanical integrity of the device and its functionality as an implant.

RESULTS

These studies demonstrated anticoagulation requirements, established operating guidelines, incorporated safety systems, and demonstrated safety and efficacy.

CONCLUSIONS

The AB-180 fulfills the stated goals on initial evaluation. A phase I human trial is underway.

Coccolith ultrastructure and biomineralisation

The relationship between calcite biomineralisation and coccolith ultrastructure is analysed across the diversity of calcifying haptophytes. The emphasis is on integration of evidence from crystallographic and ultrastructural studies but additional relevant information from biochemical and phylogenetic work is reviewed. We attempt to identify aspects of ultrastructure which are most likely to be the product of self-organising processes. The principal topics reviewed are heterococcolith rim nucleation, including reassessment of the V/R model; crystal growth regulation in heterococcoliths; holococcolith biomineralisation; and the diversity of other biomineralisation modes in haptophytes. It is concluded that the diverse range of calcareous structures produced by haptophytes probably has a common phylogenetic origin and is produced via operation of a limited set of mainly shared genetic and biochemical pathways. Copyright 1999 Academic Press.

Left ventricular support with the implantable AB-180 centrifugal pump in sheep with acute myocardial infarction

A small, 257 g centrifugal pump was tested as a left ventricular assist device (LVAD) in sheep given a myocardial infarction. Pump performance, hemolysis, end organ function, weaning, explant procedure, and the incidence of thromboemboli at autopsy were studied over intervals of 1 to 44 days. Twelve sheep were given acute myocardial infarction by ligation of the anterior descending coronary artery and 11 had insertion of the AB-180 Circulatory Support System (CSS). One sheep served as a control for the space occupying effects of the pump in the left chest. Inflow was from the left atrium and outflow was to the descending thoracic aorta. Heparin (57-83 U/ml) in sterile water was infused into the pump at a rate of 10 ml/hr. Pump flows of 1-5.7 L/min were tested. The AB-180 CSS supported 73.5% of the total cardiac output (pump + heart) of 3.89 L/min, with a mean arterial pressure of 86 +/- 7 mmHg at a pump speed of 4,162 +/- 276 rpm immediately after implant. Hemolysis was <10 mg/dl and activated partial thromboplastin time (aPTT) values were in the normal range for sheep (<52 sec) after 48 hr of pumping. Liver enzyme concentrations returned to normal within 2 weeks. There was no evidence of thrombocytopenia. No signs of infection were present during assist and none was found at autopsy. The device was successfully removed three times without the use of pressor agents or blood transfusion. Alarm systems performed appropriately. During the 106 days of cumulative pumping, two sheep showed small (<1.5 cm) renal infarcts. Both were associated with intervals of pump stasis. The AB-180 CSS pump was easily implanted into the left chest without the use of cardiopulmonary bypass. It appears to have a low thromboembolic potential in sheep, without the need for large doses of heparin to elevate aPTT values. This characteristic may ameliorate the excessive bleeding seen clinically with current LVAD systems used for post cardiotomy cardiogenic shock, which require anticoagulation with heparin. The small size and weight of the device permit implantation within the chest and allow chest closure. This may reduce the incidence of infection associated with temporary left ventricular assist and an open sternum.

p53 gene mutations in multiple myeloma

AIM

To assess whether p53 gene mutation is important in the pathogenesis and progression of multiple myeloma.

METHODS

Thirty eight DNA samples (derived predominantly from bone marrow) obtained from 31 patients with multiple myeloma were examined for mutations in p53 exons 5-9 by polymerase chain reaction single strand conformation polymorphism. Twenty three samples were analysed at the time of diagnosis (one patient had plasma cell leukaemia), three in plateau phase, and 12 at relapse (one plasma cell leukaemia and one extramedullary relapse).

RESULTS

One p53 mutation was detected in this group of patients (3.2%). This was seen in the diagnostic bone marrow sample of a 35 year old man with stage IIA disease and occurred in exon 6 as a result of a silent A to G transition at codon 213 (CGA-->CGG), a polymorphism that has been reported in about 3% of breast and lung tumours.

CONCLUSIONS

p53 gene mutations are rare events in multiple myeloma and would seem to be of limited value as a prognostic factor.

Cellular interactions of murine immune cells exposed to live Mycobacterium intracellulare, its whole lipid extract, and its serovar-specific glycopeptidolipid

In this study we examined some of the immunological responses to Mycobacterium intracellulare and its lipid components. Our results indicate that infection with M. intracellulare can increase the expression of adhesion molecules, ICAM-1 and LFA-1, only at the site of injection (peritoneum). There was no change in the expression of these adhesion molecules in the lymphoid organs (thymus and spleen). Significant increases in the adhesion molecules were observed in the spleen cells incubated with the lipid derived from mycobacteria in the presence of concanavalin (Con A) compared to the Con A alone. The expression of the Thy 1.2 and Lyt-2 markers was not affected by the bacteria or their lipids. The results indicate a marked increase in the mitogenic response by the infected spleen cells removed at an early day. The blastogenic study also indicated that the lipids can reduce the mitogen-induced blastogenesis of spleen cells removed from M. intracellulare- and saline-injected mice; moreover, they suggested that the spleen cells removed from Listeria monocytogenes-infected mice can also be affected by mycobacterial lipids. This indicates a nonspecific effect by these lipids. The results suggest that the immunological response was contingent upon prior exposure of the mice to M. intracellulare, and also was dependent on whether the cells came from the peritoneal cavity or lymphoid organs.

Influence of suspension on the oxidative burst by rat neutrophils

The influence of spaceflight on the oxidative burst of neutrophils is not known. The present study was designed to evaluate the influence of antiorthostatic suspension, a ground-based modeling system designed to simulate certain aspects of weightlessness that occur after spaceflight, on the capacity of rat neutrophils to express the oxidative burst, an important host defense mechanism against microbial pathogens. Rats were suspended in whole body harnesses in the antiorthostatic orientation for a 3- or 7-day period. Control rats were suspended orthostatically or allowed to remain in vivarium cages without the attachment of any suspension materials. After suspension, peripheral blood was harvested and neutrophils were isolated by density gradient centrifugation. The enriched neutrophil preparations were stimulated with N-formyl-methionyl-leucine-phenylalanine and phorbol myristic acid to induce the oxidative burst. It was found that neutrophils isolated from suspended animals released the same levels of superoxide anion as did vivarium control animals that were not suspended, indicating that whole body suspension did not alter this aspect of rat neutrophil function.

Beta 2-glycoprotein 1 (beta 2GP1) enhances cardiolipin binding activity but is not the antigen for antiphospholipid antibodies

Some investigators have reported that a serum protein, beta 2-glycoprotein 1 (beta 2GP1), either alone or in combination with negatively charged phospholipid, may be the antigen for anticardiolipin (aCL) antibodies. To examine these reports further, ELISA tests, inhibition experiments, Ouchterlony and Western blot techniques were used to examine anticardiolipin binding to beta 2GP1. Sera from patients with the antiphospholipid syndrome (APS) and syphilis were studied, as well as whole IgG immunoglobulin and affinity purified (a.p.) IgG aCL antibodies. Results showed no binding of aCL antibodies to beta 2GP1 in the absence of cardiolipin. beta 2GP1 caused enhanced binding of aCL antibodies to cardiolipin, but this enhancement was not observed in inhibition experiments. Binding to cardiolipin occurred in the absence of beta 2GP1. Enhancement of cardiolipin binding activity by beta 2GP1 was observed for APS, but not for syphilis. We conclude that beta 2GP1 is not the antigen for aCL antibodies, nor is it likely that the antibody recognizes shared beta 2GP1-cardiolipin epitopes. Instead, this protein may make cardiolipin more available for aCL binding on solid surfaces by some yet undefined mechanism. This effect may not extend to aqueous suspensions.

Reduction in tissue iron stores with a new regimen of continuous ambulatory intravenous deferoxamine

A new regimen of 24-hr ambulatory continuous intravenous infusion of deferoxamine (CIV DFO) through central venous ports was instituted in nine patients aged (mean +/- SD) 22.4 +/- 5.8 years over a period of 15.7 +/- 7.3 months. Central venous infusion sites were changed weekly in the clinic, eliminating the necessity for reconstitution of DFO and needle insertion at home. Because CIV DFO could be interrupted only by medical personnel, patient compliance was documented accurately; patients administered 93.0% +/- 3.2% of CIV DFO prescribed. Mean urinary iron excretion on CIV DFO (66.8 +/- 50.4 mg/24 hr) was significantly greater than that quantitated during 12-hr equivalent-dose subcutaneous DFO infusions (23.4 +/- 18.3 mg/24 hr; P less than 0.025). Mean serum ferritin declined by 71% over the treatment period (P less than 0.005). This regimen confers the advantages of uninterrupted exposure to DFO, is associated with excellent patient compliance, and should be considered in any patient with severe iron overload and erratic compliance with DFO.

Patients' acceptance of monitoring fetal movement. A randomized comparison of charting techniques

An active fetus is reassuring to both the woman and her obstetrician. Numerous techniques of charting fetal movement have been shown to assist the clinician in caring for the high-risk patient. Patients' compliance with daily monitoring is an important clinical issue, and little information exists on the fetal movement record most preferred by the patient. A comparative study evaluated patients' acceptance of three commonly used charts. The 85 enrollees were given the different charts in a random manner and questioned at the next office visit. All the patients expressed approval of the concept and a lack of anxiety about such monitoring, complied with our instructions and returned the completed records. The neonatal outcomes were favorable with all the charting techniques in our antenatal fetal surveillance plan. The "count-to-10" method was rated most preferred in 95.3% of the cases. The reasons cited included convenience and less time needed to complete the recording. The mean time to complete this record was 19.7 +/- 22.9 minutes rather than one or more hours, as with the other charting methods. The results of this randomized investigation show the simple and rapid count-to-10 method to be the most acceptable charting technique to our patients for monitoring fetal movement.

Uterine and fetal Doppler flow changes from a single dose of a long-acting intranasal decongestant

Oxymetazoline, an alpha-adrenergic agent, is the active vasoconstrictor in long-acting intranasal decongestants. This investigation studied the effects of oxymetazoline on the maternal and fetal circulations. Twelve healthy gravid patients in the third trimester (27-39 weeks) underwent flow velocity measurements by the same sonographer using a pulsed Doppler system (ATL Ultramark 4 machine). Maternal and fetal indices were recorded 15 minutes before dosing, immediately thereafter, and at 15-minute intervals during the first 2 hours after the drug was given. No significant changes were found in either the maternal blood pressures or pulse rates. Blood flow velocities did not change significantly from baseline for the uterine arcuate artery, fetal aorta, or umbilical artery circulations. In no case did absolute blood flow velocity decrease significantly or systolic/diastolic ratios elevate to worrisome values. For uncomplicated pregnancies, we conclude there are no significant acute changes in the maternal and fetal circulations after a single dose of intranasal oxymetazoline.

Analysis of field-weathered lures containing (E)-10-dodecen-1-yl acetate, a sex attractant for the pea moth,Cydia nigricana (F.)

Natural rubber stoppers treated with 1, 3, or 10 mg of (E)-10-dodecen-1-yl acetate, an attractant for male pea moth,Cydia nigricana (F.), were exposed in the field during the summer of 1978 and samples analyzed at intervals. The results for all three doses fitted well to first-order loss curves with half-lives of 63.5, 64.7, and 67.3 days, respectively. Thus, lures with an initial dose of 3 mg of the attractant retained approximately 1 mg after 3 months of field exposure; they should therefore maintain a constant level of attractiveness throughout this period because previous field studies showed that moths were equally responsive to fresh lures containing between 1 and 10 mg of the attractant. There was no loss of attractant during the preparation of lures or after 4 months at -15 ° C and only 13% was lost during 3 months of storage at room temperature.

Translation of mRNA for glutamate dehydrogenase and spectrophotometric procedure to follow the enzyme biosynthesis

Heterogeneous poly (A)-mRNA fraction was isolated from rat liver microsomes using phenol-chloroform extraction, millipore filtration and poly (U)-agarose affinity chromatography. Obtained fractions were characterized with respect to their secondary structure and poly (A) content. Isolated poly (A)-mRNA fraction contained high template activity for glutamate dehydrogenase in cell-free systems with microsomes or polysomes. A spectrophotometric procedure to follow enzyme biosynthesis was also developed.

American and British data on a three dimensional assessment of personality in college students

Reported data on American and British college student samples for the new Psychoticism, Extraversion, and Neuroticism (PEN) Inventory. Descriptive statistics for PEN dimensions for five American female samples (total 492 subjects), five American male samples (total 399 subjects), one British female sample (700 subjects) and one British male sample (700 subjects) were summarized. Intercorrelations of PEN dimensions for most of the American samples were reported. The pattern of significant intercorrelations tended to be in accord with previous work on prior related inventories. Similarities and differences among the sample descriptive statistics were discussed.