A biomaterial platform for T cell-specific gene delivery

Efficient T cell engineering is central to the success of CAR T cell therapy but involves multiple time-consuming manipulations, including T cell isolation, activation, and transduction. These steps add complexity and delay CAR T cell manufacturing, which takes a mean time of 4 weeks. To streamline T cell engineering, we strategically combine two critical engineering solutions - T cell-specific lentiviral vectors and macroporous scaffolds - that enable T cell activation and transduction in a simple, single step. The T cell-specific lentiviral vectors (referred to as STAT virus) target T cells through the display of an anti-CD3 antibody and the CD80 extracellular domain on their surface and provide robust T cell activation. Biocompatible macroporous scaffolds (referred to as Drydux) mediate robust transduction by providing effective interaction between naïve T cells and viral vectors. We show that when unstimulated peripheral blood mononuclear cells (PBMCs) are seeded together with STAT lentivirus on Drydux scaffolds, T cells are activated, selectively transduced, and reprogrammed in a single step. Further, we show that the Drydux platform seeded with PBMCs and STAT lentivirus generates tumor-specific functional CAR T cells. This potent combination of engineered lentivirus and biomaterial scaffold holds promise for an effective, simple, and safe avenue for in vitro and in vivo T cell engineering. STATEMENT OF SIGNIFICANCE: Manufacturing T cell therapies involves lengthy and labor-intensive steps, including T cell selection, activation, and transduction. These steps add complexity to current CAR T cell manufacturing protocols and limit widespread patient access to this revolutionary therapy. In this work, we demonstrate the combination of engineered virus and biomaterial platform that, together, enables selective T cell activation and transduction in a single step, eliminating multistep T cell engineering protocols and significantly simplifying the manufacturing process.

Re-centauring T cell antigen discovery around CD4+ T cells

In a recent issue of Cell, Dezfulian et al. develop a genome-scale platform to enable high-throughput identification of CD4+ T cell epitopes. This platform enables unbiased screens to discover antigens recognized by CD4+ T cells in cancer, infectious diseases, and autoimmunity.

Antigen identification and high-throughput interaction mapping by reprogramming viral entry

Deciphering immune recognition is critical for understanding a broad range of diseases and for the development of effective vaccines and immunotherapies. Efforts to do so are limited by a lack of technologies capable of simultaneously capturing the complexity of adaptive immunoreceptor repertoires and the landscape of potential antigens. To address this, we present receptor-antigen pairing by targeted retroviruses, which combines viral pseudotyping and molecular engineering approaches to enable one-pot library-on-library interaction screens by displaying antigens on the surface of lentiviruses and encoding their identity in the viral genome. Antigen-specific viral infection of cell lines expressing human T or B cell receptors allows readout of both antigen and receptor identities via single-cell sequencing. The resulting system is modular, scalable and compatible with any cell type. These techniques provide a suite of tools for targeted viral entry, molecular engineering and interaction screens with broad potential applications.

Biomarkers of Recent Cannabis Use in Blood, Oral Fluid and Breath

Proving driving under the influence of cannabis (DUIC) is difficult. Establishing a biomarker of recent use to supplement behavioral observations may be a useful alternative strategy. We determined whether cannabinoid concentrations in blood, oral fluid (OF), or breath could identify use within 3h, likely the period of greatest impairment. In a randomized trial, 191 frequent (≥4/week) and occasional (<4/week) cannabis users smoked one cannabis (placebo [0.02%], 5.9% or 13.4% THC) cigarette ad libitum. Blood, OF and breath samples were collected prior to and up to 6h after smoking. Samples were analyzed for 10 cannabinoids in OF, 8 in blood, and THC in breath. Frequent users had more residual THC in blood and were categorized as "recently used" prior to smoking; this did not occur in OF. Per se limits ranging from undetectable to 5 ng/mL THC in blood offered limited usefulness as biomarkers of recent use. Cannabinol (CBN, cutoff=1 ng/mL) in blood offered 100% specificity but only 31.4% sensitivity, resulting in 100% PPV and 94.0% NPV at 4.3% prevalence; but CBN may vary by cannabis chemovar. A 10 ng/mL THC cutoff in OF exhibited the overall highest performance to detect use within 3h (99.7% specificity, 82.4% sensitivity, 92.5% PPV, 99.2% NPV) but was still detectable in 23.2% of participants ~4.4h post smoking limiting specificity at later time points. OF THC may be a helpful indicator of recent cannabis intake, but this does not equate to impairment. Behavioral assessment of impairment is still required to determine DUIC. This study only involved cannabis inhalation and additional research evaluating alternative routes of ingestion (i.e., oral) is needed.

Differential PROTAC substrate specificity dictated by orientation of recruited E3 ligase

PROteolysis-TArgeting Chimeras (PROTACs) are hetero-bifunctional molecules that recruit an E3 ubiquitin ligase to a given substrate protein resulting in its targeted degradation. Many potent PROTACs with specificity for dissimilar targets have been developed; however, the factors governing degradation selectivity within closely-related protein families remain elusive. Here, we generate isoform-selective PROTACs for the p38 MAPK family using a single warhead (foretinib) and recruited E3 ligase (von Hippel-Lindau). Based on their distinct linker attachments and lengths, these two PROTACs differentially recruit VHL, resulting in degradation of p38α or p38δ. We characterize the role of ternary complex formation in driving selectivity, showing that it is necessary, but insufficient, for PROTAC-induced substrate ubiquitination. Lastly, we explore the p38δ:PROTAC:VHL complex to explain the different selectivity profiles of these PROTACs. Our work attributes the selective degradation of two closely-related proteins using the same warhead and E3 ligase to heretofore underappreciated aspects of the ternary complex model.

The Advantages of Targeted Protein Degradation Over Inhibition: An RTK Case Study

Proteolysis targeting chimera (PROTAC) technology has emerged over the last two decades as a powerful tool for targeted degradation of endogenous proteins. Herein we describe the development of PROTACs for receptor tyrosine kinases, a protein family yet to be targeted for induced protein degradation. The use of VHL-recruiting PROTACs against this protein family reveals several advantages of degradation over inhibition alone: direct comparisons of fully functional, target-degrading PROTACs with target-inhibiting variants that contain an inactivated E3 ligase-recruiting ligand show that degradation leads to more potent inhibition of cell proliferation and a more durable and sustained downstream signaling response, and thus addresses the kinome rewiring challenge seen with many receptor tyrosine kinase inhibitors. Combined, these findings demonstrate the ability to target receptor tyrosine kinases for degradation using the PROTAC technology and outline the advantages of this degradation-based approach.

Lessons in PROTAC Design from Selective Degradation with a Promiscuous Warhead

Inhibiting protein function selectively is a major goal of modern drug discovery. Here, we report a previously understudied benefit of small molecule proteolysis-targeting chimeras (PROTACs) that recruit E3 ubiquitin ligases to target proteins for their ubiquitination and subsequent proteasome-mediated degradation. Using promiscuous CRBN- and VHL-recruiting PROTACs that bind >50 kinases, we show that only a subset of bound targets is degraded. The basis of this selectivity relies on protein-protein interactions between the E3 ubiquitin ligase and the target protein, as illustrated by engaged proteins that are not degraded as a result of unstable ternary complexes with PROTAC-recruited E3 ligases. In contrast, weak PROTAC:target protein affinity can be stabilized by high-affinity target:PROTAC:ligase trimer interactions, leading to efficient degradation. This study highlights design guidelines for generating potent PROTACs as well as possibilities for degrading undruggable proteins immune to traditional small-molecule inhibitors.

A trans-Atlantic examination of haddock Melanogrammus aeglefinus food habits

The food habits of Melanogrammus aeglefinus were explored and contrasted across multiple north-eastern and north-western Atlantic Ocean ecosystems, using databases that span multiple decades. The results show that among all ecosystems, echinoderms are a consistent part of M. aeglefinus diet, but patterns emerge regarding where and when M. aeglefinus primarily eat fishes v. echinoderms. Melanogrammus aeglefinus does not regularly exhibit the increase in piscivory with ontogeny that other gadoids often show, and in several ecosystems there is a lower occurrence of piscivory. There is an apparent inverse relationship between the consumption of fishes and echinoderms in M. aeglefinus over time, where certain years show high levels of one prey item and low levels of the other. This apparent binary choice can be viewed as part of a gradient of prey options, contingent upon a suite of factors external to M. aeglefinus dynamics. The energetic consequences of this prey choice are discussed, noting that in some instances it may not be a choice at all.

Quantifying alosine prey in the diets of marine piscivores in the Gulf of Maine

The objectives of this work were to quantify the spatial and temporal distribution of the occurrence of anadromous fishes (alewife Alosa pseudoharengus, blueback herring Alosa aestivalis and American shad Alosa sapidissima) in the stomachs of demersal fishes in coastal waters of the north-west Atlantic Ocean. Results show that anadromous fishes were detectable and quantifiable in the diets of common marine piscivores for every season sampled. Even though anadromous fishes were not the most abundant prey, they accounted for c. 5-10% of the diet by mass for several marine piscivores. Statistical comparisons of these data with fish diet data from a broad-scale survey of the north-west Atlantic Ocean indicate that the frequency of this trophic interaction was significantly higher within spatially and temporally focused sampling areas of this study than in the broad-scale survey. Odds ratios of anadromous predation were as much as 460 times higher in the targeted sampling as compared with the broad-scale sampling. Analyses indicate that anadromous prey consumption was more concentrated in the near-coastal waters compared with consumption of a similar, but more widely distributed species, the Atlantic herring Clupea harengus. In the context of ecosystem-based fisheries management, the results suggest that even low-frequency feeding events may be locally important, and should be incorporated into ecosystem models.

Non-invasive method for rapid bedside estimation of inotropy: theory and preliminary clinical validation

BACKGROUND

There are numerous techniques which attempt to quantify inotropy (or myocardial contractility). None has yet found general acceptance in anaesthesia and critical care as a practical method. We report a novel approach to the determination of inotropy as a bedside procedure which could identify low inotropy states in patients with clinical heart failure.

METHODS

We estimated the potential and kinetic energy delivered by the left ventricle using continuous-wave Doppler ultrasound (ultrasonic cardiac output monitor, Uscom, Sydney, Australia) and data available at the point of care. A formula to calculate effective inotropy [Smith-Madigan inotropy index (SMII)] was tested against historical haemodynamic data for 250 control subjects (ASA I patients from preoperative clinic) and 83 patients with acute left ventricular failure (LVF) of New York Heart Association Grade 4 (LVF group). The ratio of potential to kinetic energy (PKR) was investigated as a measure of arterial impedance.

RESULTS

Significant differences were found between the control and LVF groups for cardiac index, mean (range)=3.37 (2.84-5.32) vs 1.84 (1.43-2.26) litre min(-1) m(-2); stroke volume index (SVI), 49.2 (39-55) vs 34.3 (23-37) ml m(-2); systemic vascular resistance, 893 (644-1242) vs 1960 (1744-4048) dyn s cm(-5); SMII, 1.78 (1.35-2.24) vs 0.73 (0.43-0.97) W m(-2); and PKR, 29:1 (24-35:1) vs 124:1 (96-174:1), P<0.001 in each case. Normal ranges were calculated for SMII and PKR as mean (+/-1.96) standard deviations, yielding 1.6-2.2 W m(-2) for SMII, and 25-34:1 for PKR.

CONCLUSION

The method clearly identified the two clinical groups with no overlap of data points. The discriminant power of SMII and PKR may offer valuable diagnostic methods and monitoring tools in anaesthesia and critical care. This is the first report of normal ranges for SMII and PKR.

Synthesis and toxicity of some metabolites of the microbial degradation of synthetic naphthenic acids

Some ill-defined carboxylic acids, termed 'naphthenic acids' (NA), are best known as important constituents of the >720billionlitres of process-affected water associated with the expanding oil sands industries. Other NA are components of some immature and biodegraded crude oils and these may enter the environment via produced water discharges from oil production platforms. Yet others are used as biocides and in the manufacture of steel radial tyres and these may also enter the environment through disposal and/or weathering. The environmental fate of NA, including the mechanisms of biodegradation, therefore needs to be better understood. In order to better elucidate such mechanisms, previously we studied the biodegradation in the laboratory of some alkylcyclohexylbutanoic synthetic NA. However, we could only tentatively identify the metabolites produced. In the present study we report the synthesis and characterisation of six alkylcyclohexylethanoic NA. Each was characterised by gas chromatography-mass spectrometry (GC-MS; trimethylsilyl esters) and we show by co-chromatography that these were indeed the metabolites. Also, a preferential degradation of the trans- isomers was revealed. Assessment of the toxicity of the synthetic NA (Microtox assay), revealed that the relative toxicity of the alkylcyclohexylbutanoic acids was reduced by biotransformation to the alkylcyclohexylethanoic acids, as observed recently for the corresponding aromatic acids. Very recent studies have shown that at least one commercial NA mixture contains cyclohexylbutanoic and alkylcyclohexylethanoic acids, suggesting that the biotransformation of the acids studied herein may be quite relevant to the environmental fate of such acids. A similar study of the acid extractables of one oil sands process-affected water sample suggests that the synthetic acids may be less good 'models' for oil sands NA. The consortia of microbes present in oil sands process-affected water may also be different to those used herein. However, the heterogeneity of oil sands process water is well-known and further detailed studies will need to be made in order to establish whether degradation of oil sands NA proceeds by beta oxidation as observed for the acids herein, or whether the oil sands acids are more resistant to bioremediation.

Demonstration of ignition radiation temperatures in indirect-drive inertial confinement fusion hohlraums

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core.

You are what you eat, whenever or wherever you eat it: an integrative analysis of fish food habits in Canadian and U.S.A. waters

The degree to which fish diet differs by season and area, particularly over broad scales, was examined for the first time in temperate, contiguous north-west Atlantic Ocean waters by comparing food habit data for 10 species of fishes collected concurrently during the spring and autumn surveys in the U.S.A. (Gulf of Maine proper and Georges Bank) and in the summer survey in Canada (western Scotian Shelf and Bay of Fundy). For most species, there was a general concurrence among the three seasons and four areas: summer diets had the same dominant prey items as spring and autumn diets. Although a suite of multivariate analyses did elucidate some differences in specific proportions of the diet for these species across seasons and areas, the main prey did not substantially change for most of these species. These results suggest that there are (1) minimal differences in diet across season for these species at these taxonomic resolutions, (2) there are minimal differences in diet geographically for these species and (3) differences across species, as expected, are important. Many fisheries ecosystem and multispecies models are dependent on food habit data, where resolving seasonal and spatial differences in diet remains an important consideration; however, the present work implies that amalgamated estimates of diet from seasonal surveys may be a reasonable approach when no finer seasonal resolution exists, as long as due diligence is exercised.

Clinical and electrodiagnostic findings in copper deficiency myeloneuropathy

INTRODUCTION

Copper deficiency is an increasingly recognised cause of neurological impairment. This retrospective review highlights clinical and electrodiagnostic findings in patients diagnosed at our institution with copper deficiency.

METHODS

Clinical, radiographic and electrodiagnostic findings were reviewed in patients with evidence of copper deficiency. Patients with other potential causes of myelopathy or neuropathy were excluded.

RESULTS

The predominant clinical feature in all six patients was a sensory ataxia, resulting in marked gait unsteadiness. Nerve conduction studies and needle EMG were performed in all patients and revealed a mild to moderate distal, axonal, sensorimotor peripheral neuropathy. Median and tibial somatosensory evoked potentials were abnormal in all five patients in which it was performed, showing impaired conduction in central or proximal peripheral somatosensory pathways.

CONCLUSIONS

This pattern of electrodiagnostic findings suggests that impairment in somatosensory pathways demonstrated by somatosensory evoked potential testing is the main cause of the sensory ataxia in patients with copper deficiency.

A derivatisation and liquid chromatography/electrospray ionisation multistage mass spectrometry method for the characterisation of naphthenic acids

Naphthenic acids (NAs) are partially uncharacterised complex mixtures of carboxylic acids, resulting from the microbial oxidation of petroleum hydrocarbons. They are associated with the fouling of pipelines and process equipment in oil production and with corrosion in oil refineries. As by-products of the rapidly expanding oil (tar) sands industries, NAs are also pollutants and have proved to be toxic to a range of organisms. They also have important beneficial uses as fungicides, tyre additives and, paradoxically, also in the manufacture of corrosion inhibitors. These features make the characterisation of NAs an important goal for analytical chemists. Here we describe the synthesis of amide derivatives of NAs for characterisation by liquid chromatography/electrospray ionisation multistage mass spectrometry (LC/ESI-MS(n)). The method was applied to commercially available carboxylic acids, novel synthetic NAs, commercial NAs refined from crude oils, crude oil NAs and Athabasca oil sands NAs. In addition to confirming the number of alicyclic rings and length of alkyl side chain substituents (confirming information from existing methods), the MS(n) results provided further structural information. Most important of these was the finding that bi- to polycyclic acids containing ethanoate side chains, in addition to alkyl substituents, were widespread amongst the oil and oil sands NAs. The latter NAs are known end members of the beta-oxidation of NAs with even carbon number alkanoate chains. Since such NA mixtures are toxic, they should be targets for bioremediation. Bioremediation of NAs can also be monitored better by application of the methods described herein.

Observation of the suppression of the flux of cosmic rays above 4 x 10 (19) eV

The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.

Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV.

Copper deficiency myeloneuropathy resembling B12 deficiency: partial resolution of MR imaging findings with copper supplementation

Copper deficiency has been associated with a clinical syndrome, myeloneuropathy. Radiographic changes resembling B(12) deficiency in the cervical spinal cord have been described. We present a case of copper deficiency myeloneuropathy, with cervical MR imaging findings resembling B(12) deficiency, which partially reversed following copper supplementation. This is, to our knowledge, the first described case of radiographic improvement with copper supplementation.

The influence of xenon, nitrous oxide and nitrogen on gas bubble expansion during cardiopulmonary bypass

BACKGROUND AND OBJECTIVE

Xenon may have favourable applications in the setting of cardiac surgery. Its advantages include a desirable haemodynamic profile as well as potential cardiac and neuroprotective properties. However, its low solubility may lead to enhanced diffusion into enclosed gas spaces. The purpose of this study was to compare the effects of xenon (Xe), nitrous oxide (N2O) and nitrogen (N2) on gas bubble size during cardiopulmonary bypass (CPB).

METHODS

Rats were randomized to receive 70% Xe, 26% oxygen (O2), 4% carbon dioxide (CO2) (xenon group); 70% N2O, 26% O2, 4% CO2 (nitrous oxide group) or 70% N2, 26% O2, 4% CO2 (nitrogen group) during 90 min of normothermic CPB. Small gas bubbles (300-500 microL; n = 12 per group) were injected into a bubble chamber on the venous side of the bypass circuit. After 10 min of equilibration, they were removed for volumetric analysis.

RESULTS

The increase in bubble size was 2 +/- 2% with nitrogen, 17 +/- 6% with xenon (P = 0.0192 vs. nitrogen) and 63 +/- 23% with nitrous oxide (P = 0.0001 vs. nitrogen). The nitrous oxide group had significantly increased bubble size compared to the xenon group (P = 0.0001).

CONCLUSIONS

During CPB, xenon anaesthesia produced a small increase in gas bubble size compared to nitrogen. Nitrous oxide resulted in significantly larger bubbles compared to both nitrogen and xenon.

Structures of a blue-copper nitrite reductase and its substrate-bound complex

Copper-containing nitrite reductases (NiR's) have been conveniently subdivided into blue and green NiR's which are thought to be redox partners of azurins and pseudo-azurins, respectively. Crystal structures of two green NiR's have recently been determined. Alcaligenes xylosoxidans has been shown to have a blue-copper nitrite reductase (AxNiR) and two azurins with 67% homology both of which donate electrons to it effectively. The first crystal structure of a blue NiR (AxNiR) in its oxidized and nitrite-bound forms, with particular emphasis to the Cu sites, is presented. The Cu-Smet distance is the same as those in the green NiR's. Thus, the length of this interaction is unlikely to be responsible for differences in colour. Crystallographic data presented here taken together with structural data of other single Cu type-1 proteins and their mutants suggest that the displacement of Cu from the strong ligand plane is perhaps the cause for the differences in colour observed for otherwise 'classical' blue Cu centre. Nitrite is observed binding to the catalytic Cu in a bidentate fashion displacing the water molecule, offering a neat rationalization for the XAFS observation that the type-2 Cu-ligand distances increase on nitrite binding as a result of increased coordination. These results are discussed in terms of enzyme mechanism.

Pain and anxiety reduction using a manual stimulation distraction device when administering local analgesia oro-dental injections: a multi-center clinical investigation

OBJECTIVE

This study was designed to assess the effects of a manual stimulating distraction device (Isoflex referred to as Manual Stimulation Distraction Device or MSDD) for reducing pain and anxiety experienced with standard dental local anesthetic injections. Additionally, the memory recall effects on injection pain and anxiety were also explored.

METHODOLOGY

Patients from different dental clinics were identified by their practitioners as requiring dental procedures under local anesthesia, in the same area on both sides of the mouth. A local anesthetic solution was injected on either the left or right side at different times by random selection; one side using MSDD, while the opposite side used a solution without MSDD. Each patient acted as his or her own symmetrical split-mouth control. The same dentist administered both injections, using identical technique and equipment for each side. Forty-six patients used the MSDD first with the injection, while 54 used MSDD second when they received the injection. Using 10-point visual analogue nominal and ordinal scales, pain and stress were recorded by the patient each time after receiving the injection. The results were pooled and subjected to statistical analysis. Student's paired t-test was employed to test for significant differences in pain and anxiety (stress) when injections were administered with and without MSDD.

RESULTS

Results showed significant reductions in perceived pain and stress from local analgesia injections (p < 0.001) when MSDD was used. There was no correlation of pain reduction with age, gender, upper or lower jaw, with or without MSDD. There was a trend for pain and stress to be scored higher for those subjects who had a lower period since the first injection (POFI) scores. This was attributed to recent memory of pain, as POFI scores over one week were significantly lower (p < 0.05). Stress reduction for POFI scores greater than one week proved to be non-significant (p = 0.099).

CONCLUSION

In this study, MSDD was effective at reducing pain and stress experienced with local regional analgesic injections.

Motor unit number estimates in idiopathic Parkinson's disease

We previously reported changes in motor unit morphology in patients with Parkinson's disease (PD) using subjective and computerized quantitative electromyography. Now, we present data on motor unit number estimates (MUNE) to address the hypothesis of motor neuron dropout in PD. Twenty patients with PD and 20 age-matched control subjects were screened by clinical criteria and nerve conduction studies to exclude those with neuropathy. Motor unit number estimates in the extensor digitorum brevis and hypothenar group were assessed by three different MUNE techniques. The MUNE technique types included (1) the statistical method developed by Daube, (2) a threshold method, and (3) an F-wave method. The overall multivariate comparison for the six MUNE measurements was significantly lower for the patients than the controls (P=0.02). The only significant difference in the individual measures was found in the threshold MUNE method of the hypothenar group (P<0.05). These results are consistent with those of our previous work, and both support the hypothesis that mild motor neuron dropout occurs in idiopathic PD. However, MUNE methods characteristically have large standard deviations which make it difficult to detect small changes. Progress in decreasing the variance of MUNEs will facilitate their use in detecting small motor unit number changes in neurodegenerative disease.

Kroeyerina deetsorum n. sp. (Copepoda: Kroyeriidae) from the olfactory sacs of Atlantic sharpnose sharks (Rhizoprionodon terraenovae) captured in the Gulf of Mexico and northwestern Atlantic and first report of copepodids representing Kroyeriidae

Kroeyerina deetsorum n. sp. (Copepoda: Kroyeriidae) is described from female and male specimens collected from the olfactory sacs of Atlantic sharpnose sharks, Rhizoprionodon terraenovae (Richardson, 1836), captured in the Gulf of Mexico and northwestern Atlantic. Kroeyerina deetsorum is easily distinguished from known congeners by the extremely small size of its adults (i.e., females about 1.2 mm total length and males about 1.0 mm total length). Kroeyerina deetsorum is also distinguished from its congeners by possessing a subquadrate rostrum without lobes or upturned horns. It is suspected that K. deetsorum belongs to a clade within Kroeyerina whose members only infect sharks. This report also provides first descriptions of a nauplius representing Kroeyerina and copepodids representing Kroyeriidae. The early-stage copepodid of K. deetsorum lacks a frontal organ and frontal filament and uses its chelate antennae to attach to its host.

The frequency of carpal tunnel syndrome in computer users at a medical facility

A survey was done of employees who were identified as frequent computer users. Although 29.6% of the employees reported hand paresthesias, only 27 employees (10.5%) met clinical criteria for carpal tunnel syndrome, and in 9 (3.5%) the syndrome was confirmed by nerve conduction studies. Affected and unaffected employees had similar occupations, years using a computer, and time using the computer during the day. The frequency of carpal tunnel syndrome in computer users is similar to that in the general population.

Changes in speech following maxillary distraction osteogenesis

OBJECTIVE

The purpose of this study was to describe changes in articulation and velopharyngeal function following maxillary distraction osteogenesis.

DESIGN

This is a descriptive, post hoc clinical report comparing the performance of patients before and after maxillary distraction. The independent variable was maxillary distraction while the dependent variables were resonance, articulation errors, and velopharyngeal function.

SETTING

The data were collected at a tertiary health care center in Chicago.

PATIENTS

The data from pre- and postoperative evaluations of 18 maxillary distraction patients were used.

OUTCOME MEASURES

The outcome measures were severity of hypernasality and hyponasality, velopharyngeal orifice size as estimated using the pressure-flow technique, and number and type of articulation errors.

RESULTS

At the long-term follow-up, 16.7% exhibited a significant increase in hypernasality. Seventy-five percent of patients with preoperative hyponasality experienced improved nasal resonance. Articulation improved in 67% of patients by the 1-year follow-up.

CONCLUSIONS

In a predominately cleft palate population, the risk for velopharyngeal insufficiency following maxillary distraction is similar to the risk observed in Le Fort I maxillary advancement. Patients being considered for maxillary distraction surgery should receive pre- and postoperative speech evaluations and be counseled about risks for changes in their speech.

Changes in speech following unilateral mandibular distraction osteogenesis in patients with hemifacial microsomia

OBJECTIVE

The purpose of this study was to describe changes in articulation, resonance, and velopharyngeal function following mandibular distraction osteogenesis.

DESIGN

This is a descriptive, post hoc study comparing the performance of patients on measures of articulation, resonance, and velopharyngeal function before and after mandibular distraction.

SETTING

The data were collected at a tertiary health care center located in Chicago.

PATIENTS

The clinical data from preoperative and postoperative evaluations of seven mandibular distraction patients were used.

OUTCOME MEASURES

The outcome measures were number of articulation errors, severity of hypernasality and audible nasal emission, and velopharyngeal orifice size as estimated using the pressure-flow technique.

RESULTS

Immediately after distraction, 28% (2/7) experienced a temporary deterioration in articulation and 42% (3/7) experienced a deterioration in nasal resonance. But by the long-term follow-up evaluation, all had returned to their preoperative levels. Pressure-flow test results generally support the perceptual findings.

CONCLUSIONS

Patients being considered for mandibular distraction surgery should receive preoperative and postoperative speech evaluations and be counseled about risks for changes in their speech following surgery.

Transition state complexes of the Klebsiella pneumoniae nitrogenase proteins. Spectroscopic properties of aluminium fluoride-stabilized and beryllium fluoride-stabilized MgADP complexes reveal conformational differences of the Fe protein

Stable inactive 2 : 1 complexes of the Klebsiella pneumoniae nitrogenase components (Kp2/Kp1) were prepared with ADP or the fluorescent ADP analogue, 2'(3')-O-[N-methylanthraniloyl] ADP and AlF(4)(-) or BeF(3)(-) ions. By analogy with published crystallographic data [Schindelin et al. (1997) Nature 387, 370-376)], we suggest that the metal fluoride ions replaced phosphate at the two ATP-binding sites of the iron protein, Kp2. The beryllium (BeF(x)) and aluminium (AlF(4)(-)) containing complexes are proposed to correspond to the ATP-bound state and the hydrolytic transition states, respectively, by analogy with the equivalent complexes of myosin [Fisher et al. (1995) Biochemistry 34, 8960-8972]. (31)P NMR spectroscopy showed that during the initial stages of complex formation, MgADP bound to the complexed Kp2 in a manner similar to that reported for isolated Kp2. This process was followed by a second step that caused broadening of the (31)P NMR signals and, in the case of the AlF4- complex, slow hydrolysis of some of the excess ADP to AMP and inorganic phosphate. The purified BeFx complex contained 3.8 +/- 0.1 MgADP per mol Kp1. With the AlF(4)(-) complex, MgAMP and adenosine (from MgAMP hydrolysis) replaced part of the bound MgADP although four AlF(4)(-) ions were retained, demonstrating that full occupancy by MgADP is not required for the stability of the complex. The fluorescence emission maximum of 2'(3')-O-[N-methylanthraniloyl] ADP was blue-shifted by 6-8 nm in both metal fluoride complexes and polarization was 6-9 times that of the free analogue. The fluorescence yield of bound 2'(3')-O-[N-methylanthraniloyl] ADP was enhanced by 40% in the AlF(4)(-) complex relative to the solvent but no increase in fluorescence was observed in the BeFx complex. Resonance energy transfer from conserved tyrosine residues located in proximity to the Kp2 nucleotide-binding pocket was marked in the AlF(4)(-) complex but minimal in the BeFx fluoride complex, illustrating a clear conformational difference in the Fe protein of the two complexes. Our data indicate that complex formation during the nitrogenase catalytic cycle is a multistep process involving at least four conformational states of Kp2: similar to the free Fe protein; as initially complexed with detectable (31)P NMR; as detected in mature complexes with no detectable (31)P NMR; in the AlF(4)(-) complex in which an altered tyrosine interaction permits resonance energy transfer with 2'(3')-O-[N-methylanthraniloyl] ADP.

Time for a new paradigm in pediatric medical education: teaching neonatal resuscitation in a simulated delivery room environment

OBJECTIVES

Acquisition and maintenance of the skills necessary for successful resuscitation of the neonate are typically accomplished by a combination of completion of standardized training courses using textbooks, videotape, and manikins together with active participation in the resuscitation of human neonates in the real delivery room. We developed a simulation-based training program in neonatal resuscitation (NeoSim) to bridge the gap between textbook and real life and to assess trainee satisfaction with the elements of this program.

METHODS

Thirty-eight subjects (physicians and nurses) participated in 1 of 9 full-day NeoSim programs combining didactic instruction with active, hands-on participation in intensive scenarios involving life-like neonatal and maternal manikins and real medical equipment. Subjects were asked to complete an extensive evaluation of all elements of the program on its conclusion.

RESULTS

The subjects expressed high levels of satisfaction with nearly all aspects of this novel program. Responses to open-ended questions were especially enthusiastic in describing the realistic nature of simulation-based training. The major limitation of the program was the lack of fidelity of the neonatal manikin to a human neonate.

CONCLUSION

Realistic simulation-based training in neonatal resuscitation is possible using current technology, is well received by trainees, and offers benefits not inherent in traditional paradigms of medical education.

Motor unit changes in sporadic idiopathic Parkinson's disease

We studied motor unit changes in 20 patients with Parkinson's disease (PD) and 20 age-matched control subjects to look for evidence of motorneuron degeneration in sporadic idiopathic PD. Patients and control subjects were screened by clinical criteria and nerve conduction studies to exclude those with peripheral neuropathic processes. Changes in motor unit morphology were investigated with subjective and computerized quantitative electromyography (QEMG) of the anterior tibialis (AT) and first dorsal interosseous. Multivariate comparisons showed a significant difference in the QEMG analysis for motor unit enlargement in patients with PD versus control subjects. Some of the univariate comparisons for both the subjective and QEMG analyses of the AT were also significant. These results demonstrate that motorneuron drop-out with reinnervation occurs in sporadic idiopathic PD. In summary, our findings provide evidence that clinically silent motorneuron disease occurs in typical cases of sporadic idiopathic PD, suggesting that it may be a normal part of the pathologic picture of PD. Any hypothesis concerning the pathogenic mechanism of PD would need to take into account such a finding.

Laryngeal airway resistance in cleft palate children with complete and incomplete velopharyngeal closure

OBJECTIVE

This study investigated the effect of velopharyngeal insufficiency on aerodynamic measures of laryngeal function in children with cleft palate.

DESIGN

Data were analyzed using analysis of covariance. The independent variable was velopharyngeal closure, and the dependent variables were laryngeal resistance, laryngeal airflow, and transglottal pressure. Age and gender were covariates.

SETTING

The data were collected at The Craniofacial Center, University of Illinois, a tertiary health care center located in Chicago.

PATIENTS

Thirty-six children with cleft palate were recruited from among the patients at The Craniofacial Center. Ten children with velopharyngeal areas >5 mm2 during oral speech were placed in the incomplete closure group, while 26 children with areas <1 mm2 were placed in the complete closure group.

OUTCOME MEASURES

The three dependent variables (transglottal pressure, transglottal airflow, and laryngeal resistance) were measured.

RESULTS

Laryngeal resistance and transglottal pressure were significantly higher, and transglottal airflow was significantly lower in the group with complete closure.

CONCLUSIONS

In summary, cleft palate patients with complete velopharyngeal closure exhibited higher laryngeal resistances than those with incomplete closure.

Symptoms of 100 patients with electromyographically verified carpal tunnel syndrome

To determine the symptoms of carpal tunnel syndrome (CTS), screening evaluations were performed in 244 consecutive patients with sensory symptoms in the hand and unequivocal slowing of median nerve conduction at the wrist. This yielded 100 patients thought to have no explanation other than CTS for their upper limb complaints. These patients completed a hand symptom diagram (HSD) and questionnaire (HSQ) about their symptoms. CTS symptoms were most commonly reported in median and ulnar digits, followed by median digits only and a glove distribution. Unusual sensory patterns were reported by some patients. Based on the HSQ, paresthesias or pain proximal to the wrist occurred in 36.5% of hands. The usefulness of the HSD and HSQ for diagnosis was determined by asking three physicians, blinded to the diagnosis, to rate the likelihood of CTS in the patients with CTS and in 50 patients with other causes of upper extremity paresthesia. The sensitivities of the instruments ranged from 54.1% to 85.5%. Combining the HSD and HSQ ratings increased the range of sensitivities to 79.3% to 93.7%.

New insights into structure-function relationships in nitrogenase: A 1.6 A resolution X-ray crystallographic study of Klebsiella pneumoniae MoFe-protein

The X-ray crystal structure of Klebsiella pneumoniae nitrogenase component 1 (Kp1) has been determined and refined to a resolution of 1.6 A, the highest resolution reported for any nitrogenase structure. Models derived from three 1.6 A resolution X-ray data sets are described; two represent distinct oxidation states, whilst the third appears to be a mixture of both oxidized and reduced states (or perhaps an intermediate state). The structures of the protein and the iron-molybdenum cofactor (FeMoco) appear to be largely unaffected by the redox status, although the movement of Ser beta90 and a surface helix in the beta subunit may be of functional significance. By contrast, the 8Fe-7S P-cluster undergoes discrete conformational changes involving the movement of two iron atoms. Comparisons with known component 1 structures reveal subtle differences in the FeMoco environment, which could account for the lower midpoint potential of this cluster in Kp1. Furthermore, a non-proline- cis peptide bond has been identified in the alpha subunit that may have a functional role. It is within 10 A of the FeMoco and may have been overlooked in other component 1 models. Finally, metal-metal and metal-sulphur distances within the metal clusters agree well with values derived from EXAFS studies, although they are generally longer than the values reported for the closely related protein from Azotobacter vinelandii. A number of bonds between the clusters and their ligands are distinctly longer than the EXAFS values, in particular, those involving the molybdenum atom of the FeMoco.

Structural and kinetic evidence for an ordered mechanism of copper nitrite reductase

The crystallographic structures of several copper-containing nitrite reductases are now available. Despite this wealth of structural data, no definitive information is available as to whether the reaction proceeds by an ordered mechanism where nitrite binds to the oxidised type 2 site, followed by an internal electron transfer from the type 1 Cu, or whether binding occurs to the reduced type 2 Cu centre, or a random mechanism operates. We present here the first structural information on both types of Cu centres for the reduced form of NiR from Alcaligenes xylosoxidans (AxNiR) using X-ray absorption spectroscopy. The reduced type 2 Cu site EXAFS shows striking similarity to the EXAFS data for reduced bovine superoxide dismutase (Cu2Zn2 SOD), providing strong evidence for the loss of the water molecule from the catalytic Cu site in NiR on reduction resulting in a tri-coordinate Cu site similar to that in Cu2Zn2 SOD. The reduced type 2 Cu site of AxNiR is shown to be unable to bind inhibitory ligands such as azide, and to react very sluggishly with nitrite leading to only a slow re-oxidation of the the type 1 centre. These observations provide strong evidence that turnover of AxNiR proceeds by an ordered mechanism in which nitrite binds to the oxidised type 2 Cu centres before electron transfer from the reduced type 1 centre occurs. We propose that the two links between the Cu sites of AxNiR, namely His129-Cys130 and His89-Asp92-His94 are utilised for electron transfer and for communicating the status of the type 2 Cu site, respectively. Nitrite binding at type 2 Cu is sensed by the proton abstracting group Asp92 and the type 2 Cu ligand His94, and relayed to the type 1 Cu site via His89 thus triggering an internal electron transfer. The similarity of the type 2 Cu NiR catalytic site to the reduced Cu site of SOD is examined in some detail together with the biochemical evidence for the SOD activity of AxNiR.

Integrative research review of risk behaviors among adolescents in rural, suburban, and urban areas

PURPOSE

The purpose of this integrative review was to describe the state of the science regarding adolescent risk behaviors, with particular emphasis on comparisons among rural, urban, and suburban populations.

METHOD

The review was done at two levels, moving from the major national survey studies which included data collected in the late 1980s up to 1993, to more focused topical areas including studies with data collection and publication between 1990 and 1996 within each identified category of adolescent health issues. A total of 137 published works across several disciplines were reviewed. Suggestions for clinical practice were drawn from the significant research findings. In addition, risk behaviors were compared to national baseline data and objectives.

RESULTS

The level of research in this topic area was primarily descriptive. Currently, only a small portion of the national objectives for decreasing adolescent risk behaviors have been met. Successful intervention programs, although few in number, usually included not only topical education but also adolescent interaction with peers and support systems to raise awareness and change behaviors.

CONCLUSIONS

The risk behaviors for the adolescent population as a whole have been well described. Education alone is not sufficient to change behaviors. Objective outcomes must be identified and health care providers need to use research findings in their practice with adolescents. It is time to intervene with developmentally and culturally appropriate strategies. There was a large gap in the literature regarding risk behaviors and protective factors for rural adolescents. The few studies that included subjects from rural settings indicated that the view that rural adolescents are engaged in fewer or less severe risk behaviors is misleading.

Biochemical characterization and solution structure of nitrous oxide reductase from Alcaligenes xylosoxidans (NCIMB 11015)

Nitrous oxide reductase (N2OR) is the terminal enzyme involved in denitrification by microbes. No three-dimensional structural information has been published for this enzyme. We have isolated and characterised N2OR from Alcaligenes xylosoxidans (AxN2OR) as a homodimer of M(r) 134,000 containing seven to eight copper atoms per dimer. Comparison of sequence and compositional data with other N2ORs suggests that AxN2OR is typical and can be expected to have similar domain folding and subunit structure to other members of this family of enzymes. We present synchrotron X-ray-scattering data, analysed using a model-independent method for shape restoration, which gave a approximately 20 A resolution structure of the enzyme in solution, providing a glimpse of the structure of any N2OR and shedding light on the molecular architecture of the molecule. The specific activity of AxN2OR was approximately 6 mumol of N2O reduced.min-1. (mg of protein)-1; N2OR activity showed both base and temperature activation. The visible spectrum exhibited an absorption maximum at 550 nm with a shoulder at 635 nm. On oxidation with K3Fe(CN)6, the absorption maximum shifted to 540 nm and a new shoulder at 480 nm appeared. Reduction under anaerobic conditions resulted in the formation of an inactive blue form of the enzyme with a broad absorption maximum at 650 nm. As isolated, the enzyme shows an almost featureless EPR spectrum, which changes on oxidation to give an almost completely resolved seven-line hyperfine signal in the gII region, g = 2.18, with AII = 40 G, consistent with the enzyme being partially reduced as isolated. Both the optical and EPR spectra of the oxidized enzyme are characteristic of the presence of a CuA centre.

Spinal anesthesia for cesarean section. 1963

Safety in spinal anesthesia for cesarean section is achieved by strict adherence to the cardinal principles of proper evaluation and selection of patients, the use of prophylactic vasopressors, preanesthetic establishment of a reliable intravenous channel, small doses of the local anesthetic, close monitoring and maintenance of systolic blood pressure above 100 mm. Hg, and avoidance of ergot compounds in the presence of vasopressors.

Nucleotide binding by the nitrogenase Fe protein: a 31P NMR study of ADP and ATP interactions with the Fe protein of Klebsiella pneumoniae

Investigation of the interaction of MgADP- and MgATP2- with the Fe protein of Klebsiella pneumoniae nitrogenase by 31P NMR showed that the adenine nucleotides are reversibly bound in slow exchange with free nucleotides. Dissociation of the MgADP--Fe protein complex was slow enough to enable its isolation by gel filtration, thus permitting the assignment of resonances to bound nucleotides. Spectra of ADP bound to Kp2 were similar to spectra of ADP bound to the myosin motor domain. Oxidative inactivation of a Kp2-MgADP- complex with excess ferricyanide ion eliminated exchange between bound and free ADP, indicating that the intact iron sulphur cluster, located 20 A from the binding sites, is required for the reversible binding of MgADP-. A change in conformation on controlled oxidation of Kp2 with indigocarmine increased the chemical shift of the beta phosphate resonance of bound MgADP-. Both oxidized and reduced conformers were observed transiently in the absence of dithionite. The 31P resonances of both the beta and gamma phosphates of bound MgATP2- indicated major changes in environment and labilization of both groups on binding to the Fe protein. Highly purified Kp2 slowly hydrolysed ATP, resulting in mixtures of bound nucleotides. Partial occupation of Kp2 MgATP2--binding sites (N=1.9+/-0.2, Kd=145 microM) in concentrated protein solutions was demonstrated by flow dialysis. Scatchard plots of data for bound and free ligand obtained after equilibration with Kp2 were linear and no co-operative interactions were detected. We conclude that MgADP- stabilizes the oxidized Fe protein conformer and this conformation in turn triggers the dissociation of the Fe protein from the MoFe protein in the rate-limiting step of the overall process of dinitrogen reduction.

Assessment of clinical performance during simulated crises using both technical and behavioral ratings

BACKGROUND

Techniques are needed to assess anesthesiologists' performance when responding to critical events. Patient simulators allow presentation of similar crisis situations to different clinicians. This study evaluated ratings of performance, and the interrater variability of the ratings, made by multiple independent observers viewing videotapes of simulated crises.

METHODS

Raters scored the videotapes of 14 different teams that were managing two scenarios: malignant hyperthermia (MH) and cardiac arrest. Technical performance and crisis management behaviors were rated. Technical ratings could range from 0.0 to 1.0 based on scenario-specific checklists of appropriate actions. Ratings of 12 crisis management behaviors were made using a five-point ordinal scale. Several statistical assessments of interrater variability were applied.

RESULTS

Technical ratings were high for most teams in both scenarios (0.78 +/- 0.08 for MH, 0.83 +/- 0.06 for cardiac arrest). Ratings of crisis management behavior varied, with some teams rated as minimally acceptable or poor (28% for MH, 14% for cardiac arrest). The agreement between raters was fair to excellent, depending on the item rated and the statistical test used.

CONCLUSIONS

Both technical and behavioral performance can be assessed from videotapes of simulations. The behavioral rating system can be improved; one particular difficulty was aggregating a single rating for a behavior that fluctuated over time. These performance assessment tools might be useful for educational research or for tracking a resident's progress. The rating system needs more refinement before it can be used to assess clinical competence for residency graduation or board certification.

Evaluation of a medical diagnosis system using simulator test scenarios

This paper describes an informal but systematic method for how to test and verify a knowledge-based system in a large open-ended medical target domain. The system used is Guardian, an intelligent system for monitoring and diagnosis of post-cardiac surgery patients in an intensive-care unit. The knowledge base is tested and verified by running the system on a series of realistic test scenarios, both with an embedded simulator and with an external simulation system. The same scenarios are presented to human test subjects, making it possible to compare and analyze the performance of the knowledge-based system with that of human physicians. The use of simulators instead of clinical data also means that it is possible to test crucial scenarios which occur seldom in medical practice. Our results show that a system like Guardian might indeed be useful in medical care.

Objective assessment of the breathe-right device during exercise in adult males

In order to improve nasal breathing during competition, many athletes recently have been wearing a spring-loaded, external nasal dilator referred to as the Breathe-Right device (BRD). Although there are many subjective claims that this device improves breathing during exercise, there are currently no controlled studies documenting its efficacy. To determine objectively whether the device improves the nasal airway, 20 subjects (10 Caucasian and 10 African-American) were studied during rest and after 15 minutes of exercise using anterior rhinomanometry and acoustic rhinometry to measure changes in airway resistance and minimal cross-sectional area, respectively. We found that the BRD exerts its main effect in the region of the nasal valve improving the airway an overall 21% in our group of subjects. This anatomic improvement in nasal airway resulted in an overall 27% reduction in nasal resistance in the Caucasian group. However, in the African-American group, a wider range of resistance changes was observed with application of the BRD with significant improvement in nasal resistance in some subjects but paradoxical worsening in others. In the African-American group as a whole, no significant change in nasal resistance occurred with application of the BRD. These measured differences are likely due to variations in nasal anatomy that exist not only between races but also between individuals within a given race. In addition, this study confirms the well known decongestant effects of exercise providing anatomic data with acoustic rhinometry not previously documented in the literature. Overall improvement in nasal airway seen with application of the BRD occurred independent of these exercise-related decongestant effects.

pH-dependence for binding a single nitrite ion to each type-2 copper centre in the copper-containing nitrite reductase of Alcaligenes xylosoxidans

The first quantitative characterization of the interaction of NO2(-) with the Cu-containing dissimilatory nitrite reductase (NiR) of Alcaligenes xylosoxidans using steady-state kinetics, equilibrium gel filtration and EPR spectroscopy is described. Each molecule of this protein consists of three equivalent subunits, each containing a type-1 Cu atom and also a type-2 Cu atom at each subunit interface. Enzyme activity increased in a biphasic manner with decreasing pH, having an optimum at pH 5.2 and a plateau between pH 6.1 and 5.8. Equilibrium gel filtration showed that binding of NO2(-) to the oxidized NiR was also pH-dependent. At pH 7.5, no binding was detectable, but binding was detectable at lower pH values. At pH 5.2, the concentration-dependence for binding of NO2(-) to the enzyme showed that approx. 4.1 NO2(-) ions bound per trimeric NiR molecule. Unexpectedly, NiR deficient in type-2 Cu centres bound 1.3 NO2(-) ions per trimer. When corrected for this binding, a value of 3 NO2(-) ions bound per trimer of NiR, equivalent to the type-2 Cu content. The NO2(-)-induced changes in the EPR parameters of the type-2 Cu centre of the oxidized enzyme showed a similar pH-dependence to that of the activity. Binding constants for NO2(-) at a single type of site, after allowing for the non-specifically bound NO2(-), were 350+/-35 microM (mean+/-S.E.M.) at pH 7.5 and <30 microM at pH 5.2. The apparent Km for NO2(-) with saturating concentrations of dithionite as reductant was 35 microM at pH 7.5, which is 10-fold tighter than for the oxidized enzyme, and is compatible with an ordered mechanism in which the enzyme is reduced before NO2(-) binds.

Covalent modification of nitrogenase MoFe protein by ADP

MgADP- reacted with the nitrogenase molybdenum-iron (MoFe) protein of Klebsiella pneumoniae (Kp1) over a period of 2 h to yield a stable, catalytically active conjugate. The isolated protein exhibited a new, broad 31P NMR resonance at -1 p.p.m. lacking phosphorus J coupling. The adenine ring of [8-14C]ADP remained associated with the conjugate. A covalently bound nucleotide was identified as AMP by NMR and TLC. Extended dialysis of Kp1 against MgADP- resulted in further AMP binding at the protein surface. ADP was initially bound tightly to Kp1 at a site distinct from the AMP sites. ATP did not replace ADP. The time course of the formation of the Kp1-AMP was altered by the nitrogenase iron protein (Kp2) and was dependent on redox potential. Kp1-AMP was stable to concentration and oxidation with ferricyanide ion at -350 mV. Slow hydrolysis of Kp1-AMP over a period of 6 h yielded AMP and unaltered Kp1. The adenine ring of ADP exchanged with adenine of MgATP2- during reductant-limited turnover of nitrogenase under N2, indicating reversibility of ATP hydrolysis at 15 degrees C. [32P]Pi exchanged with the terminal phosphate group of both ADP and ATP on incubation with Kp1. 32P exchange and the catalytic activity of Kp1 were inhibited by a 20-fold molar excess of the lysine-modifying reagent, o-phthalaldehyde (OPT). Preincubation with MgADP- protected against OPT inactivation. Two potentially reactive lysine residues on the alpha chain of the MoFe protein near a putative hydrophobic docking site for the nitrogenase Fe protein are proposed as sites of OPT and nucleotide binding. Azotobacter vinelandii MoFe protein (Av1) also formed an AMP adduct but Kp2 did not. Catalase did not interact with ADP. The reactions of the nitrogenase MoFe protein with adenine nucleotides have no counterpart in known protein-nucleotide interactions.

The first glimpse of a complex of nitrogenase component proteins by solution X-ray scattering: conformation of the electron transfer transition state complex of Klebsiella pneumoniae nitrogenase

An essential feature of the mechanism of nitrogenase, the enzyme responsible for biological nitrogen fixation, is the formation of a transient electron transfer complex between the MoFe protein containing the active site at which N2 is reduced, and the Fe protein, which functions as a specific electron donor to the MoFe protein. We have obtained high quality solution X-ray scattering data using synchrotron X-rays of a stable putative electron transfer complex, (MoFe-protein)(Fe-protein.ADP.AIF4)2, of Klebsiella pneumoniae and used the model-independent approach based on the multipole expansion method to provide a stable and unique shape restoration at approximately 15 A resolution. The biological significance of this first molecular structure of a nitrogenase complex is discussed.

Crystallization and preliminary X-ray studies of nitrogenase component 1 (the MoFe protein) from Klebsiella pneumoniae

Two crystal forms of component 1 (the MoFe protein) of nitrogenase from Klebsiella pneumoniae have been isolated and characterized. The triclinic form has cell dimensions a = 76.0, b = 109.6, c = 144.6 A, alpha = 80.3, beta = 74.9 and gamma = 69.6 degrees, diffracts to around 3.0 A and has two molecules in the asymmetric unit. The monoclinic form belongs to space group P2(1) with a = 76.6, b = 127.8, c = 109.1 A and beta = 104.6 degrees (frozen at 100 K), diffracts to 1.5 A and has one molecule in the asymmetric unit. At this resolution the outstanding questions concerning the structure and the operation of the enzyme, in particular the linkage between the Fe(4)S(4) units in the P clusters, the true geometry of the apparently trigonal Fe atoms in the FeMoco and the reduction site itself, should be answerable.

Effect of septal perforations on measures of nasal resistance

OBJECTIVE

The purpose of this investigation was to determine the effect of septal perforations on posterior and anterior rhinomanometric measures of nasal resistance in an analog model.

DESIGN

The data were analyzed using a repeated-measures ANOVA. Nasal resistance was the dependent variable, while type of rhinomanometry, septal perforation size, and position of resistance (proximal vs. distal) were nominal scale independent variables.

PARTICIPANTS

The analog model used in this study was similar to that described by Warren and Devereux (1966), except that the nasal cavities of the model were modified to create septal perforations.

OUTCOME MEASURES

The main dependent measure was nasal resistance.

RESULTS

An Important finding of this investigation was that septal perforations resulted in large differences (> 3 cm H2O/L/sec) between posterior and anterior nasal resistance values in the bilateral proximal resistor condition.

CONCLUSIONS

Anterior rhinomanometry may underestimate true nasal resistance when a septal perforation is present, because the septal perforation prevents accurate measurement of nasopharyngeal pressure. Posterior rhinomanometric measures should accurately reflect nasal resistance despite septal perforations, because the perforation does not invalidate the estimate of nasopharyngeal pressure.

Isolation and characterization of nitrogenase MoFe protein from the mutant strain pHK17 of Klebsiella pneumoniae in which the two bridging cysteine residues of the P-clusters are replaced by the non-coordinating amino acid alanine

Nitrogenase MoFe protein (Kp1) from the mutant strain pHK17 or Klebsiella pneumoniae has been purified to give three catalytically active fractions. In this mutant, each of the two bridging cysteine ligands to the P-clusters, alpha-Cys-89 and beta-Cys-94, has been replaced by a non-coordinating residue, alanine. SDS/PAGE and earlier native gels showed that the three fractions retained the normal alpha 2 beta 2 tetrameric form of wild-type Kp1; therefore we conclude that in each of the fractions the subunits are folded differently, thus resulting in different surface charges and allowing separation of the fractions on ion-exchange chronatography. Earlier EPR and magnetic CD data had shown that the mutant fractions contain P-clusters, and thus the mutated residues are not as essential for maintaining the integrity of the P-clusters as they appear from the X-ray structure. The specific activity of each of the three fractions was less than that of wild-type Kp1, the most active fraction having only 50% of wild-type activity. No change in substrate specificity or in the relative distribution of electrons to various substrates was found. The relationship between ATP hydrolysis and substrate-reducing activity, the EPR spectra of the S = 3/2 spin state of the iron-molybdenum cofactor (FeMoco) and the pH profile of acetylene-reduction activities of the three fractions did not differ significantly from those exhibited by wild-type Kp1. The specific activities of the three mutant fractions and of wild-type Kp1 were linearly proportional to the intensity of the S = 3/2 EPR signal from the FeMoco centres. This implies that those molecules of the three mutant fractions and the wild-type protein that contain EPR-active FeMoco are fully active, i.e. that the Cys to Ala substitution of the P-cluster ligands does not affect the specific activity of the protein. This in turn implies that the P-clusters are not directly associated with the rate-limiting step in enzyme turnover. We conclude that the lower specific activities of the mutant fractions are observed because the fractions are mixtures of species containing a full complement of FeMoco and P-clusters and species lacking some or all of these clusters. On the basis of the Mo contents and EPR spectroscopy of the mutant fractions, we propose that the loss of the P-clusters causes (i) the physical loss or inhibition of binding of some FeMoco; (ii) the EPR and catalytic inactivation of some FeMoco; and/or (iii) the incorporation of a FeMoco-like species into the FeMoco site of the mutant molecules.

Long-term follow-up of tracheoesophageal puncture results

Since its introduction by Blom and Singer in 1980, tracheoesophageal puncture with a voice prosthesis has become the most frequently recommended choice for speech rehabilitation of total laryngectomies. Many studies have reviewed the initial speech acquisition success rates following tracheoesophageal puncture; however, long-term follow-up in these initial successes has been lacking. In addition, factors predictive of long-term success with tracheoesophageal speech have not been defined. Over a 10-year period, we retrospectively reviewed all total laryngectomy patients, including those who have undergone primary or secondary tracheoesophageal puncture, at the University of Illinois Hospital and Clinics and the Westside Veterans Administration Hospitals. Survival in the total laryngectomy cohort of 202 patients ranged from 35% to 50%. Forty of these patients underwent tracheoesophageal puncture, in whom survival was 75%. Short-term success with tracheoesophageal speech was approximately 70% for our patients, while long-term success was achieved in 66%. Despite low socioeconomic status and relatively high alcoholism rates, successful maintenance of tracheoesophageal speech was achieved in the majority of cases. Tracheoesophageal speech should therefore be considered as a primary method of vocal rehabilitation in all patients undergoing total laryngectomy.

Human SY5Y neuroblastoma cell interactions with laminin isoforms: neurite outgrowth on laminin-5 is mediated by integrin alpha 3 beta 1

Laminin (Ln) isoforms may play important roles in neuronal development, particularly axon guidance, but neural receptors mediating interactions with Ln are not entirely understood. In this paper, we have compared the adhesive and process outgrowth activities of a human neuroblastoma cell line SY5Y on various laminin isoforms. Cell adhesion and process outgrowth were examined on murine Ln-1 (Englebreth-Holm-Swarm sarcoma laminin), human placental Ln-1 (human Ln-1[p]), human Ln-2 (merosin), human Ln-5 (kalinin/epiligrin/nicein), and human foreskin keratinocyte extracellular matrix extract (human HFK-ECM). Ln-5 was shown to evoke process outgrowth in amounts comparable to other Ln isoforms. Antibody perturbation experiments showed that adhesion and process outgrowth on murine Ln-1 was primarily mediated by the integrin alpha 1 beta 1, whereas adhesion and outgrowth on human Ln-5 and human HFK-ECM were mediated by alpha 3 beta 1. Adhesion to human Ln-1(p) and Ln-2 was not blocked by addition of anti-alpha 1 or anti-alpha 3 antibodies alone, but adhesion was partially perturbed when these antibodies were added in combination. Process outgrowth on human Ln-1(p) was blocked when either anti-alpha 3 or anti-beta 1 antibodies were added, indicating that alpha 3 beta 1 is the primary integrin heterodimer responsible for process extension on this substrate. These results demonstrate that Ln-5 and other Ln isoforms support comparable levels of adhesion and process outgrowth, but different integrin heterodimers, alone and in combination, are used by SY5Y cells to mediate responses.