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.

Determinants of prolonged oral cecal transit time during late phase pregnancy

We examined the course of delayed oral cecal transit time (OCTT) and the impact of different variables in late pregnancy. Thirty-three women in late trimester were evaluated and 29 were re-tested post partum. Results were compared with 17 controls. A breath hydrogen test was used to measure OCTT. The impact of 3 demographic and 5 biochemical parameters was evaluated. Oral cecal transit time (99.2 +/- 7.8 min) during pregnancy was significantly prolonged compared both with controls (63.5 +/- 8.7 min) (p = 0.0042) and post partum (68.5 +/- 6.4 min) (p < 0.002). However, 40% during pregnancy had a normal OCTT. Post partum, 8 (29.6%) continued to have delayed OCTT. Serum free T4 levels were significantly lower than in controls (p < 0.0001) and post partum (p < 0.001), but did not correlate with OCTT. Gravidity rank correlated with OCTT (p = 0.022). By multivariate analysis, only 17% of the observed variability during pregnancy could be explained by these parameters. In controls, a formula including progesterone and gastrin levels was significant in explaining 54.7% of variability. Application of both formulae to post-partum returnees overpredicted OCTT; however, the one from pregnancy was more accurate. We conclude that in pregnancy multiple factors account for delayed OCTT and these may be different from controls and post partum. Pregnancy may still influence OCTT post partum.

Pressure-flow differences in performance during production of the CV syllables /pi/ and /pa/

Inconsistencies in velopharyngeal function were observed to have been reported in pressure-flow reports. This article introduces our findings from a sample of pressure-flow records and discusses possible implications for management. A retrospective review of the pressure-flow records for 51 patients was completed. All patients had been evaluated at the Craniofacial Center, University of Illinois at Chicago. Records were selected based on the following criteria: patients were referred for evaluation of velopharyngeal function and had no secondary surgeries on the velopharyngeal mechanism, no fistulae, no neurologic disorders, and no compensatory articulations. At the time of testing, patients ranged in age from 4 to 38 years with most being under 18 years of age. Velopharyngeal orifice areas were obtained using the pressure-flow technique during repeated CV syllables, including /pi/ and /pa/. Our results show that 8 of 51 patients exhibited a specific type of inconsistent velopharyngeal function (i.e., they exhibited velopharyngeal closing during /pa/ repetitions, but had openings during /pi/ repetitions). The reverse finding was not observed among any of the 51 patients. We concluded that the velopharyngeal incompetence observed during utterances involving /i/ may have been due to the downward pull on the palate of the palatoglossus muscle, which could not be counteracted by the already maximized levator activity in borderline patients.

Structure of a new azurin from the denitrifying bacteriumAlcaligenes xylosoxidansat high resolution

It has been reported previously that Alcaligenes xylosoxidans (NC1MB 11015) grown under denitrifying conditions produces two azurins instead of the single previously identified azurin [Dodd, Hasnain, Hunter, Abraham, Debenham, Kanzler, Eldridge, Eady, Ambler & Smith (1995). Biochemistry. In the press]. The new azurin, called azurin II, has been crystallized as blue elongated rectangular prisms with the tetragonal space group P4(1)22 and unit-cell parameters a = b = 52.65, c = 100.63 A. X-ray crystallographic data extending to 1.9 A resolution were collected by the Weissenberg method using 200 x 400 mm image plates and synchrotron X-rays of wavelength 0.97 A. The three-dimensional structure of azurin II has been solved by the molecular-replacement method using the structure of azurin from Alcaligenes denitrificans NCTC 8582 with which this new azurin shows a close homology. The quality of the initial map was sufficient to predict a number of sequence differences. The model is currently refined to an R-factor of 18.8% with X-ray data between 8.5 and 1.9 A. The final model of 961 protein atoms, one Cu atom and 50 water molecules has r.m.s. deviations from ideality of 0.009 A for bond lengths and 1.7 degrees for bond angles. The overall structure is similar to that of the azurin from A. denitrificans NCTC 8582. It has a beta-barrel structure with the Cu atom located near the top end of the molecule. The Cu atom is coordinated to Ndelta of His46 and His117 at 2.02 A and to Sgamma of Cys112 at 2.12 A, while the carbonyl O atom of Gly45 and Sdelta atom of Met121 provide the additional interactions at 2.75 and 3.26 A, respectively.