A Mössbauer spectroscopic investigation of the redox behaviour of the molybdenum-iron protein from Klebsiella pneumoniae nitrogenase. Mechanistic and structural implications

The redox properties of the nitrogenase Mo-Fe protein from Klebsiella pneumoniae have been monitored by 57Fe Mössbauer spectroscopy between -460 and -160mV (relative to the normal hydrogen electrode). Two redox processes associated with the atoms of the protein were observed. One at -216mV (pH 8.7) was associated with the Fe-Mo cofactor centres in the protein and allowed identification of the Mössbauer parameters of the oxidized form of these centres. The other redox process at -340mV (pH 8.7) was associated with species M5 [Smith & Lang (1974) Biochem. J. 137, 169-180]. This latter redox process may be involved in enzyme turnover. The oxidized form of species M5 interacts magnetically with species M4. The structural implications of the data have been considered in relation to other published data. It is concluded that an unequivocal assignment of the M4 and M5 atoms to Fe-S cluster types is not yet possible.

Driving Performance and Cannabis Users' Perception of Safety: A Randomized Clinical Trial

IMPORTANCE

Expanding cannabis medicalization and legalization increases the urgency to understand the factors associated with acute driving impairment.

OBJECTIVE

To determine, in a large sample of regular cannabis users, the magnitude and time course of driving impairment produced by smoked cannabis of different Δ9-tetrahydrocannabinol (THC) content, the effects of use history, and concordance between perceived impairment and observed performance.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, placebo-controlled parallel randomized clinical trial took place from February 2017 to June 2019 at the Center for Medicinal Cannabis Research, University of California San Diego. Cannabis users were recruited for this study, and analysis took place between April 2020 and September 2021.

INTERVENTIONS

Placebo or 5.9% or 13.4% THC cannabis smoked ad libitum.

MAIN OUTCOMES AND MEASURES

The primary end point was the Composite Drive Score (CDS), which comprised key driving simulator variables, assessed prior to smoking and at multiple time points postsmoking. Additional measures included self-perceptions of driving impairment and cannabis use history.

RESULTS

Of 191 cannabis users, 118 (61.8%) were male, the mean (SD) age was 29.9 (8.3) years, and the mean (SD) days of use in the past month was 16.7 (9.8). Participants were randomized to the placebo group (63 [33.0%]), 5.9% THC (66 [34.6%]), and 13.4% THC (62 [32.5%]). Compared with placebo, the THC group significantly declined on the Composite Drive Score at 30 minutes (Cohen d = 0.59 [95% CI, 0.28-0.90]; P < .001) and 1 hour 30 minutes (Cohen d = 0.55 [95% CI, 0.24-0.86]; P < .001), with borderline differences at 3 hours 30 minutes (Cohen d = 0.29 [95% CI, -0.02 to 0.60]; P = .07) and no differences at 4 hours 30 minutes (Cohen d = -0.03 [95% CI, -0.33 to 0.28]; P = .87). The Composite Drive Score did not differ based on THC content (likelihood ratio χ24 = 3.83; P = .43) or use intensity (quantity × frequency) in the past 6 months (likelihood ratio χ24 = 1.41; P = .49), despite postsmoking blood THC concentrations being higher in those with the highest use intensity. Although there was hesitancy to drive immediately postsmoking, increasing numbers (81 [68.6%]) of participants reported readiness to drive at 1 hour 30 minutes despite performance not improving from initial postsmoking levels.

CONCLUSIONS AND RELEVANCE

Smoking cannabis ad libitum by regular users resulted in simulated driving decrements. However, when experienced users control their own intake, driving impairment cannot be inferred based on THC content of the cigarette, behavioral tolerance, or THC blood concentrations. Participants' increasing willingness to drive at 1 hour 30 minutes may indicate a false sense of driving safety. Worse driving performance is evident for several hours postsmoking in many users but appears to resolve by 4 hours 30 minutes in most individuals. Further research is needed on the impact of individual biologic differences, cannabis use history, and administration methods on driving performance.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02849587.

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.

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.

Linking Theory and Practice in Teaching Basic Nursing Skills

In an attempt to integrate theory and practice in baccalaureate nursing education, students were taught nursing skills with two cognitive strategies (Vee heuristics and concept maps) that consciously identify and reinforce connections between scientific theory and practice. The research showed that students using Vee heuristics and concept maps, rather than traditional modes, were significantly better able to identify scientific principles to describe why specific steps of a nursing skill were done.

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.

Vocal roughness and jitter characteristics of vowels produced by esophageal speakers

Audiotape recordings of sustained vowels produced by nine esophageal speakers were subjected to acoustic and perceptual analysis. Results indicated that (1) the magnitude of vocal jitter present in the vowels was substantially larger than that observed in normal speakers and speakers with laryngeal/vocal disturbance, (2) listeners could reliably rate the severity of vocal roughness in the vowels, (3) voices of esophageal speakers were characterized by varying degrees of vocal roughness, and (4) mean fundamental frequency, mean jitter, or jitter ratio measures did not serve as useful predictors of the perceived severity of vocal roughness. These findings are interpreted to suggest that the mechanism esophageal speakers employ to regulate fundamental frequency is substantially different from that employed by normal speakers and that the identity of physical variables underlying the perception of roughness severity in naturally produced human speech is not well understood.

Validation of a liquid chromatography-tandem mass spectrometry method for analyzing cannabinoids in oral fluid

A liquid chromatography tandem mass spectrometry method was developed for quantifying ten cannabinoids in oral fluid (OF). This method utilizes OF collected by the Quantisal™ device and concurrently quantifies cannabinol (CBN), cannabidiol (CBD), Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-THC (11-OH-THC), 11-nor-9-carboxy-Δ9-THC (THC-COOH), 11-nor-9-carboxy-Δ9-THC glucuronide (THC-COOH-gluc), Δ9-THC glucuronide (THC-gluc), cannabigerol (CBG), tetrahydrocannabiverin (THCV), and Δ9-tetrahydrocannabinolic acid A (THCA-A). Solid phase extraction was optimized using Oasis Prime HLB 30 mg 96-well plates. Cannabinoids were separated by liquid chromatography over a BEH C18 column and detected by a Waters TQ-S micro tandem mass spectrometer. The lower limits of quantification (LLOQ) were 0.4 ng/mL for CBN, CBD, THC, 11-OH-THC, THC-gluc, and THCV; and 1.0 ng/mL for THC-COOH, THC-COOH-gluc, CBG and THCA-A. Linear ranges extended to 2000 ng/mL for THC and 200 ng/mL for all other analytes. Inter-day analytical bias and imprecision at three levels of quality control (QC) was within ±15%. Mean extraction efficiencies ranged from 26.0-98.8%. Applicability of this method was tested using samples collected from individuals randomly assigned to smoke either a joint containing <0.1%, 5.9%, or 13.4% THC content. This method was able to identify and calculate the concentration of 6 of 10 cannabinoids validated in this method.

The fate of prelabeled Clarke's column neurons after axotomy

We studied Clarke's Column of the L-1 spinal cord segment of young adult female rats after first prelabeling its neurons by the intracerebellar injection of Fluoro-Gold or true blue and subsequently axotomizing the labeled cells by a complete spinal cord transection at T-9. In control rats, the number of labeled neurons at 1, 5, 10, and 20 weeks showed a progressive decrease, probably due to leakage of dye from the cells. A much greater loss of labeled neurons was found in T-9 spinal cord-transected rats than in their matched controls. At 5 weeks after transection, loss of large neurons was somewhat offset by an increase in small neurons; neuron shrinkage was a likely cause of this increase, because small, very intensely labeled neurons were found in transected rats but not in control rats. By 10 and 20 weeks post-transection, the number of all prelabeled neurons in transected rats had sharply decreased. In transected rats, but not in controls, very significant increases in labeled astroglia and microglia and other labeled small cells were found at 5 weeks. At 10 weeks, the identifiable labeled astroglia had decreased but marked increases in microglia and other labeled small cells persisted. We conclude that, following a complete T-9 spinal cord transection, axotomized Clarke's column neurons first shrink in size and then die. Labeled reactive astrocytes, which are most evident 5 weeks after injury, probably indicate phagocytosis of axotomized neurons.

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.

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.

Retrograde transport in corticospinal neurons after spinal cord transection

Complete spinal cord transection at T-6/T-7 in rats caused a decrease in the number of surviving corticospinal neurons. Cell death began 5 and 10 weeks after cord injury. The number of surviving cells decreased progressively for at least 25 weeks after injury. Surviving cells were identified by their ability to transport horseradish peroxidase (HRP) retrograde from a T-1/T-2 insertion site to cortical cell somas. Therapy aimed at promoting corticospinal tract regeneration must be started early after spinal cord injury.

Pressure-flow measurements for selected oral and nasal sound segments produced by normal adults

Pressure-flow data are often used to provide information about the adequacy of velopharyngeal valving for speech. However, there is limited information available concerning simultaneous pressure-flow measurements for oral and nasal sound segments produced by normal speakers. This study provides normative pressure, flow, and velopharyngeal orifice area measurements for selected oral and nasal sound segments produced by 10 male and 10 female adult speakers. An aerodynamic categorization scheme of velopharyngeal function, including one typical category and three atypical categories (open, closed, and mixed) is proposed.

Aerodynamic assessment of the results of pharyngeal flap surgery: a preliminary investigation

Voice-quality (i.e., nasality) judgments are commonly used to evaluate the results of pharyngeal flap surgery. However, these are subjective judgments of questionable validity and reliability. This project was designed to systematically evaluate the outcome of pharyngeal flap surgery utilizing objective, quantifiable physiologic (pressure-flow) information. Thirty-one patients who had undergone pharyngeal flap surgery were selected. Pressure-flow measurements and perceptual judgments of speech were obtained following surgery. Results indicated that using pressure-flow criteria, only 52 percent of the outcomes were considered successful. Results also indicated that 35 percent of the cases were characterized by substantial nasopharyngeal airway obstruction. In the present study, these findings, along with the related perceptual phenomenon of denasality, were considered unsuccessful. Finally, results suggest that aerodynamic measurements can be used to assess other surgical techniques designed to correct velopharyngeal insufficiency.

Prophylactic administration of histamine1 and histamine2 receptor blockers in the prevention of protamine-related haemodynamic effects

We studied the effects of the prophylactic administration of histamine1 and histamine2 receptor blockers on haemodynamic changes, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MBP), central venous pressure (CVP), and heart rate (HR, beats.min-1) before and after the administration of protamine in two groups of patients having coronary artery bypass graft surgery. Group I patients received no histamine blockers, whereas patients in Group II were treated prophylactically with both H1 (diphenhydramine) and H2 (cimetidine) receptor blockers. The mean SBP, DBP, MBP, CVP, and HR before (and after) administration of protamine in group I patients were 114 +/- 16 (90 +/- 16) mmHg, 64 +/- 11 (51 +/- 8) mmHg, 81 +/- 11 (65 +/- 10) mmHg, 10 +/- 3 (11 +/- 7) mmHg, and 92 +/- 10 (87 +/- 13) before (and after) protamine administration. Group II patients had mean SBP, DBP, MBP, CVP, and HR of 113 +/- 19 (113 +/- 17) mmHg, 61 +/- 12 (62 +/- 11) mmHg, 79 +/- 15 (80 +/- 13) mmHg, 9 +/- 3 (9 +/- 2) mmHg, and 88 +/- 6 (86 +/- 4) before (and after) protamine administration. Our data show that only in Group I patients who did not receive histamine receptor blockers, were there significant haemodynamic changes following protamine administration (P less than 0.05). We conclude that the prophylactic administration of histamine receptor blockers prevents some of the adverse haemodynamic effects associated with protamine administration.

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.

Low-temperature magnetic-circular-dichroism spectroscopy of the iron-molybdenum cofactor and the complementary cofactor-less MoFe protein of Klebsiella pneumoniae nitrogenase

The major metal clusters of the MoFe protein, Kpl , of Klebsiella pneumoniae nitrogenase were characterized separately by low-temperature magnetic-circular-dichroism spectroscopy. The spectra and magnetization curves of the extracted iron-molybdenum cofactor, FeMoco , and of 'P' clusters in NifB - Kpl , the inactive, FeMoco -less, MoFo protein from an nifB mutant, were measured and compared with those of the holoprotein. (When FeMoco and NifB - Kpl are combined, active Kpl is formed.) Reduced NifB - Kpl had a spectrum with a weak, paramagnetic, component superimposed on a diamagnetic background. The paramagnetic component was assigned to a contaminating, e.p.r.-active, species. Thionine-oxidized NifB - Kpl had a spectrum and magnetization properties very similar to those of thionine-oxidized Kpl , demonstrating that the 'P' clusters are not significantly affected by the absence of the FeMoco clusters. The spectra of reduced isolated FeMoco had similar magnetization curves but sharper features and higher intensities than those of this centre in dithionite-reduced Kpl . Furthermore, a shoulder near 580 nm in the Kpl spectrum was absent from that of FeMoco . This may be due to the loss of a ligand or to a change in symmetry of the FeMoco cluster on extraction.

The inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae. Its interaction with FeMo-cofactor and the properties of the active MoFe protein formed

The inactive MoFe protein (NifB-Kp1) of nitrogenase from nifB mutants of Klebsiella pneumoniae may be activated by addition of the iron-molybdenum cofactor (FeMoco) extracted from active MoFe protein (Kp1). However, when apparently saturated with FeMoco, our preparations of NifB-Kp1 yielded activated protein, Kp1-asm, with a specific activity that was at best only 40% of that expected. This was not due to degradation of Kp1-asm, NifB-Kp1 or FeMoco during the activation reaction. Nor could activation be enhanced by addition of other nif-gene products or other proteins. Whereas fully active Kp1 contains 2 FeMoco/molecule, apparent saturation of our NifB-Kp1 preparations required the binding of only 0.4-0.65 FeMoco/molecule. By using chromatography Kp1-asm could be largely resolved from NifB-Kp1 that had not been activated. However, we were unable to isolate fully active MoFe protein (i.e. Kp1-asm containing 2 FeMoco/molecule) from solutions of NifB-Kp1 activated with FeMoco. The maximum activity/ng-atom of total Mo obtained for our purified Kp1-asm was approximately half the maximum activity for FeMoco. Since all NifB-Kp1 preparations contained some Mo, we suggest that FeMoco activated only those NifB-Kp1 molecules already containing one atom of (non-FeMoco) Mo, thus forming Kp1-asm with 2 Mo but only 1 FeMoco/molecule. Kp1-asm was identical with normal Kp1 in terms of its Mr, stability, e.p.r. signals, pattern of substrate reductions, CO inhibition and ATP/2e ratio. In addition, for preparations of differing specific activity, there was a constant and identical relationship between the e.p.r. signal intensity (from FeMoco) and the activity of both Kp1 and Kp1-asm. Assuming the above hypothesis on the structure of Kp1-asm, these data demonstrate that the two FeMoco sites in wild-type Kp1 operate independently.

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.

Blood levels of bupivacaine after arthroscopy of the knee joint

Toxic levels of bupivacaine have been reported in other types of surgery, but have not been previously noted in arthroscopic procedures. The purpose of this study was to evaluate bupivacaine levels after an intraarticular bolus of bupivacaine administered after arthroscopic surgery. Blood levels of bupivacaine were found to be significantly higher in patients in whom synovial surgery had been performed compared with those patients in whom the procedure involved only meniscal or articular cartilage surgery. A reduction in the bupivacaine dosage when the synovium has been resected or divided is recommended to keep the serum level below the potentially toxic range.