Diastereodivergent Catalysis

Alongside enantioselective catalysis, synthetic chemists are often confronted by the challenge of achieving catalyst control over the relative configuration to stereodivergently access desired diastereomers. Typically, these approaches iteratively or simultaneously control multiple stereogenic units for which dual catalytic methods comprising sequential, relay, and synergistic catalysis emerged as particularly efficient strategies. In this Perspective, the benefits and challenges of catalyst-controlled diastereodivergence in the construction of carbon stereocenters are discussed on the basis of illustrative examples. The concepts are then transferred to diastereodivergent catalysis for atropisomeric systems with twofold and higher-order stereogenicity as well as diastereodivergent catalyst control over E- and Z-configured alkenes.

Friction reducing ability of a poly-l-lysine and dopamine modified hyaluronan coating for polycaprolactone cartilage resurfacing implants

Frictional properties of cartilage resurfacing implants should be sufficiently low to limit damaging of the opposing cartilage during articulation. The present study determines if native lubricious molecule proteoglycan 4 (PRG4) can adsorb onto a layer-by-layer bioinspired coating composed of poly-l-lysine (PLL) and dopamine modified hyaluronic acid (HADN) and thereby can reduce the friction between implant and articular cartilage. An ELISA was developed to quantify the amount of immobilized human recombinant (rh)PRG4 after exposure to the PLL-HADN coating. The effect on lubrication was evaluated by comparing the coefficient of friction (CoF) of bare polycaprolactone (PCL) disks to that of PLL-HADN coated PCL disks while articulated against cartilage using a ring-on-disk geometry and a lubricant solution consisting of native synovial fluid components including rhPRG4. The PLL-HADN coating effectively immobilized rhPRG4. The surface roughness of PCL disks significantly increased while the water contact angle significantly decreased after application of the coating. The average CoF measured during the first minute of bare PCL against cartilage exceeded twice the CoF of the PLL-HADN coated PCL against cartilage. After 60 min, the CoF reached equilibrium values which were still significantly higher for bare PCL compared to coated PCL. The present study demonstrated that PCL can effectively be coated with PLL-HADN. Additionally, this coating reduces the friction between PCL and cartilage when a PRG4-rich lubricant is used, similar to the lubricating surface of native cartilage. This makes PLL-HADN coating a promising application to improve the clinical success of PCL-based cartilage resurfacing implants.

Catalyst Control over Threefold Stereogenicity: Selective Synthesis of Atropisomeric Sulfones with Stereogenic C-S Axes

Catalyst control over higher-order stereogenicity addresses significantly extended stereochemical space, but selective methods to govern threefold stereogenic units remained elusive. Herein, we report the stereoselective synthesis of threefold stereogenic triptycyl sulfones with atropisomerism arising from a C(sp3)-S bond. An oxidation of a stereodynamic thioether controlled by a chiral phosphoric acid catalyst allowed to selectively access enantioenriched triptycyl sulfoxides. The ensuing enantiospecific and diastereoselective catalytic oxidation to a threefold stereogenic sulfone provided overall control over the stereogenic C-S axis. All three stereoisomers were addressable with enantio- and diastereodivergence and a stereoselectivity of up to (-sc):(+sc):(ap)=94:6:<1.

Photocatalytic deracemisation of cobalt(III) complexes with fourfold stereogenicity

The deracemisation of fourfold stereogenic cobalt(III) diketonates with a chiral photocatalyst is described. With only 0.5 mol% menthyl Ru(bpy)32+ photocatalyst, an enantiomeric enrichment of up to 88 : 12 e.r. was obtained for the major meridional diastereomers. Moreover, a distribution of configurationally stable diastereomers distinct from the thermodynamic ratio was observed upon reaching the photostationary state.

Synovial and cartilage responsiveness to peri-operative hyaluronic acid ± dexamethasone administration following a limited injury to the rabbit stifle joint

Posttraumatic osteoarthritis (PTOA) can develop after an injury to the knee. Previous studies have indicated that an intra-articular (IA) injection of the potent glucocorticoid dexamethasone (DEX) may significantly prevent induction of PTOA. The aim of the present study was to investigate the effectiveness of a single IA injection of hyaluronic acid (HA), alone and in combination with DEX following a localized intra-articular injury as a PTOA-preventing treatment option. An established rabbit model of surgical injury consisting of dual intra-articular (IA) drill holes in a non-cartilaginous area of the femoral notch near the origin of the anterior cruciate ligament (ACL) to allow for bleeding into the joint space was used. Immediately following surgery, subjects were treated with HA, HA + DEX, or received no treatment. An uninjured control group was used for comparison (N = 5/group). Rabbits were sacrificed and investigated at 9 weeks post-injury. At 9 weeks post-injury, there was a significant protective capacity of the single IA treatment of DEX + HA on the histological grade of the synovial tissue, and some variable location-specific effects of HA alone and HA + DEX interactions on cartilage damage. Thus, it is possible that co-treatment with HA may interfere with the effectiveness of the DEX. In vitro friction testing indicated that DEX did not interfere with the lubricating ability of HA or synovial fluid on cartilage. These results suggest that a single IA administration of HA in combination with DEX following an IA injury is not recommended for inhibition of PTOA progression in this model.

Catalyst-Controlled Stereoselective Barton-Kellogg Olefination

Overcrowded alkenes are expeditiously prepared by the versatile Barton-Kellogg olefination and have remarkable applications as functional molecules owing to their unique stereochemical features. The induced stereodynamics thereby enable the controlled motion of molecular switches and motors, while the high configurational stability prevents undesired isomeric scrambling. Bistricyclic aromatic enes are prototypical overcrowded alkenes with outstanding stereochemical properties, but their stereocontrolled preparation was thus far only feasible in stereospecific reactions and with chiral auxiliaries. Herein we report that direct catalyst control is achieved by a stereoselective Barton-Kellogg olefination with enantio- and diastereocontrol for various bistricyclic aromatic enes. Using Rh2 (S-PTAD)4 as catalyst, several diazo compounds were selectively coupled with a thioketone to give one of the four anti-folded overcrowded alkene stereoisomers upon reduction. Complete stereodivergence was reached by catalyst control in combination with distinct thiirane reductions to provide all four stereoisomers with e.r. values of up to 99:1. We envision that this strategy will enable the synthesis of topologically unique overcrowded alkenes for functional materials, catalysis, energy- and electron transfer, and bioactive compounds.

Catalyst Control over Twofold and Higher-Order Stereogenicity by Atroposelective Arene Formation

Contradictory to the first intuitive impression that forging putatively flat aromatic rings evades stereoisomerism, a striking variety of atropisomeric compounds are conceivable by the formation of arenes, offering captivating avenues for catalyst-controlled stereoselective strategies. Since the assembled atropisomeric products that contain one or several rotationally restricted single bonds are characterized by especially well defined molecular architectures, they are distinctly suitable for numerous pertinent applications. In view of the fascinating arene-forming aldol condensation pathways taking place in polyketide biosynthesis (cyclases/aromatases (CYC/ARO)), the versatile small-molecule-catalyzed aldol reaction appeared as an exceptionally appealing synthetic means to prepare various unexplored atropisomeric compounds in our efforts presented herein. In our initial studies, the use of secondary amine organocatalysts provided excellent selectivities in stereoselective arene-forming aldol condensations for a broad range of atropisomeric products, such as biaryls and rotationally restricted aromatic amides. In further analogy to polyketide biosynthesis, it was also conceivable that several aromatic rings are formed in catalytic cascade reactions. The use of small-molecule catalysts thereby enabled us to transfer this concept to the conversion of unnatural and noncanonical polyketide substrates, thus giving access to atropisomers with particular value for synthetic applications. The versatility of the stereoselective aldol reactions with numerous catalytic activation modes further provided a strategy to individually control several stereogenic axes, similar to the various methodologies developed for controlling stereocenter configurations. By the use of iterative building block additions combined with catalyst-controlled aldol reactions to form the aromatic rings, stereodivergent pathways for catalyst-substrate-matched and -mismatched products were obtained. Besides secondary amines, cinchona-alkaloid-based quaternary ammonium salts also proved to be highly efficient in overcoming severe substrate bias. The obtained atropisomeric multiaxis systems, with all of the biaryl bonds suitably restricted in rotation even at high temperatures, are spatially distinctly defined. The helical secondary structure is therefore excellently suited for several captivating applications.While previous catalyst-controlled stereoselective methods distinguish two stereoisomers for each stereogenic unit, catalyst control beyond the realms of this dualistic stereoisomerism remained unexplored. By the selective preparation of O̅ki atropisomers characterized by their sixfold stereogenicity in Rh-catalyzed [2 + 2 + 2] cyclotrimerizations, one out of the six possible stereoisomers resulting from the restricted rotation of a single bond was shown to be catalytically addressable. Catalyst control over higher-order stereogenicity therefore further interconnects conformational analysis and stereoselective catalysis and offers captivating avenues to explore uncharted stereochemical space for creating a broad range of unprecedented molecular motifs.

Proteoglycan 4 reduces friction more than other synovial fluid components for both cartilage-cartilage and cartilage-metal articulation

OBJECTIVE

The clinical success of focal metallic resurfacing implants depends largely on the friction between implant and opposing cartilage. Therefore, the present study determines the lubricating ability of the synovial fluid components hyaluronic acid (HA), proteoglycan 4 (PRG4) and a surface-active phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC), on the articulation between cartilage and a Cobalt Chromium Molybdenum (CoCrMo) implant surface, compared with two cartilage surfaces.

METHODS

A ring-on-disk geometry was used to perform repeated friction measurements at physiologically relevant velocities (6 and 60 mm/s) using lubricants with an increasing number of components present. Shear measurements were performed in order to evaluate the viscosity. To ensure that it is clinically relevant to explore the effect of these components, the presence of PRG4 in synovial fluid obtained from primary and revision knee and hip implant surgeries was examined.

RESULTS

PRG4 in the presence of HA was found to significantly reduce the coefficient of friction for both cartilage-cartilage and cartilage-CoCrMo interface. This is relevant, as it was also demonstrated that PRG4 is still present at the time of revision surgeries. The addition of POPC had no effect for either configurations. HA increased the viscosity of the lubricating fluid by one order of magnitude, while PRG4 and POPC had no effect.

CONCLUSION

The present study demonstrates the importance of selecting the appropriate lubrication solution to evaluate implant materials with biotribology tests. Because PRG4 is a key component for reducing friction between cartilage and an opposing surface, developing coatings which bind PRG4 is recommended for cartilage resurfacing implants.

Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives

Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a Pd^II or Pd⁰ precursor in loadings as low as 0.75 mol % and α,α'-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.

YAP/TAZ regulates the expression of proteoglycan 4 and tenascin C in superficial-zone chondrocytes

The roles of cell division control protein 42 homologue (CDC42) and actin polymerisation in regulating the phenotype of superficial-zone chondrocytes (SZCs) have been demonstrated in vitro; however, the signalling pathway(s) downstream have yet to be fully elucidated. The study hypothesis was that Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) act downstream to regulate proteoglycan 4 (PRG4) and tenascin C (TNC). Bovine SZCs grown in monolayer were treated with ML141 (CDC42 inhibitor) or the actin depolymerising agents, latrunculin B and cytochalasin D, to determine the effect on YAP/TAZ. Verteporfin (YAP/TAZ inhibitor) and YAP/TAZ siRNA-mediated knockdown were used to determine their role in regulating PRG4 and TNC. ML141 treatment reduced total YAP/TAZ protein, nuclear TAZ levels and the YAP/TAZ target gene, connective tissue growth factor (CTGF) mRNA levels. Latrunculin B decreased nuclear TAZ, while cytochalasin D treatment trended towards increased nuclear TAZ (p = 0.06), correlating with decreased and increased CTGF mRNA levels, respectively. Verteporfin treatment decreased PRG4 and TNC expression, with no effect on actin polymerisation. siRNA-mediated knockdown of YAP/TAZ revealed that PRG4 was regulated by YAP/TAZ while TNC was regulated by TAZ only. As cytochalasin D can activate myocardin-related transcription factor-A (MRTF-A), siRNA-mediated knockdown was performed to determine the role of MRTF-A in regulating YAP/TAZ. Although nuclear TAZ decreased, no significant changes in total protein levels were observed. Findings suggested that CDC42 and actin polymerisation regulated SZCs through multiple actin-regulated pathways. Understanding the regulation of these chondroprotective molecules may have important implications for prevention/treatment of osteoarthritis.

Cellular electrophysiological principles that modulate secretion from synovial fibroblasts

Rheumatoid arthritis (RA) is a progressive disease that affects both pediatric and adult populations. The cellular basis for RA has been investigated extensively using animal models, human tissues and isolated cells in culture. However, many aspects of its aetiology and molecular mechanisms remain unknown. Some of the electrophysiological principles that regulate secretion of essential lubricants (hyaluronan and lubricin) and cytokines from synovial fibroblasts have been identified. Data sets describing the main types of ion channels that are expressed in human synovial fibroblast preparations have begun to provide important new insights into the interplay among: (i) ion fluxes, (ii) Ca²⁺ release from the endoplasmic reticulum, (iii) intercellular coupling, and (iv) both transient and longer duration changes in synovial fibroblast membrane potential. A combination of this information, knowledge of similar patterns of responses in cells that regulate the immune system, and the availability of adult human synovial fibroblasts are likely to provide new pathophysiological insights.

Lubricin/Proteoglycan 4 binds to and regulates the activity of Toll-Like Receptors In Vitro

Proteoglycan 4 (PRG4/lubricin) is secreted by cells that reside in articular cartilage and line the synovial joint. Lubricin may play a role in modulating inflammatory responses through interaction with CD44. This led us to examine if lubricin could be playing a larger role in the modulation of inflammation/immunity through interaction with Toll-like receptors (TLRs). Human Embryonic Kidney (HEK) cells overexpressing TLRs 2, 4 or 5 and surface plasmon resonance were employed to determine if full length recombinant human lubricin was able to bind to and activate TLRs. Primary human synovial fibroblasts were also examined using flow cytometry and Luminex multiplex ELISA. A rat destabilization model of osteoarthritis (OA) was used to determine if lubricin injections were able to regulate pain and/or inflammation in vivo. Lubricin can bind to and regulate the activity of TLRs, leading to downstream changes in inflammatory signalling independent of HA. We confirmed these findings in vivo through intra-articular injections of lubricin in a rat OA model where the inhibition of systemic inflammatory signaling and reduction in pain were observed. Lubricin plays an important role in regulating the inflammatory environment under both homeostatic and tissue injury states.

Cartilage boundary lubrication of ovine synovial fluid following anterior cruciate ligament transection: a longitudinal study

OBJECTIVE

To assess ovine synovial fluid (oSF) from different post-injury time points for (1) proteoglycan-4 (PRG4) and hyaluronan (HA) concentration, (2) HA molecular weight (MW) distribution, (3) cartilage boundary lubrication function, and (4) lubricant composition-function relationships. The association between cartilage boundary lubrication and gross cartilage changes after injury was also examined.

METHODS

oSF was collected 2, 4, 10, and 20 weeks post anterior cruciate ligament (ACL) transection in five skeletally mature sheep. PRG4 and HA concentrations were measured using sandwich enzyme-linked immunosorbent assay, and HA MW distribution by agarose gel electrophoresis. Cartilage boundary lubrication of oSF was assessed using a cartilage-cartilage friction test. Gross damage to articular cartilage was also quantified at 20 weeks using modified Drez scoring protocol.

RESULTS

Early (2-4 weeks) after ACL injury, PRG4 concentrations were significantly higher (P = 0.045, P = 0.037), and HA concentrations were substantially lower (P = 0.005, P = 0.005) compared to 20 weeks. The HA MW distribution also shifted towards lower ranges in the early post-injury stage. The kinetic friction coefficients were significantly higher 2-4 weeks post injury (P = 0.008 and P = 0.049) compared to 20 weeks. Poor cartilage boundary lubricating ability early after injury was associated with cartilage damage at 20 weeks.

CONCLUSION

Altered composition and diminished boundary lubrication of oSF early after ACL transection may pre-dispose the articular cartilage to degenerative changes and initiate osteoarthritis (OA). These observations also provide potential motivation for biotherapeutic interventions at earlier time points post injury.

The impact of early intra-articular administration of interleukin-1 receptor antagonist on lubricin metabolism and cartilage degeneration in an anterior cruciate ligament transection model

OBJECTIVE

Study the impact of intra-articular interleukin-1 receptor antagonist (IL-1 ra) treatment on lubricin biosynthesis following anterior cruciate ligament transection (ACLT) in the rat and evaluate the effect of combined IL-1 ra and recombinant human lubricin (rhPRG4) treatments on chondrocyte apoptosis.

METHODS

ACLT was performed in male Lewis rats. Treatments included IL-1 ra or vehicle (n = 36 in each group). IL-1 ra intra-articular dosing was performed on days 1, 3, 5 and 7 following ACLT using Anakinra (150 mg/ml; 40 μl). At 3 and 5 weeks, animals were sacrificed and RNA was isolated. Histological analyses included Safranin O and H&E. Lubricin synovial fluid (SF) lavage concentrations were determined at 5 weeks. ACLT animals were treated with a single injection of vehicle, IL-1 ra (75 mg/ml; 40 μl), rhPRG4 (200 μg/ml; 40 μl), or IL-1 ra + rhPRG4 (75 mg/ml + 200 μg/ml; 40 μl) (n = 6 in each group) on day 7 following ACLT and cartilage was probed for cleaved caspase-3 at 5 weeks.

RESULTS

IL-1 ra treatment improved lubricin expression (P < 0.001) and lubricin SF lavage concentrations in the IL-1 ra group was higher (P = 0.005) than the vehicle. IL-1 ra treatment reduced cartilage and synovial scores (P < 0.001) compared to vehicle. IL-1 ra and rhPRG4 acted synergistically to reduce caspase-3 positive chondrocytes (P < 0.001) compared to individual treatments.

CONCLUSION

IL-1 ra treatment preserved lubricin following ACLT and a combined treatment of IL-1 ra + rhPRG4 may act synergistically to reduce cartilage catabolism.

Molecular weight characterization of PRG4 proteins using multi-angle laser light scattering (MALLS)

OBJECTIVES

Alternative splicing and variable post-translational modifications result in proteoglycan 4 (PRG4) proteins with historically reported apparent molecular weights (Ma) ranging from 150 to 400 kDa. The objectives of this study were to (1) identify and determine the weight averaged molecular weights (M(W)'s) of PRG4 proteins purified from medium with transforming growth factor-beta 1 (TGF-β1) conditioned by mature bovine articular cartilage explants and (2) to examine the effect of reduction and alkylation (RA) on PRG4.

METHODS

Non-reduced (NR) and RA preparations of PRG4 were separated using high performance liquid chromatography-size-exclusion chromatography with an in-line multi-angle laser light scattering (MALLS) detector, which was used for absolute determination of PRG4 M(W). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting, and tandem mass spectrometry (MS/MS) analysis were used to confirm the identity of separated proteins.

RESULTS

Three putative PRG4 monomers, one with previously uncharacterized M(W), were identified in NR and RA PRG4 preparations of 239 (223,255), 379 (369,389), and 467 (433,501) kDa. Additionally ∼1 MDa putative PRG4 dimer was identified. Release of a ∼90 kDa PRG4 fragment was also observed on SDS-PAGE after RA. Western Blotting with anti-PRG4 antibodies detected immunoreactive bands with Ma similar to M(W) for all species and excised bands were confirmed to be PRG4 by MS/MS.

CONCLUSIONS

A variety of monomeric PRG4 proteins and a disulfide-bonded dimer/multimer are secreted by chondrocytes in bovine cartilage explants. The observed decrease in M(W)'s of monomeric PRG4 species upon RA may be due to the release of post-translationally cleaved fragments. Further study of these species will provide insight into the PRG4 molecular structure and function relationship.

Differential regulation of proteoglycan 4 metabolism in cartilage by IL-1alpha, IGF-I, and TGF-beta1

OBJECTIVES

To determine (1) if interleukin-1 alpha (IL-1alpha), insulin like growth factor I (IGF-I), and transforming growth factor-beta 1 (TGF-beta1) regulate proteoglycan 4 (PRG4) metabolism in articular cartilage, in terms of chondrocytes expressing PRG4 and PRG4 bound at the articular surface, and (2) if these features of cartilage PRG4 metabolism correlate with its secretion.

METHODS

Articular cartilage explants were harvested and cultured for 6 days with or without 10% fetal bovine serum (FBS), alone, or with the addition of 10ng/ml IL-1alpha, 300ng/ml IGF-I, or 10ng/ml TGF-beta1. PRG4 expression by chondrocytes in the cartilage disks was assessed by immunohistochemistry (IHC). PRG4 bound to the articular surface of disks was quantified by extraction and enzyme-linked immunosorbent assay (ELISA). PRG4 secreted into culture medium was quantified by ELISA and characterized by Western Blot.

RESULTS

PRG4 expression by chondrocytes near the articular surface was markedly decreased by IL-1alpha, stimulated by TGF-beta1, and not affected by IGF-I. The level of PRG4 accumulation in the culture medium was correlated with the number of chondrocytes expressing PRG4. The amount of PRG4 bound at the articular surface was modulated by incubation in medium including FBS, but did not correlate with levels of PRG4 secretion.

CONCLUSIONS

Cartilage secretion of PRG4 is highly regulated by certain cytokines and growth factors, in part through alteration of the number of PRG4-secreting chondrocytes near the articular surface. The biochemical milieu may regulate the PRG4 content of synovial fluid during cartilage injury or repair.

A model of synovial fluid lubricant composition in normal and injured joints

The synovial fluid (SF) of joints normally functions as a biological lubricant, providing low-friction and low-wear properties to articulating cartilage surfaces through the putative contributions of proteoglycan 4 (PRG4), hyaluronic acid (HA), and surface active phospholipids (SAPL). These lubricants are secreted by chondrocytes in articular cartilage and synoviocytes in synovium, and concentrated in the synovial space by the semi-permeable synovial lining. A deficiency in this lubricating system may contribute to the erosion of articulating cartilage surfaces in conditions of arthritis. A quantitative intercompartmental model was developed to predict in vivo SF lubricant concentration in the human knee joint. The model consists of a SF compartment that (a) is lined by cells of appropriate types, (b) is bound by a semi-permeable membrane, and (c) contains factors that regulate lubricant secretion. Lubricant concentration was predicted with different chemical regulators of chondrocyte and synoviocyte secretion, and also with therapeutic interventions of joint lavage and HA injection. The model predicted steady-state lubricant concentrations that were within physiologically observed ranges, and which were markedly altered with chemical regulation. The model also predicted that when starting from a zero lubricant concentration after joint lavage, PRG4 reaches steady-state concentration approximately 10-40 times faster than HA. Additionally, analysis of the clearance rate of HA after therapeutic injection into SF predicted that the majority of HA leaves the joint after approximately 1-2 days. This quantitative intercompartmental model allows integration of biophysical processes to identify both environmental factors and clinical therapies that affect SF lubricant composition in whole joints.

Effect of synovial fluid on boundary lubrication of articular cartilage

OBJECTIVES

The lubrication of articulating cartilage surfaces in joints occurs through several distinct modes. In the boundary mode of lubrication, load is supported by surface-to-surface contact, a feature that makes this mode particularly important for maintenance of the normally pristine articular surface. A boundary mode of lubrication is indicated by a kinetic friction coefficient being invariant with factors that influence formation of a fluid film, including sliding velocity and axial load. The objectives of this study were to (1) implement and extend an in vitro articular cartilage-on-cartilage lubrication test to elucidate the dependence of the friction properties on sliding velocity, axial load, and time, and establish conditions where a boundary mode of lubrication is dominant, and (2) determine the effects of synovial fluid (SF) on boundary lubrication using this test.

METHODS

Fresh bovine osteochondral samples were analyzed in an annulus-on-disk rotational configuration, maintaining apposed articular surfaces in contact, to determine static (mu(static) and mu(static),(N(eq)) and kinetic ([mu(kinetic)] and [mu(kinetic),(N(eq))]) friction coefficients, each normalized to the instantaneous and equilibrium (N(eq)) normal loads, respectively.

RESULTS

With increasing pre-sliding durations, mu(static) and mu(static),(N(eq)) were similar, and increased up to 0.43 +/- 0.03 in phosphate buffered saline (PBS) and 0.19 +/- 0.01 in SF, whereas [mu(kinetic)] and [mu(kinetic),(N(eq))] were steady. Over a range of sliding velocities of 0.1-1 mm/s and compression levels of 18% and 24%, [mu(kinetic)] was 0.072 +/- 0.010 in PBS and 0.014 +/- 0.003 in SF, and [mu(kinetic),(N(eq))] was 0.093 +/- 0.005 in PBS and 0.018 +/- 0.002 in SF.

CONCLUSIONS

A boundary mode of lubrication was achieved in a cartilage-on-cartilage test configuration. SF functioned as an effective friction-lowering boundary lubricant for native articular cartilage surfaces.

Static and dynamic compression regulate cartilage metabolism of PRoteoGlycan 4 (PRG4)

The boundary lubrication function of articular cartilage is mediated in part by molecules at the articular surface and in synovial fluid, encoded by Prg4. The objective of this study was to determine whether static and dynamic compression regulate PRG4 biosynthesis by cartilage explants. Articular cartilage disks were harvested to include the articular surface from immature bovines. Some disks were subjected to 24 h (day 1) of loading, followed by 72 h (days 2-4) of free-swelling culture to assess chondrocyte responses following unloading. Loading consisted of 6 or 100 kPa of static compression, with or without superimposed dynamic compression (10 or 300 kPa peak amplitude, 0.01 Hz). Other disks were cultured free-swelling as controls. PRG4 secretion into culture medium was inhibited by all compression protocols during day 1. Following unloading, cartilage previously subjected to dynamic compression to 300 kPa exhibited a rebound effect, secreting more PRG4 than did controls, while cartilage previously subjected to 100 kPa static loading secreted less PRG4. Immunohistochemistry revealed that all compression protocols also affected the number of cells expressing PRG4. The paradigm that mechanical stimuli regulate biosynthesis in cartilage appears operative not only for load bearing matrix constituents, but also for PRG4 molecules mediating lubrication.

Tissue engineering of stratified articular cartilage from chondrocyte subpopulations

OBJECTIVE

To test if subpopulations of chondrocytes from different cartilage zones could be used to engineer cartilage constructs with features of normal stratification. ESIGN: Chondrocytes from the superficial and middle zones of immature bovine cartilage were cultured in alginate, released, and seeded either separately or sequentially to form cartilage constructs. Constructs were cultured for 1 or 2 weeks and were assessed for growth, compressive properties, and deposition, and localization of matrix molecules and superficial zone protein (SZP).

RESULTS

The cartilaginous constructs formed from superficial zone chondrocytes exhibited less matrix growth and lower compressive properties than constructs from middle zone chondrocytes, with the stratified superficial-middle constructs exhibiting intermediate properties. Expression of SZP was highest at the construct surfaces, with the localization of SZP in superficial-middle constructs being concentrated at the superficial surface.

CONCLUSIONS

Manipulation of subpopulations of chondrocytes can be useful in engineering cartilage tissue with a biomimetic approach, and in fabricating constructs that exhibit stratified features of normal articular cartilage.

Sexual growth dimorphism affects birth sex ratio in house mice

We present the first empirical evidence that mammalian sex-ratio deviations result from variation in adult-weight sexual dimorphism via correlated effects on blastocyst development. Two selection lines of mice exhibiting high and low sexual dimorphism in adult weight showed correlated sexual weight differences at birth and at weaning, caused by relatively decelerated growth of males in the low line from before birth. The sex ratio at birth was significantly female-biased in the low line, and significantly lower than in the highly dimorphic line. Concomitantly, blastomere numbers were at significantly higher variance in the low than in the highly dimorphic line, owing to an increased frequency of slowly growing blastocysts. Since low-dimorphism mice produced more corpora lutea and more female pups than the high-dimorphism mice, but not more males, birth sex-ratio bias most parsimoniously resulted from the loss of slowly growing male blastocysts. This is in agreement with the observation that sex-ratio skews in mammals arise when timing of uterine responsiveness (i.e. its temporally limited capacity for implantation) varies in relation to sex-specific embryonic growth rates. Hence, natural mammalian sex-ratio variation that stems from developmental asynchrony might be a by-product of natural selection for sexual dimorphism in adult weight.

Hospital follow-up of patients categorized as not needing an ambulance using a set of emergency medical technician protocols

OBJECTIVE

Using hospital outcomes, this study evaluated emergency medical technicians' (EMTs') ability to safely apply protocols to assign transport options.

METHODS

Protocols were developed that categorized patients as: 1) needs ambulance; 2) may go to emergency department (ED) by alternative means; 3) contact primary care provider (PCP); or 4) treat and release. After education on application of the protocols, EMTs categorized patients at the scene prior to transport but did not change current practice. Hospital charts were reviewed to determine outcome of patients whom EMTs categorized as not needing an ambulance. Category 2 patients were assumed to need the ambulance if they were admitted to a monitored bed or intensive care unit. Category 3 and 4 patients were assumed to need the ED if they were admitted.

RESULTS

The EMTs categorized 1,300 study patients: 1,023 (79%) ambulance transport, 200 (15%) alternative means, 63 (5%) contact PCP, and 14 (1%) treat and release. Hospital data were obtained for 140 (51%) patients categorized as not needing ambulance transport. Thirteen of 140 (9%) patients who transporting EMTs determined did not need the ambulance were considered to be undertriaged: five in category 2, six in category 3, and one in category 4. Six of 13 (46%) undertriaged patients had dementia or a psychiatric disorder as one of their presenting complaints.

CONCLUSION

These protocols led to a 9% undertriage rate. Patients with psychiatric complaints and dementia were at high risk for undertriage.

Oregon physicians' attitudes about and experiences with end-of-life care since passage of the Oregon Death with Dignity Act

CONTEXT

The Oregon Death with Dignity Act, passed by ballot measure in 1994 and enacted in October 1997, legalized physician-assisted suicide for competent, terminally ill Oregonians, but little is known about the effects of the act on clinical practice or physician perspective.

OBJECTIVE

To examine Oregon physicians' attitudes toward and practices regarding care of dying patients since the passage of the Death with Dignity Act.

DESIGN, SETTING, AND PARTICIPANTS

A self-administered questionnaire was mailed in February 1999 to Oregon physicians eligible to prescribe under the act. Of 3981 eligible physicians, 2641 (66%) returned the questionnaire by August 1999.

MAIN OUTCOME MEASURES

Physicians' reports of their efforts to improve care for dying patients since 1994, their attitudes, concerns, and sources of information about participating in the Death with Dignity Act, and their conversations with patients regarding assisted suicide.

RESULTS

A total of 791 respondents (30%) reported that they had increased referrals to hospice. Of the 2094 respondents who cared for terminally ill patients, 76% reported that they made efforts to improve their knowledge of the use of pain medications in the terminally ill. Nine hundred forty-nine responding physicians (36%) had been asked by a patient if they were potentially willing to prescribe a lethal medication. Seven percent of all survey participants reported that 1 or more patients became upset after learning the physician's position on assisted suicide, and 2% reported that 1 or more patients left their care after learning the physician's position on assisted suicide. Of the 73 physicians who were willing to write a lethal prescription and who had received a request from a patient, 20 (27%) were not confident they could determine when a patient had less than 6 months to live.

CONCLUSION

Most Oregon physicians who care for terminally ill patients report that since 1994 they have made efforts to improve their ability to care for these patients and many have had conversations with patients about assisted suicide.

The strength of specific EMS dispatcher questions for identifying patients with important clinical field findings

INTRODUCTION

There is growing interest in more efficiently matching emergency medical services (EMS) resources to patient need. Emergency medical services dispatchers may be asked to distinguish between callers with an immediate need for EMS and those who may safely use alternative services. New dispatcher protocols are required or existing protocols must be shown to be reliable for this new task.

OBJECTIVE

To examine whether answers to currently asked dispatcher questions in one urban center can identify callers with important clinical field findings (ICFFs).

METHODS

Audio recordings of EMS dispatcher-caller conversations within three nature codes (falls, sick, trauma) were retrospectively reviewed. Specifically scripted "cardinal" questions, asked of all callers, identify what happened, whether the patient is breathing okay, and whether the patient is conscious. "Key" questions are specific to each nature code and further specify patient circumstances. Compliance with protocol and caller answers were documented. Researchers developed a list of ICFFs that, if present on the corresponding EMS record, were judged to justify an immediate EMS response. Logistic regression was used to analyze the relationship between caller answers and the presence of ICFFs. A p-value of 0.10 was used.

RESULTS

Of 430 recordings, 383 (89%) were usable. Falls: 103 (26%); trauma: 136 (37%); sick: 144 (37%). The caller was the patient 41 (11%) times. There were 198 (52%) females in the sample. There was no matching EMS record for 96 (25%) cases. An ICFF was determined to be present in 191 (67%) of the 287 recordings with matching EMS data. Compliance across the cardinal and key questions ranged from 62% to 88%. Age alone was suggestive of a patient who may be identified at dispatch as having an ICFF [adjusted OR 1.01 (90% CI: 0.999-1.025), p < 0.10]. No other key or cardinal questions were related to ICFFs.

CONCLUSION

Cardinal questions are most often asked. Implied or volunteered information is often relied upon to answer key questions. Key questions for certain nature codes are not answered about one third of the time. Increasing age may suggest a stronger likelihood for an ICFF to be identified at dispatch. Otherwise, in this sample, caller answers to currently asked questions do not appear useful if the goal is to identify at dispatch those without an ICFF.

Receptor occupancy with digoxin vs receptor occupancy with a putative endogenous digitalislike factor

The possibility that an endogenous ligand for the digitalis receptor might exist has been a source of speculation resulting in efforts over the past decades to identify such a hormone. In the current context it is of interest that prolonged wash of myocardial and skeletal muscular samples from subjects who were not in digoxin treatment generally resulted in small tendencies to increase 3H-ouabain binding ranging from 2 to 9% and from -2 to 7%, respectively. It may be appreciated that neither wet weight nor water content of left ventricular or skeletal muscular samples have been found to change as a result of the prolonged wash. Although these tendencies most likely are a mere play of chance, it may be argued that the studies did not entirely rule out the possibility of the existence of a quantitatively small amount of endogenous digitalislike factor. However, based on the evaluations of receptor occupancy with digoxin during treatment of 24-34% in the left ventricle and 9-13% in skeletal muscle, it would seem reasonable to expect that a comparatively larger fraction of digitalis receptors should be occupied by a putative endogenous digitalislike factor, if such a factor were to be of any physiological significance.

A randomized controlled trial to assess decay in acquired knowledge among paramedics completing a pediatric resuscitation course

BACKGROUND

Critical pediatric illness or injury occurs infrequently in out-of-hospital settings, making it difficult for paramedics to maintain physical assessment, treatment, and procedure skills.

OBJECTIVES

To document the ability of paramedics to retain clinical knowledge over a one-year interval after completing a pediatric resuscitation course and to determine whether clinical experience or retesting improves retention.

METHODS

This was a randomized controlled study assessing retention of knowledge in pediatric resuscitation soon after, six months after, and 12 months following completion of a pediatric advanced life support course. Forty-three paramedics participated in pre- and post-pediatric resuscitation course testing and were randomly assigned to one of four groups. Group 1 received a knowledge examination (KE) and mock resuscitation scenarios (MR) at six months. Group 2 received only the KE at six months. Group 3 received the MR only at six months. Group 4 received no intermediate testing. All groups were reassessed at 12 months.

RESULTS

Pediatric clinical knowledge (as measured by KE) rose sharply immediately after the course but returned to baseline levels within six months. There was no difference between the groups in knowledge scores at 12 months, despite the interventions at six months.

CONCLUSIONS

Although intensive out-of-hospital pediatric education enhances knowledge, that knowledge rapidly decays. Emergency medical services programs need to find novel ways to increase retention and ensure paramedic readiness.

Physicians' experiences with the Oregon Death with Dignity Act

BACKGROUND

Physician-assisted suicide was legalized in Oregon in October 1997. There are data on patients who have received prescriptions for lethal medications and died after taking the medications. There is little information, however, on physicians' experiences with requests for assistance with suicide.

METHODS

Between February and August 1999, we mailed a questionnaire to physicians who were eligible to prescribe lethal medications under the Oregon Death with Dignity Act.

RESULTS

Of 4053 eligible physicians, 2649 (65 percent) returned the survey. Of the respondents, 144 (5 percent) had received a total of 221 requests for prescriptions for lethal medications since October 1997. We received information on the outcome in 165 patients (complete information for 143 patients and partial for on an additional 22). The mean age of the patients was 68 years; 76 percent had an estimated life expectancy of less than six months. Thirty-five percent requested a prescription from another physician. Twenty-nine patients (18 percent) received prescriptions, and 17 (10 percent) died from administering the prescribed medication. Twenty percent of the patients had symptoms of depression; none of these patients received a prescription for a lethal medication. In the case of 68 patients, including 11 who received prescriptions and 8 who died by taking the prescribed medication, the physician implemented at least one substantive palliative intervention, such as control of pain or other symptoms, referral to a hospice program, a consultation, or a trial of antidepressant medication. Forty-six percent of the patients for whom substantive interventions were made changed their minds about assisted suicide, as compared with 15 percent of those for whom no substantive interventions were made (P<0.001).

CONCLUSIONS

Our data indicate that in Oregon, physicians grant about 1 in 6 requests for a prescription for a lethal medication and that 1 in 10 requests actually result in suicide. Substantive palliative interventions lead some--but not all--patients to change their minds about assisted suicide.

Flexibility of lumbar spinal motion segments correlated to type of tears in the annulus fibrosus

OBJECT

The authors conducted a study in which their objective was to measure the effect of tears in the annulus fibrosus on the motions of lumbar spinal motion segments.

METHODS

Lumbar spinal motion segments were harvested from human cadavers and studied using a 1.5-tesla magnetic resonance imager. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Displacements and rotations were measured using a kinematic system. The segments were sectioned on a cryomicrotome to verify the presence of tears in the annulus fibrosus.

CONCLUSIONS

Tears in the annulus fibrosus increase the amount of motion that results from a torque applied to the motion segment. Radial and transverse tears of the annulus fibrosus have a greater effect on motions produced by an axial rotatory torque than on those produced by flexion, extension, or lateral bending torques. The difference between normal discs and discs with annular tears is more marked during moments of axial rotational than during those of flexion, extension, or lateral bending.

Suicidal patients in the ED: ethical issues

Emergency physicians frequently are expected to evaluate and develop treatment plans for potentially suicidal patients. The struggle to prevent someone from self-injury while respecting their personal autonomy is frequently present in the ED, as physicians must decide whether to intervene with a patient who does not seek treatment. The implications of this struggle are discussed in the article.

State insurance commissioner actions against health maintenance organizations for denial of emergency care

OBJECTIVE

Concerns have emerged from two west coast communities that health maintenance organizations (HMOs) may deter their members from calling 911. One means of influence is retrospective denial of emergency department (ED) or emergency medical services (EMS) claims. The study objective was to systematically assess legal action taken to contest HMO denial of claims.

METHODS

Telephone survey of all state insurance commissioners (SICs). The specific question asked was: "What actions, if any, have been taken by the Office of Insurance Commissioner since 1990 against HMOs for denying claims for emergency department care or care provided by paramedics after a person has called 911?" Each office was contacted at least three times.

RESULTS

Representatives from 49 states were interviewed. Three states (6%, Oregon, Texas, and Virginia) have taken formal action since 1990. Oregon fined two HMOs a total of $25,000 for inappropriate systematic claim denial of ED care. Texas fined one HMO $1,000,000 for similar practices. Virginia, with no authority to fine, has issued citations. No action had been taken for denying EMS claims. Thirty-eight states (78%) reported no formal actions. Eight (16%) state SICs could not easily retrieve these data and did not report. Fourteen (29%) representatives reported receiving these complaints. Most of these complaints were resolved without formal SIC action.

CONCLUSIONS

Three health plans in two states received financial penalties for systematic denial of ED claims. A fourth was cited. This may underrepresent the true incidence of appealed ED and EMS claim denials. While complaints occurred in 29% of states, recent actions by SICs are relatively rare (6% of states). These results speak more to the extent systematic claim denials are discovered by SICs than to the true incidence of this practice.

The stiffness of lumbar spinal motion segments with a high-intensity zone in the anulus fibrosus

STUDY DESIGN

Biomechanical and anatomic study of human cadaveric spinal motion segments.

OBJECTIVES

To measure the stiffness of spinal motion segments by disc type and by load type (flexion, extension, axial rotation, or lateral bending). To compare stiffness in motion segments with and without a high-intensity zone or radial tear in the anulus fibrosus.

SUMMARY OF BACKGROUND DATA

The high-intensity zone, that is a linear zone of high-intensity on T2-weighted magnetic resonance images corresponding to a radial tear in the anulus fibrosus, is a marker for a painful disc at discography. The high-intensity zone is hypothetically associated with diminished stiffness of the motion segment.

METHODS

Human cadaveric lumbar spinal motion segments with normal disc morphology or a high-intensity zone of the anulus fibrosus were selected on the basis of magnetic resonance imaging. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Rotation was measured with a kinematic system. Torque-rotation curves and stiffness were calculated for each motion segment and for each torque. The motion segments were sectioned on a cryomicrotome to verify the disc morphology as normal or as that of a radial tear.

RESULTS

In four motion segments with normal discs, stiffness was greater in axial rotation (8.4 Nm/degree) than in lateral bending (2.3 Nm/degree), flexion (1.8 Nm/degree), or extension (2.6 Nm/degree). In 16 motion segments with a high-intensity zone, stiffness was 2.4 Nm/degree in axial rotation, and less severely reduced in lateral bending, flexion, and extension. Stiffness in motion segments with a high-intensity zone was significantly less with smaller than with larger axial rotation loads.

CONCLUSIONS

The presence of a high-intensity zone in the intervertebral disc is associated with reduced stiffness of motion segments. The reduction is greater in axial rotation than in other torques. The reduction is more in smaller than in larger axial torques.

Oregon emergency medical technicians' attitudes toward physician-assisted suicide

OBJECTIVES

To determine Oregon intermediate and advanced emergency medical technicians' (EMTs') attitudes toward physician-assisted suicide (PAS) and factors associated with those attitudes.

METHODS

An anonymous survey was sent to a random sample of 498 EMTs registered in Oregon.

RESULTS

Surveys were delivered to 498 EMTs and 343 completed surveys were returned, for a response rate of 69%. The mean age of the respondents was 37.5 years (+/-8.73) and 79% were male. 232 (68%) agreed that PAS should be legal, 263 (77%) agreed that terminally ill people have a right to decide to commit suicide, while 57 (17%) thought not attempting resuscitation would be immoral. 251 (73%) reported seeing attempted suicide in terminally ill patients at least once, with 117 (34%) experiencing such calls >5 times. Only 22 (6%) stated that they would be unable to work in a system that directed them to withhold resuscitation after a PAS attempt, and 277 (81%) agreed that treatment protocols should direct EMTs to withhold resuscitation. 105 (31%) thought EMTs should participate in the decision to withhold resuscitation. 206 (60%) thought the law should allow lethal injection for terminally ill patients. 201 (59%) agreed there were circumstances under which they might personally consider PAS. If PAS were legal, EMTs stated they would withhold treatment from a terminally ill patient following attempted suicide in the following circumstances: based on standing orders, 78%; with on-line medical direction, 67%; after speaking with the primary physician, 53%; if the patient had decision-making capacity, 45%; with written documentation from the patient's physician, 68%; and never, 6%.

CONCLUSIONS

A majority of Oregon EMTs responding to this survey expressed support for PAS, think treatment protocols should direct paramedics to withhold resuscitation in such cases, and would feel comfortable withholding resuscitation given appropriate protocols. Nearly 3 out of 4 Oregon EMTs report seeing at least 1 terminally ill patient who had attempted suicide.

Do patients refusing transport remember descriptions of risks after initial advanced life support assessment?

OBJECTIVE

To determine patient recall and understanding of instructions given to patients who refuse transport after initial paramedic assessment and medical treatment.

METHODS

Following patient consent, a phone interview was completed for consecutive persons living in a large urban area for whom 9-1-1 was contacted but who subsequently refused transport after advanced life support (ALS) assessment. Subjects were asked about their recall of explained risks and benefits of transport, their understanding of those risks at the time of assessment, and subsequent use of medical care, including hospitalization.

RESULTS

From October 1, 1996, to February 23, 1997, 324 people refused transport after ALS arrival. Sixty-eight people could not be contacted, providing a response rate of 79% (256/324). Six percent were subsequently admitted to the hospital for the same problem and an additional 59% sought care from a health care provider (66 ED visits, 63 personal physician, 16 urgent care, 5 other). There were no unexpected deaths. Ninety (35%) respondents were still experiencing symptoms at the time of phone contact. Despite the routine practice of providing a verbal explanation of risks and written instructions, only 141 (55%) recalled receiving written instructions and 56 (22%) recalled an explanation of risks. Twenty-six percent believed they did not fully understand their conditions or circumstances surrounding the 9-1-1 call when they refused transport and 18% would now take an ambulance if the same incident were to recur.

CONCLUSION

A substantial proportion of patients refusing transport do not recall receiving verbal or written instructions and would reconsider their transport decision, raising doubts about people's ability to make informed decisions at a time of great vulnerability. The majority of patients accessed health care after refusing transport and 6% were hospitalized.

Multiple options and unique pathways: a new direction for EMS?

The same forces transforming the health care delivery system also are reshaping EMS. The changing economic and organizational structures of the health services delivery system may predict how EMS systems will redesign themselves. We discuss one template for future EMS systems.

Lumbar facet joint tropism does not accelerate degeneration of the facet joints

PURPOSE

To study the relationship of lumbar facet joint tropism to degeneration of the cartilage and subcortical bone in the facet joints and the effect of tropism in intervertebral disk degeneration.

METHODS

The orientation of 104 cadaveric lumbar facet joints with respect to sagittal plane was measured on CT scans, and the joints were classified as having no tropism, mild tropism, or severe tropism. On MR images, the severity of cartilage degeneration and bony sclerosis was measured. The correlation between tropism and degeneration was calculated, as was the relationship among age, spinal level, and degeneration.

RESULTS

We identified four spinal levels with severe tropism, six with moderate tropism, and 94 without tropism. Cartilage degeneration was not significantly more severe in the joints with tropism than in the joints without. Sclerosis was slightly greater in the joints with tropism than in the joints without it. Sclerosis and cartilage degeneration were significantly related to age and spinal level.

CONCLUSION

Age, spinal level, and overall facet joint angle are more important factors in facet joint degeneration than is tropism.

K+ supplementation increases muscle [Na+-K+-ATPase] and improves extrarenal K+ homeostasis in rats

Effects of K+ supplementation (approximately 200 mmol KCl/100 g chow) on plasma K+, K+ content, and Na+-K+-adeonsinetriphosphatase (ATPase) concentration ([Na+-K+-ATPase]) in skeletal muscles as well as on extrarenal K+ clearance were evaluated in rats. After 2 days of K+ supplementation, hyperkalemia prevailed (K+-supplemented vs. weight-matched control animals) [5.1 +/- 0.2 (SE) vs. 3.2 +/- 0.1 mmol/l, P < 0.05, n = 5-6], and after 4 days a significant increase in K+ content was observed in gastrocnemius muscle (104 +/- 2 vs. 97 +/- 1 micromol/g wet wt, P < 0.05, n = 5-6). After 7 days of K+ supplementation, a significant increase in [3H] ouabain binding site concentration (344 +/- 5 vs. 239 +/- 8 pmol/g wet wt, P < 0.05, n = 4) was observed in gastrocnemius muscle. After 2 wk, increases in plasma K+, K+ content, and [3H]ouabain binding site concentration in gastrocnemius muscle amounted to 40, 8, and 68% (P < 0.05) above values observed in weight-matched control animals, respectively. The latter change was confirmed by K+-dependent p-nitrophenyl phosphatase activity measurements. Fasting for 1 day reduced plasma K+ and K+ content in gastrocnemius muscle in rats that had been K+ supplemented for 2 wk by 3.1 +/- 0.3 mmol/l (P < 0.05, n = 5) and 15 +/- 2 micromol/g wet wt (P < 0.05, n = 5), respectively. After induction of anesthesia, arterial plasma K+ was measured during intravenous KCl infusion (0.75 mmol KCl x 100 g body wt(-1) x h(-1)). The K+-supplemented fasted group demonstrated a 42% (P < 0.05) lower plasma K+ rise, associated with a significantly higher increase in K+ content in gastrocnemius muscle of 7 micromol/g wet wt (P < 0.05, n = 5) compared with their control animals. In conclusion, K+ supplementation increases plasma K+, K+ content, and [Na+-K+-ATPase] in skeletal muscles and improves extrarenal K+ clearance capacity.

Reduced concentration of myocardial Na+,K(+)-ATPase in human aortic valve disease as well as of Na+,K(+)- and Ca(2+)-ATPase in rodents with hypertrophy

Myocardial Na+,K(+)-ATPase was studied in patients with aortic valve disease, and myocardial Na+,K(+)- and Ca(2+)-ATPase were assessed in spontaneously hypertensive rats (SHR) and hereditary cardiomyopathic hamsters using methods ensuring high enzyme recovery. Na+,K(+)-ATPase was quantified by [3H]ouabain binding to intact myocardial biopsies from patients with aortic valve disease. Aortic stenosis, regurgitation and a combination hereof were compared with normal human heart and were associated with reductions of left ventricular [3H]ouabain binding site concentration (pmol/g wet weight) of 56, 46 and 60%, respectively (p < 0.01). Na+,K(+)- and Ca(2+)-ATPases were quantified by K(+)- and Ca(2+)-dependent p-nitrophenyl phosphatase (pNPPase) activity determinations in crude myocardial homogenates from SHR and hereditary cardiomyopathic hamsters. When SHR were compared to age-matched Wistar Kyoto (WKY) rats an increase in heart-body weight ratio of 75% (p < 0.001) was associated with reductions of K(+)- and Ca(2+)-dependent pNPPase activities (mumol/min/g wet weight) of 42 (p < 0.01) and 27% (p < 0.05), respectively. When hereditary cardiomyopathic hamsters were compared to age-matched Syrian hamsters an increase in heart-body weight ratio of 69% (p < 0.001) was found to be associated with reductions in K(+)- and Ca(2+)-dependent pNPPase activities of 50 (p < 0.001) and 26% (p = 0.05), respectively. The reductions in Na+,K(+)- and Ca(2+)-ATPases were selective in relation to overall protein content and were not merely the outcome of increased myocardial mass relative to Na+,K(+)- and Ca(2+)-pumps. In conclusion, myocardial hypertrophy is in patients associated with reduced Na+,K(+)-ATPase concentration and in rodents with reduced Na+,K(+)- and Ca(2+)-ATPase concentrations. This may be of importance for development of heart failure and arrhythmia in hypertrophic heart disease.

Reduction of cerebral cortical [3H]ouabain binding site (Na+,K(+)-ATPase) density in dementia as evaluated in fresh human cerebral cortical biopsies

Na+,K(+)-ATPase density in human cerebral cortex was for the first time studied by vanadate facilitated [3H]ouabain binding to intact samples. Fresh human cerebral cortical biopsies were obtained as a result of diagnostic frontal lobe biopsy from patients with normal pressure hydrocephalus (NPH) syndrome and associated dementia. For control measurements post-mortem samples were obtained from patients without clinically observed dementia. [3H]ouabain binding kinetics were evaluated: when incubating samples in 1 microM [3H]ouabain binding equilibrium was obtained after 6 h of incubation, non-specific uptake and retention amounted to only 2.3% of total uptake and retention of [3H]ouabain and release of specifically bound [3H]ouabain during washout in the cold occurred only slowly (T1/2 = 37 h). Evaluation of receptor affinity for ouabain was in agreement with a heterogeneous population of [3H]ouabain binding sites. [3H]Ouabain binding was significantly reduced after frozen storage of samples before measurements. Post-mortem degradation of cerebral [3H]ouabain binding sites occurred only slowly (T1/2 = 75 h). No significant variation in [3H]ouabain binding site density was observed between the cerebral lobes with occipital, parietal and temporal values (means +/- S.E.M., n = 5) amounting to 10281 +/- 649, 11267 +/- 1011 and 9263 +/- 615 pmol/g wet wt., respectively. [3H]Ouabain binding measured in frontal cortical samples gave values of (means +/- S.E.M., n = 5) 4274 +/- 1020 and 11397 +/- 976 pmol/g wet wt. delta % = 62; P < 0.05) in patients with dementia and controls, respectively. Human cerebral cortical capacity for active K+ uptake was around 37- and 16-fold greater than in skeletal muscular and myocardial tissue, respectively.

Oregon emergency physicians' experiences with, attitudes toward, and concerns about physician-assisted suicide

OBJECTIVE

To determine emergency physicians' (EPs') attitudes toward physician-assisted suicide (PAS), factors associated with those attitudes, current experiences with attempted suicides in terminally ill persons, and concerns about the impact of legalizing PAS on emergency medicine practice.

METHODS

A cross-sectional, anonymous mailed survey was taken of EPs in the state of Oregon.

RESULTS

Of 356 eligible physicians, 248 (70%) returned the survey. Of the respondents, 69% indicated that PAS should be legal, 65% considered PAS consistent with the physician's role, and 19% believed that it is immoral. The respondents were concerned that patients might feel pressure if they perceived themselves to be either a care burden on others (82%) or a financial stress to others (69%). Only 37% indicated that the Oregon initiative has enough safeguards to protect vulnerable persons. Support for legalization was not associated with gender, age, or practice location. Respondents with no religious affiliation were most supportive of PAS (p < 0.001), and Catholic respondents were least suppportive (p = 0.03). A majority (58%) had treated at least 1 terminally ill patient after an apparent overdose. Most respondents (97%) indicated at least 1 circumstance for which they would sometimes be willing to let a terminally ill patient die without resuscitation after PAS if the Oregon initiative becomes law: if verified with an advance directive from the patient (81%), with documentation in writing from the physician (73%), after speaking to the primary physician (64%), if a competent patient verbally confirmed intent (60%), or if the family verbally confirmed intent (52%).

CONCLUSIONS

Although the majority of Oregon EPs favor the concept of legalization of PAS, most have concerns that safeguards in the Oregon initiative are inadequate to protect vulnerable patients. These physicians would consider not resuscitating terminally ill patients who have attempted suicide under the law's provisions, only in the setting of documentation of the patient's intent.

Occult lumbar lateral spinal stenosis in neural foramina subjected to physiologic loading

PURPOSE

To measure the effect of extension, flexion, lateral bending, and axial rotation loads applied to the spine on the anatomic relationship of the spinal nerves in the neural foramen to the ligamentum flavum and the intervertebral disk, anc to determine the effect of disk degeneration on the response to loading.

METHODS

Cadaveric lumbar motion segments were examined with CT and MR imaging, loaded with pure moment forces, frozen in situ, reexamined with CT, and sectioned with a cryomicrotome. The morphology of the intervertebral disks was classified on the basis of the appearance of the cryomicrotome sections. The neural foramina were classified as having no evident stenosis, as being stenotic, as having occult stenosis, or as showing resolved stenosis on the basis of the images and sections before and after loading. The stenotic and nonstenotic foramina were stratified by disk level, intervertebral disk classification, and type of loading applied. The effect of spinal level, disk type, and load type on the prevalence of stenosis was studied.

RESULTS

On average, extension, flexion, lateral bending, and axial rotation resulted in the ligamentum flavum or intervertebral disk contacting or compressing the spinal nerve in 18% of the neural foramina. Extension loading produced the most cases of nerve root contact, and lateral bending produced the fewest cases. Each of the loading types resulted also in diminished contact between the spinal nerve and the intervertebral disk or ligamentum flavum in some cases. Disk degeneration significantly increased the prevalence of spinal stenosis. All foramina associated with advanced disk degeneration and half of the foramina associated with disks having radial tears of the annulus fibrosus either developed occult stenosis or were stenotic before loading.

CONCLUSIONS

The study supports the concept of dynamic spinal stenosis; that is, intermittent stenosis of the neural foramina. Flexion, extension, lateral bending, and axial rotation significantly changed the anatomic relationships of the ligamentum flavum and intervertebral disk to the spinal nerve roots.

Advanced life support in the wilderness: 5-year experience of the Reach and Treat team

Increasing recreation in the wilderness raises questions about the value of providing advanced life support (ALS) care in the backcountry. Since 1989 the Reach and Treat (RAT) team has provided ALS care in the wilderness area that surrounds Mount Hood, Oregon. The purpose of our study was to describe patient demographics, terrain, injuries, and ALS treatment in the wilderness environment. We utilized a retrospective, observational analysis of RAT missions from 1989 to 1994 based on data sheets maintained by the RAT team, prehospital run sheets, and hospital charts. Of the 114 missions analyzed, the median time of missions was 3 h, 9 min (range, 44 min-76 h) and 20% required technical climbing skills. Of the 74 patients treated, 55 (90%) received ALS care: 8 were intubated, 52 had intravenous lines established, and 24 received morphine for pain. Twenty patients were entered into the local trauma system. The most common injuries were extremity injuries (58), head injuries (18), and hypothermia (15). Mean time from arrival to return to staging area was 95 min. No injuries to RAT team members occurred during these missions, although two minor injuries occurred during training and testing. We found that wilderness-trained paramedics safely provided ALS care in a backcountry environment. This care may improve patient comfort during long extrication and speeds the arrival of potentially life-saving interventions such as advanced airway management.