The crystal structure of the human smacovirus 1 Rep domain

Replication initiator proteins (Reps) from the HUH endonuclease family process specific single-stranded DNA sequences to initiate rolling-circle replication in viruses. Here, the first crystal structure of the apo state of a Rep domain from the smacovirus family is reported. The structure of the human smacovirus 1 Rep domain was obtained at 1.33 Å resolution and represents an expansion of the HUH endonuclease superfamily, allowing greater diversity in bioconjugation-tag applications.

Designing Efficient Enzymes: Eight Predicted Mutations Convert a Hydroxynitrile Lyase into an Efficient Esterase

Hydroxynitrile lyase from rubber tree (HbHNL) shares 45% identical amino acid residues with the homologous esterase from tobacco, SABP2, but the two enzymes catalyze different reactions. The x-ray structures reveal a serine-histidine-aspartate catalytic triad in both enzymes along with several differing amino acid residues within the active site. Previous exchange of three amino acid residues in the active site of HbHNL with the corresponding amino acid residue in SABP2 (T11G-E79H-K236M) created variant HNL3, which showed low esterase activity toward p-nitrophenyl acetate. Further structure comparison reveals additional differences surrounding the active site. HbHNL contains an improperly positioned oxyanion hole residue and differing solvation of the catalytic aspartate. We hypothesized that correcting these structural differences would impart good esterase activity on the corresponding HbHNL variant. To predict the amino acid substitutions needed to correct the structure, we calculated shortest path maps for both HbHNL and SABP2, which reveal correlated movements of amino acids in the two enzymes. Replacing four amino acid residues (C81L-N104T-V106F-G176S) whose movements are connected to the movements of the catalytic residues yielded variant HNL7TV (stabilizing substitution H103V was also added), which showed an esterase catalytic efficiency comparable to that of SABP2. The x-ray structure of an intermediate variant, HNL6V, showed an altered solvation of the catalytic aspartate and a partially corrected oxyanion hole. This dramatic increase in catalytic efficiency demonstrates the ability of shortest path maps to predict which residues outside the active site contribute to catalytic activity.

Watson-Crick Base-Pairing Requirements for ssDNA Recognition and Processing in Replication-Initiating HUH Endonucleases

Replication-initiating HUH endonucleases (Reps) are sequence-specific nucleases that cleave and rejoin single-stranded DNA (ssDNA) during rolling-circle replication. These functions are mediated by covalent linkage of the Rep to its substrate post cleavage. Here, we describe the structures of the endonuclease domain from the Muscovy duck circovirus Rep in complex with its cognate ssDNA 10-mer with and without manganese in the active site. Structural and functional analyses demonstrate that divalent cations play both catalytic and structural roles in Reps by polarizing and positioning their substrate. Further structural comparisons highlight the importance of an intramolecular substrate Watson-Crick (WC) base pairing between the -4 and +1 positions. Subsequent kinetic and functional analyses demonstrate a functional dependency on WC base pairing between these positions regardless of the pair's identity (i.e., A·T, T·A, G·C, or C·G), highlighting a structural specificity for substrate interaction. Finally, considering how well WC swaps were tolerated in vitro, we sought to determine to what extent the canonical -4T·+1A pairing is conserved in circular Rep-encoding single-stranded DNA viruses and found evidence of noncanonical pairings in a minority of these genomes. Altogether, our data suggest that substrate intramolecular WC base pairing is a universal requirement for separation and reunion of ssDNA in Reps. IMPORTANCE Circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses are a ubiquitous group of viruses that infect organisms across all domains of life. These viruses negatively impact both agriculture and human health. All members of this viral family employ a multifunctional nuclease (Rep) to initiate replication. Reps are structurally similar throughout this family, making them targets of interest for viral inhibition strategies. Here, we investigate the functional dependencies of the Rep protein from Muscovy duck circovirus for ssDNA interaction. We demonstrate that this Rep requires an intramolecular Watson-Crick base pairing for origin of replication (Ori) recognition and interaction. We show that noncognate base pair swaps are well tolerated, highlighting a local structural specificity over sequence specificity. Bioinformatic analysis found that the vast majority of CRESS-DNA Oris form base pairs in conserved positions, suggesting this pairing is a universal requirement for replication initiation in the CRESS-DNA virus family.

Molecular underpinnings of ssDNA specificity by Rep HUH-endonucleases and implications for HUH-tag multiplexing and engineering

Replication initiator proteins (Reps) from the HUH-endonuclease superfamily process specific single-stranded DNA (ssDNA) sequences to initiate rolling circle/hairpin replication in viruses, such as crop ravaging geminiviruses and human disease causing parvoviruses. In biotechnology contexts, Reps are the basis for HUH-tag bioconjugation and a critical adeno-associated virus genome integration tool. We solved the first co-crystal structures of Reps complexed to ssDNA, revealing a key motif for conferring sequence specificity and for anchoring a bent DNA architecture. In combination, we developed a deep sequencing cleavage assay, termed HUH-seq, to interrogate subtleties in Rep specificity and demonstrate how differences can be exploited for multiplexed HUH-tagging. Together, our insights allowed engineering of only four amino acids in a Rep chimera to predictably alter sequence specificity. These results have important implications for modulating viral infections, developing Rep-based genomic integration tools, and enabling massively parallel HUH-tag barcoding and bioconjugation applications.

The impact of different hair-removal behaviours on the biophysical and biochemical characteristics of female axillary skin

Objective

The impact of hair removal on the biophysical and biochemical characteristics of human axillary skin is not fully understood. This study investigated the effect of different hair‐removal techniques on biophysical parameters and the concentrations of key inflammatory biomarkers in the axillae of female Thai subjects. Axillary hair was removed by shaving, plucking or waxing.

Methods

Following a 2‐week washout phase without hair removal, subjects underwent visual assessment for erythema and skin dryness in one (randomized) axilla, then, hair was removed from the axilla by shaving, plucking or waxing according to each subject’s established habit. Erythema and dryness were assessed again 30 min after hair removal, and buffer scrubs collected from depilated and non‐depilated axillae and analysed for inflammatory cytokines; after a further 48 h, erythema, dryness and post‐inflammatory hyperpigmentation (PIHP) were assessed in the depilated axilla. Biophysical assessments (skin hydration, barrier integrity, elasticity and roughness) were made in depilated and non‐depilated axillae.

Results

All three hair‐removal techniques induced an increase in axillary erythema and skin dryness. Shaving was associated with significantly less erythema (P < 0.01), but significantly greater skin dryness (P < 0.05) versus the other techniques 30 min after hair removal. There were no between‐technique differences in PIHP or biophysical parameters. Interleukins IL‐1α and IL‐1RA concentrations increased, and IL‐8 concentration decreased following hair removal by each technique.

Conclusion

This is the first study to identify the principal cytokines associated with the inflammatory process triggered by axillary hair removal. A single hair‐removal treatment did not appear to induce PIHP or further biophysical changes to the skin.

Larger active site in an ancestral hydroxynitrile lyase increases catalytically promiscuous esterase activity

Hydroxynitrile lyases (HNL's) belonging to the α/β-hydrolase-fold superfamily evolved from esterases approximately 100 million years ago. Reconstruction of an ancestral hydroxynitrile lyase in the α/β-hydrolase fold superfamily yielded a catalytically active hydroxynitrile lyase, HNL1. Several properties of HNL1 differ from the modern HNL from rubber tree (HbHNL). HNL1 favors larger substrates as compared to HbHNL, is two-fold more catalytically promiscuous for ester hydrolysis (p-nitrophenyl acetate) as compared to mandelonitrile cleavage, and resists irreversible heat inactivation to 35 °C higher than for HbHNL. We hypothesized that the x-ray crystal structure of HNL1 may reveal the molecular basis for the differences in these properties. The x-ray crystal structure solved to 1.96-Å resolution shows the expected α/β-hydrolase fold, but a 60% larger active site as compared to HbHNL. This larger active site echoes its evolution from esterases since related esterase SABP2 from tobacco also has a 38% larger active site than HbHNL. The larger active site in HNL1 likely accounts for its ability to accept larger hydroxynitrile substrates. Site-directed mutagenesis of HbHNL to expand the active site increased its promiscuous esterase activity 50-fold, consistent with the larger active site in HNL1 being the primary cause of its promiscuous esterase activity. Urea-induced unfolding of HNL1 indicates that it unfolds less completely than HbHNL (m-value = 0.63 for HNL1 vs 0.93 kcal/mol·M for HbHNL), which may account for the ability of HNL1 to better resist irreversible inactivation upon heating. The structure of HNL1 shows changes in hydrogen bond networks that may stabilize regions of the folded structure.

Larger active site in an ancestral hydroxynitrile lyase increases catalytically promiscuous esterase activity.. [DOI: 10.1101/2020.04.06.027797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Hydroxynitrile lyases (HNL’s) belonging to the α/β-hydrolase-fold superfamily evolved from esterases approximately 100 million years ago. Reconstruction of an ancestral hydroxynitrile lyase in the α/β-hydrolase fold superfamily yielded a catalytically active hydroxynitrile lyase, HNL1. Several properties of HNL1 differ from the modern HNL from rubber tree (HbHNL). HNL1 favors larger substrates as compared to HbHNL, is two-fold more catalytically promiscuous for ester hydrolysis (p-nitrophenyl acetate) as compared to mandelonitrile cleavage, and resists irreversible heat inactivation to 35 °C higher than for HbHNL. We hypothesized that the x-ray crystal structure of HNL1 may reveal the molecular basis for the differences in these properties. The x-ray crystal structure solved to 1.96-Å resolution shows the expected α/β-hydrolase fold, but a 60% larger active site as compared to HbHNL. This larger active site echoes its evolution from esterases since related esterase SABP2 from tobacco also has a 38% larger active site than HbHNL. The larger active site in HNL1 likely accounts for its ability to accept larger hydroxynitrile substrates. Site-directed mutagenesis of HbHNL to expand the active site increased its promiscuous esterase activity 50-fold, consistent with the larger active site in HNL1 being the primary cause of its promiscuous esterase activity. Urea-induced unfolding of HNL1 indicates that it unfolds less completely than HbHNL (m-value = 0.63 for HNL1 vs 0.93 kcal/ mol·M for HbHNL), which may account for the ability of HNL1 to better resist irreversible inactivation upon heating. The structure of HNL1 shows changes in hydrogen bond networks that may stabilize regions of the folded structure.

VIP and muscarinic synergistic mucin secretion by salivary mucous cells is mediated by enhanced PKC activity via VIP-induced release of an intracellular Ca2+ pool

Mucin secretion by salivary mucous glands is mediated predominantly by parasympathetic acetylcholine activation of cholinergic muscarinic receptors via increased intracellular free calcium ([Ca²⁺]_i) and activation of conventional protein kinase C isozymes (cPKC). However, the parasympathetic co-neurotransmitter, vasoactive intestinal peptide (VIP), also initiates secretion, but to a lesser extent. In the present study, cross talk between VIP- and muscarinic-induced mucin secretion was investigated using isolated rat sublingual tubuloacini. VIP-induced secretion is mediated by cAMP-activated protein kinase A (PKA), independently of increased [Ca²⁺]_i. Synergistic secretion between VIP and the muscarinic agonist, carbachol, was demonstrated but only with submaximal carbachol. Carbachol has no effect on cAMP ± VIP. Instead, PKA activated by VIP releases Ca²⁺ from an intracellular pool maintained by the sarco/endoplasmic reticulum Ca²⁺-ATPase pump. Calcium release was independent of phospholipase C activity. The resultant sustained [Ca²⁺]_i increase is additive to submaximal, but not maximal carbachol-induced [Ca²⁺]_i. Synergistic mucin secretion was mimicked by VIP plus either phorbol 12-myristate 13-acetate or 0.01 μM thapsigargin, and blocked by the PKC inhibitor, Gö6976. VIP-induced Ca²⁺ release also promoted store-operated Ca²⁺ entry. Synergism is therefore driven by VIP-mediated [Ca²⁺]_i augmenting cPKC activity to enhance muscarinic mucin secretion. Additional data suggest ryanodine receptors control VIP/PKA-mediated Ca²⁺ release from a Ca²⁺ pool also responsive to maximal carbachol. A working model of muscarinic and VIP control of mucous cell exocrine secretion is presented. Results are discussed in relation to synergistic mechanisms in other secretory cells, and the physiological and therapeutic significance of VIP/muscarinic synergism controlling salivary mucous cell exocrine secretion.

Discovery of Hydroxylase Activity for PqqB Provides a Missing Link in the Pyrroloquinoline Quinone Biosynthetic Pathway

Understanding the biosynthesis of cofactors is fundamental to the life sciences, yet to date a few important pathways remain unresolved. One example is the redox cofactor pyrroloquinoline quinone (PQQ), which is critical for C1 metabolism in many microorganisms, a disproportionate number of which are opportunistic human pathogens. While the initial and final steps of PQQ biosynthesis, involving PqqD/E and PqqC, have been elucidated, the precise nature and order of the remaining transformations in the pathway are unknown. Here we show evidence that the remaining essential biosynthetic enzyme PqqB is an iron-dependent hydroxylase catalyzing oxygen-insertion reactions that are proposed to produce the quinone moiety of the mature PQQ cofactor. The demonstrated reactions of PqqB are unprecedented within the metallo β-lactamase protein family and expand the catalytic repertoire of nonheme iron hydroxylases. These new findings also generate a nearly complete description of the PQQ biosynthetic pathway.

Crystal structures reveal metal-binding plasticity at the metallo-β-lactamase active site of PqqB from Pseudomonas putida

PqqB is an enzyme involved in the biosynthesis of pyrroloquinoline quinone and a distal member of the metallo-β-lactamase (MBL) superfamily. PqqB lacks two residues in the conserved signature motif HxHxDH that makes up the key metal-chelating elements that can bind up to two metal ions at the active site of MBLs and other members of its superfamily. Here, we report crystal structures of PqqB bound to Mn²⁺, Mg²⁺, Cu²⁺, and Zn²⁺. These structures demonstrate that PqqB can still bind metal ions at the canonical MBL active site. The fact that PqqB can adapt its side chains to chelate a wide spectrum of metal ions with different coordination features on a uniform main chain scaffold demonstrates its metal-binding plasticity. This plasticity may provide insights into the structural basis of promiscuous activities found in ensembles of metal complexes within this superfamily. Furthermore, PqqB belongs to a small subclass of MBLs that contain an additional CxCxxC motif that binds a structural Zn²⁺. Our data support a key role for this motif in dimerization.

Nuclear Magnetic Resonance Structure and Binding Studies of PqqD, a Chaperone Required in the Biosynthesis of the Bacterial Dehydrogenase Cofactor Pyrroloquinoline Quinone

Biosynthesis of the ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is initiated when the precursor peptide, PqqA, is recognized and bound by the RiPP precursor peptide recognition element (RRE), PqqD, for presentation to the first enzyme in the pathway, PqqE. Unlike other RiPP-producing, postribosomal peptide synthesis (PRPS) pathways in which the RRE is a component domain of the first enzyme, PqqD is predominantly a separate scaffolding protein that forms a ternary complex with the precursor peptide and first tailoring enzyme. As PqqD is a stable, independent RRE, this makes the PQQ pathway an ideal PRPS model system for probing RRE interactions using nuclear magnetic resonance (NMR). Herein, we present both the solution NMR structure of Methylobacterium extorquens PqqD and results of ¹H-¹⁵N HSQC binding experiments that identify the PqqD residues involved in binding the precursor peptide, PqqA, and the enzyme, PqqE. The reported structural model for an independent RRE, along with the mapped binding surfaces, will inform future efforts both to understand and to manipulate PRPS pathways.

(1)H, (13)C, and (15)N resonance assignments and secondary structure information for Methylobacterium extorquens PqqD and the complex of PqqD with PqqA

The ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is a dehydrogenase cofactor synthesized by, but not exclusively used by, certain prokaryotes. RiPPs represent a rapidly expanding and diverse class of natural products-many of which have therapeutic potential-and the biosynthetic pathways for these are gaining attention. Five gene products from the pqq operon (PqqA, PqqB, PqqC, PqqD, and PqqE) are essential for PQQ biosynthesis. The substrate is the peptide PqqA, which is presented to the radical SAM enzyme PqqE by the small protein PqqD. PqqA is unstructured in solution, and only binds to PqqE when in complex with PqqD. PqqD is a member of a growing family of RiPP chaperone proteins (or domains in most cases) that present their associated peptide substrates to the initial RiPP biosynthesis enzymes. An X-ray crystal structure exists for dimeric Xanthomonas campestris PqqD (PDB ID: 3G2B), but PqqD is now known to act as a monomer under physiological conditions. In this study, the PqqD truncation from naturally fused Methylobacterium extorquens (Mex) PqqCD was overexpressed in Escherichia coli and MexPqqA was chemically synthesized. Solution NMR (1)H-,(15)N-HSQC chemical shift studies have identified the PqqD residues involved in binding PqqA, and (1)H, (13)C, and (15)N peak assignments for PqqD alone and for PqqD bound to PqqA are reported herein.

Role of calcium and PKC in salivary mucous cell exocrine secretion

Fluid and exocrine secretion of mucins by salivary mucous glands is regulated predominantly by parasympathetic activation of muscarinic receptors. A direct role for subsequent putative signaling steps, phospholipase C (PLC), increased intracellular calcium ([Ca(2+)](i)), and isoforms of protein kinase C (PKC) in mediating muscarinic exocrine secretion has not been elucidated, and these are potential therapeutic targets to enhance mucin secretion in hyposalivary patients. We found that muscarinic-induced mucin secretion by rat sublingual tubulo-acini was dependent upon PLC activation and the subsequent increase in [Ca(2+)](i), and further identified a transient PKC-independent component of secretion dependent upon Ca(2+) release from intracellular stores, whereas sustained secretion required entry of extracellular Ca(2+). Interactions among carbachol, PKC inhibitors, phorbol 12-myristate 13-acetate, and thapsigargin to modulate [Ca(2+)](i) implicated conventional PKC isoforms in mediating sustained secretion. With increasing times during carbachol perfusion of glands, in situ, PKC-α redistributed across glandular membrane compartments and underwent a rapid and persistent accumulation near the luminal borders of mucous cells. PKC-β1 displayed transient localization near luminal borders, whereas the novel PKCs, PKC-δ or PKC-ε, displayed little or no redistribution in mucous cells. Collective results implicate synergistic interactions between diacylglycerol (DAG) and increasing [Ca(2+)](i) levels to activate cPKCs in mediating sustained muscarinic-induced secretion.

Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA

While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km(3) in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (10(4) km(3)) and passive margins globally (3 x 10(5) km(3)). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages.

Effect of antiperspirants on whole body sweat rate and thermoregulation

It is well established that the evaporation of sweat from the human body surface is the main mechanism by which heat balance is maintained following a rise in body core temperature. Since the introduction of the first brand name antiperspirant in the United States during the early 1900s, antiperspirant products designed to control underarm wetness have grown to represent one of the largest cosmetic categories in most global markets. However, although axillary sweating only constitutes less than 1% of whole body sweat rate, consumers, particularly in hot countries, have begun to articulate the concern that antiperspirants may interfere with the body's natural cooling process. To investigate this, we undertook carefully designed experiments that measured the effects of axillary antiperspirant application on whole body sweat rate and body core temperature, following a regimen of exercise-induced heat stress in a hot environment in human volunteers. Our data show clearly that although antiperspirant prevents sweat production in the axillary area, this does not impact the ability of the body to thermoregulate following a rise in body core temperature. Thus, recent consumer questioning over this aspect of antiperspirant use appears to be unwarranted.

Survivorship of the St Georg Sled medial unicompartmental knee replacement beyond ten years

There have been several reports of good survivorship and excellent function at ten years with fixed-bearing unicompartmental knee replacement. However, little is known about survival beyond ten years. From the Bristol database of over 4000 knee replacements, we identified 203 St Georg Sled unicompartmental knee replacements (174 patients) which had already survived ten years. The mean age of the patients at surgery was 67.1 years (35.7 to 85) with 67 (38.5%) being under 65 years at the time of surgery. They were reviewed at a mean of 14.8 years (10 to 29.4) from surgery to determine survivorship and function. There were 99 knees followed up for 15 years, 21 for 20 years and four for 25 years. The remainder failed, were withdrawn, or the patient had died. In 58 patients (69 knees) the implant was in situ at the time of death. Revision was undertaken in 16 knees (7.9%) at a mean of 13 years (10.2 to 21.6) after operation. In seven knees (3.4%) this was for progression of arthritis, in three (1.5%) for wear of polyethylene, in four (2%) for tibial loosening, in two (1%) for fracture of the femoral component and in two (1%) for infection. Two knees (1%) were revised for more than one reason. The mean Bristol knee score of the surviving knees fell from 86 (34 to 100) to 79 (42 to 100) during the second decade. Survivorship to 20 years was 85.9% (95% CI 82.9% to 88.9%) and at 25 years was 80% (95% CI 70.2% to 89.8%). Satisfactory survival of a fixed-bearing unicompartmental knee replacement can be achieved into the second decade and beyond.

Hidden blood loss following hip and knee arthroplasty. Correct management of blood loss should take hidden loss into account

Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the 'visible' measured blood loss is usually known. This underestimates the 'true' total loss, as some loss is 'hidden'. Correct management of blood loss should take hidden loss into account. We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation. THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.

Hidden blood loss following hip and knee arthroplasty. Correct management of blood loss should take hidden loss into account

Following total hip arthroplasty (THA) and total knee arthroplasty (TKR) only the 'visible' measured blood loss is usually known. This underestimates the 'true' total loss, as some loss is 'hidden'. Correct management of blood loss should take hidden loss into account. We studied 101 THAs and 101 TKAs (with re-infusion of drained blood). Following THA, the mean total loss was 1510 ml and the hidden loss 471 ml (26%). Following TKA, the mean total loss was 1498 ml. The hidden loss was 765 ml (49%). Obesity made no difference with either operation. THA involves a small hidden loss, the total loss being 1.3 times that measured. However, following TKA, there may be substantial hidden blood loss due to bleeding into the tissues and residual blood in the joint. The true total loss can be determined by doubling the measured loss.

Lateral unicompartmental knee replacement survivorship and clinical experience over 21 years

We describe 88 knees (79 patients) with lateral unicompartmental osteoarthritis which had been treated by the St Georg Sled prosthesis. At a mean follow-up of nine years (2 to 21) 15 knees had revision surgery, nine for progression of arthritis, six for loosening, four for breakage of a component and four for more than one reason. Six patients complained of moderate or severe pain at the final follow-up. Only five knees were lost to follow-up in the 21-year period. We performed survivorship analysis on the group using revision for any cause as the endpoint. At ten years the cumulative survival rate was 83%, and at 15 years, when ten knees were still at risk, it was 74%. Based on our clinical results and survival rate the St Georg Sled may be considered to be a suitable unicompartmental replacement for isolated lateral compartment osteoarthritis.

Development and deployment of an internet-based data management system for use by the Asthma Clinical Research Network

Data management system development for the first Asthma Clinical Research Network (ACRN) study began at the data coordinating center (DCC) in May 1995 with the requirement for delivery of a production system by November 1995. Special methods had to be used to establish an internet local area network (LAN), place clinical client systems, and achieve an accelerated software development cycle. The development of a fully integrated data management system prior to the start of the study was not possible. Therefore an early analysis focused on identifying discrete groupings of data management functions that would allow development of distinct database modules to provide specific functionality such as subject randomization, subject registration, and data entry. The modules were categorized as either being associated with clinical centers or the DCC so that the clinical center modules could be developed and delivered to meet the start date of the study. In the second phase of development during the relatively slow patient-enrollment period, the DCC functional modules were delivered discretely over time. While at the time this development model was a necessity due to limited DCC resources, it continues to be used today as it permits the DCC to implement studies more rapidly and efficiently for the ACRN. This paper describes the methodologies used to develop an internet-based LAN, establish clinical center client systems, establish DCC client and server operations, and develop a data management system. It describes the circumstances that contributed to the development of these systems and the special methodologies developed. The technical aspects of the data management system and LAN are presented as well as a description of the requirements and constraints analysis used to develop the hardware and software systems.

Modem remote support of pulmonary-function testing and quality control systems

The data coordinating center (DCC) of the Asthma Clinical Research Network (ACRN) is responsible for the support of 11 pulmonary-function testing systems and two quality control systems. Pulmonary-function data from these systems are used as outcome indicators in studies conducted by the ACRN. Each of these systems is composed of a spirometer, a personal computer for data acquisition from the spirometer, a modem, and a printer. These systems are located at six clinical centers nationwide. An analysis conducted at the beginning of the first ACRN protocol identified the following requirements: (1) standard pulmonary-function testing, (2) standard methacholine-challenge testing, (3) the ability to handle simultaneous multiple protocols as well as have data from non-ACRN subjects, (4) the ability to separate data from different protocols as well as separate ACRN and non-ACRN data, (5) the ability to transmit data from the remote clinical centers to the DCC, (6) the ability to ensure quality data and to report on those results, and (7) the ability to provide remote support.

Comparison of subacute rehabilitative care with outpatient primary medical care

PURPOSE

Prior rehabilitation outcome studies have had many weaknesses. but they gradually observe a lack of long-term benefits from inpatient care alone. The goal of this study was to measure the additive effect of outpatient, subacute rehabilitation (compared with usual outpatient primary medical care) for adults diagnosed with a disabling disorder in four major diagnostic groups (nervous, circulatory, musculoskeletal and injury).

METHOD

A randomized clinical trial was conducted to determine the effects of outpatient, subacute rehabilitative care on: (1) physical function; (2) health; (3) well being; (4) family function; and (5) social support. Patients hospitalized for the first time with a disabling condition (n = 180) were provided inpatient rehabilitation and then were randomly assigned to either outpatient, subacute rehabilitation at home (n = 90) or to usual outpatient follow-up (n = 90) in which only primary care medical services were provided. To compare the two groups, univariate analyses of covariance were conducted for the outcome variables.

RESULTS

The major finding of this study was that of no significant effect of the intervention on any outcome variable.

CONCLUSIONS

Based on current study results, we conclude that any long term additive benefit of outpatient, subacute rehabilitation may not be detectable across disability categories and may require closer evaluation in studies with a more homogeneous population than in the current study. Providing complex follow-up case management services to all clients is apparently not beneficial and might better be provided using selection criteria based on need. Future studies should determine if services are more effective when provided to those with the most unmet rehabilitative needs. Further outpatient, subacute care rehabilitation studies should address the specific needs of the patients and be adapted individually to those needs.