The C-terminal Region of D-DT Regulates Molecular Recognition for Protein-Ligand Complexes

Systematic analysis of molecular recognition is critical for understanding the biological function of macromolecules. For the immunomodulatory protein D-dopachrome tautomerase (D-DT), the mechanism of protein-ligand interactions is poorly understood. Here, 17 carefully designed protein variants and wild type (WT) D-DT were interrogated with an array of complementary techniques to elucidate the structural basis of ligand recognition. Utilization of a substrate and two selective inhibitors with distinct binding profiles offered previously unseen mechanistic insights into D-DT-ligand interactions. Our results demonstrate that the C-terminal region serves a key role in molecular recognition via regulation of the active site opening, protein-ligand interactions, and conformational flexibility of the pocket's environment. While our study is the first comprehensive analysis of molecular recognition for D-DT, the findings reported herein promote the understanding of protein functionality and enable the design of new structure-based drug discovery projects.

Changes in an enzyme ensemble during catalysis observed by high-resolution XFEL crystallography

Enzymes populate ensembles of structures necessary for catalysis that are difficult to experimentally characterize. We use time-resolved mix-and-inject serial crystallography at an x-ray free electron laser to observe catalysis in a designed mutant isocyanide hydratase (ICH) enzyme that enhances sampling of important minor conformations. The active site exists in a mixture of conformations, and formation of the thioimidate intermediate selects for catalytically competent substates. The influence of cysteine ionization on the ICH ensemble is validated by determining structures of the enzyme at multiple pH values. Large molecular dynamics simulations in crystallo and time-resolved electron density maps show that Asp17 ionizes during catalysis and causes conformational changes that propagate across the dimer, permitting water to enter the active site for intermediate hydrolysis. ICH exhibits a tight coupling between ionization of active site residues and catalysis-activated protein motions, exemplifying a mechanism of electrostatic control of enzyme dynamics.

Mapping protein dynamics at high spatial resolution with temperature-jump X-ray crystallography

Understanding and controlling protein motion at atomic resolution is a hallmark challenge for structural biologists and protein engineers because conformational dynamics are essential for complex functions such as enzyme catalysis and allosteric regulation. Time-resolved crystallography offers a window into protein motions, yet without a universal perturbation to initiate conformational changes the method has been limited in scope. Here we couple a solvent-based temperature jump with time-resolved crystallography to visualize structural motions in lysozyme, a dynamic enzyme. We observed widespread atomic vibrations on the nanosecond timescale, which evolve on the submillisecond timescale into localized structural fluctuations that are coupled to the active site. An orthogonal perturbation to the enzyme, inhibitor binding, altered these dynamics by blocking key motions that allow energy to dissipate from vibrations into functional movements linked to the catalytic cycle. Because temperature jump is a universal method for perturbing molecular motion, the method demonstrated here is broadly applicable for studying protein dynamics.

Changes in an Enzyme Ensemble During Catalysis Observed by High Resolution XFEL Crystallography

Enzymes populate ensembles of structures with intrinsically different catalytic proficiencies that are difficult to experimentally characterize. We use time-resolved mix-and-inject serial crystallography (MISC) at an X-ray free electron laser (XFEL) to observe catalysis in a designed mutant (G150T) isocyanide hydratase (ICH) enzyme that enhances sampling of important minor conformations. The active site exists in a mixture of conformations and formation of the thioimidate catalytic intermediate selects for catalytically competent substates. A prior proposal for active site cysteine charge-coupled conformational changes in ICH is validated by determining structures of the enzyme over a range of pH values. A combination of large molecular dynamics simulations of the enzyme in crystallo and time-resolved electron density maps shows that ionization of the general acid Asp17 during catalysis causes additional conformational changes that propagate across the dimer interface, connecting the two active sites. These ionization-linked changes in the ICH conformational ensemble permit water to enter the active site in a location that is poised for intermediate hydrolysis. ICH exhibits a tight coupling between ionization of active site residues and catalysis-activated protein motions, exemplifying a mechanism of electrostatic control of enzyme dynamics.

Molecular-dynamics simulation methods for macromolecular crystallography

It is investigated whether molecular-dynamics (MD) simulations can be used to enhance macromolecular crystallography (MX) studies. Historically, protein crystal structures have been described using a single set of atomic coordinates. Because conformational variation is important for protein function, researchers now often build models that contain multiple structures. Methods for building such models can fail, however, in regions where the crystallographic density is difficult to interpret, for example at the protein-solvent interface. To address this limitation, a set of MD-MX methods that combine MD simulations of protein crystals with conventional modeling and refinement tools have been developed. In an application to a cyclic adenosine monophosphate-dependent protein kinase at room temperature, the procedure improved the interpretation of ambiguous density, yielding an alternative water model and a revised protein model including multiple conformations. The revised model provides mechanistic insights into the catalytic and regulatory interactions of the enzyme. The same methods may be used in other MX studies to seek mechanistic insights.

Comparing serial X-ray crystallography and microcrystal electron diffraction (MicroED) as methods for routine structure determination from small macromolecular crystals

Innovative new crystallographic methods are facilitating structural studies from ever smaller crystals of biological macromolecules. In particular, serial X-ray crystallography and microcrystal electron diffraction (MicroED) have emerged as useful methods for obtaining structural information from crystals on the nanometre to micrometre scale. Despite the utility of these methods, their implementation can often be difficult, as they present many challenges that are not encountered in traditional macromolecular crystallography experiments. Here, XFEL serial crystallography experiments and MicroED experiments using batch-grown microcrystals of the enzyme cyclophilin A are described. The results provide a roadmap for researchers hoping to design macromolecular microcrystallography experiments, and they highlight the strengths and weaknesses of the two methods. Specifically, we focus on how the different physical conditions imposed by the sample-preparation and delivery methods required for each type of experiment affect the crystal structure of the enzyme.

Co-occurring Alterations in the RAS-MAPK Pathway Limit Response to MET Inhibitor Treatment in MET Exon 14 Skipping Mutation-Positive Lung Cancer

PURPOSE

Although patients with advanced-stage non-small cell lung cancers (NSCLC) harboring MET exon 14 skipping mutations (METex14) often benefit from MET tyrosine kinase inhibitor (TKI) treatment, clinical benefit is limited by primary and acquired drug resistance. The molecular basis for this resistance remains incompletely understood.

EXPERIMENTAL DESIGN

Targeted sequencing analysis was performed on cell-free circulating tumor DNA obtained from 289 patients with advanced-stage METex14-mutated NSCLC.

RESULTS

Prominent co-occurring RAS-MAPK pathway gene alterations (e.g., in KRAS, NF1) were detected in NSCLCs with METex14 skipping alterations as compared with EGFR-mutated NSCLCs. There was an association between decreased MET TKI treatment response and RAS-MAPK pathway co-occurring alterations. In a preclinical model expressing a canonical METex14 mutation, KRAS overexpression or NF1 downregulation hyperactivated MAPK signaling to promote MET TKI resistance. This resistance was overcome by cotreatment with crizotinib and the MEK inhibitor trametinib.

CONCLUSIONS

Our study provides a genomic landscape of co-occurring alterations in advanced-stage METex14-mutated NSCLC and suggests a potential combination therapy strategy targeting MAPK pathway signaling to enhance clinical outcomes.

Temperature-jump solution X-ray scattering reveals distinct motions in a dynamic enzyme

Correlated motions of proteins are critical to function, but these features are difficult to resolve using traditional structure determination techniques. Time-resolved X-ray methods hold promise for addressing this challenge, but have relied on the exploitation of exotic protein photoactivity, and are therefore not generalizable. Temperature jumps, through thermal excitation of the solvent, have been utilized to study protein dynamics using spectroscopic techniques, but their implementation in X-ray scattering experiments has been limited. Here, we perform temperature-jump small- and wide-angle X-ray scattering measurements on a dynamic enzyme, cyclophilin A, demonstrating that these experiments are able to capture functional intramolecular protein dynamics on the microsecond timescale. We show that cyclophilin A displays rich dynamics following a temperature jump, and use the resulting time-resolved signal to assess the kinetics of conformational changes. Two relaxation processes are resolved: a fast process is related to surface loop motions, and a slower process is related to motions in the core of the protein that are critical for catalytic turnover.

Extending chemical perturbations of the ubiquitin fitness landscape in a classroom setting reveals new constraints on sequence tolerance

Although the primary protein sequence of ubiquitin (Ub) is extremely stable over evolutionary time, it is highly tolerant to mutation during selection experiments performed in the laboratory. We have proposed that this discrepancy results from the difference between fitness under laboratory culture conditions and the selective pressures in changing environments over evolutionary timescales. Building on our previous work (Mavor et al., 2016), we used deep mutational scanning to determine how twelve new chemicals (3-Amino-1,2,4-triazole, 5-fluorocytosine, Amphotericin B, CaCl₂, Cerulenin, Cobalt Acetate, Menadione, Nickel Chloride, p-Fluorophenylalanine, Rapamycin, Tamoxifen, and Tunicamycin) reveal novel mutational sensitivities of ubiquitin residues. Collectively, our experiments have identified eight new sensitizing conditions for Lys63 and uncovered a sensitizing condition for every position in Ub except Ser57 and Gln62. By determining the ubiquitin fitness landscape under different chemical constraints, our work helps to resolve the inconsistencies between deep mutational scanning experiments and sequence conservation over evolutionary timescales.

Bringing diffuse X-ray scattering into focus

X-ray crystallography is experiencing a renaissance as a method for probing the protein conformational ensemble. The inherent limitations of Bragg analysis, however, which only reveals the mean structure, have given way to a surge in interest in diffuse scattering, which is caused by structure variations. Diffuse scattering is present in all macromolecular crystallography experiments. Recent studies are shedding light on the origins of diffuse scattering in protein crystallography, and provide clues for leveraging diffuse scattering to model protein motions with atomic detail.

Effects of pericardiectomy on training- and myocardial infarction-induced left ventricular hypertrophy, chamber dimensions and gene expression

The primary purpose of the study was to evaluate whether a pericardiectomy (PERI) alters training- or myocardial infarction (MI)-induced left ventricular hypertrophy (LVH), chamber geometry, gene expression and/or running performance. Mice were randomized into 6 groups: naïve control (CONT)-sedentary (Sed), CONT-trained (Tr), PERI-Sed, PERI-Tr, MI-Sed and MI-Tr. MI mice also received a pericardiectomy as part of the MI surgical procedure. 10 weeks of treadmill running resulted in enhanced running performance-to-exhaustion in all 3 trained groups (CONT-Tr, PERI-Tr, MI-Tr) compared to sedentary cohorts (P<0.001). Training also resulted in similar increases in normalized LVH (LV/BW) in CONT-Tr and PERI-Tr mice. 2D-echocardiographic evaluation of LV internal chamber dimensions revealed that stroke diameter (SD) was larger in PERI compared to MI (P<0.01) but not CONT mice. Ventricular B-type natriuretic peptide mRNA (BNP) was elevated only in the 2 MI groups. Left ventricle β₁-adrenergic receptor (β₁-AR) and melusin transcripts both demonstrated an overall increase in trained compared to sedentary mice (both P<0.05). Additionally long-term pericardiectomy did not further enhance running performance or increase LV/BW in either sedentary or trained mice.

A multicopy vector system for genetic studies in Mucor circinelloides and other zygomycetes

Transformation of Mucor circinelloides is routinely achieved by using a plasmid containing the wild-type leuA gene to complement the leucine requirement of an auxotrophic host strain. As is the case for other zygomycetes, the transforming DNA is usually not integrated into the genome of M. circinelloides, but is maintained as an autonomously replicating plasmid. However, even under selective conditions, the plasmid is segregationally unstable, resulting in a rather low number of cells carrying the plasmid. We report here on a new transformation vector based on a dominant selection marker conferring resistance to geneticin, which allows for plasmid maintenance in high copy numbers. The vector was also used to transform Mucor rouxii and Rhizomucor pusillus, and should therefore be a valuable tool for gene expression studies in zygomycetes. The functionality and regulatory properties of the promoter of the M. circinelloides gpd1 gene (which codes for glyceraldehyde-3P-dehydrogenase) were demonstrated in R. pusillus using geneticin selection. In this work, we have also determined the molecular basis of the Leu(-) phenotype of the M. circinelloides host strain R7B. The leucine requirement is due to a single point mutation in the leuA gene that results in the replacement of a glutamic acid by a lysine residue.

Detecting and reducing adverse events in an Australian rural base hospital emergency department using medical record screening and review

OBJECTIVE

To determine if retrospective medical record screening and clinical review followed by appropriate action can effectively and efficiently detect and reduce adverse events in an emergency department.

METHOD AND PARTICIPANTS

The medical records of 20 050 patients who attended the emergency department over a two year period were screened for adverse events using five general patient outcome criteria. Records that screened positive were reviewed by the hospital's clinical risk manager. If an adverse event was detected, the record was also reviewed by the director of emergency. For the first three months details of adverse events were recorded to determine a baseline adverse event rate, but no further action was taken. When an adverse event was found in the remaining 21 months, further analysis and recommendations for action to prevent a recurrence were made to relevant hospital staff.

SETTING

A rural base hospital in the Wimmera region of Victoria, Australia between October 1997 and September 1999.

RESULTS

Of all the patient attendances 573 (2.85%) were screened positive for one or more criteria. An adverse event was confirmed in 250 patient attendances (1.24% of all attendances). Of the adverse occurrences, 81 (32.4%) were determined to be of major severity and 169 (67.6%) of minor severity. Quality improvement activities, mostly changes to hospital policies and work processes, were implemented with the aim of preventing the recurrence of specific adverse patient events. Over two years the number of adverse events fell from 84 (3.26% of all patient attendances) in the pre-intervention quarter to 12 (0.48% of all patient attendances) in the final quarter (relative risk reduction 85.3% (95% CI, 62.7% to 100%)).

CONCLUSIONS

Adverse events in emergency departments can be efficiently detected and their rate reduced using retrospective medical record screening together with clinical review, analysis and action to prevent recurrences.

Optimization of the production of Chondrus crispus hexose oxidase in Pichia pastoris

Hexose oxidase (D-hexose:O(2)-oxidoreductase, EC 1.1.3.5, HOX) normally found in the red alga Chondrus crispus was produced heterologously in different host systems. Full-length HOX polypeptide was produced in Escherichia coli, but no HOX activity could be detected. In contrast, active HOX could be produced in the methylotrophic yeast Pichia pastoris. Several growth physiological and genetic approaches for optimization of hexose oxidase production in P. pastoris were investigated. Our results indicate that specific growth conditions are essential in order to produce active HOX with the correct conformation. Furthermore, HOX seems to be activated by proteolytic cleavage of the full-length polypeptide chain into two fragments, which remain physically associated. Attempts to direct HOX to the extracellular compartment using the widely used secretion signals from Saccharomyces cerevisiae invertase or alpha-mating factor failed. However, we show in this study that HOX is transported out of P. pastoris via a hitherto unknown mechanism and that it is possible to enhance this secretion by mutagenesis from below the detection limit to at least 250 mg extracellular enzyme per liter.

Detecting and reducing hospital adverse events: outcomes of the Wimmera clinical risk management program

OBJECTIVES

To determine if an integrated clinical risk management program that detects adverse patient events in a hospital, analyses their risk and takes action can alter the rate of adverse events.

DESIGN

Longitudinal survey of adverse patient events over eight years of progressive implementation of the risk management program.

PARTICIPANTS AND SETTING

49,834 inpatients (July 1991 to September 1999) and 20,050 emergency department patients (October 1997 to September 1999) at a rural base hospital in the Wimmera region of Victoria.

MAIN OUTCOME MEASURES

Rates of adverse events detected by medical record review and clinical incident and general practitioner reporting.

RESULTS

The annual rate of inpatient adverse events decreased between the first and eighth years of the study from 1.35% of all patient discharges (69 events) to 0.74% (49 events) (P<0.001). Absolute risk reduction was 0.61% (95% CI, 0.23%-0.99%), and relative risk reduction was 44.9% (95% CI, 16.9%-72.9%). The quarterly rate of emergency department adverse events decreased between the first and eighth quarters of monitoring from 3.26% of all attendances (84 events) to 0.48% (12 events) (P< 0.001). Absolute risk reduction was 2.78% (95% CI, 2.04%-3.52%), and relative risk reduction was 85.3% (95% CI, 62.7%-100%).

CONCLUSIONS

Adverse patient events can be detected, and their frequency reduced, using multiple detection methods and clinical improvement strategies as part of an integrated clinical risk management program.

Reducing medical errors: a practical guide

Healthcare delivery involves complex systems Preventable injuries occur more frequently than in other complex industries. Clinical risk management aims to reduce the probability of adverse patient events occurring. Adverse events can be detected by medical record review, clinical incident reporting and other methods. Events are analysed to determine latent and active errors and ranked in order of risk severity. Action is then planned and implemented to prevent the event from recurring. Effective actions include simplifying systems, standardising procedures, introducing constraints, using reminders and checklists, providing timely information, and small-group interactive education. Organisational factors that may increase the probability of successfully reducing medical errors in hospitals include the availability of adequate resources and education, the presence of clinical, executive and board of management quality champions, and quality improvement and risk management as key objectives in a hospital's strategic plan. Governments can aid the implementation of risk management programs by financially rewarding high quality care.

The open reading frame YAL048c affects the secretion of proteinase A in S. cerevisiae

Over-expression of the yeast PEP4 gene encoding the vacuolar aspartic protease proteinase A (PrA) leads to saturation of the vacuolar targeting system of the cell and missorting of PrA to the growth medium. In a screen for genes affecting the secretion of over-expressed PrA we found that multiple copies of the open reading frame (ORF) YAL048c enhanced PrA secretion. Since no function has hitherto been ascribed to YAL048c, we undertook further studies of this ORF. Deletion of YAL048c resulted in slightly reduced secretion of over-produced PrA. Furthermore, strains deleted for YAL048c showed a growth inhibition phenotype resulting in wrinkled colony morphology when grown on rich medium containing high concentrations of calcium. YAL048c is predicted to encode a polypeptide of 662 amino acid residues containing two consensus ATP/GTP-binding site motifs and a putative carboxy-terminal transmembrane region. In addition, the amino acid sequence contains two putative calcium-binding domains. The YAL048c protein may be evolutionarily conserved, as homologues exist in humans and Caenorhabditis elegans. We suggest that the YAL048c protein is involved in vesicle transport in the secretory pathway.

Mechanism and ion-dependence of in vitro autoactivation of yeast proteinase A: possible implications for compartmentalized activation in vivo

Yeast proteinase A is synthesized as a zymogen which transits through the endoplasmic reticulum, the Golgi complex and the endosome to the vacuole. On arrival in the vacuole, activation takes place. It has previously been found that proteinase A can activate autocatalytically; however, the propeptide of proteinase A shows essentially no similarity to other known aspartic proteinase propeptides. To understand why proteinase A activation occurs rapidly in the vacuole but not at all in earlier compartments, we have purified the zymogen and investigated the conditions that trigger autoactivation and the mechanism of autoactivation. Autoactivation was triggered by acidic pH and its rate increased with increasing ionic strength. Kinetic evidence indicates that autoactivation mainly occurs via a bimolecular product-catalysed mechanism in which an active proteinase A molecule activates a zymogen molecule. Both the pH- and ionic-strength-dependence and the predominance of a product-catalysed mechanism are well adapted to the situation in vivo, since slow activation in the absence of active proteinase A helps to prevent activation in prevacuolar compartments, whereas, on delivery to the vacuole, lower pH, higher ionic strength and the presence of already active proteinases ensure rapid activation. Product-catalysed autoactivation may be a general mechanism by which cells ensure autoactivation of intracellular enzymes to be both rapid and compartmentalized.

Recruitment of medical practitioners to rural areas: a practical approach from the coalface

The successful recruitment of medical staff to country areas is a difficult process. This paper outlines strategies designed to increase the probability of a successful recruitment program. Strategies include determining if the position is truly required, designing an advertising campaign that reaches the target audience and addressing the significant regional and medical factors influencing the attractiveness of positions. Other areas discussed include the role of local hospitals, factors unique to individual medical practitioners, contracts and two possible long-term solutions--familiarising medical students with rural practice and recruiting overseas doctors.

Vacuolar and extracellular maturation of Saccharomyces cerevisiae proteinase A

The vacuolar aspartyl protease proteinase A (PrA) of Saccharomyces cerevisiae is encoded as a preproenzyme by the PEP4 gene and transported to the vacuole via the secretory route. Upon arrival of the proenzyme proPrA to the vacuole, active mature 42 kDa PrA is generated by specific proteolysis involving the vacuolar endoprotease proteinase B (PrB). Vacuolar activation of proPrA can also take place in mutants lacking PrB activity (prb1). Here an active 43 kDa species termed pseudoPrA is formed, probably by an autocatalytic process. When the PEP4 gene is overexpressed in wild-type cells, mature PrA can be found in the growth medium. We have found that prb1 strains overexpressing PEP4 can form pseudoPrA extracellularly. N-terminal amino acid sequence determination of extracellular, as well as vacuolar pseudoPrA showed that it contains nine amino acids of the propeptide, indicating a cleavage between Phe67 and Ser68 of the preproenzyme. This cleavage site is in accordance with the known substrate preference for PrA, supporting the notion that pseudoPrA is formed by autoactivation. When a multicopy PEP4 transformant of a prb1 mutant was grown in the presence of the aspartyl protease inhibitor pepstatin A, a significant level of proPrA was found in the growth medium. Our analyses show that overexpression of PEP4 leads to the secretion of proPrA to the growth medium where the zymogen is converted to pseudoPrA or mature PrA in a manner similar to the vacuolar processing reactions. Amino acid sequencing of secreted proPrA confirmed the predicted cleavage by signal peptidase between Ala22 and Lys23 of the preproenzyme.

Limited adverse occurrence screening: using medical record review to reduce hospital adverse patient events

OBJECTIVES

To determine whether continuous detection of adverse patient occurrences followed by analysis and medical intervention can alter the rate of adverse occurrences.

DESIGN AND PARTICIPANTS

15912 patients discharged from one hospital were reviewed in two stages. Medical records were screened retrospectively by medical records staff for one or more of eight general patient outcome criteria. Those that screened positive for the criteria were reviewed by one of four doctors. If an adverse occurrence was confirmed, further analysis and recommendations for action to prevent its recurrence were made at meetings of the four doctors, and forwarded to a committee of visiting medical officers who decided on the appropriate course of action.

SETTING

A rural base hospital in Horsham, Victoria, between July 1991 and June 1994.

MAIN OUTCOME MEASURES

The rate and severity of adverse patient occurrences in each year.

RESULTS

1465 records were screened positive for one or more criteria, and an adverse patient occurrence was confirmed in 155. 88 cases were determined to be minor or not preventable and further action (mostly by changes to hospital policies) was recommended for the remaining 67. Over the three years, the number of adverse occurrences fell from 69 (1.35% of all patient discharges in the first year) to 33 (0.58% of all patient discharges in the third year) (P < 0.0001) and there was no significant change in severity.

CONCLUSIONS

The rate of adverse patient occurrences can be significantly reduced by their continuous detection using retrospective screening in conjunction with review, analysis and action to prevent recurrences.

Laundry performance of subtilisin proteases

Effective laundry protease performance against susceptible stains depends upon both the enzyme itself and the environment in which it must work. In order to technically design superior laundry proteases, a model for protease's mechanism of action in detergents was developed which has been substantiated through-the-wash. While evaluation of this model and/or a given protease's effectiveness could be judged by a variety of methods, the utility of using visual wash performance comparisons, analytical, and stain characterization studies is described. Finally, data comparing the performance of wild type Subtilisin proteases with mutants designed via the projected model are given, demonstrating possible utility of the system.

Limited adverse occurrence screening: an effective and efficient method of medical quality control

The objective of the present study was to determine the rate of adverse patient occurrences in a medium sized hospital and to assess the effectiveness and efficiency of limited adverse occurrence screening as a method of medical quality control. The medical records of inpatients discharged from a base hospital in Horsham, Victoria, were screened by the medical records department using eight general outcome criteria. Histories found to meet a criterion were sent to a medical reviewer to determine if an adverse patient occurrence had taken place. A random sample of histories not meeting any criteria was also reviewed. The main outcome measures were the rate of adverse patient occurrences and the proportion of these events detected by limited occurrence screening, the accuracy of the screening process, the time taken and the cost of finding adverse events. The total adverse patient occurrence rate was estimated to be 2.75% (95% CI 1.36-4.14%). Limited adverse occurrence screening using eight screening criteria detected 49.1% (95% CI 32.6-99.3%) of all adverse patient occurrences and 64.4% (95% CI 37.8-100%) of all adverse occurrences of major severity. This was achieved by reviewing the records of 9.72% of all patients discharged. Screening was quick and accurate (false positive rate 2.0%, false negative rate 0.4%). Medical review took on average 5 min (s.d. +/- 3.03). The method required 500 h of staff time over one year and cost $22000 (0.1% of total hospital budget). The proportion of adverse patient occurrences found by limited screening was much higher than that found by traditional quality assurance methods. Limited adverse occurrence screening using retrospective review requires a small proportion of total budget that should be available to most hospitals for medical quality assurance activities.

A review of methods used for medical quality assurance in hospitals: advantages and disadvantages

This paper reviews the advantages and disadvantages of medical quality assurance methods commonly used in hospitals. A computer-based literature search up to April 1993 was done using the terms quality assurance, quality control, audit, utilization review, accreditation, occurrence screening and total quality management. In addition, a manual search was undertaken of references of papers obtained by the computer search and of the contents of the following journals: Quality Review Bulletin, Australian Clinical Review and the British Medical Journal. An assessment of the advantages and disadvantages of 15 quality assurance methods used in hospitals was made. Many quality assurance methods used in hospitals have significant disadvantages. A systematic method that provides meaningful and useful information to clinicians and improves patient care is urgently required. New methods such as occurrence screening and total quality management are slowly emerging and have much potential.

Limited adverse occurrence screening. A medical quality control system for medium sized hospitals

OBJECTIVE

To determine whether adverse occurrence screening of inpatient discharge summaries by means of a limited number of criteria can provide an effective medical quality control system without requiring substantial additional resources.

DESIGN

The medical records department used 14 criteria to screen all inpatient discharge summaries shortly after discharge. Summaries that met particular criteria were sent for medical review. If an adverse patient event was found, appropriate action was determined by a committee of four doctors.

SETTING

200 bed base hospital in country Victoria.

PATIENTS

All inpatients discharged over a two year period.

MAIN OUTCOME MEASURES

The incidence of negative patient outcomes and the cost of resources required to conduct the program.

RESULTS

A reduction in the incidence of some negative patient outcomes was achieved and the nature of postgraduate education meetings was changed. Minimal additional resources were required to run the program.

CONCLUSION

Limited adverse occurrence screening has provided a simple, inexpensive and effective medical quality control system in a medium-sized hospital.

The effect of extraarticular varus and valgus deformity on total knee arthroplasty

Because of trauma, metabolic bone disease, congenital deformity, or prior osteotomy, an extraarticular deformity may be present in patients requiring total knee arthroplasty. If the extraarticular deformity is not corrected extraarticularly, it must be corrected by compensatory distal femoral or proximal tibial wedge resection to produce overall limb alignment. Because such a wedge resection between the proximal and distal attachments of the collateral ligaments will produce asymmetrical ligament length, complex instabilities may result. This article, through overlay templates and trigonometric analysis, evaluates all the issues confronting the surgeon deciding whether to pursue intraarticular or extraarticular correction. The conclusions are as follows: (1) the closer a deformity is to the knee, the greater its importance, (2) femoral deformities are more difficult to correct intraarticularly than tibial deformities because femoral compensatory wedge resection produces instability only in extension, and (3) intraarticular correction of varus deformities produces lateral instability that is usually better tolerated than medial instability, and some extraarticular deformities are best treated by extraarticular correct, independent, or total knee arthroplasty.

The treatment of nonunion of proximal tibial osteotomy with internal fixation

Nonunion of proximal tibial osteotomy is a rare occurrence. Treatment goals should emphasize preservation of proximal tibial bone stock in view of possible subsequent total knee arthroplasty (TKA). Previous reports, in mostly smaller series, have emphasized the use of external fixation in the management of this problem. There have been no previous reports regarding the use of internal fixation in the treatment of nonunion occurring after tibial osteotomy performed proximal to the tibial tubercle. In this report, the results of internal fixation in the treatment of six cases of nonunion after proximal tibial osteotomy are analyzed with regard to functional and roentgenographic results. Healing of the nonunion was obtained in all six patients. Realignment of angulatory deformities was uniformly achieved. Achievement of union and correction of axial malalignment, in addition to creating an improved substrate for later TKA, provided other objectives as well. Elimination of pain and instability at the nonunion site allowed these patients to derive some of the intended benefits from the original osteotomy.

Osteotomy of the tibial tubercle during total knee replacement. A report of twenty-six cases

The cases of twenty-four patients who had twenty-six osteotomies of the tibial tubercle in conjunction with total knee replacement were analyzed with regard to complications and technical considerations. The patients were followed for a minimum of two years (average, three years and six months). Major complications related to the surgical technique occurred in 23 per cent of the knees and complications not related to the technique, in an additional 8 per cent. Rheumatoid arthritis and a history of at least one previous operation about the knee were predisposing factors for these complications.

Family-planning clinics and educational programmes--a rural experience

Although family-planning clinics are numerous and well-accepted in most Australian capital cities, such clinics have been difficult to establish in some Victorian rural towns. One such clinic was established at a rural base hospital in a Victorian town in 1984. The history of the clinic's development and its mode of operation are discussed. The profiles of 157 consecutive new patients who attended the clinic are presented. Comparisons are made with the patient profiles from a Melbourne family-planning clinic. The clinic also provides a separate weekly educational programme. The effect of the educational service in attracting patients to the clinic also was evaluated. Over all, it was concluded that the successful establishment of this clinic has been a result of the appointment of female medical and nursing staff members, the support of the local base hospital, an active media campaign and the development of a separate and concurrent educational programme that was conducted by clinic staff members. It is recommended that these factors be considered in the future development of such clinics in rural areas.

Photoaffinity reagents for use with pepsin and other carboxyl proteases

Two compounds have been designed to serve as photoaffinity reagents for use with carboxyl proteases. 1,2-Epoxy-3-(4'-azido-2'-nitrophenoxy)propane has been synthesized and shown to react with porcine pepsin in the same fashion as the traditional inhibitor 1,2-epoxy-3-(p-nitrophenoxy)propane, while p-azidophenacyl bromide is similar to other phenacyl bromides in its reaction with pepsin. In combination with p-azido-alpha-diazoacetophenone, previously shown to resemble alpha-diazo carbonyl reagents in its reaction with pepsin, photoaffinity analogs are now available for all three of the widely-used carboxyl protease inhibitors.

Reticulum cell sarcoma (histiocytic lymphoma) of the orbit

The clinical and pathologic features of 13 patients with biopsy-proven reticulum cell sarcoma of the orbit are reviewed. All of the patients were adults, in contrast to many previous reports that have emphasized how common this tumor is in children. Eight patients presented with proptosis and without prior diagnosis of lymphoma, and 5 patients developed orbital deposits in the course of a known systemic lymphoma. Of the 8 patients whose orbital biopsies established the diagnosis, 4 were found concomitantly to have other sites of disease, and 4 patients developed other evidence of lymphoma from 2 to 15 months after orbital biopsy. None of the cases in this series was interpreted as a primary orbital lymphoma. The histopathologic findings, the problem of histogenesis, and the need for systemic staging of cytologically malignant orbital lymphoma are discussed.