Repeat two-stage exchange arthroplasty for prosthetic hip re-infection

Aims

Recurrent infection following two-stage revision total hip arthroplasty (THA) for prosthetic joint infection (PJI) is a devastating complication. The purpose of this study was to report the survival of repeat two-stage revision hip arthroplasty, describe complications, and identify risk factors for failure.

Patients and Methods

We retrospectively identified 19 hips (19 patients) that had undergone repeat two-stage revision THA for infection between 2000 to 2013. There were seven female patients (37%) and the mean age was 60 years (30 to 85). Survival free from revision was assessed via Kaplan-Meier analysis. The patients were classified according to the Musculoskeletal Infection Society (MSIS) system, and risk factors for failure were identified. Mean follow-up was four years (2 to 11).

Results

Gram-positive bacteria were responsible for 16/17 (94%) of the re-infections where microbes were identified. Following the repeat two-stage exchange arthroplasty, survival free from any revision was 74% (95% confidence interval (CI) 56% to 96%, 14 at risk) at two years and 45% (95% CI 25% to 75%, five at risk) at five years. Failure to control infection resulted in re-operation or revision in 42%A of patients (8/19). Survival free from revision was not dependent on host grade.

Conclusion

Re-infection after two-stage exchange hip arthroplasty for PJI presents a challenging scenario. Repeat two-stage exchange arthroplasty has a low survival free from revision at five years (45%) and a high rate of re-infection (42%). Cite this article: Bone Joint J 2018;100-B:1157-61.

Reconstruction of the hip after resection of periacetabular oncological lesions: a systematic review

Aims

Reconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes.

Patients and Methods

A search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction.

Results

A total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing’s sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34).

Conclusion

Both the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes.

Cite this article: Bone Joint J 2018;100-B(1 Supple A):22–30.

The use of highly crosslinked polyethylene in total knee arthroplasty

Advances in polyethylene (PE) in total hip arthroplasty have led to interest and increased use of highly crosslinked PE (HXLPE) in total knee arthroplasty (TKA). Biomechanical data suggest improved wear characteristics for HXLPE inserts over conventional PE in TKA. Short-term results from registry data and few clinical trials are promising. Our aim is to present a review of the history of HXLPEs, the use of HXLPE inserts in TKA, concerns regarding potential mechanical complications, and a thorough review of the available biomechanical and clinical data. Cite this article: Bone Joint J 2017;99-B:996-1002.

Serum Inflammatory Cytokine Markers of Invasive Fungal Infection in Previously Immunocompetent Battle Casualties

BACKGROUND

Invasive fungal infection (IFI) is described increasingly in individuals experiencing high-energy military trauma. Hallmarks of successful treatment involve aggressive surgical debridement and early initiation of systemic antimicrobial therapy. Currently, intravenous anti-fungal therapy commences based on appearance of wounds and patient's clinical course. Whereas some clinical protocols exist to predict which critically injured patients should receive anti-fungal therapies, there are no established serum markers associated with IFI. Our hypothesis is that serum inflammatory cytokines exist that can assist in identifying individuals at risk for IFI.

METHODS

This is a retrospective case control study at a single institution. Nine patients with IFI (Saksenaea vasiformis, Fusarium sp., Graphium sp., Scedosporium sp., Aspergillus sp., Mucor sp., and Alternaria sp.) after battlefield trauma were matched to nine individuals with similar injury patterns whose laboratory results were negative for IFI. The combination of serum inflammatory cytokines from the first and second debridements was examined with multiplex platform proteomic analysis. We defined statistical significance as a two-tailed α<0.05 after adjusting for multiple comparisons using the false discovery rate method. This model was refined further with correlation-based filter selection and the area under the curve of the receiver operating characteristics (AUROC) was tested.

RESULTS

Both groups had similar Injury Severity Scores (ISS) (mean±standard deviation [SD]) (26.8±15.5 vs. 29.2±16.8, p=0.766). Elevated RANTES (regulated on activation, normal T cell expressed and secreted) alone (10,492.8±4,450.1 vs. 5,333.3±4,162.2, p=0.006) correlated with IFI. Also, the combination of persistent elevations in RANTES, interleukin (IL)-2R, and IL-15 was a robust model for predicting IFI with the AUROC being 0.9.

CONCLUSIONS

Elevation in serum cytokines, particularly RANTES, correlated with IFI in this small group of patients. This demonstrates the potential of future rapid serum testing for early initiation and guidance of anti-fungal therapies.

Proteomic sample preparation for blast wound characterization

Background

Blast wounds often involve diverse tissue types and require substantial time and treatment for appropriate healing. Some of these subsequent wounds become colonized with bacteria requiring a better understanding of how the host responds to these bacteria and what proteomic factors contribute wound healing outcome. In addition, using reliable and effective proteomic sample preparation procedures can lead to novel biomarkers for improved diagnosis and therapy.

Results

To address this need, suitable sample preparation for 2-D DIGE proteomic characterization of wound effluent and serum samples from combat-wounded patients was investigated. Initial evaluation of crude effluent and serum proved the necessity of high abundant protein depletion. Subsequently, both samples were successfully depleted using Agilent Multiple Affinity Removal system and showed greatly improved 2-D spot maps, comprising 1,800 and 1,200 protein spots, respectively.

Conclusion

High abundant protein removal was necessary for both wound effluent and serum. This is the first study to show a successful method for high abundant protein depletion from wound effluent which is compatible with downstream 2-D DIGE analysis. This development allows for improved biomarker discovery in wound effluent and serum samples.

Wound outcome in combat injuries is associated with a unique set of protein biomarkers

Background

The ability to forecast whether a wound will heal after closure without further debridement(s), would provide substantial benefits to patients with severe extremity trauma.

Methods

Wound effluent is a readily available material which can be collected without disturbing healthy tissue. For analysis of potential host response biomarkers, forty four serial combat wound effluent samples from 19 patients with either healing or failing traumatic- and other combat-related wounds were examined by 2-D DIGE. Spot map patterns were correlated to eventual wound outcome (healed or wound failure) and analyzed using DeCyder 7.0 and differential proteins identified via LC-MS/MS.

Results

This approach identified 52 protein spots that were differentially expressed and thus represent candidate biomarkers for this clinical application. Many of these proteins are intimately involved in inflammatory and immune responses. Furthermore, discriminate analysis further refined the 52 differential protein spots to a smaller subset of which successfully differentiate between wounds that will heal and those that will fail and require further surgical intervention with greater than 83% accuracy.

Conclusion

These results suggest candidates for a panel of protein biomarkers that may aid traumatic wound care prognosis and treatment. We recommend that this strategy be refined, and then externally validated, in future studies of traumatic wounds.

Bilateral lower-extremity amputation wounds are associated with distinct local and systemic cytokine response

BACKGROUND

Approximately 25% of U.S. military members sustaining extremity amputations in recent military conflicts have bilateral lower-extremity amputations (BLA). We investigated among combat-related extremity wounds whether BLA exhibit different bacterial burden, inflammatory response, and local complications.

METHODS

A total of 75 patients with combat-related extremity wounds (19 BLA) were evaluated for age, tobacco use, body mass index, Injury Severity Score, Acute Physiology and Chronic Health Evaluation II, and delayed primary closure time. Blood, wound exudates, and muscle biopsies were obtained and analyzed for cytokine and quantitative bacteriology, excluding patients using nonsteroidal anti-inflammatory medications and corticosteroids, due to potential effects on their inflammatory profile.

RESULTS

BLA was not associated with differences in age, tobacco use, body mass index, and delayed primary closure time, but these patients had increased Injury Severity Score, Acute Physiology and Chronic Health Evaluation II, and rates of critical colonization. Proinflammatory cytokines including tumor necrosis factor-α (exudate), interleukin (IL)-1 (exudate) and IL-6 (serum) were increased in BLA patients. They also had serum and exudate increased IL-8 and decreased IL-13 and granulocyte-macrophage colony-stimulating factor. Both wound dehiscence (WD) and heterotopic ossification (HO) were more common in BLA patients.

CONCLUSION

BLA patients were more likely to exhibit critical bacterial colonization, a distinct inflammatory response, and develop WD and HO. Modulating this response represents an attractive target in an effort to prevent complications such as WD and HO.

Bayesian modeling of pretransplant variables accurately predicts kidney graft survival

INTRODUCTION

Machine learning can enable the development of predictive models that incorporate multiple variables for a systems approach to organ allocation. We explored the principle of Bayesian Belief Network (BBN) to determine whether a predictive model of graft survival can be derived using pretransplant variables. Our hypothesis was that pretransplant donor and recipient variables, when considered together as a network, add incremental value to the classification of graft survival.

METHODS

We performed a retrospective analysis of 5,144 randomly selected patients (age ≥18, deceased donor kidney only, first-time recipients) from the United States Renal Data System database between 2000 and 2001. Using this dataset, we developed a machine-learned BBN that functions as a pretransplant organ-matching tool.

RESULTS

A network of 48 clinical variables was constructed and externally validated using an additional 2,204 patients of matching demographic characteristics. This model was able to predict graft failure within the first year or within 3 years (sensitivity 40%; specificity 80%; area under the curve, AUC, 0.63). Recipient BMI, gender, race, and donor age were amongst the pretransplant variables with strongest association to outcome. A 10-fold internal cross-validation showed similar results for 1-year (sensitivity 24%; specificity 80%; AUC 0.59) and 3-year (sensitivity 31%; specificity 80%; AUC 0.60) graft failure.

CONCLUSION

We found recipient BMI, gender, race, and donor age to be influential predictors of outcome, while wait time and human leukocyte antigen matching were much less associated with outcome. BBN enabled us to examine variables from a large database to develop a robust predictive model.

Lymphocyte depletion in experimental hemorrhagic shock in Swine

BACKGROUND

Hemorrhagic shock results in systemic activation of the immune system and leads to ischemia-reperfusion injury. Lymphocytes have been identified as critical mediators of the early innate immune response to ischemia-reperfusion injury, and immunomodulation of lymphocytes may prevent secondary immunologic injury in surgical and trauma patients.

METHODS

Yorkshire swine were anesthetized and underwent a grade III liver injury with uncontrolled hemorrhage to induce hemorrhagic shock. Experimental groups were treated with a lymphocyte depletional agent, porcine polyclonal anti-thymocyte globulin (PATG) (n = 8) and compared to a vehicle control group (n = 9). Animals were observed over a 3 day survival period. Circulating lymphocytes were examined with FACS analysis for CD3/CD4/CD8, and central lymphocytes with mesenteric lymph node and spleen staining for CD3. Circulating and lung tissue16 infiltrating neutrophils were measured. Circulating CD3 lymphocytes in the blood and in central lymphoid organs (spleen/lymph node) were stained and evaluated using FACS analysis. Immune-related gene expression from liver tissue was quantified using RT-PCR.

RESULTS

The overall survival was 22% (2/9) in the control and 75% (6/8) in the PATG groups, p = 0.09; during the reperfusion period (following hemorrhage) survival was 25% (2/8) in the control and 100% (6/6) in the PATG groups, p = 0.008. Mean blood loss and hemodynamic profiles were not significantly different between the experimental and control groups. Circulating CD3+CD4+ lymphocytes were significantly depleted in the PATG group compared to control. Lymphocyte depletion in the setting of hemorrhagic shock also significantly decreased circulating and lung tissue infiltrating neutrophils, and decreased expression of liver ischemia gene expression.

CONCLUSIONS

Lymphocyte manipulation with a depletional (PATG) strategy improves reperfusion survival in experimental hemorrhagic shock using a porcine liver injury model. This proof of principle study paves the way for further development of immunomodulation approaches to ameliorate secondary immune injury following hemorrhagic shock.

Lymphocyte modulation with FTY720 improves hemorrhagic shock survival in swine

The inflammatory response to severe traumatic injury results in significant morbidity and mortality. Lymphocytes have recently been identified as critical mediators of the early innate immune response to ischemia-reperfusion injury. Experimental manipulation of lymphocytes following hemorrhagic shock may prevent secondary immunologic injury in surgical and trauma patients. The objective of this study is to evaluate the lymphocyte sequestration agent FTY720 as an immunomodulator following experimental hemorrhagic shock in a swine liver injury model. Yorkshire swine were anesthetized and underwent a grade III liver injury with uncontrolled hemorrhage to induce hemorrhagic shock. Experimental groups were treated with a lymphocyte sequestration agent, FTY720, (n = 9) and compared to a vehicle control group (n = 9). Animals were observed over a 3 day survival period after hemorrhage. Circulating total leukocyte and neutrophil counts were measured. Central lymphocytes were evaluated with mesenteric lymph node and spleen immunohistochemistry (IHC) staining for CD3. Lung tissue infiltrating neutrophils were analyzed with myeloperoxidase (MPO) IHC staining. Relevant immune-related gene expression from liver tissue was quantified using RT-PCR. The overall survival was 22.2% in the vehicle control and 66.7% in the FTY720 groups (p = 0.081), and reperfusion survival (period after hemorrhage) was 25% in the vehicle control and 75% in the FTY720 groups (p = 0.047). CD3⁺ lymphocytes were significantly increased in mesenteric lymph nodes and spleen in the FTY720 group compared to vehicle control, indicating central lymphocyte sequestration. Lymphocyte disruption significantly decreased circulating and lung tissue infiltrating neutrophils, and decreased expression of liver immune-related gene expression in the FTY720 treated group. There were no observed infectious or wound healing complications. Lymphocyte sequestration with FTY720 improves survival in experimental hemorrhagic shock using a porcine liver injury model. These results support a novel and clinically relevant lymphocyte immunomodulation strategy to ameliorate secondary immune injury in hemorrhagic shock.

Biomarker use in tailored combat casualty care

Modern war wounds are complex and primarily involve extremities. They require multiple operative interventions to achieve wound closure and begin rehabilitation. Current assessment of the suitability of surgical wound closure is based upon subjective methods coupled with a semiquantitative determination of the wound bacterial burden. Measurement of the systemic and local response to injury using inflammatory biomarkers may allow for accelerated wound closure and treatment of other combat-related morbidity. This article presents the introduction of personalized medicine into combat casualty care.

Development of a Bayesian model to estimate health care outcomes in the severely wounded

BACKGROUND

Graphical probabilistic models have the ability to provide insights as to how clinical factors are conditionally related. These models can be used to help us understand factors influencing health care outcomes and resource utilization, and to estimate morbidity and clinical outcomes in trauma patient populations.

STUDY DESIGN

Thirty-two combat casualties with severe extremity injuries enrolled in a prospective observational study were analyzed using step-wise machine-learned Bayesian belief network (BBN) and step-wise logistic regression (LR). Models were evaluated using 10-fold cross-validation to calculate area-under-the-curve (AUC) from receiver operating characteristics (ROC) curves.

RESULTS

Our BBN showed important associations between various factors in our data set that could not be developed using standard regression methods. Cross-validated ROC curve analysis showed that our BBN model was a robust representation of our data domain and that LR models trained on these findings were also robust: hospital-acquired infection (AUC: LR, 0.81; BBN, 0.79), intensive care unit length of stay (AUC: LR, 0.97; BBN, 0.81), and wound healing (AUC: LR, 0.91; BBN, 0.72) showed strong AUC.

CONCLUSIONS

A BBN model can effectively represent clinical outcomes and biomarkers in patients hospitalized after severe wounding, and is confirmed by 10-fold cross-validation and further confirmed through logistic regression modeling. The method warrants further development and independent validation in other, more diverse patient populations.

Probabilistic (Bayesian) modeling of gene expression in transplant glomerulopathy

Transplant glomerulopathy (TG) is associated with rapid decline in glomerular filtration rate and poor outcome. We used low-density arrays with a novel probabilistic analysis to characterize relationships between gene transcripts and the development of TG in allograft recipients. Retrospective review identified TG in 10.8% of 963 core biopsies from 166 patients; patients with stable function were studied for comparison. The biopsies were analyzed for expression of 87 genes related to immune function and fibrosis by using real-time PCR, and a Bayesian model was generated and validated to predict histopathology based on gene expression. A total of 57 individual genes were increased in TG compared with stable function biopsies (P < 0.05). The Bayesian analysis identified critical relationships between ICAM-1, IL-10, CCL3, CD86, VCAM-1, MMP-9, MMP-7, and LAMC2 and allograft pathology. Moreover, Bayesian models predicted TG when derived from either immune function (area under the curve [95% confidence interval] of 0.875 [0.675 to 0.999], P = 0.004) or fibrosis (area under the curve [95% confidence interval] of 0.859 [0.754 to 0.963], P < 0.001) gene networks. Critical pathways in the Bayesian models were also analyzed by using the Fisher exact test and had P values <0.005. This study demonstrates that evaluating quantitative gene expression profiles with Bayesian modeling can identify significant transcriptional associations that have the potential to support the diagnostic capability of allograft histology. This integrated approach has broad implications in the field of transplant diagnostics.

Monitoring the healing of combat wounds using Raman spectroscopic mapping

Soldiers wounded in modern warfare present with extensive and complicated acute wounds, confounded by an overwhelming inflammatory response. The pathophysiology of acute wounds is unknown and timing of wound closure remains subjective. Collagen gene expression profiles are presented for 24 patients. Impaired healing wounds showed a twofold decrease in the up-regulation of COL1A1 and COL3A1 genes in the beginning of the wound healing process, compared with normal healing wounds. By the final debridement, however, collagen gene expression profiles for normal and impaired healing wounds were similar for COL1A1 and COL3A1. In addition, Raman spectroscopic maps were collected of biopsy tissue sections, from the first and last debridements of 10 wounds collected from nine patients. Tissue components obtained for the debridement biopsies were compared to elucidate whether or not a wound healed normally. Raman spectroscopy showed a loss of collagen in five patients, indicated by a negative percent difference in the 1,665/1,445 cm(-1) band area ratios. Four healed patients showed an increased or unchanged collagen content. Here, we demonstrate the potential of Raman spectroscopic analysis of wound biopsies for classification of wounds as normal or impaired healing. Raman spectroscopy has the potential to noninvasively monitor collagen deposition in the wound bed, during surgical wound debridements, to help determine the optimal time for wound closure.

Evaluation of lyophilized platelets as an infusible hemostatic agent in experimental non-compressible hemorrhage in swine

INTRODUCTION

Human lyophilized platelets hold promise as a novel hemostatic infusion agent for the control of traumatic hemorrhage. Rehydrated, lyophilized platelets (Stasix) were investigated as an infusible hemostatic agent in experimental non-compressible hemorrhage, using a porcine liver injury model.

METHODS

Yorkshire swine underwent a grade III liver injury and uncontrolled bleeding. After 15 min, animals were infused with Stasix (n = 10) or normal saline vehicle (n = 10). At 2 h, the liver was repaired, and the animals were monitored for another4 h. Resuscitation, including blood transfusion, was administered during the hospital phase. Laboratory data, including arterial blood gas, complete blood count, thromboelastography (TEG), and coagulation parameters, were collected. All animals underwent necropsy with complete histopathologic examination.

RESULTS

Overall survival in the Stasix group [8/10 (80%)] was significantly higher than in the control group [2/10 (20%)] (P = 0.023). Mean total blood loss index (g kg(-1)) was lower in Stasix-treated animals (22.2 +/- 3.5) than in control animals (34.7 +/- 3.4) (P = 0.019). Hemodynamic parameters were improved in the Stasix group, and a trend towards higher hemoglobin and lower lactate was observed. Coagulation and TEG parameters were not different between the groups. One surviving animal in the Stasix group had evidence of thrombi on necropsy.

CONCLUSIONS

This is the first reported study to evaluate rehydrated, lyophilized platelets as an infusible hemostatic agent for non-compressible hemorrhage. Stasix improved survival and reduced blood loss in a liver injury porcine model. However, evidence of thrombotic complications warrants further investigation prior to human use in the setting of traumatic hemorrhage.

Correlation of procalcitonin and cytokine expression with dehiscence of wartime extremity wounds

BACKGROUND

Despite technological advances in the treatment of severe extremity trauma, the timing of wound closure remains the subjective clinical decision of the treating surgeon. Traditional serum markers are poor predictors of wound-healing. The objective of this study was to evaluate the cytokine and chemokine profiles of severe extremity wounds prior to closure to determine if wound effluent markers can be used to predict healing.

METHODS

Serum and effluent (exudate) samples were collected prospectively from adult volunteers with multiple high-energy penetrating extremity wounds sustained during military combat. Samples were collected prior to definitive wound closure or flap coverage. Wounds were followed clinically for six weeks. The primary clinical outcome measures were wound-healing and dehiscence. Control serum samples were collected from normal age and sex-matched adult volunteers. All samples were analyzed for the following cytokines and chemokines: procalcitonin; eotaxin; granulocyte macrophage colony stimulating factor; interferon (IFN)-gamma; interleukin (IL)-1 through 8, 10, 12, 13, and 15; IFN-gamma inducible protein-10; monocyte chemotactic protein-1; macrophage inflammatory protein-1alpha; the protein regulated on activation, normal T expressed and secreted (RANTES); and tumor necrosis factor (TNF)-alpha.

RESULTS

Fifty wounds were analyzed in twenty patients. Four of the fifty wounds dehisced. An increased rate of wound dehiscence was observed in patients with a concomitant closed head injury as well as in those with an associated arterial injury of the affected limb (p < 0.05). Among the serum chemokines and cytokines, only serum procalcitonin levels correlated with wound dehiscence (p < 0.05). Effluent analysis showed that, compared with wounds that healed, wounds that dehisced were associated with elevated procalcitonin, decreased RANTES protein, and decreased IL-13 concentrations (p < 0.05). No wound with an effluent procalcitonin concentration of <220 pg/mL, an IL-13 concentration of >12 pg/mL, or a RANTES protein concentration of >1000 pg/mL failed to heal.

CONCLUSIONS

Effluent procalcitonin, IL-13, and RANTES protein levels as well as serum procalcitonin levels correlate with wound dehiscence following closure of severe open extremity wounds. These preliminary results indicate that effluent biomarker analysis may be an objective means of determining the timing of traumatic wound closure.

Continuous monitoring of enzyme reactions on a microchip: application to catalytic RNA self-cleavage

Kinetic analysis of RNA enzymes, or ribozymes, typically involves the tedious process of collecting and quenching reaction time points and then fractionating by polyacrylamide gel electrophoresis (PAGE). As a way to automate and simplify this process, continuous analysis of a ribozyme reaction is demonstrated here using completely automated capillary sample introduction onto a microfabricated device with laser-induced fluorescence detection. The method of injection is extremely reproducible thereby standardizing data analysis. A 30-nucleotide ribozyme model, the self-cleaving lead-dependent ribozyme, or "leadzyme", which cleaves into a 24-mer and a 6-mer in the presence of Pb(2+), was end-labeled with fluorescein (FAM) and used to demonstrate the potential of this technique. After manually initiating the cleavage reaction by Pb(2+) addition, reaction samples were automatically injected directly into the parallel separation lanes of the chip via a capillary at predetermined time intervals, thus eliminating the need for additional sample-handling steps. The FAM-labeled leadzyme starting material and products were monitored for 60 min in order to ascertain kinetic information. The effect of lead acetate concentration on cleavage rates was also studied, and the results are in agreement with rates determined by conventional hand-mixing/PAGE analysis. This work demonstrates, through the use of a simple ribozyme model, the potential of this method to provide valuable kinetic information for other, more complex, biologically relevant RNA and protein enzymes.

Linkage between proton binding and folding in RNA: implications for RNA catalysis

Small ribozymes use their nucleobases to catalyse phosphodiester bond cleavage. The hepatitis delta virus ribozyme employs C75 as a general acid to protonate the 5′-bridging oxygen leaving group, and to accomplish this task efficiently, it shifts its pKa towards neutrality. Simulations and thermodynamic experiments implicate linkage between folding and protonation in nucleobase pKa shifting. Even small oligonucleotides are shown to fold in a highly co-operative manner, although they do so in a context-specific fashion. Linkage between protonation and co-operativity of folding may drive pKa shifting and provide for enhanced function in RNA.

Simple method for determining nucleobase pK(a) values by indirect labeling and demonstration of a pK(a) of neutrality in dsDNA

Phosphorothioates were substituted into double-stranded DNA to study protonated Class I A+.C basepairs by 31P NMR. The method was effective in reporting the A+.C pKa. pKa values near 7.0 were found with optimal nearest-neighbor partners. Such pKa values could expand the catalytic repertoire of nucleic acids.

Design of a highly reactive HDV ribozyme sequence uncovers facilitation of RNA folding by alternative pairings and physiological ionic strength

The hepatitis delta virus (HDV) ribozyme is a self-cleaving RNA that resides in the HDV genome and regulates its replication. The native fold of the ribozyme is complex, having two pseudoknots. Earlier work implicated four non-native pairings in slowing pseudoknot formation: Alt 1, Alt 2, Alt 3, and Alt P1. The goal of the present work was design of a kinetically simplified and maximally reactive construct for in vitro mechanistic and structural studies. The initial approach chosen was site-directed mutagenesis in which known alternative pairings were destabilized while leaving the catalytic core intact. Based on prior studies, the G11C/U27Delta double mutant was prepared. However, biphasic kinetics and antisense oligonucleotide response trends opposite those of the well-studied G11C mutant were observed suggesting that new alternative pairings with multiple registers, termed Alt X and Alt Y, had been created. Enzymatic structure mapping of oligonucleotide models supported this notion. This led to a model wherein Alt 2 and the phylogenetically conserved Alt 3 act as "folding guides", facilitating folding of the major population of the RNA molecules by hindering formation of the Alt X and Alt Y registers. Attempts to eliminate the strongest of the Alt X pairings by rational design of a quadruple mutant only resulted in more complex kinetic behavior. In an effort to simultaneously destabilize multiple alternative pairings, studies were carried out on G11C/U27Delta in the presence of urea or increased monovalent ion concentration. Inclusion of physiological ionic strength allowed the goal of monophasic, fast-folding (kobs approximately 60 min(-1)) kinetics to be realized. To account for this, a model is developed wherein Na+, which destabilizes secondary and tertiary structures in the presence of Mg2+, facilitates native folding by destabilizing the multiple alternative secondary structures with a higher-order dependence.

Catalytic roles for proton transfer and protonation in ribozymes

Utilization of proton transfer in catalysis, which is well known in the mechanisms of protein enzymes, has been described only relatively recently for RNA enzymes. In this article, we present a current understanding of proton transfer by nucleic acids. Rate enhancement and specificity conferred by general acid-base catalysis are discussed. We also present possibilities for electrostatic catalysis from general acids and bases as well as cationic base pairs. The microenvironments of a large RNA provide the possibility of histidine-like pK(a)s for proton transfer, as well as lysine- and arginine-like pK(a)s for electrostatic catalysis. Discussion on proton transfer focuses on the hepatitis delta virus (HDV) and hairpin ribozymes, with select examples drawn from the protein literature. Discussion on electrostatic catalysis also draws on these two ribozymes, and a postulate for electrostatic catalysis by a cationic base pair in the mechanism of peptidyl transfer in the ribosome is presented. We also provide a perspective on possibilities for phosphoryl transfer mechanisms involving phosphorane intermediates and unusual tautomeric forms of the bases. Lastly, a distinction is made between ground state and "transition state" pK(a)s. We favor a model in which changes in pH lead to changes in the distribution of reactive and nonreactive ionizations of the ribozyme molecules in the ground state, and therefore suggest that "pK(a) changes in the transition state" do not provide an acceptable explanation for observed pH-rate profiles.

Rheumatoid neutrophilic dermatitis in a woman with seronegative rheumatoid arthritis

Rheumatoid neutrophilic dermatitis (RND) is an unusual cutaneous reaction in patients with rheumatoid arthritis (RA). RND is characterized by symmetric, erythematous papules, plaques, nodules, and urticarial lesions often located over the joints, extensor surfaces of the extremities, or the trunk. This entity demonstrates an intense neutrophilic dermal infiltrate without vasculitis. All patients previously reported with RND had severe RA with relatively high titers of rheumatoid factor when tested. A 67-year-old woman had a 2-month history of multiple, tender, 4 to 8 mm erythematous, crusted papules and nodules that occurred in clusters on her anterior thighs, knees, and legs. She suffered from severe disabling seronegative RA. RND may complicate seronegative RA.

Cavitating pulmonary infiltrate in an adolescent with pyoderma gangrenosum: a rarely recognized extracutaneous manifestation of a neutrophilic dermatosis

Neutrophilic dermatoses such as pyoderma gangrenosum are characterized by sterile, neutrophilic cutaneous infiltrates. Extracutaneous neutrophilic infiltrates can occur, primarily in the joints, lungs, heart, central nervous system, gastrointestinal tract, and eyes. Pulmonary disease is the most frequently reported extracutaneous manifestation of pyoderma gangrenosum and is characterized by patchy infiltrates or interstitial pneumonitis. We describe an adolescent with typical pyoderma gangrenosum who presented with cavitary pneumonia and responded completely to oral corticosteroids. In patients with inflammatory ulcers, extracutaneous neutrophilic disease should be considered, once an infectious process has been excluded.

Atypical presentation of herpes simplex virus in a patient with chronic lymphocytic leukemia

Perianal infections caused by herpes simplex virus are common in immunocompromised patients. The cutaneous presentation in these patients is often atypical, overlaps with the clinical features of other diseases, poses a difficulty in diagnosis, and responds poorly to treatment. An immunocompromised patient with chronic lymphocytic leukemia, treated with oral corticosteroids, presented with chronic perianal ulcerations. This patient was referred for evaluation and treatment of "recalcitrant" pyoderma gangrenosum. Prompt diagnosis was possible when the clinical features were recognized and appropriate biopsy and cultures were obtained. We describe an atypical presentation of herpes simplex virus associated with both an endogenous and exogenous induced immunodeficiency, and stress the importance of routinely performing cultures on all perianal ulcerations and anal fissures to avoid the misdiagnosis, inappropriate treatment, and prolonged discomfort of these afflicted patients.

Hypersensitivity reaction in a child due to lamotrigine

Lamotrigine is an anticonvulsant with a broad spectrum of activity that has been approved in the United States for use in adults with either partial or generalized seizures. This drug is being widely prescribed by pediatricians and neurologists because it is effective in children with idiopathic, resistant, generalized seizures and does not impair cognition. As with other anticonvulsants, a hypersensitivity syndrome has been described. Anticonvulsant hypersensitivity syndrome consists of the hallmark features of fever, rash, and lymphadenopathy. We report the first case of hypersensitivity syndrome in a child due to lamotrigine in which we believe the coadministration of valproic acid increased the duration of the reaction. Our patient had a high spiking fever, generalized morbilliform eruption, facial edema, lymphadenopathy, eosinophilia, atypical lymphocytosis, and an elevation in his liver function tests. The syndrome resolved with the discontinuation of the medication. Anticonvulsant hypersensitivity syndrome may occur with the administration of lamotrigine. Variable presentations may be seen, as hypersensitivity syndromes may be multisystem in nature. The prompt recognition of the signs and symptoms of this condition allows an accurate diagnosis so that the drug may be discontinued and other anticonvulsant treatment options instituted.

Transthoracic needle biopsy for suspected thoracic malignancy in elderly patients using CT guidance

There are few reports of transthoracic needle biopsy (TNB) in elderly (>70 years) patients although there is some evidence that age may be a risk factor in developing pneumothorax. We report our experience of 38 patients, age range 70-90 years, who underwent computed tomography (CT)-guided TNB for suspected malignancy of the chest, with particular reference to sensitivity and complication rate following the procedure. The biopsy was obtained using either a spinal needle or, if appropriate, a core of tissue was obtained using a cutting needle. The biopsy showed evidence of malignancy in 27 patients. Pneumothorax occurred in 10 of 40 biopsies. Two patients with pneumothorax required pleural drains; one was discharged the following day and the other required drainage for 3 days. Haemoptysis was not a problem but occurred as a transient postbiopsy event in three patients. In 26 of 40 (65%) episodes the patients were sent home within 24 h of the diagnostic procedure. It is thus quite possible to undertake the procedure on a day case basis. CT-guided TNB is a safe and reliable procedure in elderly patients with suspected chest malignancy and is well tolerated.

Leukocytosis in labor: what are its implications?

OBJECTIVE

The objective of this study was to determine the usefulness of the peripheral white blood count (WBC) drawn during labor as a predictor of postpartum morbidity.

METHOD

Hospital charts on 309 consecutive obstetrical deliveries performed by residents of the Cox Family Practice Residency were reviewed for evidence of maternal or neonatal postpartum morbidity. An analysis of means was used to compare the average antepartum WBC in the morbid and non-morbid groups.

RESULTS

The average WBC in a laboring patient was 12,450, with a range of 4,400 to 29,100. Patients with postpartum complications had a WBC similar to that of patients without complications (12,900 vs 12,300 p = 0.449).

CONCLUSION

An elevated WBC obtained on admission to the labor ward is not helpful in predicting postpartum complications in mothers or newborns.

Breast imaging in women under 35 with symptomatic breast disease

With the increasing utilization of mammography, young women under the age of 35 are being referred for mammographic examination more frequently. A review of the mammograms of 159 consecutive patients aged under 35 was conducted to evaluate the clinical value of the examination in the age group for whom the probability of malignancy is low. 74% of patients referred had no discrete palpable mass and presented predominantly with lumpy or tender breasts, the remaining 24% had a discrete palpable mass. In neither group did radiographic examination beneficially influence clinical management. We propose protocol where no imaging is performed in women under 35 in the absence of a palpable mass unless there is a localized bloody discharge or a strong family history or previous personal history of breast cancer. In patients with a palpable mass, ultrasound should be performed initially to identify simple cysts and if negative only then progressing to mammography.

Aluminum accumulation in serum, liver and spleen of Fe-depleted and Fe-adequate rats

The study described here was planned to test the hypothesis that Al absorption and accumulation in the body are inversely related to Fe status. Aluminum3+ and Fe3+ have similar ionic radii and charge densities, pH-solubility relationships, and affinities for ligands, such as citrate and transferrin. Male weanling Sprague-Dawley rats were pair fed an Fe-deficient or Fe-adequate (control) diet for 2 wk. Each diet group was then randomly assigned to receive for four more weeks the Fe-deficient or adequate diet with: 1. 2% AlCl3; 2. AlCl3 + 3.5% Na citrate; or 3. No Al or citrate. Iron depletion, confirmed by measurements of hemoglobin, hematocrit, serum Fe, and Fe binding capacity, increased concentrations of serum, liver, and spleen Al in all groups fed AlCl3. However, the increase owing to Fe deficiency was significant only when Al was fed with citrate. The data suggest that Fe deficiency enhances both Al absorption and accumulation in liver and spleen.

Double-blind, placebo-controlled trial of twice-daily nifedipine as a step-2 agent in mild essential hypertension

Nifedipine is a calcium-channel blocker that produces vasodilatation and decreased peripheral resistance in humans. Several clinical reports document blood-pressure-lowering effects of nifedipine with either acute or chronic administration. Little data are available to evaluate sustained-release nifedipine as a step-2 agent. We performed a multicenter double-blind, placebo-controlled trial of twice-daily nifedipine in the treatment of mild essential hypertension not controlled by diuretic alone. Seventy-one subjects completed 8 weeks of treatment with nifedipine or placebo in combination with a stable dose of diuretic. Treatment groups were comparable with respect to age, sex, race, duration of hypertension, and pretreatment weight. Baseline supine blood pressure was no different in the two treatment groups (144 +/- 15/98 +/- 6 mmHg in the nifedipine/diuretic-treated group and 145 +/- 16/98 +/- 6 mmHg in the placebo/diuretic-treated group). After 8 weeks of treatment, supine blood pressure was 132 +/- 11/88 +/- 6 mmHg in the nifedipine/diuretic-treated group and 140 +/- 16/92 +/- 8 mmHg in the placebo/diuretic-treated subjects (p less than 0.01 for both systolic and diastolic blood pressure when compared to placebo/diuretic). Nifedipine with diuretic had similar effects on standing blood pressure. Nifedipine/diuretic decreased blood pressure from baseline values within 1 week of treatment, and the effect persisted for 8 weeks. Heart rate increased in nifedipine/diuretic-treated subjects during the first 2 weeks of treatment but returned to baseline by 4 weeks. No laboratory abnormalities could be attributed to nifedipine/diuretic treatment. Side effects were mild and infrequent. In summary, nifedipine/diuretic is effective and well tolerated in the treatment of uncomplicated essential hypertension inadequately controlled with diuretic therapy alone.

Tuberculosis affecting the oesophagus

Three Asian patients presenting with dysphagia were shown to have oesophageal involvement secondary to adjacent tuberculous mediastinal lymph nodes. The findings included fistula between the oesophagus and the tracheobronchial tree and extrinsic compression of the oesophagus. These cases reflect the increasing incidence of mediastinal lymphadenopathy in adult tuberculosis, especially in our immigrant community.

Effects of TRH injection on hippocampal-hypothalamic-pituitary-thyroid interactions

The first experiment was conducted in an attempt to ascertain the effects of hippocampal lesions on plasma levels of total T4, total T3, free T4, and TSH. Animals with hippocampal lesions had significantly lower levels of total T4, free T4 and TSH than cortical control and normal animals. There were no significant differences in total T3 among the three groups. Since these results indicated that animals with hippocampal lesions manifested a dysfunction in the hypothalamic-pituitary-thyroid axis, a second experiment was undertaken to determine the site of mediation. A TRH injection test demonstrated that the dysfunction occurs at the level of the hypothalamus. It is hypothesized that in the normal animal the hippocampus exerts a facilitating effect on the hypothalamic-pituitary-thyroid axis.

Tuberculous mediastinal lymphadenopathy in Bradford

During the calendar year 1978, 18 patients who commenced treatment for pulmonary tuberculosis in the Bradford Chest Clinic were found to have enlarged mediastinal lymph glands. Sixteen of these 18 patients were adults who thus presented radiographic patterns which have been classically regarded are representing primary tuberculous infection and are usually seen in children but only rarely in adults. All 16 adult patients were immigrants of either Indian or Pakistani origin. Tuberculosis is therefore a common cause of mediastinal lymphadenopathy in the immigrant population and in view of the successful response to therapy it should be considered ahead of the more usual diagnoses of lymphoma, sarcoidosis or metastatic carcinoma.

Tuberculosis of the ribs

The radiological appearances of seven cases of rib tuberculosis are discussed. The combination of rib destruction and an extrapleural soft tissue opacity in an Asian immigrant makes tuberculosis a highly likely diagnosis. The presence of an associated fluctuant chest wall swelling, enables a diagnosis of tuberculosis to be made with confidence even in Caucasians.

Tuberculosis of the skull vault

Tuberculosis of the skull vault is very rare and recently has only been reported from Africa. Two cases have presented in the city of Bradford during the past 10 years, both in young Asians. The radiology is discussed.

Plasma corticosterone levels and ulcer formation in rats with hippocampal lesions

In order to examine the effects of hippocampal lesions on plasma corticosterone levels and ulcer formation, 4 conditions were studied: (1) unrestrained nondeprived (2) unrestrained 24 h food-deprived (3) simple restraint and (4) restraint plus intermittent shock. In the unrestrained and unrestrained plus 24 h food-deprived conditions, neither animals with hippocampal lesions nor control animals developed ulcers. In both instances plasma corticosterone levels were similar in experimental and control animals. Differences appeared in the simple restraint and restraint plus intermittent shock conditions. In both of these conditions animals with hippocampal lesions developed more ulcers and had a higher corticosterone level than controls. It is concluded that animals with hippocampal lesions show an enhanced reaction to stress.

Chronic intermittent ethyl alcohol inhalation and avoidance learning

Weanling male and female rats were chronically exposed to alcohol for 50 days using an intermittent inhalation technique which does not cause alcohol dependency. After 17 days of no exposure to alcohol, animals began two-way active avoidance testing. Results indicated that males were impaired on this task and females were not while at the same time males had reduced body weights. The male weight reduction was not responsible for the avoidance impairment. It was concluded that impaired avoidance learning following chronic esposure to alcohol is not specific to dependency models of animal alcoholism.