The local and systemic effects of immune function on fracture healing

The immune system plays an integral role in the regulation of cellular processes responsible for fracture healing. Local and systemic influences on fracture healing correlate in many ways with fracture-related outcomes, including soft tissue healing quality and fracture union rates. Impaired soft tissue healing, restricted perfusion of a fracture site, and infection also in turn affect the immune response to fracture injury. Modern techniques used to investigate the relationship between immune system function and fracture healing include precision medicine, using vast quantities of data to interpret broad patterns of inflammatory response. Early data from the PRECISE trial have demonstrated distinct patterns of inflammatory response in polytrauma patients, which thereby directly and indirectly regulate the fracture healing response. The clearly demonstrated linkage between immune function and fracture healing suggests that modulation of immune function has significant potential as a therapeutic target that can be used to enhance fracture healing.

Transcutaneous osseointegration for amputees

Transcutaneous osseointegration for amputees (TOFA) is an evolving technology that has the potential to revolutionize the interface between the amputee and their prosthesis, showing potential at many levels of amputation. While no amputation is without its challenges, TOFA requires a highly specialized prosthesis and a multidisciplinary team that includes specialized surgeons, physical therapists, wound care teams, and social workers who guide the amputee through surgery, postoperative rehabilitation, and the chronic wound care that goes into maintaining the prosthesis. The infrastructure required to facilitate care pathways that lead to reliable, successful outcomes are unique in each health care setting, including those in advanced health care systems such as the United States and Australia. This article details the emerging evidence supporting the use of this prosthetic interface design and many of the challenges that providers face when establishing programs to offer this type of care in the United States.

Fracture healing-orthobiologics: from basic science to clinical application

Orthopaedics as a field and a profession is fundamentally concerned with the treatment of musculoskeletal disease, in all of its many forms. Our collective understanding of the cellular mechanisms underlying musculoskeletal pathology resulting from injury continues to evolve, opening novel opportunities to develop orthobiologic treatments to improve care. It is a long path to move from an understanding of cellular pathology to development of successful clinical treatment, and this article proposes to discuss some of the challenges to achieving translational therapies in orthopaedics. The article will focus on challenges that clinicians will likely face in seeking to bring promising treatments forward to clinical practice and strategies for improving success in translational efforts.

Osteoporosis and Fragility Fractures

Osteoporosis and fragility fractures (FFs) are closely intertwined as the former is a common predisposing factor to the latter. This causal relationship is due to low bone density of osteoporosis and compromised bone microarchitecture, leading to structural failure, decreased ability to withstand applied stresses, and increased propensity to fracture. Osteoporosis can be idiopathic or due to a variety of secondary causes, and numerous treatment strategies are available. FFs are common injuries among the elderly and are caused by factors both intrinsic and extrinsic to the patient. The clinical and economic significances of osteoporosis and FFs are substantial, with considerable associated morbidity and mortality, and billions spent on healthcare expenditures in the US annually. Osteoporosis and FFs are two of the most important topics related to fracture liaison services (FLSs), and their understanding is integral to appreciating the benefits an FLS can provide for patients and providers.

Long-term Orthopedic Manifestations of COVID-19: Heterotopic Ossification and Digital Necrosis

Despite its classification as an atypical pneumonia, COVID-19 is a disease that is capable of inflicting damage beyond the respiratory system. The wide range of musculoskeletal complications secondary to acute COVID-19 are a significant source of morbidity in hospitalized patients. We present the case of a 23-year-old woman with severe COVID-19 who required intubation and had a prolonged hospital course that was complicated by partial-thickness necrosis of her fingers and heterotopic ossification of the distal thigh. We review current treatments for these orthopedic conditions in the setting of SARS-CoV-2 infection as well as highlight areas for future research. Additionally, we discuss the subacute musculoskeletal complications of COVID-19, which are among the most common long-term manifestations of the disease and are increasingly important for a growing number of COVID-19 survivors.

Successful Fracture Healing for Femoral Neck Nonunion with Bone Marrow Aspirate Concentrate

INTRODUCTION

Femoral neck fractures in the young patient require prompt anatomic reduction and stabilization to preserve the vascular supply to the femoral head and minimize future need for arthroplasty. Secondary to unique biomechanical and vascular considerations, these injuries are prone to nonunion.

CASE REPORT

A 29-year-old male with a chronic femoral neck fracture nonunion who experienced successful fracture healing and symptom resolution following Bone Marrow Aspirate Concentrate (BMAC) administration.

DISCUSSION

Femoral neck nonunion in young patients is a challenging problem with treatment strategies aimed at improving the biological and biomechanical fracture environment. While the use of both vascularized and nonvascularized bone grafting has shown promising results, they have high complication rates and substantial donor site morbidity. BMAC has demonstrated multiple uses throughout orthopedic surgery and may result in an improved fracture healing environment with minimal patient morbidity.

CONCLUSION

The success of the BMAC procedure for this patient is promising and may be considered in similar patients, with or without revision internal fixation methods.

Effect of Intrawound Vancomycin Powder in Operatively Treated High-risk Tibia Fractures: A Randomized Clinical Trial

Importance

Despite the widespread use of systemic antibiotics to prevent infections in surgically treated patients with fracture, high rates of surgical site infection persist.

Objective

To examine the effect of intrawound vancomycin powder in reducing deep surgical site infections.

Design, Setting, and Participants

This open-label randomized clinical trial enrolled adult patients with an operatively treated tibial plateau or pilon fracture who met the criteria for a high risk of infection from January 1, 2015, through June 30, 2017, with 12 months of follow-up (final follow-up assessments completed in April 2018) at 36 US trauma centers.

Interventions

A standard infection prevention protocol with (n = 481) or without (n = 499) 1000 mg of intrawound vancomycin powder.

Main Outcomes and Measures

The primary outcome was a deep surgical site infection within 182 days of definitive fracture fixation. A post hoc comparison assessed the treatment effect on gram-positive and gram-negative-only infections. Other secondary outcomes included superficial surgical site infection, nonunion, and wound dehiscence.

Results

The analysis included 980 patients (mean [SD] age, 45.7 [13.7] years; 617 [63.0%] male) with 91% of the expected person-time of follow-up for the primary outcome. Within 182 days, deep surgical site infection was observed in 29 of 481 patients in the treatment group and 46 of 499 patients in the control group. The time-to-event estimated probability of deep infection by 182 days was 6.4% in the treatment group and 9.8% in the control group (risk difference, -3.4%; 95% CI, -6.9% to 0.1%; P = .06). A post hoc analysis of the effect of treatment on gram-positive (risk difference, -3.7%; 95% CI, -6.7% to -0.8%; P = .02) and gram-negative-only (risk difference, 0.3%; 95% CI, -1.6% to 2.1%; P = .78) infections found that the effect of vancomycin powder was a result of its reduction in gram-positive infections.

Conclusions and Relevance

Among patients with operatively treated tibial articular fractures at a high risk of infection, intrawound vancomycin powder at the time of definitive fracture fixation reduced the risk of a gram-positive deep surgical site infection, consistent with the activity of vancomycin.

Trial Registration

ClinicalTrials.gov Identifier: NCT02227446.

Bone healing: Advances in biology and technology

Fracture healing is a complex cascade of cellular and molecular processes. These processes require the appropriate cellular and molecular environment to ensure the restoration of skeletal stability and resolution of inflammation. In order for fracture healing to occur, the necessary building blocks for bone metabolism and synthesis must be supplied through proper nutrition. Pharmacologic therapies aimed at modulating the inflammatory response to fractures have the potential to interfere with the synthesis of molecules needed for the production of bone. Infection can interfere with, and even prevent normal fracture healing from occurring. Cellular and genetic treatment strategies are actively being developed to target deficiencies, and bridge gaps that can influence how fractures heal. Evolving technologies, including nutritional supplementation, pharmacotherapies, antibiotics, surgical techniques, as well as genetic and cellular therapies, have the potential to enhance, optimize, and even revolutionize the process of fracture healing.

The effect of trichloroethylene metabolites on the hepatic vitamin B12-dependent methionine salvage pathway and its relevance to increased excretion of formic acid in the rat

The industrial solvent trichloroethylene (TCE) and its two major metabolites trichloroethanol (TCE-OH) and trichloroacetic acid (TCA) cause formic aciduria in male F344 rats. Prior treatment of male F344 rats with 1-aminobenzotriazole a cytochrome P450 inhibitor, followed by TCE (16mk/kg, po), completely prevented formic aciduria, but had no effect on formic acid excretion produced by TCA (8 or 16 mg/kg, po), suggesting TCA may be the proximate metabolite producing this response. Dow and Green reported an increase in the concentration of 5-methyltetrahydrofolate (5-MTHF) in the plasma of rats treated with TCE-OH, suggesting a block in the cycling of 5-MTHF to tetrahydrofolate (THF). This pathway is under the control of the vitamin B12-dependent methionine salvage pathway. We therefore treated rats with three daily doses of methylcobalamin (CH3Cbl) or hydroxocobalamin (OHCbl), a cofactor for methionine synthase, or L-methionine, followed by TCE (16 mg/kg) to determine if they could alleviate the formic aciduria. These pretreatments only partially reduced the excretion of formic acid in the urine. Although prior treatment with S-adenosyl-L-methionine had no effect on formic acid excretion. Consistent with these findings, the activity of methionine synthase in the liver of TCE-treated rats was not inhibited. Transcriptomic analysis of the liver-identified nine differential expressed genes, of note, was downregulation of Lmbrd1 involved in the conversion of vitamin B12 into CH3Cbl, a cofactor for methionine synthase. Our findings indicate that the formic aciduria produced by TCE-OH and TCA may be the result of a block in the recycling of 5-MTHF to THF, the effect on the methionine salvage pathway being a secondary response following acute exposure.

Inferring diet, feeding behaviour and causes of mortality from prey-induced injuries in a New Zealand fur seal

New Zealand fur seals Arctocephalus forsteri are the most abundant of the 4 otariid (eared seal) species distributed across Australasia. Analyses of stomach contents, scats and regurgitates suggest a diet dominated by bony fish and squid, with cartilaginous species (e.g. sharks and rays) either absent or underrepresented because of a lack of preservable hard parts. Here we report on a subadult specimen from south-eastern Australia, which was found ashore emaciated and with numerous puncture wounds across its lips, cheeks, throat and the inside of its oral cavity. Fish spines embedded in the carcass revealed that these injuries were inflicted by chimaeras and myliobatiform rays (stingrays and relatives), which matches reports on the diet of A. forsteri from New Zealand, but not South Australia. Shaking and tearing of prey at the surface may help to avoid ingestion of the venomous spines, perhaps contributing to their absence from scats and regurgitates. Nevertheless, the number and severity of the facial stab wounds, some of which led to local necrosis, likely affected the animal's ability to feed, and may account for its death. Despite their detrimental effects, fish spine-related injuries are difficult to spot, and may be a common, albeit cryptic, type of trauma. We therefore recommend that stranded seals be systematically examined for this potentially life-threatening pathology.

Acridone alkaloids from the stem bark of Citrus aurantium display selective cytotoxicity against breast, liver, lung and prostate human carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus aurantium L. (Rutaceae) is used, either singly or as a part of a polyherbal preparation, in Nigerian traditional medicine for the management of cancer and inflammatory diseases. Currently, there is a dearth of knowledge demonstrating its anticancer potential.

AIM OF THE STUDY

This study was carried out to determine the in vitro cytotoxicity of the crude extract of the stem bark of C. aurantium, identify and isolate the bioactive constituents and to establish the cytotoxicity of such constituents.

MATERIALS AND METHODS

The powdered bark of C. aurantium was extracted by MeOH at room temperature (25-34 °C) and the crude extract was partitioned successively, with n-hexane, dichloromethane and methanol. Amongst the fractions, the DCM fraction was the most active and compounds were isolated from this fraction using a combination of chromatographic techniques. The structures of the isolated compounds were elucidated by spectroscopic means (MS, 1D and 2D NMR). The cytotoxicity of the extract, and the isolated compounds were evaluated by the MTT assay against four human cancer cell lines: A549 (lung), HepG2 (liver), MCF7 (breast) and PC3 (prostate). The selectivity of the isolated compounds was assessed using the normal human prostate epithelium cells (PNT2).

RESULTS AND DISCUSSION

Of the three plant fractions, the DCM fraction showed significant cytotoxicity, with its highest activity against A549 cells (IC₅₀ = 3.88 µg/mL) and the least activity on HepG2 cells (IC₅₀ = 5.73 µg/mL). Six acridone alkaloids, citrusinine-I (1), citracridone-I (2), 5-hydroxynoracronycine (3), natsucitrine-I (4), glycofolinine (5) and citracridone-III (6), were isolated from the DCM fraction of C. aurantium. The isolated compounds demonstrated potent to moderate cytotoxicity (IC₅₀ = 12.65-50.74 µM) against the cancer cells under investigation. It is noteworthy that the compounds exerted cytotoxicity at least four times more selective towards the carcinoma cells than the PNT2 cells.

CONCLUSION

The results obtained from this study have provided some evidence for the ethnomedicinal use of C. aurantium against cancer and the acridone alkaloids present in its stem bark, have appeared to be responsible for the anticancer effects.

Resveratrol derivatives from Commiphora africana (A. Rich.) Endl. display cytotoxicity and selectivity against several human cancer cell lines

Commiphora africana (A. Rich.) Endl. (Burseraceae) is a medicinal plant widely used in Nigerian ethnomedicine. The in vitro cytotoxicity of the stem bark extract of C. africana and isolated cytotoxic compounds was investigated. Three resveratrol derivatives: (E)-resveratrol 3-O-rutinoside (1), 5-methoxy-(E)-resveratrol 3-O-rutinoside (2), and pinostilbene (3), together with 3-hydroxy-5-methoxybenzoic acid (4) were isolated from the methanol fraction of C. africana. Their structures were determined by extensive analysis of their HREIMS and NMR spectra. The cytotoxicity of the isolated compounds against four human carcinoma cells was determined using the MTT assay. Compound 1 displayed the highest antiproliferative effect on the cell lines, with IC₅₀ values of 16.80, 21.74, 17.89, and 17.44 μM, against MCF7, A549, PC3, and HepG2 human cancer cell lines, respectively. In addition, compounds 1-3 showed low toxicity against normal human prostate cell line, with selectivity indices greater than five across the carcinoma cells, indicating that the compounds possess potential in the development of low-toxicity chemotherapeutic agents. These results support the traditional use of this plant in the treatment of cancer.

Analysis of mortality and fixation failure in geriatric fractures using quantitative computed tomography

OBJECTIVES

While osteoporosis has been shown to be a contributing factor in low energy fractures in the elderly, limited data exists regarding the correlation of bone mineral density (BMD) and T-Scores to mortality and failure of fracture fixation. This study seeks to determine the relationship between femoral neck BMD in elderly patients with typical geriatric fractures and mortality and fracture fixation failure using Quantitative Computed Tomography (QCT).

MATERIALS AND METHODS

Patients over the age of 65 who sustained fractures of the proximal humerus, distal radius, pelvic ring, acetabulum, hip, proximal tibia, and ankle who also underwent a CT scan that included an uninjured femoral neck were retrospectively reviewed. QCT was used to assess bone mineral density and T scores. Mortality and fixation failure were recorded. Standard descriptive statistics, as well as logistic regression were used to correlate BMD and mortality, and BMD and fixation failure.

RESULTS

Of the 173 patients initially screened, 150 met inclusion criteria. Patients who remained alive at the end of the study (LP) had significantly (P = .019) higher adjusted mean femoral neck BMD (0.502 g/cm²) than non-polytrauma patients who died (MNPT) (0.439 g/cm²) when controlling for age, time to mortality, follow up, CCI, and ASA. Patients who had fixation failure events (FE) had significantly (P = .002) lower adjusted mean femoral neck BMD (0.342 g/cm²) than patients without failure events (NE) (0.525 g/cm²) when controlling for age and time to radiographic follow-up.

CONCLUSIONS

Our study illustrates that QCT is a reliable method for the determination of femoral neck BMD in elderly patients with geriatric fractures. Furthermore, lower BMD/T-Scores are associated with increased mortality and fixation failures in this patient population.

Staged treatment of high energy midfoot fracture dislocations

BACKGROUND

Staged care with interval external fixation is a successful established treatment strategy for high energy periarticular fractures with often extensive soft tissue damage such as the tibial plateau and plafond. The aim of the current study was to determine whether staged care of high energy midfoot fracture/dislocation with interval external fixation prior to definitive open reconstruction in the polytraumatized patient was both safe and efficacious.

METHODS

One hundred twenty-three patients were operated on for high energy midfoot fracture/dislocation during the 8-year study period. Eighteen polytrauma patients were selectively treated with a staged protocol. Radiographic assessment was utilized to determine if the fixator achieved gross skeletal alignment. Further, final alignment after definitive reconstruction and postoperative complications were analyzed.

RESULTS

The fixator improved both length and alignment of all high energy midfoot fracture/dislocations. Loss of acceptable reduction while in the temporary frame occurred in only 1 case. Final alignment after definitive reconstruction was anatomic in all cases. No cases of wound-related complication and/or deep infection occurred.

CONCLUSION

Delayed reconstruction of high energy midfoot fracture/dislocation using interval external fixation should be an accepted care paradigm in selected polytrauma patients.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Comparison of outcomes after triceps split versus sparing surgery for extra-articular distal humerus fractures

OBJECTIVES

To compare elbow range of motion (ROM), triceps extension strength, and functional outcome of AO/OTA type A distal humerus fractures treated with a triceps-split or -sparing approach.

DESIGN

Retrospective review.

SETTING

Two level one trauma centres.

PATIENTS

Sixty adult distal humerus fractures (AO/OTA 13A2, 13A3) presenting between 2008 and 2012 were reviewed. Exclusion criteria removed 18 total patients from analysis and three patients died before final follow-up.

INTERVENTION

Patients were divided into two surgical approach groups chosen by the treating surgeon: triceps split (16 patients) or triceps sparing (23 patients).

MAIN OUTCOME MEASUREMENTS

Elbow ROM and triceps extension strength testing were completed in patients after fractures had healed. All patients were also given the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire.

RESULTS

Compared to the triceps-split cohort, the triceps-sparing cohort had greater elbow flexion (sparing 143 ± 7° compared to split 130 ± 12°, p=0.03) and less extension contracture (sparing 6 ± 8° compared to split 23 ± 4°, p<0.0001). Triceps strength compared to the uninjured arm also favoured the triceps-sparing cohort (sparing 88.9 ± 28.3% compared to split 49.4 ± 17.0%, p=0.007). DASH scores were not statistically significant between the two cohorts (sparing 14.5 ± 12.2 compared to split 23.6 ± 22.3, p=0.333).

CONCLUSIONS

A triceps-sparing approach for surgical treatment of extra-articular distal humerus fractures can result in better elbow ROM and triceps strength than a triceps-splitting approach. Both approaches, however, result in reliable union and similar functional outcome.

LEVEL OF EVIDENCE

Level III.

Open reconstruction of complex proximal metadiaphyseal fragility fractures of the humerus

PURPOSE

A proactive surgical and rehabilitation protocol was implemented to manage humeral fractures involving both the proximal end and shaft in an older patient population. Primary treatment goals were early return to function and reliable fracture union with minimal complications.

METHODS

From 2008 to 2012, 21 such operations were performed; 18 were considered "fragility" fractures based on mechanism, patient age, and evidence of osteopenia or osteoporosis. Open reduction and internal fixation (ORIF) was employed using direct reduction and fixation with a long periarticular locking plate. Physiotherapy was commenced 2 weeks postoperatively. The Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire was used to assess functional outcome at a time point greater than 1 year postoperative.

RESULTS

The study group consisted primarily of elderly females (83% with a median age of 69 years) whom sustained complex metadiaphyseal proximal humeral fractures after simple mechanical fall (78%). Uneventful union occurred in all cases. Local complications included 1 case of partial radial nerve palsy, which had resolved completely by 1 year. No cases of infection were identified. Long-term return to functionality was evident with a median DASH score of 12 (mean = 21, standard deviation = 20, n = 13). Seventy five percent of patients reported minimal or no pain (question [Q] 24), and 75% achieved return of overhead function (Q6, 12, and 15).

CONCLUSION

Treatment of complex metadiaphyseal fragility fractures with anatomic reduction, fixed angle plating, and early physiotherapy returns the older patient to optimized functionality with minimal risk of complication. The DASH outcomes are equivalent to ORIF of isolated proximal humerus fractures and clinically indistinguishable from the general population.

What is the rate of methicillin-resistant Staphylococcus aureus and Gram-negative infections in open fractures?

BACKGROUND

There have been increasing reports of methicillin-resistant Staphylococcus aureus (MRSA) infections in the community, but it is unclear whether infectious organisms in open fracture infections have changed and if our current regimen of antibiotic prophylaxis is therefore obsolete.

QUESTIONS/PURPOSES

We determined the recent incidence of MRSA and Gram-negative organism infections after open fractures.

METHODS

We performed a retrospective cohort study on 189 patients with 202 open fractures treated from 2009 to 2010. During the followup, patients were evaluated for signs of infection using the Centers for Disease Control and Prevention criteria. We determined the organisms using routine microbiology culture. The minimum followup was 3 months (median, 47 months; range, 3-108 months).

RESULTS

Of the 202 open fractures, 20 (10%) developed infections. The most common organism was Staphylococcus, whereas five (25%) of those infected were positive for MRSA, and 11 (55%) of those with infection were cultured for at least one Gram-negative organism. Six (30%) open fractures had infections that grew out multiple organisms. The incidence of MRSA infections in our open fracture population was 2.5%.

CONCLUSIONS

There is a high incidence of MRSA and Gram-negative infections after open fractures, which may indicate that current antibiotic regimens need to be changed.

LEVEL OF EVIDENCE

Level IV, retrospective case-series. See the Guidelines for Authors for a complete description of levels of evidence.

Prodigious alcohol consumption by Australian rugby league footballers

As an incidental finding in a general 'life-style' survey, amateur rugby footballers were found to drink prodigious (12-24 schooners per session) quantities of beer. Such drinking was regarded by the players as part of the traditions of mateship associated with the game. The need for intervention is discussed.

Increased attendances of people of eastern European origin at sexual health services in London

OBJECTIVE

To describe the service use of migrants from eight central and eastern European (CEE) countries at two central London genitourinary medicine (GUM) clinics before and after accession to the European Union on 1 May 2004.

METHODS

KC60 data collected between 1 June 2001 and 30 April 2007. Data refer to new attendances and exclude those attending for follow-up appointments.

RESULTS

102,604 people attended the clinics at least once over the study period. Between May 2006 and 30 April 2007 individuals born in the eight CEE countries accounted for 7.9% of attendances among women and 2.5% of attendances made by men; the proportion increasing significantly over the 6-year study period (p<0.001). Syphilis was more likely in CEE men (age-adjusted odds ratio (OR) 2.98, 95% CI 1.07 to 8.29) and family planning services were more likely to be required for CEE women (23.9% vs 12.4%, age-adjusted OR 2.33, 95% CI 2.02 to 2.68, p<0.001), than for those born elsewhere. A larger proportion of men from CEE countries were recorded as homosexual or bisexual than men from other countries (38.3% vs 31.9%, p = 0.003).

CONCLUSIONS

CEE migrants already have a substantial impact on GUM services in London. If attendance rates continue at the current level CEE women will soon account for over 10% of new attendances. Although the majority of CEE migrants are men, proportionately fewer CEE men accessed GUM services than women. Sexual and reproductive health services need to adapt quickly to meet the needs of this growing population.

Mirels' rating for humerus lesions is both reproducible and valid

Mirels' rating system is commonly used to predict risk of fracture in patients with metastatic bone lesions to long bones, but it has not been independently validated for use in humeral bone lesions. We asked whether this system was a valid and reproducible instrument for predicting impending pathologic fractures in the humerus. We presented 17 case histories and plain radiographs of 16 patients with humeral metastases through a web-based survey to 39 physicians with varying training and experience. Participants scored each case using Mirels' criteria and provided a fracture prediction, which was compared with actual outcome in the subset of 12 patients with three fractures not treated prophylactically. Using Mirels' definition of impending pathologic fracture (nine points or greater), the sensitivity and specificity for determining the likelihood of pathologic humeral fracture were 14.5% and 82.9%, respectively. When we used seven or more points as the definition of impending pathologic humeral fracture, sensitivity improved to 81% but specificity was reduced to 32%. Kappa analysis suggested moderate reproducibility across groups for prediction of pathologic fracture. The Mirels rating system for humeral lesions is reproducible and valid, but low specificity at acceptable sensitivity levels as reported remains a problem as for femoral lesions.

LEVEL OF EVIDENCE

Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Functional analysis of CHX21: a putative sodium transporter in Arabidopsis

The functional role of CHX21, a member of the Arabidopsis thaliana CHX cation transporter family, has been investigated in plants growing under "ideal" conditions and in the presence of elevated NaCl levels. In public databases, AtCHX21 (At2g31910) is annotated as a putative Na+/H+ antiporter. In this study, Southern analysis was used to identify a genotype that contained a single transposon insertion within its genome; using PCR, this insertion was shown to be within the CHX21 locus. No CHX21 transcript was detectable in Atchx21 (mutant) plants using RT-PCR. In the absence of salt stress, Atchx21 showed significant quantitative differences from the wild type (AtCHX21) in development with respect to characters such as rosette width and flowering time. In the presence of 50 mM NaCl, (i) roots of Atchx21 elongated more slowly than the wild type, (ii) the leaf sap Na+ concentration was significantly lower in Atchx21 compared with the wild type, and (iii) the concentra) in the xylem was lower compared with the wild type. The concentration of Na+ exported from the leaf in the phloem was unchanged. Thus, loading of Na+ into the root xylem could explain changes in leaf concentration of Na+. This hypothesis was supported by immunolocalization which demonstrated that the AtCHX21 transporter could only be detected in root endodermal cells. Immunogold labelling of ultra-thin sections, followed by transmission electron microscopy, demonstrated the localization of the protein in the plasma membrane. The data demonstrate that the CHX21 transporter may play a role in regulation of xylem Na+ concentration and, consequently, Na+ accumulation in the leaf.

Health-related quality of life of patients with diabetes and foot ulcers

Thirty-four patients with diabetes who attended a university diabetic foot clinic for treatment of a foot ulcer completed the American Academy of Orthopaedic Surgeons Musculoskeletal Outcomes Measure. The purpose of the study was to measure the impact of foot ulcers in patients with diabetes on the physical, mental, emotional, and social aspects of patients' lives. Thirty had at least a high school education. Only six were employed at the time. Nineteen were retired or disabled due to poor health. Sixteen were obese, 10 were considered overweight, and eight had a BMI within the acceptable range. Subjects had an average of four to five bodily systems affected by comorbid illness for which they were receiving treatment, some of which limited their activities. Approximately 85% of the study population required some type of ambulatory assist device or were unable to ambulate independently. The study population was significantly limited in performing all physical activities, especially those requiring use of the foot and ankle, and viewed their own health as being significantly worse than that of the general population. All stated that their foot/ankle disease interfered with their lives. Pain was not a significant component of their disability. The results of this study confirm the hypothesis that foot ulcers in patients with diabetes have a negative impact on quality of life in affected individuals.

Interactions between proteins bound to biomembranes

We study a physical model for the interaction between general inclusions bound to fluid membranes that possess finite tension gamma, as well as the usual bending rigidity kappa. We are motivated by an interest in proteins bound to cell membranes that apply forces to these membranes, due to either entropic or direct chemical interactions. We find an exact analytic solution for the repulsive interaction between two similar circularly symmetric inclusions. This repulsion extends over length scales approximately sqrt[kappa/gamma] and contrasts with the membrane-mediated contact attraction for similar inclusions on tensionless membranes. For noncircularly symmetric inclusions we study the small, algebraically long-ranged, attractive contribution to the force that arises. We discuss the relevance of our results to biological phenomena, such as the budding of caveolae from cell membranes and the striations that are observed on their coats. These, and other, "gnarly buds" may prove fascinating to study further.

Confocal imaging, visualization and 3-D surface measurement of small mammalian teeth

The difficulties traditionally faced by functional morphologists in representing and interpreting three-dimensional objects can now be mostly overcome using available laser and computer imaging technologies. A practical method for three-dimensional imaging of small mammalian teeth using confocal microscopy is reported. Moulding and casting of the teeth were first performed, followed by confocal fluorescence imaging. Accuracy and precision of the scanned structures were tested in morphometric studies by using a new technique to measure the noise in the scan of a three-dimensional surface, and linear and angular dimensions of the scans were compared with measurements made using traditional morphological tools. It is shown that measurements can be taken with less than 4% difference from the original object. Teeth of the microchiropteran bat Chalinolobus gouldii were scanned and measured to show the potential of the techniques. Methods for visualizing the small teeth in three-dimensional space, and animating the teeth in occlusion, show the power of this approach in aiding a three-dimensional understanding of the structure and function of teeth and other three-dimensional structures.

Going APE over ref-1

The DNA base excision repair (BER) pathway is responsible for the repair of cellular alkylation and oxidative DNA damage. A crucial and the second step in the BER pathway involves the cleavage of baseless sites in DNA by an AP endonuclease. The major AP endonuclease in mammalian cells is Ape1/ref-1. Ape1/ref-1 is a multifunctional protein that is not only responsible for repair of AP sites, but also functions as a reduction-oxidation (redox) factor maintaining transcription factors in an active reduced state. Ape1/ref-1 has been shown to stimulate the DNA binding activity of numerous transcription factors that are involved in cancer promotion and progression such as Fos, Jun, NF(B, PAX, HIF-1(, HLF and p53. Ape1/ref-1 has also been implicated in the activation of bioreductive drugs which require reduction in order to be active and has been shown to interact with a subunit of the Ku antigen to act as a negative regulator of the parathyroid hormone promoter, as well as part of the HREBP transcription factor complex. Ape1/ref-1 levels have been found to be elevated in a number of cancers such as ovarian, cervical, prostate, rhabdomyosarcomas and germ cell tumors and correlated with the radiosensitivity of cervical cancers. In this review, we have attempted to try and assimilated as much data concerning Ape1/ref-1 and incorporate the rapidly growing information on Ape1/ref-1 in a wide variety of functions and systems.

Isoprostanes, novel eicosanoids that produce nociception and sensitize rat sensory neurons

Isoprostanes are a novel class of eicosanoids primarily formed by peroxidation of arachidonic acid. Because of their potential as inflammatory and/or hyperalgesic agents whose formation is largely independent of cyclooxygenases, we examined whether 8-iso prostaglandin E(2) (8-iso PGE(2)) or 8-iso prostaglandin F(2alpha) (8-iso PGF(2alpha)) reduces mechanical and thermal withdrawal threshold in rats, and whether they sensitize rat sensory neurons. Injection of 1 microg of 8-iso PGE(2) (in 2.5 microl) into the hindpaw of rats significantly reduced mechanical and thermal withdrawal thresholds, whereas 1 microg of 8-iso PGF(2alpha) elicited a transient decrease in only the mechanical withdrawal threshold. Both isoprostanes enhanced the firing of C-nociceptors in a concentration-dependent manner when injected into peripheral receptive fields. Exposing sensory neurons grown in culture to 1 microM 8-iso PGE(2) or 8-iso PGF(2alpha) augmented the number of action potentials elicited by a ramp of depolarizing current. In contrast, 8-iso PGE(2) but not 8-iso PGF(2alpha) enhanced the release of substance P- and calcitonin gene-related peptide-like immunoreactivity from isolated sensory neurons. Ten micromolar 8-iso PGE(2) stimulated peptide release directly, whereas treatment with 1 microM 8-iso PGE(2) augmented the release evoked by either bradykinin or capsaicin. Pretreating neuronal cultures with the nonsteroidal anti-inflammatory drug ketorolac did not alter the sensitizing action of 8-iso PGE(2) on peptide release, suggesting that this action of the isoprostane was not secondary to the production of prostaglandins via the cyclooxygenase pathway. These data support the notion that isoprostanes are an important class of inflammatory mediators that augment nociception.

The epidemiology of pediatric glaucoma: the Toronto experience

BACKGROUND

This study was conceived to provide an insight into the spectrum of glaucoma in the pediatric population. We also set out to compare the success of disease control and the prognosis for vision within the different diagnostic subgroups. This is the largest single population of children with glaucoma that has been so described and compared.

METHODS

The charts of children who were first seen between birth and age 16 years and who attended the Hospital for Sick Children with any form of glaucoma between January 1974 and January 1995 were reviewed and entered into the study.

RESULTS

Data are presented for 306 children. Congenital glaucoma was the most common subtype, accounting for 38%. Patients with congenital glaucoma were young, had surgery, and had more operations than any other group except those with aniridia. Goniotomy offered a cure in 47.8% of the patients. A bimodal distribution reflected their visual performance. Patients with aphakic glaucoma, the next most prevalent group (20%), presented at an older age (4.5 years). Surgical intervention was performed in 50% of these children. Nearly all patients with Sturge-Weber syndrome (80%) had surgery. The following glaucoma groups were associated with a poor visual outcome: aniridia, anterior segment developmental anomalies involving the cornea, uveitis with glaucoma other than steroid induced, retinopathy of prematurity, and persistent hyperplastic primary vitreous. Steroid-induced glaucoma and anterior segment dysgenesis, excluding Peters anomaly, had uniformly good outcomes.

CONCLUSION

The ability to control glaucoma in childhood and visual prognosis is highly variable. Particular diagnostic categories do consistently well and some do poorly.

The cAMP transduction cascade mediates the PGE2-induced inhibition of potassium currents in rat sensory neurones

1. The role of the cyclic AMP (cAMP) transduction cascade in mediating the prostaglandin E2 (PGE2)-induced decrease in potassium current (IK) was investigated in isolated embryonic rat sensory neurones using the whole-cell patch-clamp recording technique. 2. Exposure to 100 microM chlorophenylthio-adenosine cyclic 3', 5'-monophosphate (cpt-cAMP) or 1 microM PGE2 caused a slow suppression of the whole-cell IK by 34 and 36 %, respectively (measured after 20 min), without a shift in the voltage dependence of activation for this current. Neither of these agents altered the shape of the voltage-dependent inactivation curve indicating that the suppression of IK did not result from alterations in the inactivation properties. 3. To determine whether the PGE2-mediated suppression of IK depended on activation of the cAMP pathway, cells were exposed to this prostanoid in the presence of the protein kinase A (PKA) inhibitor, PKI. The PGE2-induced suppression of IK was prevented by PKI. In the absence of PGE2, PKI had no significant effect on the magnitude of IK. 4. Results obtained from protocols using different conditioning prepulse voltages indicated that the extent of cpt-cAMP- and PGE2-mediated suppression of IK was independent of the prepulse voltage. The subtraction of control and treated currents revealed that the cpt-cAMP- and PGE2-sensitive currents exhibited little time-dependent inactivation. Taken together, these results suggest that the modulated currents may be delayed rectifier-like IK. 5. Exposure to the inhibitors of IK, tetraethylammonium (TEA) or 4-aminopyridine (4-AP), reduced the control current elicited by a voltage step to +60 mV by 40-50 %. In the presence of 10 mM TEA, treatment with cpt-cAMP did not result in any further inhibition of IK. In contrast, cpt-cAMP reduced IK by an additional 25-30 % in the presence of 1 mM 4-AP. This effect was independent of the conditioning prepulse voltage. 6. These results establish that PGE2 inhibits an outward IK in sensory neurones via activation of PKA and are consistent with the idea that the PGE2-mediated sensitization of sensory neurones results, in part, from an inhibition of delayed rectifier-like IK.

Necrotising fasciitis as a complication of botulinum toxin injection

PURPOSE

To highlight the need for early diagnosis and treatment of the rare condition of necrotising fasciitis as a complication of botulinum toxin injection, and to illustrate that injections in immunocompromised patients carry a rare but serious risk.

RESULTS AND METHODS

A case report is presented of an 80-year-old woman suffering from blepharospasm and chronic myeloid leukaemia, who developed necrotising fasciitis 3 days after a botulinum toxin injection.

CONCLUSIONS

Chronic debilitating processes such as diabetes, alcoholism and polymyositis have been suggested as predisposing factors in the development of necrotising fasciitis. We believe this is the first reported case of necrotising fasciitis occurring secondary to a botulinum toxin injection. The fact that this infection extended through the fascial planes and led to the death of muscle was, probably, because an inoculum was introduced directly into the muscle at the time of botulinum toxin treatment. This may have led to its deep spread and difficulty in debriding the area. Chronic myeloid leukaemia does not in itself cause significant immunosuppression, but our patient was on anti-proliferative treatment and had a low leucocyte count, which may have been a predisposing factor in this case.

Prostaglandins suppress an outward potassium current in embryonic rat sensory neurons

The cellular mechanisms giving rise to the enhanced excitability induced by prostaglandin E2 (PGE2) and carba prostacyclin (CPGI2) in embryonic rat sensory neurons were investigated using the whole cell patch-clamp recording technique. Exposing sensory neurons to 1 microM PGE2 produced a twofold increase in the number of action potentials elicited by a ramp of depolarizing current, but this eicosanoid had no effect on the resting membrane potential or the amplitude of the slow afterhyperpolarization. Characterization of the outward potassium currents in the embryonic sensory neurons indicated that the composition of the total current was variable among these neurons. A steady-state inactivation protocol was used to determine the extent of residual noninactivating current. A conditioning prepulse to +20 mV demonstrated that some of these neurons exhibited only a sustained potassium current with little steady-state inactivation whereas other exhibited some combination of a sustained as well as a rapidly inactivating IA-type current. Treatment with 1 microM PGE2 or 1 microM CPGI2, but not 1 microM prostaglandin F2 alpha (PGF2 alpha) produced a time-dependent suppression of the total potassium current. After a 20-min exposure, PGE2 and CPGI2 inhibited the maximal current obtained at +60 mV by 48 and 40%, respectively. The prostaglandin-induced suppression of the potassium current was not associated with a shift in the voltage dependence for activation. Subtraction of the currents remaining after PGE2 or CPGI2 treatment from their respective control recordings revealed that the prostaglandin-sensitive current had characteristics that were consistent with a sustained-type of potassium current. This idea is supported by the following observation. The steady-state inactivation protocol revealed that for prepulse voltages activating both rapidly inactivating and sustained currents, the relaxation of the current was accelerated after treatment with PGE2 or CPGI2 suggesting the removal of a slower component. This effect was not observed in neurons exhibiting only the sustained type current. These results suggest that pro-inflammatory prostaglandins enhance the excitability of rat sensory neurons, in part, through the suppression of an outward potassium current that may modulate the firing threshold for generation of the action potential.

Differential regulation of evoked peptide release by voltage-sensitive calcium channels in rat sensory neurons

To determine whether the sensitizing action of prostaglandins on sensory neurons are due to modulation of voltage-sensitive calcium channels (VSCC) we examined the effects of inhibiting these channels on PGE2-induced enhancement of evoked peptide release from isolated dorsal root ganglion neurons. The inhibitory effects of the VSCC blockers on stimulated release were dependent upon the type of chemical agent used to evoke the release. Bradykinin-stimulated release of immunoreactive substance P (iSP) and calcitonin gene-related peptide (iCGRP) was attenuated by the N-type VSCC blocker, omega-conotoxin GVIA (100 nM), but was unaffected by blockade of L-type (1 microM nifedipine) or P-type (200 nM omega-agatoxin IVA) VSCC. In contrast, potassium-stimulated release of peptides was inhibited by nifedipine, but not by omega-conotoxin GVIA or omega-agatoxin IVA. None of the VSCC blockers tested attenuated capsaicin-stimulated release of iSP and iCGRP. The combination of 1 microM nifedipine and 100 nM omega-conotoxin GVIA reduced the whole cell calcium current 89% +/- 1.7%. Administration of 100 nM PGE2 potentiated bradykinin- and capsaicin-evoked peptide release by 2-3-fold. Neither nifedipine nor omega-conotoxin GVIA attenuated the PGE2-mediated potentiation of bradykinin-evoked release, and neither omega-conotoxin GVIA nor omega-agatoxin IVA blocked the potentiation of capsaicin-evoked release induced by PGE2. These results indicate that the sensitizing actions of PGE2 as measured by enhanced peptide release, are not mediated by L-, N-, or P-type VSCC.

Effects of vagal afferent nerve stimulation on noxious heat-evoked Fos-like immunoreactivity in the rat lumbar spinal cord

Electrophysiological and behavioral studies have described modulation of nociception by vagal afferent fibers. The objectives of this study were to 1) use Fos-like immunoreactivity as a marker for neuronal activity to examine populations of neurons in the spinal cord that are activated by a noxious heat stimulus, 2) determine whether heat-evoked Fos-like immunoreactivity can be modulated by vagal afferent stimulation, and 3) determine whether vagally-mediated effect on heat-evoked Fos-like immunoreactivity can be blocked by intrathecally administered serotoninergic receptor and alpha-adrenergic receptor antagonists. Neurons demonstrating Fos-like immunoreactivity were located in the ipsilateral superficial and deep dorsal horn laminae extending from the caudal L3 through the rostral L6 region of the spinal cord. Stimulation of the right cervical vagus nerve attenuated significantly (42%) heat-evoked Fos-like immunoreactivity in the superficial laminae. The reduction in Fos-like immunoreactivity by vagal stimulation was abolished by intrathecal administration of methysergide, a nonselective serotoninergic receptor antagonist, but not by phentolamine, a nonselective alpha-adrenoceptor antagonist. These results suggest that vagal afferent modulation of spinal nociceptive transmission is mediated, at least in part, by serotonin receptors.