Comparison of T-cell receptor diversity of people with myalgic encephalomyelitis versus controls

OBJECTIVE

Myalgic Encephalomyelitis (ME; sometimes referred to as Chronic Fatigue Syndrome) is a chronic disease without laboratory test, detailed aetiological understanding or effective therapy. Its symptoms are diverse, but it is distinguished from other fatiguing illnesses by the experience of post-exertional malaise, the worsening of symptoms even after minor physical or mental exertion. Its frequent onset after infection suggests autoimmune involvement or that it arises from abnormal T-cell activation.

RESULTS

To test this hypothesis, we sequenced the genomic loci of α/δ, β and γ T-cell receptors (TCR) from 40 human blood samples from each of four groups: severely affected people with ME; mildly or moderately affected people with ME; people diagnosed with Multiple Sclerosis, as disease controls; and, healthy controls. Seeking to automatically classify these individuals' samples by their TCR repertoires, we applied P-SVM, a machine learning method. However, despite working well on a simulated data set, this approach did not allow statistically significant partitioning of samples into the four subgroups. Our findings do not support the hypothesis that blood samples from people with ME frequently contain altered T-cell receptor diversity.

Prehospital Ultrasound Diagnosis of Massive Pulmonary Embolism by Non-Physicians: A Case Series

Massive pulmonary embolism (hemodynamically unstable, defined as systolic BP <90 mmHg) has significant morbidity and mortality. Point of care ultrasound (POCUS) has allowed clinicians to detect evidence of massive pulmonary embolism much earlier in the patient's clinical course, especially when patient instability precludes computerized tomography confirmation. POCUS detection of massive pulmonary embolism has traditionally been performed by physicians. This case series demonstrates four cases of massive pulmonary embolism diagnosed with POCUS performed by non-physician prehospital personnel.

Envisioning the development of a CRISPR-Cas mediated base editing strategy for a patient with a novel pathogenic CRB1 single nucleotide variant

BACKGROUND

Inherited retinal degeneration (IRD) associated with mutations in the Crumbs homolog 1 (CRB1) gene is associated with a severe, early-onset retinal degeneration for which no therapy currently exists. Base editing, with its capability to precisely catalyse permanent nucleobase conversion in a programmable manner, represents a novel therapeutic approach to targeting this autosomal recessive IRD, for which a gene supplementation is challenging due to the need to target three different retinal CRB1 isoforms.

PURPOSE

To report and classify a novel CRB1 variant and envision a possible therapeutic approach in form of base editing.

METHODS

Case report.

RESULTS

A 16-year-old male patient with a clinical diagnosis of early-onset retinitis pigmentosa (RP) and characteristic clinical findings of retinal thickening and coarse lamination was seen at the Oxford Eye Hospital. He was found to be compound heterozygous for two CRB1 variants: a novel pathogenic nonsense variant in exon 9, c.2885T>A (p.Leu962Ter), and a likely pathogenic missense change in exon 6, c.2056C>T (p.Arg686Cys). While a base editing strategy for c.2885T>A would encompass a CRISPR-pass mediated "read-through" of the premature stop codon, the resulting missense changes were predicted to be "possibly damaging" in in-silico analysis. On the other hand, the transversion missense change, c.2056C>T, is amenable to transition editing with an adenine base editor (ABE) fused to a SaCas9-KKH with a negligible chance of bystander edits due to an absence of additional Adenines (As) in the editing window.

CONCLUSIONS

This case report records a novel pathogenic nonsense variant in CRB1 and gives an example of thinking about a base editing strategy for a patient compound heterozygous for CRB1 variants.

[Gene therapy as a treatment concept for inherited retinal diseases]

BACKGROUND

Gene therapy for inherited retinal diseases (IRDs) is currently being validated in several clinical trials and is becoming a promising therapeutic option for these previously incurable diseases.

OBJECTIVES

The aim of this review is to give an overview of the concept, the application and the challenges associated with gene therapy. In particular, the pertinence of gene therapy for IRDs will be highlighted along with ongoing clinical trials in the field.

MATERIAL AND METHODS

A systematic review of relevant entries on gene therapy and on gene therapy for IRDs, in particular in PubMed and ClinicalTrials.gov.

RESULTS

Gene therapy is emerging not only as a therapy for monogenetic retinal diseases but also for complex genetic diseases, such as neovascular age-related macular degeneration. The discovery of adeno-associated viral vectors (AAVs) has marked a great improvement for IRD gene therapy. All clinical studies since 2006 demonstrated the safety and initial efficacy; however, not all expectations based on very successful preclinical studies were met.

CONCLUSION

In future we can expect gene therapy to continue to become more clinically relevant. More than ever, it is now essential to generate precise characterizations of the natural disease progression of IRDs through observational or retrospective studies in order to guarantee a most effective study design.

[Stem Cells for Retina Replacement]

In ophthalmology, regenerative medicine is rapidly becoming a reality. Cell based treatment strategies in end stage retinal degeneration may be of therapeutic value, whatever the mechanism of disease mechanism. However, while corneal transplantation is commonly performed with excellent results, many obstacles must be overcome before retinal transplants can become clinically useful. The major problems are the production of appropriate transplants and functional integration in situ. New technologies allow the production of autologous transplants by inducing pluripotency in adult somatic cells. Driven by this development, exciting new research has been conducted on the development of artificial retinal tissue for basic research and transplantation. This article reviews this progress and discusses its clinical utility.

A global call for action to include gender in research impact assessment

Global investment in biomedical research has grown significantly over the last decades, reaching approximately a quarter of a trillion US dollars in 2010. However, not all of this investment is distributed evenly by gender. It follows, arguably, that scarce research resources may not be optimally invested (by either not supporting the best science or by failing to investigate topics that benefit women and men equitably). Women across the world tend to be significantly underrepresented in research both as researchers and research participants, receive less research funding, and appear less frequently than men as authors on research publications. There is also some evidence that women are relatively disadvantaged as the beneficiaries of research, in terms of its health, societal and economic impacts. Historical gender biases may have created a path dependency that means that the research system and the impacts of research are biased towards male researchers and male beneficiaries, making it inherently difficult (though not impossible) to eliminate gender bias. In this commentary, we – a group of scholars and practitioners from Africa, America, Asia and Europe – argue that gender-sensitive research impact assessment could become a force for good in moving science policy and practice towards gender equity. Research impact assessment is the multidisciplinary field of scientific inquiry that examines the research process to maximise scientific, societal and economic returns on investment in research. It encompasses many theoretical and methodological approaches that can be used to investigate gender bias and recommend actions for change to maximise research impact. We offer a set of recommendations to research funders, research institutions and research evaluators who conduct impact assessment on how to include and strengthen analysis of gender equity in research impact assessment and issue a global call for action.

[Stem cell therapy for retinal diseases]

BACKGROUND

Due to an ageing population the incidence and prevalence of retinal diseases and visual disabilities will continue to grow. A great number of patients would principally be able to benefit from a stem cell-based therapy.

OBJECTIVES

To introduce readers to the terminology and current concepts associated with stem cell therapy in ocular research and to provide an overview of the current status of preclinical and clinical research.

MATERIAL AND METHODS

We performed a systematic review of relevant entries on ocular stem cell therapy for retinal diseases in PubMed and ClinicalTrials.gov. Differences between various stem cell types are displayed systematically, followed by a discussion of preclinical studies. Translational aspects are highlighted leading to the first clinical trials, including surgical and ethical facets.

RESULTS

In preclinical studies, photoreceptor cell precursors and retinal pigment epithelium (RPE) cells were differentiated and subretinally transplanted into animal models. Besides exclusion of a teratoma formation, some functional improvements were also observed. Intraocular transplantation of stem cell-derived RPE cells was the first successful clinical application of pluripotent stem cells in man.

CONCLUSION

Promising results of preclinical and clinical studies have identified important challenges and confirmed the potential of stem cell therapy for ophthalmology.

In vivo biocompatibility of a new cyanine dye for ILM peeling

PURPOSE

To investigate the biocompatibility of the new cyanine dye: 3,3'-Di-(4-sulfobutyl)-1,1,1',1'-tetramethyl-di-1H-benz[e]indocarbocyanine (DSS) as a vital dye for intraocular application in an in vivo rat model and to evaluate the effects of this dye on retinal structure and function.

METHODS

DSS at a concentration of 0.5% was applied via intravitreal injections to adult Brown Norway rats with BSS serving as a control. Retinal toxicity was assessed 7 days later by means of retinal ganglion cell (RGC) counts, light microscopy, optical coherence tomography (OCT), and electroretinography (ERG).

RESULTS

No significant decrease in RGC numbers was observed. No structural changes of the central retina were observed either in vivo (OCT) or under light microscopy. ERGs detected a temporary reduction of retinal function 7 days after injection; this was no longer evident 14 days after injection.

CONCLUSIONS

DSS showed good biocompatibility in a well-established experimental in vivo setting and may be usable for intraocular surgery as an alternative to other cyanine dyes. In contrast to indocyanine green, it additionally offers fluorescence in the visual spectrum. Further studies with other animal models are needed before translation into clinical application.

Violation of the 12/23 rule of genomic V(D)J recombination is common in lymphocytes

V(D)J genomic recombination joins single gene segments to encode an extensive repertoire of antigen receptor specificities in T and B lymphocytes. This process initiates with double-stranded breaks adjacent to conserved recombination signal sequences that contain either 12- or 23-nucleotide spacer regions. Only recombination between signal sequences with unequal spacers results in productive coding genes, a phenomenon known as the “12/23 rule.” Here we present two novel genomic tools that allow the capture and analysis of immune locus rearrangements from whole thymic and splenic tissues using second-generation sequencing. Further, we provide strong evidence that the 12/23 rule of genomic recombination is frequently violated under physiological conditions, resulting in unanticipated hybrid recombinations in ∼10% of Tcra excision circles. Hence, we demonstrate that strict adherence to the 12/23 rule is intrinsic neither to recombination signal sequences nor to the catalytic process of recombination and propose that nonclassical excision circles are liberated during the formation of antigen receptor diversity.

Organizational Turbulence, Trouble and Trauma: Theorizing the Collapse of a Mental Health Setting

Turbulence is usually considered a negative property of an organization’s environment. Yet turbulence is also a feature of an organization’s internal dynamics and may be useful for productivity. This article argues that interactions between the formal and informal management of trouble produce relational turbulence that may mobilize resources and collective action, or conversely lead to dysfunction and crisis. The author links relational psychoanalytic theory with social constructionist perspectives in exploring intersubjective dynamics of trouble and its repercussions of turbulence. Based on a longitudinal interorganizational ethnography, an atypical mental healthcare organization is described – a democratic therapeutic community – in which turbulence plays a central function, but in two very different ways. In a restorative mode, turbulence generates formative spaces that are creative and have a regulating function, useful for organizational productivity. Conversely, a perverse mode is destructive and may produce intractable perverse spaces, leading to organizational dysfunction, crisis and even collapse. This is theorized by extending the psychoanalytic concept of liminal, transitional space. In contrast to the notion of transitional space as a safe, protective area, the author develops a model of distinct formative and perverse spaces created by relational turbulence in organizations. In human service organizations, where the generation, trading and management of trouble are inherent in an organization’s internal dynamics, turbulence may be a valuable resource, but one that, in the perverse mode, can be immensely destructive.

[Spectral domain optical coherence tomography in the treatment of myopic choroidal neovascularization]

Spectral domain optical coherence tomography (SD-OCT) investigations provide additional information about the morphological characteristics of myopic choroidal neovascularization (mCNV). Reproducible measurements of intraretinal and subretinal fluid are of growing importance for an evaluation of progression. The non-invasive technique reduces the need for frequent fluorescence angiography after individual assessment. Appropriate correction of the reference arm is mandatory. Automatic adjustment of transversal measured values due to alterations in the paraxial field (depending on the axial length) has been implemented in a new device. Mirror artefacts and excess curvature can be avoided by reducing the length of the OCT cross-section (15°). New possibilities to record the choriocapillaris and choroid have expanded the knowledge of potential pathomechanisms and risk factors.

Preparation of high-quality next-generation sequencing libraries from picogram quantities of target DNA

New sequencing technologies can address diverse biomedical questions but are limited by a minimum required DNA input of typically 1 μg. We describe how sequencing libraries can be reproducibly created from 20 pg of input DNA using a modified transpososome-mediated fragmentation technique. Resulting libraries incorporate in-line bar-coding, which facilitates sample multiplexes that can be sequenced using Illumina platforms with the manufacturer's sequencing primer. We demonstrate this technique by providing deep coverage sequence of the Escherichia coli K-12 genome that shows equivalent target coverage to a 1-μg input library prepared using standard Illumina methods. Reducing template quantity does, however, increase the proportion of duplicate reads and enriches coverage in low-GC regions. This finding was confirmed with exhaustive resequencing of a mouse library constructed from 20 pg of gDNA input (about seven haploid genomes) resulting in ∼0.4-fold statistical coverage of uniquely mapped fragments. This implies that a near-complete coverage of the mouse genome is obtainable with this approach using 20 genomes as input. Application of this new method now allows genomic studies from low mass samples and routine preparation of sequencing libraries from enrichment procedures.

Topical imiquimod and intralesional interleukin-2 increase activated lymphocytes and restore the Th1/Th2 balance in patients with metastatic melanoma

BACKGROUND

Patients with metastatic skin disease in malignant melanoma are difficult to treat, with unresectable lesions proving the biggest challenge. We have recently published data showing a significant clinical response in patients with multiple in-transit melanoma metastases treated with a combination of topical imiquimod and intralesional interleukin (IL)-2. Here we report the results of immunological analysis with the aim of highlighting correlations with our clinical findings.

OBJECTIVES

To investigate the systemic effects of our localized combination treatment in patients with accessible metastases of melanoma, and to correlate this with their clinical responses.

METHODS

The peripheral blood mononuclear cells of patients were collected at various time points throughout the treatment. Using antibodies to T-cell subsets we measured the changes in cell populations, and along with polyclonal stimulation, changes in cytokine production from these cells over a treatment course.

RESULTS

We report an increase in the mean CD4/CD8 ratio from 2.78 to 3.54 with treatment (P < 0.01), and a rise in the percentage of CD25+ cells in the CD4+ population from 14.52% to 38.56%. Furthermore, staining with activation and T-regulatory markers showed that the majority of this population is activated T cells. Cytokine analysis on polyclonally stimulated peripheral blood mononuclear cells showed an increase in the ability of cells to produce interferon (IFN)-gamma over the treatment course, with an initial rise in the IFN-gamma/IL-5 ratio in five of six patients.

CONCLUSIONS

The results of this study provide evidence that, in the majority of patients with in-transit metastases of melanoma, therapy with a combination of topical imiquimod and intralesional IL-2 induces a systemic immunological effect by reversing some of changes noted in patients with malignant disease.

Phase I/II study of topical imiquimod and intralesional interleukin-2 in the treatment of accessible metastases in malignant melanoma

BACKGROUND

Patients with metastatic skin disease in malignant melanoma can be difficult to treat effectively, often requiring repeated treatments with different modalities in an attempt to control their disease. Treatment of nonsurgically resectable melanoma deposits is unsatisfactory, as they are often multiple and recurring. Anecdotal evidence from individual use of imiquimod in superficial metastases and intralesional interleukin (IL)-2 in subcutaneous deposits suggests that the combination may be more effective in bulky subcutaneous disease.

OBJECTIVES

To investigate the combination of topical imiquimod and, for selected lesions, intralesional IL-2, to treat a small cohort of patients with accessible melanoma metastases resistant to other treatments.

METHODS

Thirteen patients were recruited: all had evidence of multiple cutaneous and/or subcutaneous metastases. Imiquimod was applied to the metastases on a daily basis for 4 weeks, before the introduction of intralesional IL-2. This was injected up to three times a week, into selected lesions, with 0.1 mL injected per lesion at a concentration of 3.6 MIU mL(-1), a total of 1 mL being given at each session. The treated lesions were assessed individually at intervals of 3 months.

RESULTS

Thirteen patients were treated, with 10 being eligible for assessment. In total, 182 lesions were treated: 137 purely cutaneous lesions and 41 subcutaneous lesions. Overall, a clinical response was seen in 92 lesions (50.5%) with 74 (40.7%) of these being a complete response (CR) with 91% of the CRs being in the cutaneous lesions. New lesions did appear during the treatment course; however, patients with cutaneous disease experienced a marked slowing of the appearance of new cutaneous lesions. No cutaneous lesions that responded reappeared on cessation of treatment.

CONCLUSIONS

The combination of imiquimod and IL-2 is effective in controlling this mixed cutaneous and subcutaneous disease, and is well tolerated. Imiquimod alone is often enough to elicit a response in purely cutaneous lesions. The addition of intralesional IL-2 increases the response rates in subcutaneous lesions, and in otherwise refractory cutaneous lesions.

Accommodation of females in the high-G environment: the USAF Female Acceleration Tolerance Enhancement (FATE) Project

BACKGROUND

In 1993, the U.S. Secretary of Defense opened combat aircraft assignments to women. To verify the adequacy of acceleration (+Gz) protection for female high-G aircrew, USAF investigators conducted fit tests of standard and developmental G-protective equipment and determined the effectiveness of a unique laboratory modification (AL Mod) of the standard (CSU-13B/P) anti-G suit during gender-comparative centrifuge evaluations.

METHODS

Investigators determined relaxed +Gz tolerance and straining endurance to +4.5 to +7 Gz and +5 to +9 Gz simulated aerial combat maneuver (SACM) centrifuge profiles (4.5-7 SACM: 8 females and 10 males; and 5-9 SACM: 6 females and 8 males, respectively). Additionally, in the 5-9 SACM study, between and within gender SACM endurance differences were assessed before and after female subjects' use of the AL Mod. Ten female subjects also were fit tested in extended coverage, developmental G-protective equipment.

RESULTS

There was no gender difference in 4.5-7 SACM endurance. Male 5-9 SACM endurance exceeded that of females in the unmodified CSU-13B/P (p < 0.05), but gender parity was achieved when females wore the AL Mod. Fit modifications of developmental G-protective equipment were not required, but smaller sizes of the standard CSU-13B/P and a developmental anti-G suit were indicated and developed.

CONCLUSION

In properly fitted anti-G suits, gender parity in SACM endurance is achievable; however, full accommodation of female aircrew in the high-G environment will require the AL Mod and/or smaller sized anti-G suits.

The effect of exposure to 35,000 ft on incidence of altitude decompression sickness

INTRODUCTION

Exposure to 35,000 ft without preoxygenation (breathing 100% oxygen prior to decompression) can result in severe decompression sickness (DCS). Exercise while decompressed increases the incidence and severity of symptoms. Clarification of the level of activity vs. time to symptom onset is needed to refine recommendations for current operations requiring 35,000-ft exposures. Currently, the U.S. Air Force limits these operations to 30 min following 75 min of preoxygenation. The objective of this study was to determine the effect of exercise intensity on DCS incidence and severity at 35,000 ft.

METHODS

Following 75 or 90 min of ground-level preoxygenation, 54 male and 38 female subjects were exposed to 35,000 ft for 3 h while performing strenuous exercise, mild exercise, or seated rest. The subjects were monitored for venous gas emboli (VGE) with an echo-imaging system and observed for signs and symptoms of DCS.

RESULTS

Exposures involving strenuous and mild exercise resulted in higher incidence (p < 0.05) and earlier onset of symptoms (p < 0.05) of DCS than exposure at rest. Mild and strenuous exercise during exposure did not differ in incidence or rate of onset. Incidence at 30 min of exposure was 8% at rest and 23% while exercising.

CONCLUSION

The results showed that current guidelines for 35,000-ft exposures keep DCS risk below 10% at rest. Exercise, even at mild levels, greatly increases the incidence and rate of onset of DCS.

Exercise-induced altitude decompression sickness

BACKGROUND

It has been known since World War II that exercise at altitude increases incidence of decompression sickness (DCS). However, data on the effects of specific exercise types at altitude are lacking. This research focused on the relative hazards of exercise without motion (isometric, straining) vs. dynamic exercise involving motion. The study also compared arm vs. leg exercise.

METHODS

There were 32 healthy male subjects exposed, while resting, to 29,500 ft (8992 m) for 4 h or until DCS occurred, at which time they were brought to ground level. If the subject developed DCS on this exposure, he was exposed in successive months to lower altitudes, using the same procedure, until the subject was free of symptoms for the 4-h exposure. At this symptom-free altitude, as low as 20,000 ft (6096 m), the subject performed isometric arm, isometric leg, dynamic arm and dynamic leg exercises at less than 10% of maximal oxygen consumption, each during separate exposure months. Precordial venous gas emboli (VGE) were monitored every 20 min during each exposure with a Hewlett-Packard SONOS 1000 Echo Imaging System.

RESULTS

Dynamic arm, dynamic leg, isometric arm, and isometric leg exercise induced DCS in 50%, 38%, 41% and 31% of the subjects, respectively. VGE incidence varied from 47-66%. No significant differences in DCS or VGE were found.

CONCLUSIONS

Under our test conditions, there was no difference between dynamic and isometric exercise in eliciting DCS. Exercise during exposure to the symptom-free altitude for 4 h produced a 40% incidence DCS.

Male/female SACM endurance comparison: support for the Armstrong Laboratory modifications to the CSU-13B/P anti-G suit

BACKGROUND

The standard anti-G suit (CSU-13B/P) was designed based on male body structure. Females differ from males with respect to body proportionality. In Armstrong Laboratory (AL) studies, females have terminated centrifuge simulated air combat maneuvers (SACM) because of anti-G suit (CSU-13B/P modified according to original T.O. 14P3-6-121)(OTO) discomfort. AL modifications to the suit have since been adopted in the OTO in an attempt to provide females a best-fit suit (AL Mod). The study examined male/female SACM endurance with females wearing both the OTO and the AL Mod suits.

METHODS

There were 6 females and 8 males who performed a +5.0 to +9.0 Gz SACM to fatigue using the anti-G straining maneuver with anti-G suit inflation. The females performed in both the OTO and AL Mod suits while the males performed in the OTO suit only (OTO was their best-fit suit).

RESULTS

Wearing the OTO, males performed the SACM significantly longer than the females, three of whom reported severe suit discomfort. However, when the females wore the AL Mod suit, their SACM endurance almost doubled over their OTO performance and none reported suit discomfort. When wearing their best-fit suits, there was no significant gender difference in SACM endurance.

CONCLUSIONS

These data support the efficacy of the AL modifications to the CSU-13B/P anti-G suit through greatly improved performance during the +5.0 to +9.0 SACM in females. These data also suggest that, in the small sample examined, when fitted with a best-fit anti-G suit, females can endure the +5.0 to +9.0 SACM to the same degree as males.

Female acceleration tolerance: effects of menstrual state and physical condition

INTRODUCTION

The literature contains a paucity of information on female tolerance to high sustained acceleration. With women now flying high-performance aircraft, gender-specific factors that may affect female acceleration tolerance have become increasingly important. The purpose of this investigation was to determine how menstrual state and physical condition affect acceleration tolerance. We hypothesized the menstrual cycle would have no effect on acceleration tolerance and that a positive correlation would exist between physical fitness level and tolerance to high sustained acceleration.

METHODS

Centrifuge exposures on 8 female subjects consisted of a relaxed gradual-onset run (0.1 G.s-1) to the visual endpoint, a rapid-onset run (6 G.s-1) to +5 GZ for 15 s, and a +4.5 to +7 GZ simulated aerial combat maneuver (SACM) to physical exhaustion. Acceleration tolerance data were collected at onset of menstruation and 1, 2 and 3 weeks following the onset for two complete menstrual cycles. On separate days, body composition, anaerobic power output and peak oxygen uptake were determined. Retrospective data from 10 male subjects who had performed the +4.5 to +7 GZ SACM were analyzed and compared to these data.

RESULTS

Analysis of variance revealed no significant difference in relaxed tolerance or SACM duration between the four selected menstrual cycle time points. Time-to-fatigue on the +4.5 to +7 GZ SACM was positively (p < or = 0.05) correlated with absolute fat-free mass (r = 0.87) and anaerobic power production (r = 0.76) in female subjects. However, when these variables were adjusted for total body mass, the significant correlations no longer existed. No correlation was found between SACM duration and absolute (L min-1) nor relative (ml.kg-1.min-1) aerobic fitness. Time-to-fatigue during the SACM was not significantly different between male and female subjects (250 +/- 97 and 246 +/- 149 s, respectively).

Treatment of unstable distal radius fractures: methods and comparison of external distraction and ORIF versus external distraction-ORIF neutralization

Twenty-six closed unstable distal radius fractures were treated using a combination of internal fixation, external distraction (intraoperative), and, in some cases, up to 4 weeks of postoperative external fixation (neutralization). Intraoperative stability check determined the need for external neutralization. This combined technique allowed a comprehensive approach to even the most unstable fracture by merging the advantages of internal and external fixation. Up to 4 weeks of external fixation (neutralization) was not associated with the complications of external fixation usually reported.

Exercise-enhanced preoxygenation increases protection from decompression sickness

INTRODUCTION

Prevention of decompression sickness (DCS) during exposure to altitude equivalents of 30,000 ft (9144 m) requires extensive denitrogenation. In preparation for extravehicular activity (EVA), present NASA policy is to denitrogenate using a 10.2 psia staged decompression of the entire shuttle for at least 12 h, including 100 min of preoxygenation (breathing 100% oxygen at 14.7 psia prior to decompression), before decompression to the 4.3 psia (30,000 ft; 9144 m) suit pressure. This staged decompression provides the same or better protection from DCS as a 3.5- or 4-h preoxygenation used on earlier Shuttle EVA's. For high altitude reconnaissance flights at similar cockpit altitudes, a 1-h preoxygenation is currently required.

METHODS

We have investigated the use of a 1-h and a 15-min preoxygenation period, each beginning with 10 min of dual-cycle ergometry performed at 75% of each subject's peak oxygen consumption (VO2peak) to enhance preoxygenation efficiency by increasing perfusion and ventilation. Male subjects accomplished a 1-h preoxygenation with exercise, a 15-min preoxygenation with exercise, or a 1-h resting preoxygenation before exposure to 4.3 psia for 4 h while performing light to moderate exercise.

RESULTS

Incidence of DCS following the 1-h preoxygenation with exercise (42%; n = 26) was significantly less than that following the 1-h resting preoxygenation (77%; n = 26). Incidence and onset of DCS following the 15-min preoxygenation with exercise (64%; n = 22) was not significantly different from the incidence following the 1-h resting control.

CONCLUSION

Preoxygenation with exercise has been shown to provide significantly improved DCS protection when compared with resting preoxygenation.

Physeal and periphyseal injuries of the hand. Patterns of injury and results of treatment

To the authors' knowledge, this is the largest study assembled of finger fractures in children. Distribution of fractures according to location within the hand (see Fig. 1), location within the phalanges themselves, and the percent of epiphyseal fractures as well as the age distribution of the patients are all similar to what has previously been presented in smaller studies. Previously unreported synchronous and double epiphyseal injuries were identified. For the most part, thanks to the remodeling capacity and rapid healing of children's bone, treatment is short and complications are few. Nevertheless, as in other locations, there is a limited capacity to remodel angular deformity and no capacity to remodel rotational deformity. The clinical information in our study conflicts somewhat with previously described anatomic information about the insertion of ligaments with respect to the growth plate. Bogumill and Hankin and Janda have suggested that the ligaments insert primarily on the epiphysis in the proximal phalanx, and on the epiphysis and metaphysis in the middle and distal phalanges. Taken by itself, this information would suggest that a Salter-Harris III mechanism would be relatively more common at the MP joint, and the Salter-Harris II and IV mechanism (where the proximal fragment includes bone both proximal and distal to the growth plate at the point where the ligament is attached) would be relatively more common at the more distal levels. In fact, the opposite was true. The Salter-Harris II mechanism made up an overwhelming majority of the percentage of injuries of the MP joint, whereas the Salter-Harris III mechanism predominated at the PIP joint and was relatively common at the DIP joint as well. This would seem to suggest that either the contribution of ligament insertion distal to the growth plate of the PIP and DIP joints is not functionally important or that other factors are involved in the injury mechanism at both levels and play a role in producing these injuries. Further study will be required, possibly involving experimental fracture production to help elucidate this issue. Finally, it is critical to recognize and properly treat the four major categories of injury that constitute a small percentage of the total but a large percentage of the complications. The condylar and subcondylar fractures must be identified by obtaining a true lateral film by whatever means necessary. If undisplaced, they need to be adequately immobilized, possibly including the entire arm of a small child, and if displaced, they almost always require internal fixation.(ABSTRACT TRUNCATED AT 400 WORDS)

The timing of flap coverage, bone-grafting, and intramedullary nailing in patients who have a fracture of the tibial shaft with extensive soft-tissue injury

The cases of forty-three patients who had a Type-IIIB open fracture of the tibial shaft were reviewed to determine the effect of treatment of the soft-tissue injury on the rate of major complications. An infection developed in two of the eleven patients who had had early muscle-flap coverage compared with ten of the nineteen who had been managed by open care of the wound and nine of the thirteen who had had later flap coverage. Patients who had had bone-grafting after complete re-epithelialization of the wound, regardless of the method of closure, had a lower rate of early infection (none of sixteen compared with four of fifteen) and an earlier average time to union (fifty-four compared with sixty-three weeks) than those in whom the wound was not completely closed or was draining at the time of bone-grafting. Delayed intramedullary nailing with reaming was associated with a high rate of infection (nine of nineteen patients), regardless of the condition of the soft tissue at the time of nailing. In our opinion, adequate débridement and early assessment of the soft-tissue defect are necessary so that appropriate soft-tissue coverage can be provided within the first one to two weeks. When the soft-tissue portion of the injury is addressed promptly and definitively and then allowed to heal completely, secondary osseous reconstruction may proceed with fewer complications.

Recurrent pulmonary emboli and Buerger's disease

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Adrenocorticotropin-cortisol axis abnormalities in hemodialysis patients

The ACTH-cortisol axis was studied in 15 hemodialysis patients. Basal plasma cortisol concentrations were found to be elevated and ACTH to be in the high normal range. Cortisol responded normally to exogenous ACTH, but neither cortisol nor ACTH were suppressed in response to oral dexamethasone. 11-Deoxycortisol and ACTH concentrations did not rise normally in response to either oral or iv metyrapone. We conclude that standard testing of the ACTH-cortisol axis in dialysis patients yields results suggesting Cushing's syndrome.