The Biomechanical Effects of Intramedullary Fixation to the Level of the Physeal Scar on Distal Tibia Fracture Stability

INTRODUCTION

The purpose of this study was to evaluate whether intramedullary nail contact with physeal scar improves construct mechanics when treating distal tibial shaft fractures.

METHODS

Axially unstable extra-articular distal tibia fractures were created in 30 fresh frozen cadaveric specimens (15 pairs, mean age 79 years). Specimens underwent intramedullary nailing to the level of the physeal scar locked with one or two interlocks or short of the physeal scar locked with two interlocks (reference group). Specimens were subjected to 800N of axial load for 25,000 cycles. Primary outcomes were stiffness before and after cyclic loading. Secondary outcomes were load to failure, load at 3 mm displacement, plastic deformation, and total deformation.

RESULTS

The physeal scar with one interlock cohort demonstrated 3.8% greater stiffness before cycling ( P = 0.75) and 1.7% greater stiffness after cycling ( P = 0.86) compared with the reference group. The physeal scar with two interlocks group exhibited 0.3% greater stiffness before cycling ( P = 0.98) and 8.4% greater stiffness after cycling ( P = 0.41) in relation to the reference group. No differences were identified regarding load to failure or load at 3 mm displacement. In specimens with two interlocks, those in contact with the physeal scar demonstrated significantly less plastic ( P = 0.02) and total ( P = 0.04) deformation.

CONCLUSIONS

Constructs ending at the physeal scar demonstrated stiffness and load to failure similar to those without physeal scar contact. Less plastic and total deformation was noted in two-interlock constructs with physeal scar contact, suggesting a possible protective effect provided by the physeal scar. These data argue that physeal scar contact may offer a small mechanical benefit in nailing distal tibia fractures, but clinical relevance remains unknown.

Development of a Highly Sensitive Hybrid LC/MS Assay for the Quantitative Measurement of CTLA-4 in Human T Cells

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a check point protein expressed on the surface of T cells and plays a central role in regulating the immune response. In recent years, CTLA-4 has become a popular target for cancer immunotherapy in which blocking CTLA-4 can restore T-cell function and enhance the immune response against cancer. Currently, there are many CTLA-4 inhibitors in a variety of modalities, including cell therapies, which are being developed in both preclinical and clinical stages to further harness the potential of the target for the treatment of certain types of cancer. In drug discovery research, measuring the level of CTLA-4 in T cells is important for drug discovery and development because it provides key information for quantitative assessment of the pharmacodynamics, efficacy, and safety of the CTLA-4-based therapies. However, to our best knowledge, there is still no report of a sensitive, specific, accurate, and reliable assay for CTLA-4 measurement. In this work, an LC/MS-based method was developed to measure CTLA-4 in human T cells. The assay demonstrated high specificity with an LLOQ of 5 copies of CTLA-4 per cell when using 2.5 million T cells for analysis. As shown in the work, the assay was successfully used to measure CTLA-4 levels in subtype T-cell samples from individual healthy subjects. The assay could be applied in supporting the studies of CTLA-4-based cancer therapies.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

The Operative Treatment of Scapula Fractures: An Analysis of 10,097 Patients

BACKGROUND

The indications for operative treatment of scapula fractures have been debated over the past decade. Our purpose was to determine 1) the incidence and trends in the operative treatment of scapula fractures, 2) the incidence of conversion from operative fixation to total or hemi-shoulder arthroplasty (THSA) and 3) rates of associated injuries in scapula fractures. We hypothesized that the operative treatment of scapula fractures is increasing over time and that scapula fractures treated with open reduction and internal fixation (ORIF) would have increased risk for conversion to THSA.

METHODS

The Humana Inc. administrative claims database was queried from 2008 to 2015. Patients with any scapular fracture, ORIF of scapula fracture, total or hemi-shoulder arthroplasty, and associated injuries were identified by ICD-9 and CPT codes. Analysis was performed for 1) all patients with a scapula fracture undergoing operative fixation (i.e. ORIF and THSA), 2) all scapular fractures treated with ORIF with subsequent conversion to ipsilateral THSA, and 3) all associated injuries.

RESULTS

There were 10,097 scapula fractures (28.4% glenoid, 48% female). 60% occurred in patients 65 years and older. There were 198 (1.96%) fractures (70% glenoid) treated with ORIF. There were 287 (2.84%) fractures (45% glenoid) treated with THSA (76% total shoulder). The rate of ORIF of scapular fractures did not significantly increase (RR=0.87, p=0.58). There was a significant increase in THSA as primary treatment of scapula fractures in 2015 compared to 2007 (RR=0.43, p=0.0016). Conversion from ORIF to THSA was 12.6% (25/198). Scapula fractures treated with ORIF were at significant risk for conversion to THSA (RR=4.77, p<0.0001). Associated injuries occurred in nearly 50% of scapula fractures-other fractures, lung contusion and pneumothorax/hemothorax ranking the highest, accounting for 37%, 14.5% and 8.3% of all associated injuries, respectively.

CONCLUSION

The incidence of operative treatment of scapula fractures was 1.96% and 2.84% for ORIF and THSA, respectively. Scapular fractures previously treated with ORIF were at significant risk for conversion to THSA. Although ORIF in scapular fractures did not significantly increase over time, both THSA and overall (ORIF+THSA) operative treatment of scapula fractures increased significantly. Level of Evidence: IV.

The Success and Evolution of a Urological "Boot Camp" for Newly Appointed UK Urology Registrars: Incorporating Simulation, Nontechnical Skills and Assessment

BACKGROUND

Urological training has dramatically changed in recent years. Training durations are shorter and a drive toward consultant led care has reduced trainees experience. Within the UK, approximately 50 registrars annually embark on a 5-year Urology training programme, with variable levels of basic urological experience.

OBJECTIVE

To describe a simulation programme aimed at delivering the knowledge and skills necessary to safely and effectively start working as a registrar in Urology by intensive training with a 1:1 faculty to delegate ratio.

DESIGN, SETTING, AND PARTICIPANTS

Our course content mirrors the UK training syllabus for junior Urology registrars. We delivered 8 modules over a 4-day programme with a fifth day of assessments. Delegates level of urological knowledge, operative competency and confidence pre-, immediately post-training and at 3-months postcourse were assessed. Objective delegate and faculty feedback was also collected. Technical skills modules include; inguinoscrotal surgery, ureteroscopy, transurethral resection, urodynamics, and Botox administration as well as basic reconstructive and laparoscopic operative skills. "Nontechnical" skills included simulated ward round, out-patient, and emergency scenarios.

RESULTS

Feedback from delegates and faculty members has been overwhelmingly positive. We have used this feedback to tailor the content of the course for following years. An increased knowledge level (based on mean examination scores [precourse 55.5%, postcourse 70.1%]) and operative competency was observed in all skills assessed (transurethral resection of the prostate, transurethral resection of bladder tumor, Ureteroscopy, laparoscopic skills, and instrument assembly). Operative confidence was increased immediately and at 3-months postcourse.

CONCLUSIONS

Our "boot camp" course provides a realistic introduction and foundation to begin Urological practice. Being delivered at the beginning of the training scheme, prior to intensive patient exposure, registrars are in an optimum position to develop their newly acquired knowledge and skills to enhance training and intends to improve patient safety and satisfaction.

Sarcopenia Predicts Overall Survival in Patients with Lung, Breast, Prostate, or Myeloma Spine Metastases Undergoing Stereotactic Body Radiation Therapy (SBRT), Independent of Histology

BACKGROUND

Predicting survival of patients with spinal metastases would help stratify treatments from aggressive to palliation.

OBJECTIVE

To evaluate whether sarcopenia predicts survival in patients with lung, breast, prostate, or multiple myeloma spinal metastases.

METHODS

Psoas muscle measurements in patients with spinal metastasis were taken from computed tomography scans at 2 time points: at first episode of stereotactic body radiation therapy (SBRT) and from the most recent scan available. Overall survival and hazard ratios were calculated with multivariate cox proportional hazards regression analyses.

RESULTS

In 417 patients with spinal metastases, 40% had lung cancer, 27% breast, 21% prostate, and 11% myeloma. Overall survival was not associated with age, sex, ethnicity, levels treated, or SBRT volume. Multivariate analysis showed patients in the lowest psoas tertile had shorter survival (222 d, 95% CI = 185-323 d) as compared to the largest tertile (579 d, 95% CI = 405-815 d), (HR1.54, P = .005). Median psoas size as a cutoff value was also strongly predictive for survival (HR1.48, P = .002). Survival was independent of tumor histology. The psoas/vertebral body ratio was also successful in predicting overall survival independent of tumor histology and gender (HR1.52, P &lt; .01). Kaplan–Meier survival curves visually represent survival (P = .0005).

CONCLUSION

In patients with spine metastases, psoas muscle size as a hallmark of frailty/sarcopenia is an objective, simple, and effective way to identify patients who are at risk for shorter survival, regardless of tumor histology. This information can be used to help with surgical decision making in patients with advanced cancer, as patients with small psoas sizes are at higher risk of death.

The early radiological results of the uncemented Oxford medial compartment knee replacement

We carried out a prospective investigation into the radiological outcomes of uncemented Oxford medial compartment unicondylar replacement in 220 consecutive patients (231 knees) performed in a single centre with a minimum two-year follow-up. The functional outcomes using the mean Oxford knee score and the mean high-activity arthroplasty score were significantly improved over the pre-operative scores (p < 0.001). There were 196 patients with a two-year radiological examination performed under fluoroscopic guidance, aiming to provide images acceptable for analysis of the bone–implant interface. Of the six tibial zones examined on each knee on the anteroposterior radiograph, only three had a partial radiolucent line. All were in the medial aspect of the tibial base plate (zone 1) and all measured < 1 mm. All of these patients were asymptomatic. There were no radiolucent lines seen around the femoral component or on the lateral view. There was one revision for loosening at one year due to initial inadequate seating of the tibial component. These results confirm that the early uncemented Oxford medial unicompartmental compartmental knee replacements were reliable and the incidence of radiolucent lines was significantly decreased compared with the reported results of cemented versions of this implant. These independent results confirm those of the designing centre.

Improved pain, physical functioning and health status in patients with rheumatoid arthritis treated with CP-690,550, an orally active Janus kinase (JAK) inhibitor: results from a randomised, double-blind, placebo-controlled trial

OBJECTIVES

To determine the efficacy of CP-690,550 in improving pain, function and health status in patients with moderate to severe active rheumatoid arthritis (RA) and an inadequate response to methotrexate or a tumour necrosis factor alpha inhibitor.

METHODS

Patients were randomised equally to placebo, CP-690,550 5, 15 or 30 mg twice daily for 6 weeks, with 6 weeks' follow-up. The patient's assessment of arthritis pain (pain), patient's assessment of disease activity, Health Assessment Questionnaire-Disability Index (HAQ-DI) and Short Form-36 (SF-36) were recorded.

RESULTS

At week 6, significantly more patients in the CP-690,550 5, 15 and 30 mg twice-daily groups experienced a 50% improvement in pain compared with placebo (44%, 66%, 78% and 14%, respectively), clinically meaningful reductions in HAQ-DI (> or =0.3 units) (57%, 75%, 76% and 36%, respectively) and clinically meaningful improvements in SF-36 domains and physical and mental components.

CONCLUSIONS

CP-690,550 was efficacious in improving the pain, function and health status of patients with RA, from week 1 to week 6.

Towards engineered polyketides

Rapid advances have been made over the past 10 years in the identification of the biosynthetic machinery that carries out the biosynthesis of polyketide natural products. Many such compounds are used in various therapeutic areas, including antibacterials, anticancer, antifungals and cholesterol lowering. It is now possible to alter the biosynthetic machinery to produce radically altered structural analogues that are not accessible by conventional technologies, such as total synthesis or semi synthesis. The most rapid progress has been achieved in the antibiotic field through the production of a large number of novel erythromycins.

Requirement for sustained MAPK signaling in both CD4 and CD8 lineage commitment: a threshold model

Although there is general agreement that the RAS/MAPK signaling pathway is required for positive selection of CD4 T cells in the thymus, the role of this pathway in CD8 lineage commitment remains controversial. We show here that the differentiation of isolated cultured thymocytes to the CD8 as well as CD4 T cell lineage is sensitive to MEK inhibition and that both CD4 and CD8 thymocyte differentiation requires sustained MEK signaling. However, CD4 lineage commitment is promoted by a stronger stimulus for longer duration than required for CD8 lineage commitment. Interestingly, CD4 lineage commitment is not irreversibly set even after 10 h of signaling, well past early changes in gene expression. These findings are presented in the context of a model of lineage commitment in which a default pathway of CD8 lineage commitment is altered to CD4 commitment if the thymocyte achieves a threshold level of active MAPK within a certain time frame.

Engineering a polyketide with a longer chain by insertion of an extra module into the erythromycin-producing polyketide synthase

BACKGROUND

Modular polyketide synthases catalyse the biosynthesis of medically useful natural products by stepwise chain assembly, with each module of enzyme activities catalysing a separate cycle of polyketide chain extension. Domain swapping between polyketide synthases leads to hybrid multienzymes that yield novel polyketides in a more or less predictable way. No experiments have so far been reported which attempt to enlarge a polyketide synthase by interpolating additional modules.

RESULTS

We describe here the construction of tetraketide synthases in which an entire extension module from the rapamycin-producing polyketide synthase is covalently spliced between the first two extension modules of the erythromycin-producing polyketide synthase (DEBS). The extended polyketide synthases thus formed are found to catalyse the synthesis of specific tetraketide products containing an appropriate extra ketide unit. Co-expression in Saccharopolyspora erythraea of the extended DEBS multienzyme with multienzymes DEBS 2 and DEBS 3 leads to the formation, as expected, of novel octaketide macrolactones. In each case the predicted products are accompanied by significant amounts of unextended products, corresponding to those of the unaltered DEBS PKS. We refer to this newly observed phenomenon as 'skipping'.

CONCLUSIONS

The strategy exemplified here shows far-reaching possibilities for combinatorial engineering of polyketide natural products, as well as revealing the ability of modular polyketide synthases to 'skip' extension modules. The results also provide additional insight into the three-dimensional arrangement of modules within these giant synthases.

Combinatorial biosynthesis of polyketides and nonribosomal peptides

The engineering of polyketide biosynthesis has begun to provide robust targeted libraries for screening against pharmaceutically relevant targets. New technologies that offer methodology for the rapid generation of more structurally diverse libraries have now been demonstrated.

Imiquimod 5% cream in the treatment of Bowen's disease

BACKGROUND

Large-diameter lesions of Bowen's disease at sites such as the shin may be difficult to treat surgically and may require alternate treatment modalities.

OBJECTIVE

We investigated whether imiquimod 5% cream, a topical immune response modifier that stimulates the production of interferon alfa and other cytokines, is an effective topical treatment for Bowen's disease.

METHODS

This was a phase II, open-label study in 16 patients, treating a single biopsy-proven plaque of Bowen's disease that was 1 cm or larger in diameter, with once-daily self-application of imiquimod 5% cream for 16 weeks. A biopsy was performed on the treated area 6 weeks after the end of treatment, with patient follow-up at 3 and 6 months. Lymphocyte CD4/CD8 ratios were analyzed in pretreatment and posttreatment biopsy specimens by immunophenotyping the lymphocytic infiltrate.

RESULTS

Sixteen patients with Bowen's disease lesions ranging from 1 to 5.4 cm in diameter (0.7-21.6 cm(2) in area) were treated. Fifteen of these lesions were on the legs, and one was on the shoulder. Fourteen of the 15 patients (93% per protocol analysis) had no residual tumor present in their 6-week posttreatment biopsy specimens. One patient died of unrelated intercurrent illness before a biopsy specimen could be obtained. The median CD4/CD8 lymphocyte ratio in pretreatment biopsy specimens was 2:1, and this was reversed to a median of 1:2.2 in the posttreatment specimens. Ten patients completed 16 weeks of treatment, but 6 patients ceased treatment early (between 4 and 8 weeks) because of local skin reactions.

CONCLUSION

Imiquimod 5% cream appears to be an effective treatment for Bowen's disease on the lower limbs. The 93% positive treatment response in biopsy-proven cases (excludes patient who died from an intercurrent illness who did not undergo a posttreatment biopsy) compares favorably with other current treatment modalities. The dosing schedule and length of treatment for Bowen's disease require further evaluation.

Analysis of dendritic cell populations using a revised histological staging of morphoea

BACKGROUND

Recent studies have suggested that dermal dendritic cells (DDCs) may play a part in maintaining the structure of the dermis and in dermal immune modulation. Alteration in the population of DDCs has been noted in localized and systemic scleroderma, particularly a decline in the number of CD34+ DDCs. Objectives To define the alteration of the DDC populations with respect to the histological stage of morphoea.

METHODS

We examined 33 biopsies of morphoea, categorized into four histological stages, and examined the DDC population (CD34+ DDCs and factor XIIIa+ DDCs), the lymphocytic infiltrate, and tenascin (extracellular matrix glycoprotein) and transforming growth factor (TGF)-beta1 expression in each biopsy.

RESULTS

As the dermis became less inflammatory and more sclerotic, there was a significant decline in the number of CD34+ DDCs and an increase in the number of factor XIIIa+ DDCs. The pan-T-cell infiltrate (UCHL-1/CD45RO) and tenascin deposition exhibited a similar pattern, with elevated expression in inflammatory stages and a decrease in expression as the dermis became sclerotic. TGF-beta1 was significantly elevated in three of the four histological stages of morphoea, in both the inflammatory and sclerotic stages. The proposed four-stage histological analysis of morphoea biopsies was a useful basis for studying dendritic cells and mediators in cutaneous sclerosis.

CONCLUSIONS

Our study indicates that there is a reciprocal relationship between CD34+ DDCs and factor XIIIa+ DDCs in morphoea that correlates with the relative degrees of inflammation and sclerosis.

Lipid and giant cell poor necrobiotic xanthogranuloma

An 88-year-old man over a 7-month period developed multiple yellow firm focally ulcerative papules and nodules over his face, neck and forearms. Seven skin biopsies showed a diffuse infiltrate of epithelioid histiocytes associated with areas of necrosis with neutrophilia. Two biopsies showed xanthogranulomatous foci, but cholesterol clefts, prominent giant cells or lymphoid aggregates were not evident. Necrosis with leukocytoclastic debris overshadowed the presence of hyaline necrobiosis. Ultrastructural examination and oil red-o stains on frozen sections revealed focal lipid vacuoles within histiocytes. A paraprotein was detected in the patient's serum. This presentation may represent a lipid and giant cell poor variant of necrobiotic xanthogranuloma (NXG) and may potentially lead to a delay in diagnosis.

Novel octaketide macrolides related to 6-deoxyerythronolide B provide evidence for iterative operation of the erythromycin polyketide synthase

BACKGROUND

The macrolide antibiotic erythromycin A, like other complex aliphatic polyketides, is synthesised by a bacterial modular polyketide synthase (PKS). Such PKSs, in contrast to other fatty acid and polyketide synthases which work iteratively, contain a separate set or module of enzyme activities for each successive cycle of polyketide chain extension, and the number and type of modules together determine the structure of the polyketide product. Thus, the six extension modules of the erythromycin PKS (DEBS) together catalyse the production of the specific heptaketide 6-deoxyerythronolide B.

RESULTS

A mutant strain of the erythromycin producer Saccharopolyspora erythraea, which accumulates the aglycone intermediate erythronolide B, was found unexpectedly to produce two novel octaketides, both 16-membered macrolides. These compounds were detectable in fermentation broths of wild-type S. erythraea, but not in a strain from which the DEBS genes had been specifically deleted. From their structures, both of these octaketides appear to be aberrant products of DEBS in which module 4 has 'stuttered', that is, has catalysed two successive cycles of chain extension.

CONCLUSIONS

The isolation of novel DEBS-derived octaketides provides the first evidence that an extension module in a modular PKS has the potential to catalyse iterative rounds of chain elongation like other type I FAS and PKS systems. The factors governing the extent of such 'stuttering' remain to be determined.

Knowledge-based design of bimodular and trimodular polyketide synthases based on domain and module swaps: a route to simple statin analogues

BACKGROUND

Polyketides are structurally diverse natural products that have a range of medically useful activities. Nonaromatic bacterial polyketides are synthesised on modular polyketide synthase (PKS) multienzymes, in which each cycle of chain extension requires a different 'module' of enzymatic activities. Attempts to design and construct modular PKSs that synthesise specified novel polyketides provide a particularly stringent test of our understanding of PKS structure and function.

RESULTS

We have constructed bimodular and trimodular PKSs based on DEBS1-TE, a derivative of the erythromycin PKS that contains only modules 1 and 2 and a thioesterase (TE), by substituting multiple domains with appropriate counterparts derived from the rapamycin PKS. Hybrid PKSs were obtained that synthesised the predicted target triketide lactones, which are simple analogues of cholesterol-lowering statins. In constructing intermodular fusions, whether between modules in the same or in different proteins, it was found advantageous to preserve intact the acyl carrier protein-ketosynthase (ACP-KS) didomain that spans the junction between successive modules.

CONCLUSIONS

Relatively simple considerations govern the construction of functional hybrid PKSs. Fusion sites should be chosen either in the surface-accessible linker regions between enzymatic domains, as previously revealed, or just inside the conserved margins of domains. The interaction of an ACP domain with the adjacent KS domain, whether on the same polyketide or not, is of particular importance, both through conservation of appropriate protein-protein interactions, and through optimising molecular recognition of the altered polyketide chain in the key transfer of the acyl chain from the ACP of one module to the KS of the downstream module.

Slow accumulation of active mitogen-activated protein kinase during thymocyte differentiation regulates the temporal pattern of transcription factor gene expression

Thymocyte-positive selection is believed to result from low affinity/avidity interactions of TCR and MHC proteins, but how these weak interactions translate into downstream biochemical signals and how such signals modulate gene expression is unknown. Using a culture system where isolated immature thymocytes can be induced to differentiate along the CD4 lineage pathway, we show that sustained low level mitogen-activated protein/extracellular regulated kinase activity is required for cell differentiation and survival. Furthermore, induction of mitogen-activated protein/extracellular regulated kinase activity is surprisingly slow under conditions that induce differentiation. This pattern of kinase activity not only selects which genes are expressed but also regulates the temporal pattern of expression of transcription factor genes that are induced during double-positive thymocyte differentiation.

Baculovirus-derived hemagglutinin vaccines protect against lethal influenza infections by avian H5 and H7 subtypes

Baculoviruses were engineered to express hemagglutinin (HA) genes of recent avian influenza (AI) isolates of the H5 and H7 subtypes. The proteins were expressed as either intact (H7) or slightly truncated versions (H5). In both cases purified HA proteins from insect cell cultures retained hemagglutination activity and formed rosettes in solution, indicating proper folding. Although immunogenic in this form, these proteins were more effective when administered subcutaneously in a water-in-oil emulsion. One or two-day-old specific pathogen free (SPF) White Rock chickens, free of maternal AI antibodies, responded with variable serum HI titers, but in some cases the titers were comparable to those achieved using whole virus preparations. Vaccination of three-week-old chickens with 1.0 microg of protein per bird generated a more consistent serum antibody response with an average geometric mean titer (GMT) of 121 (H5) and 293 (H7) at 21 days postvaccination. When challenged with highly pathogenic strains of the corresponding AI subtypes, the vaccinated birds were completely protected against lethal infection and in some cases exhibited reduced or no cloacal shedding at 3 days postinfection. Vaccine protocols employing these recombinant HA proteins will not elicit an immune response against internal AI proteins and thus will not interfere with epidemiological surveys of natural influenza infections in the field.

Factors Regulating Stem Cell Recruitment to the Fetal Thymus

Colonization of the thymic rudiment during development is initiated before vascularization so that hemopoietic precursors must leave the pharyngeal vessels and migrate through the perithymic mesenchyme to reach the thymus, suggesting that they may be responding to a gradient of chemoattractant factors. We report that diffusible chemoattractants are produced by MHC class II+ epithelial cells of the fetal thymus, and that the response of precursors to these factors is mediated via a G protein-coupled receptor, consistent with factors being members of the chemokine family. Indeed, a number of chemokine receptors are expressed by thymic precursors, and several chemokines are also expressed by thymic epithelial cells. However, these chemokines are also expressed in a tissue that is unable to attract precursors, although the thymus expressed chemokine, TECK, is expressed at higher levels in thymic epithelial cells and we show that it has chemotactic activity for isolated thymic precursors. Neutralizing Ab to TECK, however, did not prevent thymus recolonization by T cell precursors, suggesting that other novel chemokines might be involved in this process. In addition, we provide evidence for the involvement of matrix metalloproteinases in chemoattractant-mediated T cell precursor recruitment to the thymus during embryogenesis.

Factors regulating stem cell recruitment to the fetal thymus

Colonization of the thymic rudiment during development is initiated before vascularization so that hemopoietic precursors must leave the pharyngeal vessels and migrate through the perithymic mesenchyme to reach the thymus, suggesting that they may be responding to a gradient of chemoattractant factors. We report that diffusible chemoattractants are produced by MHC class II+ epithelial cells of the fetal thymus, and that the response of precursors to these factors is mediated via a G protein-coupled receptor, consistent with factors being members of the chemokine family. Indeed, a number of chemokine receptors are expressed by thymic precursors, and several chemokines are also expressed by thymic epithelial cells. However, these chemokines are also expressed in a tissue that is unable to attract precursors, although the thymus expressed chemokine, TECK, is expressed at higher levels in thymic epithelial cells and we show that it has chemotactic activity for isolated thymic precursors. Neutralizing Ab to TECK, however, did not prevent thymus recolonization by T cell precursors, suggesting that other novel chemokines might be involved in this process. In addition, we provide evidence for the involvement of matrix metalloproteinases in chemoattractant-mediated T cell precursor recruitment to the thymus during embryogenesis.

Neural spectrum: palisaded encapsulated neuroma and verocay body poor dermal schwannoma

We examined 25 palisaded encapsulated neuromas (PEN) of the skin and used peripherin antibody as an immunohistochemical label for axons. Quantitative analysis of the axon to schwann cell nuclear ratio for each PEN was determined by examining cross-sectioned neuroid fascicles. This revealed that 120 of the 253 cross-sectioned fascicles in PEN lacked axon and only 5% of the fascicles had an axon to schwann cell nuclear ratio greater than 1:2. In contrast, all fascicles in 40 dermal nerves adjacent to PENs as well as 35 traumatic neuromas in surgical scars had an axon to schwann cell nuclear ratio of at least 1:2 and the majority a ratio of 1:1 or higher. These results suggest that there is a spectrum between PENs which are axon rich to a form of schwannoma with an identical histopathology which lacks significant axonal content and that not all PENs are true neuromas.

Letters

USE OF MEPITEL IN SKIN CRAFT DONOR SITES USE OF MEPITEL ON PUNCH CRAFT SITES EPIDERMOLYSIS BULLOSA.

Letters

COMMUNITY GUIDELINES ON PRESSURE AREA CARE NECROTISING FASCIITIS INTERNET SOURCES MEPITEL: A 'STICKY' SUBJECT.