Single-Cell RNA-Seq Analysis of Patient Myeloid-Derived Suppressor Cells and the Response to Inhibition of Bruton's Tyrosine Kinase

Myeloid-derived suppressor cell (MDSC) levels are elevated in patients with cancer and contribute to reduced efficacy of immune checkpoint therapy. MDSC express Bruton's tyrosine kinase (BTK) and BTK inhibition with ibrutinib, an FDA-approved irreversible inhibitor of BTK, leads to reduced MDSC expansion/function in mice and significantly improves the antitumor activity of anti-PD-1 antibody treatments. Single-cell RNA sequencing (scRNA-seq) was used to characterize the effect of ibrutinib on gene expression of fluorescence-activated cell sorting-enriched MDSC from patients with different cancer types [breast, melanoma, head and neck squamous cell cancer (HNSCC)]. Melanoma patient MDSC were treated in vitro for 4 hours with 5 μmol/L ibrutinib or DMSO, processed for scRNA-seq using the Chromium 10× Genomics platform, and analyzed via the Seurat v4 standard integrative workflow. Baseline gene expression of MDSC from patients with breast, melanoma, and HNSCC cancer revealed similarities among the top expressed genes. In vitro ibrutinib treatment of MDSC from patients with melanoma resulted in significant changes in gene expression. GBP1, IL-1β, and CXCL8 were among the top downregulated genes whereas RGS2 and ABHD5 were among the top upregulated genes (P < 0.001). Double positive CD14+CD15+ MDSC and PMN-MDSC responded similarly to BTK inhibition and exhibited more pronounced gene changes compared with early MDSC and M-MDSC. Pathway analysis revealed significantly downregulated pathways including TREM1, nitric oxide signaling, and IL-6 signaling (P < 0.004).

IMPLICATIONS

scRNA-seq revealed characteristic gene expression patterns for MDSC from different patients with cancer and BTK inhibition led to the downregulation of multiple genes and pathways important to MDSC function and migration.

Microenvironmental control of hematopoietic stem cell fate via CXCL8 and protein kinase C

Altered hematopoietic stem cell (HSC) fate underlies primary blood disorders but microenvironmental factors controlling this are poorly understood. Genetically barcoded genome editing of synthetic target arrays for lineage tracing (GESTALT) zebrafish were used to screen for factors expressed by the sinusoidal vascular niche that alter the phylogenetic distribution of the HSC pool under native conditions. Dysregulated expression of protein kinase C delta (PKC-δ, encoded by prkcda) increases the number of HSC clones by up to 80% and expands polyclonal populations of immature neutrophil and erythroid precursors. PKC agonists such as cxcl8 augment HSC competition for residency within the niche and expand defined niche populations. CXCL8 induces association of PKC-δ with the focal adhesion complex, activating extracellular signal-regulated kinase (ERK) signaling and expression of niche factors in human endothelial cells. Our findings demonstrate the existence of reserve capacity within the niche that is controlled by CXCL8 and PKC and has significant impact on HSC phylogenetic and phenotypic fate.

Dysregulation of PRMT5 in chronic lymphocytic leukemia promotes progression with high risk of Richter's transformation

Richter's Transformation (RT) is a poorly understood and fatal progression of chronic lymphocytic leukemia (CLL) manifesting histologically as diffuse large B-cell lymphoma. Protein arginine methyltransferase 5 (PRMT5) is implicated in lymphomagenesis, but its role in CLL or RT progression is unknown. We demonstrate herein that tumors uniformly overexpress PRMT5 in patients with progression to RT. Furthermore, mice with B-specific overexpression of hPRMT5 develop a B-lymphoid expansion with increased risk of death, and Eµ-PRMT5/TCL1 double transgenic mice develop a highly aggressive disease with transformation that histologically resembles RT; where large-scale transcriptional profiling identifies oncogenic pathways mediating PRMT5-driven disease progression. Lastly, we report the development of a SAM-competitive PRMT5 inhibitor, PRT382, with exclusive selectivity and optimal in vitro and in vivo activity compared to available PRMT5 inhibitors. Taken together, the discovery that PRMT5 drives oncogenic pathways promoting RT provides a compelling rationale for clinical investigation of PRMT5 inhibitors such as PRT382 in aggressive CLL/RT cases.

687 MDSC gene expression analysis in patients with cancer and the response to inhibition of Bruton's tyrosine kinase

Background

Myeloid-derived suppressor cells (MDSC) are an immunosuppressive immature population of myeloid cells that are elevated in cancer patients. Increased levels of MDSC has been linked to dysregulated anti-tumor responses and reduced efficacy of immune checkpoint therapies thus making them an attractive target. MDSC express Bruton's tyrosine kinase (BTK) and can be depleted using ibrutinib, an FDA-approved irreversible inhibitor of BTK. BTK inhibition leads to reduced MDSC expansion/function in murine models and significantly improved activity of anti-PD-1 antibodies. In this study, single cell RNA-seq (scRNA-seq) was used to characterize the gene expression of MDSC from different cancer types and the effect of ibrutinib on MDSC gene expression.

Methods

Peripheral blood mononuclear cells were isolated from patients with melanoma (n=2), head & neck (n=1), and breast cancer (n=1). MDSC were isolated via fluorescence activated cell sorting. MDSC isolated from melanoma patients (n=2) were treated in vitro for 4h with 1 uM ibrutinib or DMSO and scRNA-seq was performed using the Chromium 10x Genomics platform. ScRNA-seq samples were analyzed using the standard integrative workflow of Seurat v3, which addresses the sample heterogeneity. Cell clusters were identified using Seurat and annotated using SingleRversion3.12. Identification of gene markers for each cell cluster and cell-cluster-specific differential expression analyses were conducted using Seurat.

Results

Baseline gene expression of MDSC from patients with breast and head & neck cancer revealed similarities among the top expressed genes (S100A8, VCAN, and LYZ). In vitro ibrutinib treatment of MDSC from patients with melanoma resulted in significant changes in gene expression within the MDSC cluster compared to DMSO treatment. GBP1(-1.72 log fold change), IL 1β(-1.27 log fold change), and CXCL8(-0.63 log fold change) were among the top downregulated genes (p<0.001) and RGS2 (0.68 log fold change) and ABHD5(0.52 log fold change) were among the top upregulated genes (p<0.001). MDSC subset (PMN-MDSC, M-MDSC, early-MDSC, and CD14+/CD15+ double positive) gene expression changes mirrored total MDSC gene changes. Ingenuity pathway analysis revealed significant downregulated pathways including TREM1 (p<0.001), nitric oxide signaling (p<0.003), and IL-6 signaling (p<0.004). Multiple genes associated with cellular movement (CXCL8, CXCL10) and activation of macrophages (CXCL10, CCL3) were downregulated (p<0.001). PCR analysis on isolated melanoma MDSC (n=2) treated in vitro with ibrutinib verified downregulation of CXCL8 (0.42 fold decrease, p<0.05) and CXCL10 (0.40 fold decrease, p<0.001).

Conclusions

Analysis via scRNA-seq revealed similar gene expression patterns for MDSC from different cancer patients. There was downregulation of multiple genes and pathways important to MDSC function and migration after BTK inhibition.

Ethics Approval

The study obtained ethics approval.

IRB# 1999C0348

An Optimized Zebrafish Nursery Feeding Regimen Improves Growth Rates and Labor Costs

Setting nutritional standards for larval zebrafish (Danio rerio) that maximize growth, survival, and reproductive success is challenging. We evaluated the effects of different feeding regimens on larval zebrafish by comparing Gemma Micro 75 pelleted diet and live-type L rotifers (Brachionus plicatilis) in 3 feeding regimens starting at 9 days postfertilization (dpf): bolus feeding of live diet (BL), continuous feeding of live diet (CL), and pelleted diet (PD). Animals in the PD and CL groups were longer than the BL group at 4-5 weeks postfertilization. The PD group was also greater in body depth than both live diet groups. There was no significant difference in weight between the groups. There were also no significant differences in fecundity or sex ratios indicating that all feeding methods successfully promote growth of a useful breeding stock of fish. In addition, we quantified the equipment, consumable, and labor costs associated with these methods, and found that the PD regimen was superior to both live diet regimens. These data suggest that providing a high nutrient-density pelleted diet to larval and juvenile zebrafish is an effective means to increase early growth and to decrease cost and labor associated with nursery care.

Exploring factors influencing physiotherapists' perceptions of measuring reactive balance following a theory-based multi-component intervention: a qualitative descriptive study

Purpose: Reactive balance is a critical consideration for mobility and fall avoidance, but is under-assessed among physiotherapists. The objective of this study was to explore factors influencing physiotherapist perceptions about measuring reactive balance upon completion of a 12-month theory-based, multi-component intervention to increase use of a measure of reactive balance.Methods: A qualitative descriptive approach was used. Semi-structured interviews were conducted with 28 physiotherapists treating adults with balance impairment in three urban Canadian rehabilitation hospitals that participated in the intervention. Interviews explored perceptions of reactive balance measurement and perceived changes in clinical behavior. Thematic analysis involved multiple rounds of coding, review and discussion, theme generation, and interpretation of findings through individual analysis and team meetings.Findings: Participants expressed contrasting views about integrating reactive balance measurement in their practice, despite consistent acknowledgement of the importance of reactive balance for function. Three themes were identified highlighting factors that mediated perceptions about measuring reactive balance: patient characteristics; trust between physiotherapist and patient; and the role of physiotherapist fear.Conclusions: The findings highlight that decision making for measuring reactive balance in rehabilitation settings is complex. There is a need for additional work to facilitate long-term implementation of clinical reactive balance measurement, such as refining patient criteria for administration, ensuring sufficient time to establish a trusting relationship, and developing and testing strategies to address physiotherapist fear.IMPLICATIONS FOR REHABILITATIONReactive balance is important for falls prevention and mobility, but is under-assessed among physiotherapists.This study identified three factors that influenced uptake of reactive balance measurement among physiotherapists in rehabilitation settings: patient characteristics; trust between physiotherapist and patient; and the role of physiotherapist fear.Knowledge of the identified factors may assist with design and use of reactive and other balance measurements.Strategies aimed at developing trusting relationships between physiotherapist and patient along with addressing physiotherapist fear could facilitate the uptake of clinical reactive balance measurement.

Dental Caries Severity and Nutritional Status of Nigerian Preschool Children

INTRODUCTION

Malnutrition in children is one of the most prevalent global health challenges, and malnourished children have a higher risk of death from childhood diseases. Early childhood caries (ECC) is the most common chronic disease of childhood. Complications from ECC such as pain, loss of tooth/teeth, and infection can undermine a child's nutrition and growth.

AIM

This study aims to evaluate the severity of decay, missing, and filled tooth (dmft) by nutritional status using the z scores of the anthropometric measurements: height for age (HFA), weight for age (WFA), weight for height (WFH), and body mass index for age (BMIA) among children with ECC in Nigeria.

STUDY DESIGN

This is a cross-sectional study conducted in 5 local government areas (LGAs) in Lagos State, Nigeria. A multistage sampling technique was used.

RESULTS

A total of 273 cases of ECC were included in the analyses (mean age 4.19 ± 0.96 y). Overall, the mean dmft was 3.04 ± 2.28, and most (96%) were accounted for by untreated decay. The distribution of dmft within the different z score categories of BMIA (<-3 = severely wasted, -2 to -3 = wasted, -2 to +2 = normal, +2 to +3 = overweight and >+3 = obese) showed the highest dmft scores among the combined severely wasted and wasted groups, lowest among children with normal z scores, and intermediate in the overweight and obese groups. There was a significant negative correlation between BMIA z score, WFH z score, and dmft (r = -0.181, P < 0.05 and r = -0.143, P < 0.05, respectively). However, the correlations between HFA z score, WFA z score, and dmft were positive but not significant (r = 0.048, P = 0.44 and r = 0.022, P = 0.77, respectively).

CONCLUSION

Our study showed an increased severity of dental caries among severely wasted or wasted children with ECC compared to those of normal or overweight.

KNOWLEDGE TRANSFER STATEMENT

The results from this study will raise awareness among clinicians and policy makers on the need for a primary prevention program for early childhood caries in countries with high burden of malnutrition and limited resources. Also, it will help draw the attention of clinicians to the caries status of malnourished children that can be managed to improve the nutritional outcomes.

CD200 promotes immunosuppression in the pancreatic tumor microenvironment

BACKGROUND

A significant challenge to overcome in pancreatic ductal adenocarcinoma (PDAC) is the profound systemic immunosuppression that renders this disease non-responsive to immunotherapy. Our supporting data provide evidence that CD200, a regulator of myeloid cell activity, is expressed in the PDAC microenvironment. Additionally, myeloid-derived suppressor cells (MDSC) isolated from patients with PDAC express elevated levels of the CD200 receptor (CD200R). Thus, we hypothesize that CD200 expression in the PDAC microenvironment limits responses to immunotherapy by promoting expansion and activity of MDSC.

METHODS

Immunofluorescent staining was used to determine expression of CD200 in murine and human PDAC tissue. Flow cytometry was utilized to test for CD200R expression by immune populations in patient blood samples. In vivo antibody blocking of CD200 was conducted in subcutaneous MT-5 tumor-bearing mice and in a genetically engineered PDAC model (KPC-Brca2 mice). Peripheral blood mononuclear cells (PBMC) from patients with PDAC were analyzed by single-cell RNA sequencing. MDSC expansion assays were completed using healthy donor PBMC stimulated with IL-6/GM-CSF in the presence of recombinant CD200 protein.

RESULTS

We found expression of CD200 by human pancreatic cell lines (BxPC3, MiaPaca2, and PANC-1) as well as on primary epithelial pancreatic tumor cells and smooth muscle actin+ stromal cells. CD200R expression was found to be elevated on CD11b+CD33+HLA-DRlo/- MDSC immune populations from patients with PDAC (p=0.0106). Higher expression levels of CD200R were observed in CD15+ MDSC compared with CD14+ MDSC (p<0.001). In vivo studies demonstrated that CD200 antibody blockade limited tumor progression in MT-5 subcutaneous tumor-bearing and in KPC-Brca2 mice (p<0.05). The percentage of intratumoral MDSC was significantly reduced in anti-CD200 treated mice compared with controls. Additionally, in vivo blockade of CD200 can also significantly enhance the efficacy of PD-1 checkpoint antibodies compared with single antibody therapies (p<0.05). Single-cell RNA sequencing of PBMC from patients revealed that CD200R+ MDSC expressed genes involved in cytokine signaling and MDSC expansion. Further, in vitro cytokine-driven expansion and the suppressive activity of human MDSC was enhanced when cocultured with recombinant CD200 protein.

CONCLUSIONS

These results indicate that CD200 expression in the PDAC microenvironment may regulate MDSC expansion and that targeting CD200 may enhance activity of checkpoint immunotherapy.

Review article: the management of long-term parenteral nutrition

BACKGROUND

Home parenteral nutrition (HPN) is currently the management of choice for patients with chronic intestinal failure.

AIM

To summarise the major issues in delivering long-term parenteral nutrition (>3 months) and assess outcome as per complications, mortality and quality of life. To assess the evidence for the therapeutic use of trophic factors such as teduglutide and to review evolving therapeutic options in the treatment of chronic intestinal failure.

METHODS

A literature search using PubMed and MEDLINE databases was performed.

RESULTS

Safe delivery of HPN relies upon individualised formulations of parenteral nutrition administered via carefully maintained central venous catheters by trained patients or carers, supported by a skilled multidisciplinary team. Early diagnosis and treatment of complications including catheter-associated blood stream infection (reported incidence 0.14-0.83 episodes/patient-year on HPN) and central venous thrombosis (reported incidence 0.03 episodes/patient-year) is important to minimise mortality and morbidity. There is a significant variation in the reported incidence of both hepatobiliary complications (19-75%) and advanced liver disease (0-50%). Five-year survival rates in large centres are reported between 60% and 78% with survival primarily related to underlying diagnosis. Long-term survival remains higher on HPN than with intestinal transplantation. The role of intestinal lengthening procedures is yet to be validated in adults.

CONCLUSIONS

Home parenteral nutrition delivered by skilled nutrition teams has low incidences of catheter-related complications. Most deaths relate to the underlying disease. Therapies such as teduglutide and small bowel transplantation appear promising, but home parenteral nutrition appears likely to remain the bedrock of management in the near term.

Mechanisms of donor-specific tolerance in recipients of haploidentical combined bone marrow/kidney transplantation

We recently reported long-term organ allograft survival without ongoing immunosuppression in four of five patients receiving combined kidney and bone marrow transplantation from haploidentical donors following nonmyeloablative conditioning. In vitro assays up to 18 months revealed donor-specific unresponsiveness. We now demonstrate that T cell recovery is gradual and is characterized by memory-type cell predominance and an increased proportion of CD4⁺ CD25⁺ CD127⁻ FOXP3⁺ Treg during the lymphopenic period. Complete donor-specific unresponsiveness in proliferative and cytotoxic assays, and in limiting dilution analyses of IL-2-producing and cytotoxic cells, developed and persisted for the 3-year follow-up in all patients, and extended to donor renal tubular epithelial cells. Assays in two of four patients were consistent with a role for a suppressive tolerance mechanism at 6 months to 1 year, but later (≥ 18 months) studies on all four patients provided no evidence for a suppressive mechanism. Our studies demonstrate, for the first time, long-term, systemic donor-specific unresponsiveness in patients with HLA-mismatched allograft tolerance. While regulatory cells may play an early role, long-term tolerance appears to be maintained by a deletion or anergy mechanism.

B-cell immunity in the context of T-cell tolerance after combined kidney and bone marrow transplantation in humans

Five patients with end-stage kidney disease received combined kidney and bone marrow transplants from HLA haploidentical donors following nonmyeloablative conditioning to induce renal allograft tolerance. Immunosuppressive therapy was successfully discontinued in four patients with subsequent follow-up of 3 to more than 6 years. This allograft acceptance was accompanied by specific T-cell unresponsiveness to donor antigens. However, two of these four patients showed evidence of de novo antibodies reactive to donor antigens between 1 and 2 years posttransplant. These humoral responses were characterized by the presence of donor HLA-specific antibodies in the serum with or without the deposition of the complement molecule C4d in the graft. Immunofluorescence staining, ELISA assays and antibody profiling using protein microarrays demonstrated the co-development of auto- and alloantibodies in these two patients. These responses were preceded by elevated serum BAFF levels and coincided with B-cell reconstitution as revealed by a high frequency of transitional B cells in the periphery. To date, these B cell responses have not been associated with evidence of humoral rejection and their clinical significance is still unclear. Overall, our findings showed the development of B-cell allo- and autoimmunity in patients with T-cell tolerance to the donor graft.

New insights into the link between cardiovascular disease and depression

INTRODUCTION

Although the association between depression and cardiovascular disease (CVD) is well documented, the underlying mechanisms for this relationship remain unclear. In this paper, we present three possible models which account for the comorbidity between depression and cardiovascular disease.

MODELS

The first model outlines depression as a risk factor for CVD and the second model presents CVD as a risk factor for depression. The third model proposes a common underlying pathway related to the effects of chronic stress on the body in manifesting as depression or cardiovascular disease.

CONCLUSIONS

If the proposed model holds true, it may be possible that an intervention initiated before overt manifestations of CVD or depression become apparent, may delay or prevent the onset of these serious clinical entities.

Home parenteral nutrition--an effective and safe long-term therapy for systemic sclerosis-related intestinal failure

OBJECTIVES

To examine the outcome in patients with SSc requiring parenteral nutrition (PN), and to compare their clinical characteristics with those of other SSc patients and of patients requiring PN/home parenteral nutrition (HPN) for other conditions.

METHODS

Retrospective review of SSc and Intestinal Failure Unit databases at a tertiary referral centre for SSc/national unit for intestinal failure over a 13-yr period.

RESULTS

Eight patients with SSc requiring PN during the study period were identified (2 males, 6 females: median age at commencement of PN 51 yrs, range 42-56 yrs). All patients commencing PN had bacterial overgrowth and malabsorption not responding to antibiotic therapy. The median duration of PN therapy in the eight patients was 40 months (range 0.8-192 months). Between them the eight patients had a total of 13,851 catheter-use days and only two line infections (0.14/1000 catheter days), a lower rate of line infection than in other HPN-treated patients at Hope Hospital (0.52/1000 catheter days). Three patients died during the 13-yr period, none of causes related to their PN. Six were unable to manage their HPN regime themselves, mainly because of problems with hand function.

CONCLUSIONS

Although patient numbers were small, our findings suggest that HPN can be safely and successfully used long-term in patients with SSc and should be considered for patients unable to maintain their nutritional status because of severe gastrointestinal involvement. Impaired hand function should not preclude SSc patients from receiving HPN: family members or community nurses may be trained in the care of the HPN line.

Comparison of outcomes after transplantation of peripheral blood stem cells versus bone marrow following an identical nonmyeloablative conditioning regimen

This is the first study to examine the outcomes in 54 patients with hematologic malignancies who received an HLA-matched related donor bone marrow (BM, n = 42) or GCSF-mobilized peripheral blood stem cells (PBSC, n = 12) following identical nonmyeloablative conditioning with the intention of induction of mixed chimerism (MC) followed by prophylactic donor leukocyte infusion (pDLI) to convert MC to full donor chimerism (FDC) and capture a graft-versus-tumor effect without clinical graft-versus-host disease (GVHD). Neutrophil and platelet recovery were faster and transfusion requirement was less in PBSC recipients (P < 0.05). A total of 48% of BMT recipients achieved FDC with a median conversion time of 84 days, including 13 following pDLI. In contrast, 83% (P = 0.04) in the PBSC group had spontaneous FDC at a median of 14 days, precluding the administration of pDLI. There was no significant difference in the incidences of acute or chronic GVHD, though the rates of chronic GVHD were considerably higher in PBSC group than in the BM group (6/7, 86% vs 10/24, 42%). CD4 and CD8 T-cell recovery was faster in PBSC recipients. In PBSC recipients, a higher number of CD34+ cells was associated with increased rates of severe, grade III-IV acute GVHD.

Myeloma responses and tolerance following combined kidney and nonmyeloablative marrow transplantation: in vivo and in vitro analyses

Six patients with renal failure due to multiple myeloma (MM) received simultaneous kidney and bone marrow transplantation (BMT) from HLA-identical sibling donors following nonmyeloablative conditioning, including cyclophosphamide (CP), peritransplant antithymocyte globulin and thymic irradiation. Cyclosporine (CyA) was given for approximately 2 months posttransplant, followed by donor leukocyte infusions. All six patients accepted their kidney grafts long-term. Three patients lost detectable chimerism but accepted their kidney grafts off immunosuppression for 1.3 to >7 years. One such patient had strong antidonor cytotoxic T lymphocyte (CTL) responses in association with marrow rejection. Two patients achieved full donor chimerism, but resumed immunosuppression to treat graft-versus-host disease. Only one patient experienced rejection following CyA withdrawal. He responded to immunosuppression, which was later successfully withdrawn. The rejection episode was associated with antidonor Th reactivity. Patients showed CTL unresponsiveness to cultured donor renal tubular epithelial cells. Initially recovering T cells were memory cells and were enriched for CD4+CD25+ cells. Three patients are in sustained complete remissions of MM, despite loss of chimerism in two. Combined kidney/BMT with nonmyeloablative conditioning can achieve renal allograft tolerance and excellent myeloma responses, even in the presence of donor marrow rejection and antidonor alloresponses in vitro.

Multiple scattering and the density distribution of a Cs MOT

Multiple scattering is studied in a Cs magneto-optical trap (MOT). We use two Abel inversion algorithms to recover density distributions of the MOT from fluorescence images. Deviations of the density distribution from a Gaussian are attributed to multiple scattering.

Can we use mid upper arm anthropometry to detect malnutrition in medical inpatients? A validation study

BACKGROUND AND AIMS

Mid upper arm anthropometry (MUAA) is often used as a measure of nutritional status to detect changes in body composition. The aim of this study was to investigate the reliability and validity of MUAA including mid arm circumference (MAC) and triceps skin fold thickness (TSFT) to determine the usefulness in clinical practice.

METHOD

We measured MUAA in 158 consecutive admissions along with subjective global assessment (SGA) and body mass index (BMI). Inter- and intra-rater reliability was evaluated in an additional 50 patients.

RESULTS

The sensitivity and specificity of MUAA <5th percentile was compared with SGA and BMI. MAC and TSFT had a low sensitivity and a high specificity with low positive predictive values when compared with criterion values which were BMI </=18 and SGA-C. The intra-class correlation coefficient for inter- and intra-rater reliability for MAC were 0.98 (95% CI 0.96-0.98) and 0.99 (95% CI 0.98-0.99) respectively and for TSFT were 0.97 (95% CI 0.91-0.97) and 0.98 (95% CI 0.95-0.98) respectively.

CONCLUSION

MUAA <5th percentile had a high specificity but low sensitivity when compared with indicators of malnutrition. Although MUAA could be reliably measured, it has poor validity and is thus unlikely to be a good predictor of clinical outcome. Percentiles based on healthy populations do not generalize well to the individuals seen in clinical practice.

Adult small intestinal transplantation in England and Wales

BACKGROUND

In 1996 two transplantation centres in the UK were commissioned by the National Specialist Commissioning Advisory Group for England and Wales to assess small intestinal transplantation in adults. The joint experience of the two centres is presented.

METHODS

Patients with irreversible small intestinal failure and complications of parenteral nutrition, and those with abdominal disease requiring extensive visceral resection, were assessed as candidates and where appropriate listed for surgery.

RESULTS

Thirty-six patients were assessed for small intestinal transplantation and, of these, 14 underwent surgery. Twelve patients survived the transplantation procedure. Of these, seven patients were alive at 1 year, five at 3 years and three at 5 years. Three patients remain alive. Patient and graft survival improved with experience; the 1-year survival rate improved in the last 4 years of this experience from 43 to 57 per cent, and the 3-year survival rate from 29 to 43 per cent.

CONCLUSION

Small intestinal transplantation is associated with a high mortality rate but may benefit carefully selected patients in whom conservative management is likely to carry a greater mortality rate.

Home enteral nutrition in adults: a European multicentre survey

AIMS

This study was undertaken to report indications and practice of home enteral nutrition (HEN) in Europe.

METHODS

A questionnaire on HEN practice was sent to 23 centres from Belgium (B), Denmark (D), France (F), Germany (G), Italy (I), Poland (P), Spain (S) and the United Kingdom (UK). This involved adult patients newly registered in HEN programme from 1 January 1998 to 31 December 1998.

RESULTS

A total of 1397 patients (532 women, 865 men) were registered. The median incidence of HEN was 163 patients/million inhabitants/year (range: 62-457). Age distribution was 7.5%, 16-40 years; 37.1%, 41-65 years; 34.5%, 66-80 years and 20.9% >80 years. The chief underlying diseases were a neurological disorder (49.1%), or head and neck cancer (26.5%); the main reason for HEN was dysphagia (84.6%). A percutaneous endoscopic gastrostomy (58.2%) or a naso-gastric tube (29.3%) were used to infuse commercial standard or high energy diets (65.3%), or fibre diets (24.5%); infusion was cyclical (61.5%) or bolus (34.1%). Indications and feeds were quite similar throughout the different centres but some differences exist concerning the underlying disease. There was greater variation in the choice of tubes and mode of infusion. In F, G, I, S, and UK, costs of HEN are fully funded. In B, D, and P patients have to pay part or all of the charges.

CONCLUSIONS

In Europe, HEN was utilised mainly in dysphagic patients with neurological disorders or cancer, using a standard feed via a PEG. However, there were important differences among the countries in the underlying diseases treated, the routes used, the mode of administration and the funding.

Tolerance, mixed chimerism, and chronic transplant arteriopathy

Much evidence supports the conclusion that immunological responses to donor-specific incompatibilities are a major factor in producing "chronic" transplant rejection, including the arteriopathy (atherosclerosis) commonly present. Our experiments explored the effects of altered immunological responsiveness to these Ags on the formation of arteriopathy in transplanted mouse hearts. Specific immunological nonreactivity, or tolerance, was induced either by neonatal administration of allogeneic spleen cells (from F(1) donors between class I-mismatched donor and recipient strains), resulting in "classical" immunological tolerance, or by bone marrow infusion to suitably prepared adult recipients, either fully MHC mismatched or class I mismatched, yielding "mixed chimerism." Both approaches obviated systemic graft-versus-host effects. In both groups, donor-specific skin grafts survived perfectly and donor cell chimerism persisted. Specific Abs were undetectable in all recipients. Most transplants to either group of tolerant recipients developed striking vasculopathy in their coronary arteries (12 of 15 in neonatal tolerance and 15 of 23 in mixed chimeras). Neointimal infiltrates included CD4 and CD8 T cells and macrophages. Only 2 of 29 contemporary isotransplants showed any evidence of vasculopathy. Recipients essentially incapable of T and B cell responses (C.B-17/SCID and RAG1(-/-)) were also used. Transplants into these animals developed vasculopathy in 16 of 31 instances. Accordingly, in this setting, vasculopathy develops in the presence of H-2 gene-determined incompatibility even with minimal conventional immune reactivity. Perhaps innate responsiveness, that could include NK cell activity, can create such arteriopathic lesions. More evidence is being sought regarding this process.

Mechanisms involved in the establishment of tolerance through costimulatory blockade and BMT: lack of requirement for CD40L-mediated signaling for tolerance or deletion of donor-reactive CD4+ cells

We have previously shown that high levels of multiline-age mixed hematopoietic chimerism and systemic T-cell tolerance can be achieved in mice without myeloablation through the use of anti-CD40L and costimulatory blockade alone (plus CTLA4Ig) or with recipient CD8 depletion and allogeneic bone marrow transplantation. Chimeric mice permanently accept donor skin grafts (> 100 days), and rapidly reject third-party grafts. The mechanisms by which costimulatory blockade facilitates the engraftment of allogeneic hematopoietic cells have not been defined. To further understand the in vivo mechanisms by which the administration of anti-CD40L mAb facilitates the engraftment of donor bone marrow and rapidly tolerizes CD4+ T cells, we analyzed the establishment of chimerism and tolerance in CD40L -/- mice. We demonstrate here that anti-CD40L mAb treatment is required only to prevent CD40L/CD40 interactions, and that no signal to the T cell through CD40L is necessary for the induction of CD4+ tolerance. Peripheral deletion of donor-reactive CD4+ T cells occurs rapidly in CD40L -/- mice receiving bone marrow transplantation (BMT), indicating that this deletion in the presence of anti-CD40L is not due to targeting of activated CD4+ cells by the antibody. Complete CD4+ cell tolerance is observed by both skin graft acceptance and in vitro assays before deletion is complete, indicating that additional mechanisms play a role in inducing CD4+ T-cell tolerance as the result of BMT in the presence of CD40/CD40L blockade.

Nucleotide release and associated conformational changes regulate function in the COOH-terminal Src kinase, Csk

The COOH-terminal Src kinase (Csk) regulates a broad array of cellular processes via the specific phosphorylation and downregulation of Src family protein kinases. While Csk has been a topic for steady-state kinetic studies, the individual steps associated with substrate phosphorylation have not been investigated. To understand active-site phenomena, pre-steady-state and transient-state kinetic methods were applied to develop a catalytic pathway for substrate processing. Rapid quench flow techniques show that the phosphorylation of a substrate peptide, generated from a random library, occurs in two kinetic phases: a rapid, exponential "burst" phase followed by a slow, linear phase. The amplitude of the burst phase increases as a function of enzyme concentration, indicating that the biphasic kinetics are not the result of product inhibition. Analysis of the burst rate as a function of substrate concentration indicates that the phosphoryl transfer step is fast (k3 > or = 140 s(-1) and highly favorable (k3/k-3 > or = 6). The apparent dissociation rate constant for ADP (0.6 s(-1), measured using stopped-flow kinetic methods and a fluorescent trapping agent, mant-ATP, is close to kcat. Since the substrate dissociation constant is high, the release of phosphopeptide is not likely to limit turnover. These findings indicate that Csk rapidly delivers the gamma-phosphate of ATP to the substrate and rapidly releases the phosphoproduct. Overall rate limitation in the steady state is then attributed to the slow, net dissociation of ADP. Viscosometric studies suggest that this final event in the catalytic cycle is coupled with slow conformational changes.

Clinical, social and rehabilitation status of long-term home parenteral nutrition patients: results of a European multicentre survey

BACKGROUND

Home parenteral nutrition (HPN) is a lifesaving treatment in patients with intestinal failure. Dependency of nutritional support becomes permanent for the majority of patients who had received HPN for at least 2 years. The alternative to long term HPN in selected patients is intestinal transplantation.

AIMS

To study some of the clinical, social and rehabilitation aspects of long-term HPN treatment.

METHODS

A survey was performed in nine European HPN centres. The questionnaire covered epidemiologic data, underlying diseases, intestinal anatomy, nutritional support and status, marital status, rehospitalization rate, HPN complications, rehabilitation score, drugs use, coexistent diseases and interest in intestinal transplantation. For some items, data were collected within 12 months prior to the evaluation.

RESULTS

This survey included 228 patients with a median age of 49 years. The median duration of HPN was 7 years (range 2--24 years). Short bowel length less than 100 cm was reported in 65% of patients with a predominance of end-jejunostomy or jejuno-colonic anastomosis. Global subjective nutritional status was normal in 79% of the patients, who were supplied with a mean number of 5.6 bags of parenteral nutrition weekly. Rehospitalizations within the 12 months prior to evaluation accounted for a mean period of 23 days and were due to HPN complications in half of the cases. Catheter-related sepsis was the most frequent HPN-complication. Bone metabolism disorders, which seemed to be more common than liver diseases, were directly related to HPN duration. One-third of the HPN patients was regularly consuming analgesics or opiates. HPN impair complete rehabilitation status but may improve the status of patients who had a very low rehabilitation score before starting HPN. An interest of intestinal transplantation was noted in only 10% of medical teams and in 8% of HPN patients.

CONCLUSIONS

This study is the largest European survey on long-term HPN patients with long standing or permanent intestinal failure. Data enlighten clinical, social and rehabilitation aspects of patients who could face the option of intestinal transplantation in the future.

Structural characterization of protein kinase A as a function of nucleotide binding. Hydrogen-deuterium exchange studies using matrix-assisted laser desorption ionization-time of flight mass spectrometry detection

Transient state kinetic studies indicate that substrate phosphorylation in protein kinase A is partially rate-limited by conformational changes, some of which may be associated with nucleotide binding (Shaffer, J., and Adams, J. A. (1999) Biochemistry 38, 12072-12079). To assess whether specific structural changes are associated with the binding of nucleotides, hydrogen-deuterium exchange experiments were performed on the enzyme in the absence and presence of ADP. Four regions of the protein are protected from exchange in the presence of ADP. Two regions encompass the catalytic and glycine-rich loops and are integral parts of the active site. Conversely, protection of probes in the C terminus is consistent with nucleotide-induced domain closure. One protected probe encompasses a portion of helix C, a secondary structural element that does not make any direct contacts with the nucleotide but has been reported to undergo segmental motion upon the activation of some protein kinases. The combined data suggest that binding of the nucleotide has distal structural effects that may include stabilizing the closed state of the enzyme and altering the position of a critical helix outside the active site. The latter represents the first evidence that the nucleotide alone can induce changes in helix C in solution.

CD4 T cell-mediated alloresistance to fully MHC-mismatched allogeneic bone marrow engraftment is dependent on CD40-CD40 ligand interactions, and lasting T cell tolerance is induced by bone marrow transplantation with initial blockade of this pathway

Costimulatory blockade can be used to promote allogeneic marrow engraftment and tolerance induction, but on its own is not 100% reliable. We sought to determine whether one or the other of the CD4 or CD8 T cell subsets of the recipient was primarily responsible for resistance to allogeneic marrow engraftment in mice receiving costimulatory blockade, and to use this information to develop a more reliable, minimal conditioning regimen for induction of mixed chimerism and transplantation tolerance. We demonstrate that a single anti-CD40 ligand mAb treatment is sufficient to completely overcome CD4 cell-mediated resistance to allogeneic marrow engraftment and rapidly induce CD4 cell tolerance, but does not reliably overcome CD8 CTL-mediated alloresistance. The data suggest that costimulation, which activates alloreactive CTL, is insufficient to activate alloreactive CD4 cells when the CD40 pathway is blocked. The addition of host CD8 T cell depletion to anti-CD40 ligand treatment reliably allows the induction of mixed chimerism and donor-specific skin graft tolerance in 3 Gy-irradiated mice receiving fully MHC-mismatched bone marrow grafts. Thus, despite the existence of multiple costimulatory pathways and pathways of APC activation, our studies demonstrate an absolute dependence on CD40-mediated events for CD4 cell-mediated rejection of allogeneic marrow. Exposure to donor bone marrow allows rapid tolerization of alloreactive CD4 cells when the CD40 pathway is blocked, leading to permanent marrow engraftment and intrathymic tolerization of T cells that develop subsequently.

Peripheral deletion after bone marrow transplantation with costimulatory blockade has features of both activation-induced cell death and passive cell death

Two major pathways of death of previously activated T cells have been described: activation-induced cell death can be triggered by restimulating activated T cells with high concentrations of Ag, is Fas-dependent, is not influenced by proteins of the Bcl family, and is blocked by cyclosporin A; in contrast, passive cell death is induced by the withdrawal of growth factors and activation stimuli, is Fas-independent, and is blocked by Bcl family proteins. We examined the role of these two forms of cell death in the peripheral deletion of donor-reactive host T cells after allogeneic bone marrow transplantation and costimulatory blockade with anti-CD154 plus CTLA4Ig in two murine models. The substantial decline in donor-reactive CD4 cells seen in wild-type recipients 1 wk after bone marrow transplantation with costimulatory blockade was largely inhibited in Fas-deficient recipients and in Bcl-x(L)-transgenic recipients. We observed these effects both in a model involving low-dose total body irradiation and a conventional dose of bone marrow, and in a radiation-free regimen using high-dose bone marrow transplantation. Furthermore, cyclosporin A did not completely block the deletion of donor-reactive CD4(+) T cells in recipients of bone marrow transplantation with costimulatory blockade. Thus, the deletion of donor-reactive T cells occurring early after bone marrow transplantation with costimulatory blockade has features of both activation-induced cell death and passive cell death. Furthermore, these in vivo data demonstrate for the first time the significance of in vitro results indicating that proteins of the Bcl family can prevent Fas-mediated apoptosis under certain circumstances.

Home enteral tube feeding following cerebrovascular accident

BACKGROUND AND AIMS

In the UK, cerebrovascular accident (CVA) is the third commonest cause of death and the commonest diagnosis in patients receiving home enteral feeding (HETF). This study aimed to use data from the British Artificial Nutrition Survey (BANS) collected between 1996 and 1999 to assess the outcome of patients on HETF, including mortality, return to oral feeding, level of physical activity, and level of dependency, which has resource implications.

RESULTS

it is estimated that about 1.7% of all patients suffering a CVA in the UK between 1996 and 1999 received HETF. At one year, 29.6% died while receiving HETF and another 13% returned to oral feeding. Mortality increased with age and was twice as high in those managed in nursing homes compared to those in their own homes. The patients receiving tube feeding spent only 0.6% of their time in hospital. A total of 43.9% of patients were bed-bound at home (1.9% unconscious) and an additional 30.3% were house-bound. Only 21.2% were independent, and the majority were totally dependent on their carers. In CVA patients on HETF the level of dependency was greater than for those with all types of diagnoses (n=12,997).

CONCLUSION

This study has described the outcome of a large number of patients receiving HETF in the UK. Since patients spent less than 1% of their time in hospital, HETF relieves pressure on the expensive hospital environment, but places more demands on the carers, who have to deal with severely disabled patients. Recovery of swallowing function should be assessed intermittently to prevent unnecessary HETF.

Maturation and function of mouse T-cells with a transgenic TCR positively selected by highly disparate xenogeneic porcine MHC

Remarkably normal cellular immune function, along with specific T-cell tolerance to highly disparate xenogeneic donors, can be achieved by grafting fetal pig thymus (FP THY) tissue to T and NK cell-depleted, thymectomized (ATX) mice. Porcine MHC can mediate positive selection of mouse CD4+ T-cells with a mouse MHC-restricted TCR in FP THY-grafted, T- and NK cell-depleted, ATX TCR-transgenic "AND" mice. However, functional studies were not performed on transgenic mouse T-cells selected in a FP THY graft. We have now performed further studies to confirm the ability of porcine MHC to mediate the positive selection of mouse T-cells with a mouse MHC-restricted TCR, and to exclude the possibility that the maturation of mouse T-cells with a mouse MHC-restricted TCR in FP THY grafts in ATX "AND" mice is a special case. For this purpose, TCR-transgenic mice with an unrelated transgenic TCR ["3A9", specific for hen egg lysozyme (HEL) peptide 46-61 presented by I-Ak] were employed. Similar to FP THY-grafted ATX "AND" mice, large numbers of mouse CD4 single positive thymocytes expressing the transgenic TCR (Vbeta8.2) and expressing a mature phenotype (Qa-2high and heat stable antigen, HSAlow) were detected in FP THY grafts. Porcine thymus grafting led to a high level of peripheral repopulation with mouse naive-type (CD44low CD45RBhigh CD62Lhigh) CD4+ cells expressing the transgenic TCR in T and NK cell-depleted ATX "3A9" mice, regardless of whether the recipients had a positive selecting or a non-selecting, class II deficient MHC background. The mouse CD4+ T-cells expressing the "3A9" TCR showed efficient primary proliferative responses to the protein antigen (HEL) when it was presented by mouse class II+ antigen presenting cells (APC) in vitro. These results, collectively, support the general conclusion that discordant xenogeneic porcine MHC can mediate positive selection of mouse T-cells with mouse MHC-restricted TCR. This study has implications for the potential clinical use of xenogeneic thymus transplantation to reconstitute cellular immunity in the setting of thymic insufficiency or thymectomy, and hence for its applicability to the induction of xenograft tolerance and in the treatment of immunodeficiency diseases.

A case of a hard inguinal nodule

Dermatofibrosarcoma protuberans (DFSP) is an uncommon tumor with its onset typically in the second to fifth decades of life. It most commonly presents on the trunk, and recent cytogenetic studies suggest a neural origin. A case presentation and review of the recent literature on the diagnosis, differential diagnosis, and treatment of DFSP is presented.

Insights into nucleotide binding in protein kinase A using fluorescent adenosine derivatives

The binding of the methylanthraniloyl derivatives of ATP (mant-ATP), ADP (mant-ADP), 2'deoxyATP (mant-2'deoxyATP), and 3'deoxyATP (mant-3'deoxyATP) to the catalytic subunit of protein kinase A was studied to gain insights into the mechanism of nucleotide binding. The binding of the mant nucleotides leads to a large increase in fluorescence energy transfer at 440 nm, allowing direct measurements of nucleotide affinity. The dissociation constant of mant-ADP is identical to that for ADP, while that for mant-ATP is approximately threefold higher than that for ATP. The dissociation constant for mant-3'deoxyATP is approximately fivefold higher than that for 3'deoxyATP while derivatization of 2'deoxyATP does not affect affinity. The time-dependent binding of mant-ATP, mant-2'deoxyATP, and mant-ADP, measured using stopped-flow fluorescence spectroscopy, is best fit to three exponentials. The fast phase is ligand dependent, while the two slower phases are ligand independent. The slower phases are similar but not identical in rate, and have opposite fluorescence amplitudes. Both isomers of mant-ATP are equivalent substrates, as judged by reversed-phase chromatography, although the rate of phosphorylation is approximately 20-fold lower than the natural nucleotide. The kinetic data are consistent with a three-step binding mechanism in which initial association of the nucleotide derivatives produces a highly fluorescent complex. Either one or two conformational changes can occur after the formation of this binary species, but one of the isomerized forms must have low fluorescence compared to the initial binary complex. These data soundly attest to the structural plasticity within the kinase core that may be essential for catalysis. Overall, the mant nucleotides present a useful reporter system for gauging these conformational changes in light of the prevailing three-dimensional models for the enzyme.

Intestinal failure after surgery for complicated radiation enteritis

Between 1983 and 1997, a total of 16 patients were referred to a tertiary Intestinal Failure Unit (IFU) following surgery elsewhere for complications of radiation enteritis. Eleven were female with a mean age of 43 years (range 21-71 years) and the most common primary site of malignancy was genitourinary (n = 13). Patients had undergone an average of two laparotomies (range 1-7 laparotomies) for complications of radiation enteritis prior to transfer to the IFU. On admission, the principal problem in eight patients was persisting intestinal fistulation, four patients had continuing intestinal obstruction and four had the short bowel syndrome after extensive intestinal resection. Only one patient had evidence of residual malignancy; this patient with short bowel syndrome was allowed home without invasive therapy. Of the remaining 15 patients, 12 required an abdominal surgical procedure, while three were discharged without further surgery after training for home parenteral nutrition (HPN). Following abdominal surgery, five patients died in hospital, but the remaining seven patients went home alive--including two further patients on HPN. Overall, of the 15 patients referred with intestinal failure after surgery for complications of radiation enteritis and actively treated, one-third died in hospital and a further third required institution of HPN before being able to be discharged home.

Allogeneic bone marrow transplantation with co-stimulatory blockade induces macrochimerism and tolerance without cytoreductive host treatment

Allogeneic bone marrow transplantation (in immunocompetent adults) has always required cytoreductive treatment of recipients with irradiation or cytotoxic drugs to achieve lasting engraftment at levels detectable by non-PCR-based techniques ('macrochimerism' or 'mixed chimerism'). Only syngeneic marrow engraftment at such levels has been achieved in unconditioned hosts. This requirement for potentially toxic myelosuppressive host pre-conditioning has precluded the clinical use of allogeneic bone marrow transplantation for many indications other than malignancies, including tolerance induction. We demonstrate here that treatment of naive mice with a high dose of fully major histocompatibility complex-mismatched allogeneic bone marrow, followed by one injection each of monoclonal antibody against CD154 and cytotoxic T-lymphocyte antigen 4 immunoglobulin, resulted in multi-lineage hematopoietic macrochimerism (of about 15%) that persisted for up to 34 weeks. Long-term chimeras developed donor-specific tolerance (donor skin graft survival of more than 145 days) and demonstrated ongoing intrathymic deletion of donor-reactive T cells. A protocol of high-dose bone marrow transplantation and co-stimulatory blockade can thus achieve allogeneic bone marrow engraftment without cytoreduction or T-cell depletion of the host, and eliminates a principal barrier to the more widespread use of allogeneic bone marrow transplantation. Although efforts have been made to minimize host pre-treatment for allogeneic bone marrow transplantation for tolerance induction, so far none have succeeded in eliminating pre-treatment completely. Our demonstration that this can be achieved provides the rationale for a safe approach for inducing robust transplantation tolerance in large animals and humans.

Use of a cell-based, lawn format assay to rapidly screen a 442,368 bead-based peptide library

A cell-based, lawn format assay utilizing an in situ photocleavage method has been developed that allows the rapid examination of large bead-based compound libraries as discrete molecules. The format uses frog melanophore cells in a contiguous, adherent, confluent layer in small petri dishes covered with a 0.5-1-mm layer of agarose containing 130 micron diameter TentaGel beads at a density of 2-20 beads/mm2. Employing this technique a 9-mer, 442,368-member peptide library (designed around the 13 amino acid alpha-MSH peptide sequence) made up of 12 separate pools of 36,864 peptides/pool was assayed. Initially, a fraction (approximately 10%) of each pool was scanned (approximately 3700 beads from each pool) in 60-mm petri dishes to identify the most active pools. Upon direct photocleavage of the beads with UV light (365 nm), each petri dish was photographed over a 60-min period with a CCD camera to record changes in light intensity as an index of melanosome dispersion. Active beads were those that were surrounded by a localized decrease in light transmittance indicating melanosome dispersed cells. Upon examination with a dissecting microscope, single beads centrally located to a circular array of dispersed cells were identified and removed from the agarose and sequenced by Edman degradation to determine the peptide sequence. Re-synthesized peptides were re-examined against alpha-MSH receptor to confirm and quantify the activity. Several 9-mer peptides were identified with potencies similar to the natural 13-mer peptide. This method allows for the rapid screening of large bead-based photo-cleavable peptide libraries with the advantage that each compound is screened as a discrete molecule in a well-less format.

Detection of conformational changes along the kinetic pathway of protein kinase A using a catalytic trapping technique

The dissociation rate constants for the two products of the reaction catalyzed by protein kinase A, ADP and phosphopeptide, were measured using a catalytic trapping technique to determine the role of product release in enzyme turnover. The enzyme was preequilibrated with ADP, and the reaction was initiated with a peptide substrate, LRRASLG, and ATP in a rapid quench flow instrument. At high, free magnesium concentrations (>2 mM), the large 'burst' in phosphopeptide production disappears, and, at low concentrations of free magnesium (0.5-1 mM), the kinetic transients become sigmoidal prior to the linear turnover phase. Increasing the concentrations of ATP or ADP did not influence the shape of the kinetic transients in the first 20 ms. ADP preequilibration protects the enzyme from inhibition by the covalent inactivator p-fluorosulfonylbenzoyl 5'-adenosine at 0.5 mM free magnesium, indicating that a competent E. ADP complex forms at low metal concentrations and the sigmoidal behavior in the catalytic trapping experiment is not due to free enzyme at high ATP concentrations. Simulations of the data indicate that ADP release is rate-limiting for turnover at high magnesium concentrations, but, at lower physiological levels of 0.5 and 1 mM, the off rate of ADP is 3- and 2-fold higher than k(cat), respectively. In contrast, the initial portions of the kinetic transients at 0.5 mM free magnesium were unaffected by phosphopeptide preequilibration, indicating that the release rate of this product is significantly larger than turnover. The transient kinetic data, coupled with a previous report [Shaffer and Adams (1999) Biochemistry 38, 5572-5581], support a phosphorylation mechanism under physiological magnesium concentrations that incorporates two partially rate-determining conformational changes, one prior to and one after the phosphoryl transfer step. We propose that the initial step activates the enzyme through key positioning of one or more active-site residues and the second step relaxes this conformation, a prerequisite for a subsequent catalytic cycle.

Home parenteral nutrition in adults: a european multicentre survey in 1997. ESPEN-Home Artificial Nutrition Working Group

A retrospective survey on home parenteral nutrition (HPN) in Europe was performed from January to December 1997. Data were compared to a similar study performed in 1993. A questionnaire of HPN practice was designed by the members of the ESPEN-HAN group. This involved adult patients (older than 16 years) newly registered in an HPN program between 1 January and 31 December 1997 and included: number of patients, underlying diseases and a 6-12 month outcome. Incidence and prevalence (at 1.1.1998) of adult HPN were calculated according to the estimated total population in 1997 for the countries in which more than 80% of HPN patients were reported.A total of 494 patients were registered in 73 centres from nine countries (Belgium (B), Denmark (D), France (F), Poland (P), Spain (S), Sweden (Sw), United Kingdom (UK), The Netherlands (N) and Germany (G). The underlying diseases for HPN in 494 patients were cancer (39%), Crohn's (19%), vascular diseases (15%), radiation enteritis (7%), AIDS (2%), other diseases with intestinal failure (18%). Incidence (patients/million inhabitants/year) were in N (3), F. (2.9), D. (2.8), B. (2.6), UK (1. 2), S (0.7) and P (0.36), respectively. Prevalence were in D. (12.7). U.K. (3.7), N. (3.7), F (3.6), B (3.0), P (1.1), S (0.65). After this 6-12 months follow-up (n=284), the mortality was respectively 4% in Crohn's disease, 13% in vascular diseases, 16% in others, 21% in radiaton enteritis, 34% in AIDS, 74% in cancer. Incidences and prevalences modestly increased in these seven European countries in 1997 in comparison to 1993. The percentages of underlying diseases in these countries remained similar except for AIDS that significantly decreased (from 7% to 2%). Outcomes did not significantly differ in the 4-year period except for AIDS (34% instead of 88% mortality) and could have been related to newer, more efficacious therapy.

An ATP-linked structural change in protein kinase A precedes phosphoryl transfer under physiological magnesium concentrations

The kinetic mechanism for the catalytic subunit of protein kinase A was evaluated using physiological concentrations of free magnesium (0.5 mM) and a rapid quench flow technique. When the enzyme is pre-equilibrated with ATP, the peptide substrate, LRRASLG (Kemptide), is phosphorylated in a biphasic manner with a rapid, exponential "burst" phase (kb) followed by a slower, linear phase (kL) that corresponds to the steady-state kinetic rate. Both the amplitude and the substrate-rate dependence of the initial, burst phase indicate that the rate of phosphoryl transfer is fast (approximately 500 s-1) and does not limit turnover (45 s-1). Viscosity studies indicate that, while Kemptide is in rapid equilibrium, ATP does not exchange rapidly with the active site and kcat/KATP is limited by the rate constant for nucleotide encounter. When the pre-steady-state kinetic experiments are initiated with ATP, a lag phase is observed at low ATP concentrations consistent with rate-limiting association. At high ATP concentrations (>1 mM), a burst phase is observed but the rate and amplitude are low on the basis of the bimolecular rate constant for ATP association and the rate constant for phosphoryl transfer. The kinetic data indicate that the phosphoryl transfer step is fast at physiological magnesium concentrations, but an ATP-linked conformational change precedes this step, limiting the burst phase rate constant. Simulations of the pre-steady-state kinetic transients indicate that turnover (45 s-1) is limited both by net product release (70 s-1) and by this structural change (170 s-1). This structural change may also occur at high free magnesium concentrations, but it must be significantly faster than 170 s-1 and, consequently, not rate-limiting for turnover (kcat = 20 s-1 at 10 mM free Mg2+). We propose that this conformational event is an obligatory component of the kinetic pathway and includes a movement of the catalytic residues necessary for supporting phosphoryl group donation.

Tartrate-resistant acid phosphatase forms complexes with alpha2-macroglobulin in serum

Tartrate-resistant acid phosphatase (TRAP) is a standard histochemical marker of differentiated osteoclasts and has been proposed as a serum/plasma marker for osteoclast activity. Enzyme assays have been described that show elevated TRAP enzyme activity in the serum or plasma of patient groups known to have increased bone metabolism. However, the poor stability of the enzyme and potential contribution from nonosteoclastic sources make it problematic to measure in patient samples. Immunoassays developed to measure TRAP in serum and plasma have yielded widely varying TRAP levels in both normal and disease states. It is not clear if this variability is caused by differences in assay calibration, antibody specificity, and/or TRAP instability. In this paper, we report that purified TRAP spiked into serum forms high molecular weight complexes. Complex formation results in greatly decreased TRAP enzyme activity and immunoreactivity. The complexing protein in serum has been identified as alpha2-macroglobulin (alpha2M). Similar complexes are observed in stored patient samples. In vitro studies with purified components show that TRAP binds to alpha2M primarily through noncovalent ionic interactions. Our results demonstrate that one mechanism of TRAP instability in serum is complex formation with alpha2M and suggest further that current TRAP enzyme and immunoassays may not accurately measure the circulating level of TRAP.

Patients with stable chronic obstructive pulmonary disease can safely undergo intravenous dipyridamole thallium-201 imaging

BACKGROUND

Patients with chronic obstructive pulmonary disease are usually excluded from intravenous dipyridamole thallium-201 testing. We developed a nurse-administered protocol to screen and pretreat patients so they could be safely tested.

METHODS AND RESULTS

We prospectively screened patients referred for intravenous dipyridamole thallium testing and retrospectively reviewed a comparison group of patients who had undergone intravenous dipyridamole testing before our bronchospasm protocol. We studied 492 consecutive patients referred for intravenous dipyridamole thallium testing, separating those with complete data (n = 451) into two groups: group A (n = 72), patients assessed to be at risk for intravenous dipyridamole-induced bronchospasm who received our bronchospasm treatment protocol; and group B (n = 379), patients assessed to be free of risk, who did not receive our bronchospasm protocol. Group C (n = 89) was a retrospective comparison group of patients who had undergone intravenous dipyridamole testing before initiation of the protocol. Patients were considered at risk for an adverse event if any of the following were present: peak flow < or =400 ml at the time of the test (spirometry by nurse) that increased to >400 ml after bronchodilator treatment, wheezing audible with stethoscope, history of chronic obstructive pulmonary disease or asthma or dyspnea on exertion at less than four blocks, or resting respiratory rate >18 breaths/min. The test was considered contraindicated if resting oxygen saturation was <85%, respiratory rate < or =36 breaths/min, or peak flow measured by peak flowmeter <400 ml after bronchodilator inhalant (albuterol or metaproterenol sulfate by spacer) at a dose of up to six puffs. One minute after injections of thallium-201, patients at risk were given 50 mg aminophylline by slow intravenous injection. We looked for major and minor adverse effects and divided them into three categories: (1) minor events (transient headache, abdominal discomfort, or nausea), wheezing (audible by stethoscope but without marked respiratory distress), (2) marked events (severe bronchospasm or severe ischemia defined as wheezing audible with or without stethoscope, respiratory rate >20 breaths/min or increased by 10 from pretest evaluation, oxygen desaturation to <90%, hypoventilation [reduced respiratory rate with decreased mental status], respiratory arrest, chest pain, horizontal ST-segment depression > or =1 mm on the electrocardiogram in any lead, symptomatic hypotension), or (3) other intravenous dipyridamole-induced side effects (persistent headache, dizziness, flushing, nausea, dyspnea, and ischemic chest pain) or anginal equivalent. The protocol properly identified patients with impaired pulmonary function. There was no difference in the frequency of adverse marked events among groups A, B, or C (1 % vs 4% vs 2%, p = 0.25). Patients in group A had more minor side effects than those in group B (53% vs 35%, p = 0.004). Specifically, patients in group A were more likely to wheeze (39% vs 1 %, p = <0.001), but wheezing in group A was self-limited or responded to treatment as described in the protocol. The prevalence of positive thallium-201 scans in group A (44%) compared with group C (49%) was not different (p = 0.15).

CONCLUSIONS

A nurse-administered risk assessment and pretreatment protocol (1) properly identified patients with impaired pulmonary function, (2) permitted completion of intravenous dipyridamole testing in patients at risk for bronchospasm without an increased incidence of marked adverse events, and (3) did not appear to influence the interpretation of the thallium test.