Further characterization of growth hormone-dependent somatomedin-binding proteins in rat serum and demonstration of somatomedin-binding proteins produced by rat liver cells in culture.

The somatomedin-like peptide multiplication-stimulating activity (MSA) binds specifically to rat serum. The pattern of MSA binding is GH dependent. Specific binding of [125I]iodo-MSA in normal rat serum is primarily in the gamma-globulin region (peak II) on Sephadex G-200, while MSA binding in hypophysectomized (hypox) rat serum is near the albumin region (peak III). This study further characterizes the peak II and peak III somatomedin-binding proteins produced by rat liver cells in culture. [125I]Iodo-MSA binding to normal rat serum is abolished by trypsin pretreatment of rat serum, suggesting that MSA binds to protein components of serum. The only detectable somatomedin activity (measured by [3H]thymidine incorporation into chick embryo fibroblast DNA) in fractions of normal rat serum chromatographed on Sephadex G-200 coincides with peak II binding of [125I]iodo-MSA. In hypox rat serum, the majority of detectable somatomedin activity is in the peak III region. There is complete displacement of the human somatomedins [125I]iodoinsulin-like growth factor I and II and [125I]iodosomatomedin A from the rat serum-binding sites by unlabeled MSA, suggesting that the human somatomedins bind to the same sites as MSA. Treatment of normal rat serum with 1 M acetic acid dissociates somatomedin activity from its binding proteins and converts somatomedin-binding proteins from peak II to peak III. Scatchard analysis of competitive binding data using [125I]iodo-MSA yields a binding affinity that is not appreciably different for either normal or hypox rat sera. The binding capacity of normal or acid-treated normal rat serum for MSA is significantly greater than that for comparably treated hypox rat sera. Although the site of synthesis of somatomedin-binding proteins in vivo is unknown, specific somatomedin-binding proteins are synthesized by two rat liver cell lines in culture. These rat liver cell somatomedin-binding proteins have the same molecular size and the same binding affinity for MSA as the peak III somatomedin-binding protein(s) in rat serum.     

Prothrombin complex concentrates: potentially thrombogenic materials and clues to the mechanism of thrombosis in vivo.

Factors affecting the coagulant activity of two different prothrombin complex concentrates have been investigated using a sensitive in vitro assay developed in this laboratory. One concentrate contained substantial amounts of potentially thrombogenic material, while the other, which was deliberately fortified with antithrombin III and heparin during production, was judged to be relatively nonthrombogenic. The coagulant activity of the thrombogenic concentrate has been partially identified and was due largely to the presence of coagulation factos IXa and Xa. Neither concentrate contained detectable thrombin. However, after incubation with calcium or various polyamines, large amounts of additional coagulant material, including thrombin, appeared. Heparin and antithrombin III not only neutralized the thrombogenic materials present in the thrombogenic concentrate, but also inhibited the de novo generation of coagulant enzymes during incubation with calcium. The implication of these studies on the preparation of prothrombin complex concentrates and on host susceptibility to thrombosis during the clinical use of these concentrates is discussed.     

Use of endoscopic ultrasound to guide combination medical and surgical therapy for patients with Crohn's perianal fistulas

BACKGROUND: This study was performed to assess if using endoscopic ultrasound (EUS) to assess and guide combination medical and surgical therapy during fistula healing will lead to a high rate of durable fistula closure and a low or absent incidence of perianal abscess formation in patients with Crohn's perianal fistulas. METHODS: This is a retrospective analysis of 21 patients who presented with a symptomatic Crohn's perianal fistula. Patients were enrolled in a clinical practice protocol of serial EUS exams. All patients underwent a baseline rectal EUS and were placed on maximal medical treatment with 6-mercaptopurine (6-MP) or azathioprine, Cipro, and infliximab (5 mg/kg at 0, 2, and 6 wk and then every 8 wk). Patients were also assessed at baseline by a colorectal surgeon who was aware of the EUS findings. Seton placement and incision and drainage were performed when appropriate. Serial EUS examinations were performed, and the findings were used to guide therapy (i.e., the presence of fistula healing on EUS was used to guide seton removal, discontinuation of infliximab, and Cipro). RESULTS: In the 21 patients enrolled, the median duration of active perianal symptoms was 9 wks (1-36). 10 patients (48%) had previous perianal surgery and 5 (24%) had received infliximab previously. The fistulas treated included 8 trans-sphincteric, 2 superficial, 3 recto-vaginal, and 7 with multiple and horseshoe fistulas. 13 patients (62%) had associated abscesses at presentation. Eighteen of 21 patients (86%) had complete cessation of drainage initially. Median time to cessation of drainage was 10.6 weeks (range, 4-32 wk). Sixteen of 21 patients (76%) maintained long-term cessation of drainage. The median length of follow-up was 68 weeks (range, 35-101 wk). No abscess developed during treatment in any patient. EUS evidence of persistent fistula activity was seen in 10 patients (48%). Of the 11 patients (52%) in whom EUS showed no persistent fistula activity, 7 (64%) have maintained fistula closure off of infliximab and Cipro. Median duration from last infliximab infusion was 47 weeks (range, 20-80 wk). The remaining 4 patients continued infliximab to maintain remission of their luminal disease. Only 1 patient with a horseshoe fistula showed complete healing on EUS. CONCLUSION: In conclusion, using EUS to guide therapy for Crohn's perianal fistulas with infliximab, an immunosuppressive, and an antibiotic is associated with a high short and long-term fistula response rate. EUS may identify a subset of patients who can discontinue infliximab without recurrence of fistula drainage.     

Structure of human steroid 21-hydroxylase genes.

We have determined the structure of cDNA and two genomic genes encoding steroid 21-hydroxylase [21-OHase; steroid 21-monooxygenase; steroid, hydrogen-donor:oxygen oxidoreductase (21-hydroxylating); EC 1.14.99.10]. If this cytochrome P-450 enzyme is defective, cortisol cannot be synthesized, resulting in congenital adrenal hyperplasia. The cDNA encoding this enzyme is 2.0 kilobases long, and the encoded protein is predicted to contain 494 amino acid residues with a molecular weight of 55,000. This enzyme is at most 28% homologous to other P-450 enzymes that have been studied. The 21-OHase genomic genes, which are located in the HLA major histocompatibility complex on chromosome 6, each contain 10 exons. This structure is distinct from other characterized P-450 genes, which contain 7 or 9 exons. Studies of individuals with homozygous deletions of the 21-OHase A or B genes suggest that only the B gene encodes an active enzyme. This is confirmed by the finding that the A gene has an 8-base deletion within codons 110-112, resulting in a frameshift that brings a stop codon into the reading frame at codon 130. A second frameshift and a nonsense mutation occur downstream. In contrast, the sequence of the exons of the B gene is identical to the cDNA sequence. The 21-OHase A gene is, therefore, a pseudogene.     

The severe combined immunodeficient-human peripheral blood stem cell (SCID-huPBSC) mouse: a xenotransplant model for huPBSC-initiated hematopoiesis

Mononuclear cells (MNCs) containing peripheral blood stem cells (PBSCs) were obtained from solid-tumor patients undergoing mobilizing chemotherapy followed by granulocyte colony-stimulating factor for PBSC transplantation-supported dose-intensified anticancer chemotherapy and were transplanted into unconditioned "nonleaky" young severe combined immunodeficient mice. Multilineage engraftment was shown by flow cytometry and immunocytochemistry using monoclonal antibodies to various human cell surface antigens as well as identification of human immunoglobulin in murine sera. Within a dose range of MNCs suitable for transplantation (10 to 36 x 10(6) cells/graft) the number of CD34+ cells injected (optimal at > 0.7 x 10(6)/graft) determined the yield of human cells produced in recipient animals. Engraftment of hu PBSC preparations resulted in prolonged generation of physiologic levels of human cytokines including interleukin-3 (IL-3), IL-6, and granulocyte- macrophage colony-stimulating factor, which were detectable in the murine blood over a period of at least 4 months. In vivo survival of immature human progenitor cells was preserved even 9 months after transplantation. Because human IL-3 is known to stimulate early hematopoiesis, a rat fibroblast cell line was stably transfected with a retroviral vector carrying the human IL-3 gene and cotransplanted subcutaneously as additional source of growth factor. Cotransplants of this cell line producing sustained in vivo levels of circulating human IL-3 for at least 12 weeks significantly accelerated the process of engraftment of huPBSC and spurred the spread of mature human cells to the murine spleen, liver, thymus, and peripheral blood. Cotransplants of allogeneic human bone marrow stromal cells derived from long-term cultures resulted in a comparable--though less prominent--support of engraftment.     

Treatment of poor risk acute leukemia with sequential high-dose ARA-C and asparaginase

Resistance of leukemia cells to cytosine arabinoside (ARA-C) may be due to any one or combination of biochemical processes, which in certain instances may be substantially reversed by an appropriate increase in ARA-C dosage. Based on these and other laboratory observations indicating pharmacologic synergy between sequential high-dose ARA-C and asparaginase (HiDAC----ASNase), a therapeutic program was developed for the treatment of patients with acute nonlymphocytic leukemia (ANLL) refractory to conventional doses of ARA-C, as well as patients with high risk ANLL and advanced acute lymphocytic leukemia (ALL). Treatment consisted of 3-hr intravenous infusions of 3 g/sq m of ARA-C given at 12-hr intervals for 4 doses, followed by 6,000 IU/sq m ASNase given i.m. at hour 42. The same schedule was repeated on day 8. In 32 induction attempts, only 4 patients proved to be truly refractory, i.e., failed to achieve substantial leukemia cell cytoreduction. Complete remissions were achieved with HiDAC---- ASNase in 9 of 13 patients with refractory ANLL, 6 of 9 patients with antecedent hematologic disorders, and 3 of 10 patients with advanced ALL. These include 9 of 14 patients who had either failed induction or who had relapsed on active ARA-C therapy and 6 of 8 patients who had had no prior exposure to ARA-C. The median duration of unmaintained remission in ANLL was 5 mo. In a patient with central nervous system (CNS) leukemia, there was clearance of cerebral spinal fluid (CSF) blasts without intrathecal therapy, suggesting a role for HiDAC in CNS prophylaxis. In general, toxicity was tolerable and reversible. These data suggest that HiDAC----ASNase is an exceptionally effective and well tolerated regimen in leukemic patients with antecedent hematologic disorders and in those refractory to conventional doses of ARA-C.     

Using a baculovirus display library to identify MHC class I mimotopes

We have developed a baculovirus-based display system for identifying antigen mimotopes for MHC class I-specific T cells. The mouse MHC class I molecule, Dd, was displayed on baculovirus-infected insect cells with a library of 9- and 10-mer peptides tethered via a flexible linker to the N terminus of beta2 microglobulin. As a test case, the library was screened by flow cytometry by using a multimeric fluorescent alphabetaTCR from a mouse T cell specific for Dd plus an unknown self peptide. A mimotope was identified that, when bound to Dd, stimulated the T cell to secret IL-2. The sequence of the mimotope was used to identify a self peptide present in a mouse protein, Spin. The Spin peptide, when complexed with Dd, also activated the T cell. This technique should be generally useful in identifying and manipulating MHC class I peptide mimotopes and epitopes.     

Spirometry and peak expiratory flow in the primary care management of COPD.

Spirometry is essential for the diagnosis of chronic obstructive pulmonary disease (COPD). In patients with COPD the decline in lung function is usually so slow that spirometry is unlikely to provide significantly new information more than every 1-2 years. However, it is useful to have an objective measure of lung function in the assessment of acute exacerbations of COPD and in the assessment of treatments. Peak expiratory flow (PEF) has been dismissed by national and international guidelines as an inappropriate test for the assessment of the impact of COPD, but with poor evidence in support of this position. This seems short-sighted since PEF is a reliable and reproducible test and could contribute to the management of COPD in the short term and in support of spirometry. As a result of infection or in response to treatment there may be changes in airway calibre in COPD which could be captured in the consultation by PEF. In a primary care setting spirometry is too time consuming and complex to be provided in the context of normal acute consulting. Furthermore there is no evidence that spirometry provides more information than PEF in the day-to-day management of a patient already diagnosed with COPD using forced expiratory volume in the first second/forced vital capacity (FEV1/FVC). Primary care teams should ensure that their patients have adequate access to high quality spirometry. This can be provided in primary care or in local centres or in hospitals depending on the interest, motivation and resources of primary care teams. In support of spirometry general practitioners (GPs) should then consider using PEF in the day-to-day management of COPD.