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.     

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.     

Administration of pegylated recombinant human megakaryocyte growth and development factor to humans stimulates the production of functional platelets that show no evidence of in vivo activation

This report describes the effect of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) on platelet production and platelet function in humans. Subjects with advanced solid tumors received PEG-rHuMGDF daily for up to 10 days. There was no increase in circulating platelet count at doses of 0.03 or 0.1 microgram/kg/d by day 12 of study. At doses of 0.3 and 1.0 microgram/kg/d there was a threefold median increase (maximum 10-fold) in platelet count by day 16. The platelets produced in vivo in response to PEG-rHuMGDF showed unchanged aggregation and adenosine triphosphate (ATP)-release responses in in vitro assays. Tests included aggregation and release of ATP in response to adenosine diphosphate (ADP) (10, 5, 2.5, and 1.25 mumol/L), collagen (2 micrograms/mL), thrombin-receptor agonist peptide (TRAP, 10 mumol/L) and ristocetin (1.5 mg/mL). Administration of aspirin to an individual with platelet count of 1,771 x 10(3)/L resulted in the typical aspirin-induced ablation of the normal aggregation and ATP-release response to stimulation with arachidonic acid (0.5 mg/mL), collagen, and ADP (2.5 and 1.25 mumol/L). There was no change in the expression of the platelet-surface activation marker CD62P (P-selectin) nor induction of the fibrinogen binding site on glycoprotein IIb/IIIa as reported by the monoclonal antibody, D3GP3. An elevation of reticulated platelets was evident after 3 days of treatment with PEG-rHuMGDF and preceded the increase in circulating platelet count by 5 to 8 days; this reflected the production of new platelets in response to PEG-rHuMGDF. At later time points, the mean platelet volume (MPV) decreased in a manner inversely proportional to the platelet count. Levels of plasma glycocalicin, a measure of platelet turnover, rose 3 days after the initial increase in the peripheral platelet count. The level of plasma glycocalicin was proportional to the total platelet mass, suggesting that platelets generated in response to PEG-rHuMGDF were not more actively destroyed. Thus, the administration of PEG-rHuMGDF, to humans, increased the circulating platelet count and resulted in fully functional platelets, which showed no detectable increase in reactivity nor alteration in activation status.     

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.     

Effects of the selective aldosterone blocker eplerenone versus the calcium antagonist amlodipine in systolic hypertension

Eplerenone is a highly selective aldosterone blocker, which is under development for the treatment of hypertension and heart failure. To assess its usefulness in older patients with systolic hypertension and widened pulse pressure, we compared the effects of eplerenone with amlodipine, on clinic blood pressure (BP) and pulse pressure and in a subset of the patients, ambulatory BP, vascular compliance, and urinary albumin excretion. The study involved 269 patients > or =50 years of age who were randomly assigned to either eplerenone (50 to 200 mg daily) or amlodipine (2.5 to 10 mg daily) in a double-blind titration to effect design. After 24 weeks of therapy, reductions in clinic systolic BP were similar for both treatments (eplerenone, -20.5+/-1.1 mm Hg; amlodipine, -20.1+/-1.1 mm Hg). Reductions in clinic diastolic BP were modestly larger on amlodipine (-6.9+/-0.7 mm Hg) compared with eplerenone (-4.5+/-0.7 mm Hg) (P=0.014). Pulse pressure was also reduced similarly from baseline by the 2 treatment groups (eplerenone, -15.9 mm Hg versus amlodipine, -13.4 mm Hg, P=0.07). Changes from baseline in pulse wave velocity after 24 weeks of therapy were statistically similar for eplerenone and amlodipine. In patients with microalbuminuria at baseline (>30 mg albumin/g creatinine), eplerenone reduced the urinary albumin/creatinine ratio by 52% compared with a reduction of 10% by amlodipine (P=0.04). Thus, eplerenone was as effective as amlodipine in lowering systolic BP and pulse pressure as well as pulse wave velocity in older patients with widened pulse pressure hypertension. Furthermore, eplerenone reduced microalbuminuria to a greater extent than amlodipine in this older patient group.     

A comparison of the in vivo kinetics of Plasmodium falciparum ring-infected erythrocyte surface antigen-positive and -negative erythrocytes.

Ring-infected erythrocyte surface antigen (RESA)-positive, Plasmodium falciparum-negative red blood cells (RBCs) are cells from which the malaria parasite has been removed by the host without the destruction of the erythrocyte ("pitting"). The survival of RESA-RBCs in vivo was assessed in 14 severe and 6 uncomplicated falciparum malaria patients. The mean RESA-RBC life of 183 hours (95% confidence interval [CI], 136-246) was longer than the median parasite clearance time of 66 hours (range, 30-108 hours) but shorter than the mean red cell life of 1027 hours (95% CI, 840-1213) (P =.0004), with a median ratio of 0.2:1.0 (range, 0.1-0.7). The estimated median percentage of parasites pitted/body transit was 0.003% (range, 0.001%-0.05%). The rate of rise of the RESA-RBC count during the first 24 hours after antimalarial treatment was significantly faster (P =.036) and the subsequent RESA-RBC survival significantly shorter (P =.017) after treatment with an artemisinin derivative than after treatment with quinine. Parasitization of red cells leads to changes in the erythrocyte that shorten their survival even if the parasite is removed subsequently.     

Structure of canine pulmonary surfactant apoprotein: cDNA and complete amino acid sequence.

The apoproteins of pulmonary surfactant (PSAP) are thought to be critical for normal surfactant function. They bind to surfactant phospholipids and enhance their ability to form surface films in vitro. These acidic glycoproteins have monomeric molecular weights of 36,000, 32,000, and 28,000 (PSAP-36, -32, and -28). Each member of this family of proteins has a similar amino acid composition and their differences in electrophoretic mobility are due in part to glycosylation. We have derived the full amino acid sequence of PSAP-32 from the nucleotide sequence of PSAP cDNA. A cDNA library was prepared from canine lung poly(A)+ RNA and screened with oligonucleotide probes that were based on the NH2-terminal amino acids of PSAP-32 determined by Edman degradation. This protein has the striking feature of collagen-like and non-collagen-like sequences in the same polypeptide chain. There are 24 Gly-Xaa-Yaa triplets, where Yaa is often hydroxyproline. These repeats comprise one-third of PSAP near the NH2 terminus. The remaining two-thirds of PSAP is resistant to bacterial collagenase digestion and contains a possible N-glycosylation site near the carboxyl terminus. The NH2-terminal one-third of PSAP-32 probably contains the cysteine involved in interchain disulfide bonds.