Platelet-derived growth factor in vivo: levels, activity, and rate of clearance

Platelet-derived growth factor (PDGF) is a potent mitogen for many cultured connective tissue cells. It is present in concentrated form within the platelet alpha-granules and is believed to be released during platelet degranulation at sites of vascular injury. We have used a sensitive radioreceptor assay to measure PDGF levels in whole blood serum from normal humans [17.5 +/- 3.1 (SD) ng/mL] and baboons (2.7 +/- 1.2 ng/mL). PDGF was not detected in plasma from either species. In addition, plasma was found to substantially reduce the ability of added purified PDGF to bind to the cell surface PDGF receptor on cultured cells, suggesting that plasma may contain a PDGF-binding protein that would serve to inactivate PDGF released into plasma. Calculations of PDGF concentrations in serum have been corrected for the effects of the binding protein. 125I-PDGF injected intravenously into normal baboons was cleared rapidly from the plasma (t1/2 = two minutes). The rapid clearance of 125I-PDGF did not result from iodination damage, as purified unlabeled PDGF was cleared with comparable kinetics. The rapid clearance of purified and iodinated PDGF did not result from changes in PDGF structure during purification or from removal of PDGF-associated proteins during purification, as PDGF present in freeze-thaw lysates of fresh platelets was cleared equally rapidly. We conclude that release of PDGF at sites of vascular injury would greatly increase the local concentration of PDGF and that PDGF not localized to the site of injury would be rapidly cleared from the circulation.     

Transfected leukocyte integrin CD11b/CD18 (Mac-1) mediates phorbol ester-activated, homotypic cell:cell adherence in the K562 cell line

The CD11b/CD18 leukocyte integrin molecule mediates diverse neutrophil adherence-related functions, including cell:cell and cell:extracellular matrix attachments. To study the individual role of this leukocyte integrin in cell adherence in hematopoietic cells, we expressed the CD11b/CD18 complex on the surface of K562 cells, a cell line derived from an individual with chronic myelogenous leukemia in blast crisis. We used an amphotrophic retroviral vector designated LCD18SN, harboring the complete coding sequence for the CD18 subunit, to transfer the CD18 cDNA into K562 cells and select stable cell lines. The CD11b subunit in the expression plasmid pREP4 was transfected into these K562/CD18 cells by electroporation and stable cell clones were selected. These K562 cells possessed RNA and intracellular protein for each subunit, and they expressed the CD11b/CD18 heterodimer on the cell surface. When CD11b/CD18 expressing K562 cells were stimulated with phorbol myristate acetate (50 ng/mL) for 24 to 48 hours, these K562 cells formed dense cell:cell aggregates. This homotypic aggregation required both activation of the CD11b/CD18 complex and the induction of the counter- receptor for CD11b/CD18 on the conjugate cell. This cell line will (1) enable the structure-function relationships between cell activation and homotypic adherence to be assessed, (2) provide the opportunity to identify accessory molecules required for activation of the CD11b/CD18 complex, and (3) facilitate the identification of novel ligands for the CD11b/CD18 complex.     

Effect of Sham Feeding and Acute Suppression of Acid Secretion on Human Gastric Lipase Secretion

Objective : Gastric lipase and gastric acid are secreted simultaneously. The aim of this study was to investigate whether the acid interferes with the lipase secretion. The secretion of human gastric lipase was studied during blockade of gastric acid secretion and modified sham feeding to estimate the impact of these conditions on both gastric lipase enzyme activity and immunoreactivity. Methods : Eight healthy volunteers were intubated with a nasogastric tube. We examined gastric aspirates for the amount and activity of lipase secretion during basal conditions, after blockade of acid secretion with a proton pump inhibitor (omeprazole i.v. infusion), and in response to sham feeding (chewing gum) during the blockade. Results : The amount of secreted gastric lipase was unaffected by blockade of acid secretion and increased significantly after sham feeding (169.9 ± 35.7 g/15 min to 348.1 ± 79.2 g/15 min;   p < 0.01  ). Likewise, the output of enzyme activity increased after sham feeding (0.63 ± 0.09 kU/15 min to 1.52 ± 0.36 kU/15 min;   p < 0.03  ). The concentration of enzyme activity remained unchanged by blockade of acid secretion, whereas the output of enzyme activity was decreased, probably because of reduced volume secretion or denaturation and conformational changes of the enzyme. Plasma concentrations of gastrin increased in response to blockade of acid secretion (basal 9.6 ± 1.4 pmol/L to 13.3 ± 2.9 pmol/L;   p < 0.02  ). Conclusions : Gastric acid secretion is not a prerequisite for gastric lipase secretion. Lipase enzyme activity, though, is sensitive to anacidic conditions.     

Two‐year outcomes after deployment of XIENCE V everolimus‐eluting stents in patients undergoing percutaneous coronary intervention of bifurcation lesions: A report from the SPIRIT V single arm study

The aim of this analysis was to analyze outcomes of patients undergoing Xience V EES treatment of bifurcation lesions, a subset in which treatment is particularly challenging. The SPIRIT V Study provided an evaluation of the Xience V everolimus eluting stent (EES) performance in complex patient and lesion population. The SPIRIT V Single Arm Study enrolled 2700 patients with de novo coronary artery lesions suitable to be optimally treated with a maximum of four planned Xience V EES. Lesion evaluation was by visual assessment. The outcomes of the 492 patients undergoing Xience V EES stenting of ≥1 bifurcation lesion were compared to those with no bifurcation lesion treated. Compared to those without bifurcation treatment, patients with bifurcation treatment were more likely to have multi‐vessel disease (49% vs 40%), left main treatment (3.1% vs 0.9%), more lesions treated (1.5 vs 1.3), calcification (36.4% vs 27.5%), and ostial (17.1% vs 8.2%) and angulated lesions (29.3% vs 21.1%), all P < 0.001. The 30‐day composite rate of death, myocardial infarction (MI), target vessel revascularization (TVR) was 4.3% in patients with bifurcation PCI and 2.2% in those with non‐bifurcation PCI (P = 0.017). At 2 years, this composite event rate was 11.3% and 10.0% in these two groups, respectively (P = 0.403). Rates of cardiac death, MI, target lesion revascularization (TLR), TVR, and ARC defined definite or probable stent thrombosis (0.4% vs 0.9%, P = 0.402) were not significantly different between the two groups. Despite greater patient and lesion complexity, treatment of patients with bifurcation lesions using the Xience V EES in the SPIRIT V prospective Single Arm Study was safe and effective, with low overall event rates that were similar to those without bifurcation lesion treatment. © 2013 Wiley Periodicals, Inc.     

Differentiating Acute Hepatitis B from the First Episode of Symptomatic Exacerbation of Chronic Hepatitis B

In countries with intermediate or high endemicity for chronic hepatitis B virus (HBV) infection, exacerbations of chronic hepatitis B (CHB) are common. We studied the clinical, biochemical, and virologic characteristics of patients first presenting clinically with features of acute icteric hepatitis B, to identify features that might differentiate between acute viral hepatitis B (AVHB) from first episode of exacerbation of chronic hepatitis (ECHB). We retrospectively analyzed 79 patients (mean age 35.4 ± 14 years; M:F = 60:19) who first presented clinically as AVHB, within 4 weeks of onset of symptoms. Patients who on follow-up cleared HBsAg and/or did not develop any clinical, radiologic, or histologic evidence of chronic liver disease (CLD) were categorized as AVHB (group 1). Patients who had persistence of HBsAg and developed clinical, biochemical, radiologic, or histologic evidence of chronic liver disease were categorized as ECHB (group 2). Forty-nine patients were in group 1 and 30 in group 2. The 2 groups were comparable with respect to prodrome, onset of jaundice, serum bilirubin, ALT, prothrombin time prolongation, serum albumin, and A/G ratio. Among group 1 patients, 78% had IgM anti-HBc positive in titers > 1:1000; in group 2, there were negative or positive in titers < 1:1000 in 70% patients (P < .001). Forty-seven of 49 (95.9%) patients in group 1 had HBV-DNA levels < 0.5 pg/mL, whereas 26 of 30 (86.73%) patients in group 2 had levels > 0.5 pg/mL (P ≤ .001). Quantitative HBV DNA and IgM anti-HBc titers at initial presentation can differentiate patients with a true episode of acute hepatitis B from patients with first episode of symptomatic exacerbation of chronic hepatitis B. Clinical and biochemical features do not help in differentiating the two.