Preparation of polyethylene glycol-tissue plasminogen activator adducts that retain functional activity: characteristics and behavior in three animal species

Conditions were defined for the derivatization of recombinant tissue plasminogen activator (rt-PA) with polyethylene glycol (PEG) so as to retain functional activity as a possible means of producing a t-PA species with a prolonged circulating lifetime. Derivatives with a wide range of retention of activities were prepared by varying the concentration and species of activated PEG. The specific activities of the PEG-rt-PA derivatives were dependent on the method of assay. Assays using preformed fibrin gave higher estimates of retention of activity than assays using soluble components. Plasma elimination studies in mice and rats indicated prolonged circulating lifetimes for the radiolabeled PEG-rt-PA derivatives after a rapid clearance and distribution phase; however, the disappearance of functional activity was much more rapid than the disappearance of radiolabeled material. The PEG-rt-PA derivatives appeared to accumulate in tissues above their interstitial fluid concentrations and were rapidly inactivated, apparently by reaction with the plasma protease inhibitors. These results were consistent with the inactivation of the PEG-rt-PA derivatives in rat plasma in vitro. A somewhat longer half-life (t1/2) of the one derivative studied was observed in dogs (t1/2, 16 minutes) as compared with the rat (t1/2, five minutes). This was sufficient to confer thrombolytic activity upon the derivative (administered by bolus injection) in contrast to native rt-PA. The potential of PEG-modified rt-PA as a long-lived thrombolytic agent in humans will depend, however, on whether there will be a further extension of the t1/2 because of a reduction in clearance and/or a reduction in the rate of inactivation.     

The role of endothelium in factor Xa regulation: the effect of plasma proteinase inhibitors and hirudin

The role of endothelium in the inhibition of human factor Xa was studied in a plasma environment. Human factor Xa can bind to and function on bovine aortic endothelium in a manner similar to that of bovine factor Xa. Approximately 70% of the bound factor Xa is subject to inhibition by plasma proteinase inhibitors, and the remaining 30% is irreversibly bound as part of a 125 Kd membrane-associated complex not subject to proteolytic degradation. The proportion reversibly bound and its rate of release do not alter with changes in calcium, citrate, heparin, or active proteinase inhibitor concentrations. The principal plasma proteinase inhibitor of human factor Xa was antithrombin III, which accounted for 60% to 65% of factor Xa released from endothelium, with alpha 1-proteinase inhibitor inactivating 20% to 25% and alpha 2- macroglobulin approximately 15%. All of the reversibly bound factor Xa was identified in complex with one of these three proteinase inhibitors. The thrombin active-site inhibitor hirudin was found to markedly accelerate the displacement of reversibly bound factor Xa from the endothelium and to associate specifically with factor Xa without a loss of activity toward chromogenic substrates, perhaps accounting for a novel mechanism of anticoagulation.     

Electron microscopic localization of factor-VIII-related antigen in adult human blood vessels

We have localized factor-VIII-related antigen, using immunofluorescence and electron microscopy, in adult human blood vessels. In addition to its presence in endothelial cells, the antigen was localized within subendothelium and the layers of elastic lamina closest to the lumen. Also, we provide the first morphological evidence that factor-VIII- related antigen is associated with collagen fibrils within the vessel wall. These studies suggest that this subendothelial factor-VIII- related antigen may play a role in the adhesion of platelets to subendothelial components following endothelial injury.     

Demographic and clinical predictors of depressive symptoms among incarcerated women

Background  

Imprisonment may lead to the development of mental illness, especially depression. This study examines the clinical and sociodemographic profiles of imprisoned women, identifies indicative signs of depression, and relates these indicators to other variables.     

The Introduction of H2-Receptor Antagonists to Scandinavia: Effects of Experts' Opinions

To evaluate the therapeutic potential of the newly developed proton pump inhibitor lansoprazole in patients with reflux oesophagitis, we performed a double-blind randomized clinical trial comparing 20 mg omeprazole and 30 mg lansoprazole, involving 229 patients at 9 Scandinavian hospitals. The treatment period was 4 or 8 weeks, and main efficacy variables were healing of endoscopic changes, relief of reflux symptoms, and occurrence of adverse events. No significant difference in terms of healing was found, either after 4 or after 8 weeks' treatment. Patients receiving lansoprazole experienced a greater improvement in heartburn after 4 weeks (p = 0.03), and there was a similar trend for acid regurgitation. Lansoprazole was found to be an effective and safe alternative to omeprazole in short-term treatment of moderate reflux oesophagitis.     

Pulmonary hydatid disease mimicking sequestration: Differentiation on magnetic resonance imaging

A case of hydatid disease of the lung proven by thoracotomy and histopathological evaluation is described. It was clinically and radiologically suggestive of a complicated pulmonary sequestration or non-resolving consolidation.     

Analysis of 7-methylbenz[a]anthracene-DNA adducts formed in SENCAR mouse epidermis by 32P-postlabeling

The present study has analysed the DNA adducts formed in SENCAR mouse epidermis following topical application of 7-methylbenz[a]anthracene (7- MBA). Mice were treated with 400 nmol of 7-MBA, which represents an initiating dose of this hydrocarbon for SENCAR mice. DNA adducts were analysed 24 h after topical application of the hydrocarbon by 32P- postlabeling coupled with either HPLC analysis or an improved TLC procedure giving better resolution of DNA adducts through the use of a D6 solvent [isopropanol:4N NH4OH (1:1)] following D5. Twenty-four hours after topical application of 400 nmol 7-MBA, the level of total covalent binding was 0.37 +/- 0.07 pmol/mg DNA as determined by 32P- postlabeling. This level of binding correlated well with the relative tumor initiating activity of this hydrocarbon compared to 7,12- dimethylbenz[a]anthracene (6.4 +/- 0.01 pmol/mg DNA) and dibenz[a,j]anthracene (0.03 +/- 0.01 pmol/mg DNA). Analysis of the 32P- labeled 3',5'-diphosphodeoxyribonucleosides by HPLC and TLC revealed the presence of deoxyguanosine (dGuo) and deoxyadenosine (dAdo) adducts formed from both the anti- and syn-bay-region diol-epoxides of 7-MBA (anti- and syn-7-MBADEs). The major DNA adduct derived from 7-MBA in mouse epidermis was tentatively identified as (+) anti-7-MBADE-trans-N2- dGuo. In addition, a minor dGuo adduct derived from the bay-region syn- diol-epoxide of 7-MBA was detected as well as a minor dAdo adduct from this diol-epoxide. Another minor dAdo adduct was also detectably present which arose from either the anti- or syn-diol epoxide. Furthermore, several unidentified DNA adducts were present in both HPLC and TLC chromatograms of DNA samples from 7-MBA-treated mice. These results are discussed in terms of the role of specific 7-MBA-DNA adducts in tumor initiation by this hydrocarbon.      

Giant cell tumor of bone: radiographic changes following local excision and allograft replacement

The authors retrospectively evaluated the clinical records and radiographs obtained from 41 patients who had giant cell tumor of bone and who were treated by local resection and allograft replacement. Postoperative complications developed in 41% of the patients. However, the eventual clinical outcome was considered to be satisfactory in 85% of all cases. There were no instances of tumor recurrence, and surprisingly, postoperative arthritis was not a major problem. The major complications encountered were infection and allograft fracture; bone infection accounted for most of the clinical failures. All infections were associated with the increasing soft-tissue swelling and bone resorption detected on radiographic studies. Other radiographic parameters that were associated with an increased rate of complications included osteopenia, increased periosteal reaction, and decreased bone formation at the host-donor junction site. The clinical outcome was distinctly less favorable in those cases in which the patient had had a pathologic fracture or a previous resection, or in whom the graft was implanted at the distal radius.