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.     

Effect of the reperfusion after cerebral ischemia in neonatal rats using MRI monitoring

Cerebral hypoxia-ischemia is an important cause of brain injury in the newborn infant. Our purpose was to study magnetic resonance (MR) imaging changes in P7 rat brains submitted to permanent or reversible ischemia. Ischemia was induced by permanent electro-cauterization of the middle cerebral artery combined with a permanent or a transient (50 min) common carotid artery occlusion. The early events during ischemia and reperfusion were investigated by T2-weighted images (T2WI) at 1 and 3 h and by serial diffusion-weighted images (DWI) during 3 h in a 7 T magnet with a standard weighted diffusion sequence (b=1282.04 s mm(-2)) and a SEMS sequence. Within the first hour after MCA occlusion, the T2WI areas of contrast enhancement increased to a mean volume of 12.9+/-6.4%, a steady state still detected at 3 h after the ischemic onset (10.5+/-2.5%). Contrast enhancement in DWI increased as soon as 15 min of ischemia in all animals up to 50 min after CCA occlusion. In permanent ischemia, DWI abnormalities volume then increased more slowly from 50 min to 3 h after CCA occlusion (+25%, n=5). In reversible ischemia, the DWI abnormalities volume either moderately decreased and reached a plateau (-8.4%, n=4) or dramatically decreased (-53.0%, n=3). Both T2WI and DWI evidenced a "patchy" pattern of recovery as also shown on cresyl violet-stained sections. In contrast to the adult, early ischemic injury in P7 rat brains is detected as an increase in hyper-intensities both in T2WI and DWI. Our data indicate that reperfusion is able to block edema evolution after neonatal stroke and that early T2WI and more accurately DWI allow to distinguish between different patterns of injury in reversible ischemia.     

Preadolescent and adolescent endocrinology: physiology and physiopathology. II. Hormonal changes during abnormal pubertal development.

Based on the knowledge of the physiology of regulation of gonadotropins and gonadal steroids, basal levels of these hormones might be indicative of the etiologic factors of abnormal pubertal development. In addition, stimulatory tests may help in the diagnosis of such conditions. It is interesting that the pubertal maturation of the adrenal cortex is independent of the hypothalamic-pituitary-gonadal axis. The role of the adrenal cortex for the pubertal development remains questionable: adrenal androgens are low in isosexual precocious puberty, low in delayed adolescence, and normal in hyper- or hypogonadotropic hypogonadism. The importance of this role is doubled in congenital virilizing adrenal hyperplasia. When the disease is untreated, although adrenal androgens in excess advance bone age and hypothalamic maturation, girls remain prepubertal. When the therapeutic control is good, normal puberty occurs. The action of the adrenal androgens on growth and puberty remains to be determined.     

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.