Polyarylenealkenylenes and polyheteroarylenealkenylenes, 16. Syntheses and electrical conductivities of poly[(alkoxy-1,4-phenylene)vinylene-1,4-phenylenevinylene]s

Poly[(2-alkoxy (or 2,5-dialkoxy)-1,4-phenylenevinylene-1,4-phenylene)vinylene]s containing alkyl groups of different lengths ( 8a, b or 9a – c ), were prepared by Wittig-reaction of terephthalaldehyde with “bis(Wittig-salt)s”. To establish the structure of the polymers, alkoxy(and dialkoxy)di-α-styrylbenzenes 10a, b and 11a – c were prepared as model compounds under similar conditions. Electrical conductivities, σ_288K, of the polymers and their charge transfer (donor-acceptor) complexes with iodine were studied. The doped polymers show increased room temperature conductivities by several orders of magnitude.     

The effect of repeated administration of hexarelin, a growth hormone releasing peptide, and growth hormone releasing hormone on growth hormone responsivity

OBJECTIVE Hexarelin is a synthetic six-amino-acid compound capable of releasing GH in animals and in man. Its mechanism of action is not understood and little is known about the GH response after repeated administration. The aim of this study was to determine the GH response to the administration of two intravenous boluses of hexarelin, growth hormone releasing hormone (GHRH) or hexarelin with GHRH. DESIGN Single boluses of hexarelin (1 μg/kg), GHRH-(1–29)-NH₂ (1 μg/kg) or hexarelin with GHRH-(1–29)-NH₂ were administered intravenously. Each study was performed on two further occasions, with a second bolus being administered 60 or 120 minutes after the first. A control study was performed giving saline intravenously. Studies were performed in a random order. SUBJECTS Six healthy adult males (25.4–34.1 years) were studied. MEASUREMENTS Serum GH was measured by radioimmunoassay. GH secretion rates were derived from the measured serum GH concentrations using the technique of deconvolution analysis. RESULTS The peak GH secretion rate following the first intravenous bolus of hexarelin was greater than that following the first bolus of GHRH-(1–29)-NH₂ (P < 0.001), and was greatest following the administration of hexarelin with GHRH-(1–29)-NH₂ (P < 0.001). The coadministration of the two secretagogues resulted in peak GH secretion rates significantly greater than the arithmetic sum of those following their isolated administration (P = 0.001), demonstrating synergism. Compared to saline, the administration of a second bolus of hexarelin, GHRH-(1–29)-NH₂ or both resulted in significant further GH secretion (P = 0.02, P = 0.002, P = 0.03, respectively). The administration of a second bolus of hexarelin or hexarelin with GHRH-(1–29)-NH₂ 120 minutes after the first bolus resulted in lower peak GH secretion rates (P = 0.03). The reductions in peak GH secretion rates following the 60-minute boluses were not statistically significant. The peak GH secretion rates following the first GHRH-(1–29)-NH₂ boluses were similar to those following the 60 and 120-minute GHRH-(1–29)-NH₂ boluses (P = NS). Irrespective of the interval between the boluses of hexarelin with GHRH-(1–29)-NH₂, the peak GH secretion rates following the second boluses were not significantly different from the arithmetic sum of those following the administration of the second boluses of hexarelin or GHRH-(1–29)-NH₂, indicating loss of synergism on repeated administration. CONCLUSIONS This study shows that hexarelin is a potent GH secretagogue active after two successive doses; the magnitude of the GH response to the second dose was influenced by the dosing interval. Hexarelin and GHRH-(1–29)-NH₂ are synergistic, a property which is lost after repeated administration. These findings may help our understanding of GHRPs and may have implications for the potential use of hexarelin and other GHRPs as therapeutic agents.     

EBV strain variation: geographical distribution and relation to disease state.

The strains of Epstein-Barr virus (EBV) were characterized in epithelial and lymphoid malignancies from geographic regions with high or low incidence. The predominant strains in nasopharyngeal carcinoma (NPC) from regions with elevated incidence were EBV type 1 in southeast Asia and Mediterranean Africa. In Alaskan Eskimos, a distinct variant of EBV type 2 was found in NPC and carcinoma of the parotid gland. This strain contained polymorphisms characteristic of the Asian EBV type 1. The strains prevalent in southeast Asia and Mediterranean Africa were also found in NPC which developed in caucasian Americans. These variants were not detected in lymphomas which developed in central Africa, Mediterranean Africa, or continental United States. These results suggest that distinct EBV strains predominate in geographic areas with elevated incidence of NPC. The detection of these distinct strains in epithelial tumors from areas of low incidence may reflect an epithelial cell tropism or pathogenicity.     

Polyarylenealkenylenes and polyheteroarylenealkenylenes, 17. Syntheses of alkoxylated poly(2-nitro-1,4-phenylenevinylene-1,4-phenylenevinylene)s and poly(2,5-dimethoxy-1,4-phenylenevinylene-1,4-phenylenevinylene)s,and study of their electrical conductivity

The influence of different substituents (nitro and methoxy groups) on the physical properties — fusibility and solubility — and the electrical conductivity of alkoxylated poly(1,4-phenylenevinylene-1,4-phenylenevinylene)s ( 9, 10, 12 and 13 ) and of the corresponding model compounds ( 15, 16, 18 and 19 ), were studied. The conductivity at room temperature, σ_298K, was found to be generally increased for polymers with nitro substituents by 2–3 orders of magnitude and for dimethoxy substituted polymers up to 4 orders of magnitude, as compared with the unsubstituted polyvinylenes. Iodine doped polyvinylenes show as an average d. c. electrical conductivities 2 orders of magnitude higher than those of the original polymers.     

Endovascular treatment of arteriovenous malformations with selective intranidal occlusion by detachable platinum electrodes: technical feasibility in a swine model.

The technical feasibility of selective intranidal endovascular occlusion of experimental arteriovenous malformations with detachable superfine platinum electrodes was assessed in a swine model. The delivery and release of electrodes were performed within normal carotid retia mirabilia, the faster-flowing nidus (bilateral retia) of a carotid-jugular fistula-type model of an arteriovenous malformation, and a small-caliber H-type direct arteriovenous fistula. Controllable atraumatic placement of the electrodes was possible deep within each rete and in the middle of the fistula. The devices were soft and flexible, allowing them to conform to the tight turns and branches of rete vessels. Marked diminution of flow was achieved by release of multiple devices within each rete. Migration of the electrode occurred when detached within the larger-caliber arteriovenous fistula. The main advantages of this technique appear to be the controlled delivery and assured release of an occlusive radiopaque embolic agent within the nidus.     

Histologic evaluation of the glenohumeral joint capsule after radiofrequency capsular shrinkage for atraumatic instability

We evaluated histologically 10 biopsy specimens taken preoperatively from the anterior-inferior glenohumeral ligament from patients with atraumatic instability who had undergone radiofrequency capsular shrinkage, 10 taken immediately postoperatively, and 13 taken before revision. The synovial and subsynovial layers returned to normal histology in biopsy specimens taken from 6 months onwards. Collagen bundles in the fibrous layer continued to have a reparative histology during the period of the study (up to 37 months). The type of radiofrequency probe used (monopolar or bipolar) had no effect on the histologic healing process (P > 0.5, chi2 test). A histologic score was introduced, and this was found to have an excellent intraobserver agreement (weighted kappa, 0.840) and a moderate interobserver agreement (weighted kappa, 0.698).