Neoclerodane diterpenoids from Scutellaria caerulea.

Five new neoclerodane diterpenoids have been isolated from Scutellaria caerulea: (11S*)-6 alpha-acetoxy-7 beta,11-diisobutiryloxy-1 beta,8 beta-dihydroxy-4(18),13-neoclerodadien-15,16-olide (scuterulein A) (1); (13R*)-1 beta-6 alpha-7 beta-triacetoxy-11 beta-benzoyloxy-8 beta,13-epoxy-4(18)-neocleroden-15,16-olide (scuterulein B) (2); (11S*)-1 beta,6 alpha,11-triacetoxy-7 beta-isobutiryloxy-8 beta-hydroxy-4(18),13-neoclerodadien-15,16-olide (scuterulein C) (3); (11S*)-6 alpha,11-diacetoxy-7 beta-isobutiryloxy-1 beta,8 beta-dihydroxy-4(18),13-neoclerodadien-15,16-olide (deacetyl scuterulein C) (4), and (11E)-6 alpha-acetoxy-7 beta-isobutiryloxy-1 beta,8 beta-dihydroxy-4(18),11,13-neoclerodatrien-15,16-olide (scuterulein D) (5). Structures were established by spectroscopic and chemical methods. An X-ray analysis was carried out on scuterulein B (2).     

Why small caliber vascular grafts fail: a review of clinical and experimental experience and the significance of the interaction of blood at the interface

The results using polytetrafluoroethylene (PTFE) and tanned human umbilical cord vein (HUV) grafts are discussed. These two grafts perform well for reconstructions above the knee and the results are similar to the autogenous saphenous vein (ASV) grafts in several series; however, in more distal reconstructions the PTFE and HUV are far inferior to ASV grafts. The factors responsible for graft failure including the events which take place at the blood interface are reviewed. New material surfaces under investigation such as degradable grafts, heparin-bonded surfaces, and endothelial-seeded fabrics are also addressed.     

假细锥香茶菜新二萜成分——假细锥甲素的结构

从假细锥香茶菜(Rabdosia coetsoides C.Y.Wu)叶分离得到新二萜成分,根据紫外光谱、红外光谱、质谱、核磁共振氢谱及碳谱等分析,推定了化学结构,并经X-射线衍射确证,命名为假细锥甲素。     

Cerebral blood flow relationships associated with a difficult tone recognition task in trained normal volunteers

Tone recognition is partially subserved by neural activity in the right frontal and primary auditory cortices. First we determined the brain areas associated with tone perception and recognition. This study then examined how regional cerebral blood flow (rCBF) in these and other brain regions correlates with the behavioral characteristics of a difficult tone recognition task. rCBF changes were assessed using H2(15)O positron emission tomography. Subtraction procedures were used to localize significant change regions and correlational analyses were applied to determine how response times (RT) predicted rCBF patterns. Twelve trained normal volunteers were studied in three conditions: REST, sensory motor control (SMC) and decision (DEC). The SMC-REST contrast revealed bilateral activation of primary auditory cortices, cerebellum and bilateral inferior frontal gyri. DEC-SMC produced significant clusters in the right middle and inferior frontal gyri, insula and claustrum; the anterior cingulate gyrus and supplementary motor area; the left insula/claustrum; and the left cerebellum. Correlational analyses, RT versus rCBF from DEC scans, showed a positive correlation in right inferior and middle frontal cortex; rCBF in bilateral auditory cortices and cerebellum exhibited significant negative correlations with RT These changes suggest that neural activity in the right frontal, superior temporal and cerebellar regions shifts back and forth in magnitude depending on whether tone recognition RT is relatively fast or slow, during a difficult, accurate assessment.      

Determinants of vancomycin clearance by continuous venovenous hemofiltration and continuous venovenous hemodialysis

The clearance of vancomycin is significantly reduced in patients with acute, as well as, chronic renal failure. Although multiple-dosage regimen adjustment techniques have been proposed for these patients, there is little quantitative data to guide the individualization of vancomycin therapy in acute renal failure patients who are receiving continuous renal replacement therapy (CRRT). To determine appropriate vancomycin dosing strategies for patients receiving continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodialysis (CVVHD), we performed controlled clearance studies in five stable hemodialysis patients with three hemofilters: an acrylonitrile copolymer 0.6 m2 (AN69), polymethylmethacrylate 2.1 m2 (PMMA), and polysulfone 0.65 m2 (PS). Patients received 500 mg of vancomycin intravenously at least 12 hours before the start of the clearance study. The concentration of vancomycin in multiple plasma and dialysate/ultrafiltrate samples was determined by EMIT (Syva, Palo Alto, CA). The diffusional clearance and sieving coefficient (SC) of vancomycin were compared by a mixed-model repeated-measures analysis of variance (ANOVA) with filter and blood (Q(B)), dialysate inflow (Q(DI)), or ultrafiltration rate (Q(UF)) as the main effects and patient as a random effect. Vancomycin was moderately protein bound in these patients; free fraction ranged from 49% to 83%. The SCs of the three filters were similar and significantly correlated with the free fraction of vancomycin (P = 0.01; r2 = 0.465). Significant linear relationships were observed between the diffusional clearance of vancomycin and Q(DI) for all three filters: AN69 (slope = 0.482; r2 = 0.880); PMMA (slope = 0.853; r2 = 0.966); and PS (slope = 0.658; r2 = 0.887). The slope of this relationship for the PMMA filter was significantly greater than that of the AN69 and PS filters. The clearance of vancomycin, urea, and creatinine, however, was essentially constant at all Q(B)s for all three filters. Thus, the clearance of vancomycin was not membrane dependent during CVVH. However, during CVVHD, membrane dependence of vancomycin clearance was noted at a Q(DI) greater than 16.7 mL/min; vancomycin clearance with PMMA at a Q(DI) of 25 mL/min was 66% and 43% greater than that with the AN69 and PS filters, respectively. CVVH (62% to 262%) and CVVHD (90% to 540%) can significantly augment the clearance of vancomycin in acute renal failure patients. Dosing strategies for individualization of vancomycin therapy in patients receiving CVVH and CVVHD are proposed.     

Measurement of functioning hepatocyte mass via [99mTc]galactosyl-neoglycoalbumin

Technetium-99m-galactosyl-neoglycoalbumin (TcNGA) is a synthetic radiolabeled ligand specific for hepatic binding protein (HBP), a receptor that resides exclusively on hepatocytes.In vivo measurement of receptor concentration was obtained via kinetic analysis of liver and blood time-activity data obtained during the hepatic clearance of intravenously administered TcNGA. The purpose of this study was to assess receptor concentration as a measure of the functioning hepatocyte mass. Therefore, TcNGA and dualinjection indocyanine green maximal removal rate (ICG R_max) studies were performed on nine patients with hepatic cirrhosis associated or not with hepatocellular carcinoma. Receptor concentration was compared with ICG R_max, which is a validated method for the estimation of the functioning hepatocyte mass. The correlation coefficient was 0.76 (P=0.017). It is concluded that HBP concentration ([HPB]_o) as measured by functional imaging is a measure of functioning hepatocyte mass. This implies that measurement of an individual's receptor concentration by using nuclear medicine techniques provides an objective index of hepatic functional mass and supports attempts to rigorously evaluate [HBP]_o for its clinical efficacy.