Dietary polyamines promote the growth of azoxymethane-induced aberrant crypt foci in rat colon

We have examined whether dietary polyamines influence the formation and initial growth of azoxymethane (AOM)-induced aberrant crypt foci (ACF) in rat colon. Effects of a combination of dietary polyamines at three dose levels (putrescine: 50, 280, 740 nmol/g; spermidine: 10, 261, 763 nmol/g; spermine: 1, 31, 91 nmol/g) in the polyamine-poor AIN-76A diet were studied in animals in two different experimental situations: animals treated with AOM alone and animals treated with AOM + difluoromethylornithine (DFMO), a specific inhibitor of endogenous polyamine synthesis. In both experimental situations, dietary polyamines enhanced the growth of ACF, expressed as the number of large ACF (foci with three or more aberrant crypts, ACF > or = 3), whereas the formation of ACF, expressed as the number of ACF, was apparently not altered. In animals treated with AOM alone, maximal growth enhancing effect on ACF was nearly obtained with the median level of dietary polyamine. In rats fed a low polyamine diet, basic AIN-76A, DFMO reduced the growth of AOM-induced ACF by 83%. This inhibitory effect of DFMO was counteracted by dietary polyamines in a dose- dependent manner, and it was abolished at the highest level of polyamines. In conclusion, it was demonstrated that dietary polyamines are able to enhance the growth of AOM-induced ACF. Further, dietary polyamines reversed the DFMO-caused inhibition of ACF growth, probably by compensating for the DFMO-reduced endogenous polyamine synthesis.      

Propylene oxide in blood and soluble nonprotein thiols in nasal mucosa and other tissues of male Fischer 344/N rats exposed to propylene oxide vapors--relevance of glutathione depletion for propylene oxide-induced rat nasal tumors.

High concentrations of propylene oxide (PO) induced inflammation in the respiratory nasal mucosa (RNM) of rodents. Concentrations > or =300 ppm caused nasal tumors. In order to investigate if glutathione depletion could be relevant for these effects, we determined in PO exposed male Fischer 344/N rats PO in blood and soluble nonprotein SH-groups (NPSH) in RNM and other tissues. Rats were exposed once (6 h) to PO concentrations between 0 and 750 ppm, and repeatedly for up to 20 days (6 h, 5 days/week) to concentrations between 0 and 500 ppm. At the end of the exposures, PO in blood and NPSH in tissues were determined. PO in blood was dependent on concentration and duration of exposure. After the 1-day exposures, NPSH depletion was most distinctive (RNM > liver > lung). Compared to controls, NPSH levels were 43% at 50 ppm PO in RNM and 16% at > or =300 ppm in both RNM and liver. Lung NPSH fell linearly to 20% at 750 ppm. After repeated exposures over 3 and 20 days to 5, 25, 50, 300, and 500 ppm, NPSH losses were less pronounced. At both time points, NPSH were 90%, 70%, 50%, 30%, and 30% of the control values in RNM. Liver NPSH decreased to 80% and 50% at 300 and 500 ppm, respectively. After 20 days, lung NPSH declined to 70% (300 ppm) and 50% (500 ppm). We conclude that continuous, severe perturbation of GSH in RNM following repeated high PO exposures may lead to inflammatory lesions and cell proliferation, critical steps on the path towards tumorigenicity.     

Spectrophotometric determination of pyrrole-like substances in urine of rat and man: An assay for the evaluation of 2,5-hexanedione formed fromn-hexane

Male Wistar rats exposed to atmosphericn-hexane excreted in their urine substances which gave rise to absorption spectra like those of pyrroles after the reaction with Ehrlich's reagent. A simple spectrophometric assay was developed to determine these pyrrole-like substances in urine. Their excretion kinetics were evaluated by exposing rats for 8 h to atmosphericn-hexane concentrations between 50 and 3000 ppm. The dose-response curve revealed saturation kinetics according to Michaelis-Menten, V_max being 1.12 [E ⁵²⁶ml urine/8 hn-hexane exposure] and Km, the atmosphericn-hexane concentration at V_max/2, being 250 ppm. The excretion of pyrrolelike substances closely correlated with that of 2,5-hexanedione measured by Fedtke and Bolt (1987). Pyrrole-like substances were also found in the urine of a male volunteer. When exposing the person for 3 h to atmosphericn-hexane at a concentration of 146 ppm (equivalent to 55 ppm/8 h) the excreted amount was twice the background value. Due to the sensitivity of this assay it is possible to determine pyrrole-like substances in urine according to the present German MAK or US TLV conditions forn-hexane (50 ppm/8 h).     

改良性治疗法联合西地那非治疗勃起功能障碍维吾尔族患者2505例回顾性分析

目的:性治疗法目前尚未普及,本研究旨在评价性治疗法联合西地那非治疗勃起功能障碍(ED)的疗效。方法:根据治疗方法的不同将在本院治疗随访过的3130例维吾尔族ED患者分成2组。对照组625例,单纯口服西地那非3个月;试验组2505例,采用性治疗法联合西地那非治疗3个月。采用国际勃起功能问卷表(IIEF-5)在各组治疗前、后进行疗效评估,并随访12个月。结果:对照组治疗前、后及在6个月、12个月随访的IIEF-5评分分别为12.80±3.76、18.10±2.61、17.35±2.73和16.64±2.63;试验组治疗前、后及在6个月、12个月随访的IIEF-5评分分别为12.73±3.52、19.06±4.07、19.86±2.42和20.47±2.38。两组治疗前后IIEF-5评分自身对比差异均有显著性(P<0.05)。组间比较,试验组较对照组6个月和12个月随访IIEF-5评分均有显著性差异(P<0.05)。结论:性治疗法联合西地那非治疗ED的效果优于单纯西地那非治疗,并在12个月的随访中稳定性良好。     

Role of the B domain for factor VIII and factor V expression and function

Factor V and factor VIII are homologous cofactors in the blood coagulation cascade that have the domain structure A1-A2-B-A3-C1-C2, of which the B domain has extensively diverged. In transfected COS-1 monkey cells, expression of factor VIII is approximately 10-fold less efficient than that of factor V, primarily because of inefficient protein secretion and, to a lesser extent, reduced mRNA expression. To study the functional significance and effect of the B domain on expression and activity, chimeric cDNAs were constructed in which the B domains of factor V and factor VIII were exchanged. Expression of a factor VIII chimera harboring the B-domain of factor V yielded a fully functional factor VIII molecule that was expressed twofold more efficiently than wild-type factor VIII because of increased mRNA expression. Thus, sequences within the factor VIII B domain were not responsible for the inefficient secretion of factor VIII compared with factor V. Expression of a factor V chimera harboring the B domain of factor VIII was slightly reduced compared with wild-type factor V, although the secreted molecule had significantly reduced procoagulant activity correlating with dissociated heavy and light chains and resistance to thrombin activation. Interestingly, the factor V chimera containing the factor VIII B domain was efficiently activated by Russell's viper venum (RVV). A factor V B domain deletion (residues 710- 1545) molecule also exhibited significantly reduced procoagulant activity caused by resistance to thrombin cleavage and activation, although this molecule was activatable by RVV. These results show that, in contrast to factor VIII, thrombin activation of factor V requires sequences within the B domain. In addition, thrombin activation of factor V occurs through a different mechanism than activation by RVV.     

Identification of the molecular defect in the erythrocyte membrane skeleton of some kindreds with hereditary spherocytosis

We have localized the molecular alteration in the membrane skeleton of two of four kindreds with hereditary spherocytosis (HS) to an alteration in the spectrin-protein-4.1 interaction due to a defective spectrin molecule. The defective spectrin-protein-4.1 interaction in these kindreds (referred to as type I HS) leads to a weakened spectrin- protein-4.1-actin ternary complex, which in turn may lead to the friable membrane skeleton and suggested membrane instability related to this disorder. Type I HS spectrin binds approximately 63% as much protein-4.1 as normal spectrin (with equal affinity). This defect does not correlate with splenic function or erythrocyte age in the circulation. However, the approximately 37% reduction in binding of protein-4.1 to HS spectrin approaches the theoretical value of 50% expected in this autosomal dominant disorder. All other type I membrane skeletal interactions (spectrin-syndein, spectrin heterodimer- heterodimer, syndein-band-3) were found to be normal. It would appear therefore that the defective HS spectrin-protein-4.1 interaction in type I hereditary spherocytosis may be the primary molecular defect rather than a secondary phenomena.     

Smoothelin is an indicator of reversible phenotype modulation of smooth muscle cells in balloon-injured rat carotid arteries

Restenosis is the major obstacle interfering with a successful long-term outcome of balloon angioplasty. Neointima formation following endothelial injury is the result of phenotype modulation and proliferation of smooth muscle cells (SMC). To characterize these time-dependent changes, a rat balloon injury model of carotid artery restenosis was assessed. We applied monoclonal antibodies recognizing desmin, sm-α-actin and smoothelin, a novel marker specific for the differentiated phenotype of SMC. Neointima formation could be seen from day 7 after injury onwards. During early phases, the number of smoothelin-positive cells in the media was decreased compared with uninjured controls. Smoothelin staining was absent in the neointima during formation. Increased levels of smoothelin in both media and neointima were observed at days 28 and 56, correlating with a decrease in proliferation as assessed by Ki-67 antigen staining. No such changes were observed for desmin and sm-α-actin. Following balloon injury, SMC in both the media and the neointima underwent an early, reversible dedifferentiation, followed by proliferation. The novel SMC-specific marker protein smoothelin can be used to monitor this SMC (de)differentiation in neointima and media. These findings support the pivotal role of SMC phenotype modulation in neointima formation and restenosis. Received: 29 January 2001, Returned for revision: 20 February 2001, Revision received: 26 June 2001, Accepted: 2 July 2001