抑肽酶对实验性慢性肝损伤大鼠肝细胞增殖能力的影响

目的:探讨抑肽酶对实验性慢性肝损伤大鼠肝细胞增殖能力的影响,为抑肽酶对慢性肝损伤的保护作用研究提供理论依据.方法:Wistar大鼠随机分为正常对照组、四氯化碳(CCl4)模型组、抑肽酶小剂量组、抑肽酶中剂量组、抑肽酶大剂量组和促肝细胞生长素组,采用免疫组织化学方法检测各组增殖细胞核抗原(PCNA)阳性细胞数和形态学表现.结果:正常对照组阳性细胞数为(4±2)个/视野,模型组阳性细胞数为(5±2)个/视野,抑肽酶小、中和大剂量组阳性细胞个数分别为(39±13)个/视野、(49±14)个/视野和(57±12)个/视野,促肝细胞生长素组中阳性细胞个数为(26±8)个/视野.抑肽酶各剂量组与模型组相比,阳性细胞数目均显著增加(P<0.05);随着抑肽酶剂量的增加,阳性细胞数目也增加.抑肽酶各剂量组阳性细胞数多于促肝细胞生长素组(P<0.05).抑肽酶各剂量组PCNA阳性细胞增殖活跃,以抑肽酶大剂量组表现明显.结论:抑肽酶能够促进慢性肝损伤大鼠肝细胞增殖,其作用随着剂量的增加而增强.     

A three stage model of awareness: formulation and initial experimental support

The various components which together make up the complex state of consciousness require neural support involving a connected network of many brain areas at differing levels. At the lowest level is non-aware processing, of which there is not direct awareness. There are also modules involved in processing with awareness but without focussed attention. Finally there must be a set of modules involved in directing attention in a controlled manner. We expect to be able to dissociate the various components of the three-stage network by using different levels of attention. The results of an auditory experiment performed under three different levels of awareness and attention are analysed to show support for the three-stage model of awareness. The relevant auditory areas are delineated.     

Change in strength of aponeurotic tissue enclosed in the suture during the initial healing period. An experimental investigation in rabbits

In order to ascertain whether tissue in which suture thread is inserted undergoes weakening, the strength against sutures in healing aponeurotic layer was determined in rabbits. The dorsal aponeurosis was used as test tissue. A paravertebral incision 10 cm long was made in it, and this was sutured with 00 (USP) multifil steel thread. The strength measured as holding strength against a single suture was noted 3, 5, 7, 10, and 14 days after the procedure. The contralateral aponeurosis was used as control in each animal, and was tested in identical fashion. Two series of experiments were carried out, one with loosely tensed thread (Series I) and one with tightly pulled sutures (Series II). In series I the strength on the experimental side was reduced by 10 percent (average) on the 3rd, 5th, and 7th days compared to the controls. Increase in strength was seen, however, from the 3rd to 14th days, and was significant (p less than 0.05). In series II the measured values showed significantly (p less than 0.05) lower strength on the experimental side compared with the controls throughout the 14-day period of the experiment. Moderate reduction in the strength of healing aponeurosis was thus recorded. The duration of this weakening depended on how tightly the suture loops were tied.     

Enhanced coronary vasa vasorum neovascularization in experimental hypercholesterolemia

Coronary arteries contain a network of vasa vasorum in the adventitia. The three-dimensional anatomy of the vasa vasorum in early coronary atherosclerosis is unknown. This study was designed to visualize and quantitate the three-dimensional spatial pattern of vasa vasorum in normal and experimental hypercholesterolemic porcine coronary arteries, using a novel computed tomography technique. Animals were killed after being fed either a high cholesterol diet (n = 4) or a control diet (n = 4) for 12 wk. The proximal left anterior descending coronary artery was removed from the heart, scanned, and reconstructed, and quantitation of vasa vasorum density was performed. Two different types of vasa vasorum were defined: first-order vasa vasorum ran longitudinally parallel to the vessel and second-order originated from first-order vasa circumferentially around the vessel wall. Compared with controls in hypercholesterolemic coronary arteries, there was a significant increase in the area of the vessel wall (3.86+/-0.22 vs. 8.07+/-0.45 mm2, respectively, P < 0.01) and in the density of vasa vasorum (1. 84+/-0.05/mm2 vs. 4.73+/-0.24/mm2; respectively, P = 0.0001). This occurred especially by an increase of second-order vasa vasorum and disorientation of normal vasa vasorum spatial pattern. This study suggests that adventitial neovascularization of vasa vasorum occurs in experimental hypercholesterolemic coronary arteries and may be a part of the early atherosclerotic remodeling process.     

Quantitative evaluation of newly formed bone in the alveolar wall surrounding the root during the initial stage of experimental tooth movement in the rat

By using a chronological lead-labelling technique and computer image analysis the volume of this newly formed bone was evaluated. Rat maxillary first molars were moved mesially by a fixed, closed coil-spring appliance for 6 days using three different magnitudes of initial tensile force (27, 60 and 136 g). Sham-treated rats wearing an inactivated appliance were used for the control study. All animals were injected twice intraperitoneally with lead-disodium EDTA, 3 hr before the beginning and 3 hr before the end of treatment. The unit volumes of newly formed bone (mm3/mm2) were assessed with reference to lead-labelling lines in the alveolar walls of the root socket by computer image analysis. In the control group, two distinct lead-labelling lines indicated continuous bone formation on the mesial side of the root sockets, but only a jagged line was found on the distal side. After experimental mesial tooth movement, only a single lead line could be found on the mesial/pressure side of the root sockets; on the distal/tension side, a wide layer could be detected between the two lead lines. The volume of newly formed bone on the distal/tension side in the experimental groups was significantly greater than that in the control group. However, there was no significant difference in the volumes of newly formed bone among the three experimental groups. The study demonstrates that the volume of newly formed bone in the alveolar walls during the initial stage of tooth movement can be quantified and that the magnitude of the tensile force of tooth movement may not influence directly the volume of newly formed bone in the alveolar wall on the tension side.     

Zymosan-induced experimental hypersensitivity pneumonitis in rabbits

An experimental model of hypersensitivity pneumonitis is presented. New Zealand white rabbits, previously immunized against yeast-derived zymosan, reacted to intratracheal challenge developing extensive pneumonitis. The lesions healed in a few weeks. Control animals challenged with inert particulate material (latex beads) or suspending fluid (PBS-Mg++) did not show pulmonary inflammation. Nonimmunized rabbits developed only transient pneumonitis after zymosan challenge. This reaction was clearly different from that seen in the group of immunized animals. The model reveals that biologically active substances such as zymosan, which is able to activate the alternate pathway of complement and mononuclear phagocytes, requires an active immune state in order to cause significant tissue damage. Isolated exposure to this kind of substance may not be sufficient to cause lung disease.     

Apoptosis and proliferation of growth plate chondrocytes in rabbits

The growth plates of the femoral head of Japanese white rabbits aged 5, 10, 15 and 20 weeks were stained for apoptotic and proliferating chondrocytes using the TUNEL and PCNA antibody staining techniques. Both TUNEL- and PCNA-positive chondrocytes were detected in all of the specimens. The positive ratios of both stainings were calculated for the whole plate and for the resting, proliferating and hypertrophic zones. The highest ratios in both stainings occurred in the hypertrophic zone in all age groups. With growth, the TUNEL-positive ratio increased whereas the proliferating ratio decreased. We suggest that the increase in chondrocytic death by apoptosis and the decrease in cell proliferation potential led to closure of the growth plate.     

The hypocholesterolemic and antiatherogenic effects of topically applied phosphatidylcholine in rabbits with heritable hypercholesterolemia

To test possible hypocholesterolemic and antiatherogenic effects of transdermally administered phosphatidylcholine (PC), we applied a 33% solution of PC in ethanol containing 0.01% butylated hydroxytoluene as antioxidant, to the shaved back of a strain of inbred rabbits which spontaneously developed hypercholesterolemia (serum cholesterol above 110 mg/dl) and severe atherosclerotic lesions especially in the aortic arch. After the topical application of PC, increases of choline-containing phospholipids in blood were observed, reaching a plateau in 24-48 hr. There were significant reductions in serum cholesterol and LDL cholesterol in the treated animals 2-3 weeks after the treatment. Atherosclerotic lesions in the aortic arch were clearly less severe in the animals repeatedly treated with topical PC. The hypocholesterolemic and antiatherogenic effects of topical PC could be the result of increased cholesterol efflux from extrahepatic tissues and enhanced reverse cholesterol transport.     

Endothelial-cell proliferation in experimental tumours

The proliferation characteristics of vascular endothelium have been studied in 131 individual experimental tumours, representing 18 transplanted tumour lines. The labelling index (LI) is high in most tumours, with a mean value of 0.9%, regardless of the growth rate of the tumours, or whether different tumour types are considered or individual tumours from within one line are studied in detail. A similar high LI value has been found by others for a human tumour. These high LI values may even underestimate the proliferation in new capillary buds. The high proliferative index of tumour endothelium is in marked contrast with the previously reported low 3HTdR uptake into normal tissue blood vessels. It seems likely that it is the type of new vessels formed that will influence tumour growth rates more than the simple rate of endothelial-cell proliferation. The large difference between the proliferation characteristics of tumour endothelium and normal tissue endothelium, recently identified as a possible approach for tumour therapy, has now been confirmed for a range of animal tumours and a human tumour.     

Serum hepatocyte growth factor activity and hepatocyte proliferation in Long-Evans with a cinnamon-like coat color rats with hepatic lesions

We classified hepatic lesions spontaneously developed by Long-Evans with a cinnamon-like coat color (LEC) rats into the following four stages: Normal liver, acute hepatitis, chronic hepatitis, and hepatoma, by biochemical tests of the sera, and anatomical and histopathological examination of the livers. Hepatocyte growth factor (HGF) activity in the sera of LEC rats which developed acute hepatitis, chronic hepatitis, and hepatoma was higher than that of normal LEC rats. In particular, HGF activity in the sera of the LEC rats with acute hepatitis was about 70-fold that of normal LEC rats. However, primary cultured hepatocytes of LEC rats with hepatic lesions were hardly proliferated by stimulation with EGF and insulin in vitro or with increased HGF in vivo. These results suggest that the hepatocytes of LEC rats with hepatic lesions disorder the signal transduction of growth factors.     

Ethanol inhibits hepatocyte proliferation in insulin receptor substrate 1 transgenic mice

BACKGROUND & AIMS: Long-term ethanol consumption is known to impair the ability of the liver to regenerate, but the molecular mechanisms are poorly understood. Multiple growth factors promote hepatocyte proliferation, some of which involve the insulin receptor substrate 1 (IRS-1)-mediated signal transduction pathway. To explore effects of ethanol on the IRS-1 signal liver growth in vivo, studies in transgenic mice overexpressing IRS-1 in the liver were performed because these mice show constitutive activation of the downstream signal transduction pathways leading to enhanced hepatocyte proliferation. METHODS: Tyrosyl phosphorylation of IRS-1 and subsequent protein-protein interactions were examined in liver lysates from animals fed ethanol or control diet. Activity of phosphatidylinositol-3 kinase (PI3K) and mitogen-activated protein kinase (MAPK) was assessed by specific enzymatic assays. Hepatocyte proliferation was measured by incorporation of [3H]thymidine into liver DNA. RESULTS: Tyrosyl phosphorylation of IRS-1, association of IRS-1 with PI3K, and activation of downstream PI3K and MAPK pathways were greatly reduced as a result of long-term ethanol consumption. Ethanol virtually abolished the enhanced hepatocyte DNA synthesis induced by expression of the IRS-1 transgene. CONCLUSIONS: Altered transmission of growth signals through the IRS-1-mediated signal transduction cascade may represent a molecular mechanism of how ethanol inhibits hepatocyte proliferation.     

Scintigraphic evaluation of experimental colitis in rabbits

Scintigraphic techniques are frequently used for evaluation of inflammatory bowel disease. The radiopharmaceutical of choice is labeled leukocytes. In this study, two new agents, 111In-labeled polyethylene glycol-coated liposomes and 111In-labeled human nonspecific gamma globulin (immunoglobulin G; IgG), were compared with 111In-leukocytes in a rabbit model of colitis. METHODS: In rabbits, acute colitis was induced by colonic instillation of trinitrobenzene sulfonic acid at 25 cm from the anal sphincter. After 24 hr, 15 MBq of the radiopharmaceuticals was injected intravenously in groups of four rabbits. Twenty-four hours after injection, the animals were killed and macroscopic abnormalities were scored in seven consecutive affected colonic segments of 5 cm each (0 = normal, 1 = inflammation, 2 = ulcers). The ex vivo uptake was measured in the normal ascending colon and the affected colonic segments. The colitis index (CI, affected-to-normal colon-uptake ratio) was calculated. RESULTS: Histologically, an acute, patchy, transmural colitis was observed at the site of instillation and the distal colon. The CI of all agents in colitis lesions correlated with the severity of the abnormalities. With increasing severity, the CI for liposomes was 1.86 +/- 0.24, 4.88 +/- 0.42 and 7.42 +/- 0.54 (r2 = 0.68, p < 0.001); for leukocytes 1.77 +/- 0.32, 3.10 +/- 0.58 and 5.54 +/- 0.83 (r2 = 0.31, p < 0.01); for IgG 1.60 +/- 0.29, 2.81 +/- 0.21 and 2.65 +/- 0.21 (r2 = 0.29, p < 0.02). CONCLUSION: Indium-111-labeled-leukocytes, -IgG and -liposomes all show increased uptake in inflamed colonic tissue. Indium-111-liposomes showed the highest CI, which correlates best with the morphological abnormalities. Indium-111-leukocytes and 111In-liposomes are superior to 111In-IgG for this indication.     

Fluctuation melting and the initial stage of nanopowder sintering

The initial stage of nanopowder sintering at low temperatures has been theoretically studied. Analytical expressions are obtained to control the nanopowder shrinkage at this stage. They also indicate that the nanopowder densification and the increase in the nanoparticle size at the initial stage of sintering are determined by a nondiffusion mechanism and that they can be calculated with a fluctuational sintering model. The effect of the granulometric composition of nanoparticles on sintering has been studied. It is shown that the shrinkage and the increase in the average particle size in the cases of sintering a nanopowder with a normal size distribution of particles and a nanopowder consisting of the same particles are the same.