Effect of plant polysaccharides on phosphatidylinositol turnover of sarcoma S180 cell membranes

Mice sarcoma S180 cell membranes, [r-32 P]ATP and plant polysaccharides (PPS, ASPS, TF and lentinan) were incubated together for 5 min at 30 degrees C. Phosphatidylinositides were isolated and subjected to scintillation fluid counting. The results showed that PPS and ASPS, especially the latter, could inhibit the phosphatidylinositol turnover obviously, while TF and lentinan had no such effect.     

Protein turnover in intestinal mucosal villus and crypt brush border membranes

Following a concomitant oral dose of salicylamide and acetaminophen (5 mg/kg of each) the urinary excretion of glucuronide and sulfate conjugates of the drugs were followed in children (ages seven to ten years) and adults. No significant difference were observed between the two age groups in the half-lives for appearance of salicylamide conjugates in urine. Age-related changes in the metabolic pathways, however, were observed. The mean percentage of dose excreted as salicylamide sulfate was significantly higher in children (78%) than in adults (36%). In contrast, salicylamide glucuronide was the major excretory product in adults. Similar age-related differences were observed for acetaminophen conjugation. Pharmacokinetic analysis indicated that the deficiency in glucuronide conjugation of these drugs in children is accompanied by a higher rate of sulfate formation.     

Formation and recovery of Co,Ni, Cu macromolecular complexes with polystyrene and acrylic acid

The formation and structure of Co²⁺, Ni²⁺ and Cu²⁺ macromolecular complexes with a series of polystyrene and acrylic acid copolymers (PSt/AA) were studied. Both the copolymers and the metal complexes (M-PSt/AA) were characterized by FTIR, elemental analysis, Gel Permeation Chromatography and AAS. It is shown that the PSt/AA copolymer has rather strong coordination ability to the metal ions by chelation with the carboxylate group, and the microstructures of the M-PSt/AA complexes can be well controlled. Its adsorption behavior toward Co²⁺, Ni²⁺ or Cu²⁺ and various related parameters in the separation process were determined. The results indicate that the adsorption capability varies with pH and the maximum adsorption capacities were 337 mg/g for Co²⁺, 338 mg/g for Ni²⁺ and 341 mg/g for Cu²⁺ at around pH 7. Adsorption isotherms reveal that the adsorption process is consistent with the Freundlich equation. Experiments show that PSt/AA can recover Co²⁺, Ni²⁺ or Cu²⁺ with a high adsorption rate and high selectively coefficient from a simulated industry solution containing Ca²⁺ and Mg²⁺ as impurities. The resin can be readily stripped with acid and recycled for re-use after transformation to its sodium form.     

Formation and properties of S-protein complex with S-peptide-containing fusion protein

A fusion protein (FP) comprised of the RNase A S-peptide and human epidermal growth factor was shown to form a stable noncovalent catalytically active complex with the RNase A S-protein at a stoichiometric ratio 1:1 with Kdiss = 5.0 x 10(-7) M. The S-protein complex with FP exhibits the pyrimidine specificity toward substrates in both reactions catalyzed by RNase S, transesterification and hydrolysis. The fusion protein can be determined specifically and quantitatively in the presence of S-protein by RNase activity assays. The possibility of effective purification of S-peptide-containing proteins by affinity chromatography on an S-protein-Sepharose column has been demonstrated.     

Formation of RuvABC-Holliday junction complexes in vitro

In Escherichia coli, the RuvA, RuvB and RuvC proteins are required for the late stages of homologous recombination and DNA repair. RuvA and RuvB form a complex that interacts with Holliday junctions--crossed DNA structures that are recombination intermediates--and promotes branch migration; RuvC is a junction-specific endonuclease that resolves Holliday junctions and completes the recombination process. Because genetic and biochemical experiments suggest that the processes of branch migration and resolution are linked, coimmunoprecipitation experiments were carried out to determine whether the three Ruv proteins interact to form a functional complex (RuvABC). Using a synthetic Holliday junction, a multisubunit complex containing the junction and RuvA, RuvB and RuvC was detected. In the absence of RuvB, RuvAC-junction complexes were observed. Complex formation was not facilitated by duplex DNA. The identification of a RuvABC-junction complex provides direct evidence that the RuvABC proteins interact at the Holliday junction.     

Studies on membrane fusion. I. Interactions of pure phospholipid membranes and the effect of myristic acid, lysolecithin, proteins and dimethylsulfoxide

The interaction and mixing of membrane components in sonicated unilamellar vesicles and also non-sonicated multilamellar vesicles prepared from highly purified phospholipids suspended in NaCl solutions has been examined. Electron microscopy and differential scanning calorimetry were used to characterize the extent and kinetics of mixing of membrane components between different vesicle populations. No appreciable fusion was detected between populations of non-sonicated phospholipid vesicles incubated in aqueous salt (NaCl) solutions. Mixing of vesicle membrane components via diffusion of phospholipid molecules between vesicles was observed in populations of negatively charged phosphatidylglycerol vesicles but similar exchange diffusion was not detected in populations of neutral phosphatidylcholine vesicles. Incubation of sonicated vesicle populations at temperatures close to or above the phospholipid transition temperature resulted in an increase in vesicle size and mixing of vesicle membrane components as determined by a gradual change in the thermotropic properties of the mixed vesicle population. The interaction of purified phospholipid vesicles was also examined in the presence of myristic acid and lysolecithin. Our results indicate that while these agents enhance mixing of vesicle membrane components, in most cases mixing probably proceeds via diffusion of phospholipid molecules rather than by fusion of entire vesicles. Increased mixing of vesicle membrane components was also produced when vesicles were prepared containing a purified hydrophobic protein (myelin proteolipid apoprotein) or were incubated in the presence of dimethylsulfoxide. In these two systems, however, the evidence suggests that mixing of membrane components results from the fusion of entire vesicles.     

大方坯角部"冷疤"和面部渣沟缺陷成因分析

文章重点对出现在包钢炼钢厂大方坯表面的"冷疤"和渣沟缺陷的形成机理进行了分析,结果表明大方坯的"冷疤"缺陷和渣沟缺陷形成于结晶器,与渣圈的状况有密切关系.消除这两种缺陷的关键在于保证结晶器设备状况和使用较为合适的保护渣.     

Formation of ring-shaped structures on erythrocyte membranes after treatment with botulinolysin, a thiol-activated hemolysin from Clostridium botulinum

Damage to erythrocyte membranes by botulinolysin (BLY) was studied by electron microscopy, which revealed ring-shaped structures with inner diameters and widths of approximately 32 and 6.7 nm, respectively. BLY bound to membranes at 0 degrees C, but subsequent treatment with glutaraldehyde prevented ring formation during further incubation at 37 degrees C. Zn2+ ions inhibited ring formation but not binding of BLY to membranes.     

Signalling properties of glycosylphosphatidylinositols and their regulated release from membranes in the turnover of glycosylphosphatidylinositol-anchored proteins

Glycosylphosphatidylinositols are involved in transmembrane signalling, and their signal mediated release from the cell membrane has been demonstrated for several hormones and growth factors. Presently, however, only indirect evidence exists for the enzyme responsible for the signal mediated release of glycosylphosphatidylinositols. Indirect evidence from product identification led to the conclusion that in mammals the hormone sensitive activity is that of a glycosylphosphatidylinositol anchor hydrolyzing phospholipase C. On the other hand a mammalian glycosylphosphatidylinositol anchor hydrolyzing phospholipase D is well-established. This enzyme most likely functions in the intracellular turnover of glycosylphosphatidylinositols, however, its possible relation to the signalling properties of glycosylphosphatidylinositols remains unclear.     

挤压铝型材表面"吸附颗粒"的形成机理及对策

在铝型材的挤压生产中，型材表面不同程度地存在一些“吸附颗粒”。这些“吸附颗粒”严重影响电泳涂漆及喷涂型材的表面美观度，降低生产效率和成品率。本文分析了“吸附颗粒”的形成机理，提出了有效预防措施。     

410S不锈钢带表面“砂金”缺陷成因及机理分析

系统地分析了不锈钢分公司410S冷轧成品带钢部分出现表面“砂金”缺陷(表面点状发亮花纹)的成因及其形成机理。对带钢表面“砂金”缺陷进行了表面形貌观察和成分分析以及金相观察,结合国外类似经验,指出产生该缺陷的成因———晶间腐蚀。在系统阐述了不锈钢敏化及晶间腐蚀理论的基础上,详细分析了410S产生晶间腐蚀的过程及原因,并简要探讨了大生产中控制该缺陷的可行措施。     

41OS不锈钢带表面"砂金"缺陷成因及机理分析

系统地分析了不锈钢分公司41OS冷轧成品带钢部分出现表面"砂金"缺陷(表面点状发亮花纹)的成因及其形成机理.对带铜表面"砂金"缺陷进行了表面形貌观察和成分分析以及金相观察,结合国外类似经验,指出产生该缺陷的成因--晶间腐蚀.在系统阐述了不锈钢敏化及晶间腐蚀理论的基础上,详细分析了41OS产生晶间腐蚀的过程及原因,并简要探讨了大生产中控制该缺陷的可行措施.     

Bacterial endosymbiont-derived lipopolysaccharides and a protein on symbiosome membranes in newly infected amoebae and their roles in lysosome-symbiosome fusion

L-691,121 is a class III antiarrhythmic agent which blocks potassium currents, leading to prolongation of cardiac potential and prevention of cardiac arrhythmia. In a developmental toxicity study in rats, there was a dose-dependent decrease in embryonic/fetal survival, and death of the entire litter was seen at an oral dose of 0.8 mg/kg per day. The critical period for embryolethality was determined as gestational days (GD) 10-13. In a study where females received 1 mg/kg on a critical day (GD 10 or 12) and were killed at 24-h intervals, a high embryonic mortality was seen at 72 h (GD 10 treatment) or 48 h (GD 12 treatment) after dosing. The surviving embryos had morphological abnormalities such as enlarged cardiac tube and pericardium, generalized edema, and hematoma. In order to investigate a possible mechanism for the embryolethality, GD 11 embryos were dissected from females at 4 h after dosing of 1 mg/kg and incubated for 5 h in vitro. The embryonic heart rates were decreased for the first 2 h after incubation but tended to recover to control levels thereafter. When GD 11 embryos were incubated for 4 h with the drug, there were decreases in the heart rates during the entire observation period. In a washout study where the embryos were transferred to drug-free medium after 1-h exposure, decreased heart rates recovered to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)