Controlled delivery of antibacterial proteins from biodegradable matrices

Prosthetic valve endocarditis is an infrequent, but serious complication of cardiac valve replacement. The infection is caused by the adherence of bacteria to the prosthetic valve or to tissue at the site of implantation. Recently it was shown that antibacterial peptides from blood platelets are involved in clearance and killing of bacteria adhering to vegetations induced in a model for prosthetic valve endocarditis using rabbits. The application of these antibacterial proteins in a release system, incorporated in the Dacron sewing ring of the prosthetic heart valve would diminish the incidence of endocarditis. In this study a release system for small cationic proteins based on cross-linked gelatin was developed and characterised. Furthermore, the system was evaluated with respect to the uptake and in vitro release of lysozyme, a small cationic protein that was chosen as a model protein for small cationic antibacterial proteins. Variation of gelatin type (A and B), and cross-link density resulted in differences in swelling, thermal behaviour, and number of charged groups. Lysozyme uptake was proportional to swelling, but was governed by the number of anionic groups. The latter was also observed for the release profiles: when the amount of free carboxylic acids is higher (gelatin B compared to gelatin A), the lysozyme release lasts for a longer time period. The release into solidified agarose medium, as a model for heart muscle tissue, was measured. After 50 h, 40-100% of the lysozyme was released, which is in accordance with the aimed release period of 24-48 h. The adsorption experiments in vitro suggest an influence of the electrostatic interactions between lysozyme and gelatin. This hypothesis was validated with a mathematical model which takes both diffusion and adsorption interactions into account.     

发泡工艺对泡沫铝夹芯板孔结构及压缩性能的影响

采用包套轧制-粉末冶金发泡法制备了具有良好冶金结合界面的泡沫铝夹芯板,利用X射线衍射仪、扫描电镜、电子万能试验机等研究了发泡工艺对泡沫铝夹芯板宏观泡孔结构、微观芯层结构和压缩性能的影响.结果表明:发泡温度、发泡时间对泡孔结构起着决定性作用,而对微观组织几乎没有影响,发泡后芯层组织表现为在元素晶界处形成了Mg2 Si相、CuAl2相,620℃/15 min下发泡后得到的泡沫铝夹芯板具有最佳的综合力学性能.     

Determination of embutramide in biological matrices by gas chromatography with nitrogen-phosphorus detection

Embutramide is a general anesthetic having a strong narcotic effect on the central nervous system where it paralyzes the brain center that controls respiration. It is a constituent of T61, a veterinary euthanasia drug. This paper describes a gas chromatographic procedure using nitrogen-phosphorus detection for the determination of embutramide in biological matrices. The drug and the internal standard (ambucetamide) are extracted with dichloromethane under alkaline conditions. The method is linear from 100 to 3000 ng/ml. The within-day and day-to-day coefficients of variation range from 5.1 to 5.7% and from 9.1 to 10.0%, respectively. The recovery is above 80% while the minimum detectable level under the conditions described is 40 ng/ml analyzing a 1-ml or a 1-g aliquot of a sample (blood or tissue). The method is also applied to different samples from dogs euthanized with T61.     

发泡剂对高碱度LF精炼渣泡沫化性能的影响

外加发泡剂对LF实现埋弧加热和提高精炼效率具有重要意义.本文系统研究了发泡剂种类、加入量和粒度对高碱度精炼渣发泡效果的影响.结果表明,在碳酸盐中,CaCO3最为理想.在一定范围内增大碳酸盐粒度,有利于发泡的持续性.在碳化物中,复合碳化物的发泡效果最好,CaC2好于SiC.随碳化物粒度增大,发泡效果变差.以碳酸盐与碳化物按适当比例混合作为发泡剂,较单一发泡剂具有更好的发泡效果,且应根据渣中FeO含量调整二者比例.     

Effect of entrapped inert gas on pore filling during liquid phase sintering

The effect of an inert gas entrapped in isolated pores on liquid flow into them during liquid phase sintering has been studied. An analysis of the balance between the capillary pressure of the liquid menisci and the gas pressure shows that the entrapped gas delays the pore filling and produces bubbles. If the gas pressure exceeds a critical level, the pores remain intact and the critical point for their filling will never be reached. These predictions are confirmed by experimental observations on large spherical pores produced artificially in an Fe-Cu alloy. Argon gas is trapped in the pore by first sintering in Ar-H₂ mixture gas and then in H₂ after the isolated pores are formed. The entrapped inert gas of even low pressure is thus shown to cause a substantial porosity in liquid phase sintered specimens. Formerly a Doctoral Student at the Korea Advanced Institute of Science and Technology.     

Size analysis of slag eye formed by gas blowing in ladle refining

The formation of slag eye in a gas stirred ladle was studied through cold models and industrial trials.In the cold model,water and sodium tungstate solution were employed to simulate liquid steel,and silicon oil was employed to simulate slag.The simulation results revealed that the gas flow rate and bath height had strong effects on the slag eye size.In particular,the thickness of slag layer played a strong role in the slag eye size.In addition,the slag eye could not be formed when the thickness of the top layer was more than 4 cm in water-silicone oil model.Besides,the section area of vessel had a great impact on the slag eye size.Industrial trials results showed a similar trend that the gas flow rate was very significant on the slag eye size.The predictions of the existing models showed larger predictions deviations compared with the experimental data.Moreover,a new model without fitting parameters was developed based on force balance and mathematical derivation,and verified by the experimental data.The new model provides the prediction with small deviations by comparing with the data acquired from cold models and industrial trials.     

HP295钢中非金属夹杂物形成的热力学分析

针对HP295钢,采用热力学计算预测了冶炼和凝固过程中夹杂物的组成,同时,用扫描电镜（SEM）及能谱仪（EDS）对夹杂物的形貌和成分进行分析．结果表明：采用硅锰脱氧时,钢液中形成的夹杂物主要为鳞石英（SiO2）、锰铝榴石（3MnO·Al2O3·3SiO2）、莫来石（3Al2O3·2SiO2）和刚玉（A1203）等4类,且随【Al】含量提高或[01含量降低,夹杂物逐渐从鳞石英为主向刚玉为主转变,[A1]〈1×10^-6时主要为鳞石英,a[O]〈3×10^-3时则以刚玉为主;凝固过程析出夹杂物的组成与[Al]、[O]含量有关,1550℃时,当n[O]〉115．6×10^-5及[A1]〈4．5×10^-6时析出鳞石英,当口【O】〈115．6×10^5及[A1]〈10．5×10^-6时析出莫来石,当[A1]〉10．5×10^-6时析出刚玉;1510℃时,当a[01〉75．2×10^-5及[Al]〈3．51×10^-6时析出鳞石英,a[O]〈75．2×10^-5及[A1]〈8．18×10^-6时析出莫来石,[A1]〉8．18×10^-6时析出刚玉;另外,当3钢中有[Ca]存在时,凝固时可能析出钙斜长石甚至假硅灰石,析出物的成分及数量与钙的活度有关．热力学计算预测结果与扫描电镜分析结果基本一致,表明该热力学计算方法是可行的．     

Binding of antibodies to functional epitopes on the pore formed by Escherichia coli hemolysin in cells and model membranes

Escherichia coli hemolysin (HlyA) inserts into target membranes producing a cation-selective pore. We approached the problem of determining which portions of this protein remain exposed on the side of attack by applying specific antibodies. Results obtained with resealed erythrocyte ghosts and planar phospholipid membranes were compared. The effects of one polyclonal and four monoclonal anti-hemolysin antibodies (mAbs) were studied. Using ghosts we found one mAb which strongly reduced the ion-permeability through the preinserted HlyA channels and one which clearly increased it. Experiments with planar bilayers corroborated these results by showing that the former mAb effectively promoted the closed state of the channel whereas the latter forced the HlyA channel into an open configuration. Anti-hemolysin polyclonal antibodies initially stimulated but then prevented channel opening, indicating they contained clones able to act on both these channel determinants. They were effective only when applied on the same side as the hemolysin indicating that the epitopes were exposed to that side. Finally, the antigenic epitopes of three of the mAbs were localised on the HlyA molecule by using different mutants (amber and frame shift mutants and hemolysin gene hybrids).     

The influence of MgO,K2O,Na2O and gas pressure on slag foaming behaviour under reducing conditions

Using a photoelectric measuring technique to determine the foaming behaviour of iron oxide-containing slag, investigations were carried out into the influences of magnesium oxide and the alkali oxides K₂O and Na₂O on melt foaming behaviour under reducing conditions. An MgO content of just a few percent intensifies the foaming action of acidic and self-fluxing melts. This behaviour is also induced by a relatively low addition of alkali oxide. If the magnesium oxide and alkali oxide addition is further increased, slag volume growth during foaming declines. With basic compositions, both the magnesium oxide and the alkali oxides may reduce the volume increase of the foaming slag. Overall, melts undergo maximum foaming under conditions of medium basicity and in the medium temperature range. Alkali oxides promote the phenomenon of melt resolidification often observed in the tests. Tests with different furnace gas pressures up to max. 3 bar reveal that foaming volume of the melt increases with rising gas pressures.     

Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas

In recent studies, NMR imaging has been used to investigate the swelling of hydroxypropylmethylcellulose (HPMC) tablets and to determine polymer concentration distributions in the swollen matrix. The total amount of polymer in the system was computed from these distributions and was up to 35% greater than the known weight of HPMC in the tablet. This deviation was traced to the presence of air bubbles in the swollen matrix which occupied a significant volume previously assumed to be occupied by polymer and water. When the air in the tablet was removed by vacuum, the swollen gel contained no evidence of air bubbles and the calculated total polymer weights from the HPMC distributions were equal to the amount of HPMC in the tablet.     

Influence of gases on the sintering of porous solids. VIII. Behavior of a pore filled with a constant amount of gas

Conclusions Equations have been derived describing the behavior of a spherical pore filled with a constant amount of gas. It is shown that under certain conditions such a pore tends to an equilibrium size. The rate of attainment of equilibrium depends on the relative values of the external pressure, surface tension, and gas pressure.Translated from Poroshkovaya Metallurgiya, No. 6(198), pp. 34–38, June, 1979.     

Porous-coated titanium implant impregnated with a biodegradable protein delivery system

Tissue ingrowth into porous-coated orthopedic and dental implants is commonly used as a means to achieve long-term fixation of these prostheses. However, the degree of tissue ingrowth is often inadequate and inconsistent. If the pores of these implants are impregnated with a controlled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present study introduces such a system based on biodegradable polymers and investigates its protein release profile and polymer degradation characteristics. Porous coated titanium implants were impregnated with a mixture of a 50%-50% polylactic acid-polyglycolic acid copolymer and a model protein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degradation in phosphate buffered saline at 37 degrees C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weight of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant difference in the polymer degradation characteristics between the control and test implants, which might be the result of some complex polymer-protein interactions.     

Spout eyes formed by an emerging gas plume at the surface of a slag-covered metal melt

This article deals with the spout eyes developing, at the surface of a metal melt, in the ladle during argon stirring. Cold model experiments involving a mercury bath with an oil layer as slag and industrial experiments on a 350 t steel ladle have been carried out. The eye geometry as measured with a video technique is highly dynamic. The time average of the free surface area and the time fraction of complete coverage have been determined and are represented with dimensionless correlations.     

W-stapled ileal neo-bladder formed entirely with absorbable staples

Orthotopic bladder replacement after total cystoprostatectomy for bladder cancer has gained broader use. Continent diversion has historically increased the complexity of the surgical procedure, often discouraging its adoption by many urologists. Absorbable staples on a GIA* instrument became available in 1992 and have been incorporated into reservoir formation in this preliminary study. A novel W-shaped ileal reservoir entirely fashioned from absorbable staples using the GIA and TA instruments has been developed and used in 15 patients undergoing cystoprostatectomy. The advantages of this technique are its simplicity and the speed with which the reservoir can be fashioned. In the first 15 patients operative time to construct the reservoir ranged from 12 to 21 minutes. Functional aspects of urodynamic studies and continence appear comparable to those of other ileal reservoirs. These preliminary data justify comparative trials on an expanded scale.     

Bone regeneration by basic fibroblast growth factor complexed with biodegradable hydrogels

The objective of this study is to enhance the bone induction activity of basic fibroblast growth factor (bFGF) for reconstruction of skull bone defects which has been clinically recognized as almost impossible. For this purpose, we prepared biodegradable hydrogels from gelatin with an isoelectric point of 4.9 which is capable of polyionic complexing with basic bFGF. When implanted in rabbit skull defects of 6 mm in diameter (6 defects per experimental group), the gelatin hydrogels incorporating 100 microg of bFGF promoted bone regeneration at the defect in marked contrast to free bFGF of the same dose, finally closing the bone defects after 12 weeks of implantation as is apparent from histological examination. In dual energy X-ray absorptometry analysis, the bone mineral density at the skull defects enhanced by the hydrogels was significantly higher than that by free bFGF at doses ranging from 2 to 200 microg/defect (P < 0.05). The extent of bone regeneration induced by gelatin hydrogels incorporating 100 microg of bFGF increased with a decrease in their water content. Histological examination indicated that more slowly degrading hydrogels of lower water content prolonged the retention period of osteoblasts in the bone defects. This led to enhanced bone regeneration compared with faster degrading hydrogels of higher water content. It was concluded that this biodegradable hydrogel system was a promising surgical tool to assist self-reconstruction of the skull bone.