Influence of the microencapsulation method and peptide loading on poly(lactic acid) and poly(lactic-co-glycolic acid) degradation during in vitro testing

Three methods were used, namely spray drying, w/o/w solvent evaporation and the aerosol solvent extraction system (ASES), for the preparation of microparticles having the same size range, to study the influence of the preparation method on polymer degradation in vitro (PBS, 37 degrees C, one month). The following five polymers of the biodegradable poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) group were selected: L-PLA, MW 81 200; DL-PLGA 75:25, MW 64-300; DL-PLGA 50:50 MW 52 600; DL-PLGA 50:50 MW 14 500, AND DL-PLGA 50:50, MW 3400, to prepare drug-free and drug-loaded microparticles. Tetracosactide was selected as model peptide. When microparticles were prepared by solvent evaporation, the mean diameter and, more markedly, the drug encapsulation efficiency tended to decrease when decreasing the molecular weight and increasing the proportion of glycolic acid in the polymer. In contrast, no direct influence of the polymer nature on these parameters was observed in spray dried microparticles. Polymer degradation was heterogenous in L-PLA and DL-PLGA 75:25 microparticles and was not influenced by the presence of the drug at a nominal loading of 1% (w/w), when prepared by the three methods (note that with ASES, only L-PLA could be used for microencapsulation). In batches made of DL-PLGA 50:50 MW 52 600, the degradation rate decreased slightly when increasing the drug loading. Only in the case of DL-PLGA 50:50 MW 14 500, the polymer degradation rate for spray dried microparticles was higher compared to that for microparticles prepared by the w/o/w solvent evaporation method. Generally, the degradation rates of the different microparticles followed the expected order: L-PLA相似文献   

Comparison of methods for the detection and enumeration of lactic acid bacteria in yogurt

It is generally agreed that the population of lactic acid bacteria in yogurt must be not less than 10(6) ufc/g. Viability of the lactic flora until the end of shelf-life is affected for many factors, which has incidence in the recuperability of this microflora. MRS and LEE agar were selected for the total count of lactic bacteria, the M17 was used for the S salivarius ssp thermophilus and the RCA for L. delbrueckii ssp bulgaricus. Different methodologies were used for detection and enumeration of this bacteria: direct plate count; thermal treatment and recuperation of the injured cells in Soy Tripticase broth. The enumeration was done at time zero and 3 hours after the start of the fermentative process and during storage at 4, 12 and 21 days. The results shown an excellent recuperability of the lactic flora in the selected media and methods that were used: however the enumeration was significatively lower in the RCA agar. The counts in the LEE agar shown a better recuperability. The thermal treatment affected negatively the counts of lactic flora and the repair method shown better results in the yogurt sample during storage. pH and acidity were determined at the beginning and during the storage period. It was observed a pH decrease because of the lactic acid production at the end of shelf-life.     

A new collection method for the evaluation of nasal mucus proteins

BACKGROUND: Although it is generally recognized that poverty and depression can coexist among single parents receiving social assistance, there is insufficient research on this topic. The goals of this study therefore were to investigate the prevalence, correlates and health care expenditures associated with depression among sole-support parents receiving social assistance. METHODS: Sole-support parents who had applied for social assistance in 2 regions of southwestern Ontario were included in the study. Depression was diagnosed with the 1994 University of Michigan Composite International Diagnostic Interview short forms. RESULTS: The 12-month prevalence rate of depressive disorder among the parents interviewed was 45.4% (345/760). A total of 247 (32.5%) had major depressive disorder alone, 19 (2.5%) had dysthymia, and 79 (10.4%) had both major depressive disorder and dysthymia ("double depression"). Those with major depressive disorder, particularly double depression, had significantly higher rates of coexisting psychiatric disorder than those without depressive disorders. Parents with depression reported higher rates of developmental delay and behaviour problems in their children than parents without depression. Expenditures for health care services were higher for parents with depression and for their children than for parents without depressive disorder and their children. INTERPRETATION: Single parents receiving social assistance have high rates of depression. Such parents with depression also have higher rates of other psychiatric disorders and higher expenditures for health care services, and their children have higher rates of developmental delay and behaviour problems.     

A biological model study of the effect of Aerococcus viridans on pathogenic bacteria

Morphological researches studies showed that the treatment of infected skin wounds with Aerobact quickly eliminated inflammation, promoted regeneration of damaged tissues, that actively stimulated formation of granulations. A decrease of S. aureus virulence which completely or partially loose lethal and necrotic activity is one of the reasons of the observed phenomenon. On the model of S. typhimurium infection the expressed protective action of bacteria of Aerococcus genus was shown; this gives us a good prospect in the expansion of the indications for application of probiotic Aerobact.     

New approaches for encapsulation of peptides into poly(lactic/glycolic acid) microspheres

The aim of the work was to develop small microspheres made from a biodegradable polymer, poly(lactide-co-glycolide), in order to entrap small peptides. Microspheres prepared by a water-in-oil-in-water emulsion solvent evaporation technique displayed a mean diameter below than 10 microns and showed high encapsulation efficiency of a 33 amino acid peptide (V3 BRU). In vitro release kinetics studies showed that such microparticles could be employed for both oral immunization and controlled release. The encapsulation of a seven aminoacid peptide in the same conditions, led to a very low encapsulation efficiency. In order to increase the entrapment efficiency, two strategies were adopted: taking into account the solubility of pBC 264 at different pH, a pH gradient was created to prevent the leakage of the encapsulated peptide into the outer aqueous phase. The inner aqueous phase was maintained at basic pH where the peptide was soluble, while the external aqueous phase was acidic: ovalbumin was added during preparation to stabilize the inner emulsion. These two strategies allowed to increase significantly the encapsulation rate of pBC 264. Nevertheless, the in vitro release kinetics of the peptide were strongly influenced by the presence of ovalbumin which seems to form pores in the microsphere structure (80% of the total peptide content was released after 30 minutes). By contrast, when ovalbumin was replaced by Pluronic F 68 microspheres did not have pores, thus the release profile and the extent of the burst were much smaller. When microspheres were stereotactically implanted in the rat brain, in vivo release profiles were in good agreement with the release observed in vitro. In conclusion, these microspheres are well suited for the slow delivery of neuropeptides in the brain, a feature expected to facilitate the study of long term effects of these compounds.     

A new method for evaluation of motor deficits in 3-acetylpyridine-treated rats

BACKGROUND: approximately one-third of patients with Alzheimer's disease (AD) respond favourably to the anticholinesterase tacrine, but the drug's usefulness is marred by a high incidence of side-effects. OBJECTIVE: to discover if AD patients with white matter low attenuation (WMLA) represents a subgroup that responds differently to tacrine from those with no WMLA. DESIGN: the results come from a combination of double-blind and open studies. Seventy-two AD patients prescribed tacrine in our centre were divided into two groups according to the presence or absence of WMLA on brain CT scans. We compared the rate of response to and withdrawal from tacrine between the groups. Response was defined as an improvement in the Mini-Mental State Examination score of three or more points at 3 months. RESULTS: 18 of the 72 patients were found to have WMLA. There was no significant difference in the proportion of patients responding to tacrine in each group (28.5% in those with WMLA and 31% in those without), but the rate of withdrawal from tacrine did differ: 11 patients with WMLA (61%) had to be withdrawn prematurely, compared with 14 patients (26%) in the group without evidence of WMLA (P = 0.015). CONCLUSION: AD patients with WMLA can still respond to tacrine, although the rate of withdrawal from treatment is much higher in such patients.     

A new method for the determination of steroidal hormones in biological material (adrenal tissue) (author's transl)

A rapid method is described for the determination of some steroidal hormones in adrenal tissue. The following steroids were measured: pregnenolone, progesterone, deoxycorticosterone, corticosterone, aldosterone, 17-alpha-OH-pregnenolone, deoxycortisol, cortisol, cortisone, 17-alpha-OH-progesterone, dehydroepiandrosterone, androstendione, and testosterone. After extraction of the steroids the purification steps were performed by thin layer chromatography. Gas chromatography was used for further separation and quantitative analysis of underivatized steroids. The GC-analysis of steroids without any derivatisation makes this procedure comparatively simple and exact. Recovery of the steroid content of the tissue ranged from 30% to 70%. This method described herewith has several advantages, and allows the analysis of two tissues at the same time for a large number of adrenal steroids within two weeks.     

苎麻纤维增强聚乳酸复合材料性能研究

通过密炼?注塑成型工艺制备了不同苎麻纤维含量的聚乳酸基复合材料,研究了纤维含量对复合材料性能的影响规律,并揭示了纤维增强机理。研究表明,苎麻纤维的添加提高了复合材料的耐热性能,尤其是当纤维质量分数为40%时,复合材料的热变形温度提高了10.5%。此外,苎麻纤维均匀地分散在基体中,由于纤维与聚乳酸的界面强度较弱,断面上有大量的纤维拔出和纤维孔洞;差示扫描量热仪测试表明高含量的纤维限制了聚乳酸分子链的运动,促进复合材料形成更加致密完善的晶核;同时,流变行为也表明苎麻纤维含量的增加有助于提高复合材料的黏弹响应和复合黏度;最后,苎麻纤维的加入提高了复合材料的拉伸和弯曲强度,且随纤维含量的增加而增大。与聚乳酸相比,当纤维质量分数为40%时复合材料的拉伸和弯曲强度分别提高了30%和21.9%。      

A new method for tracheobronchial implantation of a self expandable endoprosthesis (stent)

In the treatment of malignant tracheobronchial stenosis stents are playing an increasing role. Most frequently silicone stents are used. A long-term complication of brachytherapy and laser is malacia-tracheobronchial stenosis. To improve the dyspnea and stridor, a novel technique is described by implanting a self-expanding metal-stent via the flexible fiberoptic-bronchoscope only in local anaesthesia. This procedure is fast, easy to handle and atraumatic and has lower risk of perforation, fistula, migration, bleeding and plugging by phlegm. The self-expanding metal-stent is very useful and reasonably effective for palliative treatment of tracheomalacia and malignant tracheobronchial stenosis.     

A new method for in vivo evaluation of biofilms on surface-modified silicone rubber voice prostheses

A new method is presented that permits a rapid and accurate in vivo evaluation of biofilm formation on surface-modified silicone rubber voice prostheses. The method is based on partial modification of a Groningen button voice prosthesis by exposing half of the prosthesis to an argon plasma. This results in one side of the prosthesis becoming hydrophilic while leaving the unmodified side hydrophobic as a control. Modified prostheses were placed in patients for an evaluation period of approximately 4 weeks. Despite making the silicone rubber surface hydrophilic, biofilm formation was stimulated when compared to unmodified, hydrophobic silicone rubber. Findings show that biofilm formation on voice prostheses is influenced by hydrophobicity of a silicone rubber surface. The method of partial surface modification used was seen to be suitable for demonstrating such influences regardless of nutrition and other variations in the patient's lifestyle. Microbiological analysis of the biofilms on both sides of the prosthesis valve did not show any changes in microbial composition, with Candida albicans, streptococci and staphylococci being the most commonly isolated strains.     

A dual mechanism for the anticonvulsant action of aminooxyacetic acid

The intramuscular injection of aminooxyacetic acid (AOAA) into mice elevated the concentration of gamma-aminobutyric acid (GABA) in the brain, inhibited glutamic acid decarboxylase activity and delayed the onset of isonicotinic acid hydrazide induced seizures. Analyses of these results and of those obtained previously by the authors and other workers indicated that the anticonvulsant action of AOAA involved two mechanisms. One, involving GABA metabolism, was most effective 6 h after AOAA administration, and the other, not involving GABA, was maximally effective 1.5 h after AOAA injection and was completely absent after 6 h. Depending on the convulsant agent under study, the mechanism of the anticonvulsant action of AOAA was purely of the GABA type, purely of the non-GABA type or a combination of both types.     

2-(1,3,4-三氮唑偶氮)-5-二乙氨基苯甲酸作为络合滴定铜指示剂的研究

研究了新指示剂 2 ( 1,3 ,4 三氮唑偶氮 ) 5 二乙氨基苯甲酸 (TZDBA)作为络合滴定铜指示剂的分析性能。结果表明 ,在 pH 10 0的NH3·H2 O -NH4 Cl缓冲溶液中 ,加入 10滴指示剂TZDBA ,用EDTA溶液进行目视滴定 ,滴定终点溶液由紫色变为亮绿色 ,变色敏锐 ,准确度高 ,具有一定的实用价值 ,用于锰黄铜和铜盐中铜的测定 ,结果满意     

Mechanism of the negative action of a bacterial lipopolysaccharide (pyrogenal) on the course of experimental ornithosis infection

The intravenous injection of pyrogenal into mice following their intravenous infection aggravates the course of ornithosis infection and leads to more intensive multiplication of the infective agent. After the injection of pyrogenal is discontinued a change in the course of the infectious process occurs and the infective agent is quickly eliminated from the body. This is accompanied by increased formation of specific antibodies. The negative effect of pyrogenal is due to its high toxicity for macrophages containing the colonies of the infective agent, the suppression of the reaction of neutrophil leukocytes at the sites of the destruction of infected cells and the suppression of the general reaction of the mononuclear phagocytic system. Pyrogenal does not damage lymphoid tissue and even produces an immunostimulant effect on it, but the increased immune response can be completely realized only after pyrogenal injections are stopped and the reaction of mononuclear phagocytes is restored.     

Development of a detection system for histidine decarboxylating lactic acid bacteria based on DNA probes, PCR and activity test

On the basis of the comparison of the nucleotide sequences of the histidine decarboxylase genes (hdcA) of Lactobacillus 30A and Clostridium perfringens and the amino acid sequences of these histidine decarboxylases and those of Lactobacillus buchneri and Micrococcus, oligonucleotides unique to the hdcA genes were synthesized and used in PCR. All histidine-decarboxylating lactic acid bacteria gave a signal with primer set JV16HC/JV17HC in PCR. In addition to this primer set, CL1/CL2 and CL1/JV17HC were also useful for the detection of histamine-forming Leuconostoc aenos strains in PCR. The 150 base pair amplification product of the decarboxylating Leuc. aenos strain generated with primer set CL1/CL2 was sequenced. Alignment studies showed a high degree of relatedness among the hdcA gene products of Gram-positive bacteria. The amplification products of the hdcA genes from Lac. buchneri and Leuct. aenos were used to serve as a DNA probe in hybridization studies. All histidine-decarboxylating lactic acid bacteria gave a hybridization signal with the DNA probes. In hybridization only one false-positive signal with a Lactobacillus lindneri strain was observed, which was anticipated to contain a truncated hdcA gene. In addition to these DNA probe tests, a simple and reliable activity test is presented, which can be used during starter selection to test strains for histidine decarboxylase activity.     

The effect of dietary fermented milk products and lactic acid bacteria on the initiation and promotion stages of mammary carcinogenesis

A prospective weekly home surveillance study was undertaken to determine morbidity patterns within the Butajira Rural Health project in central Ethiopia. Overall prevalence of illness was 5.8% in 1216 person-years observed among rural Ethiopian children aged under 5 years. Acute respiratory infections (ARI) (prevalence 2.8%) and acute diarrhoea (2.4%) were the commonest conditions. Episodes of illness were distributed unequally among children, with a mean of 2.34 episodes per child. These included an average of 1.13 episodes of ARI (of which 0.16 had lower respiratory symptoms [ALRI]) and 1.17 episodes of acute diarrhoea. Sanitation factors were the principal risks for gastroenteritis, while living in rural areas predisposed children to ARI. Parental factors such as illiteracy were also linked to morbidity.