Nonstarter lactobacilli isolated from soft and semihard Argentinean cheeses: genetic characterization and resistance to biological barriers

Nonstarter lactic acid bacteria isolated from Argentinean cheeses were identified and characterized by focusing on their resistance to biological barriers, along with other physiological features of potential interest, in the search for future probiotic organisms. Lactobacilli were enumerated and isolated from semihard and soft cheeses made with multistrain Streptococcus thermophilus starters. Lactobacilli counts in 1-week-old cheeses were between 10(5) and 10(7) CFU/g and then reached 10(7) CFU/ g in all 1-month samples, while streptococci were always above 10(9) CFU/g. A total number of 22 lactobacilli isolates were retained, identified, and characterized by in vitro tests. Species identity was determined by carbohydrate metabolism and species-specific PCR assays. Genetic diversity was explored by random amplified polymorphic DNA (RAPD) PCR analysis. The Lactobacillus strains were assigned to the species L. casei, L. plantarum, L. rhamnosus, L. curvatus, L. fermentum, and L. perolens. All the strains studied tolerated 25 ppm of lysozyme, and most of them showed resistance to 0.3% bile. After incubation in gastric solution (pH 2.0), counts decreased by several log units, ranging from 3.2 to 7.0. The strains were able to grow in the presence of bile salts, but only three isolates were capable of deconjugation. The nonstarter lactobacilli that were assayed fermented the prebiotic substrates (especially lactulose and inulin). Some strains showed high cell hydrophobicity and beta-galactosidase activity, as well as inhibitory activity against pathogenic bacteria. It was concluded that most of the lactobacilli isolated in this study demonstrated resistance to biological barriers and physiological characteristics compatible with probiotic properties, which make them suitable for further research in in vivo studies aimed at identifying new probiotic organisms.     

Proteolysis in Mozzarella cheeses manufactured by different industrial processes

The objective of the present study was to investigate the influence of stretching temperature, fat content, and time of brining on proteolysis during ripening of Mozzarella cheeses. Seventeen cheese-making experiments (batches) were carried out on an industrial scale on successive days, following the standard procedure with some modifications. Fat content of cheese milk, temperature at the stretching step, and time of brining varied from one batch to another as required by the experimental design, outlined by a surface response model. Proteolysis was assessed during ripening of samples, which was prolonged for at least 3 mo, by means of electrophoresis, nitrogen fractions, and soluble peptide mapping. The amount of soluble nitrogen at pH 4.6 was not significantly different in cheeses obtained by diverse procedures, but it increased during ripening of all samples. This result was coincident with the breakdown of α_s1- and β-caseins evidenced by electrophoresis, which reached similar extents at late stages of ripening, regardless of the cheese-making process. Multivariate analysis on soluble peptide profiles obtained by liquid chromatography also detected sample grouping according to ripening time, but did not evidence any separation caused by the cheese-making technology. We concluded that the changes in the cheese-making process assayed in this work were insufficient to produce significant differences in proteolysis of the cheeses. Ripening time had more influence on proteolysis of Mozzarella cheeses than any other assayed variable.     

Thermal Annealing of Gold Thin Films on the Structure and Surface Morphology Using RF Magnetron Sputtering

Gold(Au)thin films were deposited on SiO2 substrate under argon(Ar)gas environment using RF(radio frequency)magnetron sputtering at room temperature for various...     

Distinct annexin subfamilies in plants and protists diverged prior to animal annexins and from a common ancestor

Annexin homologues in the kingdoms of Planta and Protista were characterized by molecular sequence analysis to determine their phylogenetic and structural relationship with annexins of Animalia. Sequence fragments from 19 plant annexins were identified in sequence databases and composite sequences were also assembled from expressed sequence tags for Arabidopsis thaliana. Length differences in protein aminotermini and evidence for unique exon splice sites indicated that plant annexins were distinct from those of animals. A third annexin gene of Giardia lamblia (Anx21-Gla) was identified as a distant relative to other protist annexins and to those of higher eukaryotes, thus providing a suitable outgroup for evolutionary reconstruction of the family tree. Rooted evolutionary trees portrayed protist, plant, and Dictyostelium annexins as early, monophyletic ramifications prior to the appearance of closely related animal annexin XIII. Molecular phylogenetic analyses of DNA and protein sequence alignments revealed at least seven separate plant subfamilies, represented by Anx18 (alfalfa, previously classified), Anx22 (thale cress), Anx23 (thale cress, cotton, rape and cabbage), Anx24 (bell pepper and tomato p34), Anx25 (strawberry, horseradish, pea, soybean, and castor bean), Anx26-Zma, and Anx27-Zma (maize). Other unique subfamilies may exist for rice, tomato p35, apple, and celery annexins. Consensus sequences compiled for each eukaryotic kingdom showed some breakdown of the "annexin-fold" motif in repeats 2 and 3 of protist and plant annexins and a conserved codon deletion in repeat 3 of plants. The characterization of distinct annexin genes in plants and protists reflects their comparable diversity among animal species and offers alternative models for the comparative study of structure-function relationships within this important gene family.     

Simulation of friction welding of alumina and steel with aluminum interlayer

Friction welding is a complicated metallurgical process that is accompanied by frictional heat generation and plastic deformation. Since the thermal cycle of friction welding is very short, simulation becomes very significant. In the present work, a finite element-based numerical model has been developed to understand the thermo-mechanical phenomenon involved in the process of friction welding. The developed model is capable of predicting thermal distribution during friction welding of ceramics with metal using an aluminum interlayer for various time increments. Frictional heating at the interfacial region consumes the aluminum interlayer and establishes a bond between alumina and mild steel. Though there is mechanical mixing, the bond is incomplete in the aluminum-alumina interface. Due to the variation of thermal properties between alumina and mild steel, more amount of thermal stress is induced at the joint interface. Numerical simulation predicts the formation of residual stress in the alumina-mild steel side of the interface. This leads to incomplete interlocking that results in poor joint strength.     

Proteolytic activity of three probiotic strains in semi-hard cheese as single and mixed cultures: Lactobacillus acidophilus,Lactobacillus paracasei and Bifidobacterium lactis

The influence of three probiotic strains (Lactobacillus acidophilus, Lactobacillus paracasei and Bifidobacterium lactis) in semi-hard cheese proteolysis patterns was assessed. Probiotics were inoculated both as single cultures and as a three-strain mix, and added to milk either after a pre-incubation step or directly to the vat. B. lactis did not show any effect on proteolysis of cheeses, while L. paracasei showed limited impact at the end of the ripening. In contrast, L. acidophilus significantly influenced secondary proteolysis from the beginning of ripening, causing an increase in the levels of small nitrogen-containing compounds and free amino acids and changes in the peptide profiles. The effect of Lactobacillus acidophilus on peptidolysis was more noticeable when it was added to cheese–milk after pre-incubation in an enriched milk fat substrate. Similar results obtained with the three-strain mixed culture, suggesting that L. acidophilus played a major role in secondary proteolysis of probiotic cheeses in this trial.     

Effect of high-pressure homogenisation on metabolic potential of Lacticaseibacillus paracasei 90: in vitro and in situ studies in fermented milk and semihard cheese

The influence of high-pressure homogenisation (HPH) at 100 MPa on Lacticaseibacillus paracasei 90 (L90) was studied in vitro and in situ (fermented milk and cheese). Lysis and injury signs were observed in cells treated with HPH, which were linked to the release of intracellular enzymes and changes in the metabolic activity of L90. HPH treatment led to a higher lactic acid content and lower pH and pyruvic acid levels in fermented milk. The microbiological and peptide profiles of cheeses were modified by using cells or cell-free extracts of L90. Finally, this study suggests that L90 could release bioactive peptides.     

An audit of magnetic resonance imaging in the paediatric orthopaedic setting

AIMS: To determine when magnetic resonance imaging (MRI) is helpful in the management of a selected group of paediatric orthopaedic patients. METHODS: A retrospective analysis of 131 MRI scans was undertaken with allocation into seven categories based on clinical presentation. RESULTS: MRIs performed for spinal, congenital and intra-articular pathology, as well as for growth plate assessment correlated well with subsequent clinical and/or surgical findings. Three of ten MRIs (30%) incorrectly assessed whether a foreign body was present with a sensitivity of 0.60 and specificity of 0.80. Three of 20 MRIs (15%) could not accurately distinguish between oedema/effusion and frank infection. Here sensitivity was 1.00 and specificity was 0.73. MRIs performed for assessment of tumours were accurate with respect to margins and extent. Assessment of pathology with MRI was never the indication for MRI, thus it was not surprising that in four of 27 soft tissue tumours (sensitivity of 0.88 and specificity of 0.63) MRI did not correlate with subsequent histological findings. CONCLUSIONS: MRI plays an important role in the assessment of a wide range of musculo-skeletal pathology. MRI does not, and could not be expected to, replace the need for incisional biopsy for tumour diagnosis. It must be used with caution where tissues have been previously explored for foreign bodies. Interpretation of MRI in musculoskeletal infection must consider its timing in the evolution of the patient's infection.     

Percutaneous aspiration liver biopsy using a large-caliber disposable needle: a preliminary report

A modification of the aspiration liver biopsy technique using a large-caliber disposable needle is described in an 18-month experience. One hundred forty liver biopsies were performed, obtaining adequate tissue in 98% of the patients. Complications occurred in 12 patients and were limited to pain at the biopsy site, epigastrium, or right shoulder; one instance of tachycardia and three of transient hypotension occurred. Thirty patients studied prospectively with liver scans and hematologic parameters failed to disclose subclinical complications. While the number of patients biopsied is still too small to provide definite conclusions , it appears that this technique is safe, similar and has a very high yield of excellent specimens. In addition, the needle offers the advantage of being disposable and easy to use by a single operator.