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Biomedical subjects

A Ricciardi

Publications and source records attributed to A Ricciardi.

At least 19 recordsLinked to original sources
PubMed2001

Yeasts from Water Buffalo Mozzarella, a traditional cheese of the Mediterranean area.

Countries of the Mediterranean area are characterized by production of artisanal cheeses, obtained from goat, sheep, cow and buffalo raw milk. The numbers and species of yeasts in the different cheeses are variable, but some species are more frequently detected than others. Kluyveromyces marxianus, K. lactis with their anamorph, Candida kefir, Debaryomyces hansenii and C. famata, C. colliculosa and C. catenulata are dominant species in several cheeses. However, Saccharomyces cerevisiae is often detected in pasta filata cheeses, such as Water Buffalo Mozzarella (WBM) or Cacio Cavallo Podolico. Recently, a comprehensive study of yeasts isolated from Mozzarella cheese produced in Basilicata (Southern Italy) has been carried out. The study has focused on lactose and/or galactose fermenting species (Kluyveromyces and Saccharomyces) to evaluate their role on the functional and sensory properties of the product. End products in milk were evaluated and the biodiversity in terms of production of sulphur dioxide, higher alcohols, ethyl acetate, and acetaldehyde was studied. In particular, S. cerevisiae strains from Water Buffalo Mozzarella cheese, compared to strains isolated from different habitats, such as wine, exhibited considerable difference in the production of some volatile compounds. The diversity observed could be related to the particular microhabitat of S. cerevisiae occurring in whey cheese of water buffalo milk.

Animals↗
PubMed2000

Do structural deviations between toxins adopting the same fold reflect functional differences?

Three-finger proteins form a structurally related family of compounds that exhibit a great variety of biological properties. To address the question of the prediction of functional areas on their surfaces, we tentatively conferred the acetylcholinesterase inhibitory activity of fasciculins on a short-chain curaremimetic toxin. For this purpose, we assimilated the three-dimensional structure of fasciculin 2 with the one of toxin alpha. This comparison revealed that the tips of the first and second loops, together with the C terminus residue, deviated most. A first recombinant fasciculin/toxin alpha chimera was designed by transferring loop 1 in its entirety together with the tip of loop 2 of fasciculin 2 into the toxin alpha scaffold. A second chimera (rChII) was obtained by adding the point Asn-61 --> Tyr substitution. Comparison of functional and structural properties of both chimeras show that rChII can accommodate the imposed modifications and displays nearly all the acetylcholinesterase-blocking activities of fasciculins. The three-dimensional structure of rChII demonstrates that rChII adopts a typical three-fingered fold with structural features of both parent toxins. Taken together, these results emphasize the great structural flexibility and functional adaptability of that fold and confirm that structural deviations between fasciculins and short-chain neurotoxins do indeed reflect functional diversity.

Amino Acid Sequence↗
PubMed2000

Stability of a structural scaffold upon activity transfer: X-ray structure of a three fingers chimeric protein.

Fasciculin 2 and toxin alpha proteins belong to the same structural family of three-fingered snake toxins. They act on different targets, but in each case the binding region involves residues from loops I and II. The superimposition of the two structures suggests that these functional regions correspond to structurally distinct zones. Loop I, half of loop II and the C-terminal residue of fasciculin 2 were therefore transferred into the toxin alpha. The inhibition constant of the resulting chimera is only 15-fold lower than that of fasciculin 2, and as expected the potency of binding to the toxin alpha target has been lost. In order to understand the structure-function relationship between the chimera and its "parent" molecules, we solved its structure by X-ray crystallography. The protein crystallized in space group P3(1)21 with a=b=58.5 A, and c=62.3 A. The crystal structure was solved by molecular replacement and refined to 2.1 A resolution. The structure belongs to the three-fingered snake toxin family with a core of four disulphide bridges from which emerge the three loops I, II and III. Superimposition of the chimera on fasciculin 2 or toxin alpha revealed an overall fold intermediate between those of the two parent molecules. The regions corresponding to toxin alpha and to fasciculin 2 retained their respective geometries. In addition, the chimera protein displayed a structural behaviour similar to that of fasciculin 2, i.e. dimerization in the crystal structure of fasciculin 2, and the geometry of the region that binds to acetylcholinesterase. In conclusion, this structure shows that the chimera retains the general structural characteristics of three-fingered toxins, and the structural specificity of the transferred function.

Amino Acid Sequence↗
PubMed1999

Production, recovery and purification of bacteriocins from lactic acid bacteria.

Bacteriocins produced by lactic acid bacteria are a heterogeneous group of peptide inhibitors which include lantibiotics (class I, e.g. nisin), small heat-stable peptides (class II, e.g. pediocin AcH/PA1) and large heat-labile proteins (class III, e.g. helveticin J). Many bacteriocins belonging to the first two groups can be successfully used to inhibit undesirable microorganisms in foods, but only nisin is produced industrially and is licensed for use as a food preservative in a partially purified form. This review focuses on the production and purification of class I and class II bacteriocins from lactic acid bacteria. Bacteriocin production is growth associated but the yield of bacteriocin per unit biomass is affected by several factors, including the producing strain, media (carbohydrate and nitrogen sources, cations, etc.) and fermentation conditions (pH, temperature, agitation, aeration and dilution rate in continuous fermentations). Continuous fermentation processes with cell recycle or immobilized cells can result in a dramatic improvement in productivity over batch fermentations. Several simple recovery processes, based on adsorbing bacteriocin on resins or silica compounds, have been developed and can be used to build integrated production processes.

Adsorption↗
PubMed1998

The combined effect of nisin, leucocin F10, pH, NaCl and EDTA on the survival of Listeria monocytogenes in broth.

The combined effect of the bacteriocins nisin (1-2100 IU/ml) and leucocin F10 (1-2100 AU/ml), pH (4.7-6.5), NaCl (0.7-4.5% w/l), ethylene diaminetetraacetic acid disodium salt (EDTA, 0.08-4.72 mmol/l) and inoculum level (10(3)-10(8) cfu/ml) on the survival of a pool of three strains of Listeria monocytogenes in broth was evaluated in three factorial experiments. Several factor combinations were found to prevent growth. Logistic regression analysis of the categorical data (survival/no survival) was used to generate predictive models for the probability of survival in 0.01 ml (P0.01) or 1 ml (P1). Predicted and observed probabilities of survival were not significantly different in 72% and 68.9% of treatments for P0.01 and P1, respectively. Unsafe predictions were obtained in 9.4% and 14.8% of treatments for P0.01 and P1, respectively. Nisin had a major effect on the probability of survival but the addition of leucocin F10 was necessary to prevent the survival of L. monocytogenes. Lower pH values significantly decreased the probability of survival, while NaCl and EDTA had only a minor effect. Doses of bacteriocins > 250 AU/ml, pH < 5.6 and EDTA > 0.2 mmol/l (0.074 g/l) were needed to reliably prevent survival of Listeria monocytogenes.

Bacteriocins↗
PubMed1997

Growth and bacteriocin production by Enterococcus faecium DPC1146 in batch and continuous culture.

Production of the bacteriocin enterocin 1146 (E1146) by Enterococcus faecium DPC1146 was studied in batch and continuous fermentation. Growth was strongly inhibited by lactic acid. In batch fermentations maximum E1146 activity (2.8 MBU L-1) was obtained in 9 h with 20 g L-1 glucose. Increase in initial glucose concentration did not lead to a proportional increase in E1146 activity. A simple linear model was found to be adequate to explain the relationship between specific bacteriocin production rate and specific growth rate in batch fermentations with initial glucose concentration higher than 20 g L-1. Maximum bacteriocin activity (2.9-3.2 MBU L-1) was obtained in continuous fermentations at dilution rates between 0.12 and 0.17 h-1 and specific bacteriocin production rate increased linearly with dilution rate.

Bacteriocins↗
PubMed1996

Chaetogaster limnaei (annelida: oligochaeta) as a parasite of the zebra mussel Dreissena polymorpha, and the quagga mussel Dreissena bugensis (mollusca: bivalvia).

Dreissenid mussels, Dreissena polymorpha and D. bugensis, were found to be infected by the naidid oligochaete Chaetogaster limnaei at four sites in the St. Lawrence River. This is the first report of this species infecting dreissenids anywhere in the world. Most worms inhabited the mantle cavity, where they caused erosion of the mantle and gill epithelia as determined by histopathological examination. Others penetrated various tissues; one had invaded the ovary and was feeding on oocytes and ovarian tissues. Of 606 mussels examined, 166 (27.4%) harbored at least 1 C. limnaei. The prevalence varied between 1% and 80%, depending on the collection site and date. The worms were slightly but significantly more prevalent in D. bugensis than in D. polymorpha. The intensity ranged from 1 to 18 worms per infected host. Variations in prevalence and intensity were not related to the size or sex of the host, but the data did suggest some seasonality.

Animals↗
PubMed1996

Leucocin F10, a bacteriocin from Leuconostoc carnosum.

Leucocin F10 is a bacteriocin produced by a strain of Leuconostoc carnosum isolated from fermented meat. It is sensitive to proteolytic enzymes and alpha-amylase, heat resistant up to 121 degrees C for 10 min at pH 3.0 and is inhibitory to Listeria spp., Leuconostoc spp., Enterococcus faecalis and Lactobacillus sake. Bactericidal activity against L. innocua in potassium phosphate buffer was strongly dependent of the growth phase of the indicator cells. A rapid sub-lethal damage, followed by slow death was observed for log-phase cells of L. innocua. The bacteriocin induced a rapid release of K+ from energized L. innocua cells. Leucocin F10 production occurred at temperatures between 4 and 30 degrees C and followed a primary metabolite kinetics in batch fermentations at controlled pH. Maximum bacteriocin activity was obtained at pH 6.0.

Bacteriocins↗
PubMed1996

[Medullary carcinoma of the thyroid].

Medullary thyroid carcinoma represents 4-8% of thyroid malignancies; regional nodal involvement is commonly found, even at the time of first surgical approach. In these patients after surgical resection, other therapeutic choices are really limited. The Authors evaluated their experience in the period 1981-1994, concerning 14 patients, 9 females and 5 males, all affected with sporadic MTC. Diagnosis was preoperative in 10 patients and intraoperative in 4; as for the staging: in 8 patients the tumor resulted confined to the thyroid, while in the remaining 6 patients it was extra-thyroidal. In 5 patients a total thyroidectomy with regional lymphadenectomy was performed, with in 6 patients a total thyroidectomy with cervico-mediastinic total lymphadenectomy was achieved. Survival was evaluated with a short, follow-up (3 months) and calculated using the K-Mayer method. Average survival was: 5 years in patients undergoing only total thyroidectomy; 3 years and 1 month in patients undergoing total thyroidectomy and lymphadenectomy; 6 months in patients undergoing no treatment at all. Among the factors negatively affecting patients survival, the Authors pointed out: metastasis occurrence; incomplete resection and mediastinal metastasis. In conclusion surgical resection (total thyroidectomy) associated with radical lymphadenectomy resulted to be a good approach. However, prognostic factors require further investigation.

Adult↗
PubMed1994

Cotrel-dubousset instrumentation in thoracolumbar seat belt-type and flexion-distraction injuries.

For many years, all the internal fixation devices available for the surgical treatment of thoracolumbar fractures [Harrington rods (HR); Luque rods (LR); Hartshill rectangle (HTR); Roy Camille plates (RCP)] were not always able to distribute all the reductive strains (distraction, compression, derotation), or to guarantee solid stabilization without external supports. In some cases (with HR), only distraction forces might be applied, but stability of the assembly was very poor. Otherwise (with LR, HTR, or RCP), stability was well achieved using segmental fixation systems (with SSW, screws), but reduction was possible only by deflecting the spine towards the rods (or plates), by winging the sublaminar wires (or screws). Restoration of normal sagittal alignment was also very difficult to obtain. The use of internal fixation systems for reduction of thoracolumbar fractures when distraction or compression forces are needed are essential for the spinal surgeon and the patient. In some cases of thoracolumbar fractures (seat belt; flexion-distraction), in fact, the use of distraction forces is not suitable, leading only to overdistraction, not to reduction. The introduction of Cotrel-Dubousset instrumentation (CDI) in 1983, and its subsequent use in spinal traumatology, seems to answer all these unresolved questions.

Adult↗
PubMed1994

Influence of pH on the production of enterocin 1146 during batch fermentation.

The production of enterocin 1146, a bacteriocin from Enterococcus faecium DPC1146, was studied during batch fermentation at pH 5, 5.5, 6 and 6.5. The bacteriocin was produced throughout the growth of the micro-organism, showing primary metabolite kinetics. Bacteriocin production stopped at the end of growth and was followed by a decrease in activity due primarily to adsorption on the cells of the producer. The optimal pH for enterocin 1146 production was 5.5, because of higher bacteriocin yield per unit of biomass and slower adsorption/degradation, while optimal pH for growth was between 6.0 and 6.5.

Adsorption↗