Effects of serum albumin on the photophysical characteristics of synthetic and endogenous protoporphyrin IX.

The study of the interaction of synthetic protoporphyrin IX (PpIXs) and protoporphyrin IX extracted from Harderian glands of ssp Rattus novergicus albinus rats (PpIXe) with bovine serum albumin (BSA) was conducted in water at pH 7.3 and pH 4.5 by optical absorption and fluorescence spectroscopies. PpIXs is present as H- and J-aggregates in equilibrium with themselves and with monomers. The PpIXs charge is 2- at pH 7.3 and 1- at pH 4.5. This increases its aggregation at pH 4.5 and shifts the equilibrium in favor of J-aggregates. In spite of electrostatic attraction at pH 4.5, where BSA is positive, the binding constant (Kb) of PpIXs to BSA is 20% less than that at pH 7.3, where BSA is negative. This occurs because higher aggregation of PpIXs at pH 4.5 reduces the observed Kb value. At both pHs, water-soluble PpIXe exists in the monomeric form with the charge of 1- and its Kb exceeds that of PpIXs. At pH 4.5, its Kb is 12 times higher than that at pH 7.3 due to electrostatic attraction between the positively charged BSA and the negatively charged PpIXe. The higher probability of PpIXe binding to BSA makes PpIXe more promising as a fluorescence probe for fluorescence diagnostics and as a photosensitizer for photodynamic therapy. The existence of PpIXe in the monomeric form can explain its faster cell internalization. Aggregation reduces quantum yields and lifetimes of the PpIXs excited states, which explains higher phototoxicity of PpIXe toward malignant cells compared with PpIXs.

Effects of serum albumin on the photophysical characteristics of synthetic and endogenous protoporphyrin IX

The study of the interaction of synthetic protoporphyrin IX (PpIXs) and protoporphyrin IX extracted from Harderian glands of ssp Rattus novergicus albinus rats (PpIXe) with bovine serum albumin (BSA) was conducted in water at pH 7.3 and pH 4.5 by optical absorption and fluorescence spectroscopies. PpIXs is present as H- and J-aggregates in equilibrium with themselves and with monomers. The PpIXs charge is 2− at pH 7.3 and 1− at pH 4.5. This increases its aggregation at pH 4.5 and shifts the equilibrium in favor of J-aggregates. In spite of electrostatic attraction at pH 4.5, where BSA is positive, the binding constant (Kb) of PpIXs to BSA is 20% less than that at pH 7.3, where BSA is negative. This occurs because higher aggregation of PpIXs at pH 4.5 reduces the observed Kb value. At both pHs, water-soluble PpIXe exists in the monomeric form with the charge of 1− and its Kb exceeds that of PpIXs. At pH 4.5, its Kb is 12 times higher than that at pH 7.3 due to electrostatic attraction between the positively charged BSA and the negatively charged PpIXe. The higher probability of PpIXe binding to BSA makes PpIXe more promising as a fluorescence probe for fluorescence diagnostics and as a photosensitizer for photodynamic therapy. The existence of PpIXe in the monomeric form can explain its faster cell internalization. Aggregation reduces quantum yields and lifetimes of the PpIXs excited states, which explains higher phototoxicity of PpIXe toward malignant cells compared with PpIXs.

Glutamine use in feeding juvenile pirarucu, Arapaima gigas (Schinz, 1822) / [Uso da glutamina na alimentação de juvenis de pirarucu, Arapaima gigas (Schinz, 1822)]

This study aimed to evaluate glutamine supplementation effects on variables of growth performance, body composition, intestinal morphology and enzymatic aspects of juvenile Arapaima gigas. Research was conducted at the Fish Nutrition and Feeding Laboratory, where 60 examples of pirarucu (initial average weight of 82.12g) were distributed over 15 polyethylene tanks (310L), in a completely randomized design, with five treatments and three repetitions (four fish per experimental unit). Experimental diets were prepared containing five inclusion levels of the amino acid glutamine (0.0, 0.5, 1.0, 1.5 and 2.0%), supplied three times a day for 45 days. Quadratic effect was observed for the variables of growth performance, weight gain, food consumption, food conversion, and specific growth and protein efficiency rates. A significant effect was observed on intestinal villi at the height of the anterior portion and on activity of the enzyme's alkaline proteases, lipase, amylase and aspartate aminotransferase. However, glutamine supplementation had no significant effect on survival rate. Inclusion of 1.02% of glutamine in the diets of juvenile pirarucu improved growth performance and influenced intestinal villi height and activity of important digestive enzymes, favoring nutrient digestion and absorption.(AU)

Objetivou-se avaliar os efeitos da suplementação com glutamina sobre variáveis de desempenho produtivo, composição corporal, morfologia do intestino e aspectos enzimáticos de juvenis de Arapaima gigas. O experimento foi conduzido no Laboratório de Nutrição e Alimentação de Peixes, onde 60 exemplares de pirarucu (peso médio inicial de 82,12g) foram distribuídos em 15 tanques de polietileno (310L), em delineamento inteiramente ao acaso, com cinco tratamentos e três repetições (quatro peixes por unidade experimental). As dietas experimentais foram confeccionadas contendo cinco níveis de inclusão do aminoácido glutamina (0,0; 0,5; 1,0; 1,5 e 2,0%), fornecidas três vezes ao dia, ao longo de 45 dias. Foi observado efeito quadrático para variáveis de desempenho produtivo: ganho de peso, consumo alimentar, conversão alimentar, taxa de crescimento específico e taxa de eficiência proteica. Observou-se ainda efeito significativo sobre a altura das vilosidades da porção anterior do intestino e a atividade das enzimas: proteases alcalinas, lipase, amilase e aspartato aminotransferase. Entretanto, a suplementação com glutamina não influenciou significativamente a sobrevivência dos animais. A adição de 1,02% de glutamina nas dietas para juvenis de pirarucu melhorou o desempenho produtivo e influenciou a altura das vilosidades intestinais e a atividade de enzimas digestivas importantes, favorecendo a digestão e a absorção de nutrientes.(AU)

Lipid composition modulates ATP hydrolysis and calcium phosphate mineral propagation by TNAP-harboring proteoliposomes.

Bone biomineralization is mediated by a special class of extracellular vesicles, named matrix vesicles (MVs), released by osteogenic cells. The MV membrane is enriched in sphingomyelin (SM), cholesterol (Chol) and tissue non-specific alkaline phosphatase (TNAP) compared with the parent cells' plasma membrane. TNAP is an ATP phosphohydrolase bound to cell and MV membranes via a glycosylphosphatidylinositol (GPI) anchor. Previous studies have shown that the lipid microenvironment influences the catalytic activity of enzymes incorporated into lipid bilayers. However, there is a lack of information about how the lipid microenvironment controls the ability of MV membrane-bound enzymes to induce mineral precipitation. Herein, we used TNAP-harboring proteoliposomes made of either pure dimyristoylphosphatidylcholine (DMPC) or DMPC mixed with either Chol, SM or both of them as MV biomimetic systems to evaluate how the composition modulates the lipid microenvironment and, in turn, TNAP incorporation into the lipid bilayer by means of calorimetry. These results were correlated with the proteoliposomes' catalytic activity and ability to induce the precipitation of amorphous calcium phosphate (ACP) in vitro. DMPC:SM proteoliposomes displayed the highest efficiency of mineral propagation, apparent affinity for ATP and substrate hydrolysis efficiency, which correlated with their highest degree of membrane organization (highest ΔH), among the tested proteoliposomes. Results obtained from turbidimetry and Fourier transformed infrared (FTIR) spectroscopy showed that the tested proteoliposomes induced ACP precipitation with the order DMPC:SM>DMPC:Chol:SM≈DMPC:Chol>DMPC which correlated with the lipid organization and the presence of SM in the proteoliposome membrane. Our study arises important insights regarding the physical properties and role of lipid organization in MV-mediated mineralization.

Cholesterol Regulates the Incorporation and Catalytic Activity of Tissue-Nonspecific Alkaline Phosphatase in DPPC Monolayers.

Matrix vesicles (MVs) are a special class of extracellular vesicles that drive bone and dentin mineralization by providing the essential enzymes and ions for the nucleation and propagation of mineral crystals. Tissue-nonspecific alkaline phosphatase (TNAP) is an integral protein of MV membrane and participates in biomineralization by hydrolyzing extracellular pyrophosphate (PPi), a strong mineralization inhibitor, and forming inorganic phosphate (Pi), necessary for the growth of mineral crystals inside MVs and their propagation once released in the extracellular matrix. MV membrane is enriched in cholesterol (CHOL), which influences the incorporation and activity of integral proteins in biologic membranes; however, how CHOL controls the incorporation and activity of TNAP in MV membrane has not yet been elucidated. In the present study, Langmuir monolayers were used as a MV membrane biomimetic model to assess how CHOL affects TNAP incorporation and activity. Surface pressure-area (π-A) isotherms of binary dipalmitoilphosphatidylcholine (DPPC)/CHOL monolayers showed that TNAP incorporation increases with CHOL concentration. Infrared spectroscopy showed that CHOL influences the conformation and orientation of the enzyme. Optical-fluorescence micrographs of the monolayers revealed the tendency of TNAP to incorporate into CHOL-rich microdomains. These data suggest that TNAP penetrates more efficiently and occupies a higher surface area into monolayers with a lower CHOL concentration due to the higher membrane fluidity. However, the quantity of enzyme transferred to solid supports as well as the enzymatic activity were higher using monolayers with a higher CHOL concentration due to increased rigidity that changes the enzyme orientation at the air-solid interface. These data provide new insights regarding the interfacial behavior of TNAP and CHOL in MVs and shed light on the biochemical and biophysical processes occurring in the MV membrane during biomineralization at the molecular level.

Interface-driven Sr-morin complexation at Langmuir monolayers for bioactive coating design.

Flavonoid-metal complexes are widely studied because of their interesting luminescent behavior and biological activity. Despite the extensive exploration of flavonoid-metal coordination processes in solution, the formation of complexes using the flavonoid molecule inserted in a lipid membrane has been little investigated. This effect could provide important insight into the biological activity of flavonoids at lipid membranes and could represent an attractive strategy to design supramolecular structures. Here, we studied the complexation between Sr2+ and morin inserted in an octadecylphosphonic acid (OPA) Langmuir monolayer. This is a relevant system due to the synergism imposed by the association of the Sr2+ ability to control bone formation/resorption with the morin antioxidative effect. Morin incorporation into the OPA monolayers and further Sr2+ complexation were monitored by surface pressure isotherms. Electronic absorption spectroscopy and fluorescence techniques showed Sr-morin complexation both in solution and at the air-liquid interface. Although morin complexation has been described to occur only at basic pH, the specific thermodynamic properties at the air-liquid interface drove metal complexation. LB films were deposited on Ti surfaces, and the resulting OPA/Sr-morin coatings exhibited high surface free energy and increase on its polar component. This optimized surface feature supported further serum protein adsorption and osteoblast growth and differentiation, indicating that these lipid-based coatings are promising for bioactive coating design. This study paves the way for the use of this lipid-based coating in the design of implants for faster osteointegration. Moreover, flavonoid-metal complexation at membranes could also help to shed light on the biological role played by flavonoids.

Lipid-mediated growth of SrCO3/CaCO3 hybrid films as bioactive coatings for Ti surfaces.

SrCO3 is frequently used as Sr2+ source in ceramic cements, but its application as bioactive coating for metallic implants has not been explored yet. Aiming at rapid osteointegration and because of the well-known Sr2+ effects on bone metabolism, researchers have sought to design Sr2+-containing biomaterials. In this context, developing simple techniques to prepare Sr2+-based coatings is a must nowadays. Here, we describe the use of a bioinspired lipid-mediated approach to grow SrCO3 hybrid films on Ti surfaces at room temperature. To obtain these coatings, we applied the Langmuir-Blodgett technique to deposit phospholipid films with high degree of organization on Ti. In this way, we expected that controlled SrCO3 crystal growth could be templated by the array of nucleation points arising from electrostatic interaction between Sr2+ and the phospholipid polar heads. To control surface composition and the amount of Sr2+ released from the coatings, we also promoted CaCO3 co-precipitation in the hybrid films. We characterized the hybrid coatings in terms of morphology, chemical structure, wettability, and ability to release Sr2+ upon immersion in biological medium. In vitro osteoblast culture on mixed SrCO3/CaCO3 films revealed that the osteogenic response depended on surface composition, as indicated by alkaline phosphatase activity overexpression, which is an early indicator of osteoblast differentiation. Results showed that the mixed SrCO3/CaCO3 hybrid film created a synergic environment for osteoblasts, and that proper Sr2+ release associated with a Ca2+-rich environment might have optimized the Sr2+ anabolic effect. In conclusion, we have proposed a bioinspired and versatile technique to grow hybrid films that can control surface composition and Sr2+ release. Our results open an opportunity to explore the use of SrCO3-based coatings for rapid metallic implant osteointegration.

Effect of the presence of cholesterol in the interfacial microenvironment on the modulation of the alkaline phosphatase activity during in vitro mineralization.

Mineralization of the skeleton starts within cell-derived matrix vesicles (MVs); then, minerals propagate to the extracellular collagenous matrix. Tissue-nonspecific alkaline phosphatase (TNAP) degrades inorganic pyrophosphate (PPi), a potent inhibitor of mineralization, and contributes Pi (Phosphate) from ATP to initiate mineralization. Compared to the plasma membrane, MVs are rich in Cholesterol (Chol) (∼32%) and TNAP, but how Chol influences TNAP activity remains unclear. We have reconstituted TNAP in liposomes of dipalmitoylphosphatidylcholine (DPPC) or dioleoylphosphatidylcholine (DOPC) combined with Chol or its derivatives Cholestenone (Achol) and Ergosterol (Ergo). DPPC plus 36% sterols in liposome increased the catalytic activity of TNAP toward ATP. The presence of Chol also increased the propagation of minerals by 3.4-fold. The catalytic efficiency of TNAP toward ATP was fourfold lower in DOPC proteoliposomes as compared to DPPC proteoliposomes. DOPC proteoliposomes also increased biomineralization by 2.8-fold as compared to DPPC proteoliposomes. TNAP catalyzed the hydrolysis of ATP more efficiently in the case of the proteoliposome consisting of DOPC with 36% Chol. The same behavior emerged with Achol and Ergo. The organization of the lipid and the structure of the sterol influenced the surface tension (γ), the TNAP phosphohydrolytic activity in the monolayer, and the TNAP catalytic efficiency in the bilayers. Membranes in the Lα phase (Achol) provided better kinetic parameters as compared to membranes in the Lo phase (Chol and Ergo). In conclusion, the physical properties and the lateral organization of lipids in proteoliposomes are crucial to control mineral propagation mediated by TNAP activity during mineralization.

Estrogen and phenol red free medium for osteoblast culture: study of the mineralization ability.

To design an estrogen and phenol red free medium for cell culture and check its effectiveness and safety on osteoblast growth it is necessary to maintain the estrogen receptors free for tests. For this purpose, we tested some modifications of the traditional culture media: estrogen depleted fetal bovine serum; estrogen charcoal stripped fetal bovine serum and phenol red free α-MEM. The aim of this work is to examine the effects of its depletion in the proliferation, differentiation, and toxicity of mesenchymal stromal cells differentiated into osteoblasts to obtain an effective interference free culture medium for in vitro studies, focused on non-previously studied estrogen receptors. We performed viability tests using the following techniques: MTT, alkaline phosphatase specific activity, formation of mineralized matrix by Alizarin technique and analysis of SEM/EDX of mineralized nodules. The results showed that the culture media with estrogen free α-MEM + phenol red free α-MEM did not impact viability, alkaline phosphatase activity and mineralization of the osteoblasts culture compared to control. In addition, its nodules possess Ca/P ratio similar to hydroxyapatite nodules on the 14th and 21st day. In conclusion, the modified culture medium with phenol red free α-MEM with estrogen depleted fetal bovine serum can be safely used in experiments where the estrogen receptors need to be free.

Sirolimus as rescue therapy after liver transplantation.

UNLABELLED: Sirolimus has immunosuppressive properties and antitumor effects. It was prescribed in liver transplantation initially in association with calcineurin inhibitors because of its lower nephrotoxic and neurotoxic effects and its potential antitumor effects. The aim of this study was to analyze the use of sirolimus as rescue therapy for liver transplant patients. METHODS: We retrospectively analyzed all 15 patients treated with sirolimus from 2009 to 2011 among 150 liver transplantations. We analyzed pre- and postconversion data. With statistical analysis using the Student's t-test. RESULTS: Sirolimus was the immunosuppressant therapy in 15 of 150 (10%) patients. Their average age was 56.2 years (range, 42-69) including 9 men (60%). The mean time between liver transplantation and the introduction of sirolimus was 24.6 months (range, 1-120). Sirolimus remained as the sole medication for 4 patients (26.6%). The overall time of sirolimus thereby averaged 14.3 months (range, 1-18). The reasons for the introduction of sirolimus were acute rejection (n = 8; 53.3%), chronic rejection (n = 2; 13.3%), development of malignancy (n = 3; 20%) or prior hepatocellular carcinoma (n = 2; 13.3%). Among 9 patients who initiated sirolimus because of rejection, 7 (77.7%) showed improvement in serum liver enzymes. Among the 3 (33.3%) patients who displayed renal insufficiency before the introduction of sirolimus (creatinine level > 1.5 mg/dL) 1 showed improvement with a decrease of ≥50%. The average follow-up was 18 months (range, 1-36). The average sirolimus level during the first 3 months was 10.3 ng/mL (range, 6.1-19.3). All patients developed side effects such as anemia, hypertriglyceridemia, hypercholesterolemia, and infection. In conclusion, sirolimus was useful as rescue therapy.

Microbiological and physicochemical analysis of the coastal waters of southern Brazil.

The aim of this study was to assess the impact of sewage discharge on coastal waters by evaluating the influence of physicochemical parameters on the presence of enteric microorganisms in seawater samples collected from 11 beaches in Florianopolis, Santa Catarina, Brazil, over a one-year period (August 2009 to July 2010). Samples were assessed for the presence of human adenoviruses (HAdV), polyomavirus (JCPyV), hepatitis A virus (HAV), and noroviruses (HuNoV GI and GII). Escherichia coli and physicochemical parameters (salinity, temperature, pH and dissolved oxygen) were also evaluated. From the 132 samples analyzed, 55% were positive for HAdV, 51.5% for HAV, 7.5% for HuNoV GI, 4.5% for HuNoV GII, and 3% for JCPyV. E. coli levels ranged from 8 to 1325 CFU/100mL at all sites. The overall results highlight the problem of sewage discharge into coastal waters and confirm that there is no correlation between viral presence and bacterial contamination.

Portal vein thrombosis and liver transplantation: long term.

Obstruction of the portal vein may be related to constriction by malignant tumors or thrombosis associated with liver disease. We herein have reported our experience with patients undergoing liver transplantation with portal vein thrombosis (PVT) whose diagnosis was made intraoperatively. From September 1991 to May 2009, we studied 27/419 (6.4%) patients with PVT who were evaluated according to the presence of esophagogastric varices, underlying disease, malignancy, and if there was previous surgery, review of medical records on data collected prospectively. We observed 24 (88.9%) patients with PVT grade 1, 2 (7.4%) with grade 2, and 1 (3.7%) with grade 3. The average age of the PVT patients was 47.5 years; the average model for End-Stage Liver Discase score was 18.3, and the predominant diagnosis, hepatitis C cirrhosis. Eighteen underwent a sclerotherapy/ligature. The sensitivity of ultrasound for grade 1 thrombosis was 39.1%; for grade 2, 50%; and for grade 3, 100%. Portal vein thrombectomy was performed in 24 patients. In other patients (grade 2), we performed an anastomosis of the donor portal vein to the recipient gastric vein or to a greater splanchnic collateral vein. In only 1 patient was the graft performed using the donor portal vein-donor iliac vein-recipient superior mesenteric vein. None of the patients displayed PVT in the immediate postoperative period. Actuarial survivals at the years 1, 3, and 5 were 85%, 74%, and 63%, respectively. We concluded that PVT cannot be considered to be a contraindication for liver transplantation.

Steatosis and hepatic markers before and shortly after bariatric surgery.

BACKGROUND: We present new findings on liver steatosis detected in a group of 20 morbidly obese patients who were reassessed shortly after bariatric surgery (BS) by assaying hepatic markers in their serum. METHODS: We assayed aspartate aminotransferase (AST), alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, gamma-glutamyl transferase (gamma-GT), cholinesterase, cholesterol, total protein, and albumin, and measured the weight and the body mass index (BMI) of patients, before and one and three months after surgery. RESULTS: There were significant reductions in BMI following surgery and also falls in transaminases and gamma-GT activities three months after BS. No changes occurred in other parameters between periods, except that cholesterol was above reference values before BS and fell to normal levels three months after BS. CONCLUSIONS: We suggest that before undergoing surgery, the patients suffered from slight steatosis, while after BS the reduction in AST and gamma-GT indicated that this condition was corrected within three months. Moreover, these enzymes may be useful markers for excess fat in the liver.

[Historical review about the research on toxoplasmosis]. / Reseña histórica acerca de las investigaciones relacionadas con la toxoplasmosis.

Toxoplasmposis is one of the zoonotic diseases which is widely spread all over the world. It is caused by Toxoplasma gondii. In this paper we made a chronological synthesis of some of the numerous investigations that have been made in the world and in Cuba.

Concentration of airborne pollen from Cupressaceae in Lisbon.

The concentration of airborne pollen from Cupressaceae was regularly monitored++ in Lisbon during 1997 and 1999, and the phenology of flowering cypress was studied in several species of the genus from 1992 to February 2000. Both methods showed a peak of pollen abundance during the month of February, with the airborne pollen concentration decreasing strongly to March and April. The results obtained are in accordance with the literature for the Mediterranean area, but in Lisbon the peak started and finished earlier than in other Mediterranean towns already studied.

The stability of porcine rotavirus in feces.

Rotaviruses are known as major causal agents of diarrhea in humans and animals. They affect young animals in intensive rearing and cause great economic losses. This study evaluated the infectivity of porcine rotavirus maintained for 32 months at approximately 10 degrees C in the original stool specimens. Thirty stool specimens of 1-4-week-old piglets from breeding farms located in the southwest of the State of Parana were selected for this study. They were randomly chosen from stool samples positive for rotavirus RNA by polyacrylamide gel electrophoresis (PAGE) at the time of collection. The thirty stool samples maintained for 32 months were re-tested by PAGE and 11 out of 30 were still positive showing physical integrity of the eleven segments of viral RNA. In order to demonstrate the maintenance of viral infectivity processed fecal homogenates were inoculated in MA-104 cell cultures. After an average of three blind passages 5 out of 11 samples demonstrated cytopathic effect similar to that of a simian rotavirus (SA-11) used as positive control. To confirm these findings an immunofluorescence test was performed and typical cytoplasmatic granular fluorescence was observed. Electron microscopy of stool samples showed that most of the virus particles were single-shelled and some were found to be in advanced state of degradation. The viral nucleic acid extracted from six fecal specimens out of those that showed physical integrity of rotavirus RNA by PAGE were also amplified when submitted to RT-PCR demonstrating stability of viral RNA. We therefore concluded that porcine rotavirus infectivity is maintained for a long period of time in stool specimens at low temperature.

A dhfr-ts- Leishmania major Knockout Mutant Cross-protects against Leishmania amazonensis

E10-5A3 is a dhfr-ts- Leishmania major double knockout auxotrophic shown previously to induce substantial protection against virulent L. major infection in both genetically susceptible and resistant mice. We investigated the capacity of dhfr-ts- to protect against heterologous infection by L. amazonensis. The degree of protection was evaluated by immunization of BALB/c or C57BL/6 mice with E10-5A3, followed by L. amazonensis challenge. Whether immunized by subcutaneous (SC) or intravenous (IV) inoculation, susceptible and resistant mice displayed a partial degree of protection against challenge with virulent L. amazonensis. SC-immunized BALB/c mice developed lesions 40 to 65 percent smaller than non immunized mice, while IV immunization led to protection ranging from 40 to 75 percent in four out of six experiments compared to non immunized animals. The resistant C57BL/6 mice displayed comparable degrees of protection, 57 percent by SC and 49 percent by IV immunization. Results are encouraging as it has been previously difficult to obtain protection by SC vaccination against Leishmania, the preferred route for human immunization

Infecciosidade de rotavírus suíno em fezes / The infectivity of pig rotavirus in stools

Os rotavírus constituem-se nos principais patógenos da diarréia em humanos e animais. Afetam os animais jovens em criaçöes intensivas e causam grandes perdas econômicas. Este estudo avaliou a infecciosidade do rotavírus suíno mantido por 32 meses a aproximadamente 10ºC nas amostras originais de fezes. Trinta amostras de fezes de leitöes de 1-4 semanas de idade, provenientes de granjas da regiäo sudoeste do Paraná, foram selecionadas para o estudo. As amostras foram colhidas no período de março a outubro de 1991 e selecionadas ao acaso dentre as positivas para rotavírus pela eletroforese em gel de poliacrilamida (EGPA), à época da colheita. Estas foram retestadas por EGPA 32 meses após manutençäo à temperatura de aproximadamente 10ºC. Onze das 30 amostras ainda foram positivas, mostrando a integridade das 11 bandas de RNA viral. Com o intuito de demonstrar a manutençäo da infecciosidade viral, os homogenatos fecais clarificados, previamente tratados com tripsina, foram inoculados em culturas de células MA-104. Das 11 amostras, 5 demonstraram efeito citopático semelhante ao do rotavírus símio (SA-11), após em média 3 passagens cegas e confirmado pelo teste de imunofluorescência indireta, demonstrado pela fluorescência específica citoplasmática tipicamente granular. A microscopia eletrônica das amostras fecais mostrou que a maioria das partículas virais apresentavam-se sem capsídio externo e outras encontravam-se em adiantado estado de degradaçäo. Concluiu-se, portanto, que a infecciosidade do rotavírus suíno é mantida por longo período em amostras fecais em baixa temperatura. Este certamente é um aspecto importante para a manutençäo do vírus viável em condiçäo natural assim como para a transmissäo da doença