Extraction and characterization of hydroxyapatite-based materials from grey triggerfish skin and black scabbardfish bones

The conversion of food industry by-products to compounds with high added value is nowadays a significant topic, for social, environmental, and economic reasons. In this paper, calcium phosphate-based materials were obtained from black scabbardfish (Aphanopus carbo) bones and grey triggerfish (Balistes capriscus) skin, which are two of the most abundant fish by-products of Madeira Island. Different calcination temperatures between 400 and 1000°C were employed. Materials obtained from calcination of bones of black scabbard fish were composed by homogeneous mixtures of hydroxyapatite (Ca₁₀(PO4)₆(OH)₂, HAp) and β-tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP). Because of the high biocompatibility of HAp and the good resorbability of β-TCP, these natural biphasic materials could be very relevant in the field of biomaterials, as bone grafts. The ratio between HAp and β-TCP in the biphasic compound was dependent on the calcination temperature. Differently, the material obtained from skin of grey triggerfish contained HAp as the main phase, together with small amounts of other mineral phases, such as halite and rhenanite, which are known to enhance osteogenesis when used as bone substitutes. In both cases, the increase of calcination temperature led to an increase in the particles size with a consequent decrease in their specific surface area. These results demonstrate that from the fish by-products of the most consumed fishes in Madeira Island it is possible to obtain bioceramic materials with tunable composition and particle morphology, which could be promising materials for the biomedical field.     

Viral dynamics of primary viremia and antiretroviral therapy in simian immunodeficiency virus infection

Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus.     

Influence of lead on metabolism of vitamins B group in alimentary iron deficient rats

Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells.     

The current aspects of seroepidemiological research in combined foci of leishmaniasis

The accuracies of ultrasonography (US) and computed tomography (CT) for determining tumor invasion of the chest wall in lung cancer were compared in a retrospective study of 120 patients. US findings were evaluated preoperatively according to the following criteria: disruption of pleura, extension through the chest wall, and fixation of tumor during breathing. CT findings were evaluated with the following criteria: obtuse angle of the mass to the pleural surface, more than 3 cm contact with the pleural surface, and visible pleural thickening associated with the mass. Chest wall invasion was judged as positive when at least two of the three findings were present with either technique. Nineteen of the 120 patients had chest wall invasion by tumor. The sensitivity of US was 100% and the specificity was 98%. The sensitivity of CT was 68% and the specificity was 66%. The accuracy of US and CT were 98% and 67%, respectively.     

Preparation and characterization of chitosan‐based dispersions

Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry     

The function of the reproductive system in x-ray-irradiated male rats after the transplantation of a culture of testicular cells from newborn piglets

The effect exerted by transplantation of the 5 day culture of testicles from newly born piglets on the hypogonadal state of mature X-ray irradiated (3 Gy) rats was studied. It has been found that a month after transplantation (two months after irradiation) the hypogonadal state disappeared for a while, which is confirmed by normalization of the weight of seminal vesicles, content of testosterone and biologically active lutropine, restoration of the reproductive function of rats. No significant changes in steroidogenesis activity have been found, which proves a substituent character of transplantation. The effect disappears three months later but certain restoration of the content of nucleic acids in the testicles is observed.     

An in vitro model of traumatic neuronal injury: loading rate-dependent changes in acute cytosolic calcium and lactate dehydrogenase release

We developed a new in vitro model of neuronal injury using NT2-N cells to examine the effects of hydrodynamic loading rate on intraneuronal calcium dynamics and lactate dehydrogenase (LDH) release. Our apparatus consisted of a parallel disk viscometer which induced fluid shear stress with well-defined magnitudes and loading rates to cultured cells. We found that the deformation response of the cells was dependent on the severity of the insult, with increased cellular strains generated for higher shear stresses at a constant loading rate. Peak intracellular free calcium concentration correlated with strain, suggesting that mechanical deformation may regulate calcium response. Slowly applied fluid shear stress elicited no response, whereas high loading rates resulted in peak calcium increases 2.9 to 3.6 times baseline values as injury severity was increased. LDH release measured within 5 min after the insult correlated with loading rate. In addition, LDH release continued to increase out to 24 h following high loading rate conditions, demonstrating that the application of fluid shear stress led to prolonged cell damage. The acute response in NT2-N cells subjected to an insult with the CSID is dependent on the loading rate, and these results suggest that initial membrane deformation may trigger subsequent events.     

Insulin and insulin-like growth factor-1 regulate tau phosphorylation in cultured human neurons

Hyperphosphorylated tau is the major component of paired helical filaments in neurofibrillary lesions associated with Alzheimer's disease. Hyperphosphorylation reduces the affinity of tau for microtubules and is thought to be a critical event in the pathogenesis of this disease. Recently, glycogen-synthase kinase-3 has been shown to phosphorylate tau in vitro and in non-neuronal cells transfected with tau. The activity of glycogen-synthase kinase-3 can be down-regulated in response to insulin or insulin-like growth factor-1 through the activation of the phosphatidylinositol 3-kinase pathway. We therefore hypothesize that insulin or insulin-like growth factor-1 may affect tau phosphorylation through the inhibition of glycogen-synthase kinase-3 in neurons. Using cultured human neuronal NT2N cells, we demonstrate that glycogen-synthase kinase-3 phosphorylates tau and reduces its affinity for microtubules and that insulin and insulin-like growth factor-1 stimulation reduces tau phosphorylation and promotes tau binding to microtubules. We further demonstrate that these effects of insulin and insulin-like growth factor-1 are mediated through the inhibition of glycogen-synthase kinase-3 via the phosphatidylinositol 3-kinase/protein kinase B signaling pathway.     

Control and diagnosis in the biotechnical systems of artificial clearance

Controlling and diagnostic processes in the bioengineering artificial clearance systems despite of the procedures applied, their functional use and design seem to occur in the artificial organs, each of them consists of controlling and actuating processors ensuring their homogeneous (material, energy-producing, informational) or combined interaction with the patient's body. Centralized control over artificial clearance is proposed by using universal controlling processes which are informationally connected with the operator, the central computer and other controlling processes of the bioengineering system.