Biomedical subjects

A Bee

Publications and source records attributed to A Bee.

8 recordsLinked to original sources

PubMed2002

Size-selective chemical synthesis of tartrate stabilized cobalt ferrite ionic magnetic fluid.

Ionic magnetic fluid (ferrofluid) is a stable suspension of magnetic nanoparticles in water. Cobalt ferrite nanoparticles are interesting in view of high-density recording storage. The size of the magnetic particles strongly influences the physical properties of the ferrofluids. In this study, we describe the synthesis of ionic magnetic fluid in the presence of tartrate ions. By varying the amount of organic ligands, nanoparticles in a large range of size are obtained: the mean diameter varies from 3 to 10 nm. The effect of tartrate ions on the stability of the ionic magnetic fluid is also studied in relation with the size of the magnetic particles and the amount of adsorbed ligand.

Journal Article↗

PubMed2001

Novel in vitro assays for assessing the haemorrhagic activity of snake venoms and for demonstration of venom metalloproteinase inhibitors.

Standard methods used for assessing the haemorrhagic toxicity of snake venoms and the effectiveness of antivenoms are laborious, expensive and involve the use of large numbers of laboratory animals. This paper examined the feasibility of using a gelatin degradation ELISA for preliminary screening of snake venom metalloproteinases (MPs). Potent gelatinolytic activity was observed in venoms from snakes of the family Viperidae and, as expected, little or no activity was evident in the venoms of snakes that induce neurotoxic pathology (most elapids). A reverse gelatin zymography assay was used on a variety of venoms to demonstrate a number of inhibitors of MP activity, the first such demonstration of its kind.

Electrophoresis, Polyacrylamide Gel↗

PubMed2001

Transformation of Leishmania mexicana metacyclic promastigotes to amastigote-like forms mediated by binding of human C-reactive protein.

Infective metacyclic promastigote forms of Leishmania mexicana are introduced by the bite of sandfly vectors into their human hosts where they transform into the amastigote form. The kinetics of this process was examined in vitro in response to different combinations of temperature (26 degrees C or 32 degrees C), pH (7.2 or 5.5), and exposure to human serum. Little transformation occurred at 26 degrees C/pH 7.2, intermediate levels at 26 degrees C/pH 5.5 and 32 degrees C/pH 7.2, and the greatest response at 32 degrees C/pH 5.5. Transformation was stimulated by exposure to normal human serum, but was markedly reduced when serum previously incubated at 56 degrees C for 1 h was used (complement heat-inactivated). This stimulatory effect was reproduced by exposure to a single purified component of human serum, C-reactive protein (CRP). Binding of CRP to the whole surface of L. mexicana metacyclic promastigotes, including the flagella, was demonstrated by an indirect fluorescent antibody test. The effect of purified CRP was dose dependent and occurred using normal serum concentrations. The stimulatory effect of whole serum was oblated by CRP depletion and restored by addition of purified CRP. The effects of cAMP analogues indicated that transformation could be mediated via an adenylate cyclase cascade.

Adenylyl Cyclases↗

PubMed2000

Adsorption Isotherms of Cetylpyridinium Chloride with Iron III Salts at Air/Water and Silica/Water Interfaces.

The interaction of iron III salts and cetylpyridinium chloride (CPC) has been studied at the air/water and silica/water interfaces. The surface tension of cetylpyridinium chloride has been determined in aqueous solutions in the presence of iron III chloride and iron III nitrate at two constant pH values, namely, 3.5 and 1.2. It is shown that the surface tension of the cationic surfactant depends upon the ionic strength of the solution through the pH adjustment in the presence of the former salt but not in the presence of the latter. The effect of iron III nitrate on the surface tension of CPC is similar to that of potassium nitrate, indicating that the iron III various-hydrolyzed species do not interfere with the composition of the air/water interface. The competitive adsorption of iron III nitrate salt and the cationic surfactant at a silica/water interface was next investigated. The adsorption isotherms were determined at pH 3.5. It is shown that although the iron III ions, which were added to the silica dispersion in the presence of the cetylpyridinium ions, were strongly bound to the anionic surface sites, the surfactant ions are not salted out in the solution but remain in close vicinity of the silica surface. Conversely as the cationic surfactant is added first to the silica dispersion in the presence of the adsorbed iron III ions, the metal ions and the surfactant ions are both coadsorbed onto the silica surface. It is suggested that iron III hydrolyzed or free cations and the cationic surfactant molecules may not compete for the same adsorption sites onto the silica surface. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Immunological and inflammatory characterisation of three canine cell lines: K1, K6 and DH82.

Three canine cell lines, K1, K6 and DH82, derived from canine malignant neoplasms, were characterised. They were examined for expression of surface antigens, cytokines, neuropeptide receptors, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The growth characteristics of the cell lines were established and bioassays used to detect production of TNF-alpha, IL-1 and IL-6. In the DH82 cell line, production of TNF-alpha and IL-6 was readily detected. Neither K1 or K6 cell lines produced any measurable amounts of TNF-alpha, IL-1 or IL-6. At a molecular level, using reverse transcription-polymerase chain reaction (RT-PCR) to detect specific mRNA, the DH82 cell line expressed TNF-alpha, IL-1 and IL-6, whereas the K1 and K6 cell lines expressed TNF-alpha. Canine IL-5, IL-8 and IL-10 mRNA were detected in the DH82 cell line but only IL-5 and IL-8 mRNA were detected in the K1 and K6 cell lines. Gelatin zymography was used for the detection of MMP-2 and MMP-9 and all three cell lines produced MMP-2 but only the DH82 cell line produced MMP-9. Reverse zymography was used to detect TIMP-1 and TIMP-2 and all three cell lines produced both proteins. The presence of these MMPs and TIMPs was confirmed at a molecular level using RT-PCR. Canine MMP-14 mRNA was detected in all three cell lines. For this investigation several genes for canine inflammatory molecules were cloned and sequenced for molecular detection; these included IL-1, IL-6, IL-8, TNF-alpha, MMP-9, MMP-14, TIMP-1, TIMP-2 and beta-actin. Of all the cell surface antigens tested, only CD14 was expressed on the DH82 cell line although CD5 and CD45 was partially expressed. The K1 and K6 cell lines were negative for all of the CD markers tested. K1 and K6 were negative for Neurokinin 1 receptor (NK1-R) but positive for Calcitonin gene related peptide receptor type 1 (CGRP-1R) and Calcitonin gene related peptide receptor component protein (CGRP-RCP). The DH82 cell line expressed neither NK1-R or CGRP-1R; however, it did express CGRP-RCP. Generally the DH82 cell line exhibited considerable similarity to canine monocytes, but all three cell lines will be useful as standards and for the purification of various immunological and inflammatory mediators in the dog.

Animals↗

PubMed2000

Canine TIMP-2: purification, characterization and molecular detection.

Matrix metalloproteinases (MMPs), which degrade tissues in health and disease are under the control of the tissue inhibitors of MMPs, the TIMPs. TIMP-2 is particularly important for control of MMP-2 and both have been implicated in many pathological processes from arthritis to tumour invasion. This study characterized and detected TIMP-2 from canine cells; including synovial fibroblasts and three tumour-derived canine cell lines, K1, K6 and DH82. Gelatin zymography demonstrated that pro-MMP-2 is produced by synovial fibroblasts and the three cells lines. Reverse zymograms showed that all the cell sources tested secrete both TIMP-1 and TIMP-2. The 22 kDa band was purified and n-terminal amino acid sequencing showed it to be highly homologous to equine and human TIMP-2. Analysis of purified canine MMP-2 and MMP-9 showed that TIMP-2 is associated, and co-purifies with MMP-2. Polymerase chain reaction, using consensus primers, was used to detect TIMP-2 mRNA from the cell sources and proved positive in all cases. This work highlights the importance of TIMP-2 as the main inhibitor for MMP-2 and, therefore, opens the possibilities of targeting TIMP-2 for therapeutic intervention against connective amino acid tissue degradation in a range of diseases.

Animals↗

PubMed1998

Adsorption Isotherm of Sodium Octylbenzenesulfonate on Iron Oxide Particles in Aqueous Solutions.

The adsorption isotherm of sodium octylbenzene sulfonate has been determined at two pH values on dispersed maghemite particles in water. The isotherms present an adsorption maximum in the region of the surfactant critical micelle concentration. Additional adsorption experiments at the alumina/water interface as well as at the air/water interface in the presence of ferric ions suggest that the adsorption maximum in the case of the iron oxide particles is due to the presence of very small concentrations of ferric ions in the aqueous solution. These ions form surface active complexes with sodium octylbenzenesulfonate. These complexes are adsolubilized in the surfactant layers on the particles below the critical micelle concentration. They are desorbed from the surface and transferred into free micelles above the critical micelle concentration. These two phenomena are shown to be responsible for the adsorption maximum observed. The presence of ferric ions induces a surface tension minimum of the anionic surfactant at the air/water interface. This effect is discussed in relation to the adsorption maximum at the solid/water interface. Copyright 1998 Academic Press.

Journal Article↗

PubMed1997

Thiolation of Maghemite Nanoparticles by Dimercaptosuccinic Acid

Magnetic particle-effector conjugates are widely used in vitro for cell sorting in various pathologies. The coupling between the particles and the effectors being realized through S-S bridges, the particles must first be thiolated before the coupling. In this work, the synthesis, in aqueous medium, of nanoparticles of maghemite thiolated by dimercaptosuccinic acid is described. The superficial complexation by a thiol-containing ligand induces a reductive dissolution of the oxide and leads to the adsorption of polydisulfide species coming from the oxidation of the ligand. Adsorption and redox reactions being strongly correlated to the composition of the medium, the amount of adsorbed ligand and the quantity of iron(II) released into the medium have been simultaneously determined, at various pH, for different concentrations of ligand added. The charge of the particles is drastically modified in the presence of a chelating agent; as a consequence, the colloidal stability is greatly affected and so the flocculation ranges of the complexed particles have been established for different pH. When the quantity of ligand added is sufficient (0.05 mol/mol of iron), the ferrofluid based on thiolated maghemite particles is stable between pH 3 and 11 and can be used for biomedical applications. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗