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At least 235 records · Page 13Linked to original sources
PubMed1994

The 2-5A system and HIV infection.

2',5'-Oligoadenylates (2-5A) have an essential role in the establishment of the antiviral state of a cell exposed to virus infection. The key enzymes of the 2-5A system are the 2-5A forming 2',5'-oligoadenylate synthetase (2-5OAS), the activity of which depends on the presence of viral or cellular double-stranded RNA (dsRNA), and the 2-5A-activated ribonuclease (RNase L). Basic research in recent years has shown that the 2-5A system is a promising target for anti-HIV chemotherapy, particularly due to its interaction with double-stranded segments within HIV RNA. Two new strategies have been developed which yield a selective antiviral effect of 2-5A against HIV-1 infection: (1) development of 2-5A analogues displaying a dual mode of action (activation of RNase L and inhibition of HIV-1 RT) and (2) intracellular immunization of cells against HIV-1 infection by application of the HIV-1-LTR--2-5OAS hybrid gene. A further strategy is the inhibition of DNA topoisomerase I by longer 2-5A oligomers.

2',5'-Oligoadenylate Synthetase↗
PubMed1996

Stochastic model of receptor-mediated cytomechanics and dynamic morphology of leukocytes.

The proposed mathematical model investigates the simplified cytomechanics of cell shape change driven by stochastic stimulation from chemosensory receptors. The cytomechanical component of our model describes the dynamical distribution of F-actin and associated forces in an idealized cortical actin network around the cell periphery. The chemosensory component describes the distribution of chemotactic receptors in the cell membrane surrounding the cortex, where bound receptors give rise to an intracellular signal which modulates some property of the cortical network. As in our earlier models, an account is made for (1) the reactive, contractive properties of cortical actin, but here also for a stress induced by curvature of the cortex-membrane complex which carries an effective surface tension, and (2) statistical fluctuations in receptor binding, but generalized here to include statistical fluctuations in the spatial distribution of receptors, entirely determined by the additional prescription of membrane diffusion coefficients along with total receptor number, receptor binding rate constants and the local concentration field of chemotactic factor. We simplify the analysis by restricting the model to a prototype in which viscous stresses in the cortical network are negligible and the radial extension of the cell cortex is a prescribed function of the cortical actin concentration. We assume in particular that the assembly rate of cortical actin depends on the local density of bound receptors. These assumptions lead to a 4th-order parabolic differential equation on the unit circle coupled to a system of stochastic differential equations. We characterize via bifurcation analysis, stochastic simulations, and analytical correlation functions the spatial-temporal pattern of cell morphology under the influence of fluctuations in the bound receptor distribution for the case of a uniform concentration field of chemotactic factor. In addition to addressing the biological significance of our model, we remark on its relevance to the generic problem of the influence of correlated stochastic perturbations on spatial patterns in morphogenetic media.

Actins↗
PubMed1975

Localization of acetylcholinesterase in granule-containing cells of glomus-like bodies in pre- and postnatal rabbits by electron microscopy.

The distribution of acetylcholinesterase (ACHE) was studied in the granule-containing cells which constitute the glomus-like bodies found near the origin of the great vessels in pre- and postnatal rabbits. Karnovsky's method for localization of ACHE at the electron-microscope level was used and suitable controls were carried out. In the granule-containing cells, ACHE reaction product was evident in the perinuclear cisternae and cisternae of the rough endoplasmic reticulum as well as at the cell membrane. ACHE activity was also localized at the axolemma of unmyelinated axons found near the granule-containing cells and around afferent synaptic terminals to these cells. Possible functions of ACHE associated with the monoamine-storing granule-containing cells are presented.

Acetylcholinesterase↗
PubMed1993

Stereoselective detection of amino acids by lobster olfactory receptor neurons.

1. Biochemical and electrophysiological assays were used to test the hypothesis that the olfactory system of the Caribbean spiny lobster, Panulirus argus, contains populations of chemosensory receptors that are differentially sensitive to the L- and D-stereoisomers of the amino acid alanine. 2. Independent binding sites for L-alanine (dissociation constant (KD) of 6.6 microM and maximum binding (Bmax) of 16.8 fmole/microgram protein) and for D-alanine (KD of 21.6 microM and Bmax of 17.8 fmole/microgram protein) were characterized biochemically. The interaction of ligand with each binding site is rapid, reversible and saturable with respect to both time and concentration. 3. Based on a difference of at least 20% in the relative sensitivity of an olfactory receptor cell to alanine enantiomers, 44% and 34% of the 77 neurons tested were classified as L-alanine and D-alanine sensitive, respectively. The relative sensitivity to alanine enantiomers was independent of the concentration tested. Stereoselective receptors are likely for 17 of 20 other amino acids tested. 4. The congruence of biochemical and electrophysiological results leads to the conclusion that the lobster's responses to D- and L-alanine are mediated by receptors specific for each stereoisomer and that the receptors are differentially distributed among receptor cells.

Alanine↗
PubMed1984

Dendritic membrane from insect olfactory hairs: isolation method and electron microscopic observations.

Sensory hairs from antennae of male saturniid moths (Antheraea polyphemus) were separated while deep-frozen by shaking antennal branches with glass beads. The hairs were collected through their differential adhesion to the surface of a petri dish. The yield, determined by the length of the isolated hair fragments, was about 38% of the estimated total hair length per antenna. The dendritic membrane was separated from the hair fragments by centrifugation through Sephadex and further purified by ultracentrifugation in sucrose buffers. Transmission electron microscopy was used to monitor the steps of the hair and membrane isolation and to investigate the membrane pellet. Some membrane vesicles bound cationized ferritin, thus indicating a negatively charged cell surface coat. Negatively stained membrane vesicles exhibited a pattern of repetitive substructures irregularly distributed over the vesicle surface. The units had a diameter of about 3 nm and a maximal density of 30,000/micron2.

Animals↗