Effect of Cholesterol and Myelin Basic Protein (MBP) Content on Lipid Monolayers Mimicking the Cytoplasmic Membrane of Myelin.

Myelin basic protein (MBP) is located in the insulating covers of nerve cells in the brain and spinal cord. By interacting with lipid membranes, it is responsible for compaction of the myelin sheath in the central nervous system, which is weakened in demyelinating diseases. The lipid composition of the myelin leaflet has a high impact on the interaction between the membrane and MBP.

Myelin basic protein (MBP) charge variants show different sphingomyelin-mediated interactions with myelin-like lipid monolayers.

Multiple sclerosis (MS) is correlated with increased deimination of myelin basic protein (MBP) in the central nervous system. Here, the interaction of MBP C1 (charge: +19) and MBP C8 (charge: +13) with the major lipids of the cytoplasmic side of the oligodendrocyte membrane is analysed using monolayer adsorption experiments and epifluorescence microscopy. Our findings show that the electrostatic attraction between the positively charged proteins and negatively charged lipids in the myelin-like monolayers competes with the incorporation of MBP into regions directly bordering cholesterol-rich domains.

Interaction of Myelin Basic Protein with Myelin-like Lipid Monolayers at Air-Water Interface.

Interaction of myelin basic protein (MBP) and the cytoplasmic leaflets of the oligodendrocyte membrane is essential for the formation and compaction of the myelin sheath of the central nervous system and is altered aberrantly and implicated in the pathogenesis of neurodegenerative diseases like multiple sclerosis. To gain more detailed insights into this interaction, the adsorption of MBP to model lipid monolayers of similar composition to the myelin of the central nervous system was studied at the air-water interface with monolayer adsorption experiments. Measuring the surface pressure and the related maximum insertion pressure of MBP for different myelin-like lipid monolayers provided information about the specific role of each of the single lipids in the myelin.

Characterisation of hydration and nanophase separation during the temperature response in hydrophobic/hydrophilic elastin-like polypeptide (ELP) diblock copolymers.

To understand the complex nanoscale dehydration process during the lower critical solution temperature (LCST) based inverse phase transition of a class of thermoresponsive biopolymers, diblock elastin-like polypeptides (ELPs) were investigated by spin probing continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The diblock copolymers composed of a hydrophobic block and a hydrophilic block showed different mechanisms of a temperature-driven phase transition. While the phase transition temperature is a function of the hydrophobic mass fraction of the diblock ELPs, the hydrophilic block length determines the molecular structure of the polymer aggregates formed above the transition temperature.

Detection of correlated conformational fluctuations in intrinsically disordered proteins through paramagnetic relaxation interference.

Functionally relevant conformational states of intrinsically disordered proteins (IDPs) are typically concealed in a vast space of fast interconverting structures. Here we present a novel methodology, NMR-based paramagnetic relaxation interference (PRI), that allows for direct observation of concerted motions and cooperatively folded sub-states in IDPs. The proposed NMR technique is based on the exploitation of cross correlated electron-nuclear dipolar relaxation interferences in doubly spin-labeled proteins and probes the transient spatial encounter of electron-nucleus spin pairs.

Reductions in serum vitamin A arrest accumulation of toxic retinal fluorophores: a potential therapy for treatment of lipofuscin-based retinal diseases.

Purpose: Excessive accumulation of lipofuscin is observed in numerous degenerative retinal diseases. A toxic vitamin A-based fluorophore (A2E) present within lipofuscin has been implicated in the death of RPE and photoreceptor cells. Here, we used an animal model that manifests accelerated lipofuscin accumulation (ABCA4-/- mutant) to evaluate the efficacy of a therapeutic approach based on reduction of serum retinol.

Lack of bioeffects of ultrasound energy after intravenous administration of FS069 (Optison) in the anesthetized rabbit.

The current study was designed to provide a sensitive in vivo model to maximize the potential bioeffects (measured by hemolysis) of B-mode ultrasound energy in combination with FS069 (Optison). B-mode ultrasound energy was delivered to anesthetized male New Zealand white rabbits with a phased array 5 MHz transducer on a Hewlett-Packard Sonos 1500 ultrasonograph, with transmit level set to maximum (40 dB, approx 135 W/cm2). FS069 (Optison), latex particles in human albumin, or human albumin alone (vehicle) was infused via an ear vein at 0.

Treatment of a syngeneic rat tumor with magnetically responsive albumin microspheres labeled with doxorubicin or protein A.

The tumoricidal activity of magnetically responsive albumin microspheres tagged with either doxorubicin or Staphylococcal protein A was tested against an induced mammary adenocarcinoma, 13762, implanted subcutaneously in the tail of female Fischer-344 rats. Magnetically responsive albumin microspheres containing Fe3O4 particles were prepared by an emulsion polymerization method incorporating either doxorubicin or protein A into the albumin matrix. Microspheres were produced with an average diameter of 1 micron (0.

Magnetite albumin microspheres: a new MR contrast material.

A superparamagnetic MR contrast agent was synthesized by incorporating 150-250-A particles of magnetite (Fe3O4, Fe2O3) in 1-5 microns human serum albumin microspheres. Magnetite albumin microspheres (MAM) target almost exclusively to the reticuloendothelial system after IV administration, are stable in vitro and in vivo, and possess a long shelf life. The agent has a large magnetic susceptibility effect that selectively reduces T2 with little effect on T1.

Elevated erythrocyte adenosine deaminase activity in patients with acquired immunodeficiency syndrome.

Acquired immunodeficiency syndrome (AIDS) is an often fatal disease caused by a retrovirus frequently resulting in malignancy and/or opportunistic infection. Because the immune deficiency in AIDS is similar to that in some purine enzyme deficiencies, we measured erythrocyte adenosine deaminase (ADA) and purine nucleoside phosphorylase activities in patients with AIDS, heterosexual controls, and a high-risk asymptomatic population. We found that erythrocyte ADA activity was significantly elevated in patients with AIDS (40 +/- 11 nmol/mg of hemoglobin per hr, mean +/- SD) relative to heterosexual controls (25 +/- 10, P less than 0.

In vivo alteration of RES phagocytosis by magnetic albumin microspheres.

The effect of non-localized magnetically responsive albumin microspheres (MR-AMS) on RES phagocytic function was investigated. MR-AMS and MR-AMS containing Adriamycin (MR-AMS-ADR) were injected intravenously in rats at a dose which saturated all RES phagocytes. The ability of the RES to clear the bloodstream of a subsequent suspension of MR-AMS or streptococci was then analyzed over a three day period.

Magnetic targeting of microspheres in blood flow.

Magnetically responsive albumin microspheres can be targeted to the vasculature of specific organs, using extracorporeal magnetic sources. Experiments have been performed on targeting these microspheres to specific regions of normal and tumorous rat tails. This paper quantitatively analyzes the relationship between magnetic forces and the observed microsphere holding.

Selective targeting of magnetic albumin microspheres to the Yoshida sarcoma: ultrastructural evaluation of microsphere disposition.

Magnetic albumin microspheres (1 micron average diameter) were selectively targeted to subcutaneous solid Yoshida sarcoma tumors (average size 450 mm2) in Holtzman rats. This was accomplished by placing an external magnet adjacent to the tumor while the microspheres were infused. Microspheres contained ultra-fine particles of Fe3O4 and no drug (placebo).

Selective targeting of magnetic albumin microspheres containing low-dose doxorubicin: total remission in Yoshida sarcoma-bearing rats.

Magnetically responsive albumin microspheres containing doxorubicin hydrochloride were selectively localized in Yoshida sarcoma tumors. Tumors were implanted subcutaneously in the tail of Holtzman rats and allowed to grow to at least 200 mm2 size before initiation of experimental treatment. Drug-bearing microspheres at a dose level of either 0.

A rapid method for immunofluorescent staining of paraffin sections using iron-containing protein A microspheres.

A method to rapidly perform immunofluorescence or light microscopic staining on formalin-fixed paraffin sections has been devised utilizing magnetic albumin microspheres containing Staphylococcal protein A. Because the protein A constituent of the microspheres has the property of binding the Fc portion of immunoglobulin G (IgG) class antibodies, the microspheres can be used to rapidly bind antigen-antibody complexes by the Fc portion of the antibody. Deparaffinized sections were stained with fluorescein isothiocyanate-conjugated antibody (IgG fractions) by standard techniques, after which the protein A microspheres were layered over the sections.

In vivo kinetics of magnetically targeted low-dose doxorubicin.

The in vivo kinetics of low-dose doxorubicin (0.05 mg/kg), entrapped in a carrier and magnetically targeted, were characterized in a rat tail model. Tissue concentrations of doxorubicin at a preselected target site and in various organs were followed over time.

Specific cell binding using staphylococcal protein A magnetic microspheres.

Protein A, a protein derived from Staphylococcus aureus, was incorporated into the matrix of magnetic albumin microspheres. Because staphylococcal protein A binds most subclasses of immunoglobulin G through their Fc portions, immunoglobulin may be rapidly bound to microspheres without chemical coupling agents or a diamino-heptane spacer group. Microspheres so prepared bind specifically to a given cell type when incubated in vitro with a heterogeneous cell population.

Tumor remission in Yoshida sarcoma-bearing rts by selective targeting of magnetic albumin microspheres containing doxorubicin.

Magnetically responsive albumin microspheres containing doxorubicin and magnetite (Fe3O4) were selectively targeted to Yoshida sarcoma tumors in rats by utilizing an extracorporeal magnet. Tumor cells were inoculated subcutaneously in the tail of rats, and the tumors were allowed to grow to an average size of 9 X 45 mm prior to initiating treatment. Drug-bearing microspheres (0.

In vitro release of biologically active adriamycin by magnetically responsive albumin microspheres.

The kinetic release of therapeutically active Adriamycin from two different heat-stabilized preparations of magnetically responsive albumin microspheres (1 micron) has been evaluated using a rapid in vitro bioassay-harvesting system. Release products are added to freshly plated monolayers of a malignant Fisher 344 rat fibrosarcoma cell line, and the inhibition of [3H]uridine incorporation into trichloroacetic acid-precipitable material (RNA) and whole cells is determined in a 6-hr microtiter assay. The latter harvesting technique utilizes semiautomated cell collection using a multiple sample harvester.