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B Goins

Publications and source records attributed to B Goins.

26 records · Page 2Linked to original sources
PubMed1992

Liposome encapsulated hemoglobin: long-term storage stability and in vivo characterization.

Liposome Encapsulated Hemoglobin (LEH) has been the focus of research and development at the Naval Research Laboratory in an effort to find a viable oxygen-carrying resuscitative fluid. Previous reports from our laboratory have shown that LEH binds and releases oxygen in a manner similar to red blood cells, and that it can sustain life when red cell hematocrits are decreased to critical levels. We have also reported on LEH with regards to preparative methods, scale-up feasibility, toxicity, hemodynamics, hemoglobin P50 modification by coencapsulation of organic phosphates, liposomal surface modification, and storage strategies. In this report, the issue of LEH efficacy following long-term storage in the dry state will be addressed. We have shown that hemoglobin, liposomes, and LEH may be successfully lyophilized and rehydrated to viable states. The modification of the LEH formulation by addition of the carbohydrate trehalose results in the successful lyophilization and storage of LEH. In vitro characterization of LEH stored in the dry state for up to six months includes measurement of oxygen-carrying capacity, liposome size retention, methemoglobin production, and the intraliposomal hemoglobin concentration. The in vivo studies report on physiological parameters such as circulation persistence, blood chemistry, and pathological examination in mice.

Animals↗
PubMed1992

Biodistribution studies of liposome encapsulated hemoglobin (LEH) studied with a newly developed 99m-technetium liposome label.

A new method has been developed to label preformed liposomes with 99m-Technetium (99mTc) using hexamethylpropylenamine oxime (HMPAO). 99mTc is an ideal isotope for performing non-invasive dynamic biodistribution studies. This labeling method results in a high labeling efficiency (greater than 95%) and is stable as determined by both in vitro and in vivo studies. In vitro studies indicated that glutathione encapsulated in the LEH is important in the labeling process with 99mTc-HMPAO. In vivo studies with LEH were performed on 7 rabbits with dynamic scintigraphic 1 minute images performed from 1-120 minutes. Delayed images were performed at 20 hours followed by sacrifice and organ counting. Dynamic images reveal a gradual deposition of the LEH in the liver and spleen. Twenty hour biodistributions revealed 50% of the LEH remaining in the blood, 15% in the liver, 14% in the spleen, 3% in lungs, 3% in muscle with trace amounts in the brain, kidneys, and heart. Doses per gram were highest in the spleen with 12.5% of the injected dose per gram of spleen vs. 0.2% per gram of liver. This labeling technique is an effective method for non-invasively monitoring dynamic changes in liposome biodistribution and can be used to study the effects of various liposome modifications on biodistribution.

Animals↗
PubMed1991

In vivo biodistribution of a radiolabeled blood substitute: 99mTc-labeled liposome-encapsulated hemoglobin in an anesthetized rabbit.

Liposome-encapsulated hemoglobin (LEH) is an erythrocyte substitute that is a potential resuscitative fluid for the in vivo delivery of oxygen. We have noninvasively imaged radiolabeled LEH in vivo with technetium-99m (99mTc) to study the biodistribution in an anesthetized rabbit. Rabbits (2.5 kg, n = 8) were infused with 30 ml of LEH (200 mg of phospholipid, 2.5 g of hemoglobin per kg of body weight) and imaged with a gamma camera continuously for 2 hr. At 20 hr postinfusion, the animals were imaged again and sacrificed; the organs were weighted and their radioactivity was determined for autopsy organ distribution. Organ uptake from the images was corrected for organ-associated blood pool, which was determined by infusion of 99mTc-labeled rabbit erythrocytes. Blood pool and decay-corrected biodistribution data reveal the kinetics of LEH distribution, with an initial rapid uptake by the liver, 8% at 30 min and 15% at 2 hr. The spleen accumulates less LEH initially, 3% at 30 min and 7% at 2 hr, with an apparent linear uptake of LEH over this time period. Image biodistribution data was also validated at 20 hr by tissue sampling. At 20 hr postinfusion, autopsy biodistribution data reveals approximately 42.6% of the total counts remaining in the blood, 15.4% in the liver, 18.1% in spleen, 3.2% in the lungs, 2.4% in muscle, 1.6% in urine, and trace levels in the kidney, brain, and heart (less than 1%). There is no evidence of hemoglobin release from LEH or kidney dysfunction (normal creatinine and blood urea nitrogen) at any time over the course of the study.

Alanine Transaminase↗
PubMed1991

The effect of hydration stress solutes on the phase behavior of hydrated dipalmitoylphosphatidylcholine.

We have investigated the interaction of solutes found to accumulate in biological systems during chilling, dehydration, and salt stress with fully hydrated multilamellar and unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). We have focused on a series of mono-, di-, and tri-substituted amines (glycine, 4-hydroxyproline, proline, and betaine) and contrasted the action of these solutes to trehalose, a protective disaccharide. Differential scanning calorimetry studies show that when DPPC is scanned in the presence of increasing concentrations of these solutes (up to 3 M), there is a moderate increase in the pre-transition temperature (1-6 degrees C) with a smaller increase (1-2 degrees C) in the main transition temperature of hydrated multilamellar vesicles of DPPC. Other calorimetric parameters (delta H, delta T1/2, Cpmax) determined for the pre-transition and main transition were similar independent of the solute. In each case, the main phase transition was broadened with increasing solute while the transition enthalpy was not significantly affected.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Thermal stability and intersubunit interactions of cholera toxin in solution and in association with its cell-surface receptor ganglioside GM1.

The thermal stability of cholera toxin free in solution and in association with its cell-surface receptor ganglioside GM1 has been studied by using high-sensitivity differential scanning calorimetry and differential solubility thermal gel analysis. In the absence of ganglioside GM1, cholera toxin undergoes two distinct thermally induced transitions centered at 51 and 74 degrees C, respectively. The low-temperature transition has been assigned to the irreversible thermal denaturation of the active A subunit. The second transition has been assigned to the reversible unfolding of the B subunit pentamer. The isolated B subunit pentamer exhibits a single transition also centered at 74 degrees C, suggesting that the attachment of the A subunit does not contribute to the stability of the pentamer. In the intact toxin, the A subunit dissociates from the B subunit pentamer at a temperature that coincides with the onset of the B subunit thermal unfolding. In aqueous solution, the denatured A subunit precipitates after dissociation from the B subunit pentamer. This phenomenon can be detected calorimetrically by the appearance of an exothermic heat effect. In the presence of ganglioside GM1, the B subunit is greatly stabilized as indicated by an increase of 20 degrees C in the transition temperature. In addition, ganglioside GM1 greatly enhances the cooperative interactions between B subunits. In the absence of ganglioside, each monomer within the B pentamer unfolds in an independent fashion whereas the fully ganglioside-bound pentamer behaves as a single cooperative unit. On the contrary, the thermotropic behavior of the A subunit is only slightly affected by the presence of increasing concentrations of ganglioside GM1.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry, Differential Scanning↗
PubMed1986

Lateral diffusion of ganglioside GM1 in phospholipid bilayer membranes.

The lateral diffusion coefficient of ganglioside GM1 incorporated into preformed dimyristoylphosphatidylcholine (DMPC) vesicles has been investigated under a variety of conditions using the technique of fluorescence photobleaching recovery. For these studies the fluorescent probe 5-(((2-Carbohydrazino)methyl)thio)acetyl) amino eosin was covalently attached to the periodate-oxidized sialic acid residue of ganglioside GM1. This labeled ganglioside exhibited a behavior similar to that of the intact ganglioside, and was able to bind cholera toxin. The lateral diffusion coefficient of the ganglioside was dependent upon the gel-liquid crystalline transition of DMPC. Above Tm the lateral diffusion coefficient of the ganglioside was 4.7 X 10(-9) cm2 s-1 (with greater than 80% fluorescence recovery). This diffusion coefficient is significantly slower than the one previously observed for phospholipids in DMPC bilayers. The addition of increasing amounts of ganglioside, up to a maximum of 10 mol %, did not have a significant effect on the lateral diffusion coefficient or in the percent recovery. At 30 degrees C, the lateral mobility of ganglioside GM1 was not affected by the presence of 5 mM Ca2+, suggesting that, at least above Tm, Ca2+ does not induce a major perturbation in the lateral organization of the ganglioside molecules. The addition of stoichiometric amounts of cholera toxin to samples containing either 1 or 10 mol % ganglioside GM1 produced only a small decrease in the measured diffusion coefficient. The fluorescence recovery after photobleaching experiments were complemented with excimer formation experiments using pyrene-phosphatidylcholine. Above the transition temperature the presence of 10 mol % ganglioside GMI induced a large decrease in the rate of excimer formation. These results also indicated that the addition of ganglioside GMI to phospholipid bilayer vesicles induces a significant restriction in the lateral mobility parameters of the lipid bilayer and that the presence of Ca2' does not have a further effect in the mobility of the probe molecules.

Animals↗
PubMed1985

Lipid phase separations induced by the association of cholera toxin to phospholipid membranes containing ganglioside GM1.

The interactions of cholera toxin and their isolated binding and active subunits with phospholipid bilayers containing the toxin receptor ganglioside GM1 have been studied by using high-sensitivity differential scanning calorimetry and steady-state and time-resolved fluorescence and phosphorescence spectroscopy. The results of this investigation indicate that cholera toxin associates with phospholipid bilayers containing ganglioside GM1, independent of the physical state of the membrane. In the absence of Ca2+, calorimetric scans of intact cholera toxin bound to dipalmitoylphosphatidylcholine (DPPC) large unilamellar vesicles containing ganglioside GM1 result in a broadening of the lipid phase transition peak and a slight decrease (less than 5%) in the transition enthalpy. In the presence of Ca2+ concentrations sufficient to cause ganglioside phase separation, the association of the intact toxin to the membrane results in a significant decrease of enthalpy change for the lipid transition, indicating that under these conditions the toxin molecule perturbs the hydrophobic core of the bilayer. Calorimetric scans using isolated binding subunits lacking the hydrophobic toxic subunit did not exhibit a decrease in the phospholipid transition enthalpy even in the presence of Ca2+, indicating that the binding subunits per se do not perturb the hydrophobic core of the bilayer. On the other hand, the hydrophobic A1 subunit by itself was able to reduce the phospholipid transition enthalpy when reconstituted into DPPC vesicles. These calorimetric observations were confirmed by fluorescence experiments using pyrene phospholipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗