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Biomedical subjects

L Huang

Publications and source records attributed to L Huang.

At least 595 records · Page 33Linked to original sources
PubMed1992

Some negatively charged phospholipid derivatives prolong the liposome circulation in vivo.

A series of negatively charged phospholipid derivatives has been synthesized by coupling aliphatic dicarboxylic acids, HOOC(CH2)nCOOH, to dioleoylphosphatidylethanolamine (DOPE). The individual derivatives were incorporated into egg phosphatidylcholine/cholesterol liposomes (2:1, molar ratio) and injected into mice to test its effect on liposome circulation in vivo. The effectiveness of DOPE derivatives was dependent on the hydrocarbon chain length between the terminal carboxyl group and the amide bond. N-Glutaryl DOPE and N-adipyl DOPE were effective in prolonging the circulation time of liposomes. On the other hand, liposome uptake by the liver and spleen was increased by the addition of N-malonyl DOPE or N-succinyl DOPE, while it was not changed by the addition of N-pimelyl DOPE and N-suberyl DOPE. Our observation suggested that not all negatively charged phospholipids enhance liposome uptake by RES, some even reduce the uptake.

Animals↗
PubMed1992

Cationic liposomes enhance targeted delivery and expression of exogenous DNA mediated by N-terminal modified poly(L-lysine)-antibody conjugate in mouse lung endothelial cells.

A new and improved system for targeted gene delivery and expression is described. Transfection efficiency of N-terminal modified poly(L-lysine) (NPLL) conjugated with anti-thrombomodulin antibody 34A can be improved by adding to the system a lipophilic component, cationic liposomes. DNA, antibody conjugate and cationic liposomes form a ternary electrostatic complex which preserves the ability to bind specifically to the target cells. At the same time the addition of liposomes enhance the specific transfection efficiency of antibody-polylysine/DNA binary complex by 10 to 20-fold in mouse lung endothelial cells in culture.

Animals↗
PubMed1992

Cryoprotective activity of synthetic glycophospholipids and their interactions with trehalose.

A series of glycophospholipids have been synthesized by conjugating mono-, di- and trisaccharides with dioleoylphosphatidylethanolamine (DOPE) by reductive amination. These synthetic glycophospholipids were incorporated into egg phosphatidylcholine (PC) vesicles and tested for the release of vesicle-entrapped calcein after five cycles of freeze and thaw. N-isomaltotriosyl-DOPE and N-(N-acetylneuramin-lactosyl)-DOPE had approximately equal activity in cryoprotection; whereas N-lactosyl-DOPE and N-galactosyl-DOPE were without effect. However, the cryoprotective effect of trehalose was significantly reduced with the incorporation of N-lactosyl-DOPE and N-galactosyl-DOPE, but not with the trisaccharide-DOPE conjugates. FTIR studies of mixtures of trehalose and glycophospholipid revealed that trehalose forms H-bonding with the phosphodiester group of N-(N-acetylneuramin-lactosyl)-DOPE but not that of N-galactosyl-DOPE. The presence of interaction of trehalose with the trisaccharide-DOPE conjugate and the absence of interaction with the monosaccharide-DOPE conjugate were also demonstrated by the change of the HII phase transition temperature of dielaidoyl phosphatidylethanolamine as measured by the differential scanning calorimetry. The ability of trehalose to restore the membrane order of the rigid dipalmitoyl phosphatidylcholine bilayer perturbed by the presence of glycophospholipids is also correlated with the ability of trehalose to interact with trisaccharide-DOPE conjugate but not with the monosaccharide-DOPE conjugate. These observations have shed some light on the mechanism of the cryoprotective activity of the membrane bound carbohydrates.

Calorimetry, Differential Scanning↗
PubMed1992

Stable target-sensitive immunoliposomes.

Interaction of immunoliposomes composed of dioleoylphosphatidylethanolamine (DOPE) (80%), dioleoylphosphatidic acid (DOPA) (20%), and a small amount of specific antibody with Herpes Simplex virus (HSV) were studied by detecting the immune-dependent lysis of liposomes. DOPA was used as the principal stabilizer of the immunoliposomes. Antibodies conjugated with N-glutarylphosphatidylethanolamine or oxidized GM1 served as the target-specific ligands of immunoliposomes. These immunoliposomes (d = 160-180 nm) were stable for at least one month when stored at 4 degrees C. However, they undergo a rapid aggregation and lysis reaction in the presence of a membrane-bound target such as intact HSV virions. We have also employed epitope peptide-containing liposomes (target liposomes) to mimic the virus and showed that the immunoliposomes could be aggregated and lysed by the target liposomes in an antigen-dependent manner. Immunoliposome lysis could be accelerated by increasing the incubation temperature to 60-70 degrees C. No immunoliposome lysis was observed if the target liposomes were absent, indicating the prolonged stability of the immunoliposomes. Liposome lysis was always accompanied by liposome aggregation. However, the aggregation-induced liposome destabilization is unique to the HII phase-forming lipids such as DOPE. DOPC-containing immunoliposomes did not lyse despite the fact that massive liposome aggregation had taken place.

Amino Acid Sequence↗
PubMed1992

In vivo cytotoxic T lymphocyte induction with soluble proteins administered in liposomes.

The in vivo induction of a CTL response usually requires that Ag be endogenously synthesized so that appropriate processing can occur. In most of the few examples where successful CTL induction was reported with proteins and peptides, unacceptable adjuvants or means of Ag formulation were used. In the present report, liposomes were used to incorporate the soluble proteins OVA and beta-galactosidase. This simple and convenient to use approach, which requires minimal amounts of Ag, results in priming for a CD8+ CTL response and the establishment of immunologic memory. The liposome approach may not only prove a convenient means of inducing CTL responses in vivo but may also be useful to study the mechanisms of Ag processing.

Animals↗
PubMed1992

Role of liposome size and RES blockade in controlling biodistribution and tumor uptake of GM1-containing liposomes.

We have examined the effect of liposome size on liposome circulation time in the blood. Liposomes composed of phosphatidylcholine, cholesterol and ganglioside GM1 were prepared in the various size range. Optimal circulation activity (55% injected dose at 4 h post injection) of GM1-containing liposomes, which correlated with a relatively high uptake of liposomes by EMT6 tumor in mouse, was obtained with a size range of 70 to 200 nm in diameter. Increasing the diameter of liposome to greater than 200 nm resulted in an enhancement of the spleen uptake and decrease of the blood level. For liposomes with a diameter of less than 70 nm, 70% of the injected dose were taken up by the liver, presumably by the parenchymal cells. In contrast, the biodistribution of phosphatidylserine-containing liposomes was relatively insensitive to changes in liposome size; most of the injected dose was found in the liver. The effect of RES blockade on the circulation time of large (d greater than 300 nm), GM1-containing liposomes was also studied. Dextran sulfate 500, a commonly used blockade reagent for Kupffer cells, had no effect. On the other hand, preinjection of a large dose of liposomes with a diameter greater than 500 nm showed variable results depending on the lipid composition of the blocking liposomes. Preinjection of liposomes containing GM1, phosphatidylinositol or (N-polyethyleneglycol) phosphatidylethanolamine effectively reduced the spleen uptake of the large GM1-containing liposomes, whereas liposomes containing phosphatidic acid showed no effect. These results indicate that only spleen homing liposomes can be used as a blocking reagent to prolong the circulation time of the large GM1-containing liposomes.

Animals↗
PubMed1992

Biodistribution and immunotargetability of ganglioside-stabilized dioleoylphosphatidylethanolamine liposomes.

The biodistribution and immunotargetability of liposomes composed primarily of dioleoylphosphatidylethanolamine (DOPE) or dioleoylphosphatidylcholine (DOPC) in mice injected via the tail vein were examined and compared. The ganglioside GM1 (7 mol%) prolonged the circulation of DOPC but not DOPE liposomes. Gangliosides GD1a and GT1b (7 mol%) also increased the amount of DOPC liposomes remaining in circulation, and to a similar extent as GM1, at 15 min post injection. However, these liposomes were cleared from the circulation by 2.5 h. Monoclonal antibody 34A, which specifically binds to a surface glycoprotein (gp 112) of the pulmonary endothelial cell surface, was coupled with N-glutarylphosphatidylethanolamine and incorporated into liposomes by a dialysis procedure. These 34A-immunoliposomes, composed of DOPE and GM1 (7 mol%), but not the antibody-free liposomes, accumulated efficiently (approximately 24% of the injected dose) in the lungs. Inclusion of cholesterol (31 mol%) enhanced the lung accumulation of both DOPE/GM1 immunoliposomes and DOPC/GM1 immunoliposomes to 33% and 51% of the injected dose, respectively. The transient increase in DOPC liposome circulation provided by GD1a and GT1b was sufficient to enhance DOPC immunoliposome binding, where 44% and 43% of the injected dose of DOPC/Chol/GD1a and DOPC/Chol/GT1b immunoliposomes accumulated in lung at 15 min after injection, respectively. In general, cholesterol-containing DOPC liposomes were more targetable than DOPE liposomes, and the degree to which these liposomes avoid RES uptake influences their targetability. The results presented here are relevant to the design of targetable drug delivery vehicles.

Animals↗
PubMed1992

Soluble proteins delivered to dendritic cells via pH-sensitive liposomes induce primary cytotoxic T lymphocyte responses in vitro.

Effective immunity to many infectious agents, particularly viruses, requires a CD8+ cytotoxic T lymphocyte (CTL) response. Understanding how to achieve CTL induction with soluble proteins is important for vaccine development since such antigens are usually not processed appropriately to induce CTL. In the present report, we have demonstrated that a potent primary CTL response against a soluble protein can be achieved by delivering antigen in pH-sensitive liposomes to dendritic cells (DC) either in vivo or in vitro. Since the pH-sensitive liposome delivery system is efficient and easy to use, the approach promises to be valuable both in the study of basic mechanisms in antigen processing, and as a practical means of immunization.

Animals↗
PubMed1992

Bilayer stabilization of phosphatidylethanolamine by N-biotinylphosphatidylethanolamine.

We have examined the ability of biotinylated phosphatidylethanolamine and similar lipids to stabilize the bilayer phase of polymorphic dioleoylphosphatidylethanolamine (DOPE). Sonicated lipid mixtures were characterized in terms of their aggregation state, size and ability to encapsulate and retain the fluorescent dye, calcein. Titration of DOPE with N-biotinyl-PE indicated that stable liposomes could be produced by sonication of DOPE based dispersions containing N-biotinyl-PE at concentrations greater than 8 mol%. These liposomes were relatively small, could efficiently encapsulate calcein, and showed minimal leakage upon prolonged storage at 4 degrees C. Maleimido-4-(p-phenylbutyrate)-PE (MPB-PE) was equally effective at stabilizing the bilayer phase of DOPE whereas N-dinitrophenyl-PE and N-(dinitrophenyl-caproyl)-PE were relatively poor stabilizers, requiring at least 15 mol% for stabilization at pH 7.4. Differential scanning calorimetry of dielaidoylphosphatidylethanolamine (DEPE)/N-biotinyl-PE mixtures indicated that stabilizer concentrations as low as 2 mol% could abolish the L alpha/HII phase transition of DEPE.

Biotin↗
PubMed1992

Effect of treated infection on microvascular anastomosis.

The effect of established infection with penicillin-resistant Staphylococcus aureus on microarterial and microvenous anastomosis was studied in a rat experimental model. The infection was treated with wound debridement and systemic antibiotics at the time of the surgical procedure. It was found that the patency rate of microarterial repairs at 10-14 days was 95.1%. Veins were less resistant to infection than arteries. Two types of vein involvement were found. These were classified according to the degree of thrombosis resulting from endophlebitis. The patency rate of anastomoses performed on the more mildly infected veins was 56.5% and that on the more severely infected veins was 0%.

Anastomosis, Surgical↗
PubMed1992

In vitro interactions of integration host factor with the ompF promoter-regulatory region of Escherichia coli.

Previous work has shown that integration host factor (IHF) mutants have increased expression and altered osmoregulation of OmpF, a major Escherichia coli outer membrane protein. By in vitro analysis the possibility was investigated that IHF interacts directly with the ompF promoter region. Gel retardation assays and DNase I protection experiments showed that IHF binds to two sites in the ompF promoter region centered at positions -180 and -60 relative to the start of transcription. Gel electrophoresis studies with circularly permuted ompF promoter fragments indicated that IHF binding strongly increased a small intrinsic bend in the ompF promoter region. The addition of IHF to a purified in vitro transcription system strongly and specifically inhibited ompF transcription. This inhibition was reversed by increasing the concentration of OmpR, a positive activator required for ompF expression, suggesting that IHF may inhibit ompF transcription by altering how OmpR interacts with the ompF promoter.

Bacterial Outer Membrane Proteins↗
PubMed1992

Trypsin-induced lysis of lipid vesicles: effect of surface charge and lipid composition.

We have made a curious observation that the proteolytic enzyme, trypsin, induced a rapid and complete release of the contents of vesicles composed of dioleoylphosphatidylethanolamine (DOPE) and oleic acid (OA). Content release at 37 degrees C, monitored by the release of an entrapped fluorescence marker (calcein), was accompanied by an extensive vesicle aggregation. The lytic activity of trypsin on the vesicles depended on pH and liposome composition. The optimal pH for vesicle lysis was below pH 7.4, which was different from the optimal pH for catalytic activity of trypsin. The lytic activity of trypsin was specific for vesicles composed of DOPE and fatty acids such as OA and palmitoleic acid; vesicles composed of dioleoylphosphatidylcholine, N-methyl-DOPE, and OA, or DOPE combined with other negatively charged lipids such as phosphatidylserine and phosphatidic acid were not sensitive to trypsin. Inhibition of enzyme activity by trypsin inhibitors did not abolish the lytic activity, suggesting that the lytic activity of trypsin is not related to the catalytic activity. However, the lytic activity of trypsin on vesicles composed of DOPE and OA was inhibited in the presence of excess vesicles containing negative charges, or by a pretreatment of trypsin with acylating reagent to reduce the positive-charge content of trypsin. These data demonstrate that vesicle aggregation and lysis are the results of electrostatic interactions of positive charges on trypsin and negative charges on the vesicles. Phase separation and transition to nonbilayer phases of the vesicle lipids are likely involved.

Fluoresceins↗
PubMed1992

Insulin mediator stimulation of pyruvate dehydrogenase phosphatases.

A two stage assay for detecting insulin mediator based upon its stimulation of soluble pyruvate dehydrogenase (PDH) phosphatase to activate soluble pyruvate dehydrogenase complex (PDC) has been developed. This coupled assay determines the activation of PDC by monitoring production of [14C]CO2 from [1-14C]pyruvic acid. In addition to being more sensitive than the rat liver mitoplast assay previously used, it allows for the separation and investigation of the effects of mediator on the PDH phosphatases individually. It has been previously shown that the insulin mediator stimulates the most abundant PDH phosphatase, the divalent cation dependent PDH phosphatase, by decreasing the phosphatase's metal requirement (1). A metal independent PDH phosphatase has been found in bovine heart mitochondria. This phosphatase is not immunoprecipitated by antiphosphatase 2A antibody, it is not inhibited by okadaic acid, and it is not stimulated by spermine. However, it is stimulated (more than threefold) by insulin mediator prepared from isolated rat liver membranes. It is inhibited by Mg-ATP, with half-maximal inhibition at 0.3 mM; however, this inhibition is overcome by the insulin mediator.

Adenosine Triphosphate↗
PubMed1992

Potentiation of the humoral response of intravenous antigen by splenotropic liposomes.

We have recently described that large liposomes composed of egg phosphatidylcholine (PC), cholesterol (chol) and monosialoganglioside GM1 show elevated accumulation in the red pulp of the spleen when they are i.v. administered into mice. Up to 50% of the injected dose was found in spleen at 4 h post injection. In this report, we have investigated the potential application of such liposomes in the stimulation of anti-lysozyme response in mice. Lysozyme entrapped in the splenotropic liposomes composed of PC/chol/GM1 showed higher efficiency in potentiating the humoral response than that of either free lysozyme or lysozyme entrapped in hepatotropic liposomes composed of PC/chol. The results demonstrate that high levels of i.v. antigen delivery by liposomes to the splenic macrophage instead of the liver Kupffer cells is important in the liposomal adjuvanticity. The antibody elicited by the liposome entrapped antigen was mainly IgG1 subtype.

Animals↗
PubMed1992

Evaluation of the in vivo effect of naproxen on zidovudine pharmacokinetics in patients infected with human immunodeficiency virus.

OBJECTIVE: To determine if therapeutic doses of naproxen affect the in vivo disposition of zidovudine. METHODS: This was designed as a randomized, two-period, two-treatment, crossover study. The patients were 12 men infected with human immunodeficiency virus who had acquired immunodeficiency syndrome (AIDS) or AIDS-related complex. On two separate occasions 14 days apart, patients received either zidovudine alone (200 mg every 4 hours while awake) or zidovudine (200 mg every 4 hours while awake) and naproxen (500 mg every 12 hours for 4 days). On the morning of the fifth day, each patient received the final dose of each regimen and blood and urine were serially collected for 8 hours. Pharmacokinetic parameters (area under the serum concentration-time curve [AUC], maximum plasma concentration, terminal half-life, renal clearance, and urinary recovery) were assessed for zidovudine and its glucuronide metabolite. MAIN RESULTS: Naproxen had no significant effect (< 10% difference between treatment means, p > 0.15, ANOVA) on the above pharmacokinetic parameters for both zidovudine and its metabolite. Although the power of the study to detect these small differences was < 80% at the 5% significance level, differences ranging from 12.6% for AUC to 38.8% for urinary recovery could be detected with 80% power. CONCLUSION: Therapeutic doses of naproxen do not significantly affect the pharmacokinetic disposition of zidovudine.

Adult↗
PubMed1992

Gene transfer in vivo with DNA-liposome complexes: safety and acute toxicity in mice.

DNA can be introduced into a variety of cell types after formation of liposomal complexes with cationic lipids. In this report, conditions have been established to optimize the production of DNA-liposome complexes that efficiently transfect cells. The safety and toxicity of this method of gene delivery have been assessed after in vivo administration, either by intravenous or direct intratumor injection. Nine to eleven days after intravenous injection, DNA was found primarily in heart and lung tissue by PCR analysis. No abnormalities were evident from histologic examination of tissue, examination of tissue-specific serum enzymes, routine biochemical parameters, or electrocardiographic monitoring. DNA-liposome complexes can therefore be used for the delivery of recombinant genes in vivo with minimal toxicity.

Animals↗