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Biomedical subjects

K Hong

Publications and source records attributed to K Hong.

At least 73 records · Page 4Linked to original sources
PubMed1997

Stabilization of cationic liposome-plasmid DNA complexes by polyamines and poly(ethylene glycol)-phospholipid conjugates for efficient in vivo gene delivery.

Stable complexes of cationic liposomes with plasmid DNA were prepared by (1) including a small amount of poly(ethylene glycol)-phospholipid conjugate or (2) condensing the DNA with polyamines prior to the formation of liposome-plasmid complexes. These preparations were stable for months at 4 degrees C and gave reproducible high transfection activity for in vivo gene delivery after intravenous injection in mice. Under these conditions, the expression of marker gene (luciferase) was primarily in the lungs (reaching values up to 3 ng expression per mg tissue protein), but also in other tissues to a lesser extent. Non-stabilized formulations lost all their transfection activity in 4 days. In these formulations cholesterol, not dioleoylphosphatidylethanolamine, was the helper lipid effective for sustaining high transfection activity in vivo. These new developments in formulation technology should enhance the potential for liposome-mediated gene therapy.

Animals↗
PubMed1997

Human IgG binding ability of streptococcal M3 protein: its related complement activation-dependent M3 protein polymerization.

We previously showed that M3 protein bound both fibrinogen and human serum albumin. Here, I report that M3 protein also has affinity for human immunoglobulin G. In contrast, M3 protein did not show affinity for polyclonal immunoglobulin G from other mammalian species (rabbit and goat). On the human immunoglobulin G molecule, the Fab domain was mainly responsible for the interaction with M3 protein, although the Fc region had a low degree of interaction with the M3 protein. Also, since the 35 kDa C-terminal fragment of M3 protein bound human immunoglobulin G, the binding site for human immunoglobulin G on M3 protein is present in this portion of the protein. The M3 protein-human immunoglobulin G complexes initiated complement activation via both classical and alternative pathways in normal human serum. When C3 was precipitated in the fluid phase with anti-C3 antibody and analyzed by SDS-PAGE under reducing conditions, M3 protein coprecipitated with the complexes and was polymerized. However, there was no polymerization of M3 protein when incubated with normal human serum treated with magnesium-ethyleneglycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid in the presence of M3 protein. Thus, this polymerization is mostly mediated via the classical activation pathway. It is probably helpful for the understanding of the antiphagocytic activity of M protein.

Animals↗
PubMed1997

Genetic immunization with adeno-associated virus vectors expressing herpes simplex virus type 2 glycoproteins B and D.

Intramuscular injection of mice with an adeno-associated virus (AAV) vector expressing herpes simplex virus type 2 glycoprotein B led to the generation of both gB-specific major histocompatibility complex class I-restricted cytotoxic T lymphocytes and anti-gB antibody. AAV-mediated immunization was more potent than plasmid DNA or protein in generating antibody responses.

Animals↗
PubMed1997

Isolation and characterization of human papillomavirus type 6-specific T cells infiltrating genital warts.

The potential role of T cells in the control of human papillomavirus type 6 (HPV-6) infections is an appealing premise, but their actual role has been sparsely investigated. Since HPV-6 infections are confined to the epithelium, such an investigation should focus on the T cells present at the site of infection (i.e., the warts). Therefore, we isolated wart-infiltrating lymphocytes (WIL) from patients with clinically diagnosed anogenital warts. These WIL were characterized by their phenotype and their specificity for E7 and L1 proteins of HPV-6. The phenotype of WIL varied drastically from patient to patient, as determined by their expression of CD4, CD8, T-cell receptor alpha/beta chain (TCR alpha beta), and TCR gamma delta. Despite this heterogeneity in phenotype, HPV-6 E7 and/or L1-specific WIL, as determined by lymphoproliferation, could be isolated from more than 75% of the patients studied. Among all L1 peptides recognized by WIL, peptides 311-330 and 411-430 were the most consistently detected, with seven of nine patients for whom L1 peptide reactivity was observed responding to at least one of them. Moreover, the HPV-6 epitopic peptides recognized by WIL differed to some extent from those recognized by peripheral T cells.

Adult↗
PubMed1997

Liposomes-coated hydroxyapatite and tricalcium phosphate implanted in the mandibular bony defect of miniature swine.

Hydroxyapatite and tricalcium phosphate have been used as bone implants for some period of time. Now unfortunately, these materials have failed to become the nucleation sites for bone regeneration. We hypothesized that coating hydroxyapatite and tricalcium phosphate with negatively charged liposomes may improve the nucleation process for new bone formation. The present study was designed to test this hypothesis. Experiments were carried out in 15 miniature swines' mandibular angle with artificial bony defects. In each of the swine, the bony defects on one side were implanted with either liposomes coated with hydroxyapatite or liposomes coated with tricalcium phosphate, while the other side served as control. At the end of the third and sixth weeks following the operation, we observed result, took histology and radiographs of the operated area. The results showed that liposomes-coated materials were biocompatible and their clinical endpoint was enhanced. At the end of the third week, the implant material was surrounded by dense connective tissues. At the end of the sixth week, there were new bone formations near the implanted material. In addition, liposomes which were immobilized in agarose gel and implanted in the defects showed new bony bridge formation. These observations suggest that liposomes have the ability in promoting repair of osseous deficiencies.

Alveolar Process↗
PubMed1996

Thermosensitive liposomes: extravasation and release of contents in tumor microvascular networks.

PURPOSE: The purpose of this study was to determine whether hyperthermic exposure would accelerate drug release from thermosensitive sterically stabilized liposomes and enhance their extravasation in tumor tissues. MATERIALS AND METHODS: In vivo fluorescence video microscopy was used to measure the extravasation of liposomes, as well as release of their contents, in a rat skin flap window chamber containing a vascularized mammary adenocarcinoma under defined thermal conditions (34 degrees, 42 degrees, and 45 degrees C). Images of tissue areas containing multiple blood vessels were recorded via a SIT camera immediately before, and for up to 2 h after i.v. injection of two liposome populations with identical lipid composition: one liposome preparation was surface labeled with Rhodamine-PE (Rh-PE) and the other contained either Doxorubicin (Dox) or calcein at self-quenching concentrations. The light intensity of the entire tissue area was measured at 34 degrees C (the physiological temperature of the skin) for 1 h, and at 42 degrees or 45 degrees C for a second hour. These measurements were then used to calculate the fluorescent light intensity arising from each tracer (liposome surface label and the released contents) inside the vessel and in the interstitial region. RESULTS: The calculated intensity of Rh-PE for the thermosensitive liposomes in the interstitial space (which represents the amount of extravasated liposomes) was low during the first hour, while temperature was maintained at 34 degrees C and increased to 47 times its level before heating, when the tumor was heated at 42 degrees or 45 degrees C for 1 h. The calculated intensity of the liposome contents (Dox) in the interstitial space was negligible at 34 degrees C, and increased by 38- and 76-fold, when the tumor was heated at 42 degrees and 45 degrees C for 1 h, respectively. Similar values were obtained when calcein was encapsulated in liposomes instead of Dox. A similar increase in liposome extravasation was seen with nonthermosensitive liposomes, but negligible release of Dox occurred when the window chamber was heated to 45 degrees C for 1 h. Extravasation of liposomes continued after heating was stopped, but content release stopped after removal of heat. Release of Dox from extravasated liposomes was also seen if heating was applied 24 h after liposome administration, but no further enhancement of liposome extravasation occurred in this case. CONCLUSIONS: Our data suggest that hyperthermia can be used to selectively enhance both the delivery and the rate of release of drugs from thermosensitive liposomes to targeted tissues.

Animals↗
PubMed1996

Fluctuations in red cell flux in tumor microvessels can lead to transient hypoxia and reoxygenation in tumor parenchyma.

Hypoxia occurs in two forms in tumors. Chronic or diffusion-limited hypoxia is relatively well characterized. In contrast, intermittent or perfusion-limited hypoxia is not well characterized, and it is not known how common it is in tumors. The purpose of this study was to determine whether spontaneous fluctuations in tumor microvessel flow rate can modify vessel oxygen tension (pO2) sufficiently to cause intermittent hypoxia (IH; tissue pO2 < 3 mmHg) in the tumor parenchyma supplied by such vessels. Microvessel red cell flux (RCF) and perivascular pO2 were measured simultaneously and continuously in dorsal flap window chambers of Fischer-344 rats with implanted R3230Ac tumors. In all vessels, RCF was unstable, with apex/nadir ratios ranging from 1.5 to 10. RCF and pO2 were temporally coordinated, and there were linear relationships between the two parameters. Vascular pO2 was less sensitive to changes in RCF in well-vascularized tumor regions compared with poorly vascularized regions. Simulations of oxygen transport in a well-vascularized region of a tumor demonstrated that two-fold variations in RCF can produce IH in 30% of the tissue in that region. In poorly vascularized regions, such fluctuations would lead to an even greater percentage of tissue involved in transient hypoxia. These results suggest that IH is a relatively common phenomenon. It could affect binding of hypoxic cytotoxins to tumor cells, in addition to being an important source of treatment resistance. Intermittent hypoxia also could contribute to tumor progression by providing repeated exposure of tumor cells to hypoxia-reoxygenation injury.

Adenocarcinoma↗
PubMed1996

Increased liposome extravasation in selected tissues: effect of substance P.

We have used a pharmacologic mediator to open intercellular connections in selected vessels to allow liposomes to escape from the blood stream and to extravasate into tissues that have appropriate receptors. We have examined the effects of substance P (SP), a peptide known to increase vascular permeability in selected tissues, such as trachea, esophagus, and urinary bladder in rats. We used quantitative fluorescence analysis of tissues to measure two fluorescent markers, one attached to the lipid (rhodamine-phosphatidylethanolamine) and another, doxorubicin (an anti-tumor drug), encapsulated within the aqueous interior. We have also examined the deposition of liposomes microscopically by the use of encapsulated colloidal gold and silver enhancement. Analysis of the biochemical and morphological observations indicate the following: (i) Injection of SP produces a striking increase in both liposome labels, but only in tissues that possess receptors for SP in postcapillary venules; (ii) liposome material in these tissues has extravasated and is found extracellularly near a variety of cells beyond the endothelial layer over the first few hours; (iii) 24 h following injection of liposomes and SP, liposome material is found in these tissues, localized intracellularly in both endothelial cells and macrophages. We propose that appropriate application of tissue-specific mediators can result in liposome extravasation deep within tissues that normally do not take up significant amounts of liposomes from the blood. Such liposomes are able to carry a variety of pharmacological agents that can be released locally within selected target tissues for therapeutic purposes.

Animals↗
PubMed1996

Liposomes with detachable polymer coating: destabilization and fusion of dioleoylphosphatidylethanolamine vesicles triggered by cleavage of surface-grafted poly(ethylene glycol).

Plasma-stable liposomes (100 nm) were prepared from dioleoylphosphatidylethanolamine (DOPE) and 3-6 mol% of a new disulfide-linked poly(ethylene glycol)-phospholipid conjugate (mPEG-DTP-DSPE). In contrast to similar preparations containing non-cleavable PEG-phospholipid conjugate, thiolytic cleavage of the grafted polymer chains facilitated rapid and complete release of the liposome contents. Furthermore, the detachment of PEG from DOPE liposomes resulted in liposomal fusion. Finally, while formulation of pH-sensitive DOPE/cholesterol hemisuccinate liposomes with mPEG-DTP-DSPE abolished the pH sensitivity, cleavage of the PEG chains completely restored this property. These are the first examples of new useful properties of liposomes grafted with cleavable polymer.

Animals↗
PubMed1996

Sequence and transmembrane topology of MEC-4, an ion channel subunit required for mechanotransduction in Caenorhabditis elegans.

The process by which mechanical stimuli are converted into cellular responses is poorly understood, in part because key molecules in this mode of signal transduction, the mechanically gated ion channels, have eluded cloning efforts. The Caenorhabditis elegans mec-4 gene encodes a subunit of a candidate mechanosensitive ion channel that plays a critical role in touch reception. Comparative sequence analysis of C. elegans and Caenorhabditis briggsae mec-4 genes was used to initiate molecular studies that establish MEC-4 as a 768-amino acid protein that includes two hydrophobic domains theoretically capable of spanning a lipid bilayer. Immunoprecipitation of in vitro translated mec-4 protein with domain-specific anti-MEC-4 antibodies and in vivo characterization of a series of mec-4lacZ fusion proteins both support the hypothesis that MEC-4 crosses the membrane twice. The MEC-4 amino- and carboxy-terminal domains are situated in the cytoplasm and a large domain, which includes three Cys-rich regions, is extracellular. Definition of transmembrane topology defines regions that might interact with the extracellular matrix or cytoskeleton to mediate mechanical signaling.

Amino Acid Sequence↗
PubMed1996

Genetic evaluation of candidate genes for the Mom1 modifier of intestinal neoplasia in mice.

As genetic mapping of quantitative trait loci (QTL) becomes routine, the challenge is to identify the underlying genes. This paper develops rigorous genetic tests for evaluation of candidate genes for a QTL, involving determination of allelic status in inbred strains and fine-structure genetic mapping. For the Mom1 modifier of intestinal adenomas caused by ApcMin, these tests are used to evaluate two candidate genes: Pla2g2a, a secretory phospholipase, and Rap1GAP, a GTPase activating protein. Rap1GAP passes the first test but is excluded by a single fine-structure recombinant. Pla2g2a passes both tests and is a strong candidate for Mom1. Significantly, we also find that ApcMin-induced adenomas remain heterozygous for the Mom1 region, consistent with Mom1 acting outside the tumor lineage and encoding a secreted product.

Adenoma↗
PubMed1996

Depletion of alveolar macrophages decreases neutrophil chemotaxis to Pseudomonas airspace infections.

The mechanism for neutrophil (PMN) influx into infected airspaces of the lung is not known. To determine whether alveolar macrophage products are important in the initiation of chemotaxis, we depleted rats of alveolar macrophages by aerosolizing negatively charged oligolamellar liposomes complexed to clodronate disodium. Ninety-five percent of the alveolar macrophages were depleted, and lung injury and inflammation were minimized with this depletion technique. Rats depleted of alveolar macrophages were then anesthetized, and either 5 x 10(6) colony-forming units (CFU) or 5 x 10(7) CFU of Pseudomonas aeruginosa were instilled into the airspaces of these animals. When recombinant macrophage inflammatory protein MIP-2 was intratracheally instilled into rats depleted of alveolar macrophages, PMN were recruited to their airspaces. Nonetheless, PMN numbers were decreased in the lavage fluids when moderate or large inoculums of bacteria were instilled into depleted rats, although the PMN response appeared dose dependent. Levels of bioactive tumor necrosis factor-alpha and immunoreactive proteins CINC/gro (cytokine-induced PMN chemoattractant) in the lavage fluids obtained from infected rats depleted of alveolar macrophages were significantly decreased compared with the levels in the lavage fluids obtained from normal infected rats. MIP-2 mRNA expression, as detected by Northern analysis, was also decreased in the infected lungs of depleted rats, and the lavage fluid from these rats had significantly decreased chemotactic activity. Therefore these results suggest that alveolar macrophage products play a direct role in the initial recruitment of PMN into infected lungs.

Animals↗
PubMed1996

Microvascular studies on the origins of perfusion-limited hypoxia.

Two forms of hypoxia are thought to exist in tumours: (1) hypoxia caused by limitations of its diffusion (chronic hypoxia); and (2) hypoxia caused by changes in perfusion (acute hypoxia). Indirect information suggests the existence of perfusion-limited hypoxia, but there is no direct proof that fluctuations in blood flow can lead to hypoxia, nor is there any information regarding potential causes of fluctuant flow. In this study, we have begun to explore these questions using R3230AC tumours transplanted into rat dorsal-flap window chambers. Two types of fluctuant flow have been observed. The first type, usually confined to single vessels, is typified by instability of flow magnitude and direction, and total vascular stasis occurs, but only for a few seconds at a time (4% incidence). The second type of fluctuation occurs in groups of vessels and is cyclic, with cycle times ranging from 20-60 min. Total vascular stasis does not necessarily occur, but the fluctuations in red cell flux are accompanied by changes in vascular oxygen content, as measured by microelectrodes. Another source of chronic hypoxia has also been identified in these experiments. Nine per cent (9%) of vessels examined had plasma flow, but very low or absent red cell flux over periods of many minutes.

Animals↗
PubMed1995

Interaction of cationic liposomes with cells of electrically active neuronal networks in culture.

Incubation of rhodamine-labeled cationic liposomes with mature murine spinal cultures results in strong fluorescence that is evenly distributed on somata and neurites of neurons in 7 different cultures. Staining of the glial carpet is minimal. Rhodamine-labeled dextran, encapsulated in liposomes, also stains neurons. Electron microscope data show external attachment and intact internalization of liposomes. Spontaneous electrical bursting activity is altered but not lost after incubation.

Animals↗