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Biomedical subjects

A Huang

Publications and source records attributed to A Huang.

At least 217 records · Page 12Linked to original sources
PubMed1989

Metabolic derangement of glucose, bile acid and amino acids after portasystemic shunts in cirrhotic rats.

Carbon tetrachloride was used to induce cirrhosis in 81 Wistar rats. The animals were divided into three groups to receive end-to-side mesocaval shunt (MCS), end-to-side portacaval shunt (PCS) and Sham operation as control, respectively. Dynamic values of blood glucose and hormones for regulating glucose metabolism, SGPT, serum glycine conjugated cholic acid (CCA) and free serum amino acids were determined and compared with those obtained from 10 normal rats. The determinations suggested that the insulin level depended on the severity of hepatocellular damage with hyperglucagonemia after portasystemic shunt, and CCA was markedly elevated in MCS rats after interruption of the enterohepatic circulation. Changes of CCA were also influenced by hyperglucagonemia and poor liver function in PCS rats. Increase in the aromatic amino acids (AAA) level was related to the impaired hepatic function and hyperglucagonemia. However, decrease in the branched-chain amino acids (BCAA) level was not likely in response to the serum insulin level. Therefore, it is concluded that imbalance of serum amino acids has partial relationship with the derangement of glucose metabolic hormones.

Amino Acids↗
PubMed1988

Expression of the HSV-2 ribonucleotide reductase subunits in adenovirus vectors or stably transformed cells: restoration of enzymatic activity by reassociation of enzyme subunits in the absence of other HSV proteins.

We have cloned the large subunit (RR1) of the HSV-2 ribonucleotide reductase into a helper-independent adenovirus 5 vector under control of the viral major late promoter. Infection of 293 cells with the AdRed-1 recombinant virus resulted in the expression of the HSV-2 RR1 protein. We have also produced cells which constitutively express the small (RR2) subunit of the HSV-2 enzyme by transfecting 293 cells with a plasmid encoding this protein and the neo resistance marker (pSV2neo-RR2). Infection of the A439-14 producer cells with AdRed-1 resulted in the expression of enzymatically active HSV-2 ribonucleotide reductase. HSV-2 reductase activity could also be detected upon mixing of extracts from cells expressing either subunit. Our results indicate that the HSV-2 holoenzyme can be reconstituted in vivo and in vitro and that no HSV-2 proteins, beyond the enzyme subunits, are required for the formation and activity of the viral reductase.

Adenoviridae↗
PubMed1988

Atypical epiglottitis.

Early diagnosis of acute epiglottitis may be difficult in the child presenting atypically. The cases of four patients who displayed atypical presentation are reported. The initial diagnosis in three children was croup and in one, pharyngitis. In the fourth patient, a child who had coexisting meningitis, epiglottitis was an incidental finding. All patients recovered with no sequelae.

Acute Disease↗
PubMed1988

A multicenter trial of antithymocyte globulin in aplastic anemia and related diseases.

One hundred fifty patients with bone marrow failure were treated in three groups with antithymocyte globulin (ATG; Upjohn, Kalamazoo, MI) in a multicenter trial. Patients were assessed at 3, 6, and 12 months after initiation of treatment by three criteria: transfusion independence, clinical improvement, and blood counts. Group I consisted of 77 patients with acute severe aplastic anemia, randomized to receive either ten or 28 days of ATG. There was no significant difference between the two arms of this protocol: 47% of all patients were clinically improved and 31% were transfusion independent at 3 months. Of the severely affected patients, 27% died before 3 months; most deaths occurred early in treatment. Factors associated with survival in severely affected patients included male sex, age less than 40 years, absolute neutrophil count greater than 200/microL, and idiopathic etiology. Neutrophil counts generally increased by 8 weeks after treatment, but patients continued to show improvement to 1 year posttreatment. In Group II, 44 patients with moderate or chronic severe aplastic anemia were randomized to receive either ten days of ATG or 3 months of high-dose nandrolone decanoate. No patient initially treated with androgens recovered, but 28% of ATG-treated cases achieved transfusion independence at 3 months. Group III consisted of patients with a variety of bone marrow failure syndromes. Patients with pancytopenia and cellular bone marrow showed response rates similar to those of patients with chronic or moderate aplastic anemia.

Anemia, Aplastic↗
PubMed1987

The differentiated form of nasopharyngeal carcinoma contains Epstein-Barr virus DNA.

Immunologic studies of Epstein-Barr virus (EBV) have implicated EBV in undifferentiated and partially differentiated, non-keratinizing nasopharyngeal carcinoma (NPC). Patients with the well-differentiated, keratinizing form of NPC have EBV serologic patterns similar to those of control populations. In addition, viral DNA has not been detected in the differentiated tumors using viral cRNA probes to DNA immobilized on filters. In this study we have tested for EBV DNA using recombinant DNA probes to Southern blots of DNA from 33 NPC specimens. The 24 undifferentiated and 4 partially differentiated specimens generally contained a relatively high number of EBV genome equivalents, while the 5 well-differentiated NPC all contained detectable EBV, but at low copy number. The viral DNA from one of the well-differentiated specimens was cloned into a cosmid vector. Five recombinant clones representing the fused viral termini were obtained, indicating the presence of episomal, intracellular DNA in the tumor. These findings indicate that all histologic subsets of NPC contain EBV DNA.

Antibodies, Viral↗
PubMed1987

Characterization of a bacteriophage that carries the genes for production of Shiga-like toxin 1 in Escherichia coli.

The Shiga-like toxin 1-converting bacteriophage H-19B was recently shown to carry the structural genes for the toxin and was shown to have DNA sequence homology with phage lambda. We present evidence that the linear genome of bacteriophage H-19B has cohesive termini which become covalently associated during prophage integration. Integration occurs through a site on a 4-kilobase-pair EcoRI fragment located near the center of the bacteriophage chromosome. The relationship between bacteriophages H-19B and lambda was examined by Southern hybridization. Homologous regions were mapped on the respective chromosomes which corresponded to the regions of the J gene, the int-xis area, and the O and P genes of phage lambda. The H-19B tox genes were mapped to the right of the O and P gene homology, which was far away from the phage attachment site. We concluded that H-19B is a lambdoid bacteriophage. Unlike other toxin-converting bacteriophages, the toxin genes were not located adjacent to the phage attachment site. It appeared that the Shiga-like toxin 1 genes were not picked up by a simple imprecise prophage excision. H-19B could, however, have acquired chromosomally located toxin genes by a series of events involving deletion and duplication followed by aberrant excision.

Bacterial Toxins↗
PubMed1986

Cloning and expression of the genes specifying Shiga-like toxin production in Escherichia coli H19.

Some strains of Escherichia coli produce a protein which is cytotoxic for Vero cell and HeLa cell monolayers. This toxin is very similar to the toxin of Shigella dysenteriae 1 and has been named verotoxin or E. coli Shiga-like toxin. It has been shown that toxin conversion is due to a group of bacteriophages, one of which has been designated H-19B. In this study we report hybridization experiments showing that part of the H-19B genome is homologous to phage lambda. We have cloned a 1.7-kilobase BalI-BglII fragment from the genome of H-19B into pUC18. The recombinant plasmid confers the ability to produce high levels of Shiga-like toxin on transformed E. coli cells. We demonstrate using an in vitro transcription/translation system that the cloned fragment specifies the two verotoxin subunit peptides which have masses of 31 and 5.5 kilodaltons. The identity of peptides was confirmed by immunoprecipitation with verotoxin antiserum and protein A-Sepharose beads.

Animals↗
PubMed1984

Antibody-dependent cellular cytotoxicity and disease course in North American patients with nasopharyngeal carcinoma: a prospective study.

It has previously been reported that antibody-dependent cellular cytotoxicity (ADCC) levels determined at diagnosis against Epstein-Barr virus (EBV)-specific membrane antigens (MA) are predictive of disease course following therapy in patients with nasopharyngeal carcinoma (NPC). In general, survival was significantly shorter following therapy in patients with low ADCC titers at diagnosis versus those with high titers. To examine this further, a prospective study on North Americans with different histopathological types of this disease was initiated approximately 5 years ago. The results to date tend to support the conclusions drawn from the retrospective study for patients with the more poorly differentiated types (WHO 2 and WHO 3) of this disease. Over the first 3 years of this study, approximately 75% of the patients in the "high" category have remained clinically disease-free for 3 years or longer as opposed to approximately 35% of the patients in the "low" group. Disease progression rates were calculated to be approximately four times higher in the low group. Similar trends were noted in actual survival rates over a 3-year period. ADCC titers were in general found to be relatively stable in sequential serum samples from the same patient, with some exceptions. With the exceptions, however, changes in ADCC titers also reflected disease course. These results indicate, therefore, that anti-EBV ADCC titers are predictive of disease course in patients with the poorly differentiated types of NPC.

Actuarial Analysis↗
PubMed1983

Interactions of immunoliposomes with target cells.

We have covalently attached a monoclonal antibody (11-4.1) against the murine major histocompatibility antigen, H-2Kk, on the surface of liposomes. The interaction of these antibody-coated liposomes (immunoliposomes) with target cells, RDM-4 lymphoma (H-2Kk), was investigated. About 90% of the immunoliposomes taken up by target cells at 4 degrees C could be removed by a mild protease treatment of the cells, whereas only 30% of the uptake at 37 degrees C was labile to the same treatment. Furthermore, the uptake of immunoliposomes at 37 degrees C was inhibitable by cytochalasin B or by a combination of 2-deoxyglucose and NaN3. These results suggest that immunoliposome binding to the target cell surface is the primary uptake event at 4 degrees C and that the surface-bound liposomes are rapidly internalized by the cells at 37 degrees C, probably via an endocytic pathway. Studies with fluorescence microscopy of target cells treated with immunoliposomes containing carboxyfluorescein also supported this conclusion. If endocytosis is the mechanism by which immunoliposomes gain entry into target cells, the efficacy of a cytotoxic drug encapsulated would depend on the resistance of the drug to lysosomal inactivation and its ability to escape from the lysosomal system. Consistent with this notion, we observed that methotrexate encapsulated in liposomes bearing 11-4.1 antibody specifically inhibited deoxy[6-3H]uridine incorporation into DNA in target RDM-4 cells but not in P3-X63-Ag8 myeloma cells (H-2Kd) at the same doses. The observed cytotoxic effect of encapsulated methotrexate could be reversed by the treatment of cells with a lysosomotropic amine, chloroquine, which has been shown to increase the intralysosomal pH of mammalian cells. On the other hand, cytosine-beta-D-arabinofuranoside encapsulated in immunoliposomes showed no target-specific killing, probably because the drug is readily inactivated in the lysosomal system. These results are discussed in terms of the drug carrier potential of immunoliposomes.

Animals↗
PubMed1983

Application of Epstein-Barr virus (EBV) serology to the diagnosis of North American nasopharyngeal carcinoma.

A cooperative study was established among a number of institutions in the USA to determine the clinical value of Epstein-Barr virus (EBV) serology for the diagnosis of different histopathological types of North American nasopharyngeal carcinoma (NPC) including occult primary tumors. One hundred-twenty-four patients with confirmed NPC have now been entered into the study. For each patient, anti-EBV antibody titers were determined at diagnosis and related to the histopathology as classified according to the World Health Organization (WHO). The results suggest that certain anti-EBV antibodies are of potential value for the diagnosis of undifferentiated types of NPC but not for the well-differentiated cancer. The IgA anti-VCA antibody response is the most specific for this disease and of the greatest diagnostic value when used alone or in combination with the anti-EA test. These tests have also been used successfully for the detection of occult NPC. These results indicate that these tests can be useful aids to the clinician for the diagnosis of certain histopathologic types of this disease.

Antigens, Viral↗
PubMed1982

An improved method for covalent attachment of antibody to liposomes.

A rapid and simple method is described for the incorporation of monoclonal antibody coupled with palmitic acid into liposomes prepared by the reverse-phase evaporation method (Szoka, F. and Papahadjopoulos, D. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4194-4198). Palmitoyl antibody in 0.15% deoxycholate is added to a liposome suspension after the majority of the organic solvent has been removed by evaporation. Efficient incorporation (over 80%) of palmitoyl antibody occurred without leakage of the encapsulated drug. Native, unmodified antibody did not incorporate under identical conditions. About 50% of the incorporated antibodies could be readily digested by protease, while most of an internal protein marker was not, suggesting that about half of the antibodies were exposed on the outer surfaces of liposomes. Target-specific binding of antibody-liposomes has also been demonstrated in vitro with the RDM-4 lymphoma cells. This method offers a rapid and highly efficient attachment of functional antibody molecules to liposomes with high capture efficiency of drugs, and therefore should be useful in target-specific delivery of drugs mediated by liposomes.

Animals↗
PubMed1981

Immunoliposome labeling: a sensitive and specific method for cell surface labeling.

A simple, one-step procedure for fluorescence labeling of cultured cells with high sensitivity and specificity is described. We term this method immunoliposome labeling. Monoclonal IgG antibody was first covalently coupled with palmitic acid. The palmitoyl IgG was then incorporated into unilamellar liposomes (about 100 nm diameter) containing either N-(4-nitrobenzo-2-oxa-1,3-diazole)- or N-(fluorescein isothiocyanyl)-phosphatidylethanolamine by a detergent-dialysis procedure. A monoclonal antibody to the mouse major histocompatibility antigen, H-2k, was tested as a model system. Fluorescent liposomes with covalently coupled anti-H-2k specifically labeled the mouse L-929 cells (H-2k type), but not the A-31 cells (H-2d type). The degree of labeling was quantitated by a microscope photometer. Cells labeled with fluorescent liposomes showed 4--6-fold stronger fluorescence than cells labeled with either fluorescein-conjugated antibody or with primary antibody followed by fluorescein-conjugated secondary antibody (indirect immunofluorescence). Since different types of label (fluorescent, radioactive, etc.) can be incorporated into liposomes, this specific and sensitive method is potentially very versatile.

4-Chloro-7-nitrobenzofurazan↗
PubMed1981

The reliability of IgA antibody to Epstein-Barr virus (EBV) capsid antigen as a test for the diagnosis of nasopharyngeal carcinoma (NPC).

Since patients with nasopharyngeal carcinoma were first reported to have elevated levels of IgA antibody to Epstein-Barr virus (EBV) in their sera, workers in a number of countries have studied the possibility that this assay could be used in the diagnosis and monitoring of patients with this disease. In the United States, a collaborative project involving seven centers has been established to investigate the potential value of IgA antibody to EBV viral capsid antigen (VCA) as a clinical tool. In this report, we will summarize the results obtained from three studies: a comparison of EBV serology in three laboratories; a retrospective study of 37 nasopharyngeal carcinoma (NPC) patients and controls, and a prospective study of 126 NPC patients and 683 controls, including 149 patients with other malignancies involving the head and neck. The study of testing comparability in three laboratories demonstrated the feasibility of using this assay in a number of laboratories. The retrospective study confirmed the difference in IgA antibody titers between NPC patients and matched controls. The prospective study showed a relationship between IgA antibody titers and histopathology but not disease stage. IgA antibody titers were elevated more frequently in patients with nonkeratinizing or poorly differentiated types of NPC than for the well-differentiated squamous cell carcinomas. While IgA antibodies to EBV VCA appear to be of value in the early detection and diagnosis of NPC, it is possible that additional serologic tests for immunity to EBV, such as IgG antibody to VCA or early antigen (EA), will improve even further the clinical value of EBV serology in the management of NPC.

Antibodies, Viral↗
PubMed1980

Monoclonal antibody covalently coupled with fatty acid. A reagent for in vitro liposome targeting.

Monoclonal antibody to the mouse histocompatibility antigen, H-2k, was derivatized with palmitic acid using an activated ester of N-hydroxysuccinimide. About 70% of the resulting amphipathic antibody could be incorporated into liposomes by a detergent-dialysis method. The antibody-bound liposomes were about 900 A in diameter and were heterogeneous in terms of the number of antibody molecules per liposome. These liposomes showed specific binding affinity to mouse L-929 cells (H-2k), but not to A-31 cells (H-2d), whereas native liposomes showed no detectable binding to either cell type. The specific binding of anti-H-2k-bound liposomes to L-929 cells could be blocked by a preincubation of cells with an excess of free, underivatized anti-H-2k antibody but not by normal mouse IgG. Using a fluorescent phospholipid, liposomes containing anti-H-2k specifically labeled L-929 cells but not A-31 cells in a mixed culture. Liposomes containing normal mouse IgG did not significantly label either cell type. These results clearly demonstrated the effectiveness of the monoclonal antibody for liposome targeting.

Animals↗
PubMed1980

Characterization of benzodiazepine receptors in primary cultures of fetal mouse brain and spinal cord neurons.

Primary cultures of fetal mouse brain and spinal cord were examined for the presence of binding sites for [3H]diazepam. Both brain and spinal cord cultures contain high affinity binding sites which resemble benzodiazepine receptors found in mammalian CNS with respect to both pharmacologic profile and response to exogenously applied GABA. These observations, coupled with the electrophysiologic properties of these cells suggest that primary cultures of fetal mouse brain and spinal cord may be valid models for studying the role and regulation of the benzodiazepine receptor.

Animals↗