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Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 865 records · Page 48Linked to original sources
PubMed1993

Adipose cell hyperplasia and enhanced glucose disposal in transgenic mice overexpressing GLUT4 selectively in adipose tissue.

To gain insight into the molecular pathogenesis of obesity and specifically the role of nutrient partitioning in the development of obesity, we overexpressed the insulin-responsive glucose transporter (GLUT4) in transgenic mice under the control of the fat-specific aP2 fatty acid-binding protein promoter/enhancer. Two lines of transgenic mice were generated, which overexpressed GLUT4 6-9-fold in white fat and 3-5-fold in brown fat with no overexpression in other tissues. In vivo glucose tolerance was enhanced in transgenic mice. In isolated epididymal, parametrial, and subcutaneous adipose cells from transgenic mice, basal glucose transport was 20-34-fold greater than in nontransgenic littermates. Insulin-stimulated glucose transport was 2-4-fold greater in cells from transgenic mice. Total body lipid was increased 2-3-fold in transgenic mice overexpressing GLUT4 in fat. Surprisingly, fat cell size was unaltered and fat cell number was increased > 2-fold. This is the first animal model in which increased fat mass results solely from adipocyte hyperplasia and it will be a valuable model for understanding the mechanisms responsible for fat cell replication and/or differentiation in vivo.

Adipocytes↗
PubMed1993

Isolation and characterization of three cDNAs coding for Rab proteins from the albumen gland of the mollusc Lymnaea stagnalis.

Three cDNA clones encoding small GTP-binding proteins, LS-Rab1, LS-Rab2 and LS-Rab18a were isolated from a cDNA library from the albumen gland of the pulmonate snail Lymnaea stagnalis. Comparison of the deduced amino acid sequences with available sequences from the EMBL/Data Bank revealed that LS-Rab1 and LS-Rab2 show a sequence identity of 89-90% to the mammalian Rab1 and Rab2 proteins, and can therefore be regarded as the L. stagnalis homologs. LS-Rab18a may be considered a new member of the Rab subfamily, closely related to mouse Rab18 (74% amino acid identity). Interestingly, LS-Rab1 and LS-Rab2 share a very high sequence conservation with their mammalian homologs (95-97%) over the first 178-191 N-terminal amino acids, whereas the C-terminal part is almost completely divergent, except for their extreme ends (2-4 amino acids). The implications of these observations for the understanding of Rab-targeting signals are discussed. The LS-rab cDNAs were expressed in COS-7M6 cells. The resulting 22-kDa products were shown to bind GTP. In the albumen gland mRNA, levels of LS-rab1 appeared to be much higher than those of LS-rab2 and LS-rab18a, suggesting an important role for the LS-Rab1 protein in the albumen gland.

Amino Acid Sequence↗
PubMed1993

Synthesis and antiviral activity of 2'-substituted 9-[2-(phosphonomethoxy)ethyl]guanine analogues.

A series of 2'-substituted derivatives of 9-[2-(phosphonomethoxy)ethyl]guanine (PMEG, 1) have been synthesized and evaluated in vitro for anti-human immunodeficiency virus (HIV) activity in the XTT assay and for anti-herpes activity in the plaque reduction assay. It has been observed that the anti-HIV activity of these derivatives depends on the size and the nature of the substituent as well as the chirality at the 2'-position of PMEG. In addition, these compounds generally demonstrated greater activity against HIV than herpes viruses. The most interesting analogues which emerged from these studies are (R)-2'-(azidomethyl)-PMEG [(R)-5] and (R)-2'-vinyl-PMEG [(R)-11]. The former showed anti-HIV activity with an IC50 of 5 microM and a cytotoxicity (CC50) greater than 1.4 mM in CEM cells. The latter has an IC50 of 13 microM for anti-HIV activity and a CC50 of greater than 1.6 mM. Furthermore, we have demonstrated that replacement of the guanine base of these 2'-substituted PMEG analogues with cytosine drastically reduces anti-HIV and anti-herpes activity.

Antineoplastic Agents↗
PubMed1993

Isolation and characterization of cDNA clones encoding jacalin isolectins.

Four jacalin cDNA clones (pSKcJA1, pSKcJA3, pSKcJA15, and pSKcJA17) have been obtained from an Artocarpus integrifolia (jackfruit) seed cDNA library. These clones share over 94% sequence homology, and their deduced polypeptide sequences confirm the existence of multiple jacalin isolectins in jackfruit seeds. The deduced amino acid sequences show that jacalin appears to be initially synthesized as a prepropeptide with the following structure: N-signal (21 residues)-->propeptide (39 residues)-->beta-peptide (20 residues)-->linker region (4 residues)-->alpha-peptide (133 residues). These observations are supported by Western blot analysis of jackfruit seed extract and by immunoprecipitation of in vitro translated products of both pSKcJA3 transcript and jackfruit seed poly(A)+ RNA. Sequence analysis of the 39-residue propeptide reveals that it has the potential to facilitate proper folding of jacalin protein. The unusual primary structure of jacalin prepropeptide suggests a quite interesting processing of this lectin precursor into mature alpha- and beta-subunits.

Amino Acid Sequence↗
PubMed1993

Molecular characterization of the 5'-flanking region of human genomic ETA gene.

A clone containing the promoter, the exon 1 and exon 2 of human genomic ETA gene was isolated and sequenced. The transcription initiation site and TATA box were identified at 528 bp upstream of the initiation codon and 24 bp upstream of the transcription initiation site, respectively. The 534 bp fragment containing 5'-flanking sequence and most of the exon 1 of the human ETA gene showed a promoter activity corresponding to 55% of SV40 early promoter activity when placed upstream of the luciferase gene and transfected into CHO cells. Thus, the TATA box which consists of the TAAAAA sequence is functional for transcription of the human ETA gene. The coding region of the human ETA receptor, therefore, starts from exon 2 which contained the first and the second transmembrane regions. The human ETA gene was demonstrated to be a single pair of copy by Southern blot analysis, and it was localized in chromosome 4 by analysis with a panel of human-rodent somatic cell hybrid lines.

Amino Acid Sequence↗
PubMed1993

Modulation by adjuvants and carriers of the immunogenicity in xenogeneic hosts of mouse anti-idiotypic monoclonal antibody MK2-23, an internal image of human high molecular weight-melanoma associated antigen.

The mouse anti-idiotypic monoclonal antibody (mAb) MK2-23 recognizes an idiotope in the antigen-combining site of the immunizing anti-human high-molecular-weight melanoma-associated antigen (HMW-MAA) mAb 763.74. Administration with an adjuvant of mAb MK2-23 conjugated to a carrier has been shown to induce anti-HMW-MAA antibodies both in syngeneic hosts and in patients with malignant melanoma. Adjuvant and carrier are required for the induction of anti-HMW-MAA immunity in BALB/c mice immunized with mAb MK2-23. Whether both adjuvant and carrier are required also in patients with malignant melanoma is not known and cannot be deduced from results obtained in a syngeneic animal model system. Therefore the present study has evaluated for the first time the effect of a carrier and an adjuvant on the immunogenicity of mAb MK2-23 in a xenogeneic host. Rabbits were selected for this purpose, since they have a constitutive expression of HMW-MAA in their normal tissues with a distribution similar to that in humans. The combined use of an adjuvant and a carrier enhances the immunogenicity of mAb MK2-23 in rabbits markedly more than each of them individually. Specifically, all the rabbits immunized with mAb MK2-23 conjugated to keyhole limpet hemocyanin (KLH) and mixed with Freund's adjuvant (FA) produced antibodies which were shown with serological and immunochemical assays to be specific for HMW-MAA and to be both IgG and IgM. In contrast anti-HMW-MAA antibodies were detected in only one of the 3 rabbits immunized with mAb MK2-23 mixed with FA and were not detected in the rabbits immunized with mAb MK2-23 conjugated to KLH or with mAb MK2-23 without KLH and FA. These results indicate that active specific immunotherapy with mAb MK2-23 in patients with malignant melanoma is likely to benefit from the use of a carrier and an adjuvant, provide additional evidence that mAb MK2-23 bears the internal image of HMW-MAA, and suggest that the immune response elicited by mAb MK2-23 is T-cell dependent.

Adjuvants, Immunologic↗
PubMed1993

Idiotypic cascade in the human high molecular weight melanoma-associated antigen system: fine specificity and idiotypic profile of anti-anti-idiotypic monoclonal antibodies.

The mouse anti-idiotypic (anti-id) monoclonal antibody (mAb) MK2-23 bears the internal image of the determinant defined by the syngeneic immunizing anti-human high molecular weight melanoma-associated antigen (HMW-MAA) mAb 763.74, since it induces anti-HMW-MAA antibodies in syngeneic and xenogeneic hosts. To dissect the humoral immune response induced by mAb MK2-23 at the clonal level, 1351 hybridomas were generated from a BALB/c mouse immunized with mAb MK2-23. Serological and immunochemical assays showed that the anti-anti-idiotypic (anti-anti-id) mAb GH827, GH1002 and GH1081 react only with the immunizing anti-id mAb MK2-23 and that the anti-anti-id mAb GH149, GH368, GH464, GH518, GH586, GH704, GH786 and GH1151 react with both mAb MK2-23 and HMW-MAA. The eight HMW-MAA binding anti-anti-id mAb resembled mAb 763.74 in their reactivity patterns with a panel of cell lines, although the extent of reactivity was lower. Staining of surgically removed melanoma lesions detected subtle differences in the reactivity patterns of the eight HMW-MAA binding anti-anti-id mAb. This finding in conjunction with the differential ability of the eight anti-anti-id mAb to inhibit the binding of anti-HMW-MAA mAb 763.74 to melanoma cells and to mAb MK2-23 and with the different avidity of the binding to mAb MK2-23 suggest diversity in the fine specificity of the eight HMW-MAA binding anti-anti-id mAb. Like mAb 763.74, the eight HMW-MAA binding anti-anti-id mAb express the idiotopes recognized by the anti-id mAb MK2-23 and MK2-120. In contrast, the three anti-anti-id mAb GH827, GH1002 and GH1081, which do not bind HMW-MAA binding anti-anti-id mAb to the antibodies elicited by the membrane-bound HMW-MAA corroborates the validity of the use of anti-id mAb MK2-23 as an immunogen to implement active specific immunotherapy in patients with malignant melanoma.

Animals↗
PubMed1993

Bidirectional modulation of TNF-alpha production by alveolar macrophages in asbestos-induced pulmonary fibrosis.

Bronchoalveolar lavage (BAL) cells were isolated from rats 1, 3, and 6 weeks after a single intratracheal instillation of saline, UICC chrysotile asbestos (5 mg), or silica (5 mg). In asbestos-exposed rats, the pulmonary response was characterized by a significant increase in the number of alveolar macrophages (AMs) and the appearance of fibrotic lesions within 1 week. By contrast, mixed macrophage and neutrophil accumulations were observed in the silica group without evidence of fibrosis. Tumor necrosis factor-alpha (TNF-alpha) production by lipopolysaccharide (LPS)-stimulated BAL cells from asbestos-treated rats was significantly lower than controls 1 and 3 weeks after exposure. However, by 6 weeks higher levels of TNF-alpha production were noticeable in this group. Decreases in LPS-induced TNF-alpha production were also observed with BAL cells from silica-treated animals at all time points studied. Lower levels of TNF-alpha were not related to decreased BAL cell viability or the presence of a significant proportion of neutrophils in the silica group. Furthermore, biphasic changes in TNF-alpha production seen in the asbestos group were correlated with concomitant decreases (3 weeks) and increases (6 weeks) in levels of TNF-alpha mRNA in AMs. These data indicate that lower levels of TNF-alpha resulted from inhibition at the gene expression level and provide evidence for bidirectional modulation of TNF-alpha production by AMs during inflammatory reactions.

Animals↗
PubMed1993

Expression and regulation of the porcine CD44 molecule.

The expression and regulation of porcine CD44 were studied under various experimental conditions and in the context of lymphocyte differentiational and functional status. The CD44 molecule was subject to antigenic modulation by the anti-CD44 mAbs to different degrees depending on the type of cross-linking reagent and could be induced to shed from the cell surface. The reexpression of CD44 on papain-denuded lymphocytes was heterogeneous, as about half of the cells failed to resynthesize the molecule after prolonged culture, whereas the rest of the cells had a high turnover. Stimulation of lymphocytes by mitogens caused prolonged, dose-dependent elevation of the expression of CD44. Expression of CD44 on lymph node cells was found to be correlated with the expression of CD2 and sIgM. A CD2-CD4-sIgM-CD44-MHC Class IIhiCD45+ cell subset was identified, which was present in small numbers in lymph nodes but was enriched in gut-associated lymphoid tissues. In the thymus, CD44 expression seemed to be correlated with the differentiation status of thymocytes. In general, the expression of CD44 in the lymphoid tissues tested appeared to be related to their level of cell migration capacity.

Animals↗
PubMed1993

CD44 is involved in porcine natural cytotoxicity.

A polyclonal anti-porcine CD44 antibody was used to elucidate the possible role of the CD44 molecule in porcine natural cytotoxicity. It was found that the antibody inhibited porcine NK activity in a dose-dependent manner. The inhibition was reversed by incubation with soluble porcine CD44. The F(ab')2 but not Fab fragment of the antibody was effective, suggesting that the CD16 pathway was not involved and that cross-linking of the CD44 molecule might be essential for the inhibition. The antibody exerted the inhibition by acting on the effector cells, without preventing them from forming conjugates with the target cells. Kinetic studies showed that the inhibition was exerted at a late postbinding stage.

Animals↗