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Biomedical subjects

Y Liang

Publications and source records attributed to Y Liang.

At least 325 records · Page 18Linked to original sources
PubMed1994

SIS/PDGF-B promoter isolation and characterization of regulatory elements necessary for basal expression of the SIS/PDGF-B gene in U2-OS osteosarcoma cells.

Platelet-derived growth factor BB, encoded by the SIS/PDGF-B gene, is a potent mitogen for cells of mesenchymal origin, and the SIS/PDGF-B gene is expressed in a large percentage of human mesenchymal tumor cells establishing a growth-promoting, autocrine growth circuit. A 4-kb fragment, containing the SIS/PDGF-B promoter, was isolated from a human genomic library, and a series of 5'-nested deletions and linker-scanning mutants were used to identify positive regulatory elements that are necessary for the constitutive expression of this gene in human U2-OS osteosarcoma cells. A 250-bp fragment, lying immediately 5' to the SIS/PDGF-B mRNA initiation site (+1), retained full promoter activity, and positive regulatory elements at -228 to -219, -97 to -88 (SIS distal element) and -58 to -39 (SIS proximal element, SPE) were identified. Insertion of the 20-bp SPE into a heterologous, minimal promoter resulted in >5-fold transcriptional activation which was ablated by mutations to the SPE. High resolution mutagenesis within the 20-bp SPE, indicated the necessity of a CACCC motif for activity. Gel shift analysis of SPE-binding proteins in U2-OS nuclear extracts identified Sp1 and two additional binding factors that could be competed away from SPE binding by adding excess consensus Sp1 or CACC oligonucleotides. The individual and aggregate roles of the SPE and two weaker positive regulatory elements in regulating SIS/PDGF-B transcription in these tumor cells is considered.

Base Sequence↗
PubMed1994

Distribution and regulation of rab3C, a small molecular weight GTP-binding protein.

We have investigated the expression and regulation of rab3C in rat tissues and rat pheochromocytoma PC12 cells by using a polyclonal antibody that specifically recognizes this protein. Rab3C was expressed in the neuroendocrine systems, as is its highly homologous family member, rab3A. Strong immunoreactivity of rab3C was also observed in testis, heart and 3 different adipose tissues. In addition, induction of neuronal differentiation in PC12 cells, which causes an increase in catecholamine secretion, also led to an increase in rab3C expression. In summary, our data demonstrate a defined pattern of rab3C expression in the rat; such expression is not limited to the neuroendocrine systems. Regulated secretion of various hormones occurs from all of these rab3C-containing tissues. Our results provide important insight into understanding the potential role of rab3C in regulated exocytosis.

Adrenal Medulla↗
PubMed1994

Analysis of upstream glucokinase promoter activity in transgenic mice and identification of glucokinase in rare neuroendocrine cells in the brain and gut.

A transgene consisting of an upstream glucokinase (GK) promoter fragment linked to coding sequences of the human growth hormone gene was expressed in certain neuroendocrine cells of the pancreas, pituitary, brain, gut, thyroid, and lungs of mice. In pancreas, the transgene was expressed in a nonuniform manner among beta cells and in a variable but substantial fraction of the other islet cell types. In pituitary, it was expressed in corticotropes, and in brain, it was expressed in cells of the medial hypothalamus. Within the gut transgene expression was detected in a subset of enteroendocrine cells of the stomach and duodenal epithelium, some of which also exhibited glucagon-like polypeptide-1 immunoreactivity. In thyroid, transgene expression was observed in C cells of neonatal animals, whereas in the lung, it was expressed among rare endocrine cells of the bronchopulmonary mucosa. RNA polymerase chain reaction analysis of human growth hormone mRNA corroborated the tissue-specific transgene expression pattern. Prompted by the finding of transgene expression in specific neuroendocrine cells, we sought to determine whether GK mRNA and GK itself was also expressed in the brain and gut, tissues not previously associated with the expression of this enzyme. Using rat tissues, GK mRNA was detected by RNA polymerase chain reaction in both the brain and intestine and was localized to specific cells in the hypothalamus and enteric mucosa by in situ hybridization. A high Km glucose phosphorylating activity was detected from isolated rat jejunal enterocytes that displayed a chromatographic elution profile identical to hepatic GK. GK immunoreactivity was detected in cells of the medial hypothalamus with many of the same cells also displaying GLUT2 immunoreactivity. Together, these studies provide evidence for upstream GK promoter activity, GK mRNA, and GK itself in certain neuroendocrine cells outside the pancreatic islet and lead us to suggest that GK may play a broader role in glucose sensing by neuroendocrine cells than was thought previously.

Animals↗
PubMed1994

Are the associations between Alzheimer's disease and polymorphisms in the apolipoprotein E and the apolipoprotein CII genes due to linkage disequilibrium?

Allele frequencies for polymorphisms in the apolipoprotein E and the apolipoprotein CII genes were determined in subjects of Ashkenazi Jewish origin with late-onset Alzheimer's disease and in unaffected control subjects from the same ethnic group. A significant association was observed between late-onset Alzheimer's disease and the epsilon 4 (112Cys-->Arg) allele of apolipoprotein E; however, no association was detected with apolipoprotein CII. These results suggest that the association with epsilon 4 is probably not due to linkage disequilibrium.

Aged↗
PubMed1994

Effects of sterigmatocystin and T-2 toxin on the induction of unscheduled DNA synthesis in primary cultures of human gastric epithelial cells.

Primary cultures of human gastric epithelial cells were tested for induction of unscheduled DNA synthesis (UDS) by sterigmatocystin (ST) and T-2 toxin. Autoradiographic results indicated that ST (10(-6)-10(-4)M) induced UDS in the presence of S9 activation system. The repair rates were 24-91% (net grains > or = 3) and 2-71% (net grains > or = 5). T-2 toxin did not induce UDS in this study.

Animals↗
PubMed1994

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord.

It is well-known that a large number of factors can influence the expression of neuropeptides in the nervous system. In the present study, the effects of unilateral and bilateral irradiation to the rat head and neck on the expression of neuropeptides in the innervation of the submandibular gland and in the ganglionic cells of the submandibular ganglion was examined ten days and six months after treatment. Antisera directed against enkephalin and bombesin and immunohistochemical methods were used. The effects of bilateral irradiation on the staining pattern of various neuropeptides in the cervical spinal cord were also studied. In the submandibular gland and in the submandibular ganglionic cells, there was a markedly increased neuropeptide expression ten days after bilateral treatment, as seen after staining with both antisera used, while no changes occurred after unilateral treatment. Six months after treatment, the pattern of neuropeptide expression in the submandibular gland/ganglion corresponded to that seen in controls. Irradiation did not lead to any changes in the staining pattern of neuropeptides in the spinal cord. The observations show that there is a great complexity in the susceptibility of nervous tissues to radiotherapy with respect to influences on the expression of neuropeptides.

Animals↗
PubMed1994

The presence of K54 capsular polysaccharide increases the pathogenicity of Escherichia coli in vivo.

Proven isogenic capsule-negative derivatives (CP9.29, CP9.108, CP9.137, CP9.171, CP9.443, and CP9.C56), generated from an O4/K54/H5 blood isolate (CP9) of Escherichia coli by IS50L::phoA (TnphoA)-mediated transposon mutagenesis, were used to assess the function of a non-K1 capsule in three animal models. Intraperitoneal injection of CP9 (K54+) into mice resulted in an LD50 at 24 h of 5.5 x 10(6) cfu compared with LD50s of 2.6 x 10(7) cfu and 3.8 x 10(7) cfu for CP9.108 (K54-) and CP9.C56 (K54-) (P < .001). CP9 was cleared less rapidly from the bloodstream, after intravascular injection, than was CP9.108 (P < .01). In the rat granuloma pouch model, CP9 could proliferate from starting inocula as low as 1.0 x 10(3) cfu/mL. In contrast, capsule-deficient derivatives underwent transient log kills with starting inocula as high as 1.0 x 10(6) cfu/mL. Because proven isogenic strains were evaluated, a clear contribution of the K54 capsular polysaccharide to virulence in vivo is demonstrated.

Animals↗
PubMed1994

Location of a lepidopteran specificity region in insecticidal crystal protein CryIIA from Bacillus thuringiensis.

The Bacillus thuringiensis insecticidal crystal protein CryIIA has both high mosquito activity and gypsy moth activity; in contrast CryIIB, which is 87% homologous, displays no mosquito activity and has a three-fold lower gypsy moth activity. The regions responsible for specificity against gypsy moth (Lymantria dispar) and mosquito (Aedes aegypti) larvae were located by introducing MluI and XhoI sites into homologous positions within the putative domain II of both cryIIA and cryIIB genes, which divided almost equally the respective second domains into three regions. Taking advantage of naturally occurring NheI and NarI sites that border the putative domain II, a set of seven chimeric proteins were produced by exchanging all combinations of those regions between CryIIA and CryIIB. Analysis of the toxicity of these chimeric proteins demonstrated that the lepidopteran and dipteran specificity regions of CryIIA were not colinear. While the specificity region of CryIIA against mosquito larvae involved region 1 and probably also region 2, the specificity region of CryIIA against gypsy moth larvae was located within region 2.

Aedes↗
PubMed1994

Multiple products from the shavenbaby-ovo gene region of Drosophila melanogaster: relationship to genetic complexity.

The Drosophila melanogaster shavenbaby (svb)-ovo gene region is a complex locus, containing two distinct but comutable genetic functions. ovo is required for survival and differentiation of female germ line cells and plays a role in germ line sex determination. In contrast, svb is required in both male and female embryos for the production of epidermal locomotor and sensory structures. Sequences required for the two genetic functions are partially overlapping. ovo corresponds to a previously described germ line-dependent 5.0-kb poly(A)+ mRNA that first appears in the germarium and accumulates in nurse cells during oogenesis. The 5.0-kb mRNA is stored in the egg, but it is rapidly lost in the embryos except for its continued presence in the germ line precursor pole cells. The ovo mRNA predicts a 1,028-amino-acid 110.6-kDa protein homologous with transcription factors. We have identified an embryonic mRNA, 7.1 kb in length, that contains exons partially overlapping those of the 5.0-kb poly(A)+ mRNA. The spatial distribution of this newly discovered transcript during midembryogenesis suggests that it corresponds to the svb function. The arrangement of exons common to the 5.0- and 7.1-kb mRNAs suggests that the Ovo and Svb proteins share DNA-binding specificity conferred by four Cys2-His2 zinc finger motifs but differ functionally in their capacity to interact with other components of the transcription machinery.

Amino Acid Sequence↗