Search PubMed⌕ Search

Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 739 records · Page 41Linked to original sources
PubMed1989

The promoter-regulatory region of the major immediate-early gene of human cytomegalovirus responds to T-lymphocyte stimulation and contains functional cyclic AMP-response elements.

Prior studies have demonstrated that a small proportion of blood lymphocytes from patients with human cytomegalovirus (HCMV) infection express only the viral immediate-early (IE) genes (L. Einhorn and A. Ost, J. Infect. Dis. 149:207-214, 1984; G. P. A. Rice, R. D. Schrier, and M. B. A. Oldstone, Proc. Natl. Acad. Sci. USA 81:6134-6138, 1984). The present studies demonstrate that the IE genes of HCMV are transcribed in Jurkat cells (T lymphocytes) only after activation of the cells with mitogens. Transcription of the IE genes is from an upstream enhancer promoter-regulatory region containing several different repeated sequence motifs. Chimeric plasmids were constructed with just a single copy or three copies of a synthetic oligonucleotide sequence of either the 16-, 18-, 19-, or 21-base-pair (bp) repeat elements upstream of the minimal wild-type promoter sequence to drive expression of the indicator gene, chloramphenicol acetyltransferase (CAT). The 18- or 19-bp motifs in the enhancer region were found to be important in mediating the effect of the mitogens. However, the CAT activity detected with the 19-bp repeat was always significantly higher than that found with the 18-bp repeat. There was an additive effect by multiple copies of the 18- or 19-bp repeat sequences on gene expression. The 19-bp repeat contains a sequence identical to that described for a cyclic AMP (cAMP) response element, and plasmids containing only this sequence and the minimal promoter sequences upstream of the CAT gene respond to agents which increase intracellular cAMP. Functional cAMP response elements are present in the wild-type promoter-regulatory region and are associated with the 19-bp repeat sequences. It is proposed that activation of lymphocytes results in expression of the IE genes of HCMV, in part via the activation of cellular trans-acting factors which interact with the 18- and 19-bp motifs in the HCMV IE promoter-regulatory region. The 19-bp repeat is the major contributor to the strength of this enhancer-containing promoter-regulatory region.

Base Sequence↗
PubMed1989

[Changes in platelet aggregation and coronary collateral circulation during the early phase of myocardial ischemia in dogs].

Experiments were performed on 18 anesthetized open-chest dogs to observe the changes in platelet aggregation and coronary collateral circulation during the early phase of acute myocardial ischemia. An increase in platelet aggregation rates (PAgR) and a decrease in platelet counts (PC) were found in the blood collected from the ischemic myocardium after coronary occlusion. PAgR was increased by 58.7 +/- 5.6% and PC was reduced by 39.5 +/- 23.6% at 50 min after occlusion (P less than 0.01). Under the condition of controlling aortic blood pressure, collateral coronary vascular capacity (CVC) was not changed (P greater than 0.05), but the effective collateral coronary flow to the ischemic zone, calculated by Wyatt et al's equation, was significantly reduced by 23.5 +/- 9.7% at 50 min after occlusion (P less than 0.05). There was a negative correlation between the changes in PAgR and the effective collateral coronary flow ( r = -0.857, P less than 0.01), and between the collateral indices and infarct size (r = -0.847, P less than 0.01). Abnormal changes in parameters of platelet and coronary collateral circulation after myocardial ischemia were nearly abolished by intravenous injection of aspirin before coronary occlusion. The results suggest that the deleterious changes of platelet aggregation during the early phase of the acute myocardial ischemia may decrease the effective collateral coronary flow significantly and thereby enlarge the infarct size.

Animals↗
PubMed1989

[Epidemiological surveillance of filariasis after its being basically eradicated in Shandong Province].

This paper reports the results of epidemiological surveillance in areas where filariasis has been basically eradicated and control measures no longer adopted in Shandong Province. A 3-year longitudinal surveillance in 18 villages in 5 counties and a cross-sectional survey in 13 villages of 4 counties were carried out. The results showed that the average microfilaria rate was further reduced from 0.28% and 0.15% in 1980 to 0.19% and 0.05% in 1986, decreased by 32.1% and 66.7% respectively. 34.2% of the microfilaremic cases were found to be negative during the two-year follow-up. The positive rate of IFA and skin test was 34.2% and 38.6% respectively. In longitudinal surveillance. of the 240,992 Culex pipiens pallens dissected, 152(0.06%) were found to harbour different stages of larvae, among them, 5 were infective larvae from 4 vector mosquitoes. In cross-sectional survey, of the 3,875 Culex pipiens pallens dissected only 1 which had bitten immigrant from Zhejiang was found to contain one larvae at stage 1. No positive mosquito was found in the household of native villagers. No new infection was discovered at longitudinal and cross-sectional survey. The transmission of filariasis in these areas was interrupted. The results showed that in areas where filariasis has been basically eradicated, further control measures may not be instituted, but the management population movement and surveillance should be strengthened.

Animals↗
PubMed1989

Immune response to gamma-irradiated injectable human amnion and human skin collagens in the rat.

The immune response in rats to gamma-irradiated human amnion and human skin collagen was characterized through histologic and immunologic methods. Pepsin-extracted human amnion collagen and skin collagen were purified and reconstituted. Implants of amnion collagen demonstrated greater persistence than skin collagen. For amnion collagen implants, no significant inflammatory response was found. Fibroblast and adipocyte ingrowth and neovascularization were present. Conversely, obvious inflammatory infiltration was evident in the skin collagen implants. Enzyme-linked immunosorbent assay results showed that anti-amnion collagen antibody levels were significantly lower than anti-skin collagen antibody levels against their respective implant materials. The ratios of type I to type III collagen are 56:44 and 95:5 for amnion collagen and skin collagen, respectively. These findings suggest that in this heterologous type system, type III collagen-rich amnion collagen preparations appear superior to skin collagen for soft-tissue augmentation.

Amnion↗
PubMed1988

Atrial natriuretic factor R1 receptor from bovine adrenal zona glomerulosa: purification, characterization, and modulation by amiloride.

The atrial natriuretic factor (ANF) R1 receptor from bovine adrenal zona glomerulosa was solubilized with Triton X-100 and purified 13,000-fold, to apparent homogeneity, by sequential affinity chromatography on ANF-agarose and steric exclusion high-performance liquid chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of the purified receptor preparation in the absence or presence of dithiothreitol revealed a single protein band of Mr 130,000. Affinity cross-linking of 125I-ANF to the purified receptor resulted in the labeling of the Mr 130,000 band. The purified receptor bound ANF with a specific activity of 6.8 nmol/mg of protein, corresponding to a stoichiometry of 0.9 mol of ANF bound/mol of Mr 130,000 polypeptide. Starting with 500 g of adrenal zona glomerulosa tissue, we obtained more than 500 pmol of purified receptor with an overall yield of 9%. The purified receptor showed a typical ANF-R1 pharmacological specificity similar to that of the membrane-bound receptor. The homogeneous Mr 130,000 receptor protein displayed high guanylate cyclase activity [1.4 mumol of cyclic GMP formed min-1 (mg of protein)-1] which was not stimulated by ANF. This finding supports the notion that the ANF binding and the guanylate cyclase activities are intrinsic components of the same polypeptide. Finally, the purified ANF-R1 receptor retained its sensitivity to modulation by amiloride, suggesting the presence of an allosteric binding site for amiloride on the receptor protein.

Amiloride↗
PubMed1988

Detection of autocrine motility factor in urine as a marker of bladder cancer.

Cell locomotion is an essential requirement for invasion and metastasis of malignant cells. We have previously described the characterization of a 50-kilodalton autocrine motility factor (AMF), a cytokine that stimulates motility in human tumor cells. In this study, we investigated the elaboration of this factor in vivo by human bladder carcinoma and in vitro by a cultured transitional cell carcinoma (TCC) of the bladder cell line T24P. Urine samples from patients with bladder cancer were assayed for their capacity to stimulate migration of tumor cells. Comparing all TCC cases (22 patients) with all nonmalignant diagnoses (27 patients), we found a statistically significant (P less than .001) difference in the motility values. Invasive TCC cases (15 patients) were significantly (P less than .002) higher in regard to motility values compared with noninvasive TCC cases (8 patients), including one case of carcinoma in situ. In follow-up screening studies evaluating TCC recurrence, the recurrent tumors (9 patients) were higher (P less than .001) in regard to motility values than the tumor-free cases (11 patients). Furthermore, T24P cells showed a dose-dependent motile response to their own serum-free conditioned medium as well as to the AMF present in the urine of TCC patients. This finding is consistent with the source of AMF in the urine of these patients being the cancer itself. An enzyme-linked immunosorbent assay (ELISA) for AMF was also developed. Values determined by ELISA correlated well with the motility values measured separately. These data support the potential usefulness of AMF as a urine marker for bladder TCC.

Adult↗
PubMed1988

Isolation and identification of vasopressin- and oxytocin-immunoreactive substances from bovine pineal gland. Presence of N alpha-acetyloxytocin.

Peptides with vasopressin- and oxytocin-immunoreactivity were purified from bovine pineal glands. Three immunoreactive peptides were purified by successive high performance liquid chromatography steps in sufficient quantities for identification by fast atom bombardment-mass spectrometry. Two peptides were characterized as authentic vasopressin and oxytocin. Their identities were in agreement with the observed immunoreactivities, high performance liquid chromatography behavior, and biological activity. The third peptide was identified as N alpha-acetyloxytocin. The presence of the acetyl group was demonstrated by the molecular mass of the peptide, and the N alpha position was shown to be the modified site by the presence of a blocked NH2 terminus. N alpha-Acetylation of oxytocin may be involved in altering the biological properties of the peptide.

Acetylglucosaminidase↗
PubMed1988

The identification of furanose and pyranose ring forms of the reducing units of oligosaccharides.

Several types of oligosaccharides with glucose, arabinose, or galactose units have been prepared by chemical degradation of oligosaccharides of known structures and by enzymatic syntheses utilizing macerans amylase or yeast galactosyltransferase and appropriate substrates and cosubstrates. The ring forms of reducing units of these oligosaccharides and of oligosaccharides composed of glucose and mannose have been identified by a combined method of analysis based on methylation, gas-liquid chromatography, and mass spectrometry. In the dimethyl sulfoxide solvent used for the methylations, the oligosaccharides with arabinose or galactose units at the reducing ends occur as arabinofuranose or galactofuranose ring forms to the extent of 55 and 65%, respectively. The remainder of these monosaccharide units are present in the pyranose ring form. Oligosaccharides with glucose or mannose units at the reducing ends occur primarily in the pyranose ring form. An interesting observation is the finding that the reducing units which carry substituents linked by alpha-glycosidic linkages occur in a higher percentage in the furanose ring forms than those which carry substituents linked by beta-glycosidic linkages.

Carbohydrate Conformation↗
PubMed1988

Diurnal variation in vasopressin and oxytocin messenger RNAs in hypothalamic nuclei of the rat.

Diurnal changes in the expression of the vasopressin (VP) and oxytocin (OT) genes in the supraoptic (SON), paraventricular (PVN) and suprachiasmatic nuclei (SCN) of the rat were investigated by dot-blot and in situ hybridization of the VP and OT mRNAs. A significant diurnal variation in VP mRNA level was measured in the SCN, with highest levels around 17.00 h and lowest levels around midnight. No variations in levels of VP mRNA and OT mRNA were detected in SON and PVN. The data indicate that the regulation of the VP gene in the SCN is independent of that in the magnocellular nuclei.

Animals↗
PubMed1988

The C4H7+ cation. A theoretical investigation.

The potential energy surface of the C4H7+ cation has been investigated with ab initio quantum chemical theory. Extended basis set calculations, including electronic correlation, show that cyclobutyl and cyclopropylcarbinyl cation are equally stable isomers. The saddle point connecting these isomers lies 0.6 kcal/mol above the minima. The global C4H7+ minimum corresponds to the 1-methylallyl cation, which is 9.0 kcal/mol more stable than the cyclobutyl and the cyclopropylcarbinyl cation and 9.5 kcal/mol below the 2-methylallyl cation. These results are in excellent agreement with experimental data.

Carbon↗
PubMed1988

Oxytocin and vasopressin gene expression in the hypothalamo-neurohypophyseal system of the rat during the estrous cycle, pregnancy, and lactation.

To study the state of hypothalamic expression of the oxytocin (OT) and vasopressin (VP) genes in different conditions of the female rat, OT and VP mRNA levels were determined during the estrous cycle, pregnancy, and lactation. OT and VP mRNA levels of the supraoptic nucleus were quantified by Northern blot and dot-blot analysis. OT and VP contents of the pituitary gland were determined by RIA. During the estrous cycle, OT mRNA levels of the supraoptic nucleus were significantly increased 1.5- to 2-fold at estrous relative to the other periods of the cycle. No significant cyclic variation was observed in VP mRNA levels. The OT content of the pituitary gland was significantly decreased at estrus and also the VP contents showed a cyclic variation with the lowest levels occurring at estrus and metestrus. At the last day of gestation a 3- and 2-fold increase of OT mRNA and VP mRNA, respectively, was measured, but no changes were observed at gestational day 12, 15, and 18. In rats lactating for 15 days, OT and VP mRNA levels were approximately 3-fold higher than during the estrous cycle. Concomitantly the OT and VP contents of the pituitary gland were decreased by approximately 50%. It is concluded that both OT and VP gene expression are stimulated just before birth and during lactation indicating that both genes are sensitive to common factors. A dissociation of the regulation of the OT and VP genes occurs in the estrous cycle.

Animals↗
PubMed1987

Detection and high performance liquid chromatography identification of the summer rises of vasopressin and oxytocin immunoreactivity in the rat pineal gland.

The vasopressin (VP) and oxytocin (OT) contents of the rat pineal gland during the summer period were determined by RIAs. Both the levels of VP immunoreactivity and OT immunoreactivity rose markedly in August. The highest level of VP immunoreactivity occurred on August 6 [82 +/- 19 fmol/gland (+/- SEM)], compared to basal levels of 14 +/- 2 fmol/gland. Basal levels of OT immunoreactivity of 20 +/- 8 fmol/gland increased to a peak level of 193 +/- 72 fmol/gland on August 14. Analysis of immunoreactive components by HPLC demonstrated that rises were due to the peptides coeluting with authentic VP and OT, respectively. Levels of immunoreactive VP and OT in the hypothalamus, pituitary gland, and hippocampus did not show variation during the summer. The results show that the VP and OT content of the pineal gland is regulated in a tissue-specific fashion by seasonal influences.

Animals↗