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Biomedical subjects

B Sun

Publications and source records attributed to B Sun.

At least 181 records · Page 10Linked to original sources
PubMed1997

Rabbit ubiquitin-activating enzyme E1: cDNA cloning, sequence and expression.

A cDNA clone encoding ubiquitin-activating enzyme E1 has been isolated from a rabbit heart cDNA library and sequenced. The 3.485 kb cDNA contains an open reading frame of 1058 amino acid residues which predicts a protein of approx. 118 kDa. The deduced protein sequence exhibits a very high homology to other ubiquitin-activating enzymes identified in a variety of organisms. Northern blot analysis reveals a single transcript of approx. 3.5 kb in all the rabbit tissues examined. The entire coding region of the rabbit E1 cDNA has been expressed as a his-tagged protein. The recombinant protein has been verified by its ability to cross-react with anti-human E1 antibodies. Ubiquitin thiolester assay shows that the recombinant rabbit E1 protein is functional.

Amino Acid Sequence↗
PubMed1997

Genetic susceptibility to experimental autoimmune uveitis involves more than a predisposition to generate a T helper-1-like or a T helper-2-like response.

This study examines whether genetic susceptibility vs resistance to experimental autoimmune uveoretinitis (EAU) in mice is associated with dominant type 1 vs type 2 cytokine response profiles. Mice from six strains were immunized with the uveitogenic retinal Ag IRBP. EAU was evaluated by histopathology. As judged by disease scores, three of the strains were susceptible, one was minimally susceptible, and two were resistant. Ag-specific type 1 vs type 2 cytokine responses (protein and/or mRNA) in draining lymph node cells, and IgG2a vs IgG1 Ab isotypes to IRBP, were measured as indicators of Th1-like vs Th2-like responses, respectively. The three susceptible strains (B10.A, C57BL/10, and BALB/k) showed a dominant Th1-like response profile characterized by high IFN-gamma and IL-12p40 (but not IL-4) responses, and a predominance of IgG2a Abs. The minimally susceptible strain (A/J) had an IFN-gamma response detectable only at the mRNA level, but produced predominantly IgG2a Abs. One of the two resistant strains (BALB/c) showed a characteristic Th2-like response with dominant Ag-specific IL-4 and IL-10 responses but no IFN-gamma, and predominantly IgG1 Abs. However, the other resistant strain (AKR) did not show a Th2-dominated response pattern, in that it had low, or no, IL-4 and IL-10 responses, and made predominantly IgG2a Abs to IRBP. These results suggest that whereas a Th1 response is required for susceptibility, resistance is not dependent on a Th2 response pattern. We suggest that regulatory influences other than skewing the response toward the Th2 pathway may be equally effective at conferring genetic resistance to EAU.

Animals↗
PubMed1997

Live astrocytes visualized by green fluorescent protein in transgenic mice.

Green fluorescent protein (hGFP-S65T) was expressed in transgenic mice under the control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. Tissues from two independent transgenic lines were characterized by Northern blot analysis and by confocal microscopy. The expression pattern in these two lines was identical in all tissues examined, and similar to that found previously with a lacZ transgene driven by the same promoter. Bright fluorescence was observed in the cell bodies and processes of unfixed or fixed astrocytes, using both whole mount and brain slice preparations, from multiple areas of the central nervous system. However, in contrast to GFAP-lacZ transgenics, retinal Müller cells expressed the GFP transgene in response to degeneration of neighboring photoreceptors. These data indicate that the 2.2-kb hGFAP promoter contains sufficient regulatory elements to direct expression in Müller cells, and that GFP is a suitable reporter gene for use in living preparations of the mammalian nervous system. Such mice should prove useful for studies of dynamic changes in astrocyte morphology during development, and in response to physiological and pathological conditions.

Animals↗
PubMed1997

Cloning, characterization and expression of a cDNA clone encoding rabbit ubiquitin-conjugating enzyme, E2(32k).

A cDNA clone encoding rabbit E2(32k) was obtained by library screening and PCR. The cDNA contains an open reading frame coding for 238 amino acids which shows an overall identity of 81% to human CDC34, the cell cycle-related ubiquitin-conjugating enzyme. A 50% homology to yeast CDC34 within the conserved core domain was also observed. Northern blot analysis indicated that three transcripts existed in all six rabbit tissues examined but their expression levels varied over a wide range. The putative cDNA coding region was highly expressed in Escherichia coli as a his-tagged protein which was purified to homogeneity. The ability of this expressed protein to form a thiolester bond with ubiquitin showed that it was functionally active. The ability of this protein to catalyze the conjugation of ubiquitin to histone H2A and H2B was also examined.

Amino Acid Sequence↗
PubMed1997

Tyrosine hydroxylase gene promoter activity is regulated by both cyclic AMP-responsive element and AP1 sites following calcium influx. Evidence for cyclic amp-responsive element binding protein-independent regulation.

Membrane depolarization of PC12 cells using 50 mM KCl leads to induction of tyrosine hydroxylase (TH) mRNA. This induction of TH mRNA is apparently due to increased TH gene promoter activity mediated by the influx of Ca2+. In PC12 cells transiently transfected with a chimeric gene expressing chloramphenicol acetyltransferase (CAT) driven by the proximal TH gene 5'-flanking region, 50 mM KCl increases TH gene promoter activity 3-4-fold. Promoter analysis utilizing TH-CAT constructs containing mutagenized sequences indicates that this response to the depolarization-mediated influx of Ca2+ is primarily dependent on both the TH cAMP-responsive element (CRE) and TH activating protein-1 (AP1) site. Minimal promoter constructs that contain a single copy of either the TH CRE or TH AP1 site fused upstream of the TH gene basal promoter are only modestly responsive or nonresponsive, respectively, to depolarization. However, both these constructs are strongly responsive to the calcium ionophore, A23187. Gel shift assays indicate that TH AP1 complex formation is dramatically increased after treatment with either 50 mM KCl or A23187. Using antibodies to transcription factors of the Fos and Jun families, we show that the nuclear proteins comprising the inducible TH AP1 complex include c-Fos, c-Jun, JunB, and JunD. In cAMP-responsive element binding protein (CREB)-deficient cell lines that express antisense RNA complementary to CREB mRNA, the response of the TH gene promoter to cyclic AMP is dramatically inhibited, but the response to A23187 remains robust. This result indicates that transcription factors other than CREB can participate in the Ca2+-mediated regulation of the TH gene. In summary, our results support the hypothesis that regulation of the TH gene by Ca2+ is mediated by mechanisms involving both the TH CRE and TH AP1 sites and that transcription factors other than or in addition to CREB participate in this response.

Adaptor Protein Complex 1↗
PubMed1997

Spinning sidebands in slow-magic-angle-spinning NMR spectra arising from tightly J-coupled spin pairs.

Complex spinning sidebands are observed in magic-angle-spinning (MAS) NMR spectra arising from isolated tightly J-coupled spin pairs under slow spinning conditions. Such spinning sidebands are sensitive to the magnitude and relative orientation of the chemical-shift tensors, the dipolar-coupling tensor, and the sign of the indirect spin-spin (J) coupling. We show that it is possible to extract information concerning such NMR parameters from an analysis of the observed spinning sidebands. As an example, numerical simulations are carried out to reproduce observed 31P MAS NMR spectra of a phosphole tetramer (1) and o-bis(diphenylphosphino)benzene (2), so that invaluable information concerning the orientations of the phosphorus chemical-shift tensors and the sign of J(31P, 31P) can be deduced. Simulations are carried out by numerically evaluating the spin-density matrix of the spin system.

Anisotropy↗
PubMed1997

Stereochemical influence on the stability of radio-metal complexes in vivo. Synthesis and evaluation of the four stereoisomers of 2-(p-nitrobenzyl)-trans-CyDTPA.

Distinct differences in in vivo stability of the two diastereomeric C-Functionalized CyDTPA chelating agents, (CHX-A DTPA and CHX-B DTPA, both racemates), as recently reported prompted further investigation as to why differences in configuration produced striking effects on the in vivo stability of their yttrium complexes. To this end, the four individual component stereoisomers of CHX-A and CHX-B were synthesized and ability to bind yttrium was investigated both in vitro and in vivo.

Animals↗
PubMed1997

T cell mechanisms in experimental autoimmune uveoretinitis: susceptibility is a function of the cytokine response profile.

This study addresses the question whether susceptibility versus resistance to experimental autoimmune uveoretinitis (EAU) is connected to a Th1-type (interferon-gamma high, interleukin-4 low), versus a Th2-type (IFN-gamma low, IL-4 high) response. Primed lymph node cells of susceptible Lewis rats produced IFN-gamma in response to antigen in culture and transferred EAU to syngeneic recipients, whereas lymph node cells of resistant F344 rats made no IFN-gamma and did not transfer disease. Reversal of the disease pattern, by treatment of F344 rats with B. pertussis toxin and immunisation of Lewis rats with antigen in incomplete Freund's adjuvant, resulted in a parallel reversal of these response patterns. Neither strain produced significant IL-4 responses. A study of the response patterns in mice confirmed that high Th1 responders were susceptible, whereas low Th1 responders and Th2 responders were resistant. We conclude that susceptibility to EAU is connected with a Th1-dominant response, but resistance can involve either a 'null', F344-like response (Th1-low/Th2-low) or a Th2-dominant response.

Adoptive Transfer↗
PubMed1997

Heel reconstruction.

From 1987 through 1990 we used the compound flap formed by the lateral leg flap, the fibula, and its surrounding soft tissues, pedicled on the distal peroneal vessels, to reconstruct heel and calcaneus defect in two patients. Both were successful and functionally good.

Adolescent↗
PubMed1997

Surfactant improves lung function and mitigates bacterial growth in immature ventilated rabbits with experimentally induced neonatal group B streptococcal pneumonia.

AIMS: To study the influence of surfactant on lung function and bacterial proliferation in immature newborn rabbits with experimental group B streptococcal (GBS) pneumonia. METHODS: Preterm rabbit fetuses (gestational age 28 days) underwent tracheotomy and were mechanically ventilated in a warmed body plethysmograph that permitted measurement of lung-thorax compliance. Fifteen minutes after the onset of ventilation the animals received either GBS or saline intratracheally; at 30 minutes, a bolus of saline or 200 mg/kg of a porcine surfactant (Curosurf) was administered via the airway. Bacterial proliferation was evaluated in lung homogenate at the end of the experiments and the results expressed as mean log10 cfu/g lung (SD). Animals receiving only saline (n = 20) or saline and surfactant (n = 20) served as controls. RESULTS: The average survival time was about three hours in all groups. Infected animals receiving surfactant (n = 22) had significantly less bacterial growth (9.09 (0.45) vs 9.76 (0.91)) and improved lung function (compliance: 0.61 (0.14) vs 0.34 (0.19) ml/kg. cm H2O) than infected rabbits receiving saline at 30 minutes (n = 22). CONCLUSION: Surfactant improves lung function and mitigates bacterial growth in preterm rabbits infected with group B streptococci.

Animals↗
PubMed1997

Pathophysiology of neonatal lung injury induced by monoclonal antibody to surfactant protein B.

Near-term newborn rabbits were exposed via the airways to a monoclonal antibody to surfactant protein B and ventilated for 0-120 min. Control animals received nonspecific rabbit or mouse immunoglobulin G, saline, or no material via the airways. Administration of the antibody at > or = 40 mg/kg elicited an immediate, significant fall in lung-thorax compliance associated with progressive intra-alveolar edema and/or alveolar collapse and necrosis and desquamation of airway epithelium, and hyaline membranes. The vascular-to-alveolar leak of human albumin and human immunoglobulin G, injected intravenously at birth and determined in lung lavage fluid 60-120 min after instillation of the antibody, was 1.8% for the left lung, with no difference between the markers. The average leak in control animals ventilated for 120 min was < 0.3% (P < 0.05). Cytospin preparations of lung lavage fluid from animals exposed to the antibody showed significantly increased recruitment of neutrophilic granulocytes. The pathology and pathophysiology of neonatal lung injury induced by the monoclonal antibody to surfactant protein B probably reflect a combination of direct inactivation of surfactant and an inflammatory response triggered by the immune reaction.

Animals↗
PubMed1997

Biophysical and physiological properties of a modified porcine surfactant enriched with surfactant protein A.

Surfactant protein A (SP-A), a major protein component of natural pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. We investigated the physical and physiological properties of one of these modified natural surfactants (Curosurf) after enrichment with 5% SP-A (SP-A-Curosurf). A pulsating bubble system was used for in vitro assessments and ventilated newborn rabbits for evaluation of in vivo effects. In the presence of various potential inhibitors (meconium 5 mg.mL-1, fibrinogen 5 mg.mL-1, albumin 25 mg.mL-1, or whole serum proteins 25 mg.mL-1), Curosurf at a concentration of 5 mg.mL-1 was inactivated while SP-A-Curosurf and natural porcine surfactant at the same concentration had normal maximum and minimum surface tension. This protective effect of SP-A was calcium dependent. In immature newborn rabbits, the improvement of lung-thorax compliance observed after treatment with 100 mg.kg-1 of SP-A-Curosurf was equivalent to that obtained with 200 mg.kg-1 of Curosurf. Similarly, in near-term newborn rabbits with respiratory failure induced by instillation of fibrinogen via the airways, the increase in compliance after administration of 100 mg.kg-1 of SP-A-Curosurf corresponded to that seen after treatment with 200 mg.kg-1 of Curosurf, whereas Curosurf at a dose of 100 mg.kg-1 had no substantial effect. Our data thus indicate that surfactant protein A increases the resistance of Curosurf to inactivation under in vivo conditions.

Albumins↗
PubMed1997

[Effects of hypoxia and taurine on vasoconstriction peptides from cultured bovine pulmonary arterial endothelial cells].

OBJECTIVE: To study roles of endothein-1 (ET-1), angiotensin-II (AT-II) and endogenous digitalis-like factor (EDF) from cultured bovine pulmonary arterial endothelial cells (PAEC) in the pathogenesis of hypoxic pulmonary hypertension, and to evaluate whether Taurine is capable of protecting tissue cells from injury. METHODS: Culture of bovine pulmonary arterial endothelial cells and dot blot hybridization. RESULTS: PAEC cultured under hypoxia resulted in an increase in ET-1 mRNA expression. PAEC cultured under hypoxia induced increase in ET-1, AT-II and EDF release. By adding taurine to the culture medium, ET-1 mRNA express was inhibited. ET-1, AT-II and EDF release were inhibited. CONCLUSIONS: Expression of ET-1 mRNA and release of ET-1, AT-II and EDF from PAEC increased under hypoxia. Taurine can inhibit the hypoxia-induced expression of ET-1 mRNA of PAEC and reduce the release of ET-1, AT-II and EDF from PAEC.

Angiotensin II↗
PubMed1997

[Apoptosis and expression of its regulating genes in adenoma and adenocarcinoma of large intestine].

OBJECTIVE: To investigate the effects of apoptosis and its regulating genes in different stages of malignant transformation of large intestine epithelium in colorectal adenoma and adenocarcinoma. METHODS: The density and distribution of the apoptotic cells and the positive expression of p53 and bcl-2 oncoprotein were observed in situ in 32 villous adenomas and 33 papillary adenocarcinomas of the large intestine, using DNA nick end labelling technique and immunohistochemical staining for p53 and bcl-2 oncoprotein. 15 nontumor mucosa were used as controls. RESULTS: The density of apoptotic cells in adenoma and adenocarcinoma was significantly higher than that in nontumor mucosa (P < 0.01), and their density in adenoma was higher than in adenocarcinoma (P < 0.01). The positive rate and staining intensity of p53 and bcl-2 oncoprotein in adenoma and adenocarcinoma were significantly higher than in non tumor mucosa (P < 0.01), their staining intensity in adenocarcinoma was higher than that in adenoma (P < 0.01). In adenoma, the density of apoptotic cells in the bcl-2 oncoprotein positive group was higher than that in the bcl-2 oncoprotein negative group (P < 0.01). CONCLUSION: The abnormal regulation of apoptosis may play an important role in the pathogenesis of large intestine carcinoma. The bcl-2 oncoprotein can inhibit apoptosis in adenoma and adenocarcinoma. However, mutational p53 oncoprotein may likely block apoptosis in adenocarcinoma.

Adenocarcinoma, Papillary↗
PubMed1997

[Mutual regulation of proliferation between pulmonary artery endothelial cells and pulmonary smooth muscle cells in vitro].

Vascular endothelial cell are closely related to vascular smooth muscle cells in structure and function. The interactions between them may play important roles in the modulation of function and structure of vascular wall. In the present study, the mitogenic regulations between cultured new bovine pulmonary arterial endothelial cell (PAEC) and pulmonary arterial smooth muscle (PASM) were investigated. When PAECs and PASMs were mixcultured, 3H-TdR incorporation into the mixed cells decreased significantly (P < 0.001 vs control). When PAECs and PASMs were cultured in conditioned medium from PASMs and PAECs respectively or they were cocultured, the proliferation of PAECs was inhibited while that of PASM was stimulated significantly (P < 0.05 vs control). It was also found that the concentration of cAMP increased but cGMP decreased in cocultured PASMs (P < 0.01 vs control), while the concentration of both cAMP and cGMP decreased significantly in cocultured PAECs (P < 0.01 vs control). These findings suggest that PAECs and PASMs may regulate their proliferation each other through the second messenger system.

Animals↗
PubMed1997

[The effects of hypoxia on angiotensin II secretion by cultured pulmonary artery endothelial cells].

The alterations of paracrine function of pulmonary arterial endothelial cells (PAEC) might play an important role in the development of hypoxic artery hypertension (HPAH). To test this hypothesis, the effects of hypoxia on angiotensin II (AT II) secretion by new born bovine PAEC were investigated. AT II secretion increased significantly when PAECs were incubated under 2.5% O2 hypoxic condition for 1.5 h (P < 0.01 vs control). But it decreased from 1.5 h to 12 h incubation and increased from 12 h to 48 h incubation under 0% O2 hypoxic condition, with significance compared with control group (P < 0.01). NO donor SIN-1 inhibited but endogenous NO inhibitor L-nitro-arginine promoted AT II secretion significantly under both normorxic and hypoxic conditions. It was also found that the concentration of cyclic guanine monophosphate in PAEC decreased significantly at 24 h incubation in 0% O2. The above results suggest that changes of AT II in PAEC may participate in the development of HPAH.

Angiotensin II↗