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Biomedical subjects

H Shao

Publications and source records attributed to H Shao.

At least 73 records · Page 4Linked to original sources
PubMed1995

Characterization of B61, the ligand for the Eck receptor protein-tyrosine kinase.

B61 was originally described as a novel secreted tumor necrosis factor-alpha-inducible gene product in endothelial cells (Holzman, L. B., Marks, R. M., and Dixit, V. M. (1990) Mol. Cell. Biol. 10, 5830-5838). It was recently discovered that soluble recombinant B61 could serve as a ligand for the Eck receptor protein-tyrosine kinase, a member of the Eph/Eck subfamily of receptor protein-tyrosine kinases (Bartley, T.D., Hunt, R. W., Welcher, A. A., Boyle, W. J., Parker, V. P., Lindberg, R. A., Lu, H. S., Colombero, A. M., Elliott, R. L., Guthrie, R. A., Holst, P. L., Skrine, J. D., Toso, R. J., Zhang, M., Fernandez, E., Trail, G., Yarnum, B., Yarden, Y., Hunter, T., and Fox, G. M. (1994) Nature 368, 558-560). We now show that B61 can also exist as a cell surface glycosylphosphatidyl-inositol-linked protein that is capable of activating the Eck receptor protein-tyrosine kinase, the first such report of a receptor protein-tyrosine kinase ligand that is glycosylphosphatidylinositol-linked. In addition, the expression patterns of B61 and Eck during mouse ontogeny were determined by in situ hybridization. Both were found to be highly expressed in the developing lung and gut, while Eck was preferentially expressed in the thymus. Finally, the gene for B61 was localized to a specific position on mouse chromosome 3 by interspecific back-cross analysis.

Animals↗
PubMed1995

cDNA cloning and characterization of a Cek7 receptor protein-tyrosine kinase ligand that is identical to the ligand (ELF-1) for the Mek-4 and Sek receptor protein-tyrosine kinases.

We have isolated a murine cDNA encoding a ligand for the Cek7 receptor protein-tyrosine kinase (RPTK), a member of the Eph/Eck RPTK subfamily. Sequence analysis predicts an open reading frame of 209 amino acids with a predicted molecular mass of 24 kDa. The Cek7 ligand shows a 48% sequence identity at the protein level to B61, a ligand for the related Eck RPTK, 30% to the Cek5 ligand, 59% to the recently cloned Ehk1-L, and identity to ELF-1, a recently described ligand for the Mek4 and Sek RPTKs. The expressed Cek7 ligand is functionally active as it induces autophosphorylation of the Cek7 RPTK.

Amino Acid Sequence↗
PubMed1995

Regulation of signal transduction and DNA fragmentation in thymocytes by ethanol.

We demonstrated previously that ethanol enhances apoptosis of murine thymocytes. In this report, we determined intracellular cAMP and cytosolic free calcium ([Ca2+]i) levels in mouse thymocytes following acute exposure to ethanol and investigated the involvement of cAMP, [Ca2+]i, protein kinase A (PKA), and protein kinase C (PKC) in thymocyte apoptotic death induced by ethanol. It was found that ethanol did not alter basal cAMP levels, but produced a dose-dependent, prolonged small [Ca2+]i increase within thymocytes. This dose dependence of [Ca2+]i increase was paralleled by the magnitude of DNA fragmentation induced by ethanol at various concentrations. Additionally, the ethanol-enhanced DNA fragmentation was blocked by H7, a PKC inhibitor, but not by potent PKA inhibitors having little or no effect on PKC. These data suggest that both [Ca2+]i increase and PKC activation triggered by ethanol may belong to the signal pathway(s) leading to thymocyte programmed death.

Animals↗
PubMed1995

[Dynamic changes of the platelet granule membrane glycoprotein level in patients with acute myocardial infarction before and after thrombolysis].

Platelet granule membrane glycoprotein (GMP-140) level was measured by using 125I labelled monoclonal antibody in 37 patients with acute myocardial infarction before and after thrombolytic therapy. In a nonthrombolysis group, it was shown that platelet GMP-140 increased significantly at the moment of admission and reached peak value 48 hours after AMI attack, then it decreased gradually and returned to baseline on the fifth day. In the thrombolysis group, with the patency of infarct related arteries, it dropped quickly (1-6 hours) after thrombolytic therapy; if the infarct related arteries were not patent, platelet GMP-140 increased rapidly after thrombolytic therapy and reached the highest at 6 hours, then it returned to baseline on the third day. It is suggested that the changes of platelet function could play an important role in thrombus formation and lysis; the rapid decrease of the number of GMP-140 molecules on platelet surface might be a new index for the pateacy of infarct related arteries.

Adult↗
PubMed1994

cDNA cloning and characterization of a ligand for the Cek5 receptor protein-tyrosine kinase.

We have isolated a murine cDNA encoding a ligand for the Cek5 receptor protein-tyrosine kinase (RPTK), a member of the Eph/Eck RPTK subfamily. Sequence analysis predicts an open reading frame of 345 amino acids with a predicted molecular mass of 38 kDa. Metabolic labeling and immunoprecipitation of cells transfected with a cDNA encoding the Cek5 ligand revealed the mature protein to have an apparent molecular mass of 45 kDa. The extracellular domain of the Cek5 ligand shows a 27% sequence identity at the protein level to B61, a ligand for the related Eck RPTK (Bartley, T. D., et al. (1994) Nature 368, 558-560). Consistent with the presence of a transmembrane domain, flow cytometry analysis revealed the Cek5 ligand to be expressed on the cell surface. The expressed Cek5 ligand is functionally active as it induces autophosphorylation of the Cek5 RPTK.

Amino Acid Sequence↗
PubMed1994

B94, a primary response gene inducible by tumor necrosis factor-alpha, is expressed in developing hematopoietic tissues and the sperm acrosome.

B94 was originally described as a novel tumor necrosis factor-alpha-inducible primary response gene in endothelial cells which was also induced in an in vitro model of angiogenesis. To further characterize its expression, we cloned the mouse homologue and mapped its developmental and tissue specific expression. The predicted amino acid sequence of mouse B94 was found to be 83% similar to its human homologue. The gene was localized to mouse chromosome 12 just centromeric to the immunoglobulin heavy chain locus, in a region that is often rearranged in T-cell neoplasms. To explore the possibility that B94 is expressed during vasculogenesis and other developmental processes, the expression of its transcript was determined during mouse development by in situ hybridization. In 10-day embryos B94 was expressed prominently in the myocardium and in the aortic arch. By the 15th day of gestation, expression was restricted largely to the liver, the bone forming regions of the jaw, the aortic endothelium, and the nasopharynx: a pattern that was maintained until just prior to birth. Postnatally, expression shifted to the red pulp of the spleen and the thymic medulla. B94 expression was extinguished in most adult tissues but was detectable in lymphopoietic tissues including the spleen, tonsil, and lymphatic aggregates in the gut. Consistent with this was the finding that mononuclear progenitor cells in bone marrow and mature peripheral blood monocytes expressed B94. A truncated testis-specific transcript previously identified by Northern blot analysis was determined to result from the use of an alternate polyadenylation signal which was surprisingly located within the open reading frame. This shorter transcript was expressed at high levels exclusively in late stage spermatids. Immunostaining with an affinity-purified polyclonal antiserum revealed B94 to be localized to the acrosomal compartment of mature sperm. These studies demonstrate that B94 expression is tightly regulated during development and suggests distinct roles for B94 in myelopoiesis and spermatogenesis.

Acrosome↗
PubMed1994

Tilted amides in amino acid and peptide derivatives.

BACKGROUND: Amide bonds in peptides and proteins typically adopt planar cis or trans conformations. Conversions between cis and trans amide conformations are necessary for protein folding and for many other processes, but are difficult to achieve since they involve disruption of the planarity of the bond. As a first step to understanding cis-trans isomerization, we set out to synthesize and characterize peptides that mimic the tilted or twisted amide structures that are postulated to form the intermediate states in this process. RESULTS: We have synthesized a model amino acid and four dipeptide derivatives containing a methyl-substituted aziridine residue. Single crystals of phenacyl (2R, 3R)-benzyloxycarbonyl-3-methyl-2-aziridinecarboxylate and phenacyl (2R, 3R)-acetyl-glycyl-3-methyl-2-aziridine-carboxylate were obtained. Using X-ray diffraction analysis, we determined that the amide nitrogens of the aziridine rings have tetrahedral sp3-like geometry with tilt angles in the range of 37-38 degrees. The 13C-NMR spectra indicate that the amide carbonyl is dramatically shifted downfield as a consequence of the tilt. CONCLUSIONS: In peptides containing a substituted aziridine ring, the orbitals of the amide nitrogen are constrained into a tilted configuration. These peptides may mimic the transition state between cis and trans amide conformations. This technique thus provides a novel strategy for the study of isomerization and other biorecognition processes.

Amides↗
PubMed1994

[Preserving intestinal function after severe burn injury].

To study the changes of the bowel-barrier function and its preservation, we developed a new animal model. A specially bred miniswine (Guizhou species) was used with multiple catheterizations for sampling different blood from portal, inferior mesenteric as will as jugular (central) veins. The animals were sustained with 30% III burns of TBSA 7 days after catheterization and divided randomly into early feeding (EF) group, given a complete diet beginning from 2 hours postburn (n = 6) and delayed feeding (DF) group, given the same diet initiating on 4 days postburn (n = 6). The results indicated that the bowel-barrier function was weakened significantly early postburn so that the translocation of both endotoxin and bacteria from the gut to portal vein was evidently increased. However, improving the intestinal mucosa ischemia, preserving mucosal mass and maintaining bowel-microecological balance through early enteral feeding, as revealed in this study, could enhance the barrier function, and the translocation of bacteria and endotoxin would be thus decreased to some extent.

Animals↗
PubMed1994

[Changes in fat absorption and effect of early enteral feeding following burn injury].

In order to approach this problem, a new animal model was developed in this study. Results indicated that the intestinal ability of absorbing nutrients was not markedly attenuated, and the reduction of portal blood flow was the primary cause of decrement of absorption of nutrients after burn injury. Therefore it is proposed that a timely and effective restoration of the portal circulation might improve the absorption ability. From the results of our present study, it seems probable that early enteral feeding can significantly increase the portal blood flow.

Animals↗
PubMed1994

[Severe burn injury: glucose absorption and early enteral nutrition].

We investigated the changes of glucose absorption and the effect of early enteral nutrition after severe burn injury. A new animal model was developed with a specially bred miniswine (Gui Zhou species) to which multiple catheterizations were applied for sampling different blood from the portal, inferior mesenteric as well as jugular (central) veins. The animals were sustained with 30% III burns of TBSA 7 days after the catheterizations and divided randomly into early feeding (EF) group, given a complete diet beginning from 2 hours postburn, and delayed feeding (DF) group, given the same diet on 4 days postburn. After burn injury, glucose absorption was significantly decreased, but the absorption was much lower in group DF than that in group EF. However, the intestinal ability of absorbing nutrients was not attenuated greatly, and the reduction of portal blood flow was attributed to the decrease of absorption of nutrients. Early enteral feeding can increase portal blood flow obviously.

Animals↗
PubMed1994

[Study on preserving intestinal function and the possible mechanism of hypermetabolic response following severe burn injury].

In order to approach the mechanism of hypermetabolic response following severe burn injury, a new animal model was developed with a specially bred miniswine (Guizhou species). Multiple catheterizations were applied for sampling different blood from portal, inferior mesenteric as will as jugular (central) veins. The animals were sustained with 30% III burn of TB-SA and divided randomly into early feeding group, given a complete diet beginning from 2 hours postburn (N = 6), and delayed feeding group, given the same diet initiating on 4 day postburn (N = 6). The results showed that compared with delayed feeding, early enteral feeding could strengthen the barrier function, decline the rate of translocation of bacteria and endotoxin from the gut to portal vein, reduce obviously blood TNF, CRP and catabolic-hormones, and significantly decrease REE (resting energy expenditure) and urinary 3-Mehis excretion. During the hypermetabolism (PBD7-10), the metabolic response mediated by "intestinal way" was at least 35%. The way of "intestinal tract--macrophages in liver--Hypermetabolism" is a possible mechanism of hypermetabolic response following severe burn injury, and the bacteria and endotoxin translocated from the gut, the active products (IL-1, TNF, etc) released by Kupffer's cells might be the mediating factors of the mechanism.

Animals↗
PubMed1994

[Comparison of 0.1% dipivalyl epinephrine and 1% epinephrine in patients with glaucoma or ocular hypertension].

The effect of 0.1% dipivalyl epinephrine on intraocular pressure was compared with 1% epinephrine in patients with primary open-angle glaucoma or ocular hypertension. In this study, the two drugs significantly lowered intraocular pressure, with no significant differences being observed. In dipivalyl epinephrine group, no significant ocular or systemic adverse reactions, including heart rate and blood pressure, were observed except mild dilation of pupil.

Adolescent↗
PubMed1993

Effect of ethanol on development of fetal mouse thymocytes in organ culture.

Exposure of mouse fetuses to ethanol in utero retards thymus development. The direct effect of ethanol on growth and differentiation of thymocytes was studied using organ cultures of 14-day fetal mouse thymuses. Fetal thymus organ cultures containing 0.2 or 0.4% ethanol produced fewer total thymocytes, proportionately fewer CD4+CD8+ (immature) thymocytes, and proportionately more CD4+CD8- (mature) cells than untreated control cultures after 5 days of culture. Total cell numbers and proportions of CD4+CD8+ thymocytes declined in a dose-dependent manner with increasing ethanol concentrations from 0.2 to 0.8%. In time course studies, thymuses cultured with 0.4% ethanol had an increased percentage of CD4+CD8- cells at all days examined between Days 4 and 6. In the same experiments, thymuses exposed to ethanol underwent accelerated loss of the interleukin-2 receptor (a marker of immature prothymocytes) and had higher percentages of cells positive for the gamma delta-T-cell receptor. Exposure to ethanol for 16 to 20 hr increased the percentage of noncycling thymocytes. Furthermore, ethanol increased apoptosis in fetal thymocytes. Acetaldehyde, the immediate product of ethanol catabolism, had no effect on thymocyte subpopulation ratios or cell numbers at a physiologic concentration (50 microM). Results indicate that in a controlled in vitro model of thymus development, ethanol reduced cell numbers and altered proportions of thymocyte subsets defined by differentiation antigens.

Acetaldehyde↗
PubMed1993

Ethanol increases apoptotic cell death of thymocytes in vitro.

Exposure of animals to ethanol causes thymic atrophy in adults and fetuses. Whether direct effects of ethanol contribute to thymic atrophy or whether indirect effects are entirely responsible is at present unknown. In the normal animal, large numbers of thymocytes undergo a physiological form of cell death referred to as "apoptosis." To determine if ethanol affects the process of apoptosis, studies were undertaken in which mouse thymocytes were cultured overnight in the presence or absence of ethanol. Apoptotic cell death was analyzed by flow cytometric quantitation of apoptotic nuclei, by fluorometric measurement of DNA fragments, and by gel electrophoretic analysis of DNA fragments. Ethanol in concentrations of 0.2% to 0.8% produced significantly higher levels of apoptosis than were seen in control cultures. The DNA fragmentation was characterized as apoptotic on the basis of inhibition by aurintricarboxylic acid (an inhibitor of nucleases) and by the presence of characteristic oligonucleosomal-sized fragments of DNA. The effect of ethanol on apoptosis was additive to that induced by immobilized anti-CD3 monoclonal antibody. CD4+CD8+ cells underwent apoptosis as indicated by reduction in CD4 and CD8 surface antigen expression. An inhibitor of protein kinases (H-7) reduced the DNA degradation induced by ethanol and by anti-CD3. These results suggest that direct effects of ethanol contribute to thymic atrophy in alcohol-consuming animals.

Animals↗
PubMed1992

A general method for chimerization of monoclonal antibodies by inverse polymerase chain reaction which conserves authentic N-terminal sequences.

Chimerization of antibodies (Ab) by cloning the V (variable) regions encoding the light and heavy chains with degenerate oligodeoxyribonucleotide primers matching to framework region 1 and to the joining regions, leads to Ab with altered amino acids at the N-terminus compared to those of the parental Ab. This is due to N-terminal framework 1 sequences in the expression vectors [Larrick et al., Bio/Technology 7 (1989) 937-938; Le Boeuf et al., Gene (1989) 371-377; Orlandi et al., Proc. Natl. Acad. Sci. USA 86 (1989) 3833-3837]. This might lead to Ab with altered affinity to the antigen due to interaction of framework sequences with complementarity determining regions. Moreover, some V regions may be refractory to cloning by this procedure. Here, we describe a method to circumvent these potential problems. The V regions for both chains of the Ab are cloned by inverse polymerase chain reaction (PCR) with primers matching the known constant region sequences of the Ab. After sequencing, PCR fragments corresponding to the V regions of both chains are inserted in-frame into appropriate expression vectors leading to Ab with unaltered N-terminal sequences after expression in mammalian cells. The procedure is illustrated with an Ab directed against the beta chain of the human interleukin-2 receptor.

Amino Acid Sequence↗