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Biomedical subjects

H Sun

Publications and source records attributed to H Sun.

At least 397 records · Page 22Linked to original sources
PubMed1995

Cytokine mRNA profiles in mouse orthotopic liver transplantation. Graft rejection is associated with augmented TH1 function.

Although mouse liver allografts are spontaneously accepted without immunosuppression in many strain combinations, rejection can be induced by presensitization with a donor skin graft two weeks prior to transplantation. In this study, the semiquantitative reverse transcription polymerase chain reaction (RTPCR) was used to assess the involvement of T helper (TH) cell subsets in liver allograft acceptance by determining cytokine mRNA in the graft and spleen of recipients with (A) spontaneously accepting allografts (B) rejecting liver allografts after previous skin sensitization, and (C) syngeneic controls. Spontaneously accepted liver allografts showed upregulation of TH1 (IL-2, IFN-gamma) and TH2 (IL-4, IL-10) intragraft cytokine mRNA, which peaked at day 6 and tapered off thereafter, when compared with levels in syngeneic grafts, but both IFN-gamma and IL-10 mRNA persisted up to day 30. This cytokine mRNA profile correlated with the transient intragraft inflammation associated with spontaneously resolving rejection. Presensitized recipients that rejected their grafts revealed marked upregulation of TH1 (IL-2 and IFN-gamma) and TH2 (IL-4, IL-6) intragraft cytokine mRNAs compared with spontaneously accepting recipients, although IL-10 mRNA levels showed no differences between the two groups. The most striking difference was seen in IFN-gamma levels, which correlated well with the preferential deposition of IgG2a antibody isotype in the rejecting compared with the spontaneously accepting liver allograft recipients. These results suggested an association between liver allograft rejection and enhanced TH1 cytokine immune response. The ability to reject liver allografts by the adoptive transfer of splenocytes, but not serum, from a sensitized mouse ruled out preformed antibodies alone as a cause of rejection. However, spleen cytokine mRNA profiles showed no differences or trends in TH1 or TH2 expression in spontaneously accepting versus rejecting recipients, which suggested that the spleen is not a major site of alloreactive immune expansion. These data suggest that spontaneous acceptance of mouse liver allografts is associated with an insufficient intragraft TH1 cytokine response, the cause of which is currently under investigation.

Animals↗
PubMed1995

Transforming growth factor-beta 1 modulates adenylyl cyclase signaling elements and epidermal growth factor signaling in cardiomyocytes.

Studies presented in this report were designed to investigate the effects of transforming growth factor-beta 1 (TGF-beta 1) on epidermal growth factor (EGF)-mediated stimulation of cAMP accumulation in cardiac myocytes and elucidate the mechanism(s) involved in this modulation. TGF-beta 1 (20 pM) treatment of cardiac myocytes, in a time-dependent manner, decreased the ability of EGF (100 nM) to increase cAMP accumulation. Significant attenuation of EGF-elicited cAMP accumulation was observed 2 h after exposure to TGF-beta 1 and 18 h after addition of TGF-beta 1, the ability of EGF to increase cAMP accumulation was completely obliterated. TGF-beta 1 neither decreased immunoprecipitable EGF receptors in membranes from cardiomyocytes nor altered the specific binding of [125I]EGF to cardiomyocyte membranes. However, TGF-beta 1 decreased the ability of EGF to phosphorylate membrane proteins on tyrosine residues. TGF-beta 1 treatment of cardiomyocytes also decreased the ability of forskolin to augment cAMP accumulation in intact cells and stimulate adenylyl cyclase activity. Similarly, in membranes of TGF-beta 1-treated cells, neither isoproterenol nor EGF stimulated adenylyl cyclase activity. Interestingly, as assessed by the ability of A1F4- to stimulate adenylyl cyclase, TGF-beta 1 did not alter the coupling between Gs and catalytic subunits. Likewise, TGF-beta 1 did not alter the functional activity of the inhibitory regulatory element of the system, Gi. Western analysis of cellular proteins revealed that TGF-beta 1 did not alter the amounts of Ga alpha, Gi alpha 2, and Gi alpha 3. We conclude that TGF-beta 1 attenuates EGF-elicited cAMP accumulation in cardiomyocytes, in part, by decreasing the EGF receptor kinase function and that TGF-beta 1-mediated alterations in the activity of adenylyl cyclase catalytic subunit also contribute toward the regulation of adenylyl cyclase by various agonists.

Adenylyl Cyclases↗
PubMed1995

Preparation of Tyr-C-peptide from genetically altered human insulin precursor.

C-peptide radioimmunoassay (C-peptide RIA) is widely used in determination of pancreatic B-cell secretion activity. 125I labeled Tyr-C-peptide is indispensable in C-peptide RIA kit. Herein we discuss a way of obtaining recombinant Tyr-C-peptide. Arg32Tyr human pro-insulin mutant (R32Y-proinsulin) gene was constructed by site-directed mutagenesis and overexpressed in Escherichia coli. Purified R32Y-proinsulin was converted to insulin and Tyr-C-peptide by trypsin and carboxypeptidase B codigestion. Tyr-C-peptide was isolated through reverse-phase HPLC (RP-HPLC) and identified by C-peptide RIA and amino acid analysis.

Base Sequence↗
PubMed1995

Effect of levonorgestrel-releasing intrauterine device on hormonal profile and menstrual pattern after long-term use.

In the present study 14 women after 6 years' use of levonorgestrel-releasing IUD were investigated for the changes of LH, progesterone (P), estradiol (E2), prolactin (PRL) and serum binding globulin (SHBG) in relation to the levonorgestrel levels throughout a segment of 26-40 days with the aim of comparing the hormonal profiles with those during the first year of use of Lng-IUD. Ultrasound scanning was used to follow the development of follicles along with the RIA measurement of hormones. The results of serum LH, P and E2 showed ovulation in 11 cases with either normal menstrual cycles (5 cases), prolonged or irregular cycles (4 cases) or with amenorrhea for 2-3 years (2 cases). One case showed insufficiency of luteal function and 2 cases showed anovulation but with follicular hyperactivity. Higher percentages of ovulatory cycles (78.5%) were found after 6 years of use. No case of complete suppression of ovulation was found. Anovulatory cycles only constituted 14.3%. Clinically, the development of follicles followed by ultrasound scanning further confirmed the hormonal findings. The persistent enlargement of follicles coincided with high levels of E2. After 6 years of use, the serum levels of levonorgestrel were still maintained at mean levels of 314.26 pmol/L and 470.63 pmol/L in the ovulatory and anovulatory groups, respectively. It is concluded that over two-thirds of the cases have ovulatory cycles after long-term use of Lng-IUD; the contraceptive effect is mainly due to its local action on the endometrium, with much less effect on the ovarian function.

Adult↗
PubMed1995

The expression pattern of the Distal-less homeobox-containing gene Dlx-5 in the developing chick limb bud suggests its involvement in apical ectodermal ridge activity, pattern formation, and cartilage differentiation.

Here we report the isolation from a chick limb bud cDNA library of a cDNA that contains the full coding sequence of chicken Dlx-5, a member of the Distal-less (Dlx) family of homeobox-containing genes that encode homeodomains highly similar to that of the Drosophila Distal-less gene, a gene that is required for limb development in the Drosophila embryo. The expression pattern of Dlx-5 in the developing chick limb bud suggests that it may be involved in several aspects of limb morphogenesis. Dlx-5 is expressed in the apical ectodermal ridge (AER) which directs the outgrowth and patterning of underlying limb mesoderm. During early limb development Dlx-5 is also expressed in the mesoderm at the anterior margin of the limb bud and in a discrete group of mesodermal cells at the mid-proximal posterior margin that corresponds to the posterior necrotic zone. These mesodermal domains of Dlx-5 expression roughly correspond to the anterior and posterior boundaries of the progress zone, the group of highly proliferating undifferentiated mesodermal cells underneath the AER that will give rise to the skeletal elements of the limb and associated structures. The AER and anterior and posterior mesodermal domains of Dlx-5 expression are regions in which the homeobox-containing gene Msx-2 is also highly expressed, suggesting that Dlx-5 and Msx-2 might be involved in regulatory networks that control AER activity and demarcate the progress zone. In addition, Dlx-5 is expressed in high amounts by the differentiating cartilaginous skeletal elements of the limb, suggesting it may be involved in regulating the onset of limb cartilage differentiation.

Amino Acid Sequence↗
PubMed1995

Monte Carlo simulation of radon emanation from dry building materials.

Prediction of radon release from building materials is a general problem. Since it is impractical to follow each recoil radon path and measure the surface area of porous texture by experimental methods, a powerful computer simulation approach is conducted in this paper. The Monte Carlo simulation program TRIM, based on the momentum and energy conservation of the ion transport in matter, is modified to simulate the recoil path in a 3-D frame. A follow-up Monte Carlo program was established further to calculate the detailed recoil range distribution and the recoil probability (emanating power). The powerful Turning Bands Method (TBM) of random field is applied to simulate the 3-D porous texture based on the porosity and the correlation function of the porous texture. Based on the simulated porous texture, the fractal dimension of the surface is calculated and used to calculate the effective surface area for radon recoil. The relations between the air buffer thickness, embedding effect of recoil, and the measuring scale of the surface area for the porous texture are discussed and numerically calculated. After these calculations are performed, the relations between the emanating rate, surface area, material density, and porosity are established to calculate the radon emanation rate from porous materials. This paper provides a clear theoretical picture of the mechanism of radon release from the building materials. It has also potential application to the recoil release calculations of other radioactive elements from solid materials.

Construction Materials↗
PubMed1995

African swine fever virus gene j13L encodes a 25-27 kDa virion protein with variable numbers of amino acid repeats.

The African swine fever virus (ASFV) j13L gene encodes a 177 amino acid protein (19.0 kDa) with a putative transmembrane domain between residues 32 and 52. There is a potential signal peptide cleavage site at residue 54 and several possible motifs for phosphorylation and myristylation. Rabbit antisera raised against a synthetic peptide from the C terminus of the j13L ORF identified proteins of 25-27 kDa in cells infected with a recombinant vaccinia virus expressing the j13L ORF, in ASFV-infected cells and in purified extracellular ASF virions. In ASFV-infected cells the j13L protein was expressed late during infection and exhibited size variation (25-27 kDa) between the different ASFV strains. Nucleotide sequence analysis of the gene in these strains showed that these size differences were due to variation in the number and sequence of tandemly repeated amino acid repeats. Although ASFV-infected animals made antibodies to the j13L protein, no protection was observed when pigs were vaccinated with a recombinant vaccinia virus expressing the j13L ORF.

African Swine Fever Virus↗
PubMed1995

[Placental ureaplasma urealyticum infection and low birth weight].

Ureaplasma urealyticum (UU) infection during pregnancy may result in poor outcome. Placentae from 116 normal healthy pregnancies were cultured for UU with a recovery rate of 28.45%. 94 cases ended by normal vaginal delivery had a UU positive rate of 29.79%. The UU positive rate of 22 placenta from cases by cesarean section was 22.73%. The 2 positive rates showed no difference of significance (P > 0.05). This result indicated that UU infection of the placenta was present before passing through the birth canal and not due to contaminant during delivery. The birth weight of the neonates with positive UU infection was on the average 2,919g, while that in the negative UU cases was 3,490g, being 571g higher than in the positive group (P < 0.01). This study showed that placental infection with UU is associated with a low birth weight.

Adult↗
PubMed1995

Immunoregulatory effects of the herba Epimediia glycoside icariin.

The in vitro effects of the Chinese Herba Epimediia glycoside icariine (ICA), a chinese herbal extract, on human immune responses were investigated. ICA induced a weak and delayed proliferation of peripheral blood mononuclear cells from healthy donors when compared to phytohemagglutinin. Both T- (TCR alpha beta+) and B cells were the ICA-responding cells. Within T-cells, the relative proportion of CD4-8+ cells increased but that of CD4+8- cells decreased. ICA in certain concentrations could increase lymphokine-activated killer cell (LAK) activity (0.1 to 1.0 microgram/ml) in both tumor patients and healthy donors, and natural killer cell (NK) activity (1.0 to 5.0 micrograms/ml) in tumor patients. Moreover, ICA stimulated the production of tumor necrosis factor-alpha in monocytes from healthy donors. These findings provide evidence that ICA could be applied to adoptive immunotherapy. Generation of LAK cells in presence of an appropriate dose of ICA might be superior to interleukin-2 alone.

Adjuvants, Immunologic↗
PubMed1995

A method of determining the in vivo drug release rate constant of sustained-release preparation.

Assuming a one-compartment model and first-order processes for drug release, absorption, and elimination, a new equation to describe the fraction of drug to be absorbed (1-Ft) for a sustained-release product is derived. Based on this equation, when In(1-Ft) vs. time is plotted, the slopes yield the drug release rate constant (Kr), the drug absorption rate constant (Ka), and two intercepts that are a mixed function of Ka, Kr, and the fraction of sustained-release (Fs). The accuracy of this equation to generate pharmacokinetic parameters, such as Ka, Kr, Fs, and the bioavailability-volume of distribution ratio (FD/V) was tested by fitting this equation to multiple simulated plasma concentration-time data (5 sets errorless and 75 sets errant data). The absolute percentage error of Ka and FD/V estimated by this equation is much less than that of traditional polyexponential equation, whereas the absolute percentage error of Kr estimated by this equation is statistically significantly less than that of traditional polyexponential equation. Furthermore, with this equation, it is easier to estimate Fs than with traditional equation. An application of this equation in generating these parameters is illustrated for a quinidine sustained-release dosage form-quinidex.

Delayed-Action Preparations↗
PubMed1995

Alterations in messenger RNA encoding atrial natriuretic hormone receptor A and C subtypes during hepatic regeneration.

Previously, we demonstrated that, 48 hours after partial hepatectomy, in the regenerating liver the number of both atrial natriuretic hormone (ANF) receptor subtypes, the guanylyl cyclase-linked and ANF-C receptors, is increased twofold. Subsequently, we demonstrated that activation of ANF-C receptors inhibits growth of hepatocytes. Therefore, studies were performed to determine whether, during hepatic regeneration, the increase in ANF receptor subtypes is accompanied by an increase in their respective transcripts. Our data demonstrate that in the normal and regenerating rat liver, the predominant guanylyl cyclase-linked ANF receptor is of the ANF-A subtype. Moreover, messenger RNA (mRNA) encoding the ANF-A and ANF-C receptors are transiently increased after surgery; the levels of mRNA encoding both receptor subtypes remain unchanged in livers of sham-operated animals. ANF-A receptor mRNA is maximally increased 12 hours after partial hepatectomy, whereas the maximal increase in ANF-C receptor mRNA is observed between 0.5 hour and 4 hours after hepatectomy. The increase in ANF-C receptor transcript is accompanied by increased expression of protein, 4 hours after hepatectomy. However, the ANF-C receptor protein is also elevated 48 hours after partial hepatectomy when ANF-C receptor mRNA levels are not different from controls. Likewise, although ANF-A receptors are increased when hepatic levels of mRNA encoding the protein are maximally elevated, the maximal increase in ANF-A receptor protein occurs at times when transcript levels are low and similar to those in sham-operated controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗