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S P Jiang

Publications and source records attributed to S P Jiang.

14 recordsLinked to original sources
PubMed1999

The fetus and the maternal immune system: pregnancy as a model to study peripheral T-cell tolerance.

In this article, we discuss recent findings that describe how maternal T cells respond upon encountering fetal antigens. Many earlier studies have characterized changes in the maternal T-cell repertoire of both humans and mice, yet it has been difficult to understand the significance of these findings since there has been no way to decipher if the alterations were the result of encounters with fetal antigens or were nonspecific changes related to pregnancy itself. Now, in the mouse, the availability of TCR transgenic mice and other technological advances allow direct visualization of the fate of maternal T cells that are reactive to the fetus and provide a means to probe the mechanisms by which tolerance to the fetus is maintained. This article focuses on how the fetus more closely resembles "developmental self' than a true allograft and how the study of maternal T-cell interactions with fetally derived antigens can be useful as a model for the study of peripheral T-cell tolerance.

Animals↗
PubMed1998

Multiple mechanisms of peripheral T cell tolerance to the fetal "allograft".

The fetus represents a foreign entity to the maternal immune system, yet this "natural" allograft is not normally rejected. This unique situation provides a physiologic system to evaluate peripheral tolerance in which the maternal immune system is challenged with relatively rare Ags not previously encountered in the thymus. Using H-Y-specific TCR transgenic mice, we demonstrate that T cells specific for fetal Ags decrease in an Ag-specific manner during pregnancy and remain low postpartum, the result of an encounter with fetal cells expressing the appropriate MHC/peptide complexes. The finding that placental trophoblasts can induce Fas-mediated death of T cells is consistent with peripheral clonal deletion as one mechanism of tolerance. The remaining clonotypic T cells are unresponsive to antigenic stimulation, although neither TCR nor coreceptor is down-regulated. Our study demonstrates that specific recognition of fetal allogeneic Ags by maternal T cells results in tolerance induction of reactive T cells via multiple mechanisms.

Animals↗
PubMed1995

[A prospective epidemiological investigation on the effect of China-mode attenuated live vaccine against hepatitis A in the population of Liu Zhou].

An 24-month prospective epidemiological investigation on the results of China-mode Hepatitis A attenuated live vaccine against hepatitis A by random group sampling was carried out. The incidence of case group was 15.91/10(5) (5/31421), the incidence of control group was 95.92/10(5) (30/ 31277) which showed a significant difference. In case group 2081 persons who missed vaccination, there was one person developed hepatitis A, making the incidence 48.05/10(5). In control group 760 persons were vaccinated by mistake and there was no case developed in this sub-population. There were 644 cases of hepatitis A in the external control group, the incidence was 90.14/10(5). Data showed that there was no significant difference among external control group, control group and persons from case group who missed vaccination. Comparing the data from case group and from the above 3 groups, the protective rates were 82.35%, 83.41% and 66.89%. respectively. When conparing the data from persons who had been mistakenly vaccinated in control group, there was no significant difference being noticed.

Adolescent↗
PubMed1994

Geometries, charges, dipole moments and interaction energies of normal, tautomeric and novel bases.

Ab initio molecular orbital calculations with the STO-3G and 4-31G basis sets are performed to study the geometries and interactions of natural and "novel" Watson-Crick base pairs, as well as some non-Watson-Crick base pairs. First the optimized geometries of bases are determined using the STO-3G basis set, and then for the base pairs with the STO-3G and 4-31G basis sets. Interaction energies of these base pairs are evaluated, and their relative stabilities are discussed. Hydrogen bond features, partial charges and dipole moments of the base pairs are described. The calculated stabilities are in reasonable agreement with the limited available experimental data from thermal melting studies. Hydrogen bond geometries at the 4-31G level are in good agreement with the crystal structure data. The order of relative stabilities is found to be: iG:iC > G:C > G:T* > rG:rC > A*:C > Am:U > tau:kappa > chi:kappa > G*:T > A:C* > A:U = A:T where, A*, T*, G* and C* are tautomers, iG and iC are iso-G and iso-C, Am is 2-amino adenine, chi is xanthosine, kappa is 2,4-diaminopyrimidine, tau is 7-methyl oxoformycin B, rG is modified guanine with substitutions at positions 5 and 7, and rC is modified cytosine with a substitution at position 6. Pairing strengths with modified bases may affect the efficiency of protein production.

Adenine↗
PubMed1994

Stability and cooperativity of nucleic acid base triplets.

Geometries and stabilities of various base triplets have been studied using ab initio quantum chemical methods. Their optimized geometries are determined using the STO-3G basis set, and those of Hoogsteen and reverse Hoogsteen base pairs are evaluated with the 4-31G basis set. Moreover, the preferred hydrogen bond patterns of the bases in triple helices are discussed. A cooperative effect for base pairing in triplets is presented, and it can be either positive or negative. Almost all base triplets that contain Watson-Crick G:C base pairs show a positive cooperativity. Conversely, the base triplets with Watson-Crick A:T base pairs mostly display a negative cooperativity. The interaction energies of base triplets are reported and the relative stabilities of base triplets are found as follows: A+.GC > C+.GC(H) > C+.GC(rH) > G.GC(H) > G.GC(rH) > A.GC > T.AT(rH) > U.AU(H) > U.AT(H) > A.AT > G.AT > T.AT(m) > G.TA(2) > G.TA(1) H and rH denote the Hoogsteen and reverse Hoogsteen positions of the third base that would lead to parallel and antiparallel orientations respectively of the third chain with respect to the Watson-Crick paired purine chain. 'm' denotes the middle pairing scheme, in which the third base hydrogen bonds to both bases of Watson-Crick pair.

Base Composition↗
PubMed1992

Conformational analysis of receptor selective tachykinin analogs: senktide and septide.

The conformational behavior in solution of two receptor selective tachykinin agonists, senktide (succinyl-D-F-MeF-G-L-M-NH2) and septide (pQ-F-F-P-L-M-NH2) is described. Two dimensional cross relaxation NMR spectroscopy is used together with coupling constant data to obtain interproton distance constraints. These results are used in conjunction with semi-empirical energy computations to indicate favorable conformations. Senktide is found to have a high degree of conformational order which is attributed to rotational restriction associated with the N-methylation of phenylalanine. The lowest energy conformation in accord with the experimental interproton distances contains a beta-turn. Interproton distances indicate that septide exists as a random coil or in an extended chain conformation. Energy computations suggest that septide is primarily an extended chain with internal reorientation restricted by the proline residue. These results may be related to the selectivity of these peptides for different receptors, in that the analogs, with conformations more stable than tachykinins, are more receptor selective.

Amino Acid Sequence↗
PubMed1988

Laser-induced multiphoton fluorescence of hemoglobin.

Hemoglobin (Hb) and other samples were irradiated by the 1064 nm nanosecond pulses of an Nd:YAG laser. At room temperature, we observed two red fluorescence bands, which resulted from the absorption of two 1064 nm photons in Hb, and measured the fluorescence emission spectra in the red spectral region for Hb and hematoporphyrin derivative. A red shift of the wavelength and a mirror image in the intensity of fluorescence emissions by two-photon excitation were observed. It is shown that the fluorescence of Hb originates from the heme group. In addition, we also observed fluorescence emission at 392 nm for Hb, which may be from its tryptophan groups.

Fluorescence↗
PubMed1988

Wounding effects of small fragments of different shapes at different velocities on soft tissues of dogs.

The wounding effects of small fragments of the same weight (0.44 gm) but different shapes and at different impact velocities (708-1,560 m/s) on the soft tissues of the hind legs of 156 dogs were studied. The experiments showed that velocity was the major factor in causing wounds. For fragments of the same shape, the energy transmission, volume of wound cavity, sectional areas at entrance and exit, and amount of tissue that had to be excised increased rapidly with increasing velocity. In particular, as the velocity reached about 1,500 m/s, a shallow and wide wound tract was liable to occur, peripheral tissue lesion was relatively apparent, even extended to the whole leg, and the rate of occurrence of bone fracture was high. The wounding effect of the shape of the fragment closely related to its sectional specific weight (W) and drag coefficient (CD). Given the weight of the projectile and the density and thickness of the tissue, the energy transmission (delta E) was directly proportional to the square of the velocity and to the drag coefficient, and inversely proportional to the sectional specific weight of the fragment. Therefore, under certain conditions, reducing the sectional specific weight often increased the drag coefficient, in favour of causing a wound. In this experiment, the extent of wounds caused by the triangular, the square, and the cylindrical, and the spherical fragments decreased in that order, in agreement with their values of sectional specific weight and drag coefficient.

Animals↗
PubMed1987

Fluorescence of proteins induced by two-photon absorption.

At room temperature, the UV fluorescence of trypsin, thyroglobulin, hemoglobin and albumin are observed; these molecules undergo two-photon absorption when they are excited with the radiation of a frequency-duplicated Q-switched Nd:YAG laser. It is shown that the fluorescence of these proteins comes from the tryptophan residues and that it has a red shift of about 20 nm relative to the one-photon fluorescence. We suggest that the weak emission from tyrosine arises from the forbidden two-photon transition. The influence of concentration on the fluorescence of hemoglobin and tryptophan is discussed. The two-photon absorption cross-sections are estimated.

Hemoglobins↗
PubMed1987

A molecular orbital study on adenosine phosphates.

AMP, ADP and ATP are calculated using the CNDO method, and ATP is studied by an ab initio calculation. The essential features of the electronic structure of these molecules are described in detail. Their ionization potentials, dipole moments and bond orders are given. The interaction between ATP with metal ions and enzyme molecules is discussed.

Adenosine Diphosphate↗
PubMedDate not supplied

Role of gastroesophageal reflux disease in asthmatic patients.

The association between gastroesophageal reflux disease (GERD) and asthma is well accepted. The prevalence of GERD increases in asthmatics compared with normal controls, whereas GERD may induce or exacerbate asthma. They interact with each other in a cause and effect relationship. But the mechanism by which GERD might induce or aggravate asthmatic symptoms remains unclear. Two mechanisms have been proposed, including (1) acid in the inflamed esophagus acting on exposed receptor causes an increase in bronchial hyper-responsiveness via the vagal reflex; (2) microaspiration of gastric contents damage the bronchial mucosa, which result in inflammation of the mucosa and bronchial hyper-responsiveness. Among the GERD diagnostic methods, ambulatory esophageal pH monitoring bears the highest sensitivity. Ambulatory esophageal pH monitoring is recommended in patients without classic reflux symptoms or those with difficult to control asthma. Both medical and surgical antireflux therapy could improve asthma symptoms, asthma medication requirements, and even pulmonary function in a proportion of asthmatics.

Asthma↗