Biomedical subjects

Y H Zhang

Publications and source records attributed to Y H Zhang.

At least 19 recordsLinked to original sources

PubMed1992

Delivery of an accessory signal for cell activation by exogenous phosphatidylinositol-specific phospholipase C.

Digestion of phosphatidylinositol (PI) or glycosylphosphatidylinositol (GPI) anchors of membrane proteins on the external cell surface with exogenous PI-specific phospholipase C (PIPLC) from Bacillus thuringiensis was shown to transmit a signal into the thymocyte to modulate the TCR/CD3 complex-induced signal delivery for cell activation. This was demonstrated for very early protein tyrosine phosphorylation, early c-fos transcription and late DNA synthesis. For this effect preincubation of the cells with PIPLC was required, but there was no evidence of involvement of any soluble products released from the cell surface by PIPLC in the signaling, suggesting a crucial role of the membrane-bound counterpart (diacylglycerol or diradylglycerol) of the PI/GPI hydrolysate. A possible role for this accessory signal in the microorganism-linked control of the (diacylglycerol or diradylglycerol) of the PI/GPI hydrolysate. A possible role for this accessory signal in the microorganism-linked control of the T cell receptor function is discussed.

Animals↗

PubMed1992

RNA analysis from newborn screening dried blood specimens.

We have previously demonstrated that DNA can be extracted from the dried blood specimen of the type used for newborn screening. The technique presented here allows us to extract RNA from newborn screening specimens for cDNA synthesis by reverse transcriptase and amplification by the polymerase chain reaction (PCR). Products of the PCR reaction are then analyzed by restriction enzymes. This method successfully distinguishes beta A and beta S transcripts in unaffected (AA), carrier (AS), and affected (SS) individuals. The value of this approach for identification of a compound heterozygous patient with S/beta-thalassemia, using the original newborn screening specimen, is also demonstrated. This work shows that mRNA is stable in dried blood specimens and that analysis of the mRNA phenotype can be a useful adjunct in the application of molecular genetic technology to newborn screening.

Anemia, Sickle Cell↗

PubMed1992

Bidirectional control by glycyrrhizin of the growth response of lymphocytes stimulated through a receptor-bypassed pathway.

This study demonstrates a unique action of glycyrrhizin (GL) in bidirectionally controlling the growth response of lymphocytes stimulated through a receptor-bypassed pathway by calcium ionophore A23187 and phorbol 12-myristate 13-acetate (PMA). GL up-regulated the response of lymphocytes in vitro to lower concentrations of A23187 and PMA, and down-regulated the response to higher concentrations. We also provide evidence that GL controls the response of lymphocytes of different cell types or maturation stages in different ways, probably because these lymphocytes require different levels of signals as optimum. Finally, the GL-mediated bidirectional controls of the lymphocyte growth response were shown to be adherent cell-independent. The bidirectional controls demonstrated may be significant in normalizing the lymphocyte responses to very weak or very high stimuli.

Animals↗

PubMed1992

Rapid determination of conditional partition constants in an FIA system.

This paper presents a simple and rapid method for the screening of substances for their conditional partition constants in the chloroform-water system. Samples are injected in either aqueous or organic solution into the corresponding phase. After equilibration in segmented flow the amount of sample remaining is measured photometrically. Performing the measurements at a series of phase volume ratios enables calculation of conditional partition constants knowing neither the amount injected nor the absorptivity of the substance under study. The time needed for a determination is about 15 min per substance, in many cases even shorter and the sample consumption is, in most cases, less than 1 mg. These characteristics make the method suitable for screening purposes. A series of compounds has been examined with this method, and acceptable results for the conditional partition constants were obtained in the range 0.2 less than D' less than 100 (-0.7 less than log D' less than 2.0).

Flow Injection Analysis↗

PubMed1992

T cell maturation stage-linked heterogeneity of the glycosylphosphatidylinositol membrane anchor of Thy-1.

We showed that some of Thy-1 molecules on murine thymocytes are resistant to phosphatidylinositol-specific phospholipase C (PI-PLC) derived from Bacillus thuringiensis. Both immature thymocytes with low CD3 expression and mature thymic T lymphocytes with high CD3 expression carried the PI-PLC-resistant Thy-1, and the PI-PLC-sensitivity of Thy-1 extensively varied among thymocyte subpopulations. In contrast, the same PI-PLC fully hydrolysed the anchor of Thy-1 on peripheral T lymphocytes. When the latter cells were activated with mitogen in vitro, however, some Thy-1 on them became resistant to PI-PLC. We then found that virtually all Thy-1 molecules on thymocytes became sensitive to PI-PLC when they were treated with hydroxylamine that should cleave ester-linked lipids. The result ruled out the possibility that the PI-PLC-resistant Thy-1 had a transmembranous peptide sequence, and suggested the presence of an additional fatty acyl group on the inositol ring of the Thy-1 anchor. In addition, the molecular size of the PI-PLC-resistant membrane-bound Thy-1 was only marginally larger than that of the PI-PLC-sensitive solubilized Thy-1 in detergent-partitioning SDS-PAGE analysis.

Animals↗

PubMed1992

Non-neutralizing monoclonal antibodies against Ras GTPase-activating protein: production, characterization and use in an enzyme immunometric assay.

We studied several monoclonal antibodies (mAbs) raised against the 100 kD Ras GTPase activating protein (p100-GAP), which was purified from human placenta. These antibodies recognized p120-GAP and p100-GAP in native and in denatured forms. The most reactive, GP15 and GP200, both recognized distinct epitopes and did not neutralize GTPase stimulatory activity. These two mAbs were selected for a two-site enzyme immunoassay, using covalent conjugates of the antibodies coupled to the tetrameric form of acetylcholinesterase as tracer. This assay was used to quantify Ras-GAP in both normal and tumor tissues and cell extracts.

Animals↗

PubMed1992

Novel adjuvant action of lipopolysaccharides that possess mannose homopolysaccharides as O-specific polysaccharides on immune responses to nonimmunogenic autoantigens in mice.

The adjuvant action of various lipopolysaccharides on immune responses to syngeneic tissue extract in mice was examined. Only lipopolysaccharides possessing the linear mannose homopolysaccharides as O-specific polysaccharides exhibited definite adjuvant action on immune responses to the autoantigens. The intensity of this adjuvant activity of lipopolysaccharide from Klebsiella O3 seemed to be the strongest.

Animals↗

PubMed1992

Genotypic confirmation from the original dried blood specimens in a neonatal hemoglobinopathy screening program.

Dried blood spots are used for newborn screening because of ease of sample collection, handling, and shipment. DNA is stable and accessible in the filter paper matrix. Genotypic confirmation using initial specimens is demonstrated for a regional screening program. Seventy-five blinded samples underwent DNA analysis after Hb electrophoresis. DNA was microextracted from a 1/2-inch semicircle (25 microL whole blood equivalent), amplified, and analyzed by four different methods. Direct amplification without microextraction and automated sequencing from microextracted DNA also was performed. All four analyses agreed for the A and S alleles in 70 of 75 specimens. Three disagreements were clarified by the other semicircle from the original sample: two were due to polymerase chain reaction contamination and one to contamination of one of four analytical tests. Two would have required analysis of a second specimen, one because of polymerase chain reaction failure and the second because the patient had S/beta-thalassemia. Direct amplification without microextraction was successful in an additional 77 of 78 specimens for analysis of the A, S, C, and E alleles. Automated direct sequencing from microextracted DNA was demonstrated for the A, S, and C alleles. Analysis of microextracted DNA from dried blood specimens for A and S alleles reduced the need for and costs of obtaining a second specimen for confirmation by 97%. Direct amplification without microextraction for analysis of A, S, and C alleles permits additional reduction in personnel time and costs. We have demonstrated that microextracted DNA is amenable to automated sequencing after asymmetric polymerase chain reaction. Direct genotypic confirmation can facilitate diagnosis and initiation of medical intervention.

Alleles↗

PubMed1992

[A clinical study of vertical saccadic eye movements].

The authors studied the vertical saccadic movements of 12 patients with vertical paretic strabismus (< 6 degrees) by Scott's method, comparing the saccade of the paretic muscle with that of its antagonist. The results showed that the former was reduced in amplitude by 15%-50%, averaging 31.5%, and improved to 0%-25%, averaging 8.1%, after operations. The authors proposed that a difference of saccadic amplitude over 15% between a muscle and its antagonist indicated presence of muscle paresis. Besides, the methods of assessing saccadic movements were discussed.

Adolescent↗

PubMed1992

Curative effects of highly active atrial natriuretic peptide on severe pregnancy-induced hypertension.

A new highly active atrial natriuretic peptide (haANP), synthesized by a solid phase technique, was given by intravenous infusion to 20 patients with severe pregnancy-induced hypertension (PIH) and the curative result of haANP was observed. Compared with basal values, supine systolic and diastolic BP was lowered significantly (P < 0.01), which may be related to the specific receptor of hANP and inhibition of renin-angiotensin-aldosterone system (RAAS). The haANP was found to possess significant effects of antispasm, detumescence and reducing proteinuria, probably by repairing mildly injured glomerulae, strong effects of diuresis and improving heart function with no side effects. Auto-antibody of hANP was found in patients with severe PIH, which affected the function of target cells of highly concentrated endogenous hANP. This auto-antibody might be one of the causes for PIH.

Adult↗

PubMed1992

[Anti-tumour study of combined therapy of yi kang ling with chemotherapeutic agents].

Result of animal experiment proved that Yi Kang Ling, a TCM compound preparation, could markedly inhibit the growth of implanted tumour in mice. The inhibiting effect to the experimental tumour of combined therapy of Yi Kang Ling and the chemotherapeutic agents-CTX or MMC was better than that using singly. The Yi Kang Ling could alleviate toxicity of chemotherapy which caused the weight loss of mice. It could markedly increase the immune organs' weight, raise the phagocytosis of abdominal macrophage and promote the formation of serum hemolysin inhibited by CTX. The experimental result revealed that the combined therapy of Yi Kang Ling and the chemotherapeutical agents could enhance anti-tumour effect and lower the toxicity of chemotherapy. Toxicological experiment showed that the Yi Kang Ling did not have any toxic effect against organism.

Adjuvants, Immunologic↗

PubMed1992

[Studies on the strain differences of Schistosoma japonicum in the mainland of China. XI. Enzyme linked immunoelectrotransfer blot analysis].

Antigens prepared from S. japonicum adult worms of different isolates i. e. Anhui, Hubei, Guangxi, Yunnan and Sichuan by origin were analyzed by enzyme linked immunoelectrotransfer blot (EITB) probed with rabbit anti-snail antibody (Figs 1,2). Anti-sera against Oncomelania h. hupensis from Anhui, Hubei, Yunnan and Sichuan localities were prepared separately and used in the tests. The EITB patterns were similar in S. j. isolates of Anhui and Hubei, and it was also the case among S. j. isolates of Yunnan and Sichuan except Yunnan female worms with a marked band of 84 kDa but it was almost invisible in EITB pattern of Sichuan female worms. Like Yunnan isolate, female worms of Guangxi isolate also showed marked 84 kDa bands. The EITB pattern of male worms from Guangxi isolate showed 2 main bands of mw > 130 kDa against anti-Anhui snail anti-serum, which corresponded with the male worms of Anhui isolate whereas the color of the bands was darker and denser in the former isolates, and these bands can not be seen in the male worms from isolates of Yunnan and Sichuan. Based on the above mentioned results in connection with the information about the susceptibility between different isolates of schistosomes and their snail hosts which we have reported before, some preliminary analysis and discussion were made.

Animals↗

PubMed1992

[Studies on the strain differences of Schistosoma japonicum in the mainland of China. X. Comparison of SDS-page protein patterns].

The purpose of the present study was to investigate the SDS-PAGE separation of proteins of the 5 different isolates of Schistosoma japonicum from the mainland of China to determine their similarities and/or differences and to gain additional data which could give an added insight into the degree of relationship. Soluble proteins of freshly sonicated adult worm extract of the 5 different isolates (i.e., Anhui, Hubei, Guangxi, Sichuan and Yunnan) were compared by SDS-polyacrylamide gel electrophoresis. The results indicated that no marked difference could be observed among the isolates after gels were stained by Coomassie blue white both male and female worms of Guangxi isolate showed some definite differences in their protein profile, i.e., lack of 50-75 kDa band in male worms and a marked reduction in the quantity of > 110 and 30 kDa bands in female worms as shown by silver stain.

Animals↗

PubMed1992

Distribution and characteristics of placental ANP receptors in normal and hypertensive pregnancy.

The ANP (atrial natriuretic peptide) receptor binding site was studied in human placentas of normal and hypertensive pregnancy. The results showed there were specific high affinity ANP receptors in the nonbrush border (fetal side), and their affinity to ANP was higher than that in the microvillous membrane (meternal side). The ANP receptor affinity in the nonbrush border and microvillous membrane of normal pregnancy was higher than that of hypertensive pregnancy. Though the weight of placentas of hypertensive pregnancy was lower than that of normal pregnancy, high ANP concentrations in the placental tissues, umbilical and maternal blood were found in hypertensive pregnancy. It is believed that the distribution of ANP receptors in the placentas is related to hemodynamics, maternal exchange and fluid and electrolyte balance. The decrease of ANP receptors and lowering of affinity in hypertensive pregnancy may influence the the target cell effect of ANP, especially in the fetal side. This may be related to the pathogenesis of hypertensive pregnancy.

Atrial Natriuretic Factor↗

PubMed1992

[Studies on the strain differences of Schistosoma japonicum in the mainland of China. VIII. Immunoreactions in experimental animals].

Observations on the immunoreactivities toward egg antigens of different experimental animals infected with Schistosoma japonicum were made, which included mouse, rat, hamster, rabbit and rhesus monkey. The cercariae applied for infection were shed by snails collected from 5 different isolates, i.e., Anhui, Hubei, Sichuan, Yunnan and Guangxi in the mainland of China. Sera from the same sort of animals were separately pooled according to the different sources of infection mentioned above. Antibody reactivities were evaluated by COPT, LAT and ELISA. In COPT each serum sample was tested with ova from homologous and heterologous isolates, whereas soluble egg antigen merely prepared from Anhui isolate was used in LAT and ELISA. The level of antibodies detected by homologous or heterologous worm isolate antigens was compared. The results suggested that the positive antibody detection rate might not be influenced by antigens prepared from S. japonicum eggs of different isolates in the mainland of China.

Animals↗

PubMed1991

ATP-dependent regulation of flagellar adenylylcyclase in gametes of Chlamydomonas reinhardtii.

Adenylylcyclase activity in the flagella of gametes of Chlamydomonas reinhardtii was inhibited by prior incubation at or below 30 degrees C in the presence of ATP. This decrease did not occur in the absence of ATP, in the presence of the ATP analog 5'-adenylylimidodiphosphate (App(NH)p), or in the presence of ATP plus the protein kinase inhibitor staurosporine (2 microM). If ATP treatment was performed in the absence of an ATP-regenerating system, activity initially declined and subsequently recovered. Incubation of flagella at 45 degrees C in the absence of ATP or incubation at lower temperatures in the presence of either App(NH)p or staurosporine both increased adenylylcyclase activity (over 10-fold) and blocked subsequent ATP-dependent loss of activity at 30 degrees C. This heat-induced activation was prevented by the presence of ATP plus an ATP-regenerating system. Incubation of flagella with [gamma-32P]ATP followed by gel electrophoresis in sodium dodecyl sulfate indicated the presence of endogenous protein kinase and protein phosphatase activities. These data suggest that the flagellar adenylylcyclase in Chlamydomonas gametes is inhibited by phosphorylation and stimulated by dephosphorylation. This mechanism for regulating adenylylcyclase may underlie the rapid increase in cyclic AMP that is induced by flagellar adhesion during fertilization in Chlamydomonas.

Adenosine Triphosphate↗

PubMed1991

Evidence of synergy between Thy-1 and CD3/TCR complex in signal delivery to murine thymocytes for cell death.

The potential role of Thy-1 in CD3/TCR complex-mediated signal delivery to murine thymocytes was studied. Ag-mimicking cross-linked anti-CD3 mAb stimulated suspension of thymocytes from adult (6 to 8 wk old) mice for a brisk free cytoplasmic calcium ion ([Ca2+]i) rise, low level of inositol phosphate production, and marginal increase in tyrosine-specific phosphorylation of 110/120-kDa and 40-kDa cellular proteins. Weak but sustained [Ca2+]i rise, low inositol phosphate production, and weak protein tyrosine phosphorylation were also induced by the cross-linked anti-Thy-1 mAb that mimicked the putative natural ligand. The signal delivered via either of these two pathways was however insufficient for definitively promoting cell death and DNA fragmentation in the adult thymocytes. Here we demonstrated that anti-Thy-1 mAb synergized with anti-CD3 mAb for inducing a long-lasting prominent [Ca2+]i rise, definite inositol 1,4,5-triphosphate and inositol 1,3,4,5-tetrakiphosphate production, and extensive tyrosine-specific phosphorylation of 110/120-, 92-, 75-, and 40-kDa proteins, which resulted in marked promotion of cell death and DNA fragmentation in the adult thymocytes. This unique anti-Thy-1 antibody activity was confirmed to be directed to glycosylphosphatidylinositol-anchored Thy-1, and was distinguished from the known anti-L3T4 activity that augmented the CD3-mediated signal transduction in a different manner. The synergistic actions of anti-CD3 and anti-Thy-1 mAb obligatorily required the cross-linking of the two mAb together. The anti-CD3 and anti-Thy-1 mAb cross-linked together acted on immature thymocytes from newborn (less than 24 h after birth) mice for rather more extensive promotion of protein tyrosine phosphorylation and cell death. In addition, they affected peripheral T lymphocytes for accelerating protein tyrosine phosphorylation but not cell death. These results suggest a novel function of glycosylphosphatidylinositol-anchored Thy-1 as a possible unique intrathymic intensifier of the CD3/TCR complex-delivered signal for negative thymocyte selection.

Animals↗

PubMed1991

Modulation of the secondary antibody response of murine lymphocytes to sheep red blood cells in vitro by neuraminidase and exoglycosidases.

The effect of digestion of lymphocytes with neuraminidase and exoglycosidases on the secondary antibody response in vitro to sheep red blood cell (SRBC) antigen was tested. Treatment of spleen cells from SRBC-primed mice with 3 micrograms/ml of neuraminidase slightly but significantly augmented their plaque-forming cell response to SRBC, whereas treatment with 100 micrograms/ml of a mixture of exoglycosidases did not. Rather unexpectedly, however, treatment of the spleen cells with the mixture of both neuraminidase and exoglycosidases greatly augmented the response. This enzyme action was substrate specific inasmuch it was ablated by addition of mucin as a neuraminidase inhibitor to the enzyme mixture. The target of the enzyme activity was not glass-adherent macrophages, but was glass-non-adherent suppressor cells in the antigen-primed cell population. Evidence was provided that the phenotype of suppressor cells whose activity was ablated by the enzyme treatment was Thy-1+. It is suggested from these results that sialylated complex type oligosaccharides on antigen-primed T cells play a critical role in their suppressor activity.

Animals↗