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Biomedical subjects

M Zhao

Publications and source records attributed to M Zhao.

At least 325 records · Page 18Linked to original sources
PubMed1993

Differential downregulation of beta 2-adrenergic receptors in tissue compartments of rat heart is not altered by sympathetic denervation.

With agonist stimulation, cardiac beta 2-adrenergic receptors (beta 2ARs) are downregulated to a much greater extent than are beta 1ARs. It has been hypothesized that this effect is due to sympathetic innervation inhibiting the downregulation of beta 1ARs. To test this hypothesis, the technique of coverslip autoradiography was used to localize and quantify beta 1AR and beta 2AR subtypes in tissue compartments of the heart in rats subjected to sympathetic denervation by two intravenous injections of 6-hydroxydopamine (50 mg/kg per dose). After denervation, the rats were infused with L-isoproterenol (400 micrograms.kg-1 x h-1 for 7 days) or vehicle (0.001N HCI) by implantation of osmotic minipumps. Sections were incubated with 70 pmol/L of the beta AR antagonist [125I]iodocyanopindolol (ICYP) alone or in the presence of 5 mumol/L DL-propranolol or 5 x 10(-7) mol/L CGP 20712A (a beta 1AR antagonist). Binding of ICYP to sections of rat hearts was saturable and stereoselective and was displaced by beta AR agonists with the rank order of potency expected for beta ARs. There was an 89% reduction in catecholamine concentration in rat ventricles after 1 week of 6-hydroxydopamine treatment, before implantation of the minipumps. Chronic infusion of isoproterenol induced significant downregulation (63% to 74%) of beta 2ARs in atrial and ventricular myocytes, coronary arterioles, and connective tissue but no change in beta 1ARs in these regions in rats with intact sympathetic innervation. Similar changes were seen in denervated animals. There was a marked reduction in beta 2ARs but small insignificant decreases in beta 1ARs, despite the fact that in the denervated animals there was upregulation of beta 1ARs in atrial and ventricular myocytes (approximately 25%). Our study suggests that beta 1ARs in the heart are not significantly downregulated by chronic agonist exposure and that this is unrelated to sympathetic innervation. The underlying mechanism of preferential regulation of beta AR subtypes remains to be elucidated but may be related to differences in the molecular structure between beta 1ARs and beta 2ARs.

Animals↗
PubMed1993

[Effects of epidermal growth factor on growth and differentiation of rat granulosa cells].

It was known that epidermal growth factor (EGF) plays an important role in the regulation of reproduction. The present study was undertaken to investigate the effect of EGF on the proliferation and differentiation of cultured rat granulosa cells. The results showed that EGF inhibited the 3H-TdR incorporation into DNA of granulosa cells, while the progesterone production was increased due to enhanced 3 beta-HSD activity. Radioreceptor assay (RRA) suggested that there were specific receptors for EGF on the granulosa cell with a Kd of 1.83 +/- 0.30 x 10(-8) mol/L and a Bmax of 1.75 +/- 0.29 x 10(4) sites/cell. Using method of immunohistochemistry, no EGF-like immunoreactivity was found in the granulosa cells at different age or different estrous cycle, but in the theca folliculi, interstitium and corpus luteum. These results suggest that EGF can regulate the growth and differentiation of the granulosa cells in the course of maturation of the folliculi and granulosa cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

"Neuroendocrine" differentiation in hepatocellular carcinomas (HCCs): immunohistochemical reactivity is related to distinct tumor cell types, but not to tumor grade.

We have analyzed neuroendocrine differentiation (ND) in hepatocellular carcinomas (HCCs) of fifty patients. It turned out that ND is frequent in HCCs, and that it is not restricted to fibrolamellar hepatocellular carcinoma (FL-HCC). Multiexpression is seen in a quarter of the cases, and marker coexpression may occur within the same tumor cell. ND predominates in trabecular and mixed HCCs, but does not appear to be related to grade. Most positive cases showed a hepatocyte-like cell morphology, frequently associated with bile formation. It thus appears that the HCC cell type most likely to show ND is a hepatocyte-like one, i.e. differentiated cell, frequently polarized and producing bile, rather than a small and poorly-differentiated cell. Possible pathogenic mechanisms leading to ND in HCCs are briefly discussed.

Adult↗
PubMed1993

Detection of clonal B cell populations in paraffin-embedded tissues by polymerase chain reaction.

A method was established to detect clonal B cell populations in frozen and paraffin-embedded tissues. The method is based on the polymerase chain reaction amplification of rearranged VH and V kappa genes using V gene family-specific primers. Monoclonal B cell populations could be detected in peripheral blood lymphocyte DNA in all 16 cases of B-CLL and immunocytoma investigated and in 8 of 10 cases of B cell non-Hodgkin's lymphoma using frozen and paraffin sections. The amplification of V kappa rearrangements in addition to the VH amplification is a useful tool to verify the results of the heavy chain rearrangement and to detect proliferation of a B cell clone in cases in which no VH product was obtained. In spite of the degradation of DNA in paraffin-embedded tissues, we were able to find amplified polymerase chain reaction products of about 350 bp length in 8 of 10 cases analyzed. The method presented here may be helpful in routine diagnosis of B cell non-Hodgkin's lymphoma using frozen or paraffin-embedded specimens.

B-Lymphocyte Subsets↗
PubMed1992

Graphic analysis of relaxation times of enzyme-catalysed reactions. An extension of the graphic method of King and Altman.

An extension of the graphic method of King & Altman (1956) (J. Phys. Chem. 60, 1375-1378) is applied to the analysis of relaxation times of enzyme-catalysed reactions and a simple graphic method is presented. Clear-cut graphs, simple drawing, easy operation (without the need to perform the usual complex mathematical operations), and reliable results are the main characteristics of this kind of graphic method. A system of enzyme-catalysed reactions (E <--> ES <--> EP) is used as the actual example for illustrating the graphic method.

Enzymes↗
PubMed1992

Modulation of cytosolic-[Ca2+] oscillations in hepatocytes results from cross-talk among second messengers. The synergism between the alpha 1-adrenergic response, glucagon and cyclic AMP, and their antagonism by insulin and diacylglycerol manifest themselves in the control of the cytosolic-[Ca2+] oscillations.

Hepatocytes respond to stimulation by glycogenolytic agonists acting via phosphoinositide (PI) breakdown through oscillations of the free cytosolic concentration of Ca2+ ([Ca2+]cyt.). Since the second-messenger repertoire of hepatocytes includes many other factors besides Ca2+, we investigated to what degree the regulation of [Ca2+]cyt. oscillations is integrated into these other signalling systems. [Ca2+]cyt. was recorded in single rat hepatocytes by using the Ca(2+)-indicator fura-2. Parallel stimulation with phenylephrine (an alpha 1-adrenergic agonist of PI breakdown) and glucagon resulted in a synergistic stimulation of [Ca2+]cyt. oscillations. Direct activation of the cyclic-AMP-dependent pathway with several stimuli (forskolin, 8-bromo cyclic AMP, 8-CPT cyclic AMP) mimicked the response to glucagon. In contrast, [Ca2+]cyt. oscillations induced by various combinations of these agonists could be antagonized by the glycogenic hormone insulin. As one of the options in the insulin-signalling network, we tested a diacylglycerol activator of protein kinase C, DiC8. It also acted as an inhibitor of [Ca2+]cyt. oscillations. We investigated how these observations could be reconciled with our previously introduced model of [Ca2+]cyt. oscillations in hepatocytes [Somogyi and Stucki (1991) J. Biol. Chem. 266, 11068-11077]. First of all, the effect of calmodulin inhibitors (calmidazolium and CGS 9343 B), acting at the core of our model on the feedback of Ca2+ on Ins(1,4,5)P3-induced Ca2+ release, was not altered by the new modulators. In addition, all agonists and antagonists could be used interchangeably in combination and introduced no significant change in the oscillatory pattern or spike shape. Since the response was solely limited to frequency modulation, over- or understimulation of the oscillatory system, there is no need to create a new oscillator or to introduce further reaction steps into the core of the model. We conclude that the regulation of [Ca2+]cyt. via the explored second-messenger pathways can be embedded into the oscillatory system as modulation of rate constants already present in this model.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Expression of a gene encoding a rabbit sperm membrane protein in mammalian cells.

A general mammalian expression vector designated pSV2-EP was reconstructed by inserting an oligonucleotide fragment into pSV2-dhfr. This vector allowed insertion of cDNAs with EcoRI cohesive ends. The pSV2-EP contains a simian virus 40 (SV40) early promoter, origin for DNA replication, SV40 poly-A site, splicing site, an initiator ATG downstream from the promoter and an EcoRI site for the insertion of cDNA fragment screened from lambda gt11 expression libraries. A recombinant plasmid (pS-VRS-1) was constructed by inserting RSD-1, a cDNA encoding a rabbit sperm tail protein, into the EcoRI site of the pSV2-EP vector. Chinese hamster ovarian (CHO) dhfr-negative cells were cotransformed with pSV2-dhfr and pSVRS-1 by the calcium phosphate method. In selective culture medium without thymidine and hypoxanthine, several cell lines were obtained containing mRNA and DNA that hybridized with RSD-1. One of these transformed cell lines stained intensely with anti-rSMP-B antibodies, demonstrating that the RSD-1 was expressed in the transformed CHO cells.

Animals↗
PubMed1992

Increase in myofilament separation in the "stunned" myocardium.

This study explores the effects of ischemic reperfusion injury on the radial separation distance between thick and thin myofilaments. The left anterior descending coronary artery was occluded for 5 mins and reperfused for 10 mins twelve times repetitively in 6 dogs. At the end of a final 90 min reperfusion period, the hearts were fixed by perfusion with glutaraldehyde, and subepicardial and subendocardial tissue from both normal and ischemic areas were prepared for transmission electron microscopy. Quantitative analysis of inter-filament distance (IFD) was performed on micrographs of transverse sections. The center-to-center IFD was calculated from the numerical density of thick filaments at the A band level using a hexagonal array conversion formula. Sarcomere length was measured on micrographs of longitudinal sections. The results showed that center-to-center thick IFD in the stunned subendocardium was 43.9 +/- 0.8 nm which was significantly greater than the control distance of 40.6 +/- 0.4 nm (P less than 0.001) from normal zone tissue. Thick IFD in the subepicardium was also significantly different: 43.4 +/- 0.6 nm in the stunned tissue as compared with 39.0 +/- 0.7 nm in the non-ischemic tissue (P less than 0.001). Sarcomere length in the normally perfused subendocardium was 2.01 +/- 0.07 micron and was increased to 2.20 +/- 0.08 micron in the stunned subendocardium (P less than 0.005). Sarcomere length in the normal and the stunned subepicardium was also different: 2.02 +/- 0.04 vs. 2.10 +/- 0.09 micron (P less than 0.005). The significant increase in spatial separation between the contractile filaments may affect optimal cross-bridge force generation at the molecular level.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1992

Collagen loss in the stunned myocardium.

BACKGROUND: This study was performed to biochemically assess and quantify the previously observed ultrastructural alterations in the collagen matrix of stunned myocardium. METHODS AND RESULTS: The stunned myocardium was produced in 13 mongrel dogs by a series of 12 coronary artery occlusions of 5 minutes followed by 10-minute reperfusion periods, with a final reperfusion period of 90 minutes. Regional systolic function in the stunned myocardium was 17% of control. Relative end-diastolic length in the stunned region increased up to 8%. There was a nonuniform transmural loss of collagen. Hydroxyproline in the stunned endocardium was not different from control. The stunned midwall and epicardium demonstrated 12.5% (p less than 0.05) and 14.6% (p less than 0.005) decreases, respectively. All transmural layers in the stunned myocardium had significant increases in collagenase activity before procollagenase activation, averaging a 73.6% increase (p less than 0.025). Complete activation of all procollagenase forms with aminophenylmercuric acetate revealed no differences in fully activated collagenase between the stunned and normal regions. The lysosomal enzymes, elastase and cathepsin G, were not different between stunned and normal zone tissue. These results would tend to exclude exogenous sources of protease in the stunned myocardium at the 90-minute final reperfusion time frame. Collagen fibers were isolated from the stunned and normal zone tissue and underwent dansyl chloride reaction. Stunned collagen fibers had 9% greater dansyl labeling, suggesting greater numbers of exposed N-terminal amino acid residues on the fiber and compatible with greater enzymatic cleavage activity on the stunned collagen matrix. Tissue water content was consistently greater in the stunned region compared to the normal: a uniform transmural increase of approximately 1.7%. CONCLUSIONS: The stunned myocardium is characterized by both systolic dysfunction and diastolic expansion or dilatation. Endogenous procollagenase is activated by the ischemic process leading to degradation of the extracellular matrix. The underlying mechanisms may be relevant in ischemic enlargement of the heart and cardiomyopathy.

Animals↗
PubMed1992

[Detection of clonal immunoglobulin rearrangements in paraffin embedded tissues by PCR].

A polymerase chain reaction based method was established using immunoglobulin VH and VK gene rearrangements as markers to detect clonal B cell populations in paraffin embedded sections. Family specific VH and VK primers are used in separate reactions together with the corresponding J primers to amplify rearranged VH and VK genes from genomic DNA. This allows to distinguish clonal from polyclonal B cell populations in most of the cases. The method may be helpful in routine diagnosis of B cell NHL and some morphological and immunohistochemical difficult cases.

Base Sequence↗
PubMed1992

[Clinical analysis of Vogt-Koyanagi-Harada's disease and its association with HLA].

Clinical analysis of 34 patients with Vogt-Koyanagi-Harada's disease in Hunan Province showed that most patients had good visual prognosis following intensive corticosteroid therapy. A multivariate stepwise regression analysis indicated that visual acuity at the first visit, elapse of time before treatment began, duration of papilledema, and presence of ocular complications were significant factors for eventual visual acuity. HLA typing on 25 patients and 65 normal controls suggested that HLA-DR4 and DRW53 might be an immunogenetic background for the high incidence of the disease in oriental populations.

Adolescent↗
PubMed1991

The rat vitamin D binding protein (Gc-globulin) gene. Structural analysis, functional and evolutionary correlations.

The complete rat vitamin D binding protein (DBP) gene has been cloned and characterized. Genomic mapping suggests that there is only one copy of this gene in the haploid genome. The gene spans 35 kilobase pairs and contains 13 exons. All exons, exon/intron borders, and 2196 base pairs of 5'-flanking region have been sequenced. The transcription cap site, determined by primer extension analysis, is 62 base pairs upstream from the start of translation and predicts that an unusual TGTAAA motif may serve as a surrogate TATA. The promoter region contains about 50% nucleotide sequence similarity to the corresponding region of the partially characterized human DBP gene and is uniquely interrupted by a repetitive element. Although lacking in overall sequence similarity to the albumin (ALB) and alpha-fetoprotein (AFP) genes, the 5'-flanking region of the DBP gene contains a number of conserved segments which may correspond to critical proximal promoter elements in this gene family. The location of the introns in the coding region of the DBP gene is highly conserved when compared with the ALB and AFP genes. Detailed comparison of exon size and content confirms the previous prediction that the smaller size of the DBP protein results from loss of internal exons 12 and 13 from the DBP progenitor gene during its evolutionary divergence from ALB and AFP.

Amino Acid Sequence↗
PubMed1991

Association of HLA antigens with Vogt-Koyanagi-Harada syndrome in a Han Chinese population.

Vogt-Koyanagi-Harada syndrome, or the uveomeningitis syndrome, is one of the most commonly identified types of endogenous uveitis diagnosed in China. Because its incidence is higher in Orientals than in whites, immunogenetic background [corrected] may be an important factor in its incidence. We performed HLA-A, -B, and -DR typing on 25 patients with Vogt-Koyanagi-Harada syndrome and on 65 healthy control subjects from the Han Chinese population. The results showed that HLA-DR4 and -Dw53 were closely associated with Vogt-Koyanagi-Harada syndrome (P less than .001 [relative risk = 16.0] and P less than .001 [relative risk = 34.2], respectively). This association is similar to that reported in patients with Vogt-Koyanagi-Harada syndrome in Japan, suggesting that DR4 and DRw53 may play important roles in the development of Vogt-Koyanagi-Harada syndrome in Oriental populations.

Adolescent↗
PubMed1991

Isolation and characterization of insoluble collagen of dog hearts.

A procedure for isolating insoluble heart collagen has been developed. The method involves the use of defined optimal conditions of sonication that yield no thermal denaturation of the triple-helical structure nor disruption of the primary structure of the collagen molecules; this is followed by extraction of isolates with nondenaturing agents. The amino acid residues of the isolates are then reacted with dansyl chloride to allow determination of amino-terminal residues and quantification of the collagen. The method has several advantages over existing procedures: (i) There is no other method available for isolation of undenatured insoluble heart collagen in almost pure form (consists of 96% of type I collagen) and in a good yield. Sonication of tissue at or below 4 degrees C for a total of 120 s (15 s sonication repeated 8 times at 120-s intervals) yielded insoluble collagen fibers with 90% yield and a 20-fold purification as determined by the increase in Hyp content of the isolates. Extraction of these isolates with 0.6 M KCl and 1 M NaCl at 4 degrees C resulted in a 22-fold purification with 70% yield, while the classical extraction method with nondenaturing reagents yielded only 5-fold purification. (ii) There has been little study of the derivatization of an insoluble protein (collagen) with dansyl chloride. The Lys residues of collagen could be recovered as epsilon-Dns-Lys in 84% yield from a reverse-phase C-18 column by high-performance liquid chromatography. This assay allows measurement of 0.1-100 nmol epsilon-Dns-Lys. (iii) The method generates direct information concerning the quantity of collagen and its nature with respect to amino groups.

Animals↗
PubMed1991

[The serogroup and serotype distribution of Leptospira in Sichuan Province from 1958-1987].

This paper summarized the serogroup and serotype distribution of 7,560 strains Leptospira in Sichuan province from 1958 to 1987. At present, Leptospira 16 serogroup and 35 serotype have been found. The Icterohaemorrhagiae group Lai type is the major and stable serogroup and serotype in patients. We have proved that Rodents insectivores and domestic animals are the main reservoir host. The former carries Icterohaemorrhagiae group and the latter carries Pomona group. The serotype carried on the reservoir animal Apodemus agrarius is mostly Icterohaemorrhagiae Lai and is the principal infection source of Leptospirosis in Sichuan province. In addition, this paper discussed the reason of main serogroup change, the possible role of frog as an infection source of Hebdomadis Leptospirosis.

Animals↗
PubMed1991

[Effects of yin-tonics and yang-tonics on serum thyroid hormone levels and thyroid hormone receptors of hepatic cell nucleus in hyperthyroxinemic and hypothyroxinemic rats].

Hyperthyroxinemia model was made by giving thyroid tablet suspension to Wistar rats and hypothyroxinemia model was made by thyroidectomy. We measured serum thyroid hormone levels by RIA and the parameters of triiodothyronine receptors in rat hepatic cell nucleus by radio-ligand binding assay: Maximal binding capacity (Bmax) and Dissociation constant (Kd). It is found that (1) Yin-tonics can lower serum thyroid hormone levels and Bmax of hepatic nuclear T3R of hyperthyroxinemia rat from 167.14 +/- 25.62 fmol/100 micrograms DNA to 98.98 +/- 15.24 fmol/100 micrograms DNA, P less than 0.001. (2) Both Yang-tonics I and II can raise serum thyroid hormone levels of hypothyroxinemia rats, but not Bmax of hepatic nuclear T3R. Yang-tonics I even lowers Bmax. All the Chinese herbs have no effect on the Kd of rat hepatic nuclear T3R. The results may have some value in studying the effects of Chinese medical drugs.

Animals↗
PubMed1990

Peptidyl aminosteroids as potential new antiarrhythmic agents.

The synthesis of peptidyl derivatives of the aminosteroid, amafalone (Am), is described. Six analogs were synthesized: the hydrochloride salts of Gly-Am (2) Ala-Gly-Am (3), D-Ala-Gly-Am (4), Pro-Am (6), Pro-Pro-Am (7), and D-Ala-Pro-Am (8). The peptide bonds were formed by the polymeric reagent method using polymeric hydroxybenzotriazole as the activating polymer. Peptidyl aminosteroids 2, 6, 7, and 8, when administered to rats intravenously, had protective antiarrhythmic effects similar to those of amafalone. By the oral route, less marked protection, in comparison to amafalone, was observed with 6, while 7 and 8 were disappointingly inactive.

Administration, Oral↗