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Biomedical subjects

Z Yang

Publications and source records attributed to Z Yang.

At least 847 records · Page 47Linked to original sources
PubMed1993

Ascorbic acid enhances forskolin-induced cyclic AMP production and pro-ANF mRNA expression of hypothalamic neurons in culture.

Besides acting as an important cofactor in the biosynthesis of catecholamine, ascorbic acid (AA) also modulates the activity of peptidyl-glycine alpha-amidating monooxygenase for the post-translational modification of neuropeptides such as alpha-MSH and TRH. We report here a novel action of AA in modulating the secretion and mRNA expression of atrial natriuretic factor (ANF) in rat hypothalamic neurons. Primary cultures of hypothalamic neurons from neonatal rats as previously described were employed in the present studies. Six days after plating, cultures were replenished with serum free media and incubated with vehicle or various doses of AA, alone or in the presence of forskolin. Treatment with AA alone significantly increased irANF secretion from the cultures in a time-related and a dose-dependent manner with an ED50 of approximately 3 microM and an Emax of 100 microM. At the concentration of 10 microM, AA augmented irANF release approximately 3 fold that of the controls (55 +/- 7 pg/well; mean +/- SE, n = 3; P < 0.01), but it failed to affect the abundance of pro-ANF mRNA in the cultures. However, 10 microM of AA markedly enhanced forskolin-induced irANF secretion and pro-ANF mRNA abundance of the cultured cells. This potentiating effect of AA on forskolin stimulation showed a good parallelism to the levels of cAMP produced in the hypothalamic cultures. We thus conclude that AA acts alone or in synergism with forskolin to stimulate the secretion and production of ANF in rat hypothalamic neurons; this latter effect may operate at the genomic level and is mediated, at least in part, through the protein kinase A dependent pathway.

Animals↗
PubMed1993

In vitro evidence for atrial natriuretic factor-(5-28) production by macrophages of adult rat thymi.

Although recent evidence suggests the presence of the 15-kilodalton (K) mol wt (Mr) precursor of atrial natriuretic factor (ANF) and pro-ANF mRNA in the thymus of human and rat neonates, the cellular origin of the peptides in the tissues remains to be elucidated. We report here that in adult male rats, the 15K M(r) presumptive precursor for ANF and a smaller 3K M(r), N-terminal truncated congener of the peptide, ANF-(5-28), are localized in a small population of thymic macrophages. The production of ANF in the thymus was further confirmed by demonstrating the presence of a single band of pro-ANF mRNA signal of approximately 0.8 kilobases from the tissue extract, corresponding to that in the heart. To examine the distribution of pro-ANF mRNA at a cellular level, colorimetric in situ hybridization with digoxigenin-labeled 30-mer oligonucleotides complementary to the first 10-amino acid sequence of ANF-(1-28) was employed. Positive staining was found in thymic cells localized mainly in subcapsular areas, with diffuse staining of positive cells in both the cortex and medulla mainly concentrated around the cortico-medullary junction of the tissue. The identity of the ANF-positive cells was further investigated using a double staining technique to costain immunoreactive (ir) ANF and the macrophage markers ED1 and S22 or the T-cell marker OX-19 in both thymic sections and in monolayer cultures of thymic cells. In the latter, approximately 17% of the adherent cells stained positive for irANF after 48 h in culture. Of these cells, more than 95% also stained positive for the macrophage marker ED1, whereas approximately 36% of the ED1-positive cells were colocalized with irANF. In contrast, no irANF-positive cells were colocalised with the pan-T-cell marker OX-19. In tissue sections, irANF was found in cells distributed predominantly around the cortico-medullary junctions and subcapsular areas, with diffuse staining of the cells in the medullary and cortical regions. Sephadex G-50 gel chromatographic profiles of thymic extracts revealed a major peak of immunoreactivity consistent with 15K M(r) and a smaller peak that coeluted with rat ANF-(1-28) of 3K M(r). HPLC analysis of the 3K M(r) species showed a single peak of immunoreactivity, which eluted with a retention time identical to that of synthetic rat ANF-(5-28).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Coexpression of atrial natriuretic factor and beta-endorphin in a subpopulation of rat splenic macrophages: age-related differences.

Separate demonstration of immunoreactive (ir) atrial natriuretic factor (ANF) and ir-beta-endorphin (beta EP) in macrophages of the rat spleen prompted a reexamination of their distribution and cellular localization in addition to their developmental regulation. Double labeling immunohistochemistry was carried out on paraffin-embedded spleen sections of adult male Sprague-Dawley rats. Cells stained positive with antiserum (S118) raised against rat ANF-(99-126) were colocalized in more than 95% of cases with immunofluorescent staining of ir beta EP-(1-31) and distributed sparsely throughout the venous sinusoidal regions of the red pulp. In 1- or 5-day monolayer cultures of adherent splenocytes, 11-16% of the cells stained positive for either irANF or ir beta EP. Under these conditions, more than 95% of irANF- and ir beta EP-positive cells were also fluorescence stained for the histiocyte marker S22 or the rat macrophage marker ED-1. Colorimetric in situ hybridization similarly revealed signals for pro-ANF mRNA in more than 95% of ir beta EP-positive adherent cells. Thus, taken together with previous reports, our present findings suggest that in the rat spleen, both ANF and beta EP are produced by the same population of macrophages. However, the tissue levels and processing of the two peptides over the developmental period of the animal differed markedly in several ways. In splenic extracts of 2-day-old neonatal rats, Northern blot analysis and RIA revealed a greater abundance of pro-ANF mRNA signal and an irANF concentration about 6-fold greater than those in 30-day-old animals. In contrast, the ir beta EP concentration did not vary significantly over the same period, consistent with the level of POMC mRNA. Sephadex G-50 gel chromatography of splenic extracts from 2-day-old animals revealed predominantly higher mol wt forms of irANF and ir beta EP. From days 16-60, a significant proportion of irANF eluted in the same fractions as the mature circulating form, rat ANF-(99-126); the proportion of 3.5-kilodalton ir beta EP increased progressively to become the predominant species in adult tissues. Thus, it appears that although ANF and beta EP are coexpressed by the same population of splenic macrophages, they differ markedly during the developmental period with respect to their constitutive regulation.

Aging↗
PubMed1993

Calcium antagonists and ACE inhibitors. Effect on endothelium and vascular smooth muscle.

The effects of cardiovascular drugs on endothelium and vascular smooth muscle function are important for the prevention of cardiovascular disease. Changes in endothelial function are an early event in most forms of cardiovascular disease and, later in the disease process, vascular smooth muscle cells are functionally altered and begin to migrate to and proliferate in the intima. Calcium antagonists and angiotensin converting enzyme (ACE) inhibitors are widely used in patients with cardiovascular disease and are thought to have vascular protective effects. ACE, an enzyme located in the endothelial cell membrane, activates angiotensin I and angiotensin II, and deactivates bradykinin. Bradykinin activates endothelial bradykinin (B2) receptors, which results in the formation of nitric oxide and prostacyclin. Hence, ACE inhibitors not only prevent the formation of angiotensin II, but also increase the local levels of bradykinin and in turn nitric oxide and prostacyclin. These compounds are vasodilators and potent inhibitors of platelet function, and therefore may mediate important protective effects of ACE inhibitors. Furthermore, nitric oxide may have antiproliferative effects in vascular smooth muscle cells. Calcium antagonists do not appear to affect the release of endothelium-derived relaxing factors or any other endothelial product. However, they facilitate endothelium-dependent relaxation and reduce the contracting effects of endothelin-1 at the level of smooth muscle. Indeed, in some blood vessels, e.g. the large coronary arteries and the human forearm circulation, verapamil and nifedipine antagonise endothelin-induced contractions. In addition, calcium antagonists inhibit the effects of platelet-derived growth factor and may have antiproliferative effects in vascular smooth muscle cells. In conditions involving progressive dysfunction of the endothelium, vascular deposition of platelets increases the local levels of platelet-derived growth factor, and the antiproliferative effects of calcium antagonists may thus be particularly important.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

[The experimental study of the double intra aortic balloon (DIAB) pumping].

In vitro and animal experiments showed that the double intra aortic balloon (DIAB) pumping can provide 30% greater blood flow to the coronary arteries than does a single intra aortic balloon (SIAB) pumping of the same volume during counterpulsation. It significantly improves the hemodynamic parameters so as to raise the efficiency of the counterpulsation. The results are consistent with computer studies.

Animals↗
PubMed1993

[Serotyping of patients with epidemic hemorrhagic fever (EHF) and serotyping and antigen typing of main hosts of EHF in Shandong province].

Serotyping with hemagglutination-inhibition test (HI) on 458 patients with EHF showed that 419 (91.48%) of them belonged to the house-rat type, 33 (7.21%) belonged to the wild-rat type, and 6 (1.31%) were undetermined. The majority (80-100%) of the patients in various regions belonged to the house-rat type. The type of the virus antigen and the type of the antibody of rats were in conformity with the species of rats. These indicate that the epidemic areas of EHF in Shandong Province are mixed-type epidemic areas, predominantly the house-rat type.

Adolescent↗
PubMed1993

[Study of teratogenicity and sensitive period of vanadium pentoxide in Wistar rats].

Pregnant Wistar rats were administered with vanadium pentoxide (V2O5) in three different ways single intraperitoneal injection (ip) of V2O5 5mg/kg on days 9, 10, and 11 of gestation; ip 5mg/kg/day on days 9-12 of gestation; and ip 3mg/kg/day on days 6-15 of gestation. The results showed that the female rats had such toxic symptoms as decreased weight gain, increase fetal mortality, decreased fetal weight and crown-rump, retarded ossification of the bone, increased incidence of subcutaneous hemorrhage, rib wavy, dilation of lateral ventricles and renal pelvis in the two groups, i.e., on days 6-15, and 9-12 of gestation, Decreased weight gain, increased incidence of subcutaneous hemorrhage and visceral anomalies were found on day 11 of gestation group. Increased incidence of fetal death, retarded ossification of the bone on day 10 of gestation group; and increased incidence of subcutaneous hemorrhage and visceral anomalies on days 9, and 10 of gestation were observed. These data suggest that V2O5 can induce teratogenicity in Wistar rat with or without obvious maternal toxicity. There was no obvious teratogenic sensitive period of V2O5 on embryo, but as for single treatment, it was more sensitive on gestation day 10 than on gestational day 11 or 9; as for multi-treatment, it was more sensitive on days 9-12 than on days 6-15 of gestation for teratogenicity and fetal death. It is suggested that V2O5 may act mainly on the middle or late stage of organogenetic period.

Abnormalities, Drug-Induced↗
PubMed1993

[The isolation and identification of a Clostridium botulinum serotype A strain].

319 soil specimens were collected from different places of China for isolating Clostridium botulinum. A strain of Clostridium botulinum was isolated from a culture of soil specimens in Ruoergai of Sichuan Province, the strain was called As-3. The As-3 was identified as Clostridium botulinum serotype A according to its biological properties, biochemical serological and toxicological characteristics and DNA determination. Its DNA G + C mol is 24.9%. The toxin produced by As-3 strain can only be neutralized by type A antiserum.

Animals↗
PubMed1993

The effect of laminin on molecular motion in the cell membrane and on cell motility.

We have studied the variation of lateral diffusion of proteins in the cell membrane, of membrane lipid fluidity and of the electrophoretic motility (EPM) of macrophages after treatment with extrinsic laminin. The results showed that the lateral diffusion coefficient D value of membrane proteins, the fluidity of membrane lipids and the EPM of macrophages were decreased after laminin had bound to its membrane receptor on the macrophages. These results are important for developing an understanding of the early reaction of plasma membranes and cells in the presence of laminin.

Animals↗
PubMed1993

Basic cellular mechanisms of coronary bypass graft disease.

The internal mammary artery (IMA) grafts have a higher patency than the saphenous vein (SV) grafts. The biological properties of the arterial and venous grafts (i.e. endothelial and smooth muscle cell function) are crucial determinants of graft function. The endothelial cells in arterial grafts release larger amounts of endothelium-derived nitric oxide formed from the precursor amino acid L-arginine in response to several vasoactive hormones than do venous grafts. In IMA, platelet-derived adenosine nucleotides activate the endothelium to release nitric oxide, thereby causing vascular relaxation, while in the saphenous vein this important protective mechanism is absent. Therefore, platelet-derived thromboxane A2 and serotonin evoke marked vasoconstriction in the saphenous vein in spite of an intact endothelium. Smooth muscle cell growth plays a significant part in intimal thickening and vascular occlusion of bypass grafts, in particular, SV grafts. Mechanical forces such as pulsatile stretch and platelet-derived growth factor are potent mitogens for SV but not IMA smooth muscle proliferation. Hence, the different endothelial and smooth muscle cell function of IMA and SV may contribute considerably to the different graft functions in patients with coronary artery disease.

Cell Division↗
PubMed1993

[A study on developmental toxicity of vanadium pentoxide in Wistar rats].

Timed-pregnant Wistar rats were injected intraperitoneally with V2O5 at 0.33, 1.0 and 3.0 mg/kg/day on days 6-15 of gestation. Maternal toxic symptoms, decreased of weight gain during treatment and placenta weight, increased incidence of embryo-fetus mortality and external or skeletal malformation and fetal growth retardation were observed in the 3.0 mg/kg group. Increased incidence of embryo-fetus mortality and external or skeletal malformation, delayed ossification of bone and decreased placenta weight were observed in the 1.0 mg/kg group. These results indicate that V2O5 is a developmental toxicant with or without obvious maternal toxicity in Wistar rats. Although vanadium can be accumulated in placenta, it could passed through placenta. In this study, vanadium could induce a decrease of placenta weight without obvious maternal toxicity, and an A/D ratio of 3 was noted. These results suggest that vanadium may exert a direct effect on embryo-fetues or a "double effect" on the placenta function and embryo-fetus both. It has been reported that vanadium does not increase mal formation in NIN, Kunming, Swiss, NMRI mice or Syrian golden hamster. The dose for inducing developmental toxicity of vanadium in mice is higher than that in rats. This suggests that rats be more sensitive than mice to the developmental toxicity of vanadium.

Abnormalities, Drug-Induced↗
PubMed1993

An epidemiological survey of deformities and disabilities among 14,257 cases of leprosy in 11 counties.

This study was planned and conducted in Yang Zhou Prefecture, covering 11 counties that were formerly areas with a high prevalence of leprosy. Out of 14,257 leprosy patients, 8122 (56.97%) cases with deformities and disabilities were found. The disability rate is much higher in patients with MB leprosy (81.15%) than in PB leprosy (53.04%). The statistical data and the type of deformities and disabilities are presented. The influences of various host factors and disease factor which cause disability and deformity are discussed.

Adolescent↗
PubMed1993

[Liver microcirculative disturbance in schistosomiasis portal hypertension].

Using reing resin vascular casts, ink perfusion, VG and electron microscope. We studied the liver microcirculative disturbance in rabbits (n = 20) and mice (n = 10) with chronic schistosomiasis. The results showed a decrease in the liver sinusoid number, tortuosity of the terminal branches of the portal vein, formation of a basement membrane in the space of Disse, capillarization of the sinusoid. These results suggest that liver microcirculative disturbance can contribute to schistosomiasis portal hypertension.

Animals↗
PubMed1992

Molecular cloning and functional expression of cDNA encoding a mammalian inorganic pyrophosphatase.

Extracts of soluble proteins from bovine retina contain multiple species of inorganic pyrophosphatase (PPase) that can be resolved by hydroxylapatite or ion exchange chromatography. We have purified one of these isoforms by a combination of chromatography and electrophoresis under denaturing conditions and have partially sequenced four peptides generated from it by CNBr digestion. This sequence information was used to clone PPase cDNA from a retinal cDNA library. Of five cDNA inserts, three were 1.3 kilobase pairs in length and two of these contained a complete open reading frame that was 867 base pairs long and encoded a 289-amino acid protein of 33 kDa. The deduced amino acid sequence is 49.5% identical to that of PPase from Saccharomyces cerevisiae, and contains identical amino acid residues at all of the positions previously identified as essential for catalytic activity in that enzyme. When the bovine PPase cDNA was expressed in Escherichia coli, catalytically active PPase was produced that comigrated with bovine retinal PPase in a nondenaturing gel and was clearly distinguishable from the host PPase. Northern analysis of poly(A)+ RNA from human, canine, and bovine retinas revealed that each contained a single major band of 1.4 kilobases that hybridized strongly with a pyrophosphatase cDNA probe. Southern analysis of bovine genomic DNA was consistent with the existence of one PPase gene. Thus, the multiple forms separated by chromatography may be derived from a common precursor or from mRNAs of very similar size.

Amino Acid Sequence↗
PubMed1992

Inorganic pyrophosphatase from bovine retinal rod outer segments.

Rod outer segments from bovine retina contain a higher level of intracellular inorganic pyrophosphatase (EC 3.6.1.1) activity than has been found in any other mammalian tissue; the specific activity in extracts of soluble outer segment proteins is more than 6-fold higher than in extracts from bovine liver and more than 24-fold higher than in skeletal muscle extracts. This high activity may be necessary to keep inorganic pyrophosphate concentrations low in the face of the high rates of pyrophosphate production that accompany the cGMP flux driving phototransduction. We have begun to explore the role of inorganic pyrophosphatase in photoreceptor cGMP metabolism by 1) studying the kinetic properties of this enzyme and its interactions with divalent metal ions and anionic inhibitors, 2) purifying it and studying its size and subunit composition, and 3) examining the effects of pyrophosphate on rod outer segment guanylyl cyclase. Km for magnesium pyrophosphate was 0.9-1.5 microM, and the purified enzyme hydrolyzed > 885 mumol of PPi min-1 mg-1. The enzyme appears to be a homodimer of 36-kilodalton subunits when analyzed by gel electrophoresis and density gradient centrifugation, implying that kcat = 10(3) s-1, and kcat/Km = 0.7-1 x 10(9) M-1 s-1. The enzyme was inhibited by Ca2+ at submicromolar levels: 28% inhibition was observed at 138 nM [Ca2+], and 53% inhibition at 700 nM [Ca2+]. Imidodiphosphate acted as a competitive inhibitor, with Ki = 1.2 microM, and fluoride inhibited half-maximally approximately 20 microM. Inhibition studies on rod outer segment guanylyl cyclase confirmed previous reports that pyrophosphate inhibits guanylyl cyclase, suggesting an essential role for inorganic pyrophosphatase in maintaining cGMP metabolism.

Animals↗
PubMed1992

N-myristoylation of the rod outer segment G protein, transducin, in cultured retinas.

Bovine retinas incubated with [3H]myristic acid incorporated detectable radiolabel into only a few proteins. The most heavily labeled was the alpha subunit of the rod outer segment G protein transducin (Gt alpha). The radiolabeled protein was specifically eluted from illuminated membranes in the presence of GTP, displaying the unique solubility properties of Gt alpha. It comigrated with Gt alpha in electrophoresis and chromatography and was immunoprecipitated by Gt alpha-specific antibodies. The radiolabel was confirmed by hydrolysis, chemical derivatization, and chromatography to be amide-linked myristic acid. The solubility of the myristoylated Gt alpha indicates that myristoylation is not sufficient to cause tight membrane association of this normally membrane-bound subunit. Incorporation of [3H]myristate was blocked by the protein synthesis inhibitor cycloheximide, suggesting that that fatty acid group is introduced during or soon after translation in the rod inner segment.

Animals↗
PubMed1992

Implications of pulsatile stretch on growth of saphenous vein and mammary artery smooth muscle.

Internal mammary artery (IMA) coronary bypass grafts have a higher patency than saphenous vein (SV) grafts. Intimal hyperplasia and occlusion of venous grafts result from smooth muscle proliferation. Mechanical factors, such as pulsatile stretch, are potential mediators of this process. Smooth muscle cells from IMA and SV were cultured on deformable membranes and exposed to pulsatile stretch (60 cycles/min). This stimulus increased 3H-thymidine incorporation into venous (a two-fold increase) but not arterial smooth muscle cells after 24 h. Smooth muscle cell numbers from SV, but not IMA, were increased (p less than 0.05) after 6 days of stretch. Thus, pulsatile stretch stimulates smooth muscle cell proliferation in SV, but not IMA, and may contribute to venous bypass graft disease.

Cell Division↗