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M Gao

Publications and source records attributed to M Gao.

At least 109 records · Page 6Linked to original sources
PubMed1998

Ethylene-mediated phenotypic plasticity in root nodule development on Sesbania rostrata.

Leguminous plants in symbiosis with rhizobia form either indeterminate nodules with a persistent meristem or determinate nodules with a transient meristematic region. Sesbania rostrata was thought to possess determinate stem and root nodules. However, the nature of nodule development is hybrid, and the early stages resemble those of indeterminate nodules. Here we show that, depending on the environmental conditions, mature root nodules can be of the indeterminate type. In situ hybridizations with molecular markers for plant cell division, as well as the patterns of bacterial nod and nif gene expression, confirmed the indeterminate nature of 30-day-old functional root nodules. Experimental data provide evidence that the switch in nodule type is mediated by the plant hormone ethylene.

Journal Article↗
PubMed1998

Functional conservations of the alkaline nuclease of herpes simplex type 1 and human cytomegalovirus.

The herpes simplex virus type 1 UL12 gene product, alkaline nuclease (AN), appears to be involved in viral DNA processing and capsid egress from the nucleus (Shao, L., Rapp, L. M., and Weller, S. K., Virology 196, 146-162, 1993). Although the HSV-1 AN is not absolutely essential for viral replication in tissue culture, conservation of the AN gene in all herpesviruses suggests an important role in the life cycle of herpesviruses. The counterpart of HSV-1 AN for human cytomegalovirus (HCMV) is the UL98 gene product. To examine whether the HCMV AN could substitute for HSV-1 AN, we performed trans-complementation experiments using a HSV-1 amplicon plasmid carrying the HCMV UL98 gene. Our results indicate (i) HCMV AN can complement the growth of the HSV-1 AN deletion mutant UL12lacZ virus in trans; (ii) a new recombinant virus, UL12laZcUL98/99, appears to be generated by the integration of the HCMV UL98 gene into the HSV-1 UL12lacZ viral genome; (iii) in contrast to its parental HSV-1 UL12lacZ virus, capsids formed in UL12lacZUL98/99-infected Vero cells were able to transport from the nucleus to the cytoplasm and mature into infectious viruses. Our results demonstrate a functional conservation of AN between HSV-1 and HCMV.

Animals↗
PubMed1998

Genomic organization and promoter activity of the maize starch branching enzyme I gene.

Starch branching enzymes (SBE) which catalyse the formation of alpha-1,6-glucan linkages are of crucial importance for the quantity and quality of starch synthesized in plants. In maize (Zea mays L.), three SBE isoforms (SBEI, IIa and IIb) have been identified and shown to exhibit differential expression patterns. As a first step toward understanding the regulatory mechanisms controlling their expression, we isolated and sequenced a maize genomic DNA (-2190 to +5929) which contains the entire coding region of SBEI (Sbe1) as well as 5'-and 3'-flanking sequences. Using this clone, we established a complete genomic organization of the maize Sbe1 gene. The transcribed region consists of 14 exons and 13 introns, distributed over 5.7kb. A consensus TATA-box and a G-box containing a perfect palindromic sequence, CCACGTGG, were found in the 5'-flanking region. Genomic Southern blot analysis indicated that two Sbe1 genes with divergent 5'-flanking sequences exist in the maize genome, suggesting the possibility that they are differentially regulated. A chimeric construct containing the 5'-flanking region of Sbe1 (-2190 to +27) fused to the beta-glucuronidase gene (pKG101) showed promoter activity after it was introduced into maize endosperm suspension cells by particle bombardment. 1998 Elsevier Science B.V.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1998

Multidrug resistance protein. Identification of regions required for active transport of leukotriene C4.

Multidrug resistance protein (MRP) is a broad specificity, primary active transporter of organic anion conjugates that confers a multidrug resistance phenotype when transfected into drug-sensitive cells. The protein was the first example of a subgroup of the ATP-binding cassette superfamily whose members have three membrane-spanning domains (MSDs) and two nucleotide binding domains. The role(s) of the third MSD of MRP and its related transporters is not known. To begin to address this question, we examined the ability of various MRP fragments, expressed individually and in combination, to transport the MRP substrate, leukotriene C4 (LTC4). We found that elimination of the entire NH2-terminal MSD or just the first putative transmembrane helix, or substitution of the MSD with the comparable region of the functionally and structurally related transporter, the canalicular multispecific organic anion transporter (cMOAT/MRP2), had little effect on protein accumulation in the membrane. However, all three modifications decreased LTC4 transport activity by at least 90%. Transport activity could be reconstituted by co-expression of the NH2-terminal MSD with a fragment corresponding to the remainder of the MRP molecule, but this required both the region encoding the transmembrane helices of the NH2-terminal MSD and the cytoplasmic region linking it to the next MSD. In contrast, a major part of the cytoplasmic region linking the NH2-proximal nucleotide binding domain of the protein to the COOH-proximal MSD was not required for active transport of LTC4.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Cloning and characterization of human eIF4E genes.

Two human eukaryotic initiation factor 4E (eIF4E) genes were isolated and characterized from placental and chromosome 4-specific genomic libraries. One of the genes (EIF4E1) contained six introns, but the other gene (EIF4E2) was intronless, flanked by Alu sequences and 14-base pair (bp) direct repeats, and terminated by a short poly(A) stretch, all characteristics of retrotransposons. Numerous additional intronless eIF4E pseudogenes were found, but unlike EIF4E2, all contained premature in-frame stop codons. The entire EIF4E1 gene spanned >50 kilobase pairs. The coding regions of these two genes differed in four nucleotide residues, resulting in two amino acid differences in the predicted proteins. The promoter of EIF4E1 has been characterized previously. The putative promoter of EIF4E2 contained no TATA box but did contain a transcription initiator region (Inr) and numerous other sequence motifs characteristic of regulated promoters. EIF4E2 contained only two of the three polyadenylation signals present in EIF4E1. Evidence for transcription of both genes was obtained from primer extension, S1 mapping, ribonuclease protection, and reverse transcriptase-polymerase chain reaction experiments. Transcription was found to initiate 19 bp upstream of the translational initiation codon in the case of EIF4E1 and 80 bp in the case of EIF4E2. The two genes were differentially expressed in four human cell lines, Wish, Chang, K562, and HeLa.

Base Sequence↗
PubMed1998

Increased expression of adenylylcyclase type VI proportionately increases beta-adrenergic receptor-stimulated production of cAMP in neonatal rat cardiac myocytes.

Cellular content of cAMP generated by activation of adenylylcyclase (AC; EC 4.6.1.1) is a key determinant of functional responsiveness in the heart and other tissues. We have tested two hypotheses regarding the relationship between AC content and beta-adrenergic receptor (betaAR)-mediated signal transduction in cardiac myocytes. First, that AC content limits adrenergic signal transduction, and, second, that increased AC, independent of (betaAR) number and G-protein content, yields a proportional increase in betaAR-mediated transmembrane signaling. We used recombinant adenovirus to increase AC isoform VI (ACVI) expression in neonatal cardiac myocytes. Cells that overexpressed ACVI responded to agonist stimulation with marked increases in cAMP production in proportion to protein expressed. In parallel experiments performed on cells transfected with lacZ (control) or ACVI, [3H]forskolin binding, used to assess AC protein expression, was amplified 6-fold, while betaAR-stimulated cAMP production from these cells was increased 7-fold. No changes in betaAR number, or in the heterotrimeric GTP-binding proteins, Galphas or Galphai2, were observed. Previous studies indicate that increased cardiac expression of betaAR or Galphas does not yield proportional increases in transmembrane adrenergic signaling. In contrast, the current data demonstrate that increased ACVI expression provides a proportional increase in beta-adrenergic signal transduction. Our results show that the amount of AC sets a limit on transmembrane beta-adrenergic signaling. We speculate that similar functional responses are possible in other cell types in which AC plays an important physiological role.

Adenylyl Cyclases↗
PubMed1998

Molecular cloning and characterization of the Amylose-Extender gene encoding starch branching enzyme IIB in maize.

The amylose-extender (Ae) gene encoding starch-branching enzyme IIb (SBEIIb) in maize is predominantly expressed in endosperm and embryos during kernel development. A maize genomic DNA fragment (-2964 to +20,485) containing the Ae gene was isolated and sequenced. The maize Ae mRNA is derived from 22 exons distributed over 16,914 bp. Twenty-one introns, differing in length from 76 bp to 4020 bp, all have conserved junction sequences (GT..AG). Sequence analysis of the 5'- and 3'-flanking regions revealed a consensus TATA-box sequence located 28 bp upstream of the transcription initiation site as determined by primer extension analysis, and a putative polyadenylation signal observed 29 bp upstream of the polyadenylation site based on cDNA sequence. Genomic Southern blot analysis suggests that a single Ae gene is present in the maize genome. Promoter activity was confirmed by testing a transcriptional fusion of the Ae 5'-flanking region between -2964 and +100 to a luciferase reporter gene in a transient expression assay using maize endosperm suspension cultured cells. 5' deletion analysis revealed that the 111 bp region from -160 to -50 is essential for high-level promoter activity.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1998

Epitope mapping of monoclonal antibodies specific for the 190-kDa multidrug resistance protein (MRP).

Inherent or acquired resistance to multiple natural product drugs in human tumour cells is often associated with increased expression of multidrug resistance protein (MRP), a 190-kDa integral membrane protein that belongs to the ATP-binding cassette (ABC) superfamily of transport proteins. Both clinical and experimental investigations of MRP have been facilitated by several monoclonal antibodies (MAbs) generated against intracellular epitopes of the molecule. Recently, however, several new ABC transporters that are quite closely related to MRP have been identified, raising concerns about the specificity of the MRP-reactive MAbs. In the present study, we have mapped the epitopes of MAbs MRPr1 and MRPm6 to the decapeptides 238GSDLWSLNKE247 (located in the intracellular loop between the first and second membrane-spanning domains of MRP) and 1511PSDLLQQRGL1520 (located near the carboxy terminus of MRP) respectively. Alignment of the MRPr1 and MRPm6 epitope sequences with the comparable regions in mammalian ABC proteins most closely related to MRP indicates that, with the exception of murine mrp, the sequences are poorly conserved. We conclude that MAbs MRPm6 and MRPr1, together with MAb QCRL-1, which has previously been mapped to the heptapeptide 918SSYSGDI924, remain highly specific probes for detection of different regions of the MRP molecule.

ATP-Binding Cassette Transporters↗
PubMed1998

OA1 mutations and deletions in X-linked ocular albinism.

X-linked ocular albinism (OA1), Nettleship-Falls type, is characterized by decreased ocular pigmentation, foveal hypoplasia, nystagmus, photodysphoria, and reduced visual acuity. Affected males usually demonstrate melanin macroglobules on skin biopsy. We now report results of deletion and mutation screening of the full-length OA1 gene in 29 unrelated North American and Australian X-linked ocular albinism (OA) probands, including five with additional, nonocular phenotypic abnormalities (Schnur et al. 1994). We detected 13 intragenic gene deletions, including 3 of exon 1, 2 of exon 2, 2 of exon 4, and 6 others, which span exons 2-8. Eight new missense mutations were identified, which cluster within exons 1, 2, 3, and 6 in conserved and/or putative transmembrane domains of the protein. There was also a splice acceptor-site mutation, a nonsense mutation, a single base deletion, and a previously reported 17-bp exon 1 deletion. All patients with nonocular phenotypic abnormalities had detectable mutations. In summary, 26 (approximately 90%) of 29 probands had detectable alterations of OA1, thus confirming that OA1 is the major locus for X-linked OA.

Albinism, Ocular↗
PubMed1998

Characterization of dull1, a maize gene coding for a novel starch synthase.

The maize dull1 (du1) gene is a determinant of the structure of endosperm starch, and du1- mutations affect the activity of two enzymes involved in starch biosynthesis, starch synthase II (SSII) and starch branching enzyme IIa (SBEIIa). Six novel du1- mutations generated in Mutator-active plants were identified. A portion of the du1 locus was cloned by transposon tagging, and a nearly full-length Du1 cDNA sequence was determined. Du1 codes for a predicted 1674-residue protein, comprising one portion that is similar to SSIII of potato, as well as a large unique region. Du1 transcripts are present in the endosperm during the time of starch biosynthesis, but the mRNA was undetectable in leaf or root tissue. The predicted size of the Du1 gene product and its expression pattern are consistent with those of maize SSII. The Du1 gene product contains two repeated regions in its unique N terminus. One of these contains a sequence identical to a conserved segment of SBEs. We conclude that Du1 codes for a starch synthase, most likely SSII, and that secondary effects of du1- mutations, such as reduction of SBEIIa, result from the primary deficiency in this starch synthase.

Amino Acid Sequence↗
PubMed1998

Dissociation between regional dysfunction and beta-adrenergic receptor signaling in heart failure.

We have previously shown that left ventricular (LV) pacing-induced heart failure is associated with preserved wall thickening in the interventricular septum (IVS) compared with the posterolateral wall (PLW). The current study focuses on the relationship between regional myocardial function and altered beta-adrenergic receptor (beta-AR) signaling. We studied 15 pigs: 6 controls and 9 paced from the left ventricle (225 beats/min, 26 +/- 3 days). Heart failure was documented by decreased LV fractional shortening (P < 0.0001) and increased left atrial pressure (P < 0.0001). In heart failure, despite marked differences in basal regional function (percent wall thickening: IVS, 33 +/- 10% vs. PLW, 13 +/- 7%; P = 0.0003), there were no differences between the two regions in beta-AR responsiveness, measured by regional wall thickening in response to dobutamine infusion and any measurement of adrenergic signaling. Adenylyl cyclase activity, beta-AR number, and beta-AR/Gs coupling were markedly reduced in failing LV without regional differences. In animals with heart failure, LV G protein receptor kinase (GRK) isoform 2 content was unchanged and GRK5, the other major GRK isoform, was increased more than threefold (IVS, 0.51 +/- 0.20 vs. 0. 12 +/- 0.12 arbitrary densitometric units, P = 0.01; PLW, 0.47 +/- 0. 15 vs. 0.13 +/- 0.09 arbitrary densitometric units, P = 0.03), but again, there were no regional differences. These data indicate that systemic rather than regional factors govern LV adrenergic signaling and that regional adrenergic signaling abnormalities poorly predict wall thickening in the same regions.

Adenylyl Cyclases↗
PubMed1998

Difference in susceptibility to CC-chemokines among HIV-1 isolates.

In this study, we examined the difference in susceptibility to anti-HIV activity of the CC-chemokines (RANTES, MIP-1 alpha and MIP-1 beta) among HIV-1 isolates and analysed its relation with phenotype (syncytium inducibility) and V3 domain of gp120 of the HIV-1 isolates. Of 11 cases tested in endogenous assay, at a concentration of 200 ng/ml, RANTES, MIP-1 alpha, and MIP-1 beta showed more than 80% suppression of HIV-1 replication in 10, 8, and 7 cases, respectively. HIV-1 isolates sensitive to more than one CC-chemokine showed non-syncytium-inducing phenotype, whereas HIV-1 isolates resistant to all of the 3 CC-chemokines showed syncytium-inducing phenotype. HIV-1 isolates resistant to all of the 3 CC-chemokines contained more positively charged amino acid residues in the V3 domain of the gp120. These results indicated that utilization of the CC-chemokine receptors as co-receptors for virus entry could vary among HIV-1 isolates.

CD4-Positive T-Lymphocytes↗
PubMed1998

Rearrangement of the ventricular capillary network in stroke-prone spontaneously hypertensive rats (SHRSP) following a late start of treatment with the angiotensin converting enzyme blocker temocapril.

The effects of the angiotensin converting enzyme (ACE) blocker temocapril on the capillary network of the left ventricle were studied in stroke-prone spontaneously hypertensive rats (SHRSP). The ACE blocker was dissolved in the drinking water and supplied to 24 and 32 week old SHRSP ad libitum for 5 weeks. The capillaries of the wall of the left ventricle were studied using a double staining method to differentiate the arteriolar, intermediate and venular capillary portions. Capillary density increased and capillary domain areas decreased in all capillary portions compared with untreated control SHRSP in both age groups. The proportion of venular capillary portions was increased by temocapril treatment. The results indicate that the late start of ACE blockade caused the regression of the hypertrophied cardiomyocytes, which is characteristic of SHRSP, and the rearrangement of capillary portions. The plasma concentration of angiotensin II was significantly lower in temocapril-treated SHRSP compared to the control group. The implication is that intrinsic angiotensin II exerts an appreciable effect on the function, structure and capillary network in the left ventricular wall in SHRSP.

Angiotensin II↗
PubMed1998

Adaptive changes in the capillary network in the left ventricle of rat heart.

Capillaries are nonuniform thin tubes: The arteriolar and venular capillary portions express alkaline phosphatase (AP) and dipeptidyl peptidase IV (DPPIV), respectively. Differences in enzyme activities between arteriolar and venular capillary portions could be shown by staining sections of cardiac tissues for AP and DPPIV after coronary infusion of microspheres and by staining cultured endothelial cells that had been collected from coronary microvessels. Through use of a double staining method for AP and DPPIV, adaptive changes in the capillary network were studied in rat hearts exposed to cold, exercise, hypertension, chronic coronary occlusion, and transient coronary occlusion followed by reperfusion. Two patterns could be seen in the adaptations of the ventricular capillary network. The increase in the venular capillary portions is accompanied by remarkable increases in capillary density and capillary-to-myocyte ratio. The increase in the arteriolar capillary portion seemed to be accompanied by a decrease or only a limited increase in capillary density in stressed hearts. The increase in the total capillary density improves the capacity for oxygen transport to tissues with a high tissue perfusion and a short diffusion distance for oxygen. The increase in the arteriolar capillaries may also improve oxygen transport by increasing the arterial blood perfusing the tissue. This seems, however, a compensation for the limited angiogenesis: The alleviation of stresses, such as pharmacological treatment of the hypertrophied heart and reperfusion after transient ischemia, increases venular capillary portions and capillary density. These changes are discussed with immunohistochemical observations of rapid and prolonged expressions of angiogenic growth factors.

Adaptation, Physiological↗
PubMed1998

[Comparative study of left ventricular morphology and function of patients with left ventricular systolic and diastolic heart failure on echocardiography].

Left ventricular pathology and pathophysiological characteristics of fifty patients with left ventricular diastolic heart failure (LVDHF), and 35 patients with left ventricular systolic heart failure (LVSHF) diagnosed by clinical manifestations and radionuclide ventriculography, were examined by echocardiography and 20 healthy persons were served as control group. Left atrial diameter (LAD), interventricular septum thickness (IVST) and posterior wall thickness (PWT) and left ventricular mass index (LVMI) were significantly increased in the patients with LVDHF, while left ventricular diameter (LVD) was significantly increased in the patients with LVSHF. Left ventricular ejection fraction (LVEF), cardiac index (CI) were significantly decreased in the patients with LVSHF. Early peak filling velocity (EPFV), atiral peak filling velocity (APFV), deceleration of early peak filling velocity (DC) and isovolumic relaxation time (IRT) in the patients with LVDHF and LVSHF observed no significant difference.

Adult↗
PubMed1998

[Observation of enalapril on treating the patients with left ventricular diastolic dysfunction].

The effects of enalapril on 50 patients with left ventricular diastolic dysfunction (LVDD), confirmed by clinical features and radionuclid ventriculography, were assessed in a randomized, double-blind, and controlled method for eight weeks. The results showed that left atrial diameters (LAD), interventricular septum thicknesses (IVST) and left ventricular mass indexes (LV-MI) except left ventricular diameters (LVD) were decreased in the enalapril treatment group. The left ventricular diastolic function parameters such as the early peak filling velocity (EPAV), the atrial peak filling velocity (APAV), the deceleration of early peak filling velocity (DC) and the isovolumic relaxation time (IRT) were improved, the NYHA class and the exercise tolerance were increased, the left ventricular ejection fraction (LVEF), and the cardiac index (CI) were not altered in the enalapril treatment group. The patients with LVDD were well tolerated with enalapril. The parameters mentioned above were not altered in control group. It is suggested that enalapril is an effective drug in the treatment of LVDD.

Adult↗
PubMed1998

[Study on changes of plasma substance P in essential hypertension with left ventricular hypertrophy patients and the effect of promoting blood circulation and eliminating phlegm].

OBJECTIVE: Exploring the relationship between the plasma substance P(SP) and essential hypertension with left ventricular hypertrophy (EH-LVH) and the effect of promoting blood circulation and eliminating phlegm. METHODS: Before and after treatment, the changes of SP in patients wiith EH-LVH were measured by radioimmunoassay. Meanwhile, the changes of plasma renin activity (PRA), angiotension II (Ang II), left ventricular mass index (LVMI) and mean arterial pressure (MAP) were measured. RESULTS: The level of plasma SP in patients with EH-LVH was markedly lower than that of patients without EH-NLVH and healthy subjects (P < 0.001); the levels of PRA and Ang II were higher than those in control group (P < 0.01 or < 0.05). After treatment, the level of SP was significantly increased, while LVMI, MAP, PRA and Ang II were significantly decrease (P < 0.01 or < 0.05). The levels between SP and LVMI, MAP, PRA, Ang II were markedly negative correlated (P < 0.01) while levels between LVMI and PRA, Ang II were markedly positive correlated. CONCLUSIONS: The SP may be involved in the pathogenesis of EH-LVH; the mechanism of promoting blood circulation and eliminating phlegm reversing LVH might be related to its increasing the plasma SP.

Aged↗