Search PubMed⌕ Search

Biomedical subjects

G Hu

Publications and source records attributed to G Hu.

At least 109 records · Page 6Linked to original sources
PubMed1999

Msx1 antagonizes the myogenic activity of Pax3 in migrating limb muscle precursors.

The migration of myogenic precursors to the vertebrate limb exemplifies a common problem in development - namely, how migratory cells that are committed to a specific lineage postpone terminal differentiation until they reach their destination. Here we show that in chicken embryos, expression of the Msx1 homeobox gene overlaps with Pax3 in migrating limb muscle precursors, which are committed myoblasts that do not express myogenic differentiation genes such as MyoD. We find that ectopic expression of Msx1 in the forelimb and somites of chicken embryos inhibits MyoD expression as well as muscle differentiation. Conversely, ectopic expression of Pax3 activates MyoD expression, while co-ectopic expression of Msx1 and Pax3 neutralizes their effects on MyoD. Moreover, we find that Msx1 represses and Pax3 activates MyoD regulatory elements in cell culture, while in combination, Msx1 and Pax3 oppose each other's trancriptional actions on MyoD. Finally, we show that the Msx1 protein interacts with Pax3 in vitro, thereby inhibiting DNA binding by Pax3. Thus, we propose that Msx1 antagonizes the myogenic activity of Pax3 in migrating limb muscle precursors via direct protein-protein interaction. Our results implicate functional antagonism through competitive protein-protein interactions as a mechanism for regulating the differentiation state of migrating cells.

Animals↗
PubMed1999

The regulation of dopamine transmission by metabotropic glutamate receptors.

Receptor subtype nonselective metabotropic glutamate receptor (mGluR) agonists have been shown to regulate the release of dopamine. The eight mGluR subtypes have been pharmacologically categorized into three groups, and the present study used in vivo microdialysis to examine the capacity of mGluR subgroup-selective drugs to modulate the extracellular levels of dopamine in the nucleus accumbens. By administering the drugs in the dialysis buffer, it was found that the group 3 mGluR agonist L-amino-4-phosphonobutyrate produced a dose-dependent reduction in extracellular dopamine, whereas the group 1 agonist 3,5-dihydroxyphenylglycine was ineffective. The group 2 agonist (2S,1'R,2'R,3'R)-2-(2, 3-dicarboxycyclopropyl)glycine produced a reduction that was biphasic with respect to dose. The group 2/3 antagonist alpha-methyl-4-phosphnophenylglycine elicited a dose-dependent increase in extracellular dopamine that was antagonized by coperfusion with either the L-type calcium channel blocker diltiazem or the group 3 agonist L-amino-4-phosphonobutyrate. These data demonstrate that group 3 and to a lesser extent group 2 mGluR may presynaptically regulate dopamine release or reuptake. Moreover, there exists significant in vivo glutamatergic tone on group 2/3 mGluRs to suppress extracellular dopamine levels.

Animals↗
PubMed1999

[Effects of MMP-1 expressing plasmid on rat liver fibrosis].

OBJECTIVE: To observe the effects of MMP-1(Matrix Metalloproteinase-1) expressing plasmid on rat liver fibrosis. METHODS: We constructed the rat's MMP-1 recombinant plasmid which can be expressed in eucaryotic cells. After encapsulating the MMP-1 recombinant plasmid by lipofectin, we transferred it to the rat's fibrotic liver in vivo intraperitoneally, then observed the effects of the plasmid on the fibrotic liver by RT-PCR, immunohistochemistry and the observation of pathology. RESULTS: The recombinant plasmid of MMP-1 could increase the degradation of type I and type III collagen in the rat's fibrotic liver according to immunohistochemistry compared with fibrotic modal group(P < 0.01) or compared with colchicine group(P < 0.05). According to the observation of pathology, recombinant plasmid of MMP-1 has some reverse effects on the rat's fibrotic liver compared with fibrotic model group(P < 0.05), but no obvious difference was found between the plasmid and colchicine(P > 0.05). CONCLUSION: The recombinant plasmid of MMP-1 has some reverse effects on liver fibrosis, but the effects is limited.

Animals↗
PubMed1999

[Detection of fetal DNA in maternal plasma using the nested polymerase chain reaction].

OBJECTIVE: To search for a new method of non-invasive prenatal gene diagnosis. METHODS: A single-copy human DYS14 gene of Y-chromosome of fetal DNA sequence was amplified by nested polymerase chain reaction (PCR) from twelve pregnant maternal plasma (12-40 weeks). A 239 bp and 198 bp specific fragment were obtained. The maternal plasma samples of twelve pregnant women were used directly for nested PCR. RESULTS The fragment was identified in 8 of 10 male-bearing pregnant women plasma. The diagnostic accordance rate was 80% (8/10), 6 to 8 women gave positive signals in two consecutive amplifications, 2 of 8 women gave positive signals in the second amplification. The rate of positive was increased greatly by nested PCR (from 60% to 80%). None of the other 2 female-bearing pregnant women had positive results. The final accuracy of 83.3% (10/12) was attained in all cases. CONCLUSION: The finding of circulating fetal DNA in maternal plasma may have new implications for non-invasive prenatal gene diagnosis, and the nested PCR possesses the advantages of sensitivity and specificity which improves the clinical application.

Adult↗
PubMed1999

[Studies on apoptosis of human lung adenocarcinoma cells induced by oltipraz].

OBJECTIVE: To study whether oltipraz can induce apoptosis of human lung adenocarcinoma (GLC-82) cells and its possible mechanism. METHODS: Light microscopy, DNA electrophoresis, flow cytometry and video time-lapse monitoring were used to observe apoptosis of GLC-82 induced by oltipraz. RESULTS: GLC-82 cells treated with oltipraz underwent the arrest of cell mitosis at metaphase, higher percentage of G(2)/M and peak of apoptosis were found, and cell body shrunk, nuclear chromosome condensed or fragmented and nuclear DNA fragment displayed "laden" bands in apoptic cells. Apoptosis of GLC-82 induced by oltipraz was more obvious at a concentration of 120 microg/ml. CONCLUSION: Oltipraz could induce apoptosis of GLC-82 at certain concentrations, which associated closely with the arrest of mitotic cycle.

Adenocarcinoma↗
PubMed1999

[Studies on appropriate methods for dust scrubbing from dust-laden gas in shaft kilns of small-sized cement plants].

OBJECTIVE: To study an appropriate method for dust scrubbing from dust-laden gas in the shaft kilns of small-sized cement plants. METHODS: Characteristics of dust-laden gas, including its temperature, dew point, dust concentration, diameters of dust particles and their distribution, as well as fractional dust collection efficiencies of the dust precipitator settling chamber, cyclone, impinging scrubber, impinging-spray scrubber, were measured according to the National Standards for Measurement of Particulate in Exhaust Gas Emitted from the Stationary Pollution Sources and Sampling Methods of Gaseous Pollutants (GB/T16157 - 1996), with a WY-1 In-stack 7-Stage Cascade Impactor for fractional dust collection. RESULTS: The fractional dust collection efficiency of the settling chamber for the particles greater than 12 microm was 72%, while that of the cyclone for the particles of 2 microm, 5 microm and 10 microm were 40.0%, 72.5% and 88.9%, respectively, and that of impinging scrubber was 55.0%, 91.0% and 98.9%, respectively; and that of impinging-spray scrubber were 96.0%, 99.2% and 99.6%, respectively. Results showed that 81% of the dust (by weight) from the shaft kilns were greater than 10 microm, so the settling chamber was effective for the removal of this fraction of dust. But dust particles behind the settling chamber were finer, and about 59% - 69% of them were less than 2 microm in diameters. In that case, the cyclone, impinging scrubber and impinging-spray scrubber could give an overall collection efficiency of 54%, 57% and 96%, respectively. Based on this, the following combination of dust collectors were adopted to meet the national standards for exhaust emission: a settling chamber plus an electrostatic precipitator, a settling chamber plus an impinging-spray scrubber and a settling chamber plus an impinging scrubber. The cement plants could select appropriate dust collectors according to their technical and economical conditions. CONCLUSION: Based on the results of the studies, appropriate dust collectors used to treat dust-laden gas from shaft kilns to meet the national standards for exhaust emission were recommended.

Air Pollutants, Occupational↗
PubMed1999

[The determination of coumarin in foods by high performance liquid chromatography (HPLC)].

An HPLC procedure for determination of coumarin in foods has been developed. The samples were extracted with ether. The extract was evaporated at 40 degrees C under dry N2. The residue was diluted by adding 10.0 mL MeOH-H2O(9:1) and keep standing. A 10 microL clear liquid was analysed by HPLC on a Nova Pak C18 column (5 microns, 150 mm x 3.9 mm. i.d.) with MeOH/10 mmol/L-phosphate buffer of pH 5.4(45:55) as mobile phase (1.0 mL/min) and UV detection at 275 nm. The calibration curve was linear in the range from 2 to 10 mg/L and the detection limit was 0.015 mg/L. Recoveries of the method were from 97.6% to 100.8%. The CV (n = 6) was 1.3%. The method is simple, rapid and accurate.

Beverages↗
PubMed1999

[Experimental study of ablation effect on canine esophagus irradiated by pulsed Ho:YAG laser].

To evaluate the influence of power, irradiation time, energy of per pulse and frequency on ablation effect of pulsed Ho:YAG laser, five canine esophagi were studied. We irradiated the mucosa in different power and different irradiation time. For the same power, the samples were divided into two groups: the high energy per pulse low frequency (H)group and the low energy per pulse high frequency (L)group. The two groups were paired. We compared the effects of ablation effect in different laser settings. The results reveal that the ablation effect is positively correlated to the power and irradiation time. The ablation in H group is more obviouse than that in L group. When Ho:YAG is used in high power, ablation is the main biological effect.

Animals↗
PubMed1999

Pilot study of schistosomiasis control in Poyang lake region.

AIM: To perform a longitudinal survey of the control of schistosomiasis in Fanhu Village hyperendemic for schistosomiasis, Poyang Lake region of Jiangxi Province from 1992 to 1996. METHODS: Annual mass chemotherapy and health education were implemented in all investigated individuals, in 1996, artesunate was used in high risk population in transmission season as a prophylactic measure. RESULTS: The prevalence of S. japonicum infection reduced from 26.0% in 1992 to 10.7% in 1994, the intensity of infection (geometric mean of EPG of feces) in residents decreased from 1.92 in 1992 to 0.55 in 1994, and the morbidity indicators such as hepatomegaly and splenomegaly in the cases also have been improved significantly after chemotherapy. In 1995, both the infection rate and intensity of infection of schistosomiasis were recurred from 10.7% and 0.55 in 1994 to 18.4% and 1.04 respectively due to the floods. In 1996, the infection rate reduced to 5.0% and the intensity of infection also decreased to 0.25 due to the additional measure. CONCLUSION: A mass chemotherapy in conjunction with health education and oral artesunate for preventing reinfection in transmission season is effective for the control of schistosomiasis in lake regions.

Adolescent↗
PubMed1999

Netrin-1: interaction with deleted in colorectal cancer (DCC) and alterations in brain tumors and neuroblastomas.

Netrins, a family of laminin-related secreted proteins, have critical roles in axon guidance and cell migration during development. The deleted in colorectal cancer (DCC) protein has been implicated as a netrin-1 receptor component. The expression and function of netrins in adult tissues remain unknown, and direct interaction of netrin-1 with DCC has not been demonstrated. We cloned the human netrin-1 (NTN1L) gene, mapped it to chromosome 17p12-13, and found that it encodes a 604 amino acid protein with 98% identity to mouse netrin-1 and 50% identity with the Caenorhabditis elegans UNC-6 protein. NTN1L transcripts were detected in essentially all normal adult tissues studied, and markedly reduced or absent NTN1L expression was seen in approximately 50% of brain tumors and neuroblastomas. In one neuroblastoma, missense mutations at highly conserved NTN1L codons were found. Netrin-1 protein could be cross-linked to DCC protein on the cell surface, but it did not immunoprecipitate with DCC in the absence of cross-linking and it failed to bind to a soluble fusion protein containing the entire DCC extracellular domain. Our findings demonstrating NTN1L loss of expression and mutations suggest that NTN1L alterations may contribute to the development of some cancers. Furthermore, the binding of netrin-1 to DCC appears to depend on the presence of a coreceptor or accessory proteins.

Amino Acid Sequence↗
PubMed1998

An early phase of embryonic Dlx5 expression defines the rostral boundary of the neural plate.

Relatively little is known about the molecular events that specify the rostrocaudal axis of the neural plate. Here we show that a member of the Distal-less (Dlx) homeobox gene family, Dlx5, is one of the earliest known markers for the most rostral ectoderm, before the formation of an overt neural plate. During late gastrulation Dlx5 expression becomes localized to the anterior neural ridge, which defines the rostral boundary of the neural plate, and also extends caudolaterally, marking the region of the presumptive neural crest. Subsequently, Dlx5 is expressed in tissues (olfactory epithelium, ventral cephalic epithelium) that are believed to derive from the anterior neural ridge, based on the avian fate map. The early phase of Dlx5 expression in the anterior neural ridge and its derivatives is distinct from a later phase of expression in the ventral telencephalon and diencephalon and also appears to be unique for Dlx5 among members of the Dlx family. Another distinctive feature of Dlx5 expression is the occurrence of an alternative transcript (deltaDlx5), which encodes a truncated protein lacking the homeodomain, and represents a significant fraction of total Dlx5 transcripts at all embryonic stages that were examined. In contrast with full-length DLX5, the deltaDLX5 truncated protein is deficient in DNA-binding activity and does not interact with the homeoprotein partner MSX1. Taken together, our findings suggest that Dlx5 activity may be regulated via the expression of an alternative transcript and demonstrate that Dlx5 marks the anterior boundary of the neural plate.

Alternative Splicing↗
PubMed1998

Dietary vitamin C intake and lung function in rural China.

The relation between dietary vitamin C intake and pulmonary function was investigated in a cross-sectional study carried out in 69 counties in rural China in 1989. Within each of the 69 counties, 120 subjects aged 35-64 years were identified using a three-stage random clustering procedure. Each subject underwent pulmonary function testing, completed a detailed questionnaire, and provided a blood sample. Dietary vitamin C intakes were estimated among half of the subjects using a 3-day weighed record of household food intake. Plasma vitamin C was measured in sex-specific blood pools created from individual samples in each geographic area. Among the 3,085 subjects for whom there were complete data, dietary intake of vitamin C (151 mg/day (standard deviation, 111)) was significantly related to forced expiratory volume in the first second (FEV1) and forced vital capacity after adjustment for sex, age, height, weight, total caloric intake, tobacco smoking, and education. An increase of 100 mg/day in vitamin C intake was associated with an increase of 21.6 ml (95% confidence interval -0.4 to 43.5) in FEV1 and an increase of 24.9 ml (95% confidence interval 0.2 to 49.6) in forced vital capacity. No significant interaction with smoking status was observed. A significant positive association was also observed at the geographic level, between county-pooled plasma vitamin C and mean FEV1. These data support the hypothesis that dietary vitamin C may protect against the loss of pulmonary function.

Adult↗
PubMed1998

Subcellular localization of beta-1,3-glucanase in Puccinia recondita f.sp. tritici-infected wheat leaves.

An antiserum raised against the purified 33-kDa beta-1,3-glucanase of wheat (Triticum aestivum L.) was employed to investigate the ultrastructural localization of the enzyme in wheat leaves infected with Puccinia recondita Rob. ex Desm. f.sp. tritici Eriks. and Henn. using a post-embedding immunogold labelling technique. In both compatible and incompatible interactions, beta-1,3-glucanase was detected in the host plasmalemma and in the domain of the host cell wall near the plasmalemma of the mesophyll cells, but higher concentrations of the enzyme were detected in infected resistant wheat leaves than in infected susceptible ones. beta-1,3-Glucanase was also found in the secondary thickening of xylem vessels and in the walls of guard cells, epidermal cells and phloem elements, while no labelling was observed in host organelles, viz. vacuoles, mitochondria, endoplasmic reticulum, Golgi bodies, nuclei and chloroplasts. A low concentration of the enzyme was detected on the intercellular hyphal wall and in the hyphal cytoplasm. In the compatible interaction, beta-1,3-glucanase was demonstrated to accumulate predominantly in the haustorial wall and extrahaustorial matrix. In the incompatible interaction, strong labelling for beta-1,3-glucanase was found in host cell wall appositions, in the extracellular matrix in the intercellular space, and in electron-dense structures of host origin which occurred in the incompatible interaction only.

Basidiomycota↗
PubMed1998

A porphyrin pathway impairment is responsible for the phenotype of a dominant disease lesion mimic mutant of maize.

The maize lesion mimic gene Les22 is defined by dominant mutations and characterized by the production of minute necrotic spots on leaves in a developmentally specified and light-dependent manner. Phenotypically, Les22 lesions resemble those that are triggered during a hypersensitive disease resistance response of plants to pathogens. We have cloned Les22 by using a Mutator-tagging technique. It encodes uroporphyrinogen decarboxylase (UROD), a key enzyme in the biosynthetic pathway of chlorophyll and heme in plants. Urod mutations in humans are also dominant and cause the metabolic disorder porphyria, which manifests itself as light-induced skin morbidity resulting from an excessive accumulation of photoexcitable uroporphyrin. The phenotypic and genetic similarities between porphyria and Les22 along with our observation that Les22 is also associated with an accumulation of uroporphyrin revealed what appears to be a case of natural porphyria in plants.

Amino Acid Sequence↗
PubMed1998

Haploinsufficiency of MSX1: a mechanism for selective tooth agenesis.

Previously, we found that the cause of autosomal dominant selective tooth agenesis in one family is a missense mutation resulting in an arginine-to-proline substitution in the homeodomain of MSX1. To determine whether the tooth agenesis phenotype may result from haploinsufficiency or a dominant-negative mechanism, we have performed biochemical and functional analyses of the mutant protein Msx1(R31P). We show that Msx1(R31P) has perturbed structure and reduced thermostability compared with wild-type Msx1. As a consequence, the biochemical activities of Msx1(R31P) are severely impaired, since it exhibits little or no ability to interact with DNA or other protein factors or to function in transcriptional repression. We also show that Msx1(R31P) is inactive in vivo, since it does not display the activities of wild-type Msx1 in assays of ectopic expression in the limb. Furthermore, Msx1(R31P) does not antagonize the activity of wild-type Msx1 in any of these assays. Because Msx1(R31P) appears to be inactive and does not affect the action of wild-type Msx1, we propose that the phenotype of affected individuals with selective tooth agenesis is due to haploinsufficiency.

Amino Acid Substitution↗
PubMed1998

[A study on HBV DNA pre C region A83 mutation in patients with hepatitis B].

Mismatched polymerase chain reaction (MPCR) and restriction fragment length polymorphism assay(RFLP) were performed to detect the HBV DNA pre core A83 mutation in 97 patients with chronic HBV infection in Hunan. HBV DNA pre core A83 mutation were detected in 37 out of 97 patients (37/97,38.1%). It was found that the prevalence of HBV DNA pre core A83 mutation of the patients with severe hepatitis and with CAH(chronic active hepatitis) were significantly higher than those with CPH(chronic persistent hepatitis) and carriers of HBV, and the patients with elevated transaminase (ALT > 70U) or positive HBeAb were significantly higher than those with normal transaminase (ALT < 70U) and with positive HBeAg, respectively. The results suggest that the HBV DNA pre core A83 mutation is associated with active and severe liver tissue in patients with hepatitis B.

Adolescent↗
PubMed1998

[Four-year follow-up and molecular epidemiologic investigation of intrafamilial transmission of HCV infection].

OBJECTIVE: To study the intrafamilial transmission of HCV infection. METHODS: Four-year follow-up and molecular epidemiologic investigation of HCV infection in a village was carried out. The diversity of HCV core region was analysed by reverse transcription nested polymerase chain reaction, Okamoto genotyping method, and single strand conformation polymorphism analysis (SSCP). RESULTS: The incidence of positivity of anti-HCV and -HCVRNA raised from 21.30% (75/352) to 43.18% (152/352). There were 42 families with two or more members serological positive for anti-HCV and/or -HCVRNA. There were a 3.46-fold increase of intrafamilial propagation of HCV infection in the past 4 years. HCV genotyping by Okamoto method showed that 90.67% (136/150) belonged to Type 1b/II, two cases (1.33%) belong to type 2a/III and three cases (2.00%) were co-infection of both types. Comparison of SSCP patterns revealed that the SSCP of HCV cDNA was identical among members of the same family, but the single strand conformation of HCV cDNA exhibited polymorphism patterns in different families. CONCLUSION: The results indicate that the cause of marked increase of HCV infection rate in this village in a 4-year period is mainly because of intrafamilial propagation. SSCP is more feasible for molecular epidemiologic investigation of HCV infection than genotyping.

Adolescent↗