Search PubMed⌕ Search

Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 649 records · Page 36Linked to original sources
PubMed1990

Excitatory amino acid-mediated transmission of inspiratory drive to phrenic motoneurons.

1. The role of excitatory amino acids (EAAs) in the bulbospinal transmission of inspiratory drive was studied by intracellular and single-electrode voltage-clamp recordings from phrenic motoneurons in the in vitro neonatal rat brain stem spinal cord. 2. In all brain stem-spinal cord preparations there were spontaneously generated rhythmic membrane depolarizations and associated spiking of phrenic motoneurons during the inspiratory phase of the respiratory cycle. The envelope of the motoneuron drive potential had a rapid onset to peak (50 ms) followed by a plateau/declining phase that lasted 400-700 ms. The peak potential was approximately 10-20 mV above base-line potential. The drive current under voltage clamp had a similar shape and duration to the drive potential with a peak current greater than 1.5 nA. 3. The involvement of EAAs in the bulbospinal transmission of inspiratory drive was demonstrated by checking the effects of various EAA receptor antagonists on the phrenic motoneuron inspiratory drive. When kynurenic acid (KYN), an antagonist acting on all three subtypes of EAA receptors, was applied to the solution bathing the spinal cord, the motoneuron action potentials were abolished, and the amplitude of inspiratory drive potential was significantly reduced. To further classify the role of the different EAA receptor subtypes in the synaptic transmission of inspiratory drive, the effects on the drive potential of either 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a specific non-N-methyl-D-aspartic acid (non-NMDA) receptor antagonist, or DL-2-amino-5-phosphonovaleric acid (AP5), DL-2-amino-7-phosphonoheptanoic acid (AP7), and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imin emaleate (MK-801), NMDA receptor antagonists, were investigated. Bath or local application of CNQX induced a dose-dependent decrease of the inspiratory drive potential without changing intrinsic motoneuron membrane properties. On the other hand, application of AP7 or MK 801 had a small effect on the inspiratory drive potential or the inspiratory drive current when the motoneuron membrane potential was clamped near end-expiratory potentials (-60 to -75 mV). 4. To establish the presence of EAA receptors on the phrenic motoneuronal membrane and to provide information on the available receptor subtypes for action of the endogenously released transmitter, we tested the effects of agonists for the major EAA receptor subtypes after blocking synaptic transmission (produced by axonal action potentials) by bath application of tetrodotoxin (TTX).(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1990

Production of somatic and germline chimeras in the chicken by transfer of early blastodermal cells.

Cells were isolated from stage X embryos of a line of Barred Plymouth Rock chickens (that have black pigment in their feathers due to the recessive allele at the I locus) and injected into the subgerminal cavity of embryos from an inbred line of Dwarf White Leghorns (that have white feathers due to the dominant allele at the I locus). Of 53 Dwarf White Leghorn embryos that were injected with Barred Plymouth Rock blastodermal cells, 6 (11.3%) were phenotypically chimeric with respect to feather colour and one (a male) survived to hatching. The distribution of black feathers in the recipients was variable and not limited to a particular region although, in all but one case, the donor cell lineage was evident in the head. The male somatic chimera was mated to several Barred Plymouth Rock hens to determine the extent to which donor cells had been incorporated into his testes. Of 719 chicks hatched from these matings, 2 were phenotypically Barred Plymouth Rocks demonstrating that cells capable of incorporation into the germline had been transferred. Fingerprints of the blood and sperm DNA from the germline chimera indicated that both of these tissues were different from those of the inbred line of Dwarf White Leghorns. Bands that were present in fingerprints of blood DNA from the chimera and not present in those of the Dwarf White Leghorns were observed in those of the Barred Plymouth Rocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

A model for urbanizing rural population and development measures: survey of a large specialized market in Xiliu town, Liaoning province.

The authors present an urbanization model using the example of Xiliu town in Liaoning province, China. Xiliu has developed from a rural commune into a large-scale clothing market during the period since 1979. "The purpose...is to show, by means of a survey conducted in the town, the characteristics and formative factors of the model and to discuss the prospect of and measures for furthering this development."

Asia↗
PubMed1990

[Protective effects of biphenyl dimethyl dicarboxylate on damage in isolated rat hepatocytes induced by carbon tetrachloride and D-galactosamine].

The protective effect of DDB on chemically induced damages was studied in primary culture of rat hepatocytes. The experimental results showed that DDB (200 ug/10(6) cells) efficiently protected the hepatocytes against carbon tetrachloride (10 mM) and D-galactosamine (1 mM) induced damages. Membrane lipid peroxidation (malondialdehyde, MDA) formation and Glutamic Pyruvic Transaminase (GPT) released from the hepatocytes were markedly decreased. The damage of the cell surfaces of the hepatocytes were also reduced as seen under a scanning electron microscope (SEM). Pretreatment with DDB (300 mg/kg) orally could ameliorate the reduction of liver glycogen and blood glucose caused by injection of D-gal (800 mg/kg i. p) in mice. When normal rats received 300 mg/kg of DDB once daily for 10 days, free ribosomal protein and RNA in the liver increased significantly. These results indicated that DDB is of beneficial effects on damaged and normal hepatocytes.

Animals↗
PubMed1990

Signal transduction for chemotaxis in Dictyostelium amoebae.

The signal for chemotaxis in D. discoideum is cyclic AMP. This molecule binds to cell surface receptors and triggers the production of inositol (1,4,5)trisphosphate which releases Ca2+ from non-mitochondrial stores. The subsequent chain of signal transduction events brings about the polymerization of cytoskeletal actin (associated with pseudopodium formation) within five seconds and the formation of a peak of cyclic GMP within 10 s. Evidence from streamer F mutants indicates that the cyclic GMP regulates the association of myosin with the cytoskeleton that occurs at 25-50 s and that this phenomenon is concerned with elongation of the amoebae during chemotactic movement.

Calcium↗
PubMed1990

[The influence of electric needling "Juci" on nail-bed microcirculation of apoplectic patients].

UNLABELLED: "Juci" is one kind of acupuncture methods. It is that acupoints of the one side are used to treat the disease of the another side. In order to prove this theory and the difference from puncturing paralytic side (Tanci) 30 patients with hemiplegia due to cerebral infarction were observed under the same condition and stimulative parameter. Selecting points: Hegu and Quchi acupoint were electrified for 15 minutes. The changes of Nail-bed microcirculation were observed for half an hour and recorded after pulling out needles. CONCLUSION: Through the observation of outline of blood vessel, colour of blood vessel ansa, ansa's top blood-stasis of blood vessel, condition of blood flow and the rate of blood flow before and after Juci (puncturing healthy side) they were different or quite different on the hemiplegic side (p less than 0.05 or p less than 0.01). however, only the colour of blood-vessel ansa and rate of blood flow were different, others had no statistical significance on healthy side. Though puncturing paralytic side can make the nail-bed microcirculation improved, only rate of blood flow was different. Others had no statistical significance. In short both Juci and Tanci improve the nail-bed microcirculation of hemiplegic side, but the former is much better than the latter.

Acupuncture Therapy↗
PubMed1990

[Mixed gonadal dysgenesis. Report of 11 cases].

Eleven cases of Mixed Gonadal Dysgenesis are reported. The disease is characterized by gonadal asymmetry, as well as retained Mullerian duct structures. These individuals exhibit varying degrees of masculinization of the external genitalia, the spectrum of phenotypic expression extending from the normal male to the normal female. 45,/46, XY is the typical karyotype. The etiology, the role of H-Y antigen, pathogenesis and management are discussed. The risk of neoplastic transformation in gonads is a significant threat and must be considered at all the stages of management.

Adolescent↗
PubMed1990

[Sampling survey of mentally deficient people in Sichuan].

From first April to 15th May 1987, 145,201 people were investigated by using the ways of layer, equal probability and mass sampling. Two thousand three hundred and forty two of them were confirmed to be mentally deficient. The incidence was 16.13%. It was estimated that 1,665,000 people have mental deficiency in Sichuan. The estimated range of reliability of 95% was 1,528,000-1,801,000. One million and three hundred ninety three thousand of them only had mental deficiency, while 272,000 had other organic deficiency. Male:female ratio was 101.4:100. The incidence of 6-14 year-old was 38.14%, which was 3 times higher than that of other age groups. Mild mental deficiency was 16.4 times more than severe mental deficiency. The most common causes were hereditary diseases, encephalitis, malnutrition, cerebral trauma, pregnant diseases, etc. All of the causes belonged to preventable diseases.

Adolescent↗
PubMed1990

[Characterization of the expression of LDH isozymes genes during non-hibernation Himalayan marmots].

The lactate dehydrogenase (LDH) isozymes from heart, liver, kidney and skeletal muscle in Himalayan marmots (Marmota himalayana robusta) in non-hibernation were investigated in the present experiment. The isozyme patterns were analyzed by means of disc electrophoresis and the ultraviolet enzymatic determination. The following conclusions were obtained: 1. It was found that two expression patterns of LDH genes presented in the skeletal muscle of Himalayan marmots. There was a LDH-B4 band only in one marmots and absent in others. The interindividual polymorphism of LDH isozyme patterns may be attribute to one or more regulator genes controlling synthesis of B-subunit of LDH. 2. LDH zymograms of various tissues of Himalayan marmots showed different subbands. This is presumably due to the existence of both symmetrical and asymmetrical conformers of this tetramer.

Animals↗
PubMed1990

[Pharmacological functions of Chinese ant oral syrup].

Experiments show that Chinese Ant Oral Syrup has functions as calmatives, fatigue-resisting agents and androgen. Also it can cause thymic atrophy in small mice, increase their oxygen-deficient endurance under normal pressures, inhibit leucocyte-decrease induced by cyclophosphamidum. The syrup is slightly toxic.

Animals↗