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Biomedical subjects

M Jia

Publications and source records attributed to M Jia.

At least 19 recordsLinked to original sources
PubMed2001

Ion chromatographic analysis of selected free amino acids and cations to investigate the change of nitrogen metabolism by herbicide stress in soybean (glycine max).

A simple and reliable method for the determination of NH4+, K+, Na+, aspartic acid, asparagine, glutamine, and alanine by ion chromatography has been developed. It is suitable for monitoring changes of nitrogen metabolism in soybean because it can accurately measure concentrations o asparagine and NH4+, two key substances for nitrogen storage and transport in this plant species Analysis of asparagine distribution in soybean indicated that higher levels (up to 18.4 micromol g(-1) of fresh mass) occur in stems and lower levels in roots (2.0 micromol g(-1) of fresh mass) and leaves (1.6 micromol g(-1) of fresh mass). When the herbicide metsulfuron-methyl (0.5, 5, and 50 ppb) was applied via the nutrient solution to the root system, asparagine concentrations increased 3-6 times in stems roots, and leaves. Metsulfuron-methyl is known to impair the synthesis of branched amino acids and, in consequence, protein synthesis. Thus, nitrogen consumption was limited, leading to ar accumulation of asparagine. The possible use of this physiological response in agricultural practice to identify herbicide stress in soybean and to detect low-level residues of sulfonylurea herbicides ir the soil is discussed.

Alanine↗
PubMed2001

Opposing actions of protein kinase A and C mediate Hebbian synaptic plasticity.

A compartmental nerve-muscle tissue culture system expresses Hebbian activity-dependent synapse modulation. Protein kinase C (PKC) mediates a heterosynaptic loss of efficacy, and we now show that protein kinase A (PKA) is involved in homosynaptic stabilization. Both work through postsynaptic changes in the acetylcholine receptor (AChR) as measured electrophysiologically and by imaging techniques.

Cyclic AMP-Dependent Protein Kinases↗
PubMed2001

One hundred and seven middle-aged and senile cases of coronary heart disease with ventricular premature beat treated by qing xin an shen fang.

The therapeutic principle of clearing away the heart-heat to induce tranquilization was adopted in 107 middle-aged and senile patients with ventricular premature beat of coronary heart disease on the basis of pathogenic features of phlegm, heat, blood stasis and deficiency in this condition. Qing Xin An Shen Fang ([symbol: see text] a formula for clearing away the heart-heat to induce tranquilization) was used in the treatment group and compared with mexiletine and Fu Fang Dan Shen Tablets ([symbol: see text] Compound Salvia Tablets) used in the control group. The results turned to be that the markedly effective rate was 85.1% and the total effective rate 96.3% in the treated group, better than that in the control group, with the former having a good antihypertensive and antihyperlipemic effect and an effect of improving microcirculation and clinical symptoms.

Aged↗
PubMed2001

[The effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats].

OBJECTIVE: To observe the effects of safflor yellow on microcirculation and hemorheology of acute blood stasis rats. METHODS: The acute blood stasis medel was made by i.p. adrenalin (0.07 ml/(kg.time) for 2 times and the stimulation of ice-water. RESULTS: Safflor could markedly improve the number of net dot in microcirculation, and eta b, eta p, eta f in hemorheology (P < 0.05). CONCLUSION: Safflor yellow played an important role on blood stasis of rats.

Animals↗
PubMed2000

Air sampling with porous solid-phase microextraction fibers

A new, rapid air sampling/sample preparation methodology was investigated using adsorptive solid-phase microextraction (SPME) fiber coatings and nonequilibrium conditions for volatile organic compounds (VOCs). This method is the fastest extraction technique for air sampling at typical airborne VOC concentrations. A theoretical model for the extraction was formulated based on the diffusion through the interface between the sampled (bulk) air and the SPME coating. Parameters that affect the extraction process including sampling time, air velocity, air temperature, and relative humidity were investigated with the porous (solid) PDMS/DVB and Carboxen/PDMS coatings. Very short sampling times from 5 s to 1 min were used to minimize the effects of competitive adsorption and to calibrate the extraction process in the initial linear extraction region. The predicted amounts of extracted mass compared well with the measured amounts of target VOCs. Findings presented in this study extend the existing fundamental knowledge related to sampling/sample preparation with SPME, thereby enabling the development of new sampling devices for the rapid sampling of air, headspace, water, and soil.

Journal Article↗
PubMed2000

Protein kinase C-mediated changes in synaptic efficacy at the neuromuscular junction in vitro: the role of postsynaptic acetylcholine receptors.

Activation of a mouse in vitro neuromuscular synapse produces a reduction in synaptic efficacy which is greater for nonactivated than for activated inputs to the myotubes. This has been shown to require thrombin and thrombin receptor activation and to involve a protein kinase C (PKC)-mediated step. We show in the present work that phorbol ester activation of PKC produces physiological loss of synapses in a time- and dose-related manner. We observe, using quantitative imaging methods, a parallel loss of acetylcholine receptors (AChR) from synaptically functional neurite-associated receptor aggregates in nerve-muscle cocultures. Biochemical measurements of total AChR show that PKC activation reduces both AChR stability (increases receptor loss) and receptor insertion into the surface membrane. Taken together, the data suggest that PKC activation decreases the stability of AChR aggregates in the muscle surface membrane. We conclude that PKC plays a crucial role in activity-dependent synapse reduction and does so, at least in part, by altering AChR stability.

Animals↗
PubMed2000

Thrombin action decreases acetylcholine receptor aggregate number and stability in cultured mouse myotubes.

Neurons develop and make very stable, long-term synaptic connections with other nerve cells and with muscle. Synaptic stability at the neuromuscular junction changes over development in that a proliferation of synaptic input are made to individual myotubes and synapses from all but one neuron are lost during development. In an established co-culture paradigm in which spinal motoneurons synaptically contact myotubes, thrombin and associated protease inhibitors have been shown to affect the loss of functional synaptic contacts [6]. Evidence has not been provided which clearly demonstrate whether protease/protease inhibitors affect either the pre- or postsynaptic terminal, or both. In an effort to determine whether these reagents directly affect postsynaptic receptors on myotubes, myotubes were cultured in the absence of neurons and the spontaneous presence and stability of aggregates of acetylcholine receptors (AChR) in control and thrombin-containing media were evaluated. In dishes fixed after treatment and in dishes in which individual aggregates were observed live, thrombin action appeared to increase loss of AChR aggregates over time. Hirudin, a specific inhibitor of the thrombin protease, diminished this loss. Neither reagent affected the overall incorporation or degradation of AChR; therefore, it appears these protease/protease inhibitors affect the state of AChR aggregation.

Animals↗
PubMed2000

[Reconstruction of the mandible and soft tissue defects with the osteomyocutaneous free fibula flap].

OBJECTIVE: In order to ascertain a material that is ideal both for reconstruction of the composite mandibular defects and for osseointegrated implantation. METHODS: Fifteen osteomyocutaneous fibula flaps were transferred for reconstruction of the mandible and surrounding soft tissues. The characters of the blood supply of the flap, the operation course, the relation of the fibula and dental implants were observed. RESULTS: The osteomyocutaneous fibula flap was supplied by double vessels. The blood supply was reliable even after the fibula was cut into several segments. Periosteal circulation was its main blood supply. The postoperative contour and function of the mandibular region were good. The flap also favours dental implants and denture. CONCLUSION: The osteomyocutaneous fibula flap was the ideal material to reconstruct the defects of mandible and surrounding soft tissues.

Adult↗
PubMed1999

Botulinum neurotoxin A blocks synaptic vesicle exocytosis but not endocytosis at the nerve terminal.

The supply of synaptic vesicles in the nerve terminal is maintained by a temporally linked balance of exo- and endocytosis. Tetanus and botulinum neurotoxins block neurotransmitter release by the enzymatic cleavage of proteins identified as critical for synaptic vesicle exocytosis. We show here that botulinum neurotoxin A is unique in that the toxin-induced block in exocytosis does not arrest vesicle membrane endocytosis. In the murine spinal cord, cell cultures exposed to botulinum neurotoxin A, neither K(+)-evoked neurotransmitter release nor synaptic currents can be detected, twice the ordinary number of synaptic vesicles are docked at the synaptic active zone, and its protein substrate is cleaved, which is similar to observations with tetanus and other botulinal neurotoxins. In marked contrast, K(+) depolarization, in the presence of Ca(2+), triggers the endocytosis of the vesicle membrane in botulinum neurotoxin A-blocked cultures as evidenced by FM1-43 staining of synaptic terminals and uptake of HRP into synaptic vesicles. These experiments are the first demonstration that botulinum neurotoxin A uncouples vesicle exo- from endocytosis, and provide evidence that Ca(2+) is required for synaptic vesicle membrane retrieval.

Animals↗
PubMed1999

The thrombin receptor mediates functional activity-dependent neuromuscular synapse reduction via protein kinase C activation in vitro.

Activity-dependent selective reduction of synaptic efficacy is expressed in an in vitro system involving mouse spinal cord and muscle cells. Thrombin or electrical stimulation of the innervating axons induces a decrease in neuromuscular synapse strength, and a specific thrombin inhibitor, hirudin, blocks the electrically evoked down-regulation of synapse effectiveness. We further demonstrate that a thrombin receptor-activating peptide (TRAP), SFLLRNPNDKYEPF, produces a decrement of synapse strength. Both TRAP and electrically evoked synapse decrement are prevented by the specific protein kinase C blocker calphostin C, and the TRAP-evoked synapse decrement is unaffected by a specific protein kinase A blocker, H-89. Thus, we propose that muscle activity, thrombin release, and thrombin receptor and PKC activation are initial steps in the process of the activity-dependent synapse reduction expressed in our system.

Action Potentials↗
PubMed1999

Voltage-sensitive calcium currents are acutely increased by nerve growth factor in PC12 cells.

Whole cell calcium currents were recorded from PC12 cells with the perforated patch technique. Currents were evoked by step depolarization from a holding potential of -90 mV. Nerve growth factor (NGF) increased calcium currents through L-type calcium channels by >75% within 3-5 min. This increase was inhibited by K-252a, by nifedipine, and by inhibition or down-regulation of kinase C. Brain-derived neurotrophic factor (BDNF) also increased calcium current, but to a smaller extent. Thus increases in calcium current can be linked to activation of either the high- or the low-affinity nerve growth factor receptor. Increases in presynaptic calcium uptake appear to be a crucial element in the short-term actions of the neurotrophins on neurotransmitter release leading to long-term potentiation. Also, the control of calcium uptake is likely to be an important factor in the long-term actions of the neurotrophins on neuronal survival and neuronal protection. The present data indicate that the PC12 cell may be a useful model for studying the effect of the neurotrophins on calcium uptake.

Animals↗
PubMed1999

[A study on the relationship between lymphocyte micronucleus rates and blood plasma benzo(a)pyrene levels in coking workers].

OBJECTIVE: To study the relationship between lymphocyte micronucleus rates and blood plasma levels of benzo(a)pyrene [B(a)P] in coking workers. METHODS: One hundred coking workers and 100 unexposed workers were selected, and their lymphocyte micronucleus rates and plasma levels, as well as workplace air concentrations, of B(a)P were determined. RESULTS: It showed that there was significant difference in plasma B(a)P level between coking workers and unexposed workers, and it correlated with air concentration of B(a)P in the workplace. Positive rates of micronucleus and rates of micronucleus lymphocyte were 60% and 1.79per thousand in coking workers and 29% and 1.10per thousand in controls, respectively, with very significantly statistical difference. It also showed that positive micronucleus rate correlated with plasma level of B(a)P in dose-effect pattern. Multivariate analysis showed that factors contributing to positive micronucleus rate ranked in such an order: plasma level of B(a)P, economic status, regularity of their lifestyle and smoking status of the coking workers. CONCLUSION: Accumulation of B(a)P in blood plasma played a major role in the formation of lymphocyte micronucleus. Results of micronucleus test in coking workers could reflect preliminary damage to their health caused by it.

Adult↗
PubMed1999

[Experimental studies on antioxidative effect of tongcao and xiao-tongcao polysaccharides].

OBJECTIVE: To observe the antioxidative effect of four kinds of Tongcao and Xiao-Tongcao polysaccharides. METHOD: Aged mice (nine months) were abdominal administrated with four kinds of polysaccharides (Tongtuomu, Ximashanjingjiehua, Xinanxiuqiu, Ditanghua) at dosages of 160 mg/kg and 80 mg/kg for 45 days. RESULT: Four kinds of polysaccharides could obviously decrease the content of serum and liver lipoperoxide(LPO) as well as the content of lipofuscin(LF) in brain and cardiac muscle of aged mice, and also increase the activity of superoxide dismutase(SOD) of red cells in aged mice. CONCLUSION: The polysaccharide components of Tongtuomu and three kinds of Xiao-Tongcao have antioxidative effect, suggesting that these substances have antiageing function.

Animals↗
PubMed1998

[Experimental studies on anti-inflammatory, antipyretic and diuretic effects of several species of tongcao and xiao-tongcao].

OBJECTIVE: To observe and compare the anti-inflammatory, antipyretic and diuretic effects of three kinds of Tongcao(Tongtuomu, Panyezhangyeshu and Luosan) and seven kinds of Xiao-tongcao(Ximashanjinjiehua, Xinanxiuqiu1. 2., Ditanghua, Suixuezhangcai, Qingjiaye and Zhongguo jinjiehua). METHOD: Decoctions prepared from the above kinds of Tongcao and Xiao-tongcao crude drugs were given to rats at dosages of 8 g/kg and 4 g/kg by ig. Pharmacological actions were observed by means of carrageenan-induced swelling paws, fever models induced by beer-yeast or carrageenan and metabolic cage method in rats. RESULT: All the experimental decoctions could inhibit carrageenan-induced swelling of rat paws in different degrees and exerted anti-pyretic effect on rat fever models induced by beer-yeast or carrageenan. Three kinds of Xiaotongcao(Ximashanjingjiehua, Xinanxiuqui2., Zhongguojinjiehua) had obvious diuretic effect on rats. CONCLUSION: Decoctions of different species of Tongcao and Xiao-tongcao all have anti-inflammatory, antipyretic and diuretic effects, thus providing some pharmacologic basis for the efficacy assay, clinical application, species collation and quality study of Tongcao and Xiao-tongcao.

Analgesics, Non-Narcotic↗
PubMed1998

[The reconstruction of mandible and soft tissue defects with the osteocutaneous free fibula flap].

OBJECTIVE: To find a new material to reconstruct the defects involving mandible and the surrounding soft tissues with the donor site morbidity mild and transient. METHODS: Ten consecutive fibula free flaps were used to reconstruct composite defect of mandible and soft tissue. The average length of the fibular graft was 9.1 cm, and the average size of the cutaneous-flap was 4.5 cm x 6.2 cm. RESULTS: 99mTcO4- scan demonstrated that 9 flaps were survivial (9/10) 2 weeks postsurgery. The function and the contour of the mandible were excellent. The donor site morbidity was mild and transient. CONCLUSION: Fibula has a high density of cortical bone. There is enough bone available to reconstruct mandible defect. The osteocutaneous fibula flap is a new material to reconstruct the composite mandible and soft tissue defects.

Adult↗
PubMed1998

[Preliminary studies on pharmacological actions of tongca and xiao-tongcao polysaccharides].

OBJECTIVE: To study and compare the immunologic function and antioxidative effect of Tongcao(Tongtuomu) and Xiao-Tongcao(Ximashanjingjiehua, Xinanxiuqiu, Ditanghua) polysaccharides. METHOD: Mice were abdominally administrated with four kinds of polysaccharides at dosages of 80 mg/kg and 40 mg/kg for 7-10 days. RESULT: Four kinds of polysaccharides could increase the serum-lysozyme activity, phagocytic function of MPS and the serum hemolysin-antibody level in mice, inhibit the delayed hypersensitivity induced by DNCB in mice and raise the serum-catalase activity in mice. CONCLUSION: Four kinds of Tongcao or Xiao-Tongcao polysaccharides have immunoregulative function and antioxidative effect. The results could enrich the contents of "A Study on Species-Sorting and Quality of Tongcao-Xiao-Tongcao Crude Drugs".

Adjuvants, Immunologic↗
PubMed1997

[Survey of botanical origin of tongcao (medulla Tetrapanacis) and identification of its commercial products].

Through the investigation on botanical origin, output and sales of Togcao in producing areas, it has been proved that there are twenty-two species of six families used as Tongcao. The medicinal parts are the pith of stems or petioles. The provinces featuring more species and larger output of Tongcao are Sichuan, Yunnan, Guizhou, Guangxi, Hunan and Shaanxi. A hundred and two pieces of commercial samples collected from twenty-six provinces in China, Hongkong area, Japan, Malaysia, Thailand, Singapore and Republic of Korea have been identified. The result shows that both Xiaotongcao and Datongcao are called by the same name Tongcao. The main species is Xiaotongcao, which takes a proportion of 70% in Tongcao. And the Tongcao(Tetrapanax papyriferus, taking a proportion of 20%) as recorded in the Chinese Pharmacopoeia (1995 edition) is seldom used.

China↗