PubMed Health⌕ Search

Biomedical subjects

X Ma

Publications and source records attributed to X Ma.

At least 19 recordsLinked to original sources
PubMed1992

Protein tyrosine phosphorylation as an indicator of 2,3,7,8-tetrachloro-p-dioxin exposure in vivo and in vitro.

A dose-dependent increase in tyrosine phosphorylation of five hepatic intracellular proteins with approximate molecular weights of 17, 21, 27, 29, and 34 kDa was seen 24 h after administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to C57BL/6J female mice. The ED50 values for tyrosylphosphorylation of these five proteins, respectively, were 0.26, 0.21, 0.26, 0.31, and 0.38 micrograms TCDD/Kg. TCDD induction of 7-ethoxyresorufin O-deethylase activity (EROD) was characterized by an ED50 of 2.5 micrograms/Kg. An eighteen h exposure of a human lymphoblastoma cell line (X3) to TCDD increased tyrosylphosphorylation status of ten proteins with approximate molecular weights of 16, 17, 24, 26, 27, 32, 33, 34, 35, and 36 kDa in a dose-dependent manner. The EC50 values for these TCDD-dependent tyrosylphosphorylation ranged from 0.01 to 0.07 nM TCDD. EROD induction by TCDD in X3 cells exhibited an EC50 of 0.14 nM. These data indicate that TCDD alters intracellular protein tyrosine phosphorylation and these changes are more sensitive biological indicators of TCDD exposure than induction of EROD.

Animals↗
PubMed1992

Urinary catecholamine excretion and severity of PTSD symptoms in Vietnam combat veterans.

In the present study, we replicated and extended our previous findings of increased 24-hour urinary catecholamine excretion in posttraumatic stress disorder (PTSD). Dopamine, norepinephrine, and epinephrine concentrations were measured in 22 male patients with PTSD (14 inpatients and eight outpatients) and in 16 nonpsychiatric normal males. The PTSD inpatients showed significantly higher excretion of all three catecholamines compared with both outpatients with PTSD and normal controls. Dopamine and norepinephrine, but not epinephrine, levels were significantly correlated with severity of PTSD symptoms in the PTSD group as a whole. In particular, these catecholamines seemed related to intrusive symptoms. None of the catecholamines were correlated with severity of depression. The findings support the hypothesis of an enhanced sympathetic nervous system activation in PTSD, and suggest that increased sympathetic arousal may be closely linked to severity of certain PTSD symptom clusters.

Ambulatory Care↗
PubMed1992

Sequence comparison of the capsid region of hepatitis E viruses isolated from Myanmar and China.

Hepatitis E viruses (HEVs) were isolated during epidemics, one from Myanmar (formerly called Burma) and one from China and were partially sequenced. Another HEV Myanmar strain from sporadic hepatitis was previously sequenced by us. A cDNA sequence comparison was performed among them in the 3'-terminal region, approximately 750-base long. This region contained at least two immunological epitopes and was considered to correspond to the structural protein. The nucleotide sequence identity was 97.2% between the two Myanmar strains and 93.3 and 92.5% between the two Myanmar and the China strain. The deduced amino acid sequence identity ranged from 98.4 to 100.0% among the three strains. Thus this segment was well conserved on the amino acid level among the different strains isolated from these two Asian countries, although the China strain diverged more from the Myanmar strains on the nucleotide sequence level. This data may provide important information for the development of a vaccine and for identification of the virological link between different geographical locations.

Amino Acid Sequence↗
PubMed1992

Numerical simulation for the propagation of nonlinear pulsatile waves in arteries.

The behavior of nonlinear pulsatile flow of incompressible blood contained in an elastic tube is examined. The theory takes into account the nonlinear convective terms of the Navier-Stokes equations. The motion of the arterial wall is characterized by a set of linearized differential equations. The region bounded by the flexible arterial wall is mapped into a fixed area in which numerical discretization takes place. The finite element method (Galerkin weighted residual approach) is used for the solution of this nonlinear system. The results obtained are pressure distribution, velocity profile, flow rate and wall displacements along the elastic tube (20 cm long).

Blood Flow Velocity↗
PubMed1992

Intracellular potentials of visceronociceptive neurons in posterior group of thalamic nuclei and its labeling with HRP intracellularly in cat.

The intracellular potentials (ICP) of 42 visceronociceptive neurons related to stimulating greater splanchnic nerve (SPL) in Posterior group of thalamic nuclei (PO) were investigated. We analyzed the electrophysiological features, such as amplitude of resting potentials and action potentials of the neurons. Following acquisition of electrophysiological data, (HRP) was injected into 3 neurons, whose responses were inducted by stimulating SPL (related neurons) and able to be inhibited by morphine intravenously. Two neurons revealing spontaneous discharges but are not able to evoke response by stimulating SPL (non-related neurons), also were stained by HRP. Two kinds of neurons, related and non-related ones, display different dendrite branching patterns.

Action Potentials↗
PubMed1992

[Mechanisms of protective action of radix Salviae miltiorrhizae (RSM) against experimental hepatic injury in rats].

The results indicated that RSM could significantly inhibit the lipid peroxidation of normal livers and cultured hepatocytes of rats, induce liver microsomal cytochrome P450 in normal rats, increase nucleic acids, proteins, urea and cerolloplasmin of damaged cultured hepatocytes of rats, relieve ultrastructural damage of cultured hepatocytes induced by CCl4. The pharmacological actions mentioned above should be considered as important mechanisms of RSM against liver injury.

Animals↗
PubMed1992

[The variations of PRL, LH, FSH and testosterone in renal disease].

Blood PRL was measured with RIA in 22 males and 19 females with various degrees of renal insufficiency. At the same time, blood LH, FSH, testosterone were studied in all the male patients and 20 sex-age matched healthy subjects. The results showed that the levels of PRL and LH were increased, and the level of testosterone was decreased significantly in male uremic patients. There was a significant negative correlation between PRL and testosterone. All the above parameters were measured again 8-25 days after continuous ambulatory peritoneal dialysis (CAPD) therapy in 5 male uremic patients. The BUN and Cr levels decreased and the clinical manifestations of uremia improved, but the levels of PRL, LH, FSH and testosterone showed no significant changes. The mechanisms of these variations were discussed.

Adolescent↗
PubMed1992

[X-ray diffraction studies on tolbutamide solid dispersion].

D860 (tolbutamide) solid dispersions prepared with urea, polyvinyl pyrrolidone (PVP), and polyethylene glycal (PEG) 6000 as carriers were studied by X-ray diffraction, relating to their dissolution rates. D860 in D860-PVP dispersion was shown to be in an amorphous state and to have greater dissolution rate. D860-urea and D860-PEG melts were found to be partly in miscible solid solution state and partly in microcrystal state and possess higher activity and greater dissolution rate. D860-PEG coprecipitate was a physical mixture and its dissolution rate is slower than its melt. No variation in the crystal structure of the D860 dispersions was observed during the ageing test.

Drug Carriers↗
PubMed1992

[Effect of ribosome binding site sequence on the expression level of HBcAg in E. coli].

The recombinant (pKL series) Plasmids showing different levels of HBcAg antigenicity in ELISA were constructed by inserting the HBcAg gene which was randomly deleted at the non-coding region by Bal-31 exonuclease into plasmid vector pKK223-3 containing tac promoter and SD sequence. SDS-PAGE and Western blot experiments indicated that molecular weight of the HBcAg protein generated by these positive clones was 21000D. Three plasmids with high, moderate and low HBcAg expression level were sequenced and the distance between SD sequence and HBcAg gene ATG codon was 12, 13 and 19bp respectively. Computer analysis of secondary structure of the ribosome binding sites on RNA transcripts also revealed energy and structure differences between the low and high level expression plasmids, suggesting the importance of this distance and the mRNA structure to gene expression.

Base Sequence↗
PubMed1991

An MRI perfusion model incorporating nonequilibrium exchange between vascular and extravascular compartments.

A model of MRI signal intensity which is a function of perfusion is developed based upon the assumption that biological tissue can be represented by a blood and tissue compartment. The longitudinal magnetization is derived from the Bloch equations which are modified to model the magnetization in both the blood and tissue as a function of the following physiological parameters: blood flow velocity; perfusion fraction, which in the model is parameterized in terms of the ratio of the cross-sectional areas of the tissue and blood compartments; diffusion; rate of exchange between the blood and extravascular tissue compartments. Simulations of slice profiles excited by a repetitive sequence of 90 degrees slice-selective pulses show that the signal intensity in the blood and tissue compartments are modulated by the physiological parameters. A key factor in the modulation of the MRI signal is a time-of-flight effect whereby unexcited spins perfuse the excited region and exchange with blood and tissue compartments, thus immediately increasing the slice signal intensity but also delaying the spin exits from the slice, thereby decreasing their contribution to slice signal intensity in future repetitive pulse measurements.

Blood Flow Velocity↗
PubMed1991

[Preliminary study on soilless cultivation techniques of Panax quinquefolium L].

Our experiment has shown 1. Vermiculite with sand (volume 1:1) is a good substrate of soil for American Ginseng. The yield and contents of ginsenoside of American ginseng in this soilless substrate are a little higher than those in ordinary soil. 2. This kind of substrate can be used continuously with fewer occurrences of insect pest and plant diseases and contributes significantly to the reduction of production cost.

Ginsenosides↗
PubMed1991

[The preservation capacity of water and fertility of soilless cultivation substrate for Panax quinquefolium L.)].

The preservation capacity of water and fertility of several soilless cultivation substrates for Panax quinquefolium was compared in a large area. The data indicate that vermiculite mixed with sand (volume 1:1) is the most suitable soilless substrate for P. quinquefolium, for it is loose and features good preservation of fertility, water retaining, drainage, and air permeability. Timely analysis of nutrient contents in the substrates during cultivating period may serve as a guideline for correct application of fertilizer.

Panax↗
PubMed1991

[Effects of stimulating periaqueductal gray on the nociceptive neuron discharges of post-thalamic nucleus evoked by stimulation of splanchnic nerve in cats].

The effects of stimulating periaqueductal gray (PAG) on the nociceptive neuron discharges of pronucleus evoked by stimulating the splanchnic nerve in cats were studied. The two kinds of inhibitory action were observed. One was called early phase or prompt inhibition phase which occurred within 30 ms to 150 ms after stimulation of PAG. The other was called slow-pase or sustained inhibition which occurred from a few minutes to more than ten minutes after the stimulation of PAG. The results showed that PAG played an important role in the analgesia of visceral pain. Both kinds of inhibition may be blocked by naloxone, this suggests that endogenous opiate like substances involved in these inhibitory processes caused by stimulating role in the inhibitory effect of PAG.

Animals↗
PubMed1991

Pylorus and antroseromuscular flap-preserving gastrectomy--a new type of reconstruction after subtotal gastrectomy for treatment of gastroduodenal ulcer: clinical and experimental study.

To avoid motility disturbances after Billroth gastrectomy, the authors designed pylorus and antroseromuscular flap-preserving subtotal gastrectomy (PAFPG). Results showed that gastric motility and emptying time of dogs after PAFPG were close to normal. PAFPG was applied to 125 consecutive patients with gastroduodenal ulcers (gastric ulcer, 15 patients; duodenal ulcer, 94 patients; and combined ulcers, 16 patients) confirmed by barium examination and fibro-gastroendoscopy. All patients recovered smoothly, none of them had postoperative complication. Gastric acid output reduction rates were as follows: basal acid output, 85.05% +/- 8.13%; maximal acid output, 81.76% +/- 10.85%; peak acid output, 81.42% +/- 10.15%. The incidence of postoperative enterogastric reflux (endoscopically) and the concentration of cholic acids in gastric juice were significantly lower in patients after PAFPG than after Billroth I or II gastrectomy. Results suggest that PAFPG reduced gastric acid outputs definitely and overcame adverse motility consequences after Billroth I or II gastrectomy desirably.

Animals↗