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T Xu

Publications and source records attributed to T Xu.

At least 127 records · Page 7Linked to original sources
PubMed1995

The spinally mediated 10-Hz rhythm in the sympathetic nerve activity of cats.

To examine the origin of the so-called '10-Hz rhythm' in the sympathetic nerves, the mass discharges of the white ramus of the third thoracic segment (T3WR) and the inferior cardiac nerve (ICN) and the activities of single postganglionic neurons in the stellate ganglion were recorded in spinal cats. During the chemical or electrical stimulation of the spinal cord, the time of peak of discharges in the sympathetic nerves was analyzed. Both intrathecal administration of N-methyl-D-aspartic acid (NMDA; 3-10 mM) and continuous high frequency (80-200 Hz) electrical stimulation of the dorsolateral funiculus at the second cervical level increased activity of the sympathetic nerves in a similar fashion. In these conditions, modes of the inter-peak interval histograms (IPIH) were about 100 ms (range; 90-130 ms), the inverse of about 10 Hz, but no correlation was observed in autocorrelograms of these peaks of discharges. Therefore, this 100-ms interval activity might have some significance for the 10-Hz rhythm. In order to make this point clear, we stimulated the dorsolateral funiculus with intermittent trains of electrical pulses (0.2-ms duration, 10-35 pulses of 80-200 Hz frequency, in every 300-800 ms). While intermittent trains of pulses were applied, multiple peaks of discharges were evoked in the sympathetic nerves. IPIHs of the nerves were multimodal. The first mode (shortest interval) was about 100 ms. The first mode depended on none of the stimulus parameters but the probability of the about 100-ms interval activity depended on the interval of trains of pulses and the stimulus intensity. With this intermittent stimulation, the autocorrelogram of the peaks revealed the 100-ms interval rhythm. To confirm that the peak of discharges in the ICN was composed of synchronized spikes of postganglionic fibers, single neuronal activities of postganglionic neurons were recorded during the intermittent stimulation. Inter-spike interval histograms showed almost same profile as the IPIHs of the ICN. These results can be explained if the following two assumptions are valid; (i) There are mechanisms that limit minimum firing interval of most preganglionic neurons to about 100 ms. (ii) Simultaneously a interneuron in the spinal cord resets the spike generation of multiple preganglionic neurons. Similarity of the spike activities of the sympatho-excitatory reticulospinal neurons to the intermittent stimulation can explain the 10-Hz rhythm in the peripheral sympathetic nerves in intact spinal cord animals. It is not necessary to postulate the specific 10-Hz rhythm generator in the brain stem for the sympathetic nervous system.

Action Potentials↗
PubMed1995

Functional comparison of native and recombinant human salivary histatin 1.

Histatin 1 is a histidine-rich phosphoprotein present in human parotid saliva that possesses candidacidal activity and functions in mineralization by adsorbing to hydroxyapatite. The objective of the present study was to develop a system for recombinant production of histatin 1 and to examine the role of phosphorylation in the functional activities of this molecule. Native histatin 1 (containing a phosphoserine at residue 2) was purified from parotid saliva, whereas a bacterial expression system was used to produce a recombinant form of histatin 1 (re-Hst1) that lacked phosphorylated serine. Histatin 1 cDNA was inserted into the vector pGEX-3X, which expresses foreign genes as soluble fusion proteins attached to the carboxyl-terminus of glutathione S-transferase (GST). The GST/re-Hst1 fusion protein was isolated from cell lysates by affinity chromatography on glutathione (GSH)-Sepharose and digested with cyanogen bromide to separate re-Hst1 from the GST fusion partner. The digest was subjected to reversed-phase high-performance liquid chromatography on a C18 column, and re-Hst1 was eluted as a well-defined peak. The yield of re-Hst1 was 4 mg/L of bacterial culture. Amino-terminal sequencing and amino acid analysis confirmed the final product as re-Hst1. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that native histatin 1 and re-Hst1 had the same apparent molecular weights, while cationic PAGE showed that re-Hst1 was more basic. Phosphate analysis indicated 1 mol phosphate/mol of native histatin 1, while re-Hst1 lacked any detectable phosphate. Re-Hst1 demonstrated candidacidal activity comparable to that of native histatin 1, but displayed substantially lower binding to hydroxyapatite. These results show that phosphorylation of histatin 1 at residue 2 contributes significantly to its ability to bind to hydroxyapatite.

Antifungal Agents↗
PubMed1995

Identifying tumor suppressors in genetic mosaics: the Drosophila lats gene encodes a putative protein kinase.

We have identified recessive overproliferation mutations by screening and examining clones of mutant cells in genetic mosaics of the fruitfly Drosophila melanogaster. This type of screen provides a powerful approach for identifying and studying potential tumor suppressors. One of the identified genes, lats, has been cloned and encodes a putative protein kinase that shares high levels of sequence similarity with three proteins in budding yeast and Neurospora that are involved in regulation of the cell cycle and growth. Mutations in lats cause dramatic overproliferation phenotypes and various developmental defects in both mosaic animals and homozygous mutants.

Amino Acid Sequence↗
PubMed1995

[Lymphatic interventional radiology in the treatment of lymphatic neoplasmas].

We treated 22 cases of lymphatic neoplasma with chemotherapy via lymphatic ducts under the control of X-ray monitor, a method we called interventional trans-lymphatic chemotherapy. The method includes: (1) lymphography, (2) trans-lymphatic infusion with anticancer agents, (3) lavage of lymphatic vessel, (4) treatment of complications. Six cases of primary lymphoma and 16 cases of lymph-metastatic carcinoma were treated this way. The short-term results were excellent. Main symptoms and signs disappeared in 19 cases (19/22), and markedly improved in 2. X-ray features of 18 cases showed that enlarged lymph nodes returned to normal after the therapy. Follow-up for 28 months showed no recurrence.

Adult↗
PubMed1995

[The changing of orofacial structure by bite opening with Begg technique].

Cephalometric study of 30 deep-bite cases treated with extraction of four first premolars and Begg stage I appliance shows that the bite opening consists of not only intrusion of the upper and lower incisors but also extrusion of the upper and lower molars, furthermore, the lower incisors depressed more than the upper ones and the lower molars are elevated more than the upper ones. The moving type of teeth, the changing of base bone and soft tissue profile are also discussed in this article.

Adolescent↗
PubMed1995

Cholecystokinin octapeptide reverses mu-opioid-receptor-mediated inhibition of calcium current in rat dorsal root ganglion neurons.

Cholecystokinin octapeptide (CCK-8) is reported to antagonize the analgesic effect produced by mu- and kappa- but not delta-opioid agonist in spinal cord. However, the mechanisms of interaction remain obscure. In the present study, whole-cell patch-clamp recording was performed on acutely isolated rat dorsal root ganglion (DRG) neurons to evaluate the effects of the highly specific mu-opioid agonist ohmefentanyl and the delta-opioid agonist DPDPE on voltage-gated calcium channels and the possible interaction between CCK-8 receptor and mu- or delta-opioid receptor. The results indicated that ohmefentanyl, but not DPDPE, can suppress the voltage-gated calcium currents elicited in DRG neurons, an effect readily reversed by naloxone or by the antiopioid peptide CCK-8. The effect of CCK-8 can in turn be abolished by the CCK-B receptor antagonist L365,260. CCK-8 used by itself has no enhancing effect, but rather a depressant effect, on calcium currents. However, used simultaneously with ohmefentanyl, CCK-8 shows a clear-cut reversal of depression of the mu-opioid. We conclude that the depressant effect produced by mu-opioid on voltage-gated calcium current in DRG neurons can be antagonized by CCK-8 through CCK-B receptor located in the same neuron. The delta-opioid DPDPE has no direct effect on the voltage-gated calcium current in DRG neurons.

Animals↗
PubMed1995

[Influence of changing Ca++ concentration in neiguan (PC 6) on the effect of acupuncture treating experimental arrhythmia of rabbits].

We have made two kinds of experimental arrhythmia of rabbits by injecting aconitine and stimulating hypothalamus. Acupuncture could improve arrhythmia, after Ca++ in Neiguan (PC6) was chelated with EDTA solution the effect of acupuncturing Neiguan (PC6) was abolished. It indicates that Ca++ may be the key factor of acupuncture effect and one of the important material bases of the functional activity of meridians and collaterals.

Aconitine↗
PubMed1994

A member of the Notch group of interacting loci, deltex encodes a cytoplasmic basic protein.

Prior genetic studies have suggested a functional relationship between the product of the deltex gene and those of three of the so-called "neurogenic" loci, Notch, Delta and mastermind. To gain further insight into this relationship, we have proceeded with a molecular characterization of deltex. We report that deltex encodes a maternally and zygotically expressed transcript that conceptually translates to a basic protein of novel sequence. Immunolocalization of the protein reveals an apparently ubiquitous distribution in embryonic and imaginal tissues. Because our detection methods also reveal a very low level of protein accumulation within the cytoplasm of cells, we have used transgenic flies to confirm this observation by ectopically expressing deltex under the control of a heat shock gene promoter. The resulting overexpression rescues deltex mutant defects but does not produce any obvious phenotypic abnormalities in otherwise wild-type flies. Finally, we examine genetically several Supressor of deltex mutations for evidence of functional integration with deltex and other neurogenic genes. We demonstrate that in addition to suppressing all adult morphological defects of deltex alleles, these suppressors also are capable of suppressing most synergistic effects involving deltex and Notch, Delta and mastermind.

Amino Acid Sequence↗
PubMed1994

Physiological regulation of the secretion of histatins and statherins in human parotid saliva.

The small salivary phosphoproteins, histatins and statherins, have important functions in the oral cavity in terms of antimicrobial actions and regulation of calcium phosphate homeostasis. Neither the effects of various physiological stimuli on their secretion nor the nature of the efferent receptor involved in the stimulus-secretion coupling has been determined previously. These aspects are important for improved understanding of the secretory control of salivary proteins and may have implications regarding the effects of specific medications on salivary constituents and oral health. The effects of graded mechanical (chewing on short and long silicone tubings) and gustatory stimulation (0.5, 1.5, and 5.0% citric acid) on the secretion of histatins and statherins were studied in the presence and absence of adrenolytic agents (n = 10). In this model, secretory rates of both proteins increased with increases in flow rate, with 5.0% citric acid representing a particularly potent stimulus. Histatin and statherin secretory rates were significantly reduced by the beta 1-adrenolytic agent (histatins to 58 to 72% and statherins to 11 to 29% of that in corresponding control experiments), but not by the alpha 1-adrenolytic agent. Since the beta 1-adrenergic receptors played an important role in the stimulus-secretion coupling of these proteins, protective salivary functions in the oral cavity may be compromised during beta 1-adrenolytic treatment.

Adult↗
PubMed1993

Cholesterol trafficking in steroidogenic cells. Reversible cycloheximide-dependent accumulation of cholesterol in a pre-steroidogenic pool.

Peptide hormones activate steroid hormone biosynthesis in responsive tissues by stimulating the delivery of cholesterol to a steroidogenic pool, thought to be located in the inner mitochondrial membrane. At this site, it is metabolized to pregnenolone, the precursor of the steroid hormones, by side-chain-cleaving cytochrome P-450 (cytochrome P-450scc). In the presence aminoglutethimide (an inhibitor of cytochrome P-450scc) and an activating stimulus, cholesterol accumulates in the steroidogenic pool, and increased pregnenolone generation is observed upon removal of the inhibitor. Using Y-1 adrenocortical cells and MA-10 Leydig tumor cells, we now provide evidence for a distinct, functionally relevant cholesterol pool which precedes the steroidogenic pool, which we designate the pre-steroidogenic pool. This pool was defined by activating the cells with 8-bromo-adenosine 3',5'-cyclic monophosphoric acid in the presence of cycloheximide, an inhibitor of steroidogenesis. Following a wash procedure, which removed 8-bromo-adenosine 3',5'-cyclic monophosphoric acid and cycloheximide, augmented pregnenolone synthesis was observed. Unlike synthesis from the steroidogenic pool, pregnenolone formation from pre-steroidogenic pool in Y-1 cells indicates that this pool is somewhat smaller than the steroidogenic pool. The results support a cholesterol-trafficking model in which cycloheximide-sensitive transport from the pre-steroidogenic pool to the steroidogenic pool precedes metabolism, and is regulated by cAMP.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Effectiveness of functional ankle taping for judo athletes: a comparison between judo bandaging and taping.

This study was conducted to compare the effectiveness of the traditional method of ankle bandaging and the new method of ankle taping for judo athletes in Japan, and to introduce a functionally effective taping method for judo players. Four university judo athletes with ankle instability were selected to undertake radiography of the ankles before and after exercise, with bandaging at one time and taping at the other. Talar tilt (TT) angles were measured in order to compare the ankle-supporting effects. The results showed that the old ankle bandaging method had no role in eliminating the talar tilt during judo practice. In contrast, the new taping method was more effective in eliminating the talar tilt and supporting the involved ankles both mechanically and functionally.

Ankle Injuries↗
PubMed1993

Analysis of genetic mosaics in developing and adult Drosophila tissues.

We have constructed a series of strains to facilitate the generation and analysis of clones of genetically distinct cells in developing and adult tissues of Drosophila. Each of these strains carries an FRT element, the target for the yeast FLP recombinase, near the base of a major chromosome arm, as well as a gratuitous cell-autonomous marker. Novel markers that carry epitope tags and that are localized to either the cell nucleus or cell membrane have been generated. As a demonstration of how these strains can be used to study a particular gene, we have analyzed the developmental role of the Drosophila EGF receptor homolog. Moreover, we have shown that these strains can be utilized to identify new mutations in mosaic animals in an efficient and unbiased way, thereby providing an unprecedented opportunity to perform systematic genetic screens for mutations affecting many biological processes.

Animals↗
PubMed1993

[The influence of changing the Ca2+ concentration of the point quze (PC3) on the curative effect of puncturing neiguan (PC6) in experimental arrhythmic rabbits].

The experimental arrhythmic model was made with Aconitin in rabbits. The Neiguan (PC6) point was punctured to observe the influence on recovering time of arrhythmia. After the curative effect of puncturing Neiguan(P6) was confirmed, Ca2+ in the Quze (PC3) point of the Pericardium is chelated by EDTA solution to observe the influence on curative effect of arrhythmia by puncturing Neiguan. The result shows that the curative effect doesn't exist after the Ca2+ in Quze is chelated. It is probable that Ca2+ is one of the most important factors producing acupuncture effect. As a result, Ca2+ probably involves in the activities of channels and collaterals.

Aconitine↗
PubMed1993

[Effects of seeds, leaves and fruits of Ziziphus spinosa and jujuboside A on central nervous system function].

The seeds and leaves of Ziziphus Spinosa exert a similar inhibiting effect on central nervous system function, while the fruits have a synergism with pentobarbitol sodium and thiopental sodium on prolongation of sleep and sedation, also decreases coordinated action. Jujuboside A exerts no inhibiting effect, but a synergism with phenylalanine on central nervous system function.

Animals↗
PubMed1992

Involvement of opioid receptors in nucleus tractus solitarii in modulating endotoxic hypotension in rats.

Opioid antagonists selective for the mu-receptor (naltrexone) and kappa-receptor (nalmefene), respectively, were unilaterally microinjected into the nucleus tractus solitarii (NTS) of the pentobarbital anaesthetized (50 mg/kg, i.p.) rat subjected to E. coli endotoxin (15 mg/kg, i.v.). Naltrexone (0.5 microgram) ameliorated or totally abolished the endotoxic hypotension and tachycardia, and nalmefene at a dose of 1/25 (0.02 microgram) that of naltrexone showed a similar effect. The results suggest that the kappa- and mu-opioid receptors in NTS are actively involved in mediating the hypotensive and tachycardiac effects induced by systemic endotoxin in rats.

Animals↗
PubMed1992

Centrally acting endogenous hypotensive substances in rats subjected to endotoxic shock.

Cerebroventricular perfusate (CVP) from rats subjected to endotoxic shock was infused into the lateral ventricle of the naive rat. This procedure produced a hypotensive response in the recipient rat which could be reversed by the intravenous injection of the opioid antagonist naltrexone. The degree of endotoxemic hypotension in the donor rat was attenuated by perfusing the cerebroventricular system with mock CSF. The results suggest the existence of endogenous hypotensive substances in rat central nervous system, possibly opioid in nature, which may play a critical role in the pathogenesis of endotoxic shock.

Animals↗