Biomedical subjects

Z Q Xu

Publications and source records attributed to Z Q Xu.

At least 19 recordsLinked to original sources

PubMed2003

High-sensitivity capillary gel electrophoretic analysis of DNA fragments on an electrophoresis microchip using electrokinetic injection with transient isotachophoretic preconcentration.

The research adopted a single-channel microchip as the probe, and focused electrokinetic injection combined with transient isotachophoresis preconcentration technique on capillary electrophoresis microchip to improve the analytical sensitivity of DNA fragments. The channel length, channel width and channel depth of the used microchip were 40.5 mm, and 110 and 50 microm, respectively. The separation was detected by CCD (charge-coupled device) (effective length=25 mm, 260 nm). A 1/100 diluted sample (0.2 mg/l of each DNA fragment) of commercially available stepladder DNA sample could be baseline separated in 120 s with S/N=2-5. Compared with conventional chip gel electrophoresis, the proposed method is ideally suited to improve the sensitivity of DNA analysis by chip electrophoresis.

Buffers↗

PubMed2001

Effects of galanin receptor agonists on locus coeruleus neurons.

Galanin exerts an inhibitory effect on locus coeruleus (LC) neurons via a postsynaptic, as yet unidentified galanin receptor. Using an in vitro intracellular recording technique the effect of two galanin receptor agonists on LC neurons was investigated. Bath application of [Sar(1), D-Ala(12)]gal(1-16)-NH(2) (AR-M961), an agonist both at galanin R1 and R2 (GALR1, GALR2) receptors, evoked a reversible membrane hyperpolarization and inhibition of spike discharge in all LC neurons tested (n=42). The action of AR-M961 was blocked by tetraethylammonium chloride. Hyperpolarizing responses induced by AR-M961 were retained in the presence of tetrodotoxin and high Mg(2+)/low Ca(2+) media. The selective GALR2 agonist Gal(2-11)-NH(2) (AR-M1896) only caused inhibition of spike discharge and a slight hyperpolarization in 26 of 34 LC neurons tested, and was on a molar basis much weaker than AR-M961. These results suggest that it mainly is the GALR1 receptor that mediates hyperpolarization of LC neurons.

Action Potentials↗

PubMed2001

Suppressed kindling epileptogenesis in mice with ectopic overexpression of galanin.

The neuropeptide galanin has been shown to suppress epileptic seizures. In cortical and hippocampal areas, galanin is normally mainly expressed in noradrenergic afferents. We have generated a mouse overexpressing galanin in neurons under the platelet-derived growth factor B promoter. RIA and HPLC analysis revealed up to 8-fold higher levels of galanin in transgenic as compared with wild-type mice. Ectopic galanin overexpression was detected especially in dentate granule cells and hippocampal and cortical pyramidal neurons. Galanin-overexpressing mice showed retardation of seizure generalization during hippocampal kindling, a model for human complex partial epilepsy. The high levels of galanin in mossy fibers found in the transgenic mice were further increased after seizures. Frequency facilitation of field excitatory postsynaptic potentials, a form of short-term synaptic plasticity assessed in hippocampal slices, was reduced in mossy fiber-CA3 cell synapses of galanin-overexpressing mice, indicating suppressed glutamate release. This effect was reversed by application of the putative galanin receptor antagonist M35. These data provide evidence that ectopically overexpressed galanin can be released and dampen the development of epilepsy by means of receptor-mediated action, at least partly by reducing glutamate release from mossy fibers.

Animals↗

PubMed2001

Galanin enhances noradrenaline-induced outward current on locus coeruleus noradrenergic neurons.

Interactions between galanin and noradrenaline (NA) were studied in a locus coeruleus (LC) slice preparation using intracellular recording technique. Both galanin (10-100 nM) and NA induced an outward current. Idazoxan, an alpha2-adrenoceptor antagonist, blocked the NA- but not the galanin-induced outward current, indicating that different receptors mediate these responses. Moreover, the outward current induced by NA was enhanced and prolonged by preincubation with a low concentration of galanin (0.05-0.1 nM), which had no detectable effect on the membrane current by itself. This sensitizing effect may be of physiological importance and could be caused by galanin released from dendrites and soma of galanin/NA neurons and/or from galanin afferents. Thus, besides a direct action of galanin on locus coeruleus neurons, our results also indicate an indirect, modulating effect.

Adrenergic alpha-Agonists↗

PubMed2001

Effect of peripheral nerve injury on dorsal root ganglion neurons in the C57 BL/6J mouse: marked changes both in cell numbers and neuropeptide expression.

Several types of changes have been reported to occur in dorsal root ganglia following peripheral nerve injury, including loss of neurons and increases and decreases in peptide expression. However, with regard to loss of neurons, results have not been consistent, presumably due to different quantitative methodologies employed and species analyzed. So far, most studies have been conducted on rats; however, with the fast development of the transgenic techniques, the mouse has become a standard model animal in primary sensory research. Therefore we used stereological methods to determine the number of neurons, as well as the expression of galanin message-associated peptide, a marker for galanin-expressing neurons, neuropeptide Y, and calcitonin gene-related peptide in lumbar 5 dorsal root ganglia of both control C57 BL/6J mice and in mice subjected to a 'mid-thigh' sciatic nerve transection (axotomy). In control animals the total number of lumbar 5 dorsal root ganglion neurons was about 12000. Seven days after axotomy, 24% of the dorsal root ganglion neurons were lost (P<0.001), and 54% were lost 28 days after axotomy (P<0.001). With regard to the percentage of peptide-expressing neurons, the results obtained showed that both galanin message-associated peptide (from <1% to about 21%) and neuropeptide Y (from <1% to about 16%) are upregulated, whereas calcitonin gene-related peptide is downregulated (from about 41% to about 14%) following axotomy. Results obtained with retrograde labeling of the axotomized dorsal root ganglion neurons indicate that the neuropeptide regulations may be even more pronounced, if the analysis is confined to the axotomized dorsal root ganglion neurons rather than including the entire neuron population. We also applied conventional profile-based counting methods to compare with the stereological data and, although the results were comparable considering the trends of changes following axotomy, the actual percentage obtained with the two methods differed markedly, both for neuropeptide Y- and, especially, for galanin message-associated peptide-positive neurons. These present results demonstrate that marked species differences exist with regard to the effect of nerve injury on dorsal root ganglion neurons. Thus, whereas no neuron loss is seen in rat up to 4 weeks after a 'mid-thigh' transection [Tandrup et al. (2000) J. Comp. Neurol. 422, 172-180], the present results indicate a dramatic loss already after 1 week in mouse. It is suggested that the proximity in physical distance of the lesion to the cell body is a critical factor for the survival of the target-deprived neurons. Finally, stereological methodology seems warranted when assessing the total number of neurons as well as changes in peptide regulations after axotomy in mouse.

Animals↗

PubMed2001

Dopamine D(2) receptors regulate tyrosine hydroxylase activity and phosphorylation at Ser40 in rat striatum.

In the striatum, dopamine release is inhibited by activation of dopamine D(2) autoreceptors. Changes in dopamine release have been attributed to changes in the synthesis of dopamine, which is regulated via phosphorylation of tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamines. Here, we have studied the involvement of dopamine D(2) receptors in the regulation of TH phosphorylation at distinct seryl residues, using phosphorylation site-specific antibodies and a preparation of rat striatal slices. The D(2) receptor agonist, quinpirole, reduced basal TH phosphorylation at Ser40 but not at Ser19 or Ser31. Quinpirole was also able to reduce the increase in Ser40 phosphorylation caused by forskolin, an activator of adenylyl cyclase, without affecting the increase in Ser19 phosphorylation produced by the glutamate receptor agonist, N-methyl-D-aspartate (NMDA). In addition, the dopamine D(2) receptor agonist reduced both basal and forskolin-stimulated activity of TH, measured as 3,4-dihydroxyphenylalanine (DOPA) accumulation. Quinpirole decreased phosphorylation of Ser40 induced by okadaic acid, an inhibitor of protein phosphatase 1 and 2A and Ro-20-1724, a phosphodiesterase inhibitor. In contrast, quinpirole did not affect the increase in Ser40 phosphorylation caused by the cAMP analogue, 8-Br-cAMP. These data indicate that, in the striatum, activation of dopamine D(2) receptors results in selective inhibition of TH phosphorylation at Ser40 via reduction of the activity of adenylyl cyclase. They also provide a molecular mechanism accounting for the ability of dopamine D(2) autoreceptors to inhibit dopamine synthesis and release from nigrostriatal nerve terminals.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2001

Safety and pharmacokinetics of single doses of (+)-calanolide a, a novel, naturally occurring nonnucleoside reverse transcriptase inhibitor, in healthy, human immunodeficiency virus-negative human subjects.

(+)-Calanolide A is a novel, naturally occurring, nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase first isolated from a tropical tree (Calophyllum lanigerum) in the Malaysian rain forest. Previous studies have demonstrated that (+)-calanolide A has specific activity against the reverse transcriptase of HIV-1 and a favorable safety profile in animals. In addition, (+)-calanolide A exhibits a unique HIV-1 resistance profile in vitro. The safety and pharmacokinetics of (+)-calanolide A was examined in four successive single-dose cohorts (200, 400, 600, and 800 mg) in healthy, HIV-negative volunteers. In this initial phase I study, the toxicity of (+)-calanolide A was minimal in the 47 subjects treated. Dizziness, taste perversion, headache, eructation, and nausea were the most frequently reported adverse events. These events were not all judged to be related to study medication nor were they dose related. While 51% of subjects reported mild and transient dizziness, in many cases this appeared to be temporally related to phlebotomy. Calculation of the terminal-phase half-life (t(1/2)) was precluded by intrasubject variability in the 200-, 400-, and 600-mg dose cohorts but was approximately 20 h for the 800-mg dose group. (+)-Calanolide A was rapidly absorbed following administration, with time to maximum concentration of drug in plasma (T(max)) values occurring between 2.4 and 5.2 h postdosing depending on the dose. Plasma levels of (+)-calanolide A at all dosing levels were quite variable; however, both the mean concentration in plasma (C(max)), and the area under the plasma concentration-time curve increased proportionately in relation to the dose. Although raw plasma drug levels were higher in women than in men, when doses were normalized for body mass, the pharmacokinetic profiles were virtually identical with those observed for males. In general, levels of (+)-calanolide A in human plasma were higher than would have been predicted from animal studies, yet the safety profile remained benign. In conclusion, this study demonstrated the safety and favorable pharmacokinetic profile of single doses of (+)-calanolide A in healthy, HIV-negative individuals.

Adolescent↗

PubMed2001

Pressure assessment in intercavernous embedding of bulboperineal urethra for treatment of urinary incontinence after prostatic operation.

AIM: To put forward criteria for the pressure assessment in the operation of intercavernous embedding of bulboperineal urethra for the treatment of urinary incontinence after prostatic operation. METHODS: A F14 urethral catheter is inserted during the operation and upon suturing the corpora cavemosa centrally, the catheter is slowly pushed in and pulled out in order that the operator feels a certain degree of close-fit resistance. The degree of tightness of the stitches, which regulate the compression pressure, is adjusted in accordance with this close-fit sensation. To further ascertain the adequacy of the force of compression, the bladder is filled with 300 ml physiological saline and observe the appropriateness (size and continuity) of the outflow stream when the lower abdomen is depressed with a pressure of 80-90 cm H2O. The operation was given to six patients suffered from urinary incontinence for 20 or more months after prostatic operation. RESULTS: Five cases achieved complete recovery, while the therapeutic effect of the 6th one was not satisfactory. A second stage operation was carried out 3 months later with the addition of one more stitch both proximally and distally to reinforce the compression force. The condition was improved dramatically. The follow-up period averaged 3.5 years. CONCLUSION: The adequacy of the compression pressure exerted by the juxtaposed corpora cavernosa is the key point determining the outcome of the operation. The measures for assessing the compression pressure suggested by the authors are helpful in obtaining the good results of the present paper (6/6 success) as compared with 25/34 success in the previous report.

Aged↗

PubMed2001

[Effects of the physical configuration of plasmid DNA and other factors on production of fertile transgenic wheat plants].

The applicability of hyperosmotic treatment and different configurations of plasmid DNA for stable transformation of wheat mediated by particle bombardment was investigated. Hyperosmotic treatment increased the frequency of transient expression and had also a positive effect on stable transformation. Denaturation of plasmid DNA prior to bombardment led to dramatic reduction of transient expression. However, there were no marked differences between single-stranded and double-stranded DNA in stable transformation. Single-stranded plasmid DNA, double-stranded plasmid DNA in linear state and double-stranded plasmid DNA in circular state could all be used to produce transgenic wheat plants. A total of 26 independent transgenic plants of winter wheat genotype Florida and 4 independent transgenic plants of spring wheat genotype Veery were obtained. Most transgenic plants have set seeds. T2 seeds of some spring wheat transgenic plants have also been harvested.

Aminobutyrates↗

PubMed2000

Fatty acids and beta-carotene in australian purslane (Portulaca oleracea) varieties.

The fatty acid profile and beta-carotene content of a number of Australian varieties of purslane (Portulaca oleracea) were determined by GC and HPLC. The total fatty acid content ranged from 1.5 to 2.5 mg/g of fresh mass in leaves, 0.6 to 0.9 mg/g in stems and 80 to 170 mg/g in seeds. alpha-Linolenic acid (C18:3omega3) accounted for around 60% and 40% of the total fatty acid content in leaves and seeds, respectively. Longer-chain omega-3 fatty acids were not detected. The beta-carotene content ranged from 22 to 30 mg/g fresh mass in leaves. These results indicate that Australian purslane varieties are a rich source of alpha-linolenic acid and beta-carotene.

Chromatography, Gas↗

PubMed2000

Quantification of (+)-calanolide A, a novel and naturally occurring anti-HIV agent, by high-performance liquid chromatography in plasma from rat, dog and human.

A HPLC method was validated for quantification of (+)-calanolide A (1), a novel anti-HIV agent, in rat, dog and human plasma. The synthetic intermediate (+/-)-12-oxocalanolide A (2) was found to be a suitable internal standard. Compounds were extracted from plasma using a solid-phase C(18) cartridge and quantified over the assay range of 12.5 to 800 ng/ml. The method was utilized to determine (+)-calanolide A pharmacokinetics in rats, dogs and humans. This is the first report of a validated HPLC assay for determination of (+)-calanolide A concentrations in rat and dog plasma as well as human plasma obtained from clinical trials. There was no evidence of in vivo epimerization of (+)-calanolide A to its inactive epimer (+)-calanolide B (3).

Administration, Oral↗

PubMed2000

Neuropeptides--an overview.

The present article provides a brief overview of various aspects on neuropeptides, emphasizing their multitude and their wide distribution in both the peripheral and central nervous system. Interestingly, neuropeptides are also expressed in various types of glial cells under normal and experimental conditions. The recent identification of, often multiple, receptor subtypes for each peptide, as well as the development of peptide antagonists, have provided an experimental framework to explore functional roles of neuropeptides. A characteristic of neuropeptides is the plasticity in their expression, reflecting the fact that release has to be compensated by de novo synthesis at the cell body level. In several systems peptides can be expressed at very low levels normally but are upregulated in response to, for example, nerve injury. The fact that neuropeptides virtually always coexist with one or more classic transmitters suggests that they are involved in modulatory processes and probably in many other types of functions, for example exerting trophic effects. Recent studies employing transgene technology have provided some information on their functional role, although compensatory mechanisms in all probability could disguise even a well defined action. It has been recognized that both 'old' and newly discovered peptides may be involved in the regulation of food intake. Recently the first disease-related mutation in a peptidergic system has been identified, and clinical efficacy of a substance P antagonist for treatment of depression has been reported. Taken together it seems that peptides may play a role particularly when the nervous system is stressed, challenged or afflicted by disease, and that peptidergic systems may, therefore, be targets for novel therapeutic strategies.

Animals↗

PubMed2000

Inhibition of the 26S proteasome induces expression of GLCLC, the catalytic subunit for gamma-glutamylcysteine synthetase.

The majority of short- and long-lived cellular proteins are degraded by the activities of the 26S proteasome, a large multi-catalytic protease. Its unique function places it as a central regulatory activity for many important physiological processes. Lactacystin is a very specific 26S proteasome inhibitor and represents an excellent tool for demonstrating that a pathway exhibits proteasome-dependent biochemical regulation. Exposure of HepG2 cells to lactacystin resulted in robust elevation of GLCLC mRNA levels, followed by an increase in GSH concentrations. GLCLC is the gene that encodes the catalytic subunit for gamma-glutamylcysteine synthetase, the rate-limiting enzyme for the synthesis of glutathione (GSH). Inhibition of non-proteasome, protease activities did not induce GLCLC. Gel mobility shift assays and expression of CAT activity from heterologous reporter vectors identified Nrf2 mediation of the GLCLC antioxidant response element, ARE4, as the mechanism by which lactacystin induced GLCLC. These studies have identified 26S proteasome activity as a central regulatory pathway for glutathione synthesis.

Acetylcysteine↗

PubMed2000

Regulation of tyrosine hydroxylase activity and phosphorylation at Ser(19) and Ser(40) via activation of glutamate NMDA receptors in rat striatum.

The activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine, is stimulated by phosphorylation. In this study, we examined the effects of activation of NMDA receptors on the state of phosphorylation and activity of tyrosine hydroxylase in rat striatal slices. NMDA produced a time-and concentration-dependent increase in the levels of phospho-Ser(19)-tyrosine hydroxylase in nigrostriatal nerve terminals. This increase was not associated with any changes in the basal activity of tyrosine hydroxylase, measured as DOPA accumulation. Forskolin, an activator of adenylyl cyclase, stimulated tyrosine hydroxylase phosphorylation at Ser(40) and caused a significant increase in DOPA accumulation. NMDA reduced forskolin-mediated increases in both Ser(40) phosphorylation and DOPA accumulation. In addition, NMDA reduced the increase in phospho-Ser(40)-tyrosine hydroxylase produced by okadaic acid, an inhibitor of protein phosphatase 1 and 2A, but not by a cyclic AMP analogue, 8-bromo-cyclic AMP. These results indicate that, in the striatum, glutamate decreases tyrosine hydroxylase phosphorylation at Ser(40) via activation of NMDA receptors by reducing cyclic AMP production. They also provide a mechanism for the demonstrated ability of NMDA to decrease tyrosine hydroxylase activity and dopamine synthesis.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

Plant-derived and semi-synthetic calanolide compounds with in vitro activity against both human immunodeficiency virus type 1 and human cytomegalovirus.

Plant-derived and semi-synthetic calanolide compounds with anti-human immunodeficiency virus type 1 (HIV-1) activity were tested for anti-human cytomegalovirus (HCMV) activity in both cytopathic effect inhibition and plaque reduction assays. The results indicated that the anti-HCMV activity of calanolide compounds does not correlate with their activity against HIV-1. The semi-synthetic 12-keto derivatives tended to be more active against HCMV than the corresponding 12-OH congeners, which were more active against HIV-1. It appeared that the 7,8-unsaturated double bond in the chromene ring played a certain role in maintaining activities against both HCMV and HIV-1. Saturation of the double bond increased the EC50 values against both viruses, with concomitant increase in toxicity. The calanolide compounds reported here are the first non-nucleoside analogues capable of inhibiting both HIV-1 and HCMV and, therefore, may be useful chemoprophylactic agents for HCMV in HIV-infected people or vice versa.

Anti-HIV Agents↗

PubMed2000

Anti-HIV-1 activity of calanolides used in combination with other mechanistically diverse inhibitors of HIV-1 replication.

The natural product (+)-calanolide A, a unique non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1 replication, is currently being evaluated in clinical trials in the USA. (+)-Calanolide A, the congeners costatolide and dihydrocostatolide, and (+)-12-oxo(+)-calanolide A, were evaluated in combination with a variety of mechanically diverse inhibitors of HIV replication to define the efficacy and cellular toxicity of potential clinical drug combinations. These assays should be useful in prioritizing the use of different combination drug strategies in a clinical setting. The calanolides exhibited synergistic antiviral interactions with other nucleoside and non-nucleoside reverse transcriptase inhibitors and protease inhibitors. Additive interactions were also observed when the calanolides were used with representative compounds from each of these classes of inhibitors. No evidence of either combination toxicity or antagonistic antiviral activity was detected with any of the tested compounds. The combination antiviral efficacy of three-drug combinations involving the calanolides, and the efficacy of two- and three-drug combinations using a (+)-calanolide A-resistant challenge virus (bearing the T139I amino acid change in the reverse transcriptase), was also evaluated in vitro. These assays suggest that the best combination of agents based on in vitro anti-HIV assay results would include the calanolides in combination with lamivudine and nelfinavir, since this was the only three-drug combination exhibiting a significant level of synergy. Combination assays with the (+)-calanolide A-resistant strain yielded identical results as seen with the wild-type virus, although the concentration of the calanolides had to be increased.

Antiviral Agents↗

PubMed2000

[Molecular identification of intergeneric somatic hybrid plants between alfalfa and sainfoin].

Somatic hybrid plants between alfalfa and sainfoin were regenerated by protoplast fusion and culture. DNA samples of the hybrid plants, hydroxyproline-resistant sainfoin plants, alfalfa cell line transformed with Agrobacterium tumefaciens 702 were isolated with a new and simple method. The hybridity was identified by random amplified polymorphic DNAs and Southern hybridization. Significant differences can be seen in the sequences amplified, which are specific for each parent/primer combination under the amplification conditions used. In 20 random oligonucleotide primers used, six could amplified more DNA fragments and had better polymorphisms. The results suggested that besides containing nuclear substances of two parents, the hybrid genome was inclined to eliminate sainfoin chromosome with DNA reconstruction. However, the somatic genome also could produce the sainfoin-specified DNA fragments which further confirmed by Southern hybridization. The hybrids were asymmetric and had certain regeneration ability just because the intervention of sainfoin DNA.

Blotting, Southern↗

PubMed2000

[Immunologic histochemical observation of anti-crypt keratin of cryptic epithelium of tonsilla in children with chronic tonsillitis].

OBJECTIVE: To investigate anti-crypt keratin (CK) immunologic histochemical changes in children with chronic tonsillitis. METHOD: Removed tonsilla were fixed by 10% formaldehyde. Immunologic histochemical method was used to determine the changes of anti-broad spectrum (KD 68, 56, 56, 50) CKSP. RESULT: In 230 cases, obvious keratosis was 90.9%, no keratosis was 9.1%, 3 cases were found with fungus filaments and bacteria in the bottom of crypts. Anti-broad spectrum and hypermolecule CK of tonsil cryptic epithelium were positive reaction, anti-broad spectrum CK of cryptic keratosis in all cases was positive reaction. CONCLUSION: During the period of episode, cryptic epitheliums of tonsilla was destroyed repeatly, therefore, immunoglobulin production was reduce. Because the immune function of tonsilla was reduced, bacteria and virus might be invade into organism. This reduplicative malignant circles must be interrupted or blocked only by tonsillectomy.

Adolescent↗