Biomedical subjects

Y X Tao

Publications and source records attributed to Y X Tao.

At least 19 recordsLinked to original sources

PubMed2002

LC-MS determination of urinary toluenediamine in workers exposed to toluenediisocyanate.

To improve the biological monitoring method for 2,6- and 2,4-toluenediisocyanate (TDI) exposure, we developed a simple and rapid method for analysis of the corresponding urinary metabolites, 2,6- and 2,4-toluenediamine (TDA) using liquid chromatograph-mass spectrometry (LC-MS). One ml of urine was hydrolyzed at 100 degrees C for 1.5 h with H(2)SO(4). Alkalinized hydrolysate was extracted with dichloromethane (DCM) and analyzed by atmospheric pressure chemical ionization (APCI) LC-MS, in positive-ion mode. The mass spectra of TDA isomers showed the protonated molecule [M+H](+), at m/z 123 as the base peak. Calibration curves of 2,6-TDA were linear up to 400 microg/l. TDA isomers in urine of exposed workers as determined by LC-MS correlated well with those obtained by gas chromatography-mass spectrometry. 2,6- and 2,4-TDA were not detected in non-exposed subjects, whereas exposed workers showed urinary levels up to 250 and 63 microg/l, respectively.

Chromatography, Liquid↗

PubMed2001

Knockdown of PSD-95/SAP90 delays the development of neuropathic pain in rats.

Our previous work has shown that PSD-95/SAP90 is required for NMDA receptor-mediated thermal hyperalgesia. To address the role of PSD-95/SAP90 in chronic pain, the present study investigated the effect of the deficiency of PSD-95/SAP90 on nerve injury-induced neuropathic pain. Following unilateral L5 spinal nerve injury, mechanical and thermal hyperalgesia developed within 3 days and persisted for 9 days or longer on the injured side. The intrathecal administration of antisense oligodeoxynucleotide specifically against PSD-95/SAP90, but not sense or missense oligodeoxynucleotide, dose-dependently delayed the onset of tactile allodynia and thermal hyperalgesia. These results suggest that PSD-95/SAP90 might be involved in the central mechanisms of the development of chronic neuropathic pain.

Animals↗

PubMed2001

Effect of the deficiency of spinal PSD-95/SAP90 on the minimum alveolar anesthetic concentration of isoflurane in rats.

BACKGROUND: Spinal N-methyl-D-aspartate (NMDA) receptor activation has been demonstrated to play an important role in the processing of spinal nociceptive information and in the determination of the minimum alveolar anesthetic concentration (MAC) of inhalational anesthetics. Postsynaptic density-95 (PSD-95)/synapse-associated protein-90 (SAP90), a molecular scaffolding protein that binds and clusters the NMDA receptor perferentially at synapses, was implicated in NMDA-induced thermal hyperalgesia. The current study investigated the possible involvement of PSD-95/SAP9O in determining MAC for isoflurane anesthesia. METHODS: Sprague-Dawley rats were pretreated intrathecally with PSD-95/SAP90 antisense oligodeoxyribonucleotide (ODN), sense ODN, missense ODN, or saline every 24 h for 4 days. After initial baseline determination of the MAC, NMDA or saline was injected intrathecally. Ten minutes later, MAC measurement was repeated. The rats also were evaluated for the presence of locomotor dysfunction by intrathecal administration of NMDA or saline in the saline- and ODN-treated rats. RESULTS: In the groups treated with antisense ODNs, but not in those treated with sense or missense ODNs, there was a significant decrease in isoflurane MAC that was not accompanied by marked changes in either blood pressure or heart rate. In the saline-treated group, intrathecal NMDA caused an increase in isoflurane MAC. In contrast, in the antisense ODN-treated group, intrathecal NMDA did not produce a significant change in isoflurane MAC. An NMDA-induced increase in blood pressure but not heart rate was found in both saline- and antisense ODN-treated groups. Locomotor activity was not changed in any of the treated animals. CONCLUSION: The results indicate not only a significant decrease in MAC for isoflurane but also an attenuation in the NMDA-induced increase in isoflurane MAC in the PSD-95/SAP90 antisense-treated animals, which suggests that PSD-95/SAP90 may mediate the role of the NMDA receptor in determining the MAC of inhalational anesthetics.

Anesthetics, Inhalation↗

PubMed2000

Synaptic relationship of the neurons containing a metabotropic glutamate receptor, MGluR5, with nociceptive primary afferent and GABAergic terminals in rat spinal superficial laminae.

Recent pharmacological evidence showed that metabotropic glutamate receptors (mGluRs), particularly mGluRs1/5, had a potential role in spinal nociceptive processing. However, previous morphological studies on mGluRs have been limited mainly to their distribution in the spinal cord. In the present study, electron microscopic immunocytochemistry was employed to identify the synaptic relationship of the neurons containing mGluR5, with nociceptive primary afferent and gamma-aminobutyric acid-ergic (GABAergic) terminals in the superficial dorsal horn of the spinal cord. Nociceptive C- and A(delta)-primary afferent terminals selectively labeled with horseradish peroxidase conjugated to wheat-germ agglutinin were in asymmetric synaptic contacts with or in direct apposition to mGluR5 positive dendritic profiles. The double-labeling studies revealed that mGluR5 immunoreactive dendrites also received symmetric synaptic contacts from axon terminals labeled with immunogold particles indicating GABA. The present demonstration of mGluR5 neurons receiving inputs from both nociceptive primary afferents and GABAergic terminals of presumed interneurons further supports the involvement of mGluR5 in the transmission and modulation of nociceptive information in the spinal cord.

Animals↗

PubMed2000

Activation of cGMP-dependent protein kinase Ialpha is required for N-methyl-D-aspartate- or nitric oxide-produced spinal thermal hyperalgesia.

The effect of a selective cyclic guanocine 3',5'-monophosphate (cGMP)-dependent protein kinase Ialpha inhibitor, Rp-8-[(4-chlorophenyl)thio]-cGMPS triethylamine (Rp-8-p-CPT-CGMPS), on either N-methyl-D-aspartate (NMDA)- or N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)ethanamine (NOC-12, a nitric oxide (NO) donor)-produced thermal hyperalgesia was examined in the rat. Intrathecal administration of NMDA (15 pg/10 microl) or NOC-12 (10, 20 and 30 microg/10 microl) produced a marked curtailment of the tail-flick latency. Maximal NMDA- or NOC-12-produced facilitation of the tail-flick reflex was significantly and dose-dependently blocked by intrathecal pretreatment with Rp-8-p-CPT-CGMPS (7.5, 15 and 30 microg/10 microl). Rp-8-p-CPT-CGMPS given alone did not markedly alter baseline tail-flick latency. These results suggest that the activation of cGMP-dependent protein kinase Ialpha is required for NMDA- or NO-produced facilitation of thermal hyperalgesia at the spinal cord level.

Animals↗

PubMed2000

Expression of PSD-95/SAP90 is critical for N-methyl-D-aspartate receptor-mediated thermal hyperalgesia in the spinal cord.

PSD-95/SAP90, a molecular scaffold protein, attaches the N-methyl-D-aspartate receptor to cellular signaling pathways through PSD-95/DLG/Z0-1 domain interactions at neuronal synapses.(5,9) This suggests that PSD-95/SAP90 might be involved in many physiological and pathophysiological actions triggered via the N-methyl-D-aspartate receptor in the central nervous system. Here, we present evidence that suppression of the expression of PSD-95/SAP90 in the spinal cord significantly attenuated facilitation of the tail-flick reflex triggered through N-methyl-D-aspartate receptor activation but not baseline tail-flick reflex latency. Moreover, PSD-95/SAP90's messenger RNA and protein were enriched in the spinal cord and selectively distributed in the superficial dorsal horn, where PSD-95/SAP90 overlapped with the N-methyl-D-aspartate receptor. In spinal cord neurons, PSD-95/SAP90 interacted with the N-methyl-D-aspartate receptor subunits 2A/2B. It is indicated that activation of the N-methyl-D-aspartate receptor in spinal hyperalgesia results in association of the N-methyl-D-aspartate receptor with PSD-95/SAP90 and that PSD-95/SAP90 is required for noxious thermal hyperalgesia triggered via the N-methyl-D-aspartate receptor at the spinal cord level. The present findings may provide novel insights into the mechanisms for persistent sensitization of the somatosensory system.

Animals↗

PubMed2000

Expression and action of cyclic GMP-dependent protein kinase Ialpha in inflammatory hyperalgesia in rat spinal cord.

Several lines of evidence have shown a role for the nitric oxide/cyclic guanosine monophosphate signaling pathway in the development of spinal hyperalgesia. However, the roles of effectors for cyclic guanosine monophosphate are not fully understood in the processing of pain in the spinal cord. The present study showed that cyclic guanosine monophosphate-dependent protein kinase Ialpha but not Ibeta was localized in the neuronal bodies and processes, and was distributed primarily in the superficial laminae of the spinal cord. Intrathecal administration of a selective inhibitor of cyclic guanosine monophosphate-dependent protein kinase Ialpha, Rp-8-[(4-chlorophenyl)thio]-cGMPS triethylamine, produced a significant antinociception demonstrated by the decrease in the number of flinches and shakes in the formalin test. This was accompanied by a marked reduction in formalin-induced c-fos expression in the spinal dorsal horn. Moreover, cyclic guanosine monophosphate-dependent protein kinase Ialpha protein expression was dramatically increased in the lumbar spinal cord 96 h after injection of formalin into a hindpaw, which occurred mainly in the superficial laminae on the ipsilateral side of a formalin-injected hindpaw. This up-regulation of cyclic guanosine monophosphate-dependent protein kinase Ialpha expression was completely blocked not only by a neuronal nitric oxide synthase inhibitor, 7-nitroindazole, and a soluble guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, but also by an N-methyl-D-aspartate receptor antagonist, dizocilpine maleate (MK-801). The present results indicate that noxious stimulation not only initially activates but also later up-regulates cyclic guanosine monophosphate-dependent protein kinase Ialpha expression in the superficial laminae via an N-methyl-D-aspartate-nitric oxide-cyclic guanosine monophosphate signaling pathway, suggesting that cyclic guanosine monophosphate-dependent protein kinase Ialpha may play an important role in the central mechanism of formalin-induced inflammatory hyperalgesia in the spinal cord.

Animals↗

PubMed2000

Intrathecally administered cGMP-dependent protein kinase Ialpha inhibitor significantly reduced the threshold for isoflurane anesthesia: implication for a novel role of cGMP-dependent protein kinase Ialpha.

BACKGROUND: Inhalational anesthetics have been shown to inhibit the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway. Previous studies indicated that inhibition of the NO-cGMP pathway decreased the level of consciousness and augmented anesthesia, analgesia, or sedation. The current study investigated the possible involvement of cGMP-dependent protein kinases (PKGs) as major effectors for the NO-cGMP pathway in the anesthetic state. METHODS: After initial baseline determination of the minimum alveolar concentration (MAC), a selective cGMP-dependent protein kinase Ialpha inhibitor, Rp-8-p-CPT-cGMPS, or an NO donor, (NOC-12), were injected intrathecally. Ten minutes later, MAC measurement was repeated. The rats also were evaluated for the presence of locomotor dysfunction by intrathecal administration of Rp-8-p-CPT-cGMPS and NOC-12 in conscious rats. RESULTS: Rp-8-p-CPT-cGMPS at 25, 50, 100, and 200 microg/10 microl produced a significant decrease from isoflurane control MAC of -4+/-3.1%, 16+/-4.5%, 30+/-5.0%, and 21+/-2.2%, respectively, which was not accompanied by significant changes in either blood pressure or heart rate. In contrast, NOC-12 at 100 microg/10 microl caused an increase from isoflurane control MAC of 23+/-5.8%, which was accompanied by significant decrease in blood pressure but not in heart rate. Rp-8-p-CPT-cGMPS (100 microg/10 microl) produced a significant reversal of isoflurane MAC increase induced by NOC-12 (100 microg/10 microl), which was accompanied by significant reversal of the reduction of blood pressure induced by NOC-12. Locomotor activity was not changed. CONCLUSIONS: The results indicate that cGMP-dependent protein kinase Ialpha inhibitor not only markedly reduces MAC for isoflurane, but also completely blocks the NO-induced increase in isoflurane MAC, which suggests that cGMP-dependent protein kinase Ialpha may mediate the action for the NO-cGMP pathway in anesthetic mechanisms at the spinal cord level.

Anesthesia, Inhalation↗

PubMed2000

Constitutive activation of G protein-coupled receptors as a result of selective substitution of a conserved leucine residue in transmembrane helix III.

Whereas numerous mutations of the human lutropin receptor (hLHR) and human TSH receptor (hTSHR) have been shown to cause constitutive activation of these receptors, it has been suggested that either the hFSHR as a whole, or the i3/TM VI region of the hFSHR, is less susceptible to mutation-induced constitutive activation. However, as shown herein, substitution of a highly conserved leucine residue in transmembrane III (TM III) of the hFSHR (Leu 111.18) with arginine causes a 5-fold increase in basal cAMP in transfected cells, consistent with a strong constitutive activation of the hFSHR. Interestingly, this mutant is unresponsive to further hormonal stimulation. Substitutions of hFSHR(L460) with lysine, alanine, or aspartate show that only arginine causes constitutive activation. However, all result in decreased FSH responsiveness, suggesting a role for L460 in FSH-stimulated cAMP production by the hFSHR. Because Leu 111.18 is highly conserved in rhodopsin-like G protein-coupled receptors (GPCRs), we tested the effects of substitution of the comparable leucine in the human beta2-adrenergic receptor (hbeta2-AR). Substitution of L124 in the hbeta2-AR with arginine, lysine, or alanine resulted in constitutive activation as evidenced by increased basal levels of cAMP that could be attenuated by an inverse agonist. In all cases, isoproterenol-stimulated cAMP was unaffected. Taken altogether, our data support a model whereby Leu 111.18 may play a general role in GPCRs by stabilizing them in an inactive state. Constitutive activation may arise by both a disruption of Leu 111.18 as well as the introduction of a specific residue that serves to stabilize the active state of the receptor.

Amino Acid Sequence↗

PubMed2000

Synaptic interaction between GABAergic terminals and substance P receptor-positive neurons in rat spinal superficial laminae.

AIM: To identify synaptic relationship between gamma-aminobutyric acid (GABA)-containing terminals and substance P receptor-positive neurons in the superficial dorsal horn of rat spinal cord. METHODS: A combination of preembedding immunoperoxidase staining for substance P receptor with postembedding immunogold staining for GABA was employed. RESULTS: Intense substance P receptor-expressing neurons were concentrated in medial half of the lamina I and the outer lamina II of the spinal cord. Under electron microscopy, substance P receptor immunoreactivity was found mainly in perikarya and dendrites, and deposited along neuronal membranes, in Golgi complex, in rough endoplasmic reticulum and on the surface of mitochondria with patch- or granular-like staining. The double-labeling studies revealed that substance P receptor-expressing dendrites received symmetric synaptic contacts from axonal terminals labeled with immunogold particles indicating GABA. GABA also co-localized with substance P receptors in the dendrites. CONCLUSION: The synaptic contact between GABA-containing terminal and substance P receptor-expressing neuron provided important morphological evidence for previous pharmacological studies concerning antinociceptive function of GABA in the spinal cord.

Animals↗

PubMed1998

The urinary bladder of a woman is a novel site of luteinizing hormone-human chorionic gonadotropin receptor gene expression.

OBJECTIVE: The female reproductive tract contains functional luteinizing hormone-human gonadotropin receptors; therefore our objective was to test the hypothesis that bladder trigone, which is derived from intermediate mesoderm along the urogenital ridge during embryonic development of the female reproductive tract, may also contain these receptors. STUDY DESIGN: Bladder trigones or domes were biopsied from 15 premenopausal and 19 postmenopausal women undergoing surgical correction of genital prolapse, incontinence, or both. The biopsy specimens were submitted for luteinizing hormone-human chorionic gonadotropin receptor analysis by in situ hybridization and immunocytochemical examination. The receptor immunostaining was visually scored by 3 investigators without knowing the identity of the menopausal status. RESULTS: In situ hybridization demonstrated the presence of receptor transcripts, and immunocytochemical examination revealed the presence of receptor protein in bladder trigone. The bladder trigones from postmenopausal women contained lower levels compared with those from premenopausal women, implying that luteinizing hormone might down-regulate its own receptors. Transitional epithelium contained the highest receptor levels followed by smooth muscle and blood vessels. The bladder dome contained receptor levels similar to those in trigone, which suggests that a common embryologic origin is not the only reason for bladder trigone containing the luteinizing hormone-human chorionic gonadotropin receptors. Rather, they are present because luteinizing hormone-human chorionic gonadotropin may regulate bladder functions in women. CONCLUSIONS: A woman's urinary bladder, which has never been thought of as a gonadotropin target, has now been demonstrated to contain luteinizing hormone-human chorionic gonadotropin receptors. These findings suggest for the first time that gonadotropins directly regulate bladder functions in women.

Adult↗

PubMed1998

NMDA receptors mediating Fos expression in rat spinal cord induced by subcutaneous injection of formalin.

AIM: To examine the effects of N-methyl-D-aspartate (NMDA) and non-NMDA receptors on noxious stimulation-induced Fos expression in the rat spinal cord. METHODS: Formalin (2%) was injected s.c. into one hindpaw of the rat. Fos expression was exhibited by immunocytochemical technique. RESULTS: Two hours after s.c. formalin, Fos-like immunoreactive (FLI) neurons were distributed mainly in medial part of the lamina I and the outer lamina II of the ipsilateral dorsal horn. dl-2-Amino-5-phosphonovalerate (APV) administered intrathecally (10 microL, 0.01, 0.1, or 1 g.L-1) before injection of formalin into a hindpaw reduced the number of FLI neurons dose-dependently in the dorsal horn (P < 0.01), while 6,7-dinitroquinoxaline-2, 3(1H,4H)-dione (DNQX) (1 g.L-1) was ineffective. CONCLUSION: NMDA receptor mediated noxious stimulation-induced Fos expression in the rat spinal cord.

2-Amino-5-phosphonovalerate↗

PubMed1998

[Neurokinin-1 receptor mediated formalin-induced c-fos expression in the rat spinal cord].

In the present work, the effects of tachykinin receptor antagonists on formalin-induced c-fos expression in the rat spinal cord were studied by a combination of immunocytochemical and neuropharmacological methods. Formalin injected into a hindpaw of rat only resulted in c-fos expression in the ipsilateral dorsal horn neurons of the spinal cord. Fos-positive neurons were distributed mainly in medial parts of the lamina I and the outer lamina II. A moderate number of Fos-positive neurons were present in laminae IV-V, and a few in the inner lamina II and in laminae III, VI and X. Selective NK-1 antagonist L-668, 169 (0.1, 1 and 10 micrograms) administered intrathecally before injection of formalin into a hindpaw significantly reduced the number of Fos-labeled neurons in the dorsal horn in a dose-dependent manner (P < 0.01), while selective NK-2 antagonist L-659, 877 (10 micrograms) and selective NK-3 antagonist SR-142, 801 (10 micrograms) were ineffective (P > 0.05). Our results indicated that NK-1 receptor mediated formalin-induced c-fos expression in the spinal cord, suggesting NK-1 receptor might play an important role in the spinal transmission of nociceptive messages.

Animals↗

PubMed1997

A contribution of neurokinin-1 receptor to formalin-induced c-fos expression in the rat spinal dorsal horn.

Formalin applied to a hindpaw of the rat resulted in c-fos expression in the spinal dorsal horn neurons on the ipsilateral side of stimulation. The role of neurokinin-1 (NK-1) receptor in this response was examined using a selective NK-1 antagonist L-668169. L-668169 administered intrathecally (1 microg/10 microl, 10 microg/10 microl) 15 min before injection of 2% formalin into one hindpaw significantly decreased the number of Fos-labeled neurons in the dorsal horn. A smaller dose of L-668169 (0.1 microg/10 microl) was ineffective. It was also showed that a selective NK-1 agonist Sar-SP perfused intrathecally (10 microg/10 microl) did result in the production of c-fos mainly in laminae I and that SP-like immunoreactive varicosities apposed neurons with Fos-labeled nuclei at their perikaryal membrane in the superficial laminae. These results indicate that NK-1 receptors may contribute to the activation of c-fos in the spinal dorsal horn neurons.

Animals↗

PubMed1997

The presence of luteinizing hormone/human chorionic gonadotropin receptors in lactating rat mammary glands.

Previous studies have implied that mammary glands might contain luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors. But no one ever previously investigated them. We now demonstrate, by using several techniques, that lactating rat mammary glands contain LH/hCG receptor mRNA transcripts and receptor protein which can bind 125I-hCG. Primarily mammary epithelial cells, and to a lesser extent the interductal stromal cells, contain the receptor transcripts and the receptor protein. These findings support the concept that mammary glands are also the targets of direct regulation by LH/hCG.

Animals↗

PubMed1997

Ultrastructure of Fos-labeled neurons relating to nociceptive primary afferent and substance P terminals in rat spinal superficial laminae.

The presence of Fos-labeled neurons at ultrastructural level was confirmed in the spinal superficial laminae following an injection of formalin into rat hindpaw in the present study. The Fos-like immunoreactive products were found exclusively in regions associated with the euchromatin in the nuclei of Fos-labeled neurons. By the methods used-of anterograde transport of horseradish peroxidase conjugated to wheat-germ agglutinin and immunocytochemistry-it was observed that some Fos-labeled neuronal bodies received synaptic contacts from, or were apposed directly to, small diameter primary afferent terminals in the spinal superficial laminae. By means of double-labeled immunocytochemistry, a direct apposition was often observed and a synaptic relationship was occasionally found between Fos-labeled neuronal bodies and substance P-like immunoreactive terminals.

Afferent Pathways↗

PubMed1997

Expression of luteinizing hormone/human chorionic gonadotropin receptor gene in benign prostatic hyperplasia and in prostate carcinoma in humans.

The findings that normal rat prostates express functional LH/hCG receptors led us to test the hypothesis that benign prostatic hyperplasia (BPH) and prostate carcinomas may also express this receptor gene. The data revealed the presence of LH/hCG receptor transcripts and receptor protein in normal and hyperplastic but not in atrophic glands present in BPH tissue. Smooth muscle and blood vessels in stroma of BPH tissue also contained receptors. Prostate carcinomas contain lower and more heterogeneous receptor levels than BPH tissue. Two human prostate cancer cell lines (LNCaP and DU 145) that were investigated showed the presence of a major 4.5-kilobase transcript and several minor transcripts and also the protein of LH/hCG receptors. However, androgen-sensitive LNCaP cells contained more receptors than androgen-insensitive DU 145 cells. In summary, we demonstrate for the first time that BPH and prostate cancer tissues and cell lines express LH/hCG receptor gene. These findings suggest that higher LH levels in aged men may play a role in BPH and/or prostate carcinomas.

Aged↗

PubMed1997

Fetal rat brains contain luteinizing hormone/human chorionic gonadotropin receptors.

The reverse transcription-polymerase chain reaction/Southern, Northern and Western blottings demonstrated that 19-day-old fetal rat brains contained the luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptor transcripts and receptor protein. Further investigation with Western blotting demonstrated that diencephalon, mesencephalon, rhombencephalon and telencephalon and several areas in each of these regions contained the LH/hCG receptor protein. The receptor protein levels in different regions were somewhat variable but they were not different from each other or from the whole brain. The 15-day-old fetal rat brains contained lower receptor protein levels which increased by 3-fold in 17-day-old and by 12-fold in 19-day-old fetal rat brains with no further significant increase in 21-day-old fetal, neonatal or adult rat brains. In summary, fetal rat brains contained LH/hCG receptors and these receptors were developmentally regulated. These findings suggest that the gonadotropins LH and hCG may regulate growth, development and differentiation in fetal brain.

Animals↗