Biomedical subjects

X M Yu

Publications and source records attributed to X M Yu.

At least 19 recordsLinked to original sources

PubMed2001

Ethylene induces antifreeze activity in winter rye leaves.

Antifreeze activity is induced by cold temperatures in winter rye (Secale cereale) leaves. The activity arises from six antifreeze proteins that accumulate in the apoplast of winter rye leaves during cold acclimation. The individual antifreeze proteins are similar to pathogenesis-related proteins, including glucanases, chitinases, and thaumatin-like proteins. The objective of this study was to study the regulation of antifreeze activity in response to ethylene and salicyclic acid, which are known regulators of pathogenesis-related proteins induced by pathogens. Nonacclimated plants treated with salicylic acid accumulated apoplastic proteins with no antifreeze activity. In contrast, when nonacclimated plants were exposed to ethylene, both antifreeze activity and the concentration of apoplastic protein increased in rye leaves. Immunoblotting revealed that six of the seven accumulated apoplastic proteins consisted of two glucanases, two chitinases, and two thaumatin-like proteins. The ethylene-releasing agent ethephon and the ethylene precursor 1-aminocyclopropane-1-carboxylate also induced high levels of antifreeze activity at 20 degrees C, and this effect could be blocked by the ethylene inhibitor AgNO(3). When intact rye plants were exposed to 5 degrees C, endogenous ethylene production and antifreeze activity were detected within 12 and 48 h of exposure to cold, respectively. Rye plants exposed to drought produced both ethylene and antifreeze activity within 24 h. We conclude that ethylene is involved in regulating antifreeze activity in winter rye in response to cold and drought.

Antifreeze Proteins↗

PubMed2000

Direct protein-protein coupling enables cross-talk between dopamine D5 and gamma-aminobutyric acid A receptors.

GABA(A) (gamma-aminobutyric-acid A) and dopamine D1 and D5 receptors represent two structurally and functionally divergent families of neurotransmitter receptors. The former comprises a class of multi-subunit ligand-gated channels mediating fast interneuronal synaptic transmission, whereas the latter belongs to the seven-transmembrane-domain single-polypeptide receptor superfamily that exerts its biological effects, including the modulation of GABA(A) receptor function, through the activation of second-messenger signalling cascades by G proteins. Here we show that GABA(A)-ligand-gated channels complex selectively with D5 receptors through the direct binding of the D5 carboxy-terminal domain with the second intracellular loop of the GABA(A) gamma2(short) receptor subunit. This physical association enables mutually inhibitory functional interactions between these receptor systems. The data highlight a previously unknown signal transduction mechanism whereby subtype-selective G-protein-coupled receptors dynamically regulate synaptic strength independently of classically defined second-messenger systems, and provide a heuristic framework in which to view these receptor systems in the maintenance of psychomotor disease states.

Amino Acid Motifs↗

PubMed2000

[Establishment of symbiotic system for Anoectochilus roxburghii (Wall.) Lindl. and endophytic fungi].

OBJECTIVE: Setting up a symbiotic system for Anoectochilus roxburghii and endophytic fungi, so as to study the relationship between them and try to set up new cultural methods for A. roxburghii. METHOD: A. roxburghii and its endophytic fungi were cultured together on five kinds of media in flasks. The growth of the plantlets and fungi were observed. Symbiotic conditions were selected according to symbiotic characteristics. RESULTS: A symbiotic system for A. roxburghii and endophytic fungi was set up. The optimum composition of the system induded NH4NO3 825 mg.L-1, KNO3 950 mg.L-1, MgSO4 185 mg.L-1, and inositol 100 mg.L-1, other organic components being 2/3 times those of MS medium, sugrose 15 g.L-1, and other components being the same as those of MS medium, agar 9 g.L-1, pH 5.8. The culture was effected at 24-25 degrees C under cool white fluorescent light (150 lx) for a photoperiod of 11 hours. CONCLUSION: A. roxburghii and endophytic fungi can grow well together and form endomycorrhiza in the symbiotic system. Moreover, endophytic fungi help stimulate the growth and development of A. roxburghii.

Culture Media↗

PubMed1999

Src, a molecular switch governing gain control of synaptic transmission mediated by N-methyl-D-aspartate receptors.

The N-methyl-D-aspartate (NMDA) receptor is a principal subtype of glutamate receptor mediating fast excitatory transmission at synapses in the dorsal horn of the spinal cord and other regions of the central nervous system. NMDA receptors are crucial for the lasting enhancement of synaptic transmission that occurs both physiologically and in pathological conditions such as chronic pain. Over the past several years, evidence has accumulated indicating that the activity of NMDA receptors is regulated by the protein tyrosine kinase, Src. Recently it has been discovered that, by means of up-regulating NMDA receptor function, activation of Src mediates the induction of the lasting enhancement of excitatory transmission known as long-term potentiation in the CA1 region of the hippocampus. Also, Src has been found to amplify the up-regulation of NMDA receptor function that is produced by raising the intracellular concentration of sodium. Sodium concentration increases in neuronal dendrites during high levels of firing activity, which is precisely when Src becomes activated. Therefore, we propose that the boost in NMDA receptor function produced by the coincidence of activating Src and raising intracellular sodium may be important in physiological and pathophysiological enhancement of excitatory transmission in the dorsal horn of the spinal cord and elsewhere in the central nervous system.

Animals↗

PubMed1999

Involvement of trigeminal subnucleus caudalis (medullary dorsal horn) in craniofacial nociceptive reflex activity.

We have previously shown that an increase in electromyographic (EMG) activity of digastric (DIG) and masseter (MASS) muscles can be reflexly evoked by injection into the rat's temporomandibular joint (TMJ) region of the small-fibre excitant and inflammatory irritant mustard oil (MO). Since the trigeminal (V) subnucleus caudalis (Vc, i.e. medullary dorsal horn) has traditionally been viewed as an essential brainstem relay site of nociceptive information from craniofacial tissues, an EMG study was carried out in 45 anaesthetized rats to determine if Vc is involved in the MO-evoked increases in jaw muscle EMG activity. The effects of histologically confirmed surgical or chemical lesions of Vc on this evoked EMG activity were tested in different groups of rats. MO injection into the left TMJ region of intact rats evoked bilateral increases in EMG activity of DIG and MASS which could be significantly reduced by surgical transection of the left caudal brainstem at the obex level; MO injection into the right TMJ region in these same rats still readily evoked increases in EMG activity. A sagittal section medial to Vc or transection at the level of the second cervical spinal segment did not produce any significant reduction in the reflexly evoked EMG activity. Neurones in Vc, as opposed to fibres of passage, appear to be important for the MO-evoked EMG activity, since injection into Vc of the neurotoxic chemical ibotenic acid significantly reduced the mustard oil-evoked EMG activity. The Vc also appears to play a role in the activation of contralateral V motoneurons, as evidenced by the activation of the contralateral DIG and MASS muscles by the injection of MO into the left TMJ region of intact rats and by the reduction of this evoked EMG activity in the contralateral DIG and MASS of rats with a surgical transection or ibotenic acid lesion of the left Vc. These findings suggest that Vc may be a critical element in the neural pathways underlying the reflex responses evoked bilaterally in DIG and MASS muscles by noxious stimulation of the TMJ region.

Animals↗

PubMed1998

Gain control of NMDA-receptor currents by intracellular sodium.

The influx of Na+ is fundamental to electrical signalling in the nervous system and is essential for such basic signals as action potentials and excitatory postsynaptic potentials. During periods of bursting or high levels of discharge activity, large increases in intracellular Na+ concentration ([Na+]i) are produced in neuronal soma and dendrites. However, the intracellular signalling function of raised postsynaptic [Na+]i is unknown. Here we show that [Na+]i regulates the function of NMDA (N-methyl-D-aspartate) receptors, a principal subtype of glutamate receptor. NMDA-receptor-mediated whole-cell currents and NMDA-receptor single-channel activity were increased by raising [Na+]i and channel activity decreased upon lowering [Na+]i; therefore, the activity of NMDA channels tracks changes in [Na+]i. We found that the sensitivity of the channel to Na+ was set by a Src kinase that is associated with the channel. Raising [Na+]i selectively increased synaptic responses mediated by NMDA receptors, but not by non-NMDA receptors. Thus, the change in postsynaptic [Na+]i that occurs during neuronal activity is a signal for controlling the gain of excitatory synaptic transmission. This mechanism may be important for NMDA-receptor-dependent plasticity and toxicity in the central nervous system.

Animals↗

PubMed1997

NMDA channel regulation by channel-associated protein tyrosine kinase Src.

The N-methyl-D-aspartate (NMDA) receptor mediates synaptic transmission and plasticity in the central nervous system (CNS) and is regulated by tyrosine phosphorylation. In membrane patches excised from mammalian central neurons, the endogenous tyrosine kinase Src was shown to regulate the activity of NMDA channels. The action of Src required a sequence [Src(40-58)] within the noncatalytic, unique domain of Src. In addition, Src coprecipitated with NMDA receptor proteins. Finally, endogenous Src regulated the function of NMDA receptors at synapses. Thus, NMDA receptor regulation by Src may be important in development, plasticity, and pathology in the CNS.

Amino Acid Sequence↗

PubMed1997

[Studies on clinical epidemiology of Tsutsugamushi disease of the autumn-winter type in the easten suburbs of Jinan].

This paper reported the epidemiological characteristics of 154 cases under investigation for tsutsugamushi disease of autumn-winter type in the eastern suburb of Jinan. Results showed that the characteristics differed greatly from those in the southern part of China. Majority of patients had toxic symptoms due to infections but specific characteristics were less obvious. Eschars and ulcers appeared only in 14.94% of the cases and occurred only in autumn-winter season. Clinically mild cases constituted the majority. Cases not only distributed sporadically, but also had multi-organ lesions (MOL). Young peasants seemed to be most vulnerable. The pathogen of the disease belonged to low virulent strain. Serological typing belonged to the Gilliam type. The diagnosis and the treatment of the disease were discussed. Specific serum IgG of the disease was detected 6 years after convalescence.

Adolescent↗

PubMed1996

Ca(2+)-independent reduction of N-methyl-D-aspartate channel activity by protein tyrosine phosphatase.

Regulation of ion channel function by intracellular processes is fundamental for controlling synaptic signaling and integration in the nervous system. Currents mediated by N-methyl-D-aspartate (NMDA) receptors decline during whole-cell recordings and this may be prevented by ATP. We show here that phosphorylation is necessary to maintain NMDA currents and that the decline is not dependent upon Ca2+. A protein tyrosine phosphatase or a peptide inhibitor of protein tyrosine kinase applied intracellularly caused a decrease in NMDA currents even when ATP was included. On the other hand, pretreating the neurons with a membrane-permeant tyrosine kinase inhibitor occluded the decline in NMDA currents when ATP was omitted. In inside-out patches, applying a protein tyrosine phosphatase to the cytoplasmic face of the patch caused a decrease in probability of opening of NMDA channels. Conversely, open probability was increased by a protein tyrosine phosphatase inhibitor. These results indicate that NMDA channel activity is reduced by a protein tyrosine phosphatase associated with the channel complex.

Adenosine Triphosphate↗

PubMed1996

The major transcriptional transactivation domain of simian virus 40 large T antigen associates nonconcurrently with multiple components of the transcriptional preinitiation complex.

Simian virus 40 (SV40) large T antigen (Tag) is a promiscuous transcriptional transactivator; however, its mechanism of transactivation remains unknown. Recent studies have suggested the possible involvement of protein-protein interactions with TBP, the TATA box-binding protein of TFIID, and TEF-1, an enhancer-binding factor. We show here that (i) the Tag domain containing amino acids 133 to 249 directly interacts with the general transcription factor TFIIB, the activator protein Sp1, and the 140-kDa subunit of RNA polymerase II, as well as with TBP and TEF-1; (ii) these interactions can also occur when these transcription factors are present in their functional states in cellular extracts; (iii) binding of Tag to TBP is eliminated by preincubation of TBP either at 48 degrees C or with the adenovirus 13S E1a protein; (iv) this domain of Tag cannot bind concurrently to more than one of these transcription factors; and (v) the substitution of Tag amino acid residues 173 and 174 inactivates the ability of this Tag domain both to associate with any of these transcription factors and to transactivate the SV40 late promoter. Thus, we conclude that SV40 Tag probably does not transactivate via the concurrent interaction with multiple components of the preinitiation complex. Rather, we hypothesize that transactivation by Tag may primarily occur by removing or preventing the binding of factors that inhibit the formation of preinitiation complexes.

Antigens, Polyomavirus Transforming↗

PubMed1996

[Study on the mode of transmission of EHFV among host animals and its epidemiologic significance].

In our study, IFA was adopted to detect the epidemic haemorrhagic fever virus (EHFV) antigen and antibody. We studied on the mode of transmission of EHFV in mice and its epidemiologic significance. The results demonstrated that both horizontal and vertical modes of transmission existed in mice under natural circumstances. Horizontal transmission was noticed as the major mode of transmission of EHFV in mice which played an important role in the spread and development of EHF natural foci. Vertical transmission seemed to act merely on the maintenance of EHF natural foci in mice.

Animals↗

PubMed1994

Vasopressin and vasopressin-receptor immunoreactivity in small-cell lung carcinoma (SCCL) cell lines: disruption in the activation cascade of V1a-receptors in variant SCCL.

Four classical and three variant small-cell carcinoma of the lung (SCCL) cell lines were examined for vasopressin and vasopressin V1a-receptor immunoreactivity. One of these classical cell lines, NCI-H345, and one variant cell line, NCI-H82, were further investigated for binding of V1 and V2 vasopressin-receptor antagonists, vasopressin-induced calcium mobilization, and vasopressin-induced thymidine uptake. All classical and variant SCCL cell lines examined contained vasopressin and vasopressin-receptors as determined by immunocytochemistry. Both NCI-H82 and NCI-H345 demonstrated similar binding patterns with the V1 and V2 vasopressin-receptor antagonists, indicating the presence of both receptor subtypes. For the classical cell line (NCI-H345), vasopressin (1 microM) induced an increase in cytosolic free calcium, while the peptide was ineffective at increasing cytosolic calcium in the variant cell line (NCI-H82). However, vasopressin (0.1 or 1 microM) was unable to stimulate thymidine uptake in the classical (NCI-H345) or variant (NCI-H82) cell lines for the conditions used. These results indicate that both classical and variant SCCL produce vasopressin, and vasopressin V1a and V2 receptors. In the variant cell line, there appears to be a disruption in the activation cascade for V1a receptors as indicated by the lack of vasopressin-induced calcium mobilization.

Calcimycin↗

PubMed1994

A sequence in the main cytoplasmic loop of the alpha subunit is required for assembly of mouse muscle nicotinic acetylcholine receptor.

We have investigated the role of intracellular cytoplasmic sequences in the assembly of the mouse muscle nicotinic acetylcholine receptor (AChR) transiently expressed in COS cells. A chimeric protein in which the region from M1 to M4 of the alpha subunit was replaced by the corresponding region in the beta subunit was unable to support AChR assembly when substituted for the alpha subunit; a chimeric alpha subunit containing only the long cytoplasmic loop from the beta subunit was likewise inactive. Systematic mutation of short segments of the loop identified a sequence of 17 amino acids near the C-terminal end of the loop for which the beta sequence could not be substituted. Each of the inactive chimeric and mutated alpha subunits bound alpha-bungarotoxin when expressed alone and formed a heterodimer when expressed with the delta subunit. An alpha subunit truncated after M1 formed both an alpha delta heterodimer and an alpha delta beta heterotrimer, demonstrating that the cytoplasmic loop is dispensable for the early steps of assembly. A sequence in the long cytoplasmic loop of the alpha subunit thus appears to play a role in a late step of AChR assembly.

Amino Acid Sequence↗

PubMed1994

Products of vasopressin gene expression in small-cell carcinoma of the lung.

Small-cell neuroendocrine carcinoma of the lung is known to express products related to the vasopressin gene, although these products have been reported to sometimes differ from those generated by neurones of the hypothalamo-neurohypophyseal system. To further investigate vasopressin gene expression in neuroendocrine carcinomas, we performed immunohistochemistry on 24 histologically classified small-cell carcinomas using antibodies directed against different regions of the vasopressin precursor. All of the tumours examined contained at least two parts of the vasopressin precursor, suggesting that vasopressin might have a biological role in these tumours and indicating a role for these products in tumour diagnosis and treatment. Sixty-seven per cent of the tumours contained immunoreactivity for all major regions of the precursor: vasopressin, vasopressin-associated human neurophysin, the bridging region between the hormone and the neurophysin, and vasopressin-associated human glycopeptide. However, 33% of the tumours examined appeared to express only part of the vasopressin precursor, as evidenced by the absence of immunoreactivity for the neurophysin and/or the glycopeptide. These results support the proposition that both normal and abnormal vasopressin gene expression occurs in small-cell carcinoma of the lung.

Carcinoma, Small Cell↗

PubMed1994

Administration of opiate antagonist naloxone induces recurrence of increased jaw muscle activities related to inflammatory irritant application to rat temporomandibular joint region.

1. Our recent studies in rats have demonstrated that the small-fiber excitant and inflammatory irritant mustard oil injected into the temporomandibular joint (TMJ) region can evoke a sustained and reversible increase of electromyographic (EMG) activity in jaw muscles and an acute inflammatory response. The aim of the present study was to test if opioid mechanisms are involved in modulating the EMG increase evoked by mustard oil. 2. Mustard oil injected into the rat TMJ region evoked significant increases of jaw muscle EMG activity; the vehicle mineral oil had no such effect. The increased EMG activity lasted up to 20 min, and by 30 min after the mustard oil injection had returned to control (preinjection) levels, at which time administration of the opiate antagonist naloxone (1.3 mg/kg i.v.) induced a significant recurrence of the increase in EMG activity. This "rekindling" of EMG activity appeared at 5 to 10 min after the naloxone administration and lasted for 10 to 20 min. In contrast, naloxone administration in the animals receiving mineral oil injection into the TMJ region did not "rekindle" the EMG activity, nor did the administration of the peripherally acting opiate antagonist methylnaloxone or the vehicle of naloxone. 3. These findings reveal that the application of the opiate antagonist naloxone produces a recurrence of increased jaw muscle activity reflexively evoked by mustard oil injection into the rat TMJ region. They suggest that central opioid depressive mechanisms activated by the mustard oil-induced afferent barrage limit the duration of the evoked EMG changes.

Afferent Pathways↗

PubMed1994

[Detection of cervical human papillomavirus infection from women with external genital condyloma acuminata].

Cervical biopsy specimens were taken from 36 women with external genital condyloma acuminata in order to diagnose a concomitant cervical human papillomavirus (HPV) infection. Positive HPV infection rate of cervix was 16% (6/36) by routine visual examination, 69% (25/36) by colposcopy and 56% (18/32) by pathology. Among those patients 31% (10/32) have grade I-II cervical intraepithelial neoplasia (CIN) according to pathology. In 8 cases, both vulva and cervical specimens were examined by Southern blot, dot blot and polymerase chain reaction (PCR) technique. HPV DNA positive was detected in 7 of 8 cervical specimens. It is concluded cervical HPV infection was rather common in women with external genital condyloma acuminata and it is valuable to examine cervical HPV infection by colposcopy and biopsy to detect the concomitant CIN.

Adolescent↗

PubMed1994

Amino- and carboxyl-terminal domains specify the identity of the delta subunit in assembly of the mouse muscle nicotinic acetylcholine receptor.

We have used transient expression in COS cells of the subunits of the nicotinic acetylcholine receptor (AChR) from mouse skeletal muscle to investigate the role of transmembrane and cytoplasmic domains of the delta subunit in assembly of the AChR. When chimeric subunits whose extracellular amino- and carboxyl-terminal domains were from the delta subunit and whose transmembrane and cytoplasmic domains were from either the beta, gamma, or epsilon subunit were expressed with alpha, beta, and epsilon subunits, alpha-bungarotoxin-binding activity appeared on the surface of the transfected cells. The resulting receptor complexes each had sedimentation constants resembling those of the native AChR, consistent with a pentameric structure. Further investigation of the delta beta chimeric subunit showed that it formed a heterodimer with the alpha subunit and that the resulting subunit bound d-tubocurarine with an affinity similar to that of the alpha delta heterodimer; delta beta also formed a heterodimer with a form of the alpha subunit that is truncated after the first transmembrane domain. A heterodimer formed from the epsilon beta and alpha subunits also bound d-tubocurarine with an affinity similar to that of the alpha epsilon heterodimer. When both epsilon beta and delta beta subunits were substituted for the epsilon and delta subunits, respectively, a receptor complex was formed whose structure appeared to be alpha 2 beta(epsilon beta)(delta beta). These results show that, as with the epsilon subunit, the identity of the delta subunit in AChR assembly arises from the extracytoplasmic domains of the subunit.

Animals↗

PubMed1994

[A comparable study of microwave tissue coagulation (MTC) and CO2 laser in treatment of cervical erosion].

In a randomized study, 300 patients with cervical erosion were allocated to either MTC(154) or CO2 Laser(146). The patients were treated on an outpatient basis without anesthesia. In the case of initial treatment failure the same method was to be used for retreatment. All the patients were followed-up for an average of 11 weeks (8-12). 142 of 154 microwave-coagulated patients (92.20%) and 116 of 146 Laser-evaporated patients (79.45%) were cured after one treatment, and there was significant difference between MTC and Laser group (P < 0.005). Bleeding during operation occurred in 5 of 154 MTC group (3.25%) and 32 of 146 Laser group (21.92) (P < 0.005). The result suggested that MTC had higher cure rate and less complications. It is easy to handle, safe and economic.

Adult↗