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Biomedical subjects

Y Gu

Publications and source records attributed to Y Gu.

At least 289 records · Page 16Linked to original sources
PubMed1995

The opioid peptide dynorphin directly blocks NMDA receptor channels in the rat.

1. The actions of dynorphin on N-methyl-D-aspartate (NMDA) responses were examined in acutely dissociated trigeminal neurons in rat. Whole-cell and single-channel currents were recorded using the patch clamp technique. 2. Dynorphins reduced NMDA-activated currents (INMDA). The IC50 was 0.25 microM for dynorphin (1-32), 1.65 microM for dynorphin (1-17) and 1.8 microM for dynorphin (1-13). 3. The blocking action of dynorphin is voltage independent. 4. The inhibitory action of dynorphin cannot be blocked by high concentration of the non-selective opioid receptor antagonist naloxone, nor by the specific kappa-opioid receptor antagonist nor-Binaltorphimine (nor-BNI). 5. Single-channel analyses indicate that dynorphin reduces the fraction of time the channel is open without altering the channel conductance. 6. We propose that dynorphin acts directly on NMDA receptors.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1995

Tumor necrosis factor production by human T-cells stimulated with bacterial superantigens.

Tumor necrosis factor (TNF) production from T-cells stimulated with superantigenic exotoxins, staphylococcal enterotoxin B and streptococcal pyrogenic exotoxin A was investigated in the presence of cells bearing distinct isotypes of HLA class II molecules. The main T-cell subset for TNF production was investigated in parallel. Similarly high levels of TNF production were induced upon stimulation with the toxins in the presence of DR+ or DQ+ cells, but only marginal levels of TNF production were induced in the presence of DP+ cells. Although both CD4+ T-cells and CD8+ T-cells produced TNF-alpha and TNF-beta in response to toxin stimulation in the presence of HLA class II+ cells, the former T-cell subset was the major source of producers of TNF-alpha and TNF-beta.

Bacterial Proteins↗
PubMed1995

Cooperative medical schemes in contemporary rural China.

Improvements in rural health care in China in the 1950s, 1960s and 1970s were largely due to the development of cooperative medical schemes (CMSs) and the establishment of a three-tier rural health network. Since the economic reforms were instituted in the late 1970s, the financing and delivery of rural health services have seen many changes, some positive, others not. Most CMSs have collapsed. In the absence of CMSs, the rural population has to pay for health care out-of-pocket and poor families have greater difficulty in getting access to essential health care. In the meantime, emphases of health services have tended to shift from lower to higher levels, from preventive to curative services, and from planning and management to market forces. This paper outlines the evolution of CMSs, reasons for their collapse, and their likely impact on rural health services. The main focus is on the development of a new generation of rural cooperative health care schemes, given their importance in the process of consolidating the rural three-tier health network after the impact of the economic reforms: the characteristics of some schemes, the apparent conditions for success, and government policy towards the development of cooperative health care financing are presented.

China↗
PubMed1995

130 kb of DNA sequence reveals two new genes and a regional duplication distal to the human iduronate-2-sulfate sulfatase locus.

Deficiency of IDs activity results in Hunter Syndrome (mucopolysaccharidosis type II), a fatal X-linked recessive disorder. We report characterization of 28 cosmids around the IDS locus in Xq28. Four overlapping cosmids have been sequenced in their entirety generating a 130-kb contig. These studies show the fine structure of the IDS gene and identify an IDS pseudogene-like structure located 20 kb distal to the active gene. Two novel genes have also been identified in this sequence, and one of these genes is also locally duplicated. Both homologs are expressed, and a number of alternative transcript products have been characterized. The presence of a highly conserved pseudogene-like structure within a larger duplicated region close to the IDS gene has significant implications for the study of mutations at this locus.

Base Sequence↗
PubMed1995

Does the rat corpus luteum express the progesterone receptor gene?

To determine whether the progesterone receptor (PR) gene is expressed in rat corpora lutea (CL), PR messenger RNA (mRNA) and protein levels were examined in CL of both cycling and pregnant rats using in situ hybridization, reverse transcription-polymerase chain reaction, and Western blotting analyses. During the estrous cycle, levels of luteal PR mRNA were below the sensitivity of in situ hybridization. Although no signal could be detected in luteal cells, granulosa cells of preovulatory follicles of the same ovary expressed PR mRNA at high levels during the evening of proestrus. Likewise, CL of pregnant rats expressed undetectable levels of PR mRNA, which remained unchanged throughout pregnancy, as determined by in situ hybridization and reverse transcription-polymerase chain reaction. In addition, no PR protein could be detected in rat CL by Western analysis, indicating that luteal expression of the PR gene, if any, is negligible. To determine whether the lack of PR mRNA in the rat CL is due to progesterone-induced down-regulation of PR mRNA or to low levels of estrogen, aminoglutethimide was used to block the synthesis of progesterone in the presence and absence of exogenous estrogen, and PR mRNA levels were examined in the CL as well as the placenta. Inhibition of progesterone synthesis did increase PR mRNA levels in the placenta, and additional estrogen treatment further increased PR mRNA levels in this tissue. In contrast, neither aminoglutethimide alone nor aminoglutethimide plus estrogen induced PR mRNA expression in CL of the same rats. The temperature-sensitive luteal cell line derived from the rat CL, which produces very low levels of progesterone, also did not express PR mRNA. These results indicate that the rat corpus luteum expresses undetectable levels of PR mRNA and protein, which is not attributable to progesterone-induced down-regulation of PR mRNA or to a lack of estrogen-induced up-regulation of PR mRNA in this tissue.

Aminoglutethimide↗
PubMed1995

Development and characterization of a simian virus 40-transformed, temperature-sensitive rat antimesometrial decidual cell line.

The rat decidual tissue is formed by two cell populations, which express different genes and play diverse roles in pregnancy. Cells that decidualize in the antimesometrial region secrete several hormones and serve as a true endocrine gland. Isolation and maintenance of these decidual cells in primary culture is difficult. The goal of these experiments was to develop a cell line to serve as a model to study the expression and regulation of various genes specific to the antimesometrial decidual cells. Decidualization was induced in pseudopregnant rats. The antimesometrial decidua was dissected out, and cells were enzymatically dissociated and were cultured for 18 h at 37 C in RPMI-1640 medium containing 10% fetal bovine serum. Cells were washed repeatedly and then infected with a temperature-sensitive mutant of the simian virus. Transformed cells were maintained at the permissive temperature (33 C) until colonies were identified and harvested. Whereas primary cells in culture did not divide, the cloned decidual cell lines demonstrated transformed features; they multiplied at 33 C and formed multilayers. At the nonpermissive temperature (39 C), cell replication decreased, and after 4 days of culture the cells lost their transformed phenotype and continued to grow as a monolayer similar to primary cells. Cells under these conditions also assumed morphological characteristics similar to antimesometrial cells: polynucleated, large, and having cytoplasm filled with lipid droplets. Interestingly, cells cultured at 39 C that were shifted back to 33 C resumed rapid growth. To determine whether these cells also express messenger RNAs (mRNAs) found in normal antimesometrial decidual cells, the presence of activin beta A mRNA was investigated by Northern analysis and reverse transcription polymerase chain reaction. A single 6.8-kilobase activin beta A transcript was expressed abundantly at both 33 and 39 C, indicating that even when cells are rapidly dividing they express activin beta A. Activin beta B mRNA was also expressed in these cells, although in lower abundance, as were two binding proteins for activin, activin receptor II and follistatin. The activin beta A and beta B genes were responsive to cAMP stimulation in these cells. Since the hallmark of the antimesometrial decidual cells is the secretion of PRL-related hormones, the expression of decidual PRL-related protein and PRL-like protein B was examined. Northern analysis revealed a major 1.2-kilobase transcript of PRL-like protein B expressed equally at both temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Isolation, culture, and characterization of the two cell subpopulations forming the rat decidua: differential gene expression for activin, follistatin, and decidual prolactin-related protein.

The decidual tissue of the pregnant rat is formed primarily by two markedly different decidual cell populations located in the mesometrial and antimesometrial sites of the uterus. The antimesometrial decidua functions as an endocrine organ, secreting PRL-like hormones and expressing activin and follistatin. In contrast, the mesometrial decidua has no apparent endocrine activity, but secretes abundant alpha 2-macroglobulin. To determine whether the profound difference in morphology and gene expression is inherent to each cell population or whether it results from the position of these cells in the uterus and their subjection to regionally restricted information, we isolated the giant antimesometrial decidual cells from the small mesometrial decidual cells by elutriation. We examined, using Northern and reverse transcription-polymerase chain reaction analysis, the expression of PRL-related protein (DPRP), follistatin, activin, and alpha 2-macroglobulin in the two cell populations just after cell separation and after primary culture. We also examined, using coculture, the possible cross-talk between the two cell populations. In culture, the cells maintained the morphological appearance seen in the decidua; the mesometrial cells remained less differentiated, whereas the antimesometrial cells formed giant cells. In addition, the antimesometrial cells, which have been shown previously to be the only site of DPRP messenger RNA (mRNA) expression, remained, after several days of culture, the only cells able to express this gene. The coculture experiment suggested that the absence of DPRP mRNA in the mesometrial cells is not due to inhibitory signals from the antimesometrial cells, but, rather, to the inherent inability of the mesometrial decidual cells to express the DPRP gene. The cellular expression pattern of follistatin was also not changed by cell separation. However, in sharp contrast to that of DPRP and follistatin, the cell-specific expression of activin-beta A and alpha 2-macroglobulin was markedly affected by cell separation. A remarkable switch in activin-beta A cell expression was observed when mesometrial cells were separated from antimesometrial cells and maintained in culture. Activin-beta A mRNA, which was barely detectable in these cells in situ, became expressed in higher levels than in antimesometrial cells. The isolated antimesometrial cells also acquired the ability to express the alpha 2-macroglobulin gene, whose expression is highly restricted to the mesometrial cells in vivo. No down-regulation of antimesometrial alpha 2-macroglobulin mRNA could be induced by mesometrial cells in a coculture experiment. However, alpha 2-macroglobulin mRNA levels in mesometrial cells were clearly up-regulated by antimesometrial cell signal(s).(ABSTRACT TRUNCATED AT 400 WORDS)

Activins↗
PubMed1995

Cell-specific expression of activin and its two binding proteins in the rat decidua: role of alpha 2-macroglobulin and follistatin.

Rat decidual tissue is formed by two distinct decidual cell populations located either antimesometrially or mesometrially in the uterus. They differ in morphology, the genes they express, the proteins they secrete, and the role they play during pregnancy. Recently, we have shown that rat decidua expresses follistatin and alpha 2-macroglobulin (alpha 2-MG), two binding proteins to activin. In the present study, we determined whether the decidua of pregnant and pseudopregnant rats also expresses activin, whether activin messenger RNA (mRNA) is confined to a particular cell population, and whether it is regulated by its binding proteins. Decidual and placental tissues were collected at different stages of pseudopregnancy or pregnancy. mRNA expression was examined by in situ hybridization, reverse transcription-polymerase chain reaction, and Northern analysis. Developmental studies revealed that activin A became highly expressed in the antimesometrial decidua only from day 11 at a time when this tissue was undergoing extensive degeneration. Very little activin A mRNA could be detected in the mesometrial decidua. However, late in pregnancy, significant expression of activin A mRNA was detected in the mesometrial decidua undergoing extensive cell death at this stage. Developmental study revealed that activin A mRNA became expressed in the antimesometrial decidua only when follistatin mRNA disappeared from this tissue. Furthermore, mesometrial decidua expressing the most alpha 2-MG mRNA had reduced levels of activin A mRNA. These data suggest that follistatin and alpha 2-MG may, by binding to activin, prevent activin A from stimulating the expression of its own gene. To examine this possibility we first established that the rat decidua expresses activin receptor II at a constant level between days 11-15. Then we examined whether follistatin and alpha 2-MG down-regulate activin expression in a simian virus 40-transformed decidual cell line (GG-AD). These cells express activin A mRNA in abundance, very little follistatin, and no alpha 2-MG. Follistatin and alpha 2-MG caused a dose-related decrease in activin A mRNA levels in these cells. The same inhibitory effect was observed with activin A-blocking antibody. In summary, the results of this investigation demonstrate that rat decidual tissue expresses mRNAs for activin A and its two binding proteins; follistatin and alpha 2-MG. The expression of each mRNA is cell specific and developmentally regulated. The finding that both activin-binding proteins and antibody inhibit the expression of activin A in cultured decidual cells suggests that activin regulates its own gene expression in the decidua.(ABSTRACT TRUNCATED AT 400 WORDS)

Activins↗
PubMed1995

Serrate expression can functionally replace Delta activity during neuroblast segregation in the Drosophila embryo.

Serrate and Delta encode structurally related proteins in D. melanogaster that bind within a common extracellular region on the NOTCH receptor molecule. We used ectopic expression to determine if SERRATE could mediate in vivo functions parallel or antagonistic to those proposed for the putative NOTCH ligand DELTA. Our results demonstrate that Serrate can replace Delta gene function during embryonic neuroblast segregation and that expression of Serrate leads to a NOTCH-dependent suppression of achaete expression in proneural clusters. Our findings strongly suggest that SERRATE functions as an alternative ligand capable of NOTCH activation.

Animals↗
PubMed1995

The mechanism of action for the block of NMDA receptor channels by the opioid peptide dynorphin.

Dynorphin is one of the endogenous opioids that modulates the excitability of nociceptive (pain-sensing) neurons. We have shown recently that dynorphin blocks NMDA-activated currents directly without the participation of kappa-opioid receptors. In order to understand the mechanism underlying this novel action of dynorphin, we examined, in detail, the interactions between dynorphin and NMDA receptors in isolated trigeminal neurons. Dynorphin reversibly blocks NMDA-activated current (INMDA). The onset and recovery of the block were determined with concentration jump experiments. The association rate (k+) of dynorphin(1-17) is 4.9 x 10(6) sec-1 M-1 and the dissociation rate (k-) is 7.5 sec-1. The apparent dissociation constant (KD) of dynorphin, calculated from these rate constants, is 1.6 microM. Dynorphin does not change the EC50 of NMDA, nor the potentiating action of glycine. The binding site for dynorphin is distinct from that of Zn2+ or H+. Upon treatment with the disulfide reducing agent dithiothreitol (DTT), NMDA receptors become less susceptible to dynorphin block. The affinity of dynorphin for the modified NMDA receptors is reduced by 2.7-fold. In analyses of single NMDA channels in cell-free patches, we found that dynorphin shortens the mean open time, decreases the probability of opening of NMDA channels, but has no effect on the single channel conductance. These results suggest that dynorphin interacts with a site conformationally linked with the redox site(s) on the NMDA receptor, thus altering the gating properties of the channel.

Animals↗
PubMed1995

[Effect of electric fields on the proteins in nerve regeneration conditioned fluid].

80 SD rats were randomly divided into four groups of 20 each: local electrostimulation of nerve stump (Group LS); electro-stimulation of myeloneure (Group N); electrostimulation of the denervated muscle (Group M); and controls (Group C). The left lateral sciatic nerve of rats was excised 5mm in length, and the severed nerve was bridged with the silicon tube. The gap between the stumps was about 10mm. At 3rd, 7th, 14th, 21st and 28th day after nerve transection and tube implantation, the fluid in the silicon tube was aspirated. The sample of fluid was spun and 4 microliters aliquots were taken from the supernatant. Then the electrophoresis of the aliquots was made by phase-system and assayed to the amount and variety by Gel Scan system. The results showed that the group LS had a high increase in the protein amount than others in the range of 6.16-10.23 x 10(3)D molecular weight. We believe that it is one of the mechanisms of the electric fields promoting nerve regeneration.

Animals↗
PubMed1995

Dorsal scapular nerve compression. Atypical thoracic outlet syndrome.

The dorsal scapular nerve and long thoracic nerve of 10 cadavers (20 sides) and 36 patients with dorsal scapular nerve compression were studied anatomically. The origin of the dorsal scapular nerve of a section frequently shared a common trunk with the long thoracic nerve, and went through the scalenus medius anterointernally and posterolaterally with the presence of some tendinous tissues. Leaving the long thoracic nerve, it might give branches to the shoulder and the subaxillary region and finally have the branches join the long thoracic nerve again. The compression of the section near the origin caused discomfort and sourness of the neck, shoulder and back region. Clinically, the severance of the scalenus anterior and medius ameliorated or relieved the compression of the dorsal scapular nerve. Complete decompression required cutting of the scalenus medius and its tendinous tissue superficial to the dorsal scapular nerve. Among 24 sides of 22 patients undergoing surgery, the symptoms of 20 sides of 19 patients were completely or partially relieved.

Adult↗
PubMed1995

Quadrilateral space syndrome.

We studied 4 cases of quadrilateral space syndrome. Though the syndrome is quite uncommon, it might be discovered by examination of the patient complaining of pain of neck and shoulder especially when the tenderness in the quadrilateral space. Early surgical decompression is indicated as soon as diagnosis is made.

Adult↗
PubMed1995

Degenerative mechanism of articular cartilage induced by low stress. A morphological study.

Immobilization leads not only to diminished joint movement but also low stress of articular cartilage. The present investigation was undertaken to observe the morphological changes which arose in articular cartilage with low stress. The joint motion remained intact. Articular cartilage from the left knees of 66 rats whose left calcaneal tendons had been transected was examined under transmission electron microscope and light microscope. The degenerative changes were observed: decreased functional activity of chondrocytes progressively degenerated cartilage and lack of compensatory proliferation of chondrocytes at the early stage. We propose that the degeneration of articular cartilage induced by immobilization is the result of combination of low stress and lack of joint motion. The following degenerative mechanism begins with chondrocytes. Chondrocyte and matrix influence each other in a vicious cycle. Low stress may restrain the repair activities.

Animals↗
PubMed1995

[Clinical and pathologic analysis of 33 cases of brachial plexus neurinoma].

Clinical and pathological findings in 33 cases of brachial plexus neurinoma are reported. In 30 cases (90.91%) the diagnosis was proved to be correct by postoperative histological sections, and in other 3 cases (9.09%) the diagnosis couldn't be made preoperatively. The 33 cases were subjected to surgical resections and 18 (54.55%) of them still felt numbness and pain within two weeks after surgery. Sixteen cases were followed up for three months and 14 (87.5%) of them felt numbness by percussion over the incision. All the 33 cases had no brachial plexus traumatic complication postoperatively.

Adolescent↗