Biomedical subjects

G Gu

Publications and source records attributed to G Gu.

At least 19 recordsLinked to original sources

PubMed2005

Mechanisms of antinociception of spinal galanin: how does galanin inhibit spinal sensitization?

Galanin by a spinal action has been shown to have an antihyperalgesic action. Thus, in rats with lumbar intrathecal (IT) catheters, the thermal hyperalgesia evoked by carrageenan paw injection was blocked by IT delivery of galanin(1-29) (Gal(1-29)) and galanin(2-11) (Gal(2-11)) with the rank order of activity being Gal(1-29)>Gal(2-11). We sought to determine whether this spinal action reflects an effect upon afferent transmitter release, e.g., substance P (SP), and/or on secondary neurons, e.g., signaling postsynaptic to neurokinin 1 (NK1) receptor activation. To address the question on afferent release, we investigated the effect of IT administration of galanin on tissue injury-induced spinal NK1 internalization (an indicator of SP release). Noxious stimulation (paw compression) produced an increase in NK1 internalization in dorsal horn lamina I. IT pretreatment of rats with Gal(1-29) and Gal(2-11) significantly attenuated the evoked NK1 internalization, with the rank order of activity being Gal(1-29)>Gal(2-11)>saline. To address the question of postsynaptic action, we examined the effects of IT galanin upon IT SP-induced thermal hyperalgesia and spinal PGE2 release. Application of SP (30 nmol) directly to spinal cord led to a decrease in thermal thresholds and a profound increase in PGE(2) concentration in spinal dialysates. Both phenomena were reversed by Gal(1-29) and Gal(2-11) (10nmol, IT). These findings suggest that the antihyperalgesic effect of spinal galanin is due to its action on sites both presynaptic (inhibition of SP release) and postsynaptic (blockade of SP-evoked hyperalgesia and PGE2 production) to the primary afferents.

Animals↗

PubMed2005

Estrogen protects primary osteocytes against glucocorticoid-induced apoptosis.

Glucocorticoid-induced osteoporosis may be at least in part due to the increased apoptosis of osteocytes. To study the role of osteocyte apoptosis in glucocorticoid-induced osteoporosis, we isolated primary osteocytes from murine calvaria for the analysis of the effects of dexamethasone in in vitro culture. The cells were identified by morphology, cytochemical staining, immunocytochemical staining and mRNA expression of phosphate-regulating gene with homology to endopeptidases on the X chromosome (PHEX) and sclerosteosis/van Buchem disease gene (SOST). We found that dexamethasone induced osteocyte apoptosis in a dose-dependent manner. A glucocorticoid receptor antagonist, mifepristone (RU486), suppressed dexamethasone-induced osteocyte apoptosis, suggesting that it was mediated by glucocorticoid receptor. Immunocytochemical stainings showed that glucocorticoid receptors are present in primary osteocytes, and they were translocated to nuclei after the exposure to dexamethasone. Addition of estrogen prevented glucocorticoid receptor translocation into nuclei. Corresponding antiapoptotic effects in primary osteocytes were also seen after the pretreatment of primary osteocytes with a picomolar concentration of estrogen. The pure antiestrogen ICI 182,780 inhibited estrogen effect on apoptosis induced by dexamethasone. These data suggest that glucocorticoid receptors play an important role in glucocorticoid-induced osteocyte apoptosis. Most importantly, estrogen has a protective effect against osteocyte apoptosis. To conclude, the mechanism of glucocorticoid-induced osteoporosis may be due to the apoptosis of osteocytes, which can be opposed by estrogen.

Animals↗

PubMed2004

Neurons in the principal nucleus of the bed nuclei of the stria terminalis provide a sexually dimorphic GABAergic input to the anteroventral periventricular nucleus of the hypothalamus.

Neurons of the principal nucleus of the bed nuclei of the stria terminalis (BSTp) process pheromonal and viscerosensory stimuli associated with reproduction and relay this information to preoptic and hypothalamic cell groups that regulate reproductive function. The anteroventral periventricular nucleus of the hypothalamus (AVPV), a nucleus involved in the regulation of gonadotropin secretory patterns, receives dense projections from BSTp neurons in males but not in females. By injecting the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHAL), into the BSTp of rats and immunohistochemically colocalizing the GABA synthetic enzyme, GAD65, to PHAL-immunoreactive fibers in the AVPV, we tested the hypothesis that these sex-specific projections arise from BSTp neurons that synthesize the inhibitory neurotransmitter GABA. Although dense GAD65-immunoreactive fiber terminals were observed in both the male and female AVPV, higher numbers of GAD65-labeled terminals were found in the male, and those localized to PHAL-immunoreactive fibers were seen almost exclusively in males. Treatment of newborn females with testosterone or neonatal orchidectomy of males reversed these sex differences, while GAD65-immunoreactivity in the AVPV was not altered in response to exogenous hormone treatments administered to peripubertal animals. Our results suggest that projections from BSTp neurons constitute a stable, sex-specific GABAergic input to the AVPV that is patterned permanently by perinatal hormone exposure.

Age Factors↗

PubMed2003

Dependence of upper critical field and pairing strength on doping in cuprates.

We have determined the upper critical field Hc2 as a function of hole concentration in bismuth-based cuprates by measuring the voltage induced by vortex flow in a driving temperature gradient (the Nernst effect), in magnetic fields up to 45 tesla. We found that Hc2 decreased steeply as doping increased, in both single and bilayer cuprates. This relationship implies that the Cooper pairing potential displays a trend opposite to that of the superfluid density versus doping. The coherence length of the pairs xi(0) closely tracks the gap measured by photoemission. We discuss implications for understanding the doping dependence of the critical temperature Tc0.

Journal Article↗

PubMed2002

Unraveling the symmetry of the hole states near the Fermi level in the MgB2 superconductor.

We use x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) to study the fine structure at the K edge of boron in MgB(2). We observe in XAS a peak of width 0.7 eV at the edge threshold, signaling a narrow energy region with empty boron p states near the Fermi level. The changes in the near edge structure observed in EELS with direction of the momentum transfer imply that these states have p(x)p(y) symmetry. Our observations are consistent with electronic structure calculations indicating a narrow energy window of empty p(x)p(y) states that falls to zero at 0.8 eV above the Fermi level. The disappearance of the p(x)p(y) feature in EELS at grain boundaries suggests that this signature may become powerful in probing superconductivity at nanoscale.

Journal Article↗

PubMed2002

The mitochondrial common deletion in Parkinson's disease and related movement disorders.

The mitochondrial 4977-bp common deletion has been reported in some studies to occur exclusively or with increased frequency in the midbrain of patients with Parkinson's disease (PD). Other studies could not confirm these results; rather, it was suggested that the mitochondrial common deletion is associated with aging in the midbrain and not PD. One possible explanation for these conflicting results is the difficulty in quantifying mitochondrial DNA deletions or mutations in the whole midbrain or substantia nigra (SN) while only a subset of midbrain neurons degenerate in PD. In addition, none of the studies has addressed the cell types with the common deletion within the midbrain. In this study we used in situ hybridization to detect the common deletion in sections of midbrain from patients with PD, multiple system atrophy-parkinsonian type (MSA-P), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), age-matched controls, and individuals of different ages. The results demonstrated that the mitochondrial common deletion accumulated primarily in neurons but not glia in both the SN and other midbrain regions. There was no significant difference in the number or distribution of neurons with the common deletion or the average of the mean densities (AMD) of staining with the common deletion in nigral neurons among patients with PD, MSA-P, PSP, DLB, or age-matched controls. In addition, there was no difference in the number or distribution of neurons with the common deletion in nigral neurons between any age group, although there was a tendency for the common deletion to increase in the non-nigral neurons in older patients. These data indicate that accumulation of the 4977-bp common deletion in mitochondrial DNA in midbrain occurred primarily in neurons, and by this cytological approach, it was not associated with nigral neurodegeneration in the common movement disorders or aging.

Adolescent↗

PubMed2001

Synthesis of a hexasaccharide that relates to the arabinogalactan epitope.

A hexasaccharide derivative of the arabinogalactan epitope, methyl beta-D-galactopyranosyl-(1-->6)-[alpha-L-arabinofuranosyl-(1-->3)]-beta-D-galactopyranosyl-(1-->6)-beta-D-galactopyranosyl-(1-->6)-[alpha-L-arabinofuranosyl-(1-->3)]-alpha-D-galactopyranoside, was synthesized efficiently using a 3+3 strategy. The key step is the preparation of the trisaccharide donor, isopropyl 2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl-(1-->6)-[2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosyl-(1-->3)]-2,4-di-O-benzoyl-1-thio-beta-D-galactopyranoside, from isopropyl 1-thio-beta-D-galactopyranoside using a one-pot synthesis of a 3,6-differentially protected building block.

Epitopes↗

PubMed2001

Target-dependent sexual differentiation of a limbic-hypothalamic neural pathway.

Neural pathways between sexually dimorphic forebrain regions develop under the influence of sex steroid hormones during the perinatal period, but how these hormones specify precise sex-specific patterns of connectivity is unknown. A heterochronic coculture system was used to demonstrate that sex steroid hormones direct development of a sexually dimorphic limbic-hypothalamic neural pathway through a target-dependent mechanism. Explants of the principal nucleus of the bed nuclei of the stria terminalis (BSTp) extend neurites toward explants of the anteroventral periventricular nucleus (AVPV) derived from male but not female rats. Coculture of BSTp explants from male rats with AVPV explants derived from females treated in vivo with testosterone for 9 d resulted in a high density of neurites extending from the BSTp to the AVPV explant, as was the case when the BSTp explants were derived from females and the AVPV explants were derived from males or androgen-treated females. These in vitro findings suggest that during the postnatal period testosterone induces a target-derived, diffusible chemotropic activity that results in a sexually dimorphic pattern of connectivity.

Animals↗

PubMed2001

Effect of acid and surfactant treatment on activated sludge dewatering and settling.

The effect of pretreating activated sludge with sulfuric acid and surfactant on its exocellular polymer(ECP), dewaterability and settleability was investigated. It was observed that the centrifugal dewatering efficiency was increased with the decrease of sludge pH value, and which was further improved if the surfactant was simultaneously applied. However, to the filtration dewatering, the water content reached the minimum in the case of pH 2.5, and the additional use of surfactant was also favorable. The water content of sludge dewatered with filtration reached 73.99% when a pH 2.5 and a 0.1 g surfactant were employed, which was reduced by around 2% as compared with surfactant unused. Experimental results indicated that the sludge sedimentation rate was significantly accelerated under pH 2.5 condition, and which was increased once more by the utilization of surfactant. Further studies revealed that treating activated sludge with sulfuric acid at pH 2.5 or combined with surfactant was an effective method to remove the polymers from sludge surface and induced the decrease of ECP, which resulted in the improvement of dewaterability and settleability. This study suggested the potentiality of improving activated sludge mechanical dewaterability by the use of sulfuric acid to control its pH at 2.5 or together with a surfactant.

Acids↗

PubMed2001

Osteoclast clearance from periodontal tissues during orthodontic tooth movement.

The presence of osteoclasts at locations of alveolar bone remodeling is antecedent to orthodontic tooth movement. Cell recruitment and clearance are the mechanisms by which osteoclast populations are regulated. Research in other tissues has revealed that many cells die after their functional lives are past by a process called apoptosis, or programmed cell death. The purpose of this study was to examine the role of apoptosis in osteoclast clearance at orthodontically treated sites as a function of time and location. Orthodontic appliances were placed on 96 rats of the Sprague-Dawley strain. The rats were assigned to either treatment or sham (control) groups and killed 1, 3, 5, and 7 days after appliance placement. Tissue samples were prepared for histochemical evaluation and quantification of morphologic features. Tartrate-resistant acid phosphatase (TRAP) and ApopTag (TdT-mediated dUTP-biotin nick 3' end labeling) stains were used to identify osteoclasts and committed preosteoclasts and to discriminate between apoptotic and nonapoptotic nuclei. Pyknotic nuclei and apoptotic bodies were also counted as a morphologic assessment of apoptosis. The percentages of TRAP/ApopTag-positive nuclei were measured in 4 different periodontal regions. There was a highly significant difference in the overall percentage of TRAP/ApopTag-positive nuclei between the control and the treatment groups at 3, 5, and 7 days (P <.001). Morphologic criteria were also statistically different at days 5 and 7 (P <.05). These data strongly suggested that osteoclasts recruited for orthodontic tooth movement are, at least in part, cleared by apoptosis.

Acid Phosphatase↗

PubMed2001

Osteoclast recruitment to sites of compression in orthodontic tooth movement.

Although it is widely acknowledged that osteoclasts are formed by the fusion of mononuclear cells of hematopoietic origin, it has been extremely difficult to understand how they originate after appliance activation. The purpose of this study was to quantify osteoclast recruitment at compression sites as a function of time following orthodontic force application. Appliances were placed in 96 rats. At day 0, the animals were randomized to either appliance activation or sham activation followed by the injection of 5-bromo-2'-deoxyuridine (BrdU). Thus, BrdU was incorporated into the nuclei of cells in S-phase, including hematopoietic stem cells. Groups of 10 to 13 rats were killed at 1, 3, 5, and 7 days after activation/sham, and the tissue samples were prepared. The numbers of BrdU-labeled cells positively stained with tartrate-resistant acid phosphatase (TRAP) were measured in the periodontium. A significant number of BrdU-positive preosteoclasts was observed in the periodontal ligament (PDL) and bone surface at day 3. The number of osteoclastic cells in the bone marrow also peaked at day 3; however, the highest percentage of cells in this location was observed at day 1. These data suggest that osteoclasts in the PDL originate by the fusion of recently recruited preosteoclasts from the marrow instead of from local PDL cells. Furthermore, the alveolar bone marrow plays a role in the formation of osteoclasts during orthodontic tooth movement.

Acid Phosphatase↗

PubMed2001

One-year outcome of auditory-tactile-visual-vestibular intervention in the neonatal intensive care unit: effects of severe prematurity and central nervous system injury.

Thirty-seven infants with severe central nervous system injury or extreme prematurity were randomly assigned to a multisensory (auditory-tactile-visual-vestibular) intervention or control group. Intervention began in the hospital at 33 weeks' postconceptional age and continued twice daily in the home until 2 months' corrected age. Mother-infant interactions during feedings were videotaped, and the Bayley Scales of Infant Development were administered. Control mothers stimulated their infants more during feeding, but these significant differences dissipated by 4 months. The presence of periventricular leukomalacia was associated with significantly poorer mental development, regardless of group assignment. Experimental infants tended to exhibit better motor and mental performance and had 23% fewer cerebral palsy diagnoses at 1 year, but these trends were not statistically significant. The type of brain injury was more important in determining 1-year developmental outcome than type of postnatal experience, suggesting that periventricular leukomalacia presents a major challenge for infant development.

Birth Injuries↗

PubMed2001

Reclaimed municipal wastewater--a potential water resource in China.

Due to water resource shortage and socio-economic development within twenty years, China faces serious problems of water supply and water pollution. Several criteria and suitable reclamation processes related to water reuse have been created in China, which are helpful to improve the situation of water scarcity. In the future, reclaimed municipal wastewater reuse will mainly be developed for urban and industrial use. Potential supply quantity of reclaimed water, quality of reclaimed water, and reclamation cost are favorable to potential reuses. Based on further public environmental education, on a relevant development of national and local standards for reclaimed water quality, and on an increase of sanitary rate, more and more planned reclaimed water reuse projects would be expected in China.

Agriculture↗

PubMed2001

[Effect of anaerobic acidification treatment on nitrogen removal and toxicity reduction of coke plant wastewater].

Coke plant wastewater was treated by anaerobic acidification-anoxic-aerobic (A1-A2-O) biofilm process and anoxic-aerobic (A/O) biofilm process respectively. Toxicity reduction effects of the two processes were compared. The toxicity of coke plant wastewater was equal to that of mercury chloride with concentration of 0.19 mg/L. Its toxicity reduction was related to the removal of organic nitrogen. Anaerobic acidification unit acted an important role on removal of both organic nitrogen and reduction of toxicity of the wastewater. After treatment by A1-A2-O process, its toxicity can be decreased greatly. When HRT was 37.9 hours, The relative luminosity of the treated effluent to photobacterium can attain 96.8%, that is equal to the toxicity of mercury chloride with concentration of 0.023 mg/L.

Anaerobiosis↗

PubMed2001

Mechanism and kinetics of low-temperature thermochemical conversion process for sewage sludge.

The low-temperature thermo-chemical conversion process for sewage sludge is a prospective technology, through which the energy in the sludge can be recovered. With the help of elementary analysis of sewage sludge and its conversion products, thermal gravimetric analysis (TGA) of the sludge and GC/MS analysis of the derived oil, a study was carried out on element transfer, characteristic conversion temperature and conversion reaction mechanism of the process. The following results are obtained: 1) the predominant conversion reactions are distillation of aliphatic compounds, splitting of protein peptide bonds and group transfer; and 2) the main components involved in the conversion are aliphatic compounds and protein, with the lower reaction temperature for the former, the higher for the latter and the highest for saccharides. Based on the mechanism analyses, the simplified reaction model of the thermo-chemical conversion process for sewage sludge consists of two serial competitive reactions (producing volatile matter and char respectively). The estimated Arrhennius kinetic parameters of the reaction model based on TGA testing resultsare A1 = 4.15 x 10(6) 1/s, n1 = 2, E1 = 98 kJ/mol; A2 = 1.42 x 10(5) 1/s, n2 = 2, E2 = 85 kJ/mol; A3 = 1.01 x 10(12) 1/s, n3 = 4, E3 = 190 kJ/mol; A4 = 1.33 x 10(9) 1/s, n4 = 4, E4 = 146 kJ/mol.

Conservation of Natural Resources↗

PubMed2001

[Irradiation of 235 uranium on the growth, behavior and some biochemical changes of brain in neonatal rats].

The effects of enriched uranium on growth, behavior and biochemical changes of brain in neonatal Wistar rats was studied. Neonatal rats were irradiated with a single injection of 2 microliters enriched uranium (containing 0, 1, 5 and 10 micrograms of 235U) into left lateral ventricle of brain at the first day (< 24 h) after birth. The growth and neurobehavior development of the rats was delay and abnormal. The microautoradiographic tracing technique showed that the radionuclide was mainly accumulated in the nucleus, also appeared in the cytoplasm of cells and between cells. The activity of superoxide dismutase (SOD) and the level of endothelin (ET) of cerebellum, cerebral cortex, hippocampus and diencephalons of brain after exposure to alpha irradiation were examined with radioimmunoassay. The data indicated that SOD and ET was elevated by low dose irradiation and distinctly inhibited by high dose irradiation. It was concluded that alpha irradiation could have damages on the developing brain of neonatal rats characterized by changing the sensibility, fragility and compensation of nerve cells.

Animals↗

PubMed2000

Evidence for an energy scale for quasiparticle dispersion in Bi2Sr2CaCu2O8

Quasiparticle dispersion in Bi2Sr2CaCu2O8 is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at 50+/-15 meV binding energy where the velocity changes by a factor of 2 or more. This change provides an energy scale in the quasiparticle self-energy. This break in dispersion is evident at and away from the d-wave node line, but the magnitude of the dispersion change decreases with temperature and with increasing doping.

Journal Article↗

PubMed2000

Hyoid position, pharyngeal airway and head posture in relation to relapse after the mandibular setback in skeletal Class III.

This study evaluates the process of relapse after mandibular setback surgery by an analysis of the role of craniofacial morphology, hyoid position, pharyngeal airway and head posture. Subjects examined were 62 patients who received the sagittal split ramus osteotomies (SSRO). Changes of the craniofacial and related structures were evaluated from the serial cephalograms up to 3 years after the surgery. Results indicated that mandibular relapse represented by Pg occurred mostly within 6 months after the surgery. A net setback of the mandible was 9.1 mm and the superior move was 1.7 mm, with a reduction of 7.2 mm in mandibular length, 4.2 mm in ramus height, 3.7 mm in posterior face height, 2.6 degrees in gonial angle, an increase of 2.9 degrees in mandibular plane angle (MPA) by the last examination. Hyoid bone moved backward and downward and head posture was raised. The forward relapse of Pg was correlated with the changes of ANB, MPA, ramus height and hyoid position. Only hyoid position was predictably correlated with mandibular morphology and head posture. These findings suggest that mandibular setback alters the relationship among the hyoid position, pharyngeal airway and the head posture. It might be critical, therefore, relapse is closely monitored and controlled before the full healing of fragments and new muscular balance is established.

Journal Article↗