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Biomedical subjects

C Xiao

Publications and source records attributed to C Xiao.

At least 73 records · Page 4Linked to original sources
PubMed1998

[The influence of several factors on automated DNA sequencing].

OBJECTIVE: To investigate the influence of several factors on isothermal automated DNA sequencing. METHODS: The effects of DNA purity and DNA concentration, as well as the quality of water used during sequencing on automated DNA sequencing results were retrospectively analyzed. RESULTS: When the DNA was not pure enough, the nucleotide curve showed lower ratio of signal to noise, or compression would occur, leading to difficulty in correctly judging the nucleotides; the readable length of nucleotides was shorter when low concentration of DNA was used; when the quality of water used in sequencing reaction and polyacrylamide gel solution was not high enough, the peaks of nucleotides became wider and flatter, or double peaks would occur, resulting in unreadable sequences. CONCLUSION: DNA purity and concentration as well as quality of water used in sequencing reaction and polyacrylamide gel solution had apparent influence on isothermal automated DNA sequencing. This suggests that high purity of DNA and high quality of water should be used in isothermal automated DNA sequencing; if longer DNA sequence needs to be obtained, DNA concentration should not be too low.

DNA↗
PubMed1998

Actinosporean stages of myxozoan parasites of oligochaetes from Lake Sasajewun, Algonquin Park, Ontario: new forms of triactinomyxon and raabeia.

Eight forms of triactinomyxon and 6 forms of raabeia of oligochaetes from Lake Sasajewun, Algonquin Park are described. Of the 8 forms of triactinomyxon, 2 designated as triactinomyxon 'B' and 'E' were found in both Limnodrilus hoffmeisteri and Tubifex tubifex. Three additional forms, designated as triactinomyxon 'A,' 'C,' and 'D,' occurred in L. hoffmeisteri. One form infecting L. hoffmeisteri was identified as Triactinomyxon ignotum Stolc, 1899, and another infecting T. tubifex was tentatively identified as Triactinomyxon dubium Granata, 1924. One form infecting L. hoffmeisteri and Rhyacodrilus coccineus was designated as triactinomyxon 'F.' Of the 6 forms of raabeia, 4 designated as raabeia 'A,' 'B,' 'C,' and 'F' were found in L. hoffmeisteri, and 2 designated as raabeia 'D' and 'E' were recorded in T. tubifex. The sporoplasmic mass of each form of triactinomyxon usually moved posteriorly within the cavity of the spore axis and was released through its posterior end, whereas the sporoplasmic mass of each form of raabeia was released through the anterior end of the epispore. An increase in the number of germ cells was observed in the floating spore stage of triactinomyxon 'B,' 'D,' 'E,' and raabeia 'B.'

Animals↗
PubMed1998

Actinosporean stages of myxozoan parasites of oligochaetes from Lake Sasajewun, Algonquin Park, Ontario: new forms of echinactinomyxon, neoactinomyxum, aurantiactinomyxon, guyenotia, synactinomyxon and antonactinomyxon.

Six forms (5 of which are new) of echinactinomyxon and 5 new forms of the collective groups neoactinomyxum, aurantiactinomyxon, guyenotia, synactinomyxon, and antonactinomyxon of oligochaetes in Lake Sasajewun, Algonquin Park are described. Five forms of echinactinomyxon designated as echinactinomyxon 'A,' 'B,' 'C,' 'D,' and 'E,' a form of neoactinomyxum, and a form of aurantiactinomyxon were found in Limnodrilus hoffmeisteri. Echinactinomyxon radiatum, a form of synactinomyxon, and a form of antonactinomyxon were recorded from Tubifex tubifex. A form of guyenotia was found in Lumbriculus variegatus. The sporoplasmic mass of these actinosporeans was released through the anterior end of the epispore. An increase in the number of germ cells was observed in the floating spore stage of all forms except echinactinomyxon 'C' and the form of antonactinomyxon.

Animals↗
PubMed1998

The oligochaetes and their actinosporean parasites in Lake Sasajewun, Algonquin Park, Ontario.

There is little ecological information on actinosporean parasites and their oligochaete hosts. Between 1995 and 1997, about 14,100 oligochaetes belonging to 19 species were collected from Lake Sasajewun. The oligochaete fauna consisted of 5 tubificid, 10 naidid, 3 enchytraeid, and 1 lumbriculid species. The most widely distributed species in the lake were Limnodrilus hoffmeisteri, Dero nivea, and Stylaria lacustris, with L. hoffmeisteri being the most prevalent. The diversity and abundance of worms decreased with increased water depth. Four species, L. hoffmeisteri, Tubifex tubifex, Rhyacodrilus coccineus, and Lumbriculus variegatus, harbored actinosporean parasites and were distributed along shallow areas of the lake shore where the sediment was comprised mainly of clay-mud, with the shoregrass, Littorella americana. The actinosporean parasites of the oligochaetes belong to 25 forms of 8 collective groups. Triactinomyxon 'F' was the most prevalent form, whereas triactinomyxon, raabeia, and echinactinomyxon were the most speciose groups. The overall prevalence of actinosporeans was about 1%. Waterborne spores of different actinosporean forms showed distinct temporal patterns. Spores of triactinomyxon 'F' occurred throughout the sampling season, whereas spores of other forms occurred only at certain times. The presence of waterborne spores peaked from late June to August when water temperatures ranged from 18 to 24 C and coincided with the feeding and growing season of larval fish.

Animals↗
PubMed1997

Tight links between adenine and guanine nucleotide pools in mouse pancreatic islets: a study with mycophenolic acid.

Glucose metabolism in pancreatic B-cells leads to an increase in the ATP/ADP ratio that might participate in the regulation of insulin secretion. Good correlations have also been observed between guanine nucleotide levels in isolated pancreatic islets and insulin secretion. To assess whether guanine nucleotides have a specific role in stimulus-secretion coupling, their concentration should be modified selectively. This was attempted by culturing mouse islets overnight in the presence of mycophenolic acid (MPA), an inhibitor of GMP synthesis at the level of IMP dehydrogenase. The drug (25-50 microg/ml) did not affect the insulin content but decreased the GTP content of the islets and inhibited insulin secretion during subsequent incubation in the presence of 15 mM glucose. However, MPA also decreased the ATP/ADP ratio in the islets. The addition of guanine to the culture medium (to stimulate the salvage pathway of GTP synthesis) restored normal GTP levels, corrected the ATP/ADP ratio and partly prevented the inhibition of insulin release. In contrast, attempts to stimulate ATP synthesis specifically (by provision of adenine or adenosine) failed to reverse any of the effects of MPA. It is concluded that guanine and adenine nucleotide pools are tightly linked and cannot be specifically affected by MPA in pancreatic islet cells, probably because of the activity of nucleoside diphosphate kinase and because of the role of GTP in several reactions leading to adenine nucleotide generation. Contrary to previous claims, MPA is not an adequate tool for evaluating a specific role of guanine nucleotides in the control of insulin secretion.

Adenine Nucleotides↗
PubMed1997

Central projection of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive trigeminal primary neurons in the rat.

Substance P (SP) is implicated in transmission of primary afferent nociceptive signals. In primary neurons, SP is colocalized with calcitonin gene-related peptide (CGRP), which is another neuropeptide marker for small to medium primary neurons. CGRP coreleased with SP augments the postsynaptic effect of SP and thereby modulates the nociceptive transmission. This study demonstrates the distribution of CGRP-like immunoreactivity (-ir) and SP-ir in the lower brainstem of normal rats and after trigeminal rhizotomy or tractotomy at the level of subnucleus interpolaris (Vi). By comparing the results obtained from normal and deafferented rats, we analyzed the central projection of trigeminal primary nociceptors. The CGRP-immunoreactive (-ir) trigeminal primaries projected to the entire rostrocaudal extent of the spinal trigeminal nucleus, the principal nucleus (PrV), the paratrigeminal nucleus (paraV), and the lateral subnucleus of solitary tract nucleus (STN) on the ipsilateral side. The trigeminal primaries projecting to the spinal trigeminal nucleus, paraV and STN also contained SP-ir. The ipsilateral trigeminal primaries were the exclusive source of CGRP-ir terminals in the PrV, the Vi and the dorsomedial nucleus within the subnucleus oralis (Vo). The medullary dorsal horn (MDH) and the lateral edge of Vo received convergent CGRP-ir projection from the ipsilateral trigeminal primaries and other neurons. The glossopharyngeal and vagal primaries are candidates for the source of CGRP-ir projection to the Vo and the MDH, while the dorsal root axons supply the MDH with CGRP-ir terminals. In addition, contralateral primary neurons crossing the midline appear to contain CGRP and to terminate in the MDH.

Animals↗
PubMed1997

Exaggerated C-fiber activation prevents peripheral nerve injury-induced hyperinducibility of c-Fos in partially deafferented spinal dorsal horn.

Dorsal horn neurons chronically deafferented by peripheral nerve injuries acquire hypersensitivity to noxious input from outside the original receptive field. This study examines the effect of electrical nerve stimulation at the time of injury on such injury-induced hypersensitivity. The medial 3/8 of the dorsal horn laminae I/II around the junction of 4th and 5th lumbar segments (the tibial territory) was deafferented by transection of the ipsilateral tibial nerve in rats. At 2 days or 3 weeks postinjury, the hindpaw was injected with formalin to induce c-fos. At 2 days, neurons with induced c-Fos protein-like immunoreactivity (fos-neurons) were largely confined in the lateral 5/8 of laminae I/II (the peroneal and hip, thus P and H territory). At 3 weeks, fos-neurons significantly increased in the deafferented tibial territory. A similar increase was also noted in the P and H territory. Thus the dorsal horn neurons exhibited c-fos hyperinducibility, an indication of hypersensitivity. Electrical stimulation with a train of 150 shocks (10 V, 2 ms) of the proximal nerve stump immediately after transection prevented the c-fos hyperinducibility. The effect was greater with the stimulation frequency of 0.5 Hz than 0.1 Hz or 10 Hz. The stimulation had no effect on the c-fos inducibility at 2 days postinjury.

Animals↗
PubMed1997

Trigeminal primary projection to the rat brain stem sensory trigeminal nuclear complex and surrounding structures revealed by anterograde transport of cholera toxin B subunit-conjugated and Bandeiraea simplicifolia isolectin B4-conjugated horseradish peroxidase.

Trigeminal primary afferent neurons were labeled by injecting the rat trigeminal ganglion with either wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), cholera toxin B subunit (B)-HRP or Bandeiraea simplicifolia isolectin B4 (IB4)-HRP. B-HRP stained medium to large cells (> 600 microm2), while IB4-HRP mostly small cells (< 400 microm2). WGA-HRP labeled trigeminal ganglion neurons of all sizes. Cell bodies in the mesencephalic trigeminal tract nucleus were labeled with WGA-HRP and B-HRP but not IB4-HRP. B-HRP revealed dense projection to the entire brain stem sensory trigeminal nuclear complex (BSTC) except for lamina II of the medullary dorsal horn (MDH). Some contralateral projection was also seen in the caudal part of MDH. Non-trigeminal nuclei receiving B-HRP-labeled terminals included the paratrigeminal nucleus (paraV), solitary tract nucleus, supratrigeminal nucleus, Probst's nucleus and median accessory nucleus. Following IB4-HRP application, terminal label was found in more restricted regions within the BSTC. Modest terminal label was seen in the dorsal part of principal sensory nucleus and at the medial edge of subnucleus interpolaris, while relatively dense terminal fields were seen in the dorsal half of subnucleus oralis. The MDH laminae I and II contained dense terminal label. Non-trigeminal nuclei were almost devoid of the IB4-HRP-labeled terminals excepting the paraV that contained dense terminal label. The terminal areas revealed with WGA-HRP coincided with B-HRP-labeled and IB4-HRP-labeled areas combined.

Animals↗
PubMed1997

Infiltration of eosinophils into the asthmatic airways caused by interleukin 5.

Interleukin (IL)-5 is thought to play an important role in asthmatic bronchial mucosal inflammation and is a potential therapeutic target. To investigate the effect of IL-5 on the infiltration of eosinophils in airway in vivo, we compared eosinophil counts and their activation status in airways without and after the topical instillation of recombinant human IL-5. Eight subjects with mild atopic asthma underwent initial bronchoscopy during which control bronchoalveolar lavage (BAL) fluid as well as bronchial mucosa were obtained, and at the same time, normal saline and IL-5 were administered to two sublobar segments separately. The second bronchoscopy were carried out and samples from challenged sites were taken 24 h later. It was found that the total eosinophils (BMK-13+ cells) and the activated eosinophils (EG2+ cells) in bronchial mucosa, the eosinophil numbers in BAL fluid, as well as eosinophil cationic protein (ECP) in BAL fluid from saline-challenged segments were not different from those in unchallenged segments. However, a significant eosinophilia was observed in bronchial mucosa and BAL fluid from IL-5-challenged sites. Eosinophil activation, as assessed by secretion of ECP, was also increased significantly in bronchial mucosa and BAL fluid. The results strongly suggested that IL-5 is capable of inducing eosinophil infiltration into the asthmatic airways, as well as the activation of infiltrating eosinophils.

Adult↗
PubMed1997

[A study on the possible mechanism for the second control site of insulin secretion in islets].

Glucose stimulation of insulin release involves closure of ATP-sensitive K+ channels (K(+)-ATP channels) in beta cells. However, by using diazoxide to open K(+)-ATP channels, it has been reported that another mechanism exists, by which glucose can control insulin release independently from changes in K(+)-ATP channel activity. These data suggested that there is a second control site in islets when insulin is secreted. To probe the possible existence of this site, mouse islets were used to investigate the energy state of islets in insulin secretion when the activity of K(+)-ATP channels was eliminated by diazoxide. In the present study, isolated islets were cultured in PRMI 1640 medium for 18 hours. The islets were then divided into 6 groups randomly, with 10 islets per group, placed in 1 ml KREBS medium containing 30 mmol/L K(+) and 250 mmol/L diazoxide with 0, 3, 6, 10, 15, 20 mmol/L glucose respectively and incubated in 37 degrees C water for 60 minutes. A portion of the supernatant was withdrawn at the end of the incubation for insulin assay, the islets were treated with trichloracetic acid and diethyl ether for the measurements of ATP, ADP, GTP and UTP. The above findings demonstrated that insulin secretion increases with the rise of glucose concentration. In the same time, the level of ATP increaseded and the level of ADP decreased gradully. The ratio of ATP/ADP in islets correlated with the insulin secretion very well. The level of GTP and UTP also increased with the rise of glucose concentration. It is suggested that glucose can control insulin secretion independently from its action of K(+)-ATP channels and the existence of a second control site as an another mechanism for insulin release. The ratio of ATP/ADP is an important factor in this mechanism; GTP and UTP also participated in the control of insulin secretion.

Adenosine Diphosphate↗
PubMed1997

[Efficacy of unfixed continuation phase short-course chemotherapy].

OBJECTIVE: To evaluate the efficacy of the short-course chemotherapy shorter than six months. METHOD: The 2SHRZ/xHR regimen was used in 290 smear positive new untreated tuberculosis patients. The duration of continuation phase was not fixed, just in accordance with the speed of sputum negative conversion. The treatment was continued until sputum negative conversion mantained for three consecutive months. RESULT: Two hundred eighty-three out of 290 patients were cured. The sputum negative conversion rate at the end of the sixth month was 98.3%. The duration of treatment was 4.7 months on the average. The rate of two-year follow-up was 94.3%, and the rate of bacteriological relapse during two-year follow-up was 1.9%. CONCLUSION: The results showed that the length of the six-month short-course chemotherapy could be shortened, and its recent and long-term efficacy was found satisfactory.

Adult↗
PubMed1996

Bax protein-like immunoreactivity in primary sensory and hypothalamic neurons of adult rats.

Bax protein-like immunoreactivity (Bax-ir) was examined in the perfusion-fixed, cryosectioned rat nervous system. In the central nervous system, hypothalamic neurons were the only neurons that exhibited Bax-ir in the cell body. Their axons traveled toward the median eminence, suggesting that the Bax-like immunoreactive (Bax-ir) hypothalamic neurons included neurosecretory ones. Bax-ir axons were observed in the solitary tract nucleus, and spinal and medullary dorsal horns. They appear to have been derived from Bax-ir primary sensory neurons in the viscerosensory nodose ganglion and somatosensory dorsal root and trigeminal ganglia. In the somatosensory ganglia, smaller cells exhibited stronger Bax-ir. Accordingly, the ir axons in the dorsal horn were most concentrated in lamina II.

Animals↗
PubMed1996

Two-dimensional crystallization of rabbit C-reactive protein on lipid monolayers.

Two-dimensional (2D) crystals of rabbit C-reactive protein (CRP) have been obtained by protein binding on lipid monolayers at the air/water interface. Two different types of crystalline arrays of CRP were obtained, by specific binding and non-specific adsorption to the lipids. Electron crystallographic analysis of the negatively stained specimens showed that the unit cell parameters of the CRP 2D crystals formed by specific binding were a=81 angstroms, b=78 angstroms, gamma=118.35 degrees, and those formed by nonspecific adsorption were a=74 angstroms, b=67 angstroms, gamma=95.5 degrees, both with the layer group p1. Projection maps were obtained at a resolution of 26 angstroms and 22 angstroms respectively. They showed that only the monomers of the CRP were packed in the 2D arrays and the orientations of the monomers on the lipid monolayers were different in the two types of crystals. By comparing the two projection maps, a preliminary shape of the CRP monomer has been derived. A model of the pentameric structure of the oligomeric CRP has been proposed.

Adsorption↗
PubMed1996

Parvalbumin-immunoreactive nerve endings in the periodontal ligaments of rat teeth.

Parvalbumin-immunoreactive nerve fibres were most abundant in the lingual periodontal ligaments of incisor teeth. In the part of the ligament adjacent to the alveolar bone, thick and smooth parvalbumin-immunoreactive nerve fibres left main nerve bundles and passed towards the part of the ligament adjacent to the tooth. In the ligament, halfway between the bone and tooth surfaces, these nerve fibres repeatedly branched and extended one to four twigs to produce bush-like endings. Parvalbumin-immunoreactive fibres and terminals were infrequent in the periodontal ligaments of the molar teeth. It is possible that parvalbumin-immunoreactive endings are periodontal mechanoreceptors, but at present it is difficult to account for the different representations around rat molar and incisor teeth.

Alveolar Process↗
PubMed1996

Studies on high-density cultivation of Vero cells with biosilon solid microcarrier.

From eight kinds of microcarriers, Biosilon has been chosen as the most suitable microcarrier for high-density cultivation of African green monkey kidney (Vero) cells. Conditions affecting high-density cultivation were studied with a 500 ml modified Wheaton spinner flask. When cultivation with a 1.5 L CelliGen bioreactor at inoculum density of 4.9 x 10(6)/ml and perfusion volume increased from 0.20 L to 3.65 L gradually, the cell density could reach 2.05 x 10(7)/ml after 22 days of cultivation. When Vesicular Stomatitis Virus (VSV) was inoculated into the cultures of 1.21 x 10(6) ml at the some MOI (multiplicity of infection), the virus titers reached 7 log TCID50/ml and 8 log TCID50/ml, respectively.

Animals↗
PubMed1996

Study on serum-free media for genetically engineered CHO cells producing prourokinase.

Based on the initial optimization of DMEM:F12(1:1), two kinds of serum-free media, 11G-SG-SFM and 11G-SE-SFM, were formulated by using orthogonal experiments for the growth of genetically engineered CHO cell line 11G and the production of recombinant prourokinase (pro-UK) in a suspension culture, respectively. Growth of 11G cells in 11G-SG-SFM was comparable with that observed in DMEM:F12 + 5% NBS and CHO-S-SFM. 11G cells grew slowly in 11G-SE-SFM, but secreted a relatively high level of pro-UK. The pro-UK productivity of 11G cells in 11G cells in 11G-SE-SFM reached 800 to 1,000 IU/10(6). d-1 and was about 80% and 20% higher than in DMEM:F12 + 5% NBS and CHO-S-SFM, respectively.

Animals↗
PubMed1995

Specific binding of avidin to biotin containing lipid lamella surfaces studied with monolayers and liposomes.

The interaction of avidin (from egg white) with phospholipid (monolayer and bilayer) model membranes containing biotin-conjugated phospholipids has been studied. In the first part, using surface sensitive techniques (ellipsometry and surface plasmon resonance) we demonstrated that the nonspecific adsorption of avidin to phospholipid lamella could be abolished by adding an amount of Ca2+, Mg2+ or Ba2+ that led to an electrostatic interaction. The specific binding of avidin to lipid mixtures containing biotin-conjugated phospholipids was obviously composition dependent. The ratio 1:12 of a B-DPPE/DPPE mixture was found to be the optimum molar ratio. When we compared the results from the surface sensitive techniques with those from the electron micrographs of a two dimensional crystal of avidin (obtained in our laboratory), the optimum ratio was found to be determined by the effect of lateral steric hindrance. In the second part, we observed the pattern of the layers of fluorescently labeled phospholipid and adsorbed proteins with a home-made micro fluorescence film balance. The fluorescence images showed that avidin was preferentially bound to the receptors that were in the fluid domains. Further, with a sensitive fluorescence assay method, the effect of the phase behavior of liposomes on the specific binding of avidin was measured. This showed that avidin interacted with biotinlipid more weakly in the gel state liposome than in the liquid state liposome. The major conclusion was that the binding of avidin to a membrane bound model receptor was significantly restricted by two factors: one was the lateral steric hindrance and the other was the fluidity of the model membrane.

Adsorption↗