Biomedical subjects

Z Xiang

Publications and source records attributed to Z Xiang.

At least 55 records · Page 3Linked to original sources

PubMed2000

[The value of STIR pulse sequence MR imaging in patients with pulmonary carcinoma].

OBJECTIVE: To evaluate the value of short TI inversion-recovery (STIR) MR imaging technique in diagnosing pulmonary carcinoma. METHODS: One hundred and eight patients with pathologically confirmed pulmonary carcinoma were examined by STIR pulse sequence and the results were compared with these by SE pulse sequence. RESULTS: STIR MR imaging was superior to conventional SE pulse sequences in significantly increasing the detection rate of lesions, improving images along the edge of the lesion, tumor invasion to adjacent structures, and demonstrating lymph node enlargement. CONCLUSION: STIR, with its sensitivity, is particularly useful to reveal metastatic lymph nodes and invasion to the pleura and chest wall.

Adult↗

PubMed1999

A sequence-ready map of the human chromosome 17p telomere.

A half-YAC clone derived from human chromosome 17p was mapped at high resolution using cosmid subclone fingerprint analysis. Colinearity of the half-YAC with the telomeric human genomic DNA fragment was ascertained by RecA-assisted restriction endonuclease cleavage mapping. Previously isolated and radiation hybrid-mapped markers TEL17P37, TEL17P49, and TEL17P80 mapped 30-60 kb from the 17p terminus. This sequence-ready map permits high-resolution integration of genetic maps with the DNA sequences directly adjacent to the tip of human chromosome 17p, and will provide the cloned DNA required for ascertaining the nucleotide sequence of this subtelomeric region.

Chromosome Mapping↗

PubMed1999

Induction of mucosal immunity with a replication-defective adenoviral recombinant.

A replication-defective adenoviral recombinant expressing the rabies virus glycoprotein was tested for induction of transgene specific central and mucosal antibodies upon systemic inoculation or upon application to the mucosa of the airways, the rectum or the female genital tract. Mice developed serum and mucosal antibody titers to rabies virus upon subcutaneous or intranasal immunization with the latter route favoring induction of genital and intestinal secretion of antibodies of the IgA isotype. Immunization through the mucosa of the genital tract or the rectum was inefficient. Mucosal and systemic antibody titers could be increased by intranasal priming followed by a booster immunization with the same construct.

Adenoviruses, Human↗

PubMed1999

Localization of ATP-gated P2X2 and P2X3 receptor immunoreactive nerves in rat taste buds.

P2X receptors have been suggested to play a role in the transduction of sensory signals such as pain and sound. In the present study, polyclonal antibodies against P2X1 to P2X6 receptors were used to localize P2X receptors in circumvallate and fungiform papillae of rats. Nerve fibres innervating the taste buds stained intensely with P2X3 receptor antibodies. P2X3 receptor-positive nerves were observed in the intra- and subgemmal regions. The nerve fibres were also stained with P2X2 receptor antibodies, but the intensity was much lower. The distribution of P2X2 receptor immunoreactivity overlaps with that of P2X3. These results suggest that ATP might be a neurotransmitter in taste reception cells in the taste buds, where it transducts the taste signals to the afferent taste nerves by activating P2X receptors at the synapses. This is the first experiment indicating such a role for ATP, although supplementary functional studies are required.

Adenosine Triphosphate↗

PubMed1999

Some state space models of HIV pathogenesis under treatment by anti-viral drugs in HIV-infected individuals.

In this paper we have extended the model of HIV pathogenesis under treatment by anti-viral drugs given by Perelson et al. [A.S. Perelson et al., Science 271 (1999) 1582] to a stochastic model. By using this stochastic model as the stochastic system model, we have developed a state space model for the HIV pathogenesis under treatment by anti-viral drugs. In this state space model, the observation model is a statistical model based on the observed numbers of RNA virus copies over different times. For this model we have developed procedures for estimating and predicting the numbers of infectious free HIV and non-infectious free HIV as well as the numbers of different types of T cells through extended Kalman filter method. As an illustration, we have applied the method of this paper to the data of patient Nos. 104, 105 and 107 given by Perelson et al. [A.S. Perelson et al., Science 271 (1999) 1582] under treatment by Ritonavir. For these individuals, it is shown that within two weeks since treatment, most of the free HIV are non-infectious, indicating the usefulness of the treatment. Furthermore, the Kalman filter method revealed a much stronger effect of the treatment within the first 10 to 20 h than that predicted by the deterministic model.

CD4 Lymphocyte Count↗

PubMed1999

DNA sequencing and analysis of a 67.4 kb region from the right arm of Schizosaccharomyces pombe chromosome II reveals 28 open reading frames including the genes his5, pol5, ppa2, rip1, rpb8 and skb1.

67 393 bp of contiguous DNA located between markers cdc18 and cdc14 on the right arm of fission yeast chromosome II has been sequenced as part of the European Union Schizosaccharomyces pombe genome sequencing project. The complete sequence, contained in cosmid clones c15C4 and c21H7, has been determined on both strands. Sequence analysis shows that it contains 28 open reading frames capable of coding for proteins, 16 split by one or more introns, but no tRNA, rRNA or transposon sequences. The gene density is one per 2. 4 kb. Six genes have been previously described (his5, pol5, ppa2, rip1, rpb8 and skb1) and 22 are novel. Of the novel genes, 14 have significant similarity with proteins of known function, three have similarities with proteins of unknown function and five show no extensive similarities with known proteins. Sequence similarities suggest that three of the novel genes encode ATP-dependent RNA helicases, two encode transcription factor components and others encode a G-protein, a dehydrogenase, a Rab escort protein, an Abc1-like protein, a lipase, an ATP-binding transport protein, an amino acid permease, an acid phosphatase and a mannosyltransferase.

Chromosome Mapping↗

PubMed1999

The comprehensive evaluation on four indices of drug resistance in acute myeloid leukemia.

To study sensitivity of drug resistance indexes and resistance manner in acute myeloid leukemia (AML), MTT drug sensitivity, growth types of CFU-L in vitro, Bcl-2 antigen and Bcl-2/Bax ratio and intracellular fluorescence intensity of daunorubicin (DNR) were determined. In 62 cases of AML, the positive coincidence rate was 73% with MTT test and the negative coincidence rate was 70%. In 3 commonly used drugs, if one drug showed sensitivity, the coincidence remission rate reached 71%. In 51 cases of AML, there were 31 patients in the group of complete remission (CR), in which CFU-L of 29 patients showed independent growth. CFU-L of 2 patients showed no growth. However, there were 20 patients in the group of non-remission (NR), in which CFU-L of 14 patients showed independent growth. CFU-L of 6 patients showed non-growth pattern. Statistical analysis showed significant difference (P < 0.05). In 32 cases of AML, the expression rate of Bcl-2 was 59.55% +/- 19.56% in drug-sensitive group, and one was 77.36% +/- 11.91% in drug-resistant group, respectively (P < 0.05). At the same time, the ratio of Bcl-2/Bax was 7.50 +/- 5.04 in drug-sensitive group and one was 14.32 +/- 8.99 in drug-resistant group, respectively (P < 0.05). In 15 case of clinically drug-resistant AML, the fluorescence histogram of DNR showed left-shift of main peak (LSMP) in 12 patients. They were diagnosed as classical drug resistance. Meanwhile, 1 patient showed right-shift of main peak (RSMP) in 3 patients. They were diagnosed as re-growth drug resistance. It is concluded that MTT and CFU-L might be used for prediction of drug sensitivity or resistance when patients were on treatment. Bcl-2 and ratio of Bcl-2/Bax might be associated with the prognosis. DNR histogram could be employed for identify the pattern drug resistance. The strength and weakness of these techniques were discussed.

Adult↗

PubMed1999

P53 gene mutations in non-Hodgkin's lymphoma.

To understand P53 gene change of non-Hodgkin's lymphoma (NHL) and human malignant lymphoma cell lines, the exons 5-7 of 29 patients with NHL and 9 kinds of human malignant lymphoma cell lines were studied by silver staining PCR-SSCP technique. Three cases of P53 gene point mutation was found in 29 cases of NHL. Mutation developed in exon 5 in 2 cases, and in exon 6 in 1 case. They were all diffuse lymphoma. In mutation cases, B-cell lymphoma accounted for 2 cases and the other one was T-cell lymphoma. There was no P53 gene mutation in low-grade follicular lymphoma. Seven strains out of 9 kinds of lymphoma cell lines had P53 gene point mutation. One strain had the mutation in exon 5; 5 strains in exon 6 and 1 strain in exons 5, 6, 7. There was a high mutation rate in lymphoma cell lines and low mutation rate in NHL patients. P53 gene plays an important role in lymphoma cell line establishment, cell regeneration and disease evolution.

Exons↗

PubMed1999

P2X receptor immunoreactivity in the rat cochlea, vestibular ganglion and cochlear nucleus.

P2X receptors have been reported to be involved in neurotransmission in both central and peripheral nerves. In the present study, polyclonal antibodies against P2X1, P2X2, P2X3, P2X4, P2X5, and P2X6 were used to study the distribution of P2X receptors in rat cochlea and vestibulocochlear nerve pathways. It was found that in the vestibular ganglion all six types of antibodies stained the neurons to different intensities. The strongest signal was obtained with the P2X2 antibodies, followed by P2X3 antibodies. The other four antibodies produced weak signals, of approximately the same intensity. In the spiral ganglion, the six types of antibodies also stained almost all neurons. However, the rank order of intensity was different from that in the vestibular ganglion: the strongest signal was still obtained with P2X2 antibodies, followed by P2X4, P2X1, and P2X3 antibodies. The immunolabelling was much weaker with P2X5, and P2X6 antibodies compared with the other four types of antibodies. In the cochlea, besides the spiral ganglion neurons, other tissues such as stria vascularis, the organ of Corti and the tectorial membrane were labelled intensively with P2X2 antibodies only. High density P2X2 immunoreactivity was also observed in the vestibulocochlear nerve fibres. In the cochlear nucleus, neurons and nerve fibres were stained with the P2X2 antibodies, as were the neurons in the trapezoid body. These results suggested that P2 receptors, especially the P2X2 receptors, may play important roles in the signal transduction involved in the perception of sound and balance.

Animals↗

PubMed1999

Brain TXA(2)and PGI(2)levels related to diffuse brain injury with secondary insults.

Secondary insults such as hypotension and hypoxia with head injury are associated with increased mortality and morbidity in comparison with head injury alone. In the present study the changes of brain thromboxane A(2)(TXA(2)) and prostacyclin (PGI(2)) levels in a Marmarou's rodent model of diffuse brain injury with hypotension and hypoxia were observed and the effect of diaspirin cross linked haemoglobin solution (DCLHb) were also investigated. Thirty-two male Sprague-Dawley (SD) rats were randomized into four groups: sham; head injury alone; head injury with secondary insults; and injury with insults followed by DCLHb administration. The results showed that there were no changes in TXB(2)and 6-keto-PFG(1a)(metabolites of TXA(2)and PGI(2)) levels in the injury alone group, while TXB(2)levels in the secondary insults group were elevated significantly; both TXB(2)and 6-keto-PGF(1a)levels in the injury with insults followed by DCLHb administration group were augmented significantly in comparison with the corresponding value of sham at 4 postimpact. The only increase in TXA(2)levels in the secondary insults rats suggests that an imbalance in TXA(2)-PGI(2)production contributes to the traumatic secondary processes, which include ischaemia and oedema. It is hypothesized that DCLHb may exert its protective properties through increasing PGI(2)production in injured brain by improving blood supply to injured blood vessels. Copyright 1999 Harcourt Publishers Ltd.

Journal Article↗

PubMed1999

[Culture of the transformed human embryonic tendon cells and its biological characteristics in vitro].

OBJECTIVE: This paper was to study the biological characteristics of the transformed human embryonic tendon cells, the relation between cell growth and culture conditions, and to compare these features with that of human embryonic tendon cells. METHODS: The pts A58H plasmid had successfully used to transform a tendon cell line from human embryo in our past work. The human embryonic tendon cells and the transformed human embryonic tendon cells were cultured in vitro. In different culture conditions, the growth curve were drawn respectively. Population dependence and proliferation capability of the cells were investigated through plate cloning test and soft agar culture. The collagen secreted by cells was identified by immunohistochemical method. RESULTS: In routine culture condition, the growth properties of the human embryonic tendon cell and transformed cells were almost identical. The growth properties of the transformed cells were not changed when the cells were frozen storage. There were changes of growth characteristics of the transformed cells when the culture temperature was changed. The transformed cells could subcultured continually and permanently. The proliferation capability of the transformed cells were stronger than that of the human embryonic tendon cells. Moreover, the growth of the transformed cells was serum-dependent, and the phenomenon of contact inhibition was observed. The transformed cells were not able to grow on soft agar culture. They had the capacity of secreting collagen type I. CONCLUSION: The transformed human embryonic tendon cells could be subcultured continually and permanently, and their growth could be controlled by changing their culture conditions and they had no malignant tendency in biological characteristics. They could be taken as an ideal experimental material for tendon engineering.

Cell Division↗

PubMed1999

[Analysis of organic acids in human dental plaque by means of gas chromatography/mass spectrometry].

The purpose of this study was to investigate the composition of plaque fatty acids in the healthy population. The study was made on 10 volunteers over the age of 18 who were divided into three sub-groups (3-4 individuals). Neither subject exhibited clinical evidence of salivary gland disorder and any medication affecting salivary functions were not used. A sensitive GC/MS method with VG7070E mass spectrometer was developed in our study. The sample separation was carried out on a fused silica capillary column with OV-1. The column size was 23 m x 0.23 mm. The temperature program was as follows: from 40 degrees C to 120 degrees C fast, then from 120 degrees C to 240 degrees C at 6 degrees C/min. The results showed that there were 14 organic acids and isomers present in plaque. They were C12:0, C14:0, C15:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:0 and phenylacetic acid, phenylpropionic acid. The higher content of fatty acids in the sample were C16:0, C18:0, and C18:1. The aromatic acids were detected only in some samples. The odd-numbers fatty acids and aromatic acids were for the first time detected. The origin of organic acids in plaque is an ongoing area of research. Our data clearly identify the bacterial contribution to the organic acids of plaque matrix, which may have a special relationship with bacteria metabolism. The research will help us to understand fatty acids metabolism of dental plaque and to determine their role in the microbial homeostasis of dental plaque.

Adult↗

PubMed1998

Localization of ATP-gated P2X2 receptor immunoreactivity in the rat hypothalamus.

Previous pharmacological studies have indicated that ATP receptors may be involved in the regulation of physiological functions in hypothalamus. In the present study, the distribution of P2X2 receptor in the rat hypothalamus was studied with immunohistochemistry. It was shown that P2X2 immunoreactivity-positive neurons and nerve fibres were localized in many hypothalamic nuclei. Intense labelling of both neuronal cell bodies and nerve fibres was observed in the paraventricular nucleus, arcuate nucleus, retrochiasmatic area, periventricular nucleus, and the ventral part of tuber cinereum area. In supraoptic, circular, and ventral tuberomammillary nuclei the neuronal cell bodies were strongly positive, but few nerve fibres were positive. Axons with strong P2X2 immunoreactivity were found in the organum vasculosum of the lamina terminalis and median eminence. Some scattered positive neurons and nerve fibres were found in many hypothalamic nuclei including preoptic nucleus. The results of the present study demonstrated the existence of P2X receptors in hypothalamus, as a basis for detailed studies of the roles of P2X receptors in the regulation of hypothalamic functions.

Adenosine Triphosphate↗

PubMed1998

Localization of ATP-gated P2X receptor immunoreactivity in rat sensory and sympathetic ganglia.

The distribution of P2X1, P2X2, P2X3, P2X4, P2X5 and P2X6 receptors, a family of ATP-gated cation channels, in rat trigeminal, dorsal root, nodose, superior cervical, and coeliac ganglia was studied immunohistochemically. It was found that polyclonal antibodies for the six P2X receptor subtypes could label over 90% of neurones in these ganglia to different intensities. There was also considerable variation in intensity of immunoreactivity in individual neurones within each ganglion. In dorsal root and trigeminal ganglia expression of the P2X3 receptor was much higher than for the other five subtypes. P2X3 immunoreactivity was much more intense in the small-diameter neurones than in the large-diameter neurones. In nodose ganglion, both P2X2 and P2X3 antibodies labelled the neurones intensely. In sympathetic superior cervical and coeliac ganglia, immunoreactivity to five P2X receptor subtypes were detected (exception, P2X5), with P2X2, P2X4 and P2X6 showing higher intensity. Low level expression of P2X3 receptor in sympathetic ganglia indicates that this receptor subtype is not limited to the sensory ganglia where it was highly expressed. The results have demonstrated that both sensory and sympathetic ganglia express a variety of P2X receptor subtypes and that different subtypes are expressed to different levels and by different subpopulations of neurones.

Adenosine Triphosphate↗

PubMed1998

A state space model for the HIV epidemic in homosexual populations and some applications.

In this paper we have developed a state space model for the HIV epidemic in homosexual populations which have been divided into subpopulations according to sexual activity levels. In this model, the stochastic dynamic system model is the stochastic model of the HIV epidemic in terms of the chain multinomial model whereas the observation model is a statistical model based on the observed AIDS incidences. This model is applied to the San Francisco homosexual population for estimating the numbers of susceptible people, infective people and AIDS cases and for estimating the probabilities of HIV transmission from infective people to susceptible people given sexual contacts. The results show that the estimated numbers of AIDS incidence trace closely the observed numbers indicating the usefulness of the model. It is observed that the estimated numbers of latent people show multimodal curves and that HIV infection takes place during the primary stage and very late stage. The results have further shown that there are significant differences between the observed AIDS incidences and the estimates by the embedded deterministic model. These results indicate that using the embedded deterministic model to estimate the HIV-infected people and to predict future AIDS cases can be very misleading in some cases.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Cholinergic switching within neocortical inhibitory networks.

Differential actions of acetylcholine on the excitability of two subtypes of interneurons in layer V of the rat visual cortex were examined. Acetylcholine excited low-threshold spike (LTS) cells through nicotinic receptors, whereas it elicited hyperpolarization in fast spiking (FS) cells through muscarinic receptors. Axons of LTS cells were mainly distributed vertically to upper layers, and those of FS cells were primarily confined to layer V. Thus, cortical cholinergic activation may reduce some forms of intralaminar inhibition, promote intracolumnar inhibition, and change the direction of information flow within cortical circuits.

Acetylcholine↗

PubMed1998

Pharmacological and histochemical evidence for P2X receptors in human umbilical vessels.

The presence of P2X purinoceptors in human umbilical vessels were studied with organ bath recording, radioligand binding assays, autoradiography, and immunohistochemistry. In isolated umbilical arteries and veins from normal term pregnancy, both ATP and alpha,beta-methylene ATP caused concentration-dependent contractions. ATP-induced responses were blocked by desensitisation with alpha,betamethylene ATP. However, both the ATP- and alpha,beta-methylene ATP-induced responses were not antagonised by suramin. No significant difference in responses was observed in the vessels with or without endothelial cells. Radioligand binding assays using [3H]alpha,beta-methylene ATP showed the presence of a population of high-affinity binding sites in both the arteries and veins. The Kd values of the binding sites were 2.77 + 1.10 nM for the arteries, and 3.23+/-1.22 nM for the veins. The maximum binding site densities were 634+/-237 and 947+/-308 fmol/mg protein for the arteries and the veins, respectively. Autoradiographic localisation with [3H]alpha,beta-methylene ATP demonstrated that the specific binding sites were only distributed over the smooth muscle cells of the vessels. Immunohistochemical studies with specific polyclonal antibodies against P2X1-6 receptors showed that positive immunostaining was also restricted to smooth muscle cells. Antibodies against P2X1 receptors produced the strongest signals, while antibodies against the other five P2X subtypes produced much weaker signals. The results in the present study indicate the existence of P2X purinoceptors in the smooth muscle of human umbilical vessels. Their physiological functions remain to be studied.

Autoradiography↗

PubMed1998

GABAA receptor-mediated currents in interneurons and pyramidal cells of rat visual cortex.

1. We compared gamma-aminobutyric acid (GABA)-mediated responses of identified pyramidal cells and fast spiking interneurons in layer V of visual cortical slices from young rats (P11-14). 2. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was similar in pyramidal cells and interneurons (1.7 vs. 1.9 Hz). For events with 10-90% rise times less than 0.9 ms, no significant differences were found in mean amplitude (61 vs. 65 pA), mean rise time (0.58 vs. 0.61 ms), or the first time constant of decay (tau 1, 6.4 vs. 6.5 ms) between pyramidal cells and interneurons. The second decay time constant (tau 2) was significantly longer in interneurons than in pyramidal cells (49 vs. 22 ms). The difference in sIPSC decay kinetics between two cell types also existed in adult rats (P36-42), suggesting the kinetic difference in not due to differential development of GABAA receptors in these cell types. 3. The decay kinetics of monosynaptic evoked IPSCs were also longer in interneurons. As in the case of sIPSCs, the difference was accounted for by the second decay time constant. tau 1 and tau 2 were, respectively, 13 and 64 ms for interneurons and 12 and 47 ms for pyramidal cells. 4. Cell-attached patch recordings revealed that the mean open time for single Cl- channels in response to 2 microM GABA was significantly longer in interneurons than pyramidal cells (5.0 vs. 2.8 ms). The chord conductance of these channels in interneurons (12 pS) was significantly smaller than in pyramidal cells (15 pS). Single channel currents reversed polarity when the pipette potential was approximately -10 mV for both cell types. 5. These results show that there is a functional diversity of GABAA receptors in electrophysiologically and morphologically identified cortical pyramidal cells and interneurons. This diversity might derive from the different molecular composition of the receptors in these two cell types.

Action Potentials↗