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Biomedical subjects

K Xia

Publications and source records attributed to K Xia.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Giant-cell tumor of bone: a review of diagnosis and treatment of 105 cases].

OBJECTIVE: To summarize the experience in the diagnosis and treatment of giant-cell tumor of bone, the selection of various operation methods and their effects were evaluated and discussed. METHODS: From 105 cases of giant-cell tumor of bone data were collected and reviewed. The clinical features were analyzed in association with radiological and histological characteristics. Prognosis was assessed by long-term follow-up. RESULTS: Among 105 cases, one had multiple giant-cell tumors and two had distant metastases. In some cases, the radiological and histological appearances didn't accord with the clinical findings. The recurrence rate was 36% in patients treated with curettage. Although no recurrence was seen in patients treated by local excision, the joint function could not be fully retained. CONCLUSION: Diagnosis should be made on the basis of integrated clinical, radiological and pathological manifestations. Early diagnosis and operation are important. The function of joint must be retained as much as possible. Pre-operative embolization of tumor of sacrum and pelvis is very helpful to ensure operative success and to minimize recurrence.

Adolescent↗
PubMed1996

The cytokine-activated tyrosine kinase JAK2 activates Raf-1 in a p21ras-dependent manner.

JAK2, a member of the Janus kinase superfamily was found to interact functionally with Raf-1, a central component of the ras/mitogen-activated protein kinase signal transduction pathway. Interferon-gamma and several other cytokines that are known to activate JAK2 kinase were also found to stimulate Raf-1 kinase activity toward MEK-1 in mammalian cells. In the baculovirus coexpression system, Raf-1 was activated by JAK2 in the presence of p21ras. Under these conditions, a ternary complex of p21ras, JAK2, and Raf-1 was observed. In contrast, in the absence of p21ras, coexpression of JAK2 and Raf-1 resulted in an overall decrease in the Raf-1 kinase activity. In addition, JAK2 phosphorylated Raf-1 at sites different from those phosphorylated by pp60v-src. In mammalian cells treated with either erythropoietin or interferon-gamma, a small fraction of Raf-1 coimmunoprecipitated with JAK2 in lysates of cells in which JAK2 was activated as judged by its state of tyrosine phosphorylation. Taken together, these data suggest that JAK2 and p21ras cooperate to activate Raf-1.

Animals↗
PubMed1996

Role of protein kinase A and the serine-rich region of herpes simplex virus type 1 ICP4 in viral replication.

Efficient expression of herpes simplex virus genes requires the synthesis of functional ICP4, a nuclear phosphoprotein that contains a prominent serine-rich region between amino acids 142 and 210. Residues in this region not only are potential sites for phosphorylation but also are involved in the functions of ICP4. By comparing the growth of a virus in which this region is deleted (d8-10) with wild-type virus (KOS) in PC12 cells or PC12 cells that are deficient in cyclic AMP-dependent protein kinase (PKA), two observations were made: (i) the growth of wild-type virus was impaired by 1 to 2 orders of magnitude in the PKA-deficient cells, indicating the involvement of PKA in the growth cycle of herpes simplex virus type 1, and (ii) while the growth of d8-10 was impaired by almost 2 orders of magnitude in wild-type cells, it was not further impaired (as was that of wild-type virus) in PKA-deficient cells, implicating the region deleted in d8-10 as a possible target for cellular PKA. In trigeminal'ganglia of mice, the d8-10 mutant virus grew poorly; however, it established latency in nearly 90% of ganglia tested. Studies of the phosphorylation of wild-type and d8-10 ICP4 proteins revealed that the serine-rich region is a major determinant for phosphorylation of ICP4 in vivo and that the phosphorylation state could change as a function of the PKA activity. Consistent with this observation, the serine-rich region of ICP4 was shown to be a target for PKA in vitro. While intact ICP4 was readily phosphorylated by ICP4 in vitro, the d8-10 mutant ICP4 was not. Moreover, a synthethic peptide representing a sequence in the serine tract that is predicted to be a substrate for PKA was phosphorylated by PKA in vitro, having a Km within the physiological range. These data suggest that PKA plays a role in viral growth through phosphorylation of one or more sites on the ICP4 molecule.

Amino Acid Sequence↗
PubMed1996

Analysis of phosphorylation sites of herpes simplex virus type 1 ICP4.

The herpes simplex virus ICP4 protein is required for induction of early and late viral gene transcription as well as for repression of expression of its own gene and several other viral genes. Several electrophoretic forms of ICP4 have been observed, and phosphorylation is thought to contribute to this heterogeneity and possibly to the multiple functions of ICP4. To define the complexity of the site(s) of phosphorylation of ICP4 and to initiate mapping of this site(s), we have performed two-dimensional phosphopeptide mapping of wild-type and mutant forms of ICP4 labeled in infected cells or in vitro. Wild-type ICP4 labeled in infected cells shows a complex pattern of phosphopeptides, and smaller mutant forms of ICP4 show progressively fewer phosphopeptides, arguing that multiple sites on ICP4 are phosphorylated. The serine-rich region of ICP4, residues 175 to 198, was shown to be a site for phosphorylation. Furthermore, the serine-rich region itself or the phosphorylation of this region increases phosphorylation of all phosphopeptides. A mutant ICP4 molecule lacking the serine-rich region showed low levels of phosphorylation by protein kinase A or protein kinase C in vitro. These results suggest that there may be a sequential phosphorylation of ICP4, with phosphorylation of the serine-rich region stimulating phosphorylation of the rest of the molecule. In addition, purified ICP4 showed an associated kinase activity or an autophosphorylation activity with properties different from those of protein kinase A or protein kinase C.

Amino Acid Sequence↗
PubMed1996

[Determination of genkwanin in flos Genkwa by HPLC].

In this paper, the method for determining genkwanin in Flos Genkwa was established by HPLC. Detected at 332nm on a Lichrosorb 5 RP-18 column with a mobile phase of methanol-water-acetic acid (65:35:5), the content of genkwanin in Flos Genkwa was determined to be 0.16%. The recovery rate was 95.46% and RSD 1.15%.

Antitussive Agents↗
PubMed1996

[HPLC analysis of mimic vinegar-processed yuanhuacine].

In this paper, the variation of yuanhuacine samples after vinegar-processing and hydrolysis has been analyzed by HPLC. The result has shown that the content of yuanhuacine decreases hearly 22% after mimic vinegar-processing. Also this procedure has brought a new compound-hydrolytic product of yuanhuacine, whose UV lambda max is 264nm. The research work is to be continued.

Acetic Acid↗
PubMed1996

[HPLC analysis of the influence of processing on the contents of genkwanin in flos Genkwa].

The contents of genkwanin in differently processed samples of Flos Genkwa have been analyzed by HPLC. The result shows that the contents in all these samples are decreased, the least decreased being the one processed with vinegar. The contents of genkwanin in samples of Flos Genkwa from the main habitats of china have also been analyzed by HPLC. Experimental criteria are provided for the quality control of Flos Genkwa.

Chromatography, High Pressure Liquid↗
PubMed1996

[HPLC analysis of mimic vinegar-processing of genkwanin].

In this paper, the variation of genkwanin content before and after mimic vinegar-processing has been analyzed by HPLC. The result has shown that there is no difference between the quantity and quality of genkwanin before and after mimic vinegar-processing. It is clarified that acetic acid is not the main reason for the decrease of genkwanin content in the flower of Daphne genkwa during the process of vinegar-fry.

Acetic Acid↗
PubMed1994

Interaction of the protein kinase Raf-1 with 14-3-3 proteins.

Members of a family of highly conserved proteins, termed 14-3-3 proteins, were found by several experimental approaches to associate with Raf-1, a central component of a key signal transduction pathway. Optimal complex formation required the amino-terminal regulatory domain of Raf-1. The association of 14-3-3 proteins and Raf-1 was not substantially affected by the activation state of Raf.

14-3-3 Proteins↗
PubMed1994

[Determination of yuanhuacine in Daphne genkwa Sieb. et Zucc. by HPLC].

Separated on phenox RP18 column with a mobile phase of methyl alcohol-water (82:18) and detected at wavelength 232nm, yuanhuacine has shown a good linearity in the range from 7.6 x 10(-3) to 0.76 microgram. The recovery is 99.56% with RSD 3.61% (n = 9). The content of yuanhuacine in Daphne genkwa is 0.00848%.

Chromatography, High Pressure Liquid↗
PubMed1992

[Studies of cockroachcidal toxin].

A cockroachcidal bacterial isolate CW-W-90-3 was selected by egg yolk agar plate. The isolate produced phospholipase C (PLC) which was pathogenic to the nymph of cockroach. The conditions for production of high level PLC indicated that using LB medium supplement Tween-80 or minimal medium could effectively increase the activity of PLC. The optical phase for production of PLC was in the period of 12-18 hours and below pH8.0. The activity of PLC was reduced along with the culture time until 48 hours. The PLC was resistant to heat. The partially purified PLC from the culture supernatant was assayed by using cockroach nymphes and produced 71.74% mortality.

Animals↗
PubMedDate not supplied

ADME evaluation in drug discovery. 4. Prediction of aqueous solubility based on atom contribution approach.

A novel method for the estimation of aqueous solubility was solely based on simple atom contribution. Each atom in a molecule has its own contribution to aqueous solubility and was developed. Altogether 76 atom types were used to classify atoms with different chemical environments. Moreover, two correction factors, including hydrophobic carbon and square of molecular weight, were used to account for the inter-/intramolecular hydrophobic interactions and bulkiness effect. The contribution coefficients of different atom types and correction factors were generated based on a multiple linear regression using a learning set consisting of 1290 organic compounds. The obtained linear regression model possesses good statistical significance with an overall correlation coefficient (r) of 0.96, a standard deviation (s) of 0.61, and an unsigned mean error (UME) of 0.48. The actual prediction potential of the model was validated through an external test set with 21 pharmaceutically and environmentally interesting compounds. For the test set, a predictive r=0.94, s=0.84, and UME=0.52 were achieved. Comparisons among eight procedures of solubility calculation for those 21 molecules demonstrate that our model bears very good accuracy and is comparable to or even better than most reported techniques based on molecular descriptors. Moreover, we compared the performance of our model to a test set of 120 molecules with a popular group contribution method developed by Klopman et al. For this test set, our model gives a very effective prediction (r=0.96, s=0.79, UME=0.57), which is obviously superior to the predicted results (r=0.96, s=0.84, UME=0.70) given by the Klopman's group contribution approach. Because of the adoption of atoms as the basic units, our addition model does not contain a "missing fragment" problem and thus may be more simple and universal than the group contribution models and can give predictions for any organic molecules. A program, drug-LOGS, had been developed to identify the occurrence of atom types and estimate the aqueous solubility of a molecule.

Drug Design↗