Biomedical subjects

L F Xu

Publications and source records attributed to L F Xu.

At least 19 recordsLinked to original sources

PubMed2005

Dissolution dynamics of NaCl nanocrystal in liquid water.

The dissolution dynamics of a NaCl nanocrystal in liquid water was studied using molecular dynamics simulations. The dissolution process was found to start with a Cl(-) ion at a corner site, followed by a Na(+) ion nearby. Both show directional preference in the dissolution path. An ion sequence with alternating charge, i.e., Cl(-), Na(+), Cl(-), Na(+), etc. was found to dominate the dissolution process. This image can be understood from the ionic hydration structures and the Coulomb interaction between the ions.

Journal Article↗

PubMed2004

Ice tessellation on a hydroxylated silica surface.

The adsorption of water on a fully hydroxylated silica surface is studied by using density-functional total-energy and molecular dynamics calculations. The (100) surface of beta(alpha)-cristobalite covered by geminal hydroxyls has been taken as the substrate. A well-ordered and stable two-dimensional ice with quadrangular and octagonal patterns of hydrogen bond (H-bond) networks-an ice tessellation-is found on the surface for the first time. With the vibrational recognition, the four water molecules in the quadrangle are found to be bonded by strong H bonds while the quadrangles are connected to each other by weak H bonds. This configuration is the most stable, because all the water molecules are fully saturated with H bonds either to each other or to the surface hydroxyl groups.

Journal Article↗

PubMed2002

Vibrational recognition of hydrogen-bonded water networks on a metal surface.

The adsorption of water on Pt(111) surface has been studied with ab initio molecular dynamics simulation. Both the energetics and vibrational dynamics indicate the existence of a well-ordered molecular bilayer on this surface. This conclusion is in contrast to the recent result of water on Ru(0001) surface, but agrees with available experiments. In addition, our calculation identifies two different hydrogen bonds in the bilayer. Both can be directly recognized from the vibrational spectra of the OH stretch modes.

Journal Article↗

PubMed1998

The use of suicide gene systems in vascular cells in vitro.

To investigate the efficiency of suicide gene systems on vascular cells, HSV-tk/GCV and EC-CD/5-FC systems were established on vascular endothelial cells in vitro by retroviral transduction. Both modified cell lines were highly sensitive to prodrugs, the IC50 for GCV was less than 0.4 microM, and IC50 for 5-FC was less than 75 microM, while the parental endothelial cells were insensitive even at the highest concentrations of prodrugs in this experiment. Mixed cellular assay showed that significant bystander effect was exhibited in modified endothelial cells. When only 10% or 30% of the mixed cells were tk positive and exposed to 20 microM GCV for 6 days, more than 60% or 90% of the whole population was killed. Similar result was also found in CD positive cells. These results indicated that both HSV-tk/GCV and EC-CD/5-FC systems could efficiently suppress endothelial cell growth in vitro.

Animals↗

PubMed1996

[Experimental treatment of brain tumor cells using CD suicide gene].

A negative selection system for glioma gene therapy was established in vitro. C 6 rat glioma cells were infected with recombined retrovirus which contain Escherichia coli cytosine deaminase (EC-CD) gene. The enzyme CD can transform the non-toxic prodrug 5-Fluorocytosine (5-FC) to the highly cellular toxic compound 5-Fluorouracil (5-FU). The growth inhibition studies proved that CD-positive cells were highly sensitive to 5-FC, the IC50 about 3 mumol/L, compared with an IC50 of approximately 6000 mumol/L in parental C 6 cells. Both CD-positive and negative cells were sensitive to 5-FU at very low concentration (IC50 < 1 mumol/L). Mixed cellular assay showed CD-positive cells had "bystander effect" on CD-negative cells when exposed to 5-FC. Our results demonstrate that EC-CD gene should be an efficient suicide gene for the treatment of glioma.

Animals↗

PubMed1992

[Studies on the chemical constituents from the skin of Bufo bufo gargarizans Cantor].

Four bufotoxins were isolated by means of preparative reversed phase HPLC from the water soluble fraction of the skin of Bufo bufo gargarizans Cantor. On the basis of their spectral data (UV, IR, 1HNMR, 13CNMR, EIMS and FDMS), amino acid analyses and chemical properties, they were identified as bufotalin 3-succinoylarginine ester(I), bufalin 3-succinoylarginine ester(II), cinobufagin 3-succinoylarginine ester(III), and resibufogenin 3-succinoylarginine ester(IV). Compound I is a new bufotoxin.

Animals↗

PubMed1992

[The first record of human natural infection of Echinochasmus liliputanus].

Human natural infection with Echinochasmus liliputanus was found for the first time from the inhabitants of Hexian county of Anhui Province in Spring, 1991. Sixty worms collected from 3 infected persons were studied morphologically. The adult worms are leaf-shaped, 1519.4-2056.3 x 466.4-564.0 microns in size. The width of the collar is 235.8-297.3 microns. A row of 24 collar spines with size of 22.5-35.6 x 8.8-10.6 microns is arranged on the collar symmetrically with dorsal and ventral interruption. The oral sucker is terminal, 107.6-148.6 x 102.5-148.6 microns. The length of the prepharynx is 25.6-66.7 microns, the pharynx, 97.3-127.8 microns and the oesophagus 117.9-205.0 microns. The caeca 764.3-1,248.8 x 21.0-39.0 microns extends to the distal end of the body. The acetabulum is anterior to the middle level of the body, 205.0-240.9 x 205.0-235.8 microns in size. Two testes, situated in the posterior one third of the body, is slightly oval, in tandem; the anterior one is 133.3-199.9 x 199.9-256.4 microns in size, and the posterior one, 178.9-251.3 x 164.0-246.0 microns. The Cirrus pouch is kidney-shaped, 211.5-248.5 x 112.8-194.8 microns in size, located between the bifurcation of the intestine and the acetabulum, containing the seminal vesicle and cirrus. The ovary is oval in shape, 71.8-92.3 x 76.8-97.4 microns in size, situated in the middle of the body. The vitellaria are distributed on each side from the acetabulum to subterminal, consisting of many follicles. The uterus is short, convoluted between the anterior testis and the acetabulum, containing 0-6 eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Effect of dietary ascorbic acid on heat-induced eye lens protein damage in guinea pigs.

The effect of large intake of dietary ascorbic acid on heat-induced eye lens protein damage has been studied. Male guinea pigs of the Hartley strain were used. Ascorbic acid was administered to the experimental animals in the drinking water. The mean daily ascorbic acid intakes for the control and experimental animals were 10 and 366 mg/kg body weight, respectively. The ascorbic acid level in the lens of the experimental animals was significantly higher than in the controls, but no differences in the content of water-soluble lens proteins were observed. When a solution of water-soluble protein was incubated at 60 degrees C, insoluble aggregates were formed. The loss of water-soluble proteins from the lens of the experimental animals was significantly less than that of the controls. The results indicated that large quantities of dietary ascorbic acid were able to protect lens constituents against heat-induced damage.

Animals↗

PubMed1989

[Clinical effects and experimental study on gossypol in endometriosis].

Effects of the gossypol on endometriosis in 12 cases of control were observed. The results showed that the gossypol administered orally was effective in endometriosis patients. The basal body temperature changed from biophase to monophase. Dysmenorrhea disappeared in 11/12 patients. Amenorrhea occurred in 10/12 patients and the ovarian endometrial cyst was shrinkable. Serum progesterone and estradiol were decreased after gossypol administration, but follicle-stimulating hormone and luteinizing hormone were increased evidently. Histochemical and cytochemical observations revealed that the activity of acid phosphate (ACP), nonspecific esterase (NSE) and alkaline phosphate (AKP) in both aberrant uterine endometrium and uterine endometrium in situ were decreased evidently. The above results suggest that the satisfactory therapeutic effect of gossypol on endometriosis may be due to not only the indirect but also the direct action on uterine endometrium.

Adult↗

PubMed1987