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Biomedical subjects

X Han

Publications and source records attributed to X Han.

At least 235 records · Page 13Linked to original sources
PubMed1993

[Electroacupuncture promotes the regeneration of different fibers in rat's tibial nerve].

METHODS: 45 rats (150-200g) were divided into 9 groups. The experimental steps as follows: (1) injured left tibial nerve (group 1-8) and sham operation (group 9); (2) three days after operation, group 1, 3, 5 and 7 were stimulated with electro-acupuncture (EA) in Huantiao (+) and Sanyinjiao (-); (3) according to different survival time (group 1, 2/10 days, group 3, 4/15 days, group 5, 6/20 days, group 7, 8, 9/25 days), 48h before sacrifice, the left femoral nerve was cut, HRP was injected into the hypodermis of paw pad and gastrocnemius; (4) observe HRP labelled cells in the lumber sympathetic ganglia, ganglion spinale (L4-6) and cornu ventrale of spinal cord (L3-S3). RESULTS: EA 7 days, 2-5 labeled cells were only found in ganglion spinales of group 1; EA for 12 days, the more HRP labeled cells were observed in the lumber sympathetic ganglions (mean = 2.6), ganglion spinales (mean = 4.8) and cornu ventrale (mean = 6) of group 3 as compared with group 4 (P < 0.05); 25 days after operation, the quantity of labeled cells in group 8 was close to group 9. CONCLUSION: (1) EA promote the regeneration of three or more kinds of fibers in tibial nerve; (2) The regeneration velocity of sensory fibers was faster than sympathetic and somatic efferent fibers.

Animals↗
PubMed1993

32P-postlabelling in studies of hormonal carcinogenesis.

The nature of the covalent modification of DNA by estrogens has been investigated by 32P-postlabelling and other techniques. Three different classes of covalent DNA alteration are induced by estrogens in vivo and are evaluated in this review for their potential to play a role in hormonal carcinogenesis: (a) estrogen-DNA adducts formed by reactive estrogen quinone metabolites; (b) enhancement of endogenous DNA modification by estrogen specifically in the target organ for cancer; (c) 8-hydroxyguanine bases formed by free radicals generated by redox cycling of estrogen. Additional studies are required to identify the class or classes of DNA adducts that are crucial for the induction of hormonal cancer.

Animals↗
PubMed1993

Microsomal hydroxylation of 2- and 4-fluoroestradiol to catechol metabolites and their conversion to methyl ethers: catechol estrogens as possible mediators of hormonal carcinogenesis.

In male Syrian hamsters, an animal model for estradiol-induced carcinogenesis, 2-fluoroestradiol was not carcinogenic, whereas 4-fluoroestradiol induced kidney tumors after a prolonged latency period, compared with estradiol (100% tumor incidence), when the compounds were administered to hamsters in hormonally equipotent doses. Catechol estrogen metabolites have previously been postulated to mediate this estrogen-induced kidney carcinogenesis. To examine this proposed mechanism of tumor induction by estrogens, we investigated the conversion of 2- and 4-fluoroestradiol to catechol metabolites by kidney and liver microsomes of hamsters and the further conversion to methyl ethers by catechol-O-methyltransferase, and we compared the values with those obtained with nonfluorinated estrogens as substrates. The rates of conversion of 2-fluoroestradiol to 2-hydroxyestradiol and 2-fluoro-4-hydroxyestradiol by hepatic microsomes were 30-50% lower than corresponding rates with estradiol as substrate. With renal microsomes the rate of 4-hydroxylation was 10 times faster than that of estradiol, whereas 2-hydroxylation was at best marginal. With 4-fluoroestradiol as substrate the rate of 2-hydroxylation by hepatic microsomes was enhanced 5-fold, compared with values for estradiol, but 4-hydroxyestradiol formation was almost eliminated. In contrast, the conversion of this substrate to 4-fluoro-2-hydroxyestradiol by kidney microsomes occurred at a rate 15 times faster than 2-hydroxylation of estradiol, whereas 4-hydroxyestradiol formation proceeded at a rate of 315 pmol/mg of protein/min. Except for the decrease in both 2- and 4-hydroxylation of 2-fluoroestradiol by liver microsomes, fluorine substitution of estrogenic phenols enhanced microsome-mediated aromatic hydroxylation at sites unoccupied by substituents. At pH 7.5, the highest rates of catechol-O-methyltransferase-mediated methylation were observed with the catechol metabolites of 2-fluoroestradiol, 2-fluoro-4-hydroxyestradiol and 2-hydroxyestradiol (3780 and 2960 pmol/mg of protein/min, respectively). Lower rates were found with those of 4-fluoroestradiol, 4-fluoro-2-hydroxyestradiol and 4-hydroxyestradiol (1670 and 470 pmol/mg of protein/min, respectively). These data are consistent with the postulate that catechol metabolites of estrogens are reactive intermediates in estrogen-induced carcinogenesis. For the noncarcinogenic 2-fluoroestradiol, a high metabolic flux was observed through a pathway of renal 2-fluoro-4-hydroxyestradiol formation and further conversion to methyl ethers. This flux likely results in low steady state concentrations of catechol metabolites in kidneys of hamsters treated with this modified estrogen and therefore in its lack of carcinogenic activity. In contrast, the carcinogenic activity of 4-fluoroestradiol is consistent with its rapid conversion in the kidney to 2- and 4-hydroxylated metabolites and a less rapid methylation of these catechols.

Animals↗
PubMed1992

TDM35--a new monoclonal antibody to the XH1 cervical carcinoma cell line. Characterization and immunoperoxidase localization in benign and malignant tissues.

The murine monoclonal IgG1 kappa antibody TDM35 was raised against the cervical carcinoma cell line XH1. The antibody recognizes 18.5-66 kDa NCA-like glycoproteins and immunostains a variety of formalin-fixed, paraffin-embedded normal, benign, and malignant tissues. It is of value in the diagnosis of carcinoma of the exocrine pancreas and it identifies foci of squamous and glandular differentiation in other tumours. TDM35 should form a useful addition to a panel of antibodies for the evaluation of epithelial lesions.

Adenocarcinoma↗
PubMed1992

Differential molecular dynamics and transmembrane fluidity gradients in canine myocardial sarcolemma and sarcoplasmic reticulum.

The molecular dynamics of highly purified preparations of canine myocardial sarcolemma (SL) and sarcoplasmic reticulum (SR) were quantified by electron spin resonance spectroscopy (ESR). Canine myocardial SL and SR have substantially different motional regimes in their membrane interiors as demonstrated by alterations in the relative peak height ratios, peak widths and peak splittings in ESR spectra of 16-doxylstearate incorporated into SL and SR. Quantification of the apparent order parameters (S) of 16-doxylstearate in SL and SR by analyses of ESR spectra demonstrated that the interior of the SL membrane was substantially more immobilized than the interior of the SR membrane (e.g. S = 0.168 +/- 0.002 for SL and S = 0.128 +/- 0.003 for SR). In contrast, only modest differences in membrane dynamics near the hydrophobic-hydrophilic interface were present in SL and SR as ascertained by ESR spectra of the probe 5-doxylstearate incorporated into these membranes. Myocardial sarcolemma contained heretofore unsuspected amounts of cholesterol (1.4 +/- 0.1 mumol cholesterol/mg protein) while sarcoplasmic reticulum contained only small amounts of cholesterol (0.17 +/- 0.06 mumol cholesterol/mg protein). Model systems employing binary mixtures of plasmenylcholine/cholesterol and phosphatidylcholine/cholesterol demonstrated that the observed alterations in molecular dynamics were due, in large part, to the differential cholesterol content in these two subcellular membrane compartments. Taken together, these results demonstrate that these two functionally distinct myocardial subcellular membranes have markedly disparate molecular dynamics and transmembrane fluidity gradients which may facilitate their performance of specific functional roles during excitation-contraction coupling in myocardium.

Animals↗
PubMed1992

Nonmonotonic alterations in the fluorescence anisotropy of polar head group labeled fluorophores during the lamellar to hexagonal phase transition of phospholipids.

The temperature dependence of the fluorescence anisotropy of polar head group labeled fluorophores (i.e., N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-L- alpha-phosphatidylethanolamine or N-(lissamine rhodamine B sulfonyl)dipalmitoyl-L-alpha-phosphatidylethanol- amine) incorporated into multiple phosphatidylethanolamine molecular species was parabolic, possessing minima (dr/dT = 0) that precisely correlated with the respective lamellar (L alpha) to hexagonal (HII) phase transition temperature of each species. The parabolic alterations in the thermotropic behavior of these fluorophores were due to increased motional constraints in the polar head group region during heating (dr/dT greater than 0), because significant alterations in the fluorescence lifetimes of these probes during the phase transition did not occur. The sensitivity inherent in identification of peak minima was exploited to determine the lamellar to hexagonal phase transition temperatures of several homogeneous molecular species of plasmenylethanolamine (e.g., the transition temperature of 1-O-(Z)-hexadec-1'-enyl-2-octadec-9'- enoyl-sn-glycero-3-phosphoethanolamine was 28 degrees C). Experiments using ethanolamine glycerophospholipids containing either an ester or a vinyl ether linkage at the sn-1 position demonstrated that introduction of the vinyl ether constituent increased the propensity of these species to assume the hexagonal phase. Collectively, these results identify and substantiate a new technique for the characterization of the lamellar to hexagonal phase transition in phospholipids that requires only small amounts of phospholipids present in dilute membrane suspensions.

Fluorescence Polarization↗
PubMed1992

Epimeric (20R,20S)-Verazine Isolated from Veratrum maackii: Two-Dimensional NMR Studies and Total Assignment of 1H- and 13C-Resonances.

(13)C-NMR evidence shows that verazine [(25 S)-iminocholesta-5,22( N)-diene-3beta-ol] isolated from the Chinese plant VERATRUM MAACKII (Melanthiaceae) consists of a 20 R/20 S mixture of epimers. The determination of the configurations at the chiral epimeric center and of the conformation of the 17beta-side chain is based on the total assignment of the (13)C- and (1)H-NMR resonances. This goal was achieved by the extensive use of homo- and heteronuclear shift correlation and two-dimensional NOE spectroscopy methods at high magnetic field.

Journal Article↗
PubMed1992

Regulation of IL-2 beta receptor expression and beta-chain mRNA by human thymocytes.

The high affinity form of the human IL-2 receptor (IL-2R) has two known components, the IL-2R alpha (p55) and the IL-2R beta chain (p75). We have previously shown that recombinant IL-2 (rIL-2) could induce the expression of the alpha-chain (p55) on T cells and thymocytes, and increase this expression following suboptimal activation with concanavalin A (Con A) in combination with IL-2. An increase in the accumulation of IL-2R alpha-specific mRNA induced by rIL-2 in T cells and thymocytes had also been documented. We report here that the expression of IL-2R beta on the cell surface can be demonstrated on human thymocytes by the binding of Mik beta1, a MoAb directed against an epitope of the beta-chain. The IL-2R beta chain is constitutively expressed on freshly isolated thymocytes; this expression can be increased in thymocytes activated with Con A in combination with IL-2 or tetradecanoylphorbol 13-acetate (TPA). Blocking the formation of high affinity receptors with a MoAb directed against the alpha-chain of the receptor results in an increase in the display of IL-2R beta as evidenced by binding of MoAb Mik beta1. The accumulation of IL-2R-beta-specific mRNA is observed in freshly isolated thymocytes and it is increased in thymocytes cultured with rIL-2 alone, with Con A, and further enhanced by the addition of rIL-2 in combination with Con A or with TPA. Cyclosporine (CsA), which inhibits the accumulation of lymphokine-specific mRNA of thymocytes, does not inhibit the induction of the accumulation of IL-2R beta-specific mRNA. This is analogous to its effect on the expression of the alpha-chain (p55), and the accumulation of alpha-chain-specific mRNA.

Animals↗
PubMed1992

Ionic mechanisms of transient inward current in the absence of Na(+)-Ca2+ exchange in rabbit cardiac Purkinje fibres.

1. Membrane currents were measured with a two-microelectrode technique in voltage clamped rabbit cardiac Purkinje fibres under conditions known to cause intracellular calcium overload and to eliminate or minimize Na(+)-Ca2+ exchange. 2. Increasing [Ca2+]o from 2.5 to 5 mM or above and substituting external sodium with either sucrose, choline or Li+ induced an oscillatory transient inward current (TI) which peaked 200-300 ms after repolarization from a previous depolarizing pulse. The TI quickly disappeared upon return to normal Tyrode solution. Both the rate and configuration of action potentials of Purkinje fibres also returned to control upon return to Tyrode solution after 30 min of high Ca2+ exposure, if the Ca2+ concentration was 30 mM or less. 3. The TI in Na(+)-free solution was Ca2+ dependent. Either zero or low (2.5 mM) [Ca2+]o, or replacement of [Ca2+]o by BaCl prevented induction of the TI current upon repolarization from a previous depolarizing pulse. 4. In the presence of 30 mM-CaCl2 and with choline chloride as the substitute for NaCl, TI had a distinct reversal potential (Erev) of -25 mV. The time-to-peak TI, either inward or outward, did not shift significantly with change in voltage. Both inward and outward TI were simultaneously abolished by exposure to 1 microM-ryanodine, suggesting they were both activated by transient release of Ca2+ from the sarcoplasmic reticulum. The occurrence of TI in the absence of [Na+]o is not compatible with an electrogenic Na(+)-Ca2+ exchange mechanism. The existence of a clear-cut reversal potential suggests that an ionic channel may be responsible for the TI under these conditions. 5. Both the magnitude of peak TI and the Erev were affected by changes of CaCl2 concentration. (i) Under steady-state conditions, peak inward TI was significantly increased when the [Ca2+]o was elevated from 5 to 15 mM. The peak TI in the outward direction was significantly increased when [Ca2+]o was elevated from 15 to 30 mM; however, the difference in peak inward TI at 15 and 30 mM [Ca2+]o was small. (ii) Clear-cut reversals of TI were found at Ca2+ concentrations of 10 mM (Erev = -19.5 mV) or greater, and elevation of [Ca2+]o to 20, 30, 50 and 105 mM shifted the Erev to more negative potentials. (iii) In the presence of 5 mM [Ca2+]o the inward TI declined to zero at about -30 mV, and test voltages between -55 and +5 mV failed to reveal a distinct outward TI.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Cytoblock preparations for examination of cervical and other cells.

There are a number of antibodies which may be of value in the investigation of cervical smears, effusion, and cells grown in monolayer culture. The Shandon Cytoblock method was used to prepare discs of such cells suitable both for diagnosis and for a variety of other techniques.

Cervix Uteri↗
PubMed1992

[Research on serotonergic neurons in lateral raphe nucleus of rat with intracellular injection HRP technique].

UNLABELLED: This experiment was carried out on 35 rats with stereotaxic apparatus following a new coordinate which was designed by ourselves. The microelectrode was pushed into the lateral dorsal raphe nucleus (LDR) under direct vision. The neurons with regular rhythm and slow firing rate were searched by intracellular recording, then the singular cell in LDR was filled with HRP by intracellular iontophoresis. RESULTS: 7 HRP labelling neurons with serotoninergic firing characteristics were observed in LDR. The labelling dendrites were found in neighboured structure (periaqueductal gray, laterodorsal tegmental nucleus, dorsal tegmental nucleus, 4th ventricle). This work demonstrated that LDR plays some role in acupuncture analgesia.

Action Potentials↗
PubMed1991

XH1--a new cervical carcinoma cell line and xenograft model of tumour invasion, 'metastasis' and regression.

A new cell line, XH1, has been derived from an invasive focally keratinising adenosquamous carcinoma of the cervix in a 32 year old patient. It has been maintained in long term monolayer culture for 26 months, and passaged over 100 times (much greater than 300 population doublings). It is aneuploid with a mean chromosome number of 78. Examination using two minisatellite hypervariable DNA probes has shown it to be different from other cell lines maintained in this laboratory and from HeLa. Two sublines, XH1a and XH1b, show marked differences in monolayer culture, growth in soft agar, and xenograft formation. XH1 and XH1a cells readily form subcutaneous xenografts, and lung colonies can be established by their intravenous injection. Subcutaneous injection of XH1b cells results in rapid cell growth for a few days after which the tumour undergoes degeneration and then regresses completely. The XH1 karyotype has many rearranged chromosomes. Parental XH1 cells and both sublines show integration of HPV16 into the genome.

Adult↗
PubMed1991

[Continuous observation of the electrocardiogram following experimental cerebral hemorrhage].

An intracranial injection of 5 ml of heparinized autoblood was made into 14 healthy domestic dogs. Model of experimental cerebral hemorrhage was made. 7 dogs of a control group were not injected with the blood. Electrocardiograms (ECG) were recorded before operation, 6 hours after operation and once a day from the first to the seventh day after operation in order to observe the changes of ECG after cerebral hemorrhage. The result indicated that 11 dogs (78.57%) among the dogs of the hemorrhage group had abnormal ECG after operation, but only 2 (28.57%) of the 7 dogs of the control group were so. Comparison between the two groups showed significant difference, P less than 0.01. Abnormal ECG displayed the earliest during the postoperation 6 hours. These abnormal phenomena, mainly obvious in T wave changes and prolongation of the Q-T interval, were transient and began to disappear on the third day.

Animals↗
PubMed1991

[Studies on the quality standards of huaijiao wan].

TLC and PC have been used in the qualitative study of huaijiao wan. The contents of the total flavones and volatile oils in huaijiao wan have been determined. The proposed method can be used to control the quality of huaijiao wan.

Chromatography, Paper↗
PubMed1991

Multistage prostate carcinogenesis: the role of hormones.

Prostate cancer is the most frequently occurring non-skin cancer in men in the U.S.A. and other Western countries, but its etiology is poorly understood. Human prostate carcinogenesis has been viewed as a multi-step process involving progression from low histologic grade, small latent carcinoma, to large, higher grade, metastasizing carcinoma. However, recent data suggest that a variety of pathogenetic pathways exist. The precise role of hormones in the genesis of human prostate cancer remains largely undefined. It is difficult to investigate stages in the development of human prostate cancer, but some animal models provide opportunities in this regard. Short-term treatment of rats with chemical carcinogens will produce a low incidence (5-15%) of prostate cancer, provided that prostatic cell proliferation is enhanced during carcinogen exposure. A high carcinoma incidence can only be produced by chronic treatment with testosterone following administration of carcinogens such as N-methyl-N-nitrosourea (MNU). Testosterone markedly enhances prostate carcinogenesis even at doses that do not measurably increase circulating testosterone. Thus, testosterone is a strong tumor promoter for the rat prostate. All such MNU-initiated, testosterone-promoted tumors are adenocarcinomas mostly originating from the dorsolateral and anterior, but not ventral, prostate lobes. A high frequency (70%) of activation of the K-ras gene by a G35 to A mutation occurs in these carcinomas. A variable frequency of activation of H-ras and K-ras genes occurs in human prostate carcinomas. Another rat model, representing a different pathogenetic pathway, involves chronic administration of estradiol-17 beta in combination with low-dose testosterone. The resulting carcinomas are low-grade and originate exclusively from periurethral ducts of the dorsolateral and anterior prostate. We recently found a major adduct by 32P postlabeling analysis in the tissue region that includes these ducts, but not in, e.g., the ventral prostate, of rats treated for 16-24 weeks. While it is unknown whether testosterone is a tumor promoter in this system, the presence of a DNA adduct suggests that estradiol-17 beta acts as a tumor-initiating agent in this system.

Animals↗
PubMed1991

[Dietary factors and esophageal cancer: a case-control study].

A hospital-based case-control study of 112 patients with esophageal cancer was conducted to explore the association of dietary factors with cancer of the esophagus. Each case was matched to one non-cancerous patient from surgical department in the hospital of the same sex, age (+/- 5 years), occupation (farmer or nonfarmer), and residence as control. Multivariate conditional logistic regression analysis showed that the consumption of moldy grains (odds ratio (OR), 4.08), pickled vegetables (OR, 2.57), tea drinking habit (OR, 5.65), and hot food consumption (OR, 2.53) were significant risk factors for esophageal cancer. Intake of eggs (OR, 0.30) and higher proportion of flour and rice in the grain ration (greater than 30% vs. less than or equal to 30%) (OR, 0.43) were protective factors. Relations between factors were also discussed in the paper.

Adult↗