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Biomedical subjects

X Huang

Publications and source records attributed to X Huang.

At least 613 records · Page 34Linked to original sources
PubMed1994

Relation between chloride secretion and intracellular cyclic adenosine monophosphate in a cloned human intestinal cell line HT-29 cl 19A.

The relation between the intracellular cyclic adenosine monophosphate (cAMP) content and the electrogenic chloride secretion induced by cholera toxin was studied in secretory HT-29 cl 19A cell monolayers. Cells were treated by the mucosal addition of cholera toxin (5 micrograms/ml) for 10, 45, or 90 minutes in Ussing chambers. After 10 minutes, the mean (SEM) intracellular cAMP content (3.2 (0.2) pmol/mg protein) and short circuit current (Isc) (1.9 (0.3) microA.cm-2) did not differ significantly from the corresponding basal values. At 45 minutes, a significant increase in the Isc (22.2 (5.7) microA.cm-2) was accompanied by a significant elevation in cAMP (10(1.7) pmol/mgh protein). At 90 minutes, when the stimulated Isc plateaued (35.2 (5.2) microA.cm-2), the cAMP value (99.2 (23.8) pmol/mg protein) increased further. The protein kinase C (PKC) activity of the cells was not affected by cholera toxin. Treatment of cell monolayers by different concentrations of DbcAMP (10(5), 5 x 10(-5), 10(-3) M) showed that the minimal concentration of DbcAMP (serosal) which significantly increased the Isc (delta 4.5 microA.cm-2) was 10(-4) M, and that this was accompanied by an increase in cAMP of delta 6.7 pmol/mg protein: Compared with DbcAMP, cholera toxin stimulated the Isc (at 45 minutes) to a much higher degree with a comparable elevation of cAMP. It is concluded that in cl 19A cells there is a threshold value of increase in intracellular cAMP that induces chloride secretion. Cholera toxin stimulated chloride secretion can be explained predominantly by an increase in intracellular cAMP that is unrelated to PKC activity.

Bucladesine↗
PubMed1994

Chronic central versus peripheral ouabain, blood pressure, and sympathetic activity in rats.

To assess whether chronic ouabain administration causes hypertension by increasing sympathetic activity, we recorded arterial blood pressure and heart rate at rest and after ganglionic blockade in conscious Wistar rats following 10 to 14 days of central or peripheral administration of ouabain. Intracerebroventricular or intravenous infusion of ouabain (10 micrograms/d for both) as well as subcutaneous ouabain pellets (releasing 25 micrograms ouabain/d per pellet) increased mean arterial pressure by 20 to 30 mm Hg and heart rate by 40 to 60 beats per minute. Ouabain pellets increased blood pressure and heart rate in a dose-related manner. After 2 weeks of all ouabain treatments, ouabainlike activity in plasma was not changed but increased significantly in hypothalamus and adrenals. Ouabainlike activity in the adrenals was increased more by intravenous than subcutaneous or intracerebroventricular ouabain treatment, but the different treatment modes caused similar increases in the hypothalamus. Concomitant central infusion of antibody Fab fragments against ouabain prevented the ouabain pellet-induced increases in blood pressure and heart rate. Ganglionic blockade by intravenous hexamethonium normalized blood pressure and heart rate in ouabain-treated rats. These data suggest that in normotensive rats exogenous ouabain, regardless of the mode of administration, may act centrally to cause sympathoexcitation and thus hypertension.

Animals↗
PubMed1994

Parathyroid hormone (PTH)/PTH-related protein (PTHrP) receptor and its messenger ribonucleic acid in rat aortic vascular smooth muscle cells and UMR osteoblast-like cells: cell-specific regulation by angiotensin-II and PTHrP.

PTH-related protein (PTHrP) is produced in vascular smooth muscle, where it is believed to act as a local vasorelaxant by activating either the classical PTH or a unique PTHrP receptor. We used a newly cloned complementary DNA encoding the rat PTH/PTHrP receptor to study the expression of its messenger RNA (mRNA) in primary aortic vascular smooth muscle cells (VSMC) and in UMR-106 osteoblast-like cells under basal conditions and in response to treatment with agonists. Both cell types expressed a 2.4-kilobase PTH/PTHrP receptor mRNA transcript and exhibited hormone-induced desensitization of PTHrP-(1-34)NH2-stimulated cAMP. In VSMC, angiotensin-II, which induces PTHrP expression, also rapidly (30 min) desensitized the cAMP response and down-regulated (75-90%) receptor mRNA within 1 h. Treatment of cells with phorbol 12-myristate 13-acetate (0.1 microM) mimicked these effects, whereas neither PTHrP-(1-34)NH2, forskolin, nor (Bu)2cAMP altered receptor mRNA expression. By contrast, in UMR-106 cells, PTHrP-(1-34)NH2 induced time- and dose-dependent decreases in receptor mRNA that were preceded by pronounced desensitization (cAMP and ligand binding) of cell surface receptors. These effects were mimicked by (Bu)2cAMP and forskolin, but not by phorbol 12-myristate 13-acetate, suggesting that both receptor mRNA down-regulation and receptor desensitization in UMR cells were mediated through a protein kinase-A pathway. We suggest that VSMC and UMR cells express a common receptor, which is subject to cell-specific regulation. Such diversity in the PTH/PTHrP receptor regulatory mechanisms provides a means for restricting the length and duration of the cellular response to hormone in a cell/tissue-specific manner.

Angiotensin II↗
PubMed1994

Molecular mechanisms of nickel carcinogenesis.

Carcinogenic, water-insoluble Ni compounds are phagocytized by cells; and the particles undergo dissolution inside the cell, releasing Ni ions that interact with chromatin. Ni produces highly selective damage to heterochromatin. The longest contiguous region of heterochromatin in the Chinese hamster genome is found on the q arm of the X chromosome, and this region is selectively damaged by Ni. More than half of the male mice in which there were Ni-induced transformations of Chinese hamster cells exhibited complete deletion of the long arm of the X chromosome. The introduction of a normal X chromosome into these cells resulted in cellular senescence, suggesting that the Ni interacted with Chinese hamster genome to inactivate a senescence gene. Investigations were conducted into the mechanisms by which Ni produced damage to chromatin. Ni ions have a much higher affinity for proteins and amino acids than for DNA (by five to seven orders of magnitude). Therefore, Ni interacted with chromatin because of the protein present, not because of its reactivity for DNA. Studies have shown that Ni produced an increase in oxidative products in cells as indicated by oxidation of the fluorescent dye dichlorofluorescein; Ni has also been shown to produce oxidation of proteins in cells, as measured by carbonyl formation. Ni cross-linked certain amino acids and proteins to DNA. These covalent cross-links were not dissociated by EDTA and are inconsistent with direct Ni involvement, but they are consistent with Ni acting catalytically. Using subtractive hybridization, we have isolated a number of clones that are expressed in normal but not in Ni-transformed cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The role of nickel and nickel-mediated reactive oxygen species in the mechanism of nickel carcinogenesis.

Increasing evidence demonstrates the reactive oxygen species (ROS) are implicated in metal carcinogenesis. Exposure of cultured Chinese hamster ovary (CHO) cells to several nickel compounds, i.e. NiS, Ni3S2, NiO (black and green), and NiCl2 has been shown to increase oxidation of 2',7-dichlorofluorescein to the fluorescent 2',7-dichlorofluorescein (DCF), suggesting that nickel compounds increased the concentration of oxidants in CHO cells. This fluorescence can be attenuated by addition of exogenous catalase to the extracellular media, indicating that H2O2 is one of the formed oxidants in this system. Fluorimetric measurements of chromogens following thiobarbituric acid reaction showed that nickel compounds also induce lipid peroxidation with a decreasing potency NiS, Ni3S2 > black NiO > green NiO > NiCl2. These results suggest that lipid hydroperoxides may also be produced through the action of nickel in intact cells. MgCl2, an antagonist of Ni-induced DNA strand breaks and cell transformation, has no effect on the formation of DCF fluorescence induced in CHO cells by nickel. The results suggest that nickel is an active inducer of ROS in intact mammalian cells and that the molecular mechanism of nickel carcinogenesis may involve multiple steps of nickel-mediated ROS.

Animals↗
PubMed1994

Pericardiocentesis and drainage by a silicon rubber line without echocardiographic guidance. Experience in 55 consecutive patients.

Pericardiocentesis and drainage with a silicon rubber line were performed safely in 55 patients via the subxiphoid (80 times) or apical (1 time) approach at the bedside without echocardiographic guidance. The subxiphoid approach, which is close to the posterior of the sternum or the costal cartilage with a small acute-angle (15-30 degrees) to the parietal pericardium in front of the right ventricle, can avoid injuring the heart, liver and lungs. A line with sideholes near the distal end, which provides convenient drainage and has better histocompatibility, can be kept in place for a long period of time (1-82 days). It was also convenient to inject air, drugs or fluid through the line. There were no procedure-related serious complications or deaths. Emergency drainage with the Seldinger technique, especially for small to moderate effusions, is safe and simple.

Catheters, Indwelling↗
PubMed1994

[The complications of senile patients with diabetic retinopathy].

From December, 1990 to June, 1992, 114 patients with diabetic retinopathy were treated ambulatorally in our department. Among them 109 cases (42 males and 67 females) were older than 45 years with 210 diseased eyes. 65 eyes suffered from simple diabetic retinopathy, 145 eyes proliferative one. The visual acuity of 105 eyes (50%) was lower than 0.3, 65 eyes (30.95%) was lower than 0.05. 100 cases (91.74%) were complicated with cardiovascular diseases, 5 cases (4.5%) with cerebrovascular accident, 56 cases (51.40%) with hyperlipemia, 42 cases (61.76%) with high viscosity of the blood. Among the ophthalmic complications, macular disease occurred in 122 eyes, cataract in 88 eyes, central retinal vein obstruction in 15 eyes, neovascular glaucoma in 5 eyes.

Aged↗
PubMed1994

[Study on mechanism of eustachian tube active opening ventilation and pump-like function].

A modified methods for assessing the eustachian tube function (ETF) in patients with traumatic tympanic membrane perforation and otitis media were developed by using a custom-designed ETF measuring instrument. These methods consist of dynamic flow swallow test (DFST), positive pressure swallow test (PST), negative pressure swallow test (NST) and micro-negative pressure swallow test (MNST). With these methods, the graphs and parameters presenting ET active opening function were obtained. The results suggested that the ET active swallow opening is a rather complex process of biomechanical action. It is not only closely related to the function of middle ear ventilation but also related to pump-like function and the protective function against reflux infection from nasopharynx.

Adolescent↗
PubMed1994

[Potentiation of electroacupuncture analgesia on visceral pain by metoclopramide and its mechanism].

The present study was to investigate the effect of metoclopramide (MCP) on electroacupuncture analgesia (EAA) and its mechanism on a rabbit visceral pain model. The results showed that MCP 8mg/kg i.v. could potentiate EAA and prolong the analgesic duration. The potentiation effect could be attenuated by icv apomorphine (APO) (a mixed D1/D2 agonist). The analgesic duration was shortened by icv SKF38393 (a selective D1 agonist) or LY171555 (a selective D2 agonist). Using HPLC-ECD, we also found that the HVA content in CSF significantly increased at 20 min. after electroacupuncture (EA) or MCP 8mg/kg i.v. (P < 0.05), but the change of HVA content was not significant when EA and MCP 8mg/kg i.v. were used together. All these observations indicate that MCP have effects of potentiating EAA and prolonging analgesic duration. These effects are related to the blockade of the central DA receptor. The activations of D1 or D2 receptor is unfavourable to the expression of EA after effect.

Acupuncture Analgesia↗
PubMed1994

[Electron microscope observation on chronic vulvar dystrophy and vulvar carcinoma].

Nine cases of hyperplastic type, ten cases of lichen type, two cases of mixed type of chromic vulvar dystrophy and six cases of vulvar carcinoma were observed under electron microscope. Six cases of squamous carcinoma were moderately to highly differentiated under microscope, but they were cells of squamous carcinoma, adenocarcinoma, undifferentiated carcinoma, squamous-mucus carcinoma, squamous-melanin carcinoma, squamous-adenocarcinoma under electron microscope. All of the six cases consisted of several differentiated characteristic carcinoma cells similar to lung cancer. It indicated that vulvar carcinoma might originate from basal cells of squamous epithelia with polypotentiality differentiation. Infiltrating lymphocytes were encountered both among carcinoma cells and epithelial cells. Pseudopodia extensions of lymphocyte cell membranes were in contact with portions of carcinoma cell and epithelial membranes. Destroying membranes of carcinoma cells by lymphocytes was more serious than that of epithelial cells. The results of this study indicate that destroying carcinoma cells by lymphocytes is a part of immunity response of the body, but significance of lymphocytes present at epithelia remains to be studied.

Chronic Disease↗
PubMed1994

[Pharmacokinetic characteristics of tetramethylpyrazine and study on hemorheology in rat model of spleen deficiency syndrome].

UNLABELLED: In this experiment, the essence of Spleen Deficiency Syndrome (SDS) was explored with the rat model of SDS using tetramethylpyrazine (TMP). 120 Wistar rats were divided into two groups, 60 each for control and test group, they were treated with normal saline and reserpine respectively. The hemorheological parameters were also studied in 6 each of both groups. The pharmacokinetic properties were investigated in the remaining control group and test group. RESULTS: (1) Two-compartment open model of the control group was turned into that of one-compartment in test group; (2) The SDS model significantly affected the absorption and distribution of TMP in rats. AUC was much higher and serum concentration of TMP increased significantly than that of control. Hemorheological parameters (viscosity of whole blood, fibrinogen, etc.) increased significantly (P < 0.05-0.01), it demonstrated that the SDS model was in a state of Blood Stasis. It might be one of the pharmacokinetic mechanisms of TMP in the SDS model of rats.

Animals↗
PubMed1994

[Influence of combined Salvia miltiorrhiza and Ligusticum wallichii on pharmacokinetics of tetramethylpyrazine in rats].

Influence of Salvia miltiorrhiza (SM) and/or Ligusticum wallichii (LW) on pharmacokinetics of tetramethylpyrazine (TMP) was observed in rats. The content of TMP in LW and LW-SM decoctions were 375.8 and 236.2 micrograms/ml respectively. The rat serum components after oral administration of LW were analyzed by modified HPLC. One of 3 compounds was detected, which was identified as TMP by the comparison of the parameters of 4 spectrums (UV, IR, MS and NMR) with those of TMP in literature. Pharmacokinetics of TMP in rats after the oral administration of LW and LW-SM decoction respectively showed that: (1) both of the data fitted adequately to two-compartment open model; (2) Ka, AUC and serum concentration were higher (P < 0.05-0.01) for LW decoction than that for LW-SM decoction, indicating a higher bioavailability. It demonstrated that the absorption of TMP of LW-SM decoction was slower and the bioavailability of TMP of LW-SM decoction reduced. Contents of TMP in LW and LW-SM decoction and serum concentration of TMP were determined by HPLC method.

Animals↗
PubMed1994

[Cytogenetic studies on a human cecum adenocarcinoma cell line (HCe-8693)].

Human undifferentiated cecum adenocarcinoma cell line (HCe-8693) was established by Zhejiang Cancer Hospital in 1986. This paper reports the results of cytogenetic studies on the 23rd (early) and 125th (late) passages of this cell line. The numerical distribution range of chromosomes was rather narrow, showing a near diploid karyotype, and no significant difference was observed between early and late passages. The modal number of chromosomes was 49. G-banding karyotypic analysis revealed that the karyotype of this cell line was close to that of normal diploid cells, with few, easily identified abnormal chromosomes. The most significant changes were a distal deletion of the short arm of chromosome No. 1 and a trisomy of chromosome No. 13. The morphological characteristics and possible correlation with pathogenesis of colorectal cancer were briefly discussed.

Adenocarcinoma↗
PubMed1994

[Immunohistochemical observation of anti-human hepatocellular carcinoma monoclonal antibody HL2 in cancers].

Molecular weight of human hepatocellular carcinoma (HCC)-associated antigen-HL2 antigen was detected to be about 50,000 dalton by SDS-PAGE and Western blot. One hundred and twenty-seven paraffin sections of cancers and pathological liver tissue were tests by ABC immunohistochemical staining. MAb HL2 reacted with 62.7% HCC and also with 8 of the 10 stomach carcinomas but only with a few other digestive system carcinomas (pancreas carcinoma, rectum carcinoma and duodenum carcinoma) and hepatitis. MAb HL2 was negative in hepatocirrhosis and other tumors (vesica carcinoma, skin carcinoma, breast carcinoma, neurogliocytoma and carcinoma of the lung). The results suggest that MAb HL2 has values in diagnosis of HCC and differential diagnosis between HCC and other tumours. HL2 antigen might be a new tumor-associated antigen (TAA). Further study of HL2 antigen will significantly show the actions of TAA in the occurrence and development of tumor.

Antibodies, Monoclonal↗
PubMed1994

Esophageal Crohn's disease--a case report.

A case of esophageal Crohn's disease in a 52-year-old man is described. The patient was treated successfully by surgical excision of the esophagus. Because esophageal Crohn's disease is uncommon, we would like to discuss its clinical characteristics and to review the literature.

Crohn Disease↗
PubMed1993

Absence of androgen receptors in LHRH immunoreactive neurons.

Androgen has a negative feedback effect upon reproductive functions. Studies have suggested that this effect is mediated partially at the hypothalamic level. However, it is not clear whether the action is direct or indirect on LHRH neurons. In the present study, double immunocytochemistry was used to localize LHRH and androgen receptors. Out of 5892 LHRH immunoreactive neurons, no double-labelled neurons were observed. We conclude that the feedback effect of androgen on the central nervous system is mediated by indirect pathway(s).

Animals↗
PubMed1993

Correlations between the receptive field properties and morphology of neurons in the deep layers of the hamster's superior colliculus.

Extracellular and intracellular recording, receptive field mapping, and intracellular HRP injection techniques were used to define the morphological classes of cells in the deep laminae of the hamster's superior colliculus and to determine whether there are any correlations between the structural and functional characteristics of these neurons. A total of 110 neurons were characterized and reconstructed. Of these, 23.6% (N = 26) were visual, 60% (N = 66) were somatosensory, 0.9% (N = 1) were bimodal (visual-somatosensory), and 15.4% (N = 17) were unresponsive. Of the somatosensory neurons, 72.7% (N = 48) were low threshold, 4.5% (N = 3) had a wide dynamic range, 9.1% (N = 6) responded only to noxious stimulation, and 13.6% (N = 9) had complex somatosensory receptive fields. Deep layer cells were divided into eight morphological classes. These classes were multipolar cells (26.4%, N = 29), bipolar cells (9.1%, N = 10), widefield vertical cells (7.3%, N = 8), horizontal cells (13.6%, N = 15), stellate cells (10.9%, N = 12), ventrally directed cells (5.5%, N = 6), sparse radial cells (17.3%, N = 19), and small sparse radial cells (6.4%, N = 7). Four cells (3.6%) did not fit into this classification scheme. Univariate and multivariate analyses of variance of properties such as soma area, number of branch points, total dendritic length, and volume and orientation of dendritic arbor indicated that these classes were significantly different. However, chi 2 analysis and multivariate analysis of variance indicated no significant relationships between morphological class and either laminar location or receptive field type. There was a significant positive relationship between the possession of dendrites that extended into the superficial laminae and visual responsivity.

Animals↗