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Biomedical subjects

D Zhou

Publications and source records attributed to D Zhou.

At least 307 records · Page 17Linked to original sources
PubMed1993

Porcine pancreatic islets: isolation, microencapsulation, and xenotransplantation.

To provide a plentiful source of pancreatic islets for future clinical transplants into diabetic patients, we have developed a simple and reliable method to isolate porcine islets of a high degree of purity. Porcine pancreata were perfused and digested with collagenase, and the islets were then purified on dextran density gradients. In order to avoid any damage to the islets, no mechanical devices nor any strenuous treatment was employed. As many as 5 x 10(5) islets were isolated from a single porcine pancreas. Islets were encapsulated in alginate-polylysine-alginate membranes with the aid of an electrostatic droplet generator. In vitro studies demonstrated that the isolated islets secreted insulin in response to glucose and 3-isobutyl-L-methylxanthine (IBMX) challenge for at least 4 weeks. Perifusion studies showed that the kinetics of insulin release from the encapsulated islets was similar to that exhibited by free islets. In in vivo studies, 18 diabetic BALB-c mice were transplanted with 1,500-2,500 encapsulated islets each. In 13 recipients, the diabetic condition was reversed for at least 85 days. When capsules were removed from 2 transplant recipients, their diabetic condition quickly recurred.

Animals↗
PubMed1993

Cerebellar control of expiratory activities of medullary neurons and spinal nerves.

Expiratory-related activities of spinal nerves are augmented after stimulation of the infracerebellar nucleus of the cerebellum. These stimulations alter neither inspiratory spinal neural activities nor inspiratory and expiratory laryngeal neural activities. It was hypothesized that efferents from the infracerebellar nucleus impinge on spinal motoneurons by a pathway that bypasses the medulla. In decerebrate, paralyzed, and vagotomized cats, phrenic and expiratory triangularis sterni activities and activities of medullary respiratory neurons were recorded. During infracerebellar stimulation, activities increased for expiratory bulbospinal neurons and neurons with tonic discharge patterns. After unilateral ablation of the infracerebellar nucleus by kainic acid, triangularis sterni discharge was eliminated and activities of expiratory bulbospinal neurons continued at reduced frequencies. Stimulations of the anterior interposed nucleus caused both inspiratory and expiratory activities to increase, whereas no systematic changes followed stimulations of the vermis. Results establish that at least a portion of the changes in expiratory activities of spinal motoneurons after perturbations of the infracerebellar nucleus occurs secondarily to changes in activities of medullary neurons. The possibility of separate cerebellar projections to medullary and spinal neurons is discussed.

Animals↗
PubMed1993

Expression of beta 2-adrenergic receptor mRNA in peripheral lung in asthma and chronic obstructive pulmonary disease.

Previous studies have indicated an increased number of beta 2-adrenergic receptors (beta 2AR) on bronchial smooth muscle in fatal asthma. This study evaluates the utility of autopsy lung for studies of gene expression and examines the hypothesis that increased expression of beta 2 AR mRNA in peripheral lung underlies the increased receptor number reported in central airways in fatal asthma. beta 2AR mRNA levels have been quantitated using the ribonuclease protection assay on RNA from peripheral lung obtained both at autopsy and thoracotomy from subjects with normal lungs as well as subjects with asthma or chronic obstructive pulmonary disease (COPD). Glucocorticosteroid and serum induction of beta 2AR mRNA in human epidermoid carcinoma A431 cells, which display a high abundance of beta 2AR receptors, was also examined to provide aliquots of RNA containing relatively high levels of beta 2AR mRNA for use as positive controls and internal standards. In A431 cells maintained after confluence in serum-free media for 72 h, maximal beta 2AR mRNA levels in response to 10% fetal bovine serum were 85% of maximal levels following serum plus 10 microM dexamethasone. Both autopsy and resected lung yielded undegraded RNA with a similar relative abundance of beta 2AR mRNA. Although geometric mean beta 2AR mRNA levels were similar in all three patient groups, relatively high levels were observed in resected lung in a subpopulation of subjects with mild or moderate asthma but not in autopsy lung from subjects with severe asthma. High levels of beta 2AR mRNA, presumably reflecting lung growth or asthma, were demonstrated in peripheral lung of a 4-yr-old child with asthma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Exposure to physical and psychological stressors elevates plasma interleukin 6: relationship to the activation of hypothalamic-pituitary-adrenal axis.

Interleukin 6 (IL-6) is a pleiotropic cytokine produced by the cells of immune and nonimmune origin. Increased production of IL-6 is associated with disturbances of homeostasis, such as trauma, sepsis, or inflammatory diseases. Endotoxemia, tissue injury, or immune inflammatory reactions as well as physical or psychological stress are known to cause increased production of IL-6. We have confirmed this by showing that rats exposed to electric footshock, physical restraint, or a conditioned aversive stimulus have increased levels of plasma IL-6. Interestingly, the kinetics of the increase in plasma IL-6 resembled that of increase in plasma corticosterone. As no detectable endotoxin was found in the plasma samples from stressed and nonstressed rats and there is no evidence of tissue damage and inflammation in situations of restraint or conditioned aversive stimulus, a nonimmune origin of IL-6 is possible. Thus, the releasing of IL-6 into plasma may be under the regulation of neural and endocrine responses to stress. This hypothesis is supported by the decreased production of IL-6 in cultures of splenic cells and peripheral blood mononuclear cells from stressed animals. Furthermore, substantial attenuation of increased plasma IL-6 was achieved by adrenalectomy but not by pretreatment with the beta-receptor antagonist propranolol. The important role of the adrenal gland in the IL-6 response to stress suggests that increased plasma IL-6 may be part of the hormonal responses to stress. As IL-6 induces acute-phase proteins along with glucocorticoids from the adrenal, and regulates the secretion of various hormones from neuroendocrine and endocrine tissues, it is possible that stress-induced increase in plasma IL-6 contributes to the maintenance of homeostasis.

Adrenalectomy↗
PubMed1993

Comparison of Shams' test for rectal mucus to an immunological test for fecal occult blood in large intestinal carcinoma screening. Analysis of a check-up of 6480 asymptomatic subjects.

The sugar moiety detected from rectal mucus by the Galactose oxidase-schiff (Shams' test) is considered a substitutive test for immunological fecal occult blood test (FOBT) in screening colorectal carcinoma. Two strategies of screening were applied in 6480 subjects over 40 years of age, and 130 cm flexible colonoscope used for sigmoidoscopy or pancolonoscopy. Of them, 3820 were taken for immune FOBT (SPA test) and Shams' test. Only those who showed positive tests were chosen for 60 cm flexible sigmoidoscopy, while another 2660 subjects for both sigmoidoscopy and tests at the same time. Additionally, 130 cm flexible pancolonoscopy was carried out in 103 individuals with positive Shams' test for evaluating the false positive rate. Shams' test showed a sensitivity of 85.7% for colorectal cancer, 47.1% for adenomas in preselected patients, while the positive rate of SPA test were 90.5% and 41.2% respectively. In 3820 asymptomatic subjects undergoing sequential screening (aged 45 years and higher), Shams' test showed 9.1% positive, SPA showed 11.2% and 620 (16.2%) subjects were selected for sigmoidoscopy based on their positive galactose oxidase result or positive FOBT result. Two early stage carcinomas and 33 adenomas (0.32% and 4.2% respectively in sigmoidoscopy) were found. Another 2 660 subjects were taken for sigmoidoscopy screening. Four carcinomas and 78 adenomas were found. Of them, only two carcinoma (50%) and 17 (21.8%) or 22 (28.2%) adenomas were positive in Shams' or SPA test. But both tests combined in screening showed a rate of 61.3% in adenomas and 75.0% in cancers. 103 subjects with positive Shams' test were taken for pancolonoscopy. 82.5% showed no lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Daunorubicin uptake by leukemic cells: correlations with treatment outcome and mdr1 expression.

The in vitro daunorubicin (DNR) cell uptake was investigated by flow cytometry in K562/DOX resistant cell line and in 42 patients with acute myeloid leukemia (AML). The proportion of cells able to take up DNR was higher in untreated patients (50% +/- 30) than in previously treated patients (31% +/- 31) (p = 0.04). We noted a good correlation (p < 0.001) between the drug uptake after exposure to 0.1 microM DNR and achievement of complete remission. Cyclosporin A (CsA, 1 microgram/ml) and verapamil (5 micrograms/ml), but not cefoperazone (10 mM), completely reversed (CsA) or partially reversed (verapamil) the DNR efflux from K562/DOX mdr1(+) cell line. CsA significantly increased (p < 0.01) the DNR uptake of fresh leukemic cells, but not consistently, with no relationship to mdr1 mRNA cellular level. This absence of correlation was explained by the fact that several patients with no mdr1 gene expression exhibited a low in vitro DNR uptake, showing that the MDR phenotype is not the only mechanism responsible for the alteration of DNR pharmacokinetics in AML.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Immunohistochemical localization of the D1 dopamine receptor in rat brain reveals its axonal transport, pre- and postsynaptic localization, and prevalence in the basal ganglia, limbic system, and thalamic reticular nucleus.

D1 dopamine receptor localization was examined by immunohistochemistry using a polyclonal anti-peptide antibody which (i) immunoprecipitated a protein fragment encoded by a D1 receptor cDNA and (ii) on Western blots of solubilized striatal and hippocampal membranes recognized two proteins of approximately 50 kDa and 75 kDa, corresponding to reported sizes of D1 receptor proteins. Immunoreactivity overlapped with dopamine-containing pathways, patterns of D1 receptor binding, and mRNA expression. Staining was concentrated in prefrontal, cingulate, parietal, piriform, entorhinal, and hippocampal cortical areas and subcortically in the basal ganglia, amygdala, septal area, substantia inominata, thalamus, hypothalamus, and neurohypophysis. Prominent labeling was seen in the thalamic reticular nucleus, a region known to integrate ascending basal forebrain inputs with thalamocortical and corticothalamic pathways and in fiber bundles interconnecting limbic areas. In striatal neuropil, staining appeared in spines (heads and necks), at postsynaptic sites in dendrites, and in axon terminals; in the pars reticulata of the substantia nigra, labeling was prevalent in myelinated and unmyelinated axons and dendrites. These data provide direct evidence for the regional and subcellular distribution of D1 receptor protein in the brain and for its pre- and postsynaptic localization in the basal ganglia. The prominent immunoreactivity seen in the limbic system and thalamic reticular nucleus supports an important role for this receptor subtype in mediating integrative processes involved with learning, memory, and cognition.

Animals↗
PubMed1992

Functional domains of aromatase cytochrome P450 inferred from comparative analyses of amino acid sequences and substantiated by site-directed mutagenesis experiments.

Several functional domains, especially the active site regions, in aromatase cytochrome P450 were inferred by alignment of amino acid sequences of the enzyme from five species, human, rat, mouse, chicken, and trout, and that of Pseudomonas putida cytochrome P450cam, whose x-ray structure has been determined (Poulos, T.L., Finzel, B.C., and Howard, A.J. (1987) J. Mol. Biol. 195, 687-700). The predicted functions of these domains have been evaluated by site-directed mutagenesis. Eighteen mutants, including seven new mutants, have been generated in this laboratory. The seven newly prepared mutants are Q123E, Q123H, T310S, T310C, R365K, R365A, and N delta 20 (a mutant without the first 20 amino acids). The preparation and characterization of these new mutants are described. The structural model described in this paper should be very useful for future structure-function studies of aromatase by site-directed mutagenesis.

Amino Acid Sequence↗
PubMed1992

Liquid chromatographic separation of alkanesulfonate and alkyl sulfate surfactants: effect of ionic strength.

The retention of alkanesulfonate and alkyl sulfate surfactants, which was determined on a reversed stationary phase as a function of mobile-phase ionic strength, is consistent with a double-layer type interaction at the stationary-phase surface. Increasing the mobile-phase ionic strength not only increases retention but also improves resolution because peak widths are significantly reduced. The type of cation provided by the ionic strength salt also enhances retention, reduces peak width, and improves resolution. Lithium hydroxide is an ideal electrolyte for the separation of multicomponent mixtures of alkanesulfonate and alkyl sulfate surfactants. When the column effluent is passed through a postcolumn anion micromembrane suppressor, the conductivity due to the electrolyte is minimized and conductivity detection is sensitive, yielding a detection limit of about 0.3 nmol of injected analyte for a 3:1 signal:noise ratio. Multicomponent alkanesulfonate and alkyl sulfate mixtures from C2 to C18 are baseline resolved by using a mobile-phase gradient whereby CH3CN concentration increases and LiOH concentration decreases.

Chromatography, Liquid↗
PubMed1992

Radioiodinated anti-hepatocellular carcinoma (HCC) ferritin. Targeting therapy, tumor imaging and anti-antibody response in HCC patients with hepatic arterial infusion.

Radioimmunoimaging and radioimmunotherapy with radioiodinated anti-(hepatocellular carcinoma ferritin) antibody (131I- or 125I-FtAb) have been applied in patients with primary liver cancer. A total of 41 patients with surgically unresectable hepatocellular carcinoma (HCC) and receiving hepatic artery ligation and cannulation during exploratory laparotomy were treated with this regimen by intrahepatic arterial infusion. Compared with the control group, a decline of serum alpha-fetoprotein (65.7% versus 42.9%) and shrinkage of tumor (68.3% versus 33.9%) were observed in the treated group, and a higher second-look resection rate (31.7% versus 5.1%) and longer survival (1-year: 61.0% versus 37.3%, 3-year: 25.0% versus 6.9%) resulted. The administration of antibody through a hepatic arterial catheter (n = 16) was compared with intravenous injection (n = 17) in terms of the tumor-imaging sensitivity in 33 patients with liver cancer. The results indicated that hepatic arterial infusion was superior to intravenous injection. The sensitivity 7 days after the administration was 100% in the i.a. group and 76.5% in the i.v. group, the uptake ratio of tumor to liver being 1.74 +/- 0.57 in the former and 1.34 +/- 0.29 in the latter. Furthermore, intrahepatic arterial infusion revealed a lower anti-antibody detection rate than intravenous injection (0/14 versus 4/11).

Antibody Formation↗
PubMed1992

Neurobiotin, a useful neuroanatomical tracer for in vivo anterograde, retrograde and transneuronal tract-tracing and for in vitro labeling of neurons.

The biotin derivative, N-(2-aminoethyl) biotinamide hydrochloride, or Neurobiotin, has been shown recently to be a useful marker for intracellular and anterograde tracing. The properties of Neurobiotin as a tracer were further examined in this study by making pressure injections into different regions of the cerebral cortex or the rostral neostriatum of rats or by incubating striatal cells in culture with the tracer. Results showed extensive anterograde transport of Neurobiotin in cortical axons and terminals within the neostriatum 2-70 h after single or multiple cortical injections of the tracer. Similarly, profuse axonal projections to the medial portion of the globus pallidus were seen after an injection of Neurobiotin into the rostral neostriatum. Transneuronal labeling of medium-size neostriatal neurons was observed following injections of Neurobiotin into the prefrontal cortex. At the ultrastructural level, anterogradely labeled cortical axon terminals and transneuronally labeled neurons were readily identified in the caudate-putamen by the presence of both fine particulate and large punctate reaction products. Retrograde fillings of neurons resembling a Golgi-impregnation were seen in the ventral posterior complex of the thalamus after injections in the sensorimotor cortex. Neurons in the medial globus pallidus were also retrogradely labeled following tracer injections in the rostral caudate-putamen. Finally, Neurobiotin was readily and selectively taken up by striatal neurons in culture, where it extensively labeled somata and neurites. These results show that Neurobiotin is a versatile new tracer, which can be potentially useful for the study of neuronal organization in vivo and in vitro.

Animals↗
PubMed1992

Kinetic properties of aromatase mutants Pro308Phe, Asp309Asn, and Asp309Ala and their interactions with aromatase inhibitors.

Mutant forms of aromatase cytochrome P-450 bearing modifications of amino acid residues Pro308 and Asp309 and expressed in transfected Chinese hamster ovary cells were subjected to kinetic analysis and inhibition studies. The Km for androstenedione for expressed wild type (11.0 +/- 0.3 nM SEM, n = 3) increased 4-, 25- and 31-fold for mutants Pro308Phe, Asp309Asn and Asp309Ala, respectively. There were significant differences in sensitivity among wild type and mutants to highly selective inhibitors of estrogen biosynthesis. 4-Hydroxyandrostenedione (4-OHA) a strong inhibitor of wild type aromatase activity (IC50 = 21 nM and Ki = 10 nM), was even more effective against mutant Pro308Phe (IC50 = 13 nM and Ki = 2.8 nM), but inhibition of mutants Asp309Asn and Asp309Ala was considerably less (IC50 = 345 and 330 nM and Ki = 55 and 79 nM, respectively). Expressed wild type aromatase and Pro308Phe aromatase were strongly inhibited by CGS 16949A (IC50 = 4.0 and 4.6 nM, respectively) whereas mutants Asp309Asn and Asp309Ala were markedly less sensitive (IC50 = 140 and 150 nM, respectively). CGS 18320B produced similar inhibition. Kinetic analyses produced Ki = 0.4 nM for CGS 16949A inhibition of wild type versus 1.1, 37 and 58 nM, respectively, against Pro308Phe, Asp309Asn and Asp309Ala. The results demonstrate significant changes in function resulting from single amino acid modifications of the aromatase enzyme. Our data indicate that mutation in Asp309 creates a major distortion in the substrate binding site, rendering the enzyme much less efficient for androstenedione aromatization. The substitution of Pro308 with Phe produces weaker affinity for androstenedione in the substrate pocket, but this alteration favors 4-OHA binding. Similarly, mutant Pro308Phe exhibits a slightly greater sensitivity to inhibition by CGS 18320B than does the wild type. These results indicate that residues Pro308 and Asp309 play critical roles in determining substrate specificity and catalytic capability in aromatase.

Animals↗
PubMed1992

Effect of exogenous sialylation of the lipooligosaccharide of Neisseria gonorrhoeae on opsonophagocytosis.

Serum-sensitive Neisseria gonorrhoeae strains become serum resistant when grown in the presence of a sialic acid precursor, cytidine monophospho-N-acetylneuraminic acid. We examined the abilities of human neutrophils to phagocytose sialylated and nonsialylated gonococci and observed a decrease in the complement-dependent phagocytosis of sialylated gonococci compared with that of nonsialylated gonococci (50.7 versus 25.9% survival at 30 min). This decrease in opsonophagocytosis after sialylation may contribute to the pathogenicity of gonococcal infections.

Humans↗
PubMed1992

5-(p-aminophenyl)-1,2,3,4-tetrahydroxypentane, a structural component of the modified folate in Sulfolobus solfataricus.

The partial characterization of the modified folate present in Sulfolobus solfataricus has been carried out. Separation of ethanol-water extracts of these cells on a DEAE-Sephadex column led to the isolation of a small amount of intact oxidized cofactor, which, when subjected to reductive cleavage with Zn-HCl, produced 6-methylpterin. This indicated that the modified folate in these cells contained a nonmethylated pterin linked, via a methylene group at the C-6 position of the pterin, to an arylamine, as is found in folate. Oxidative cleavage of intact reduced cofactor produced pterin and a single arylamine. The azo dye derivative of this arylamine was prepared and purified by chromatography on a Bio-Gel P-6 column. The resulting purified compound was shown to be readily hydrolyzed in dilute acid to the azo dye derivative of 5-(p-aminophenyl)-1,2,3,4-tetrahydroxypantane, which was, in turn, readily cleaved to 5-(p-aminophenyl)-1,2,3,4- tetrahydroxypentane by Zn-HCl reduction. The stereochemistry of the resulting 5-(p-aminophenyl)-1,2,3,4-tetrahydroxypentane was shown to be ribo, the same as that of the 5-(p-aminophenyl)-1,2,3,4- tetrahydroxypentane moiety found in methanopterin. The complete arylamine side chain of the modified folate thus contains 5-(p-aminophenyl)-1,2,3,4-tetrahydroxypentane attached, via an acid-labile bond, to a currently unidentified substituent. The modified folate present in S. solfataricus thus contains structural features common to both folates and methanopterin.

Folic Acid↗
PubMed1992

Reductions of neural activities to upper airway muscles after elevations in static lung volume.

We evaluated the hypothesis that the tonic discharge of pulmonary stretch receptors significantly influences the respiratory-modulated activities of cranial nerves. Decerebrate and paralyzed cats were ventilated with a servo-respirator, which produced changes in lung volume in parallel with integrated phrenic activity. Activities of the facial, hypoglossal, and recurrent laryngeal nerves and nerves to the thyroarytenoid muscle and triangularis sterni were recorded. After a stereotyped pattern of lung inflation, tracheal pressure was held at 1, 2, 4, or 6 cmH2O during the subsequent ventilatory cycle. Increases in tracheal pressure caused progressive reductions in both inspiratory and expiratory cranial nerve activities and progressive elevations in triangularis sterni discharge; peak levels of phrenic activity declined modestly. Similar changes were observed in normocapnia and hypercapnia. We conclude that the tonic discharge of pulmonary stretch receptors is an important determinant of the presence and magnitude of respiratory-modulated cranial nerve activity. This reflex mechanism may maintain upper airway patency and also regulate expiratory airflow.

Anesthesia↗
PubMed1992

Multidrug resistance (MDR) gene expression in acute non lymphoblastic leukemia: sequential analysis.

Sequential evaluation of P-glycoprotein expression was performed in 29 patients with acute nonlymphoblastic leukemia using immunocytochemistry with the C219 antibody. At diagnosis, 32% of the patients exhibited more than 5% of the P-gp(+) leukemic cells. Under chemotherapy, 62% of the patients eventually expressed a subset of P-gp positive leukemic cells. After conventional doses of cytosine-arabinoside (Ara-C) and daunorubicin or mitoxantrone, positive P-gp cells were noted in 65% of the cases. This percentage was significantly higher (p = 0.002) than the proportion of positive cases (15%) observed after regimens containing either intermediate doses of Ara-C or cyclosporine A, a P-gp modulator.

ATP Binding Cassette Transporter, Subfamily B, Mem↗