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Biomedical subjects

Z Yu

Publications and source records attributed to Z Yu.

At least 343 records · Page 19Linked to original sources
PubMed1993

Effect of esophageal intraluminal mechanical and chemical stressors on salivary epidermal growth factor in humans.

Although various animal and clinical studies have demonstrated the significant effect of salivary epidermal growth factor (sEGF) on esophageal morphology and function, its secretory patterns still remain inadequately explored. Therefore, we have studied the impact of esophageal mechanical and chemical stimuli on sEGF in humans. sEGF was measured in saliva collected during basal conditions, chewing of parafilm, placement of esophageal tubing, inflation of intraesophageal balloons, and perfusion with NaCl, HCl, and HCl/pepsin solutions. The concentration of sEGF was measured with a radioimmunoassay kit from Amersham (Arlington Heights, IL). The concentration of sEGF in basal saliva was (mean +/- SEM) 2.08 +/- 0.22 ng/ml. Chewing the parafilm resulted in a significant decline of sEGF concentration to the value of 1.39 +/- 0.16 ng/ml (p < 0.0005). Similar decline in sEGF concentration also prevailed after placement of intraesophageal tubing (p < 0.03), and inflation of intraesophageal balloons (p < 0.01). This decline intensified significantly when prolonged esophageal perfusion with saline was implemented (p < 0.03 vs. tubing). Substitution of NaCl with HCl in the second and third perfusion periods prevented the decline in sEGF concentration, whereas HCl accompanied by pepsin enhanced sEGF concentration. The rate of sEGF output was 0.90 +/- 0.13 ng/min during basal conditions and increased significantly during parafilm chewing (1.53 +/- 0.25 ng/min; p < 0.05). However, sEGF secretion during both placement of esophageal tubing and inflation of balloons increased 4.1- and 4.9-fold, respectively (p < 0.002 and < 0.00005), over the basal value, and 2.4- and 2.9-fold, respectively, over the parafilm stimulated secretion. Subsequently, we observed a further significant decline of sEGF output (p < 0.05) which was sustained during perfusion of the esophagus with saline. Interestingly, esophageal perfusion with HCl prevented the decline of sEGF secretion observed during perfusion with saline. sEGF output during esophageal perfusion with HCl/pepsin exhibited a strong increase, reaching the value of 5.86 +/- 0.70 ng/ml. This value corresponds to a 58% increase over the secretory rate observed during mechanical stimulation by placement of esophageal tubing (3.71 +/- 0.47; p < 0.05). HCl/pepsin-induced potentiation of sEGF secretion was also highly significantly increased over both the value recorded during basal (p < 0.0005) and parafilm-stimulated (p < 0.002) conditions. Subsequent substitution of HCl/pepsin solution with a final saline perfusate still maintained enhanced sEGF output, compared with both basal (p < 0.02) and parafilm-stimulated conditions (p < 0.02).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Chemically-modified tetracycline normalizes collagen metabolism in diabetic rats: a dose-response study.

An earlier study indicated that a chemically-modified non-antimicrobial tetracycline (4-de-dimethylaminotetracycline; CMT-1) can inhibit excess collagenase activity in the connective tissues of diabetic rats, however, the optimum oral dose and resulting serum concentration were not determined. In the current study, adult male Sprague-Dawley rats (body weight approx. 350 g) were made diabetic by streptozotocin injection and administered by oral gavage either 0, 1, 2, 5, or 10 mg CMT-1 per day. After 3 weeks of drug therapy, the rats were killed and gingiva, skin, and serum collected. The tissues were 1) extracted, partially purified and analyzed for collagenase activity using [3H-methyl] collagen as substrate and SDS-PAGE/fluorography; 2) extracted in neutral salt and dilute acid solutions (4 degrees C) to assess collagen solubility; and 3) analyzed for hydroxyproline to determine tissue (skin) collagen mass. Serum was analyzed for glucose and CMT-1 concentration, the latter by HPLC. Inducing diabetes dramatically increased both gingival and skin collagenase activity and reduced skin collagen mass by 69.8%. Increasing the oral dose of CMT-1 progressively increased the serum concentration of the drug from 0.6-6.5 micrograms/ml and progressively decreased the excessive collagenase activity in gingiva and skin (p < 0.01 vs untreated diabetics). Although skin collagen mass tended to be increased at all oral doses of CMT-1, only the 5 mg dose effect was statistically significant (p < 0.01). The diabetes-induced reduction in collagen solubility, a classic abnormality (reflecting excessive collagen crosslinking) of this disease, was also normalized by CMT-1 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Evidence on secretion of epidermal growth factor by the esophageal mucosa in humans.

Luminal release of esophageal epidermal growth factor (EGF) into the perfusing solutions (saline, HCl, and HCl/pepsin), aspirated with the newly developed esophageal perfusion catheter, was measured in 20 healthy volunteers (12 male, 8 female; mean age 40 yr; range 30-56 yr). A potential salivary contamination was excluded by a complete seal (with two balloons) of perfused esophageal segment and by a simultaneous, carefully monitored, collection of saliva. The concentration of EGF in each of 16 fully recovered 2-min perfusion samples was measured by RIA kit (Amersham, IL). The concentration of EGF in recovered NaCl perfusate varied between (mean +/- SEM) 1.78 +/- 0.19 and 2.14 +/- 0.14 ng/ml, whereas output varied between 9.25 +/- 0.98 and 11.14 +/- 0.82 ng/min. During perfusion with HCl, both the concentration of EGF within the esophageal perfusate and its secretion declined significantly to a value of 0.68 +/- 0.17 ng/ml (p < 0.0001) and 3.56 +/- 0.90 ng/min (p < 0.0001), respectively. Introduction of pepsin into an acidic perfusion solution (0.5 mg/ml of HCl) resulted in a significant increase in EGF concentration (1.99 +/- 0.36 ng/ml; p < 0.001) and output (10.24 +/- 1.84; p < 0.01), compared with EGF values recorded during perfusion with HCl. EGF output, calculated from a sealed 7.5-cm segment of the esophagus, was 10.39 +/- 0.89 ng/min, and was maintained at a steady state throughout an entire saline perfusion procedure. We present evidence that human esophageal mucosa has an enormous EGF secretory potential. The rapid esophageal EGF secretory response to intraluminal challenge with aggressive factors implies its role in the maintenance of the mucosal integrity.

Adult↗
PubMed1992

The effect of adhesive luting agent-dentinal surface interactions on film thickness.

This study investigated the effect of luting agent-dentinal surface interactions on the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. In the control groups the luting agents were placed between two glass plates, as described in ADA Specification No. 8, but in the test groups the luting agents were positioned between a glass and a dentinal plate. The materials selected were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. A two-way analysis of variance was performed, and t tests were computed to compare glass with the dentinal plate within each material. Zinc phosphate and glass ionomer cements exhibited a significant decrease in film thickness when measured in contact with dentin, as compared with contact with the glass plate. However, polycarboxylate cement and the resinous cement with its dentin bonding agent showed a slight nonsignificant increase when contacting dentin, as compared with the glass plate. An explanation was offered and suggestions were made regarding future research.

Adhesives↗
PubMed1992

Effect of seating force on film thickness of new adhesive luting agents.

This study examined the effect of seating force on the film thickness of new adhesive luting agents. The method was in compliance with American National Standards/American Dental Association Specification No. 8 for zinc phosphate cement. The materials tested were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. All materials were manipulated exactly as described in the manufacturer's instructions, and an electronic gauge with an accuracy of 0.5 micron was used. Each class of material was measured 10 times at six different seating forces. Analysis of variance and multiple comparisons testing disclosed that the seating force and class of material strongly influenced the film thicknesses of luting agents. A mathematical model describing the response of zinc phosphate cement within the range tested was reported.

Analysis of Variance↗
PubMed1992

Film thickness of new adhesive luting agents.

This study determined and compared the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. Each of the 20 materials tested was manipulated exactly as described in the manufacturers' instructions. An electronic gauge with an accuracy of 0.5 micron was recalibrated after each recording, and each luting agent was measured 10 times. The mean film thickness and standard deviation were calculated for each luting agent; an analysis of variance and a multiple comparison test were also performed. Nine materials satisfied the ADA type I specification for film thicknesses less than 25 microns, and these included a hydroxyapatite cement, glass ionomer cements, zinc phosphate cements, and polycarboxylate cements. Five other materials met the ADA type II specification for film thicknesses of less than 40 microns, and these included a glass ionomer cement, a resinous cement, a zinc phosphate cement, and glass ionomer-resinous hybrids. Six resinous cements recorded film thicknesses greater than 40 microns, and suggestions were made regarding future development and research.

Adhesives↗
PubMed1992

Nonconditional logistic regression analysis of risk factors in rheumatic heart disease.

The prognostic risk factors in 4323 patients with rheumatic heart disease, admitted from 1970 to 1990, were analysed. The overall mortality was 31.75% in this group of patients. Single factor analysis indicated that cardiac functional classification, time of death, month of death, cardiothoracic ratio, valvular lesions, cardiogenic shock, digitalis-induced arrhythmias, intercurrent pneumonia, pleurorrhea, and hypotension were related to the overall mortality and cardiac death. Multiple factor logistic analysis indicated that for the overall mortality, the independent prognostic factors included presence of cardiac functional classification, cardiothoracic ratio and cardiogenic shock; for cardiac death, the independent factors included cardiac functional classification, cardiothoracic ratio, cardiogenic shock, digitalis-induced arrhythmias and valvular lesions. The data analysis showed that these five factors were contributory to rheumatic heart disease with synergism.

Adolescent↗
PubMed1992

HPLC determination of a chemically modified nonantimicrobial tetracycline: biological implications.

Chemically modified tetracycline (4-de-dimethylamino tetracycline), like commercially available tetracyclines, is known to inhibit experimentally induced pathologic collagen breakdown. A method for measurement of chemically modified tetracycline in small volumes (50 microliters) of rat serum was developed using reversed-phase HPLC; this was necessary because this tetracycline analog lacks antimicrobial activity and, therefore, cannot be measured with standard bioassays. This method uses the same solution for extraction and elution thus providing a simple and rapid assay for both drugs. Using this technique, the concentration of chemically modified tetracycline and tetracycline were determined in rat serum at different times after oral administration. The serum concentration of chemically modified tetracycline was much higher than that for tetracycline, and its serum half-life was greater. The IC50 of chemically modified tetracycline and tetracycline, as inhibitors of collagenase from rat polymorphonuclear leukocytes, was determined and found to be 4.1 x 10(-8) M (0.02 micrograms/ml) and 2.4 x 10(-4) M (120 micrograms/ml), respectively. Based on the serum levels of these drugs after oral administration, and their IC50 values, chemically modified tetracycline is potentially a far more potent inhibitor of excess collagenase activity than tetracycline, during pathologic conditions, and may have the added advantage of not producing some of the typical complications of long-term antibiotic therapy.

Animals↗
PubMed1992

Genetic engineering of a Lymantria dispar nuclear polyhedrosis virus for expression of foreign genes.

A bacterial lacZ gene was inserted into an isolate of the Lymantria dispar nuclear polyhedrosis virus (LdMNPV). The transfer vector was constructed by site-directed mutagenesis of the translation start site of the LdMNPV polyhedrin gene, within the BglII E fragment of the viral genome. A multiple cloning sequence was inserted at this start site and used for the insertion of the lacZ gene into the transfer plasmid. Liposome transfection was used to cotransfect L. dispar tissue culture cells with viral DNA and the transfer plasmid. Recombinant LdMNPV isolates were purified by isolation of plaques producing beta-galactosidase but not polyhedra. Restriction enzyme fragment profiles were used to determine the site of the lacZ gene insertion, and DNA sequencing of the 5' and 3' ends of the lacZ gene insert and the adjoining polyhedrin promoter and coding regions was performed to identify its precise location. Expression of the lacZ gene was examined by studying virus-induced protein using [35S]methionine pulse-labelling, SDS-PAGE fractionation and autoradiography. Expression of beta-galactosidase was examined in tissue culture cells using colorimetric assays. The maximum rate of beta-galactosidase production was approximately 50 international units (IU)/10(6) tissue culture cells/day between 3 and 4 days post-infection (p.i), and the peak total expression was 158 IU/10(6) cells 5 days p.i. beta-Galactosidase activity was first detected 48 h p.i. in haemolymph samples from fourth instar L. dispar larvae injected with 10(6) p.f.u. of virus. The peak beta-galactosidase activity in larval haemolymph samples was 1931 IU/ml of haemolymph at 11 days p.i., just prior to death.

Animals↗
PubMed1992

Tetracycline administration increases protein (presumably procollagen) synthesis and secretion in periodontal ligament fibroblasts of streptozotocin-induced diabetic rats.

Streptozotocin-induced, insulin-deficient diabetic adult rats were daily administrated either minocycline or a chemically-modified non-antimicrobial tetracycline (CMT) by oral gavage for a 3-week time period; untreated diabetic and non-diabetic rats served as controls. On day 21, all rats received an intravenous injection of 3H-proline followed by perfusion fixation with an aldehyde mixture at 20 minutes and 4 hours after isotope injection. The upper and lower mandibles of these rats were dissected and processed for quantitative electron microscopic autoradiography to study 3H-proline utilization by fibroblasts in the periodontal ligament (PDL) of molars. In the non-diabetic controls, at 20 min after 3H-proline injection, radioprecursor was incorporated by the Golgi-RER system of PDL fibroblasts. At the 4-h time period, most of the label was present over the collagen fibers around these cells. In contrast, PDL fibroblasts in the untreated diabetic rats showed marked abnormalities ultrastructurally and minimal uptake (20 min) and secretion (4 h) of labeled proline. At both time periods, in both minocycline- and CMT-treated diabetic rats, fibroblasts were structurally more normal and the radioprecursor was localized in the fibroblasts and the PDL matrix in a pattern similar to that seen in the control rats. These results suggest that the diabetes-induced structural abnormalities and suppression of synthesis and secretion of protein (presumably collagen and its precursor) by PDL fibroblasts can be restored to near-normal by administration of a tetracycline and that this effect is mediated by a non-antimicrobial property of this family of antibiotics.

Animals↗
PubMed1992

Blood pressure and heart rate response to vasoactive agents in conscious diabetic rats.

Blood pressure and heart rate responses to different vasoactive agents were observed in conscious streptozotocin-diabetic rats. An indwelling femoral artery catheter was used for direct measurement of arterial pressure and heart rate. The femoral vein was cannulated for drug administration. In a resting state diabetic rats showed lower heart rates and lower systolic blood pressure. The vasodepressor response to both acetylcholine and sodium nitroprusside was decreased, while the heart rate increase induced by the baroreceptor reflex was not altered. Both the increase in blood pressure and the reflex bradycardia to norepinephrine were decreased in the diabetic group. When the change in heart rate was plotted against blood pressure in response to norepinephrine, there was no difference in the two groups of animals. The vasodepressor response to isoproterenol, hydralazine, and verapamil in diabetic rats was unchanged. The results demonstrate a decreased vascular responsiveness in diabetic rats to norepinephrine, acetylcholine, and nitroprusside. The diabetes-induced vascular system changes require further study to understand the mechanisms involved.

Acetylcholine↗
PubMed1992

[Inhibitory effect of electro-acupuncture on penicillin-induced amygdala epileptiform discharges].

Epileptiform discharge induced by microinjection of penicillin in the rat's amygdala was attenuated after acupuncture of certain "acupoints", as revealed by reduction of frequency and amplitude. The effect of acupuncture was reversed by microinjection of naloxone or 3M-P into peritoneal cavity, thus suggesting the participation of endorphin and GABA in antiepileptic action of acupuncture.

Amygdala↗
PubMed1992

Detection of human cytomegalovirus antigen and DNA in lymph nodes and peripheral blood mononuclear cells of patients with angioimmunoblastic lymphadenopathy with dysproteinemia.

The cause of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) remains unknown. It is characterized by acute onset, severe constitutional symptoms, cervical or generalized lymphadenopathy, lymphopenia, and polyclonal hypergammaglobulinemia, all of which are highly suggestive of a viral origin. Using immunohistochemical methods, employing murine monoclonal antibody as the primary antibody, we detected human cytomegalovirus antigen in the lymph nodes of eight of 11 patients with AILD. Cytomegalovirus DNA was also detected in the peripheral blood mononuclear cells by DNA dot hybridization in all five of the patients with AILD who were tested using this technique. None of the lymph nodes from the 11 patients stained positive for the rubella virus antigen. Based on the above evidence and the similarity of the immunologic abnormalities found in both AILD and cytomegalovirus infection, the possible role of cytomegalovirus as one of the causative agents for AILD is proposed.

Adult↗