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W Tang

Publications and source records attributed to W Tang.

At least 289 records · Page 16Linked to original sources
PubMed1993

Food-borne heterocyclic amines. Chemistry, formation, occurrence and biological activities. A literature review.

This review summarizes the abundant literature on food-borne heterocyclic amines, their chemistry and formation, their occurrence in food, their biological activities including mutagenicity, induction of DNA damage and carcinogenicity. Pharmacokinetics and biotransformation are also discussed. Factors that influence these effects are given consideration, with special emphasis on dietary factors that might counteract detrimental biological effects. The annual per capita intake of heterocyclic amines via food is estimated. Risk extrapolations that have been published suggest that food-borne heterocyclic amines are relevant for human cancer etiology.

Amines↗
PubMed1993

Immunocytological test to detect adult carriers of (--SEA/) deletional alpha-thalassaemia.

The gene frequency for (--SEA/) deletional alpha-thalassaemia is high in Southeast Asian populations. We report a simple immunocytological test that is highly sensitive and specific for the detection of adult carriers of the (--SEA/) deletion. We prospectively studied 206 consecutive adult blood samples. All 41 with the (--SEA/) deletion had a positive test; all but 1 of the 165 non-carriers were negative. This test, whose major requirement is a fluorescence microscope, should be useful to identify couples at risk of conceiving fetuses with homozygous alpha-thalassaemia.

Adult↗
PubMed1993

Angiotensin II type 2 receptor expression in neuronal cultures from spontaneously hypertensive rat brain.

We have compared the levels of angiotensin II (AII) type 2 (AT2) receptors in neuronal cultures from 1-day-old Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rat hypothalamus and brainstem. These studies were performed to determine if the increase in total AII receptors observed in SH neurons in previous studies includes the AT2 receptor subtype. Specific binding of the AT2 receptor selective ligand [125I]CGP42112 to WKY and SH rat neuronal cultures was time dependent and saturable in each case. Kd (approximately 0.35 nM) and Bmax (approximately 95 fmol/mg protein) values for [125I]CGP42112 specific binding did not significantly differ between WKY and SH rat cultures. In addition, AT2 receptor-mediated reductions in cellular cGMP exhibited no significant differences in WKY and SH rat neuronal cultures. We conclude that the greater levels of AII receptors found in SH rat hypothalamus/brainstem neuronal cultures, compared with WKY rat neurons from these areas, do not include the AT2 receptor subtype.

Angiotensin II↗
PubMed1993

Expression of embryonic zeta-globin and epsilon-globin chains in a 10-year-old girl with congenital anemia.

A 10-year-old Danish girl with congenital anemia is described. At birth, she had severe anemia and erythroblastosis and was transfused a number of times during the first year. The need for transfusions has since declined steadily. Her reticulocyte counts varied between 2% and 15%, and her bone marrow aspirate showed some dyserythropoietic features. Her hemoglobin F level was consistently elevated, up to as much as 41%. Her erythrocytes had a normal level of I antigen but an undetectable level of i antigen. Moreover, embryonic zeta-globin and epsilon-globin chains were present in some of her circulating erythrocytes. These findings may represent the manifestations of a new variant of congenital anemia.

Adolescent↗
PubMed1993

Exofacial epitope-tagged glucose transporter chimeras reveal COOH-terminal sequences governing cellular localization.

The insulin-regulated adipocyte/skeletal muscle glucose transporter (GLUT4) displays a characteristic steady-state intracellular localization under basal conditions, whereas the erythrocyte/brain transporter isoform (GLUT1) distributes mostly to the cell surface. To identify possible structural elements in these transporter proteins that determine their cellular localization, GLUT1/GLUT4 chimera cDNA constructs that contain the hemagglutinin epitope YPYDVPDYA (HA) in their major exofacial loops were engineered. Binding of monoclonal anti-HA antibody to non-permeabilized COS-7 cells expressing HA-tagged transporter chimeras revealed that expression of transporters on the cell surface was strongly influenced by their cytoplasmic COOH-terminal domain. This method also revealed a less marked, but significant effect on cellular localization of amino acid residues between transporter exofacial and middle loops. The subcellular distribution of expressed chimeras was confirmed by immunofluorescence microscopy of permeabilized COS-7 cells. Thus, HA-tagged native GLUT4 was concentrated in the perinuclear region, whereas a chimera containing the COOH-terminal 29 residues of GLUT1 substituted onto GLUT4 distributed to the plasma membrane, as did native GLUT1. Furthermore, a chimera composed of GLUT1 with a GLUT4 COOH-terminal 30-residue substitution exhibited a predominantly intracellular localization. Similar data was obtained in CHO cells stably expressing these chimeras. Taken together, these results define the unique COOH-terminal cytoplasmic sequences of the GLUT1 and GLUT4 glucose transporters as important determinants of cellular localization in COS-7 and CHO cells.

Amino Acid Sequence↗
PubMed1993

Myocardial hypercarbic acidosis reduces cardiac resuscitability.

BACKGROUND: The severity of spontaneous myocardial hypercarbic acidosis during cardiac arrest previously has been predictive of the likelihood of restoring spontaneous circulation. The present study investigated whether hypercarbia itself impairs cardiac resuscitation. Since coronary perfusion pressure is the overriding determinant of cardiac resuscitability, we used a porcine model of cardiac arrest in which coronary perfusion pressure was controlled. METHODS: In 31 domestic pigs anesthetized with pentobarbital, the lungs were mechanically ventilate. Myocardial carbon dioxide tension and hydrogen ion concentration were measured by sensors advanced into the myocardium. After 15 min of untreated ventricular fibrillation, venoarterial extracorporeal circulation was initiated. Animals were randomized to receive a carbon dioxide gas fraction in the extracorporeal perfusate of 0.00, 0.10, 0.30, or 0.50 with oxygen concentration maintained constant at 0.50. Extracorporeal flow was adjusted to maintain a coronary perfusion pressure in the range of 60-80 mmHg, a level of predictive resuscitability. RESULTS: The proportion of animals successfully resuscitated and the proportion of animals maintaining spontaneous circulation for 60 min or longer decreased with increasing perfusate PCO2 and concurrent increases in myocardial CO2 tension in the absence of altered oxygen utilization (P < .01). CONCLUSIONS: Hypercarbia, in this experimental setting, was therefore a quantitative determinant of both myocardial resuscitability and the restoration of spontaneous circulation.

Acidosis↗
PubMed1993

Progressive myocardial dysfunction after cardiac resuscitation.

OBJECTIVE: To investigate left ventricular function by the Langendorff method after successful cardiac resuscitation in rats. DESIGN: Prospective, randomized, controlled animal study. SETTING: University research laboratory. SUBJECTS: Adult, male Sprague-Dawley rats. INTERVENTIONS: Myocardial function was investigated in three subsets of isolated, perfused rat hearts that were harvested either before inducing ventricular fibrillation (controls) or at defined intervals after successful resuscitation from ventricular fibrillation. Ventricular fibrillation was induced with an electrode catheter advanced into the right ventricle of 15 mature, mechanically ventilated Sprague-Dawley rats. After an interval of 4 mins of untreated ventricular fibrillation and an additional 5 mins of precordial compression, spontaneous circulation was restored by a direct current, transthoracic countershock. The heart of each animal was then harvested at either 2 or 20 mins after successful cardiac resuscitation. The same model was utilized for harvesting the controls. Animals were randomized to each of the three subsets immediately before induction of cardiac arrest. MEASUREMENTS AND MAIN RESULTS: There was a progressive decrease in myocardial contractility of the isolated, perfused hearts. Mean left ventricular systolic pressure was 128 +/- 8 mm Hg in control animals. In hearts harvested at 2 mins after successful resuscitation, the maximal generated pressure was reduced to 106 +/- 9 mm Hg. When harvested at 20 mins after successful resuscitation, it was reduced to 81 +/- 11 mm Hg. There were corresponding decreases in the mean maximal rate of left ventricular pressure increase (dP/dtmax) from 2880 +/- 110 to 2470 +/- 120 mm Hg/sec at 2 mins and to 1810 +/- 135 mm Hg/sec at 20 mins. These decreases in contractility were associated with striking decreases in myocardial relaxation and compliance. CONCLUSION: These studies, therefore, document progressive systolic and diastolic myocardial dysfunction immediately after successful cardiac resuscitation with restoration of spontaneous circulation.

Animals↗
PubMed1993

Dilution kinetics of H(2)18O for the measurement of total body water in preterm babies in the first week after birth.

The aim of this study was to determine the kinetics of H(2)18O equilibration and elimination in preterm babies for the estimation of total body water. Thirteen, clinically stable, preterm babies of less than 32 weeks' gestation were studied in the first week after birth. Blood and urine samples were obtained for baseline measurement of 18O:16O ratio and 1 ml/kg of 10% H(2)18O (0.1 g/kg isotope) administered orally. Eleven blood samples were obtained over the next six hours and between one and four over the next 18 hours. During the same 24 hour period between three and eight urine samples were also obtained. The dilution space at zero time (volume of distribution or total body water) was estimated using double exponential curve fitting using all available points, from single samples and from linear regression on the log data using two or three samples. Equilibration time was variable and showed a significant correlation with percentage change in body weight from birth. For blood samples, the median time to equilibrium was 81 minutes (range 2 to 191). A plateau phase was not detected, with H(2)18O enrichment declining after the point of maximum enrichment. The median volume of distribution at time 0, based on double exponential curve fit analysis, was 859 ml/kg (range 755 to 995). The volume of distribution, estimated from linear regression on the log data using two serum samples obtained at three and six hours, approximated most closely to that based on exponential curve fit analysis with a median difference of -4 ml/kg (range -41 to 73). It was concluded that in most situations blood sampling at three and six hours may be acceptable. However, as equilibration time is variable and influenced by the state of expansion or depletion of body water compartments, when studying overhydration states, multiple sampling is advised in order to be certain that the elimination phase has been reached.

Blood Specimen Collection↗
PubMed1993

ANP receptors in neurons and astrocytes from spontaneously hypertensive rat brain.

In this study we compared the levels and responsiveness of atrial natriuretic peptide (ANP) receptors in neuronal and astrocyte glial cultures from spontaneously hypertensive (SH) and normotensive (Wistar-Kyoto: WKY) rat brain. Both neuronal and astrocyte glial cultures from the hypothalamus and brain stem of 1-day-old SH and WKY rats display specific high-affinity binding sites for 125I-labeled ANP. The presence of a large population of ANP-C receptors in each type of culture is indicated by the strong competition of 125I-ANP binding by the ring-deleted analogue of ANP [C-ANF-(4-23)]. In neuronal cultures from both strains, C-type natriuretic peptide (CNP-22) was the most effective natriuretic peptide in stimulating guanosine 3',5'-cyclic monophosphate (cGMP) levels, suggesting the presence of ANP-B receptors in these cells. By contrast, ANP was the most effective stimulator of cGMP levels in SH and WKY rat astrocyte glial cultures, suggesting the presence of ANP-A receptors. Here, we have determined that there is a decrease in the maximum binding capacity for 125I-ANP-specific binding in both SH rat neuronal and astrocyte glial cultures compared with their respective control cells. The stimulatory effects of CNP-22 on cGMP levels in SH rat neurons and of ANP on cGMP levels in SH rat astrocytes were significantly reduced compared with their respective WKY rat cultures. Our data suggest that the lower number of ANP receptors in SH rat neuronal and astrocyte glial cultures includes a reduction in the guanylate cyclase-coupled ANP receptors.

Animals↗
PubMed1993

Osmoregulation of the magnocellular system during pregnancy and lactation.

We compared the responsiveness of both the vasopressin (VP) and oxytocin (OT) magnocellular systems to osmotic stimulation during pregnancy and lactation to determine if changes in thresholds and sensitivities were similar for both neuropeptides. Virgin, pregnant (day 20), and lactating (day 6) Sprague-Dawley rats were injected with a hypertonic NaCl solution (0.25 M-8.0 M NaCl; 15 ml/kg sc) and decapitated 2 h later. Late in gestation, the apparent osmotic threshold for both VP and OT release was lower by approximately 10 mosmol/kgH2O than that of virgin and lactating animals. The sensitivity (i.e., slope of the linear regression relating plasma osmolality and VP or OT levels) of the magnocellular system to osmoregulation, however, was unchanged in pregnant animals but was significantly attenuated (P < 0.01) for both peptides during lactation (slopes of lactating vs. virgin rats: OT, 1.7 vs. 3.4; VP, 1.1 vs. 1.9). The neural lobe content of VP decreased (P < 0.05) in pregnant rats, whereas OT stores were reduced (P < 0.05) in lactating animals. Thus, during pregnancy, the lower tonicity of plasma is perceived as normal by both VP and OT neuroendocrine systems enabling excretion of an acute sodium or water load.

Animals↗
PubMed1993

Regional blood flow during closed-chest cardiac resuscitation in rats.

Quantitative measurement of regional blood flow during cardiac arrest and resuscitation has been confined to large animals. We report on a rodent model utilizing radioactive microspheres during cardiac arrest and resuscitation for investigation of regional blood flow. Ventricular fibrillation was electrically induced in 10 pentobarbital-anesthetized Sprague-Dawley rats. Resuscitation was attempted by precordial compression followed by external direct current countershock. During precordial compression, cardiac output corresponded to 12% of prearrest flow. Similarly low flows were observed in the myocardium and brain. However, much lower flows were observed in the adrenal glands, kidneys, intra-abdominal viscera, skin, and skeletal muscle. Five of ten animals were successfully resuscitated. During precordial compression, resuscitated animals had significantly higher cardiac output (13.1 +/- 4.1 vs. 8.6 +/- 1.46 ml/min), myocardial blood flow (0.70 +/- 0.24 vs. 0.22 +/- 0.15 ml.min-1.g-1), cerebral blood flow (0.17 +/- 0.04 vs. 0.06 +/- 0.02 ml.min-1.g-1), and adrenal blood flow (1.09 +/- 0.60 vs. 0.27 +/- 0.16 ml.min-1.g-1). Thirty minutes after successful resuscitation, cardiac output and myocardial, cerebral, renal, and adrenal blood flows and blood flow to splanchnic viscera (with the exception of the spleen) had returned to > or = 70% of prearrest flows. These studies confirm the conclusion of earlier investigations in larger animals that visceral blood flow during cardiac arrest and precordial compression is preferentially distributed to the brain and myocardium. Successful cardiac resuscitation is contingent on threshold levels of myocardial blood flow that exceed 0.4 ml.min-1.g-1.

Adrenal Glands↗
PubMed1993

Augmented efficacy of external CPR by intermittent occlusion of the ascending aorta.

BACKGROUND: After prolonged cardiac arrest, conventional methods of closed-chest cardiac compression are ineffective. This is primarily because of failure to generate minimal threshold levels of coronary perfusion pressure for cardiac resuscitation. This report introduces a new option for cardiac resuscitation by use of a combination of intermittent ascending aortic balloon occlusion, aortic infusion, and precordial compression to increase the pressure gradient for coronary perfusion. METHODS AND RESULTS: Twenty anesthetized, mechanically ventilated, normovolemic domestic pigs were investigated. A 10F balloon catheter was advanced from the left femoral artery into the ascending aorta. Ventricular fibrillation was induced with an AC current delivered through an electrode catheter advanced into the right ventricle. Precordial compression was initiated after 7 minutes of untreated ventricular fibrillation. The animals were randomized to one of four groups: (1) balloon occlusion with proximal infusion of oxygenated saline, (2) balloon occlusion alone, (3) proximal aortic infusion together with epinephrine without balloon occlusion, and (4) injection of epinephrine without balloon occlusion or proximal infusion. For balloon occlusion, the balloon was inflated for 30 seconds during each minute of cardiopulmonary resuscitation. In the subsets of animals that received infusions, oxygenated saline (30 mL) was injected into the proximal aorta immediately after balloon occlusion. Epinephrine was used in two subsets: It was injected as a bolus in amounts of 30 micrograms/kg into the right atrium at 30 seconds after start of precordial compression and repeated as required to maintain coronary perfusion pressure within the range of 25 to 30 mm Hg. Defibrillation was attempted at 1 minute after start of precordial compression and at 1-minute intervals thereafter. Resuscitation attempts were continued until there was return of spontaneous circulation or for a total of 30 minutes after start of precordial compression. Coronary perfusion pressure generated by precordial compression was significantly increased after balloon occlusion. Each of 10 animals was successfully resuscitated and survived for 48 hours after balloon occlusion whether or not it was combined with infusion. Three of five animals were resuscitated by a combination of infusion and epinephrine in the absence of aortic occlusion, but none survived for 48 hours (P = .02). Only one epinephrine-treated animal was successfully resuscitated and survived for 48 hours in the absence of balloon occlusion or infusion (P < .05). CONCLUSIONS: Ascending aortic balloon occlusion with or without proximal aortic infusion strikingly increased resuscitability and 48-hour survival after cardiac arrest under conditions when conventional methods failed.

Animals↗
PubMed1993

Increased angiotensin II type-1 receptor gene expression in neuronal cultures from spontaneously hypertensive rats.

In this study we compared the expression of angiotensin II type 1 (AT1) receptor messenger RNA (mRNA) and AT1 receptors in neurons cultured from Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rat brains. Neuronal cultures from the hypothalamus and brain-stem of 1-day-old SH rats exhibited approximately 4-fold higher steady-state levels of AT1 receptor mRNA than the corresponding WKY cultures. This was attributable to greater levels of both AT1A and AT1B receptor mRNA subtypes in SH rat neuronal cultures compared with WKY rat neurons. SH rat neuronal cultures also exhibited increased numbers (approximately 2.3-fold) of binding sites for [3H]DuP753, an AT1 receptor selective ligand, and enhanced (approximately 3.4-fold) stimulation of inositol phospholipid hydrolysis by angiotensin II compared with WKY neurons. By contrast, cultured astroglia from SH and WKY rat brain exhibited no significant differences in either the levels of AT1 receptor mRNA or the specific binding of [3H]DuP753. These data suggest that in SH rat neurons, AT1 receptor transcription and translation is increased, compared with neurons from WKY rats.

Amino Acid Sequence↗
PubMed1993

Gastric intramural PCO2 during peritonitis and shock.

OBJECTIVE: To define whether increases in gastric intramural tissue CO2 and H+ increase during experimentally induced peritonitis with circulatory shock as they do under conditions of hemorrhagic shock and cardiac arrest. DESIGN AND SETTING: Peritonitis was induced in Sprague-Dawley rats by cecal ligation and fecal spillage. MEASUREMENTS AND RESULTS: Over an interval of 260 +/- 20 min in 5 animals, there was a progressive reduction in mean aortic pressure from 153 +/- 12 to 40 +/- 20 mm Hg and a decline in cardiac index from 429 +/- 135 to 178 +/- 7 ml/min. This was associated with increases in gastric intramural [H+] from 34 +/- 5 to 217 +/- 93 mmol/L (p = 0.001). Arterial blood lactate content concurrently increased from 0.9 +/- 0.1 to 4.6 +/- 0.7 mmol/L (p = 0.001). Only a late increase in gastric intramural PCO2 from 45 +/- 5 to 128 +/- 38 mm Hg (p = 0.01) was observed. CONCLUSION: In contrast to the gastric acid base changes that accompany hemorrhagic shock, in which there is an early and prominent increase in both PCO2 and [H+] in close relationship to decreases in cardiac output and arterial pressure, there was a prominent increase in gastric [H+] but only a delayed rise in gastric intramural PCO2. Arterial blood lactate and central venous oxygen saturation were earlier indicators of perfusion failure. Since the bicarbonate concentration in the stomach wall was substantially greater than that of simultaneously measured arterial blood, this has bearing on the current clinical method of gastric tonometry which assumes that arterial blood bicarbonate is equivalent to gastric wall bicarbonate.

Animals↗
PubMed1993

Carrier detection and prenatal diagnosis of hemoglobinopathies in Ontario.

The province of Ontario has a total population of approximately 10 million people, with approximately 20% being of African, Southeast Asian, East Indian, Mediterranean, or Middle Eastern ancestry in whom the gene frequency for hemoglobinopathies is relatively high. In 1989, the Ontario Ministry of Health funded the establishment of the Provincial Hemoglobinopathy DNA Diagnostic Laboratory located at the McMaster University Medical Centre in Hamilton, Ontario. The Laboratory provides DNA analysis to identify the globin gene mutations in carriers and affected individuals, and performs prenatal diagnosis for severe hemoglobinopathies. Annually, more than 400 patient samples are referred to the Laboratory for investigation, of which 25-35 are fetal samples from pregnancies at risk for either homozygous alpha-thalassemia, beta-thalassemia major, or sickling disorders. We have detected more than 70 different globin gene mutations, including several mutations not previously reported in the literature. Here we present examples of the approaches used to detect globin gene mutations in a heterogeneous "at risk" population such as in Ontario, and discuss the impact of this service on patient care, genetic counselling, and the incidence of severe hemoglobinopathies in Ontario.

DNA↗
PubMed1993

Nude mouse interim host model for human parathyroid grafts. Part III. Mechanism of modification of allograft antigenicity.

The alterations of number and DR antigen expression of antigen presenting cells (APCs) in human PTG grafts during the interim hosting period were analyzed. The results were as follows: 1) In C-PTG grafts, the APC number was reduced obviously within 100 days in the interim host. In F-PTG and A-PTG grafts, the APC number was increased at 30 d of interim hosting, and then decreased gradually. 2) No obvious change in D-related (DR) antigen expression of individual APCs was seen in C-PTG and F-PTG grafts. In A-PTG grafts, DR antigen expression was increased at 30 d of interim hosting, but then dropped gradually and asynchronously.

Animals↗