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Biomedical subjects

B C Wang

Publications and source records attributed to B C Wang.

At least 91 records · Page 5Linked to original sources
PubMed1991

Carcinoma induction following direct in situ transfer of v-Ha-ras into rat mammary epithelial cells using replication-defective retrovirus vectors.

Chemically induced mammary carcinomas often contain the activated Ha-ras oncogene. The role of this oncogene in the multistage process of carcinogenesis remains undefined. In order to model the role of ras in mammary carcinogenesis, gene transfer into adult rat mammary epithelial cells was accomplished by infusing helper-free, replication-defective retrovirus vectors into the central duct of each gland. In the initial experiments, the beta-galactosidase reporter gene was used to optimize the efficiency of this in situ gene transfer method. Stable infection of greater than 0.1% of mammary cells could be achieved following exposure to the beta-galactosidase gene-expressing vector. v-Ha-ras was then introduced into in situ adult rat mammary epithelial cells using this method. Cellular infection frequencies of less than 1% resulted in the frequent and rapid appearance of mammary carcinomas without any further treatment. Tumors arising following v-Ha-ras oncogene transfer resembled those induced by chemical carcinogens in both the kinetics of their development and histopathological spectrum. These observations support the hypothesis that ras activation can act as an initiation event in chemically induced mammary carcinogenesis. However, only a small percentage of v-Ha-ras infected cells, even with hormonal promotion, were neoplastically transformed, suggesting that ras-driven transformation is not a one-step event.

Animals↗
PubMed1991

Lumbar subarachnoid catheterization in rats.

An animal model was developed for the study of subarachnoid (spinal) anesthesia and analgesia under unanesthetized, unsedated and unrestrained conditions. Sprague-Dawley rats were anesthetized with intraperitoneal ketamine (75-100 mg.kg-1). A PE10 catheter was inserted under direct vision into the lumbar subarachnoid space, through partial laminectomy of L1 or L2 with or without removal of adjacent intervertebral ligament. One week after surgery, correct position of the catheter was verified by subarachnoid injection of 0.03-0.05 ml of 1.5% lidocaine, which produced temporary hind limb paralysis in all but one animal in 28 consecutive operations. There was neither mortality nor major complication, intraoperatively or postoperatively. Only 2 animals developed minor subcutaneous would infections which responded to incision, drainage and debridement.

Animals↗
PubMed1990

Single crystals of a chimeric T7/T3 RNA polymerase with T3 promoter specificity and a nonprocessive T7 RNAP mutant.

Two RNA polymerases homologous to bacteriophage T7 RNA polymerase, bacteriophage Sp6 and T3 RNA polymerases, were screened for crystallization under conditions identical or similar to those reported for the growth of large single crystals of T7 RNA polymerase (Sousa, R., Rose, J. P., Chung, Y. J., Lafer, E. M., and Wang, B.-C. (1989) Proteins 5, 266; Sousa, R., Lafer, E. M., and Wang, B.-C. (1990) J. Crystal Growth, in press; Sousa, R., and Lafer, E. M. (1990) Methods 1, in press). A number of mutant T7 RNAPs were also screened under these conditions as were three chimeric RNA polymerases consisting of T7 RNAP N-terminal and T3 RNAP C-terminal sequences. One chimeric polymerase and two mutant polymerases crystallized readily under T7 RNAP crystallization conditions. The chimeric polymerase crystallized in a space group different from T7 RNA polymerase: orthorombic with unit cell parameters a = 75 A, b = 98 A, c = 159 A; space group P2(1)2(1)2(1) and 4 molecules/unit cell. This chimeric enzyme exhibits T3 promoter specificity and will make it possible to investigate how structural differences between the T3 and T7 RNA polymerase promoter recognition domains determine their different promoter specificities. One of the mutant polymerases successfully crystallized was an enzyme which can carry out promoter recognition and abortive transcription but cannot carry out processive transcription. Its structure may provide information on the nature of the conformational changes undergone by T7 RNAP in the abortive-processive switch. Crystals of the second mutant T7 RNA polymerase were unsuitable for x-ray analysis.

Chimera↗
PubMed1990

Preliminary crystallographic analysis of class 3 rat liver aldehyde dehydrogenase.

NAD-linked aldehyde dehydrogenases (A1DH) (EC 1.2.1.3) catalyze the irreversible oxidation of a wide variety of aldehydes to their respective carboxylic acids. Crystals of a class 3 AIDH (from an Escherichia coli expression system) suitable for X-ray analysis have been obtained. These crystals, which can be grown to a size of 0.8 x 0.3 x 0.2 mm, diffract to 2.5 A resolution. Analysis of the diffraction pattern indicates that the crystals belong to the monoclinic space group P21, with cell parameters a = 65.11 A, b = 170.67 A, c = 47.15 A, and beta = 110.5 degrees. Assuming one dimer per asymmetric unit, the value Vm is calculated to be 2.45 and the solvent content of the crystal is estimated to be 50%. A self-rotation function study produced significant rotation peaks (58% of the origin) on the kappa = 180 section at psi = 90 degrees and phi = 71 degrees and 341 degrees, indicating that the pseudo-dimer axis is (or is very nearly) perpendicular to the b-axis.

Aldehyde Dehydrogenase↗
PubMed1990

Norepinephrine-induced atriopeptin release in conscious dogs is mediated by alterations in atrial pressure.

This study was designed to determine whether the increase in atriopeptin secretion induced by an intravenous infusion of norepinephrine is mediated directly by adrenergic receptor stimulation or indirectly by the associated increase in atrial pressure. Norepinephrine was infused at 0.5 microgram.kg-1.min-1 for 30 min into both sham-operated (intact) and cardiac-denervated conscious dogs. The infusion increased mean arterial pressure in all dogs. On the other hand, left atrial pressure increased from 5.0 +/- 0.7 to 9.6 +/- 1.6 mmHg (p less than 0.01) in intact dogs, but decreased from 5.5 +/- 1.0 to 2.0 +/- 0.7 (p less than 0.01) in cardiac-denervated dogs. Right atrial pressure changes followed similar trends, but were not significant in the intact group. Plasma atriopeptin increased from 73 +/- 12 to 110 +/- 18 pg/ml (p less than 0.01) as left atrial pressure increased in intact dogs and decreased from 79 +/- 15 to 54 +/- 10 pg/ml (p less than 0.01) as left atrial pressure decreased in cardiac-denervated dogs. The changes in plasma atriopeptin correlated closely with the changes in left atrial pressure (r = 0.941, p less than 0.001) and to a lesser extent with the changes in right atrial pressure (r = 0.413, p less than 0.05). These results suggest that the change in plasma atriopeptin induced by infusion of norepinephrine into conscious dogs is mediated by the concomitant change in atrial pressures.

Animals↗
PubMed1990

Pentobarbital anesthesia alters renal actions of alpha-hANP in dogs.

The magnitude of the natriuretic response to an infusion of alpha-human atrial natriuretic peptide (alpha-hANP) has varied considerably in different studies. The greatest renal responses to alpha-hANP infusion have been observed in barbiturate-anesthetized dogs. We therefore examined the renal, hormonal, and cardiovascular responses to alpha-hANP infusion in eight female dogs, once awake and again anesthetized with pentobarbital sodium (25 mg/kg body wt). After a 20-min control period, alpha-hANP was infused at a rate of 25 ng.kg-1.min-1 for 60 min. In dogs when awake, infusion of alpha-hANP produced a significant increase in sodium excretion from a control value of 39 +/- 7 to 73 +/- 13 and 89 +/- 15 mu eq/min after 40 and 60 min. In dogs when anesthetized, infusion of alpha-hANP produced an increase in sodium excretion from 21 +/- 3 to 105 +/- 12 and 143 +/- 21 mu eq/min after 40 and 60 min. The increase in sodium excretion was significantly greater in dogs when anesthetized than when awake. We also investigated the role of the renal sympathetic nerves on these responses in six dogs after chronic bilateral renal denervation. In dogs with denervated kidneys when awake, infusion of alpha-hANP did not change sodium excretion significantly. In dogs with denervated kidneys when anesthetized, infusion of alpha-hANP significantly increased sodium excretion; however, the increase was significantly attenuated when compared with anesthetized dogs with intact kidneys. We conclude that the natriuretic response to an infusion of alpha-hANP is enhanced in dogs when anesthetized. Also, the natriuretic response was attenuated by renal denervation in dogs when anesthetized.

Anesthesia↗
PubMed1990

Enhanced atrial peptide natriuresis during angiotensin and aldosterone blockade in dogs.

The hypothesis that the weak natriuretic effect elicited by modest amounts of atrial peptide is mediated via the inhibition of renin and aldosterone was evaluated in the conscious dog. The formation of angiotensin II (ANG II) and the effects of aldosterone (Aldo) were blocked acutely by enalaprilat and canrenoate, respectively. Infusion of alpha-human atrial natriuretic peptide (alpha-hANP) for 2 h at 25 ng.kg-1.min-1 increased plasma atrial peptide concentration 7- to 10-fold. In control experiments, i.e., experiments without ANG II-Aldo blockade, infusion of atrial peptide doubled urine volume (UV) from 0.21 +/- 0.01 to 0.43 +/- 0.09 ml/min and sodium excretion (UNaV) from 18 +/- 5 to 37 +/- 7 mueq/min; mean arterial blood pressure (AP) and atrial pressures decreased, whereas total peripheral resistance increased. The induction of ANG II-Aldo blockade elevated UNaV and UV 10- and 6-fold, respectively, and decreased AP. The subsequent 2-h infusion of atrial peptide elicited a further increase in UNaV (from 195 +/- 28 to 334 +/- 60 mueq/min); the hemodynamic changes were similar to those seen in the absence of ANG II-Aldo blockade, except that AP did not decrease significantly during the administration of atrial peptide. The data demonstrate that pharmacological inhibition of the effects of converting enzyme and Aldo does not impede the natriuretic response elicited by a 7- to 10-fold increase in circulating atrial peptide; in fact, the magnitude of the natriuresis is markedly enhanced during this blockade.

Angiotensin II↗
PubMed1990

Atriopeptin alters the vasopressin and renin responses elicited by hemorrhage.

This study was designed to investigate whether an infusion of atrial peptide is capable of modulating the hormonal and hemodynamic responses elicited by acute hemorrhage. Conscious dogs were bled at a rate of 0.8 ml.kg-1.min-1 until 20 ml of blood/kg body wt had been removed. Two experiments were performed on each dog; in one experiment the animal was given alpha-human atrial natriuretic peptide (alpha-hANP) (50 ng.kg-1.min-1) dissolved in saline; in the other only the saline vehicle was given. Right and left atrial pressures decreased during hemorrhage in all experiments; the absolute decreases were greater when the animals received atriopeptin, but the differences between treatments were statistically significant only for right atrial pressure. Cardiac output decreased (P less than 0.05) and total peripheral resistance increased (P less than 0.05) during hemorrhage when atriopeptin was infused; although these variables showed similar trends when vehicle alone was infused during hemorrhage, no significant changes occurred. Infusion of atrial peptide did not affect the decrease in arterial blood pressure that occurred during hemorrhage. The increase in plasma vasopressin induced by hemorrhage was potentiated, but the increase in plasma renin activity was attenuated when alpha-hANP was infused. Hemorrhage increased circulating aldosterone levels in each experiment, but the response was less pronounced when alpha-hANP was given during the experiment. Intravenous administration of alpha-hANP modulates the hemodynamic responses elicited by hemorrhage, potentiates the rise in plasma vasopressin, and attenuates the rise in plasma renin activity induced by acute blood loss in conscious dogs.

Aldosterone↗
PubMed1989

A new crystal form of ricin-OR.

Ricin-OR, an antitumor toxin, has been crystallized in space group P2 with cell parameters a = 8.77 nm, b = 4.64 nm, c = 7.64 nm and beta = 101 degrees. There is one molecule in the asymmetric unit and the solvent content is estimated to be 48% by volume. The crystals diffract to 0.25 nm resolution which is higher than that of the previously reported C2 crystal form which had a solvent content of 65%.

Antineoplastic Agents↗
PubMed1989

Preliminary crystallographic analysis of glutamine-binding protein from Escherichia coli.

Glutamine-binding protein from Escherichia coli, an essential component in the active transport of L-glutamine across the cytoplasmic membrane, has been crystallized by vapor diffusion in the presence of ammonium sulfate. The crystals exhibit pseudo-tetragonal symmetry with cell constants a = 77.5 A, b = 78.5 A and c = 90.2 A. Analysis of the diffraction data indicates that the space group is P2(1)2(1)2(1). There are two molecules per asymmetric unit and the solvent content is estimated to be 53%.

Carrier Proteins↗
PubMed1989

Single crystals of bacteriophage T7 RNA polymerase.

Single crystals of T7 RNA polymerase have been grown to a maximum size of 1.8 x 0.3 x 0.3 mm. The crystals are composed of fully intact T7 RNA polymerase which is enzymatically active upon dissolution. These crystals belong to the monoclinic space group P2(1) and have unit cell parameters a = 114.5 A, b = 139.6 A, c = 125.7 A, and beta = 98.1 degrees. Self-rotation function studies indicate that there are three molecules per asymmetric unit. The crystals diffract to at least 3.0 A resolution. These are the first crystals of a DNA-dependent RNA polymerase suitable for high-resolution X-ray structure determination.

Crystallization↗
PubMed1989

Distribution of 3H-morphine following lumbar subarachnoid injection in unanesthetized rabbits.

Morphine sulfate (40-100 micrograms) and 3H-morphine (125-200 pmol) were injected into the lumbar subarachnoid space of 18 unanesthetized rabbits through a surgically implanted catheter. Radioactivity remaining in the spinal cord 2, 4, 6, and 12 h later revealed recovery (mean +/- SEM) of 45 +/- 5.6% (n = 3), 30.5 +/- 14.1% (n = 4), 11.23 +/- 4.4% (n = 3), and 3.7 +/- 1.1% (n = 3), respectively, of the injected radioactivity. Tritiated morphine was found to be predominantly centered around the injection site, with limited rostral and caudal spread in the cord. No significant radioactivity was detected in plasma or cerebrospinal fluid (CSF) samples from the cisterna magna taken at 5, 15, 30, min and 1, 2, 4, 6, 12, and 24 h after receiving radioactive labeled drug (with the exception of that in one rabbit). Of the injected radioactivity, 75% was recovered in the urine in 12 h. These results suggest that the persistence of morphine in the spinal cord could account for its prolonged analgesic effect following intrathecal administration.

Animals↗
PubMed1989

Subarachnoid injection--a potential complication of retrobulbar block.

This study was undertaken to illustrate the potential for subarachnoid injection during retrobulbar block as a cause of respiratory arrest. Cadaver orbits were used to document the connection between the optic nerve sheath and the subarachnoid space. Following dissections of the orbits on one side of 24 cadavers, the optic nerve sheaths were identified and injected with 0.5 ml of water for measurement of pressure generated during injection. This was followed by intrasheath injection of equal volume of methylene blue for demonstrating the subarachnoid space surrounding the optic nerves. All injections were performed with a 1-ml syringe with a one-and-one-half-inch 22-G needle over a period of 10 s. The blue dye was found to track along the subarachnoid space of the optic nerve sheath to the chiasmatic cistern in the middle cranial fossa. Retrobulbar injections were performed on the contralateral undissected orbits and intrascleral injections were performed on undissected eyes. The size of the syringes, the gauge of the needles, and the speed of injection were uniform for all injections. The pressure generated by injection into the optic nerve sheath or intrascleral injection (approximately 138 mmHg) was three- to fourfold that produced by injection into the retrobulbar adipose tissue (approximately 35 mmHg) (P less than 0.05). The authors conclude that any resistance encountered during retrobulbar block should serve as a warning signal, mandating redirection of the needle, in order to prevent subarachnoid injection.

Anesthetics, Local↗
PubMed1989

Cardiovascular effects of calcitonin gene-related peptide in conscious dogs.

To elucidate the cardiovascular effects of alpha-human calcitonin gene-related peptide (CGRP), we infused CGRP intravenously at increasing rates of 3, 10, and 30 pmol.kg-1.min-1 during successive 15-min intervals into intact dogs, cardiac-denervated (CD) dogs, and cardiac-denervated dogs pretreated with beta-blockers. In intact dogs, the initial infusion rate of CGRP at 3 pmol.kg-1.min-1 did not produce significant hemodynamic changes, but the two higher infusion rates produced dose-dependent decreases in total peripheral resistance, mean arterial pressure, and left and right atrial pressures and produced dose-dependent increases in heart rate (HR) and cardiac output (CO). In addition, stroke volume decreased and pulmonary vascular resistance increased at the highest infusion rate. In CD dogs, CGRP produced qualitatively similar responses, although the increase in HR was markedly attenuated. The increase in CO was also attenuated, but the difference did not reach statistical significance. In CD dogs pretreated with beta-blockers, CGRP did not increase HR and the increase in CO was further attenuated. In a separate experiment, the lowest dose of CGRP (3 pmol.kg-1.min-1) was infused intravenously for 60 min in intact dogs; significant cardiovascular responses, qualitatively similar to those produced by higher rates of infusion, occurred. We conclude that CGRP is an extremely potent vasodilator and that the increase in HR is mediated primarily by autonomic reflexes.

Animals↗
PubMed1989

Endothelin and sarafotoxin produce dissimilar effects on renal blood flow, but both block the antidiuretic effects of vasopressin.

Human endothelin, a 21-residue peptide produced by vascular endothelial cells, was infused intravenously into trained conscious dogs at a rate of 20 ng.kg-1.min-1 for 1 hr. Endothelin produced a renal vasoconstriction that persisted during a 40-minute recovery period. Sarafotoxin S6b, a closely related 21-residue peptide that has been isolated from the venom of the burrowing asp, was also infused into the same conscious dogs at 20 ng.kg-1.min-1. Sarafotoxin produced a renal vasodilation that persisted throughout the infusion; when the infusion ended, however, renal blood flow decreased rapidly to below control levels. Both endothelin and sarafotoxin produced marked decreases in urine osmolality even though plasma vasopressin remained normal, thus indicating that these peptides inhibit the antidiuretic effects of vasopressin. These results imply that a broad spectrum of structure-activity relationships may exist among analogues of this unique group of 21-residue peptides.

Animals↗
PubMed1989

Clinical analysis of four Chinese hemophiliacs with human immunodeficiency virus infection.

Human immunodeficiency virus (HIV) is now considered as the causative agent of acquired immunodeficiency syndrome (AIDS). A high risk of AIDS has been reported among patients with hemophilia who received lyophilized commercial factor VIII and IX concentrates of American origin. At a prevalent survey from September to December 1985, HIV antibodies were found in all four patients with hemophilia treated with the batch number W87307, 955 I.U. of American commercial factor VIII concentrate supplied by Armour Pharmaceutical Company, USA. One of the sero-positive patients developed AIDS-related complex (ARC) and died of cerebral hemorrhage. The other three sero-positive patients had abnormalities in cell-mediated immunity. Of them two developed left lumbosacral radiculopathy and hemorrhagic herpes zoster and one remained well so far.

AIDS-Related Complex↗