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Y F Chen

Publications and source records attributed to Y F Chen.

At least 181 records · Page 10Linked to original sources
PubMed1993

An analysis of GABAergic afferents to basket cell bodies in the cat's cerebellum.

An antibody to glutamic acid decarboxylase (GAD) was used to identify GABAergic terminals around the somata of basket cells in the cat's cerebellar cortex. Two sources for GAD immunoreactive terminals were identified based on size and cytological characteristics including the recurrent collaterals derived from Purkinje cells and the axons of stellate cells. The majority of the unlabeled terminals likely arise from parallel fibers. The present analysis indicates that GAD-positive terminals form 13% of the synaptic contacts on basket cells. The remaining 87% are unlabeled. Thus, GAD-positive terminals represent a small proportion of the synaptic input to basket cell bodies as compared to afferent endings that likely mediate excitation.

Animals↗
PubMed1993

Simplified method for quantitation of angiotensin peptides in tissue.

A simple method for extraction, separation, identification and quantitation of angiotensin-like immunoactivity from tissue is described. Homogenized acetic acid extracts of tissue samples were lyophilized and reconstituted in mobile phase. Separation was performed by reversed-phase high-performance liquid chromatography on a phenyl silica gel column with an eluent consisting of 20% acetonitrile in 0.1 M aqueous ammonium phosphate buffer, pH 4.9. Elution of standard peptides under isocratic conditions revealed clear resolution of angiotensin I, II and III and the (1-7) and (3-8) peptides. Recoveries of labeled angiotensin peptide standards from the extraction step were > 90%. Radioimmunoassay of relevant peaks revealed detectable levels of angiotensin I-, II- and III-like immunoactivity in single rat hypothalami and brain stems.

Angiotensin I↗
PubMed1993

An analysis of HRP-filled basket cell axons in the cat's cerebellum. II. Axonal distribution.

The axons of basket cells course horizontally within the lower molecular layer of the cerebellar cortex and give rise to three types of axon collaterals. One collateral distributes around the somata and axon hillocks of Purkinje cells, forming a complex pericellular basket-like formation or "pinceau". The other two axonal specializations have the form of beaded tendrils, but differ in their origin and laminar distribution. In the previous paper, the morphometry and configuration of these axonal branches were described. In the present account, their synaptic relationships are analyzed based on serial section analysis and computer reconstructions. Our data indicate that: (1) Purkinje cells receive descending collaterals from more than one basket cell; (2) the contribution of the descending collaterals to individual pinceau is not uniform; Purkinje cells located close to the basket cell of origin receive a greater number of descending collaterals when compared to Purkinje cells located more distally; (3) few synaptic junctions are formed by the descending collaterals within the pinceaux; (4) beaded tendrils make synaptic contacts with the somata and dendrites of Purkinje cells, and (5) the horizontal axon forms synaptic junctions with the dendritic shafts and spiny branchlets of Purkinje cells. Functional considerations of these synaptic relationships are discussed in the light of the classic concept of off-beam inhibition mediated by basket cells.

Animals↗
PubMed1993

Excitatory sympathetic reflex in NaCl-sensitive spontaneously hypertensive rats.

We have previously demonstrated blunted reflex responses of lumbar sympathetic nerve activity during volume expansion in NaCl-sensitive spontaneously hypertensive rats maintained on basal (1% NaCl) diets compared with NaCl-resistant spontaneously hypertensive rats, Wistar-Kyoto rats, and Sprague-Dawley rats. The current study tested the hypothesis that chronic ingestion of a high (8%) NaCl diet further blunts cardiopulmonary reflex function in the NaCl-sensitive spontaneously hypertensive rat. After 3 weeks of a 1% or 8% NaCl diet, male rats of all four strains were instrumented with femoral arterial and venous cannulas and lumbar nerve recording electrodes at 10 weeks of age. Two days later, conscious rats were infused with whole blood to expand blood volume. NaCl-sensitive spontaneously hypertensive rats maintained on a 1% NaCl diet had blunted responses of nerve activity to acute volume expansion compared with control strains. NaCl-sensitive spontaneously hypertensive rats maintained on an 8% NaCl diet had increases in nerve activity responses to volume expansion. In a second experiment, the volume expansion protocol was repeated in anesthetized NaCl-sensitive spontaneously hypertensive rats that had been subjected to sinoaortic denervation after 3 weeks of a 1% or 8% NaCl diet. After sinoaortic denervation, an increase in nerve activity was again observed during volume expansion in animals fed the 8% NaCl diet. In animals fed the 1% NaCl diet, changes in nerve activity were variable. The excitatory response was significantly reduced after bilateral vagotomy. These studies suggest that blood pressure regulation in NaCl-sensitive spontaneously hypertensive rats is a complex interaction of excitatory and inhibitory sympathetic reflex systems that is altered by high dietary NaCl exposure.

Animals↗
PubMed1993

Open heart surgery in a patient with an implanted pacemaker: case report.

When a patient has a pacemaker and requires operation, surgeons have to consider some possible intraoperative pacemaker complications induced by electrocautery. Electrocautery is commonly used during surgery to achieve hemostasis. However, this very effective tool may introduce innumerable problems in the paced patient, including irreversible damage to the pulse generator, pacemaker reprogramming, induction of a rise in the capture threshold, and ventricular fibrillation. Although electrocautery may be avoided in some surgical procedures, open heart surgery cannot be performed without it. One case is presented to illustrate how to achieve hemostasis while decreasing electric interference and how to protect the permanent pacemaker while avoiding those possible complications during the defibrillation. The purpose of this article is to call attention to potential problems induced by electrocautery and in an effect to facilitate the perioperative management of the paced patient undergoing open heart surgery.

Aortic Valve↗
PubMed1992

Restoration of motility to an Escherichia coli fliA flagellar mutant by a Bacillus subtilis sigma factor.

The activation of additional promoter sites by production of an alternative sigma subunit for RNA polymerase is a common strategy for the coordinate regulation of gene expression. Many alternative sigma factors control genes for specialized, and often narrowly distributed, functions. For example, most of the alternative sigma factors in Bacillus subtilis control genes necessary for endospore formation. In contrast, the B. subtilis sigma D protein controls the expression of genes important for flagellar-based motility and chemotaxis, a form of locomotion very broadly distributed in the eubacteria. A homologous sigma factor, sigma F, controls a similar group of motility genes in the enteric bacteria. The conservation of both promoter specificity and genetic function in these two regulons allowed us to test the ability of a B. subtilis sigma factor to function within an Escherichia coli host. We demonstrate that expression of the B. subtilis sigD gene restores motility to an E. coli strain mutant in the fliA locus encoding the sigma F factor. This result suggests that the B. subtilis sigma D protein can bind to the E. coli core RNA polymerase to direct transcription initiation from at least four of the late operon promoters, thereby leading to the synthesis of flagellin, motor, and hook-associated proteins. Conversely, expression of sigma D protein in a normally chemotactic strain of E. coli (fliA+) leads to a hyperflagellated, nonchemotactic phenotype.

Bacillus subtilis↗
PubMed1992

Ganglion atrial natriuretic peptide in NaCl sensitive spontaneously hypertensive rats.

Reports from other laboratories have shown that atrial natriuretic peptide (ANP) stores in sympathetic ganglia are increased during dietary NaCl supplementation in normotensive rats. We have previously demonstrated that dietary NaCl supplementation in NaCl sensitive spontaneously hypertensive rats (SHR-S) exacerbates hypertension and enhances peripheral sympathetic nervous system activity, while NaCl resistant Wistar-Kyoto (WKY) rats show neither response. Since endogenous ANP may inhibit ganglion transmission, an inability of SHR-S to increase ganglion ANP appropriately in response to high NaCl feeding could contribute to the NaCl induced increase in sympathetic nervous system activity and blood pressure in this model, while an increase in ganglion ANP in NaCl supplemented WKY would tend to prevent sympathetic activity and blood pressure from rising. The current study tested the hypothesis that ganglion ANP levels increase in WKY but not in SHR-S during dietary NaCl supplementation. Male SHR-S and WKY rats were placed on 1% or 8% NaCl diets at 7 weeks of age. The rats were decapitated without prior anesthesia 3 weeks later, and the superior cervical and celiac ganglia were removed for the measurement of ANP by radioimmunoassay. Dietary NaCl supplementation produced significant increases in blood pressure in SHR-S, but not in WKY rats; the high NaCl diet was associated with significant increases in the ANP content of superior cervical and celiac ganglia in WKY rats, but not in SHR-S.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of acute and chronic blockade of neutral endopeptidase with Sch 34826 on NaCl-sensitive hypertension in spontaneously hypertensive rats.

We have previously demonstrated that dietary NaCl supplementation is associated with increased circulating atrial natriuretic peptide (ANP) levels in Wistar-Kyoto (WKY) rats but not in spontaneously hypertensive rats (SHR), and that replacement with exogenous ANP prevents NaCl-sensitive hypertension in NaCl-sensitive SHR (SHR-S). The current study tested the hypothesis that chronic administration of the neutral endopeptidase (NEP) inhibitor Sch 34826 prevents NaCl sensitive hypertension in SHR-S by increasing endogenous ANP. Male SHR-S received Sch 34826 (90 mg/kg/day) or vehicle by gavage for 4 weeks beginning immediately before the initiation of 1% or 8% NaCl diets at age 7 weeks. Sch 34826 prevented the increase in arterial pressure in response to 8% NaCl in SHR-S, but had no effect on blood pressure in 1% NaCl fed SHR-S; plasma ANP levels were increased by 63 and 68% in the 1% and 8% NaCl groups, respectively, in response to Sch 34826. To examine the mechanism(s) of the antihypertensive effect of Sch 34826 in NaCl-supplemented SHR-S, a single dose (90 mg/kg) of Sch 34826 or vehicle was administered by gavage to SHR-S that had consumed 1% or 8% NaCl diets for 3 weeks. Sch 34826 abolished the NaCl-induced increase in blood pressure 3 h after treatment in 8% NaCl fed SHR-S, but had no effect in SHR-S fed the 1% NaCl diet. This effect was associated with increased urine volume and urinary sodium, ANP, and cyclic GMP in 8% NaCl fed SHR-S.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Altered-function mutations of the transcriptional regulatory gene virG of Agrobacterium tumefaciens.

Three point mutations were isolated in the Agrobacterium tumefaciens virG gene by screening for vir gene expression in the absence of added phenolic inducing compounds. All three mutations were localized in the predicted amino-terminal phosphoryl receiver domain of the protein. One mutant (N54D) bypasses the requirement for VirA and phenolic inducers both for transcriptional activation of all tested vir promoters and for plant tumorigenesis. This mutant also activates vir gene expression efficiently at neutral pH, indicating that the step in induction that is normally stimulated by acid pH occurs before or during VirG phosphorylation. The other two mutants (M13T and H15R) require VirA for activity but are sensitized to low levels of inducing stimuli.

Acetophenones↗
PubMed1992

Normobaric hypoxia stimulates endothelin-1 gene expression in the rat.

The current study tested the hypothesis that exposure to hypoxia enhances endothelin-1 (ET-1) gene expression and elevates circulating ET-1 levels in the rat. Rats were exposed to normobaric hypoxia (10% O2) or room air for 24 or 48 h. ET-1 in arterial blood was measured by radioimmunoassay. ET-1 gene transcript levels were measured by the slot blot technique on total RNA isolated from lung, right and left atria, right and left ventricles, kidney, spleen, liver, brain, main trunk of pulmonary artery, and thoracic aorta. Blots were probed with a 0.5 kb rat prepro ET-1 cDNA that does not cross-hybridize with mRNA for ET-2 or ET-3. Plasma ET-1 levels were increased significantly at 24 (10.03 +/- 2.33 pg/ml) and 48 h (14.02 +/- 3.44 pg/ml) of hypoxia compared with air controls (4.14 +/- 0.66 pg/ml). ET-1 mRNA levels were increased significantly (2-fold) in lung and right atrium after 48 h of hypoxia; no change was seen in organs perfused by the systemic vascular bed. These findings suggest that the hypoxia-induced increase in circulating ET-1 levels is mainly of pulmonary origin. A paracrine effect of ET-1 produced by lung endothelial cells could account for hypoxic pulmonary hypertension.

Animals↗
PubMed1992

Pressor effect of blocking atrial natriuretic peptide in nucleus tractus solitarii.

Previous studies have shown that microinjection of atrial natriuretic peptide into the caudal nucleus tractus solitarii produces significant increases in local neuronal firing rate associated with reductions in arterial pressure in anesthetized Wistar rats. Single units excited by microinjection of atrial natriuretic peptide into the caudal nucleus tractus solitarii were also excited by activation of arterial baroreceptors and inhibited by baroreceptor unloading. To test the hypothesis that endogenous atrial natriuretic peptide in caudal nucleus tractus solitarii is involved in the tonic control of blood pressure in the rat, we administered a blocking monoclonal antibody to atrial natriuretic peptide in a volume of 50 nl artificial cerebrospinal fluid via microinjection into the caudal nucleus tractus solitarii of spontaneously hypertensive and Wistar-Kyoto rats and observed the effects on mean arterial pressure and heart rate. Control injections of monoclonal antibody were administered into the rostral nucleus tractus solitarii, hypoglossal nucleus, spinal trigeminal nucleus, and cuneate nucleus of spontaneously hypertensive rats. Microinjection of monoclonal antibody into the caudal nucleus tractus solitarii caused significant increases in mean arterial pressure in spontaneously hypertensive rats but not in Wistar-Kyoto rats. There was no concomitant change in heart rate. Control injections of purified mouse immunoglobulin into the caudal nucleus tractus solitarii and of monoclonal antibody into the control neuronal groups listed above had no effect on mean arterial pressure. These results suggest that endogenous atrial natriuretic peptide in the caudal nucleus tractus solitarii mediates tonic control of blood pressure in spontaneously hypertensive rats but not in normotensive Wistar-Kyoto rats.

Animals↗
PubMed1992

Quantitation of hypothalamic atrial natriuretic peptide messenger RNA in hypertensive rats.

Previous studies from our laboratory have shown that spontaneously hypertensive rats have increased atrial natriuretic peptide stores and reduced norepinephrine release from nerve terminals in the anterior hypothalamus. We have postulated that atrial natriuretic peptide inhibits norepinephrine release in anterior hypothalamus, reducing excitation of sympathoinhibitory neurons, increasing sympathetic outflow, and elevating blood pressure in this model. The current study tested the hypothesis that atrial natriuretic peptide messenger RNA (mRNA) transcript levels are increased in anterior hypothalamus of spontaneously hypertensive rats compared with normotensive Wistar-Kyoto rats. Atrial natriuretic peptide mRNA in hypothalamic regions was measured by the quantitative polymerase chain reaction technique using a p-SELECT mutant atrial natriuretic peptide RNA as an internal standard. Atrial natriuretic peptide mRNA from hypothalamic regions of spontaneously hypertensive and Wistar-Kyoto rats and the internal standard were coamplified in a single reaction in which the same primers were used. Since the polymerase chain reaction product of the internal standard contained a new EcoRI restriction site, it could be distinguished from the atrial natriuretic peptide mRNA product by EcoRI digestion after the polymerase chain reaction. We found regional inhomogeneity of atrial natriuretic peptide mRNA in the hypothalamus of spontaneously hypertensive and Wistar-Kyoto rats, but we found no significant differences in atrial natriuretic peptide mRNA levels in anterior, posterior, or ventral hypothalamic areas between spontaneously hypertensive rats and Wistar-Kyoto rats fed normal (1%) or high (8%) salt diets. These data do not support the hypothesis that increased atrial natriuretic peptide stores in anterior hypothalamus of spontaneously hypertensive rats are related to increased gene transcription.

Animals↗
PubMed1992

Androgen-dependent angiotensinogen and renin messenger RNA expression in hypertensive rats.

Our previous studies demonstrated that the sexually dimorphic pattern of hypertension in the spontaneously hypertensive rat is androgen dependent. Gonadectomy retards the development of hypertension in young males, but not in females, and administration of testosterone propionate to gonadectomized spontaneously hypertensive rats of both sexes confers a male pattern of blood pressure development. The current study tested the hypothesis that renal and hepatic renin and angiotensinogen gene expression are also androgen dependent in the spontaneously hypertensive rat. Male and female spontaneously hypertensive rats underwent gonadectomy or a sham operation at 4 weeks of age. Subgroups of gonadectomized rats of both sexes were implanted with a 15-mm or 30-mm Silastic capsule filled with testosterone at the same time the gonadectomy was performed; a third group received an empty Silastic capsule. Northern and slot blot analyses were used to characterize and quantitate renin and angiotensinogen messenger RNA (mRNA) in the kidney and liver 18 weeks after the gonadectomy. Blood pressure, plasma renin activity, and hepatic angiotensinogen mRNA levels were higher in intact males than in females. Orchidectomy retarded the development of hypertension and lowered plasma renin and renal and hepatic angiotensinogen mRNA levels, and testosterone replacement restored the male pattern of hypertension and plasma renin and increased renal and hepatic angiotensinogen mRNA. Ovariectomy did not alter blood pressure or plasma renin but did lower renal renin and renal and hepatic angiotensinogen mRNA; testosterone increased blood pressure, plasma renin, renal renin and angiotensinogen mRNA, and hepatic angiotensinogen mRNA levels in ovariectomized females.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensinogen↗
PubMed1992

Salt supplementation does not alter the pressor effect of blocking atrial natriuretic peptide in nucleus tractus solitarii.

We have previously shown that microinjection of monoclonal antibody to atrial natriuretic peptide (ANP) into the caudal nucleus tractus solitarii causes a pressor response in salt-sensitive spontaneously hypertensive rats (SHR) fed a basal (1%) salt diet, suggesting that endogenous ANP in this region may be involved in the centrally mediated regulation of blood pressure in this model. The present study tested the hypothesis that the pressor effect of blocking endogenous ANP in caudal nucleus tractus solitarii is enhanced by dietary salt supplementation in salt-sensitive SHR. Monoclonal antibody to ANP (0.55 micrograms) in 50 nl artificial cerebrospinal fluid or control immunoglobulin G was microinjected into the caudal nucleus tractus solitarii of conscious salt-sensitive SHR, salt-resistant SHR, and Wistar-Kyoto rats fed 1% or 8% salt diets for 3 weeks. Microinjection of the monoclonal antibody into the caudal nucleus tractus solitarii evoked similar increases in mean arterial pressure in salt-sensitive SHR on both 1% and 8% salt diets and in salt-resistant SHR on a 1% salt diet but had no effect in Wistar-Kyoto rats. In contrast, microinjection of control immunoglobulin G into this brain area did not alter mean arterial pressure or heart rate in any experimental group. Thus, endogenous ANP in caudal nucleus tractus solitarii mediates tonic control of blood pressure in both salt-sensitive and salt-resistant SHR but not in Wistar-Kyoto rats, and this effect is independent of the salt sensitivity of hypertension and of dietary salt intake.

Animals↗
PubMed1992

Comparison of an immunoperoxidase "sandwich" staining method and western blot detection of P-glycoprotein in human cell lines and sarcomas.

The applicability of a multilayer immunoperoxidase "sandwich" method (IpS) developed by Chan14 for the amplified detection of P-glycoprotein (Pgp) was investigated. The authors examined 15 formalin-fixed cell lines, as well as formalin-fixed, paraffin-embedded sections from single biopsies of 46 sarcomas. The cell lines included sensitive and multidrug resistant sublines (KB, A2780, MCF-7, HeLa) with various relative degrees of resistance to doxorubicin (Dox). The sarcoma biopsy specimens were selected on the basis of the results obtained in Western blot (WB) detection of Pgp (22 positive and 24 negative by WB) using C219 and C494 monoclonal antibodies to Pgp. The IpS method employed C219. The least resistant cell line in which Pgp could be detected by IpS was fivefold resistant to doxorubicin, whereas Pgp was detected by WB in cells greater than twofold resistant. Cell lines having greater than fivefold resistance to Dox were positive by both IpS and WB analyses. The less resistant cell lines contained more nonreactive cells whereas the highly resistant cell lines showed more homogeneous strong membrane reactions. Among the six cell lines determined to be Pgp negative by WB analysis, no false positive immunostaining by IpS existed. One of 22 WB positive and 7 of 24 WB-negative sarcoma biopsy specimens were positive by IpS methods. Reaction varied and was always focal (a minimum of 3-5 cells, ranging up to 3-4 high power fields) indicating pronounced heterogeneous distribution of Pgp. Thus, WB can detect low average (overall) levels of Pgp in tumor samples but such low concentrations of PgP at the single cell are not detectable by IpS methods. However, IpS can discern among many Pgp-negative cells small subpopulations of immunoreactive cells, which are not detected by WB analysis due to Pgp dilution by the membrane protein of numerous Pgp negative cells. IpS and WB used together as complementary methods can provide more complete information about Pgp distribution and content, particularly in the case of heterogeneous human tumors. The IpS method is more suitable for less drastically treated (not embedded) cell line specimens than for paraffin-embedded (routine) sections. Some modification of the present IpS protocol seems necessary to increase its sensitivity and reduce the disparity with WB results.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Successful surgical correction of acute ascending aortic dissection: a case report.

The prognosis of patients with acute aortic dissection is extremely poor, especially when involving the ascending aorta. It has long been recognized as a catastrophic cardiovascular event. Acute dissections involving an ascending aorta have approximately a 90 percent acute mortality rate if left untreated or treated medically. Therefore, nearly all patients with acute ascending aortic dissection should be surgically treated immediately after a diagnosis has been established. A 60-year-old man having an acute ascending aortic dissection was successfully operated on with a resection of the dissecting aorta which was replaced with a Dacron graft. The postoperative course was complicated with a respiratory insufficiency and a disruption of the sternal wound. A 4 years follow-up confirmed the patient was in good condition. This is the first successfully operated case of acute ascending aortic dissection at our hospital.

Acute Disease↗
PubMed1991

Decreased norepinephrine release in anterior hypothalamus of NaCl-sensitive spontaneously hypertensive rats during high NaCl intake.

We previously demonstrated that dietary NaCl supplementation reduces endogenous norepinephrine stores and turnover in the anterior hypothalamic area (AHA) of male NaCl sensitive spontaneously hypertensive rats (SHR-S) but not in NaCl resistant control rats and have implicated this mechanism in the pathogenesis of NaCl sensitive hypertension. In the current study, we tested directly the hypothesis that dietary NaCl supplementation decreases the release of norepinephrine from nerve terminals in the AHA of SHR-S using the push-pull perfusion technique. Conscious, freely moving SHR-S and control Wistar-Kyoto (WKY) rats were studied after 2-3 weeks of 8% or 1% NaCl feeding. In the 1% NaCl fed SHR-S, 3-methoxy-4-hydroxyphenylglycol (MOPEG, the major metabolite of norepinephrine in brain) levels averaged 272 +/- 32 pg/10 min; norepinephrine levels, 17 +/- 2 pg/10 min; in the 8% NaCl fed SHR-S, MOPEG levels averaged 72 +/- 7 pg/10 min; norepinephrine levels were 6 +/- 1 pg/10 min. There was a positive linear correlation (r = 0.777; P less than 0.01) between MOPEG and norepinephrine levels in AHA perfusates, indicating that perfusate MOPEG levels provide a useful index of norepinephrine release from AHA nerve terminals. In contrast, MOPEG levels in AHA perfusates were not affected by dietary NaCl intake in control WKY, and in control posterior hypothalamic perfusates, were not affected by dietary NaCl intake in SHR-S.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗