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C Chen

Publications and source records attributed to C Chen.

At least 1,099 records · Page 61Linked to original sources
PubMed1991

Effects of endogenous dopamine on kinetics of [3H]N-methylspiperone and [3H]raclopride binding in the rat brain.

Competition by endogenous dopamine with the binding of D2 dopamine receptor ligands may be important in the interpretation of positron emission tomography (PET) neuroreceptor studies. PET studies with N-methylspiperone (NMSP) have revealed increased D2 dopamine receptors in schizophrenia, whereas studies with raclopride (RAC) have not detected such differences. This may be due, at least in part, to differences in competition with endogenous dopamine for ligand binding. To determine effects of endogenous dopamine on in vivo receptor binding, adult male rats were preinjected with amphetamine and reserpine prior to [3H]NMSP or [3H]RAC. Striatal to cerebellar ratios of ligand binding were determined. To approximate the conditions of a PET study, a kinetic model was employed to examine effects of pharmacologically increasing brain dopamine levels (amphetamine pretreatment) on PET ligand binding. In these experiments, tail veins and arteries were cannulated and kinetic parameters determined from normalized integral plots in rats treated with amphetamine prior to radioligand injection. Both [3H]NMSP (43.5%) and [3H]RAC (41.5%) binding were significantly decreased after amphetamine pretreatment, whereas after reserpine pretreatment [3H]RAC binding was increased (52.7%). Kinetic studies revealed a marked resistance of [3H]NMSP to competition with endogenous dopamine released by amphetamine. In contrast, kinetic parameters of [3H]RAC were markedly reduced at all time intervals. This suggests significant differences in competition with endogenous dopamine by [3H]NMSP and [3H]RAC, determined kinetically. These findings may have important implications for the interpretation of PET neuroreceptor studies.

Amphetamine↗
PubMed1991

Determination of infundibular innervation and amine receptor content in cyanotic and acyanotic myocardium: relation to clinical events in tetralogy of Fallot.

Right ventricular myocardium was assessed for cholinergic and adrenergic innervation, as well as alpha-adrenergic, beta-adrenergic, and muscarinic receptors, in 18 cyanotic patients with tetralogy of Fallot (TOF) and four acyanotic control patients with ventricular septal defect, each of whom underwent a cardiac repair from June through December 1987. Neurons containing acetylcholine (ACH), neuron-specific enolase (NSE), S-100 protein, neuropeptide-Y (NPY), dopamine-beta-hydroxylase (DBH), and calcitonin gene-related polypeptide (CGRP) were detected surrounding arterioles and myocytes in all specimens. NSE and S-100 immunoreactivities were also identified in the cytoplasm of TOF cardiocytes, possibly indicating a neuroendocrine origin of these cells. Cardiocyte size was increased in TOF (p = 0.05). Acetylcholine (cholinergic) (p = 0.04) and CGRP (cholinergic) positive neurons (p = 0.07) were decreased in the TOF as compared to controls. Adrenergic fiber content (p = 0.15) and beta receptors (p = 0.21) were similar in both groups. There was an increase in muscarinic receptors in the controls (p = 0.002), and a marked increase in alpha receptors in TOF (p = 0.019). There were no intragroup differences in the TOF patients according to degree of cyanosis. In conclusion, there were important differences in neuronal and amine receptor content between TOF and control patients. Increased alpha receptors in TOF could account for differences in clinical and hemodynamic events.

Acetylcholine↗
PubMed1991

Actuarial survival and other events following valve surgery in octogenarians: comparison with an age-, sex-, and race-matched population.

From January 1973 to December 1989, 54 patients over 80 years of age underwent an intracardiac repair which included a cardiac valve operation. There were 21 males and 33 females. Mean age at operation was 82 years, range 80-89 years. Fifty-two patients (96%) were in New York Heart Association functional class III or IV preoperatively. Six patients had undergone previous valve surgery (11%). There were eight hospital deaths (14.8%). Risk factors for hospital death included older age at repair (p = 0.008), increased total cardiopulmonary bypass time (p = 0.06), and, possibly, smaller aortic valve prosthesis (p = 0.10). All 46 hospital survivors were followed up at a mean of 28.8 months after hospital discharge. There were 11 late deaths (23.9%), occurring at a mean of 32.3 months postoperatively. Survival analysis indicated that increased age (p = 0.06) and increased pulmonary artery diastolic pressure preoperatively (p less than 0.07) were multivariate risk factors for overall mortality. Actuarial survival at 5 years was 44%, with no difference from survival in an age-, sex-, and race-matched population. We conclude that octogenarians in the modern era have good chance for survival following valvular surgery. As hazards for full anticoagulation were low in this series, if valve repair is not feasible, we presently recommend the use of mechanical valves in the elderly to reduce the requirement for late reoperation due to bioprosthesis degeneration.

Actuarial Analysis↗
PubMed1991

Molecular cloning and expression of the cDNA for alpha 3 subunit of human alpha 3 beta 1 (VLA-3), an integrin receptor for fibronectin, laminin, and collagen.

alpha 3 beta 1 (VLA-3), a member of the integrin family of cell adhesion receptors, may function as a receptor for fibronectin, laminin, and collagen. A partial cDNA clone (2.4 kb) for the human alpha 3 subunit was selected from an endothelial cell lambda gt11 cDNA library by specific antibody screening. Several overlapping cDNA clones were subsequently obtained, of a total length of 4.6 kb from various cDNA libraries. The reconstructed alpha 3 cDNA was expressed on the surface of chinese hamster ovary cells as detected by an alpha 3-specific mAb after transfection, suggesting that the cDNA is authentic. Within this sequence was an open reading frame, encoding for 1,051 amino acids, including a signal peptide of 32 residues, a long extracellular domain (959 residues), a transmembrane domain (28 residues), and a short cytoplasmic segment (32 residues). Overall, the alpha 3 amino acid sequence was 25-37% similar to the other integrin alpha subunits that are cleaved, with most similarity to the alpha 6 sequence (37%), and less similarity to those alpha subunits that have I domains (15-20%, excluding the I domain sequence itself). Features most like those in other alpha subunits are (a) the positions of 18/19 cysteine residues, (b) three potential metal binding domains of the general structure DX(D/N)X(D/N)GXXD, and (c) the predicted transmembrane domain. The mass of alpha 3 calculated from its amino acid sequence is 113,505. The human alpha 3 sequence was 89% identical to hamster galactoprotein b3, and 70% similar to the chicken CSAT antigen band 2 protein partial sequence, suggesting that these two polypeptides are homologues of human alpha 3.

Amino Acid Sequence↗
PubMed1991

Glucose Respiration in the Intact Chloroplast of Chlamydomonas reinhardtii.

Chloroplastic respiration was monitored by measuring (14)CO(2) from (14)C glucose in the darkened Chlamydomonas reinhardtii F-60 chloroplast. The patterns of (14)CO(2) evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide, glycolate-2-phosphate, and phosphoenolpyruvate were those expected from the oxidative pentose phosphate cycle and glycolysis. The K(m) for glucose was 56 micromolar and for MgATP was 200 micromolar. Release of (14)CO(2) was inhibited by phloretin and inorganic phosphate. Comparing the inhibition of CO(2) evolution generated by pH 7.5 with respect to pH 8.2 (optimum) in chloroplasts given C-1, C-2, and C-6 labeled glucose indicated that a suboptimum pH affects the recycling of the pentose phosphate intermediates to a greater extent than CO(2) evolution from C-1 of glucose. Respiratory inhibition by pH 7.5 in the darkened chloroplast was alleviated by NH(4)Cl and KCl (stromal alkalating agents), iodoacetamide (an inhibitor of glyceraldehyde 3-phosphate dehydrogenase), or phosphoenolpyruvate (an inhibitor of phosphofructokinase). It is concluded that the site which primarily mediates respiration in the darkened Chlamydomonas chloroplast is the fructose-1,6-bisphosphatase/phosphofructokinase junction. The respiratory pathways described here can account for the total oxidation of a hexose to CO(2) and for interactions between carbohydrate metabolism and the oxyhydrogen reaction in algal cells adapted to a hydrogen metabolism.

Journal Article↗
PubMed1991

Tissue distribution of mucosal antibody-producing cells specific for respiratory syncytial virus in severe combined immune deficiency (SCID) mice engrafted with human tonsils.

Groups of C.B-17 SCID mice were reconstituted intraperitoneally with human tonsillar mononuclear cells (hu-TMC) from children seropositive for antibody to respiratory syncytial virus (RSV) and subsequently challenged intraperitoneally with inactivated RSV or sham-immunized. The synthesis and the distribution characteristics of human antibody to RSV in various murine tissues were studied using an enzyme-linked immunospot assay (ELISPOT). No specific antibody was observed in sham-immunized animals. In contrast, mice engrafted with hu-TMC exhibited the appearance of specific human antibody secreting cells (hu-ASC) after i.p. immunization with inactivated RSV. RSV-specific hu-ASC were detected only in animals engrafted with cells from donors seropositive for antibodies to Epstein-Barr virus. Hu-TMC engrafted mice showed RSV-specific IgM and, in lower numbers, IgG hu-ASC in several tissues including the lungs. Numbers of RSV-specific IgA hu-ASC were low, however, and detected only in the lung. No RSV-specific hu-ASC were detected in the intestine. These data demonstrate for the first time that hu-TMC-SCID chimeras respond to immunization with viral antigen. Furthermore, the results suggest that hu-TMC engraft in lungs but not in the intestinal tissue.

Adolescent↗
PubMed1991

Virulent human strains of group G streptococci express a C5a peptidase enzyme similar to that produced by group A streptococci.

Specific proteolytic destruction of the human chemotaxin, C5a, is a property of group A and B streptococcal pathogens. Here we show that virulent group G streptococci from human sources also express C5a peptidase activity. The enzyme responsible for this activity is approximately the same size as and is antigenically similar to that produced by group A streptococci. On the basis of Southern hybridization analysis with an internal fragment of the group A C5a peptidase gene (scpA) as a probe, a copy of this gene was found in the genome of all group G human isolates tested. Comparison of partial restriction maps of scpA and scpG revealed significant similarity between the two genes. Group G strains isolated from dogs and cows were found to lack C5a peptidase activity and did not hybridize to the scpA-specific probe. The association of this activity with three streptococcal species suggests that elimination of phagocyte chemotactic attractants is a more universal virulence mechanism than originally anticipated.

Adhesins, Bacterial↗
PubMed1991

Noninvasive estimation of the instantaneous first derivative of left ventricular pressure using continuous-wave Doppler echocardiography.

BACKGROUND: The complete continuous-wave Doppler mitral regurgitant velocity curve should allow reconstruction of the ventriculoatrial (VA) pressure gradient from mitral valve closure to opening, including left ventricular (LV) isovolumic contraction, ejection, and isovolumic relaxation. Assuming that the left atrial pressure fluctuation is relatively minor in comparison with the corresponding LV pressure changes during systole, the first derivative of the Doppler-derived VA pressure gradient curve (Doppler dP/dt) might be used to estimate the LV dP/dt curve, previously measurable only at catheterization (catheter dP/dt). METHODS AND RESULTS: This hypothesis was examined in an in vivo mitral regurgitant model during 30 hemodynamic stages in eight dogs. Contractility and relaxation were altered by inotropic stimulation and hypothermia. The Doppler mitral regurgitant velocity spectrum was recorded along with simultaneously acquired micromanometer LV and left atrial pressures. The regurgitant velocity profiles were digitized and converted to VA pressure gradient curves using the simplified Bernoulli equation. The instantaneous dP/dt of the VA pressure gradient curve was then derived. The instantaneous Doppler-derived VA pressure gradients, instantaneous Doppler dP/dt, dP/dtmax, and -dP/dtmax were compared with corresponding catheter measurements. This method of estimating dP/dtmax from the instantaneous dP/dt curve was also compared with a previously proposed Doppler method of estimating dP/dtmax using the Doppler-derived mean rate of LV pressure rise over the time period between velocities of 1 and 3 m/sec on the ascending slope of the Doppler velocity spectrum. Both instantaneous Doppler-derived VA pressure gradients (r = 0.95, p less than 0.0001) and Doppler dP/dt (r = 0.92, p less than 0.0001) correlated well with corresponding measurements by catheter during systolic contraction and isovolumic relaxation (pooled data). The Doppler dP/dtmax (1,266 +/- 701 mm Hg/sec) also correlated well (r = 0.94) with the catheter dP/dtmax (1,200 +/- 573 mm Hg/sec). There was no difference between the two methods for measurement of dP/dtmax (p = NS). Although Doppler -dP/dtmax was slightly lower than the catheter measurement (961 +/- 511 versus 1,057 +/- 540 mm Hg/sec, p less than 0.01), the correlation between measurements by Doppler and catheter was excellent (r = 0.93, p less than 0.0001). The alternative method of mean isovolumic pressure rise (896 +/- 465 mm Hg/sec) underestimated the catheter dP/dtmax (1,200 +/- 573 mm Hg/sec) significantly (on average, 25%; p less than 0.001). CONCLUSIONS: The present study demonstrated an accurate and reliable noninvasive Doppler method for estimating instantaneous LV dP/dt, dP/dtmax, and -dP/dtmax.

Animals↗
PubMed1991

Endothelin induces a nonselective cation current in vascular smooth muscle cells.

The potent vasoconstrictor endothelin leads to smooth muscle cell depolarization and increases in intracellular Ca2+. Although effects of endothelin on calcium channels have been described, it also has been speculated that endothelim may activate additional ion channels. The purpose of the present study was to identify an alternative ion current that could play a role in depolarizing cells in response to vasoconstrictors like endothelin and vasopressin. The effects of endothelin, vasopressin, sarafotoxin S6b, and phenylephrine were assessed using whole-cell patch-clamp recordings from primary dissociated rat aortic or mesenteric arterial smooth muscle cells cultured for 24-72 hours. From the usual resting potentials of these cells of -50 to -60 mV, endothelin (1-100 nM) induced a depolarization via an increase in membrane conductance. This depolarization was phasic, oscillating repeatedly from the resting potential to a relatively depolarized level and back to the resting potential. From a holding potential of -60 mV, endothelin-1, endothelin-3, vasopressin, or sarafotoxin S6b (but not phenylephrine) induced transient inward currents that also could be phasic. In external sodium, lithium, or cesium (but not Tris) and in internal potassium or cesium, these currents reversed near 0 mV. Although nifedipine-insensitive, the inward currents were absent in zero calcium, barium, or strontium, or in the presence of cobalt or nickel. These results represent the first report of a nonselective cation current in primary vascular smooth muscle cells that is calcium dependent and that could be responsible for the depolarizations induced from the resting potential by vasoconstrictors such as endothelin.

Animals↗
PubMed1991

Models for analyzing data in initiation-promotion studies.

The objective of this paper is to construct a class of models for analyzing data in initiation-promotion (IP) studies. After the application of an initiator in animals IP studies, histochemical and/or histopathologic criteria are used to define the foci that are postulated to be the origin of tumors. Thus, the dynamics of foci growth are of inherent interest in the study of the mechanism of carcinogenesis. In this paper, models to explain these dynamics are developed and can be used to differentiate among proposed mechanisms of tumor formation and promotion. Examples are given to illustrate useful concepts for analyzing data from IP studies.

Animals↗
PubMed1991

Phrenic nerve injury. A prospective study.

In cardiac surgery, topical iced saline solution slush has become an important adjunct in maintaining myocardial hypothermia during cardioplegic arrest. One complication of this technique is phrenic nerve injury (PNI). In an attempt to reduce the incidence of PNI, a prospective study was undertaken to evaluate the impact of phrenic nerve insulation on PNI during cardiac surgery. Seventy-six consecutive patients who underwent coronary revascularization constituted the control group (CG) and were compared with 76 patients who underwent a similar procedure with the addition of phrenic nerve insulation. In the intervention group (IG), a foam insulation pad was placed between the heart and the pericardium in an effort to reduce exposure of the phrenic nerve to iced saline solution slush. There was no difference in major demographic descriptors or operative variables between the CG and the IG, except that the internal mammary artery was used more frequently in the IG (64 percent vs 36 percent, p = 0.0006). The in-hospital mortality was similar between the groups (CG, 0.0 percent; IG, 1.3 percent; p = 1.0); however, the incidence of roentgenographically diagnosed PNI was much greater in the CG (14/76 patients [18 percent] vs 0/76 patients [0 percent]; p = 0.0006). Patients with and without PNI were similar with regard to age, gender, aortic cross clamp time, cardiopulmonary bypass time, and number of grafts (p greater than 0.05). All unilateral PNI occurred on the left. Three patients with bilateral PNI required tracheostomy and prolonged mechanical ventilation. In-hospital mortality was similar for patients with and without PNI (0 percent vs 0.7 percent), but mean postoperative hospital stay for patients with clinically diagnosed PNI was longer than for those without PNI (32 vs 11 days, p = 0.04). This prospective study demonstrates that the incidence of PNI can be significantly reduced by the routine use of phrenic nerve insulation.

Adult↗
PubMed1991

Migration selectivity and its consequences on the occupational structure in the Taipei metropolis.

Migrants' destination choices and their consequences are discussed using data for Taipei, Taiwan, and its surrounding areas. "We limit our focus on migration selectivity in terms of occupational structure only.... We try to decompose the migration selectivity and its consequences by streams and moving motivation....[The author concludes that] overall the influence of migration selectivity on occupational structures is still dominated by the selectivity due to job and education needs." (SUMMARY IN CHI)

Asia↗
PubMed1991

[The diagnosis and treatment of Clostridium difficile enterocolitis].

Sixteen strains of Clostridium difficile (C.d) were isolated from 29 patients with antibiotic-associated diarrhoea (AAD). 9 of 14 C.d positive and 1 of 6 C.d negative fecal specimens were detected as cytotoxin positive. 10 AAC patients received colonoscopy and 6 had congestion, edema and erosion of mucosa. Three had yellow-white pseudomembrane on the surface of colon. In 17 Clostridium difficile enterocolitis (CDEC) was diagnosed by C.d isolation, cytotoxin detection and (or) colonoscopic finding. All the 17 patients received antibiotics before diarrhoea. The risk antibiotics were gentamycin, ampicillin and cephalosporin. Of 17 CDEC, 4 were cured when the complicated antibiotics were discontinued. 7 received vancomycin therapy. 6 cured but 1 had once symptomatic recurrence and C.d re-appearance. 4 were cured by metronidazole. 2 patients died of CDEC and respiratory failure prospectively before diagnosis. Eleven fecal specimens of CDEC were analysed for intestinal microflora. The results showed that E. coli and Bifidobacteria in CDEC patients were significantly lower.

Adult↗
PubMed1991

[Studies on the analysis of beta-blocking agents].

A method for the separation and identification of 13 beta-blockers using GC/MS and GC/NPD are described. The TFA and TMS derivatives were prepared by adding TFAA, MSTFA and MBTFA to the standard drugs. The mixture was heated at 65 degrees C for 20 min and chromatographed on FS capillary columns (HP-5). Preliminary results show that the derivatization with MSTFA is better than that with TFAA or MBTFA. There is not much difference between TFAA and MBTFA derivatization. The method is reliable, rapid and simple and may be used to screen these drugs and further applied to the analysis of biological fluids such as plasma and urine.

Adrenergic beta-Antagonists↗
PubMed1991

[Prolongation of hyperbaric bupivacaine spinal anesthesia with clonidine].

Recent reports showed that spinal clonidine might provide satisfactory analgesia via a nonopioid mechanism. In this study we tried to evaluate the prolongation of analgesic effect of the hyperbaric bupivacaine spinal anesthesia with clonidine. 40 ASA class I-II patients scheduled for TURP were randomly classified into two groups of 20 each. In saline group, 3 ml 0.5% hyperbaric bupivacaine plus 1 ml normal saline was given. In clonidine group, 1 ml (0.15 mg) clonidine in addition to 3 ml 0.5% bupivacaine was given. All the patients were placed in lateral position and dural puncture was made at the L3-4 interspace using a 25G spinal needle. Assessment of the sensory blockade by "pinprick" and motor blockade by Bromage scale and measurement of blood pressure and heart rate were performed after injection. All data were analyzed by Student's t-test. A p value less than 0.05 was considered statistically significant. Our results showed that the highest sensory blockade level and the time required for maximal spread of the sensory blockade were of no significant difference between groups. The mean time for two segments regression and mean time for regression to L2 were significantly greater in the clonidine group than in the saline group (p less than 0.001). Motor blockade was also prolonged in the clonidine group than the clonidine group. Side effects such as hypotension (10 in clonidine gp vs 4 in saline gp) and bradycardia (4 clonidine gp vs 2 in saline gp) commonly occurred in the clonidine group, but all patients could be effectively treated with ephedrine and atropine respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗