Search PubMed⌕ Search

Biomedical subjects

Y F Chen

Publications and source records attributed to Y F Chen.

At least 289 records · Page 16Linked to original sources
PubMed1985

Comparison of the effectiveness of myocardial preservation in right atrium and left ventricle.

Ten patients underwent cardiac operations during which myocardial preservation was provided by systemic hypothermia, topical cardiac cooling, and cold blood cardioplegia. The duration of ischemia ranged from 45 to 142 minutes (mean, 84.2 +/- 36.2 minutes). Two serial specimens (preischemic and ischemic) were obtained from the right atrium and the left ventricle, respectively; thus, a total of 40 biopsy specimens was obtained from these 10 patients. A combination of grading of ischemic injury and stereological morphometric measurement of mitochondria was performed to assess the effectiveness of myocardial preservation. Our findings from the mitochondrial score studies (grading of ischemic injury) were as follows. In the right atrium, the average mitochondrial score rose from 0.337 +/- 0.235 in the preischemic stage to 1.969 +/- 0.492 in the ischemic stage. In contrast, the average mitochondrial score for the left ventricle was only elevated from 0.380 +/- 0.161 to 1.353 +/- 0.396. The difference between preischemia of the right atrium and left ventricle is not statistically significant, but the difference between ischemia of these chambers is significant (p less than 0.01). Our stereological morphometric studies revealed that in the left ventricle, the average mitochondrial surface area was 0.316 +/- 0.046 micron 2 in the preischemic stage and 0.347 +/- 0.073 micron 2 in the ischemic stage, a 9.8% increase in mitochondrial size (not significant). In contrast, the mitochondrial surface area of the right atrium showed a mean increase of 65.8%, from 0.231 +/- 0.038 micron 2 in the preischemic stage to 0.383 +/- 0.057 micron 2 in the ischemic stage (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Comparison of blood cardioplegia to electrolyte cardioplegia on the effectiveness of preservation of right atrial myocardium: mitochondrial morphometric study.

The right atrium differs from the left ventricle in two respects during cardioplegic arrest: a higher proportion of noncoronary collateral flow is delivered to the right atrium, and the atrium is frequently excluded from topical ice cooling because of its higher position relative to the left ventricle. These factors result in early rewarming of atrial myocardium. To the best of our knowledge, the surgical literature contains no reports on whether blood cardioplegia can provide better atrial myocardial preservation than electrolyte cardioplegia. Twenty consecutive patients who underwent cardiac operations were randomly selected to receive blood cardioplegia (Group 1) or electrolyte cardioplegia (Group 2). Hypothermia was achieved by systemic cooling and continuous topical cooling with ice slush. Stereological morphometric study of mitochondria was performed on 40 biopsy specimens taken from the right atrium prior to aortic cross-clamping (preischemia) and at the end of ischemia. In Group 1, total aortic cross-clamp time was 72.8 +/- 32.5 minutes. The mean mitochondrial surface area before ischemia was 0.224 +/- 0.032 mu 2 and after ischemia, 0.336 +/- 0.032 mu 2, a 50.0% increase in mitochondrial size. In Group 2, total aortic cross-clamp time was 69.7 +/- 30.9 minutes. The mean mitochondrial surface area before ischemia was 0.205 +/- 0.025 mu 2 and after ischemia, 0.439 +/- 0.111 mu 2, an average increase in mitochondrial size of 114.2%. There was no significant difference between the two groups in mitochondrial size before ischemia. However, after ischemia the mean mitochondrial surface areas were significantly different (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Duodenal acidification releases cholecystokinin.

We studied the effect of hydrochloric acid (HCl) in the proximal small intestine on release of cholecystokinin (CCK) and secretin and on exocrine pancreatic secretion in conscious dogs with gastric cannulas and modified Herrera pancreatic cannulas. Intraduodenal administration of HCl in a concentration of 50 or 100 mM at rates of 0.05, 0.1, 0.2, and 0.4 mmol/min significantly increased plasma concentration of CCK in a dose-dependent manner, whereas plasma gastrin levels decreased. The increased plasma CCK level paralleled a significant increase in pancreatic trypsin output. Plasma secretin concentration and pancreatic bicarbonate output also increased in response to the acid, and the increase was dependent on the acid loads delivered in the duodenum. Thus, in dogs, HCl in the duodenum releases both CCK and secretin to stimulate pancreatic secretion of bicarbonate as well as enzymes.

Animals↗
PubMed1985

Enhanced depressor effect of bromocriptine in the DOCA/NaCl hypertensive rat.

To elucidate the role of the dopaminergic system in the maintenance of hypertension in the deoxycorticosterone acetate (DOCA)/NaCl hypertensive rat, the responses of mean arterial pressure (MAP), plasma norepinephrine (NE), epinephrine (E), and prolactin (PRL) to intravenous (iv) administration of bromocriptine, a dopamine agonist, and hexamethonium bromide, a ganglion blocker, were examined in conscious, unrestrained 4-wk DOCA/NaCl hypertensive rats. Bromocriptine was administered to adrenomedullectomized (ADMX) rats to assess the role of the adrenal medulla in its depressor effect. Bromocriptine (50, 250, and 500 micrograms/kg) and hexamethonium (3 and 30 mg/kg) caused dose-dependent decreases in MAP that were greater in DOCA/NaCl rats than in uninephrectomized controls. Basal plasma NE, E, and PRL were significantly higher in DOCA/NaCl rats than in controls. Bromocriptine (500 micrograms/kg iv) decreased plasma PRL to undetectable levels and increased plasma E significantly without changing NE levels in DOCA/NaCl and uninephrectomized control rats. In ADMX rats bromocriptine (500 micrograms/kg iv) decreased MAP, PRL, and NE without affecting E levels. These results suggest that the depressor response to bromocriptine could be related to inhibition of sympathetic outflow without participation of the adrenal medulla. The hyperprolactinemia and enhanced depressor response to bromocriptine observed in DOCA/NaCl animals suggest that the dopaminergic system might be altered in this model of hypertension.

Adrenal Medulla↗
PubMed1985

Hyperresponsiveness of monoaminergic mechanisms in DOCA/NaCl hypertensive rats.

To examine the role of the sympathetic nervous system in the development of deoxycorticosterone acetate (DOCA)/NaCl hypertension and to test the hypothesis that the responsiveness of the sympathetic nervous system to stress is enhanced during the developmental phase of hypertension in this model before resting sympathetic activity becomes increased, DOCA/NaCl-treated rats and uninephrectomized control animals were studied after 3, 7, 14, and 28 days of treatment. Basal plasma norepinephrine and epinephrine in conscious, unrestrained resting DOCA/NaCl-treated rats were the same as in controls at 3, 7, and 14 days but were significantly elevated at 28 days of treatment. Ganglionic blockade resulted in a significantly greater decrease in mean arterial pressure in DOCA/NaCl rats than in controls at 14 and 28 days of treatment. At 14 days, DOCA/NaCl rats exhibited significantly greater increments in plasma norepinephrine and epinephrine following cold stress than did H2O controls. Basal plasma prolactin levels were elevated and release of dopamine from isolated superfused mediobasal hypothalami reduced in 28-day DOCA/NaCl hypertensive rats. These results indicate that sympathetic nervous system activity increases progressively during the development of DOCA/NaCl hypertension and that the sympathoadrenal system is hyperresponsive to environmental stress even early in the course of DOCA/NaCl treatment and suggest that hypothalamo-hypophyseal function is altered in this model of hypertension.

Animals↗
PubMed1984

Potentiating effect of secretin on cholecystokinin-stimulated pancreatic secretion in dogs.

A possible potentiating effect of cholecystokinin octapeptide (CCK-OP) on the action of secretin on exocrine pancreatic secretion was studied in five dogs with gastric fistulas and modified Herrera pancreatic fistulas. Secretin in a dose, 2.45 pmol (0.03 clinical units) X kg-1 X h-1, that mimics the plasma secretin level in the postprandial state increased pancreatic bicarbonate secretion, but the increase was not statistically significant. CCK-OP in graded doses, 26.2, 52.5, 109, and 219 pmol (0.03, 0.06, 0.125, and 0.25 microgram) X kg-1 X h-1, given intravenously produced a significant increase in both bicarbonate and protein secretion, and the increase was dose related. The plasma concentrations of immunoreactive CCK during intravenous infusion of CCK-OP in doses of 26.2 and 52.5 pmol X kg-1 X h-1 were found to mimic the postprandial plasma concentrations of immunoreactive CCK in eight dogs. When CCK-OP in four graded doses was added to intravenous infusion of secretin, 2.45 pmol X kg-1 X h-1, the actual bicarbonate output at each dose level of CCK-OP was greater than the sum of the bicarbonate outputs produced by secretin alone and CCK-OP alone in a corresponding dose. Thus, we conclude that the action of secretin in a physiological dose that mimics the plasma level of secretin after a meal is potentiated by CCK-OP in a dose range that produces a plasma CCK-OP level comparable with that in the postprandial state and vice versa. The study indicates that, like secretin, CCK-OP is another necessary agent for pancreatic secretion of bicarbonate during digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Non-gastrin secretogogue in ulcerogenic tumors of the pancreas.

In 18 patients with hypersecretion of acid, severe ulcer diathesis, and pancreatic islet cell tumor or hyperplasia, 14 had hypergastrinemia and 4 had normal plasma gastrin concentration. The neoplasms contained several gut peptides beside gastrin. The immunoreactive gastrin in the tumor extracts measured less than 7 ng/g, less than the amount previously reported. The extracts of each patient's tumor also contained a secretogogue other than gastrin that stimulated gastric acid secretion in rats. In addition, the plasma extracts of 2 patients also contained a secretogogue that stimulated acid secretion. After surgical resection of a recurrent metastatic tumor in 1 patient, basal acid secretion decreased from 13.9 to less than 1 meq/h, and the bioactivity of the plasma disappeared. These observations suggest the existence of a secretogogue that appears to be a protein in the pancreatic tumors of some patients with severe ulcer diathesis and hypersecretion.

Adenoma↗
PubMed1984

Characterization of gamma-glutamyltranspeptidase in murine cervical cancer by biochemical and immunological techniques.

Immunodiffusion, immunofluorescence, and flow cytometric techniques were used to characterize the expression of murine gamma-glutamyltranspeptidase (gamma GT) on normal and cervical cancer tissue. In immunodiffusion tests, the rabbit antiserum produced against highly purified murine kidney gamma GT formed two lines against normal kidney and one line with pancreas which fused with the major line of kidney. gamma GT purified by similar techniques from a murine cervical tumor produced a single line of identity with the kidney preparation, indicating that the gamma GT of the tumor was immunologically identical with normal enzyme. Both kidney and tumor gamma GT were labile to heating at 56 degrees, and neither enzyme was protected by dithiothreitol. Polyacrylamide gel electrophoresis indicated three components from the tumor material and four from the normal kidney. Both tissue sites expressed several isozymes which appeared to be antigenically identical. Biochemical methods indicated there was at least 50-fold more gamma GT in kidney than in tumor cells. In contrast, the level of membrane-associated gamma GT determined by flow cytometry was similar in the two cell types. Two-parameter flow cytometric analysis with DNA and antibody defined the presence of two proliferating gamma GT-positive tumor cell populations in the cervical tumor. Thus, although tumor and normal gamma GT are antigenically identical, the antisera can be combined with DNA and other markers to better describe tumor heterogeneity and progression.

Animals↗
PubMed1984

Mechanism of the depressor effect of bromocriptine in the spontaneously hypertensive rat.

Bromocriptine, a dopamine (DA) agonist which passes the bloodbrain barrier, has been shown to have a depressor effect in the spontaneously hypertensive rat of the Okamoto strain. To elucidate the mechanism of this depressor effect, the responses of mean arterial blood pressure and plasma epinephrine (EP), norepinephrine, prolactin and renin activity to i.v. administration of bromocriptine (500 micrograms/kg), alone and after pretreatment with i.v. metoclopramide, a DA antagonist which crosses the blood-brain barrier, and domperidone, a DA antagonist which does not cross the blood-brain barrier, were examined in conscious unrestrained spontaneously hypertensive rats. Metoclopramide attenuated the depressor action of bromocriptine in a dose-related manner, but domperidone had no effect. Neither metoclopramide nor domperidone given alone altered mean arterial blood pressure. Bromocriptine given alone decreased plasma prolactin and increased plasma EP without altering plasma norepinephrine or plasma renin activity. Pretreatment with either metoclopramide or domperidone completely blocked the EP-stimulating effects of bromocriptine. Neither DA antagonist given alone had an effect on plasma EP, norepinephrine or plasma renin activity; both agents stimulated prolactin release. These results suggest that the depressor action of i.v. administered bromocriptine is mediated mainly through a central dopaminergic mechanism rather than by peripheral effects and that plasma EP responses to bromocriptine do not directly contribute to its depressor action.

Animals↗