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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 649 records · Page 36Linked to original sources
PubMed1984

R-wave amplitude responses to rapid atrial pacing: a marker for myocardial ischemia.

Atrial pacing-induced changes in the sum of R-wave amplitude were measured in leads V5, X, Y, and Z at rates of 100 bpm (phase I), 150 bpm (phase II), and immediately after pacing (phase III) in 33 patients undergoing cardiac catheterization for evaluation of chest pain. Seventeen (51%) patients showed evidence of ischemia during atrial pacing (typical anginal pain and/or at least a 1 mm ST-segment depression) and 16 (49%) showed no evidence of ischemia. Mean R-wave amplitude changes from baseline in the ischemic patients were: phase I: -8% (p = not significant), phase II: +3% (p = not significant), and phase III: +13% (p less than 0.01); and in nonischemic patients: phase I: -11% (p less than 0.02), phase II: -18% (p less than 0.01), and phase III: +2% (p = not significant). These two distinct patterns of R-wave amplitude changes were highly sensitive (85%), specific (92%), and predictive (92%) for identifying patients with myocardial ischemia but did not correlate (p = not significant) with either the angiographically determined extent of coronary artery obstructive disease (CAD), resting left ventricular function, or the dynamic, atrial pacing-induced changes in left ventricular dimensions determined by M-mode and two-dimensional echocardiography. Thus, R-wave amplitude changes induced by atrial pacing can be used to identify patients with myocardial ischemia independent of coronary anatomy or resting left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

The cardiokymography exercise test compared to the thallium-201 perfusion exercise test in the diagnosis of coronary artery disease.

To determine the usefulness of exercise cardiokymography (CKG) compared to thallium-201 perfusion scanning in the diagnosis of coronary artery disease (CAD), 179 patients with a mean age of 54 +/- 10 years (73% men) were studied. Previously documented CAD was present in 73 patients (41%); 13 (7%) were asymptomatic and 93 (53%) had chest pain syndrome. Exercise stress testing, CKG, and thallium-201 perfusion scanning were independently correlated with coronary angiographic data. Treadmill exercise stress test alone without CKG had a sensitivity of 68% and specificity of 62%. CKG showed a sensitivity of 76% and a specificity of 90%, and easily interpreted cardiokymograms were obtained in 78% of patients studied. Thallium-201 scans had a sensitivity of 79% and a specificity of 88%. However, when the CKG and treadmill exercise test results were concordant (both positive or both negative), the CKG exercise test had a sensitivity of 87% and specificity of 100%. Thus, when the CKG and exercise test results are concordant, the sensitivity and specificity are equal to or better than thallium-201 perfusion scanning for the prediction of CAD. Since CKG is an inexpensive and noninvasive test, its adjunctive use with routine exercise stress testing may be of great value.

Adolescent↗
PubMed1984

Genetic selection for tolerance to niclosamide and copper in Biomphalara glabrata (Mollusca: Pulmonata).

Successive generations of the PR-79 and M-line laboratory stocks of Biomphalaria glabrata were exposed in the LC90 of niclosamide or copper sulfate. Survivors from each generation produced the succeeding generation by self fertilization. The PR-79 stock showed no evidence of tolerance to either molluscicide following five generations of selection. On the other hand, M-line F5 snails demonstrated approximately two-fold higher tolerance to both molluscicides than did non-selected M-line snails.

Animals↗
PubMed1983

Prosthetic mitral valve motion during cardiac dysrhythmias as determined by echocardiography.

To assess the changes and physiologic mechanisms of prosthetic valve motion during cardiac dysrhythmias as well as the role of atrial systole in the closure of the mitral valve, M-mode echocardiography was performed in 36 patients with normally functioning prosthetic mitral valves (Björk-Shiley, Starr-Edwards, and Beall valve). Premature closure of the prosthetic mitral valve in diastole with a "sharp" closing motion was seen during first-degree atrioventricular block, atrial fibrillation with ventricular rates less than 60 beats/min, and atrial flutter. A "rounded" premature valve closure due to atrial systole was seen during atrial tachycardia and complete heart block. Atrial systole initiates a closing motion of the prosthetic mitral valve at end-diastole, and ventricular systole completes this closure during normal sinus rhythm. When first-degree atrioventricular block is present, atrial systole alone completes this closure before ventricular contraction. Atrial contraction alone also can effectively close the prosthetic mitral valve during atrial flutter and atrial tachycardia. Other factors (such as left ventricular diastolic volume) may play a role in the effective closure of the prosthetic mitral valve during atrial fibrillation with slow ventricular rates and complete heart block. These findings must be considered in the echocardiographic evaluation of suspected malfunctioning prosthetic mitral valves. A baseline postoperative echocardiogram after prosthesis insertion is important for future evaluation when clinically indicated.

Aged↗
PubMed1983

Topically applied oxymetazoline. Ocular vasoconstrictive activity, pharmacokinetics, and metabolism.

Two double-blind, random-assignment clinical trials demonstrated the effectiveness of topical oxymetazoline hydrochloride in reducing histamine-induced hyperemia. Oxymetazoline hydrochloride at an optimum strength of 0.025% produced a marked and prolonged reduction of hyperemia, with the onset of effect occurring within one to five minutes of instillation. Safety indicators, including BP, heart rate, intraocular pressure, pupil size, and visual acuity, did not change significantly from baseline values. Oxymetazoline was absorbed slowly into the eye: only 0.006% of the original drug concentration was found in the aqueous humors of rabbits 30 minutes after instillation; the balance remained primarily in external ocular tissues. Metabolic studies in rabbits indicated that excreted amounts of unmetabolized radioactive oxymetazoline in urine following drug administration were similar (23%) for the ocular and nasal routes of application. The proportions of oxymetazoline metabolite to unchanged oxymetazoline were constant for all administration routes tested.

Administration, Topical↗
PubMed1983

Variable diastolic rumbling murmur caused by floating left atrial thrombus.

A 53 year old man with a history of rheumatic mitral stenosis was admitted to hospital because of recurrent fainting spells. Auscultation showed a variable diastolic rumbling murmur. Simultaneous echo- and phonocardiograms demonstrated a floating left atrial thrombus; when this passed into the left ventricular inflow tract and obstructed the mitral valve orifice the diastolic murmur disappeared.

Diastole↗
PubMed1983

Diastolic "locking" of the mitral valve: the importance of atrial systole and intraventricular volume.

Diastolic mitral valve "locking," defined as sustained diastolic closure of the mitral valve after atrial systole, was investigated by simultaneous hemodynamic and echocardiographic recordings during a protocol of programmed pacing in six dogs with surgically induced atrioventricular block. Atrial extrasystoles were introduced at progressively increasing coupling intervals during programmed prolonged pauses in ventricular pacing. As the coupling interval of the atrial extrasystole was increased, both the mitral reopening time (MRT) and the calculated left ventricular volume (LVV) at the end of the MRT increased proportionally. These interrelations could be best expressed by a general logarithmic function of the form y = a + b ln (x), where x = the coupling interval of the atrial extrasystole and y = the MRT or the LVV. Correlations between the measured data and the predicted data were excellent (r greater than or equal to 0.95). In each dog, a specific LVV had to be attained to allow a diastolic "locking" of the mitral valve. Atrial standstill and atrial fibrillation were also induced in each dog to study the relative role of atrial systole in locking of the mitral valve. During either atrial standstill or atrial fibrillation, the mitral valve closed transiently, but did not lock, despite the accumulation of a LVV larger than the LVV necessary to lock the valve during sinus rhythm. Thus, diastolic locking of the mitral valve has several determinants, including the presence of active atrial systole and the accumulation of a sufficient intraventricular volume.

Animals↗
PubMed1983

Acute exacerbation of paranoid psychotic state after long-term abstinence in patients with previous methamphetamine psychosis.

From a population of 111 patients with chronic methamphetamine (MAP) psychosis, who were treated at ten mental hospitals during the past 3 years, 21 patients were selected for study. Sixteen patients who experienced MAP psychosis again used MAP one or more times after long-term abstinence and experienced acute exacerbation of a paranoid psychotic state which was almost identical to the initial psychotic episode. Four of these patients relapsed following a single MAP reuse of an amount less than that initially used, and one relapsed without evidence of MAP reuse. In eight patients, small doses of neuroleptics, e.g., 3 mg per day of haloperidol, prevented the acute provocation of a psychotic state by MPA reuse. Subsequently, three of these relapsed into a psychotic state following MAP reuse without concurrent haloperidol medication. The clinical data were compared with animal experiments which indicate that chronic MAP use can induce a long-term susceptibility to sensitization to MAP. The positive prophylactic effect of small doses of haloperidol on the acute exacerbation may suggest the participation of dopaminergic supersensitivity as a mechanism for the paranoid psychotic state.

Adult↗
PubMed1983

Time-lapse microcinematographic and phase contrast studies on the cell reformation of Chirocephalus yolk granules in vitro.

In this article we report on a time-lapse microcinematographic and phase contrast study of the cell reformation of yolk granules which were isolated from mature oocytes in the genital sac of the middle female intersex of Chirocephalus nankinensis. The observations on yolk granules were made in fixed positions and the morphological changes of cell reformation were continuously recorded in vitro. The transformation of yolk granules into cellular structures may be tentatively described as follows: At the early stages in culture, it can be seen that the granular or bubbly structures gradually appear within the hyaloid and homogeneous yolk granules; the appearance of yolk granules gradually changes from elliptical into round shape. With further transformation, their appearances in general take the shape of oblate spheroids, their size is smaller than before and inside the yolk granules their granular and bubbly structures become more and more obvious. Finally, the nuclear and cellular structures can be seen in these transforming yolks. By means of time-lapse microcinematographic and phase contrast examinations in fixed positions, single yolk granules obtained from the mature oocyte with little amounts of adhering cytoplasm are continuously recorded and have been shown to occur, steadily and gradually build up cellular structures by self-organization and self-assembly. Up to the present, we have cultured these kinds of cellular organizations repeatedly. Therefore, it can be concluded that the existence of cell reformation on the basis of yolk granules according to the dynamic morphological changes is an objective reality.

Animals↗
PubMed1982

Disposition of topical flurbiprofen in normal and aphakic rabbit eyes.

In a study of the ocular absorption and elimination of a topically applied non-steroidal anti-inflammatory drug (NSAID), flurbiprofen, the compound was well absorbed into rabbit ocular tissues and was highly concentrated in the rabbit cornea. In aphakic eyes, more drug penetrated to the vitreous and choroid-retina area than in normal rabbit eyes, although corneal concentrations were still high. No ocular metabolism of flurbiprofen could be detected, and the ocular route of application did not lead to any changes in blood elimination rates or metabolism when compared with intravenously injected drug. Currently, no NSAID is available for topical ocular use, and the development of such a drug is desirable for treatment of ocular inflammations, especially when long-term treatment is indicated.

Absorption↗