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Biomedical subjects

C Liang

Publications and source records attributed to C Liang.

156 records · Page 9Linked to original sources
PubMed1981

The temperamental characteristics of Chinese babies.

This paper investigates the usefulness of Carey's Revised Infant Temperament Questionnaire in the Chinese culture and uses the questionnaire to assess the temperamental characteristics of Chinese babies. The revised questionnaire was administered to the mothers of 349 4--8-year-old infants in Taipei, Taiwan. The face validity of the questionnaire was supported within the different context: the distribution of scores was normal, and the mothers had no trouble in answering the questions. While the general pattern of results was similar to those found in Carey's American sample, differences were found, which may be interpreted in terms of response biases, racial differences, or a combination of these 2 factors. The data are analyzed for possible effects of sex and socioeconomic status, and these findings are in turn compared to results of American studies. Observational studies are seen as necessary in the future to understand the nature of cultural differences in temperament. Follow-up studies will examine the different ways a given temperamental characteristic may be responded to by different cultural environments.

Cross-Cultural Comparison↗
PubMed1980

Acute renovascular hypertension in conscious dogs. Interaction of the renin-angiotensin system and sympathetic nervous system in systemic hemodynamics and regional blood flow responses.

The effects of acute renovascular hypertension on the sympathetic nervous system, regional blood flow and cardiac function were studied in conscious dogs submitted to renal artery occlusion by inflation of a cuff implanted previously around one renal artery. We then compared the alterations in plasma renin and catecholamine levels and in the various hemodynamic parameters induced by those maneuvers in intact dogs, to those in dogs pretreated with alpha- and beta-adrenergic receptor blockers. Subsequently, the converting enzyme inhibitor teprotide was administered to inhibit angiotensin formation in both experiments. Our results suggest that both the renin-angiotensin system and the sympathetic system contribute to the rise in blood pressure. The hemodynamic changes and alterations in regional blood flows accompanying this acute hypertension appear to be due mostly to the increase in plasma angiotensin, since prior adrenoceptor blockade only attenuated their magnitude but did not alter their direction. However, angiotensin-induced coronary vasoconstriction was observed only in adrenergically blocked but not intact animals, probably because of the protective effect of baroreceptor-mediated reflex sympathetic coronary vasodilation.

Acute Disease↗
PubMed1979

Conditioning effects of chronic infusions of dobutamine. Comparison with exercise training.

We studied the conditioning effects of chronic infusion of dobutamine and exercise training in three groups of chronically instrumented dogs. One group was infused with normal saline, a second group was infused with dobutamine (40 mug/kg per min), and the third group was exercised on a treadmill at 4 mph, up a 10 degrees incline. Each group was either infused or exercised for 2 h a day, 5 d a week for 5 consecutive wk. Resting heart rate and arterial blood lactate concentration, measured at weekly intervals, decreased progressively in the dobutamine and exercise groups, but not in the group that received normal saline infusion. Cardiovascular responses to submaximal treadmill exercise were not changed by 5 wk of normal saline infusion. However, the increases in heart rate, cardiac output, mean aortic blood pressure, arterial blood lactate, plasma renin activity, and norepinephrine concentration during exercise were significantly smaller after 5 wk of conditioning with either dobutamine or exercise training. After conditioning, the increases in arteriovenous oxygen difference during exercise were larger in the latter two groups, but the increases in total body oxygen consumption did not differ before and after conditioning. To assess ventricular function, we intravenously infused methoxamine both before and after conditioning. The slope of the line that related systolic aortic blood pressure and mean left atrial pressure increased in the animals conditioned with either dobutamine or exercise, indicating enhanced myocardial contractility. Left ventricular blood flow was lower in these two groups of animals than it was in the normal saline group. Left ventricular weight did not differ among the three groups. Our results show that chronic infusion of dobutamine produced cardiovascular and metabolic conditioning effects like those produced by exercise training, and further suggest that sympathetic stimulation during exercise plays a role in physical conditioning.

Animals↗
PubMed1977

Regulation of cardiac output during 2,4-dinitrophenol-induced tissue hypermetabolism in the dog.

1. Cardiac output increased in proportion to oxygen consumption in intact chloralose-anaesthetized dogs after four successive intravenous infusions of 2,4-dinitrophenol (11 mumol/kg; 2 mg/kg). 2. Splenectomy abolished the increase in cardiac output after the first three doses of 2,4-dinitrophenol. beta-Adrenoreceptor blockade by practolol, on the other hand, did not prevent the cardiac output rise after the first 2,4-dinitrophenol infusion, but further increases by 2,4-dinitrophenol infusion were abolished. When splenectomy and beta-adrenoreceptor blockade were combined, cardiac output did not increase significantly after all four doses of 2,4-dinitrophenol. 3. Cardiac output and mean systemic arterial blood pressure increased when the splenic venous blood collected after 2,4-dinitrophenol infusion was infused intraportally. 4. In a vascularly isolated, but normally innervated, lower half-body cross-perfusion preparation, cardiac output and mean systemic arterial blood pressure increased in the upper half-body when tissue hypermetabolism was produced in the cross-perfused area by 2,4-dinitrophenol. Neith pulmonary artery wedge pressure nor heart rate changed significantly. 5. This circulatory stimulation, after regional 2,4-dinitrophenol infusion, was abolished or was prevented from occurring by splenectomy. 6. It appears that the normal cardiac output response to tissue hypermetabolism requires both an intact spleen and normally functioning beta-adrenoreceptors.

Animals↗
PubMed1975

Effects of arterial hypoxemia and splenic nerve stimulation on myocardial adenosine 3',5'-Monophosphate in dogs.

Epinephrine infusion, 5-percent oxygen breathing, and splenic nerve stimulation were employed to increase cardiac output by 50-100% in anesthetized dogs. Epinephrine infusion as expected, increased plasma and myocardial cyclic AMP concentrations. Arterial hypoxemia increased cyclic AMP concentration in plasma but not in the heart. Practolol pretreatment abolished the increase in plasma cyclic AMP concentration and reduced the rise in cardiac output during hypoxemia. Splenic nerve stimulation was not associated with increases in either plasma or myocardial cyclic AMP. Adenylate cyclase activity was increased by addition of plasma into the incubation medium. However, splenic venous plasma obtained during splenic nerve stimulation did not increase adenylate cyclase activity more than control plasma obtained before stimulation. We conclude that the positive inotropic action of arterial hypoxemia and splenic nerve stimulation does not depend on the adenylate cyclase-cyclic AMP system.

Adenylyl Cyclases↗
PubMed1973

Mechanisms regulating the cardiac output response to cyanide infusion, a model of hypoxia.

When tissue metabolic changes like those of hypoxia were induced by intra-aortic infusion of cyanide in dogs, cardiac output began to increase after 3 to 5 min, reached a peak (220% of the control value) at 15 min, and returned to control in 40 min. This pattern of cardiac output rise was not altered by vagotomy with or without atropine pretreatment. However, this cardiac output response could be differentiated into three phases by pretreating the animals with agents that block specific activities of the sympatho-adrenal system. First, ganglionic blockade produced by mecamylamine or sympathetic nerve blockade by bretylium abolished the middle phase of the cardiac output seen in the untreated animal, but early and late phases still could be discerned. Second, beta-adrenergic receptor blockade produced by propranolol shortened the total duration of the cardiac output rise by abolishing the late phase. Third, when given together, propranolol and mecamylamine (or bretylium) prevented most of the cardiac output rise that follows the early phase. When cyanide was given to splenectomized dogs, the duration of the cardiac output response was not shortened, but the response became biphasic, resembling that seen after chemical sympathectomy. A similar biphasic response of the cardiac output also resulted from splenic denervation; sham operation or nephrectomy had no effect on the monophasic pattern of the normal response. Splenic venous blood obtained from cyanide-treated dogs, when infused intraportally, caused an increase in cardiac output in recipient dogs; similar infusion of arterial blood had no effects. THESE RESULTS SUGGEST THAT THE CARDIAC OUTPUT RESPONSE TO CYANIDE INFUSION CONSISTS OF THREE COMPONENTS: an early phase, related neither to the autonomic nervous system nor to circulating catecholamines; a middle phase, caused by a nonadrenergic humoral substance released from the spleen by sympathetic stimulation; and a late phase, dependent upon adrenergic receptors but not upon sympathetic transmission.

Animals↗
PubMed1973

Effects of splenectomy and beta-adrenoceptor blockade on cardiac output response to acute hypoxemia.

Acute hypoxemia produced by the inhalation of 8% and 5% oxygen increased cardiac output in intact anesthetized dogs by 38% and 62%, respectively. Although practolol, a cardioselective beta-adrenergic blocking agent, reduced the increase in cardiac output in dogs subjected to severe hypoxemia (5% O(2) breathing) from 62% to 43%, it only slightly reduced the cardiac output rise in dogs subjected to moderate hypoxemia (8% O(2) breathing). Splenectomy, on the other hand, abolished the increase in cardiac output produced by moderate hypoxemia except for a small initial rise, but it reduced the increase in cardiac output during severe hypoxemia only to 37%. The entire increase, except for a small initial rise, disappeared only when splenectomized dogs were pretreated with practolol. Sham operation did not affect the cardiac output response to hypoxemia. It is concluded that an intact spleen is required for a significant portion of the increased cardiac output that occurs during both moderate and severe hypoxemia and that catecholamines do not participate in the regulation of cardiac output unless severe hypoxemia occurs.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Prophylaxis of experimental Pseudomonas aeruginosa endophthalmitis after vitrectomy using ceftazidime in the irrigating solution.

PURPOSE: To test the efficacy of ceftazidime in irrigating solution during vitrectomy to prevent experimental Pseudomonas aeruginosa endophthalmitis. METHODS: Thirty-two rabbit eyes were divided into 6 groups. Vitrectomy using one of two different irrigating solutions was followed by intravitreal injection of P. aeruginosa: Group 1, balanced salt solution (BSS) followed by 100 colony-forming units (CFU) P. aeruginosa; Group 2, BSS fortified with ceftazidime 175 microg/mL (CBSS) followed by intravitreal injection of 100 CFU P. aeruginosa; Group 3, BSS followed by 500 CFU P. aeruginosa; Group 4, CBSS followed by 500 CFU P. aeruginosa; Group 5, BSS followed by 5000 CFU P. aeruginosa; and Group 6, CBSS followed by 5000 CFU P. aeruginosa. The eyes were examined clinically. Vitreous samples were cultured and histology was performed. RESULTS: Group 1: Three of 5 eyes showed mild to moderate vitreous opacities. Group 2: No vitreous opacities developed. Group 3: All eyes demonstrated endophthalmitis. Group 4: All 6 eyes had clear vitreous with visible fundus. Group 5: Severe endophthalmitis occurred in all 6 eyes. Group 6: Four eyes had clearly visible fundus, 2 eyes had hazy vitreous with red reflex of the fundus. Bacterial growth in groups 3, 4, 5, and 6 was seen in 4/4, 1/6, 6/6, and 0/6 eyes, respectively. CONCLUSION: When 100-5000 CFU P. aeruginosa were injected after vitrectomy, ceftazidime in the irrigating solution inhibited the signs of intraocular inflammation, and the rate of positive bacterial culture.

Administration, Topical↗
PubMedDate not supplied

Use of perfluorocarbon liquids, silicone oil, and 5-fluorouracil in the management of experimental PVR.

PURPOSE: To evaluate the toxicity and efficacy of 5-fluorouracil (5-FU) in combination with perfluoroperhydrophenanthrene (Vitreon), silicone oil, or a combination of silicone oil and Vitreon in a ratio of 3:2 in the management of experimental proliferative vitreoretinopathy (PVR). METHODS: Toxicity study. Seventy rabbit eyes underwent vitrectomy followed by intravitreal injection of 5-FU in doses of 800, 400, or 200 microg: Group 1, 5-FU alone; Group 2, 5-FU plus 1 mL Vitreon; Group 3, 5-FU plus 1 mL silicone oil; Group 4, 5-FU plus 0.6 mL silicone oil and 0.4 mL Vitreon; Group 5, 0.6 mL silicone oil plus 0.4 mL Vitreon. Electroretinography was performed preoperatively and 8 weeks postoperatively before the animals were sacrificed. Efficacy study. Seventy-two rabbit eyes underwent vitrectomy and were injected intravitreally with 100,000-200,000 retinal pigment epithelial cells to induce PVR. Groups were injected with 200 microg 5-FU alone or with 1 mL silicone oil, 1 mL Vitreon, or a combination of 0.6 mL silicone oil and 0.4 mL Vitreon. Others were given only 1 mL Vitreon or 1 mL silicone oil. The animals were followed for 8-12 weeks; PVR was graded using Fastenberg's system. RESULTS: Toxicity study. Eyes given 200 microg 5-FU, silicone, and Vitreon showed mild inflammation and vitritis which resolved in 1 week; the dose was nontoxic by electroretinography and histopathology. Doses of 400 and 800 microg 5-FU were toxic. Efficacy study. Clinical severity of PVR was less in the groups which received 5-FU plus vitreous substitutes when compared to the control groups at all time points. The lowest incidences were in groups given 5-FU plus Vitreon or 5-FU plus Vitreon and silicone oil: 33.33% and 11.11%, respectively. CONCLUSIONS: A dose of 200 microg 5-FU with silicone oil and Vitreon combined was nontoxic to the rabbit retina. The combination of 5-FU, Vitreon, and silicone oil showed significant efficacy in the prevention of experimental PVR.

Animals↗
PubMedDate not supplied

Prevention of organophosphate-induced toxicity in mice.

bis-Quaternary amines, which are acetal analogues of hemicholinium-3, were synthesized and several compounds were potent chemicals to antagonize toxicity induced by the organophosphate, paraoxon. Structural requirements were specific and included two oxygen atoms (bis-acetal substitution) within 6 or 7 atom heterocyclic rings, oxygen atoms spaced 2-carbon atoms from the quaternary nitrogen, and carbonyl substitutions adjacent to the spacing moieties, either bicyclohexyl or biphenyl. Biological testing showed a positive potency correlation between the chemicals when data from the following tests were compared: antagonism in mice of paraoxon-induced motor impairment using the incline screen and toxicity, and ability to induce contractions of guinea-pig isolated ilea. The compounds were compared with the often used protective antagonist of organophosphate-induced toxicity, pyridostigmine. One compound, MFS-3, was seven times more efficacious and possessed a much higher therapeutic index. Possible mechanisms of action for these chemicals are discussed.

Animals↗