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Biomedical subjects

C N Lee

Publications and source records attributed to C N Lee.

At least 145 records · Page 8Linked to original sources
PubMed1989

Intra-atrial smoke-like echoes and thrombi formation.

Between December 1980 and December 1987, approximately 6,000 two-dimensional echocardiographic examinations were performed in our noninvasive cardiac laboratory. During this period, five cases of intra-atrial smoke-like echoes were diagnosed. The four patients with dense smoke-like echoes in the left atria all had echocardiographic evidence of severe mitral stenosis and thrombi in the left atrial cavity, both of which were confirmed at open-heart surgery. One patient with right-sided cardiomyopathy had echocardiographic evidence of dense smoke-like echoes and thrombus in the right atrial cavity. One of our five patients was receiving anticoagulant therapy, and none had a history of thromboembolism. We conclude that using conventional two-dimensional echocardiographic techniques, smoke-like echoes in the atria are a very infrequent finding and are very commonly associated with formation of thrombi.

Adult↗
PubMed1989

Effects of chronic infusion of dibutyryl c-AMP or adenosine on luteal function in sheep.

Adenosine or vehicle; dibutyryl c-AMP, a c-AMP analogue, or vehicle in two separate experiments were infused through an indwelling cannula every four hours around the ovarian vascular pedicle of ewes unilaterally ovariectomized on day 8 postestrus. Adenosine or vehicle was infused from day 8 through 22 postestrus and dibutyryl-cAMP was infused from day 8 through 20 postestrus or until the ewes returned to estrus. Interestrous intervals were greater (p less than or equal to 0.05) in ewes receiving adenosine (27.3 +/- 2.4 days) than in control ewes (17.2 +/- 1.3 days). The length of the estrous cycle of ewes receiving dibutyryl c-AMP was greater (22.4 +/- 1.1; p less than or equal to 0.05) than in control ewes which averaged 16.7 +/- 0.6 days. Profiles of progesterone were different (p less than or equal to 0.05) for ewes receiving adenosine or dibutyryl c-AMP when compared to their respective controls. In addition, the overall mean concentrations of progesterone were greater (p less than or equal to 0.05) in dibutyryl c-AMP or adenosine-treated ewes than in controls. In a third experiment, infusions of adenosine or dibutyryl c-AMP intrauterine every 4 hours through a cannula from day 8 through 22 postestrus had no effect (p less than or equal to 0.05) on the interestrous interval or profiles of progesterone. It is concluded that dibutyryl c-AMP or adenosine in vivo can delay luteolysis and adenosine and c-AMP may play roles in luteal secretion of progesterone in sheep but are probably not the uterine embryonic antiluteolysin of early pregnancy in sheep.

Adenosine↗
PubMed1988

Distribution of progesterone to the uterus and associated vasculature of cattle.

Multiparous dairy cows were sampled to study the concentrations of progesterone in tissue of the uterus and associated vasculature and to determine whether progesterone was delivered to the uterus locally. In study 1, progesterone was greater (p less than or equal to 0.05) in the first venous branch draining the cranial portion of the uterine cornu adjacent to the vary with a corpus luteum than in jugular blood or in the same vein draining the opposite uterine cornu on day 11 postestrus. Concentrations of progesterone were also greater (p less than or equal to 0.05) in the cranial than in the caudal half of the uterine cornu adjacent to the luteal-bearing ovary or in the cranial and caudal halves of the opposite uterine cornu. Concentrations of progesterone were also greater (p less than or equal to 0.05) in the uterine or ovarian arterial tissue adjacent to the ovary with the corpus luteum than in those same vessels on the contralateral side. In a second study, progesterone at 0 h on day 11 postestrus was greater (p less than or equal to 0.05) in the first venous branch draining the cranial portion of the uterine horn adjacent to the luteal-bearing ovary than in jugular blood, the same vein in the contralateral uterine cornu or in the same uterine vein 48 h after ligation and resection of the oviductal vein adjacent to the ovary with the corpus luteum. It is concluded that progesterone is delivered locally to the uterus and associated vasculature and the route of local delivery appears to be via the oviductal vein.

Animals↗
PubMed1988

Relationship of pre- and post-ovulatory gonadotropin concentrations to subnormal luteal function in postpartum beef cattle.

Early weaning of calves from anestrous cows results in formation of short-lived corpora lutea (CL) unless the animals are pretreated with a progestagen (norgestomet). This study was conducted to investigate the relationship between pre- and post-ovulatory gonadotropin secretion and luteal lifespan. Postpartum beef cows were assigned randomly into two groups, control (n = 5) and norgestomet (implant given at weaning for 9 d; n = 7). Calves from all cows were weaned 30 to 33 d postpartum. Coccygeal artery cannulas were placed into cows in the control group 1 d prior to weaning and 2 d before implant removal in cows in the norgestomet group. Plasma for determination of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol-17 beta (E) and progesterone (P) was collected daily at 10-min intervals for 6 h from weaning (control) or the day prior to implant removal (norgestomet) to estrus (d 0) and on d 2, 4 and 6 following estrus. Average interval (X +/- SE; P less than .05) from weaning to estrus or implant removal was 4.2 +/- .8 and 2.3 +/- .2 d for the control and norgestomet groups, respectively. Estrous cycle length for the control group was 12.4 +/- 1.8 d compared with 20.4 +/- .3 d for the norgestomet group (P less than .05). Four of five control cows had an estrous cycle length of 7 to 14 d; all cows in the norgestomet group and the remaining control cow had an estrous cycle of normal length (16 to 21 d).2+ estrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Induction of persistent ovarian follicular structures following administration of progesterone near the onset of estrus in dairy cattle.

The objective of this study was to determine if progesterone administered near the onset of estrus in dairy cows would block the preovulatory surge of LH and result in subsequent persistence of ovarian follicular structures. Following synchronization of estrus with prostaglandin F2 alpha, 20 multiparous, non-lactating Holstein cows were randomly assigned into three groups: 1 ml ethanol administered i.m. at 12-h intervals for 24 h (n = 6; group 1); 1 mg progesterone administered i.m. at 12-h intervals for 24 h (n = 7; group 2); 2.5 mg progesterone administered i.v. at the onset of standing estrus (n = 7; group 3). Ovarian structures were palpated per rectum on the day of estrus and twice weekly for 14 d. Blood was collected every 2 h from onset of standing estrus for 30 h, and concentrations of LH and progesterone were determined. Numbers of cows diagnosed with persistent follicles 10 d after estrus were 1 of 6 (group 1), 2 of 7 (group 2), and 5 of 7 (group 3). The preovulatory surge of LH did not occur during the sampling period (30 h) for 1 of 6, 7 of 7 and 5 of 7 cows, for groups 1, 2, and 3, respectively, and mean serum concentrations of LH were higher in group 1 than in groups 2 and 3. Serum concentration of progesterone (ng/ml) was higher in group 1 (1.9 +/- .4) than in groups 2 (.9 +/- .4) and 3 (.9 +/- .4) 10 d following estrus. Blocking the preovulatory surge of LH with exogenous progesterone resulted in persistence of ovarian follicles.

Animals↗
PubMed1987

Determination of minimal inhibitory concentrations of antituberculosis drugs by radiometric and conventional methods.

Minimal inhibitory Concentrations (MIC) of 5 antituberculosis drugs (isoniazid, rifampin, streptomycin, ethionamide, and ethambutol) were determined by the radiometric (BACTEC) broth method and by the agar plate proportion method. Seventeen M. tuberculosis strains, isolated from patients before treatment, were tested. The MIC values of 4 of the 5 drugs (the exception was streptomycin) were 2 to 4 times lower in 7H12 broth than in 7H11 agar. The broth-determined MIC were also at least 2 to 4 times lower than the achievable serum concentrations. The broth-determined MIC are probably much closer to the true MIC values than those determined in agar plates because of the lower degree of absorption and degradation in the liquid medium. The radiometric broth method is a simple and rapid quantitative method for accurate determination of the MIC values of the antituberculosis drugs. The data obtained in this study will be used for further evaluation of the MIC values as complementary or alternative to the conventional qualitative testing against critical concentrations.

Antitubercular Agents↗
PubMed1987

Short-course chemotherapy of pulmonary tuberculosis in pneumoconiotic patients.

This is the first prospective clinical trial recorded to date of short-course chemotherapy in pulmonary tuberculosis complicated by pneumoconiosis. Forty-eight anthrasillicotic and 11 silicotic patients with previously untreated pulmonary tuberculosis completed 9-month, short-course chemotherapy regimens: 2 months of daily streptomycin, isoniazid, rifampicin, and pyrazinamide followed by daily isoniazid and rifampicin for 7 months (2SHRZ/7HR). There were 3 treatment failures (5%). The remaining 56 patients (95%) all had their sputum converted within 4 months (mean, 1.5 months). Bacteriologic relapses were noted in 3 patients (5%) after 18 to 40 months of follow-up (mean, 28.4 months). The relapses occurred within 7 months after chemotherapy was stopped. There were 2 deaths from nontuberculosis causes during the follow-up period. Fifty-one patients (90%) remained bacteriologically sterile for 28.4 +/- 6.1 months. These results suggest that the 2SHRZ/7HR regimen is satisfactory in treating anthrasilicotic or silicotic patients with pulmonary tuberculosis, though antituberculosis chemotherapy seemed less effective in patients with pneumoconiosis than in those without pneumoconiosis.

Adult↗
PubMed1987

Differentiation of poliovirus type I isolates in the 1982 epidemic from Sabin-I strain by antigenic and temperature markers.

Poliovirus type 1 strains recovered from patients with poliomyelitis during the epidemic of 1982, were distinct antigenically from Sabin-1 strain by comparing homologous and heterologous neutralization rate constants of Sabin-1 specific antiserum. With the reproductive capacity at 40 degrees C, these isolates could be easily differentiated from vaccine strain. It was suggested that the epidemic of poliomyelitis in 1982 was not caused by vaccine strain. The 24 isolates reacted with LSc and/or Sabin-1 antisera to the same extent. It was speculated that they might be antigenically similar if not identical. Three isolates which were collected from the later part of epidemic formed small plaques at 40 degrees C. Rabbit antisera against poliovirus strains 3844, Sabin-1, Mahoney and Brunhilde were produced. Antigenic relatedness among the strains was tested by kinetic neutralization. The strain 3844 was distinct from Brunhilde, Mahoney and Sabin-1. Asymmetric cross-reactions between Mahoney and Sabin-1 strains were clearly demonstrated.

Antigens, Viral↗
PubMed1986

Glycosaminoglycans in ewe reproductive tracts and their influence on acrosome reactions in bovine spermatozoa in vitro.

Glycosaminoglycans (GAG) promote acrosome reactions (AR) in bovine and rabbit spermatozoa in vitro. Female bovine reproductive tract secretions contained GAG and the concentrations and composition of those GAG varied with different regions and stages of the estrous cycle. This study was designed to evaluate the types of GAG found in reproductive tract secretions of ewes at different stages of the estrous cycle and the ability of the secretions to promote AR. Ewes (n = 48) were slaughtered at 0, 12, 24, 36, 72 and 144 h following observations of standing estrus. Reproductive tracts were flushed with a modified Tyrode's medium (TALP: 7 ml) not containing calcium. Concentrations and composition of GAG in the tract were determined by high performance liquid chromatography. Concentrations of GAG decreased anterior to the cervix: 2.28 to .74 mg/100 mg protein (P less than .05). Increases in heparin-like GAG during the estrual phase and chondroitin sulfate GAG during the luteal phase were noted. Bovine sperm were incubated in tract flushings standardized to contain 4 micrograms/ml of GAG and supplemented with calcium. Sperm incubated in estrual flushings for 9 h exhibited a higher incidence of AR than those incubated in luteal flushings or control, 50% vs 36% and 29%, respectively (P less than .0001). It is concluded that during the estrous cycle there were changes in concentrations and composition of GAG in ewe reproductive tracts and the potencies of those female secretions causing AR varied.

Acrosome↗
PubMed1986

Comparison of atriopulmonary versus atrioventricular connections for modified Fontan/Kreutzer repair of tricuspid valve atresia.

This study compares the clinical results of two basic variations of the modified Fontan/Kreutzer operation, direct atriopulmonary connection without an interposed valve versus atrioventricular connection using the native pulmonary valve and the potential pumping capability of the subpulmonary ventricular chamber. From January 1979 through June 1985, 84 patients with tricuspid atresia and ventriculoarterial concordance underwent the modified Fontan/Kreutzer operation at the Mayo Clinic. Sixty patients had atriopulmonary connection and 24 patients had atrioventricular connections. Preoperative characteristics of the two patient groups were similar, but there was a greater frequency of Waterston shunts in the atriopulmonary group (38% versus 17%) and greater frequency of Glenn shunts in the atrioventricular group (46% versus 15%). Mean pulmonary arteriolar resistance was 1.9 +/- 0.7 units in the atriopulmonary group and 1.1 +/- 0.8 units in the atrioventricular group (p less than 0.01). Early postoperatively, mean right atrial pressure was slightly higher in the atriopulmonary group than in the atrioventricular group (18 +/- 3 versus 16 +/- 3 mm Hg, p less than 0.01), but this difference was not reflected in the early or late results. Operative mortality was 5% for patients with atriopulmonary connections and 4% for patients with atrioventricular connections. At 3.5 years postoperatively, the overall survival rate was 89% +/- 4% for patients with atriopulmonary connection and 88% +/- 7% for patients with atrioventricular connections. We conclude that there is no important difference in the clinical outcome of patients undergoing modified Fontan/Kreutzer repair for tricuspid atresia with atrioventricular concordance with either of the two operative methods. The choice of the connection should be dictated by the anatomy, such as presence of pulmonary valve or arterial stenoses, size of outlet chamber, and the presence of anomalous coronary arteries.

Adolescent↗
PubMed1986

Flow capacity of the canine internal mammary artery.

The internal mammary artery has excellent long-term patency when used as a conduit for coronary artery bypass, and clinical and experimental studies have shown that blood flow through an internal mammary artery graft is satisfactory for most coronary artery branches. Multiple distal anastomoses from a single internal mammary artery, either with sequential anastomoses or with a Y-graft, might require additional blood flow through the vessel, and there has been concern that the flow capacity of the internal mammary artery is insufficient with these techniques. To better define the immediate postoperative flow capacity and pattern of the internal mammary artery, we performed experiments in seven dogs in which the left internal mammary artery was anastomosed to the circumflex coronary artery. In situ, blood flow in the internal mammary artery was 27 ml/min. Blood flow was 63 ml/min in the circumflex coronary artery and 42 ml/min in the left anterior descending coronary artery. After anastomosis of the left internal mammary artery to the circumflex coronary artery, the left main coronary artery was ligated; flow through the bypass graft increased to 92 ml/min, and systemic hemodynamics remained stable. Isoproterenol stimulation further increased flow through the left internal mammary artery graft to 160 ml/min. This study suggests that the canine internal mammary artery is capable of substantial early increase in flow and can, in fact, support the entire left coronary circulation.

Animals↗