Vascular endothelium-specific overexpression of human catalase in cloned pigs.

The objective of this study was to develop transgenic Yucatan minipigs that overexpress human catalase (hCat) in an endothelial-specific manner. Catalase metabolizes hydrogen peroxide (H(2)O(2)), an important regulator of vascular tone that contributes to diseases such as atherosclerosis and preeclampsia. A large animal model to study reduced endothelium-derived H(2)O(2) would therefore generate valuable translational data on vascular regulation in health and disease. Yucatan minipig fetal fibroblasts stably co-transfected with human catalase (Tie2-hCat) and eGFP expression constructs were isolated into single-cell populations. The presence of the Tie2-hCat transgene in individual colonies of fibroblasts was determined by PCR. Transgenic fibroblasts were used for nuclear transfer into enucleated oocytes by electrofusion. A minimum of 140 cloned embryos were transferred per surrogate sow (n = 4). All four surrogates maintained pregnancies and piglets were delivered by cesarean section. Nine male piglets from three of the four litters carried the Tie2-hCat transgene. Expression of human catalase mRNA and overall elevated catalase protein in isolated umbilical endothelial cells from transgenic piglets were verified by RT-PCR and western blot, respectively, and endothelial localization was confirmed by immunohistochemistry. Increased enzymatic activity of catalase in transgenic versus wild-type endothelial cells was inferred based on significantly reduced levels of H(2)O(2) in culture. The similarities in swine and human cardiovascular anatomy and physiology will make this pig model a valuable source of information on the putative role of endothelium-derived H(2)O(2) in vasodilation and in the mechanisms underlying vascular health and disease.

Relation of coagulation parameters to patency and recurrent ischemia in the Thrombolysis in Myocardial Infarction (TIMI) Phase II Trial.

Current protocols for use of tissue-type plasminogen activator in acute myocardial infarction include heparin estimated by the activated partial thromboplastin time (aPTT). Recent reports indicate a risk of recurrent ischemic events with long aPTT values. Longer aPTT values in the Thrombolysis in Myocardial Infarction-II (TIMI II) Trial, obtained within the first 48 hours, were associated with patency at 18 to 48 hours and better left ventricular function at discharge (average 9.6 days), but also with emergency catheterizations within the first 48 hours and, weakly, with recurrent ischemia during the first 18 hours. A moderate decrease in fibrinogen, compared with a "small" decrease, was also associated with patency, but a "large" decrease was associated with hemorrhagic events. Patency was associated with higher fibrinogen values and higher plasminogen values at baseline. The aPTT results support frequent monitoring during the first 24 to 48 hours to ensure optimal clinical outcome. The coagulation factor results suggest that there may be an optimum window for fibrinogenolysis in this setting.

Transesophageal echocardiographic diagnosis of multicentric left ventricular myxomas mimicking a left atrial tumor.

We report a case of multicentric left ventricular myxomas with prolapse of one myxoma into the left atrium during ventricular systole that mimicked a left atrial tumor. The transthoracic echocardiogram showed large masses in the region of the mitral valve leaflets consistent with vegetations or tumors. A computed tomographic scan of the chest demonstrated two distinct left atrial masses, one of which appeared to prolapse from the left atrium into the left ventricle. Intraoperative transesophageal echocardiography showed a large pedunculated mass moving between the two left-sided cardiac chambers with intermittent trapping of the mass in the left atrium. The mass was attached to the left ventricular posteromedial papillary muscle by a long stalk. Another adjacent large ventricular mass was also noted in the left ventricle. These findings were confirmed at operation, which also demonstrated a third small tumor arising from the atrial aspect of the posterior mitral leaflet.

Value and limitations of color Doppler echocardiography in the evaluation of percutaneous balloon mitral valvuloplasty for isolated mitral stenosis.

The limitations of 2-dimensional and pulsed Doppler echocardiography in patients undergoing mitral valvuloplasty are well known. This study was undertaken to assess the value of color Doppler flow imaging in 36 symptomatic mitral stenosis patients who subsequently underwent successful balloon mitral valvuloplasty by comparing the results to those obtained at cardiac catheterization. Color Doppler-guided conventional Doppler assessment agreed well with cardiac catheterization results in classifying mitral stenosis as mild, moderately severe and severe, both before and after valvuloplasty. Color Doppler was also useful in identifying patients who had moderate to severe mitral regurgitation before and after valvuloplasty. Color Doppler flow mapping was more sensitive than oximetry in the detection of iatrogenic atrial septal defects, which were noted in 25 patients. The defects of those patients with smaller defects by color Doppler (diameter less than 0.7 cm) or echocardiographic shunt volume less than 0.7 liters/min tended to close, usually within 6 months, as opposed to those with larger defects or higher shunt volumes, which tended to persist. Echocardiographic shunt volumes revealed a fair correlation with oximetric results.

Use of the smaller pediatric transesophageal echocardiographic probe in adults.

Transesophageal echocardiography in the adult uses a relatively large diameter probe, which may be poorly tolerated by certain patients. The use of a smaller probe designed for pediatric patients was studied in 50 adults (21 males and 29 females), and concomitant transesophageal echocardiography studies were performed using the regular adult-sized probe in 28 of these patients. The smaller pediatric transesophageal echocardiography probe was easier to pass, better tolerated, caused a smaller heart rate increase (13 +/- 3 vs 20 +/- 4 beats/min, P = 0.0029), and required no sedation in more patients than the adult transducer. The resolution of the two-dimensional and color Doppler images in the mid and near fields of the smaller probe were comparable to the larger probe, as were the maximal area of mitral regurgitation and the ratio of the maximal proximal width of the aortic insufficiency jet to the left ventricular outflow tract diameter in patients with these lesions. However, the image resolution was noticeably inferior to the adult probe in the far field, such as when imaging the distal left ventricle or imaging structures transgastrically. Therefore, the smaller probe designed for pediatric use allows satisfactory near- and mid-field two-dimensional and color Doppler flow imaging in comparison to the adult probe and would be expected to be beneficial in adult patients in whom superior quality imaging of the far-field is not required clinically, those who tolerate poorly the adult probe, relatively high-risk patients in whom no sedation is desirable, and in those patients in whom passage of the larger probe is unsuccessful.

Two-dimensional echocardiography and Doppler color flow mapping in the diagnosis and prognosis of ventricular septal rupture.

Doppler color flow mapping in conjunction with two-dimensional echocardiography was used to evaluate ventricular septal rupture after myocardial infarction (seven anterior and eight inferior) in 15 patients and to correlate these findings with cardiac catheterization and surgical or autopsy data. Ventricular septal rupture was diagnosed by turbulent flow traversing the ventricular septum. The direction and velocity of shunt flow was determined by color M-mode and conventional Doppler methods. In all patients, Doppler color flow mapping correctly defined the site of septal rupture, which occurred at areas of discordant septal wall motion or "hinge points" (six posterior inlet, three anterior inlet, and six apical trabecular septum). Each of three patients with moderate tricuspid regurgitation and three of four patients with right-to-left shunting during diastole died, and all had an elevated right ventricular end-diastolic pressure. Right ventricular wall motion index was significantly higher in the patients who died compared with those who survived (mean +/- SEM; 2.8 +/- 0.2 vs. 2.0 +/- 0.2, p = 0.012), but there was no difference in left ventricular wall motion index. The rupture size measured by Doppler color flow imaging (1.7 +/- 0.1 cm) correlated with the size determined during surgery or autopsy (1.8 +/- 0.2 cm, r = 0.68, p = 0.022) and the pulmonic-to-systemic shunt flow ratio by cardiac catheterization (2.4:1 +/- 0.3, r = 0.74, p = 0.004). Color-guided continuous-wave Doppler estimates of right ventricular systolic pressure (47 +/- 2 mm Hg) correlated with cardiac catheterization measurements (48 +/- 3 mm Hg, r = 0.90, p = 0.0002).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic evaluation of prosthetic cardiac valves.

Comprehensive echocardiographic examination of patients with prosthetic cardiac valves using M-mode, two-dimensional, conventional, and color Doppler echocardiography represents an invaluable clinical tool in the serial follow-up of these patients. A thorough knowledge of these techniques and their limitations allows accurate assessment and prevention of misdiagnoses.

Heparin and infarct coronary artery patency after streptokinase in acute myocardial infarction.

Anticoagulant therapy is frequently used after thrombolytic agents in the treatment of acute myocardial infarction (AMI) although it is unclear that such therapy will prevent subsequent infarct vessel reocclusion. The role of duration of heparin therapy in maintaining infarct artery patency was studied retrospectively in 53 consecutive AMI patients who received streptokinase therapy and underwent coronary angiography acutely and at 14 +/- 1 days. Of the 39 patients with initial infarct vessel patency, patency at follow-up angiography was observed in 100% (22 of 22) of those who received greater than or equal to 4 days of intravenous heparin but in only 59% (10 of 17) of those patients who received less than 4 days of heparin (p less than 0.05). Of the 14 patients not initially recanalized after streptokinase, patent infarct-related arteries at follow-up angiography were found in 3 of 8 (38%) treated with greater than or equal to 4 days of heparin therapy but in none of the 6 patients treated for less than 4 days (difference not significant). No significant difference in hemorrhagic complications was noted between the short- and long-term heparin treatment groups. Thus, greater than or equal to 4 days of intravenous heparin therapy after successful streptokinase therapy in AMI is more effective in maintaining short-term infarct vessel patency than a shorter duration of therapy and it may maintain the short-term patency of the infarct vessel in those patients who later spontaneously recanalize.

Assessment of pancreatic islet-cell population in the hyperglycemic athymic nude mouse: immunohistochemical, ultrastructural, and hormonal studies.

Previous studies in diabetic animal models have demonstrated altered pancreatic islet-cell populations. To further characterize the diabetic syndrome in our athymic nude mouse colony, we studied the population of endocrine cells in pancreatic islets of 4-week-old normoglycemic and 8-week-old hyperglycemic athymic nude (nu/nu) mice using immunohistochemistry, morphometry, and electron microscopy. In normoglycemic 4-week athymic nu/nu mice, the proportions of B (insulin-secreting) cells and A (glucagon-secreting) cells were similar to those in control Balb/c mice; however, the D (somatostatin-secreting) cells were significantly decreased in nu/nu mice. The populations of B and A cells appeared to be normal in hyperglycemic 8-week-old nu/nu mice while there was a significant increase in the proportion of D cells when compared with the proportion in Balb/c mice. Electron microscopic studies indicated that the appearance of B and A cells was similar in the 8-week-old hyperglycemic nu/nu and in controls; however, the D cells appeared to be enlarged and were finely packed with electron-dense secretory granules. Radioimmunoassays of the pancreatic content (micrograms/g fresh pancreas) of insulin, glucagon, and somatostatin in pancreata in 8-week-old normal Balb/c and hyperglycemic athymic nude mice were similar; however, the somatostatin content was significantly increased in the 8-week-old hyperglycemic nu/nu mice compared with age and sex-matched controls. These results demonstrate an altered D cell population and an increase in somatostatin levels in the pancreatic islets of the hyperglycemic athymic nude mouse animal model.(ABSTRACT TRUNCATED AT 250 WORDS)