Aqueous central cavity in aspartate transcarbamylase from Escherichia coli.

A three-dimensional x-ray diffraction study of aspartate transcarbamylase to 5.5-angstrom resolution, with the aid of four isomorphous heavy atom derivatives, indicates the presence of a central aqueous cavity approximating an oblate spheroid about 25 by 50 by 50 angstroms in dimension, within a molecule about 90 by 110 by 110 angstroms in largest dimensions.

Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.

OBJECTIVES: This study describes changes in high-frequency QRS components (HF-QRS) during percutaneous transluminal coronary angioplasty (PTCA) and compares the ability of these changes in HF-QRS and ST-segment deviation in the standard 12-lead electrocardiogram (ECG) to detect acute coronary artery occlusion. BACKGROUND: Previous studies have shown decreased HF-QRS in the frequency range of 150-250 Hz during acute myocardial ischemia. It would be important to know whether the high-frequency analysis could add information to that available from the ST segments in the standard ECG. METHODS: The study population consisted of 52 patients undergoing prolonged balloon occlusion during PTCA. Signal-averaged electrocardiograms (SAECG) were recorded prior to and during the balloon inflation. The HF-QRS were determined within a bandwidth of 150-250 Hz in the preinflation and inflation SAECGs. The ST-segment deviation during inflation was determined in the standard frequency range. RESULTS: The sensitivity for detecting acute coronary artery occlusion was 88% using the high-frequency method. In 71% of the patients there was ST elevation during inflation. If both ST elevation and depression were considered, the sensitivity was 79%. The sensitivity was significantly higher using the high-frequency method, p<0.002, compared with the assessment of ST elevation. CONCLUSIONS: Acute coronary artery occlusion is detected with higher sensitivity using high-frequency QRS analysis compared with conventional assessment of ST segments. This result suggests that analysis of HF-QRS could provide an adjunctive tool with high sensitivity for detecting acute myocardial ischemia.

Effectiveness of low-dose lovastatin in lowering serum cholesterol. Experience with 56 patients.

This study reviews the progress of 56 consecutive patients with type IIa and IIb hyperlipoproteinemia following treatment with lovastatin. Lovastatin, a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, has been shown to have a cholesterol-lowering effect in doses ranging from 10 to 80 mg/d. Thus far, however, no large study has been performed to show the effectiveness of low-dose lovastatin (20 mg/d) for more than a 6-week duration. Fifty-six patients with known coronary artery disease were prospectively studied, with fasting lipid values being measured at baseline and after 6, 12, 18, and 24 weeks of 20-mg/d lovastatin therapy given as a single evening dose. The total cholesterol level fell 26% from a mean baseline of 8.12 mmol/L (314 mg/dL) and triglyceride levels fell by 12% from a mean baseline of 2.46 mmol/L. The high-density lipoprotein levels increased 7.6%. One patient with known preexisting liver disease was withdrawn from the study owing to an asymptomatic significant rise in liver function test results; one subject complaining of proximal muscle weakness was also withdrawn. The maximal decrease in total cholesterol level occurred within 6 weeks of initiation of therapy. We conclude that low-dose (20-mg/d) lovastatin was effective in lowering serum cholesterol levels in patients with primary type IIa or IIb hyperlipoproteinemia with minimal short-term side effects. Further studies are needed to establish the long-term safety and effectiveness of this drug.

Long-term propranolol therapy for angina pectoris.

Sixty-three patients with stable, severe typical angina pectoris (New York Heart Association functional class III or IV) were treated with propranolol and studied prospectively with a follow-up period of 5 to 8 years to assess the rate of complications and long-term effectiveness after an initial control period. The patients' mean age was 56 years; the mean daily dose of propranolol was 255 mg. The average yearly mortality rate was 3.8 percent with a cumulative 5 year mortality rate of 19 percent. Patients whose reduction of angina with propranolol was less than 50 percent had a nearly four-fold greater mortality rate than those whose reduction was 50 percent or more (P less than 0.01). Thirty-two percent of patients per year were angina-free with propranolol and 84 percent per year had 50 percent or more reduction in anginal episodes. There was no evidence for tachyphylaxis. Heart failure developed in 25 percent of patients, two thirds of whom had either congestive heart failure with an acute infarction or a prior history of congestive heart failure. All patients whose initial cardiothoracic ratio was greater than 0.5 had heart failure during the first 3 years of propranolol therapy. Of 12 patients who had an acute infarction during therapy, 7 died, 6 with cardiogenic shock; in contrast, 8 of 9 patients who had congestive heart failure without acute infarction survived. Eight percent of patients had other significant side effects, including gastrointestinal symptoms (three patients), hallucinations (one) and postural hypotension (one). The occurrence of asthma in three patients was dose-related and did not require drug discontinuation. Propanolol is an effective form of long-term therapy for severe angina pectoris; it does not induce tachyphylaxis or increase the overall mortality rate, although it may increase the risk of cardiogenic shock in acute myocardial infarction. Previous history of congestive heart failure, a cardiothoracic ratio of more than 0.5 without overt heart failure and mild asthma are relative contraindications. A 50 percent or greater reduction in anginal pain with propranolol predicts a low mortality group.

Aortocoronary bypass surgery: Correlation of angiographic symptomatic and functional improvement at 1 year.

Angiographic changes in the coronary circulation were evaluated in 60 patients 1 year after aortocoronary bypass surgery, and their relation to the postoperative clinical status was examined. Of 124 grafts implanted, 26 were closed, 7 stenotic and 91 (74 percent) patent at 1 year. Progression of occlusive disease occurred in 21 of 57 (37 percent) nongrafted and 78 of 123 (63 percent) grafted vessels. On the basis of location and severity of progression, significant lesions bypassed and patency of grafts, postoperative coronary perfusion was considered optimal in 16 patients (Group I), better in 24 (Group III). Complete freedom from chest pain or lessening of pain (improvement by two New York Heart Association functional classes) occurred in 88 and 79 percent of patients in Group III. Positive preoperative treadmill stress tests became negative after surgery in five of six patients in Group I, five of eight in Grojp II and three of eight in Group III. This study demonstrates that when progression of disease, graft patency and extent of revasculariztion are considered in combination, the postoperative angiographic status of the coronary circulation correlates well with clinical improvement at 1 year. These findings support the hypothesis that improved blood supply to ischemic myocardium is a major factor contributing to relief of angina pectoris after saphenous vein bypass surgery.

Spatial and nonspatial learning across the rat estrous cycle.

Recent evidence has demonstrated that there are fluctuations in both the anatomy and physiology of the hippocampus across the estrous cycle of the female rat. In the present study we examined the behavioral implications of these changes by testing females on either a hippocampal or nonhippocampal version of the Morris water maze during the various phases of the estrous cycle. Males were also tested on these tasks. Although there was little variance on the nonhippocampal cue task, females in proestrus performed significantly better than those in estrus. Optimal female performance on the spatial version of the task occurred during the phase of estrus, whereas the least efficient performance occurred during proestrus. These results do not support the traditional view that hippocampal long-term potentiation is positively correlated with spatial learning.

Impaired delay eyeblink classical conditioning in individuals with anterograde amnesia resulting from anterior communicating artery aneurysm rupture.

Anterior communicating artery (ACoA) aneurysm rupture can lead to an anterograde amnesia syndrome similar to that observed after damage to the hippocampus and medial temporal lobes (MT). It is currently believed that ACoA amnesia results from basal forebrain damage that disrupts hippocampal processing without direct hippocampal damage. Converging evidence from animal studies and computational modeling suggests that qualitative differences may exist in the pattern of memory impairment after basal forebrain or MT damage. For example, animals with basal forebrain but not hippocampal damage are impaired at delay eyeblink classical conditioning (EBCC). In this study, individuals with ACoA amnesia were shown to be impaired at delay EBCC compared with matched controls; this contrasts with the spared delay EBCC previously observed in MT amnesia. This finding suggests the beginning of a possible dissociation between the memory impairments in MT versus ACoA amnesia.

Postpartum pneumopericardium.

Postpartum pneumopericardium has been previously reported in only 4 patients, but it may occur more frequently than is currently recognized. Two patients are presented with pneumopericardium and pneumomediastinum with symptoms appearing on the first and second postpartum days. The second stage of labor was prolonged in both patients and associated with strenuous maternal effort. Both patients were primiparous and developed dyspnea, pleuritic chest pain, and had Hamman sign. Chest x-rays established the diagnosis in both patients. Echocardiography was nondiagnostic in one patient and mimicked pericardial effusion in the other. Although fatal tension pneumopericardium has been reported in association with other causes, the course in these 2 patients and in the other 4 reported patients has been benign. Symptoms resolved spontaneously in these 2 patients by 72 hours after their appearance. A postulated mechanism for postpartum pneumopericardium is presented.

LTP varies across the estrous cycle: enhanced synaptic plasticity in proestrus rats.

Previous studies have shown that the number of dendritic spines and synapses in hippocampal CA1 stratum radiatum decreases more than 30% between the proestrus (high estrogen) and estrus (low estrogen) phases of the rat estrous cycle [10,27]. In the present study, we investigated whether hippocampal synaptic plasticity, as measured by long-term potentiation (LTP), might also vary across the estrous cycle of the female rat. Male rats, and female rats at each phase of the estrous cycle were tested in either the morning or afternoon. There were no significant group differences in the pre-LTP I/O curves. However, females examined during the afternoon of proestrus, the phase during which prior studies indicate synapse number to be highest, demonstrated the greatest degree of potentiation. Diestrus, proestrus and estrus females tested in the morning demonstrated similar amounts of potentiation. There were also significant differences in post-LTP I/O curves between the afternoon proestrus females and males tested in the afternoon. These results suggest that gonadal hormones, interacting with the time of day, may regulate neural processes underlying learning and memory.

Compression of a subintimal or false lumen stent by stenting in the true lumen.

Subintimal or false lumen deployment is a rare complication of coronary stenting. The authors present a case of false lumen right coronary artery stenting with subsequent closure of the false lumen followed by stenting of the true lumen and compression of the false lumen stent.

Quantification of myocardial hypoperfusion with 99m Tc-sestamibi in patients undergoing prolonged coronary artery balloon occlusion.

Percutaneous transluminal coronary angioplasty provides an excellent opportunity to investigate the location and quantity of hypoperfusion during sudden complete occlusion of one of the major coronary arteries. Thirty-five patients referred for elective percutaneous transluminal coronary angioplasty were injected intravenously with 99mTc-sestamibi during balloon inflation. To visualize and quantify the hypoperfused region, a map of perfusion was constructed from that occlusion study and from the control study performed on the following day. Patients were divided into groups according to proximal or distal occlusion within each of the three coronary arteries. The region of myocardium supplied by each coronary artery varied in location and extended outside the typical borders for all arteries, but most prominently for the left circumflex coronary artery. The quantities of hypoperfusion varied within each artery group, but the average hypoperfusion was greater for the left anterior descending coronary artery than for either the right coronary artery or the left circumflex coronary artery. It is concluded that the quantities of hypoperfusion were highly variable within each artery group. Occlusion of the left anterior descending coronary artery was associated with the largest ischaemic region. The area of hypoperfusion extended outside the typical borders, most prominently for the left circumflex coronary artery.

Hyperhomocysteinemia in West Virginians with documented atherosclerotic disease.

Plasma homocysteine levels in a population of 282 West Virginians with atherosclerotic disease were significantly lower than in previous population studies of atherosclerotic subjects. Elevated homocysteine levels correlated positively with age and with serum creatinine levels. There was a trend toward higher homocysteine levels in men, but this did not reach statistical significance. Elderly men and individuals with elevated serum creatinine were the most likely populations to have elevated homocysteine levels. In 54 patients treated with 1 mg folic acid, plasma homocysteine levels fell by 21% with similar responses in both men and women. Elevated creatinine levels decreased the efficacy of folic acid treatment in reducing plasma homocysteine levels. All three patients with a homocysteine level in excess of 100 mmoles/L were found to have B12 deficiency.

Coronary artery muscle bridging causing class III angina in a patient with no coronary atherosclerosis.

The significance of coronary artery muscle bridging (MB) has been debated since its first angiographic description by Portsmann and colleagues in 1960 (1). The course is usually benign; however, angina, myocardial infarction, sudden death, arrhythmias, and complete heart block have been reported. In this article, we present a case of coronary artery muscle bridging which caused a patient with no angiographic evidence of atherosclerosis to experience Class III angina.

Continued benefit of lovastatin in the treatment of hypercholesterolemia in 36 patients.

After one year of treatment, low-dose (20 mg/d) lovastatin achieved continued efficacy without tachyphylaxis in 36 patients with Type IIa or IIb hyperlipoproteinemia. Six week and one year reductions in low density lipoprotein (LDL) cholesterol were significant at 33% and 31% in these patients respectively; reductions in total cholesterol were also significant at 25% and 22% respectively. Increases in high density lipoprotein cholesterol (HDL) were 6% at six weeks and 10% at one year; triglycerides were reduced 16% and 11% respectively. The cholesterol lowering effects were similar for males and females (23% and 21% respectively). Low-dose lovastatin (20 mg/d) is a good choice for reducing cholesterol in patients with primary Type IIa or IIb hyperlipoproteinemia refractory to diet therapy because it is effective in lowering LDL-cholesterol, while raising HDL-cholesterol with few side effects and without tachyphylaxis.

New guiding catheter configuration for aortocoronary vein graft angioplasty.

A new family of four guiding catheters (8 French and 9 French) has been developed for angioplasty of aortocoronary vein grafts and native coronary arteries beyond vein graft insertions. In 67 consecutive grafts and native vessels dilated through the grafts in 54 patients, the procedural success rate was 97%. The G-1 standard catheter was employed for the majority of the procedures (66%), but the G-3 catheter was better for high anterior grafts and the G-4 catheter was better for high left grafts. The G-2 catheter was better for lower right grafts, especially in dilated aortas. Balloon angioplasty alone using 8 French catheters was performed in 60 procedures, and excimer laser with adjunctive balloon angioplasty using 9 French catheters was performed in 7 procedures. These unique guiding catheters provide an attractive alternative to existing vein graft guides by their improved seating and backup support. They may be the primary choice for vein graft angioplasty and may have future application in stent deployment and transluminal extraction catheter (TEC) atherectomy.

Guiding catheter exchange during coronary angioplasty.

A new technique to exchange one angioplasty guiding catheter for another with the guide wire in place and across a coronary artery stenosis has been developed to decrease the dangers of having to recross the stenosis with a guide wire. This technique utilizes a regular extended angioplasty guide wire and enables the exchange of guiding catheters during the angioplasty procedure. In 683 consecutive angioplasty procedures by one operator, this technique has been attempted 57 times in 43 patients (6.3%) and has been successful 51 times (90%). The only failures were when the second catheter had a large or open curve (left Amplatz II, 5/22 unsuccessful or multipurpose, 1/3 unsuccessful). There have been no complications. We conclude that exchange of a guiding catheter over a guide wire by the method described is safe and helpful in cases where different guiding catheters are needed for back-up power once the lesion has been crossed with a guide wire.

Coronary angioplasty: current concepts.

Percutaneous transluminal coronary angioplasty is a nonsurgical method of dilating stenotic coronary arteries and relieving angina. Successful outcome is directly related to operator experience. Although the complication rate is low, restenosis remains a significant problem. The role of percutaneous transluminal coronary angioplasty is still evolving, but it has already become a reasonable treatment option for many patients with symptomatic ischemic heart disease.