Differential effects of midazolam and pentylenetetrazole on behavioral repetition and variation.

The present study investigated the effects of midazolam and pentylenetetrazole upon repeating and varying sequences of responses. Rats were exposed to a multiple schedule with two components. Under the VARY component, water was provided if the current sequence of four responses differed from each of the five previous ones; under the REPEAT component, water delivery was contingent upon a particular four-response sequence. Each component was signaled by specific exteroceptive stimuli. Overall, sequence variability was affected by midazolam, and to a lesser degree, by pentylenetetrazole. With the REPEAT contingency, drug administration increased behavior variation, thus reducing accuracy; with the VARY contingency, behavior variation and accuracy were not altered. These results were explained on the basis of the disruptive effects of both drugs upon the discriminative control exerted by previous responses within a sequence and by exteroceptive stimuli.

Drug resistance in Chromobacterium violaceum

Chromobacterium violaceum is a free-living bacterium commonly found in aquatic habitats of tropical and subtropical regions of the world. This bacterium is able to produce a large variety of products of biotechnological and pharmacological use. Although C. violaceum is considered to be non-pathogenic, some cases of severe infections in humans and other animals have been reported. Genomic data on the type strain ATCC 12472(T) has provided a comprehensive basis for detailed studies of pathogenicity, virulence and drug resistance genes. A large number of open reading frames associated with various mechanisms of drug resistance were found, comprising a remarkable feature of this organism. Amongst these, beta-lactam (penicillin and cephalosporin) and multidrug resistance genes (drug efflux pumps) were the most numerous. In addition, genes associated with bacitracin, bicyclomycin, chloramphenicol, kasugamycin, and methylenomycin were also found. It is postulated that these genes contribute to the ability of C. violaceum to compete with other bacteria in the environment, and also may help to explain the common drug resistance phenotypes observed in infections caused by this bacterium

Bacteriophages and insertion sequences of Chromobacterium violaceum ATCC 12472

A fluid genome is a great advantage to prokaryotes, enabling quick adaptation to various types of ecological niches and to diverse environmental selective pressures. A substantial portion of these sudden changes is mediated by lateral gene transfer (LGT), through genetic recombination mechanisms, such as transformation, conjugation and transduction. The recent sequencing of several organisms has offered a new approach to the study of LGT, using comparison and analysis of nucleotide sequences dispersed throughout the genome of these species. This analysis in Choromobacterium violaceum has revealed four prophage and 12 insertion sequences, suggesting genetic exchange with several other bacterial species, including Salmonella enterica, Ralstonia and Xanthomonas. An Rhs (recombination hot spot) element (containing a vgr-like gene) was also observed, the function of which remains unknown, but it has a sequence related to species of Acinetobacter and Sphingomonas. These results support the role of LGT in the acquisition of new traits by C. violaceum

Stimulus effects on concurrent performance in transition.

Six experimentally naive pigeons were exposed to concurrent variable-interval variable-interval schedules in a three-key procedure in which food reinforcement followed pecks on the side keys and pecks on the center key served as changeover responses. In Phase 1, 3 birds were exposed to 20 combinations of five variable-interval values, with each variable-interval value consistently associated with a different color on the side keys. Another 3 pigeons were exposed to the same 20 conditions, but with a more standard procedure that used a nondifferential discriminative stimulus on the two side keys throughout all conditions. In Phase 2, the differential and nondifferential stimulus conditions were reversed for each pigeon. Each condition lasted for one 5-hr session and one subsequent 1-hr session. In the last 14 conditions of each phase, the presence of differential discriminative stimuli decreased the time necessary for differential responding to develop and increased the sensitivity of behavior to reinforcement distribution in the 1st hr of training; during the last hours of training in each condition, however, the effects of the differential discriminative stimuli could not be distinguished from the effects of reinforcement distribution per se. These results show the importance of studying transitions in behavior as well as final performance. They may also be relevant to discrepancies in the results of previous experiments that have used nonhuman and human subjects.

Cardiac surgery in patients over the age of 80 years.

The risk-benefit relationship of open heart surgery in octogenarians is not well established. Eighty consecutive patients over the age of 80 who underwent cardiac operations under cardiopulmonary bypass were evaluated. Twenty-five patients were in functional class IV, 42 in class III, and 13 in class II. Forty-four patients had only coronary artery bypass grafts (CABG), 12 only aortic valve replacement (AVR), 6 only mitral valve replacement (MVR), 12 CABG and AVR, 4 CABG and MVR, 1 CABG and aneurysmectomy, and 1 had resection of left atrial myxoma. Operative mortality (within 30 days) was 12.5% for the group. Mortality was related to bleeding, left ventricular failure, primary ventricular fibrillation, pulmonary failure, and renal failure. Mortality was higher in patients with (1) advanced functional class, (2) mitral valve replacement, (3) postoperative hemorrhage, and (4) associated pulmonary disease. While a generally conservative approach is recommended for octogenarian patients, many with life-threatening cardiac disease, especially those free of major multisystem illnesses, should not be denied the benefit of surgical treatment.

Ruptured abdominal aortic aneurysms: experience with 70 cases.

During the period 1965-1983, 270 patients underwent resection of abdominal aortic aneurysm. In 70 patients (26%) the aneurysm was ruptured. Overall hospital mortality of patients with ruptures was 34%. Five patients died before the graft could be completed. Common denominators associated with mortality were hypotension, renal failure, cardiac arrest, and postoperative hemorrhage. The average age over the first 10 years was 68, but subsequently, has risen gradually, with a corresponding increase in mortality despite improved surgical technique and postoperative care. Only with more widespread elective resections and earlier diagnosis of rupture followed by prompt operative management, can the outlook for patients with abdominal aortic aneurysm be improved.

Argon laser radiation of human clots: differential photoabsorption in red cell rich and red cell poor clots.

Since argon laser radiation (454-514 nm) can vaporize human clots, we determined whether the absorption of laser energies can differ among different types of blood clots. Thus we performed spectrophotometric studies and examined the ability of this laser to penetrate red cell rich and red cell poor clots. Fifty-four red cell rich and red cell poor clot samples, varying in depth from 1.8 to 5.0 mm, were subjected to 3, 5 and 7 watts from an argon laser beam. At a given power intensity, the deeper the red cell rich clot, the longer was the time needed to penetrate the clot. The higher the power used, the shorter was the red clot penetration time. In contrast, all power levels used up to 5 minutes did not penetrate any of the varying depths of red cell poor clots. Spectrophotometrically, the red cell rich clot had an absorption curve typical of hemoglobin pigment while the red cell poor clot, in the absence of hemoglobin, had poor absorption between 350 and 600 nm and was unable to absorb argon laser energies. Thus, the argon laser provides a therapeutic modality for human red cell rich clot dissolution but the present approach does not appear to be effective against red cell poor clots.

Laser therapy of coronary artery obstructions.

Laser energies can be transmitted through flexible optical fiber to vaporize and penetrate coronary atherosclerotic and thrombotic obstructions. There are risks and complications involved in this therapy, however, including perforation, aneurysm formation, and thromboembolic risks, and further research is needed to render the laser recanalization procedure safe.

Iatrogenic left main coronary artery stenosis following PTCA or valve replacement.

We report three patients who developed iatrogenic severe left main coronary artery stenosis. In two, it was secondary to coronary cannulation during aortic valve replacement and in one it followed distention of the artery during balloon dilatation of a proximal lesion in the left anterior descending artery. In all three, the stenosis was clinically manifest a few months after the intervention. All were successfully treated by aortosaphenous coronary bypass. A common mechanism for the three cases may be mechanical distention of the left main coronary artery resulting in intimal damage with secondary fibrosis and stenosis. The percutaneous transluminal coronary angioplasty-related stenosis is, to our knowledge, the first reported case of this nature, and represents a previously unrecognized complication of this procedure.

Risk of combined coronary artery bypass and mitral valve replacement.

During a period of 6 years and 5 months, a group of 26 men and 16 women between 53 and 80 years of age underwent combined coronary artery bypass and mitral valve replacement. All patients were catheterized preoperatively, and hemodynamic and surgical variables were noted. In accordance with the variables, operative mortality was evaluated and compared among subgroups. Eight patients died, and the factors found to adversely change successful treatment were instability of ischemia, advanced New York Heart Association functional class, severe mitral regurgitation, associated aortic regurgitation, extensive coronary artery disease, the extent of left ventricular dysfunction as estimated by left ventricular end-diastolic pressure and ejection fraction, and elevated pulmonary vascular resistance. Prolonged operative time was also significant. The only variable that did not seem to influence mortality was the pathology type of mitral valve involvement. Analysis of our data confirms the high risk of coronary artery by pass combined with valve replacement for mitral regurgitation reported by others, and it appears advisable at present to exercise caution in recommending combined coronary artery by pass and mitral valve replacement in patients with extensive coronary artery disease and advanced left ventricular dysfunction. Pre-and postoperative utilization of afterload reduction, with the use of circulatory assist devices, may prove effective in some patients, and deserves special evaluation.

Effects of laser radiation on the morphology of human coronary atherosclerotic disease.

Laser energy delivered through optical fibers can produce potent controlled thermal dissolution of human coronary obstructive disease, thus widening the stenotic vascular lumen. The ease of vaporization and penetration depends not only on the physical properties of the laser beam but also on the physical characteristics of the atherosclerotic plaque. Lipid-laden plaques are more easily vaporized compared with plaques that are heavily calcified. In atherosclerotic animal models studied in vivo, laser radiation produced a charred lining around the evacuated area and rapid regeneration of a new endothelial lining. After several weeks, the laser-induced crater was still evident, and thrombogenesis was not a significant complication. Focal aneurysmal dilatation may develop when there is thermal injury of the medial layer, and acute perforation can occur if severe laser burn is extended beyond the adventitial layer. Further technical advances and achievements are needed before laser recanalization becomes a clinical reality.