Protein-based organelles in bacteria: carboxysomes and related microcompartments.

Many bacteria contain intracellular microcompartments with outer shells that are composed of thousands of protein subunits and interiors that are filled with functionally related enzymes. These microcompartments serve as organelles by sequestering specific metabolic pathways in bacterial cells. The carboxysome, a prototypical bacterial microcompartment that is found in cyanobacteria and some chemoautotrophs, encapsulates ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBisCO) and carbonic anhydrase, and thereby enhances carbon fixation by elevating the levels of CO2 in the vicinity of RuBisCO. Evolutionarily related, but functionally distinct, microcompartments are present in diverse bacteria. Although bacterial microcompartments were first observed more than 40 years ago, a detailed understanding of how they function is only now beginning to emerge.

The carboxysome shell is permeable to protons.

Bacterial microcompartments (BMCs) are polyhedral organelles found in an increasingly wide variety of bacterial species. These structures, typified by carboxysomes of cyanobacteria and many chemoautotrophs, function to compartmentalize important reaction sequences of metabolic pathways. Unlike their eukaryotic counterparts, which are surrounded by lipid bilayer membranes, these microbial organelles are bounded by a thin protein shell that is assembled from multiple copies of a few different polypeptides. The main shell proteins form hexamers whose edges interact to create the thin sheets that form the facets of the polyhedral BMCs. Each hexamer contains a central pore hypothesized to mediate flux of metabolites into and out of the organelle. Because several distinctly different metabolic processes are found in the various BMCs studied to date, it has been proposed that a common advantage to packaging these pathways within shell-bound compartments is to optimize the concentration of volatile metabolites in the BMC by maintaining an interior pH that is lower than that of the cytoplasm. We have tested this idea by recombinantly fusing a pH-sensitive green fluorescent protein (GFP) to ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), the major enzyme component inside the carboxysome. Our results suggest that the carboxysomal pH is similar to that of its external environment and that the protein shell does not constitute a proton barrier. The explanation for the sundry BMC functions must therefore be sought in the characteristics of the pores that traverse their shells.

Structure of Halothiobacillus neapolitanus carboxysomes by cryo-electron tomography.

Carboxysomes are polyhedral bodies consisting of a proteinaceous shell filled with ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO). They are found in the cytoplasm of all cyanobacteria and some chemoautotrophic bacteria. Previous studies of Halothiobacillus neapolitanus and Nitrobacter agilis carboxysomes suggest that the structures are either icosahedral or dodecahedral. To determine the protein shell structure more definitively, purified H. neapolitanus carboxysomes were re-examined by cryo-electron tomography and scanning transmission electron microscopy (STEM). Due to the limited tilt angles in the electron microscope, the tomographic reconstructions are distorted. Corrections were made in the 3D orientation searching and averaging of the computationally extracted carboxysomes to minimize the missing data effects. It was found that H. neapolitanus carboxysomes vary widely in size and mass as shown by cryo-electron tomography and STEM mass measurements, respectively. We have aligned and averaged carboxysomes in several size classes from the 3D tomographic reconstruction by methods that are not model-biased. The averages reveal icosahedral symmetry of the shell, but not of the density inside it, for all the size classes.

Gastric and hepatocellular carcinomas do not overexpress the same ribosomal protein messenger RNAs as colonic carcinoma.

The levels of a number of ribosomal protein mRNAs are reported to be increased in human colon cancer. We have assessed whether selected ribosomal protein mRNAs are overexpressed in other gastrointestinal malignancies, namely gastric and hepatocellular carcinomas. Subtracted complementary DNA libraries were generated from paired samples of human (a) colorectal carcinoma minus adjacent normal colonic mucosa and (b) hepatocellular carcinoma minus adjacent normal liver. Screening of approximately 3% of these library clones determined that ribosomal protein mRNAs encoding L18 and L37 (not previously reported) and P0 and S6 were overexpressed in one or the other library. Their complementary DNA inserts were then used as probes to evaluate their expression in a larger number of paired tumor/normal surgical samples of human colonic, gastric, and hepatocellular carcinomas, by Northern hybridization. The mRNA signal was greater in the colonic carcinoma than in paired adjacent normal colonic mucosa in 38 of 42 cases for P0 [tumor/normal (T/N) ratio = 3.0 +/- 0.3, mean +/- SE, P < 0.001] (G. F. Barnard, R. J. Staniunas, S. Bao, K. Mafune, J. L. Gollan, G. D. Steele, Jr., and L. B. Chen, Cancer Res., 52: 3067-3072, 1992), in 25 of 28 cases for L18 (T/N ratio = 3.7 +/- 0.5, P < 0.001), in 27 of 28 cases for L37 (T/N ratio = 5.3 +/- 0.4, P < 0.001), and in 24 of 28 cases for S6 (T/N ratio = 3.1 +/- 0.5, P < 0.01). The level of mRNA overexpression of L18 and S6 did not correlate with the Dukes' stage of disease. In hepatocellular carcinoma samples, using the same four ribosomal protein complementary DNA probes, only P0 mRNA was significantly increased (T/N ratio = 2.8 +/- 0.4, n = 6, P = 0.047). In gastric carcinoma samples, none of these mRNAs was increased (mean T/N ratios = 0.9-1.2, n = 6). Therefore, gastric and hepatocellular carcinomas do not overexpress the same ribosomal protein mRNAs as do colonic carcinoma.

Cognitive function in patients with symptomatic dilated cardiomyopathy before and after cardiac transplantation.

Pre- and postoperative cognitive performance of candidates for heart transplantation was examined by means of an extensive battery of neuropsychological measures. A total of 54 patients completed the preoperative cognitive protocol, 20 of whom also completed postoperative testing. Age (less than 50 or greater than or equal to 50 years of age) and the primary cause of cardiac deterioration (idiopathic, ischemic disease or rheumatic/congenital defects) were the major classification variables. The main findings of this study were: 1) Preoperative neuropsychological measures revealed a high frequency of impaired performance, particularly in measures of memory, higher level processing of information and motor speed. A pattern consistent with diffuse rather than focal or lateralized cerebral deficits was observed. Significant differences were not found on the basis of the cause of cardiac disease, but some were observed for age (the older group was more impaired). 2) A comparison of pre- and postoperative cognitive scores failed to show significant cognitive improvement despite greatly improved physical health. The cause of cardiac deterioration was not differentially associated with postoperative cognitive performance, and there was equivocal evidence for age effects. These findings may have implications for the selection of transplant recipients and the timing of transplantation surgery.

Multi-level assessment protocol (MAP) for adoption in multi-site clinical trials.

The National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN) is intended to test promising drug abuse treatment models in multi-site clinical trials, and to support adoption of new interventions into clinical practice. Using qualitative research methods we asked: How might the technology of multi-site clinical trials be modified to better support adoption of tested interventions? A total of 42 participants, representing 8 organizational levels ranging from clinic staff to clinical trial leaders, were interviewed about their role in the clinical trial, its interactions with clinics, and intervention adoption. Among eight clinics participating in the clinical trial, we found adoption of the tested intervention in one clinic only. In analysis of interview data we identified four conceptual themes which are likely to affect adoption and may be informative in future multi-site clinical trials. We offer the conclusion that planning for adoption in the early stages of protocol development will better serve the aim of integrating new interventions into practice.

Effects of low dose enoximone for chronic congestive heart failure.

To examine the short-term hemodynamic and long-term clinical effects of oral enoximone at low doses, 12 patients with severe, chronic congestive heart failure (CHF) were given 1 mg/kg oral enoximone and followed with serial hemodynamic measurements for 24 hours. Control cardiac index was 1.9 +/- 0.5 liters/min/m2 and it increased significantly by 1 hour, with a peak effect at 2 hours to 2.4 +/- 0.4 liters/min/m2 (p less than 0.05). Similarly, wedge pressure, 22 +/- 8 mm Hg at control, decreased to 16 +/- 10 by 1 hour (p less than 0.05). Six of the 12 patients received 1 mg/kg of enoximone on day 1 and 2 mg/kg on day 2. The higher dose of enoximone caused no further improvement in cardiac performance but prolonged the salutary hemodynamic effect. Subsequently, 79 patients (18 in New York Heart Association class III and 61 in class IV) with CHF (ejection fraction 17 +/- 8%) were followed over a 3 year period; the average enoximone dose was 1.7 +/- 0.7 mg/kg 3 times daily. Improvement of at least 1 functional class occurred in 55 patients (70%) at 1 month, 27 patients (34%) at 6 months and 19 (24%) maintained their improvement for over 1 year. Enoximone was discontinued in 20 patients (25%); in 5 (6%) for adverse effects and in 13 patients because of no clinical benefit. Adverse effects occurred in 14 patients (18%); 6% of all patients required discontinuation of drug. Six month survival was 50%, 42% at 1 year and 30% at 2 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic cardiomyoplasty: expectations and results.

BACKGROUND: Cardiac transplantation is an option for only a small minority of patients with severe, chronic congestive heart failure. Transformed skeletal muscle has the potential to provide a durable form of fatigue-resistant muscle power to assist the cardiovascular system. METHODS: Since the first dynamic cardiomyoplasty performed by Carpentier and colleagues in 1985, the techniques to make this operative procedure an effective assist to the failed myocardium have been refined. Much has been learned about optimum patient selection so that perioperative morbidity and mortality is minimized. The cardiomyostimulator developed by Medtronic has undergone several revisions, primarily so that the stimulation of the muscle wrap is adaptive to variations in cardiac performance, such as those that occur with arrhythmia or during exercise. RESULTS: A review of the data to date suggest a substantial number of patients who undergo the procedure experience an enhanced quality of life, and an alleviation of their heart failure symptoms. Details of patient selection underscore that cardiomyoplasty is not an alternative to transplant. Seriously compromised patients with low peak oxygen uptake and very low ejection fractions have the highest short term mortality. CONCLUSIONS: Dynamic cardiomyoplasty remains a promising surgical option for patients with moderately-severe congestive heart failure (i.e. NYHA Class III patients). The ongoing randomized trial comparing cardiomyoplasty to standard medical therapy is expected to provide more detailed information about the benefits of this procedure.

Retrospective risk analysis for early heart-related death after cardiomyoplasty. The Worldwide Cardiomyoplasty Group.

BACKGROUND: Dynamic cardiomyoplasty is an evolving treatment for heart failure that uses an electrically stimulated latissimus dorsi muscle wrapped around the heart to improve cardiac function. Preoperative patient characteristics and deaths after cardiomyoplasty have been recorded during the past 5 years in a cumulative database representing worldwide experience of 42 medical centers. METHODS: Statistical models of hazards (monthly death rates) were used to identify risk factors for transiently increased risk of cardiovascular mortality within 2 months after cardiomyoplasty. RESULTS: Actuarial survival (n = 261) was 88%, 80%, and 76% at 1, 3, and 6 months after cardiomyoplasty, respectively. The peak hazard of 6% dying per month occurred during the first month after the surgical procedure. Lower ejection fraction, increased number of major coronary arteries with > or = 70% stenotic lesions, and lower chronotropic responses during exercise were independent risk factors for the transient increase in early cardiovascular mortality. Early risk of cardiovascular mortality was significantly reduced as centers gained experience with more than 3 patients. CONCLUSION: Early survival after cardiomyoplasty has improved with experience and might be reduced further by preoperative assessments that identify patients at highest risk.

Diagnosis and management of iron-induced heart disease in Cooley's anemia.

Patients with homozygous beta-thalassemia are chronically transfused and, if not assiduously chelated, are at risk for cardiac dysfunction. Available data suggest that even in optimally chelated patients, cardiac pathology is abnormal secondary to iron deposition, fibrosis, hypertrophy, and the structural effects of chronic anemia. Evidence of myopericarditis may also be found. Cardiac performance is usually only subtly affected, primarily with diastolic abnormalities not routinely detected on echocardiograms or nuclear scan. In poorly chelated patients, severe heart failure occurs and is easily predictable but invariably fatal, despite treatment with diuretics, vasodilators, inotropes, and antiarrhythmics. Based on successful prevention of heart failure with ACE inhibitors in other forms of cardiomyopathy, we suggest multicenter trials to explore methods to stabilize cardiac function in patients at risk for iron-induced heart disease. Long-term adverse effects of iron deposition, diastolic dysfunction, and abnormal hormone regulation need to be quantitated in patients reaching their third and fourth decades when the potential for ischemic cardiac disease could compound cardiac dysfunction.

Diagnosing proximal tubal obstruction: evaluation of peak intrauterine pressures using four common cannula techniques in extirpated uteri.

OBJECTIVE: To compare the ability of four chromotubation techniques to generate and maintain intrauterine pressures in the diagnosis of proximal tubal obstruction. METHODS: Sixteen extirpated uteri were used for this study. A pressure catheter was placed through the fundus into the endometrial cavity. Three cannulas were evaluated: 1) the Cohen cannula with hold and no-hold techniques, 2) the BARD cervical cannula (dual intrauterine and intracervical balloons), and 3) the Harris-Kronner uterine manipulator-injector catheter with an intrauterine balloon. Intrauterine pressures were monitored while warm saline was infused. The studies were performed with the tubes obstructed, and measurements of peak attainable intrauterine pressures were recorded. Data were analyzed by t test, with significance set at P < .05. RESULTS: Peak intrauterine pressures for the four groups were as follows: 1) Cohen cannula, not holding, 40.7 +/- 5.1 mmHg; 2) Cohen cannula, holding in place, 63.6 +/- 5.3 mmHg; 3) BARD cannula, 112.4 +/- 3.5 mmHg; and 4) Harris-Kronner cannula, 106.3 +/- 4.3 mmHg. The BARD and Harris-Kronner cannulas achieved significantly higher intrauterine pressures than either method of using the Cohen cannula (P < .001). There was no statistically significant difference between the BARD and Harris-Kronner cannulas. CONCLUSION: Significant differences in achievable intrauterine pressures were demonstrated among catheters in our in vitro model. Based on these findings, we believe that the BARD, Harris-Kronner, or other intrauterine balloon-type cannula should be used before diagnosing proximal tubal obstruction.

Lisinopril versus placebo in the treatment of heart failure: the Lisinopril Heart Failure Study Group.

Lisinopril, a long-acting, angiotensin-converting enzyme inhibitor, was compared with placebo in a randomized, parallel, double-blind, 12-week study of 193 patients with heart failure. All patients were New York Heart Association Functional Class II, III, or IV and had remained symptomatic despite optimal dosing with digoxin and diuretics. After 12 weeks of therapy, the improvement in treadmill exercise duration was greater in the lisinopril group (113 seconds) compared with the placebo group (86 seconds). This improvement in exercise duration was particularly evident in patients with left ventricular ejection fractions less than 35% (lisinopril = 130 seconds; placebo = 94 seconds). In patients receiving lisinopril, the increase in exercise duration was accompanied by an improvement in quality of life as measured by the Yale Scale Dyspnea/Fatigue Index and in signs and symptoms of heart failure. In addition, the lisinopril group had a larger mean increase (3.7%) in left ventricular ejection fraction when compared with the placebo group (1.3%). Thus, lisinopril, administered once daily for 12 weeks, was well tolerated and efficacious in the treatment of heart failure when used concomitantly with diuretics and digoxin.

Identification and management of potential heart transplant recipients.

Transplantation should be performed to improve the quality and duration of life in patients with end-stage cardiac disease. Symptoms, left ventricular ejection fraction, previous and present medications, and an exercise tolerance test serve as basic screening information to identify potential transplant candidates. Patients need to have a psychological, financial, and behavioral profile that will allow them to withstand the rigors of the entire transplantation process, and have no other medical problems that would jeopardize their survival following transplant surgery. Maintenance of the patient's status while awaiting a cardiac donor begins with patient education and a search into the causes of underlying ventricular dysfunction. Medications subsequently used include diuretic agents, vasodilators, digitalis, anticoagulants, antiarrhythmics, and possibly beta-blocker therapy. When standard measures fail, potent inotropes and even mechanical assist devices are sometimes necessary. Future donor heart allocations will require more rigid criteria for the selection of cardiac transplant candidates.

Treatment of advanced heart failure.

The incidence of chronic heart failure has increased, with a corresponding increase in morbidity and mortality, and has made a substantial financial impact on our society. Improved therapy for heart failure has resulted in a significant prolongation of survival, a decreased number of hospitalizations, and an enhanced quality of life for many patients. It can reasonably be expected, therefore, that adherence to a rational medical regimen for these patients might decrease costs as well. Management of patients with severe heart failure begins with identifying the etiology and educating the patients and their families. Angiotensin-converting enzyme inhibitors are the cornerstone of therapy but only after diagnostic tests are performed to establish the etiology and extent of myocardial dysfunction. Because cardiac transplantation is a therapeutic option for only a limited number of patients, other surgical and medical therapies have to be viewed as the mainstay of a treatment strategy.

Designing clinical trials on energy healing: ancient art encounters medical science.

Demand for energy healing is growing rapidly in the United States. Until recently, however, few clinical trials have been conducted to investigate its clinical efficacy, risks, and cost-effectiveness. This article discusses principles underlying the research design of clinical trials on energy healing, based on the experience of an interdisciplinary team conducting a large-sample clinical study on qigong funded by the National Institutes of Health. The first part overviews the background and contemporary practice of qigong therapy. The second addresses some difficulties and unique issues to be considered in designing a clinical trial on energy healing. These issues include research emphasis on outcome versus mechanism, randomization, control, expectations/placebo effects, staff and practitioner bias/conflict of interest, patients' belief, selection bias, intent-to-treat analysis, ethics, informed consent, sample size, and outcome report. The ultimate goal is to promote more scholarly and clinical discussion on the evaluation of energy healing.

Managing congestive heart failure.

Congestive heart failure, a constellation of signs and symptoms that result from the heart's inability to provide sufficient oxygenated blood to metabolizing tissues, is a major cause for concern in the elderly. The prognosis is ominous, with a 10% per year mortality rate after the initial CHF episode, and a 30 to 60% per year rate for patients who remain symptomatic despite digitalis and diuretic treatment. Common etiologies in CHF are discussed, and a case history illustrating CHF symptomatology is provided. The role of diuretics, digitalis, ACE-inhibitors, and other pharmacologic agents is reviewed and updated, and the value of patient education is discussed.

Heart failure: clinical implications of systolic and diastolic dysfunction.

Morbidity and mortality from congestive heart failure (CHF) remain high for older patients with systolic or diastolic dysfunction. These two disease processes differ in clinical manifestations, physical findings, treatment options, and prognosis. No one physical findings is diagnostic, which underlines the importance of assessing LV function with Doppler echocardiography. Diastolic dysfunction has been shown to increase with age, although most data demonstrating effective medical therapy for CHF applies to patients with systolic dysfunction. The treatment of older patients with preserved systolic function and CHF is therefore difficult, due to incomplete understanding of diastolic dysfunction and limited data about specific drug therapies.

Addiction in women: prevalence, profiles, and meaning.

Biologic predisposition, stressors in the environment, and the extent and quality of social support in part explain the development of alcoholism and other drug dependencies in women. The nurse's approach to patients and use of effective tools for assessment of alcohol and drug use can result in increased identification and referrals for treatment.

Therapeutic jurisprudence: judicial and corrections panel.

Innovative therapeutic initiatives for the treatment of persons with substance abuse problems have been implemented in the criminal justice systems of California and Arizona. Judicial perspectives and reflections on these programs reveal the multiple issues inherent in innovation and day-to-day operations, from collaboration to implementation, including attitudinal shifts, resource allocation, client issues, and the changing role of judges who practice therapeutic jurisprudence. A pioneering program of treatment for dual disorders among male offenders addresses multiple issues in the provision of psychological services in a forensic setting in California.

Mirror, mirror on the wall: who is the true nurse after all?

This somewhat colloquial reflection on personal experience reveals some commonly perceived images and metaphors pertaining to nursing that have been birthed in history, perpetuated by the media, and entrenched in the minds of both onlookers and, unfortunately, of those not quite so detached. The reader might identify with some, and be amazed at others, or be provoked on a similar journey of reminiscence and reconsideration of the images that have shaped and informed their practice. The literature presents the not always positive portrayal of nursing, and the resultant adverse effect this exerts not only upon the profession, but upon its practitioners as well. Thus is set forth the challenge of how to respond.