Effect of anatomical fractionation on the enzymatic hydrolysis of acid and alkaline pretreated corn stover.

Due to concerns with biomass collection systems and soil sustainability there are opportunities to investigate the optimal plant fractions to collect for conversion. An ideal feedstock would require a low severity pretreatment to release a maximum amount of sugar during enzymatic hydrolysis. Corn stover fractions were separated manually and analyzed for glucan, xylan, acid soluble lignin, acid insoluble lignin, and ash composition. The stover fractions were also pretreated with either 0%, 0.4%, or 0.8% NaOH for 2 h at room temperature, washed, autoclaved and saccharified. In addition, dilute sulfuric acid pretreated samples underwent simultaneous saccharification and fermentation (SSF) to ethanol. In general, the two pretreatments produced similar trends with cobs, husks, and leaves responding best to the pretreatments, the tops of stalks responding slightly less, and the bottom of the stalks responding the least. For example, corn husks pretreated with 0.8% NaOH released over 90% (standard error of 3.8%) of the available glucan, while only 45% (standard error of 1.1%) of the glucan was produced from identically treated stalk bottoms. Estimates of the theoretical ethanol yield using acid pretreatment followed by SSF were 65% (standard error of 15.9%) for husks and 29% (standard error of 1.8%) for stalk bottoms. This suggests that integration of biomass collection systems to remove sustainable feedstocks could be integrated with the processes within a biorefinery to minimize overall ethanol production costs.

Knowledge, compliance and serum phenylalanine concentrations in adolescents and adults with phenylketonuria and the effect of a patient-focused educational resource.

BACKGROUND: There is a lack of dedicated resources for adolescent and adult patients with phenylketonuria (PKU) and few studies have examined dietary practices within this group. METHODS: One hundred and seventy-seven PKU patients were sent questionnaires to assess dietary compliance and the preferred format for an educational resource. Seventy-one patients responded; 32 following diet were recruited to assess the resource's impact on test variables. The results were compared for the intervention group (n = 22) and control group (n = 10) at baseline, and 1 and 6 months after resource intervention. RESULTS: Most patients were aware of dietary recommendations, although this did not always result in compliance. The preferred resource format was a filofax-style folder with inserts (P < 0.05). There was a significant difference in the extent of change in knowledge score between baseline and 1 month in favour of the intervention group (P < 0.05). The improvement in knowledge was not accompanied by a significant improvement in measures of compliance. CONCLUSIONS: These findings add to the knowledge base about this patient group and support the use of patient involvement in resource development. It is likely that the test parameters used were not sensitive enough to pick up subtle and longer-term effects on compliance.

The Patient With Excessive Worry

Worry is a normal response to uncertainty. Education; empathetic support; reassurance; and passage of time usually ameliorate ordinary worries. However; these common-sense strategies for dealing with transient worries often prove ineffective for patients with excessive worry; many of whom meet the criteria for disorders in the Diagnostic and Statistical Manual of Mental Disorders; 4th ed. Evidence-based treatments for such disorders can assist family physicians in management of persistent worry as a self-perpetuating habit across diagnostic categories. Antidepressants and cognitive behavioural therapy are effective treatments for various disorders characterised by excessive worry. Cognitive behavioural strategies that may be adapted to primary care contacts include education about the worry process; repeated challenge of cognitive distortions and beliefs that underpin worry; behavioural exposure assignments (e.g.; scheduled worry periods; worry journals); and learning mindfulness meditation

Determining nitrogen fractions in swine slurry.

Nutrient management plans are used to reduce non-point source pollution from animal operations. These plans require manure analysis and use indices to determine nutrient availability. This study evaluated a modified method for determining nitrogen fractions in swine slurry stored under slatted floors, calculating plant available nitrogen, and characterizing nitrogen fractions by holding pit depth. Manure samples were collected from gestating sow and finishing pig holding pits at discrete depths. Ammonium, amino acid, and amino sugar concentrations were significantly different for gestation holding pits by depth, but finishing pig holding pit values were not significantly different by depth. Plant available nitrogen was approximately 74% for gestation and 67% for finishing barn manures. Nitrogen fraction analysis suggests land application of swine manure for crop growth should be managed based on type of nitrogen present in the manure, which can be highly correlated to animal growth stage.

HIV-1 and recurrence, relapse, and reinfection of tuberculosis after cure: a cohort study in South African mineworkers.

BACKGROUND: The proportion of recurrent tuberculosis cases attributable to relapse or reinfection and the risk factors associated with these different mechanisms are poorly understood. We followed up a cohort of 326 South African mineworkers, who had successfully completed treatment for pulmonary tuberculosis in 1995, to determine the rate and mechanisms of recurrence. METHODS: Patients were examined 3 and 6 months after cure, and then were monitored by the routine tuberculosis surveillance system until December, 1998. IS6110 DNA fingerprints from initial and subsequent episodes of tuberculosis were compared to determine whether recurrence was due to relapse or reinfection All patients gave consent for HIV-1 testing. FINDINGS: During follow-up (median 25.1 months, IQR 13.2-33.4), 65 patients (20%) had a recurrent episode of tuberculosis, a recurrence rate of 10.3 episodes per 100 person-years at risk (PYAR)-16.0 per 100 pyar in HIV-1-positive patients and 6.4 per 100 pyar in HIV-1-negative patients. Paired DNA fingerprints were available in 39 of 65 recurrences: 25 pairs were identical (relapse) and 14 were different (reinfection). 93% (13/14) of recurrences within the first 6 months were attributable to relapse compared with 48% (12/25) of later recurrences. HIV-1 infection was a risk factor for recurrence (hazard ratio 2.4, 95% CI 1.5-4.0), due to its strong association with disease caused by reinfection (18.7 2.4-143), but not relapse (0.58; 0.24-1.4). Residual cavitation and increasing years of employment at the mine were risk factors for relapse. INTERPRETATION: In a setting with a high risk of tuberculous infection, HIV-1 increases the risk of recurrent tuberculosis because of an increased risk of reinfection. Interventions to prevent recurrent disease, such as lifelong chemoprophylaxis in HIV-1-positive tuberculosis patients, should be further assessed.

Family physicians' observations of their practice, well being, and health care in the United States.

OBJECTIVE: Our goal was to characterize how family physicians perceive recent changes in the health care system and how content they are with various factors. STUDY DESIGN: We performed a cross-sectional mailed survey. POPULATION: The survey was completed by a random sample of 361 family physicians practicing in the United States. OUTCOME MEASURES: The survey evaluated attitudes about corporate managed care, health care reform, career satisfaction, compensation, personal life satisfaction, workload stress, personal well-being, and residency training. We reported percentages for Likert-rated survey items, factor analysis of the survey, and a regression model for statistical prediction of the 4 major factors. RESULTS: Relative to survey data gathered in 1996, fewer family physicians in our survey reported that they were satisfied with their careers (59% vs 82%); fewer were satisfied with their compensation (55% vs 65%); and fewer would again choose family practice as their specialty (66% vs 75%). Thirty-one percent worried that they were "burning out" as physicians, and 48% reported that they had experienced more stress-related symptoms in the past year. Only 7% agreed that corporate managed care is the best way to provide the health care America needs at a cost society can afford, but only 36% unequivocally endorsed the concept of a national health plan. Forty-two percent of the respondents reported that they had witnessed bad patient outcomes they perceived to be attributable to managed care business processes. CONCLUSIONS: The morale and career satisfaction of family physicians seems to have eroded in recent years, and discontent is common. As a group, family physicians are unhappy with the current health care system and quite unified about certain specific reforms, yet they are far from such consensus about more sweeping reform.

Tuberculosis control and molecular epidemiology in a South African gold-mining community.

BACKGROUND: Gold miners have very high rates of tuberculosis. The contribution of infections imported into mining communities versus transmission within them is not known and has implications for control strategies. METHODS: We did a prospective, population-based molecular and conventional epidemiological study of pulmonary tuberculosis in a group of goldminers. Clusters were defined as groups of patients with Mycobacterium tuberculosis isolates with identical IS6110 DNA fingerprints. We compared the frequency of possible risk factors in the clustered and non-clustered patients whose isolates had fingerprints with more than four bands, and re-interviewed members of 45 clusters. FINDINGS: Of 448 patients, ten were excluded because they had false-positive cultures. Fingerprints were made in 419 of 438, of which 371 had more than four bands. 248 of 371 were categorised into 62 clusters. At least 50% of tuberculosis cases were due to transmission within the community. Patients who had failed treatment at entry to the study were more likely to be in clusters (adjusted odds ratio 3.41 [95% CI 1.25-9.27]). Patients with multidrug-resistant isolates were more likely to have failed treatment but were less likely to be clustered than those with a sensitive strain (0.27 [0.09-0.83]). HIV infection was common (177 of 370 tested) but not associated with clustering. INTERPRETATION: Despite a control programme that cures 86% of new cases, most tuberculosis in this mining community is due to ongoing transmission. Persistently infectious individuals who have previously failed treatment may be responsible for one third of tuberculosis cases. WHO targets for cure rates are not sufficient to interrupt transmission of tuberculosis in this setting. Indicators that are more closely linked to the rate of ongoing transmission are needed.

Drug-resistant pulmonary tuberculosis in a cohort of southern African goldminers with a high prevalence of HIV infection.

OBJECTIVES: To determine rates of drug resistance to Mycobacterium tuberculosis and associated risk factors, including HIV infection. DESIGN: Prospective cohort study of patients with pulmonary tuberculosis. SETTING: The study population comprised 28,522 men working on four goldmines in Westonaria, Gauteng. Health care is provided at a 240-bed mine hospital, Gold Fields West Hospital, and its primary health care facilities. SUBJECTS: All 425 patients with culture-positive pulmonary tuberculosis identified in 1995. OUTCOME MEASURES: Tuberculosis drug resistance on enrollment and after 6 months' treatment. RESULTS: There were 292 cases of new tuberculosis, 77 of recurrent disease and 56 prevalent cases in treatment failure. Two hundred and seven patients (48.7%) were HIV infected. Primary resistance to one or more drugs (9%) was similar to the 11% found in a previous study done on goldminers in 1989. Primary multidrug resistance (0.3%) was also similar (0.8%). Acquired multidrug resistance was 18.1%: 6.5% for recurrent disease and 33.9% in treatment failure cases. Neither HIV infection nor the degree of immunosuppression as assessed by CD4+ lymphocyte counts was associated with drug resistance at the start or end of treatment. New patterns of drug resistance were present in 9 of 52 patients in treatment failure at 6 months, 1 of whom was HIV-infected. CONCLUSION: Primary and acquired drug resistance rates are stable in this population and are not affected by the high prevalence of HIV infection.

Risk factors for pulmonary disease due to culture-positive M. tuberculosis or nontuberculous mycobacteria in South African gold miners.

The aim of this study was to determine risk factors for disease due to nontuberculous mycobacteria (NTM) compared to those due to Mycobacterium tuberculosis in South African gold miners with pulmonary mycobacterial disease. A case/control study comparing tuberculosis and NTM cases amongst all patients with a positive sputum mycobacterial culture in 1995 was carried out. The 51 cases of disease due to NTM and 425 tuberculosis cases were similar with regard to age, education, home region, smoking habits and percentage of CD4 cells. After adjustment for confounders, those with NTM were more likely to have had previous tuberculosis treatment (odds ratio (OR) 3.61; 95% confidence interval (CI) 1.9-6.9), have worked longer underground (p-value for trend=0.05) or have evidence of silicosis (OR 12.6; 95% CI 2.2-71) and were less likely to drink regularly (OR 0.12; 95% CI 0.02-0.93) than patients with tuberculosis. In patients with disease due to NTM, 35.3% were human immunodeficiency virus-positive compared with 48.8% of tuberculosis patients (p=0.2) and an estimated 21% overall in the mines at the time of the study. Previous tuberculosis treatment, silicosis and duration of underground work are even more strongly associated with disease due to nontuberculous mycobacteria than with tuberculosis. Attempts to reduce the incidence of all pulmonary mycobacterial disease in this community should address recognized risk factors and ensure that those with tuberculosis are diagnosed, treated and cured.

Reperfusion induces myocardial apoptotic cell death.

OBJECTIVE: The purpose of the present study was to investigate whether apoptosis is triggered during ischemia (I) and reperfusion (R) and whether I/R-induced apoptosis is correlated with changes in expression of Bcl-2 and Bax. METHODS: Anesthetized open-chest dogs were divided into two groups. Group I: 7 h of permanent I without R (PI, n = 7); Group II: 60 min I followed by 6 h R (I/R, n = 8). Apoptosis was identified as "DNA ladder" by agarose gel electrophoresis or confirmed histologically using the terminal transferase UTP nick end labeling (TUNEL) assay. RESULTS: Collateral myocardial coronary blood flow during I, confirmed by colored microspheres was comparable in both groups. Although PI caused 72 +/- 5% infarct size, very few TUNEL-positive cells were detected in the necrotic area (0.2 +/- 0.1% of total normal nuclei), consistent with an absence of DNA laddering. In contrast, the appearance of TUNEL-positive cells was significantly displayed after 6 h R in the necrotic area in I/R group (26 +/- 4%, P < 0.001 vs. PI group), and DNA ladder occurred in all experimental animals, suggesting that myocardial apoptosis is primarily elicited by R. Densitometrically, Western blot analysis showed significant reduction in expression of Bcl-2 (16 +/- 1%) and increase in Bax (29 +/- 8%) after 6 h R in the necrotic area compared with normal tissue while expression of these two proteins was not changed in the PI group. Polymorphonuclear neutrophil (PMN) accumulation in the necrotic area determined either by immunohistochemistry with anti-CD18 antibody or by myeloperoxidase activity was significantly increased in the I/R group compared to the PI group (358 +/- 24 vs. 24 +/- 2, mm2 myocardium, P < 0.01) and (2.9 +/- 0.3 vs. 0.4 +/- 0.1, U/100 mg tissue, P < 0.01). There was a significant linear relationship between CD18-positive PMNs and TUNEL-positive cells (P < 0.05) in the I/R group. CONCLUSIONS: These results indicate that (1) PI without R did not induce apoptotic cell death, while two types of cell death, necrosis and apoptosis were found after I/R, (2) the Bcl-2 family may participate in early R-induced myocardial apoptosis, (3) PMN accumulation may play a role in the development of apoptosis.

Tuberculosis treatment failure and drug resistance--same strain or reinfection?

Tuberculosis patients may have Mycobacterium tuberculosis in their sputum at the end of treatment, and may show new drug resistance, due to either inadequate treatment of the original episode or reinfection with a new strain during therapy. In a cohort study of mineworkers with tuberculosis in South Africa, 57 of 438 patients had positive sputum cultures 6 months after recruitment in 1995. Of the 31 patients who initially had fully sensitive strains, 3 developed multidrug resistance (MDR) and 3 single-drug resistance (SDR). Of the 6 who started with SDR, 3 became MDR. HIV infection was not associated with drug resistance at enrollment or 6 months later. We compared pairs of DNA fingerprints from isolates of M. tuberculosis at recruitment and 6 months later in the 48 patients for whom we had both available. In 45, the pairs were identical. In 1 patient, although both isolates were fully sensitive, the later fingerprint had 1 less band (transposition). In 2 pairs, the fingerprint patterns were completely different: one seemed to be the result of laboratory error and the other was a true reinfection with an MDR strain. Despite a high risk of infection, with a moderate proportion of background drug-resistant strains (11% SDR, 6% MDR), reinfection is not a common cause of treatment failure or drug resistance at 6 months.

Proposed design modifications to reduce risk of operating rotary field mowers.

The primary objective of this project was to reduce risk of injury associated with operating a rotary mower driven by a tractor power take-off (PTO) by developing and evaluating design improvements and determining their economic feasibility. Researchers have concluded that alteration of machinery design has a greater impact on the reduction of accidents than safety training. Implementation of an Operator Presence Sensing System (OPSS) and removal of the PTO are the two injury-reducing, engineering modifications evaluated by this research. Hydraulic power allows this to occur by providing dynamic braking, few moving parts (removal of the PTO), and controllable power. A hydraulic circuit was developed to power the mower and to enable an OPSS. Tractor hydraulics were simulated using a hydraulic training bench. Two mower configurations were tested: 6.55 cm3 rev(-1) (0.4 in.3 rev(-1)) displacement motor with a 0.748 kg blade and 47.5 cm3 rev(-1) (2.9 in.3 rev(-1)) displacement motor with a 9.4 kg blade. A PTO-driven rotary mower was not used to test the circuit due to spatial and safety limitations of the hydraulic training bench. Results from the first mower configuration verified the concepts behind the hydraulic circuit. The second configuration verified the OPSS and indicated the applicability of the circuit to a rotary mower.

Administration of adenosine during reperfusion reduces injury of vascular endothelium and death of myocytes.

INTRODUCTION: To test the hypothesis that administration of adenosine during reperfusion attenuates endothelial dysfunction and extension of infarct size by inhibiting polymorphonuclear neutrophil (PMN)-mediated events and apoptosis. METHODS: Anesthetized dogs were subjected to 1 h coronary artery occlusion and 6 h of reperfusion with infusion of saline (vehicle, n = 8) or 140 micrograms/kg per min adenosine, n = 8) continuously into the left atrium starting 5 min before reperfusion and continuing for 2 h. RESULTS: There was no intergroup difference in collateral myocardial blood flow measured by using colored microspheres in the area at risk during ischemia. Infusion of adenosine transiently improved segmental shortening (4.1 +/- 3.1% versus -2.5 +/- 2.3%, P < 0.05) and segmental work (41.4 +/- 22 versus 15 +/- 13 mmHg/mm, P < 0.05) after 4 h of reperfusion. Infusion of adenosine reduced size of infarct (determined by staining with triphenyltetrazolium chloride) from 27 +/- 2% with vehicle to 14 +/- 1%, (P < 0.05). This was confirmed by measuring that it lowered activity of plasma creatine kinase (from 19 +/- 2 versus 8 +/- 1 IU/g protein, P < 0.05). It also reduced the proportion of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive nuclei in the perinecrotic zone from 17.3 +/- 1.6 to 10.3 +/- 1.0% (P < 0.05) and reduced the appearance of DNA ladders in gel electrophoresis. In addition, it significantly decreased accumulation of PMN in the ischemic area (determined by immunohistochemistry with anti-CD18 antibody) and activity of cardiac myeloperoxidase compared with vehicle (439 +/- 52 versus 183 +/- 20 PMN/mm2 myocardium and 1.1 +/- 0.1 versus 2.4 +/- 0.2 U/100 mg tissue, P < 0.05, respectively). Furthermore, infusion of adenosine during reperfusion preserved vascular endothelial function expressed in terms of a decrease in adherence of PMN to postischemic coronary artery endothelium (63 +/- 3 versus 36 +/- 4 PMN/mm2 endothelium, P < 0.05, basal function) and agonist (acetylcholine)-induced endothelium-dependent relaxation (negative logarithm to base 10 of concentration (mol/l) for half-maximal effect 7.7 +/- 0.1 versus 7.2 +/- 0.1, P < 0.05, stimulated function). Infusion of adenosine directly inhibited generation of superoxide radical from canine PMN in vitro dose dependently from 27.8 +/- 6.3 to 5.8 +/- 2.1 nmol/l/5 x 10(6) PMN (P < 0.05). CONCLUSION: Intra-atrial infusion of adenosine during reperfusion reduced accumulation of PMN in area at risk, preserved vascular endothelial function after ischemia-reperfusion by inhibiting interaction between PMN and endothelial cells, and decreased extension of infarct, possibly by limiting apoptosis.

Adenosine-supplemented blood cardioplegia attenuates postischemic dysfunction after severe regional ischemia.

BACKGROUND: Various studies have reported that the administration of adenosine (ADO) in cardioplegia reduces myocardial ischemic injury, but this timing may not utilize ADO's potential against myocardial reperfusion injury. This study tested the hypothesis that ADO-supplemented blood cardioplegia (BCP) or ADO administered during reperfusion reduces postischemic dysfunction after severe regional ischemia. METHODS AND RESULTS: After 75 minutes of left anterior descending coronary artery occlusion, total cardiopulmonary bypass was initiated; cold (4 degrees C) antegrade BCP (8:1 blood:crystalloid) was delivered every 20 minutes for the first 3 doses, and 27 degrees C BCP was delivered for the terminal infusion. Dogs (n=6 per group) received unsupplemented BCP, ADO (100 micromol/L/L) supplemented in all infusions of BCP (ADO-CP), or ADO (100 micromol x L(-1) x L(-1)) supplemented only in the terminal infusion of BCP followed by intravenous ADO (140 microg x kg(-1) x min(-1)) infusion for the first 30 minutes of reperfusion (ADO-R). Postischemic regional systolic shortening was significantly greater in the ADO-R group (5+/-2.0%) than in the BCP group (-3+/-1.0%), but not in the ADO-CP group (2+/-0.2%). Postischemic regional diastolic stiffness in the area at risk during end reperfusion was lower with ADO-R (1.8+/-0.3%) than with ADO-CP (2.7+/-0.3%) or BCP (4.4+/-0.5%). Infarct size was reduced in the ADO-CP (29+/-2%) and ADO-R (21+/-2%) groups compared with the BCP group (42+/-4%). Edema in the myocardial area at risk was decreased in the ADO-CP (82+/-0.2%) and ADO-R (80+/-0.4%) groups compared with the BCP group (86+/-0.7%). Adherence of fluorescently labeled neutrophils (PMNs) to postischemic coronary artery endothelium was attenuated by ADO-R (55+/-2 PMNs/mm(2)), but not by ADO-CP (114+/-5 PMNs/mm(2)), compared with BCP (118+/-3 PMNs/mm(2)). CONCLUSIONS: The results show that BCP supplemented with ADO reduces infarct size, preserves postischemic systolic and diastolic regional function but does not attenuate coronary artery endothelial dysfunction unless administered during reperfusion.

Human immunodeficiency virus and the outcome of treatment for new and recurrent pulmonary tuberculosis in African patients.

The purpose of this study was to evaluate the impact of human immunodeficiency virus (HIV) infection on treatment for tuberculosis (TB). The study population comprised 28,522 black Southern African gold miners. Patients with sputum culture-positive new or recurrent pulmonary TB diagnosed in 1995 were prospectively enrolled in the cohort. Directly observed therapy (DOT) was practiced and outcomes were assessed at 6 mo after treatment was begun. There were 376 cases of TB (incidence 1,318 per 100,000), of which 190 (50%) were HIV positive and 82 (22%) had recurrent TB. There was no association between HIV status and history of previous TB or drug resistance. Neither the treatment interruption rate (2%) nor the rate at which patients transferred out of the treatment program (1.6%) were associated with HIV status. Excluding deaths, cure rates were similar for HIV-positive and HIV-negative patients (89% versus 88%), but significantly lower in those with recurrent than in those with new TB (77% versus 92%). Mortality was 0.5% in HIV-negative patients versus 13.7% in HIV-positive patients, and in the latter group was associated with CD4(+) lymphocyte depletion. Autopsy examination showed that in HIV-positive patients, early mortality was due to TB whereas late deaths were most commonly due to cryptococcal pneumonia. The study showed that a well-run TB control program can result in acceptable cure rates even in a population with a very high incidence of TB and HIV infection. Particular vigilance is needed for concurrent infections, which may contribute significantly to mortality during treatment of TB in HIV-positive patients.

Ischemic preconditioning attenuates postischemic coronary artery endothelial dysfunction in a model of minimally invasive direct coronary artery bypass grafting.

OBJECTIVE: Unmodified reperfusion without cardioplegia in minimally invasive direct coronary artery bypass grafting procedures causes endothelial dysfunction that may predispose to polymorphonuclear neutrophil-mediated myocardial injury. This study tested the hypothesis that ischemic preconditioning in a minimally invasive direct coronary artery bypass grafting model attenuates postischemic endothelial dysfunction in coronary vessels. METHODS: In anesthetized dogs, the left anterior descending coronary artery was occluded for 30 minutes and reperfused for 3 hours without ischemic preconditioning (no-ischemic preconditioning; n = 7); in 7 dogs, the left anterior descending occlusion was preceded by 5 minutes occlusion followed by 5 minutes of reperfusion. Relaxation responses to stimulators of nitric oxide synthase were used to evaluate endothelial function in arteries from the ischemic-reperfused (left anterior descending) and nonischemic (left circumflex coronary artery) zones. RESULTS: Stimulated endothelial-dependent relaxation of epicardial left anterior descending artery to incremental concentrations of acetylcholine in the no-ischemic preconditioning animals was shifted to the right, and maximal relaxation was attenuated compared with the nonischemic left circumflex coronary artery (117% +/- 4% vs 138% +/- 5%). In contrast, acetylcholine-induced maximal relaxation was comparable in the left anterior descending artery versus left circumflex coronary artery in the ischemic preconditioning group (130% +/- 6% vs 135% +/- 5%). In 150- to 200- microm left anterior descending microvessels, 50% relaxation occurred with a lower concentration (log[M]) of acetylcholine in ischemic preconditioning versus no-ischemic preconditioning (-8.0 +/- 0.4 vs -7.0 +/- 0.1) with no group differences in smooth muscle relaxation to sodium nitroprusside, suggesting endothelial-specific damage. Adherence of fluorescent labeled polymorphonuclear neutrophils to epicardial coronary artery endothelium, used as an index of basal (unstimulated) anti-polymorphonuclear neutrophil function, was significantly attenuated by ischemic preconditioning versus no-ischemic preconditioning (293 +/- 25 polymorphonuclear neutrophils/mm2 vs 528 +/- 29 polymorphonuclear neutrophils/mm2). CONCLUSION: In this minimally invasive direct coronary artery bypass grafting model, both agonist-stimulated and basal postischemic endothelial dysfunction were attenuated by ischemic preconditioning.

Controlled intermittent asystole: pharmacologic potentiation of vagal-induced asystole.

BACKGROUND: Minimally invasive direct coronary artery bypass graft operations have, to date, displayed a higher rate of early graft failure than conventional coronary artery bypass procedures using extracorporeal technology. Construction of the coronary artery anastomosis on a beating heart versus a quiescent heart is likely an important factor in this difference between the two approaches. Controlled intermittent asystole induced by vagal stimulation to give transient nonchemically induced asystole for brief intervals sufficient for placement of coronary artery sutures might improve the precision of minimally invasive direct coronary artery bypass graft anastomoses and reduce graft failure while increasing the technical ease of operation. METHODS: The feasibility of producing transient, reversible asystole with combined vagus nerve stimulation and treatment with a pharmacologic regimen of (1) an acetylcholinesterase inhibitor (pyridostigmine, 0.5 mg/kg), (2) a beta-adrenergic receptor blocker (propranolol, 80 microg/kg), and (3) a calcium-channel blocker (verapamil, 50 microg/kg) was studied in a sheep model. Seven animals underwent right vagus nerve stimulation in two modes: (1) a single continuous 60-second impulse and (2) multiple sequential 15-second impulses. RESULTS: Vagal stimulation alone achieved bradycardia without consistent and reproducible cardiac arrest. After drug administration 6 animals displayed significant potentiation of vagal-induced asystole in the 60-second stimulation protocol (1.6+/-0.9 seconds non-drug-treated versus 52.0+/-5.6 seconds drug-treated; p < 0.05). In the sequential 15-second impulse protocol after drug treatment, 6 animals achieved consistent, escape-free asystole during five to six sequential 15-second stimulations versus a brief pause and bradycardia produced without drug treatment. CONCLUSIONS: Increased acetylcholine activity by acetylcholinesterase inhibition and prevention of electromechanical escape activity by beta-adrenergic receptor and calcium-channel blockade during vagal stimulation produced a marked potentiation of vagal-induced asystole and a means of achieving controlled intermittent asystole. Controlled intermittent asystole achieved by pharmacologic potentiation of vagal-induced asystole may be a useful technique for enhancing technical ease in minimally invasive direct coronary artery bypass graft operations.

Preconditioning during simulated MIDCABG attenuates blood flow defects and neutrophil accumulation.

BACKGROUND: Ischemic preconditioning (IP) may be cardioprotective in minimally invasive direct coronary artery bypass where cardioplegia is not used. This study tested the hypothesis that IP of the area at risk (AAR) would attenuate postischemic injury from transient coronary artery occlusion. METHODS: In 19 anesthetized dogs, the left anterior descending coronary artery was occluded for 30 minutes (simulating coronary occlusion during anastomosis) followed by 3 hours of reperfusion. In 10 dogs, occlusion was preceded by 5 minutes of occlusion and 5 minutes of reperfusion (IP), whereas 9 other dogs had no IP (control, C). RESULTS: Thirty minutes of left anterior descending occlusion caused comparable dyskinesis (systolic shortening, sonomicrometry) in the AAR in C (baseline, 29% +/- 3% to 3% +/- 2%) and in IP (baseline, 29% +/- 2% to -0.3% +/- 2%). After 3 hours of reperfusion, systolic shortening was significantly depressed in C (20% +/- 4%), and was not significantly improved by IP (24% +/- 3%, p = 0.8 versus C). Postischemic diastolic stiffness in the AAR was not altered by IP versus C (0.60 +/- 0.12 versus 0.41 +/- 0.13). Plasma creatine kinase activity was similar between C and IP at the end of reperfusion (20 +/- 11 versus 16 +/- 5 U/g). Postischemic AAR blood flow (in milliliters per minute per gram of tissue) at 180 minutes of reperfusion decreased by 56% versus baseline in C (from 1.04 +/- 0.4 to 0.46 +/- 0.12; p < 0.05) compared with no change in IP (from 0.74 +/- 0.23 to 0.60 +/- 0.10), but there was no significant group difference at this time. Myeloperoxidase activity as an index of neutrophil accumulation in AAR was decreased in IP versus C (0.4 +/- 0.09 versus 0.7 +/- 0.04 U/microg tissue). CONCLUSIONS: Ischemic preconditioning does not decrease postischemic wall motion and only modestly increases postischemic blood flow abnormalities in the AAR, but does significantly inhibit neutrophil accumulation.