Out of America: tracing the genetic footprints of the global diffusion of maize.

Maize was first domesticated in a restricted valley in south-central Mexico. It was diffused throughout the Americas over thousands of years, and following the discovery of the New World by Columbus, was introduced into Europe. Trade and colonization introduced it further into all parts of the world to which it could adapt. Repeated introductions, local selection and adaptation, a highly diverse gene pool and outcrossing nature, and global trade in maize led to difficulty understanding exactly where the diversity of many of the local maize landraces originated. This is particularly true in Africa and Asia, where historical accounts are scarce or contradictory. Knowledge of post-domestication movements of maize around the world would assist in germplasm conservation and plant breeding efforts. To this end, we used SSR markers to genotype multiple individuals from hundreds of representative landraces from around the world. Applying a multidisciplinary approach combining genetic, linguistic, and historical data, we reconstructed possible patterns of maize diffusion throughout the world from American "contribution" centers, which we propose reflect the origins of maize worldwide. These results shed new light on introductions of maize into Africa and Asia. By providing a first globally comprehensive genetic characterization of landraces using markers appropriate to this evolutionary time frame, we explore the post-domestication evolutionary history of maize and highlight original diversity sources that may be tapped for plant improvement in different regions of the world.

Statistical properties of QTL linkage mapping in biparental genetic populations.

Quantitative trait gene or locus (QTL) mapping is routinely used in genetic analysis of complex traits. Especially in practical breeding programs, questions remain such as how large a population and what level of marker density are needed to detect QTLs that are useful to breeders, and how likely it is that the target QTL will be detected with the data set in hand. Some answers can be found in studies on conventional interval mapping (IM). However, it is not clear whether the conclusions obtained from IM are the same as those obtained using other methods. Inclusive composite interval mapping (ICIM) is a useful step forward that highlights the importance of model selection and interval testing in QTL linkage mapping. In this study, we investigate the statistical properties of ICIM compared with IM through simulation. Results indicate that IM is less responsive to marker density and population size (PS). The increase in marker density helps ICIM identify independent QTLs explaining >5% of phenotypic variance. When PS is >200, ICIM achieves unbiased estimations of QTL position and effect. For smaller PS, there is a tendency for the QTL to be located toward the center of the chromosome, with its effect overestimated. The use of dense markers makes linked QTL isolated by empty marker intervals and thus improves mapping efficiency. However, only large-sized populations can take advantage of densely distributed markers. These findings are different from those previously found in IM, indicating great improvements with ICIM.

The role of the nurse in screening asymptomatic male and female patients in a sexual health clinic.

We allocated 278 patients, who said they were asymptomatic and agreed to be randomized to a nurse or doctor clinic, to appointments using a random number system. In all, 35 patients did not attend and 16 were excluded because they did not meet the entry criteria. We used a screening protocol which excluded microscopy from the immediate assessment of patients. The outcome measures were completeness of documentation, proportion of patients accepting HIV tests, infections detected and patient satisfaction. Overall, 3% of items were not completed by doctors and 6% by nurses. HIV tests were carried out on 65% of patients who saw a doctor and 52% who saw a nurse. Thirteen infections were detected by doctors and 27 by nurses. No new cases of gonorrhoea, syphilis or HIV infection were identified. Eighty-eight patients completed a questionnaire after their attendance. Almost all patients were very satisfied with the service and most were prepared to see a nurse on a subsequent visit. We concluded that there are few differences between the performance of doctors and nurses in routine screening of asymptomatic patients.

Origin of compressive residual stress in polycrystalline thin films.

We present a model for compressive stress generation during thin film growth in which the driving force is an increase in the surface chemical potential caused by the deposition of atoms from the vapor. The increase in surface chemical potential induces atoms to flow into the grain boundary, creating a compressive stress in the film. We develop kinetic equations to describe the stress evolution and dependence on growth parameters. The model is used to explain measurements of relaxation when growth is terminated and the dependence of the steady-state stress on growth rate.

Paths across generations: academic competence and aggressive behaviors in young mothers and their children.

This research compared the social and cognitive development of young mothers when they were children with the social and cognitive development of their offspring. Intergenerational development was investigated over a 17-year period for 57 women who had been studied longitudinally from childhood to adulthood and who became young mothers (R. B. Cairns & B. D. Cairns, 1994). The children of these women, in turn, were followed prospectively from 1 to 2 years old through the early school years. The academic competence of mothers when they were children was significantly linked to the academic competence of their children at school age. In contrast, the across-generation correlations between measures of aggressive behavior of the mothers when they were children and measures of aggressive behavior of their children in early school grades were modest and unreliable. Certain within-generation continuities were observed in both cognitive and aggressive development.

Diagnosing coronary arterial stent thrombosis and arterial closure.

This single-center review of a consecutive series of patients requiring reexamination by angiography within 1 week of a coronary stent placement due to chest pain reveals that patients treated with a poststent anticoagulation regimen of warfarin and aspirin, and those with lower poststent deployment dilation pressures, have an increased risk of subacute stent thrombosis. Repeat cardiac catheterization within the first week after coronary artery stent implantation should be reserved for patients with significant electrocardiographic changes.

Internal mammary artery graft angioplasty: acute and long-term outcome.

Secondary to the low attrition rate of internal mammary artery grafts, limited data are available on the clinical and angiographic outcome of patients who have undergone balloon angioplasty of an internal mammary artery stenosis. This study examined a consecutive series of 68 patients who underwent balloon angioplasty of an internal mammary artery graft over a 9-year period. Procedural success was achieved in 60 of 68 (88%) patients. The primary reason for procedural failure was extreme vessel tortuosity. There were no major in-hospital complications. Angiographic follow-up was obtained in 78% of the patients with an angiographic restenosis rate of 19%. The overall event-free survival in patients with an initially successful procedure was 92%. In conclusion, internal mammary artery balloon angioplasty has both an excellent initial success rate as well as a low incidence of restenosis and repeat target lesion revascularization.

Lossy (15:1) JPEG compression of digital coronary angiograms does not limit detection of subtle morphological features.

BACKGROUND: Development of the "all-digital" cardiac catheterization laboratory has been slowed by substantial computer archival and transfer requirements. Lossy data compression reduces this burden but creates irreversible changes in images, potentially impairing detection of clinically important angiographic features. METHODS AND RESULTS: Fifty image sequences from 31 interventional procedures were viewed both in the original (uncompressed) state and after 15:1 lossy Joint Photographic Expert's Group (JPEG) compression. Experienced angiographers identified dissections, suspected thrombi, and coronary stents, and their results were compared with those from a consensus panel that served as a "gold standard." The panel and the individual observers reviewed the same image sequences 4 months after the first session to determine intraobserver variability. Intraobserver agreement for original images was not significantly different from that for compressed images (89.8% versus 89.5% for 600 pairs of observations in each group). Agreement of individual observers with the consensus panel was not significantly different for original images from that for compressed images (87.6% versus 87.3%; CIs for the difference, -4.0%, 4.0%). Subgroup analysis for each observer and for each detection task (dissection, suspected thrombus, and stent) revealed no significant difference in agreement. CONCLUSIONS: The identification of dissections, thrombi, and coronary stents is not substantially impaired by the application of 15:1 lossy JPEG compression to digital coronary angiograms. These data suggest that digital angiographic images compressed in this manner are acceptable for clinical decision-making.

Role of right ventricular and pulmonary functional abnormalities in limiting exercise capacity in adults with congenital heart disease.

This study evaluates right ventricular (RV) and pulmonary function during exercise in adults with congenital heart disease (CHD). Thirty-one patients with CHD involving the right side of the heart underwent symptom-limited bicycle exercise testing with simultaneous expired gas analysis and measurement of RV ejection fraction (EF). Twenty-one age-matched normal controls underwent the identical exercise protocol. Maximal oxygen consumption was lower in the CHD than in normal controls (19.5 +/- 6.4 vs 30.5 +/- 0.8 ml/kg/min, p = 0.0001 patients vs controls). Both heart rate (156 +/- 25 vs 171 +/- 13 beats/min, p = 0.01) and oxygen pulse (9.3 +/- 3.7 vs 12.3 +/- 3.7 ml/beat, p = 0.01), an indirect measure of stroke volume, were found to be lower in the CHD group at peak exercise. Pulmonary dysfunction was evidenced in the CHD group by decreased forced expiratory volume, forced vital capacity and maximum voluntary ventilation, and by a higher ventilation/expired carbon dioxide ratio at peak exercise (37.2 +/- 6.9 vs 33.0 +/- 5.4, p = 0.02), suggesting an increase in dead space ventilation. Maximal oxygen consumption was lower in patients whose RVEF decreased with exercise (17.6 +/- 5.4 vs 22.8 +/- 6.4 ml/kg/min, p = 0.03 "decrease RVEF" group vs "increase RVEF" group). Maximal oxygen consumption correlated with the change in RVEF only in the group whose RVEF decreased with exercise (r = 0.5, p = 0.03). In the group that had increased RVEF with exercise, maximal oxygen consumption correlated with forced expiratory volume (r = 0.7, p = 0.02). Thus, adults with CHD have a reduced functional capacity compared with normal controls. This phenomenon appears to be associated with both RV and pulmonary abnormalities.

Effect of inadequate cardiac output reserve on exercise tolerance in patients with moderate mitral stenosis.

Twenty-nine patients with moderate mitral stenosis and 29 age-matched normal controls underwent symptom-limited upright bicycle exercise testing with simultaneous hemodynamic monitoring. Exercise tolerance in the mitral stenosis group was found to be limited by inadequate cardiac output reserve and not by resting mitral valve area or exercise pulmonary capillary wedge pressure.

Esophageal varices in association with unilateral pulmonary vein atresia.

A 27-yr-old woman with recurrent episodes of hemoptysis (and hematemesis due to esophageal varices) was found to have unilateral pulmonary vein atresia. Reversed flow in the left pulmonary artery, a finding highly suggestive of this rare congenital anomaly, was demonstrated during cardiac catheterization. The definitive diagnosis was afforded by pulmonary wedge angiography, which not only demonstrated the atretic leftsided pulmonary veins, but also revealed a serpiginous system of systemic collateral veins to be the cause of her esophageal varices. Pneumonectomy of the nonfunctioning hypoplastic lung, the most successful approach to this disorder, may be complicated by severe bleeding of the numerous systemic arterial collateral vessels transected during surgical mobilization of the affected lung. Percutaneously delivered vascular occlusion coils were used in this case to occlude the large systemic to pulmonary artery collateral arteries immediately prior to pneumonectomy. Intra- and perioperative bleeding was minimal, and the patient has done well without further episodes of hemoptysis or hematemesis. Percutaneous occlusion of systemic to pulmonary collaterals may prove useful as a preoperative step for other congenital heart disease patients requiring lung or heart/lung transplantation.

Total pulmonary artery occlusion immediately after lung transplantation: successful revascularization with intravascular stents.

Occlusion of the pulmonary artery anastomosis is an uncommon early complication of lung transplantation which necessitates emergency surgical revision. Percutaneous correction of such a complication has not been previously reported. We report a patient who had total pulmonary artery occlusion less than 24 hours after right single lung transplantation with successful revascularization achieved by means of percutaneously delivered endovascular stents.

Left ventricular performance improves late after aortic valve replacement in patients with aortic stenosis and reduced ejection fraction.

EF in patients with aortic stenosis and reduced EF who underwent aortic valve replacement did not improve by 1 week postoperatively despite rectification of afterload mismatch. By 6 months, however, EF significantly improved without any further change in ventricular loading conditions. This implies that the benefit from aortic valve replacement (when measured by LV ejection performance) may not be evident until late postoperatively.

Complications related to percutaneous transvenous mitral commissurotomy.

Recent randomized studies have demonstrated that percutaneous transvenous mitral commissurotomy (PTMC) has similar efficacy compared to surgical commissurotomy. Compared with surgery, PTMC is associated with shorter hospital stays, reduced patient discomfort, and significantly lower costs. The challenge of PTMC remains to provide increased safety. The most serious risks of balloon commissurotomy include cardiac perforation and embolic stroke. The creation of severe mitral regurgitation also limits the effectiveness of the procedure and occasionally leads to the requirement for emergency mitral valve replacement. Since 1986, procedure-related mortality has ranged from 0-2.7% with lower mortality rates reported recently. The most frequent cause of procedure-related death has been left ventricular (LV) perforation. This is almost exclusively a complication associated with the double balloon technique, which requires LV guidewires. Cardiac perforation due to inadvertent atrial perforation during transseptal catheterization may occur with the Inoue technique as well, but this tends to be less severe and has not resulted in death. Embolic stroke has occurred in 1.1-5.4% of cases. The incidence of embolic events has been favorably influenced by routine preprocedure transesophageal echocardiography (TEE), eliminating patients with left atrial thrombi. Significant mitral regurgitation occurs in 3.3-10.5% of patients undergoing balloon mitral commissurotomy. Fortunately, mitral regurgitation infrequently requires emergency surgery (0.3-3.3% of cases). Iatrogenic atrial septal defects are usually of no clinical consequence. Their frequency has been reduced with the use of the Inoue balloon catheter system and they rarely require surgical repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of pulsed-dye laser-mediated vasodilatation in a rabbit femoral artery model of vasoconstriction.

Vasoconstriction is a clinical problem associated with invasive vascular procedures, microvascular reconstruction and subarachnoid hemorrhage. We sought to characterize the ability of pulsed-dye laser irradiation to reverse and prevent vasoconstriction in an anesthetized rabbit model of surgically and pharmacologically induced vasoconstriction. Five groups of experiments were performed to study the effect of pulsed-dye laser irradiation delivered through a 320 microns core ball-tip fiber into the femoral artery. The studies demonstrated that pulsed-dye irradiation can reproducibly cause vascular dilatation. The zone of vasodilatation propagated equally proximal and distal to the site of irradiation within the vessel. When saline was infused into the vessel to replace flowing blood during delivery of laser irradiation, no significant vasodilatation occurred. After laser irradiation reversed surgical and pharmacologic vasoconstriction, the vessel was resistant to further pharmacologic vasoconstriction. This resistance to pharmacologic vasoconstriction did not occur if the vessel was pharmacologically predilated before delivery of laser irradiation. Pathologic analysis of the vessels revealed endothelial damage and mild to moderate medial necrosis, most significant at the site of energy delivery. These studies provide characterization of pulsed-dye laser-mediated vasodilatation in an in vivo model. Delivery of pulsed-dye laser energy has potential clinical application and warrants further investigation.

Comparison of DNA adducts and sister chromatid exchange in lung cancer cases and controls.

In a molecular epidemiological study of lung cancer cases (n = 81) and noncancer controls (n = 67), polycyclic aromatic hydrocarbon (PAH)-DNA adducts were evaluated in peripheral blood leukocytes from all subjects and in a smaller number of lung tissue specimens collected prior to or at surgery. Sister chromatid exchanges (SCE) in lymphocytes were also studied in a subset of cases and controls. Questionnaire, medical record, or tumor registry data provided a family history of cancer, as well as information on cigarette smoking, dietary and occupational exposure to PAHs, and other factors related to SCEs. In both cases and controls PAH-DNA adducts in leukocytes measured by an enzyme-linked immunosorbent assay were not significantly related to age, sex, ethnicity, amount of cigarette smoking, passive smoking, dietary charcoal, or caffeine consumption. Nor did family history of cancer or histological type of cancer significantly affect adduct levels. However, when subjects were stratified by smoking status (current, former, and nonsmoker), lung cancer cases who were current smokers had significantly higher levels of covalent adducts than current smoker controls. A seasonal variation was observed in PAH-DNA binding, with a peak in adduct levels during July-October. This peak corresponds to that seen in a prior study of aryl hydrocarbon hydroxylase inducibility by other investigators. The finding of significant levels of PAH-DNA adducts in former smokers and non-smokers supports an earlier observation that this marker is not smoking specific but reflects a pervasive and variable "background" exposure to PAH. These results are consistent with a genetically determined enhancement of PAH-DNA adduct formation in leukocytes of lung cancer cases which is evident in current smokers. The results in lung tissue are limited by the small number of samples. Adduct levels were not significantly increased in lung tissue of smokers compared with nonsmokers. An inverse linear correlation was seen between adduct values in lung tissue and age of the donors. SCEs were significantly related to pack years of smoking. However, there was no difference in the frequency of SCE between cases and controls; nor were SCE and DNA adducts significantly correlated in this small sample.

High-energy versus low-energy defibrillation: experience in patients (excluding those in the intensive care unit) at Mayo Clinic-affiliated hospitals.

/he purpose of this study was to determine whether electric shocks of low (200 to 240 J), intermediate (300 to 320 J), or high (400 to 440 J) delivered energy were most successful in defibrillating hospitalized patients (excluding those in intensive care units) in whom resuscitation was attempted by a code emergency team. From January 1980 through December 1982, 101 cases of ventricular fibrillation in 100 patients were treated by Mayo Clinic code emergency teams. Many of the patients in this trial had secondary or agonal ventricular Defibrillation. Most patients (64%) were defibrillated by one to eight shocks. For the first shock, intermediate and high energy seemed to be more effective than low energy. Patient weight, time of delivery of shock 1 after onset of the code emergency, blood pH, acute and chronic medical diagnoses, and pharmacotherapy before the onset of ventricular fibrillation were not clearly related to the response to shock 1. Nine of 16 patients who did not initially respond to shocks of low or intermediate energy were defibrillated when higher energy was subsequently used. Only 14 patients ultimately survived and were dismissed from the hospital. These results suggest that in this patient population, high levels of delivered energy are preferable to low energy for the first shocks administered; we recommend that 400 J of delivered energy be used initially. The 360-J maximal energy dose available in most currently manufactured defibrillators should be sufficiently close to this recommendation to justify use of that dose with the initial shock.(ABSTRACT TRUNCATED AT 250 WORDS)