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Biomedical subjects

S Dillon

Publications and source records attributed to S Dillon.

13 recordsLinked to original sources
PubMed2025

Optimising parent selection in plant breeding: comparing metaheuristic algorithms for genotype building.

Stacking desirable haplotypes across the genome to develop superior genotypes has been implemented in several crop species. A major challenge in Optimal Haplotype Selection is identifying a set of parents that collectively contain all desirable haplotypes, a complex combinatorial problem with countless possibilities. In this study, we evaluated the performance of metaheuristic search algorithms (MSAs)-genetic algorithm (GA), differential evolution (DE), particle swarm optimisation (PSO), and simulated annealing (SA) for optimising parent selection under two genotype building (GB) objectives: Optimal Haplotype Selection (OHS) and Optimal Population Value (OPV). Using a diverse wheat population of 583 lines genotyped for 29,972 SNPs, forming 7645 haplotype blocks and phenotyped for stripe rust scores, we assessed each algorithm's performance across fitness optimisation, convergence speed, and computational efficiency. GA consistently achieved high fitness and rapid convergence, while DE showed robustness but required longer runtime and careful tuning. PSO performed well under the OHS criterion but was less effective for OPV. SA, although computationally lighter, was less consistent in finding optimal solutions. Simulation over 100 breeding cycles showed that OHS outperformed both OPV and GEBV-based selection in long-term genetic gain and diversity retention. OHS maintained heterozygosity and additive variance, which are key for sustainable improvement, while GEBV selection led to early allele fixation. Our findings underscore the potential of GB strategies that prioritise the collective performance of parent sets rather than individual ranking to enhance selection outcomes in genomic-assisted breeding programmes.

Plant Breeding↗
PubMed1992

The effect of exercise-induced myocardial ischemia on postischemic left ventricular diastolic filling.

To determine whether exercise-induced ischemia impairs left ventricular diastolic filling in the postischemic period in humans, 101 men (mean age 57 +/- 10 years) were studied before and 2 h after a symptom-limited thallium-201 tomographic treadmill with pulsed Doppler echocardiography of mitral valve inflow. In the postischemic period 2 h after exercise, diastolic filling was significantly impaired in the ischemia group (reversible thallium defect; n = 24) as reflected by a decrease in the peak early filling velocity (44.5 +/- 10.1 to 39.9 +/- 9.9 cm/s, p less than 0.01), peak early to atrial filling velocity ratio (0.91 +/- 0.27 to 0.76 +/- 0.25, p less than 0.001), and deceleration rate of early filling (281 +/- 104 to 245 +/- 86 cm/s2, p less than 0.01). Similar alterations in the postischemic period occurred in the myocardial infarction-ischemia group (partially reversible defect; n = 28) as seen by a decrease in the peak early filling velocity (47.6 +/- 11.6 to 41.8 +/- 12.0 cm/s, p less than 0.001), peak early to atrial filling velocity ratio (0.84 +/- 0.21 to 0.68 +/- 0.18, p less than 0.001), and early time-velocity integral (7.06 +/- 1.78 to 5.64 +/- 2.07 cm, p less than 0.001). In the control group (no defects; n = 33) and myocardial infarction group (fixed defect; n = 16), diastolic filling was unchanged in the postexercise period. Heart rate and blood pressure were unchanged post-exercise in all groups. Exercise-induced ischemia impairs diastolic filling in the postischemic period in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Circulation↗
PubMed1992

The influence of obesity on left ventricular filling and systolic function.

Little information on the possible influence of obesity on diastolic function is available. Thus we studied 24 asymptomatic obese volunteers (greater than 120% ideal body weight; mean 153 +/- 30%), aged 34 +/- 11 years. Each obese subject was matched for age, height, and sex, with a healthy normal-weight control subject. Isovolumic relaxation time (IVRT) and diastolic filling indexes were determined by pulsed Doppler echocardiography. The IVRT was significantly prolonged in the obese group (84 +/- 17 msec) as compared with the control group (57 +/- 13 msec; p less than 0.0002). Multiple regression analysis showed that percentage of ideal body weight was the most important predictor of peak early filling velocity (r = 0.59, p less than 0.005) and mean deceleration rate of early filling (r = 0.61, p less than 0.005) in the obese group. However, age as compared with percentage of ideal body weight was a more important determinant of the relative distribution of early and atrial filling, such as peak early-to-atrial filling velocity ratio (r = -0.75, p less than 0.0001). Ejection fraction, heart rate, and blood pressure did not differ between the obese and control groups. In conclusion, obesity is associated with preclinical abnormalities of IVRT, which may reflect impaired relaxation. The IVRT may be useful in the early detection of left ventricular dysfunction in obesity. Last, studies comparing Doppler indexes of diastolic filling among groups must control for potential differences in percentage of ideal body weight.

Adolescent↗
PubMed1992

Left ventricular ejection fraction is increased during transesophageal echocardiography in patients with impaired ventricular function.

Transesophageal echocardiography (TEE) is increasingly being used to assess left ventricular function (LVF). However, little data exist on the quantitative accuracy of this technique and its influence on LVF. Thus 50 ambulatory adult patients (mean age 62 +/- 15 years) were studied with transthoracic echocardiography (TTE) immediately before, before the end, and 10 minutes after TEE. Left ventricular ejection fraction (LVEF) was calculated using the modified Simpson's method. In subjects (n = 24) with impaired LVF (LVEF less than 55% by TTE), TTE-derived LVEF increased from 37 +/- 13% to 45 +/- 15% (p less than 0.001) during TEE. In 13 of 24 subjects with abnormal LVF, LVEF significantly increased during TEE as defined by an increase in LVEF by at least 5 ejection fraction units. In four of these subjects LVF normalized during TEE. LVEF was unchanged during and after TEE in the subjects (n = 26) with normal LVF (LVEF greater than 55%). An excellent correlation was found between LVEF derived by TEE and that derived by TTE performed during TEE (r = 0.93, SEE = 6.6%, p less than 0.001). LVEF determined by TEE compared well with that derived by TTE and should be a useful measure of global left ventricular function. However, an increase in LVEF during TEE occurs in over 50% of patients with impaired LVF and may be important to consider in individual subjects.

Adult↗
PubMed1991

Two-dimensional transesophageal echocardiographic determination of aortic valve area in adults with aortic stenosis.

To determine if aortic stenosis severity could be accurately measured by two-dimensional transesophageal echocardiography (TEE), 62 adult subjects (mean age 66 +/- 12 years) with aortic stenosis had their aortic valve area (AVA) determined by direct planimetry using TEE, and with the continuity equation using combined transthoracic Doppler and two-dimensional echocardiography (TTE). Eighteen subjects had AVA calculated by the Gorlin method during catheterization. An excellent correlation (r = 0.93, SEE = 0.17 cm2) was found between AVA determined by TEE (mean 1.24 +/- 0.49 cm2; range 0.40 to 2.26 cm2) and TTE (mean 1.23 +/- 0.46 cm2; range 0.40 to 2.23 cm2). The absolute (0.13 +/- 0.12 cm2) and percent (10.8 +/- 8.9%) differences between AVA determined by TEE versus TTE were small. Excellent correlations between AVA by TEE and TTE were also found in subjects with normal systolic function (r = 0.95, SEE = 0.14 cm2; n = 38) and impaired function (r = 0.91, SEE = 0.21 cm2; n = 24). AVA determined by catheterization correlated better with AVA measured by TEE (r = 0.91, SEE = 0.15 cm2) than AVA measured with TTE (r = 0.84, SEE = 0.19 cm2). These data demonstrate that AVA can be accurately measured by direct planimetry using TEE in subjects with aortic stenosis. TEE may become an important adjunct to transthoracic echocardiography in the assessment of aortic stenosis severity.

Adult↗
PubMed1991

An O antigen can interfere with the function of the Yersinia pseudotuberculosis invasin protein.

Escherichia coli strains harbouring the Yersinia pseudotuberculosis inv gene are able to enter cultured mammalial cells. We show here that this property is not shared by all enteric bacteria, since Shigella flexneri 2a cured of its virulence-associated plasmid and harbouring the inv gene is unable to enter mammalian cells efficiently. Mapping studies showed that the region of the chromosome responsible for this phenotype includes rfaB, a locus involved in the production of O antigen. S. flexneri 2a strains that express O antigen were unable to enter mammalian cells, even though invasin was efficiently expressed and localized, showing that this structure interferes with invasin activity. The O antigen either masks invasin or sterically hinders the ability of the mammalian cell receptor to bind this protein.

Adhesins, Bacterial↗
PubMed1991

HIV infection, genital ulcer disease, and crack cocaine use among patients attending a clinic for sexually transmitted diseases.

BACKGROUND: Recently there has been a rise in genital ulcer disease (GUD) in urban minority heterosexuals in the United States. The impact of these increased GUD rates on HIV transmission patterns in this population is unknown. METHODS: Sexually transmitted disease (STD) diagnoses were correlated with HIV antibody status and risk factor history in 194 patients who consented to HIV testing at an STD clinic in central Brooklyn. RESULTS: Of 36 HIV-positive patients, 23 (64%) denied HIV risk factors other than heterosexual contact with persons of unknown HIV status. HIV antibody was associated with GUD (odds radio [OR] = 2.72, 95% confidence interval [CI] = 1.20-6.24), multiple concurrent STDs (OR = 2.51, 95% CI = 1.08-5.81), and a history of crack cocaine use (OR = 2.98, 95% CI = inexact-9.61). Crack use was also associated with GUD (OR = 15.15, 95% CI = 3.27-inexact) and multiple simultaneous STDs (OR = 13.87, 95% CI = 4.62-inexact). In a log-linear model analysis, HIV infection was independently associated with GUD and crack use. HIV infection, genital ulcer disease, and crack cocaine use were more common in women than men. CONCLUSIONS: The association between HIV infection and GUD seen here may be secondary to high-risk sexual behavior, which in turn may be partially attributable to crack cocaine use and drug-related prostitution. The high rate of coinfection with HIV and GUD raises a concern about the increased efficiency of sexual transmission of HIV in this population.

Comorbidity↗
PubMed1986

An acousto-optically steered laser scanning system for measurement of action potential spread in intact heart.

An optical scanning device that combines a voltage-sensitive dye and an acousto-optically steered He-Ne laser beam is described. This device is capable of scanning 128 sites every 4 ms and recording and storing the fluorescence signals for a duration of up to 1 s (several beats). Comparison of an activation map constructed from laser scanning to those obtained from multiple extracellular electrodes suggests that this technique is highly reliable. Although motion-induced light scattering appears to alter the shape of the action potential, the upstroke can be distinguished quite reliably even in a vigorously contracting muscle. This technique provides high resolution (up to 50 micron) and high flexibility (i.e., the scanned sites can be concentrated over a small or very large area) in measuring the spread of activation in heart muscle. By having only one excitation and one measurement element, the approach offers simplicity and high flexibility to the user. We have shown that this system can be readily applied to the task for which it was intended--probing the mechanisms of arrhythmias in the mammalian myocardium. It has been demonstrated, for example, that arrhythmias due to automaticity can be readily distinguished from those due to reentry through the mapping capability of the laser scanner. In addition, the ability of laser scanner to measure membrane depolarization directly during arrhythmias may make this technique superior to conventional electrocardiographic mapping techniques.

Acoustic Stimulation↗
PubMedDate not supplied

Venomous snakebite: past, present, and future treatment options.

BACKGROUND: Venomous snakebites continue to cause great morbidity, and treatment options are confusing the attending physician. In the United States approximately 45,000 snakebites occur each year, of which some 8000 are by 20 species of venomous snakes. METHODS: Information on venomous snakes and snakebite treatment was gathered from the libraries of the Wilderness Medical Society and the Rocky Mountain Center for Wilderness Medicine in Boise, Idaho (co-supported by the Boise State University and the Family Practice Residency of Idaho), as well as from current literature files of physicians practicing wilderness medicine. RESULTS AND CONCLUSIONS: Three genera of venomous snakes account for the majority of poisonous snake envenomations in this country. Most hospitalized victims are bitten either by rattlesnakes or copperheads or by unidentified snakes. Most of these bites occur during the summer months and are found on the extremities. Field treatment focuses on the application of a vacuum extractor and transportation to the nearest medical facility. Although constriction band use can be helpful, tourniquets, incision and suction, and ice therapy are contraindicated. Electric shock therapy is of no use and could cause serious injury. Hospital management focuses on rapid clinical evaluation and laboratory tests to establish the degree of envenomation, looking for clotting abnormalities. If envenomation has occurred and is reactive, polyvalent antivenin should be administered according to the degree of envenomation. Errors in diagnosis and treatment result in increased morbidity and put attending physicians at risk for litigation. Prevention remains the most successful approach to snakebite management.

Antivenins↗