University of Iowa

About: University of Iowa is a education organization based out in Iowa City, Iowa, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 49229 authors who have published 109171 publications receiving 5021465 citations. The organization is also known as: UI & The University of Iowa.

Decrease in anogenital distance among male infants with prenatal phthalate exposure

Abstract: Prenatal phthalate exposure impairs testicular function and shortens anogenital distance (AGD) in male rodents. We present data from the first study to examine AGD and other genital measurements in relation to prenatal phthalate exposure in humans. A standardized measure of AGD was obtained in 134 boys 2–36 months of age. AGD was significantly correlated with penile volume (R = 0.27, p = 0.001) and the proportion of boys with incomplete testicular descent (R = 0.20, p = 0.02). We defined the anogenital index (AGI) as AGD divided by weight at examination [AGI = AGD/weight (mm/kg)] and calculated the age-adjusted AGI by regression analysis. We examined nine phthalate monoester metabolites, measured in prenatal urine samples, as predictors of age-adjusted AGI in regression and categorical analyses that included all participants with prenatal urine samples (n = 85). Urinary concentrations of four phthalate metabolites [monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), and monoisobutyl phthalate (MiBP)] were inversely related to AGI. After adjusting for age at examination, p-values for regression coefficients ranged from 0.007 to 0.097. Comparing boys with prenatal MBP concentration in the highest quartile with those in the lowest quartile, the odds ratio for a shorter than expected AGI was 10.2 (95% confidence interval, 2.5 to 42.2). The corresponding odds ratios for MEP, MBzP, and MiBP were 4.7, 3.8, and 9.1, respectively (all p-values < 0.05). We defined a summary phthalate score to quantify joint exposure to these four phthalate metabolites. The age-adjusted AGI decreased significantly with increasing phthalate score (p-value for slope = 0.009). The associations between male genital development and phthalate exposure seen here are consistent with the phthalate-related syndrome of incomplete virilization that has been reported in prenatally exposed rodents. The median concentrations of phthalate metabolites that are associated with short AGI and incomplete testicular descent are below those found in one-quarter of the female population of the United States, based on a nationwide sample. These data support the hypothesis that prenatal phthalate exposure at environmental levels can adversely affect male reproductive development in humans.

Pollen-ovule ratios: a conservative indicator of breeding systems in flowering plants

Abstract: The evolutionary shift from xenogamy (outcrossing) to autogamy (selfing) has been mediated through decreased flower size and alterations in floral morphology (Ornduff, 1969) which reduce the energetic cost per flower (Cruden, unpubl.) and facilitate self-pollination, respectively. Recently, a number of workers have shown that the flowers of self-incompatible and other xenogamous taxa produce more pollen grains than closely related self-compatible and/or autogamous taxa (Arroyo, 1973; Baker, 1967; Cruden, 1973; Gibbs et al., 1975; Lloyd, 1965; Vries, 1974). In contrast to other floral characteristics the number of ovules per ovary in the taxa studied did not decrease. In these taxa the evolutionary shift from xenogamy to autogamy has been accompanied by a decrease in the ratio of pollen grains to ovules (PIO). It is generally accepted that differences in breeding systems tend to be correlated with successional stages. Colonizers of disturbed habitats and plants of early successional stages tend to be self-compatible and/or autogamous (Baker, 1955, 1959, 1965; Stebbins, 1958) whereas plants of later successional stages, including tropical forest trees, tend to be xenogamous (Baker, 1959; Bawa, 1974; Bawa and Opler, 1975; Stebbins, 1950, 1958). Since, as I will show, PIO's are an integral part of a plant's breeding system, they also should be correlated with habitat or successional stage. My overall objective is to show that PIO's reflect the likelihood of sufficient pollen grains reaching each stigma to result in maximum seed set. The more efficient the transfer of pollen, the lower the PIO should be. It follows logically that cleistogamous flowers should have the lowest PIO's, and that autogamous flowers will have lower PIO's than xenogamous flowers, i.e., that PIO's are correlated with breeding systems. My data show that this is the case and suggest that PI O's are integrated with other facets of a plant's breeding system. Second, I show that there is a strong correlation between the breeding system, hence PIO's, and successional stage. In addition, I briefly circumscribe what constitutes a sufficient number of pollen grains to assure maximum seed set and discuss evidence that supports the notion that some plants tend to minimize pollen production. Finally, I discuss deviations from the general pattern to show that PIO's are a better predictor of a plant's breeding system than other morphological characteristics.

Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex

Abstract: Luck, Steven J., Leonardo Chelazzi, Steven A. Hillyard, and Robert Desimone. Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex. J. Neurophysiol. 77: ...

Quorum-sensing signals indicate that cystic fibrosis lungs are infected with bacterial biofilms

Abstract: The bacterium Pseudomonas aeruginosa permanently colonizes cystic fibrosis lungs despite aggressive antibiotic treatment. This suggests that P. aeruginosa might exist as biofilms--structured communities of bacteria encased in a self-produced polymeric matrix--in the cystic fibrosis lung. Consistent with this hypothesis, microscopy of cystic fibrosis sputum shows that P. aeruginosa are in biofilm-like structures. P. aeruginosa uses extracellular quorum-sensing signals (extracellular chemical signals that cue cell-density-dependent gene expression) to coordinate biofilm formation. Here we found that cystic fibrosis sputum produces the two principal P. aeruginosa quorum-sensing signals; however, the relative abundance of these signals was opposite to that of the standard P. aeruginosa strain PAO1 in laboratory broth culture. When P. aeruginosa sputum isolates were grown in broth, some showed quorum-sensing signal ratios like those of the laboratory strain. When we grew these isolates and PAO1 in a laboratory biofilm model, the signal ratios were like those in cystic fibrosis sputum. Our data support the hypothesis that P. aeruginosa are in a biofilm in cystic fibrosis sputum. Moreover, quorum-sensing signal profiling of specific P. aeruginosa strains may serve as a biomarker in screens to identify agents that interfere with biofilm development.

Alterations in Shoulder Kinematics and Associated Muscle Activity in People With Symptoms of Shoulder Impingement

Abstract: Background and Purpose. Treatment of patients with impingement symptoms commonly includes exercises intended to restore “normal” movement patterns. Evidence that indicates the existence of abnormal patterns in people with shoulder pain is limited. The purpose of this investigation was to analyze glenohumeral and scapulothoracic kinematics and associated scapulothoracic muscle activity in a group of subjects with symptoms of shoulder impingement relative to a group of subjects without symptoms of shoulder impingement matched for occupational exposure to overhead work. Subjects. Fifty-two subjects were recruited from a population of construction workers with routine exposure to overhead work. Methods. Surface electromyographic data were collected from the upper and lower parts of the trapezius muscle and from the serratus anterior muscle. Electromagnetic sensors simultaneously tracked 3-dimensional motion of the trunk, scapula, and humerus during humeral elevation in the scapular plane in 3 hand-held load conditions: (1) no load, (2) 2.3-kg load, and (3) 4.6-kg load. An analysis of variance model was used to test for group and load effects for 3 phases of motion (31°–60°, 61°–90°, and 91°–120°). Results. Relative to the group without impingement, the group with impingement showed decreased scapular upward rotation at the end of the first of the 3 phases of interest, increased anterior tipping at the end of the third phase of interest, and increased scapular medial rotation under the load conditions. At the same time, upper and lower trapezius muscle electromyographic activity increased in the group with impingement as compared with the group without impingement in the final 2 phases, although the upper trapezius muscle changes were apparent only during the 4.6-kg load condition. The serratus anterior muscle demonstrated decreased activity in the group with impingement across all loads and phases. Conclusion and Discussion. Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work.