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.

A molecular timeline for the origin of photosynthetic eukaryotes

Abstract: The appearance of photosynthetic eukaryotes (algae and plants) dramatically altered the Earth's ecosystem, making possible all vertebrate life on land, including humans. Dating algal origin is, however, frustrated by a meager fossil record. We generated a plastid multi-gene phylogeny with Bayesian inference and then used maximum likelihood molecular clock methods to estimate algal divergence times. The plastid tree was used as a surrogate for algal host evolution because of recent phylogenetic evidence supporting the vertical ancestry of the plastid in the red, green, and glaucophyte algae. Nodes in the plastid tree were constrained with six reliable fossil dates and a maximum age of 3,500 MYA based on the earliest known eubacterial fossil. Our analyses support an ancient (late Paleoproterozoic) origin of photosynthetic eukaryotes with the primary endosymbiosis that gave rise to the first alga having occurred after the split of the Plantae (i.e., red, green, and glaucophyte algae plus land plants) from the opisthokonts sometime before 1,558 MYA. The split of the red and green algae is calculated to have occurred about 1,500 MYA, and the putative single red algal secondary endosymbiosis that gave rise to the plastid in the cryptophyte, haptophyte, and stramenopile algae (chromists) occurred about 1,300 MYA. These dates, which are consistent with fossil evidence for putative marine algae (i.e., acritarchs) from the early Mesoproterozoic (1,500 MYA) and with a major eukaryotic diversification in the very late Mesoproterozoic and Neoproterozoic, provide a molecular timeline for understanding algal evolution.

Induction of NK activity in murine and human cells by CpG motifs in oligodeoxynucleotides and bacterial DNA.

Abstract: We have recently shown that oligodeoxynucleotides (ODN) containing unmethylated CpG dinucleotides (CpG motif) can induce B cells to proliferate, differentiate, and secrete cytokines. In this study we demonstrate that CpG motifs contained in ODN as short as 15 bases in length were quite effective at inducing NK cell lytic activity in vitro in both human and murine lymphocytes. Such ODN were also effective at inducing NK lytic activity, in vivo, in mice. Experiments designed to determine the cellular and cytokine requirements for NK cell induction revealed that B and T cells are not necessary, that the ODN do not augment the activity of highly purified NK cells, and that the ODN augment NK cell activity indirectly by inducing the secretion of IL-12, IFN-alpha beta, and TNF-alpha. Various ODN sequences were prepared to determine the optimal ODN length, motif, palindrome, backbone modification, and dose requirements. We found no requirement for a palindromic sequence but a definite requirement for an unmethylated CpG motif. While necessary, however, a CpG motif was not sufficient for NK cell induction. Instead, there appeared to be stringent requirements for the immediate flanking bases at the 5' and 3' ends as well as for flanking sequences outside the immediate 5' and 3' bases. In particular poly(G) ends seemed to exert a complex qualitative and quantitative effect which could be up- or down-modulating depending on whether the ODN backbone was phosphorothioate modified or not.

Errors in Estimating Accruals: Implications for Empirical Research

Abstract: This paper examines the impact of measuring accruals as the change in successive balance sheet accounts, as opposed to measuring accruals directly from the statement of cash flows. We demonstrate that the balance sheet approach to measuring accruals, which is the dominant method used in the literature to date, introduces significant measurement error into accruals estimates. Results show that the direction and magnitude of the bias in accruals estimates is related to the presence of mergers and acquisitions, discontinued operations, and to a lesser extent, foreign currency translations. Our primary finding is that studies using a balance sheet approach to test for earnings management are potentially contaminated. In particular, if the partitioning variable used to indicate the presence of earnings management is correlated with the occurrence of mergers and acquisitions or discontinued operations, researchers are likely to erroneously conclude that earnings management exists when there is none. Additional results show that the bias in balance sheet accruals estimation can confound regressions where discretionary and non-discretionary accruals are used as explanatory variables. Moreover, we demonstrate that tests of market mispricing of accruals will be understated due to erroneous classification of "extreme" accruals firms.

Visuospatial Judgment: A Clinical Test

Abstract: • We constructed and developed a brief test assessing capacity for discriminating the direction of lines. Application of the test to patients with unilateral brain disease disclosed a remarkably high frequency of defective performance in those with right hemisphere lesions. The performance of patients with left hemisphere lesions was comparable to that of control patients. Brevity and ease of administration make the test convenient for clinical use.