Teaching the Process of Molecular Phylogeny and Systematics: A Multi-Part Inquiry-Based Exercise

Three approaches to molecular phylogenetics are demonstrated to biology students as they explore molecular data from Homo sapiens and four related primates. By analyzing DNA sequences, protein sequences, and chromosomal maps, students are repeatedly challenged to develop hypotheses regarding the ancestry of the five species. Although these exercises were designed to supplement and enhance classroom instruction on phylogeny, cladistics, and systematics in the context of a postsecondary majors-level introductory biology course, the activities themselves require very little prior student exposure to these topics. Thus, they are well suited for students in a wide range of educational levels, including a biology class at the secondary level. In implementing this exercise, we have observed measurable gains, both in student comprehension of molecular phylogeny and in their acceptance of modern evolutionary theory. By engaging students in modern phylogenetic activities, these students better understood how biologists are currently using molecular data to develop a more complete picture of the shared ancestry of all living things

NUCLEAR SPINS OF SOME NEUTRON-DEFICIENT AS ISOTOPES

The nuclear spins of some neutron-deficient arsenic isotopes have been measured using the atomic beam magnetic resonance technique. The results are

HYPERFINE-STRUCTURE AND NUCLEAR MOMENTS OF SOME NEUTRON-DEFICIENT AS ISOTOPES

The hyperfine structure of th

Mass Spectrometric Detection of Cholesterol Oxidation in Bovine Sperm

We report on the presence and formation of cholesterol oxidation products (oxysterols) in bovine sperm. Although cholesterol is the most abundant molecule in the membrane of mammalian cells and is easily oxidized, this is the first report on cholesterol oxidation in sperm membranes as investigated by state-of-the-art liquid chromatographic and mass spectrometric methods. First, oxysterols are already present in fresh semen samples, showing that lipid peroxidation is part of normal sperm physiology. After chromatographic separation (by high-performance liquid chromatography), the detected oxysterol species were identified with atmospheric pressure chemical ionization mass spectrometry in multiple-reaction-monitoring mode that enabled detection in a broad and linear concentration range (0.05–100 pmol for each oxysterol species detected). Second, exposure of living sperm cells to oxidative stress does not result in the same level and composition of oxysterol species compared with oxidative stress imposed on reconstituted vesicles from protein-free sperm lipid extracts. This suggests that living sperm cells protect themselves against elevated oxysterol formation. Third, sperm capacitation induces the formation of oxysterols, and these formed oxysterols are almost completely depleted from the sperm surface by albumin. Fourth, and most importantly, capacitation after freezing/thawing of sperm fails to induce both the formation of oxysterols and the subsequent albumin-dependent depletion of oxysterols from the sperm surface. The possible physiological relevance of capacitationdependent oxysterol formation and depletion at the sperm surface as well as the omission of this after freezing/thawing semen is discussed.Supported by the research program Biology of Reproductive Cells of the Graduate School of Animal Sciences from the Faculty of Veterinary Medicine of Utrecht University. P.F.N.S. is supported by Portuguese Foundation for Science and Technology, Ministry for Science, Technology, and Higher Education grant SFRH/2888/2000; R.A.v.G. was financed by ZonMw grant 903-44-156; A.B. was financed by the High Potentials program of Utrecht University; and N.G.-G. was funded by Spanish Ministry of Education and Science grant EX 2005- 0460.info:eu-repo/semantics/publishedVersio

A Comprehensive Functional Characterization of Escherichia coli Lipid Genes

Summary: Lipid membranes are the border between living cells and their environments. The membrane’s lipid composition defines fluidity, thickness, and protein activity and is controlled by the intricate actions of lipid gene-encoded enzymes. However, a comprehensive analysis of each protein’s contribution to the lipidome is lacking. Here, we present such a comprehensive and functional overview of lipid genes in Escherichia coli by individual overexpression or deletion of these genes. We developed a high-throughput lipidomic platform, combining growth analysis, one-step lipid extraction, rapid LC-MS, and bioinformatic analysis into one streamlined procedure. This allowed the processing of more than 300 samples per day and revealed interesting functions of known enzymes and distinct effects of individual proteins on the phospholipidome. Our data demonstrate the plasticity of the phospholipidome and unexpected relations between lipid classes and cell growth. Modeling of lipidomic responses to short-chain alcohols provides a rationale for targeted membrane engineering. : Jeucken et al. analyzed lipidomes of E. coli strains with knockout or overexpression of known lipid-related genes. They demonstrate relationships between lipid species and classes and investigate their link to cell growth. The high-throughput lipidomic method is then used to model lipidomic changes to exogenous alcohols. Keywords: lipidomics, systems biology, Escherichia coli, lipids, phospholipids, lipid genes, lipid network, high-throughput, LC-MS, bioinformatic

The Cumulus Cell Layer Protects Bovine Maturing Oocyte Against Fatty Acid-Induced Lipotoxicity

Mobilization of fatty acids from adipose tissue during metabolic stress increases the amount of free fatty acids in blood and follicular fluid and is associated with impaired female fertility. In a previous report we described the effects of the three predominant fatty acids in follicular fluid (saturated palmitate and stearate; unsaturated oleate) on oocyte maturation and quality. In the current study the effects of elevated fatty acid levels on cumulus cells were investigated. The three fatty acids dose-dependently induced lipid storage in cumulus cells accompanied by an enhanced immune labeling of perilipin-2, a marker for lipid droplets. Lipidomic analysis confirmed incorporation of the administered fatty acids into triglyceride, resulting in a 3-6 fold increase of triglyceride content. In addition, palmitate selectively induced ceramide formation, which has been implicated in apoptosis. Indeed, of three fatty acids tested, palmitate induced reactive oxygen species formation, caspase 3 activation, and mitochondria deterioration, leading to degeneration of the cumulus cell layers. This effect could be mimicked by addition of ceramide C2 analog and could be inhibited by the ceramide synthase inhibitor fumonisin B1. Interfering with the intactness of the cumulus cell layers, either by mechanical force or by palmitate treatment, resulted in enhanced uptake of lipids in the oocyte and increased radical formation. Our results show that cumulus cells act as a barrier, protecting oocytes from in vitro induced lipotoxic effects. We suggest that this protective function of the cumulus cell layers is important for the developmental competence of the oocyte. The relevance of our findings for assisted reproduction technologies is discussed