Engines of change: Transposable element mutation rates are high and variable within Daphnia magna

Transposable elements (TEs) represent a major portion of most eukaryotic genomes, yet little is known about their mutation rates or how their activity is shaped by other evolutionary forces. Here, we compare short- and long-term patterns of genome-wide mutation accumulation (MA) of TEs among 9 genotypes from three populations of Daphnia magna from across a latitudinal gradient. While the overall proportion of the genome comprised of TEs is highly similar among genotypes from Finland, Germany, and Israel, populations are distinguishable based on patterns of insertion site polymorphism. Our direct rate estimates indicate TE movement is highly variable (net rates ranging from -11.98 to 12.79 x 10⁻⁵ per copy per generation among genotypes), differing both among populations and TE families. Although gains outnumber losses when selection is minimized, both types of events appear to be highly deleterious based on their low frequency in control lines where propagation is not limited to random, single-progeny descent. With rate estimates 4 orders of magnitude higher than base substitutions, TEs clearly represent a highly mutagenic force in the genome. Quantifying patterns of intra- and interspecific variation in TE mobility with and without selection provides insight into a powerful mechanism generating genetic variation in the genome.     

Adjuvant I-131 therapy for T0–3 N1b M0 differentiated thyroid cancer with many (≥ 5) positive nodes

BackgroundIn patients with well-differentiated thyroid cancer, there is controversy about the prognostic importance of a large number of positive neck nodes and the potential value of radioiodine therapy. The purpose of this study was to evaluate this issue in the group of patients for whom it is most clinically important — those with classic histology and favorable T and M stage.Materials and methodsTwenty-five patients met the following inclusion criteria: classic histology of papillary or follicular thyroid carcinoma treated with total thyroidectomy and neck dissection followed by adjuvant I-131 treatment in our department between January 1, 2003, and December 31, 2013; adult age of > 21 years; and American Joint Committee on Cancer (AJCC ) stage (8^th edition) of T0–3, N1b with ≥ 5 positive nodes, and M0.ResultsThe median positive node number was 10 (range, 5–31). The median adjuvant I-131 dose was 158 mCi (range, 150–219 mCi). The median follow-up in patients without recurrence after treatment was 7.3 years. The 10-year actuarial rates were favorable: overall survival, 100%; freedom from visible recurrence, 82%; and visible or biochemical recurrence, 72%.ConclusionRecurrence was infrequent in our study population with ≥ 5 positive nodes following moderate-dose adjuvant I-131 treatment. These results are valuable in directing initial adjuvant therapy and follow-up intensity. Our results do not inform the question of the use of postoperative thyroglobulin (Tg) level to select N1b patients for low-dose I-131 treatment.     

Giant,accordioned sperm acrosomes of the greater bulldog bat,Noctilio leporinus

Sperm of the greater bulldog bat Noctilio leporinus display an architecture that is totally unique among mammalian spermatozoa. The sperm head of Noctilio is extraordinarily large and flat and lies eccentrically with respect to the sperm tail. The major portion of the atypically large acrosome lies anterior to the nucleus and is shaped into a dozen accordionlike folds that run parallel to the long axis of the sperm. The ridge of each fold is shaped into ∼60 minute, evenly spaced rises that extend along the entire length of the fold. We speculate that acrosome ridges may serve to strengthen the sperm head during transport. Mol. Reprod. Dev. 48:90–94, 1997 © 1997 Wiley-Liss, Inc.     

An airlift loop reactor for the transformation of steroids by immobilized cells

Summary The flow behaviour of calcium alginate beads in an airlift reactor (ALR) with external loop was dependent on the airflow rate into and the amount of beads in the reactor. The performance of immobilizedArthrobacter simplex for the ¹-dehydrogenation of hydrocortisone in the ALR compared favourably to that in a stirred tank reactor. The physical stability of the calcium alginate beads was significantly greater in the ALR.     

Filtration of a yeast suspension using an enclosed microporous metal filter

Summary A microporous (3 m) metal filter was very efficient for the recovery of Saccharomyces cerevisiae from a suspension. The filtration could be described by a cake filtration model, the cake resistance being dependent on the pressure drop applied and the concentration of bodyfeed added. The mean filtration capacity was 0.4 m³/m² h.     

Optimal sex ratio as a function of EGG incubation temperature in the crocodilians

Recently, there has been a growing consensus as to the adaptive significance of temperature-dependent sex determination in the Crocodilia. The observationally and experimentally motivated hypotheses are that male fitness depends more strongly on quality of incubation environment than female fitness, and that there is a strong correlation between a female's egg incubation temperature choice and her own egg incubation temperature. A population genetics model based on these hypotheses is derived. A method for finding the optimal sex ratio as a function of temperature, which is an evolutionary stable strategy (ESS), is stated and applied under various assumptions. This extends ESS theory to thefunctional case. Cases where there is no ESS and the population sex ratio oscillates in evolutionary time are discovered. Numerical computation is needed to solve the full problem and the resulting optimal sex ratio is compared to laboratory sex ratio data. The general pattern of TSD in crocodilians (female-male-female with female biased overall sex ratio) agrees well with the theory, but details of the pattern are problematic.     

Isolation and Characterization of Opioid Peptides from Rabbit Cerebellum

The rabbit cerebellum has been shown to contain significant quantities of opioid receptors consisting of both mu- and kappa-subtypes. To determine the nature of the endogenous opioid ligands in this tissue, extracts from rabbit cerebellum were separated by various chromatography techniques and fractions were assayed initially for opioid peptides with a radioimmunoassay capable of detecting all peptides with an amino-terminal Tyr-Gly-Gly-Phe sequence. This sequence is common to all mammalian opioid peptides and is critical for recognition by all known opioid receptors. Each of the three immunoreactive opioid peptide peaks detected was purified to homogeneity and subjected to amino acid composition and sequence analysis. One peak was analyzed further by mass spectrometry. This identified the major opioid peptides in the cerebellum as [Met5]enkephalin, [Leu5]enkephalin, and heptapeptide [Met5]enkephalyl-Arg6-Phe7. The comprehensiveness of this initial detection scheme in identifying biologically active opioid peptides was substantiated through subsequent analysis. Using specific radioimmunoassays for representative opioid peptides of the three opioid systems currently known, no other peptides of either the proenkephalin, proopiomelanocortin, or prodynorphin series were detected in any appreciable amounts. Collectively, these results are consistent with the position that rabbit cerebellar opioids are derived from proenkephalin. However, given that no appreciable quantities of either [Met5]enkephalyl-Arg6-Arg7-Val8-NH2 (metorphamide) or [Met5]enkephalyl-Arg6-Gly7-Leu8 were detected suggests that rabbit proenkephalin may have a slightly altered sequence and/or is differentially processed relative to other mammalian species studied.