Complementary Domains of Retinoic Acid Production and Degradation in the Early Chick Embryo

AbstractExcess retinoids as well as retinoid deprivation cause abnormal development, suggesting that retinoid homeostasis is critical for proper morphogenesis. RALDH-2 and CYP26, two key enzymes that carry out retinoic acid (RA) synthesis and degradation, respectively, were cloned from the chick and show significant homology with their orthologs in other vertebrates. Expression patterns of RALDH-2 and CYP26 genes were determined in the early chick embryo by in situ hybridization. During gastrulation and neurulation RALDH-2 and CYP26 were expressed in nonoverlapping regions, with RALDH-2 transcripts localized to the presumptive presomitic and lateral plate mesoderm and CYP26 mRNA to the presumptive mid- and forebrain. The two domains of expression were separated by an approximately 300-μm-wide gap, encompassing the presumptive hindbrain. In the limb region, a similar spatial segregation of RALDH-2 and CYP26 expression was found at stages 14 and 15. Limb region mesoderm expressed RALDH-2, whereas the overlying limb ectoderm expressed CYP26. RA-synthesizing and -degrading enzymatic activities were measured biochemically in regions expressing RALDH-2 or CYP26. Regions expressing RALDH-2 generated RA efficiently from precursor retinal but degraded RA only inefficiently. Conversely, tissue expressing CYP26 efficiently degraded but did not synthesize RA. Localized regions of RA synthesis and degradation mediated by these two enzymes may therefore provide a mechanism to regulate RA homeostasis spatially in vertebrate embryos

Upotreba koncentrata dušika iz krumpira u proizvodnji α-amilaze s pomoću plijesni Aspergillus oryzae

The influence of various nitrogen sources and media supplements on α-amylase (EC 3.2.1.1) formation by Aspergillus oryzae ATCC 1011 was investigated in shake flask experiments and batch fermentations. Both inorganic and organic nitrogen-containing supplements have been applied, while corn starch and ammonium sulphate were used as the major source of carbon and nitrogen, respectively. Shake flask experiments revealed that potato nitrogen concentrate (PNC) is almost equivalent to corn steep liquor (CSL) in supporting amylase formation. A pretreatment step consisting of clarification of the turbid material did not show any significant effect. The replacement of the inorganic nitrogen source by sodium nitrate led to lower enzyme yields. Other complex supplements may reduce the enzyme level formed, e.g. casein hydrolysate, or increase the amylase titre slightly, e.g. yeast extract or malt extract. Cultivations in instrumented bench top reactors on media supplemented with PNC led to higher cell growth rates and yields of α-amylase in comparison with the medium without any supplement. Replacement of PNC by CSL revealed a slightly increased enzyme level, which is in the range of 9–17 % after 100 h of cultivation. Only minor differences were revealed in the growth kinetics and enzyme formation when PNC was used as the sole nitrogen source, replacing a mixture of soybean meal, yeast extract, malt extract and casein hydrolysate in bioreactor cultivations with lactose as the carbon source. However, metabolic differences as seen from the course of dissolved oxygen tension (DOT), α-amino nitrogen concentration and the amount of acid needed to maintain a constant pH were observed.Istražen je utjecaj različitih izvora dušika i dodataka podlozi na proizvodnju α-amilaze (EC 3.2.1.1) s pomoću plijesni Aspergillus oryzae ATCC 1011 u pokusu na tresilici i šaržnim uzgojem. Primijenjeni su anorganski i organski dušikovi spojevi, a kao glavni izvori ugljika i dušika korišteni su kukuruzni škrob i amonijev sulfat. Pokusima na tresilici dokazano je da je utjecaj koncentrata dušika iz krumpira (potato nitrogen concentrate – PNC) na proizvodnju amilaze skoro jednak onom ekstrakta kukuruza (corn steep liquor – CSL). Pročišćavanjem zamućenog materijala prije obrade nije se postigao značajan učinak. Zamjenom anorganskog izvora dušika natrijevim nitratom dobiveni su manji prinosi enzima. Dodatkom drugih kompleksnih spojeva, kao što je hidrolizat kazeina, smanjio se prinos enzima, a dodatkom ekstrakta kvasca ili slada neznatno se povećao titar amilaze. Veći rast stanica i bolji prinos α-amilaze postignut je uzgojem na podlozi obogaćenoj s PNC u reaktoru na postolju nego bez tih dodataka. Zamjenom PNC sa CSL postignuto je povećanje prinosa enzima za 9-17 % nakon 100 sati uzgoja. Upotreba PNC kao jedinog izvora dušika, uz zamjenu sojine kaše, ekstrakta kvasca i slada te hidrolizata kazeina laktozom kao izvorom ugljika, dovela je do neznatnih razlika u kinetici rasta i formiranju enzima u bioreaktoru. Međutim, uočene su metaboličke razlike u zasićenosti otopljenim kisikom (dissolved oxygen tension – DOT), koncentraciji α-amino dušika i količini kiseline potrebne za održavanje konstantnog pH

A Minimization Method for Relativistic Electrons in a Mean-Field Approximation of Quantum Electrodynamics

We study a mean-field relativistic model which is able to describe both the behavior of finitely many spin-1/2 particles like electrons and of the Dirac sea which is self-consistently polarized in the presence of the real particles. The model is derived from the QED Hamiltonian in Coulomb gauge neglecting the photon field. All our results are non-perturbative and mathematically rigorous.Comment: 18 pages, 3 figure

Self-consistent solution for the polarized vacuum in a no-photon QED model

We study the Bogoliubov-Dirac-Fock model introduced by Chaix and Iracane ({\it J. Phys. B.}, 22, 3791--3814, 1989) which is a mean-field theory deduced from no-photon QED. The associated functional is bounded from below. In the presence of an external field, a minimizer, if it exists, is interpreted as the polarized vacuum and it solves a self-consistent equation. In a recent paper math-ph/0403005, we proved the convergence of the iterative fixed-point scheme naturally associated with this equation to a global minimizer of the BDF functional, under some restrictive conditions on the external potential, the ultraviolet cut-off $\Lambda$ and the bare fine structure constant $\alpha$. In the present work, we improve this result by showing the existence of the minimizer by a variational method, for any cut-off $\Lambda$ and without any constraint on the external field. We also study the behaviour of the minimizer as $\Lambda$ goes to infinity and show that the theory is "nullified" in that limit, as predicted first by Landau: the vacuum totally kills the external potential. Therefore the limit case of an infinite cut-off makes no sense both from a physical and mathematical point of view. Finally, we perform a charge and density renormalization scheme applying simultaneously to all orders of the fine structure constant $\alpha$, on a simplified model where the exchange term is neglected.Comment: Final version, to appear in J. Phys. A: Math. Ge

Pedicle De-epithelialization in Reduction Mammoplasty: A Systematic Review of the Literature

Reduction mammoplasty is among the most commonly performed plastic surgery procedures. The reduction pedicle is traditionally de-epithelialized. Many practitioners propose that preservation of the subdermal blood supply results in improved circulation for the nipple-areolar complex. However, this is a time-consuming step of the procedure. Presumed benefits have not been definitively demonstrated. To evaluate current evidence regarding pedicle de-epithelialization in inferior pedicle reduction mammoplasty. The MEDLINE database was searched for studies evaluating pedicle de-epithelialization in reduction mammoplasty surgery. Studies reporting outcomes after reduction mammoplasty with pedicle de-epithelialization and deskinning were included. Additionally, reports detailing novel techniques or modification for pedicle de-epithelialization were evaluated and included. One hundred and thirty-eight articles were identified on a systematic review. Thirty-six articles met the study criteria. This includes 23 reporting outcomes after reduction mammoplasty procedures and 13 describing novel techniques for pedicle de-epithelialization. Of the 23 studies reporting outcomes, 6 studies evaluated deskinning of the pedicle. Two of the six studies directly compared deskinning and de-epithelialization. They reported no significant difference in outcomes. The remaining 17 articles described outcomes of inferior pedicle reduction mammoplasty with pedicle de-epithelialization. Studies evaluating deskinning reported ischemic nipple-areolar complex complication rates between 0 and 1.4%. Studies evaluating de-epithelialization reported ischemic nipple-areolar complex complication rates between 0 and 11.1%. Pedicle de-epithelialization is commonly performed despite limited definitive evidence evaluating its surgical necessity or benefits. Available evidence suggests deskinning may yield acceptable results; however, further investigation is necessary. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266

Use of Potato Nitrogen Concentrate in the Production of α-Amylase by Aspergillus oryzae

The influence of various nitrogen sources and media supplements on α-amylase (EC 3.2.1.1) formation by Aspergillus oryzae ATCC 1011 was investigated in shake flask experiments and batch fermentations. Both inorganic and organic nitrogen-containing supplements have been applied, while corn starch and ammonium sulphate were used as the major source of carbon and nitrogen, respectively. Shake flask experiments revealed that potato nitrogen concentrate (PNC) is almost equivalent to corn steep liquor (CSL) in supporting amylase formation. A pretreatment step consisting of clarification of the turbid material did not show any significant effect. The replacement of the inorganic nitrogen source by sodium nitrate led to lower enzyme yields. Other complex supplements may reduce the enzyme level formed, e.g. casein hydrolysate, or increase the amylase titre slightly, e.g. yeast extract or malt extract. Cultivations in instrumented bench top reactors on media supplemented with PNC led to higher cell growth rates and yields of α-amylase in comparison with the medium without any supplement. Replacement of PNC by CSL revealed a slightly increased enzyme level, which is in the range of 9–17 % after 100 h of cultivation. Only minor differences were revealed in the growth kinetics and enzyme formation when PNC was used as the sole nitrogen source, replacing a mixture of soybean meal, yeast extract, malt extract and casein hydrolysate in bioreactor cultivations with lactose as the carbon source. However, metabolic differences as seen from the course of dissolved oxygen tension (DOT), α-amino nitrogen concentration and the amount of acid needed to maintain a constant pH were observed

Developing a 670k genotyping array to tag ~2M SNPs across 24 horse breeds.

BackgroundTo date, genome-scale analyses in the domestic horse have been limited by suboptimal single nucleotide polymorphism (SNP) density and uneven genomic coverage of the current SNP genotyping arrays. The recent availability of whole genome sequences has created the opportunity to develop a next generation, high-density equine SNP array.ResultsUsing whole genome sequence from 153 individuals representing 24 distinct breeds collated by the equine genomics community, we cataloged over 23 million de novo discovered genetic variants. Leveraging genotype data from individuals with both whole genome sequence, and genotypes from lower-density, legacy SNP arrays, a subset of ~5 million high-quality, high-density array candidate SNPs were selected based on breed representation and uniform spacing across the genome. Considering probe design recommendations from a commercial vendor (Affymetrix, now Thermo Fisher Scientific) a set of ~2 million SNPs were selected for a next-generation high-density SNP chip (MNEc2M). Genotype data were generated using the MNEc2M array from a cohort of 332 horses from 20 breeds and a lower-density array, consisting of ~670 thousand SNPs (MNEc670k), was designed for genotype imputation.ConclusionsHere, we document the steps taken to design both the MNEc2M and MNEc670k arrays, report genomic and technical properties of these genotyping platforms, and demonstrate the imputation capabilities of these tools for the domestic horse

The Sad Mad 'Un

Background: To date, genome-scale analyses in the domestic horse have been limited by suboptimal single nucleotide polymorphism (SNP) density and uneven genomic coverage of the current SNP genotyping arrays. The recent availability of whole genome sequences has created the opportunity to develop a next generation, high-density equine SNP array. Results: Using whole genome sequence from 153 individuals representing 24 distinct breeds collated by the equine genomics community, we cataloged over 23 million de novo discovered genetic variants. Leveraging genotype data from individuals with both whole genome sequence, and genotypes from lower-density, legacy SNP arrays, a subset of ~5 million high-quality, high-density array candidate SNPs were selected based on breed representation and uniform spacing across the genome. Considering probe design recommendations from a commercial vendor (Affymetrix, now Thermo Fisher Scientific) a set of ~2 million SNPs were selected for a next-generation high-density SNP chip (MNEc2M). Genotype data were generated using the MNEc2M array from a cohort of 332 horses from 20 breeds and a lower-density array, consisting of ~670 thousand SNPs (MNEc670k), was designed for genotype imputation. Conclusions: Here, we document the steps taken to design both the MNEc2M and MNEc670k arrays, report genomic and technical properties of these genotyping platforms, and demonstrate the imputation capabilities of these tools for the domestic horse