A benign approach to the preparation of freshwater bryozoan statoblasts for scanning electron microscopy (SEM) imaging

Abstract

Several different species of freshwater Bryozoa, belonging to the genera Plumatella, Rumarcanella and Fredericella, were detected within the Northern Mallee Pipeline (NMP) system in Victoria, Australia, that required definitive identification. These organisms produce asexual buds called statoblasts, with valves composed of sclerotised chitin that bear minute micro-ornamentations of considerable taxonomical significance. Imaging and analysis of these distinctive micro-ornamentations using scanning electron microscopy (SEM) is often employed for species identification. Meticulous preparation of statoblast samples is therefore required that necessitates the removal of adhering debris, dehydration and drying—whilst mitigating specimen damage and distortion. This technical note describes an approach whereby each of these three steps have been individually designed to be as benign as possible, using mild detergent/sonication to remove debris, a gradual and gentle dehydration procedure using ethanol, and critical point drying. For the overall process, these methods are chosen to optimise control and to minimise the use of harsh and hazardous chemicals.     

Complete genome sequence of Ignisphaera aggregans type strain (AQ1.S1)

Ignisphaera aggregans Niederberger et al. 2006 is the type and sole species of genus Ignisphaera. This archaeal species is characterized by a coccoid-shape and is strictly anaerobic, moderately acidophilic, heterotrophic hyperthermophilic and fermentative. The type strain AQ1.S1(T) was isolated from a near neutral, boiling spring in Kuirau Park, Rotorua, New Zealand. This is the first completed genome sequence of the genus Ignisphaera and the fifth genome (fourth type strain) sequence in the family Desulfurococcaceae. The 1,875,953 bp long genome with its 2,009 protein-coding and 52 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Transmissible and nontransmissible complex chromosome aberrations characterized by three-color and mFISH define a biomarker of exposure to high-LET alpha particles

Insertions have been proposed as potential stable biomarkers of chronic high-LET radiation exposure. To examine this in vitro, we irradiated human peripheral blood lymphocytes in G(0) with either 50 cGy (238)Pu alpha particles (LET 121.4 keV/microm) or 3 Gy 250 kV X rays and stimulated their long-term culture up to approximately 22 population doublings postirradiation. Mitotic cells were harvested at regular intervals throughout this culture period and were assayed for chromosome aberrations using the techniques of three-color and 24-color mFISH. We observed the stable persistence of transmissible-type complex rearrangements, all involving at least one insertion. This supports the hypothesis that insertions are relevant indicators of exposure to high-LET radiation. However, one practical caveat of insertions being effective biomarkers is that their frequency is low due to the complexity and cell lethality of the majority of alpha-particle-induced complexes. Therefore, we propose a "profile of damage" that relies on the presence of insertions, a low frequency of stable simple reciprocal translocations (2B), and, significantly, the complexity of the damage initially induced. We suggest that the complexity of first- and second-division alpha-particle-induced nontransmissible complex aberrations reflects the structure of the alpha-particle track and as a consequence adds radiation-quality specificity to the biomarker, increasing the signal:noise ratio of the characteristic 2B:insertion ratio.     

The objective structured interview for medical student selection

An objective structured interview is an integral part of the process of selecting and admitting applicants to study medicine at this university. During the nine years (to the end of 1986) that the interview has been used 1600 candidates were interviewed out of roughly 13 000 applicants, and from these, 584 students were admitted to the course. Analysis of the interview data was carried out based on two aspects of student progress: graduation with honours and failure to complete the course of study.The interview as a whole, and especially some of the subscales, appears to identify students who may fail to complete the course: it may also help to predict which students are likely to graduate with honours.     

Lactate uptake by the fetal sheep liver

Lactate is produced by the sheep placenta and is an important metabolic substrate for fetal sheep. However, lactate uptake and release by the fetal liver have not been assessed directly. We measured lactate flux across the liver in 16 fetal sheep at 129 (120-138) days gestation that had catheters chronically maintained in the fetal descending aorta, inferior vena cava, right or left hepatic vein, and umbilical vein. Lactate and hemoglobin concentrations and oxygen saturation were measured in blood drawn from all vessels. Umbilical venous, portal venous, and hepatic blood flow were measured by injecting radionuclide-labeled microspheres into the umbilical vein while obtaining a reference sample from the descending aorta. We found net hepatic uptake of lactate (5.0 +/- 4.4 mg/min per 100 g liver). A large quantity of lactate was delivered to the liver (94.2 +/- 78.1 mg/min per 100 g), so that the hepatic extraction of lactate was only 7.7 +/- 6.5%. Hepatic oxygen consumption was 3.18 +/- 3.3 ml/min per 100 g, and the hepatic lactate/oxygen quotient was 2.07 +/- 1.54. There was no significant correlation between hepatic lactate uptake and hepatic lactate or glucose delivery, hepatic oxygen consumption, hepatic blood flow, hepatic glucose flux, total body oxygen consumption, arterial pH, oxygen content, or oxygen saturation. There was, however, a significant correlation between hepatic lactate uptake and umbilical lactate uptake (r = 0.74, P less than 0.005) such that net hepatic lactate uptake was nearly equivalent to that produced across the umbilical-placental circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Ku protein complex interacts with YY1, is up-regulated in human heart failure, and represses alpha myosin heavy-chain gene expression

Human heart failure is accompanied by repression of genes such as alpha myosin heavy chain (alphaMyHC) and SERCA2A and the induction of fetal genes such as betaMyHC and atrial natriuretic factor. It seems likely that changes in MyHC isoforms contribute to the poor contractility seen in heart failure, because small changes in isoform composition can have a major effect on the contractility of cardiac myocytes and the heart. Our laboratory has recently shown that YY1 protein levels are increased in human heart failure and that YY1 represses the activity of the human alphaMyHC promoter. We have now identified a region of the alphaMyHC promoter that binds a factor whose expression is increased sixfold in failing human hearts. Through peptide mass spectrometry, we identified this binding activity to be a heterodimer of Ku70 and Ku80. Expression of Ku represses the human alphaMyHC promoter in neonatal rat ventricular myocytes. Moreover, overexpression of Ku70/80 decreases alphaMyHC mRNA expression and increases skeletal alpha-actin. Interestingly, YY1 interacts with Ku70 and Ku80 in HeLa cells. Together, YY1, Ku70, and Ku80 repress the alphaMyHC promoter to an extent that is greater than that with YY1 or Ku70/80 alone. Our results suggest that Ku is an important factor in the repression of the human alphaMyHC promoter during heart failure.     

Anaerobic methane oxidation in a coastal oxygen minimum zone: spatial and temporal dynamics

Coastal waters are a major source of marine methane to the atmosphere. Particularly high concentrations of this potent greenhouse gas are found in anoxic waters, but it remains unclear if and to what extent anaerobic methanotrophs mitigate the methane flux. Here we investigate the long-term dynamics in methanotrophic activity and the methanotroph community in the coastal oxygen minimum zone (OMZ) of Golfo Dulce, Costa Rica, combining biogeochemical analyses, experimental incubations and 16S rRNA gene sequencing over 3 consecutive years. Our results demonstrate a stable redox zonation across the years with high concentrations of methane (up to 1.7 μmol L⁻¹) in anoxic bottom waters. However, we also measured high activities of anaerobic methane oxidation in the OMZ core (rate constant, k, averaging 30 yr⁻¹ in 2018 and 8 yr⁻¹ in 2019–2020). The OPU3 and Deep Sea-1 clades of the Methylococcales were implicated as conveyors of the activity, peaking in relative abundance 5–25 m below the oxic–anoxic interface and in the deep anoxic water respectively. Although their genetic capacity for anaerobic methane oxidation remains unexplored, their sustained high relative abundance indicates an adaptation of these clades to the anoxic, methane-rich OMZ environment, allowing them to play major roles in mitigating methane fluxes.     

Immunoprophylaxis of respiratory syncytial virus: global experience

In sarcoidosis, host genetic factors are discussed as contributing to disease susceptibility and course. Since tumor necrosis factor (TNF)-α is a central mediator of granuloma formation and since elevated TNF-α levels are found during active phases of sarcoidosis, genetic polymorphisms correlating with influences on TNF-α levels are of special interest. The complete sequencing of the MHC region and the increase in the number of identified gene polymorphisms in this locus associated with TNF-α production offer the opportunity of detecting new genes associated with sarcoidosis and perhaps of defining disease-associated haplotypes that bear the potential of serving as predictive markers for this disease.