Oxygen-dependent quenching of phosphorescence used to characterize improved myocardial oxygenation resulting from vasculogenic cytokine therapy

This study evaluates a therapy for infarct modulation and acute myocardial rescue and utilizes a novel technique to measure local myocardial oxygenation in vivo. Bone marrow-derived endothelial progenitor cells (EPCs) were targeted to the heart with peri-infarct intramyocardial injection of the potent EPC chemokine stromal cell-derived factor 1α (SDF). Myocardial oxygen pressure was assessed using a noninvasive, real-time optical technique for measuring oxygen pressures within microvasculature based on the oxygen-dependent quenching of the phosphorescence of Oxyphor G3. Myocardial infarction was induced in male Wistar rats (n = 15) through left anterior descending coronary artery ligation. At the time of infarction, animals were randomized into two groups: saline control (n = 8) and treatment with SDF (n = 7). After 48 h, the animals underwent repeat thoracotomy and 20 μl of the phosphor Oxyphor G3 was injected into three areas (peri-infarct myocardium, myocardial scar, and remote left hindlimb muscle). Measurements of the oxygen distribution within the tissue were then made in vivo by applying the end of a light guide to the beating heart. Compared with controls, animals in the SDF group exhibited a significantly decreased percentage of hypoxic (defined as oxygen pressure ≤ 15.0 Torr) peri-infarct myocardium (9.7 ± 6.7% vs. 21.8 ± 11.9%, P = 0.017). The peak oxygen pressures in the peri-infarct region of the animals in the SDF group were significantly higher than the saline controls (39.5 ± 36.7 vs. 9.2 ± 8.6 Torr, P = 0.02). This strategy for targeting EPCs to vulnerable peri-infarct myocardium via the potent chemokine SDF-1α significantly decreased the degree of hypoxia in peri-infarct myocardium as measured in vivo by phosphorescence quenching. This effect could potentially mitigate the vicious cycle of myocyte death, myocardial fibrosis, progressive ventricular dilatation, and eventual heart failure seen after acute myocardial infarction.     

Tropospheric 14CO2 at Wellington, New Zealand: the world??s longest record

Measurements of near-sea-level tropospheric ??¹⁴CO₂ have been made at Wellington, New Zealand since December 1954; these measurements comprise the longest such record available. The ??¹⁴C rose from ?10?? in 1955 peaking at 695?? in 1965 as a result of ??bomb ¹⁴C?? production, before falling thereafter to the present day (2005) value of 73??. The ??¹⁴C peak occurred about 1?year later in the southern hemisphere than in the northern hemisphere. The post-1965 fall is due to the transfer of ¹⁴C-enriched CO₂ to the biospheric and oceanic pools together with ongoing release of ¹⁴C-free CO₂ from fossil fuel combustion, during an era without major atmospheric nuclear-weapon tests. Time series analysis of the data using Loess decomposition and filtering indicates an approximately exponential decline in excess ??¹⁴CO₂ over 1967?C2005 with an e-folding time of 18?years. The seasonal cycle from 1954 until 1980 had a maximum in the late (austral) summer, a minimum in winter, with peak-to-trough amplitude that peaked at 20?? in 1966. For the period 1980?C1989, a new seasonal cycle emerged, with a maximum in winter and a minimum in late summer/early autumn and peak-to-trough amplitude of 3.5??, transitioning to a new seasonal structure after about 1990.     

Molecular stiffness of selectins

During inflammation, selectin-ligand interactions provide forces for circulating leukocytes to adhere to vascular surfaces, which stretch the interacting molecules, suggesting that mechanical properties may be pertinent to their biological function. From mechanical measurements with atomic force microscopy, we analyzed the molecular characteristics of selectins complexed with ligands and antibodies. Respective stiffness of L-, E-, and P-selectins (4.2, 1.4, and 0.85 piconewton/nm) correlated inversely with the number (2, 6, and 9) of consensus repeats in the selectin structures that acted as springs in series to dominate their compliance. After reconstitution into a lipid bilayer, purified membrane P-selectin remained a dimer, capable of forming dimeric bonds with P-selectin glycoprotein ligand (PSGL)-1, endoglycan-Ig, and a dimeric form of a glycosulfopeptide modeled after the N terminus of PSGL-1. By comparison, purified membrane L- and E-selectin formed only monomeric bonds under identical conditions. Ligands and antibodies were much less stretchable than selectins. The length of endoglycan-Ig was found to be 51 ± 12 nm. These results provide a comprehensive characterization of the molecular stiffness of selectins and illustrate how mechanical measurements can be utilized for molecular analysis, e.g. evaluating the multimericity of selectins and determining the molecular length of endoglycan.     

Migration patterns and navigation cues of Atlantic salmon post-smolts migrating from 12 rivers through the coastal zones around the Irish Sea

The freshwater phase of the first seaward migration of juvenile Atlantic salmon (Salmo salar) is relatively well understood when compared with our understanding of the marine phase of their migration. In 2021, 1008 wild and 60 ranched Atlantic salmon smolts were tagged with acoustic transmitters in 12 rivers in England, Scotland, Northern Ireland and Ireland. Large marine receiver arrays were deployed in the Irish Sea at two locations: at the transition of the Irish Sea into the North Atlantic between Ireland and Scotland, and between southern Scotland and Northern Ireland, to examine the early phase of the marine migration of Atlantic salmon smolts. After leaving their natal rivers' post-smolt migration through the Irish Sea was rapid with minimum speeds ranging from 14.03 to 38.56 km.day⁻¹ for Atlantic salmon smolts that entered the Irish Sea directly from their natal river, to 9.69–39.94 km.day⁻¹ for Atlantic salmon smolts that entered the Irish Sea directly from their natal estuary. Population minimum migration success through the study area was strongly correlated with the distance of travel, populations further away from the point of entry to the open North Atlantic exhibited lower migration success. Post-smolts from different populations experienced different water temperatures on entering the North Atlantic. This was largely driven by the timing of their migration and may have significant consequences for feeding and ultimately survivorship. The influence of water currents on post-smolt movement was investigated using data from previously constructed numerical hydrodynamic models. Modeled water current data in the northern Irish Sea showed that post-smolts had a strong preference for migrating when the current direction was at around 283° (west-north-west) but did not migrate when exposed to strong currents in other directions. This is the most favorable direction for onward passage from the Irish Sea to the continental shelf edge current, a known accumulation point for migrating post-smolts. These results strongly indicate that post-smolts migrating through the coastal marine environment are: (1) not simply migrating by current following (2) engage in active directional swimming (3) have an intrinsic sense of their migration direction and (4) can use cues other than water current direction to orientate during this part of their migration.     

Lz-0 × Berkeley: a new Arabidopsis recombinant inbred line population for the mapping of complex traits

This study describes the generation and test of a genetic resource suited to identify determinants of cell biological traits in plants. The use of quantitative trait loci (QTL) mapping for a better genetic understanding of cell biological traits is still at an early stage, even for biotechnologically important cell properties, such as the dimensions of fiber cells. A common strategy, the mapping of QTLs in recombinant inbred line (RIL) populations, is limited by the fact that the existing RIL populations exploit only a small fraction of the existing natural variation. Here, we report the mapping of QTLs impacting on the length of fiber cells in Arabidopsis inflorescence stems in a newly generated RIL population derived from a cross between the accessions Berkeley and the little known Lz-0. Through inbreeding of individual F₂ plants, a total of 159 new F₈ lines were produced and genotyped with a set of 49 single nucleotide polymorphism markers. The population was successfully used not only for the mapping of three QTLs controlling fiber length, but also to map five QTL controlling flowering time under short and long-day conditions. Our study demonstrates the usefulness of this new genetic resource by mapping in it QTLs underlying a poorly explored cellular trait as well as an already better explored regulatory pathway. The new RIL population and an online platform for the continuous supplementation of genetic markers will be generally available to substantially broaden the genetic diversity through which loci with impact on plant quantitative traits can be identified.     

Forces Required to Initiate Membrane Tether Extrusion from Cell Surface Depend on Cell Type But Not on the Surface Molecule

When a cell adhered to another cell or substratum via surface proteins is forced to detach, lipid membrane tethers are often extruded from the cell surface before the protein bond dissociates. For example, during the inflammatory reaction leukocytes roll on the surface of activated endothelial cells. The rolling adhesion is mediated by interactions of selectins with their ligands, e.g., P-selectin glycoprotein ligand (PSGL)-1, which extrudes membrane tethers from the surfaces of both leukocytes and endothelial cells. Membrane tether extrusion has been suggested to regulate leukocyte rolling. Here we examine several factors that may affect forces required to initiate membrane tethers, or initial tether force. It was found that initial tether forces were similar regardless of the presence or absence of the cytoplasmic tail of P-selectin and regardless of whether the tethers were extruded via binding to PSGL-1 or Fcγ receptors. Initial tether forces were found to depend on the cell types tested and were greatly reduced by treatment of latrunculin A, which inhibits actin polymerization. These data provide additional insights to the control of membrane tether extrusion, which should be taken into account when cellular functions such as rolling where tether extrusion plays a regulatory role are compared using different cell types expressing the same molecule.     

Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

Walking humansconserve mechanical and, presumably, metabolic energy with an invertedpendulum-like exchange of gravitational potential energy and horizontalkinetic energy. Walking in simulated reduced gravity involves arelatively high metabolic cost, suggesting that the inverted-pendulummechanism is disrupted because of a mismatch of potential and kineticenergy. We tested this hypothesis by measuring the fluctuations andexchange of mechanical energy of the center of mass at differentcombinations of velocity and simulated reduced gravity. Subjects walkedwith smaller fluctuations in horizontal velocity in lower gravity, suchthat the ratio of horizontal kinetic to gravitational potential energyfluctuations remained constant over a fourfold change in gravity. Theamount of exchange, or percent recovery, at 1.00 m/s was notsignificantly different at 1.00, 0.75, and 0.50 G (average 64.4%),although it decreased to 48% at 0.25 G. As a result, the amount ofwork performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

     

Different Levels of Food Restriction Reveal Genotype-Specific Differences in Learning a Visual Discrimination Task

In behavioural experiments, motivation to learn can be achieved using food rewards as positive reinforcement in food-restricted animals. Previous studies reduce animal weights to 80–90% of free-feeding body weight as the criterion for food restriction. However, effects of different degrees of food restriction on task performance have not been assessed. We compared learning task performance in mice food-restricted to 80 or 90% body weight (BW). We used adult wildtype (WT; C57Bl/6j) and knockout (ephrin-A2^−/−) mice, previously shown to have a reverse learning deficit. Mice were trained in a two-choice visual discrimination task with food reward as positive reinforcement. When mice reached criterion for one visual stimulus (80% correct in three consecutive 10 trial sets) they began the reverse learning phase, where the rewarded stimulus was switched to the previously incorrect stimulus. For the initial learning and reverse phase of the task, mice at 90%BW took almost twice as many trials to reach criterion as mice at 80%BW. Furthermore, WT 80 and 90%BW groups significantly differed in percentage correct responses and learning strategy in the reverse learning phase, whereas no differences between weight restriction groups were observed in ephrin-A2^−/− mice. Most importantly, genotype-specific differences in reverse learning strategy were only detected in the 80%BW groups. Our results indicate that increased food restriction not only results in better performance and a shorter training period, but may also be necessary for revealing behavioural differences between experimental groups. This has important ethical and animal welfare implications when deciding extent of diet restriction in behavioural studies.     

Software for genome mapping by fingerprinting techniques

A genome mapping package has been developed for reading andassembling data from clones analysed by restriction enzyme fragmentationand polyacrylamide gel electrophoresis. The package comprises:data entry; matching; assembly; statistical analysis; modelling.Data entry can be either manual or by a semiautomatic systembased on a scanning densitometer. The primary emphasis in theanalytical routines is on flexibility and interactive convenience,so that the operator has full knowledge of and control overthe growing map, but a variety of automatic options are included.The package continually grows to meet the needs of the Caenorhabditisproject. Received on July 17, 1987; accepted on November 20, 1987