Changes in caridac output and hemolymph flow during hypoxic exposure in the gravid grass shrimp, <Emphasis Type="Italic">Palaemonetes pugio</Emphasis>

The cardiovascular response of decapod crustaceans to hypoxic exposure is well documented; however, information is limited concerning the influence of reproductive state on cardiovascular demands during hypoxic exposure. Given the additional metabolic demand of reproduction, we investigated the cardiovascular adjustments employed by gravid grass shrimp Palaemonetes pugio to maintain oxygen delivery during hypoxic stress. Cardiac output values were elevated in gravid compared to nongravid grass shrimp. Gravid grass shrimp were exposed to hypoxia and the stroke volume, heart rate, cardiac output and hemolymph flow were determined using video-microscopy and dimensional analysis. Oxygen consumption rates were determined using respirometry. There where no changes in the cardiac output values of gravid females until reaching 6.8 kPa O₂, with a significant redistribution of hemolymph flow at 13.7 kPa O₂. Flow was significantly decreased to the anterior lateral arteries that supply the ovaries and hepatopancreas, the anterior aorta and the posterior aorta. The redistribution of hemolymph flow away from these vessels results in an enhanced hemolymph flow to the sternal artery that supplies the ventral segmental system, the gills, the buccal apparatus and the ventral nerve cord. The data suggest that during hypoxic stress, gravid females place a priority on survival.     

Hybrid Weakness in Phaseolus vulgaris L. I. Disruption of Development and Hormonal Allocation

A reduced concentration of cytokinins may cause the abnormal growth and development found in F1 hybrids between Andean and Mesoamerican races of Phaseolus vulgaris L. In this study, concentrations of the transportable cytokinin zeatin riboside (ZR) were measured by ELISA for ZR (cross reactivities dihydrozeatin, 14%, zeatin 7.6%) in roots, stems, and leaves of a Phaseolus Mesoamerican landrace (P. vulgaris L. cv. Redkloud), an Andean landrace (P. vulgaris L. cv. Batt), and their F1 hybrids. Concentrations of ZR in roots and leaves of F1 hybrids were significantly less than that found in roots and leaves of parental cultivars. Approximately 90% of the ZR found in F1 hybrids was found sequestered in the stems, whereas cytokinins of the parental cultivars were distributed throughout the plant (roots: Batt 37%, Redkloud, 44%; stems: Batt 35%, Redkloud 42%; leaves: Batt 28%, Redkloud 14%). These results suggest that abnormal growth and development of F1 hybrids may involve interruption of the regulation of cytokinin allocation, thereby disrupting the root-shoot feedback loop between root-sourced cytokinins and putative shoot-produced factors. Received October 15, 1998; accepted May 12, 1999     

Covalent binding of LTA(4) to nucleosides and nucleotides

Leukotriene A(4) (LTA(4)) is a chemically reactive conjugated triene epoxide that is formed by 5-lipoxygenase and is an intermediate in the formation of the biologically active eicosanoids leukotriene B(4) and leukotriene C(4). The present study was undertaken to determine whether or not LTA(4) could serve as an electrophilic species that nucleosides and nucleotides could attack, ultimately resulting in a covalent adduct. Electrospray ionization mass spectrometry and tandem mass spectrometry were used to study the covalent binding of LTA(4) with uridine, cytidine, adenosine, and guanosine. The reaction with guanosine was found to yield five major and at least six minor adduct species. Reversed phase HPLC and mass spectrometric data suggested that the guanosine attacked LTA(4) either at carbon-12 or carbon-6 with opening the epoxide at carbon-5 to yield a series of adducts characterized by the molecular anion [M-H](-) at m/z 600.3. Reactions of LTA(4) with mixtures of nucleosides and nucleotides revealed that guanine-containing nucleosides were the most reactive toward LTA(4). The facility of the reaction of guanine with LTA(4) raises the possibility that this intermediate of leukotriene biosynthesis formed on or near the cellular nuclear envelope may react with nucleosides and nucleotides present in RNA or DNA.     

Kinetics of protein agglomeration. A nephelometric method for the determination of total protein in biological samples

The kinetics of agglomeration of proteins precipitating in a viscous solution was measured by light scattering. The resulting transitory maximum was linearly proportional to the mass of protein over three orders of magnitude. The change in scattering intensity is described as a change in scattering symmetry due to a continuous in particle size.This method is both fast (minutes) and sensitive (30 ng protein) and is independent of the chemical composition of the different protein species and is barely influenced by size and shape of the proteins.By solubilising the protein in an alkaline dedecyl sulfate solution this method can be applied to all types of biological samples (e.g. tissue homogenates proteins) and also to all types of biological preparations containing detergents as well as urea, sucrose, salts and lipids.     

Magnetic resonance imaging of the siliceous skeleton of the demosponge Lubomirskia baicalensis

The skeletal elements (spicules) of the demosponge Lubomirskia baicalensis were analyzed; they are composed of amorphous, non-crystalline silica, and contain in a central axial canal the axial filament which consists of the enzyme silicatein. The axial filament, that orients the spicule in its longitudinal axis exists also in the center of the spines which decorate the spicule. During growth of the sponge, new serially arranged modules which are formed from longitudinally arranged spicule bundles are added at the tip of the branches. X-ray analysis revealed that these serial modules are separated from each other by septate zones (annuli). We describe that the longitudinal bundles of spicules of a new module originate from the apex of the earlier module from where they protrude. A cross section through the oscular/apical-basal axis shows that the bundle rays are organized in a concentric and radiate pattern. High resolution magnetic resonance microimaging studies showed that the silica spheres of the spicules in the cone region contain high amounts of 'mobile' water. We conclude that the radiate accretive growth pattern of sponges is initiated in the apical region (cones) by newly growing spicules which are characterized by high amounts of 'mobile' water; subsequently spicule bundles are formed laterally around the cones.     

Automated analysis of three-dimensional stress echocardiography

Real-time three-dimensional (3D) ultrasound imaging has been proposed as an alternative for two-dimensional stress echocardiography for assessing myocardial dysfunction and underlying coronary artery disease. Analysis of 3D stress echocardiography is no simple task and requires considerable expertise. In this paper, we propose methods for automated analysis, which may provide a more objective and accurate diagnosis. Expert knowledge is incorporated via statistical modelling of patient data. Methods for identifying anatomical views, detecting endocardial borders, and classification of wall motion are described and shown to provide favourable results. We also present software developed especially for analysis of 3D stress echocardiography in clinical practice. Interobserver agreement in wall motion scoring is better using the dedicated software (96%) than commercially available software not dedicated for this purpose (79%). The developed tools may provide useful quantitative and objective parameters to assist the clinical expert in the diagnosis of left ventricular function.     

Discrimination between different types of low-level luminescence in mammalian cells: The biophysical radiation

Cellular low-level luminescence was measured after various disintegrative processes in brain cell preparations. In addition to known origins of low-level luminescence, e.g. oxygen radical reactions or enzymatic and non-enzymatic redox systems, a further source of photon emission is reported which is independent of external oxygen, oxygen radicals and enzyme activities. Vital cells from rat brain homogenates or pig oligodendrocytes could be kept for hours at 37 °C without any photon emission. Only after disintegrative processes a cellular photon emission could be induced. The maximal intensity of about 400 impulses/s/mg protein and a total radiation of about 6 × 10⁶ I/mg depended on the type of cells. The signal could be retained completely at 4 °C or in frozen samples. Heating (10 min, 90 °C) did not suppress the photon emission. Luminol and lucigenin did not amplify the signal as is usually observed in oxygen radical-producing cells. Non-specific radical scavengers as well as detergents suppressed the cellular photon emission completely. It is suggested that this cellular luminescence represents a biophysical radiation which originates from the interruption of an intermolecular radiationless energy transfer.