Rapid natriuretic action of aldosterone in the rat.

Rapid, nongenomic actions of aldosterone have been demonstrated in a number of cell types in vitro, including renal cell lines, but there remains little direct evidence that it is able to exert rapid effects on the kidney in the whole animal. Accordingly, the aim of this study was to determine whether aldosterone induces rapid changes in the renal handling of electrolytes or acid-base balance in the anesthetized rat. With the use of a servo-controlled fluid replacement system, spontaneous urine output by anesthetized male Sprague-Dawley rats was replaced with 2.5% dextrose. After a 3-h equilibration and a 1-h control period, rats were infused with aldosterone (42 pmol/min) or vehicle for 1 h. Aldosterone infusion induced a rapid (within 15 min) increase in sodium excretion that peaked at 0.24 +/- 0.08 compared with 0.04 +/- 0.01 micromol x min(-1) 100 x body weight(-1) (P = 0.041) in the vehicle-infused rats. This natriuresis was not associated with changes in glomerular filtration rate; urine flow rate; potassium, chloride, or bicarbonate excretion; or urine pH. The mechanisms involved are unclear, but because we have previously shown that aldosterone stimulates a rapid (4 min) increase in cAMP generation in the rat inner medullary collecting duct (IMCD) (Sheader EA, Wargent ET, Ashton N, and Balment RJ. J Endocrinol 175: 343-347, 2002), they could involve cAMP-mediated activation of the cystic fibrosis transmembrane conductance regulator chloride channel, which drives sodium secretion in the IMCD.     

Novel microsatellite loci identified from the Australian eastern small‐eyed snake (Elapidae: Rhinocephalus nigrescens) and cross species amplification in the related genus Suta

A total of 15 microsatellite primers pairs were developed for the Australian small‐eyed snake Rhinoplocephalus nigrescens. Five primers were used to screen 93 individuals of R. nigrescens and were also tested against eight species of the closely related genus Suta. Allelic diversity in R. nigrescens was high in three loci (12–27) and there was high heterozygosity (0.58–0.82). Observed heterozygosity did not deviate from Hardy–Weinberg expectations for the five loci tested. These primers will be useful in studies of population genetics and mating systems of small‐eyed snakes and related species.     

Structural and Transcriptional Variation of Mitochondrial DNA in Pollen-Sterile Agamospermous Sugar Beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.) Progeny

The cytoplasm status according to mitochondrial sequence tags was determined in agamospermous sugar beet progenies characterized by unstable manifestation of cytoplasmic male sterility. The detected variations in the ratios of homologous sequences related to the N and S mtDNA types did not correlate with pollen phenotypes of the plants. Polymerase chain reaction allowed semiquantitative evaluation of these variations and their detection. A cDNA corresponding to a hitherto unknown minor RNA and containing a consensus sequence of dicotyledonous plant promoters was detected by mtRNA display. Probable sources of CMS variability in agamospermous sugar beet progenies are discussed.     

Study of X-ray and neutron emission in experiments with Al wires in an MA plasma focus

Results are presented from experimental studies of the correlation between X-ray and neutron emissions generated in the implosion of a deuteron plasma shell onto an Al wire. The experiments were carried out on the PF-1000 facility at currents of 1.5–1.8 MA. An Al wire 80 μm in diameter and 7–9 cm in length was placed at the end of the inner electrode. During the implosion of the plasma shell, Al K-shell X-rays were first emitted at the dip of the current derivative. After the X-ray pulse, a relatively stable corona with a diameter of 2–3 mm and lifetime of a few hundred nanoseconds formed around the wire. The presence of the wire did not considerably reduce the total neutron yield (at most 10¹¹ neutrons per shot) in comparison to discharges without a wire. As a rule, the intensity of neutron emission was maximal a few tens of nanoseconds after the peak of X-ray emission. A detailed comparison of two shots with low and high neutron yields have shown that the neutron yield depends on the configuration and dynamics of the discharge. The possible influence of the self-generated axial component of the magnetic field on the development of the plasma focus and the acceleration of fast deuterons is discussed.     

Long-lived plasmoids generated by surface microwave discharges in chemically active gases

The generation of long-lived microplasmoids is observed during the irradiation of a metal-dielectric surface with a high-power microwave beam in a chemically active gas mixture (H₂ + O₂; CH₄ + O₂). The lifetime of these plasmoids substantially exceeds the characteristic recombination and cooling times of plasmoids arising at the target surface in a chemically inactive medium.     

Clonal analysis of adult human olfactory neurosphere forming cells.

Olfactory neuroepithelium (ONe) is unique because it contains progenitor cells capable of mitotic division that replace damaged or lost neurons throughout life. We isolated populations of ONe progenitors from adult cadavers and patients undergoing nasal sinus surgery that were heterogeneous and consisted of neuronal and glial progenitors. Progenitor lines have been obtained from these cultures that continue to divide and form nestin positive neurospheres. In the present study, we used clonal and population analyses to probe the self-renewal and multipotency of the neurosphere forming cells (NSFCs). NSFCs plated at the single cell level produced additional neurospheres; dissociation of these spheres resulted in mitotically active cells that continued to divide and produce spheres as long as they were subcultured. The mitotic activity of clonal NSFCs was assessed using bromodeoxyuridine (BrdU) incorporation. Lineage restriction of the clonal cultures was determined using a variety of antibodies that were characteristic of different levels of neuronal commitment: ss-tubulin isotype III, neural cell adhesion molecule (NCAM) and microtubule associated protein (MAP2), or glial restriction: astrocytes, glial fibrillary acidic protein (GFAP); and oligodendrocytes, galactocerebroside (GalC). Furthermore, nestin expression, a marker indicative of progenitor nature, decreased in defined medium compared to serum-containing medium. Therefore, adult human ONe-derived neural progenitors retain their capacity for self-renewal, can be clonally expanded, and offer multipotent lineage restriction. Therefore, they are a unique source of progenitors for future cell replacement strategies in the treatment of neurotrauma and neurodegenerative diseases.     

Growth,photosynthesis, and metabolism of sugar beet at an early stage of exposure to elevated CO<Subscript>2</Subscript>

The effects of CO₂ concentration (C _a) on growth, photosynthesis, and the activity of enzymes associated with the translocation and assimilation of CO₂ were studied in sugar beet (Beta vulgaris L. subsp. saccharifera, cv. Ramonskaya) plants. The plants were grown in controlled-climate chamber to the stage of 3–4 leaves and then used in experiments. Experimental plants were exposed in boxes to doubled C _a (700 µl/l, 2C plants), whereas control plants were kept in a chamber with ambient atmosphere (350 µl/l, 1C plants). As compared with 1C plants, in 3 and 8 days, the leaf area of 2C plants increased by 14 and 26%, respectively. The rate of their photosynthesis (P _n) measured in 3, 6, and 8 days increased by 85, 47, and 52%, respectively, whereas in normal air, the values of P _n in 2C plants were by 12, 19, and 15% lower than in 1C plants. After 8-day growth, the content of soluble carbohydrates in the leaves of 2C plants attained 7.2%, being by 80% greater than in 1C plants; the content of starch did not exceed 3%. The total content of chlorophylls a and b in the leaves of 2C plants was by 14% greater than in 1C plants, but their ratio was essentially the same. The level of protein in 2C plants was by 13.4% lower than in 1C plants. The activity and content of Rubisco in 1C and 2C plants were similar. As compared with 1C plants, in 2C plants the activity of soluble carbonic anhydrase (sCA) was lower by 34% in 3 days and by 18% in 8 days; the activity of carbonic anhydrase of membrane preparations (mCA), was lower by 24 and 77%, respectively. Catalase activity in 2C plants became by 8% lower than in 1C plants only after 8 days. A reduction in the photosynthetic ability of 2C plants in ambient atmosphere, a decrease in activity of sCA and, especially, of mCA observed together with invariable activity and content of Rubisco in the leaf extracts are interpreted as early symptoms of acclimation of young plants of sugar beet to elevated CO₂.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 184–190.Original Russian Text Copyright © 2005 by Ignatova, Novichkova, Mudrik, Lyubimov, Ivanov, Romanova.This revised version was published online in April 2005 with a corrected cover date.     

Origin of Multiphase Reduction of P700<Superscript>+</Superscript> in Broad Bean Leaves after Irradiation with Far-Red Light

The kinetic curves of dark reduction of P700⁺ (oxidized primary donor of PSI) after far-red light irradiation were studied on broad bean (Vicia faba L.) leaves treated with antimycin A, methyl viologen, or diuron. Four components of P700⁺ reduction were found in untreated leaves, namely, an ultrafast component with a half-time of 25 ms, and fast (210 ms), middle (790 ms), and slow (6100 ms) components. The fast component disappeared in leaves treated with antimycin A or methyl viologen. At the same time, these substances did not affect other components of P700⁺ reduction. Treatment of leaves with diuron abolished both the ultrafast and fast components of P700⁺ reduction. As the length of far-red light exposure was increased, a lag phase appeared in the development of middle component in leaves treated with diuron, antimycin A, or methyl viologen. In thus treated leaves, an exponential pattern of the middle component was displayed with a certain delay after darkening. A conclusion was drawn that the minor ultrafast component of P700⁺ dark reduction in broad bean leaves was caused by electron donation to PSI from PSII, whereas the fast component of this process was determined by the operation of ferredoxin-dependent electron transport around PSI. The middle and slow components were supposed to be related to electron input to PSI from reductants localized in the chloroplast stroma.From Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 492–498.Original English Text Copyright © 2005 by Egorova, Nikolaeva, Bukhov.The article was translated by the authors.     

Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada

Climate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence‐absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm‐water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.