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41.
Recent explorations of hydrothermal vents in the eastern Pacific (Juan de Fuca spreading zone, Guaymas Basin in the Gulf of California, East Pacific Rise at 21° N and 13° N, and Galapagos Rift) and on the Mid-Atlantic Ridge have revealed many copepods, mostly siphonostomatoids with few poecilostomatoids. In these habitats in depths from 1 808 to 3 650 m water temperatures may reach nearly 15 ° C. Among more than 22 000 copepods from vents examined two new families, 11 new genera, and 32 new species were represented.In addition, two new copepods were found in 3 260 m at cold seeps at the base of the West Florida Escarpment in the Gulf of Mexico, an environment not thermally active, with water temperatures about 4.39 °C.Some of these copepods were associated with host invertebrates such as a Nuculana-like protobranch bivalve, a polychaete, and two species of shrimps. Others were obtained from washings of bivalves or vestimentiferans or by means of corers or slurp guns. 相似文献
42.
43.
Delorme Evelyne; Gomez-Silva Benito; Stern Arthur I.; Schiff Jerome A. 《Plant & cell physiology》1986,27(1):177-182
Highly purified condensed mitochondria obtained from bleachedmutant. W10BSmL of Euglena gracilis Klebs var bacillaris Coriincorporate [35S]methionine into protein when fortified withmalate, ADP, Mg2+, phosphate and a sucrose osmoticum. Twentyto twenty-five polypeptide bands were found to be labeled inorganello when the labeled protein was subjected to sodium dodecylsulfatepolyacrylamide gel electrophoresis. Methionine incorporation,but not respiration or oxidative phosphorylation, was blockedby chloramphenicol and other 70S ribosomal translation inhibitorsbut cycloheximide and ribonuclease were without effect. Inhibitorsof electron transport and uncouplers of oxidative phosphorylationwere excellent inhibitors of protein synthesis. Thus, thesemitochondrial preparations carry out protein synthesis in organellothat is linked to respiration and oxidative phosphorylation.
1Present address: VA Hospital Outpatient Clinic, 17 Court St.,Boston, MA 02115, U.S.A.
2Present address: Laboratories de Microbiologia e Inmunologia,Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile.
3Present address: Botany Department, University of Massachusetts,Amherst, MA 01003, U.S.A. (Received June 17, 1985; Accepted October 28, 1985) 相似文献
44.
Antonio Fernández Tiburcio Ravindar Kaur-Sawhney Arthur W. Galston 《Plant physiology》1986,82(2):375-378
We have attempted to improve the viability of cereal mesophyll protoplasts by pretreatment of leaves with dl-α-difluoromethylarginine (DFMA), a specific `suicide' inhibitor of the enzyme (arginine decarboxylase) responsible for their osmotically induced putrescine accumulation. Leaf pretreatment with DFMA before a 6 hour osmotic shock caused a 45% decrease of putrescine and a 2-fold increase of spermine titer. After 136 hours of osmotic stress, putrescine titer in DFMA-pretreated leaves increased by only 50%, but spermidine and spermine titers increased dramatically by 3.2- and 6-fold, respectively. These increases in higher polyamines could account for the reduced chlorophyll loss and enhanced ability of pretreated leaves to incorporate tritiated thymidine, uridine, and leucine into macromolecules. Pretreatment with DFMA significantly improved the overall viability of the protoplasts isolated from these leaves. The results support the view that the osmotically induced rise in putrescine and blockage of its conversion to higher polyamines may contribute to the lack of sustained cell division in cereal mesophyll protoplasts, although other undefined factors must also play a major role. 相似文献
45.
13C-nmr has been employed to probe the molecular conformation and crystal structure of (1 → 6)-β-D -glucan (pustulan) in the solution, gel, and solid states. CP/MAS 13C-nmr spectra recorded for partially crystalline solid pustulan display a resonance near 82 ppm that is absent in solution spectra. The intensity and peak width of this resonance were found to depend on relative crystallinity as determined by x-ray diffraction. CP/MAS spectra of aqueous pustulan gels also exhibit the 82-ppm resonance, suggesting that the gelation mechanism may involve microcrystalline junction zones. Since the 82-ppm resonance is absent in the CP/MAS spectrum of the (1 → 6)-β-linked dimer gentiobiose, we tentatively conclude the crystal structure of this dimer does not adequately model the yet undetermined structure of pustulan. 相似文献
46.
Donald M. Bers Kenneth D. Philipson Arthur Peskoff 《The Journal of membrane biology》1985,85(3):251-261
Summary Calcium binding and Na–Ca exchange activity were measured in isolated cardiac plasma membrane vesicles under various ionic conditions. A model was developed to describe the Ca binding characteristics of cardiac sarcolemmal vesicles using the Gouy-Chapman theory of the diffuse double layer with specific cation binding to phospholipid carboxyl and phosphate groups. The surface association constants used for Ca, Na, K and H binding to both of these groups were 7, 0.63, 0.3 and 3800m
–1, respectively. This model allows the estimation of surface [Ca] under any specific ionic conditions. The effects of the divalent screening cation, dimethonium, on Ca binding and Na–Ca exchange were compared. Dimethonium had no significant effect on Ca binding at high ionic strength (150mm KCl), but strongly depressed Ca binding at low ionic strength. Dimethonium had no significant effect on Na–Ca exchange (Na-inside dependent Ca influx) at either high or low ionic strength. These results suggest that the Ca sites of the Na–Ca exchanger are in a physical environment where they are either not exposed to or not sensitive to surface [Ca]. 相似文献
47.
Arthur L. Koch 《Journal of molecular evolution》1985,21(3):270-277
Summary It is proposed that the first entity capable of adaptive Darwinian evolution consisted of a liposome vesicle formed of (1) abiotically produced phospholipidlike molecules; (2) a very few informational macromolecules; and (3) some abiogenic, lipid-soluble, organic molecule serving as a symporter for phosphate and protons and as a means of high-energy-bond generation. The genetic material had functions that led to the production of phospholipidlike materials (leading to growth and division of the primitive cells) and of the carrier needed for energy transduction. It is suggested that the most primitive exploitable energy source was the donation of 2H++2e– at the external face of the primitive cell. The electrons were transferred (by metal impurities) to internal sinks of organic material, thus creating, via a deficit, a protonmotive force that could drive both the active transport of phosphate and high-energy-bond formation.This model implies that proton translocation in a closed-membrane system preceded photochemical or electron transport mechanisms and that chemically transferable metabolic energy was needed at a much earlier stage in the development of life than has usually been assumed. It provides a plausible mechanism whereby cell division of the earliest protocells could have been a spontaneous process powered by the internal development of phospholipids. The stimulus for developing this evolutionary sequence was the realization that cellular life was essential if Darwinian survival of the fittest was to direct evolution toward adaptation to the external environment. 相似文献
48.
Superoxide dismutase and glutathione peroxidase activities in neutrophils from selenium deficient and copper deficient cattle 总被引:3,自引:0,他引:3
Oxygen consumption and the activities of the selenoenzyme glutathione peroxidase, and of the hexose monophosphate shunt were lower than normal in neutrophils from Se deficient cattle. However, these activities and the activity of Cu/zinc superoxide dismutase were unaffected in neutrophils from Cu deficient cattle. These results are discussed with reference to impaired neutrophil microbicidal activity previously demonstrated to result from Se or Cu deficiency in cattle. 相似文献
49.
Paul D. Cooper Arthur M. Jungreis 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(6):743-750
Summary Moulting fluid ofManduca sexta contains high concentrations of potassium and bicarbonate (100 mM) and low concentrations of chloride (5 mM). This fluid begins to disappear from the exuvial space approximately 9–10 h before the actual shedding of the integument. During this time, the integument can be isolated in an Ussing cell and electrical properties measured in vitro. In a normal 32 mM KHCO3 saline, potential difference (PD) is around 10 mV, exuvial side positive, and short-circuit current (SCC) is 15–20 A cm–2. Substitution of chloride slightly reduces both PD and SCC, although resistance does not change significantly. Measurement of chloride transport in the absence of K+ indicates that 100% of the SCC can be accounted for by the net chloride flux (2 A cm–2). TheK
m andJ
max for transepithelial chloride transport are 14 mM and 0.1 Eq cm–2 h–1. Bilateral potassium addition stimulates chloride transport, doubling net chloride flux as potassium concentration increases from 2 to 5 mM. Chloride net flux is not inhibited by the presence of furosemide (1 mM), nor in HCO
3
–
-free saline by thiocyanate (1 or 10 mM) or acetazolamide (0.1 mM), but is inhibited by 100% N2. The pattern of chloride transport inM. sexta is similar to that previously reported for the rectum of locusts. As chloride is normally at low concentrations in the moulting fluid, it is suggested that this transport system acts to maintain low intracellular concentrations which may be necessary for enzymatic functions in the epidermal cells and has little importance in fluid transport.Abbreviations
PD
potential difference
-
PPI
pharate pupal integument
-
SCC
short circuit current
In the time since this research was performed, A.M. Jungreis passed away. He will be missed by his friends and colleagues 相似文献
50.
Stephen M. Lasley Robert D. Greenland Daniel J. Minnema I. Arthur Michaelson 《Neurochemical research》1985,10(7):933-944
Investigations of the mechanisms involved in the neurotoxicity resulting from chronic inorganic lead (Pb) exposure have centered on CNS biogenic amine function on the basis of behavioral and neurochemical findings. The following study examined the time course of the response of dopamine (DA) and 5-hydroxytryptamine (5-HT) neurons to d-amphetamine (AMPH) in rats chronically exposed to Pb from birth in order to further examine neurochemical mechanisms implicated by previous work. Offspring were exposed to 0.2% Pb acetate via the lactating dam and then weaned to the same drinking solution. At 120–140 days animals were injected with 1.0 mg/kg s.c. of the drug or with saline and sacrificed after various intervals. DA content in nucleus accumbens and corpus striatum in Pb-exposed animals was significantly higher than corresponding levels in controls at 20 minutes post-drug and remained significantly higher than baseline values at 80 minutes after the drug when DA concentrations in controls had returned to normal. These data suggest enhanced AMPH-induced DA synthesis in exposed rats. 5-Hydroxyindoleacetic acid (5-HIAA) content was significantly increased in three brain regions in exposed rats given AMPH compared to values in saline-injected exposed animals, indicating a compensation in these areas for the decreases in 5-HIAA values produced by Pb exposure alone. The results of this study reinforce the hypothesis that DA and 5-HT neurons are sensitive to relatively low levels of Pb exposure. 相似文献