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61.
Hanna M. Pappius 《Neurochemical research》1991,16(9):941-949
The studies reviewed here represent a continuing search for mechanisms which play a role in neurological disturbances resulting from brain injury. Focal cortical freezing lesions in rats were shown to cause a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity. Such an interpretation was supported by the finding that in lesioned brain reduction of cerebral metabolism by pentobarbital and isoflurane was limited by the metabolic depression that has already occurred as a result of injury and by the demonstration that the energy status and substrate (glucose) supply in the cortical areas in the injured brain have not been compromised at the time when LCGU was decreased. Both the serotonergic and the noradrenergic neurotransmitter systems were implicated in functional alterations associated with injury. Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere and complete inhibition of 5-HT synthesis withp-chlorophenylalanine ameliorated the decrease in cortical LCGU, interpreted as reflecting cortical functional depression. Cortical norepinephrine metabolism was bilaterally increased in focally injured brain, while prazosin, a selective 1-noradrenergic receptor blocker, normalized cortical LCGU in the lesioned hemisphere. Low-affinity in vivo binding of [125I]HEAT, another selective 1-receptor ligand, was specifically increased in cortical areas of the lesioned hemisphere at the time of the greatest depression in LCGU, suggesting that 1-adrenoreceptors may be of functional importance in injured brain. The general conclusion from this series of studies on mechanisms underlying functional disturbances in injured brain is that both the serotonergic and the noradrenergic neurotransmitter systems are involved in the widespread cortical depression which develops with time as a consequence of a focal lesion. The data are compatible with the inhibitory effects of NE and 5-HT in the cortex and with the hypothesis that these two transmitter systems affect cortical information processing. 相似文献
62.
Identification of an insertion sequence, IS1081, in Mycobacterium bovis 总被引:12,自引:0,他引:12
Abstract: An insertion sequence, IS1081, in the genome of Mycobacterium bovis has been identified and sequenced. It is 1324 bp long with 15 bp inverted repeat ends and contains a large ORF. There are six copies of IS1081 in the genome of M. bovis and the element is also present in Mycobacterium tuberculosis . IS1081 is not closely related to other DNA elements described in actinomycetes but its putative transposase bears some resemblance to that of IS256 from Staphylococcus aureus . IS1081 may be useful for genetic manipulations and for developing a diagnostic test for bovine tuberculosis based on the polymerase chain reaction. 相似文献
63.
A bioluminescent assay for the determination of phosphoenolpyruvate carboxykinase activity in nanogram-sized tissue samples 总被引:1,自引:0,他引:1
Monika Wimmer 《Analytical biochemistry》1988,170(2):376-381
A highly specific and sensitive assay for the determination of phosphoenolpyruvate carboxykinase (PEPCK) in nanogram-sized tissue samples is described. This test system is based on the stoichiometric transformation of phosphoenolpyruvate into ATP. In a subsequent step ATP is quantified by bioluminescent techniques. The applicability of this assay system is shown by measurements in liver samples with normal and high PEPCK activity levels. 相似文献
64.
M. A. Khan 《Hydrobiologia》1986,135(3):233-242
L. Naranbagh (alt. 1587 m) is a polymictic, shallow marl lake in the flood-plain valley of Kashmir, India. Macrofloral affinities resemble Potamogeton Type of Forsberg (1965) with alkaline waters, not rich in phosphorus. CaCO3 precipitation coupled with decline in Ca2+ and alkalinity values are characteristic of the lake. Fluctuations in Mg2+, Na+, K+, and Cl– were relatively conservative. The levels of PO
inf4
sup3–
-P and NO
inf3
sup–
-N indicate moderate fertility of the lake water.Persistence of a summer-autumn planktonic algal pulse is related to favourable irradiance, high water temperatures, and increased photosynthetic efficiency values. The most striking seasonality in photosynthetic rates (m–2 h–1) between winter minimum (3 mg Cassim) and summer maximum (75.4 mg Cassim) is determined by mainly climatic changes. Energy flow gave annual phytoplankton production of 51.95 × 102 KJ m–2 for the ecosystem.The nutrient levels and productivity rates suggest mesotrophic status of L. Naranbagh in classic oligoeutrophic classification of lake types. 相似文献
65.
Summary Active HCO
3
t-
secretion in the anterior rectal salt gland of the mosquito larva,Aedes dorsalis, is mediated by a 11 Cl–/HCO
3
–
exchanger. The cellular mechanisms of HCO
3
–
and Cl– transport are examined using ion- and voltage-sensitive microelectrodes in conjunction with a microperfused preparation which allowed rapid saline changes. Addition of DIDS or acetazolamide to, or removal of CO2 and HCO
3
–
from, the serosal bath caused large (20 to 50 mV) hyperpolarizations of apical membrane potential (V
a) and had little effect on basolateral potential (V
bl). Changes in luminal Cl– concentration alteredV
a in a repid, linear manner with a slope of 42.2 mV/decaloga
Cl
l
–. Intracellular Cl– activity was 23.5mm and was approximately 10mm lower than that predicted for a passive distribution across the apical membrane. Changes in serosal Cl– concentration had no effect onV
bl, indicating an electrically silent basolateral Cl– exit step. Intracellular pH in anterior rectal cells was 7.67 and the calculated
was 14.4mm. These results show that under control conditions HCO3 enters the anterior rectal cell by an active mechanism against an electrochemical gradient of 77.1 mV and exits the cell at the apical membrane down a favorable electrochemical gradient of 27.6 mV. A tentative cellular model is proposed in which Cl enters the apical membrane of the anterior rectal cells by passive, electrodiffusive movement through a Cl–-selective channel, and HCO
3
–
exits the cell by an active or passive electrogenic transport mechanism. The electrically silent nature of basolateral Cl– exit and HCO3 entry, and the effects of serosal addition of the Cl–/HCO3 exchange inhibitor, DIDS, on
and transepithelial potential (V
ic) suggest strongly that the basolateral membrane is the site of a direct coupling between Cl– and HCO
3
–
movements. 相似文献
66.
VIRGINIA SEYMOUR 《Plant, cell & environment》1985,8(9):631-638
Abstract The leaves of Berberis aquifolium (Pursh.) exhibit either diffuse or specular (shiny) reflection, depending on the variety, but in no case are the leaves obviously glaucous. The dull-surfaced leaves were less wettable than the glossy ones. Using scanning electron microscopy it was determined that the diffuse reflection was due to tubular crystals of wax 250 nm in diameter. The crystals were primarily composed of 19-nonacosanol, a 29-carbon secondary alcohol, as determined by gas chromatography-mass spectrometry. The chemical constituents of the wax underlying the tubes appeared to be the same as those of the wax from glossy leaves, with 29-carbon and 31-carbon n-alkanes and n-heptacosanol as major constituents. The reflection spectra of dull-surfaced (diffuse reflection) or glossy (specular reflection) leaves were the same, as were those of leaves with different amounts of epicuticular wax. Removing the epicuticular wax with chloroform did not change the spectrum. 相似文献
67.
Abstract A most-probable-number technique was used to quantify the abundance of myxomycetes (myxogastrids) in soil samples taken from 23 'Sites of Special Scientific Interest' and one other site in the West of England. Associated organisms and soil conditions were also recorded. Sixteen of the 24 sites yielded myxomycete plasmodium-forming units (PFUs) in numbers averaging 230 cm−3 fresh soil. Where detectable in samples of grassland soil, the numbers ranged from 20–2750 cm−3 , in woodland soil from 20–800 cm−3 , and in sand dunes from 80–400 cm−3 . Repeated sampling revealed changing numbers at single sites. The abundance of PFUs was correlated positively with numbers of soil amoebae, ciliates and nematodes, and with levels of magnesium and soil density, and negatively with organic matter content and levels of NH4 -nitrogen and phosphate. Each PFU probably corresponded to one or several uninucleate cells in the soil rather than to a plasmodium. 相似文献
68.
Cytochrome c oxidase preparations from bovine heart muscle contain 1 zinc per 2 irons. Metal contents of nine preparations determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) show that Cu, Fe and Zn are the only metals present in significant amounts with average Cu/Fe, Fe/Zn, and Cu/Zn atom ratios of 1.3, 2.1 and 2.8, respectively. Removal of adventitious copper results in a Cu:Fe:Zn stoichiometry of 2:2:1. The zinc is tightly bound. Dialysis against a solution of 1,10-phenanthroline at pH 7.4 or an acidic buffer (pH 4.4) does not remove Zn. Dialysis against 0.8 M KCN at pH 10 causes partial loss of both Cu and Zn. This is the first evidence for the presence of Zn in a cytochrome c oxidase. 相似文献
69.
Estimation in change-point hazard rate models 总被引:1,自引:0,他引:1
70.
Phytochrome (120 kdalton or 60 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa München). Irradiation with red light of the Pr form at −23°C in aqueous medium or at −40°C in 66% glycerol leads to the intermediate meta-Rb. Acidification of the glycerol solution at −40°C leads to the absorption of the 15(E) phytochrome chromophore (= Pfr chromophore). Subsequent irradiation transforms this into the 15(Z) chromophore (= Pr chromophore). The presence of the 15(E) chromophore was demonstrated by the same methods also in phytochrome bleached either as Pfr in the dark by 4 M urea, methanol, acetone, ethylene glycol, 8-anilinonaphthalene-1-sulfonate, or as Pr by irradiation with red light in the presence of the same agents. Phytochrome bleached by sodium dodecylsulfate or by dehydration was also investigated. It was concluded that bleached phytochrome contains the Pfr chromophore without specific interaction with the protein. 相似文献