共查询到20条相似文献,搜索用时 20 毫秒
1.
Summary The electrical transients produced by chloroplast bilayer lipid membranes (Chl-BLM) from flash excitation are seen to result from three photocurrents and a discharge current. Each of the three photo-initiated charge transports in Chl-BLM (designated as Components A, B and C) exhibits an action spectrum similar to chlorophyll absorption spectra. The fast components (A and B), which are induced by electron acceptors such as Fe+3, have rise-times of 3 sec and 20 msec, and occur in TLM (thin lipid membranes, i.e., colored membranes up to 1 thick) as well as in BLM. Component C is induced by a transmembrane pH difference or applied voltage, has a rise-time of 1 sec, and occurs only in BLM. Component C is associated with exciton dissociation and proton transport. The mobility of the Component A current carriers in TLM is estimated to be about 1×10–2 cm2/volt sec, and are, hence,electronic. The photovoltage waveforms are described by equations developed, which consider Component A as being caused by a direct charge separation proportional to the illumination intensity (within 0.5 sec), and Components B and C being caused by two types of exciton processes which cause charge transport after the illumination period. 相似文献
2.
Summary Several rat tissues (liver, spleen, kidney, pancreas, skin, heart, lung and brain) were shown to contain a peptidase capable of liberating naphthylamine from glycyl-dl-proline naphthylamide (Gly-Pro-NA). A single DEAE-cellulose chromatography of autodigested homogenates of the above tissues produced a partial separation of the peptidase from the enzymes hydrolysing l-leucine -naphthylamide. The Gly-Pro-NA hydrolysing enzyme was localised in tissue sections by using diazo coupling reaction and indirect immunologic techniques. Antibodies were prepared against the enzyme purified from rat liver and kidney in the rabbit. Rabbit -globulin was localized by using goat anti-rabbit -globulin labeled with fluorescein or with peroxidase. 相似文献
3.
Characterization of a chloride channel reconstituted from cardiac sarcoplasmic reticulum 总被引:1,自引:0,他引:1
We have characterized a voltage-sensitive chloride channel from cardiac sarcoplasmic reticulum (SR) following reconstitution of porcine heart SR into planar lipid bilayers. In 250 mm KCl, the channel had a main conductance level of 130 pS and exhibited two substrates of 61 and 154 pS. The channel was very selective for Cl– over K+ or Na+ (
and
). It was permeable to several anions and displayed the following sequence of anion permeability: SCN– > I– > NO
3
–
Br– > Cl– > f– > HCOO–. Single-channel conductance saturated with increasing Cl– concentrations (K
m= 900 mm and max = 488 pS). Channel activity was voltage dependent, with an open probability ranging from 1.0 around 0 mV to 0.5 at +80 mV. From –20 to +80 mV, channel gating was time-independent. However, at voltages below –40 mV the channel entered a long-lasting closed state. Mean open times varied with voltage, from 340 msec at –20 mV to 6 msec at +80 mV, whereas closed times were unaffected. The channel was not Ca2+-dependent. Channel activity was blocked by disulfonic stilbenes, arylaminobenzoates, zinc, and cadmium. Single-channel conductance was sensitive to trans pH, ranging from 190 pS at pH 5.5 to 60 pS at pH 9.0. These characteristics are different from those previously described for Cl– channels from skeletal or cardiac muscle SR.We thank Dr. Barry Pallotta for help with open and closed intervals analysis and Dr. Gerhard Meissner for his suggestions for the preparation of cardiac sarcoplasmic reticulum membranes. This work was supported by a grant from the National Institutes of Health to R.L.R. and a Student Grant-in-Aid from the American Heart Association, North Carolina affiliate to C.T. R.L.R. is an Established Investigator of the American Heart Association. 相似文献
4.
A case of 21q-syndrome with half normal SOD-1 activity 总被引:2,自引:0,他引:2
K. Yoshimitsu S. Hatano Y. Kobayashi Y. Takeoka M. Hayashidani K. Ueda K. Nomura K. Ohama T. Usui 《Human genetics》1983,64(2):200-202
A male Japanese infant was found to have a chromosomal aberration of del(21)(qter leads to q22.1-2) and decreased superoxide dismutase (SOD) activity in erythrocytes and polymorphonuclear and mononuclear leukocytes. The cuprozinc enzyme (SOD-1) level was 40-50% of normal, while the cyanide-insensitive manganese enzyme (SOD-2) activity was within the normal range. Determination of SOD activity in blood cells is a valuable method of classification of the syndrome. 相似文献
5.
Type-1-protein phosphatase (PP-1) activity is reduced in skeletal muscle from human subjects with insulin resistance (Kida et al. 1990). This reduced phosphatase activity probably leads to the abnormal insulin action for glucose storage observed in insulin-resistant subjects. In the present study, a human homolog of rat liver PP-11 cDNA was isolated from human skeletal muscle. The nucleotide sequence contains a 957-nucleotide open reading frame encoding an amino acid sequence identical to that encoded by rat liver PP-11 cDNA. Northern blot analysis shows PP-11-specific mRNA is expressed in human heart, brain, placenta, lung, liver, skeletal muscle, kidney, and pancreas. PP-11 was localized to human Chromosome 12. 相似文献
6.
K. Ono 《Histochemistry and cell biology》1979,62(2):113-124
Summary Ultrastructural localization of acid phosphatase activity was investigated in ultrathin (0.05 m) and semithin (0.5 and 0.75 m) sections of the small intestinal epithelial cells of adult rats. The results showed that the enzyme activity was localized on the membrane of microvilli, lateral cell membranes, lysosomes, the Golgi complex, and the GERL of Novikoff (a part of the smooth-surfaced endoplasmic reticulum located in close proximity to the inner Golgi saccules) of duodenal absorptive cells. The lysosomes contained within the duodenal and jejunal absorptive cells appeared to be mainly heterolysosomes rather than autolysosomes. The enzyme activity of absorptive cells was lower in the jejunum than in the duodenum, and was barely detectable except in the GERL and lysosomes of the ileum. The average numbers of lysosomes having a diameter of 0.21.0 m, per cell profile in sections of 214 duodenal, 226 jejunal and 318 ileal epithelial cells were 8.9±0.189, 6.4±0.155 and 3.5±0.027 (mean±SE), respectively. From these results, it was assumed that both the Golgi apparatus and GERL produce some lysosomes in the duodenal and jejunal absorptive cells, but only GERL does so in the ileum. It was considered also that because of an unexpectedly high number of lysosomes contained within the epithelial absorptive cells of the proximal intestine of adult rats, these cells may possess the strong heterophagic, as well as absorptive capacity. 相似文献
7.
Summary The objective of this study has been to determine the intracellular localization of calcium in cryofixed, cryosectioned suspensions of kidney proximal tubules using quantitative electron probe X-ray microanalysis. Two populations of cells have been identified: 1) Viable cells, representing the majority of cells probed, are defined by their relatively normal K/Na concentration ratio of 41. Their measured Ca content is 4.1±1.4 (sem) mmol/kg dry wt in the cytoplasm and 3.1 ± 1.1 mmol/kg dry wt in the mitochondria, or an average cell calcium content of 3.8 mmol/kg dry wt. 2) Nonviable cells, defined by the presence of dense inclusions in their mitochondria and a K/Na concentration ratio of 1. The Ca content is 15±2 mmol/kg dry wt in the cytoplasm and 685±139 mmol/kg dry wt in the mitochondria of such cells. Assuming 25 to 30% of the cell volume is mitochondrial, the overall calcium content of such nonviable cells is 210 mmol/kg dry wt. The presence of these inclusions in 4 to 5% of the cells would account for the average total Ca content measured in perchloric acid extracts of isolated proximal tubule suspensions ( 18 nmol/mg protein or 12.6 mmol/kg dry wt). Whole kidney tissues display a large variability in toal Ca content (4.5 to 18 nmol/mg protein, or 3.4 to 13.5 mmol/kg dry wt), which could be accounted for by inclusion in 0 to 4% of the cells. The electron probe X-ray microanalysis (EPXMA) data conclusively demonstrate that thein situ mitochondrial Ca content of viable cells from the kidney, proximal tubule is low and support the idea that mitochondrial Ca may regulate dehydrogenase activity but probably does not normally control cytosolic free Ca. 相似文献
8.
Chakraborty Nilanjan Sarkar Gouranga M. Lahiri Sujit C. 《World journal of microbiology & biotechnology》2003,19(2):145-150
Biomethanation is one of the desirable options for obtaining clean fuel from abundant renewable biomass resources. Improvement of biomethane production may be achieved by using improved strains of microbes, particularly the terminal microbes – the methanogens. Attempts have been made to improve the efficiency of the methanogens isolated from local sources by subjecting the methanogens to mutagenic changes by physical (by irradiation, neutron bombardment) or chemical (by addition of chemicals like acridine orange, colchicine) means. The effects of the treated methanogens on biomethanation were studied. Irradiation or neutron bombardment mutagenesis was dose-dependent and time-dependent. High doses proved to be lethal but methanogens were found to be to some extent radiation resistant when subjected to irradiation at small doses for short duration (5–10 s). No or marginal improvement of methane production occurred for the two strains TDM and TRM. Improvement of methane production occurred from successive transfers of radiation treated strain SSM. Chemical mutagens invariably inhibited biomethanation and the inhibition was dose dependent. 相似文献
9.
Temperature, dissolved oxygen and dissolved methane profiles were measured during autumn and summer, in a shallow floodplain lake in south-eastern Australia to determine the effects of water-column stability on methane and oxygen dynamics. The water column was well mixed in autumn. Strong thermal stratification developed in the late afternoon in summer, with top-to-bottom temperature differences of up to 6 °C. Methane concentrations in surface waters varied over a daily cycle by an 18-fold range in summer, but only by a 2-fold range in autumn. The implication of short-term temporal variation is that static chambers deployed on the water surface for short times (less than a day) in summer will significantly underestimate the diffusive component of methane emissions across the water–atmosphere interface. There was a marked diel variation in dissolved oxygen concentrations in summer, with the highest oxygen values (commonly 5–8 mg l–1) occurring in the surface waters in late afternoon; the bottom waters were then devoid of oxygen (< 0.2 mg l–1). Because of high respiratory demands, even the surface water layers could be nearly anoxic by morning in summer. The concentration of dissolved oxygen in the surface waters was always less than the equilibrium value. When the water column became thermally stratified in summer, the dissolved oxygen and methane maxima were spatially separated, and planktonic methanotrophy would be limited to a moving zone, at variable depth, in the water column. In summer the whole-wetland rates of oxygen production and respiration, calculated from long-term (5 h) shifts in dissolved oxygen concentrations over a diel period, were approximately 6–10 and 3–6 mmol m–3 h–1, respectively. These values correspond to net and gross primary production rates of 0.7–1.2 and 1.0–1.9 g C m–3 day–1, respectively. 相似文献
10.
Kidney -glucuronidase activity in C57BL/K1 and DBA/2/K1 male mice differs about ten times, C57 giving low and DBA high values. F1 males have intermediate activities. Male liver as well as female kidney and liver invariably give low values. The most likely interpretation for this difference between the two strains is a genetic variation at a single locus.This work was supported by the Nilsson-Ehle fund, the Marcus Borgström fund, and the Hierta memorial fund. 相似文献
11.
C. T. Garten Jr. 《Oecologia》1988,76(1):43-50
Summary Two deciduous tree species (yellow poplar and red maple) on Walker Branch Watershed (WBW), near Oak Ridge, Tennessee, were radiolabeled with 35S (87 day halflife) to study internal cycling, storage, and biogenic emission of sulfur (S). One tree of each species was girdled before radiolabeling to prevent phloem translocation to the roots, and the aboveground biomass was harvested prior to autumn leaf fall. Aboveground biomass, leaf fall, throughfall, and stemflow were sampled over a 13 to 24 week period. Sulfur-35 concentrations in tree leaves reached nearly asymptotic levels within 1 to 2 weeks after radiolabeling. Foliar leaching of 35S and leaf fall represented relatively unimportant return pathways to the forest soil. The final distribution of 35S in the nongirdled trees indicated little aboveground storage of S in biomass and appreciable (>60%) capacity to cycle S either to the belowground system by means of translocation or to the atmosphere by means of biogenic S emissions. Losses of volatile 35S were estimated from the amount of isotope missing (33%) in final inventories of the girdled trees. Estimated 35S emission rates from the girdled trees were 10-6 to 10-7 Ci cm-2 leaf d-1, and corresponded to an estimated gaseous S emission of approximately 0.1 to 1 g S cm-2 leaf d-1. Translocation to roots was a significant sink for 35S in the red maple tree (40% of the injected amount). Research on forest biogeochemical S cycles should further explore biogenic S emissions from trees as a potential process of S flux from forest ecosystems. 相似文献
12.
Yoshifumi Yamamoto N. Ogasawara A. Gotoh H. Komiya H. Nakai Y. Kuroki 《Human genetics》1979,48(3):321-327
Summary A female infant with del(21)(pterq22.1-2:) constitution identified by G, Q, and R banding is reported. She had marked mental and physical retardation, generalized hypertonia, microphthalmia with persistent hypoplastic primary vitreous, blepharochalasia, high nasal bridge, micrognathia, malformed ears with preauricular pits, and overlying fingers. The assay for superoxide dismutase-1 (SOD-1) activity in the patient revealed a normal value and it was suggested that the gene locus for SOD-1 in 21q22.2qter is not compatible with the presence of the gene dosage effect in the monosomic state. 相似文献
13.
Philip H. Johnson Alastair S. R. Donald Julia L. Clarke Winifred M. Watkins 《Glycoconjugate journal》1995,12(6):879-893
1,3-Fucosyltransferase solubilized from human liver has been purified 40 000-fold to apparent homogeneity by a multistage process involving cation exchange chromatography on CM-Sephadex, hydrophobic interaction chromatography on Phenyl Sepharose, affinity chromatography on GDP-hexanolamine Sepharose and HPLC gel exclusion chromatography. The final step gave a major protein peak that co-chromatographed with 1,3-fucosyltransferase activity and had a specific activity of 5–6 µmol min–1 mg–1 and anM
r 44 000 deduced from SDS-PAGE and HPLC analysis. The purified enzyme readily utilized Gal1-4GlcNAc, NeuAc2-3Gal1-4GlcNAc and Fuc1-2Gal1-4GlcNAc, with a preference for sialylated and fucosylated Type 2 acceptors. Fuc1-2Gal1-4Glc and the Type 1 compound Gal1-3GlcNAc were very poor acceptors and no incorporation was observed with NeuAc2-6Gal1-4GlcNAc. A polyclonal antibody raised against the liver preparation reacted with the homologous enzyme and also with the blood group Lewis gene-associated 1,3/1,4-fucosyltransferase purified from the human A431 epidermoid carcinoma cell line. No cross reactivity was found with 1,3-fucosyltransferase(s) isolated from myeloid cells. Examination by Northern blot analysis of mRNA from normal liver and from the HepG2 cell line, together with a comparison of the specificity pattern of the purified enzyme with that reported for the enzyme expressed in mammalian cells transfected with theFuc-TVI cDNA, suggests a provisional identification ofFuc-TVI as the major 1,3-fucosyltransferase gene expressed in human liver.Died June, 1991 相似文献
14.
A method is described for the measurement of intracellular volume (Vi) in cell cultures. In principle, any stable compound that neither penetrates the plasma membrane nor binds to the cells can be used to trace the total extracellular (apoplastic) volume and hence to estimate the intracellular volume. No suitable coloured or UV-absorbing compound could be found among those tested; the main problems were binding to the cell surface and/or instability in the medium. However, [14C]mannitol was an acceptable apoplastic marker, by use of which we showed that 21–47% of total packed cell volume (PCV) was intracellular, and 14–33% of total settled cell volume (SCV) was intracellular. Therefore, measurements of PCV and SCV misrepresent cell expansion to a variable extent. Cultures of Acer, Rosa, Spinacia and Zea achieved final symplastic volumes of only 9, 14, 6 and 6%, respectively, of the total suspension culture volume. 相似文献
15.
Concentrations of Al, Fe, Mn, Cd, Cu, Pb, and Zn were measured in thereference and treatment basins of Little Rock Lake (Vilas County, Wisconsin), alow-alkalinity, seepage system (pH 6.1, alkalinity25eq/L) during six years of a whole-basinacidificationand the first four years of the lake's recovery. The treatment basin wasacidified with H2SO4 in three two-year steps to pH5.6, 5.1, and 4.7. By the end of year 4 of recovery, treatmentbasin pH increased to 5.3 as a result of internal alkalinity generation.During acidification, dissolved Mn and Fe (0.4mpore-size filters) increased at pH 5.6; dissolved Al, Cd, and Zn becameelevated at pH 5.1; and dissolved Pb at pH 4.7. Dissolved Cu remainedsimilar in both basins to pH 4.7. Al, Fe and Mn levels declinedsignificantly during the recovery period, approaching values at pH 5.3intermediate between the concentrations at pH 5.6 and 5.1 during acidification.Dissolved Al and Fe in the reference basin were near the equilibrium levels forsolubility of gibbsite (Al(OH)3) and amorphousFe(OH)3(s).The acidified basin was undersaturated relative to gibbsite, and dissolved Alwas limited by pH disequilibrium between the water column and sediments andpossibly by Al-DOC precipitation. Dissolved Fe apparently was controlled bysolubility of amorphous Fe(OH)3(s) and Fe-DOC precipitation.Dissolved Mn levels in both basins were consistent with manganite[-MnOOH(s)] solubility. Elevated levels of Cd, Pb, and Zn in thetreatment basin during acidification probably resulted from less efficientscavenging of atmospherically-deposited Cd, Pb, and Zn by settling particles. 相似文献
16.
Lanio ME Alvarez C Martinez FD Casallanovo F Schreier S Campos AM Abuin E Lissi E 《Journal of Protein Chemistry》2002,21(6):401-405
N-hexadecyl-N-N-dimethyl-3-ammonio-1-propane-sulfonate (HPS) is a zwitterionic surfactant that readily binds to sticholysins I and II, two sea toxins isolated from Stichodactyla helianthus. The binding constants, evaluated from changes in fluorescence intensities elicited by the surfactant, are 0.5–0.7 M–1. The binding of the surfactant changes the conformation of the tertiary protein, without significant changes in its secondary structure, as reported from far-ultraviolet circular dichroism spectra. The changes elicited by HPS lead to loss of the native conformation (as reported from near-ultraviolet circular dichroism spectra) and to a shift of the intrinsic protein fluorescence toward longer wavelengths, an increase in fluorescence intensities and lifetimes, and a faster quenching by acrylamide. All these changes are indicative of a more expanded tertiary conformation. Despite this, the toxins fully retain their hemolytic activities, indicating that spectroscopic changes can be poor predictors of toxin activity. 相似文献
17.
The effect of regucalcin, a regulatory protein of Ca2+ signaling, on guanosine-5-triphosphatase (GTPase) activity in isolated rat liver plasma membranes was investigated. GTPase activity was significantly increased by the addition of Ca2+ (25–100 M) in the enzyme reaction mixture. Such an increase was not seen by other metals (Mg, Co, Zn, Cu, Ni, and Mn) with 50 M. The activatory effect of calcium (50 M) was significantly decreased by calmodulin (2.5 and 5 g/ml), indicating that it does not depend on calmodulin. The presence of regucalcin (0.1–0.5 M) in the enzyme reaction mixture caused a significant increase in GTPase activity. This increase was not significantly enhanced by calcium (50 M). GTPase activity was significantly increased by dithiothreitol (DTT; 5 mM), a protecting reagent of thiol (SH)-groups, while it was decreased by N-ethylmaleimide (NEM; 5 mM), a modifying reagent of SH-groups. The effect of calcium or regucalcin in increasing GTPase activity was not seen in the presence of NEM. Also, the activatory effect of calcium or regucalcin on GTPase was not seen in the presence of vanadate, an inhibitor of protein phosphorylation, which could inhibit GTPase activity. Moreover, the effect of regucalcin was not seen in the presence of digitonin (0.01%), a solubilizing reagent of membranous lipids, while the effect of calcium was not inhibited by digitonin. The present study demonstrates that regucalcin has an activatory effect on GTPase activity independently of Ca2+ in rat liver plasma membranes. 相似文献
18.
Walter L. Davis M. Kipnis K. Shibata Gene R. Farmer Elma Cortinas James L. Matthews David B. P. Goodman 《The Histochemical journal》1989,21(4):210-215
Summary Superoxide dismutase (SOD) is a scavenger enzyme which catalyses the dismutation (reduction—oxidation) of the superoxide anion (O2
–), a toxic free radical generated during normal cellular respiration. Light microscopy employing immunohistochemistry was utilized for localizing SOD activity in the chick epiphyseal cartilage. Antibodies to mammalian liver CuZn—SOD were prepared and the avidin—biotin—peroxidase technique (ABC complex) was utilized to localize activity for this enzyme in the growth plate cartilage. The localization of enzyme activity varied in accordance with the characteristic zonation pattern of the growth plate (zone of proliferation, zone of maturation, zone of cell hypertrophy and zone of matrix calcification). In the upper regions of the epiphyseal cartilage (the zones of proliferation and maturation), where the vascularity is poor and the oxygen tension low, SOD activity was localized within the chondrocytes. No extracellular activity was observed. However, in the lower regions of the growth plate (the zones of cell hypertrophy and matrix calcification), where both the vascularity and the oxygen tensions are increased, SOD activity was intense in both the chondrocytes and the surrounding extracellular matrix. Thus, the distribution of SOD enzyme activity in this tissue seems to vary in accordance with the level of oxygen present. The significance of the extracellular SOD activity, seen in the lower aspects of the growth plate cartilage, may indicate the sensitivity of matrix components, especially collagen, to toxic free radicals such as the superoxide anion. 相似文献
19.
Summary The distribution and ultrastructure of serotonin- and dopamine-immunoreactive (5-HTi and DAi) neurones have been investigated in the terminal ganglion of the cricket, Acheta domestica, using a pre-embedding chopper technique. Special attention has been paid to the immunoreactive structures in the neuropil. 5-HTi structures are extensively distributed and densely packed throughout the 5 neuromeres of the terminal ganglion and originate from several interneurones and efferent neurones. In contrast, DAi fibres are distributed sparsely although they extend to all neuromeres of the ganglion and originate from 6 interneurons only. For both 5-HTi and DAi neurones characteristic axonal projections and branching patterns can be distinguished. The 5-HTi axons exhibit rich varicose arborizations, whereas DAi neurones possess fewer varicosities in the neuropil. Electron microscopy shows that 5-HTi varicosities contain small ( 60 nm) and large ( 100 nm) agranular vesicles, and large ( 100 nm) granular vesicles, whereas in DAi varicosities small ( 60 nm) agranular and large ( 100 nm) granular vesicles are seen. Both 5-HTi and DAi varicosities form synaptic contacts. We conclude that both serotonin and dopamine may be used as neurotransmitters in the terminal ganglion of the cricket.Fellow of the Alexander von Humboldt-Stiftung 相似文献
20.
Rush JW Laughlin MH Woodman CR Price EM 《American journal of physiology. Heart and circulatory physiology》2000,279(5):H2068-H2076
Coronary arterioles of exercise-trained (EX) pigs have enhanced nitric oxide (NO.)-dependent dilation. Evidence suggests that the biological half-life of NO. depends in part on the management of the superoxide anion. The purpose of this study was to test the hypothesis that expression of cytosolic copper/zinc-dependent superoxide dismutase (SOD)-1 is increased in coronary arterioles as a result of exercise training. Male Yucatan pigs either remained sedentary (SED, n = 4) or were EX (n = 4) on a motorized treadmill for 16-20 wk. Individual coronary arterioles ( approximately 100-microm unpressurized internal diameter) were dissected and frozen. Coronary arteriole SOD-1 protein (via immunoblots) increased as a result of exercise training (2.16 +/- 0.35 times SED levels) as did SOD-1 enzyme activity (measured via inhibition of pyrogallol autooxidation; approximately 75% increase vs. SED). In addition, SOD-1 mRNA levels (measured via RT-PCR) were higher in EX arterioles (1.68 +/- 0.16 times the SED levels). There were no effects of exercise training on the levels of SOD-2 (mitochondrial), catalase, or p67(phox) proteins. Thus chronic aerobic exercise training selectively increases the levels of SOD-1 mRNA, protein, and enzymatic activity in porcine coronary arterioles. Increased SOD-1 could contribute to the enhanced NO.-dependent dilation previously observed in EX porcine coronary arterioles by improving management of superoxide in the vascular cell environment, thus prolonging the biological half-life of NO. 相似文献