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1.
Raul A. Saavedra 《BioEssays : news and reviews in molecular, cellular and developmental biology》1994,16(12):913-918
Osteopotin is a secreted glycosylated phosphoprotein found in bone and other normal and malignant tissues. Osteopontin can be autophosphorylated on tyrosine residues and can also be phosphorylated on serine and threonine residues by several protein kinases. Autophosphorylation of osteopontin may generate sites for specific interactions with other proteins on the cell surface and/or within the extracelluar matrix. These interactions of osteopontin are thought to be essential for bone mineralization and function. The polyaspartic acid motif of osteopontin, in combination with neighboring sequences that include serine residues phosphorylated by protein kinases, could fold and assemble into a molecular structure that participates in the mineralization of the bone matrix. 相似文献
2.
Summary A water soluble agent made from waste crustacean shells that controls the growth of algal cells was identified. Growth of an Anabaena sp. was inhibited in the presence of varied concentrations of a chitosan-derivative, N-carboxymethylchitosan (NCMC). Application of a dilute water solutions of NCMC prevented algae from multiplication and enhanced aggregation of cells and assured clearing of algal suspension by filtration. 相似文献
3.
Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components 总被引:9,自引:0,他引:9
Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 mole m-2 s-1) or low (L) intensity (55 mole m-2 s-1) white light. Plants were transferred from high to low (H L) and low to high (L H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (QB), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. QB and Cytf were elevated in H plants compared with L plants. The acclimation of H L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H L plants was associated with a decrease in both QB and Cytf. In L H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L H electron transport was associated with increased levels of QB and Cytf. In contrast to the light intensity effects on QB levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.Abbreviations Asc
ascorbate
- BQ
2,5-dimethyl-p-benzoquinone
- DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- DCIP
2,6-dichlorophenolindophenol
- H
control plants grown under high light intensity
- H L
plants transferred from high to low light intensity
- L
low control plants grown under low light intensity
- L H
plants transferred from low to high light intensity
- MV
methyl viologen
- P-700
photoreaction center of Photosystem I
- QB
atrazine binding site
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC. Paper No. 11990 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA. 相似文献
4.
A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro 总被引:5,自引:0,他引:5
Flavio Costa Miguens Ricardo Pereira Louro Raul Dodsworth Machado 《Plant Cell, Tissue and Organ Culture》1993,32(1):109-113
The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function. 相似文献
5.
Cody Raul Cardenas Andrew J. Mularo Andreas S. Chavez Rachelle M. M. Adams 《Biotropica》2023,55(1):145-159
The coevolutionary relationship between fungus-growing ants (Formicidae: Attini: Attina) and their symbionts has been well studied in the Panamanian rain forests. To further understand the ecological context of these evolutionary relationships, we have examined the population-genetic structure of the fungus-growing ant species Mycetomoellerius mikromelanos Cardenas, Schultz, Adams 2021 in the Panama Canal Zone. We specifically investigated the presence of population structure, the significance of geographic features (i.e., creeks) limiting gene flow, and relatedness between ant colonies. To accomplish this, we genotyped 85 ant colonies from nine creeks across an approximately 30 km transect in Parque National Soberanía, Panama, using double-digest restriction-site-associated DNA sequencing. We did not find distinct population structure using two genetic clustering methods; however, we did detect an effect of isolation by distance. Furthermore, related colonies were frequently detected on the same creek or neighboring creeks, and some at further geographic distances. Collectively, these findings demonstrate that new colonies tend to establish on natal creeks and occasionally on distant creeks following long-distance dispersal events. We discuss how population-genetic patterns reveal the natural history of M. mikromelanos in Parque National Soberanía and how these results fit into the context of fungus-growing ant mutualisms. Abstract in Spanish is available with online material. 相似文献
6.
Jose L. Lopez-Lacomba M. Guzman Manuel Cortijo Pedro L. Mateo Raul Aguirre Stephen C. Harvey Herbert C. Cheung 《Biopolymers》1989,28(12):2143-2159
The thermal unfolding of myosin rod, light meromyosin (LMM), and myosin subfragment 2 (S-2) was studied by differential scanning calorimetry (DSC) over the pH range of 6.5–9.0 in 0.5M KCl and either 0.20M sodium phosphate or 0.15M sodium pyrophosphate. Two rod samples were examined: one was purified by Sephadex G-200 without prior denaturation (native rod), and the other was purified by a cycle of denaturation-renaturation followed by Sephacryl S-200 chromatography (renatured rod). There were clearly distinguishable differences in the calorimetric behavior of these two samples. At pH 7.0 in phosphate the DSC curves of native rod were deconvoluted into six endothermic two-state transitions with melting temperatures in the range of 46–67°C and a total enthalpy of 4346 kJ/mol. Under identical conditions the melting profile of LMM was resolved into five endothermic peaks with transition temperatures in the range of 45–66°C, and the thermal profile of long S-2 was resolved into two endotherms, 46 and 57°C. Transition 4 observed with native rod was present in the deconvoluted DSC curve for long S-2, but absent in the DSC curve for LMM. This transition was identified with the high-temperature transition detected with long S-2 and attributed to the melting of the coiled-coil α-helical segment of subfragment 2 (short S-2). The low-temperature transition of long S-2 was attributed to the unfolding of the hinge region. The smallest transition temperatures observed for all three fragments were 45–46°C. It is suggested that the most unstable domain in rod (domain 1) responsible for the 46°C transition includes both the hinge region, which is the C-terminal segment of long S-2, and a short N-terminal segment of LMM. This domain, accounting for 21% of the rod structure, contains the S-2/LMM junction, and upon proteolytic cleavage yields the C-terminal and N-terminal ends of long S-2 and LMM, respectively. Over the pH range of 6.5–7.5, the observed specific heat of denaturation of rod was approximately equal to the sum of the specific heats of LMM and S-2. This finding provides an additional argument for the existence of independent domains in myosin rod. 相似文献
7.
Differing Neurochemical and Morphological Sequelae of Global Ischemia: Comparison of Single- and Multiple-Insult Paradigms 总被引:3,自引:0,他引:3
Baowan Lin Mordecai Y.-T. Globus W. Dalton Dietrich Raul Busto Elena Martinez Myron D. Ginsberg 《Journal of neurochemistry》1992,59(6):2213-2223
The purpose of this investigation was to investigate pathomechanisms responsible for the deleterious effects of repeated episodes of brief forebrain ischemia. Halothane-anesthetized male Wistar rats were subjected to either (a) a single 15-min period or (b) three 5-min periods (separated by 1 h) of global forebrain ischemia by bilateral carotid artery occlusions plus hypotension (50 mm Hg), followed by various periods of recirculation. Brain temperature was normothermic throughout. In one series of rats, extracellular levels of glutamate, glycine, and gamma-aminobutyric acid (GABA) were measured in the dorsolateral striatum (n = 6-8 per group) and lateral thalamus (n = 4-6 per group) by microdialysis and HPLC before and during ischemia and during 3-5 h of recirculation. In a parallel series of rats (n = 6 per group), ischemic cell change was quantified at 2 (dark neurons), 24, or 72 h following either single or multiple ischemic insults. A single 15-min ischemic period led to massive glutamate release (13-fold increase; p = 0.001), which returned to normal by 20-30 min of recirculation and remained normal thereafter. By contrast, in rats with three 5-min periods of ischemia, the glutamate level rise with each repeated insult (four- to 4.5-fold; p < or = 0.02) was smaller than that observed during the single 15-min insult, but a late sustained rise (five- to six-fold; p < 0.05) occurred at 2-3 h of recirculation. Brief ischemia-induced elevations of glycine and GABA levels were detected in both the single- and multiple-insult groups, with normalization during recirculation. In contrast, the excitotoxic index, a composite measure of neurotransmitter release ([glutamate] x [glycine]/[GABA]), differed markedly following single versus multiple insults (p = 0.002 by repeated-measures analysis of variance) and increased by seven- to 12-fold (p < 0.05) at 1-3 h following the third insult. The total amount of glutamate released was 3.3-fold higher in the multiple-insult than in the single-insult group (p < 0.02). At 2 h of recirculation, histopathological analysis of dorsolateral striatum showed a significantly greater frequency of dark neurons in the multiple- than in the single-insult group (p < 0.05 by analysis of variance). In the thalamus, a higher frequency of ischemic neurons was seen in the multiple-than in the single-insult group at all intervals studied. Thus, in rats with multiple ischemic insults, accelerated ischemic damage was found in the striatum, and severe ischemic injury was documented in the thalamus.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
8.
9.
Suzanne Desjardins-Giasson Jolanta Gutkowska Raul Garcia Jacques Genest 《Prostaglandins & other lipid mediators》1982,24(1):105-114
Prostaglandin E2 (PGE2) and 6 keto-PGF1α, the stable metabolite of prostacyclin (PGI2), have been measured in the effluent of perfused rat mesenteric arteries by the use of a sensitive and specific radioimmunoadday (RIA) method. The PGE2 and 6-keto-PGF1α were continuousyl released by the unstimulated mesenteric artery over a period of 145 min. After 100 min of perfusion the release of PGE2 and 6-keto-PGF1α was 4.5 ± 8.4 pg/min and 254 ± 75 pg.min respectively, which is in accord with the general belief that PGI2 is the major PG synthesized by arterial tissue. Angiotensin II (AII) 5 ng/ml) induced an increased of PGE2 and 6-keto-PGF1α release without changing the perfusion pressure. The effect of norepinephrine (NE) injections on release of PGs depended on the duration of the stabilization period. The changes of perfusion pressure induced by NE were not related to changes in release of PGs. Thus, it seems that the increase of PG release induced by AII and NE was due to a direct effect of the drugs on the vascular wall. This may represent an important modulating mechanism in the regulation of vascular tone. 相似文献
10.
Epigenetic control of early neurodegenerative events in diabetic retinopathy by the histone deacetylase SIRT6 下载免费PDF全文
Ada Yeste Francisco J. Quintana Debra Toiber Raul Mostoslavsky Dafne M. Silberman 《Journal of neurochemistry》2018,144(2):128-138