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41.
42.
Molecular cloning and characterization of senescence-related genes from carnation flower petals 总被引:3,自引:3,他引:0
The senescence of carnation (Dianthus caryophyllus L.) flower petals is associated with increased production of ethylene which plays an important role in regulating this developmental event. Three senescence-related cDNA clones were isolated from a cDNA library prepared from mRNA isolated from senescing petals. These cDNAs are representative of two classes of mRNAs which increase in abundance in senescing petal tissue. The mRNA for one class is present at low levels during the early stages of development and begins to accumulate in mature petals prior to the increase in ethylene production. The accumulation of this mRNA is reduced, but not eliminated, in petals treated with aminooxyacetic acid, an inhibitor of ethylene biosynthesis, or silver thiosulfate, an ethylene action inhibitor. In contrast, expression of the second class of mRNAs appears to be highly regulated by ethylene. These mRNAs are not detectable prior to the rise in ethylene production and increase in abundance in parallel with the ethylene climacteric. Furthermore, expression of these mRNAs is significantly inhibited by both aminooxyacetic acid and silver thiosulfate. Expression of these mRNAs in vegetative and floral organs was limited to floral tissue, and predominantly to senescing petals. 相似文献
43.
Although isoproterenol is a very effective hyperglycemic agent in dogs, other species such as rats, baboons and man are resistant to this effect. In each of these species catecholamines exert pronounced effects on insulin and glucagon release from the pancreas. In man, baboons, and rats catecholamine-induced alterations in pancreatic hormone release indirectly influence the hyperglycemic response to these amines: glucagon release supports and insulin release limits hyperglycemic responses. In contrast, the present study demonstrates that in dogs catecholamine-induced hyperglycemic responses are relatively independent of concurrent alterations in pancreatic hormone release. In dogs isoproterenol produces hyperglycemia equal to or greater than responses to epinephrine despite large increases in insulin release produced by isoproterenol. Moreover, catecholamine-induced hyperglycemia is not significantly altered when insulin and glucagon release are blocked with somatostatin. 相似文献
44.
The objective of this study was to characterize proteinase activities expressed during development and maturation of the prostate gland and seminal vesicles of the rat by using gelatin-and casein-containing SDS polyacrylamide gel zymography. The prostatic complexes of 2- and 10-day-old animals and the individual lobes of the prostate (ventral, dorsolateral, and anterior [coagulating gland]) and the seminal vesicles of 15-day-old animals expressed prominent gelatinolytic activities of approximately 64, 71, and 76 kDa. These activities had properties of metalloproteinases; i.e., they were stimulated by Ca2+ and inhibited by EDTA and EGTA. They were greatly diminished by 52 days of age (immediately postpuberty) and were not detected in the dorsal lobe of the adult. Less active gelatinolytic proteinases with molecular masses of approximately 34 and 43 kDa were expressed in the developing prostatic complexes and individual lobes and seminal vesicles, but they were not detected in postpubertal animals. Weak gelatinolytic activities of 82, 85, and 89 kDa were found in the prostatic complexes; these activities were greatly diminished in all prostate lobes with sexual maturation but were expressed in the seminal vesicles at all ages. A large-molecular-mass Ca(2+)-independent proteinase of 130 kDa or greater was first detected in the dorsolateral prostate at 21 days of age. This activity was expressed in both the lateral and dorsal lobes of the adult but was greater in the lateral lobe. Proteinase activities of about 22 and 26 kDa that were not stimulated by Ca2+ were detected in the ventral prostate at 15 days of age by means of both gelatin and casein gels.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
45.
Structural model for an oligonucleotide containing a bulged guanosine by NMR and energy minimization 总被引:7,自引:0,他引:7
We present three-dimensional structural models for a DNA oligomer containing a bulged guanosine based on proton NMR data and energy minimization computations. The nonexchangeable proton resonances of the duplex 5'd(GATGGGCAG).d(CTGCGCCATC) are assigned by nuclear Overhauser effect spectroscopy (NOESY) and correlated spectroscopy connectivities, and the NMR spectrum is compared with that of a regular 8-mer of similar sequence, 5'd(GATGGCAG).d(CTGCCATC). Experimental proton-proton distances are obtained from NOESY spectra acquired with mixing times of 100, 150, and 200 ms. A refined three-dimensional structure for the bulge-containing duplex is calculated from regular B DNA starting coordinates by using the AMBER molecular mechanics program [Weiner, S. J., Kollman, P. A., Case, D. A., Singh, U. C., Ghio, C., Alagona, G., Profeta, S., & Weiner, P. (1984) J. Am. Chem. Soc. 106, 765-784]. We compare structures obtained by building the helix in three and four base pair increments with structures obtained by direct minimization of the entire nine base sequence, with and without experimental distance constraints. The general features of all the calculated structures are very similar. The helix is of the B family, with the extra guanine stacked into the helix, and the helix axis is bent by 18-23 degrees, in agreement with gel mobility data for bulge-containing sequences [Rice, J. A. (1987) Ph.D. Thesis, Yale University]. 相似文献
46.
Vaccinia mRNA synthesis under conditions which prevent uncoating 总被引:13,自引:0,他引:13
B Woodson 《Biochemical and biophysical research communications》1967,27(2):169-175
47.
Several species and developmental stages of calanoid copepodswere tested for responses to environmental cues in a laboratoryapparatus that mimicked conditions commonly associated withpatches of food in the ocean. All species responded to the presenceof phytoplankton by feeding. All species responded by increasingproportional residence time in one, but not both, of the treatmentsdefined by gradients of velocity or density. Most species increasedswimming speed and frequency of turning in response to the presenceof chemical exudates or gradients of velocity. Only one species,Eurytemora affinis, increased proportional time of residencein response to gradients in density of the water. Responsesof E. affinis to combined cues did not definitively demonstratea hierarchical use of different cues as previously observedfor Temora longicornis and Acartia tonsa. A simple foragingsimulation was developed to assess the applicability in thefield of the behavioral results observed in the laboratory.These simulations suggest that observed fine-scale behaviorscould lead to copepod aggregations observed in situ. The presentstudy demonstrates that behavioral response to cues associatedwith fine-scale oceanographic gradients and biological patchinessis functionally important and prevalent among copepods and likelyhas significant impacts on larger-scale distributional patterns. 相似文献
48.
JB Parentes-Vieira PV Lopes-Costa CG Pires AR dos Santos JD Pereira-Filho BB da Silva 《International Seminars in Surgical Oncology : ISSO》2007,4(1):22
Background
The objective of this study was to evaluate angiogenesis according to CD34 antigen expression in estrogen receptor (ER)-positive and negative breast carcinomas.Methods
This study comprised 64 cases of infiltrating ductal carcinoma in postmenopausal women divided into two groups: Group A: ER-positive, n = 35; and Group B: ER-negative, n = 29. The anti-CD34 monoclonal antibody was used as a marker for endothelial cells. Microvessel count was carried out in 10 fields per slide using a 40× objective lens (magnification 400×). Statistical analysis of the data was performed using Student's t-test (p < 0.05).Results
The mean number of vessels stained with the anti-CD34 antibody in the estrogen receptor-positive and negative tumors was 23.51 ± 1.15 and 40.24 ± 0.42, respectively. The number of microvessels was significantly greater in the estrogen receptor-negative tumors (p < 0.001).Conclusion
ER-negative tumors have significantly greater CD34 antigen expression compared to ER-positive tumors.49.
Teng YK Verburg RJ Verpoort KN Diepenhorst GM Bajema IM van Tol MJ Jol-van der Zijde EC Toes RE Huizinga TW van Laar JM 《Arthritis research & therapy》2007,9(5):R106
In order to identify pathogenic correlates of refractory rheumatoid arthritis (RA), antibodies against anti-cyclic citrullinated
protein (ACPAs) were investigated in RA patients in whom the dysregulated immune system had been ablated by high-dose chemotherapy
(HDC) and autologous haematopoietic stem cell transplantation (HSCT). Six patients with refractory RA were extensively characterized
in terms of levels of total immunoglobulins, RA-specific autoantibodies (ACPAs and rheumatoid factor) and antibodies against
rubella, tetanus toxoid (TT) and phosphorylcholine before and after HDC plus HSCT. Additionally, the avidity of ACPAs was
measured before and after treatment and compared with the avidity of TT antibodies following repeated immunizations. Synovial
biopsies were obtained by arthroscopy before HDC plus HSCT, and analyzed by immunohistochemistry. In the three patients with
clinically long-lasting responses to HDC plus HSCT (median 423 days), significant reductions in ACPA-IgG levels after therapy
were observed (median level dropped from 215 to 34 arbitrary units/ml; P = 0.05). In contrast, stable ACPA-IgG levels were observed in three patients who relapsed shortly after HDC plus HSCT (median
of 67 days). Clinical responders had ACPA-IgG of lower avidity (r = 0.75; P = 0.08) and higher degree of inflammation histologically (r = 0.73; P = 0.09). Relapse (after 38 to 530 days) in all patients was preceded by rising levels of low avidity ACPA-IgG (after 30 to
388 days), in contrast to the stable titres of high avidity TT antibodies. In conclusion, humoral autoimmune responses were
differentially modulated by immunoablative therapy in patients with synovial inflammation and low avidity ACPA-IgG autoantibodies
as compared with patients with high levels of high avidity ACPA-IgG. The distinct clinical disease course after immunoablative
therapy based on levels and avidity of ACPA-IgG indicates that refractory RA is not a single disease entity. 相似文献
50.
The bacterial Sm-like protein Hfq forms a ring-shaped homo-hexamer that is necessary for Hfq to bind nucleic acids and to act in small noncoding RNA regulation. Using semi-native gels and fluorescence anisotropy, we show that Hfq undergoes a cooperative conformational change from monomer to hexamer around 1 μM protein, which is comparable to the in vivo concentration of Hfq and above the dissociation constant of the Hfq hexamer from many RNA substrates. Above 2 μM protein, Hfq hexamers associate in high-molecular-weight complexes. Mutations that impair RNA binding to the proximal face strongly destabilize the hexamer, while the mutation R16A near the outer rim prevents hexamer association. Stopped-flow fluorescence resonance energy transfer experiments showed that Hfq subunits interact within a few seconds, suggesting that Hfq monomers, hexamers and multi-hexamer complexes are in dynamic equilibrium. Finally, we show that Hfq is most active in RNA annealing when the hexamer is present. These results suggest that RNA binding is coupled to hexamer assembly and that the biochemical activity of Hfq reflects the equilibrium between different quaternary structures. 相似文献