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2.
M.M. van Katwijk D. C. R. Hermus D.J. de Jong R. M. Asmus V.N. de Jonge 《Helgoland Marine Research》2000,54(2-3):117-128
A conceptual model is proposed, describing potential Zostera marina habitats in the Wadden Sea, based on reported data from laboratory, mesocosm and field studies. Controlling factors in the
model are dynamics, degree of desiccation, turbidity, nutrients and salinity. A distinction has been made between a higher
and a lower zone of potential habitats, each suitable for different morphotypes of Z. marina. The model relates the decline of Z. marina in the Wadden Sea to increased sediment and water dynamics, turbidity, drainage of sediments (resulting in increased degree
of desiccation) and total nutrient loads during the twentieth century. The upper and lower delineation of both the higher
and the lower zone of potential Z. marina habitats appear to be determined by one or a combination of several of these factors. Environmental changes in one of these
factors will therefore influence the borderlines of the zones. The lower zone of Z. marina will be mainly affected by increased turbidity, sediment dynamics, degree of desiccation during low tide and nutrient load.
The higher zone will be affected by increases in water and sediment dynamics, desiccation rates and nutrient loads. Potential
Z. marina habitats are located above approx. –0.80 m mean sea level (when turbidity remains at the same level as in the early 1990s)
in sheltered, undisturbed locations, and preferably where some freshwater influence is present. At locations with a high,
near-marine, salinity, the nutrient load has to be low to allow the growth of Z. marina. The sediment should retain enough water during low tide to keep the plants moist. Our results suggest that the return of
Z. marina beds within a reasonable time-scale will require not only suitable habitat conditions, but also revegetation measures, as
the changes in the environment resulting from the disappearance of Z. marina may impede its recovery, and the natural import of propagules will be unlikely. Furthermore, the lower zone of Z. marina may require a genotype that is no longer found in the Wadden Sea.
Received: 26 April 1999 / Received in revised form: 15 October 1999 / Accepted: 16 October 1999 相似文献
3.
Comparison of bone marrow extracellular matrices. 总被引:1,自引:0,他引:1
M Lee I P Christopherson J M Lehman C J Bennett H T Cheung 《Biochimica et biophysica acta》1999,1428(2-3):300-304
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues. 相似文献
4.
Random Amplified Polymorphic DNA Variation among and within Selected Ixora (Rubiaceae) Populations and Mutants 总被引:1,自引:0,他引:1
RAJASEGER G.; TAN H. T. W.; TURNER I. M.; SAW L. G.; KUMAR P. P. 《Annals of botany》1999,84(2):253-257
Random amplified polymorphic DNA (RAPD) analysis was used tostudy variation among and within selectedIxora (Rubiaceae) populationsand mutants. Six populations of I. congesta yielded identicalbanding patterns suggesting genetic uniformity of this species.However, six populations of I. coccinea varieties (three red-flowered,two yellow-flowered and one red-flowered wild-type) exhibitedinfraspecific differences in RAPD profiles. Small and largeleaves of an atavistic mutant cultivar of I. coccinea were alsosubjected to RAPD analysis. An extra band was amplified in thelarge leaves that was absent in small leaves, suggesting thatthe phenotypic alteration in this taxon is due to genetic mutationrather than epigenetic changes. Similarly, an extra band wasdetected in the white sectors of I. Variegated compared to thegreen sectors, suggesting that the shoot apical meristems ofthis cultivar exist as a genetic chimera. DNA gel blot hybridizationwas performed to confirm the specificities of selected bands.Our study indicates that differences among individuals of variouspopulations and mutants may be detected using RAPD markers.Copyright 1999 Annals of Botany Company Ixora L., variegated variety, RAPD fingerprinting, DNA gel blot, intraspecific genetic similarity, atavistic mutant. 相似文献
5.
Based on its proven anabolic effects on bone in osteoporosis patients, recombinant parathyroid hormone (PTH1-34) has been evaluated as a potential therapy for skeletal repair. In animals, the effect of PTH1-34 has been investigated in various skeletal repair models such as fractures, allografting, spinal arthrodesis and distraction
osteogenesis. These studies have demonstrated that intermittent PTH1-34 treatment enhances and accelerates the skeletal repair process via a number of mechanisms, which include effects on mesenchymal
stem cells, angiogenesis, chondrogenesis, bone formation and resorption. Furthermore, PTH1-34 has been shown to enhance bone repair in challenged animal models of aging, inflammatory arthritis and glucocorticoid-induced
bone loss. This pre-clinical success has led to off-label clinical use and a number of case reports documenting PTH1-34 treatment of delayed-unions and non-unions have been published. Although a recently completed phase 2 clinical trial of PTH1-34 treatment of patients with radius fracture has failed to achieve its primary outcome, largely because of effective healing
in the placebo group, several secondary outcomes are statistically significant, highlighting important issues concerning the
appropriate patient population for PTH1-34 therapy in skeletal repair. Here, we review our current knowledge of the effects of PTH1-34 therapy for bone healing, enumerate several critical unresolved issues (e.g., appropriate dosing regimen and indications)
and discuss the long-term potential of this drug as an adjuvant for endogenous tissue engineering. 相似文献
6.
Cytochrome P450 2E1-derived reactive oxygen species mediate paracrine stimulation of collagen I protein synthesis by hepatic stellate cells. 总被引:3,自引:0,他引:3
Natalia Nieto Scott L Friedman Arthur I Cederbaum 《The Journal of biological chemistry》2002,277(12):9853-9864
To evaluate possible fibrogenic effects of CYP2E1-dependent generation of reactive oxygen species, a model was developed using co-cultures of HepG2 cells, which do (E47 cells) or do not (C34 cells) express cytochrome P450 2E1 (CYP2E1) with stellate cells. There was an increase in intra- and extracellular H(2)O(2), lipid peroxidation, and collagen type I protein in stellate cells co-cultured with E47 cells compared with stellate cells alone or co-cultured with C34 cells. The increase in collagen was prevented by antioxidants and a CYP2E1 inhibitor. CYP3A4 did not mimic the stimulatory effects found with CYP2E1. Collagen mRNA levels remained unchanged, and pulse-chase analysis indicated similar half-lives of collagen I protein between both co-cultures. However, collagen protein synthesis was increased in E47 co-culture. Hepatocytes from pyrazole-treated rats (with high levels of CYP2E1) induced collagen protein in primary stellate cells, and antioxidants and CYP2E1 inhibitors blocked this effect. These results suggest that increased translation of collagen mRNA by CYP2E1-derived reactive oxygen species is responsible for the increase in collagen protein produced by the E47 co-culture. These co-culture models may be useful for understanding the impact of CYP2E1-derived ROS on stellate cell function and activation. 相似文献
7.
The effect of carbohydrate depletion on procoagulant activity and in vivo survival of highly purified human factor VIII 总被引:1,自引:0,他引:1
P J Fay S I Chavin J E Malone D Schroeder F E Young V J Marder 《Biochimica et biophysica acta》1984,800(2):152-158
Human factor VIII procoagulant protein (factor VIII) was purified using a modification of our previously described method, in which Sephacryl S-400 elution, rather than QAE-cellulose chromatography, served as the final purification step. The protein had a specific activity of more than 2500 U/mg and consisted of a single polypeptide (Mr 100 000) when analyzed by SDS-polyacrylamide gel electrophoresis. Factor VIII was shown to be a glycoprotein by staining with periodic acid-Schiff's reagent following electrophoresis. Treatment of factor VIII with a mixture of exo- and endoglycosidases caused a reduction by about 50% in the intensity of periodic acid-Schiff staining, as determined by scanning densitometry, and an increase in electrophoretic mobility (equivalent to a new Mr 95 000). Removal of this portion of the total carbohydrate had no significant effect on factor VIII clotting activity or on thrombin potentiation of clotting activity. The in vivo survival curves of a native and sugar-depleted 125I-labeled factor VIII both showed similar patterns of initial rapid decay to 60 and 40% activity, respectively, followed by a one-half decay time of 4 h for both. These results suggest that the carbohydrate portion of human factor VIII does not contribute significantly to either clotting function in vitro or to biological turnover in vivo. 相似文献
8.
S V Prozorovski? L P Tsarevski? G A Levina A L Gorelov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(8):10-14
To simulate the infectious process and to study the persistence of L-forms, rabbits and guinea pigs were infected with S. typhi stable L-forms. The materials presented in this work indicate that both subconjunctival and intraperitoneal infection led to the development of the clinically indistinct, but morphologically pronounced pathological process with characteristic localization and typical changes in the gastrointestinal tract. The typical features of the process were the generalized immunomorphological reaction of the lymphoid apparatus with the appearance of light-colored reticulomacrophagal elements, the signs of the activation of humoral and cell-mediated immunity and the formation of small epitheloidocellular granulomas. The results of the investigation indicate that the stable cultures of S. typhi L-forms are highly pathogenic and capable of inducing the infectious process in experimental animals. 相似文献
9.
10.
Y Tani I Ohkubo S Higashiyama M Kunimatsu M Sasaki 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,88(2):429-441
1. High mol. wt kininogen (HMW kininogen) was purified to a homogeneous state from porcine plasma. 2. The protein exhibited a strong inhibitory activity for thiol proteinases such as ficin, papain and calpain I, whereas it did not inhibit serine proteinases, trypsin and chymotrypsin. 3. The mol. wt, isoelectric point, amino acid and carbohydrate compositions, stabilities to temperature and pH, kinetic constants, and immunological properties of the porcine HMW kininogen were determined and compared with those of human HMW kininogen. 相似文献