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181.
Ruth G. Shaw 《Evolution; international journal of organic evolution》1991,45(1):143-151
A statistical method for comparing matrices of genetic variation and covariation between groups (e.g., species, populations, a single population grown in distinct environments) is proposed. This maximum-likelihood method provides a test of the overall null hypothesis that two covariance component matrices are identical. Moreover, when the overall null hypothesis is rejected, the method provides a framework for isolating the particular components that differ significantly between the groups. Simulation studies reveal that discouragingly large experiments are necessary to obtain acceptable power for comparing genetic covariance component matrices. For example, even in cases of a single trait measured on 900 individuals in a nested design of 100 sires and three dams per sire in each population, the power was only about 0.5 when additive genetic variance differed by a factor of 2.5. Nevertheless, this flexible method makes valid comparison of covariance component matrices possible. 相似文献
182.
183.
184.
Cysteine sulfinic acid decarboxylase (CSAD), the rate-limiting enzyme in taurine biosynthesis, appears to be present in the brain in multiple isoforms. Two distinct forms of CSAD, referred to as CSAD I and CSAD II, were obtained on Sephadex G-100 column. CSAD I and CSAD II differ in (1) the elution profile on Sephadex G-100 column; (2) the sensitivity towards Mn2+, methione, and other sulfur-containing amino acids and (3) their immunologic properties. CSAD II has been purified to about 2,500-fold by a combination of column chromatographies and polyacrylamide gel electrophoresis (PAGE). The purity of the enzyme preparation was established as judged from the following observations: (1) a single protein band was observed under various electrophoretic conditions, e.g., 5–20% nondenaturing PAGE, 7% nondenaturing PAGE and 10% SDS-PAGE and (2) in nondenaturing PAGE, the protein band comigrated with CSAD activity. CSAD II has a molecular weight of 90 kDa and is a homodimer consisting of two 43 ± 2 kDa subunits. CSAD appears to require Mn2+ for its maximum activity. Other divalent cations fail to replace Mn2+ in activation of CSAD activity. However, the precise role of Mn2+ in the action of CSAD remains to be determined. 相似文献
185.
Jerry L. Ruth 《Molecular biotechnology》1996,6(2):163-178
The simple use of nonisotopic hybridization probes to detect complementary sequences provides valuable information in a large
number of research and commercial applications. In hybridization assays, the four ‘S’s (speed, simplicity, sensitivity, and
specificity) are important criteria for determining the choice of probe and label. The direct chemical combination of synthetic
oligonucleotide probes and enzyme labels offer advantages unmatched by other approaches, with the oligonucleotide providing
rapid hybridization and high specificity, and the direct enzyme label providing simple and sensitive detection. Such oligonucleotide-enzyme
conjugates (“oligozymes”) can be used in a variety of hybridization and detection formats, including dot blots, Southern/northern
blots,in situ, and solution hybridization/capture schemes. The practical synthesis and use of such oligozymes are summarized. 相似文献
186.
Brian K. Speake Ruth J. McCartney Marieke Feast André Maldjian Raymond C. Noble 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》1996,115(4):493-499
Although substantial information is available regarding the fatty acid composition of lipids of the yolk and of the developing tissues of the chicken embryo, there is little knowledge on this topic for other avian species. The aim of the present study was to compare the yolk and embryonic tissue fatty acid profiles for a species selecting its food in the wild (the lesser black backed gull) with one fed on a standard commercial diet (the commercially reared pheasant). The fatty acid compositions of the yolk lipids were determined, and major differences were observed between the two species. In particular, the phospholipid of the gull yolk was enriched in 20:4n-6 and 22:6n-3 (18.8 and 7.1%, respectively, by weight of total fatty acids) in comparison with the pheasant (4.0 and 4.1%, respectively). The fatty acid compositions of the embryonic tissues were determined using eggs incubated in the laboratory. For the liver and heart, the fatty acid composition of the lipids in the two species reflected the initial yolk composition, with the gull tissue lipids generally containing higher proportions of 20:4n-6 and 22:6n-3 than those of the pheasant. In contrast, the fatty acid profiles of the brain phospholipid were essentially identical in the two species, with 20:4n-6 and 22:6n-3 comprising approximately 9 and 17%, respectively, of total fatty acids in both cases. 相似文献
187.
Berit M. Mortensen Hanne W. Lund Greg Jablonski Ruth H. Paulssen Jan O. Gordeladze 《Bioscience reports》1995,15(3):135-150
In normal rats treated with 1,25(OH)2D3 or 24,25(OH)2D3, serum Ca2+, ALP, PRL and GH are significantly altered. In order to study the primary effect of vitamin D3 analogues on target organ function, rat UMR 106 osteosarcoma and GH3 pituitary adenoma cells in monolayer culture were exposed accordingly.Surprisingly, prolonged exposure of these cell lines to physiological levels of either 1,25(OH)2D3 or 24,25(OH)2D3 did not significantly affect the secretory parameters (ALP, PRL or GH) tested. However, 1,25(OH)2D3 exposure significantly reduced PTH- and Gpp(NH)p-elicited AC as well as Gpp(NH)p-stimulated PLC activities in the UMR 106 cells. These changes were accompanied by an increase and decrease in the membrane contents of the G-protein subunits G36 and Gq/11, respectively. In contrast, 24,25(OH)2D3 remained without significant biological effect on these signalling systems despite concomitantly augmented levels of G36. TRH- and Gpp(NH)p-elicited PLC activities in the GH3 cells were significantly reduced by 1,25(OH)2D3 with a concurrent reduction in cellular amounts of Gq/11, however, 24,25(OH)2D3 did not significantly alter any signalling systems nor G-proteins analyzed.It is concluded that the osteoblastic and pituitary cell secretion of ALP, PRL and GH remain unaffected by the presence of 1,25(OH)2D3 and 24,25(OH)2D3, despite distinct alterations in components of G-protein mediated signalling pathways. Hence, other factors like ambient Ca2+ may be responsible for the perturbed secretory patterns of ALP and PRL seen in vitamin D3 treated rats.Abbreviations AC
adenylate cyclase
- ALP
alkaline phosphatase
- BGP
osteocalcin
- BSA
bovine serum albumin
- DA
dopamine
- DAG
diacylglycerol
- GH
growth hormone
- GHRH
growth hormone releasing hormone
- Gpp(NH)p
guanosine 5-[-imido]triphosphate
- G-protein
guanine nucleotide-binding regulatory protein
- Gs etc.
Gs protein -subunit
- IP3
inositol 1,4,5 trisphosphate
- OAF
osteoclast activating factor
- PGE2
prostaglandin E2
- PKA & PKC
protein kinase A & C
- PLC
phospholipase C
- PRL
prolactin
- PTH
parathyroid hormone
- SRIF
somatostatin
- TRH
thyrotropin releasing hormone
- VIP
vasoactive intestinal peptide
- 25(OH)D3
25 hydroxy vitamin D3
- 1,25(OH)2D3
1·25 dihydroxy vitamin D3
- 24,25(OH)2D3
24,25 dihydroxy vitamin D3 相似文献
188.
Chlorella was used to study the effects of dehydration on photosynthetic activities. The use of unicellular green algae assured that the extent of dehydration was uniform throughout the whole cell population during the course of desiccation. Changes in the activities of the cells were monitored by measurements of fluorescence induction kinetics. It was found that inhibition of most of the photosynthetic activities started at a similar level of cellular water content. They included CO2 fixation, photochemical activity of Photosystem II and electron transport through Photosystem I. The blockage of electron flow through Photosystem I was complete and the whole transition occurred within a relative short time of dehydration. On the other hand, the suppression of Photosystem II activity was incomplete and the transition took a longer time of dehydration. Upon rehydration, the inhibition of Photosystem II activity was fully reversible when samples were in the middle of the transition, but was not thereafter. The electron transport through Photosystem I was also reversible during the transition, but was only partially afterward.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethyl urea
- Fm
maximum fluorescence yield
- F0
non-variable fluorescence level emitted when all PS II centers are open
- Fv
variable part of fluorescence
- PS
photosystem
- QA
primary quinone acceptor of Photosystem II 相似文献
189.
Henri Wintz Hsu-Ching Chen Claudia A. Sutton Catharine A. Conley Angela Cobb David Ruth Maureen R. Hanson 《Plant molecular biology》1995,28(1):83-92
The expression of a 25 kDa protein, encoded by the fused mitochondrial pcf gene, is associated with cytoplasmic male sterility (CMS) in petunia. To investigate the role of the 25 kDa protein in CMS we have transformed petunia and tobacco plants with constructs expressing a portion of the urfS sequence of the pcf cDNA which encodes the 25 kDa protein. The urfS sequence was fused with two different mitochondrial targeting sequences. The chimeric gene coding region was placed under the control of the CaMV 35S promoter or a tapetum-specific promoter. Expression of the PCF protein was obtained in mitochondria of transgenic petunia and tobacco plants, yet fertility of the plants was not affected. Analysis of the location of the urfS-encoded protein revealed that it fractionates primarily into the soluble fraction in the transgenic plants whereas the genuine 25 kDa protein is found primarily in the soluble fraction but also in the membrane portion of immature buds from CMS petunia plants. Fertile transgenic plants were obtained which expressed the 25 kDa protein in the tapetal layer of post-meiotic anthers, while CMS plants express the endogenous 25 kDa protein in both the tapetal layer and sporogenous tissue of pre-meiotic anthers. 相似文献
190.
Tsui-Ling C. Hsu Daniel S. Engebretson Sara A. Helvoigt Daniel G. Nocera 《Inorganica chimica acta》1995,240(1-2):551-557
The quadruple metal-metal bonded complexes, W2Cl4(PR3)4 (PR3 = PMe3, PMe2Ph, PBu3), photoreact in dichloromethane with near-UV excitation (λ>375 nm) to yield a mixed valence W2(II,III) photoproduct. Electronic absorption and EPR spectra of photolyzed solutions are identical to those obtained from the thermal oxidation of W2Cl4(PR3)4 by PhICI2, which is known to yield W2Cl5(PR3)3. Subsequent reaction of the photolyzed solution yields the oxidized, confacial biotahedral W2(III,III) halophosphine. Analysis of the organic photoproduct reveals that the halocarbon solvent is reduced by one electron to yield the chloromethyl radical. When the radical is produced in low yields, hydrogen abstraction from solvent appears to be sufficiently efficient to compete with dimerization and only chloromethane is observed; however, at higher concentrations, the chloromethyl radicals couple to produce dichloroethane. Photoreaction is observed only with near-UV excitation of the LMCT absorption manifold of W2Cl4(PR3)4. At lower energy wavelengths, transient absorption spectroscopy shows the production of the 1δδ* excited state, which decays to ground state over times commensurate with the decay of 1δδ* luminescence. In hydrocarbon solutions, no transient intermediate or photochemistry is observed, indicating that the LMCT excited state, although capable of reducing a C---X bond, cannot activate the stronger C---H bonds of hydrocarbons. The photochemistry and transient absorption spectroscopy results of the W2Cl4(PR3)4 complexes are compared to our previous studies of the
homologs. 相似文献