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1.
W. S. Stark D. Schilly J. S. Christianson R. A. Bone J. T. Landrum 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,166(4):429-436
Summary
Drosophila rearing media had only -carotene, zeaxanthin or lutein as precursors for photopigment chromophores. Zeaxanthin and lutein are potentially optimum sources of the 3-hydroxylated retinoids of visual and accessory photopigments. Mutants made the electroretinogram in white (w) eyes selective for compound eye photoreceptors R1–6, R7 and R8: R1–6 domiantes w's electroretinogram; R7/8 generates w;ora's (ora = outer rhabdomeres absent); R8 generates w sev;- ora's (sev = sevenless). Microspectrophotometry revealed R1-6's visual pigment. In w, all 3 carotenoids yielded monotonic dose-responses for sensitivity (Fig. 4) or visual pigment (Fig. 7). An ultraviolet sensitivity peak from R1-6's sensitizing pigment was present at high but not low doses (Fig. 1). In w;ora, all 3 carotenoids gave similar spectra dominated by R7's high ultraviolet sensitivity (Fig. 2). For w sev;ora, all spectra were the shape expected for R8, peaking around 510 nm (Fig. 3). The sensitivity dose-response was at its ceiling except for low doses in w;ora (Fig. 5) and zero supplementation in w sev;ora (Fig. 6). Hence, without R1-6, most of our dose range mediated maximal visual pigment formation. In Drosophila, -carotene, zeaxanthin and lutein mediate the formation of all major photopigments in R1-6, R7 and R8.Abbreviations
ERG
electroretinogram
-
MSP
microspectrophotometry
-
HPLC
high pressure liquid chromatography
-
n.a.
numerical aperture
-
w, sev, ora Drosophila
mutants
-
y, p, r
marg types of R7 and R8 相似文献
2.
Christophe N. N'soukpo-Kossi Jan Sielewiesiuk Roger M. Leblanc Richard A. Bone John T. Landrum 《生物化学与生物物理学报:生物膜》1988,940(2)
The linear dichroism of single monolayers of lutein, zeaxanthin and a mixture of lutein and synthetic phosphatidylcholine has been measured. The angle of orientation of the carotenoid molecules was found to lie between 45° and 51° relative to the plane of the solid support. Although the adsorbed monolayers were mostly in a monomeric state, microscopic observations, as well as the II-A isotherms, indicated the existence of crystalline islets. The results have been interpreted in connection with Haidinger's polarization brushes. 相似文献
3.
The ammonium uptake system of Rhodobacter capsulatus B100 was examined using the ammonium analog methylammonium. This analog was not transported when cells were grown aerobically on ammonium. When cultured on glutamate as a nitrogen source, or when nitrogen-starved, cells would take up methylammonium. Therefore, in cells grown under nitrogen-limiting conditions, a second system of ammonium uptake (or a modified form of the first) is present which is distinguished by its capacity for transporting the analog in addition to ammonium. The methylammonium uptake system exhibited saturation kinetics with a K
m of 22 M and a V
max of about 3 nmol per min · mg protein. Ammonium completely inhibited analog transport with a K
i in the range of 1 M. Once inside the cell methylammonium was rapidly converted to -N-methylglutamine; however, a small concentration gradient of methylammonium could still be observed. Kinetic parameters reflect the effects of assimilation.The methylammonium uptake system was temperature and pH dependent, and inhibition studies indicated that energy was required for the system to be operative. A glutamine auxotroph (G29) lacking the structural gene for glutanime synthetase did not accumulate the analog, even when nitrogen starved. The Nif- mutant J61, which is unable to express nitrogenase structural genes, also did not transport methylammonium, regardless of the nitrogen source for growth. However, the mutant exhibited wild-type ammonium uptake and glutamine synthetase activity. These data suggest that transport of ammonium is required for growth on limited nitrogen and is under the control of the Ntr system in R. capsulatus.Abbreviations CCCP
carbonyl cyanide-m-chlorophenyl hydrazone
- CHES
cyclohexylaminoethanesulfonic acid
- DMSO
dimethyl sulfoxide
- GMAD
-N-methylglutamine
- GS
glutamine synthetase
- MES
2-(N-morpholino) ethanesulfonic acid
- MSX
methionine-Dl-sulfoximine
- pCMB
p-chloromercuribenzoate
- Tricine
N-tris(hydroxymethyl)methylglycine 相似文献
4.
5.
Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
6.
A ligand field calculation of magnetic circular dichroism (MCD) spectra is described that provides new insights into the information contained in electronic spectra of copper sites in metalloenzymes and synthetic analogs. The ligand field model uses metal-centered p- and f-orbitals to model sigma, pi LMCT mixing mechanism for intensity, allowing the basic features of optical absorption, MCD, and electron paramagnetic resonance spectra to be simultaneously computed from a single set of parameters and the crystallographically determined ligand coordinates. We have used the model to predict changes in spectra resulting from the transformation of electronic wavefunctions under systematic variation in geometry in pentacoordinate ML5 complexes. The effectiveness of the calculation is demonstrated for two synthetic copper model compounds and a galactose oxidase enzyme complex representing limiting coordination geometries. This analysis permits immediate recognition of characteristic patterns of MCD intensity and correlation with geometry. A complementarity principle between MCD and CD spectra of transition metal complexes is discussed. 相似文献
7.
The genusPereskia, which contains numerous morphological features considered relictual in the Cactaceae, has numerous anatomical features that
we consider to be relictual also. These were studied to establish a basis for determining the ways that morphogenic mechanisms
and anatomical characters diversified as the family evolved. ThesePereskia features may be relictual in the family: epidermis predominantly unistratose and lacking crystals; hypodermis absent or of
about three layers of weakly collenchymatous cells with druses; cortex thin and predominantly parenchyma with druses and mucilage
cells but lacking cortical bundles; secondary phloem without early differentiation of sclerenchyma but with secondary sclereids
developing later, either idioblastically or in clusters; ergastic substances lacking from old secondary phloem; wood with
a matrix of libriform fibers (mostly septate and nucleate), scanty paratracheal parenchyma, vessels solitary or in small clusters,
perforations simple, pitting circular, oval or very broad; wide-band tracheids absent; ray cells slightly thick-walled, lignified,
upright, isodiametric or procumbent; all primary rays narrow; pith without medullary bundles; leaves lacking hypodermis, with
only weak development of palisade mesophyll; veins of four orders, strongly distinct in size, none with fibers; vessels in
leaves narrower than those in stems. 相似文献
8.
Mauseth James D. Uozumi Yoriko Plemons Brandon J. Landrum James V. 《Journal of plant research》1995,108(4):517-526
Wide-band tracheids are a specialized tracheid type in which an annular or helical secondary wall projects deeply into the
cell lumen. They are short, wide and spindle-shaped, and their bandlike secondary walls cover little of the primary wall,
leaving most of it available for water diffusion. Wide-band tracheids appear to store and conduct water while preventing the
spread of embolisms. They may be the most abundant tracheary element in the xylem, but they are always accompanied by at least
a few vessels. Typically, fibers are absent wherever wide-band tracheids are present. Wide-band tracheids occur in the primary
and secondary xylem of succulent stems, leaves and roots in genera of all three subfamilies of Cactaceae but were not found
in the relictual genusPereskia, which lacks succulent tissues. In the large subfamily Cactoideae, wide-band tracheids occur only in derived members, and
wide-band tracheids of North American Cactoideae are narrower and are aligned in a more orderly radial pattern than those
of South American Cactoideae. Wide-band tracheids probably arose at least three times in Cactaceae. 相似文献
9.
10.