In the mouse, alleles at the agouti locus determine eumelanin or pheomelanin synthesis by the follicular melanocytes. Previous studies have identified the dermis as the site of action of these alleles. However, a recent investigation utilizing the yellow (Ay) allele suggested a possible role of the epidermis in the expression of agouti locus alleles. Using dermal-epidermal recombinations of embryonic skin of various agouti genotypes, the present investigation supports the role of both the dermis and epidermis. If nonagouti () dermis is recombined with agouti () epidermis, the resulting hairs are pigmented in the nonagouti pattern. The reciprocal recombination of agouti dermis and nonagouti epidermis results in hairs pigmented in the agouti pattern. The recombinations of yellow () dermis and agouti or extreme nonagouti () epidermis result in hairs completely pigmented in the yellow pattern (pheomelanin). However, when extreme nonagouti or agouti dermis is recombined with yellow epidermis, the resulting hairs are completely pigmented with pheomelanin. Similar results occur in recombinations of “young” yellow epidermis (13 days) and “old” dermis (17 days) even though dermal papillae are present. The role of dermal-epidermal interactions in the expression of agouti alleles as well as possible explanations for the unique action of the yellow allele are discussed. 相似文献
Depilated is a recessive mutation on Chromosome 4 in the position b-1.93±0.51- dep-3.45±0.68.-Pt. It causes severe abnormalities of hair structure. The site of action of dep was investigated by the method of dermal-epidermal recombination. Skins from 14-day mutant and normal mouse embryos were separated into dermal and epidermal components, recombined, and grown in histocompatible mouse testes for 20 days. The recombinations made were +/+ epidermis with +/+ dermis, +/+ epidermis with dep/dep dermis, dep/dep epidermis with +/+ dermis and dep/dep epidermis with dep/dep dermis. Grafts that contained mutant epidermis as one of the components produced hairs that were similar to those found in depilated mice. There was no observable effect of the dermis on hair types produced in this experiment. 相似文献
In the mouse, the extension locus determines whether eumelanin or pheomelanin is synthesized by the melanocytes of the hair follicle. To establish whether this locus acts autonomously within the melanocyte or within the follicular milieu, the kind of pigment produced by various dermal-epidermal combinations of (recessive yellow) and (nonyellow) embryonic skin has been investigated. The results are in complete accord with the extension locus acting within the melanocyte. 相似文献
The site of gene action of the extension (e) locus in the mouse was investigated through the use of the neural tube-skin recombination grafting technique. Recessive yellow () neural tubes were grown with nonyellow () skin, and nonyellow neural tubes with recessive yellow skin. It was found that the production of phaeomelanin was controlled by the genotype of the melanocyte and that the skin genotype had no influence on the type of pigment synthesized. However, recessive yellow melanocytes synthesized phaeomelanin only in the hair follicle environment. Eumelanin is produced in all extrafollicular environments. The action of the extension and agouti loci therefore differ in determining the production of phaeomelanin in the mouse. 相似文献
The alleles at the agouti locus in mice determine whether eumelanin or pheomelanin is synthesized by the follicular melanocytes. Previous studies have indicated the dermis as the site of action of the agouti alleles, while implying that the epidermis plays only a passive role. Using methods of dermal-epidermal recombinations of embryonic yellow (Ay) and nonagouti (a) mouse skin, the study reported here indicates that the epidermis, as well as the dermis, plays a role in the action of the agouti alleles. When yellow dermis is recombined with nonagouti epidermis, the hairs produced contain only pheomelanin, thus substantiating the role of the dermis. However, the reciprocal combination of nonagouti dermis and yellow epidermis also produces hairs containing pheomelanin, indicating a more important role for the epidermis. The role of the dermal-epidermal interactions in the action of the alleles at the agouti locus is discussed. 相似文献
α-(1→2)--Fucosidase, β--galactosidase and galactose oxidase are sterically hindered by certain types of branching in the oligosaccharide chains. 1) β--Galactosidase will not cleave galactose when the penultimate sugar carries a sialic acid residue as in I. 2) Galactose Oxidase will not oxidize the galactose residue in trisaccharide I but will in II. Moreover, neither galactose nor -acetylgalactosamine, glycosidically bound as in III, is susceptible to oxidation with galactose oxidase until the α-(1→2) linkage between them is cleaved by . 3) α-(1→2)--Fucosidase action is inhibited by or galactosyl residue, as in III and IV. Removal of the terminal sugars makes the fucosyl residue susceptible to fucosidase action. 相似文献
The site of action of the sex-linked tabby (Ta) locus was analyzed by the technique of dermal-epidermal recombination grafting. Skin components from normal and tabby 14-day embryos were separated, recombined and grown 21 days in testes of histocompatible mice. Grafts of the combinations normal epidermis-normal dermis and normal epidermis-tabby dermis produced predominantly zig-zag hairs. Grafts of the combination tabby epidermis-normal dermis and tabby epidermis-tabby dermis produced hairs with a morphology similar to hairs found in tabby mice. We conclude from these results that the tabby locus acts within the epidermis, and has no effect on the dermis. 相似文献
Motility of a marine alkali-tolerant bacterium, Vibrio alginolyticus, can be observed in the presence of high concentrations of a protonophorous uncoupler, CCCP. Motility in the CCCP-containing media is completely inhibited by decrease in extracellular [Na+] or by monensin-induced increase in intracellular [Na+]. A mutant has been selected that grows only in media supplemented with a substrate such as acetate requiring no ΔNa to be transported into the cell. Motility of the mutant was found to be completely inhibited by CCCP. Cyanide, CCCP and vanadate added separately or in twos inhibit motility only partially. The three poisons added together completely paralyse the cells. In this inhibitor cocktail, arsenate can substitute for CCCP + vanadate; cyanide can be replaced by anaerobiosis. It is concluded that (i) ΔNa rather than ΔNH powers the flagellar motor of V. alginolyticus in the presence of CCCP, and (ii) in addition to the Na+-motive respiratory chain [Tokuda, H. and Unemoto, T. (1982) J. Biol. Chem. 257, 10007–10014] there is a vanadate and arsenate-sensitive oxygen-independent mechanism of ΔNa generation, presumably an ion-motive ATPase. A suggestion is put forward that circulation of Na+ can replace that of H+ in V. alginolyticus, ΔNa being formed by the Na+-motive respiratory chain and utilized by Na+-solute symporters, the Na+-driven flagellar motor and maybe by a reverse ion-motive ATPase. 相似文献
In the development of structures formed by the interaction of an epithelium and its underlying mesenchyme, the mesenchyme appears to be generally responsible for inducing the initiation of development. On the other hand, the epithelium must be competent to respond to the inductive stimulus if a structure is to be produced. One of the effects of the autosomal recessive mouse mutation downless is to suppress tail hair follicle initiation. Failure of initiation could therefore be due to failure in either the epidermal or the dermal component of the system, or both. Reciprocal recombinations between downless homozygote and heterozygote tail epidermis and dermis were made prior to the time when the first signs of follicle formation are visible in the tails of normal mice, and the recombined elements were allowed to continue growth and differentiation on the chick chorioallantoic membrane. The results suggest that the primary mutant effect is restricted to the epidermis. Explants composed of heterozygote epidermis with either heterozygote or homozygote dermis produced follicles, whereas explants composed of homozygote epidermis with either homozygote or heterozygote dermis did not. 相似文献
Yeast phosphofructokinase (PFK) exists in two forms, an ATP-sensitive form, PFKs, and a desensitized form, PFKd(MgF+). PFKs exhibits sigmoidal kinetics with respect to Fru-6-P, whereby the S0.5, Fru-6-P is determined by [ATP]. This form of PFK is inhibited by ATP and citrate and allosterically activated by Fru-6-P and AMP. NH4+ activates PFKs and enhances its affinity for substrate Fru-6-P (1–3).PFKd(MgF+) in contrast is not inhibited by ATP and citrate, nor activated by Fru-6-P and AMP. Kinetics of the reaction with PFKd(MgF+) with respect to Fru6-P are hyperbolic, with of S0.5, Fm-6-P for PFKs. NH4+ strongly activates this form.In terms of the model of Monod et al. (4), PFKd(MgF+) corresponds to a fixed R-conformation, while PFKs is a limiting T-conformation. 相似文献
Oocytes of Platynereis dumerilii in early vitellogenesis were injected into female worms with oocytes of similar diameter. The donor oocytes were labeled by the or gene controlling eye pigmentation and, after some weeks of growth, were spawned together with the host oocytes. In most cases, a few donor progeny could be found among the offspring produced by the hosts. Donor progeny were examined with respect to an or gene-dependent maternal effect which normally causes wild-type eye color in homozygous () larvae originating from the crossings of heterozygous () females and homozygous () males. This maternal effect was absent from homozygous () larvae derived from homozygous () donor oocytes which had developed in heterozygous females. Conversely, this maternal effect was observed in homozygous () larvae derived from heterozygous () donor oocytes which had developed in homozygous () host females. It is concluded that the oocyte genome is active at the or+ locus during oogenesis and that the oocyte is autonomous with respect to the product of synthesis of the or+ locus. In the present case, the “maternal effect” is therefore caused by synthetic activity in the growing oocyte. The results are discussed with respect to current information on gene products from animal genomes. 相似文献
Application of the tumor-promoting phorbol diester 12--tetradecanoylphorbol-13-acetate to mouse epidermis causes a large increase in the activity of ornithine decarboxylase and in polyamine accumulation. Concurrent application of fluocinolone acetonide, an anti-inflammatory steroid that dramatically inhibits tumor promotion, resulted in a dose-dependent decrease in the 12--tetradecanoylphorbol-13-acetate-stimulated ornithine decarboxylase activity and the subsequent rise in spermidine levels. Spermine and putrescine levels were not greatly affected by fluocinoline acetonide treatment except that maximal putrescine values occurred later in time. Doses of the glucocorticoid as low as 0.1 μg inhibited the 12--tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase activity by as much as 50% and the rise in spermidine accumulation by 30% after coincident treatment of female Sencar mice. 相似文献
(1) A quantitative study has been made of the binding of ouabain to the ( in homogenates prepared from brain tissue of the hawk moth, Manduca sexta. The results have been compared to those obtained in bovine brain microsomes. (2) The insect brain ( will bind ouabain either in the presence of Mg2+ and Pi, (‘Mg2+, Pi’ conditions) or in the presence of Na+, Mg2+, and an adenine nucleotide (‘nucleotide’ conditions) as is the case for the bovine brain (. The binding conditions did not alter the total number of receptor sites measured at high ouabain concentrations in either tissue. (3) Potassium ion decreases the affinity (increases the ) of ouabain to the M. sexta brain ( under both binding conditions. However, ouabain binding is more sensitive to K+ inhibition under the nucleotide conditions. In bovine brain ouabain binding is equally sensitive to K+ inhibition under the both conditions. (4) The enzyme-ouabain complex has a rate of dissociation that is 10-fold faster in the M. sexta preparation than in the bovine brain preparation. Because of this, the M. sexta ( has a higher for ouabain binding and is less sensitive to inhibition by ouabain than the bovine brain enzyme. (5) This data supports the hypothesis that two different conformational states of the M. sexta ( can bind ouabain. 相似文献
Analysis of the cell lineage of the Drosophila retina is reported. Mitotic recombination within the white locus results in the formation of small red spots in white eyes; these are found under the dissecting microscope. The spot frequency is low (never more than eyes) so that there can be no doubt that each spot is a single clone. Eyes bearing a clone are serially sectioned and all retinula and all pigment cells scored as white or white+. We describe the constitution of 101 clones and examine the disposition of the marked cells in the retinal lattice. The clones are apparently random combinations of the marked cell types—for example, two-celled clones containing one pigment and one retinula cell are frequently found. Our results appear to rule out fixed cell lineage as a determinative mechanism in ommatidial development. 相似文献
Partial acid hydrolyzates of the extracellular polysaccharide from Porphyridiunm cruentum yield three disaccharides and two uronic acids. These constitute all of the uronic acid in the polymer. The novel disaccharides are 3-O-(α--glucopyranosyl- uronic acid)--galactose, 3-O-(2-O-methyl-ca-glucopyranosyluronic acid)-- galactose, and 3-0-(2-0-methyl-a--glucopyranosyluronic acid)--glucose. The polyanion of high molecular weight contains - and -galactose, xylose, -glucose, -glucuronic acid and 2-O-methyl-D-glucuronic acid, and sulfate in molar ratio (relative to -glucose) of 2.12:2.42:1.00:1.22:2.61. Preliminary periodate-oxidation studies suggest that the hexose and uronic acids are joined to other residues by ( 1→3) glycosidic linkages. About one-half of the xylose residues are (1→3)-linked. 相似文献
The potencies of (?)--Δ9-THC, (+)--Δ9-THC, (+)--Δ9-THC, (?)--Δ8-THC and (+)--Δ8-THC were compared in several different species. (?)--Δ9-THC was 100 times more potent than (+)--Δ9-THC in depressing schedule-controlled responding in monkeys. The (+)- isomers were less effective than their corresponding (?)- isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)- isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)--Δ9-THC in the dog static-ataxia test was comparable to that of (+)--Δ9-THC. The hypothermia in mice produced by the (?) isomers of -Δ9-THC and -Δ8-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)--Δ9-THC was 5.6 as measured by depression of spontaneous activity in mice. The magnitude of the potency ratios of the THC stereo-isomers is dependent upon the species and the pharmacological test used. 相似文献
As part of a program to synthesize the ceramide trisaccharide (1) related to Fabry's disease, methyl 4-O-(4-O-α--galactopyranosyl-β--galactopyranosyl)-β--glucopyranoside (12) was prepared. Methyl β-lactoside (2) was converted into methyl 4-O-(4,6-O-benzylidene-β--galactopyranosyl)-β--glucopyranoside (4). Methyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-β--galactopyranosyl)-β--glucopyranoside (7) was synthesized from 4 through the intermediates methyl 2,3,6-tri-O-benzoyl-4-O-(4,6-O-benzylidene-2,3-di-O-benzoyl-β--galactopyranosyl)-β--glucopyranoside (5) and methyl 2,3,6-tri-O-benzoyl-4-O-(2,3-di-O-benzoyl-β--galactopyranosyl)-β--glucopyranoside (6). The halide-catalyzed condensation of 7 with 2,3,4,6-tetra-O-benzyl--galactopyranosyl bromide (8) gave methyl 2,3,6-tri-O-benzoyl-4-O-[2,3,6-tri-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzyl-α--galactopyranosyl)- β--galactopyranosyl]-β--glucopyranoside (10). Stepwise deprotection of 10 led to 12, the methyl β-glycoside of the trisaccharide related to Fabry's disease. 相似文献
The role of T cells in the development and expression of antigen-nonspecific immunosuppression in experimental African trypanosomiasis was addressed. Nude () C57BL/ 6 NIH mice and their thymus-bearing () littermates were infected with Trypanosoma rhodesiense and examined for suppression of splenic B-cell responses in vitro to the mitogen LPS. All animals developed splenic unresponsiveness to LPS. Further, both nu/nu and nu/ + infected mice displayed suppressor cell activity in their spleen cell populations upon transfer to normal uninfected mouse spleen cell cultures. On the basis of these findings we suggest that both the generalized immunosuppression and the development of suppressor cell activity in the spleens of mice infected with T. rhodesiense are T-independent processes. 相似文献
Stationary current voltage characteristics and the action potential of single myelinated nerve fibres were measured to examine the effect of (methanol to octanol) on the electrophysiological function of the axon membrane. K+-depolarized membranes show alkanol-dependent shifts of , the membrane transition voltage, whereas in veratridine-depolarized membranes such are not observed. In the latter case, reduce both the stationary Na+ current and the conductivity step between the high- and low-ohmic conductivity state of the membrane. Action potential amplitude, however, is less affected by the alkanols as is the stationary Na+ current. The results are compared with the alkanol-dependent changes of the thermotropic phase transition in phospholipid bilayers. 相似文献
A derivative of Escherichia coli K-12 (strain ) has been developed in which mutations in several genes can be detected simultaneously by plating parts of the bacterial population on different selective media. The mutation types include reversions from differently induced auxotrophies (nad-, arg-) aand (forward) mutations leading to resistance against 5-methytryptophan and to gal+ phenotype. It is assumed that many types of DNA alteration, including deletions and changes involving gross DNA regions, will lead to viable detectable mutants.The usefulness of strain E. coli was tested in spot tests, in liquid tests, in tests with extracts of mammalian organs, and in mammalian-mediated tests. It is concluded that strain is at least as useful in routine mutagenicity testing (especially in mammalian-mediated assays) as other present bacterial strains. 相似文献