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1.
Summary We have determined the sequence of a rat A3/A1-crystallin complementary DNA (cDNA) clone and the (partial) sequence of the human B3-crystallin gene. Calculation of the ratio of silent to nonsynonymous substitution between orthologous A3/A1-, B3-, and other - and -crystallin sequences revealed that the region encoding the two globular domains of the A3/A1-crystallin sequence is the best conserved during evolution, much better than the corresponding region of the B1-, B3-, or the -crystallin sequences, and even better (at least in the rodent/frog comparison) that the well-conserved A-crystallin sequence. Remarkably, the rate of change of the A3/A1-crystallin coding sequence does not differ in the rodent and primate lineages, in contrast with previous findings concerning the evolution rates of the A- or -crystallin sequences in these two lineages. Comparison of the regions that encode the four motifs of the -crystallin between orthologous mammalian sequences showed that the extent of nonsynonymous substitution in each of these four homologous motif regions is the same. However, when the orthologous -crystallin genes of more distantly related species (mammals vs chicken or frog) are compared, the extent of nonsynonymous substitution is higher in the regions encoding the external motifs I and III than in the regions encoding the internal motifs II and IV. This phenomenon is also observed when paralogous members of the /-crystallin supergene family are compared.  相似文献   

2.
The PI3 kinase signalling pathway is an important pathway in mediating the glucoregulatory effects of insulin and skeletal muscle (SKM) is the major tissue involved in glucose utilization. In diabetes this pathway is impaired, either due to lack of insulin as in Type 1 diabetes, or due to insulin resistance as in Type 2 diabetes. Bis(maltolato)oxovanadium IV (BMOV), an insulin mimetic/enhancing agent, produces a marked glucose lowering effect in models of both types of diabetes. Some in vitro studies have shown that phosphatidylinositol 3 kinase (PI3 kinase) activity is enhanced by vanadium. In the present study we looked at changes in PI3 kinase expression and activity in SKM from STZdiabetic and fa/fa Zucker rats treated with BMOV for 3 weeks. Although BMOV treatment completely normalized glucose levels in STZdiabetic rats, no effect was observed on basal or insulin-stimulated PI3 kinase activity. In fatty Zucker rats, activation of PI3 kinase activity after insulin injection was impaired as compared to age matched lean controls, but BMOV again did not affect the activity. These results suggest that although PI3 kinase is an important signalling factor in glucose utilization, vanadium treatment does not reduce hyperglycemia through activation of SKM PI3 kinase in vivo.  相似文献   

3.
Summary Association of -amylase with starch granules in the starchy endosperm of barley (Hordeum vulgare L. cv. Menuet) grains was characterized biochemically. In whole homogenates of dry seeds, two forms of -amylase were detected: one is free -amylase extractable with saline solution and the other is bound -amylase extractable with saline solution containing a reducing agent. The two forms of -amylase were shown to be identical in terms of mobility on disc gels, antigenicity, and molecular specific activity, indicating that the -amylase molecules of the two forms are identical. The starch granules were isolated from either dry seeds or mature seeds harvested before the desiccation phase. Both starch granule preparations were morphologically identical by microscopic inspection. The bound -amylase was predominantly associated with starch granules isolated from dry seeds, whereas it was not associated with starch granules from mature seeds harvested before desiccation. Overall results show that the periphery of starch granules is the major site of deposition for bound -amylase in dry seeds. The association of -amylase with starch granules occurs during the desiccation phase of seed development, resulting in the conversion of free -amylase into a bound form.Recipient of an award from the Union Générale de la Brasserie Française (I. H.-N.) and from the Centre National de la Recherche Scientifique and the Japan Society for the Promotion of Science under the France-Japan Cooperative Science Programme, 1985 (M.N.).  相似文献   

4.
The role of -tocopherol uptake system in human erythrocyte in the uptake of plasma -tocopherol has been suggested. However no information is available on -tocopherol uptake activity of human erythrocytes in the presence of high levels of D-glucose which is known to lead to pathological alterations in different cells including human erythrocytes. Therefore, in order to examine the effect of D-glucose on the binding of -tocopherol to human erythrocytes, the binding characteristics of -tocopherol to these cells were established first. Binding of [3H]-tocopherol to human erythrocytes was both saturable and specific. Scatchard analysis of -tocopherol binding to these cells showed the presence of two independent classes of binding sites with widely different affinities. The high affinity binding sites had a dissociation constant (Kd1) of 90 nM with a binding capacity (n1) of 900 sites per cell, whereas the low affinity binding sites had a dissociation constant (Kd2) of 5.2 M and a binding capacity (n2) of 105,400 sites per cell. Trypsin treatment abolished all the -tocopherol binding activity. Competition for the binding of -tocopherol to human erythrocytes was effective with other homologues of -tocopherol (-tocopherol, -tocopherol and -tocopherol) and their potency was almost equal to -tocopherol itself. The order of preference was -tocopherol > -tocopherol -tocopherol -tocopherol. Incubation of human erythrocytes with various concentrations of D-glucose did not affect -tocopherol uptake activity. Our data demonstrate the presence of an -tocopherol uptake system in human erythrocytes and that the -tocopherol uptake activity is not modulated by the presence of D-glucose.  相似文献   

5.
The release of [3H]-aminobutyric acid (GABA) from pre-loaded slices of rat cerebral cortex was investigated in the presence and absence of the GABA-transaminase inhibitors gabaculine and -vinyl GABA. In the experiments carried out without an inhibitor, an ion-exchange column chromatographic technique was used to separate [3H]GABA from tritiated metabolites released with it into the superfusate. The presence of gabaculine (5 M) substantially reduced the Ca2+-dependence of the release of [3H]GABA evoked by a 4 min 30 mM K+ pulse, whereas this was not appreciably reduced by the presence of -vinyl GABA (2 mM or 10 mM). Nevertheless, the characteristics of [3H]GABA release were not identical in the presence and absence of either inhibitor.  相似文献   

6.
Summary The BSG test was used in a comparative study of the linear chromosome differentiation and the idiograms of T. Macha ssp. tubalicum v. letschchumicum Dek. et Men., T. georgicum Dek., T. timopheevi. Zhuk., T. carthlicum Nevski, T. dicoccum Schrank, v. rufum, T. durum Desf. v. Arnautka were compiled.The karyotype of each polyploid wheat species consists of two groups of chromosomes. The first is formed by ten pairs of constant chromosomes occurring almost in all species and the second by all the rest of the variable chromosomes that are either fully specific for the species in question or occur only in a few species. T. timopheevi largely differs from other species of polyploid wheats in the high level and specific localization of structural heterochromatin on chromosomes. The rols of introgression in wheat evolution and the necessity of establishing a General Cytological Nomenclature of Cereal Chromosomes are discussed.  相似文献   

7.
    
Alternating poly(Glu-Leu) exhibits a random coilstructure in pure water at neutral pH. The addition of 0.5 equiv of Ca2+ induces a coil-to--sheet transitionand the addition of 0.15 equivof Fe3+ induces a coil-to--helixtransition. Conformational competition between thesetwo structures was studied by mixing preformed-sheets and -helices in differentproportions. Circular dichroism spectra clearly show that-sheets are favored at the expense of-helices in -sheet-rich mixtures.  相似文献   

8.
Our interest in thecis-acting elements that promote the up-regulation of the globin gene has led to a systematic deletion analysis of portions of the globin gene in the context of the HS2 and globin gene using transgenic mice. In constructs that delete the 5 region to only 265 bp, high-level erythroid-specific expression was observed. Further deletion to 122 bp, however, results in significantly reduced expression levels A substitution of a minilocus control region for the single HS2 site was also produced, resulting in increased globin expression over that seen with the HS2 alone. These results are consistent with the presence of an enhancer-like element between –122 and –265. In addition, a construct in which the entire globin gene promoter was replaced by a thymidine kinase promoter was tested. Interestingly, no expression was detected in these transgenic mice. This may indicate the requirement for an erythroid-specific promoter to drive this gene. Finally, the 3 region of the globin gene was deleted in order to examine the effect of a previously defined 3 enhancer region. With deletion of this region, the expression of the human globin gene in transgenic mice is unchanged relative to the parental constructs.  相似文献   

9.
The migratory history of Sakhalin taimen, Hucho perryi, was examined in terms of strontium (Sr) and calcium (Ca) uptake in the otolith by using wavelength dispersive X-ray spectrometry on an electron microprobe. Otolioth Sr:Ca ratios of freshwater-reared samples remained consistently at low levels throughout the otolith. The Sr:Ca ratios of samples from Lake Aynskoye of Sakhalin Island showed a low value from the core up to a point of 700–2140µm. Thereafter, the ratios increased sharply and remained at higher levels up to the outermost regions. The difference in Sr:Ca ratio might be the result of the presence of individuals that underwent seawater and freshwater life history phases, probably reflecting the ambient salinity or the seawater–freshwater gradient in Sr concentration. Otolith Sr:Ca ratio analysis revealed downstream migration history in H. perryi.  相似文献   

10.
Summary Nitrogen indole protection of the -methyltryptophan side-chain residue is important for avoiding undesired side reactions during peptide synthesis. Of great importance is the choice of a side-chain protecting group for orthogonal peptide synthesis and its stability under a variety of chemical conditions required for synthesis of the four isomers of this unusual amino acid. We report here the successful use of the mesitylenesulfonyl (Mts) protecting group for -methyltryptophan in the synthesis of melanotropin and CCK peptide analogues and the ready cleavage of this protecting group under HF conditions.  相似文献   

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