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1.
Changes in state of adenylation and time course of degradation of maternal mRNAs during oocyte maturation and early embryonic development in the mouse 总被引:14,自引:0,他引:14
Previous work has shown that more than 50% or about 50 pg of polyadenylated RNA found in the full-grown mouse oocyte is deadenylated or degraded during meiotic maturation. Here we show that rRNA declines by 60 pg during this period, accounting for most of the 80-pg decline in total RNA and indicating that a significant amount of mRNA is deadenylated but not degraded during maturation. Actin mRNA is deadenylated at about 7 hr of in vitro maturation, following the decline in its translation. The poly(A) tail on hypoxanthine phosphoribosyltransferase (HPRT) mRNA is elongated at 7 hr of maturation, preceding an increase in HPRT activity. Actin mRNA is partially degraded in the one-cell embryo and falls to near the limit of detection in the late two-cell stage, while HPRT mRNA shows no change in early two-cell embryos, but is deadenylated and declines greatly during the two-cell stage. In aging unfertilized eggs, most of these changes occur on a delayed schedule. The various species of alpha-tubulin mRNA are largely deadenylated and more than half are degraded during maturation. Taken together with other published results, we conclude that each mRNA has its own pattern of changes in the length of the poly(A) tail (correlated with translation) and degradation during the period of maternal control of protein synthesis, and, for those examined, the maternal mRNAs remaining in the early two-cell embryo are degraded to low levels by the late two-cell stage. 相似文献
2.
Temperature-sensitive vaccinia virus mutants identify a gene with an essential role in viral replication. 总被引:13,自引:11,他引:2
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Vaccinia virus mutants ts2 and ts25, members of the same complementation group, exhibit a temperature-dependent arrest at the stage of viral DNA replication. The lesions responsible for the mutant phenotypes have been localized to the far left region of the HindIII B genomic fragment by marker rescue studies. Hybrid selection analyses established that the DNA fragments positive for rescue represented the first open reading frame of the HindIII B fragment and encoded a 30-kilodalton protein. The gene is expressed early after infection as a rightwardly transcribed 1-kilobase-pair mRNA whose coordinates were determined by S1 nuclease mapping. To further the phenotypic analysis of the mutants, the accumulation of viral DNA sequences during permissive and nonpermissive infections was quantitated. The extent of the DNA- phenotype was shown to vary in different cell types. In mouse L cells at either high or low multiplicity of infection, nonpermissive DNA synthesis was less than 5% of that seen in permissive infections. This severe defect was mirrored by correspondingly low viral yields. In infections of BSC40 monkey cells, however, the deficiencies in both DNA synthesis and virus production were far less severe. For one mutant (ts2), the temperature sensitivity in BSC40 cells varied inversely with the multiplicity of infection. 相似文献
3.
Emile CL. Marnette Harm Houweling Herman Van Dam Jan Willem Erisman 《Biogeochemistry》1993,23(2):119-144
The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982
to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying
lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur
budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO4
2− concentrations after a decrease of atmospheric input. However, SO4
2− concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused
the unexpectedly high SO4
2− concentrations. The possible supply of SO4
2− from the sediment through regulation by (K-)Al-SO4 containing minerals or desorption of SO4
2− from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite,
basaluminite and jurbanite indicated that SO4
2− concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO4
2− from peaty sediments may account for the estimated SO4
2− supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments
and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation
of reduced S, the amount of SO4
2− may be provided which complements the decreasing depositional SO4
2− input. In future research these two mechanisms need to be investigated. 相似文献
4.
Vaccinia virus B1 kinase: phenotypic analysis of temperature-sensitive mutants and enzymatic characterization of recombinant proteins. 总被引:2,自引:0,他引:2
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The vaccinia virus B1 gene encodes a 34-kDa protein with homology to protein kinases. In L cells infected nonpermissively with mutants containing lesions in the B1 gene (ts2 and ts25), the infectious cycle arrests prior to DNA replication. In this report, we demonstrate that DNA synthesis ceases when cultures infected with these mutants at 32 degrees C are shifted to the nonpermissive temperature (39.5 degrees C) in the midst of DNA replication. We also show that B1 protein is synthesized transiently during the early phase of infection, even when the progression to later stages of gene expression is prevented. Although wild-type (wt) B1 is stable, the ts B1 proteins are markedly labile in both L and BSC40 cells at both permissive and nonpermissive temperatures. These results suggest that the ts phenotype of the mutants is complex and may in part reflect a temperature-dependent requirement for kinase activity, an induction of temperature sensitivity in B1 substrates under nonpermissive conditions, and/or ts complementation by host factors. To facilitate biochemical analyses, recombinant wt B1, ts2 B1, and ts25 B1 were produced in Escherichia coli. The wt protein was able to phosphorylate serine and threonine residues on several exogenous substrates in vitro. The activity of ts25 B1 was 3% that of the wt enzyme, and no detectable kinase activity was associated with ts2 B1. In light of the inactivity of the ts2 B1 protein in vitro and its extreme lability in vivo, we attempted to isolate a vaccinia virus B1 null mutant by targeted interruption of the B1 gene at 32 degrees C. No null mutants were isolated. These results indicate that the B1 protein kinase provides a vital function which cannot be supplied by the host or circumvented by incubation at 32 degrees C. 相似文献
5.
Sulfate reduction and S-oxidation in a moorland pool sediment 总被引:3,自引:2,他引:1
In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO4
2– reduction rates in the sediment, (2) depletion of SO4
2– in the overlying water column and (3) release of35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core35SO4
2– injection. Rates of SO4
2– consumption in the overlying water were estimated by changes in SO4
2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m–2 d–1. Rates of SO4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m–2 d–1 (November) to 0.43–1.81 mmol m–2 d–1 (July, August and April). Maximum rates of oxidation to SO4
2– in July 1990 estimated by combination of SO4
2– reduction rates and rates of in situ SO4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m–2 d–1 at an organic rich and at a sandy site respectively.Experiments with35S2– and35SO4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO4
2– and (2) the presence of mainly non SO4
2–-S derived from reduced S transported from the sediment into the overlying water. A35S2– tracer experiment showed that about 7% of35S2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author 相似文献
6.
Monika M. Lulsdorf Hans Rempel Jennie A. Jackson David S. Baliski Shaun L. A. Hobbs 《Plant cell reports》1991,9(9):479-483
For optimization of the transformation procedure with Pisum sativum L. stern explant callus was used to test the effect of disarmed Agrobacterium tumefaciens strains, cocultivation procedures (preconditioning of explants; use of Nicotiana tabacum L. nurse cultures), duration of cocultivation (2, 3 or 4 days), and agents for selection (kanamycin or hygromycin). The succinamopine strain EHA101(pBI1042) produced the highest percentage of transformed calli (77%) when used in conjunction with tobacco nurse culture during four days of cocultivation. Using this strain, kanamycin (76%) and hygromycin (77%) were equally effective selective agents, but for strain LBA4404(pBI1042) percentage of transformed calli was higher for hygromycin (63%) than for kanamycin (17%). The procedures and strains shown to be optimal for transformation of pea callus will now be complemented by a pea regeneration system. 相似文献
7.
8.
P. D. Blanc N. Maizlish P. Hiatt K. R. Olson D. Rempel 《The Western journal of medicine》1990,152(2):181-184
In a study of occupational illness reported to a regional poison control center and to gauge the center''s outreach and services, we did follow-up interviews of 301 case contacts over a 6-month period. We ascertained referral routes, reasons for contacting the poison control center, and awareness of the center''s function. For 122 cases a nonphysician was the initial poison control center contact. Of the nonphysician contacts, 41 had already consulted a health care provider and been referred to the poison control center for assistance. Of the 70 persons with exposure, only 21 had been aware before their exposures that poison control center services might include occupational chemical illness consultation. Physicians and nonphysicians expressed similar reasons for contacting the poison control center, with 118 of 301 identifying the need for an exposure hazard risk assessment. These data suggest that although those contacting a poison control center because of occupational illness include a variety of cases, they have many similar service needs. 相似文献
9.
Robert S. Rempel Matthew Carlson Arthur R. Rodgers Jennifer L. Shuter Claire E. Farrell Devin Cairns Brad Stelfox Len M. Hunt Robert W. Mackereth Janet M. Jackson 《The Journal of wildlife management》2021,85(7):1355-1376
Wildlife models focused solely on a single strong influence (e.g., habitat components, wildlife harvest) are limited in their ability to detect key mechanisms influencing population change. Instead, we propose integrated modeling in the context of cumulative effects assessment using multispecies population dynamics models linked to landscape-climate simulation at large spatial and temporal scales. We developed an integrated landscape and population simulation model using ALCES Online as the model-building platform, and the model accounted for key ecological components and relationships among moose (Alces alces), grey wolves (Canis lupus nubilus), and woodland caribou (Rangifer tarandus caribou) in northern Ontario, Canada. We simulated multiple scenarios over 5 decades (beginning 2020) to explore sensitivity to climate change and land use and assessed effects at multiple scales. The magnitude of effect and the relative importance of key factors (climate change, roads, and habitat) differed depending on the scale of assessment. Across the full extent of the study area (654,311km2 [ecozonal scale]), the caribou population declined by 26% largely because of climate change and associated predator-prey response, which led to caribou range recession in the southern part of the study area. At the caribou range scale (108,378 km2), which focused on 2 herds in the northern part of the study area, climate change led to a 10% decline in the population and development led to an additional 7% decline. At the project scale (8,331 km2), which was focused more narrowly on the landscape surrounding 4 proposed mines, the caribou population declined by 29% largely in response to simulated development. Given that observed caribou population dynamics were sensitive to the cumulative effects of climate change, land use, interspecific interactions, and scale, insights from the analysis might not emerge under a less complex model. Our integrated modeling framework provides valuable support for broader regional assessments, including estimation of risk to caribou and Indigenous food security, and for developing and evaluating potential caribou recovery strategies. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society. 相似文献
10.
MARTIN CLÉMENT CAROLINE CHAMBERLAND JACQUELINE PÉRODIN RICHARD LEDUC GAÉTAN GUILLEMETTE EMANUEL ESCHER 《Journal of receptor and signal transduction research》2013,33(5-6):417-433
Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT1)1 receptor mutant N111G-hAT1 which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT1 receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT1 series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form. 相似文献