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  • Aerospace Medicine  (3)
  • Cell & Developmental Biology  (2)
  • GEOPHYSICS
  • 1995-1999  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 41 (1995), S. 16-19 
    ISSN: 1040-452X
    Keywords: Mouse embryo ; Transcription ; Two-cell block ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Mouse embryos produced by the fertilization of eggs from (B6D2)F1 and CF-1 mice differ in their ability to complete the second cell cycle in the presence of α-amanitin. Essentially all embryos obtained from CF-1 mothers arrest at the two-cell stage when cultured from the late one-cell stage in α-amanitin at concentrations that prevent zygotic genome activation, while up to 15% of the embryos obtained from (B6D2)F1 mothers can progress to the three- to four-cell stage. This occurs even at α-amanitin concentrations that are fivefold greater than that required to prevent gene transcription. We propose that eggs of certain strains of mice may be endowed with greater supplies of macromolecules to support early development and that a percentage of these embryos can complete the second cell cycle in the absence of transcription. This difference may contribute to the strain-dependent differences in development in vitro. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 41 (1995), S. 314-324 
    ISSN: 1040-452X
    Keywords: Signal transduction ; Maternal mRNA ; Polyadenylation ; G protein ; RT-PCR ; Gene expression ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have developed a novel reverse transcription-polymerase chain reaction (RT-PCR)-based approach for systematically quantifying in a single experiment the abundances of many different mRNAs in preimplantation mouse embryos. With this approach, the entire mRNA population from a small number of embryos is amplified while preserving the relative abundance of each mRNA in the cDNA population. The cDNA is analyzed by quantitative hybridization to radiolabeled probes. The approach is very sensitive and provides reliable, quantitative data regarding changes in mRNA abundance. A major advantage of this method is that estimates of mRNA copy number can be obtained and compared between different mRNAs. With this approach, we analyzed the patterns of expression of nine G protein α subunit mRNAs (Gαs, Gαi, Gαq′, Gαo′, and Gα11-15) in oocytes, eggs, and preimplantation embryos from fertilization to the blastocyst stage. Six α subunit mRNAs were expressed at significant levels, all of which underwent significant temporal alterations in expression. The mRNAs encoding some α subunit types were expressed predominantly in the egg and 1-cell embryo, underwent sharp reductions during the 2-cell stage, and were re-expressed between the 8-cell and blastocyst stages. One α subunit mRNA increased in abundance at the early blastocyst stage. The possible significance of these alterations in G protein mRNA abundance to embryonic development is discussed. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 3
    Publication Date: 2011-08-24
    Description: Dynamics of the left heart ventricular muscle contractility and compliance was studied in 4 monkeys in the head down position (antiorthostatic hypokinesia) with the body angle 10 during 2 weeks. Functional tests on a tilt table and under two conditions of centrifuge rotation were performed prior to and after the antiorthostatic hypokinesia. No changes in the left heart ventricular muscle contractility was found. However, the sensitivity level of the baroreflex control decreased. Compliance of the left heart myocardial fibre increased in the first hours and days of the antiorthostatic hypokinesia.
    Keywords: Aerospace Medicine
    Type: Fiziologicheskii zhurnal imeni I.M. Sechenova / Rossiiskaia akademiia nauk (ISSN 1027-3646); Volume 82; 10-11; 34-45
    Format: text
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  • 4
    Publication Date: 2011-08-24
    Description: We measured hemodynamic responses during 4 days of head-down tilt (HDT) and during graded lower body negative pressure (LBNP) in invasively instrumented rhesus monkeys to test the hypotheses that exposure to simulated microgravity increases cardiac compliance and that decreased stroke volume, cardiac output, and orthostatic tolerance are associated with reduced left ventricular peak dP/dt. Six monkeys underwent two 4-day (96 h) experimental conditions separated by 9 days of ambulatory activities in a crossover counterbalance design: 1) continuous exposure to 10 degrees HDT and 2) approximately 12-14 h per day of 80 degrees head-up tilt and 10-12 h supine (control condition). Each animal underwent measurements of central venous pressure (CVP), left ventricular and aortic pressures, stroke volume, esophageal pressure (EsP), plasma volume, alpha1- and beta1-adrenergic responsiveness, and tolerance to LBNP. HDT induced a hypovolemic and hypoadrenergic state with reduced LBNP tolerance compared with the control condition. Decreased LBNP tolerance with HDT was associated with reduced stroke volume, cardiac output, and peak dP/dt. Compared with the control condition, a 34% reduction in CVP (P = 0.010) and no change in left ventricular end-diastolic area during HDT was associated with increased ventricular compliance (P = 0.0053). Increased cardiac compliance could not be explained by reduced intrathoracic pressure since EsP was unaltered by HDT. Our data provide the first direct evidence that increased cardiac compliance was associated with headward fluid shifts similar to those induced by exposure to spaceflight and that reduced orthostatic tolerance was associated with lower cardiac contractility.
    Keywords: Aerospace Medicine
    Type: The American journal of physiology (ISSN 0002-9513); Volume 275; 4 Pt 2; R1343-52
    Format: text
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  • 5
    Publication Date: 2011-08-24
    Description: Central circulatory hemodynamic responses were measured before and during the initial 9 days of a 12-day 10 degrees head-down tilt (HDT) in 4 flight-sized juvenile rhesus monkeys who were surgically instrumented with a variety of intrathoracic catheters and blood flow sensors to assess the effects of simulated microgravity on central circulatory hemodynamics. Each subject underwent measurements of aortic and left ventricular pressures, and aortic flow before and during HDT as well as during a passive head-up postural test before and after HDT. Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure were measured, and dP/dt and left ventricular elastance was calculated from hemodynamic measurements. The postural test consisted of 5 min of supine baseline control followed by 5 minutes of 90 degrees upright tilt (HUT). Heart rate, stroke volume, cardiac output, and left ventricular end-diastolic pressure showed no consistent alterations during HDT. Left ventricular elastance was reduced in all animals throughout HDT, indicating that cardiac compliance was increased. HDT did not consistently alter left ventricular +dP/dt, indicating no change in cardiac contractility. Heart rate during the post-HDT HUT postural test was elevated compared to pre-HDT while post-HDT cardiac output was decreased by 52% as a result of a 54% reduction in stroke volume throughout HUT. Results from this study using an instrumented rhesus monkey suggest that exposure to microgravity may increase ventricular compliance without alternating cardiac contractility. Our project supported the notion that an invasively-instrumented animal model should be viable for use in spaceflight cardiovascular experiments to assess potential changes in myocardial function and cardiac compliance.
    Keywords: Aerospace Medicine
    Type: Acta astronautica (ISSN 0094-5765); Volume 42; 1-8; 255-63
    Format: text
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