scholarly journals Selection for an invariant Character, Vibrissa Number, in the House Mouse III. Correlated Responses

1962 ◽  
Vol 15 (1) ◽  
pp. 188 ◽  
Author(s):  
AS Fraser ◽  
BM Kindred
Keyword(s):  
House Mouse ◽  
Low Frequency ◽  
Mutant Mice ◽  
Selection Experiment ◽  
Correlated Responses ◽  
Very Low Frequency ◽  
Selection For

Selection for increased and decreased total number of secondary vibrissae has been practised on the mutant mice of a stock in which the tabby gene is segregating. Five separate groups of vibrissae contribute to the total number and differences were found in the response of individual groups of vibrissae to selection. These differences occur both in the main selection experiment and in subsidiary experi-ments based on rare non-tabby mice with abnormal scores which occur with very low frequency in ordinary mouse stocks.

SELECTION PRESSURE IN CELL POPULATIONS OF VICIA HAJASTANA CULTURED IN VITRO

1972 ◽  
Vol 14 (1) ◽  
pp. 65-70 ◽  
Author(s):  
B. D. Singh ◽  
B. L. Harvey ◽  
K. N. Kao ◽  
R. A. Miller
Keyword(s):  
Frequency Distribution ◽  
Selection Pressure ◽  
Low Frequency ◽  
Cell Populations ◽  
Tissue Cultures ◽  
Very Low Frequency ◽  
Selection For ◽  
Diploid Cells ◽  
Mature Seeds

Tissue cultures from mature seeds of Vicia hajastana Grossh (2n = 10) were maintained in liquid B5 medium with 4.5 × 10−6 M 2,4-D. Initially the cultures had a very low frequency of diploid cells, which increased to 91.7% after 295 days in culture, indicating a strong selection for diploid cells. Chromosomes with changed morphology were observed and anaphase analysis showed various abnormalities. The frequency distribution of different chromosomes of the genome in aneuploid cells was nonrandom.

scholarly journals Selection for an Invariant Character, Vibrissa Number, in the House Mouse II. Limits to Variability

1960 ◽  
Vol 13 (1) ◽  
pp. 48 ◽  
Author(s):  
AS Fraser ◽  
BM Kindred
Keyword(s):  
House Mouse ◽  
Phenotypic Variation ◽  
Reproductive Fitness ◽  
Selection Experiment ◽  
Frequency Distributions ◽  
Selection For ◽  
Seven Generations

A selection experiment for vibrissa number in tabby mice has been extended for 13 generations. Progress of selection for the first seven generations has already been reported. The results of the next six generations of selection are given and the whole experiment is considered with regard to (1) the shapes of the frequency distributions for the three genotypes (+, Ta+, and Ta�) for succeeding generations; (2) limits to phenotypic variation, i.e. canalization mechanisms; and (3) reproductive fitness.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

Selection for Increased Rate or Efficiency of Lean Growth in Rats: Correlated Responses in Reproductive Performance

1981 ◽  
Vol 53 (6) ◽  
pp. 1458-1464 ◽  
Author(s):  
R. D. Allrich ◽  
C. T. Wang ◽  
G. E. Dickerson ◽  
Dwane R. Zimmerman
Keyword(s):  
Reproductive Performance ◽  
Correlated Responses ◽  
Or Efficiency ◽  
Lean Growth ◽  
Selection For

VLF/LF (Very Low Frequency/Low Frequency) Reflection Properties of the Low Latitude Ionosphere

1988 ◽  
Author(s):  
Wayne I. Klemetti ◽  
Paul A. Kossey ◽  
John E. Rasmussen ◽  
Maria Sueli Da Silveira Macedo Moura
Keyword(s):  
Low Frequency ◽  
Low Latitude ◽  
Very Low Frequency ◽  
Low Latitude Ionosphere
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