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  • 1
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five oligomycin-resistant (oli r) mutant strains of Neurospora crassa were analyzed for their growth rate and for the periodicity of their circadian rhythm. The most resistant strains had periods of 18–19 h while the least resistant strain had a normal period of 21.0 h. There was a rough correlation between the in vivo degree of oligomycinresistance and the amount of change in the period. Several of the oli r mutations have been previously described by Sebald et al. (1977) in terms of known amino acid changes in the primary structure of the proteolipid, or DCCD-binding protein, found in the F0 membrane portion of the mitochondrial ATP synthetase. Amino acid changes in the structure of this protein are reported here for two other oli r mutations. The proteolipid isolation procedures were slightly modified to include a delipidation step, and an HPLC procedure was developed to separate the hydrophobic peptides of this protein. Analysis of heterocaryons carrying both the oli r and oli s markers indicated that the oli r and oli s mutations were codominant to each other in terms of period and growth rate. The changes in the primary structure of this DCCD-binding protein reported here are the first known examples of changes in the primary structure of a protein which alter the period of a circadian rhythm.
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  • 2
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Suppressor mutations have been isolated for bal and col-2, two slow-growing and nonallelic morphological mutants of Neurospora that carry defective G6PDs. Both suppressor mutations are located on linkage group I but are unlinked to the particular mutant that they suppress. The bal suppressor (su-B) increases the growth rate of bal and produces a more spreading morphology. su-B also decreases the G6P K m of G6PD in bal;su-B double mutants. The col-2 suppressor (su-C) has similar positive effects on the morphology of col-2 and influences the electrofocusing pattern of the col-2 G6PD. su-C is an unusual type of suppressor mutation in that, when present in a wild-type background, it affects the electrofocusing pattern and kinetic properties of the normal enzyme. The nature of the su-C mutation, plus the complex genetic control of the Neurospora G6PD, is discussed.
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  • 3
    ISSN: 1573-3572
    Keywords: antihypertensive treatment ; hypertension ; compliance ; quality of life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract If patients notoriously violate treatment regimens known to effectively control hypertension, then there must be some subjective costs associated with adherence to these regimens. Generally speaking, there must be some reduction in quality of life associated with antihypertensive medication. Unfortunately the concept of quality of life, due to its lack of specificity, is of little help in further investigating the nature of these subjective costs. We developed a simple neuropsychophysiological model based on fundamental psychological and physiological processes: corticoinhibitory effects of phasic blood pressure elevation reduce the aversive or painful qualities of many stressors. This negative reinforcement increases the rate of the reinforced physiological behavior, i.e., phasic analgesic blood pressure increases. Such negatively reinforced operant behavior is known to be extremely resistant to extinction. Counter actions such as taking antihypertensive medication not only lead to reduced quality of life due to their cancellation of the analgesic effect of conditioned blood pressure increase, but also lead to some form of reluctance to comply with treatment. The model not only provides an innovative etiological path to the emergence of neurogenic essential hypertension, but also yields a highly specific and “lean” concept of quality of life. Furthermore, it supplies the health care community with a concise explanation for the well-known low compliance of patients with their antihypertensive regimens. In addition to its parsimony, the model fits well with various experimental findings and has been operationalized and tested empirically. Specific therapeutic implications can be derived.
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  • 4
    ISSN: 1573-3270
    Keywords: biofeedback ; slow cortical potentials ; threshold regulation of EEG ; startle probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Selfcontrol of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.
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  • 5
    ISSN: 1573-3521
    Keywords: blood pressure ; stress ; stability ; longitudinal study ; reactivity ; sex differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract The 4-year stability of cardiovascular responses to laboratory psychological stress (mental arithmetic) was examined in 75 adults. The stability coefficients were .76 for heart rate (HR) change and .81 for absolute HR, .66 for systolic blood pressure (SBP) change and .52 for absolute SBP, .16 for diastolic blood pressure (DBP) change and .27 for absolute DBP. Males had greater SBP and DBP reactivity than females in the first session, but this reactivity decreased by the 4-year follow-up session (which was not the case for women).
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  • 6
    ISSN: 1573-2800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
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  • 7
    ISSN: 1573-2800
    Keywords: AIDS ; HIV ; anal intercourse ; social desirability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract Research in determining risks for human immunodeficiency virus (HIV) transmission is confounded by many issues. They include lack of clarity or specificity in terminology used, respondents misunderstanding of questions, and lying. The base rate of lying (or social desirability responding) by itself is sufficient to account for the small percentage of Americans and Europeans claiming “heterosexual” transmission from partners not known to be intravenous drug users. This study integrates the physiological and epidemiological data on risk factors for HIV transmission with the psychological literature on the frequency of anal intercourse and of lying (in this case to researchers and clinicians about risk factors). When these factors are considered, intravenous and anal activities remain the only clear vectors for HIV transmission. Research suggesting that spermicidals are more effective at inactivating HIV than condoms are at physically containing HIV is also noted.
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  • 8
    ISSN: 1439-6327
    Keywords: Phase related external suction ; Carotid baroreceptors ; Baroreceptor stimulation ; Blood pressure measurement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Phase related external suction (PRES), a new controlled method for manipulating activity in human baroreceptors, applies precisely timed bursts of suction and pressure within the cardiac cycle through an external neck cuff. Seven healthy adult men participated in 32 pseudo-random trials of baroreceptor stimulation and inhibition. Blood pressure was assessed both intra-arterially and with a noninvasive device. In the present study, PRES baroreceptor stimulation elicited invasively measured blood pressure decreases of about 2.5 mmHg (0.33 kPa) and heart rate decreases of about 5 beats · min−1, while baroreceptor inhibition increased invasively measured blood pressure by about 1.5 mmHg (0.20 kPa) and heart rate about 2.5 beats · min−1. It was concluded that PRES is an effective method for baroreceptor manipulation with weaker size effect but better control of nonspecific factors in human subjects than other baroreceptor manipulation techniques. The noninvasive blood pressure measurement device was less sensitive to experimental variation than was the invasive device.
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  • 9
    ISSN: 1439-6327
    Keywords: Key words T-wave amplitude  ;  Beta-adrenergic activation  ;  Impedance cardiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The responsivity of several cardiovascular indices to a computerized mental arithmetic stress and a cold pressor stress were investigated in 22 healthy adult subjects. The major findings were that the largely β-adrenergically driven T-wave amplitude, pre-ejection period, R-wave to pulse interval, and left ventricular ejection time values responded only to mental arithmetic; a significant decrease in cardiac output and increase in peripheral resistance were elicited during the cold pressor test; inter-beat-interval and subjective stress ratings responded significantly to both stresses compared to baseline levels, but more intensely to mental arithmetic than the cold pressor test; blood pressure, stroke volume and the maximum of the first derivative of the raw impedance signal responded unspecifically to both stresses. These findings support the idea that cardiovascular responses to psychological challenge depend on the level of cognitive processing required for the task. In addition, the superfluity of multiple variable measurements to study cardiovascular reactivity in such situations is discussed.
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  • 10
    ISSN: 1439-6327
    Keywords: Stress ; Heart rate ; Blood pressure ; R to pulse interval ; T-wave
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The first part of the experiment compared the relative reactivity of various cardiovascular measurements and self-reported assessment of mental arithmetic, an active coping stress task. It was found that the self-reported stres rating was more responsive (student's t=9.4) than the physiological measurements. Among the cardiovascular indices, heart rate was the most responsive (student's t=6.5), followed by the interval between R-wave and the maximal systolic pressure (student's t=5.0). The second part of the study used a multiple regression to examine the cardiovascular components of change in stres rating following mental arithmetic. Both resting (psychophysiological “trait” varibles) and change under stress (psychophysiological “state” variables) were used to predict change in stress rating. Stress rating increase were associated with greater maximal systolic pressure rate of rise (finger dP/dt) at baseline and less heart rate increase during mental arithmetic, yielding a multiple r of 0.67. The dual autonomic nature of active coping stress response is discussed. The shortcomings of using a correlate of a correlate are noted.
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