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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Genetica 39 (1968), S. 82-93 
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The behaviour of supergenes (closely linked blocks of co-adapted loci) can be studied by using various parameters of gametic excess (= linkage disequilibrium). Three useful parameters are the gametic determinant (D), the relative determinant (D'), and the log of the eross product ratio. The behaviour of the gametic determinant under mating and recombination is described. Formulae are given for estimating gametic excess in natural populations, Recombination, and the fitness of double heterozygotes, may be estimated from the determinants at different stages of the life cycle; this would be useful in human population genetics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-3270
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Restricted Environmental Stimulation Therapy (REST), which involves placing an individual into an environment of severely reduced stimulation for brief periods, has been subjectively reported to produce deep relaxation. The present study determines the effects of REST-assisted relaxation on plasma cortisol, ACTH, and luteinizing hormone (LH). These parameters were also measured in a group exposed to a similar relaxation paradigm, but without REST (non-REST). Each subject experienced two baseline sessions (1 and 2), four REST (or non-REST) relaxation sessions (3, 4, 5, 6), and two follow-up sessions (7 and 8). Pre- and postsession plasma hormone levels were measured in sessions 1, 2, 5, and 8. Both REST and non-REST subjects reported that the experience was relaxing. During the treatment period (session 5) pre- to postsession changes in cortisol and ACTH, but not in LH, were significantly greater for the REST group than for the non-REST group. Plasma cortisol level also decreased across sessions in the REST group, with levels in sessions 5 and 8 significantly lower than the baseline (sessions 1 and 2). Non-Rest subjects showed no change in plasma cortisol across sessions. No significant change in plasma ACTH or LH occurred across sessions in the REST or non-REST groups, although ACTH showed a decreasing trend. These data demonstrate that repeated brief REST-assisted relaxation produces a relaxation state associated with specific decreases in pituitary-adrenal axis activity.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Evolutionary ecology 13 (1999), S. 807-827 
    ISSN: 1573-8477
    Keywords: conditioning ; dietary complementation ; mimicry ; mutualism ; nutrition ; palatability spectrum ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Classical mimicry theory distinguishes clearly between the mutualistic resemblance between two or more defended species (muellerian mimicry), and the parasitic resemblance of a palatable species to a defended species (batesian mimicry). Modelling the behaviour of predators, without initially taking ecological complications into account, is a good strategy for exploring whether this division is valid. Two such behavioural models are described: conditioning theory, which simulates changes in motivational attack levels according to the norms of current learning theory; and saturation theory, which considers how a predator may become saturated with a particular toxic compound, and then cease feeding on the prey species that delivers it. This effect is to be clearly distinguished from simple satiation. Most formulations of the conditioning model allow the direction of reinforcement produced by a particular prey to change according the predator's current state of motivation: this leads to the existence of quasi-batesian mimicry, a parasitic mimicry between two species that could both be described as defended. At high densities, two prey species that share a chemical defense will be ‘muellerian mutualists’, mutually protecting each other against predators that have been saturated with the defensive compound. This mutualism may be accompanied by true muellerian mimicry of the colour patterns, or the patterns may be completely different. This can therefore be regarded as a form of mimicry in a non-visual communication channel. Even an apparently palatable prey species may be effectively unavailable to predators if its density is such as to deliver a particular nutrient in excess of the predator's need for a balanced diet. Such a nutrient in effect becomes a toxin, and such an abundant prey species would be partly defended and potentially able to act as the model in a mimicry system. Thus there might be protective mimicry between ‘palatable’ species, and a ‘palatable’ species might even function as the model for a ‘defended’ mimic. These unorthodox kinds of mimicry probably exist transiently during fluctuations of prey populations. It is less likely that these conditions persist for long enough to induce the evolution of mimicry, and the relationships perhaps usually occur when mimicry already exists for other reasons. Mimicry rings may be mutually stabilised by a combination of toxic mutualism and the exchange of species between the rings. Colour polymorphism in a defended species is strictly neutral whenever the population is dense enough to saturate the predator. This, as well as quasi-batesian mimicry, may help to explain the minority of warningly coloured species that are polymorphic.
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  • 4
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rest Thallium-201 myocardial images were abnormal in 20 out of 40 patients with arteriographically proven coronary artery disease. The myocardial image appearances did not accurately reflect the extent of coronary artery disease present. However, in 35 of the 40 patients (88%) the presence or absence of abnormalities on the rest myocardial image correleted respectively with the presence or absence of abnormal wall motion at left ventriculography. Most rest image abnormalities could be attributed to previous myocardial infarction, but in six patients myocardial ischaemia was possibly the cause. These results suggest that though myocardial fibrosis is usually the cause of rest myocardial image abnormalities in coronary artery disease, this is not invariably so. The possible therapeutic implications are discussed.
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  • 5
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Certain easily recognisable features are commonly seen in the bone scans of patients with metabolic bone disorders. Seven such features have been numerically graded by three independent observers in the scans of 100 patients with metabolic bone disease and of 50 control subjects. The total score for each patient is defined as the metabolic index. The mean metabolic index for each group of patients with metabolic bone disease is significantly greater than that for the control group (P〈0.001).
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  • 6
    ISSN: 1573-4919
    Keywords: cystic fibrosis ; uridine 5′-triphosphate ; 1321N1 astrocytoma ; HT-29 epithelial cells ; protein kinase C isoforms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract UTP activates P2Y2 receptors in both 1321N1 cell transfectants expressing the P2Y2 receptor and human HT-29 epithelial cells expressing endogenous P2Y2 receptors with an EC50 of 0.2- 1.0 μM. Pretreatment of these cells with UTP diminished the effectiveness of a second dose of UTP (the IC50 for UTP-induced receptor desensitization was 0.3 - 1.0 μM for both systems). Desensitization and down-regulation of the P2Y2 nucleotide receptor may limit the effectiveness of UTP as a therapeutic agent. The present studies investigated the phenomenon of P2Y2 receptor desensitization in human 1321N1 astrocytoma cells expressing recombinant wild type and C-terminal truncation mutants of the P2Y,2 receptor. In these cells, potent P2Y2 receptor desensitization was observed after a 5 min exposure to UTP. Full receptor responsiveness returned 5-10 min after removal of UTP. Thapsigargin, an inhibitor of Ca2+-ATPase in the endoplasmic reticulum, induced an increase in the intracellular free calcium concentration, [Ca2+]i, after addition of desensitizing concentrations of UTP, indicating that P2Y2 receptor desensitization is not due to depletion of calcium from intracellular stores. Single cell measurements of increases in [Ca2+]i induced by UTP in 1321N1 cell transfectants expressing the P2Y2 receptor indicate that time- and UTP concentration-dependent desensitization occurred uniformly across a cell population. Other results suggest that P2Y2 receptor phosphorylation/dephosphorylation regulate receptor desensitization/resensitization. A 5 min preincubation of 1321N1 cell transfectants with the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), reduced the subsequent response to UTP by about 50% whereas co-incubation of PMA with UTP caused a greater inhibition in the response. The protein phosphatases - 1 and -2A inhibitor, okadaic acid, partially blocked resensitization of the receptor. Furthermore, C-terminal truncation mutants of the P2Y2 receptor that eliminated several potential phosphorylation sites including two for PKC were resistant to UTP-, but not phorbol ester-induced desensitization. Down regulation of protein kinase C isoforms prevented phorbol ester-induced desensitization but had no effect on agonist-induced desensitization of wild type or truncation mutant receptors. These results suggest that phosphorylation of the C-terminus of the P2Y2 receptor by protein kinases other than protein kinase C mediates agonist-induced receptor desensitization. A better understanding of the molecular mechanisms of P2Y2 nucleotide receptor desensitization may help optimize a promising cystic fibrosis pharmacotherapy based on the activation of anion secretion in airway epithelial cells by P2Y2 receptor agonists.
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  • 7
    ISSN: 1573-3270
    Keywords: relaxation ; cortisol ; restricted environment ; blood pressure ; mood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined the effect of light on relaxation associated with flotation restricted environmental stimulation therapy (REST), as measured by plasma cortisol, mean arterial pressure, and psychometric parameters. Twenty-one subjects were paired by baseline cortisol levels into two groups: one experiencing flotation REST in the presence of light (REST-L) and one experiencing flotation REST in the absence of light (REST-D). Subjects were 15 male and 6 female students aged 22–28 in normal health who had not experienced REST. Repeated flotation REST (8 sessions) either with light or without light was associated with a decrease in plasma cortisol and a decrease in mean arterial pressure, with no differences in effectiveness between groups. The psychometric assessment of mood, using the POMS scale, before and after sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D groups. These data suggest that the presence of light did not compromise the flotation REST experience, as evidenced by the lack of difference between REST-L and REST-D groups.
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  • 8
    ISSN: 1573-2592
    Keywords: HIV-1 Immunogen ; antivirals ; viral load ; CD4 ; delayed-type hypersensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two trials of subjects inoculated with the inactivated, gp120-depleted HIV-1 Immunogen are reported. In one study, in which 19 subjects received ZDV and 8 subjects received ddI, treatment with the HIV-1 Immunogen did not affect the pharmacokinetic parameters of the antiviral drugs. In another study, 65 subjects who were previously immunized with the HIV-1 Immunogen over a mean period of 4.0 years (range, 1.2–5.4 years) received inoculations at 0 and 6 months. At some point during this 48-week study, 72% of the subjects (47/65) were receiving antiviral drug therapy. The HIV-1 DNA load in CD4 cells and CD4 percentage were found to be stable over the 48-week period. Delayed-type hypersensitivity to HIV-1 antigens increased after two inoculations with the HIV-1 Immunogen. In these two trials, no serious treatment-related adverse events were documented in the subjects. The two studies presented herein are the first to suggest that an immune-based therapy such as the HIV-1 Immunogen can be combined safely with antiviral drugs, supporting further study to evaluate the clinical utility of this approach.
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  • 9
    ISSN: 1573-0530
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Invariance conditions which link a class of ordinary differential equations with a type of Bäcklund-like transformation are developed and solved. These nonpoint transformations are used to obtain ‘super-position principles’ and as an illustration of their consequences a derivation of the duplication law for the Jacobian elliptic sine function is sketched. The group properties of these transformations are identified in all but one case and in one case it leads to a ‘double group’.
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  • 10
    ISSN: 1573-689X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Bernstein et al.1 have suggested a method for the detection of myocardial infarction using the combined measurement of serum LD activity and inhibition of LD by pyruvate (which depends on the amount of LD from damaged myocardium). This is another in the growing number of applications of discriminant analysis in medical diagnosis. As is often the case, the true underlying distribution of the data is not known. In this case, in particular, an attempt is made at defining the distribution to more accurately assess those patients among whom the diagnosis of myocardial infarction is suspect but is not clearly identified. Tsokos and Welch2 have shown that discriminant procedures based on incorrect assumptions of the underlying distribution led to substantially higher error rates. In this paper, we consider the application of a nonparametric probability density estimator recently developed by David W. Scott.3 This leads to a rather accurate discriminant procedure that is applicable to many other types of data.
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