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1.
Early environment influences later performance in fishes 总被引:1,自引:0,他引:1
Conditions fish encounter during embryogenesis and early life history can leave lasting effects not only on morphology, but also on growth rate, life‐history and behavioural traits. The ecology of offspring can be affected by conditions experienced by their parents and mother in particular. This review summarizes such early impacts and their ecological influences for a variety of teleost species, but with special reference to salmonids. Growth and adult body size, sex ratio, egg size, lifespan and tendency to migrate can all be affected by early influences. Mechanisms behind such phenotypically plastic impacts are not well known, but epigenetic change appears to be one central mechanism. The thermal regime during development and incubation is particularly important, but also early food consumption and intraspecific density can all be responsible for later life‐history variation. For behavioural traits, early experiences with effects on brain, sensory development and cognition appear essential. This may also influence boldness and other social behaviours such as mate choice. At the end of the review, several issues and questions for future studies are given. 相似文献
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In this article, we discuss molecular mechanisms involved in the evolution of amygdala kindling and the episodic loss of response
to pharmacological treatments during tolerance development. These phenomena allow us to consider how similar principles (in
different neurochemical systems) could account for illness progression, cyclicity, and drug tolerance in affective disorders.
We describe the phenomenon of amygdala-kindled seizures episodically breaking through effective daily pharmacotherapy with
carbamazepine and valproate, suggesting that these observations could reflect the balance of pathological vs compensatory
illness-induced changes in gene expression. Under certain circumstances, amygdala-kindled animals that were initially drug
responsive can develop highly individualized patterns of seizure breakthroughs progressing toward a complete loss of drug
efficacy. This initial drug efficacy may reflect the combination of drug-related exogenous neurochemical mechanisms and illness-induced
endogenous compensatory mechanisms. However, we postulate that when seizures are inhibited, the endogenous illness-induced
adaptations dissipate (the “time-off seizure” effect), leading to the re-emergence of seizures, a re-induction of a new, but
diminished, set of endogenous compensatory mechanisms, and a temporary period of renewed drug efficacy. As this pattern repeats,
an intermittent or cyclic response to the anticonvulsant treatment emerges, leading toward complete drug tolerance.
We also postulate that the cyclic pattern accelerates over time because of both the failure of robust illness-induced endogenous
adaptations to emerge and the progression in pathophysiological mechanisms (mediated by long-lasting changes in gene expression
and their downstream consequences) as a result of repeated occurrences of seizures. In this seizure model, this pattern can
be inhibited and drug responsivity can be temporarily reinstated by several manipulations, including lowering illness drive
(decreasing the stimulation current.), increasing drug dosage, switching to a new drug that does not show crosstolerance to
the original medication, or temporarily discontinuing treatment, allowing the illness to re-emerge in an unmedicated animal.
Each of these variables is discussed in relation to the potential relevance to the emergence, progression, and suppression
of individual patterns of episodic cyclicity in the recurrent affective disorders. A variety of clinical studies are outlined
that specifically test the hypotheses derived from this formulation. Data from animal studies suggest that illness cyclicity
can develop from the relative ratio between primary pathological processes and secondary endogenous adaptations (assisted
by exogenous medications). If this proposition is verified, it further suggests that illness cyclicity is inherent to the
neurobiological processes of episode emergence and amelioration, and one does not need to postulate a separate defect in the
biological clock. The formulation predicts that early and aggressive long-term interventions may be optimal in order to prevent
illness emergence and progression and its associated accumulating neurobiological, vulnerability factors. 相似文献
5.
A.N. Reshetilov A.B. Medvinsky T.P. Eliseeva V.Yu. Shakhbazian M.A. Tsyganov A.M. Boronin G.R. Ivanitsky 《FEMS microbiology letters》1992,94(1-2):59-62
A method of pH distribution measurements in agar nutrient media containing expanding bacterial populations is described. It is based on measuring pH microsamples taken at different points of the media. The sample volume was 10 microliters. A pH sensitive field effect transistor was used as a measuring electrode. Acidification was found to occur in glucose media, while alkalization occurred in the media containing peptone. 相似文献
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Mitochondrial dehydrogenase activity was measured in seven taxa of Tetrahymena (T. pyriformis G1, T. hegewishi, T. malaccensis, T. pigmentosa, T. shapiro, T. thermophila CU-399, T. thermophila MS-1). Enzyme activity was different in the taxa investigated. Insulin reduced enzyme activity in six of the seven taxa studied. The duration of activity reduction was relatively long (5–10 min.) in most of the cases, and in T. hegewishi this lasted up to the end of the measurements (30 min.). There was no interrelation between the basic dehydrogenase activity of the taxon and the effect of insulin. There was also no correlation between the degree of relationship (of the taxa) and the dehydrogenase profile after insulin treatment. 相似文献
8.
P. S. Gill 《Biometrical journal. Biometrische Zeitschrift》1993,35(3):343-354
Design and analysis of field experiments in the presence of local and remote treatment effects are considered. The design criteria are optimality and balance for estimating local and remote effects. A nonlinear model, where remote effects are assumed to be proportional to the local effects, has been discussed. 相似文献
9.
Using cub growth as an index, I examine the influence of maternalnutrition, litter size, and cub sex on maternal care in cheetahs(Acinonyx jubatus) and compare cub and litter growth rates withthose of other large feilds. Seventy-nine free-living cheetahcubs in 21 litters from 15 mothers were weighed at least oncebetween 6 and 48 days of age. Eleven litters were weighed atthe beginning and end of a 5-day observation of their mothers.The mean cub growth rate varied significantly between litters,due primarily to differences in maternal food intake. Growthdeclined sharply when maternal food intake was less than 1.5kg/ day, but did not increase with greater levels of food intake.Lower limits of growth rates may therefore have been set bythe mother's food intake, whereas upper limits may be set bythe intrinsic physiological ability of cubs to grow. Althoughmale cubs were heavier than female cubs in the same litter whenfirst weighed, major differences in growth rate between thesexes were not apparent at this stage. Both cheetah cubs andlitters grow fast relative to other large felids, and I arguethat this may be an adaptation to the high rate of cheetah juvenilemortality from predation. 相似文献
10.
In this work we describe a non‐invasive and precise technique to record the heartbeats of a spider. A linear output Hall effect transducer in conjunction with a small magnet was used to monitor the micromovements on the dorsal surface of the abdomen of the tarantula Aphonopelma hentzi (Girard) (Theraphosidae). The exoskeleton in this region is in direct contact with suspensory ligaments connected to the heart, and the dorsal cuticle of the opisthosoma moves with each heartbeat. The technique allowed the discrimination of the different stages of the spider's cardiac cycle. The method can be also adapted for a smaller spider or other arthropods. We believe that the method proposed in this paper allows investigators to gain insights into a spider's natural heart rate by gathering unbiased data with a non‐invasive and very precise technique. We have found the resting heart rate of A. hentzi to be 5.6 ± 1.47 beats/min, which is lower than previously reported values. 相似文献