Placental invasiveness and brain-body allometry in eutherian mammals

Brain growth is a key trait in the evolution of mammalian life history. Brain development should be mediated by placentation, which determines patterns of resource transfer from mothers to fetal offspring. Eutherian placentation varies in the extent to which a maternal barrier separates fetal tissues from maternal blood. We demonstrate here that more invasive forms of placentation are associated with substantially steeper brain-body allometry, faster prenatal brain growth and slower prenatal body growth. On the basis of the physiological literature we suggest a simple mechanism for these differences: in species with invasive placentation, where the placenta is bathed directly in maternal blood, fatty acids essential for brain development can be readily extracted by the fetus, but in species with less invasive placentation they must be synthesized by the fetus. Hence, with regard to brain-body allometry and prenatal growth patterns, eutherian mammals are structured into distinct groups differing in placental invasiveness.     

Effects of juglone on growth of cucumber seedlings with respect to physiological and anatomical parameters

Effects of juglone on seedling growth of cucumber (Cucumis sativus cv. Beith Alpha) with respect to physiological and anatomical parameters were investigated. Growth parameters (seedling elongation, fresh and dry weights) were reduced by 1 mM juglone. Juglone also decreased chlorophyll a and b contents and reduced some anatomical tissues (xylem vessel and bundle radius of stem, stomata length and stomata number of the cotyledons). The anatomical changes in stem and cotyledon of the seedlings were related to growth inhibiting effect of juglone. On the other hand, increase in catecholase and tyrosinase activities by the effect of juglone were also recorded.     

Phylogeny, regression, and the allometry of physiological traits

Physiological and ecological allometries often pose linear regression problems characterized by (1) noncausal, phylogenetically autocorrelated independent (x) and dependent (y) variables (characters); (2) random variation in both variables; and (3) a focus on regression slopes (allometric exponents). Remedies for the phylogenetic autocorrelation of species values (phylogenetically independent contrasts) and variance structure of the data (reduced major axis [RMA] regression) have been developed, but most functional allometries are reported as ordinary least squares (OLS) regression without use of phylogenetically independent contrasts. We simulated Brownian diffusive evolution of functionally related characters and examined the importance of regression methodologies and phylogenetic contrasts in estimating regression slopes for phylogenetically constrained data. Simulations showed that both OLS and RMA regressions exhibit serious bias in estimated regression slopes under different circumstances but that a modified orthogonal (least squares variance-oriented residual [LSVOR]) regression was less biased than either OLS or RMA regressions. For strongly phylogenetically structured data, failure to use phylogenetic contrasts as regression data resulted in overestimation of the strength of the regression relationship and a significant increase in the variance of the slope estimate. Censoring of data sets by simulated extinction of taxa did not affect the importance of appropriate regression models or the use of phylogenetic contrasts.     

Basal metabolic rates in mammals: taxonomic differences in the allometry of BMR and body mass

No single equation adequately describes the allometric relation between body mass and BMR for mammals. Least squares regression of log-transformed data for 248 eutherian species results in a line with a slope (-0.30) significantly different from that of Kleiber's line (-0.25). Interordinal comparisons of least squares regressions of log-transformed BMR and mass suggest that the Insectivora have a significantly steeper slope to their allometric relationship than do most other orders, while the non-insectivore orders are statistically homogeneous with respect to slope. With respect to elevation, Edentata have the lowest BMRs; Marsupialia, Primates and Chiroptera are indistinguishable from each other but above the edentates; Primates, Chiroptera, Rodentia, Lagomorpha and Carnivora form the next highest homogeneous grouping; and Artiodactyla have the highest BMRs, significantly greater than all but Lagomorpha and Carnivora. Analysis of intraordinal variation within the Rodentia suggests significant heterogeneity among families in BMR-mass allometry.     

The physiological costs of reproduction in small mammals

Life-history trade-offs between components of fitness arise because reproduction entails both gains and costs. Costs of reproduction can be divided into ecological and physiological costs. The latter have been rarely studied yet are probably a dominant component of the effect. A deeper understanding of life-history evolution will only come about once these physiological costs are better understood. Physiological costs may be direct or indirect. Direct costs include the energy and nutrient demands of the reproductive event, and the morphological changes that are necessary to facilitate achieving these demands. Indirect costs may be optional 'compensatory costs' whereby the animal chooses to reduce investment in some other aspect of its physiology to maximize the input of resource to reproduction. Such costs may be distinguished from consequential costs that are an inescapable consequence of the reproductive event. In small mammals, the direct costs of reproduction involve increased energy, protein and calcium demands during pregnancy, but most particularly during lactation. Organ remodelling is necessary to achieve the high demands of lactation and involves growth of the alimentary tract and associated organs such as the liver and pancreas. Compensatory indirect costs include reductions in thermogenesis, immune function and physical activity. Obligatory consequential costs include hyperthermia, bone loss, disruption of sleep patterns and oxidative stress. This is unlikely to be a complete list. Our knowledge of these physiological costs is currently at best described as rudimentary. For some, we do not even know whether they are compensatory or obligatory. For almost all of them, we have no idea of exact mechanisms or how these costs translate into fitness trade-offs.     

Use of physiological parameters to predict milk yield and feed intake in heat-stressed dairy cows

Holstein cows were tested to determine which measures of thermal strain are the better predictors of production over 24–96 h at constant air temperatures of 19 and 29 °C. Both rectal temperature and respiration rate increased within 24 h, followed by milk yield and feed intake reductions after 48 h of heat stress. There were significant correlations between milk yield, feed intake, and rectal temperature. Several physiological strain indices were created to determine if combinations of measures are better than single measures in predicting production under these acute conditions. Mean daily rectal temperature was superior to maximum and minimum daily values of rectal temperature, as well as other indicators of thermal status in predicting dairy cow production. Likewise, mean daily rectal temperature was equal if not better than the physiological strain indices used in this study in predicting production. These data suggest that rectal temperature is superior to both single and combined indicators of thermal status in predicting dairy cow production, and should be considered for future development of physiological strain indices over a longer time period in both laboratory and field environments.     

Static allometry of mammalian teeth and the correlation of tooth size and body size in contemporary mammals

Functional least squares regression was used to fit the allometric equation, y = bx^k, to data on head-body lengths and body weights for 123 species of mammals. These measurements were found to be highly correlated and to scale isometrically. The scaling of M ₁ area with head-body length was investigated for 288 species of terrestrial mammals. A method was described for estimating the body size of extinct mammals from M ₁ area and the tooth size-body size relationships discovered among contemporary forms.     

蟋蟀脑的解剖结构与生理机能

蟋蟀脑由前脑、中脑和后脑三部分组成。前脑由1对蕈形体、中央复合体和视叶构成;每个蕈形体由2个冠、柄及与柄相连的α叶和β叶组成,是信息联络整合部位;中央复合体由中央体和脑桥组成,主要参与感觉信息的加工过程;视叶由神经节层、外髓和内髓组成,是视觉系统的中心。中脑由主要组成成分为嗅觉纤维球的嗅叶组成,是嗅觉系统的中心。后脑向后与食道下神经节相连。     

High physiological levels of melatonin in the bile of mammals

Bile is an important physiological bodily fluid which functions in the regulation of cholesterol metabolism, promotes the absorption of lipid and fat-soluble vitamins by the gut and serves in the excretion of toxic substances from the liver. Conversely, due to autooxidative processes bile is highly toxic to the hepatocyte and gastrointestinal epithelium. In this investigation, extremely high day time physiological levels of the endogenous antioxidant, melatonin, were measured in the bile of several mammals including rat, guinea pig, rabbit, pig, monkey and humans. Melatonin concentrations in the bile samples ranged from 2,000 to 11,000 pg/ml when measured by radioimmunoassay (RIA). These melatonin levels in bile are 2 to 3 orders of magnitude higher than those in day time serum. The presence of melatonin in bile was confirmed by HPLC with an electrochemical detector. This method, like the RIA, also documented very high levels of melatonin in bile. The presence of high levels of melatonin in bile may be essential to prevent oxidative damage to biliary and small intestinal epithelium induced by bile acids and oxidized cholesterol derivatives.     

Competitive anatomical and physiological plasticity: a neurotrophic bridge

Understanding the mechanisms of competitive synaptic plasticity, both anatomical and physiological, is of central importance to developmental neuroscience. Neurotrophic factors (NTFs) are implicated at almost every level of synaptic plasticity, from rapid physiological effects to slower anatomical effects, in addition to being implicated in competitive plasticity. Previously, we have built and analysed a mathematical model of anatomical synaptic plasticity based on competition for neurotrophic support. Here, we extend our work to build a combined, anatomical and physiological model. We find that, in order to understand the mechanisms of competitive physiological plasticity, we must postulate a central role for the change in expression of NTF receptors (NTFRs) on afferent synaptic terminals. Only by supposing that the expression of NTFRs is governed by NTF uptake do we find that physiological plasticity is competitive in character. We perform a fixed point analysis that establishes when afferent segregation is possible as a function of the parameters in the model, and simulate the model numerically to shed further light on its properties. A very clear prediction emerges from our model: that, as the efficacy of a terminal that is destined to be retracted due to competitive interactions reduces to zero, the NTFRs on that terminal should be down-regulated. Furthermore, our model requires that this reduction in synaptic efficacy never occurs significantly before the down-regulation in NTFRs. Such a prediction should be testable, and renders our model capable of being invalidated, in contrast to many other models of synaptic competition, which merely impose rather than seek to illuminate the quintessential feature of developmental synaptic plasticity. Received: 14 May 1999 / Accepted in revised form: 29 November 1999     

蟋蟀视觉系统的解剖结构与生理机能

蟋蟀视觉系统由单眼、复眼、视叶三部分组成。蟋蟀的单眼为背单眼,由角膜、角膜生成细胞、视网膜等组成,是提高昆虫复眼所感知的视觉刺激的兴奋水平部位;复眼是最主要的视觉器官,由角膜、晶锥、感杆束和网膜细胞、基膜组成,是光电转导和视觉级联反应的中心;视叶由神经节层、外髓和内髓组成,是视觉神经系统的中心。     

Use of QTL analysis in physiological research

Quantitative trait locus (QTL) analysis is a powerful approach to map and subsequently identify genes involved in complex traits. Here we describe the basic principles and recent achievements of this method, and its application in physiological research in plants. The rapidly increasing amount of molecular and “omics” data and genetic resources and tools, in model species (Arabidopsis) and crops, will greatly support and stimulate the use of this approach in the near future. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 1, pp. 15–21. The text was submitted by the authors in English.