Effects of body mass,temperature, and season on resting metabolism of the nocturnal gecko Hemidactylus flaviviridis

Abstract

The resting metabolic rate (RMR) of Hemidactylus flaviviridis was measured at different temperatures from 20 to 35°C during winter and summer acclimatization. The mass exponent b values ranged between 0.67 and 0.72. Winter-acclimatized geckos of various body masses had significantly lower RMRs than summer-acclimatized geckos only at 20°C. It seems that low thermal sensitivity for summer–acclimatized group may facilitate activity during its active seasons, and high thermal sensitivity between 20 and 25°C for winter–acclimatized group may conserve energy during inactivity in winter.     

Further studies on the influence of ions on the muscle fibre resting potential in the cricket Acheta domesticus

Experiments were carried out on tergosternal muscle fibres of the house cricket Acheta domesticus. Conventional microelectrode methods were used. All the investigated fibres depolarized with time (0, 60, 120 min) in statistically significant manner. Replacing CL- in the physiological solution by carbonate prevents this depolarization. Citrate anions added to the bath depolarize the fibers. Acetate does not change the resting potential. Increasing osmolarity by adding 100 or 200 mM saccharose exerts no significant influence on the level of the resting potential. Lowering the level of sodium ions leads to a slight but significant depolarization. The present work confirmed the opinion that skeletal muscle fibers of Acheta domesticus are at rest multiionic electrodes.     

Effects of ingested ivermectin on body mass

Abstract. Adults of Neomyia cornicina (F.) given continuous access to cow dung containing ivermectin at concentrations of 0.5.0.25 and 0.125 μg g^-1, the range found in the dung of injected cattle (Sommer et al. , 1992), were monitored every 12 h for changes in mass and excretory rates over a period of 3–5 days. Compared with the control insects, adult females that had ingested ivermectin showed disrupted patterns of daily mass change, an increase in dawn mass, and greatly reduced rates of excretion. Flies fed continuously with dung containing ivermectin at 0.25 μg g^-1 and 0.125 μg g^-1 in a regime identical to the above showed significantly increased abdominal mass compared with the controls. The observations are discussed in relation to other known effects of ivermectin on insect physiology.     

Neurotensin receptor 1 immunoreactivity in the peripheral ganglia and carotid body

In the present study we investigated, through immunohistochemistry, the presence and location of neurotensin receptor 1 (NTR1) in the peripheral ganglia and carotid body of 16 humans and 5 rats. In both humans and rats, NTR1 immunostained ganglion cells were found in superior cervical ganglia (57.4±11.6% and 72.4±11.4%, respectively, p<0.05), enteric ganglia (51.9±10.4% and 64.6±6.1%, p<0.05), sensory ganglia (69.2±10.7% and 73.0±13.1%, p>0.05) and parasympathetic ganglia (52.1±14.1% and 59.4±14.0%, p>0.05), supporting a modulatory role for NT in these ganglia. Positivity was also detected in 45.6±9.2% and 50.8±6.8% of human and rat type I glomic cells, respectively, whereas type II cells were negative. Our findings suggest that NT produced by type I cells acts in an autocrine or paracrine way on the same cell type, playing a modulatory role on chemoception.Key words: neurotensin receptor 1, carotid body, autonomic ganglia, sensory ganglia, immunohistochemistry.Neurotensin (NT) is a tridecapeptide which was first isolated from bovine hypothalamus (Carraway and Leeman, 1973) and is widely distributed in the nervous system and intestine. In the nervous system, neurotensin acts as a neurotransmitter and neuromodulator (Dobner, 2006); in the periphery, as a paracrine or endocrine factor (Mazzocchi et al., 1997; Malendowicz, 1998). It also acts as a growth factor on various cell types (Malendowicz, 1993; Markowska et al., 1994a, 1994b; Evers, 2006).Three different NT receptors, termed NTR1, NTR2 and NTR3, have been identified and cloned to date. NTR1 and NTR2 are, respectively, high- and low-affinity seven trans-membrane domain G protein-coupled receptors. NTR3 is a high-affinity single trans-membrane domain type 1 receptor, with 100% homology with the sorting protein, gp95/sortilin (Kitabgi, 2006; Mazella et al., 1998). NTR3 can also form heterodimers with NTR1 in the plasma membrane (Martin et al., 2002). Nuclear internalization of the NTR1 has been reported and has been suggested to play a role in the production of long-term genomic effects (Feldberg et al., 1998; Laduron, 1992). It has also been reported that NTR2, but not NTR1, returns to the plasma membrane after NT-induced sequestration (Mazella and Vincent, 2006).In the peripheral nervous system, pregangliar fibers containing NT have been found in sympathetic, parasympathetic and enteric ganglia, and functional studies also suggest the expression of NTRs in ganglion cells. However, direct evidence of NTR1 protein expression in the different cell types of the ganglia has not yet been provided for human and rat. Only in rat dorsal root ganglia has evidence of NTR1 expression been given through hybridization in situ (Zhang et al., 1995), but there are no data on protein location or internalization.The carotid body is an arterial chemoreceptor, sensitive to reductions in partial blood oxygen pressure and pH and to increases in partial CO2 pressure, the stimulation of which induces increases in ventilatory frequency and volume.The carotid body is situated at the carotid bifurcation, and is composed of parenchymal lobules separated by connective tissue, in which afferent fibers of the glossopharyngeal nerve, arising from the petrosal ganglion, occur (Porzionato et al., 2005).Two different cell populations are present in the carotid body: type I cells, in turn separated into light, dark and pyknotic, and type II cells, at the edges of the clusters. Post-ganglionic sympathetic nerve fibers from the superior cervical ganglion are present, innervating blood vessels and type I cells, and preganglionic parasympathetic and sympathetic fibers reaching ganglion cells near the glomic cells. NT has been detected in glomic cells (Heath et al., 1988; Heym and Kummer, 1989; Smith et al., 1990) but the presence of the corresponding receptors in the various glomic cell types has not yet been investigated.Thus, the aim of the present study was to investigate, through immunohistochemistry, the presence and location of NTR1 in the peripheral ganglia and carotid body of both human and rat, with particular reference to the different cell types.     

慢性低氧对颈动脉体可塑性的影响和调节

颈动脉体是机体重要的化学感受器.它不仅可以瞬间感知机体氧浓度的变化,迅速做出反应,同时在慢性低氧环境中能自发的适应和调节,包括形态和功能的改变.颈动脉体慢性低氧调节机制的阐明对于多种临床疾病(如呼吸暂停综合征等)的研究具有重要意义.本文就近几年关于慢性低氧对颈动脉体可塑性影响的相关研究进展予以综述.     

How the carotid body works: different strategies and preparations to solve different problems

This is a review of the different experimental approaches developed to solve the problems in our progress towards a comprehensive understanding of how arterial chemoreceptors operate. An analysis is performed oi the bases, advantages and limits of the following preparations: studies of ventilatory reflexes originated from carotid bodies (CBs) in the entire animal; recordings of CB chemosensory discharges in situ; CB preparations perfused in situ; CB explants in oculo; CB explants in ovo; CB preparations incubated in vitro; CB preparations superfused in vitro; CB preparations perfused and superfused in vitro: CB tissue slices in vitro; cells acutely dissociated from CBs; CB cells in tissue culture; petrosal ganglia superfused in vitro; petrosal ganglion cells in tissue culture; and co-cultures of CB and sensory ganglion cells. A brief historical account is given of the passage from one preparation to the next one. Emphasis is placed on personal experience with the different preparations whenever possible. Examples are given of the importance of selecting the appropriate experimental preparation for solving each particular theoretical problem. In fact, brilliant ideas on how the CB works have been unproductive until finding the adequate experimental approach to explore the validity of such ideas.     

酸碱胁迫对不同体质量尼罗罗非鱼幼鱼能量代谢的影响

利用6×3析因试验设计,设置6组pH(5.0、6.0、7.0、8.0、9.0和10.0)和3组体质量(1.02、5.13和10.31 9),在试验室条件下研究了酸碱胁迫对不同体质量尼罗罗非鱼幼鱼的呼吸、排泄、乳酸脱氢酶(LDH)和Na+-K+ATPase活力的影响.结果表明:尼罗罗非鱼幼鱼的耗氧率和排氨率随pH值的升高先上升后下降,在pH7.0～8.0时达到最高值.耗氧量与排氨量随体质量的增加而增加并呈幂函数相关.体质量的一次和pH的一次、二次效应对尼罗罗非鱼幼鱼的耗氧率和排氨率有极显著的影响(P＜0.0l);体质量与pH之间无互作效应(P＞0.05);建立了pH与体质量对耗氧率、排氨率之间的回归方程,决定系数分别达到0.942和0.936;体质量对氧氮比(O:N)值有显著影响(P＜0.01),酸碱胁迫使尼罗罗非鱼幼鱼的能源物质利用模式发生改变.高pH条件不利于LDH活力的增加,但有利于Na+-K+ ATPase活力的上升,pH的一次和二次效应对酶活有极显著影响(P＜0.01),体质量对Na+-K+ ATPase活力没有显著影响,且pH与体质量对酶活无互作效应(P＞0.05).     

Influence of sodium and calcium ions and membrane potential on glutamate receptor desensitization

1. The effects of Na, Ca and membrane potential on desensitization of postjunctional glutamate receptors on locust muscle were investigated. 2. The kinetics of desensitization were measured ionophoretically. 3. Replacement of Na by equimolar concentrations of the permeant cations Li, NH4 and guanidine and the impermeant cation choline accelerated desensitization onset, increased the steady-state leve of desensitization and reduced the rate of recovery from desensitization. 4. Desensitization onset rates and steady-state levels of desensitization were not significantly altered either by changing the extracellular Ca concentration or by changing the membrane potential of voltage clamped muscle fibres.