Exposure to endocrine disrupting chemicals perturbs lipid metabolism and circadian rhythms

A growing body of evidence indicates that exposure to environmental chemicals can contribute to the etiology of obesity by inappropriately stimulating adipogenesis as well as perturbing lipid metabolism and energy balance. One potential mechanism by which chemical exposure can influence lipid metabolism is through disturbance of circadian rhythms, endogenously-driven cycles of roughly 24hr in length that coordinate biochemical, physiological, and behavioral processes in all organisms. Here we show for the first time that exposure to endocrine disrupting compounds (EDCs), including the pesticide tributyltin, two commercial flame retardants, and a UV-filter chemical found in sunscreens, can perturb both circadian clocks and lipid metabolism in vertebrates. Exposure of developing zebrafish to EDCs affects core clock activity and leads to a remarkable increase in lipid accumulation that is reminiscent of the effects observed for longdaysin, a known disruptor of circadian rhythms. Our data reveal a novel obesogenic mechanism of action for environmental chemicals, an observation which warrants further research. Because circadian clocks regulate a wide variety of physiological processes, identification of environmental chemicals capable of perturbing these systems may provide important insights into the development of environmentally-induced metabolic disease.     

Light,timing of biological rhythms,and chronodisruption in man

This paper reviews abundant evidence suggesting that causes and course of aging and cancers can be considered as being both light- and rhythm-related. We define chronodisruption as a relevant disturbance of orderly biological rhythms over days and seasons and years in man. Light is the primary external mediator and melatonin a primary internal intermediary of such disturbances, which can result in earlier deaths via premature aging and cancers. We conclude that experimental and epidemiological research can provide further insights into common denominators of these chronic processes and may offer novel and uniform targets for prevention.     

Pinealectomy shortens resynchronisation times of house sparrow (Passer domesticus) circadian rhythms

In many birds periodic melatonin secretion by the pineal organ is essential for the high-amplitude self-sustained output of the circadian pacemaker, and thus for the persistence of rhythmicity in 24 h oscillations controlled by it. The elimination of the pineal melatonin rhythm, or a reduction of its amplitude, renders the circadian pacemaker a less self-sustained, often highly damped, oscillatory system. A reduction in the degree of self-sustainment of a rhythm should not only increase its range of entrainment but also shorten the resynchronization times following phase-shifts of the zeitgeber. This hypothesis has not yet been directly tested. We therefore carried out the present study in which house sparrows (Passer domesticus) were subjected to both 6-h advance and 6-h delay phase-shifts of the light–dark cycle before and after the pinealectomy, and the rhythms in locomotion and feeding were recorded. The results indicate that following the delay, but not the advance, phase shift, resynchronization times were significantly shorter after pinealectomy. The dependence of resynchronization times on the presence or absence of the pineal organ is not only of theoretical interest but might also be of functional significance in the natural life of birds. A reduction or elimination of the amplitude of the melatonin secretion rhythm by the pineal organ might be responsible for faster adjustment to changes in zeitgeber conditions in nature. Professor Dr E. Gwinner died on 07 September 2004.     

Seasonality and microhabitat selection in a forest-dwelling salamander

Many small terrestrial vertebrates exhibit limited spatial movement and are considerably exposed to changes in local environmental variables. Among such vertebrates, amphibians at present experience a dramatic decline due to their limited resilience to environmental change. Since the local survival and abundance of amphibians is intrinsically related to the availability of shelters, conservation plans need to take microhabitat requirements into account. In order to gain insight into the terrestrial ecology of the spectacled salamander Salamandrina perspicillata and to identify appropriate forest management strategies, we investigated the salamander’s seasonal variability in habitat use of trees as shelters in relation to tree features (size, buttresses, basal holes) and environmental variables in a beech forest in Italy. We used the occupancy approach to assess tree suitability on a non-conventional spatial scale. Our approach provides fine-grained parameters of microhabitat suitability and elucidates many aspects of the salamander’s terrestrial ecology. Occupancy changed with the annual life cycle and was higher in autumn than in spring, when females were found closer to the stream in the study area. Salamanders showed a seasonal pattern regarding the trees they occupied and a clear preference for trees with a larger diameter and more burrows. With respect to forest management, we suggest maintaining a suitable number of trees with a trunk diameter exceeding 30 cm. A practice of selective logging along the banks of streams could help maintain an adequate quantity of the appropriate microhabitat. Furthermore, in areas with a presence of salamanders, a good forest management plan requires leaving an adequate buffer zone around streams, which should be wider in autumn than in spring.     

国外旅游季节性研究综述

旅游季节性是一个旅游研究的常态问题。本文对近年来旅游季节性研究成果进行了综述,有助于深入了解旅游季节性影响因素以及动力机制,尤其指出旅游的季节性对生态环境的影响尤为严重,应格外重视旅游季节性问题,积极发展生态旅游,从而实现旅游地的可持续发展。     

雨水中碳丰度季节性特征及对酸雨形成的贡献

针对广州市连续1 a内降雨展开碳丰度的研究,通过对雨水中总有机碳(TOC)、可溶性有机碳(DOC)、颗粒物有机碳(POC)和颗粒物元素碳(PEC)的测定,进一步探讨雨水中碳丰度的季节性特征及其对酸雨形成的贡献作用.结果表明,TOC年均含量7.10 mg/L,DOC年均含量3.58 mg/L,POC年均含量3.60 mg/L,PEC年均含量O.72 mg/L,证明广州市污染物排放对降雨影响较严重.雨水中碳丰度具有一定季节性特征,TOC和DOC含量春季最高,夏季较低,表明广州市春季的总污染物排放量相对大于其它季节;POC对TOC的贡献率夏季要明显高于其它季节,说明固体颗粒物的排放量在夏季达到最高;干季POC相对含量要明显高于湿季,表明由机动车尾气排放导致的有机污染物排放量在秋冬季节要明显高于其它季节.TOC、DOC含量与pH值具有一定负相关性.这些特征从碳丰度角度证明机动车尾气等有机污染物排放对酸雨形成有一定的贡献作用.     

Seasonality of carbonaceous aerosol composition and light absorption properties in Karachi, Pakistan

Characteristics of carbonaceous aerosol(CA) and its light absorption properties are limited in Karachi,which is one of the most polluted metropolitan cities in South Asia.This study presents a comprehensive measurement of seasonality of CA compositions and mass absorption cross-section(MAC) of elemental carbon(EC) and water-soluble organic carbon(WSOC) in total suspended particles(TSP) collected from February 2015 to March 2017 in the southwest part of Karachi.The average TSP,organic carbon(OC),and EC concentrations were extremely high with values as 391.0±217.0,37.2±28.0,and 8.53±6.97 μg/m~3,respectively.These components showed clear seasonal variations with high concentrations occurring during fall and winter followed by spring and summer.SO_4~(2-),NO_3~-,K~+,and NH_4~+showed similar variations with CA,implying the significant influence on atmospheric pollutants from anthropogenic activities.Relatively lower OC/EG ratio(4.20±2.50)compared with remote regions further indicates fossil fuel combustion as a primary source of CA.Meanwhile,sea salt and soil dust are important contribution sources for TSP.The average MAC of EC(632 nm) and WSOC(365 nm) were 6.56±2.70 and 0.97±0.37 m~2/g,respectively.MAC_(EC) is comparable to that in urban areas but lower than that in remote regions,indicating the significant influence of local emissions.MACwsoc showed opposite distribution with EC,further suggesting that OC was significantly affected by local fossil fuel combustion.In addition,dust might be an important factor increasing MACwsoc particularly during spring and summer.     

Seasonality of spawning by tropical anguillid eels around Sulawesi Island, Indonesia

Remarkably little is known about the life histories of the many tropical anguillid eels distributed across the Indo-Pacific region, and since the Danish expedition to study eels in the region in 1928 and 1929, research on these eels has only begun again in recent years. Sampling for anguillid leptocephali in the Indonesian Seas has been carried out recently to learn about the spawning ecology and larval distributions of tropical eels there. The leptocephali of Anguilla marmorata, Anguilla bicolor pacifica, Anguilla borneensis, Anguilla interioris, and Anguilla celebesensis were collected around Sulawesi Island both in May 2001 and October of 2002. The development of genetic identification techniques has enabled these leptocephali to be identified to species, and their distributions and sizes during different seasons indicated that there are differing life history patterns among sympatric species in the region. A. celebesensis was found to have been spawning in Tomini Bay of northeastern Sulawesi Island in March and April 2001, but apparently, no spawning had occurred in the late summer and fall of 2002. Studies on anguillid glass eels have suggested that tropical anguillids may spawn throughout much of year, but our research on leptocephali in Tomini Bay and data on the downstream migration of tropical anguillids in the major tributary to Tomini Bay indicate that A. celebesensis may have a distinct seasonal pattern of spawning possibly related to the regional monsoon cycles. This is the first evidence of seasonality of spawning in tropical anguillid eels whose life histories are only just beginning to be revealed.