Tyramine and octopamine: antagonistic modulators of behavior and metabolism

The phenolamines tyramine and octopamine are decarboxylation products of the amino acid tyrosine. Although tyramine is the biological precursor of octopamine, both compounds are independent neurotransmitters, acting through various G-protein coupled receptors. Especially, octopamine modulates a plethora of behaviors, peripheral and sense organs. Both compounds are believed to be homologues of their vertebrate counterparts adrenaline and noradrenaline. They modulate behaviors and organs in a coordinated way, which allows the insects to respond to external stimuli with a fine tuned adequate response. As these two phenolamines are the only biogenic amines whose physiological significance is restricted to invertebrates, the attention of pharmacologists was focused on the corresponding receptors, which are still believed to represent promising targets for new insecticides. Recent progress made on all levels of octopamine/tyramine research enabled us to better understand the molecular events underlying the control of complex behaviors.     

A Framework for Development and Communication of Absolute Environmental Sustainability Assessment Methods

An absolute environmental sustainability assessment (AESA) addresses whether a production or consumption activity can be considered environmentally sustainable in an absolute sense. This involves a comparison of its environmental pressure to its allocated environmental carrying capacity. AESA methods have been developed in multiple academic fields, each using their own set of concepts and terms with little communication across the fields. A recent growing interest in using AESA methods for decision support calls for a better common understanding of the constituents of an AESA method and how it can be communicated to scientific peers and to potential users. With this aim, we develop a framework for AESA methods, composed of a succession of four assessment steps and involving six methodological choices that must be made by the method developer or the user. We then use the framework to analyze and compare five selected AESA methods that focus on the release of phosphorus and nitrogen to the environment. In this manner, we show that the framework is able to systematically differentiate AESA methods that initially appear to be similar. Intended users of the framework include (1) method developers communicating new AESA methods to academic peers or potential method users and (2) researchers comparing a group of existing AESA methods and communicating their differences to their peers and to potential users looking for guidance on method selection.     

香港的生物多样性及其保育工作

香港位于热带,属海洋性气候。地势崎岖多山,山地约占全港总面积的3/4。城市发展多集中在沿海平坦地带。目前香港的城市和乡镇面积约占总面积的20%,农地约占5%(当中大部份已遭荒废),余下的均为郊野地区,这包括天然林和人工林(约占14%)、灌丛(约占36%)及草地(约占17%)。由于良好的气候和地理条件,形成了众多不同的生态环境,使总面积仅1090 km²的弹丸之地孕育出种类多样的动植物,生物多样性十分丰富。香港约有2500种原生植物,包括被子植物约1900种,裸子植物7种,蕨类植物220多种及苔藓植物300多种。动物方面,已记录的野生哺乳类动物有40多种,鸟类超过459种,两栖类23种,爬行类70多种。昆虫种类繁多,其中蜻蜓目100多种,鳞翅目2200多种(蝴蝶200多种,蛾类2000多种)。有很多是国家保护物种和特有种。植物方面属国家一级保护的有1种——刺桫椤(Alsophila spinulosa);国家二级保护的有6种,如四药门花(Tetrathryrium subcordatum);国家三级保护的有8种,如穗花杉(Amentotaxus argotaenia)。此外,香港特有种有16种,例如紫萁科(Osmundaceae)的粤紫萁(Osmunda mildei)、马兜铃科(Aristolochiaceae)的香港细辛(Asarum hongkongense)和兰科(Orchidaceae)的谢氏卷瓣兰(Bulbophyllum tseanum)。动物方面有9种属国家一级保护,例如中华白海豚(Sousa chinensis);79种属国家二级保护。特有种则有卢氏小树蛙(Philautus romeri)、包氏双足蜥(Dibamus bogadeki)及多种昆虫。为了保护丰富的野生动植物及其栖息的环境,香港特别行政区政府制定了一些法例并推行了不少保护措施,例如设立了21个郊野公园和14个特别地区,占全港陆地总面积约38%。此外,还成立了2个禁区、3个海岸公园和1个海洋保护区。另一方面,政府还设立了59个“具特殊科学价值地点”,以保护及研究各种动植物、生态系统和特殊的地质地貌。香港地少人多,总人口超过600万,是世界上人口最稠密的地区之一。多年来香港这个生物宝库不断地遭受人类活动的威胁,近年来由于人口急剧上升,对土地需求迫切,不少郊野地区被开发利用,环境污染亦日益严重。此外,一些野生植物因具有药用价值、观赏价值或其他用途而遭盗伐或采集。上述种种因素已使香港野生动植物及其生境受到严重损害,一些物种更濒于灭绝,进行生物多样性的保育工作刻不容缓。因此,香港确实需要制定整体的生物多样性保护策略。有鉴于此,香港大学生态及分类学系于1996年展开了一项为期3年的香港生物多样性调查,以增加对动植物资源现况的了解,为保护香港的珍稀濒危物种和日益恶化的自然环境提出补救方案,并为制订长远的保育策略奠定基础。     

The non-native chironomid Eretmoptera murphyi in Antarctica: erosion of the barriers to invasion

Antarctica is the continent least affected by invasive species, but climate change and increasing human activity are increasing this threat. Antarctic terrestrial ecosystems generally have low biodiversity with simple community structures and little competition for resources. Consequently, species with pre-adaptations or capabilities that allow them to tolerate polar conditions may have disproportionately large ecosystem impacts when introduced to Antarctica compared with other regions of the Earth. Here we investigate the invasion risk associated with the flightless chironomid midge, Eretmoptera murphyi, which was accidentally introduced from South Georgia (54°S) to Signy Island, South Orkney Islands (61°S), probably during plant transplantation experiments in the 1960s. Larval size class distribution analysis indicated that E. murphyi has a 2 year life cycle on Signy Island, supporting previous suggestions. Estimates of litter turnover show that recent large increases in E. murphyi population density and extent are likely to increase nutrient cycling rates on Signy Island substantially. Existing physiological adaptations may allow E. murphyi to colonise higher latitude locations. Growth rate and microhabitat climatic modelling show that temperature constraints on larval development on Anchorage Island (68°S) are theoretically similar to those on Signy Island even though it is ~750 km further south. Establishment of this non-native midge at climatically similar intervening locations along the western Antarctic Peninsula is therefore plausible. Currently, lack of effective natural dispersal mechanisms is probably limiting the spread of the midge. However, dispersal to other areas of the Antarctic Peninsula may occur via human-assisted transportation, highlighting the importance of appropriate biosecurity measures.     

Structure-activity relationships of pyrazole-4-carbodithioates as antibacterials against methicillin–resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of serious hospital-acquired infections and is responsible for significant morbidity and mortality in residential care facilities. New agents against MRSA are needed to combat rising resistance to current antibiotics. We recently reported 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioate (HMPC) as a new bacteriostatic agent against MRSA that appears to act via a novel mechanism. Here, twenty nine analogs of HMPC were synthesized, their anti-MRSA structure-activity relationships evaluated and selectivity versus human HKC-8 cells determined. Minimum inhibitory concentrations (MIC) ranged from 0.5 to 64?μg/mL and up to 16-fold selectivity was achieved. The 4-carbodithioate function was found to be essential for activity but non-specific reactivity was ruled out as a contributor to antibacterial action. The study supports further work aimed at elucidating the molecular targets of this interesting new class of anti-MRSA agents.     

Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity

Interactions between biotic and abiotic processes complicate the design and interpretation of ecological experiments. Separating causality from simple correlation requires distinguishing among experimental treatments, experimental responses, and the many processes and properties that are correlated with either the treatments or the responses, or both. When an experimental manipulation has multiple components, but only one of them is identified as the experimental treatment, erroneous conclusions about cause and effect relationships are likely because the actual cause of any observed response may be ignored in the interpretation of the experimental results. This unrecognized cause of an observed response can be considered a “hidden treatment.” Three types of hidden treatments are potential problems in biodiversity experiments: (1) abiotic conditions, such as resource levels, or biotic conditions, such as predation, which are intentionally or unintentionally altered in order to create differences in species numbers for “diversity” treatments; (2) non-random selection of species with particular attributes that produce treatment differences that exceed those due to “diversity” alone; and (3) the increased statistical probability of including a species with a dominant negative or positive effect (e.g., dense shade, or nitrogen fixation) in randomly selected groups of species of increasing number or “diversity.” In each of these cases, treatment responses that are actually the result of the “hidden treatment” may be inadvertently attributed to variation in species diversity. Case studies re-evaluating three different types of biodiversity experiments demonstrate that the increases found in such ecosystem properties as productivity, nutrient use efficiency, and stability (all of which were attributed to higher levels of species diversity) were actually caused by “hidden treatments” that altered plant biomass and productivity. Received: 16 December 1996 / Accepted: 2 March 1997     

Mutations in the fumarate hydratase gene cause hereditary leiomyomatosis and renal cell cancer in families in North America

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant disorder characterized by smooth-muscle tumors of the skin and uterus and/or renal cancer. Although the identification of germline mutations in the fumarate hydratase (FH) gene in European families supports it as the susceptibility gene for HLRCC, its role in families in North America has not been studied. We screened for germline mutations in FH in 35 families with cutaneous leiomyomas. Sequence analysis revealed mutations in FH in 31 families (89%). Twenty different mutations in FH were identified, of which 18 were novel. Of these 20 mutations, 2 were insertions, 5 were small deletions that caused frameshifts leading to premature truncation of the protein, and 13 were missense mutations. Eleven unrelated families shared a common mutation: R190H. Eighty-one individuals (47 women and 34 men) had cutaneous leiomyomas. Ninety-eight percent (46/47) of women with cutaneous leiomyomas also had uterine leiomyomas. Eighty-nine percent (41/46) of women with cutaneous and uterine leiomyomas had a total hysterectomy, 44% at age < or =30 years. We identified 13 individuals in 5 families with unilateral and solitary renal tumors. Seven individuals from four families had papillary type II renal cell carcinoma, and another individual from one of these families had collecting duct carcinoma of the kidney. The present study shows that mutations in FH are associated with HLRCC in North America. HLRCC is associated with clinically significant uterine fibroids and aggressive renal tumors. The present study also expands the histologic spectrum of renal tumors and FH mutations associated with HLRCC.