雖然黑腹果蠅（Drosophila melanogaster）幾十年以來早成為了一種模式生物,，在許多生物研究中發(fā)揮著不可替代的作用,，但是近期來自德國埃朗根—紐倫堡弗里德里希—亞力山大大學(xué)（University of Erlangen—Nuernberg）的研究人員在果蠅心臟中發(fā)現(xiàn)了新的機(jī)制，這有助于解釋果蠅心跳逆轉(zhuǎn)（heartbeat reversals）方向現(xiàn)象,。這一研究成果公布在《實驗生物學(xué)雜志》（Journal of Experimental Biology）上,。
來自加州大學(xué)河畔分校的昆蟲學(xué)家Tom Miller認(rèn)為，此次發(fā)現(xiàn)“從某種意義上來說就像是發(fā)現(xiàn)了第三只眼,，至少在循環(huán)系統(tǒng)研究領(lǐng)域里來說意義重大”,，“尤其是在黑腹果蠅中，我們對于這種昆蟲了解得比其它動物的多,。”
科學(xué)家們在許多不同的昆蟲中都發(fā)現(xiàn)過心跳逆轉(zhuǎn)的現(xiàn)象,，這被認(rèn)為是能改善血淋巴（hemolymph，昆蟲的“血”,，并不攜帶氧）循環(huán)的一種方式。
埃朗根—紐倫堡大學(xué)的Lutz Wasserthal利用穿過身體的紅外線光束（infrared beam）觀測黑腹果蠅和大型種果蠅（D.hydei）的心臟活動,，并記錄下來,。除了描述了這種逆轉(zhuǎn)，研究人員也利用光學(xué)和電子顯微鏡發(fā)現(xiàn)了引起這種行為的解剖構(gòu)造,，他們在心臟中識別出了保證血淋巴循環(huán)的ostia -openings的五分之一結(jié)構(gòu),。果蠅中，已知的4對心門（ostia）能在心跳調(diào)控過程中,，指導(dǎo)從腹部流向心臟的虛幻的血淋巴過程,。
來自美國Burnham醫(yī)學(xué)研究所（Burnham Institute for Medical Research）的Rolf Bodmer認(rèn)為，“這一新發(fā)現(xiàn)的解剖學(xué)機(jī)制加深了我們對于胸腔在血淋巴循環(huán)過程中的作用的了解”,。
這一發(fā)現(xiàn)支持了Wasserthal有關(guān)為什么果蠅周期性地逆轉(zhuǎn)血淋巴運(yùn)動方向的理論——這樣能幫助果蠅攝入更多的空氣,。Wasserthal表示，“所有的人至今都認(rèn)為果蠅并不能進(jìn)行空氣交換,。”大型的昆蟲通過氣管收縮膨脹交換空氣,，由于果蠅體形小，其血淋巴并不攜帶氧氣,，因此一般假設(shè)認(rèn)為其呼吸系統(tǒng)與其它小型昆蟲一樣是被動擴(kuò)散,，然而Wasserthal的這一研究證實果蠅也可以通過心跳逆轉(zhuǎn)交換空氣。下一步他們將檢測心跳過程血淋巴循環(huán),。
原始出處:
First published online October 19, 2007
Journal of Experimental Biology 210, 3707-3719 (2007)
Drosophila flies combine periodic heartbeat reversal with a circulation in the anterior body mediated by a newly discovered anterior pair of ostial valves and `venous' channels
Lutz T. Wasserthal
Institute of Biology, University of Erlangen-Nuernberg, Staudtstrasse 5, D-91058 Erlangen, Germany
e-mail: [email protected]
Accepted 21 August 2007
Heartbeat activity in tethered adult drosophilids was recorded using a linear optosensor chip and an IR-light beam. Recording from two to five sensor elements within 250 µm along the anterior heart, it was possible to analyze periodic reversals. In intact Drosophila melanogaster and D. hydei, longer anterograde pulse periods with lower pulse rates generally alternated with shorter retrograde pulse periods having higher pulse rates. These differences are dependent on heart anatomy: a newly discovered first pair of ostia is connected to bilateral thoraco-abdominal hemolymph channels. These channels are part of a venous space separated from the abdominal hemocoel by a septum, consisting of a metanotal ridge and the pericardial diaphragm lined by a special form of fat body. The channels are sealed, and their lumen is possibly controlled by the metathoracic tergo-pleural muscle. During retrograde pulses, the heart chamber works like a suction pump, aspiring hemolymph through the first ostia from the venous channels and discharging it through a newly described caudal opening. During forward beating, the anterior chamber receives hemolymph via all inflow ostia from the entire heart and drives it like a pressure pump through the narrow aorta. Also, during forward pulses, a lateral circulation occurs in the thorax as a result of the venous supply. Inhibition of abdominal mobility leads to an irregular heart rate, with pulse-wise alternating heartbeat reversals. The possible involvement of slow abdominal movements in heartbeat periodicity is discussed. The heartbeat periods are superimposed with intermittent bouts of abdominal pumping movements.
Key words: anatomy, cardiogenesis, dorsal vessel, Drosophila melanogaster, Drosophila hydei, fruitfly, heart development, inflow tract, insect heart, linear optosensor array, ostium, optocardiography, svp-lacZ
