Erwin Bünning and Tony Lees, two giants of chronobiology, and the problem of time measurement in insect photoperiodism

This paper examines the views of Erwin Bünning and Tony Lees on the mechanism of photoperiodic time measurement, the former advocating a circadian basis for the phenomenon and the latter a non-circadian hourglass-like timer. This difference in opinion led to a protracted split among workers on photoperiodism, some supporting an oscillatory clock and others an "hourglass", and gave rise to the often stated opinion that the two forms of time measurement were mutually exclusive. This paper, however, suggests that both oscillatory and hourglass-like properties are to be seen in insect photoperiodism. Furthermore, the differences between the two apparently conflicting models may be resolved if, following Bünning, "hourglasses" are regarded as damping circadian oscillators, with the more self-sustained (clearly oscillatory) and more highly damped (hourglass-like) responses being parts of a continuous series. Since circadian rhythmicity is an all-pervading and fundamental aspect of insect biology, currently opening up to genetic and molecular analysis, recognition of the basic similarity of a wide range of insect photoperiodic timers may help to unravel the biochemical nature of the mechanism(s) involved.     

An improved method for the isolation,quantitation, and identification of bile acids in rat feces

An improved method for the isolation and quantitation of bile acids from rat feces was developed. This method employs an initial Soxhlet extraction of the solid fecal material, esterification of the bile acid fraction with dry methanol/HCl and quantitation using a combination of tlc and glc techniques. In addition, identification of the individual components of the fecal bile acid fraction is accomplished by tlc and glc-ms. This method has proven useful for the quantitation and identification of the fecal bile acids during sterol metabolism measurements.     

A new method for purification of mature elastin.

Stable low-noise dual-beam spectrophotometric detection systems have been built to measure protein in the effluent from chromatographic columns. Measurements are carried out at the magnesium 285.2 nm atomic resonance line isolated either by the technique of selective modulation or by the use of a narrow bandpass interference filter. The noise level is about 0.0005-0.001 absorbance units and the drift rate is ±0.001 absorbance units in 24 hr. While slightly better noise performance could be obtained using the interference filter, selective modulation gives better linearity at higher absorbance values (up to 2.0).     

A serendipic legacy: Erwin Esmarch's isolation of the first photosynthetic bacterium in pure culture

During the 1880's, Erwin von Esmarch was a junior associate (Assistent) of Robert Koch studying bacteria of medical significance. In 1887, he isolated the first example of spiral-shaped bacteria in pure culture, from the dry residue of a dead mouse that he had suspended sometime earlier in Berlin tap-water. Under certain conditions, colonies of the organism were the color of red wine, and this led Esmarch to name the bacterium Spirillum rubrum. Twenty years later, Hans Molisch demonstrated that S. rubrum, an apparent heterotroph, was in fact a non-oxygenic purple photosynthetic bacterium, and it was renamed Rhodospirillum rubrum. Esmarch was a careful investigator and his classic paper of 1887 details the serendipitous isolation and general characteristics of the first pure culture of an anoxyphototroph, which later played a prominent role as an experimental system for study of basic aspects of bacterial photosynthesis. This report includes an English translation of his original paper (in German), a commentary on the historical significance of Esmarch's spirillum, and a summary of Esmarch's career.     

History of chloroplast genomics

The presence of chloroplast DNA was established in 1963. With the development of recombinant DNA technologies, chloroplast DNA was selected as one of the first candidates for genome sequencing. The first physical map was reported for maize chloroplasts in 1976. As tobacco has been popular as an experimental system, tobacco chloroplast DNA has been extensively analyzed and the complete nucleotide sequence was established in 1986. This sequencing and the availability of tobacco chloroplast transformation techniques and of in vitro expression systems have formed the basis of an ongoing functional genomics program. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Architects of the Evolutionary Synthesis in National Socialist Germany: Science and Politics

The Synthetic Theory of Evolution (SyntheticDarwinism) was forged between 1925 and 1950.Several historians of science have pointed outthat this synthesis was a joint venture ofSoviet, German, American and Britishbiologists: A fascinating example of scientificcooperation, considering the fact that theevolutionary synthesis emerged during thedecades in which these countries were engagedin fierce political, military and ideologicalconflicts. The ideological background of itsAnglo-American representatives has beenanalyzed in the literature. We have examinedthe scientific work and ideological commitmentsof the German Darwinians during the ThirdReich. We based our analysis on four criteria:1) General attitude towards the Third Reich. 2) Membership in the NSDAP and other nationalsocialist organizations. Endorsement anddisapproval of the state ideology in 3) scientific and 4) other publications. We willmainly discuss the various authors that havecontributed to Die Evolution derOrganismen (1943), a collection thatrepresented the evolutionary synthesis inGermany. Most of the authors promoted eugenicideas, but not all of them adopted the racistinterpretation of the Third Reich. Anotherfinding is that there existed no directconnection between party membership andpromotion of the state ideology.