Tipping back the balance: recolonization of the Macquarie Island isthmus by king penguins (Aptenodytes patagonicus) following extermination for human gain

During the late 19th and early 20th centuries, when blubber oil fuelled house lamps, the king penguin population at Macquarie Island was reduced from two very large (perhaps hundreds of thousands of birds) colonies to about 3000 birds. One colony, located on the isthmus when the island was discovered in 1810, was extinct by 1894 and it took about 100 years for king penguins to re-establish a viable breeding population there. Here we document this recovery. The first eggs laid at Gadget Gully on the isthmus were recorded in late February 1995 but in subsequent years egg laying took place earlier between November and February (this temporal discontinuity is a consequence of king penguin breeding behaviour). The first chick was hatched in April 1995 but the first fledging was not raised until the following breeding season in October 1996. The colony increased on average 66% per annum in the five years between 1995 and 2000. King penguins appear resilient to catastrophic population reductions, and as the island\u27s population increases, it is likely that other previously abandoned breeding sites will be reoccupied

Proton endor study of the photoexcited triplet state PT in Rps. sphaeroides R-26 photosynthetic reaction centres

The photoexcited triplet state PT of Rhodopseudomonas sphaeroides R-26 has been investigated by ENDOR measurements performed on frozen photosynthetic reaction centre solutions. For the first time hyperfine data could be obtained for PT. These data indicate a delocalisation of the triplet state over two bacteriochlorophyll a molecules

Towards quantitative in situ hybridization

In situ hybridization analysis of tissue mRNA concentrations remains to be accepted as a quantitative technique, even though exposure of tissue sections to photographic emulsion is equivalent to Northern blot analysis. Because of the biological importance of in situ quantification of RNA sequences within a morphological context, we evaluated the quantitative aspects of this technique. In calibrated microscopic samples, autoradiographic signal (density of silver grains) was proportionate to the radioactivity present, to the exposure time, and to time of development of the photographic emulsion. Similar results were obtained with tissue sections, showing that all steps of the in situ hybridization protocol, before and including the detection of the signal, can be reproducibly performed. Furthermore, the integrated density of silver grains produced in liver and intestinal sections by the in situ hybridization procedure using 35S-labeled riboprobes is directly proportionate to the signal obtained by quantitative Northern blot analysis. The significance of this finding is that in situ quantification of RNA can be realized with high sensitivity and with the additional advantage of the possibility of localizing mRNA within the cells of interest. Application of this procedure on fetal and adult intestinal tissue showed that the carbamoylphosphate synthetase (CPS)-expressing epithelial cells of both tissues accumulated CPS mRNA to the same level but that whole-organ CPS mRNA levels decreased four-to fivefold in the same period, owing to a comparable decrease in the number of CPS-expressing cells in total intestinal tissu