How to move with no rigid skeleton? The octopus has the answers

The octopus is amazingly flexible and shows exceptional control and coordination in all its movements. It seems remarkable to us skeletal creatures that the octopus achieves all this without a single bone.     

Are islands more susceptible to be invaded than continents? Birds say no

Island communities are generally viewed as being more susceptible to invasion than those of mainland areas, yet empirical evidence is almost lacking. A species-by-species examination of introduced birds in two independent island-mainland comparisons is not consistent with this hypothesis. In the New Zealand-mainland Australia comparison. 16 species were successful in both regions. 19 always failed and only eight had mixed outcomes. Mixed results were observed less often than expected by chance, and in only 5 cases was the relationship in the predicted direction. This result is not biased by differences in introduction effort because, within species, the number of individuals released in New Zealand did not differ significantly from those released in mainland Australia. A similar result emerged in the Hawaiian islands-mainland USA comparison: among the 35 species considered, 15 were successful in both regions, seven always failed and 13 had mixed outcomes. In this occasion, the results fit well to those expected by chance, and in only seven cases was the relationship in the direction predicted. I therefore conclude that, if true, the view that islands are less resistant than continents to invasions is far from universal.     

Receptors coupling to G proteins: is there a signal behind the sequence?

Upon the binding of their ligands, G protein-coupled receptors couple to the heterotrimeric G proteins to transduce a signal. One receptor family may couple to a single G protein subtype and another family to several ones. Is there a signal in the receptor sequence that can give an indication of the G protein subtype selectivity? We used a sequence analysis method on biogenic amine and adenosine receptors and concluded that a weak signal can be detected in receptor families where specialization for coupling to a given G protein occurred during a recent divergent evolutionary process. Proteins 2000;41:448-459.     

Centrosomes: Central no more?

It has recently been found that the zygotic development of a morphologically normal fly can occur without properly functioning mitotic centrosomes. Does this mean that centrosomes are not required for cell division in animals at all?     

Does muscle activation occur by direct mechanical coupling of transverse tubules to sarcoplasmic reticulum?

Our knowledge of the physiological and biochemical constituents of skeletal muscle excitation has increased greatly during the last few years but this has not led to a consensus of the physiological mode of muscle activation. Three hypotheses of transmission, involving either transmitter-receptor interaction or direct mechanical coupling, are still under active consideration. The hypothesis of direct mechanical coupling currently being evaluated proposes that the dihydropyridine receptor in the transverse tubules serves as a voltage sensor that communicates directly with the junctional foot protein/Ca2+ channel of sarcoplasmic reticulum to initiate opening of the channel.     

The spliceosome: no assembly required?

In this issue of Molecular Cell, Stevens et al. purify a large particle from yeast extracts that contains all five of the U snRNPs required for pre-mRNA splicing. The existence of this "penta-snRNP" suggests the provocative possibility that spliceosome assembly does not depend upon a pre-mRNA substrate.     

Personal cytometers: slow flow or no flow?

BACKGROUND: Although some manufacturers have optimistically described instruments with prices in the 40,000 US dollars range as "personal cytometers", analogy with the personal computer suggests that the target price for a true "personal" cytometer should be under 5,000 US dollars. Since such an apparatus could find a wide range of applications in cytomics in both developing and developed countries, it seemed desirable to consider its technical and economic feasibility. METHODS: Using resolution targets and a variety of fluorescent bead standards immobilized on filters and/or slides, we evaluated high-intensity LEDs as fluorescence excitation sources, relatively inexpensive CCD cameras as detectors, and 35 mm camera lenses and plastic low-power microscope optics for light collection in a simple, inexpensive low-resolution imaging cytometer. RESULTS: The components tested could be combined toproduce an instrument capable of detecting fewer than 10,000 molecules of cell-associated fluorescent label, and thus applicable to a broad range of cytometric tasks. CONCLUSIONS: Given the requirements for light sources, detectors, optics, mechanics, electronics and data analysis hardware and software, and the components presently available, it should be easier to reach the desired 5,000 US dollars price point with an image cytometer than with a flow cytometer.