Quote of the Week: Spirals

Of true organic spirals we have no lack. We think at once of horns of ruminants, and of still more exquisitely beautiful molluscan shells ... Closey related spirals may be traced in the florets of a sunflower; a true spiral, though not, by the way, so easy of investigation, is seen in the outline of a clodiform leaf; and yet again, we can recognise typical though transitory spirals in a lock of hair, in a staple of wool, in the coil of an elephant's trunk, in the 'circling spirals' of a snake, in the coils of a cuttle-fish's arm, or of a monkey's or a chameleon's tail.

Among such forms as these, and the many others which we might easily add to them, it is obvious that we have to do with things which, though mathematically similar, are biologically speaking fundamentally different; and not only are they biologically remote, but they are also physically different, in regard to the causes to which they are severally due.

Sir D'Arcy Thompson, On Growth and Form

Quote of the Week: Ready or Not

There is a widespread view that scientific discoveries are more or less inevitable, and that it makes little difference whether or not a particular individual makes a discovery at a given time: if the time is not ripe for it, it will not be understood and will have little or no effect on future events; if the time is ripe, then someone else will soon make the discovery anyhow.

The history of Mendelism is one of the often-cited examples here. According to this interpretation, Mendel's paper was not understood in 1866 because the time was not ripe ... To me, this account seems greatly oversimplified--though it must be admitted that the development of the subject would probably have been much the same, even to the dates, if Mendel's paper had never been written.

It it true that the paper was ahead of its time, but it was not difficult to understand, and it seems unlikely that it would have remained unappreciated for so long if it had appeared in a less obscure journal, or if Mendel himself had published the further cases that he reported to his letters to Nageli.

A History of Genetics (1965) by A.H. Sturtevant, Cold Spring Harbor Laboratory Press.

Quote of the Week: Beach Colors

The insect-species confined to the sea-coasts, as every collector knows, are often brassy or lurid.

from Charles Darwin's The Origin of Species.

Quote of the Week: Cell Line Selection

I was asked this week about choosing a cell line appropriate to a specific assay. 

One thing to think about is the biology of the cells. Ask yourself, Does the cell line have the characteristics necessary for the topic I want to address? Express the right genes (or can I add them)? Respond to the stimulus? 

But practical concerns are also important. Although S2 is a popular choice for screens at the DRSC, the choice for an imaging screen is often S2R+, as these cells tend to adhere better to the bottom of the plate, an important feature for automated imaging at 384-well format.

Today's quote is from Section 1.1., Identifying a Suitable Cell Line, in B. Baum & L. Cherbas (2007) Drosophila Cell Lines as Model Systems and as an Experimental Tool.  In Drosophila: Methods & Protocols. C. Dahmann, Ed. Methods in Molecular Biology series Vol. 420. ISBN: 978-1-58829-817-1.

More than 100 cell lines have been established from Drosophila embryos and larvae over the last 40 yr. The first of these, including the commonly used S2 and Kc lines (10–12), were generated from spontaneously immortalized cells in cultures of mechanically dissociated embryos. In subsequent years, similar methods were used to derive cell lines from the early embryos of genetically defined fly stocks (11,13–15). Interestingly, these embryonic lines all share characteristics that suggest that they are derived from immortalized hematopoietic cells. This idea is supported by the similarities of these lines to mbn-2 and mbn 3 lines that were established from primary cultures of mutant embryos carrying blood cell tumors (16). Furthermore, the S2R+ cell line, an isolate of the S2 cell line (17), bears a striking resemblance in form and behavior to larval hemocytes isolated by bleeding larvae.

Please see the full chapter for reference citations.

Quote of the Week: If only ...

I recently overheard a now familiar conversation, one fly biologist lamenting to another that there is no feasible way to cryopreserve flies the way one can do with C. elegans, mammalian cells and (thankfully for the DRSC) cultured fly cell lines. But perhaps--given what some other flies can do--there is still hope for some solution to endless stock flipping?

... the larvae of Polypedilum vanderplanki can be completely dehydrated, and will enter into a state of 'cryptobiosis' during which all metabolic processes apparently cease ... The larva consumes no oxygen--it will survive in an atmosphere of pure nitrogen and it can withstand injuries that in normal life would set up a chain of disturbances that would kill the larva. When it is put back into water it quickly swells to normal size, and quietly resumes its breathing and feeding.

H. Oldryod, The Natural History of Flies

Quote of the Week--Act III, Scene 2

Poor harmless fly,

That with his pretty buzzing melody

Came here to make us merry!

William Shakespeare, Titus Andronicus

Quote of the Week--We've Made Progress Since?

... if only there were more liaison between the butterfly man, the mosquito man, the Drosophila man, and those interested in other groups.

Harold Oldroyd (1964) The Natural History of Flies. (W.W. Norton & Co. New York) 

Quote of the Week: Genes Defined

It is doubtful if we shall ever see the gene, but ... we really do not need to see it. By its work we know it.

L.C. Dunn (1932) Heredity and Variation.

Quote of the Week: Perspective

It is no easy matter to acquire a laboratory in the open fields, when harassed by a terrible anxiety about one's daily bread.

J.H. Fabre, The Life of the Fly (1915) 

Dodd Mead & Co. New York 

Translated by A.T. De Mattos

Quote of the Week: Insect Wonders

The student of [insects] finds beauty not only in the brilliant hues of a butterfly's wing or the metallic sheen of a beetle's elytron, but also in the wonderfully adapted form of those minute organs and structures which subserve the needs of life; graceful feathered feelers that are the seat of delicate sense-organs, claws and pads on feet that ensure firm hold in walking -- all might well be acclaimed as "miracles of design." 

The Biology of Insects, George H. Carpenter, D. Sc. (1928, MacMillan & Co. New York)

Quote of the Week: Unstoppable Evolution

"Drosophila ... even now is spreading about the world and evolving new species. There is a great irony in the fact that, while the laboratory geneticist is showing his powers over nature by molding his fruit-flies as he pleases, the flies themselves are staging a quiet demonstration of their own."

Harold Oldroyd (1965) The Natural History of Flies. W.W. Norton, New York.

Quote of the Week: Fame and Fortune

"Drosophila has now been drawn from its modest retirement in fruit shops and cider mills and has become a public character."

L.C. Dunn (1934) in Heredity and Variation

"Classic" Reads--Edge Effects

What I am reading today:  

A Simple Technique for Reducing Edge Effect in Cell-Based Assays. (2003) Lundholt, Scudder & Pagliaro, Journal of Biomolecular Screening 8(5).  

(Thanks to Amy G. at LiCor for the heads up on the paper.)

Why am I reading it?

Edge effects can be a bane of any plate-based assay. What are they? Let's say you look at your plate-based results and see a pattern that relates not to the biology you want to study but instead, to the position of the wells on the plate. That might be an edge effect. Commonly, the outer wells of the plate will give skewed values and/or contain unhappy cells.

Edge effects have not been a big problem at the DRSC (info on how we accomplish that below). Nonetheless, it's worth thinking about. And exploring ways to keep edge effects at a minimum.

In the paper cited above, the authors describe placing a plate at room temperature prior to incubation at 37 degrees C (their study is on mammalian cells). As fly cells grow at 25 and ambient air is usually about 22, the method might not do much for Drosophila cell-based assays. But if you're visiting us from the mammalian screening world--or interested to do follow-up assays in that system after a fly cell screen--then the quick fix Lundholt et al. propose is probably worth keeping in mind.

How does the DRSC reduce edge effects?  We use a very low-tech tool--wet paper towels--to keep humidity (which appears to be a contributing factor) even and high.  Our incubator is humidified. But nonetheless, our screeners are encouraged to take the extra precaution of putting the plates on top of a layer of damp paper towels and close them up in plastic containers.

This simple solution seems to do the trick.  In general, we see little or no edge effects, and thus our users typically can include the outermost wells in data analysis.