Hummingbird Attracted to Fluorescent Lights

Image credit: This image was obtained from Flickr.com under a creative commons license. The artist is jeffreyw.

During the morning (8:30 AM DST) on a bright summer day in Chapel Hill, NC, USA my garage doors were open and four ceiling fixtures, each with four five-foot  fluorescent bulbs behind plastic diffusers, were on. After a few minutes a ruby-throated hummingbird (Archilochus colubris) arrived, actively pushing his beak around the upper portion of the fixtures. The hummingbird calls, usually faint and squeaky, were intense, prolonged, and seemed through my anthropomorphic filter to be alarmed, agitated or ecstatic.

This continued for an hour until the lights were turned off; the hummingbird almost immediately flew from the garage (which faces 53 degrees NE) to the back yard, where a hummingbird feeder and butterfly bushes (Purple Buddleia) reside.

[I realize this reads like an original report from an eighteenth century English clergyman (except for the part about the electric lights).]

A Google search returned a small number of reports from birders describing similar incidents, and I was interested in the mechanism.

Birds have a retinal cone visual receptor for ultraviolet (UV) light, peaking at 370 nm. Two review papers in the vision literature are of interest (Goldsmith, 1994 (no relation)); and Bennett and Cuthill, 1994). Many bird species, insects (e.g., bees),  and rare mammals (some rodents) can see in the UV spectrum.  UV Light can be phototaxic for bees. Functions for UV light for birds fit into three main categories: 1) Orientation, using  atmospherically scattered polarized UV light, suggesting a role in short and long migrations;  2) Foraging, due to portions of plants reflecting UV light; and 3) Detecting mates.  Mating with a large fluorescent light seems a heroic task for a hummingbird; perhaps this explains the squealing.

More remarkable to me was that when the light was turned off the bird returned almost immediately to its ambient environment.

The amateur backyard biologist morphed into  those with special scientific interests, e.g., groups of birders  collecting data for activities in  the Audubon Christmas bird count, and similar  citizen-scientists who are participating in scientific experiments through crowd-sourcing.

This is a call for citizen-scientists to share their  experiences with birds, especially  hummingbirds, who may be attracted to intense light sources so that we may all learn together.  Please report?

Are all bird species attracted to lights?

Type of light and intensity of light (e.g., size, watts).

I look forward to your comments.  Data will be compiled and shared in this space.

 

REFERENCES

Goldsmith, TH (1994) Ultraviolet receptors and color vision: Evolutionary implications and a dissonance of  paradigms. Vision Res 34: 1479-1487

Bennett, ATD and Cuthill, LC (1994) Ultraviolet Vision in Birds: What is its Function.  Vision Res. 34:1471-78

 

Modern Alchemy: Nanoparticle gold and nucleic acids (siRNA-AuNPs)

Reprinted from Science 132:1027-1030, 2006, with permission from AAAS

 

Classical alchemists were obsessed with converting base metals into gold. A similar conundrum for cutaneous researchers is enhancing the penetration of biologically active molecules through the epidermal stratum corneum.  Modern technology and chemistry allow an elegant approach to increasing penetration (Zheng et al, 2012). Alas, transmutation of lead into gold is a more difficult problem.

Zheng et al chemically modified 13 nm gold nanoparticles, and up to 120 siRNAs [small interfering RNA] were covalently attached per particle (see Rosi et al, 2006 for details and schematic figures)..The particles look like a scalp with electrically charged hairs standing on end. In addition to passing through cell membranes and modifying the biological functions of cells, the particles could penetrate through intact hairless mouse skin and human skin equivalents and retain their inhibitory function.  Most remarkably, the particles could be suspended in traditional topical vehicles such as hydrated petrolatum or buffered salt solutions and highly penetrate the skin. The new technology bypasses the solvents and physical methods previously required to circumvent the stratum corneum’s barrier function.

It is exciting enough that this method will be suitable for use with siRNAs and anti-sense DNA, and the underlying concept may be modifiable for other molecules that have proven difficult to  penetrate through  untreated stratum corneum.  The devil (a patron of alchemy) is, of course, in the details. And it is possible that there is not a special magic in the gold; but no doubt the transfer molecules will be constantly improved.

Using siRNAs with this technology may allow physicians to treat disorders of keratinization such as pachyonychia congenita and epidemolytic hyperkeratosis with highly specific molecules.

Are you ready for the new alchemy?

 

REFERENCES

Zheng D, Giljohann DA, Chen DL, et al (2012) Topical delivery of siRNA-based spherical nucleic acid nanoparticle  conjugates for gene regulation. PNAS 109:11975-80

Rosi NL, Giljohann Da, Thaxton CS,et al (2006) Oligonucleotide-modified gold nanoparticles for intracellular gene regulation. Science 312:1027-1030

Research Techniques Made Simple — FLOW CYTOMETRY Q&A

These questions and answers relate to the Research Techniques Made Simple article on FLOW CYTOMETRY by Richard R. Jahan-Tigh, Caitriona Ryan, Gerlinde Obermoser, and Kathryn Schwarzenberger in the October 2012 issue of JID.

We welcome your comments on the article and the quiz!

QUESTIONS:

1. Side Scatter (SSC) and Forward Scatter (FSC) provide information on ___________ and _________ , respectively.

A. tissue architecture, granularity
B. granularity, size
C. size, cell-cell interactions
D. cell-surface markers, intracellular signaling

2. “Gating” refers to:

A. the process of cells lining up single-file before entering the laser path.
B. the field the cells enter during the sorting process.
C. the restriction of a portion of the analyzed cells for further analysis.
D. the overlapping fluorophore signals generated in flow experiments with many fluorophores.

3. In a fluorescent by fluorescent scatter plot, cells present in the upper right quadrant of the plot are generally:

A. negative for one marker, positive for the other.
B. negative for both markers.
C. positive for aberrant marker expression.
D. positive for both markers.

ANSWERS:

1. B
Side scatter provides information that correlates to the cell granularity while forward scatter is a marker of cell size. With the aid of these two parameters and a few other stains, commercial blood analyzers are able to generate complete blood counts (CBC) with differentials. Remember, flow cytometry cannot provide information on tissue architecture or cell-cell interactions, as the cells must be suspended in solution for flow analysis. Flow cytometry can provide information on cell surface markers and intracellular signaling, but this is performed using fluorophore labeled antibodies, while measuring SSC and FSC does not require antibodies.

2. C
Gating refers to the process of selecting cell subsets of interest from parent populations during flow cytometry data analysis. For example, in a blood sample forward and side scatter can be used to define the lymphocyte region, and a second gate can be placed around CD3+ cells to discern them from CD3- natural killer cells. The field that the cells enter for a sorting is usually an electromagnetic field that separates based on charge. The overlapping signals generated from multiple fluorophores are termed “spillover”.

3. D
The interpretation of the basic fluorescent by fluorescent scatter plot is important, as virtually all flow experiments employ them. Cells in the upper right are positive for both markers, while cells in the bottom left are generally negative for both markers. The other two quadrants are negative for one marker and positive for the other as depicted in Figure 1ciii. Also, the axes for fluorescent by fluorescent plots are displayed logarithmically, meaning that even small visual differences reflect potentially large differences in fluorophore expression.

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