As a third year medical student, I am required to prepare various evidence-based medicine projects related to patients that I see during a given rotation. Rotations are where I get the opportunity to see patients in the hospital in various specialty settings and apply the knowledge that I have acquired during the first two years of my medical education. My first rotation was psychiatry, where I met an adolescent girl with a very interesting diagnosis. The diagnosis was depersonalization disorder (DPD). This diagnosis and its potential treatment are the focus of my post this week. I investigated the current pathophysiologic theories along with current pharmacologic ideas for treatment.
DPD is characterized by an altered perception of self in which an individual experiences detachment from his or her body and personal memories, emotional and physical numbing, and a sense of living in a dream-like state. DPD patients often feel as though they are watching things happen to them. They do, however, remain aware of this unreality and feel like something is wrong with them (1). They can have a tendency to resort to extreme measures, such as cutting, in an attempt to “feel” and overcome the sensation of numbness.
There are currently no definitive treatments that have been developed regarding DPD. This is due largely to the fact that there is no well-defined pathology regarding its onset. Given its estimated prevalence of 0.8-2.0% in the general population, it is about as widespread as schizophrenia. Yet little research has been done to understand its root cause and treatment (1). Despite the epidemiologic studies that have shown this prevalence rate, it is still assumed to be rare and associated with other anxiety or psychotic disorders instead of being a primary condition on its own.
A cane toad would probably like its coffee with a side order of cane toad.
Every Friday at Nothing in Biology Makes Sense! our contributors pass around links to new scientific results, or science-y news, or videos of adorable wildlife, that they’re most likely to bring up while waiting in line for a latte.
From Sarah, a great New York Times article on cannibalism in the animal world:
Life after metamorphosis brought scant relief from fraternal threats. The scientists also demonstrated that midsize cane toads wriggle digits on their hind feet to lure younger cane toads, which the bigger toads then swallow whole. “A cane toad’s biggest enemy is another cane toad,” Dr. Shine said. “It’s a toad-eat-toad world out there.”
From Devin, a study that shows how epidemiologists can predict the spread of diseases through human social networks by tracking three properties of those networks:
For networks of intermediate density, different structural attributes have a profound impact on disease behaviour. By including the clustering coefficient and mean path length along with the mean degree of the contact network, we can reduce the uncertainty of our model predictions of disease performance (by nearly 14%).
Biologist Jon Wilkins, author of Lost in Transcription and the webcomic Darwin Eats Cake, gives us a nice welcome to the blogosphere, and reminded me that the gang at Darwin Eats Cake took on the Dobzhansky quote behind our name …
Jon also addressed the origins of the epigram in some detail, which is an interesting read.
A euglossine bee collects scent from an orchid
Orchids have some of the most remarkable pollination relationships of all the flowering plants. Their flowers are adapted into wild shapes for placing packets of pollen on precisely the right part of a pollinator’s body, and many species attract pollinators with lures that are somewhat kinkier than simply offering nectar—such as mimicking a female pollinator’s scent and appearance, to dupe males of the species into, er, making intimate contact.
A somewhat less exploitative orchid-pollinator interaction involves offering scent compounds to euglossine bees. Male euglossines collect scents from their environment—things that smell pleasant to humans, as well as things that really don’t—in special structures on their legs. It’s thought that they use the collected scents to attract females. Three large, diverse groups of orchids transport pollen by generating bee-attractive scent compounds, then saddling any bee who comes to collect the scent with a packet of pollen.
From the outside, this looks like a mutually beneficial relationship. The bees get their perfume, the orchids a pollen transporter. Over millions of years, such an interaction should lead bees and orchids to diversify together—when one orchid species splits into two, the bees that collect scent from them might very well speciate with the orchids. A recent paper in Science provides pretty good evidence that, over the long history of euglossines and the orchids that perfume them, the interaction hasn’t worked like that at all.