Anumber of known factors can, under certain circumstances,

compel someone to attemptsuicide. Mental illness, family historyand life events often contribute signifi-cantly. Mere opportunity, too, increasesthe risk: for every firearm death attrib-uted to self-protection, there are some37 suicides. Even so, individual suicidesare exceedingly difficult to predict. In-deed, a recent survey showed that al-

though roughly half of all suicide vic-tims visit clinicians during the 90 dayspreceding their death, only a quarter re-ceive any psychiatric treatment.

To remedy that situation—and preventtens of thousands of deaths each year—

neuroscientists are now actively search-ing for the biological triggers behindsuicidal behavior. So far their findingspoint to mixed-up chemical messengersin the prefrontal cortex, an area of thebrain involved in processing emotionsand inhibitions. “New research indicatesthat suicide is not a normal response tosevere distress,” says J. John Mann ofColumbia University and the New YorkState Psychiatric Institute, “but [is] theresponse of a person with a vulnerabili-ty to act on powerful feelings.”

Mann has focused his studies on theneurotransmitter serotonin. Scientistshave long known that monkeys withdepleted serotonin metabolites in theirspinal fluid tend to be more impulsiveand aggressive. In 1976 it was firstdemonstrated that depressed suicide at-tempters had similarly low levels. Morerecently, Mann and his colleague KevinM. Malone reported that these levels arein fact lowest in people who make themost lethal attempts to end their life.From these facts, the researchers guessthat serotonin signaling in the brains ofsuicidal individuals is inadequate.

Testing that idea is somewhat difficult.“The technology for looking at seroto-nin activity directly in the living brain isstill under development,” Mann says.

News and Analysis18 Scientific American March 1997

F I E L D N O T E S

Amphibians On-line

It’s no secret why conferences are typically held in placeslike New Orleans or Sun Valley. In between the long talks,

people want to wander around the French Quarter or take afew runs down the slope. So, of course, I’m curious to checkout the “Field Trips” listing in the guide to the third annualmeeting of the North American Amphibian Monitoring Proj-ect (NAAMP). I’m a bit shocked to see “Exotic Dancers” as anoption, but I take a peek anyway. Dancing frogs? Where am I?

This winter the NAAMP confer-ence was held in cyberspace—athttp://www.im.nbs.gov/naamp3/naamp3.html, to be precise. Meet-ings began in November 1996and ended in mid-February 1997.In addition to the unusual fieldtrips (another favorite: a virtualvoyage to see and hear the frogsof Kenya’s Arabuko-Sokoke For-est at http://www.calacademy.org/research/herpetology/frogs/list.html), the conference offeredsome 50 papers on topics that in-cluded aquatic sampling tech-niques and frog-calling surveys.

Sam Droege of the U.S. Geo-logical Service Biological Resources Division headed the on-line conference—seemingly the first one of this size to havebeen held on the World Wide Web. Droege is pleased with theresponse. “We have reached a much wider audience than [wedid in] our previous meetings,” he writes by e-mail. “Folks canattend when they like, can look closely at the data and state-ments made, can respond publicly (or privately) to the authorif they disagree or want further details.” Papers from themeeting will be archived on the Web site, but the discussiongroups will become inactive after February 14.

Despite the various humorous diversions, much of the busi-ness conducted was quite serious: several reports presentedfindings of exceptionally high numbers of malformed am-phibians. David M. Hoppe of the University of Minnesota atMorris points to what he calls a “recent, rapid-onset phenom-enon” of limb deformities—which include missing or extra legsand digits. In his paper “Historical Observations and RecentSpecies Diversity of Deformed Anurans in Minnesota,” Hoppenotes that in the course of handling thousands of frogs be-tween 1975 and 1995, he saw only two with visible limb de-fects; in 1996 alone he saw more than 200. Hoppe speculatesthat an environmental agent in the water where the creatures

breed could be the cause.Stanley K. Sessions of Hartwick

College has also encountered anunusually high frequency of am-phibian limb abnormalities, inparticular, among Pacific treefrogs and long-toed salamandersin northern California. In hisNAAMP paper, Sessions arguesthat parasitic flatworms knownas trematodes triggered the limbdefects. He also comments thatthe infestation by trematodescould be linked to human-causedenvironmental problems.

Just as reporters do at any con-ference, I interview some of the

participants. Sessions e-mails me from Costa Rica, where he iscurrently doing fieldwork. He has mixed feelings about thecyberconference—although he is pleased with how easy andinexpensive it was to participate, he has been disappointedby a lack of interaction with other scientists during the meet-ing. “A cyberconference such as this one is no substitute for aconventional conference, because the important face-to-facesocial interactions are not happening,” he writes. So, alas, thenext NAAMP conference will be more conventional, withoutany dancing frogs. —Sasha Nemecek

SCIENCE AND THE CITIZEN

SUICIDE PREVENTION

Biochemistry offers some new clues

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He has, however, devised an approxima-tion technique: he made positron emis-sion tomographic (PET) scans of pa-tients shortly after they took the sero-tonin-releasing compound fenfluramine.In healthy adults the drug increasedmetabolic activity in the prefrontal cor-tex. But as expected, this change wasminimal in depressed patients.

Mann’s colleague Victoria Arango hasfound additional evidence linking di-minished serotonin activity to suicide.It is impossible to measure serotoninlevels directly after death because thecompound quickly dissipates. So Aran-go prepared slides of prefrontal cor-tex—taken from depressed and alco-holic suicide victims—and counted thenumber of serotonin receptors. Mostsamples, compared with control sub-jects, contained more receptors. Thiswas no great surprise. Such a changecould represent the body’s own effortsto compensate for naturally weak sero-tonin signals; the more antennae eachneuron puts forth, the better its chancesfor clear communications.

“In alcoholics, however, we foundsome unexpected results,” Arango says.These samples revealed a dearth of sero-tonin receptors. The shortage may begenetic or developmental and so helppredispose someone to alcoholism. Orit may just be yet another of alcohol’s

many toxic effects, Arango suggests.Whatever the cause, alcoholics, it ap-pears, lack the ability to compensate forweak serotonin signals—a fact that couldhelp explain why suicide rates in thisgroup are astonishingly high. Some 18percent of alcoholics take their own life,compared with 15 percent of depressedor manic-depressive people and 10 per-cent of schizophrenics.

Other biochemical abnormalities ap-pear in suicide victims as well. Mary Pa-checo of the University of Alabama atBirmingham has developed an assay forstudying secondary-messenger systemsin postmortem tissues. These systemsrelay information from a cell’s surfaceto its nucleus, where an appropriate re-sponse is generated. “If this communi-cation system does not work well, be-havioral responses to the environment,such as emotion and learning, may beaffected,” Pacheco states.

She found that in depressed suicidevictims, one such system, the phospho-inositide system, was impaired by some30 percent. Further investigation showedthat the problem lay in a class of pro-teins, called G-proteins, that are acti-vated by cell receptors and that are ca-pable of rousing the phosphoinositidesystem. “If we can find out why the G-protein does not work correctly, it mightenable us to develop better therapeuticagents for treating depression,” Pache-co adds. Certainly, many people hopeshe is right. —Kristin Leutwyler

News and Analysis20 Scientific American March 1997

Clues from SclerodermaNew results have shed light on why thebody sometimes attacks its own tissues:Antony Rosen and colleagues at JohnsHopkins University developed novelmeans for tracking the biochemistrybehind scleroderma, an autoimmunedisorder that damages the arteries, jointsand internal organs. They found thattoxic oxygen products, caused by an ir-regular blood supply, break apart com-mon tissue molecules when high levelsof metals are present. The fragmentedmolecules then present unfamiliar fa-cades to the immune system, whichproduces antibodies against them.

Rapid-Fire Gamma RaysFour gamma-ray bursts, recorded byNASA instruments over two days last Oc-tober, have shot down several key theo-ries. Astrophysicists long thought thatwhatever caused the high-energyevents, which usually occur at randomthroughout the sky, might well be de-stroyed in the making. But this new se-ries appeared too quickly, and too closetogether, to support that idea.

Grape ExpectationsScientists grappling for ways to preventcancer have found new hope in thehumble grape. John M. Pezzuto and his

colleagues at the Univer-sity of Illinois found thatresveratrol, an abundantcompound in grapeskins, can block an en-zyme called cyclooxyge-nase, which catalyzesthe conversion of sub-stances that stimulatetumor growth.

Cautioned by ChaosEcologists are learning a little mathe-matics of late. A group led by R. A. De-sharnais of California State University atLos Angeles used chaos theory to builda model of population dynamicsamong flour beetles. The model fore-cast chaotic fluctuations in the beetle’snumbers after a rise in adult mortality—a transition later confirmed in laborato-ry trials. Based on this finding, the au-thors caution ecologists managinglarge populations: the slightest inter-vention can topple a population fromstability.

IN BRIEF

SUICIDEis currently the ninth leading cause of death among adults and third

among adolescents.

Disclosures by Russia that ithad dumped 16 nuclear reac-tors from ships and subma-

rines into the Arctic’s Kara Sea shockedWestern sensibilities a few years ago. Andalthough it never purposefully plungednuclear reactors into the Pacific, the So-viet navy had routinely disposed of ra-dioactive liquids in those waters. Inter-estingly, researchers have detected littlepollution from these former practices,showing the ocean’s resiliency and, per-haps, unique capacity for absorbing ra-dioactive wastes.

Not only do ocean waters dilute such

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Could ocean mud trap nuclear waste from old Russian subs?

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