TIPS - April 1988 [Vol. 91 119

19 Dubovsky, S. L., Franks, R. D., 22 Lifschitz, M. and Coen, P. (1982) Am. 1. Psychiatry 139,502-504

20 Giannini, A. J., Houser, W. L., Loiselle, R. H., Giannini, M. C. and Price, W. A. (1984) Am. I. Psych&y 141,1602-1603

21 Dubovsky, S. L. and Franks, R. D. (1983) Biof. Psychiatry 18, 781-797

23

24

Pollack, M. H. and Rosenbaum, J. F. (1987) Biol. Psychiatry 22, 776-779

Del Pozo, E., Caro. G. and Baevens. J. M. (1987) Eur. 1. ~harmacol. 137,‘15< 160

25 Ben-Sreti, M. M., Gonzalez, J. P. and Sewell, R. D. E. (1983) Eur. J. Phnrmacol. 90, 385-391

Benedek, G. and Szikszay, M. (1984) Bay K-8644: methyl-1,4-dihydro-2,6-d&

Phnrmacol. Res. Commun. 16, lOG9-1013 methyl-3-mtro-4-(2+rifluorom~thylphenyl)- pyridine-5-carboxyiate

Mow you’ll start yawning and you won’t know- why -

Because reading about yawning, watching other people yawn, or even thinking about yawning makes you yawnl,‘. Most species simply lack this behaviour’; people who sit in too many com- mittees and are then forced to get to sleep late in order to get some real work done, are, on the other hand, great specialists.

In spite of the great sociobio- logical importance and the extra- ordinarily widespread incidence of this stereotyped behaviour (which, by the way, if practised in excess may even be symptomatic of serious disease such as chorea, brain tumours, or encephalitis3) very few have endeavoured to study the physiology or pharma- cology of yawning.

Robert Provine and his col- leagues have recently studied an aspect of the ecotoxicology of yawning’. For no apparent reason, it was assumed for years that

hypoxia or high blood CO2 levels trigger yawning and that yawning may reverse those respiratory changes4. Provine et ~1.~ submitted 17- to 21-year-old healthy volun- teers to normal room air (21% 02, 0.03% CO*, 79% N2), to atmo- spheres containing 100% O2 or 3-S% CO*, or to 10 min of exercise (stepping up and down a IO-inch step once every 2 s). The environ- mental changes had no effect on the rate of breathing or yawning or on yawn duration. The exercise doubled the respiratory rate, which went back to normal 3-4 min after the exercise was stopped; the rate of yawning declined monotonically from the beginning of exercise on, and went on declin- ing over the IO-min post-exercise rest period, i.e. it bore no relation to respiratory rate changes.

So, respiration, 02 and CO2 seem to have little to do with yawning. There must be some

other explanation for the remark- able contagiousness of this be- haviour and for its tendency to occur when one gets bored or sleepy. If readers of this article have been induced to yawn a lot just because of reading it, I can offer them just one consolation: I did too, when writing it. And we don’t really know why. To parody Walt Whitman:

0 friend unseen, unborn, unknown Student of our sweet English tongue Read out my wo& at night, aione. . . And for a reason still unsung Like me, my friend, you‘ll yawn and

yawn. IVAlV IZQUIERDO

Centro de Memoria. Department0 de Bio- quimicn, Institulo de Biociencias, UFRGS, 90049 Port0 Alegre, RS, Brazil.

References 1 Provine, R. R. (1986) Ethology, 72,109-122 2 Provine, R. R., Tate, 8. C. and Celd-

macher, L. L. (1987) Behav. Neural Biol. 48, 382-393

3 Barbizet, J. (1958) J. Neural. Neurosurg. Psychiatry 21,203-209

4 Montagu, A. (1962) J. Amer. Med. Assoc. 182,732

Liquid secondary ion MS: an emerging technique The introduction of fast atom bombardment (FAB) mass spec- trometry (MS) by Barber and colleague&* has had a significant impact on analytical capabilities in pharmacological and other bio- medical sciences. Biologically important analytes which were previously intractable to MS analysis, by virtue of lability or involatility, may now be routinely examined.

The practical details of the tech- nique are simple. The analyte is introduced to the mass opectro- metry ion source as a solution in a viscous, involatile liquid (fre- quently glycerol or thioglycerol)

and is bombarded with high energy (- 8 keV) neutral atoms of argon or xenon to effect sputtering from the matrix. The use of a neut- ral primary beam is not, in fact, essential but a liquid matrix is generally necessary to obtain a stable mass spectrometric signal; accordingly ‘liquid secondary ion MS (SIMS)’ is probably a prefer- able term to describe the tech- nique, though ‘FAB MS’ is still in more common use. me mechan- isms of production of gas phase ions remain imperfectly under- stood; yields are greatly improved if the enalyte is ‘pre-ionized’ in the condensed phase but gas

phase processes certainly also play a part.

Widespread and productive use of the technique has preceded mechanistic understanding. Ap- plications of pharmacological interest have included direct analyses of sulfate, glucuronide and glutathione conjugates and of other highly polar compounds such as N-oxide drug metabolites3. The effective ionization of involatile molecules has led to a burgeoning interest in the analysis of peptides and other biopolymers by MS, which has in turn spurred signifi- cant developments to extend the mass ranges of mass spectrometers of several types.

The extensive use of FAB MS has, howeverc revea!ed a number of limitations, particularly in bio- medical applications. The liquid matrix, while being essential to satisfactory secondary ion produc- tion, produces a high background

@ 19lM, lilw~lcr I’ubllcallon,, Cambrldgc 0169 - 6147/8B602.00