[1] 125w Both substances caused dose-related reductions in fever (Fig. 1), but a-MSH was much more potent. Whereas 0.50 mg of acetaminophen reduced the area un- der the fever curve 47 percent, only 200 ng of ot-MSH was required to cause a 50 percent reduction in the area under the fever curve (Fig. 2). This indicates that a-MSH was more than 2500 times more potent, by weight, than acetaminophen in reducing fever by about one-half. When the molecular weights of oa-MSH (1665) and acetaminophen (151) are considered, ae-MSH was more than 25,000 times more potent than acetaminophen. No endogenous substance other than ACTH is known to have such potency in reducing fever. This finding supports the idea that ot-MSH is important in the limitation of fever (6-9).

[1] 62w cabbage host plants on the basis of leaf color. The ability of the flies to distin- guish colors was improved in intermedi- ate-aged and mature plants as compared with young plants. The degree to which leaf color differences, in concert with host olfactory stimuli, might influence female landings in large homogeneous agricultural patches of these three culti- vars remains to be determined.

[2] 159w Our findings together with those of other workers (5)(6)(7)(8) lead us to suggest that with some exceptions (3, 7) leaves of cultivated or naturally growing plants that appear whitish to the human eye, owing to buildup of epicuticular bloom (16,18) or pubescence (19), or that are reddish, owing to masking or replace- ment of chlorophyll by other pigments, may be less detectable by (or less attrac- tive to) certain insect herbivores than are green leaves. Although the presence of bloom produces an increase in overall intensity of leaf reflectance, it acts to desaturate chlorophyll reflectance and thereby to decrease the distinctiveness of peak green leaf reflectance at 500 to 600 nm and to decrease the magnitude of the difference between total insect-de- tectable energy reflected above 500 nm and that reflected below 500 nm (2, 5). In red-colored leaves, the masking or re- placement of chlorophyll results in the absence of a reflectance peak at 500 to 600 nm.

[3] 84w In certain cases, buildup of epicuticular bloom could have evolved in re- sponse to strong selection pressure from a damaging insect herbivore. It is much more likely, however, that in most cases such buildup evolved in response to abi- otic environmental factors or microorga- nisms (16,18), with insects then obliged to "track" this character (20). Alterna- tively, insect herbivory may have con- tributed to the evolution of nonsenescing red-colored leaves in various plant spe- cies in which flushes of new growth are sometimes red.

[4] 68w Several crop cultivars with bloomed or red leaves are less preferred for landing or oviposition by certain insect species than are their green-leaved counterparts (5-8, 18, 21). We believe that, provided plant yield and quality can be main- tained, leaf color characteristics merit further investigation by entomologists involved in plant breeding to determine whether it is possible to reduce the at- traction of certain insect pests to plants.

[5] 444w RONALD J. PROKOPY* ROSEMARY H. COLLIER STANLEY FINCH National Vegetable Research Station, Wellesbourne, CV35 9EF, England 12. E. D. Owens, thesis, University of Massachu- setts, Amherst (1982). 13. Oil pigments (Winsor and Newton, London) were mixed in the following proportions by weight: radish (83 percent cadmium yellow 222, 12 percent Winsor green 170, and 5 percent mars black 248); green cabbage (same as radish, but when dry a thin overlay of 95 percent flake white 238 plus 5 percent cobalt blue 203 was added to mimic epicuticular bloom); red cabbage (40 per- There is evidence that the neuro- peptides adrenocorticotropic hormone (ACTH)(1-24) and a-melanocyte stimu- lating hormone (a-MSH)(1-13), which share a 13-amino-acid sequence, can in- fluence centrally mediated processes (1, 2), including central control of body tem- perature (3-5). Both peptides lower core temperature of afebrile rabbits when given peripherally or centrally in sufficient doses (6-8), and much smaller doses reduce fever without altering normal temperature (6,7,9). a-MSH is found in brain regions that govern temperature regulation, including the anterior hypo- thalamus and the septum (2). The con- centration of a-MSH in the septum rises during fever (10), and the concentration in the arcuate nucleus tends to decline at the same time, presumably reflecting axoplasmic transport of a-MSH from its source in cell bodies of the arcuate nu- cleus to fibers in the septum. Microinjections of a-MSH into the septat region reduce fever (H)-possibly mimicking the result of the natural transport. To evaluate the physiological significance of fever reduction by endogenous ot-MSH, it is important to compare the antipyretic cent French ultramarine 149, 40 percent flake white 238, 20 percent crimson lake 146, plus a thin overlay of the preceding type). 14. S. Finch and T. H. Coaker, Bull. Entomol. Res. 58, 619 (1969). 15. The only appreciable deviation from close approximation occurred at about 350 to 390 nm, where the overlay of artists' pigments on green and red cabbage leaf mimics failed to reflect as much energy as the real leaf counterparts. This made no detectable difference, however, to the flies' landing rate. 16. J. T. Martin and B. E. Juniper, The Cuticle of Plants (Clark, Edinburgh, 1970). 17. Onion odor may have been somewhat repellent at close range, as some females approaching to within 2 cm of onion leaves veered away abrupt- ly without alighting. Such abrupt veering behav- ior was not observed in female approaches to any other type of leaf tested. 18. T. W. Mulroy, Oecologia 38, 349 (1979). 19. J. Ehleringer, 0. Bjorkman, H. A. Mooney, Science 192, 376 (1976). 20. T. Jermy, Symp. Biol. Hung. 16, 109 (1976). 21. E. B. Radcliff and R. K. Chapman, J. Econ.

[6] 131w Entomol. 59, 116 (1966). 22. We thank J. B. Adams and the Campden Food Preservation Research Association of Chipping Campden (Glos) for use of the spectrophotometer, J. S. Kennedy for helpful criticisms, and E. D. Owens and G. F. Hubbell for assistance on pigment mixture preparation. Supported in part by a John Simon Guggenheim Memorial Foun- dation fellowship to R.J.P. * Present address: Department of Entomology, University of Massachusetts, Amberst 01003. 30 December 1982; revised I I April 1983 effect of this peptide with that of a well- known antipyretic drug, such as acet- aminophen. Since acetaminophen and a- MSHI appear to reduce fever through actions in the central nervous system, and since changes in potency can result from peripheral administration, both substances were given centrally in the experiments described here.

[7] 174w Adult New Zealand White rabbits were implanted with cannulas in a lateral cerebral ventricle (6) and restrained in conventional stocks in an environmental chamber at 23°C. A thermistor probe (Yellow Springs No. 701) was inserted 10 cm into the rectum and taped in place. Temperature measurements were made automatically at 10-minute intervals with a MINC 11 computer connected to a Datalogger digital temperature recorder (United Systems). Leukocytic pyrogen (6) was injected intravenously after a 1- hour baseline temperature had been determined. Tests of the antipyretic effect of a-MSH and acetaminophen were per- formed in two separate experiments on the same animals, with the control re- sponse to leukocytic pyrogen being de- termined for each animal before each SCIENCE, VOL. 221 Antipyretic Potency of Centrally Administered a-Melanocyte Stimulating Hormone Abstract. Centrally administered a-melanocyte stimulating hormone is much more potent in reducing fever than the widely used antipyretic acetaminophen. This finding supports the hypothesis that the endogenous neuropeptide has a role in the limitation offever and suggests that it may be clinically useful as an antipyretic.

[8] 71w experiment. Doses of ot-MSH (12), acet- aminophen ( 13), and sterile saline were assigned according to a table of random numbers. Each dose was injected intracerebroventricularly 30 minutes after the test injection of pyrogen. The 30-minute delay was to ensure that each rabbit was producing the appropriate febrile re- sponse to pyrogen. All injections of py- rogen were separated by at least 48 hours to minimize the development of toler- ance.

[9] 197w Previous research with larger doses of *a-MSH showed that the hypothermic effect was the result of reductions in heat production and conservation and not of lowering of the thermoregulatory set point (6). However, when administered centrally to afebrile adult rabbits in a thermoneutral environment, low doses caused no significant changes in body temperature. One possibility is that, in small amounts, a-MSH competes with leukocytic pyrogen for receptor sites in the brain without altering central tem- perature control pathways, much as common antipyretics are thought to do (14). Alternatively, although a-MSH has no effect on normal body temperature in low doses, it may still reduce fever by inhibiting heat production and conserva- tion pathways, but only when activity in these pathways is at greater than normal levels, as in fever. However, we recently found that central injections of ot-MSH in the low doses used in this study did not cause significant changes in body tem- perature in afebrile adult rabbits exposed to cold (100C) (15). If low doses of a- MSH simply inhibit heat production and conservation pathways in the central nervous system, then body temperature should decrease in the cold when activity in these pathways is increased.

[10] 181w -MSH and the fact t even whe have clin used to re fever sooi 4, 16), bi corticoste peated a( ing's sykn the short 100 -, 10 75 - 1.5 r ) 1.0 0 = 0.5 0coon 0 E 0.0 0 -; 1.5 0-0 s 1.0 0 ac 0.5 0 0.0 F I . 'hat this peptide reduces fever derived from ACTH, does not stimulate n given peripherally (6-9) may steroid release, and there appear to be no ical significance. ACTH was irreversible deleterious effects when duce clinical and experimental very large doses are given to rabbits and n after it was first described (3, to man (6-9, 17-19), nor have side ef- ut this peptide also stimulates fects been noted after administration of -roid release, and can, with re-low doses in rabbits (6)(7)(8)(9)15). Although dministration, result in Cusha-MSH is relatively expensive, only drome (17). On the other hand, very small amounts may be required to er a-MSH molecule, which is effectively reduce fever. Since this peptide occurs naturally in man, its use as an antipyretic may amount to simply aug-