Reactions of family medicine community preceptors to teaching medical students.

BACKGROUND AND OBJECTIVES: In 1993, the University of California, Los Angeles introduced an interdisciplinary course called ¿Doctoring¿ for all first-year medical students in which students visited family physicians' offices once a month for a total of four visits. The study's objectives were to ascertain preceptors' attitudes about having students in their offices and determine if this experience resulted in professional growth. METHODS: A survey was mailed to the 101 preceptors recruited to teach in the ¿Doctoring¿ course. Thirty of the respondents were selected randomly for a follow-up telephone interview. In addition, a second survey was mailed to the 31 preceptors who chose not to participate in the course the following year. RESULTS: More than 75% of the preceptors surveyed reported that the medical students had positive effects on their patients' satisfaction with their care. However, interviews with some respondents revealed worries about balancing time with the student vs maintaining a busy practice. Preceptors reported professional growth in the teaching process and greater knowledge and skills in the specific medical content areas of the ¿Doctoring¿ course. Preceptors who did not participate in the course during the subsequent year reported that their decision was based on issues other than satisfaction with the course. CONCLUSIONS: Based on the results of the study, preceptors experience professional growth through students' direct presence in their offices. Time management while precepting is the greatest challenge reported by preceptors.

Caffeoyltartronic acid from catnip (Nepeta cataria): A precursor for catechol in lubber grasshopper (Romalea guttata) defensive secretions.

Adults of the lubber grasshopper (Romalea guttata) secrete increased amounts of catechol from their defensive glands when fed diets containing only catnip leaves (Nepeta cataria). Model compound bioassays showed that these insects were able to sequester and biomagnify simple phenols, such as catechol and hydroquinone, in their defense gland secretions. Excessive catechol secretions from caffeic acid-fortified diets indicated metabolic pathways exist to perform efficiently more complex biochemical conversions. Reverse-phase HPLC of methanol extracts of catnip revealed only one major caffeoyl-polyphenol as a possible precursor for the observed elevated catechol secretions, when this plant is fed to lubbers. The compound was shown to be caffeoyltartronic acid (CTA). During analysis of CTA by probe-MS or gas chromatography (of its silylated derivative), CTA decomposed by loss of carbon dioxide to form caffeoylglycolic acid (CGA), making identification by these methods ambiguous. Only fast atom bombardment mass spectrometry (FAB-MS, negative mode) gave a true molecular weight. Groundivy (Glecoma hederacea), a relative of catnip, was also shown to contain CTA. The mung bean (Phaseolus radiatus=Vigna radiata), a species totally unrelated to catnip, is the only other reported plant source of CTA. Catnip leaves were found to contain about twice as much CTA as mung bean leaves.

Orientation ofMicroplitis croceipes (Hymenoptera: Braconidae) to green leaf volatiles: Dose-response curves.

FemaleMicroplitis croceipes wasps were tested in a wind tunnel for their ability to orient to various concentrations of eight different green leaf volatile (GLV) substances [hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (E)-2-hexenyl acetate, (Z)-3-hexenyl acetate, (Z)-3-hexenyl propionate, and (Z)-3-hexenyl butyrate]. Overall, the esters elicited the greatest percentage of successful orientation flights, the alcohols elicited an intermediate response, and the aldehydes elicited a low response. The semilog dose-response curves were generally hill-shaped with high responses at medium release rates and low responses at high or low release rates. For the aldehydes, positive responses occurred at all GLV release rates between 0.01 and 100 nl/min. For some alcohols and esters, positive responses occurred at release rates as low as 1 pl/min and as high as 1µl/min. These data show thatM. croceipes wasps are strongly attracted to GLVs and are capable of orienting to GLV concentrations that would occur in nature when a caterpillar feeds on a green leaf. Hence, in nature, GLVs may be important clues, enablingM. croceipes to locate their hosts.

A generalist herbivore in a specialist mode Metabolic, sequestrative, and defensive consequences.

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the "overload" in a monophagous diet.

Reduction in diet breadth results in sequestration of plant chemicals and increases efficacy of chemical defense in a generalist grasshopper.

The lubber grasshopper,Romalea guttata, is a generalist feeding on a broad diet of many herbaceous plant species and has a metathoracic defensive secretion normally containing phenolics and quinones synthesized by the insect. When insects were reared on a restricted diet of wild onion, they sequestered sulfur volatiles from the plant into their defensive secretions. These compounds were not detected by gas chromatography-mass spectroscopy in secretions of insects on an artificial diet or a natural, generalist diet of 26 plants that included wild onion as a component, nor were they present in secretions from field-collected insects. Defensive secretions of insects reared on wild onion were significantly more deterrent, by as much as an order of magnitude, to two species of ant predators than secretions from insects on either of the other two diets, despite a reduction in the concentration of autogenous defensive chemicals in secretions of insects on the onion diet. Sequestration of plant chemicals that increased defensive efficacy occurred when diet breadth was reduced. We suggest that this occurs because under conditions of specialization, plant secondary metabolites are more likely to be ingested and bioaccumulated in sufficient concentrations to have biological activity against predators. What we define as casual bioaccumulation of bioactive plant chemicals following dietary specialization may lead to evolution of sequestered defense syndromes in insects, and this process may not necessarily require specific adaptation to or coevolution with a toxic host plant.

A tephritid fly mimics the territorial displays of its jumping spider predators.

The tephritid fly Zonosemata vittigera (Coquillett) has a leg-like pattern on its wings and a wing-waving display that together mimic the agonistic territorial displays of jumping spiders (Salticidae). Zonosemata flies initiate this display when stalked by jumping spiders, causing the spiders to display back and retreat. Wing transplant experiments showed that both the wing pattern and wing-waving displays are necessary for effective mimicry: Zonosemata flies with transplanted house fly wings and house flies with transplanted Zonosemata wings were attacked by jumping spiders. Similar experiments showed that this mimicry does not protect Zonosemata against nonsalticid predators. This is a novel form of sign stimulus mimicry that may occur more generally.

Effects of diet breadth on autogenous chemical defense of a generalist grasshopper.

The lubber grasshopper,Romalea guttata, produces a metathoracic defensive secretion containing primarily phenolics and quinones. This insect feeds on a wide range of plant species. Insects reared on an artificial diet and a diet of onion,Allium canadense, had secretions that contained fewer compounds, lower concentrations of compounds, and markedly altered relative composition of components compared to insects reared on a varied diet of 26 plant species that included onion. The study demonstrates that diet breadth has a major effect on the quality and quantity of the autogenous defensive secretion of this generalist herbivore. The results are compared to diet effects known in chemically defended specialists. Two possible mechanisms explaining the effects of diet breadth are proposed: one involves changes in precursor availability with changing diet breadth; the other suggests that physiological stress due to diet restriction changes allocation of resources to chemical defense.

Idiosyncratic variation in chemical defenses among individual generalist grasshoppers.

The defensive secretion of the lubber grasshopper,Romalea microptera, shows extreme chemical variation among individual adults of the same sex within a single wild population. Certain phenolic compounds were absent in some individuals and present in others. Concentrations of compounds, when present, varied over two to three orders of magnitude. Chemical variation attributable to individuals accounted for 60-88% of the total quantitative variation and was evenly contributed by all individuals in both sexes. Cluster and regression analyses showed no discernible predictable patterns in the defensive secretion variation. The specificity of chemical cues used by predators may explain why these defenses are so idiosyncratic.

Olfactorily mediated attack suppression in the southern grasshopper mouse toward an unpalatable prey.

Predatory behavior toward an unpalatable sympatric prey was examined in the southern grasshopper mouse, Onychomy torridus (Coues). Mice preferred the palatable grasshopper Brachystola magna over the unpalatable secretion-producing grasshopper Taeniopoda eques. Consumption of T. eques decreased 35% while consumption of B. magna remained stable during three nights of testing. Olfactorily mediated attack suppression was demonstrated when O. torridus rejected palatable B. magna which had been coated with 5 ul of T. eques defense secretion. These results show that O. torridus discriminates and is capable of rejecting prey at any point in the prey capture sequence. These are adaptive attributes for a predator like O. torridus, which commonly attacks well-defended or dangerous prey.