Plant genomics: More than food for thought

In all but the poorest countries of South Asia and Africa, the supply and quality of food will rise to meet the demand. Biotechnology, accelerated by genomics, will create wealth for both producers and consumers by reducing the cost and increasing the quality of food. Famine and malnutrition in the poorest countries may be alleviated by applying genomics or other tools of biotechnology to improving subsistence crops. The role of the public sector and the impact of patent law both could be great, but government policies on these issues are still unclear.     

A 60-minute dosing interval is safer than a 30- or 40-minute interval in oral food challenge

BackgroundThe interval between antigen ingestion may influence the safety of oral food challenge tests (OFCs), especially in patients with severe food allergies.MethodsThis retrospective chart review of OFCs eliciting objective reactions to wheat, egg, and milk that were performed between April 2012 and January 2021 evaluated an equivalent number of low-dose OFCs performed at 30-, 40-, or 60-min intervals. To avoid the influence of the potential allergy severity of the patients, the prediction scores of all intervals were matched. We evaluated the total symptom score (TS), total ingested dose, and the proportions of severe reactions (TS ≥ 30) and adrenaline use.ResultsWe analyzed 945 OFCs (wheat, n = 186; egg, n = 561; milk, n = 198). The 60-min OFC had significantly lower TS than the 30- and 40-min OFC methods in wheat (p < 0.001 and p = 0.003, respectively), egg (p < 0.001 for both), and milk (p < 0.001 and p = 0.018, respectively). The total dose in the 60-min method was significantly lower than in the 30-min method (p < 0.001 for all). The proportion of severe reaction (TS ≥ 30) in the 60-min method was significantly lower than that in the 30-min method for the egg and milk OFCs (p = 0.001 and p < 0.001, respectively). There was no difference in the rates of adrenaline injection.ConclusionsThe 60-min interval is safer than 30- or 40-min intervals in wheat, egg, and milk OFCs in patients with a low threshold dose for food allergy.     

The symbol of modern medicine: why one snake is more than two

Today, two serpent motifs are commonly used to symbolize the practice and profession of medicine. Internationally, the most popular symbol of medicine is the single serpent-entwined staff of Asklepios (Latin, Aesculapius), the ancient Greco-Roman god of medicine. However, in the United States, the staff of Asklepios (the Asklepian) and a double serpent-entwined staff with surmounting wings (the caduceus) are both popular medical symbols. The latter symbol is often designated as the "medical caduceus" and is equated with the ancient caduceus, the double serpent-entwined staff of the Greco-Roman god Hermes (Latin, Mercury). Many physicians would be surprised to learn that the medical caduceus has a quite modern origin: Its design is derived not from the ancient caduceus of Hermes but from the printer's mark of a popular 19th-century medical publisher. Furthermore, this modern caduceus became a popular medical symbol only after its adoption by the U.S. Army Medical Corps at the beginning of the 20th century. This paper describes the ancient origin of the Asklepian and how a misunderstanding of ancient mythology and iconography seems to have led to the inappropriate popularization of the modern caduceus as a medical symbol.     

Omega-3 long-chain polyunsaturated fatty acids support aerial insectivore performance more than food quantity

Once-abundant aerial insectivores, such as the Tree Swallow (Tachycineta bicolor), have declined steadily in the past several decades, making it imperative to understand all aspects of their ecology. Aerial insectivores forage on a mixture of aquatic and terrestrial insects that differ in fatty acid composition, specifically long-chain omega-3 polyunsaturated fatty acid (LCPUFA) content. Aquatic insects contain high levels of both LCPUFA and their precursor omega-3 PUFA, alpha-linolenic acid (ALA), whereas terrestrial insects contain much lower levels of both. We manipulated both the quantity and quality of food for Tree Swallow chicks in a full factorial design. Diets were either high-LCPUFA or low in LCPUFA but high in ALA, allowing us to separate the effects of direct LCPUFA in diet from the ability of Tree Swallows to convert their precursor, ALA, into LCPUFA. We found that fatty acid composition was more important for Tree Swallow chick performance than food quantity. On high-LCPUFA diets, chicks grew faster, were in better condition, and had greater immunocompetence and lower basal metabolic rates compared with chicks on both low LCPUFA diets. Increasing the quantity of high-LCPUFA diets resulted in improvements to all metrics of performance while increasing the quantity of low-LCPUFA diets only resulted in greater immunocompetence and lower metabolic rates. Chicks preferentially retained LCPUFA in brain and muscle when both food quantity and LCPUFA were limited. Our work suggests that fatty acid composition is an important dimension of aerial insectivore nutritional ecology and reinforces the importance of high-quality aquatic habitat for these declining birds.Aerial insectivores, a paraphyletic group that includes the swallows, swifts, nightjars, and at least five different families of flycatchers, were once abundant throughout both temperate and tropical regions. However, in the last half century, a number of North American aerial insectivores across a diversity of families and species, ranging from Common Nighthawks (Chordeiles minor) and Chimney Swifts (Chaetura pelagica) to Olive-sided Flycatchers (Contopus cooperi) and Tree Swallows (Tachycineta bicolor), have undergone major declines (1, 2). For example, Tree Swallows, one of the best-studied model aerial insectivore taxa in North America, have declined by 36% over the past 2 to 3 decades (2). Experts have proposed several hypotheses, including (i) declines in aerial insects (3), (ii) habitat loss and degradation (3–5), (iii) environmental contaminants (6, 7), and (iv) climate change and phenological mismatch (8, 9). Evidence exists to support all of these hypotheses, yet, at present, the exact causes of aerial insectivore declines remain unresolved, pointing to the need for a more thorough understanding of all aspects of aerial insectivore ecology.Past studies have documented the importance of food resources for aerial insectivores, and numerous studies have suggested that aerial insectivore declines are linked to decreasing overall insect abundance (e.g., ref. 1). Research on Tree Swallows shows that food availability is linked with chick growth rates and fledging success as well as egg size and composition (10, 11). Winkler et al. (11) found that environmental temperature had a strong effect on patterns of Tree Swallow chick mortality, most likely through its effect on insect activity levels. However, the sheer quantity of food resources may not be the only important factor. Food quality and the potential for mismatch between insect composition and the nutritional needs of aerial insectivores may also be important drivers of reproductive output and overall fitness for these birds (e.g., ref. 12).Food quality can be defined in many ways, including caloric density, nutrient composition, and digestibility (13). Here, we focus on differences in composition of macronutrients. Aerial insectivores, like all animals, require organic compounds [e.g., vitamins, amino acids, and fatty acids (FAs)] in addition to elemental nutrients (e.g., nitrogen, phosphorus, and calcium) to grow, develop, and complete their life cycles. Omega-3 long-chain polyunsaturated FAs (LCPUFA), in particular the FAs docosahexaenoic acid (22:6n-3, DHA) and eicosapentaenoic acid (20:5n-3, EPA), are especially important organic compounds for most animals, affecting a range of important physiological processes, from immune function to vision and brain development (14). Birds and all other vertebrates must either consume EPA and DHA directly from diet or indirectly by consuming their molecular precursor, the short-chain omega-3 PUFA, alpha linolenic acid (18:3n-3, ALA), and then converting ALA into EPA and DHA. The capability of any particular animal species to convert ALA to the bioactive EPA and DHA depends on whether its diet contains EPA and DHA (14). Mammalian herbivores typically synthesize all EPA and DHA endogenously from ALA, whereas carnivores such as cats must obtain all of their DHA from diet (15). The ability of wild birds to synthesize DHA is not well characterized, but DHA concentrations are inversely related to mass (16). For example, DHA constitutes 12% of FAs in the muscles of House Sparrows (Passer domesticus) (16), which are similar in size to Tree Swallows, but can reach over 20% in Ruby-throated Hummingbird (Archilochus colubris) muscle (17).In the wild, aerial insectivores consume a combination of terrestrial and aquatic insects (18), which differ in their FA composition (19). Aquatic insects contain much higher levels of LCPUFA than do terrestrial insects, a difference driven by differences in the FA composition of aquatic and terrestrial primary producers (19, 20). Aquatic primary producers, such as diatoms and dinoflagellates, are rich in EPA and DHA (21), which can be incorporated into aquatic insect tissue (22). In contrast, vascular terrestrial plants contain little to no LCPUFA but do contain their molecular precursor ALA (14), which can be either incorporated into tissue or converted to LCPUFA to a minor degree by terrestrial insects (19). As a consequence, from the perspective of LCPUFA content, aquatic insects may constitute a higher-quality food for aerial insectivores than do terrestrial insects.However, because both aquatic and terrestrial insects contain ALA, the relative value of aquatic insects depends on the capacity of aerial insectivores to convert ALA into LCPUFA (19). The ability to elongate ALA into LCPUFA varies greatly across taxa: Strict carnivores, such as cats (23, 24), and animals from environments rich in LCPUFA, including most marine fish (25), have lost the ability to elongate ALA into LCPUFA and must obtain them directly from diet. In contrast, terrestrial herbivores appear to be relatively efficient at converting ALA to LCPUFA (26). The capacity of aerial insectivores to convert ALA to LCPUFA remains untested, but, as predators living around riparian areas with emergent aquatic insects rich in LCPUFA, they appear likely to be limited by LCPUFA content in diet.The majority of past studies on avian FA requirements have focused on domesticated herbivorous taxa, especially chickens (e.g., refs. 27 and 28). These studies found domestic hens to be relatively efficient at elongating ALA, EPA, and DHA (e.g., refs. 27 and 28). Far fewer studies have experimentally manipulated dietary FA composition for wild birds (but see refs. 29–32). These studies have found that both dietary composition and elongation capacity of individual species affect avian FA composition (32). However, with the exception of work by Pierce et al. (31) on Red-Eyed Vireos (Vireo olivaceus), these studies have either looked at seed- and fruit-eating passerines or fish-eating seabirds. To our knowledge, no studies have explicitly examined the omega-3 FA requirements of any aerial insectivores. Therefore, we sought to understand the importance of food FA composition for aerial insectivores by varying both food quality and quantity in a balanced factorial experimental design.In nature, the effects of food quality and quantity may be confounded because parents may provide chicks with an increased quantity of food to make up for low-quality food. To address this, we experimentally manipulated both the quantity and FA composition of food for wild-hatched nestling Tree Swallow chicks. Chicks were fed one of four diets: (i) a high-LCPUFA, high-quantity diet containing EPA and DHA (Hh); (ii) a low-LCPUFA, high-quantity diet containing high ALA and low omega-3 LCPUFA (Lh); (iii) a high-LCPUFA, low-quantity diet (Hl); and (iv) a low-LCPUFA, low-quantity diet (Ll). We assessed size-specific growth rates, body condition, immunocompetence, and basal metabolic rates (BMR) as metrics of performance. We also determined the FA composition of brain and breast muscle tissue from a subset of chicks from each treatment group.     

Numbers are better than words: Verbal specifications of frequency have no place in medicine

We were concerned about the precision (i.e., consensus as to meaning) of adjectives and adverbs used to express frequency in the medical literature. We asked 103 physicians and 106 nonphysicians to assign to each of 22 such modifiers a percentage representing their understanding of the term. As indexed by the standard deviations, the degree of imprecision for 17 terms was so great for both physicians and for laymen as to make their use unacceptable. Consensus was significantly less among laymen than among physicians for 10 of the terms. Greater consensus was shown by native English-speaking physicians than by those with other native languages. Our data suggest further that American graduates of American medical schools show more consensus than American graduates of foreign medical schools. Board-certified physicians did not show greater consensus than physicians who were not board-certified. Verbal expressions of frequency should be eliminated from medical communications; failing that, the author should specify numerically the frequency he intends when he uses any such expression.