So what do your sugars do?

Up to about fifteen years ago the above question was quite often asked of glycoconjugates enthusiasts. It was always a silly question, the answer being ‘How many doings do you want to hear about?’ Since then our understanding of the structures, biosynthesis and varied functions of the glycoconjugates has developed incredibly and come to have a major impact on much of present-day biological and medical research.     

Plant biology: do DELLAs do defence?

DELLA proteins repress plant growth and developmental processes. Recent data suggest that DELLAs improve survival by imposing growth restraint during plant stress, enabling limited resources to be diverted to pathogen defence.     

Mechanosensitive channels: what can they do and how do they do it?

While mechanobiological processes employ diverse mechanisms, at their heart are force-induced perturbations in the structure and dynamics of molecules capable of triggering subsequent events. Among the best characterized force-sensing systems are bacterial mechanosensitive channels. These channels reflect an intimate coupling of protein conformation with the mechanics of the surrounding membrane; the membrane serves as an adaptable sensor that responds to an input of applied force and converts it into an output signal, interpreted for the cell by mechanosensitive channels. The cell can exploit this information in a number of ways: ensuring cellular viability in the presence of osmotic stress and perhaps also serving as a signal transducer for membrane tension or other functions. This review focuses on the bacterial mechanosensitive channels of large (MscL) and small (MscS) conductance and their eukaryotic homologs, with an emphasis on the outstanding issues surrounding the function and mechanism of this fascinating class of molecules.     

Collagen-binding I domain integrins--what do they do?

Collagens are the most abundant proteins in the mammalian body and it is well recognized that collagens fulfill an important structural role in the extracellular matrix in a number of tissues. Inactivation of the collagen alpha 1(I) gene in mice results in embryonic lethality and collagen mutations in humans cause defects leading to disease. Integrins constitute a major group of receptors for extracellular matrix components, including collagens. Currently four collagen-binding I domain-containing integrins are known, namely alpha 1 beta 1, alpha 2 beta 1, alpha 10 beta 1 and alpha 11 beta 1. Unlike the undisputed role of collagens as structural elements, the biological importance of integrin mediated cell-collagen interactions is far from clear. This is in part due to the limited information available on the most recent additions of the integrin family, alpha 10 beta 1 and alpha 11 beta 1. Future studies using gene inactivation of individual and multiple integrin genes will allow testing of the hypothesis that collagen-binding integrins have redundant functions but will also shed light on their importance in pathological conditions. In this review we will describe what is currently known about the collagen-binding integrins and discuss their biological functions.     

Examining the developing bone: What do we measure and how do we do it?

The clinical tools available to evaluate bone development in children are often ambiguous, and difficult to interpret. Unfortunately bone densitometry methods (i.e., dual energy X-ray absorptiometry, DXA) which have a relatively straightforward application in adult osteoporosis, are far more difficult to evaluate in the growing skeleton. Even with adequate "adjustment" for bone size or maturity, bone "density" (areal or volumetric) alone often gives an inaccurate assessment of bone strength--especially in children. Ideally, we would like to measure both material and geometric properties of bone to accurately estimate "strength". Mechanically meaningful measures of bone geometry (bone cross-sectional area, cortical thickness) and estimates of bending strength (section modulus, or SSI) are available with non-invasive techniques such as (p)QCT and some DXA software. With new technology it might be possible to also measure bone material properties, which will be especially important in some pediatric disorders. In children, we also need to know something about the loads imposed on a child's bone and consider not only absolute bone strength, but also the strength of bone relative to the physiologic loads. Interpreting bone strength in light of the loads imposed (particularly muscle force) is critical for an accurate diagnosis of the developing bone.     

POPP the question: what do LEA proteins do?

Late embryogenesis abundant (LEA) proteins are produced in maturing seeds and anhydrobiotic plants, animals and microorganisms, in which their expression correlates with desiccation tolerance. However, their function has remained obscure for 20 years. We argue that novel computational tools devised for non-globular proteins might now overcome this problem. Predictions arising from bioinformatics fit well with recent data on Group 3 proteins, which potentially form cytoskeletal filaments, and suggest experimentally testable functions for these and other LEA protein groups.     

What to do, or how to do it?

In this issue of Neuron, Ajemian et al. present a computational model of the activity of neurons in primary motor cortex (M1) during isometric movements in different postures. By modeling the output of M1 neurons in terms of their influence on muscles, they find each M1 neuron maps its output into a particular pattern of muscle actions.     

Pathogen effectors: What do they do at plasmodesmata?

Plants perceive an assortment of external cues during their life cycle, including abiotic and biotic stressors. Biotic stress from a variety of pathogens, including viruses, oomycetes, fungi, and bacteria, is considered to be a substantial factor hindering plant growth and development. To hijack the host cell's defence machinery, plant pathogens have evolved sophisticated attack strategies mediated by numerous effector proteins. Several studies have indicated that plasmodesmata (PD), symplasmic pores that facilitate cell-to-cell communication between a cell and neighbouring cells, are one of the targets of pathogen effectors. However, in contrast to plant-pathogenic viruses, reports of fungal- and bacterial-encoded effectors that localize to and exploit PD are limited. Surprisingly, a recent study of PD-associated bacterial effectors has shown that a number of bacterial effectors undergo cell-to-cell movement via PD. Here we summarize and highlight recent advances in the study of PD-associated fungal/oomycete/bacterial effectors. We also discuss how pathogen effectors interfere with host defence mechanisms in the context of PD regulation.     

Why do men marry and why do they stray?

Humans are quite unusual compared to other great apes in that reproduction typically takes place within long-term, iteroparous pairings--social arrangements that have been culturally reified as the institution of marriage. With respect to male behaviour, explanations of marriage fall into two major schools of thought. One holds that marriage facilitates a sexual division of labour and paternal investment, both important to the rearing of offspring that are born helpless and remain dependent for remarkably long periods (provisioning model). And the other suggests that the main benefits which men receive from entering into marriage derive from monopolizing access to women's fertility (mating effort model). In this paper, we explore extramarital sexual relationships and the conditions under which they occur as a means of testing predictions derived from these two models. Using data on men's extramarital sexual relationships among Tsimane forager-horticulturists in lowland Bolivia, we tested whether infidelity was more common when men had less of an opportunity to invest in their children or when they risked losing less fertility. We found that Tsimane men appear to be biasing the timing of their affairs to when they are younger and have fewer children, supporting the provisioning model.     

The timing of hibernation in Tasmanian echidnas: why do they do it when they do?

We investigated the patterns of hibernation and arousals in seven free-ranging echidnas Tachyglossus aculeatus setosus (two male, five female) in Tasmania using implanted temperature data loggers. All echidnas showed a ‘classical’ pattern of mammalian hibernation, with bouts of deep torpor interrupted by periodic arousals to euthermia (mean duration 1.04±0.05 (n=146). Torpor bout length increased as body temperature fell during the hibernation season, and became more variable as temperature rose again. Hibernation started in late summer (February 28±5 days, n=6) and males aroused just before the winter solstice (June 15±3 days, n=3), females that subsequently produced young aroused 40 days later (July 25±3, n=4) while females that did not produce young hibernated for a further two months (arousal Sept 27±5, n=7). We suggest that hibernation in Tasmanian echidnas can be divided into two phases, the first phase, marked by declining minimum body temperatures as ambient temperature falls, appears to be obligatory for all animals, while the second phase is ‘optional’ and is utilised to varying amounts by females. We suggest that early arousal and breeding is the favoured option for females in good condition, and that the ability to completely omit breeding in some years, and hibernate through to spring is an adaptation to an uncertain climate.     

Physician prescribing practices: What do we know? Where do we go? How do we get there?

Although drug prescribing is one of the most important components of medical care, little is known about how prescribing practices are determined and how they can be influenced. Enhancing the quality and effectiveness of drug prescribing requires research and better dissemination of information to physicians and other decision-makers. This requires a collaborative effort and a coordinated action plan. Participants at the Physician Prescribing Practices Workshop, held in Ottawa in October 1995, addressed issues and made recommendations in three areas: current knowledge and issues for research in the field of prescribing practices, and the capacity of Canadian databases to study these issues, strategies for disseminating and implementing knowledge and research findings to enhance the quality of prescribing; and the formation of a network to foster collaboration among stakeholders.     

Nurse practitioners in accident and emergency departments: what do they do?

OBJECTIVE--To determine the distribution and scope of nurse practitioner schemes in accident and emergency departments in England and Wales; to describe the caseloads of doctors and nurse practitioners on two representative days; and to estimate the number of patients managed by nurse practitioners in the year to 31 March 1991. DESIGN--A postal survey of accident and emergency departments and a content analysis of case notes of new patients attending a representative sample of accident and emergency departments on two days. SETTING--All accident and emergency departments in England and Wales. PARTICIPANTS--Survey: 560 nurses in charge of accident and emergency departments. Census: case notes of 5814 patients in 37 accident and emergency departments. MAIN OUTCOME MEASURES--Survey: number of accident and emergency departments with nurse practitioner schemes. Census: demographic and clinical characteristics of new patients attending and whether nurse practitioner or doctor made diagnoses and ordered investigations, treatments, referrals, discharges. RESULTS--513 replies (92%) from 465 surveyed functioning accident and emergency departments and 48 departments recently closed. 27 (6%) departments used designated nurse practitioners and 159 (34%) "unofficial" nurse practitioners. Only 530 (9%) of the 5814 patients in the census were managed entirely or mainly by nurse practitioners, with higher proportions in ophthalmic departments (nearly 30%) and minor casualty departments (over 40%) than in major departments (3%). Most patients managed by nurse practitioners (86%) had minor trauma. In the year ending 31 March 1991 an estimated 390,000 (95% confidence interval 260,000 to 520,000) patients out of a total of 12.5 million (3.1%, 2.1% to 4.1%) were clinically managed by a nurse practitioner. CONCLUSIONS--Designated nurse practitioner schemes are rare. The volume and range of nurse practitioner work in major general accident and emergency departments is small compared with those in specialised and minor accident and emergency departments.