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One major challenge in the study of late-Quaternary extinctions (LQEs) is providing better estimates of past megafauna abundance. To show how megaherbivore population size varied before and after the last extinctions in interior Alaska, we use both a database of radiocarbon-dated bone remains (spanning 25–0 ka) and spores of the obligate dung fungus, Sporormiella, recovered from radiocarbon-dated lake-sediment cores (spanning 17–0 ka). Bone fossils show that the last stage of LQEs in the region occurred at about 13 ka ago, but the number of megaherbivore bones remains high into the Holocene. Sporormiella abundance also remains high into the Holocene and does not decrease with major vegetation changes recorded by arboreal pollen percentages. At two sites, the interpretation of Sporormiella was enhanced by additional dung fungal spore types (e.g., Sordaria). In contrast to many sites where the last stage of LQEs is marked by a sharp decline in Sporormiella abundance, in interior Alaska our results indicate the continuance of megaherbivore abundance, albeit with a major taxonomic turnover (including Mammuthus and Equus extinction) from predominantly grazing to browsing dietary guilds. This new and robust evidence implies that regional LQEs were not systematically associated with crashes of overall megaherbivore abundance.
The Taipan galaxy survey (hereafter simply ‘Taipan’) is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z < 0.4. Taipan will use the newly refurbished 1.2-m UK Schmidt Telescope at Siding Spring Observatory with the new TAIPAN instrument, which includes an innovative ‘Starbugs’ positioning system capable of rapidly and simultaneously deploying up to 150 spectroscopic fibres (and up to 300 with a proposed upgrade) over the 6° diameter focal plane, and a purpose-built spectrograph operating in the range from 370 to 870 nm with resolving power R ≳ 2000. The main scientific goals of Taipan are (i) to measure the distance scale of the Universe (primarily governed by the local expansion rate, H0) to 1% precision, and the growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated ‘virtual observer’ software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.
Intracranial volume (ICV) has been proposed as a measure of maximum lifetime brain size. Accurate ICV measures require neuroimaging which is not always feasible for epidemiologic investigations. We examined head circumference as a useful surrogate for ICV in older adults.
99 older adults underwent Magnetic Resonance Imaging (MRI). ICV was measured by Statistical Parametric Mapping 8 (SPM8) software or Functional MRI of the Brain Software Library (FSL) extraction with manual editing, typically considered the gold standard. Head circumferences were determined using standardized tape measurement. We examined estimated correlation coefficients between head circumference and the two MRI-based ICV measurements.
Head circumference and ICV by SPM8 were moderately correlated (overall r = 0.73, men r = 0.67, women r = 0.63). Head circumference and ICV by FSL were also moderately correlated (overall r = 0.69, men r = 0.63, women r = 0.49).
Head circumference measurement was strongly correlated with MRI-derived ICV. Our study presents a simple method to approximate ICV among older patients, which may prove useful as a surrogate for cognitive reserve in large scale epidemiologic studies of cognitive outcomes. This study also suggests the stability of head circumference correlation with ICV throughout the lifespan.
Asymptomatic carriage of gastrointestinal zoonoses is more common in people whose profession involves them working directly with domesticated animals. Subclinical infections (defined as an infection in which symptoms are either asymptomatic or sufficiently mild to escape diagnosis) are important within a community as unknowing (asymptomatic) carriers of pathogens do not change their behaviour to prevent the spread of disease; therefore the public health significance of asymptomatic human excretion of zoonoses should not be underestimated. However, optimal strategies for managing diseases where asymptomatic carriage instigates further infection remain unresolved, and the impact on disease management is unclear. In this review we consider the environmental pathways associated with prolonged antigenic exposure and critically assess the significance of asymptomatic carriage in disease outbreaks Although screening high-risk groups for occupationally acquired diseases would be logistically problematical, there may be an economic case for identifying and treating asymptomatic carriage if the costs of screening and treatment are less than the costs of identifying and treating those individuals infected by asymptomatic hosts.
The illegal trade in wild harvested plants and animals is a significant threat to populations and species worldwide. There is concern that in many countries sanctions for wildlife trade crimes are insufficient to act as a deterrent, and do not reflect the seriousness of offences. For these reasons it is important to understand professional and public opinions as to which aspects of such crimes make them more or less serious, and so deserving of a greater or lesser sentence. Conjoint analysis, a method used in marketing to understand which characteristics of a product are valued by consumers, was used to investigate which attributes of hypothetical wildlife trade offences (threat status and taxon of species involved, illegal profit, previous convictions and plea) UK-based conservation professionals, magistrates and the general public considered most important when sentencing wildlife criminals in the UK. Eighty-seven per cent of 682 respondents completed enough of the survey to be included in the analysis. Magistrates and the public considered illegal profit to be the single most important attribute, while conservationists considered the threat status of the species involved to be most important (considered second most important by magistrates and the public). Magistrates, when presented with adequate information, considered the threat status and corresponding legal protection afforded to wildlife when considering how serious a wildlife trade crime was, and doing so is in line with public opinion on sentencing such offences. This study highlights the importance of ensuring that judiciaries are presented with information concerning both the potential profit and conservation impact of wildlife trade crimes. Sentencing councils must develop appropriate guidelines to support judiciaries in their sentencing of wildlife crimes.
Few hard data are available on emergent diseases. However, the need to mitigate and manage emergent diseases has prompted the use of various expert consultation and opinion elicitation methods. We adapted best-worst scaling (BWS) to elicit experts' assessment of the relative practicality and effectiveness of measures to reduce human exposure to E. coli O157. Cattle vaccination was considered the most effective and hand-washing was considered the most practical measure. BWS proved a powerful tool for expert elicitation as it breaks down a cognitively burdensome process into simple, repeated, tasks. In addition, statistical analysis of the resulting data provides a scaled set of scores for the measures, rather than just a ranking. The use of two criteria (practicality and effectiveness) within the BWS process allows the identification of subsets of measures judged as potentially performing well on both criteria, and conversely those judged to be neither effective nor practical.
In Chapter 5, we discussed the normal responses to a variety of noxious stimuli and their modulation by peripheral and central neural mechanisms. This review showed that noxious stimuli preferentially and most commonly activate a set of interconnected structures, namely the insula and secondary (SII) somatosensory cortices, anterior cingulate gyrus and thalamus. Several additional structures are also activated during normal acute pain although somewhat less frequently: the primary (SI) somatosensory cortex, components of the striatum, the cerebellum, premotor cortex, dorsolateral and orbitofrontal regions of the prefrontal cortex, and the medial midbrain in the region of the periaqueductal gray matter.
In this chapter we review the evidence that chronically painful conditions, whether of peripheral or central origin, may alter the nociceptive processing that normally follows the application of noxious or innocuous stimuli (see Chapter 7). In clinical practice and in the interpretation of the results of pain research, the assumption is often made that the perceptual abnormalities sometimes associated with chronic pain states are attributable only to changes occurring at the peripheral or spinal level. Although this assumption may be correct in most instances, functional imaging studies provide evidence to the contrary in some cases. We cannot assume that, in pathological or chronically painful conditions, information ascending through the spinothalamic tract will be processed by the same mechanisms used for acute pain; this has important clinical implications for the management of chronic pain.
Neuropathic pain is pain following a disease or injury to the nervous system, and can be categorized by the location of the causative injury. Chronic pain following injury of the peripheral nervous system, distal to the oligodendroglial cell – Schwann cell junction, can be termed deafferentation pain or peripheral neuropathic pain. Chronic pain “associated with lesions of the CNS” is termed central pain syndrome (Merskey, 1986; Bonica, 1991). There are many situations in which there is injury of both the peripheral and central nervous system, particularly with injuries of the conus medullaris. In this chapter we will consider primate neuropathic pain states, beginning with peripheral neuropathic or deafferentation syndromes, and concluding with central pain syndromes.
In general terms, both central and peripheral chronic pain syndromes have similar characteristics. These include evidence of sensory loss, ongoing pain and pain evoked by stimuli that are not normally painful (allodynia or hyperalgesia). The sensory loss and hypersensitivity are demonstrated by quantitative sensory testing (QST). In addition, a number of primate models have been developed which mimic the sensory abnormalities in patients with neuropathic pain.
Clinical characteristics of peripheral neuropathic pain
The cause of most neuropathies is based on the medical history, supported by laboratory investigations (Casey et al., 1996b). Diabetes is the most common cause of painful neuropathy. Generally, a progressive course suggests an inherited, metabolic or recurrent toxic etiology.
Nociceptors are sensory receptors that respond to stimuli that are damaging or potentially damaging to tissues (Sherrington,1906). The thresholds for activation of many nociceptors can be reached when stimuli of only moderate or non-damaging intensities are applied, but responses continue to increase as stimulus intensity is progressively increased to a level that produces overt damage. By contrast, other nociceptors respond only to intense stimuli and some may not respond at all, even to the strongest mechanical stimuli, unless they are first sensitized (Lynn and Carpenter, 1982; Meyer et al., 1991; Kress et al., 1992; Davis et al., 1993; Treede et al., 1998). The last mentioned have been called “silent nociceptors” (Schaible and Schmidt, 1985, 1988a, 1988b; Schmidt et al., 1995, 2000). Overall, if we include receptors responding to innocuous warming and cooling of the skin, there may be as many as six receptor classes specific for cooling, warming, noxious heat or cold, destructive mechanical or mixed noxious stimuli in humans and other animals.
Types of nociceptors
Nociceptors can be subdivided according to the tissue in which they are found, the size or conduction velocity of the afferent fiber supplying them and the type of stimulus that activates them. Most experimental studies of nociceptors have been performed on common laboratory animals, especially rodents and cats. Some of the most informative, however, have been made during recordings from peripheral nerves of monkeys or human subjects (reviewed in Willis and Coggeshall, 2004).
The clinical descriptions of cordotomy played a major role in elucidating the function and the anatomy of the human spinothalamic tract (STT) (Chapter 1). There are a number of other examples of surgical interventions which have informed our understanding of the pain system. In particular, the pain-related role of the cingulate gyrus is suggested by imaging studies and by the effect of cingulotomy on experimental pain (Rainville et al., 1997; Gildenberg, 2004). Similarly the role of the motor cortex in these systems has suggested the effects of stimulation on activity throughout the pain system (Brown and Barbaro, 2003; Brown, 2004; Peyron et al., 2007). The purpose of this chapter is to examine these surgical interventions in terms of the anatomy and function of structures involved in these interventions. The inclusion of procedures in this chapter is arbitrary and many other such procedures which might have been included have been excluded.
Cordotomy and myelotomy
Percutaneous cordotomy produces relief of pain by interrupting the transmission of signals in the STT from below the level of intervention (Tasker, 1988; Tasker, 2004). The anterolateral quadrant of the spinal cord has long been recognized as the location of the STT (Chapter 1). Recent findings indicate that the dorsal column system also has an important role in visceral nociception (Nauta et al., 1997; Willis et al., 1999). The STT terminates in the primate thalamus, brainstem and other structures such as the hypothalamus and amygdala whereas the dorsal column system terminates in the dorsal column nuclei (Newman et al., 1996).
Before the introduction of computerized tomographic (CT) brain imaging, studying human brain mechanisms of pain was largely limited to clinical reports and the post-mortem analysis of brain lesions. Although this approach provided important information and established the background for current investigations, these studies were usually limited by clinical descriptions of each patient's condition. Somatosensory psychophysics seldom included studies of pain and even then it was not possible to relate these observations to brain function or physiology. Because the living brain was invisible (except in the neurosurgery operating suite), research on pain mechanisms focused almost exclusively on the peripheral nervous system.
Brain CT scans introduced the opportunity to apply quantitative sensory testing to the study of living patients with visible, localized brain lesions and to begin to test hypotheses about functional localization and brain mechanisms of pain. The introduction of functional imaging by positron emission tomography (PET) and magnetic resonance imaging (MRI; fMRI) launched a new investigational paradigm into the study of pain mechanisms. Now it is possible to go well beyond the lesion analysis method and to relate human experience, in this case using somatosensory psychophysics, directly to a surrogate measure of activity in groups of neurons at the level of visible, localized brain structure. Since the early 1990s, the number and technical sophistication of functional brain imaging studies, including those related to pain, has increased at a rate that makes it almost impossible to incorporate the results into a conceptual framework.