Assessing hepatic metabolic changes during progressive colonization of germ-free mouse by 1H NMR spectroscopy

It is well known that gut bacteria contribute significantly to the host homeostasis, providing a range of benefits such as immune protection and vitamin synthesis. They also supply the host with a considerable amount of nutrients, making this ecosystem an essential metabolic organ. In the context of increasing evidence of the link between the gut flora and the metabolic syndrome, understanding the metabolic interaction between the host and its gut microbiota is becoming an important challenge of modern biology.1-4 Colonization (also referred to as normalization process) designates the establishment of micro-organisms in a former germ-free animal. While it is a natural process occurring at birth, it is also used in adult germ-free animals to control the gut floral ecosystem and further determine its impact on the host metabolism. A common procedure to control the colonization process is to use the gavage method with a single or a mixture of micro-organisms. This method results in a very quick colonization and presents the disadvantage of being extremely stressful5. It is therefore useful to minimize the stress and to obtain a slower colonization process to observe gradually the impact of bacterial establishment on the host metabolism. In this manuscript, we describe a procedure to assess the modification of hepatic metabolism during a gradual colonization process using a non-destructive metabolic profiling technique. We propose to monitor gut microbial colonization by assessing the gut microbial metabolic activity reflected by the urinary excretion of microbial co-metabolites by 1H NMR-based metabolic profiling. This allows an appreciation of the stability of gut microbial activity beyond the stable establishment of the gut microbial ecosystem usually assessed by monitoring fecal bacteria by DGGE (denaturing gradient gel electrophoresis).6 The colonization takes place in a conventional open environment and is initiated by a dirty litter soiled by conventional animals, which will serve as controls. Rodents being coprophagous animals, this ensures a homogenous colonization as previously described.7 Hepatic metabolic profiling is measured directly from an intact liver biopsy using 1H High Resolution Magic Angle Spinning NMR spectroscopy. This semi-quantitative technique offers a quick way to assess, without damaging the cell structure, the major metabolites such as triglycerides, glucose and glycogen in order to further estimate the complex interaction between the colonization process and the hepatic metabolism7-10. This method can also be applied to any tissue biopsy11,12

Factors affecting breeding status of wading birds in the Everglades.

This goals of this research and monitoring effort are to document nesting effort and roughly categorize success of nesting by wading birds in the central Everglades of Florida, and to investigate the causes of nonbreeding in a high proportion of the adult wading birds in the ecosystem The latter goal has focused on breeding of White Ibises (Eudocimus albus) and has been approached through 1) understanding the nutritional, behavioral, and hormonal aspects of normal breeding in a captive colony ofScarlet Ibises (considered conspecific to White Ibises) in central Florida, and 2) comparing breeding and nonbreeding wild White Ibises in the Everglades, in their physiology, nutritional state, breeding phenology, contaminant load, and hormonal status. This report covers work on this project between January and November, 2000. (81 page docoument

Cutaneous sensory input to the spinocervical tract of the cat and the corticofugal modulation of transmission from the forelimb component

SECTION I - LITERATURE REVIEW The literature is reviewed with special reference to knowledge of cutaneous afferent fibres and their representation in spinocervical tract fibres in the lumbar spinal cord of the cat. Attention is drawn to the paucity of information about forelimb afferents and their representation in the cervical spinal cord. The control of transmission through ascending sensory pathways and in particular the spinocervical tract is discussed. Finally relevant work on the somatosensory cortex and corticofugal inhibition is reviewed and comment is made on the influence of anaesthetics on our knowledge of sensory mechanisms.SECTION II - RECEPTIVE FIELDS AND CONDUCTION VELOCITIES OF IDENTIFIED SPINOCERVICAL TRACT AXONS IN THE CERVICAL SPINAL CORD. Recordings were made with micro-electrodes from single axons in the dorsolateral funiculus of the cervical spinal cord of decerebrate cats. Some of these axons could be designated on electrophysiological criteria as belonging to the spinocervical tract. Such axons conveyed tactile information qualitatively similar to that found by other workers in the lumbar cord. Quantitatively SCT axons with receptive fields in the forelimb were most common and were more frequently activated only by hair movement. Axonal conduction velocities were analysed in relation to the site and type of their afferent input.SECTION III - HOMOSEGMENTAL AND HETEROSEGMENTAL INHIBITION OF TRANSMISSION THROUGH THE SPINOCERVICAL TRACT IN DECEREBRATE CATS. Discharges evoked in SCT axons by electrical and natural stimulation were tested for inhibition from other cutaneous nerves both by electrical and natural stimulation. Inhibition was most easily elicited from the homologous limb and least easily from the heterologous contralateral limb. Conditioning curves of segmental inhibition were plotted and were consistent with a pre-synaptic mechanism. In two spinalized decerebrate cats, only homosegmental inhibition was found.SECTION IV - IPSI- AND CONTRALATERAL CORTICOFUGAL INHIBITION OF TRANSMISSION THROUGH THE SPINOCERVICAL TRACT. Chloralose anaesthetised curarised cats were used to demonstrate corticofugal inhibition of spinocervical tract cells which were excited by electrical stimulation of the superficial radialX^nerve . Surf ace , sprung ball ,stimulating electrodes were u^ed to make a grid map of the cortical surface for areas of maximum inhibitory effect and glass micro-electrodes were used to stimulate the depth of the cortex. For both types of stimulation cathodal currents were most effective. Those areas of cortex eliciting most inhibition at a given current strength corresponded with the contralateral forelimb sensory receiving areas S.I and S.II. Weaker inhibition was elicited from the ipsilateral cortex. Conditioning curves of corticofugal inhibition were plotted.SECTION V - CONCLUSION AND GENERAL DISCUSSION OF THE FUNCTION OF THE SPINOCERVICAL TRACT. The results of the previous sections are discussed in relation to present knowledge of the ascending sensory pathways and the problems they raise. Theories concerning the function of the spinocervical tract are discussed and it is postulated that the spinocervical tract may be concerned in the control of certain types of movement

Towards human technology symbiosis in the haptic mode

Search and rescue operations are often undertaken in dark and noisy environments in which rescue teams must rely on haptic feedback for exploration and safe exit. However, little attention has been paid specifically to haptic sensitivity in such contexts or to the possibility of enhancing communicational proficiency in the haptic mode as a life-preserving measure. Here we discuss the design of a haptic guide robot, inspired by careful study of the communication between blind person and guide dog. In the case of this partnership, the development of a symbiotic relationship between person and dog, based on mutual trust and confidence, is a prerequisite for successful task performance. We argue that a human-technology symbiosis is equally necessary and possible in the case of the robot guide. But this is dependent on the robot becoming 'transparent technology' in Andy Clark's sense. We report on initial haptic mode experiments in which a person uses a simple mobile mechanical device (a metal disk fixed with a rigid handle) to explore the immediate environment. These experiments demonstrate the extreme sensitivity and trainability of haptic communication and the speed with which users develop and refine their haptic proficiencies in using the device, permitting reliable and accurate discrimination between objects of different weights. We argue that such trials show the transformation of the mobile device into a transparent information appliance and the beginnings of the development of a symbiotic relationship between device and human user. We discuss how these initial explorations may shed light on the more general question of how a human mind, on being exposed to an unknown environment, may enter into collaboration with an external information source in order to learn about, and navigate, that environment

Lincoln on Secession

The recent spate of secessionist conflicts has inspired many of us to return to the classics of political theory for moral guidance on statebreaking. Because Hobbes, Locke, Rousseau, et al. are virtually silent on this topic, however, we look in this paper at the writing of Abraham Lincoln