Determining the dimension of the central subspace and central mean subspace

The central subspace and central mean subspace are two importanttargets of sufficient dimension reduction. We propose a weightedchi-squared test to determine their dimensions based on matriceswhose column spaces are exactly equal to the central subspaceor the central mean subspace. The asymptotic distribution ofthe test statistic is obtained. Simulation examples are usedto demonstrate the performance of this test.     

Urban allergophytes of central Italy

This research was designed to compare allergenic flora of various cities of central Italy. Because the data on this problem are rather scant, we wanted to highlight the relationships among the ecological conditions of the urban habitats, and the plants whose pollens cause allergic manifestations in the human population. Our results pointed out that the structural design of the urban land use types play an important role in the distribution of allergophytes. The compact structure of the historic city center does not impede the establishment of allergophytes. Actually, it promotes some species that come from the dry pastures and rocky walls of the surrounding ecosystems. Allergenicity was revealed throughout the urban area, with a prevalence of species with monoporate pollens characteristic of the Poaceae. Highly allergenic plants are present in the central zone (within the city walls) and in some peripheral land use models (urban road verges). The particular abundance of Urticaceae with small triporate pollen grains and of various cultivated species, introduced by man for aesthetic reasons, contributes to the increase of allergophytism. The study points out the role of the interactions between the allergenic flora, human impact through the land use patterns, urban fauna, and the meso- and microclimatic conditions of the cities studied.     

The CAMplexities of central ghrelin

The gut hormone ghrelin is known to activate hypothalamic AMPK, a crucial metabolic sensor controlling energy balance. In this issue of Cell Metabolism, Anderson et al. (2008) show that CaMKK2 mediates this effect by forming a unique complex of AMPKalpha/beta with acetyl-CoA carboxylase (ACC) in a pathway distinct from the more established AMP/LKB1 pathway.     

The central cells of sponges

Summary Twenty-one species of Porifera have been surveyed by light microscopy for the presence, form, and relative abundance of a little known cell type known as central cells. They are found to be present in fifteen of these species and occur in six morphologically recognizable forms. Their functional roles are reinterpreted in the light of new distributional and abundance data. The central cells of the siliceous ceractinomorph demosponges are common and intimately associated with the choanocyte population. They probably play an important role in control of water currents within individual choanocyte chambers to mediate cleaning of the outer chamber surfaces. The central cells of keratosan and tetractinomorph demosponges appear to represent stages in egestive processes of wandering mesenchyme cells.This investigation was supported by an operating grant, No. A9554, from the National Research Council of Canada     

Reserpine-induced central effects: pharmacological evidence for the lack of central effects of reserpine methiodide

Reserpine, an alkaloid from Rauwolfia serpentina, was widely used for its antihypertensive action. However, its use has been reduced because of its sedative and extra pyramidal symptoms. In the present investigation, reserpine methiodide (RMI), a quaternary analogue of reserpine, was synthesized and pharmacologically evaluated in rats and mice for its central (barbiturate hypnosis, spontaneous motor activity, body temperature, and avoidance of conditioned response) and peripheral actions (blood pressure) in comparison with reserpine. The results indicate that reserpine produced a dose-dependent depression of the central nervous system. RMI at doses equal to and double the equimolar doses of reserpine did not produce any behavioural changes compared with control animals. Nevertheless, both reserpine and RMI were found to produce dose-dependent reduction in the blood pressure of anaesthetized rats, although only at higher doses of RMI, indicating that quaternization of reserpine not only attenuated the entry of RMI into the central nervous system, but also reduced its access to the target tissue in the periphery. It is speculated that the hypotensive actions of RMI may also be due to peripheral depletion of catecholamines.     

Mitochondria: execution central

Mitochondria play an essential function in eukaryotic life and death. They also play a central role in apoptosis regulation, reflected by the convergence of Bcl-2 family members on the mitochondrial outer membrane, and the presence of 'death factors' in the intermembrane space. Mitochondrial structure and function must be taken into consideration when evaluating mechanisms for cytochrome c release. The core machinery for caspase activation is conserved from Caenorhabditis elegans to man, and we consider parallels in the role of mitochondria in this process.     

Alcohol and central neurotransmission

The study of the relationships between alcohol consumption and central neurotransmission is difficult: they are different from one individual to another, from one neurotransmission system to another and from one cerebral area to another. Moreover, there is no fully satisfactory animal model of alcoholism and the human studies have to cope with a lot of methodological problems. In spite of these difficulties a bidirectional relationship between alcohol and central neurotransmission is well established. Neuronal dysfunctions are the neurobiological basis for the alcohol behaviour, and ethanol craving seems specifically related to hypofunction of the noradrenergic, GABAergic and serotoninergic systems, and maintained by a positive reinforcement mediated by the dopaminergic and opioid systems. Ethanol alters almost all membrane functions, but it behaves essentially like a barbiturate-type GABAergic agonist. In the short-term, it also stimulates central monoaminergic neurotransmissions. With chronic intoxication, membrane tolerance develops, which is the substratum for tolerance and dependence. Concurrently there are adaptative processes and a depletion of the capacities for synthesis of neurotransmitters, therefore a hypofunctioning of all neurotransmission systems. This hypofunctioning is an additive mechanism for tolerance and dependence, pushing the individual into drinking always more alcohol to palliate it; it is sharply revealed during withdrawal, particularly the GABAergic deficiency.     

Formation of novel central and peripheral connections between molluscan central neurons in organ cultured ganglia

An in vitro organ culture system for buccal ganglia of the adult snail, Helisoma, is described. The system supports: (1) maintenance of characterstic electrophysiological parameters of identified neurons over seven days of culture; (2) choline metabolism including uptake and synthesis over the same duration; (3) sprouting and growth of neurons in response to axotomy; (4) the formation of novel central electrotonic connections between identified neurons as a result of sprouting and growth. These observations on neuronal growth and the formation of connections are similar to those made with in vivo culture. The use of in vitro culture allows precise manipulations not previously possible. When buccal ganglia are cultured in vitro with the cut distal ends of peripheral nerve trunks held closely apposed, axons of neurons 5R and 5L in the nerve trunks are capable of forming electrotonic connections similar to central connections. The capability of these neurons to form electrotonic connections via their peripheral axons implies that special structures (i. e., central neurites) are not required for the formation of connections; and neither are special environments (i. e., the central neurites) required for these connections.     

Adenosine receptors in the central nervous system: relationship to the central actions of methylxanthines

Adenosine has a significant role in many functions of the central nervous system. Behaviorally, adenosine and adenosine analogs have marked depressant effects. Electrophysiologically, adenosine reduces spontaneous neuronal activity and inhibits transsynaptic potentials $\text{via}$ interaction with extracellular receptors. Biochemically, adenosine inhibits adenylate cyclase $\text{via}$ a “high” affinity receptor, and activates adenylate cyclase $\text{via}$ a “low” affinity receptor. These receptors, called “A₁” and “A₂” respectively, show differing profiles for activation by adenosine analogs. Radioactive N⁶-cyclohexyladenosine binds selectively to the “high” affinity receptor. One major class of antagonists is known at adenosine receptors: the alkylxanthines, including caffeine and theophylline. Radioactive 1,3-diethyl-8-phenylxanthine, a particularly potent antagonist, appears to bind to both low and high affinity adenosine receptors. Behavioral, electrophysiological, and biochemical effects of alkylxanthines are consistent with the hypothesis that the central stimulatory actions of caffeine and theophylline are due in large part to antagonism of central adenosine receptors.