718 research outputs found
The physiological significance of the water soluble components of nervous tissue
Part I. The mechanisms of acetylcholine synthesis1) Both citrate and acetate can act as acetyl
donors for choline acetylation by crude brain
extracts.2) In order to demonstrate the action of acetate
three conditions have to be observed: a) that
acetate is not added as a contaminant of the ATP:
b) that the enzymes bringing acetate into reaction
are protected during extraction from the acetone - dried powder by cysteine: c) that a ten times
higher level of coenzyme than for the citrate
system is used.á) Citrate acts as an acetyl donor by breaking
down to acetate and oxaloacetate. Mg, ATP and
the coenzyme are essential for this reaction.
The coenzyme requirement is low.4) Citrate can act in a similar manner in the
acetylation of sulphanilamide. Probably acetate
and oxaloacetate are not the only products of
citrate dismutation.5 The citrate and acetate "priming reactions"
carried out by the brain enzymes (in the absence
of choline) can be coupled with a liver fraction
(sulphanilamide condensing enzyme) to acetylate
sulphanilamide.6) At least two steps are involved in enzymic
acetylation. Activation of acetate (probably a coenzyme acetate complex) and condensation with
the acetyl acceptor are the main enzymic steps.7) "Choline acetylase" includes more than one
enzyme; it should only refer to the enzyme catalysing the condensation of active acetate with
choline.8) The validity of studies on the distribution of
"choline acetylase" in the nervous system is discussed. No change in the ability of various
parts of the system to synthesise acetylcholine is
expected since the "citrate enzyme" probably has a universal distribution.Part II:
The Purification and Structure of Coenzyme A.1) Evidence is presented to prove the identity of th
activator with the coenzyme of acetylation.2) The coenzyme is not responsible for the blue
fluorescence described by Comline (1948).3) A method of purification, based on the acidic
and reducing properties of the coenzyme is described.4) Acid hydrolysatevof the coenzyme contain a sulphur fragment which is probably identical with
the Lactobacillus bulgaricus factor.5) Digestion of the coenzyme with an enzyme derived from rabbit spleen releases two phosphoruscontaining fragments which can be resynthesised to
the coenzyme by a liver enzyme.6) Digestion of the coenzyme with a crude intestinal phosphatase releases three phosphorus-containing fragments which cannot be resynthesised
to the coenzyme under the conditions described.7) The structure of the coenzyme is discussed
Range-separated density-functional theory with random phase approximation: detailed formalism and illustrative applications
Using Green-function many-body theory, we present the details of a formally
exact adiabatic-connection fluctuation-dissipation density-functional theory
based on range separation, which was sketched in Toulouse, Gerber, Jansen,
Savin and Angyan, Phys. Rev. Lett. 102, 096404 (2009). Range-separated
density-functional theory approaches combining short-range density functional
approximations with long-range random phase approximations (RPA) are then
obtained as well-identified approximations on the long-range Green-function
self-energy. Range-separated RPA-type schemes with or without long-range
Hartree-Fock exchange response kernel are assessed on rare-gas and
alkaline-earth dimers, and compared to range-separated second-order
perturbation theory and range-separated coupled-cluster theory.Comment: 15 pages, 3 figures, 2 table
Shining new light on mammalian diving physiology using wearable near-infrared spectroscopy
Investigation of marine mammal dive-by-dive blood distribution and oxygenation has been limited by a lack of non-invasive technology for use in freely diving animals. Here, we developed a non-invasive near-infrared spectroscopy (NIRS) device to measure relative changes in blood volume and haemoglobin oxygenation continuously in the blubber and brain of voluntarily diving harbour seals. Our results show that seals routinely exhibit preparatory peripheral vasoconstriction accompanied by increased cerebral blood volume approximately 15 s before submersion. These anticipatory adjustments confirm that blood redistribution in seals is under some degree of cognitive control that precedes the mammalian dive response. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to ambient air. We suggest that this frequent and reproducible reoxygenation pattern, without access to ambient air, is underpinned by previously unrecognised changes in cerebral drainage. The ability to track blood volume and oxygenation in different tissues using NIRS will facilitate a more accurate understanding of physiological plasticity in diving animals in an increasingly disturbed and exploited environment
Scattering length of the ground state Mg+Mg collision
We have constructed the X 1SIGMAg+ potential for the collision between two
ground state Mg atoms and analyzed the effect of uncertainties in the shape of
the potential on scattering properties at ultra-cold temperatures. This
potential reproduces the experimental term values to 0.2 inverse cm and has a
scattering length of +1.4(5) nm where the error is prodominantly due to the
uncertainty in the dissociation energy and the C6 dispersion coefficient. A
positive sign of the scattering length suggests that a Bose-Einstein condensate
of ground state Mg atoms is stable.Comment: 15 pages, 3 figures, Submitted Phys. Rev.
The FeH Wing-Ford Band in Spectra of M Stars
We study the FeH Wing-Ford band at 9850 - 10200 Angstrons by means of the fit
of synthetic spectra to the observations of M stars, employing recent model
atmospheres. On the basis of the spectrum synthesis, we analyze the dependence
of the band upon atmospheric parameters. FeH lines are a very sensitive surface
gravity indicator, being stronger in dwarfs. They are also sensitive to
metallicity (Allard & Hauschildt 1995). The blending with CN lines, which are
stronger in giants, does not affect the response of the Wing-Ford band to
surface gravity at low resolution (or high velocity dispersions) because CN
lines, which are spread all along the spectrum, are smeared out at convolutions
of FWHM \simgreat 3 Angstrons. We conclude that the Wing-Ford band is a
suitable dwarf/giant indicator for the study of composite stellar populations.Comment: 23 pages + 11 figures in postscript format + 3 ps figures (Nos. 2, 6
and 7) available under request to [email protected]. Accepted
for publication in The Astrophysical Journa
Lactobacillus GG in inducing and maintaining remission of Crohn's disease
BACKGROUND: Experimental studies have shown that luminal antigens are involved in chronic intestinal inflammatory disorders such as Crohn's disease and ulcerative colitis. Alteration of the intestinal microflora by antibiotic or probiotic therapy may induce and maintain remission. The aim of this randomized, placebo-controlled trial was to determine the effect of oral Lactobacillus GG (L. GG) to induce or maintain medically induced remission. METHODS: Eleven patients with moderate to active Crohn's disease were enrolled in this trial to receive either L. GG (2 × 10(9 )CFU/day) or placebo for six months. All patients were started on a tapering steroid regime and received antibiotics for the week before the probiotic/placebo medication was initiated. The primary end point was sustained remission, defined as freedom from relapse at the 6 months follow-up visit. Relapse was defined as an increase in CDAI of >100 points. RESULTS: 5/11 patients finished the study, with 2 patients in each group in sustained remission. The median time to relapse was 16 ± 4 weeks in the L. GG group and 12 ± 4.3 weeks in the placebo group (p = 0.5). CONCLUSION: In this study we could not demonstrate a benefit of L. GG in inducing or maintaining medically induced remission in CD
La comunicazione interculturale e l’approccio comunicativo: dall’idea allo strumento
il saggio si inserisce in un filone di ricerca aperto nel 199 e proseguito con saggi e volumi: in questo caso di descrive e discute la progettazione di un passo fondamentale, dall'elaborazione teorica del modello di riferimento alla traduzione di tale modello in strumento operativo per la consultazione e la didattica
A phase I study of bendamustine hydrochloride administered day 1+2 every 3 weeks in patients with solid tumours
The aim of the study was to determine the maximum tolerated dose (MTD), the dose limiting toxicity (DLT), and the pharmacokinetic profile (Pk) of bendamustine (BM) on a day 1 and 2 every 3 weeks schedule and to recommend a safe phase II dose for further testing. Patients with solid tumours beyond standard therapy were eligible. A 30-min intravenous infusion of BM was administered d1+d2 q 3 weeks. The starting dose was 120 mg m−2 per day and dose increments of 20 mg m−2 were used. Plasma and urine samples were analysed using validated high-performance liquid chromatography/fluorescence assays. Fifteen patients were enrolled. They received a median of two cycles (range 1–8). The MTD was reached at the fourth dose level. Thrombocytopaenia (grade 4) was dose limiting in two of three patients at 180 mg m−2. One patient also experienced febrile neutropaenia. Lymphocytopaenia (grade 4) was present in every patient. Nonhaematologic toxicity including cardiac toxicity was not dose limiting with this schedule. Mean plasma Pk values of BM were tmax 35 min, t1/2 49.1 min, Vd 18.3 l m−2, and clearance 265 ml min−1 m−2. The mean total amount of BM and its metabolites recovered in the first micturition was 8.3% (range 2.7–26%). The MTD of BM in the present dose schedule was 180 mg m−2 on day 1+2. Thrombocytopaenia was dose limiting. The recommended dose for future phase II trials with this schedule is 160 mg m−2 per day
A critical appraisal of appendage disparity and homology in fishes
Fishes are both extremely diverse and morphologically disparate. Part of this disparity can be observed in the numerous possible fin configurations that may differ in terms of the number of fins as well as fin shapes, sizes and relative positions on the body. Here, we thoroughly review the major patterns of disparity in fin configurations for each major group of fishes and discuss how median and paired fin homologies have been interpreted over time. When taking into account the entire span of fish diversity, including both extant and fossil taxa, the disparity in fin morphologies greatly complicates inferring homologies for individual fins. Given the phylogenetic scope of this review, structural and topological criteria appear to be the most useful indicators of fin identity. We further suggest that it may be advantageous to consider some of these fin homologies as nested within the larger framework of homologous fin‐forming morphogenetic fields. We also discuss scenarios of appendage evolution and suggest that modularity may have played a key role in appendage disparification. Fin modules re‐expressed within the boundaries of fin‐forming fields could explain how some fins may have evolved numerous times independently in separate lineages (e.g., adipose fin), or how new fins may have evolved over time (e.g., anterior and posterior dorsal fins, pectoral and pelvic fins). We favour an evolutionary scenario whereby median appendages appeared from a unique field of competence first positioned throughout the dorsal and ventral midlines, which was then redeployed laterally leading to paired appendages.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151971/1/faf12402_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151971/2/faf12402.pd
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