bluuebunny/crossref_metadata_2025_split huggingface dataset:
FACTORS AFFECTING THE SPONTANEOUS RELEASE OF [3H] γ‐AMINOBUTYRIC ACID FROM THE FROG RETINA IN VITRO
Authors: Kennedy A. J. , Voaden Mary J. 
Published: December 2006

Abstract— The spontaneous efflux of [3H]GABA and its metabolites from the frog retina has been studied. The efflux of radioactivity was multiphasic in the presence or absence of amino‐oxyacetic acid (AOAA), an inhibitor of GABA metabolism, and was not affected by light or dark adaptation.Strong retention of radioactivity was evident in the presence of AOAA, about 90% of the label remaining in the tissue after 4 h superfusion. Under these conditions, increases in the rate of release of radioactivity were evoked by electrical stimulation, 40 mm‐potassium. unlabelled GABA (5 mm), ouabain (5 × 10−5m) and the absence of calcium. The amount of [3H]GABA released by electrical stimulation was not markedly calcium dependent, whereas the response to 40 mm‐potassium was reduced by 96% in the absence of calcium.
THE EFFECTS OF SOLUBILIZATION PROCEDURES ON THE RELEASE AND MOLECULAR STATE OF ACETYLCHOLINESTERASE FROM ELECTRIC ORGAN TISSUE
Authors: Dudai Y. , Silman I. 
Published: December 2006

Abstract— A study was made of the effect of various solubilization procedures on the release of AChE from electric organ tissue of the electric eel and on the molecular state of the enzyme. The procedures employed included homogenization in different ionic media or in the presence of detergents, etuymic treatment and chemical modification. Studies were performed on intact electroplax, tissue homogenates and membrane fractions. The apparent AChE activity of intact cells, homogenates and membrane fractions was shown to be governed by diffusion‐controlled substrate and hydrogen ion gradients, generated by AChE‐catalyscd hydrolysis, leading to a lower substrate concentration and a lower pH in the vicinity of the particulate enzyme.Treatment of homogenates with NaCl solutions or with NaCl solutions containing the nonionic detergent Triton X‐100 causes release of the native’molecular forms of the enzyme (primarily the 18 S species) which aggregate at low ionic strength. For optimal extraction both high ionic strength (e.g. 1 M‐NaCl) and the detergent are needed AChE is also solubilized by treatment of tissue homogenates with trypsin, bacterial protease or collagenase. The first two enzymes caused its release as an 11 S non‐aggregating form, while collagenase also produces a minor non‐aggregating ‐ 16 S component. Treatment of tissue homogenates with maleic anhydride causes release of AChE as a non‐aggregating 18 S species. On the basis of the solubilization experiments it is concluded that the interaction of AChE with the excitable membrane is primarily electrostatic. The possible orientation of the enzyme within the synaptic gap is discussed.
METABOLISM OF BRAIN SPHINGOMYELINS: HALF‐LIVES OF SPHINGOSINE, FATTY ACIDS AND PHOSPHATE FROM TWO TYPES OF RAT BRAIN SPHINGOMYELIN
Authors: Freysz L. , Lastennet A. , Mandel P. 
Published: December 2006

Abstract— The metabolism of rat brain sphingomyelins containing short‐chain (C16‐C18) and long‐chain (C20‐ C24) fatty acids has been studied by determination of the content of radioactivity in the sphingo‐sinc. fatty acids and phosphate of the sphingomyelins over a period of 60 days following the intracisternal injection of [14C]acetate and [32P]phosphate. From the rate of decrease of the specific radioactivities of the different constituents of short‐chain fatty acid sphingomyelins, we have calculated a half‐life of 65 days for sphingosine. 41 days for fatty acids and 62 days for phosphate. For the long‐chain fatty acid sphingomyelins the half‐life of sphingosine was approximately 465 days. The fatty acids and phosphate from these sphingomyelins had fast and slow turnover pools. The half‐life for the fast pool was 7 days for the two constituents and the estimated half‐lives for the slow pool were 220 days for fatty acids and 480 days for phosphate.These results suggest that one can distinguish at least three metabolic pools of brain sphingomyelins: (a) sphingomyelins with long‐chain fatty acids situated in myelin whose half‐lives are 465 days for sphingosine, 220 days for fatty acids and 480 days for phosphate; (b) sphingomyelins with long‐chain fatty acids located mainly in non‐myelin structures having half‐lives of 465 days for sphingosine. 7 days for fatty acids and 7 days for phosphate; (c) sphingomyeiins with short‐chain fatty acids with half‐lives of 65 days for sphingosine. 41 days for fatty acids and 62 days for phosphate. The differences between the half‐lives of the three metabolic pools of sphingomyelin, together with the subcellular localizations of the two molecular species of these compounds, suggest that the metabolism of the different molecular species of sphingomyelin are independent and that in various subcellular fractions the long‐chain fatty acid and short‐chain fatty acid sphingomyelins have different turnover rates.
A MODULATING ROLE OF PITUITARY‐ADRENAL AXIS IN CEREBRAL METABOLISM OF ADENOSINE 3′,5′‐MONOPHOSPHATE
Authors: Nakagawa K. , Kuriyama K. 
Published: December 2006

Abstract— The effect of adrenalectomy or hypophysectomy on the metabolism of adenosine 3′,5′‐monophosphate (cyclic AMP) in the cerebral cortex of male Wistar rats was investigated.The bilateral removal of adrenal glands reduced significantly the activity of cerebral adenylate cyclase [EC 4.6.1.1]. whereas that of cyclic 3′.5′‐nucleotide phosphodiesterase [EC 3.1.4.17] remained unchanged. The formation of cyclic AMP measured in cerebral cortical slices from adrenalectomized or hypophysectomized rats was also diminished. Decreases in the activity of adenylate cyclase and formation of cyclic AMP following adrenalectomy were antagonized by in vivo administration of dexamethasone or aldosterone, while those observed in hypophysectomized rats were restored by ACTH or dexamethasone. It is suggested that the pituitary adrenal axis has a modulating role in the metabolism of cerebral cyclic AMP, possibly by changing adenylate cyclase activity.
EFFECT OF ZUCLOMIPHENE ON CHOLESTEROL FORMATION IN THE DEVELOPING CENTRAL NERVOUS SYSTEM OF THE RAT
Authors: Ramsey R. B. , Fredericks M. , Fischer V. W. 
Published: December 2006

Abstract— The effect of zuclomiphene, a hypocholesterolemic agent, on developing rat CNS cholesterol biosynthesis was examined. Sterol content and composition was studied in relation to age in four regions of the CNS, cerebrum, brain stem, spinal cord and cerebellum. Sterol content of all four regions was slightly lower in drug‐treated animals than in controls. Brain stem and spinal cord were more susceptible to the effects of zuclomiphene than were cerebrum and cerebellum. Drug treatment resulted in the accumulation of desmosterol and zymosterol (5x‐cholesta‐8,24‐dien‐3β‐ol) in all CNS regions. After 15 days of drug treatment, desmosterol constituted more than 50% of the total sterol in the four examined regions. Six to 9% of the total sterol was zymosterol.Examination by electron microscopy indicated only minimal morphological changes. Occasionally, neuronal membranous cytoplasmic inclusion bodies were evident.
GABA‐TRANSAMINASES OF HUMAN BRAIN AND PERIPHERAL TISSUES—KINETIC AND MOLECULAR PROPERTIES
Authors: White Helen L. , Sato Takao L. 
Published: December 2006

Abstract— Kinetic experiments with 4‐aminobutyrate‐2‐ketoglutarate transaminase (GABA‐T), partially purified from human brain tissue, supported a Bi Bi Ping‐Pong type of enzyme mechanism in which the enzyme oscillates between forms bound to pyridoxal phosphate and pyridoxamine phosphate. Extrapolated Km values were 0.31 mm for γ‐aminobutyrate, 0.16 mm for α‐ketoglutarate, and 3.8 μm for pyridoxal phosphate. Very similar kinetic parameters were observed with rat brain enzyme. Apparent molecular weight of human GABA‐T by gel filtration was 70,000 ± 3000. Electrofucusing experiments indicated a single ionic form with isoelectric pH = 5.7. Enzyme activity was inhibited by Tris, halides, cadmium and cupric ions, and known GABA‐T inhibitors.GABA‐transaminating enzymes isolated from human kidney and liver were found to be similar to the brain enzyme with respect to substrate affinities, cofactor requirements, isoelectric pH values, molecular weights, and response to inhibitors.
TIME‐DEPENDENT PARTITIONING OF GLUCOSE CARBONS METABOLIZED BY THE SUPERIOR CERVICAL GANGLION FROM CALVES
Authors: Quadflieg K. H. , Brand K. 
Published: December 2006

Abstract— Glucose metabolism in the superior cervical ganglion for calves has been studied by incubating slices with [1‐14C]‐, [6‐14C]‐ and [U‐14C]‐labelled glucose at 37°C and pH 7.4. Glucose utilization and the metabolic partitioning of glucose carbon in products during different incubation periods ranging from 5 to 60 min were determined by isotopic methods.Separation and identification of labelled compounds have been achieved by anion and cation exchange chromatography as well as by TLC and enzymatic analyses.From the data obtained a carbon balance could be constructed showing lactate to be the major product of glucose metabolism followed by CO2 and amino acids. Measuring the release of 14CO2 from differently 4C‐labelled glucose, the existence of an active pentose phosphate pathway in the ganglion could be demonstrated although this pathway seems to contribute only to a small extent to glucose metabolism. The marked decrease of the C‐U: C‐6 and the C‐U:C‐1 ratios in 14CO2 observed in the course of incubation is discussed in terms of a time‐dependent change in the rate of synthesis of amino acids which are directly connected with intermediates of the citric acid cycle.
MULTIPLE FORMS OF PROTEIN KINASES IN MYELIN AND MICROSOMAL FRACTIONS OF BOVINE BRAIN
Authors: Miyamoto E. , Miyazaki K. , Hirose R. , Kashiba A. 
Published: December 2006

Abstract— The activity profiles of the solubilized protein kinases from the microsomal and myelin fractions of bovine brain were examined by column chromatography and sucrose density gradient centrifugation. The main peak of adenosine 3′,5′‐monophosphate (cyclic AMP)‐dependent activity with histone as substrate for each membrane enzyme was eluted with about 0.2 m‐NaCl on a DEAE‐cellulose column. A peak of activity stimulated with cyclic AMP was also eluted with about 0.1 m‐NaCl for the microsomal enzyme. A peak with protamine and casein as substrate for the microsomal or myelin enzyme, respectively, was larger than that with histone as substrate for each enzyme. The first peak with histone as substrate on a DEAE–cellulose column appeared as two peaks on the Sepharose 6B column. The second peak with histone as substrate on DEAE–cellulose column was shown to be a holoenzyme consisting of regulatory and catalytic subunits. The holoenzyme and subunits were eluted at similar positions to each other between both membrane enzymes on Sepharose 6B column. The holoenzyme sedimented as two peaks of activity on sucrose density gradient centrifugation, both of which were stimulated with cyclic AMP. The preincubation of the holoenzyme with cyclic AMP resulted in shifting to a position of a smaller molecular size.The results indicate the occurrence of multiple forms of protein kinases in membrane fractions of brain with respect to substrate specificity and physical property.
Contractile activity of ATP and diadenosine tetraphosphate on urinary bladder in the rat: role of A1‐ and P2X‐purinoceptors and nitric oxide
Authors: Khattab M. M. , Al‐Hrasen M. N. , El‐Hadiyah T. M. 
Published: December 2006

Summary1 Both adenosine‐5′‐triphosphate (ATP) and diadenosine tetraphosphate (AP4A) produced a dose‐dependent contraction of the isolated rat urinary bladder rings. AP4A dose–response curve was to the left of that of ATP, and maximum response was greater than that produced by ATP.2 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX), the A1‐purinergic receptor blocker (0.01 mm) significantly inhibited the ATP‐ and AP4A‐induced contractions at the whole dose range. The inhibition was between 31–41%, and 15–25% for ATP and AP4A respectively.3 Pyridoxal phosphate 6‐azophenyl‐2′,4′‐disulphonic acid (PPADS), the P2X‐purinoceptor antagonist (0.01 mm) potently inhibited the bladder contractions in response to ATP and AP4A by around 75–80%.4 The nitric oxide (NO) precursorl‐arginine reduced the bladder contractile response to ATP by about 22–41% and that of AP4A to a lesser extent by around 20–32%.5 The nitric oxide synthase inhibitor,NG‐nitro‐l‐arginine methyl ester (l‐NAME, 0.1 mm), did not produce any significant effect on ATP except for a weak inhibition of about 14% at the lowest dose of ATP. The contractions in response to AP4A were only slightly reduced byl‐NAME by about 20%.6 In conclusion, the contractile response of the bladder to ATP and to the dinucleotide AP4A is mediated mainly through P2X‐purinoceptors and A1‐purinergic receptors. In the detrusor muscle, NO donation possesses an inhibitory effect on ATP‐mediated contractility more than that produced by the dinucleotide AP4A.
Potential antioxidant activity of celecoxib and amtolmetin guacyl: in vitro studies
Authors: Kirkova M. , Alexandova A. , Kesiova M. , Tsvetanova E. , Georgieva A. , Todorov S. 
Published: December 2006

Summary 1 In vitro studies of the potential antioxidant activity of the selective cyclo‐oxygenase‐2 inhibitor celecoxib and the non‐steroid anti‐inflammatory drug amtolmetin guacyl (AMG) were carried out. The study included experiments on the ability of these drugs to affect some indices of the oxidative stress [lipid peroxidation (LP), activity of antioxidant enzymes, glutathione (GSH) level] in rat stomach and colon mucosa and in liver. 2 Celecoxib and AMG did not change the activity of the enzymes GSH‐peroxidase, oxidased glutathione (GSSG)‐reductase and glucose‐6‐phosphate‐dehydrogenase, as well as the GSH level in all tissue preparations. An increased superoxide dismutase (SOD) activity and a tendency to a decreased Fe/ascorbic acid‐induced LP in stomach and colon mucosa were found, but only in the presence of AMG. 3 In the liver, both celecoxib and AMG decreased spontaneous and Fe/ascorbic acid‐induced LP. SOD activity was enhanced only in the presence of AMG. 4 Experiments aimed at studying celecoxib and AMG in free oxygen radical‐generating systems were also carried out. AMG and tolmetin (the main metabolite of AMG) inhibited OH•‐provoked deoxyribose degradation in a Fenton system. Celecoxib had no effect on free radicals when tested in the same system. 5 In conclusion, the results of the present in vitro studies suggest that AMG and celecoxib possess antioxidant and metal‐chelating abilities, which might contribute to their beneficial effects.
Effect of short‐term outlet obstruction on rat bladder nerve density and contractility
Authors: Barendrecht M. M. , Chichester P. , Michel M. C. , Levin R. M. 
Published: December 2006

Summary 1 The present study was designed to investigate the relationship between innervation density and contractile responses to field stimulation and exogenous agonists at early time points after induction of bladder outlet obstruction (BOO) in rats. 2 When compared with sham‐operated animals, 1, 3 and 7 days of BOO were associated with a 75%, 80% and 90% increase of bladder weight. Field stimulation caused a frequency‐dependent increase in force of contraction. The force of contraction was reduced at each frequency in BOO rats with the greatest decrease after 1 day and a gradual but incomplete recovery thereafter. In contrast, contractile responses to ATP, carbachol and KCl were markedly reduced after 1 day of BOO and fully recovered after 7 days. The neurofilament staining was not altered by 1 day of BOO, but gradually decreased with increasing duration of BOO reaching the lowest levels after 7 days. 3 We conclude that impaired cellular contractility seems to underlie the early reductions of field stimulation‐induced contraction, possibly reflecting surgical trauma of the tissue. However, at later time points a reduced nerve density, possibly reflecting a partial denervation, appears to be the main reason for impaired contractile response to field stimulation.
Automated metric calibration of colour digital cameras
Authors: Cronk Simon , Fraser Clive , Hanley Harry 
Published: December 2006

AbstractConsumer‐grade digital cameras have become commonplace and with calibration there is significant potential for their use in photogrammetric applications. This paper describes a new method for automatic camera calibration, which is suited to colour digital cameras. Two innovations are central to the developed process. The first is exploitation of RGB colour attributes in the design of automatically detected and identified coded targets. The second is a new approach to initial value determination for relative orientation, which then supports fully automatic initial network exterior orientation and subsequent bundle adjustment with self‐calibration. Accuracy aspects are also touched upon and the impact of chromatic aberration is discussed. Finally, an example of the automatic calibration process, which is implemented in the iWitness system, is presented for the case of multiple zoom settings of a consumer‐grade digital camera.
Of Love and Politics: Reassessing Manuela Sáenz and Simón Bolívar, 1822–1830
Authors: Murray Pamela S. 
Published: December 2006

AbstractThis article critically examines the relationship between Simon Bolívar (aka the “Liberator”) and Manuela Sáenz, dispelling some of the romantic mist that long has surrounded it and that has obscured historical understanding of the famous couple. It also reassesses the relationship from Sáenz's perspective. It shows not only how Sáenz actively pursued an affair with her lover, but, how she integrated herself into his organization, becoming his informant and personal staff archivist and ultimately, one of his premier political allies. It, thus, seeks to shed light both on her remarkable career and on the nature of female citizenship in Spanish America in the early republican era.
Empire, Cultures and Identities in Nineteenth‐ and Twentieth‐Century Britain
Authors: Potter Simon J. 
Published: December 2006

AbstractOver the last twenty years, historians have sought to gauge how the experience of establishing an empire overseas impacted upon the ways that British people thought about themselves and the world around them. As evidence has accumulated, so an increasingly heated historical debate about the exact significance of that source material has been generated. This article looks at where this controversy has taken us, assessing the range of evidence available and the different viewpoints adopted by various historians. It argues that, rather than present our conclusions in polarised terms, we need to acknowledge the wide range of imperial influences working on multiple British cultures and identities in the nineteenth and twentieth centuries. Moreover, given the problematic nature of the available evidence, we should acknowledge the difficulties inherent in any attempt to gauge the impact of those influences. Empire may well have helped to shape British cultures and identities, but it is not clear that it did so in a simple fashion, or that we have sufficient evidence to come to firm conclusions about its impact.
Efficacy of zinc treatment against iron‐induced toxicity in rat hepatoma cell line H4‐II‐E‐C3
Authors: Formigari A. , Santon A. , Irato P. 
Published: December 2006

AbstractObjective: In this study, we have attempted to explore the possible protection afforded by Zn with regard to its antioxidant potential properties in the iron‐induced toxicity.Methods: Rat hepatoma cell line H4‐II‐E‐C3 was treated with 150 μM ZnSO4, 200 μM FeSO4 or 150 μM ZnSO4+ 200 μM FeSO4 for 24 h. We studied the effect of metallothionein (MT), glutathione and metal (Fe and Zn) accumulation. We evaluated the levels of both MT‐1 and MT‐2 mRNAs, activities of antioxidant enzymes, and also determined the distribution of MT and cell death index.Results: The cotreatment produced highest levels of MT. Fe concentration was significantly lower in the Zn–Fe‐treated cells compared with Fe‐treated cells. In both Zn treatments, the superoxide dismutase/glutathione peroxidase ratio was similar to control. The cell death index was lower in the Zn–Fe‐treated cells compared with Fe‐treated cells.Conclusions: Zn may act as antioxidant by competitive inhibition of iron uptake by the divalent metal transporter and/or by MT induction.
Historic Anthropogenically Maintained Bear Grass Savannas of the Southeastern Olympic Peninsula
Authors: Peter David , Shebitz Daniela 
Published: December 2006

Abstract This paper documents the existence and character of a little known fire‐maintained anthropogenic ecosystem in the southeastern Olympic Peninsula of Washington State, U.S.A. Due to cessation of anthropogenic burning, there is no longer an intact example of this ecosystem. We present evidence from Skokomish oral tradition, historical documents, floral composition, tree‐ring analysis, stand structure, and site potential to describe former savanna structure and function. We believe this system was a mosaic of prairies, savannas, and woodlands in a forest matrix maintained through repeated burning to provide culturally important plants and animals. The overstory was dominated by Douglas‐fir (Pseudotsuga menziesii). Bear grass (Xerophyllum tenax) likely was a dominant understory component of the savannas, woodlands, and prairie edges. These lands grew forests in the absence of anthropogenic burning. Wide spacing of older trees or stumps in former stands and rapid invasion by younger trees in the late 1800s and early 1900s suggest a sudden change in stand structure. Shade‐intolerant prairie species are still present where openings have been maintained but not in surrounding forests. Bark charcoal, fire scars, tree establishment patterns, and oral traditions point to use of fire to maintain this system. A common successional trajectory for all these lands leads to forested vegetation. These findings suggest that frequent application of prescribed burning would be necessary to restore this ecosystem.
Use of a Computer‐Based Reminder to Improve Sedative–Hypnotic Prescribing in Older Hospitalized Patients
Authors: Agostini Joseph V. , Zhang Ying , Inouye Sharon K. 
Published: December 2006

OBJECTIVES: To develop a feasible, inexpensive, point‐of‐care computerized reminder to improve sedative‐hypnotic prescribing in hospitalized older people.DESIGN: Pre‐postintervention with a computer‐based reminder.SETTING: Academic medical center.PARTICIPANTS: Hospitalized patients aged 65 and older.INTERVENTION: Computer‐based reminder directing clinicians to prescribe a nonpharmacological sleep protocol, to minimize the potential for harm with diphenhydramine and diazepam use by choosing an alternative medication (trazodone or lorazepam), or both.MEASUREMENTS: Frequency of prescription of four sedative‐hypnotic drugs (diphenhydramine, diazepam, lorazepam, and trazodone) during the 12 months before (n=12,356 patients) and after (n=12,153) the reminder was instituted.RESULTS: Prescribing of sedative‐hypnotics decreased from 2,208 per 12,356 (18%) patients preintervention to 1,832 per 12,153 (15%) postintervention (odds ratio for the intervention=0.82, 95% confidence interval=0.76–0.87), an 18% risk reduction. Combined prescription rates for all four drugs fell consistently throughout the postintervention period. Diphenhydramine, diazepam, and lorazepam orders declined overall, with lorazepam prescriptions decreasing 39% during the intervention. Ninety‐five percent of patients were successfully directed to a safer sedative‐hypnotic drug or a nonpharmacological sleep protocol.CONCLUSION: Using real‐time computer‐based reminders could lead to improved sedative‐hypnotic prescribing for older persons in acute care. This study highlights the potential to address patient safety concerns, and the quality of medication prescribing in particular, in vulnerable hospitalized patients.