bluuebunny/crossref_metadata_2025 huggingface dataset:
Curare Alkaloids from
Chondodendron tomentosum
Authors: Wintersteiner O. , Dutcher J. D.
Published: October 2006

Crystalline d-tubocurarine has been isolated in good yield from curare prepared from a single plant species, namely,
Chondodendron tomentosum
. This result establishes with certainty the botanical origin of this compound and substantiates the supposition that it is this species which furnishes the active constituent in certain types of curare.

The extract from this plant furthermore yielded two new tertiary alkaloids which could be converted into physiologically active quaternary bases.

Methylation of the phenolic hydroxyl groups in the quaternary bases resulted in a 3-9-fold increase in physiological potency.
Dopaminergic Agents: Influence on Serotonin in the Molluscan Nervous System
Authors: Stefano George B. , Catapane Edward , Aiello Edward
Published: October 2006

Treatment of the mussel
Mytilus edulis
with 6-hydroxydopamine or with α-methyl-
p
-tyrosine decreased dopamine and increased serotonin in the nervous system. Treatment with dopamine decreased serotonin concentrations and prevented the effect of 6-hydroxydopamine. The serotonin concentration appears to be determined in part by the concentration of dopamine.
Sleep in Mammals: Ecological and Constitutional Correlates
Authors: Allison Truett , Cicchetti Domenic V.
Published: October 2006

The interrelationships between sleep, ecological, and constitutional variables were assessed statistically for 39 mammalian species. Slow-wave sleep is negatively associated with a factor related to body size, which suggests that large amounts of this sleep phase are disadvantageous in large species. Paradoxical sleep is associated with a factor related to predatory danger, which suggests that large amounts of this sleep phase are disadvantageous in prey species.
HOW COMPLETE RANDOM PERMUTATIONS AFFECT THE DEPENDENCE STRUCTURE OF STATIONARY SEQUENCES WITH LONG-RANGE DEPENDENCE
Authors: ZHOU YINGCHUN , TAQQU MURAD S.
Published: October 2006

A stationary time series is said to be long-range dependent (LRD) if its autocovariance function decays as a power of the lag, in such a way that the sum (over all lags) of the autocovariances diverges. The asymptotic rate of decay is determined by a parameter H, called the Hurst parameter. The time series is said to be short-range dependent (H = 1/2) if the sum converges. It is commonly believed that a random permutation of a sequence maintains the marginal distribution of each element but destroys the dependence, and in particular, that a random permutation of an LRD sequence creates a new sequence whose estimate of Hurst parameter H is close to 1/2. This paper provides a theoretical basis for investigating these claims. In reality, a complete random permutation does not destroy the covariances, but merely equalizes them. The common value of the equalized covariances depends on the length N of the original sequence and it decreases to 0 as N → ∞. Using the periodogram method, we explain why one is led to think, mistakenly, that the randomized sequence yields an "estimated H close to 1/2.".
Axial stretch: a novel mechanism of the lower esophageal sphincter relaxation
Authors: Dogan Ibrahim , Bhargava Valmik , Liu Jianmin , Mittal Ravinder K.
Published: October 2006

Swallow and esophageal distension-induced relaxations of the lower esophageal sphincter (LES) are associated with an orad movement of the LES because of a concurrent esophageal longitudinal muscle contraction. We hypothesized that the esophageal longitudinal muscle contraction induces a cranially directed mechanical stretch on the LES and therefore studied the effects of a mechanical stretch on the LES pressure. In adult opossums, a silicon tube was placed via mouth into the esophagus and laparotomy was performed. Two needles with silk sutures were passed, 90° apart, through the esophageal walls and silicon tube, 2 cm above the LES. The tube was withdrawn, and one end of each of the four sutures was anchored to the esophageal wall and the other end exited through the mouth to exert graded cranially directed stretch on the LES by using pulley and weights. A cranially directed stretch caused LES relaxation, and with the cessation of stretch there was recovery of the LES pressure. The degree an d duration of LES relaxation increased with the weight and the duration of stretch, respectively. The mean LES relaxation in all animals was 77.7 ± 4.7%. The required weight to induce maximal LES relaxation differed in animals (714 ± 348 g). NG-nitro-L-arginine, a nitric oxide inhibitor, blocked the axial stretch-induced LES relaxation almost completely (from 78 to 19%). Our data support the presence of an axial stretch-activated inhibitory mechanism in the LES. The role of axial stretch in the LES relaxation induced by swallow and esophageal distension requires further investigation.
Students’ and Teachers’ Views of Gender-Related Aspects of Aggression
Authors: Yubero Santiago , Navarro Raúl
Published: October 2006

This article enquires into the role of gender in the use of different forms of aggression and in the appearance of conflicts within the interactions between students of 12-17 years of age. In order to understand both aspects, the conversational fragments of students and teachers from two high schools are expounded; discourses obtained using a qualitative methodology with focus groups and individual interviews. The results suggest that aggression is used as a tool to solve certain problems between pairs of the same sex, but is also present in relationships between genders as a form of intimidation that tries to influence heterosexual encounters. The aggression between genders adopts subtle and less visible forms than the aggression in pairs of the same sex due to the negative social opinion that exists about forms of aggression directed towards women. The information presented possesses implications for researchers and teachers if we bear in mind that relationships between genders at these ages reflect future relationships as adults.
Ether à go-go potassium channel expression in soft tissue sarcoma patients
Authors: Mello de Queiroz Fernanda , Suarez-Kurtz Guilherme , Stühmer Walter , Pardo Luis A
Published: October 2006

Background

The expression of the human Eag1 potassium channel (Kv10.1) is normally restricted to the adult brain, but it has been detected in both tumour cell lines and primary tumours. Our purpose was to determine the frequency of expression of Eag1 in soft tissue sarcoma and its potential clinical implications.

Results

We used specific monoclonal antibodies to determine the expression levels of Eag1 in soft tissue sarcomas from 210 patients by immunohistochemistry. Eag1 was expressed in 71% of all tumours, with frequencies ranging from 56% (liposarcoma) to 82% (rhabdomyosarcoma). We detected differences in expression levels depending on the histological type, but no association was seen between expression of this protein and sex, age, grade or tumour size. Four cell lines derived from relevant sarcoma histological types (fibrosarcoma and rhabdomyosarcoma) were tested for Eag1 expression by real-time RT-PCR. We found all four lines to be positive for Eag1. In these cell lines, blockage of Eag1 by RNA interference led to a decrease in proliferation.

Conclusion

Eag1 is aberrantly expressed in over 70% sarcomas. In sarcoma cell lines, inhibition of Eag1 expression and/or function leads to reduced proliferation. The high frequency of expression of Eag1 in primary tumours and the restriction of normal expression of the channel to the brain, suggests the application of this protein for diagnostic or therapeutic purposes.
Differential Utilization of Transcription Activation Subdomains by Distinct Coactivators Regulates Pit-1 Basal and Ras Responsiveness
Authors: Duval Dawn L. , Jonsen Matthew D. , Diamond Scott E. , Murapa Patience , Jean Annie , Gutierrez-Hartmann Arthur
Published: October 2006

The POU-homeodomain transcription factor Pit-1 governs ontogeny and cell-specific gene expression of pituitary lactotropes, somatotropes, and thyrotropes. The splice isoform, Pit-1β, inserts a 26-amino acid (AA) repressor at AA48 in the Pit-1 transcription activation domain (TAD). The Pit-1 TAD contains a basal regulatory subregion, R1 (AA1–45), and a basal and Ras-responsive region, R2 (AA46–80). To precisely map these activities, we generated GAL4-Pit-1/Pit-1βTAD fusions and, in full-length HA-Pit-1, a series of substitution mutants of R2. Analysis in GH4 cells identified an activation domain at AA50–70, followed by an overlapping, dual-function, Ras-responsive-inhibitory domain, located from AA60–80. In contrast, GAL4-Pit-1βTAD repressed both basal and Ras-mediated TAD activity. To determine the functional interplay between TAD subregions and the β-domain, we inserted the β-domain every 10 AA across the 80-AA Pit-1 TAD. Like wild-type Pit-1β, each construct retained transcriptional activity in HeLa cells and repressed the Ras response in GH4 cells. However, β-domain insertion at AA61 and 71 resulted in greater repression of Ras responsiveness, defining a critical R2 TAD spanning AA61–71 of Pit-1. Furthermore, Ras activation is augmented by steroid receptor coactivator 1, whereas cAMP response element binding protein-binding protein is not a Ras mediator in this system. In summary, the Pit-1/Pit-1β TADs are composed of multiple, modular, and transferable subdomains, including a regulatory R1 domain, a basal activation region, a selective inhibitory-Ras-responsive segment, and a β-specific repressor domain. These data provide novel insights into the mechanisms by which the Pit-1 TAD integrates DNA binding, protein partner interactions, and distinct signaling pathways to fine-tune Pit-1 activity.
Cardiovascular changes under normoxic and hypoxic conditions in the air-breathing teleostSynbranchus marmoratus: importance of the venous system
Authors: Skals Marianne , Skovgaard Nini , Taylor Edwin W. , Leite Cleo A. C. , Abe Augusto S. , Wang Tobias
Published: October 2006

Synbranchus marmoratus is a facultative air-breathing fish, which uses its buccal cavity as well as its gills for air-breathing. S. marmoratus shows a very pronounced tachycardia when it surfaces to air-breathe. An elevation of heart rate decreases cardiac filling time and therefore may cause a decline in stroke volume (VS), but this can be compensated for by an increase in venous tone to maintain stroke volume. Thus, the study on S. marmoratus was undertaken to investigate how stroke volume and venous function are affected during air-breathing. To this end we measured cardiac output(Q̇), heart rate(fH), central venous blood pressure(PCV), mean circulatory filling pressure (MCFP), and dorsal aortic blood pressures (PDA) in S. marmoratus. Measurements were performed in aerated water(PO2>130 mmHg), when the fish alternated between gill ventilation and prolonged periods of apnoeas, as well as during hypoxia(PO2≤50 mmHg), when the fish changed from gill ventilation to air-breathing. Q̇increased significantly during gill ventilation compared to apnoea in aerated water through a significant increase in both fH and VS. PCV and MCFP also increased significantly. During hypoxia, when the animals surface to ventilate air, we found a marked rise in fH, PCV, MCFP, Q̇ and VS, whereas PDA decreased significantly. Simultaneous increases in PCV and MCFP in aerated, as well as in hypoxic water,suggests that the venous system plays an important regulatory role for cardiac filling and VS in this species. In addition, we investigated adrenergic regulation of the venous system through bolus infusions of adrenergic agonists (adrenaline, phenylephrine and isoproterenol;2 μg kg–1). Adrenaline and phenylephrine caused a marked rise in PCV and MCFP, whereas isoproterenol led to a marked decrease in PCV, and tended to decrease MCFP. Thus,it is evident that stimulation of both α- and β-adrenoreceptors affects venous tone in S. marmoratus.
Doing Media Studies: reflections on an unruly discipline
Authors: Geraghty Christine
Published: October 2006

Media studies and its related areas such as communications, cultural studies and film studies are frequently the subjects of ill-informed attack, both inside and outside the academy. This article offers a series of reflections on some of the key issues facing the subject area including
its status and disciplinary formation, the tensions and possibilities of the theory/practice mix on many courses, questions of vocationalism and the views of students. Although the article tries to set the record straight in some areas, it is essentially a personal and sometimes polemical
view which seeks to generate further discussion.
History and cultural identity in Haitian literature
Authors: Crosta Suzanne
Published: October 2006

As the title of this article may allusively suggest, the history of Haitian literature is tied to the island's distinctive political status as the first Caribbean nation to gain its freedom from French colonial rule. According to historical accounts, it took more than thirteen years
of militant resistance and tactical warfare to defeat Napoleon's expeditionary force and proclaim its national independence on 1 January 1804. Names of militant resisters like Makandal, Daniel Boukman, Toussaint L'Ouverture, Jean-Jacques Dessalines, Henri Christophe are etched in the national
collective consciousness and figure prominently in Haitian cultural expressions. Once the 'pearl of the French Antilles' to now the third poorest nation of the planet, Haiti continues to struggle for its freedom and its dignity. 1 January 2004 will mark Haiti's bicentennial and it appears
befitting to revisit Haiti's past which fuelled and yielded a rich literary legacy. This article will focus more specifically on the wealth and breadth of literary writings and discourses that have shaped, influenced and enriched Caribbean narratives within a continuum of tradition and innovation.
Collectivisations: The Spanish Revolution Revisited, 193639
Authors: Bosch Aurora
Published: October 2006

This article analyses the agricultural revolution which took place in Spain during the Civil War focusing on Valencia, and attempting to highlight the important role played by the war in the formation and operation of collectives. According to this analysis the amount of land seized
and collectivised in Valencia was smaller than in other parts of Spain and there were few cases of libertarian communism or complete collectivisation, but their importance was increased due to the fact that they dealt in export crops, in particular oranges. It was in relation to the export
of oranges that the conflicts between individualists and collectivists, between the Communist party and the trade unions were greatest, and they were linked to the controversy surrounding war and revolution. In spite of these conflicts and the organisational deficiencies of collectivised agriculture,
the Valencian collectives were more successful than those in other parts of Spain and attempted to solve the conflict with the individualists and adapt to the needs of a war economy.
Book Reviews
Authors: Baia Manuel , Dunphy Richard , Newell James
Published: October 2006

Antnio Costa Pinto, The Blue Shirts: Portuguese fascists and the New State, Boulder: Social Science Monographs (2000), 271 pp. ISBN 0-88033-982-9 (cloth)

Joo de Pina Cabral and Antnia Pedroso de Lima (eds.), Elites: choice, leadership and succession, Oxford: Berg (2000).
ISBN 1-85973-399-9 (paper), 1-85973-394-8 (cloth)

Anna Bosco, Comunisti: trasformazioni di partito in Italia, Spagna e Portogallo, Bologna: Il Mulino (2000), 334 pp. ISBN 88-15-07900-9
Flocculation as a Treatment Method for Printing Ink Wastewater
Authors: Meteš Azra , Koprivanac Natalija , Glasnovic Antun
Published: October 2006

To find a suitable method for treating printing ink wastewater, the fundamental behavior and characteristics of two kinds of experimental flexographic printing ink wastewater were studied. The differences between the two prepared wastewaters were the use of different kinds of binders–resins and pigments and different solvent contents representative of real printing inks. Examination of the water quality characteristics of the simulated wastewaters confirmed that the wastewaters were too highly loaded with organic substances for discharge and were not biodegradable. The prepared wastewaters also showed some colloidal dispersion properties. Such properties were strongly affected by pH. As pH decreased, the negative electrical charge of the particles was neutralized, resulting in their aggregation. Therefore, the present study focused on optimizing flocculation processes to destabilize the dispersions. Inorganic electrolytes were found to be more efficient flocculants than the organic polyelectrolytes tested. Even when added in very small quantity, inorganic electrolytes caused extensive neutralization of particle charges and consequent floc formation. The optimum flocculant concentration was determined on the basis of electrokinetic (zeta) potential and turbidity measurements. Mixing intensity, expressed as the mean mixing velocity gradient (G), and time of mixing (t) were investigated, and the optimum Gt product (GtOPT 4.45 × 104) was determined using turbidity values of supernatant water and sedimentation velocity of obtained flocs as criteria for flocculation efficiency. Flocculation was shown to be a simple and efficient treatment from an economic and technical point of view. It was capable of removing a substantial portion of the organic content, completely removing color and turbidity.
IN VIVO FORMATION AND CATABOLISM OF [14C]HISTAMINE IN MOUSE BRAIN
Authors: Schayer R. W. , Reilly Margaret A.
Published: October 2006

Abstract— The formation of histamine in brain was studied in mice injected with l‐[14C]‐histidine (ring 2‐14C) intravenously (i.v.) or intracerebrally; [14C]histamine appeared rapidly and exhibited a rapid rate of turnover. Drugs known to block various pathways of histamine catabolism were tested for effects on brain–[14C]histamine and [14C]‐methyl‐histamine in mice given (1) [14C]histamine i.v., (2) [14C]histamine intracerebrally, and (3) l‐[14C]histidine i.v. Blood‐borne histamine did not enter brain; brain histamine was formed locally by decarboxylation of histidine Methylhistamine did cross the blood‐brain barrier. Methylation was the major route of histamine catabolism in mouse brain and some of the methylhistamine formed was destroyed by monoamine oxidase. No evidence for catabolism by the action of diamine oxidase was found.
OXIDATION AND PHOSPHORYLATION PROCESSES IN BRAIN MITOCHONDRIA OF RATS EXPOSED TO CARBON DISULPHIDE
Authors: Tarkowski S , Sobczak Hanna
Published: October 2006

Abstract— The effects of acute and long‐term exposure to CS2 on oxidation and phosphorylation processes in brain mitochondria of rats were studied. Although rats developed different symptoms of poisoning, depending on the type of exposure, the brain mitochondria of both groups of animals exhibited the same types of disturbances in oxidative phosphorylation. The main characteristic of these disturbances was the uncoupling of oxidative phosphorylation indicated by lower respiratory control indices due to stimulation of oxidation of respiratory substrates by mitochondria in the metabolic state 4. This effect was accompanied by a decreased P:O ratio and a lower ATP‐Pi exchange rate. An inhibitory effect of CS2 on the energy transfer processes is also suggested.

The observed changes in oxidative phosphorylation were more distinct in the case of acute poisoning, with a longer period of an uninterrupted exposure enabling a more complete tissue saturation with CS2, than in the case of long‐term exposure with shorter periods of intoxication within the day.
EFFECTS OF BACTRACHOTOXIN ON ELECTROPLAX Na+‐K+‐ATPase AND LEVELS OF ATP IN RAT MUSCLE1
Authors: Daly J. , Albuquerque E. X. , Kauffman F. C. , Oesch F.
Published: October 2006

—Batrachotoxin (BTX) in low concentrations (20 nm) depolarizes electrically excitable membranes (Albuquerque, Daly and Witkop, 1971). At these levels, BTX does not inhibit Na+‐K+‐ATPase. At much higher concentrations (60 μm) BTX partially inhibits Na+‐K+‐ATPase from electroplax of Electrophorus electricus. In contrast to inhibition by cardiac glycosides, the inhibition of Na+‐K+‐ATPase by batrachotoxin is not antagonized by KCl. BTX had no effect on ATP levels in stimulated nerve muscle preparations at the time when sustained contracture was initiated by the drug. Phosphocreatine levels were decreased and levels of glucose‐6‐phosphate and 6‐phosphogluconate were increased, while levels of fructose‐1,6‐diphosphate and α‐ketoglutarate were unchanged. It is concluded that the inhibition of Na+‐K+‐ATPase or lowering of ATP levels by BTX is not significantly involved in the membrane depolarization produced by the toxin.
REGULATION OF OXYGEN CONSUMPTION IN NEUROBLASTOMA CELLS: EFFECTS OF DIFFERENTIATION AND OF POTASSIUM
Authors: Nissen C. , Ciesielski‐Treska J. , Hertz L. , Mandel P.
Published: October 2006

Abstract— The rate of oxygen consumption has been measured micromanometrically in fresh mouse neuroblastoma cells and in corresponding cells cultivated with and without 20% calf serum known to suppress differentiation. Fresh cells and cells cultivated in the serum depleted medium showed a relatively intense respiration (0.5–1.0 × 10−5μl/h/cell), whereas the proliferating, cultivated cells had a low rate of oxygen uptake (0.2 × 10‐5μl/h/cell), provided they did not differentiate morphologically during the 4 h of measurement in the serum‐free diver medium. Both morphological and metabolic differentiation of such cells occurs rapidly but may be completely prevented by siliconization of the divers.

An increase of the potassium concentration in the medium to 50 mM had essentially no effect on cultivated, differentiated cells, but led to an abolishment of oxygen uptake by fresh cells. No stimulatory effect of potassium was observed.
NEURONAL AND GLIAL SYSTEMS FOR γ‐AMINOBUTYRIC ACID TRANSPORT
Authors: Sellstroum Å. , Hamberger A.
Published: October 2006

—The uptake of [2,3‐3H]γ‐aminobutyric acid (GABA) by bulk prepared neuronal perikarya, nerve endings and glial cells has been studied in an in vitro‐system. The uptake in the different fractions had a similar dependence for sodium, potassium and magnesium. Calcium stimulated the synaptosomal GABA uptake at concentrations which inhibited the glial uptake. Bicuculline strongly inhibited the uptake in all fractions. Picrotoxin and strychnine had little effect on the neuronal uptake whereas glial uptake was stimulated. l‐2,4‐di‐aminobutyric acid and chlorpromazine inhibited GABA uptake in all fractions. The effect of cyclic AMP was not significant.
PARTICIPATION OF DOPAMINE‐ AND SEROTONIN‐RECEPTORS IN THE DISAGGREGATION OF BRAIN POLYSOMES BY l‐DOPA AND l‐5‐HTP
Authors: Weiss B. F. , Liebschutz J. L. , Wurtman R. J. , Munro H. N.
Published: October 2006

Abstract— It has previously been shown that the disaggregation of brain polysomes and suppression of brain protein synthesis observed in rats given the amino acids l‐dopa or l‐5‐HTP is mediated by the decarboxylation products dopamine and serotonin. Present studies demonstrate that the poly‐some disaggregation is caused by the interactions of the monoamines with specific receptor sites. Thus, dopa‐induced disaggregation is blocked if rats are pretreated with haloperidol or pimozide (but not methysergide or cyproheptadine), while 5‐HTP‐induced disaggregation is blocked by methysergide or cyproheptadine (but not by haloperidol or pimozide).

Pretreatment of rats with MK‐486, a drug that inhibits dopa decarboxylase in blood vessels and peripheral tissues but not brain, does not block dopa‐induced brain polysome disaggregation; hence this disaggregation depends on the interaction of dopamine with receptors in the brain parenchyma. Brain polysomes are not disaggregated in rats given intraperitoneal apomorphine (or intracisternal dopamine). The disaggregation caused by dopa is not reduced in animals pretreated with sufficient intracisternal 6‐hydroxydopamine to cause major damage to catecholaminergic nerve terminals.
BIOCHEMICAL DEVELOPMENT OF RAT FOREBRAINS IN SEVERE PROTEIN AND ESSENTIAL FATTY ACID DEFICIENCIES
Authors: Karlssonand I. , Svennerholm L.
Published: October 2006

Abstract—

The effect of a low‐protein diet (6 calorie‐% protein) and a low essential fatty acid diet EFA (0.1 calorie‐% EFA) on the biochemical composition of the forebrain was compared with that of a control diet (16 calorie‐% protein and 3.0 calorie‐%: EFA). The low‐protein diet was fed from 1 week before mating, while the other two diets were fed for more than two generations before mating. Four litters of each dietary group were assayed at 10, 15, 21, 30 and 120 days of age but only one sample from several litters of newborns.

The forebrain growth was retarded between 10 and 15 days of age in the low‐protein group, but afterwards the growth was faster than in the control group. Also the low‐EFA group showed similar changes though less pronounced with retarded growth between 10 and 15 days of age. In the two deficiency groups the DNA content in the forebrain was reduced, but less than the weight. The gangliosides were used as a marker substance for neuronal membranes. In the low‐protein group the normally rapid accretion of gangliosides between 10 and 15 days of age was significantly retarded, but afterwards faster than in the control group. From 30 days of age the ganglioside concentration was significantly higher in the low‐protein group than in the control group. The low EFA diet resulted in similar but less pronounced changes than the low protein diet. The cerebroside content was lower in both the low‐protein and low EFA groups at all ages than in the control group indicating a lower myelin content. The cerebroside content differed more than any other parameter studied. The findings suggest that severe nutritional deficiencies only delay the development of the neuronal membranes but irreversibly reduce the formation of myelin.
STOP‐FLOW ANALYSIS OF THE AXONAL TRANSPORT OF DOPA DECARBOXYLASE (EC 4.1.1.26) IN RABBIT SCIATIC NERVES
Authors: Starkey Randall R. , Brimijoin Stephen
Published: October 2006

Abstract—

The axonal transport of DOPA‐decarboxylase (EC 4.1.1.26) was investigated in rabbit sciatic nerves by means of in vitro stop‐flow techniques. Enzyme activity accumulated just proximal to a region that was locally cooled to 5°C in nerves that were elsewhere incubated at 37°C. The accumulation of enzyme activity was linear with time and corresponded to an average orthograde transport velocity of 11 mm/day. Retrograde transport was not detected. When nerves that had been locally cooled for 3 h were rewarmed, the accumulated enzyme activity moved distally along them as a wave with a narrow range of velocities. The front of this wave traveled at a rate of about 150mm/day, and the mean velocity of the wave was about 120 mm/day. These values are much lower than those previously obtained for tyrosine hydroxylase (EC 1.14.16.2), dopamine‐β‐hydroxylase (EC 1.14.2.1) and norepinephrine in similarly designed experiments. Thus DOPA‐decarboxylase appeared to be transported at intermediate velocities, and, since the mean velocity of the moving fraction was about 11 times the average velocity, it is ljkely that only 9% of the enzyme was undergoing transport at any given moment.
STORAGE OF SEROTONIN AND SEROTONIN BINDING PROTEIN IN SYNAPTIC VESICLES
Authors: Tamir Hadassah , Gershon Michael D.
Published: October 2006

We have used the newly introduced method of DeLorenzo & Freedman (1978) for isolating synaptic vesicles to determine if such vesicles contain both serotonin (5‐HT) and serotonin binding protein (SBP). Two fractions were obtained. A 55, 000 g fraction was morphologically heterogeneous and contained coated vesicles. A 135, 0000 vesicle (dia. 51.3 nm) fraction was homogeneous in ultra‐structure and contained no coated vesicles. The specific activity of SBP in this fraction was much higher than that in the supernatant. Unlike SBP, very little lactic dehydrogenase activity appeared in the 135, 000 g fraction. Qualitative and quantitative differences were observed between the polypeptide profiles of soluble proteins extracted from the vesicles and supernatant proteins on SDS gels. Therefore, entrapment of cytosol in the vesicles of the 135, 000 g fraction was minimal. The 5‐HT concentration of the 135, 000 g vesicles was 5.5 ng/mg protein and in the supernatant, 11.3 ng/mg protein. The ATP concentration in the 135, 000 g vesicle fraction was only 0.8 ng/mg Pr. Rabbit spinal cords were transected in order to determine if SBP is moved proximo‐distally in axons by rapid axonal transport as would be predicted for a constituent of synaptic vesicles. SBP accumulated above the cut at a rate consistent with fast transport (78 mm/day). SBP activity fell caudal to the point of transection and there was no evidence, such as an accumulation below the lesion, that might indicate retrograde transport of SBP. These experiments indicate that SBP is probably synthesized in the cell bodies of serotonergic neurons and some is rapidly transported down axons to be stored in terminals in vesicles.
A Halothane‐Related Effect on Rat Brain Myelination: A Comparison of Chronic Prenatal or Postnatal Exposure
Authors: Patsalos P. N. , Rigor B. M. , Wiggins R. C.
Published: October 2006

Rats were exposed to 0.5% halothane in air for 8 h per day during the intervals (1) 5 days postconception to birth, (2) birth to 5 days postnatal age, or (3) birth to 10 days postnatal age. Controls were exposed to an equivalent flow of air. Prenatal exposure had no significant effect on body or brain weight and no subsequent effect on the relative synthesis of brain subcellular membranes. Five days of postnatal exposure caused a 10% reduction in body and brain weight and a 10% relative reduction in the synthesis of brain myelin. The effect persisted throughout the period of rapid postnatal brain myelination. Ten days of postnatal exposure produced equivalent, more severe effects on body and brain weights and a more severe effect on myelin synthesis. Postnatal exposure had no apparent effect on the relative synthesis of non‐myelin particulate proteins.
Indoleamine Metabolism in Rat Brain Studied Through Measurements of Tryptophan, 5‐Hydroxyindoleacetic Acid, and Indoleacetic Acid in Cerebrospinal Fluid
Authors: Young Simon N. , Anderson George M. , Purdy William C.
Published: October 2006

Tryptophan, 5‐hydroxyindoleacetic acid (5HIAA), and indoleacetic acid (IAA) were measured in rat cerebrospinal fluid (CSF) using high‐performance liquid chromatography with fluorometric detection in order to study brain indoleamine metabolism. Previously we have shown that IAA in CSF is derived from tryptamine in the CNS. In this study our results indicated that the synthesis of both 5‐hydroxytryptamine (5HT) and tryptamine varied with changes in brain tryptophan. After a tryptophan load, tryptamine synthesis increased much more than 5HT synthesis; under these circumstances, it can be of the same order of magnitude as 5HT synthesis. Studies with treatments that cause release of 5HT (reserpine and cold stress) indicated that tryptamine is not released with 5HT and is probably not stored in vesicles. Use of selective monoamine oxidase inhibitors suggested that results obtained in vitvo concerning the substrates for monoamine oxidase A and B apply in vivo. Thus, 5HT was acted on preferentially by the A enzyme, and tryptamine by the B enzyme. Measurement of IAA in brain, CSF, and plasma before and after probenecid indicated that there are active transport systems moving IAA from CSF and brain to blood, and from brain to CSF. Our data suggest that measurements of CSF IAA are a simple and convenient way of studying CNS tryptamine metabolism and should be applied clinically.
Purification and Preliminary Biochemical Characterisation of the Human and Rat Forms of the Central Nervous System‐Specific Molecule, F3‐87‐8
Authors: Lakin Kenneth H. , Allen A. K. , Fabre John W.
Published: October 2006

Abstract: The F3‐87‐8 monoclonal antibody recognises a phylogenetically conserved antigenic determinant found exclusively in the mammalian CNS. We used this monoclonal antibody as the major purification step for obtaining pure F3‐87‐8‐bearing molecules from rat and human brains for biochemical analysis. In both rat and man, the F3–87–8 molecule is a heavily glycosylated protein, consisting of 47.6 and 47.0% carbohydrate by weight, respectively. In both species, it occurs as a doublet on polyacrylamide gel electrophoresis in sodium dodecyl sulphate, the Mr of the human form being 130,000 and 100,000. In the rat, the Mr of the doublet is slightly but consistently lower than in man, and the higher‐Mr band is more pronounced. The amino acid composition of the rat and human forms is virtually identical, with a high content of serine and threonine. Significant differences are seen in carbohydrate composition, the rat form containing more sialic acid and neutral sugar and less hexosamine than the human form. β‐Elimination studies, in conjunction with carbohydrate analysis, suggest the presence of approximately 40 O‐linked and 10–15 N‐linked oligosaccharides per polypeptide chain of 500 amino acids, the N‐linked chains predominantly of the high‐mannose type. This makes it likely that the molecule adopts an extended rather than a coiled conformation on the membrane.
L‐[3H]Glutamate Binding to Hippocampal Synaptic Membranes: Two Binding Sites Discriminated by Their Differing Affinities for Quisqualate
Authors: Werling Linda L. , Doman Kathleen A. , Nadler J. Victor
Published: October 2006

Abstract: The excitatory glutamate analogs quisqualate and ibotenate were employed to distinguish multiple binding sites for l‐[3H]glutamate on freshly prepared hippocampal synaptic membranes. The fraction of bound radioligand that was displaceable by 5 μM quisqualate was termed GLU A binding. That which persisted in the presence of 5 μM quisqualate, but was displaceable by 100 μM ibotenate, was termed GLU B binding. GLU A binding equilibrated within 5 min and remained unchanged for up to 80 min. GLU B binding appeared to equilibrate at least as rapidly, but incubation with ligand unmasked latent binding sites. Saturation binding curves were best fitted by single exponentials, which yielded Kd values of about 200 nM (GLU A) and 1 μM (GLU B). On the average, GLU B binding sites were about twice as abundant in these membranes as were GLU A sites. Rapid freezing of the membranes, followed by storage at ‐26°C and rapid thawing markedly diminished GLU A binding, but nearly tripled GLU B binding. Both sites bound l‐glutamate with 10–30 times the affinity of d‐glutamate. The GLU A site also bound l‐glutamate with about 10 times the affinity of l‐aspartate and discriminated poorly between l‐ and d‐aspartate. In contrast, the GLU B site bound l‐aspartate with an affinity similar to that for l‐glutamate, and with an order‐of‐magnitude greater affinity than d‐aspartate. The structural specificities of the GLU A and GLU B binding sites suggest that these sites may correspond to receptors on hippocampal pyramidal cell dendrites that are activated by iontophoretically applied l‐glutamate.
Dopamine Uptake by Rat Striatal Synaptosomes: A Compartmental Analysis
Authors: Schoemaker Hans , Nickolson Victor J.
Published: October 2006

Abstract: Dopamine (DA) uptake into synaptosomes from rat corpus striatum was studied in the presence of a monoamine oxidase (MAO) inhibitor and dithiothreitol, by means of a filtration technique. Under these conditions a steady state develops rapidly in which the synaptosomal DA content remains constant while the continuing DA uptake is counterbalanced by DA efflux from the synaptosome. Exchange of synaptosomal [3H]DA and [14C]DA was measured under these conditions. In timecourse experiments it was found that exchange could be described significantly better by a three‐compartment model than by a two‐compartment model. However, if synaptosomes from reserpine‐pretreated animals were used, analysis according to a three‐compartment model did not result in a significantly better fit compared with a two‐compartment model. Subsequently, kinetic transfer parameters describing DA fluxes between compartments at different DA concentrations were calculated from the fitted exchange curves. A Michaelis‐Menten kinetic analysis indicated that only the in‐series three‐compartment configuration, in which DA is taken up from the medium into one synaptosomal compartment, from which it can subsequently be transferred to a second compartment without direct access to the medium, gave kinetically acceptable results. Transfer parameters in synaptosomes from reserpine‐treated rats were comparable to those parameters describing DA transport between the medium and the first intrasynaptosomal compartment as measured under control conditions. Morover, it was found that potassium depolarization of synaptosomes resulted in a release of DA in a quantity similar to that found in the second intrasynaptosomal compartment. It is suggested that the two intrasynaptosomal compartments found correspond to a cytoplasmatic and vesicular DA pool, respectively. The functional significance of these findings is discussed in terms of the regulation of DA levels within the nerve terminal.
Comparison of the Effects of a Convulsant Barbiturate on the Release of Endogenous and Radiolabeled Amino Acids from Slices of Mouse Hippocampus
Authors: Holtman Joseph R. , Richter Judith A.
Published: October 2006

Abstract: The convulsant barbiturate 5‐(2‐cyclohexylidene‐ethyl)‐5‐ethyl barbituric acid (CHEB) stimulates the spontaneous release of endogenous and radiolabeled acetylcholine (ACh) from mouse hippocampal slices in vitro. In order to determine if the ability of CHEB to release ACh was unique to this neurotransmitter, we have studied the action of this drug in vitro on the release of both radiolabeled and endogenous putative neurotransmitter and non‐transmitter amino acids in the hippocampus. Although CHEB stimulated the spontaneous release of both [3H] γ‐n‐aminobutyric acid (GABA) and endogenous GABA, CHEB had different effects on the spontaneous release of radiolabeled and endogenous l‐glutamate and l‐aspartate: l‐[3H]glutamate release was inhibited by CHEB, but endogenous l‐glutamate release was unaffected by the drug; l‐[3H]aspartate release was not affected by CHEB, but endogenous l‐aspartate release was stimulated. The spontaneous release of the amino acids l‐alanine and glycine (not thought to be neurotransmitters in the hippocampus) was not affected by CHEB. The results of this study indicate that CHEB does not always stimulate the release of all putative neurotransmitters. The ability of this drug to release ACh, GABA, and l‐aspartate may be the result of some specific interaction of CHEB with nerves using these neurotransmitters in the hippocampus. In addition, the results suggest some problems that may be encountered when radiolabeled substances are used to study neurotransmitter release.
Glycine Release from Y79 Retinoblastoma Cells
Authors: Yorek Mark A. , Spector Arthur A.
Published: October 2006

Abstract: Glycine release, induced by a high concentration of potassium chloride (K+), was investigated in cultured human Y79 retinoblastoma cells. The cells were labeled by incubation with [2‐3H]glycine prior to K+ depolarization. Depolarization with 55 mM K+ caused an immediate, Ca2+‐dependent release of approximately 20% of the cellular radiolabeled glycine content. Chemical analysis of the intracellular free glycine content also showed that approximately 20%, 2.4 nmol/mg protein, was released after K+ depolarization. Glycine release from labeled Y79 cells was not stimulated by incubation with 55 mM choline chloride. Based on measurements with an amino acid analyzer, it is concluded that of the free amino acids contained in the Y79 cell, only glycine is specifically released into the extracellular fluid by K+ depolarization. Although the intracellular content of serine and glutamate decreased, these amino acids were not released from the cells. Further studies with [U‐14C]serine suggest that serine is converted into glycine in Y79 cells. Veratridine also caused an immediate release of [2‐3H]glycine from the cells, and this was blocked by tetrodotoxin. This suggests that the Y79 cells possess voltage‐dependent Na+ channels. These results indicate that K + ‐ and veratridine‐stimulated glycine release occurs in Y79 retinoblastoma cells, providing additional evidence that this continuously cultured line may be a useful model for certain human retinal and central nervous system functions.
Role of Calmodulin in the Effect of Guanyl Nucleotides on Rat Hippocampal Adenylate Cyclase: Involvement of Adenosine and Opiates
Authors: Girardot Jean‐Marie , Kempf Jules , Cooper Dermot M. F.
Published: October 2006

Abstract: The adenylate cyclase activity of rat hippocampal plasma membranes can be stimulated by vaso‐active intestinal polypeptide (VIP). Low concentrations (10−9 to 10−7M) of 5′‐guanylyl‐imido diphosphate (GppNHp) evoke a transient inhibition of the enzyme, which is followed by stimulation with increasing GppNHp concentrations (10−6 to 10−4M). Inclusion of ethyleneglycol ‐ bis ‐ (β ‐ aminoethylether) ‐ N,N′ ‐ tetraacetic acid (EGTA) during incubation abolishes the GppNHp inhibition while preserving GppNHp activation. The stimulation induced by GppNHp is amplified by VIP, but the inhibition is unaffected. Adenosine analogs and opiates are inhibitory ligands in the presence of GTP, and their effects can be reversed by the appropiate receptor antagonists, 3‐isobutyl‐1‐methylxanthine and naloxone. Treatment of membranes with trypsin abolishes the GppNHp‐induced inhibition without affecting the GppNHp stimulation. The inhibition induced by GppNHp is also abolished by EGTA treatment followed by washing, which coincides wtih a reduction in the adenosine‐ and opiate‐mediated, GTP‐dependent inhibition. The GppNHp inhibition can be restored in EGTA‐treated but not in trypsin‐treated membranes by addition of calcium‐calmodulin but not by Ca2+ or Mg2+. Calcium‐calmodulindepleted membranes lack calcium stimulation as well as GppNHp‐induced inhibition, whereas untreated membranes and calcium‐calmodulin‐depleted membranes plus exogenous calcium‐calmodulin showed calcium stimulation and GppNHp inhibition. These results suggest that calmodulin is involved in both Ca2+ stimulation and guanine nucleotide‐mediated inhibition of rat hippocampal adenylate cyclase.
Distribution of Free and Conjugated Dopamine in Human Caudate Nucleus, Hypothalamus, and Kidney
Authors: Elchisak Mary Ann
Published: October 2006

Abstract: The occurrence of free and conjugated dopamine was determined by HPLC in human caudate nucleus, hypothalamus, and kidney. Free norepinephrine and dihydroxyphenylacetic acid levels in some tissues were also determined. Conjugated dopamine was found to account for 25% of the total DA in the kidney. Conjugated DA accounted for 2.9% and 5.1% of the total DA in the caudate nucleus and hypothalamus, respectively. These results indicate that conjugated dopamine is not homogenously distributed in human tissue.
Effects of Phospholipases on the Kinetic Properties of Rat Striatal Membrane‐Bound Tyrosine Hydroxylase
Authors: Kuczenski Ronald
Published: October 2006

Abstract: Rat striatal tyrosine hydroxylase can be isolated in both a soluble and a synaptic membrane‐bound form. The membrane‐bound enzyme, which exhibits lower Kms for both tyrosine (7 μM) and reduced pterin cofactor (110 μM) relative to the soluble enzyme (47 μM and 940 μM, respectively), can be released from the membrane fraction with mild detergent, and concomitantly its kinetic properties revert to those of the soluble enzyme. Treatment of membrane‐bound tyrosine hydroxylase with C.perfringens phospholipase C increased the Km of the enzyme for tyrosine to 27 μM and the Vmax by 60% without changing the Km for cofactor. In contrast, treatment of membrane‐bound tyrosine hydroxylase with V. russelli phospholipase A2 increased the Km for tyrosine to 48 μM increased the Vmax and increased the Km for cofactor to 560 μM. The enzyme remained bound to the membrane fraction following both phospholipase treatments. Addition of phospholipids to treated enzyme could partially reverse the effects of phospholipase A2 treatment, but not the effects of phospholipase C treatment. The kinetic properties of phospholipase‐treated, detergent‐solubilized tyrosine hydroxylase were identical to those of the control solubilized enzyme. Tyrosine hydroxylase appears to interact with synaptic membrane components to produce at least two separately determined consequences for the kinetic properties of the enzyme.
Characterization of an Adenylate Cyclase‐Linked Serotonin (5‐HT1) Receptor in a Neuroblastoma × Brain Explant Hybrid Cell Line (NCB‐20)
Authors: Berry‐Kravis Elizabeth , Dawson Glyn
Published: October 2006

Clonal cell line NCB‐20 (a hybrid of mouse neuroblastoma N18TG2 and Chinese hamster 18‐day embryonic brain expiant) expressed both high‐ (KD 180 nM) and low‐affinity (>3000 nM) binding sites for [3H]serotonin (5‐HT) which were absent from the parent neuroblastoma. The low‐affinity binding site was eliminated by 1 μM spiperone. The order of drug potency for inhibition of high‐affinity [3H]5‐HT binding was consistent with a 5‐HT1 receptor (5,6 ‐ dihydroxytryptamine = 5‐HT = methysergide = 5‐methoxytryptamine > cyproheptadine = clozapine = mianserin > spiperone > dopamine = morphine = ketanserin = norepinephrine). [3H]5‐HT binding was inhibited by guanine nucleotides (e.g., GTP and Gpp(NH)p), whereas antagonist binding was not; as‐corbate was also inhibitory. A 30‐min exposure of cells to 1—2 μM 5‐HT or other agonists produced a three‐ to fivefold stimulation of cyclic AMP levels. The order of potency for 5‐HT agonist stimulation of basal cyclic AMP levels and 5‐HT antagonist reversal of agonist‐stimulated levels was the same as the order of drug potency for inhibition of high‐affinity [3H]5‐HT binding, suggesting linkage of the 5‐HT1 receptor to adenylate cyclase in NCB‐20 cells.
Inhibition of Calcium Uptake, Sodium Uptake, and Catecholamine Secretion by Methoxyverapamil (D600) in Primary Cultures of Adrenal Medulla Cells
Authors: Corcoran James J. , Kirshner Norman
Published: October 2006

The calcium‐entry antagonist D600 (methoxyverapamil) inhibited nicotine‐ and veratridine‐induced ‐45Ca‐4 uptake, 22Na+ uptake, and catecholamine secretion in primary cultures of bovine adrenal medulla cells. Inhibition of nicotine‐induced effects occurred at D600 concentrations approximately 3‐10‐fold lower than those needed to produce similar inhibition of veratridine‐induced effects. Inhibition of the veratridine‐induced effects was competitive, but inhibition of the nicotine‐induced effects was not competitive. These re‐sults suggest that D600, in addition to blocking “slow” Ca‐ channels and tetrodotoxin‐sensitive Na+ channels also blocks nicotine transmission, possibly either by noncompetitively inhibiting the interaction of nicotine with the receptor binding site or by blockade of the receptor‐associated ion conductance channel.