bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends in Australian Defence Policy
Authors: Millar T. B.
Published: April 2011

For the past thirty years, events in Southeast Asia have substantially shaped Australian defence policy. Japan became an imminent threat only when it moved into Indo-China, Malaya, and the Netherlands East Indies. As a result Australians became understandably alarmed, and concentrated their defence programme on this situation rather than events in Europe, the Middle East, or even South Asia. Since World War II, a sense of continuing threat or potential threat from Asia has prompted the raising and maintaining of a regular, standing army, units of which have been deployed almost continuously since 1950 on the Asian mainland – in Korea, Malaya, Singapore and South Vietnam, as well as in northern Borneo. As this is being written, there are still Some 8,000 Australian servicemen in the Vietnam theatre, and nearly 3,000 in Malaysia and Singapore.
Land and Economy in Traditional Vietnam
Authors: Adams John , Hancock Nancy
Published: April 2011

When the French assumed effective political control of Vietnam in the late nineteenth century they were confronted with the dual problem of raising revenues and securing administrative control of the countryside. In seeking a solution they were forced to consider Vietnamese land tenures and the distribution of agricultural output prevailing at that time. Their early moves reflected a sharp bias in favour of French law and almost total ignorance of the wide divergence between their system of property and taxation and Vietnamese custom and procedure. On a broad scale what was involved was an attempt to reinterpret indigenous practices to achieve compatibility with the French conception of private and public property categories and the legitimate rights and claims inherent in each. Le Code Annamite was translated by P.L.F. Philastre and gradually Vietnamese property laws were drawn towards conformity with French practices.
Copulatory system of the spider crab Libinia spinosa (Crustacea: Brachyura: Majoidea)
Authors: Sal Moyano M.P. , Gavio M.A. , Cuartas E.I.
Published: April 2011

Functional morphology of the male gonopods, female holding systems and vulvae of Libinia spinosa are described using scanning electron microscopy and histological sections, establishing differences between immature and mature individuals. The first gonopod of mature males, larger than 35.1 mm of carapace width (CW), is long, slender, and ending in two wing-like processes; abdominal, characterized by the presence of a sub-terminal seminal canal, and sternal, closed and where the cuticle holds setae. In immature males, smaller than 29.9 mm CW, both processes are shorter, and the tip of the abdominal process closed. Six different types of setae are described for both gonopods. Internally, the gonopods have rosette glands in immature and mature individuals. The presence of secretions, which may be involved in the moulting process, was observed in immature males towards the external cuticle corresponding to the rosette glands. The rosette glands may be related to reproduction in mature males. Females presented a press-button holding system and a biconcave vulva. In immature females, smaller than 36.1 mm CW, the vulva aperture was closed by integument bulging to the outside. In mature females, larger than 42.6 mm CW, the locking system was almost fused to the cuticle, and the vulvae showed an open biconcave form with a more inner flexible membrane. Morphological characteristics shown by the gonopods of mature males develop synchronously with the acquisition of physiological maturity, not with morphometrical maturity. The mature holding systems and vulvae of females are developed synchronously with physiological and morphometrical maturity.
Pacifigorgia marviva(Anthozoa: Octocorallia) a new species from Coiba National Park, Pacific Panama
Authors: Guzman Hector M. , Breedy Odalisca
Published: April 2011

Pacifigorgia marviva, a new shallow-water species of the family Gorgoniidae, was found in Coiba National Park, Pacific Panama at 35–40 m depth. It is characterized by having white to cream, small, erect colonies composed of 1–4 fronds, stems short or absent network irregular and open without fan midribs, and polyp mounds slightly raised and sparsely distributed. All sclerites are colourless. Coenenchymal sclerites mostly composed of long spindles reaching up to 0.25 mm in length, and long and thin anthocodial rods, up to 0.16 mm in length. Morphological characters are analysed and illustrated. Scanning electron microscopy was used for sclerite study. The new species is herein described and compared with other similar species reported from the eastern Pacific.Pacifigoria marvivaincreases the number ofPacifigorgiaspecies to 35; 20 in Panama representing 57% of the genus in the eastern Pacific, followed by Costa Rica and Ecuador with 14 and 10 species, respectively.
Development of morphological awareness and vocabulary knowledge in Spanish-speaking language minority learners: A parallel process latent growth curve model
Authors: KIEFFER MICHAEL J. , LESAUX NONIE K.
Published: April 2011

Despite acknowledgement of the limited English vocabularies demonstrated by many language minority (LM) learners, few studies have identified skills that relate to variation in vocabulary growth in this population. This study investigated the concurrent development of morphological awareness (i.e., students’ understanding of complex words as combinations of meaningful smaller units) and vocabulary for LM learners in early adolescence. A cohort of Spanish-speaking LM learners (n = 90) was followed from fourth through seventh grade and assessed annually. Latent growth modeling results indicated a strong relationship between rates of growth in the two skills, such that learners with rapid growth in derivational morphological awareness also demonstrated rapid growth in vocabulary. Despite positive vocabulary growth during this period, the learners remained far below national norms. Findings highlight the need for language-focused instructional intervention for this population and suggest that morphological awareness may be a promising point of leverage for such instruction.
Revival of an old problem: an increase inSalmonella entericaserovar Typhimurium definitive phage type 8 infections in 2010 in England and Northern Ireland linked to duck eggs
Authors: NOBLE D. J. , LANE C. , LITTLE C. L. , DAVIES R. , PINNA E. De , LARKIN L. , MORGAN D.
Published: April 2011

Salmonella entericaserovar Typhimurium definitive phage type (DT) 8 is uncommon in humans in the UK. In July 2010, the Health Protection Agency reported an excess isolation rate of pan-susceptibleS. Typhimurium DT8 in England and Northern Ireland. By the end of October, this amounted to 81 laboratory-confirmed human cases for all regions of England and Northern Ireland in 2010, an increase of 26% and 41% on 2009 and 2008, respectively. Descriptive epidemiological investigation found a strong association with infection and consumption of duck eggs. Duck eggs contaminated withS. Typhimurium DT8 were collected from a patient's home and also at farms in the duck-egg supply chain. Although duck eggs form a small part of total UK eggs sales, there has been significant growth in sales in recent years. This is the first known outbreak of salmonellosis linked to duck eggs in the UK since 1949 and highlighted the impact of a changing food source and market on the re-emergence of salmonellosis linked to duck eggs. Control measures by the duck-egg industry should be improved along with a continued need to remind the public and commercial caterers of the potential high risks of contracting salmonellosis from duck eggs.
Many Random Walks Are Faster Than One
Authors: ALON NOGA , AVIN CHEN , KOUCKÝ MICHAL , KOZMA GADY , LOTKER ZVI , TUTTLE MARK R.
Published: April 2011

We pose a new and intriguing question motivated by distributed computing regarding random walks on graphs: How long does it take for several independent random walks, starting from the same vertex, to cover an entire graph? We study thecover time– the expected time required to visit every node in a graph at least once – and we show that for a large collection of interesting graphs, running many random walks in parallel yields a speed-up in the cover time that is linear in the number of parallel walks. We demonstrate that an exponential speed-up is sometimes possible, but that some natural graphs allow only a logarithmic speed-up. A problem related to ours (in which the walks start from some probabilistic distribution on vertices) was previously studied in the context of space efficient algorithms for undirecteds–tconnectivity and our results yield, in certain cases, an improvement upon some of the earlier bounds.
Effects of chemically defined medium on early development of porcine embryos derived from parthenogenetic activation and cloning
Authors: Cao Zubing , Sui Liucai , Li Yunsheng , Ji Suofei , Zhang Xiaorong , Zhang Yunhai
Published: April 2011

The present study was to investigate if a completely chemically defined medium (PZM-4) could support the early development of porcine embryos derived from parthenogenetic activation (PA) and cloning (somatic cell nuclear transfer, SCNT), and to lay the foundation for determining the physiological roles of certain supplements in this medium. Porcine embryos derived from PA and SCNT were cultured in media: PZM-3 (a chemically semi-defined medium), PZM-4 (a fully defined medium), and PZM-5 (an undefined medium). Early embryo development was observed. We found that the three medium groups (PZM-3, PZM-4 and PZM-5) exhibited no significant differences in cleavage rates of PA embryos (p > 0.05), while the blastocyst rate in PZM-3 was significantly higher than in PZM-4 and PZM-5 (78.9% vs. 36.0% and 52.3%) (p < 0.05). Moreover, total cell number per blastocyst in PZM-3 was clearly higher than in PZM-5 but similar to that in PZM-4. As for SCNT embryos, no significant differences were observed for the cleavage rates or the blastocyst rates among the three groups (p > 0.05). However, total cell number per blastocyst in PZM-3 was notably higher than in PZM-5, but was similar to that in PZM-4. In conclusion, our results suggested that the completely chemically defined medium PZM-4 can be used to efficiently support the early development of porcine PA and SCNT embryos.
Early childhood bilingualism leads to advances in executive attention: Dissociating culture and language
Authors: YANG SUJIN , YANG HWAJIN , LUST BARBARA
Published: April 2011

This study investigated whether early especially efficient utilization of executive functioning in young bilinguals would transcend potential cultural benefits. To dissociate potential cultural effects from bilingualism, four-year-old U.S. Korean–English bilingual children were compared to three monolingual groups – English and Korean monolinguals in the U.S.A. and another Korean monolingual group, in Korea. Overall, bilinguals were most accurate and fastest among all groups. The bilingual advantage was stronger than that of culture in the speed of attention processing, inverse processing efficiency independent of possible speed-accuracy trade-offs, and the network of executive control for conflict resolution. A culture advantage favoring Korean monolinguals from Korea was found in accuracy but at the cost of longer response times.
Lexical development in Mandarin–English bilingual children
Authors: SHENG LI , LU YING , KAN PUI FONG
Published: April 2011

Two groups of Mandarin–English bilingual children (3–5-year-olds, 6–8-year-olds) participated in a picture identification task and a picture naming task in both languages. Results revealed age-related growth in English, but not Mandarin vocabulary. Composite vocabulary was larger than either single-language vocabulary in the younger children but was similar to English vocabulary in the older children. Furthermore, children showed a larger receptive–expressive modality difference in their weaker language (Mandarin) than in their stronger language (English). These patterns indicate rapid growth in English vocabulary along with early stabilization of Mandarin vocabulary despite considerable Mandarin input in the home setting.
A tool for empirical forecasting of major flares, coronal mass ejections, and solar particle events from a proxy of active‐region free magnetic energy
Authors: Falconer David , Barghouty Abdulnasser F. , Khazanov Igor , Moore Ron
Published: April 2011

This paper describes a new forecasting tool developed for and currently being tested by NASA's Space Radiation Analysis Group (SRAG) at Johnson Space Center, which is responsible for the monitoring and forecasting of radiation exposure levels of astronauts. The new software tool is designed for the empirical forecasting of M‐ and X‐class flares, coronal mass ejections, and solar energetic particle events. For each type of event, the algorithm is based on the empirical relationship between the event rate and a proxy of the active region's free magnetic energy. Each empirical relationship is determined from a data set of ∼40,000 active‐region magnetograms from ∼1300 active regions observed by SOHO/Michelson Doppler Imager (MDI) that have known histories of flare, coronal mass ejection, and solar energetic particle event production. The new tool automatically extracts each strong‐field magnetic area from an MDI full‐disk magnetogram, identifies each as a NOAA active region, and measures the proxy of the active region's free magnetic energy from the extracted magnetogram. For each active region, the empirical relationship is then used to convert the free‐magnetic‐energy proxy into an expected event rate. The expected event rate in turn can be readily converted into the probability that the active region will produce such an event in a given forward time window. Descriptions of the data sets, algorithm, and software in addition to sample applications and a validation test are presented. Further development and transition of the new tool in anticipation of SDO/HMI are briefly discussed.
Acoustic and mechanical properties of Nankai accretionary prism core samples
Authors: Raimbourg Hugues , Hamano Yozo , Saito Saneatsu , Kinoshita Masataka , Kopf Achim
Published: April 2011

We studied undeformed sediment and accreted strata recently recovered by Ocean Drilling Program/Integrated Ocean Drilling Program (ODP/IODP) drilling in Nankai Trough convergent margin to unravel the changes in physical properties from initial deposition to incipient deformation. We have derived acoustic (Vp) and mechanical (uniaxial poroelastic compliance, compaction amplitude) properties of samples from various drill sites along the Muroto (ODP 1173) and Kii transects (IODP C0001, C0002, C0006, and C0007) from isotropic loading tests where confining and pore pressure were independently applied. We quantified the dependence of Vp on both effective (Peff) and confining (Pc) pressure, which can be used to correct atmospheric pressure measurements of Vp. Experimental Vp obtained on core samples extrapolated to in situ conditions are slightly higher than logging‐derived velocities, which can be attributed either to velocity dispersion or to the effect of large‐scale faults and weak zones on waves with longer wavelength. In the high‐porosity (30%–60%) tested sediments, velocities are controlled at first order by porosity and not by lithology, which is in agreement with our static measurements of drained framework incompressibility, much smaller than fluid incompressibility. Rather than framework incompressibility, shear modulus is probably the second‐order control on Vp, accounting for most of the difference between actual Vp and the prediction by Wood's (1941) suspension model. We also quantified the mechanical state of Nankai samples in terms of anisotropy, diagenesis, and consolidation. Both acoustic and mechanical parameters reveal similar values in vertical and horizontal directions, attesting to the very low anisotropy of the tested material. When considering the porous samples of the Upper Shikoku Basin sediments (Site 1173) as examples of diagenetically cemented material, several mechanical and acoustic attributes appeared as reliable experimental indicators of the presence of intergrain cementation. We also detected incipient cementation in samples from IODP Site C0001 (accretionary prism unit). In terms of consolidation, we distinguished two classes of material response (shallow, deformable samples and deep, hardly deformable ones) based on the amount of compaction upon application of a Peff large with respect to the inferred in situ value, with a transition that might be related to a critical porosity.
Sharing Experiences on Underground Storage and Disposal in the Energy Sector
Authors: Chapman Neil , West Julia , Bruno Jordi
Published: April 2011

Carbon Capture and Storage: Can Anything Be Learned From 35 Years Experience in Geological Disposal of Radioactive Wastes?; Meiringen, Switzerland, 26–29 October 2010; Safely sequestering by‐products that are hazardous to the environment deep underground is an objective shared by different energy generation systems. There are analogies between different applications in many aspects of their science, technology, strategy, and implementation. However, bringing specialists together to discuss common issues has proved more difficult than people might think. This is nowhere truer than in the separate fields of carbon capture and storage (CCS) and geological disposal of radioactive wastes (RWD), where years of caution have either kept practitioners apart or led to an effective partitioning of their work. To many specialists, especially those in the hydrocarbons industry, which will be a key player in commercial CCS, there is no benefit perceived in relating what is seen as a benign technology that is to be deployed for the global good to a technology associated with a nuclear industry that has had an unremittingly rough ride for most of the past 25 years.
Priority Planetary Science Missions Identified
Authors: Showstack Randy
Published: April 2011

The U.S. National Research Council's (NRC) planetary science decadal survey report, released on 7 March, lays out a grand vision for priority planetary science missions for 2013–2022 within a tightly constrained fiscal environment. The cost‐conscious report, issued by NRC's Committee on the Planetary Science Decadal Survey, identifies high‐priority flagship missions, recommends a number of potential midsized missions, and indicates support for some smaller missions. The report states that the highest‐priority flagship mission for the decade is the Mars Astrobiology Explorer‐Cacher (MAX‐C)—the first of three components of a NASA/European Space Agency Mars sample return campaign—provided that the mission scope can be reduced so that MAX‐C costs no more than $2.5 billion. The currently estimated mission cost of $3.5 billion “would take up a disproportionate near‐term share of the overall budget for NASA's Planetary Science Division,” the report notes.
First Spacecraft Orbit of Mercury
Authors: Showstack Randy
Published: April 2011

After a 7.9‐billion‐kilometer flight since its launch on 3 August 2004—which included flybys of Earth, Venus, and Mercury—NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft entered a planned, highly elliptical orbit around the closest planet to our Sun on 17 March. Engineers in the mission operations center at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) in Laurel, Md., which manages the mission for NASA, received radiometric signals indicating a successful orbit insertion at 9:10 P.M. local time. “Tonight we will have orbited the fifth planet in the solar system. This is a major accomplishment,” Ed Weiler, NASA assistant administrator for the Science Mission Directorate, said at a 17 March public forum at JHU/APL, noting that spacecraft have previously entered orbit around several other planets. “You only go into orbit for the first time around Mercury once in human history, and that is what was accomplished tonight.”
Influence of Nitrous Oxide on Local Cerebral Blood Flow in Awake, Minimally Restrained Rats
Authors: Dahlgren Nils , Ingvar Martin , Yokoyama Hideo , Siesjö Bo K.
Published: April 2011

In order to evaluate the effect of 70–80% N2O on local cerebral blood flow (l-CBF) in the rat brain, we developed a procedure for measuring CBF by an autoradiographic [14C]iodoantipyrine technique in awake, minimally restrained animals. Results on l-CBF, as measured in 22 different structures, showed little variability between animals. In the majority of structures analyzed, 70–80% N2O failed to alter l-CBF. These included all cerebral cortical and most subcortical structures. However, nitrous oxide reduced CBF in the the inferior colliculus and the superior olive, in two of the limbic structures analyzed, and in the hypothalamus. In no structure, except the striatum ( p < 0.05), was a significant increase in l-CBF obtained in N2O-breathing animals. However, the results suggest that CBF may have been increased in the auditory cortex. Immobilization was found to reduce l-CBF in the cerebellum, inferior colliculus, superior olive, hippocampus, and septal nuclei. The results also suggest that the procedure somewhat increased CBF in frontal and parietal cortex. When the results obtained in awake, air-breathing animals were compared with those obtained in immobilized animals ventilated on N2O, there was no significant increase in any of the structures analyzed, although there were suggested increases in all cortical areas except the visual cortex. However, the data showed that ventilation with 70–80% N2O significantly decreased CBF in several structures (inferior colliculus, superior olive, hippocampus, amygdala, septal nuceli, and hypothalamus). In some of these, the effects of 70–80% N2O and of immobilization were obviously additive.
Cerebral Circulation and Histamine: 2. Responses of Pial Veins and Arterioles to Receptor Agonists
Authors: Gross Paul M. , Harper A. Murray , Teasdale Graham M.
Published: April 2011

H2-receptors predominantly mediate pial arteriolar dilatation in response to histamine, but the reaction of pial veins to histamine has not been clearly identified. In anesthetized cats, we examined responses of pial veins and arterioles to perivascular microapplication of histamine and specific histamine H1 and H2 receptor agonists. Arterioles were very sensitive to the H2-receptor agonist impromidine, with significant dilatation (+16%) occurring at concentrations as low as 10−10 m. Arteriolar responses to H1 receptor stimulation by 2,2-pyridylethylamine were small, even at high concentrations. The order of potency and maximum dilatations found for the receptor agonists were: H2 (43%) > histamine (28%) > H1 (17%). By contrast, pial veins did not respond to histamine or the receptor agonists. The results indicate that pial venomotor activity to histamine is negligible, and suggest a sparse distribution of histamine receptors on the outer surfaces of pial veins.
Perivascular Substance P: Occurrence and Distribution in Mammalian Pial Vessels
Authors: Uddman R. , Edvinsson L. , Owman C. , Sundler F.
Published: April 2011

Nerve fibres containing immunoreactive substance P (SP) were demonstrated in the wall of cerebral blood vessels of several mammalian species. Pial arteries of cat and guinea-pig were richly supplied with SP nerve fibres, while those of rat, rabbit, pig, and man had a moderate number. SP fibres were more numerous in pial vessels belonging to the rostral parts of the circle of Willis as compared to more caudally located blood vessels. In cat and guinea-pig, blood vessels in the choroid plexus were surrounded by few SP nerve fibres; also spinal cord blood vessels of cat contained few such fibres.
Canine Cerebral Metabolism and Blood Flow during Hypoxemia and Normoxic Recovery from Hypoxemia
Authors: Artru Alan A. , Michenfelder John D.
Published: April 2011

There are conflicting reports regarding the effects of hypoxemia on the cerebral metabolic rate for oxygen (CMRO2). Accordingly, we examined the changes in CMRO2 during normoxia, progressive hypoxia (PaO2 of 37, 27, and 23 mm Hg), and normoxic recovery from hypoxia, Measurements were made in dogs anesthetized with nitrous oxide (60–70%) and halothane (<0.1%) in oxygen. Arterial-cerebral venous blood oxygen content differences and cerebral blood flow (CBF) were measured simultaneously, the latter by a technique (collection of sagittal sinus outflow) previously validated for conditions of near-maximal CBF, The duration of each of the three hypoxic exposures was approximately 10 min. CMRO2 was significantly decreased (14%) only when the arterial blood oxygen tension was reduced to 23 mm Hg. CBF increased progressively to a maximum of 153% of control. Posthypoxemic brain biopsy values for cerebral metabolites obtained 40 min after normoxemia had been restored were normal. These results, in conjunction with an unchanged CMRO2 at 40 min normoxic recovery, suggest that no gross irreversible brain cell damage occurred. We conclude that with progressive hypoxemia. CMRO2 remains stable until oxygen demand exceeds oxygen delivery, resulting there after in a progressive reduction in CMRO2.
Pial Arterial Response to Systemic Hypoxia in Anaesthetised Cats
Authors: Craigen M. Louise , Jennett Sheila
Published: April 2011

Pial arterial responses to reduction in arterial oxygen tension were studied in anaesthetised cats. In 12 cats under chloralose, dilatation occurred in vessels of all sizes between 20 and 200 μm, at variable levels of Pao2, and to a very variable extent. At Pao2 25–35 mm Hg, dilatation ranged from negligible to 175% above initial diameter. The variations in response were largely dependent on associated blood pressure (BP) changes. Increase in BP counteracted dilatation; dilatation was greater during hypoxia when the BP change was prevented. At the induction of hypoxia, the first response of the vessels was a constriction, which occurred about 5 s after the chemoreflex increase in BP. Dilatation was delayed a further 30–90 s, and this delay was similar when BP was prevented from rising. Vessels of all sizes responded in the appropriate manner when only BP was transiently changed within the autoregulatory range. In 3 cats in which similar procedures were compared under pentobarbitone anaesthesia, there were smaller and less consistent changes in responses to BP changes alone and to hypoxia and its associated BP changes. The findings were compatible with a local effect of lowered Po2. From the time course of the changes there was no indication of a chemoreflex component in the responses of these vessels at the induction of hypoxia.
Adrenergic and Cholinergic Receptors of Cerebral Microvessels
Authors: Harik Sami I. , Sharma Virendra K. , Wetherbee John R. , Warren Robert H. , Banerjee Shailesh P.
Published: April 2011

The presence of α- and β-adrenergic and muscarinic cholinergic receptors in cerebral microvessels of the rat and pig was assessed by ligand binding techniques. The results demonstrate the presence of specific binding to α2- and β-adrenergic receptors but no appreciable specific binding to α1-adrenergic or muscarinic cholinergic receptors. β-Adrenergic receptors of pig cerebral microvessels are similar to those of the brain and other organs in their binding characteristics to the tritiated ligand and in their stereospecificity of binding to the biologically active isomers of β-adrenergic agonists. Further evidence derived from the differential potency of binding displacement by the various β-adrenergic agonists and selective β1- and β2-adrenergic antagonists indicates that β-adrenergic receptors of pig cerebral microvessels are mostly of the β2-subtype.
Effects of Extracellular Calcium and of Calcium Antagonists on the Contractile Responses of Isolated Human Pial and Mesenteric Arteries
Authors: Brandt Lennart , Andersson Karl-Erik , Edvinsson Lars , Ljunggren Bengt
Published: April 2011

In isolated human pial arteries (diameter 0.4–0.5 mm), contractions were produced by potassium, noradrenaline, serotonin, and prostaglandin F2α. For comparison, experiments were also performed on human mesenteric arteries. Threshold concentration for potassium-induced contraction in pial arteries was about 10 mm; in mesenteric arteries it was 3–5 mm higher. In pial arteries the calcium antagonists nifedipine and nimodipine caused an almost complete relaxation of contractions induced by potassium at drug concentrations relaxing prostaglandin F2α-contracted vessels to only about 60%. Both nifedipine and nimodipine effectively inhibited contraction elicited by noradrenaline and serotonin in pial arteries. Nifedipine had a higher potency for relaxing cerebral than mesenteric arteries contracted by potassium ( p < 0.001). No such difference was demonstrated for nimodipine. In pial arteries pretreated in a calcium-free medium for 30 min, potassium depolarisation elicited contractions reaching a maximum amplitude of about 40% of that evoked in normal Krebs solution. Both nifedipine and nimodipine effectively inhibited contractions induced by calcium in pial arteries pretreated in a calcium-free medium and depolarised by potassium. The results suggest that potassium, amines, and prostaglandin F2α activate isolated pial and mesenteric arteries by different calcium-dependent mechanisms and confirm the potent relaxant effects of nifedipine and nimodipine in these vessels.
Effects of Pentobarbital on Contractile Responses of Feline Cerebral Arteries
Authors: Edvinsson L. , McCulloch J.
Published: April 2011

The effects of pentobarbital on the contractile responses of isolated feline middle cerebral arteries have been examined. In the presence of pentobarbital (3 × 10−4 M), the maximum contractions effected by potassium, noradrenaline, and prostaglandin F2α were reduced by 37 ± 3, 69 ± 3, and 10 ± 6%, respectively. The results caution against the use of pentobarbital as an anaesthetic agent in investigations of cerebrovascular reactivity.
Focal Cerebral Ischaemia in the Rat: 1. Description of Technique and Early Neuropathological Consequences following Middle Cerebral Artery Occlusion
Authors: Tamura A. , Graham D. I. , McCulloch J. , Teasdale G. M.
Published: April 2011

A procedure for occluding the stem of the proximal middle cerebral artery of the rat is described. The operation is performed under anaesthesia through a small subtemporal craniectomy. After occlusion, 3 animals were perfused with carbon black and 8 with a FAM fixative (40% formaldehyde, glacial acetic acid, and methanol). The findings were compared with sham-operated animals. Carbon black studies demonstrated an area of impaired perfusion corresponding to the territory of the occluded artery in each animal. Neuropathological studies invariably showed that there was ischaemic brain damage in the cortex and basal ganglia. The frontal cortex was involved in every animal, as was the lateral part of the neostriatum; the sensorimotor and auditory cortex were involved in most animals, whereas the occipital cortex and medial striatum were involved only infrequently. The damage produced by ischaemia could be readily distinguished from the small local lesion seen at the surgical site in sham-operated animals. The ability to produce a consistent focal ischaemic lesion in the rodent brain provides a technical approach that is sufficiently reproducible to enable investigation of the pathophysiology of ischaemia using recently developed autoradiographic and neurochemical methods.
Focal Cerebral Ischaemia in the Rat: 2. Regional Cerebral Blood Flow Determined by [14C]Iodoantipyrine Autoradiography following Middle Cerebral Artery Occlusion
Authors: Tamura A. , Graham D. I. , McCulloch J. , Teasdale G. M.
Published: April 2011

Local cerebral blood flow has been measured by quantitative autoradiography, employing [14C]iodoantipyrine as tracer, in rats killed half an hour after occlusion of the middle cerebral artery. The results were compared with pattern of local cerebral blood flow (CBF) in sham-operated rats and with neuropathological findings. In every animal there was a profound reduction (to 13% of control levels) in blood flow in the neocortex previously supplied by the occluded artery. The level of blood flow in the areas in which ischaemic brain damage occurred was 0.24 ±0.03 ml g−1 min−1 (mean ± SEM). This level of CBF is considerably greater than that reported following a similar surgical procedure in cats and primates. Moderate reductions in blood flow were also seen outside the territory of the occluded artery and in parts of the opposite hemisphere. Absolute increases in blood flow (hyperaemia) were seen only in the substantia nigra and globus pallidus ipsilateral to the occlusion. It is suggested that this finding and the reductions in blood flow outside the territory of the middle cerebral artery are reflections of alterations in neuronal function and metabolic activity secondary to the ischaemic lesion.
Effects of Agents Used in the Pharmacotherapy of Cerebrovascular Disease on the Oxygen Consumption of Isolated Cerebral Mitochondria
Authors: Nowicki Jean-Pierre , MacKenzie Eric T. , Spinnewyn Brigitte
Published: April 2011

A number of drugs used in the pharmacotherapy of cerebral metabolic and vascular disease have been studied for their effects on the respiration of mitochondria isolated from the rat brain. Some of these agents increased the respiratory control ratio by more than 5% from base-line values (at p < 0.05), namely, aminophylline, dihydroergotoxine, ifenprodil, nicergoline, raubasine, and vincamine. The ability of these agents to increase the efficiency of mitochondrial respiration could be correlated with two other attributes peculiar to these five drugs: their ability to contract cerebrovascular smooth muscle when studied in vitro and their ability to decrease the volume of infarcted brain tissue following experimental occlusion of the middle cerebral artery in the cat. Papaverine and its derivatives (naftidrofuryl, viquidil, YC-93) decreased respiratory control, an effect that might correlate with their capacity to effect a vasodilatation of the cerebral vessels and their inefficacy in models of acute cerebral infarction. There is a considerable body of evidence suggesting that one of the earliest and most fundamental perturbations of cerebral ischaemia is a loss of respiratory control. Ifenprodil, vincamine, and some related “anti-ischaemic” compounds are capable of increasing respiratory control in normal cerebral mitochondria, and this capacity might well help to explain their therapeutic potential in cerebrovascular disorders in which energy supply to the brain is limited.
Cerebrovascular Effects of Prostaglandin Inhibitors in the Gerbil
Authors: Crockard Alan , Iannotti Fausto , Ladds Graeme
Published: April 2011

Autoregulation of cerebral blood flow (CBF) to mean arterial blood pressure (MABP) of 40–50 mm Hg has been demonstrated in the spontaneously breathing gerbil anaesthetised with barbiturate (60 mg/kg). CO2 reactivity has also been assessed at 2.8% change CBF/mm Hg change in arterial Pco2 In six animals pretreated with indomethacin (3 mg/kg), autoregulation was preserved although the resting CBF was significantly reduced, but CO2 reactivity was completely abolished. 1- n-Butyl imidazole, a specific thromboxane synthetase inhibitor, was used in six other animals (3 mg/kg), and this abolished CO2 reactivity while preserving autoregulation; the effect of this agent has not been described previously. Both drugs inhibit different pathways of prostaglandin metabolism and may interfere with normal CO2 reactivity in several ways. Two explanations are that prostaglandins constitute the final common pathway in effecting cerebrovascular response to CO2 or, alternatively, that the free radicals and ionic fluxes generated during prostaglandin metabolism are a coincidental source of the hydrogen ion changes required.
Topographic Electroencephalographic Study of Cerebral Infarction Using Computed Mapping of the EEG
Authors: Nagata Ken , Mizukami Masahiro , Araki Goro , Kawase Takeshi , Hirano Masaharu
Published: April 2011

Computed mapping of the electroencephalogram (CME) is a newly developed method using a microcomputer system that displays the scalp topograph as the square roots of the average power spectra over each EEG frequency band on a color television screen. This new device has been employed in an examination of functional lesions in 20 patients with aphasia due to cerebral infarction. The results were compared with those of computed tomography (CT) and regional cerebral blood flow (rCBF) studies using intracarotid 133Xe. A high-voltage focus of slow components and an asymmetrical distribution of alpha activity were regarded as signs of functional lesions on CME. Twelve patients showed high-voltage foci and six showed asymmetrical alpha activity on CME, which correlated well with the lesions on CT and/or rCBF studies. Especially in patients with motor aphasia, CME demonstrated the abnormality in advance of the appearance of a low-density area on CT. Compared with conventional EEG interpretation, CME is very useful in topographic and objective diagnosis of functional lesions, although the source of the data is the same as for the conventional EEG.
Respiratory Activity of Isolated Rat Brain Mitochondria following in vitro Exposure to Oxygen Radicals
Authors: Hillered Lars , Ernster Lars
Published: April 2011

Respiratory activity of isolated rat brain mitochondria was measured following in vitro exposure to oxygen radicals. The radicals were generated by hypoxanthine and xanthine oxidase in the presence of a suitable iron chelate and caused a severe inhibition of respiration stimulated by phosphate plus ADP (with malate + glutamate as substrate). The damage could be prevented by catalase or high concentrations of mannitol, but not by superoxide dismutase. A similar effect was observed when hypoxanthine and xanthine oxidase were replaced by glucose and glucose oxidase or by hydrogen peroxide. Most of the findings indicate that the hydroxyl radical is the damaging agent. It is concluded that brain mitochondria exposed to oxygen radicals in vitro show an inhibition of respiratory activity similar to that reported by other investigators as occurring in mitochondria in vivo following transient cerebral ischemia. Therefore, oxygen radicals may contribute to this type of cell damage.
Selection of Experimental Conditions for the Accurate Determination of Blood — Brain Transfer Constants from Single-Time Experiments: A Theoretical Analysis
Authors: Blasberg Ronald G. , Patlak Clifford S. , Fenstermacher Joseph D.
Published: April 2011

Reliable blood–brain transfer constants can be determined from data obtained in single-time experiments (i.e., a single experimental time for tissue sampling). The accuracy of such measurements depends on factors such as the test molecule used and the experimental time chosen; therefore, the selection of optimal experimental conditions is important. In this presentation, a model of transport across the blood–brain barrier (BBB) was developed and used to determine appropriate experimental protocols for single-time experiments. Transfer numbers derived from published data with α-aminoisobutyric acid (AIB; a compound of low BBB permeability that is readily taken up by brain cells) and diethylenetriaminepentaacetic acid (DTPA; a compound of very low BBB permeability that is not taken up by brain cells) were inserted into the model and apparent blood-to-brain transfer constants ( K1) were obtained. In addition, the two basic sets of transfer numbers were altered to mimic various experimental and pathological changes in blood–brain transport. The results of this analysis indicate that moderate to large transfer rates across the BBB (0.01–1.0 ml g−1 min−1) are more easily and reliably measured by AIB-like compounds. In contrast, compounds like DTPA are better test-molecules for measuring small changes in the BBB transfer rate (0.0001–0.001 ml g−1 min−1), provided an appropriate experimental time is chosen.
Cerebral Glucose Metabolism as a Function of Age in Man: Influence of the Rate Constants in the Fluorodeoxyglucose Method
Authors: Hawkins Randall A. , Mazziotta John C. , Phelps Michael E. , Huang Sung-Cheng , Kuhl David E. , Carson Richard E. , Metter E. Jeffrey , Riege Walter H.
Published: April 2011

Measurement of the local cerebral metabolic rate of glucose (LCMRGlc) with the fluorodeoxyglucose (FDG) method requires the utilization of appropriate values for the rate constants of the transport and phosphorylation processes. We measured these rate constants as a function of age to determine whether a decline in LCMRGlc as a function of age, in prior studies with the FDG method, actually represents changes in the rate constants. We found that measurements of LCMRGlc are not significantly affected by changes in rate constants as a function of aging, and that LCMRGlc did not change significantly with age.
In vivo Cerebral Protein Synthesis Rates with Leucyl-Transfer RNA Used as a Precursor Pool: Determination of Biochemical Parameters to Structure Tracer Kinetic Models for Positron Emission Tomography
Authors: Keen Randy E. , Barrio Jorge R. , Huang Sung-Cheng , Hawkins Randall A. , Phelps Michael E.
Published: April 2011

Leucine oxidation and incorporation into proteins were examined in the in vivo rat brain to determine rates and compartmentation of these processes for the purpose of structuring mathematical compartmental models for the noninvasive estimation of in vivo human cerebral protein synthesis rates (CPSR) using positron emission tomography (PET). Leucine specific activity (SA) in arterial plasma and intracellular free amino acids, leucyl-tRNA, α-ketoisocaproic acid (KIC), and protein were determined in whole brain of the adult rat during the first 35 min after intravenous bolus injection of l-[1-14C]leucine. Incorporation of leucine into proteins accounted for 90% of total brain radioactivity at 35 min. The lack of [14C]KIC buildup indicates that leucine oxidation in brain is transaminase limited. Characteristic specific activities were maximal between 0 to 2 min after bolus injection with subsequent decline following the pattern: plasma leucine ≥ leucyl-tRNA ≈ KIC > intracellular leucine. The time integral of leucine SA in plasma was about four times that of tissue leucine and twice those of leucyl-tRNA and KIC, indicating the existence of free leucine, leucyl-tRNA, and KIC tissue compartments, communicating directly with plasma, and separate secondary free leucine, leucyl-tRNA, and KIC tissue compartments originating in unlabeled leucine from proteolysis. Therefore, a relatively simple model configuration based on the key assumptions that (a) protein incorporation and catabolism proceed from a precursor pool communicating with the plasma space, and (b) leucine catabolism is transaminase limited is justified for the in vivo assessment of CPSR from exogenous leucine sources using PET in humans.
The Effects of Extracellular Acidosis on Neurons and Glia in vitro
Authors: Goldman Steven A. , Pulsinelli William A. , Clarke Wendy Y. , Kraig Richard P. , Plum Fred
Published: April 2011

Cerebral lactic acid, a product of ischemic anaerobic glycolysis, may directly contribute to ischemic brain damage in vivo. In this study we evaluated the effects of extracellular acid exposure on 7-day-old cultures of embryonic rat forebrain. Mixed neuronal and glial cultures were exposed to either lactic or hydrochloric acid to compare the toxicities of relatively permeable and impermeable acids. Neurons were relatively resistant to extracellular HCl acidosis, often surviving 10-min exposures to pH 3.8. In the same cultures, immunochemically defined astrocytes survived 10-min HCl exposures to a maximum acidity of pH 4.2. Similarly, axonal bundles defasciculated in HCl-titrated media below pH 4.4, although their constituent fibers often survived pH 3.8. Cell death occurred at higher pH in cultures subjected to lactic acidosis than in those exposed to HCl. Over half of forebrain neurons and glia subjected for 10 min to lactic acidification failed to survive exposure to pH 4.9. Longer 1-h lactic acid incubations resulted in cell death below pH 5.2. The potent cytotoxicity of lactic acid may be a direct result of the relatively rapid transfer of its neutral protonated form across cell membranes. This process would rapidly deplete intracellular buffer stores, resulting in unchecked cytosolic acidification. Neuronal and glial death from extracellular acidosis may therefore be a function of both the degree and the rapidity of intracellular acidification.
Preischemic Hyperglycemia Enhances Postischemic Depression of Cerebral Metabolic Rate
Authors: Kozuka Masao , Smith Maj-Lis , Siesjö Bo K.
Published: April 2011

The objective of the present study was to explore metabolic correlates to the appearance of postischemic seizures and the enhancement of brain damage observed in subjects that are made hyperglycemic prior to the induction of ischemia. To that end, transient forebrain ischemia of 10-min duration was induced in normo- and hyperglycemic rats, with subsequent measurements of local CMRglc (LCMRglc) after 3,6,12, and 18 h of recirculation. We posed the questions of whether postischemic depression of LCMRglc is exaggerated by preischemic hyperglycemia and whether there are signs of localized increases in LCMRglc in hyperglycemic rats, reflecting subclinical seizure activity. The results confirmed the presence of a long-lasting postischemic depression of LCMRglc in normoglycemic rats. This depression was partially but not tightly related to the degree of reduction of local CBF during ischemia. The depression was most pronounced in neocortical areas and in the hippocampus, but notably it was less pronounced in the densely ischemic caudoputamen. Little or no reduction of LCMRglc was observed in moderately or mildly ischemic structures such as the hypothalamus, red nucleus, and cerebellum. Preischemic hyperglycemia markedly accentuated the postischemic depression of LCMRglc. For example, although the subjects quickly regained wakefulness and motility, they had LCMRglc values in neocortical areas that remained below 50% of control. Corresponding but quantitatively less pronounced reductions in LCMRglc were observed in other areas. Notably, preischemic hyperglycemia reduced postischemic LCMRglc also in areas that showed only moderate to mild reductions in CBF during the ischemia. The results thus demonstrate that preischemic hyperglycemia has pronounced metabolic effects in the postischemic recovery period. The data provide no indication that postischemic seizures, which develop after a recovery period of ∼24 h, are preceded by the appearance of hypermetabolic “seizure” foci.
Lack of Capillary Recruitment in the Brains of Awake Rats during Hypercapnia
Authors: Göbel Ulrich , Klein Burkhard , Schröck Helmut , Kuschinsky Wolfgang
Published: April 2011

The present study investigates the question of whether increases in CBF induced by hypercapnia in awake rats are accompanied by increases in the number of perfused capillaries. For the detection of perfused capillaries, gamma-globulin-coupled fluorescein isothiocyanate was injected intravenously. In 10 brain structures the density of perfused capillaries per square millimeter was determined from coronal sections using a highly sensitive fluorescent microscopical method that, in contrast to others, avoided air drying of the frozen brain sections. The results showed an inhomogeneous local distribution of the density of perfused capillaries during normo- and hypercapnia. The density of perfused capillaries was unchanged during hypercapnia compared with normocapnia, although blood flow was markedly increased. It is concluded that a capillary recruitment does not exist in the brain during the high-flow situation of hypercapnia.