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  • 1
    ISSN: 1432-1106
    Keywords: Cochlea ; Perfusion ; Elevated potassium ; Electrical potentials ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scala tympani (ST) in guinea pig was perfused with modified Ringer's solutions containing 5–50 mM potassium; tone-induced cochlear responses from the basal turn of ST were compared before, during and after perfusions. The compound nerve action potential (N1) and afterpotential (a/p) amplitudes were reduced, especially above 20 mM; the summating potential (SP) was variable, but its onset shape changed consistently with 13–20 mM levels. However, the cochlear microphonic amplitude (CM) remained substantially unchanged even at the 35 mM level. K+ concentration was monitored in ST with ion-sensitive pipettes. Stable levels were reached within 2 min, but N1 responses continued to fall beyond this time. Recovery to normal K+ levels took place spontaneously and the concentration curve which resulted showed a 2-slope characteristic. These experiments question whether elevated potassium concentration in scala tympani depolarizes the hair cells, and if it does, whether the hair cell resting potential is involved in the generation of the CM.
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Plasticity ; Glutamate ; AP5 ; Visual Deprivation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  N-methyl-D-aspartate (NMDA) receptor-mediated activity is considered important for experience-dependent plasticity in the developing visual system. We investigated the influence of age and experience on the role of NMDA receptors in the visual transmission in the superficial grey layer of the superior colliculus (SGS) of the superior colliculus, where, in the adult, NMDA receptors mediate a substantial part of the visual response. In normally reared (postnatal day 14, P14, to adult) rats, visual responses were challenged with NMDA receptor-selective iontophoretic applications of the antagonist D-2-amino-5-phosphonovalerate (AP5). After eye opening (at P14), there was a significant increase in the number of neurones whose visual responses were reduced during AP5 ejection, which peaked at P22 (85%; n = 21), and then declined to adult levels (66%; n = 47) at P25. The mean reduction of the response (from control levels) by AP5 was similar at all ages (approximately 40%). Dark rearing had striking effects on the role of NMDA receptors in visual transmission, especially when comparisons were made between age-matched subjects greater than P25. In these subjects, AP5 ejection reduced the visual responses of all neurones studied. In addition, AP5 ejection caused a significantly larger reduction of visual responses in dark-reared rats (mean reduction 62 ± 4; n = 29) compared with age-matched controls (mean reduction 44 ± 8; n = 23). The D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) reduced the visual responses of every neurone studied and there were no age- or experience-dependent effects. We conclude that NMDA receptors, but not AMPA receptors, assume greater importance for visual transmission in the SGS of dark-reared rats.
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  • 3
    ISSN: 1432-1106
    Keywords: Key words Metabotropic glutamate receptors ; 2R ; 4R-4-Aminopyrrolidine-2 ; 4-dicarboxylate ; Somatosensory thalamus ; Presynaptic inhibition ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Recordings were made from single neurones responsive to somatosensory input in the ventrobasal thalamus of the anaesthetised rat. GABAergic afferent inhibition arising from the thalamic reticular nucleus was evoked using a condition-test vibrissal stimulation paradigm. Local iontophoretic application of the group II metabotropic glutamate receptor (mGluR) agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the vicinity of the recorded neurones produced a reduction of the afferent inhibition (from 78±3.0% to 25±5.3%), presumably via a presynaptic mechanism. This effect could be antagonised by LY307452, a known group II mGluR antagonist. In contrast, two selective group I mGluR agonists, (S)-3,5-dihydroxyphenylglycine (DHPG) and trans-azetidine-2,4-dicarboxylate (tADA), were without effect on the GABAergic inhibition. These data show that group II but not group I mGluRs can have a significant role in the modulation of GABAergic afferent inhibition in the ventrobasal thalamus. This could be of importance in the control of sensory discriminative processes and functions of sleep, arousal and seizure generation.
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  • 4
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The antigenic profiles of serotype O strains of FMDV collected from the oropharynx of persistently infected cattle were defined with a panel of monoclonal antibodies (mAb's) in an indirect antigen-trapping ELISA. The mAb profiling showed no significant loss of reactivity in two neutralising antigenic sites of persistent FMDV isolates collected over a period of eight months. Early and late serum taken from a carrier animal showed similar neutralising activity against early and late carrier isolates. The antigenic stability of serotype O strains of FMDV collected during the carrier state suggests that antigenic variation facilitated by pressure from the host humoral immune response is not critical to the establishment or maintenance of a persistent infection with FMDV.
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  • 5
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  The baculovirus expression system was found to be efficient at expressing the 3D, the 3AB and the 3ABC non-structural proteins (NSP) of foot-and-mouth disease virus (FMDV) as antigens recognised by immune sera in ELISA. ELISA’s using 3D, 3AB and 3ABC detected antibodies from day 8 and 10 after experimental infection of susceptible cattle and sheep and cattle remained seropositive for more than 395 days. The ELISA’s detected antibodies against any of the seven serotypes of FMDV. The 3D ELISA was specific and precise and as sensitive as established ELISA’s which measure antibody to structural proteins. The assay may be used as a resource saving alternative to established ELISA’s for the detection of antibodies against any of the seven serotypes. The 3AB and the 3ABC ELISA were also specific and precise. FMDV infected cattle could be differentiated from those that had been merely vaccinated as they gave a positive result in both the 3AB and the 3ABC ELISA’s. Two cattle that had been both vaccinated and infected also gave positive results in both tests, suggesting that the 3AB and 3ABC ELISA’s, but not the 3D ELISA might represent a reliable means of detecting infection in a vaccinated population.
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  • 6
    ISSN: 1432-2242
    Keywords: Key words Brassica juncea ; Screening ; Mutants ; Cadmium ; Lead
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A new screening method for non-destructive, high-sensitivity, high-throughput isolation of plant mutants capable of accumulating large amounts of heavy metals has been developed. This method is based on incubating seedlings in a solution containing radioisotopes of the metals of interest and visualizing the tissue accumulation of these metals with a phosphorimager. We used this technique to isolate mutants of Brassica juncea (L.) Czern with increased accumulation of Cd and Pb for use in phytoremediation, an emerging technology using plants to remediate polluted soil and water. Approximately 50,000 M2 seedlings were screened and 21 mutants were recovered that retained increased accumulation through the third generation. Mutant 7/15–1 is characterized by enhanced Pb accumulation per unit of root fresh weight, stunted root growth, and decreased root cell size. Data indicate that roots of 7/15–1 contain more cell-wall material on a fresh-weight basis than roots of the wild-type, which may at least partially explain its ability to accumulate more Pb.
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  • 7
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Nitric oxide has been identified as having a role in synaptic transmission in the central nervous system. In the ventrobasal complex of the thalamus (VB), the precursor of nitric oxide synthesis, L-arginine, causes enhancement of excitatory amino acid responses and somatosensory transmission. In this study, the nitric oxide donors sodium nitroprusside, 3-morpholinosydnonimine and S-nitrosoglutathione were applied to VB relay neurons by iontophoresis and responses of single neurons were recorded extracellularly. Sodium nitroprusside caused selective inhibition of responses to NMDA, probably mediated by a by-product, ferrocyanide, as described in previous studies. 3-Morpholinosydnonimine and S-nitrosoglutathione, however, caused potentiation of responses to sensory stimuli and to excitatory amino acids. In contrast, glutathione in both its reduced and oxidized forms reduced such responses, and this suggests that the potentiating effect of S-nitrosoglutathione could be due to nitric oxide production. These results are consistent with the hypothesis that nitric oxide may have a local modulatory role in the thalamus. Data are presented which suggest that glutathione may have a negative modulatory influence on neurotransmission and excitatory amino acid responses in the ventrobasal thalamus.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Child 25 (1999), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: The area of child disability is the ‘Cinderella’ of community child health services. It lacks a clear commissioning model, agreed quality standards or guidance on the level of resources required. In this climate of uncertainty, a national survey of Child Development Teams was undertaken in order to describe their basic structure and processes. The paper reports information from 242 multidisciplinary teams providing local services, with statutory funding, to children with neurodevelopmental disability and their families. The picture presented is encouraging in part. For example, 79% of teams operate from a Child Development Centre, which may be expected to enhance team communication. In terms of the initial assessment process for a developmentally delayed child, most teams (91%) report that they would hold a case discussion afterwards, although only 74% would always include parents, and only 70% always give their report(s) to parents. The impression of management practices is weak, with only 62% giving a clear answer about who manages the team, and less than half having a written policy or contract for the team's work. The survey findings provide a sampling framework from which further evaluative research can be generated.
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  • 9
    ISSN: 1432-0789
    Keywords: Key words Forest floor ; Microbial phosphorus ; Microbial carbon ; C:P ratio ; Gross phosphorus mineralization and immobilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Information on the mineralization of inorganic phosphate (Pi) from organically bound P (Po) during decomposition of forest floor and soil organic matter is vital for understanding P supply in forest ecosystems. Carbon (C) and phosphorus (P) fluxes were determined for forest floor samples from three Pinus radiata plots which had received no P (Control), 62.5 kg P ha–1 (Low P) and 125 kg P ha–1 (High P) 20 years before sampling. The P concentration of the forest floor samples had increased with fertilizer application, and the C:P ratio ranged between 585 and 1465. During a 9-week laboratory incubation 8.2–19.0% of the forest floor C was evolved as CO2-C. The amount of CO2 evolved from the forest floor of the Control plot was more than twice the amounts from the Low P and High P plots. There was little change in net P mineralization in the Control and Low P treatments throughout the incubation, but it increased slightly for the High P samples, suggesting a critical forest floor C:P ratio of 550 for net P mineralization. Changes in the 32P-specific activities of the Pi and microbial P pools during incubation, and concurrent changes in microbial-32P and 32Pi, indicated internal P cycling between these pools. The rate of internal P cycling varied with forest floor quality, and was highest in the High P forest floor. The High P samples had microbial C:P ratios of 22 : 1 which remained constant during the incubation, suggesting the microorganisms had adequate P levels.
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  • 10
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effects of polyethyleneimine, electrolyte concentration and pH on the electrophoretic mobility values for whole yeast, yeast homogenate and borax clarified homogenate were observed. The polyethyleneimine concentration at which there is optimum clarification of the borax-clarified homogenate corresponded to a mobility value of zero. Increased floc size up to the point of zero mobility was obtained by use of polyethyleneimine of larger molecular weight and also higher concentration. The effect of ageing under shear on the size of the flocs was examined and indicated reversibility of break-up at low shear rates while at higher shear rates the flocs were irreversibly broken. Such growth and ageing observations suggest floc formation comprises a two-stage process; the initial formation of primary particles by polymer bridging, and the subsequent formation of larger flocs as these primary particles are brought together by charge neutralisation.
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