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  • 1
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have achieved spectrum narrowing to 1 pm in a high-power ArF excimer laser injection locked by an all solid-state fourth harmonic (193.4 nm) seed source of 773.6 nm Ti:sapphire laser radiation. Superior laser properties such as sufficient output energy (90 mJ/pulse, 50 pps), locking efficiency exceeding 90%, wavelength drift less than 0.4 pm, and spectrum bandwidth fluctuation less than 0.2 pm were obtained, which meet the requirements for 1 Gbit dynamic random access memory microlithography. © 1995 American Institute of Physics.
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  • 2
    ISSN: 1432-0827
    Keywords: Key words: Bone metabolic markers — Predictor — Osteoporosis — Epidemiology — Bone mineral density.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this study was to ascertain whether biochemical markers of bone turnover predict bone loss. The survey was carried out in Taiji, Wakayama Prefecture, Japan. From a list of inhabitants aged 40–79 years, 400 participants (50 men and 50 women in each of four age groups) were selected randomly. Bone mineral density (BMD) was measured, and blood and urine samples of all participants were examined to obtain values for eight biochemical markers: alkaline phosphatase (ALP), bone Gla protein (BGP), type I procollagen (carboxyterminal peptide of type I procollagen; PICP), cross-linked carboxyterminal telopeptide region of type I collagen (ICTP), and urinary excretion of calcium (Ca), phosphate (P), pyridinoline (Pyr), and deoxypyridinoline (D-Pyr). Each marker was evaluated as a predictor of the rate of bone change in lumbar spine and femoral neck BMD over a 3-year period. The value of Pyr was significantly related to the change of lumbar spine BMD in men (P= 0.009), and that of BGP was found to be significant in women (P= 0.045). By contrast, none of the bone markers significantly correlated with bone loss at the femoral neck. The coefficient of determination at the lumbar spine was 5% and 7% at the femoral neck only. We conclude that biochemical markers of bone turnover cannot predict bone loss rates in middle-aged or elderly Japanese men and women over a 3-year period with sufficient accuracy for use in clinical decision making.
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  • 3
    ISSN: 1432-1106
    Keywords: Cat locus coeruleus ; Antidromic activation ; Afferent connection ; Visual inputs ; Catecholamine histofluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A total of 208 single neurons were extracellularly recorded in the locus coeruleus (LC) of 11 cats. In later histofluorescence studies, greenish fluorescent LC neurons, from which we believed to have recorded well-isolated action potentials, were always found in or close to the center of red fluorescent halo due to an injected dye which marked the recording site. One hundred twelve of these 208 neurons were further subjected to electrical stimulation of the dorsal bundle of ascending axons originating from the norepinephrine (NE)-containing LC neurons and thus activated antidromically with a mean latency of 8.9 ms (the remaining neurons were lost before this examination). The mean conduction velocity was 1.2 m/s. Furthermore, it is suggested that 22% of thus antidromically identified NE neurons in the cat LC had an ascending axon of the conduction velocity faster than 2.4 m/s. This finding may be related with an electron-microscopic observation which indicated the presence of myelinated catecholamine (CA) axons, though not many in number, in the cat visual cortex. Responses by the NE-containing LC neurons to various natural visual stimuli, such as flashlight, moving and stationary light-slit, multiple spots, and gratings were examined. It turned out, however, that flash alone was effective to activate LC neurons. The latency of flash evoked activity was between 48 and 96 ms (N = 12; mean: 60 ms). Furthermore, the following areas in the central visual pathway were electrically stimulated to activate LC neurons orthodromically: the optic chiasm (OX), the dorsal lateral geniculate nucleus (LGN), the superior colliculus (SC), and the visual cortex (VC). The range and the mean of the latency for orthodromic responses were as follows: OX (N = 36, 8.4–42 ms; mean: 21 ms); LGN (N = 17, 6.0–17 ms; mean: 8.1 ms); SC (N = 12, 3.6–12 ms; mean: 5.6 ms); VC (N = 10, 7.8–40 ms; mean: 16.4 ms). The long latency of these orthodromic responses and its wide distribution suggest that afferents to the LC from the above-mentioned visual structures are most likely polysynaptic in nature. The extensive input convergence, including acoustic and nociceptive afferents, and the polysynaptic connection in each afferent pathway indicated a strong similarity between the afferent connectivity of NE-containing LC neurons revealed in the present study and that known for reticular formation neurons. Then, we would like to suggest that visual signals from the eyes impinge upon the NE-containing LC neurons via the reticular formation and that the afferents from the LGN, the SC, and the VC also join this common path through the reticular formation to reach the LC.
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  • 4
    ISSN: 1432-1106
    Keywords: Visual deprivation ; Catecholamine ; Development ; Striate cortex ; Anesthesia ; Paralysis ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied the ocular dominance distribution in visual cortex of kittens which had been monocularly exposed to moving-pattern stimuli under anesthesia and paralysis. 1. We did not obtain any discernible changes in ocular dominance, confirming the previous reports that anesthesia and paralysis prevent ocular dominance plasticity from occurring. 2. The plasticity, however, was restored under the acute experimental condition by a cortical infusion of 1-noradrenaline (1-NA). In the 1-NA-infused visual cortex, the ocular dominance distribution was clearly shifted to the open eye after monocular exposure for about 20–24 h. 3. We also studied how quickly and to what extent the changes were induced when the duration of the combined treatment was varied. The results were: (i) the earliest change was observed in ∼ 12 h with disappearance of binocular cells, (ii) the treatment was most effective after 20–24 h in inducing the shift of ocular dominance, and (iii) the treatment longer than 24 h (up to 45 h) did not necessarily enhance the shift, though the state of reduced binocularity was sustained throughout. 4. The effects of the cortical 1-NA infusion combined with monocular exposure became less with increasing the age of experimental animals, suggesting the presence of the “susceptible period” in the acute experiments. 5. The effects seemed to become smaller toward the end of a given recording session, suggesting that the restored plasticity wanes with time. The present results further support the idea that the direct activation of the NA system enhances cortical plasticity, in principle, independent of general conditions of experimental animals.
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  • 5
    ISSN: 1432-1106
    Keywords: Monoamines ; Receptors ; Cat visual cortex ; Postnatal critical period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The postnatal development of monoamine levels and receptors in the occipital cortex of the cat has been investigated using neurochemical techniques. The endogenous catecholamines (noradrenaline and dopamine) gradually increased with age, displaying an about 12–13-fold increase in their concentration from the newborn to the adult stage. 3H-dihydroalprendol (β-adrenoceptor ligand) binding showed a rapid increase from the low value (25% of the adult value) at birth, peaking at the age of 7–9 weeks with a value of about 150% of adults. The β-adrenoceptor binding stayed relatively constant at adult value from the age of 11 weeks throughout. Endogenous 5-hydroxytryptamine levels were at birth about 20% of the adult value and thereafter rapidly increased, peaking at the age of 3–5 weeks when it reached the adult value. Between the age of 7–13 weeks the 5-hydroxytryptamine level was about 50–60% of adult. The developmental pattern for 3H-5-hydroxytryptamine binding was similar to that of endogenous 5-hydroxytryptamine, although with certain quantitative differences. The 3H-5-hydroxytryptamine receptor binding showed a steep peak at an age of about 4 weeks when the binding was about 300% of the adult value. Thereafter the binding gradually levelled off in adulthood. Similar results were obtained in the frontal cortex, except for some quantitative differences. The present results thus indicate that both noradrenaline and 5-hydroxytryptamine nerve terminals develop, largely independent of their postsynaptic receptors, probably due to different developmental programs regulating their expression. The development of monoamine receptors appear to precede that of their nerve terminals. The different roles played by β-adrenoceptors and 5-hydroxytryptamine receptors for the maturation of occipital cortex during postnatal critical period were discussed.
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  • 6
    ISSN: 1432-1106
    Keywords: β-adrenergic receptors ; Ocular dominance plasticity ; Kitten visual cortex ; Monocular deprivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We wanted to know whether ocular dominance plasticity can increase under the condition in which the number of available β adrenoreceptors is expected to increase within kitten visual cortex. We adopted a paradigm in which monocular lid suture was carried out some time after the termination of direct infusion of the cortex with a β adrenoreceptor antagonist. A significant change in ocular dominance was obtained as shown by a decrease in binocular cortical neurons, when time interval between the end of the d,l-propranolol infusion and the start of monocular deprivation was one week. With a 3-week interval (the longest tested), an even greater change in ocular dominance was evident. This consisted of a marked decrease in binocular neurons and a shift in ocular dominance toward the nondeprived eye. In a control study an inert stereoisomer, d-propranolol, did not block the ocular dominance shift. These results were interpreted as suggesting that the level of ocular dominance plasticity becomes high in parallel to an expected increase in availability of β adrenoreceptors for endogenous noradrenaline (NA). We next asked whether it is possible to accelerate or decelerate the naturally occurring recovery of ocular dominance plasticity. When either NA or tunicamycin (an inhibitor of protein glycosylation) was infused into the same cortical area immediately after the end of the propranolol infusion, opposite effects were observed: exogenous NA accelerated the recovery of the shift in ocular dominance and tunicamycin suppressed it. When tunicamycin infusion was delayed by one week, however, its suppressive effect was negligible. Thus, the restoration of ocular dominance plasticity seems to occur in parallel to an increase in the availability of β adrenoreceptors for endogenous as well as exogenous NA.
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  • 7
    ISSN: 1432-1106
    Keywords: Non-classical receptive fields ; Steady-state field potentials ; Postsynaptic potentials ; Long-range horizontal connections ; Muscimol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Field potentials were recorded from cat striate cortex, either between an epidural screw electrode and a cannula-electrode inserted deep in the gray matter (transcortical recording) or with a pair of metal microelectrodes. Electrodes were placed bilaterally near the cortical projection of the area centralis. The horizontal separation of the recording tips was ∼2 mm and ∼300 μm, respectively. The area of the visual field providing input to the recording site (receptive field) was determined by measuring the field potentials generated by contrast reversal of high-contrast, achromatic bar gratings. Five-degree-diameter grating patches were presented individually over a large area of the visual field. The gratings were contrast-reversed at 4, 6 or 10 Hz, while also being swept in spatial frequency between 0.56 and 5.24 c/deg. The receptive fields were ∼20 deg across or more, substantially larger than expected on the basis of cortical retinotopy. Responses were also elicited by stimulation of the hemi-field contralateral to that contributing to the classical receptive field, implicating the presence of a callosal projection. The large, spatially distributed receptive fields consisted of patches of high and low sensitivity. Continuous cortical infusion of either 100 μM tetrodotoxin or 10 mM muscimol at the recording site totally suppressed the transcortically recorded field potentials, proving that the local field potentials were generated postsynaptically. The present findings suggest that a cluster of cortical cells near the projection site of the area centralis receives input from remote cortical regions to an extent that is comparable with that of anatomically demonstrated long-range lateral connections.
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  • 8
    ISSN: 1432-1106
    Keywords: Kitten visual cortex ; Critical period ; Reversible optic nerve blockade ; Binocular competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of reversible blockade of tonic retinal discharges upon the excitability of binocular visual cortical neurons was studied in kittens during the “critical period”. Following the direct application of a small amount of blocking agent to the unilateral optic nerve, the responsiveness of single cortical neurons to ipsilateral eye (non-blocked side) stimulation was enhanced while that to contralateral stimulation was suppressed. Changes started soon after blocking and were long lasting, over 1 hour, compared with the duration of blocking (7 min) as measured at the level of the lateral geniculate nucleus. This effect was found to be age-dependent: in older kittens which were out of the critical period, results were ambiguous and in young adult cats the same treatment induced no obvious changes. The results favor the idea of binocular competition at postsynaptic sites of the geniculo-cortical projection during the critical period. Furthermore, tonic afferent activity in the visual system is proposed as one of the primary carriers of effects of the environmental manipulation of visual inputs in the developing visual cortex. This is consistent with the previous notion that tonic afferent activity is indispensable for maintenance of existing synaptic contacts in the matured brain.
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  • 9
    ISSN: 1432-1106
    Keywords: Noradrenaline ; Iontophoresis ; Receptive fields ; Cat visual cortex ; Neuronal plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied how iontophoresis of noradrenaline (NA) changes responsiveness of individual cells in the feline visual cortex when their visual receptive fields are stimulated with the appropriate visual stimulus. We found three populations of cortical cells which either increased, decreased or did not change their visual responsiveness during NA iontophoresis. About equal numbers of cells belonged to each of these three groups. In the majority of such cells that changed visual responsiveness during NA iontophoresis and that had measurable amounts of spontaneous activity, the ratio of visually evoked to spontaneous activity (signal-to-noise ratio) improved during NA iontophoresis. This improvement was independent of the direction of changes in the response magnitude to visual stimulation. There was a differential effect of NA on simple and complex visual cortical cells: Although most simple cells (86%) clearly changed their responsiveness during NA iontophoresis, the effects were seen in only one-third of complex cells. Furthermore, the effects on complex cells were usually weak compared to those typically seen in simple cells. In some cases the effects of NA were more complicated than an overall enhancement or suppression of the cortical cell's responses to visual stimulation. The possible dual role of NA in the visual cortex is briefly discussed.
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  • 10
    ISSN: 1432-1106
    Keywords: β Adrenoreceptors ; Neuronal plasticity ; Ocular dominance ; Monocular lid suture ; Kitten visual cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the visual cortex of young kittens, the extent of ocular dominance shift following brief monocular lid suture was less than expected in the hemisphere which had been locally perfused with β-adrenergic receptor blockers at a moderate concentration. The present result was not due to the effect similar to binocular deprivation, since “local anesthetic effect” of β-adrenergic blockers was unlikely to be involved in the present paradigm. Thus, the present results are consistent with the idea that β-adrenergic receptors within the visual cortex are necessary, at least in part, for the regulation of visuocortical plasticity.
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