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Notes: Epitaxial Tl2Ba2CaCu2O8 films of thickness 0.65±0.05 μm and Tc of 105±1 K were prepared on (100) LaAlO3 through a two-step post-deposition thallination process and patterned by standard photolithographic techniques and ion beam milling. Using the voltage per unit length criteria Ec=1.0 μV/cm, transport critical current density Jc in zero applied field for a 1.8-m-long, 12±1-μm-wide meander line separated by 8±1 μm spaces was measured to be 1.04×107 A/cm2 at 20 K, 1.82×106 A/cm2 at 80 K, and 1.02×105 A/cm2 at 100 K. The uniformity in Jc was measured for eight line segments of about 11.7 cm length, yielding variations in Jc of 1.44–3.02×106 A/cm2 at 80 K. Jc values independent of linewidth were also measured for three 0.7-cm-long lines with widths of 7, 27, and 52 μm. For design of electronic circuits, resistivity may be a more useful design parameter than Jc, and detailed measurements of resistivity ρ as a function of current density J were carried out. At low temperatures (T/Tc〈0.2), ρ increased by about two orders of magnitude for a 10% increase in J, and Jc is well defined. At high temperatures (T/Tc(approximately-greater-than)0.7), ρ is less strongly dependent on J near Jc. At 90 K, where Jc=7.6×105 A/cm2, ρ remained less than 10−10 Ω cm (3000× less than oxygen free high conductivity copper at 90 K) even for J=1.4×106 A/cm2. The results suggest the potential for the use of patterned Tl2Ba2CaCu2O8 films in high Jc electronic applications such as chip-to-chip interconnects operating at temperatures below 90 K.

Notes: Single-phase aluminum nitride thin films with preferred crystallographic orientations have been grown on single-crystal sapphire by pulsed-laser ablation. The orientation of the films was found to be determined by the atmosphere and the nitrogen pressure during deposition and the substrate temperature. The films were examined by x-ray diffraction, and scanning electron microscopy.

Notes: Abstract: We have studied the regional distribution and characteristics of polyamine-sensitive [3H]ifenprodil binding sites by quantitative autoradiography in the rat brain. In forebrain areas ifenprodil displaced [3H]ifenprodil (40 nM) in a biphasic manner with IC50 values ranging from 42 to 352 nM and 401 to 974 µM. In hindbrain regions, including the cerebellum, ifenprodil displacement curves were monophasic with IC50 values in the high micromolar range. Wiping studies using forebrain slices (containing both high- and low-affinity sites) or cerebellar slices (containing only the low-affinity site) showed that high- and low-affinity ifenprodil sites are sensitive to spermine and spermidine, to the aminoglycoside antibiotics neomycin, gentamicin, and kanamycin, and to zinc. Two calmodulin antagonists, W7 and calmidazolium, also displaced [3H]ifenprodil from both sites. Other calmodulin antagonists, including trifluoperazine, prenylamine, and chlorpromazine, selectively displaced [3H]ifenprodil from its low-affinity site in hindbrain and forebrain regions. High-affinity [3H]ifenprodil sites, defined either by ifenprodil displacement curves or by [3H]ifenprodil binding in the presence of 1 mM trifluoperazine, were concentrated in the cortex, hippocampus, striatum, and thalamus with little or no labeling of hindbrain or cerebellar regions. This distribution matches that of NMDAR2B mRNA, supporting data showing that ifenprodil has a preferential action at NMDA receptors containing this subunit. Low-affinity [3H]ifenprodil sites have a more ubiquitous distribution but are especially concentrated in the molecular layer of the cerebellum. [3H]Ifenprodil was found to bind to calmodulin-agarose with very low affinity (IC50 of ifenprodil = 516 µM). This binding was displaced by calmodulin antagonists and by polyamines, with a potency that matched their displacement of [3H]ifenprodil from its low-affinity site in brain sections. However, the localization of the low-affinity [3H]ifenprodil site does not strictly correspond to that of calmodulin, and its identity remains to be further characterized. The restricted localization of high-affinity [3H]ifenprodil binding sites to regions rich in NMDAR2B subunit mRNA may explain the atypical nature of this NMDA antagonist.

Notes: Abstract: Polyunsaturated fatty acid (PUFA) levels (an index of the amount of substrate available for lipid peroxidation) were measured in several brain regions from patients who died with Parkinson's disease and age-matched control human postmortem brains. PUFA levels were reduced in parkinsonian substantia nigra compared to other brain regions and to control tissue. However, basal malondialdehyde (MDA; an intermediate in the lipid peroxidation process) levels were increased in parkinsonian nigra compared with other parkinsonian brain regions and control tissue. Expressing basal MDA levels in terms of PUFA content, the difference between parkinsonian and control substantia nigra was even more pronounced. Stimulating MDA production by incubating tissue with FeSO4 plus ascorbic acid, FeSO4 plus H2O2, or air alone produced lower MDA levels in the parkinsonian substantia nigra, probably reflecting the lower PUFA content. These results may indicate that an increased level of lipid peroxidation continues to occur in the parkinsonian nigra up to the time of death, perhaps because of continued exposure to excess free radicals derived from some endogenous or exogenous neurotoxic species.

Notes: Abstract: Noradrenaline potently antagonizes the effects of N-methyl-D-aspartate (NMDA) (80 μM) on cyclic GMP production in immature rat cerebellar slices in vitro (IC50 = 0.6 μM). The effect is stereospecific (D-noradrenaline, IC50 = 100 μM), and also observed with adrenaline (IC50= 0.5 μM) and isoprenaline (IC50= 1.2 μM). The α1-adrenoceptor agonists methoxamine or phenylephrine or the mixed α/α2 agonists oxymetazoline or xylometazoline (100 μM) do not block the effects of NMDA, but the α2-adrenoceptor agonist clonidine is weakly active (IC50 = 200 μM). Salbutamol and terbutaline were also inactive except at high concentrations (300 μM), as were a number of other catechol and phenylethylamine derivatives. The antagonistic effects of noradrenaline on the NMDA response were insensitive to phentolamine, atenolol, or propranolol (up to 100 μM), but were blocked by the α2 antagonist idazoxan (1–10 μM). The Na+,K+-ATPase inhibitor ouabain (0.1–10 μM) markedly potentiates the effects of NMDA in this model, and also antagonizes and reverses the ability of noradrealine (10 μM) to block the effects of NMDA. The results suggest that noradrenaline and Na+,K+-ATPase activity have potent modulatory effects on the NMDA response.

Notes: Abstract: NMDA receptor stimulation concomitantly increases the release of [14C]acetylcholine and [3H]spermidine from rat striatal slices in vitro. The NMDA-induced release of both acetylcholine and spermidine was blocked with equal potency by the NMDA channel blocker phencyclidine (0.1–10 µM). However, certain other channel blockers, including dextromethorphan (1–100 µM), which antagonized NMDA-evoked acetylcholine release without affecting NMDA-evoked spermidine release, and dextrorphan (1–100 µM) and memantine (1–100 µM), which block NMDA-evoked acetylcholine release more potently than NMDA-evoked spermidine release, showed greater selectivity of action. As previously shown for ifenprodil, eliprodil (SL82.0715; 1–100 µM) blocked NMDA-evoked acetylcholine but not spermidine release. This selectivity is also observed for other agents interacting with the polyamine site(s) on the NMDA receptor, including arcaine (1–1,000 µM), philanthotoxin343, and argiotoxin636 (10 µM) and was also noted for desipramine (1–100 µM). The NMDA-induced release of acetylcholine and spermidine is likely to be mediated by different native NMDA receptor subtypes, and several NMDA antagonists may be candidates for a selective action at a particular NMDA receptor subtype.