Showing papers by "James Taylor published in 1991"

D1 and D2 dopamine receptors independently regulate spontaneous blink rate in the vervet monkey.

Abstract: Previous studies have revealed the involvement of a dopaminergic link in the regulation of spontaneous eye blink rate in primates. Based on the effect of dopamine D2 receptor-selective drugs and the anecdotal failure of the partial D1 agonist, SKF 38393, to alter blink rate in monkeys, it was assumed that D1 dopamine receptors did not control blink rate. The recent availability of dihydrexidine, a full D1 agonist, prompted us to reevaluate the role of D1 and D2 receptors in the regulation of blink rate. African green monkeys (n = 5) were used in all studies. Dihydrexidine produced a rapid and dose-dependent (up to 1 mg/kg, i.m.) increase in blink rate. The elevation in blink rate elicited by 0.3 mg/kg dihydrexidine was completely reversed by prior administration of a specific D1 antagonist, SCH 23390 (0.01 mg/kg, i.m.), but was unaffected by prior administration of a specific D2 antagonist, remoxipride (1 mg/kg, i.m.). Treatment with the specific D2 agonist, (+)-4-propyl-9-hydroxynaphthoxazine, led to a rapid and dose-dependent (up to 0.01 mg/kg, i.m.) increase in blink rate. The raised blink rate produced by (+)-4-propyl-9-hydroxynaphthoxazine (0.001 mg/kg) was abolished by pretreatment with remoxipride, but was not influenced by pretreatment with SCH 23390. These data indicate that spontaneous blink rate in the primate can be regulated by both D1 and D2 dopamine receptors. Furthermore, the receptor subtypes appear to affect blink rate in the same direction, yet function independently. Measurement of blink rate may provide a noninvasive method to assess the potency and selectivity of dopamine agonists and antagonists in primates.

Grafting of fetal substantia nigra to striatum reverses behavioral deficits induced by MPTP in primates: a comparison with other types of grafts as controls.

Abstract: Fetal substantia nigra (SN) cells were transplanted into the caudate nucleus (CN) of four vervet monkeys (Cercopithecus aethiops sabaeus) that had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP treatment appears to produce a syndrome similar to that observed in patients with idiopathic Parkinson's disease. Normal and parkinsonian behaviors were quantitated by trained observers 5 days/week. Twenty-eight behaviors based on previous factor analyses were individually scored and rated. Parkinsonian signs included freezing, head and limb tremor, difficulty in eating, delayed initiation of movement, poverty of movement, tremor that stopped with intention, decreased response to threats, and lying immobile in the cage. These signs were combined to give an overall rating of parkinsonism. A summary measure of ‘normal’ healthy behavior was also examined, including such behaviors as yawning, scratching, self-grooming, shifting, and eating. Overall ratings of parkinsonism increased and those of healthy behavior decreased after MPTP. In the 4 monkeys grafted with fetal SN cells into the CN, behavior returned to pre-treatment levels by the time of sacrifice (2, 5, or 7.5 months after grafting). Three control subjects were transplanted with either SN cells into an inappropriate brain site (cortex) or inappropriate, non-dopaminergic, cells (cerebellar) into the CN. Subjects were also compared with three control animals that did not receive MPTP but received cryopreserved or fresh SN and other cells into the CN. Only MPTP-treated subjects that received SN cells into the CN showed evidence of a reversal of the MPTP syndrome after transplantation. In addition, grafting in animals that were not MPTP-treated did not appear to affect behavior. This paper reports the specific behavioral effects of severe MPTP toxicity that were or were not reversed after transplantation and suggests that only fetal SN cells grafted into the CN may be able to reverse behavioral deficits in MPTP-treated monkeys.

High-precision timing of millisecond pulsars. II - Astrometry, orbital evolution, and eclipses of PSR 1957 + 20

Abstract: Pulse time-of-arrival measurements have been acquired for PSR 1957 + 20 on 61 days over a 2.7 yr interval, including the times of 44 eclipse disappearance or reappearance events. The timing data provide a reliable measurement of the pulsar's proper motion, 29 +/- 3 mas/yr, at position angle 216 +/- 6 deg; this direction is in excellent agreement with that suggested by the cometlike shape of a surrounding optical emission nebula. The rate of change of the orbital period has been measured: a surprisingly large (-3.9 +/- 0.9) x 10 exp -11, implying that significant orbital evolution must take place on a time scale of 30 Myr. Finally, the present observations extend the eclipse measurements to higher frequencies and provide better statistics for these highly variable phenomena. The eclipse data are used to compute a column-density profile of free electrons in the outer parts of the eclipsing region, and thereby provide an important glimpse into the material being ablated from the companion star.

Yohimbine co-treatment during chronic morphine administration attenuates naloxone-precipitated withdrawal without diminishing tail-flick analgesia in rats.

Abstract: Noradrenergic neuronal hyperactivity following chronic morphine administration has been postulated to cause withdrawal signs and symptoms. Suppression of this hyperactivity, for example, by clonidine attenuates withdrawal. It might follow, therefore, that the prevention of suppression of noradrenergic systems during chronic morphine administration might diminish hyperactivity and prevent withdrawal. If the normalization of noradrenergic activity during opioid administration did not also suppress analgesia, it might be of medical and theoretical interest. To test this hypothesis, we gave the alpha-2-antagonist yohimbine to rats in order to increase noradrenergic activity during morphine treatment and then subsequently precipitated morphine withdrawal with naloxone. Six groups were examined: saline controls (N=11), morphine (N=11), morphine + 2.0 mg/kg/day yohimbine (N=15), morphine + 3.0 mg/kg/day yohimbine (N=5), 2.0 mg/kg/day yohimbine (N=11) and 3.0 mg/kg/day yohimbine (N=5). Subjects received 75 mg morphine pellets implanted on day 1,4 and 6 of the treatment or sham implantation. Yohimbine was delivered throughout the morphine treatment by subcutaneously implanted osmotic pumps. On day 7, all subjects were given 1.0 mg/kg naloxone and rated for behavioral signs of withdrawal. Analgesia was measured by observing tail flick latencies (TFL) before and after chronic drug treatments. Naloxone-precipitated withdrawal was characterized by irritability, ptosis, penile erection, diarrhea, rhinorrhea, abnormal posture, wetdog shakes, jumping, and teeth chattering, none of which were observed in groups receiving only saline or yohimbine. Withdrawal behavior was attenuated in a dose-dependent manner when yohimbine was administered during morphine treatment but analgesia was not attenuated. It appears that yohimbine-induced antagonism of alpha-2-adrenergic receptors diminishes the development of the potential for adrenergic hyperactivity and morphine withdrawal without reducing opioid analgesia.

α-l-iduronidase in normal and mucopolysaccharidosis-type-I human skin fibroblasts

Abstract: alpha-L-Iduronidase synthesis and maturation were analysed in fibroblasts from normal controls and from alpha-L-iduronidase-deficient mucopolysaccharidosis-type-I (MPS-I) patients Fibroblasts were radiolabelled with [3H]leucine and alpha-L-iduronidase was isolated from cell lysates or culture medium by monoclonal-antibody affinity chromatography Pulse-chase labelling of normal control fibroblasts showed that alpha-L-iduronidase was synthesized as an 81 kDa precursor and processed within 24 h via intermediates of 76 kDa and 70 kDa to a 69 kDa species The incorporation of radiolabel into alpha-L-iduronidase in fibroblasts from three of four MPS-I patients was at levels that were either very low or undetectable Fibroblasts from one MPS-I patient, however, exhibited levels of incorporation of radiolabelled amino acid into alpha-L-iduronidase similar to those shown by normal control fibroblasts, despite having undetectable alpha-L-iduronidase enzyme activity The maturation of alpha-L-iduronidase in fibroblasts from this patient was delayed compared with normal controls and showed accumulation of the 76 kDa intermediate, as well as the major 69 kDa, form of the enzyme

Picosecond optical fibre sampling oscilloscope

Abstract: An optical sampling oscilloscope, based simply on a dual wavelength, stroboscopic switching operation, in a nonlinear loop mirror has been used to directly measure, with picosecond resolution, the pulses generated from a gain switched semiconductor laser. The detected pulses were directly compared to those obtained with an electronically driven, optical sampling oscilloscope.

Elements of intelligent process control for plasma deposition

Abstract: Induction-coupled plasma deposition (ICPD) is currently a laboratory process relying on operator expertise rather than automated control. Intelligent process control for the ICPD process, which consists of integration of processing knowledge, process models, process sensors and control technology, offers the opportunity to provide closed-loop control as well as intelligent supervisory control to accelerate process development and bring the ICPD process to full-scale production. Intelligent process control for ICPD offers benefits such as higher material quality, control of the matrix micro-structure, cost reduction, higher process yield, and shorter development and production cycle times.

In situ ellipsometric measurements of x‐ray resists

Abstract: This paper presents the results of in situ ellipsometry of x‐ray photoresists during development. PMMA was used to verify the results of previous studies and confirm the validity of the technique and the theoretical models. The technique was then applied to a negative chemically amplified photoresist Microposit XP‐90104C (Shipley). Because the chemically amplified resist uses an aqueous‐base developer (instead of the alcohol solvents such as in the PMMA system), in situ ellipsometry was employed to test the assumption that the resist does not swell during development. No appreciable swelling of exposed XP‐90104C was observed in MF‐322 developer for temperatures below 35 °C. At 40 °C, the onset of swelling was detected. The process of dissolution measured by ellipsometry departed slightly from a theoretical model of uniform film dissolution with an abrupt resist‐developer interface. Scanning electron microscopy (SEM) images of 0.3 μm lines printed with XP‐90104C indicate that surface roughening of the resi...

MEAD II - An Improved CAD Environment for Controls Engineering

Abstract: Recent and future efforts at GE to develop modern environments for Computer-Aided Control Engineering (CACE) are discussed. The basic elements of these systems are: *a User Interface which combines a "point-and-click" menu- and forms-driven interface with other access modes for the more experienced user, *a Data-Base Manager organized in terms of projects, models and corresponding results and other related data elements and including control, *an Expert System Shell, which performs routine higher-level CACE tasks, and *a data-driven Supervisor that integrates the above elements with existing CACE packages for linear and nonlinear simulation, analysis and design. As is usually the case, it has been learned that much more can be done to provide a fully supportive environment for controls engineering, and it has also become clear that certain things might better be done differently. This presentation will focus on such areas.

Raman amplification of gain switched laser diode signal at 1.35 mu m to soliton power levels

Abstract: The authors describe the amplification by stimulated Raman scattering of signals from a distributed feedback (DFB) laser diode operating at 1.35 mu m in a singlemode optical fibre with a dispersion minimum at 1.34 mu m. The pump radiation was from a CW ML Nd:YAG laser operating at 1.319 mu m. Picosecond pulses to soliton power levels were achieved with a maximum gain of approximately 30 dB.