Simulation of adaptive modification of the vestibulo-ocular reflex with an adaptive filter model of the cerebellum

An adaptive linear filter model of the cerebellum (Fujita, 1982), which functions as a phase lead or lag compensator with learning capability, is applied to a problem of the cerebellar control of the vestibuloocular reflex (VOR). Under the assumption that the cerebellar flocculus accounts for adaptive modification of dynamic characteristics of the VOR, the cerebellar model was incorporated into a linear control model of the oculomotor system. The results of a simulation study are in good agreement with experimental data on eye movement.     

Effects of orally administered ethyl ester of eicosapentaenoic acid (EPA; C20:5, ω-3) on PGI2-like substance production by rat aorta

A highly purified ethyl ester of EPA (EPAEE) (74%) was manufactured from sardine oil. Sixty mg/kg/day of EPAEE was given orally to male Wishar rats for 8 weeks. No side effect or toxicity from the administration of EPAEE was observed. Plasma EPA concentration and the ratio of EPA to arachidonic acid were significantly increased, compared with control Wistar rats. An enhancement of PGI₂-like substance production by aortas obtained from rats fed EPAEE was noted. Conversion of EPA to Λ¹⁷-6-keto-PGF_1α, a stable metabolite of PGI₃, could not be detected by an incubation study of ¹⁴C-EPA and aortas either from rats fed EPAEE or from control rats. Therefore, PGI₂-like substance produced by rat aorta is most likely to be PGI₂. itself and not PGI₃.     

Determination of the anti-ulcer agent geranylgeranylacetone in serum by gas chromatography—mass spectrometry

A highly specific and sensitive method for the determination of the anti-ulcer drug geranylgeranylacetone (GGA) in human serum is described. The extract from serum with hexane was saponified with potassium hydroxide and subjected to silica gel column chromatography to remove interfering substances. GGA in the partially purified extract was then reacted with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and measured by selected ion monitoring using gas chromatography—mass spectrometry. A low detection limit (1 ng/ml) and high precision were obtained.     

Highly Sensitive Assay for Dopamine-β-Hydroxylase Activity in Human Cerebrospinal Fluid by High Performance Liquid Chromatography-Electrochemical Detection: Properties of the Enzyme

Abstract: This paper describes a new, sensitive assay for dopamine-β-hydroxylase (DBH) activity in human cerebrospinal fluid (CSF), serum and brain tissues by high performance liquid chromatography (HPLC) with electrochemical detection (ED). Dopamine (DA) was used as a substrate and was incubated under optimal conditions. Norepinephrine (NE) formed enzymatically from DA was isolated by a double-column procedure, the first column of Dowex-50-H⁺ and the second column of aluminum oxide. NE was adsorbed on the second aluminum oxide column and then eluted with 0.5 M-hydrochloric acid and assayed by HPLC-ED. Epinephrine (EN) was added to each incubation mixture as an internal standard, and this assay was therefore highly reproducible. The peak height in HPLC was linear from 500 fmol to 100 pmol of NE and EN. The lower limit of detection for NE formed enzymatically was about 30 pmol, which indicated that the sensitivity of this procedure was comparable to that of radioassay procedures. We applied the method to measurement of the activity of and examination of some of the characteristics of DBH in human CSF. DBH activity in CSF of Parkinsonian patients was lower than that of control patients. The properties of DBH in human CSF were similar to those in serum and adrenal medulla.     

Changes in predominant energy substrate after hepatectomy

The changes in the energy substrate utilized by the remnant liver were studied in relation to the changes in the cellular energy status of 25 and 70% hepatectomized rabbits. In 25% hepatectomized rabbits, the energy charge $\text{(}\text{(}\text{ATP}\text{+0.5}\text{ADP}\text{)}\text{(}\text{ATP}\text{+}\text{ADP}\text{+}\text{AMP}\text{)}\text{)}$ level of the remnant liver remained unchanged, the energy substrate of which was predominantly glucose, rather than fatty acid. In contrast, in 70% hepatectomized rabbits, the energy production by the mitochondria was mainly dependent upon fatty acid oxidation at the early period after hepatectomy when the energy charge level decreased remarkably, and then upon glucose oxidation, concomitant with the restoration of the energy charge. It is suggested that the changes in the energy substrate utilized are closely related to those in the energy charge level and the mitochondrial phosphorylative activity of the remnant liver following hepatectomy.     

Isolation of the diterpenoid teuflin (6-epiteucvin) from Teucrium viscidum var. miquelianum

The diterpenoid teuflin (6-epiteuevin) has been isolated from Teucrium viscidum var. miquelianum. Its base catalysed epimerization into teucvidin was studied under mild conditions and the pathway is discussed.     

An extra idic(15p)(q11) chromosome in Prader-Willi syndrome

Using a nonfluorescent AT-specific oligopeptide antibiotic, Distamycin A, on DAPI fluorescent banding of human chromosome (DA-DAPI) as described by Schweizer et al. (1978), we have detected an additional idic(15p) chromosome in a patient with typical Prader-Willi syndrome. On the basis of the evidence available in previous studies and of our own present results, we suspect that the fundamental genetic error in the syndrome is not caused by a chromosome aberration but by a gene aberration on chromosome 15.     

Ecological studies ofRoparidia fasciata in Okinawa island I. Distribution of single- and multiple-foundress colonies

To compare between a single-foundress colony and a multiple-foundress colony at the pre-emergence state of a social wasp, R. fasciata, nest distributions and colony terminations were investigated in 8 sites with different environmental conditions. Marking experiments were also conducted in two sites at high wasp density.

1. Foundress populations were composed of single-foundress colonies in sites C, D and E, new environments where have recently suited for inhaviting, at low wasp density. In sites like A and B which were used year after year, at high wasp density, coexistence of multiple-and single-foundress colonies was observed.
2. From the marking experiment, nests initiated by a single foundress were more distant away from the nest where the original foundress emerged the fall before, compared to multiple-foundress nests which were initiated by multiple foundress.
3. Greater percentage of colony termination was observed in single-foundress nests than in multiple-foundress nests, and the colony termination in single-foundress colonies increased with the nest density.
4. Ant predation was the key factor causing the variation of the percentage of colony termination.

     

Na+-driven Ca2+ transport in alkalophilic Bacillus

Ca²⁺ transport was studied in membrane vesicles of alkalophilic Bacillus. When Na⁺-loaded membrane vesicles were suspended in KHCO₃/KOH buffer (pH 10) containing Ca²⁺, rapid uptake of Ca²⁺ was observed. The apparent $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ value for Ca²⁺ measured at pH 10 was about 7 μM, and the $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ value shifted to 24 μM when measured at pH 7.4. The efflux of Ca²⁺ was studied with Ca²⁺-loaded vesicles. Ca²⁺ was released when Ca²⁺-loaded vesicles were suspended in medium containing 0.4 M Na⁺.Ca²⁺ was also transported in membrane vesicles driven by an artificial pH gradient and by a membrane potential generated by K⁺-valinomycin in the presence of Na⁺.These results indicate the presence of Ca²⁺/Na⁺ and H⁺/Na⁺ antiporters in the alkalophilic Bacillus A-007.     

Inhibition of azoreductase activity by antibodies against cytochromes P-450 and P-448

Hepatic microsomal azoreductase activity in mice was induced with phenobarbital (PB) and 3-methylcholanthrene (3-MC). Antibodies against cytochrome P-450 inhibited azoreductase activity of PB-treated animals while antibodies against cytochrome P-448 inhibited liver azoreductase activity of 3-MC-treated animals, each by about 90%. These antibodies also inhibited microsomal 7-ethoxycoumarin-O-deethylase activity to the same extent. It is concluded that hepatic microsomal azoreductase activity is almost totally dependent on cytochromes P-450 and P-448 and the contribution, if any, of other microsomal components is negligible.