Desorption dynamics of deuterium molecules from the Si(100)-(3x1) dideuteride surface.

We measured polar angle (theta)-resolved time-of-flight spectra of D2 molecules desorbing from the Si(100)-(3x1) dideuteride surface. The desorbing D2 molecules exhibit a considerable translational heating with mean desorption kinetic energies of approximately 0.25 eV, which is mostly independent of the desorption angles for 0 degrees

Coverage dependent desorption dynamics of deuterium on Si(100) surfaces: interpretation with a diffusion-promoted desorption model.

We studied coverage dependence of time-of-flight (TOF) spectra of D2 molecules thermally desorbed from the D/Si(100) surface. The mean translational energies Et of desorbed D2 molecules were found to increase from 0.20+/-0.05 eV to 0.40+/-0.04 eV as the desorption coverage window was decreased from 1.0 ML> or =thetaD> or =0.9 ML to 0.2 ML> or =thetaD> or =0 ML, being consistent with the kinetics switch predicted in the interdimer mechanism. The measured TOF spectra were deconvoluted into 2H, 3H, and 4H components by a curve fitting method along the principle of detailed balance. As a result, it turned out that the desorption kinetics changes from the 4H to the 3H situation at high coverage above thetaD=0.9 ML, while the 2H desorption is dominant for a quite wide coverage region up to thetaD=0.8 ML. A dynamic desorption mechanism by which the desorption is promoted by D-atom diffusion to dangling bonds was proposed.

Response properties of corticotectal and corticostriatal neurons in the posterior lateral suprasylvian cortex of the cat.

Lateral suprasylvian cortex (LS) is an important source of visual projections to both the striatum and superior colliculus. Although these two LS efferent systems are likely to be involved in different aspects of visual processing, little is known about their functional properties. In the present experiments, 86 neurons in halothane-anesthetized, paralyzed cats were recorded along the posterior aspects of the medial and lateral banks of LS (PMLS and PLLS). Neurons were selected for analysis on the basis of antidromic activation from electrodes chronically implanted in the superior colliculus and caudate nucleus. The segregated nature of corticostriatal and corticotectal neurons was apparent; in no instance could a neuron be antidromically activated from both the superior colliculus and the caudate nucleus. Many common features were revealed between corticotectal and corticostriatal neurons; the majority of neurons in both populations were binocular and contralaterally dominant, showed similar responses to stationary flashed light, and expressed within-field spatial summation and surround inhibition. However, a number of information-processing features distinguished between corticotectal and corticostriatal neurons; the former were generally tuned to lower velocities than were the latter, and, for a given eccentricity in visual space, corticotectal neurons had smaller receptive fields than did corticostriatal neurons. Moreover, most corticotectal neurons displayed a marked preference for movements toward temporal visual space, whereas corticostriatal neurons revealed no specialization for a particular direction of movement. In addition, whereas corticotectal neurons were selective for receding stimuli, corticostriatal neurons were selective for approaching stimuli. The presence of these two corticofugal pathways is discussed in relation to their presumptive functional roles in the facilitation of attentive and orientation behaviors.

Direct parasympathetic pathway from midbrain to ciliary muscles in cats and monkeys.

In cats and monkeys, we examined the parasympathetic component of the oculomotor complex, which directly innervates the ciliary muscle, using horseradish peroxidase (HRP). Labeled neurons of varying form and size were found in the Edinger-Westphal(EW) and the Perlia nuclei of the cat and in the anteromedian, EW, and Perlia nuclei of the monkey. Our study confirmed that a direct parasympathetic pathway exists from the midbrain to the ciliary muscles, and that accommodation is controlled in part by this direct link from the midsagittal region via a parasympathetic neuron of the oculomotor nuclear complex.

Cloning, sequencing, and high level expression of the genes encoding adenosylcobalamin-dependent glycerol dehydrase of Klebsiella pneumoniae.

The gld genes encoding adenosylcobalamin-dependent glycerol dehydrase of Klebsiella pneumoniae were cloned by cross-hybridization with a DNA fragment of Klebsiella oxytoca diol dehydrase genes. Since the Escherichia coli clones isolated did not show appreciable enzyme activity, plasmids for high level expression of cloned genes were constructed. The enzyme expressed in E. coli was indistinguishable from the wild-type glycerol dehydrase of K. pneumoniae by the criteria of polyacrylamide gel electrophoretic, immunochemical, and catalytic properties. It was also shown that the recombinant functional enzyme consists of Mr 61,000, 22,000, and 16, 000 subunits. Sequence analysis of the genes revealed four open reading frames separated by 2-12 bases. The sequential three open reading frames from the first to the third (gldA, gldB, and gldC genes) encoded polypeptides of 555, 194, and 141 amino acid residues with predicted molecular weights of 60,659(alpha), 21,355(beta), and 16,104(gamma), respectively. High level expression of these three genes in E. coli produced more than 14-fold higher level of fully active apoenzyme than that in K. pneumoniae. It was thus concluded that these are the genes encoding the subunits of glycerol dehydrase. The deduced amino acid sequences of the three subunits were 71, 58, and 54% identical with those of the alpha, beta, and gamma subunits of diol dehydrase, respectively, but failed to show any apparent homology with other proteins.

Quantitative measurement of upper eyelid movements.

A simple and noncontact method for recording upper eyelid movement by means of a solid state image sensor has been developed. Physiological parameters of blink and lid movements during gaze change were studied in 30 normal subjects. Maximum velocity against lid displacement was analyzed. Electromyography (EMG) of the levator palpebrae as well as orbicularis oculi muscles was conducted and vertical eye movement was recorded by electrooculography (EOG). The maximum lid velocity both for upward and downward gaze change was measured; it was always faster in the downward than in the upward gaze. The duration of lid movement during upward gaze change was about 70 msec longer than that of the vertical saccadic eye movement. By EMG, a pulse-step discharge has been well known to occur in the superior rectus muscle but it was never seen in the levator palpebrae muscle in the present observation. The maximum lid velocity of downward spontaneous blink showed two-phase distributions: phase 1 with an initial flat phase in small displacement and phase 2 with a steep phase in large displacement. By EMG, only the pretarsal portion of the orbicularis muscle discharged at the initial phase; preseptal as well as pretarsal orbicular muscle discharges were noted in the second phase. The simplicity of this technique would permit its wide clinical application.

31P-NMR spectroscopy of myopathies: clinical application of whole-body MR.

Patients with myopathies were examined by 31P-NMR spectroscopy using a whole body MR system operating at 1.5 T. Spectra from the femoral muscles were measured as a function of time during a post-exercise recovery period. A 4-min scanning time was used to obtain a good S/N ratio and enable us to evaluate the relative intensity and position of each absorption line. The results were expressed by PCr/Pi ratio and pH value and compared with values before exercise. Clear changes were observed in the recovery process after workload depending on the stage of disease. We were able to observe the in vivo dynamic energy metabolism of myopathies by whole-body MR.

Novel glycosidase inhibitors, nojirimycin B and D-mannonic-delta-lactam. Isolation, structure determination and biological property.

A new aminosugar named nojirimycin B (1) has been isolated as its bisulfite adduct from the culture broth of Streptomyces lavendulae SF-425, together with nojirimycin. Microbiological oxidation of 1 with Gluconobacter suboxydans IAM 1829 gave a delta-lactam (2). The structures of 1 and 2 were determined to be 5-amino-5-deoxy-D-mannopyranose and D-mannonic-delta-lactam, respectively, on the basis of 1H NMR spectroscopy and X-ray structural analysis. Both 1 and 2 exhibited powerful inhibitory activity against rat epididymal alpha-mannosidase and apricot beta-glucosidase.

Synthesis and biological activity of 7 beta-(2-amino-2-carboxy)-ethylthioacetamido-7 alpha-methoxycephalosporin derivatives.

C-7 and C-3 substituents of a new antibiotic SF-1623 were chemically modified to improve the bioactivity, and substituent effect at C-7 and C-3 was examined on the basis of MIC and ED50 values against selected bacteria. Among a large number of derivatives, MT-141 possessing 2-D-2-amino-2-carboxyethylthioacetamido residue at C-7 and N-methyltetrazolyl-thiomethyl residue at C-3 showed a high order of antibacterial activity in vitro and especially in vivo.

Discovery, isolation and structure of novel cephamycins of Streptomyces chartreusis.

By the use of HPLC technique after treatment with beta-lactamases, two novel cephamycins, SF-1623 and SF-1623B, were discovered and isolated from the fermentation broth of Streptomyces chartreusis SF-1623. The structures of SF-1623 and SF-1623B were determined to contain 3-sulfothiomethyl and 3-hydroxymethyl groups respectively, by chemical and enzymatic transformation reactions. Studies on the fermentation condition and process for the large scale preparation of antibiotic SF-1623 are also described.