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Biomedical subjects

M Nomoto

Publications and source records attributed to M Nomoto.

At least 199 records · Page 11Linked to original sources
PubMed1982

Large-scale isolation and fractionation of Tetrahymena histones. Purification of H2B and H4 histones.

The histones of the ciliated protozoan Tetrahymena were isolated and fractionated on a large scale by revised procedures, and the H2B and H4 histones were highly purified for sequence determination. The nuclei of an amicronucleate strain, GL, of Tetrahymena pyriformis were isolated, without cell harvesting, from cultures reaching the stationary state, which were continuously centrifuged through 1.0 M sucrose, pH 7.5, containing Nonidet P-40. From the nuclei further purified and washed with 0.15 M NaCl, pH 7.5, histones were extracted with 0.25 M HCl. Thus 1,620 liters of cultures yielded 5.20 g of histone extract. The histones were first separated into a 0.5 M HClO4 soluble fraction (H1) and an insoluble fraction (H2A, H2B, H3, and H4). The insoluble fraction was chromatographed on a large column of Bio-Gel P-60 with 20 mM HCl containing 250 mM NaCL at 15 degrees C, yielding H2A + H3, H2B, and H4 fractions. The H4 fraction was highly pure; the H2B fraction was further purified by the same Bio-Gel P-60 chromatography without NaCl, yielding pure H2B.

Chromatography, Gel↗
PubMed1982

Tetrahymena histone H2B. Complete amino acid sequence.

The complete amino acid sequence of Tetrahymena pyriformis H2B histone was determined. The histone was obtained as described in the preceding paper [Nomoto, M. & Iwai, K. (1982) J. Biochem. 91, 719--723]. The purified histone was digested with an arginine-specific protease, clostripain, and the peptides, fragmented at 7 arginyl bonds and also at many of the 20 lysyl bonds, were fractionated by repeating column chromatography; most of these peptides were sequenced by Edman degradation. The chymotryptic peptides overlapping the clostripain peptides were obtained by limited or more extensive digestion of intact histone. The sequencing of these peptides led to reasonable aligning of the clostripain peptides. Thus, the sequence of 119 amino acid residues (mol. wt, 13,316 for the unmodified form) has a completely alpha-N-blocked proline at residue 1 and a partially epsilon-N-acetylated lysine at residue 3. This sequence is compared with the known sequences of calf thymus and other H2B histones, and the implications for the structure and function relationship of this histone species and also for the phylogeny of protozoa are discussed.

Amino Acid Sequence↗
PubMed1982

N-Trimethylalanine, a novel blocked N-terminal residue of Tetrahymena histone H2B.

Our previous study showed that the amino acid sequence of Tetrahymena histone H2B has a blocked N-terminal residue followed by 119 amino acid residues, X-Pro-Lys.... [J. Biochem. (1982) 91, 897-904]. Now, X has been found to be N-trimethylalanine by 1H nuclear magnetic resonance spectroscopy of the isolated X-Pro-Lys and X. This identification was supported by mass spectrometry of X-Pro-Lys and by column and paper chromatography of X. This is the first time that N-terminal blocking by methylation has ever been found in histones.

Alanine↗
PubMed1980

Representation of cochlear innervation patterns in single auditory nerve fiber responses.

Unit responses of auditory afferent fibers in the monkey could be classified into two distinct populations according to two criteria: (i) the shape of the response area (in particular, the sharpness of tuning, "Q(10)," and high frequency cutoff), and (ii) the impulse rate-sound intensity functions at different frequencies. These two populations have different log-normal distributions of the Q (10)s The smaller population has a relatively rounded (smaller Q(10)) response area with a slow high frequency cutoff and rate-intensity functions with ramps of different slopes. The larger population has a sharp (larger Q (10)) response area and rate functions with parallel ramps. These differences in discharge properties give reasonable grounds to suppose that the smaller and the larger populations correspond to the outer spiral and inner radial fibers in the cochlea, respectively.

Animals↗
PubMed1980

Discharge patterns of the primary auditory cortex in cats.

Single unit responses of the primary auditory cortex of unanesthetized cats were studied using three standard sets of sound stimuli, i.e., clicks, white noise bursts, and pure tone bursts. The units studied were classified into eight categories according to whether they responded to all three, two, one or none of the standard sets of stimuli; there were no units responding only to clicks. This suggests that excitation of some cortical neurons requires a special sound spectrum as well as temporal factors. Frequency-modulated (FM) sounds were usually more effective eliciting responses than the standard sets of stimuli. Responses to FM in burst seemed to be classified into three groups, i.e., sharp monopeak post-stimulus time (PST) histograms, broad monopeak, and sharp multipeaks. The existence of the last group suggests a firm convergence from the lower auditory neurons. In some units, complex stimuli were more effective in evoking responses than simple FM sounds. These units responded only to sounds with complex temporal patterns. For example, a neuron did not respond to any FM sound with a constant modulation magnitude, but showed a transient response whenever the magnitude of FM varied from a continuous pure tone to a certain range of FM. These complex units often showed a response with hysteresis.

Acoustic Stimulation↗
PubMed1979

Spatial firing patterns of auditory neuron network modelling by computer simulation.

This communication examines, in digital computer simulated network, input signals and response patterns established at excitatory neurons' level i.e. the membrane potential of neuron soma. It is restricted to spatial patterns of the auditory neuron networks and time factor for nervous conduction and transmission is neglected compared with long maintained membrane potentials of neuron somas. The model analyzes the change in the spatial patterns of the membrane potential in the two dimensional networks of the auditory system. In order to evaluate the contribution of the various parameters, it is started that the simplest model has only one parameter, lateral inhibition. The other parameters are then added, one at a time, to successive models. The lateral inhibition is a necessary condition in the auditory nervous system if any sharpening of the response areas in the single neurons is to occur. A necessary condition for the validity of the model is that is should be applicable to the other senses such as vision and chemical patterns, taste. The threshold feature of auditory neurons aids in producing a sharpening in the neuron of the auditory relay nuclei. It does this clipping the spatial response patterns in one dimensional arrays of excitatory neurons. Recurrent inhibition seems a necessary condition in the sensory nervous system that any kinds of input signals are to be preserved over a wide range of stimulus intensity. In other words, this network has a wide dynamic range against any kinds of input signals. A simple self-recurrent negative feedback does not contribute to the sharpening, but more complex socalled averaged type does. A neuron network is capable of responding stably to stimuli with a wide range of intensity and with any kind of spatial patterns if there is a simple negative feedback mechanism. When there is no negative feedback, input signals soon disappear or saturate in the neuron network. Therefore, recurrent inhibition is the most important mechanism. Spontaneous activity appears to aid in the sharpening by providing a kind of contrast, that is by reducting the amount of activity in neurons adjacent to the excitatory area. Moreover, the effect of spontaneous activity in the model seems to make repples around the excitatory area and suggests that an introduction of activity at any stage of the networks, from whatever source for example reticulum formation and thalamus, might appreciably alter the response patterns at subsequent neuron network. This suggests that the mechanism of the consciousness that might be controlled by the thalamus and or reticular formation. These two dimensional neuron networks may be expanded to three dimensional neuron networks. The former might simulate the auditory nervous system while the latter might simulate the visual system.

Animals↗