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Biomedical subjects

Y Satow

Publications and source records attributed to Y Satow.

At least 91 records · Page 5Linked to original sources
PubMed1977

Crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor, at 2.3 angstrom resolution.

The crystal structure of a protein proteinase inhibitor, Streptomyces subtilisin inhibitor which strongly inhibits bacterial alkaline proteinases, was determined at 2.3 angstrom resolution. The subunit (molecular weight, 11,485) of this dimeric molecule has a unique fold of polypeptide chain with a five-fold anti-parallel beta-sheet structure (about 21% of the 113 amino acid residues) and two small segments of alpha-helices (about 16%). The region around the apparent reactive site, Met(73)-Val(74), is held tight by a combination of various structural features. The conformation of this region seems to have close similarity to that found in substrate analogues of low molecular weight bound to subtilisin BPN'.

Crystallography↗
PubMed1977

Direct effects of trypan blue on cardiac extracellular macromolecule synthesis.

The direct effects of the cardiac teratogen trypan blue on some parameters of embryonic chick heart metabolism were examined in vitro. Trypan blue inhibits chondroitin sulfate biosynthesis but stimulates incorporation of 3H-glucosamine into hyaluronate, heparin, and glycopeptides. 3H-fucose incorporation into glycoprotein is also stimulated. Total incorporation of 14C-labeled amino acids is elevated in the presence of trypan blue. Trypan blue does not cause qualitative changes in labeled end products; rather the metabolic alterations are quantitative. The possible exceptions are glucosamine-labeled glycoproteins since quantitative differences in glycopeptides could reflect qualitative differences in parent glycoproteins. These observations suggest that abnormal heart development, induced by trypan blue, may result from a multiplicity of metabolic alterations and not from any single chemical change.

Animals↗
PubMed1976

Mutants with reduced Ca activation in Paramecium aurelia.

Two heat-sensitive "pawn" mutants of Paramecium aurelia are capable of avoiding reactions when grown at 23 degrees C but not at 35 degrees C. Electrophysiological analyses show that Ca activation is reduces in the mutants even when they are grown at 23 degrees C. The maximal rate of rise and the peak of the evoked action potential (Ca-spike) in the mutants are smaller than those of wild type in a K-solution. After suppression of K conductance by either TEA+ or Ba++, the action potentials of the mutants peak at the same level as that of wild type. However, the maximal rate of rise of the mutants remains only about half that of wild type. Thus, the mutations affect Ca activation but not K activation. Incubation at a high temperature (35 degrees C) further reduces Ca activation to almost zero in the mutants but has little or no effect on wild type. This almost complete loss of Ca activation explains the lack of avoiding reactions when the mutants are grown at high temperatures. A double mutant containing two heat-sensitive mutations shows extremely reduced Ca activation even when grown at 23 degrees C.

Action Potentials↗
PubMed1976

A mutant of Paramecium with increased relative resting potassium permeability.

Fast-2, a membrane mutant of Paramecium aurelia, is due to a single-gene mutation and has behavioral abnormalities. Intracellular recordings through changes of external solutions were made. The mutant membrane hyperpolarized when it encountered solutions with low K+ concentration. This hyperpolarization and other associated activities were best observed in Ca- or Na-solutions devoid of K+. Membrane potential was plotted against the concentration of K+ (0.5 to 16 mM) in solutions of fixed Na+ or Ca++ concentration. The slopes of the curves for the mutant membrane were steeper than those for the wild type at the lower concentrations of K+. Inclusion of 2 mM tetraethylammonium chloride (TEA-Cl) counteracted the mutational effects. Spontaneous action potentials in Ba-solution and the electrically evoked action potentials in various solutions are normal in this mutant. We conclude that the resting permeability to K+ relative to the permeabilities to Na+ and Ca++ has been increased by the mutation.

Animals↗
PubMed1976

A 'TEA+-insensitive' mutant with increased potassium conductance in Paramecium aurelia.

A single-gene mutant of Paramecium aurelia is analysed electrophysiologically. (a) The regenerative Ca-response, triggered by small or moderate current, was smaller and slower in the mutant than in wild type. (b) Input resistance of the mutant membrane is about half of that of wild type bathed in various solutions. This is true for the zero-current input resistance and the chord resistance measured with high depolarizing current. (c) Membrane resistance of the mutant measure with hyperpolarizing currents is smaller than that of wild type only when K+ is the major external cation. (d) Internally applied TEA+ or externally applied Ba+ increases the membrane resistance of the mutant to that of wild type similarly treated. We conclude that the mutant has an increased K conductance.

Action Potentials↗
PubMed1976

[Pattern stimulation and salivary secretion (author's transl)].

Experiments were carried out to investigate the effect of temporal stimulus pattern of chorda or sympathetic stimulation on salivary secretion of the rabbit or the dog. Stimulation of short or long period was adopted. The latency and the velocity of secretion were recorded. The amount of secretion increased with the increase of the number of stimuli within moderate range. The optimum interval of chorda stimulation was about 50 msec, but it was somewhat longer for shorter period of stimulation. Various patterns of stimulation were adopted (1) by varying the interval, the number of stimuli and the period of stimulation, (2) by changing stepwise the interval halfway through stimulation and (3) by intermittent stimulation. Experiments on the effect of sympathetic stimulation were also reported. Fitness of Michaelis-Menten's equation for the relationship between the number of stimuli and the amount of secretion was tested. Moreover, the other equation that described this relation satisfactorily was derived from the hypothesis of superposition of unitary processes. It is suggested that the response of a excitable tissue to repetitive stimuli, if it be pattern sensitive, can not be predicted only from the intensity, the frequency and the number of stimuli without considering their temporal configuration.

Animals↗
PubMed1975

[Pattern stimulation and action potential of frog skin (author's transl)].

Experiments were carried out to investigate the relationship between the pattern of stimulus of efferent or afferent nerve and the size of action potential of frog's skin. Two kinds of preparations were used: the excised nerve skin preparation and the spinal preparation. In the range of moderate intervals of stimuli, the size of skin action potential of the nerve-skin preparation became larger with the increase of number of stimuli, (i) during a definite period of stimulation with various frequencies, or (ii) during various long periods of stimulation with constant frequency. The size of potential depended not only on number of stimuli but also on their interval. The latter property may be called pattern-sensitive. In some state of preparation the size of potential evoked by a constant number of stimuli was nearly constant, being independent from stimulus frequencies, that is, pattern insensitive. Both kinds of results were obtained in cases of the spinal preparation. Michaelis-Menten's equation could be applied to describe the relation between the size of potential and the number of stimuli. However, there was no reason to interprete this relation with a simple concentration-effect relationship. Another hypothesis was then testoned on the supposition that the response is composed of sequentially superposed unitary processes each of which was promptly evoked by each stimulus and decayed exponentially. The calculated response curve reasonably fit with the observed data. Slower processes commonly called accomodation were excluded from the present discussion and only the effect of relatively short period of stimulation was examined.

Action Potentials↗
PubMed1974

Membrane excitability: made temperature-dependent by mutations.

Three mutants of Paramecium aurelia with genetic lesions at two unlinked loci lost their ability to generate action potentials when grown at high temperatures. Action potentials found at room temperature were slightly aberrant. Kinetics of phenotypic changes after temperature shifts showed that excitation is not immediately sensitive to temperature change in these mutants. The initiation of an action potential must rely on many different gene products (presumably membrane proteins) which are open to modification by conditional as well as unconditional mutations.

Action Potentials↗