(

3H

) Tobramycin was used as a probe to determine the relationship between the structure of aminoglycoside antibiotics and their ability to remove this drug from its higher affinity binding site on the ribosome. The dissacharide moieties (neamine, tobramine, gentamine) appeared to have a common binding site, whereas the kanosamine, garosamine and ribose moieties determined the specificity of this binding. Amikacin and butikacin behaved in an anomalous manner in spite of their close structural relationship to tobramycin.

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The activities of tobramycin derivatives acetylated and ethylated on the 6'-N, 2'-N and -N positions were examined. The MICs of these derivatives against tobramycin sensitive strains indicated that 2'-N-ethylated and 6'-N-ethylated derivatives have a fairly good activity, and confirmed that the -N position is the most important one for antibiotic activity since -N derivatives were less active. The MICs of these derivatives against tobramycin resistant strains, and their inactivation by tobramycin modifying enzymes were examined. These results showed that 2'-N or 6'-N ethylation protects the drug against inactivation by AAC(2') or AAC(6'), respectively, and 2'-N-ethyltobramycin and 6'-N-ethyltobramycin were active against strains containing these modifying enzymes. On the other hand, -N ethylation protects the drug against inactivation by AAC() but -N-ethyl tobramycin does not inhibit strains containing this enzyme.

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Field data indicate that the P-wave velocity in sand or gravel is sometimes much lower than that of water, even if the soil is below the water table. It is well understood that a slight decrease in saturation normally evaluated by the B-value has a significant effect on undrained shear behavior like liquefaction of saturated soil. In the first part of this research, theoretical formulations of the B-value, P-wave velocity and Poisson's ratio are made by taking into account the decrease in bulk modulus of water due to a mixture of air bubbles. Then, computations are carried out using formulas based on the soil properties of a typical sand or gravelly soils and Masa soil from the Kobe area to make charts correlating the variables. These charts indicate that a small decrement in the B-value in the interval of B=1.0 to 0. will considerably decrease the P-wave velocity. Thus, the P-wave velocity which is easily measured in the field can serve as a convenient index to quantitatively evaluate the insitu soil B-value.

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We screened the differentiation-inducing activities of 39 mushroom extracts from Akita prefecture, Japan, on the mouse osteoblastic cell line, MCT-1. Sixteen phosphate buffered saline (PBS), boiled PBS, 14 ethanol and 12 methanol extracts induced alkaline phosphatase (ALP) activities, an indicator of MCT-1 cell differentiation. The enzyme activities were markedly induced by extracts of Tricholoma auratum, and we isolated the active compound from methanol extracts of this mushroom. Physical data for the isolated active compound were identical to those for (,24R)-ergosta-,-diene-,,6β-triol (1). 1 induced ALP activities of MCT-1 cells and promoted cell proliferation. To investigate the relationships between the chemical structure and differentiation-inducing activity of the compound, ALP-inducing activities of MCT-1 cells by 1, ergosterol (2), ergocalciferol (), cholesta-,,6β-triol (4), -dehydrocholesterol () and cholecalciferol (6) were tested. The enzyme activities of MCT-1 cells were increased .0-fold by 10 μM 1 and 2.4-fold by 10 μM 4. However, 2, , and 6 did not induce MCT-1 cell ALP activity at 0.1—10 μM. These results suggested that the OH groups at - and/or -6 of 1 and 4 played an important role in their differentiation-inducing activities on MCT-1 cells. Furthermore, 1 suppressed induction of MCT-1 cell apoptosis by serum starvation.

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New-type inducers of differentiation of human promyelocytic leukemia cells HL-60, i.

e

., 4- (, 6, , -tetrahydro-, , , -tetramethyl-2-naphthalenylcarbamoyl) benzoic acid (Am 80) and () -4- [- (, -di-tert-butylphenyl) --oxo-l-propenyl] benzoic acid (Ch 55), suppress -myc expression as all-trans-retinoic acid (RA) does. The decreased level of -myc expression was detected within -14 h after the start of treatment, and preceded morphological differentiation and functional differentiation measured in terms of nitroblue tetrazolium (NBT) reduction. Treatment of HL-60 cells with 0.1 μm Am 80, Ch 55 or RA for 96 h caused more than % suppression of -myc expression and around 10-fold increase in the percentage of NBT-positive cells.

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A sample of [

3H

] tobrarnycin (

5

, 000 Ci/Mole) has been synthetized and incubated with
the bacterial ribosome and its subunits. The results obtained show that this antibiotic has
two types of binding sites. The primary one is probably responsible for the inhibition of
protein synthesis whereas the secondary one is probably related to the misreading and reading
tiirough of the messenger RNA.

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The behavior of the soft clay grounds subjected to repeated loading is different from that subjected to sustained loading. The difference in settlement between these two loading patterns should be due to secondary compression over a long period of time. Consequently, soft clay grounds subjected to repeated loading tend to be more compressible than those subjected to sustained loading. Therefore, it is necessary for engineers to predict post-construction settlements under repeated loading. In this respect, the preloading is considered to be promising as a countermeasure to reduce the settlement of clay under repeated loading as well as under sustained loading. The effect of preloading on post-construction consolidation settlement of soft clay subjected to repeated loading after removal of a part of preload is investigated in the present paper. It has become clear that the settlement of a clay sample after preconsolidation is mainly affected by the amount of preload, the degree of consolidation due to the preload, the amount of permanent load and the amount of repeated load after removal of preload. The calculated settlement versus time relations using a method to estimate the amount of consolidation settlement of soft clay grounds subjected to repeated loading after removal of preloading were compared with the observed degree of consolidation as parameters of the intensities of preload and repeated load.

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Leakage of water due to internal erosion through a dam body or foundation is a major problem with fill-type dams. Recent case histories and research suggest that most cases of internal erosion are possibly triggered by hydraulic fracturing. However, the quantitative mechanism of hydraulic fracturing still remains to be solved. Therefore in-situ hydraulic fracture tests were carried out with a cheap, concise apparatus using boreholes dug in the soft clayey volcanic soil foundation of a low earth dam (Oyachi Dam) in Niigata Prefecture. Water was injected into the foundation through a perforated pipe by two methods : one was under a controlled injection pressure and the other was a controlled injection flow rate. In the former method, the relationship between flow rate and injection pressure was observed and it was found that a yield pressure or fracture pressure existed in all the tests. By repeating the injection test it was confirmed that once a crack is developed, it is very easily reopened by a water pressure a little higher than the earth pressure exerted on the crack. In the latter method, the relationship between injection pressure and time was observed and it was found that fracture pressure varied with flow rate. The boreholes were excavated to observe the development of fracture cracks and it was also found that the cracks had developed perpendicular to the borehole periphery, which means that fracture cracks were induced by tensile stress and denies the explanation that fractures are caused by shear failure.

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Six new cembranoids sarcophytol P (), R (4), S (), K (), F (11), and T (13) were isolated from the soft coral Sarcophyton glaucum. Sarcophytol P () was shown to be the 20-hydroxy derivative of the major component sarcophytol A (1), and afforded the cyclization product 6 in CHCl_ at room temperature, in a same way as in 1. Sarcophytols R (4) and S () were correlated to 1, by conversion of its R,R and S,S epoxide derivatives. Sarcophytol K() was a 13, 14-dihydroxycembranoid having a 1,Z-diene moiety. The absolute configuration of and its 1Z,- and 1Z,Z-isomers sarcophytol B (2) and J (10) were determined by circular dichroism study of their bis-p-dimethylaminobenzoate derivatives. Sarcophytols F (11) and T (13) were 1- and 1,Z-isomers of 1. Compound 11 showed characteristic broadening of the ^1H-NMR chemical shifts, due to the restricted conformational interconversion. Using the three cembranoids sarcophytols F (11, 1,), N (15, 1Z,Z) and T (13,1,Z), spontaneous autoxidation-cyclization, in CHCl_,was examined, in order to compare the stereochemical course of the reaction with that of 1 (1Z,), which affords trans-fused bicyclo[9..0]tetradecene systems. The 1,Z-isomer 13 gave the same cyclization product 18, as in the reaction of 1, even though it is isomeric at -1,. The 1Z,Z isomer 15 gave 19, in consequence of the reversed geometry at - of 15. The 1,-isomer (11) gave the bicyclic product , having an antipodal fusion as compared with 19. This was confirmed by PCC oxidation of 19 and , giving enantiomeric ketones 23 and 24 respectively. The 1(14)-epoxide 26 was shown to be the immediate precursor of , and acounted for the inversion of the geometry at -1 of the cyclization product. Compound 26 is isomeric with the epoxide 17 derived from 1. The epoxide 17 is the postulated precursor in the conversion of 13 to 18. It is noteworthy that the mode of antipodal fusion of the cyclopentane rings, in 18 and , was controlled by the chirality of the epoxy rings. The -14 hydroxyl group participates in the transannular cyclization, but was found not to be the requisite functional group for the reaction. Similar treatment of cembrene (30), the parent hydrocarbon of 1, also reacted in CHCl_ giving the bicyclic product 32.

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The mechanism of wave-induced instability in a permeable seabed have been studied for more than two decades. The distinction between shear failure and liquefaction, however, has not been clearly defined. This paper presents a fundamental study on the differences in two failure modes for a fully saturated seabed of both finite and infinite thickness. The wave-induced effective stresses and pore pressure, obtained from an analytical solution of Biot's pore-elastic consolidation theory, were employed to examine the failure modes under a two-dimensional plane strain condition. A case study is presented to examine the failure modes with respect to several parameters, such as excess pore pressure, seepage flow, seepage force, failure areas and stress path in the seabed. The conclusions obtained from this study were as follows ; (1) the thickness of a permeable seabed affects the pore pressure and effective stress response to ocean waves and the failure mode of the seabed, (2) either a liquefaction or shear failure, or both, occur in the seabed, even in the saturated seabed, () the Mohr-Coulomb's failure criterion, when combined with elastic stresses, can not be employed to estimate the liquefaction failure in the seabed, (4) the liquefaction can be evaluated by a criterion in terms of the excess pore pressure, () The liquefied zone in the seabed is significantly different from the shear failure zone. The shape beneath the seabed surface for the former is almost identical to the contour where the upward seepage flow is concentrated.

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An analytical model is presented for steady-state lateral response of earthfill and rockfill dams in canyons subjected to a steady train of harmonic SH waves incident at an arbitrary angle θ. The dam is idealized as a 2-dimensional shear beam with a triangular cross-section, while the canyon is considered rectangular and consisting of elastic rock. A parametric study is undertaken to investigate the influence on the steady-state response of (a) the angle of incidence θ of the incoming waves, (b) the impedance ratio and () the canyon narrowness. It is shown that the acceleration amplification is considerably less for a dam built in flexible canyon than for a dam in a rigid canyon and, hence, the effect of radiation damping may be very important. For obliquely incident waves travelling from the left to the right, the response of the dam depends mainly on the interference of the waves transmitted through the base and the left boundary, leading to a maximum response at a θ about 30°-35°. For very long dams subjected to high frequency obliquely incident waves, it is found that there is no amplification of the motion by the dam. For low-frequency excitation, the response of the dam shows little variation along the crest and approaches the response of the elastic half-space. The results are in agreement with published results for the response of alluvial valleys subjected to incident SH waves.

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An improved version of steady state Rayleigh wave method is presented for the determination of shear wave velocity (V_s) Profiles of a horizontally stratified soil deposit. A dispersion curve and particle orbits of Rayleigh waves can readily be determined in the field through measurements of ground motions induced by an exciter using sensors placed on the ground surface. To determine V_s-profile from the dispersion curve, an inverse analysis which can take into account higher modes of Rayleigh waves is presented and used. To increase the effectiveness of the proposed method, desirable distances among the exciter and sensors are indicated, and the measured particle orbits are used to validate the inverted V_s-profile. Comparative field tests are made at two sites using the proposed method and the conventional down hole method. The V_s-profiles from the two methods are in good agreement with each other, indicating the effectiveness of the proposed method.

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The Nihonkai-chubu Earthquake, with a magnitude of ., occurred on May 26, 1983 in northwest Japan and produced liquefaction sites in the coastal plain of Akita and Aomori Prefectures. About one month later, the maximum aftershock, with a magnitude of .1, again induced liquefaction at several sites in Aomori Prefecture. The authors surveyed the affected area and discovered almost ten reliquefaction sites. Initial liquefaction at these sites had not occurred solely because of the main shock of the Nihonkai-chubu Earthquake. Initial liquefaction at some sites was attributable to the Niigata Earthquake in 1964, the Tokachi-oki Earthquake in 1968, and other earlier earthquakes. Although it had earlier been thought that the occurrence of reliquefaction would be improbable, the authors' investigation shows that reliquefaction occurs frequently, even when the acceleration caused by a later earthquake was less than that caused by a former earthquake. It can therefore be said that a site liquefied by an earthquake can be reliquefied by a subsequent earthquake.

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This paper is concerned with dynamics of the standard penetration test (SPT). The usefulness of mounting strain gages at two different stations along a driven rod is described, together with a workable procedure of analysis. The analysis procedure makes use of the traveling time between the two gage points and enables one to identify the particle velocity, the displacement and the stress at any station of the rod, as well as the energy actually transmitted from a hammer to the rod. Particular attention is called for the consequence of inevitable, small errors in strain data upon such identifications. A pertinent procedure of error-correction is proposed and its validity is substantiated against the performance of well instrumented SPTs performed by the authors.

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In view of the significant role of the water film effect in flow failure for a liquefied sandy deposit, the mechanism of water film generation is numerically studied based on a 1-dimensional model test. The process of water film growth and decay can be simulated to a certain extent by a simple consolidation analysis, which indicates that only a small difference in permeability in layered sand is enough for a water film to develop. A 1 G shaking table test for a two-dimensional slope model with an arc of silt within a saturated sand is then addressed to discuss the dilatancy effect exerted in sheared sand during flow failure. It is possible that, once the water film is formed, the transmission of shear stress through it is interrupted, leaving the sand below free from the dilatancy ; this eventually allows the water film to stay without being absorbed during flow failure. The result of another shaking table test for a trapezoidal slope with horizontal silt seams indicate that water films beneath the seams enable the soil mass above them to laterally flow along water films very gently inclined even after shaking. If a silt seam breaks due to excessive pressure in the water film, it triggers re-liquefaction in the upper sand and leads to further instability.

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