Potentiative effects of sulfhydryl compounds on carrageenin-induced oedema in rats and relationship to their potencies as inhibitors of angiostin-coverting enzyme in vivo

Carrageenin-induced oedema in rats was potentiated by oral administration of (4R)-3-[(2S)-3-mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (SA291) and related sulfhydryl compounds, and the effect was closely correlated with their potencies as inhibitors of angiotensin-converting enzyme in vivo.

Nonlinear Viscoelastic Behavior of Butadiene—Acrylonitrile Copolymers Filled with Carbon Black

Various viscoelastic measurements including dynamic mechanical measurements in tension at 110 Hz from −60–160°C, tensile stress relaxation measurements with 100% elongation at 25, 54, and 98°C, capillary flow measurements at 70, 100, and 125°C, and high-speed tensile stress-strain measurements carried to break at 25, 56, and 98°C were performed on four samples of carbon-black-filled butadiene—acrylonitrile copolymers. All the data were treated with the same equation for time-temperature conversion. The capillary viscosity—shear rate curves were significantly lower than the complex viscosity—angular frequency curves, indicating “strain softening” with extrusion. The viscosity was estimated from the stress-strain relationship at the yield point. The viscosity as a function of the strain rate is significantly higher than the complex viscosity as a function of angular frequency, indicating “strain hardening” with extension. The strain softening and strain hardening are attributable to the structural changes upon deformation of the carbon-black-filled elastomers. With the unfilled elastomers, neither strain softening nor strain hardening were observed in similar measurements.

Viscoelastic Properties of SBR Containing Particles of Crosslinked Polystyrene

It has been shown that methods are available for fundamental characterization of viscoelastic behavior of elastomers containing crosslinked particles. With the Rheometrics mechanical spectrometer and the Mooney rheometer operated at slow speeds, the elastic modulus and loss modulus were obtained at 100°C in the frequency range of 2.5×10−4−2.5×102 rad·s−1. In this frequency range, both the rubbery response of the SBR matrix and the response of polystyrene copolymer particles were observed. The former was in the higher frequencies and the latter in the lower frequencies, with a considerable overlap of both responses. From the magnitude of the temperature-time shift, it was learned that the deformations of both SBR matrix and polystyrene copolymer particles were involved. The steady-shear viscosities were measured with the Instron capillary rheometer. At extrusion temperatures of 85 and 100°C, the extrudates were distorted at the high shear rates. Calculations show that the polystyrene copolymer phase attains the glassy state, because pressure and frequency raise the glass transition from 51°C to the extrusion temperature.

New enzymatic assay of cholinesterase activity

A new enzymatic method for the determination of serum pseudo-cholinesterase activity is described. Choline, which is liberated from benzoylcholine as substrate by cholinesterase, is oxidized by choline oxidase to betaine with the simultaneous production of hydrogen peroxide, which oxidatively couples with 4-aminoantipyrine and phenol in the presence of peroxidase to yield a chromogen with maximal absorbance at 500 nm. The calibration curve is linear up to 1500 units per liter of serum. The method is reproducible, and the results correlate well with those obtained by the method using butyrylthiocholine as substrate and 5,5'-dithiobis-(2-nitrobenzoic acid) as color reagent.

Fundamental Observation on Deformation and Failure Characteristics of SBR 1500

The processing of raw elastomers involves viscoelastic properties at both small and large deformations. It also involves ultimate properties, because the deformation under processing conditions often exceeds the failure limit. The present work describes these properties in the processing ranges of temperature and deformation rate. Therefore, the results may be used for interpreting processability. Also, relative differences in molecular weight, its distribution, long-chain branching, and gels may be detected by comparing the above data for different samples. The results summarized in master curves and a failure envelope indicate that the essential information is obtainable with limited experiments, for example, with the Rheovibron and the variable-speed Mooney rheometer.

Viscoelastic Characterization of Ethylene-Propylene-Diene Terpolymer Elastomers

A practical range of frequency with the Rheometric mechanical spectrometer for the determination of G′ and G″ was shown to be from 2.5×10−2 to 2.5×102s−1, but one decade lower frequency may be reached routinely. The values G′ and G″ may be calculated from the steady-state viscosity curve obtained with the variable-speed Mooney rheometer. However, with samples having long-chain branching, the calculated G′ and G″ are somewhat higher, the difference being close in magnitude to the error of the measurements. With the variable-speed Mooney rheometer, the highest available shear rate is 16 s−1, about one decade less than that with the Rheometrics instrument. With high-molecular-weight rubbers, the range is further reduced, because of “slipping” or “fracturing” of the polymer. On the other hand, the Mooney rheometer enables one to extend the low-frequency range to 2×10−3s−1 very conveniently. The degree of long-chain branching may be estimated from the viscoelastic behavior by comparing complex viscosity and steady-state viscosity at the same time scale, both measurements being made with a Mooney rheometer at a slow speed with a single charge of sample.

Effects of intravenous bolus dosages of methylprednisolone and local radiation on renal allograft rejection and patient mortality

One hundred and thirty of 179 rejection episodes encountered in 205 transplants were reversed by treatment with a bolus preparation of methylprednisolone. Ninety-six of these episodes also required an increase in oral prednisone dosage. No beneficial effect on over-all graft survival was noted, but a significant rise in the mortality, secondary to sepsis, was noted in those who received more than 5 grams of methylprednisolone. Local radiation to the graft did not contribute to better graft survival or mortality.

Rheological Characteristics of Gum Elastomers

A systematic characterization of gum elastomers may be done by measuring viscoelastic and ultimate properties. The viscoelastic properties of amorphous elastomers can be reduced to a master curve by means of the temperature-time, pressure-time, and strain-time correspondence principles. If a structure, e.g. crystallinity, develops with a change of temperature, pressure, or strain, such structural change may be regarded as a deviation. The ultimate properties may be represented either as stress-strain at break, modulus-strain at break, rupture-energy-deformation-rate, or stress-at-break-deformation-rate and strain-at-break-deformation-rate. The modulus-strain-at-break plot shows promise for interpreting mill processability in terms of the basic rheological properties. The rupture-energy-deformation-rate plot supplies a useful quantitative input for mill mixing.

Clinical study of second kidney transplantation

During the period from November 1972 to February 1975, 39 patients received second renal grafts in our institution. The clinical course of the patients was analyzed and compared with 121 patients who received only one graft during the same period. The graft survival either from living related or cadaveric sources was inferior in the second graft group. However, mortality was not increased by re-transplantation. Major differences were noted in the occurrence of hyperacute or accelerated type rejections. There was a high incidence of this type of rejection in the second graft group, especially in the simultaneous retransplant group.

Capillary Rheometry of Carbon-Black-Filled Butadiene—Acrylonitrile Copolymers

Capillary rheometry of carbon-black-filled butadiene—acrylonitrile copolymers at 125°C was performed over a wide shear rate range. The data were corrected for pressure loss in the barrel and at the capillary entrance, and for the non-Newtonian velocity profile (Rabinowitsch correction). No appreciable effect of pressure on viscosity was observed. The die swell values were very small, 1.1–1.4. This fact and the shape of the plots of shear stress vs. shear rate imply the presence of a particulate structure, which is probably built by carbon black surrounded with bound rubber. Unlike the behavior of raw amorphous elastomers, the steady-shear viscosity, the dynamic complex viscosity, and the viscosity calculated from tensile stress-strain behavior were significantly different from each other. That is, the capillary flow data indicated an alteration of the structure towards strain softening, and the tensile stress-strain behavior showed strain hardening, indicating retention of the structure up to the yield point. In the dynamic measurement, being conducted at very small strain, the structure is least disturbed. With unfilled elastomers essentially the same deformational mechanism was believed to be responsible in these three measurements, because the results can be expressed by a single master curve.