Thermoresistance Test Research Articles

Activity and thermoresistance of fused iron catalysts for ammonia synthesis

The activity and thermoresistance of five industrial catalysts were examined. Kinetic measurements were carried out in an isothermal, flow differential reactor under 10.0 MPa in the 400–520°C temperature range. In thermoresistance tests, overheating of the catalysts was carried out at 650°C for 24 h, or at 620°C for 24 to 192 h. The relationships obtained during both experimental tests were similar, with 24-h operating at 650°C giving a similar activity decrease as ageing for 192 h at 620°C. The chemical composition of the catalysts (XRF) was determined.

Entamoeba moshkovskii (Tshalaia, 1941): morpho-biological characterization of new strains isolated from the environment, and a review of the literature.

After an investigation carried out with samples from several sewage sludges from the town of Pavia (Italy) the AA. report the isolation of two new strains of Entamoeba moshkovskii. The usefulness and reliability of two methods, i.e. growth in hypotonic media and the thermoresistance tests in vitro for the biological typing of this species are analyzed and discussed. Both methods had already proven useful to characterize the Laredo-type strains of E. histolytica too, as reported by other AA.

Estudo comparativo entre as microscopias de contraste de fase e contraste de interferência diferencial para análise de sêmen congelado de bovinos

Two hundred ampules of frozen bull semen were evaluated for per cent acrosomal pathology and major and minor defects of spermatozoa. The ampules referred to 4 groups of 50 each, corresponding to semen frozen in 1975, 1976, 1977 and 1978. Semen examinations were made after thawing and after being placed in a 38°C water bath for 5 hours (Slow Thermo resistance Test) or in a 45°C water bath for 1 hour (Quick Thermo resistance Test). Analysis of variance showed highly significant differences (P<.01)between phase-contrast and differential interference contrast microscopies for evaluation of acrosomal pathology and major defects of spermatozoa. For minor defects analysis of variance did not show statistical differences between the two technics employed.

Correlações entremotilidade progressiva e retenção do acrossomo em semen congeladode bovinos após o descongelamento e após provas de termo resistência

Correlation determinations for the relationship between progressive motility of sperm cells and acrosomal retention were calculated on 200 ampules of frozen bull semen after thawing and after incubation at 45°C for 1 hour or at 38°C for 5 hours (Quick and Slow Thermoresistance Tests). Evaluations of progressive motility were estimated at 200 magnifications in optics microscope and those of acrosomal retention under 1000X magnifications phase-contrast or 1250X magnifications differential interference contrast microscopies, both in oil immersion. Highly significant correlations(P <.01) were so observed for progressive motility and acrosomal retention: a) negative correlation between both characteristics after thawing; b) positive correlation between progressive motility after Quick Thermoresistance Test and acrosomal retention after thawing; c) negative correlation between both characteristics after Quick and Slow Thermoresistance Tests.

Influence of Boars on the Relationship between Fertility and Post Thawing Sperm Quality of Deep Frozen Boar Spermatozoa*

The aim of this investigation was to evaluate the possibility of selecting boars for deep freezing by means of laboratory tests on frozen-thawed spermatozoa. Thirty-one randomly selected frozen ejaculates from four boars were investigated by a thermoresistance test after thawing in boar seminal plasma and in OLEP. Extracellular ASAT activity was measured in samples from 30 of the ejaculates after thawing in OLEP and in isotonic glucose solution. Twenty of the ejaculates were utilized for fertility tests by artificial insemination of 37 gilts preceding the laboratory investigation. Three of the boars proved fertile with frozen semen. One of these boars seemed to yield superior fertility to the other two boars. No fertility was obtained with frozen spermatozoa from the fourth boar. Prior to the freezing trial this boar had been used for fresh semen inseminations giving higher pregnancy rates than the average of Swedish A.I.-boars. This boar was therefore considered a case of “low freezability”. In the laboratory tests the samples from this boar showed the lowest motility after 3 hrs.’ storage at 37°C, the highest relative decrease of motility during the thermoresistance test, the highest release of ASAT after thawing in OLEP and the highest relative release of ASAT. Analyses of variance indicated significant and almost significant variation among boars in relative decrease of motility during the thermoresistance test and in relative release of ASAT. The results indicate that the boars were the main cause of variation in fertility as well as in outcome of the laboratory tests. These results do not permit a complete evaluation of the relationship between fertility and outcome of the applied laboratory tests. However, the results indicate a possibility of detecting boars producing spermatozoa with low freezability by means of laboratory tests.

Influence of Thawing Diluents on Vitality, Acrosome Morphology, Ultrastructure and Enzyme Release of Deep Frozen Roar Spermatozoa*

The present investigation was performed to study the effect of freezing and thawing on boar spermatozoa. Thirty-one ejaculates from four boars were investigated after thawing in three different thawing diluents (seminal plasma, OLEP, isotonic glucose solution). From each ejaculate one sample of 1 × 109 spermatozoa was thawed in each of the thawing diluents. Each sample was examined in a thermoresistance test in which motility was stimulated with caffeine 30 min. and 3 hrs. after thawing. Furthermore, acrosome morphology and ASAT release from the spermatozoa were investigated for each sample. One ejaculate from the two most frequently used boars was examined by electron microscopy after thawing in each of the thawing diluents. Differences in the aspects studied appeared between isotonic glucose solution and the other two thawing diluents in the thermoresistance test, in the response to caffeine stimulation 3 hrs. after thawing and in the amount of ASAT released from the spermatozoa. The influence on the acrosome morphology varied between the thawing diluents, but the acrosomal alterations did not seem to be connected with the damage reflected by the thermoresistance test and by the measurement of extracellular ASAT activity. The ultrastructural investigation showed that all spermatozoa examined had some degree of ultrastructural alteration as compared with freshly ejaculated boar spermatozoa treated in the same way. This alteration could not be related to any of the thawing diluents. Of the various laboratory tests the thermoresistance test and the measurement of ASAT release are suggested to be sensitive indicators of sperm damage during freezing and thawing. These tests might be useful indicators of variations in sensitivity of spermatozoa to the freezing-thawing procedure.

Significance of thermoresistance test in assessing the fertility of frozen semen: Dimitropoulos, E. Ann. Med. Vet., 111: 215, 1967 (Belg.)

Significance of thermoresistance test in assessing the fertility of frozen semen: Dimitropoulos, E. Ann. Med. Vet., 111: 215, 1967 (Belg.)