The importance of understanding the response of structural composites to impact cannot be overstated. This understanding includes both the impact phenomena themselves and the influence of materials properties on the impact response. This paper presents the need for instrumented testing to optimize our understanding of the impact event, especially the response of the impacted material. The conclusion is drawn that the impact force history is a more relevant measure of a materials characteristics than is the total kinetic energy of the impactor. Static and dynamic impact phenomena are assessed to lay the foundation for the eventual development of a standardized test method focused on the lower velocity range impact response behavior of composites. In addition, a relatively inexpensive but very versatile low-velocity, instrumented pendulum impact tester is described and actual test data for both graphite fiber/thermoset matrix and graphite fiber/thermoplastic matrix are compared. Actual energy absorption curves are shown. A simple method is described to allow direct measurement of the total energy exchanged during the impact event, and the use of these data to permit the vital dynamic calibration of the load cell for every different impact event is illustrated. The different stages in the damage process are characterized, for the first time, for the two materials systems studied.
The enzyme A'-3-oxosteroid 5P-reductase (3-0x0-5P-steroid : NADP' oxidoreductase and 4,5& dihydrocortisone : NADP+ d4-oxidoreductase) catalyzes the reduction of the d' double bond of bile acid intermediates and steroid hormones carrying the d4-3-one structure in the A/B cis configuration. Human d4-3-oxosteroid SP-reductase cDNA was isolated from a liver cDNA library by cross hybridization with a previously cloned rat cDNA, which was used as a probe [Onishi, Y., Noshiro, M., Shimosato, T. & Okuda, K.4. (1991) FEBS Lett. 283, 215-2181. DNA sequence analysis of a hybridization-positive clone predicted the human d4-3-oxosteroid 5P-reductase to contain 326 amino acids. The amino acid sequence of the human d4-3-oxosteroid SP-reductase had 79% overall identity to the rat enzyme sequence. It also showed 54% and 50% overall identity with rat 3a-hydroxysteroid dehydrogenase and human aldose reductase, respectively. RNA blotting analysis demonstrated the existence of a single d4-3-oxosteroid 5P-reductase mRNA of approximately 2.7 kb in human liver. Transfection of the cDNA into COS cells resulted in the expression of an active enzyme with a high activity toward the bile acid intermediates 7a,l2a-dihydroxy-4-cholesten-3-one and 7a-hydroxy-4-cholesten-3-one. In addition, the expressed enzyme showed a small but significant 5P-reduction activity toward 11~,17a,21-trihydroxy-d4-pregnene-3,20-dione (cortisol) and 17P-hydroxy-d4-androsten-3-one (testosterone) whereas no activity was observed toward d4-pregnene-3,20-dione (progesterone) or d'-androstene-3-17-dione (androstenedione). The substrate specificity of the human enzyme is considerably narrower than that of the rat enzyme, and the enzyme seems to be more important for bile acid biosynthesis than for metabolism of steroid hormones.The catabolism of cholesterol to bile acids in the liver is the major pathway for the removal of cholesterol from the body and plays an essential role in cholesterol homeostasis. This conversion involves modification of the steroid nucleus and oxidation and cleavage of the side chain [l]. To reduce the d5 double bond of cholesterol, to give the A/B cis configuration, cholesterol is first oxidized to d4-3-one structures, e.g. 7a,l2a-dihydroxy-4-cholesten-3-one, a precursor to 3a,7a,l2a-trihydroxy-5/3-cholan-24-oic acid (cholic acid) and Abbreviations. Cholic acid, 3a,7a,12a-trihydroxy-5j?-cholan-24-oic acid ; chenodeoxycholic acid, 3a,7a-dihydroxy-5~-cholan-24-oic acid; 5p-reductase, A4-3-oxosteroid 5p-reductase ; testosterone, 17p-hydroxy-A4-androsten-3-one ; cortisol, 1 lp, 17a,21 -trihydroxy-A4-pregnene-3,20-dione ; progesterone, A4-pregnene-3 ,20-dione ; androstenedione, A"-androstene-3,17-dione ; DMEM, Dulbecco's modified Eagle's medium; SV40, simian virus 40.Enzymes. A4-3-Oxosteroid 5p-reductase [3-oxo-SP-steroid: NADP'-oxidoreductase (EC 1.3.1.23) and 4,5p-dihydrocortisone : NADP' A4-oxidoreductase (EC 1.3.1.3)] ; 3a-hydroxysteroid dehydrogenase (EC 1.1.1.50); aldose reductase (EC 1.1.1.21).Note. Kyu-Ichiro Okuda was previously Kyuichiro Oku...
The limited RCT evidence to date does not show adverse metabolic risk with the use of the OCP compared with metformin. Further long-term RCTs are required.
Open testicular biopsy is a classic method of investigation in men with azoospermia. Recently, percutaneous needle biopsy of the testis has been used in attempts to obtain material for histopathological diagnosis in such cases and to retrieve spermatozoa for intracytoplasmic sperm injection (ICSI). To determine whether a 19 gauge (G) and a 21G butterfly needle could be used for percutaneous aspiration of testicular tissue to determine the presence of mature spermatids and assess spermatogenesis, 10 patients (16 testes) and 12 patients (17 testes) underwent 19G or 21G needle biopsy respectively, immediately followed by open testicular biopsy, with both procedures under local anaesthesia. Biopsy with each needle size was compared with open biopsy. With the 19G needle, in the 14 cases where material was obtained there was full agreement with open biopsy regarding the presence or absence of mature spermatozoa, whereas with the 21G needle only nine of the 13 biopsies yielding material were predictive in this respect. Each needle size correlated poorly with open biopsy regarding evaluation of spermatogenesis. We conclude that percutaneous biopsy with a 19G butterfly needle is a quick and reliable method for demonstrating spermatozoa for ICSI. But for a detailed histopathological diagnosis, however, the needle biopsies gave poor results, whereas the material from the open testicular biopsies was assessable.
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