Studies on Trypanosoma vivax: Infectivity and serial maintenance of natural bovine isolates in mice

Studies were carried out on the ability of T. vivax to infect laboratory mice and on its subsequent maintenance between mice. On 38 out of 75 occasions, inoculation of mice with bovine T. vivax resulted in infection; in 3 instances, bovine blood, negative by other diagnostic tests, infected mice. Ten out of 21 bovine isolates could be subpassaged in mice for only a limited number of passages. Three additional isolates infective to mice, were maintainable serially between mice for an indefinite time. It appeared that only early natural infections were capable of infecting mice, each individual isolate surviving in the mice for a characteristic period. Those bovine isolates with the inherent property of serial maintenance between mice, did not change in their pathogenicity for ruminants.     

野生人参种子的超低温保存

人参（ＰａｎａｘｇｉｎｓｅｎｇＣ．Ａ．Ｍｅｙ．）是珍贵的药用植物，由于长期过度采挖，资源枯竭，现存于我国东北地区的野生人参已处于濒临绝灭的边缘，被列为国家一级重点保护植物［１，２］。所以在加强其就地保护的同时，人参种质资源的迁地保存也是非常必要的。按...     

Gradual Thawing Improves the Preservation of Cryopreserved Arteries

This study was designed to test a slow, controlled, automated process for the thawing of cryopreserved arteries, whereby specimen warming is synchronized with the warming of its environment. Segments of minipig iliac artery, 4-5 cm in length, were subjected to controlled, automated cryopreservation in a biological freezer at a cooling rate of 1 degrees C/min to -120 degrees C, followed by storage in liquid nitrogen at -196 degrees C for 30 days. Following storage, the arterial segments were subjected to rapid (warming rate of approximately 100 degrees C/min) or gradual (1 degrees C/min) thawing. Thawed specimens were processed for light microscopy and for scanning and transmission electron microscopy, Cell death was determined by the TUNEL method. Metalloproteinase (MMP) expression was estimated by immunohistochemical analysis. Most of the cryopreserved vessels subjected to rapid thawing showed spontaneous fractures, mainly microfractures, whereas these were absent in slowly thawed specimens. In rapidly thawed vessels, the proportion of damaged cells was double that observed in those thawed more gradually. Increased intensity and extent of MMP-2 expression was shown by rapidly thawed specimens. The slow-thawing protocol tested avoids the formation of spontaneous fractures and microfractures and the accumulation of fluid within the arterial wall tissue. This results in improved tissue preservation.