Evidence of Damage in Cryopreserved and Fresh Bovine Embryos Using the Tunel Technique

The objective of the present study was to evaluate the quality of bovine embryos cryopreserved in different years in Chiapas, Mexico. The embryos were obtained from a government institution (FIMEGEN) dedicated to promoting embryo transfer among dual-purpose cattle farmers. Forty-three embryos frozen in 1988, 1989, 2000 and 2002 were analysed with the Tunel technique to detect programmed cell death (apoptosis). Eleven fresh embryos were used as controls. Analysis of variance was used in embryos stored in the different years with averages tested using Tukey's test. Student's t-test was employed to compare fresh and frozen cells. Embryos with shorter storage time presented a lower number (p < 0.001) of Tunel-positive cells compared with embryos stored for longer time. On the contrary, when comparing the number of apoptotic cells between frozen and fresh embryos a higher number of positive cells (p < 0.05) were found in the former. The present results suggest that the cryopreservation per se caused damage that compromises the viability of the embryo. Another explanation for the lower pregnancy rate found in the tropics could be irreversible damage caused by poor storage technique in these large operations.     

The Design and Synthesis of Inhibitors of Imidazoleglycerol Phosphate Dehydratase as Potential Herbicides

The discovery and exploration of a new class of broad-spectrum post-emergent herbicides with a novel mode of action, namely the disruption of histidine biosynthesis via inhibition of imidazoleglycerol phosphate dehydratase (IGPD; E.C. 4.2.1.19), are described. Clear structural similarities between the first member, produced during an attempt to produce analogues of glyphosate, and intermediates in histidine biosynthesis were noted. Several series of targets were designed, to mimic both the enzyme substrate and a putative reaction intermediate, and synthesised. Some examples were found to be both extremely potent inhibitors of the enzyme, having K_i values as low as 0·3 nM , and phloem-mobile herbicides with levels of weed control similar to those shown by glyphosate. Further logical progress awaits a high-resolution X-ray structure determination of an enzyme-inhibitor complex. © 1997 SCI     

Investigation of the sensitivity and specificity of radiological signs for diagnosis of periapical infection of equine cheek teeth

Reasons for performing study: Radiography is commonly used for the diagnosis of equine cheek teeth (CT) infection but, to our knowledge, no study to date has evaluated the relative values of individual specific radiographic signs when making a diagnosis. Objectives: To investigate the sensitivity and specificity of individual radiographic signs identified from the literature for the diagnosis of CT apical infection using a retrospective case‐control study. Methods: Cropped radiographs taken using computed radiography of 41 apically infected CT and 41 control CT were independently blindly evaluated by 3 clinicians for the presence of 12 predetermined radiographic signs associated with CT apical infection. A final diagnosis of either noninfected or infected was made. Sensitivity and specificity were calculated for the presence or absence of each radiographic sign for each clinician. Uni‐ and multivariable conditional logistic regression were used to determine strength of association of the 12 radiographic signs with apical infection. Results: Median sensitivity and specificity for the diagnosis of CT apical infection were 76 and 90%, respectively. Periapical sclerosis, clubbing of one or 2 roots, degree of clubbing and periapical halo formation had the highest sensitivities (73–90%), with moderate specificity (61–63%). Multivariable conditional logistic regression revealed that severity of periapical sclerosis and extensive periapical halo were strongly associated with CT apical infection. Conclusions: The presence of periapical sclerosis and formation of a periapical halo were strongly associated with CT apical infection. Computed radiography appears to have a higher sensitivity but similar specificity to previously published results using film radiography to detect CT apical infection. Potential relevance: These findings may aid practitioners when interpreting radiographs of equine CT as to the relative significance of their findings.     

Effects of Prolonged Exposure to Low‐Dose Fumonisin B1 in Pigs

From the point of view of human exposure, fumonisins (FB₁, FB₂, FB₃, FB₄), a relatively recently (1988) discovered and identified group of mycotoxins, represent one of the five most important mycotoxin groups causing human disease. In an earlier experiment studying the effects of relatively low doses (10, 20 and 40 p.p.m.) of FB₁ in weaned piglets, it was established that the 4‐week feeding of 10 p.p.m. (mg/kg feed) FB₁ produced mild pulmonary oedema. This suggested the importance of studies with even lower doses of the toxin to determine the tolerable limits. The objective of this experiment was therefore to study the effects of prolonged (8‐week) exposure to still lower concentrations (0, 1, 5 and 10 mg/kg feed) of FB₁. The 8‐week feeding of FB₁ in low concentrations (1–10 p.p.m.) did not cause clinical signs and significant performance impairment in pigs, but rendered irreversible the chronic changes that had already developed in the animals in a dose‐dependent manner. Dissection revealed pathological alterations of the lungs in one of the animals given 1 p.p.m. (n=4), in two animals exposed to 5 p.p.m. (n=5), and in three animals given 10 p.p.m. (n=4). In all three treatment groups, proliferation of the connective tissue fibres, primarily of those around the lymphatic vessels, in the subpleural and interlobular connective tissue of the lungs, extending to the peribronchial and peribronchiolar areas, was seen. The results of this experiment call attention to the risk of prolonged low‐dose toxin exposure, which has very important public health implications.