Oxidants and antioxidants in atherogenesis. An appraisal

Oxidized low density lipoprotein (Ox-LDL) has a plethora of components that are not present in native LDL. Their presence and quantity depends on the nature, type, and extent of oxidation. Lipids esterified to oxidized fatty acids are the major components formed during the early phase of oxidation and these show a number of proatherogenic properties in in vitro cell culture systems. Recently, evidence has been forthcoming to suggest that some of these oxidized lipids also could elicit "antioxidant;-antiatherogenic" responses from cells. Moreover, some of the cellular effects of Ox-LDL that were previously interpreted as atherogenic could also be reinterpreted to suggest an antiatherogenic cellular response. In addition to the above, the antioxidants that are carried in lipoproteins could have anomalous behavior attributable to their metabolism, ability to be internalized by arterial cells, and the presence of oxidative systems that could render them prooxidants. In conclusion, there are numerous contributing factors that need to be studied and understood before antioxidant therapy becomes an option for the treatment for cardiovascular diseases.     

Calcium and myocardial cell injury. An appraisal in the cardiomyopathic hamster

The heart muscle is very compliant within a wide range of physiologic impulses. The adaptive energy of the myocardium depends, however, upon adequate oxygen supply and the functional state of the plasmalemma. These limitations have been well demonstrated in a number of experimental models with emphasis on the essential role of Ca2+ transmembrane movements for maintenance of heart functions and its viability. This postulate appeared quite important when we found that Ca2+ slow channel blockers could prevent necrotic changes in hamster hereditary cardiomyopathy. However, the effectiveness of beta-adrenoagonists when given in low doses seems more difficult to interpret since these agonists can only promote Ca2+ transmembrane movements. We can only surmise that Ca2+ accumulation in cardiomyopathic hearts does not derive from a primary defect of the plasmalemma but rather from an exhausted hypokinetic state that favours Ca2+ accumulation with progressive deterioration of the structural proteins. It is thus inferred that Ca2+ mediates rather than initiates the degradation process which characterizes this inherited cardiomyopathy.     

C.D. Darlington and the British and American reaction to Lysenko and the Soviet conception of science

The Anglo-American reaction to the Lysenkoaffair has been treated primarily either fromthe point of view of the political Right orLeft, or as a consequence of post-WWIIinternational relations. None of the accountshave considered the central role of the Britishcytogeneticist and evolutionist C.D.Darlington. This article considers Darlington'srole, and illustrates how, through an analysisof his divergent reaction, it becomes possibleto see the response to Lysenko as a reflectionof internal scientific and political debatesconcerning the planning, funding, utility, andfreedom of science in post-war Britain.     

An appraisal of the epidemiology of Trypanosoma cruzi serology in Brazil.

A large bibliographic survey provided data on Trypanosoma cruzi serology covering the period 1948-1984. Epidemiological-demographic methods provided an estimate of 11% for the prevalence of positive serology in Brazil, by 1984. Significant temporal trends were observed for most of the Brazilian geographical regions as well as for Brazil, as a whole. The parabolic curve that fit best for the entire country, indicates that by 1991, the incidence of new positive serology would be close to zero. This conclusion needs further fine-adjustment, since the forecast point is somewhat distant from the measured period.     

Ethnicity and the British Army in Ireland during the American Revolution

People of German‐speaking background have been permanent residents in Australia and Canada for an extensive period of time and are perceived favourably in these multicultural contexts. This has not always been the case. The event of war has the potential to influence the formation of self‐images and stereotypes of ‘others’ and hence to affect the cohesion of ethnic communities. It follows that altered perceptions of ethnicity are likely to alter the ways governments behave towards ethnic minorities. This, in turn, brings a modification in ethnic relations policy. The focus of this article is to examine official attitudes to Germans resident in these countries and external to them during the second world war and in the immediate post‐war period. A particular concern is that of internment. To look comparatively should develop a deeper understanding of its use in two similar (but also different) commonwealth countries.     

Allelic melanism in American and British peppered moths

Parallel evolutionary changes in the incidence of melanism are well documented in widely geographically separated subspecies of the peppered moth (Biston betularia). The British melanic phenotype (f. carbonaria) and the American melanic phenotype (f. swettaria) are indistinguishable in appearance, and previous genetic analysis has established that both are inherited as autosomal dominants. This report demonstrates through hybridizations of the subspecies and Mendelian testcrosses of melanic progeny that carbonaria and swettaria are phenotypes produced by alleles (isoalleles) at a single locus. The possibility of close linkage at two loci remains, but the simpler one-locus model cannot be rejected in the absence of contrary evidence.     

Late Ordovician extinction of North American and British crinoids

After reaching a diversity peak in the Caradocian, North American Ordovician crinoids underwent a gradual decline to a nadir in the early Ashgillian (Maysvillian). This interval, recording extinction of the Cleiocrinidae, Merocrinidae, Ottawacrinidae, Hybocystitidae, and several lineages of camerate crinoids, was apparently caused by major environmental shifts in seas of eastern North America resulting from a westward-prograding wedge of terrigenous clastics derived from the Taconic Highlands, possibly coupled with a marine transgression in the Maysvillian that allowed colder water slope biofacies to invade the craton. Crinoids suffered a major episode of extinction in the late Ashgillian (late Richmondian/Rawtheyan). This event, preceding the end of the Ordovician by at least one stage or 2 to 4 million years, resulted in extinction of 12 families of crinoids including the Xenocrinidae, Tanaocrinidae, Reteocrinidae, Archaeocrinidae, Anthracocrinidae, Cincinnaticrinidae, Iocrinidae, Anomalocrinidae, Carabocrinidae, Cupulocrinidae, Porocrinidae, and Hybocrinidae. Glacio-eustatic lowering of sea level may have triggered this crisis by partially draining the North American craton, resulting in changes in oceanic circulation, salinity, and temperature. Latest Ordovician (Hirnantian) carbonates of the North American mid-continent region contain pelmatozoan assemblages from which Silurian crinoids radiated. These taxa were largely unaffected by a minor extinction event at the Ordovician/Silurian boundary.     

Localization of estrogen receptors in uterine cells. An appraisal of translocation.

The nuclear localization of estrogen receptors has been examined under conditions which minimize redistribution and localization artifacts. A procedure is presented which rapidly lyses suspensions of cells from immature rat uteri by using 0.04% Triton X-100 in isotonic buffer. The ‘nuclei’ which are obtained after lysis have a median diameter of 1μm and are devoid of nuclear membranes. There is close agreement between the number of cells before lysis and the number of nuclear particles after lysis. Triton X-100 gave no interference with quantitative binding of estradiol to receptor and no alteration in the sedimentation behavior of receptor on sucrose gradients containing high or low salt. Using this procedure to monitor the dynamics of estrogen receptor distribution within uterine cells after exposure to estradiol, translocation of estrogen receptor to the nucleus was observed to occur at a rate slightly slower than the rate at which estradiol was specifically bound to free cells or receptors. The difference in these rates is compatible with a model in which estradiol must first bind to the receptor before the binding complex moves to the nucleus. The rate of nuclear translocation was temperature-dependent and was observed to occur at 0 °C, provided that enough time was allowed for steroid entry, receptor charging and transit to the nucleus. Two distinct phases were observed to characterize nuclear receptor localization. In the first phase after hormone exposure, estrogen receptor progressively accumulated in the nucleus; afterwards, estrogen receptor was progressively lost from the nucleus but could not be detected in other subcellular compartments in a form still binding hormone. Since high cell viability was maintained during these manipulations, loss of nuclear receptor was not due to cell damage during in vitro incubation. These studies suggest that this decline in nuclear receptor level after hormone interaction, which is known to occur in vivo, may be a normal event during estrogen interaction with target cells.