MAMMALIAN EXTINCTIONS IN THE LATE PLEISTOCENE OF NORTHERN EURASIA AND NORTH AMERICA

The 'mass extinctions' at the end of the Pleistocene were unique, both in the Pleistocene and earlier in the geological record, in that the species lost were nearly all large terrestrial mammals. Although a global phenomenon, late Pleistocene extinctions were most severe in North America, South America and Australia, and moderate in northern Eurasia (Europe plus Soviet Asia). In Africa, where nearly all of the late Pleistocene 'megafauna' survives to the present day, losses were slight. Ruling out epidemic disease or cosmic catastrophe, the contending hypotheses to explain late Pleistocene extinctions are: (a) failure to adapt to climatic/environmental change; and (b) extermination by human hunters ('prehistoric overkill'). This review focuses on extinctions in northern Eurasia (mainly Europe) in comparison with North America. In addition to reviewing the faunal evidence, the highly relevant environmental and archaeological backgrounds are summarized. The latest survival dates of extinct species are estimated from stratigraphic occurrences of fossil remains, radiocarbon dates, or association with archaeological industries. The Middle and Upper Pleistocene (ca. 700,000-10,000 BP) in northern Eurasia and North America was a time of constantly changing climate, ranging from phases of extensive glaciation in cold stages, to temperate periods (interglacials). In the Lateglacial (ca. 15,000-10,000 BP), during which most extinctions occurred, there was a major reorganization of vegetation, mainly involving the replacement of open vegetation by forests. These changes were more profound than earlier in the Last Cold Stage, but similar in nature to vegetational changes that took place at previous cold stage/interglacial transitions. The archaeological record shows that humans have been present in Europe since the early Middle Pleistocene. The arrival in Europe ca. 35,000 BP of 'anatomically modern humans', with their technologically more advanced upper palaeolithic industries, was a 'quantum leap' in human history. Extinctions occurred throughout the European Pleistocene, but until the late Pleistocene most losses were replaced by the evolution or immigration of new species, and most of those lost without replacement were small mammals. In marked contrast, extinctions without replacement in the late Pleistocene were almost entirely confined to the largest mammals (greater than 1000 kg) and some medium-large species (100-1000 kg).(ABSTRACT TRUNCATED AT 400 WORDS)     

Extracellular Killing of Trypanosoma cruzi Amastigotes by Human Eosinophils1

Granules released from human eosinophils upon interaction with Trypanosoma cruzi amastigotes in vitro were seen attached to the surface of non-internalized parasites by electron microscopy. Amastigote damage was preceded by the binding of eosinophil granule material to its membrane, and eosinophil granule major basic protein (MBP) bound to the parasite surface was readily detectable. Additional evidence of eosinophil cytotoxicity for extracellular amastigotes was the observation that amastigotes trapped between two eosinophils, without being ingested by either one, were destroyed at the interface. Amastigotes isolated from the spleens of infected mice or grown in culture were similarly sensitive to the lytic effects of purified MBP. These results demonstrate the ability of human eosinophils to lyse T. cruzi amastigotes extracellularly in the absence of antibody and suggest that MBP may be involved in the effect. Thus, eosinophils, known to be capable of destroying phagocytosed amastigotes, could also contribute to the clearance of these parasites through extracellular killing.     

Dynamics of tuberculosis in a naturally infected Badger population

The dynamics of bovine tuberculosis infection in a wild Badger population have been studied since 1981. Faeces are sampled regularly to determine the distribution of infection in the study area. Badgers in known infected social groups, plus the neighbouring groups, are periodically caught and subjected to full clinical and bacteriological examination to monitor the progression of infection within and between groups of Badgers. The interim results of this study are presented and discussed. During 5 years (1981–1985), the temporal spread of infection between social groups in the study area was slow and restricted. Some clinically affected Badgers have survived for long periods. Evidence of infection in individual Badgers indicates that pseudo-vertical (mother to cub) transmission may be important in the maintenance of infection in the Badger population. There is also evidence of horizontal transmission by bite wounding and aerosol infection. Badger mortality due to Mycobacterium bovis infection was low, and the prevalence of infection in male Badgers is greater than in females. The data accumulated so far show no apparent relationship between Badger population density and the prevalence of M. bovis infection, nor is there any evidence to support the hypothesis that M. bovis infection acts to depress Badger population density significantly below disease-free levels. Cattle and infected Badgers can co-exist for long periods without the disease necessarily being transmitted to cattle.     

Further Studies on Substrates Inducing Metacyclogenesis in Trypanosoma cruzi

Epimastigotes of Trypanosoma cruzi, Peru strain, incubated in Contreras' artificial triatomine urine transformed into metacyclic trypomastigotes when 10 mM L-glutamine, L-asparagine or D-fructose was added to the medium. Metacyclogenesis with these substrates was comparable to the percent metacyclic morphotype formation induced by L-proline and significantly greater than that stimulated by 10 mM D-glucose. Sodium acetate (10 mM) increased transformation induced by L-proline, and L-hydroxyproline (10 mM) increased transformation induced by D-fructose. Phosphoenolpyruvate (10 mM) inhibited L-proline-induced metacyclic trypomastigote stage formation. Three antimetabolites, azetidine 2-carboxylate (5 mM), malonic acid (1 mM), and desthiobiotin (5 mM), completely inhibited D-fructose-induced but not L-proline-induced transformation. The Costa Rica, Y, and CL strains of T. cruzi showed different patterns of percent metacyclogenesis with substrates that induce transformation in the Peru strain.     

Derivation of Plant Cell Wall Water Content by Examination of the Water-Holding Capacity of Membrane-Disrupted Tissues10

Plant cell lumina are several orders of magnitude larger thancell wall pores. If the membranes of the plant sample are disruptedand the tissue dried out, a value should be reached at whichthe cell lumina have drained but the cell walls remain relativelyhydrated. The water content of membrane-disrupted tissues atlow may, therefore, serve as a good approximation of plantcell wall water content (CW). The relationship between and water content of membrane-disruptedtissues was measured for four grass spaces over the range of0 to –40 MPa. It was found that most water loss occurredabove a of – 10 MPa. CW was estimated from the watercontent of membrane-disrupted tissues at lower and it was foundthat there was very little intra-or intraspecific variabilityin CW estimates when water content was expressed as a percentagedry weight of the tissue. This is in contrast to the high variabilityin CW estimated from the analysis of inverse water potential—watercontent (IP—WC) curves measured with the thermocouplepsychrometer. Applications of the membrane-disruption methodof estimating CW of plant tissue are discussed. Key words: Cell wall water, thermocouple psychrometer, membrane-disruption     

Fighting the stigma caused by mental disorders: past perspectives,present activities,and future directions

People who live with mental illnesses are among the most stigmatized groups in society. In 1996, in recognition of the particularly harsh burden caused by the stigma associated with schizophrenia, the WPA initiated a global anti-stigma program, Open-the-Doors. In 2005, a WPA Section on Stigma and Mental Health was created, with a broader mandate to reduce stigma and discrimination caused by mental disabilities in general. In light of these impor-tant developments, and the growing public health interest in stigma reduction, this paper reflects on the past perspectives that have led us to our current position, reviews present activities and accomplishments, and identifies challenges that the Section members will face in their future efforts to reduce the stigma caused by mental disorders.