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The evolutionary events during the Ediacaran–Cambrian transition (~541 Ma) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in early Cambrian. Molecular clocks and biomarkers provide independent estimates for the timing of animal origins, and both suggest a cryptic Neoproterozoic history for Metazoa that extends considerably beyond the Cambrian fossil record. We report an assemblage of ichnofossils from Ediacaran–Cambrian siltstones in Brazil, alongside U-Pb radioisotopic dates that constrain the age of the oldest specimens to 555–542 Ma. X-ray microtomography reveals three-dimensionally preserved traces ranging from 50–600μm in diameter, indicative of small-bodied, meiofaunal tracemakers. Burrow morphologies suggest they were created by a nematoid-like organism that utilised undulating locomotion to move through the sediment. This assemblage demonstrates animal-sediment interactions in the latest Ediacaran Period, and provides the oldest known fossil evidence for meiofaunal bilaterians. Our discovery highlights meiofaunal ichnofossils as a hitherto unexplored window for tracking animal evolution in deep time, and reveals that both meiofaunal and macrofaunal bilaterians began to explore infaunal niches during the late Ediacaran., Field costs for L.A.P. were supported by an undergraduate travel grant from St. Anne’s College, University of Oxford. Fieldwork costs for M.D.B. were supported by CNPq-Conselho Nacional Desenvolvimento Científico e Tecnológico- Brazil (Proc. 451245/2012-1). This project was supported by an NERC Isotope Geoscience Facilities Steering Committee grant (project IP-1560-0515). J.M.L., P.C.B., R.T., G.A.C.C., C.Q.C.D. and M.L.A.F.P. were supported by grant numbers 2009/02312-4, 2010/02677-0, 2013/17835-8 and 2016-06114-6, São Paulo Research Foundation (FAPESP), Brazil. A.G.L. and L.A.P. are supported by the Natural Environment Research Council (grant numbers NE/L011409/2 and NE/L501554/1, respectively). R.J.G. is a Scientific Associate at the Natural History Museum, London, and a member of the Interdisciplinary Centre for Ancient Life (UMRI). D.M. recognizes the support of an NSERC discovery grant.

Energia é um tema central em ciências e que está associado a problemáticas complexas e relevantes para as sociedades modernas. Nos diversos países, é abordado, de modo diferenciado, em diferentes níveis de escolaridade. Em Portugal a abordagem é efectuada, entre outros, no 3° ciclo do Ensino Básico, último nível de escolaridade destinado a todos os cidadãos. Com a sua abordagem pretende-se, entre outros, sensibilizar os cidadãos para a importância das questões energéticas, enquanto factor determinante da sustentabilidade do futuro do Planeta. Na escola, esta abordagem é mediada pelos manuais escolares, os quais podem concretizar, ou não, devidamente as orientações curriculares. Por outro lado, a relevância da abordagem didáctica do tema depende da compatibilidade entre as temáticas que interessam aos alunos e as temáticas que são abordadas pelos manuais. O objectivo desta investigação foi o de analisar a relação entre as questões sobre energia que 100 alunos de 9° ano de escolaridade gostariam de ver respondidas e a abordagem da energia efectuada por seis manuais escolares de Física, no âmbito do tema organizador "Terra em Transformação". Constatou-se que existem desfasamentos consideráveis entre os interesses dos alunos e os manuais, com implicações importantes para a educação em ciências para a cidadania.

Leucopenic rats were injected i.v. with either allogeneic or syngeneic lymphocyte suspensions and their capacity to respond to carrageenin tested at various intervals after the injection of the cells. The carrageenin-induced inflammatory response, which is characteristically attenuated in leucopenic animals, was partially but none the less definitely restored when allogeneic cells were transfused 20 min before the irritant, and less so when they were given 1 or 2 h before. Syngeneic cells were effective in restoring this response up to 2 h after injection. Only a small fraction of the exogenous cells, either allogeneic or syngeneic, remained in the blood, and this for short intervals. One hour after administration of cell suspensions blood leucocyte counts again attained previous values. The same rate of disappearance of the cells from blood was observed in splenectomized rats. Removal of the cells from circulation was thought to reflect "homing" into lymphoid tissues and other tissues, but not selectively in the spleen. Lymphocyte constituents, obtained by cell disintegration and injected i.v. into leucopenic rats, did not cause any change in blood leucocyte counts and yet restored the previously inhibited inflammatory response to carrageenin, as much as the viable cells. It is suggested that inflammation-producing materials, either deposited in tissues or formed or transformed at a site of injury, might gain access to the lymphatics during the early stages of a non-immune, inflammatory response, and "stimulate" lymphoid cells in adjacent lymphoid tissues either to release pro-inflammatory factors or to migrate to the site of injury, where they would exert pro-inflammatory activities. Apparently, only a small number of these cells in involved in the response.

Rats selectively depleted of lymphocytes by chronic drainage from the thoracic duct during a 3-day period presented a marked lymphopenia, and decreased responses to carrageenin injected into one of the hind paws. The intensity of the inflammatory responses in thse animals was restored by the i.v. administration of suspensions of viable or lysed lymphocytes, collected from the spleen or lymph of normal animals. A spontaneous reversal of the depressed responses to carrageenin was observed 40 days after the period of lymph drainage, when lymphocyte counts were again normal in blood. If highly inbred rats were used, the i.v. injection of syngeneic lymphoid cells was equally effective in restoring the inhibityed inflammatory responses resulting from lymphocyte depletion. Artificial obstruction of the thoracic duct, with interruption of lymphocyte recirculation, was followed by decreased lymphocyte counts in blood and severely depressed inflammatory responses to carrageenin. This unresponsive state was corrected as the animals recuperated, probably coincidentally with the development of collateral lymph channels and as the temporarily disturbed blood picture returned to normal. It is concluded that lymphocytes can participate in the development of non-immune inflammation through the release of pro-inflammatory factors. This release is independent of previous sensitization of the cells.

Rats were subjected to various experimental procedures which affected lymphocyte numbers, in an attempt to investigate the participation of individual subpopulations of these cells in the development of acute, non-immune inflammation. Deficient T function, as evidenced in neonatally thymectomized animals, or in 6-week-old animals thymectomized and afterwards exposed to multiple total-body X-ray irradiations, did not interfere with the development of the acute inflammatory responses of the animals to carrageenin. In the former circumstance, the numbers of circulating B lymphocytes, identified by the presence of surface immunoglobulins, were increased. In thymectomized and irradiated rats, the B-lymphocyte subpopulation was reduced. Circumstances causing attenuated inflammatory reactions to carrageenin resulted, first, from lymphocyte depletion by chronic drainage from the thoracic duct and, second, from irradiation of the animals with a single large dose of X-ray, the animals being tested 24 h after irradiation. B lymphocytes in blood remained within the normal range after chronic lymphatic drainage, but a large dose of X-ray markedly reduced their number. In both cases the attenuation of the responses to carrageenin did not seem to be associated with nonspecific hyporeactivity, or with the effect of the treatments on the other blood cells, It is suggested that the development of acute, non-immune inflammation is influenced by lymphoid cells which might constitute a specific subclass of cells, distinct from fully differentiated T and B lymphocytes.

Light and electron microscopic studies showed that blood vessels of the cremaster muscle of alloxan-diabetic rats under the local influence of histamine or serotonin presented less labelling by colloidal carbon, previously injected i.v., than vessels of normal rats. The hyporeactive state of these vessels was promptly reversed to normal conditions by the administration of insulin. Insulin also potentiated leakage of carbon particles in the vessels of normal animals. These findings add new evidence that insulin might be involved in vascular events following injury and that decreased levels of the hormone, as occurring in diabetes, might result in decreased inflammatory reactions.