The archaebacteria and eukaryotic origins

Critical analysis of the phylogeny of prokaryotes is in its infancy. Woese and others have made the startling proposal that methane-producing bacteria and a few others form a phyletically unified group, the Archaebacteria, as old and as diverse (although not now as numerous) as all other bacteria. The only critique of this proposal is inadequate. Here we present an alternative view, that the Archaebacteria were derived from other bacteria and contain the ancestor of a cell which engulfed others, eventually to become the first eukaryote.     

Acute changes in dopamine metabolism in the medio-basal hypothalamus following adrenalectomy

Summary During the first hour following adrenalectomy the -MPT-induced disappearance of dopamine was increased in the arcuate nucleus compared to that in sham-operated rats. In a number of other brain regions of both adrenalectomized and sham-adrenalectomized rats only stress-induced changes were observed in catecholamine utilization. These data suggest that corticosterone selectively modulates dopamine utilization in the medio-basal hypothalamus.Acknowledgment. The skilful technical assistance of Ms Joke Van Put, Ms Henny De Vos Burchart-Lodewijks and Mr Henk Spierenburg is gratefully acknowledged.     

Corticotropin releasing factor increases the adrenocortical responsiveness to adrenocorticotropin

Summary In the course of studying the plasma adrenocorticotropic hormone (ACTH) and corticosterone responses to synthetic corticotropin releasing factor (CRF), we noted some disparity in the responses. A higher dose (20 g compared with 5 g per rat i.a.) produced an equal plasma ACTH but greater plasma corticosterone response in adult male rats. Thus, we examined the possibility that CRF increases adrenocortical responsiveness to ACTH. CRF significantly (p<0.0005) increased the plasma corticosterone response to ACTH in rats pretreated with dexamethasone. Thus, synthetic CRF increases corticosterone secretion in rats not only by stimulating ACTH secretion, but also by increasing the adrenocortical responsiveness to ACTH.Acknowledgments. This research was supported by grant MT-5183 from the Medical Research Council of Canada and by the Department of Medicine, University of Kentucky.     

The intrapulmonary neuroepithelial bodies after vagotomy: demonstration of their sensory neuroreceptor-like innervation

Summary In the neonatal rabbit, infranodosal vagotomy destroys most of the intracorpuscular nerve endings of the pulmonary neuroepithelial bodies (NEB), while supranodosal vagotomy leaves these nerve endings intact. We conclude that NEB are mainly innervated by sensory neurons whose cell bodies lie in the nodose ganglion of the vagus nerve. These findings support the hypothesis that although secretory in nature, NEB are neuroreceptor structures.This study was supported by the Nationaal Fonds voor Wetenschappelijk Onderzoek. Fonds voor Geneeskundig Wetenschappelijk Onderzoek, Belgium. The authors thank R. Renwart and K. Armee for technical, G. Pison for photographical assistance.     

Host macrophages are involved in systemic adoptive immunity against tumors

Summary The positive systemic therapeutic results obtained with adoptive transfer of immune spleen cells could not be reproduced in macrophage depleted mice. Thus, host macrophages are involved in systemic adoptive immunity against tumors.This study was supported by the Rijksuniversiteit Utrecht and the Netherlands Cancer Society (Konigin Wilhelmina Fonds, KWF).     

Effect of light at night on the pineal rhythm in N-acetyltransferase activity in the Syrian hamsterMesocricetus auratus

Summary Pineal N-acetyltransferase activity in the male Syrian hamster exhibited a daily rhythm; the maximal night-time value was 3.5-fold higher than the day-time value. When hamsters were exposed to light at night N-acetyltransferase declined within 30 min to 1/5 of its former activity. These results indicate that in the Syrian hamster the pineal melatonin rhythm may be regulated at least partly via changes in N-acetyltransferase activity.The authors are grateful to Mrs Marie Svobodová for her skillful technical assistance.     

Immunocytochemical localization of hyperglycemic hormone (HGH) in the neurosecretory system of the eyestalk of the crayfishAstacu leptodactylus

Summary Hyperglycemic hormone (HGH) fromAstacus leptodactylus can be visualized by an immunocytochemical procedure using a specific antiserum against HGH and the peroxidase-anti-peroxidase (PAP) method. HGH containing cells are localized in the most distal portion of the x-organ in the medulla terminalis. Their cell diameter is about 47±7 m; the nucleus measures about 22±2 m. They form a subgroup of neurosecretory cell type 1, already described for the crayfish. A large amount of this HGH material is homogeneously stored in the sinus gland. A group of fibres in the x-organ — sinus gland — tractus can be followed, due to their positive reaction with the PAP-reagent.     

Ketoconazole — a new broad spectrum orally active antimycotic

Summary Oral treatment with ketoconazole prevented and cured artificial crop candidosis of the turkey, vaginal candidosis of the rat and skin candidosis of the guinea-pig. It was also highly effective against artificial systemic candidosis of the guinea-pig and chicken as well as against dermatophytoses of the guinea-pig.This work was supported by the Instituut tot Aanmoediging van het Wetenschappelijk Onderzoek in Nijverheid en Landbouw.     

Chaos in a long-term experiment with a plankton community

Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos in a long-term experiment with a complex food web. Our food web was isolated from the Baltic Sea, and consisted of bacteria, several phytoplankton species, herbivorous and predatory zooplankton species, and detritivores. The food web was cultured in a laboratory mesocosm, and sampled twice a week for more than 2,300 days. Despite constant external conditions, the species abundances showed striking fluctuations over several orders of magnitude. These fluctuations displayed a variety of different periodicities, which could be attributed to different species interactions in the food web. The population dynamics were characterized by positive Lyapunov exponents of similar magnitude for each species. Predictability was limited to a time horizon of 15-30 days, only slightly longer than the local weather forecast. Hence, our results demonstrate that species interactions in food webs can generate chaos. This implies that stability is not required for the persistence of complex food webs, and that the long-term prediction of species abundances can be fundamentally impossible.