Neighbor Recognition in Two "Solitary" Carnivores: The Raccoon (Procyon lotor) and the Red Fox (Vulpes fulva)

Male raccoons and red foxes were trapped alive and exposed to each other in captivity. Animals of each species trapped close to one another demonstrated a higher frequency of initial dominance-subordinance relationships and lower frequencies of more intense aggressive interactions than did animals trapped at greater distances from each other. This suggests the existence of neighbor recognition and thus a rudimentary social structure within these free-living "solitary" species.     

Photosynthetic pathway and biomass energy production

The current interest in locating new or alternative sources of energy has focused attention on solar energy capture by crops that can be subsequently utilized as a substitute for fossil fuels. The very high productivity of sugarepane and the fact that it accumulates sugars that are directly fermentable to alcohol may have caused seemingly less productive crops to be overlooked. We show here that recoverable alcohol from achievable commercial yields of pineapple can actually equal that of sugarcane, with the pineapple crop requiring only a fraction of the water used by sugarcane. Pineapple is well adapted to the subhumid or semiarid tropics and thus is particularly well suited for exploiting large areas not now under cultivation with any crop of commercial value.     

Mutant Trp repressors with new DNA-binding specificities

Oligonucleotide-directed mutagenesis of the codons for glutamine-68 (Gln68), lysine-72 (Lys72), isoleucine-79 (Ile79), alanine-80 (Ala80), and threonine-81 (Thr81) of the Escherichia coli trpR (tryptophan aporepressor) gene was used to make mutant repressors with each of 36 different amino acid changes. Mutant repressors were tested for binding to each member of a set of 28 different operators closely related to the consensus trp operator. Of the 36 mutant repressors, 11 bind a subset of the 28 operators; 5 of these have new binding specificities. These new specificities indicate that the hydroxyl group of Thr81 makes a specific contact with one of the four critical base pairs in a trp operator half-site, and the methyl group of Thr81 determines specificity at a second, critical base pair. The Trp repressor does not use the first two amino acids of its "recognition alpha-helix," Ile79 and Ala80, to make sequence-specific DNA contacts, and interacts with its operator in vivo in a way fundamentally different from the way that phage lambda repressor, lambda Cro protein, and coliphage 434 repressor contact their respective binding sites.     

Single-nutrient microbial competition: qualitative agreement between experimental and theoretically forecast outcomes

When microbial strains compete for the same limiting nutrient in continuous culture, resource-based competition theory predicts that only one strain will survive and all others will die out. The surviving strain expected from theory will be the one with the smallest subsistence or "break-even" concentration of the limiting resource, a concentration defined by the J parameter. This prediction has been confirmed in the case of auxotrophic bacterial strains competing for limiting tryptophan. Because the value of J can be measured on the strains grown alone, the theory can predict the qualitative outcomes of mixed-growth competition in advance of actual competition.     

Oxygen-18 enrichment of planktonic foraminifera due to gametogenic calcification below the euphotic zone

Empty shells of spinose planktonic foraminifera on the seabed are significantly enriched in oxygen-18 as compared with the shells of their living counterparts in surface waters. This enrichment is due to gametogenic calcification, which extracts calcium carbonate from deeper and colder waters as the shell sinks below the euphotic zone. JEAN-CLAUDE DUPLESSY.     

Forms of memory failure

Memory may fail in a variety of ways. Patients with Korsakoff's syndrome demonstrate global memory deficits similar to those seen in patients with early progressive dementia. Korsakoff's patients, however, may recall rules and principles for organizing information and can gain access to their previously acquired knowledge (semantic memory), whereas recent memory may be grossly impaired. In contrast, dementia patients may have little access to previously acquired knowledge and therefore have great difficulty in organizing and encoding ongoing events. These contrasting forms of memory failure have implications for understanding the structure and mechanisms of memory and learning, particularly the relationship between episodic and semantic memory, as well as the development of therapeutic strategies for cognitive impairments.     

The Ischigualasto Tetrapod Assemblage (Late Triassic, Argentina) and 40Ar/39Ar Dating of Dinosaur Origins

(40)Ar/(39)Ar dating of sanidine from a bentonite interbedded in the Ischigualasto Formation of northwestern Argentina yielded a plateau age of 227.8 +/- 0.3 million years ago. This middle Carnian age is a direct calibration of the Ischigualasto tetrapod assemblage, which includes some of the best known early dinosaurs. This age shifts last appearances of Ischigualasto taxa back into the middle Carnian, diminishing the magnitude of the proposed late Carnian tetrapod extinction event. By 228 million years ago, the major dinosaurian lineages were established, and theropods were already important constituents of the carnivorous tetrapod guild in the Ischigualasto-Villa Unión Basin. Dinosaurs as a whole remained minor components of tetrapod faunas for at least another 10 million years.     

Fossil Occurrence of Murine Rodent (Nesokia indica) in the Sudan

A specimen of the murid rodent Nesokia indica has been recovered from a late Paleolithic archeological site in the Sudan. This is a range 1200 km south of the site of any known occurrences, and it indicates a different environment near the Nile River than that which exists at the present time. The late Paleolithic water table is inferred to have been more stable, allowing for permanent moist soil.     

簇毛麦抗白粉病基因的RAPD及RFLP标记

 分析了来自前苏联簇毛麦及其抗病衍生系的抗白粉病基因对不同生理小种的抗性反应。用120个随机引物对6D/6V代换系Pm930640进行RAPD分析，检测到5个引物OPAN03、OPAI01、OPAL03、OPAD07和OPAG15，分别在大约1 700、700、750、480和580 bp处有区别于小麦亲本的多态性条带。对Chancellor×Pm930640 F2群体进行OPAN03、OPAI01和OPAL03等3个RAPD标记与抗白粉病基因的连锁分析，表明这些标记同簇毛麦的抗白粉病基因是连锁的。对大部分分别含有Pm1－Pm20的已知抗病基因、含有簇毛麦抗病基因及其相关亲本的29个小麦品系进行RAPD标记分析。结果表明，这些标记不仅可以鉴定簇毛麦的抗病基因，而且可以判断其遗传背景。OPAL03750仅出现在含有前苏联簇毛麦6VS染色体的抗病材料中，可作为区别于Pm21的分子标记。RFLP标记的结果也表明两个不同簇毛麦的6VS染色体有明显的多态性。