Some quantitative aspects of Acridine Orange fluorescence in unfixed, sucrose-isolated mammalian nuclei

Synopsis Nuclei were isolated from mouse liver and central nervous system (CNS). These nuclei were fluorochromed without fixation in a 0.25m sucrose medium containing 5.5×10^–5 m Acridine Orange and measured with an incident microfluorometric system. In the case of mouse CNS nuclei, the major and minor axes of the nuclei were measured with a filar micrometer. Three modal values were obtained from the hepatocyte suspension corresponding to 2C, 4C, and 8C nuclei, respectively. While the CNS nuclei displayed substantial variability in size, the Acridine Orange emission values at 530 nm were nearly constant. The data suggest that under these conditions, Acridine Orange fluorescence reflects DNA content. Further, the 530 nm fluorescence emission is not affected by chromatin condensation or proteins complexed with DNA.     

The genome of Rhizobium leguminosarum has recognizable core and accessory components

Background

Rhizobium leguminosarum is an α-proteobacterial N₂-fixing symbiont of legumes that has been the subject of more than a thousand publications. Genes for the symbiotic interaction with plants are well studied, but the adaptations that allow survival and growth in the soil environment are poorly understood. We have sequenced the genome of R. leguminosarum biovar viciae strain 3841.

Results

The 7.75 Mb genome comprises a circular chromosome and six circular plasmids, with 61% G+C overall. All three rRNA operons and 52 tRNA genes are on the chromosome; essential protein-encoding genes are largely chromosomal, but most functional classes occur on plasmids as well. Of the 7,263 protein-encoding genes, 2,056 had orthologs in each of three related genomes (Agrobacterium tumefaciens, Sinorhizobium meliloti, and Mesorhizobium loti), and these genes were over-represented in the chromosome and had above average G+C. Most supported the rRNA-based phylogeny, confirming A. tumefaciens to be the closest among these relatives, but 347 genes were incompatible with this phylogeny; these were scattered throughout the genome but were over-represented on the plasmids. An unexpectedly large number of genes were shared by all three rhizobia but were missing from A. tumefaciens.

Conclusion

Overall, the genome can be considered to have two main components: a 'core', which is higher in G+C, is mostly chromosomal, is shared with related organisms, and has a consistent phylogeny; and an 'accessory' component, which is sporadic in distribution, lower in G+C, and located on the plasmids and chromosomal islands. The accessory genome has a different nucleotide composition from the core despite a long history of coexistence.     

Overconfidence in wargames: experimental evidence on expectations, aggression, gender and testosterone

Overconfidence has long been noted by historians and political scientists as a major cause of war. However, the origins of such overconfidence, and sources of variation, remain poorly understood. Mounting empirical studies now show that mentally healthy people tend to exhibit psychological biases that encourage optimism, collectively known as 'positive illusions'. Positive illusions are thought to have been adaptive in our evolutionary past because they served to cope with adversity, harden resolve, or bluff opponents. Today, however, positive illusions may contribute to costly conflicts and wars. Testosterone has been proposed as a proximate mediator of positive illusions, given its role in promoting dominance and challenge behaviour, particularly in men. To date, no studies have attempted to link overconfidence, decisions about war, gender, and testosterone. Here we report that, in experimental wargames: (i) people are overconfident about their expectations of success; (ii) those who are more overconfident are more likely to attack; (iii) overconfidence and attacks are more pronounced among males than females; and (iv) testosterone is related to expectations of success, but not within gender, so its influence on overconfidence cannot be distinguished from any other gender specific factor. Overall, these results constitute the first empirical support of recent theoretical work linking overconfidence and war.     

Carbon and nitrogen content based estimation of the fat content of animal carcasses in various species

The objective of this study was to explore whether the C and N content can be used to estimate the fat content of animal carcasses. Considering the mean C and N contents of body fat and body protein, the fat content (EE) [%] can be predicted from C and N values [%] according to the generally valid equation EE=1.3038·C – 4.237·N. The application of this equation to estimate the total fat content of all animal carcasses results in significant differences in fat content between predicted and measured values. Therefore, we derived specific equations for rats, pigs, cattle, sheep, broilers and mice to predict the fat content by dual linear regression analysis (y=EE [% DM], x₁=C [% DM], x₂=N [% DM]) based on measured fat, C, and N contents of animal body samples. The specific equations for different animals showed residual standard deviations of 1.55, 1.63, 1.12, 1.35, 1.85 and 0.92% fat for rats, pigs, cattle, sheep, broilers and mice, respectively.     

A cytological and cytochemical study of hydranths of the hydroid coelenterate,Pennaria tiarella

Summary Cytological and cytochemical studies were undertaken on hydranths of the gymnoblastic hydroid, Pennaria tiarella and compared with conditions in the more abundantly studied but less typical genus, Hydra. The histological organization of Pennaria was more complex than in Hydra. This was particularly noted in: the regional organization of the endoderm into a pharynx, digestive region, and basal region; in the enhanced role of the epitheliomusculature in binding the endodermal epithelium to the mesolammella; and in the presence of two types of tentacles. The most striking cellular specialization was a much enlarged secretory cell in the digestive region which exhibited high levels of cytoplasmic and nucleolar RNA and protein. Current notions concerning form maintenance in coelenterates were discussed in connection with observations on nematocyst replacement and gonophore development in Pennaria.This work was supported by grants from the National Institutes of Health (RG-10003-02) and the National Science Foundation (G-18666), as well as a research career award (5-K3-HD-6176-02) from the National Institute of Child Health and Human Development.Contribution number 357 of the Bermuda Biological Station.     

Fluorescence Cytochemical Studies on Oocyte Growth in Chiton tuberculatum, with Special Emphasis on Protein End-Group Methods

Microfluorometric and microspectrophotometric measurements were undertaken on three classes of oocytes of Chiton tuberculatum: pre-vitellogenic oocytes, immature oocytes containing some yolk, and mature oocytes. Particular emphasis was placed on the fluorometric evaluation of protein end-group methods, including those directed toward basic groups, side-chain carboxyl groups, sulph-hydryl groups alone, and the sum of sulph-hydryl and disulphide groups. For comparison, neutral carbohydrates were measured by a fluorescent PAS procedure, while azure B-stained RNA was measured by absorption microspectrophotometry.
RNA declined during oocyte growth, while PAS-positive material increased in the terminal phases. The concentrations of both protein sulph-hydryl and side-chain carboxyl groups gradually increased in the successive stages of oocyte growth. Basic groups of proteins remained at nearly constant levels until the final phase, and then sharply increased. Disulphide groups were high in small oocytes, but they declined during enlargement of the oocytes. The percentage decline in concentration of disulphide groups during development of the oocytes closely paralled that of RNA.
These results indicate that fluorescent procedures for the selective demonstration of different end-groups of proteins do not yield indentical patterns in developing Chiton oocytes. The significance of this finding is discussed, particularly in relation to complex intracellular metabolic events, such as the synthesis and utilization of ribosomes and the incorporation of exogenous proteins, which are known to accompany the growth and differentiation of oocytes.     

Cytochemical observations of larval development in Eunapius fragilis (Leidy): Porifera; spongillidae

Freshwater sponges of the family Spongillidae reproduce sexually through formation of a parenchymula larva. The cytochemical characteristics of parenchymula larval metamorphosis — beginning with the blastula and terminating with the motile escape stage — for the spongillid Eunapius fragilis (Leidy) have been defined using both absorption and fluorescent cytochemical methods, particularly those demonstrating protein end-groups. Morphogenesis of the parenchymula larva of E. fragilis involves the interrelated processes of cytodifferentiation and mobilization of reserve materials. Larval development has been categorized into five stages, from blastula (stage I) through the escape stage (stage V). Parenchymula development is characterized by morphogenetic precocity, a fact influencing the rate of mobilization of cytoplasmic reserves, cytodifferentiation, and the fate of individual cell types. With attainment of the stage V parenchymula, the larva is, essentially, a mobile adult sponge exhibiting flagellated chambers, canal systems, a well defined connective tissue stroma, a diverse cell population consisting of specialized elements and a totipotent archeocyte reserve, and a terminal epitheliocyte line. The present study recognizes differences in development within the spongillids as well as within more remote poriferan taxa — emphasizing the need for detiled understanding of particular processes in individual species before proposing major generalizations about development in this ancient but evolutionally specialized group.