Physiology of the cell surface of neurospora ascospores

Summary Acids like hydrogen fluoride, hydrazoic and fluoroacetic have been shown to prevent the germination of ascospores of N. tetrasperma when dormant spores are treated. On the other hand, propionate, cysteine and others are ineffective when used in this way. When activated ascospores were treated, much lower concentrations of the acids were sufficient to poison the spores. As in other systems, these substances are most effective at a p_H below their pK_a.The kinetics of uptake of fluoride by dormant ascospores were studied and shown to be very different from those reported for cations. However, P³² was not absorbed by dormant ascospores, even at p_H 1.5.Respiratory inhibition by azide and fluoroacetate occurred immediately after the spores were activated, but in the case of 5-nitro-2-furfuryl methyl ether no effect was observed until just before germination occurred.These results suggest that a permeability barrier exists in the dormant ascospore which disappears upon germination. Moreover, the dormant spore seems to be permeable to acids of small size but impermeable to those possessing more than 3 methylene groups or of equivalent size.This work was made possible by a grant from the Michigan-Memorial Phoenix Project of the University of Michigan to whom the authors would like to express their gratitude.     

c-AMP and Morphogenesis of Acetabularia

The c-AMP content has been found to double when Acetabularia develop from 5–10 mm long to grown or almost full-grown algae.
The biological significance of this fact has been approached by studying the effects of drugs known to influence the intracellular c-AMP content on the development of Acetabularia. When grown in the presence of theophyllin or papaverin, inhibitors of phosphodiesterase, the Acetabularia display a striking response during the exponential growth period; the final length, however, is not affected. Both substances increase the c-AMP content of the algea. Isoproterenol, which activates adenylate cyclase in many systems, also influences Acetabularia during the exponential growth period and, in addition, slightly affects cap formation.
The change in c-AMP content in the course of development and the effects of drugs influencing (theophyllin and papaverin) or likely to influence (isoproterenol) the c-AMP content of the algae suggest that this nucleotide plays a role at the time of intense growth.
The same phosphodiesterase activity has been found in the 5–10 mm and the 19–25 mm long algae, whereas two enzymes were found in cap-bearing Acetabularia.
The results are discussed as well as the involvement of c-AMP in the development of this alga.     

Socioecology Explains Individual Variation in Urban Space Use in Response to Management in Cape Chacma Baboons (Papio ursinus)

International Journal of Primatology - The presence of wildlife adjacent to and within urban spaces is a growing phenomenon globally. When wildlife’s presence in urban spaces has negative...     

A transfer function approach to measuring cell inheritance

Background  

The inheritance of cellular material between parent and daughter cells during mitosis is highly influential in defining the properties of the cell and therefore the population lineage. This is of particular relevance when studying cell population evolution to assess the impact of a disease or the perturbation due to a drug treatment. The usual technique to investigate inheritance is to use time-lapse microscopy with an appropriate biological marker, however, this is time consuming and the number of inheritance events captured are too low to be statistically meaningful.     

Structural and functional analysis of nitrogenase genes from the broad-host-range Rhizobium strain ANU240

The genes encoding the structural components of nitrogenase, nifH, nifD and nifK, from the fast-growing, broad-host-range Rhizobium strain ANU240 have been identified and characterized. They are duplicated and linked in an operon nifHDK in both copies. Sequence analysis of the nifH gene from each copy, together with partial sequence analysis of the nifD and nifK genes, and restriction endonuclease analysis suggested that the duplication is precise. Comparison of the Fe-protein sequence from strain ANU240 with that from other nitrogen-fixing organisms revealed that, despite its broad host range and certain physiological properties characteristic of Bradyrhizobium strains, ANU240 is more closely related to the narrow-host-range Rhizobium strains than to the broad-host-range Bradyrhizobium strains. The promoter regions of both copies of the nif genes contain the consensus sequence characteristic of nif promoters, and functional analysis of the two promoters suggested that both nif operons are transcribed in nodules.