Neural coding in antennal olfactory cells of tsetse flies (Glossina spp.)

Spike trains from individual antennal olfactory cells of tsetse flies (Glossina spp.) obtained during steady-state conditions (spontaneous as well as during stimulation with 1-octen-3-ol) and dynamic stimulation with repetitive pulses of 1-octen-3-ol were investigated by studying the spike frequency and the temporal structure of the trains. In general, stimulation changes the intensity of the spike activity but leaves the underlying stochastic structure unaffected. This structure turns out to be a renewal process. The only independently varying parameter in this process is the mean interspike interval length, suggesting that olfactory cells of tsetse flies may transmit information via a frequency coding. In spike records with high firing rates, however, the stationary records had significant negative first- order serial correlation coefficients and were non-renewal. Some cells in this study were capable of precisely encoding the onset of the odour pulses at frequencies up to at least 3 Hz. Cells with a rapid return to pre-stimulus activity at the end of stimulation responded more adequately to pulsed stimuli than cells with a long increased spike frequency. While short-firing cells process information via a frequency code, long-firing cells responded with two distinctive phases: a phasic, non-renewal response and a tonic, renewal response which may function as a memory of previous stimulations.      

Optimization of monoclonal antibody immobilization on hydrazide-preactivated hollow fiber membrane.

Immobilization of an IgG1 monoclonal antibody (MAb) was optimized using a unique hydrazide-preactivated hydrophilic hollow fiber membrane as the support matrix. Modules containing 0.42 milliliters of membrane volume (mlmv) were offered varying amounts of purified MAb. The highest immobilization efficiency on the hollow fiber membranes was 88% at a MAb loading concentration of 0.35 mg/ml. The optimum range of MAb concentrations to achieve the best immobilization efficiency was 0.18-0.45 mg/ml. A larger module containing 9.7 mlmv immobilized greater than 3.0 mg MAb/mlmv at an efficiency of greater than 90%. The total amount of MAb immobilized on the membranes within each module was in direct proportion to the total amount of membrane volume. Preliminary data suggest the optimized immunoaffinity hollow fiber membrane matrix produced in this study is stable and can achieve a product capacity of greater than 2.0 mg/mlmv. In concert with an automated fluid handling system, such as the TRIO(TM) Bioprocessing System, rapid accurate information can be easily generated on process parameters and scale-up considerations where an immunoaffinity step is included in the downstream purification protocol.     

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.     

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.