Removal of GABA(A) receptor γ2 subunits from parvalbumin neurons causes wide-ranging behavioral alterations

We investigated the behavioral significance of fast synaptic inhibition by αβγ2-type GABA(A) receptors on parvalbumin (Pv) cells. The GABA(A) receptor γ2 subunit gene was selectively inactivated in Pv-positive neurons by Cre/loxP recombination. The resulting Pv-Δγ2 mice were relatively healthy in the first postnatal weeks; but then as Cre started to be expressed, the mice progressively developed wide-ranging phenotypic alterations including low body weight, motor deficits and tremor, decreased anxiety levels, decreased pain sensitivity and deficient prepulse inhibition of the acoustic startle reflex and impaired spatial learning. Nevertheless, the deletion was not lethal, and mice did not show increased mortality even after one year. Autoradiography with t-butylbicyclophosphoro[(35)S]thionate suggested an increased amount of GABA(A) receptors with only α and β subunits in central nervous system regions that contained high levels of parvalbumin neurons. Using BAC-transgenesis, we reduced some of the Pv-Δγ2 phenotype by selectively re-expressing the wild-type γ2 subunit back into some Pv cells (reticular thalamic neurons and cerebellar Pv-positive neurons). This produced less severe impairments of motor skills and spatial learning compared with Pv-Δγ2 mice, but all other deficits remained. Our results reveal the widespread significance of fast GABAergic inhibition onto Pv-positive neurons for diverse behavioral modalities, such as motor coordination, sensorimotor integration, emotional behavior and nociception.     

Contribution of aggregation-promoting factor to maintenance of cell shape in Lactobacillus gasseri 4B2

Aggregation-promoting factor (APF) was originally described as a protein involved in the conjugation and autoaggregation of Lactobacillus gasseri 4B2, whose corresponding apf gene was cloned and sequenced. In this report, we identified and sequenced an additional apf gene located in the region upstream of the previously published one. Inactivation of both apf genes was unsuccessful, indicating that APF function may be essential for the cell. Overproduction of APF proteins caused drastic alteration in the cell shape of this strain. These cells were irregular, twisted, enlarged, and tightly bound in unbreakable clumps of chains. Down-regulation of APF synthesis was achieved by cloning of the apf2 promoter region on a high-copy-number plasmid, which recruited a putative apf activator. As a consequence, the shape of the corresponding recombinant cells was elongated (filamentous) and cell division sites were no longer visible. None of the induced changes in APF production levels was clearly correlated with modifications of the aggregation phenotype. This report shows, for the first time, that APF proteins are mainly critical for L. gasseri 4B2 cell shape maintenance.     

Action pattern of human pancreatic α-amylase on maltoheptaose,a substrate for determining α-amylase in serum

An enzymatic assay for the determination of α-amylase in serum was developed which employed a soluble substrate, maltoheptaose, and a coupled enzymatic indicator reaction consisting of α-glucosidase and the hexokinase—glucose-6-phosphate dehydrogenase system. We used high-performance liquid chromatography (HPLC) to establish the action pattern of maltoheptaose under the test conditions: (A) the action pattern of α-amylase alone, (B) that of the combined action of α-amylase and α-glucosidase. Conducive to this effort was: the availability of pure maltoheptaose and human pancreatic α-amylase; the development of an adequate procedure for sample pretreatment (partition chromatography on a mixed-bed ion exchanger) and of an HPLC system for separation of substrate and reaction products without interference from by-products of the assay (partition chromatography on a cation-exchange column with acetonitrile—water); and the use of a new, very sensitive refractometric detector revealing sugar amounts as low as 40 ng.We derived the following stoichiometric equations:

The standard deviation of the rate coefficients is about 5%.     

How are arthopod communities structured and why are they so diverse? Answers from Mediterranean mountains using hierarchical additive partitioning

Mountains are complex ecosystems supporting a great variety of taxa. Here, we explored the diversity patterns of arthropods in two mountains, pinpointing the spatial scale that accounts most for overall diversity variation, using an additive partitioning framework. Butterflies and Orthoptera were sampled in Rodopi (2012) and Grammos (2013) mountains. Diversity was partitioned into five hierarchical levels (mountain, elevational zone, habitat, transect and plot). We compared the estimated diversity values for each level to the respective permuted values expected by chance, for all species, as well as for species identified as “rare” or “common”. At broader spatial levels, the variation in total diversity was attributed to the beta diversity component: mountains accounted for 20.94 and 26.25% of butterfly and Orthoptera diversity, and elevational zones accounted for 28.94 and 35.87% respectively. At finer spatial scales, beta diversity was higher than expected by chance in terms of the Shannon index. The type of habitat was found to play a significant role only for rare orthopterans. Finally, common species were recognized for shaping overall species diversity. We highlight the importance of the spatial levels of elevation zone and then mountain position in conservation planning, due to the greater beta diversity recorded at this scale as compared to habitat or more finite scales. Monitoring programs might need to adapt different strategies with respect to the focal organisms, and consider patterns of common rather than rare species that found to drive the patterns of the entire community.     

Stimulation of Photophosphorylation by Ascorbate as a Function of Light Intensity

When isolated, stroma-free thylakoids are illuminated in the presence of ADP and orthophosphate in the absence of any electron acceptor except O2, the addition of ascorbate stimulates electron transport through the formation of the radical monodehydroascorbate and the coupled synthesis of ATP (G. Forti and G. Elli [1995] Plant Physiol 109: 1207-1211). The stimulation is shown here to be higher at low light intensity. These observations are explained in terms of the increase of the electron transport rate by ascorbate, which established a higher value of the steady-state pH gradient, causing activation of ATP synthase, which is known to be dependent on the level of the H+-electrochemical potential difference, and a higher rate of proton flux across the membranes available for utilization by ATP synthesis.