The Rap1 small GTPase is a critical mediator of the effects of stress on prefrontal cortical dysfunction.

The neural molecular and biochemical response to stress is a distinct physiological process, and multiple lines of evidence indicate that the prefrontal cortex (PFC) is particularly sensitive to, and afflicted by, exposure to stress. Largely through this PFC dysfunction, stress has a characterized role in facilitating cognitive impairment, which is often dissociable from its effects on non-cognitive behaviors. The Rap1 small GTPase pathway has emerged as a commonly disrupted intracellular target in neuropsychiatric conditions, whether it be via alterations in Rap1 expression or through alterations in the expression of direct and specific upstream Rap1 activators and inhibitors. Here we demonstrate that escalating, intermittent stress increases Rap1 in mouse PFC synapses, results in cognitive impairments, and reduces the preponderance of mature dendritic spines in PFC neurons. Using viral-mediated gene transfer, we reveal that the hyper-induction of Rap1 in the PFC is sufficient to drive stress-relevant cognitive and synaptic phenotypes. These findings point to Rap1 as a critical mediator of stress-driven neuronal and behavioral pathology and highlight a previously unrecognized involvement for Rap1 in novelty-driven PFC engagement.

The dendritic spine morphogenic effects of repeated cocaine use occur through the regulation of serum response factor signaling.

The nucleus accumbens (NAc) is a primary brain reward region composed predominantly of medium spiny neurons (MSNs). In response to early withdrawal from repeated cocaine administration, de novo dendritic spine formation occurs in NAc MSNs. Much evidence indicates that this new spine formation facilitates the rewarding properties of cocaine. Early withdrawal from repeated cocaine also produces dramatic alterations in the transcriptome of NAc MSNs, but how such alterations influence cocaine's effects on dendritic spine formation remain unclear. Studies in non-neuronal cells indicate that actin cytoskeletal regulatory pathways in nuclei have a direct role in the regulation of gene transcription in part by controlling the access of co-activators to their transcription factor partners. In particular, actin state dictates the interaction between the serum response factor (SRF) transcription factor and one of its principal co-activators, MAL. Here we show that cocaine induces alterations in nuclear F-actin signaling pathways in the NAc with associated changes in the nuclear subcellular localization of SRF and MAL. Using in vivo optogenetics, the brain region-specific inputs to the NAc that mediate these nuclear changes are investigated. Finally, we demonstrate that regulated SRF expression, in turn, is critical for the effects of cocaine on dendritic spine formation and for cocaine-mediated behavioral sensitization. Collectively, these findings reveal a mechanism by which nuclear-based changes influence the structure of NAc MSNs in response to cocaine.

Control of interneuron dendritic growth through NRG1/erbB4-mediated kalirin-7 disinhibition.

Neuregulin 1 (NRG1) is a secreted trophic factor that activates the postsynaptic erbB4 receptor tyrosine kinase. Both NRG1 and erbB4 have been repeatedly associated with schizophrenia, but their downstream targets are not well characterized. ErbB4 is highly abundant in interneurons, and NRG1-mediated erbB4 activation has been shown to modulate interneuron function, but the role for NRG1-erbB4 signaling in regulating interneuron dendritic growth is not well understood. Here we show that NRG1/erbB4 promote the growth of dendrites in mature interneurons through kalirin, a major dendritic Rac1-GEF. Recent studies have shown associations of the KALRN gene with schizophrenia. Our data point to an essential role of phosphorylation in kalirin-7's C terminus as the critical site for these effects. As reduced interneuron dendrite length occurs in schizophrenia, understanding how NRG1-erbB4 signaling modulates interneuron dendritic morphogenesis might shed light on disease-related alterations in cortical circuits.

The effect of 100% CO2 on the growth of nonproteolytic Clostridium botulinum at chill temperatures.

The growth of a cocktail of spores from six nonproteolytic Clostridium botulinum type B and E isolates at 5 and 10 degrees C was used to assess the combined effect of NaCl (0.5-4.5% w/v), pH (5.5-6.5) and atmosphere (10% H2:90% N2, 5% CO2:10% H2:85% N2, or 100% CO2) in buffered peptone, yeast, glucose, starch broth with an Eh of approximately -350 mV. Under all atmospheres growth tended to be slower as the concentration of NaCl increased and with NaCl combined with pH levels below 6.0. Of the atmospheres tested, growth occurred at a slower rate and over a narrower range of conditions when C. botulinum was exposed to 100% CO2. This effect was enhanced when the incubation temperature was 5 degrees C. The results indicate that while CO2 decreased C. botulinum growth at chill temperatures, prevention of growth also depended on the NaCl concentration and the pH of the medium.

Nisin and ALTA 2341 inhibit the growth of Listeria monocytogenes on smoked salmon packaged under vacuum or 100% CO2.

The effects of nisin and ALTA 2341 on the growth of Listeria monocytogenes were assessed on smoked salmon packaged under vacuum or 100% CO2. Smoked salmon slices (pH 6.3) were inoculated with a cocktail of seven L. monocytogenes isolates at a level of approximately 2.5 log10 colony forming units (cfu) g-1. After inoculation, the surface of the smoked salmon slices was treated with either nisin (400 or 1250 IU g-1) or ALTA 2341 (0.1 or 1%). The smoked salmon was packaged and stored at 4 degrees C (28 d) or 10 degrees C (9 d). On untreated vacuum-packaged smoked salmon, L. monocytogenes grew by 3.8 log10 cfu g-1 at 4 degrees C and 5.1 log10 cfu g-1 at 10 degrees C. Growth was reduced on nisin- and ALTA 2341-treated vacuum-packaged smoked salmon. On the nisin-treated samples, L. monocytogenes increased by 2.5 (400 IU g-1) and 1.5 (1250 IU g-1) log10 cfu g-1 at 4 degrees C, and by 4.3 (400 IU g-1) and 2.7 (1250 IU g-1) log10 cfu g-1 at 10 degrees C. With the ALTA 2341-treated samples, L. monocytogenes increased by 2.8 (0.1%) or 1.6 (1.0%) log10 cfu g-1 at 4 degrees C, and 3.3 (0.1%) or 3.6 (1.0%) log10 cfu g-1 at 10 degrees C. The growth of L. monocytogenes was retarded by packaging the smoked salmon in 100% CO2. On untreated smoked salmon, only a 0.8 log10 cycle increase was observed at 10 degrees C. Under all the other conditions tested with 100% CO2, L. monocytogenes was detected but growth was prevented.

The combined affects of modified atmosphere, temperature, nisin and ALTA 2341 on the growth of Listeria monocytogenes.

A cocktail of seven Listeria monocytogenes isolates of food, human and environmental origin was used to assess the antilisterial activity of the bacteriocins nisin and ALTA 2341 in combination with various atmospheres: air, 100% N2, 40% CO2:60% N2, or 100% CO2. Buffered tryptone soya broth (pH 6.0) was used as the growth medium and incubation was at 4 degrees C (21 days) or 12 degrees C (7 days), or when temperature fluctuated between these values for defined periods. It was observed that atmosphere alone influenced the growth rate of L. monocytogenes, with 100% CO2 exerting the greatest inhibition. A 5 log population increase was observed in all atmospheres after 7 days at 12 degrees C. At 4 degrees C a 4-5 log population increase was observed in air, 100% N2 and 40% CO2:60% N2 within 21 days. Growth was prevented by 100% CO2. In the presence of nisin (400 IU/ml), an increase in the lag phase was observed before growth (5 log population increase after 7 days) in all atmospheres at 12 degrees C. This effect was enhanced at 4 degrees C where a maximum 2 log population increase was observed in all atmospheres except 100% CO2, in which growth was prevented. Increasing the concentration of nisin to 1250 IU/ml prevented L. monocytogenes growth in all atmosphere combinations at 4 and 12 degrees C. Two concentrations of ALTA 2341 were also tested. In the presence of 0.1% ALTA 2341 and at 12 degrees C, a 3-5 log population increase was observed in all atmospheres with the exception of 100% CO2, which prevented L. monocytogenes growth. At 4 degrees C, growth was observed in the combination of 0.1% ALTA 2341 and 100% N2 only (3 log population increase). Use of a higher concentration of ALTA 2341 (1.0%) resulted in a population decrease below the detection level within 24 h in all atmosphere/temperature combinations. Re-growth occurred in the presence of 1.0% ALTA 2341 in all atmospheres at 12 degrees C, and in combination with air or 100% N2 at 4 C. When the effectiveness of either nisin or ALTA 2341 and atmosphere was tested against L. monocytogenes as temperature fluctuated for periods between 4 and 12 degrees C, only the combination of 100% CO2 and 1.0% ALTA 2341 prevented growth. Cells surviving exposure to nisin or ALTA 2341 were recovered from 28 of the 32 combinations tested that contained bacteriocin. Nisin survivors remained sensitive to the bacteriocin. ALTA 2341 survivors had become resistant to the bacteriocin.

Pancreatic cystosis in cystic fibrosis.

We describe a case of pancreatic cystosis in an 18-year-old man suffering from cystic fibrosis, who presented with acute epigastric pain. Ultrasound and computed tomographic studies revealed multiple pancreatic cysts of various size, measuring up to 5 cm. Pancreatic macrocystosis is an extremely rare manifestation in cystic fibrosis.