Amygdala Intercalated Cells: Gate Keepers and Conveyors of Internal State to the Circuits of Emotion.

Generating adaptive behavioral responses to emotionally salient stimuli requires evaluation of complex associations between multiple sensations, the surrounding context, and current internal state. Neural circuits within the amygdala parse this emotional information, undergo synaptic plasticity to reflect learned associations, and evoke appropriate responses through their projections to the brain regions orchestrating these behaviors. Information flow within the amygdala is regulated by the intercalated cells (ITCs), which are densely packed clusters of GABAergic neurons that encircle the basolateral amygdala (BLA) and provide contextually relevant feedforward inhibition of amygdala nuclei, including the central and BLA. Emerging studies have begun to delineate the unique contribution of each ITC cluster and establish ITCs as key loci of plasticity in emotional learning. In this review, we summarize the known connectivity and function of individual ITC clusters and explore how different neuromodulators conveying internal state act via ITC gates to shape emotionally motivated behavior. We propose that the behavioral state-dependent function of ITCs, their unique genetic profile, and rich expression of neuromodulator receptors make them potential therapeutic targets for disorders, such as anxiety, schizophrenia spectrum, and addiction.

Regional Specialization of Pyramidal Neuron Morphology and Physiology in the Tree Shrew Neocortex.

The mammalian cerebral cortex is divided into different areas according to their function and pattern of connections. Studies comparing primary visual (V1) and prefrontal cortex (PFC) of primates have demonstrated striking pyramidal neuron (PN) specialization not present in comparable areas of the mouse neocortex. To better understand PFC evolution and regional PN specialization, we studied the tree shrew, a species with a close phylogenetic relationship to primates. We defined the tree shrew PFC based on cytoarchitectonic borders, thalamic connectivity and characterized the morphology and electrophysiology of layer II/III PNs in V1 and PFC. Similar to primates, the PFC PNs in the tree shrew fire with a regular spiking pattern and have larger dendritic tree and spines than those in V1. However, V1 PNs showed strikingly large basal dendritic arbors with high spine density, firing at higher rates and in a more varied pattern than PFC PNs. Yet, unlike in the mouse and unreported in the primate, medial prefrontal PN are more easily recruited than either the dorsolateral or V1 neurons. This specialization of PN morphology and physiology is likely to be a significant factor in the evolution of cortex, contributing to differences in the computational capacities of individual cortical areas.

Molecular characterization and detection of mutations associated with resistance to succinate dehydrogenase-inhibiting fungicides in Alternaria solani.

Early blight, caused by Alternaria solani, is an economically important foliar disease of potato in several production areas of the United States. Few potato cultivars possess resistance to early blight; therefore, the application of fungicides is the primary means of achieving disease control. Previous work in our laboratory reported resistance to the succinate dehydrogenase-inhibiting (SDHI) fungicide boscalid in this plant pathogen with a concomitant loss of disease control. Two phenotypes were detected, one in which A. solani isolates were moderately resistant to boscalid, the other in which isolates were highly resistant to the fungicide. Resistance in other fungal plant pathogens to SDHI fungicides is known to occur due to amino acid exchanges in the soluble subunit succinate dehydrogenase B (SdhB), C (SdhC), and D (SdhD) proteins. In this study, the AsSdhB, AsSdhC, and AsSdhD genes were analyzed and compared in sensitive (50% effective concentration [EC50] < 5 µg ml(-1)), moderately resistant (EC50 = 5.1 to 20 µg ml(-1)), highly resistant (EC50 = 20.1 to 100 µg ml(-1)), and very highly resistant (EC50 > 100 µg ml(-1)) A. solani isolates. In total, five mutations were detected, two in each of the AsSdhB and AsSdhD genes and one in the AsSdhC gene. The sequencing of AsSdhB elucidated point mutations cytosine (C) to thymine (T) at nucleotide 990 and adenine (A) to guanine (G) at nucleotide 991, leading to an exchange from histidine to tyrosine (H278Y) or arginine (H278R), respectively, at codon 278. The H278R exchange was detected in 4 of 10 A. solani isolates moderately resistant to boscalid, exhibiting EC50 values of 6 to 8 µg ml(-1). Further genetic analysis also confirmed this mutation in isolates with high and very high EC50 values for boscalid of 28 to 500 µg ml(-1). Subsequent sequencing of AsSdhC and AsSdhD genes confirmed the presence of additional mutations from A to G at nucleotide position 490 in AsSdhC and at nucleotide position 398 in the AsSdhD, conferring H134R and H133R exchanges in AsSdhC and AsSdhD, respectively. The H134R exchange in AsSdhC was observed in A. solani isolates with sensitive, moderate, highly resistant, and very highly resistant boscalid phenotypes, and the AsSdhD H133R exchange was observed in isolates with both moderate and very high EC50 value boscalid phenotypes. Detection and differentiation of point mutations in AsSdhB resulting in H278R and H278Y exchanges in the AsSdhB subunit were facilitated by the development of a mismatch amplification mutation assay. Detection of these two mutations in boscalid-resistant isolates, in addition to mutations in AsSdhC and AsSdhD resulting in an H134R and H133R exchange, respectively, was achieved by the development of a multiplex polymerase chain reaction to detect and differentiate the sensitive and resistant isolates based on the single-nucleotide polymorphisms present in all three genes. A single A. solani isolate with resistance to boscalid did not contain any of the above-mentioned exchanges but did contain a substitution of aspartate to glutamic acid at amino acid position 123 (D123E) in the AsSdhD subunit. Among A. solani isolates possessing resistance to boscalid, point mutations in AsSdhB were more frequently detected than mutations in genes coding for any other subunit.

First Report of QOI-insensitive Powdery Mildew (Erysiphe polygoni) on Sugar Beet in the United States.

The $2.1 billion United States sugar beet (Beta vulgaris L.) industry is the primary provider of domestic sucrose. Sugar beet powdery mildew is caused by Erysiphe polygoni DC and occurs principally in sugar beet growing regions in the western United States. In these regions, the quinone outside inhibitor (QOI) fungicides pyraclostrobin (Headline, BASF, NC) and trifloxystrobin (Gem, Bayer Crop Science, NC) have been important tools to manage powdery mildew since registration in 2002 and 2005, respectively. However, researchers in Idaho reported poor disease management despite QOI application starting in 2011. In 2013, a research plot near Parma, ID, containing natural powdery mildew infection received treatments of pyraclostrobin, trifloxystrobin, or was untreated (control). Since there was no significant reduction in disease levels between QOI-treated blocks and untreated control blocks, experiments were conducted to clone a partial fragment of the E. polygoni cytochrome b (cytb) gene to gain insight into the molecular basis of QOI resistance in this pathosystem. The primers MDB-920 (5'-CACATCGGAAGAGGTTTATA-3') and MDB-922 (5'-GGTATAGATCTTAATATAGCATAG-3') were designed based on consensus sequences of several fungal cytb genes obtained from GenBank (data not presented) and used to amplify a 575-bp fragment of the E. polygoni cytb gene using DNA isolated from 12 infected leaf samples collected in September 2013 from the Parma research plot. Each sample consisted of three leaves harvested from three plants (one leaf per plant) in an experimental block. All DNA extraction, PCR, and sequencing procedures were as described previously (1). PCR products derived from six QOI-treated samples and six untreated samples were sequenced directly. Without exception, all QOI-treated samples harbored a point mutation at nucleotide position 143 that encoded a G143A mutation compared with cytb sequence from untreated samples. The two identified cytb haplotypes have been deposited in GenBank under accession numbers KF925325 and KF925326. This is the first report of QOI resistance and the associated cytb G143A mutation in E. polygoni. The G143A mutation has been reported in most QOI-resistant pathogens to date (2). When the G143A mutation dominates in a pathogen population, there is a consistent association with a loss of disease management despite QOI application (3). Careful monitoring and judicious use of QOI fungicides will be necessary to ensure QOI fungicides remain efficacious for sugar beet powdery mildew management in the United States. References: (1) M. D. Bolton et al. Pest Manag. Sci. 69:35, 2013. (2) N. Fisher and B. Meunier. FEMS Yeast Res. 8:183, 2008. (3) U. Gisi et al. Pest Manag. Sci. 58:859, 2002.

First Evidence of a Binucleate Rhizoctonia as the Causal Agent of Dry Rot Canker of Sugar Beet in Nebraska.

Sugar beet (Beta vulgaris L.) is the primary source of domestic sucrose in the United States. In 2011, a sugar beet field in Morrill County, NE, was noted with wilting and yellowing symptoms suggestive of Rhizoctonia root and crown rot (RRCR), an important disease of sugar beet primarily caused by Rhizoctonia solani anastomosis group 2-2 (4). While the foliar symptoms were consistent with RRCR, the symptoms on the root were not. Root symptoms consisted of localized, dry, sunken lesions covering brown spongy tissue penetrating deeply into taproots. The surface tissues of the cankers distinctively produced a series of concentric circles. These root symptoms are inconsistent with RRCR, but are suggestive of a rarely occurring disease known as dry rot canker (DRC). DRC was first identified from Utah in 1921 (1), and assumed at the time to be caused by an uncharacterized strain of R. solani. It has since been sporadically but empirically noted from most western sugar beet growing states (4), but little is known about the pathogen or disease due to its infrequent appearances. To investigate the etiology of this disease, necrotic lesion borders were excised from diseased taproots, surface disinfested in 1% (v/v) sodium hypochlorite for 90 s, rinsed with distilled water for 90 s, and after drying on sterile tissue paper, placed on half-strength potato dextrose agar (½PDA) and incubated at 25 to 27°C. After 24 to 36 h, Rhizoctonia-like fungal growth was readily observed emerging from tissue pieces. Resulting colonies were tan to light brown. The ITS region of the rDNA was amplified from 4 isolates obtained from 4 distinct lesions and roots using the ITS1 and ITS4 primers (3) with standard PCR conditions, and sequenced (GenBank KC842197 to KC842200). The ITS regions were 100% identical between the 4 isolates and 96% (E-value = 0.0) identical to binucleate Rhizoctonia and Ceratobasidium sp. AG-F (e.g., JF519832, FR734295, JF705217). Hyphal cells were observed to be binucleate after staining 48-h-old cultures with lactophenol blue. Therefore, these isolates were identified to be a binucleate Rhizoctonia group AG-F based on morphological and molecular characteristics. Although distinct from DRC, a similar phenomenon has been recently reported from China implicating binucleate Rhizoctonia species with seedling disease in sugar beets (2). To determine pathogenicity of DRC isolates, 1- and 2-month-old sugar beet plants grown in 10 cm pots (5 plants per pot with 4 replications per isolate) were inoculated with all 4 isolates by placing 3 mycelial plugs (8 mm diameter) taken from the leading edge of ½PDA plates onto the soil surface of each pot. PDA plugs were utilized as controls. After ~3 weeks, root lesions resembling DRC were observed and isolates were recovered and identified from diseased plants as described above. No symptoms developed on control plants. To our knowledge, this is the first formally confirmed report of DRC on sugar beets in more than 75 years from the Western Hemisphere. The original investigator suspected that the isolates he found inducing this disease were different from typical R. solani isolates based on different symptoms (1). Our results, based on different symptoms but also with distinct molecular, biological, and pathogenicity traits, validate those suspicions while also fulfilling Koch's postulates with binucleate Rhizoctonia AG-F pathogenic to sugar beet that is distinct from the more common R. solani. References: (1) B. L. Richards. J. Agric. Res. 22:47, 1921. (2) P. P. Wang and X. H. Wu. Plant Dis. 96:1696, 2012.(3) T. J. White et al. Academic Press, San Diego, CA. 1990. (4) C. E. Windels et al. Rhizoctonia Root and Crown Rot. Page 33 in: Compendium of Beet Diseases and Pests. R. M. Harveson et al., eds. APS Press, St. Paul, MN, 2009.

First Report of Root Rot of Chicory Caused by Phytophthora cryptogea in Chile.

Chicory (Cichorium intybus L. var sativum Bisch.), a relatively new high-value crop in Chile, was introduced for commercial production of inulin. Inulins are polysaccharides extracted from chicory tap roots that are used in processed foods because of their beneficial gastrointestinal properties. Approximately 3,000 ha of chicory are grown for local processing in the BioBio Region near Chillan in south central Chile. Recently, a severe rot of 1 to 3% of mature roots in the field and after harvest has been observed in most fields, which caused yield and quality losses. Typical symptoms include a brown discoloration and a soft, watery decay of the root. Tissue pieces from symptomatic roots were placed on water agar and clarified V8 juice agar medium amended with antibiotics (1) for isolation of the causal pathogen. A Phytopthora sp. had been consistently isolated from root lesions, and axenic cultures were obtained using single-hypha transfers. The species was provisionally identified as Phytopthora cryptogea (Pethybridge and Lafferty, 1919) on the basis of morphological and cultural characteristics (1). Mycelia grew between 5 and 30°C with optimal growth at 20 to 25°C and no growth at 35°C. All isolates produced hyphal swellings and nonpapillate, persistent, internally proliferating, and ovoid to obpyriform sporangia with mean dimensions of 45 × 31 µm in sterile soil extract. The isolates were of A1 mating type because they produced oospores only when paired with reference isolates of P. cinnamomi A2 on clarified V8 juice agar amended with thiamine, tryptophan, and ß-sitosterol (1) after 20 days at 20°C in the dark. On the basis of morphological and sequence data from cytochrome c oxidase subunit 1 and 2, internal transcribed spacer 2, and ß-tubulin (GenBank Accession Nos. JQ037796 to JQ037798, respectively), the pathogen was identified as P. cryptogea. Pathogenicity tests were conducted using three isolates of P. cryptogea by placing a 7-mm-diameter disk from a 1-week-old V8 agar culture on 10 wounded and nonwounded healthy chicory roots (2). Control roots were mock inoculated with agar plugs. The inoculated roots were incubated at 20°C in a moist chamber. Root rot symptoms, identical to those observed both in field and storage, developed after 4 to 6 days only on wounded sites inoculated with the pathogen, and P. cryptogea was reisolated from these inoculated plants. Mock-inoculated roots remained healthy. This experiment was completed twice and similar results were obtained. To our knowledge, this is the first report of Phytophthora root rot of chicory caused by P. cryptogea in Chile. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) M. E. Stanghellini and W. C. Kronland. Plant Dis. 66:262, 1982.

First Confirmed Report of Sugar Beet Cyst Nematode, Heterodera schachtii, in North Dakota.

Sugar beet (Beta vulgaris L.) and canola (Brassica napus L.) are major crops in North Dakota, with sugar beet production primarily in the eastern part of the state in the Red River Valley and canola production across the northern half of the state. Both crops are hosts of sugar beet cyst nematode (SBCN), Heterodera schachtii Schmidt. In April 2011, soil samples were collected from four sugar beet fields belonging to three growers who believed the fields were infested with SBCN. The fields were located in a 65-km2 area in the Yellowstone Valley of western North Dakota. Cysts were extracted by sieving and Heterodera-like cysts with eggs were observed in all four soil samples. Population densities in the four fields ranged from 100 to 1,750 eggs/100 cm3 soil. Sugar beet seedlings (cv. M832224) were grown in a potting mix for 6 weeks in the greenhouse and then transferred to conetainers (type D40; volume 656 ml) containing autoclaved river sand. Conetainers were placed in sand in plastic pots immersed in a water bath at 27°C. Three plants were each infested with 800 eggs from field No. 2. After 55 days of incubation, the average number of females was 115 per plant. A similar experiment was conducted with canola cvs. Hyclass 940, Caliber 30, and Westar, which were inoculated with 500 eggs each from field No. 2. After 53 days of incubation, there was an average of 39, 20, and 30 females for each respective cultivar. Flask-shaped cysts (n = 26) from canola roots were light to dark brown; the vulval cone was ambifinestrate with dark brown, molar-shaped bullae positioned underneath the vulval bridge. Body length (excluding neck) ranged from 600 to 850 µm (mean 701.2 µm); body width, 350 to 580 µm (mean 469.2 µm); and length/width ratio, 1.2 to 1.8 (mean 1.5). Second-stage juvenile (J2) (n = 21) body length ranged from 400 to 485 µm (mean 437.1 µm); stylet length was 25 µm (no variation) with forwardly directed knobs; conical tail with rounded tip ranged from 37.5 to 55.0 µm long (mean 46.6 µm) with hyaline region from 20.0 to 32.5 µm (mean 27.3 µm); and lateral field presented four incisures. These morphometrics were used to identify H. schachtii according to Subbotin et al. (4). Confirmation of identification was by amplification and sequencing of a 28S rDNA gene fragment (1) from individual females (GenBank Accession No. JQ040526), which was 100% identical to H. schachtii 28S rDNA sequence (GenBank Accession No. GU475088). To our knowledge, this is the first confirmed report of H. schachtii in North Dakota. A 1958 report of SBCN in North Dakota (2) was not subsequently confirmed (3). Because there is extensive canola production across the northern part of the state bordering western and eastern sugar beet- production areas, canola may serve as a bridge for movement of SBCN from west to east. SBCN is a potential threat to these two important crops. References: (1) A. Amiri et al. Eur. J. Plant Pathol. 108:497, 2002. (2) F. Caveness. J. Sugar Beet Res. 10:544, 1958. (3) P. Donald and R. Hosford. Plant Dis. 64:45, 1980. (4) S. A. Subbotin et al. Systematics of Cyst Nematodes (Nematoda: Heteroderinae). Nematology Monographs and Perspectives. Vol. 8B. Brill, The Netherlands. 2010.

Case-control study: Productivity and longevity of dairy cows that tested positive for infection with Mycobacterium avium ssp. paratuberculosis as heifers compared to age-matched controls.

A case-control study was performed to determine if dairy heifers testing positive for Mycobacterium avium ssp. paratuberculosis (MAP) before 2 yr of age by either fecal culture or serum ELISA had decreased productivity and longevity as cows compared with age-matched herdmates. Cases were individually matched with 4 controls. Survival analysis was conducted to determine differences in longevity between cases and controls. Conditional logistic regression was used to assess differences in mean 3.5% fat-corrected 305-d mature-equivalent milk, milk fat, and milk protein production, linear somatic cell count, and MAP test and clinical status as mature cows. No significant difference was found between cases and controls for any parameter assessed. Herd production performance and longevity did not appear to be impaired; therefore, testing immature dairy heifers for MAP is not economically justifiable, using currently available culture methods and commercial serum ELISA tests.

Detection of Mycobacterium avium subspecies paratuberculosis in naturally exposed dairy heifers and associated risk factors.

An observational prospective study was conducted to identify risk factors associated with fecal shedding of Mycobacterium avium ssp. paratuberculosis (MAP) in naturally exposed dairy heifers. The study population consisted of heifers from 8 dairy herds in Michigan participating in a MAP control demonstration project. Ten heifers from 4 age groups (0 to 3, 4 to 6, 7 to 14, and 15 to 24 mo) were selected from each herd every 4 mo for 28 mo and tested for the presence of MAP by fecal culture (FC). Heifers from dams testing positive for MAP by serum ELISA or FC were preferentially selected, with the remainder of the age cohort filled with randomly selected heifers. Logistic regression using generalized estimating equations to account for clustering of data within herds and repeated measures across heifers was used to evaluate the relationship between MAP FC status of heifers and herd risk factors. In total, 1,842 fecal samples were collected from 1,202 heifers. Thirty-six (2%) fecal samples, representing 27 individual heifers, cultured positive for MAP. Heifers shedding MAP were more likely to occur in herds with adult-cow MAP ELISA prevalence >10% (odds ratio = 4.7; 95% confidence interval: 2.0-11.1) and herds milking >300 cows (odds ratio = 5.7; 95% confidence interval: 2.4-13.4). Mycobacterium avium ssp. paratuberculosis can be cultured from the feces of naturally infected dairy heifers. The future performance of these MAP FC-positive heifers is unknown and needs to be explored.

Deletion of ErbB4 Disrupts Synaptic Transmission and Long-Term Potentiation of Thalamic Input to Amygdalar Medial Paracapsular Intercalated Cells.

Identification of candidate risk genes and alteration in the expression of proteins involved in regulating inhibitory neuron function in various psychiatric disorders, support the notion that GABAergic neuron dysfunction plays an important role in disease etiology. Genetic variations in neuregulin and its receptor kinase ErbB4, expressed exclusively by GABAergic neurons in the CNS, have been linked with schizophrenia. In the amygdala, ErbB4 is highly expressed in GABAergic intercalated cell clusters (ITCs), which play a critical role in amygdala-dependent behaviors. It is however unknown whether ErbB4 deletion from ITCs affects their synaptic properties and function in amygdala circuitry. Here, we examined the impact of ErbB4 deletion on inhibitory and excitatory circuits recruiting medial paracapsular ITCs (mpITCs) using electrophysiological techniques. Ablation of ErbB4 in mpITCs suppressed NMDA receptor-mediated synaptic transmission at thalamo-mpITC synapses and enhanced thalamic driven GABAergic transmission onto mpITCs. Furthermore, long-term potentiation (LTP) at thalamo-mpITC synapses was compromised in ErbB4 mutant mice, indicating that ErbB4 activity is critical for LTP at these synapses. Together, our findings suggest that ErbB4 deletion from mpITCs disrupts excitation-inhibition balance and learning mechanisms in amygdala circuits.

Autonomous Purkinje cell activation instructs bidirectional motor learning through evoked dendritic calcium signaling.

The signals in cerebellar Purkinje cells sufficient to instruct motor learning have not been systematically determined. Therefore, we applied optogenetics in mice to autonomously excite Purkinje cells and measured the effect of this activity on plasticity induction and adaptive behavior. Ex vivo, excitation of channelrhodopsin-2-expressing Purkinje cells elicits dendritic Ca2+ transients with high-intensity stimuli initiating dendritic spiking that additionally contributes to the Ca2+ response. Channelrhodopsin-2-evoked Ca2+ transients potentiate co-active parallel fiber synapses; depression occurs when Ca2+ responses were enhanced by dendritic spiking. In vivo, optogenetic Purkinje cell activation drives an adaptive decrease in vestibulo-ocular reflex gain when vestibular stimuli are paired with relatively small-magnitude Purkinje cell Ca2+ responses. In contrast, pairing with large-magnitude Ca2+ responses increases vestibulo-ocular reflex gain. Optogenetically induced plasticity and motor adaptation are dependent on endocannabinoid signaling, indicating engagement of this pathway downstream of Purkinje cell Ca2+ elevation. Our results establish a causal relationship among Purkinje cell Ca2+ signal size, opposite-polarity plasticity induction, and bidirectional motor learning.

Apical intercalated cell cluster: A distinct sensory regulator in the amygdala.

GABAergic neurons regulate different aspects of information processing in the amygdala. Among these are clusters of intercalated cells (ITCs), which have been implicated in fear-related behaviors. Although a few of the ITC clusters have been studied, the functional role of apical ITCs (apITCs) is unknown. Here, we combine monosynaptic rabies tracing with optogenetics and demonstrate that apITCs receive synaptic input from medial geniculate nucleus (MGm), posterior intralaminar nucleus (PIN), and medial dorsal nucleus of the thalamus and from a diverse range of cortical areas including temporal association, entorhinal, insular, piriform, and somatosensory cortex. Upon fear learning, PIN/MGm inputs are strengthened, indicative of their involvement in fear behaviors. 3-D reconstruction of apITCs reveals local arborization and innervation of the dorsal striatum and lateral amygdala. We further show that apITCs provide sensory feedforward inhibition to LA principal cells, a putative mechanism for controlling plasticity during fear learning.

Sympatric speciation by allochrony in a seabird.

The importance of sympatric speciation (the evolution of reproductive isolation between codistributed populations) in generating biodiversity is highly controversial. Whereas potential examples of sympatric speciation exist for plants, insects, and fishes, most theoretical models suggest that it requires conditions that are probably not common in nature, and only two possible cases have been described for tetrapods. One mechanism by which it could occur is through allochronic isolation-separation of populations by breeding time. Oceanodroma castro (the Madeiran or band-rumped storm-petrel) is a small seabird that nests on tropical and subtropical islands throughout the Atlantic and Pacific Oceans. In at least five archipelagos, different individuals breed on the same islands in different seasons. We compared variation in five microsatellite loci and the mitochondrial control region among 562 O. castro from throughout the species' range. We found that sympatric seasonal populations differ genetically within all five archipelagos and have ceased to exchange genes in two. Population and gene trees all indicate that seasonal populations within four of the archipelagos are more closely related to each other than to populations from the same season from other archipelagos; divergence of the fifth sympatric pair is too ancient for reliable inference. Thus, seasonal populations appear to have arisen sympatrically at least four times. This is the first evidence for sympatric speciation by allochrony in a tetrapod, and adds to growing indications that population differentiation and speciation can occur without geographic barriers to gene flow.

Low-threshold spiking interneurons perform feedback inhibition in the lateral amygdala.

Amygdala plays crucial roles in emotional learning. The lateral amygdala (LA) is the input station of the amygdala, where learning related plasticity occurs. The LA is cortical like in nature in terms of its cellular make up, composed of a majority of principal cells and a minority of interneurons with distinct subtypes defined by morphology, intrinsic electrophysiological properties and neurochemical expression profile. The specific functions served by LA interneuron subtypes remain elusive. This study aimed to elucidate the interneuron subtype mediating feedback inhibition. Electrophysiological evidence involving antidromic activation of recurrent LA circuitry via basolateral amygdala stimulation and paired recordings implicate low-threshold spiking interneurons in feedback inhibition. Recordings in somatostatin-cre animals crossed with tdtomato mice have revealed remarkable similarities between a subset of SOM+ interneurons and LTS interneurons. This study concludes that LTS interneurons, most of which are putatively SOM+, mediate feedback inhibition in the LA. Parallels with cortical areas and potential implications for information processing and plasticity are discussed.

Contact area inside the distal radioulnar joint: effect of axial loading and position of the forearm.

BACKGROUND: A biomechanical study was performed to define the normal profiles of contact area inside the distal radioulnar joint and how these profiles change as a result of damage to the distal radioulnar ligaments. METHODS: Twelve cadaver arms were used and a custom-made jig was designed to allow axial loading of the hand. Tekscan sensor film was used to measure the contact area inside the joint. Measurements were taken with different loads and in different positions of the forearm. The same measurements were taken after dividing either the volar or dorsal distal radioulnar ligament. Finally the measurements were repeated after reconstruction of the divided ligament. FINDINGS: The contact area increases with axial loading of the hand and is greater in supination than pronation. Division of a single distal radioulnar ligament increases the contact area inside the distal radioulnar joint (123% of normal) and reconstruction of the divided distal radioulnar ligament restores the contact patterns towards the normal values (113% of normal). INTERPRETATION: The results show that axial loading of the hand and position of the forearm has a significant effect on the contact area inside the distal radioulnar joint. The study also shows that injury of the distal radioulnar ligament disturbs the normal profiles of contact.

The load-bearing characteristics of the forearm: pattern of axial and bending force transmitted through ulna and radius.

A biomechanical study was performed on 12 cadaveric arms to define the normal profiles of force transmission through the ulna and radius and demonstrate the effect on these of simulated injury of the distal radioulnar joint (DRUJ). Strain gauges were used to measure the axial and bending forces transmitted through each bone. Axial force transmitted through the ulna is, broadly, reciprocal to that seen in the radius, with the greatest force seen in supination. In all 12 arms, axial loading of the hand created an anterior bending force (to create a posterior convexity) in the distal radius. Axial loading of the hand created an anterior bending force in the distal ulna for half the specimens and a posterior bending force in the remaining half. Division and division with reconstruction of either the volar or the dorsal distal radioulnar ligament (DRUL) had no significant effect on force transmission through the ulna and radius, while excision of the ulnar head significantly disrupted the profiles of the axial and bending forces.

Specificity of isozymes of murine hepatic glutathione S-transferase for the conjugation of glutathione with L-phenylalanine mustard.

Glutathione S-transferase (GST) isozymes play a central role in the protection of cells from cytotoxic chemicals and have a putative role in the intrinsic and acquired resistance of tumors to cytotoxic drugs. We have isolated and purified GST isozymes from mouse liver (M. Warholm et al., Biochemistry, 25: 4119-4125, 1986) and analyzed the metabolic products of the reaction of L-phenylalanine mustard (L-PAM) with glutathione in the presence of GST isozymes, using reverse phase high performance liquid chromatography. At pH 6.5, the spontaneous conjugation of L-PAM and glutathione is suppressed and the major product at 60 min is the monochloro, monohydroxyl derivative of L-PAM. Addition of neither class mu nor class pi isozymes to the reaction has any effect on the metabolism of L-PAM. Only isozymes of the alpha GST class catalyze the conjugation of L-PAM with glutathione. In this case, the major metabolite at 1 h is the monochloro, monoglutathionyl conjugate. Increasing the amount of mu or pi isozyme in the reaction mixture has no effect on the metabolism of L-PAM, whereas increasing the amount of alpha isozyme completely supplants hydrolysis with conjugation. Thus, increased levels of class alpha GST isozyme may represent a specific mechanism whereby cells can acquire resistance to nitrogen mustards.

Transient intervention with oltipraz protects against aflatoxin-induced hepatic tumorigenesis.

Oltipraz [5-(2-pyrazinyl)-4-methyl-1,2-dithiole-3-thione] protects against aflatoxin B1-induced hepatocarcinogenesis in rats when fed before and during carcinogen exposure; however, such an exposure-chemoprotection intervention paradigm is not directly relevant to most human populations. To model and assess the possible efficacy of short term interventions targeted at individuals at risk for sustained exposure to aflatoxins, 175-g male F344 rats were treated daily with 25 micrograms of aflatoxin B1, p.o., for 28 days. One week after the start of aflatoxin B1 exposure, half of the animals were fed a diet supplemented with 0.075% oltipraz for 10 days; these rats were then restored to the unsupplemented AIN-76A diet for the remainder of the experimental period. Livers were analyzed 2 or 3 months after the last aflatoxin B1 dose for burden of glutathione S-transferase P (GST-P)-positive foci, as an index of presumptive preneoplastic tumors. The transient intervention with oltipraz reduced the volume percent of hepatic GST-P-positive foci by 54% (P = 0.047) and 72% (P = 0.004) at 2 and 3 months, respectively. A strong positive correlation was also observed between the extent of fibrosis in the livers of these animals and the hepatic burden of GST-P-positive foci, implying that cytotoxicity is associated with the tumorigenic process. This protection may reflect alterations in the metabolism and disposition of aflatoxin B1 induced by oltipraz. Glutathione S-transferase catalyze the detoxication of aflatoxin-8,9-oxide and were found to be rapidly induced in the livers of animals after the beginning of the oltipraz intervention. Glutathione S-transferase activity remained significantly (P < 0.05) higher until 9 days after the end of the oltipraz intervention. In contrast, levels of hepatic aflatoxin-DNA adducts were not significantly reduced until 4 days after the beginning of the intervention but remained significantly (P < 0.05) lower up to 11 days after the end of the intervention. The cumulative reduction in levels of hepatic aflatoxin-DNA adducts (approximately 25%) by the oltipraz intervention underestimated the reduction in the hepatic burden of GST-P-positive foci. The significant protection against presumptive preneoplastic tumors, despite the delay of intervention, suggests that oltipraz may exert substantial activity against the cytotoxic and autopromoting action of repeated exposures to aflatoxin B1 and supports the utility of intervention trials with oltipraz in individuals chronically consuming aflatoxin B1-contaminated foods, particularly in regions with high incidences of liver cancer.

Cellular resolution circuit mapping with temporal-focused excitation of soma-targeted channelrhodopsin.

We describe refinements in optogenetic methods for circuit mapping that enable measurements of functional synaptic connectivity with single-neuron resolution. By expanding a two-photon beam in the imaging plane using the temporal focusing method and restricting channelrhodopsin to the soma and proximal dendrites, we are able to reliably evoke action potentials in individual neurons, verify spike generation with GCaMP6s, and determine the presence or absence of synaptic connections with patch-clamp electrophysiological recording.

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.