Synaptic wiring motifs in posterior parietal cortex support decision-making

The posterior parietal cortex exhibits choice-selective activity during perceptual decision-making tasks1-10. However, it is not known how this selective activity arises from the underlying synaptic connectivity. Here we combined virtual-reality behaviour, two-photon calcium imaging, high-throughput electron microscopy and circuit modelling to analyse how synaptic connectivity between neurons in the posterior parietal cortex relates to their selective activity. We found that excitatory pyramidal neurons preferentially target inhibitory interneurons with the same selectivity. In turn, inhibitory interneurons preferentially target pyramidal neurons with opposite selectivity, forming an opponent inhibition motif. This motif was present even between neurons with activity peaks in different task epochs. We developed neural-circuit models of the computations performed by these motifs, and found that opponent inhibition between neural populations with opposite selectivity amplifies selective inputs, thereby improving the encoding of trial-type information. The models also predict that opponent inhibition between neurons with activity peaks in different task epochs contributes to creating choice-specific sequential activity. These results provide evidence for how synaptic connectivity in cortical circuits supports a learned decision-making task.

Natural sensory context drives diverse brain-wide activity during C. elegans mating

Natural goal-directed behaviors often involve complex sequences of many stimulus-triggered components. Understanding how brain circuits organize such behaviors requires mapping the interactions between an animal, its environment, and its nervous system. Here, we use brain-wide neuronal imaging to study the full performance of mating by the C. elegans male. We show that as mating unfolds in a sequence of component behaviors, the brain operates similarly between instances of each component but distinctly between different components. When the full sensory and behavioral context is taken into account, unique roles emerge for each neuron. Functional correlations between neurons are not fixed but change with behavioral dynamics. From individual neurons to circuits, our study shows how diverse brain-wide dynamics emerge from the integration of sensory perception and motor actions in their natural context.

Reconstruction of motor control circuits in adult Drosophila using automated transmission electron microscopy

To investigate circuit mechanisms underlying locomotor behavior, we used serial-section electron microscopy (EM) to acquire a synapse-resolution dataset containing the ventral nerve cord (VNC) of an adult female Drosophila melanogaster. To generate this dataset, we developed GridTape, a technology that combines automated serial-section collection with automated high-throughput transmission EM. Using this dataset, we studied neuronal networks that control leg and wing movements by reconstructing all 507 motor neurons that control the limbs. We show that a specific class of leg sensory neurons synapses directly onto motor neurons with the largest-caliber axons on both sides of the body, representing a unique pathway for fast limb control. We provide open access to the dataset and reconstructions registered to a standard atlas to permit matching of cells between EM and light microscopy data. We also provide GridTape instrumentation designs and software to make large-scale EM more accessible and affordable to the scientific community.

A Customizable Low-Cost System for Massively Parallel Zebrafish Behavioral Phenotyping

High-throughput behavioral phenotyping is critical to genetic or chemical screening approaches. Zebrafish larvae are amenable to high-throughput behavioral screening because of their rapid development, small size, and conserved vertebrate brain architecture. Existing commercial behavioral phenotyping systems are expensive and not easily modified for new assays. Here, we describe a modular, highly adaptable, and low-cost system. Along with detailed assembly and operation instructions, we provide data acquisition software and a robust, parallel analysis pipeline. We validate our approach by analyzing stimulus response profiles in larval zebrafish, confirming prepulse inhibition phenotypes of two previously isolated mutants, and highlighting best practices for growing larvae prior to behavioral testing. Our new design thus allows rapid construction and streamlined operation of many large-scale behavioral setups with minimal resources and fabrication expertise, with broad applications to other aquatic organisms.

A petascale automated imaging pipeline for mapping neuronal circuits with high-throughput transmission electron microscopy

Electron microscopy (EM) is widely used for studying cellular structure and network connectivity in the brain. We have built a parallel imaging pipeline using transmission electron microscopes that scales this technology, implements 24/7 continuous autonomous imaging, and enables the acquisition of petascale datasets. The suitability of this architecture for large-scale imaging was demonstrated by acquiring a volume of more than 1 mm3 of mouse neocortex, spanning four different visual areas at synaptic resolution, in less than 6 months. Over 26,500 ultrathin tissue sections from the same block were imaged, yielding a dataset of more than 2 petabytes. The combined burst acquisition rate of the pipeline is 3 Gpixel per sec and the net rate is 600 Mpixel per sec with six microscopes running in parallel. This work demonstrates the feasibility of acquiring EM datasets at the scale of cortical microcircuits in multiple brain regions and species.

Deregulation of Domestic Passenger Air Transport Services in the United Kingdom, 1980–89: A Case Study of Northern Ireland

In the first instance, an analysis of the deregulatory aviation policies applied in the United Kingdom during the 1980s is provided. Discussion is placed within the particular context of studies of US deregulation, and their wider relevance to proposed European Community liberalisation. From these, a consensus is emerging that deregulation can succeed only if accompanied by vigorous government measures to act against merger, acquisition, and other anticompetitive devices used by existing carriers to protect their positions. Thus, in part, successful deregulation demands both airport capacity and airport competition in order to increase the number of potential routes for new-market entrants and to obviate at least some of those advantages which accrue to incumbent carriers. Because these conditions are satisfied in Northern Ireland, that region is used as a case study of the efficacy of UK domestic deregulatory policy. The analysis concludes that, given sufficient airport capacity, the increased competition between airlines and airports sponsored by deregulatory policies can have significantly positive benefits for producers in terms of increased demand. Consumers also gain on fares but particularly from enhanced frequency of services. In turn, the advantage of greater frequency is dependent upon the utilisation of a different type of domestic aircraft fleet.

Regulation and Liberalisation in the UK Scheduled Airline Industry

The general aims of the paper are, first, to discuss the role of the Civil Aviation Authority (CAA) as a regulator of the UK scheduled airline industry, prior to the implementation of European Community liberalisation of air transport on 1 January 1993. Second, the reactions of the industry itself to CAA policies are examined. Prior to a detailed consideration of the principles which illuminated the CAA's strategy, the constraints upon that policy are elaborated. Largely, these derive from the characteristics of airline economics and also from the UK government's commitment to privatisation, even at the expense of industry competitiveness. The three principles constituting the CAA's strategy—namely, the multi-airline industry, the primacy of long-term user benefits, and the promotion of a profitable UK airline industry—which were implemented primarily through a process of route licensing, are discussed in turn. It is concluded that user benefits have been realised from the CAA's regulation of both the structure and the behaviour of the industry, although a more pronounced latter-day emphasis on competition is detected. This may be related to the advent of European liberalisation which places only the most modest constraints on carriers' rights to fly whichever routes they wish.

A self-calibrating, camera-based eye tracker for the recording of rodent eye movements

Much of neurophysiology and vision science relies on careful measurement of a human or animal subject's gaze direction. Video-based eye trackers have emerged as an especially popular option for gaze tracking, because they are easy to use and are completely non-invasive. However, video eye trackers typically require a calibration procedure in which the subject must look at a series of points at known gaze angles. While it is possible to rely on innate orienting behaviors for calibration in some non-human species, other species, such as rodents, do not reliably saccade to visual targets, making this form of calibration impossible. To overcome this problem, we developed a fully automated infrared video eye-tracking system that is able to quickly and accurately calibrate itself without requiring co-operation from the subject. This technique relies on the optical geometry of the cornea and uses computer-controlled motorized stages to rapidly estimate the geometry of the eye relative to the camera. The accuracy and precision of our system was carefully measured using an artificial eye, and its capability to monitor the gaze of rodents was verified by tracking spontaneous saccades and evoked oculomotor reflexes in head-fixed rats (in both cases, we obtained measurements that are consistent with those found in the literature). Overall, given its fully automated nature and its intrinsic robustness against operator errors, we believe that our eye-tracking system enhances the utility of existing approaches to gaze-tracking in rodents and represents a valid tool for rodent vision studies.

A randomized trial of preexercise stretching for prevention of lower-limb injury

PURPOSE

This study investigated the effect of muscle stretching during warm-up on the risk of exercise-related injury.

METHODS

1538 male army recruits were randomly allocated to stretch or control groups. During the ensuing 12 wk of training, both groups performed active warm-up exercises before physical training sessions. In addition, the stretch group performed one 20-s static stretch under supervision for each of six major leg muscle groups during every warm-up. The control group did not stretch.

RESULTS

333 lower-limb injuries were recorded during the training period, including 214 soft-tissue injuries. There were 158 injuries in the stretch group and 175 in the control group. There was no significant effect of preexercise stretching on all-injuries risk (hazard ratio [HR] = 0.95, 95% CI 0.77-1.18), soft-tissue injury risk (HR = 0.83, 95% CI 0.63-1.09), or bone injury risk (HR = 1.22, 95% CI 0.86-1.76). Fitness (20-m progressive shuttle run test score), age, and enlistment date all significantly predicted injury risk (P < 0.01 for each), but height, weight, and body mass index did not.

CONCLUSION

A typical muscle stretching protocol performed during preexercise warm-ups does not produce clinically meaningful reductions in risk of exercise-related injury in army recruits. Fitness may be an important, modifiable risk factor.

Predicting attrition in basic military training

This cohort study investigated whether the risk of attrition during Australian Army recruit training was predicted by the fitness, age, date of enlistment, or injury status of recruits. Subjects were 1,317 male Australian Army recruits undertaking 12 weeks of intensive training. Fitness was measured using a 20-m progressive shuttle run test (20 mSRT) in which higher scores reflected higher fitness. A total of 184 subjects failed to complete training. Two hundred seventy-six disabling lower limb training injuries were recorded; 100 were stress fractures or periostitis. Scores on the 20 mSRT ranged between 3.5 and 13.5. Multivariate survival analysis revealed a strong negative association between 20 mSRT score and risk of attrition (p < 0.001) and a positive association between sustaining a lower limb injury and risk of attrition (p < 0.001). These effects were additive. Age and enlistment date were not significantly associated with risk of attrition. Fitness and training procedures may be important, modifiable risk factors for attrition.

Supply and demand of bone allograft for revision hip surgery in Scotland

The Scottish National Blood Transfusion Service is the main provider of bone for grafting in Scotland. Bone is procured only from live donors, following very strict selection criteria, and we have investigated whether the amount being collected was adequate. Our current harvest of approximately 1700 femoral heads per year is shown not to be enough to meet the future demand for revision surgery of the hip. Many more of these operations are being undertaken, and impaction grafting is being used increasingly. We have calculated the predicted rates of collection and usage for the next four to five years so that we can expand our service in a controlled fashion.

Interactions between neuropeptide Y, luteinizing hormone-releasing hormone and estradiol in the control of luteinizing hormone release from cultured ovine pituitary cells

This study used pituitary cells in culture firstly to test the hypothesis that NPY may augment the pituitary LH response to LHRH and secondly to determine whether this interaction is dependent on the presence of estradiol. LHRH (10(-10)-10(-6) M) caused a significant increase in LH secretion from dispersed ovine pituitary cells maintained in culture for six days, a response which was enhanced when cells were pretreated for three days with 4 x 10(-11) M estradiol. NPY 10(-10)-10(-6) M) had no effect on basal LH release from ovine pituitary cells maintained either in the presence or absence of estradiol. NPY (10(-10) and 10(-8) M) also had no effect on LHRH-stimulated LH release either in the presence or absence of estradiol. These results substantiate previous observations that physiologically relevant concentrations of estradiol enhance the LH response to LHRH in cultured ovine pituitary cells. However, in contrast to experiments carried out using rat pituitary cells in culture, the present data provide no evidence to support the hypothesis that NPY alone interacts with LHRH in the control of LH secretion from the ovine pituitary gland.

Measurement of PGE2 as the methyl oxime by radioimmunoassay using a novel iodinated label

A radioimmunoassay has been developed for prostaglandin E2 (PGE2) using methyl oxime (MOX) derivatisation and a novel 125Iodine radiolabel. PGE2-methyl oxime (PGE2-MOX) is coupled through an imide linkage to proline in a pro-gly-tyr or similar peptide rather than through the conventional amide linkage to histamine or tyrosine methyl ester. The main advantage of this method is that the imide linkage in the label does not resemble the amide link used in the original antigen and the conjugate is therefore readily displaced by the natural PGE2. This overcomes the traditional difficulty encountered in hapten RIAs where the antiserum has a higher affinity for the label than it has for the compound to be measured. The assay that has been developed using these modifications and a solid-phase second antibody separation step, is both sensitive (with a lower detection limit of 0.5 pg/tube), reliable and simple and has the advantage that methyl oximation of the sample protects the PGE from degrading prior to and during the assay.

Physical map of the origin of defective DNA in herpes simplex virus type 1 DNA

The origin of defective DNA (dDNA) of the Patton strain of herpes simplex virus type 1 (HSV-1) was physically mapped with BamHI in the parental DNA. The dDNA obtained from virus passaged at high multiplicities of infection was resistant to cleavage with HindIII, whereas digestion with EcoRI yielded a cluster of fragments 5.4 to 5.7 megadaltons (Mdal) in size. Cleavage with BamHI gave a cluster of fragments 2.6 to 3.2 Mdal in size, plus two homogeneous, comigrating 1-Mdal fragments. One of the latter fragments contained the single EcoRI site approximately 65 base pairs from one end. Hybridization of in vitro labeled dDNA probe to EcoRI, HindIII, BamHI, and Hpa I digests of nondefective HSV-1 DNA demonstrated that, in addition to the S-region terminal repeat, only one end of the S region was involved in the generation of this class of dDNA. Thus, the dDNA probe did not hybridize to either the S region 3.0-Mdal HindIIIN fragment or a 3.0-Mdal BamHI fragment of the adjacent 8.7-Mdal HindIIIG fragment, but did hybridize to four BamHI fragments of HindIII G (approximately 5.7 Mdal). The cluster of 2.6- to 3.2-Mdal fragments obtained with BamHI digestion of dDNA appears to represent a novel junction between the termination of dDNA adjacent to the 3.0-Mdal BamHI fragment in HindIII G and the 2.0- to 2.3-Mdal BamHI fragment terminal in HSV-1 DNA.

Persistent herpes simplex virus infections established in two Burkitt lymphoma derived cell lines

Examination of P3HR-I cells (Epstein-Barr virus [EBV] producer) persistently infected with the MAL strain of herpes simplex virus type I (HSV-I) suggested that only a few cells were actively producing a virus indistinguishable from HSV-I (MAL) despite the presence of immunofluorescent HSV-I antigens associated with the majority of cells. EBV-specific immunofluorescence was not altered in HSV-I persistently infected P3HR-I cells. HSV-I persistently infected cells, labelled for 72 h with 14C-thymidine, incorporated approx. 8% of the label into cell associated HSV-I DNA as resolved by caesium chloride gradients. Values greater than 8% of the total were suggested by hybridization of gradient fractions with 3H-HSV-I DNA. To determine whether the establishment of HSV persistent infections in Burkitt lymphoma derived cells was a general phenomenon, six strains of HSV-I (MAL, KOS, Patton, Syn R, BF and SYN V) and two strains of type 2 (333 and MS) were used to infect the P3HR-I and Raji (EBV non-producer) cell lines derived from Burkitt lymphomas. In P3HR-I cells, persistent infections were established with all strains of HSV-I but not with HSV-2. In Raji cells, persistent infections were established with all strains of HSV-I, except Syn V, and with both strains of HSV-2. No external support was required to maintain these infections.

Purification of herpesvirus saimiri and properties of the viral DNA

Conditions for growth, concentration, and purification of Herpesvirus saimiri were determined. Optimal yields of infectious Herpesvirus saimiri (HVS) were obtained from infected owl monkey kidney (OMK) cells grown at 32.5 degrees C in medium containing 10 per cent fetal calf serum. Forth-five percent of the initial infectious HVS was recovered after an 18-fold concentration using 8 per cent polyethylene glycol 6000 in the presence of 0.5 M NaCl. Polyethylene glycol concentrated HVS was purified in an isopycnic-linear Renografin gradient (1.0-1.3 g/cm3. Ninety-six percent of the infectivity was recovered in a single 1.16 g/cm3 density region. DNA extracted from purified HVS was resolved into two distinct density classes by CsCl equilibrium centrifugation (1.727 and 1.709 g/cm3). DNase treated HVA virions yield four DNA species with densities of 1.727, 1.718, 1.712, and 1.706 g/cm3 in CsCl centrifugation.

Neutralizing antibodies to cytomegaloviruses in normal simian and human sera

Simian and human sera were examined for neutralizing antibodies to simian and human cytomegaloviruses (CMV). Neutralizing antibody to simian CMV was found in sera from 12 of 12 African green monkeys, 8 of 10 rhesus monkeys, and 7 of 7 baboons captured in the wild. The antibody did not cross-react with human CMV strain AD169 but cross-reacted with human strain C87, particularly in the presence of complement. Thirty-six baboons and 10 rhesus monkeys born and hand-reared in captivity remained free of neutralizing antibody both to simian and human CMV for as long as 4 years. Fifteen of 24 human sera (63%) revealed only species-specific neutralizing antibody.