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Rationale: The isotopic composition of hydrocarbons trapped in rocks on the microscale (fluid inclusions, mineral grain boundaries, microfractures) can provide powerful information on geological and biological processes but are an analytical challenge due to low concentrations. We present a new approach for the extraction and carbon isotopic analysis of methane (CH 4 ) and hydrocarbons in trapped volatiles in crystalline rocks., Methods: An off-line crusher with cryogenic trapping and a custom-made silica glass U-trap were attached to an external injector port on a continuous flow gas chromatograph/combustion/isotope ratio mass spectrometer to demonstrate the accuracy, reproducibility, and sensitivity of δ 13 C measurements for CH 4 ., Results: The method can isotopically characterize CH 4 in crushed rock samples with concentrations as low as 3.5 × 10 -9 mol/g of rock, and both sample and isotopic standards are analyzed with an accuracy and reproducibility of ±0.5‰. High H 2 O/CH 4 ratios of 98 to 500 have no effect on measured δ 13 C CH4 values. The method is successfully applied to natural samples from the north range of Sudbury Basin, Ontario, Canada. The δ 13 C isotopic signatures of CH 4 trapped microscopically in rock from the north range overlap significantly with that of CH 4 contained in larger scale flowing fracture fluids from the same part of the Sudbury Basin, indicating a potential genetic link., Conclusions: A novel method for δ 13 C CH4 analysis was developed for the extraction of nanomole quantities of CH 4 trapped microscopically in rocks. The technique has an accuracy and reproducibility comparable to that of on-line crushing techniques but importantly provides the capability of crushing larger rock quantities (up to 100 g). The benefit is improved detection levels for trace hydrocarbon species. Such a capability will be important for future extension of such crushing techniques for measurement of 2 H/ 1 H for CH 4 , clumped isotopologues of CH 4 and other trapped volatiles species, such as C 2 H 6 , C 3 H 8 , C 4 H 10 , CO 2 and N 2 ., (© 2021 John Wiley & Sons Ltd.)

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU 69 , a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU 69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU 69 's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Understanding of the geochemistry of the chalcophile elements [i.e., Os, Ir, Ru, Pt, Pd (platinum-group elements), and Au, Cu, Ni] has been informed for at least 20 years by the common assumption that when crust-forming partial melts are extracted from the upper mantle, sulfide liquid in the restite sequesters chalcophile elements until the extent of partial melting exceeds approximately 25% and all of the sulfide has been dissolved in silicate melt [Hamlyn, P. R. & Keays, R. R. (1985) Geochim. Cosmochim. Acta 49, 1797-1811]. Here we document very high, unfractionated, chalcophile element concentrations in small-degree partial melts from the mantle that cannot be reconciled with the canonical residual sulfide assumption. We show that the observed high, unfractionated platinum-group element concentrations in small-degree partial melts can be attained if the melting takes place at moderately high oxygen fugacity, which will reduce the amount of sulfide due to the formation of sulfate and will also destabilize residual monosulfide solid solution by driving sulfide melts into the spinel-liquid divariant field. Magmas formed at high oxygen fugacity by small degrees of mantle melting can be important agents for the transfer of chalcophile elements from the upper mantle to the crust and may be progenitors of significant ore deposits of Pt, Pd, and Au.

Deformation and melting of the crust during the formation of large impact craters must have been important during the Earth's early evolution, but such processes remain poorly understood. The 1.8-billion-year-old Sudbury structure in Ontario, Canada, is greater than 200 km in diameter and preserves a complete impact section, including shocked basement rocks, an impact melt sheet and fallback material. It has generally been thought that the most voluminous impact melts represent the average composition of the continental crust, but here we show that the melt sheet now preserved as the Sudbury Igneous Complex is derived predominantly from the lower crust. We therefore infer that the hypervelocity impact caused a partial inversion of the compositional layering of the continental crust. Using geochemical data, including platinum-group-element abundances, we also show that the matrix of the overlying clast-laden Onaping Formation represents a mixture of the original surficial sedimentary strata, shock-melted lower crust and the impactor itself.

Cortical afferents to the basal ganglia, and in particular the corticostriatal projections, are critical in the expression of basal ganglia function in health and disease. The corticostriatal projections are topographically organized but also partially overlap and interdigitate. To determine whether projections from distinct cortical areas converge at the level of single interneurons in the striatum, double anterograde labeling from the primary motor (M1) and primary somatosensory (S1) cortices in the rat, was combined with immunolabeling for parvalbumin (PV), to identify one population of striatal GABAergic interneurons. Cortical afferents from M1 and S1 gave rise to distinct, but partially overlapping, arbors of varicose axons in the striatum. PV-positive neurons were often apposed by cortical terminals and, in many instances, apposed by terminals from both cortical areas. Frequently, individual cortical axons formed multiple varicosities apposed to the same PV-positive neuron. Electron microscopy confirmed that the cortical terminals formed asymmetric synapses with the dendrites and perikarya of PV-positive neurons as well as unlabelled dendritic spines. Correlated light and electron microscopy revealed that individual PV-positive neurons received synaptic input from axon terminals derived from both motor and somatosensory cortices. These results demonstrate that, within areas of overlap of functionally distinct projections, there is synaptic convergence at the single cell level. Sensorimotor integration in the basal ganglia is thus likely to be mediated, at least in part, by striatal GABAergic interneurons. Furthermore, our findings suggest that the pattern of innervation of GABAergic interneurons by cortical afferents is different from the cortical innervation of spiny projection neurons.

The basal ganglia are a group of subcortical nuclei involved in a variety of processes including motor, cognitive and mnemonic functions. One of their major roles is to integrate sensorimotor, associative and limbic information in the production of context-dependent behaviours. These roles are exemplified by the clinical manifestations of neurological disorders of the basal ganglia. Recent advances in many fields, including pharmacology, anatomy, physiology and pathophysiology have provided converging data that have led to unifying hypotheses concerning the functional organisation of the basal ganglia in health and disease. The major input to the basal ganglia is derived from the cerebral cortex. Virtually the whole of the cortical mantle projects in a topographic manner onto the striatum, this cortical information is 'processed' within the striatum and passed via the so-called direct and indirect pathways to the output nuclei of the basal ganglia, the internal segment of the globus pallidus and the substantia nigra pars reticulata. The basal ganglia influence behaviour by the projections of these output nuclei to the thalamus and thence back to the cortex, or to subcortical 'premotor' regions. Recent studies have demonstrated that the organisation of these pathways is more complex than previously suggested. Thus the cortical input to the basal ganglia, in addition to innervating the spiny projection neurons, also innervates GABA interneurons, which in turn provide a feed-forward inhibition of the spiny output neurons. Individual neurons of the globus pallidus innervate basal ganglia output nuclei as well as the subthalamic nucleus and substantia nigra pars compacta. About one quarter of them also innervate the striatum and are in a position to control the output of the striatum powerfully as they preferentially contact GABA interneurons. Neurons of the pallidal complex also provide an anatomical substrate, within the basal ganglia, for the synaptic integration of functionally diverse information derived from the cortex. It is concluded that the essential concept of the direct and indirect pathways of information flow through the basal ganglia remains intact but that the role of the indirect pathway is more complex than previously suggested and that neurons of the globus pallidus are in a position to control the activity of virtually the whole of the basal ganglia.

Tyrosine Hydroxylase is the rate-limiting enzyme in the synthesis of dopamine, and as such, it is widely used as a marker of dopaminergic cells. Within the basal ganglia, the dopaminergic cells are located in the substantia nigra pars compacta, and project to the striatum. It is this pathway which degenerates during Parkinson's disease. The data presented here illustrate examples of tyrosine-hydroxylase immunoreactive cells in striatum following intrastriatal injection with the neurotoxin MPP+. We further show by electron microscopy that these cells are, in fact, neurons and that they possess ultrastructural features of interneurons.

The patch-matrix organization of the striatal complex, which is fundamental to the structural and functional organization of the basal ganglia, is characterized on the basis of both connections and neurochemistry. In order to determine whether differences in the connections and neurochemistry are reflected in differences in synaptic organization, we examined the synaptology of the dopaminergic nigrostriatal projection in the patch-matrix complex of the rat. Three approaches were used. First, deposits of the anterograde tracer, biotinylated dextran amine, were placed in the substantia nigra. Sections of perfuse-fixed neostriatum were then processed to reveal anterogradely-labelled nigrostriatal axons and calbindin-D28k immunoreactivity, a marker for the patch-matrix complex. Secondly, sections of perfuse-fixed neostriatum were immunolabelled to reveal both tyrosine hydroxylase, a marker for dopaminergic structures and calbindin-D28k. Labelled axons in the patches and the matrix were examined at both the light and the electron microscopic levels. Finally, in order to test for the presence of fixed GABA in sub-type of anterogradely-labelled terminals in the neostriatum, ultrathin sections were immunolabelled by the post-embedding immunogold method. Based on morphological analysis, anterogradely-labelled nigrostriatal axons were divided into two types (Type I and Type II). The density of tyrosine hydroxylase labelling in the neostriatum prevented the classification of immunolabelled nigrostriatal axons. The Type I anterogradely-labelled axons and tyrosine hydroxylase-positive axons were found both in the patches and in the matrix. They both formed symmetrical synapses with spines, dendrites and occasionally somata. The morphology, dimensions, type of synaptic specialization and the distribution of postsynaptic targets of axons labelled by both methods were similar in the patches and the matrix. The Type I anterogradely-labelled axons were immunonegative for GABA. The Type II anterogradely-labelled axons were GABA-immunopositive, were found only in the matrix and were only present in those animals in which retrograde labelling was observed in the globus pallidus, they are thus not part of the dopaminergic nigrostriatal projection. It is concluded that although the patch-directed and matrix-directed dopaminergic projections from the ventral mesencephalon arise from different populations of dopaminergic neurons, their innervation of neurons in the patches and matrix is similar. The anatomical substrate, and therefore probably also the mechanism, for dopaminergic modulation of the flow of cortical information through the striatal complex in essentially the same in the patch and in the matrix sub-divisions of the striatal complex.

A method of quantitatively determining the volume of fat emboli in a tissue using an image analysis system (I.B.A.S.) was developed. This procedure is an interactive, semi-automated tool allowing the quick and accurate gathering of large quantities of data from sections of different tissue samples stained by osmium tetroxide. The development of this procedure was aimed at producing a system which is reliable, reproducible and semi-automated thereby enabling epidemiological and serial studies to be made of a large number of histological sections from different tissues. The system was tested in a study of tissue sections from a series of fatalities from an aircraft crash in an attempt at correlating the incidence of fat emboli with the presence of multiple fractures and soft tissue injuries, the correlation to be made being between the quantitative presence of fat emboli and the extent and severity of injuries suffered.