Experimental and computational analyses reveal that environmental restrictions shape HIV-1 spread in 3D cultures

Here, using an integrative experimental and computational approach, Imle et al. show how cell motility and density affect HIV cell-associated transmission in a three-dimensional tissue-like culture system of CD4+ T cells and collagen, and how different collagen matrices restrict infection by cell-free virions

Comparative studies on the structure of an upland African stream ecosystem

Upland stream systems have been extensively investigated in Europe, North America and Australasia and many of the central ideas concerning their function are based on these systems. One central paradigm, the river continuum concept is ultimately derived from those North American streams whose catchments remain forested with native vegetation. Streams of the tropics may or may not fit the model. They have been little studied. The Amani Nature Reserve in the East Usambara Mountains of north-eastern Tanzania offers an opportunity to bring these naturally forested systems to the attention of the ecological community. This article describes a comparison made between two lengths of the River Dodwe in this area. The work was carried out by a group of postgraduate students from eighteen European and African countries with advice from five staff members, as part of a course organised by the Tropical Biology Association. Rigorous efforts were made to standardise techniques, in a situation where equipment and laboratory facilities were very basic, through a management structure and deliberate allocation of work to specialists in each area.The article offers a summary of invertebrate communities found in the stream and its biomass. Crabs seem to be the key organism in both sections of the streams

Spatial heterogeneity and peptide availability determine CTL killing efficiency in vivo

The rate at which a cytotoxic T lymphocyte (CTL) can survey for infected cells is a key ingredient of models of vertebrate immune responses to intracellular pathogens. Estimates have been obtained using in vivo cytotoxicity assays in which peptide-pulsed splenocytes are killed by CTL in the spleens of immunised mice. However the spleen is a heterogeneous environment and splenocytes comprise multiple cell types. Are some cell types intrinsically more susceptible to lysis than others? Quantitatively, what impacts are made by the spatial distribution of targets and effectors, and the level of peptide-MHC on the target cell surface? To address these questions we revisited the splenocyte killing assay, using CTL specific for an epitope of influenza virus. We found that at the cell population level T cell targets were killed more rapidly than B cells. Using modeling, quantitative imaging and in vitro killing assays we conclude that this difference in vivo likely reflects different migratory patterns of targets within the spleen and a heterogeneous distribution of CTL, with no detectable difference in the intrinsic susceptibilities of the two populations to lysis. Modeling of the stages involved in the detection and killing of peptide-pulsed targets in vitro revealed that peptide dose influenced the ability of CTL to form conjugates with targets but had no detectable effect on the probability that conjugation resulted in lysis, and that T cell targets took longer to lyse than B cells. We also infer that incomplete killing in vivo of cells pulsed with low doses of peptide may be due to a combination of heterogeneity in peptide uptake and the dissociation, but not internalisation, of peptide-MHC complexes. Our analyses demonstrate how population-averaged parameters in models of immune responses can be dissected to account for both spatial and cellular heterogeneity

Social organization of a solitary carnivore: spatial behaviour, interactions and relatedness in the slender mongoose

The majority of carnivore species are described as solitary, but little is known about their social organization and interactions with conspecifics. We investigated the spatial organization and social interactions as well as relatedness of slender mongooses (Galerella sanguinea) living in the southern Kalahari. This is a little studied small carnivore previously described as solitary with anecdotal evidence for male associations. In our study population, mongooses arranged in spatial groups consisting of one to three males and up to four females. Male ranges, based on sleeping sites, were large and overlapping, encompassing the smaller and more exclusive female ranges. Spatial groups could be distinguished by their behaviour, communal denning and home range. Within spatial groups animals communally denned in up to 33% of nights, mainly during winter months, presumably to gain thermoregulatory benefits. Associations of related males gained reproductive benefits likely through increased territorial and female defence. Our study supports slender mongooses to be better described as solitary foragers living in a complex system of spatial groups with amicable social interactions between specific individuals. We suggest that the recognition of underlying ‘hidden' complexities in these apparently ‘solitary' organizations needs to be accounted for when investigating group living and social behaviour

Quark helicity distributions in the nucleon for up, down, and strange quarks from semi--inclusive deep--inelastic scattering

Polarized deep--inelastic scattering data on longitudinally polarized hydrogen and deuterium targets have been used to determine double spin asymmetries of cross sections. Inclusive and semi--inclusive asymmetries for the production of positive and negative pions from hydrogen were obtained in a re--analysis of previously published data. Inclusive and semi--inclusive asymmetries for the production of negative and positive pions and kaons were measured on a polarized deuterium target. The separate helicity densities for the up and down quarks and the anti--up, anti--down, and strange sea quarks were computed from these asymmetries in a ``leading order'' QCD analysis. The polarization of the up--quark is positive and that of the down--quark is negative. All extracted sea quark polarizations are consistent with zero, and the light quark sea helicity densities are flavor symmetric within the experimental uncertainties. First and second moments of the extracted quark helicity densities in the measured range are consistent with fits of inclusive data

The Q^2-Dependence of Nuclear Transparency for Exclusive ρ0\rho^0 Production

Exclusive coherent and incoherent electroproduction of the $\rho^0$ meson from $^1$H and $^{14}$N targets has been studied at the HERMES experiment as a function of coherence length ($l_c$), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon ($-Q^2$). The ratio of $^{14}$N to $^1$H cross sections per nucleon, known as nuclear transparency, was found to increase (decrease) with increasing coherence length for coherent (incoherent) $\rho^0$ electroproduction. For fixed coherence length, a rise of nuclear transparency with $Q^2$ is observed for both coherent and incoherent $\rho^0$ production, which is in agreement with theoretical calculations of color transparency.Comment: 5 pages, 4 figure

Nuclear Polarization of Molecular Hydrogen Recombined on a Non-metallic Surface

The nuclear polarization of $\mathrm{H}_2$ molecules formed by recombination of nuclear polarized H atoms on the surface of a storage cell initially coated with a silicon-based polymer has been measured by using the longitudinal double-spin asymmetry in deep-inelastic positron-proton scattering. The molecules are found to have a substantial nuclear polarization, which is evidence that initially polarized atoms retain their nuclear polarization when absorbed on this type of surfac

Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron

The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2] for the proton and neutron have been determined from measurements of polarised cross section asymmetries in deep inelastic scattering of 27.5 GeV longitudinally polarised positrons from polarised 1H and 3He internal gas targets. The data were collected in the region above the nucleon resonances in the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the proton the contribution to the generalised Gerasimov-Drell-Hearn integral was found to be substantial and must be included for an accurate determination of the full integral. Furthermore the data are consistent with a QCD next-to-leading order fit based on previous deep inelastic scattering data. Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte

Assistierte Suizide in München – eine Analyse vorliegender Gutachten

Hintergrund Die Autoren hatten in 3 vorangehenden Publikationen dieser Fachzeitschrift erste Daten zu assistierten Suiziden (AS) in München vorgestellt. Ergänzend wird nun die Qualität vorliegender Gutachten von AS-Fällen untersucht. Methode Alle Münchner Todesbescheinigungen vom 01.01.2020 bis zum 31.12.2023 wurden auf AS-Sterbefälle geprüft. Waren in den korrespondierenden staatsanwaltschaftlichen Akten Gutachten enthalten, wurden diese AS-Fälle anonymisiert und deskriptiv ausgewertet. Ergebnisse Psychiatrische Erkrankungen mit einem potenziellen Einfluss auf die Freiverantwortlichkeit wie Depressionen, kognitive Einschränkungen und Demenz lagen bei knapp 24 %, 3 % bzw. 7 % der Fälle vor. In diesen Fällen wurden in weniger als der Hälfte Fachgutachter aus Psychiatrie oder Psychologie beauftragt. In fast zwei Dritteln der Fälle handelte es sich bei Gutachter, assistierendem Arzt und Leichenschauer um dieselbe Person. Fast ein Fünftel der Gutachten wurde von den Autoren lediglich als Attest eingestuft. Nur in etwa zwei Dritteln der Fälle waren die Nennung von Alternativen zum AS und die Überprüfung der körperlichen Voraussetzungen für die Tatherrschaft des Suizidwilligen dokumentiert. Diskussion Die vom Bundesverfassungsgericht geforderte Freiverantwortlichkeit als Voraussetzung für die Straffreiheit eines AS umfasst nach fachlicher Bewertung der Autoren: 1. kompetente Begutachtung der Einwilligungsfähigkeit, 2. ergebnisoffene, umfassende, frühzeitige und ggf. interdisziplinäre Aufklärung, 3. transparente Vorbereitung des AS mit Trennung der Rollen von behandelndem und aufklärendem Arzt, Gutachter, assistierendem Arzt sowie Leichenschauer und 4. ausreichende Reflexionsphasen für den Suizidenten. Eine Überprüfung der Eignung der Gutachter wäre wünschenswert. Jedenfalls bei Anhaltspunkten für mangelnde Freiverantwortlichkeit sollten Fachärzte für Psychiatrie miteinbezogen werden. Gutachten sollten standardisiert abgefasst werden.Background In three previous publications the authors presented first data on assisted suicides (AS) in Munich. In addition, the quality of expert reports on AS were examined. Methods All death certificates in Munich from January 1, 2020, to December 31, 2023, were examined for cases of AS. If the corresponding public prosecutor’s files contained expert reports, these cases of AS were anonymized and analyzed descriptively. Results Psychiatric disorders with a potential impact on free will, such as depression, cognitive impairment, and dementia, were present in approximately 24%, 3% and 7% of cases, respectively. In less than half of these cases no psychiatric or psychological experts were appointed. In almost two thirds of the cases the expert, suicide assistant and postmortem examiner were the same person. Almost one fifth of the expert reports were classified by the authors merely as attestation. Only in about two thirds of the cases were alternatives to AS and the physical prerequisites for the suicide documented. Discussion The free will required by the Federal Constitutional Court as a prerequisite for exemption from prosecution of AS, in the view of the authors includes: 1) competent assessment of the ability to give consent, 2) open-ended, comprehensive, early and, if necessary, interdisciplinary information about AS, 3) transparent preparation with separation of the roles of pretreatment and informing physician, expert, assisting physician and postmortem examiner and 4) sufficient reflection phases. An assessment of the qualification of the experts would be desirable. In any case, if there are indications of a lack of free will specialists in psychiatry should be involved. Expert reports should be standardized