Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object.

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 MU69, 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. MU69 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. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

The Pluto system: Initial results from its exploration by New Horizons.

The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.

Immunological characterization of canine hematopoietic progenitor cells.

Canine hematopoietic progenitor cells were characterized by separation with monoclonal antibodies. Depleted and enriched fractions were studied for growth of CFU-GM in semisolid agar and for repopulating capacity of lethally irradiated dogs. CFU growth was not reduced by depletion of marrow using monoclonal antibodies F 3-20-7 (anti-dog Thy-1), MT606 (anti-human CD 6), and IOT2a (anti-human DR). CFU growth was variable following treatment with the anti-canine T-cell antibody MdT-P 1 and immunomagnetic bead separation. It was regularly enriched when MdT-P 1 treatment was followed by immunorosetting with staphylococcal protein A-loaded sheep red blood cells and density gradient separation. Lethally irradiated dogs were reconstituted by autologous marrow depleted of MdT-P 1-positive cells using immunorosetting and density gradient centrifugation, whereas immunomagnetic bead-depleted marrow was ineffective. Fluorescence-activated cell sorting showed enrichment of hematopoietic progenitor cells in the weakly MdT-P 1-positive fraction.

Functional characterization of canine lymphocyte subsets.

Functional characterization of subsets of T lymphocytes is essential for transplantation studies in dogs, as it is in other species. We studied the function of T cells separated by two mouse monoclonal antibodies recognizing complementary subsets--an antibody directed to canine T cells (MdT-P1) with an up-regulating function, and an antibody directed to human CD 8 (MT811) that cross-reacts with down-regulating canine T cells. Immunorosetting with sheep red blood cells and Percoll gradient allowed us to study depleted and enriched fractions. Their function was tested in mixed lymphocyte culture (MLC), cell-mediated cytotoxicity (CML), and coculture with B cells in a hemolytic plaque assay (PFC). In MLC, MdT-P1-positive cells showed a high proliferative response, and MT811-positive cells responded poorly to allogeneic cells. Vice versa, MT811- negative cells responded strongly, and MdT-P1-negative cells were poor responders but strong stimulators. Effector cells of CML were separated following 8 days of culture and prior to mixing with target cells. Enriched and depleted fractions with either antibody showed low cytotoxic activity as compared with unseparated cells. When added to unseparated effector cells MT 811-positive cells suppressed cytotoxicity. B cells were obtained by rosetting with staphylococcal protein A (SPA). Their immunoglobulin production was studied following 6 days of culture stimulated by pokeweed mitogen in a reverse hemolytic plaque assay. Again, MT 811-positive cells added to the culture suppressed, and MT 811-negative cells enhanced immunoglobulin production. In conclusion, immunorosetting with two monoclonal antibodies allowed us to distinguish subpopulations of canine T cells with up-regulating (helper/inducer) from those with down-regulating (suppressor) activity.

[Experimental studies of in vitro cultivation of the cells of Kärtner honeybees (Apis mellifera carnica Pollmann, 1879)]. / Experimentelle Untersuchungen zur in vitro-Kultivierung von Zellen der Kärntner Honigbiene (Apis mellifera carnica Pollmann, 1879).

A synopsis about published methods and results on experiments to cultivate bee cells in vitro is given. Experimental investigations were performed with haemocytes of larvae of the L-5 stage using many different media and methods for the preparation of primary tissue culture. Monolayers could be prepared and a high rate of reproduction has been achieved, although subpassages could not be obtained. Haemocytes could be kept alive up to 27 days by using BML-TC/7A medium according to Gardiner and Stockdale, modified by Skatulla (pers. communic., 1987). Further experiments are necessary in order to study the suitability of bee cells to detect specific pathogens and toxic substances.

Dose rate and fractionation of total body irradiation in dogs: short and long term effects.

Variations of regimens of total body irradiation (TBI) were investigated in the dog as a preclinical model for bone marrow transplantation. Inactivation of hemopoietic precursor cells (CFU-GM) was studied following irradiation of marrow in vitro, following TBI at sublethal doses in vivo and following autologous transplantation of marrow obtained after sublethal TBI. Inactivation and recovery of CFU-GM as well as restoration of hemopoiesis following autologous transplantation was independent of the dose rate, but nadirs of blood counts were lower following sublethal TBI with the higher dose rate. Acute non-hemopoietic toxicity of TBI depended on the dose, the dose rate and the total treatment time and not on the fractionation regimen. At a total dose of 25 Gy acute mortality was prevented by prophylactic administration of oral, non-absorbable antibiotics. Late mortality was due to degenerative and autoimmune-like disorders with or without infections and to malignant tumors. Evaluation of long-term survival is still preliminary, since surviving dogs of two groups (10 Gy as single dose, 25 Gy as hyperfractionated TBI) have not yet reached the median survival time of their group. So far, long-term survival depended on the total dose (p = 0.05) and, possibly, the fractionation regimen (p = 0.12). The latency period until development of malignant tumors was influenced by the total doses given in the same treatment time (p = 0.05) and by the total treatment time for equal doses (p = 0.04). It was concluded that TBI at a low dose rate may give the best therapeutic ratio of inactivation of hemopoietic precursor cells to acute toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)