Interaction effects of visual contours on the discharge frequency of simple striate neurones

1. The discharge frequency of simple neurones in the cat striate cortex responding to the two edges of a slit of light moving over their receptive fields was studied as a function of slit width. While one edge of the slit was discharging the cell, the other edge had a modifying influence on that discharge either by way of facilitation or of inhibition.2. The most common form of the curve relating discharge frequency and slit width had a maximal discharge at narrow slit widths (< 0.5 degrees ) and relative inhibition at medium widths (between 0.5 degrees and 2 degrees ). At greater slit widths there was usually a region of facilitation before the effects of the two edges became independent of one another. Three other response patterns to slits of different width are described.3. The curve relating slit width and response amplitude for a particular cell provides an important clue to the various activity profiles for that cell. An activity profile plots the excitability of a cell along a line through the receptive field in the direction of stimulus movement. Each type of edge, light and dark, has its own set of activity profiles which differ depending upon stimulus parameters such as the direction of the movement of the edge.4. Two other methods were used to provide further data concerning the activity profiles and as a check on the evidence provided by the responses to slits of different width. One of these two methods used the test stimulus against the background of an artificially produced maintained discharge and the other involved the interaction of the two receptive fields of binocularly activated cells.5. A model is put forward to explain the receptive field organization of simple striate neurones which takes into account not only the main features of what is known concerning the synaptology of the visual cortex but also the new data provided by the present paper and the one which precedes it.     

A comparative study of Leishmania mexicana amastigotes and promastigotes. Enzyme activities and subcellular locations

Leishmania mexicana mexicana amastigotes have been shown to contain greater activities than promastigotes of the enzymes that catalyse the beta-oxidation of fatty acids, but lower activities of several glycolytic enzymes, with the activity of pyruvate kinase being especially low. The results suggest the beta-oxidation of fatty acids is relatively more important to Leishmania amastigotes than promastigotes, whereas the reverse is true for glycolysis. Succinic dehydrogenase and peptidase activities were much higher in promastigotes than amastigotes. The activities of glucose-6-phosphatase, fructose-1,6-bisphosphatase, acid phosphatase and glucose-6-phosphate dehydrogenase varied less, although in each case the activity was significantly lower in the mammalian stage. A method for lysing and fractionating L. m. mexicana promastigotes has been developed. Using this procedure it has been established that many of the glycolytic and functionally related enzymes are located in cell organelles, that hexokinase is intimately connected with the particulate part of the parasite, and that the microsomal fraction of L. m. mexicana is very different in composition from the microsomes of mammalian liver cells.     

Markers of HIV infection prior to IgG antibody seropositivity

During a 1-year period of study at two plasma collection centers, 7 of 35,000 plasma donors seroconverted to the human immunodeficiency virus (HIV) and had stored plasma samples that predated or antedated the seroconversion period. From each donor, three to eight plasma samples that had been collected at 2- to 7-day intervals were tested for IgG and IgM antibodies to HIV with enzyme immunoassays, Western blot testing, and radioimmunoprecipitation assays. The presence of an HIV viremic phase was demonstrated by the infectivity of plasma on normal, phytohemagglutinin-stimulated peripheral blood mononuclear cells and by the detection of HIV antigen. In 5 of these donors, HIV antigen was detected prior to or simultaneously with IgG to HIV; these HIV-antigen-positive samples overlapped an IgM immune response. The disappearance of detectable HIV antigen, and to a lesser extent plasma infectivity, was concurrent with the development of an IgG immune response. Although the improved sensitivity of a recombinant DNA-derived anti-HIV screening assay shortened the "window period" between initial HIV infection and antibody detection, HIV antigen and plasma HIV viremia were the only markers of HIV infection for several days in 2 donors. These results demonstrate that HIV plasma viremia and antigenemia occur prior to seroconversion in healthy plasma donors.     

Evaluation of the molecular Xpert Xpress Flu/RSV assay vs. Alere i Influenza A & B assay for rapid detection of influenza viruses

A new FDA-approved Xpert Xpress Flu/RSV assay has been released for rapid influenza virus detection. We collected 134 nasopharyngeal specimens to compare the diagnostic performance of the Xpert assay and the Alere i Influenza A & B assay for influenza A and B virus detection. The Xpert assay demonstrated 100% and 96.3% sensitivity to influenza A and influenza B virus respectively. Its specificity was 100% for both viruses. The Alere i assay demonstrated slightly lower sensitivity but similar specificity to the Xpert Xpress assay. Although the Xpert assay (30 min) required longer processing time than the Alere assay (15 min), the handling procedure of the Alere assay was more complicated than the Xpert assay. As the GenXpert system has higher throughput than the Alere system, it is more suitable for hospital clinical laboratories. Overall, the new Xpert Xpress Flu/RSV assay is a reliable and useful tool for rapid influenza detection.     

Admissions for antibiotic‐resistant infections in cancer patients during first year of cancer diagnosis: a cross‐sectional study

In this study, linked Western Australian health data were used to determine presence of an antibiotic‐resistant infection (ABRI) for all people diagnosed with a primary invasive cancer in 2009. Of 10 858 cancer cases, 154 (1.42%) had an ABRI. Patients with an ABRI were older (71.5 vs 66 years), and more had died in the year following diagnosis (37.7 vs 20.2%, P < 0.001). The ABRI cohort had a higher proportion of colorectal, genitourinary and haematological cancers (19.5 vs 11.9%; 14.3 vs 9.7% and 16.9 vs 5.8%, respectively). Hospital admissions with an ABRI were longer (22.3 vs 2.9 days, P < 0.001) and had a higher proportion of unplanned admissions (60.3 vs 15.2%), admissions through emergency department (36.8 vs 8.3%) and intensive care admissions (14.9 vs 1.7%, P < 0.001). Patients with solid tumours who developed an ABRI were more likely to have received chemotherapy (35.9 vs 27.8%, P = 0.04). In haematological cancer patients, a greater proportion of the admissions with an ABRI occurred after radiation therapy or chemotherapy (P = 0.01 and P = 0.005, respectively). This study is the first to report population‐level data on ABRI in cancer patients. Patients with an ABRI had more hospital admissions and poorer outcomes.     

日本核电泄漏与医学应对

2011年3月11日，日本东部发生强烈地震和海啸，引起世界各国政府和人民广泛同情和全力支援。但此后，日本福岛核电站爆炸、放射性物质泄漏和日本向海洋排放大量低放射性污水；4月12日，日本将其核泄漏事故等级上调至7级。