Fixation light hue bias revisited: implications for using adaptive optics to study color vision.

Current vision science adaptive optics systems use near infrared wavefront sensor 'beacons' that appear as red spots in the visual field. Colored fixation targets are known to influence the perceived color of macroscopic visual stimuli (Jameson, D., & Hurvich, L. M. (1967). Fixation-light bias: An unwanted by-product of fixation control. Vision Research, 7, 805-809.), suggesting that the wavefront sensor beacon may also influence perceived color for stimuli displayed with adaptive optics. Despite its importance for proper interpretation of adaptive optics experiments on the fine scale interaction of the retinal mosaic and spatial and color vision, this potential bias has not yet been quantified or addressed. Here we measure the impact of the wavefront sensor beacon on color appearance for dim, monochromatic point sources in five subjects. The presence of the beacon altered color reports both when used as a fixation target as well as when displaced in the visual field with a chromatically neutral fixation target. This influence must be taken into account when interpreting previous experiments and new methods of adaptive correction should be used in future experiments using adaptive optics to study color.

[Foreign labor in a reunited Germany]. / Les travailleurs etrangers dans l'Allemagne reunifiee.

PIP: The author discusses migration into Germany, primarily since World War II, with a focus on the impact on the German labor market. The radical changes that came about in the late 1980s as a result of granting political asylum to third-world refugees and of the readmittance of persons of German descent who wanted to repatriate are then assessed. Following reunification, the author foresees new trends in migration into the country and predicts some of their effects. (SUMMARY IN ENG AND GER)^ieng

Studies on levamisole--induced agranulocytosis.

Widespread clinical trials of leavo-tetramisole (levamisole) as an immunopotentiating agent in rheumatoid arthritis, metastatic carcinoma, and immunodeficiency states have been complicated by agranulocytosis (AGC) in 2.5%-13% of patients. Other than a relationship with prolonged high dosage, very little is known regarding the pathogenesis of levamisole-induced AGC. Whereas leukoagglutination was negative, fluorochromatic microgranulocytotoxicity (GCY) tests were positive with serum from 10 of 10 acutely neutropenic patients. The antibody was IgM, reacted with 100% of unrelated granulocytes, but not with T or B lymphocytes. Some sera also reacted with monocytes and the myeloid cell line, K-562. Tests for antigen-antibody complexes or cold autoantibodies were negative. Although clinical evidence strongly suggests a haptene (drug) mechanism, in vitro mixing experiments were also negative. An alternative choice parallels the model of aldomet-induced Coombs'-positive hemolytic anemia. Finally, GCY first became positive 2-3 mo prior to the onset of AGC on two patients, suggesting the possibility of identifying those at risk well before the onset of neutropenia.

Investigations on ploidy levels of haploid and diploid callus and cell suspension cultures of Datura innoxia Mill.

Using haploid and diploid Datura innoxia Mill, callus cultures and cell suspensions it was shown that meristematic material usually attains the lowest possible C-value of a given ploidy level. Parenchyma material of callus cultures, however, indicates a broad scattering of C-values up to 16 C, which is paralleled by C-value distribution of the free cell fraction in actively dividing cell suspensions. In these suspensions, cell division activity seems to be restricted to small meristem-like clusters.

Acquired agranulocytosis with granulocyte specific cytotoxic autoantibody.

Multiple infections and severe neutropenia were found in a previously healthy 29 year old man with no history of similar syndromes in the family, drug ingestion or exposure to environmental toxins. There was no evidence at the time of presentation of diseases previously associated with agranulocytosis (e.g., neoplasia, thyrotoxicosis, chronic infection, collagen-vascular disease or leukoagglutinating antibody). His serum contained a nonagglutinating, complement-dependent, cytotoxic antibody, however, reactive with peripheral blood granulocytes from 35 per cent of normal donors. The neutropenia was not affected by steroids but resolved promptly after splenectomy. Microscopic examination of the spleen revealed ingestion of polymorphonuclear leukocytes by splenic macrophages. Family studies indicated that the target antigen was non-HLA and that the antibody was not absorbed by lymphocytes or platelets. We conclude that the agranulocytosis was autoimmune in origin and suggest that similar myeloid-specific immune responses could influence granulocyte tranfusion and bone marrow transplantation by alloimmune "rejection" that would not be avoided by matching only for HLA specificities.

Investigations on the cell cycle of haploid and diploid tissue cultures of Datura innoxia Mill. and its synchronization.

Using a (14)C/(3)H double-labelling technique, the influence of kinetic on the length of the cell cycle of meristematic cells in haploid and diploid callus cultures of Datura innoxia was determined. The total length of the cell cycle of haploid cells as compared to that of diploid cells was reduced by 2.3 h (-kinetin) or 1.4 h (+kinetin). Furthermore, the addition of kinetin to the nutrient solution also reduces cell cycle duration at both ploidy levels. For synchronization of the cell cycle, a fluorodesoxyuridine/thymidine system was successfully employed. Apparently, the reduction of total cell cycle duration of cycling cells due to treatment with kinetin occurred at the expense of the G1phase. Nevertheless, kinetin seems to exert an influence on the transition of cells from the G2 into the M phase as well.

Microgranulocytotoxicity.

The microcytotoxicity assay technique has been extensively refined to permit the use of granulocytes as target cells in an effort to identify neutrophil-specific antigens. Virtually every aspect of the test required revision to obtain clear, reproducible results. The most radical modification was the adoption of double-fluorescent vital staining to detect cytotoxicity. The reactions detected with this new assay did not correlate with defined human histocompatibility systems (e.g., HLA, ABH, NA, NB, NC), nor were the target antigens detected on lymphocytes or platelets. Cytotoxicity was highly specific and was produced by the immunoglobulin fraction of alloantisera only in the presence of complement, thus implicating an antigen-antibody phenomenon rather than variable viability of the ephemeral PMN's in vitro. These specificities may have an impact on some aspects of human transplantation (especially of bone marrow) as well as playing a role in some febrile transfusion reactions. Of perhaps greater import is the suggested role of the antigens in immunoneutropenias and therefore in the response of myelosuppressed patients to adjunctive leukocyte transfusion therapy.