Tumor Gene Expression and Interphase Chromatin Appearance in Xiphophorus

SYNOPSIS. Xiphophorus maculatus (platyfish) exhibits spots whichconsist of neoplastically transformed pigment cells (T-cells).The spots actually represent extreme benign melanomas. Transformationto T-cells is mediated by a "tumor gene" (Tu). Platyfish whichdevelop from X-irradiated embryos reveal an increase of Tu-expressionresulting in an overproduction of T-cells to benign melanomaswhich can be compared to that observed in certain hybrids betweenthe platyfish and Xiphophorus helleri (swordtail). Both theX irradiation-induced and the crossing conditioned increaseof Tu-expression represent a heritable alteration which mightbe related to a conversion from dispersed to condensed chromatinin the interphase nuclei.     

Comparison of Mitomycin C and X-irradiation as Blocking Agents in One-way Mixed Leucocyte Cultures

THE mixed leucocyte culture (MLC) test^1,2 has been widely used as a measure of histocompatibility in man and as a model for the recognition phase of the homograft response in vitro. Two methods have been proposed to achieve unidirectional stimulation in MLC: treatment of stimulating cells with either mitomycin C³ or X-irradiation³. The mitomycin C method has the advantage of not requiring expensive X-ray equipment and being immediately available in the laboratory; the X-ray method has the advantage of not requiring washing of the cells following treatment. Although much of the quantitative MLC work for histocompatibility testing in man has been done using mitomycin C, the general impression gained from the literature as well as the studies we report here would support the use of either method. A previous study⁴ suggested that irradiation is superior to mitomycin C treatment for a number of reasons, but we question those conclusions.     

Coiled Supercoiled DNA in Critical Point Dried and Thin Sectioned Human Chromosome Fibres

SUPERCOILING of the DNA double helix in the deoxynucleo-histone fibril (100 Â in diameter with a pitch of 120 Â) has been well documented by X-ray diffraction^1–3. The main structural element of eukaryotic metaphase chromosomes and inactive interphase chromatin, however, is a long, irregularly folded fibre, 200 to 300 Â in diameter, as electron microscopy has shown^4–10. The arrangement of DNA within this fibre has not yet been established clearly. I wish to present electron micrographs of critical point dried and thin sectioned fibres of human metaphase chromosomes, which demonstrate more or less regularly distributed electron densities which could be explained by supercoiling of the 100 Â deoxynucleohistone fibril.     

A Role for Auxin and Auxin Transport Inhibitors on the Ca Content of Artificially Induced Parthenocarpic Fruits

Artificially induced parthenocarpic fruits of apples, pears and tomatoes, as well as seeded fruits treated with 2,3,5-triiodobenzoic acid, frequently show symptoms of Ca deficiency and a low Ca content. It was concluded that auxins, probably produced by the seeds, play a significant role in Ca translocation into fruits. Exogenous indoleacetic acid but not 4-chlorophenoxyacetic acid applications could replace the effect of seeds in this respect. Auxin transport, rather than auxin accumulation, seems to be necessary for Ca transport, as can be concluded from the effect of auxin transport inhibitors.     

Remote sensing of sun-induced fluorescence to improve modeling of diurnal courses of gross primary production (GPP)

Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield ( F _Syield) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale.     

Comparative analysis of end wall resistivity in xylem conduits

The hydraulic resistivity (R, pressure gradient/flow rate) through end walls of xylem conduits was estimated in seven species of diverse anatomy and affinity including a vessel-bearing fern, a tracheid-bearing gymnosperm, and angiosperms with versus without vessels. Conduit lengths were measured with a silicone injection method which was easier and more accurate than the usual paint injection. The R declined linearly with the removal of end walls as stems were shortened from 10 to 0.3 cm. This relationship gave the minimum R with no end walls present, or the lumen resistivity (R_L). This was indistinguishable from the Hagen–Poiseuille value. The maximum R with all end walls present gave R_C, the resistivity of end wall and lumen in series. Average end-wall resistivity (R_W) was the difference R_C − R_L and the ‘wall fraction’ was R_W/R_C. Wall fraction was approximately constant, averaging 0.54 ± 0.07. This suggests that end wall and lumen resistivities are nearly co-limiting in vascular plants. Average conduit length was proportional to the diameter squared across species (r² = 0.94). Together with a constant wall fraction, this was consistent with the end wall resistance (r_w, pressure difference/flow rate) being inversely proportional to conduit length. Lower r_w in longer conduits is consistent with their having more end wall pits than shorter conduits.     

The mating systems of pinnipeds and marine iguanas: convergent evolution of polygyny

The convergent polygynous mating systems of marine iguanas and otariid pinnipeds depend on the existence of large female aggregations. These can build up where abundant marine food resources occur around oceanic islands which harbour fewer predators than continental areas. For marine iguanas distribution of food resources appears to determine the location of colonies, while for pinnipeds habitat choice is more decisive. In marine iguanas females benefit from gregariousness through reduced predation risk and social thermoregulation. In pinnipeds, sea lions may derive thermoregulatory benefits from gregariousness, while fur seals appear to be largely non-gregarious. In both groups males defend territories in areas of high female density. Large sexual size dimorphism presumably evolved in response to strong selection for high fighting potential of males. The capability to fast for prolonged periods of territory tenure is considered a secondary benefit of large male size, but not the driving force behind its evolution. We hypothesize that marginal males, through continuous sexual harassment of females that stay outside territories, have exerted pressure towards the evolution of female gregariousness.     

The effectiveness of child and adolescent psychiatric treatments in a naturalistic outpatient setting

Data concerning the effectiveness of naturalistic treatments (treatment-as-usual) in child and adolescent psychiatric (CAP) services are scarce. The purpose of this prospective observational study was to examine the effectiveness of CAP treatments in a naturalistic outpatient setting. Three hundred six patients (attention-deficit/hyperactivity disorder, ADHD, n=94; conduct disorder, CD, n=57; anxiety disorder, AD, n=53; depressive disorder, DD, n=38; other diagnostic categories, n=64), from nine child and adolescent psychiatric practices in Germany, were evaluated. Treatment effects were compared between patients who received frequent treatment and patients who only participated in diagnostics and short interventions. Since randomization was not feasible, propensity score analysis methods were used. Regarding the total sample, no significant treatment effects were found. However, a subgroup analysis of the four most frequent disorders (ADHD, CD, AD, DD) showed small to moderate treatment effects in patients with ADHD and AD. In CD and DD subgroups, no significant treatment effects could be found. “Real-world” CAP outpatient treatment seems to produce significant effects for ADHD and AD, but not for CD and DD. Compared to efficacy studies, our results show that naturalistic treatment might be better than expected.     

Inter-vessel pitting and cavitation in woody Rosaceae and other vesselled plants: a basis for a safety versus efficiency trade-off in xylem transport

The hypothesis that greater safety from cavitation by air-seeding through inter-vessel pits comes at the cost of less porous pit membranes with greater flow resistance was tested . Sixteen vessel-bearing species were compared: 11 from the Rosaceae, four from other angiosperm families, and one fern. Unexpectedly, there was no relationship between pit resistance (and hence the prevailing membrane porosity) and cavitation pressure. There was, however, an inverse relationship between pit area per vessel and vulnerability to cavitation (r² = 0.75). This suggests that cavitation is caused by the rare largest membrane pore per vessel, the average size of which increases with total pit area per vessel. If safety from cavitation constrains pit membrane surface area, it also limits vessel surface area and the minimum vessel resistivity. This trade-off was consistent with an approximately three-fold increase in vessel resistivity with cavitation pressure dropping from −0.8 to −6.6 MPa. The trade-off was compensated for by a reduction in the percentage of vessel wall pitted: from 10–16% in vulnerable species to 2–4% in resistant species. Across species, end-wall pitting accounted for 53 ± 3% of the total xylem resistivity. This corresponded to vessels achieving on average 94 ± 2% of their maximum possible conductivity if vessel surface area is constrained.