Breeding effects on canopy light attenuation in maize: a retrospective and prospective analysis.

The light attenuation process within a plant canopy defines energy capture and vertical distribution of light and nitrogen (N). The vertical light distribution can be quantitatively described with the extinction coefficient (k), which associates the fraction of intercepted photosynthetically active radiation (fPARi) with the leaf area index (LAI). Lower values of k correspond to upright leaves and homogeneous vertical light distribution, increasing radiation use efficiency (RUE). Yield gains in maize (Zea mays L.) were accompanied by increases in optimum plant density and leaf erectness. Thus, the yield-driven breeding programs and management changes, such as reduced row spacing, selected a more erect leaf habit under different maize production systems (e.g., China and the USA). In this study, data from Argentina revealed that k decreased at a rate of 1.1% year-1 since 1989, regardless of plant density and in agreement with Chinese reports (1.0% year-1 since 1981). A reliable assessment of changes in k over time is critical for predicting (i) modifications in resource use efficiency (e.g. radiation, water, and N), improving estimations derived from crop simulation models; (ii) differences in productivity caused by management practices; and (iii) limitations to further exploit this trait with breeding.

Artificial selection for grain yield has increased net CO2 exchange of the ear leaf in maize crops.

Identifying the physiological traits indirectly selected during the search for high-yielding maize hybrids is useful for guiding further improvements. To investigate such traits, in this study we focused on the critical period of kernel formation because kernel number is the main yield component affected by breeding. Our results show that breeding has increased the number of florets per ear and ear growth rate but not the vegetative shoot growth rate, suggesting localised effects around the ear. Consistent with this possibility, breeding has increased the net CO2 exchange of the ear leaf in field-grown crops grown at high population densities. This response is largely accounted for by increased light interception (which increases photosynthesis) and by reduced rates of respiration of the ear leaf in modern hybrids compared to older ones. Modern hybrids show increased ear-leaf area per unit leaf dry matter (specific leaf area), which accounts for the reduced respiratory load per unit leaf area. These observations are consistent with a model where the improved ear leaf CO2 exchange helps the additional florets produced by modern hybrids to survive the critical period of high susceptibility to stress and hence to produce kernels.

Impact of preformed T-cell alloreactivity by means of donor-specific and panel of reactive T cells (PRT) ELISPOT in kidney transplantation.

Donor-specific (d-sp) interferon gamma enzyme-linked immunosorbent spot (d-sp ELISPOT) and Panel of reactive T-cell (PRT) ELISPOT assays have been developed to detect alloreactive memory T (Tmem) cells in order to estimate the risk of acute rejection after kidney transplantation. Adding IL15 to the PRT assay (PRT+IL15) may uncover the presence of pathogenic alloreactive CD28-Tmem. Face-to-face comparisons of these assays have not been done yet. We performed pre-transplant d-sp ELISPOT and PRT assays (±IL15, against six B-cell lines) in 168 consecutive kidney transplant recipients and evaluated the multivariable-adjusted associations with biopsy-proven acute rejection (BPAR), de novo donor-specific antibodies (DSA), and eGFR decline over a 48-month follow-up period. D-sp ELISPOT was positive in 81 (48%) subjects, while 71 (42%) and 81 (48%) subjects displayed positive PRT and PRT+IL15, respectively. Their median [interquartile range] numerical test result was 23 [6-65], 18 [8-37], and 26 [10-45] spots/3x105 PBMCs, respectively. The number of PRT spots were weakly correlated with those of d-sp ELISPOT, but highly correlated with PRT+IL15 (rho = 0.96, P<0.001). d-sp ELISPOT, but not PRT (±IL15) was independently associated with BPAR (adjusted Odds Ratio of BPAR associated with d-sp ELISPOT positivity: 4.20 [95%CI: 1.06 to 21.73; P = 0.041]). Unlike d-sp ELISPOT, median PRT and PRT+IL15 were independently associated with higher Δ3-48month eGFR decline post-transplantation (for both assays, about -3mL/min/1.73m2 per one standard deviation unit increase in the spot number). Pre-transplant T-cell immune-monitoring using d-sp ELISPOT and PRT assays identifies kidney transplant candidates at high risk of BPAR and worse kidney allograft progression.

Effector Antitumor and Regulatory T Cell Responses Influence the Development of Nonmelanoma Skin Cancer in Kidney Transplant Patients.

BACKGROUND: Chronic immunosuppression promotes nonmelanocytic squamous cell carcinoma (SCC) after kidney transplantation. Adaptive and innate immunity play a key role controlling tumor growth and are influenced by different immunosuppressive agents. We hypothesized that functional impairment of tumor-specific T cell responses due to calcineurin inhibitors (CNI) could contribute to SCC development, whereas conversion to mammalian target of rapamycin inhibitors (mTOR-i) could recover this protective immune response. METHODS: Peripheral tumor-specific T cell responses against main SCC-derived antigens using the IFN-γ enzyme-linked immunospot assay and intratumor (IT) and circulating immune phenotypes (CD4 + T, CD8 + T, CD20 + B, CD56 + NK, FOXP3 + regulatory T [Treg] cells) were explored in a cross-sectional analysis in 59 kidney transplant patients with SCC on CNI (KT-CNI-SCC) or mTOR-i (KT-mTORi-SCC), 25 nontransplants developing SCC (NoKT-SCC) and 6 healthy controls. Moreover, 25 KT-CNI-SCC were switched to mTOR-i and evaluated after 12 months. RESULTS: Kidney transplant patients showed lower IT infiltrates and tumor-specific T cell responses than NoKT-SCC, and intratumoral and circulating FOXP3 + Treg cells were higher in KT-mTORi-SCC (P < 0.05). Tumor-specific T cell responses were significantly lower in KT-CNI-SCC than KT-mTORi-SCC and NoKT-SCC and predicted SCC relapses (area under the curve = 0.837; P < 0.05). One-year after mTOR-i conversion, a significant increase in FOXP3 + Treg cell numbers and tumor-specific T cell responses were observed, reaching similar levels than KT-mTORi-SCC and NoKT-SCC patients. CONCLUSIONS: Tumor-specific T cell responses are strongly impaired in CNI-treated patients but recover after mTOR-i conversion, reducing SCC relapses.

Molecular and Functional Noninvasive Immune Monitoring in the ESCAPE Study for Prediction of Subclinical Renal Allograft Rejection.

BACKGROUND: Subclinical acute rejection (sc-AR) is a main cause for functional decline and kidney graft loss and may only be assessed through surveillance biopsies. METHODS: The predictive capacity of 2 novel noninvasive blood biomarkers, the transcriptional kidney Solid Organ Response Test (kSORT), and the IFN-γ enzyme-linked immunosorbent spot assay (ELISPOT) assay were assessed in the Evaluation of Sub-Clinical Acute rejection PrEdiction (ESCAPE) Study in 75 consecutive kidney transplants who received 6-month protocol biopsies. Both assays were run individually and in combination to optimize the use of these techniques to predict sc-AR risk. RESULTS: Subclinical acute rejection was observed in 22 (29.3%) patients (17 T cell-mediated subclinical rejection [sc-TCMR], 5 antibody-mediated subclinical rejection [sc-ABMR]), whereas 53 (70.7%) showed a noninjured, preserved (stable [STA]) parenchyma. High-risk (HR), low-risk, and indeterminate-risk kSORT scores were observed in 15 (20%), 50 (66.7%), and 10 (13.3%) patients, respectively. The ELISPOT assay was positive in 31 (41%) and negative in 44 (58.7%) patients. The kSORT assay showed high accuracy predicting sc-AR (specificity, 98%; positive predictive value 93%) (all sc-ABMR and 58% sc-TCMR showed HR-kSORT), whereas the ELISPOT showed high precision ruling out sc-TCMR (specificity = 70%, negative predictive value = 92.5%), but could not predict sc-ABMR, unlike kSORT. The predictive probabilities for sc-AR, sc-TCMR, and sc-ABMR were significantly higher when combining both biomarkers (area under the curve > 0.85, P < 0.001) and independently predicted the risk of 6-month sc-AR in a multivariate regression analysis. CONCLUSIONS: Combining a molecular and immune cell functional assay may help to identify HR patients for sc-AR, distinguishing between different driving alloimmune effector mechanisms.

Pre-transplant donor-specific T-cell alloreactivity is strongly associated with early acute cellular rejection in kidney transplant recipients not receiving T-cell depleting induction therapy.

Preformed T-cell immune-sensitization should most likely impact allograft outcome during the initial period after kidney transplantation, since donor-specific memory T-cells may rapidly recognize alloantigens and activate the effector immune response, which leads to allograft rejection. However, the precise time-frame in which acute rejection is fundamentally triggered by preformed donor-specific memory T cells rather than by de novo activated naïve T cells is still to be established. Here, preformed donor-specific alloreactive T-cell responses were evaluated using the IFN-γ ELISPOT assay in a large consecutive cohort of kidney transplant patients (n = 90), to assess the main clinical variables associated with cellular sensitization and its predominant time-frame impact on allograft outcome, and was further validated in an independent new set of kidney transplant recipients (n = 67). We found that most highly T-cell sensitized patients were elderly patients with particularly poor HLA class-I matching, without any clinically recognizable sensitizing events. While one-year incidence of all types of biopsy-proven acute rejection did not differ between T-cell alloreactive and non-alloreactive patients, Receiver Operating Characteristic curve analysis indicated the first two months after transplantation as the highest risk time period for acute cellular rejection associated with baseline T-cell sensitization. This effect was particularly evident in young and highly alloreactive individuals that did not receive T-cell depletion immunosuppression. Multivariate analysis confirmed preformed T-cell sensitization as an independent predictor of early acute cellular rejection. In summary, monitoring anti-donor T-cell sensitization before transplantation may help to identify patients at increased risk of acute cellular rejection, particularly in the early phases after kidney transplantation, and thus guide decision-making regarding the use of induction therapy.

Grading nuclear, cortical and posterior subcapsular cataracts using an objective scatter index measured with a double-pass system.

PURPOSE: To evaluate objectively intraocular scattering in eyes with nuclear, cortical and posterior subcapsular cataracts by means of an objective scatter index (OSI) obtained from double-pass images. To compare the results with those obtained using clinical conventional procedures. METHODS: In this prospective, observational, cross-sectional, non-consecutive case series study, 188 eyes with cataracts of 136 patients were analysed (123 eyes had nuclear, 41 eyes had cortical and 24 eyes had posterior subcapsular cataracts). The control group consisted of 117 eyes of 68 healthy patients. Patient examination included subjective refraction, best spectacle-corrected visual acuity (BSCVA), cataract grade using the lens opacities classification system III (LOCS III) and OSI. RESULTS: We found a decrease in the BSCVA and an increase in the OSI with increasing cataract grade. Statistically significant differences were observed when the OSI of eyes without cataracts and those with different LOCS III were compared. The comparison between the OSI and LOCS III reported good percentages of agreement regarding the number of eyes classified in equivalent levels: 72.4% (nuclear cataracts), 86.6% (cortical cataracts) and 84.3% (posterior subcapsular cataracts). A non-linear regression model was applied between OSI and BSCVA, which resulted in the following multiple correlation coefficients: r=0.878 (nuclear), r=0.843 (cortical) and r=0.844 (posterior subcapsular). CONCLUSIONS: The results of the study showed that OSI is a useful parameter for evaluating large amounts of intraocular scattering that can be used, in combination with other conventional procedures, as a valuable tool in clinical practice to grade cataracts objectively.

In vivo imaging of the fine structure of rhodamine-labeled macaque retinal ganglion cells.

PURPOSE: The extent to which the fine structure of single ganglion cells, such as dendrites and axons, can be resolved in retinal images obtained from the living primate eye was investigated. METHODS: Macaque retinal ganglion cells were labeled with retrograde transport of rhodamine dextran injected into the lateral geniculate nucleus. Fluorescence images of the ganglion cells were obtained in vivo with an adaptive optics scanning laser ophthalmoscope. RESULTS: Axons and dendritic arborization could be resolved in primate retinal ganglion cells in vivo, comparing favorably in detail with ex vivo confocal images of the same cells. The full width at half maximum of the transverse line spread function (LSF) was 1.6 microm, and that of the axial point spread function (PSF) was 115 microm. The axial positional accuracy of fluorescence-labeled objects was approximately 4 microm. CONCLUSIONS: This in vivo method applied to ganglion cells demonstrates that structures smaller than the somas of typical retinal cells can be accessible in living eyes. Similar approaches may be applied to image other relatively transparent retinal structures, providing a potentially valuable tool for microscopic examination of the normal and diseased living retina.

Curvature sensor for ocular wavefront measurement.

We describe a new wavefront sensor for ocular aberration determination, based on the curvature sensing principle, which adapts the classical system used in astronomy for the living eye's measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann-Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.