Involvement of uncoupled antenna chlorophylls in photoinhibition in thylakoids

AbstractEvidence is presented, by means of both fluorescence and action spectroscopy, that a small, spectroscopically heterogeneous population of both Chl a and Chl b molecules is present in isolated spinach thylakoids and is active in photoinhibition. The broadness of the action spectrum suggests that degraded or incompletely assembled pigment–protein complexes may be involved

The relation between the minor chlorophyll spectral forms and fluorescence quenching in aggregated light harvesting chlorophyll a b complex II

The hypothesis that fluorescence quenching in aggregated light harvesting chlorophyll a/b protein complex II is associated with the formation of minor spectral forms absorbing near 655 nm and between 680 nm-690 nm is examined. Using an homogeneous LHCII preparation, steady-state absorption changes measured at room temperature are quantitatively compared with the associated steady state fluorescence changes by means of the Stepanov relation. It is demonstrated that upon LHCII aggregation, the relative fluorescence yield is constant for chlorophyll forms absorbing between 650 nm and 690 nm. This indicates that the minor chlorophyll forms formed upon LHCII aggregation are not quenching species

Dynamic contrast-enhanced magnetic resonance imaging of the wrist in early arthritis

Objectives: MRI has been proposed as the imaging method of choice to evaluate the long-term outcome in patients with early arthritis. The role of dynamic MRI, performed at presentation, in predicting the outcome of patients with early arthritis has been addressed in the present study. Methods: 39 patients with early arthritis, involving at least one wrist, were studied with clinical visits and laboratory investigations, every 3 months. Dynamic MRI was performed with a low-field (0.2T), extremity-dedicated machine (Artoscan, Esaote, Genova, Italy) equipped with a permanent magnet and with a dedicated hand and wrist coil. During the intravenous injection of Gd-DTPA, twenty consecutive fast images of 3 slices of the wrist were acquired. The synovial contrast enhancement ratio was calculated both as rate of early enhancement (REE) per second during the first 55" and as relative enhancement (RE) at t seconds. Results: In our cohort of patients, REE and RE were significantly lower than those observed in a historical cohort of 36 patients with active rheumatoid arthritis. In univariate analysis, low RE predicted complete remission of arthritis. In multivariate analysis, fulfillment of RA criteria during follow-up was predicted by high RE. The need for immunosuppressive treatment at the end of follow-up was predicted by both low RE and high REE. Conclusions: Dynamic MRI may be used to predict several outcomes of early arthritis involving the wris

Plantar pain is not always fasciitis

The case is described of a patient with chronic plantar pain, diagnosed as fasciitis, which was not improved by conventional treatment. Magnetic resonance imaging revealed flexor hallucis longus tenosynovitis, which improved after local glucocorticoid injection

On phytochrome absorption and the phytochrome photoequilibrium in a green leaf: environmental sensitivity and photoequilibrium time

The average, corrected attenuance spectra for both spectral forms of phytochrome in a mature leaf were calculated. Optical masking by chlorophyll together with the detour effect (optical path lengthening effect) due to multiple light scattering led to large changes in both the Qy band shape and wavelength position and the effective intensity of the weak vibrational bands increases. The Pfr/Pr oscillator-strength-ratio between 400-750 nm (0.93 in vitro), becomes 1.63 in a leaf. Thus the dominant absorption form is Pfr. These two values permit calculation of the phytochrome photoequilibrium under conditions of daylight illumination both in vitro and in folia. These values are 0.6 and 0.38 respectively. Previous literature estimates for the situation in vitro, based on the 660/730 nm absorption ratio, yielded values close to 0.6. It is demonstrated that this large decrease in the phytochrome photoequilibrium in a leaf has the effect of translating this parameter to a position on the dose (red/far-red light ratio)-response (Pfr/Ptot) plot towards greater sensitivity to changes in the environmental red/far-red ratio. The increased sensitivity factor is almost five-fold for the daylight environment and is even greater for the various shade-light environments. The approximate time taken to attain photoequilibrium (1/e lifetime) has also been calculated for phytochrome in a leaf in different light environments. For the daylight environment the photoequilibration time is 5 s, which increases into the 20-80 s interval under different degrees of shade light. Thus, despite the strong optical masking by chlorophyll in a mature leaf, the phytochrome photoequilibrium is attained quite rapidly on a physiological time scale

Magnetic resonance imaging of the peripheral joints in psoriatic arthritis

Objective: Magnetic resonance imaging (MRI) has been widely used for the evaluation of rheumatoid arthritis (RA), with only a minority of studies considering other types of arthritis. This review is concerned with an evaluation of the MRI appearance of peripheral joints in psoriatic arthritis (PsA). Methods: A Medline search was performed to identify all publications from the years 1985 to 2006 concerning MRI of the peripheral joints and PsA. Additional papers were retrieved by scanning the references to the Medline-listed articles. Articles written in English, French, German, and Italian were included. Results: Most papers studied the hand and wrist, and only few of them were concerned with the knee, foot, temporomandibular joint, and elbow. Patients with PsA showed often, but not always, a pattern of joint inflammation which extended beyond the capsule into the extraarticular tissue. Bone oedema and erosions were less frequent than in RA. In particular, bone oedema at the entheseal junction was seen, especially in the knee. The degree of synovitis, assessed by dynamic MRI, was similar in PsA and RA. Discussion: Data on MRI of the peripheral joints in PsA are scanty. Only few studies were specifically designed to evaluate the pattern of arthritis in PsA, with most information deriving from papers where different types of arthritis were considered together. An enthesis-related origin of PsA has been proposed in contrast to the primarily synovial inflammation of RA. This pathogenic interpretation is likely to be true, but does not explain all cases of PsA, and needs to be confirmed by further studies

Plasma Cell-Free DNA Integrity Assessed by Automated Electrophoresis Predicts the Achievement of Pathologic Complete Response to Neoadjuvant Chemotherapy in Patients with Breast Cancer

PURPOSE The study of plasma cell-free DNA integrity (cfDI) has shown potential for providing useful information in neoplastic patients. The aim of this study is to estimate the accuracy of an electrophoresis-based method for cfDI evaluation in the assessment of pathologic complete response (pCR) in patients with breast cancer (BC) undergoing neoadjuvant chemotherapy (NACT). PATIENTS AND METHODS Fifty-one patients with BC undergoing anthracycline-/taxane-based NACT were recruited. Plasma samples were collected from each patient at diagnosis (t0), after anthracycline administration (t1), and after NACT completion (t2). The concentration of differently sized cell-free DNA fragments was assessed by automated electrophoresis. cfDI, expressed as cfDI index, was calculated as the ratio of 321-1,000 bp sized fragment concentration to 150-220 bp sized fragment concentration assessed at t2. cfDI index was then used to build an exploratory classifier for BC response to NACT, directly comparing its sensitivity and specificity with magnetic resonance imaging (MRI), through bootstrapped logistic regression. RESULTS cfDI index was assessed on 38 plasma samples collected from as many patients at t2, maintaining a 30/70 ratio between pCR and non-pCR patients. cfDI index showed an area under the receiver operating characteristic curve in predicting the achievement of pCR of 81.6, with a cutoff above 2.71 showing sensitivity = 81.8 and specificity = 81.5. The combination of cfDI index and MRI showed, in case of concordance, an area under the receiver operating characteristic curve of 92.6 with a predictive value of complete response of 87.5 and a predictive value of absence of complete response of 94.7. CONCLUSION cfDI index measured after NACT completion shows great potential in the assessment of pCR in patients with BC. The evaluation of its use in combination with MRI is strongly warranted in prospective studies