Probing the kinetics of photosystem I and photosystem II fluorescence in pea chloroplasts on a picosecond pulse fluorometer.

Picosecond fluorescence kinetics of pea chloroplasts have been investigated at room temperature using a pulse fluorometer with a resolution time of 10-11 s. Fluorescence has been excited by both a ruby and neodymium-glass mode-locked laser and has been reocrded within the 650 to 800 nm spectral region. We have found three-component kinetics of fluorescence from pea chloroplasts with lifetimes of 80, 300 and 4500 ps, respectively. The observed time dependency of the fluorescence of different components on the functional state of the photosynthetic mechanism as well as their spectra enabled us to conclude that Photosystem I fluoresces with a lifetime of 80 ps (tauI) and Photosystem II fluoresces with a lifetime of 300 ps (tauII). Fluorescence with a lifetime of 4500 ps (tauIII) may be interpreted as originating from chlorophill monomeric forms which are not involved in photosynthesis. It was determined that the rise time of Photosystem I and Photosystem II fluorescence after 530 nm photoexcitation is 200 ps, which corrsponds to the time of energy migration to them from carotenoids.

Footprinting of DNA secondary structure by high-intensity (laser) ultraviolet irradiation.

The action of high-intensity ultraviolet pulse laser radiation on a 161 bp fragment of pBR 322 DNA (EcoRI-MspI fragment) was studied. At doses up to 5 X 10(18) photons/cm2 the N-glycosidic bond splitting is negligible. The action of hot piperidine on irradiated DNA leads to chain splitting at the residues, modified via biphotonic processes. The modification and, hence, splitting efficiencies depend on the type of base (G greater than T greater than A greater than C) and on its position in the sequence. Preferentially modified bases in the opposite strands of double-stranded DNA belong, mainly, to the same or adjacent base pairs. Residues in the Pribnow box are modified considerably less, than in the sequences, immediately upstream and downstream. This approach seems to be useful in footprinting of DNA secondary structure peculiarities and alterations, conjugated with the functional role and state of the respective fragment.

Fluorescent diagnostics of human gastric cancer and sodium fluorescein accumulation in experimental gastric cancer in rats.

Patients (459) with chronic gastritis, ulcers, polyposis and different types of gastric cancers were examined by endoscopic fluorescent technique using a special drug based on the sodium salt of fluorescein (F1). Eighty-five percent of gastric cancers showed positive fluorescence. The F1 distribution in the stomach of the rat with induced gastric cancer was examined. In all cases the level of F1 fluorescence in the tumor was higher than in the adjacent normal tissues of the stomach. Thus, all the obtained results confirm the selective accumulation of F1 in tumors of the stomach.

Thyroid function before and after four-week light treatment in winter depressives and controls.

Thyroid function in patients in a current major depressive episode during the course of recurrent major mood disorder with seasonal pattern according to DSM-IIIR was compared to that of controls before and after 4 weeks' light treatment, and to that of controls at baseline and after 4 weeks' of arising early without exposure to bright light. No consistent abnormalities in thyroxine, free thyroxine index, triiodothyronine, reverse triiodothyronine, thyrotropin, thyrotropin response to TRH infusion, or thyroid autoantibodies were seen in depressives at baseline. No differences in these parameters were seen at baseline between depressives and controls. No intergroup differences were seen with treatment, although reverse T3 decreased significantly during the protocol in all groups. These data do not support the hypothesis that the thyroid axis plays a role in the pathogenesis of winter depressive symptoms or their response to light treatment.

Mood and behavioral effects of four-week light treatment in winter depressives and controls.

This study investigated (1) the time-course and durability of antidepressant effects of bright light in winter depressives, and (2) the effects of bright light on mood and behavior in normal controls in a 4-week open treatment paradigm. Twelve subjects in a major depressive episode during recurrent major depressive or bipolar disorder with seasonal pattern and 12 control subjects received 2,500 lux light between 0600 and 0800 hours, while 12 controls arose at 0600 hours for quiet activities without exposure to bright light. In depressives, maximal decrements in depression ratings were not reached until the fourth week of treatment. Four depressives experienced clinically significant hypomanic symptoms. Controls treated with light demonstrated significantly higher clinician ratings of hypomanic symptoms than no-light controls. When depressives and controls were combined, seasonality, but not diagnosis, predicted the emergence of manic-like symptoms. Implications for bright light treatment in the clinical setting are discussed.

Sodium fluorescein accumulation in cultured cells.

The mechanism of intracellular fluorescein accumulation was investigated by studying fluorescein accumulation kinetics in individual cells in culture. The experiments were done with K562 human erythroleukemia cell culture and a primary culture of human embryonic skin fibroblasts. Various experimental conditions were used by varying pH and ion composition of the external media, and/or temperature. All the experimental results obtained are in support of the proposed theoretical model describing fluorescein accumulation in cells along the pH gradient. In addition, we could show that fluorescein molecules are bound to some intracellular macromolecules. Fluorescein accumulation in the cells studied does not depend on their malignant nature. It is therefore reasonable to conclude that fluorescein accumulation observed in clinical investigations of human gastric cancer is governed by the ph gradient between the cells and the extracellular fluid; this gradient is much greater in the tumor than in normal tissues.

[Dynamics of electronic excitation in the photosynthetic pigment apparatus]. / Dinamika elektronnogo vozbyzhdeniia v pigmentnom apparate totosinteza.

The fluorescence lifetime and quantum yield as a function of single picosecond laser pulse intensity were experimentally studied in chloroplasts and subchloroplast particles. The intensity of laser pulse were changed from 3 x 10(12) to 10(17) photon/cm2. To explain experimental results it was considered that energy transport in the light harvesting antenna occurs by localised excitons. Parameters governing dynamic of electronic excitation within light harvesting antenna were determined. The diffusion coefficient was found to be 2 x 10(-2) cm2sec-1; diffusion length L greater than or equal to 900 A, energy transfer probability W approximately 10(12)sec-1. The rate of constant of energy transfer from light harvesting antenna to PS1 and PS2 reaction centers and effectiveness of the exciton capture by the PS2 reaction center were estimated.

[Spectrophotometric study of the initial stage of lymphocyte transformation]. / Spektrofotometricheskoe issledovanie nachal'noi stadii aktivatsii limfotsitov.

Results are presented of temporal variations of light current which passed through mouse lymphocyte suspension at introduction of phytohemagglutinin mitogen or concentrated cell suspension on liquid surface. Based on comparing the calculated time of phytohemagglutinin molecules diffusion, velocity of lymphocyte precipitation and recorded time of the system response a hypothesis is advanced concerning the existence of an ordered structure formed by cells in suspension, and a relay--race transmission of surface disturbance deep into the volume.

[Morphologic evaluation of the potential of fluorescent analysis in the diagnosis of gastric diseases]. / Morfologicheskaia otsenka vozmozhnostei fliuorestsentnogo analiza v diagnostike zabolevanii zheludka.

A method based on the secondary luminescence of malignant tumours facilitates a more precise taking of biopsies in ulcers and polyps undergoing malignant transformation in carcinoma developing against gastritis background as well as during emergency intraoperative diagnosis. 478 gastroscopies were performed in order to clarify the correlation between fluorescence and the presence of carcinoma in the luminescent biopsies. Biopsies were obtained from both fluorescent and non-fluorescent areas. Besides that, fluorescent study of operative edges of 117 stomachs removed because of carcinoma was carried out. It is proved that the use of fluorescent method increases the value of biopsies.