THE THEORY OF PHOTODYNAMIC THERAPY DOSIMETRY: CONSEQUENCES OF PHOTO-DESTRUCTION OF SENSITIZER

Photodynamic dose is defined as the area under the curve of sensitizer level plotted as a function of light dose. This is a photochemical definition of dose. We will show that this definition is useful in predicting photobiological response. The photodestruction of sensitizer during photodynamic therapy is shown to result in an upper limit on the photodynamic dose which can be delivered by an unlimited light dose. This limit results in the opportunity to make total photodynamic dose uniform to considerable depths (one to two centimeters). The existence of thresholds for permanent tissue damage allows protection of normal tissue from the large light doses required to achieve this limiting dose deep in the tissue. Higher sensitizer levels in the tumor permit tumor destruction while the normal tissues are protected. A clinical trial to determine the proper level of injected dose necessary for these results is required. This theory of photodynamic therapy (PDT) dosimetry is tested in the DBA-SMT experimental mouse tumor system. Combinations of drug and light which are not reciprocal but are nearly equal by this theory are shown to give equivalent tumor control at seven days post treatment. Reciprocal combinations of drug and light fail to give equivalent results when they ae selected using the theory to choose a combination where reciprocity should fail.     

SEASONAL PHOTOSENSITIVITY OF BLEPHARISMA: THE ROLE OF TEMPERATURE

Red blepharismas (B. japonicum) in Pyrex test tubes exposed near noon to clear summer daylight are killed. If similarly exposed at dawn, they turn blue as the red pigment blepharismin is oxidized to oxyblepharismin. and they resist further exposure to daylight. Red blepharismas similarly exposed to sunlight at dawn in winter are killed. The experiments reported seek the reasons for the seasonal difference in photosensitivity and the way in which blepherismas survive winter. Red blepharismas (B. japonicum) exposed to visible and near ultraviolet (UV) radiation from two 4W coolwhite fluorescent lamps (5 Wm^-2; 2151ux) resist an 8h exposure between 15° and 34°C. turning blue. Blue and colorless blepharismas also resist 8h exposures to the light at 15° and 34°C. At 8°C both red and blue populations are killed, death appearing to result from deranged water regulation; colorless ones are not affected. Red blepharismas are killed by fluorescent light at 8° C even when the near-UV radiation is largely excluded by a Corning glass filter; blue and colorless ones are not. The reds are also killed at all temperatures by sunlight filtered through Pyrex glass if exposed near noon on a sunny day. At temperatures above 8° C they are not killed by direct sunlight passed through glass if exposed at dawn, but they turn blue. Blepharismas in fluorescent light divide at the same rate as controls in the dark, but they get smaller. When exposed to sunlight at dawn, at temperatures above 8°C. blepharismas in Pyrex test tubes containing stones or fruiting spikes of grass, hid in the shade of these objects, apparently by random movements. If exposed under similar conditions near noontime, the majority failed to find cover and were killed. Blepharismas survive in summer by avoiding sunlight, in winter by encystment. Colorless protozoans Paraineciurn multimicronucleatum, Colpidium colpoda and Spirostomum teres resisted killing in summer sunlight and with fluorescent light at all temperatures tested.     

CROSS-FLOW MICROFILTRATION OF BKNTOMTE-IN-WATER DISPERSIONS: EFFECTS OF SUSPENSIONRHEOLOGY

Cross-How filtration of bentonite-in-water suspensions is studied experimentally in a small laboratory device. The Theological behaviour and the filtration resistance in batch filtration are independently established. Both transient and steady-state data indicate channel constriction by a dense cake layer. Quantitative estimates based on measured parameters show that steady-state conditions can be ensured by tangential flow of the dense pseudoplastic bentonite cake. Steady-state is possible when the shear stress at the moving boundary feed suspension/dense cake exceeds appr.l Pa (at lower values of the shear stress the cross-flow microfiltration channel gets plugged). The material characteristics of the dense cake, which determine cross-flow filtration behaviour, are the viscosity and the specific filtration resistance. Indirect estimates of these quantities from measured cross-flow filtration parameters are consistent with results from direct measurements. The data support the convective model of cross-flow microfiltration.     

PHOTOBLEACHING OF MEROCYANINE 540: INVOLVEMENT OF SINGLET MOLECULAR OXYGEN

The purpose of this study was to assess the mechanism of merocyanine 540 (MC540) photobleaching in a liposomal system. Broad based visible irradiation of MC540 in unilamellar dilauroylphosphatidylcholine (DLPC) vesicles resulted in dye bleaching that was strictly O2 dependent. The rate of self-sensitized photobleaching was enhanced in D2O and inhibited by both azide and histidine, consistent with 1O2 intermediacy (Type II chemistry). Supportive evidence for this mechanism was obtained by using a Type II sensitizer, aluminum phthalocyanine tetrasulfonate (AlPcS lambda max = 678 nm). Irradiation of AlPcS and MC540 in DLPC with lambda greater than 630 nm (absorbed only by AlPcS) light resulted in rapid bleaching of MC540, which was stimulated by D2O and inhibited by azide. A rate constant of 10(7) M-1 s-1 was determined for the chemical quenching of 1O2 by MC540. The rate constant for physical quenching of 1O2 by MC540 was estimated to be ca 10(9) M-1 s-1.     

ULTRAVIOLET INACTIVATION OF THE MIDI VARIANT OF QP RNA: CHARACTERIZATION OF TEMPLATE ACTIVITY

Abstract— MDV-1 RNA is a 218 nucleotide variant of bacteriophage Qβ RNA. Qβ replicase catalyzes the formation of a strand complementary to a single-stranded (SS) MDV-I template. Upon phenol extraction, the template and complementary strands become double-stranded (DS). Polyacrylamide gel electrophoresis of the products of this reaction revealed SS RNA, DS RNA, and discrete intermediate bands. UV irradiation of the template caused a decrease in DS RNA production which followed single-hit kinetics with a quantum yield of 1.6 × 10^--³. Concomitant with this diminished DS RNA production were increases in SS RNA and intermediate sized RNA. The latter was shown to consist of a full sized SS template annealed to a partially completed nascent strand. Upon electrophoresis, these partially completed duplexes migrated in the same positions as those found in the analysis of unirradiated template, suggesting that this RNA contains replication obstruction areas in which UV lesions cause an increase in replication inhibition.     

PHOTO ACTIVATION OF ISOFLAVONOID PHYTOALEXINS: INVOLVEMENT OF FREE RADICALS

Abstract— Upon irradiation with ultraviolet light the isoflavonoid phytoalexins phaseollin, 3,6a, 9-trihydroxypterocarpan, glyceollin, tuberosin and pisatin, but not medicarpin, brought about inactivation ofglucose–6-phosphate dehydrogenase in an in vitro assay system. Photoinactivation of the enzyme by photoactivated pisatin in air-saturated solutions was hardly affected by singlet oxygen quenchers such as NaN₃, bovine serum albumin, histidine or methionine. Neither addition of the hydroxyl radical scavengers mannitol, Na-benzoate and ethanol nor the presence of catalase or supcroxide dismutase protected the enzyme against photoinactivation, suggesting that OH, H₂O₂ and O₂ are not the reactive oxygen species involved. However, the free radical scavenger S-(2-amino-ethyl)isothiouronium bromide hydrobromide (AET) protected the enzyme against inactivation by photoactivated pisatin. Direct evidence for the generation of free radicals was obtained by ESR measurements of solutions of phaseollin, pisatin and medicarpin in hexane irradiated with ultraviolet light in the presence or absence of O₂. Phaseollin produced the most stable free radicals, whereas medicarpin hardly gave rise to free radical formation; pisatin took a somewhat intermediate position by producing a strong ESR signal which, however, decayed rather quickly. Photodegradation of all phytoalexins, except for medicarpin, was accompanied with loss of fungitoxicity, as shown in thin-layer chromatographic bioassays, and formation of new products.
These results indicate free radical formation as the causative process for photoinactivation of enzymes by photoactivated isoflavonoid phytoalexins.     

ELECTROCHEMISTRY OF EXCITED MOLECULES: PHOTO-ELECTROCHEMICAL REACTIONS OF CHLOROPHYLLS*

Abstract— Semiconductors with a sufficiently large energy gap, in contact with an electrolyte, can be used as electrodes for the study of electrochemical reactions of excited molecules. The behavior of excited chlorophyll molecules at single crystal ZnO-electrodes has been investigated. These molecules inject electrons from excited levels into the conduction band of the electrode, thus giving rise to an anodic photocurrent. The influence of various agents on this electron transfer has been studied. In the presence of suitable electron donors (e.g., hydroquinone, phenylhydrazine) in the electrolyte chlorophyll molecules, absorbing quanta, mediate the pumping of electrons from levels of the reducing agents into the conduction band of the semiconductor-electron acceptor. The electron capture by the semiconductor electrode is irreversible, when an adequate electrochemical gradient is provided in the electrode surface. Some properties of excited chlorophyll at semiconductor electrodes (unidirectional electron transfer, highly efficient charge separation, chlorophyll as electron pump and able to convert electronic excitation into electric energy) show similarity to the behavior of chlorophyll in photosynthetic reaction centers.     

THEORETICAL INVESTIGATION OF EXCIMER AND EXCIPLEX STATES OF URACIL AND HALOGEN DERIVATIVES: EFFECT OF NONPARALLELISM OF BASES

Theoretical modeling of initial steps of the photodimerization mechanism of uracil, 5-methyl-and 5-halogen derivatives was performed. The interaction energy of bases in stacked dimers in the ground and lowest excited states was calculated as a function of the distance between the base planes and of the rotation angles within the perturbation theory for the extended Hückel treatment. The existence of excimer and exciplex region on the potential surface of the excited state was revealed. The excimer (exciplex) geometry has the planes nonparallel with more close contact of the C5-C6 bonds as compared to the ground state of dimers. The results provide new information useful for understanding the photodimerization mechanism of bases and testifies that the singlet excimer state can be a precursor of the photodimerization reaction.     

PICOSECOND FLUORESCENCE STUDY OF PHOTOSYNTHETIC MUTANTS OF Chlamydomonas reinhardii: ORIGIN OF THE FLUORESCENCE DECAY KINETICS OF CHLOROPLASTS

Abstract— The fluorescence decay kinetics of photosynthetic mutants of Chlamydomonas reinhardii which lack photosystem II (PS II), photosystem I (PS I), and both PS II and PS I have been measured. The PS II mutant strain8–36C exhibits fluorescence decay lifetime components of 53, 424 and 2197 ps. The fluorescence decay of a PS I mutant strain12–7 contains two major fluorescence decay components with lifetimes of 152 and 424 ps. The fluorescence decay of mutant strain C2, which lacks both PS II and PS I, is nearly single exponential with a lifetime of 2561 ± 222 ps. In simulations in which it is assumed that wild-type decays are a simple sum of the major decay components of the isolated parts of the photosynthetic unit as measured in the mutants, curves are obtained that fit the wild-type C. reinhardii fluorescence decay data when the absorption cross-sections of PS II and PS I are weighted approximately equally. The 89 ps lifetime component in the wild-type is an average of 53 and 152 ps components arising from excitation transfer to and trapping in PS I and PS II. The single step transfer time in PS I is estimated to be between 100 and 700 fs depending on assumptions about array size. We find that between two and four visits to the PS I reaction center are required before final trapping.     

EMULSIFICATION OF NONMINERAL OILS: EFFECT OF TYPE AND SOURCE

A uniform battery of tests were run on nine natural oils, using three different surfactants. Differences in composition and performance are tabulated and analyzed using the technique of glyphs.     

PHOTOTRANSFORMATIONS OF PHYTOCHROME: THE CHARACTERIZATION OF LUMI-F AND META-Fa

Abstract— …Phototransformations of the red/far red reversible plant pigment phytochrome involve several intermediates. At 77K, lumi-F , the initial product of phototransformation of the far red absorbing form P _fr and some of its relaxation products are shown to undergo further phototransformations. Lumi-F has an absorption maximum in the region 690–730nm. The product, giving rise to a maximum in the difference spectra at 650nm, formerly thought to be lumi-F , is now believed to represent one of its relaxation products. The nature of the reactions connecting these various intermediates are discussed.     

SYNTHESIS OF GLYCOSYLAMINES: IDENTIFICATION AND QUANTIFICATION OF SIDE PRODUCTS

The synthesis of some glycosylamines (1-amino-1-deoxy D-glucose, 1-amino-1-deoxy-D-galactose and 1-amino-1-deoxylactose) was carried out by treatment of the corresponding reducing sugars with ammonium hydrogencarbonate in concentrated ammonia. The reaction mixture was first analyzed by capillary electrophoresis with indirect absorbance detection and high performance anion-exchange chromatography with pulsed amperometric detection. Beside glycosylcarbamate, a known reaction by-product, fructose and lactulose were detected during the synthesis of 1-amino-1-deoxyglucose and 1-amino-1-deoxylactose, respectively. Quantification of glycosylamines was carried out by micellar electrokinetic chromatography with UV detection of their 9-fluorenylmethyloxycarbonyl (Fmoc) derivatives; lactulosylamine was thus detected in the synthesis mixture of 1-amino-1-deoxylactose. The Fmocglycosylamines were easily purified from the other components of the crude synthesis mixtures.     

INVESTIGATION OF THE KINETICS OF DISPERSION POLYMERIZATION BY MEANS OF A DILATOMETER OF NEW DESIGN: ROTARY DILATOMETER

An instrument for the measurement of the kinetics of dispersion polymerisation reactions has been developed. The main part of the instrument consists of a glass dilatometer of a new design which rotates along the vertical axis. The direction of rotation changes in short intervals. Stirring inside the dilatometer occurs through the action of baffles and the inertia forces of the rotating liquid. The said dilatometer excels in simplicity, correct function, easy cleaning and perfect reaction heat transfer. It was tested out by performing measurements of the kinetics of acrylamide polymerisation in inverse emulsion.     

ON THE ACCURACY OF DIFFERENTIAL MEASUREMENTS OF THE MINIMAL ERYTHEMA DOSE: INFLUENCE OF THE DISCRETENESS OF THE SCALE

The minimal erythema dose (MED) is often used as a quantity by which the influence of certain treatments of the skin can be measured. Differential measurements are performed by assessing the difference of the MED on the skin treated in some way and the untreated skin.
As the MED-measuring scale is discrete, the question is sometimes raised whether it is possible to measure differences smaller than one scale unit. In the present paper it is shown that this is indeed possible; in principle the discreteness of the scale does not impose any restriction on the smallest value of the difference that can be measured. The discreteness of the scale introduces an extra random variation into the measurement. This variation is estimated theoretically. It is automatically included in the usual error analysis.
The discreteness variance is small when compared to other variance components, which are computed from an analysis of variance of actual experiments. Reducing the discreteness variance, by reducing the dose decrement of the MED-measuring scale, therefore, does not enhance the overall accuracy considerably. Finally, it is found that the assessments of the MED by the various observers do not differ significantly from each other, and that multiple assessments do increase the accuracy, especially for small effects.     

火焰原子吸收法测定ZnS：Mn交流电致发光薄膜屏中锰

利用火焰原子吸收光度法，分别测定了ＺｎＳ：Ｍｎ交流电致发光薄膜屏中锰和锌的含量，当样品符合硫化锌的化学量时，可由锌的含量计算出硫化锌的质量和锰在硫化锌薄膜中的浓度。与处理样品的称样量相比较，方法相比误差小于２％，回收率和相对标准偏差分别为１００％－１０２％和０．７％。样品自理容易分析简易，快速。     

AUGMENTATION OF ULTRAVIOLET ERYTHEMA BY INDOMETHACIN IN ACTINIC PRURIGO: EVIDENCE OF MECHANISM OF PHOTOSENSITIVITY

Abstract— The effect of topical indomethacin on the intensity of erythema induced by ultraviolet radiation was measured by reflectance spectrophotometry in six patients with actinic prurigo. The intensity of UV-C erythema was decreased by indomethacin in five patients. The intensity of UV-B erythema was increased by indomethacin in five patients, and UV-A erythema was increased by indomethacin in all patients. The increased inflammatory response induced by UV-B and UV-A with indomethacin application was related to erythemal sensitivity at these wavelengths. Topical indomethacin caused no change in the intensity of UV-A erythema in a group of non-photosensitive subjects.
That inhibition of cyclo-oxygenase augments the inflammatory response to ultraviolet radiation suggests that lipoxygenase metabolites of arachidonic acid may be involved in the mechanism of photosensitivity in actinic prurigo.