New drugs and future developments in photodynamic therapy

New photosensitizing drugs are becoming available which should improve on some of the disadvantages of haematoporphyrin derivates for photodynamic therapy (PDT). The main features are shorter duration of systemic photosensitisation, activation by longer and more penetrating light and better tumour to normal tissue drug uptake ratios. These drugs together with better understanding of in vivo light dosimetry promise to improve both results and clinical acceptability for PDT in future studies.

Improved technique of 70% hepatectomy in dogs

An improved anatomical technique for extended hepatectomy in dogs is described as a model to study the process of liver regeneration. The crucial steps in the technique as well as the site of bile duct ligation and dissection of the left hepatic vein are described in detail. Using this method extended hepatectomy was done without any mortality or morbidity in more than 20 dogs.

Slow Crack Growth in Single-Crystal Silicon

Time-dependent crack growth has been measured on a precracked, single-crystal silicon cantilever beam 75 micrometers long that was excited at resonance. Growth of the precrack changes the resonant frequency of the beam, which is correlated to crack length. The measured steady-state crack growth rate was as slow as 2.9 x 10(-13) meter per second, although the apparatus can measure crack growth rates as low as 10(-15) meter per second. It is postulated that static fatigue of the native surface silica layer is the mechanism for crack growth. These experiments demonstrate the possibility of rate-dependent failure of silicon devices and the applicability of linear elastic fracture mechanics to small-scale micromechanical devices. The results indicate that slow crack growth must therefore be considered when evaluating the reliability of thin-film silicon structures.

Development of a sensitive peptidase assay: in search of cell associated proteases responsible for the cleavage of preproTGF alpha

A radiometric assay has been developed for the detection of proteolytic activity capable of releasing transforming growth factor alpha (TGF alpha) from its membrane bound precursor. The assay is dependent upon the separation by thin layer chromatography of hydrolytic products of a nonapeptide substrate containing a radioactive iodinated tyrosine residue as a reporting group N-terminal to an octapeptide which is cognate to the N-terminal cleavage sequence of TGF alpha. We describe the selectivity of the peptidase assay with commercially purified proteases and with cell-associated peptidases, its exquisite sensitivity, and its applicability to defining peptidase activity, which may be responsible for the processing of the membrane-bound prepro TGF alpha. The activity of two different elastases had different profiles which thus may be of use in characterizing them. The characteristics of the intact and extracted HeLa cell assay with respect to time, cell density, and peptidase concentration are defined, as are conditions needed to remove endogenous, confounding, proteolytic activity from the serum used to support cell culture. Intact HeLa cell cultures exhibit both exo- and endo-peptidase activity at approximately equal levels in both sparse and dense monolayer culture without relationship to cell density, and at a level equal to 1-2% of total cell activity of these enzyme classes.

Effects of cortisol on aspects of 3,5,3'-triiodo-L-thyronine metabolism in rainbow trout (Oncorhynchus mykiss)

Aspects of 3,5,3'-triiodo-L-thyronine (T3) metabolism were studied in fed rainbow trout (Oncorhynchus mykiss) held at 11.5-14 degrees and intraperitoneally implanted with hydrogenated corn oil (controls) or oil containing cortisol. Cortisol implants caused dose-related plasma cortisol elevations within the physiological range for 2-3 weeks, loss in body weight, and depression in plasma T3 and free T3 index with no consistent change in plasma thyroxine (T4) or free T4 index. Plasma T3 clearance rate and plasma T3 appearance rate were both increased by cortisol, with no change in hepatic microsomal T4 5'-monodeiodinase activity (Km or Vmax), but with a significant decrease in muscle T3 concentration. It is concluded that chronic physiologic cortisol treatment enhances plasma T3 clearance without change in hepatic T4 to T3 conversion, resulting in a decline in T3 concentration in both plasma and tissue (muscle) compartments.

Determination of 3,5,3'-triiodo-L-thyronine (T3) levels in tissues of rainbow trout (Salmo gairdneri) and the effect of low ambient pH and aluminum

Tissue T3 (3,5,3'-triiodo-L-thyronine) concentrations were measured in rainbow trout, Salmo gairdneri, after digestion by Pronase or collagenase and extraction with ethanolic ammonia (99:1, v/v) followed by 2N NH4OH and chloroform. Recoveries of [(125)I]T3 administered in vivo or in vitro were high and consistent and there was close parallelism between sample dilutions and the radioimmunoassay curve, but recoveries of unlabeled T3 administered in vitro were low and variable. Alternatively, trout were brought to isotopic equilibrium by [(125)I]T3 infusion for 96 h, the extracted [(125)I]T3 determined by gel filtration and the tissue T3 content calculated from the specific activity of plasma [(125)I]T3. By the latter method, tissue T3 concentrations were: intestine (4.2 ng/g), kidney (2.5), liver (2.8), stomach (1.5), heart (1.0), muscle (0.7), gill (0.6) and skin (0.3). Muscle (67% of body weight) comprised the largest tissue T3 pool (82% of all tissues examined). Seven days exposure of trout to water acidified with H2SO4 (pH 4.8) or acidified water containing aluminum (21.6 mM), decreased tissue T3 content generally and particularly in muscle (14% of controls). In conclusion, skeletal muscle is the largest T3 tissue pool and seems highly responsive to altered physiologic state.

The response of a rodent fibrosarcoma to superficial/interstitial photochemotherapy, chemotherapy or radiotherapy

Growth and dose-response curves were established for a subcutaneously implanted isogenic fibrosarcoma in BD9 rats after treatment with photochemotherapy (PCT), using Photofrin II or polyhaematoporphyrin with superficial or interstitial 630 nm light, cyclophosphamide or gamma-irradiation. Tumour response to PCT increased with dose up to 200 J.cm-2 for superficial light or 200 J for interstitial light but no further response occurred after higher light doses. The maximum response after interstitial treatment was significantly greater than after superficial treatment where only a small margin of normal tissue was treated. The incidence of necrosis in the overlying skin was significantly less after interstitial than superficial light suggesting a better therapeutic ratio after interstitial than superficial PCT. Tumour response increased with the diameter of the treatment field after superficial light supporting the possibility of a tumour bed effect associated with PCT. The largest tumour that could be effectively treated with a single optical fibre was 12 mm. The dose-response curves for interstitial PCT and cyclophosphamide were similar but ionizing irradiation produced increasing tumour response throughout the range of doses used (5 to 30 Gy) and the maximum response was greater after radiotherapy than after PCT or chemotherapy suggesting that in this tumour model interstitial PCT is as effective as cyclophosphamide but less effective than radiotherapy.

Effects of low ambient pH and aluminum on plasma kinetics of cortisol, T3, and T4 in rainbow trout (Oncorhynchus mykiss)

Plasma kinetics for cortisol, 3,5,3′-triiodo-L-thyronine (T3), and L-thyroxine (T4), and other blood parameters were examined in catheterized rainbow trout (Oncorhynchus mykiss) exposed for 7 days to a sublethal ambient pH of 4.7 (adjusted with H2SO4), an ambient pH of 4.7 plus Al (AlKSO4, 20 μmol/L), or an ambient pH of 7.7 (control). Sublethal pH alone increased the cortisol level and the plasma degradation rate but did not change the plasma clearance rate; it did not modify plasma T3 and T4 levels and their kinetics or hepatic microsomal 5′-monodeiodinase activity; it increased plasma glucose and decreased plasma Cl− and osmolality with no change in packed cell volume. Low pH in combination with Al increased the cortisol plasma level, plasma clearance rate and plasma degradation rate; it increased the T4 plasma degradation rate but decreased the T3 plasma clearance rate, T3 plasma appearance rate, and 5′-monodeiodinase activity by increasing Km and decreasing Vmax; it also increased plasma glucose and depressed plasma Cl− and osmolality but increased packed cell volume. We concluded that Al exacerbates the effects of low ambient pH to increase cortisol prodcntion and decrease T3 production. Depressed T3 production through 5′-monodeiodinase inhibition may contribute to the poor growth of Al-exposed fish.

Biosynthesis of phycobilins. Formation of the chromophore of phytochrome, phycocyanin and phycoerythrin

Phycobiliproteins play important roles in photomorphogenesis and photosynthesis. The light-absorbing chromophores of the phycobiliproteins are linear tetrapyrroles (bilins) very similar in structure to the mammalian bile pigments. 5-Aminolaevulinate (5-ALA) is the first committed intermediate in phycobilin synthesis. The biosynthesis of 5-ALA, destined for phycobilins, occurs via the five-carbon pathway, now well established for tetrapyrrole synthesis in plants and distinct from the mammalian pathway. The phycobilins are formed by reduction of biliverdin which results from the synthesis and degradation of haem. This haem is an essential intermediate in the biosynthesis of phycobilins. Phycocyanobilin, the blue-green pigment found in certain algae and cyanobacteria, is formed from biliverdin via phytochromobilin, the chromophore of phytochrome. This leads to the likelihood that phytochromobilin is formed as an end product, or intermediate, in the synthesis of all phycobilins.

Interaction of azole antifungal antibiotics with cytochrome P-450-dependent 14 alpha-sterol demethylase purified from Candida albicans

The interaction of azole antifungal antibiotics with purified Candida albicans cytochrome P-450-dependent 14 alpha-sterol demethylase (P-450DM) was measured spectrophotometrically and by inhibition of enzyme activity. Ketoconazole and ICI 153066 (a triazole derivative) formed low-spin complexes with the ferric cytochrome and induced type II difference spectra. These spectra are indicative of an interaction between the azole moiety and the sixth co-ordination position of P-450DM haem. Both azoles inhibited the binding of CO to the sodium dithionite-reduced ferrous cytochrome, and inhibited reconstituted P-450DM activity by binding to the cytochrome with a one-to-one stoichiometry. Similarly, total inhibition of enzyme activity occurred when equimolar amounts of clotrimazole, miconazole or fluconazole were added to reconstituted P-450DM. These results correlated with the inhibition of P-450DM in broken cell preparations, confirming that all five azoles are potent inhibitors of ergosterol biosynthesis in C. albicans.

Segmental liver transplantation from living donors. Report of the technique and preliminary results in dogs

A technique of orthotopic liver transplantation using a segmental graft from living donors was developed in the dog. Male mongrel dogs weighing 25-30 kg were used as donors and 10-15 kg as recipients. The donor operation consists of harvesting the left lobe of the liver (left medial and left lateral segments) with the left branches of the portal vein, hepatic artery and bile duct, and the left hepatic vein. The grafts are perfused in situ through the left protal branch to prevent warm ischemia. The recipient operation consists of two phases: total hepatectomy with preservation of the inferior vena cava using total vascular exclusion of the liver and veno-venous bypass, implantation of the graft in the orthotopic position with anastomosis of the left hepatic vein to the inferior vena cava and portal, arterial and biliary reconstruction. Preliminary experiments consisted of four autologous left lobe transplants and nine non survival allogenic left lobe transplants. Ten survival experiments were conducted. There were no intraoperative deaths in the donors and none required transfusions. One donor died of sepsis, but all the other donor dogs survived without complication. Among the 10 grafts harvested, one was not used because of insufficient bile duct and artery. Two recipients died intraoperatively of air embolus and cardiac arrest at the time of reperfusion. Three dogs survived, two for 24 hours and one for 48 hours. They were awake and alert a few hours after surgery, but eventually died of pulmonary edema in 2 cases and of an unknown reason in the other. Four dogs died 2-12 hours postoperatively as a result of hemorrhage for the graft's transected surface. An outflow block after reperfusion was deemed to be the cause of hemorrhage in these cases. On histologic examination of the grafts, there were no signs of ischemic necrosis or preservation damage. This study demonstrates the technical feasibility of living hepatic allograft donation. It shows that it is possible, in the dog, to safely harvest non ischemic segmental grafts with adequate pedicles without altering the vascularization and the biliary drainage of the remaining liver. We propose that this technique is applicable to human anatomy.

Purification and properties of cytochrome P-450-dependent 14 alpha-sterol demethylase from Candida albicans

The purification of cytochrome P-450-dependent 14 alpha-sterol demethylase (P-450DM) from the important opportunistic fungal pathogen, Candida albicans, is described. Optimal purification (875-fold) was achieved by extracting the cytochrome from microsomes with sodium cholate followed by hydroxyapatite, octyl-Sepharose and CM-Sepharose chromatographies, giving a cytochrome preparation of 17.5 nmol/mg of protein. By the use of SDS/polyacrylamide-gel electrophoresis the cytochrome was judged to be highly purified on the basis of Coomassie Brilliant Blue staining of protein. The Mr of P-450DM was estimated to be 51,000. The absorption spectrum of oxidized P-450DM was characteristic of a low-spin cytochrome, and its reduced CO complex had a Soret absorption peak at 447 nm. When reconstituted in a model membrane system of dilauroylphosphatidylcholine with NADPH and O2, P-450DM catalysed the complete 14 alpha-demethylation of lanosterol, which was inhibited by CO. The cytochrome appeared to have a high degree of substrate specificity; it was unable to oxidize a number of xenobiotic compounds in the reconstituted assay.

Percutaneous transluminal aortic angioplasty: techniques and results

Percutaneous transluminal angioplasty of the infrarenal abdominal aorta has been reported by a few authors. In the present series, aortic stenoses in 32 patients were treated with various percutaneous angioplasty techniques. Isolated aortic stenoses and primary aortic stenoses extending into the iliac arteries were successfully dilated. The initial success rate was 100%, without evidence of rupture, thrombosis, dissection, or distal embolization. In only three of the 28 patients who returned for follow-up did symptoms recur or noninvasive vascular laboratory indexes deteriorate (mean follow-up, 25 months). Percutaneous transluminal aortic angioplasty has proved safe and efficacious in the treatment of atherosclerotic aortic stenoses.

The biosynthesis of the chromophore of phycocyanin. Pathway of reduction of biliverdin to phycocyanobilin

The later stages in the pathway of biosynthesis of phycocyanobilin, the chromophore of phycocyanin, were studied by using radiolabelled intermediates. Three possible pathways from biliverdin IX-alpha to phycocyanobilin were considered. 14C-labelled samples of key intermediates in two of the pathways, 3-vinyl-18-ethyl biliverdin IX-alpha and 3-ethyl-18-vinyl biliverdin IX-alpha, were synthesized chemically and were administered to cultures of Cyanidium caldarium that were actively synthesizing photosynthetic pigments in the light. Neither of these two compounds was apparently incorporated into the phycobiliprotein chromophore, suggesting that two of the three pathways were not operative. By elimination, the results imply that the third possible pathway, which involves phytochromobilin, the chromophore of phytochrome, represents the route for biosynthesis of phycocyanobilin. Unfortunately, since 14C-labelled phytochromobilin is not available, no direct proof of this pathway could be obtained. However, if correct, the present interpretation represents a unified pathway for biosynthesis of all plant bilins, via the intermediacy of phytochromobilin.

Cytochrome P-450-dependent 14 alpha-demethylation of lanosterol in Candida albicans

A novel assay for cytochrome P-450-dependent 14 alpha-sterol demethylase of the important opportunistic fungal pathogen, Candida albicans, is described. The enzyme was assayed in microsomal preparations (microsomes) by measuring the incorporation of [14C]lanosterol into (4,14)-desmethylated sterols. The efficacy of different cell-breakage methods was compared; desmethylated-sterol biosynthesis was maximal when cells were broken with a Braun disintegrator. The solubilization of [14C]lanosterol with detergent in the assay system was essential for enzyme activity, which was enhanced considerably when microsomes were gassed with O2. Under these conditions, there was a reciprocal relationship between the amount of radioactivity incorporated into desmethylated sterols and that lost from lanosterol. The major radiolabelled desmethylated sterol was ergosterol. The enzyme had an apparent Km of 52.73 +/- 2.80 microM and an apparent Vmax of 0.84 +/- 0.14 nmol/min per mg of protein (n = 3). Enzyme activity was decreased greatly when microsomes were treated with CO or the triazole antifungal ICI 153066.

Lymphoceles: percutaneous treatment with povidone-iodine sclerosis

Although percutaneous procedures have gained a degree of acceptance for treatment of lymphoceles, success rates for aspiration and drainage have been less than optimal. The authors investigated transcatheter sclerosis of pelvic lymphoceles with povidone-iodine as a method to increase the success rate of percutaneous management. Eight patients with a total of nine pelvic lymphoceles were treated with this method. Eight of the nine lymphoceles (89%) resolved without complications. Four patients had undergone lymphadenectomy and four, renal transplantation. The duration of catheter drainage ranged from 15 to 37 days. Four of the lymphoceles were found to be infected at initial drainage, but this did not alter the amount of time the catheter was left in place. One lymphocele failed to heal with sclerotherapy and required internal drainage. The early results with transcatheter povidone-iodine sclerosis of postoperative lymphoceles are encouraging and warrant further evaluation.

Mouse skin photosensitivity with dihaematoporphyrin ether (DHE) and aluminium sulphonated phthalocyanine (AlSPc): a comparative study

Skin photosensitivity of sun exposed sites is the major side effect of dihaematoporphyrin ether (DHE) photodynamic therapy (PDT). Reports of severe oedema and erythema have generally been anecdotal. We have studied aluminium sulphonated phthalocyanine (AlSPc) as a potential photosensitiser for PDT. In this paper we report our work comparing the skin photosensitivity reactions of DHE and AlSPc. We have studied: (i) the time course of the skin reactions, (ii) the effect of increasing time from administration of photosensitiser to irradiation, (iii) drug-skin reaction dose response. Groups of Skh I female hairless albino mice were given an intravenous bolus dose of either 0.9% saline solution, AlSPc or DHE (Photofrin II). Drug doses ranged from 0.5 to 50 mg/kg. At times ranging from 1 h to 1 month animals were irradiated with a range of doses of solar simulated radiation (SSR). The skin reaction was observed over a 2 week period. DHE reactions were always more severe than those with AlSPc. Peak skin reaction was seen at 3 h for DHE and 6 h for AlSPc. DHE reactions were still visible 2 weeks after irradiation whereas the AlSPc reaction disappeared by 48 h. Irradiation evoked a reaction up to 2 months after administration of DHE but only up to 2 weeks with AlSPc. The mean SSR dose at which a skin reaction was seen decreased with increasing dose of both agents. The rate of decrease was slower with AlSPc than DHE. This study suggests that in PDT, AlSPc will cause much less skin photosensitivity than DHE.

The distribution of porphyrins with different tumour localising ability among human plasma proteins

The distribution among the main fractions of human plasma lipoproteins of a number of porphyrins with different tumour localising ability has been determined by means of ultracentrifugation. A main trend is that the fraction of the dyes that are bound to low density lipoprotein (LDL) increases, and the fraction bound to HSA decreases with decreasing polarity of the dyes. An asymmetric charge distribution, such as in TPPS2a, favours LDL-binding more than expected on the basis of lipophilicity. No correlation between the known tumour localising ability of the drugs tested in the present work and their relative affinity for LDL was found. One of the best tumour localisers reported in the literature, TPPS4, hardly binds to LDL, while Hp and Pp, which are commonly considered inefficient tumour localisers, do have a significant affinity for LDL. On the other hand, the LDL binding capacity for a drug is suggested to be a good index for cellular uptake. Such an index does not necessarily imply that the actual uptake occurs by the LDL pathway.

Conformational analysis of thioredoxin using organoarsenical reagents as probes. A time-resolved fluorescence anisotropy and size exclusion chromatography study

Reduced thioredoxin was subjected to chemical modification studies employing organoarsenical reagents specific for "spatially close" thiols. Modification was monitored by the loss in the free thiol content, by the percent incorporation of radiolabelled organoarsenical reagents, and by observing the changes in the amounts of the various thioredoxins by size exclusion chromatography. The rate of modification depends upon the polarity, rigidity, and size of the reagents. Small nonpolar organoarsenical reagents readily modified reduced thioredoxin, whereas polar and large reagents do not. Modifications resulted in the formation of stable 15-membered cyclodithioarsenite ring structures with no apparent changes in the secondary structure of the protein. Modification was reversed by the extrusion of the arsenical moiety by addition of 2,3-dimercaptopropanol. We have further characterized the oxidized, reduced, and modified thioredoxins by size exclusion chromatography and fluorescence anisotropy decay measurements. Both techniques show an increase in the hydrated volume of the protein upon reduction. Upon modification, the hydrodynamic volume of the protein further swells. Fluorescence anisotropy decay reveals that with modification there is loosening of the protein so that a "domain" containing the fluorophores can relax independently of the whole protein structure.

The effect of gabaculine on tetrapyrrole biosynthesis and heterotrophic growth in Cyanidium caldarium

Pigment synthesis in four strains of the unicellular red alga Cyanidium caldarium with different pigment-synthesizing patterns was inhibited in the presence of gabaculine (3-amino-2,3-dihydrobenzoic acid). Parallel inhibition of light-induced chlorophyll and phycocyanin synthesis was observed in strain III-D-2, which only synthesizes pigments in the light. Similar parallel inhibition was observed in the dark in mutant CPD, which is able to synthesize chlorophyll and phycocyanin in the absence of light. Inhibition of pigment synthesis in all strains was overcome by addition of 5-aminolaevulinic acid. Inhibition of phycocyanin synthesis in mutant GGB (unable to synthesize chlorophyll) and inhibition of chlorophyll synthesis in mutant III-C (unable to synthesize phycocyanin) were also observed. Gabaculine also inhibited the heterotrophic growth of C. caldarium in the dark. However, inhibition was overcome after an extended lag period, following which cell growth proceeded at a similar rate to that of control cells not exposed to gabaculine. Heterotrophic growth in cells pre-exposed to gabaculine was not inhibited by subsequent exposure. Possible mechanisms for this adaptation are discussed.

Structural comparison between oxidized and reduced Escherichia coli thioredoxin. Proton NMR and CD studies

Escherichia coli thioredoxin (Mr 11,700) usually functions as a hydrogen carrier protein that undergoes reversible oxidation/reduction reactions of its active-site disulfide linkage. By use of a number of assigned and identified resonances in one- and two-dimensional 1H NMR spectra, the two forms of the protein have been compared. Only groups that are relatively close to the active-site Cys-32, Cys-35 linkage such as Trp-28, Trp-31, Phe-27, Ala-29, and Val-25 undergo substantial changes in their 1H NMR chemical shift upon reduction. Various residues that are further removed from the active site, like Tyr-49, Tyr-70, His-6, Phe-12, Phe-81, and Phe-102, appear to be little affected (less than 0.02 ppm) by the reduction, suggesting that the rest of the protein structure is not much affected. Thus, the structural changes that occur upon reduction appear to be localized to the disulfide-containing turn and the central strand of the twisted beta-sheet that directly leads to this turn. Notwithstanding the apparent similarity in the secondary and tertiary structures of the oxidized and reduced forms of the protein, the thermal stability of the protein decreases by 10 degrees C upon the reduction of the single disulfide. This was found by both 1H NMR and near- and far-ultraviolet circular dichroism studies. Oxidized thioredoxin was also more resistant to alkaline denaturation. Furthermore, the exchange rate of the relatively stable slow-exchanging backbone amide protons that are part of the core of the twisted five-stranded beta-sheet of thioredoxin increases substantially after reduction.(ABSTRACT TRUNCATED AT 250 WORDS)