Further studies on the regulation of the Harderian glands of golden hamsters by the thyroid gland

Summary Long-term increased or decreased circulating levels of thyroid hormones significantly modify porphyrin concentrations and morphology in the Harderian glands of male and female hamsters. Administration of T₃ reduced porphyrin concentrations in females; this treatment or decreasing thyroid hormone levels with KClO₄ suppressed the post-castration rise of porphyrins in males. Hypophysectomy led to increased porphyrins in the Harderian glands of males; this rise was suppressed in hypophysectomized males by T₃ or T₄. In females, hypophysectomy reduced porphyrins which were further reduced by daily administration of T₃ or T₄. These modifications in the normal females were identical in castrated males. Mitotic activity in the Harderian glands of females was stimulated by KClO₄ and by hypophysectomy with or without exogenous T₃. In males, castration increased mitotic activity which was suppressed by T₃ and exacerbated by KClO₄. Increased mitotic activity seemingly follows loss of tissue mass. The data show that thyroid hormones act directly on the Harderian glands rather than indirectly through modification of TSH synthesis/release. Female type glands in males are a consequence of loss of gonadal androgens by castration, or by suppression or loss of thyroid hormones by hypophysectomy or by treatment with KClO₄. However, male type glands in females are the result of androgen treatment, and/or increased levels of thyroid hormones via reduced ambient temperatures or of photic input. We conclude that regulation of the Harderian gland appears to be different in the two sexes.Abbreviations T ₃ Triiodothyronine - T ₄ Thyroxine - TSH Thyroid Stimulating Hormone - KClO ₄ Potassium Perchlorate - h hours - ml milliliter - mg milligram - g gram - male - female - castrated male - AP hypophysectomized - CON Control - ALA delta aminole-vulenic acid - HG Harderian Gland     

High-performance liquid chromatography with spectrophotometric and electrochemical detection of a series of manganese(III) cationic porphyrins

Recent studies have revealed potent pharmacological activities of manganese-containing cationic porphyrins. An analytical method employing high-performance liquid chromatography with spectrophotometric and electrochemical detection (HPLC-UV/EC) suitable for in vivo applications is described for a series of manganese(III) cationic porphyrins with good separation and resolution. In particular, this method resolved the four atropisomers of manganese(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+ or AEOL-10113), verified by mass spectrometry. Electrochemical and spectrophotometric methods of detection were compared using manganese(III) meso-tetrakis(1,3-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP5+ or AEOL-10150), the lead catalytic antioxidant of this series. Both methods of detection were quantitative, but electrochemical detection, although less specific for in vivo applications, appears to be considerably more sensitive than spectrophotometric detection.     

Synthesis, spectral and electrochemical properties of cyclotriphosphazene appended with six metalloporphyrins

The metal derivatives (Co^II, Ni^II, Cu^II, Zn^II and Sn^IV) of hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assembly on cyclotriphosphazene ring with the appropriate metal salt under standard metallation conditions. The complete metallation of all six porphyrin units in hexaporphyrin assembly required 10-12 h reflux as judged by the absorption spectroscopy. The metal derivatives were confirmed by molecular ion peak in mass spectra for all compounds. ³¹P and ¹H NMR spectra for Ni(II), Zn(II) and Sn(IV) derivatives and ESR spectra for Cu(II) derivative also confirmed the complete metallation of all six porphyrin units. The hexametalloporphyrin assemblies are freely soluble in common organic solvents. The spectral, electrochemical and fluorescence studies indicate that the six porphyrin units in assemblies interact very weakly and retain their individual characteristic features in the ground and excited states.     

Effect of ferrocene-substituted porphyrin RL-91 on Candida albicans biofilm formation

Ferrocene-substituted porphyrin RL-91 exhibits antifungal activity against opportune human pathogen Candida albicans. RL-91 efficiently inhibits growth of both planktonic C. albicans cells and cells within biofilms without photoactivation. The minimal inhibitory concentration for plankton form (PMIC) was established to be 100 μg/mL and the same concentration killed 80% of sessile cells in the mature biofilm (SMIC80). Furthermore PMIC of RL-91 efficiently prevents C. albicans biofilm formation. RL-91 is cytotoxic for human fibroblasts in vitro in concentration of 10 μg/mL, however it does not cause hemolysis in concentrations of up to 50 μg/mL. These findings open possibility for application of RL-91 as an antifungal agent for external antibiofilm treatment of medical devices as well as a scaffold for further development of porphyrin based systemic antifungals.     

Harderian glands of golden hamsters: morphological and biochemical responses to thyroid hormones

Summary Manipulation of circulating levels of thyroid hormones modifies Harderian gland structure and porphyrin concentrations in male and female golden hamsters. Specifically, thyroxine (T₄) and triiodothyronine (T₃) induce the morphological conversion of the Harderian glands of females to approximate those of the male. Further, porphyrin concentrations are markedly decreased by this treatment. This effect occurs in ovariectomized animals as well, indicating that the gonads are not involved. Suppression of thyroid function by potassium perchlorate (KClO₄) drastically reduces Harderian gland weight in both males and females. However, KClO₄ decreases porphyrin levels in the Harderian glands of females and increases it in the male. Concurrently, KClO₄ also induces a morphological conversion of the Harderian glands of males to the female type. This effect is evident in photoperiods of either 14:10 (h) or 8:16 (h).     

Spectroscopic and electrochemical studies of novel model compounds for cytochrome c oxidase

Different metalated porphyrin compounds were studied as model complexes for cytochrome c oxidase. All models contain a tyrosine molecule and a copper binding site. Two of the compounds are bearing an axial pyridine ligand that could possibly coordinate with Fe porphyrins. All complexes were studied using NMR and UV-Vis spectroscopies and it was found that the coordination of the axial ligand is possible only in one of the porphyrins. Moreover, the synthesized catalysts were studied as promising enzyme mimics using a rotating disc electrode in the presence of molecular oxygen.     

Mechanisms of 5-aminolevulinic acid uptake at the choroid plexus

5-Aminolevulinic acid (5-ALA) is a precursor of porphyrins and heme that has been implicated in the neuropsychiatric symptoms associated with porphyrias. It is also being used clinically to delineate malignant gliomas. The blood-CSF barrier may be an important interface for 5-ALA transport between blood and brain as in vivo studies have indicated 5-ALA is taken up by the choroid plexuses whereas the normal blood-brain barrier appears to be relatively impermeable. This study examines the mechanisms of 5-[(3)H]ALA uptake into isolated rat lateral ventricle choroid plexuses. Results suggest that there are two uptake mechanisms. The first was a Na(+)-independent uptake system that was pH dependent (being stimulated at low pH). Uptake was inhibited by the dipeptide Gly-Gly and by cefadroxil, an alpha-amino-containing cephalosporin. These properties are the same as the proton-dependent peptide transporters PEPT1 and PEPT2, which have recently been shown to transport 5-ALA in frog oocyte expression experiments. Choroid plexus uptake was not inhibited by captopril, a PEPT1 inhibitor, suggesting PEPT2-mediated uptake. The presence of PEPT2 and absence of PEPT1 in the choroid plexus were confirmed by western blotting. The second potential mechanism was both Na(+) and HCO(3)(-) dependent and appears to be an organic anion transporter, although it is possible that removal of Na(+) and HCO(3)(-) may indirectly affect PEPT2 by affecting intracellular pH. The presence of PEPT2 and a putative Na(+)/HCO(3)(-)-dependent organic anion transporter is important not only for an understanding of 5-ALA movement between blood and brain but also because these transporters may affect the distribution of a number of drugs between blood and CSF.     

A thiolate ligand on a cytochrome P-450 mimic permits the use of simple environmentally benign oxidants for biomimetic steroid hydroxylation in water

Manganese porphyrin systems carrying cyclodextrin binding groups can regioselectively and stereoselectively hydroxylate bound steroid substrates, using iodosobenzene as oxidant, but hydrogen peroxide and other simple oxidants such as sodium hypochlorite are not effective in water. Thiol ligands were then added to the catalyst, both covalently attached and hydrophobically bound, and with these ligands hydrogen peroxide was now an effective oxidant.     

Photodynamic Activity of Plant Extracts from Sarawak,Borneo

Photodynamic therapy (PDT) is a medical treatment that involves the irradiation of an administered photosensitizing drug with light of a particular wavelength to activate the photosensitizer to kill abnormal cells. To date, only a small number of photosensitizers have been clinically approved for PDT, and researchers continue to look for new molecules that have more desirable properties for clinical applications. Natural products have long been important sources of pharmaceuticals, and there is a great potential for discovery of novel chemotypes from under‐explored biodiversities in the world. The objective of this study is to mine the terrestrial plants in Sarawak, Borneo Island, for new photosensitizers for PDT. In a screening program from 2004 to 2008, we prepared and studied 2,400 extracts from 888 plants for their photosensitizing activities. This report details the bioprospecting process, preparation and testing of extracts, analysis of the active samples, fractionation of four samples, and isolation and characterization of photosensitizers.     

Photodynamic and light independent action of 8 to 2 carboxylic free porphyrins on some haem-enzymes

Backgrounds and aims: skin lesions in cutaneous porphyrias appear to be determined by the structural properties of the porphyrins accumulated. To better understand the relationship between the structure and physicochemical properties of porphyrins and their specific effect on protein configuration, the action of a whole range of 8 to 2 carboxylic porphyrins has been studied. Materials and methods: δ-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) partially purified from bovine liver, were exposed to 10 μM uroporphyrin (Uro), phyriaporphyrin (Phyria), hexaporphyrin (Hexa), pentaporphyrin (Penta), coproporphyrin (Copro) or protoporphyrin (Proto), either in the dark or under UV light. All experiments were performed in the enzyme solutions after removing the porphyrins. Results: under both illuminating conditions, all porphyrins inactivated the enzymes (20–70% under control values), indicating photodynamic action mediated by oxidative reactions and conformational changes due to direct binding of porphyrins to the protein. Total thiol content in ALA-D was not significantly changed by most porphyrins under UV light, while all porphyrins increase total sulfhydryl groups in PBG-D (23–52% over the control values) indicating changes in the redox status of SH residues. Free amino groups were reduced by all porphyrins in ALA-D (23–56% under controls), instead they were enhanced in PBG-D (23–51% over controls), suggesting protein fragmentation. The formation of molecular aggregates would be the consequence of cross-links between oxidation products, while fragmentation can be attributed to either rupture of disulphur bridges and/or enhancement of free amino groups on the protein enzyme. Conclusions: the effect of the porphyrins on enzyme activity, total SH groups and free amino groups content, was different for ALA-D and PBG-D, even under the same illuminating conditions. On the basis of these results, no correlation between enzyme alterations and the physico-chemical properties of porphyrins could be established.