Identification of a single peridinin sensing Chl-a excitation in reconstituted PCP by crystallography and spectroscopy

The peridinin-chlorophyll a-protein (PCP) of dinoflagellates is unique among the large variety of natural photosynthetic light-harvesting systems. In contrast to other chlorophyll protein complexes, the soluble PCP is located in the thylakoid lumen, and the carotenoid pigments outnumber the chlorophylls. The structure of the PCP complex consists of two symmetric domains, each with a central chlorophyll a (Chl-a) surrounded by four peridinin molecules. The protein provides distinctive surroundings for the pigment molecules, and in PCP, the specific environment around each peridinin results in overlapping spectral line shapes, suggestive of different functions within the protein. One particular Per, Per-614, is hypothesized to show the strongest electronic interaction with the central Chl-a. We have performed an in vitro reconstitution of pigments into recombinant PCP apo-protein (RFPCP) and into a mutated protein with an altered environment near Per-614. Steady-state and transient optical spectroscopic experiments comparing the RFPCP complex with the reconstituted mutant protein identify specific amino acid-induced spectral shifts. The spectroscopic assignments are reinforced by a determination of the structures of both RFPCP and the mutant by x-ray crystallography to a resolution better than 1.5 Å. RFPCP and mutated RFPCP are unique in representing crystal structures of in vitro reconstituted light-harvesting pigment-protein complexes.     

Redox properties of Met(35) in neurotoxic beta-amyloid peptide. A molecular modeling study

The beta-amyloid peptide (betaAP) is the principal component of plaque associated with the pathology of Alzheimer's disease. Part of its neurotoxicity appears to correlate with the ability of the peptide to reduce Cu(II) and form free radicals. Both processes are dependent on the presence and oxidizability of Met(35) in the C-terminus of the peptide but no mechanistic details on the reactions leading to Met oxidation are known. On the basis of previous studies with model peptides, we hypothesize that a one-electron oxidation of Met(35) in betaAP is facilitated through a neighboring group effect. Complexed to Cu(II) and/or in a lipid-mimicking environment, the solution structure of betaAP includes a large alpha-helical part. The solution NMR structure of betaAP1-40 in aqueous SDS micelles reveals an alpha-helix between residues 27 and 36, containing Met(35). In this helical C-terminus of betaAP, the peptide bond C=O group C-terminal of Ile(31) is located very close to the Met(35) sulfur and could stabilize a Met(35) sulfide radical cation through formation of an (S-O) three-electron bond. In the present paper, we have computationally validated this hypothesis using Langevin dynamics methods to determine the collision frequency of the Met(35) thioether sulfur and the oxygen atoms of several peptide bonds in the betaAP sequence. Nanosecond time scale computations were carried out for four distinct betaAP congeners, betaAP26-40, betaAP26-36, betaAP26-40(Ile(31)Pro), betaAP40-26, and their respective Met(35)-sulfur-centered cation radicals. Here, betaAP26-40, betaAP26-40(Ile(31)Pro) and betaAP40-26 are representative fragments of the full length betaAP1-42 or betaAP42-1 sequence, respectively, whereas betaAP26-36 represents a unique betaAP sequence for which biological data are available. Initial structures of betaAP26-40, betaAP26-40(Ile(31)Pro), and betaAP26-36 were selected to be identical to that of the betaAP26-40 or betaAP26-36 sequence in full-length betaAP1-40. As the structures of betaAP40-26 and betaAP42-1 are not known, various initial conformations such as alpha-helix and antiparallel beta-sheet were selected for betaAP40-26. Our computational results show that betaAP26-40, representative for the same sequence in full-length betaAP1-42, has the highest tendency to form (S-O) bonds between Ile(31)C=O and Met(35)S. We conclude that native betaAP1-42 has a higher tendency to support Met(35) oxidation through (S-O) bond formation, consistent with the experimental observation that betaAP1-42 is more neurotoxic compared to the other investigated sequences.     

Tryptase levels in patients after acute coronary syndromes: The potential new marker of an unstable plaque?

BACKGROUND: Mast cells (MCs) are multifunctional immune cells that produce a number of vasoactive or thromboactive mediators. Elevated numbers of human heart MCs are observed in the shoulder regions of coronary atherosclerotic plaques, suggesting that they play a role in plaque rupture. Cardiac MC degranulation after myocardial ischemia has been documented in animal models. Cardiac MCs are highly profibrinolytic cells and release tryptase, their specific protease, after ischemic events. HYPOTHESIS: Mast cell activation and release of tryptase may differentiate among patients with acute coronary syndromes (ACS), potentially determining the clinical course of ACS. Tryptase levels may indirectly reflect the fibrinolytic status of patients. METHODS: Mast cell activation after ACS was estimated in 10 controls and 52 patients by measuring the serum levels of tryptase in the acute phase, at 2 weeks, and at 3 months after the ACS episode. Total tryptase levels were determined by using the UniCAP system and analyzed with respect to the patients' clinical types of ACS on admission (ACS with persistent ST-segment elevation on electrocardiogram or with ST-segment depression). RESULTS: Significant differences in serum tryptase levels between the groups were found, with higher serum tryptase concentrations in the ST-segment depression group in the acute phase, and at follow-up. CONCLUSIONS: Serum tryptase concentration differences among patients with distinct types of ACS may indicate a more important role of human heart MCs in ACS with ST-segment depression pathogenesis. To our knowledge, this is the first report indicating that serum tryptase levels may differentiate patients with distinct types of ACS.     

Clinical and epidemiological analysis of patients with botulism hospitalized at the Department of Infectious Disease,Medical University of Lublin in 1990-2000

In the paper we presented results of clinical and epidemiological analysis of 32 patients with botulism hospitalized at the Department of Infectious Diseases, Medical University of Lublin in 1990-2000. In the studied group, the relationships between botulism incidence and sex and place of residence were not significant. The incubation period ranged from 7 hours to 5 days (average 36 hrs). The clinical manifestations of botulism were typical in all cases. In one female patient the course of disease was complicated. She developed right-sided bronchopneumonia and left-sided purulent parotitis. The type B botulinum toxin occurred more frequently than the other types and the cases without serological confirmation (Chi 2 = 6.125 p = 0.01). It was found in serum of 23 patients (in 2 cases together with the type A toxin). The type E toxin was found in serum of one patient. The presence of toxin in serum was not detected in 8 patients. In all patients trivalent (types A, B and E) equine antitoxin was administered. The dose ranged from 50 to 150 cm3. Symptomatic treatment was given in all cases. Nobody required mechanical ventilation. The duration of hospitalization ranged from 5 to 28 days (average 16.6 days). A few patients complained of long-lasting blurred vision or dry mouth.     

An attempt at evaluating borderline conditions of Parkinson's disease and its preclinical stage on the basis of clinical and morphological correlation

The aim of the investigations was to find to what extent neurodegenerative changes develop in the brains of patients with no clinical symptoms of dementia, parkinsonism and other neurodegenerative diseases. It has been found that neurodegenerative pathology, as evaluated using immunohistochemical methods with monoclonal antibodies (Mab) against ubiquitin, tau protein, alpha-synuclein, and beta-amyloid, occurs more frequently than the presence of Lewy bodies. The degenerative changes involved the neurones of cerebral and cerebellar cortex, basal ganglia and medulla oblongata, where neurofibrillary tangles were found. Mab positive materials have been found in the cytoplasm of the cell body and the cell processes (axons) of the neurones and glial cells. Senile plaques, beta-amyloid positive, were frequently noted.     

Synthesis and pharmacological activity of new carbonyl derivatives of 1-aryl-2-iminoimidazolidine: part 2. Synthesis and pharmacological activity of 1,6-diaryl-5,7(1H)dioxo-2,3-dihydroimidazo[1,2-a][1,3,5]triazines

Synthesis and pharmacological activity of 1,6-diaryl-5,7(1H)dioxo-2,3-dihydroimidazo-[1,2-a][1,3,5]triazines (C) are presented. The title compounds were obtained from 1-arylimidazolinurea derivatives in cyclization reaction with difunctional carbonyl reagents--phosgene (method I) or carbonyldiimidazole (CDI) (method II). Their molecular structures were confirmed by the X-ray analysis of 1-phenyl-6-(4-chlorophenyl)-5,7(1H)-dioxo-2,3-dihydroimidazo[1,2-a][1,3,5]triazine (C2) crystals. Compounds C exhibited significant depressive action on the central nervous system (CNS) of the laboratory animals, correlated with very low acute toxicity (LD(50) > 2000 mg kg(-1) i.p.), and showed antinociceptive activity in behavioural models. Reversion of this effect by small dose of naloxone (5 mg kg(-1)) can suggest opioid-like mechanism of antinociception produced by these and other carbonyl derivatives of 1-aryl-2-iminoimidazolidine. Additionally, an effect on the serotonin neurotransmission pathway was also observed. The receptor mechanism of activity for investigated compounds was confirmed only for the opioid mu receptor in binding affinity assay test. Same tests performed for the serotonin 5-HT(2) and benzodiazepine BZD receptors showed no affinity for tested compounds. The opioid-like and serotonergic activities are similar to these described earlier for chain carbonyl 1-aryl-2-iminoimidazolidine derivatives containing urea moiety, mainly due to similar chemical structure, although compounds C are not able to adopt any of the higher energy conformations of urea derivatives. Rigid location of aromatic ring (Ar') at N6, acting as a spacer blocking any direct access to the carbonyl groups (e.g. through the hydrogen bonding), could be responsible for lack of affinity toward 5-HT(2) expressed in the binding assay test.     

Synthesis and pharmacological activity of new carbonyl derivatives of 1-aryl-2-iminoimidazolidine. Part 3. Synthesis and pharmacological activity of 1-aryl-5,6(1H)dioxo-2,3-dihydroimidazo[1,2-a]imidazoles

Synthesis and pharmacological activity of 1-aryl-5,6(1H)dioxo-2,3-dihydroimidazo[1,2-a]imidazoles (D) are presented. The title compounds were obtained from 1-aryl-2-iminoimidazolidines (1) by cyclization reaction with oxalic acid derivatives-ethyl ester (2) or chloride (3). They were tested for pharmacological activity in animal and binding assay tests. With moderate acute toxicity (LD(50) approximately 200 mg kg(-1), i.p.), they exhibited significant analgesic and serotonergic activities as results of the 'writhing' and the 'hot plate' tests indicated, and reduced number of 'head twitch' episodes after 5-HTP (5-hydroxytryptophan) administration. Reversion of the antinociception produced in the 'writhing' test by small dose of naloxon (5 mg kg(-1)) can suggest an opioid-like mechanism of their analgesic activity. The probable receptor inhibition mechanism of their analgesic and serotonergic activity was confirmed in the binding assay tests (by radioligand displacement) toward the opioid mu and serotonin 5-HT(2) receptors. Additionally, they exhibited affinity toward the benzodiazepine (BZD) receptor as well, although in behavioral tests compounds did not produce any clear depressive effect on the central nervous system (CNS) of mice. Simple chemical structure of the title compounds, in comparison to other carbonyl derivatives of 1-aryl-2-iminoimidazolidine presented in this series of papers, underline very important role both of a hydrophobic moiety (aromatic ring) and polar groups (hydrogen-bond acceptors) in the serotonin receptor interaction. The co-existence of opioid-like, serotonergic and BZD receptor inhibition activity can be very interesting and can lead to creation of the novel group of antidepressants.     

Cystic meningioma: report of three cases

Meningioma with cystic component is not a commonly encountered tumor. We report three patients with cystic meningioma histologically confirmed. Tomographic images of these tumours resembled those of a glial or metastatic origin with cystic or necrotic changes and were easily confused. In a 2-year period (1997-1999) in our Department we had three patients with cystic meningioma who account for 5.4% of all patients with meningiomas we have.