The cyclooxygenases

Cyclooxygenases (COXs) catalyze the rate-limiting step in the production of prostaglandins, bioactive compounds involved in processes such as fever and sensitivity to pain, and are the target of aspirin-like drugs. COX genes have been cloned from coral, tunicates and vertebrates, and in all the phyla where they are found, there are two genes encoding two COX isoenzymes; it is unclear whether these genes arose from an early single duplication event or from multiple independent duplications in evolution. The intron-exon arrangement of COX genes is completely conserved in vertebrates and mostly conserved in all species. Exon boundaries largely define the four functional domains of the encoded protein: the amino-terminal hydrophobic signal peptide, the dimerization domain, the membrane-binding domain, and the catalytic domain. The catalytic domain of each enzyme contains distinct peroxidase and cyclooxygenase active sites; COXs are classified as members of the myeloperoxidase family. All COXs are homodimers and monotopic membrane proteins (inserted into only one leaflet of the membrane), and they appear to be targeted to the lumenal membrane of the endoplasmic reticulum, where they are N-glycosylated. In mammals, the two COX genes encode a constitutive isoenzyme (COX-1) and an inducible isoenzyme (COX-2); both are of significant pharmacological importance.     

Biosynthesis of chlorophyll P-680 of photosystem II in greening leaves of plants adapted to heat shock

In etiolated pea and maize leaves illuminated after incubation at 38 degreesC, a new dark reaction was shown manifested in the bathochromic shift of spectral bands and accompanied by esterification of the product of protochlorophyllide photochemical reduction--Chld 684/676: Chld 684/676 --> Chl 688/680. After completion of the reaction a rapid (20-30 sec) quenching of the fluorescence of the reaction product (Chl 688/680) was observed. The reaction Chld 684/676 --> Chl 688/680 is inhibited under anaerobic conditions and in the presence of cyanide; the reaction accompanied by Chl 688/680 fluorescence quenching is not observed in pea mutants with impaired function of photosystem II reaction centers. The spectral properties of the formed Chl form with the absorption maximum at 680 nm, fluorescence quenching, and simultaneous synthesis of pheophytin suggest that the reaction is connected with the chlorophyll of photosystem II reaction center--P-680.     

Late thrombotic occlusion of a malapposed stent 10 months after intracoronary brachytherapy

We report a patient who received a stent following intracoronary 3-irradiation. Despite a good initial angiographic result, the stent appeared to be not fully expanded on intravascular ultrasound imaging at 6-month follow-up. Four months later, sudden thrombotic occlusion occurred shortly after aspirin cessation.     

Comparison of ribosomal dna nucleotide sequences of the mosquito genera Aedes and Ochlerotatus (Diptera: Culicidae: Aedini)

Nucleotide rDNA sequences of 9 species of the mosquito genus Ochlerotatus and 2 species of the genus Aedes were obtained and compared. Variation both within and between these genera was characterized. The phylogenetic relationships among the studied species of Ochlerotatus generally correspond to the grouping of species based on morphological characters.     

Lectin histochemistry for detecting cadmium-induced changes in the glycosylation pattern of rat placenta

Cadmium (Cd) is an industrial and environmental pollutant that produces toxic effects on gametogenesis, pre- and post-implantation embryos, and the placenta. Because the effects of acute Cd intoxication on the placenta are not well understood, we investigated changes in its glycosylated components in Cd treated dams at days 4, 7, 10 and 15 of gestation using lectin histochemistry. CdCl₂ was administered to pregnant rats; control animals received sterile normal saline. Placentas were processed for DBA, Con A, SBA, PNA, UEA-I, RCA-I and WGA lectin histochemistry to evaluate changes in the carbohydrate pattern of the placenta that might modify cell interactions and contribute to embryonic alterations. Lectin binding was analyzed in the yolk sac; trophoblast giant cells; trophoblast I, II and III; spongiotrophoblast cells and endovascular trophoblast cells in the chorioallantoic placenta. Our lectin binding patterns showed that Cd caused alteration of SBA and DBA labeling of trophoblast-derived cells, which suggested increased expressions of α and β GalNAc. Cd also caused decreased UEA-1 binding affinity, which indicated fewer α-L-Fuc residues in placentas of Cd treated dams. The nonreactivity in trophoblast I of the control placentas incubated with Con-A contrasted with the labeling in placentas of experimental dams, which indicated increased expression of terminal α-D-Man, and α-D-Glc residues. We found that Cd altered the reactivity of placenta to several lectins, which indicated modification of the glycotype presented by the fetal component of the placenta. We report that Cd exerts a deleterious effect on the glycosylation pattern of the placenta.     

Blakeslea trispora mutants with a disrupted sexual process

Three groups of Blakeslea trispora (+) and (-) mutants were obtained and their phenotypical characteristics were studied as well as biochemical changes in the course of mating and the ability to synthesize carotenoids when the sexual process of these mutants was disordered. The first group of mutants synthesized carotenoids at the control level, the second group produced them below the control level, and the third group accumulated less than 1% of carotenoids as compared to the control. The difference in the yields of carotenoids among the three groups of mutants in the mated culture is attributed to the presence (or absence) of the ability to synthesize trisporic acids in them.