The 33 kDa protein of photosystem II is a low-affinity calcium- and lanthanide-binding protein

We have shown that the isolated 33 kDa protein of photosystem II contains one calcium and one lanthanide low-affinity binding site with binding constants (K(D)) on the order of 10(-5) M. Binding of calcium or lanthanides to this site induces conformational changes in the protein that manifest in fluorescence emission spectra of the protein, circular dichroism spectra, and calorimetric thermograms where the phase transitions are shifted to lower temperatures. The role of calcium binding to the 33 kDa protein in the attainment of its native structure and the significance of this interaction for the oxygen evolution process are discussed.     

Administration of a nitric oxide synthase inhibitor counteracts prostaglandin F2-induced luteolysis in cattle

The objective of this study was to determine whether nitric oxide (NO) is produced locally in the bovine corpus luteum (CL) and whether NO mediates prostaglandin F2alpha (PGF2alpha)-induced regression of the bovine CL in vivo. The local production of NO was determined in early I, early II, mid, late, and regressed stages of CL by determining NADPH-d activity and the presence of inducible and endothelial NO synthase immunolabeling. To determine whether inhibition of NO production counteracts the PGF2alpha-induced regression of the CL, saline (10 ml/h; n = 10) or a nonselective NOS inhibitor (Nomega-nitro-l-arginine methyl ester dihydrochloride [L-NAME]; 400 mg/h; n = 9) was infused for 2 h on Day 15 of the estrous cycle into the aorta abdominalis of Holstein/Polish Black and White heifers. After 30 min of infusion, saline or cloprostenol, an analogue of PGF2alpha (aPGF2alpha; 100 microg) was injected into the aorta abdominalis of animals infused with saline or L-NAME. NADPH-diaphorase activity was present in bovine CL, with the highest activity at mid and late luteal stages (P < 0.05). Inducible and endothelial NO synthases were observed with the strongest immunolabeling in the late CL (P < 0.05). Injection of aPGF2alpha increased nitrite/nitrate concentrations (P < 0.01) and inhibited P4 secretion (P < 0.05) in heifers that were infused with saline. Infusion of L-NAME stimulated P4 secretion (P < 0.05) and concomitantly inhibited plasma concentrations of nitrite/nitrate (P < 0.05). Concentrations of P4 in heifers infused with L-NAME and injected with aPGF2alpha were higher (P < 0.05) than in animals injected only with aPGF2alpha. The PGF2alpha analogue shortened the cycle length compared with that of saline (17.5 +/- 0.22 days vs. 21.5 +/- 0.65 days P < 0.05). L-NAME blocked the luteolytic action of the aPGF2alpha (22.6 +/- 1.07 days vs. 17.5 +/- 0.22 days, P < 0.05). These results suggest that NO is produced in the bovine CL. NO inhibits luteal steroidogenesis and it may be one of the components of an autocrine/paracrine luteolytic cascade induced by PGF2alpha.     

Binding of the basic fibroblast growth factor (bFGF) by soluble components of human umbilical cord

Pre-eclampsia, the most common pregnancy associated syndrome, is connected with remodelling of extracellular matrix of the umbilical cord tissues. Since the fibroblast growth factor (FGF) is known to be a stimulator of collagen and glycosaminoglycan biosynthesis, one may expect that it plays an important role in such a remodelling. Studies performed on the umbilical cords of 10 control and 10 pre-eclamptic newborns demonstrated that both the umbilical cord arterial wall and Wharton's jelly contain FGF mainly in complexes with the components of different molecular mass. Pre-eclampsia is associated with a decrease of endogenous FGF-binding by soluble high molecular mass components of the umbilical cord. It is suggested that FGF released from these complexes may be actively bound by fibroblasts of the umbilical cord, stimulating them to produce collagen and sulphated glycosaminoglycans.     

The influence of intracellular idarubicin and daunorubicin levels on drug cytotoxicity in childhood acute leukemia

Uptake and efflux of two anthracyclines, idarubicin (IDA) and daunorubicin (DNR), was studied in childhood acute leukemia samples. A comparison of IDA and DNR transport phenomena in relation to drug cytotoxicity and expression of P-glycoprotein (PGP) was made. Intracellular content of IDA/DNR was determined by flow cytometry using the fluorescent properties of the drugs. In vitro drug cytotoxicity was measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. PGP expression was analysed by flow cytometry. The uptake and efflux rates were non-significantly higher for IDA than DNR. There were no differences between three types of leukemia with respect to drug content during accumulation and retention. After correction for the cell volume, intracellular concentration of both drugs in each moment of uptake and efflux was significantly lower in relapsed ALL and AML samples in comparison with initial ALL cells. Efflux, but not uptake, of both drugs was inversely correlated with PGP expression and IDA, but not DNR, cytotoxicity. The cytotoxicity was correlated with drug accumulation for both drugs and with drug retention for IDA. In conclusion, it seems that (1) intracellular content was related to the lipophilic properties of the drugs rather than to the type of leukemia, (2) decreased intracellular concentration of both drugs might have an impact on compromised therapy results in AML and relapsed ALL children, (3) IDA presents higher cytotoxicity, which possibly might be decreased by the presence of PGP. These results might have a practical impact on the rational design of new chemotherapy protocols.     

Umbraviruses--the unique plant viruses that do not encode a capsid protein

Umbraviruses are plant viruses that are unusual in that they lack within their genomes information for a capsid protein, and thereby for aphid transmission. They are transmitted by mechanical inoculation, but may become aphid-transmissible when the plants are co-infected with suitable luteoviruses which act as the helper viruses. In mixed infection the umbravirus can be encapsidated by the capsid protein shell provided from the luteovirus helper and, as a result, gain aphid transmissibility. The associations of some umbraviruses with luteoviruses result in specific, lasting disease complexes, showing interesting biological properties. However, umbraviruses are generally not sufficiently recognized, although several of them are significant pathogens in some regions of the world, including Europe. This review describes the development of studies upon umbraviruses and characterizes the genus Umbravirus and its best recognized members.     

In vitro activity of oxazaphosphorines in childhood acute leukemia: preliminary report

Glufosfamide (beta-D-glucosyl-ifosfamide mustard) is a new agent for cancer chemotherapy. Its pharmacology is similar to commonly used oxazaphosphorines, but it does not require activation by hepatic cytochrome P-450 and preclinically demonstrates lower nephrotoxicity and myelosuppression than ifosfamide. The aim of the study was a comparison of the drug resistance profiles of glufosfamide and other oxazaphosphorines in childhood acute leukemias. Leukemic cells, taken from children with ALL on diagnosis (n = 41), ALL on relapse (n = 12) and AML on diagnosis (n = 13) were analyzed by means of the MTT assay. The following drugs were tested: glufosfamide (GLU), 4-HOO-ifosfamide (IFO), 4-HOO-cyclophosphamide (CYC) and mafosfamide cyclohexylamine salt (MAF). In the group of initial ALL samples median cytotoxicity values for GLU, IFO, CYC and MAF were 15.5, 33.8, 15.7 and 7.8 microM, respectively. In comparison with initial ALL samples, the relative resistance for GLU and IFO in relapsed ALL samples was 1.9 (p = 0.049) and 1.3 (ns), and in initial AML samples 31 (p < 0.001) and 5 (p = 0.001), respectively. All oxazaphosphorines presented highly significant cross-resistance. Glufosfamide presented high activity against lymphoblasts both on diagnosis and on relapse.     

Allograft rejection by primed/memory CD8+ T cells is CD154 blockade resistant: therapeutic implications for sensitized transplant recipients

We have shown that CD8(+) CTLs are the key mediators of accelerated rejection, and that CD8(+) T cells represent the prime targets of CD154 blockade in sensitized mouse recipients of cardiac allografts. However, the current protocols require CD154 blockade at the time of sensitization, whereas delayed treatment fails to affect graft rejection in sensitized recipients. To elucidate the mechanisms of costimulation blockade-resistant rejection and to improve the efficacy of CD154-targeted therapy, we found that alloreactive CD8(+) T cells were activated despite the CD154 blockade in sensitized hosts. Comparative CD8 T cell activation study in naive vs primed hosts has shown that although both naive and primed/memory CD8(+) T cells relied on the CD28 costimulation for their activation, only naive, not primed/memory, CD8(+) T cells depend on CD154 signaling to differentiate into CTL effector cells. Adjunctive therapy was designed accordingly to deplete primed/memory CD8(+) T cells before the CD154 blockade. Indeed, unlike anti-CD154 monotherapy, transient depletion of CD8(+) T cells around the time of cardiac engraftment significantly improved the efficacy of delayed CD154 blockade in sensitized hosts. Hence, this report provides evidence for 1) differential requirement of CD154 costimulation signals for naive vs primed/memory CD8(+) T cells, and 2) successful treatment of clinically relevant sensitized recipients to achieve stable long term graft acceptance.     

Cyanogenesis in glucosinolate-producing plants: Carica papaya and Carica quercifolia

(R)-2-(beta-D-Glucopyranosyloxy)-2-phenylacetonitrile (prunasin) was isolated from Carica papaya L. and C. quercifolia (A. St.-Hil.) Hieron. (syn. C. hastata Brign.). Earlier reported presence of cyclopentanoid cyanohydrin glycosides in C. papaya could not be confirmed, and no cyclopentanoid amino acids could be detected in extracts of C. papaya and C. quercifolia. Conversion of [2,3,4,5,6-3H]phenylalanine into tritiated prunasin was demonstrated in both species. On the other hand, when the plants were administered [2-14C]-2-(2'cyclopentenyl)glycine, extracted, and the extracts hydrolyzed with beta-glucosidase (Helix pomatia), formation of labelled cyanide was not observed. The absence of cyclopentanoids, which are typical for the Passifloraceae, and the inability of Carica species to utilize 2-(2'-cyclopentenyl)glycine as a precursor of cyanogenic glycosides are in agreement with the relative phylogenetic position of the Caricaceae and the Passifloraceae. Carica species are thus rare examples of taxa in which glucosinolates and cyanogenic glycosides co-occur, both types of natural products being derived from the same amino acid, phenylalanine.