Characterization of pNiXa,a serpin of Xenopus laevis oocytes and embryos,and its histidine-rich,Ni(II)-binding domain

A Ni(II)-binding serpin, pNiXA, is abundant in Xenopus oocytes and embryos. Kinetic assays show that purified pNiXa strongly inhibits bovine α-chymotrypsin (K₁ = 3 mM), weakly inhibits porcine elastase (K₁ = 0.5 μM), and does not inhibit bovine trypsin. The reversible, slow-binding inhibition of α-chymotrypsin by pNiXa is unaffected by Ni(II). Ovochymase in egg exudates is inhibited by pNiXa, but to a limited extent, even at high pNiXa concentrations. An octadecapeptide that models the His-rich domain (-HRHRHEQQGHHDSAKHGH-) of pNiXa forms six-coordinate, octahedral Ni(II)-complexes when the N-terminus is acetylated, and a square-planar Ni(II)-complex when the N-terminus is unblocked. Spectroscopy reveals two distinct types of octahedral Ni(II)-coordination to the N-acetylated octadecapeptide, involving, respectively, 3–4 and 5–6 imidazole nitrogens; the octadecapeptide undergoes partial, reversible precipitation in pH-and Ni(II)-dependent fashion, suggesting an insoluble, Ni(II)-coupled (Hx)_n-dimer. Such (Hx)_n-peptide interaction is confirmed by an enzyme-linked biotin-avidin assay with N-biotin-KHRHRHE-amide and N-acetyl-KHRHRHE-resin beads, which become coupled after adding Ni(II) or Zn(II). H₂O₂ oxidation of 2′-deoxyguanosine to mutagenic 8-hydroxy-2′deoxyguanosine is enhanced by the octahedral Ni(II)-octadecapeptide complex, although the effect is more intense with the square-planar Ni(II) octadecapeptide complex. Immunoperoxidase staining of whole mounts wish pNiXa antibody shows that pNiXa is distributed throughout gastrula-stage embryos and is localized during organogenesis in the brain, eye, spinal cord, myotomes, craniofacial tissues, and other sites of Ni(II) induced anomalies. Patterns of pNiXa staining are similar in controls and Ni(II)-exposed embryos. Binding of Ni(II) to pNiXa may cause embryotoxicity by enhancing oxidative reactions that produce tissue injury and genotoxicity. Although the natural target proteinases for pNiXa inhibition have not been established, pNiXa may be an important regulator of proteolysis during embryonic development. © 1996 Wiley-Liss, Inc.     

Proteins reacting with anti-spectrin antibodies are present in Chlamydomonas cells.

It was found either in Western-blot analysis or in indirect immunofluorescence microscopy that cells of the alga Chlamydomonas reinhardtii contain polypeptides cross-reacting with antibodies directed against red blood cell spectrin. The protein could also be detected by immunoprecipitation with anti-spectrin antibodies. C. reinhardtii cells contain distinct polypeptide chains reacting with antibodies directed against either α- or β-spectrin subunits. This protein was extracted from the cells with low ionic strength solution but was not with nonionic detergent.     

Immunomodulatory effect of selenosemicarbazides and selenium inorganic compounds, distribution in organs after selenium supplementation

Antioxidant properties of selenium producing a protective barrier against free radicals play an important role in numerous metabolic and immunologic processes associated with oxidation- reduction reactions which take place during intracellular digestion of phagocyted bacteria. The aim of our study was to examine the properties of an organic compound of selenium, 4-(o-tolilo)- selenosemicarbazide of p-chlorobenzoic acid in terms of its retention in organs, effect on erythropoesis and phagocytic abilities of neutrophiles as well as antioxidant properties in neutrophiles tested with NBT test. This compound as well as inorganic sodium selenate was given to Swiss mice at the dose of 10^–3 g Se/kg for the period of 10 days. The concentrations of selenium in livers of mice treated with sodium selenate and selenosemicarbazide were found to be higher than in controls (18,7 g lg^–1 and 23.2 g lg^–1 vs. 12 g lg^–1, respectively). Analysis of blood cells count has shown a significant decrease in neutrophile levels in both groups treated with selenium. The influence of selenium compounds on phagocytosis and especially NBT test has been determined (3.8% of positive cells in the controls vs. 2.2% and 0.9% in the groups treated with sodium selenate and selenosemicarbazide, respectively). Our preliminary investigations suggest that selenosemicarbazides are biologically active compounds and can modify neutrophile functions.     

Dark reoxidation of the plastoquinone-pool is mediated by the low-potential form of cytochrome b-559 in spinach thylakoids

We have found that in isolated spinach thylakoids, plastoquinone-pool (PQ-pool), after its photoreduction, undergoes dark-reoxidation with the half-time of _1/2 = 43 ± 3 s. To explain the observed rates of PQ-pool reoxidation, a nonenzymatic plastoquinol (PQH₂) autoxidation under molecular oxygen and an enzymatic oxidation by the low-potential form of cytochrome b-559 (cyt. b-559LP), as the postulated PQ-oxidase in chlororespiration, were investigated. It was found that the autoxidation rate of PQH₂ in organic solvents and liposomes was too low to account for the observed oxidation rate of PQH₂ in thylakoids. The rate of cyt. b-559LP autoxidation in isolated Photosystem II was found to be similar (_1/2 = 26 ± 5 s) to that of the PQ-pool. This suggests that the LP form of cyt. b-559 is probably responsible for the PQ-oxidase activity observed during chlororespiration.     

Bone marrow angiogenesis and proliferation in B-cell chronic lymphocytic leukemia

OBJECTIVE: To assess angiogenesis and the proliferative activity of bone marrow in patients with chronic lymphocytic leukemia (CLL) in relation to the bone marrow infiltration pattern. STUDY DESIGN: Bone marrow samples were obtained by trephine biopsy from 46 patients with B-cell CLL (B-CLL). Infiltration pattern was diffuse in 20 patients and nondiffuse--i.e., nodular, interstitial or mixed--in the remaining 26 patients. Ten normal bone marrow samples were used as a control group. Studies were carried out by immunohistochemical staining of paraffin-embedded bone marrow samples. Angiogenesis was assessed in the zones of highest vascular density (hot spots), visualized by the expression of endothelial antigen CD34 and expressed as a number of microvessels per high-powerfield (hpf) (final magnification, 400x). Proliferative activity was estimated by the expression of nuclear protein Ki-67, cyclin A and mean number of nucleolar organizer regions (AgNORs). RESULTS: Microvessel density was higher in B-CLL marrow than in normal marrow (30.1 and 16.44 per hpf, respectively) and was higher in the diffuse than nondiffuse pattern (33.6 and 27.5 per hpf, respectively). B-CLL bone marrow also showed higher proliferative activity, as assessed by mean number of AgNORs, than did normal marrow (1.52 and 1.25, respectively) and a higher mean percentage of cyclin A-positive cells (7.5 and 6.8, respectively). In contrast, mean Ki-67 expression was similar in B-CLL and the control group. Mean AgNORs number, Ki-67 and cyclin A-positive cell percentage were significantly higher in B-CLL marrow with a diffuse as compared to nondiffuse involvement pattern (AgNORs, 1.75 and 1.35; cyclin A, 9.27% and 3.95%; Ki-67, 34.9% and 23.3%, respectively). CONCLUSION: Our results indicate enhancement of bone marrow angiogenesis in B-CLL and a relationship between microvessel density and the bone marrow infiltration pattern. The study points also to a possible relationship between the bone marrow infiltration pattern and proliferative activity of bone marrow cells.     

Immunomodulating polysaccharide fractions of Menyanthes trifoliata L

Looking for new plant sources of immunomodulating agents polysaccharide-rich fractions (PS) from Menyanthes trifoliata L. (Menyanthaceae) have been isolated. The herb of Menyanthes trifoliata L. was sequentially extracted with water, 0.1 M NaOH, 8% CH3COOH, and 1 M NaOH. After dialysis and resolution on Biogel P-10 four homogenic (B-4, B-5, C-4, D-5) and two nonhomogenic (A-3 and D-4) PS were isolated. About 0.5% of PS over 3500 Da were found in the dry plant material. They were characterized through chemical analysis, NMR and vibrational spectroscopy. Speciation analysis of chosen metal/metaloid elements was performed and an exceptionally high concentration of Se was found in PS of a pure water extract (A-3). The biological tests on the immunomodulating influence with human blood-derived lymphocytes and granulocytes revealed that two fractions, B-4 and B-5, were strong stimulators of immune cells, whereas fractions D-5 and A-3 were found as potent suppressive and anti-inflammatory agents. The applied isolation procedures led to the separation of active compounds into stimulatory and inhibitory fractions.     

A sensitive and specific HPLC method for the determination of total pentosidine concentration in plasma

Pentosidine is an advanced glycation end-product (AGE) appearing when arginine and lysine residues in proteins are cross-linked with carbonyl derivatives. This paper presents an improved method for the synthesis of pentosidine and reversed-phase chromatography of this substance with fluorometric detection that enables sensitive (0.01 pmol/mg protein) and specific determination of pentosidine in plasma. Separation is done twice on the same C(18) Vydac 218TP54 column, first with trifluoroacetic acid and next with heptafluorobutyric acid as ion pair. The inter-day coefficient of variation is 6.4% at pentosidine concentration in plasma of 25 pmol/mg protein and 8% at 1.7 pmol/mg protein. Spectral properties of pentosidine exploited during identification of the substance with UV absorption and fluorescence detectors are described. Maximum of absorbance was observed at 325 nm, maximum fluorescence at lambda(ex)/lambda(em)=330/373 nm. The method may prove useful for the study of processes associated with generation and accumulation of pentosidine in the body as a marker of AGE production in healthy subjects and patients with chronic renal failure.     

A high frequency of apoptosis was found in cultures of lymphocytes isolated from the venous blood of children born with a low birth weight

Children born with a low birth weight (below 2500 g) exhibit a slower rate of development, and a greater tendency towards morbidity and mortality, together with a deficit of weight and height. One reason could be an increase in the level of cell elimination by apoptosis. The aim of this study was to evaluate and compare the incidence of apoptotic and necrotic (dead) cells in cultures of peripheral blood lymphocytes obtained from children born with a low birth weight and from children with a normal birth weight. Peripheral blood lymphocytes were obtained by venipuncture (10 ml) and isolated using the density gradient centrifugation method. The lymphocytes were cultured for 48 h in a culture medium containing low concentrations of fetal calf serum. A comparison study was performed between low birth weight children and normal birth weight children and the susceptibility of their lymphocytes to apoptosis and to necrosis in serum-deficient feeding culture conditions. The amount of apoptotic cells and the percentage of dead cells were significantly higher in cultures of lymphocytes obtained from low birth weight children than in cultures from normal birth weight children. The two estimated parameters inversely correlated with the concentration of fetal calf serum in the culture medium. Pulsed field gel electrophoresis showed increased DNA degradation patterns in the cultures of lymphocytes obtained from low birth weight children. Our results should be perceived as an indication that, under worse feeding conditions, the elimination of cells by apoptosis and by necrosis is significantly higher for lymphocytes of low birth weight children than for those of normal birth weight children. The enhanced elimination of lymphocytes is related to a greater susceptibility to infections, especially of the respiratory tract, as established in the retrospective analysis of the anamneses of the examined group of low birth weight children.     

Cytogenetic comparison of the sensitivity to mutagens in mice selected for high (HA) and low (LA) swim stress-induced analgesia

Sensitivity to mutagens was studied in mouse lines selectively bred for high analgesia (HA) and for low analgesia (LA) induced by 3-min swimming in 20 degrees C water. Apart from pain-related traits HA mice also manifest, as compared to the LA line, higher emotionality in various behavioural tests, and cope worse with the hypothermic challenge of swimming in cold water. In the present study HA mice appeared more susceptible to the mutagenic effect of whole-body gamma-radiation and mitomycin-C injection. Both treatments caused higher frequencies of chromosomal aberrations and micronucleus in bone marrow cells in the HA than in the LA line. The results are discussed in terms of a genetic correlation between animals' susceptibility to environmental stressors and the mechanism of mutagenesis. As shown by our recent molecular study, the selection for magnitude of swim analgesia has differentiated the parental outbred population into two distinct genotypes characterised by specific minisatellite and microsatellite sequences for each line, which may be genetic markers of particular traits. We conceive that the breeding strategy, along with the differentiation of stress-related phenomena, has altered the frequencies of genes controlling DNA repair in each line.