Unexpected differences between D- and L- tyrosine lead to chiral enhancement in racemic mixtures.

We report here an unexpected difference in the solubilities of D- and L-tyrosine in water, which could be discerned by their rate of crystallization and the resulting concentrations of their saturated solutions. A supersaturated solution of 10 mM L-tyrosine at 20 degrees C crystallized much more slowly than that of D-tyrosine under the same conditions, and the saturated solution of L-tyrosine was more concentrated than that of D-tyrosine. Supersaturated solutions of 10 mM DL-tyrosine in water formed precipitates of predominantly D-tyrosine and DL-tyrosine, resulting in an excess of L-tyrosine in the saturated solution. The experimental setups were monitored independently by UV-absorption, radioactivity tracing, optical rotation and X-ray diffraction. The process of nucleation and crystallization of D- and L-tyrosine is characterized by an exceptionally high cooperativity. It is possible that minute energy differences between D- and L-tyrosine, originating from parity violation or other non-conservative chiral discriminatory rules, could account for the observations. The physical process that initiated chiral selection in biological systems remains a challenging problem in understanding the origin of life, and it is possible that chiral compounds were concentrated from supersaturated racemic mixtures by preferential crystallization.     

Anti-CEA monoclonal antibody: technetium-99m labeling and the validation process of a scintigraphic animal model with a non-cellular antigenic implant.

Animal models are currently used to verify the biodistribution of different radiopharmaceuticals before its clinical application in Nuclear Medicine; however, there may be some limitations. The utilization of labelled anti-tumor monoclonal antibodies (MoAb) in experimental models often requires implant of human antigens (usually a cellular implant), which cannot be achieved in immunocompetent animals. Our purpose was to label an anti-CEA MoAb with technetium-99m (99Tc) and to validate a simplified animal model using a noncellular antigenic implant. MoAb was directly labelled with 99mTc, after reduction with 2-mercaptoethanol. Labeling efficiency was checked by ascending chromatography and immunoreactive fraction was measured in plastic wells sensitized with the antigen. Radiopharmaceutical biodistribution was evaluated by dissection and scintigraphy in 5 mice groups; following the subcutaneous administration of Al(OH)3, CEA adsorbed Al(OH)2 and a control group evaluation. Labeling efficiency was 94+/-3%, which showed to be stable for 24 hr, with immunoreactive fraction above 50%. Invasive biodistribution evaluation showed prolonged blood retention, hepatic and renal uptake. A significant increase in uptake was observed in scintigraphic studies of animals with CEA-adsorbed Al(OH)3 implants compared with the other groups (p<0.05). The non-cellular antigenic implant model simplifies the pre-clinical evaluation of labelled MoAb.     

DIVERSITY,LIFE HISTORY,AND ECOLOGY OF TRENTEPOHLIA AND PRINTZINA (TRENTEPOHLIALES,CHLOROPHYTA) IN URBAN HABITATS IN WESTERN IRELAND 1

On the basis of field and culture investigations, five species of the genera Trentepohlia and Printzina were found to occur in urban habitats in western Ireland: Trentepohlia abietina (Flotow) Hansgirg, T. aurea (Linnaeus) Martius, T. iolithus (Linnaeus) Wallroth, T. cf. umbrina (Kützing) Bornet, and Printzina lagenifera (Hildebrandt) Thompson et Wujek. These species formed perennial populations on a variety of substrata. T. abietina occurred on bark of trees; T. cf. umbrina occurred on stone walls; and P. lagenifera grew on several substrata, mainly cement and asbestos sheeting. T. aurea and T. iolithus were found on old concrete and cement walls; in particular, the latter species formed characteristic, extensive, deep‐red patches on many buildings. In culture, best growth and reproduction of these species were observed at 10 and 15° C, 16:8 h light:dark. Both in culture and in the field, reproduction took place by release of biflagellate swarmers behaving as asexual spores, germinating to produce new plants without any evidence of sexual fusion; release of biflagellate swarmers in the field was generally observed in all seasons throughout a whole annual cycle. Confirmation of the occurrence of sexual reproduction in Trentepohlia was not obtained.     

Human hnRNP protein A1: A model polypeptide for a structural and genetic investigation of a broad family of RNA binding proteins

The hnRNP fiber is the substrate on which pre-mRNA processing occurs. The protein moiety of the fiber (hnRNP proteins) constitutes a broad family of RNA binding proteins that revealed, upon molecular analysis, a number of interesting features.Heterogeneous nuclear ribonucleoprotein A1 is a major component of the human hnRNP complex. In recent years this protein has attracted great attention because of several emerging evidences of its direct involvement in pre-mRNA processing and it has become one of the best characterized RNA binding proteins. Detailed knowledge of the structure of protein A1 has laid the basis for the understanding of its function, and for this reason A1 can be considered as a model polypeptide for the investigation of a large number of RNA binding proteins.In this work we report recent findings regarding the binding properties of protein A1 as well as new data on the gene structure of A1 and of its closely related hnRNP protein A2. Our results show that a single A1 molecule contains the determinants for simultaneous binding of two single-stranded nucleic acid molecules and we demonstrate that the glycine-rich domain of A1, isolated from the rest of the molecule, is capable of sustaining protein-protein interactions. These features probably account for the reannealing activity of the protein and for its capacity to modulate the binding of snRNPs to intron sequencesin vitro. Comparison of A1 and A2 gene sequences revealed a remarkable conservation of the overall structural organization, suggesting important functions for the different structural elements.     

Effects of Ethylene Control and Dynamic Controlled Atmosphere Storage on ‘Galaxy’ Apple Quality

Journal of Plant Growth Regulation - This study aimed to evaluate the interaction of ethylene management in the pre- and post-harvest stages using different storage techniques on the...     

B-50/GAP-43 Binds to Actin Filaments Without Affecting Actin Polymerization and Filament Organization

Abstract: To investigate a possible function of the nervous tissuespecific protein kinase C substrate B-50/GAP-43 in regulati of the dynamics of the submembranous cytoskeleton. we studii the interaction between purified 6–50 and actin. Both the phosphorylated and dephosphorylated forms of 8–50 cosedi-mented with filamentous actin (F-actin) in a Ca²⁺-independent manner. Neither 6–50 nor phospho-6–50 had any effect on the kinetics of actin polymerization and on the critical concentration at steady state, as measured using pyrenylated actin. tight scattering of F-actin samples was not increased in the presence of 550, suggesting that 550 does not bundle actin filaments. The number of actin filaments, determined by [³H]cytochalasin B binding, was not affected by either phospho- or dephospho-B-50, indicating that 550 has neither a severing nor a capping effect. These observations were confirmed by electron microscopic evaluation of negatively stained F-actin samples, which did not reveal any structural changes in the actin meshwork on addition of 6–50, We conclude that 6–50 is an actin-binding protein that does not directly affect actin dynamics.     

Steroid biochemistry and categorization of breast cyst fluid: relation to breast cancer risk

Patients bearing macrocysts of the breast are at higher risk of later developing cancer. The fluid filling the cysts (breast cysts fluid, BCF) contains unusual amounts of steroid conjugates, first androgen and estrogen sulfates. Measuring BCF cations (K⁺, Na⁺) allows categorization of cysts into two major subsets (type I and type II) that are associated with a different degree and/or turnover of apocrine metaplastic cells in the lining epithelium. Type I cysts (high K⁺/ Na⁺ ratio) accumulate huge amounts of dehydroepiandrosterone sulfate, estrone sulfate, androstane-3, 17β-diol glucuronide, androsterone glucuronide and contain more testosterone and dihydrotestosterone than type II. Conversely, type II cysts (low K⁺/Na⁺ ratio) contain more progesterone and pregnenolone. A cohort study was started in 1983 at the Cancer Prevention Center, Ravenna, Italy, with the aim of evaluating the relationships between the biochemistry of BCF and the incidence of breast cancer in women with gross cystic disease (GCD) of the breast. The bimodal distribution of the cationic pattern has been confirmed from data obtained in 798 patients aspirated. The risk of cyst relapse was significantly higher among women with type I cysts or with multiple cysts at presentation. Twelve incident cases of breast cancer have been diagnosed among women whose BCF was categorized. Eleven out of 12 cases had type I or multiple cysts. The cumulative incidence of breast cancer among patients bearing type I cysts was 2.5%. We conclude that women with GCD bearing type I cysts have an increased breast cancer risk when compared with the counterpart bearing type II cysts or the general population.     

MLC-specific suppressor T lymphocytes in man. I. Their induction in vitro by soluble HLA-DR antigens

Human T lymphocytes precultured for 36 hr in the presence of soluble HLA-DR antigens suppress the MLR response of autologous peripheral blood lymphocytes to allogeneic stimulating cells. The suppression is DR antigen-specific in that it appears that the MLR stimulating cell donor and the soluble suppressor-inducing antigen must share DR specificities. The soluble DR antigens were fractionated from the sera of normal donors using QAE-Sephadex chromatography and CNBr-activated Sepharose immunoadsorption. Similarly prepared HLA-A and -B antigens failed to induce suppressive activity. The suppressive activity of DR-antigen cultured T cells is resistant to mitomycin C treatment and, further, the antigen specificity is maintained with or without mitomycin C treatment. The kinetics of suppressor cell induction as well as the kinetics of suppression in the test MLR cultures are presented. The implications of these results are discussed.     

The human CD38 gene: polymorphism, CpG island, and linkage to the CD157 (BST-1) gene

 CD38 is a leukocyte activation antigen and ectoenzyme [NAD(P)⁺ glycohydrolase; EC 3.2.2.6] involved in numerous immune functions. The human CD38 gene is complex [eight exons, >80 kilobases (kb) long] located on Chromosome 4p15, and part of the eukaryotic NAD⁺ glycohydrolase/ADP-ribosyl cyclase gene family. Because of the increasing relevance of the CD38 molecule in the host immune response to infectious, tumoral, and metabolic diseases, we investigated the genetic variability and linkage of the human CD38 locus. We report that (1) the restriction endonuclease Pvu II identifies a bi-allelic polymorphism here defined as formed by the alleles CD38 ^* A (12 kb) and CD38 ^* B (9/2.5 kb); (2) their frequency in the healthy Italian Caucasian population is 14% and 86%, respectively; (3) the polymorphic Pvu II site is located at the 5′ end of the first intron of the CD38 gene; (4) in conjunction with the polymorphic site, we identified a 900 base pair CpG island associated with the CD38 gene, with two potential Sp1 binding sites; (5) the CpG island may play a role in the regulation of CD38 expression and is hypomethylated in various cell lines; (6) by pulsed-field gel electrophoresis we show that CD38 and its paralogue, the bone-marrow stromal cell antigen BST-1 (CD157), map to the same 800 kb Avi II fragment, indicating that the two human ecto-NADase genes are closely linked. Received: 16 December 1998 / Revised: 26 January 1999     

SO2-induced decrease in photosynthetic activity in two barley cultivars. Evidence against specific damage at the protein-pigment complex level

This research investigated the SO₂-induced effects on photosynthetic apparatus in two barley (Hordeum vulgare L.) cultivars (cv), Panda and Express. Following a chronic treatment with SO₂ (80 ppb, 75 d) neither cv showed any visible signs of injury or chlorosis on leaf surfaces, while a significant reduction in A_max and G_w was detected in both cvs, although to different extents. Thylakoids of SO₂-treated plants showed a decrease in the electron transport activity at the whole chain, photosystem II (PSII) and photosystem I (PSI) level in both cvs. The high performance liquid chromatography (HPLC) analysis of leaf pigments revealed a significant decrease in both cvs, more pronounced in Panda than in Express. Deriphat-polyacrilamide gel electrophoresis (Deriphat-PAGE) and two dimensional (2-D) electrophoretic analyses of the pigment-protein complexes did not show differences in SO₂-treated samples of either cv. HPLC analysis of the green bands also showed no differences in the pigment content of fumigated samples of either cv, except for a decrease in β-carotene content and xanthophyll cycle pigment (VAZ) content respectively at band 1 (PSI) and band 5 (minor light-harvesting polypeptides of PSII) level in cv Panda, where the de-epoxidation index (DEP) significantly increased, while in Express, an increase in VAZ content and DEP value of band 5 was observed. These results suggest that the decrease in the photosynthetic activity can be ascribed, in addition to stomata closure induced by SO₂, to a generalised, rather than specific, pollutant effect on photosynthetic apparatus, which could be interpreted as an adaptation to the adverse environment.