DNA interaction, cytotoxicity, and radiosensitization with PtCl4(Nile Blue)2 and PtCl4(Neutral Red)2

Complexes of the positively charged, nuclear staining, quinone-imine dyes Nile Blue and Neutral Red with negatively charged tetrachloroplatinum (II) have been prepared in an effort to form neutral drugs which could gain ready access to the cellular nucleus and deliver significant quantities of the reactive tetrachloroplatinum anion to the vicinity of the DNA. Elemental analysis showed that both the Nile Blue and Neutral Red complexes with tetrachloroplatinum (II) comprised 2 mol of dye and 1 mol of tetrachloroplatinum, forming Pt(Nile Blue)2 and Pt(Neutral Red)2. Exposure of superhelical pBR322 DNA to the complexes or the dyes for 24 h followed by agarose gel electrophoresis showed that Neutral Red and Pt(Neutral Red)2 had little effect on DNA conformation, but that both Nile Blue and Pt(Nile Blue)2 could produce single-strand DNA breaks in a dose-dependent fashion. Studies in exponentially growing asynchronous, hypoxic, and normally oxygenated EMT6 cells at normal pH (7.40) and pH 6.45 demonstrated that neither dye was highly toxic, but that both complexes were capable of producing significant cytotoxicity. Both complexes killed normally oxygenated cells more efficiently than hypoxic cells, but Pt(Neutral Red)2 was more cytotoxic at pH 6.45, while Pt(Nile Blue)2 killed significantly more cells at normal pH. Both complexes decreased the survival of hypoxic EMT6 cells as indicated by the slope of the radiation survival curve [dose modifying factor (DMF) 2.90 for Pt(Nile Blue)2 and 1.45 for Pt(Neutral Red)2]. Studies with the FSaIIC murine tumor showed that both complexes were active radiosensitizing agents in vivo [DMF 1.76 for Pt(Nile Blue)2 and 1.25 for Pt(Neutral Red)2]. These results indicate that these new platinum complexes have characteristics which may make them and similar complexes effective radiosensitizing agents in humans.     

Regulation of intracellular pH by a neuronal homolog of the erythrocyte anion exchanger

We have isolated AE3, a novel gene expressed primarily in brain neurons and in heart. The predicted AE3 polypeptide shares a high degree of identity with the anion exchange and cytoskeletal binding domains of the erythrocyte band 3 protein. Expression of AE3 cDNA in COS cells leads to chronic cytoplasmic acidification and to chloride- and bicarbonate-dependent changes in intracellular pH, confirming that this gene product is an anion exchanger. Characterization of an AE3 mutant lacking the NH2-terminal 645 amino acids demonstrates that the COOH-terminal half of the polypeptide is both necessary and sufficient for correct insertion into the plasma membrane and for anion exchange activity. The NH2-terminal domain may play a role in regulating the activity of the exchanger and may be involved in the structural organization of the cytoskeleton in neurons.     

The effect of alkaline borohydride treatment onN-linked carbohydrates of glycoproteins

The effects of treatments of the glycoprotein ribonuclease-B, the proteins ribonuclease-A and myoglobin, and the glyco-amino acid GlcNAc(1-N) Asn with alkalil alkaline sodium borohydride, and aqueous sodium borohydride were systematically studied as a function of the concentration of the reagents, the temperature, and the length of the treatment. High-field¹H-NMR spectroscopy, chromatographic methods and amino-acid analysis were used to characterize products of the treatments of the various compounds. Our results indicate that mild alkaline borohydride treatment, as well as aqueous borohydride treatment alone, is capable of extensively degrading polypeptides and of partially releasing theN-linked glycans from ribonuclease-B. Initially, glycopeptides are produced, the peptide portion of which consists of several amino acids, which are further hydrolyzed to yield a mixture of glyco-asparagines and oligosaccharide-alditols in the ratio of 4:1. Strong alkaline borohydride treatment of ribonuclease-B is capable of completely releasing theN-linked carbohydrates as oligosaccharide-alditols.Abbreviation RNase ribonuclease     

Genetic and Biochemical Characterization of Mutations Affecting the Ability of the Yeast Pachysolen tannophilus To Metabolize d-Xylose

Induced mutants, selected for their defective growth on d-xylose while retaining the ability to grow normally on d-glucose, were studied in Pachysolen tannophilus, a yeast capable of converting d-xylose to ethanol. Fourteen of the mutations were found to occur at nine distinct loci, and data indicated that many more loci remain to be detected. Most of the mutations were pleiotropic in character, and the expression of some of them was much affected by nutritional conditions and by genetic background. Mutations at several loci resulted in poor growth on at least one compound that was either an intermediate of the tricarboxylic acid cycle, succinate or alpha-ketoglutarate, or on compounds metabolizable via this cycle, ethanol or glycerol. An initial biochemical characterization of the mutants was undertaken. Analysis for xylose reductase, xylitol dehydrogenase, and xylulose kinase activity showed that one or more of these activities was affected in 12 of 13 mutants. However, drastic reduction in activity of a single enzyme was confined to that of xylitol dehydrogenase by mutations at three different loci and to that of d-xylose reductase by mutation at another locus. Growth of these latter four mutants was normal on all carbon sources tested that were not five-carbon sugars.     

Isolation and structure determination of two peptides occurring in human seminal plasma

Two previously unknown peptides with a high amount of polar amino acids were isolated from human seminal plasma by a combination of dialysis, gel filtration, ion-exchange chromatography, and RP-HPLC. Their structures were determined by gas-phase sequencing simultaneously considering the different peak intensities.     

The effect of ferricyanide with iodoacetate in calcium-free solution on passive cation permeability in human red blood cells: comparison with the Gardos-effect and with the influence of PCMBS on passive cation permeability

Freshly prepared human red blood cells incubated with 5 mM ferricyanide, 0.2 mM iodoacetate and 2 mM adenosine in the presence of 5 mM EGTA demonstrate comparable increases in Na+ and K+ permeability (ferricyanide effect). This effect is unrelated to the Ca2+-activated K+ channel (Gardos effect) since influx of Ca2+ from outside the cell is excluded. Also this effect is different from the non-specific Na+ and K+ permeability change elicited by PCMBS. These differences become obvious by using various reagents. For example, A23187 and quinidine exert opposite effects in Gardos and ferricyanide experiments, where A23187 and atebrin react oppositely in the latter and in PCMBS experiments. The ferricyanide effect described here does not involve formation of nonspecific channels. The change in Na+ permeability separately from K+ permeability under certain circumstances suggests a more specific effect.     

Expression of interleukin 2 and the interleukin 2 receptor in aging rats

Lymphocytes of aged animals exhibit a marked decrease in proliferative capacity in response to mitogen stimulation when compared to those of younger animals. In humans and mice the decreased proliferation is due at least in part (i) to the inability of lymphocytes to synthesize sufficient interleukin 2 (IL-2) and (ii) to decreased expression of IL-2 receptors (IL-2R) on the surface of aged lymphocytes. We compared proliferative abilities, IL-2 production, and IL-2R expression in splenocyte cultures of 4- to 5- and 22- to 24-month-old Fischer 344 rats stimulated with either concanavalin A (Con A) or A23187 and phorbol myristate acetate (PMA). Proliferation was significantly decreased in aged lymphocytes (30-50%) with both treatment protocols. However, unlike mice and humans we observed no difference in IL-2 activity, IL-2 mRNA levels, or IL-2R cell surface expression of lymphocytes from young and aged rats stimulated with either Con A or A23187 and PMA. These results indicate that factors other than decreased expression of IL-2 and IL-2R are responsible for the diminished proliferative capacity of aged rat lymphocytes following mitogen stimulation.     

Comparison of the NH2-terminal amino acid sequences of the four non-identical subunits of the NAD-linked hydrogenases from Nocardia opaca 1b and Alcaligenes eutrophus H16

The cytoplasmic, NAD-linked hydrogenase of the Gram-positive hydrogen-oxidizing bacterium Nocardia opaca 1b was compared with the analogous enzyme isolated from the Gram-negative bacterium Alcaligenes eutrophus H16. The hydrogenase of N. opaca 1b was purified by a new procedure applying chromatography on phenyl-Sepharose and DEAE-Sephacel with two columns in series. A homogeneous enzyme preparation with a specific activity of 74 mumol H2 oxidized.min-1.mg protein-1 and a yield of 32% was isolated. The A. eutrophus enzyme was purified as previously published. Both enzymes are tetrameric proteins composed of four non-identical subunits (alpha, beta, gamma, delta). The four subunits of both of these enzymes were separated and isolated as single polypeptides by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Immunological comparison of the four subunits of the Nocardia hydrogenase with those of the Alcaligenes enzyme showed that the alpha, beta, gamma, and delta subunits of one organism were serologically related to the analogous subunits of the other organism. Among themselves, the four subunits do not have any serological relationship. The eight individual polypeptides were also compared with respect to the NH2-terminal amino acid sequences determined by automated Edman degradation and to the amino acid compositions. Strong sequence similarities exist between the analogous subunits isolated from the two bacteria. Within the established N-terminal sequences the similarities between both alpha, beta, gamma and delta subunits amount to 63%, 79%, 80% and 65%, respectively. No similarities exist between the different, non-analogous subunits alpha, beta, gamma and delta.     

The superficial cerebral veins

Estimated were the number, the course, and the width of the superficial cerebral veins. The veins on the superolateral surface of the brain are the prefrontal superficial lateral superior, the precentral superficial lateral superior, the central superficial lateral superior, the parietal superficial lateral superior, and the occipital superficial lateral superior veins which drain to the superior sagittal sinus, to bridging veins, and to the falx cerebri. The veins which drain the lateral surface of the brain downwards are the middle superficial cerebral veins, the temporal inferior, occipital inferior, and anastomotic veins. The diameters of these veins were measured at the perforation of the arachnoid membrane and the diameters of the anastomotic veins on their narrowest area. On the medial side of the hemispheres, we divided in precentral superficial superior medial, central superficial medial, parietal superficial medial, occipital superficial medial dorsal veins of the corpus callosum, and internal occipital veins. On the basal surface of the hemispheres, we studied and described the uncal veins and the inferior hemispheric veins. Studied and discussed are also the bridging veins in the course of the inferior cerebral veins, the paracavernous sinuses, and the last course of the veins and their connections with the dura mater or the course inside the dura. Given are besides the numbers of these veins, the area of perforation of the arachnoid membrane, and their width and medical importance.