Tracing the ingredients for a habitable earth from interstellar space through planet formation

We use the C/N ratio as a monitor of the delivery of key ingredients of life to nascent terrestrial worlds. Total elemental C and N contents, and their ratio, are examined for the interstellar medium, comets, chondritic meteorites, and terrestrial planets; we include an updated estimate for the bulk silicate Earth (C/N = 49.0 ± 9.3). Using a kinetic model of disk chemistry, and the sublimation/condensation temperatures of primitive molecules, we suggest that organic ices and macromolecular (refractory or carbonaceous dust) organic material are the likely initial C and N carriers. Chemical reactions in the disk can produce nebular C/N ratios of ∼1–12, comparable to those of comets and the low end estimated for planetesimals. An increase of the C/N ratio is traced between volatile-rich pristine bodies and larger volatile-depleted objects subjected to thermal/accretional metamorphism. The C/N ratios of the dominant materials accreted to terrestrial planets should therefore be higher than those seen in carbonaceous chondrites or comets. During planetary formation, we explore scenarios leading to further volatile loss and associated C/N variations owing to core formation and atmospheric escape. Key processes include relative enrichment of nitrogen in the atmosphere and preferential sequestration of carbon by the core. The high C/N bulk silicate Earth ratio therefore is best satisfied by accretion of thermally processed objects followed by large-scale atmospheric loss. These two effects must be more profound if volatile sequestration in the core is effective. The stochastic nature of these processes hints that the surface/atmospheric abundances of biosphere-essential materials will likely be variable.The development of a habitable world and a stable biosphere requires the delivery of biogenic elements of which carbon and nitrogen are crucial. Carbon is the backbone for the chemistry of life and, in the form of CO₂, combines with water to provide the greenhouse needed for a habitable Earth. Nitrogen is a key component of DNA, RNA, and proteins, while also present as the dominant constituent of our atmosphere. The processes that supply these crucial ingredients remain poorly understood. In interstellar space, C and N are abundant, but inherently volatile and so chiefly remain in the gas. Thus, the terrestrial planets, which accrete primarily from rocks and ices, are fed from C- and N-depleted materials and are carbon and nitrogen poor compared with the nebular disk from which they descend (1, 2). The carbon and nitrogen depletion of rocky bodies is a general phenomenon, observable not just in our solar system, but also in the polluted atmospheres of white dwarf stars, which trace the composition of disrupted planetesimals (3, 4). This volatile poor state of terrestrial planets is partially imparted from the starting materials. However, further differential loss of C and N can occur due to parent body processes such as thermal metamorphism, core segregation, planetary outgassing, and atmospheric loss (5–11).In this work we document the evolution in the relative concentrations of C and N from the interstellar medium (ISM) through planetary assembly. We show that the C/N ratio contains clues regarding the formation of terrestrial planets and the delivery/fate of crucial volatile compounds. We first discuss the relative carbon and nitrogen inventories beginning with the ISM as it evolves to the protoplanetary disk, using the perspectives of kinetic chemistry, our growing understanding regarding the composition of planet-forming disks, and volatile loss within thermally processed planetesimals. We then explore the evolution of C/N during geochemical differentiation of a young Earth-like planet, built up by accretion of planetesimals of a range of sizes. Key processes during this last stage of C/N evolution include sequestration into the metallic core and outgassing to the nascent atmosphere. It is, of course, the latter that can provide ingredients for early environments and life, but early atmospheres are also prone to impact-driven escape, providing additional mechanisms for C and N processing and alteration.     

Formation of benzene in the interstellar medium

Polycyclic aromatic hydrocarbons and related species have been suggested to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block--the aromatic benzene molecule--has remained elusive for decades. Here we demonstrate in crossed molecular beam experiments combined with electronic structure and statistical calculations that benzene (C(6)H(6)) can be synthesized via the barrierless, exoergic reaction of the ethynyl radical and 1,3-butadiene, C(2)H + H(2)CCHCHCH(2) → C(6)H(6) + H, under single collision conditions. This reaction portrays the simplest representative of a reaction class in which aromatic molecules with a benzene core can be formed from acyclic precursors via barrierless reactions of ethynyl radicals with substituted 1,3-butadiene molecules. Unique gas-grain astrochemical models imply that this low-temperature route controls the synthesis of the very first aromatic ring from acyclic precursors in cold molecular clouds, such as in the Taurus Molecular Cloud. Rapid, subsequent barrierless reactions of benzene with ethynyl radicals can lead to naphthalene-like structures thus effectively propagating the ethynyl-radical mediated formation of aromatic molecules in the interstellar medium.     

Immunohistochemical and functional studies of glycoprotein 60 (gp60) in platelets

Summary We showed by immunofluorescence, immunoelectron microscopy and Western blot analysis that the plasma glycoprotein (gp60), an Fc binding protein which inhibits complement-mediated prevention of immune precipitation, is present in platelets. The pg60 content of platelets in normal individuals and patients with rheumatoid arthritis was similar (mean 0.028 and 0.024 fg/platelet respectively). Immunoelectron microscopic studies showed that pg60 was present in the cytoplasm and the surface connecting structures but not in the granules, dense granules or lysosomes. Using this technique gp60 was also found on platelet membranes, an observation which was confirmed by immunofluorescence. Activation of platelets with thrombin, calcium ionophore, and immune complexes (IC) resulted in the release of the contents of the granules (-thromboglobulin), dense granules (5-hydroxytryptamine) and lysosomes (-glucuronidase) but did not induce gp60 secretion. The inability of Fab anti-gp60 to inhibit IC-mediated platelet aggregation and of F(ab)₂ anti-gp60 to produce platelet aggregation suggested that IC-mediated platelet aggregation did not occur as a result of the interaction of IC with platelet gp60. However, as the preincubation of IC with purified gp60 produced dose-dependent inhibition of the ability of IC to aggregate platelets it is possible that fluid-phase plasma gp60 modulates the interaction of IC with platelets.     

X-ray crystal structure of an anti-Buckminsterfullerene antibody fab fragment: biomolecular recognition of C(60)

We have prepared a monoclonal Buckminsterfullerene specific antibody and report the sequences of its light and heavy chains. We also show, by x-ray crystallographic analysis of the Fab fragment and by model building, that the fullerene binding site is formed by the interface of the antibody light and heavy chains. Shape-complementary clustering of hydrophobic amino acids, several of which participate in putative stacking interactions with fullerene, form the binding site. Moreover, an induced fit mechanism appears to participate in the fullerene binding process. Affinity of the antibody-fullerene complex is 22 nM as measured by competitive binding. These findings should be applicable not only to the use of antibodies to assay and direct potential fullerene-based drug design but could also lead to new methodologies for the production of fullerene derivatives and nanotubes as well.     

Fatal meningococcal meningitis in a HIV-infected patient caused by serogroup C Neisseria meningitidis belonging to the non-hypervirulent clonal complex ST-60 (cc60)

Meningococcal strains belonging to clonal complex cc60 are not associated with hypervirulent lineages and were never reported as causing disease in Latin American countries. This is the first report of a fatal meningitis case caused by a cc60 clonal complex meningococcus in Brazil. Despite the immune-compromised state of the patient, the fatal outcome here described shows the potential pathogenic behavior of strains belonging to this clonal complex and how compromised hosts can be susceptible to meningococcal infections even if the strain is not particularly invasive.     

Mechanism of superconductivity in K3C60

Using electronic states and phonon states from the first-principles calculations and including both conventional electron-phonon charge coupling and Jahn-Teller coupling, we predict Tc and other superconducting properties. The only adjustable parameter in the theory is the screening length, Rsc. Using Rsc = 0.8-1.0 A, we find excellent agreement with experiment for Tc (16-18 K), pressure dependence of Tc (Delta Tc = -6 to -10 K for 1 GPa), and 12 C to 13 C isotope shift (alphaC = 0.2); experimental values: 19 K, -7 K, and 0.3, respectively.     

Gamma (60)Co DL(50/30) of Biomphalaria glabrata (SAY, 1818)

The variation of resistance to (60)Co gamma-rays of Biomphalaria glabrata was studied. A population of 480 mollusks was observed during 30 days - distributed in 8 groups of snails isolated and 8 groups of snails in colonies - after exposure (30 snails per group per dose) to increasing doses of gamma radiation. Doses of 10, 20, 40, 60, 80, 160, 320 and 640 Gy from a Gamma-cell (60)Co irradiator, were applied to the test groups and two groups control (non-irradiated) of snails - isolated and colony - were kept apart. After have been exposed, the snails were drew back to the aquaria where they were maintained before. The survival was estimated on a daily score of the alive animals in each group-dose, starting after the irradiation exposure day. As a result, the survival self-fertilization forms (DL(50/30) = 218.2 Gy) was found greater than in cross-fecundation forms. These data point to a low radio-resistance on the cross-fertilization forms - the sexual reproductive form - which is most found in nature. The lower radio-resistance of the cross-fertilization forms suggests the presence of some sex-linked hormonal factor related to this phenomenon.     

Tumor necrosis factor (TNF)-induced protein phosphorylation in a human rhabdomyosarcoma cell line is mediated by 60-kD TNF receptors (TR60)

In the present study, we used a cloned derivative, KYM-1D4, of the human rhabdomyosarcoma cell line, KYM-1, known to express high numbers of the two tumor necrosis factor (TNF) receptors, TR60 and TR80, and to be highly sensitive to TNF alpha-mediated cytotoxicity/antiproliferation, to investigate the role of TR60 and TR80 in protein phosphorylation. Using permeabilized KYM-1D4 cells, it was found that TNF alpha strongly induced phosphorylation of proteins of molecular weight 80, 65, 58, 42, and 30 kD. Addition of a monoclonal antibody (MoAb) against TR60 was shown to induce cytotoxicity/antiproliferation in KYM-1D4 cells and the same pattern of protein phosphorylation as TNF alpha, whereas addition of an MoAb against TR80 was both noncytotoxic and ineffective in inducing protein phosphorylation. In contrast, in a highly TNF alpha-resistant KYM-1- derived cell line, 37B8R, no protein phosphorylation was induced with either TNF alpha or the agonistic anti-TR60 MoAb. However, when 37B8R was allowed to revert to partial TNF sensitivity by culture in the absence of TNF alpha, the resultant cell line, 37B8S, was found to regain inducibility of protein phosphorylation by TNF alpha. These results indicate that expression of functional TR60 in KYM-1-related cell lines is principally involved in TNF-mediated cytotoxicity/antiproliferation and is necessary for the induction of protein phosphorylation. Nevertheless, the latter, although apparently strongly associated with cytotoxicity, was probably involved in protective mechanisms because protein kinase C inhibitors that inhibited TNF alpha and anti-TR60-induced phosphorylation increased the cytotoxic/antiproliferative response to these mediators.     

Low temperature formation of naphthalene and its role in the synthesis of PAHs (polycyclic aromatic hydrocarbons) in the interstellar medium

Polycyclic aromatic hydrocarbons (PAHs) are regarded as key molecules in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest prototype—naphthalene (C₁₀H₈)—has remained an open question. Here, we show in a combined crossed beam and theoretical study that naphthalene can be formed in the gas phase via a barrierless and exoergic reaction between the phenyl radical (C₆H₅) and vinylacetylene (CH₂ = CH-C ≡ CH) involving a van-der-Waals complex and submerged barrier in the entrance channel. Our finding challenges conventional wisdom that PAH-formation only occurs at high temperatures such as in combustion systems and implies that low temperature chemistry can initiate the synthesis of the very first PAH in the interstellar medium. In cold molecular clouds, barrierless phenyl-type radical reactions could propagate the vinylacetylene-mediated formation of PAHs leading to more complex structures like phenanthrene and anthracene at temperatures down to 10 K.     

Human placenta-conditioned medium for stimulation of human granulopoietic precursor cell (CFU-C) colony growth in vitro

Summary Human placenta-conditioned medium (HPCM) has been reported to stimulate colony formation by human granulopoietic stem cells (CFU-C) in vitro. The present work was performed to further characterize this colony formation. The majority of HPCM batches tested stimulated colony growth equivalent to recombined human leukocyte feeder layers with optimal cellular composition. A broad plateau of the dose-response curve of HPCM was found. A linear correlation exists between the number of marrow cells plated and the number of colonies grown. Optimal duration of culture is between 9 and 11 days. Colonies are large and tend to be compact. Admixture of mature granulocytes does not affect the colony growth pattern under optimal culture conditions. These data document that HPCM is a suitable source of colony-stimulating activity for the routine assay of human CFU-C. Due to the constant colony stimulation, HPCM appears particularly valuable for longitudinal studies of human CFU-C.This work was supported by the Deutsche Forschungsgemeinschaft, SFB 112     

Unassembled (soluble) vimentin in human myeloid leukemia cell line HL60

Abstract: The intermediate filament proteins which include vimentin, desmin, and the keratins are one of three major classes of cytoskeletal proteins in eukaryotic cells. In this study we found that most of the vimentin of undifferentiated HL60 and cells induced to differentiate either along the monocytoid pathway by 12-O-tetradecanoylphorbol-13-acetate (TPA) or along the granulocytic pathway by retinoic acid was soluble in a buffer containing 1% Triton X-100/0.6 mol/l KCl in which the intermediate filament proteins usually are not soluble. HL60 vimentin separated on Polyacrylamide gel electrophoresis into two proteins of Mr 55000 and 54000 that we detected by immunoblotting. The Mr 55000 species was the major form in undifferentiated HL60 cells and cells induced by retinoic acid. The distribution of both forms of vimentin changed during induction of differentiation by TPA and after 24 h the Mr 54000 species was predominant. After an additional 24 h exposure to TPA the relative levels of the two forms of vimentin approached equivalence and a high level of vimentin degradation products was seen. These results suggest that TPA may increase vimentin degradation along a pathway that has a Mr 54000 intermediate. In addition, the high levels of soluble vimentin in HL60 cells suggests that these cells may be a good model for studying components involved in vimentin assembly.     

The Anatomic Range of Examination by Fibreoptic Rectosigmoidoscopy (60 Centimetres)

Jensen J, Kewenter J, Swedenborg J. The anatomic range of examination by fibreoptic rectosigmoidoscopy (60 centimetres). Scand J Gastroenterol 1992;27:842-844

The purpose of the study was to investigate the anatomic location of the flexible rectosigmoidoscope (60 cm) when introduced as far as technically possible. One hundred and forty-nine consecutive patients referred for double-contrast enema (DCE) were examined with rectosigmoidoscopy before the radiologic examination, and C0₂ was used for insufflation. A plain abdominal film was taken to locate the tip of the instrument when 60 cm or as much as possible of the instrument had been introduced. The sigmoid loop was passed and the tip of the scope located in the ascending colon or at the left flexure in 99 (66%) of the patients, and in a further 27 (18%) the upper part of the sigmoid colon was reached. The sigmoid colon had been passed in 71%, 80%, and 44% when 60, 50, and 40 cm of the instrument was introduced, respectively. DCE could be performed at the same session as the rectosigmoidoscopy, as C0₂ was quickly absorbed. In the vast majority of patients the sigmoid colon can be inspected with a rectosigmoidoscope.     

A phorbol ester tolerant (PET) variant of HL-60 promyelocytes

The promyelocytic leukaemia cell line HL-60 differentiates to a macrophage-like cell when exposed to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) and other agents which activate protein kinase C. To investigate this phenomenon we developed an HL-60 variant which does not differentiate when exposed to TPA. HL-60 cells were exposed to the mutagen ethyl methanesulphonate and were cloned in soft agar in the presence of a normally lethal concentration of TPA. One colony of cells that proliferated in TPA was obtained. The cells of this phorbol ester tolerant (PET) line have retained their resistance to TPA for several years without selective pressure. They are somewhat larger than their phorbol ester sensitive (S) parent, but they are otherwise morphologically similar. When PET-cells are exposed to TPA their growth is arrested for approximately 48 h. Thereafter, they resume their original rate of replication at all concentrations of TPA tested. S-cells undergo changes typical of HL-60 when exposed to TPA; they aggregate, stop growing, adhere to the flask and die. The PET-cells appeared to be as sensitive as S-cells to other agents which differentiate HL-60 such as retinoic acid, dimethysulphoxide, and 1,25-dihydroxyvitamin D3, as determined by rate of proliferation in culture, Wright's stain, nitroblue tetrazolium reduction, and induction of the ectoenzyme NAD-glycohydrolase. TPA-induced protein phosphorylation was studied using one- and two-dimensional polyacrylamide gel electrophoresis. Several proteins increased their incorporation of 32P when S- and PET-cells were exposed to TPA, the most prominent of which were the two previously described nuclear matrix proteins of 80 kd and 33 kd. There was no difference in the protein phosphorylation pattern in S- and PET-cells, nor in how this pattern changed on TPA exposure. Fluorescent activated cell sorting and karyotypic analysis revealed PET-cells to be a hypotetraploid variant of S-cells, with approximately 80 chromosomes, including a marker chromosome iso(1p) not found in the S-cells. Identification of the biochemical lesion responsible for this TPA resistance in PET cells will provide clues concerning the mechanism of this important pathway for the induction of cell differentiation.