Tropomyosin from the striated muscles of carp (Cyprinus carpio) and of icefish (Channichthys rhinoceratus).

Tropomyosin of fast-twitch, slow-twitch and cardiac muscles of carp and icefish has been isolated by hydroxyapatite chromatography. The subunit distribution has been investigated by polyacrylamide gel electrophoresis and by peptide mapping. The purified skeletal muscle tropomyosins all belong to the alpha family and differ from higher vertebrate tropomyosin by the lack of beta subunits. Specific alpha isotypes are however encountered in fast-twitch fibres (alpha w subunit) and slow-twitch or intermediate (pink) fibres (alpha and alpha w subunits). The amino acid compositions and the paracrystals formed by the carp alpha w alpha w and alpha alpha w tropomyosins do not differ markedly from that of rabbit alpha alpha chains. They differ however by their capability to inhibit the ATPase activity of rabbit skeletal muscle acto-HMM system. A beta-like subunit is found in carp cardiac tropomyosin, in the proportion of 25% of the native protein, but not in icefish heart.     

Moderately High Temperatures Inhibit Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (Rubisco) Activase-Mediated Activation of Rubisco

We tested the hypothesis that light activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is inhibited by moderately elevated temperature through an effect on Rubisco activase. When cotton (Gossypium hirsutum L.) or wheat (Triticum aestivum L.) leaf tissue was exposed to increasing temperatures in the light, activation of Rubisco was inhibited above 35 and 30°C, respectively, and the relative inhibition was greater for wheat than for cotton. The temperature-induced inhibition of Rubisco activation was fully reversible at temperatures below 40°C. In contrast to activation state, total Rubisco activity was not affected by temperatures as high as 45°C. Nonphotochemical fluorescence quenching increased at temperatures that inhibited Rubisco activation, consistent with inhibition of Calvin cycle activity. Initial and maximal chlorophyll fluorescence were not significantly altered until temperatures exceeded 40°C. Thus, electron transport, as measured by Chl fluorescence, appeared to be more stable to moderately elevated temperatures than Rubisco activation. Western-blot analysis revealed the formation of high-molecular-weight aggregates of activase at temperatures above 40°C for both wheat and cotton when inhibition of Rubisco activation was irreversible. Physical perturbation of other soluble stromal enzymes, including Rubisco, phosphoribulokinase, and glutamine synthetase, was not detected at the elevated temperatures. Our evidence indicates that moderately elevated temperatures inhibit light activation of Rubisco via a direct effect on Rubisco activase.     

Structural basis for the low affinities of yeast cAMP-dependent and mammalian cGMP-dependent protein kinases for protein kinase inhibitor peptides.

Affinities of the catalytic subunit (C1) of Saccharomyces cerevisiae cAMP-dependent protein kinase and of mammalian cGMP-dependent protein kinase were determined for the protein kinase inhibitor (PKI) peptide PKI(6-22)amide and seven analogues. These analogues contained structural alterations in the N-terminal alpha-helix, the C-terminal pseudosubstrate portion, or the central connecting region of the PKI peptide. In all cases, the PKI peptides were appreciably less active as inhibitors of yeast C1 than of mammalian C alpha subunit. Ki values ranged from 5- to 290-fold higher for the yeast enzyme than for its mammalian counterpart. Consistent with these results, yeast C1 exhibited a higher Km for the peptide substrate Kemptide. All of the PKI peptides were even less active against the mammalian cGMP-dependent protein kinase than toward yeast cAMP-dependent protein kinase, and Kemptide was a poorer substrate for the former enzyme. Alignment of amino acid sequences of these homologous protein kinases around residues in the active site of mammalian C alpha subunit known to interact with determinants in the PKI peptide [Knighton, D. R., Zheng, J., Ten Eyck, L. F., Xuong, N-h, Taylor, S. S., & Sowadski, J. M. (1991) Science 253, 414-420] provides a structural basis for the inherently lower affinities of yeast C1 and cGMP-dependent protein kinase for binding peptide inhibitors and substrates. Both yeast cAMP-dependent and mammalian cGMP-dependent protein kinases are missing two of the three acidic residues that interact with arginine-18 in the pseudosubstrate portion of PKI. Further, the cGMP-dependent protein kinase appears to completely lack the hydrophobic/aromatic pocket that recognizes the important phenylalanine-10 residue in the N-terminus of the PKI peptide, and binding of the inhibitor by the yeast protein kinase at this site appears to be partially compromised.     

Family Characteristics as Risk Factors for Childhood Acute Lymphoblastic Leukemia: A Population-Based Case-Control Study

Background

To date, few risk factors for childhood acute lymphoblastic leukemia (ALL) have been confirmed and the scientific literature is full of controversial “evidence.” We examined if family characteristics, particularly maternal and paternal age and number of older siblings, were risk factors for childhood acute lymphoblastic leukemia (ALL).

Methodology/Principal Findings

In this population-based nationwide matched case-control study, patients 0–14 years of age with ALL diagnosed 1991–2006 and registered in the Swiss Childhood Cancer Registry were linked with their census records of 1990 and 2000. Eight controls per case were selected from the census. The association between family characteristics and ALL was analyzed by conditional logistic regressions. We found that increasing maternal age was associated with incidence of ALL in the offspring (OR per 5-year increase in maternal age 1.18, 95% CI 1.05–1.31; p = 0.004), remaining stable (trend OR 1.14, 95% CI 0.99–1.31; p = 0.060) after adjustment for other risk factors. The association with paternal age was weaker (OR per 5-year increase 1.14, 95% CI 1.01–1.28, p = 0.032) and disappeared after adjustments. Number of older siblings was not associated with risk of ALL in the overall group of children aged 0–14 years at diagnosis. However, we found a negative trend between number of older siblings and ALL diagnosed at age 0–4 years (OR per sibling 0.85, 95% CI 0.68–1.06; p = 0.141) and a positive trend for ALL diagnosed at age 5–9 (OR 1.34, 95% CI 1.05–1.72; p = 0.019), with some evidence for an effect modification (p-value for interaction  = 0.040).

Conclusions

As in other studies, increasing maternal, but not paternal age was associated with risk of ALL. We found only a weak association with the number of older siblings, suggesting a delay in disease manifestation rather than a decrease in incidence.     

Effects of fertilization levels in two farming systems on senescence and nutrient contents in potato leaves

The influence of fertilization on senescence and nutrient remobilization in potato leaves was investigated in two farming systems on a soil with a poor potassium availability. The Conventional farming system followed good local practices including industrial products, while in the Bio-Dynamic farming system industrial fertilizers and synthetic pesticides were avoided. Potassium concentrations in the dry matter of mature leaves varied over a wide range. Nitrogen compounds (protein, chlorophyll) were less affected, and phosphorus concentrations in the dry matter were similar. Magnesium and potassium concentrations in the leaves were negatively correlated. In both farming systems senescence was advanced in plants with a low nutrient supply. Alkaline pyrophosphatase and aminopeptidase activities (in general highest in expanding and mature leaves) were lower and endopeptidase activities peaked earlier on plots with low fertilizer levels. A high percentage of potassium was remobilized from senescing leaves on unfertilized plots, but the phosphorus concentration remained high at the end of the season. The results suggest that the differential net remobilization of nitrogen, phosphorus and potassium depended on actual source/sink relations in the plants.     

Peroxidase-positive mononuclear leukocytes as possible precursors of human dendritic reticulum cells

In this report, we provide evidence that suggests the dendritic reticulum cells (DRC) occurring in germinal centers of lymphatic follicles originate from a distinct endogenous peroxidase-positive mononuclear blood cell subset. The new monoclonal antibody Ki-M4 showed a highly restricted reactivity, tested by immune histochemistry, being confined to DRC, lining cells of lymph node sinuses, and to 0.001% of nonadherent mononuclear blood cells separated at a density of 1.077 g/ml; the latter exhibited endogenous peroxidase activity in cytoplasmic granules. Such granules being specific for myelomonocytic cells implies that DRC may derive from a committed nonadherent subpopulation of this cell line, which in turn originates from bone marrow. The Ki-M4-reactive antigen was found to be destroyed by the majority of fixatives and to resist 4% paraformaldehyde for 10 min and cold acetone for 30 sec. In cell suspensions from human tonsils, Ki-M4 showed strong reactivity with the outer surface of DRC plasma membrane. This observation demonstrates the possibility of using Ki-M4 to separate DRC from cell suspensions in functional tests.