Cation binding to membranes: Competition between mono-, di- and trivalent cations

The binding of mono-, di- and trivalent cations to negatively charged surfaces is studied within the framework of a modified Gouy-Chapman equation. For any given combination of ions of the above valences, the existence and uniqueness of the solution for the surface potential is shown. The treatment provides the surface potential and charge density. For a system containing only monovalent and divalent ions, analytical solutions are given. When trivalent ions are also present, a procedure based on numerical integration is described. The distance dependence of the electrostatic potential for planar surfaces is given. The calculations provide the amount of cations tightly bound and the amount trapped in the double layer region. The competition between cations for binding to surfaces is elucidated.     

Chlorxanthomycin, a Fluorescent, Chlorinated, Pentacyclic Pyrene from a Bacillus sp.

A gram-positive Bacillus sp. that fluoresces yellow under long-wavelength UV light on several common culture media was isolated from soil samples. On the basis of carbon source utilization studies, fatty acid methyl ester analysis, and 16S ribosomal DNA analysis, this bacterium was most similar to Bacillus megaterium. Chemical extraction yielded a yellow-orange fluorescent pigment, which was characterized by X-ray crystallography, mass spectrometry, and nuclear magnetic resonance spectroscopy. The fluorescent compound, chlorxanthomycin, is a pentacyclic, chlorinated molecule with the molecular formula C₂₂H₁₅O₆Cl and a molecular weight of 409.7865. Chlorxanthomycin appears to be located in the cytoplasm, does not diffuse out of the cells into the culture medium, and has selective antibiotic activity.     

A liquid cytokinin pulse induces adventitious shoot formation from Douglas-fir cotyledons

Summary The effects of high-concentration, 2-h liquid pulses of N⁶-benzylaminopurine (BA) and thidiazuron (TD) on adventitious bud and shoot formation were tested in cotyledons of Douglas-fir (Pseudotsuga menziesii). Seedling age proved important; on average, cotyledons from the youngest seedlings formed 10-fold more buds than cotyledons from the oldest seedlings. Optimal cytokinin concentrations for the youngest cotyledons were 400 and 800 M BA, and 100 and 200 M TD. Shoots developed best from buds induced with 300, 400, and 800 M BA. Four gelling agents were tested; BRL agarose yielded more than three times the number of buds, and Gelrite nearly twice the number of buds, as either Sigma agar or Difco Bacto-Agar. One of the best treatments (400 M BA, agarose) yielded more cotyledons with buds, and more buds per cotyledon, than when cytokinins were incorporated into the growth medium.Abbreviations BA N⁶-benzylaminopurine - TD thidiazuron - SH Schenk and Hildebrandt (1972) - NAA 1-naphthaleneacetic acid Paper 2691 of the Forest Research Laboratory, Oregon State University, Corvallis. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the authors or Oregon State University.     

Survival of Vibrio parahaemolyticus in Cooked Seafood at Refrigeration Temperatures

The growth and survival of two strains of Vibrio parahaemolyticus isolated during food-borne gastroenteritis outbreaks in Japan and surface inoculated on cooked shrimp, shrimp with sauce, or cooked crab were tested at various refrigeration temperatures during a 48-h holding period. On cooked shrimp and crab, the vibrios grew well at 18.3 C, but their numbers declined gradually at 10 C and below. At 12.8 C, vibrios remained static for the most part. Thus, it appeared that 12.8 C was the borderline temperature for growth of the organism on cooked seafood. When cocktail sauce was added to surface-inoculated shrimp at a ratio of 2:1, the vibrio die-off rate was accelerated. In the shrimp and sauce few cells remained after 48 h, but in the sauce alone die-off was complete at 6 h.     

Viral DNA in transformed cells: II. A study of the sequences of adenovirus 2 DNA in nine lines of transformed rat cells using specific fragments of the viral genome

³²P-labeled adenovirus 2 DNA was treated with restricting endonuclease from Escherichia coli strain RY-13 (Yoshimori, 1972) (EcoRI) or restricting endonuclease from Hemophilus parainfluenzae (Hpa I) and the resulting fragments of DNA were separated by gel electrophoresis. The kinetics of renaturation of each of the fragments and of complete adenovirus 2 DNA were measured in the presence of DNA extracted from nine lines of adenovirus 2-transformed rat cells and from control cells. Six of the transformed cell lines contained viral DNA sequences homologous to two of the seven Hpa I⁴ fragments and to part of one of the six EcoRI fragments. From the order of the fragments formed by EcoRI and Hpa I on the adenovirus 2 map we conclude that these cell lines contain only the segment of viral DNA that stretches from the left-hand end to a point about 14% along the viral genome. Thus, any viral function expressed in transformed cells must be coded by this small section of viral DNA. The three remaining lines of adenovirus 2-transformed rat cells are more complicated and contain not only the sequences from the left-hand end of the viral DNA, but also other segments of the viral genome. However, no adenovirus 2-transformed rat cell contained DNA sequences homologous to the complete viral genome.     

Trans-ovum transmission of a cytoplasmic polyhedrosis virus of Heliothis virescens (Lepidoptera: Noctuidae)

Adults of Heliothis virescens infected with a cytoplasmic polyhedrosis virus (CPV) produced healthy offspring when their eggs were surface sterilized with either 15% formaldehyde or 0.2% sodium hypochlorite solution. Larvae from infected parents (1) cultured on a vitamin-deficient medium, (2) exposed to cold treatment (5°C, 24 hr), or (3) as progeny of adults from diapaused infected pupae, produced the same number of infected individuals as larvae reared in the customary way. Field studies indicated that the percent of CPV infection in larvae originating from virus-infected parents was density dependent.     

Analysis for possible linkage between the loci for the Waardenburg syndrome and various blood groups and serological traits

Summary Linkage was sought between the Waardenburg syndrome locus and the loci for various genetic markers segregating in a single family. Close linkage was shown to be unlikely with the loci for Rh, MN, Ag, ADA, HL-A, and Gm. Evidence obtained is consistent with the possibility of linkage with the locus for the AB0 blood group, but study of additional families will be required to provide a definite answer.

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Zusammenfassung In einer Familie wurde nach Genkopplung zwischen dem locus für das Waardenburg-Syndrom und verschiedenen genetischen Markern gefahndet. Für die loci für Rh, MN, Ag, ADA, HL-A und Gm wurde enge Kopplung als unwahrscheinlich erwiesen. Dagegen lassen die Daten die Annahme einer Kopplung mit dem AB0-locus zu. Für eine endgültige Entscheidung müßten zusätzliche Familien untersucht werden.

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Research supported by grants No. HD 04134, HL 09011, and HL 08630 from the National Institutes of Health.     

Superoxide Dismutase in Bacillus popilliae, a Catalaseless Aerobe

Bacillus popilliae, a cytochrome-containing aerobic organism that lacks catalase and peroxidase, was examined for superoxide dismutase activity. The activity was quite high relative to a wide variety of organisms previously surveyed and was induced by oxygen. No correlation could be made between superoxide dismutase activity and the unexplained death of this organism after completion of exponential growth.     

Studies on the mechanism of freezing damage to mouse liver. IV. Effects of ultrarapid freezing on structure and function of isolated mitochondria

Mouse liver mitochondria isolated in 0.25 m sucrose were subjected to progressively increasing cooling rates by quench-thaw from liquid nitrogen, isopentane at ?155 °C, and liquid propane at ?185 °C. Structural damage, assessed by electron microscopy and by quantitation of supernatant protein, increased progressively with the cooling rate. Oxidative phosphorylation (with succinate as substrate) was destroyed at all three cooling rates, while acceptorless respiration (succinoxidase) showed a progressive increase with cooling rate, suggesting uncoupling. The succinate cytochrome c reductase system showed no functional damage. Dimethyl sulfoxide, 10–20% by volume, markedly improved structural preservation of the mitochondria, but did not restore oxidative phosphorylation, and further increased the degree of uncoupling.Upon resuspending the mitochondria in 0.15 m KCl prior to quench-thaw, the succinate cytochrome c reductase system displayed an optimal recovery after isopentane quench-thaw, with a sharp decline at still higher cooling rates, as had been encountered in tissue slice experiments, suggesting a compartmental ice-transition in mitochondria over this range of cooling rates. Structurally, however, the KCl-resuspended mitochondria were equally and maximally disrupted by all three quench-thaw procedures. Sixty percent of the mitochondrial protein was extruded into the supernate, far above the levels released from sucrose-suspended mitochondria by quench-thaw and significantly above the 45% released by sonication. Compared to isotonic KCl, isotonic sucrose was thus providing full cryoprotection for the reductase complex and moderate protection for mitochondrial structure. The discrepancies among the several structural and functional indicators of mitochondrial damage leave little possibility that a single compartmental ice-transition, occurring over this range of cooling rates, could provide a coherent explanation for freezing damage to liver mitochondria.