On the optimal harvesting of persistent age-structured populations

Summary This paper discusses optimal harvesting policies for age-structured populations harvested with effort independent of age.     

Involvement of IS1 in the dissociation of the r-determinant and RTF components of the plasmid R100.1

Summary Detailed mapping localized the PHO 1 mutation between the OLI 2 and OLI 4 loci on mitochondrial DNA of Saccharomyces cerevisiae.In its mitochondrially integrated form, the PHO 1-ATPase³ was difficult to identify either immunologically or by specific inhibitors like oligomycin and DCCD. Solubilization by Triton X-100 allowed unambiguuous identification of this enzyme as an authentic mitochondrial ATPase. However, Triton extraction produced a 2 to 3 fold enhancement of the PHO 1-ATPase activity which also became drastically cold-sensitive. The wild type ATPase was neither activated nor made cold-labile by solubilization, and retained full sensitivity to oligomycin and DCCD.Sucrose gradient analysis of the Triton-extracted ATPase from wild type, PHO 1 mutant and rho ^- strains showed a density difference between the solubilized PHO 1-and wild type ATPase, and similarity between solubilized PHO 1-and rho ^- ATPase (F₁).Whole cells of the PHO 1 mutant present considerably increased respiration rates.Comparison of oligomycin-sensitivity in whole cells, coupled isolated mitochondria and membrane-bound ATPase indicates a contrast between oligomycin-resistance of the ATPase and oligomycin-sensitivity of in vivo or in vitro coupling systems, which might characterize the products of this region of mitochondrial DNA.     

Localization of a nuclear envelope-associated protein by indirect immunofluorescence microscopy using antibodies against a major polypeptide from rat liver fractions enriched in nuclear envelope-associated material.

The location of a specific major polypeptide present in nuclear pore complex-enriched fractions from rat liver was examined by indirect immunofluorescence microscopy using chicken antibodies against this polypeptide. In both whole cell preparations of cultured cells grown on cover slips (mouse 3 T 3, rat kangaroo PtK2) and in frozen sections through liver and mammary gland tissue a strongly preferential, if not exclusive, binding to the nuclear periphery of interphase cells was observed. The specificity of this localization was demonstrated in these cells by the decoration of chromatin with antibodies against histones and of elements of the endoplasmic reticulum--outer mitochondrial membrane--system with antibodies to cytochrome b5. In addition, the localization was examined by electron microscopy using frozen sections and "immunoperoxidase" techniques. The results suggest that this polypeptide is contained in a protein specific for the nuclear periphery, probably closely associated with the peripheral chromatin.     

The gas vacuole membrane of Microcystis aeruginosa. A partial amino acid sequence.

The primary structure and hydrophobicity of the gas vacuole membrane were investigated in order to determine if this simple membrane, containing only one protein and no lipid, typifies integral membrane proteins. Peptides obtained by trypsin digestion and N-bromosuccinimide treatment of the gas vacuole protein were sequenced. Two aspects of the sequence analysis are of interest: a long stretch of 15 aliphatic residues (in peptide NPT), and a thrice repeating octapeptide. The location of the aliphatic portion of peptide NPT between the amino and carboxyl termini of the gas vacuole protein sequence means that the protein is amphipathic i.e., the protein has stretches of primarily either nonpolar residues or polar residues in its sequence. Based on this and a comparison of the relative polarities of gas vacuole protein with other integral membrane proteins, the gas vacuole protein is an integral membrane protein. The presence of the repeating octapeptide in the sequence suggests that it may serve as a structural building block for the membrane. Based on the presence of the aliphatic sequence in peptide NPT, a functional model for the gas vacuole membrane was proposed. To allow gas to pass through the membrane without a conformational change in the protein, it is speculated that either the gas must pass through the intermolecular space in the protein or through hydrophobic pores.     

Synthesis of charged amphipathic nitroxide lipid spin labels and an example of their application in membrane studies

The synthesis of a series of amphipathic nitroxide lipid spin labels is reported. Thus, 12-proxylhexadecanol has been converted into the versatile fatty acid spin label 14-proxylstearic acid. This substance was used to prepare 14-proxylstearyltrimethylammonium methanesulfonate, a positively charged label, and 14-proxylstearylmethyl phosphate sodium salt, a negatively charged label. Also prepared in the doxyl series were quaternary ammonium salts derived from 16-doxyl- and 7-doxylstearic acid. The positively charged and negatively charged proxyl labels were used in a preliminary experiment to investigate the role of charge in their interaction with reconstituted cytochrome oxidase. The average binding affinity of the negatively charged label is approximately 2-fold higher than that of the positively charged label at pH 7.4. At pH 5.5 the average relative affinity for negatively charged label is about 3.5-fold higher than that of positively charged label, suggesting that the ionizable group(s) on the protein can interact with the lipid headgroup.     

Amino acid sequence of an extracellular, phosphate-starvation-induced ribonuclease from cultured tomato (Lycopersicon esculentum) cells

The primary structure of an extracellular ribonuclease (RNase LE) from Pi-depleted media of cultured cells of Lycopersicon esculentum L. cv. Lukullus has been determined. This was carried out by analysis of peptides isolated after enzymatic and chemical cleavage of the reduced and S-ethylpyridylated protein. RNase LE consists of 205 amino acid residues and has a molecular mass of 22,666 Da and an isoelectric point of 4.24. The enzyme contains 10 half-cystines. There are no potential N-glycosylation sites in the sequence. The sequence of RNase LE is homologous with those of self-incompatibility proteins of several higher plant species and with those of a number of fungal RNases. The sequence similarity with the family of self-incompatibility proteins is greater than with the fungal RNases, suggesting that the self-incompatibility proteins arose from ancestral RNase by gene duplication after the divergence of higher plants and fungi. Two pentapeptide sequences, i.e. HGLWP and KHGTC (or KHGSC), are present at identical positions in all the aligned proteins, suggesting that they contribute to the active site.     

Evidence against the reported linkage of the cutaneous melanoma-dysplastic nevus syndrome locus to chromosome Ip36.

The reported linkage between cutaneous melanoma and the dysplastic nevus syndrome (CM/DNS) to markers located on the distal portion of the short arm of chromosome 1 was examined in three Utah kindreds ascertained for multiple cases of melanoma. Family members in these kindreds were genotyped for the two markers reported to be most closely linked in the Bale study, PND and D1S47. Both melanoma alone and a combined melanoma/DNS phenotype were analyzed; no evidence for linkage was found. By multipoint linkage analysis the CM/DNS locus was excluded from an area of 55 cM containing the PND-D1S47 region. Diagnostic or genetic heterogeneity are alternate explanations for the discrepancy between our observations and those of Bale et al.