Directionality and Nonreciprocality of Chi-Stimulated Recombination in Phage λ

Chi's are genetic elements that stimulate generalized recombination in their locale in phage λ. All Chi's, wherever located on λ's chromosome, act asymmetrically in crosses blocked in DNA replication: (1) They stimulate exchange primarily to their left on the conventional λ map, and (2) the stimulated exchange is frequently nonreciprocal, the recombinant carrying the Chi element being produced less often than the complementary product.     

Histochemical Evidence for the Occurrence of Oligomycin-sensitive Plasmalemma ATPase in Corn Roots

A cytochemical study has been made on the localization of ATPase activity in corn (Zea mays L.) roots. Light microscopy shows washing for 4 hours to increase the general ATPase activity in the peripheral layers of the root cortex; oligomycin and N,N-dicyclohexylcarbodiimide inhibit this activity, oligomycin being more effective. Ultrastructural studies of ATPase location show oligomycin treatment to inhibit both mitochondrial and plasmalemma ATPase, but only in the epidermis and outer cortex. Studies with lipid-soluble dyes indicate that oligomycin might not penetrate very deeply into root tissue in the time span of these experiments. It is suggested that the strong inhibition of ion absorption by oligomycin without a corresponding decline in ATP content is probably due to inhibition of ion absorption in the peripheral cell layers, thus limiting the supply of ion for symplastic transport to the uninhibited tissues.     

Chemoprevention clinical trials.

As part of a program to develop drugs which will delay or prevent cancer in humans, the Chemoprevention Branch, National Cancer Institute, National Institutes of Health, is sponsoring 12 Phase I and 22 Phase II and III clinical trials. Three agent classes are significantly advanced in the trials. These are the retinoids, including 13-cis-retinoic acid, retinol, and 4-hydroxyphenylretinamide (nine studies), beta-carotene (seven studies), and calcium compounds (three studies). In addition, six promising new compounds are in Phase I or Phase II trials. These are: piroxicam, ibuprofen, oltipraz (a dithiolthione), difluoromethylornithine, glycyrrhetinic acid, and N-acetylcysteine. Key concepts related to the development of cancer chemopreventive agents are (1) the need for long-term administration, (2) the need for oral route of administration, (3) the matching of toxic side effects to degree of cancer risk.     

Chick embryo fibroblasts produce two forms of hyaluronidase

Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu.     

Acyltransferases and the biosynthesis of pulmonary surfactant lipid in adenoma alveolar type II cells.

Acyltransferases are present in microsomes from alveolar type II cell adenomas (produced by urethan injections) that transfer palmitic acid in the presence of CoA, ATP, and Mg⁺⁺ to $\text{sn}$-glycerol-3-P to form phosphatidic acid, to dihydroxyacetone-P to form acyldihydroxyacetone-P, and to 1-acyl-$\text{sn}$-glycero-3-phosphocholine to form 3-$\text{sn}$-phosphatidylcholine. The data clearly demonstrate that the microsomal preparations can catalyze significant incorporation of palmitic acid into the 2-position of the disaturated species of 3-sn-phosphatidylcholine independently of phosphatidic acid formation as evidenced by the fact that $\text{sn}$-glycerol-3-P and calcium ions (which inhibit choline phosphotransferase) did not influence the incorporation of palmitic acid into the main surfactant lipid. Thus, a deacylation-acylation reaction involving 2-lysophosphatidylcholine appears to be an important pathway for the synthesis of surfactant lipid in alveolar type II cells; the control of acyl specificity at the 2-position is determined by the relative concentrations of the coparticipating substrates, l-palmitoyl-$\text{sn}$-glycero-3-phosphocholine and palmitoyl-CoA.     

MALDI mass spectrometry in prostate cancer biomarker discovery

Matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS) is a highly versatile and sensitive analytical technique, which is known for its soft ionisation of biomolecules such as peptides and proteins. Generally, MALDI MS analysis requires little sample preparation, and in some cases like MS profiling it can be automated through the use of robotic liquid-handling systems. For more than a decade now, MALDI MS has been extensively utilised in the search for biomarkers that could aid clinicians in diagnosis, prognosis, and treatment decision making. This review examines the various MALDI-based MS techniques like MS imaging, MS profiling and proteomics in-depth analysis where MALDI MS follows fractionation and separation methods such as gel electrophoresis, and how these have contributed to prostate cancer biomarker research. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.     

Proteomic identification of the cerebral cavernous malformation signaling complex

Cerebral cavernous malformations (CCM) are sporadic or inherited vascular lesions of the central nervous system characterized by dilated, thin-walled, leaky vessels. Linkage studies have mapped autosomal dominant mutations to three loci: ccm1 (KRIT1), ccm2 (OSM), and ccm3 (PDCD10). All three proteins appear to be scaffolds or adaptor proteins, as no enzymatic function can be attributed to them. Our previous results demonstrated that OSM is a scaffold for the assembly of the GTPase Rac and the MAPK kinase kinase MEKK3, for the hyperosmotic stress-dependent activation of p38 MAPK. Herein, we show that the three CCM proteins are members of a larger signaling complex. To define this complex, epitope-tagged wild type OSM or OSM harboring the mutation of F217-->A, which renders the OSM phosphotyrosine binding (PTB) domain unable to bind KRIT1, were stably introduced into RAW264.7 mouse macrophages. FLAG-OSM or FLAG-OSMF217A and the associated complex members were purified by immunoprecipitation using anti-FLAG antibody. OSM binding partners were identified by gel-based methods combined with electrospray ionization-MS or by multidimensional protein identification technology (MudPIT). Previously identified proteins that associate with OSM including KRIT1, MEKK3, Rac, and the KRIT1-binding protein ICAP-1 were found in the immunoprecipitates. In addition, we show for the first time that PDCD10 binds to OSM and is found in cellular CCM complexes. Other prominent proteins that bound the CCM complex include EF1A1, RIN2, and tubulin, with each interaction disrupted with the OSMF217A mutant protein. We further show that PDCD10 binds phosphatidylinositol di- and triphosphates and OSM binds phosphatidylinositol monophosphates. The findings define the targeting of the CCM complex to membranes and to proteins regulating trafficking and the cytoskeleton.     

Genetic consequences of Pleistocene fragmentation: Isolation, drift, and loss of diversity in rock iguanas (Cyclura)

Pleistocene fragmentation of the Great BahamaBank resulted in one large and several smallpopulations of rock iguanas (Cycluracychlura). We explore patterns of geneticvariation within and among these islandpopulations using mitochondrial sequence data(partial ND4 to tRNA^Leu) in combinationwith eight polymorphic microsatellite loci (2to 10 alleles). Genetic data support twophylogeographically distinct groups, AndrosIsland and the Exuma cays. This resultconflicts with current subspecific taxonomy inwhich three subspecies are described. Analysesof allelic data indicate that most islandpopulations are currently demographicallyindependent. Pairwise Fst values between eightisland populations range from 0.18 to 0.63, and6 of 135 individuals are misassigned in anassignment test. Population-genetic diversityis characterized using standard measures suchas number of alleles and heterozygosity (H) inaddition to a normalized Shannon-Weaver indexof diversity (D). We find genetic diversity inthe Andros Island population comparable to thatin other non-piscine animals (avg. # ofalleles = 5, avg. H = 0.56, avg. D = 0.66) while inthe Exuma cays populations these measures aremuch lower (avg. # of alleles = 2.75–1.625, avg.H = 0.43–0.17, avg. D = 0.45–0.18). These dataare used to discuss conservation managementstrategies, including prioritization andtranslocation.     

Differential mapping of Fc gamma-binding and monoclonal antibody-reactive epitopes on gE, the Fc gamma-binding glycoprotein of herpes simplex virus type 1.

The entire 396 residue extracellular sequence of gE the HSV-1 Fc gamma-binding glycoprotein has been studied to determine epitopes binding to two mAb II-481 and 88S previously demonstrated to react with gE at or near the Fc gamma-binding regions. Overlapping 7-mers constructed from the established sequence were tested with mAb II-481 and 88S along with their Fab fragments. Control mAb of the same IgG 2b subclass as well as whole rabbit and human IgG and Fc were also tested for binding to overlapping linear sequences using the ELISA pin assay to map Fc gamma-binding regions. Six sequences PKTSWRRVS, GLYTLSV, QVASVVLVVQP, PAPPRSWP, CLYHPQLP, and ASTWTSRL were found that constituted major regions binding to the two different mAb of the same specificity. Glycine substitution for each residue within these sequences indicated that arginine 29, tryptophane 70, valine 144, valine 157, arginine 208, histidine 283, and arginine 305 constituted important portions of the II 481 mAb-reactive epitope. Many of the same regions along with one other, GPLHPSW, appeared to be involved in Fc gamma binding. Substitution of glycine for each residue indicated that histidine 67, tryptophane 70, valine 71, valine 157, valine 158, valine 160, valine 161, tryptophane 210, serine 279, cysteine 280, leucine 281, tyrosine 282, histidine 283, proline 284, glutamine 285, proline 287, tryptophane 302, and arginine 305 were important for Fc gamma-binding. Inhibition by gE peptides of rosetting of E sensitized with rabbit IgG antibody around HSV-1-infected cells, as well as inhibition of rosetting using F(ab)2 fragments of rabbit antibodies to these peptides was used to assay relative contributions of all seven regions to Fc gamma-binding activity. Our results provide a tentative map of mAb binding and Fc gamma-reactive sites on gE. mAb and Fc gamma binding of a limited number of individual antigenic amino acids widely distributed among the separate reactive regions suggest that many of the same separate residues contribute both to antigenicity as well as to Fc gamma-binding activity.