The Dentition and Feeding Mechanism in Adults of the Southern Hemisphere Lamprey Geotria australis Gray

Scanning electron micrographs of the teeth and sections and dissections of the head have been used to describe the functional interrelationships between the dentition and associated cartilages, muscles and ligaments in adults of the southern hemisphere lamprey Geotria australis. These studies, together with manipulation of the piston and oral disc in living specimens, elucidated the probable feeding mechanism in this species. The main cutting action appears to result from a scissoring movement brought about by the rapid interlocking of the three sharp and stout cusps of the transverse lingual lamina with large grooves on the rear face of the supraoral lamina. The movement of excised flesh back through the oral passage to the pharynx would be facilitated by the action of the pair of strongly cuspid longitudinal lingual laminae. The unique oral disc teeth of G. australis are apparently adapted to allow the disc to slide forward over the host and yet restrict any tendency to slip backwards.     

Replication of simian herpesvirus SA8 and identification of viral polypeptides in infected cells

The replication of the simian herpesvirus SA8 in Vero cells was examined. The time course of replication of the simian herpesvirus SA8 was found to be similar to that of the herpes simplex viruses. Infectious progeny virions were first detectable by 6 h postinfection and were readily released into the extracellular fluids beginning at 9 h postinfection. All cell lines tested, with the exception of Madin-Darby canine kidney cells, were permissive for SA8. Analysis of SA8-infected cells by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed over 40 infected cell polypeptides ranging in molecular weight from 158,000 to less than 10,000. Of these proteins, 23 were present in virions. Three classes of infected cell polypeptides could be identified based on the kinetics of their synthesis. Post-translational processing of several SA8-induced proteins was also observed in pulse-chase experiments. Six distinct SA8-specific glycoproteins ranging from 118,000 to 19,500 daltons were also identified in infected cells. Of these glycoproteins, five were present in virions.     

Variation of expression of histocompatibility antigens on tumor cells: absence of H-2Kk-gene products from a gross-virus-induced leukemia in BALB.K

The antigenic profile of the K-GV tumor of BALB.K origin, induced by Gross virus and maintained in vitro and in vivo, was investigated by serological and immunochemical methods and techniques of cell-mediated immunity. The H-2K^k-gene products were absent by several criteria: (1) monoclonal antibody and conventional alloantisera directed against the H-2K^k antigenic specificities were nonreactive by direct testing and by absorptions. (2) H-2K^k products could not be precipitated from glycoprotein or protein extracts of the radiolabeled K-GV tumor. (3) Cytotoxic effectors against H-2K^k produced by sensitization in vitro and in vivo failed to kill K-GV target cells. (4) The tumor could neither stimulate BALB.B congenic mice to produce cytotoxic effectors nor specific cytotoxic antibody against H-2K^k-gene products. In contrast, the H-2D^k antigen was readily detectable by all these criteria. These findings therefore describe a tumor which has selectively lost the H-2K-gene products. The K-GV tumor was able to generate Gross-virus-specific CTL, but had greatly reduced susceptibility to lysis by Gross-virus-specific CTL generated by H-2K expressing AKR (H-2 ^k) tumors. These findings have important implications for the associative recognition of tumor antigens and the immune surveillance of virally induced tumors.Abbreviations used in this paper MHS major histocompatibility system - LcH Lens culinaris hemagglutinin - SDS sodium dodecyl sulfate - CTL cytotoxic T lymphocytes - GCSA Gross-virus-induced cell-surface antigen - MuLV murine leukemia virus     

Repair methylation of parental DNA in synchronized cultures of Novikoff hepatoma cells.

Parental and filial DNA strands were isolated from a Novikoff rat hepatoma cell line, synchronized by S-phase arrest with excess thymidine, that had completed up to one round of DNA replication in the presence of (14-C-methyl)methionine and (6-3-H) bromodeoxyuridine. Both strands were methylated, the proportion of total methyl label in parental DNA increasing slightly with time in S-phase. The studies were repeated with (14-C-methyl)methionine and (3-H)deoxycytidine to determine if parental methylation occurred on extant or repair-inserted cytosine residues. Both (14-C) and (3-H) were found in parental DNA. The (14-C)/(3-H) ration of parental DNA-5-methylcytosine was about twice that in filial DNA while the (3-H) data showed twice the concentration of 5-methylcytosine in parental compared to filial DNA. Thus parental methylation occurred on repair-inserted cytosine residues and resulted in overmethylation. That the DNA damage and repair was due to 5-phase arrest was shown by repeating the studies using a sequential mitotic-G1 arrest method. With this method little (14-C) or (3-H) was found in parental DNA. We conclude that S-phase arrest leads to DNA damage and repair with subsequent overmethylation of repair-inserted cytosines; that sequential mitotic-G1 arrest minimizes DNA damage; and, that the latter technique, suitable for synchronization of large quantities of cells, may prove useful in relatively artifact-free studies of eukaryotic DNA replication.     

The association of chloroplast peripheral reticulum with low photorespiration rates in a photorespiring plant species

Summary A peripheral reticulum occurs in mesophyll chloroplasts of the pentose cycle plantDactylis glomerata L. (orchardgrass). This structural feature was previously thought to occur primarily in the chloroplasts of tropical grasses and other species utilizing the C₄-dicarboxylic-acid photosynthesis pathway. Since the peripheral reticulum is seen in a selection ofD. glomerata which has a low rate of photorespiration, but not in a selection which has a high rate of photorespiration (Carlsonet al., 1971), photorespiratory rates may be dependent in part on the presence or absence of a chloroplast peripheral reticulum.Cooperative investigations of the University of Florida and the Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture. Trade names are mentioned for clarity and do not imply endorsement of products by the U. S. Department of Agriculture. Journal Series No. 3813 of the Florida Agricultural Experiment Station.     

In vivo imaging of C. elegans ASH neurons: cellular response and adaptation to chemical repellents

ASH sensory neurons are required in Caenorhabditis elegans for a wide range of avoidance behaviors in response to chemical repellents, high osmotic solutions and nose touch. The ASH neurons are therefore hypothesized to be polymodal nociceptive neurons. To understand the nature of polymodal sensory response and adaptation at the cellular level, we expressed the calcium indicator protein cameleon in ASH and analyzed intracellular Ca(2+) responses following stimulation with chemical repellents, osmotic shock and nose touch. We found that a variety of noxious stimuli evoked strong responses in ASH including quinine, denatonium, detergents, heavy metals, both hyper- and hypo-osmotic shock and nose touch. We observed that repeated chemical stimulation led to a reversible reduction in the magnitude of the sensory response, indicating that adaptation occurs within the ASH sensory neuron. A key component of ASH adaptation is GPC-1, a G-protein gamma-subunit expressed specifically in chemosensory neurons. We hypothesize that G-protein gamma-subunit heterogeneity provides a mechanism for repellent-specific adaptation, which could facilitate discrimination of a variety of repellents by these polymodal sensory neurons.     

Essential roles of the Fas-associated death domain in autoimmune encephalomyelitis

The Fas-associated death domain (FADD) protein mediates apoptosis by coupling death receptors with the caspase cascade. Paradoxically, it also promotes cell mitosis through its C-terminal region. Apoptosis and mitosis are opposing processes that can have radically different consequences. To determine which of the FADD effects prevails in T cell-mediated autoimmune diseases, we studied myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) using mice that express a dominant-negative FADD (FADD-DN) transgene in the T cell lineage. We found that FADD blockade in T cells prevented the development of autoimmune encephalomyelitis and inhibited both Th1 and Th2 type responses. Myelin oligodendrocyte glycoprotein-specific T cell proliferation was also dramatically reduced in FADD-DN mice despite the resistance of T cells to activation-induced cell death. These results indicate that although FADD expressed by T cells is involved in regulating both mitosis and apoptosis, its effect on mitosis prevails in EAE, and that strategies inhibiting FADD functions in T cells could be effective in preventing the disease.     

Synthesis and antibacterial activity of C2-fluoro, C6-carbamate ketolides, and their C9-oximes

Novel C6-carbamate ketolides with C2-fluorination and C9-oximation have been synthesized. The best compounds in this series displayed MIC values of 0.03-0.12 microg/mL against streptococci containing erm and mef resistance determinants and 2-4 microg/mL against Haemophilus influenzae. Several compounds also showed measurable activity against erm(B)-containing enterococci with MIC values of 2-8 microg/mL. In vivo activity was adversely affected by fluorination, possibly as a result of increased serum protein binding.     

An Integrated Proteomic Approach Uncovers Novel Substrates and Functions of the Lon Protease in Escherichia coli

Controlling the cellular abundance and proper function of proteins by proteolysis is a universal process in all living organisms. In Escherichia coli, the ATP‐dependent Lon protease is crucial for protein quality control and regulatory processes. To understand how diverse substrates are selected and degraded, unbiased global approaches are needed. We employed a quantitative Super‐SILAC (stable isotope labeling with amino acids in cell culture) mass spectrometry approach and compared the proteomes of a lon mutant and a strain producing the protease to discover Lon‐dependent physiological functions. To identify Lon substrates, we took advantage of a Lon trapping variant, which is able to translocate substrates but unable to degrade them. Lon‐associated proteins were identified by label‐free LC‐MS/MS. The combination of both approaches revealed a total of 14 novel Lon substrates. Besides the identification of known pathways affected by Lon, for example, the superoxide stress response, our cumulative data suggests previously unrecognized fundamental functions of Lon in sulfur assimilation, nucleotide biosynthesis, amino acid and central energy metabolism.