“Unblocking” Serum Activity <Emphasis Type="Italic">in vitro</Emphasis> in the Polyoma System may Correlate with Antitumour Effects of Antiserum <Emphasis Type="Italic">in vivo</Emphasis>

In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual^1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro^2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development^5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera⁹. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo^10,11, which has been tentatively attributed to its unblocking activity^8,9 or, possibly, to a complement-dependent cytotoxicity¹⁰. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity^9,10.     

On the mechanism of ATP-induced shape changes in the human erythrocyte membranes: the role of ATP

In the preceding paper (Sheetz, M. and S.J. Singer. 1977. J Cell Biol. 73:638-646) it was shown that erythrocyte ghosts undergo pronounced shape changes in the presence of mg-ATP. The biochemical effects of the action of ATP are herein examined. The biochemical effects of the action of ATP are herein examined. Phosphorylation by ATP of spectrin component 2 of the erythrocyte membrane is known to occur. We have shown that it is only membrane protein that is significantly phosphorylated under the conditions where the shape changes are produced. The extent of this phosphorylation rises with increasing ATP concentration, reaching nearly 1 mol phosphoryle group per mole of component 2 at 8mM ATP. Most of this phosphorylation appears to occur at a single site on the protein molecule, according to cyanogen bromide peptide cleavage experiments. The degree of phosphorylation of component 2 is apparently also regulated by a membrane-bound protein phosphatase. This activity can be demonstrated in erythrocyte ghosts prepared from intact cells prelabeled with [(32)P]phosphate. In addition to the phosphorylation of component 2, some phosphorylation of lipids, mainly of phosphatidylinositol, is also known to occur. The ghost shape changes are, however, shown to be correlated with the degree of phosphorylation of component 2. In such experiment, the incorporation of exogenous phosphatases into ghosts reversed the shape changes produced by ATP, or by the membrane-intercalating drug chlorpromazine. The results obtained in this and the preceding paper are consistent with the proposal that the erythrocyte membrane possesses kinase and phosphates activities which produce phosphorylation and dephosphorylation of a specific site on spectrin component 2 molecules; the steady-state level of this phosphorylation regulates the structural state of the spectrin complex on the cytoplasmic surface of the membrane, which in turn exerts an important control on the shape of the cell.     

The response of sheep to parenteral vaccination and immunizing infections against the abomasal nematode, Haemonchus contortus

Adams D. B., Beh K. J. and Davies H. I. 1982. The response of sheep to parenteral vaccination and immunizing infections against the abomasal nematode, Haemonchus contortus. International Journal for Parasitology12: 445–449. Subcutaneous injection of relatively large amounts of unfractionated homogenates of adults plus infective larvae of Haemonchus contortus emulsified in complete Freund's adjuvant produced a degree of protective immunity when challenge infection was given eight weeks after the first or only dose of vaccine. In an attempt to improve acquired immunity, parenteral vaccination was either followed or preceded by a short immunizing infection with H. contortus, which was terminated by anthelmintic before patency. This treatment aimed at stimulating general responsiveness to worm antigens and invoking mucosal immunity in the abomasum. Disparate results were obtained; immunizing infections either increased immunity or made sheep more susceptible to challenge infection. In this latter situation, the unresponsiveness associated with primary infection with H. contortus may have been increased.     

Immunity acquired by sheep from an experimental infection with haemonchus contortus

Adams D.B. and Beh K.J. 1981. Immunity acquired by sheep from an experimental infection with Haemonchus contortus. International Journal for Parasitology11: 381–386. A primary infection of sheep with a single dose of Haemonchus contortus larvae was traced by faecal egg counts until it had substantially declined after 55 weeks. These primed sheep were then given a sequence of two reinfections with the parasite. Comparison of faecal egg counts in primed sheep and in two separate groups of previously worm-free sheep showed that primary infection conferred significant immunity. This, however, was not sufficiently protective to prevent the development of further anaemia and faecal egg counts indicative of clinical haemonchosis. It is suggested that an adaptation in the host-parasite relationship which promotes the longevity of primary infection with H. contortus may also moderate the induction of acquired immunity.The titre of haemagglutinating antibody specific for H. contortus rose in serum during the course of primary infection, but the two reinfections did not stimulate a rise in titre. Titres of haemagglutinating antibody before reinfection did not correlate with subsequent faecal egg counts.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Arv1 Regulates PM and ER Membrane Structure and Homeostasis But is Dispensable for Intracellular Sterol Transport

The pan‐eukaryotic endoplasmic reticulum (ER) membrane protein Arv1 has been suggested to play a role in intracellular sterol transport. We tested this proposal by comparing sterol traffic in wild‐type and Arv1‐deficient Saccharomyces cerevisiae. We used fluorescence microscopy to track the retrograde movement of exogenously supplied dehydroergosterol (DHE) from the plasma membrane (PM) to the ER and lipid droplets and high performance liquid chromatography to quantify, in parallel, the transport‐coupled formation of DHE esters. Metabolic labeling and subcellular fractionation were used to assay anterograde transport of ergosterol from the ER to the PM. We report that sterol transport between the ER and PM is unaffected by Arv1 deficiency. Instead, our results indicate differences in ER morphology and the organization of the PM lipid bilayer between wild‐type and arv1Δ cells suggesting a distinct role for Arv1 in membrane homeostasis. In arv1Δ cells, specific defects affecting single C‐terminal transmembrane domain proteins suggest that Arv1 might regulate membrane insertion of tail‐anchored proteins involved in membrane homoeostasis .     

Overlapping functions of the yeast oxysterol-binding protein homologues

The Saccharomyces cerevisiae genome encodes seven homologues of the mammalian oxysterol-binding protein (OSBP), a protein implicated in lipid trafficking and sterol homeostasis. To determine the functions of the yeast OSBP gene family (OSH1-OSH7), we used a combination of genetics, genomics, and sterol lipid analysis to characterize OSH deletion mutants. All 127 combinations and permutations of OSH deletion alleles were constructed. Individual OSH genes were not essential for yeast viability, but the elimination of the entire gene family was lethal. Thus, the family members shared an essential function. In addition, the in vivo depletion of all Osh proteins disrupted sterol homeostasis. Like mutants that affect ergosterol production, the viable combinations of OSH deletion alleles exhibited specific sterol-related defects. Although none of the single OSH deletion mutants was defective for growth, gene expression profiles revealed that each mutant had a characteristic molecular phenotype. Therefore, each gene performed distinct nonessential functions and contributed to a common essential function. Our findings indicated that OSH genes performed a multitude of nonessential roles defined by specific subsets of the genes and that most shared at least one essential role potentially linked to changes in sterol lipid levels.     

Genetic interactions between KAR7/SEC71, KAR8/JEM1, KAR5, and KAR2 during nuclear fusion in Saccharomyces cerevisiae

During mating of Saccharomyces cerevisiae, two nuclei fuse to produce a single diploid nucleus. Two genes, KAR7 and KAR8, were previously identified by mutations that cause defects in nuclear membrane fusion. KAR7 is allelic to SEC71, a gene involved in protein translocation into the endoplasmic reticulum. Two other translocation mutants, sec63-1 and sec72Delta, also exhibited moderate karyogamy defects. Membranes from kar7/sec71Delta and sec72Delta, but not sec63-1, exhibited reduced membrane fusion in vitro, but only at elevated temperatures. Genetic interactions between kar7 and kar5 mutations were suggestive of protein-protein interactions. Moreover, in sec71 mutants, Kar5p was absent from the SPB and was not detected by Western blot or immunoprecipitation of pulse-labeled protein. KAR8 is allelic to JEMI, encoding an endoplasmic reticulum resident DnaJ protein required for nuclear fusion. Overexpression of KAR8/JEM1 (but not SEC63) strongly suppressed the mating defect of kar2-1, suggesting that Kar2p interacts with Kar8/Jem1p for nuclear fusion. Electron microscopy analysis of kar8 mutant zygotes revealed a nuclear fusion defect different from kar2, kar5, and kar7/sec71 mutants. Analysis of double mutants suggested that Kar5p acts before Kar8/Jem1p. We propose the existence of a nuclear envelope fusion chaperone complex in which Kar2p, Kar5p, and Kar8/Jem1p are key components and Sec71p and Sec72p play auxiliary roles.