Enterochromaffin-like cells in the rat stomach: effect of α-fluoromethylhistidine-evoked histamine depletion

Summary In the rat, gastric histamine is stored predominantly in the enterochromaffin-like (ECL) cells, which are located basally in the oxyntic mucosa. The functional significance of histamine in the ECL cells is a matter of speculation. In this study the effect of depletion of histamine on the properties and ultrastructure of the ECL cells was examined. Histamine synthesis was inhibited with -fluoromethylhistidine (3 mg·kg^-1·h^-1) given via osmotic minipumps over a period of 24 h. The treatment reduced the histidine decarboxylase activity (approximately 20% remaining) and histamine concentration (less than 20% remaining) in the oxyntic mucosa, as well as the intensity of histamine- and chromogranin A-immunostaining in the ECL cells, compared to control rats. The cytoplasmic (secretory) granules/vesicles were greatly reduced in number and size following -fluoromethylhistidine administration. The histamine immunostaining of the mast cells, which occurs at the mucosal surface and in the submucosa, appeared unaffected. We conclude that ECL cell histamine accounts for at least 80% of the total oxyntic mucosal histamine in the rat and that it represents a more mobile pool than mast cell histamine. The reduction in the number and size of the ECL cell granules/vesicles following histamine depletion is in accord with the idea that they represent the storage site for histamine.     

Effects of tumour necrosis factor-α (cachectin) on glucose metabolism in the rat

Intravenous administration of a single dose (20 g) of recombinant tumour necrosis factor- (TNF, cachectin) to rats decreased the rate of intestinal glucose absorption. In vivo, the oxidation of [U-¹⁴C]glucose to ¹⁴CO₂ was significantly increased by the cytokine. In addition, [¹⁴C]lipid accumulation from [U-¹⁴C]glucose was increased both in liver and brown adipose tissue of the TNF-injected animals. The decrease observed in intestinal glucose absorption was not associated with changes in intestinal metabolism. There was no difference in glucose metabolism by isolated enterocytes from either control or TNF-injected rats whether in the absence or presence of different concentrations of the cytokine in the incubation medium. In contrast, tumour necrosis factor altered the rate of gastric emptying as measured by the gastrointestinal distribution of [³H]inulin following an intragastric glucose load. These results suggest that the cytokine profoundly alters glucose metabolism by increasing its whole-body oxidation rate and delaying intestinal absorption through a reduced gastric emptying.     

Tremorgenic mycotoxins produced by strains of Penicillium spp. isolated from toxic Poa huecu parodi

Seventeen strains of Penicillium spp. have been isolated from Poa huecu Parodi from the Zapala zone, exhibiting toxicity to sheet. The following strains have been identified: P. crustosum, cyclopium, notatum, palitans, puberulum, verrucosum, viridicatum and Penicillium spp. The toxigenic capacity of the strains was studied after growing them under suitable conditions. Toxins produced were analysed by thin layer chromatography (TLC). Penitrem A (PA) and Penitrem B (PB) neurotoxins were identified and quantitated in twelve strains; verruculogen (VERR) and fumitremorgen B (FTB) being present in one of them. The effect of these mycotoxins was studied in mice. Neurological symptoms characteristic of the intoxication by tremorgenic toxins and similar to those observed in sheep suffering from huecu's disease were observed. The possible role of these toxins as causative agents of huecu's disease is discussed.     

Volatile production by Aspergillus versicolor as a possible cause of odor in houses affected by fungi

Aspergillus versicolor, which has been isolated from several mould affected houses was shown by laboratory studies under axenic conditions to produce several specific volatile compounds on water agar. These compounds were not produced by the fungus when grown on a rich malt extract medium or on several synthetic media. The volatile compounds were analysed by GC-MS. The majority of the peaks represented aromatic compounds. A non-aromatic substance which previously has been revealed by us among prominent volatile compounds sampled from building materials from so-called mould houses was produced only on water agar. According to a comparison with the mass spectrum and retention time of pure reference compound this compound is ethylhexanol, a compound not previously reported as a mould metabolite. The presence of this compound was correlated with pungent odor in the cultures.     

Regulation of ACV synthetase activity in the beta-lactam biosynthetic pathway by carbon sources and their metabolites

The activity of -l--aminoadipyl)-l-cysteinyl-d-valine catalysis. Addition of l-cysteine to fermentation media increased -lactam production in both organisms and alleviated the negative carbon source regulation by glycerol in S. clavuligerus.     

Regulation of polyphosphate metabolism in Acinetobacter strain 210A grown in carbon- and phosphate-limited continuous cultures

The response of Acinetobacter strain 210A to low phosphate concentrations was investigated in P- or C-limited chemostat cultures. The organism accumulated poly--hydroxybutyric acid under P-deprivation, at phosphate concentrations ranging from 0.1 to 0.7 mM. The amount of biomass was proportional to the phosphate concentration in the medium and no polyphosphate was formed. When shifting a culture from P- to C-limitation phosphate was accumulated as polyphosphate. No poly--hydroxybutyrate could be detected in these cells. The amount of polyphosphate in the cell showed a hysteresis. When cultures were shifted from low to high phosphate concentrations, polyphosphate reached a maximum of about 60 mg P per gram of dry weight at about 3 times excess phosphate (ca. 2.5 mM P_i). It decreased to 45 mg P per gram dry weight at approximately 5 times the phosphate needed for growth (ca. 3.5 mM P_i). In the reverse case (high to low) polyphosphate did never exceed 45 mg P per gram dry weight. The specific activities of alkaline phosphatase and the phosphate uptake system were induced at residual P_i concentrations below the detection limit (<10 M). The specific uptake rate followed also a hysteresis. The specific activities of polyphosphatase and polyphosphate: AMP phosphotransferase increased when polyphosphate formation was possible.Abbreviations HPP High polymeric polyphosphates - PHB Poly--hydroxybutyric acid - PP_n Polyphosphate - PQQ Pyrrolo-quinoline quinone - U 1 mol product formed · min^-1     

Anaerobic degradation of trans-cinnamate and ω-phenylalkane carboxylic acids by the photosynthetic bacterium Rhodopseudomonas palustris: evidence for a β-oxidation mechanism

The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and -phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO₂ dependence for growth on acids with greater side-chain lengths. Here, CO₂ was presumably acting as a redox sink for the disposal of excess reducing equivalents. Growth on benzoate did not require the addition of exogenous CO₂. Aromatic acids with an odd number of side-chain carbon atoms (3-phenylpropionate, 5-phenylvalerate, 7-phenylheptanoate) gave greater apparent molar growth yields than those with an even number of side-chain carbon atoms (4-phenylbutyrate, 6-phenylhexanoate, 8-phenyloctanoate). HPLC analysis revealed that phenylacetate accumulated and persisted in the culture medium during growth on these latter compounds. Cinnamate and benzoate transiently accumulated in the culture medium during growth on 3-phenylpropionate, and benzoate alone accumulated transiently during the course of trans-cinnamate degradation. The transient accumulation of 4-phenyl-2-butenoic acid occurred during growth on 4-phenylbutyrate, and phenylacetate accumulated to a 1:1 molar stoichiometry with the initial 4-phenylbutyrate concentration. It is proposed that the initial steps in the anaerobic degradation of trans-cinnamate and the group of acids from 3-phenylpropionate to 8-phenyloctanoate involves -oxidation of the side-chain.Abbreviation 3-PP 3-phenylpropionic acid - 4-PB 4-phenylbutyric acid - 5-PV 5-phenylvaleric acid - 6-PH 6-phenylhexanoic acid - 7-PH 7-phenylheptanoic acid - 8-PO 8-phenyloctanoic acid - 4-P2B 4-phenyl-2-butenoic acid - GC/MS Gas chromatography/Mass spectrometry - HPLC High-pressure liquid chromatography     

Comparative efficiencies of bispecific F(ab′γ)2 and chimeric mouse/human IgG antibodies in recruiting cellular effectors for cytotoxicity via Fcγ receptors

Summary The three forms of Fc receptor carried by monocytes (FcRI, II) and natural killer (NK) cells (FcRIII) are all capable of mediating cell lysis. Here we compare the use of F(ab)₂ bispecific antibodies, specifically targetting individual FcR, and chimeric IgG mouse/human antibodies which are capable of targetting all FcR, for their ability to mediate target cell destruction. The derivatives are prepared by linking hinge sulphydryl residues via tandem thioether bonds, using a bismaleimide crosslinker: Fab from an anti-FcR mAb linked to Fab from a common anti-target mAb (BsAb), or Fab from the common anti-target mouse antibody linked to human Fc (FabFc or bisFabFc). All the derivatives targetting chick red blood cells gave efficient lysis, although different effector cell donors yielded differences in both the lytic levels achieved and the comparative efficiencies of derivatives. In contrast, significant lysis of the guinea pig lymphoblastic leukaemia, L₂C, regularly resulted only via the anti-FcRIII BsAb and the chimeric derivatives. These results suggest that the chimeric, Fc-containing derivatives mediate tumour cell lysis principally through FcRIII on NK cells. This is in contrast to the situation with the chick red blood cells where the chimeric derivatives appear capable of lysing erythrocytes by utilizing either monocytes or NK cells, because significant (50%) lysis occurred with effector cell populations magnetically depleted through either FcRII or FcRIII. A major difference between these two types of antibody derivative was their ability to function in the presence of high concentrations of normal human Fc. The lysis mediated by BsAb reactive with FcRI or II was unaffected by the presence of human Fc at 2.5 mg/ml (a concentration comparable with that yielded by IgG in plasma) whereas the BsAb recognizing FcRIII and all the Fc-containing derivatives were completely inhibited.This work has been supported by Tenovus, the Cancer Research Campaign, the Leukaemia Research Fund, Italfarmaco, Milano, Italy and the Imperial Cancer Research Fund     

Effect of interferon γ on the sensitivity of bovine-papilloma-virus(BPV1)-transformed cell lines to cell-mediated cytotoxicity

Summary The effect of interferon (IFN) on the immunogenicity and immunosensitivity of mouse cell lines transformed by bovine papillomavirus type 1 (BPV1) DNA was examined in a syngeneic mouse model. The overnight incubation of BPV1-transformed cell lines with 100 IU/ml IFN did not affect their ability to induce the generation of cytotoxic effector cells but it clearly increased their sensitivity to lysis by interleukin-2-induced lymphokine-activated killer (LAK) cells and by nonspecific LAK-type effector cells induced by BPV-1-transformed cell lines. The treatment of two allogeneic lymphoid tumour cell lines, P815X2 and YAC-1, with IFN either decreased or had no effect on their sensitivity to LAK-cell-mediated lysis.     

Clinical studies on cell-mediated immunity in patients with renal cell carcinoma: interleukin-2 and interferon-γ production of lymphocytes

Summary The authors examined interleukin-2 (IL-2) production and interferon (IFN) production of peripheral blood mononuclear cells in 28 patients with renal cell carcinoma and 17 control subjects. The peripheral blood was obtained prior to the initiation of therapeutic procedures. The patients were divided into two groups according to tumor size, 5 cm and >5 cm. The production of IL-2 and IFN was measured by immunoradiometric assay. As a result, in the patients with tumors >5 cm, IL-2 and IFN production was impaired. However, in the patients with tumors 5 cm, IFN production was enhanced, though IL-2 production was not significantly different from that of the control subjects. There was no significant correlation between IL-2 production and IFN production.