Biosynthesis of D-alanyl-lipoteichoic acid: role of diglyceride kinase in the synthesis of phosphatidylglycerol for chain elongation.

Lipophilic and hydrophilic D-alanyl-lipoteichoic acids are elongated in Lactobacillus casei by the transfer of sn-glycerol 1-phosphate units from phosphatidylglycerol to the poly(glycerophosphate) moiety of the polymer. These sn-glycerol 1-phosphate units are added to the end of the poly(glycerophosphate) which is distal to the glycolipid anchor; 1,2-diglyceride results from this addition. The presence of a diglyceride kinase was suggested by the ATP-dependent phosphorylation of 1,2-diglyceride to phosphatidic acid. Inorganic phosphate was used to initiate the synthesis of lipophilic lipoteichoic acid (LTA) and the elongation of both lipophilic and hydrophilic LTA. Three observations suggest that phosphate and other anions play a role in the in vitro synthesis of LTA and its precursors. First, the conversion of 1,2-diglyceride to phosphatidic acid by diglyceride kinase was stimulated. Second, the synthesis of phosphatidylglycerol was increased. Third, the elongation of lipophilic and hydrophilic LTA was enhanced. These observations indicated that one effect of phosphate might be to enhance the utilization of 1,2-diglyceride for the synthesis of phosphatidic acid. This phospholipid is a precursor of phosphatidylglycerol, the donor of sn-glycerol 1-phosphate for elongation of LTA.     

Selenium as a growth factor for plankton algae in laboratory experiments and in some Swedish lakes

The growth requirements of inorganic and organic selenium (Se) for the dinoflagellate Peridinium cinctum fa. westii and the diatom Stephanodiscus hantzschii var. pusillus and eight species of green algae are demonstrated. A new mineral culture medium for P. cinctum is presented. Using P. cinctum as a test alga, bioassays were carried out on waters from a calciferous lake and from some acidified, fertilized, lime-enriched or humic lakes for determination of their contents of bioavailable forms of Se (bioactive Se). Some of the results were related to Tot-Se and selenite-Se, measured chemically, to pH and the occurrence of ambient phytoplankton. In calcium-rich Lake Erken (pH ～ 8) blooms and decline of algae coincided with decreases (from >70 to ～20 ng Se · l^?1) and increases (up to >80 ng · l^?1) of bioactive Se, indicating uptake and release of inorganic or organic forms of Se. Acidified lakes (pH < 5) generally demonstrated much lower concentrations of bioactive Se (<20 ng · l^?1) than neutral, fertilized, lime-enriched, slightly acidic or humic lakes (>20 ng · l^?1). The correlation between pH and bioactive Se was positive (r ～ 0.92; n = 7). The ecological importance of Se is suggested for some common species of phytoplankton.     

Properties and function of the two hemes in Pseudomonas cytochrome c peroxidase

The oxidation-reduction potentials of the two c-type hemes of Pseudomonas aeruginosa cytochrome c peroxidase (ferrocytochrome c:hydrogen-peroxide oxidoreductase EC 1.11.1.5) have been determined and found to be widely different, about +320 and -330 mV, respectively. The EPR spectrum at temperatures below 77 K reveals only low-spin signals (gz 3.24 and 2.93), whereas optical spectra at room temperature indicate the presence of one high-spin and one low-spin heme in the enzyme. Optical absorption spectra of both resting and half-reduced enzyme at 77 K lack features of a high-spin compound. It is concluded that the heme ligand arrangement changes on cooling from 298 to 77 K with a concomitant change in the spin state. The active form of the peroxidase is the half-reduced enzyme, in which one heme is in the ferrous and the other in the ferric state (low-spin below 77 K with gz 2.84). Reaction of the half-reduced enzyme with hydrogen peroxide forms Compound I with the hemes predominantly in the ferric (gz 3.15) and the ferryl states. Compound I has a half-life of several seconds and is converted into Compound II apparently having a ferric-ferric structure, characterized by an EPR peak at g 3.6 with unusual temperature and relaxation behavior. Rapid-freeze experiments showed that Compound II is formed in a one-electron reduction of Compound I. The rates of formation of both compounds are consistent with the notion that they are involved in the catalytic cycle.     

Norepinephrine Metabolism in Humans Studied by Deuterium Labelling: Turnover of 4–Hydroxy-3–methoxyphenylglycol

Abstract: D, L(±)-4-Hydroxy-3-methoxyphenylglycol (HMPG) labelled with three deuterium atoms was used to study turnover of plasma free HMPG following an intravenous injection. Ten healthy men were given a pulse dose of either 4.3 μmol or 2.2 μmol of labelled HMPG ([²H₃]HMPG piperazine salt). Plasma and urine levels of both endogenous and labelled HMPG were subsequently followed by gas chromatography-mass spectrometry with selected ion detection. Kinetic calculations based upon a single-compartment model were consistent with a monoexponential elimination of plasma free HMPG. The half-life of HMPG was 0.46 and 0.78 h (mean values in the two dose groups). The HMPG production rate was 2.01 and 2.35 μmol/hour, and the urinary excretion rate of HMPG (free and conjugated) was 0.48 and 0.47 μmol/h. The endogenous plasma level of free HMPG was 25 and 33 nmol/L. The results show that HMPG turns over rapidly and that HMPG is further metabolized extensively. About one-fourth of the HMPG produced is excreted in urine as free and conjugated HMPG.     

Compounds in urban air compete with 2,3,7,8-tetrachlorodibenzo-p-dioxin for binding to the receptor protein

Acetone extracts of filter-collected urban airborne particulate matter contain compounds which can competitively inhibit 2,3,7,8-[1,6-3H]tetrachlorodibenzo-p-dioxin (TCDD) binding to the rat liver TCDD-receptor protein. The concentration of conventional polycyclic aromatic hydrocarbons (PAHs) or chlorinated dioxins and dibenzofurans cannot account for more than 1-30% of the observed competition for [3H]TCDD binding to the receptor protein. The difference in potency between samples collected in urban areas during different periods of the year and a background sample is 25-400-fold. Collecting samples in the presence of increased concentrations of nitrogen dioxide, nitrous acid, nitric acid or ozone did not increase the amount of compounds with receptor affinity. However, with nitrogen dioxide and especially with nitric acid, a substantial increase of the mutagenic effects in the Ames Salmonella assay in the absence of mammalian activation as well as a degradation of several PAHs were noted. Affinity for the TCDD-receptor protein, mutagenicity in the absence of mammalian metabolic activation in the Ames Salmonella assay and PAH-content are characteristics of urban particulate matter showing the presence of compounds, that represent potential health risks. The compounds with affinity for the receptor may constitute a group of substances different from both conventional PAHs and direct-acting mutagens.     

Peptides with NH2-terminal tryptophan in the adenohypophysis

Summary In the mammalian pituitary formaldehyde-ozone treatment induces strong fluorescence in the cells of the pars intermedia and moderate to strong fluorescence in numerous cells of the pars distalis. Maximum excitation is at 370–375 nm and maximum emission at 495–505 nm. The properties of the cellular fluorescence are indistinguishable from those of tryptamine or peptides with NH₂-terminal tryptophan. From chemical analysis such peptides seem to occur abundantly in the mammalian pituitary. The concentration of these peptides agrees very well with the number and fluorescence intensity of the cells in all species studied. Furthermore, the tryptophyl peptides in the various parts of the pig pituitary have a distribution quite parallel to that of the fluorescent cells. As we have failed to detect tryptamine in the pituitary, we conclude that the formaldehyde-ozone-induced fluorescence in the adenohypophysis reflects the presence of tryptophyl peptides.This study was supported by grants from the Swedish Medical Research Council (04X-1007; 04X-3764), the Ford Foundation, Harald and Greta Jeanssons stiftelse and Riksföreningen mot Cancer (660-K73-01X).For brevity occasionally referred to as tryptophyl peptides.     

Amine-producing endocrine-like cells in the epithelium of urethra and prostate of the guinea-pig a chemical,fluorescence histochemical,and electron microscopic study

Summary The urethra and prostate of the guinea-pig contain at least two types of endocrine-like cells in the epithelium. The predominant type is argentaffin and stores 5-hydroxytryptamine. Treatment with reserpine or a dopa decarboxylase inhibitor markedly reduces the 5-hydroxytryptamine content of this cell type. The other less numerous cell type, which is argyrophil but not argentaffin, is devoid of 5-hydroxytryptamine but can be induced to store dopamine if supplied with dopa. Both cell types occur disseminated in the urethral epithelium, whilst only the argyrophyl, non-argentaffin cell type devoid of 5-hydroxytryptamine is found in the prostate. At the ultrastructural level the argentaffin cell type contains numerous electron-dense cytoplasmic 800–1000 Å granules. These granules are argentaffin, suggesting that they are the storage site for 5-hydroxytryptamine. The cells sometimes reach the urethral lumen via a narrow neck, the apex being endowed with microvilli. This arrangement suggests that the cells are capable of responding to stimuli in the urethral lumen. Preliminary attempts to test the effect of depriving or loading guinea-pigs with water failed to induced changes in the 5-hydroxytryptamine content of the urethral endocrine-like cells.     

Vesical Hemorrhages in Male Aleutian Mink Caused by Hypersensitivity to Sulphadimidine

During an outbreak of Salmonella abortion in mink farms receiving food from a central feed plant, sulphamezathine (a 16 % solution of sulphadimidine sodium) was added to the food to combat the infection. After 3 days of medication, some males of the Aleutian type developed severe urinary bleedings. The serum concentration of the drug was not above the recommended value in 2 severely affected animals (1.5 and 1.7 mg/100 ml, respectively). Screening tests for the extrinsic (Thrombotest and Normotest) and intrinsic (cephalin time) coagulation mechanism, fibrinogen assay, fibrinolysis (plasma clot lysis time), and platelet count were not much different from normal. Coagulation or platelet defects did not therefore seem to be the cause of the bleedings. Some of the diseased animals died, and the only necropsy finding was a greatly distended urinary bladder filled with clotted blood. Histologically, hemorrhages and necrotic changes of varying severity were found in the vesical wall. In several cases, the arteries were the structures most evidently affected, indicating that the hemorrhages were due to vascular injury (Fig. 1). The damaged vessels were sporadically occluded by thrombi. The lesions were often most evident in subserosal arteries and in the relatively large arteries situated between the inner circular and the outer longitudinal muscular layer, whereas the submucosal structures were obscured by massive extravasations of red blood cells. Occasionally, the necrotic arteries were surrounded by incipient circumferential cellular accumulations, predominantly mononuclear cells, but some eosinophils were also present (Fig. 2). Thus, in these cases the vascular damage was similar to vascular lesions frequently accompanying viral plasmacytosis (periarteritis nodosa). The possibility exists that the animals were in an early developmental stage of plasmacytosis, but no extravesical changes suggesting plasmacytosis were discovered during the microscopic examination. Although other sulphonamides have occasionally shown toxic properties when administered to mink, this preparation has not, to the authors’knowledge, previously been recorded as injurious to this species. The following experiment was performed to elucidate the toxicity of sulphadimidine sodium to male Aleutian mink.