Changes in the Cationic Regulation of Structure and Function in Thylakoids Isolated from Wheat Seedlings Treated with BASF 13.338

When wheat seedlings (Triticum vulgare cf HD 2189) were grown in the presence of BASF 13.338 (4-chloro-5-[dimethylamino]-2-phenyl-3[2H]-pyridazinone), there was a decrease in the ratio of linolenic acid to linoleic acid in the thylakoid membrane lipids (JB St John 1976 Plant Physiol 57: 38) and an increase in the ratio of photosystem II to photosystem I (RM Mannan, S Bose 1984 Photochem Photobiol 41: 63). Accompanying these gross structural changes were alterations in the cationic regulation of structure and functioning of the thylakoid membranes: (a) Mg²⁺-induced increase in the room temperature fluorescence was totally absent; (b) Mg²⁺-induced increase in absorbance at 560 nm, indicative of granal stacking, was slightly higher in thylakoids isolated from the BASF 13.338 treated plants suggesting an increased degree of stacking; and (c) absorption changes in the red and Soret regions of the absorption spectrum, normally resulting from the addition of divalent cation or alkyl anion, or from osmotic shrinkage were almost totally absent in thylakoid membranes isolated from BASF 13.338 treated plants. These observations have been interpreted in terms of: (a) significant alterations in the lipid matrix of the thylakoids from treated plants, (b) absence of cation-induced reorganization of the pigment-protein complexes in the horizontal plane of the treated thylakoid membranes suspended in low salt medium, and (c) absence of dynamic changes even within the individual pigment-protein complexes of treated thylakoids.     

Alteration of pial vessel responses to blood pressure changes in rats after hypoxia

Previous studies in newborn lamb have shown impairment of cerebral blood flow autoregulation after hypoxia followed by reoxygenation. The present study was done to see if such a phenomenon existed in the adult rat and if it could be demonstrated at the level of the pial arterioles. Using an open cranial window preparation, we assessed the changes in pial vessel diameter during blood pressure alterations induced by hemorrhage and reinfusion of blood, before and after 30 s of hypoxia, in 15 male Sprague-Dawley rats. Mean diameters of pial arteries in the study group of rats were 128 +/- 54 microns before hypoxia and 141 +/- 61 microns after normoxia following hypoxia. The corresponding diameters in rats serving as time controls were 136 +/- 52 and 138 +/- 52 microns. Slopes of pial vessel diameters as a function of mean arterial blood pressures decreased significantly (p less than 0.05) after hypoxia from -0.86 +/- 0.45 to 0.03 +/- 0.66 (mean +/- SD). In the control rats not subjected to hypoxia, the slopes remained unchanged over a similar time period (-0.60 +/- 0.16 and -0.42 +/- 0.19). The negative slopes indicate that pial vessels dilate during hypotension and constrict during hypertension. Such vascular responses may play a role in autoregulation of cerebral blood flow. We found that a relatively brief period of hypoxia can cause a long-lasting impairment of vascular responses even after restoration of normoxia. These findings are consistent with a previous report of persistent impairment of cerebral blood flow autoregulation after a brief period of hypoxia.     

Immunological Activity Associated with the Nucleocapsid and Envelope Components of an Arbovirus

Complement-fixing antigens were detected in the nucleocapsid and envelope of Sindbis virus. Neutralizing antibodies are directed against antigens in the viral envelope.     

Separation of Reticuloendotheliosis Virus from Avian Tumor Viruses

Velocity sedimentation and isopycnic density gradient centrifugation indicate that reticuloendotheliosis virus has a different mass and buoyant density than members of the avian tumor virus group. The group-specific antigen of the avian tumor virus group was not detected in concentrated and purified reticuloendotheliosis virus preparations.     

Physiological Studies of Methane- and Methanol-Oxidizing Bacteria: Comparison of a Primary Alcohol Dehydrogenase from Methylococcus capsulatus (Texas Strain) and Pseudomonas Species M27

A primary alcohol dehydrogenase has been purified from Methylococcus capsulatus (Texas strain). The purified enzyme catalyzes the oxidation of methanol and formaldehyde to formate; other primary alcohols are oxidized to their corresponding aldehydes. Ammonium ions are required for enzyme activity. The enzyme has a molecular weight of 120,000 daltons and consists of two 62,000 molecular-weight subunits which dissociate at acidic pH. The enzyme is similar to an alcohol dehydrogenase enzyme isolated from Pseudomonas sp. M27.     

Chemical lonization-mass spectrometric approach to structure determination of an intermediate in bile acid biosynthesis

In the course of a study on the details of the biosynthesis of cholic acid from cholesterol, 5β-[26,27-¹⁴C]cholestan-3α,7α,12α,24S,25-pentol, an intermediate in the 25-hydroxylation pathway of cholic acid, was incubated for 2 min with the cytosolic fraction of rat liver homogenate in the presence of NAD. A precursor to cholic acid which appeared to be a ketone was isolate from the reaction mixture by thin-layer chromatography. This material proved to be of inadequate volatility for electron impact mass spectrometry and was therefore studied, without further purification, by techniques of chemical ionization mass spectrometry using ammonia as the reagent gas. The spectrum was rerecorded using argon mixed with ammonia to induce additional fragmentation. One of these fragments corresponded to a McLafferty rearrangement of a 24-keto-25-hydroxycholestane derivative. To obtain additional evidence for this structure the following sequence of reactions was conducted on about 20 μg of the intermediate: (1) periodic acid oxidation, (2) diazomethane treatment, and (3) chromic acid oxidation. The change in molecular weight after each reaction agreed with the presence of a 25-hydroxy-24-keto side chain and three secondary hydroxyl groups in the molecule. Therefore, it could be deduced that the intermediate was 3α,7α,12α,25-tetrahydroxy-5β-cholestan-24-one. This work demonstrates that chemical ionization-mass spectrometic techniques can be a labor-saving alternative to other methods of structure determination and that 3α,7α,12α,25-tetrahydroxy-5β-cholestan-24-one is probably an intermediate in the 25-hydroxylation pathway of cholic acid from cholesterol.     

Bacteriophage-induced Inhibition of Host Functions: II. Evidence for Multiple, Sequential Bacteriophage-induced Deoxyribonucleases Responsible for Degradation of Cellular Deoxyribonucleic Acid

Degradation of bacterial deoxyribonucleic acid (DNA) after infection with T4 bacteriophage was studied in an endonuclease I-deficient host. The kinetics of degradation were similar to those seen in other hosts with a normal level of this enzyme. Irradiation of extracellular phage with ultraviolet (UV) destroyed the capacity of the infecting virus to induce extensive breakdown of host DNA, which was, however, converted to high-molecular-weight material. Addition of chloramphenicol to T4-infected cells provided data which can be interpreted to indicate the involvement of at least two endodeoxyribonucleases and one exodeoxyribonuclease having a high degree of specificity. A model is proposed showing the sequential action of two endodeoxyribonucleases followed by an exodeoxyribonuclease in the degradation of host DNA. The appearance of these hydrolytic enzymes requires protein synthesis. Infections leading to partial degradation only (UV-irradiated phages, gene 46 mutants) effectively inhibited the synthesis of bacterial messenger ribonucleic acid and of beta-galactosidase.     

Cleavage of a Viral Envelope Precursor During the Morphogenesis of Sindbis Virus

In cells infected with a temperature-sensitive mutant of Sindbis virus, the cleavage of the precursor to one of the viral envelope proteins does not occur at the nonpermissive temperature. This precursor is found associated with the plasma membrane fraction obtained from the infected cell. Since this is the site at which the virus matures, this finding suggests that during Sindbis virus replication the precursor to the smaller proteins associates with the cell membrane and is then cleaved during the maturation of the virus.     

Phosphorylated Proteins of Sindbis Virus

The capsid and two membrane proteins of Sindbis virus, grown in chicken cells, contain 0.03 to 0.1 mol of phosphate per mol of protein.     

Proteolytic activity and nitrogen transfer in maize seeds during imbibition

Ethanol-soluble and insoluble nitrogen and protease activity in maize seeds during imbibition period of 6 to 60 h at 30 ± 2 °C were determined both in light and in the dark. In light, soluble and insoluble nitrogen in the embryo were similar to that in the dark. But the increase in soluble nitrogen in the endosperm up to 38 h was higher in light than in the dark. Decrease in insoluble nitrogen was correlated with increase in soluble nitrogen, the level always being higher in the dark. Light increased protease activity also in the endosperm. Among various light qualities, red light was most effective in inducing proteolysis, and loss of nitrogen from the endosperm. Further, the growth and organic nitrogen of primary leaves from seedlings raised from light pretreated seeds were better than those from dark pretreated ones.