Accelerated transbilayer movement of phosphatidylcholine in sickled erythrocytes. A reversible process

The transbilayer mobility of phosphatidylcholine (PC) molecules in the membrane of homozygous reversible sickle cells (RSCs) was studied using a PC-specific exchange protein from beef liver. In deoxygenated RSCs, all of the PC present in the membrane of the intact cell is rapidly available for exchange, mediated by this protein. Since a substantial amount of the PC is present in the inner membrane leaflet of these cells, this observation implies that the PC molecules in their membranes do experience rapid transbilayer movements. To determine the actual rate of transbilayer movement of the PC, radioactive PC was introduced into the outer monolayer of oxygenated RSCs using the PC-specific exchange protein. Subsequently, the cells were incubated at 37 degrees C under oxy- and deoxygenating conditions to enable the PC to equilibrate within the bilayer. At various time intervals, samples were taken and treated with phospholipase A2, which selectively degrades the PC in the outer monolayer. Analysis of the specific radioactivities of the lyso-PC thus produced, as well as of the residual PC, enabled us to follow the fate of the radioactive PC previously introduced into the outer membrane layer. The half-time value for transbilayer equilibration of the PC in deoxygenated RSCs was determined to be 3.5 h, which is about four times lower than that for oxygenated RSCs. This increased transbilayer mobility of PC, observed in deoxygenated RSCs, is immediately restored to the normal low rate upon reoxygenation of the cells, indicating a complete reversibility of this phenomenon.     

Transfer RNA genes ofZea mays chloroplast DNA

A minimum of 37 genes corresponding to tRNAs for 17 different amino acids have been localized on the restriction endonuclease cleavage site map of theZea mays chloroplast DNA molecule. Of these, 14 genes corresponding to tRNAs for 11 amino acids are located in the larger of the two single-copy regions which separate the two inverted copies of the repeat region. One tRNA gene is in the smaller single-copy region. Each copy of the large repeated sequence contains, in addition to the ribosomal RNA genes, 11 tRNA genes corresponding to tRNAs for 8 amino acids. The genes for tRNA₂ ^Ile and tRNA^Ala map in the ribosomal spacer sequence separating the 16S and 23S ribosomal RNA genes. The three isoaccepting species for the tRNAs^Leu and the three for tRNAs^Ser, as well as the two isoaccepting species for tRNA^Asn, tRNA^Gly, tRNAs^Ile, tRNAs^Met, tRNAs^Thr, are shown to be encoded at different loci. Two independent methods have been used for the localization of tRNA genes on the physical map of the maize chloroplast DNA molecule: (a) cloned chloroplast DNA fragments were hybridized with radioactively-labelled total 4S RNAs, the hybridized RNAs were then eluted, and identified by two-dimensional polyacrylamide gel electrophoresis, and (b) individual tRNAs were³²P-labelledin vitro and hybridized to DNA fragments generated by digestion of maize chloroplast DNA with various restriction endonucleases.     

Plasma androgens in idiopathic hirsutism

The plasma concentrations of testosterone, androstenedione,5-androstene-3β, 17β-diol, 5α-dihydrotestosterone and 17β-hydroxy-androgens have been measured in normal women and in patients with idiopathic hirsutism. The mean levels of all the compounds studied were higher in the group of patients with hirsutism than in the controls and apart from dihydrotestosterone, this difference was statistically significant. The correlation between the plasma levels of the various steroids was examined. In the normal subjects, testosterone and androstenedione levels were well correlated, but in the hirsute patients, the correlation is poor. It is suggested that this is related to altered binding of testosterone to plasma proteins in these patients. No one of the steroid levels measured was consistently abnormal in hirsutism, but in 40% of the patients, plasma androstenedione levels were above the normal range.     

Phospholipid Composition of Bacillus subtilis

Bacillus subtilis contained at least five phospholipids, four of which have been isolated and identified as a polyglycerol phospholipid, probably cardiolipin, phosphatidylglycerol, phosphatidylethanolamine, and lysylphosphatidylglycerol. Further purification of the latter phosphoglyceride was obtained by high-voltage electrophoresis, and it was shown that this treatment removed amino acid-containing, nonlipidic material from the phosphoglyceride. This associated material, which is not covalently linked to the lipid, gave rise to minor amounts of a number of amino acids, other than lysine, in acid hydrolysates of the lysylphosphatidylglycerol. The phospholipid composition of B. subtilis appeared to depend on the growth conditions. Addition of glucose to the medium lowered the pH during growth; this was accompanied by an increase in the amount of lysylphosphatidylglycerol and a decrease in the phosphatidylglycerol content, when compared with growth at neutral pH. The amount of the other phospholipids and the total amount of phospholipid remained constant under the different conditions. The shape and the osmotic susceptibility of the protoplasts of this organism appeared to depend on the growth conditions. Cells harvested from a neutral growth medium gave spherical protoplasts which lysed rapidly, whereas cells grown in an acidic medium maintained their rod-shaped form to a great extent after the cell wall had been removed, even after being suspended in a hypotonic medium. The latter observation suggests the presence of a more rigid membranous structure in cells which have been exposed to a low environmental pH during growth.     

Lamellar bodies in the epithelial bronchiolar cells in the mouse

Summary Lamellar bodies are described in the non-ciliated epithelial bronchiolar cells of the normal mouse lung. They are constituted of smooth concentric membranes, with a cytoplasmic center. They are related to mitochondria. They seem to belong to smooth endoplasmic reticulum. An origin from Golgi elements is discussed. Acknowledgment. This work was supported by Grant No 69088 of Conseil de la Recherche Médicale du Québec.     

Lincomycin and Staphylococcal Infections: A Clinical Study of 18 Cases

Lincomycin, a chemically new antibiotic effective against Gram-positive organisms, was evaluated in vitro and tested clinically. In vitro testing indicated that lincomycin is especially effective against Staphylococcus aureus. Clinical testing showed that lincomycin was free of toxicity in a series of 18 cases of staphylococcal infection. Of particular interest was its pronounced effectiveness in nine cases of chronic osteomyelitis, one of which was of 15 years'' duration and unresponsive to all other forms of antibiotic and surgical treatment. The only side effect noted was loose stools in the occasional patient.     

Liquid-to-Gas Mass Transfer in Anaerobic Processes: Inevitable Transfer Limitations of Methane and Hydrogen in the Biomethanation Process

Liquid-to-gas mass transfer in anaerobic processes was investigated theoretically and experimentally. By using the classical definition of k(L)a, the global volumetric mass transfer coefficient, theoretical development of mass balances in such processes demonstrates that the mass transfer of highly soluble gases is not limited in the usual conditions occurring in anaerobic fermentors (low-intensity mixing). Conversely, the limitation is important for poorly soluble gases, such as methane and hydrogen. The latter could be overconcentrated to as much as 80 times the value at thermodynamic equilibrium. Such overconcentrations bring into question the biological interpretations that have been deduced solely from gaseous measurements. Experimental results obtained in three different methanogenic reactors for a wide range of conditions of mixing and gas production confirmed the general existence of low mass transfer coefficients and consequently of large overconcentrations of dissolved methane and hydrogen (up to 12 and 70 times the equilibrium values, respectively). Hydrogen mass transfer coefficients were obtained from the direct measurements of dissolved and gaseous concentrations, while carbon dioxide coefficients were calculated from gas phase composition and calculation of related dissolved concentration. Methane transfer coefficients were based on calculations from the carbon dioxide coefficients. From mass balances performed on a gas bubble during its simulated growth and ascent to the surface of the liquid, the methane and carbon dioxide contents in the gas bubble appeared to be controlled by the bubble growth process, while the bubble ascent was largely responsible for a slight enrichment in hydrogen.