Transport of hydrophobic ions in erythrocyte membrane: I. Zero membrane potential properties

Summary The permeability and partition coefficients of tetraphenylarsonium (TPA) and several other organic cations were studied in the human erythrocyte using an ion-selective electrode. The permeability constant for the different cations could be explained quite well by differences in oil/water partition coefficients. No evidence for facilitated transport could be found. Binding of the organic ions occurred to both the cell membrane and to intracellular contents. Partitioning to the membrane remained relatively constant despite variation from ion intracellular binding with blood samples from different donors. TPA flux is stimulated by substoichiometric amounts of tetraphenylboron and other organic anions, suggesting an ion-pairing mechanism.     

Continuous Measurements of the Free Dissolved CO(2) Concentration during Photosynthesis of Marine Plants: Evidence for HCO(3) Use in Chondrus crispus

An experimental system consisting of a gas exchange column linked to an assimilation chamber has been developed to record continuously the free dissolved CO₂ concentration in seawater containing marine plants. From experiments performed on the red macroalga Chondrus crispus (Rhodophyta, Gigartinales), this measurement is in agreement with the free CO₂ concentration calculated from the resistance to CO₂ exchanges in a biphasic system (gas and liquid) as earlier reported. The response time of this apparatus is short enough to detect, in conditions of constant pH, a photosynthesis-caused gradient between free CO₂ and HCO₃⁻ pools which half-equilibrates in 25 seconds. Abolished by carbonic anhydrase, the magnitude of this gradient increases with decreasing time of seawater transit from the chamber to the column apparatus. But its maximum magnitude (0.35 micromolar CO₂) is negligible compared to the difference between air and free CO₂ (11.4 micromolar CO₂). This illustrates the extent of the physical limiting-step occurring at the air-water interface when inorganic carbon consumption in seawater is balanced by dissolving gaseous CO₂. The direction of this small free CO₂/HCO₃⁻ gradient indicates that HCO₃⁻ is consumed during photosynthesis.     

Dual effects of estradiol on normal and tumor pituitary cell multiplication

We have compared the effects of estradiol on the [3H]thymidine (TdR) incorporation into the DNA of 2 rat tissues whose growth is controlled by estradiol in vivo in 2 opposite directions: the normal anterior pituitary and the MtF4 pituitary tumor transplanted under the kidney capsule. Small pieces of pituitary or tumor from Fischer rats, treated or not by estradiol in silastic tubing, were incubated in vitro with [3H]TdR. The [3H]TdR incorporated per microgram DNA was decreased in tumor after 2 to 8 day-estradiol treatment while simultaneously, in the same rats, it was increased in the pituitary. In addition, we studied the effect of estradiol in vitro on the F4C1 cell line obtained from the MtF4 tumor. A dose-dependent decrease of both the [3H]TdR incorporated into DNA and the DNA amount was observed between 10(-6) and 10(-5) M estradiol. These results suggest that the control of the pituitary or MtF4 tumor growth by estradiol in vivo is in part due to an inhibition of cell multiplication. Although estradiol inhibits the growth of a clone of MtF4 tumor cells in vitro we cannot decide whether or not the in vivo effect of estradiol is direct.     

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.     

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.