Light activation of phosphodiesterase activity in retinal rod outer segments

Light “activates” phosphodiesterase activity of bovine rod outer segments in the presence of 0.1 mM ATP. In contrast, no difference in phosphodiesterase activity can be observed between dark-adapted and light-bleached outer segments in the absence of ATP.     

Inactivated Venezuelan Equine Encephalomyelitis Vaccine Prepared from Attenuated (TC-83 Strain) Virus

Formalin-inactivated Venezuelan equine encephalomyelitis vaccine was prepared from virus propagated in rolling-bottle cultures of chicken embryo cells. The attenuated, TC-83 strain of virus was propagated in these cultures with a maintenance medium consisting of serum-free medium 199 containing 0.25% human serum albumin and antibiotics. By adjustment of maintenance medium volume (100 to 300 ml) and multiplicity of inoculum (0.04 to 0.00004), high-titered yields of virus were obtained with minimal cell destruction at convenient harvest times, viz, 18 to 24 h postinoculation. Inactivation of virus at 37 C was complete between 8 to 10 h with 0.05% Formalin and within 6 to 8 h with 0.1% Formalin. Antigen extinction potency tests in mice indicated that potent vaccines could be produced at both Formalin concentrations and, furthermore, that potency was not adversely affected by inactivation periods of up to 96 h.     

Effect of Shaking Speed on the Secretion of Enterotoxin B by Staphylococcus aureus

The concentration of enterotoxin B secreted by four strains of Staphylococcus aureus was dependent upon the shaking speed. For the conditions established, each strain demonstrated an optimal shaking speed, and speeds in excess of the optimum resulted in decreased secretion of toxin. At the optimal shaking speed, maximum secretion occurred at 37 C. At 45 C, both growth and toxin secretion were absent. By using agar containing antienterotoxin B sera, studies with strain S-6 at optimal and suboptimal shaking speeds demonstrated that individual cells vary in their toxin-synthesizing ability and that the relative numbers of high and low producers change during the growth cycle. Although most of the toxin was secreted during the first 12 hr of growth, a portion was secreted during the subsequent 6 hr, even though growth as measured by colony-forming units per milliliter decreased and Klett units increased.     

Freeze-Etching of Azotobacter vinelandii: Examination of Wall, Exine, and Vesicles

The structure of the cell wall, the arrangement of the cyst exine, and the origin and distribution of intine vesicles in Azotobacter vinelandii ATCC 12837 were examined by freeze-etching and conventional electron microscopic techniques. In the vegetative organism the cell wall appears to have a woven texture which disappears during cyst formation. The exine is composed of two different types of material: the outer layer is a fibrous, amorphous layer, and the numerous inner layers form the basic hexagonal structures which unite to form the cyst coat. The presence of intine vesicles in the encysting organism was confirmed in frozen-etched cells. The appearance of frozen-etched cells and cysts and the distribution of capsular material indicate that extracellular polysaccharide is an important factor in cyst formation.     

Ribosomal Proteins Involved in the Suppression of Streptomycin Dependence in Escherichia coli

Suppression of streptomycin dependence in Escherichia coli strain K-114, a spectinomycin-sensitive strain, is correlated with modification of 30S ribosomal protein P4, the component modified in spectinomycin-resistant mutants. The mutant is unusual in that reversion from dependence has previously been correlated only with modification in 30S protein P4a. Introduction into K-114 of another mutation conferring spectinomycin resistance results in a further alteration in protein P4.     

Benzodiazepines and Tricyclic Antidepressant Plasma Levels

Twelve patients acted successfully as subjects to study what effect if any the benzodiazepines nitrazepam, diazepam, oxazepam, and chlordiazepoxide might have on steady-state plasma levels of nortriptyline and amitriptyline. No significant detectable effect was discovered. In view of the known interaction effects of other alternative tranquillizing drugs and hypnotics it seems reasonable to choose benzodiazepines wherever possible when anxiolytics or hypnotics need to be added during treatment of depression with tricyclic antidepressants.     

In Vitro Studies of Semisynthetic α- (Substituted-Ureido) Penicillins

The activity of three alpha-(substituted-ureido) penicillins was evaluated in vitro against 599 clinical isolates of gram-negative bacilli, by use of the broth-dilution technique. At a concentration of 12.5 mug or less/ml, BL-P1597 inhibited 90% of isolates of Pseudomonas sp., 56% of Enterobacter sp., 67% of indole-positive Proteus spp., 72% of Escherichia coli, and 85% of Proteus mirabilis. BL-P1654 had similar activity, whereas BL-P1532 was much less active. At a concentration of 25 mug or less/ml, BL-P1597 also inhibited nearly 60% of isolates of Klebsiella sp. and nearly 40% of Serratia sp. BL-P1597 and BL-P1654 were as active as ampicillin and carbenicillin against E. coli and P. mirabilis. They were less active than carbenicillin against indole-positive Proteus spp. Both drugs were substantially more active than carbenicillin against Pseudomonas sp. A strain of Pseudomonas sp. which developed resistance to carbenicillin also developed resistance to the alpha-(substituted-ureido) penicillins simultaneously.     

Chromosomal Location of the C Gene Involved in the Biosynthesis of Nicotinamide Adenine Dinucleotide in Escherichia coli K-12

A gene involved in the synthesis of nicotinamide adenine dinucleotide has been found to be cotransducible with the genes involved in the utilization of arabinose (ara) and the biosynthesis of leucine (leu) and pantothenate (pan). Cotransduction frequency analysis places this nadC locus between leu and pan at approximately minute 1.5 on the genetic map of Escherichia coli. This gene codes for the enzyme, quinolate phosphoribosyl transferase, which catalyzes the conversion of quinolinic acid to nicotinic acid mononucleotide.     

Relationship Between the Location of Autolysin, Cell Wall Synthesis, and the Development of Resistance to Cellular Autolysis in Streptococcus faecalis After Inhibition of Protein Synthesis

Ten minutes after inhibition of protein synthesis with chloramphenicol (CAP) the ability of cells of Streptococcus faecalis (ATCC 9790) to autolyze decreased to less than 20% of the rate for exponential-phase cells. After threonine exhaustion, the time for a 50% drop in the rate of cellular autolysis was about 20 min. These rapid increases in resistance to cellular autolysis could not be accounted for by: (i) the relatively slow and small overall decrease in susceptibility of isolated cell walls to added autolysin, or (ii) a decreased content of either the active or latent (proteinase activatable) form of the autolysin in the wall fraction. Continued wall synthesis resulted in dilution of preexisting autolysin in the isolated wall fraction. The release of labeled "old" relative to "new" wall from CAP-treated cultures showed that wall synthesis shifted away from the areas of wall previously shown to be associated with wall synthesis (extension) in exponential-phase cells. A corresponding dispersal of active autolysin activity was not observed. By using actinomycin D and CAP, a requirement for ribonucleic acid and protein synthesis early in the recovery of cells from amino acid starvation was demonstrated for the recovery in the ability of cells to autolyze. Evidence was obtained which suggests that a protein is involved in the conversion of latent to active autolysin. During recovery from amino acid starvation, increase in wall synthesis and content of active autolysin was delayed (25 to 35 min), whereas an increase in turbidity and latent enzyme content began within 10 min. After treatment with CAP at 22 or 52 min of recovery, a further increase in levels of both active and latent autolysin was severely inhibited; however, the increase in rate of wall synthesis was indistinguishable from that of an untreated control. This suggests that an increase in rate of wall synthesis does not depend on an increase in level of active autolysin.     

Autolytic Enzyme System of Streptococcus faecalis IV. Electron Microscopic Observations of Autolysin and Lysozyme Action

Cell walls (LOG walls) were isolated from cultures of Streptococcus faecalis ATCC 9790 in the exponential phase of growth. These walls were either allowed to undergo autolytic dissolution (in the presence or absence of trypsin) or wall autolysis was inactivated with sodium dodecylsulfate (SDS walls). Inactivated walls were treated either with lysozyme or with isolated, partially purified S. faecalis autolysin. During wall lysis, samples were removed, negatively stained with phosphotungstate, and examined in the electron microscope. Both lysozyme and isolated autolysin appeared to act over the entire surface of SDS walls. After partial dissolution, a fibrous network over the surface was revealed. Lysozyme digestion revealed the presence of prominent, highly-contrasted equatorial and subequatorial bands around the walls. After trichloroacetic acid extraction, the bands were seen less frequently and less distinctly in the partially lysozyme digested walls, suggesting that the bands contained nonpeptidoglycan polymers. In the absence of trypsin (which activates a latent form of the autolysin), autolysis of LOG walls appeared to start at the equatorial bands and to proceed back towards the apex of the coccus. Ribbons of wall material coming off the wide edge of the nearly hemispherical wall fragments were observed. Activation of latent autolysis resulted in lytic action over the entire wall surface. The results are consistent with the previously postulated location of active autolysin at the areas of new wall synthesis and the random location of latent autolysin in LOG walls.