In Vitro Studies of α-Carboxyl-3-Thienylmethyl Penicillin,a New Semisynthetic Penicillin

The activity of a new semisynthetic penicillin, α-carboxyl-3-thienylmethyl penicillin (BRL-2288) was determined against 535 clinical isolates of gram-negative bacilli, by using the tube dilution technique. Nearly 80% of isolates of Proteus spp. were inhibited by 3.12 μg or less of this antibiotic per ml. BRL-2288 was as active as ampicillin against Escherichia coli. It was slightly more active than carbenicillin or 6-(d-α-sulfoaminophenylacetamido)-penicillanic acid against Pseudomonas sp., with over half of the isolates being inhibited by 50 μg or less of BRL-2288 per ml. Isolates of Klebsiella sp. were routinely resistant to this antibiotic. The drug was bactericidal against most sensitive organisms. BRL-2288 was less active against large inocula. A strain of Pseudomonas sp. which developed resistance to carbenicillin also developed resistance to BRL-2288 simultaneously.     

Certain organism-substrate relationships affecting the distribution of Uca minax (Crustacea: Decapoda)

The involvement of substrate in the ecology of the fiddler crab Uca minax was investigated by means of both field and laboratory studies. These included determination of the oxygen-holding capacities of five types of substrates on which this organism lives, as well as experiments to determine if there is substrate selection. The effect of population density on burrowing was also studied to determine the optimum number of individuals needed in the selection experiments, and to delineate the mechanisms these organisms use for avoiding dispersion onto less favorable substrates. Results indicate that Uca minax prefers substrates with high organic content, although these were shown to contain the lowest substrate oxygen. This evidence suggests that Uca minax prefers substrates of high energy value, and explains the significance of this species' adaptation in withstanding low oxygen tensions. Population density experiments indicate that at high population densities these crabs reduce intraspecific encounter and competition by burrowing and subsequently covering their burrows. Seasonal monitoring of burrow temperatures indicate the stability of this microenvironment as compared with the surrounding air temperature. These data also demonstrate the significance of the adjacent water in the habitat ecology of Uca minax.     

Proteinase Produced by Chlamydia psittaci in L Cells

L cells (mouse fibroblasts) infected with Chlamydia psittaci (strain meningopneumonitis) produced a proteinase differing in solubility in ammonium sulfate from the proteinase of uninfected L cells. Synthesis of the enzyme was inhibited by chloramphenicol but not by cycloheximide, indicating that the new proteinase in infected L cells was synthesized by Chlamydia psittaci. The chlamydial proteinase had no demonstrable ion requirements and was not inhibited by a variety of inhibitors of proteinase activity. Gel filtration experiments suggested a molecular weight of approximately 250,000. The proteinase appeared in infected L cells at the time host cells began to die and the large chlamydial cells began to reorganize into small ones. Some possible functions for the chlamydial proteinase were proposed.     

A study of the sulphur amino acids of rat tissues

1. In a study of the metabolism of l-[(35)S]methionine in vivo, the labelled sulphur compounds of rat liver and brain were separated first by ion-exchange chromatography into two fractions containing (i) free sulphur amino acids such as methionine, cystathionine, cyst(e)ine and homocyst(e)ine and (ii) glutathione. 2. Two-dimensional paper chromatography with butan-1-ol-acetic acid or propionic acid-water in the first direction and 80% acetone or acetone-ethyl methyl ketone-water in the second direction was found superior to other solvent systems for separating the sulphur amino acids. 3. At 10min. after injection of [(35)S]methionine only a small part of the (35)S was found combined in free methionine or other free sulphur amino acids. 4. Evidence was obtained of the presence of adenosyl[(35)S]methionine and adenosyl[(35)S]homocysteine in perchloric acid extracts of rat liver and brain. 5. The trans-sulphuration pathway was active in brain as well as in liver.     

The origin of lift forces in fluttering flight

A two-dimensional nonlinear integro-differential equation with time-varying coefficients describing the behavior of the fluttering wing-body systems typical of natural flight mechanisms has been deduced from the Navier-Stokes equation which generalizes local pressure and velocity distributions in the externally oscillating air field. The resulting equation for the wing forces is combined with an analogous expression for the forces of gravitation and acceleration associated with the body. The air acceleration force, not previously considered in bio-physical models of insect and bird flight, is shown to arise from a formal analysis of unsteady or time-varying contributions to the velocity field, while the square form of the conventional steady state aerodynamic forces is derived from the intertial terms in the Navier-Stokes equation with the aid of the approximations of Newtonian impact theory. Previous calculations (Houghton, 1964) have indicated that the contribution to gravitational stability of air acceleration and aerodynamic life are roughly in the ratio of 3:1.