Molecular weights of aggregation states of Busycon hemocyanin.

Molecular weights of all hemocyanin aggregates which can be homogeneously isolated have been measured by sedimentation equilibrium. The larger aggregates, which are the ones present under physiological conditions, are, to a very close approximation, integral multiples of a 4.4 x 10(6)-dalton, 60 S species. Dissociation of the 60 S species at high pH gives heterogeneous samples in which the smallest species has a molecular weight of 300,000. The smallest subunit which can be produced in denaturing solvents also has a molecular weight of 300,000.     

Serotyping and Enzyme Characterization of Pasteurella haemolytica and Pasteurella multocida Isolates Recovered from Pneumonic Lungs of Stressed Feeder Calves

Ninety-one isolates of Pasteurella multocida (Pm) and 124 of Pasteurella haemolytica (Ph) were recovered from the lungs of calves that died of bovine respiratory tract disease (BRTD). Nine Pm enzyme profiles (A through I) and 9 Ph enzyme profiles (J through R) were determined for the Pasteurella isolates. The Pm isolates were relatively evenly divided among the enzyme profiles, with one exception, profile I. The Ph isolates were not evenly distributed among the profiles. Fifty of the 91 Pm isolates were serotyped. Forty-two Pm isolates were positive for capsule type A, and 8 were untypable. Five somatic type antigen profiles (3; 3,4; 3,7; 3,4,7; and 4) were identified among the 50 serotyped Pm isolates; one isolate was untypable. The Ph isolates were further divided through serotyping and grouped as follows: 74 (60%) Pasteurella haemolytica A1 (PhA1), 12 (10%) PhA2, 4 (3%) PhA5, and 34 (27%) PhA6. Eighty-one percent of the Ph serotypes were clustered in the M and N enzyme profile. The P enzyme profile was almost unique to PhA2 (8 of 12, 67% of PhA2 isolates). Results of this study indicate a need to collect more data on Ph serotypes at the state veterinary diagnostic laboratories. Received: 29 August 1996 / Accepted: 15 October 1996     

Physicians as 'double agents.

The opportunities and stresses faced by today''s adolescent women have the potential to affect their health, either directly or through interaction with biologic and psychosocial events. Recently achieved entry into the world of endurance and competitive sports; smoking, drug, and alcohol use; the toxic shock syndrome; and the acquired immunodeficiency syndrome threaten the health of young women today. Physicians who care for adolescent women in the 1980s and in the future will require special skills to do so successfully.     

Control of N-acetylglucosaminidase specific activity in myxamoebae of Dictyostelium discoideum

Myxamoebae of Dictyostelium discoideum were grown with Aerobacter aerogenes as substrate, on nutrient agar plates or in shaken culture, with mean doubling times that varied between 3 and 6 hr. Growth in axenic culture was with mean doubling times of 5–6 or 8 hr. The specific activity of N-acetylglucosaminidase was three to four times higher in myxamoebae grown axenically than in myxamoebae grown with A. aerogenes and there was no correlation between enzyme specific activity and myxamoebal growth rate. High specific activities of N-acetylglucosaminidase were also found in myxamoebae grown with gram-positive bacteria (Bacillus megaterium, Staphylococcus lactis) as substrate while low specific activities were found in myxamoebae grown with the gram-negative bacteria Acinetobacter lwoffi and Pseudomonas aeruginosa as well as with A. aerogenes. A preparation of the cell envelope of A. aerogenes was nearly as effective as the intact bacteria at depressing myxamoebal N-acetylglucosaminidase specific activity. Lipopolysaccharide extracted from the cell envelope of gram-negative bacteria, or the lipid A component of the lipopolysaccharide, also depressed N-acetylglucosaminidase specific activity when added to axenic cultures of myxamoebae.     

Double-helical structures for polyxanthylic acid

Polyxanthylic acid has been found to exist in two different duplex forms, A_I and A_II. a_I, formed at pH5·7, occurs in a compact lattice with nearest neighbor molecules spaced at 2.11 nm. It has an axial translation per residue, h = 0·301 nm, and a rotation per residue, t = 36·0 °. The intensity distribution in its X-ray fiber diffraction pattern is analogous to that of A-RNA (h = 0·281 nm, t = 32·7 °). On the other hand A_II, formed at pH 8·0, has a less compact, statistically disordered crystal packing with nearest neighbors 2·35 nm apart. It has h = 0·252 nm and t = 32·7 ° and gives an X-ray intensity distribution essentially identical to A-DNA (h = 0·256 nm, t = 32·7 °). Similar right-handed helical duplex models, with flexible C-3′-endo sugar rings, have been developed for each molecular structure. Both have purine purine base-pairs, possibly triply hydrogen-bonded, and certainly with the same symmetry as Watson-Crick pairs but with a 0·2 nm greater C-1′ … C-1′ separation.