Rapid separation of low molecular weight solutes from liposomes without dilution

Liposomes can be separated from low molecular weight solutes on minicolumns of Sephadex G-50 made from the barrels of 1- or 5-ml plastic syringes. Excess fluid is first removed from the Sephadex beads by centrifugation and a mixture of liposomal entrapped and free solute is applied to the column bed. The centrifugation is repeated forcing the liposomal material through the column into a test tube while the free solute is quantitatively retained in the Sephadex. The procedure is applicable to a variety of solutes and 92 to 100% recovery is achieved for both charged and neutral liposomes. This technique has advantages over other methods for separating extraliposomal solutes from liposomes. Numerous samples can be processed simultaneously within minutes with no dilution of the liposomal preparation. Nonentrapped solute within the Sephadex can be easily recovered in a small volume of water or buffer.     

Catalysis by arginine deiminase: Evidence for a covalent intermediate

Arginine deiminase (EC 3.5.3.6) catalyzes the hydrolysis of arginine to ammonia and citrulline. This reaction is postulated to occur in three steps: (1) formation of the Michaelis complex, (2) the formation of an amidino-enzyme intermediate and liberation of ammonia, and (3) the rate-determining step, hydrolysis of the amidino-enzyme. The enzymic reaction is accelerated 5-fold by 0.2 M imidazole. This striking effect is expected for the amidino-enzyme mechanism but otherwise is difficult to explain. The putative amidino-enzyme intermediate can be demonstrated by quenching the [¹⁴C]arginine-arginine deiminase reaction at low pH. Under these conditions, 0.5 equivalents of ¹⁴C label per mol enzyme dimer were covalently bound.     

Evaluation of fasciotomy and vasodilator for treatment of frostbite in the dog

Severe freezing injury was produced in the hind foot of 26 mongrel dogs. All dogs were given daily whirlpool treatment and protective bandaging for 14 days following injury. In addition, certain dogs received a vasodilator, fasciotomy, or both vasodilator and fasciotomy following injury. Deep foot temperatures, foot volumes, tissue pressures, and 14 day tissue loss-salvage scores were compared. Significant differences between fasciotomy and nonfasciotomy dogs were seen in foot temperature, volume, and tissue pressure immediately following fasciotomy. Though there was no significant difference in 14 day tissue loss, there was clinically apparent prolongation of integrity of the local vascular system for 2 to 5 days following fasciotomy, and total foot salvage in several dogs receiving fasciotomy.     

Hydrostatic pressure-induced internalization of flagellar axonemes, disassembly, and reutilization during flagellar regeneration in Polytomella

Exposure of the quadriflagellate Polytomella to hydrostatic pressure was shown to result in the internalization of intact flagellar axonemes. During recovery from the pressure treatment the axonemes were disassembled concurrent with flagellar regeneration. When flagella were amputated partial regeneration occurred in the presence of cycloheximide, suggesting the presence of a limiting available pools of flagellar precursors. After a second amputation in the continued presence of cycloheximide little or no regeneration occurred, indicating depletion of the pool. However, if internalized axonemes were available, as well as the precursor pool, full-length flagella regenerated in cycloheximide. When the pool had been depleted and internalized axonemes were present, flagella regenerated to a length equal to the initial length of the internalized axonemes. We conclude that materials resulting from the disassembly of the pressure internalized axonemes are reutilized in regenerating new flagella.     

Evidence for more than one Ia antigenic specificity on molecules determined by the I-A subregion of the mouse major histocompatibility complex.

Ia antigenic specificities determined by the I-A subregion of the mouse major histocompatibility complex have been examined in strain B10.D2 (H-2d), C57BL/10 (H-2b), and in a (C57BL/6xDBA/2) hybrid (BDF1; H-2b/d). Detergent solubilized, 3H-leucine-labeled antigen preparations were mixed with appropriate alloantisera and precipitation was induced either by addition of goat anti-mouse gamma-globulin or by addition of protein A-bearing Staphylococci. Sequential precipitation analysis showed that in strain B10.D2, Ia specificities 8 and 11 were co-precipitable, and that in strain C57BL/10, Ia specificities 8 and 9 were co-precipitable. In contrast, precipitation of specificities 9 and 11 from a BDF1 antigen preparation showed that these two Ia specificities were on separate molecules. The genetic implications of these data are discussed.     

The influence of mating on autogenous egg development in the mosquito, Aedes taeniorhynchus

In several strains of Aedes taeniorhynchus, the presence of males increased the levels of autogeny. To stimulate autogenous egg production, the males had to mate with the females. Ageing further enhanced the rates of autogeny in mated females but not in virgins. Males did not influence the size of the autogenous egg batch. Even after the sixth day following emergence some females still possessed the capacity to respond to the male stimulus. With regard to ovarian maturation in A. taeniorhynchus, there appeared to be 3 types of females: (1) those that did not require a mating stimulus to be autogenous, (2) those that needed this stimulus and (3) those that remained anautogenous whether mated or not.     

Comparative immunochemical studies of primate hemoglobins

The antigenic properties of a number of chromatographically purified primate hemoglobins were compared to those of normal human hemoglobin using a sensitive radioimmunochemical procedure. The degree of inhibition of the antigen-antibody reaction with heterologous hemoglobins appeared to be related to the structural similarity of these proteins to the normal human hemoglobin immunogen. With the exception of the baboon hemoglobin, the antigenicity of the hemoglobins paralleled the phylogeny of the primates. The gorilla and chimpanzee hemoglobins were antigenically identical to normal human hemoglobin, whereas the gibbon and orangutan hemoglobins were substantially more variable. Of the Old World monkey hemoglobins examined, the baboon produced lower inhibition values, suggesting a greater degree of structural dissimilarity than other Cercopithecoidea hemoglobins, which is compatible with a greater rate of evolutionary change occurring in this protein. Using the known amino acid sequences of human and other primate hemoglobins, we have attempted to identify antigenic determinant areas of the proteins.