Simultaneous analysis of disopyramide and quinidine in plasma by high-performance liquid chromatography

A new reversed-phase high-performance liquid chromatographic method allowing simultaneous measurement of plasma concentrations of disopyramide and quinidine is described. Disopyramide and quinidine were separated on a reversed-phase column using 0.05 M phosphate buffer (pH 3.0)—acetonitrile (73:27, v/v), as mobile phase and the peaks were monitored by UV absorbance at the wavelengths of 254 and 325 nm. The drugs were extracted from alkaline plasma with chloroform containing the internal standard. The organic phase was evaporated to dryness and the residue was redissolved in a small volume of the mobile phase before analysis by high-performance liquid chromatography. The method is convenient and reliable in routine monitoring of both drugs.     

Analysis of developmentally homogeneous neural crest cell populations in vitro: I. Formation,morphology and differentiative behavior

When early embryonic quail neural tubes are dissected free from surrounding tissues and placed in culture, small stellate neural crest cells usually migrate from the explant onto the substratum. This outgrowth has been reported to consist of a mixture of cells, some of which undergo melanogenesis, while the rest remain unpigmented. We have, in contrast to earlier observations, obtained a spatial separation of the two phenotypes. In these cultures the primary outgrowth of migrating cells remained almost free of pigment-forming cells, whereas small spherical clusters containing several hundred pigment-forming cells appeared on the explanted neural tubes. Whether the clusters remained with the tube explants or were subcultured, all cluster cells differentiated into melanocytes. Prior to melanogenesis, the appearance of the cultured cells from a cluster was indistinguishable from the cells in the outgrowth. The clusters provide a source of neural crest cells, that (1) can be easily obtained in comparatively large numbers, (2) is not contaminated with any other cell type, (3) can be isolated before the onset of differentiation, and (4) is developmentally homogeneous. Thus, the cluster population is well suited for many types of experiments, such as the identification of specific environmental factors that might control neural crest cell differentiation.     

Biochemical and genetic analysis of a mutant with altered alkaline phosphatase activity in Dictyostelium discoideum

Alkaline phosphatase is one of several enzymes that accumulate in a temporally regulated sequence during the development of Dictyostelium discoideum. These enzymes can be used to monitor specific gene expression; moreover, isolation and analysis of mutations in the structural gene(s) can serve to indicate some of the essential steps in programmed synthesis and morphogenesis. A mutation (alpA) which affects the activity and substrate affinity of alkaline phosphatase was isolated in D discoideum using a procedure for screening large numbers of clones. Alkaline phosphatase activity at all stages of vegetative growth and development was altered by the mutation. Several physical properties of the enzyme from growing cells and developed cells were compared and found to be indistinguishable. It is likely that a single enzyme is responsible for the majority of alkaline phosphatase activity in growth and development. The mutation is coexpressed in diploids heterozygous for alpA and maps to linkage group III. One of the haploid segregants isolated from these diploids carries convenient markers on each of the six defined linkage groups and can be used for linkage analysis of other genetic loci.     

Growth of “Seeded” Cellulolytic Enrichment Cultures on Mesquite Wood

Eleven enrichment cultures were developed by a “seeded” enrichment culture technique, and one was developed by a simple enrichment technique. The seeded enrichment, the pure “seed,” and the simple enrichment cultures were compared during growth on mesquite wood, cotton, carboxymethylcellulose, and cellobiose. All of the enrichment cultures were cellulolytic and exceeded the pure seed cultures in mesquite wood hydrolysis and/or viable cell count. Yeast extract improved, but was not essential for, growth of the seeded enrichment cultures on carboxymethylcellulose. Two of the seeded enrichment cultures, CAD5 and CAD11, grew best at 37°C and pH 7.0 on mesquite wood. A 1.0% (wt/vol) wood concentration was optimum for their growth.     

Pyruvate metabolism after in vivo exposure to oral arsenic

This study investigated altered pyruvate metabolism after prolonged oral arsenic exposure. Male rats were given access to deionized drinking water containing 0, 40 or 85 ppm sodium arsenate (As⁵⁺) for 3 weeks. Respiration studies with mitochondria isolated from treated animals indicated decreased state 3 respiration (with ADP) and decreased respiratory control ratios (RCR) for pyruvate/malate-mediated respiration, but not for succinate-mediated respiration, as compared to control respiration values. In addition, pyruvate dehydrogenase activity was measured, in both liver and intestine, before and after Mg-activation in vitro. After 3 weeks, the effects of arsenic at the highest dose level were pronounced on the basal pyruvate dehydrogenase activity (before activation) as well as the total pyruvate dehydrogenase (after activation). The inhibition of pyruvate dehydrogenase activity both before and after Mg-activation suggests an arsenic effect on mitochondrial pyruvate metabolism which, in part, involves inhibition of pyruvate decarboxylase. Evidence is also presented which may indicate an arsenic effect on the kinase and/or phosphatase which regulate pyruvate dehydrogenase activity.     

The immune response of allophenic mice to the synthetic polymer GLΦ

The immune response of allophenic mice of type C57BL/6(A × SJL) F₁ to GL administered in complete Freund's adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F₁ generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F₁ generation, a result which may argue against the possibility that more than two genes control the response to GL in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit chimeric drift, both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GL showed a good correlation to the number of A × SJL lympho-cytes in the animal.Abbreviations used in this paper are GL an amino acid polymer of 57 %l-glutamic acid, 38%l-lysine, and 5%l-phenylalanine - GLT¹⁵ an amino acid polymer ofl-glutamic acid,l-lysine, and 15 %l-tyrosine - (T,G)-A-L an amino acid polymer having a polylysine backbone with side chains of polyd-l-alanine, terminating in short sequences of tyrosine and glutamic acid - GAT₁₀ an amino acid polymer of 60%l-glutamic acid, 30%l-alanine, and 10%l-tyrosine - GLA₅ an amino acid polymer of 57%l-glutamic acid, 38%l-lysine, and 5%l-alanine - DNP 2,4 dinitrophenyl - BGG bovine gamma globulin - FCS fetal calf serum - PWBC peripheral white blood cell - SWBC spleen white blood cell - T cell thymus-derived lymphocyte - B cell bone marrow-derived lymphocyte