Pyridoxylated adult human hemoglobin (HbAo) was prepared using a one molar equivalent of pyridoxal 5-phosphate (PLP) per heme and reduced with either NaCNBH3 or NaBH4. A separate sample was pyridoxylated and passed through a mixed-bed ion exchange column without reduction. All three preparations had a P50 of 29 +/- 2 torr and a cooperativity of n = 2.4 +/- 0.1. These preparations, in both the oxy and deoxy forms, were then treated with 7 equivalents of glutaraldehyde per tetramer at pH 6.8 at 4 degrees C and at room temperature. The polymerization invariably reduced the P50 to 18 +/- 2 torr with Hill coefficients of less than 2. These solutions, with or without further reduction using NaCNBH3, all retained the PLP in differing amounts (2-3 moles/tetramer). Methemoglobin concentrations were increased during the polymerization reaction. The normal pyridoxylation procedure, using sodium borohydride reduction, resulted in a number of different molecular species. Polymerization with glutaraldehyde caused a further proliferation of molecular species that could not be separated by anion exchange chromatography or by isoelectric focusing. The extent of polymerization, estimated by gel exclusion chromatography and SDS polyacrylamide gel electrophoresis, was from 40 to 50%. Analysis of the reverse phase chromatograms, which separate the heme and the alpha- and beta-chains, showed extensive polymerization and distribution of the radioactively labeled PLP on the protein for all preparations. All of the polymerized and pyridoxylated samples were unstable, and showed different chromatographic patterns after storage at 4 degrees C for 1 month. Attempts to stabilize these preparations by further reduction with NaCNBH3 gave products with a lower P50 and lower cooperativity. When the reactions were conducted with a purified HbAo, heterogeneity was somewhat decreased compared to the normally used stroma-free hemoglobin, but a large number of molecular species were still formed.

Aldehydes↗

PubMedDate not supplied

Wild birds as hosts of Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae).

We evaluated the prevalence, mean intensity and relative density of ticks in 467 wild birds of 67 species (12 families) from forest and cerrado habitats at two protected areas of Minas Gerais, between March and September 1997. Ticks collected (n=177) were identified as larvae and nymphs of Amblyomma cajennense and four other species of Amblyomma. We report for the first time 28 bird species as hosts of the immature stages of A. cajennense, demonstrating the lack of host specificity of the larvae and nymphs. A. cajennense had 15% prevalence on birds, with a mean infestation intensity of 0.37 ticks per host sampled, and 2.5 ticks per infested bird. Prevalence varied in relation to host species, diet and between birds from forests at two successional stages. There were no differences in relation to host forest dependence, participation in mixed flocks of birds, and nest type constructed. A. cajennense is a species of medical and veterinary importance, occurring on domestic animals but is known little of its occurrence on wildlife.

Animals↗

PubMedDate not supplied

[Insulin secretion and insulin resistance in patients failing to respond to oral hypoglycemic agents].

Explore the source record for details and available documents.

C-Peptide↗