Biomedical subjects

J J Ladasky

Publications and source records attributed to J J Ladasky.

4 recordsLinked to original sources

PubMed1999

Molecular phylogeny of new world primates (Platyrrhini) based on beta2-microglobulin DNA sequences.

Neotropical primates, traditionally grouped in the infraorder Platyrrhini, comprise 16 extant genera. Cladistic analyses based on morphological characteristics and molecular data resulted in topologic arrangements depicting disparate phylogenetic relationships, indicating that the evolution of gross morphological characteristics and molecular traits is not necessarily congruent. Here we present a phylogenetic arrangement for all neotropical primate genera obtained from DNA sequence analyses of the beta2-microglobulin gene. Parsimony, distance, and maximum likelihood analyses favored two families, Atelidae and Cebidae, each containing 8 genera. Atelids were resolved into atelines and pitheciines. The well-supported ateline clade branched into alouattine (Alouatta) and ateline (Ateles, Lagothrix, Brachyteles) clades. In turn, within the Ateline clade, Lagothrix and Brachyteles were well-supported sister groups. The pitheciines branched into well-supported callicebine (Callicebus) and pitheciine (Pithecia, Cacajao, Chiropotes) clades. In turn, within the pitheciine clade, Cacajao and Chiropotes were well-supported sister groups. The cebids branched into callitrichine (Saguinus, Leontopithecus, Callimico, Callithrix-Cebuella), cebine (Cebus, Saimiri), and aotine (Aotus) clades. While the callitrichine clade and the groupings of species and genera within this clade were all well supported, the cebine clade received only modest support, and the position of Aotus could not be clearly established. Cladistic analyses favored the proposition of 15 rather than 16 extant genera by including Cebuella pygmaea in the genus Callithrix as the sister group of the Callithrix argentata species group. These analyses also favored the sister grouping of Callimico with Callithrix and then of Leontopithecus with the Callithrix-Callimico clade.

Animals↗

PubMed1999

Residue 3 of beta2-microglobulin affects binding of class I MHC molecules by the W6/32 antibody.

Previous studies of class I MHC molecules have shown that the owl monkey (Aotus) possesses at least two variants of the beta2-microglobulin (beta2m) protein. These two variants have different isoelectric points, and exhibit differential reactivity with the monoclonal antibody W6/32. We report cDNA sequences of the B2m gene, from W6/32-positive and W6/32-negative Aotus cell lines. The two beta2m variants we identified exhibit a single amino acid difference at position three. An arginine residue at position 3 was correlated with W6/32 reactivity, whereas histidine was associated with non-reactivity. W6/32 reactivity was conferred to a W6/32-negative Aotus cell line when it was transfected with the B2m from the W6/32-positive cell line. Residue 3 of beta2m is located at the surface of the class I molecule. It is also close to position 121 of the MHC class I heavy chain, which has previously been shown to influence W6/32 antibody binding. We conclude that W6/32 binds a compact epitope on the class I molecule that includes both residue 3 of beta2m and residue 121 of the heavy chain. We examined the distribution of the two beta2m motifs in a sample Aotus population using an allele-specific polymerase chain reaction assay. The pattern of beta2m segregation we observed matches that which was defined previously by serology. Additionally, we identified laboratory-born hybrid animals who possess both variants of beta2m.

Alleles↗

PubMed1998

beta2-Microglobulin in neotropical primates (Platyrrhini).

Nucleotide sequences for the three exons of the beta2-microglobulin (beta2m) gene (B2m) were determined for 135 animals representing 37 species and all 16 genera of neotropical primates (Platyrrhini). Twenty-eight different nucleotide sequences, encoding for 26 different proteins, were obtained. In comparison with those of other primate species, the beta2-microglobulins of the Platyrrhini form a distinct clade. Individual genera of neotropical primates have distinctive B2m sequences, but within a genera species can have either the same or different B2m sequences. B2m polymorphism was found within three of the species sampled: Callicebus personatus, Saguinus midas, and Aotus azarae. Of these only the polymorphism in A. azarae has an effect upon the mature, functional beta2m protein: residue 4 being either alanine or threonine. The A. azarae B2m allele encoding alanine at position 4 is shared with another species of Aotus (A. infulatus). In pairwise comparison the mature beta2m proteins of neotropical primates differ by 1-9 amino acid substitutions which can occur at 18 positions within the sequence. The substitutions are distributed throughout the primary structure but are more commonly found in loops rather than beta strands of the tertiary structure. Of 17 residues of beta2m which hydrogen-bond with the class I heavy chain in human MHC class I molecules, 13 are conserved in the neotropical primates. The overall pattern of sequence variation in the B2m genes of the Platyrrhini is consistent with an evolution by successive selectively neutral events.

Animals↗

PubMed1993

Phase-resolved fluorescence lifetime measurements for flow cytometry.

A flow cytometer capable of measuring fluorescence lifetimes by the phase shift method has been built and evaluated. Under optimal conditions, the resolution of the fluorescence lifetime measurement is shown to be under 200 picoseconds. Pulse intensity variations are normalized using limiting amplifiers and electronic filtering. Normalization of signal intensities provides a lifetime measurement that is independent of fluorescence intensity over at least a 50-fold (17 dB) range in fluorescence intensity. The fluorescence lifetimes of unbound dye, fluorescent beads, cells stained with ethidium bromide, propidium iodide, and phycoerythrin-conjugated monoclonal antibodies have been measured. The fluorescence lifetimes measured for these particles are well correlated with lifetime measurements made using a standard fluorimeter. Cells stained with ethidium bromide and propidium iodide at various nucleotide-to-dye ratios are shown to exhibit similar behavior to static cuvette measurements. The fluorescence lifetime parameter is also shown to resolve phycoerthyrin fluorescence from propidium iodide fluorescence.

Cells, Cultured↗