Ba2+-sensitive K+ channels in luminal-membrane vesicles from pars convoluta of rabbit proximal tubule

This paper describes properties of 86Rb+ fluxes through a novel K+ channel in luminal-membrane vesicles isolated from pars convoluta of rabbit proximal tubule. The uptake of 86Rb+ into potassium salt loaded vesicles was specifically inhibited by Ba2+. The isotope accumulation is driven by an electrical diffusion potential as shown in experiments using these membrane vesicles loaded with anions of different membrane permeability and was as follows: gluconate greater than SO4(2-) greater than Cl-. Furthermore, the vesicles containing the channels show a cation selectivity with the order K+ greater than Rb+ greater than Li+ greater than Na+ = choline+.     

Renal transport of monocarboxylic acids. Heterogeneity of lactate-transport systems along the proximal tubule.

The characteristics of D- and L-lactate transport in luminal-membrane vesicles derived from whole cortex, from the pars convoluta and from the pars recta of rabbit kidney proximal tubule were studied. It was found that uptake of both isomers in vesicles from whole cortex occurred by means of dual electrogenic transport systems, namely a low-affinity system and a high-affinity system. Uptake of both isomers in vesicles from the pars recta was strictly Na+-dependent and is mediated via a single high-affinity common transport system. Vesicles from the pars convoluta contained a cation-dependent but Na+-unspecific low-affinity common transport system for these compounds. The physiological importance of this system is briefly discussed.     

Binding of monoiodinated neuropeptide Y to hippocampal membranes and human neuroblastoma cell lines

Monoiodinated radioligands of the homologous 36-amino acid peptides, neuropeptide Y (NPY) and peptide YY, were prepared by reverse phase high performance liquid chromatography with isocratic elution. [125I-Tyr1]- and [125I-Tyr36]monoiodoNPY bound equally well to a single class of high affinity binding sites on synaptosomal membranes prepared from porcine hippocampus (Kd = 1.0 X 10(-10) M) whereas iodine substitution in Tyr27, for example, partly interfered with the receptor binding. The receptors on the hippocampal membranes did not distinguish between neuropeptide Y and peptide YY either in their monoiodinated or in their unlabeled forms. Six out of twelve human neuroblastoma cell lines had high affinity binding sites for monoiodinated NPY ranging from 2 to 145 X 10(3) sites per cell. The NPY binding to three of the cell lines, SMS-MSN, SMS-KAN, and CHP-234 was of relatively high affinity (Kd = 1.3 to 6.1 X 10(-10) M), and, as in the hippocampal membranes, the long C-terminal fragment, NPY(13-36)peptide was also a relatively potent ligand for these receptors. Two other neuroblastoma cell lines, MC-IXC and CHP-212, expressed NPY receptors characterized by a lower affinity (Kd = 4.8 and 24.6 X 10(-9) M) and negligible cross-reactivity with the C-terminal fragment. It is concluded that monoiodinated radioligands of the tyrosine-rich neuropeptide Y can be prepared and that receptors for these ligands in two apparently different subtypes are found on a series of human neuroblastoma cell lines.     

Reconstructing sibling relationships in wild populations

Reconstruction of sibling relationships from genetic data is an important component of many biological applications. In particular, the growing application of molecular markers (microsatellites) to study wild populations of plant and animals has created the need for new computational methods of establishing pedigree relationships, such as sibgroups, among individuals in these populations. Most current methods for sibship reconstruction from microsatellite data use statistical and heuristic techniques that rely on a priori knowledge about various parameter distributions. Moreover, these methods are designed for data with large number of sampled loci and small family groups, both of which typically do not hold for wild populations. We present a deterministic technique that parsimoniously reconstructs sibling groups using only Mendelian laws of inheritance. We validate our approach using both simulated and real biological data and compare it to other methods. Our method is highly accurate on real data and compares favorably with other methods on simulated data with few loci and large family groups. It is the only method that does not rely on a priori knowledge about the population under study. Thus, our method is particularly appropriate for reconstructing sibling groups in wild populations.