Expression cloning of an AVP-activated, calcium-mobilizing receptor from rabbit kidney medulla

Arginine vasopressin (AVP) is a nonapeptide that regulates body fluid and blood pressure homeostasis. We have used expression cloning in the Xenopus laevis oocyte system to identify cDNA clones from a rabbit renal medullary expression library encoding an AVP receptor linked to Ca2+ mobilization. cRNA generated from positive clones conferred upon oocytes the capacity to mobilize intracellular Ca2+ in response to AVP. A cDNA clone encoding a protein of 780 amino acids was isolated, sequenced, and subcloned into an SV40-based expression vector. Expression of the cloned protein [designated the vasopressin-activated, calcium-mobilizing (VACM-1) protein] in COS-1 cells, resulted in increased 125I-labeled AVP binding [dissociation constant (Kd) of approximately 2 nM] and increased AVP-induced mobilization of Ca2+. Importantly, 125I-AVP could be immunoprecipitated both from detergent-solubilized membranes from COS-1 cells expressing VACM-1 protein and from an in vitro translation system, in which VACM-1 protein was synthesized, using antibodies prepared against a synthetic peptide derived from the NH2-terminal sequence of VACM-1. Interestingly, immunohistochemical staining of rabbit kidney sections with this antibody showed specific staining of collecting tubule epithelia. The deduced amino acid sequence is not homologous with any nucleic acid or amino acid sequences reported to date, including those of the V1 and V2 AVP receptors. The VACM-1 protein may represent a novel AVP receptor.

Structure-function interrelation and clinical effect of atrial natriuretic peptide (ANP)

Atriopeptin III (AP III) and its six analogues were synthesized by solid phase method and their diuretic and hypotensive activities were determined. Among these analogues, analogue [D-Ala-5, D-Arg-23] AP III was nearly 10 times as potent as AP III in diuretic activity while its hypotensive activity increased only 50% of that of AP III. Analogue des [Ser-15Gly-16Leu-17Gly-18Asn-20Ser-21] AP III was 15% as potent as AP III in diuretic activity, but it still maintained about 60% of the hypotensive activity of AP III. Meanwhile, we tried analogue [D-Ala-5, D-Agr-23] AP III for the treatment of hypertensive syndrome in pregnancy and obtained some good results.

OSNet: a neural network implementation of order statistic filters

A dedicated neural network model called OSNet which finds the kth largest element in an array of real numbers is proposed. Its overall processing time is constant irrespective of the number of elements in the array and is four times the processing time of a single neuron. Networks of this kind may be used as building blocks for hardware implementation of order statistic filters. Examples of using OSNet for implementing various order statistic filters and for sorting are shown.

Improving the linearity of the Michelson interferometric angular measurement by a parameter compensation method

A parameter compensation method is developed to improve the linearity of the Michelson interferometric angular measurement. The formulas for the exact calculation of the parameters are presented; different cases are discussed. By introducing a weight function in the calculation, we can change the distribution of the linearity over the whole range of measurement. The theoretical analysis and the experimental results show that this method greatly improves the linearity of the measurement even for a large range of measurement.

New optical method for measuring small-angle rotations

To measure small-angle rotations, the two mirrors of a Michelson interferometer are replaced by right-angle prisms. Rotation of the latter shifts the interference pattern. Measurement of that shift gives, after calibration, the rotation. The experimental setup is insensitive to vibrations, provides good linearity between +5 degrees and -5 degrees , and has a resolution of 10(-4) deg.