Nodular localized primary cutaneous amyloidosis: a bullous variant.

Primary cutaneous amyloidosis describes a group of disorders in which amyloid is deposited in the skin without evidence of systemic involvement. Nodular localized primary cutaneous amyloidosis (NLPCA) is a rare form of these skin-restricted amyloidoses. We present an unusual case of NLPCA in a 51-year-old man, who had clinical and histopathological evidence of subepidermal bullous formation, a unique feature in NLPCA. The possible pathogenesis of this change is discussed.

Primary structure and expression of a human CTP:phosphocholine cytidylyltransferase.

Human CTP:phosphocholine cytidylyltransferase (CT) cDNAs were isolated by PCR amplification of a human erythroleukemic K562 cell library. Initially two degenerate oligonucleotide primers derived from the sequence of the rat liver CT cDNA were used to amplify a centrally located 230 bp fragment. Subsequently overlapping 5' and 3' fragments were amplified, each using one human CT primer and one vector-specific primer. Two cDNAs encoding the entire translated domain were also amplified. The human CT (HCT) has close homology at the nucleotide and amino acid level with other mammalian CTs (from rat liver, mouse testis or mouse B6SutA hemopoietic cells and Chinese hamster ovary). The region which deviates most from the rat liver CT sequence is near the C-terminus, where 7 changes are clustered within 34 residues (345-359), of the putative phosphorylation domain. The region of the proposed catalytic domain (residues 75-235) is 100% identical with the rat liver sequence. Significant homology was observed between the proposed catalytic domain of CT and the Saccharomyces cerevisiae MUQ1 gene product, and between the proposed amphipathic alpha-helical membrane binding domains of CT and soybean oleosin, a phospholipid-binding protein. There are several shared characteristics of these amphipathic helices. An approx. 42,000 Da protein was over-expressed in COS cells using a pAX142 expression vector containing one of the full-length HCT cDNA clones. The specific activity of the HCT in COS cell homogenates was the same as that of analogously expressed rat liver CT. The activity of HCT was lipid dependent. The soluble form was activated 3 to 4-fold by anionic phospholipids and by oleic acid or diacylglycerol-containing PC vesicles.

Cloning and expression of rat liver CTP: phosphocholine cytidylyltransferase: an amphipathic protein that controls phosphatidylcholine synthesis.

CTP:phosphocholine cytidylyltransferase (EC 2.7.7.15) is a key regulatory enzyme in the synthesis of phosphatidylcholine in higher eukaryotes. This enzyme can interconvert between an inactive cytosolic form and an active membrane-bound form. To unravel the structure of the transferase and the mechanism of its interaction with membranes, we have cloned a cytidylyltransferase cDNA from rat liver by the oligonucleotide-directed polymerase chain reaction. Transfection of the rat clone into COS cells resulted in a 10-fold increase in cytidylyltransferase activity and content. The activity of the transfected transferase was lipid-dependent. The central portion of the derived protein sequence of the rat clone is highly homologous to the previously determined yeast cytidylyltransferase sequence [Tsukagoshi, Y., Nikawa, J. & Yamashita, S. (1987) Eur. J. Biochem. 169, 477-486]. The rat protein sequence lacks any signals for covalent lipid attachment and lacks a hydrophobic domain long enough to span a bilayer. However, it does contain a potential 58-residue amphipathic alpha-helix, encompassing three homologous 11-residue repeats. We propose that the interaction of cytidylyltransferase with membranes is mediated by this amphipathic helix lying on the surface with its axis parallel to the plane of the membrane such that its hydrophobic residues intercalate the phospholipids.

Stereoscopic acuity with induced refractive errors.

The relation between refractive error and stereoscopic acuity was investigated by measuring stereoacuity with different combinations of positive and negative spherical lenses over the usual refractive correction. A detailed study was performed on two subjects. In general, there was little change in stereoacuity when the added lenses were of equal power. On the other hand, power inequality almost invariably caused a reduction in stereoacuity. A technique is described for detecting a refractive overcorrection by means of a sequence of stereoacuity measurements.