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The nucleotide sequence of RNA 3 of two subgroup I strains of cucumber mosaic virus (CMV), Fny-CMV and M-CMV, was determined and compared at both the nucleic acid and protein level with the previously determined, corresponding (partial) sequences of RNA 3 of five other subgroup I strains: C-CMV, D-CMV, I17F-CMV, O-CMV and Y-CMV. Fny-CMV RNA 3 is composed of 2216 nucleotides (nt) and M-CMV RNA 3 2214 nt. Both RNAs contain two open reading frames, the 3a gene and the coat protein gene. These RNAs showed very little nucleotide sequence divergence, either from each other or from the five other subgroup I strains. The nucleotide sequence variation observed was two to 13 differences in the 120 to 123 nt 5' non-translated regions, six to 17 differences in the 840 nt 3a genes, two to 15 differences in the 296 to 299 nt intergenic regions, three to 25 differences in the 657 nt coat protein genes and two to 10 differences in the 299 to 303 nt 3' non-translated regions. Protein sequence similarity was also high, with one to four differences in the 279 amino acids of the 3a proteins and two to 13 differences in the 218 amino acids of the coat proteins. Limited nucleotide sequence variation among nine strains of CMV was also shown using an RNA protection assay and a probe specific for Fny-CMV RNA 3. The limited variation shown by RNA 3 of strains of CMV with different passage histories, isolated in different countries over a 50 year period, suggests that the maintenance of the highly conserved nucleotide sequence may be important for other viral RNA functions or interactions.

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Echinocytes were frequently found in patients with liver disease when their blood was examined in wet films, but rarely detected in dried, stained smears. When normal erythrocytes (discocytes)were incubated with physiologic concentrations of the abnormal high density lipoproteins (HDL) from some jaundiced patients, echinocytosis developed within seconds. Other plasma fractions were not echinocytogenic. There was a close correlation between the number of echinocytes found in vivo and the ability of the corresponding HDL to induce discocyte-echinocyte transformation. On incubation with normal HDL, echinocytes generated in vitro rapidly reverted to a normal shape, and echinocytes from patients showed a similar trend. Echinocytosis occurred without change in membrane cholesterol content, as did its reversal, and was not caused by membrane uptake of lysolecithin or bile acids. Abnormal, echinocytogenic HDL showed saturable binding to -5,000 sites per normal erythrocyte with an association constant of 108 M-'. Nonechinocytogenic patient HDL and normal HDL showed only nonsaturable binding. Several minor components of electrophoretically separated erythrocyte membrane proteins bound the abnormal HDL; pretreatment of the cells with trypsin or pronase reduced or eliminated binding. Echinocytosis by abnormal HDL required receptor occupancy, rather than transfer of constituents to or from the membrane, because cells reversibly prefixed in the discoid shape by wheat germ agglutinin, and then exposed to abnormal HDL, did not become echinocytes when the HDL and lectin were successively removed. Binding did not cause dephosphorylation of spectrin. We conclude that the echinocytes of liver disease are generated from discocytes by abnormal HDL, and we infer that the shape change is mediated by cell-surface receptors for abnormal HDL molecules.