The chimpanzee M blood-group antigen is a variant of the human M-N glycoproteins

Chimpanzee erythrocytes express strong M but weak, occasional N blood-group activity, as detected by anti-M and anti-N reagents. We have found that the M activity is carried by a major membrane glycoprotein that is similar but not identical to the human MM glycoprotein (glycophorin A). We have isolated and characterized this glycoprotein from erythrocyte membranes of four individual chimpanzees. The purified glycoproteins strongly inhibited agglutination of M cells by rabbit anti-human M sera and only weakly inhibited the agglutination of N cells by rabbit anti-human N sera. They also displayed medium-to-strong inhibitory activity against chimpanzee iso- and crossimmune antisera tested with chimpanzee erythrocytes of various V-A-B-D and W^c specificities, which are known as chimpanzee extensions of the human type M-N system and the Miltenberger counterpart, respectively. Each glycoprotein was cleaved with CNBr into three fragments, whose size, solubility, and composition were analogous to those obtained by similar treatment of the human M-N antigens. The amino-terminal fragment was found to be a glycooctapeptide whose amino acid composition and partial sequence indicated that it is an intermediate form of the human M and N glycooctapeptides. Its carbohydrate content comprised two threonine-linked saccharide units that, although similar in composition to the human threonine-linked units, were fewer in number than the three units found in the corresponding human glycooctapeptides. Structural similarities to the human antigens strongly suggest that the amino terminus bears the major antigenic determinants of the molecule, and the occurrence in this region of numerous, albeit rare, variants among humans and in chimpanzees indicates that the corresponding coding sequence of the structural gene is particularly susceptible to mutational events. We conclude that the chimpanzee M gene product is a variant of the human type and that the chimpanzee gene is an allele of the human polymorphic M-N locus.This research was supported by National Institutes of Health Grants GM 16389 and HL 19011 and March of Dimes Grant 1-661.     

Biochemical studies of the chromaffin granule. II. Properties of membrane-bound and water-soluble forms of chromogranin A and dopamine-β-hydroxylase activity

1. Chromogranin A has been isolated from the washed membrane fraction of highly purified chromaffin granules after solubilization in Triton X-100. A hydrated molecular weight of 2.9·10⁵ has been obtained for chromogranin A_M which in its electrophoretic mobility and molecular volume appears very similar to chromogranin A_I of the water-soluble fraction.     

Initial Stage of Transformation of Permissive Cells by Simian Virus 40: Development of Resistance to Productive Infection

A quantitative assay has been used to determine the conditions leading to acquisition of resistance of permissive cells to lytic infection. The number of cell colonies surviving infection depends on the occurrence of several cell divisions after infection. High yields of resistant colonies were obtained when infected, confluent cultures were released from contact inhibition 10 to 14 hr after infection. Infection of actively growing cells produced similar results, but halting further division by seeding these growing cells on confluent monolayers prevented the development of colonies. Colony formation was a direct function of multiplicities lower than 5. An inverse killing response was observed with higher multiplicities, yet colonies were produced at a multiplicity of infection as high as 50. Brief exposure of input simian virus 40 to ultraviolet light stimulated colony formation. Irradiation of the virus for longer periods of time led to reduction of colony formation at a rate slower than the rate of inactivation of viral infectivity. It was concluded that resistance is induced by simian virus 40 and that this alteration represents one of the earliest detectable characteristics of the transformation of permissive cells.     

Dihydrofolate reductase: low-resolution mass-spectrometric analysis of an elastase digest as a sequencing tool (Short Communication)

An elastase digest of a protein of unknown structure, dihydrofolate reductase, was studied by mass spectrometry. This soluble digest contained a large number of small peptides in different yields, within the ideal molecular-weight range (200-1200) for mixture-analysis mass spectrometry. Sequences of the major component peptides in the digest are reported.     

ULTRASTRUCTURAL AND BIOCHEMICAL CHANGES IN BROWN FAT IN COLD-EXPOSED RATS

During the first 3 days of exposure of rats to 5°C, the nitrogen concentration of interscapular brown fat increased by 50% and remained at this elevated level for the duration of the 8-wk observation period, while the mass of tissue increased fourfold. The concentration of both DNA and RNA per unit nitrogen reached a maximum after 3 days, then declined; however, the total quantity of each continued to rise. The concentration of various respiratory enzymes decreased during the first few days and then increased, but at different rates. The morphological changes in mature brown fat cells during cold acclimation were observed to be: a reduction in fat droplet size during the first 3 days, followed by a gradual increase in size through 6 wk in the cold; a continual increase in the amount of intermitochondrial ground substance during the first 3 wk, with increased granularity and glycogen content after 1 wk; initial disappearance of glycogen between mitochondria, followed by the reappearance of a few isolated particles in the intermitochondrial ground substance after 1 wk in the cold; initial increase in the density of intramitochondrial matrix for the first 3–4 days, followed by a gradual return to the control density; loss in integrity of mitochondrial outer membranes during the first 4 days, followed by gradual but incomplete restoration; temporary loss of the dense material in lipid droplets during the first 24 hr, with return after 1 wk in the cold; and a 40% increase in mitochondrial diameter within 1 day, followed by a decrease in diameter within 1 wk to a constant value about 15% larger than the controls.