Subcellular localization and properties of adenosine diphosphatase activity in human polymorphonuclear leukocytes

Adenosine diphosphatase (ADPase) activities were studied in human polymorphonuclear leukocytes with a recently developed radio-assay. The neutrophils were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation. The sucrose density gradient fractions were assayed for ADPase activity and for principal organelle marker enzymes. ADPase activity was distributed between the plasma membrane, specific granule and soluble fractions. The plasma membrane and specific granule activities had similar kinetic and inhibitor properties but the cytosolic enzyme was clearly different. Studies with the non-penetrating inhibitor diazotized sulphanilic acid and measurements of latent activity indicate that plasma membrane ADPase activity is located on the external aspect to the cell. Its possible role in inhibiting platelet aggregation is discussed. Neutrophils were isolated from control subjects, patients with chronic granulocytic leukaemia and patients in the third trimester of pregnancy. The specific activities (mU/mg protein) of ADPase activity, in contrast to those of alkaline phosphatase, were similar in all three groups. This result, together with fractionation experiments and inhibition studies strongly suggests that ADPase activity is not attributable to neutrophil alkaline phosphatase.     

Studies on the allergenic significance and structure of rat serum albumin

This study evaluated the capacity of rat serum albumin and of its proteolytic fragments to activate human basophils for IgE-mediated histamine release. The leukocytes from 8 out of 33 patients allergic to rats released histamine with rat serum albumin. Two proteolytic fragments of rat serum albumin, each constituting half of the molecule, were used to study the IgE-reactive antigenic sites. These fragments released histamine with the cells of some of the donors, thus demonstrating the presence of at least 2 antigenic determinants on each fragment for a total minimum of 4 sites on the intact rat serum albumin molecule. Most of the allergenic activity, however, was not recovered in the 2 fragments (total recovery mean = 6.4%, range between 0.1 and 31%). This loss could be due to cleavage of the rat albumin molecule in the middle of the third domain with loss of antigenic sites and/or due to minor conformational changes in the fragments as compared with the intact molecule. There was up to a 500-fold difference in the percent of activity recovered in the fragments when tested on cells from different patients. Therefore, there is no single immunodominant site on the molecule equally important for all patients. The cells of all 8 patients also reacted with mouse serum albumin but only 2 with bovine serum albumin. At least 1 determinant on mouse and rat serum albumin is cross-reactive with IgE.     

Sequence of residues 400--403 of bovine serum albumin.

A large tryptic peptide of bovine serum albumin (residues 377--582) was subjected to 32 cycles of Edman degradation to determine the sequence of the last remaining unknown segment of this protein. Residues 400--403 were identified as gly-Phe-Gln-Asn. Amide assignments were also made at positions 388 (glutamine), 389 (asparagine), 391 (aspartic acid) and 392 (glutamine).     

Protein-coding potential of mouse mammary tumor virus genome RNA as examined by in vitro translation.

The protein-coding capacity of the mouse mammary tumor virus genome has been examined by in vitro translation of genome length and polyadenylated subgenomic fragments of viral RNA. Intact genome RNA of about 35S programmed synthesis of the Pr77gag, Pr110gag and Pr160gag/pol precursors seen in infected cells in vivo. Polyadenylated RNA fragments of 18 to 28S encoded products whose tryptic peptide maps resembled those of the nonglycosylated precursor to the envelope glycoproteins, confirming the gene order 5'-gag-pol-env-3'. Translation of polyadenylated RNA fragments smaller than 18S yielded a series of related proteins whose peptide maps bore no resemblance to any of the virion structural proteins. Thus, a region of the mouse mammary tumor virus genome distal to the env gene appears to have an open reading frame sufficient to encode at least 36,000 daltons of protein as of yet unknown function.     

Herpes Zoster and Multiple Sclerosis

No significant difference was found between 50 consecutive patients with multiple sclerosis and matched controls in respect of previous infection with rubella or measles and chicken-pox, or of previous vaccination and immunizing injections. Significantly more patients had a past history of herpes zoster compared with the controls.     

Some effects of overcrowding on the respiration of larval Aedes aegypti

Changes in the respiratory rates of standard, overcrowded, and starved fourth-instar Aedes aegypti are compared. The respiratory effects of varying larval densities during and prior to measurement are investigated. In addition, the results of exposure of standard and over-crowded larvae to growth-retarding factors (GRF) at various concentrations are also evaluated.

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Résumé Le but de cette étude est d'étudier les modifications de l'activité respiratoire chez des larves du 4ème stade mises respectivement en condition d'élevage standard, en condition de surpeuplement, et en condition de restriction alimentaire.Les conditions de surpeuplement et de restriction alimentaire entrainent un abaissement significatif du niveau du métabolisme respiratoire. L'activité respiratoire des larves élevées en condition standard, prend des valeurs plus élevées quand la mesure est faite sur un plus grand nombre de larves rassemblées dans le tube-test; par contre les conditions de mesure (15, 25 ou 35 larves dans le tube-test) ne modifient pas la valeur de l'activité respiratoire des larves élevées en condition de surpeuplement. Quand des larves élevées en milieu surpeuplé et en milieu standard sont soumises à de fortes concentrations des facteurs retardant la croissance (Growth-retardant factors; GRF de Moore & Fisher 1969) l'activité respiratoire est stimulée. Dans les conditions de surpeuplement et de restriction alimentaire, deux types facteurs pourraient agir sur le métabolisme respiratoire, des facteurs chimiques et des facteurs mécaniques tels que l'agitation des individus dans un espace étroit (par exemple le tube-test).

     

Galactosyl transferase-the liver plasma membrane binding-site for asialo-glycoproteins

Agalacto-fetuin inhibits the binding of ¹²⁵I-asialo-fetuin by liver plasma membrane fragments. The chemically prepared agalacto-glycoprotein derivative is not a substrate for plasma membrane sialyl transferase and therefore this indicates that agalacto-fetuin is a true inhibitor of the membrane binding of ¹²⁵I-asialo-fetuin. The plasma membrane fraction also contains galactosyl transferase activity and the binding of ¹²⁵I-asialo-fetuin by plasma membranes is prevented by α-lactalbumin, a known inhibitor of glycoprotein-galactosyl transferase. These data indicate that galactosyl transferase is the liver plasma membrane component which binds asialo-glycoproteins.