Pertussis toxin blocks somatostatin's inhibition of stimulated cyclic AMP accumulation in anterior pituitary tumor cells

Somatostatin inhibits both forskolin and (-) isoproterenol-stimulated cyclic AMP accumulation in AtT-20 cells. Pretreatment of these cells with pertussis toxin prevents somatostatin's inhibitory effects on cyclic AMP production. This pretreatment also enhances the cyclic AMP response to forskolin and (-) isoproterenol without affecting basal cyclic AMP levels. The blockade of somatostatin's inhibitory effect was dependent both on the time of preincubation and concentration of pertussis toxin used. The rise in forskolin-stimulated cyclic AMP formation following pertussis toxin treatment preceded the blockade of somatostatin's inhibitory actions. The results suggest that somatostatin acts through an inhibitory guanine nucleotide regulatory protein to affect adenylate cyclase activity.

A review of the current impact of measles in the People's Republic of China

Before the vaccine era, epidemics of measles occurred in alternate years on the mainland of China. During epidemic years the annual incidence was as high as 1,000-5,000 cases/100,000 population, with a fatality rate of 1% to 2%. In 1965, when highly attenuated measles vaccine was developed in China, a vaccination campaign was launched throughout the country. In its early years, the immunization program was not implemented simultaneously at all places, and outbreaks that continued to occur in some areas resulted in a moderate local incidence of measles despite a decline in the overall incidence. From the late 1970s on, stronger measures were taken by local health authorities with regard to measles vaccination. By 1980 the incidence had dropped further; in that year the number of reported cases was 570,037, with 3,862 deaths. Both morbidity and mortality related to measles dropped drastically after vaccination from levels in the prevaccine era, but measles still accounts for an appreciable proportion of all cases of infectious disease.

Variability and evolutionary trends in tooth size of Gigantopithecus blacki

The measurements of Gigantopithecus blacki teeth from Liucheng are summarized and comparative statistics are calculated. Compared to the variability of tooth size in living nonhuman primates, emphasizing Pongo because of close ecological and genetic relationships, the hypothesis of a single species for Liucheng specimens is acceptable. The Liucheng sample pattern of variability in tooth size, as well as the South African robust australopithecines, differs from living nonhuman primates in the same way; the first molar is not the least variable of the molars, and the molars are relatively variable compared with the other teeth. Sexual dimorphism may be responsible for this pattern in both cases. Later G. blacki cheek teeth are significantly larger than early G. blacki. From early G. blacki to later, the expansion ratio in tooth breadth is more than in tooth length. The pattern of expansion is like that seen in South African australopithecines. Both G. blacki and South African robust Australopithecus seem to show continued adaptation to more powerful and efficient chewing. The diet of G. blacki is not known, and its reconstruction depends on estimates of body size that differ greatly.

Studies on the incorporation of membrane proteins into liposomes: --effect of "boundary lipids" on reconstitution of pig heart mitochondrial cytochrome oxidase into liposomes

The reactivation of delipidated cytochrome oxidase depends on the reformation of "annular lipids", which is tightly bounded to the enzyme molecule. In the restoration of oxidase activity, the efficiencies of phospholipids with different polar head groups decrease in this order: PS greater than DPG greater than PI greater than PA greater than PG greater than PC, PE and in the case of phosphatidylcholines with different acyl chain the order is DOPC greater than LPC greater than PC greater than DPPC, DSPC. Therefore both the polar head group and the acyl chain of phospholipids must be considered in the reactivation process. The existence and the specificity of "annular lipids" obviously influence the incorporation of cytochrome oxidase into liposomes. When acidic phospholipids are used as "annular lipids", the effectiveness of reconstitution decreases in this order: PI greater than PS greater than DPG greater than PA, PG. Divalent metallic cations would facilitate the cytochrome oxidase reconstitution, but their effects depend on the composition of "annular lipids". Using dialysis method Ca2+ and Mg2+ could facilitate the incorporation into liposomes of the enzymes having PS or DOPC as their "boundary lipids". A comparison between the effects of different metallic cations on incorporation of cytochrome oxidase also shows that, with PI as "annular lipids", the effectiveness of different cations on incorporation by incubation method decreases in this order: Ca2+ greater than Mg2+ greater than Mn2+, Sr2+ greater than La3+. Apparently, the effect of metallic cations on incorporation cannot be interpreted by considering only the neutralization of the negative charged groups on membrane protein and lipids.

Complete amino acid sequence of mung bean trypsin inhibitor

The mung bean trypsin inhibitor has been found to be microheterogeneous at N-terminal region due to the presence of several isomers. After treatment with aminopeptidase M it becomes homogeneous and is suitable for sequence determination. Based on the determination of the structures of two active fragments the complete amino acid sequence of mung bean trypsin inhibitor has been elucidated. It consists of 72 amino acid residues with 7 pairs of disulfide bonds. The results show that this inhibitor belongs to the Bowman-Birk inhibitor family.