Biosynthesis and assembly of platelet GPIIb-IIIa in human megakaryocytes: evidence that assembly between pro-GPIIb and GPIIIa is a prerequisite for expression of the complex on the cell surface

The platelet membrane glycoproteins GPIIb and GPIIIa form a calcium- dependent heterodimer that functions as a receptor for adhesive proteins on stimulated platelets. In this study, we have investigated the kinetics of the assembly reaction that result in GPIIb-IIIa dimerization. Pulse-chase experiments analysis performed on human megakaryocytes obtained from liquid cultures of chronic myelogenous leukemic patients with antibodies specific for GPIIIa or GPIIb demonstrated the existence of a pro-GPIIb-GPIIIa complex and of a large pool (60%) of unassociated GPIIIa; nearly all the GPIIb and the pro- GPIIb molecules were found associated with GPIIIa. This free GPIIIa was not exposed on the cell surface. Pulse-chase experiments on a subclone of the human megakaryocytic cell line LAMA-84 revealed that the cells from this subclone produced only the pro-GPIIb, which was neither processed into mature GPIIb nor expressed on the cell surface. The expression of GPIIIa in PMA treated cells resulted in the production of the mature GPIIb form and the expression of the GPIIb-IIIa complex on the cell surface. These results indicate that assembly between the early forms of pro-GPIIb and GPIIIa is an obligatory step for the maturation of the heterodimer and its expression on the cell surface.     

Postprandial variations in serum bile acid levels in humans free of hepatic or intestinal diseases (author's transl)

The levels of unsulfated, free or conjugated cholic, deoxycholic and chenodeoxycholic acids were measured using gas chromatography in 39 humans free of hepatic or intestinal diseases before and 10, 60, 120 and 180 min after ingestion of a standard meal. The probable maximal levels were determined with an error risk lower than 0.05. In fasting subjects, the observed values are comparable with those obtained by other authors working with gas chromatography or radioimmunoassay. Meal ingestion does not influence in the same way the serum levels of the various bile acids: the chemodeoxycholic serum level rose significantly in all cases whereas cholic and deoxycholic serum levels rose only in two-thirds of observed subjects; 60 and 120 min after the meal for chenodeoxycholic acid, and only 60 min after the meal for cholic acid, the mean values are significantly higher than the fasting ones; 120 min after the meal, the chenodeoxycholic and total bile acid probable maximal levels (respectively 7.4 and 10.3 micrometer) are twice the fasting ones. The cholic to chenodeoxycholic serum level ratio is nearly always lower than 1 but may reach 3. On the basis of these results, the validity and efficacy of the exploration tests based on serum bile acid level determinations are discussed.     

Eimeria involved in a case of coccidiosis in farmed red-legged partridges (Alectoris rufa) in France: oocyst isolation and gross lesion description after experimental infection

The aim of the present work was, after a coccidiosis outbreak in a farm rearing red-legged partridges (Alectoris rufa) in Brittany (France), to identify the Eimeria species and describe gross lesions induced by three of them (Eimeria kofoidi, Eimeria caucasica and Eimeria legionensis) after experimental infection. E. kofoidi oocysts measured 19.3 µm×16.3 µm on average; neither micropyle nor oocyst residuum were present, but one, two or more small polar granules were visible. After inoculation of 300,000 oocysts per partridge, severe gross lesions were observed in the duodenum and jejunum, characterized by thickened oedematous mucosa and lumen filled with thick mucus, gas and sometimes false-membrane due to sloughed epithelium. E. caucasica oocysts were on average 29.8 µm×19.5 µm in size; no oocyst residuum was observed, but a large granule was well visible. E. caucasica also invaded both the duodenum and jejunum, causing haemorrhagic points on the serosal surface, as well as mucoid duodenitis and catarrhal enteritis when 30,000 oocysts were inoculated per bird. E. legionensis oocysts measured 22.6 µm×14.9 µm on average; they presented a clear micropyle beneath which one or two granulations were present. E. legionensis mainly invaded the caeca; low mortality was observed at the dosage of 200,000 oocysts per bird. Caecal walls were thickened and caseous material was condensed into off-white cheesy cores. For each species, oocyst shedding started 5 days post inoculation, peaked at 9, 8 and 6 days post inoculation for E. kofoidi, E. caucasica and E. legionensis, respectively, then decreased and persisted until 15 days post inoculation (end of examinations).     

Inhibitor of growth 4 suppresses cell spreading and cell migration by interacting with a novel binding partner, liprin alpha1

Inhibitor of growth 4 (ING4) is a candidate tumor suppressor that plays a major role in gene regulation, cell cycle control, apoptosis, and angiogenesis. ING4 expression is down-regulated in glioblastoma cells and head and neck squamous cell carcinoma. Here, we identified liprin alpha1/PPFIA1, a cytoplasmic protein necessary for focal adhesion formation and axon guidance, as a novel interacting protein with ING4. ING4 and liprin alpha1 colocalized at lamellipodia in the vicinity of vinculin. Overexpressed ING4 suppressed cell spreading and cell migration. In contrast, overexpressed liprin alpha1 enhanced cell spreading and cell migration. Knockdown of endogenous ING4 with RNA interference induced cell motility, whereas knockdown of endogenous liprin alpha1 suppressed cell motility. ING4 also suppressed cell motility that was enhanced by liprin alpha1. However, ING4 did not further suppress cell motility when liprin alpha1 was suppressed with RNA interference, suggesting a functional and mechanistic interdependence between these proteins. In addition to its nuclear functions, cytoplasmic ING4 interacts with liprin alpha1 to regulate cell migration and, with its known antiangiogenic function, may prevent invasion and metastasis.     

Prostaglandin synthetase activity in bovine adrenocortical cells and subcellular preparations: Effect of ACTH

Prostaglandin (PGE₂, PGF_2α) production by bovine fasciculo-reticulata adrenocortical cell suspensions was examined using specific radioimmunoassay procedures. No detectable PGs (> 50 pg) could be measured in the extract from up to 2 × 10⁶ cell incubations after 1 h, with or without the presence of ACTH, although these cells expressed full steroidogenic capabilities under these conditions. The same preparations could produce PGs when supplemented with arachidonic acid but ACTH had no effect on this process. These negative findings could not be explained by analytical artifacts or metabolic transformation. However, an active PG synthetase system was characterized in bovine adrenocortical subcellular preparations. This system converted arachidonate and endogenous substrate(s) to PGE₂ as the major product. No thromboxane or prostacyclin pathways were detected even at high enzyme/substrate ratio. Although the microsornal adrenal cortex PG synthetase activity shares many features with those observed in other tissues (K_m = 8.3 × 10^?5 M, optimal pH at 8.0, stimulation of PGE₂ formation in the presence of glutathione and L-epinphrine), its specific activity was comparatively low (V_max = 2.5 ng PGE₂/min/mg microsornal proteins), which may explain our negative findings using cell suspensions. These findings do not provide evidence to support the hypothesis proposing a role of endogenous PGs in the mechanism of acute ACTH action in the case of bovine adrenal cortex.     

Inhibition by tamoxifen of the effects of estradiol benzoate on lipid metabolism in female quail

The effect of estradiol (EB), tamoxifen (T), and estradiol + tamoxifen on the hepatic function and lipid metabolism in immature female quails was investigated. EB (0.02 mg/day/6 days) induced increases of relative liver weight, of serum cholesterol, bile acid and fatty acid levels, and of liver fatty acid level. Bile acid and fatty acid spectra were modified by this treatment. T alone (1 mg/day/6 days) had a meager effect on these parameters. If associated with EB it thoroughly inhibited the effects of that hormone.     

Lymphographic patterns in systemic mastocytosis with diffuse bone involvement and hematological signs.

Lymphography revealed the nature of diffuse lymph node involvement in systemic mastocytosis with diffuse bone involvement and hematological signs, similar to that seen in some malignant hematological diseases or in osteomyelosclerosis. The final stages of transformation into acute lymphoblastic leukemia must also be considered.