Malaria parasite liver stages render host hepatocytes susceptible to mitochondria-initiated apoptosis.

Intracellular eukaryotic parasites and their host cells constitute complex, coevolved cellular interaction systems that frequently cause disease. Among them, Plasmodium parasites cause a significant health burden in humans, killing up to one million people annually. To succeed in the mammalian host after transmission by mosquitoes, Plasmodium parasites must complete intracellular replication within hepatocytes and then release new infectious forms into the blood. Using Plasmodium yoelii rodent malaria parasites, we show that some liver stage (LS)-infected hepatocytes undergo apoptosis without external triggers, but the majority of infected cells do not, and can also resist Fas-mediated apoptosis. In contrast, apoptosis is dramatically increased in hepatocytes infected with attenuated parasites. Furthermore, we find that blocking total or mitochondria-initiated host cell apoptosis increases LS parasite burden in mice, suggesting that an anti-apoptotic host environment fosters parasite survival. Strikingly, although LS infection confers strong resistance to extrinsic host hepatocyte apoptosis, infected hepatocytes lose their ability to resist apoptosis when anti-apoptotic mitochondrial proteins are inhibited. This is demonstrated by our finding that B-cell lymphoma 2 family inhibitors preferentially induce apoptosis in LS-infected hepatocytes and significantly reduce LS parasite burden in mice. Thus, targeting critical points of susceptibility in the LS-infected host cell might provide new avenues for malaria prophylaxis.

A structure-function analysis of serine/threonine phosphorylation of the thrombopoietin receptor, c-Mpl.

Thrombopoietin (TPO), the critical regulator of platelet production, acts by binding to its cell surface receptor, c-Mpl. Numerous studies have shown that TPO binding leads to JAK2 kinase activation and Tyr phosphorylation of c-Mpl and several intracellular signaling intermediates, events vital for the biological activity of the hormone. In contrast, virtually nothing is known of the role of Ser or Thr phosphorylation of c-Mpl. By using phosphoamino acid analysis we found that Ser residues of c-Mpl were constitutively phosphorylated in receptor-bearing cells, levels that were increased following exposure of cells to TPO. To identify which residues were modified, and to determine the functional consequences of their phosphorylation, we generated a series of Ser to Ala mutations of a truncated c-Mpl receptor (T69) capable of supporting TPO-induced cell growth. Of the eight Ser within T69 we found that at least four are phosphorylated in TPO-stimulated cells. The mutation of each of these residues alone had minimal effects on TPO-induced proliferation, but substitution of all of the phosphoserine residues with Ala reduced the capacity of the receptor to support cell growth by over 50%. Additionally, the Ser at cytoplasmic position 18 is not detectably phosphorylated. However, the mutation of Ser-18 to Ala nearly abrogates TPO-induced proliferation and co-precipitation of JAK2 with Mpl. This study provides the first systematic analysis of the role of Ser residues in c-Mpl signaling.

Benign abducens nerve palsy of childhood.

Benign acquired isolated abducens nerve palsy in infants and children is a rare condition and recurrence is even less common. The diagnosis is essentially one of exclusion. Six children (1 male, 5 females) are reported with benign isolated abducens nerve palsy, ranging in age from 8 months to 12 years (median: 5.5 years). The left side was affected in all patients. Recovery occurred within 18-55 days, but 3 patients developed recurrence with complete resolution of symptoms within 10-21 days.

Endocrine studies of the ovulatory disturbances in Wilson's disease (hepatolenticular degeneration).

Women with Wilson's disease may have severe oligomenorrhea or amenorrhea whose cause is unknown. The endocrine profile of four such cases was investigated by measuring basal values and the response to dynamic tests of hypothalamic, pituitary, thyroid, and adrenal function, which all proved normal. Ovarian function was disturbed, as witnessed by low estradiol, high total testosterone (T) levels with normal free T, and mildly elevated androstenedione. An interference of ovarian follicular aromatase activity possibly due to copper intoxication could explain these findings as the cause of the ovulatory disturbances of Wilson's disease.

Endocrine and reproductive repercussions of immunization against progesterone and oestradiol in female rats.

Mature female rats were immunized with BSA-conjugates of oestradiol-17beta-6-carboxymethyloxime or progesterone-11-hymisuccinate. Sera tested two months later at 1/2000 dilution bound 63.3% +/- 3.1 SEM and 21.2% +/- 2.3 of the homologous tritiated hormone (10 pg),--oestradiol-17beta(Oe2) and progesterone (P), respectively. Rats immunized against Oe2 had a significantly longer oestrous cycle (8.2 days vs. 4.5 days in BSA-immunized rats), with a prolonged leukocytic phase. The cycle of rats immunized against P was also prolonged (10.5 days), but in this group the cornified smear phase was abnormally extended. The luteinizing hormone (LH) normally observed on the afternoon of pro-oestrus failed to occur in the rats immunized against Oe2 and in 70% of rats immunized against P. The latter animals, however, showed sporadic LH discharges during periods of persistent cornification. Immunization against P resulted in elevated total (free plus bound) plasma P levels; immunization against Oe2 prevented the pro-oestrous rise in plasma P. Mating of rats immunized against Oe2 resulated in normal pregnanices, while none of the rats immunized against P delivered.