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We report the discovery of MED6-189, an analog of the kalihinol family of isocyanoterpene natural products that is effective against drug-sensitive and drug-resistant Plasmodium falciparum strains, blocking both asexual replication and sexual differentiation. In vivo studies using a humanized mouse model of malaria confirm strong efficacy of the compound in animals with no apparent hemolytic activity or toxicity. Complementary chemical, molecular, and genomics analyses revealed that MED6-189 targets the parasite apicoplast and acts by inhibiting lipid biogenesis and cellular trafficking. Genetic analyses revealed that a mutation in PfSec13 , which encodes a component of the parasite secretory machinery, reduced susceptibility to the drug. Its high potency, excellent therapeutic profile, and distinctive mode of action make MED6-189 an excellent addition to the antimalarial drug pipeline.

The specific effects of interferon alpha (IFNalpha), on the differentiation pathways of human osteogenic cells are not known. The aim of this study was to investigate possible effects of IFNalpha on osteogenic development by investigating cell differentiation, colony formation (colony forming unit-fibroblastic, CFU-F), cell proliferation, and gene expression, in particular bone morphogenetic protein (BMP) expression, of human bone marrow osteoprogenitor cells. Human bone marrow fibroblasts were cultured with or without the addition of IFNalpha (5-1,000 IU/ml) in the presence and absence of dexamethasone (10 nM) and ascorbate (100 microM), which are agents known to affect osteogenic differentiation. IFNalpha produced a significant dose-dependent inhibition of cell proliferation and alkaline phosphatase specific activity at concentrations as low as 50 IU/ml. IFNalpha (50-1,000 IU/ml) inhibited the stimulation of alkaline phosphatase specific activity induced by ascorbate and dexamethasone. Examination of CFU-F showed dose- and time-dependent inhibitions of colony formation and reductions in both colony size and alkaline phosphatase-positive CFU-F colonies particularly at earlier times. Reactivity with an antibody specific for osteoprogenitors (HOP-26), was reduced in IFNalpha-treated cultures. Northern blot analysis showed a significant dose-dependent up-regulation of BMP-2 mRNA, estrogen receptor alpha mRNA and osteocalcin mRNA expression in ascorbate/dexamethasone cultures. In contrast, IFNalpha significantly inhibited BMP-2 mRNA expression in the absence of ascorbate and dexamethasone. In conclusion, IFNalpha inhibits human osteoprogenitor cell proliferation, CFU- F formation, HOP-26 expression, and alkaline phosphatase specific activity and modulates BMP-2 gene expression. These results suggest a role for IFNalpha in local bone turnover through the specific and direct modulation of osteoprogenitor proliferation and differentiation., (Copyright 1999 Wiley-Liss, Inc.)

aP2 gene product (aP2 protein) expression has been shown to be a useful diagnostic marker for identification of lipoblasts and fetal fat cells in soft tissue tumours. A monoclonal antibody was developed by a mouse spleen cell-myeloma hybridoma technique to an 18 amino acid segment of the aP2 protein and was used to investigate the immunohistochemical expression of this protein in benign and malignant tumours of adipocytic differentiation and a wide variety of other soft tissue tumours. We found that aP2 protein was expressed by lipoblasts in liposarcomas and lipoblastomas and by brown fat cells in hibernomas and normal periadrenal fat. Other benign adipose tissue tumours and benign and malignant soft tissue tumours were distinguished from liposarcoma by absence of staining for aP2 protein. Immunohistochemical identification of the aP2 protein is likely to prove a useful means of distinguishing liposarcoma from other malignant mesenchymal and epithelial neoplasms, some of which contain cells that morphologically resemble lipoblasts.

Studies were carried out on 3 giant cell tumours of bone (GCTB) to characterise further the cells forming the distinctive mononuclear and multinucleated components. Samples of tumours were grown as explants in vitro and implanted subcutaneously in athymic mice. Cells were characterised in terms of their cell morphology and cytochemical, antigenic and functional phenotype. In culture, giant cells formed a non-proliferative, relatively homogeneous population of cells which expressed features characteristic of the osteoclast phenotype. The mononuclear cell component was heterogeneous and included macrophage-like cells, which persisted for a short time in culture, and fibroblast-like cells which proliferated. In subcutaneous implants, the fibroblast-like cells formed a tissue which included areas of bone formation associated with regions of alkaline phosphatase activity. These observations are consistent with earlier suggestions that the neoplastic component in GCTB consists of a mononuclear stromal cell which elicits a macrophage/osteoclast response.

Our previous studies suggest that a monoclonal antibody, BRL 12, reacts with a specific product of differentiated cells of the osteoblastic lineage. In the present study, the bone constituent recognized by this antibody has been characterized by gel filtration, ion exchange chromatography, protein blotting and immunolocalization. Our findings show that the antibody reacts with an epitope associated with the core protein of rabbit keratan sulfate proteoglycan (KSPG), a molecule which shares considerable homology with the sialoprotein present in the bone tissue of other mammalian species.

The effect of age on egg production was investigated in the domestic fowl. The rate of egg production was reduced with increasing age and the incidence of thin-shelled and cracked eggs was markedly increased. Older hens which remained in lay produced fewer but larger eggs than the younger birds. The ovaries of these two groups of hens were of similar appearance but the largest preovulatory follicle and the oviduct were significantly heavier in the older birds. No differences in the circulating levels of progesterone or estradiol were apparent between the young and old birds but the activity of the renal 25-hydroxycholecalciferol 1 alpha-hydroxylase was found to be significantly reduced with age. Circulating levels of total and ionized calcium were very similar in the young and old laying birds, plasma ionized calcium levels being markedly depressed during egg shell calcification in both groups. The decreased rate of ovulation in the older birds and the increase with age in the size of the follicles ovulated is thought to be associated with a reduced rate of recruitment of follicles for rapid growth followed by a prolonged period of follicular growth and development. The poor calcification of egg shell in old birds would appear to be due to some dysfunction of the shell gland, possibly associated with reduced synthesis of 1,25-dihydroxycholecalciferol by the kidney. The maintenance of plasma ionized calcium concentrations does not appear to be of primary importance in this respect.

The concentrations of biologically active parathyroid hormone (PTH) and ionic calcium (Ca2+) were determined in the plasma of control and calcium-deficient laying hens during the egg cycle. The same measurements were made in hens that had ceased laying because of a deficiency of vitamin D and in normal hens during pauses in egg production. Changes in the concentration of Ca2+ during the egg cycle followed the same pattern and were of the same magnitude in the control and calcium-deficient birds: mean levels were high when egg shell calcification was not occurring and they were at least 0.10 mmol/litre lower during active shell formation. There was a reciprocal relationship between the concentrations of PTH and Ca2+; thus, PTH values were high during shell calcification and low before shell formation began and after oviposition. Mean concentrations of PTH in the birds given the low-calcium diet were more than twice as high as in the control birds both during shell formation at 0700 hr (12.85 and 5.95 pg/ml, respectively) and after oviposition at 1600 hr (4.25 and 0.55 pg/ml, respectively). The results of these experiments provide direct evidence that the mobilization of skeletal calcium for egg shell formation is under parathyroid control. In the non-shell-forming control and vitamin D-deficient birds there were no significant changes over the 27-hr sampling period in either PTH or ionic calcium.(ABSTRACT TRUNCATED AT 250 WORDS)