A mechanism for P-glycoprotein-mediated apoptosis as revealed by verapamil hypersensitivity

Selection of tumor cell lines with anticancer drugs has led to the appearance of multidrug-resistant (MDR) subclones with P-glycoprotein 1 (P-gp1) expression. These cells are cross-resistant to several structurally and functionally dissimilar drugs. Interestingly, in the process of gaining resistance, MDR cells become hypersensitive or collaterally sensitive to membrane-active agents, such as calcium channel blockers, steroids, and local anaesthetics. In this report, hypersensitivity to the calcium channel blocker, verapamil, was analyzed in sensitive and resistant CHO cell lines. Our results show that treatment with verapamil preferentially induced apoptosis in MDR cells compared to drug-sensitive cells. This effect was independent of p53 activity and could be inhibited by overexpression of the Bcl-2 gene. The induction of apoptosis by verapamil had a biphasic trend in which maximum cell death occurred at 10 microM, followed by improved cell survival at higher concentrations (50 microM). We correlated this effect to a similar biphasic trend in P-gp1 ATPase activation by verapamil in which low concentrations of verapamil (10 microM) activated ATPase, followed by inhibition at higher concentrations. To confirm the relationship between apoptosis and ATPase activity, we used two inhibitors of P-gp1 ATPase, PSC 833 and ivermectin. These ATPase inhibitors reduced hypersensitivity to verapamil in MDR cells. In addition, low concentrations of verapamil resulted in the production of reactive oxygen species (ROS) in MDR cells. Taken together, these results show that apoptosis was preferentially induced by P-gp1 expressing cells exposed to verapamil, an effect that was mediated by ROS, produced in response the high ATP demand by P-gp1.     

Neural mechanisms of object recognition

Single-unit recordings from behaving monkeys and human functional magnetic resonance imaging studies have continued to provide a host of experimental data on the properties and mechanisms of object recognition in cortex. Recent advances in object recognition, spanning issues regarding invariance, selectivity, representation and levels of recognition have allowed us to propose a putative model of object recognition in cortex.     

Terpenes from Inula verbascifolia

The aerial parts of Inula verbascifolia afforded two new xanthanes and a new germacranolide derivative, together with the known compounds inusoniolide, 4-O-dihydroinusoniolide and 9beta-hydroxyparthenolide. The structures were determined by spectral methods (IR, HRMS,1H NMR, 13C NMR, DEPT, 1H-1H COSY, HMQC and HMBC).     

The marsupial placenta: a phylogenetic analysis

The structure, physiology, and endocrinology of the yolk sac placenta of different marsupial groups is compared and phylogenetically analyzed to provide information on placental characters in the marsupial stem species. We conclude that the marsupial stem species possessed a functional yolk sac placenta. Histotrophic nutrition by uterine secretion decreased during late pregnancy and at least half of the yolk sac was vascularized at the time of shell coat rupture. Due to yolk sac fusion, the larger part of the avascular, bilaminar yolk sac could not serve as a placenta at late gestation in the polyovular marsupial stem species. The bilaminar yolk sac gained a relatively greater importance for nutrition in monovular australidelphians. In macropodids a greater proportion of the yolk sac remained bilaminar at the time of shell coat rupture than in the stem species. Another derived feature of macropodids is the sustained plasma progesterone synthesis that is in turn responsible for an extended secretory phase of the uterus and a lengthened gestation. The placenta of the marsupial stem species was probably capable of metabolising histo- and hemotrophes. Recognition of pregnancy during early stages of development is a derived character of macropodids that we suggest did not occur in the marsupial stem species. However, birth and birth behaviour were apparently induced by prostaglandins in the marsupial stem species. Although the yolk sac formed the definitive placenta, it is likely that the allantois provided a supplementary placental function in the marsupial stem species, but that the role of the allantois became progressively less important during the evolution of marsupial placentation.     

Gene expression patterns in ovarian carcinomas

We used DNA microarrays to characterize the global gene expression patterns in surface epithelial cancers of the ovary. We identified groups of genes that distinguished the clear cell subtype from other ovarian carcinomas, grade I and II from grade III serous papillary carcinomas, and ovarian from breast carcinomas. Six clear cell carcinomas were distinguished from 36 other ovarian carcinomas (predominantly serous papillary) based on their gene expression patterns. The differences may yield insights into the worse prognosis and therapeutic resistance associated with clear cell carcinomas. A comparison of the gene expression patterns in the ovarian cancers to published data of gene expression in breast cancers revealed a large number of differentially expressed genes. We identified a group of 62 genes that correctly classified all 125 breast and ovarian cancer specimens. Among the best discriminators more highly expressed in the ovarian carcinomas were PAX8 (paired box gene 8), mesothelin, and ephrin-B1 (EFNB1). Although estrogen receptor was expressed in both the ovarian and breast cancers, genes that are coregulated with the estrogen receptor in breast cancers, including GATA-3, LIV-1, and X-box binding protein 1, did not show a similar pattern of coexpression in the ovarian cancers.     

Single-pad scheme for integrated optical fluorescence sensing

A new scheme for integrated optical fluorescence sensing is presented. The principle is based on a planar waveguide containing multiple sensing units, each consisting of a single-pad grating coupler structure. Single-pad means that all the following functions are incorporated in one single pad: laser light input, excitation of the labeled analyte molecules, efficient collection of the emitted fluorescent light into the waveguide, background suppression, and coupling the guided wave out to the detector. The results demonstrate a high efficiency of the fluorescence light excitation and collection, as well as a good suppression of the volume background.     

Long-term population studies and the development of an integrated management programme for control of Opuntia stricta in Kruger National Park, South Africa

1. A cactus, Opuntia stricta , has invaded almost 16 000 ha of conserved, natural habitatand has become a major weed problem in Kruger National Park (KNP), South Africa.
2. The main objectives in the control of O. stricta are to reduce the density of the weed and to curb long-range dispersal of seeds by preventing young plants from reaching the size (28 cladodes) at which they start to produce fruits.
3. Herbicides have failed to provide satisfactory control of O. stricta because the weed infestations are replenished from seeds in the soil and from small plants that are overlooked during spraying.
4. A phycitid moth, Cactoblastis cactorum , was released in KNP during 1988 in an attempt to control O. stricta biologically.
5. Population counts of the biological control agent and of the weed over a 5-year period showed that, even though C. cactorum has not provided complete control of O. stricta in KNP, the moderate levels of larval damage have stunted the growth of O. stricta and have considerably extended the time that the young plants take to reach sexual maturity.
6. Comparisons of modelled (i.e. with no C. cactorum ) and actual populations of O. stricta showed that C. cactorum is making a substantial contribution to the control of O. stricta in residual infestations of the weed that have been treated with herbicides.
7. The need for long-term evaluation studies in biological weed control is demon strated by the development of an integrated management programme for effective control of O. stricta .