The introduction and release of Chiasmia inconspicua and C. assimilis (Lepidoptera: Geometridae) for the biological control of Acacia nilotica in Australia

Two geometrid moths Chiasmia inconspicua and Chiasmia assimilis, identified as potential biological control agents for prickly acacia Acacia nilotica subsp. indica, were collected in Kenya and imported into quarantine facilities in Australia where laboratory cultures were established. Aspects of the biologies of both insects were studied and CLIMEX® models indicating the climatically favourable areas of Australia were developed. Host range tests were conducted using an approved test list of 74 plant species and no-choice tests of neonate larvae placed on both cut foliage and potted plants. C. inconspicua developed through to adult on prickly acacia and, in small numbers, Acacia pulchella. C. assimilis developed through to adult on prickly acacia and also in very small numbers on A. pulchella, A. deanei, A. decurrens, and A. mearnsii. In all experiments, the response on prickly acacia could be clearly differentiated from the responses on the non-target species. Both insects were approved for release in Australia. Over a three-year period releases were made at multiple sites in north Queensland, almost all in inland areas. There was no evidence of either insect’s establishment and both colonies were terminated. A new colony of C. assimilis was subsequently established from insects collected in South Africa and releases of C. assimilis from this new colony were made into coastal and inland infestations of prickly acacia. Establishment was rapid at one coastal site and the insect quickly spread to other infestations. Establishment at one inland area was also confirmed in early 2006. The establishment in coastal areas supported a CLIMEX model that indicated that the climate of coastal areas was more suitable than inland areas.     

Activating and inhibitory Fcγ receptors in rheumatoid arthritis: from treatment to targeted therapies

Fcγ receptors (FcγRs) bind the constant Fc region of IgG molecules. IgG/antigen-containing immune complexes elicit a variety of effector functions in cells that express activating FcγRs. Because activating FcγRs are present on cells from the innate immune system, such as dendritic cells, monocytes/macrophages and granulocytes, these IgG receptors form a crucial link between the innate and the acquired immune systems. Recently, the ability to detect the inhibitory FcγRIIb on cells has indicated an imbalance between activating and inhibitory FcγRs in rheumatoid arthritis. This progress offers an opportunity to study modulation of FcγR balance and could stimulate development of FcγR-directed immunotherapy.     

The Contribution of Mitochondrial Respiratory Complexes to the Production of Reactive Oxygen Species

This work was focused on distinguishing the contribution of mitochondrial redox complexesto the production of reactive oxygen species (ROS) during cellular respiration. We were ableto accurately measure, for the first time, the basal production of ROS under uncoupled conditionsby using a very sensitive method, based on the fluorescent probe dichlorodihydrofluoresceindiacetate. The method also enabled the detection of the ROS generated by the oxidation ofthe endogenous substrates in the mitochondrial preparations and could be applied to bothmitochondria and live cells. Contrary to the commonly accepted view that complex III(ubiquinol:cytochrome c reductase) is the major contributor to mitochondrial ROS production, wefound that complex I (NADH-ubiquinone reductase) and complex II (succinate-ubiquinonereductase) are the predominant generators of ROS during prolonged respiration under uncoupledconditions. Complex II, in particular, appears to contribute to the basal production of ROSin cells.     

Bcl-2 and mitochondrial oxygen radicals. New approaches with reactive oxygen species-sensitive probes.

Investigations into the capacity of the Bcl-2 protein to prevent apoptosis have targeted mitochondria as key sites of the preventative action accorded by Bcl-2 to cells. Using novel approaches with fluorescence probes and autofluorescence detection of endogenous NAD(P)H, we have examined the effects of expressing Bcl-2 in the Bcl-2 negative Burkitt's lymphoma cell line Daudi. We evaluated for the first time the effect of Bcl-2 expression on the intracellular distribution and production of hydrogen peroxide, under basal conditions and after treatment with apoptosis inducing agents, ceramide analogs and tumor necrosis factor (TNF)-alpha. Increased availability of mitochondrial NAD(P)H was detected in Bcl-2-expressing cells and was correlated with an increased constitutive mitochondrial production of hydrogen peroxide. Although production of hydrogen peroxide was increased by either C(6)-ceramide or TNF-alpha in Bcl-2 negative Daudi cells commensurate with the early phases of apoptosis, this increase did not occur in Bcl-2-expressing cells. Thus, Bcl-2 appears to allow cells to adapt to an increased state of oxidative stress, fortifying the cellular anti-oxidant defenses and counteracting the radical overproduction imposed by different cell death stimuli. Furthermore, we report altered cytological features of mitochondria during the early phases of apoptosis induced by C(6)-ceramide and TNF-alpha. In particular, mitochondria changed in appearance, clustering in the perinuclear region and Bcl-2 expression prevented these changes from occurring.     

Differentiation of muscle fiber types in the chicken hindlimb

The differentiation of myotubes into fiber types was studied by examining the ATPase staining characteristics of chicken embryo thigh muscles. Two distinct fiber types, designated type IEMB and IIEMB, could be distinguished as early as stage 29. Paralysis of the embryo with d-tubocurarine prevented the differentiation of type IEMB but not type IIEMB characteristics. The two embryonic fiber types differed from each other, and mature type I and II fibers, in the acid and alkali labilities of their ATPases. Myotubes which were type IEMB at stage 29 matured into type I fibers, whereas those which were type IIEMB predominantly but not exclusively developed into type II fibers. The process of maturation involved sequential changes in the staining characteristics of the myotubes. Thus, the ultimate fiber type of a myotube can be detected long before it expresses its mature characteristics.     

Diadenosine 5'',5''"-P1,P4-tetraphosphate in developing embryos of Artemia

Diadenosine 5',5'"-P1,P4-tetraphosphate (Ap4A) has been detected in cysts and developing embryos of the brine shrimp Artemia in amounts 10(4)-10(6) times lower than that of the guanine analogue, Gp4G. The unexpectedly high level of Ap4A in dormant cysts of 2.37 pmol/10(6) cells can be reduced to 0.03 pmol/10(6) cells by decapsulation and storage in saturated NaCl. When development is reinitiated, the Ap4A content of the decapsulated embryos undergoes a rapid 125 -fold increase, reaching a maximum of 3.79 pmol/10(6) cells at the point of emergence when DNA replication begins. If replication is delayed by hypoxia, the Ap4A level is adjusted in order to reach the same maximum value when replication finally begins. As replication proceeds, the level of Ap4A declines again. Unlike mammalian cells, Ap4A in Artemia is less metabolically labile than ATP. These results are consistent with the suggested role of Ap4A in the initiation of DNA synthesis.     

Deoxyribonucleic acid polymerases of Euglena gracilis. Primer-template utilization of and enzyme activities associated with the two deoxyribonucleic acid polymerases of high molecular weight.

The two high-molecular-weight DNA polymerases from Euglena gracilis, pol A (mol. wt. 190 000) and pol B (mol. wt. 240 000), were differentiated on the basis of associated enzymic activities and primer-template utilization. Neither enzyme had endodeoxyribonuclease activity, but pol B, like pol B of yeast and the corresponding enzyme from Tetrahymena pyriformis, exhibited at least one other nuclease activity directed against denatured DNA and the RNA of an RNA-DNA hybrid. These nuclease functions preferred an alkaline pH and Mg2+. Pol B also exhibited nucleoside diphosphokinase activity. Both enzymes were active with 'activated' DNA and poly[d(A-T)] as primer-templates and were sensitive, especially pol B, to inhibition by excess of native or heat-denatured DNA. Pol B also utilized oligo[d(T)] and poly(A) templates under certain conditions, whereas pol A exhibited only slight activity with poly[d(A)]. (U)6 was not used as a primer by either enzyme.     

DNA polymerases of Euglena gracilis: heterogeneity of molecular weight and subunit structure.

Sedimentation analysis of glycerol-density gradients has shown that freshly purified DNA polymerases A and B (pol A and pol B) of Euglena gracilis have molecular weights of 185,000 (8.7S) and 240,000 (10.3S) respectively. They can aggregate in fresh preparations to give forms of higher molecular weight as shown by gel filtration through Sepharose 6B, but on ageing pol B progressively generates species with sedimentation coefficients of 7.4-7.7S, 6.3-6.5S, 4.8S and finally 3.0S. Pol A apparently behaves in a similar fashion though it is unstable. Exposure of pol A and pol B to high ionic strengths can also cause their breakdown to species with lower sedimentation coefficients. The mitochondrial DNA polymerase is distinct, having a molecular weight of 170,000. It is proposed that pol A and pol B are oligomers of the 3.0S subunit and possibly other dissimilar subunits, with pol B having additional factors conferring upon it its extra catalytic functions.