Differential effects of phosphotyrosine phosphatase expression on hormone-dependent and independent pp60 c-src activity

pp60 ^c-src kinase activity can be increased by phosphotyrosine dephosphorylation or growth factor-dependent phosphorylation reactions. Expression of the transmembrane phosphotyrosine phosphatase (PTPase) CD45 has been shown to inhibit growth factor receptor signal transduction (Mooney, RA, Freund, GG, Way, BA and Bordwell, KL (1992) J Biol Chem 267, 23443–23446). Here it is shown that PTPase expression decreased platelet-derived growth factor (PDGF)-dependant activation of pp60 ^c-src but failed to increase hormone independent (basal) pp60 ^c-src activity. PDGF-dependent tyrosine phosphorylation of its receptor was reduced by approximately 60% in cells expressing the PTPase. In contrast, a change in phosphotyrosine content of pp60 ^c-src was not detected in response to PDGF or in PTPase+cells. PDGF increased the intrinsic tyrosine kinase activity of pp60 ^c-src in both control and PTPase+cells but the effect was smaller in PTPase+cells. In anin vitro assay, hormone-stimulate pp60 ^c-src autophosphorylation from PTPase+ cells was decreased 64±22%, and substrate phosphorylation by pp60 ^c-src was reduced 54±16% compared to controls. Hormone-independent pp60 ^c-src kinase activity was unchanged by expression of the PTPase. pp60 ^c-src was, however, anin vitro substrate for CD45, being dephosphorylated at both the regulatory (Tyr⁵²⁷) and kinase domain (Tyr⁴¹⁶) residues. In addition,in vitro dephosphorylation by CD45 increased pp60 ^c-src activity. These findings suggest that the PDGF receptor was anin vivo substrate of CD45 but pp60 ^c-src was not. The lack of activation of pp60 ^c-src in the presence of expressed PTPase may demonstrate the importance of compartmentalization and/or accessory proteins to PTPase-substrate interactions.Abbreviations PTPase phosphotyrosine phosphatase - PDGF platelet-derived growth factor - PMSF phenylmethylsulfonyl fluoride - LCA, CD45 leukocyte common antigen - PBS phosphate buffered saline - SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - DTT dithiothreitol - Na₃VO₄ sodium orthovanadate - PV pervanadate - -ME -mercaptoethanol     

Resource sharing among ramets in the clonal herb,Fragaria chiloensis

Summary The herbaceous perennial, Fragaria chiloensis, reproduces vegetatively on coastal sand dunes in California by growth of stolons that bear rosettes. Movement of water and photosynthates through stolons integrates water and carbon metabolism of rosettes both before and after they root. New, unrooted rosettes import sufficient water and nitrogen to maintain levels near those of established rosettes; yet support of an unrooted rosette did not decrease growth of a connected, rooted sibling given abundant light, water, and soil nutrients. Under such conditions strings of unrooted rosettes with the associated stolon appeared self-sufficient for carbon; shade and drought induced import of photosynthates. New rosettes produced and maintained a limited root mass upon contact with dry sand, which could increase probability of establishment. Rooting did not induce senescence of stolons. Connection between two established rosettes prevented death by drought and shade, even when neither rosette could have survived singly. Results suggest that physiological integration of connected rosettes may increase total growth of clones of F. chiloensis through sharing of resources among ramets, especially when resource availability is changeable or patchy.     

Statolith morphometrics as a tool to distinguish among populations of three cubozoan species

Timely identification of endangered populations is vital to save them from extirpation. Here we tested whether six commonly used early-warning metrics are useful predictors of impending extirpation in laboratory rotifer (Brachionus calyciflorus) populations. To this end, we cultured nine rotifer clones in a constant laboratory environment, in which the rotifer populations were known to grow well, and in a deteriorating environment, in which the populations eventually perished. We monitored population densities in both environments until the populations in the deteriorating environment had gone extinct. We then used the population-density time series to compute the early-warning metrics and the temporal trends in these metrics. We found true positives (i.e. correct signals) in only two metrics, the standard deviation and the coefficient of variation, but the standard deviation also generated a false positive. Moreover, the signal produced by the coefficient of variation appeared when the populations in the deteriorating environment were about to cross the critical threshold and began to decline. As such, it cannot be regarded as an early-warning signal. Together, these findings support the growing evidence that density-based generic early-warning metrics—against their intended use—might not be universally suited to identify populations that are about to collapse.     

Egg-laying patterns and in vivo egg production in the monogenean parasites Heteraxine heterocerca and Benedenia seriolae from Japanese yellowtail Seriola quinqueradiata

Egg-laying patterns and egg production in Heteraxine heterocerca from the gills and Benedenia seriolae from the skin of Japanese yellowtail Seriola quinqueradiata in Japan were investigated in vivo. Eggs were collected every 3 h from sexually mature H. heterocerca and B. seriolae infecting 3 S. quinqueradiata kept individually over 3 consecutive days and exposed to alternating periods of illumination and darkness (LD 12:12; light on 06.00, light off 18.00) and maintained at 23.8 +/- 0.1 degrees C and 35 ppt salinity. A well-defined egg-laying rhythm was demonstrated for H. heterocerca while B. seriolae was shown torelease eggs continuously. A total of 114,000 H. heterocerca eggs was collected and of these, 45.4 (42.5-49.9)% were collected during the first 3 h period following dark at 18.00 h. A total of 662,857 B. seriolae eggs was collected and these were distributed over each 3 h period ranging from 11.1 to 14.1% of the daily egg output. All eggs extracted from the uterus of each H. heterocerca were joined together forming an 'egg-string'. The contrasting egg-laying patterns of H. heterocerca and B. seriolae suggest that each species makes use of a different infection strategy to infect the same host species, S. quinqueradiata.     

Mitochondrial DNA sequence variation is associated with free-living activity energy expenditure in the elderly

The decline in activity energy expenditure underlies a range of age-associated pathological conditions, neuromuscular and neurological impairments, disability, and mortality. The majority (90%) of the energy needs of the human body are met by mitochondrial oxidative phosphorylation (OXPHOS). OXPHOS is dependent on the coordinated expression and interaction of genes encoded in the nuclear and mitochondrial genomes. We examined the role of mitochondrial genomic variation in free-living activity energy expenditure (AEE) and physical activity levels (PAL) by sequencing the entire (~16.5 kilobases) mtDNA from 138 Health, Aging, and Body Composition Study participants. Among the common mtDNA variants, the hypervariable region 2 m.185G>A variant was significantly associated with AEE (p=0.001) and PAL (p=0.0005) after adjustment for multiple comparisons. Several unique nonsynonymous variants were identified in the extremes of AEE with some occurring at highly conserved sites predicted to affect protein structure and function. Of interest is the p.T194M, CytB substitution in the lower extreme of AEE occurring at a residue in the Qi site of complex III. Among participants with low activity levels, the burden of singleton variants was 30% higher across the entire mtDNA and OXPHOS complex I when compared to those having moderate to high activity levels. A significant pooled variant association across the hypervariable 2 region was observed for AEE and PAL. These results suggest that mtDNA variation is associated with free-living AEE in older persons and may generate new hypotheses by which specific mtDNA complexes, genes, and variants may contribute to the maintenance of activity levels in late life.     

Pilot Study of Essential Drug Quality in Two Major Cities in India

Background

India is an increasingly influential player in the global pharmaceutical market. Key parts of the drug regulatory system are controlled by the states, each of which applies its own standards for enforcement, not always consistent with others. A pilot study was conducted in two major cities in India, Delhi and Chennai, to explore the question/hypothesis/extent of substandard and counterfeit drugs available in the market and to discuss how the Indian state and federal governments could improve drug regulation and more importantly regulatory enforcement to combat these drugs.

Methodology/Principal Findings

Random samples of antimalarial, antibiotic, and antimycobacterial drugs were collected from pharmacies in urban and peri-urban areas of Delhi and Chennai, India. Semi-quantitative thin-layer chromatography and disintegration testing were used to measure the concentration of active ingredients against internationally acceptable standards. 12% of all samples tested from Delhi failed either one or both tests, and were substandard. 5% of all samples tested from Chennai failed either one or both tests, and were substandard. Spatial heterogeneity between pharmacies was observed, with some having more or less substandard drugs (30% and 0% respectively), as was product heterogeneity, with some drugs being more or less frequently substandard (12% and 7% respectively).

Conclusions/Significance

In a study using basic field-deployable techniques of lesser sensitivity rather than the most advanced laboratory-based techniques, the prevalence of substandard drugs in Delhi and Chennai is confirmed to be roughly in accordance with the Indian government''s current estimates. However, important spatial and product heterogeneity exists, which suggests that India''s substandard drug problem is not ubiquitous, but driven by a subset of manufacturers and pharmacies which thrive in an inadequately regulated environment. It is likely that the drug regulatory system in India needs to be improved for domestic consumption, and because India is an increasingly important exporter of drugs for both developed and developing countries. Some poor countries with high burdens of disease have weak drug regulatory systems and import many HIV/AIDS, tuberculosis and malaria drugs from India.