Genetic modulation of Rpd3 expression impairs long-term courtship memory in Drosophila

There is increasing evidence that regulation of local chromatin structure is a critical mechanism underlying the consolidation of long-term memory (LTM), however considerably less is understood about the specific mechanisms by which these epigenetic effects are mediated. Furthermore, the importance of histone acetylation in Drosophila memory has not been reported. The histone deacetylase (HDAC) Rpd3 is abundant in the adult fly brain, suggesting a post-mitotic function. Here, we investigated the role of Rpd3 in long-term courtship memory in Drosophila. We found that while modulation of Rpd3 levels predominantly in the adult mushroom body had no observed impact on immediate recall or one-hour memory, 24-hour LTM was severely impaired. Surprisingly, both overexpression as well as RNAi-mediated knockdown of Rpd3 resulted in impairment of long-term courtship memory, suggesting that the dose of Rpd3 is critical for normal LTM.

Abnormal dosage compensation of reporter genes driven by the Drosophila glass multiple reporter (GMR) enhancer-promoter

In Drosophila melanogaster the male specific lethal (MSL) complex is required for upregulation of expression of most X-linked genes in males, thereby achieving X chromosome dosage compensation. The MSL complex is highly enriched across most active X-linked genes with a bias towards the 3′ end. Previous studies have shown that gene transcription facilitates MSL complex binding but the type of promoter did not appear to be important. We have made the surprising observation that genes driven by the glass multiple reporter (GMR) enhancer-promoter are not dosage compensated at X-linked sites. The GMR promoter is active in all cells in, and posterior to, the morphogenetic furrow of the developing eye disc. Using phiC31 integrase-mediated targeted integration, we measured expression of lacZ reporter genes driven by either the GMR or armadillo (arm) promoters at each of three X-linked sites. At all sites, the arm-lacZ reporter gene was dosage compensated but GMR-lacZ was not. We have investigated why GMR-driven genes are not dosage compensated. Earlier or constitutive expression of GMR-lacZ did not affect the level of compensation. Neither did proximity to a strong MSL binding site. However, replacement of the hsp70 minimal promoter with a minimal promoter from the X-linked 6-Phosphogluconate dehydrogenase gene did restore partial dosage compensation. Similarly, insertion of binding sites for the GAGA and DREF factors upstream of the GMR promoter led to significantly higher lacZ expression in males than females. GAGA and DREF have been implicated to play a role in dosage compensation. We conclude that the gene promoter can affect MSL complex-mediated upregulation and dosage compensation. Further, it appears that the nature of the basal promoter and the presence of binding sites for specific factors influence the ability of a gene promoter to respond to the MSL complex.

Randomized clinical trial of epidural, spinal or patient-controlled analgesia for patients undergoing laparoscopic colorectal surgery

BACKGROUND

Epidural analgesia is considered fundamental in enhanced recovery protocols (ERPs). However, its value in laparoscopic colorectal surgery is unclear. The aim of this study was to examine the effects of different analgesic regimens on outcomes following laparoscopic colorectal surgery in fluid-optimized patients treated within an ERP.

METHODS

Ninety-nine patients were randomized to receive epidural, spinal or patient-controlled (PCA) analgesia. The primary endpoints were time until medically fit for discharge and length of hospital stay. Secondary endpoints included return of bowel function, pain scores, and changes in pulmonary function and quality of life.

RESULTS

Ninety-one patients completed the study. The median length of hospital stay was 3.7 days following epidural analgesia, significantly longer than that of 2.7 and 2.8 days for spinal analgesia and PCA respectively (P = 0.002 and P < 0.001). There was also a slower return of bowel function with epidural analgesia than with spinal analgesia and PCA. Epidural analgesia did not offer better preservation of pulmonary function or quality of life, although pain scores were higher in the PCA group in the early postoperative period.

CONCLUSION

Many of the outcomes in the epidural analgesia group were significantly worse than those in the spinal analgesia and PCA groups, suggesting that either of these two modalities could replace epidural analgesia.

Conservation and sex-specific splicing of the doublesex gene in the economically important pest species Lucilia cuprina

Genetic control of sex determination in insects has been best characterized in Drosophila melanogaster, where the master gene Sxl codes for RNA that is sex specifically spliced to produce a functional protein only in females. SXL regulates the sex-specific splicing of transformer (tra) RNA which, in turn, regulates the splicing of dsx RNA to produce functional male and female proteins. In the Australian sheep blowfly (Lucilia cuprina), the tra gene (Lctra) is required for female development and Lctra transcripts are sex-specifically spliced such that only female Lctra mRNA codes for functional protein. In males, a factor encoded by the Y-linked male determining gene is thought to prevent the female-mode of splicing of Lctra RNA. To further our understanding of the sex determination regulatory hierarchy in L. cuprina, we have isolated the dsx gene (Lcdsx) from this species. We found that the Lcdsx transcripts are sex-specifically spliced in a similar manner as their counterparts in D. melanogaster, housefly and tephritids. The LcDSX proteins are well conserved and the male form of DSX contains a motif encoded by a male-specific exon that is within the female-specific intron. This intron/exon arrangement had previously been found only in the housefly dsx gene, suggesting this may be a unique feature of dsx genes of Calyptratae species.

Efficient germ-line transformation of the economically important pest species Lucilia cuprina and Lucilia sericata (Diptera, Calliphoridae)

The green blowfly species Lucilia cuprina and Lucilia sericata are economically important pests for the sheep industries of Australia and New Zealand. L. cuprina has long been considered a good target for a genetic pest management program. In addition, L. sericata maggots are used in the cleaning of wounds and necrotic tissue of patients suffering from ulcers that are difficult to treat by other methods. Development of efficient transgenesis methods would greatly facilitate the development of strains ideal for genetic control programs or could potentially improve "maggot therapy". We have previously reported the germ-line transformation of L. cuprina and the design of a "female killing system" that could potentially be applied to this species. However, the efficiency of transformation obtained was low and transformed lines were difficult to detect due to the low expression of the EGFP marker used. Here we describe an efficient and reliable method for germ-line transformation of L. cuprina using new piggyBac vector and helper plasmids containing the strong promoter from the L. cuprina hsp83 gene to drive expression of the transposase and fluorescent protein marker gene. We also report, for the first time, the germ-line transformation of L. sericata using the new piggyBac vector/helper combination.

Structural and biochemical studies on the chromo-barrel domain of male specific lethal 3 (MSL3) reveal a binding preference for mono- or dimethyllysine 20 on histone H4

We have determined the human male specific lethal 3 (hMSL3) chromo-barrel domain structure by x-ray crystallography to a resolution of 2.5 Å (r = 0.226, R(free) = 0.270). hMSL3 contains a canonical methyllysine binding pocket made up of residues Tyr-31, Phe-56, Trp-59, and Trp-63. A six-residue insertion between strands β(1) and β(2) of the hMSL3 chromo-barrel domain directs the side chain of Glu-21 into the methyllysine binding pocket where it hydrogen bonds to the NH group of a bound cyclohexylamino ethanesulfonate buffer molecule, likely mimicking interactions with a histone tail dimethyllysine residue. In vitro binding studies revealed that both the human and Drosophila MSL3 chromo-barrel domains bind preferentially to peptides representing the mono or dimethyl isoform of lysine 20 on the histone H4 N-terminal tail (H4K20Me(1) or H4K20Me(2)). Mutation of Tyr-31 to Ala in the hMSL3 methyllysine-binding cage resulted in weaker in vitro binding to H4K20Me(1). The same mutation in the msl3 gene compromised male survival in Drosophila. Combined mutation of Glu-21 and Pro-22 to Ala in hMSL3 resulted in slightly weaker in vitro binding to H4K20Me(1), but the corresponding msl3 mutation had no effect on male survival in Drosophila. We propose MSL3 plays an important role in targeting the male specific lethal complex to chromatin in both humans and flies by binding to H4K20Me(1). Binding studies on the related dMRG15 chromo-barrel domain revealed that MRG15 prefers binding to H4K20Me(3).

Sex-biased transcription enhancement by a 5' tethered Gal4-MOF histone acetyltransferase fusion protein in Drosophila

BACKGROUND

In male Drosophila melanogaster, the male specific lethal (MSL) complex is somehow responsible for a two-fold increase in transcription of most X-linked genes, which are enriched for histone H4 acetylated at lysine 16 (H4K16ac). This acetylation requires MOF, a histone acetyltransferase that is a component of the MSL complex. MOF also associates with the non-specific lethal or NSL complex. The MSL complex is bound within active genes on the male X chromosome with a 3' bias. In contrast, the NSL complex is enriched at promoter regions of many autosomal and X-linked genes in both sexes. In this study we have investigated the role of MOF as a transcriptional activator.

RESULTS

MOF was fused to the DNA binding domain of Gal4 and targeted to the promoter region of UAS-reporter genes in Drosophila. We found that expression of a UAS-red fluorescent protein (DsRed) reporter gene was strongly induced by Gal4-MOF. However, DsRed RNA levels were about seven times higher in female than male larvae. Immunostaining of polytene chromosomes showed that Gal4-MOF co-localized with MSL1 to many sites on the X chromosome in male but not female nuclei. However, in female nuclei that express MSL2, Gal4-MOF co-localized with MSL1 to many sites on polytene chromosomes but DsRed expression was reduced. Mutation of conserved active site residues in MOF (Glu714 and Cys680) reduced HAT activity in vitro and UAS-DsRed activation in Drosophila. In the presence of Gal4-MOF, H4K16ac levels were enriched over UAS-lacZ and UAS-arm-lacZ reporter genes. The latter utilizes the constitutive promoter from the arm gene to drive lacZ expression. In contrast to the strong induction of UAS-DsRed expression, UAS-arm-lacZ expression increased by about 2-fold in both sexes.

CONCLUSIONS

Targeting MOF to reporter genes led to transcription enhancement and acetylation of histone H4 at lysine 16. Histone acetyltransferase activity was required for the full transcriptional response. Incorporation of Gal4-MOF into the MSL complex in males led to a lower transcription enhancement of UAS-DsRed but not UAS-arm-lacZ genes. We discuss how association of Gal4-MOF with the MSL or NSL proteins could explain our results.

The importance of location and orientation of male specific lethal complex binding sites of differing affinities on reporter gene dosage compensation in Drosophila

The male specific lethal (MSL) complex is required for X chromosome dosage compensation in Drosophila. The complex binds to most actively transcribed X-linked genes in males and upregulates expression. High resolution chromatin immunoprecipitation assays have identified over one hundred high affinity binding sites on the X chromosome. One of the first high affinity sites discovered is at cytological location 18D11. The MSL complex binds weakly to a single copy of a 510bp fragment from 18D11 but strongly to a tetramer of the fragment. Here we have investigated the effect of insertion of sites of differing affinities, either upstream or within the transcribed gene, on complex binding and transcription upregulation. Insertion of four copies of the 18D11 fragment upstream or at the 3' end of a reporter gene led to strong MSL complex binding and increased expression in males. In contrast, the MSL complex did not bind consistently to autosomal transgenes that contained a single copy of the 18D11 site upstream of the gene promoter. However, MSL complex binding was observed in all lines if the single 18D11 fragment was inserted into the 3' end of the reporter gene in either orientation. This is consistent with previous studies that showed gene transcription facilitates MSL complex binding. Surprisingly, transcription elevation in males was only observed if the 18D11 fragment was in the forward orientation and only in some lines. Our results suggest that MSL complex binding to weaker sites and transcription enhancement is influenced by gene transcription, binding site orientation and the local chromatin environment. In contrast, strong binding sites do not need to be transcribed to recruit sufficient complex to cause transcription elevation of nearby genes.

Determination of the N=16 shell closure at the oxygen drip line

The neutron unbound ground state of (25)O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a (26)F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_+20(-10) keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the nu1s(1/2) and nu0d(3/2) orbitals. The neutron separation energies for (25)O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an (26)O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of (26)O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.

How do ncRNAs guide chromatin-modifying complexes to specific locations within the nucleus?

Transcriptome analyses have led to the realization that eukaryotic cells make a large number of noncoding RNAs (ncRNAs). It appears that some of these are involved in guiding chromatin-modifying complexes to specific locations within the nucleus. How such ncRNAs function is largely unknown but various models have been proposed. Here we briefly discuss the evidence supporting two such models; that ncRNAs function by annealing either with nascent transcripts or with homologous DNA sequences. We then review a third model that is based on our recent work on the role of the noncoding roX RNAs in the localization of the MSL complex to sites on the X chromosome in Drosophila. Our results suggest that the MSL1 and MSL2 proteins bind to chromatin but it is the incorporation of the roX RNAs into the complex that somehow alters the binding specificity of the MSL1/MSL2 proteins to recognize sites on the X chromosome.

Fibrin-targeted perfluorocarbon nanoparticles for targeted thrombolysis

Background: Reperfusion of the ischemic brain is the most effective therapy for acute stroke, restoring blood flow to threatened tissues. Thrombolytics, such as recombinant tissue plasminogen activator, administered within 3 h of symptom onset can improve neurologic outcome, although the potential for adverse hemorrhagic events limits its use to less than 3% of acute ischemic stroke patients. Targeting of clot-dissolving therapeutics has the potential to decrease the frequency of complications while simultaneously increasing treatment effectiveness, by concentrating the available drug at the desired site and permitting a lower systemic dose. Objectives: We aimed to develop a fibrin-specific, liquid perfluorocarbon nanoparticle that is surface modified to deliver the plasminogen activator streptokinase. We also aimed to evaluate its effectiveness for targeted thrombolysis in vitro using quantitative acoustic microscopy. Methods: Human plasma clots were formed in vitro and targeted with streptokinase-loaded nanoparticles, control nanoparticles or a mixture of both. Depending on the treatment group, clots were then exposed to either phosphate-buffered saline (PBS), PBS with plasminogen or PBS with plasminogen and free streptokinase. Spatially registered ultrasound scans were performed at 15-min intervals for 1 h to quantify changes in clot morphology and backscatter. Results: Nanoparticles bound to the clot significantly increased the acoustic contrast of the targeted clot surface, permitting volumetric estimates. Profile plots of detected clot surfaces demonstrated that streptokinase-loaded, fibrin-targeted perfluoro-octylbromide nanoparticles in the presence of plasminogen induced rapid fibrinolysis (<60 min) without concurrent microbubble production and cavitation. Streptokinase-loaded or fibrin-targeted control nanoparticles insonified in PBS did not induce clot lysis. Morphologic changes in the treated group were accompanied by temporal and spatial changes in backscatter. Ultrasound exposure had no effect on the digestion process. Effective concentrations of targeted streptokinase were orders of magnitude lower than equivalently efficacious levels of free drug. Moreover, increasing competitive inhibition of fibrin-bound streptokinase nanoparticles reduced clot lysis in a monotonic fashion. As little as 1% surface targeting of streptokinase nanoparticles produced significant decreases in clot volumes (∼30%) in 1 h. Conclusion: This new nanoparticle-based thrombolytic agent provides specific and rapid fibrinolysis in vitro and may have a clinical role in early reperfusion during acute ischemic stroke.

Comparison of cerebral blood volume maps generated fromT2* andT1weighted MRI data in intra-axial cerebral tumours

We compared parametric maps, measured values and value distributions of cerebral blood volume (CBV) derived from (1) first pass T1 weighted dynamic contrast-enhanced (DCE) data (T1-CBV) using the recently described leakage profile model and (2) conventional T2* weighted DCE data (T2*-CBV) using a conventional curve fitting technique, in nine patients with intraaxial tumours. Regions of interest were defined around enhancing tumour tissue on matched slices. Median tumour values and conspicuity indexes of CBV from the two techniques were compared, demonstrating good correlation (r = 0.667,p<0.05) in enhancing tumour and no significant difference in conspicuity. Pixel-by-pixel scattergrams of values in normal brain in a representative matched slice were produced for each case, which showed excellent correlation (r = 0.96,p<0.001). Distortion of blood vessels around susceptibility interfaces was evident on T2* CBV but not on T1 CBV maps. Leakage-free T1 CBV maps do not suffer from the susceptibility artifacts seen in T2* CBV maps, although they present comparable biological information.

Insulated piggyBac vectors for insect transgenesis

Background

Germ-line transformation of insects is now a widely used method for analyzing gene function and for the development of genetically modified strains suitable for pest control programs. The most widely used transposable element for the germ-line transformation of insects is piggyBac. The site of integration of the transgene can influence gene expression due to the effects of nearby transcription enhancers or silent heterochromatic regions. Position effects can be minimized by flanking a transgene with insulator elements. The scs/scs' and gypsy insulators from Drosophila melanogaster as well as the chicken β-globin HS4 insulator function in both Drosophila and mammalian cells.

Results

To minimize position effects we have created a set of piggyBac transformation vectors that contain either the scs/scs', gypsy or chicken β-globin HS4 insulators. The vectors contain either fluorescent protein or eye color marker genes and have been successfully used for germ-line transformation of Drosophila melanogaster. A set of the scs/scs' vectors contains the coral reef fluorescent protein marker genes AmCyan, ZsGreen and DsRed that have not been optimized for translation in human cells. These marker genes are controlled by a combined GMR-3xP3 enhancer/promoter that gives particularly strong expression in the eyes. This is also the first report of the use of the ZsGreen and AmCyan reef fluorescent proteins as transformation markers in insects.

Conclusion

The insulated piggyBac vectors should protect transgenes against position effects and thus facilitate fine control of gene expression in a wide spectrum of insect species. These vectors may also be used for transgenesis in other invertebrate species.

The amino-terminal region of Drosophila MSL1 contains basic, glycine-rich, and leucine zipper-like motifs that promote X chromosome binding, self-association, and MSL2 binding, respectively

In Drosophila melanogaster, X chromosome dosage compensation is achieved by doubling the transcription of most X-linked genes. The male-specific lethal (MSL) complex is required for this process and binds to hundreds of sites on the male X chromosome. The MSL1 protein is essential for X chromosome binding and serves as a central scaffold for MSL complex assembly. We find that the amino-terminal region of MSL1 binds to hundreds of sites on the X chromosome in normal males but only to approximately 30 high-affinity sites in the absence of endogenous MSL1. Binding to the high-affinity sites requires a basic motif at the amino terminus that is conserved among Drosophila species. X chromosome binding also requires a conserved leucine zipper-like motif that binds to MSL2. A glycine-rich motif between the basic and leucine-zipper-like motifs mediates MSL1 self-association in vitro and binding of the amino-terminal region of MSL1 to the MSL complex assembled on the male X chromosome. We propose that the basic region may mediate DNA binding and that the glycine-rich region may promote the association of MSL complexes to closely adjacent sites on the X chromosome.

CD40-CD154 interactions between macrophages and natural killer cells during sepsis are critical for macrophage activation and are not interferon gamma dependent

Natural killer (NK) cell interactions with macrophages have been shown to be important during bacterial sepsis in activating macrophages to improve bacterial clearance. The mechanism for this increased activation, however, is unclear. This study determines the relative roles of interferon (IFN)-gamma and CD40/CD154 direct cell interactions on macrophage and NK cell activation in an experimental model of sepsis. Splenic NK cells and peritoneal macrophages were isolated and cultured alone or in coculture, with and without LPS. CD69 expression on NK cells, phagocytosis ability of macrophages, and cell cytokine production was assessed at 24 and 48 h. Coculture of NK cells and macrophages significantly increased activation levels of both cell types, and through experiments culturing NK cells with supernatants from stimulated macrophages and macrophages with supernatants from stimulated NK cells, this activation was determined to be cell-contact-dependent. Similar experiments were conducted using NK cells from IFN-gamma deficient (-/-) mice, as well as anti-IFN-gamma neutralizing antibody. These experiments determined that IFN-gamma is not required for NK or macrophage activation, although it did augment activation levels. Experiments were again repeated using peritoneal macrophages from CD40-/- mice or splenic NK cells from CD154-/- mice. CD40/CD154 interactions were important in the ingestion of bacteria by macrophages, but did not affect NK cell activation at 24 h. There was, however, a protective effect of CD40/CD154 interactions on NK cell activation-induced cell death that occurred at 48 h. CD40/CD154 interactions between macrophages and NK cells are therefore important in macrophage phagocytosis, and are not dependent on IFN-gamma.

Progress towards the development of a transgenic strain of the Australian sheep blowfly (Lucilia cuprina) suitable for a male-only sterile release program

The Australian sheep blowfly Lucilia cuprina is the most important pest species involved in cutaneous myiasis (flystrike) of sheep in Australia and New Zealand. In New Zealand L. cuprina is primarily controlled through the application of insecticides. However, there is an increased interest in biological methods of control of this species. We have proposed to develop a genetically modified strain of L. cuprina that would be ideal for a male-only sterile release program. To that end we have developed a method for making transgenic L. cuprina using a piggyBac vector and an EGFP marker gene. We have also developed in Drosophila melanogaster a 2-component genetic system for controlling female viability. Females carrying both components of the system die unless fed a diet that contains tetracycline. We anticipate that the female-killing system will need to be optimised for L. cuprina in order to make a strain with the properties required for a male-only release program.

Germ-line transformation of the Australian sheep blowfly Lucilia cuprina

The Australian sheep blowfly, Lucilia cuprina, is the most important economic insect pest for the sheep industries in Australia and New Zealand. piggyBac-mediated germ-line transformation of L. cuprina was achieved with a helper plasmid that had the Drosophila melanogaster hsp70 promoter controlling expression of the transposase and a piggyBac vector with an EGFP marker gene. Two transformant lines were obtained, at a frequency of approximately 1-2% per fertile G0. One of these lines has a single copy of the transgene, the other most likely has four copies. This is the first report of germ-line transformation of L. cuprina and is an important step towards the generation of engineered strains that would be suitable for male-only release eradication/suppression programmes.

Immediate and delayed leukocyte apoptosis in two models of peritonitis

Leukocyte apoptosis is an energy-dependent process that facilitates resolution of the cellular inflammatory response. Levels of apoptosis can be accelerated or inhibited after exposure to various stimuli. To compare apoptosis in transmigrated leukocytes, two models of peritonitis in mice were used that both cause leukocyte influx into the peritoneal cavity: (1) intraperitoneal thioglycollate administration producing a sterile peritonitis and (2) cecal ligation and puncture (CLP) producing a polymicrobial bacterial peritonitis. Samples of blood and peritoneal exudate cells (PEC) were collected at multiple time points after induction of peritonitis. Leukocytes were either fixed immediately to determine an immediate apoptosis level or cultured for 24 h to determine a delayed apoptosis level. Apoptosis was assessed using terminal uridine-triphosphate nick-end labeling (TUNEL) assay, flow cytometry, and confocal microscopy. Leukocyte influx into the peritoneal cavity was confirmed in both models. At all time points, and in both models, there was increased immediate apoptosis in PEC compared with unmanipulated controls and this increase was maximal in CLP after 18 h, although it appeared to remain at a stable level in the sterile peritonitis model by 3 h. There was also an increase in PEC delayed apoptosis at early time points in both models, again maximal at 18 h for CLP, with the levels being significantly higher than the thioglycollate model at 6 h and 18 h. The mice had a relative peripheral neutropenia at 6 h after CLP, but not post thioglycollate injection, and this persisted until 42 h. Lung and liver MPO levels were elevated in CLP but did not increase after thioglycollate. There was no increase in immediate peripheral leukocyte apoptosis in either model, but an increase in delayed peripheral leukocyte apoptosis was observed by 18 h in both models. Peripheral leukocyte CD1lb expression, which is a marker of activation, was also persistently elevated in the CLP model, but not in sterile peritonitis. In conclusion, CLP is a more potent stimulus for apoptosis of leukocytes than their migration to the site of inflammation alone, as occurs in the thioglycollate model. Blood leukocyte apoptosis also appears not to be dependent on CD11b expression, and therefore activation status.

The molecular properties of humic substances isolated from a UK upland peat system: a temporal investigation

The study concerns the possible changes in the molecular characteristics of humic materials isolated from the same source as a function of time. A great deal of data has been reported concerning the contrast in molecular characteristics of humic substances isolated from different environments. This has primarily been an attempt to identify source-specific molecular characteristics. However, data presented in this paper suggests that humic substances isolated from a single catchment have significant changes in molecular characteristics over time. Two naturally occurring peat pools (X and Y) situated upon a small organic catchment on Great Dun Fell, Cumbria, UK were sampled monthly between November 1994 and November 1996. Dissolved organic matter (DOM) from the pool water samples was fractionated using macroporous nonionic resins (XAD8 and 4), and the humic, fulvic and hydrophilic acids were collected. These fractions were analysed for elemental composition (C, H and N), weight average molecular weight, functional group content and adsorption (340 nm) of a 1 g l(-1) solution measured in a 1-cm spectrophotometer cell. The molecular characteristics were compared to those of natural DOM described by Scott et al. (1998). Scott et al. reported that drought conditions and seasonal climatic changes could have appreciable effects upon molecular characteristics of natural DOM. Results showed that the atomic H/C ratio of the humic substances increased immediately after strong drought conditions experienced in the summer of 1995. This change was temporary with atomic H/C ratio decreasing gradually over the following months. A similar decrease was observed in the carboxyl group content of the isolated compounds. The data set suggested that atomic H/C ratio in the fulvic and hydrophilic fractions exhibited seasonal characteristics of higher ratios during the late summer/early autumn months. This was not observed in the humic fraction. Humic acids exhibited a seasonal pattern of higher weight average molecular weight during the summer months. These trends were explained in terms of summer production of DOM in the catchment soils, their sequestering in the soil due to limited soil water movement during the summer months and their relative ease of dissolution when rainfall and soil water movement increased during the late summer/early autumn period. The results were found to support seasonal and long-term patterns observed in natural DOM as reported by Scott et al. (1998).

Echocardiographic characterization of fundamental mechanisms of abnormal diastolic filling in diabetic rats with a parameterized diastolic filling formalism

Abnormalities of diastolic function (DF) precede systolic dysfunction in diabetic cardiomyopathy. Transmitral Doppler flow analysis is the primary method for noninvasively assessing DF. We used model-based Doppler E-wave analysis to evaluate diastolic function differences between normal and diabetic rat hearts. Control rats and those with diabetes underwent echocardiography with analysis by traditional Doppler indexes and by the parameterized diastolic filling (PDF) formalism, generating 3 parameters, x0, c, and k, that uniquely characterize each E-wave. Significant intergroup differences in the E/A ratios (P <.01), isovolumic relaxation times (P <.01), and the modeling parameter c (P <.05) were found. There were no significant differences in shortening fraction, deceleration time, myocardial collagen content, or the parameters x0 and k between diabetic and control rats. These results indicate that differences in diastolic function may be noninvasively quantified and that diabetic hearts may exhibit defects in uncoupling of the contractile apparatus without concomitant increases in chamber stiffness.

STAT4 is required for antibacterial defense but enhances mortality during polymicrobial sepsis

The signal transducer and activator of transcription factor 4 (STAT4) pathway mediates the intracellular effects of interleukin-12 (IL-12), leading to the production of gamma interferon, induction of a T helper type 1 response, and increased natural killer cell cytotoxicity. The purpose of this study was to determine the role of the STAT4 pathway during polymicrobial peritonitis in the cecal ligation and puncture (CLP) model. CLP was performed on STAT4-deficient (STAT4(-/-)) and wild-type control (BALB/c) mice. At 4 h after CLP, STAT4(-/-) mice had significantly higher bacterial counts in the peritoneal lavage fluid, liver, and blood. This difference persisted for 18 h in the peritoneal lavage fluid and blood. Neutrophil migration to the site of infection and into remote tissues was unaffected. Despite higher bacterial counts locally and systemically, STAT4(-/-) mice had a lower mortality rate than BALB/c controls. In contrast, blockade of IL-12 in BALB/c mice was detrimental to host survival. A blunted serum IL-12 response at 18 h after CLP was exhibited in STAT4(-/-) mice. These results suggest several critical roles for the STAT4 pathway in the resolution of polymicrobial infections. Additionally, the disparate effects observed with IL-12 blockade and STAT4 deficiency on host survival suggest that IL-12 may activate alternate pathways promoting survival.

piggyBac-mediated transposition in Drosophila melanogaster: an evaluation of the use of constitutive promoters to control transposase gene expression

Transgenic non-Drosophilid insects have been made using insect transposable elements that have a broad host range such as the piggyBac element. However, the success rate is often low. Previous piggyBac helper plasmids have used either the piggyBac or the hsp70 promoter from Drosophila melanogaster to control expression of the transposase gene. Here we show that plasmids with the piggyBac transposase gene regulated by constitutive promoters can be effective 'helpers' for mediating transposition in D. melanogaster. We also present preliminary evidence on the use of an RNA helper that encodes the transposase. Our results suggest that for germ-line transformation of non-Drosophilid insects it may be advantageous to isolate a constitutive promoter from the species of interest to control transposase expression.

Novel MRI contrast agent for molecular imaging of fibrin: implications for detecting vulnerable plaques

BACKGROUND

Molecular imaging of thrombus within fissures of vulnerable atherosclerotic plaques requires sensitive detection of a robust thrombus-specific contrast agent. In this study, we report the development and characterization of a novel ligand-targeted paramagnetic molecular imaging agent with high avidity for fibrin and the potential to sensitively detect active vulnerable plaques.

METHODS AND RESULTS

The nanoparticles were formulated with 2.5 to 50 mol% Gd-DTPA-BOA, which corresponds to >50 000 Gd(3+) atoms/particle. Paramagnetic nanoparticles were characterized in vitro and evaluated in vivo. In contradistinction to traditional blood-pool agents, T1 relaxation rate as a function of paramagnetic nanoparticle number was increased monotonically with Gd-DTPA concentration from 0.18 mL. s(-1). pmol(-1) (10% Gd-DTPA nanoparticles) to 0.54 mL. s(-1). pmol(-1) for the 40 mol% Gd-DTPA formulations. Fibrin clots targeted in vitro with paramagnetic nanoparticles presented a highly detectable, homogeneous T1-weighted contrast enhancement that improved with increasing gadolinium level (0, 2.5, and 20 mol% Gd). Higher-resolution scans and scanning electron microscopy revealed that the nanoparticles were present as a thin layer over the clot surface. In vivo contrast enhancement under open-circulation conditions was assessed in dogs. The contrast-to-noise ratio between the targeted clot (20 mol% Gd-DTPA nanoparticles) and blood was approximately 118+/-21, and that between the targeted clot and the control clot was 131+/-37.

CONCLUSIONS

These results suggest that molecular imaging of fibrin-targeted paramagnetic nanoparticles can provide sensitive detection and localization of fibrin and may allow early, direct identification of vulnerable plaques, leading to early therapeutic decisions.

Temperature dependence of ultrasonic enhancement with a site-targeted contrast agent

Molecular imaging contrast agents specifically detect the biochemical "signatures" of disease before anatomical manifestations are apparent. Sensitive and specific localization of fibrin both in vivo and in vitro has been demonstrated with the use of a ligand-directed liquid perfluorocarbon nanoparticle. Since the acoustic properties of perfluorocarbons are known to vary with temperature, it was hypothesized that temperature could be used to augment the magnitude of enhancement imparted by targeted nanoparticles. Accordingly, the acoustic backscatter of two different substrates, nitrocellulose membrane and human plasma clot, targeted by the nanoparticles was measured at temperatures ranging from 27 degrees to 47 degrees C in 5 degrees C increments. Classic avidin-biotin interactions were utilized to couple biotinylated nanoparticles to avidin-conjugated nitrocellulose membranes. Ultrasonic contrast enhancement of the nitrocellulose membrane at 25 MHz, measured by acoustic microscopy, increased from 2.0+/-0.3 dB at 27 degrees C to 3.7+/-0.4 at 47 degrees C. In a similar experiment, antifibrin nanoparticles bound to human plasma clots also exhibited temperature-dependent ultrasonic signal enhancement ranging from 13.9+/-1.5 dB at 27 degrees C to 18.1+/-1.5 dB at 47 degrees C. The increase in ultrasonic contrast enhancement measured was well described by a simple, acoustic transmission line model with temperature-dependent impedance. These results suggest that temperature-dependent changes in acoustic backscatter may be used to further differentiate tissues targeted with site-specific nanoparticles from surrounding normal soft tissues.