The complete genome sequence of Escherichia coli K-12

The 4,639,221-base pair sequence of Escherichia coli K-12 is presented. Of 4288 protein-coding genes annotated, 38 percent have no attributed function. Comparison with five other sequenced microbes reveals ubiquitous as well as narrowly distributed gene families; many families of similar genes within E. coli are also evident. The largest family of paralogous proteins contains 80 ABC transporters. The genome as a whole is strikingly organized with respect to the local direction of replication; guanines, oligonucleotides possibly related to replication and recombination, and most genes are so oriented. The genome also contains insertion sequence (IS) elements, phage remnants, and many other patches of unusual composition indicating genome plasticity through horizontal transfer.

Genome sequence of enterohaemorrhagic Escherichia coli O157:H7

The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.

Role of thioredoxin in the response of normal and transformed cells to histone deacetylase inhibitors

This study examines the basis of resistance and sensitivity of normal and transformed cells to histone deacetylase inhibitor (HDACi)-induced cell death, specifically the role of caspases and thioredoxin (Trx). An important attribute of HDACis is that they induce cancer cell death at concentrations to which normal cells are relatively resistant, making them well suited for cancer therapy. The mechanism underlying this selectivity has not been understood. In this study we found that the HDACi suberoylanilide hydroxamic acid (SAHA) and MS-275, a benzamide, cause an accumulation of reactive oxygen species (ROS) and caspase activation in transformed but not normal cells. Inhibition of caspases does not block HDACi-induced cell death. These studies provide a possible mechanism that can explain why normal but not certain transformed cells are resistant to HDACi-induced cell death. The HDACi causes an increase in the level of Trx, a major reducing protein for many targets, in normal cells but not in transformed cells. The SAHA-induced increase in Trx activity in normal cells is associated with no increase in ROS accumulation. Transfection of transformed cells with Trx small interfering RNA caused a marked decrease in the level of Trx protein with an increase in ROS, a decrease in cell proliferation, and an increase in sensitivity to SAHA-induced cell death. Thus, Trx, independent of the caspase apoptotic pathway, is an important determinant of resistance of cells to HDACi-induced cell death.

Simultaneous PET and MR imaging

We have developed a prototype PET detector which is compatible with a clinical MRI system to provide simultaneous PET and MR imaging. This single-slice PET system consists of 48 2 x 2 x 10 mm3 LSO crystals in a 38 mm diameter ring configuration that can be placed inside the receiver coil of the MRI system, coupled to three multi-channel photomultipliers housed outside the main magnetic field via 4 m long and 2 mm diameter optical fibres. The PET system exhibits 2 mm spatial resolution, 41% energy resolution at 511 keV and 20 ns timing resolution. Simultaneous PET and MR phantom images were successfully acquired.

A recent outbreak of human immunodeficiency virus type 1 infection in southern China was initiated by two highly homogeneous, geographically separated strains, circulating recombinant form AE and a novel BC recombinant

New outbreaks of human immunodeficiency virus type 1 (HIV-1) among injecting drug users (IDUs) are spreading in China along heroin trafficking routes. Recently, two separate HIV-1 epidemics among IDUs were reported in Guangxi, Southern China, where partial sequencing of the env gene showed subtype C and circulating recombinant form (CRF) AE. We evaluated five virtually full-length HIV-1 genome sequences from IDUs in Guangxi to determine the genetic diversity and the presence of intersubtype recombinants. Sequence analysis showed two geographically separated, highly homogeneous HIV-1 strains. B/C intersubtype recombinants were found in three IDUs from Baise City, in a mountainous region near the Yunnan-Guangxi border. These were mostly subtype C, with portions of the capsid and reverse transcriptase (RT) genes from subtype B. The subtype B portion of the capsid was located in the N-terminal domain, which has been shown to influence virus core maturation, virus infectivity, and binding to cyclophilin A, whereas the subtype B portion of RT was located in the palm subdomain, which is the active site of the enzyme. These BC recombinants differed from a BC recombinant found in Xinjiang Province in northwestern China. CRF AE strains were found in IDUs from Nanning, the capital of Guangxi, and in IDUs from Pingxiang City near the China-Vietnam border. The AE and BC recombinants were both remarkable for their low interpatient diversity, less than 1% for the full genome. Rapid spread of HIV-1 among IDUs may foster the emergence of highly homogeneous strains, including novel recombinants in regions with multiple subtypes.

Characterization of a virtually full-length human immunodeficiency virus type 1 genome of a prevalent intersubtype (C/B') recombinant strain in China

A molecular epidemiology study was conducted among more than 100 human immunodeficiency virus type 1 (HIV-1) subtype C seropositive intravenous drug users (IDUs) from China. Genotyping based on the envelope C2V3 coding region revealed the highest homology of the most prevalent virus strains circulating throughout China to subtype C sequences of Indian origin. Based on these results, a virtually full-length genome representing the most prevalent class of clade C strains circulating throughout China was directly amplified from peripheral blood mononuclear cells of a selected HIV-infected IDU and subcloned. Sequence analysis identified a mosaic structure, suggesting extensive intersubtype recombination events between genomes of the prevalent clade C and (B')-subtype Thai virus strains of that geographic region. Recombinant Identification Program analysis and phylogenetic bootstrapping suggested that there were 10 breakpoints (i) in the gag-pol coding region, (ii) in vpr and at the 3' end of the vpu gene, and (iii) in the nef open reading frame. (B')-sequences therefore include (i) several insertions in the gag-pol coding region; (ii) 3'-vpr, the complete vpu gene, and the first exons of tat and rev; and (iii) the 5' half of the nef gene. Breakpoints located in the vpr/vpu coding region as well as in the nef gene of 97cn54 were found at almost identical positions of all subtype C strains isolated from IDUs living in different areas of China, suggesting a common ancestor for the C/B' recombinant strains. More than 50% of well-defined subtype B-derived cytotoxic T-lymphocyte epitopes within Gag and Pol and 10% of the known epitopes in Env were found to exactly match sequences within in this clade C/B' chimeric reference strain. These results may substantially facilitate a biological comparison of clade C-derived reference strains as well as the generation of useful reagents supporting vaccine-related efforts in China.

The complete DNA sequence and analysis of the large virulence plasmid of Escherichia coli O157:H7

The complete DNA sequence of pO157, the large virulence plasmid of EHEC strain O157:H7 EDL 933, is presented. The 92 kb F-like plasmid is composed of segments of putative virulence genes in a framework of replication and maintenance regions, with seven insertion sequence elements, located mostly at the boundaries of the virulence segments. One hundred open reading frames (ORFs) were identified, of which 19 were previously sequenced potential virulence genes. Forty-two ORFs were sufficiently similar to known proteins for suggested functions to be assigned, and 22 had no convincing similarity with any known proteins. Of the newly identified genes, an unusually large ORF of 3169 amino acids has a putative cytotoxin active site shared with the large clostridial toxin (LCT) family and proteins such as ToxA and B of Clostridium difficile . A conserved motif was detected that links the large ORF and the LCT proteins with the OCH1 family of glycosyltransferases. In the complete sequence, the mosaic form can be observed at the levels of base composition, codon usage and gene organization. Insights were obtained from patterns of DNA composition as well as the pathogenic and 'housekeeping' gene segments. Evolutionary trees built from shared plasmid maintenance genes show that even these genes have heterogeneous origins.

Tumor targeting using anti-her2 immunoliposomes

We have generated anti-HER2 (ErbB2) immunoliposomes (ILs), consisting of long circulating liposomes linked to anti-HER2 monoclonal antibody (MAb) fragments, to provide targeted drug delivery to HER2-overexpressing cells. Immunoliposomes were constructed using a modular strategy in which components were optimized for internalization and intracellular drug delivery. Parameters included choice of antibody construct, antibody density, antibody conjugation procedure, and choice of liposome construct. Anti-HER2 immunoliposomes bound efficiently to and internalized in HER2-overexpressing cells in vitro as determined by fluorescence microscopy, electron microscopy, and quantitative analysis of fluorescent probe delivery. Delivery via ILs in HER2-overexpressing cells yielded drug uptake that was up to 700-fold greater than with non-targeted sterically stabilized liposomes. In vivo, anti-HER2 ILs showed extremely long circulation as stable constructs in normal adult rats after a single i.v. dose, with pharmacokinetics that were indistinguishable from sterically stabilized liposomes. Repeat administrations revealed no increase in clearance, further confirming that ILs retain the long circulation and non-immunogenicity of sterically stabilized liposomes. In five different HER2-overexpressing xenograft models, anti-HER2 ILs loaded with doxorubicin (dox) showed potent anticancer activity, including tumor inhibition, regressions, and cures (pathologic complete responses). ILs were significantly superior vs. all other treatment conditions tested: free dox, liposomal dox, free MAb (trastuzumab), and combinations of dox+MAb or liposomal dox+MAb. For example, ILs produced significantly superior antitumor effects vs. non-targeted liposomes (P values from <0.0001 to 0.04 in eight separate experiments). In a non-HER2-overexpressing xenograft model (MCF7), ILs and non-targeted liposomal dox produced equivalent antitumor effects. Detailed studies of tumor localization indicated a novel mechanism of drug delivery for anti-HER2 ILs. Immunotargeting did not increase tumor tissue levels of ILs vs. liposomes, as both achieved very high tumor localization (7.0-8.5% of injected dose/g tissue) in xenograft tumors. However, histologic studies using colloidal-gold labeled ILs demonstrated efficient intracellular delivery in tumor cells, while non-targeted liposomes accumulated within stroma, either extracellularly or within macrophages. In the MCF7 xenograft model lacking HER2-overexpression, no difference in tumor cell uptake was seen, with both ILs and non-targeted liposomes accumulating within stroma. Thus, anti-HER2 ILs, but not non-targeted liposomes, achieve intracellular drug delivery via receptor-mediated endocytosis, and this mechanism is associated with superior antitumor activity. Based on these results, anti-HER2 immunoliposomes have been developed toward clinical trials. Reengineering of construct design for clinical use has been achieved, including: new anti-HER2 scFv F5 generated by screening of a phage antibody library for internalizing anti-HER2 phage antibodies; modifications of the scFv expression construct to support large scale production and clinical use; and development of methods for large-scale conjugation of antibody fragments with liposomes. We developed a scalable two-step protocol for linkage of scFv to preformed and drug-loaded liposomes. Our final, optimized anti-HER2 ILs-dox construct consists of F5 conjugated to derivatized PEG-PE linker and incorporated into commercially available liposomal doxorubicin (Doxil). Finally, further studies of the mechanism of action of anti-HER2 ILs-dox suggest that this strategy may provide optimal delivery of anthracycline-based chemotherapy to HER2-overexpressing cancer cells in the clinic, while circumventing the cardiotoxicity associated with trastuzumab+anthracycline. We conclude that anti-HER2 immunoliposomes represent a promising technology for tumor-targeted drug delivery, and that this strategy may also be applicable to other receptor targets and/or using other delivered agents.

Inhibition of type I procollagen synthesis by damaged collagen in photoaged skin and by collagenase-degraded collagen in vitro

Type I and type III procollagen are reduced in photodamaged human skin. This reduction could result from increased degradation by metalloproteinases and/or from reduced procollagen synthesis. In the present study, we investigated type I procollagen production in photodamaged and sun-protected human skin. Skin samples from severely sun-damaged forearm skin and matched sun-protected hip skin from the same individuals were assessed for type I procollagen gene expression by in situ hybridization and for type I procollagen protein by immunostaining. Both mRNA and protein were reduced ( approximately 65 and 57%, respectively) in photodamaged forearm skin compared to sun-protected hip skin. We next investigated whether reduced type I procollagen production was because of inherently reduced capacity of skin fibroblasts in severely photodamaged forearm skin to synthesize procollagen, or whether contextual influences within photodamaged skin act to down-regulate type I procollagen synthesis. For these studies, fibroblasts from photodamaged skin and matched sun-protected skin were established in culture. Equivalent numbers of fibroblasts were isolated from the two skin sites. Fibroblasts from the two sites had similar growth capacities and produced virtually identical amounts of type I procollagen protein. These findings indicate that the lack of type I procollagen synthesis in sun-damaged skin is not because of irreversible damage to fibroblast collagen-synthetic capacity. It follows, therefore, that factors within the severely photodamaged skin may act in some manner to inhibit procollagen production by cells that are inherently capable of doing so. Interactions between fibroblasts and the collagenous extracellular matrix regulate type I procollagen synthesis. In sun-protected skin, collagen fibrils exist as a highly organized matrix. Fibroblasts are found within the matrix, in close apposition with collagen fibers. In photodamaged skin, collagen fibrils are shortened, thinned, and disorganized. The level of partially degraded collagen is approximately 3.6-fold greater in photodamaged skin than in sun-protected skin, and some fibroblasts are surrounded by debris. To model this situation, skin fibroblasts were cultured in vitro on intact collagen or on collagen that had been partially degraded by exposure to collagenolytic enzymes. Collagen that had been partially degraded by exposure to collagenolytic enzymes from either bacteria or human skin underwent contraction in the presence of dermal fibroblasts, whereas intact collagen did not. Fibroblasts cultured on collagen that had been exposed to either source of collagenolytic enzyme demonstrated reduced proliferative capacity (22 and 17% reduction on collagen degraded by bacterial collagenase or human skin collagenase, respectively) and synthesized less type I procollagen (36 and 88% reduction, respectively, on a per cell basis). Taken together, these findings indicate that 1) fibroblasts from photoaged and sun-protected skin are similar in their capacities for growth and type I procollagen production; and 2) the accumulation of partially degraded collagen observed in photodamaged skin may inhibit, by an as yet unidentified mechanism, type I procollagen synthesis.

Protein splicing involving the Saccharomyces cerevisiae VMA intein. The steps in the splicing pathway, side reactions leading to protein cleavage, and establishment of an in vitro splicing system

Protein splicing involves the excision of an internal protein segment, the intein, from a precursor protein and the concomitant ligation of the flanking N- and C-terminal regions. It occurs in mesophilic bacteria, yeast, and thermophilic archaea. The ability to control protein splicing of a thermophilic intein by temperature and pH in a foreign protein context facilitated the study of the mechanism of protein splicing in thermophiles. On the other hand, no direct studies have been done on the mechanism of protein splicing in mesophiles. We examined the splicing of a chimeric protein containing the intein of the vacuolar ATPase subunit (VMA) of Saccharomyces cerevisiae that involves cysteines rather than serines at the reaction center. The steps in the splicing process were deduced by analyzing intermediates and side products that accumulated as a result of amino acid substitutions and were found to be analogous to those occurring in thermophiles. Moreover, appropriate amino acid replacements allowed us to develop the first mesophilic in vitro protein splicing system as well as strategies for modulating the rate of protein splicing and for converting the splicing reaction to an efficient protein cleavage reaction at either splice junction.

Effect of a lipidic extract from lepidium meyenii on sexual behavior in mice and rats

OBJECTIVES

To determine the effect of oral administration of a purified lipidic extract from Lepidium meyenii (MacaPure M-01 and M-02) on the number of complete intromissions and mating in normal mice, and on the latent period of erection (LPE) in rats with erectile dysfunction.

METHODS

Mice and rats were randomly divided into several experimental and control groups. A 10% ethanol suspension of M-01 and M-02 was orally administered for 22 days to the experimental groups according to the dosage specified by the experimental design. On day 22, 30 minutes after the dose was administered to the male mice, 2 virgin female mice were placed with 1 male mouse. The number of complete intromissions of each male mouse in 3 hours was recorded. In an assessment of 1 day of mating, each male mouse was cohabited with 5 estrous female mice overnight. The number of sperm-positive females was recorded. The LPE was measured to assess the sexual function in rats with erectile dysfunction. By using a YSD-4G multifunction instrument, an electric pulse at 20 V was applied to stimulate the rat's penis, and the duration from the start of the stimulus to full erection was measured in seconds as the LPE.

RESULTS

In the normal male mice, the number of complete intromissions during the 3-hour period was 16.33 +/- 1.78, 46.67 +/- 2.39, and 67.01 +/- 2.55 for the control group, M-01 group, and M-02 group, respectively. In the assessment of mating, the number of sperm-positive females increased from 0.6 +/- 0.7 in the control group to 1.5 +/- 0.5 in the M-01 experimental group. The LPE of male rats with erectile dysfunction was 112 +/- 13 seconds with a regular diet (control group). The oral administration of M-01 at a dose of 180 or 1800 mg/kg body weight and M-02 at a dose of 45, 180, or 1800 mg/kg body weight reduced the LPE to 54 +/- 12 seconds, 54 +/- 13 seconds, 71 +/- 12 seconds, 73 +/- 12 seconds, and 41 +/- 13 seconds, respectively. The LPE of the surgical rats treated with M-01 at the lowest dose (45 mg/kg) was 121 +/- 12 seconds; thus, the change was not significant.

CONCLUSIONS

Oral administration of M-01 and M-02 enhanced the sexual function of the mice and rats, as evidenced by an increase in the number of complete intromissions and the number of sperm-positive females in normal mice, and a decrease in the LPE in male rats with erectile dysfunction. The present study reveals for the first time an aphrodisiac activity of L. meyenii, an Andean Mountain herb.

Cbl promotes ubiquitination of the T cell receptor zeta through an adaptor function of Zap-70

Triggering of the T cell antigen receptor (TCR).CD3 complex induces its ubiquitination. However, the molecular events that lead to ubiquitin conjugation to these cell surface molecules have not been defined. Here we report that Cbl, a RING-type E3 ubiquitin-protein ligase, promotes ubiquitination of TCR zeta chain, which requires its functional variant Src homology 2 domain and an intact RING finger. The tyrosine kinase Zap-70, which binds to both TCR zeta and Cbl, plays an adaptor role in these events. Mutations in TCR zeta, Zap-70, or Cbl that disrupt the interaction between TCR zeta and Zap-70 or between Zap-70 and Cbl reduce ubiquitination of TCR zeta. Our results suggest a novel mechanism by which Cbl negatively regulates T cell development and activation by inducing ubiquitination of the TCR.CD3 components.

Altered left atrial compliance after atrial appendectomy. Influence on left atrial and ventricular filling

Previous studies have shown regional differences in atrial distensibility. We studied 12 open-chest dogs to test the hypothesis that left atrial compliance is decreased after removal of the left atrial appendage and to determine the effect of altered atrial compliance on atrial reservoir and conduit function. Sonomicrometer crystal pairs were used to measure the long- and short-axis diameters of the left atrium over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after suture ligation of the left atrial appendage (appendectomy). Pulmonary venous flow was measured with an ultrasonic flowmeter, and transmitral flow velocities were measured with transesophageal Doppler echocardiography. After appendectomy, the diastolic pressure-volume relation was shifted upward and to the left in six of seven dogs. The mean dynamic stiffness constant of the left atrial diastolic pressure-volume relation was significantly greater after appendectomy than before (0.20 +/- 0.11 [mean +/- SD] versus 0.14 +/- 0.08 ml-1, p < 0.01); the mean y intercept was slightly, but significantly, less after appendectomy (0.6 +/- 0.3 versus 1.3 +/- 0.6 mm Hg, p < 0.05). The left atrial reservoir volume (maximum minus minimum left atrial volume) was significantly less after appendectomy at matched left atrial pressures. The systolic to diastolic flow integral ratio of pulmonary venous flow (JFTI/KFTI), an index of the relative reservoir to conduit functions of the left atrium, increased significantly with volume infusion only before appendectomy; at matched left atrial pressure, JFTI/KFTI was significantly less afterwards.(ABSTRACT TRUNCATED AT 250 WORDS)

Association analysis of chromosome 15 gabaa receptor subunit genes in autistic disorder

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the brain, acting via the GABAA receptors. The GABAA receptors are comprised of several different homologous subunits, forming a group of receptors that are both structurally and functionally diverse. Three of the GABAA receptor subunit genes (GABRB3, GABRA5 and GABRG3) form a cluster on chromosome 15q11-q13, in a region that has been genetically associated with autistic disorder (AutD). Based on these data, we examined 16 single nucleotide polymorphisms (SNPs) located within GABRB3, GABRA5 and GABRG3 for linkage disequilibrium (LD) in 226 AutD families (AutD patients and parents). Genotyping was performed using either OLA (oligonucleotide ligation assay), or SSCP (single strand conformation polymorphism) followed by DNA sequencing. We tested for LD using the Pedigree Disequilibrium Test (PDT). PDT results gave significant evidence that AutD is associated with two SNPs located within the GABRG3 gene (exon5_539T/C, p=0.02 and intron5_687T/C, p=0.03), suggesting that the GABRG3 gene or a gene nearby contributes to genetic risk in AutD.

Analysis of the RELN gene as a genetic risk factor for autism

Several genome-wide screens have indicated the presence of an autism susceptibility locus within the distal long arm of chromosome 7 (7q). Mapping at 7q22 within this region is the candidate gene reelin (RELN). RELN encodes a signaling protein that plays a pivotal role in the migration of several neuronal cell types and in the development of neural connections. Given these neurodevelopmental functions, recent reports that RELN influences genetic risk for autism are of significant interest. The total data set consists of 218 Caucasian families collected by our group, 85 Caucasian families collected by AGRE, and 68 Caucasian families collected at Tufts University were tested for genetic association of RELN variants to autism. Markers included five single-nucleotide polymorphisms (SNPs) and a repeat in the 5'-untranslated region (5'-UTR). Tests for association in Duke and AGRE families were also performed on four additional SNPs in the genes PSMC2 and ORC5L, which flank RELN. Family-based association analyses (PDT, Geno-PDT, and FBAT) were used to test for association of single-locus markers and multilocus haplotypes with autism. The most significant association identified from this combined data set was for the 5'-UTR repeat (PDT P-value=0.002). These analyses show the potential of RELN as an important contributor to genetic risk in autism.

Ultraviolet irradiation increases matrix metalloproteinase-8 protein in human skin in vivo

Humans express three distinct collagenases, MMP-1, MMP-8, and MMP-13, that initiate degradation of fibrillar type I collagen. We have previously reported that ultraviolet irradiation causes increased expression of MMP-1, but not MMP-13, in keratinocytes and fibroblasts in human skin in vivo. We report here that ultraviolet irradiation increases expression of MMP-8 in human skin in vivo. Western analysis revealed that levels of the full-length, 85 kDa proenzyme form of MMP-8 increased significantly within 8 h post ultraviolet irradiation (2 minimal erythema doses). Increased full-length MMP-8 protein was associated with infiltration into the skin of neutrophils, which are the major cell type that expresses MMP-8. Immunofluorescence revealed coexpression of MMP-8 and neutrophil elastase, a marker for neutrophils. Immunohistology demonstrated MMP-8 expression in neutrophils in the papillary dermis between 4 and 8 h post ultraviolet irradiation, and in the epidermis at 24 h post radiation. MMP-8 mRNA expression was not detected in nonirradiated or ultraviolet-irradiated human skin, indicating that increased MMP-8 following ultraviolet irradiation resulted from preexisting MMP-8 protein in infiltrating neutrophils. Pretreatment of skin with the glucocorticoid clobetasol, but not all-trans retinoic acid, significantly blocked ultraviolet-induced increases in MMP-8 protein levels, and neutrophil infiltration. In contrast, all-trans retinoic acid and clobetasol were equally effective in blocking ultraviolet induction of MMP-1 and degradation of collagen in human skin in vivo. Taken together, these data demonstrate that ultraviolet irradiation increases MMP-8 protein, which exists predominantly in a latent form within neutrophils, in human skin in vivo. Although ultraviolet irradiation induces both MMP-1 and MMP-8, ultraviolet-induced collagen degradation is initiated primarily by MMP-1, with little, if any, contribution by MMP-8.

Plasticity of astrocytes

It is becoming apparent that astrocytes carry out a large number of different functions in brain and are able to modify their characteristics throughout life, that is they exhibit a high degree of plasticity in their phenotype. For example, the morphology of astrocytes changes markedly during neuronal migration, maturation, and degeneration. It is conceivable that these cells must constantly adjust their abilities to meet changes in brain environment. Several examples of astrocytic plasticity are presented in this review. First, the ability of astrocytes to recognize neuronal signals can change qualitatively as well as quantitatively; evidence suggests that the expression of glial receptors may be developmentally regulated by both intrinsic and extrinsic signals. Second, the expression of adrenergic receptors by astrocytes in adult brain can change in response to neuronal degeneration. The up-regulation of beta-adrenergic receptors in this case suggests that these receptors play a role in function of reactive astrocytes. Finally, glial morphology can be reciprocally regulated by neurotransmitters such as norepinephrine and glutamate. This reciprocal regulation may be significant since both beta-adrenergic receptors and glutamate transporters are found predominantly in astrocytes in the brain. The change in glial morphology may also affect neuronal activity by changing the volume of the extracellular space.

Inhibitory activity of boswellic acids from Boswellia serrata against human leukemia HL-60 cells in culture

Four major triterpene acids including beta-boswellic acid (1), 3-O-acetyl-beta-boswellic acid (2), 11-keto-beta-boswellic acid (3), and 3-O-acetyl-11-keto-beta-boswellic acid (4) were isolated from the gum resin of Boswellia serrata and examined for their in vitro antitumor activity. They inhibited the synthesis of DNA, RNA and protein in human leukemia HL-60 cells in a dose dependent manner with IC50 values ranging from 0.6 to 7.1 microM. Among them, compound 4 induced the most pronounced inhibitory effects on DNA, RNA and protein synthesis with IC50 values of 0.6, 0.5, and 4.1 microM, respectively. The effect of 4 on DNA synthesis was found to be irreversible. Compound 4 significantly inhibited the cellular growth of HL-60 cells, but did not affect cell viability.

Design and evaluation of an LSO PET detector for breast cancer imaging

Functional imaging with positron emission tomography (PET) may be a promising technique in conjunction with x-ray mammography for breast cancer patient management. Conventional whole body PET scanners provide metabolic images of breast cancer patients with several shortcomings related to the general-purpose nature of these systems. In whole body scanners, the detectors are typically 20-30 cm away from the breast or axilla, reducing sensitivity, and these scanners have relatively large detector elements (> 4 mm), limiting spatial resolution. Dedicated PET systems for breast imaging aim to overcome these limitations and improve the overall diagnostic quality of the images by bringing the detectors closer to the area to be imaged, thereby improving sensitivity, and by using smaller detector elements to improve the spatial resolution. We have designed and developed a modular PET detector that is composed of a 9x9 array of 3x3x20 mm3 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to an optical fiber taper, which in turn is coupled to a Hamamatsu R5900-C8 position-sensitive photomultiplier tube. These detectors can be tiled together without gaps to construct large area detector arrays to form a dedicated PET breast cancer imaging system. Two complete detector modules have been built and tested. All detector elements are clearly visualized upon flood irradiation of the module. The intrinsic spatial resolution (full-width at half-maximum) was measured to be 2.26 mm (range 1.8-2.6 mm). The average energy resolution was 19.5% (range 17%-24%) at 511 keV. The coincidence time resolution was measured to be 2.4 ns. The detector efficiency for 511 keV gamma rays was 53% using a 350 keV energy threshold. These promising results support the feasibility of developing a high resolution, high sensitivity dedicated PET scanner for breast cancer applications.