[Establishment of a rabbit model of Acanthamoeba keratitis]

AIM

To establish an animal model of Acanthamoeba keratitis.

METHODS

Six New Zealand white rabbits were each injected intrastromally with Acanthamoeba suspension 3 days after subconjunctival injection with dexamethasone.

RESULTS

All of the 6 rabbits developed keratitis. Acanthamoeba protozoa were identified by the methods of corneal scraping with 10% potassium hydroxide wet mount examined under microscope, corneal protozoa culture and pathological section examination.

CONCLUSION

A rabbit model of Acanthamoeba keratitis was established.

A major QTL for acute ethanol sensitivity in the alcohol tolerant and non-tolerant selected rat lines

The Alcohol Tolerant and Alcohol Non-Tolerant rats (AT, ANT) were selectively bred for ethanol-induced ataxia as measured on the inclined plane. Here we report on a quantitative trait locus (QTL) study in an F(2) intercross population derived from inbred AT and ANT (IAT, IANT) and a follow-up study of congenics that were bred to examine one of the mapped QTLs. Over 1200 F(2) offspring were tested for inclined plane sensitivity, acute tolerance on the inclined plane, duration of the loss of righting reflex (LORR) and blood ethanol at regain of the righting reflex (BECRR). F(2) rats that were in the upper and lower 20% for inclined plane sensitivity were genotyped with 78 SSLP markers. Significant QTLs for inclined plane sensitivity were mapped on chromosomes 8 and 20; suggestive QTLs were mapped on chromosomes 1, 2 and 3. Highly significant QTLs for LORR duration (LOD = 12.4) and BECRR (LOD = 5.7) were mapped to the same locus on chromosome 1. Breeding and testing of reciprocal congenic lines confirmed the chromosome 1 LORR/BECRR QTL. A series of recombinant congenic sub-lines were bred to fine-map this QTL. Current results have narrowed the QTL to an interval of between 5 and 20 Mb. We expect to be able to narrow the interval to less than 5 Mb with additional genotyping and continued breeding of recombinant sub-congenic lines.

A phytoplasma related to 'Candidatus phytoplasma asteri' detected in citrus showing Huanglongbing (yellow shoot disease) symptoms in Guangdong, P. R. China

Citrus huanglongbing (HLB) or yellow shoot disease (i.e., greening disease) is highly destructive to citrus production worldwide. Understanding the etiology of HLB is critical for managing the disease. HLB is currently associated with infection by 'Candidatus Liberibacter spp.' around the world, including China. However, Koch's postulates have not been fulfilled. In addition, other plant pathogens also may be involved in HLB. In a survey performed in Guangdong Province, P. R. China in 2006 and 2007, 141 citrus samples showing typical symptoms of HLB from 11 different cities were collected. Polymerase chain reaction (PCR) using phytoplasma-specific primer sets fU5/rU3 nested with primer set P1/P7 identified 110 (78.0%) positive samples. A 1,785-bp amplicon was obtained with primer set P1/P7. Analysis showed a 100% identity of this sequence in the region of 16S rDNA and 16S-23S rRNA intergenic transcribed spacer to three strains of 'Candidatus Phytoplasma asteri' (onion yellows [Japan], aster yellows 'watercress' [Hawaii], and valeriana yellows [Lithuania]). Of the 141 samples, 89 (63.1%) samples were positive for 'Ca. Liberibacter asiaticus'. When mixed infection was considered, 69 (48.9%) samples were positive for both 'Ca. P. asteri' and 'Ca. L. asiaticus'. Transmission electron microscopy (TEM) showed low titers of both walled and wall-less bodies in the phloem sieve tubes of HLB citrus. When transmission from symptomatic citrus to periwinkle (Catharanthus roseus) via dodder (Cuscuta campestris) was conducted, both phytoplasma and 'Ca. L. asiaticus' were detected from the affected periwinkle. In addition to yellowing/mottling, the infected periwinkle showed symptoms of virescence and phyllody which are commonly associated with phytoplasmal diseases. TEM analysis of affected periwinkle revealed pleomorphic and wall-less organisms, characteristic of phytoplasmas, filling some phloem sieve tubes. In contrast, walled bacteria were at low titer. This study showed that in addition to 'Ca. L. asiaticus', a phytoplasma related to 'Ca. P. asteri' could also be detected in citrus showing HLB symptoms in Guangdong.

TGF-beta repression of Id2 induces apoptosis in gut epithelial cells

Transforming growth factor-beta (TGF-beta) regulates epithelial tissue homeostasis by activating processes that control cell cycle arrest, differentiation and apoptosis. Disruption of the TGF-beta signaling pathway often occurs in colorectal cancers. Earlier, we have shown that TGF-beta induces apoptosis through the transcription factor Smad3. Affymetrix oligonucleotide microarrays were used to identify TGF-beta/Smad3 target genes that regulate apoptosis in rat intestinal epithelial cells (RIE-1). We found that TGF-beta repressed the expression of the inhibitor of differentiation (Id) gene family. Knockdown of Id1 and Id2 gene expression induced apoptosis in RIE-1 cells, whereas overexpression of Id2 attenuated TGF-beta-induced apoptosis. TranSignal Protein/DNA arrays were used to identify the hypoxia-inducing factor-1 (HIF-1) as a downstream target of TGF-beta. HIF-1 is a basic helix-loop-helix protein, and overexpression of Id2 blocked HIF-1 activation by TGF-beta. Furthermore, knockdown of HIF-1 blocked TGF-beta-induced apoptosis. Thus, we have identified HIF-1 as a novel mediator downstream of Id2 in the pathway of TGF-beta-induced apoptosis.

Porphyromonas gingivalis with either Tannerella forsythia or Treponema denticola induces synergistic IL-6 production by murine macrophage-like J774.1 cells

BACKGROUND

Chronic periodontitis is caused by mixed bacterial infection. Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola are frequently detected in deep periodontal pockets. We demonstrate that these bacteria induce proinflammatory cytokine production by the mouse macrophage-like cell line J774.1.

MATERIALS AND METHODS

J774.1 cells were incubated with and without bacteria for 24h in 96-well flat-bottomed plates. The culture supernatants were analyzed by enzyme-linked immunosorbent assay for secreted mouse interleukin (IL)-6, monocyte chemoattractant protein-1, IL-23, IL-1 beta and tumor necrosis factor-alpha. The cytokine concentrations were determined using a standard curve prepared for each assay.

RESULTS

Mixed infection with P. gingivalis and either T. forsythia or T. denticola at 10(5)CFU/ml acted synergistically to increase IL-6 production, but not monocyte chemoattractant protein-1, IL-23, IL-1 beta or tumor necrosis factor-alpha production. Gingipain inhibitors KYT-1 and KYT-36 inhibited IL-6 production by J774.1 cells incubated with 10(5)CFU/ml of mixed bacteria.

CONCLUSION

These results suggest that P. gingivalis with either T. forsythia or T. denticola directly induces synergistic IL-6 protein production and that gingipains play a role in this synergistic effect.

Continuous treatment process of mercury removal from aqueous solution by growing recombinant E. coli cells and modeling study

A continuous treatment process was developed to investigate the capability of genetically engineered E. coli to simultaneously accumulate mercuric ions and reproduce itself in a continuous stirred tank reactor (CSTR) system. The influence of dilution rate and initial Hg(2+) concentration on continuous process was evaluated. Results indicated that the recombinant E. coli could effectively accumulate Hg(2+) from aqueous solution with Hg(2+) removal ratio up to about 90%, and propagate its cells at the same time in the continuous treatment system under suitable operational conditions. A kinetic model based on mass balance of Hg(2+) was proposed to simulate the continuous process. The modeling results were in good agreement with the experimental data.

Epithelial fibroblast growth factor receptor 1 regulates enamel formation

The interaction between epithelial and mesenchymal tissues plays a critical role in the development of organs such as teeth, lungs, and hair. During tooth development, fibroblast growth factor (FGF) signaling is critical for regulating reciprocal epithelial and mesenchymal interactions. FGF signaling requires FGF ligands and their receptors (FGFRs). In this study, we investigated the role of epithelial FGF signaling in tooth development, using the Cre-loxp system to create tissue-specific inactivation of Fgfr1 in mice. In K14-Cre;Fgfr1(fl/fl) mice, the apical sides of enamel-secreting ameloblasts failed to adhere properly to each other, although ameloblast differentiation was unaffected at early stages. Prior to eruption, enamel structure was compromised in the K14-Cre;Fgfr1(fl/fl) mice and displayed severe enamel defects that mimic amelogenesis imperfecta (AI), with a rough, irregular enamel surface. These results suggest that there is a cell-autonomous requirement for FGF signaling in the dental epithelium during enamel formation. Loss of Fgfr1 affects ameloblast organization at the enamel-secretory stage and, hence, the formation of enamel.

Identification and Characterization of the Huanglongbing Bacterium in Pummelo from Multiple Locations in Guangdong, P. R. China

Huanglongbing (HLB, yellow shoot disease, ex. citrus greening disease), caused by Candidatus Liberibacter spp., is highly destructive to citrus production in Asia, Africa, and South America. Although primarily affecting sweet orange and mandarin, HLB has long been observed in pummelo in Guangdong Province, People's Republic of China; however, the disease in pummelo has received little research attention. Accordingly, it remains unclear how closely related the strains of Ca. Liberibacter in pummelo are to those in other citrus species. In this study, the loci of 16S rDNA, rplAJ (β-operon of ribosomal protein), and an outer membrane protein (omp) gene were analyzed and characterized among strains of Ca. Liberibacter in pummelo samples from six different locations in Guangdong. Sequence comparisons indicated that 'Candidatus Liberibacter asiaticus', but not 'Ca. Liberibacter africanus' or 'Ca. Liberibacter americanus', was exclusively associated with HLB symptoms in pummelo. The pummelo strains of 'Ca. Liberibacter asiaticus' from Guangdong were highly homogeneous. Analyses of single-nucleotide polymorphisms in the omp locus showed that the Guangdong pummelo strains grouped with 'Ca. Liberibacter asiaticus' strains from Thailand, Nepal, and an unspecified location in China but differed from the Philippine and China-Behai strains. Based on the sequence homogeneity at the omp locus, the history of pummelo culture and the means by which HLB is known to be spread, we believe that, likely, the pummelo strain of 'Ca. Liberibacter asiaticus' recently was spread to pummelo in the study areas from infected sweet orange or mandarin trees by insect vectors or by propagation of pummelo infected elsewhere.

First Report of 'Candidatus Liberibacter asiaticus' from Atalantia buxifolia in Guangdong, China

Atalantia buxifolia (Poir.) Oliv., synonym Severinia buxifolia (Poir.) Ten. as commonly found in literature, is a common landscape plant and a popular Chinese medicinal herb known as Jiubingle or Dongfengjie. It remains unclear if this rutaceous plant could host 'Candidatus Liberibacter asiaticus', the pathogen of citrus Huanglongbing (HLB) in Guangdong, P. R. China. This information is important for HLB control in citrus because infected A. buxifolia could serve as a source of inoculum. In August of 1994, three A. buxifolia plants adjacent to a citrus experimental orchard of the South China Agricultural University at Guangzhou were found showing leaf mottle/yellowing symptoms. Two buds from each plant were grafted onto three mandarin trees (Citrus reticulata cv. Pongan) in a psyllid-proof screenhouse for indexing. By October of 1995, typical leaf mottle symptoms were observed in all three grafted trees compared with a healthy control. In March of 1996, one of the A. buxifolia plants was transferred to a screenhouse and has been maintained there. The leaf mottle/yellowing symptoms persisted but did not significantly affect plant growth. DNA was extracted from leaf samples in October 2006 by using the CTAB (cetyltrimethylammoniumbromide) method and assayed by nested-PCR using the general bacterial 16S rDNA primer set fDl/rD1 as the first round of amplification and primer set OI1/OI2c as second round amplification (1,3). After agarose gel electrophoresis and staining with ethidium bromide, an approximate 1.1-kb DNA band was detected in symptomatic samples but not healthy leaf samples of A. buxifolia and C. reticulata. XbaI digestion of the amplicons yielded approximate 500- and 600-bp fragments, characteristic of 'Ca. L. asiaticus'. Similarly, a standard PCR with primer set A5/J2 (3) yielded an approximate 700-bp DNA band characteristic of 'Ca. L. asiaticus' from symptomatic samples only. To our knowledge, this is the first report of graft transmission and PCR detection of 'Ca. L. asiaticus' from A. buxifolia in Guangdong, P. R. China. This work also confirms the findings from Taiwan (2) that A. buxifolia could serve as a source of 'Ca. L. asiaticus'. References: (1) X. Deng et al. Online publication. doi:10.1094/PHP-2007-0419-01-BR. Plant Health Progress, 2007. (2) T.-H. Hung et al. Eur. J. Plant Pathol. 107:183, 2001. (3) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996.

Nested-PCR Detection and Sequence Confirmation of 'Candidatus Liberibacter asiaticus' from Murraya paniculata in Guangdong, China

Murraya paniculata (orange jasmine) is a popular ornamental rutaceaous plant and is known to be a preferred host for the Asian citrus psyllid, Diaphorina citri (Kuwayana), the primary vector of 'Candidatus Liberibacter spp.' that causes citrus Huanglongbing (HLB). HLB is a highly destructive citrus disease worldwide. However, the presence of 'Ca. Liberibacter spp.' in M. paniculata remains uncertain (2). Clarification of M. paniculata as a host of 'Ca. Liberibacter spp.' has direct impact on HLB control programs. During June of 2006, we identified three M. paniculata trees near a mandarin orchard affected by HLB in Luoding City and two trees from Guangzhou City, Guangdong Province, People's Republic of China. All trees had leaves showing yellowing and mottling symptoms characteristic of HLB. Both symptomatic and asymptomatic leaves were collected. DNA was extracted using the CTAB (cetyltrimethylammoniumbromide) method and assayed by nested-PCR. The general bacterial 16S rDNA primer set fDl/rD1 (3) was used for the first round of amplification. Amplification was conducted as previously described (1), and 2 μl of PCR reaction product were used for a second round of amplification using the same procedure but with 35 PCR cycles with primer set OI1/OI2c (3,4). After agarose gel electrophoresis and staining with ethidium bromide, a 1.1-kb DNA band was unambiguously associated with symptomatic but not asymptomatic leaf samples. Nonnested-PCR using primer set OI1/OI2c alone did not yield a target DNA band or yielded a very weak DNA band. XbaI digestion of the nested-PCR DNA product yielded two fragments, 520 and 640 bp long, characteristic of 'Ca. L. asiaticus'. PCR amplicons were sequenced and were 1,095 bp long. This sequence shared >98% similarity to sequences of 'Ca. L. asiaticus' in the GenBank database. We observed that nested-PCR is necessary for consistent amplification of DNA from 'Ca. L. asiaticus' from M. paniculata. We excluded the possible nonspecific amplification associated with nested-PCR by XbaI restriction enzyme digestion and by nucleotide sequence analysis. Our data indicate that M. paniculata is a host of 'Ca. L. asiaticus' but the bacterial titer might be low. References: (1) X. Deng et al. Online publication. doi:10.1094/PHP-2007-0419-01-BR. Plant Health Progress, 2007. (2) M. Garnier and J. Bove. Huanglongbing (Greening). Page 46 in: Compendium of Citrus Diseases. 2nd ed. L. W. Timmer et al., eds. The American Phytopathological Society, St. Paul, MN, 2000. (3) S. Jagoueix et al. Int. J. Syst. Bacteriol. 44:379, 1994. (4) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996.

Gossypol with methyltestosterone and ethinylestradiol male does not affect rat spermatogonial stem cell differentiation

The purpose of this study was to investigate whether administration of the regimen of gossypol at 12 mg/kg/day combined with methyltestosterone at 20 mg/kg/day and ethinylestradiol at 100 microg/kg/day for a long term of twenty-four weeks could affect the existence and differentiation of rat spermatogonial stem cell. This was assessed by conducting TdT-mediated dUTP nick end-labeling detection, spermatogonial stem cell transplantation and fertility recovery evaluation. Our results showed that spontaneous apoptosis was observed in normal rats' testes from the control group with an apoptotic index (AI) average of 10.24+/-1.52. In the regimen-treated group, the predominant apoptotic cells were spermatocytes and spermatids in the seminiferous tubules. Spermatogonia were not apoptotic (AI averaged 113.42+/-13.24). Two to three months after transplantation of spermatogonial stem cells isolated from regimen-treated rats into recipient nude mice, elongated rat spermatids were identified in the seminiferous tubules of recipient nude mice. Six weeks after withdrawal of the administration, fertility of the regimen-treated rats was recovered compared with that of the control group. The number of litters produced by females mated with regimen-treated males averaged 9.88+/-0.166 matched 10.30+/-0.171 of control group and the litters of the first generation appeared to be normal. These results indicated that the administration of this regimen did not affect the existence and differentiation potential of spermatogonial stem cells of the regimen-treated rats.

Cadmium removal from aqueous solution by gene-modified Escherichia coli JM109

The article extended the study on the bioaccumulation of cadmium by genetically engineered bacterium Escherichia coli (namely M4) simultaneously expressing a cadmium transport system and metallothionein (MT). The growth of M4 showed resistance to the presence of cadmium. Compared with Cd2+ uptake capacity by original host bacterial cells, The Cd2+ accumulation of M4 was enhanced more than one-fold. M4 could effectively bind Cd2+ over a range of pH from 4 to 8. The presence of Ni2+ and Mn2+ did not influence Cd2+ uptake remarkably, but Cu2+, Pb2+ and Zn2+ posed serious adverse effects. EDTA could drastically decrease Cd2+ bioaccumulation by M4, whereas the effect of citrate was relatively slight.

Effect of lipid extraction on analyses of stable carbon and stable nitrogen isotopes in coastal organisms of the Aleutian archipelago

We tested whether extracting lipids reduced confounding variation in δ13C and δ15N values by analyzing paired lipid-extracted (LE) and non-lipid-extracted (NLE) samples of bald eagle ( Haliaeetus leucocephalus (L., 1766)) whole eggs, muscle tissue from nine seabird and one terrestrial bird species, muscle tissue from four marine fish species, and blue mussels ( Mytilus edulis L., 1758) collected from the Aleutian archipelago, Alaska. Lipid extraction significantly increased δ13C by an average of 2.0‰ in whole eggs, 0.8‰ in avian muscle, 0.2‰ in fish muscle, and 0.6‰ in blue mussels. Lower δ13C values in NLE samples covaried positively with lipid content across all sample types. Lower δ13C values in NLE samples were not correlated with lipid content within bald eagle eggs and blue mussels, but covaried positively with percent lipid in avian and fish muscles. Neither lipid extraction nor percent lipid significantly changed δ15N values for any sample type. Lower δ13C values in most NLE avian and fish muscle tissues should not confound interpretation of pelagic versus nearshore sources of primary production, but lipid extraction may be necessary when highly precise estimates of δ13C are needed. Lipid extraction may not be necessary when only δ15N is of interest.

Retention of survivors of acute lymphoblastic leukemia in a longitudinal study of bone mineral density

Attrition in longitudinal studies of survivors of childhood cancer reduces these studies' statistical power, introduces bias and threatens internal and external validity. This study investigated the variables associated with dropout of survivors of acute lymphoblastic leukemia in a trial investigating the effect of vitamin D and calcium supplementation and nutritional counseling on bone mineral density (BMD). Twenty-five participants withdrew from the study. Common reasons given for withdrawing were intolerance of the study drug, family hardship and schedule conflicts. Few statistically and clinically significant differences identified participants who completed the study. Nurses need to be aware of the reasons that participants withdraw from clinical trials, as they are in a strategic position to encourage patients to participate in health promotion studies.