Oral pathogens exacerbate Parkinson's disease by promoting Th1 cell infiltration in mice

BACKGROUND

Parkinson's disease (PD) is a common chronic neurological disorder with a high risk of disability and no cure. Periodontitis is an infectious bacterial disease occurring in periodontal supporting tissues. Studies have shown that periodontitis is closely related to PD. However, direct evidence of the effect of periodontitis on PD is lacking. Here, we demonstrated that ligature-induced periodontitis with application of subgingival plaque (LIP-SP) exacerbated motor dysfunction, microglial activation, and dopaminergic neuron loss in 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice.

RESULTS

The 16S rRNA gene sequencing revealed that LIP-SP induced oral and gut dysbiosis. Particularly, Veillonella parvula (V. parvula) and Streptococcus mutans (S. mutans) from oral ligatures were increased in the fecal samples of MPTP + LIP-SP treated mice. We further demonstrated that V. parvula and S. mutans played crucial roles in LIP-SP mediated exacerbation of motor dysfunction and neurodegeneration in PD mice. V. parvula and S. mutans caused microglial activation in the brain, as well as T helper 1 (Th1) cells infiltration in the brain, cervical lymph nodes, ileum and colon in PD mice. Moreover, we observed a protective effect of IFNγ neutralization on dopaminergic neurons in V. parvula- and S. mutans-treated PD mice.

CONCLUSIONS

Our study demonstrates that oral pathogens V. parvula and S. mutans necessitate the existence of periodontitis to exacerbate motor dysfunction and neurodegeneration in MPTP-induced PD mice. The underlying mechanisms include alterations of oral and gut microbiota, along with immune activation in both brain and peripheral regions. Video Abstract.

Brown adipocyte mineralocorticoid receptor deficiency impairs metabolic regulation in diet-induced obese mice

Activation of brown adipose tissue (BAT) contributes to energy dissipation and metabolic health. Although mineralocorticoid receptor (MR) antagonists have been demonstrated to improve metabolism under obesity, the underlying mechanisms remain incompletely understood. We aimed to evaluate the role of BAT MR in metabolic regulation. After 8 weeks of high-fat diet (HFD) feeding, BAT MR KO (BMRKO) mice manifested significantly increased bodyweight, fat mass, serum fasting glucose, and impaired glucose homeostasis compared with littermate control (LC) mice, although insulin resistance and fasting serum insulin were not significantly changed. Metabolic cage experiments showed no change in O2 consumption, CO2 production, or energy expenditure in obese BMRKO mice. RNA sequencing analysis revealed downregulation of genes related to fatty acid metabolism in BAT of BMRKO-HFD mice compared with LC-HFD mice. Moreover, H&E and immunohistochemical staining demonstrated that BMRKO exacerbated HFD-induced macrophage infiltration and proinflammatory genes in epididymal white adipose tissue (eWAT). BMRKO-HFD mice also manifested significantly increased liver weights and hepatic lipid accumulation, an increasing trend of genes related to lipogenesis and lipid uptake, and significantly decreased genes related to lipolytic and fatty acid oxidation in the liver. Finally, the level of insulin-induced AKT phosphorylation was substantially blunted in eWAT but not liver or skeletal muscle of BMRKO-HFD mice compared with LC-HFD mice. These data suggest that BAT MR is required to maintain metabolic homeostasis, likely through its regulation of fatty acid metabolism in BAT and impacts on eWAT and liver.

Periodontitis exacerbates atherosclerosis through Fusobacterium nucleatum-promoted hepatic glycolysis and lipogenesis

AIMS

Positive associations between periodontitis (PD) and atherosclerosis have been established, but the causality and mechanisms are not clear. We aimed to explore the causal roles of PD in atherosclerosis and dissect the underlying mechanisms.

METHODS AND RESULTS

A mouse model of PD was established by ligation of molars in combination with application of subgingival plaques collected from PD patients and then combined with atherosclerosis model induced by treating atheroprone mice with a high-cholesterol diet (HCD). PD significantly aggravated atherosclerosis in HCD-fed atheroprone mice, including increased en face plaque areas in whole aortas and lesion size at aortic roots. PD also increased circulating levels of triglycerides and cholesterol, hepatic levels of cholesterol, and hepatic expression of rate-limiting enzymes for lipogenesis. Using 16S ribosomal RNA (rRNA) gene sequencing, Fusobacterium nucleatum was identified as the most enriched PD-associated pathobiont that is present in both the oral cavity and livers. Co-culture experiments demonstrated that F. nucleatum directly stimulated lipid biosynthesis in primary mouse hepatocytes. Moreover, oral inoculation of F. nucleatum markedly elevated plasma levels of triglycerides and cholesterol and promoted atherogenesis in HCD-fed ApoE-/- mice. Results of RNA-seq and Seahorse assay indicated that F. nucleatum activated glycolysis, inhibition of which by 2-deoxyglucose in turn suppressed F. nucleatum-induced lipogenesis in hepatocytes. Finally, interrogation of the molecular mechanisms revealed that F. nucleatum-induced glycolysis and lipogenesis by activating PI3K/Akt/mTOR signalling pathway in hepatocytes.

CONCLUSIONS

PD exacerbates atherosclerosis and impairs lipid metabolism in mice, which may be mediated by F. nucleatum-promoted glycolysis and lipogenesis through PI3K/Akt/mTOR signalling in hepatocytes. Treatment of PD and specific targeting of F. nucleatum are promising strategies to improve therapeutic effectiveness of hyperlipidaemia and atherosclerosis.

Ncor1 Deficiency Promotes Osteoclastogenesis and Exacerbates Periodontitis

Nuclear receptor corepressor 1 (Ncor1) has been reported to regulate different transcription factors in different biological processes, including metabolism, inflammation, and circadian rhythms. However, the role of Ncor1 in periodontitis has not been elucidated. The aims of the present study were to investigate the role of Ncor1 in experimental periodontitis and to explore the underlying mechanisms through an experimental periodontitis model in myeloid cell-specific Ncor1-deficient mice. Myeloid cell-specific Ncor1 knockout (MNKO) mice were generated, and experimental periodontitis induced by ligation using 5-0 silk sutures was established. Ncor1 flox/flox mice were used as littermate controls (LC). Histological staining and micro-computed tomography scanning were used to evaluate osteoclastogenesis and alveolar bone resorption. Flow cytometry was conducted to observe the effect of Ncor1 on myeloid cells. RNA sequencing was used to explore the differentially targeted genes in osteoclastogenesis in the absence of Ncor1. Coimmunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP) experiments, and dual luciferase assays were performed to explore the relationship between NCoR1 and the targeted gene. Alveolar bone resorption in the MNKO mice was significantly greater than that in the LC mice after periodontitis induction and osteoclastogenesis in vitro. The percentage of CD11b+ cells, particularly CD11b+ Ly6G+ neutrophils, was substantially higher in gingival tissues in the MNKO mice than in the LC mice. Results of RNA sequencing demonstrated that CCAAT enhancer binding protein α (Cebpα) was one of the most differentially expressed genes between the MNKO and LC groups. Mechanistically, Co-IP assays, ChIP experiments, and dual luciferase assays revealed that NCOR1 interacted with peroxisome proliferator-activated receptor gamma (PPARγ) and cooperated with HDAC3 to control the transcription of Cebpα. In conclusion, Ncor1 deficiency promoted osteoclast and neutrophil formation in mice with experimental periodontitis. It regulated the transcription of Cebpα via PPARγ to promote osteoclast differentiation.

Periodontitis Salivary Microbiota Aggravates Ischemic Stroke Through IL-17A

Although epidemiological studies suggest that periodontitis is tightly associated with ischemic stroke, its impact on ischemic stroke and the underlysing mechanisms are poorly understood. Recent studies have shown that alteration in gut microbiota composition influences the outcomes of ischemic stroke. In the state of periodontitis, many oral pathogenic bacteria in the saliva are swallowed and transmitted to the gut. However, the role of periodontitis microbiota in the pathogenesis and progression of ischemic stroke is unclear. Therefore, we hypothesized that the periodontitis salivary microbiota influences the gut immune system and aggravates ischemic stroke. Mice receiving gavage of periodontitis salivary microbiota showed significantly worse stroke outcomes. And these mice also manifested more severe neuroinflammation, with higher infiltration of inflammatory cells and expression of inflammatory cytokines in the ischemic brain. More accumulation of Th17 cells and IL-17⁺ γδ T cells were observed in the ileum. And in Kaede transgenic mice after photoconversion. Migration of CD4⁺ T cells and γδ T cells from the ileum to the brain was observed after ischemic stroke in photoconverted Kaede transgenic mice. Furthermore, the worse stroke outcome was abolished in the IL-17A knockout mice. These findings suggest that periodontitis salivary microbiota increased IL-17A-producing immune cells in the gut, likely promoted the migration of these cells from the gut to the brain, and subsequently provoked neuroinflammation after ischemic stroke. These findings have revealed the role of periodontitis in ischemic stroke through the gut and provided new insights into the worse outcome of ischemic stroke coexisting with periodontitis in clinical trials.

Osteoblast MR deficiency protects against adverse ventricular remodeling after myocardial infarction

RATIONALE

Mineralocorticoid receptor (MR) antagonists have been clinically used to treat heart failure. However, the underlying cellular and molecular mechanisms remain incompletely understood.

METHODS AND RESULTS

Using osteoblast MR knockout (MR^obko) mouse in combination with myocardial infarction (MI) model, we demonstrated that MR deficiency in osteoblasts significantly improved cardiac function, promoted myocardial healing, as well as attenuated cardiac hypertrophy, fibrosis and inflammatory response after MI. Gene expression profiling using RNA sequencing revealed suppressed expression of osteocalcin (OCN) in calvaria from MR^obko mice compared to littermate control (MR^fl/fl) mice with or without MI. Plasma levels of undercarboxylated OCN (ucOCN) were also markedly decreased in MR^obko mice compared to MR^fl/fl mice. Administration of ucOCN abolished the protective effects of osteoblast MR deficiency on infarcted hearts. Mechanistically, ucOCN treatment promoted proliferation and inflammatory cytokine secretion in macrophages. Spironolactone, an MR antagonist, significantly inhibited the expression and secretion of OCN in post-MI mice. More importantly, spironolactone decreased plasma levels of ucOCN and inflammatory cytokines in heart failure patients.

CONCLUSIONS

MR deficiency in osteoblasts alleviates pathological ventricular remodeling after MI, likely through its regulation on OCN. Spironolactone may work through osteoblast MR/OCN axis to exert its therapeutic effects on pathological ventricular remodeling and heart failure in mice and human patients.

Effects of 2,3',4,4',5-pentachlorobiphenyl exposure during pregnancy on DNA methylation in the testis of offspring in the mouse

Polychlorinated biphenyls (PCBs) are persistent organic pollutants, and the widespread use of PCBs has had adverse effects on human and animal health. This study experiment explored the effects of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on the mammalian reproductive system. PCB118 was administered to pregnant mice from 7.5 to 12.5 days of gestation; F1 mice were obtained and the reproductive system of F1 male mice was examined. PCB118 damaged the reproductive system in male F1 mice, as evidenced by negative effects on the testicular organ coefficient (testes weight/bodyweight), a decrease in the diameter of seminiferous tubules and a significant reduction in the anogenital distance in 35-day-old F1 mice. In addition, methylation levels of genomic DNA were reduced, with reductions in the expression of the DNA methyltransferases DNMT1, DNMT3A and DNMT3B, as well as that of the epigenetic regulatory factor ubiquitin like with PHD and ring finger domains 1 (Uhrf1). Together, the results of this study provide compelling evidence that exposure of pregnant mice to PCB118 during primordial germ cell migration in the fetus affects the reproductive system of the offspring and decreases global methylation levels in the testis.

Exposure to Aroclor-1254 impairs spindle assembly during mouse oocyte maturation

Polychlorinated biphenyls (PCBs), as typical environmental estrogen disruptors, are a structurally-related group of halogenated aromatic hydrocarbons that are composed of 209 isomers and present as a mixture in the environment. PCBs congener with different numbers and positions of chlorine atoms substituted on the biphenyl moiety. Aroclor-1254 is a mixture of more than 60 PCB congeners. Previous studies have provided the evidence that PCBs have severe negative effects on reproductive functions, but the effects of PCBs on spindle assembly during mouse oocyte maturation in vitro have not been reported. In the present study, female ICR mouse immature oocytes were cultured in M2 medium with 1 and 10 μg mL^-1 Aroclor-1254 separately in vitro. The percentage of germinal vesicle breakdown (GVBD) and the first polar body extrusion were recorded. The results showed no significant difference in the percentage of GVBD or the first polar body extrusion between control oocytes and Aroclor-1254-treated oocytes. Further studies showed that the normal localization of γ-tubulin and Aurora-A kinase was interfered and α-tubulin assembling into spindle was affected when mouse oocytes were exposed to Aroclor-1254. The length of spindle from 10 μg mL^-1 Aroclor-1254-treated oocytes was longer than that from control oocytes, and the spindle area in the Aroclor-1254-treated groups were decreased. Furthermore, the percentage of DNA damage in cumulus cells revealed an increase after exposed to Aroclor-1254. These results will provide the important reference for the prevention of reproductive disorders caused by PCBs. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1652-1662, 2016.

Subcellular localization of proline-rich tyrosine kinase 2 during oocyte fertilization and early-embryo development in mice

Proline-rich tyrosine kinase 2 (Pyk2), a non-receptor tyrosine kinase, is a member of the focal adhesion kinase family and is highly expressed in oocytes. Using a combination of confocal microscopy and RNAi, we localized and studied the function of both Pyk2 and tyrosine-phosphorylated Pyk2 (p-Pyk2) during mouse oocyte fertilization and early embryo development. At the onset of fertilization, Pyk2 and p-Pyk2 were detected predominantly in sperm heads and the oocyte cytoplasm. Upon formation of male and female pronuclei, Pyk2 and its activated form leave the cytoplasm and accumulate in the two pronuclei. We detected Pyk2 in blastomere nuclei and found both Pyk2 and p-Pyk2 in the pre-blastula cytoplasm. Pyk2 and its activated form then disappeared from the blastula nuclei and localized to the perinuclear regions, where blastula cells come into contact with each other. Pyk2 knockdown via microinjection of siRNA into the zygote did not inhibit early embryo development. Our results suggest that Pyk2 plays multiple functional roles in mouse oocyte fertilization as well as throughout early embryo development.

Expression profiles of MMP-1 and TIMP-1 in lumbar intervertebral disc degeneration

Lumbar intervertebral disc degeneration (IDD) is a common clinical pathology and has become a focus for research in recent years. Matrix metalloproteinases (MMPs) are enzymes responsible for the degradation of almost all extracellular matrix proteins (ECM). The over-expression of MMPs or tissue inhibitors of metalloproteinases (TIMPs) may disrupt the dynamic balance of the ECM. Therefore, in the current study, the expression levels of MMP-1 and TIMP-1 in lumbar IDD patients were evaluated in an attempt to elucidate their role in IDD pathogenesis and progression. In total, 60 IDD patients were recruited as the experimental group, along with 20 cases of lumbar vertebral injury without disc degeneration as the control group. Preoperative venous blood samples were collected, and intervertebral disc tissues were collected from the lesion during surgery. Serum and tissue levels of MMP-1 and TIMP-1 were quantified by enzyme-linked immunosorbent assay and immunohistochemical staining, respectively. Serum and tissue MMP-1 levels in IDD patients were significantly higher than those in the control group (P < 0.05). Additionally, sub-group analysis revealed that severe IDD patients had higher MMP-1 levels compared with mild or moderate IDD patients (P < 0.05). However, there were no significant differences in TIMP- 1 levels in either the serum or tissues of IDD patients compared to patients in the control group (P > 0.05). These results demonstrate that MMP-1 expression is increased in IDD, with higher expression observed in more severe cases, whereas TIMP-1 expression was similarly expressed in both normal and degenerated discs.

Effects of Aroclor 1254 on in vivo oocyte maturation in the mouse

Polychlorinated biphenyls (PCBs) are stable, lipophilic compounds that accumulate in the environment and in the food chain. Though some studies provided evidence that PCBs had adverse effects on reproductive function, most of these results were from in vitro models. Therefore we investigated the effect of Aroclor 1254 (a commercial PCBs mixture) treatments on in vivo maturation and developmental potential of mouse oocytes. In the present study, female ICR mice were treated with different doses (12.5, 25 and 50 mg/kg) of Aroclor 1254 (a commercial PCB mixture) once every 72 hours by intraperitoneal injection for 9 days. After three treatments of Aroclor 1254, the mice were superovulated to collect oocytes one day after the last exposure. The effects of Aroclor 1254 on oocyte maturation, fertilization, and preimplantation embryonic development were investigated. Immunofluorescence-stained oocytes were observed under a confocal microscope to assess the effects of Aroclor 1254 on spindle morphology. Parthenogenic activation and the incidence of cumulus apoptosis in cumulus-oocyte complexes were observed as well. Oocytes exposed to different doses of Aroclor 1254 in vivo were associated with a significant decrease in outgrowth potential, abnormal spindle configurations, and the inhibition of parthenogenetic activation of ovulated oocytes. Furthermore, the incidence of apoptosis in cumulus cells was increased after exposed to Aroclor 1254. These results may provide reference for the treatment of reproductive diseases such as infertility or miscarriage caused by environmental contaminants.

Therapeutic effects of Sophora moorcroftiana alkaloids in combination with albendazole in mice experimentally infected with protoscolices of Echinococcus granulosus

The objective of the present study was to determine if the combination of alkaloids from Sophora moorcroftiana seeds and albendazole might be effective in the treatment of experimental echinococcosisin female NIH mice (6 weeks old and weighing 18-20 g, N = 8 in each group) infected withprotoscolices of Echinococcus granulosus. Viable protoscolices (N = 6 x 10(3)) were cultured in vitro in 1640 medium and mortality was calculated daily. To determine the in vivo efficacy, mice were inoculated intraperitoneally with viable protoscolices and then treated once daily by gavage for three months with the alkaloids (50 mg kg-1 day-1) and albendazole (50 mg kg-1 day-1), separately and in combination (both alkaloids at 25 mg kg-1 day-1 and albendazole at 25 mg kg-1 day-1). Next, the hydatid cysts collected from the peritoneal cavity of the animals were weighed and serum IL-4, IL-2, and IgE levels were analyzed. Administration of alkaloids to cultured protoscolices showed significant dose- and time-dependent killing effects. The weight of hydatid cysts was significantly decreased upon treatment with each drug (P < 0.01), but the decrease was more prominent and the rate of hydatid cyst growth inhibition was much higher (76.1%) in the group receiving the combined treatments (18.3 +/- 4.6 mg). IL-4 and total IgE were decreased (939 +/- 447 pg/mL and 2.03 +/- 0.42 IU/mL, respectively) in serum from mice treated with alkaloids and albendazole compared with the untreated control (1481 +/- 619 pg/mL and 3.31 +/- 0.37 IU/mL; P < 0.01). These results indicate that S. moorcroftiana alkaloids have protoscolicidal effects and the combination of alkaloids and albendazole has significant additive effects.

Proline-rich tyrosine kinase2 is involved in F-actin organization during in vitro maturation of rat oocyte

Microfilaments (actin filaments) regulate various dynamic events during meiotic maturation. Relatively, little is known about the regulation of microfilament organization in mammalian oocytes. Proline-rich tyrosine kinase2 (Pyk2), a protein tyrosine kinase related to focal adhesion kinase (FAK) is essential in actin filaments organization. The present study was to examine the expression and localization of Pyk2, and in particular, its function during rat oocyte maturation. For the first time, by using Western blot and confocal laser scanning microscopy, we detected the expression of Pyk2 in rat oocytes and found that Pyk2 and Try402 phospho-Pyk2 were localized uniformly at the cell cortex and surrounded the germinal vesicle (GV) or the condensed chromosomes at the GV stage or after GV breakdown. At the metaphase and the beginning of anaphase, Pyk2 distributed asymmetrically both in the ooplasm and the cortex with a marked staining associated with the chromosomes and the region overlying the meiotic spindle. At telophase, Pyk2 was observed in the cleavage furrows in addition to its cortex and cytoplasm localization. The dynamics of Pyk2 were similar to that of F-actin, and this kinase was found to co-localize with microfilaments in several developmental stages during rat oocyte maturation. Microinjection of Pyk2 antibody demolished the microfilaments assembly and also inhibited the first polar body (PB1) emission. These findings suggest an important role of Pyk2 for rat oocyte maturation by regulating the organization of actin filaments.

Role of Reactive Oxygen Species in Mediating Hepatic Ischemia-Reperfusion Injury and Its Therapeutic Applications in Liver Transplantation

Increasing evidence has shown that reactive oxygen species (ROS) are important mediators in liver ischemia/reperfusion injury(IRI). ROS include hydrogen peroxide (H(2)O(2)), superoxide anion (O(-2)), and hydroxyl radical (HO(-)), which may be generated by activated Kupffer cells in the liver, contributing to reperfusion injury. Hepatic IRI is a multistep process that damages liver graft function. To establish a series of therapeutic strategies to improve the outcome of liver transplantation, a good understanding of the mechanisms of IRI is essential. However, the detail mechanisms of how ROS lead to hepatocyte damage in IRI remains unclear. The aim of this review was to describe recent developments in the field of oxidative stress research. The first part of this review focused on the key roles and possible mechanisms of ROS in hepatic IRI. The second part of this review summarizes some findings including novel and classic antioxidant methods to ameliorate the hepatocyte damage during IRI.

Requirements of Src family kinase during meiotic maturation in mouse oocyte

The Src family kinase (SFK) is important in normal cell cycle control. However, its role in meiotic maturation in mammalian has not been examined. We used confocal microscope immunofluorescence to examine the in vitro dynamics of the subcellular distribution of SFK during the mouse oocyte meiotic maturation and further evaluated the functions of SFK via biochemical analysis using a specific SFK pharmacological inhibitor, PP(2). Our results showed that nonphospho-SFK was absent in oocyte upon its release from follicle. Nonphospho-SFK appeared in cytoplasm 0.5 hr after the release of oocyte and translocated to germinal vesicle (GV) before germinal vesicle breakdown (GVBD). After GVBD, nonphospho-SFK colocated with condensed chromosomes. In occyte at metaphase I (MI) and telophase I, nonphospho-SFK accumulated in the cortex and the cleavage furrow respectively besides its existence in cytoplasm in both stages. In oocyte at metaphase II (MII), nonphospho-SFK concentrated at the aligned chromosomes. In contrast, phospho-SFK was absent in oocyte until 1 hr after its release from the follicle. Phospho-SFK accumulated in the GV, the cortex, and cytoplasm immediately prior to GVBD. After GVBD, phospho-SFK evenly distributed in oocyte. In oocyte at MII, phospho-SFK localized throughout the cytoplasm and under the egg member. When the SFK activity was inhibited, the oocyte failed to initiate GVBD, could not go into MII, and could not extrude the first polar body. Our results demonstrated that SFK is required for meiotic maturation in mouse oocyte.

Function of donor cell centrosome in intraspecies and interspecies nuclear transfer embryos

Centrosomes, the main microtubule-organizing centers (MTOCs) in most animal cells, are important for many cellular activities such as assembly of the mitotic spindle, establishment of cell polarity, and cell movement. In nuclear transfer (NT), MTOCs that are located at the poles of the meiotic spindle are removed from the recipient oocyte, while the centrosome of the donor cell is introduced. We used mouse MII oocytes as recipients, mouse fibroblasts, rat fibroblasts, or pig granulosa cells as donor cells to construct intraspecies and interspecies nuclear transfer embryos in order to observe centrosome dynamics and functions. Three antibodies against centrin, gamma-tubulin, and NuMA, respectively, were used to stain the centrosome. Centrin was not detected either at the poles of transient spindles or at the poles of first mitotic spindles. gamma-tubulin translocated into the two poles of the transient spindles, while no accumulated gamma-tubulin aggregates were detected in the area adjacent to the two pseudo-pronuclei. At first mitotic metaphase, gamma-tubulin was translocated to the spindle poles. The distribution of gamma-tubulin was similar in mouse intraspecies and rat-mouse interspecies embryos. The NuMA antibody that we used can recognize porcine but not murine NuMA protein, so it was used to trace the NuMA protein of donor cell in reconstructed embryos. In the pig-mouse interspecies reconstructed embryos, NuMA concentrated between the disarrayed chromosomes soon after activation and translocated to the transient spindle poles. NuMA then immigrated into pseudo-pronuclei. After pseudo-pronuclear envelope breakdown, NuMA was located between the chromosomes and then translocated to the spindle poles of first mitotic metaphase. gamma-tubulin antibody microinjection resulted in spindle disorganization and retardation of the first cell division. NuMA antibody microinjection also resulted in spindle disorganization. Our findings indicate that (1) the donor cell centrosome, defined as pericentriolar material surrounding a pair of centrioles, is degraded in the 1-cell reconstituted embryos after activation; (2) components of donor cell centrosomes contribute to the formation of the transient spindle and normal functional mitotic spindle, although the contribution of centrosomal material stored in the recipient ooplasm is not excluded; and (3) components of donor cell centrosomes involved in spindle assembly may not be species-specific.

Development of PCR-Based Assays for Detecting Xanthomonas campestris pv. carotae, the Carrot Bacterial Leaf Blight Pathogen, from Different Substrates

Detection of the carrot bacterial leaf blight pathogen, Xanthomonas campestris pv. carotae, was achieved using polymerase chain reaction (PCR) along with primer pairs developed from sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Primer pairs 3S and 9B directed the amplification of ∼350-bp and ∼900-bp (or ∼2 kb) DNA fragments, respectively, from genomic DNA of all known X. campestris pv. carotae strains tested, but not from that of 13 other X. campestris pathovars or other bacterial species, including yellow non-xanthomonad bacteria isolated from carrot tissues and seeds. In tests conducted with an extensive collection of X. campestris pv. carotae-like strains isolated from different substrates from California, Idaho, Oregon, Washington, and Canada, the 3S primer pair directed the amplification of the ∼350-bp target fragment from all strains. These results indicated that the 3S primer pair is highly specific for X. campestris pv. carotae detection. Using the 3S primer pair, PCR assays were developed for detection of X. campestris pv. carotae from colonies on agar media, carrot leaf and stem tissues, and seeds. These tests could be performed in a single day. The PCR-based seed assay detected X. campestris pv. carotae from lots with contamination rates ranging from 2 × 10² to 2.3 × 10⁸ CFU per gram of seed. This assay gave results similar to a seed-wash dilution plating assay and proved more sensitive than an enzyme-linked immunosorbent assay (ELISA)-based assay.

Localization of gamma-tubulin in mouse eggs during meiotic maturation, fertilization, and early embryonic development

Gamma-tubulin, a member of the tubulin superfamily, is a peri-centriolar component which is considered to be essential for microtubule nucleation. The dynamics of gamma-tubulin during mouse oocyte meiotic maturation, fertilization, and early cleavage as well as the co-localization of gamma-tubulin and alpha-tubulin during the formation of the meiotic I spindle were studied by confocal microscopy. We found that gamma-tubulin was evenly distributed in the germinal vesicle (GV) stage oocyte. After germinal vesicle breakdown (GVBD) gamma-tubulin dots were localized in both the cytoplasm and the vicinity of the condensed chromosomes, and aligned at both poles of the meiotic spindle at prometaphase I and metaphase I. At anaphase I and telophase I, gamma-tubulin was detected between the separating chromosomes, while it was absent in the midbody. At the MII stage, gamma-tubulin was again accumulated at the spindle poles. Alpha-tubulin had a similar distribution pattern as gamma-tubulin in the cytoplasm and radiated from gamma-tubulin foci close to the chromosomes during the meiotic spindle formation. After fertilization, gamma-tubulin was translocated from spindle poles to the area between separating chromatids and distributed around the pronuclei. It aggregated into some dots during the interphase, but was distributed on the mitotic spindle poles in early embryos. Our results suggest that gamma-tubulin is essential for microtubule nucleation and spindle formation during mouse oocyte meiosis, fertilization, and early embryo cleavage.

Intra-oocyte localization of MAD2 and its relationship with kinetochores, microtubules, and chromosomes in rat oocytes during meiosis

The present study was designed to investigate subcellular localization of MAD2 in rat oocytes during meiotic maturation and its relationship with kinetochores, chromosomes, and microtubules. Oocytes at germinal vesicle (GV), prometaphase I (ProM-I), metaphase I (M-I), anaphase I (A-I), telophase I (T-I), and metaphase II (M-II) were fixed and immunostained for MAD2, kinetochores, microtubules and chromosomes. The stained oocytes were examined by confocal microscopy. Some oocytes from GV to M-II stages were treated by a microtubule disassembly drug, nocodazole, or treated by a microtubule stabilizer, Taxol, before examination. Anti-MAD2 antibody was also injected into the oocytes at GV stage and the injected oocytes were cultured for 6 h for examination of chromosome alignment and spindle formation. It was found that MAD2 was at the kinetochores in the oocytes at GV and ProM-I stages. Once the oocytes reached M-I stage in which an intact spindle was formed and all chromosomes were aligned at the equator of the spindle, MAD2 disappeared. However, when oocytes from GV to M-II stages were treated by nocodazole, spindles were destroyed and MAD2 was observed in all treated oocytes. When nocodazole-treated oocytes at M-I and M-II stages were washed and cultured for spindle recovery, it was found that, once the relationship between microtubules and chromosomes was established, MAD2 disappeared in the oocytes even though some chromosomes were not aligned at the equator of the spindle. On the other hand, when oocytes were treated with Taxol, MAD2 localization was not changed and was the same as that in the control. However, immunoblotting of MAD2 indicated that MAD2 was present in the oocytes at all stages; nocodazole and Taxol treatment did not influence the quantity of MAD2 in the cytoplasm. Significantly higher proportions of anti-MAD2 antibody-injected oocytes proceeded to premature A-I stage and more oocytes had misaligned chromosomes in the spindles. The present study indicates that MAD2 is a spindle checkpoint protein in rat oocytes during meiosis. When the spindle was destroyed by nocodazole, MAD2 was reactivated in the oocytes to overlook the attachment between chromosomes and microtubules. However, in this case, MAD2 could not check unaligned chromosomes in the recovered spindles, suggesting that a normal chromosome alignment is maintained only in the oocytes without any microtubule damages during maturation.

Effects of PKC activation on the meiotic maturation, fertilization and early embryonic development of mouse oocytes

Protein kinase C (PKC) is a family of Ser/Thr protein kinase widely distributed in eukaryotes. There is evidence that PKC plays key roles in the meiotic maturation and activation of mammalian oocytes. However, the mechanism of PKC's actions and the PKC isoforms responsible for these actions are poorly understood. In this study, we reveal in mouse eggs and early embryos: (1) the effects of PKC on the meiotic and mitotic cell cycle progression during oocyte maturation, egg activation and embryonic cleavages; (2) the functional importance of classical PKC subclasses in these processes; and (3) the subcellular localization of the PKCα isoform during development from GV stage oocytes to the blastocyst stage embryos. The results indicate that the PKC activator phorbol 12-myristate 13-acetate (PMA) inhibits the meiotic resumption of cumulus-free mouse oocytes by a mechanism dependent not only on classical PKC activity but also on other PKC isoforms. PKC activation after germinal vesicle breakdown leads to the inhibition of mitogen-activated protein kinase phosphorylation and the arrest of cell cycle at MI stage. The second polar body emission and the cleavages of early embryos are blocked after prolonged PKC activation. The subcellular localization of PKCα isoform in mouse oocytes and embryos is developmental-stage associated. All these results suggest that PKC has multiple functional roles in the cell cycle progression of mouse oocytes and embryos.

Sperm penetration of immature and maturing oocytes does not affect phosphorylation of mitogen-activated protein kinase in pigs

Pig oocytes cultured in vitro for 0, 25, 33 and 44 h were inseminated by frozen-thawed ejaculated sperm. At specified times after insemination, sperm penetration, cell cycle progression and mitogen-activated protein kinase (MAPK) phosphorylation were evaluated. It was shown that: (1) oocytes at various maturational stages could be penetrated by sperm; (2) sperm penetration did not affect meiotic cell cycle progression; (3) sperm penetration of germinal vesicle (GV) oocytes and maturing oocytes did not alter MAPK phosphorylation; and (4) when premetaphase I (pre-MI) and metaphase I (MI) oocytes, in which MAPK was activated, were fertilised, no evident MAPK dephosphorylation was detected as in metaphase II oocytes. The data suggest that sperm penetration before oocyte maturation does not affect MAPK phosphorylation and that the machinery inactivating MAPK upon fertilisation is not developed in maturing (pre-MI to MI) oocytes.

Involvement of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes

Calcium signal is important for the regulation of meiotic cell cycle in oocytes, but its downstream mechanism is not well known. The functional roles of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes were studied by drug treatment, Western blot analysis, kinase activity assay, indirect immunostaining, and confocal microscopy. The results indicated that meiotic resumption of both cumulus-enclosed and denuded oocytes was prevented by CaMKII inhibitor KN-93, Ant-AIP-II, or CaM antagonist W7 in a dose-dependent manner, but only germinal vesicle breakdown (GVBD) of denuded oocytes was inhibited by membrane permeable Ca2+ chelator BAPTA-AM. When the oocytes were treated with KN-93, W7, or BAPTA-AM after GVBD, the first polar body emission was inhibited. A quick elevation of CaMKII activity was detected after electrical activation of mature pig oocytes, which could be prevented by the pretreatment of CaMKII inhibitors. Treatment of oocytes with KN-93 or W7 resulted in the inhibition of pronuclear formation. The possible regulation of CaMKII on maturation promoting factor (MPF), mitogen-activated protein kinase (MAPK), and ribosome S6 protein kinase (p90rsk) during meiotic cell cycles of pig oocytes was also studied. KN-93 and W7 prevented the accumulation of cyclin B and the full phosphorylation of MAPK and p90rsk during meiotic maturation. When CaMKII activity was inhibited during parthenogenetic activation, cyclin B, the regulatory subunit of MPF, failed to be degraded, but MAPK and p90rsk were quickly dephosphorylated and degraded. Confocal microscopy revealed that CaM and CaMKII were localized to the nucleus and the periphery of the GV stage oocytes. Both proteins were concentrated to the condensed chromosomes after GVBD. In oocytes at the meiotic metaphase MI or MII stage, CaM distributed on the whole spindle, but CaMKII was localized only on the spindle poles. After transition into anaphase, both proteins were translocated to the area between separating chromosomes. All these results suggest that CaMKII is a multifunctional regulator of meiotic cell cycle and spindle assembly and that it may exert its effect via regulation of MPF and MAPK/p90rsk activity during the meiotic maturation and activation of pig oocytes.

High-throughput generation and engineering of recombinant human antibodies

The first version of the Human Combinatorial Antibody Library (HuCAL) is a single-chain Fv-based phage display library (HuCAL-scFv) with 2x10(9) members optimised for high-throughput generation and targeted engineering of human antibodies. 61% of the library genes code for functional scFv as judged by sequencing. We show here that since HuCAL-scFv antibodies are expressed in high levels in Escherichia coli, automated panning and screening in miniaturised settings (96- and 384-well format) have now become feasible. Additionally, the unique modular design of HuCAL-genes and -vectors allows the distinctly facilitated conversion of scFv into Fab, miniantibody and immunoglobulin formats, and the fusion with a variety of effector functions and tags not only convenient for therapeutic applications but also for high-throughput purification and detection. Thus, the HuCAL principle enables the rapid and high-throughput development of human antibodies by optimisation strategies proven useful in classical low molecular weight drug development. We demonstrate in this report that HuCAL is a very convenient source of human antibodies for various applications.

PCD1, a novel gene containing PDZ and LIM domains, is overexpressed in several human cancers

In an effort to discover novel genes differentially expressed in human pancreatic cancer, we have identified a gene named PCD1 (pancreatic cancer derived) that is up-regulated in pancreatic dysplasia and cancer relative to normal pancreatic ductal epithelium. We cloned the full length (4572 bp) of this gene, which encodes a novel protein of 1064 amino acids containing a PDZ domain and a LIM domain. An alternatively spliced form with a deletion of 30 bp in the coding region was also found. In situ hybridization results showed that PCD1 is highly expressed in a significant percentage of colon, breast, liver, lung, pancreas, stomach, and prostate tumor tissues but is expressed in very few normal tissues. Northern blot hybridization confirmed the overexpression of PCD1 in colon and breast tumor tissues and also showed strong expression of PCD1 in the heart as well as in HeLa cells. Real-time quantitative reverse transcription-PCR verified the overexpression of PCD1 in primary colon tumors or in liver metastases relative to normal colon tissues in five of eight patients. The PCD1 gene maps to human chromosome 13q21.33. Because of its high levels of expression in neoplastic tissues and the presence of both PDZ and LIM domains, we suggest that PCD1 may play an important role in cytoskeletal reorganization during carcinogenesis.

Toxin production by Clostridium difficile in a defined medium with limited amino acids

Basal defined medium (BDM) containing vitamins, minerals and seven amino acids--(/L) tryptophan 0.1 g, methionine 0.2 g, valine 0.3 g, isoleucine 0.3 g, proline 0.3 g, leucine 0.4 g and cysteine 0.5 g--which appeared to be essential for good growth of Clostridium difficile was prepared. Addition of glycine 0.2 g/L and threonine 0.4 g/L to BDM produced better growth of strain VPI 10463, and this defined medium was designated minimum amino acid-defined medium (MADM). Production of toxins A and B by strain VPI 10463 in 6 x MADM containing (/L) tryptophan 0.6 g, methionine 1.2 g, valine 1.8 g, isoleucine 1.8 g, proline 1.8 g, leucine 2.4 g, cysteine 0.5 g, glycine 0.2 g and threonine 0.4 g, was much greater than in MADM. Toxin production by 20 C. difficile strains was examined in two defined media--6 x MADM and complete amino acid-defined medium (CADM) containing 18 amino acids--and one complex medium, modified brain heart infusion medium (m-BHI). Simultaneous production of toxins A and B by all test strains was demonstrated in m-BHI and the two defined media. It was also shown that 6 x MADM was generally better than CADM and as effective as m-BHI for stimulating toxin production by 13 strains. This defined medium would be useful for studies on the physiology, metabolism and pathogenicity of C. difficile.

Haemagglutination activity of toxigenic and non-toxigenic strains of Clostridium difficile

Cell extract of Clostridium difficile strains was fractionated by ammonium sulfate precipitation and sulfated cellulofine column chromatography to detect haemagglutination (HA) activity. HA activity without cytotoxicity was detected in fractions eluted at 0.79-0.91 M NaCl in sulfated cellulofine column chromatography of the cell extract in both toxigenic strain VPI 10463 and non-toxigenic strain KZ 1678, while toxin A was detected in fractions eluted at 0.27-0.29 M NaCl. Antisera were prepared with HA substance-containing fractions of the chromatography. Antiserum to the HA substance(s) of strain VPI 10463 neutralised the HA activity of the fractions of strains VPI 10463 and KZ 1678 at nearly the same titres. Antiserum to the HA substance(s) of strain KZ 1678 also neutralised the HA activity of both strains at nearly the same titres as above. These findings suggest that haemagglutinin(s) is commonly produced by C. difficile strains irrespective of toxin A-producing ability.

Immunological comparison of intracellular toxin A and extracellular toxin A from Clostridium difficile

Intracellular toxin A and extracellular toxin A of Clostridium difficile were compared immunologically. Immunodiffusion tests with anti-intracellular toxin A and anti-extracellular toxin A sera showed that these toxins were identical. In neutralization tests, both antisera neutralized the homologous and heterologous toxins with regard to cytotoxicity, mouse lethality and loop response at nearly the same titers. Although intracellular toxin A lacks the hemagglutination (HA) activity, anti-intracellular toxin A serum neutralized HA activity of extracellular toxin A at the same titer as did anti-extracellular toxin A serum. These results suggest that these toxins are immunologically indistinguishable and that the intracellular toxin A molecule has an antigenic site(s) for the HA activity.

Purification and characterisation of intracellular toxin A of Clostridium difficile

After sonic disintegration of Clostridium difficile cells, intracellular toxin A was purified to homogeneity by thyroglobulin affinity chromatography (TGAC) followed by anion-exchange (Mono Q) by fast protein liquid chromatography (FPLC). High haemagglutinating (HA) activity was detected in TGAC-unbound fractions (2(9)/50 microliters), but not in TGAC thermal eluates (2(0)/50 microliters). The low HA titre of the thermal eluates was markedly increased to 2(5)/50 microliters after dialysis against 0.02 M Tris-HCl (pH 7.5). A disparity in the position of the peaks containing cytotoxic and HA activity was observed in the first Mono Q-FPLC step. Intracellular toxin A without HA activity was obtained by a second Mono Q-FPLC step. The M(r) of the intracellular toxin A was estimated by polyacrylamide gel electrophoresis (PAGE) to be 580 kDa under non-denaturing conditions. The minimum doses of the toxin causing cytotoxicity, mouse lethality and enterotoxicity were 0.83 ng, 8.7 ng and 5 micrograms, respectively.

Correlation between cytotoxin production and sporulation in Clostridium difficile

Correlation between cytotoxin production and sporulation was demonstrated when a Clostridium difficile culture was inoculated into fresh broth to give an initial count of less than 10 vegetative cells/ml with no spores. Under these conditions, cytotoxin was produced and released during sporulation. Addition of a sporulation inhibitor (acridine orange, 30 mg/L), resulted in a marked decrease in both sporulation and cytotoxin production, despite there being no change in the number of vegetative cells in the culture. These results indicate that sporulation might be closely related to cytotoxin production.

Production of monoclonal antibody to Clostridium difficile toxin A which neutralizes enterotoxicity but not haemagglutination activity

Nine monoclonal antibodies (mAb) to Clostridium difficile toxin A were produced. The isotype of one mAb (37B5) was IgG2b, kappa, and that of the other eight mAbs was IgM, kappa. Immunoblot analysis after non-denatured PAGE showed that with the exception of one mAb (112G6) all mAbs gave a positive reaction with the 540 kDa band of toxin A. Immunoblot analysis showed that four mAbs (2E15, 3B4, 37B5 and 49C4) gave a positive reaction with the 240 kDa major band of toxin A. In neutralisation tests with these mAbs for enterotoxicity, mouse lethality, haemagglutination activity and cytotoxicity, 37B5 neutralised enterotoxicity in a rabbit ileal loop response test but did not neutralise any other biological activities. None of the other eight mAbs showed any neutralising activities at all.