Joint distraction and movement for repair of articular cartilage in a rabbit model with subsequent weight-bearing

We have previously shown that joint distraction and movement with a hinged external fixation device for 12 weeks was useful for repairing a large articular cartilage defect in a rabbit model. We have now investigated the results after six months and one year. The device was applied to 16 rabbits who underwent resection of the articular cartilage and subchondral bone from the entire tibial plateau. In group A (nine rabbits) the device was applied for six months. In group B (seven rabbits) it was in place for six months, after which it was removed and the animals were allowed to move freely for an additional six months. The cartilage remained sound in all rabbits. The areas of type II collagen-positive staining and repaired soft tissue were larger in group B than in group A. These findings provide evidence of long-term persistence of repaired cartilage with this technique and that weight-bearing has a positive effect on the quality of the cartilage.

High efficiency thin-film crystalline Si/Ge tandem solar cell

We propose and simulate a photovoltaic solar cell comprised of Si and Ge pn junctions in tandem. With an anti-reflection film at the front surface, we have shown that optimal solar cells favor a thin Si layer and a thick Ge layer with a thin tunnel hetero-diode placed in between. We predict efficiency ranging from 19% to 28% for AM1.5G solar irradiance concentrated from 1 approximately 1000 Suns for a cell with a total thickness approximately 100 microm.

Improving prediction of malignancy of cytologically indeterminate thyroid nodules

Background

Fine-needle aspiration (FNA) is essential in the investigation of thyroid nodules. The British Thyroid Association guidelines recommend clarification of whether follicular nodules are probable follicular neoplasms that require surgical excision. This study assessed the value of the subclassification of cytologically indeterminate thyroid nodules into either follicular neoplasms or other pathology.

Methods

The cytology reports of all thyroid FNAs performed between November 2005 and December 2007 at a single institution reported as Thy 3 (follicular lesions) were reviewed. They were reclassified as Thy 3A (probable follicular neoplasm) or Thy 3B (probable non-neoplastic lesion), and subsequently correlated with final clinical outcome to determine the predictive value of this subclassification.

Results

Forty-nine specimens were categorized as Thy 3A and 55 as Thy 3B. Of excised lesions, 14 (29 per cent) of 48 Thy 3A and 4 (10 per cent) of 42 Thy 3B nodules were malignant. If Thy 3A were to predict malignancy and Thy 3B benign disease, the sensitivity of the classification was 88 per cent, with a specificity of 55 per cent and negative predictive value of 91 per cent.

Conclusion

Subclassification of Thy 3 nodules into Thy 3A and Thy 3B improves the assessment of risk for thyroid malignancy.

Recent advances in refractory coeliac disease: a review

Coeliac disease (CD) is an immune-mediated disease of the small intestine caused by intolerance to gluten. Removal of gluten from the diet results in a return to normal health for the majority of patients. A significant proportion of patients do not respond to a gluten-free diet and are considered to be suffering from refractory coeliac disease (RCD). Two types of RCD are now recognized: type 1 RCD is characterized by a polyclonal population of intraepithelial lymphocytes (IELs) with a normal immunophenotype, and type 2 RCD shows monoclonal IELs with an aberrant immunoprofile. Patients with RCD have a high risk of complications such as ulcerative jejunitis (UJ) and enteropathy-type T-cell lymphoma (ETTL). RCD2 may represent an early stage in the development of overt lymphoma. The diagnosis of RCD, therefore, has important implications, but remains a challenging area. In this paper we review the latest developments in RCD, including the diagnostic approach and a discussion of the key clinical, histological, immunohistochemical and molecular features of RCD and its complications.

The importance of and a method for including transfection efficiency into real-time PCR data analyses

The polymerase chain reaction (PCR) is widely used to ascertain absolute or relative changes in the expression levels of specific genes as a function of cell type or in response to changes in environmental stimuli. Real-time PCR is an advance which allows for the analysis of gene expression over a wide range of initial cDNA concentrations, where the cDNA is the product of reverse transcriptase reactions applied to RNA samples. With the advent and advances in gene delivery technologies, it is now common for the cellular responses under scrutiny to be initiated via the expression of an exogenously delivered gene. When transfection (or transduction) is a part of the procedure used to prepare cell samples for real-time PCR, it is necessary to take the efficiency of gene delivery into account. Here a robust mathematical model for such analyses is derived, and validated with theoretical and experimental support. Comparison to existing analysis methods is presented to demonstrate the high significance of noting transfection, loading, and primer PCR efficiencies when processing PCR data.

[Cervical adenopathy presentation of adenocarcinoma of prostate]

The metastases of prostate cancer shows the regional lymphatic dissemination, being the cervical lymphatic metastases to infrequent and little reported in Literature. In the present work we contributed a new observation of this organization. We displayed a clinical case with lateral mass cervical left, abdominal pain and diarrheic. When making biopsy of cervical adenopathy reported adenocarcinoma prostate metastases. Colonoscopy with biopsy was made whose results were carcinoma little differentiated infiltrated necrotic center to rectum. The complementary studies demonstrated bilateral aortic adenopathys without injuries in thorax. Within the diagnosis differential of the cervical adenopathys in neck in adult men it must consider the prostate carcinoma, because in an early diagnosis and adapting treatment it can prolong the survive.

Endoscopic ultrasound-guided fine needle aspiration cytology of pancreatic neuroendocrine tumours: cytomorphological and immunocytochemical evaluation

OBJECTIVES

Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) is increasingly used in preoperative localization and diagnosis of pancreatic neoplasms including neuroendocrine tumours (NETs). The objective of the present study was to identify the cytological features of pancreatic NETs obtained by EUS-FNA.

METHODS

The study group consisted of nine cases of pancreatic tumours correctly diagnosed or strongly suggestive of NETs based on EUS-FNA. Cytological smears were retrospectively reviewed. The clinical data and immunocytochemical stains applied to the cell block preparations were also reviewed and examined.

RESULTS

All cases except one showed characteristic cytomorphological features sufficient for their recognition and separation from pancreatic adenocarcinoma and other lesions. The most helpful cytological features that facilitated the cytological diagnosis of NET were a richly cellular aspirate with a monotonous, poorly cohesive population of small cells with a speckled or dusty chromatin pattern and plasmacytoid morphology. The neuroendocrine differentiation of these tumours was further confirmed by immunocytochemistry.

CONCLUSION

EUS-FNA is a valuable method in the recognition of pancreatic NETs. By adherence to the characteristic cytomorphological criteria of pancreatic NET together with collection of suitable material for ancillary immunocytochemical stains, cytopathologists could reach a correct diagnosis in most instances.

Repair of large full-thickness articular cartilage defects in the rabbit

We produced large full-thickness articular cartilage defects in 33 rabbits in order to evaluate the effect of joint distraction and autologous culture-expanded bone-marrow-derived mesenchymal cell transplantation (ACBMT) at 12 weeks. After fixing the knee on a hinged external fixator, we resected the entire surface of the tibial plateau. We studied three groups: 1) with and without joint distraction; 2) with joint distraction and collagen gel, and 3) with joint distraction and ACBMT and collagen gel.

The histological scores were significantly higher in the groups with ACBMT collagen gel (p < 0.05). The area of regenerated soft tissue was smaller in the group allowed to bear weight (p < 0.05). These findings suggest that the repair of large defects of cartilage can be enhanced by joint distraction, collagen gel and ACBMT.

Signal transduction mediated by the Ras/Raf/MEK/ERK pathway from cytokine receptors to transcription factors: potential targeting for therapeutic intervention

The Ras/Raf/Mitogen-activated protein kinase/ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) cascade couples signals from cell surface receptors to transcription factors, which regulate gene expression. Depending upon the stimulus and cell type, this pathway can transmit signals, which result in the prevention or induction of apoptosis or cell cycle progression. Thus, it is an appropriate pathway to target for therapeutic intervention. This pathway becomes more complex daily, as there are multiple members of the kinase and transcription factor families, which can be activated or inactivated by protein phosphorylation. The diversity of signals transduced by this pathway is increased, as different family members heterodimerize to transmit different signals. Furthermore, additional signal transduction pathways interact with the Raf/MEK/ERK pathway to regulate positively or negatively its activity, or to alter the phosphorylation status of downstream targets. Abnormal activation of this pathway occurs in leukemia because of mutations at Ras as well as genes in other pathways (eg PI3K, PTEN, Akt), which serve to regulate its activity. Dysregulation of this pathway can result in autocrine transformation of hematopoietic cells since cytokine genes such as interleukin-3 and granulocyte/macrophage colony-stimulating factor contain the transacting binding sites for the transcription factors regulated by this pathway. Inhibitors of Ras, Raf, MEK and some downstream targets have been developed and many are currently in clinical trials. This review will summarize our current understanding of the Ras/Raf/MEK/ERK signal transduction pathway and the downstream transcription factors. The prospects of targeting this pathway for therapeutic intervention in leukemia and other cancers will be evaluated.

Involvement of PI3K/Akt pathway in cell cycle progression, apoptosis, and neoplastic transformation: a target for cancer chemotherapy

The PI3K/Akt signal transduction cascade has been investigated extensively for its roles in oncogenic transformation. Initial studies implicated both PI3K and Akt in prevention of apoptosis. However, more recent evidence has also associated this pathway with regulation of cell cycle progression. Uncovering the signaling network spanning from extracellular environment to the nucleus should illuminate biochemical events contributing to malignant transformation. Here, we discuss PI3K/Akt-mediated signal transduction including its mechanisms of activation, signal transducing molecules, and effects on gene expression that contribute to tumorigenesis. Effects of PI3K/Akt signaling on important proteins controlling cellular proliferation are emphasized. These targets include cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors. Furthermore, strategies used to inhibit the PI3K/Akt pathway are presented. The potential for cancer treatment with agents inhibiting this pathway is also addressed.

Interactions between the PI3K and Raf signaling pathways can result in the transformation of hematopoietic cells

The PI3K/Akt and Raf/MEK/ERK signal transduction cascades are pivotal in transmitting signals from membrane receptors to downstream targets that regulate apoptosis, gene expression, and cell growth. The abilities of activated PI3K, Akt, Raf, and MEK proteins to abrogate the cytokine dependence of three different hematopoietic cell lines were determined. Activated PI3K or Akt expression by themselves did not efficiently annul cytokine dependence. Raf and MEK could abrogate the cytokine dependence of murine FDC-PI and human TF-1 cells; however, the frequency of transformation was dependent on the particular oncogene examined, as more factor-independent cells were isolated after infection with activated retroviruses encoding A-Raf or Raf-1 than were with MEK1 or B-Raf. Cytokine-independent deltaRaf-1-infected cells formed tumors on injection into immunocompromised mice, whereas cytokine-dependent cell lines did not, demonstrating the oncogenic effects of activation of the Raf/MEK/ERK pathway. Overexpression of the antiapoptotic Bcl-2 protein synergized with activation of the Raf/MEK/ERK cascade and increased the efficiency of transformation of FDC-PI and TF-1 cells. In contrast to the results observed with FDC-P1 and TF-I cells, the activated Raf genes did not relieve the cytokine dependence of murine FL5.12 cells. The abilities of the Raf and PI3K pathways to interact and annul the cytokine dependence of FL5.12 cells were determined. The combination of Raf and either PI3K or Akt expression relieved cytokine dependence of some FL5.12 cells, and the efficiency of transformation could be enhanced further by Bcl-2 or Bcl-XL overexpression. Thus, the antiapoptotic PI3K/Akt and Bcl-2/Bcl-XL proteins can interact with the growth-promoting Raf/MEK/ERK pathway and annul the cytokine dependence of certain hematopoietic cells.

Cytokinesis and the contractile ring in fission yeast

The fission yeast Schizosaccharomyces pombe provides a genetic model system for the study of cytokinesis. As in many eukaryotes, cell division in the fission yeast requires an actin-myosin-based contractile ring. Numerous components of the contractile ring that function in ring assembly, positioning and contraction have been characterized. Many of these proteins are evolutionarily conserved, suggesting that common molecular mechanisms may govern aspects of eukaryotic cell division. Recent advances in the assembly and placement of the contractile ring are discussed. In particular, major findings have been made in the characterization of myosins in cytokinesis, and in how the cell division site may be positioned by the nucleus.

Studies in fission yeast on mechanisms of cell division site placement

One fundamental problem in cytokinesis is how the plane of cell division is established. In this review, we describe our studies on searching for "signals" that position the cell division plane, using fission yeast Schizosaccharomyces pombe. First, we take a genetic approach to determine how the nucleus may position the contractile ring in fission yeast. mid1p appears to link the position of the ring with the nuclear position, as it is required for proper placement of the contractile ring and is localized in a band at the cell surface overlying the nucleus. Second, we study how microtubules may function in the establishment of cell polarity at the cell tips. tea1p may be deposited on the cell surface by microtubules and function to recruit proteins involved in making actin structures. These studies suggest how microtubules may direct the assembly of the contractile ring in animal cells.

Cytokeratin expression patterns as an indicator of tumour progression in oesophageal squamous cell carcinoma

Recent studies point out that cytokeratins (CKs) are involved in dynamic cell remodeling during cancer progression and particularly, CK expression patterns have been associated with invasion and metastasis. In oesophageal squamous cell cancer (ESCC), lymph node (LNN) metastasis is an important step in disease progression, invariably associated with an ominous prognosis. To assess whether specific CK expression patterns could represent reliable markers of tumor progression, a series of 111 ESCCs (59 lymph node-positive, 52-negative) derived from the high- incidence area of Linxian (Northern China), were subjected to immunohistochemical (IHC) analysis with an extensive panel of CK antibodies. Statistically significant differences were observed for CK18 (p=0.01), CK19 (p=0.04) and PKK1 (p=0.02) expression between the LNN-negative and LNN-positive ESCCs. Furthermore, significant correlation between specific CK distribution pattern and progressive disease (i.e., LNN metastasis) was evidenced. The results suggest that CK8, CK18 and CK19 expression and distribution pattern could be of predictive value as a marker of disease progression as defined by the appearance of lymph node metastases in oesophageal squamous cell cancer.

Roles of the fission yeast formin for3p in cell polarity, actin cable formation and symmetric cell division

BACKGROUND

Both symmetric and asymmetric cell divisions are required for the generation of appropriate cell lineages during development. Wild-type Schizosaccharomyces pombe cells divide in a symmetric fashion to produce two similar rod-shaped daughter cells. Formins are proteins with conserved roles in cell polarity, cytokinesis, and the regulation of actin and microtubule cytoskeletons.

RESULTS

Here, we identify and characterize a new S. pombe formin, for3p. for3 Delta mutant cells divide in an asymmetric manner; a mother cell divides medially to produce one daughter cell that develops into a monopolar cell and one daughter that develops into a bipolar cell. Both daughter cells recapitulate similar asymmetric lineages themselves. Inheritance of the bipolar pattern correlates with inheritance of the recent birth scar, not with asymmetry in the spindle pole bodies. for3 Delta mutants lack interphase actin cables and have delocalized actin patch and myo52p (type V myosin) distributions. for3 Delta cells have normal microtubule dynamics and cortical interactions but have defects in microtubule organization and increased numbers of microtubule bundles. for3p-GFP is localized at both cell tips in an actin-dependent manner and at the cell division site.

CONCLUSIONS

for3p is a cell polarity factor required for interphase actin cable formation and microtubule organization. The for3 Delta phenotype suggests that cells are able to grow in a polarized manner even in the absence of functional actin cables and polarized distribution of actin patches. for3p and possibly actin cables are part of a regulatory network that ensures that cell divisions are symmetric.

"Long before short" preference in the production of a head-final language

A tendency for speakers to produce short phrases before long phrases has been attributed to the accessibility of short phrases, and thought to reflect universal mechanisms of production. However, recent corpus analyses in Japanese suggest that long phrases tend to be shifted ahead of short ones (Hawkins, J. (1994). A performance theory of order and constituency. Cambridge: Cambridge University Press; Yamashita, in press). Two on-line experiments confirmed that speakers shifted long arguments to earlier positions more than short arguments, exhibiting a "long before short" preference. We reconcile these contradictory data from English and Japanese by a competition between different factors in an incremental production system.

Pretargeting with amplification using polymeric peptide nucleic acid

One goal of this investigation was to develop a polymer conjugated with multiple copies of peptide nucleic acid (PNA) and with pharmacokinetic properties suitable for applications in vivo. The second goal was to establish whether the multiple copies of PNA on the polymer could be targeted by hybridization in vitro and in vivo with (99m)Tc-labeled complementary PNA (cPNA). If successful, this approach could then be considered in further investigations as an alternative to existing pretargeting approaches because of the potential for signal amplification in the target. A 80 KDa poly(methyl vinyl ether-alt-maleic acid) (PA) polymer was conjugated with multiple copies of PNA and with multiple copies of poly(ethylene glycol) (PEG) by reacting the NHS derivative of PA with the amine derivatives of PNA and PEG. Using (99m)Tc-MAG(3)-cPNA, targeting of PNA-PA-PEG was studied in vitro and in vivo in inflammation and tumor mouse models, in both cases relying upon nonspecific diffusion for localization. In addition, cPNA-avidin was considered as a clearing agent with biotinylated PNA-PA-PEG. About 80 PNAs could be conjugated to PA provided that about 200 PEGs were also conjugated to raise the aqueous solubility of the PNA-PA-PEG polymer lowered by the addition of the PNAs. About 70% of the PNAs on this polymer in vitro either in solution or attached to beads could be successfully targeted with (99m)Tc-cPNA. In both the inflammation and tumor mouse models, between 35 and 60% of these PNAs could be targeted in the lesions. The advantage of amplification was evident when less favorable results were obtained with PNA-PA-PEG conjugated with only six PNAs. We conclude that amplification can be achieved in vivo using polymers of PNA followed by radiolabeled complementary PNA and that the application of pretargeting using polymers of PNA for amplification can improve localization.

In vivo progression of LAPC-9 and LNCaP prostate cancer models to androgen independence is associated with increased expression of insulin-like growth factor I (IGF-I) and IGF-I receptor (IGF-IR)

Androgen deprivation therapies for metastatic prostate cancer are useful initially, but progression to androgen independence usually results in relapse within 2 years. The molecular mechanisms underlying the clinically important transition from androgen dependence to androgen independence are poorly described. Several lines of investigation have suggested that insulin-like growth factors (IGFs) are involved in the biology of prostate cancer, but little is known about their relevance to progression to androgen independence. We used three in vivo models of androgen-dependent (AD) human prostate cancer to study this issue. Progression to androgen-independent (AI) growth was associated with a 60-fold increase in expression of IGF-I mRNA in LAPC-9 xenografts and a 28-fold increase in IGF-I expression in LNCAP xenografts, relative to the initial AD neoplasms. IGF type I receptor (IGF-IR) mRNA levels were approximately 2.5-fold and approximately 5-fold higher, respectively, in AI LAPC-9 and LNCaP tumors compared with the original AD neoplasms. AI growth of these xenografts was also associated with significant reductions in IGF binding protein-3 expression. LAPC-4 xenografts, which previously have been shown to exhibit molecular pathology related to HER-2/neu expression with progression to AI, showed relatively minor changes in expression of the genes investigated, but we nevertheless found evidence of increased IGF-IR phosphorylation with progression to androgen independence in this model. Taken together with prior observations, our results suggest that deregulation of expression of genes related to any one of several critical receptor tyrosine kinase regulatory systems, including IGF signaling, may confer androgen independence.

P21(Cip1) induced by Raf is associated with increased Cdk4 activity in hematopoietic cells

To investigate the functions of the different Raf genes in hematopoietic cell proliferation, the capacities of beta-estradiol-regulated Delta Raf:ER genes to induce cell cycle regulatory gene expression and cell cycle progression in FDC-P1 cells were examined. Raf activation increased the expression of Cdk2, Cdk4, cyclin A, cyclin D, cyclin E, p21(Cip1) and c-Myc and decreased the expression of p27(Kip1) which are associated with G(1) progression. However only the cell clones with moderate Raf activation, i.e. FD/Delta Raf-1:ER and FD/Delta A-Raf:ER, successfully underwent cell proliferation. The cell clones with the highest Delta Raf activity, FD/Delta B-Raf:ER, underwent apoptosis before cell proliferation. p21(Cip1) induced by Raf activation specifically bound with Cdk4/cyclin D complexes but not Cdk2/cyclin E complexes and this binding was associated with the increased Cdk4 activity. However, no binding of p27(Kip1) with either Cdk2/cyclin E or Cdk4/cyclin D was observed. Thus Raf mediated growth was associated with elevated p21(Cip1) expression, which may specifically bind with and activate Cdk4/cyclin D complexes and with decreased p27(Kip1) expression.

Effects of inducible MEK1 activation on the cytokine dependency of lymphoid cells

The Raf/MEK/MAP kinase cascade plays a critical role in transducing growth signals from activated cell surface receptors. Using deltaMEK1:ER, a conditionally active form of MEK1, we demonstrate the ability of this dual specificity protein kinase to abrogate the cytokine dependency of the murine lymphoid hematopoietic cell line FL5.12. Cytokine-independent cells were obtained from FL5.12 cells at a frequency of 1 x 10(-7), indicating that a low frequency of cells expressing deltaMEK1:ER were factor-independent. In general, cells that were converted to a cytokine-independent phenotype displayed a higher level of MAP kinase activity in response to deltaMEK1:ER activation than those that remained cytokine-dependent. deltaMEK1:ER-responsive cells could be maintained long-term in the presence of beta-estradiol, as well as the estrogen-receptor antagonist 4-hydroxy-tamoxifen. Removal of hormone led to the rapid cessation of cell growth in a manner similar to that observed when cytokine is withdrawn from the parental cells. GM-CSF mRNA transcripts were detected in the MEK1-responsive cells indicating that activated deltaMEK1:ER may induce a pathway leading to autocrine proliferation. Cytokine-dependent deltaMEK1:ER cells were found to increase the expression of GM-CSF receptor alpha (GM-CSFRalpha) in response to beta-estradiol. In contrast, MEK1-responsive cells were found to express constitutively lower levels of GM-CSFRalpha and beta common (betac) chains indicating that constitutive GM-CSF expression resulted in a decrease in GM-CSFR expression. Treatment of parental cells with supernatant from MEK1-responsive FL5.12 cells was sufficient to promote [3H]-thymidine incorporation. GM-CSF was found to enhance the viability of FL5.12 cells. The cell lines described here will be useful for elaborating the ability of the MAP kinase pathway to regulate cell proliferation in hematopoietic cells.

Role of bud6p and tea1p in the interaction between actin and microtubules for the establishment of cell polarity in fission yeast

BACKGROUND

In many cell types, microtubules are thought to direct the spatial distribution of F-actin in cell polarity. Schizosaccharomyces pombe cells exhibit a regulated program of polarized cell growth: after cell division, they grow first in a monopolar manner at the old end, and in G2 phase, initiate growth at the previous cell division site (the new end). The role of microtubule ends in cell polarity is highlighted by the finding that the cell polarity factor, tea1p, is present on microtubule plus ends and cell tips [1].

RESULTS

Here, we characterize S. pombe bud6p/fat1p, a homolog of S. cerevisiae Bud6/Aip3. bud6Delta mutant cells have a specific defect in the efficient initiation of growth at the new end and like tea1Delta cells, form T-shaped cells in a cdc11 background. Bud6-GFP localizes to both cell tips and the cytokinesis ring. Maintenance of cell tip localization is dependent upon actin but not microtubules. Bud6-GFP localization is tea1p dependent, and tea1p localization is not bud6p dependent. tea1Delta and bud6Delta cells generally grow in a monopolar manner but exhibit different growth patterns. tea1(Delta)bud6Delta mutants resemble tea1Delta mutants. Tea1p and bud6p coimmunoprecipitate and comigrate in large complexes.

CONCLUSIONS

Our studies show that tea1p (a microtubule end-associated factor) and bud6p (an actin-associated factor) function in a common pathway, with bud6p downstream of tea1p. To our knowledge, bud6p is the first protein shown to interact physically with tea1p. These studies delineate a pathway for how microtubule plus ends function to polarize the actin cytoskeleton through actin-associated polarity factors.

Establishment of a cellular axis in fission yeast

Recent studies in fission yeast Schizosaccharomyces pombe reveal how cells establish a cellular axis that specifies domains as the functional 'ends' and 'middle' of the cell. During interphase, dynamic microtubules position the nucleus at the middle of the cell and orientate microtubule 'plus' ends towards the ends of the cell. At the cell ends, the microtubule plus ends might establish a zone of polarized cell growth and actin assembly by depositing factors such as Tea1p. At the cell middle, the nucleus might specify the position of the actin contractile ring and the future cell division site by positioning cytokinesis factors such as Mid1p.

A mechanism for nuclear positioning in fission yeast based on microtubule pushing

The correct positioning of the nucleus is often important in defining the spatial organization of the cell, for example, in determining the cell division plane. In interphase Schizosaccharomyces pombe cells, the nucleus is positioned in the middle of the cylindrical cell in an active microtubule (MT)-dependent process. Here, we used green fluorescent protein markers to examine the dynamics of MTs, spindle pole body, and the nuclear envelope in living cells. We find that interphase MTs are organized in three to four antiparallel MT bundles arranged along the long axis of the cell, with MT plus ends facing both the cell tips and minus ends near the middle of the cell. The MT bundles are organized from medial MT-organizing centers that may function as nuclear attachment sites. When MTs grow to the cell tips, they exert transient forces produced by plus end MT polymerization that push the nucleus. After an average of 1.5 min of growth at the cell tip, MT plus ends exhibit catastrophe and shrink back to the nuclear region before growing back to the cell tip. Computer modeling suggests that a balance of these pushing MT forces can provide a mechanism to position the nucleus at the middle of the cell.

Evaluation of the hydrogen bonding interactions and their effects on the oxidation-reduction potentials for the riboflavin complex of the Desulfovibrio vulgaris flavodoxin

The oxidation-reduction potentials for the riboflavin complex of the Desulfovibrio vulgaris flavodoxin are substantially different from those of the flavin mononucleotide (FMN) containing native protein, with the midpoint potential for the semiquinone-hydroquinone couple for the riboflavin complex being 180 mV less negative. This increase has been attributed to the absence in the riboflavin complex of unfavorable electrostatic effects of the dianionic 5'-phosphate of the FMN on the stability of the flavin hydroquinone anion. In this study, 15N and 1H-15N heteronuclear single-quantum coherence nuclear magnetic resonance spectroscopic studies demonstrate that when bound to the flavodoxin, (1) the N1 of the riboflavin hydroquinone remains anionic at pH 7.0 so the protonation of the hydroquinone is not responsible for this increase, (2) the N5 position is much more exposed and may be hydrogen bonded to solvent, and (3) that while the hydrogen bonding interaction at the N3H appears stronger, that at the N5H in the reduced riboflavin is substantially weaker than for the native FMN complex. Thus, the higher reduction potential of the riboflavin complex is primarily the consequence of altered interactions with the flavin ring that affect hydrogen bonding with the N5H that disproportionately destabilize the semiquinone state of the riboflavin rather than through the absence of the electrostatic effects of the 5'-phosphate on the hydroquinone state.

Role of actin polymerization and actin cables in actin-patch movement in Schizosaccharomyces pombe

Factors that are involved in actin polymerization, such as the Arp2/3 complex, have been found to be packaged into discrete, motile, actin-rich foci. Here we investigate the mechanism of actin-patch motility in S. pombe using a fusion of green fluorescent protein (GFP) to a coronin homologue, Crn1p. Actin patches are associated with cables and move with rates of 0.32 microm s(-1) primarily in an undirected manner at cell tips and also in a directed manner along actin cables, often away from cell tips. Patches move more slowly or stop when actin polymerization is attenuated by Latrunculin A or in arp3 and cdc3 (profilin) mutants. In a cdc8 (tropomyosin) mutant, actin cables are absent, and patches move with similar speed but in a non-directed manner. Patches are sites of Arp3-dependent F-actin polymerization in vitro. Rapid F-actin turnover rates in vivo indicate that patches and cables are maintained continuously by actin polymerization. Our studies give rise to a model in which actin patches are centres for actin polymerization that drive their own movement on actin cables using Arp2/3-based actin polymerization.

Cardiac memory in canine atrium : identification and implications

BACKGROUND

Memory is a diverse biological phenomenon whose importance in the ventricle has been demonstrated. We hypothesized its occurrence in the atrium, contributing to the modulation of cardiac rhythm.

METHODS AND RESULTS

We analyzed P and Ta waves in conscious chronically instrumented dogs with complete heart block. Animals were atrioventricularly sequentially paced at 5% greater than the sinus rate from the lateral right atrium (RA) during control, followed by 2 periods of 1-hour test pacing at 50% greater than the sinus rate, or by equivalent test pacing from the left atrial appendage (LAA) at 5% or 50% greater than the sinus rate. Recovery RA pacing periods of 20- and 30-minute duration, respectively, succeeded each test pacing period. RA test pacing at either rate did not affect the variables measured, but changing the pacing site from RA to LAA altered the P and Ta waves. Displacement of the spatial atrial gradient vector occurred during recovery from LAA pacing, was more marked at rapid pacing rates, and manifested accumulation and resolution consistent with cardiac memory. Concurrently, the right effective refractory period decreased.

CONCLUSIONS

Memory is demonstrable in canine atrium, showing rapid onset, accumulation during successive pacing periods, and resolution on cessation of pacing. Given its association with a reduced effective refractory period, it may contribute to the substrate for atrial arrhythmias.

Risk for respiratory distress syndrome in preterm infants born to mothers complicated by placenta previa

This study examined the risk factors for respiratory distress syndrome (RDS) in preterm infants from pregnancies complicated by placenta previa. Forty preterm infants born to mothers with placenta previa between January 1989 and December 1995 in a medical center were enrolled. Each of these patients was matched in gestational age and gender with an infant born immediately after to a mother without placenta previa. Obstetric and neonatal outcome variables were collected. The mean+/-S.D. gestational age for both groups was 33.0+/-3.1 weeks. There was no difference in mean birthweight between the placenta previa and control groups (2129+/-598 vs. 2136+/-493 g). All the patients in the former and 11 (28%) in the latter were born by cesarean section. About a half of the mothers in both groups received antenatal steroids. Infants from placenta previa pregnancies had a higher incidence (21/40 vs. 10/40, P<0.01) and more severe RDS than controls. Stratified by the status of treatment with antenatal steroid, we found that gestational age was a significant risk factor for RDS in both treated and untreated groups (P<0.01), but placenta previa was an independent risk factor (odds ratio 32; CI 1-4182) by multiple exact logistic regression in antenatal steroid-treated group. We conclude that preterm infants born to mothers with placenta previa had a higher risk for RDS than controls. It played an independent role, in addition to gestational age, only in infants treated with antenatal steroid. We speculate that placenta previa was not directly contributing to RDS, but through other associated risk factors for RDS.

The Raf signal transduction cascade as a target for chemotherapeutic intervention in growth factor-responsive tumors

This review focuses on the Ras-Raf-mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) signal transduction pathway and the consequences of its unregulation in the development of cancer. The roles of some of the cell membrane receptors involved in the activation of this pathway, the G-protein Ras, the Raf, MEK and ERK kinases, the phosphatases that regulate these kinases, as well as the downstream transcription factors that become activated, are discussed. The roles of the Ras-Raf-MEK-ERK pathway in the regulation of apoptosis and cell cycle progression are also analyzed. In addition, potential targets for pharmacological intervention in growth factor-responsive cells are evaluated.

Fetal renal volume in normal gestation: a three-dimensional ultrasound study

To establish a reference chart of fetal kidneys in normal pregnancy, we performed a prospective and cross-sectional study. A total of 152 singleton fetuses ranging between 20 and 40 weeks' gestation and meeting the criteria of normal pregnancies were included. Three-dimensional ultrasound (3-D US) was used to measure the fetal renal volume. Our results revealed that both renal volumes are highly correlated with the fetal gestational age. Using gestational age (GA) as the independent variable and right renal volume (RRV) as the dependent variable, the best-fit regression equation was RRV (mL)=0.74053xGA (week)-13.318 (r = 0.89, p < 0.001). Similarly, the best-fit equation for the left renal volume (LRV) was LRV (mL)=0. 76093xGA (week)-13.421 (r = 0.86, p < 0.001). The normal growth centiles of both kidneys were established based on these two equations. There were no significant differences of the volumes between bilateral kidneys. In conclusion, our data of fetal renal volumes assessed by 3-D US may serve as a reference in evaluating fetal renal growth.

Quantitative image analysis of oesophageal squamous cell carcinoma from the high-incidence area of China, with special reference to tumour progression and papillomavirus (HPV) involvement

BACKGROUND

Despite much research effort, the major prognostic factor of oesophageal squamous cell cancer (ESCC) remains the pathological stage of the disease as defined by the TNM classification, whereas tumour grading is of limited value in this respect, mainly due to its low reproducibility. A better means for disease prognostication based on improved understanding of the pathogenetic mechanisms is urgently required.

MATERIALS AND METHODS

Among the cohort of 700 ESCC patients from the high-incidence area of China, previously subjected to extensive testing for Human papillomavirus (HPV) involvement by in situ hybridization (ISH) and PCR, a group of 273 patients was randomly selected for analysis of the primary tumour, adjacent mucosa and regional lymph nodes, by histopathology and quantitative image analysis. All these and the HPV data were subjected to extensive univariate and multivariate analysis to disclose independent predictors of progressive disease.

RESULTS

For the analyses, the tumours were graded into two categories: well-moderately and poorly-differentiated. HPV DNA was detected in 116 (18.9%) of the carcinomas by ISH and in 15.2% by PCR. In univariate analysis, lymph node status (considered as the surrogate marker of progressive disease) was significantly (p < 0.01) predicted by the following nuclear parameters: nuclear area, G0/G1 ratio, HPV DNA status, integrated optical density (IOD), mean optical density (MOD) and S-Phase. In multivariate (stepwise backward LR) analysis, 6 variables remained as independent predictors of disease progression (at p < 0.05 level), the three most significant ones being nuclear perimeter, nuclear roundness and equivalent diameter (p < 0.01).

CONCLUSION

A series of quantitatively measured nuclear parameters seem to bear a close correlation with ESCC differentiation and progression in univariate analysis and some of these variables proved to be significant independent predictors of disease progression in multivariate modelling as well. These data clearly advocate the use of quantitative image analysis in searching for additional prognostic factors of ESCC.

Evaluation of HPV, CMV, HSV and EBV in esophageal squamous cell carcinomas from a high-incidence area of China

BACKGROUND

Certain viruses, notably human papillomavirus (HPV), cytomegalovirus (CMV), herpes simplex virus (HSV) and Epstein-Barr virus (EBV), are known to produce tumors in animals and cell transformation in vitro and they have been implicated in the pathogenesis of human cancers. All these viruses are also known to infect the esophagus. This study was aimed to determine whether these viruses play any causal role in the etiology of esophageal squamous cell carcinoma.

MATERIALS AND METHODS

A series of 103 esophageal squamous cell carcinomas derived from patients in the high-incidence area of northern China were analyzed by DNA in situ hybridization and polymerase chain reaction (PCR) for the presence of HPV DNA sequences and, using immunohistochemistry, for the demonstration of CMV, HSV and EBV infections.

RESULTS

Six (5.8%) of the 103 tumors were found to contain HPV 16, 18 or 30 DNA sequences. HPV types 6, 11 and 53 were not detected in any of the cases. Amplified HPV DNA sequences were found in 17 out of 101 (16.8%) carcinoma specimens by PCR with L1 consensus primers. None of the 103 carcinomas tested was immunohistochemically positive for CMV, HSV or EBV.

CONCLUSION

Our results confirmed the HPV involvement in esophageal carcinomas and provided further evidence to support a causal association of HPV infection with esophageal squamous cell carcinoma. However, the three herpesviruses, CMV, HSV and EBV, are highly unlikely to be involved in the pathogenesis of this malignancy in the high-incidence area of China.

Analysis of mid1p, a protein required for placement of the cell division site, reveals a link between the nucleus and the cell surface in fission yeast

mid1 is required for the proper placement of the contractile actin ring for cytokinesis at a medial site overlying the nucleus. Here we find that mid1 protein (mid1p) shuttles between the nucleus and a cortical medial broad band during interphase and early mitosis. The position of this broad band, which overlies the nucleus, is linked to nuclear position even in cells with displaced or multiple nuclei. We identified and created mutations in an NLS and in two crm1-dependent NES sequences in mid1p. NES mutations caused mid1p accumulation in the nucleus and loss of function. An NLS mutations greatly reduced nuclear localization but did not perturb cytoplasmic localization or function. mid1p localization to the medial broad band was also not dependent on mid1p PH domain or microtubule and actin cytoskeletons. Overexpression of mid1p produced ectopic cell growth at this band during interphase and abnormal karmellae-like nuclear membrane structures. In plo1-1, mid1p formed a medial broad band but did not incorporate into a tight ring, suggesting that polo kinase plo1p is required for activation of mid1p function. Thus, the mid1p broad band defines a compartment at the medial cell surface, whose localization is linked to the position of the nucleus, and whose function may be to position the plane of cell division.

Combined effects of aberrant MEK1 activity and BCL2 overexpression on relieving the cytokine dependency of human and murine hematopoietic cells

The MEK1 oncoprotein plays a critical role in Ras/Raf/MEK/MAPK-mediated transmission of mitogenic signals from cell surface receptors to the nucleus. In order to examine this pathway's role in leukemic transformation, a conditionally active (beta-estradiol-inducible) form of the MEK1 protein was created by ligating a cDNA encoding an N-terminal truncated form of MEK1 to the hormone-binding domain of the estrogen receptor (ER). We introduced this chimeric deltaMEK1:ER oncoprotein into cytokine-dependent human TF-1 and murine FDC-P1 hematopoietic cell lines. Two different types of cells were recovered after drug selection in medium containing either cytokine or beta-estradiol: (1) cells that expressed the deltaMEK1:ER oncoprotein but remained cytokine-dependent and (2) MEK1-responsive cells that grew in response to deltaMEK1:ER activation. Cytokine-dependent cells were recovered 10(2) to 10(4) times more frequently than MEK1-responsive cells depending upon the particular cell line. To determine whether BCL2 overexpression could synergize with the deltaMEK1:ER oncoprotein in relieving cytokine dependence, the cytokine-dependent deltaMEK1:ER-expressing cells were infected with a BCL2-containing retrovirus, and the frequency of MEK1-responsive cells determined. BCL2 overexpression, by itself, did not relieve cytokine dependency of the parental cells, however, it did increase the frequency at which MEK1-responsive cells were recovered approximately 10-fold. DeltaMEK1:ER+BCL2 cells remained viable for at least 3 days after estradiol deprivation, whereas viability was readily lost upon withdrawal of beta-estradiol in the MEK1-responsive cells which lacked BCL2 overexpression. The MAP kinases, ERK1 and ERK2 were activated in response to deltaMEK1:ER stimulation in both deltaMEK1:ER and deltaMEK1:ER+BCL2 cells. As compared to the cytokine-dependent deltaMEK1:ER and BCL2 infected cells, MEK1-responsive BCL2 infected cells expressed higher levels of BCL2. While both MEK1-responsive deltaMEK1:ER and deltaMEK1:ER+BCL2 infected cells expressed cDNAs encoding the autocrine cytokine GM-CSF, more GM-CSF cDNAs and bioactivity were detected in the MEK1-responsive deltaMEK1:ER+BCL2 cells than in the MEK1-responsive cells lacking BCL2 or cytokine-dependent cells. These conditionally transformed cells will be useful in furthering our understanding of the roles MEK1 and BCL2 play in the prevention of apoptosis in hematopoietic cells.

Synergy between Raf and BCL2 in abrogating the cytokine dependency of hematopoietic cells

The Raf oncoprotein plays critical roles in the transmission of mitogenic signals from cytokine receptors to the nucleus. There are three Raf family members: A-Raf, B-Raf and Raf-1. Conditionally active forms of the Raf proteins were created by ligating N-terminal truncated activated forms to the estrogen-receptor (ER) hormone-binding domain resulting in beta-estradiol-inducible constructs. We introduced these chimeric deltaRaf:ER oncoproteins into the murine FDC-P1 hematopoietic cell line. Two different types of cells were recovered after drug selection in medium containing either cytokine or beta-estradiol: (1) cytokine-dependent cells that expressed the deltaRaf:ER oncoproteins; and (2) Raf-responsive cells that grew in response to the deltaRaf:ER oncoprotein. Depending upon the particular deltaRaf:ER oncoprotein, cytokine-dependent cells were recovered 10(3) to 10(5) times more frequently than Raf-responsive cells. To determine whether BCL2 could synergize with the deltaRaf:ER oncoproteins and increase the frequency of cytokine-independent cells, cytokine-dependent deltaRaf:ER-expressing cells were infected with either a BCL2 containing retrovirus or an empty retroviral vector. BCL2 overexpression, by itself, did not relieve cytokine dependency of the parental cell line. However, BCL2 overexpression increased the frequency of Raf-responsive cells approximately five- to 100-fold. Cytokine-dependent deltaRaf:ER-infected cells entered the G1 phase of the cell cycle after cytokine withdrawal and entered S phase only after cytokine addition. Raf-responsive deltaRaf:ER cells entered the G1 phase of the cell cycle after estrogen deprivation and re-entered the cell cycle after addition of either IL-3 or the estrogen receptor antagonist tamoxifen which activates the deltaRaf:ER constructs. Expression of the BCL2 oncoprotein often delayed the exit from the S and G2/M phases demonstrating the protective effects BCL2 provided to these Raf and BCL2 infected cells. The deltaRaf:ER cells expressed the deltaRaf:ER proteins and downstream MEK and ERK activities after beta-estradiol treatment. Raf-responsive cells that were also infected with BCL2 expressed higher levels of BCL2 than the cells that were not infected with BCL2. Thus BCL2 can synergize with the activated Raf in the abrogation of cytokine dependency of certain hematopoietic cells. These cells will be useful in furthering our understanding of the roles of the Raf and BCL2 oncoproteins in hematopoietic cell growth, cell cycle progression and prevention of apoptosis.

Microtubule and actin-dependent movement of the formin cdc12p in fission yeast

Although a number of gene products involved in cytokinesis have been identified, still little is known about how these proteins are localized to the proper site and assembled into a ring structure. How is the plane of cell division is positioned in the cell? Schizosaccharomyces pombe are simple rod-shaped eukaryotic cells that divide by medial fission using a medial contractile ring. S. pombe cdc12p encodes a member of the formin gene family, proteins with conserved roles in cytokinesis and actin organization. cdc12p is required specifically for the formation of the medial ring and is located in this ring during mitosis. Time-lapse microscopy of cells expressing GFP-cdc12p protein fusions reveals that during interphase, S. pombe cdc12p is present in a discrete, motile cytoplasmic particle that moves using both actin and microtubules. At the onset of mitosis, the spot moves to the future site of cell division and spreads out into a ring. These studies demonstrate that a cytokinesis factor may travel on both microtubule and actin networks to the site of contractile ring assembly. These findings suggest a potential mechanism for how the mitotic spindle positions the cell division plane in animal cells.

Structural priming as implicit learning: a comparison of models of sentence production

Structural priming reflects a tendency to generalize recently spoken or heard syntactic structures to different utterances. We propose that it is a form of implicit learning. To explore this hypothesis, we developed and tested a connectionist model of language production that incorporated mechanisms previously used to simulate implicit learning. In the model, the mechanism that learned to produce structured sequences of phrases from messages also exhibited structural priming. The ability of the model to account for structural priming depended on representational assumptions about the nature of messages and the relationship between comprehension and production. Modeling experiments showed that comprehension-based representations were important for the model's generalizations in production and that nonatomic message representations allowed a better fit to existing data on structural priming than traditional thematic-role representations.

Human papillomavirus involvement in esophageal carcinogenesis in the high-incidence area of China. A study of 700 cases by screening and type-specific in situ hybridization

BACKGROUND

Human papillomavirus (HPV) DNA has been identified in esophageal precancerous lesions and carcinomas. However, there are marked variations in the prevalence of HPV infection reported in different studies. Most previous studies on HPV and esophageal carcinomas have been based on a limited number of biopsy samples studied by different HPV detection methods with highly variable sensitivity and specificity, making systematic studies of larger series clearly warranted.

METHODS

A series of 1876 surgical specimens (primary tumor, adjacent epithelium, regional lymph nodes, resection margins) from 700 patients surgically resected for an invasive squamous cell carcinoma of the esophagus in the high-incidence area of China was analyzed for the presence of HPV DNA with screening in situ hybridization (ISH) using biotinylated HPV DNA probes and followed by type-specific ISH for HPV 6, 11, 16, 18, 30, and 53.

RESULTS

Of the 700 esophageal carcinomas, 118 (16.9%) were shown to contain HPV DNA sequences by screening ISH. Positive signals were most frequent in the cancer cells (16.6%), more rare in the surrounding hyperplastic and dysplastic epithelia (5.6%), and infrequently present in the resection margins (0.2%). HPV signals were also detected in cancer cells in 6.9% of the lymph node metastases. HPV types 6, 11, 16, 18, and 30 account for 39.8% of the HPV-positive lesions, of which the high-risk types HPV 16 and 18 were present in 27.1% (32 of 118). Notably, 60.2% of the HPV-positive lesions contained DNA sequences other than HPV types 6, 11, 16, 18, 30, and 53.

CONCLUSIONS

This study reports the largest series of esophageal cancers ever analyzed for the presence of HPV DNA. Our results confirm the presence of common mucosal HPV types in esophageal carcinomas but also suggest the involvement of other (novel?) HPV types that are unusually detected in genital cancers in a significant proportion of these lesions. The results further indicate that HVP has an etiologic role in esophageal carcinogenesis, at least in the high-incidence area of northern China.

Tandem duplication polymorphism upstream of the dopamine D4 receptor gene (DRD4)

The dopamine D4 receptor (DRD4) is a member of the D2-like dopamine receptor family. Polymorphisms at the DRD4 gene have been examined for association with a wide range of neuropsychiatric disorders and normal behavioral variation. The DRD4 gene is unusual in its high amount of expressed polymorphism in humans. Here we study the identification of a polymorphic tandem duplication of 120 bp located 1.2 kb upstream of the initiation codon. The duplicated region contains consensus sequences of binding sites for several known transcription factors, suggesting that different alleles may differ in their transcriptional activity. Because chimpanzees, gorillas, and orangutans lack the duplication, the duplicated allele is inferred to be derived. The frequency of this derived duplication allele ranges from 0.40-0.81 in the 11 populations from around the world typed for this polymorphism. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:705-709, 1999.