The breast cancer susceptibility gene BRCA1 is required for subnuclear assembly of Rad51 and survival following treatment with the DNA cross-linking agent cisplatin

Mutations in breast cancer tumor susceptibility genes, BRCA1 and BRCA2, predispose women to early onset breast cancer and other malignancies. The Brca genes are involved in multiple cellular processes in response to DNA damage including checkpoint activation, gene transcription, and DNA repair. Biochemical interaction with the recombinational repair protein Rad51 (Scully, R., Chen, J., Ochs, R. L., Keegan, K., Hoekstra, M., Feunteun, J., and Livingston, D. M. (1997) Cell 90, 425-435), as well as genetic evidence (Moynahan, M. E., Chiu, J. W., Koller, B. H., and Jasin, M. (1999) Mol. Cell 4, 511-518 and Snouwaert, J. N., Gowen, L. C., Latour, A. M., Mohn, A. R., Xiao, A., DiBiase, L., and Koller, B. H. (1999) Oncogene 18, 7900-7907), demonstrates that Brca1 is involved in recombinational repair of DNA double strand breaks. Using isogenic Brca1(+/+) and brca1(-/-) mouse embryonic stem (ES) cell lines, we investigated the role of Brca1 in the cellular response to two different categories of DNA damage: x-ray induced damage and cross-linking damage caused by the chemotherapeutic agent, cisplatinum. Immunoflourescence studies with normal and brca1(-/-) mutant mouse ES cell lines indicate that Brca1 promotes assembly of subnuclear Rad51 foci following both types of DNA damage. These foci are likely to be oligomeric complexes of Rad51 engaged in repair of DNA lesions or in processes that allow cells to tolerate such lesions during DNA replication. Clonogenic assays show that brca1(-/-) mutants are 5-fold more sensitive to cisplatinum compared with wild-type cells. Our studies suggest that Brca1 contributes to damage repair and/or tolerance by promoting assembly of Rad51. This function appears to be shared with Brca2.

Neurotrophins use the Erk5 pathway to mediate a retrograde survival response

Growth factors synthesized and released by target tissues promote survival and differentiation of innervating neurons. This retrograde signal begins when growth factors bind receptors at nerve terminals. Activated receptors are then endocytosed and transported through the axon to the cell body. Here we show that the mitogen-activated protein kinase (MAPK) signaling pathways used by neurotrophins during retrograde signaling differ from those used following direct stimulation of the cell soma. During retrograde signaling, endocytosed neurotrophin receptors (Trks) activate the extracellular signal-related protein kinase 5 (Erk5) pathway, leading to nuclear translocation of Erk5, phosphorylation of CREB, and enhanced neuronal survival. In contrast, Erk1/2, which mediates nuclear responses following direct cell body stimulation, does not transmit a retrograde signal. Thus, the Erk5 pathway has a unique function in retrograde signaling. Differential activation of distinct MAPK pathways may enable an individual growth factor to relay information that specifies the location and the nature of stimulation.

Magnification chromoendoscopy for the detection of intestinal metaplasia and dysplasia in Barrett's oesophagus

BACKGROUND

The presence of intestinal metaplasia (IM) in the columnar lined distal oesophagus defines Barrett's oesophagus with the risk of future malignant transformation. The distribution of both IM and dysplasia (low grade (LGD) and high grade (HGD)) within the columnar lined oesophagus is patchy and mosaic requiring random biopsies. Techniques that could help target areas of high yield within Barrett's mucosa would be helpful.

AIM

To study the utility of high magnification chromoendoscopy (MCE) in the detection of IM, LGD, and HGD in patients with Barrett's oesophagus.

METHODS

Consecutive patients detected with columnar mucosa in the distal oesophagus were studied using an Olympus magnification endoscope (GIF-Q16OZ, 115x). The distal oesophagus was sprayed with indigo carmine solution and the oesophageal columnar mucosa patterns were noted under high magnification and targeted for biopsy. All biopsies were read by pathologists blinded to the endoscopic findings.

RESULTS

Eighty patients with suspected Barrett's oesophagus (that is, columnar lined distal oesophagus) were studied: mean age 62.7 years (range 35-81). Mean length of columnar mucosa was 3.7 cm (range 0.5-17). Three types of mucosal patterns were noted within the columnar mucosa after spraying indigo carmine and using MCE: ridged/villous pattern, circular pattern, and irregular/distorted pattern. The yield of IM on target biopsies according to the patterns was: ridged/villous 57/62 (97%) and circular 2/12 (17%). Six patients had an irregular/distorted pattern and all had HGD on biopsy (6/6 (100%)). Eighteen patients had LGD on target biopsies; all had the ridged/villous pattern. All patients with long segment Barrett's were identified using MCE whereas 23/28 patients (82%) with short segment Barrett's had the ridged/villous pattern.

CONCLUSIONS

MCE helps visually identify areas with IM and HGD having specific patterns but not patients with LGD (appear similar to IM). MCE may be a useful clinical tool for the increased detection of patients with IM as well as for surveillance of patients for the detection of HGD. If these preliminary results are validated, MCE would help identify high yield areas, potentially eliminating the need for random biopsies.

Xrcc3 is required for assembly of Rad51 complexes in vivo

Rad51 is a member of a family of eukaryotic proteins related to the bacterial recombinational repair protein RecA. Rad51 protein localizes to multiple subnuclear foci in Chinese hamster ovary cells. Subnuclear Rad51 foci are induced by ionizing radiation or the DNA cross-linking agent cisplatin. Formation of these foci is likely to reflect assembly of a multimeric form of Rad51 that promotes DNA repair. Formation of damage-induced Rad51 foci does not occur in the Chinese hamster ovary cell line irs1SF, which is sensitive to DNA damaging agents. The Rad51 focus formation defect of irs1SF cells is corrected by a construct that encodes the repair protein Xrcc3. Xrcc3 is a human homolog of Rad51 previously isolated by virtue of its ability to correct the radiation sensitivity of irs1SF cells. Changes in the steady state level of Rad51 protein do not account for the irs1SF defect nor do they account for the appearance of foci following DNA damage. These results suggest that Xrcc3 is required for the assembly or stabilization of a multimeric form of Rad51 during DNA repair. Cell lines defective in two different components of DNA protein kinase formed Rad51 foci in response to damage, indicating DNA protein kinase is not required for damaged-induced mobilization of Rad51.

The contrasting structures of mismatched DNA sequences containing looped-out bases (bulges) and multiple mismatches (bubbles)

We have studied the structure and reactivities of two kinds of mismatched DNA sequences--unopposed bases, or bulges, and multiple mismatched pairs of bases. These were generated in a constant sequence environment, in relatively long DNA fragments, using a technique based on heteroduplex formation between sequences cloned into single-stranded M13 phage. The mismatched sequences were studied from two points of view, viz 1. The mobility of the fragments on gel electrophoresis in polyacrylamide was studied in order to examine possible bending of the DNA due to the presence of the mismatch defect. Such bending would constitute a global effect on the conformation of the molecule. 2. Sequences in and around the mismatches were studied using enzyme and chemical probes of DNA structure. This would reveal more local structural effects of the mismatched sequences. We observed that the structures of the bulges and the multiple mismatches appear to be fundamentally different. The bulged sequences exhibited a large gel retardation, consistent with a significant bending of the DNA at the bulge, and whose magnitude depends on the number of mismatched bases. The larger bulges were sensitive to cleavage by single-strand specific nucleases, and modified by diethyl pyrocarbonate (adenines) or osmium tetroxide (thymines) in a non-uniform way, suggesting that the bulges have a precise structure that leads to exposure of some, but not all, of the bases. In contrast the multiple mismatches ('bubbles') cause very much less bending of the DNA fragment in which they occur, and uniform patterns of chemical reactivity along the length of the mismatched sequences, suggesting a less well defined, and possibly flexible, structure. The precise structure of the bulges suggests that such features may be especially significant for recognition by proteins.

RNA bulges and the helical periodicity of double-stranded RNA

RNA molecules typically exhibit extensive secondary structure, including double-stranded duplex, hairpins, internal loops, bulged bases and pseudoknotted structures (reviewed in refs 3 and 4). This is intimately connected with biological function, including splicing reactions and ribozyme activity. The formation of RNA-DNA hybrids is important in the transcription of DNA, reverse transcription of viral RNA, and DNA replication. Bulged bases in RNA helices are potentially significant in RNA folding and in providing sites for specific protein-RNA interactions, as illustrated by TFIIIA of Xenopus and the coat protein of phage R17. Most information about the structure of RNA derives from fibre diffraction or crystallography of natural molecules, notably transfer RNA, but until recently there have been few systematic studies of RNA structure using designed sequences. We have used gel electrophoresis to investigate the properties of bulged bases in both RNA and RNA-DNA depending on the number and types of bases in the bulge and its position in the fragment. By varying the spacing between two bulge-induced kinks, we have measured the periodicity of RNA and RNA-DNA helices in solution.

Differential utilization of Trk autophosphorylation sites

Tyrosine autophosphorylation controls the catalytic and signaling activities of the neurotrophin receptors, the Trks. To analyze the regulation of distinct tyrosine sites, we generated a panel of antibodies that report the phosphorylation state of individual tyrosines within the Trk cytoplasmic domain. Using pheochromocytoma-derived cell lines, we show that individual tyrosines within the nerve growth factor receptor TrkA are phosphorylated in a non-coordinate fashion following receptor activation. The non-coordinate response of these tyrosines reflects their separate functions in regulating the catalytic and signaling activities of Trk receptors. The differential utilization of distinct sites on Trk receptor tyrosine kinases suggests that the receptor can specify both the timing and the nature of neurotrophin-stimulated signal transduction pathways. Moreover, we show that these Trk autophosphorylation sites, which have hitherto been mapped and characterized only in non-neuronal cell lines, are activated in normal neurons in response to ligand stimulation.

Potent and selective inhibition of human cathepsin K leads to inhibition of bone resorption in vivo in a nonhuman primate

Cathepsin K is a cysteine protease that plays an essential role in osteoclast-mediated degradation of the organic matrix of bone. Knockout of the enzyme in mice, as well as lack of functional enzyme in the human condition pycnodysostosis, results in osteopetrosis. These results suggests that inhibition of the human enzyme may provide protection from bone loss in states of elevated bone turnover, such as postmenopausal osteoporosis. To test this theory, we have produced a small molecule inhibitor of human cathepsin K, SB-357114, that potently and selectively inhibits this enzyme (Ki = 0.16 nM). This compound potently inhibited cathepsin activity in situ, in human osteoclasts (inhibitor concentration [IC]50 = 70 nM) as well as bone resorption mediated by human osteoclasts in vitro (IC50 = 29 nM). Using SB-357114, we evaluated the effect of inhibition of cathepsin K on bone resorption in vivo using a nonhuman primate model of postmenopausal bone loss in which the active form of cathepsin K is identical to the human orthologue. A gonadotropin-releasing hormone agonist (GnRHa) was used to render cynomolgus monkeys estrogen deficient, which led to an increase in bone turnover. Treatment with SB-357114 (12 mg/kg subcutaneously) resulted in a significant reduction in serum markers of bone resorption relative to untreated controls. The effect was observed 1.5 h after the first dose and was maintained for 24 h. After 5 days of dosing, the reductions in N-terminal telopeptides (NTx) and C-terminal telopeptides (CTx) of type I collagen were 61% and 67%, respectively. A decrease in serum osteocalcin of 22% was also observed. These data show that inhibition of cathepsin K results in a significant reduction of bone resorption in vivo and provide further evidence that this may be a viable approach to the treatment of postmenopausal osteoporosis.

S100 is present in developing chicken neurons and Schwann cells and promotes motor neuron survival in vivo

We used polyclonal antisera recognizing S100, a small acidic protein highly enriched in nervous tissue, to stain sections of embryonic chicken lumbosacral spinal cord and hindlimb. S100 immunoreactivity was detected in developing sensory neurons of the dorsal root ganglia (DRG) and motor neurons of the ventral spinal cord as early as embryonic day (E) 5, and staining persisted through hatching. In contrast, expression of S100 first became apparent in Schwann cells at E13, just before myelination, and was not detected in developing skin or muscle. Since S100 beta was present in motor and sensory neurons and is known to promote neuronal survival and neurite extension in vitro (Winningham-Major, Staecker, Barger, Coats, and Van Eldik, 1989), we tested the ability of S100 to promote neuron survival in an in ovo survival assay. Addition of S100 to chick embryos in ovo during the period of naturally occurring motor neuron cell death resulted in a significant increase in motor neuron survival, but had no effect on the in vivo survival of sensory neurons in the DRG. The findings that S100 is present in spinal motor neurons and that the addition of S100 enhances the survival of these cells in vivo are consistent with the possibility that S100 may act as a naturally occurring neuron survival factor during development.

Lipoarabinomannan from Mycobacterium tuberculosis promotes macrophage survival by phosphorylating Bad through a phosphatidylinositol 3-kinase/Akt pathway

Efforts in prevention and control of tuberculosis suffer from the lack of detailed knowledge of the mechanisms used by pathogenic mycobacteria for survival within host cell macrophages. The exploitation of host cell signaling pathways to the benefit of the pathogen is a phenomenon that deserves to be looked into in detail. We have tested the hypothesis that lipoarabinomannan (LAM) from the virulent species of Mycobacterium tuberculosis possesses the ability to modulate signaling pathways linked to cell survival. The Bcl-2 family member Bad is a proapoptotic protein. Phosphorylation of Bad promotes cell survival in many cell types. We demonstrate that man-LAM stimulates Bad phosphorylation in a phosphatidylinositol 3-kinase (PI-3K)-dependent pathway in THP-1 cells. Man-LAM activated PI-3K. LAM-stimulated phosphorylation of Bad was abrogated in cells transfected with a dominant-negative mutant of PI-3K (Delta p85), indicating that activation of PI-3K is sufficient to trigger phosphorylation of Bad by LAM. Since phosphorylation of Bad occurred at serine 136, the target of the serine/threonine kinase Akt, the effect of LAM on Akt kinase activity was tested. Man-LAM could activate Akt as evidenced from phosphorylation of Akt at Thr(308) and by the phosphorylation of the exogenous substrate histone 2B. Akt activation was abrogated in cells transfected with Deltap85. The phosphorylation of Bad by man-LAM was abrogated in cells transfected with a kinase-dead mutant of Akt. These results establish that LAM-mediated Bad phosphorylation occurs in a PI-3K/Akt-dependent manner. It is therefore the first demonstration of the ability of a mycobacterial virulence factor to up-regulate a signaling pathway involved in cell survival. This is likely to be one of a number of virulence-associated mechanisms by which bacilli control host cell apoptosis.

TrkA glycosylation regulates receptor localization and activity

The human nerve growth factor receptor (TrkA) contains four potential N-glycosylation sites that are highly conserved within the Trk family of neurotrophin receptors, and nine additional sites that are less well conserved. Using a microscale deglycosylation assay, we show here that both conserved and variable N-glycosylation sites are used during maturation of TrkA. Glycosylation at these sites serves two distinct functions. First, glycosylation is necessary to prevent ligand-independent activation of TrkA. Unglycosylated TrkA core protein is phosphorylated even in the absence of ligand stimulation and displays constitutive kinase activity as well as constitutive interaction with the signaling molecules Shc and PLC-gamma. Second, glycosylation is required to localize TrkA to the cell surface, where it can trigger the Ras/Raf/MAP kinase cascade. Using confocal microscopy, we show that unglycosylated active Trk receptors are trapped intracellularly. Furthermore, the unglycosylated active TrkA receptors are unable to activate kinases in the Ras-MAP kinase pathway, MEK and Erk. Consistent with these biochemical observations, unglycosylated TrkA core protein does not promote neuronal differentiation in Trk PC12 cells even at high levels of constitutive catalytic activity.

P0 is an early marker of the Schwann cell lineage in chickens

We have generated a monoclonal antibody, termed 1E8, that is specific for myelinating and nonmyelinating Schwann cells in mature chickens. 1E8 first stains cells at the edge of the neural crest; later, cells located between the neural tube and somites and in the sclerotome are immunopositive. Double labeling with HNK-1 indicates that these 1E8-positive cells represent a subset of neural crest cells in the ventral migratory pathways. 1E8-positive cells are later associated with the dorsal and ventral roots and with extending nerve trunks. In Western blots, 1E8 reacts with proteins comigrating with P0. Immunodepletion experiments establish that all P0 molecules carry the 1E8 determinant. The developmental distribution of P0, as determined by 1E8 immunoreactivity, differs from that reported for P0 in mammals and suggests that, in chicken, P0 is an early marker for the Schwann cell lineage.

Squamous islands in Barrett's esophagus: what lies underneath?

OBJECTIVE

Squamous islands are frequently visualized at the time of upper endoscopy in patients with Barrett's esophagus, especially those on proton pump inhibitor therapy (PPI). The significance of these islands is not clearly understood. The aim of this study was to systematically biopsy macroscopic squamous islands and to examine their histologic characteristics.

METHODS

Patients with Barrett's esophagus undergoing surveillance had squamous islands documented and biopsied at the time of endoscopy. Barrett's esophagus was defined as the presence of a columnar lined esophagus on endoscopy with intestinal metaplasia on biopsy. All biopsies were obtained by a single senior endoscopist and were stained with alcian blue at pH 2.5. Biopsy samples with inadequate tissue quantity were not included in the study.

RESULTS

A total of 39 biopsies were obtained from 22 patients. Twenty of the 22 patients were male, with a mean age of 65.4 yr (range 47-80 yr). The mean length of Barrett's mucosa was 5.6 cm (range 1-11 cm). Eleven of 22 patients were on omeprazole (mean dose 29.1 mg/day), whereas seven patients were on lansoprazole (60 mg/day). The mean duration of PPI therapy was 2.3 yr (range 9-71 months) at the time of biopsy of the squamous islands. Three patients were on H2-blocker therapy whereas the remaining patient had not been started on acid suppression therapy. On histology, 24 biopsy specimens (61.5%) revealed only squamous epithelium, whereas 15 (38.5%) showed the presence of intestinal metaplasia underlying the squamous epithelium. There was no significant difference between the patients with and without underlying intestinal metaplasia in regard to age, Barrett's length, dose, and duration of PPI therapy.

CONCLUSION

In more than one-third of biopsies of macroscopic squamous islands within Barrett's esophagus, microscopic intestinal metaplasia is detected. The presence of squamous islands should not be equated with regression of Barrett's esophagus or with decreased cancer risk.

Insulin lispro and regular insulin in pregnancy

We assessed the safety of insulin lispro in gestational, type 1 and type 2 diabetes mellitus, analysing 635 pregnancies over a period of 7 years. We also evaluated patient satisfaction, sending an internationally-accepted anonymous diabetes treatment satisfaction questionnaire to 22 patients (three type 1, 19 gestational diabetes) who received regular and lispro insulin in successive pregnancies. The success rate of pregnancies in women with gestational diabetes managed with diet alone (n=325) was 99.3%. All 213 pregnancies in women with gestational diabetes requiring insulin were successful. There was no difference in maternal or fetal outcomes whether patients used regular insulin (n=138) or insulin lispro (n=75), but pre-delivery HbA1c was lower with insulin lispro (p<0.05). Pregnancy loss in patients with pre-gestational diabetes (89 pregnancies in type 1 and eight in type 2 diabetes) was 18.6% for insulin and 3.7% for insulin lispro (p=0.10). The incidences of congenital anomalies with regular insulin were 7.9% and 15.8% in gestational and pre-gestational diabetes, respectively; the figures for insulin lispro were 6.6% (p=0.79) and 3.8% ( p=0.16), respectively. Nineteen of the 22 surveyed patients completed the questionnaire. Satisfaction was higher with insulin lispro (26.3+/-2.3 vs. 18+/-8.9, p=0.0005). We found no increase in adverse outcome using lispro insulin in diabetic pregnancies, in either gestational or pre-gestational diabetes. Patient satisfaction favoured insulin lispro. Several patients with type 1 diabetes who used regular insulin during pregnancy, chose lispro after delivery, but all who used lispro in pregnancy preferred to continue.

Correlation between rate constant for reduction and redox potential as a basis for systematic investigation of reaction mechanisms of electron transfer proteins

Rate constants for the reduction of approximately 40 electron transfer proteins by photoreduced flavins have been determined by laser flash photolysis techniques. The data for a series of 12 homologous cytochromes and 10 homologous high redox potential ferredoxins (HiPIPs) are in excellent agreement with semi-empirical equations relating rate constant and thermodynamic redox potential that have proven applicable to nonbiological electron transfer systems. These correlations allow the establishment of relative reactivities within structurally homologous classes of biological oxidation-reduction proteins, including cytochromes and HiPIPs, and a variety of nonhomologous heme-, iron-sulfur-, copper-, and flavin-containing proteins. A qualitative correspondence is shown to exist between such relative reactivity and the extent of solvent exposure of the redox centers in a particular structural class. The implications of these results are considered, and it is concluded that free energy relationships provide a sound basis for systematic analysis of reaction mechanisms of electron transfer proteins.

Liraglutide provides similar glycaemic control as glimepiride (both in combination with metformin) and reduces body weight and systolic blood pressure in Asian population with type 2 diabetes from China, South Korea and India: a 16-week, randomized, double-blind, active control trial(*)

AIM

To assess and compare the efficacy and safety of liraglutide with those of glimepiride, both in combination with metformin for the treatment of type 2 diabetes in Asian population from China, South Korea and India.

METHODS

A 16-week, randomized, double-blind, double-dummy, four-arm, active control trial was carried out. In total, 929 subjects with type 2 diabetes with a mean (±s.d.) age of 53.3 ± 9.5 years, HbA₁(c) of 8.6 ± 1.0% and body weight of 68.1 ± 11.7 kg were randomized (liraglutide 0.6, 1.2 or 1.8 mg once daily or glimepiride 4 mg once daily all in combination with metformin: 1 : 1 : 1 : 1). One subject withdrew immediately after randomization and before exposure.

RESULTS

HbA₁(c) was significantly reduced in all groups compared with baseline. Treatment with liraglutide 1.2 and 1.8 mg was non-inferior to glimepiride (mean HbA₁(c) reduction: 1.36% points, 1.45% points and 1.39% points, respectively). No significant difference was shown in the percentage of subjects reaching American Diabetes Association HbA₁(c) target <7% or American Association of Clinical Endocrinologists target ≤6.5% between liraglutide 1.2 and 1.8 mg and glimepiride. Liraglutide was associated with a 1.8-2.4 kg mean weight reduction, compared with a 0.1 kg mean weight gain with glimepiride. Liraglutide led to a significantly greater reduction in systolic blood pressure (SBP) compared with glimepiride. Two subjects in the glimepiride group reported major hypoglycaemia while none in the liraglutide groups. Liraglutide was associated with about 10-fold lower incidence of minor hypoglycaemia than glimepiride. Gastrointestinal disorders were the most common adverse events (AEs) for liraglutide, but were transient and resulted in few withdrawals.

CONCLUSIONS

In Asian subjects with type 2 diabetes, once-daily liraglutide led to improvement in glycaemic control similar to that with glimepiride but with less frequent major and minor hypoglycaemia. Liraglutide also induced a significant weight loss and reduced SBP and was generally well tolerated. The most frequently reported AE was transient nausea. The effect of liraglutide in this Asian population is comparable to the effects seen in Caucasian, African American and Hispanic populations in global liraglutide phase 3 trials.

Clonal chromosome abnormalities in human breast carcinomas. I. Twenty-eight cases with primary disease

Cytogenetic analysis was performed on a selected series of short-term cultures of primary breast carcinomas from 28 patients. All patients had histopathologically confirmed malignancies, with the majority (25/28 cases) demonstrating infiltrating ductal carcinoma. All 28 cases evidenced clonal chromosome abnormalities, with 10/28 displaying only numeric aberrations, whereas 18/28 displayed clonal structural alterations. In near-diploid tumors the most common numeric changes were -17 and -19. However, trisomy 7 was the only numeric change in two near-diploid tumors. Structural chromosome alterations were primarily isochromosomes, apparent terminal deletions, and unbalanced non-reciprocal translocations. Chromosomes I (10/18-56%) and 6 (8/18-44%) were most frequently altered in this series. Breakpoints of clonal structural abnormalities were shown to cluster to several chromosome segments, including 1p22-q11, 3p11, 6p11-13, 7p11-q11, 8p11-q11, and 19q13. Analysis of the gain or loss of specific chromosome segments revealed that the most consistent tendency was over-representation of 1q, 3q, and 6p.

Model for the interaction of DNA junctions and resolving enzymes

Four-way DNA junctions are thought to be important intermediates in a number of recombination processes. Resolution of these junctions occurs by cleavage of two strands of DNA to generate two duplex molecules. The interaction between DNA junctions and resolving enzymes appears to be largely structure-specific, reflecting a molecular recognition on a significant scale. We propose a working model for this interaction that takes account of the present state of knowledge of the structure of the DNA junction, and the substrate requirements of the enzymes. We note that three different enzymes introduce cleavages at phosphodiester bonds that are presented on one side of the molecule, suggesting that the enzymes selectively interact with this face of the junction. By forcing a junction of constant sequence to adopt one or other of the two possible antiparallel isomers, we show that the junction is cleaved in such a way as to suggest a constant mode of interaction with the protein that is dependent on structure rather than sequence. We propose that the feature that is recognized is a mutual inclination of two DNA helices at approximately 120 degrees. We show that a number of DNA substrates that contain similar inclined helices, such as a three-way junction, bulged duplexes and a duplex that is curved because of repeated runs of oligoadenine sequences, are each cleaved by phage T4 endonuclease VII. This mode of DNA-protein interaction could be significant in either recombination or DNA repair processes.

Design and testing of a disposable microfluidic chemiluminescent immunoassay for disease biomarkers in human serum samples

This paper presents the development of a plastic microfluidic immunosensor for rapid, reliable and on-the-spot detection of disease biomarkers in human sera. The microfluidic chips were fabricated in cyclic polyolefin by hot-embossing with a silicon master mold. The master itself was made using photolithographic techniques and Deep Reactive Ion Etching (DRIE). As a platform model, serum concentrations of C-reactive protein (CRP), a cardiac and inflammation marker, was measured on-chip using chemiluminescence based immunoassay. The assay results were read via an on-board instant photographic film, and with an imager capable of detecting chemiluminescent signals. The on-board detection module obviates the need for any dedicated bench-top analyzer for reading the immunoassay results, and therefore makes the device self-sufficient for point-of-care diagnostics when simple positive/negative results are sought. The microfluidic chemiluminescence results were compared with standard microplate ELISA analysis to assess the accuracy of the developed microfluidic immunoassay. Screening of CRP in human serum samples showed good correlation with ELISA analysis and the mean difference between the two methods using the Bland and Altman method was -0.079 +/- 0.858 mg/L for hsCRP. With approximate assay times of 25 min, the developed microfluidic immunoassay approach shows great potential for rapid plus sensitive detection of disease markers at the point-of-care.

Durability of new squamous epithelium after endoscopic reversal of Barrett's esophagus

BACKGROUND

Endoscopic reversal of Barrett's esophagus with multipolar electrocoagulation and high-dose omeprazole has been previously described but long-term results are not available. The aim of this study was to follow patients after endoscopic reversal and to perform a detailed analysis of the "new" squamous mucosa.

METHODS

After reversal, patients with Barrett's esophagus were maintained on high-dose omeprazole and underwent interval endoscopy, and large biopsies were obtained of the former Barrett's epithelium.

RESULTS

Nine of 11 patients were men; the mean age was 62 years. The mean length of Barrett's mucosa was 4.4 cm; the mean dose of omeprazole used was 49 mg/day. All patients had an initial complete response to treatment-no evidence of Barrett's endoscopically and histologically. Three patients had intestinal metaplasia underlying the new squamous mucosa in the latest follow-up biopsies. In these 3 patients, only 0.4%, 2%, and 8% of the total biopsy area had intestinal metaplasia. All but 4 patients had underlying intestinal metaplasia at variable times during the study period. Patients have been followed for a mean of 36 months (range 19 to 53 months).

CONCLUSIONS

New squamous mucosa is durable and resembles normal squamous tissue. Underlying glands of intestinal metaplasia are intermittently found. Because the significance of this residual intestinal metaplasia is unclear, surveillance endoscopy with biopsies of the treated segment is recommended even after reversal therapy.