Pathogenic soluble tau peptide disrupts endothelial calcium signaling and vasodilation in the brain microvasculature

The accumulation of the microtubule-associated tau protein in and around blood vessels contributes to brain microvascular dysfunction through mechanisms that are incompletely understood. Delivery of nutrients to active neurons in the brain relies on capillary calcium (Ca2+) signals to direct blood flow. The initiation and amplification of endothelial cell Ca2+ signals require an intact microtubule cytoskeleton. Since tau accumulation in endothelial cells disrupts native microtubule stability, we reasoned that tau-induced microtubule destabilization would impair endothelial Ca2+ signaling. We tested the hypothesis that tau disrupts the regulation of local cerebral blood flow by reducing endothelial cell Ca2+ signals and endothelial-dependent vasodilation. We used a pathogenic soluble tau peptide (T-peptide) model of tau aggregation and mice with genetically encoded endothelial Ca2+ sensors to measure cerebrovascular endothelial responses to tau exposure. T-peptide significantly attenuated endothelial Ca2+ activity and cortical capillary blood flow in vivo. Further, T-peptide application constricted pressurized cerebral arteries and inhibited endothelium-dependent vasodilation. This study demonstrates that pathogenic tau alters cerebrovascular function through direct attenuation of endothelial Ca2+ signaling and endothelium-dependent vasodilation.

Quantifying whole bladder biomechanics using the novel pentaplanar reflected image macroscopy system

Optimal bladder compliance is essential to urinary bladder storage and voiding functions. Calculated as the change in filling volume per change in pressure, bladder compliance is used clinically to characterize changes in bladder wall biomechanical properties that associate with lower urinary tract dysfunction. But because this method calculates compliance without regard to wall structure or wall volume, it gives little insight into the mechanical properties of the bladder wall during filling. Thus, we developed Pentaplanar Reflected Image Macroscopy (PRIM): a novel ex vivo imaging method to accurately calculate bladder wall stress and stretch in real time during bladder filling. The PRIM system simultaneously records intravesical pressure, infused volume, and an image of the bladder in five distinct visual planes. Wall thickness and volume were then measured and used to calculate stress and stretch during filling. As predicted, wall stress was nonlinear; only when intravesical pressure exceeded ~ 15 mmHg did bladder wall stress rapidly increase with respect to stretch. This method of calculating compliance as stress vs stretch also showed that the mechanical properties of the bladder wall remain similar in bladders of varying capacity. This study demonstrates how wall tension, stress and stretch can be measured, quantified, and used to accurately define bladder wall biomechanics in terms of actual material properties and not pressure/volume changes. This method is especially useful for determining how changes in bladder biomechanics are altered in pathologies where profound bladder wall remodeling occurs, such as diabetes and spinal cord injury.

Pathogenic soluble tau peptide disrupts endothelial calcium signaling and vasodilation in the brain microvasculature

The accumulation of the microtubule-associated tau protein in and around blood vessels contributes to brain microvascular dysfunction through mechanisms that are incompletely understood. Delivery of nutrients to active neurons in the brain relies on capillary inositol 1,4,5-triphosphate receptor (IP3R)-mediated calcium (Ca2+) signals to direct blood flow. The initiation and amplification of endothelial cell IP3R-mediated Ca2+ signals requires an intact microtubule cytoskeleton. Since tau accumulation in endothelial cells disrupts native microtubule stability, we reasoned that tau-induced microtubule destabilization would impair endothelial IP3-evoked Ca2+ signaling. We tested the hypothesis that tau disrupts the regulation of local cerebral blood flow by reducing endothelial cell Ca2+ signals and endothelial-dependent vasodilation. We used a pathogenic soluble tau peptide (T-peptide) model of tau aggregation and mice with genetically encoded endothelial Ca2+ sensors to measure cerebrovascular endothelial responses to tau exposure. T-peptide significantly attenuated endothelial Ca2+ activity and cortical capillary blood flow in vivo within 120 seconds. Further, T-peptide application constricted pressurized cerebral arteries and inhibited endothelium-dependent vasodilation. This study demonstrates that pathogenic tau alters cerebrovascular function through direct attenuation of endothelial Ca2+ signaling and endothelium-dependent vasodilation.

Plasma-based assays distinguish hyperfibrinolysis and shutdown subgroups in trauma-induced coagulopathy

BACKGROUND

Trauma patients with abnormal fibrinolysis have increased morbidity and mortality. Knowledge of mechanisms differentiating fibrinolytic phenotypes is important to optimize treatment. We hypothesized that subjects with abnormal fibrinolysis identified by whole blood viscoelastometry can also be distinguished by plasma thrombin generation, clot structure, fibrin formation, and plasmin generation measurements.

METHODS

Platelet-poor plasma (PPP) from an observational cross-sectional trauma cohort with fibrinolysis shutdown (% lysis at 30 minutes [LY30] < 0.9, n = 11) or hyperfibrinolysis (LY30 > 3%, n = 9) defined by whole blood thromboelastography were studied. Noninjured control subjects provided comparative samples. Thrombin generation, fibrin structure and formation, and plasmin generation were measured by fluorescence, confocal microscopy, turbidity, and a fluorescence-calibrated plasmin assay, respectively, in the absence/presence of tissue factor or tissue plasminogen activator (tPA).

RESULTS

Whereas spontaneous thrombin generation was not detected in PPP from control subjects, PPP from hyperfibrinolysis or shutdown patients demonstrated spontaneous thrombin generation, and the lag time was shorter in hyperfibrinolysis versus shutdown. Addition of tissue factor masked this difference but revealed increased thrombin generation in hyperfibrinolysis samples. Compared with shutdown, hyperfibrinolysis PPP formed denser fibrin networks. In the absence of tPA, the fibrin formation rate was faster in shutdown than hyperfibrinolysis, but hyperfibrinolysis clots lysed spontaneously; these differences were masked by addition of tPA. Tissue plasminogen activator-stimulated plasmin generation was similar in hyperfibrinolysis and shutdown samples. Differences in LY30, fibrin structure, and lysis correlated with pH.

CONCLUSION

This exploratory study using PPP-based assays identified differences in thrombin generation, fibrin formation and structure, and lysis in hyperfibrinolysis and shutdown subgroups. These groups did not differ in their ability to promote tPA-triggered plasmin generation. The ability to characterize these activities in PPP facilitates studies to identify mechanisms that promote adverse outcomes in trauma.

LEVEL OF EVIDENCE

Prognostic/Epidemiological; Level III.

Multimodal evoked potential monitoring in asleep patients versus neurological evaluation in awake patients during carotid endarterectomy: a single-centre retrospective trial of 651 patients

BACKGROUND

A controversy exists regarding which monitoring technique is superior in cases in which general anesthesia (GA) is necessary for carotid endarterectomy (CEA). Multimodal evoked potential (mEP) monitoring was investigated under GA during CEA and compared with a historical control group undergoing neurological evaluations awake under loco-regional anesthesia (LA).

METHODS

We retrospectively studied 651 patients undergoing elective CEA. In groupHISTORY (N.=349; 1997-1999) LA was provided using superficial or deep/superficial cervical plexus blocks. In groupmEP, (N.=302; 2009-2013) GA was performed by administering remifentanil/propofol infusion. The multimodal EPs included the median-nerve-somatosensory and motor evoked potentials. The primary outcome was the rate of technical failure. The arterio-arterial shunt rate and immediate postoperative motor outcomes were also compared.

RESULTS

GroupmEP showed a significantly lower rate of technical failure (OR 0.17; CI 0.03-0.6; P=0.002). Because the groups differed systematically, logistic regression analysis was used to compare shunt rates and motor outcomes. Since shunt rates were 8.3% (groupmEP) versus 8.2% (groupHISTORY), but logistic regression model showed significant differences (OR 3.77; CI 1.67-8.95; P=0.001) correct comparison was impossible. Immediate postoperative deficits were 4.3% (groupmEP) and 4.9% (groupHISTORY); logistic regression analysis: transient OR 0.77, CI 0.28 to 0.22, P=0.61 and permanent OR 0.37, CI 0.02-7.74, P=0.49.

CONCLUSION

Monitoring mEPs was associated with less technical failure than awake evaluation and showed similar motor outcomes. Because the groups differed systematically, the interpretation of shunt rates was impossible. Monitoring mEP should be considered to detect intraoperative ischemia in cases in which patients undergo CEA under GA.

Kit signaling is required for development of coordinated motility patterns in zebrafish gastrointestinal tract

Interstitial cells of Cajal (ICC) provide a pacemaker signal for coordinated motility patterns in the mammalian gastrointestinal (GI) tract. Kit signaling is required for development and maintenance of ICC, and these cells can be identified by Kit-like immunoreactivity. The zebrafish GI tract has two distinct ICC networks similar to mammals, suggesting a similar role in the generation of GI motility; however, a functional role for Kit-positive cells in zebrafish has not been determined. Analysis of GI motility in intact zebrafish larvae was performed during development and after disruption of Kit signaling. Development of coordinated motility patterns occurred after 5 days post-fertilization (dpf) and correlated with appearance of Kit-positive cells. Disruptions of Kit signaling using the Kit antagonist imatinib mesylate, and in Sparse, a null kita mutant, also disrupted development of coordinated motility patterns. These data suggest that Kit signaling is necessary for development of coordinated motility patterns and that Kit-positive cells in zebrafish are necessary for coordinated motility patterns.

Temporal relationships between wall motion, intraluminal pressure, and flow in the isolated rabbit small intestine

Intraluminal manometry is a tool commonly used to record motility in the human digestive tract. The recorded signal results from a combination of factors, including the hydrodynamic pressure transmitted through the intestinal contents due to contraction of the gut wall and the force of the gut wall acting on the sensors in regions of a luminal occlusion. However, the actual relationships between small bowel wall contraction, the measured intraluminal pressure, and the resultant flow have not been directly addressed. Video recording and high-resolution fiber-optic manometry were used to create spatiotemporal video maps of diameter and intraluminal pressure from isolated segments of rabbit small intestine. In the unstimulated gut, longitudinal muscle contractions were the only detectable motor pattern; circular muscle contractions were elicited by distension or erythromycin (1 μM). Longitudinal muscle contractions were not lumen-occlusive, although they caused measurable low-amplitude changes in pressure. Localized nonpropagating circular muscle contractions caused small localized, nonpropagating peaks of intraluminal pressure. Propagating contractions of circular muscle evoked larger, propagating pressure changes that were associated with outflow. Propagating circular muscle contractions often caused dilation of aboral receiving segments, corresponding to "common cavities"; these were propulsive, despite their low intraluminal pressure. The highest-amplitude pressure events were caused by lumen-occlusive circular muscle contractions that squeezed directly against the catheter. These data allow us to define the complex relationships between wall motion, intraluminal pressure, and flow. A strong correlation between circular and longitudinal muscle contraction and intraluminal pressure was demonstrated. Common-cavity pressure events, caused by propulsion of content by circular muscle contractions into a receptive segment, were often of low amplitude but were highly propulsive. Studies of wall motion in isolated preparations, combined with manometry, can assist in interpretation of pressure recordings in vivo.

Abstract P3-10-07: T5 Is a New Molecular Predictor of Distant Recurrence in Estrogen Receptor-Positive, HER2-Negative Breast Cancer

Background: Molecular tests predicting outcome of breast cancer patients may be useful for treatment decisions in addition to standard clinicopathologic features.

Methods: Using human genome HG-U133A array and qRT-PCR datasets, we developed and validated a gene-expression signature predicting the likelihood of distant recurrence in postmenopausal, early-stage breast cancer patients with estrogen receptor-positive, HER2-negative tumors treated with adjuvant endocrine therapy. RNA levels assessed by qRT-PCR in formalin-fixed paraffin-embedded tumor specimens were used to calculate a risk score (T5) and to determine a risk group (low or high) for each patient. The prospectively defined T5 risk score was then validated independently in patients from two large randomized phase III trials. Distant recurrence-free survival and overall survival were analyzed with Cox models adjusted for clinicopathological factors. The primary endpoint was time to distant recurrence.

Results: In a training set of 964 tumors, we identified a gene-expression signature consisting of three proliferation-related genes (BIRC5, UBE2C, DHCR7), five estrogen-regulated genes (RBBP8, IL6ST, AZGP1, MGP, STC2), and three reference genes (CALM2, OAZ1, RPL37A). For the validation, RNA analysis was possible in 1702 of 1725 (99%) tumors of both validation sets. Women were classified as having low risk (n=832; 49%) or high risk (n=870; 51%) by the T5 risk score. The T5 risk score provided prognostic information independent from clinicopathologic risk as estimated by Adjuvant!Online or Ki67 labeling index. Patients with a higher T5 risk score had a significantly shorter time to distant recurrence (adjusted hazard ratio, 1.24; 95% confidence interval [CI], 1.15 to 1.33; P&lt;0.001) and overall survival (adjusted hazard ratio, 1.13; 95% CI, 1.06 to 1.19; P&lt;0.001) compared to patients with a lower T5 risk score. The addition of the risk characterized by the T5 risk score to the clinicopathological risk resulted in 10-year distant recurrence-free survival rates of 95% in combined low risk patients and 82% in combined high risk patients (P&lt;0.001).

Conclusions: Using formalin-fixed paraffin-embedded tumor specimens, the multigene T5 risk score provides prognostic information independent of Adjuvant!Online or Ki67 labeling index. By combining the T5 risk score with clinicopathological risk, we were able to accurately identify breast cancer patients with low risk or high risk for distant recurrence. Using this new easy-to-use multigene tool in clinical practice will assist in optimizing adjuvant therapy by reducing both undertreatment and overtreatment and thus improves outcome and quality of life of patients with early-stage breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-07.

Expression of anoctamin 1/TMEM16A by interstitial cells of Cajal is fundamental for slow wave activity in gastrointestinal muscles

Interstitial cells of Cajal (ICC) generate pacemaker activity (slow waves) in gastrointestinal (GI) smooth muscles, but the mechanism(s) of pacemaker activity are controversial. Several conductances, such as Ca(2+)-activated Cl() channels (CaCC) and non-selective cation channels (NSCC) have been suggested to be involved in slow wave depolarization. We investigated the expression and function of a new class of CaCC, anoctamin 1 (ANO1), encoded by Tmem16a, which was discovered to be highly expressed in ICC in a microarray screen. GI muscles express splice variants of the Tmem16a transcript in addition to other paralogues of the Tmem16a family. ANO1 protein is expressed abundantly and specifically in ICC in all regions of the murine, non-human primate (Macaca fascicularis) and human GI tracts. CaCC blocking drugs, niflumic acid and 4,4-diisothiocyano-2,2-stillbene-disulfonic acid (DIDS) reduced the frequency and blocked slow waves in murine, primate, human small intestine and stomach in a concentration-dependent manner. Unitary potentials, small stochastic membrane depolarizations thought to underlie slow waves, were insensitive to CaCC blockers. Slow waves failed to develop by birth in mice homozygous for a null allele of Tmem16a (Tmem16a(tm1Bdh)(/tm1Bdh)) and did not develop subsequent to birth in organ culture, as in wildtype and heterozygous muscles. Loss of function of ANO1 did not inhibit the development of ICC networks that appeared structurally normal as indicated by Kit antibodies. These data demonstrate the fundamental role of ANO1 in the generation of slow waves in GI ICC.

Quantitative determination of predictive cancer biomarkers in formalin-fixed, paraffin-embedded tissue using a new, fully automated method for RNA isolation

11032

Background: Personalized cancer therapy depends on the evaluation of tissue-based biomarkers in routine tumor samples. As many new biomarkers are measured on the mRNA level, standardized procedures for mRNA analysis in formalin-fixed, paraffin-embedded (FFPE) tissue are needed. In this study, we present a novel, standardized, and fully automated method for fast isolation of total RNA from FFPE tissue sections. Methods: Tissue samples (n = 501) from 167 breast carcinomas which had been stored between 2 months and 21 years were investigated. Total RNA was extracted from tissue sections using a new method based on silica-coated iron oxide beads in combination with a specific liquid-handling robot. Novel and unique features of the method are an automated extraction-integrated deparaffinization step and a bead-based negative selection step to eliminate any undigested tissue. Yield of RNA was assessed using the Ribogreen assay. mRNA fragment lengths were estimated by reverse transcription PCR (RT-PCR) for G6PDH. Expression of the breast cancer biomarkers ESR1, PGR and HER2 was measured by kinetic RT-PCR (kPCR) and compared with immunohistochemistry (IHC). Results: RNA was successfully isolated from all samples, with a mean yield of 1.4 μg/sample (range: 0.1–7.8 μg) and fragment lengths of at least 150 bp in 99% of samples. PCR analyses could be performed in all samples. Investigating three sections of each tumor, we observed a low section-to-section variability of kPCR results (root of mean squared errors of relative ESR1, PGR or HER2 expression in three sections: 0.2–0.5 Ct values). Comparing kPCR results with IHC, we detected a good concordance between both methods, with agreements of 98.4% (standard error [SE]: 2.7%) for ESR1, 84.4% (SE: 5.3%) for PGR and 89.9% (SE: 8.9%) for HER2. Conclusions: This novel RNA extraction method is a major technical improvement for implementation of reproducible, high-throughput and cost-efficient testing of cancer biomarkers in the clinical routine and in gene-expression research studies using archived FFPE material in molecular labs.

[Table: see text]

Utility of a multigene prognostic algorithm in combination with TP53 expression for prediction of benefit from adjuvant taxane-containing chemotherapy in node-positive breast cancer patients

593

Background: Recently, we have shown that the Siemens Prognostic Score (SPS) based on mRNA expression of nine informative genes predicted outcome in node-positive (N+) patients with breast cancer (SABCS 2008, abstract 6044). The aim of this retrospective biomarker study was to examine the utility of the SPS in combination with TP53 expression to predict benefit from adjuvant taxane therapy. Methods: The 211 N+ patients included in this study were treated in the context of a randomized two-arm phase III study (E-T-CMF vs. E-CMF) investigating adjuvant dose-dense sequential chemotherapy with epirubicin (E) followed by CMF with or without paclitaxel (T). RNA was isolated from formalin-fixed, paraffin-embedded tissue samples, using a Siemens proprietary method, followed by kinetic one-step RT-PCR for assessment of mRNA expression of the nine SPS genes, TP53 and two normalization genes. The continuous SPS was calculated using a linear combination of expression values of the SPS genes. Patients were separated into a high- and low-risk group using a cutoff at the median of the SPS. Optimal cutoff for low or high TP53 expression was defined on the basis of a ROC curve in SPS high-risk patients. Distant metastasis-free survival (MFS) and overall survival (OS) were estimated by the Kaplan-Meier method and compared using the log-rank test. Results: For patients with high SPS or high TP53 expression, we observed a trend for a better MFS in the E-T-CMF arm (SPS: p = 0.18; HR = 0.66; TP53: p = 0.23; HR = 0.67; n = 211). Combining both parameters, patients with high SPS and high TP53 expression (n = 44) had a significantly better MFS following E-T-CMF compared to E-CMF (5-year MFS 80% vs. 40%, p = 0.003, HR = 0.21; OS: p = 0.09; HR = 0.34). On the other hand, patients with high SPS and low TP53 expression (n = 32) showed a trend for a worse outcome with E-T-CMF (MFS: p = 0.09; HR = 3.54; OS: p = 0.35, HR = 1.90). Conclusions: Our prognostic algorithm combined with TP53 mRNA expression predicts the benefit from the addition of paclitaxel to E-CMF and might be used for identification of patients who should be considered for adjuvant taxane therapy. This hypothesis needs to be confirmed in an independent clinical study.

[Table: see text]

Elevated mRNA expression of herstatin predicts poor outcome in patients with high-risk early breast cancer. A possible molecular predictor of treatment benefit in the context of a Hellenic cooperative oncology group trial

Abstract #6066

Background: Herstatin is a naturally occurring product of the HER2 gene generated by alternative mRNA splicing. It functions as a secreted inhibitor that binds to the extracellular domains of EGFR and HER2, disrupting multiple receptor combinations in response to a variety of ligands. This mode of action supports the potential utility of herstatin in the development of novel therapeutics against breast cancer. The aim of the present study was to evaluate the association of herstatin with HER family expression at the m-RNA level, as well as with other clinicopathological characteristics of patients with high-risk operable breast cancer enrolled in a randomized phase III trial. The effect of herstatin on disease-free survival (DFS) and overall survival (OS) was also investigated.&#x2028; Patients and Methods: 595 high-risk breast cancer patients were treated with anthracycline-based chemotherapy in the adjuvant setting (HE10/97 trial). This was a two-arm trial (E-CMF vs. E-T-CMF) investigating postoperative dose-dense sequential chemotherapy with epirubicin (E) followed by CMF with or without paclitaxel (T). RNA was extracted from 279 formalin-fixed paraffin-embedded tumor tissue samples followed by kinetic one-step RT-PCR for assessment of mRNA expression of herstatin, EGFR, HER2, HER3, and HER4. Values of RNA above the median were considered as positive expression, except for EGFR, where the 75th percentile was used as a cut-off. DFS and OS were estimated by the Kaplan-Meier method and compared using the log-rank test. Cox analysis for DFS and OS was also performed.&#x2028; Results: Positive herstatin expression was found to be significantly associated with ductal histology (χ2 test, p=0.004), and marginally associated with infiltrated lymph nodes (p=0.062). Furthermore, herstatin was found to be strongly correlated with HER2 expression (r=0.783, p&lt;0.001) and weakly correlated with HER3 expression (r=0.144, p=0.02). Positive herstatin expression was associated with poor DFS and OS (log-rank, p=0.004 and 0.008, respectively). This remained unchanged when adjusted for treatment group, whereas no interaction between herstatin and treatment was identified. Interaction of HER2 overexpression (&gt;75th percentile) with herstatin was found to be significant for OS (Wald, p=0.03), thus implying a possible prophylactic effect of herstatin in the subgroup of patients with HER2 overexpression.&#x2028; Conclusions: Herstatin was shown to be associated with a poor prognosis. Given the high correlation between herstatin and HER2, this finding may reflect the effect of HER2 on patient's prognosis. Our results suggest that the effect of herstatin may be altered in case of HER2 overexpression. This hypothesis should be investigated in future studies, focusing in patients with HER2 overexpression.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6066.

Comparative expression profiling with kinetic RT-PCR in paired fresh frozen and archived formalin-fixed, paraffin-embedded renal cell cancer and normal tissue

4606

Background: It would be a substantial progress if gene expression of tumor markers could be accurately analyzed on RNA isolated from formalin fixed paraffin-embedded (FFPE) tumor tissue which is routinely collected. To prove equivalence between fresh frozen and archived FFPE tissue RNA profiles, we quantified 12 different genes with kinetic RT-PCR in renal tumor and paired adjacent normal tissue archived for 8–14 years. Methods: We had access to a set of 32 clear cell renal cell cancers and its adjacent normal tissue (HELIOS Clinic, Wuppertal). Each sample existed as a FFPE tissue block and as paired fresh frozen tissue both stored over 8–14 years at RT or -80oC, respectively. RNA from FFPE tissue was isolated with a Bayer HealthCare internal silica bead-based isolation method. Each sample was analyzed with kinetic one-step RT-PCR for the gene expression of 3 housekeepers (RPL37A, GAPDH, CD63) and 9 candidate genes (EGFR, Her2/neu, Her3, Her4, EGF, TGFα, NRG1, HIF1α, VEGFα). Results: The comparative FFPE/fresh frozen expression data showed a good correlation over all data points (r = 0.87 for Ct values) and the tumor specific up- and down regulation of EGFR family genes and its ligands could be detected in both tissue types equally. We could clearly demonstrate the tumor specific up-regulation of EGFR (2-fold), TGFα (2-fold), VEGFα (4-fold) and down-regulation of EGF (60-fold), Her2/neu (4-fold), Her3 (2-fold) and Her4 (30-fold) in renal cell cancer for both tissue entities (fixed and fresh frozen). In addition a 3-dimensional Principal Component Analysis completely separated the renal tumor population from paired normal tissue in both tissue entities based on the differential gene expression. Conclusions: Here we demonstrate that a small set of genes from the EGFR family and their ligands is specifically up-/down-regulated in renal cell cancer tissue and therefore can be clearly distinguished from normal renal tissue. Furthermore, these data prove that the internal Bayer HealthCare isolation/kinetic RT-PCR detection protocol for RNA from FFPE tissue allows accurate retrospective expression profiling and validation of marker panels in archived tissue material stored for more than a decade.

[Table: see text]

Mechanical activation of rectal intraganglionic laminar endings in the guinea pig distal gut

The rectum receives specialized extrinsic afferent innervation by stretch-sensitive, low threshold, slowly adapting mechanoreceptors, with transduction sites shown to correspond to rectal intraganglionic laminar endings (IGLEs). Rectal IGLEs are located in myenteric ganglia, surrounded by the longitudinal and circular smooth muscle layers; in this study we investigated the mechanical stimuli to which they respond. Mechanoreceptors had graded responses to highly focal transmural compression with von Frey hairs. They were activated when stretched circumferentially by imposed increases of both length and load. Under both conditions, firing typically occurred in bursts associated with phasic muscle contractions. However, many contractions did not evoke firing. Longitudinal stretch also evoked firing, again associated with contractile activity. Thus, mechanoreceptors did not show directional sensitivity. Two agonists that excited smooth muscle directly (0.1 microm [beta-Ala(8)]-neurokinin A (4-10) and 1 microm carbachol) activated rectal mechanoreceptors, but not in the presence of Ca(2)(+)-free solution or when preparations were kept entirely slack. We measured the dimensions, in both longitudinal and circumferential axes, of receptive fields during smooth muscle contractile activity, using video micrography. Contractile activity within the receptive field often differed significantly from the behaviour of the preparation as a whole, providing an explanation for many of the discrepancies between gross contractility and firing. Simultaneous contraction of both muscle layers within the receptive field was the strongest predictor of mechanoreceptor activation. Our results suggest that rectal mechanoreceptors do not act simply as tension receptors: rather they appear to detect mechanical deformation of myenteric ganglia - especially flattening - associated with stretch of the receptive field, or contractions of smooth muscle within the receptive field.

Video-based spatio-temporal maps for analysis of gastric motility in vitro: effects of vagal stimulation in guinea-pigs

Our aim was to evaluate topographically specific gastric motility changes induced by graded vagal activation. A recently developed method of constructing spatio-temporal maps of motility from video movies was adapted to the in vitro perfused guinea-pig stomach with an intact vagal nerve supply. In the unstimulated preparation, spontaneous activity was low or absent. Bilateral vagal stimulation with frequencies as low as 0.2 Hz triggered weak anally, and in some cases orally, propagating antral contractions at rates of about 5-6 min-1. Upon stimulation with higher frequencies, antral contractions increased significantly in length (starting more proximally) and amplitude, and produced large pressure peaks of up to 25 hPa, with maximal effects at 2-4 Hz. In contrast, the speed of propagation and the interval between peristaltic waves did not change with vagal stimulation at any frequency. Vagal stimulation also produced a significant and frequency-dependent enlargement of the fundus with a maximal effect at 4 Hz. It is concluded that a very low tonic vagal activity is apparently necessary and sufficient to express basic antral motility, while more sustained vagal activity is necessary for high-amplitude gastric contractions and significant sustained fundic relaxation. The constant interval between propagating contractions supports the concept that vagal input impinges on intrinsic enteric neural circuits that have a modulatory role in the myogenic mechanism underlying slow-wave peristalsis, rather than directly on gastric musculature.

Somatostatin sst(2) receptors inhibit peristalsis in the rat and mouse jejunum

Somatostatin [somatotropin release-inhibitory factor (SRIF)] has widespread actions throughout the gastrointestinal tract, but the receptor mechanisms involved are not fully characterized. We have examined the effect of selective SRIF-receptor ligands on intestinal peristalsis by studying migrating motor complexes (MMCs) in isolated segments of jejunum from rats, mice, and sst(2)-receptor knockout mice. MMCs were recorded in 4- to 5-cm segments of jejunum mounted horizontally in vitro. MMCs occurred in rat and mouse jejunum with intervals of 104.4 +/- 10 and 131.2 +/- 8 s, respectively. SRIF, octreotide, and BIM-23027 increased the interval between MMCs, an effect fully or partially antagonized by the sst(2)-receptor antagonist Cyanamid154806. A non-sst(2) receptor-mediated component was evident in mouse as confirmed by the observation of an inhibitory action of SRIF in sst(2) knockout tissue. Blocking nitric oxide generation abolished the response to SRIF in rat but not mouse jejunum. sst(2) Receptors mediate inhibition of peristalsis in both rat and mouse jejunum, but a non-sst(2) component also exists in the mouse. Nitrergic mechanisms are differentially involved in rat and mouse jejunum.

Ribose cysteine protects against acetaminophen-induced hepatic and renal toxicity

Ribose cysteine (RibCys) is a cysteine prodrug that increases both hepatic and renal glutathione with documented antagonism of acetaminophen (APAP)-induced hepatotoxicity. To determine if RibCys could also protect against APAP-induced kidney damage, mice were injected with APAP (600 mg/kg) or APAP and RibCys (1.0 g/kg) (APAP/RIB) followed by additional RibCys injections 1 and 2 hours later. Mice were euthanatized 10-12 hours after APAP administration, and liver and kidney toxicity were assessed by plasma sorbitol dehydrogenase (SDH) activity and blood urea nitrogen (BUN), respectively, and by histopathology. APAP treatment resulted in elevation of SDH activity and BUN to 2,490 U/ml and 47 mg/dl, respectively. By contrast, SDH and BUN values for APAP/RIB-treated mice were not different from controls, 0 U/ml and 31 mg/dl, respectively. Histopathologic examination revealed moderate to severe hepatic centrilobular necrosis in 9/11 and renal proximal tubular necrosis in 10/11 APAP-treated mice. However, no evidence of hepatic or renal toxicity was noted in any of the 12 APAP/RIB-treated mice. Utilizing the same treatment regimen, APAP covalent binding to hepatic and renal cytosolic proteins was assessed 4 hours after APAP challenge. RibCys cotreatment decreased covalent binding to the 58-kDa acetaminophen-binding protein in both liver and kidney. RibCys decreased both toxicity and covalent binding after APAP administration, and in addition to protecting the liver, this cysteine prodrug can also effectively protect the kidney from APAP-induced injury.

Identification of motor neurons to the circular muscle of the guinea pig gastric corpus

The projections of enteric neurons to the circular muscle of the guinea pig gastric corpus were investigated systematically by using the retrogradely transported fluorescent carbocyanine dye 1,1'-didodecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI), applied to the muscle layer or myenteric plexus in vitro. DiI-labeled motor neuron cell bodies were located up to 6.3 mm aboral, 17 mm oral, and up to 20 mm circumferential to the DiI application site. Labeled nerve fibers ran for long distances from the DiI application site toward the greater and lesser curvatures, where they coursed parallel to the bundles of the "gastric sling" muscle. The majority of labeled cells were located toward the lesser curvature of the stomach. Nerve cell bodies that were aboral to the DiI application site were usually small, immunoreactive for choline acetyltransferase, and, thus, were likely to be excitatory motor neurons. Neurons that were located orally were larger, fewer in number, and immunoreactive for nitric oxide synthase and, thus, were likely to be inhibitory motor neurons. Application of DiI directly to the myenteric plexus filled neurons up to 15 mm aborally and up to 21 mm orally but labeled few neurons circumferentially. All nerve cells that were filled from either the circular muscle or the myenteric plexus had Dogiel type I morphological features. These results demonstrate a clear polarity of projection of inhibitory and excitatory motor neurons and a functionally continuous innervation of the circular and gastric sling muscle layers. Nonmotor neurons in the myenteric plexus were demonstrated, but neurons with Dogiel type II morphological features are apparently absent.

Mechanisms identified in the transcriptional control of epithelial gene expression

Epithelium-specific gene expression is fundamental in both embryogenesis and the maintenance of adult tissues, and impairment of epithelial characteristics contributes to diseases such as cancer. We have here analyzed the 5'-region of the epithelial (E-) cadherin gene in order to understand mechanisms of epithelium-specific transcription and loss of expression during epithelial-mesenchymal transitions. The regulatory region of the mouse epithelial cadherin gene is composed of a promoter (from position -94 to the transcription start site) and a 150-base pair enhancer located in the first intron. The 5'-promoter consists of positive regulatory elements (a CCAAT-box and two AP-2 binding sites in a GC-rich region) and the palindromic element E-Pal that activates and represses transcription in epithelial and mesenchymal cells, respectively. The enhancer of the first intron stimulates the activity of heterologous promoters exclusively in epithelial cells. This epithelium-specific enhancer consists of three elements (E I to E III; E II and E III bind AP-2) that are necessary and sufficient for activity. We thus propose two regulatory mechanisms by which epithelial specificity of epithelial cadherin expression is determined: suppression of promoter activity in mesenchymal cells by E-Pal and enhancement of activity in epithelial cells by both E-Pal and the epithelium-specific enhancer.

Progression of carcinoma cells is associated with alterations in chromatin structure and factor binding at the E-cadherin promoter in vivo

E-cadherin has been identified as a tumor (invasion) suppressor gene, which is mutated in 50% of diffuse-type human gastric carcinomas. In other carcinomas, the expression of E-cadherin is down-regulated in the poorly differentiated cells such as from breast, bladder, lung and colon. We have here examined the in vivo properties of the genomic E-cadherin promoter in well and poorly differentiated carcinoma cell lines in order to gain insights into the mechanisms of E-cadherin down-regulation in tumors. In vivo footprinting analysis revealed that positive regulatory elements of the E-cadherin promoter (a GC-rich region, the CCAAT-box and a palindromic element) are specifically bound by transcription factors in E-cadherin-expressing but not in non-expressing cells. The tested cell systems include more than a dozen carcinomas cell lines as well as mammary epithelial cells where E-cadherin expression can be switched off by activation of a Fos-estrogen receptor fusion protein and rhabdomyosarcoma cells where E-cadherin expression was induced by transfection with E1A. Mapping of DNase I hypersensitive sites showed that the chromatin structure in the promoter region is loosened in expressing but condensed in non-expressing cells. Furthermore, the endogenous E-cadherin promoter is specifically methylated at CpG sites in the undifferentiated cells. We also show that the in vivo properties of the promoter in E-caherin-negative carcinoma cells are similar as in mesenchymal cells, i.e. fibroblasts or sarcoma cells. These data suggest that silencing of the E-cadherin promoter during epithelialmesenchymal transition and tumor progression is due to a loss of factor binding in vivo and to chromatin rearrangement in the regulatory region.

Transcriptional activation and transformation by chimaeric Fos-estrogen receptor proteins: altered properties as a consequence of gene fusion

We have generated a series of conditionally active Fos and FosB proteins by fusion with a C-terminal fragment of the human estrogen receptor (ER) which harbours the ligand binding site and the overlapping hormone-inducible transactivation domain TAF-2. The chimaeric Fos-ER proteins showed estrogen-inducible activation of TRE (TPA-responsive element)-directed transcription and hormone-dependent transformation of fibroblasts. These properties of the fusion proteins were independent of the transregulatory and transforming properties of their normal non-fused counterparts c-Fos, v-Fos, FosB-L and FosB-S. Thus c-Fos-ER and FosB-S-ER were strong transforming proteins in the presence of hormone, although c-Fos and FosB-S possess only marginal oncogenic properties. In addition, all fusion proteins showed increased transactivation in the presence of estrogen, again most noticeable in the case of c-Fos-ER and FosB-S-ER. The ER-fusion thus basically eliminated the differences in the transactivating potential seen among the various native Fos proteins. Our data therefore provide evidence: (i) that the hormone binding domain of the human estrogen receptor, apart from delivering hormonal control to a heterologous protein, can have profound effects on the activity of certain transcription factors, particularly on proteins with weak oncogenic and/or transregulatory potential, and (ii) that the transforming potential of c-Fos and FosB-S can be dramatically elevated by increasing their transactivating properties.

Non-leucine residues in the leucine repeats of Fos and Jun contribute to the stability and determine the specificity of dimerization

Various transcription factors, including C/EBP, GCN4 and members of the Fos, Jun and Myc families have been shown to form highly specific complexes via alpha-helical structures referred to as leucine zippers. Experimental evidence has suggested that dimerization involves the formation of hydrophobic bonds between leucine residues in laterally aligned coiled coil structures. However, the specificity of interaction between leucine zipper proteins is not understood. In this study, we show that amino acids, which are located in positions a, e, and g are instrumental in the formation of Fos/Jun heterodimers, presumably by establishing intermolecular electrostatic and hydrophobic interactions. These residues are highly conserved in proteins of the Fos or Jun families but completely different between Fos and Jun, suggesting that these residues determine the specificity of interaction. This conclusion is supported by the observation that the substitution of amino acids in position a or g in Fos with the corresponding Jun amino acids facilitates the association of two Fos leucine repeats. In addition, we show that a conserved histidine residue, located 7 amino acids (i.e., two alpha-helical turns) C-terminally to the 5th leucine in Fos and Jun, is also important for complex formation.

[Transscleral magnetic fixation of the retina in complicated retinal detachment. A preliminary report of our experiences]

The authors describe a new technique for transscleral fixation of a detached retina. A small metal pin is brought into contact with the surface of the retina and is held in position by an extraocular magnet. This technique has been used successfully on three patients with giant tears and with large retinotomies as a preparation for silicone oil injection. In comparison with other fixation methods it was found to be relatively easy, and the incidence of trauma was low.

Technique and results of the colonic conduit, continent by means of a new magnetic stoma seal an experimental study

On the basis of satisfactory results with a new magnetic stoma seal in colostomy patients this seal, consisting of a magnetic ring and cap, was used in an experimental study to convert the colonic conduit into a continent reservoir. Complete continence was obtained in all of the 12 animals which survived the operation. All rings were well accepted by the tissue when the procedure was staged by implanting the ring transperitoneally several weeks prior to fashioning of the conduit. Residual urine was low, owing to an ideal energy-balance pattern. Coloureteric reflux was successfully prevented in all cases where a long-tunnel-modification of the Leadbetter-Clarke technique was used. Hyperchloraemic acidosis and deterioration in renal function were not observed. All conduits were infected.

[Technique and results of the colon conduit, continent by means of a new magnetic stoma seal. An animal experiment study. Enterocystoplasty as model of continent urinary diversion. Review and comparison of the results of colocystoplasty, coloprostatoplasty and colourethroplasty (authors transl)]

On the basis of satisfactory results with a new magnetic stoma seal in colostomy patients, this seal, consisting of a magnetic ring and cap, was used in an experimental study to convert the colonic conduit into a continent reservoir. The aim of the study, involving 16 dogs, was to find a method of ring implantation that would avoid infection of the ring and yield complete continence in a higher percentage than had been achieved so far in patients. Complete continence was obtained in all animals but there was a 75% incidence of immediate and delayed infection of the magnetic ring when the ring was inserted transcutaneously. In contrast, all rings were well accepted by the tissue when the procedure was staged with the ring being implanted transperitoneally several weeks prior to fashioning of the conduit. The general problems arising from the colonic conduit when used as continent reservoir are known from the results of colocystoplasty, coloprostatoplasty and colourethroplasty, which are reviewed and compared with our observations. Residual urine was low due to an ideal energy-balance pattern. Coloureteric reflux was successfully prevented in all cases operated on by a long-tunnel modification of the Leadbetter-Clarke technique. Hyperchloremic acidosis and renal function deterioration were not observed. All conduits were infected.

The influence of insulin on glucose and fatty acid metabolism in the isolated perfused rat hind quarter

Glucose and fatty acid metabolism of resting skeletal muscle were studied by perfusion of the isolated rat hind leg with a hemoglobin-free medium. Tissue integrity was demonstrated by normal ATP, ADP and creatine phosphate levels, by a sufficient oxygen supply, and by a normal appearance of perfused muscle specimens under the electron microscope. The rates of glucose and fatty acid uptake, and of lactate, alanine, glycerol and fatty acid release were constant over a perfusion period of 60 min. Insulin (1 unit/l) caused a more than threefold increase in glucose uptake, a stimulation of lactate production, and a 20% increase in the muscular glycogen levels. Fatty acids and alanine release were significantly diminished by insulin, but glycerol release did not change. The uptake of oleate by the rat hind leg was dependent on the medium concentration in a range of 0.7-1.9mM oleate, and was stimulated by insulin. Glucose uptake was not influenced by oleate, whether sodium was present or not. When the leg was perfused with [1-14C]oleate, 75% of the incorporated fatty acids were found in muscle lipids, 10% were oxidized to CO2, and 5% were recovered in bone lipids. The absolute amount of oleate oxidation was not altered by insulin. In all experiments with and without glucose in the medium, 70-80% of the 14C label incorporated into muscle lipids was found in the triglyceride fraction. In the presence of glucose, insulin significantly increased the incorporation of [1-14C]oleate into muscle triglycerides, whereas no insulin effect, either on fatty acid uptake or on triglyceride formation, could be observed when glucose was omitted from the perfusate. The present results indicate that a "glucose-fatty acid cycle" as found in rat heart muscle does not operate in resting peripheral skeletal muscle tissue. They also demonstrate that the stimulating effect of insulin on muscular fatty acid uptake and triglyceride synthesis is dependent on glucose supply. This finding can be intrepreted as a stimulation of fatty acid esterification by sn-glycerol 3-phosphate derived from an increased glucose turnover, which is in turn due to insulin.

[Colostomy continence achieved with an implanted circular magnet (author's transl)]

A new method of providing a colostomy continent for faeces and gas is described. It consists of the subcutaneous implantation of a magnetic ring which is led outside through the lumen of the colon and sutured to the skin. The colostomy is closed with a magnetic cover. The procedure has been used in 17 patients with a permanent colostomy after rectal excision and has been highly successful.