Loss of filamentous actin, tight junction protein expression, and paracellular barrier integrity in frataxin-deficient human brain microvascular endothelial cells-implications for blood-brain barrier physiology in Friedreich's ataxia

Introduction: Friedreich's Ataxia (FRDA) is the most prevalent inherited ataxia. FRDA results from loss of Frataxin (FXN), an essential mitochondrial iron trafficking protein. FRDA starts with an early burst of neurodegeneration of the dorsal root ganglion and cerebellar dentate nuclei, followed by progressive brain iron accumulation in the latter. End stage disease includes cardiac fibrosis that contributes to hypertrophic cardiomyopathy. The microvasculature plays an essential barrier role in both brain and heart homeostasis, thus an investigation of this tissue system in FRDA is essential to the delineation of the cellular dysfunction in this genetic disorder. Previous reports have identified cytoskeletal alterations in non-barrier forming FRDA cell models, but physiological consequences are limited. Methods: We investigated brain microvascular endothelial cell integrity in FRDA in a model of the blood-brain barrier (BBB). We have knocked down FXN in immortalized human brain microvascular endothelial cells (hBMVEC), which compose the microcapillaries of the BBB, by using shRNA. We confirmed known cellular pathophysiologies of FXN-knockdown including decreased energy metabolism, markers of oxidative stress, and increased cell size. Results: We investigated cytoskeletal architecture, identifying decreased filamentous actin and Occludin and Claudin-5 tight junction protein expression in shFXN hBMVECs. This was consistent with decreased transendothelial electrical resistance (TEER) and increased paracellular tracer flux during early barrier formation. shFXN hBMVEC start with only 67% barrier integrity of the controls, and flux a paracellular tracer at 800% of physiological levels. Discussion: We identified that insufficient FXN levels in the hBMVEC BBB model causes changes in cytoskeletal architecture and tight junction protein abundance, co-incident with increased barrier permeability. Changes in the integrity of the BBB may be related to patient brain iron accumulation, neuroinflammation, neurodegeneration, and stroke. Furthermore, our findings implicate other barrier cells, e.g., the cardiac microvasculature, loci of disease pathology in FRDA.

Frataxin-deficient human brain microvascular endothelial cells lose polymerized actin and are paracellularly permeable -implications for blood-brain barrier integrity in Friedreich's Ataxia

Background

Friedreich's Ataxia (FRDA) is the most prevalent inherited ataxia; the disease results from loss of Frataxin, an essential mitochondrial iron trafficking protein. FRDA presents as neurodegeneration of the dorsal root ganglion and cerebellar dentate nuclei, followed by brain iron accumulation in the latter. End stage disease includes cardiac fibrosis that contributes to hypertrophic cardiomyopathy. The microvasculature plays an essential barrier role in both the brain and heart, thus an investigation of this tissue system in FRDA is essential to the delineation of the cellular dysfunction in this genetic disorder. Here, we investigate brain microvascular endothelial cell integrity in FRDA in a model of the blood-brain barrier (BBB).

Methods

We used lentiviral mediated shRNA delivery to generate a novel FRDA model in immortalized human brain microvascular endothelial cells (hBMVEC) that compose the microcapillaries of the BBB. We verified known cellular pathophysiologies of FXN knockdown including increased oxidative stress, loss of energy metabolism, and increased cell size. Furthermore, we investigated cytoskeletal architecture including the abundance and organization of filamentous actin, and barrier physiology via transendothelial electrical resistance and fluorescent tracer flux.

Results

shFXN hBMVEC display the known FRDA cell morbidity including increased oxidative stress, decreased energy metabolism, and an increase in cell size. We demonstrate that shFXN hBMVEC have less overall filamentous actin, and that filamentous actin is lost at the cell membrane and cortical actin ring. Consistent with loss of cytoskeletal structure and anchorage, we found decreased barrier strength and increased paracellular tracer flux in the shFXN hBMVEC transwell model.

Conclusion

We identified that insufficient FXN levels in the hBMVEC BBB model causes changes in cytoskeletal architecture and increased barrier permeability, cell pathologies that may be related to patient brain iron accumulation, neuroinflammation, neurodegeneration, and stroke. Our findings implicate other barrier cells, e.g., the cardiac microvasculature, likely contributory also to disease pathology in FRDA.

Calcium and the Ca-ATPase SPCA1 modulate plasma membrane abundance of ZIP8 and ZIP14 to regulate Mn(II) uptake in brain microvascular endothelial cells

Manganese (II) accumulation in human brain microvascular endothelial cells is mediated by the metal-ion transporters ZRT IRT-like protein 8 (ZIP8) and ZRT IRT-like protein 14 (ZIP14). The plasma membrane occupancy of ZIP14, in particular, is increased in cells treated with Mn²⁺, lipopolysaccharide, or IL-6, but the mechanism of this regulation has not been elucidated. The calcium-transporting type 2C member 1 ATPase, SPCA1, is a Golgi-localized Ca²⁺-uptake transporter thought to support Golgi uptake of Mn²⁺ also. Here, we show using surface protein biotinylation, indirect immunofluorescence, and GFP-tagged proteins that cytoplasmic Ca²⁺ regulates ZIP8- and ZIP14-mediated manganese accumulation in human brain microvascular endothelial cells by increasing the plasma membrane localization of these transporters. We demonstrate that RNAi knockdown of SPCA1 expression results in an increase in cytoplasmic Ca²⁺ levels. In turn, we found increased cytoplasmic Ca²⁺ enhances membrane-localized ZIP8 and ZIP14 and a subsequent increase in ⁵⁴Mn²⁺ uptake. Furthermore, overexpression of WT SPCA1 or a gain-of-function mutant resulted in a decrease in cytoplasmic Ca²⁺ and ⁵⁴Mn²⁺ accumulation. While addition of Ca²⁺ positively regulated ZIP-mediated ⁵⁴Mn²⁺ uptake, we show chelation of Ca²⁺ diminished manganese transport. In conclusion, the modulation of ZIP8 and ZIP14 membrane cycling by cytoplasmic calcium is a novel finding and provides new insight into the regulation of the uptake of Mn²⁺ and other divalent metal ions–mediated ZIP metal transporters.

Short communication: Simultaneous measurements of estrus behavior and plasma concentrations of estradiol during estrus in lactating and nonlactating dairy cows

Estrus is an important behavior that can potentially be subjected to genomic selection. Circulating estradiol concentrations at estrus may be a useful phenotype if the absolute concentrations of estradiol are associated with overt phenotypes for estrus (activity, rump touches, or both; e.g., mounts, chinrests) that can be easily observed. The objective was to measure plasma estradiol concentrations at estrus and associate these measurements with the increase in activity (steps per hour) and rump touches received at estrus. We also tested the effect of lactation on the estrus traits that we measured. Cows (n = 11 lactating and n = 9 nonlactating) were treated with PGF_2α to synchronize estrus. A jugular vein was cannulated to collect blood every 2 h for plasma estradiol measurement. Plasma LH was measured during the periestrual period to determine the time of the LH surge. Cows were fitted with an accelerometer to measure activity (steps per hour) and a capacitive touch sensing device to measure the number of rump touches and total touch time. Plasma estradiol concentrations were poorly correlated with overt signs of estrus during the period leading up to maximum estrus activity. After peak estrus activity (when cows were going out of estrus and plasma estradiol concentrations were decreasing), a stronger correlation was detected between overt signs of estrus and plasma estradiol concentrations. Effective selection for improved estrus expression based on plasma estradiol concentrations will depend on whether the cow is coming into or going out of estrus at the time of blood sampling. An association existed between lactation and fewer number of hours in estrus when estrus was defined by an increase in activity (steps per hour). Lactating cows had a shorter interval from the onset of estrus to the LH surge, and the shorter interval to the LH surge may have reduced the period of elevated estradiol during estrus in the lactating cows. Understanding mechanisms that control the sensitivity of the cow to estradiol and making appropriate selection decisions based on these mechanisms will likely increase overt signs of estrus in dairy cows.

Estimates of intra- and interclass correlation coefficients for rump touches and the number of steps during estrus in postpartum cows

Estrus traits have economic value in dairy production systems and could be incorporated into genetic selection indices. In an effort to further understand selection responses, 2 studies were performed to estimate the intra- and interclass correlation coefficients for estrus traits. Holstein-Friesian cows (n = 1,197; study 1) across 5 pasture-based grazing dairy herds were fitted with a capacitive touch sensing (CTS) device on the rump (FlashMate, Farmshed Labs Limited, Hamilton, New Zealand). The daily number of rump touches were subjected to a peak detection program to objectively identify periods of increased rump touches above baseline (indicative of estrus). The number of times touched and the sum of the touch duration were used to compare farms and estimate the intraclass correlation (repeatability). For study 2, postpartum Holstein (n = 85) and Guernsey (n = 5) cows in a confinement-style dairy were used. Cows were fitted with an IceQube accelerometer (IceRobotics Ltd., Edinburgh, United Kingdom) to measure steps taken per hour and a CTS device was applied to both rumps. The interclass correlation for the number of rump touches and number of steps taken during estrus was calculated. Data collected from 5 herds (study 1) demonstrated a 2- to 3-fold difference between herds in the number of rump touches and total touch time during estrus. The intraclass correlation (repeatability; estimates of maximum heritability) for rump touches during estrus was 0.22. For study 2, the number of steps and the number of rump touches during estrus increased in a synchronous manner. The intraclass correlation (repeatability) for number of steps during estrus was 0.26. The interclass correlation (r) for the number of rump touches and the number of steps was 0.46 (R² = 0.21). Based on the R², at least 20% of the variation in the number of steps during estrus was explained by the number of touches to the rump of the cow. Selecting cows for the number of steps taken during estrus could increase the number of rump touches (mounts, chin rests, and so on, received from other cows) if a genetic correlation exists for the phenotypic correlation that we observed.

Molecular Defects in Friedreich's Ataxia: Convergence of Oxidative Stress and Cytoskeletal Abnormalities

Friedreich’s ataxia (FRDA) is a multi-faceted disease characterized by progressive sensory–motor loss, neurodegeneration, brain iron accumulation, and eventual death by hypertrophic cardiomyopathy. FRDA follows loss of frataxin (FXN), a mitochondrial chaperone protein required for incorporation of iron into iron–sulfur cluster and heme precursors. After the discovery of the molecular basis of FRDA in 1996, over two decades of research have been dedicated to understanding the temporal manifestations of disease both at the whole body and molecular level. Early research indicated strong cellular iron dysregulation in both human and yeast models followed by onset of oxidative stress. Since then, the pathophysiology due to dysregulation of intracellular iron chaperoning has become central in FRDA relative to antioxidant defense and run-down in energy metabolism. At the same time, limited consideration has been given to changes in cytoskeletal organization, which was one of the first molecular defects noted. These alterations include both post-translational oxidative glutathionylation of actin monomers and differential DNA processing of a cytoskeletal regulator PIP5K1β. Currently unknown in respect to FRDA but well understood in the context of FXN-deficient cell physiology is the resulting impact on the cytoskeleton; this disassembly of actin filaments has a particularly profound effect on cell–cell junctions characteristic of barrier cells. With respect to a neurodegenerative disorder such as FRDA, this cytoskeletal and tight junction breakdown in the brain microvascular endothelial cells of the blood–brain barrier is likely a component of disease etiology. This review serves to outline a brief history of this research and hones in on pathway dysregulation downstream of iron-related pathology in FRDA related to actin dynamics. The review presented here was not written with the intent of being exhaustive, but to instead urge the reader to consider the essentiality of the cytoskeleton and appreciate the limited knowledge on FRDA-related cytoskeletal dysfunction as a result of oxidative stress. The review examines previous hypotheses of neurodegeneration with brain iron accumulation (NBIA) in FRDA with a specific biochemical focus.

Linking monitoring and data analysis to predictions and decisions for the range-wide eastern black rail status assessment

The US Fish and Wildlife Service (USFWS) has initiated a re-envisioned approach for providing decision makers with the best available science and synthesis of that information, called the Species Status Assessment (SSA), for endangered species decision making. The SSA report is a descriptive document that provides decision makers with an assessment of the current and predicted future status of a species. These analyses support all manner of decisions under the US Endangered Species Act, such as listing, reclassification, and recovery planning. Novel scientific analysis and predictive modeling in SSAs could be an important part of rooting conservation decisions in current data and cutting edge analytical and modeling techniques. Here, we describe a novel analysis of available data to assess the current condition of eastern black rail Laterallus jamaicensis jamaicensis across its range in a dynamic occupancy analysis. We used the results of the analysis to develop a site occupancy projection model where the model parameters (initial occupancy, site persistence, colonization) were linked to environmental covariates, such as land management and land cover change (sea-level rise, development, etc.). We used the projection model to predict future status under multiple sea-level rise and habitat management scenarios. Occupancy probability and site colonization were low in all analysis units, and site persistence was also low, suggesting low resiliency and redundancy currently. Extinction probability was high for all analysis units in all simulated scenarios except one with significant effort to preserve existing habitat, suggesting low future resiliency and redundancy. With the results of these data analyses and predictive models, the USFWS concluded that protections of the Endangered Species Act were warranted for this subspecies.

The solute carriers ZIP8 and ZIP14 regulate manganese accumulation in brain microvascular endothelial cells and control brain manganese levels

Manganese supports numerous neuronal functions but in excess is neurotoxic. Consequently, regulation of manganese flux at the blood-brain barrier (BBB) is critical to brain homeostasis. However, the molecular pathways supporting the transcellular trafficking of divalent manganese ions within the microvascular capillary endothelial cells (BMVECs) that constitute the BBB have not been examined. In this study, we have determined that ZIP8 and ZIP14 (Zrt- and Irt-like proteins 8 and 14) support Mn²⁺ uptake by BMVECs and that neither DMT1 nor an endocytosis-dependent pathway play any significant role in Mn²⁺ uptake. Specifically, siRNA-mediated knockdown of ZIP8 and ZIP14 coincided with a decrease in manganese uptake, and kinetic analyses revealed that manganese uptake depends on pH and bicarbonate and is up-regulated by lipopolysaccharide, all biochemical markers of ZIP8 or ZIP14 activity. Mn²⁺ uptake also was associated with cell-surface membrane presentation of ZIP8 and ZIP14, as indicated by membrane protein biotinylation. Importantly, surface ZIP8 and ZIP14 biotinylation and Mn²⁺-uptake experiments together revealed that these transporters support manganese uptake at both the apical, blood and basal, brain sides of BMVECs. This indicated that in the BMVECs of the BBB, these two transporters support a bidirectional Mn²⁺ flux. We conclude that BMVECs play a critical role in controlling manganese homeostasis in the brain.

A cohort study of local excision followed by adjuvant therapy incorporating a contact X-ray brachytherapy boost instead of radical resection in 180 patients with rectal cancer

AIM

Recent data have suggested near-equivalent oncological results when treating early rectal cancer by local excision followed by radio- ± chemotherapy rather than salvage radical surgery. The aim of this retrospective study was to assess the use of contact X-ray brachytherapy within this paradigm.

METHOD

All patients had undergone local excision and were referred to our radiotherapy centre for treatment with contact X-ray brachytherapy. Postoperative (chemo)radiotherapy was also given in their local hospital in most cases. Variables assessed were local excision method, postoperative therapy received, follow-up duration, disease-free survival, salvage surgery and stoma-free survival.

RESULTS

In total, 180 patients with a median age of 70 (range 36-99) years were assessed. Following local excision, pT stages were pT1 = 131 (72%), pT2 = 44 (26%), pT3 = 5 (2%). All patients received contact X-ray brachytherapy boosting at our centre and, in addition, 110 received chemoradiotherapy and 60 received radiotherapy alone. After a median follow-up of 36 months (range 6-48), 169 patients (94%) remained free of local recurrence. Of the 11 patients with local recurrence (three isolated nodal), five underwent salvage abdominoperineal excision. Eight patients developed distant disease, of whom five underwent metastasis surgery. At last included follow-up 173 (96%) patients were free of all disease and 170 (94%) were stoma free.

CONCLUSIONS

Contact therapy can be offered in addition to external beam radio (±chemo) therapy instead of radical surgery as follow-on treatment after local excision of early rectal cancer. This combination can provide equivalent outcomes to radical surgery. The added value of contact therapy should be formally assessed in a clinical trial.

Contact radiotherapy boost in association with 'watch and wait' for rectal cancer: initial experience and outcomes from a shared programme between a district general hospital network and a regional oncology centre

AIM

Recent data have highlighted the potential of more intensive neoadjuvant protocols to increase and sustain the rate of complete response in rectal cancer managed nonoperatively. This study aimed to review the outcome of all patients from our district general hospitals network who had received standard neoadjuvant therapy and were additionally referred to a centre of excellence for contact X-ray brachytherapy or high-dose-rate brachytherapy boost.

METHOD

A retrospective, chart-based review of all patients co-managed in this manner was performed. Patient details were retrieved from a prospectively maintained departmental database. Indications for treatment, patient outcome and serial data from follow-up clinical and radiological assessment were analysed.

RESULTS

Seventeen patients treated over a 6-year period were identified. Median follow-up was 20 (5-54) months. Fourteen patients were clinically staged as T2 or T3 and eight were clinically node positive. Three patients died, of whom only one was initially a surgical candidate but refused an exenteration. Of the 14 patients who remain alive, 11 (79%) have a sustained complete (n = 8) or partial (n = 3) response. Two patients had an incomplete response, one is being palliated and the other awaits salvage surgery. One patient underwent abdominoperineal excision for suspected local recurrence. Currently 13 (93%) surviving patients are stoma free.

CONCLUSIONS

This series shows that the addition of a radiotherapy boost offered sustained responses and stoma-free survival even in advanced disease and adverse patient populations whilst providing the majority of care closer to home.

Assessment of a novel, full-thickness incisional biopsy model to restage rectal tumours after neoadjuvant chemoradiotherapy: results of an ex vivo pilot study

BACKGROUND

There is currently no reliable means to restage rectal cancers after neoadjuvant chemoradiation. Recent histological evidence shows that the epicentre for residual cancer cells is focussed directly underneath any residual mucosal abnormality (RMA). This proof-of-concept study aimed to determine the utility of a novel, minimally invasive method of incisional biopsy as a restaging tool. A secondary aim was to compare its performance to clinical response assessment.

METHODS

After surgical resection, 0.5 × 0.5 cm, full-thickness incisional biopsy was performed in 15 rectal cancers. Of these, 13 had RMA and 2 had mucosal cCR but a palpable intramural abnormality. In all patients, a full-thickness incisional biopsy was taken through the centre of these areas. The ypT stage of the incisional biopsy and the final total specimen were compared. Complete mucosal clinical response was deemed to have occurred when either no residual tumour or only a flat mucosal scar remained.

RESULTS

Incisional biopsy correctly identified all patients that had been downstaged to ypT0; however, it also falsely identified 5 of 10 patients (50%) with yp residual disease as ypT0. Overall performance of incisional biopsy to detect residual cancer was 50% sensitivity, 100 % specificity, 100% PPV, and 50% NPV with an accuracy of 66%. A complete mucosal clinical response occurred in only one of five patients downstaged to ypT0 (20% sensitive). It also occurred in one patient, which was ultimately staged as ypT3.

CONCLUSION

This prospective data demonstrates that incisional biopsy is not suitable as a stand-alone method to restage rectal cancer after CRT. Alternate or complementary means of restaging are needed.

Depth and lateral spread of microscopic residual rectal cancer after neoadjuvant chemoradiation: implications for treatment decisions

AIM

The aim of this study was to determine the distribution of residual tumour within the bowel wall in relation to residual mucosal abnormalities (RMAs) and surrounding normal mucosa in patients with rectal cancer who underwent neoadjuvant chemoradiation followed by curative surgery.

METHOD

Archived pathological slides from a cohort of 60 patients with residual tumour were retrieved. The incidence, distance and depth of tumour spread (ypT) under RMAs and adjacent normal mucosa were reviewed and recorded.

RESULTS

Histological sections containing both RMA and adjacent normal mucosa were available for 45 of 60 patients with ypT1 (n = 6), ypT2 (n = 18) and ypT3 (n = 21) disease. The maximal depth of invasion, as measured by ypT stage, was found underneath the RMA in 44 of 45 (98%) patients. Microscopic tumour spread lateral to the RMA and under adjacent normal mucosa was found in 32 of 45 (71%) patients. The median and maximum distances of lateral spread for ypT1 tumours were 0 and 4 mm; for ypT2 were 2.5 and 9 mm; and for ypT3 were 4 and 9 mm respectively.

CONCLUSION

Lateral tumour spread under normal mucosa adjacent to RMAs is a common finding and extended up to 9 mm in this study. The epicentre for maximum depth of invasion was directly underneath the RMAs in nearly all cases. These data have clinical and technical implications if local excision is to be considered.

Authors' reply: The surgical significance of residual mucosal abnormalities in rectal cancer following neoadjuvant chemoradiotherapy (Br J Surg 2012; 99: 993–1001)

No

The surgical significance of residual mucosal abnormalities in rectal cancer following neoadjuvant chemoradiotherapy

BACKGROUND

Local excision of rectal cancer after neoadjuvant chemoradiotherapy (CRT) has been proposed as an alternative to radical surgery in selected patients. However, little is known about the significance of the morphological and histological features of residual tumour.

METHODS

Patients who had undergone CRT at the authors' institution between 1997 and 2010 were identified. Multiple features were assessed as putative markers of pathological response. These included: gross residual disease, diameter of residual mucosal abnormalities, tumour differentiation, presence of lymphovascular/perineural invasion and lymph node ratio.

RESULTS

Data from 220 of 276 patients were suitable for analysis. Diameter of residual mucosal abnormalities correlated strongly with pathological tumour category after CRT (ypT) (P < 0·001). Forty of 42 tumours downstaged to ypT0/1 had residual mucosal abnormalities of 2·99 cm or less after CRT. Importantly, 19 of 31 patients with a complete pathological response had evidence of a residual mucosal abnormality consistent with an incomplete clinical response. The ypT category was associated with both pathological node status after CRT (P < 0·001) and lymph node ratio (P < 0·001). Positive nodes were found in only one of 42 patients downstaged to ypT0/1. The risk of nodal metastases was associated with poor differentiation (P = 0·027) and lymphovascular invasion (P < 0·001).

CONCLUSION

In this series, the majority of patients with a complete pathological response did not have a complete clinical response. In tumours downstaged to ypT0/1 after CRT, residual mucosal abnormalities were predominantly small and had a 2 per cent risk of positive nodes, thus potentially facilitating transanal excision. The presence of adverse histological characteristics risk stratified tumours for nodal metastases.

Rectum-conserving surgery in the era of chemoradiotherapy

BACKGROUND

A complete pathological response occurs in 10-30 per cent of patients with locally advanced rectal cancer undergoing neoadjuvant chemoradiotherapy (CRT). The standard of care has been radical surgery with high morbidity risks and the challenges of stomata despite the favourable prognosis. This review assessed minimalist approaches (transanal excision or observation alone) to tumours with a response to CRT.

METHODS

A systematic review was performed using PubMed and Embase databases. Keywords included: 'rectal', 'cancer', 'transanal', 'conservative', 'complete pathological response', 'radiotherapy' and 'neoadjuvant'. Original articles from all relevant listings were sourced. These were hand searched for further articles of relevance. Main outcome measures assessed were rates of local recurrence and overall survival, and equivalence to radical surgery.

RESULTS

Purely conservative 'watch and wait' strategies after CRT are still controversial. Originally used for elderly patients or those who refused surgery, the data support transanal excision of rectal tumours showing a good response to CRT. A complete pathological response in the T stage (ypT0) indicates < 5 per cent risk of nodal metastases.

CONCLUSION

Rectal tumours showing an excellent response to CRT may be suitable for local excision, with equivalent outcomes to radical surgery. This approach should be the subject of prospective clinical trials in specialist centres.

THE RELATION OF HEART WEIGHT TO THE BASAL METABOLISM AS VARIED BY THYROID ADMINISTRATION

A linear relationship exists in the albino rat between the heart weight and the basal metabolic rate when varied by the administration of active thyroid material. It is suggested that this increase in heart weight which follows the increase in metabolism after thyroid is in the nature of a simple work hypertrophy of the myocardium.

Development of the swimbladder and its innervation in the zebrafish, Danio rerio

Many teleosts including zebrafish, Danio rerio, actively regulate buoyancy with a gas-filled swimbladder, the volume of which is controlled by autonomic reflexes acting on vascular, muscular, and secretory effectors. In this study, we investigated the morphological development of the zebrafish swimbladder together with its effectors and innervation. The swimbladder first formed as a single chamber, which inflated at 1-3 days posthatching (dph), 3.5-4 mm body length. Lateral nerves were already present as demonstrated by the antibody zn-12, and blood vessels had formed in parallel on the cranial aspect to supply blood to anastomotic capillary loops as demonstrated by Tie-2 antibody staining. Neuropeptide Y-(NPY-) like immunoreactive (LIR) fibers appeared early in the single-chambered stage, and vasoactive intestinal polypeptide (VIP)-LIR fibers and cell bodies developed by 10 dph (5 mm). By 18 dph (6 mm), the anterior chamber formed by evagination from the cranial end of the original chamber; both chambers then enlarged with the ductus communicans forming a constriction between them. The parallel blood vessels developed into an arteriovenous rete on the cranial aspect of the posterior chamber and this region was innervated by zn-12-reactive fibers. Tyrosine hydroxylase- (TH-), NPY-, and VIP-LIR fibers also innervated this area and the lateral posterior chamber. Innervation of the early anterior chamber was also demonstrated by VIP-LIR fibers. By 25-30 dph (8-9 mm), a band of smooth muscle formed in the lateral wall of the posterior chamber. Although gas in the swimbladder increased buoyancy of young larvae just after first inflation, our results suggest that active control of the swimbladder may not occur until after the formation of the two chambers and subsequent development and maturation of vasculature, musculature and innervation of these structures at about 28-30 dph.

Barriers to effective drug addiction treatment for women involved in street-level prostitution: a qualitative investigation

OBJECTIVES

To examine barriers to effective drug addiction treatment for women involved in street-level prostitution.

METHODS

A qualitative approach was selected to enable a detailed exploration, in an informal and unthreatening manner, of the barriers to drug addiction treatment from the women's perspective. Nine in-depth interviews were conducted with women who were involved in street-level prostitution. Transcripts of one-to-one interviews were analysed for recurrent themes using Interpretative Phenomenological Analysis.

RESULTS

Barriers to effective addiction treatment are present at psychological, interpersonal, and wider societal levels. Themes identified included: an impoverished sense of self-worth, a lack of trust and consistency in treatment, and the absence of a comprehensive treatment package.

CONCLUSION

Current services could be improved by the provision of a structured treatment programme designed to target the specific physical and psychological requirements of this population. Also, efforts to correct the fictitious, negative portrayals of women involved in prostitution are required, if treatment efficacy is to be improved.

Regulation of growth and metabolism by imprinted genes

A small sub-set of mammalian genes are subject to regulation by genomic imprinting such that only one parental allele is active in at least some sites of expression. Imprinted genes have diverse functions, notably including the regulation of growth. Much attention has been devoted to the insulin-like growth factor signalling pathway that has a major influence on fetal size and contains two components encoded by the oppositely imprinted genes, Igf2 (a growth promoting factor expressed from the paternal allele) and Igf2r (a growth inhibitory factor expressed from the maternal allele). These genes fit the parent-offspring conflict hypothesis for the evolution of genomic imprinting. Accumulated evidence indicates that at least one other fetal growth pathway exists that has also fallen under the influence of imprinting. It is clear that not all components of growth regulatory pathways are encoded by imprinted genes and instead it may be that within a pathway the influence of a single gene by each of the parental genomes may be sufficient for parent-offspring conflict to be enacted. A number of imprinted genes have been found to influence energy homeostasis and some, including Igf2 and Grb10, may coordinate growth with glucose-regulated metabolism. Since perturbation of fetal growth can be correlated with metabolic disorders in adulthood these imprinted genes are considered as candidates for involvement in this phenomenon of fetal programming.

Pathological and molecular predictors of the response of rectal cancer to neoadjuvant radiochemotherapy

AIMS

The prediction of sensitivity and resistance to neoadjuvant therapy has great potential value for many tumour sites. A neoadjuvant regimen is increasingly the gold standard in rectal cancer management and the aim of this review was to highlight predictive markers currently assessed and evaluate their clinical utility.

METHODS

A systematic search of Medline was conducted using the following keywords 'colorectal', 'neoadjuvant', 'molecular', 'predict' and 'radiotherapy'. Original manuscripts from all relevant listings were sourced. These were hand searched for further articles of relevance.

RESULTS

Conventional indices including tumour stage and grade were unable to predict histological response. Immunohistochemical assessment of P53 gene, Bcl 2, Bax and microsatellite instability are of no predictive value. Studies utilising molecular response predictors from archival pre-treatment tumour tissues have identified several promising predictive markers including p21, spontaneous apoptosis and direct sequencing of the p53 gene. Global gene expression from fresh pre-treatment tissue using cDNA microarray has only recently been assessed but identified expression differences between 54 genes and was able to predict response with 78% sensitivity and 86% specificity.

CONCLUSIONS

Currently there are no clinically useful predictors of response based on standard pathological assessment and immunocytochemistry. Direct gene sequencing of p53, studies of apoptosis and global gene sequencing may hold promise.

A characterization of anaerobic colonization and associated mucosal adaptations in the undiseased ileal pouch

INTRODUCTION

The resolution of pouchitis with metronidazole points to an anaerobic aetiology. Pouchitis is mainly seen in patients with ulcerative colitis pouches (UCP). We have recently found that sulphate reducing bacteria (SRB), a species of strict anaerobe, colonize UCP exclusively. Herein, we aimed to correlate levels of different bacterial species (including SRB) with mucosal inflammation and morphology.

METHODS

Following ethical approval, fresh faecal samples and mucosal biopsies were taken from 9 patients with UCP and 5 patients with familial adenomatous polyposis pouches (FAPP). For the purposes of comparison, faecal samples and mucosal biopsies were also taken from the stomas of 7 of the 9 patients with UC (UCS). Colonization by four types of strict anaerobes (SRB, Clostridium perfringens, Bifidobacteria and Bacteroides) as well as by three types of facultative anaerobes (Enterococci, Coliforms and Lactobacilli) was evaluated. Inflammatory scores and mucosal morphology were assessed histologically in a blinded fashion by a pathologist.

RESULTS

In general, strict anaerobes predominated over facultative in the UCP (P = 0.041). SRB were present in UCP exclusively. Even after exclusion of SRB from total bacterial counts, strict anaerobes still predominated. In the UCS, facultative anaerobes predominated. Strict and facultative anaerobes were present at similar levels in the FAPP. Enterococci were present at significantly reduced levels in the UCP when compared with the UCS (P = 0.031). When levels of SRB and other anaerobic species were individually correlated with mucosal inflammation and morphology, no trends were observed.

CONCLUSION

We have previously identified that SRB exclusively colonize UCP. In addition we have now identified a novel increase in the strict/facultative anaerobic ratio within the UCP compared to UCS. These stark differences in bacterial colonization, however, appear to have limited impact on mucosal inflammation or morphology.

Continuous crossover femoropopliteal bypass in a 68-year-old gentleman with rest pain

Patients who have had multiple previous attempts at limb salvaging surgery frequently go on to have an amputation. This, however, results both in psychological perturbation for the patient and high rehabilitation costs for the community. Successful limb salvage surgery therefore has an important role in vascular surgery. We describe the management of a patient with critical limb ischemia that had previously undergone multiple limb salvage procedures and whose limb was saved by the use of a continuous femoropopliteal crossover bypass graft. The patient, who may have been deemed by some as a candidate for amputation, has full use of his limb 6 months after surgery with ankle brachial pressure index readings of 0.6. Continuous femoropopliteal crossover bypass grafting is a poorly described surgical technique that may be appropriate in a subgroup of patients and may allow salvage of a limb that otherwise may have been deemed fit for amputation.

Indications of disordered eating behaviour in adolescent patients with idiopathic scoliosis

We have investigated whether patients with adolescent-onset idiopathic scoliosis (AIS) are more likely to have a low body-weight. Measurements of weight, height and body mass index (BMI) were made in 44 young women with AIS and compared with age- and gender-adjusted normative data. The body mass criteria of the International Classification of Diseases for eating disorders was used to determine how many patients were within the range considered to be 'eating disordered'. Compared with the normative data, the AIS group did not differ significantly in terms of height, (p = 0.646), but they were significantly lighter (p < 0.001) and had significantly lower BMI scores (p < 0.001); 25% of the series had BMI scores which were within the range considered to be anorexic. The relationship between a diagnosis of AIS and low body-weight may indicate disordered eating and is thus a cause for concern, particularly in the light of the well-established relationship between eating psychopathology and osteoporosis. Aspects of organic health may need to be considered in addition to the cosmetic deformity.

Comparison of field measurements to predicted reaeration coefficients, k2, in the application of a water quality model, QUAL2E, to a tropical river

Some of the many tools used for watershed management are mathematical and computer models for wasteload allocations. QUAL2E is one of the most popular water quality models used for such purposes. The question arises as to whether the model is applicable in a different climate such as that in the tropics. In this study, QUAL2E was used to model Sg. Selangor River in Malaysia using the predictive equations for reaeration coefficient (k2) within the model and the measured reaeration coefficients for the river. The study results indicated that use of the reaeration coefficient (k2) measured at Sg. Selangor River did give the lowest standard error (SE) for the simulation of water quality during the 7Q10 low-flow period which is considered as the worst scene scenario in water quality modeling. But during calibration and validation using actual low-flow discharge data, the measured reaeration coefficients did not give the lowest standard error (SE). In conclusion, the results indicated that QUAL2E is applicable in tropical rivers when used with the modeled river parameters (i.e. hydraulic parameters, meteorological conditions etc.). Measured reaeration coefficients produced good results and several predictive equations also produced comparatively good results.

Effects of chronic cardiac decentralization on functional properties of canine intracardiac neurons in vitro

Although intrinsic cardiac neurons display ongoing activity after chronic interruption of extrinsic autonomic inputs to the heart, the effects of decentralization on individual neurons remain unknown. The objective of this study was to determine the effects of chronic (3-4 wk) surgical decentralization on intracellular properties of, and neurotransmission among, neurons contained within the canine intrinsic right atrial ganglionated plexus in vitro. Properties of neurons from decentralized hearts were compared with those of neurons from sham-operated hearts (controls). Two populations of neurons were identified by their firing behavior in response to intracellular current injection. Fifty-nine percent of control neurons and 72% of decentralized neurons were phasic (discharged one action potential on excitation). Forty-one percent of control neurons and 27% of decentralized neurons were accommodating (multiple discharge with decrementing frequency). After chronic decentralization, input resistance of phasic neurons increased, whereas the duration of afterhyperpolarization of accommodating neurons decreased. Postsynaptic responses to interganglionic nerve stimulation were evoked in 89% of control neurons and 83% of decentralized neurons; the majority of these responses involved nicotinic receptors. These results show that, after chronic decentralization, intrinsic cardiac neurons 1) undergo changes in membrane properties that may lead to increased excitability while 2) maintaining synaptic neurotransmission within the intrinsic cardiac ganglionated plexus.

Chronic decentralization of the heart differentially remodels canine intrinsic cardiac neuron muscarinic receptors

The objective of the study was to determine if chronic interruption of all extrinsic nerve inputs to the heart alters cholinergic-mediated responses within the intrinsic cardiac nervous system (ICN). Extracardiac nerve inputs to the ICN were surgically interrupted (ICN decentralized). Three weeks later, the intrinsic cardiac right atrial ganglionated plexus (RAGP) was removed and intrinsic cardiac neuronal responses were evaluated electrophysiologically. Cholinergic receptor abundance was evaluated using autoradiography. In sham controls and chronic decentralized ICN ganglia, neuronal postsynaptic responses were mediated by acetylcholine, acting at nicotinic and muscarinic receptors. Muscarine- but not nicotine-mediated synaptic responses that were enhanced after chronic ICN decentralization. After chronic decentralization, muscarine facilitation of orthodromic neuronal activation increased. Receptor autoradiography demonstrated that nicotinic and muscarinic receptor density associated with the RAGP was unaffected by decentralization and that muscarinic receptors were tenfold more abundant than nicotinic receptors in the right atrial ganglia in each group. After chronic decentralization of the ICN, intrinsic cardiac neurons remain viable and responsive to cholinergic synaptic inputs. Enhanced muscarinic responsiveness of intrinsic cardiac neurons occurs without changes in receptor abundance.

TUNEL-positive staining of surface contusions after fatal head injury in man

In frontal lobe contusions obtained post mortem from 18 patients who survived between 6 h and 10 days after head injury, DNA fragmentation associated with either apoptotic and/or necrotic cell death was identified by the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end labelling (TUNEL) histochemical technique. Additional histological techniques were also used to identify regional and temporal patterns of tissue damage. TUNEL-positive cells were present in both the grey and white matter of the contusion, where they peaked in number between 25 and 48 h, and were still identifiable at 10 days post injury. Fewer TUNEL-positive cells were observed in grey than in white matter; and most TUNEL-positive neurons in the grey matter demonstrated the morphological features of necrosis. However, the morphology of some TUNEL-stained neurons, and of TUNEL-stained oligodendroglia and macrophages in white matter was suggestive of apoptosis. Apoptosis was not seen in age- and sex-matched controls, none of whom had died from intracranial pathology or had pre-existing neurological disease. These findings suggest that multiple cell types in frontal lobe contusions exhibit DNA fragmentation and that both necrosis and apoptosis are likely to contribute to post-traumatic pathology. These findings provide further evidence that the observations made in animal models of traumatic brain injury have fidelity with clinical head injury.

Confocal microscopic localization of constitutive and heat shock-induced proteins HSP70 and HSP27 in the rat heart

BACKGROUND

Heat-shock treatment of rats elevates expression of heat-shock proteins, which play a role in improving the contractile recovery and reducing infarct size in hearts after ischemic injury. However, the location of these proteins in the heart is unknown.

METHODS AND RESULTS

Anesthetized rats were heat-shocked by elevation of body temperature to 42 degrees C to 42.5 degrees C for 15 minutes, followed by 24 hours of recovery. Control and heat-shocked hearts were extirpated and perfused briefly with saline followed by 2% paraformaldehyde in PBS. Confocal immunofluorescence microscopy of control hearts revealed that HSP27 was localized in cardiomyocytes in a pattern reminiscent of Z bands and was colocalized with neuronal markers in somata and axons. No obvious change in HSP27 content or distribution occurred after heat shock. Confocal microscopy revealed little or no HSP70 in control hearts. After heat shock, HSP70 was detected neither in cardiomyocytes nor in neuronal elements within the heart, but HSP70 was abundant in small blood vessels found between the ventricular cardiomyocytes.

CONCLUSIONS

Heat shock induces a cell type-specific expression of HSP70 in blood vessels but not myocytes or intrinsic cardiac neurons, suggesting that blood vessels play a primary role in myocardial protection.

Tachykinin receptor subtypes in the isolated guinea pig heart and their role in mediating responses to neurokinin A

Selective tachykinin agonists were used to identify cardiac and coronary responses mediated by specific tachykinin receptor subtypes in isolated, perfused guinea pig hearts. Receptor desensitization with selective agonists and blockade with selective antagonists were used to determine the role of specific subtypes in generating responses to neurokinin A (NKA). Dose-dependent cardiac and coronary effects were evoked by bolus injections of ¿Sar(9), Met(O(2))(11)substance P (¿Sar(9),Met(O(2))(11)SP), GR64349, and ¿MePhe(7)neurokinin B (¿MePhe(7)NKB) (selective agonists for NK(1), NK(2), and NK(3) receptors, respectively). Each agonist caused bradycardia, but GR64349 was most effective (34 +/- 4% decrease in heart rate with 32 nmol, n = 8). Prominent increases in ventricular contractility and perfusion pressure also occurred with 32 nmol of GR64349 (25 +/- 6 and 33 +/- 4%, respectively). ¿Sar(9), Met(O(2))(11)SP was unique in having a high potency for decreasing ventricular contractility and perfusion pressure. Bolus injections of 25 nmol of NKA decreased rate (48 +/- 2%, n = 51), increased contractility (26 +/- 2%), and had biphasic effects on perfusion pressure (24 +/- 1% decrease followed by 9.2 +/- 1.4% increase). Desensitization with GR64349 or treatment with the NK(2) antagonist SR48968 reduced the bradycardic response to NKA by greater than 75% and eliminated the positive inotropic response. The remaining bradycardia occurred through NK(3) receptors. Desensitization with ¿Sar(9),Met(O(2))(11)SP or NK(1) blockade with FK888 eliminated the coronary relaxant action of NKA and enhanced the pressor response. It is concluded that three tachykinin receptor subtypes are present in the guinea pig heart and that each contributes to the overall response evoked by NKA.

The heart reinnervates after transplantation

BACKGROUND

Whether cardiac reinnervation occurs after transplantation remains controversial. If reinnervation does occur, how sympathetic and parasympathetic efferent neurons do this remains unknown.

METHODS

Power spectral analysis of heart rate variability was assessed for 1 year after cardiac autotransplantation in 9 dogs. After induction of anesthesia 13 months after transplantation, cardiac and intrinsic cardiac neuronal responses elicited by both electrical stimulation of parasympathetic or sympathetic efferent neurons and systemic or local coronary artery administration of nicotine (5 microg/kg), angiotensin II (0.75 microg/kg), and tyramine (1.2 microg/kg) were studied. The transmembrane electrical properties of intrinsic cardiac neurons were studied in vitro. Ventricular tissue catecholamine content, alpha-tubulin expression, and beta-adrenergic receptor density and affinity were studied. The presence of axons crossing suture lines was sought histologically.

RESULTS

Nerves were identified crossing suture lines. Electrical or chemical (ie, nicotine or angiotensin II) activation of sympathetic efferent neurons enhanced cardiodynamics, as did tyramine. Stimulating vagal efferent preganglionic axons induced bradycardia in half of the dogs. Functional reinnervation did not correlate with specific power spectra derived from rate variability in the conscious state. Responding to nicotine and angiotensin II in situ, transplanted intrinsic cardiac neurons generated spontaneous activity. These neurons displayed nicotine-dependent synaptic inputs in vitro. Ventricular tissue had normal beta-adrenergic receptor affinity and density but reduced catecholamine and alpha-tubulin contents.

CONCLUSIONS

The intrinsic cardiac nervous system receives reduced input from extracardiac sympathetic efferent neurons after transplantation and inconsistent input from parasympathetic efferent preganglionic neurons. These heterogeneous neuronal inputs are not reflected in heart rate variability or ventricular beta-adrenergic receptor function. Transplanted angiotensin II-sensitive intrinsic cardiac neurons exert greater cardiac control than do nicotine-sensitive ones. The intrinsic cardiac nervous system remodels itself after cardiac transplantation, and this indicates that direct assessment of extracardiac and intrinsic cardiac neuronal behavior is required to fully understand cardiac control after transplantation.

Identification of amino acids within the P2X2 receptor C-terminus that regulate desensitization

1. The ATP-activated P2X2(a) and P2X2(b) receptor splice variants, which differ only in their C-terminal sequences, desensitize at different rates. We used mutational analysis to investigate the involvement of the C-terminal region in receptor desensitization. Rat wild-type and mutant P2X2 receptors were expressed in Xenopus oocytes and currents were measured using the two-electrode voltage-clamp technique. 2. Truncating P2X2 at the Lys369 splice site increased the rate of desensitization by >100-fold. Recovery from desensitization was slowed by approximately 5-fold. 3. Addition of Val370 onto the C-terminus of the truncated receptor slowed desensitization by approximately 70-fold. Point mutations that substituted either smaller or larger hydrophobic amino acids for Val370, within the P2X2(a) splice variant, had profound effects on the rate of desensitization. The rate decreased with increasing hydrophobicity but was not dependent upon the precise structure of the side group. 4. A mutant receptor, with only nine amino acids, Val-Asp-Pro-Lys-Gly-Leu-Ala-Gln-Leu, beyond the Lys369 splice site, desensitized at a similar rate to P2X2(a). Injection of the peptide of this sequence into oocytes expressing P2X2(a) increased the rate of desensitization, whereas the eight-residue peptide lacking the valine had no effect. 5. Neutralizing lysines in the vicinity of the splice site increased the rate of receptor desensitization. Substituting glutamine for Lys365 produced the greatest effect ( approximately 30-fold increase), whereas mutating lysines that were further upstream or downstream of this position had progressively less of an effect. 6. We conclude that the C-terminal splice site of the P2X2 receptor is located within a region that is critically involved in regulating the rate of receptor desensitization. The valine at position 370 interacts with an intracellular hydrophobic site to slow the rate of desensitization. Nearby lysines may facilitate this interaction.

Sulfated cholecystokinin octapeptide in the rat: pontomedullary distribution and modulation of the respiratory pattern

We performed anatomical and physiological studies to determine the site and actions of sulfated cholecystokinin octapeptide (CCK8-S) on breathing. Peptide locations were determined by combined immunodetection of CCK8-S- containing synaptic varicosities and retrograde labeling of medullary neurons projecting to the ventral respiratory group. Retrogradely labeled neurons and CCK8-S immunolabeled varicosities overlapped within the nuclei of the solitary tract, ventral respiratory group, and the Kolliker-Fuse nucleus. Additional CCK8-S immunoreactive terminals were located in the rostroventrolateral medullary reticular nucleus, lateral paragigantocellular reticular nucleus, and the caudal pontine reticular nucleus. The respiratory effects of CCK8-S, which binds to CCK(A) and CCK(B) receptors, were examined by intravenous injection in adult rats and by bath application in the in vitro neonatal rat brainstem - spinal cord preparation. CCK8-S produced an increase in the mean amplitude of diaphragmatic electromyogram (EMG) of 28 +/- 35% (SD) and a decrease in mean respiratory interval of 13 +/- 4% in vivo. In vitro, CCK8-S significantly increased inspiratory duration and decreased respiratory interval, primarily by shortening expiratory duration. CCK8-unsulfated, a specific agonist for CCK(B) receptors, did not produce these effects. CCK8-S effects in the in vitro preparation were partially blocked by the CCK receptor antagonist lorglumide (final bath concentration 600 nM). These results suggest that CCK8-S modulates the respiratory rhythm via CCK(A) receptors within one or more medullary or pontine respiratory groups in both neonatal and adult rats.

Regional distribution and extrinsic innervation of intrinsic cardiac neurons in the guinea pig

Mammalian intrinsic cardiac neurons subserve different functions in different cardiac regions, but the regional anatomical organisation of the intracardiac nervous system is not well understood. We investigated the quantitative and qualitative distribution of cholinergic and adrenergic elements, and the intracardiac pathways of extrinsic cardiac nerves, in whole-mount preparations of guinea pig atria. Protein gene product 9.5 immunoreactivity (PGP 9.5-IR) marked intracardiac neuronal elements; immunoreactions for choline acetyltransferase (ChAT-IR) and tyrosine hydroxylase (TH-IR) distinguished cholinergic and adrenergic components, respectively. Catecholamine-containing components were identified by aldehyde-induced fluorescence histochemistry. Mean total number of atrial neurons was 1510+/-251 (SE); 85% of these occurred in ganglia of < or = 20 neurons. All neuronal somata expressing PGP 9.5-IR also expressed ChAT-IR, suggesting that these neurons were cholinergic. Right (RA) and left (LA) atria had statistically similar neuronal densities (6.4+/-1.2 and 2.4+/-0.7 neurons/mm2, respectively; analysis of variance, P< or =0.05). Neurons in RA were concentrated intercavally; LA neurons were concentrated near pulmonary vein ostia. Greatest density occurred in the interatrial septum (16.3+/-4.0 neurons/mm2). No neuronal somata expressed TH-IR or contained detectable amines but these elements were expressed by somata of small cells (mean total 124+/-33) throughout the atria, primarily associated with ganglia. Amine- and TH- containing varicosities were also present in ganglia, representing potential sites for adrenergic modulation of ganglionic neurotransmission. Branches of extrinsic cardiopulmonary and vagus nerves were distributed to all parts of both atria. The organisation of the intracardiac nervous system revealed in this study will facilitate further investigations of regional autonomic control of the heart.

Extrinsic inputs to intrinsic neurons in the porcine heart in vitro

Convergence of inputs from extrinsic cardiac nerves [vagus and cardiopulmonary (CPN)] on intrinsic cardiac neurons was investigated in the pig (Sus scrofa). A segment of the right atrial wall containing epicardial neurons along with attached stumps of the right vagus nerve and CPN was maintained in vitro; intracellular recordings were made from 57 neurons. Three types of neuron were identified by their responses to long intracellular depolarizing current pulses: phasic [discharged 1 action potential (AP); 40%]; accommodating (discharged multiple APs decrementing in frequency during pulse; 33%); and tonic (discharged multiple APs at a high frequency; 27%). Sixty-six percent of the neurons responded with excitatory postsynaptic potentials (EPSP) to vagal nerve stimulation; two-thirds of these cells fired APs when EPSP amplitude exceeded threshold level. Postsynaptic responses to vagal nerve stimulation were mediated by nicotinic ion channels; responses were eliminated by hexamethonium. CPN stimulation produced EPSPs but no APs in 17% of the neurons. All neurons responding with postsynaptic depolarizations to CPN stimulation also received vagal inputs. Combined stimulation of the vagus nerve and CPN produced APs in all but one of these neurons. Timolol eliminated postsynaptic responses from CPN stimulation, indicating that these responses involved beta-adrenergic receptors and likely resulted from activation of sympathetic postganglionic terminals. These results show that some intrinsic cardiac neurons receive convergent inputs from the CPN and vagus nerve. It is suggested that such neurons represent intraganglionic sites for sympathetic-parasympathetic interactions in neural control of the heart.

Distinct subdomains of the EphA3 receptor mediate ligand binding and receptor dimerization

Eph receptor tyrosine kinases and their ligands (ephrins) are highly conserved protein families implicated in patterning events during development, particularly in the nervous system. In a number of functional studies, strict conservation of structure and function across distantly related vertebrate species has been confirmed. In this study we make use of the observation that soluble human EphA3 (HEK) exerts a dominant negative effect on somite formation and axial organization during zebrafish embryogenesis to probe receptor function. Based on exon structure we have dissected the extracellular region of EphA3 receptor into evolutionarily conserved subdomains and used kinetic BIAcore analysis, mRNA injection into zebrafish embryos, and receptor transphosphorylation analysis to study their function. We show that ligand binding is restricted to the N-terminal region encoded by exon III, and we identify an independent, C-terminal receptor-dimerization domain. Recombinant proteins encoding either region in isolation can function as receptor antagonists in zebrafish. We propose a two-step mechanism of Eph receptor activation with distinct ligand binding and ligand-independent receptor-receptor oligomerization events.

The reproductive toxicity of molinate and metabolites to the male rat: effects on testosterone and sperm morphology

Molinate causes an impairment in reproductive capability in the male rat. Administration of molinate to rats (40 mg/kg/day for 7 days) caused a distinctive sperm lesion. At higher doses of molinate (140 mg/kg for 7 days) this lesion was accompanied by morphological changes to the testis that were consistent with a delayed release of the late spermatids to the seminiferous tubular lumen, a process controlled by the release of testosterone. In accordance with this, molinate (>/=40 mg/kg) caused a marked decrease in the concentration of circulating and testicular testosterone. The Leydig cells of the testis appear to be the primary target site in that radiolabel from [3H]molinate specifically localized within this cell type. In addition, esterase activity in the Leydig cells was inhibited following molinate administration. In vitro, molinate is a poor inhibitor of esterase activity, whereas molinate sulfoxide, a major metabolite of molinate in rats, and molinate sulfone were shown to be potent inhibitors of this process, suggesting that metabolic activation of molinate is required in vivo. Molinate sulfoxide (>/=10 mg/kg) caused an identical sperm lesion to that of molinate and markedly decreased plasma and testicular testosterone concentration. These effects were not seen with the molinate metabolites 4-hydroxymolinate (10 mg/kg), molinate sulfone (10 mg/kg), and hexamethyleneimine (10 mg/kg). Since the sperm lesion is a secondary event caused by a disruption of spermatogenesis, this would imply that the testis lesion and the reproductive impairment are also a consequence of molinate sulfur oxidation.

Actions of substance P on membrane potential and ionic currents in guinea pig stellate ganglion neurons

Neuropeptides are known to modulate the excitability of mammalian sympathetic neurons by their actions on various types of K+ and Ca2+ channels. We used whole cell patch-clamp recording methods to study the actions of substance P (SP) on dissociated adult guinea pig stellate ganglion (SG) neurons. Under current-clamp conditions, SG neurons exhibited overshooting action potentials followed by afterhyperpolarizations (AHP). The K+ channel blocker tetraethylammonium (1 mM), the Ca2+ channel blocker Cd2+ (0.1-0.2 mM), and SP (500 nM) depolarized SG neurons, decreased the AHP amplitude, and increased the action potential duration. In the presence of Cd2+, the effect of SP on membrane potential and AHP was reduced. Under voltage-clamp conditions, several different K+ currents were observed, including a transient outward K+ conductance and a delayed rectifier outward K+ current (IK) consisting of Ca(2+)-sensitive [IK(Ca)] and Ca(2+)-insensitive components. SP (500 nM) inhibited IK. Pretreatment with Cd2+ (20-200 microM) or the high-voltage-activated Ca2+ channel blocker omega-conotoxin (10 microM) blocked SP's inhibitory effects on IK. This suggests that SP reduces IK primarily through the inhibition of IK(Ca) and that this may occur, in part, via a reduction of Ca2+ influx through voltage-dependent Ca2+ channels. SP's actions on IK were mediated by a pertussis toxin-insensitive G protein(s) coupled to NK1 tachykinin receptors. Furthermore, we have confirmed that 500 nM SP reduced an inward Cd(2+)- and omega-conotoxin-sensitive Ba2+ current in SG neurons. Thus the actions of SP on IK(Ca) may be due in part to a reduction in Ca2+ influx occurring via N-type Ca2+ channels. This study presents the first description of ionic currents in mammalian SG neurons and demonstrates that SP may modulate excitability in SG neurons via inhibitory actions on K+ and Ca2+ currents.

Localization and functional expression of splice variants of the P2X2 receptor

cDNAs encoding three splice variants of the P2X2 receptor were isolated from rat cerebellum. The first variant has a serine/proline-rich segment deleted from the intracellularly located carboxyl-terminal domain of the P2X2 subunit. The second and third variants have the splice site in the second half of the predicted first transmembrane domain. Either a 12-amino acid insertion or a six-amino acid deletion occurs at this position. cRNAs for these isoforms of the P2X2 subunit were injected into Xenopus laevis oocytes and tested for function. ATP evoked inward currents only with the splice variant [designated P2X2(b)] having the 69-amino acid deletion. The potencies of various agonists at the homomeric P2X2(b) receptor were not significantly different from those at the P2X2(a) homomeric channel. However, the P2X2(b) receptor showed significantly lower antagonist sensitivity. In contrast to the nondesensitizing P2X2(a) receptor, prolonged application of ATP produced a more rapid desensitization of the P2X2(b) receptor. When the P2X2(a) and P2X2(b) receptor responses were recorded in transfected mammalian cells, this difference was again found. The change in desensitization may be determined by proline/serine-rich segments and/or phosphorylation motifs that are removed from the tail region in formation of the P2X2(b) subunit. In situ hybridization of the three newly isolated isoforms of the P2X2 subunit was performed at the macroscopic and cellular levels; transcripts for two of them [P2X2(b) and p2x2(c)] but not the third [p2x2(d)], which carries the 12-amino acid addition, were present in many structures in the neonatal rat brain and on sensory and sympathetic ganglia. mRNA for the p2x2(d) splice variant was present only in the nodose ganglion, at a low level.

Confocal scanning laser Doppler flowmetry: experiments in a model flow system

PURPOSE

We conducted this study toward validating confocal scanning laser Doppler flowmetry (SLDF), a new noninvasive technique for measuring retinal and optic nerve head hemodynamics.

METHODS

We designed a model flow system using a glass capillary coupled to a microlitre syringe driven by an infusion pump. Eleven capillaries with parallel walls (internal diameters ranging 705 to 25 microm) were used. The capillaries were perfused with skim milk over a range of pump flow rates. At each flow rate, measurements were made with the Heidelberg Retina Flowmeter (HRF) to study the relationship between HRF-measured flow and actual flow. The initial experiments (n = 2) were conducted to establish the approximate velocity operating range of the HRF with single HRF measurements across a wide range of flow rates, whereas the subsequent experiments (n = 9) were concentrated within this operating range with five HRF measurements at each flow rate.

RESULTS

When pump flow rates were converted to actual velocity at the measurement point for the initial experiments, the velocity operating range of the HRF was approximately 0.08 to 1.0 mm/s. For velocities of >1 mm/s, HRF measured velocity was not linearly related to actual velocity. Within the operating range, there was a highly significant linear relationship between HRF-measured flow and actual flow (0.935 < or = r < or = 0.990, p < 0.001). When the curves of HRF-measured velocity versus actual velocity for the different experiments were plotted, they largely superimposed. The variability of the HRF measurements was between 3.57% and 4.05% and was independent of flow rate.

CONCLUSIONS

SLDF measures reliably and linearly within a given operating range.

Ligand for EPH-related kinase (LERK) 7 is the preferred high affinity ligand for the HEK receptor

HEK is a member of the EPH-like receptor tyrosine kinase family, which appear to have roles in development and oncogenesis. Recently, we purified a soluble HEK ligand which is also a ligand (AL1) for the HEK-related receptor EHK1. Promiscuity appears to be a characteristic feature of interactions between the EPH-like receptors and their ligands, termed ligands for EPH-related kinases (LERKs). This prompted us to analyze the interactions between the HEK exodomain and fusion proteins comprising candidate LERKs and the Fc portion of human IgG1 (Fc) or a FLAGTM-peptide tag by surface plasmon resonance, size exclusion high performance liquid chromatography, sedimentation equilibrium, and transphosphorylation. Our results indicate that AL1/LERK7 is the preferred high-affinity ligand for HEK, forming a stable 1:1 complex with a dissociation constant of 12 nM. As expected the apparent affinities of bivalent fusion proteins of LERKs and the Fc portion of human IgG1 had significantly reduced dissociation rates compared with their monovalent, FLAGTM-tagged derivatives. High-avidity binding of monovalent ligands can be achieved by antibody-mediated cross-linking of monovalent ligands and with LERK7 results in specific phosphorylation of the receptor. By extrapolation, our findings indicate that some of the reported LERK-receptor interactions are a consequence of the use of bivalent ligand or receptor constructs and may be functionally irrelevant.

Addressing the National League for Nursing critical-thinking outcome

The National League for Nursing outcome-oriented accreditation process challenges nursing faculty to think about teaching and evaluating critical thinking. In a survey of schools of nursing, the authors found that programs are using standardized measures and individualized assessments to address the criterion. Their greatest difficulty involves decisions about measuring critical thinking. School administrators identified a variety of approaches effective for helping faculty. The authors provide insight and ideas for nursing faculty involved with critical thinking in the curricula.

Embryonic stem cells express multiple Eph-subfamily receptor tyrosine kinases

Eph and its homologues form the largest subfamily of receptor tyrosine kinases. Normal expression patterns of this subfamily indicate roles in differentiation and development, whereas their overexpression has been linked to oncogenesis. This study investigated the potential role of Eph-related molecules during very early embryonic development by examining their expression in embryonic stem (ES) cells and embryoid bodies differentiated from ES cells in vitro. By use of a strategy based on reverse transcriptase-mediated PCR, nine clones containing Eph-subfamily sequence were isolated from ES cells. Of these, eight were almost identical to one of four previously identified molecules (Sek, Nuk, Eck, and Mek4). However, one clone contained sequence from a novel Eph-subfamily member, which was termed embryonic stem-cell kinase or Esk. Northern analysis showed expression of Esk in ES cells, embryoid bodies, day 12 mouse embryos, and some tissues of the adult animal. Levels of expression were similar in ES cells and embryoid bodies. By comparison, Mek4 showed no significant transcription in the ES cell cultures by Northern analysis, whereas Eck displayed stronger signals in ES cells than in the embryoid bodies. These results suggest that Eph-subfamily molecules may play roles during the earliest phases of embryogenesis. Furthermore, the relative importance of different members of this subfamily appears to change as development proceeds.

Modulation of intrinsic cardiac neuronal activity by nitric oxide donors induces cardiodynamic changes

Studies were performed to determine 1) whether a specific marker for nitric oxide production is associated with canine intrinsic cardiac neurons, 2) whether the transmembrane properties of these neurons can be altered by nitric oxide donors, 3) whether in situ intrinsic cardiac neurons are sensitive to nitric oxide donors, and 4) whether these neurons are involved in cardiac regulation. Thirty to forty percent of canine intrinsic cardiac neurons were labeled with a selective anatomic marker for nitric oxide production. Nitric oxide donors modified the transmembrane properties of a subpopulation of intrinsic cardiac neurons studied in vitro. The nitric oxide donors nitroglycerine, sodium nitrite, and nitroprusside induced concentration-dependent increases in neuronal activity frequently associated with cardiac augmentation. Similar neuronal responses were elicited by N-methyl-D-aspartate receptor activation as well as when the precursor of nitric oxide, L-arginine, and the exogenous nitric oxide donor, S-nitroso-N-acetylpenicillamine, were administered, indicating that intrinsic cardiac neurons can be modulated by nitric oxide donors. Such neurons apparently are tonically influenced by locally released nitric oxide as local administration of the competitive inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl ester, suppressed their spontaneous activity. These data indicate that a significant population of nitric oxide-sensitive neurons exists in the canine intrinsic cardiac nervous system that are involved in cardiac regulation.