Return to Activities of Daily Living after Breast Cancer Surgery: An Observational Prospective Questionnaire-Based Study of Patients Undergoing Mastectomy with or without Immediate Reconstruction.

Background: Patients often ask about the time taken to return to activities of daily living (ADLs) after breast surgery, but there is a lack of data to give accurate guidance. We aimed to assess the feasibility of a study to determine the time taken to return to ADLs after mastectomy with or without breast reconstruction. Materials and Methods: A prospective multicentre, self-reported questionnaire-based feasibility study of women who had undergone mastectomy ± reconstruction was performed, between Jan 2017 and Dec 2019. Women were asked to self-report when they returned to 15 ADLs with a 5-option time scale for "return to activity." Results: The questionnaire was returned by 42 patients (median [range] age: 64 [31-84]). Of these, 22 had simple mastectomy, seven mastectomy and implant reconstruction, seven mastectomy and autologous reconstruction (DIEP), and six did not specify. Overall, over 90% could manage stairs and brush hair by two weeks and 84% could get in and out of the bath by four weeks. By 1-2 months, 92% could do their own shopping and 86% could drive. 68% of women employed returned to work within four months. Compared to simple mastectomy, patients undergoing reconstruction took a longer time to return to getting in/out of bath (<2 vs. 2-4 weeks), vacuuming (2-4 weeks vs. 1-2 months), and fitness (1-2 vs. 3-4 months). There was a slower return to shopping (1-2 months vs. 2-4 weeks), driving and work (both 3-4 vs. 1-2 months), and sports (3-4 vs. 1-2 months) in autologous reconstruction compared to implant reconstruction. Conclusion: This study is feasible. It highlights slower return to specific activities (particularly strength-based) in reconstruction patients, slower in autologous compared with implant reconstruction. The impact on return to ADLs should be discussed as part of the preoperative counselling as it will inform patients and help guide their decision making. A larger study is required to confirm these results.

Risk factors for complications and implant loss after prepectoral implant-based immediate breast reconstruction: medium-term outcomes in a prospective cohort.

BACKGROUND: Prepectoral implant-based breast reconstruction with acellular dermal matrix has become an increasingly popular option for selected patients. There are no randomized data to demonstrate short- or long-term outcomes. Cohort studies to date have demonstrated safety, but risk factors for complications are unknown. METHODS: A prospective cohort study of all patients undergoing prepectoral implant-based breast reconstruction between 2013 and 2019. Clinical factors and those related to reconstruction were analysed in relation to complications and implant loss using univariable and multivariable logistic regression. RESULTS: A total of 469 reconstructions were undertaken in 289 women; the majority of reconstructions were performed using a one-stage direct-to-implant technique with acellular dermal matrix. Median follow-up was 21 (range 2-71) months. Minor complications were seen after 11·2 per cent of reconstructions, major complications after 5·9 per cent, and the rate of implant loss by 3 months was 3·1 per cent. In the final multivariable model, sentinel node biopsy (odds ratio (OR) 5·06, 95 per cent c.i. 2·00 to 12·80), axillary clearance (OR 6·67, 1·17 to 37·94) and adjuvant radiotherapy (OR 7·11, 1·60 to 31·61) were independent risk factors for development of a major complication, and sentinel node biopsy (OR 4·32, 1·23 to 15·22) for implant loss. CONCLUSION: Prepectoral implant-based breast reconstruction has acceptable medium-term results but careful patient selection is advised.

Metastases in the cervical spine from primary head and neck cancers: current concepts of diagnosis and management.

Vertebral metastases from primary head and neck cancers are uncommon, and so there are no clear guidelines about management. The spinal cord can be compressed by a vertebral fracture or invasion of a tumour, and may present as an oncological and spinal emergency. The goals of treatment are to relieve pain and maintain neurological function. However, surgical treatments in this group of patients have not been defined, and primary operative treatment of spinal metastases remains controversial. Here we discuss their contemporary management. Surgical options should be considered for treatment to achieve stability of the spine, relieve pain, and preserve neurological function in certain cases.

PO-36 - Thrombin Inhibition Preoperatively (TIP) in early breast cancer, the first clinical trial of NOACs as an anti-cancer agent: trial methodology.

INTRODUCTION: Breast cancer is associated with a 3-4 fold increased risk of VTE. These patients have a 4-fold lower survival than those remaining free of VTE, implying VTE is a surrogate marker for aggressive cancer. Tumour expression of thrombin pathway markers are increased in the oestrogen receptor negative (ER-), high Ki67, more aggressive breast cancer subtypes. In in vitro and in vivo studies, the thrombin pathway promotes cancer growth and metastases, highlighting the potential role of the thrombin pathway as a therapeutic target in cancer. AIM: To determine whether 14days of a preoperative oral Factor Xa inhibitor (Rivaroxaban) in oestrogen receptor negative early breast cancer patients results in inhibition of tumour proliferation as determined by a reduction in tumour Ki67 from baseline (pre-treatment) to 14days post treatment start (at time of surgical excision). RATIONALE: The TF-VIIa-FXa complex activates Protease Activated Receptor (PAR)2 to induce angiogensis, growth factors and tumour cell migration. Thrombin, in part via PAR1, induces angiogenesis, tumour cell proliferation as well as in vivo metastasis. In early breast cancer, TF and PAR2 expression is increased in the stroma, particularly in the more aggressive ER-, high Ki67 (proliferation) cancers. Rivaroxaban is an orally active direct Factor Xa inhibitor. Through inhibition of the TF-FVIIa-FXa complex, it can downregulate TF-FVIIa-FXa activation of PAR2, and inhibit conversion of prothrombin to thrombin. We hypothesise that 14days of Rivaroxaban will reduce breast cancer proliferation, as a surrogate marker for anti-cancer efficacy, in early breast cancer patients awaiting resectional surgery. RESULTS: Trial methodology: A multi-centre phase II preoperative 'Window-of Opportunity' randomised controlled trial of Rivaroxaban compared to no treatment in ER-, stage I-III early breast cancer patients. Patients will be randomised 1:1:1 (Rivaroxaban 20mg od: Rivaroxaban 10mg od: no treatment) and receive 14 (+/-3) days of treatment in the window between diagnosis and surgery. Randomisation will be blinded to pathologists, but not to patients or clinicians. Primary analysis will be based on the two Rivaroxaban arms being combined to form a Rivaroxaban: no treatment, 2:1 trial design, with change in Ki67 from baseline (pre) to post Rivaroxaban/no treatment (post) being the primary endpoint, and the no treatment arm acting as a reference group. Subgroup analysis of the Rivaroxaban arm (20mg od:10mg od) will allow assessment of dose-response. ACKNOWLEDGEMENT: Funder: National Institute for Health Research Eudract No: 2014-004909-33 REC Number: 15/NW/0406 UKCRN ID: 19731 Expected commencement: January 2016. For further information please contact Chief Investigator: cliona.kirwan@manchester.ac.uk.

Infection prevention in breast implant surgery - A review of the surgical evidence, guidelines and a checklist.

INTRODUCTION: As a result of increasing use of implant-based breast reconstruction, complications such as infection are being encountered more frequently. Surgical Site Infections (SSIs) cause morbidity for the patient, can lead to capsular contracture or implant loss and are costly to healthcare systems. National Guidelines suggesting methods to reduce SSI related complications have been produced, but are limited in the scope of interventions covered and underlying evidence presented. METHODS: We performed a literature review encompassing a wide variety of possible SSI prevention strategies. We aimed to present summaries of the available evidence and give pragmatic recommendations as to their validity to use as guidelines for infection prevention strategies for implant-based breast reconstruction. RESULTS: A lack of high quality data relating to the benefit of SSI prevention strategies in implant-based breast reconstruction exists. Many papers relate to orthopaedic implant surgery, or clean surgery in general. Following review of the evidence, sufficient data exists to support use of perioperative antibiotics at implant-based breast reconstruction, with continuation for an extended period in "high risk" patients. Alcohol containing skin preparations should be used over aqueous solutions. Laminar air flow use is suggested. Theatre traffic should be kept to a minimum, as should duration of operative procedure. The implant pocket should be washed prior to implantation. Double gloving and conductive warming are also endorsed. CONCLUSIONS: We have produced a perioperative "Theatre Implant Checklist" for SSI prevention in implant-based breast surgery, with a set of pragmatic up to date guidelines, which allows the reader to evaluate the evidence upon which our recommendations are based.

One-stage breast reconstruction using the inferior dermal flap, implant, and free nipple graft.

BACKGROUND: An inferior dermal flap with implant is a useful option for women hoping for immediate breast reconstruction. This one-stage procedure uses autologous tissue as an inferolateral local sling, avoiding the costs and potential morbidity of prosthetic mesh and reducing valuable operating time. Patient comorbidity or choice may restrict autologous reconstruction options available. Many patients will still require a second procedure for subsequent nipple reconstruction and further appointments and costs for tattooing. METHOD: A prospective database was kept of a single surgeon's experience with 16 patients (19 breasts) from 2010 to 2012. Reconstruction was performed following a Wise pattern skin incision. An inferior, deepithelialized dermal sling was sutured to the pectoralis major to form a pocket for a silicone implant or tissue expander. A free nipple graft was sited at the time of reconstruction, with biopsies taken from retroareolar tissue. RESULTS: Patient average age was 54 years (range 36-66). Six mastectomies were for ductal carcinoma in situ, 6 for invasive carcinoma, 2 for lobular carcinoma, and 5 of 19 mastectomies were prophylactic. Average operative time was 165 min. There were no immediate complications requiring reoperation. All retroareolar biopsies were benign and no locoregional recurrences have occurred. Two nipples had partial necrosis of the lower pole but healed with conservative treatment. No patients required any subsequent procedures to their reconstructed breast. CONCLUSION: The inferior dermal flap with implant and free nipple graft is an excellent single-stage reconstruction option. This method offers a potentially safe, reliable, and aesthetically acceptable outcome for women with larger, ptotic breasts. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The role of oncoplastic therapeutic mammoplasty in breast cancer surgery--a review.

BACKGROUND: Reduction mammoplasty is an established technique for symptom relief in women with breast hypertrophy. Therapeutic mammoplasty and radiotherapy may allow cancers to be surgically treated whilst maintaining oncological safety and improving cosmetic outcome. This article aims to review the evidence upon which therapeutic mammoplasty is based and to outline an approach for surgical planning and selection. METHODS: A systematic PubMed and Medline literature search was carried out. All abstracts were studied and papers that dealt primarily with breast conservation using plastic surgery techniques were reviewed. RESULTS AND CONCLUSION: Therapeutic mammoplasty is a useful procedure for breast conserving cancer surgery in women with large breasts, conferring a good cosmetic and functional outcome. This article proposes that breast surgeons experienced in oncological surgery can safely resect tumours from all aspects of the breast with a minimal number of variations in standard mammoplasty technique.

Sentinel lymph node biopsy in early breast cancer surgery--working with the risks of vital blue dye to reap the benefits.

AIMS: Sentinel lymph node biopsy (SLNB) is an important method of staging early breast cancer because of the inherent benefits it confers on patients in terms of arm function and quality of life. Its success depends on a high level of accuracy in detecting the sentinel node. This is achieved by a dual mapping technique that employs a radio-labelled nanocolloid and a vital blue dye. The vital dyes however carry the risk of anaphylaxis, and as more surgeons employ SLNB in their daily practice, a proportionate rise in the number of anaphylactic reactions can be expected. A comprehensive review of risks and benefits associated with using vital blues dyes has not been published and therefore a retrospective review was undertaken of the different levels of anaphylaxis associated with vital dyes as well as their benefits in SLNB. METHODS: An OVID MEDLINE search was performed of the English published literature using appropriate search terms to find published trial data and case series that focused on adverse reactions to vital blue dyes. RESULTS: The risk of severe anaphylaxis (grade 3) can be as low as 0.06%, and up to 0.4% for patients undergoing SLNB when data is analysed from large trials. Furthermore, adverse reactions associated with blue dyes are reversible with appropriate management. CONCLUSIONS: Surgeons should continue to use vital dyes to ensure that SLNB remains a highly sensitive procedure.

Modulatory effects of heparin and short-length oligosaccharides of heparin on the metastasis and growth of LMD MDA-MB 231 breast cancer cells in vivo.

Expression of the chemokine receptor CXCR4 allows breast cancer cells to migrate towards specific metastatic target sites which constitutively express CXCL12. In this study, we determined whether this interaction could be disrupted using short-chain length heparin oligosaccharides. Radioligand competition binding assays were performed using a range of heparin oligosaccharides to compete with polymeric heparin or heparan sulphate binding to I(125) CXCL12. Heparin dodecasaccharides were found to be the minimal chain length required to efficiently bind CXCL12 (71% inhibition; P<0.001). These oligosaccharides also significantly inhibited CXCL12-induced migration of CXCR4-expressing LMD MDA-MB 231 breast cancer cells. In addition, heparin dodecasaccharides were found to have less anticoagulant activity than either a smaller quantity of polymeric heparin or a similar amount of the low molecular weight heparin pharmaceutical product, Tinzaparin. When given subcutaneously in a SCID mouse model of human breast cancer, heparin dodecasaccharides had no effect on the number of lung metastases, but did however inhibit (P<0.05) tumour growth (lesion area) compared to control groups. In contrast, polymeric heparin significantly inhibited both the number (P<0.001) and area of metastases, suggesting a differing mechanism for the action of polymeric and heparin-derived oligosaccharides in the inhibition of tumour growth and metastases.

Suppression of a slow post-spike afterhyperpolarization by calcineurin inhibitors.

A subset of myenteric neurons in the intestine (AH neurons) generate prolonged (>5 s) post-spike afterhyperpolarizations (slow AHPs) that are insensitive to apamin and tetraethylammonium. Generation of slow AHPs depends critically on Ca(2+) entry and intracellular release of Ca(2+) from stores, which then leads to the activation of a K(+) conductance that underlies the slow AHP (g(sAHP)). Slow AHPs are inhibited by stimulation of the cAMP/protein kinase A (PKA) pathway, suggesting that phosphorylation of the K(+)-channels that mediate the g(sAHP) (K(sAHP)-channels) is responsible for suppression of slow AHPs and possibly for the repolarization phase of slow AHPs. In the present study, we investigated the possibility that the rising phase of the slow AHP is mediated by dephosphorylation of K(sAHP)-channels by calcineurin (CaN), a Ca(2+)-calmodulin-dependent protein phosphatase, leading to an increase in g(sAHP) and activation of the associated current I(sAHP). Slow AHPs and I(sAHP) were recorded using conventional recording techniques, and we tested the actions of two inhibitors of CaN, FK506 and cyclosporin A, and also the effect of the CaN autoinhibitory peptide applied intracellularly, on these events. We report here that all three treatments inhibited the slow AHP and I(sAHP) (>70%) without significantly affecting the ability of neurons to fire action potentials. In addition, the slow AHP and I(sAHP) were suppressed by okadaic acid, an inhibitor of protein phosphatases 1 and 2A. Our results indicate that activation of the g(sAHP) that underlies the post-depolarization slow AHPs in AH neurons is mediated by the actions CaN and non-Ca(2+)-dependent phosphatases.

Radiological outcome of innocent infant hip clicks.

Radiographic follow-up is questioned for infants with hip clicks who have normal results from ultrasound scan examination of the hips. Infants whose sole risk factor for developmental dysplasia of the hip was a soft tissue hip click who had a normal ultrasound scan on initial assessment were identified. A follow-up 6-month pelvis radiograph was assessed. The acetabular index, position of femoral ossific nucleus and Shenton's line were measured. Rotated radiographs were excluded. One hundred and seventy-one infants (193 clicking hips) met the criteria for inclusion. All parameters measured were within normal ranges. In this study infants with hip clicks and a normal hip ultrasound scan on initial assessment had a normal radiograph at 6 months.

Chemokines and breast cancer: a gateway to revolutionary targeted cancer treatments?

Breast cancer is an example of a solid tumour which is well treated in the early stages of disease by surgical excision, but once metastatic spread has occurred, medical therapies (chemotherapy and radiotherapy) are highly toxic, expensive and palliative. It is known that certain tumours exhibit specific patterns of metastasis, chemokines may provide a molecular answer to this mystery. Chemokines and their receptors play important roles in the various stages of tumour development and metastasis. Chemokines interact with their specific receptors as well as interacting with the glycosaminoglycan (GAG) component of proteoglycan. We discuss the basic metastatic process and the involvement of chemokines in breast cancer biology. Finally, we summarize potential therapeutic applications of chemokines and chemokine/glycosaminoglycan interactions including chemokine agonists, antagonists, anti-sense therapy, immunotherapy and soluble GAGs, as well as future perspectives in this field.

Action potential afterdepolarization mediated by a Ca2+-activated cation conductance in myenteric AH neurons.

We investigated the nature of afterdepolarizing potentials in AH neurons from the guinea-pig duodenum using whole-cell patch-clamp recordings in intact myenteric ganglia. Afterdepolarizing potentials were minimally activated following action-potential firing under normal conditions, but after application of charybdotoxin (40 nM) or tetraethyl ammonium (TEA; 10-20 mM) to the bathing solution, prominent afterdepolarizing potentials followed action potentials. The whole-cell current underlying afterdepolarizing potentials (I(ADP)) in the presence of TEA (10-20 mM) reversed at -38 mV and was not voltage-dependent. Reduction of NaCl in the bathing (Krebs) solution to 58 mM shifted the reversal potential of the I(ADP) to -58 mV, suggesting that the current underlying the afterdepolarizing potential was carried by a mixture of cations. The relative contributions of Na(+) and K(+) to this current were estimated to be about 1:5. Substitution of external Na(+) with N-methyl D-glucamine blocked the current while replacement of internal Cl(-) with gluconate did not block the I(ADP). The I(ADP) was also inhibited when CsCl-filled patch pipettes were used. The I(ADP) was blocked or substantially decreased in amplitude in the presence of N-type Ca(2+) channel antagonists, omega-conotoxin GVIA and omega-conotoxin MVIIC, respectively, and was eliminated by external Cd(2+), indicating that it was dependent on Ca(2+) entry. The I(ADP) was also inhibited by ryanodine (10-20 microM), indicating that Ca(2+)-induced Ca(2+) release was involved in its activation. Niflumic acid consistently inhibited the I(ADP) with an IC(50) of 63 microM. Using antibodies against the pore-forming subunits of L-, N- and P/Q-type voltage-gated Ca(2+) channels, we have demonstrated that myenteric AH neurons express N- and P/Q, but not L-type voltage-gated Ca(2+) channels. We conclude that the ADP in myenteric AH neurons, in the presence of an L-type Ca(2+)-channel blocker, is generated by the opening of Ca(2+)-activated non-selective cation channels following action potential-mediated Ca(2+) entry mainly through N-type Ca(2+) channels. Ca(2+) release from ryanodine-sensitive stores triggered by Ca(2+) entry contributes significantly to the activation of this current.

Thiol reagents and nitric oxide modulate the gating of BKCa channels from the guinea-pig taenia caeci.

1. The site of the direct modulation of the gating of BKCa channels by the nitric oxide donor s-nitroso-l-cysteine (NOCys) was examined in excised membrane patches of the guinea-pig taenia caeci by the use of various thiol (sulphydryl)-specific reagents, including N-ethylmaleimide (NEM) and three charged methanethiosulphonate (MTS) reagents, namely positively charged 2-aminoethyl MTS hydrobromide (MTSEA) and [2-(trimethylammonium)ethyl] MTS bromide (MTSET) and negatively charged sodium (2-sulphonatoethyl) MTS (MTSES), which all specifically convert sulphydryls to a disulphide. 2. At 10 micro mol/L, NOCys transiently increased the probability of opening (N.Po) of the BKCa channels (at 0 mV) after a delay of 1-2 min. 3. Disulphide-reducing agents, such as dithiothreitol (10 micro mol/L), increased N.Po in a manner that was reversed by the sulphide-oxidizing agent thimerosal (10 micro mol/L). Both positively charged MTSET (2.5 mmol/L) and negatively charged MTSES (2.5 mmol/L) rapidly increased N.Po. However, only the MTSES-evoked increase in N.Po remained after a prolonged washout period. 4. The specific alkylating agent of cysteine thiols NEM (1 mmol/L) and the positively charged, but membrane permeable, MTSEA (2.5 mmol/L) decreased N.Po (at 0 mV). 5. Pre-exposure of excised membrane patches to NEM or MTSES prevented the excitatory actions of NOCys (10 micro mol/L). 6. We conclude that MTSES and NOCys must modify thiols on cysteine residues within basic regions of the channel protein that would electrostatically exclude MTSEA and MTSET. A consensus sequence of various mammalian alpha-subunits of the BKCa channel reveals two pairs of cysteine residues surrounded by basic amino acids that could be the site of action for NOCys and MTSES.

Nitric oxide and thiol reagent modulation of Ca2+-activated K+ (BKCa) channels in myocytes of the guinea-pig taenia caeci.

The modulation of large conductance Ca2+-activated K+ (BKCa) channels by the nitric oxide (NO) donors S-nitroso-L-cysteine (NOCys) and sodium nitroprusside (SNP) and agents which oxidize or reduce reactive thiol groups were compared in excised inside-out membrane patches of the guinea-pig taenia caeci. When the cytosolic side of excised patches was bathed in a physiological salt solution (PSS) containing 130 mM K+ and 15 nM Ca2+, few BKCa channel openings were recorded at potentials negative to 0 mV. However, the current amplitude and open probability (NPo) of these BKCa channels increased with patch depolarization. A plot of ln(NPo) against the membrane potential (V) fitted with a straight line revealed a voltage at half-maximal activation (V0.5) of 9.4 mV and a slope (K) indicating an e-fold increase in NPo with 12.9 mV depolarization. As the cytosolic Ca2+ was raised to 150 nM, V0.5 shifted 11.5 mV in the negative direction, with little change in K (13.1 mV). NOCys (10 microM) and SNP (100 microM) transiently increased NPo 16- and 3. 7-fold, respectively, after a delay of 2-5 min. This increase in NPo was associated with an increase in the number of BKCa channel openings evoked at positive potentials by ramped depolarizations (between -60 and +60 mV). Moreover, this NOCys-induced increase in NPo was still evident in the presence of 1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one (ODQ; 10 microM), the specific blocker of soluble guanylyl cyclase. The sulfhydryl reducing agents dithiothreitol (DTT; 10 and 100 microM) and reduced glutathione (GSH; 1 mM) also significantly increased NPo (at 0 mV) 7- to 9-fold, as well as increasing the number of BKCa channel openings evoked during ramped depolarizations. Sulfhydryl oxidizing agents thimerosal (10 microM) and 4,4'-dithiodipyridine (4,4DTDP; 10 microM) and the thiol-specific alkylating agent N-ethylmaleimide (NEM; 1 mM) significantly decreased NPo (at 0 mV) to 40-50% of control values after 5-10 min. Ramped depolarizations to +100 mV evoked relatively few BKCa channel openings. The effects of thimerosal on NPo were readily reversed by DTT, while the effects of NOCys were prevented by NEM. It was concluded that both redox modulation and nitrothiosylation of cysteine groups on the cytosolic surface of the alpha subunit of the BKCa channel protein can alter channel gating.

Somatostatin stimulates the brush-tailed possum sphincter of Oddi in vitro and in vivo.

BACKGROUND & AIMS: Somatostatin, a neuropeptide and hormone, is found in the biliary tract of several species. The aim of this study was to map the distribution of somatostatin-like immunoreactive nerve fibers in the extrahepatic biliary tract of the Australian possum and to determine the pharmacological effects of somatostatin 1-14 on sphincter of Oddi activity in vitro and in vivo. METHODS: Tissue was harvested for immunohistochemistry and sphincter of Oddi for circular or longitudinal muscle contractility. In anesthetized possums, sphincter of Oddi motility was measured by manometry, and transsphincteric flow was measured gravimetrically. RESULTS: Somatostatin immunoreactivity was evident in gallbladder ganglia nerve cell bodies and in nerve fibers of the common bile duct and sphincter of Oddi. Somatostatin 1-14 increased circular and longitudinal muscle contraction amplitude 3-4-fold (P < 0.05), but only the longitudinal muscle contraction amplitude was tetrodotoxin sensitive. Somatostatin 1-14 stimulated spontaneous sphincter of Oddi motility in a tetrodotoxin-insensitive manner, increasing basal pressure, contraction frequency, and amplitude 2-4-fold (P < 0.05) and reducing transsphincteric flow to 25% of control (P < 0.0001). CONCLUSIONS: Somatostatin-like immunoreactivity is present in the extrahepatic biliary tree, and somatostatin 1-14 stimulates sphincter of Oddi smooth muscle and nerves. The major action is direct stimulation of sphincter of Oddi circular muscle, which reduces transsphincteric flow.

Gastrin-releasing peptide stimulates gallbladder motility but not sphincter of Oddi motility in Australian brush-tailed possum.

The neural distribution and action of gastrin-releasing peptide in the extrahepatic biliary tree of the Australian brush-tailed possum was investigated. Immunohistochemical staining of fixed specimens demonstrated gastrin-releasing peptide-containing nerves throughout the neural plexuses of the gallbladder, sphincter of Oddi, and mucosa of the common bile duct. Gastrin-releasing peptide (5-2000 ng/kg) increased gallbladder tone to a level equivalent to that produced by cholecystokinin octapeptide (160 ng/kg). This action was tetrodotoxin-insensitive. Sphincter of Oddi motility and transsphincteric flow were not altered. Possible mediation of the gallbladder response by gastrin was examined. Gastrin (50-2500 ng/kg) stimulated gastric acid secretion, elevated gallbladder motility to 64% of that produced by gastrin-releasing peptide, and did not alter sphincter of Oddi motility. In conclusion, gastrin-releasing peptide-containing nerves are found in the neural plexus of the possum extrahepatic biliary tree. Gastrin-releasing peptide induces gallbladder contraction in part by a direct action on gallbladder smooth muscle and also via release of gastrin.

Substance P stimulates sphincter of Oddi motility and inhibits trans-sphincteric flow in the Australian brush-tailed possum.

Substance P containing nerves are widely distributed throughout the gastrointestinal tract. The aims of this study were to determine the distribution of substance P containing nerves in the extrahepatic biliary tree of the Australian brush-tailed possum and to characterize the effect of exogenous substance P on the sphincter of Oddi (SO) motility and transphincteric flow in vivo. Immunohistochemical staining of fixed specimens (n = 8) found moderate numbers of substance P containing nerve cell bodies and fibres throughout the neural plexuses of the SO, in particular in the serosal and intraluminal nerve trunks of the SO and gallbladder. Synthetic porcine substance P (1-2000 ng kg-1), administered by close intra-arterial injection (i.a.; n = 7), produced a dose-dependent elevation in basal pressure [P < 0.01] and an associated dose-dependent reduction in trans-sphincteric flow [P < 0.0001]. Substance P had no significant dose-dependent effect on SO phasic contraction amplitude or frequency. Tetrodotoxin (9 micrograms kg-1, i.a.) did not inhibit the effect of substance P on SO motility and trans-sphincteric flow (n = 5). In conclusion, substance P containing nerves are found throughout the possum extrahepatic biliary tree. Exogenous substance P stimulates SO motility and reduces trans-sphincteric flow in vivo by acting directly on the sphincter smooth muscle.

Synchronization of pacemaker cell firing by weak ELF fields: simulation by a circuit model.

Entrainment of output action potentials from repetitively firing pacemaker cells, brought about by regularly spaced excitatory or inhibitory postsynaptic inputs, is a well-known phenomenon. Synchronization of neural firing patterns by extremely low frequency (ELF) external electric fields has also been observed. Whereas current densities of approximately 10 A-m(-2) are required for direct excitation of otherwise quiescent neural tissue, much lower peak current densities (approximately 10[-2] A-m2) have been reported to entrain spontaneously firing molluscan pacemaker cells. We have developed a neural spike generator circuit model that simulates repetitive spike generation by a space clamped patch (area approximately 10[-7] m2) of excitable membrane subjected to depolarizing current. Picoampere (pA) range variation of DC depolarizing current causes a corresponding smooth variation of neural spike frequency, producing a physiologically realistic stimulus-response (S-R) characteristic. When lower pA range 60 Hz AC current is superposed upon the DC depolarizing current, smooth variation of the S-R characteristic is distorted by subharmonic locking of the spike generator at 30, 20, 15, 12, 10 Hz, and higher order subharmonic frequencies. Although the additional superposition of a physiologically realistic level of "white" current noise, covering the bandwidth 4-200 Hz, suffices to obscure higher order subharmonic locking, locking at 30, 20, and 15 Hz is still clearly evident in the presence of noise. Subharmonic locking is observed at an root mean square AC simulated tissue current density of approximately 10(-5) A-m(-2).

In vitro characterisation of intramural neural pathways between the duodenum and the sphincter of Oddi of the brush-tailed possum.

The aims of this study were to determine if neural pathways between the duodenum and sphincter of Oddi are intramural, activated by duodenal electrical field stimulation (EFS) in vitro, and contain capsaicin-sensitive primary afferents. The possible involvement of cholinergic (muscarinic and/or nicotinic) and adrenergic receptors in these pathways were also investigated. Duodenal EFS (5-60 Hz, 70 V, 0.5 ms duration, 10 s train) at sites 2 cm oral and 2 cm anal to the sphincter of Oddi-duodenal junction produced frequency-dependent excitatory responses in the sphincter of Oddi, measured by manometry (n = 3). Excitatory responses from duodenal circular muscle were also evident. Tetrodotoxin (1 microM; n = 7) pretreatment abolished both sphincter of Oddi and duodenal responses to duodenal EFS. Crushing the duodenum between the site of stimulation and the sphincter of Oddi-duodenal junction also abolished sphincter of Oddi response. The sphincter of Oddi responses to duodenal EFS at the oral and anal sites were reduced by pretreatment with (i) atropine (100 nM: n = 7) to 19 +/- 6% (P < 0.05) and 22 +/- 8% (P < 0.05) of control respectively. (ii) hexamethonium (100 microM: n = 9) to 10 +/- 2% (P < 0.01) and 6.0 + 2.5% (P < 0.01) of control respectively and (iii) guanethidine (1 microM; n = 6) to 75 +/- 6% (P < 0.05) and 78 +/- 10% (P < 0.05) of control, respectively. Combined pretreatment with phentolamine and propranolol (both 1 microM; n = 7) was without effect, as was capsaicin (1 microM; n = 12) pretreatment. Excitatory intramural pathways between the sphincter of Oddi and the duodenum are primarily cholinergic in nature and contain an adrenergic component. Capsaicin-sensitive primary afferents are not involved.