Defining the Extracellular Matrix of Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood with a propensity to metastasize. Current treatment for patients with RMS includes conventional systemic chemotherapy, radiation therapy, and surgical resection; nevertheless, little to no improvement in long term survival has been achieved in decades-underlining the need for target discovery and new therapeutic approaches to targeting tumor cells or the tumor microenvironment. To evaluate cross-species sarcoma extracellular matrix production, we have used murine models which feature knowledge of the myogenic cell-of-origin. With focus on the RMS/undifferentiated pleomorphic sarcoma (UPS) continuum, we have constructed tissue microarrays of 48 murine and four human sarcomas to analyze expression of seven different collagens, fibrillins, and collagen-modifying proteins, with cross-correlation to RNA deep sequencing. We have uncovered that RMS produces increased expression of type XVIII collagen alpha 1 (COL18A1), which is clinically associated with decreased long-term survival. We have also identified significantly increased RNA expression of COL4A1, FBN2, PLOD1, and PLOD2 in human RMS relative to normal skeletal muscle. These results complement recent studies investigating whether soft tissue sarcomas utilize collagens, fibrillins, and collagen-modifying enzymes to alter the structural integrity of surrounding host extracellular matrix/collagen quaternary structure resulting in improved ability to improve the ability to invade regionally and metastasize, for which therapeutic targeting is possible.

Epithelioid Sarcoma: Opportunities for Biology-Driven Targeted Therapy

Epithelioid sarcoma (ES) is a soft tissue sarcoma of children and young adults for which the preferred treatment for localized disease is wide surgical resection. Medical management is to a great extent undefined, and therefore for patients with regional and distal metastases, the development of targeted therapies is greatly desired. In this review, we will summarize clinically relevant biomarkers (e.g., SMARCB1, CA125, dysadherin, and others) with respect to targeted therapeutic opportunities. We will also examine the role of EGFR, mTOR, and polykinase inhibitors (e.g., sunitinib) in the management of local and disseminated disease. Toward building a consortium of pharmaceutical, academic, and non-profit collaborators, we will discuss the state of resources for investigating ES with respect to cell line resources, tissue banks, and registries so that a roadmap can be developed toward effective biology-driven therapies.

Editor's choice--Angulation of the C-arm during complex endovascular aortic procedures increases radiation exposure to the head

OBJECTIVES/BACKGROUND

The increased complexity of endovascular aortic repair necessitates longer procedural time and higher radiation exposure to the operator, particularly to exposed body parts. The aims were to measure directly exposure to radiation of the bodies and heads of the operating team during endovascular repair of thoracoabdominal aortic aneurysms (TAAA), and to identify factors that may increase exposure.

METHODS

This was a single-centre prospective study. Between October 2013 and July 2014, consecutive elective branched and fenestrated TAAA repairs performed in a hybrid operating room were studied. Electronic dosimeters were used to measure directly radiation exposure to the primary (PO) and assistant (AO) operator in three different areas (under-lead, over-lead, and head). Fluoroscopy and digital subtraction angiography (DSA) acquisition times, C-arm angulation, and PO/AO height were recorded.

RESULTS

Seventeen cases were analysed (Crawford II-IV), with a median operating time of 280 minutes (interquartile range 200-330 minutes). Median age was 76 years (range 71-81 years); median body mass index was 28 kg/m(2) (25-32 kg/m(2)). Stent-grafts incorporated branches only, fenestrations only, or a mixture of branches and fenestrations. A total of 21 branches and 38 fenestrations were cannulated and stented. Head dose was significantly higher in the PO compared with the AO (median 54 μSv [range 24-130 μSv] vs. 15 μSv [range 7-43 μSv], respectively; p = .022), as was over-lead body dose (median 80 μSv [range 37-163 μSv] vs. 32 μSv [range 6-48 μSv], respectively; p = .003). Corresponding under-lead doses were similar between operators (median 4 μSv [range 1-17 μSv] vs. 1 μSv [range 1-3 μSv], respectively; p = .222). Primary operator height, DSA acquisition time in left anterior oblique (LAO) position, and degrees of LAO angulation were independent predictors of PO head dose (p < .05).

CONCLUSIONS

The head is an unprotected area receiving a significant radiation dose during complex endovascular aortic repair. The deleterious effects of exposure to this area are not fully understood. Vascular interventionalists should be cognisant of head exposure increasing with C-arm angulation, and limit this manoeuvre.

Angiogenic cell therapy for critical limb ischemia: an update on concepts and trials

Therapeutic neovascularization is a novel approach used to salvage critically ischemic limbs that are not amenable to conventional treatments. Initial efforts were based on single injections of angiogenic factors but there is now a realization that delivering angiogenic cells is more likely to achieve effective revascularization. Clinical studies to date have mostly used mixtures of mononuclear cells harvested from the bone marrow or peripheral blood. The modest results achieved with these cells, only a proportion of which are angiogenic, has stimulated a search for more potent cell types. Preclinical studies have identified several candidates, including adipose derived, embryonic and induced pluripotent stem cells. This review provides an update on the current status of angiogenic cell therapy for the ischemic limb and outlines efforts aimed at enhancing the clinical efficacy of treatments.

Rb1 loss modifies but does not initiate alveolar rhabdomyosarcoma

Background

Alveolar rhabdomyosarcoma (aRMS) is a myogenic childhood sarcoma frequently associated with a translocation-mediated fusion gene, Pax3:Foxo1a.

Methods

We investigated the complementary role of Rb1 loss in aRMS tumor initiation and progression using conditional mouse models.

Results

Rb1 loss was not a necessary and sufficient mutational event for rhabdomyosarcomagenesis, nor a strong cooperative initiating mutation. Instead, Rb1 loss was a modifier of progression and increased anaplasia and pleomorphism. Whereas Pax3:Foxo1a expression was unaltered, biomarkers of aRMS versus embryonal rhabdomyosarcoma were both increased, questioning whether these diagnostic markers are reliable in the context of Rb1 loss. Genome-wide gene expression in Pax3:Foxo1a,Rb1 tumors more closely approximated aRMS than embryonal rhabdomyosarcoma. Intrinsic loss of pRb function in aRMS was evidenced by insensitivity to a Cdk4/6 inhibitor regardless of whether Rb1 was intact or null. This loss of function could be attributed to low baseline Rb1, pRb and phospho-pRb expression in aRMS tumors for which the Rb1 locus was intact. Pax3:Foxo1a RNA interference did not increase pRb or improve Cdk inhibitor sensitivity. Human aRMS shared the feature of low and/or heterogeneous tumor cell pRb expression.

Conclusions

Rb1 loss from an already low pRb baseline is a significant disease modifier, raising the possibility that some cases of pleomorphic rhabdomyosarcoma may in fact be Pax3:Foxo1a-expressing aRMS with Rb1 or pRb loss of function.

Peri-articular diseases of the hip: emerging frontiers in arthroscopic and endoscopic treatments

The precise diagnosis of both intra and extra-capsular disease of the hip is now possible because of commonly available advanced diagnostic imaging techniques. An increasing number of reports in the orthopedic literature describe new endoscopic and arthroscopic techniques to address peri-articular pathology of the hip. The purpose of this paper is to review current techniques in the management of extra-articular hip conditions.

The utility of conditioning sequences in barostat protocols for the measurement of rectal compliance

AIM

A barostat can be used to measure rectal sensitivity, compliance and elastance all of which are potentially important physiological parameters in the pathophysiology of faecal incontinence. Current practice recommends a conditioning distension sequence be performed prior to index distensions. We questioned the validity of this by comparing values for rectal compliance during sequential conditioning (CD) and index (ID) distensions in physiologically normal subjects.

METHOD

Ten subjects (five men, mean age 55.2 years) with normal anal canal manometry, anorectal sensitivity and balloon distension thresholds were studied. After determining the minimum distension pressure, subjects underwent sequential isobaric distensions: CD 4 mmHg distensions every 45 s and ID 4 mmHg every 2 min, both to a maximum of 24 mmHg or patient tolerance. Compliance values from both sequences were calculated by measuring the maximum slope of pressure-volume curves. A paired t-test was performed to compare any differences between sequences.

RESULTS

Mean rectal compliance were 11.4 ml/mmHg (SD 5.8 ml/mmHg) and 10.9 ml/mmHg (SD 5.7 ml/mmHg) in the CD and ID, respectively, with no statistical difference noted between distensions (P = 0.78).

CONCLUSION

Rectal compliance can be measured with a single distension protocol without the need for an initial conditioning distension. Conditioning the rectum adds additional complexity to barostat protocols and is not necessary.

Effect of rectal distension on voluntary external anal sphincter function in healthy subjects

AIM

Quantification of the anorectal reflex function is critical for explaining the physiological control of continence. Reflex external anal sphincter activity increases with rectal distension in a dynamic response. We hypothesized that rectal distension would similarly augment voluntary external anal sphincter function, quantified by measuring the anal maximum squeeze pressure.

METHOD

Fifty-seven subjects (32 men, 25 women; median age 62 years), with normal anal canal manometry and endoanal ultrasound results, underwent a rectal barostat study with simultaneous anal manometry. Stepwise isovolumetric 50-ml distensions (n=35) or isobaric 4-mmHg distensions (n=22) above the minimum distending pressure were performed (up to 200 ml or 16 mmHg respectively), whilst anal resting pressure and maximum squeeze pressure were recorded and compared with the baseline pressure.

RESULTS

The distension-induced squeeze increment was calculated as the maximum percentage increase in maximum squeeze pressure with progressive rectal distension. This was observed in 53 of the 57 subjects as a mean ± standard deviation (range) increase of 32.8 ± 24.1 (-5.5 to 97.7)%. The mean ± standard deviation (range) distension-induced squeeze increment in male subjects was 36.1 ± 25.7 (-5.5 to 97.7)% and in female subjects was 28.1 ± 20.1 (-3.8 to 70.2)%. There was no significant difference between the sexes (P=0.194).

CONCLUSION

Rectal distension augments external anal sphincter function, confirming the existence of a dynamic rectoanal response. This may represent a quantifiable and important part of the continence mechanism.

Biomechanical comparison of interfragmentary compression in transverse fractures of the olecranon

Compression and absolute stability are important in the management of intra-articular fractures. We compared tension band wiring with plate fixation for the treatment of fractures of the olecranon by measuring compression within the fracture. Identical transverse fractures were created in models of the ulna. Tension band wires were applied to ten fractures and ten were fixed with Acumed plates. Compression was measured using a Tekscan force transducer within the fracture gap. Dynamic testing was carried out by reproducing cyclical contraction of the triceps of 20 N and of the brachialis of 10 N. Both methods were tested on each sample. Paired t-tests compared overall compression and compression at the articular side of the fracture.

The mean compression for plating was 819 N (sd 602, 95% confidence interval (CI)) and for tension band wiring was 77 N (sd 19, 95% CI) (p = 0.039). The mean compression on the articular side of the fracture for plating was 343 N (sd 276, 95% CI) and for tension band wiring was 1 N (sd 2, 95% CI) (p = 0.038).

During simulated movements, the mean compression was reduced in both groups, with tension band wiring at −14 N (sd 7) and for plating −173 N (sd 32). No increase in compression on the articular side was detected in the tension band wiring group.

Pre-contoured plates provide significantly greater compression than tension bands in the treatment of transverse fractures of the olecranon, both over the whole fracture and specifically at the articular side of the fracture. In tension band wiring the overall compression was reduced and articular compression remained negligible during simulated contraction of the triceps, challenging the tension band principle.

Glomus tumour following a total knee replacement: a case report

Pain following total knee replacement (TKR) is a common problem and cause of poor satisfaction amongst patients. We report on a glomus tumour causing pain on the anterolateral aspect of the knee, 2 years after an otherwise successful total knee replacement for osteoarthritis. The tumour was treated by excision biopsy under general anaesthesia and the diagnosis confirmed by histopathological examination. The removal of the tumour relieved the pain and the patient regained good function. We conclude that a thorough clinical assessment of a patient with a painful knee following TKR is essential to detect and treat coincidental painful pathology.

Advantage of a one-stop referral and management service for ruptured abdominal aortic aneurysms

Background

In 2005, 4003 deaths in England and Wales were attributed to ruptured abdominal aortic aneurysm (RAAA). This study examined the referral and management patterns of this condition within one English county.

Methods

West Sussex has a population of 811 000 and is served by five hospitals with two main vascular networks. Between January 2005 and December 2007, data for community and in-hospital RAAA interventions and deaths were obtained. Probability of intervention and outcome for each network were calculated.

Results

Of 341 RAAA, 228 (66·9 per cent) presented to hospital. The mean distance travelled to hospitals with a full on-site vascular service was 17·6 (95 per cent confidence interval 15·5 to 19·7) km (124 patients) compared with 11·0 (9·5 to 12·7) km (104 patients) to hospitals with a partial or no vascular service (P &lt; 0·001). Patients managed by the network with a one-stop RAAA management policy had an odds ratio of 2·4 for undergoing surgery and 2·5 for surviving the operation (P = 0·001 and P = 0·017 respectively).

Conclusion

Patients with RAAA should be offered a one-stop emergency vascular service even if this involves further travel. Such a strategy offers significantly higher chance of intervention and survival from ruptured AAA.

Morphine, opioids, and the feline pulmonary vascular bed

BACKGROUND

Opioid-induced vasodepressor responses have been reported in a variety of species and laboratory models. The aim of this study was to ascertain the relative potencies of different clinically relevant opioids compared with traditional vasodepressor agents in the feline pulmonary vascular bed. A second aim was to study the effects of morphine and to identify the receptors involved in the mediation or the modulation of these effects.

METHODS

This was a prospective vehicle-controlled study involving an intact chest preparation of adult mongrel cats. The effects of various opioids, morphine, fentanyl, remifentanil, sufentanil, and meperidine were compared with other vasodepressor agents. Additionally, the effects of L-N(5)-(1-iminoethyl) ornithine hydrochloride (L-NIO) (nitric oxide synthase inhibitor), nimesulide [selective cyclooxygenase (COX)-2 inhibitor], glibenclamide (ATP-sensitive K+ channel blocker), naloxone (non-selective opioid receptor antagonist), and diphenhydramine (histamine H(1)-receptor antagonist) were investigated on pulmonary arterial responses to morphine and other selected agonists in the feline pulmonary vascular bed. The systemic pressure and lobar arterial perfusion pressure were continuously monitored, electronically averaged, and recorded.

RESULTS

In the cat pulmonary vascular bed of the isolated left lower lobe, morphine, remifentanil, fentanyl, sufentanil, and meperidine induced a dose-dependent moderate vasodepressor response and it appeared that sufentanil was the most potent on a nanomolar basis. The effects of morphine were not significantly altered after administration of L-NIO, nimesulide, and glibenclamide. However, the vascular responses to morphine were significantly attenuated following administration of naloxone and diphenhydramine.

CONCLUSION

The results of the present study suggest that sufentanil appears to have slightly more potency and morphine the least of the five opioid agonists studied on a nanomolar basis. Morphine-induced vasodilatory responses appeared to be mediated or modulated by both opioid receptor and histamine-receptor-sensitive pathways.

Primary tumour resection and survival in the palliative management of metastatic colorectal cancer

AIM

To examine whether surgical resection of the primary tumour confers a survival benefit and to identify the predictive factors of outcome in patients presenting with asymptomatic metastatic colorectal cancer (CRC).

MATERIALS AND METHODS

A review of a hospital database in a tertiary institution over a 6-year period (1999-2005) revealed 70 patients with asymptomatic primary CRC and unresectable liver metastases treated initially by systemic chemotherapy. A multivariate regression analysis model was used to determine the relative influence of multiple tumours, single/multiple liver metastases, tumour site, differentiation, response of liver and primary tumour to chemotherapy, biochemical response to chemotherapy, age at presentation, performance status and surgical intervention for the CRC primary.

RESULTS

In 67 cases (3 lost to follow-up), 63 had multiple and 4 single surgically irresectable liver metastases. A total of 41 deaths were recorded. All patients received systemic chemotherapy and surgery was performed for bowel obstruction, bleeding or stable disease (n=32). Surgery (OR 0.26; p=0.00013) and clinical response of the primary tumour (OR 0.53; p=0.012) were independently associated with prolonged survival. Proximal tumours (OR 2.61; p=0.0075) and multiple primaries (OR 3.37; p=0.02) were associated with poor outcome.

CONCLUSIONS

Surgical resection and response of the primary tumour to chemotherapy may be associated with improved survival, but proximal or multiple cancers predict poor outcome in patients with asymptomatic CRC and unresectable metastatic disease.

Reduction in varicose vein services: impact on operative training

INTRODUCTION

This study examines the impact of rationing varicose vein operations on operative training on a general surgical unit with a vascular interest.

PATIENTS AND METHODS

Log-books of middle-grade surgeons were analysed for 3-month periods before and after a decision by the local Primary Care Trust to ration varicose vein referrals. Number, intermediate equivalents and type of operations were recorded, whether they were general or vascular cases and whether the trainee had carried out or assisted with the operation.

RESULTS

There was a slight fall in the total number of operations in which the middle-grade surgeons were involved (208 to 186). There was a significant increase in general surgical cases with the fall in number of varicose vein operations (P < 0.0001). The fall in case-load and work-load operative training in vascular surgery was compensated by an increase in general surgical cases (P = 0.0003). This was largely due to increased number of hernia repairs (P = 0.0035).

CONCLUSIONS

From the point of operative training, a vascular unit in a district general hospital would not be sustainable following withdrawal of varicose vein services. However, this can be off-set by increasing general surgical case-load to fill the gap created.

Intra-abdominal and gastrointestinal tuberculosis

OBJECTIVE

Reports suggest that the rates of tuberculosis (TB) continue to rise in the UK and throughout the world. The spread of the disease is aided by poverty, overcrowding, co-infection with human immunodeficiency virus and drug resistance. Consistent with the overall trend, intra-abdominal and gastrointestinal (GI) TB rates are rising. Tuberculosis is a treatable disease, whether occurring in the lungs or at extra-pulmonary sites but the nonspecific features of the disease result in difficulty in establishing a diagnosis. In this report, we have concentrated on the benefits and potential pitfalls of diagnostic methods.

METHOD

A literature review was performed using the National Library of Medicine's Pubmed Database using the keywords diagnosis, management, abdominal and GI TB.

RESULTS

Abdominal TB presents a particular challenge, as the diverse features of the disease do not readily suggest a particular diagnosis and diagnostic delays lead to significant morbidity and mortality. A number of investigative methods have been used to aid in the diagnosis of abdominal and GI TB.

CONCLUSION

The nonspecific presentation of abdominal and GI TB present challenges in the diagnosis of this increasingly common disease. A high index of suspicion is an important factor in early diagnosis. After a diagnosis has been established, prompt initiation of treatment helps prevent morbidity and mortality.

Vascular surgery within general surgery: an analysis of workload 1989-2005

INTRODUCTION

There is considerable debate as to whether vascular surgery should be a subspecialty separate from general surgery. This study examines the changing relationship between general and vascular surgery in a district general surgical unit over 16 years.

PATIENTS AND METHODS

A detailed survey of referrals, admissions and operations to one unit was carried out over 3 months in 2003. This was compared with similar surveys in 1989, 1990 and 1995. In addition a 3-month audit of operations performed was carried out in 2005 following a decision by the Primary Care Trust (PCT) to reduce varicose vein referrals.

RESULTS

There was a significant increase in the number of varicose vein and arterial referrals 1989-2003 (P = 0.0001 and P < 0.0001, respectively). This was reflected in increased number of vascular admissions (P < 0.0001). In 1989, 14% of the arterial cases were admitted as emergencies. This figure rose to 52% in 2003 (P < 0.0001). There was a significant increase in the number of arterial operations performed between 1989 and 1995; however, from 1995 to 2003 this number fell P < 0.0001). The number of varicose vein procedures increased significantly 1989-2003 (P < 0.0001), with a significant fall after the PCT decision (P < 0.0001). However, the number of operations carried out in 2005 increased slightly with the proportion of general surgical cases, mostly hernia repairs and laparoscopic cholecystectomies, increasing.

CONCLUSIONS

With increasing specialisation comes the risk that reduction in any aspect of a particular specialty may result in that unit becoming unsustainable. In vascular surgery this will inevitably lead to centralisation of services. In a large district general hospital having two general surgeons with a vascular interest, the general surgical component has maintained the workload of the unit following reduction in varicose vein referrals.

Health control beliefs and quality of life considerations before and during periodontal treatment

PURPOSE

Previous studies have indicated that health beliefs are related to the periodontal disease status and treatment behaviour of patients. However, it is possible that treatment may affect a patient's health beliefs and thus complicate this issue. The present study therefore looked for changes in health control beliefs and oral health impacts in patients undergoing periodontal treatment in a dental school.

MATERIALS AND METHODS

Questionnaires assessing dental multidimensional locus of control (LOC) and oral health impact profile (OHIP) were posted to subjects due to attend for initial periodontal consultation and were returned by 127 patients who attended. Repeat questionnaires were sent to all subjects 6 months later when they had received some oral hygiene instruction, scaling and root planing, and 55 were returned.

RESULTS

Comparison of data for those subjects who completed both questionnaires showed no difference in LOC but showed a trend (p = 0.065) towards reduced OHIP (i.e. improved oral health-related quality of life).

CONCLUSIONS

These subjects apparently did not alter their health control beliefs about periodontal disease as a result of treatment, but there may have been an improvement in their oral health-related quality of life. Further studies are required to confirm these possibilities.

Bacterial contaminants and antibiotic prophylaxis in total hip arthroplasty

We have investigated the contaminating bacteria in primary hip arthroplasty and their sensitivity to the prophylactic antibiotics currently in use. Impressions (627) of the gloved hands of the surgical team in 50 total hip arthroplasties were obtained on blood agar. The gloves were changed after draping, at intervals of 20 minutes thereafter, and before using cement. Changes were also undertaken whenever a visible puncture was detected. The culture plates were incubated at 37°C for 48 hours. Isolates were identified and tested for sensitivity to flucloxacillin, which is a recognised indicator of sensitivity to cefuroxime. They were also tested against other agents depending upon their appearance on Gram staining.

We found contamination in 57 (9%) impressions and 106 bacterial isolates. Coagulase-negative staphylococci were seen most frequently (68.9%), but we also isolated Micrococcus (12.3%), diphtheroids (9.4%), Staphylococcus aureus (6.6%) and Escherichia coli (0.9%). Of the coagulase-negative staphylococci, only 52.1% were sensitive to flucloxacillin and therefore to cefuroxime. We believe that it is now appropriate to review the relevance of prophylaxis with cefuroxime and to consider the use of other agents.

Gene profiling the effects of calcium deficiency versus 1,25-dihydroxyvitamin D induced hypercalcemia in rat kidney cortex

Determinants involved in the activation and repression of 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) synthesis in renal cortex by changes in extracellular Ca were studied. Cortical kidney RNA isolated from hypocalcemic (LC) rats generated by a low Ca diet, and hypercalcemic (HC) rats generated by a normal Ca diet and two sequential 1 microg doses of 1,25(OH)(2)D(3). Among the genes up-regulated were 1alpha-OHase (4.6-fold) in the LC group and high differential gene expression of VDR (4.0-fold) and 24-OHase (10.4-fold) in the HC group. Moreover, the exposure of renal cortex to LC versus HC conditions revealed a high differential expression of a PKA-dominated pathway involving CBP interacting protein, GATA-1 and CREB transcription factors in the LC model. In the HC model, elevated renal cortex gene expression of several growth factors, peptide receptors, and intracellular signaling molecules depicts a role for CaSR activation and receptor tyrosine kinase signaling in 1,25(OH)(2)D(3)-mediated gene activation and repression of 1alpha-OHase.

Glove perforation and contamination in primary total hip arthroplasty

We conducted a randomised, controlled trial to determine whether changing gloves at specified intervals can reduce the incidence of glove perforation and contamination in total hip arthroplasty. A total of 50 patients were included in the study. In the study group (25 patients), gloves were changed at 20-minute intervals or prior to cementation. In the control group (25 patients), gloves were changed prior to cementation. In addition, gloves were changed in both groups whenever there was a visible puncture. Only outer gloves were investigated.

Contamination was tested by impression of gloved fingers on blood agar and culture plates were subsequently incubated at 37°C for 48 hours. The number of colonies and types of organisms were recorded. Glove perforation was assessed using the water test. The incidence of perforation and contamination was significantly lower in the study group compared with the control group. Changing gloves at regular intervals is an effective way to decrease the incidence of glove perforation and bacterial contamination during total hip arthroplasty.

Effects of esophageal stimulation in healthy subjects

We studied the effects of esophageal electrical stimulation on heart rate variability power spectra (PS/HRV) and cortical evoked potentials (EPs) in healthy subjects. The intensity of stimulation was varied from 2.7 to 20 mA. We found that the amplitude of the cortical evoked potentials (amplitude of the N2/P2 peak) increased from 5.1 +/- 0.7 microV at 5 mA to 16.3 +/- 1.1 microV at 20 mA. The PS/HRV showed an increase in the vagal modulation of the sinus node. When the stimulation frequency was varied from 0.1 to 1 Hz at a constant intensity of 15 mA, the amplitude of cortical EPs (N2/P2 peak) decreased with increase in the frequency of stimulation (p < 0.05). The LF:HF ratio decreased significantly for all frequencies of stimulation (p < 0.005). An experimental paradigm to evoke the cognitive component in the cortical EPs yielded a peak around 354 ms following the stimulus.

Effects of esophageal stimulation in patients with functional disorders of the gastrointestinal tract

We studied the effects of esophageal electrical stimulation on cortical-evoked potentials (EPs) and power spectrum of heart rate variability (PS/HRV) in patients with diabetes and non-cardiac chest pain (NCCP). We also recorded cognitive-evoked potentials (P300 EPs) in response to an odd-ball stimulation in patients with NCCP. Diabetic patients did not yield reproducible cortical EPs. Their power spectra of heart rate variability (PS/HRV) showed an increased vagal modulation during stimulation. In patients with NCCP the P300 EPs were of greater amplitude (17 +/- 3 microV vs. 12 +/- 1 microV in controls, p < 0.04), while peak latencies were slightly elongated in patients (382 +/- 22 ms vs. 354 +/- 12 ms in controls). The PS/HRV in these patients also showed an increased vagal modulation of the sinus node activity. Our results suggest the following: (1) in patients with diabetes, afferent pathways and processing of sensory signals are likely to be impaired; (2) an increased perception of esophageal stimulation reflects an exaggerated brainstem response and altered cortical processing of visceral sensation in patients with NCCP.

The strategic control of gaze direction in the Tower-of-London task

In this paper, we describe a novel approach to the study of problem solving involving the detailed analysis of natural scanning eye movements during the "one-touch" Tower-of-London (TOL) task. We showed subjects a series of pictures depicting two arrangements of colored balls in pockets within the upper and lower halves of a computer display. The task was to plan (but not to execute) the shortest movement sequence required to rearrange the balls in one half of the display (the Workspace) to match the arrangement in the opposite half (the Goalspace) and indicate the minimum number of moves required for problem solution. We report that subjects are more likely to look towards the Goalspace in the initial period after picture presentation, but bias gaze towards the Workspace during the middle of trials. Towards the end of a trial, subjects are once again more likely to fixate the Goalspace. This pattern is found regardless of whether the subjects solve problems by rearranging the balls in the lower or upper visual fields, demonstrating that this strategy correlates with discrete phases in problem solving. A second experiment showed that efficient planners direct their gaze selectively towards the problem critical balls in the Workspace. In contrast, individuals who make errors spend more time looking at irrelevant items and are strongly influenced by the movement strategy needed to solve the preceding problem. We conclude that efficient solution of the TOL requires the capacity to generate and flexibly shift between control sets, including those underlying ocular scanning. The role of working memory and the prefrontal cerebral cortex in the task are discussed.

Neurocardiac and cerebral responses evoked by esophageal vago-afferent stimulation in humans: effect of varying intensities

OBJECTIVE

This study was designed to determine whether esophageal vago-afferent electrostimulation, over a wide range of stimulus intensities, can sustain a cardiac vago-efferent effect by way of central nervous system processing.

METHODS

Studies were performed in ten healthy male subjects (23.9 +/- 6.3 years). Esophageal electrostimulation was carried out using a stimulating electrode placed in the distal esophagus. Stimulation of esophageal vago-afferent fibres was employed using electrical impulses (200 microseconds at 0.2 Hz x 128 s) varying from 2.7 to 20 mA. Respiratory frequencies, beat-to-beat heart rate autospectra and cerebral evoked potentials were recorded at baseline and at each stimulus intensity in random order.

RESULTS

With esophageal electrical stimulation, we observed a small non-significant decrease in heart rate. There was a dramatic shift of the instantaneous heart rate power spectra towards enhanced cardiac vagal modulation with intensities as low as 5 mA. This effect was sustained throughout all intensities with no further change in either the low frequency or high frequency power. Conversely, there was a linear dose response relationship between cerebral evoked potential amplitude and stimulus intensity mainly occurring above perception threshold (10 mA). Esophageal stimulation had no significant effect on heart rate or respiratory frequency at any stimulus intensity.

CONCLUSIONS

These results indicate that electrical stimulation of the distal esophagus across a wide range of current intensities elicits a reproducible shift in the heart rate power spectrum towards enhanced vagal modulation. The data suggest a closed loop afferent/efferent circuitry wherein tonic visceral afferent impulses appear to elicit a phasic or modulatory vago-efferent cardiac response in healthy subjects.

Neurocardiac response to esophageal electric stimulation in humans: effects of varying stimulation frequencies

The purpose of this study was to determine if the cardioautonomic responses to esophageal electric stimulation were mediated entirely through modulation of respiratory frequency or a direct vagal effect. We performed electric stimulation of the esophagus in 13 healthy male controls (24 +/- 6 yr) using a manometric catheter to which a stainless steel electrode was attached. Stimulation frequencies ranged from 0.1 to 1 Hz and were applied in random fashion. We computed the power spectra of the heart rate variability and respiratory frequency as measures of autonomic function. Electric stimulation of the esophagus produced significant increases in the high-frequency power of the heart rate autospectrum at all stimulation frequencies (maximal at 0.2 Hz). However, regardless of the frequency of esophageal stimulation, the respiratory rate was not changed from baseline. These studies indicate that enhancement of cardiac vagal modulation observed in response to esophageal electric stimulation is not primarily due to changes in respiratory frequency, but rather occurs through a direct, vagally mediated action through sensory neural pathways involving vagal esophageal afferents.