Surgical and endoscopic management options for patients with GERD based on proton pump inhibitor symptom response: recommendations from an expert U.S. panel

BACKGROUND AND AIMS

The objective of this study was to examine expert opinion and agreement on the treatment of distinct GERD profiles from surgical and therapeutic endoscopy perspectives.

METHODS

We used the RAND/University of California, Los Angeles Appropriateness Method over 6 months (July 2018 to January 2019) to assess the appropriateness of antireflux interventions among foregut surgeons and therapeutic gastroenterologists. Patients with primary atypical or extraesophageal symptoms were not considered. Patient scenarios were grouped according to their symptom response to proton pump inhibitor (PPI) therapy. The primary outcome was appropriateness of an intervention.

RESULTS

Antireflux surgery with laparoscopic fundoplication (LF) and magnetic sphincter augmentation (MSA) were ranked as appropriate for all complete and partial PPI responder scenarios. Transoral incisionless fundoplication was ranked as appropriate in complete and partial PPI responders without a hiatal hernia. Radiofrequency energy was not ranked as appropriate for complete or partial responders. There was lack of agreement between surgery and interventional gastroenterology groups on the appropriateness of LF and MSA for PPI nonresponders. Rankings for PPI nonresponders were similar when results from impedance-pH testing on PPI therapy were available, except that LF and MSA were not ranked as appropriate for PPI nonresponders if the impedance-pH study was negative.

CONCLUSIONS

This work highlights areas of agreement for invasive therapeutic approaches for GERD and provides impetus for further interdisciplinary collaboration and trials to compare and generate novel and effective treatment approaches and care pathways, including the role of impedance-pH testing in PPI nonresponders.

Magnetic Sphincter Augmentation Superior to Proton Pump Inhibitors for Regurgitation in a 1-Year Randomized Trial

BACKGROUND & AIMS

Regurgitative gastroesophageal reflux disease (GERD) refractive to medical treatment is common and caused by mechanical failure of the anti-reflux barrier. We compared the effects of magnetic sphincter augmentation (MSA) with those of proton-pump inhibitors (PPIs) in a randomized trial.

METHODS

Patients with moderate to severe regurgitation (assessed by the foregut symptom questionnaire) despite once-daily PPI therapy (n = 152) were randomly assigned to groups given twice-daily PPIs (n = 102) or laparoscopic MSA (n = 50) at 20 sites, from July 2015 through February 2017. Patients answered questions from the foregut-specific reflux disease questionnaire and GERD health-related quality of life survey about regurgitation, heartburn, dysphagia, bloating, diarrhea, flatulence, and medication use, at baseline and 6 and 12 months after treatment. Six months after PPI therapy, MSA was offered to patients with persistent moderate to severe regurgitation and excess reflux episodes during impedance or pH testing on medication. Regurgitation, foregut scores, esophageal acid exposure, and adverse events were evaluated at 1 year.

RESULTS

Patients in the MSA group and those who crossed over to the MSA group after PPI therapy (n = 75) had similar outcomes. MSA resulted in control of regurgitation in 72/75 patients (96%); regurgitation control was independent of preoperative response to PPIs. Only 8/43 patients receiving PPIs (19%) reported control of regurgitation. Among the 75 patients who received MSA, 61 (81%) had improvements in GERD health-related quality of life improvement scores (greater than 50%) and 68 patients (91%) discontinued daily PPI use. Proportions of patients with dysphagia decreased from 15% to 7% (P < .005), bloating decreased from 55% to 25%, and esophageal acid exposure time decreased from 10.7% to 1.3% (P < .001) from study entry to 1-year after MSA (Combined P < .001). Seventy percent (48/69) of patients had pH normalization at study completion. MSA was not associated with any peri-operative events, device explants, erosions, or migrations.

CONCLUSIONS

In a prospective study, we found MSA to reduce regurgitation in 95% of patients with moderate to severe regurgitation despite once-daily PPI therapy. MSA is superior to twice-daily PPIs therapy in reducing regurgitation. Relief of regurgitation is sustained over 12 months. ClinicalTrials.gov no: NCT02505945.

Laparoscopic magnetic sphincter augmentation versus double-dose proton pump inhibitors for management of moderate-to-severe regurgitation in GERD: a randomized controlled trial

BACKGROUND AND AIMS

GERD patients frequently complain of regurgitation of gastric contents. Medical therapy with proton-pump inhibitors (PPIs) is frequently ineffective in alleviating regurgitation symptoms, because PPIs do nothing to restore a weak lower esophageal sphincter. Our aim was to compare effectiveness of increased PPI dosing with laparoscopic magnetic sphincter augmentation (MSA) in patients with moderate-to-severe regurgitation despite once-daily PPI therapy.

METHODS

One hundred fifty-two patients with GERD, aged ≥21 years with moderate-to-severe regurgitation despite 8 weeks of once-daily PPI therapy, were prospectively enrolled at 21 U.S. sites. Participants were randomized 2:1 to treatment with twice-daily (BID) PPIs (N = 102) or to laparoscopic MSA (N = 50). Standardized foregut symptom questionnaires and ambulatory esophageal reflux monitoring were performed at baseline and at 6 months. Relief of regurgitation, improvement in foregut questionnaire scores, decrease in esophageal acid exposure and reflux events, discontinuation of PPIs, and adverse events were the measures of efficacy.

RESULTS

Per protocol, 89% (42/47) of treated patients with MSA reported relief of regurgitation compared with 10% (10/101) of the BID PPI group (P < .001) at the 6-month primary endpoint. By intention-to-treat analysis, 84% (42/50) of patients in the MSA group and 10% (10/102) in the BID PPI group met this primary endpoint (P < .001). Eighty-one percent (38/47) of patients with MSA versus 8% (7/87) of patients with BID PPI had ≥50% improvement in GERD-health-related quality of life scores (P < .001), and 91% (43/47) remained off of PPI therapy. A normal number of reflux episodes and acid exposures was observed in 91% (40/44) and 89% (39/44) of MSA patients, respectively, compared with 58% (46/79) (P < .001) and 75% (59/79) (P = .065) of BID PPI patients at 6 months. No significant safety issues were observed. In MSA patients, 28% reported transient dysphagia; 4% reported ongoing dysphagia.

CONCLUSION

Patients with GERD with moderate-to-severe regurgitation, especially despite once-daily PPI treatment, should be considered for minimally invasive treatment with MSA rather than increased PPI therapy. (Clinical trial registration number: NCT02505945.).

Extended adjuvant temozolomide with cis-retinoic acid for adult glioblastoma

OBJECTIVE

To determine the toxicity and effectiveness of 24 months of adjuvant temozolomide (tmz) with cis-retinoic acid (cra) for patients with glioblastoma.

METHODS

This retrospective population-based review considered the charts of all patients diagnosed with glioblastoma in Manitoba and referred to a provincial cancer centre during 2002-2008. Consecutive patients came from a population-based referral centre and provincial cancer registry. All patients were treated according to the local standard of care with surgical resection followed by concurrent radiotherapy and tmz 75 mg/m(2) daily, followed by tmz 150-200 mg/m(2) for days 1-5, repeated every 28 days for up to 24 cycles, and cra 50 mg/m(2) twice daily for days 1-21, repeated every 28 days. The main outcome measures were safety, tolerability, and effectiveness of long-term tmz and cra.

RESULTS

Of 247 patients diagnosed with glioblastoma in Manitoba during the study period, 116 started concurrent chemoradiotherapy, and 80 received adjuvant tmz. Of the patients who started concurrent chemoradiotherapy, 80 began adjuvant chemotherapy. Patients completed a median of 5.5 cycles of tmz and 3 cycles of cra. Grade 3 or 4 hematologic toxicity was noted in 16% of patients. Median overall survival was 15.1 months, and 26.7% of patients remained alive at 2 years.

CONCLUSIONS

Extended adjuvant tmz and cra is well tolerated. However, the population-based effectiveness of this regimen is similar to the clinical trial efficacy of 6 months of adjuvant tmz. Future studies in glioblastoma should incorporate duration of adjuvant chemotherapy into the study design.

SHRiMP2: sensitive yet practical SHort Read Mapping

We report on a major update (version 2) of the original SHort Read Mapping Program (SHRiMP). SHRiMP2 primarily targets mapping sensitivity, and is able to achieve high accuracy at a very reasonable speed. SHRiMP2 supports both letter space and color space (AB/SOLiD) reads, enables for direct alignment of paired reads and uses parallel computation to fully utilize multi-core architectures.

AVAILABILITY

SHRiMP2 executables and source code are freely available at: http://compbio.cs.toronto.edu/shrimp/.

Encouraging results from a phase I study of capecitabine (X), irinotecan (I) and oxaliplatin (O) as first-line therapy in patients (pts) with metastatic colorectal cancer (MCRC)

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Background: First-line treatment with I, O and infusional 5-FU/Leucovorin (LV) triplets is associated with high response rates and long survival in MCRC. The oral fluoropyrimidine X is better tolerated and shows improved response rates vs. 5- FU/LV in MCRC. This dose-escalation study aims to establish dose-limiting toxicity (DLT), maximum tolerated dose (MTD) and recommended phase II doses (RPIID) of I, O and X and to evaluate efficacy and safety in first-line. Methods: Starting doses were: I (180mg/m2 i.v. d1), O (85mg/m2 i.v. d1), × (850mg/m2 bid orally d2–15). Dose escalations are based on toxicity observed at previous dose level (DL), until DLT, MTD and RPIID are reached. Results: We have enrolled 27 pts (21 men, 6 women), median age 59 years (range 25–74), at 6 DLs. ECOG PS was 0 or 1 in 25 pts, and 2 in 2 pts. Pts received a median of 10 cycles (range 1–23). All pts are evaluable for toxicity (24 for efficacy). Most common grade 3/4 hematological adverse events (AEs) during dose escalation: granulocytopenia (41%), anemia (7%), and thrombocytopenia (15%). Most common grade 3 non-hematological AEs: late-onset diarrhea (11%), fever (14%), and fatigue (4%). DLTs at each dose level: DL1 (1 febrile neutropenia with bowel perforation); DL2 (1 grade 3 diarrhea); DL3 (1 febrile neutropenia with grade 2 edema); DL4 (1 severe febrile neutropenia in cycles 2&3, pt deceased due to sepsis); no DLTs were reported at DL5 & 6. MTD has not yet been reached. Overall response rate is 79% (95% CI, 62–97%), including 2 CRs and 17 PRs (3 still unconfirmed). Disease control rate is 92%. Two pts had subsequent curative liver resection and 4 pts are under consideration for curative procedures. Median progression-free survival is 15 months (95% CI, 8–22). Conclusions: XIO is well tolerated and highly effective as first-line treatment for MCRC. Severe neutropenia was significant but of short duration and manageable; it is likely to be the main DLT. MTD has not yet been identified but is expected shortly. A phase II study to confirm the efficacy and safety of XIO, possibly in combination with targeted agents, will follow. Supported by Roche, Sanofi-Aventis, and Pfizer Canada.

No significant financial relationships to disclose.

A phase I/II study of capecitabine (X), irinotecan (I) and oxaliplatin (O) as first-line therapy in patients (pts) with advanced or metastatic colorectal cancer (MCRC)

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Background: Triplets of I, O and infusional 5-FU/Leucovorin (LV) are associated with high response rates and long survival in first-line MCRC [Falcone et al. JCO 2002;20:4006–14]. The oral fluoropyrimidine X has proved higher response rates and improved safety vs. 5-FU/LV in MCRC. Methods: This ongoing dose-escalation study aims to establish dose-limiting toxicity (DLT), maximum tolerated dose (MTD) and recommended phase II doses (RPIID) of I and O in combination with X as first-line therapy for MCRC and to assess the efficacy and safety of this XIO combination. Starting doses were: I (180mg/m2 i.v. on day 1), O (85mg/m2 i.v. on day 1), and X (850mg/m2 bid orally on days 2–15). Dose escalations are based on toxicity observed at the previous dose level (DL), until DLT, MTD and RPIID are documented, at which time a phase II component begins. Results: We enrolled 18 pts (13 men, 5 women), median age 61 (range 44–74) at 4 DLs. ECOG PS was 0 or 1 in 17 pts, and 2 in 1 pt. Pts received a median of 7 cycles (range 1–15) of XIO. All pts are evaluable for toxicity and 14 for response. The most common adverse events were: neutropenia (83% all grades (G) with 4 G3, 4 G4), diarrhea (67%, 4 G3, one of which was a DLT). Nausea (78%) and vomiting (56%) were mild and controlled with anti-emetics. Fatigue occurred in 50% pts, with 1 G3. The DLT was febrile neutropenia (3 pts at DLs 1, 3, & 4 respectively). One pt at DL4 developed severe neutropenia and sepsis during cycle 3, had aspiration pneumonia and died in hospital from respiratory and cardiac complications. MTD has not yet been reached. Responses were observed at all DLs: 11 partial responses with 2 still unconfirmed (79%, 95% CI 54–100), and 2 stable disease (14%). Progression-free survival and overall survival have not been reached. Conclusions: XIO is well tolerated and demonstrated significant efficacy as first-line treatment in MCRC. Severe neutropenia was significant but was of short duration and manageable. It is likely to be the main DLT. MTD has not yet been identified but is expected in the next few pts. A phase II study to confirm the efficacy and safety of the XIO combination will follow. Supported by Roche, Sanofi Aventis, and Pfizer Canada Inc.

[Table: see text]

A National Cancer Institute of Canada Clinical Trials Group Study – IND.135: Phase I/II study of irinotecan (camptosar), oxaliplatin and raltitrexed (tomudex) (COT) in patients with advanced colorectal cancer

Thirty-one patients with metastatic colorectal cancer were enrolled in this phase I/II trial of a triple combination of camptosar (C), oxaliplatin (O) and tomudex (T), all given on day one of a convenient three-week schedule. Patients received 257 cycles (1-18) in five cohorts. Toxicity was manageable and haematological toxicity was mild to moderate. Diarrhoea was the main dose-limiting toxicity; nausea and vomiting were common. Fatigue was frequent, moderate in severity and a reason for discontinuation in some patients. The recommended phase II doses were (C) 220 mg/m(2), (O) 100mg/m(2), (T) 2.75 mg/m(2). A 50% response rate in 30 evaluable patients was confirmed by an independent radiology review board; progression-free survival and overall median survival were 7.3 months and 16.6 months, respectively. Of the 16 patients treated at the recommended dose, 9 (56.3%) experienced partial response. Further evaluation in a randomized study compared to sequential doublets is warranted. Triple combinations could be relevant in curative settings for high-risk patients.

An estimate of the cost of conducting phase II trials in lung cancer

OBJECTIVE

Although it is commonly assumed that clinical trials are more costly than standard therapy, there have been no previous studies of the cost of conducting phase II trials in lung cancer. We retrospectively analyzed two National Cancer Institute of Canada phase II trials in previously untreated small cell lung cancer (SCLC) to determine the costs of conducting the trials in a cancer treatment centre. Both studies were clinical trials undertaken as part of the NCIC's Investigational New Drug program: IND 69 and IND 50 evaluated docetaxel (taxotere) and gemcitabine, respectively.

METHODS

data management costs in a Canadian cancer treatment centre were determined from the time estimates provided by data managers to complete various protocol related tasks. Nursing and pharmacy personnel measured the time and supplies necessary to prepare and administer the chemotherapy. Physician fees were determined from the type and number of care visits required by the clinical protocols. Laboratory tests and imaging studies were costed according to the Ontario Health Insurance Plan (OHIP) Schedule of Fees and Benefits. To estimate whether phase II trials are more costly than standard treatment, we determined the cost of four cycles of VP-16-cisplatin, a standard treatment for SCLC.

RESULTS

The total cost of performing the docetaxel study was $18443 for an average cost per case of $1317 and an average cost per treatment cycle of $683. The gemcitabine study cost more, due to the fact that the drug proved to be active against SCLC and more cycles of therapy were administered to a larger number of patients. Laboratory and administration costs were also higher, because of the drug administration schedule. The total cost of this study was estimated to be $64670 and the average cost per patient entered was $2230 with an average cost per treatment cycle of $898. In comparison, the estimated cost of four cycles of VP-16-cisplatin chemotherapy was $3948 or $987 per treatment cycle. The major cost drivers in the clinical trials were laboratory and imaging tests which made up 17 and 39%, respectively, of the costs of the taxotere study, and 29 and 27%, respectively, for the gemcitabine study. Data management costs contributed 21 and 13% of the total costs, respectively.

CONCLUSION

As the main cost drivers in these phase II clinical trials are laboratory and imaging tests, the cost of clinical trials could potentially be reduced by ensuring that only essential tests are required by protocol. Not surprisingly, the cost of conducting a trial of an active agent is greater than for an inactive agent, because more patients are treated and each patient receives more treatment. The implications for the per-case funding of phase II clinical trials are discussed.

The accuracy of breast ultrasound in the evaluation of clinically benign discrete, symptomatic breast lumps

INTRODUCTION

Recent reports have suggested that breast ultrasound (US) is of value in distinguishing malignant from benign processes. The aim of this study was to establish the accuracy of US in detecting invasive malignancy in clinically benign, discrete, symptomatic breast lumps.

METHODS

The US appearances of 205 clinically benign breast masses were documented prospectively and prior to mammography by one radiologist (AJE). The US appearances were then correlated with the fine needle aspiration (FNA), core biopsy and surgical findings and compared with the mammographic findings.

RESULTS

The US findings were normal 72 (35%), simple cyst 63 (31%), solid benign 51 (25%), solid indeterminate 15 (7%) and solid malignant four (2%). Ultrasound characterized 13 (93%) of the 14 patients found to have invasive carcinoma as indeterminate or malignant. No patients with normal or simple cyst US findings had invasive malignancy. Ultrasound had significantly better accuracy (97% vs 87%, P < 0.02) sensitivity (93% vs 57%, P < 0.05) and negative predictive value (99% vs 92%, P < 0.002) than mammography in the detection of invasive carcinoma when indeterminate and malignant imaging findings were taken as positive.

CONCLUSION

US is a useful adjunct to FNA/core biopsy in confirming the nature of symptomatic, clinically benign breast masses and is superior to mammography in this clinical setting.

Reduction of the infectivity of scrapie agent as a model for BSE in the manufacturing process of Trasylol

The Trasylol manufacturing process was investigated with respect to its capacity for the inactivation/removal of infectivity causing bovine spongiform encephalopathy (BSE). Four process steps were selected for this investigation and scaled down to laboratory scale. Authentic samples of bovine lungs used in the Trasylol manufacturing plant were taken and spiked in laboratory scale experiments with high infectious titres of the rodent adapted scrapie strain ME 7 which served as model for BSE. After performing the respective process steps the output samples collected were tested in C57BL mice carrying the Sinc gene. An overall reduction of the infectious agent in the order of 18 log10 was observed, indicating a very high capacity of the Trasylol process for the inactivation/removal of the BSE/scrapie agent. The discussed safety strategy for the product leads to the conclusion that Trasylol is BSE safe.

Thyroid activity in relation to growth rate and body composition in four breeds of sheep

Four breeds of sheep, Hampshire, Southdown, Cheviot and Scottish Blackface, which differ in mature body size and body composition were intensively reared under an ad libitum or a restricted feeding regime. Thyroid activity was assessed at 13 weeks of age by the 131I uptake method. Slaughter at 24 weeks (ad lib) or 32 weeks (restricted) was followed by carcass dissection. The anticipated differences in body type represented by the 4 breeds was confirmed in terms of size and fatness. The Hampshires had the highest growth rate (liveweight for age) and the lowest thyroid uptake, and the breed differences in thyroid activity were shown to be independent of liveweight. Thyroid activity was positively related to growth rate in the Hampshires and negatively related to growth rate in the 3 other breeds. No association could be found however between the thyroid activity and the proportionate growth of body fat or lean. None of these conclusions were affected by a mild restriction in fed intake.

Ethical issues in infanticide of severely defective infants

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The comparative pharmacokinetics of five quinolones

The pharmacokinetics and tissue penetration of five quinolones were studied in volunteers. The compounds were norfloxacin (400 mg po), enoxacin (400 mg iv and 600 mg po), ciprofloxacin (100 mg iv and 500 mg po), ofloxacin (600 mg po) and pefloxacin (400 mg iv). Of the oral agents studied ofloxacin and ciprofloxacin were the most rapidly absorbed (Tmax = 1.2 h) and enoxacin the least (Tmax = 1.9 h). The serum levels attained were highest in the case of ofloxacin (after allowing for the higher dose administered). The serum half-lives were norfloxacin 3.75 h, ciprofloxacin 3.9 h (po), 4.0 h (iv), ofloxacin 7.0 h, enoxacin 6.2 h (po), 5.1 h (iv) and pefloxacin 10.5 h. All agents penetrated blister fluid readily. The 24 h urine recovery was 62% for oral enoxacin, 46.4% for iv enoxacin (plus 12.2% for oxo-enoxacin), 27% for norfloxacin, 30.6% for oral ciprofloxacin, 75.7% for iv ciprofloxacin, 73% for ofloxacin and 4.9% for pefloxacin (plus 9.2% for the norfloxacin metabolite and 17.8% for pefloxacin N-oxide).

The comparative pharmacokinetics and tissue penetration of four quinolones including intravenously administered enoxacin

The pharmacokinetics and tissue penetration of four quinolones were studied. The compounds were norfloxacin (400 mg p.o.), enoxacin (600 mg p.o. and 400 mg i.v.), ciprofloxacin (100 mg i.v. and 500 mg p.o.) and ofloxacin (600 mg p.o.) given to healthy volunteers. Of the oral agents studied ofloxacin and ciprofloxacin were the most rapidly absorbed (Tmax 1.2 h) and enoxacin the least (Tmax 1.9 h). The serum levels attained were highest in the case of ofloxacin (after allowing for the higher dose administered). The serum half-lives were norfloxacin 3.75 h, ciprofloxacin 3.9 h (p.o.), 4.0 h (i.v.), ofloxacin 7.0 h and enoxacin 6.2 h (p.o.) and 5.1 h (i.v.). All agents penetrated the blister fluid readily. The 24 h urine recovery (as measured by a microbiological assay) was 62% for enoxacin (p.o.), 46.4% following i.v. enoxacin (plus 11.6% oxo-enoxacin, measured by HPLC) 27% for norfloxacin, 30.6% for oral ciprofloxacin, 75.7% for i.v. ciprofloxacin and 73% for ofloxacin.

Adipose tissue capillary blood flow in relation to fatness in sheep

Capillary blood flow rate was measured in eight fat depots in eight Blackface and eight Clun lambs using the radiolabelled microsphere technique. Adipose tissue flow ranged from 3 to 47 ml 100 g-1 min-1 depending upon depot and degree of fatness. Blood flow declined with increasing fatness suggesting that perfusion was not an important constraint on the growth of fat. Blood flow rates were also measured in the fed and 26 hour fasted states but no effect from fasting was observed.

The effect of passive immunization against somatostatin on marker retention time in lambs

The effects of passive immunization against somatostatin on retention time of marker have been investigated in sheep using Cr2O3 as a marker. The mean transit time for clearance of 50% of the marker was significantly retarded in all the anti-somatostatin-treated animals by approximately 19.0 h, as compared with control lambs given a nonspecific antiserum. The findings suggest an important role for circulating somatostatin in the regulation of the rate of flow of digesta through the gastrointestinal tract in lambs. Moreover, it enhances the claim of the immunological approach as a new technique to investigate factors controlling food utilization in farm livestock.

The effect of alpha-adrenergic blockade on the release of ACTH and cortisol in vivo

The effect of alpha-adrenergic blockade, by phentolamine, upon plasma levels of adrenocorticotrophic hormone (ACTH) and cortisol during insulin-induced hypoglycaemia was studied in pigs. Insulin administration produced a rise in ACTH which reached a maximum at about 30 minutes (p less than 0.01) and had returned to basal levels by 90 minutes. Cortisol levels had also risen by 30 minutes and remained elevated for 90 minutes. Pre-treatment with phentolamine almost completely suppressed the growth hormone response to insulin-induced hypoglycaemia, but had no effect upon the amplitude or duration of the elevation of plasma ACTH or cortisol levels following insulin administration. The hypoglycaemia-induced rise in ACTH and cortisol seem, therefore, to be independent of the alpha-adrenergic system. In addition, the inhibitory action of the alpha-adrenergic system on ACTH release reported in rats and dogs does not appear to be present in pigs.

Effect of dantrolene on leg metabolism in porcine malignant hyperthermia

The effect of the intravenous administration of dantrolene 3.5 mg/kg body weight on leg metabolism during porcine malignant hyperthermia (MH) was investigated in six Pietrain pigs. Arterial pH improved only slowly after dantrolene and was associated with the continuing efflux of lactate from the leg. Oxygen uptake by the leg had returned to control values 30 minutes after dantrolene. Glucose production by the leg was observed during malignant hyperthermia but this was rapidly abolished by dantrolene. It is concluded that the most useful indices for assessing the adequacy of the treatment of MH are those which reflect changes in oxidative muscle metabolism.

The effect of chronic neonatal guanethidine treatment on body composition in pigs

The effect of neonatal guanethidine administration (30 mg/kg/day) during the first 32 days of life on body composition at 20 weeks of age, was assessed in two breeds of pig which were known to differ in their sympathetic responsiveness. Guanethidine administration increased the proportion of fat and decreased the proportion and absolute weight of lean in the Pietrain breed; and it had no effect in Gloucester Old Spots. Thus it can be inferred that endogenous noradrenaline is responsible for promoting leanness in a pig breed with known sympathetic overactivity.

Studies on the sympathetic nervous system: the Valsalva like manoeuvre in sheep

The Valsalva like manoeuvre (VLM) was examined as a test of the responsiveness of the autonomic nervous system in sheep. Within individuals, imipramine pretreatment enhanced the peak blood pressure and heart rate responses to the VLM and atropine prolonged the tachycardia without influencing the peak responses. Between individuals, the peak blood pressure response was related to the degree of hypotension during raised airway pressure (r = 0.77). The degree of hypotension was, in turn, related to gut fill (r = 0.64). Differences in gut fill were ascribed as a cause of variation in the heart rate and blood pressure responses between individual sheep and between the Scottish Blackface and Southdown breeds.

Autonomic responsiveness in stress-sensitive and stress-resistant pigs

The responsiveness of the autonomic nervous system was studied in twenty-six 140 day old thiopentone anaesthetized lean stress-sensitive Pietrain (P) and fatter stress-resistant Gloucester (G) pigs, using the Valsalva like manoeuvre (VLM), and the i.v. tyramine, noradrenaline (NA) and phenylephrine tests. The heart rate responses to the VLM and tyramine tests were greater in P. The pressor response to NA was lower in P, and the change in heart rate per unit change in blood pressure-during phenylephrine infusion was the same in the two breeds. The sympathetic nervous system in P was, therefore, more responsive than that in G, and this was attributable to a higher pre-adrenoreceptor responsiveness in P. The potentially greater sympathetic responsiveness in stress-sensitive pigs could account for their greater leanness, their stress-induced metabolic acidosis, and for their susceptibility to myocardial failure.