Effect of urine-specific gravity on performance of bacteriuria in predicting urine culture results

OBJECTIVE

To determine the effect of urine-specific gravity (USG) on using microscopic evaluation of bacteriuria to predict urine culture results in dogs and cats.

MATERIALS AND METHODS

We performed a retrospective medical record review of canine and feline patients that had a urinalysis and urine culture performed simultaneously. The sensitivity, specificity, positive predictive value and negative predictive value of microscopic bacteriuria for predicting urine culture results were calculated, stratified by USG. Multivariable regression was performed to test the effect of USG, pyuria, haematuria and species on the agreement between microscopic bacteriuria and culture results.

RESULTS

A total of 481 dogs and 291 cats with paired urinalysis and urine culture results were included in the study. Microscopic bacteriuria had moderate sensitivity (76% in dogs, 64% in cats) and high specificity (97% in dogs, 96% in cats) for predicting urine culture bacterial growth. Samples with rod bacteria were more likely to have bacterial growth than those with cocci (OR=Infinity, 95% CI 4.8 - Infinity). As compared to isosthenuric+hyposthenuric samples (USG ≤1.012), agreement was lower in moderately concentrated (OR=0.44, 95% CI 0.19 to 0.91) samples. Absence of bacteriuria, pyuria and haematuria had a high negative predictive value for no bacterial growth (96%).

CLINICAL SIGNIFICANCE

Microscopic bacteriuria has a high specificity in predicting urine culture results, regardless of USG. The finding that microscopic bacteriuria has better agreement with urine culture results in isosthenuric+hyposthenuric urine argues against reflex culture in these samples, especially if pyuria and haematuria are also absent. Urine microscopy can aid clinicians in determining the likelihood of urine culture growth.

Fellowship training in robotic colorectal surgery within the current hospital setting: an achievable goal?

BACKGROUND

Although currently limited, the requirement for colorectal trainees to attain skills in robotic surgery is likely to increase due to further utilization of robotic platforms globally. The aim of the study is to describe the training programme utilized and assess outcomes of fellowship training in robotic colorectal surgery.

METHODS

A structured robotic training programme was generated across a tertiary hospital setting. Review of four prospectively maintained fellow operative logbooks was performed to assess caseload and skill acquisition. Operative and patient-related outcomes were compared with consultant trainer performed cases. Data were analysed using R with a P < 0.05 considered significant.

RESULTS

The structured robotic training scheme is a two-tiered system over a 12-month period. The trainer-directed pathway comprised of a robotic console safety course followed by cart-side assisting, a wet lab animal course, dual-console accreditation training course and onsite proctoring, prior to becoming an independent console surgeon. Over 2 years, 265 robotic (n = 143 primary/component surgeon) cases were undertaken with fellows A, B, C and D involved in 63, 77, 75 and 50 robotic colorectal cases, respectively. Individual learning curves revealed independent procedure competency at cases 11, 14, 15 and 12, respectively, for robotic anterior resection. There was no significant difference observed in operative time (P = 0.39), blood loss (P = 0.41), lymph node harvest (P = 0.35), conversion rates (2% versus 4%), anastomotic leaks (1% versus 3%) and R0 resection rates (100% versus 98% colonic, 96% versus 96% rectal, P = 0.48) between surgical fellows and consultant trainers. Clavien-Dindo(III-IV) complications were similar (10% versus 6%,P = 0.25) with no mortalities encountered.

CONCLUSION

It is feasible and safe to train fellows in robotic colorectal surgery without compromise of operative- and patient-related outcomes.

Association of Surgical Skill Assessment With Clinical Outcomes in Cancer Surgery

Importance

Complex surgical interventions are inherently prone to variation yet they are not objectively measured. The reasons for outcome differences following cancer surgery are unclear.

Objective

To quantify surgical skill within advanced laparoscopic procedures and its association with histopathological and clinical outcomes.

Design, Setting, and Participants

This analysis of data and video from the Australasian Laparoscopic Cancer of Rectum (ALaCaRT) and 2-dimensional/3-dimensional (2D3D) multicenter randomized laparoscopic total mesorectal excision trials, which were conducted at 28 centers in Australia, the United Kingdom, and New Zealand, was performed from 2018 to 2019 and included 176 patients with clinical T1 to T3 rectal adenocarcinoma 15 cm or less from the anal verge. Case videos underwent blinded objective analysis using a bespoke performance assessment tool developed with a 62-international expert Delphi exercise and workshop, interview, and pilot phases.

Interventions

Laparoscopic total mesorectal excision undertaken with curative intent by 34 credentialed surgeons.

Main Outcomes and Measures

Histopathological (plane of mesorectal dissection, ALaCaRT composite end point success [mesorectal fascial plane, circumferential margin, ≥1 mm; distal margin, ≥1 mm]) and 30-day morbidity. End points were analyzed using surgeon quartiles defined by tool scores.

Results

The laparoscopic total mesorectal excision performance tool was produced and shown to be reliable and valid for the specialist level (intraclass correlation coefficient, 0.889; 95% CI, 0.832-0.926; P < .001). A substantial variation in tool scores was recorded (range, 25-48). Scores were associated with the number of intraoperative errors, plane of mesorectal dissection, and short-term patient morbidity, including the number and severity of complications. Upper quartile-scoring surgeons obtained excellent results compared with the lower quartile (mesorectal fascial plane: 93% vs 59%; number needed to treat [NNT], 2.9, P = .002; ALaCaRT end point success, 83% vs 58%; NNT, 4; P = .03; 30-day morbidity, 23% vs 50%; NNT, 3.7; P = .03).

Conclusions and Relevance

Intraoperative surgical skill can be objectively and reliably measured in complex cancer interventions. Substantial variation in technical performance among credentialed surgeons is seen and significantly associated with clinical and pathological outcomes.

Delayed type III hypersensitivity reaction with acute kidney injury in two dogs following administration of concentrated human albumin during treatment for hypoalbuminemia secondary to septic peritonitis

OBJECTIVE

To describe 2 dogs with acute kidney injury secondary to type III hypersensitivity reaction to 25% human serum albumin (HSA).

CASE SERIES SUMMARY

Two dogs were presented with evidence of septic peritonitis. The dogs were hospitalized following definitive surgical correction of a jejunal laceration following routine ovariohysterectomy, and removal of a jejunal foreign body. In the postoperative period, both dogs developed hypoalbuminemia and received 25% HSA. At the time of initial discharge, both dogs were doing well clinically and had normal renal parameters. Eleven and 18 days after HSA infusion, respectively, both dogs were re-presented with clinical signs of inappetence, vomiting, and lameness that progressed to urticaria, peripheral and angioedema, and petechiae, consistent with a delayed type III hypersensitivity reaction. Treatment for the type III hypersensitivity reaction to HSA included administration of diphenhydramine and glucocorticoids. Despite partial resolution of edema and joint swelling, both dogs developed progressive azotemia together with hypoalbuminemia and proteinuria. One dog developed an anuric acute kidney injury (AKI). Both dogs were humanely euthanized. Histopathology of the kidneys of both dogs was consistent with immune complex deposition and vasculitis.

NEW OR UNIQUE INFORMATION

Severe type III hypersensitivity reactions have been documented in healthy dogs and clinical patients following the administration of HSA. This report describes the first documented delayed type III hypersensitivity reaction in 2 dogs with septic peritonitis that resulted in AKI, glomerulonephritis, and oligo- to anuria in clinical patients following administration of 25% HSA.

Measurements of echocardiographic indices and biomarkers of kidney injury in dogs with chronic kidney disease

Pathophysiological cardiac and renal interactions are termed cardiovascular-renal disorder (CvRD). Cardiovascular disease/dysfunction secondary to kidney disease (CvRD_K), is a leading cause of death in human chronic kidney disease (CKD) patients. The presence and clinical impact of CvRD_K in dogs with CKD is unknown. We hypothesized that echocardiographic measurements, and cardiac and renal biomarkers, will be altered in dogs with CKD and associated with survival. Eleven dogs with CKD (n = 6 IRIS stage 2, n = 5 IRIS stage 3) and without primary cardiac disease, plus 12 healthy age-matched control dogs, were recruited to this prospective observational study. Dogs underwent standard echocardiography, glomerular filtration rate (GFR) estimation by iohexol clearance, and measurement of plasma cardiac troponin I and N-terminal pro-B-type natriuretic peptide (NT-proBNP), plasma and urinary cystatin B, and urinary clusterin and neutrophil gelatinase-associated lipocalin (NGAL). Values were compared between groups, and their association with all-cause mortality explored. Dogs with CKD had significantly lower GFR and higher NT-proBNP, urinary cystatin B, clusterin, and NGAL, compared to controls (P < 0.05). Echocardiographic measurements were similar between dogs with CKD and controls. Median follow-up time was 666 days, during which six dogs with CKD died. Risk of death was associated with increasing age, serum total protein, and normalized left ventricular posterior wall thickness (LVPWDN) and decreasing bodyweight and packed cell volume. Although baseline differences in echocardiographic measurements were not evident between dogs with moderate CKD and controls, the presence of CvRD_K was suggested by the association between LVPWDN and survival.

Esophageal replacement by gastric transposition: A single surgeon's experience from a tertiary pediatric surgical center

BACKGROUND

Many pediatric surgeons have limited experience of esophageal replacement. This study reports outcomes of esophageal replacement by gastric transposition performed by a single UK-based pediatric surgeon.

METHODS

Consecutive patients were identified who underwent esophageal replacement by gastric transposition over a 28 year period. Clinical and demographic data were collected. Weight-for-age Z-scores were calculated for esophageal atresia patients.

RESULTS

Nineteen patients were identified. Indication in the majority was long-gap esophageal atresia (n = 17; 10 with tracheoesophageal fistula). At surgery, median age was 8.5 months (range 2-55); median weight was 7.4 kg (range 4.0-17.4 kg). A right-sided thoracotomy or transhiatal approach was used. Median postoperative length of stay was 17.5 days (range 7-130); median intensive care stay was three days (range 1-63). There were no deaths. Anastomotic leak rate at 30 days was 10.5% (n = 2). One patient required early stricture dilatation. Median weight-for-age Z-score increased from -2.17 at one year of age to -1.86, -1.70 and -1.93 at 5, 10 and 15 years.

CONCLUSIONS

Esophageal replacement by gastric transposition offers a potentially life-changing treatment; however, it is associated with significant morbidity. The majority of patients eventually achieve full oral feeding and maintenance of weight gain trajectory. A right-sided approach to the esophagus is feasible.

TYPE OF STUDY

Treatment Study.

LEVEL OF EVIDENCE

IV.

Closure of the perineal defect after abdominoperineal excision for rectal adenocarcinoma - ACPGBI Position Statement

BACKGROUND

Perineal wound morbidity is common following abdominoperineal excision of the rectum (APE). There is no consensus on the optimum perineal reconstruction method after APE, and in particular 'extra-levator APE' (ELAPE).

METHODS

A systematic review of the PubMed, Embase and Cochrane databases was performed. This position statement formulated clinical questions and graded the evidence to make recommendations.

RESULTS

Perineal wound complications may be higher following ELAPE compared to 'conventional APE (cAPE)' however there is insufficient evidence to recommend cAPE over ELAPE with regards to the impact upon perineal wound healing. The majority of cAPE studies have used primary closure with varying complication rates reported. Where concerns regarding perineal wound healing exist, myocutaneous flap closure may be considered as an alternative method. There is minimal available evidence on perineal mesh reconstruction following cAPE. Primary closure, mesh use and myocutaneous flap reconstruction following ELAPE has been reported although variations in definitions and low-quality of available evidence limit comparison. There is insufficient evidence to recommend one particular method of perineal closure after ELAPE. Primary perineal closure is likely to have a higher risk of perineal herniation. Myocutaneous flaps and biological mesh have been effectively used in ELAPE closure. There is insufficient evidence to support one particular type of flap or mesh. Perineal wound complication rates are significantly increased when neo-adjuvant radiotherapy is delivered, regardless of surgical technique. There is no evidence that laparoscopy reduces APE perineal wound complications.

CONCLUSION

This position statement updates clinicians on current evidence around perineal closure after APE surgery.

Objective assessment of minimally invasive total mesorectal excision performance: a systematic review

INTRODUCTION

Laparoscopy is widely used in colorectal practice, but recent trial results have questioned its use in rectal cancer resections. Patient outcomes are directly linked to the quality of total mesorectal excision (TME) specimen. Objective assessment of intraoperative performance could help ensure competence and delivery of optimal outcomes. Objective tools may also contribute to TME intervention trials, but their nature, structure and utilisation is unknown.

AIM

To systemically review the available literature to report on the available tools for the objective assessment of minimally invasive TME operative performance and their use within multicentre laparoscopic TME randomised controlled trials.

METHODS

A systematic search of the PubMed and Cochrane databases was performed to identify tools used in the objective intraoperative assessment of minimally invasive TME performance in accordance with the PRISMA guidelines, independently by two authors. The identified tools were then evaluated within reported TME RCTs.

RESULTS

A total of 8642 abstracts were screened of which 12 papers met the inclusion criteria; ten prospective observational studies, one randomised trial and one educational consensus. Eight assessment methods were described, which include formative and summative tools. The tools were mostly adaptations of colonic surgery tools based on either operative video review or post-operative trainer rating. All studies reported objective assessment of intraoperative performance was feasible, but only 126 (7%) of the 1762 included laparoscopic cases were TME. No multicentre laparoscopic TME trial reported using any objective surgical performance assessment tool.

CONCLUSION

Objective intraoperative laparoscopic TME performance assessment is feasible, but most of the current tools are adaptation of colonic surgery. There is a need to develop dedicated assessment tools for minimal access rectal surgery. No multicentre minimally invasive TME RCT reported using any objective assessment tool.

Surgical timing after chemoradiotherapy for rectal cancer, analysis of technique (STARRCAT): results of a feasibility multi-centre randomized controlled trial

BACKGROUND

The optimal time of rectal resection after long-course chemoradiotherapy (CRT) remains unclear. A feasibility study was undertaken for a multi-centre randomized controlled trial evaluating the impact of the interval after chemoradiotherapy on the technical complexity of surgery.

METHODS

Patients with rectal cancer were randomized to either a 6- or 12-week interval between CRT and surgery between June 2012 and May 2014 (ISRCTN registration number: 88843062). For blinded technical complexity assessment, the Observational Clinical Human Reliability Analysis technique was used to quantify technical errors enacted within video recordings of operations. Other measured outcomes included resection completeness, specimen quality, radiological down-staging, tumour cell density down-staging and surgeon-reported technical complexity.

RESULTS

Thirty-one patients were enrolled: 15 were randomized to 6 and 16-12 weeks across 7 centres. Fewer eligible patients were identified than had been predicted. Of 23 patients who underwent resection, mean 12.3 errors were observed per case at 6 weeks vs. 10.7 at 12 weeks (p = 0.401). Other measured outcomes were similar between groups.

CONCLUSIONS

The feasibility of measurement of operative performance of rectal cancer surgery as an endpoint was confirmed in this exploratory study. Recruitment of sufficient numbers of patients represented a challenge, and a proportion of patients did not proceed to resection surgery. These results suggest that interval after CRT may not substantially impact upon surgical technical performance.

Effect of Fenoldopam Continuous Infusion on Glomerular Filtration Rate and Fractional Excretion of Sodium in Healthy Dogs

BACKGROUND

Acute kidney injury (AKI) is a common problem in small-animal patients and carries a guarded prognosis with substantial morbidity and mortality, particularly in oligoanuric dogs. Fenoldopam, a selective dopamine agonist, has been shown to increase urine output in healthy dogs and cats; however, the mechanism of action is unknown.

HYPOTHESIS/OBJECTIVES

To evaluate the effect of fenoldopam infusion on glomerular filtration rate (GFR) and fractional excretion of sodium (FeNa) in healthy dogs.

ANIMALS

Ten healthy, privately owned dogs.

METHODS

Randomized, crossover design with negative control. Ten healthy dogs were given fenoldopam diluted in 5% dextrose (D5W) as a continuous IV infusion of 0.8 μg/kg/min for 5 hours and a control infusion of D5W alone, 7 days apart. Glomerular filtration rate was measured by exogenous iohexol clearance, beginning 1 hour after the start of the fenoldopam infusion. Fractional excretion of sodium (FeNa) was measured before and after the infusion. Glomerular filtration rate and change in FeNa were compared between treatment days.

RESULTS

Fenoldopam infusion resulted in a significantly increased (P = .0166) GFR (median GFR, 3.33 mL/min/kg) in healthy dogs compared with D5W infusion (median GFR, 2.71 mL/kg/min). Fenoldopam also resulted in a significantly increased (P = .0148) FeNa (mean change, 0.106), whereas infusion of D5W alone did not (mean change, 0.016).

CONCLUSIONS AND CLINICAL IMPORTANCE

In healthy dogs, fenoldopam significantly increased GFR and FeNa compared with infusion of D5W alone. No adverse effects were seen.

Application of objective clinical human reliability analysis (OCHRA) in assessment of technical performance in laparoscopic rectal cancer surgery

BACKGROUND

Laparoscopic rectal resection is technically challenging, with outcomes dependent upon technical performance. No robust objective assessment tool exists for laparoscopic rectal resection surgery. This study aimed to investigate the application of the objective clinical human reliability analysis (OCHRA) technique for assessing technical performance of laparoscopic rectal surgery and explore the validity and reliability of this technique.

METHODS

Laparoscopic rectal cancer resection operations were described in the format of a hierarchical task analysis. Potential technical errors were defined. The OCHRA technique was used to identify technical errors enacted in videos of twenty consecutive laparoscopic rectal cancer resection operations from a single site. The procedural task, spatial location, and circumstances of all identified errors were logged. Clinical validity was assessed through correlation with clinical outcomes; reliability was assessed by test-retest.

RESULTS

A total of 335 execution errors identified, with a median 15 per operation. More errors were observed during pelvic tasks compared with abdominal tasks (p < 0.001). Within the pelvis, more errors were observed during dissection on the right side than the left (p = 0.03). Test-retest confirmed reliability (r = 0.97, p < 0.001). A significant correlation was observed between error frequency and mesorectal specimen quality (r s = 0.52, p = 0.02) and with blood loss (r s = 0.609, p = 0.004).

CONCLUSIONS

OCHRA offers a valid and reliable method for evaluating technical performance of laparoscopic rectal surgery.

Opportunistic fungal infections in dogs treated with ciclosporin and glucocorticoids: eight cases

Glucocorticoids are the standard of care for the treatment of immune-mediated disorders, and ciclosporin is increasingly being used off-label as an adjunct immunosuppressive drug in dogs. However, opportunistic infections can develop during combination immunosuppressive regimens. This case series describes atypical fungal infections in eight dogs treated with immunosuppressive dosages of glucocorticoids and ciclosporin. The median duration of combined treatment prior to the identification of fungal infection was 31 (range, 13 to 201) days, although two dogs received glucocorticoids for prolonged periods prior to the addition of ciclosporin. The estimated prevalence of serious fungal infections with this drug combination appears to be low (approximately 1 · 67%), but these infections led directly or indirectly to death or euthanasia in five of eight (63%) dogs. These cases highlight the need for frequent clinical monitoring of dogs receiving immunosuppressive dosages of glucocorticoids and ciclosporin.

Impact of analgesic modality on stress response following laparoscopic colorectal surgery: a post-hoc analysis of a randomised controlled trial

BACKGROUND

Epidural analgesia is perceived to modulate the stress response after open surgery. This study aimed to explore the feasibility and impact of measuring the stress response attenuation by post-operative analgesic modalities following laparoscopic colorectal surgery within an enhanced recovery after surgery (ERAS) protocol.

METHODS

Data were collected as part of a double-blinded randomised controlled pilot trial at two UK sites. Patients undergoing elective laparoscopic colorectal resection were randomised to receive either thoracic epidural analgesia (TEA) or continuous local anaesthetic infusion to the extraction site via wound infusion catheter (WIC) post-operatively. The aim of this study was to measure the stress response to the analgesic modality by measuring peripheral venous blood samples analysed for serum concentrations of insulin, cortisol, epinephrine and interleukin-6 at induction of anaesthesia, at 3, 6, 12 and 24 h after the start of operation. Secondary endpoints included mean pain score in the first 48 h, length of hospital stay, post-operative complications and 30-day re-admission rates.

RESULTS

There was a difference between the TEA and WIC groups that varies across time. In the TEA group, there was significant but transient reduced level of serum epinephrine and a higher level of insulin at 3 and 6 h. In the WIC, there was a significant reduction of interleukin-6 values, especially at 12 h. There was no significant difference observed in the other endpoints.

CONCLUSIONS

There is a significant transient attenuating effect of TEA on stress response following laparoscopic colorectal surgery and within ERAS as expressed by serum epinephrine and insulin levels. Continuous wound infusion with local anaesthetic, however, attenuates cytokine response as expressed by interleukin-6.

Objective assessment of technique in laparoscopic colorectal surgery: what are the existing tools?

Assessment can improve the effectiveness of surgical training and enable valid judgments of competence. Laparoscopic colon resection surgery is now taught within surgical residency programs, and assessment tools are increasingly used to stimulate formative feedback and enhance learning. Formal assessment of technical performance in laparoscopic colon resection has been successfully applied at the specialist level in the English "LAPCO" National Training Program. Objective assessment tools need to be developed for training and assessment in laparoscopic rectal cancer resection surgery. Simulation may have a future role in assessment and accreditation in laparoscopic colorectal surgery; however, existing virtual reality models are not ready to be used for assessment of this advanced surgery.

Development and evaluation of a cadaveric training curriculum for low rectal cancer surgery in the English LOREC National Development Programme

AIM

The National Development Programme for Low Rectal Cancer in England (LOREC) was commissioned in response to wide variation in the outcome of patients with low rectal cancer. One of the aims of LOREC was to enhance surgical techniques in managing low rectal cancer. This study reports on the development and evaluation of a novel national technical skills cadaveric training curriculum in extralevator abdominoperineal excision.

METHOD

Three sites were commissioned for the cadaveric workshops, each delivering the same training curriculum. Training was undertaken in pairs using a fresh-frozen cadaveric model under the supervision of expert mentors. Global assessment score (GAS) forms were developed to promote reflective learning. Feedback on the impact of the workshop was obtained from a sample of delegates at the end of the course, and also after 3-23 months via an online questionnaire.

RESULTS

Overall 112 consultant colorectal surgeons attended one of 15 cadaveric technical skills training workshops. Seventy-six per cent of delegates reported easy identification of anatomy in the cadaveric model; 67% found tissue planes easy to interpret. Ninety-six per cent of delegates felt the workshop would influence their future practice; 96% reported increased awareness of important anatomy. Only 2% of delegates wished to pursue supplementary formal training from LOREC.

CONCLUSION

Fresh-frozen cadavers could provide an effective training model for low rectal surgery. A structured 1-day cadaveric workshop has facilitated the dissemination of technical skills for management of low rectal cancer. Attending the cadaveric workshop enhanced delegates' confidence in performing this procedure.

A systematic review of patient reported outcomes and patient experience in enhanced recovery after orthopaedic surgery

INTRODUCTION

Orthopaedic enhanced recovery after surgery (ERAS) providers are encouraged to estimate the actual benefit of ERAS according to the patient's opinion by using patient generated data alongside traditional measures such as length of stay. The aim of this paper was to systemically review the literature on the use of patient generated information in orthopaedic ERAS across the whole perioperative pathway.

METHODS

Publications were identified using Embase(™), MEDLINE(®), AMED, CINAHL(®) (Cumulative Index to Nursing and Allied Health Literature), the Cochrane Library and the British Nursing Index. Search terms related to experiences, acceptance, satisfaction or perception of ERAS and quality of life (QoL).

FINDINGS

Of the 596 abstracts found, 8 papers were identified that met the inclusion criteria. A total of 2,208 patients undergoing elective hip and knee arthroplasty were included. Patient satisfaction was reported in 6 papers. Scores were high in all patients and not adversely affected by length of stay. QoL was reported in 2 papers and showed that QoL scores continued to increase up to 12 months following ERAS. Qualitative methods were used in one study, which highlighted problems with support following discharge. There is a paucity of data reporting on patient experience in orthopaedic ERAS. However, ERAS does not compromise patient satisfaction or QoL after elective hip or knee surgery. The measurement of patient experience should be standardised with further research.

Serum biomarkers of clinical and cytologic response in dogs with idiopathic immune-mediated polyarthropathy

Background

Immune‐mediated polyarthopathy (IMPA) is common in dogs, and is monitored by serial arthrocenteses.

Hypothesis/Objectives

Plasma C‐reactive protein (CRP), interleukin‐6 (IL‐6), and CXCL8 (interleukin‐8) would serve as noninvasive markers of joint inflammation in IMPA.

Animals

Nine client‐owned dogs with idiopathic IMPA; 6 healthy controls.

Methods

Prospective study. Plasma CRP, IL‐6, and CXCL8 were measured by ELISA at baseline, 2, and 4 weeks during treatment with prednisone at 50 mg/m²/day. Arthrocenteses, the canine brief pain inventory (CBPI), and accelerometry collars were used to assess joint inflammation, lameness, and mobility at all 3 time points.

Results

C‐reactive protein concentrations were higher in IMPA dogs (median 91.1 μg/mL, range 76.7–195.0) compared with controls (median <6.3 μg/mL, <6.3–13.7; P = .0035), and were significantly lower at week 2 (10.6 μg/mL, <6.3–48.8) and week 4 (<6.3 μg/mL, <6.3–24.4; P < .001).

C‐reactive protein was correlated with median CBPI scores (r = 0.68; P = .0004), joint cellularity (r = 0.49, P = .011), and mobility by accelerometry (r = −0.42, P = .048). Plasma IL‐6 concentrations were also higher in IMPA dogs (median 45.9 pg/mL), compared with controls (median <15.7 pg/mL; P = .0008). IL‐6 was lower in IMPA dogs by week 4 (<15.7 pg/mL; P = .0099), and was modestly correlated with CBPI scores (r = 0.47, P = .023). CXCL8 did not differ significantly between IMPA and healthy dogs.

Conclusions

Plasma CRP and IL‐6 might be useful surrogate markers of synovial inflammation and disease activity in dogs with IMPA.

Laparoscopic extralevator abdominoperineal excision of the rectum: short-term outcomes of a prospective case series

BACKGROUND

Laparoscopic approaches for the resection of low rectal cancer and the extralevator technique for abdominoperineal excision are both becoming increasingly popular. There are little published data regarding the combined application of these techniques to the resection of low rectal tumours. The aim of this study was to assess the feasibility of such an approach and to appraise short-term outcomes in a consecutive series of patients undergoing laparoscopic extralevator abdominoperineal excision (ELAPE).

METHODS

Consecutive patients undergoing laparoscopic ELAPE at our institution between 2008 and 2011 were identified from a prospectively maintained database. The abdominal phase of the operation was performed laparoscopically, and following extralevator resection, the perineum was reconstructed using a biologic mesh. All patients were enrolled in an enhanced recovery programme.

RESULTS

Of 166 patients undergoing radical resection of rectal cancer at our institution between 2008 and 2011, 28 underwent laparoscopic ELAPE. Median age was 70 years, median body mass index was 27.5 kg/m(2), and 71% were male. The conversion rate to laparotomy was 18%. Three patients (10.8%) had circumferential resection margins <1 mm; no intraoperative tumour perforation occurred. The median length of stay was 7 days, with a 30-day readmission rate of 21% and no 30-day mortality. Post-operative perineal wound complications occurred in 25%. At median 38-month follow-up (range 23-66 months), overall survival was 75%, disease-free survival was 71%, and there were three local recurrences (11%).

CONCLUSIONS

Laparoscopic extralevator abdominoperineal excision can be safely performed without compromising short-term outcomes.

Reconstruction of the perineum following extralevator abdominoperineal excision for carcinoma of the lower rectum: a systematic review

AIM

An improvement in oncological outcome has been reported following an extralevator approach to abdominoperineal excision (ELAPE) for low rectal carcinoma. A larger perineal defect following ELAPE and the impact of neoadjuvant radiotherapy are sources of considerable morbidity for patients. We report an evidence-based systematic review of published data on the outcome of perineal reconstruction following ELAPE for low rectal carcinoma, comparing the use of tissue flap and biological mesh techniques.

METHOD

A literature search was performed of electronic databases including the Medline, Embase and Scopus databases (1995-2011). Studies describing outcomes relating to the perineum following ELAPE were included for review.

RESULTS

Eleven small cohort studies reported the outcome relating to the perineum following ELAPE. Pooled-analysis of 255 combined patients undergoing flap repair and 85 undergoing biological mesh repair showed no significant difference in the rates of perineal wound complications or perineal hernia formation.

CONCLUSION

There is little information on the optimal technique of perineal wound closure following ELAPE. With the limited data available, there was no significant difference in complication rates between biological mesh and flap repair. There is a need for high-quality prospective trials to compare methods of reconstruction to determine the long-term results, quality of life and function.

Syntaxin 1A regulates dopamine transporter activity, phosphorylation and surface expression

We investigated the functional relationship between the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) protein syntaxin 1A (syn 1A) and the dopamine transporter (DAT) by treating rat striatal tissue with Botulinum Neurotoxin C (BoNT/C) and co-transfecting syn 1A with DAT in non-neuronal cells, followed by analysis of DAT activity, phosphorylation, and regulation. Treatment of striatal slices with BoNT/C resulted in elevated dopamine (DA) transport Vmax and reduced DAT phosphorylation, while heterologous co-expression of syn 1A led to reduction in DAT surface expression and transport Vmax. Syn 1A was present in DAT immunoprecipitation complexes, supporting a direct or indirect interaction between the proteins. Phorbol ester regulation of DA transport activity was retained in BoNT/C-treated synaptosomes and syn 1A transfected cells, demonstrating that protein kinase C (PKC) and syn 1A effects occur through independent processes. These findings reveal a novel mechanism for regulation of DAT activity and phosphorylation, and suggest the potential for syn 1A to impact DA neurotransmission through effects on reuptake.

Regulation of the dopamine transporter by phosphorylation

The dopamine transporter (DAT) is a neuronal phosphoprotein and target for psychoactive drugs that plays a critical role in terminating dopaminergic transmission by reuptake of dopamine from the synaptic space. Control of DAT activity and plasma membrane expression are therefore central to drug actions and the spatial and temporal regulation of synaptic dopamine levels. DATs rapidly traffic between the plasma membrane and endosomal compartments in both constitutive and protein kinase C-dependent manners. Kinase activators, phosphatase inhibitors, and transported substrates modulate DAT phosphorylation and activity, but the underlying mechanisms and role of phosphorylation in these processes are poorly understood. Complex adaptive changes in DAT function potentially related to these processes are also induced by psychostimulant and therapeutic transport blockers such as cocaine and methylphenidate. This chapter provides an overview of the current state of knowledge regarding DAT phosphorylation and its relationship to transporter activity and trafficking. A better understanding of how dopaminergic neurons regulate DAT function and the role of phosphorylation may lead to the identification of novel therapeutic targets for the treatment and prevention of dopaminergic disorders.

Modelling the spread of scrapie in a sheep flock: evidence for increased transmission during lambing seasons

Presence of scrapie infectivity in the placenta suggests the possibility of increased transmission of scrapie during the lambing season. This hypothesis was explored here using a mathematical model of scrapie transmission dynamics which has previously been successfully used to study several scrapie outbreaks in Scottish sheep flocks. It was applied here to the Langlade experimental sheep flock (INRA Toulouse, France), in which a natural scrapie epidemic started in 1993. Extensive data were available, including pedigree, scrapie histopathological diagnoses and PrP genotypes. Detailed simulations of the scrapie outbreak reveal that the observed patterns of seasonality in incidence can not be accounted for by seasonality in demography alone and provide strong support for the hypothesis of increased transmission during lambing. Observations from several other scrapie outbreaks also showing seasonal incidence patterns support these conclusions.

Maternal transmission studies of BSE in sheep

If BSE (bovine spongiform encephalopathy) infected the UK sheep population concurrently with cattle, it would only now be maintained by transmission between sheep by routes which could include from mother to lamb either in utero or via perinatal close contact. In this study of experimental BSE, Cheviot ewes challenged orally with BSE cattle brain produced lambs of various PrP genotypes over the next 7 years. Of 72 surviving to >30 months of age, 29 are of the most susceptible PrP genotype (AQ/AQ) and born to mothers that were challenged with BSE. None of the progeny have shown any signs of disease. The results suggest that in these sheep, BSE could only transmit by the maternal route at a frequency of less than one in four (95 % confidence limit) from clinically affected ewes, a rate which if replicated in other breeds may not be sufficient to maintain BSE within the sheep population.

Comparative epidemiology of scrapie outbreaks in individual sheep flocks

Data recording the course of scrapie outbreaks in 4 sheep flocks (2 in Cheviot sheep and 2 in Suffolks) are compared. For each outbreak the data on scrapie incidence and sheep demography and pedigrees cover periods of years or decades. A key finding is that the incidence of clinical cases peaks in sheep 2-3 years old, despite very different forces-of-infection. This is consistent with age-specific susceptibility of sheep to scrapie, as has been reported for cattle to bovine spongiform encephalopathy and for humans to variant Creutzfeldt-Jakob disease. Scrapie incidence was higher in ewes than rams and at certain times of years, though these effects were not consistent between flocks. There was no evidence for high levels of vertical transmission.

Folate binding protein from kidney brush border membranes contains components characteristic of a glycoinositol phospholipid anchor

A number of cell surface proteins have been shown to be anchored to the plasma membrane by a covalently attached glycoinositol phospholipid (GPL) in amide linkage to the C-terminus of the mature protein. We applied several criteria to establish that folate binding protein (FBP) in brush border membranes of rat kidney contains a GPL anchor. Brush border membranes were isolated and labeled with [3H]folate, and the complex of FBP and [3H]folate was shown to be released to the supernatant by incubation with purified bacterial phosphatidylinositol-specific phospholipase C (PIPLC) but not by incubation with a purified bacterial phosphatidylcholine-specific phospholipase C. The FBP-[3H]folate complex both in crude extracts and after FBP purification by ligand-directed affinity chromatography interacted with Triton X-114 micelles, and prior incubation with PIPLC prevented this detergent interaction. Individual residues characteristic of GPL anchors were found to be covalently associated with FBP following polyacrylamide gel electrophoresis in sodium dodecyl sulfate. These included glucosamine and ethanolamine, which were radiolabeled by reductive methylation and identified by chromatography on an amino acid analyzer, and inositol phosphate, which was inferred by Western blotting with an anti-CRD antisera. This antisera gave positive immunostaining only after FBP had been cleaved by PIPLC, a reliable diagnostic of a GPL anchor. The relationship between GPL-anchored FBP in biological membranes and soluble FBP in biological fluids also is discussed.

Distribution of the prion protein in sheep terminally affected with BSE following experimental oral transmission

This study has examined the distribution of PrP(Sc) in sheep by immunocytochemistry of tissues recovered from terminally affected animals following their experimental infection by the oral route with BSE. Despite a wide range of incubation period lengths, affected sheep showed a similar distribution of high levels of PrP(Sc) throughout the central nervous system. PrP(Sc) was also found in the lymphoid system, including parts of the digestive tract, and some components of the peripheral nervous system. These abundant PrP(Sc) deposits in sheep in regions outside the central nervous system are in direct contrast with cattle infected with BSE, which show barely detectable levels of PrP(Sc) in peripheral tissues. A number of genetically susceptible, challenged animals appear to have survived.

Discriminant responses of the catalytic unit and glucose 6-phosphate transporter components of the hepatic glucose-6-phosphatase system in Ehrlich ascites-tumor-bearing mice

The effect of Ehrlich ascites tumor cells, in vivo, on the hepatic glucose-6-phosphatase (G6Pase) system was examined. The V(max) for glucose 6-phosphate hydrolysis by G6Pase was reduced by 40% and a greater than 15-fold decrease in mRNA encoding the catalytic unit of the G6Pase system was observed 8 days after injection with tumor cells. Blood glucose concentration was decreased from 169 +/- 17 to 105 +/- 9 mg/dl in tumor-bearing mice. There was no change in the G6P transporter (G6PT) mRNA level. However, there was a significant decrease in G6P accumulation into hepatic microsomal vesicles derived from tumor-bearing mice. Decreased G6P accumulation was also associated with a decrease in G6Pase hydrolytic activity in the presence of vanadate, a potent catalytic-unit inhibitor. In addition, G6P accumulation was nearly abolished in microsomes treated with N-bromoacetylethanolamine phosphate, an irreversible inhibitor of the G6PT. These results demonstrate that the catalytic unit and G6PT components of the G6Pase system can be discriminantly regulated, and that microsomal glucose 6-phosphate uptake is dependent on catalytic unit activity as well as G6PT action.

Population dynamics of a scrapie outbreak

A detailed analysis of a scrapie outbreak in a flock of Cheviot sheep is described. A total of 33 cases of 1473 sheep born to the flock were reported between 1985 and 1994. The epidemiology of scrapie can only be understood with reference to sheep demography, the population genetics of susceptibility to scrapie, pathogenesis during a long incubation period, and the rate of transmission (by both horizontal and vertical routes), all of which interact in complex ways. In recent work a mathematical model incorporating these elements was developed and successfully reproduced key features of an earlier outbreak of scrapie in this flock. Here an application of the model to the second outbreak is described. The model accurately reproduces observed allele frequencies and total numbers of susceptible animals remaining at the end of the outbreak. A major difference between the two outbreaks is the very much lower force of infection in the second outbreak. This provided additional information which suggested two ways in which our existing assumptions be refined; firstly, older animals have reduced susceptibility to scrapie and secondly, homozygous and heterozygous susceptibles have different incubation periods.

Clinical signs, histopathology and genetics of experimental transmission of BSE and natural scrapie to sheep and goats

This paper compares the dinical signs, histopathology, detection of PrPSc protein and PrP genetics of the transmission of BSE to sheep and goats, with the effects of the transmission of natural scrapie from a brain homogenate from a single sheep. After intracerebral and oral inoculations there were similarities in the clinical signs due to the two sources of infection, but there were differences in pathology at the end stage of disease and in the genotypes of the sheep which succumbed to the challenges. The incubation period of BSE was associated with the sheep PrP codon 171 genotype, but the natural scrapie source, despite inducing disease only in known susceptible genotypes, showed no clear association with PrP genotype.

A centuries-long epidemic of scrapie in British sheep?

The apparent persistence of scrapie in British sheep for more than 250 years is difficult to explain. Susceptibility to scrapie is associated with particular alleles at a single locus, the PrP gene. As the only known effect of these alleles is to confer susceptibility to a fatal disease, natural selection is expected to reduce their frequency, as has been observed in practice during scrapie outbreaks in single sheep flocks. Susceptibility alleles, and hence scrapie itself, are therefore expected to become rare, yet the disease remains widespread. We suggest that the paradox of scrapie's persistence can be explained by the exceptionally long time-scales inherent in the epidemiology of the disease. It is proposed that scrapie should be regarded as epidemic in British sheep but, unlike more familiar epidemics, which have time-scales of months or years, the scrapie epidemic has a time-scale of centuries. This interpretation implies that scrapie should eventually disappear from the sheep population.

Transmission of BSE by blood transfusion in sheep

We have shown that it is possible to transmit bovine spongiform encephalopathy (BSE) to a sheep by transfusion with whole blood taken from another sheep during the symptom-free phase of an experimental BSE infection. BSE and variant Creutzfeldt-Jakob disease (vCJD) In human beings are caused by the same infectious agent, and the sheep-BSE experimental model has a similar pathogenesis to that of human vCJD. Although UK blood transfusions are leucodepleted--a possible protective measure against any risk from blood transmission--this report suggests that blood donated by symptom-free vCJD-infected human beings may represent a risk of spread of vCJD infection among the human population of the UK.

N-Bromoacetylethanolamine phosphate as a probe for the identification of a liver microsomal glucose-6-phosphate transporter peptide in rats and Ehrlich ascites tumor-bearing mice

Hepatic microsomal glucose-6-phosphatase is a multicomponent system composed of substrate/product translocases and a catalytic subunit. Previously we (Foster et al. (1996) Biochim. Biophys. Acta 12, 244-254) demonstrated that N-bromoacetylethanolamine phosphate (BAEP) is a time-dependent, irreversible inhibitor of glucose-6-phosphate hydrolysis in intact but not disrupted microsomes. We proposed that BAEP manifests its inhibitory effect by binding with a glucose-6-phosphate translocase protein of the glucose-6-phosphatase system. Here we provide additional evidence that BAEP inhibits glucose-6-phosphate transport in microsomal vesicles and utilize [(32)P]BAEP as an affinity label in the identification of a glucose-6-phosphate transport protein. In this study, we identify 51-kDa rat and mouse liver microsomal proteins involved in glucose-6-phosphate transport into and out of microsomal vesicles by utilizing (1) an Ehrlich ascites tumor-bearing mouse model, which displays a decreased sensitivity to the time-dependent inhibitory effect of BAEP, and (2) another glucose-6-phosphate translocase inhibitor, tosyl-lysine chloromethyl ketone, in conjunction with [(32)P]BAEP as an affinity label.

Mineralocorticoid receptors in the mammalian olfactory mucosa

Mineralocorticoid hormones regulate secretion and absorption in a wide variety of epithelial tissues, although specific mechanisms in the olfactory mucosa are currently unknown. Utilizing reverse transcription-polymerase chain reaction (RT-PCR) analysis, we have demonstrated the expression of mineralocorticoid (type I) receptor messenger RNA in the rodent olfactory mucosa. Amplification products of predicted size were obtained with nucleotide sequences corresponding to respective mineralocorticoid receptor (MR) kidney transcripts. Immunocytochemistry, using an antibody with known specificity for MRs, was then utilized in order to localize the cellular site(s) of MR protein expression in the olfactory mucosa. The highest levels of MR immunoreactivity were localized to the supranuclear region of sustentacular cells, as well as the acinar cells of the Bowman's glands. The respiratory regions of the nasal cavity were devoid of appreciable MR immunoreactivity. This study demonstrates both MR transcript and protein expression in the olfactory mucosa. We hypothesize that the mineralocorticoid hormones may have a role in modulation of olfactory secretion and/or sensory transduction in the peripheral olfactory system.

Regulation of glucose production by the liver

Glucose is an essential nutrient for the human body. It is the major energy source for many cells, which depend on the bloodstream for a steady supply. Blood glucose levels, therefore, are carefully maintained. The liver plays a central role in this process by balancing the uptake and storage of glucose via glycogenesis and the release of glucose via glycogenolysis and gluconeogenesis. The several substrate cycles in the major metabolic pathways of the liver play key roles in the regulation of glucose production. In this review, we focus on the short- and long-term regulation glucose-6-phosphatase and its substrate cycle counter-part, glucokinase. The substrate cycle enzyme glucose-6-phosphatase catalyzes the terminal step in both the gluconeogenic and glycogenolytic pathways and is opposed by the glycolytic enzyme glucokinase. In addition, we include the regulation of GLUT 2, which facilitates the final step in the transport of glucose out of the liver and into the bloodstream.

Population dynamics of scrapie in a sheep flock

A detailed analysis of an outbreak of natural scrapie in a flock of Cheviot sheep is described. A total of 137 cases was reported over 13 years among 1307 sheep born into the flock. The epidemiology of scrapie can only be understood with reference to sheep demography, the population genetics of susceptibility to scrapie, pathogenesis during a long incubation period, and the rate of transmission (by both vertical and horizontal routes), all of which interact in complex ways. A mathematical model incorporating these features is described, parameter values and model inputs are derived from available information from the flock and from independent sources, and model outputs are compared with the field data. The model is able to reproduce key features of the outbreak, including its long duration and the ages of cases. The analysis supports earlier work suggesting that many infected sheep do not survive to show clinical signs, that most cases arise through horizontal transmission, and that there is strong selection against susceptible genotypes. However, important aspects of scrapie epidemiology remain poorly understood, including the possible role of carrier genotypes and of an environmental reservoir of infectivity, and the mechanisms maintaining alleles giving susceptibility to scrapie in the sheep population.

Olfactory secretion and sodium, potassium-adenosine triphosphatase: regulation by corticosteroids

OBJECTIVES

To investigate the cellular distribution and relative intensity of the immunoreactivity associated with the expression of sodium, potassium-adenosine triphosphatase (Na, K-ATPase) in cells of the olfactory mucosa. Second, changes in the activity of this enzyme in the olfactory mucosa are correlated with changes in the circulating corticosteroid aldosterone.

METHODS

Combination of immunohistochemical and biochemical techniques were employed to examine the olfactory Na, K-ATPase.

RESULTS

Within the olfactory epithelium, the Na, K-ATPase immunoreactivity was greatest at the supranuclear region of sustentacular cells and/or dendrites of olfactory receptor neurons (ORNs). Cell bodies of ORNs demonstrated moderate immunoreactivity, whereas the duct cells of Bowman's gland exhibited moderate to intense immunoreactivity. Acinar cells of the Bowman's gland were the most intensely stained components of the lamina propria, exhibiting strong immunoreactivity at the basolateral plasma membrane domains of the acinar cells and less within the cytoplasm. Binding of ouabain, a specific inhibitor of Na, K-ATPase, was significantly elevated for aldosterone-injected versus sham-injected controls.

CONCLUSION

These results suggest that olfactory Na, K-ATPase is regulated by the systemic corticosteroid aldosterone. The results are consistent with the hypothesis that corticosteroids regulate olfactory secretion.

Histone II-A activates the glucose-6-phosphatase system without microsomal membrane permeabilization

Many agents have been used to release the latent portion of the activities catalyzed by the glucose-6-phosphatase (Glc-6-Pase) system. Detergents, which disrupt the microsomal membrane concomitantly with Glc-6-Pase activation, have been the most widely used of these agents. The treatment of microsomes with alamethicin or histone II-A has also been reported to activate the Glc-6-Pase system to the same extent as detergent treatment. While alamethicin reportedly permeabilizes the microsomal membrane (R. Fulceri et al., 1995, Biochem. J. 307, 391-397), conflicting ideas as to histone II-A's mechanism of activation have been described (J. St.-Denis et al., 1995, Biochem. J. 310, 221-224 and J. Blair and A. Burchell, 1988, Biochim. Biophys. Acta 964, 161-167). We further investigated whether activation of the Glc-6-Pase system by histone II-A is due to permeabilization of the microsomal membrane. We treated rat liver microsomes with Triton X-100, alamethicin, or histone II-A and found them to be equally effective in maximally activating the Glc-6-Pase system. We also examined the modifying effects of alamethicin and histone II-A on the sensitivity of Glc-6-Pase activities to inhibition by N-bromoacetylethanolamine phosphate (BAEP) and 3-mercaptopicolinate (3-MP), both thiol-directed reagents. Alamethicin, but not histone II-A, abolished the inhibitory effects of BAEP and 3-MP on activities of the Glc-6-Pase system. Our studies support previous reports of Glc-6-Pase activation by alamethicin via permeabilization of microsomal membranes and histone II-A activation without microsomal membrane permeabilization.

Expression of glucocorticoid receptor mRNA and protein in the olfactory mucosa: physiologic and pathophysiologic implications

OBJECTIVES

Define the presence and distribution of glucocorticoid receptors (GRs) within the olfactory mucosa in order to assess potential physiologic and pathophysiologic effects of these hormones on olfaction.

STUDY DESIGN

The olfactory mucosa was harvested from adult male rats and guinea pigs. Kidney tissue was utilized as a known positive control.

METHODS

The techniques of reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry were utilized to examine the expression of GR mRNA and protein. To assure the presence of olfactory mucosa in the nasal tissue samples, RT-PCR was utilized to identify the olfactory marker protein (OMP).

RESULTS

The presence of GR mRNA was confirmed in both the olfactory mucosa and kidney. GR-like immunoreactivity associated with the olfactory epithelium was greatest at the apical surface, a position corresponding to the dendrites, knobs, and cilia of olfactory receptor neurons, as well as the supranuclear region of sustentacular cells. Weaker GR-like immunoreactivity was associated with the region of the cell bodies of the olfactory receptor neurons. Within the lamina propria, acinar cells of the Bowman's glands and olfactory nerve bundles were intensely immunoreactive.

CONCLUSIONS

The presence of GR mRNA and protein within the olfactory mucosa is consistent with a functional role for glucocorticoid hormones in the systemic regulation of olfaction. Furthermore, these studies suggest that corticosteroid medications may have direct effects on the cells of the olfactory mucosa in the pathologic state. The potential mechanisms whereby these hormones may act are discussed.

Low-Km mannose-6-phosphatase as a criterion for microsomal integrity

The low-Km activity of mannose-6-phosphatase (Man-6-Pase) has been used for many years to measure the structural integrity of microsomes. Recently histone II-A has been shown to activate glucose-6-phosphatase (Glc-6-Pase) and Man-6-Pase activities. However, in contrast to detergents, this compound appears to activate without disrupting microsomal vesicles (J.-F. St-Denis, B. Annabi, H. Khoury, and G. van de Werve. 1995. Biochem. J. 310: 221-224). This suggests that Man-6-Pase latency can be abolished without disrupting microsomal integrity and that even normally microsomes may manifest some low-Km Man-6-Pase activity without being "leaky." We have studied the relationship of Man-6-Pase with microsomal integrity further by measuring the latency of several enzymes reported to reside within the lumen of endoplasmic reticulum. We have also correlated this latency with the microsomal permeability of substrates for these enzymes. We found that (i) lumenal enzymes have different degrees of latency when compared with each other, (ii) permeability, as determined via osmotically induced changes in light scattering, is not always consistent with enzymatic latency, (iii) increases in the hydrolysis of Glc-6-P and Man-6-P were not parallel when microsomes were treated with low but increasing concentrations of detergent, and (iv) kinetic studies suggest that mannose-6-phosphate is hydrolyzed by untreated microsomes by more than a single mechanism. We propose that Man-6-Pase is not a reliable index of the integrity of microsomes.

Tungstate: a potent inhibitor of multifunctional glucose-6-phosphatase

The insulin-like action of tungstate in diabetic rats (A. Barberà et al., 1994, J. Biol. Chem. 269, 20047-20053) prompted us to examine the effects of tungstate on the glucose-6-phosphatase system. Our results indicate that tungstate is a potent inhibitor of glucose-6-phosphatase, with a Ki in the 10-25 microM range determined with native microsomes and in the 1-7 microM range determined with detergent-treated microsomes. With both preparations, simple linear competitive inhibition was observed versus glucose 6-phosphate (glucose-6-P) as substrate with the glucose-6-P phosphohydrolase activity of the enzyme. Tungstate was a simple linear competitive inhibitor versus carbamyl phosphate (carbamyl-P) and a linear noncompetitive inhibitor versus glucose with the carbamyl-P:glucose phosphotransferase activity of the glucose-6-phosphatase system. These findings, in addition to the observation that tungstate protected the enzyme against thermal inactivation, indicate that tungstate binds with high affinity and competes at the active site of the enzyme where the substrates glucose-6-P and carbamyl-P bind prior to catalysis. Our results suggest that potent inhibition of glucose-6-P hydrolysis by tungstate is likely responsible, at least in part, for the normalization of glycemia and the rebound in hepatic glucose-6-P levels observed in earlier studies in which tungstate exhibited insulin-like action in diabetic rats.

Effects of ionic strength and chloride ion on activities of the glucose-6-phosphatase system: regulation of the biosynthetic activity of glucose-6-phosphatase by chloride ion inhibition/deinhibition

Certain amino acids stimulate glycogenesis from glucose. The regulatory volume decrease mechanism explaining these effects was defined by Meijer et al. (1992, J. Biol. Chem. 267, 5823-5828). It involves amino acid-induced swelling of hepatocytes resulting in loss of chloride ions which leads to deinhibition of glycogen synthase phosphatase. This results in enhanced conversion of the inactive to active form of glycogen synthase and thus enhanced glycogen synthesis. We have studied the effects of amino acids and chloride ion on the glucose-6-phosphatase system (Glc-6-Pase) with rat liver microsomal preparations, and correlated our results with those reported by others with glycogen synthase. Glc-6-Pase activities are increased by elevated ionic strength varied by increasing the concentration of various buffers or charged amino acids but are not affected by changes in osmolarity, varied with disaccharides or uncharged amino acids. With undisrupted microsomes, chloride ion competitively inhibits carbamyl phosphate: glucose phosphotransferase (KCP,t,UMi,Cl- = 19 mM) more extensively than Glc-6-P phosphohydrolase (KG6P,h,UMi,Cl- = 117 mM). Inhibition by chloride ion and activation due to ionic strength may be important considerations when assessing in vitro Glc-6-Pase activities where an attempt is made to replicate physiologic conditions. Further we propose that amino acids may play a role in increasing biosynthetic activity of Glc-6-Pase, as well as previously characterized glycogen synthase (Meijer et al., op. cit.), via the regulatory volume decrease mechanism through diminished chloride ion inhibition. Reduced concentration of chloride ion will (1) deinhibit the biosynthetic activity of Glc-6-Pase, while still inhibiting Glc-6-P hydrolysis, leading to an increased cellular concentration of Glc-6-P (an important glycogenic intermediate as well as allosteric activator of glycogen synthase) and (2) increase the active form of glycogen synthase by deinhibiting glycogen synthase phosphatase both through the previously defined mechanism (see above) and via Glc-6-P-enhanced conversion of glycogen synthase from its inactive to active form. We propose that the biosynthetic activity of Glc-6-Pase may act in concert with glycogen synthase during amino acid-induced glycogenesis from glucose.

Glucose-6-phosphatase structure, regulation, and function: an update

Work on the glucose-6-phosphatase system has intensified and diversified extensively in the past 3 years. The gene for the catalytic unit of the liver enzyme has been cloned from three species, and regulation at the level of gene expression is being studied in several laboratories worldwide. More than 20 sites of mutation in the catalytic unit protein have been demonstrated to underlie glycogenesis type 1a. inhibition of glucose-6-P hydrolysis by several newly identified competitive and time-dependent, irreversible inhibitors has been demonstrated and in several instances the predicted effects on liver glycogen formation and/or breakdown and on blood glucose production have been shown. Refinements in and additions to the presently dominant "substrate transport-catalytic unit" topological model for the glucose-6-phosphatase system have been made. A new model alternative to this, based on the "combined conformational flexibility-substrate transport" concept, has emerged. Experimental evidence for the phosphorylation of glucose in liver by high-K(m),glucose enzyme(s) in addition to glucokinase has continued to emerge, and new in vitro evidence supportive of biosynthetic functions of the glucose-6-phosphatase system in this role has appeared. High levels of multifunctional glucose-6-phosphatase have been shown present in pancreatic islet beta cells. Glucose-6-P has been established as the likely insulin secretagog in beta cells. Interesting differences in the temporal responses of glucose-6-phosphatase in kidney and liver have been demonstrated. An initial attempt is made here to meld the hepatic and pancreatic islet beta-cell glucose-6-phosphatase systems, and to a lesser extent the kidney tubular and small intestinal mucosal glucose-6-phosphatase systems into an integrated, coordinated mechanism involved in whole-body glucose homeostasis in health and disease.

Natural scrapie and PrP genotype: case-control studies in British sheep

Natural scrapie in sheep is associated with polymorphisms of the PrP gene, particularly at amino acid codons 136, 154 and 171. This paper reports the results of nine scrapie case-control studies in Bleu du Maine, Herdwick, Merino x Shetland, Poll Dorset, Scottish Halfbred, Shetland, Soay, Suffolk and Swaledale sheep from British flocks affected by scrapie. In some outbreaks, scrapie was found to occur only in animals with at least one PrP allele encoding valine at codon 136 (V136), usually a relatively rare allele in healthy controls. In other outbreaks, the V136, PrP allele was either not found or was not an absolute prerequisite for scrapie to develop. Although scrapie had a strong tendency to affect sheep with PrP genotypes homozygous for glutamine at codon 171 (QQ171), these genotypes (QQ171 but varying at other codon positions) were relatively common in healthy controls. The reliable prediction of scrapie susceptibility in previously uninvestigated sheep flocks will therefore require information at least about PrP genotypes at codons 136 and 171.

Glucocorticoid (type II) receptors in the olfactory mucosa of the guinea-pig: RU 28362

The glucocorticoid RU 28362 was employed to identify glucocorticoid receptors in the olfactory mucosa of the guinea-pig. Results demonstrate significant binding of RU 28362 and suggest that the olfactory mucosa is a target site for glucocorticoid action.

Mineralocorticoid (type I) receptors in the olfactory mucosa of the mammal: studies with [3H]aldosterone and the anti-mineralocorticoid spironolactone

High-affinity, specific binding sites to mineralocorticoids, with characteristics of mineralocorticoid (type I) receptors, have been found in the mammalian olfactory mucosa. In the presence of RU 28362, which blocks low-affinity binding of the labeled hormone to glucocorticoid (type II) receptors, Scatchard analysis of the specific [3H]aldosterone binding indicates that aldosterone binds to a single class of high-affinity (type I) sites with a dissociation constant, Kd, of 1.2 x 10(-9) M and a maximum number of binding sites, Bmax, of 63 fmol/mg dry tissue. Time course of association of [3H]aldosterone and its binding sites showed maximal binding by 30 min at 25 degrees C which remained unchanged up to 90 min. Competition studies performed with 1 x 10(-7)-1 x 10(-5) M spironolactone, a competitive mineralocorticoid antagonist, showed a dose-response reduction of [3H]aldosterone binding, implying that in the olfactory mucosa this compound behaves as an aldosterone antagonist. These results demonstrate significant [3H]aldosterone binding to receptors of high affinity and mineralocorticoid specificity and suggest that the olfactory mucosa is a target site for mineralocorticoid action.

Immunolocalisation of the prion protein (PrP) in the brains of sheep with scrapie

Cheviot sheep from the Neuropathogenesis Unit flock were examined for PrP in brain sections using immunocytochemistry in order to aid scrapie diagnosis. Brains were collected from sheep which had been naturally or experimentally infected with scrapie and fixed in periodate-lysine-paraformaldehyde or in formalin. Immunolabelling was achieved using a monoclonal antibody (FH11) raised to the N-terminus of recombinant PrP protein. Several pre-treatments were studied in an effort to enhance PrP immunolabelling such as trypsin, formic acid and hydrated autoclaving. Trypsin was successful in highlighting PrP staining in formalin-fixed tissue. PrP staining was regularly observed in the dorsal vagus nucleus of the medulla oblongata and in the thalamus. Differences in the distribution and intensity of PrP immunostaining were apparent between the scrapie sources ME7 and SSBP/I.