Sentinel lymph node biopsy procedure in squamous vulvar cancer. 10 years follow-up analysis

AIM

Application of sentinel lymph node biopsy (SLNB) procedure in early-stage vulvar cancer and analysis of results, recurrences and complications.

MATERIAL AND METHODS

40 patients with vulvar cancer and SLNB between 2008 and 2018 were retrospectively reviewed. During the surgical procedure the inguinofemoral lymph nodes were checked with a gamma probe to identify the sentinel nodes that were removed and referred for intraoperative pathological assessment. Subsequently, long-term patient follow-up was performed with analysis of complications, relapse and mortality.

RESULTS

40 patients (mean age: 72 years [47-86], the overall detection rate per patient was 95% and a total of 129 Sentinel Lymph Nodes (SLNs) were removed (3.22 SLN/patient). In 3 out of 25 patients with lateral tumour lesions drainage was bilateral and in 2 out of 15 with midline lesions drainage was unilateral. On lymphoscintigraphy, 16 out of 40 had bilateral drainage and 24 unilateral. A total of 119 SLN- and 10 SLN+ were obtained, in 8 out of 10 an inguinofemoral lymphadenectomy was performed. In the SLN- group, one case of lymphatic blockage and one false negative were included. In 12 out of 40 patients there were post-surgical complications, 4 of them lymphoedemas. In the median follow-up (40 months), 6 out of 10 with SLN+ (40% mortality) and 7 out of 30 SLN- (16% mortality) had recurrences.

CONCLUSIONS

SLNB in vulvar cancer is the technique of choice for correct staging and locoregional therapy. Correct clinical lymph node staging is important before surgery in order to avoid potential blockage drainages which could induce a false negative SLN.

[Training program in endourological surgery. Future perspectives.]

Current training in urological endoscopy lacks a specific training program. However, there is a clear need for a specific and uniform program, which will ensure the training, regardless of the unit where it is carried out. So, the goal is to first evaluate the current model and then bring improvements for update. The hospital training accreditation programme are only the adjustment of the official program of the urology specialty to the specific circumstances of each center, which causes variability in training of residents. After reviewing 19 training programs belonging to 12 Spanish regions. The current outlook shows that scarcely 10% of hospitals quantify the number of procedures/ year, although the Spanish program emphasizes that the achievement of the residents should be quantified. Urology residents, sense their training as inadequate and therefore their level of satisfaction is moderate. The three main problems detected by residents as an obstacle on their training are: the lack of supervision, tutors completing their own learning. Finally, the lack of quantification in surgical activities is described as a threat. This has no easy solution, since the learning curve of the most common techniques in endourology is not correctly established. Regarding aspects that can improve the current model, they highlight the need to design a specific program. The need to customize the training, the ineludible accreditation of tutors and obviously dignify the tutor's teaching activity. Another basic aspect is the inclusion of new technologies as training tools, e-learning. As well as the implementation of an adequate competency assessment plan and the possibility of relying on simulation systems. Finally, they highlight the need to attend monographic meetings and external clinic rotations to promote critical training.

[Antirreflux ureteral catheters.]

Double-J ureteral stents disposal is associated with the appearance of side effects in up to 90% of the patients. The main causes of these symptoms are related to stent's design and the materials they are manufactured from. Vesicoureteral reflux and bladder trigone irritation are the etiopathogenic causes of ureteral stents associated morbidity. Due to this, and in order to improve patients' quality of life, stents that avoid reflux have been developed. Among anti-reflux designs, the first was a double-J stent the bladder tip of which is provided with a polymeric membrane that prevents retrograde flow of urine through its internal drainage channel. This design showed satisfactory vesicaresults, although not statistically significant. Their use in renal transplantation has also been assessed not only to decrease morbidity and ascending infection but also to improve graft survival. Other designs try to thin the distal end and even change it to a surgical suture thread, with the aim of eliminating the internal drainage channel in order to cause the minimum interference with the UVJ. Recently, two prototypes were evaluated in animal models and have achieved reduction of VUR. The first consists of a valve attached to the distal end of a traditional double-J stent, acting as a backflow prevention device. The second design is an intra-ureteral stent that acts like a double-J stent, but without crossing the UVJ and therefore preventing reflux completely. Nowadays, the use of these devices is not implemented in hospitals due to the absence of scientific evidence supporting the superiority of these designs over conventional stents.

Initial validation of a training program focused on laparoscopic radical nephrectomy

OBJECTIVE

To assess a training model focused on laparoscopic nephrectomy.

MATERIAL AND METHODS

16 residents participated in the study, who attended a training program with a theoretical session (1hour) and a dry (7hours) and a wet lab (13hours). During animal training, the first and last nephrectomies were assessed through the completion time and the global rating scale "Objective and Structured Assessment of Technical Skills" (OSATS). Before and after the course, they performed 3 tasks on the virtual reality simulator LAPMentor (1) eye-hand coordination; 2) hand-hand coordination; and 3) transference of objects), registering time and movement metrics. All participants completed a questionnaire related to the training components on a 5-point rating scale.

RESULTS

The participants performed the last nephrectomy faster (P<.001) and with higher OSATS scores (P<.001). After the course, they completed the LAPMentor tasks faster (P<.05). The number of movements decreased in all tasks (1) P<.001, 2) P<.05, and 3) P<.05), and the path length in tasks 1 (P<.05) and 2 (P<.05). The movement speeds increased in tasks 2 (P<.001) and 3 (P<.001). With regards to the questionnaire, the usefulness of the animal training and the necessity of training on them prior to their laparoscopic clinical practice were the questions with the highest score (4.92±.28).

CONCLUSIONS

The combination of physical simulation and animal training constitute an effective training model for improving basic and advanced skills for laparoscopic nephrectomy. The component preferred by the urology residents was the animal training.

[Prostate adenocarcinoma. Predictive clinical model of seminal vesicle involvement]

OBJECTIVES

Our aim is to design a predictive model of seminal vesicle involvement. using clinical data.

METHODS

We studied 1128 patients with clinically localized adenocarcinoma treated by radical prostatectomy (127 were pT3b). We identified (logistic regression) clinical variables related with pT3b. With the multivariate study influential variables a seminal vesicle involvement risk model is designed.

RESULTS

Seminal vesicle involvement related factors: In univariate study: the influential variables are: Gleason 7 (OR:2);Gleason 8-10 (OR:4.5) T2 (OR:2.6); bilateral involvement in biopsy (OR:3.1); PSA 10-20 ng/ml ( OR:3.3); PSA >20 ng/ ml (OR:9.5). In the multivariate study are influential: Gleason 7 (OR:1.56) Gleason 8-10 ( OR: 3.4); T2 (OR:1.9); PSA 10-20 ng/ml (OR:3.1) and PSA >20 ng/,ml (OR:8.8). Predictive model: using multivariate logistic regression the weight of each variable is valued and a value between 1 and 4 is given. Gleason 2-6, T1; PSA<10 ng/ml value 1; Gleason 7; T2 y PSA 10-20 ng/ml value 2; Gleason 8-10 and PSA >20 ng/ml value 4. Each patient has a marker that fluctuates between 3 and 10. 5 Groups are designed with significantly different risks (p<0.05 in all cases ): Group 1 (3 points) (OR:1) (risk: 2.4% 95%IC 0.7%-4.3%) Group 2 (4 points) (OR:2.7) (risk: 6.5% 95%IC 5%-7.9%); Group 3(5-6 points) (OR:7.1)( risk:15% 95%IC 11%-19%) Group 4 ( 7--8 points) (OR:33.4) (risk: 45.5%; 95%IC 30%-59%) Group 5 (9-10 points) (OR:57.3) (risk: 58.8% 95%IC 35%- 82%).

CONCLUSION

The clinical model allows an accurate approximation to the seminal vesicles involvement risk.

Fasting apolipoprotein B48 is a marker for peripheral arterial disease in type 2 diabetes

An earlier study showed that fasting and postprandial concentrations of apolipoprotein B48 were raised in patients with type 2 diabetes (DM2) and peripheral arterial disease (PAD) as compared with persons without DM2 or persons with DM2 but not PAD. The aim of this study was to confirm the association of PAD and B48 in a larger group of patients with DM2 and the relation of B48 with the preheparin lipoprotein lipase (LPL) mass. We studied 456 patients with DM2. PAD was defined as an ankle-brachial index (ABI) <0.9. Apolipoprotein B48 was quantified by ELISA. Apo B48 was significantly higher in the group with an ABI <0.9 than the groups with ABI of 0.9-1.3 and >1.3 (10.7 ± 6.28 vs. 9.24 ± 5.5 vs. 9.17 ± 8.8 mg/L, ANOVA test, p < 0.05). B48 was independently associated with an ABI <0.9 (OR 1.053; 95 % CI, 1.013-1.094; p < 0.05), together with smoking and duration of diabetes. The preheparin LPL mass was similar in the patients with and without PAD. In conclusion, we confirmed that fasting B48 is an independent marker of PAD in patients with DM2, unrelated to the preheparin LPL mass, statin therapy or glucose lowering treatment.

Perineal radical prostatectomy in the minimally invasive era

Radical prostatectomy is currently the standard of care for localized prostate cancer. In the last decade, the minimally invasive surgery, especially the robotic surgery has been growing and open techniques are less frequent performed. A non-systematic review of the literature is performed, highlighting the current situation of the perineal radical prostatectomy in the minimally invasive era, its indications, and functional and oncological outcomes. Radical perineal prostatectomy, when compared with other surgical approaches, still experience favorable outcomes. Urologist might be abandoning an underused surgical approach.

Percutaneous nephrolithotomy and chronic kidney disease: results from the CROES PCNL Global Study

PURPOSE

We compared the characteristics and outcomes of patients treated with percutaneous nephrolithotomy in the CROES (Clinical Research Office of the Endourological Society) Global Study according to preoperative renal function.

MATERIALS AND METHODS

Prospective data on consecutive patients treated with percutaneous nephrolithotomy in a 1-year period were collected from 96 participating centers. The glomerular filtration rate was estimated using the Modification of Diet in Renal Disease formula based on preoperative serum creatinine measurement. Patients were divided into 3 groups by glomerular filtration rate, including chronic kidney disease stages 0/I/II-greater than 60, stage III-30 to 59 and stages IV/V-less than 30 ml/minute/1.73 m(2). Patient characteristics, operative characteristics, outcomes and morbidity were assessed.

RESULTS

Estimated glomerular filtration rate data were available on 5,644 patients, including 4,436 with chronic kidney disease stages 0/I/II, 994 with stage III and 214 with stages IV/V. A clinically significant minority of patients with nephrolithiasis presented with severe chronic kidney disease. A greater number of patients with stages IV/V previously underwent percutaneous nephrolithotomy, ureteroscopy or nephrostomy and had positive urine cultures than less severely affected patients, consistent with the higher incidence of staghorn stones in these patients. Patients with chronic kidney disease stages IV/V had statistically significantly worse postoperative outcomes than those in the other chronic kidney disease groups.

CONCLUSIONS

Poor renal function negatively impacts the post-percutaneous nephrolithotomy outcome. By more aggressive removal of kidney stones, particularly staghorn stones, at first presentation and more vigilantly attempting to prevent recurrence through infection control, pharmacological or other interventions, the progression of chronic kidney disease due to nephrolithiasis may be mitigated.

[Radical prostatectomy for high risk localized prostate cancer. Prognosis and study of influential variables]

BACKGROUND

To study the biochemical progression-free survival (BPFS) achieved by a group of high risk patients in accordance with D'Amico's classification treated with radical prostatectomy. To identify the clinical-pathological variables which are influential in biochemical progression-free survival and, if possible, use them to design a prognostic model.

MATERIAL AND METHODS

The study involves 232 patients, out of a series of 1,054, diagnosed with clinically localized prostate cancer, qualified as high risk on D'Amico's classification (PSA>20 ng/ml or Gleason score 8-10 or T3) treated with radical prostatectomy. The BPFS is studied and the clinical-pathological variables obtained (PSA, Gleason score of the biopsy and of the piece, clinical and pathological study, unilateral or bilateral affectation, margins of the prostatectomy piece, Ki-67 expression) are analyzed to identify whether they influenced the BPFS. Contingency tables and tables for survival analysis: Kaplan-Meyer, log-rank and Cox models were used for the statistical study.

RESULTS

Descriptive study: PSA: 23.3 ng/ml (median); cGleason 2-6: 33%; 7: 13%; 8-10: 54%; T2: 58%; Bilateral affectation in the diagnostic biopsy: 59%; RNM T2: 60%; RNM T3: 40%. pGleason 2-6: 24%; 7: 28%; 8-10: 48%; pT2: 43%; pT3a: 30%; pT3b: 27%; Affected margin: 51%; N1:13%. Progression-free survival: with a mean and median follow-up of 64 months; 53% show biochemical progression. The median until progression: 42 months. Progression-free survival at 5 and 10 years is 43±3% and 26±7%. The multivariate study (Cox models) shows that the variables that are independently influential in the BPFS are the affectation of margins (HR: 3.5; 95% IC.1.9-6.7; p<0001); and Ki67 >10% (HR: 2.3; 95% IC: 1.2-4.3; P: 0.009). Risk groups: using the two influential variables and employing Cox models, three risk groups emerged as the best model: Group 1 (0 variables present); Group 2 (1 variable); Group 3 (2 variables). The progression-free survival is 69±8%; 27±6% and 18±11% at 5 years. The differences amongst the three groups are significant.

CONCLUSION

The high risk group according to the D'Amico classification is heterogeneous in relation to biochemical progression and can be broken down into three risk groups using the two independently influential variables (affected margins and Ki67 percentage).

The clinical research office of the endourological society percutaneous nephrolithotomy global study: staghorn versus nonstaghorn stones

PURPOSE

The study compared characteristics and outcomes in patients with staghorn or nonstaghorn stones who were treated with percutaneous nephrolithotomy (PCNL) within the Clinical Research Office of the Endourological Society (CROES) PCNL Global Study.

PATIENTS AND METHODS

Data over a 1-year period from consecutively treated patients from 96 centers worldwide were collated. The following variables in patients with staghorn or nonstaghorn stones were compared: National prevalence, patient characteristics, access method, puncture frequency and outcomes, including bleeding rates, operative time, and duration of hospital stay.

RESULTS

Data from 5335 eligible patients were collated; 1466 (27.5%) with staghorn and 3869 (72.5%) with nonstaghorn stones. Staghorn stone presentation varied between centers from 67% in Thailand to 13% in Argentina. The frequencies of previous procedures were similar between groups, but shockwave lithotripsy was less frequent in patients with staghorn stones compared with nonstaghorn (16.8% vs 22.6%) and positive preoperative urine cultures were more frequent in patients with staghorn than nonstaghorn stones (23.4% vs 13.1%). Patients with staghorn stones underwent multiple punctures more frequently than those with nonstaghorn stones (16.9% vs 5.0%). Postoperative fever, bleeding, and the need for blood transfusion were more frequent, the median operative time and duration of hospital stay were longer, while the proportion of patients remaining stone free was lower (56.9% vs 82.5%) in patients with staghorn than nonstaghorn stones.

CONCLUSIONS

The proportion of patients with staghorn stones varies widely between centers. Stone-free rates were lower, complications more frequent, and operative time and hospital stay were longer in patients with staghorn stones.

Association of steroid and xenobiotic receptor (SXR) and multidrug resistance 1 (MDR1) gene expression with survival among patients with invasive bladder carcinoma

What's known on the subject? and What does the study add? SXR and MDR1 are known as responsible for chemo and radiotherapy resistance in some cancers, like kidney cancer (MDR1). Invasive bladder cancer is an aggressive disease, with different behaviour upon its tumoral stage, and also within the same tumoral stage, therefore molecular markers are sought. This study shows a new molecular marker, which has shown as a predictor for bad prognosis cancers, therefore, allowing us for a better patient selection for aggressive therapies.

OBJECTIVE

To investigate the prognostic value of steroid and xenobiotic receptor (SXR) and multidrug resistance 1 (MDR1) gene expression in relation to survival among patients with invasive bladder cancer.

PATIENTS AND METHODS

The prospective study included 67 patients diagnosed with invasive bladder cancer and treated with radical cystectomy at one of two institutions. SXR and MDR1 gene expression was assessed by real-time quantitative polymerase chain reaction (RT-PCR) in tumoral and normal tissue from frozen surgical specimens.

RESULTS

Patients were followed for a mean of 29 months; 31 patients (46%) had progression. In univariate analysis, significant predictors of overall survival (OS) were pathological stage, lymph node (LN) status, histological grade, vascular-lymphatic invasion, and SXR expression. In multivariate analysis, independent predictors of OS were LN status (odds ratio [OR], 2.96; P=0.034), vascular-lymphatic invasion (OR, 2.50; P=0.029), and SXR expression (OR, 1.05, P=0.03). Among the 51 patients with negative LNs (pN0), univariate predictors of OS were SXR expression, MDR1 expression, and pathological stage. In multivariate analysis, SXR expression (OR, 1.06; P=0.01) and MDR1 expression (OR, 3.27; P=0.03) were independently associated with survival. Within the pN0 group, patients with SXR expression had shorter progression-free survival than did those without expression (P=0.004). This association persisted in the N0 subgroup with stage pT3-pT4 disease (P=0.028). However, in the pN1 group SXR expression did not have any influence.

CONCLUSIONS

For patients with invasive bladder cancer, SXR expression has value as a predictor of survival independent of the standard pathological predictors. Its maximum importance appears to be in patients with stage pT3-pT4 pN0 disease.

[Cryotherapy for renal tumors: current status and contemporary developments]

The proportion of renal tumors found incidentally dramatically increased in the past decade. More than half of them were diagnosed in patients over 70 years of age, a population with high associated comorbidity. Nephron-sparing minimally invasive surgical procedures are aimed at treating patients with small renal tumors and multiple comorbidities. Cryotherapy stands out among all other ablative procedures because of its better mid-term oncological outcome. A non-systematic review of the literature on cryotherapy as a treatment for renal tumors was made, analyzing its indications, actual and future application techniques, results, and complications.

Postprandial apolipoprotein B48 is associated with asymptomatic peripheral arterial disease: a study in patients with type 2 diabetes and controls

BACKGROUND

Postprandial hyperlipidemia is a common feature in type 2 diabetes; our aim was to investigate whether there is an association between subclinical peripheral arterial disease (PAD) and the levels of apolipoprotein B48, as a specific marker for postprandial lipidemia.

METHODS

We enrolled 101 patients with type 2 diabetes and 73 controls free from clinical cardiovascular disease. Main outcome measures were the presence of subclinical PAD, assessed by the ankle-brachial index, and the intestinal particles measured as the concentration of apolipoprotein B48 at fasting and 4h after a mixed breakfast.

RESULTS

No control had subclinical PAD. Of the 101 diabetic patients, 21 had subclinical PAD. The levels of apo B48, both fasting and postprandial, were only significantly raised in the diabetic patients who had PAD. The diabetic patients without vascular disease had similar concentrations of triglycerides and apo B48 to the controls. In binary logistic regression analyses, only smoking and postprandial B48 levels, in addition to diabetes, were independently associated with PAD. On the other hand, PAD but not diabetes was associated with the fasting and postprandial levels of apo B48.

CONCLUSION

Our study suggests that apolipoprotein B48 levels might be a marker of occult PAD in patients suffering from type 2 diabetes mellitus. Accordingly, subclinical PAD should be taken into account in studies on postprandial lipidemia involving patients with diabetes.

Two contemporary series of percutaneous tract dilation for percutaneous nephrolithotomy

Dilation of the tract for percutaneous nephrolithotomy can be performed with three different basic techniques. A retrospective outcome analysis of two techniques-metal telescoping dilation and balloon dilation-in a contemporary series of two European departments shows no significant difference in morbidity related to the dilation procedure. A literature survey that concentrates on publications with a focus on tract dilation shows that balloon dilation is the most frequently performed, but the morbidity reported for the different techniques appears identical. The three standard techniques have been developed more than 20 years ago. Very few new techniques have been added.

Perioperative morbidity of laparoscopic cryoablation of small renal masses with ultrathin probes: a European multicentre experience

BACKGROUND

Low morbidity has been advocated for cryoablation of small renal masses.

OBJECTIVES

To assess negative perioperative outcomes of laparoscopic renal cryoablation (LRC) with ultrathin cryoprobes and patient, tumour, and operative risk factors for their development.

DESIGN, SETTING, AND PARTICIPANTS

Prospective collection of data on LRC in five centres.

INTERVENTION

LRC.

MEASUREMENTS

Preoperative morbidity was assessed clinically and the American Society of Anaesthesiologists (ASA) score was assigned prospectively. Charlson Comorbidity Index (CCI) and Charlson-Age Comorbidity Index (CACI) scores were retrospectively assigned. Negative outcomes were prospectively recorded and defined as any undesired event during the perioperative period, including complications, with the latter classed according to the Clavien system. Patient, tumour, and operative variables were tested in univariate analysis as risk factors for occurrence of negative outcomes. Significant variables (p<0.05) were entered in a step-forward multivariate logistic regression model to identify independent risk factors for one or more perioperative negative outcomes. The confidence interval was settled at 95%.

RESULTS AND LIMITATIONS

There were 148 procedures in 144 patients. Median age and tumour size were 70.5 yr (range: 32-87) and 2.6 cm (range: 1.0-5.6), respectively. A laparoscopic approach was used in 145 cases (98%). Median ASA, CCI, and CACI scores were 2 (range: 1-3), 2 (range: 0-7), and 4 (range: 0-11), respectively. Comorbidities were present in 79% of patients. Thirty negative outcomes and 28 complications occurred in 25 (17%) and 23 (15.5%) cases, respectively. Only 20% of all complications were Clavien grade > or = 3. Multivariate analysis showed that tumour size in centimetres, the presence of cardiac conditions, and female gender were independent predictors of negative perioperative outcomes occurrence. Receiver operator characteristic curve confirmed the tumour size cut-off of 3.4 cm as an adequate predictor of negative outcomes.

CONCLUSIONS

Perioperative negative outcomes and complications occur in 17% and 15.5%, respectively, of cases treated by LRC with multiple ultrathin needles. Most of the complications are Clavien grade 1 or 2. The presence of cardiac conditions, female gender, and tumour size are independent prognostic factors for the occurrence of a perioperative negative outcome.

Collagen graft interposition in vesicovaginal fistula treatment

Vesicovaginal fistula (VVF) is a quite rare complication of gynecological surgery. The first attempt to repair the fistulous tract offers the best opportunity for cure. We report the successful repair of VVF in 2 patients using a combined anterior vaginal approach and porcine dermal collagen grafting as interposition tissue. Favorable results confirm technical simplicity, safety and efficacy of this procedure.

Anterior compartment prolapse repair with a hybrid biosynthetic mesh implant technique

The aim of the present study is to assess the safety and feasibility of a new technique for cystocele repair using a hybrid biosynthetic graft fixed by the transobturator approach. This is a retrospective study of 13 women diagnosed with symptomatic anterior compartment prolapse that were in stages II and IV, using Pelvic Organ Prolapse Quantification score and treated between 2003 and 2006. The surgical procedure was carried out through a vaginal approach, exposing the arcus tendineus and the posterior surface of the obturator foramen from the ischial spine to the inferior pubic ramus bone. The patients were followed-up after 3, 6 and 12 months. The anatomical cure rate was 85% (stage 0), although two patients had a recurrence 8 months after surgery. All patients would repeat the procedure, if necessary. No de novo dyspareunia was observed in these small series. The results suggest that this technique is safe and feasible and is a comprehensive surgical approach for anterior compartment prolapse, without postoperative morbidity.

Mapping of neurokinin b in the cat brainstem

We studied the distribution of neurokinin B-immunoreactive cell bodies and fibers in the cat brainstem using an indirect immunoperoxidase technique. The highest density of immunoreactive fibers was found in the motor trigeminal nucleus, the laminar and alaminar spinal trigeminal nuclei, the facial nucleus, the marginal nucleus of the brachium conjunctivum, the locus coeruleus, the cuneiform nucleus, the dorsal motor nucleus of the vagus, the postpyramidal nucleus of the raphe, the lateral tegmental field, the Kölliker-Fuse nucleus, the inferior central nucleus, the periaqueductal gray, the nucleus of the solitary tract, and in the inferior vestibular nucleus. Immunoreactive cell bodies containing neurokinin B were observed, for example, in the locus coeruleus, the dorsal motor nucleus of the vagus, the median division of the dorsal nucleus of the raphe, the lateral tegmental field, the pericentral nucleus of the inferior colliculus, the internal division of the lateral reticular nucleus, the inferior central nucleus, the periaqueductal gray, the postpyramidal nucleus of the raphe, and in the medial nucleus of the solitary tract. This widespread distribution of neurokinin B in the cat brainstem suggests that the neuropeptide could be involved in many different physiological functions. In comparison with previous studies carried out in the rat brainstem on the distribution of neurokinin B, our results point to a more widespread distribution of this neuropeptide in the cat brainstem.