A Multicenter Analysis of the Early Impact of COVID-19 on Junior Resident Operative Case Volume

Introduction

Institutions have reported decreases in operative volume due to COVID-19. Junior residents have fewer opportunities for operative experience and COVID-19 further jeopardizes their operative exposure. This study quantifies the impact of the COVID-19 pandemic on resident operative exposure using resident case logs focusing on junior residents and categorizes the response of surgical residency programs to the COVID-19 pandemic.

Materials and methods

A retrospective multicenter cohort study was conducted; 276,481 case logs were collected from 407 general surgery residents of 18 participating institutions, spanning 2016-2020. Characteristics of each institution and program changes in response to COVID-19 were collected via surveys.

Results

Senior residents performed 117 more cases than junior residents each year (P < 0.001). Prior to the pandemic, senior resident case volume increased each year (38 per year, 95% confidence interval 2.9-74.9) while junior resident case volume remained stagnant (95% confidence interval 13.7-22.0). Early in the COVID-19 pandemic, junior residents reported on average 11% fewer cases when compared to the three prior academic years (P = 0.001). The largest decreases in cases were those with higher resident autonomy (Surgeon Jr, P = 0.03). The greatest impact of COVID-19 on junior resident case volume was in community-based medical centers (246 prepandemic versus 216 during pandemic, P = 0.009) and institutions which reached Stage 3 Program Pandemic Status (P = 0.01).

Conclusions

Residents reported a significant decrease in operative volume during the 2019 academic year, disproportionately impacting junior residents. The long-term consequences of COVID-19 on junior surgical trainee competence and ability to reach cases requirements are yet unknown but are unlikely to be negligible.

Beyond the Surgical Time-Out: A National Needs Assessment of Preoperative Communication in US General Surgery Residency Programs

OBJECTIVE

Perioperative communication is critical for procedural learning. In order to develop a periprocedural faculty development tool, we aimed to characterize the current status of preoperative communication in US General Surgery residency programs.

DESIGN

After Association of Program Directors in Surgery approval, a survey was distributed to general surgery programs. Participants were asked about perioperative communication, including the frequency of preoperative briefings, defined as dedicated educational discussions prior to a procedure. Data were analyzed using descriptive statistics.

SETTING

An anonymous electronic survey was distributed to interested programs in early 2019.

PARTICIPANTS

US General Surgery trainees and attending surgeons.

RESULTS

A total of 348 responses were recorded from 27 programs: 199 (57%) attending surgeons and 149 (43%) surgical trainees. Most respondents (83%) were from a university-affiliated program. Attending surgeons indicated a higher frequency of performing preoperative briefings compared to trainees (p < 0.001). Both trainees and attending surgeons were more likely to select their own group when asked who initiates a preoperative briefing. The majority of respondents (58%) agreed that discussing autonomy preoperatively improves resident autonomy for the case. In regards to the timing of preoperative briefings, most took place in/adjacent to the operating room, with only 60 participants (17%) participating in preoperative briefings the day/night prior to the operation. The most frequent topic discussed during preoperative briefings was "procedural content." Most participants selected "time constraints" as the greatest barrier to preoperative briefings and indicated that attending surgeon engagement was necessary to facilitate their use. Trainees were less likely to report engaging in immediate postoperative feedback, but more likely to report postoperative self-reflection.

CONCLUSIONS

Preoperative briefings are not necessarily routine and attendings and trainees differ on their perceptions related to their content and frequency. Efforts to address timing and scheduling and encourage dual-party engagement in perioperative communication are key to the development of tools to enhance this important aspect of procedural learning.

Association Between Entrustable Professional Activities and Milestones Evaluations: Real-time Assessments Correlate With Semiannual Reviews

OBJECTIVE

Entrustable professional activities (EPAs) have been developed to refine competency-based education. The American Board of Surgery has initiated a 2-year pilot study to evaluate the impact of EPAs on the evaluation and feedback of surgical residents. The ACGME Milestones in Surgery is a semiannual competency-based evaluation program to measure resident progression through 16 professional attributes across 8 practice domains. The correlation between these 2 evaluation tools remains unclear. The purpose of this study is to evaluate this correlation through comparison of an EPA with the corresponding elements of the ACGME Milestones.

DESIGN

From July, 2018 to October, 2019, all residents submitting EPA evaluations for gall bladder disease were evaluated for preoperative, intraoperative, and/or postoperative entrustability. The ratings were converted to a numerical rank from 0 to 4. Milestones scores from May 2019 and November 2019 were obtained for each resident, with scores ranging from 0 to 4. The gall bladder EPA incorporates the operative PC3 and MK2 and nonoperative PC1, PC2, and ICS3 components. Spearman rank correlation was conducted to evaluate the association between each resident's median EPA ranking and his/her milestones scores.

SETTING

SUNY Upstate Medical University, Syracuse, NY, a university-based hospital.

PARTICIPANTS

General surgery residents.

RESULTS

Among 24 residents, 106 intraoperative EPA evaluations were. For both the May and November milestones, significant positive correlations were noted for PC3 (correlation coefficient ρ = 0.690, p < 0.001; ρ = 0.876, p < 0.001). Similarly, for MK2, a significant positive correlation was noted (ρ = 0.882, p < 0.001; ρ = 0.759, p < 0.001). Interestingly, significant positive correlations were also identified between the 3 nonoperative milestones and the intraoperative entrustability ranking.

CONCLUSIONS

We observed significant correlations between EPAs for cholecystectomy and associated milestones evaluation scores. These findings indicate that EPAs may provide more timely and specific feedback than existing tools and, on aggregate, may improve upon existing formative feedback practices provided through the biannual evaluation of surgical residents.

Concordance Between Expert and Nonexpert Ratings of Condensed Video-Based Trainee Operative Performance Assessment

OBJECTIVE

We examined the impact of video editing and rater expertise in surgical resident evaluation on operative performance ratings of surgical trainees.

DESIGN

Randomized independent review of intraoperative video.

SETTING

Operative video was captured at a single, tertiary hospital in Boston, MA.

PARTICIPANTS

Six common general surgery procedures were video recorded of 6 attending-trainee dyads. Full-length and condensed versions (n = 12 videos) were then reviewed by 13 independent surgeon raters (5 evaluation experts, 8 nonexperts) using a crossed design. Trainee performance was rated using the Operative Performance Rating Scale, System for Improving and Measuring Procedural Learning (SIMPL) Performance scale, the Zwisch scale, and ten Cate scale. These ratings were then standardized before being compared using Bayesian mixed models with raters and videos treated as random effects.

RESULTS

Editing had no effect on the Operative Performance Rating Scale Overall Performance (-0.10, p = 0.30), SIMPL Performance (0.13, p = 0.71), Zwisch (-0.12, p = 0.27), and ten Cate scale (-0.13, p = 0.29). Additionally, rater expertise (evaluation expert vs. nonexpert) had no effect on the same scales (-0.16 (p = 0.32), 0.18 (p = 0.74), 0.25 (p = 0.81), and 0.25 (p = 0.17).

CONCLUSIONS

There is little difference in operative performance assessment scores when raters use condensed videos or when raters who are not experts in surgical resident evaluation are used. Future validation studies of operative performance assessment scales may be facilitated by using nonexpert surgeon raters viewing videos condensed using a standardized protocol.

A systematic review and meta-analysis of predictors of recurrence in patients with Solid Pseudopapillary Tumors of the Pancreas

BACKGROUND

The recurrence rates and predictors of recurrence in patients with Solid Pseudopapillary tumors (SPT) are unclear, which makes it challenging to determine the duration of follow-up. The aim of the current study was to perform a systematic review and meta-analysis to determine the recurrence rates and pathologic factors associated with recurrence in patients with SPT.

METHODS

A PubMed, Scopus, and Web of Science search was conducted to identify studies of SPT published during the last 15 years: (09/2002-09/2017). Studies reporting on patients with SPT and follow-up of >5 years were included. The search strategy was conducted per 2009 PRISMA guidelines.

RESULTS

A total of 103 studies reporting on 2599 non-metastatic SPT patients were identified. Sixty-nine patients (2.6%) developed recurrence during follow-up. Pooled estimates from studies with a sample size >20 (N = 33) noted an overall recurrence rate of 2% (95% CI 1-2%). Male gender (OR 1.960), positive lymph nodes (OR 11.9), R1 margins (OR 11.1), and LVI (OR 5.5), were associated with a significantly (all p < 0.05) increased risk of recurrence.

CONCLUSION

Current meta-analysis suggests that only 2% of patients with SPT experience recurrence after resection. These data will guide the treating physicians and patients regarding recurrence rates and help identify patients at increased risk of recurrence during follow-up.

The effect of gender on operative autonomy in general surgery residents

BACKGROUND

Despite an increasing number of women in the field of surgery, bias regarding cognitive or technical ability may continue to affect the experience of female trainees differently than their male counterparts. This study examines the differences in the degree of operative autonomy given to female compared with male general surgery trainees.

METHODS

A smartphone app was used to collect evaluations of operative autonomy measured using the 4-point Zwisch scale, which describes defined steps in the progression from novice ("show and tell") to autonomous surgeon ("supervision only"). Differences in autonomy between male and female residents were compared using hierarchical logistic regression analysis.

RESULTS

A total of 412 residents and 524 faculty from 14 general surgery training programs evaluated 8,900 cases over a 9-month period. Female residents received less autonomy from faculty than did male residents overall (P < .001). Resident level of training and case complexity were the strongest predictors of autonomy. Even after controlling for potential confounding factors, including level of training, intrinsic procedural difficulty, patient-related case complexity, faculty sex, and training program environment, female residents still received less operative autonomy than their male counterparts. The greatest discrepancy was in the fourth year of training.

CONCLUSION

There is a sex-based difference in the autonomy granted to general surgery trainees. This gender gap may affect female residents' experience in training and possibly their preparation for practice. Strategies need to be developed to help faculty and residents work together to overcome this gender gap.

Development and validation of a semi-automated surveillance system-lowering the fruit for non-ventilator-associated hospital-acquired pneumonia (nvHAP) prevention

Objectives

Conducting manual surveillance of non-ventilator-associated hospital-acquired pneumonia (nvHAP) using ECDC (European Centre for Disease Prevention and Control) surveillance criteria is very resource intensive. We developed and validated a semi-automated surveillance system for nvHAP, and describe nvHAP incidence and aetiology at our hospital.

Methods

We applied an automated classification algorithm mirroring ECDC definition criteria to distinguish patients ‘not at risk’ from patients ‘at risk’ for suffering from nvHAP. ‘At risk’-patients were manually screened for nvHAP. For validation, we applied the reference standard of full manual evaluation to three validation samples comprising 2091 patients.

Results

Among the 39 519 University Hospital Zurich inpatient discharges in 2017, the algorithm identified 2454 ‘at-risk’ patients, reducing the number of medical records to be manually screened by 93.8%. From this subset, nvHAP was identified in 251 patients (0.64%, 95%CI: 0.57–0.73). Sensitivity, negative predictive value, and accuracy of semi-automated surveillance versus full manual surveillance were lowest in the validation sample consisting of patients with HAP according to the International Classification of Diseases (ICD-10) discharge diagnostic codes, with 97.5% (CI: 93.7–99.3%), 99.2% (CI: 97.9–99.8%), and 99.4% (CI: 98.4–99.8%), respectively. The overall incidence rate of nvHAP was 0.83/1000 patient days (95%CI: 0.73–0.94), with highest rates in haematology/oncology, cardiac and thoracic surgery, and internal medicine including subspecialties.

Conclusions

The semi-automated surveillance demonstrated a very high sensitivity, negative predictive value, and accuracy. This approach significantly reduces manual surveillance workload, thus making continuous nvHAP surveillance feasible as a pivotal element for successful prevention efforts.

Limiting ventilator-associated lung injury in a preterm porcine neonatal model

PURPOSE

Preterm infants are prone to respiratory distress syndrome (RDS), with severe cases requiring mechanical ventilation for support. However, there are no clear guidelines regarding the optimal ventilation strategy. We hypothesized that airway pressure release ventilation (APRV) would mitigate lung injury in a preterm porcine neonatal model.

METHODS

Preterm piglets were delivered on gestational day 98 (85% of 115day term), instrumented, and randomized to volume guarantee (VG; n=10) with low tidal volumes (5.5cm³kg^-1) and PEEP 4cmH₂O or APRV (n=10) with initial ventilator settings: P_High 18cmH₂O, P_Low 0cmH₂O, T_High 1.30s, T_Low 0.15s. Ventilator setting changes were made in response to clinical parameters in both groups. Animals were monitored continuously for 24hours.

RESULTS

The mortality rates between the two groups were not significantly different (p>0.05). The VG group had relatively increased oxygen requirements (F_iO₂ 50%±9%) compared with the APRV group (F_iO₂ 28%±5%; p>0.05) and a decrease in PaO₂/FiO₂ ratio (VG 162±33mmHg; APRV 251±45mmHg; p<0.05). The compliance of the VG group (0.51±0.07L·cmH₂O^-1) was significantly less than the APRV group (0.90±0.06L·cmH₂O^-1; p<0.05).

CONCLUSION

This study demonstrates that APRV improves oxygenation and compliance as compared with VG. This preliminary work suggests further study into the clinical uses of APRV in the neonate is warranted.

LEVEL OF EVIDENCE

Not Applicable (Basic Science Animal Study).

The Feasibility of Real-Time Intraoperative Performance Assessment With SIMPL (System for Improving and Measuring Procedural Learning): Early Experience From a Multi-institutional Trial

PURPOSE

Intraoperative performance assessment of residents is of growing interest to trainees, faculty, and accreditors. Current approaches to collect such assessments are limited by low participation rates and long delays between procedure and evaluation. We deployed an innovative, smartphone-based tool, SIMPL (System for Improving and Measuring Procedural Learning), to make real-time intraoperative performance assessment feasible for every case in which surgical trainees participate, and hypothesized that SIMPL could be feasibly integrated into surgical training programs.

METHODS

Between September 1, 2015 and February 29, 2016, 15 U.S. general surgery residency programs were enrolled in an institutional review board-approved trial. SIMPL was made available after 70% of faculty and residents completed a 1-hour training session. Descriptive and univariate statistics analyzed multiple dimensions of feasibility, including training rates, volume of assessments, response rates/times, and dictation rates. The 20 most active residents and attendings were evaluated in greater detail.

RESULTS

A total of 90% of eligible users (1267/1412) completed training. Further, 13/15 programs began using SIMPL. Totally, 6024 assessments were completed by 254 categorical general surgery residents (n = 3555 assessments) and 259 attendings (n = 2469 assessments), and 3762 unique operations were assessed. There was significant heterogeneity in participation within and between programs. Mean percentage (range) of users who completed ≥1, 5, and 20 assessments were 62% (21%-96%), 34% (5%-75%), and 10% (0%-32%) across all programs, and 96%, 75%, and 32% in the most active program. Overall, response rate was 70%, dictation rate was 24%, and mean response time was 12 hours. Assessments increased from 357 (September 2015) to 1146 (February 2016). The 20 most active residents each received mean 46 assessments by 10 attendings for 20 different procedures.

CONCLUSIONS

SIMPL can be feasibly integrated into surgical training programs to enhance the frequency and timeliness of intraoperative performance assessment. We believe SIMPL could help facilitate a national competency-based surgical training system, although local and systemic challenges still need to be addressed.

Using the ACGME Milestones for Resident Self-Evaluation and Faculty Engagement

BACKGROUND

Since July 2014 General Surgery residency programs have been required to use the Accreditation Council for Graduate Medical Education milestones twice annually to assess the progress of their trainees. We felt this change was a great opportunity to use this new evaluation tool for resident self-assessment and to furthermore engage the faculty in the educational efforts of the program.

METHODS

We piloted the milestones with postgraduate year (PGY) II and IV residents during the 2013/2014 academic year to get faculty and residents acquainted with the instrument. In July 2014, we implemented the same protocol for all residents. Residents meet with their advisers quarterly. Two of these meetings are used for milestones assessment. The residents perform an independent self-evaluation and the adviser grades them independently. They discuss the evaluations focusing mainly on areas of greatest disagreement. The faculty member then presents the resident to the clinical competency committee (CCC) and the committee decides on the final scores and submits them to the Accreditation Council for Graduate Medical Education website. We stored all records anonymously in a MySQL database. We used Anova with Tukey post hoc analysis to evaluate differences between groups. We used intraclass correlation coefficients and Krippendorff's α to assess interrater reliability.

RESULTS

We analyzed evaluations for 44 residents. We created scale scores across all Likert items for each evaluation. We compared score differences by PGY level and raters (self, adviser, and CCC). We found highly significant increases of scores between most PGY levels (p < 0.05). There were no significant score differences per PGY level between the raters. The interrater reliability for the total score and 6 competency domains was very high (ICC: 0.87-0.98 and α: 0.84-0.97). Even though this milestone evaluation process added additional work for residents and faculty we had very good participation (93.9% by residents and 92.9% by faculty) and feedback was generally positive.

CONCLUSION

Even though implementation of the milestones has added additional work for general surgery residency programs, it has also opened opportunities to furthermore engage the residents in reflection and self-evaluation and to create additional venues for faculty to get involved with the educational process within the residency program. Using the adviser as the initial rater seems to correlate closely with the final CCC assessment. Self-evaluation by the resident is a requirement by the RRC and the milestones seem to be a good instrument to use for this purpose. Our early assessment suggests the milestones provide a useful instrument to track trainee progression through their residency.

The impact of brief team communication, leadership and team behavior training on ad hoc team performance in trauma care settings

BACKGROUND

Communication breakdowns and care coordination problems often cause preventable adverse patient care events, which can be especially acute in the trauma setting, in which ad hoc teams have little time for advanced planning. Existing teamwork curricula do not address the particular issues associated with ad hoc emergency teams providing trauma care.

METHODS

Ad hoc trauma teams completed a preinstruction simulated trauma encounter and were provided with instruction on appropriate team behaviors and team communication. Teams completed a postinstruction simulated trauma encounter immediately afterward and 3 weeks later, then completed a questionnaire. Blinded raters rated videotapes of the simulations.

RESULTS

Participants expressed high levels of satisfaction and intent to change practice after the intervention. Participants changed teamwork and communication behavior on the posttest, and changes were sustained after a 3-week interval, though there was some loss of retention.

CONCLUSIONS

Brief training exercises can change teamwork and communication behaviors on ad hoc trauma teams.

Engaging medical students in the feedback process

BACKGROUND

There are potential advantages to engaging medical students in the feedback process, but efforts to do so have yielded mixed results. The purpose of this study was to evaluate a student-focused feedback instructional session in an experimental setting.

METHODS

Medical students were assigned randomly to either the intervention or control groups and then assigned randomly to receive either feedback or compliments. Tests of knowledge, skills, and attitudes were given before and after the intervention.

RESULTS

There was a significant gain of knowledge and skill in the group that received instruction. Satisfaction was higher after compliments in the control group but higher after feedback in the instructional group. There was no change in the subject's willingness to seek feedback.

CONCLUSIONS

A student-focused component should be carefully included as part of an overall effort to improve feedback in surgical education. The role of medical student attitudes about feedback requires further investigation.

Complications and treatment failures of video-assisted thoracoscopic debridement for pediatric empyema

PURPOSE

Video-assisted thoracoscopic debridement (VATD) is a well-established intervention to treat pediatric empyema. There is ongoing controversy at what stage in the treatment algorithm it should be utilized. To shed further light onto this debate, we reviewed our institutional experience looking for factors predicting treatment failure or complications of VATD.

METHODS

We retrospectively analyzed data on patients that had undergone VATD for empyema from 1995 to 2008. We used independent sample t tests and Chi-square tests (SPSS) for statistical analysis.

RESULTS

One hundred and fifty-two procedures in 151 patients [81 male (53.6%)] were identified. In 146 (96.7%) the etiology of the empyema was pulmonary, in 3 (1.98%) due to an infectious abdominal process and in 2 (1.3%) due to abdominal trauma. 118 patients (78.1%) were transferred from outside hospitals. 107 (70.1%) underwent VATD primarily, 44 (29.1%) following another procedure. The overall complication rate was 13.8%, most of which were minor. Treatment failures occurred in seven patients, resulting in three reoperations; two patients died. The average length of stay was 10.1 days, but was significantly longer if VATD followed another procedure or if a complication occurred. The risk for complications correlated with older age (6.2 vs. 8.8 years, p = 0.023) and lower hematocrit on admission (31.1 vs. 27.9%, p = 0.006).

CONCLUSIONS

VATD provided effective treatment for pediatric empyema. Complications were mostly minor, occurring more frequently in older patients and those with a lower admission hematocrit. Early VATD decreased the length of hospitalization.

Duration of Cardiopulmonary Resuscitation before Extracorporeal Rescue: How Long Is Not Long Enough?

Despite the extensive resources required, extracorporeal cardiopulmonary resuscitation (ECPR) has been recognized as an extension of traditional CPR. The reported duration of CPR before ECPR initiation is similar between survivors and nonsurvivors, but the duration of CPR that results in futility of care is unknown. We report two cases of prolonged CPR followed by ECPR resulting in acceptable neurologic outcomes. Ventricular tachycardia developed in a 4-year-old with myocarditis, resulting in a cardiac arrest requiring CPR for 176 minutes before initiation of extracorporeal membrane oxygenation (ECMO). The patient required ECMO for 9 days. He survived neurologically normal. A ventricular arrhythmia developed in a newborn after an arterial switch procedure, leading to cardiac arrest requiring CPR for 97 minutes before ECMO, which lasted for 11 days. Hydrocephalus developed, but the patient is progressing developmentally. The upper limit of CPR duration before ECPR resulting in acceptable neurological outcomes is unknown. Many clinical and biochemical factors are potential predictors of appropriate ECPR utility. The Extracorporeal Life Support Organization registry is a plausible forum to collect data regarding ECPR. We suggest that possible predictive variables be collected. Until then, practitioners must rely on experience and judgment regarding the value of ECPR in children.

Implementation of a Web- and simulation-based curriculum to ease the transition from medical school to surgical internship

BACKGROUND

Starting a surgical internship is a stressful experience. We developed a web and simulation-based curriculum to ease this transition.

METHODS

We created an educational website containing a curriculum of commonly encountered on call situations. After match day in 2003, we contacted all of our new surgical interns. We performed a confidence assessment using a Likert-scale questionnaire, and the trainees were given access to the curriculum. In June 2003, we performed human patient simulator sessions. The participants were asked to provide feedback regarding the simulator experience. During the first week of residency, they were again asked to answer the confidence questionnaire.

RESULTS

Sixteen residents (94%) used the web curriculum, and 17 (100%) participated in the simulations. Eleven (65%) filled out both questionnaires. The confidence score improved from 5.4 to 6.7 (P < .0001).

CONCLUSIONS

A web and simulation-based curriculum for incoming house staff is feasible. Studies are underway to validate this novel method and to expand its use for surgical education.

Idiopathic thrombocytopenic purpura complicated by an intracranial hemorrhage secondary to an arteriovenous malformation

OBJECTIVE

To report a case of idiopathic thrombocytopenic purpura (ITP) complicated by an intracranial hemorrhage (ICH) in a child with a previously undiagnosed arteriovenous malformation.

CASE

We describe a child with known ITP who developed a severe headache, was evaluated in an emergency department of a community hospital, and was found by computer tomography (CT) scan to have an ICH. Despite treatment with platelets, corticosteroids, and intravenous immunoglobulin, she subsequently developed an acute change in mental status. A second CT scan showed that the hemorrhage had significantly increased in size despite treatment. The patient underwent an emergent splenectomy prior to a craniotomy to remove the hemorrhage. At the time of surgery, it was discovered that she had an arteriovenous malformation at the sight of the hemorrhage. Her recovery was unremarkable and she was discharged to home with no neurologic sequelae.

CONCLUSIONS

ICH is a rare but life-threatening complication of ITP. Neurologic symptoms in a child with ITP should be quickly evaluated by CT scan. Most experts suggest careful observation for most cases of ITP. However, when neurologic symptoms occur, more aggressive treatment options must be used. Care of this child included an emergency splenectomy prior to her craniotomy. Pediatric emergency medicine practitioners must be aware of these neurologic symptoms and must not hesitate to involve pediatric surgeons and neurosurgeons in the care of the child. Prompt recognition and early intervention are the keys to improving outcomes when ICH complicates ITP.

Pulse laser acoustics for the characterization of inhomogeneities at interfaces of microstructures

Interfaces between neighbouring materials are often subjected to diffusion processes which cause layers having gradually varying mechanical properties--like densities, Young's moduli or shear moduli--perpendicular to the surface or interface. In this investigation particular interest is drawn on the question how the propagation characteristics of bulk acoustic waves are affected by diffusion layers. The reflection and transmission behavior of bulk acoustic waves encountering a continuum having a spatially dependent sound velocity is discussed based on numerical simulations as well as on experimental verifications. The simulated results are part of an on-going project in which material properties of MEMS devices are investigated by short pulse laser acoustic methods. Mechanical waves are excited and detected thermoelastically using laser pulses of 70 fs duration. For metals this leads to wavelengths of 10-20 nm and the corresponding frequencies amount to 0.3-0.6 THz. In contrast to previous work done in this field in which diffusion effects are generally considered as undesirable phenomena, the deliberate realization of microstructures having well defined gradually varying material properties in one or more dimensions represents a goal of this investigation. For metallic thin film multilayers thermally induced diffusion processes have shown to be an easy and reliable technique for the realization of layered structures having continuously varying mechanical properties within several 10 nm. Among the experimental methods suitable for the in-depth profiling of submicron metallic thin films providing resolutions of several nanometers, are short pulse laser acoustic methods, Rutherford backscattering spectroscopy (RBS), and glow discharge optical emission spectroscopy (GDOES). Short pulse laser acoustic methods and RBS have the advantage to be nondestructive. The short pulse laser acoustic method is described in detail and RBS measurements are presented for verification purposes. Finally potential engineering applications like micro-machined spectrum analyzers, acoustic isolation layers, and band pass filters, operating at very high frequencies are presented.

Extracorporeal life support for posttraumatic acute respiratory distress syndrome at a children's medical center

BACKGROUND

Primary traumatic injury was considered previously a contraindication for institution of extracorporeal life support because of high risk for persistent or new bleeding. Published experience in adults suggests that extracorporeal membrane oxygenation (ECMO) can successfully support trauma victims with pulmonary failure. The authors reviewed their experience with the use of ECMO in pediatric and adult trauma patients with acute respiratory distress syndrome (ARDS) at a children's medical center.

METHODS

ECMO Center records from 1991 through 2001 (76 children, 8 adults) were reviewed to identify all patients with a primary or secondary ICD-9 diagnostic code of posttraumatic ARDS in addition to documented trauma.

RESULTS

Five children and 3 adults with traumatic injury and ARDS received ECMO support. Seven patients were injured in motor vehicle collisions; one patient suffered a gunshot wound to the chest. Patient ages ranged from 21 months to 29 years (pediatric median, 4 years; range, 21 months to 18 years). Four patients had pre-ECMO laparotomies, including 3 who required splenectomy. Four patients had liver lacerations, 3 had pulmonary contusions, and 1 had a renal contusion. Median ventilation before ECMO was 6 days (range, 2 to 10). Seven of 8 patients were placed on venovenous (VV) ECMO. Seven patients had significant bleeding on ECMO. Patients were treated with blood product replacement, epsilon-aminocaproic acid (EACA), and aprotinin infusions. Surgical intervention was not required for bleeding. Six patients received hemofiltration. Median time on ECMO was 653 hours (range, 190 to 921 hours). Six of 8 patients overall survived (75%). Four of 5 pediatric patients survived.

CONCLUSIONS

Children and adults with severe posttraumatic ARDS can be treated successfully on VV extracorporeal support. Hemorrhage occurs frequently but is manageable.

Surgical complications of inguinal and abdominal wall hernias

Inguinal and other abdominal wall hernias are some of the most commonly encountered problems in the pediatric population that require surgical intervention. Surgical repair is straightforward in most cases and can be performed on an outpatient basis. Complications are unusual, but potentially devastating. This article focuses specifically on incidence and risk factors of these complications, reviews the currently accepted treatment options, and points out strategies to avoid them.

The future of medical education is no longer blood and guts, it is bits and bytes

In the United States, medical care consumes approximately $1.2 trillion annually (14% of the gross domestic product) and involves 250,000 physicians, almost 1 million nurses, and countless other providers. While the Information Age has changed virtually every other facet of our life, the education of these healthcare professionals, both present and future, is largely mired in the 100-year-old apprenticeship model best exemplified by the phase "see one, do one, teach one." Continuing medical education is even less advanced. While the half-life of medical information is less than 5 years, the average physician practices 30 years and the average nurse 40 years. Moreover, as medical care has become increasingly complex, medical error has become a substantial problem. The current convulsive climate in academic health centers provides an opportunity to rethink the way medical education is delivered across a continuum of professional lifetimes. If this is well executed, it will truly make medical education better, safer, and cheaper, and provide real benefits to patient care, with instantaneous access to learning modules. At the Center for Advanced Technology in Surgery at Stanford we envision this future: within the next 10 years we will select, train, credential, remediate, and recredential physicians and surgeons using simulation, virtual reality, and Web-based electronic learning. Future physicians will be able to rehearse an operation on a projectable palpable hologram derived from patient-specific data, and deliver the data set of that operation with robotic assistance the next day.

Computer-assisted training and learning in surgery

The teaching and learning of surgery is a time-honored tradition based upon the "see one, do one, teach one" apprenticeship model. Recent improvement of this model has centered upon incremental change in skills teaching and testing and curricular development. Economic pressures have strained the resources of academic health centers and faculty responsible for teaching surgery, even as information technology has opened new avenues for obtaining and benefitting from relevant information. Combining the tools of simulation theory, virtual reality, and the principles of adult education offers new opportunities to optimize surgical education as we enter a more highly connected and interdependent era, where the boundaries between teacher and student blur as the modern surgeon truly becomes a lifelong learner.

Rational treatment of empyema in children

HYPOTHESIS

Efficacious and cost-effective treatment of pediatric empyema can be accomplished following a protocol based on its radiographic appearance. Therapeutic modalities include thoracostomy tube drainage (TTD) with or without fibrinolytic therapy (FT) and video-assisted thoracoscopic debridement (VATD).

DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

RESULTS

From 1995 through 1999, 31 children were treated ranging in age from 11 months to 18 years (mean age, 5.1 years). Twenty-seven (87.1%) underwent TTD; of these, 22 (81.5%) received FT with urokinase. The TTD failed in 4 children (14.8%) who required salvage VATD. Primary VATD was performed in another 4 children (12.9%). The mean length of stay was 14.6 days (TTD, 14.1 days; salvage VATD, 20. 0 days; primary VATD, 11.5 days), ranging from 8.0 to 30.0 days. Complications included readmission for fever (2 patients [6.5%]) and gastrointestinal bleeding (1 patient [3.2%]). There were no anaphylactic reactions or bleeding episodes due to urokinase. Two patients (7.4%) treated with TTD and FT developed an air leak that resolved spontaneously. The mean hospital charges were $78,832 (TTD with or without FT, $75,450; salvage VATD, $107,476; primary VATD, $69,634). The procedural charges were highest for salvage VATD.

CONCLUSIONS

Most cases of pediatric empyema can be treated by TTD with or without FT. This therapy is safe and effective for children with nascent disease. Primary VATD is preferred in children with advanced disease. Cost-effectiveness could be further improved through better prediction of those patients likely to fail TTD and require salvage VATD. An algorithmic approach based on findings from computed tomography or (better) ultrasonography of the chest may be the best way to make this distinction and rationalize care.

Salvage laparotomy for failure of peritoneal drainage in necrotizing enterocolitis in infants with extremely low birth weight

BACKGROUND/PURPOSE

Peritoneal drainage is a temporizing procedure for infants with extremely low birth weight (ELBW) who have perforated necrotizing enterocolitis (NEC). "Salvage" laparotomy is advocated when patients worsen after drainage. Some patients have survived with intact gastrointestinal functional after drainage alone. The purpose of this study is to determine if these salvage laparotomies are beneficial.

METHODS

The authors reviewed the records of ELBW infants treated at Stanford University with perforated NEC from 1993 through 1998. Data collected included demographic makeup, type of operation, survival rate, postoperative complications, length of stay (LOS), and cost.

RESULTS

The authors treated 26 patients, 9 with laparotomy and 17 with peritoneal drainage. The peritoneal drainage group had lower birth weight and more comorbid conditions. Survival rate was similar between laparotomy and drainage: 55.6% versus 41.2%. Four patients in the drainage group underwent salvage laparotomy for perceived clinical deterioration. All of these patients died. The clinical status of patients who had salvage laparotomy and died was similar to those who did not and lived. Seven of 13 patients treated with drainage followed only by supportive care and antibiotics survived. Cost and LOS for patients undergoing salvage laparotomy were much greater than for nonsurviving patients undergoing only peritoneal drainage: 84 +/- 20 days and $660,000 compared with 34 +/- 11 days and $306,000.

CONCLUSIONS

Both primary peritoneal drainage and laparotomy should be considered primary therapy for perforated NEC. Patients undergoing peritoneal drainage typically experience clinical deterioration after operation. In this limited experience, salvage laparotomy did not appear beneficial.

Simulation and virtual reality in surgical education: real or unreal?

Rapid change is under way on several fronts in medicine and surgery. Advances in computing power have enabled continued growth in virtual reality, visualization, and simulation technologies. The ideal learning opportunities afforded by simulated and virtual environments have prompted their exploration as learning modalities for surgical education and training. Ongoing improvements in this technology suggest an important future role for virtual reality and simulation in surgical education and training.

Bromocriptine improves glycaemic control and serum lipid profile in obese Type 2 diabetic subjects: a new approach in the treatment of diabetes

Bromocriptine, a potent dopamine D(2) receptor agonist, has been shown to reduce insulin resistance, glucose intolerance and hyperlipidaemia in both numerous animal studies and in Phase II studies. Bromocriptine has been used worldwide for over 20 years to treat Parkinson's disease, macroprolactinoma and other disorders; it has been found to be generally safe. We therefore investigated the possible beneficial effects of Ergoset(R) (Ergo Science Corp.), a new quick release formulation of bromocriptine, on glycaemic control and serum lipid profile in obese Type 2 diabetic subjects in two large Phase III studies. A large, randomised, double-blind placebo-controlled study was conducted in which Ergoset was given once daily at 8 am. (4.8 mg maximum dose) for 24 weeks as adjunctive therapy to sulphonylurea (485 subjects) to obese Type 2 diabetics held on a weight- maintaining diet. Treatment efficacy parameters included change from baseline in glycated haemoglobin A(1c) (HbA(1c)), fasting and post-prandial serum glucose, insulin, triglyceride and free fatty acid levels. Baseline glycated haemoglobin, fasting glucose, insulin, triglyceride and free fatty acid levels did not differ between treatment groups. and on average were 9.4 +/- 0.05%, 222 +/- 2 mg/dl, 24 +/- 1 µU/ml, 248 +/- 11 mg/dl, and 850 +/- 32 µEq/l, respectively. A similarly designed study of Ergoset as monotherapy in Type 2 diabetics (154 subjects) with similar baseline clinical characteristics was conducted. Addition of Ergoset treatment to sulphonylurea reduced percent glycated HbA(1c) by 0.55 (P < 0.0001) (approximately 1.0 for responders, 65% of population), fasting and post-prandial glucose by 23 and 26 mg/dl (P < 0.0002), fasting and post-prandial triglycerides by 72 and 63 mg/dl (P < 0.005) and fasting and post-prandial free fatty acids by 150 and 165 µEq/l (P < 0.05), relative to placebo. Twelve percent of all Ergoset subjects, compared to 3% of placebo subjects, withdrew from the study due to adverse events. The most common events causing withdrawal were nausea, dizziness, asthenia, and rhinitis (representing 4.5, 3.3, 2.0, and 0.8% of the total Ergoset populations, respectively). The incidence of serious adverse events did not differ between Ergoset- (3.4%) and placebo- (4.3%) treated subjects. Ergoset as monotherapy also improved glycaemic control (0.56 HbA(1c) decrease relative to placebo after 24 weeks of treatment; P < 0.02). Once daily Ergoset treatment improves glycaemic control and serum lipid profile and is well-tolerated in obese Type 2 diabetics.

Timed daily administration of prolactin and corticosteroid hormone reduces murine tumor growth and enhances immune reactivity

In the present study, we investigated the time-dependent interactive effects of daily injections of prolactin (PRL) and corticosterone (CORT) on the activation of lymphocyte function and inhibition of tumor growth in vivo in mice. BALB/c mice were injected subcutaneously with EMT-6 fibrosarcoma cells (a murine connective tissue tumor cell derived from mammary gland), and then different groups of animals were treated with PRL (1 microg/g body weight [BW] ip) at Oh, 4h, 8h, 12h, 16h, or 20h after CRT (1 microg/g BW ip) daily for 10 days. Different control groups were vehicle treated or treated with either hormone alone. Mice were kept in constant light 1 week before and during injections and in a 14:10 light-dark cycle thereafter. Tumor progression was monitored for up to 21 days after the cessation of treatment, and thereafter spleen lymphocytes were harvested and tested for mitogen-triggered proliferation. Prolactin administration at 8h or 16-20h after corticosteroid treatment reduced tumor volume by 77% and 49%, respectively, relative to vehicle-treated controls. Other time relations of hormone treatment were ineffectual. Further studies indicated that the immunosuppressant cyclosporin A (CSA) substantially stimulated tumor growth; this effect was completely abrogated by a simultaneous 8h related hormone treatment. How ever, the 8h hormone treatment was ineffective in inhibiting tumor growth in T-cell-deficient nude mice. Spleen lymphocytes from tumor-bearing (TB) mice showed an elevated basal proliferative capacity stimulated by concanavalin A (ConA; a stimulus for T-cell proliferation) and lipopolysaccharide (LPS; a stimulus for B-cell proliferation) compared to non-TB mice. Spleen lymphocytes from TB mice treated with CORT and PRL at 8h intervals exhibited an increased spontaneous (as well as LPS- and ConA- triggered) proliferation (by 104%, 48%, and 70%, respectively) compared with vehicle control TB mice. Fluorescence-activated cell sorting (FACS) analysis of splenocytes from hormone-treated animals indicated a 34-100% increase in the CD4+ (e.g., T helper cell) population. Treatment of animals with either hormone alone did not inhibit tumor growth or stimulate immune function relative to vehicle controls. The daily rhythms of plasma PRL, CORT, and thyroxine were all substantially altered by the presence of tumor in these mice. These results indicate that appropriately timed daily treatment of PRL and CORT can attenuate tumor growth, in part, via activation of antitumor immune mechanisms. Collectively, these data suggest that circadian neuroendocrine activities must be temporally organized appropriately to inhibit tumor growth.

Bromocriptine/SKF38393 ameliorates islet dysfunction in the diabetic (db/db) mouse

Dysfunction of pancreatic islets plays a crucial role in the etiology of type II diabetes. Chronic hyperglycaemia or hyperlipidaemia may impair islet function. Previous studies by our laboratory have demonstrated that dopaminergic agonists ameliorated hyperglycaemia and hyperlipidaemia in obese and diabetic rodents. In the present study, we investigated the effect of a treatment with the dopamine D2/D1 receptor agonists (bromocriptine/SKF38393, BC/SKF) on islet dysfunction in db/db mice. Our results show that a 2-week BC/SKF treatment markedly reduced hyperglycaemia and hyperlipidaemia, and significantly improved islet dysfunction demonstrated by an increase of secretagogue-stimulated insulin release from islets of db/db mice to levels observed in islets from lean mice. There was also a fourfold increase of insulin content in the pancreas of BC/SKF-treated db/db mice compared with that in untreated controls. The effect of BC/SKF on islet function cannot be mimicked in pair-fed animals. BC/SKF had no direct stimulatory effect on islet insulin secretion, suggesting BC/SKF treatment improved islet function via an indirect mechanism. This treatment markedly improved the abnormally elevated daily levels of corticosterone, blood glucose and plasma lipids, supporting the view that BC/SKF may affect the neuroendocrine system that in turn regulates peripheral metabolism and thereby improves islet function.

Bromocriptine reduces obesity, glucose intolerance and extracellular monoamine metabolite levels in the ventromedial hypothalamus of Syrian hamsters

We examined whether reductions in body fat stores and insulin resistance in Syrian hamsters induced by bromocriptine are associated with reductions in daily norepinephrine (NE) and serotonin activities as indicated by their extracellular metabolite levels in the ventromedial hypothalamus (VMH). High levels of these monoamines within the VMH have been suspected to induce obesity and insulin resistance. Microdialysate samples from the VMH of freely moving obese male hamsters (BW: 208 +/- 5 g) were collected hourly over a 25-hour period before bromocriptine treatment, during the first day of and after 2 weeks of bromocriptine treatment (800 microg/animal daily, i.p.), and body composition and glucose tolerance analyses were conducted before and after 2 weeks of treatments. The microdialysate samples were analyzed by HPLC for metabolites of serotonin: 5-hydroxy-indoleacetic acid (5-HIAA), NE: 3-methoxy-4-hydroxy-phenylglycol (MHPG), and dopamine: homovanillic acid (HVA). Bromocriptine treatment for 14 days significantly reduced body fat by 60% and areas under the glucose and insulin curves during a glucose tolerance test by 50 and 46%, respectively. Concurrently, extracellular VMH contents of 5-HIAA, MHPG, and HVA were reduced by 50, 29 and 66%, respectively (p < 0.05). Similarly, VMH 5-HIAA and MHPG contents were 48 and 44% less, respectively (p < 0.05), in naturally glucose-tolerant hamsters compared with naturally glucose-intolerant hamsters. Bromocriptine induced reductions of body fat, and improvements in glucose intolerance may result in part from its ability to decrease serotonin and NE activities in the VMH.

Dopaminergic neurotoxin administration to the area of the suprachiasmatic nuclei induces insulin resistance

Dopaminergic neuron neurotoxin (6-hydroxydopamine; 6-OHDA) administration directed to the hypothalamic area of the mammalian pacemaker, the suprachiasmatic nuclei (SCN), was carried out on lean, glucose tolerant hamsters to investigate the possibility that dopaminergic input to the vicinity of the SCN is necessary to maintain this metabolic condition. Glucose tolerance tests (GTT, 3 g glucose/kg) were performed 4 days prior to and 16 days after neurotoxin lesioning. 6-OHDA administration to the area of the SCN resulted in both a significant 58% increase in daily food consumption by the 16th day post-lesioning, and a 85% increase in weight gain 4 and 8 weeks after lesioning relative to controls. Such treatment also significantly increased the total areas under the GTT glucose and insulin curves by 48% and 400% respectively, compared with controls. These findings indicate that body weight gain, glucose intolerance and insulin resistance result from decreased dopaminergic input to the area of the SCN.

Ambulatory urodynamics: extramural testing of the lower and upper urinary tract by Holter monitoring of cystometrogram, uroflowmetry, and renal pelvic pressures

This article elucidates the clinical applicability and state of the art of ambulatory urodynamics. Ambulatory urodynamics have evolved into practical investigations like EAC, HFM, and EAC combined with renal pelvimetry. EAC has been shown to be the method of preference if detrusor overactivity is involved. Conventional filling cystometry has proved to be an unreliable way to exclude detrusor instability. De novo instability after suspension surgery often indicates that an existing detrusor overactivity was not identified preoperatively. EAC including flowmetry has shown considerable variance in obstructive and contractility parameters in males with LUTS indicative for BPH. This raises doubt whether the clinical flow analysis is the suitable "gold standard" as advocated by the ICS. For a real break through of EAC, less complex automatic analysis is necessary. HFM is a newer method within the range of ambulatory urodynamic tests. It has not yet been completely evaluated. But, because the technique is analogous to the office flowmetry, noninvasive and very well accepted by the patients, it is expected to be widely used. This expectation is strengthened by the fact that HFM seems to show individual therapeutic efficacy of drugs, such as alpha-blockers. As a research tool to evaluate efficacy, it is far more powerful than conventional methods because of the reduction of within-patient standard deviation to about 10%. Finally, EAC combined with pelvimetry offers a promising method for the clinical evaluation of a combined dysfunction of upper and lower urinary tract.

Bromocriptine (Ergoset) reduces body weight and improves glucose tolerance in obese subjects

OBJECTIVE

A double-blind placebo controlled study investigated long-term effects of Ergoset, a new quick release formulation of bromocriptine, on body weight, body fat, and glucose tolerance in a group (n = 17) of obese subjects who were instructed to follow a moderate hypocaloric diet.

RESEARCH DESIGN AND METHODS

Obese individuals (> 25% body fat for men and > 30% body fat for women) were instructed to follow a calorie-restricted diet (70% of weight maintaining based on study entry weight) and were randomized to daily treatment with Ergoset (1.6-2.4 mg/day) or placebo at 0800 over an 18-week treatment period. Oral glucose tolerance tests were performed on subjects before initiation and again at termination of treatment. Body weight and body fat (determined by skinfold measurements) were quantified every 2 weeks during the course of treatment.

RESULTS

Ergoset treatment for 18 weeks significantly reduced body weight and body fat versus placebo (6.3 +/- 1.5 and 5.4 +/- 1.1 kg vs. 0.9 +/- 1.0 and 1.5 +/- 0.6 kg. respectively, P < 0.01). Ergoset, but not placebo, also improved glucose tolerance (P < 0.02); the stimulated area under the oral glucose tolerance curve was reduced by 46% (from 121 +/- 23 to 64 +/- 32 mg.h-1.dl-1), while the stimulated area under the insulin curve was reduced by 30%.

CONCLUSIONS

When combined with instruction to follow a moderate hypocaloric diet, Ergoset, but not placebo, improves glucose tolerance and promotes significant weight and body fat loss in obese subjects over an 18- week treatment period.

Bromocriptine inhibits in vivo free fatty acid oxidation and hepatic glucose output in seasonally obese hamsters (Mesocricetus auratus)

Seasonally obese hyperinsulinemic hamsters were treated for 5 weeks with bromocriptine (500 to 600 micrograms per animal) and tested for drug effects on energy balance, body fat stores, nocturnal whole-body free fatty acid (FFA) metabolism and hepatic glucose output, and diurnal glucose tolerance. After 5 weeks, bromocriptine treatment reduced retroperitoneal fat pad weight by 45% without altering either daily food consumption or end-treatment total daily energy expenditure. Also, 5 weeks of treatment improved the diurnal glucose tolerance, resulting in a 47% and 33% decrease in the area under glucose and insulin curves, respectively. After 4 weeks, bromocriptine treatment reduced nocturnal lipolysis by 28%, palmitate rate of appearance into plasma by 30%, palmitate oxidation by 33%, and hepatic glucose output by 28%. Moreover, these reductions were accompanied by a 75% reduction in plasma insulin concentration. The data suggest that bromocriptine may improve diurnal glucose tolerance in part by inhibiting the preceding nocturnal lipolysis and FFA oxidation. Reductions in nocturnal FFA oxidation and hepatic glucose production may result from bromocriptine's influences on circadian organization of hypothalamic centers known to regulate these activities. Available evidence suggests that bromocriptine may impact this neuroendocrine organization of metabolism by increasing the dopamine to noradrenaline activity ratio in central (hypothalamic) and peripheral (eg, liver and adipose) target tissues.

The immunoregulatory effects of prolactin in mice are time of day dependent

The effects of timed administration of PRL on immune activities were investigated in male BALB/c mice. Ten daily injections of PRL (1 mg/kg) were made 0/24, 4, 8, 12, 16, or 20 h after light onset (HALO). On day 11, spleen cells were harvested between 1-3 HALO and cocultured with gamma-irradiated C57BL/6 spleen cells for 5 days, and proliferative responses to alloantigen were assayed (mixed lymphocyte reaction). When given in vivo at 4-12 HALO, PRL strongly stimulated proliferation by more than 2-fold, whereas PRL injections when given at 24 HALO substantially inhibited proliferation and had no effect when given at 16-20 HALO. When endogenous PRL secretion was stimulated for 7 days with injections of domperidone or 5-hydroxytryptophan, the splenocyte response increased by 48% and 64%, respectively, when injections were given at 9-10 HALO, but did not increase when they were given at 23-0 HALO. Inhibition of endogenous PRL secretion for 7 days with bromocriptine (2.5 mg/kg.day) inhibited splenocyte responsiveness by 40% when injected at 9 HALO, but had no effect when administered at 0 HALO. Furthermore, such bromocriptine treatment inhibited T- and B-cell mitogenic responses to Concanavalin-A (by 48%) and lipopolysaccharide (38%) when administered at 10, but not 0, HALO. In a manner similar to mixed lymphocyte reaction responses, daily PRL injections for 10 days at 11 HALO stimulated (40%) the in vivo delayed-type hypersensitivity response to antigen (azobenzenearsonate), whereas injections at 0 HALO were nonstimulatory. Bromocriptine treatment (1.5 mg/kg.day) suppressed the delayed-type hypersensitivity response (43% less than the control value) when administered at 10-12 HALO, but had no effect when administered at light onset. Timed PRL injections for 28 days in adult mice increased (42%) the total thymic cell number when administered at 11 HALO, but had no effect when injected at 0 HALO. Together, these results show that immunocyte responsiveness to PRL is time of day dependent. Thus, these findings support an essential and heretofore unrecognized circadian role in PRL regulation of immunity.

In vitro incorporation of [14C]glycine into muscle protein of gulf killifish (Fundulus grandis) in response to insulin-like growth factor-I

The effect of recombinant human insulin-like growth factor I (rhIGF-I) on protein synthesis was studied in vitro in the muscle of a teleost fish. Protein synthesis was assessed by the incorporation of [14C]glycine into protein. rhIGF-I stimulated [14C]glycine incorporation in a dose-dependent manner. The minimal effective dose was 0.1 ng/ml and maximal stimulation was obtained with 1 ng/ml. A high concentration (100 ng/ml) was ineffective. Treatment with 1 ng/ml rhIGF-I produced a significant response after 3 hr of incubation and the greatest stimulation was observed after 6 hr. Responsiveness of muscle tissue to IGF-I examined at three different times (0, 6, and 12 hr after light onset, LD 12:12) was greatest at light onset. These results provide evidence that IGF-I may have a role in the regulation of growth in fish and that its activities are dose and time-of-day dependent.

Timed daily administrations of hormones and antagonists of neuroendocrine receptors alter day-night rhythms of allograft rejection in the gulf killifish, Fundulus grandis

Immune activity during scale allograft rejection, measured by melanophore destruction, is two to three times greater at night (12-hr scotophases) than during the day (12-hr photophases) in gulf killifish (Fundulus grandis). In the present study of killifish, hormones and antagonists of neuroendocrine receptors were administered daily at 0800 or 2000 hr during either 12-hr photoperiods (light onset: 0800 hr) or continuous light to examine possible neuroendocrine regulation of the allograft rejection rhythm. Immune activity peaked 0-12 hr after the time of daily growth hormone injections (0800 or 2000 hr) in fish held under continuous light and examined twice daily (0800 and 2000 hr) for melanophore breakdown. Immune activity peaked 12-24 hr after the time of day when cortisol-supplemented meals were provided (light onset or light offset) whether fish were treated throughout the days of melanophore examinations or pretreated for 3 days only prior to melanophore examinations. Daily rhythms of immune activity were not observed in fish treated with propranolol or naloxone at light offset only, growth hormone or atropine at light onset only, or prolactin at either light onset or light offset; these timed-treatments also reduced (prolactin or growth hormone) or prolonged (propranolol or naloxone) the length of time needed to destroy all melanophores within an allograft compared with controls. These results demonstrate that neuroendocrine factors can modulate a daily rhythm of immune function in fish.

Nonphotic stimuli alter a day-night rhythm of allograft rejection in gulf killifish

The influence of environmental stimuli on a daily rhythm of immune activity during scale allograft rejection was investigated in gulf killifish, Fundulus grandis. Although melanophore destruction in the grafts is largely restricted to the scotophases in killifish held on 12 h daily photoperiods (LD 12:12), timed daily netting (tank-transfer "stress"), thermoperiods (from 20 degrees to 30 degrees C for 4 or 12 h), and feeding altered the expression of this rhythm. Melanophore breakdown peaked 0-12 h after netting or thermoperiod onset and 12-24 h after feeding, whether the fish were exposed to these nonphotic daily stimuli at the onset or offset of 12-h photoperiods. In fish held under continuous light and pretreated with these daily stimuli, 24-h immune activity rhythms persisted in the altered phases for several days after the daily treatments were stopped. These findings suggest that a daily rhythm of immune activity may have adaptive significance in fish.

Effects of pulsatile glucose stimuli on long-term insulin secretory patterns in islets of Langerhans microdissected from Syrian hamsters

The long-term effects of continuous and pulsatile glucose stimulation of islets of Langerhans microdissected from Syrian hamsters were examined. In the presence of a continuous glucose stimulus insulin secretion peaked during the first 3 h of stimulation followed by a decrease. In the presence of 11.2 mM glucose a second smaller peak of insulin secretion was observed 14-16 h after the perifusion started. Irrespective of the glucose concentration, insulin secretion then steadily decreased and reached very low levels by the end of the 48-h perifusion. However, glucose stimulus provided in a pulsatile manner appeared to reduce this rate of decrease in insulin secretion. Thus, after 48 h, islets exposed to the pulsatile glucose stimulus showed greater insulin responsiveness to glucose than those exposed to a constant glucose stimulus.

Daily intervals of heat exposure alter the phase of the daily variation of plasma hormones in Holtzman rats

The effects of timed daily increases in ambient temperature (thermopulses) (from 22 +/- 1 to 40 +/- 1 degree C for 2 h) on daily variations of hormones involved in glucose and lipid metabolism were tested in male Holtzman rats (3-4 mo old) exposed to a 12-h daily photoperiod. The thermopulses were administered for 14 days either at light onset (TP0) or 16 h after light onset (TP16). Body weights and food consumption were monitored during the experiment. Retroperitoneal fat weights and plasma concentrations of insulin, glucose, glucagon, corticosterone, and prolactin were determined from blood taken every 4 h during a 24-h period commencing 24 h after the last thermopulse. TP0 treatment did not alter any of the parameters tested. Conversely, TP16 treatment obliterated the daily rhythms of insulin and corticosterone present in the controls (nonthermopulsed) and decreased body weight gains, retroperitoneal fat stores, food consumption, and the baseline levels of plasma insulin and corticosterone. The present study supports a role for circadian neuroendocrine rhythms in the reduction of fat stores induced by properly timed daily thermopulses.

Alterations in body fat stores and plasma insulin levels with daily intervals of heat exposure in Holtzman rats

The ability of timed daily increases in ambient temperature (from 22 +/- 1 degree C to 40 +/- 1 degree C for 2 h) to alter body fat stores, blood lipid levels, and insulin resistance were tested in male Holtzman rats. Of the six times of day tested only temperature pulses administered 16 h after light onset consistently decreased body weights, retroperitoneal fat stores, and plasma insulin levels. Subsequently, temperature pulses were administered either 0 (TP0) or 16 (TP16) h after light onset (light-dark 12:12 h). While no differences were observed between the TP0 group and the constant temperature (22 degrees C) controls, decreases in body weight gain, food consumption, retroperitoneal fat stores, and plasma concentrations of insulin, cholesterol, and triglycerides were consistently observed in the TP16 group. Although changes in plasma glucose during an oral glucose tolerance test were similar when the two treatment groups were compared with their respective controls, glucose tolerance was achieved with less insulin in the TP16 animals than in their respective controls. Insulin effectiveness was greater in the TP16 group as indicated by a decrease in plasma glucose, after insulin injection, that was of greater magnitude and longer duration than in controls. Hence, timed daily increases in ambient temperature may decrease obesity in part by decreasing plasma insulin levels apparently as a consequence of increased tissue sensitivity to insulin (greater glucose tolerance and less insulin intolerance). Because the treatment is effective only at a particular time of day the findings support a role for circadian neuroendocrine interactions in the regulation of these metabolic states.

Circadian neuroendocrine role in age-related changes in body fat stores and insulin sensitivity of the male Sprague-Dawley rat

A role for circadian neuroendocrine rhythms in the age-related development of obesity and insulin resistance was investigated in the male Sprague-Dawley rat. The phases and amplitudes of the plasma rhythms of several metabolic hormones (i.e., corticosterone, prolactin, insulin, and triiodothyronine) differed in lean, insulin-sensitive (3-week-old rats), insulin-resistant (8-week-old rats) and obese, insulin-resistant (44-week-old rats) animals. Simulation of the daily rhythms of endogenous corticosterone and prolactin by daily injections of the hormones at times corresponding to the peak levels found in 3-week-old rats reversed age-related increases in insulin resistance and body fat in older (5-6-month-old) rats. Ten such daily injections of corticosterone and prolactin in 12-14-week-old rats produced long-term reductions in body fat stores (30%), plasma insulin concentration (40%), and insulin resistance (60%) (determined by a glucose tolerance test) measured 11-14 weeks after the treatment. Alterations in circadian neuroendocrine rhythms may account for age-related changes in carbohydrate and lipid metabolism in the male Sprague-Dawley rat, and resetting of these rhythms by appropriately timed daily injections of corticosterone and prolactin may help maintain metabolism characteristic of younger animals.

A day-night rhythm of immune activity during scale allograft rejection in the gulf killifish, Fundulus grandis

The circadian variation of scale allograft rejection was studied in teleost fish maintained on 12-h daily photoperiods (LD 12:12). Immune activity, measured by melanophore breakdown, was two to three times greater during the dark than during the light whether scale allografts were transplanted at light onset or light offset. Because rejection occurred predominantly at night, survival times of both primary and secondary allografts were about 0.4 days longer when the transplants were made at light onset. Immune activity undergoes a robust daily variation in a teleost fish.