A life course perspective on determinants of discontinuance of active participation in sports activities

Physical inactivity remains a global public health challenge today. Determining why people stop regularly participating in sports is significant to develop targeted intervention strategies for sports promotion and healthy living. As sports participation is dynamic throughout life, a life-course perspective is needed to provide a more comprehensive understanding. This study adopts a life-course perspective to explore the determinants of the change from active participation in sports to becoming inactive. Based on online retrospective survey data collected in the Netherlands, a two-level binary logistic regression model is estimated to capture the effects of socio-demographics, sports motivations, life transitions, and neighborhood characteristics on sports dropout over the lifespan. Results show that dropout from sports is age-specific, and that people are less likely to discontinue sports participation when they have health and weight loss goals. Life transitions have different effects. The cessation of living with physically active people appears to be the most important event to make people stop sporting, followed by having a baby, and then owning the first car. Compared with education-related events, work-related events are more likely to cause people to stop sporting. Moreover, the probability of sports discontinuance may increase when residents feel unsafe doing physical activities in their neighborhoods or when the neighborhood has sufficient greenspace for walking. The findings have implications for supporting sports participants to continue exercising by addressing the barriers.

Socio-demographics, neighborhood characteristics, time use, and leisure-time physical activity engagement patterns over the life course

Physical inactivity remains a major public health challenge today. Understanding the determinants of changes in habitual leisure-time physical activity patterns by type across the life course is important for developing targeted interventions. This study presents a multiple discrete-continuous extreme value model to examine the determinants of habitual participation in and time allocation to multiple leisure-time physical activities over the life course. A comprehensive set of socio-demographics, life transitions, neighborhood characteristics, and time-related factors are considered as determinants of each activity type, including sports, recreational walking, cycling, outdoor playing, and dog walking. Results estimated on retrospective survey data collected in the Netherlands show significant differences in the determinants of the different types of leisure-time physical activity. Social-demographic factors have a strong influence on sports participation, followed by recreational walking, cycling, outdoor playing, and then dog walking. Life transitions have different effects. A change in marital status appears to be the most important life event for sports participation while changing jobs is the most important event for the other two activities. Neighborhood characteristics primarily affect participation in recreational walking, cycling, outdoor playing, and dog walking. As for time-related factors, they mainly impact sports engagement. The findings of this study could help develop effective interventions to promote leisure-time physical activity participation during life transitions and encourage healthy living.

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The determinants of different types of leisure-time physical activity differ significantly.

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Social-demographic factors have a strong impact on sports participation, followed by recreational-WCP, and then dog walking.

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Changes in marital status and work seem to be important events for joining sports and the other two activities, respectively.

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Neighborhood characteristics primarily affect participation in recreational-WCP and dog walking.

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Study-related physical activity time and work-related physical activity time mainly impact sports participation.

Influence of Neighborhood Characteristics on Physical Activity, Health, and Quality of Life of Older Adults: A Path Analysis

Background: As life expectancy and health expenditure consumed by older people increase, maintaining a better health and quality of life for older adults has become an important social issue. Research indicates that physical activity may help address this challenge. Moreover, it is believed that improved quality of life and health benefits from physical activity can be achieved through interventions in the neighborhood environments. However, existing knowledge has often been based on bivariate relationships between these factors, and few studies have formally examined the extent to which any association between neighborhood environments, health, and quality of life may be mediated by the level of physical activity. This paper aims to investigate the direct and indirect influence of neighborhood characteristics on the health and quality of life of older adults, taking into account physical activity behavior and socio-demographic characteristics in a more comprehensive framework. Methods: Data were collected using a survey among 363 older adults aged 60 years and over in China. A path analysis was used that derives all direct and indirect relationships between the variables. Results: Leisure-time physical activity levels played a mediating role in the relation between social capital and health as well as quality of life. Moreover, the study confirmed direct relationships between neighborhood characteristics such as neighborhood aesthetics and traffic safety and health as well as quality of life. However, the effect of neighborhood characteristics on health and quality of life through transport-related physical activity levels was not found. Conclusions: Leisure-time physical activity instead of transport-related physical activity should be considered a priority when developing interventions aiming to promote healthy aging. Additionally, neighborhood characteristics are important in promoting healthy aging, even though they have no or less impacts on older adults' health and quality of life through physical activity.

Location Choice in the Context of Older Adults' Leisure-Time Walking

Leisure-time walking is the most prevalent and preferred form of physical activity of older adults. In order to promote leisure-time walking and enhance the efficiency of using outdoor open spaces, the supply of different types of walking locations should match the needs, interests and preferences of older adults. However, there is limited knowledge on which location types are chosen by which groups of individuals under which conditions. This study therefore examines the effects of socio-demographics, episode participation attributes and neighborhood characteristics on the location choice of older adults for leisure-time walking. A multinomial logit model is estimated based on data collected among 316 respondents aged 60 or older in Dalian, China. The results indicate that older people’s location choices for walking are associated with their socio-demographics, episode participation attributes and neighborhood characteristics. Finally, implications of the results for the planning, design and management of open spaces are identified.

A Multiagent Model for Alternative Plan Generation

The utilization of multiagent technology for urban planning purposes has already received much attention with regard to predicting and evaluating the effects of different policy scenarios and plan alternatives. The generation of these plan alternatives, however, remains underexplored in this context. In this paper the authors describe a multiagent model for generating alternative land-use plans, in which the agents are land-use experts that initiate the development of plan proposals and communicate with each other over time in order to draw up the proposals incrementally. The authors present a probabilistic approach to agent behaviour to enable decisionmaking under conditions of uncertainty. They describe what personal and collective beliefs agents construct and use in order to choose their actions strategically. The negotiation, taking place between the initiating agent and the other agents, aimed at reaching agreement with regard to the various claims, is organized as an iterative process in which both parties consider conciliatory adjustments to their strategies, and thus their decisions, in order to try to find mutually acceptable solutions. A hypothetical case study demonstrates the operation of the model and the effects of its behavioural parameters.

Cognitive Process Model of Individual Choice Behaviour Incorporating Principles of Bounded Rationality and Heterogeneous Decision Heuristics

Although the principle of bounded rationality seems more realistic for formulating formal models of individual choice behaviour than traditional decision-outcome-based discrete choice models, existing studies have some limitations: (1) applications focus on the noncompensatory nature of the models and largely ignore the factor-selection process; (2) heterogeneity of heuristics in reaching a decision is insufficiently studied; (3) the choice of decision strategy is rarely modeled formally. A modeling approach that simultaneously deals with these issues is suggested. Factor thresholds are used as the mechanism for factor selection and representation, resulting in a set of activated and nonactivated factor states. Under the assumption of stochastic contextual effects, the model automatically generates heterogeneous decision heuristics, including the conjunctive, disjunctive, and lexicographic rule. Mental effort and risk perception are assumed to influence the evaluation and choice of heuristics. The concept of preference tolerance is used to predict the probability of selecting a particular heuristic under different decision contexts. The modeling approach is illustrated using the go-home decision of pedestrians in a shopping street in China as an example.

Predicting the evolution of social networks with life cycle events

This paper presents a model of social network evolution, to predict and simulate changes in social networks induced by lifecycle events. We argue that social networks change with lifecycle events, and we extend a model of friendship selection to incorporate these dynamics of personal social networks. The model uses theories of homophily and reciprocity and is formulated in a random utility maximization framework to predict the formation of social ties between individuals in the population. It is then extended to predict the evolution of social networks in response to life cycle events. The model is estimated using attribute data of a national sample and an event-based retrospective dataset collected in 2009 and 2011 respectively. Findings suggest that homophily has a strong effect on the formation of new ties. However, heterophily also plays a role in maintaining existing ties. Although the motivation of this research stems from incorporating social network dynamics in large-scale travel behaviour micro-simulation models, the research can be used in a variety of fields for similar purposes.

The built environment and health: introducing individual space-time behavior

Many studies have examined the relationship between the built environment and health. Yet, the question of how and why the environment influences health behavior remains largely unexplored. As health promotion interventions work through the individuals in a targeted population, an explicit understanding of individual behavior is required to formulate and evaluate intervention strategies. Bringing in concepts from various fields, this paper proposes the use of an activity-based modeling approach for understanding and predicting, from the bottom up, how individuals interact with their environment and each other in space and time, and how their behaviors aggregate to population-level health outcomes.

Cut-off Models for the ‘Go-Home’ Decision of Pedestrians in Shopping Streets

Many behavioral and nonbehavioral models have been proposed to model pedestrian behavior. Among these, pedestrians' decision processes have not been explicitly modeled. Utility-maximizing models have been prominently used, but these models may be misspecified owing to their unrealistic assumptions. As an alternative, this paper proposes cut-off models based on the satisficing heuristic founded in bounded rationality theory. The go-home decision of pedestrians in Wang Fujing Street, Beijing, is taken as an example. Results of a multinomial logit model and three cut-off models with increasing complexity are compared. The results show that the cut-off models can fit the data equally as well as the multinomial logit model, suggesting that satisficing heuristics not only have theoretical advantages but also statistical power. Introducing a decision engagement module before the satisficing decision module significantly improves the cut-off model and supports the hypothesis of a hierarchical decision process.

Social Networks, Social Interactions, and Activity-Travel Behavior: A Framework for Microsimulation

We argue that the social networks and activity-travel patterns of people interact and coevolve over time. Through social interaction, people exchange information about activity-travel choice alternatives and adapt their latent and overt preferences for alternatives to each other. At the same time, social networks are not static: new social links emerge and existing social links may dissolve in time, depending on activity-travel schedules and the attributes of persons. In this paper we propose a theoretical framework to incorporate these dynamics in microsimulations of activity-travel patterns. A core assumption of the proposed theory is that the utility that a person derives from social interaction is a function of dynamic social and information needs, on the one hand, and of similarity between the relevant characteristics of the persons involved, on the other. Furthermore, persons tend to adapt their preferences so as to increase the utility they derive from their social networks. We derive the theory and models from basic principles and discuss results of a first round of simulations conducted to examine the behavior of the model. We argue that the model is consistent with existing theories and findings in social network analysis.

Square stent: a new self-expandable endoluminal device and its applications

The square stent is a new, simply constructed, self-expanding device that has recently been described. Compared with other stents, the square stent has a minimal amount of metal and thus requires a smaller-diameter catheter for introduction. Despite the small amount of metal present, the square stent has adequate expansile force. We have been evaluating the square stent for various interventional applications. In addition to the basic square stent, combinations of square stents and coverings for square stents were developed and evaluated to expand its uses and indications. One of the coverings tested is a new biomaterial: small intestinal submucosa (SIS). This paper will discuss the various applications of the square stent, which include a retrievable inferior vena cava filter, vascular occluder, graft adapter, and venous and aortic valves. In addition, we will review the important properties of SIS as a covering for the square stent.

Intravascular US-guided direct intrahepatic portacaval shunt with a PTFE-covered stent-graft: feasibility study in swine and initial clinical results

PURPOSE

To determine the feasibility of the creation of a direct intrahepatic inferior vena cava (IVC)-to-portal-vein shunt with puncture guided by a transfemorally placed intravascular ultrasound (IVUS) probe and use of a polytetrafluoroethylene (PTFE)-covered stent-graft.

MATERIALS AND METHODS

In five swine, transjugular access was used to perform a direct puncture from the IVC to the portal vein with use of a modified Rosch-Uchida Portal Access set directed with real-time IVUS (9 MHz) introduced from a transfemoral venous approach. The direct intrahepatic portocaval shunt (DIPS) was then created with single or overlapping PTFE-covered Palmaz stents placed through a 10-F sheath and dilated to a diameter of 8 mm. Follow-up was performed with transhepatic portography at 2, 4, and 8 weeks. Animals were killed when shunts occluded or at the termination of the study at 8 weeks. Gross and microscopic histologic study was performed on sacrificed animals. A similar technique was used to create DIPS in five patients with intractable ascites, with follow-up by US and venography.

RESULTS

All experimental DIPS created in swine were created without complications. Portal vein punctures were achieved in four of five swine on the first or second pass of the needle. Follow-up transhepatic portography at 2 weeks demonstrated occlusion of two shunts, both explained by technical reasons at sacrifice. At 4 and 8 weeks, the remaining three shunts were patent on portography. Histology showed a thin neointimal lining with no significant tissue ingrowth or hyperplasia. Clinically, in five patients, successful puncture of the portal vein from the IVC was achieved in one to three passes. Creation of DIPS led to a reduction of mean portosystemic gradient from 18-29 mm Hg (mean, 24 mm Hg) to 9-10 mm Hg (mean, 9 mm Hg). One patient died of liver failure 2 days after creation of DIPS. The other four patients were doing well 2-15 months (mean, 8 months) after the procedure, with patency confirmed by US and venography.

CONCLUSION

Creation of DIPS is technically feasible, and the direct IVC-to-portal-vein puncture can be done accurately with real-time IVUS guidance. Further studies and longer follow-up are necessary to determine if the short length of the PTFE-covered stent-graft and avoidance of the hepatic vein will increase the long-term patency compared to standard transjugular intrahepatic portosystemic shunt creation.

Bifurcated drum occluder endograft for treatment of abdominal aortic aneurysm: an experimental study in dogs

PURPOSE

To evaluate a new, low profile, home-made, bifurcated drum occluder endograft (BDOEG), designed for percutaneous, transcatheter treatment of abdominal aortic aneurysm (AAA).

MATERIALS AND METHODS

AAA was created in 10 dogs with over-dilated Palmaz stents. To prevent back filling, the lumbar arteries, inferior mesenteric artery, and common internal iliac arteries were embolized. The BDOEG was constructed of a drum occluder device and two PTFE endografts. The drum device consisted of a modified Z stent with Dacron stretched across and held within the ends of the stent, each with two 8 x 6-mm slits through which PTFE endografts were delivered. The PTFE endografts were 8 mm in diameter and 9.5 cm in length. Preloaded, the BDOEG was delivered through a 10-F sheath from both femoral arteries in a three-step procedure. All 10 animals were treated with BDOEG. Aortography was performed immediately, 6 weeks, and 12 weeks after stent-graft placement. Five animals were killed at 6 weeks and five were killed at 3 months. Gross and histologic evaluation was performed.

RESULTS

The infrarenal aortic diameters and both external iliac arteries ranged from 8.0 mm to 10.3 mm (mean, 9.4 mm +/- 0.6) and from 5.2 mm to 6.8 mm (mean, 5.8 mm +/- 0.5), respectively. Creation of the AAA was successful in all 10 dogs. AAA diameters ranged from 13.7 mm to 15.9 mm (mean, 14.9 mm +/- 0.7). Complete exclusion of the AAA was achieved immediately after BDOEG placement and aneurysms remained excluded without perigraft leak to the time of killing in all 10 animals. There was a high incidence of aortoiliac limb occlusion. Occlusion of 12 aortoiliac limbs (60%) caused by intimal hyperplasia at the distal end of the endografts in iliac arteries developed in nine animals (90%). In six animals (60%), one limb occluded and, in three animals (30%), there was occlusion of both limbs.

CONCLUSION

This study suggests a new approach for treatment of AAA. BDOEG use reduces sheath size for endograft delivery and may eliminate the need for a surgical cut down on femoral arteries. Tapering of the iliac ends of endografts to the size of the artery will be needed to prevent distal intimal hyperplasia.

Recording of data of individual measurements of occupational exposure: guideline of the Dutch Society of Occupational Hygiene (October 1999)

Following the recommendations of the European Working Group on Exposure Databases, a Working Group (on Storage of Data of Measurements of Occupational Exposure) of the Dutch Occupational Hygiene Society has developed a Guideline which was presented at the International Symposium on Occupational Exposure Databases and Their Application for the Next Millennium, November 1-3, 1999, London. To establish the present situation, a small-scale telephone survey of monitoring practices and storage of data was done within the Society. The results of the telephone survey and the draft guidance document were discussed with the occupational hygienists and other stakeholders (e.g., authorities, industry, labor unions, and occupational physicians) in a society meeting. This meeting was used to gather ideas on the need and support for a guidance document and to get input for improving the draft guidance document and for implementation of the Guideline. After this meeting, the Guideline was further developed and published by the Dutch Occupational Hygiene Society. The Guideline concentrates on the data elements required when storing exposure data. The data elements presented are the minimum and should be stored minimally to ensure proper interpretation of results at present and in the future and definitions of the items used are given. The Guideline does not prescribe how the data should be stored, or which procedures need to be used to guarantee the quality of the recorded data elements.

Small intestinal submucosa covered expandable Z stents for treatment of tracheal injury: an experimental pilot study in swine

PURPOSE

To evaluate efficacy of small intestinal submucosa (SIS) as a stent covering in healing experimentally created tracheal defects and to explore the trachea's reaction to placement of SIS-covered stents.

MATERIAL AND METHODS

A tracheal defect with a diameter of approximately 10 mm was created in six swine with use of a blade or electrocauterization. A double-body, self-expandable SIS-covered Gianturco Rösch Z stent was placed into the trachea to cover the defect. The animals were observed, and were killed when they developed respiratory problems. Autopsy and histologic studies were performed.

RESULTS

The SIS-covered stents were accurately placed without immediate complications related to placement. All animals developed respiratory problems on follow-up. One animal died 9 days after procedure because of pneumonia, the others five were killed at 12, 17, 18, 28, and 56 days because of stridor, wheezing, and cough. At autopsy and histology, the tracheal defects were found to be completely healed, with epithelial lining and regeneration of submucosal glands. Animals whose defects were created with a blade demonstrated cartilage remodeling between 9 and 18 days, and apparent deposition of new cartilage at 28 days after SIS placement. The defects made by electrocauterization showed only fibrous tissue with no cartilage regeneration. The tracheal lumen was narrowed by overgrowth of granulation tissue, particularly at the end wires of the stents. In three animals, polypoid masses caused 60%, 70%, and 80% tracheal obstruction, respectively.

CONCLUSION

Placement of SIS-covered stents contributed to rapid and effective healing of large tracheal defects. Rigidity and oversizing of Gianturco Rösch Z stents led to secondary changes of the tracheal wall, causing significant airway obstructions. Smaller size and flexible stents should be selected for future work.

The square stent-based large vessel occluder: an experimental pilot study

PURPOSE

The purpose of this study is in vitro and in vivo experimental evaluation of a square stent-based vascular occlusion device for large vessels.

MATERIALS AND METHODS

Square stent-based large vessel occluders (LVO) 5 mm-50 mm in size were constructed from stainless-steel square stents covered by porcine small intestine submucosa (SIS). The LVOs with two back-side barbs were delivered through a guiding catheter. The LVOs with two back-side barbs and two frontal barbs were front-loaded and delivered coaxially. A pusher with a retention mechanism at its end was used for deployment. In vitro testing for competency was performed with use of a flow model with pressure increases. In an experimental pilot study in seven pigs and five dogs, 16 LVOs were placed into the aorta (n = 4), common iliac artery (n = 2), pulmonary artery (n = 4), and medial sacral artery (n = 6). Four animals received two LVOs in different locations. Angiography was performed before and after placement of each LVO. Animals were followed for as long as 3 months with use of angiography and were then killed for gross and histologic evaluation.

RESULTS

In vitro LVOs with two and four barbs were easily collapsed and pushed through or front-loaded into guiding catheters (6-F for a 5-mm occluder, 10-F for a 50-mm occluder). A 20-mm LVO adapted to tubular structures 10-15 mm in diameter, forming polygons 17-18.5 mm in length. In the flow model, LVOs endured pressure increases to 300 mm Hg. In vivo, the LVOs self-expanded and adapted to the vessel without migration in all cases. The locking pusher allowed precise LVO placement and engagement of its barbs into the vessel wall before complete deployment, preventing dislodgment by blood flow. Complete arterial occlusion occurred within 10-20 minutes and arteries remained occluded until the animal was killed in all cases. After 2 months, histologic evaluation revealed replacement of SIS by host tissue and its remodeling with variable fibrocytes, fibroblasts, and some inflammatory cells. Complete endothelialization was seen on both sides of the LVO.

CONCLUSION

The SIS LVO is effective and reliable for acute and chronic occlusion in a high flow model in an experimental animal.

Percutaneous transcatheter aortic disc valve prosthesis implantation: a feasibility study

PURPOSE

Over the past 30 years there have been experimental efforts at catheter-based management of aortic valve regurgitation with the idea of extending treatment to nonsurgical candidates. A new catheter-based aortic valve design is described.

METHODS

The new catheter-delivered valve consists of a stent-based valve cage with locking mechanism and a prosthetic flexible tilting valve disc. The valve cage is delivered first followed by deployment and locking of the disc. In acute experiments, valve implantation was done in four dogs.

RESULTS

Valve implantation was successful in all four animals. The implanted valve functioned well for the duration of the experiments (up to 3 hr).

CONCLUSION

The study showed the implantation feasibility and short-term function of the tested catheter-based aortic disc valve. Further experimental studies are warranted.

Polyurethane-coated Dacron-covered stent-grafts for TIPS: results in swine

PURPOSE

To evaluate shunt patency after placing a new polyurethane-coated Dacron-covered spiral Z stent-graft to create a transjugular intrahepatic portosystemic shunt (TIPS).

METHODS

TIPS stent-grafts were placed in six young swine, using polyurethane-coated, Dacron-covered spiral Z stent-grafts. Animals were followed weekly by transhepatic portal venography until shunt occlusion or up to 6 weeks, then were sacrificed for gross and histologic evaluation.

RESULTS

Five of six TIPS stent-grafts were found to be occluded by 3 weeks and none were patent at 6 weeks. Histologic evaluation demonstrated a marked foreign body reaction with superimposed thrombosis occluding the graft lumen.

CONCLUSION

Polyurethane-coated Dacron-covered stent-grafts do not improve TIPS patency.

Stent-graft in the management of superior vena cava syndrome

We report the use of a Dacron-covered Gianturco-Rösch Z (GRZ)-stent to treat malignant obstruction of the superior vena cava (SVC). Initial treatment with an uncovered GRZ-stent was suboptimal due to protrusion of tumor-thrombus through the stent struts into the SVC lumen. Placement of a coaxial Dacron-covered stent graft relieved the residual obstruction due to tumor within the SVC.

Treatment of malignant esophageal obstructions with covered metallic Z stents: long-term results in 52 patients

PURPOSE

To prospectively evaluate the clinical efficacy of silicone-covered Gianturco-Rösch self-expandable Z (GRZ) stents in the treatment of malignant esophageal obstruction.

PATIENTS AND METHODS

GRZ stents were placed in 52 patients (39 men, 13 women) with severe dysphagia due to high-grade malignant esophageal obstruction.

RESULTS

Stent placement was technically successful, and immediate relief of dysphagia was achieved in 50 of 52 patients (96%), with long-term relief in 47 patients (90%). Fifty-one patients (98%) died during follow-up (range, 1 week to 33 months; mean, 4.3 months). Late complications were most prevalent and included stent migration (n = 5), food impaction (n = 2), chest pain (n = 2), membrane disruption with tumor ingrowth (n = 1), granulomatous reaction above the stent (n = 1), esophageal perforation with mediastinitis (n = 1), and upper gastrointestinal hemorrhage (n = 4). Twelve complications were easily managed with medical, endoscopic, or radiologic intervention. Four deaths may have been related to stent placement (early mortality rate, 7.7%).

CONCLUSION

GRZ stents provide relatively safe and effective long-term palliation in patients with severe, malignant esophageal obstruction.

Experimental nonsurgical female sterilization: transcervical implantation of microspindles in fallopian tubes

PURPOSE

A nonsurgical method of female sterilization was investigated in rabbits.

MATERIALS AND METHODS

A self-expanding microspindle (length 9-18 mm, diameter 1.5-2.0 mm) made from tubular metal mesh was implanted in a single fallopian tube of 12 rabbits via catheterization of a single uterus. The contralateral fallopian tube and uterus served as controls. Each rabbit was scheduled to undergo three cycles of breeding. Before delivery, absence of pregnancy on the side with the microspindle was verified with hysterography.

RESULTS

Eight rabbits completed three cycles of breeding and pregnancy. Two rabbits had one pregnancy. Two rabbits did not conceive. Spindles were placed correctly in 11 rabbits. Successful contraception was achieved in nine rabbits, who had 25 gestations on the nonspindle side and no gestation on the spindle side. One rabbit, which received the shortest spindle, was bilaterally pregnant, indicating a failure of contraception on the spindle side. No spindles dislocated. Histologic study showed all spindles firmly embedded in the tubal wall without signs of inflammation.

CONCLUSION

Microspindles of a certain minimum length have potential as a transcervically implantable, permanent intratubal contraceptive device.

Self-expandable spindle for transcatheter vascular occlusion: in vivo experiments. Work in progress

A mechanical vascular occluder was studied in eight pigs to test its efficacy in arteries of different diameters, stability over time, and safety in placement. The main component is a self-expandable spindle made of tubular stainless steel mesh. Simple steel spindles, double spindles, and Dacron-core spindles were placed in the common carotid artery, main renal artery, renal artery branches, and infrarenal aorta. Follow-up arteriograms were obtained immediately, 30-60 minutes, and (except for aortic spindles) 7 days after deployment. The left common carotid artery was occluded in all pigs, regardless of spindle type. In the main renal artery and its branches, simple steel spindles did not achieve complete occlusion. Double and Dacron-core spindles produced immediate occlusion without recanalization on the 1-week follow-up arteriogram, except for one spindle with an incomplete Dacron core and two spindles that did not completely fill the arterial lumen. Two Dacron-core spindles achieved immediate complete occlusion of the infrarenal aorta. No migration was seen with any spindle.

Insulin stimulation tests in pituitary dependent Cushing's syndrome after complete adrenalectomy

The present study shows that in a group of 6 euadrenal patients, previously treated by complete adrenalectomy for pituitary dependent Cushing's syndrome, the stress stimulus of insulin induced hypoglycaemia is followed by a plasma ACTH response which is of similar magnitude as the response obtained with lysin-vasopressin. Both observations indicate that the central nervous system-pituitary axis is basically normal in pituitary dependent Cushing's syndrome as assessed by insulin induced hypoglycaemia. It is concluded that non-responsiveness of the pituitary-adrenocortical system to insulin induced hypoglycaemia in untreated patients with pituitary dependent Cushing's syndrome does not represent a fundamental defect of the stress mechanism, but is due to hypercorticism per se.