Effects of Sterilization on Shape Memory Polyurethane Embolic Foam Devices

Polyurethane shape memory polymer (SMP) foams have been developed for various embolic medical devices due to their unique properties in minimally invasive biomedical applications. These polyurethane materials can be stored in a secondary shape, from which they can recover their primary shape after exposure to an external stimulus, such as heat and water exposure. Tailored actuation temperatures of SMPs provide benefits for minimally invasive biomedical applications, but incur significant challenges for SMP-based medical device sterilization. Most sterilization methods require high temperatures or high humidity to effectively reduce the bioburden of the device, but the environment must be tightly controlled after device fabrication. Here, two probable sterilization methods (nontraditional ethylene oxide (ntEtO) gas sterilization and electron beam irradiation) are investigated for SMP medical devices. Thermal characterization of the sterilized foams indicated that ntEtO gas sterilization significantly decreased the glass transition temperature. Further material characterization was undertaken on the electron beam (ebeam) sterilized samples, which indicated minimal changes to the thermomechanical integrity of the bulk foam and to the device functionality.

Particulate Release From Nanoparticle-Loaded Shape Memory Polymer Foams

Highly porous, open-celled shape memory polymer (SMP) foams are being developed for a number of vascular occlusion devices. Applications include abdominal aortic and neurovascular aneurysm or peripheral vascular occlusion. A major concern with implanting these high surface area materials in the vasculature is the potential to generate unacceptable particulate burden, in terms of number, size, and composition. This study demonstrates that particulate numbers and sizes in SMP foams are in compliance with limits stated by the most relevant standard and guidance documents. Particulates were quantified in SMP foams as made, postreticulation, and after incorporating nanoparticles intended to increase material toughness and improve radiopacity. When concentrated particulate treatments were administered to fibroblasts, they exhibited high cell viability (100%). These results demonstrate that the SMP foams do not induce an unacceptable level of risk to potential vascular occlusion devices due to particulate generation.

Comparison of shape memory polymer foam versus bare metal coil treatments in an in vivo porcine sidewall aneurysm model

The endovascular delivery of platinum alloy bare metal coils has been widely adapted to treat intracranial aneurysms. Despite the widespread clinical use of this technique, numerous suboptimal outcomes are possible. These may include chronic inflammation, low volume filling, coil compaction, and recanalization, all of which can lead to aneurysm recurrence, need for retreatment, and/or potential rupture. This study evaluates a treatment alternative in which polyurethane shape memory polymer (SMP) foam is used as an embolic aneurysm filler. The performance of this treatment method was compared to that of bare metal coils in a head-to-head in vivo study utilizing a porcine vein pouch aneurysm model. After 90 and 180 days post-treatment, gross and histological observations were used to assess aneurysm healing. At 90 days, the foam-treated aneurysms were at an advanced stage of healing compared to the coil-treated aneurysms and showed no signs of chronic inflammation. At 180 days, the foam-treated aneurysms exhibited an 89-93% reduction in cross-sectional area; whereas coiled aneurysms displayed an 18-34% area reduction. The superior healing in the foam-treated aneurysms at earlier stages suggests that SMP foam may be a viable alternative to current treatment methods. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1892-1905, 2017.

Effects of Isophorone Diisocyanate on the Thermal and Mechanical Properties of Shape-Memory Polyurethane Foams

Previously developed shape-memory polymer foams display fast actuation in water due to plasticization of the polymer network. The actuation presents itself as a depression in the glass-transition temperature when moving from dry to aqueous conditions; this effect limits the working time of the foam to 10 min when used in a transcatheter embolic device. Reproducible foams are developed by altering the chemical backbone, which can achieve working times of greater than 20 min. This is accomplished by incorporating isophorone diisocyanate into the foam, resulting in increased hydrophobicity, glass transitions, and actuation time. This delayed actuation, when compared with previous systems, allows for more optimal working time in clinical applications.

Barriers to vision care for nursing home residents

OBJECTIVE

To describe the prevalence of periodic eye examinations by eye professionals and to examine nursing facility resident characteristics associated with lack of periodic screening.

DESIGN

Retrospective chart review.

SETTING

Two Midwestern nursing facilities.

PARTICIPANTS

Between 1995 and 1997, 134 subjects aged 60 and older were recruited from two metropolitan nursing facilities.

MEASUREMENTS

Nursing home charts were reviewed for: demographics, length of stay, date of eye examination, eye diagnosis,visual acuity. Nursing assessments were used to obtain information about cognition, function, behavior, and the presence of Do Not Resuscitate or Do Not Hospitalize orders. The chart was reviewed for visual acuity, intraocular pressures, and the presence of eye pathology. Individuals who had not had eye examinations in the previous 2 years were screened by an ophthalmologist. This examination included external examination of the eye, fundoscopic examination, tonometry,visual acuity with correction.

RESULTS

Only 62 (46%) of the subjects had been seen by an eye care professional in the previous 2 years. Visual acuity information was available for 37/64 previously examined subjects. Of those with no eye examination in the previous 2 years (n = 72), visual acuity was obtained in 32 (44%) of subjects. New eye diagnoses were made in 64% (41/64). Logistic regression models with "eye examination within the past 2 years" as the dependent variable show that residents who do not desire hospital transfer are 80% less likely to have had an eye examination than those without this designation. Sex, age, length of stay, functional status, presence of severe dementia, behavior problems, or DNR orders do not change the likelihood that a resident would have been examined. Logistic regression models with "visual acuity measured" as the dependent variable show that residents with severe dementia are 12.6 times less likely to have acuity measured than those without dementia. Those with a length of stay in the facility less than 6 months are 10% less likely to have visual acuity measured.

CONCLUSIONS

This study does not confirm that barriers still exist in the provision of eye care to all nursing home residents, but the prevalence of such assessments remains low. Additional screening results in a substantial increase in the identification of treatable eye diseases. Contrary to the original hypotheses that patient characteristics that make testing difficult would provide a barrier or disincentive to vision testing, this study did not show statistical differences in the rates of vision screening for those with dementia, behavior problems, or severe functional impairment. Severe dementia does seem to affect the ability of the eye care specialist to gather subjective data such as visual acuity. It also demonstrates that vision screening does take place on nursing home residents with a broad range of cognitive and functional abilities, and this screening results in the diagnosis of many treatable eye conditions. Future efforts should be made to increase vision screening and treatment in the nursing home.

The effect of visual and hearing impairments on functional status

OBJECTIVES

To describe the prevalence of visual and auditory impairment in frail older persons and to evaluate the association between sensory impairment and overall functional status.

DESIGN

Prospective patient evaluation and retrospective analysis of data.

SETTING

The outpatient geriatric assessment clinic of a university medical center.

PARTICIPANTS

Consecutive patients seen in the University of Nebraska Medical Center Outpatient Geriatric Assessment Clinic from 1986 to 1992 for whom both vision and hearing information were available (n = 576).

MEASUREMENTS

Visual acuity was measured by the Lighthouse Near Visual Acuity Test, and auditory acuity was evaluated with the whisper test. Functional status was determined by Lawton-Brody activities of daily living (ADL) and instrumental activities of daily living (IADL) scales. Comorbid illness was classified by the Cumulative Illness Rating Scale, and mental status was assessed by the Folstein Mini-Mental State Exam.

RESULTS

Eighteen percent of patients had visual impairment of 20/70 or worse. Hearing impairment was found in 64%. The mean ADL and IADL scores were 20/24 and 12/23, respectively, for patients with visual acuity better than 20/70, compared with 18/24 and 8/23 for visually impaired patients (P < .001 for both comparisons). ADL and IADL scores were also higher in hearing intact patients compared with those with hearing impairment: respectively, 21/24 vs 19/24 (P < .001) and 13/23 vs 11/23 (P < .001). The effects of visual acuity and hearing acuity on IADL score are independent of mental status and comorbid illness (P < .001). The effect of visual acuity on ADL score is independent of mental status and comorbid illness (P < .001), whereas the effect of hearing on ADL score is not. Subjects with both hearing and vision impairment had mean IADL (P < = .05) and ADL (P < = .05) scores significantly lower than those with no impairment

CONCLUSIONS

Impairments of vision and hearing are common in this frail older outpatient population. Functional status, as measured by IADL and ADL scores, is diminished for sensory impaired subjects. Combined vision and hearing impairments have a greater effect on function than single sensory impairments and influence functional status independent of mental status and comorbid illness. Overall, these results suggest that interventions to improve sensory function may improve functional independence.

Predictors of mortality in outpatient geriatric evaluation and management clinic patients

BACKGROUND

This study describes characteristics and predictors of survival in an outpatient Geriatric Evaluation and Management (GEM) population.

METHODS

Prospective evaluation and longitudinal follow-up of consecutive patients (N = 636) seen in a GEM Clinic between January 1986 and September 1991.

RESULTS

The typical patient was 78.4 years of age, White, female (73%), unmarried (66%), and living with a spouse or relative (47%). Although two-thirds were demented, most were independent in Activities of Daily Living (ADL) and partially dependent in Instrumental Activities of Daily Living (IADL). Subjects were followed for an average of 25 months. In bivariate analysis, IADL was the strongest predictor of survival (O.R. = 4.4). Higher ADL, better cognitive status, lower comorbid illness, and lack of recent hospitalization were also predictive of survival. In stepwise logistic regression, only IADL (O.R. = 4.2) and comorbid illness (O.R. = 1.5) predicted survival. In Kaplan-Meier Lifetable Analysis, survival at two years was 91% in the least dependent IADL group while survival was 75% in the most dependent group. Comorbid illness was the only factor that improved prediction of survival above that seen with IADL alone. When subjects are stratified by both function and illness, mortality was 36% in the ill and disabled group and 8% in those of high function and limited illness.

CONCLUSIONS

IADL and comorbid illness scores offer a means of stratifying subjects for risk of death and may be useful in evaluating and comparing mortality experience in outpatient GEM and control populations. Stratification may increase the likelihood that studies aimed at improving survival will detect a difference resulting from the intervention.

Helping the elderly stay active: a technique for detecting disability in the primary care office

The inability to perform essential activities of daily living such as cooking, shopping, dressing and bathing is termed functional disability. These deficits can prevent elders from enjoying independent, active lifestyles. The development of functional disability is a gradual process. Early identification and intervention by the primary care physician can often reduce functional decline. Screening for functional decline has traditionally been performed by either questionnaire or direct observation of tasks. This paper reviews methods which have been proposed to integrate functional disability screening into office practice. A method which incorporates both questionnaire and direct observation is recommended by the authors. The method of screening proposed targets specific areas prone to dysfunction. It focuses on simple screens of vision, hearing, arm and leg function, urinary incontinence, mental status, depression, nutrition, activities of daily living, environmental hazards, and social support systems. Appropriate methods of follow up evaluation and treatment are provided. This fifteen minute technique is a practical and applicable means of screening elderly patients for functional deficits in the primary care office.

Dopaminergic regulation of galanin gene expression in the rat anterior pituitary gland

Estrogen dramatically increases galanin mRNA and peptide levels in the rat anterior pituitary gland. We recently reported that galanin secretion in vitro from estrogen-exposed anterior pituitary cells is regulated by hypothalamic factors; dopamine and somatostatin inhibit galanin secretion, and thyrotrophin-releasing hormone stimulates galanin release. To determine whether galanin is regulated by a dopaminergic mechanism in vivo, we used ovariectomized Fischer 344 rats treated with 17ß-estradiol-containing or empty Silastic capsules. Rats were also administered bromocriptine, a dopamine receptor agonist, haloperidol, a dopamine receptor antagonist, or placebo for 2 weeks. Galanin peptide levels were measured in the anterior pituitary, neurointermediate lobe, medial basal hypothalamus, and plasma by radioimmunoassay. Plasma and pituitary prolactin levels were also determined. Bromocriptine decreased gaianin peptide levels in the anterior pituitary gland of ovariectomized rats by 30%, but had no effect on galanin in the neurointermediate lobe or medial basal hypothalamus. In contrast, haloperidol had no effect on galanin in the anterior pituitary or medial basal hypothalamus of ovariectomized rats, but decreased galanin peptide levels in the neurointermediate lobe. In the anterior pituitary gland of estrogen-treated rats, bromocriptine increased and haloperidol decreased both galanin and prolactin levels. Galanin mRNA levels were quantified in the anterior pituitary gland by solution hybridization. Bromocriptine increased galanin mRNA levels 3-fold in the anterior pituitary, whereas haloperidol had no effect. Galanin mRNA levels in the anterior pituitary were elevated 10-fold by estrogen. Bromocriptine reduced galanin mRNA levels in the pituitary by 50% in estrogen-treated rats, where again haloperidol had no effect. Estrogen increased plasma galanin levels 4-fold compared to ovariectomized rats and this effect was reduced 60% by bromocriptine and increased 20% by haloperidol. We conclude 1) galanin synthesis and release from the estrogen-exposed anterior pituitary gland is inhibited by a dopaminergic mechanism in vivo, 2) dopamine regulates galanin gene expression in the ovariectomized rat, 3) the changes in galanin peptide levels in the anterior pituitary of rats treated with estrogen and dopamine receptor ligands are primarily due to alterations in peptide secretion, and 4) galanin release from the neurointermediate lobe may also be regulated by a dopaminergic mechanism in vivo. These data, in conjunction with previous studies, provide evidence for the co-regulation of galanin and prolactin in estrogen-treated rats, and further discriminate between the regulation of galanin in the hypothalamus and pituitary gland.

Galanin secretion from anterior pituitary cells in vitro is regulated by dopamine, somatostatin, and thyrotropin-releasing hormone

Lactotrophs, somatotrophs, and thyrotrophs have been shown to contain immunoreactive galanin. Furthermore, estrogen stimulates galanin mRNA and peptide levels in the rat anterior pituitary, particularly within lactotrophs. To determine whether galanin is released from the anterior pituitary in a regulated manner, we used cultured pituitary cells from male and ovariectomized Fischer 344 rats implanted with estrogen-containing capsules. Anterior pituitary cells (5 x 10(5) cells/well) were challenged (0.5-3 h) with hypothalamic factors known to regulate anterior pituitary hormone secretion, and medium galanin levels were measured by RIA. In female pituitary cells, galanin secretion was inhibited by dopamine (10 and 100 nM) and stimulated by TRH (20 and 100 nM). Although galanin release was significantly lower in male pituitary cells, dopamine and TRH inhibited and stimulated galanin secretion, respectively. Medium galanin levels were also significantly reduced by somatostatin (5 nM) in both female and male cells. The pattern of PRL release in response to dopamine, TRH, and somatostatin was similar to that observed for galanin, regardless of the sex of the pituitary donor. Although galanin has been localized in somatotrophs, 5 nM GH-releasing hormone (GRF) failed to alter galanin release in male as well as female pituitary cells; GH secretion was significantly increased by GRF. LHRH (5 nM) and CRF (5 nM) failed to alter galanin release in vitro. We conclude that in estrogen-exposed pituitary cells obtained from male and ovariectomized Fischer 344 rats: 1) galanin secretion is inhibited by dopamine and somatostatin, and stimulated by TRH; 2) GRF, LHRH, and CRF do not regulate galanin release in these cells; and 3) the profile of the regulated pathway for galanin release suggests that the primary location of galanin is the lactotroph, probably within secretory granules.