Nurse managers' perceptions of power and opportunity.

This study used Rosabeth Kanter's (1977) structural theory of organizational behaviour to examine differences in the perceptions of access to job related power and opportunity of 91 nurse managers in first line and middle management positions. A convenience sample of nurse managers in three Canadian acute care urban hospitals was used to investigate the study questions. Consistent with Kanter's (1977) theory, middle managers perceived themselves as having significantly greater access to the empowerment structures than the first line managers (M = 14.66 and 12.82, respectively). Also, nurse managers in positions higher in the hierarchical structure reported having greater personal power in their organizational settings than those in lower positions.

Peripheral xenogeneic immunological response to encapsulated bovine adrenal chromaffin cells implanted within the sheep lumbar intrathecal space.

Bovine adrenal chromaffin (BAC) cells were encapsulated in polymer membranes and placed into the lumbar intrathecal (subarachnoid) space of sheep for up to 12 weeks in the absence of immunosuppression. Humoral and cellular immunological responses in the sheep were evaluated over this time course using the following assays: (1) serum-dependent cytotoxic antibody determinations, (2) flow cytometric sheep anti-bovine IgM and sheep antibovine IgG antibody analysis, (3) alterations in cellular immune markers, and (4) T cell responsiveness of the host using one-way mixed lymphocyte reactions. Complement-dependent cytotoxic antibody testing demonstrated that none of the sheep implanted with the encapsulated BAC cells were sensitized to antigens from transplanted cells in the device. There were no alterations of cellular immune markers in the blood of the transplanted sheep and no positive T cell responses were elicited by exposure of unprimed or primed in vivo host lymphocytes to unencapsulated BAC cells in vitro. Morphological analysis of the explanted devices demonstrated that all capsules contained viable cells and 20 of 21 devices released basal and nicotine-stimulated norepinephrine as determined by HPLC analysis. These observations suggest that an encapsulating membrane can provide an immunoisolatory barrier enabling successful xenogeneic transplantation.

Transplantation of encapsulated bovine chromaffin cells in the sheep subarachnoid space: a preclinical study for the treatment of cancer pain.

Chromaffin cells have been shown to release a combination of pain-reducing neuroactive compounds including catecholamines and opioid peptides. The allogeneic transplantation of chromaffin cells in the subarachnoid space has been shown to alleviate pain in various rodent models and possibly in terminal cancer patients. Because of the shortage of human cadaver donor tissue, we are investigating the possibility of transplanting xenogeneic cells in polymer capsules. In this technique, cells are surrounded by a permselective synthetic membrane whose pores are suitably sized to allow diffusion of nutrients, neurotransmitters and growth factors, but restrict the diffusion of the large molecules of the immune system and prevent contact with immunocompetent cells. The encapsulation technique therefore allows transplantation of xenogeneic tissue between species as well as retrieval of transplanted cells. Previously we have reported that encapsulated bovine chromaffin cells survive and alleviate pain in various rodent models. The purpose of the present study was to assess the feasibility of implanting a human sized device in a large animal model. Adrenals from 5 calves were surgically removed; chromaffin cells were isolated from these glands using a collagenase-based digestion-filtration technique. Cells were loaded into acrylic-based tubular (5 cm long, 920 microns wide) permselective capsules attached to silicone tethers. The capsules were maintained in vitro for at least 7 days following the encapsulation procedure. Nicotine evoked release was analyzed in a defined subgroup from each batch. One capsule was then implanted using a guiding cannula system in the lumbar subarachnoid space of each sheep for 4 (n = 5) and 8 (n = 1) wk. All capsules were retrieved intact by gentle pulling on the silicone tether. Except for one capsule, the evoked catecholamine release of the retrieved capsules was in the same range as that of other capsules from the same cohort that had been maintained in vitro. All retrieved capsules were devoid of host cell reaction. Clusters of viable cells dispersed in an alginate immobilizing matrix were observed throughout all the implanted capsules. This study demonstrates the feasibility of transplanting functional encapsulated xenogeneic chromaffin cells into the cerebrospinal fluid of a large animal model using a capsule of appropriate dimensions for human implants. We believe that these results suggest the appropriateness of human clinical trials in patients suffering from refractory terminal cancer pain.

Experience with fully bioresorbable aortic grafts in the dog.

Reorganization of the arterial wall through natural processes on the resorption of a totally bioresorbable graft was investigated in dogs with Vicryl prostheses coated with two different blends of bioresorbable polyesters capable of slowing down considerably the disintegration of a Vicryl fabric in vivo. The prostheses (8 to 9 mm in internal diameter, 8 to 10 cm long) were implanted in the infrarenal aortic position for up to 24 weeks. All 18 animals implanted with coated prostheses survived, whereas one animal implanted with an uncoated Vicryl prosthesis died because of early rupture of the graft. Patent tubular conduits were present in 14 animals at the time of retrieval. On resorption of the synthetic polymers, the tissue layers that formed on both sides of the prosthetic material either fused or remained separated, depending on the polymer used as a retardant coating. We conclude that polymer composition influences the repair process and that a fully resorbable vascular graft can function effectively in a canine model, provided that tissue organization is sufficiently advanced by the time the prosthesis has lost its mechanical integrity. Further studies are needed to document the performance of the newly formed blood conduit over extended periods, in hypertensive subjects, and when presented with a bacterial challenge.

Tissue reaction to fabrics coated with turbostratic carbon: subcutaneous versus vascular implants.

A technique allowing the deposition of an adherent thin film of turbostratic, high-density carbon on heat-sensitive polymers was recently developed. The biological response to this biomaterial on yarns and fabrics of the type used in cardiovascular surgery has been studied. Polyester yarns, knitted Dacron sheets and knitted uncrimped Dacron vascular grafts were coated with a thin film (less than 1 micron) of turbostratic carbon using a physical vapour deposition process. Coated and control discs of knitted material, as well as coated and uncoated yarns, were implanted in pairs in the subcutaneous tissue of mice, using for each type of implant two cohorts of 12 animals, with observation periods of 4 and 8 wks respectively. Vascular grafts (8 cm long, 8 mm i.d.) coated with carbon on the luminal side only, were implanted for 12 wks in the infrarenal aortic position in six dogs, and compared to uncoated Dacron grafts of the same dimensions inserted in the same location and for the same duration in the infrarenal aortic position in six control animals. With subcutaneous implants, there was no significant difference in the tissue reaction to either coated or uncoated patches. In contrast, the vascular grafts, all of which were patent upon retrieval, showed a much lower extent of thrombosis on the blood-exposure surface in the case of carbon-coated Dacron, as compared to the luminal surface of control prostheses. The internal capsule (tissue formed between the polymer fabric and the blood interface) was thinner in carbon-coated grafts than in control grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Sutureless intraluminal graft for repair of abdominal aortic aneurysm.

A series of seven patients undergoing elective repair of abdominal aortic aneurysms using sutureless intraluminal aortic prostheses for infrarenal tube grafts was reviewed. Follow-up was five to seven months. There was no morbidity related to the graft and one late mortality. In the uncomplicated cases, the average total operative time was two hours 14 minutes with no bank blood transfusions. The overall average operative time was two hours 41 minutes with an average operative transfusion of 0.28 units and total transfusions of 1.70 units of bank blood per case. Based on this experience and the observation that operative time and blood loss are major determinants of mortality with emergency abdominal aortic aneurysm repairs, we believe that use of sutureless intraluminal prostheses in suitable cases of leaking or ruptured abdominal aortic aneurysms has the potential to markedly improve survival.