Rheolytic thrombectomy in the management of acute and subacute limb-threatening ischemia

PURPOSE

To evaluate the use of a percutaneous mechanical thrombectomy (PMT) catheter (AngioJet) as an initial treatment for acute (<2 weeks) and subacute (2 weeks to 4 months) arterial occlusion of the limbs.

MATERIALS AND METHODS

A total of 86 (acute, n = 65; subacute, n = 21) patients were available for retrospective analysis, averaging 65 +/- 14 years of age. Outcomes assessed include initial angiographic success (failure = less than 50% luminal restoration [LR]; partial success = 50%-95% LR; success = more than 95% LR), pre- and postprocedural ankle-brachial index (ABI), device-related and systemic complications, 1-month amputation, mortality, and short-term patency.

RESULTS

Angiographic success was evaluated in 83 of 86 patients (guide wire unable to traverse lesion in three patients). The procedure failed in 13 of 83 (15.6%) patients, partial success was seen in 19 of 83 patients (22.9%), and successful recanalization was noted in 51 of 83 patients (61.4%). Adjunctive thrombolysis was used in 50 of 86 patients (58%). However, thrombolysis resulted in angiographic improvement at the site of PMT in only seven of 50 of these patients (14%). Adjunctive thrombolysis was uniformly unsuccessful in patients in whom initial PMT failed. The median increase in ABI was 0.64 (95% CI: 0.43-0.81). Success was more likely in the setting of in situ thrombosis, with 61 of 68 (90%) procedures successful, compared to embolic occlusions, with nine of 15 (60%) procedures successful (P =.011). Angiographic outcome was not dependent on the duration of occlusion (acute, 51 of 62; subacute, 19 of 21; P =.35) or the conduit type (graft, 28 of 31; native vessel, 42 of 52; P =.35). An underlying stenosis was identified in 53 of the 70 patients (75.7%) with a successful PMT, and 51 of these 53 unmasked lesions were successfully treated. Follow-up data were available in 56 patients for patency assessment at a median of 3.9 months (range, 0.1-28.5 months). Patency at 6 months was 79% (95% CI: 65-92). Systemic complications occurred in 16.3% of patients, local complications were noted in 18.6%, and 1-month amputation and mortality rates were 11.6% and 9.3%, respectively.

CONCLUSION

PMT offers the potential to rapidly reestablish flow to an ischemic extremity and may be the only available treatment option in patients at high risk for open surgery or with contraindications to pharmacologic thrombolysis.

Percutaneous AngioJet thrombectomy in the management of extensive deep venous thrombosis

PURPOSE

This study was undertaken to evaluate the efficacy of a percutaneous mechanical thrombectomy (PMT) device for rapid thrombus removal following deep venous thrombosis (DVT).

MATERIALS AND METHODS

Over a 37-month period, 17 patients (14 women; mean age, 41 y +/- 20) with extensive DVT were treated with initial attempts at PMT with use of the AngioJet rheolytic thrombectomy device. Sites of venous thrombosis included lower extremities in 14 patients and upper extremity and brachiocephalic veins in three. The etiology for venous thrombosis was malignancy in seven, idiopathic etiology in three, May-Thurner syndrome and immobilization in three each, and oral contraceptive use and hypercoagulable disorder in one each. The primary endpoint was venographic evidence of thrombus extraction. Perioperative complications, mortality, and recurrence-free survival were also evaluated.

RESULTS

After PMT, four of 17 patients (24%) had venographic evidence of >90% thrombus removal, six of 17 (35%) had 50%-90% thrombus removal, and seven of 17 (41%) had <50% thrombus extraction. Adjunctive thrombolytic therapy was used in nine of 13 patients with <90% thrombus extraction by PMT; six patients (35%) had contraindications to pharmacologic thrombolytic therapy. An underlying lesion responsible for the occlusion was uncovered in 10 patients (59%). Significant improvement in clinical symptoms was seen in 14 of 17 patients (82%). No complications were noted directly relating to the use of the AngioJet thrombectomy catheter. None of the patients were lost to follow-up during a mean of 8.9 months +/- 5.3 (range, 2-21 months). At 4 and 11 months, recurrence-free survival rates were 81.6% and 51.8%, respectively.

CONCLUSION

PMT with adjunctive thrombolytic therapy is a minimally invasive, low-risk therapeutic option in patients with extensive DVT, associated with clinical benefits including thrombus removal, patency, and relief of symptoms.

Death, dying and emotional labour: problematic dimensions of the bone marrow transplant nursing role?

Bone marrow transplantation (BMT) is an established intervention for a range of conditions including those of a serious, life-threatening nature such as leukaemias. The experience of those who fail to respond to such aggressive treatment, however, or those who die as a result of treatment-induced complications, is currently under-researched. In this paper the authors suggest that despite the relatively high mortality associated with BMT, cultural, biological and professional factors have contributed to a lack of attention on issues of death and dying and emotional labour within BMT care settings. Current technological, biomedical and quality of life discourses which characterize much of the BMT literature are problematic and, we suggest, may serve to disadvantage those who will not survive such procedures. In addition, the provision of effective palliative care in BMT settings remains open to review through further research and development. As a first step, the authors argue that the role of nursing needs to be reconceptualized within BMT to allow key humane concerns such as suffering and the emotional labour of care to be explored and better understood.

Percutaneous endovascular repair of infrarenal abdominal aortic aneurysms: a feasibility study

BACKGROUND

Endovascular grafting has markedly reduced the invasiveness of the treatment of abdominal aortic aneurysms. By using a modification of technique for available closure devices, we have been able to achieve percutaneous repair of aneurysms. This study reviewed our initial experience with this technique.

METHODS

Demographics and background data from patients undergoing endovascular repair of abdominal aortic aneurysms were reviewed from prospectively collected registry data. Operative notes and angiographic and computed tomography scan data were retrospectively reviewed to assess the success of the percutaneous approach.

RESULTS

Fourteen patients have undergone percutaneous placement of the AneuRx (Medtronic, Sunnyvale, Calif) endovascular graft, with a modification of the technique for the Prostar (Perclose, Redwood City, Calif) device for access site closure. Main graft body introduction with a 22F sheath proved successful in nine of 12 (75%) deployments. Contralateral limb deployment through a 16F sheath was successful in 10 of 14 deployments (71.4%). Reasons for conversion to open groin incisions include inadequate percutaneous hemostasis (six cases), iliofemoral dissection (four cases), device failure (one case), and compromised distal flow (one case). Percutaneous deployment success appears to be improved with larger iliac artery dimensions, decreased calcification, and limited tortuosity, because of the limitation of complications related to delivering a larger diameter sheath. Of the 13 percutaneous endograft insertions that were attempted, six (46.2%) were completely successful.

CONCLUSION

Percutaneous deployment of available devices is technically feasible by using modifications of technique with percutaneous closure devices, despite large introducer sizes. Further experience with this technique offers the potential for identifying patients in whom this will prove successful and for even further reducing hospital stay and recovery times for aneurysm repair.

An evaluation of the costs to health care institutions of endovascular aortic aneurysm repair

BACKGROUND

Endovascular graft techniques hold great potential as a less invasive means for the repair of aortic aneurysms, yet the impact of these new modalities remains poorly elucidated.

METHODS

Over a 10-month period at a single institution, 139 patients underwent infrarenal aortic aneurysm repair through a traditional open surgical technique (OS group, 94 patients) or an endovascular approach (ES group, 45 patients). Coated polyester prostheses (Hemashield; Boston Scientific Corporation, Boston, Mass) were used in the OS patients, whereas a modular nitinol polyester device (AneuRx; Medtronic, Sunnyvale, Calif) was used in the ES group. The hospital costs exclusive of professional charges were tabulated for the two groups using the hospital cost accounting system. Outliers were included in the data analysis.

RESULTS

The mean operating room time was longer in the OS group than in the ES group (285 minutes vs 166 minutes). The average length of stay was also longer in the OS group (9.7 days vs 3.2 days). Hospital costs related to the length of stay were higher in the OS group, including laboratory costs ($327 higher), pharmacy costs ($688 higher), and nursing costs ($780 higher). Anesthesia costs were also higher in the OS group ($493 higher). Despite these marked differences, the total hospital cost averaged $7205 more in the ES group, a finding that was driven by the cost of the implantable devices themselves ($8976 in the ES group vs $597 in the OS group).

CONCLUSIONS

Despite reductions in the length of hospitalization, the cost of care was substantially greater in patients undergoing endovascular aneurysm repair than in patients in whom an open surgical technique was used. These differences are driven by the cost of the endograft device itself, a cost that must not exceed $6000 if the economic impact of endovascular repair is to be in parity with traditional methods. Unless these economic disparities can be ameliorated, the economic impact of endovascular aneurysm repair may limit the widespread application of this technology.

Global experience in cervical carotid artery stent placement

The purpose of this article is to review and update the current status of carotid artery stent placement in the world. Surveys to major interventional centers in Europe, North and South America, and Asia were initially completed in June 1997. Subsequent information from these 24 centers in addition to 12 new centers has been obtained to update the information. The survey asked the various questions regarding the patients enrolled, procedure techniques, and results of carotid stenting, including complications and restenosis. The total number of endovascular carotid stent procedures that have been performed worldwide to date included 5,210 procedures involving 4,757 patients. There was a technical success of 98.4% with 5,129 carotid arteries treated. Complications that occurred during the carotid stent placement or within a 30-day period following placement were recorded. Overall, there were 134 transient ischemic attacks (TIAs) for a rate of 2.82%. Based on the total patient population, there were 129 minor strokes with a rate of occurrence of 2.72%. The total number of major strokes was 71 for a rate of 1.49%. There were 41 deaths within a 30-day postprocedure period resulting in a mortality rate of 0.86%. The combined minor and major strokes and procedure-related death rate was 5.07%. Restenosis rates of carotid stenting have been 1.99% and 3.46% at 6 and 12 months, respectively. The rate of neurologic events after stent placement has been 1.42% at 6-12-month follow-up. Endovascular stent treatment of carotid artery atherosclerotic disease is growing as an alternative for vascular surgery, especially for patients that are high risk for standard carotid endarterectomy. The periprocedure risks for major and minor strokes and death are generally acceptable at this early stage of development and have not changed significantly since the first survey results. Cathet. Cardiovasc. Intervent. 50:160-167, 2000.

Use of clindamycin disks To detect macrolide resistance mediated by ermB and mefE in Streptococcus pneumoniae isolates from adults and children

We studied 198 macrolide-resistant S. pneumoniae isolates obtained from adults and children to evaluate whether 2-microgram clindamycin disks can distinguish between isolates manifesting ermB- versus mefE-mediated resistance to clarithromycin and to determine the relative frequency with which each resistance mechanism occurred in these populations. The mefE gene was predominant among 109 isolates from children, occurring in 73.4% versus 50.6% of 89 isolates from adults. Three isolates (1.5%) did not amplify either gene. Among 125 mefE(+) isolates, the MIC of clarithromycin at which 90% of the isolates tested were inhibited, determined by Etest, was 32 microgram/ml versus >256 microgram/ml in 70 ermB(+) isolates. All ermB(+) isolates were highly resistant to clindamycin (MICs >256 microgram/ml), whereas all mefE(+) isolates were susceptible to clindamycin using the 2-microgram disk. Testing S. pneumoniae from the respiratory tract for susceptibility to clindamycin by agar disk diffusion is an easy and inexpensive method to estimate the frequency of resistance mediated by ermB in specific patient populations. Macrolide resistance mediated by ermB is usually of greater magnitude than that due to mefE. Clinical studies are needed to determine the significance of high- versus low-level macrolide resistance in S. pneumoniae.

Complications associated with the use of urokinase and recombinant tissue plasminogen activator for catheter-directed peripheral arterial and venous thrombolysis

PURPOSE

Catheter-directed thrombolytic dissolution of peripheral arterial and venous thrombus is in widespread use, yet the frequency and nature of associated complications remain ill defined. In an effort to better characterize the complications associated with urokinase (UK) and recombinant tissue plasminogen activator (rt-PA), the clinical course of patients treated for lower extremity vascular occlusions at a single institution was reviewed.

MATERIALS AND METHODS

Over a 9-year period, 653 consecutive patients were treated for lower extremity arterial (527 patients) or venous (126 patients) occlusions with catheter-directed UK (483 patients), rt-PA (144 patients), or both (26 patients). Decisions regarding the choice of thrombolytic agent were made by the clinician. In-hospital complications were subcategorized into hemorrhagic and nonhemorrhagic events and the rate of intracranial hemorrhage was specifically tabulated.

RESULTS

There were no significant differences in the demographics or clinical presentation of patients treated with either UK or rt-PA. Bleeding complications occurred less often in the patients treated with UK (insertion site hematoma 21.9% vs. 43.8%, P<.0001, any bleeding necessitating transfusion 12.4% vs. 22.2%, P = .004, and intracranial hemorrhage 0.6% vs. 2.8%, P = .031). Cardiopulmonary complications necessitating transfer to the intensive care unit occurred more frequently in the patients treated with rt-PA (4.9% vs. 1.5%, P = .015). The risk of mortality was not statistically different between the UK and rt-PA treated patients (2.7% vs. 6.2%, P = .221).

CONCLUSIONS

Thrombolysis appears safer with UK than with rt-PA, with a lower incidence of hemorrhagic complications. It is possible that this finding is related to differential dosing regimens or intrinsic pharmacologic differences between the agents. The observations of this retrospective analysis require confirmation with a prospective, randomized evaluation.

Estimation of cumulative lead releases (lead flux) from the maternal skeleton during pregnancy and lactation

Recent longitudinal studies with human subjects and nonhuman primates using high-precision stable lead isotopes show that lead is mobilized from the maternal skeleton during pregnancy and the postpartum period. We have now calculated the cumulative lead release (lead flux in micrograms) mobilized from the skeleton during these periods by means of analysis of monthly PbB samples from recent immigrants to Australia. Results included a statistically significant inverse relationship (P = .006) between the lead flux and the time of conception after the arrival of the subjects in Australia. By using an area-under-the-curve approach to determine the added lead inputs to blood during pregnancy and nursing versus a baseline value, the net lead release to blood varied from 0.9 to 10.1 microg/d, which is equivalent to 0.3 to 4.03 mg of lead. With group PbB concentrations usually less than 3 microg/dL, the observed releases imply a high skeletal turnover of greater than 10% and possibly greater than 30% in some subjects during pregnancy and the postpartum period. These elevated rates in some subjects may partly arise from low daily calcium intakes, being one half to two thirds of that of recommended daily requirements. The lead flux calculated from a cumulative approach was compared with other approaches: first-order kinetics, bone turnover, bone x-ray fluorescence measurements, and the International Commission for Radiological Protection lead pharmacokinetic model. Calculated lead releases and remaining bone lead concentrations would likely not be detectable by current x-ray fluorescence methods.

MRI of the cauda equina in CIDP: clinical correlations

Isolated reports have documented enhancement and/or enlargement of spinal nerve roots on magnetic resonance imaging (MRI) in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). This work examines those findings in a consecutive series of 16 patients with CIDP, with blinded comparison to MRI in 13 disease controls, including five patients with Charcot-Marie-Tooth disease type 1A. MRI sequences consisted of T1 weighted sagittal and axial views, before and after administration of gadolinium. Blinded MRI interpretation was performed independently by two neuroradiologists. MRI results were correlated with data collected from chart review. Enhancement of the cauda equina was seen in 11 of 16 CIDP patients (69%), and in none of 13 control subjects. Nerve roots were enlarged, most significantly in the extraforaminal region, in three CIDP patients, and in one patient with Charcot-Marie-Tooth type 1A. MRI findings did not correlate with disease activity and severity, nor with any clinical or laboratory features in patients with CIDP.

Immunity to cross-reactive serotypes induced by pneumococcal conjugate vaccines in infants

Infants were immunized with 1 of the 3 experimental pneumococcal conjugate vaccines that contain 6B and 19F but not 6A or 19A serotypes. Their sera were studied for the capacity to opsonize Streptococcus pneumoniae 6A, 6B, 19A, and 19F serotypes and the level of IgG antibody to the 4 serotypes. Significant increases were observed in the number of infants with detectable opsonophagocytic titers with 3 conjugate vaccines for 6B (vaccine) serotype but with only 2 vaccines for 6A (cross-reactive) serotype. Significant increases were observed with 2 conjugate vaccines for 19F serotype but with only 1 vaccine for 19A serotype. Thus, some conjugate vaccines may elicit cross-protection better than others. In addition, correlations between opsonophagocytic titers and IgG antibody levels by ELISA were high for 6B and 19F serotypes but low for 6A and 19A serotypes. Thus, ELISA may be an inadequate surrogate assay of vaccine response for cross-reactive serotypes.

Radiation safety system of the B-Factory at the Stanford Linear Accelerator Center

The radiation safety system of the B-Factory accelerator facility at the Stanford Linear Accelerator Center is described. The radiation safety system, which is designed to protect people from prompt radiation exposure due to beam operation, consists of the access control system and the radiation containment system. The access control system prevents people from being exposed to the very high radiation levels inside a beamline shielding enclosure. The access control system consists of barriers, a standard entry module at every entrance, and beam stoppers. The radiation containment system prevents people from being exposed to the radiation outside a shielding enclosure due to either normal or abnormal operation. The radiation containment system consists of power limiting devices, shielding, dump and collimator, and an active radiation monitoring system. The inter-related elements for the access control system and radiation containment system, as well as the associated interlock network, are described. The policies and practices used in establishing the radiation safety system are also compared with the regulatory requirements.

Xenogeneic transplantation of porcine hepatocytes into the CCl4 cirrhotic rat model

Liver support using extracorporeal devices and hepatocyte transplantation has received renewed interest for the management of acute and chronic liver failure. The aim of this study was to determine whether xenogeneic porcine hepatocytes could integrate into the liver parenchyma of cirrhotic Lewis rats when administered by an intrasplenic route. Cirrhosis was induced by carbon tetrachloride (CCl4) inhalation and confirmed histologically. Freshly isolated porcine hepatocytes were infused directly into the splenic pulp at laparotomy over a 5-15-min interval. Using (111)In-labeled hepatocytes, the degree of localization of porcine hepatocytes to the spleen and liver was found to be greater than 60% in both control and cirrhotic rats. Integration of porcine hepatocytes into the rat liver parenchyma was determined by immunohistochemical staining for porcine albumin in rat liver sections. Further confirmation was provided by in situ hybridization using a porcine-specific probe that binds to a distinct repetitive element (PRE) in porcine DNA. Evidence of integrated porcine hepatocytes was seen for over 50 days in animals under cyclosporine immunosuppression. These data demonstrate the integration of xenogeneic porcine hepatocytes into the liver of the cirrhotic rat and their ability to produce porcine albumin for up to 50 days.

Market incentives, plan choice, and price increases

The Federal Employees Health Benefits Program (FEHBP) has attracted considerable interest for its ability to control health care costs. We examine the impact of the FEHBP's maximum dollar contribution on incentives to select low-cost plans and the growth in insurance premiums over time. Unless the maximum dollar contribution is pegged to a low-price plan, few enrollees select such plans. Moreover, premiums rise at least five percentage points per year faster among plans below this fixed subsidy level than they do in plans above it. Our results have important implications for the design of similar market-based approaches.

Comparison of the rates of exchange of lead in the blood of newly born infants and their mothers with lead from their current environment

Newly born infants (n = 15) were monitored for 6 months after birth or for longer periods to evaluate the changes in isotopic composition and lead concentration in infants as compared with that in women from the same population groups and to determine the clearance rates of lead from blood in the infants. These data represent the first published results for serial blood sampling in a relatively large cohort of newly born infants. Blood lead concentrations decrease from the cord to samples taken at 60 to 90 days and then increase by amounts varying from negligible to 166%. In spite of concern about individual susceptibility to lead pharmacokinetics, changes in isotopic ratio followed a smooth decrease over time for 9 of the 11 infants born to migrant parents, and the patterns of variation were quite reproducible. Data for 2 of 4 infants born to multigenerational Australian parents exhibited little change in isotopic ratio over time, and in the other two cases, the changes were attributed to diet. The rate of exchange (t1/2) for the migrant infants of lead in blood derived from the mother during pregnancy and the lead from the current environment was calculated by using a linear function and ranged from 65 to 131 (91+/-19, mean+/-SD) days. The half-lives for the exchange of skeletal and environmental lead for 7 of the 8 women before significant mobilization of lead from the maternal skeleton ranged from 50 to 66 (59+/-6) days. One explanation for the longer half-lives for infants as compared with the mothers may be the proportionally higher contribution of current environmental (Australian) lead in the infants at parturition. Exchanges of lead in infants are more complex than for the adults, reflecting inputs from sources such as maternal skeletal lead during breast feeding.

Retroviral vector-mediated gene transfer into keratocytes in vitro and in vivo

PURPOSE

To determine the potential of somatic gene transfer as a technique for modulating corneal wound healing after superficial keratectomy.

METHODS

The transduction of human and rabbit keratocytes with beta-galactosidase and herpes simplex virus thymidine kinase genes was performed. In vitro, human and rabbit keratocytes were transduced with retroviral vectors bearing beta-galactosidase or HStk (herpes simplex virus thymidine kinase) genes. In vivo, rabbit keratocytes were transduced by topical application of vector supernatant after a superficial keratectomy. In vitro and in vivo, expression of the beta-galactosidase gene was examined with histochemical staining. In vitro, ganciclovir cytotoxicity in HStk gene-transduced keratocytes and bystander effect in co-cultures of HStk(+) and HStk(-) keratocytes were measured by determining the degree of confluency of cells in 6-well plates after 10 days of incubation. Corneal haze in rabbits was measured after transduction with Hstk and subsequent treatment with topical ganciclovir.

RESULTS

In vitro, both human and rabbit keratocytes were transduced successfully with both beta-galactosidase and HStk genes. Transduction efficiency was greater with human (22%) than with rabbit (16%) cells, and both HStk-transduced cell lines showed dose-dependent ganciclovir cytotoxicity and a significant bystander effect. In vivo, expression of beta-galactosidase within vimentin-positive corneal stromal cells confirmed transduction of keratocytes in the rabbit after superficial stromal keratectomy with an efficiency of 25% to 40%. Postoperative application of topical ganciclovir reduced corneal stromal haze in rabbits.

CONCLUSIONS

The ability to genetically transduce stromal keratocytes provides a new strategy for understanding the important cellular and molecular events that influence corneal wound healing, thus offering a potential approach to decrease or prevent corneal haze and scarring after superficial keratectomy.

Designed beta-sheet-forming peptide 33mers with potent human bactericidal/permeability increasing protein-like bactericidal and endotoxin neutralizing activities

Novel peptide 33mers have been designed by incorporating beta-conformation stabilizing residues from the beta-sheet domains of alpha-chemokines and functionally important residues from the beta-sheet domain of human neutrophil bactericidal protein (B/PI). B/PI is known for its ability to kill bacteria and to neutralize the action of bacterial endotoxin (lipopolysaccharide, LPS) which can induce septic shock leading to eventual death. Here, the goal was to make short linear peptides which demonstrate good beta-sheet folding and maintain bioactivity as in native B/PI. A library of 24 peptide 33mers (betapep-1 to betapep-24) were synthesized with various amino acid substitutions. CD and NMR data acquired in aqueous solution indicate that betapep peptides form beta-sheet structure to varying degrees and self-associate as dimers and tetramers like the alpha-chemokines. Bactericidal activity toward Gram-negative Pseudomonas aeruginosa was tested, and betapep-19 was found to be only about 5-fold less potent (62% kill at 1.2 x 10(-7) M) than native B/PI (80% kill at 2.9 x 10(-8) M). At LPS neutralization, betapep-2 and -23 were found to be most active (66-78% effective at 1.2 x 10(-6) M), being only about 50-100-fold less active than B/PI (50% at 1.5 x 10(-8) M). In terms of structure-activity relations, beta-sheet structural stability correlates with the capacity to neutralize LPS, but not with bactericidal activity. Although a net positive charge is necessary for activity, it is not sufficient for optimal activity. Hydrophobic residues tend to influence activities indirectly by affecting structural stability. Furthermore, results show that sequentially and spatially related residues from the beta-sheet domain of native B/PI can be designed into short linear peptides which show good beta-sheet folding and retain much of the native activity. This research contributes to the development of solutions to the problem of multiple drug-resistant, opportunistic microorganisms like P. aeruginosa and of agents effective at neutralizing bacterial endotoxin.

The use of video-imaging to assess the sub-lethal impact of plant secondary compounds on Schistosoma mansoni miracidia

The study describes methods developed for using video-imaging technology to record and measure the velocity of Schistosoma mansoni miracidia. The efficacy of the classical bioassay procedure (a qualitative behavioural assay) was compared with that of the new quantitative protocol, for assessing the sub-lethal impact of a larvicidal dichloromethane extract of the seeds of Millettia thonningii on miracidia. The new technique confirmed the efficacy of the classical bioassay for rapid determination of the lethal and sub-lethal impact of larvicides but also provided quantitative information on sub-lethal impacts on miracidial velocity and shape.

A broader vision for managed care, Part 2: A typology of community benefits

Applying a "community benefit" standard to managed care is difficult because prevailing definitions of community benefit have been drawn largely from the hospital industry, which has different operating practices and capabilities than managed care plans do. To formulate a more comprehensive and appropriate typology for managed care, we describe four different conceptual perspectives on community benefit and identify actual plan practices that match each perspective. We propose a "balanced model" for encouraging community benefit through public and private policies.

Intravenous RMP-7 increases delivery of ganciclovir into rat brain tumors and enhances the effects of herpes simplex virus thymidine kinase gene therapy

Herpes simplex virus thymidine kinase (HSV-tk) gene therapy for brain tumors depends on ganciclovir (GCV) and its transport across the blood-brain tumor barrier (BBTB). We examined whether RMP-7, the bradykinin analog and potent BBTB permeabilizer, could enhance the efficacy of GCV treatment of brain tumors by increasing the BBTB delivery of GCV. In vitro, a significant bystander cytocidal effect of GCV was shown in mixed HSV-tk-transduced (HSV-tk+) and control vector-transduced (HSV-tk-) C6 glioma cultures. A dose-dependent cytotoxic effect of GCV on untransformed C6 cells was also shown. In vivo, rats with 100% HSV-tk+ or 100% HSV-tk- intracerebral C6 gliomas were treated for 7 days with intravenous infusions of GCV alone or with GCV and RMP-7 (2.5 microg/kg/day). The growth of HSV-tk+ and HSV-tk- gliomas decreased with increasing doses of GCV. A high dosage (100 mg of GCV/kg/day) eradicated all HSV-tk- and HSV-tk+ tumors. An intermediate dosage (5 mg of GCV/kg/day) reduced the growth of HSV-tk- gliomas by 42% if given alone, and by 88% in combination with RMP-7. A low dosage (0.5 mg of GCV/kg/day) in combination with RMP-7 enhanced the regression of HSV-tk+ gliomas by 87% compared with GCV alone. Low-dose GCV was ineffective in HSV-tk- tumors. RMP-7 increased [3H] GCV tumoral uptake by 2.6- and 1.7-fold in the tumor center and periphery, respectively. We conclude that RMP-7 could be an important adjunctive treatment for suicide gene therapy of brain tumors, while an RMP-7/GCV combination may also have a significant antitumor effect in untransfected gliomas.

A broader vision for managed care, Part 1: Measuring the benefit to communities

For the past quarter-century managed care plans have been judged almost exclusively in terms of their influence on the health and health care of individual enrollees. However, policymakers are now paying attention to the ways in which health care organizations affect the broader well-being of their communities. These forms of "community benefit" emerged originally from legal criteria for tax exemption but are increasingly applied to all health care organizations, whatever their form of ownership. In this paper we identify different paradigms for defining community benefit and trace the factors that have encouraged or discouraged their application to health care. We suggest several strategies encouraging managed care plans to broaden their goals to include community benefit.