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Biomedical subjects

M E Jensen

Publications and source records attributed to M E Jensen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Experimental side-wall aneurysms: a natural history study.

We studied the natural history of canine side-wall experimental aneurysms to determine the incidence of spontaneous aneurysm thrombosis, to serve as control data for future studies focusing on development of aneurysm occlusion devices. Bilateral common carotid artery vein patch aneurysms were surgically created in eight mongrel dogs (20-25 kg). Duplex Doppler sonography was performed at 14 days and angiography between 30 and 210 days following aneurysm creation. Sonography demonstrated patency of 13 (81%) of 16 aneurysms. Patent aneurysms ranged in size from 8 x 10 mm to 14 x 16 mm. Conventional angiography was performed in four dogs approximately 30 days following aneurysm creation; in these four, all of 7 initially patent on sonography remained fully patent. One dog underwent conventional angiography at approximately 60 days following aneurysm creation; both aneurysms in this case remained widely patent. Three dogs underwent conventional angiography at approximately 200 days following aneurysm creation; all 4 aneurysms initially patent on sonography remained fully patent. None of the three aneurysms found to be occluded on sonographs demonstrated spontaneous recanalization. The canine side-wall aneurysm model is a valid tool for testing some aneurysm-occlusion devices, because control aneurysms remain patent indefinitely.

Animals↗
PubMed1999

Idiopathic supraclinoid and internal carotid bifurcation steno-occlusive disease in young American adults.

We report a series of American adults with idiopathic steno-occlusive disease of the supraclinoid internal carotid artery and its bifurcation. We reviewed the clinical records and imaging of 18 patients, 16 women and 2 men, aged 20-53 years (mean 35 years). There were no predominating risk factors for vascular occlusive disease, such as oral contraceptive use, hypertension, diabetes mellitus, or smoking. Four patients had irregularity of their cervical internal carotid arteries in a pattern not classic but suspicious of fibromuscular dysplasia. Eleven patients met the criteria for moyamoya disease, having both bilateral disease and moyamoya collateral lenticulostriate arteries. Necropsy in one case showed intimal thickening with duplication of the internal elastic lamina involving the internal carotid artery bifurcation bilaterally. We found a marked predominance of young and middle-aged females in our American adults, but our findings do not support the association with birth-control pills previously reported.

Adult↗
PubMed1999

Endovascular creation of an in vivo bifurcation aneurysm model in rabbits.

PURPOSE: To develop a rabbit model of an intracranial bifurcation aneurysm to test new endovascular therapies. MATERIALS AND METHODS: An experimental aneurysm model was created in rabbits by means of endovascular balloon occlusion of the left common carotid artery, which created an aneurysm at the bifurcation formed by the aortic arch and the brachiocephalic trunk. A total of 18 aneurysms were created. In eight rabbits, the aneurysms were incubated with intraluminal elastase to induce degeneration of the elastic laminae. The animals were followed up with angiography for as long as 3 months. The animals were sacrificed at various times, and histologic evaluation of the aneurysm was performed. RESULTS: Ten aneurysms created without elastase infusion were all very small or completely closed at 1-3 months. Six aneurysms created with elastase infusion had long-term patency (two were patent at 1 month and four, at 3 months). The elastase aneurysms had a mean width of 3 mm (range, 2-3.5 mm) and a mean length of 5 mm (range, 3-7 mm). Histologic evaluation revealed destruction of the normal elastin layers, which allowed the artery to become aneurysmal. CONCLUSION: This aneurysm model re-created the hemodynamic forces and size of human cerebral bifurcation aneurysms and maintained the integrity of the endothelium. The creation of the aneurysms was rapid, reliable, and reproducible.

Animals↗
PubMed1999

C-peptide induces a concentration-dependent dilation of skeletal muscle arterioles only in presence of insulin.

In this study we tested the hypothesis that C-peptide alone or in conjunction with insulin may cause a dilation of skeletal muscle arterioles. First-order arterioles (88 microm) isolated from rat cremaster muscles were pressurized (65 mmHg), equilibrated in a Krebs bicarbonate-buffered solution (pH 7.4), gassed with 10% O2 (balance 5% CO2, 85% N2), and studied in a no-flow state. C-peptide administered at concentrations of 0.3, 1, 3, 10, 100, 300, and 1,000 ng/ml evoked arteriolar dilation that was not concentration dependent. In contrast, the administration of the four lower physiological concentrations of C-peptide to arterioles exposed to a nondilating concentration of insulin evoked a significant concentration-dependent increase in arteriolar diameter from 8.6 to 42.3% above control. The arteriolar dilation to C-peptide in the presence of insulin was completely inhibited by administration of NG-nitro-L-arginine (10(-4) M). Responses to ACh and adenosine were not enhanced when these drugs were administered in the presence of insulin. These results indicate that C-peptide has the capacity to evoke arteriolar dilation in skeletal muscle via a nitric oxide-mediated mechanism that appears to be enhanced by an interaction with insulin. Furthermore, the effects of insulin appear to be specific for C-peptide and are not the result of a general enhancement of endothelium-dependent or endothelium-independent dilation.

Acetylcholine↗
PubMed1999

Endovascular treatment of ruptured, peripheral cerebral aneurysms: parent artery occlusion with short Guglielmi detachable coils.

We report two cases of distal cerebral aneurysms that were treated by parent artery occlusion with short Guglielmi detachable coils (GDCs). One patient had a presumed mycotic aneurysm of the distal left posterior cerebral artery, and the other had a partially clipped aneurysm of the distal right anterior inferior cerebellar artery that had hemorrhaged. Short GDCs allow controlled, accurate occlusion of the parent artery at the aneurysmal neck.

Aneurysm, Infected↗
PubMed1999

Dural arteriovenous fistula of the cervical spine presenting with subarachnoid hemorrhage.

We describe a case of dural arteriovenous fistula (DAVF) presenting with subarachnoid hemorrhage (SAH). The diagnosis of DAVF was based on spinal angiography. A review of the literature revealed that five of 13 previously reported DAVFs of the cervical spine were accompanied by SAH. SAH has not been observed in DAVFs involving other segments of the spinal canal.

Angiography↗
PubMed1999

Exposure of medical personnel to methylmethacrylate vapor during percutaneous vertebroplasty.

The occupational exposure to methylmethacrylate (MMA) vapor during percutaneous vertebroplasty was determined. During five vertebroplasty procedures, air-sampling pumps were attached to medical personnel. MMA vapor levels in the samples were then quantified using gas chromatography. The samples collected yielded MMA vapor levels of less than five parts per million (ppm). The MMA vapor concentrations measured were well below the recommended maximum exposure of 100 ppm over the course of an 8-hour workday.

Air Pollutants, Occupational↗
PubMed1999

A clinical comparison of resin composite inlay and onlay posterior restorations and cast-gold restorations at 7 years.

OBJECTIVE: The purpose of this study was to evaluate the clinical performance of Concept indirect posterior heat- and pressure-polymerized restorative material and compare it to the performance of cast gold. METHOD AND MATERIALS: Inlays and onlays placed in a standardized manner as part of a clinical study were evaluated at 7 years. Eighteen patients (45%) who had received 36 Concept restorations returned and were evaluated using the US Public Health Service criteria. Restorations were evaluated in seven categories as the percentage receiving Alfa (ideal), Bravo (clinically acceptable), or Charlie (clinically unacceptable) scores or as restoration no longer present. Fourteen of the restorations were cemented with Heliobond bonding resin and 13 were cemented with Special Bond bonding resin. Each patient also received a cast-gold restoration for comparison. RESULTS: Concept restorations received scores of Alfa at the following rates: color match, 64%; interfacial staining, 47%; secondary caries, 75%; wear, 58%; marginal integrity, 64%; surface texture, 72%; and axial contour, 58% (in 14% this category was not applicable because they were Class I restorations). Nine Concept restorations (25%) were no longer present. Fifteen of 18 gold restorations were present at this recall. Statistical analysis indicated no significant differences in any categories between the two bonding resins used with Concept restorative material and the gold restorations. CONCLUSION: At 7 years in vivo, the Concept indirect posterior restorative system yields clinically acceptable restorations, particularly in premolars.

Acrylates↗
PubMed1999

Diet and dental caries.

Dental caries is a diet-related disease that continues to be a problem for certain dental patients. Frequent consumption of fermentable carbohydrates that have low oral clearance rates increases the risk for enamel caries and perhaps is even more dangerous for root surfaces. Highly acidogenic snack foods should be consumed at mealtimes to reduce the risk, and between-meal snacks should be either nonacidogenic (such as xylitol products) or hypoacidogenic (such as sorbitol and HSH products). Cheeses present a naturally occurring situation that may provide anticariogenic effects from the diet. Certain additives as well as sugar substitutes show great promise for the provision of between-meal snack foods that reduce the risk of dental caries. The dental team should thoroughly understand the relationship of diet to caries and conscientiously apply that knowledge to educate the patients in general as well as counsel specific high-risk individuals. Further emphasis should be placed on the acquisition of sound scientific data for counseling caries patients concerning diet and dental caries.

Acids↗
PubMed1998

Assay of acetylsalicylic acid and three of its metabolites in human plasma and urine using non-aqueous capillary electrophoresis with reversed electroosmotic flow.

The separation of acetylsalicylic acid and three of its metabolites--salicylic acid, salicyluric acid and gentisic acid--is demonstrated in a non-aqueous capillary electrophoresis system with reversed electroosmotic flow. Solvent mixtures of methanol and acetonitrile are used for the electrophoresis media and different electrolytes have been investigated. The flow is reversed by the addition of the polycation hexadimethrine bromide and thus a negative voltage is used. This system provides a fast and effective separation of the four analytes. The separation method was applied to the assay of acetylsalicylic acid and its major metabolites in plasma and urine and the limits of quantification for all of these compounds are about 5 microg ml(-1) in plasma and 25 microg ml(-1) in urine.

Acetonitriles↗
PubMed1998

Effects of systemic heparinization on the thrombogenicity of hydrophilic and nonhydrophilic catheters in a swine model.

We assessed the effect of systemic heparinization on the in-vivo thrombogenicity of various micro- and guiding catheters in a swine model. Microcatheters were placed through 6-F guiding catheters into the common carotid arteries of swine for 30-min (short-term) and 90-min (medium-term) periods, with and without systemic heparinization. At the end of the placement period the microcatheters were retracted through the guiding catheters and fixed for scanning electron microscopy (SEM). Guiding catheters were harvested after 5 h placement, with and without systemic heparinization, by retraction through 8-F sheaths and fixed for SEM. The surfaces of both hydrophilic and nonhydrophilic microcatheters all demonstrated more accumulation of debris during placement without than with systemic heparinization. The difference was primarily in the amount of fibrillary material on the catheter surface. The guiding catheters also demonstrated increased debris accumulation without systemic heparinization. This suggests that, even when using relatively nonthrombogenic catheters, systemic heparinization is indicated during cerebral angiography.

Animals↗
PubMed1998

Clinical and economic outcomes of individuals with severe peptic ulcer hemorrhage and nonbleeding visible vessel: an analysis of two prospective clinical trials.

OBJECTIVE: We report the clinical outcomes and direct medical costs of 155 patients with severe peptic ulcer hemorrhage and a nonbleeding visible vessel at emergency endoscopy treated with endoscopic hemostasis or medical-surgical therapy. METHODS: In two consecutive, prospective, randomized, controlled trials, patients were randomly assigned to endoscopic hemostasis (heater probe, bipolar electrocoagulation, or injection sclerosis) or medical-surgical treatment. Study endpoints included the incidence of severe ulcer rebleeding and emergency surgery, length of hospital stay, blood transfusion requirements, mortality rate, and direct costs of utilized health care. Direct medical costs were estimated using combined fixed and variable institutional costs for consumed resources and Medicare reimbursement rates. RESULTS: Compared with medical-surgical treatment, endoscopically treated patients had significantly lower rates of severe ulcer rebleeding (p = 0.004), emergency surgery (p = 0.002 and p = 0.019, 0.024), and blood transfusions (p = 0.025). Observed inter-trial differences in ulcer rebleeding rates may be partially explained in a multivariate model by covariates of comorbid disease and inpatient ulcer bleeding. In both trials, length of hospital stay, mortality rates, and treatment-related complications were similar. Estimated median direct costs per patient differed: The first trial had lower costs with endoscopic hemostasis ($4254, vs $4620 for electrocoagulation and $5909 for medical-surgical treatment), yet the second trial yielded lower costs with medical-surgical treatment ($3169, vs $3477 for injection sclerosis and $4098 for heater probe). CONCLUSIONS: Compared with medical-surgical therapy, endoscopic hemostasis for severe ulcer hemorrhage and a nonbleeding visible vessel yielded significantly better patient outcomes and was safe. This procedure may or may not yield lower direct medical costs and cost savings.

Blood Transfusion↗
PubMed1998

In vitro proliferation and adhesion of basic fibroblast growth factor-producing fibroblasts on platinum coils.

PURPOSE: To evaluate the growth and adhesion characteristics in vitro of genetically modified, basic fibroblast growth factor-producing fibroblasts on platinum detachable coils. MATERIALS AND METHODS: Coils of two sizes were coated with laminin, poly-L-lysine, fibronectin, and type I and type IV collagen and were cultured with basic fibroblast growth factor-secreting fibroblasts. Type I collagen strands were inserted in the lumen of some coils. Cellular proliferation and adherence during passage of coils through microcatheters were studied with both light and scanning electron microscopy. Growth factor concentration in the culture medium was measured. RESULTS: Rapid cellular proliferation was noted on all coated coils except those coated with type IV collagen. Proliferation on uncoated coils was slightly slower than on most coated coils, although confluent cell layers were present on uncoated larger-diameter coils within 48 hours. Cells had a marked propensity to grow between the primary coil windings into the coil lumen, except in coils that contained collagen filaments. Passage through microcatheters caused widespread stripping of cells from the outer surface of coils, especially the uncoated samples. Viable cells remained in the coil lumen. Supernatant contained high concentrations of growth factor. CONCLUSION: Platinum embolic coils are a promising mechanism of cell delivery for stimulation of scar formation or other desirable biologic effects.

3T3 Cells↗
PubMed1998

Prevalence of cerebral aneurysms in patients with fibromuscular dysplasia: a reassessment.

OBJECT: The aim of this study was to determine the prevalence of cerebral saccular aneurysms in patients with carotid artery and/or vertebral artery (VA) fibromuscular dysplasia (FMD). METHODS: A metaanalysis was performed using data from 17 previously reported series of patients with internal carotid artery (ICA) and/or VA FMD that included information on the prevalence of cerebral aneurysms. In addition, the authors retrospectively evaluated their own series of 117 patients with ICA and/or VA FMD to determine the prevalence of cerebral aneurysms. The metaanalysis of the 17 earlier series, which included 498 patients, showed a 7.6 +/- 2.5% prevalence of incidental, asymptomatic aneurysms in patients with ICA and/or VA FMD. In the authors' series of patients with FMD, 6.3 +/- 4.9% of patients harbored an incidental, asymptomatic aneurysm. When the authors' series was combined with those included in the metaanalysis, the prevalence was found to be 7.3 +/- 2.2%. The prevalence of aneurysms in the general population would have to be greater than 5.6% for there to be no statistically significant difference (chi-square test, p < 0.05) when compared with this 7.3% prevalence in patients with FMD. CONCLUSIONS: The prevalence of intracranial aneurysms in patients with cervical ICA and/or VA FMD is approximately 7%, which is not nearly as high as the 21 to 51% prevalence that has been previously reported.

Adult↗