Biomedical subjects

Nathan D Schwade

Publications and source records attributed to Nathan D Schwade.

4 recordsLinked to original sources

PubMed2004

Molecular responses of vascular smooth muscle cells to paclitaxel-eluting bioresorbable stent materials.

We studied the influence of paclitaxel, eluted from poly(L-lactic acid) (PLLA), on cultured vascular smooth muscle cell (VSMC) proliferation as a model of bioresorbable stent-induced restenosis. We blended paclitaxel in cast PLLA films (P-PLLA), demonstrating controlled release of the drug, then studied VSMC adhesion, proliferation, and gene expression profiles. No difference in cell adhesion was found between P-PLLA and PLLA controls (105 +/- 12% of PLLA controls). However, P-PLLA significantly reduced VSMC proliferation (40 +/- 15% of PLLA controls, p < 0.05). Using cDNA microarray technology, we identified major effects of P-PLLA, including: upregulation of genes related to apoptosis, anti-proliferation and antioxidation; and suppression of cell cycle regulators and cell survival markers. The expression patterns indicate that P-PLLA regulates gene expression and cell functions via new pathways, including receptor tyrosine kinase (RTKs), mitogen-activated protein kinase (MAPKs), and protein kinase (PKs, e.g., PKA) pathways, in addition to the stabilization of polymerized-microtubules.

Absorbable Implants↗

PubMed2004

Protein-loaded bioresorbable fibers and expandable stents: Mechanical properties and protein release.

There is an increasing interest in bioresorbable polymeric stents for coronary, urethral and tracheal applications. These stents can support body conduits during their healing process and release biologically active agents from an internal reservoir to the surrounding tissue. A removal operation is not needed. Bioresorbable poly(L-lactic acid) fibers were prepared through melt spinning accompanied by a postpreparation drawing process. Novel expandable bioresorbable stents were developed from these fibers. Bioresorbable microspheres containing albumin were prepared and attached to the stents, to serve as a protein reservoir coating. The controlled release of albumin from the microsphere-loaded stent was studied. The fibers combine high strength and modulus, together with good ductility and flexibility. An increase in draw ratio increases the tensile strength and modulus and decreases the ultimate strain. The stents demonstrated excellent initial radial compression strength and good in vitro degradation resistivity, which makes them applicable for supporting blood vessels for at least 20 weeks. Microspheres bound to these stents enable effective protein loading, without reducing the stent's mechanical properties. The protein release from the microsphere-loaded stent occurs by diffusion, is determined mainly by the initial molecular weight of the bioresorbable polymer and its erosion rate, and is strongly affected by the microsphere structure.

Animals↗

PubMed2002

Suppurative complications of acute otitis media in the era of antibiotic resistance.

OBJECTIVE: To review our experience with suppurative complications of acute otitis media (AOM) in the era of antibiotic resistance, given a perceived increase in the number of such cases in recent years requiring surgical intervention. DESIGN: Retrospective review of pediatric patients presenting with suppurative complications of AOM from January 1993 to June 2000. SETTING: Academic tertiary care children's medical center. PATIENTS: A total of 90 pediatric patients, ranging in age from 3 months to 16 years (mean age, 45 months). RESULTS: A total of 104 suppurative complications of AOM occurred in 90 patients over the 7.5-year study period. The incidence of noncoalescent, coalescent, and total cases of mastoiditis and total number of suppurative complications all increased over the study period, with coalescent outpacing noncoalescent disease during the last 3 years of the study. A trend toward an increasing number of cases requiring surgical intervention was noted during the study period, corresponding to an increasing number of resistant Streptococcus pneumoniae isolates. Ten of 16 S pneumoniae isolates were resistant, primarily collected from younger children ranging in age from 4 to 24 months (mean age, 11.9 months). CONCLUSION: The rising incidence of resistant S pneumoniae corresponded to the increasing number of suppurative complications of AOM during the study period and seemed to contribute to more aggressive infectious processes requiring surgical intervention.

Adolescent↗

PubMed2002

Skull base cerebrospinal fluid fistulas: a comprehensive diagnostic algorithm.

OBJECTIVE: Our goal was to assess the efficacy of current diagnostic modalities in the management of skull base cerebrospinal fluid (CSF) fistulas. METHODS: We conducted a retrospective review of all patients presenting to our institution over the past 6 years with skull base CSF fistulas. RESULTS: Fifty-two patients were included in the study. beta2-Transferrin analysis of collected specimen was the most efficacious means of confirming a CSF leak. High-resolution computed tomography was the most informative radiographic study, yielding a sensitivity and an accuracy of 87%. Magnetic resonance cisternography, yielding a sensitivity and an accuracy of 78%, was instrumental in localizing the site of leak for a few cases but was most commonly corroborative. Using a graduated diagnostic approach, successful repair was attained in 88% of cases after 1 attempt and 98% after 1 or 2 attempts. CONCLUSION: For patients with skull base CSF fistulas, a graduated diagnostic approach with emphasis on confirmation of leak by beta2-transferrin analysis and precise localization by high-resolution computed tomography is both efficacious and cost effective.

Adolescent↗