Search PubMed⌕ Search

Biomedical subjects

L Nelsen

Publications and source records attributed to L Nelsen.

9 recordsLinked to original sources
PubMed1999

Changing roles: the radiologist in management.

RATIONALE AND OBJECTIVES: Radiologists have rarely had direct administrative control of the hospital departments in which they practice. Several years ago, the administration of the medical school at the University of Texas Health Science Center at San Antonio and its county-owned principal teaching hospital agreed to integrate the physician and administrative management of the radiology department in an attempt to improve operations and reduce expenses. This integration is a pilot plan that will eventually be extended to most departments. MATERIALS AND METHODS: The authors have collected data that measure department function for the seven quarters of physician management and compared these data with those of the previous four quarters prior to physician management. RESULTS: There are substantial increases in department activity, together with reductions in expenses and waiting time for procedures. These changes have occurred while overall hospital activity has decreased. Bench-marking studies show favorable comparison with comparable radiology departments. CONCLUSION: Radiologists can have an important effect on department operations when given the responsibility and authority for managing these affairs.

Academic Medical Centers↗
PubMed1998

Persistent activation of mitogen-activated protein kinases p42 and p44 and ets-2 phosphorylation in response to colony-stimulating factor 1/c-fms signaling.

An antibody that specifically recognized phosphothreonine 72 in ets-2 was used to determine the phosphorylation status of endogenous ets-2 in response to colony-stimulating factor 1 (CSF-1)/c-fms signaling. Phosphorylation of ets-2 was detected in primary macrophages, cells that normally express c-fms, and in fibroblasts engineered to express human c-fms. In the former cells, ets-2 was a CSF-1 immediate-early response gene, and phosphorylated ets-2 was detected after 2 to 4 h, coincident with expression of ets-2 protein. In fibroblasts, ets-2 was constitutively expressed and rapidly became phosphorylated in response to CSF-1. In both cell systems, ets-2 phosphorylation was persistent, with maximal phosphorylation detected 8 to 24 h after CSF-1 stimulation, and was correlated with activation of the CSF-1 target urokinase plasminogen activator (uPA) gene. Kinase assays that used recombinant ets-2 protein as a substrate demonstrated that mitogen-activated protein (MAP) kinases p42 and p44 were constitutively activated in both cell types in response to CSF-1. Immune depletion experiments and the use of the MAP kinase kinase inhibitor PD98059 indicate that these two MAP kinases are the major ets-2 kinases activated in response to CSF-1/c-fms signaling. In the macrophage cell line RAW264, conditional expression of raf kinase induced ets-2 expression and phosphorylation, as well as uPA mRNA expression. Transient assays mapped ets/AP-1 response elements as critical for basal and CSF-1-stimulated uPA reporter gene activity. These results indicate that persistent activation of the raf/MAP kinase pathway by CSF-1 is necessary for both ets-2 expression and posttranslational activation in macrophages.

3T3 Cells↗
PubMed1976

Use of synthetic polypeptides in the preparation of biodegradable delivery vehicles for narcotic antagonists.

Synthetic polypeptides consisting of copolymers of glutamic acid and leucine have been shown to be useful materials for the fabrication of practical, biodegradable delivery vehicles for narcotic antagonists. Model delivery vehicles in film form were prepared from copolymers containing 10 mole percent to 40 mole percent glutamic acid, and loaded with 10% to 40% naltrexone by weight. The naltrexone was found to be released by diffusion, exhibiting diffusion coefficients that varied as a function of the glutamic acid content and the initial naltrexone loading. A wide range in diffusion coefficients were achieved (0.31 x 10-7 cm2/hr to 120 x 10-7 cm2/hr), leading to release rates within practical ranges of interest for meeting the program goals. We have demonstrated that the polypeptides can be fabricated into dosage forms that are amenable to administration by trochar. For example, rods 0.4 mm to 0.8 mm in diameter containing as much as 40% naltrexone by weight were extruded using a simple compression mold and die arrangement. An in vitro evaluation of the rods showed that antagonist is released by diffusion at a continuously decreasing rate, a behavior similar to that observed with the film devices that were, nonetheless, capable of blocking an AD80 challenge of morphene sulfate in mice for more than 30 days. One of the most promising delivery vehicles that we have developed to date consists of a polypeptide tube filled with a naltrexone/polypeptide core. Preliminary experiments have shown that these devices may be capable of administering high, constant rates of release for prolonged periods of time. Additional work, however, is required to develop techniques for the preparation of reproducible delivery vehicles.

Animals↗
PubMed1975

Use of synthetic polypeptides in the preparation of biodegradable delivery vehicles for narcotic antagonists.

Synthetic polypeptides consisting of copolymers of glutamic acid and leucine have been shown to be useful materials for the fabrication of practical, biodegradable delivery vehicles for narcotic antagonists. Model delivery vehicles in film form were prepared from copolymers containing 10 mole percent to 40 mole percent glutamic acid, and loaded with 10% to 40% naltrexone by weight. The naltrexone was found to be released by diffusion, exhibiting diffusion coefficients that varied as a function of the glutamic acid content and the initial naltrexone loading. A wide range in diffusion coefficients were achieved (0.31 x 10(-7) cm2/hr to 120 x 10(-7) cm2/hr), leading to release rates within practical ranges of interest for meeting the program goals. We have demonstrated that the polypeptides can be fabricated into dosage forms that are amenable to administration by trochar. For example, rods 0.4 mm to 0.8 mm in diameter containing as much as 40% naltrexone by weight were extruded using a simple compression mold and die arrangement. An in vitro evaluation of the rods showed that antagonist is released by diffusion at a continuously decreasing rate, a behavior similar to that observed with the film devices that were, nonetheless, capable of blocking an AD80 challenge of morphine sulfate in mice for more than 30 days. One of the most promising delivery vehicles that we have developed to date consists of a polypeptide tube filled with a naltrexone/polypeptide core. Preliminary experiments have shown that these devices may be capable of administering high, constant rates of release for prolonged periods of time. Additional work, however, is required to develop techniques for the preparation of reproducible delivery vehicles.

Animals↗