[Interferon induction increased through chemical modification of a synthetic polyribonucleotide].

The alternating copolymer riboadenylic-ribouridylic acid gained asignificant increase in ability to stimulate interferon production (2-to 20-fold) and cellular resistance (100-to 10,000-fold) both in vitro and in vivo upon substitution of phosphate by thiophosphate groups. The resulting nucleotide analog was also 10 to 100 times less sensitive to degradation by pancreatic ribonuclease, as determined byresidual antiviral activity.

Biomechanical evaluation of fixation properties of fibrin glue for ventral incisional hernia repair.

INTRODUCTION: Use of adhesives for mesh fixation in hernia is increasing. There has been minimal study of mesh incorporation and interface strength with adhesive fixation for ventral hernia repair. The purpose of this study was to evaluate the fixation properties of fibrin glue as it compared to suture fixation of mesh in an onlay position. METHODS: Twenty-four mongrel pigs were divided into three study arms based on time points for biomechanical evaluation: 24 h (n = 8), 7 days (n = 8), and 14 days (n = 8). Initial procedures included placement of two 4 × 6 cm pieces of wide-pore polypropylene mesh in an onlay position. One was fixated with 4 ml of fibrin glue and the other with four interrupted 2-0 polypropylene sutures. The shear strength of fixation was evaluated using a uniaxial testing device along with histological evaluation. Maximum force was normalized by the width of the mesh. RESULTS: Mesh-tissue interface of glued and sutured specimens at 7 and 14 days did not fail in our testing configuration. Only at the 24-h time point the mesh detached from the tissue, and the sutured interface (10.4 N/cm) was significantly stronger than glued interface (4.9 N/cm, p = 0.004). Histopathologic and gross evaluations of the specimens revealed similar histologic features at all time points for both glued and sutured specimens. CONCLUSIONS: With mesh in the onlay position, fixation to the abdominal wall occurs quickly. Though sutures were stronger at 24 h, as early as 1 week, the strength of the fixation exceeded the tissue or the mesh strength in our testing configuration for both glue and suture groups. Fixation strength is independent of technique at the latter time points. There are potential clinical advantages to the exclusive use of fibrin glue for fixation including acute post-operative pain, chronic post-operative pain, and recurrence for ventral incisional hernia repair.

Risk factors associated with permanent access-site infections in chronic hemodialysis patients.

OBJECTIVE: To determine the epidemiological risk factors associated with permanent access-site (PAS) infection in a population of chronic hemodialysis patients. DESIGN: Retrospective cohort analysis. SETTING: Hemodialysis unit of a 400-bed Department of Veterans' Affairs hospital. RESULTS: A cohort of 94 males (1,316 patient months) was studied. Fifty-one PAS infections in 31 patients were observed. Six patients had two PAS infections, four patients had three infections, and two patients had four infections. Twenty-nine of the 31 patients with PAS infections were bacteremic at least once. Univariate analysis identified seven factors significantly associated with PAS infection in this population: location of PAS other than forearm, type of vascular access (polytetrafluoroethylene [PTFE] versus endogenous arteriovenous [AV] fistula), limited ambulatory status, residence in a nursing home, bacterial infection at a distant site, number of access-site revisions, and number of hospitalizations. In a logistic regression analysis, only graft type and number of PTFE graft revisions were associated independently with PAS infection. The odds ratio for PAS infection in PTFE grafts compared to endogenous AV fistula was 7.8; the odds ratio for PAS infection with each PTFE graft revision was 1.5. CONCLUSIONS: PAS infections were associated independently with the type of graft and the number of PTFE graft surgical revisions.

Transport of platelets in flowing blood.

Distribution and transport of platelets in flowing blood were studied experimentally using suspensions of washed red cells and fluorescent latex beads as platelet analogues. Distributions of the platelet analogues were obtained from stroboscopic epifluorescence photomicrographs of flow in 50-micron channels and from images of the cut cross sections of cryogenically frozen thin-walled 200-micron tubes. Concentration profiles of platelet analogues had a substantial near-wall excess for situations with a substantial hematocrit (greater than 10%) and a substantial wall shear rate (greater than 400 s-1). The viscosity of the suspending fluid was found to affect the size of the near-wall excess and its shear-dependent onset. Additionally, the shear-rate dependence of the near-wall excess did not occur with suspensions of hardened red cells. The excess extended a substantial distance from the wall in the 200-micron tubes and a portion of the profile could be fitted to an exponential curve. The random walk model that is used to describe enhanced platelet diffusion is envisioned as a walk (lateral platelet motion) caused by shear-induced collisions with red cells. A more comprehensive random walk model that includes biased collisions produces an effective lateral motion of convective nature in addition to a diffusional motion; it is used to explain the observed nonuniform distributions of platelet analogues.

A fluid dynamics study of the Trac catheter.

A fluid mechanics study of the Trac catheter was done using a 10 x scaled model. Wall pressure distributions and particle and dye flow visualization studies show that a primary vortex develops due to the spinning tip, and a secondary flow recirculates material along the chamber wall to the base of the chamber and back to the tip. Strong, nearly instantaneous mixing occurs throughout the vortex for speeds above 50,000 rpm scaled for the full-scale catheter. Close-contact pressure studies also show that wall pressures of the order of 0.4 MPa may be obtained for a full-scale catheter.

Rheophoresis--a broader concept of platelet dispersivity.

Interactions among red cells and platelets in flowing blood result in significant dispersive motions of the platelets, which are commonly modelled by an effective diffusion coefficient. This paper examines an additional platelet flux, termed rheophoresis, to model platelet motions due to the gradient of hematocrit. Rheophoretic effects occur near walls because geometric exclusion and fluid mechanical repulsion of red cells create a hematocrit gradient there. Models using rheophoretic flux show that platelet concentration near walls is elevated; such models provide a consistent interpretation of available experimental data. Estimates show the coefficients for traditional effective diffusivity and the rheophoretic diffusivity have similar magnitudes. The effects of rheophoresis on axial development of platelet concentration profiles and on surface deposition are discussed.

A freeze-capture method for the study of platelet-sized particle distributions.

A rapid freezing method was developed to study the distributions of fluorescent platelet-sized particles in flows of blood suspensions through thin-walled capillary tubes. Segments of frozen tubes were mounted in a refrigerated microtome on the stage of an epifluorescence microscope. Sections of tube were cut away, images of newly exposed cross-sections were recorded on video tape, and distances of the particles from the wall were measured from recorded images. The distance data were used to construct histograms that were proportional to the local concentration. Results indicated that this method is suitable for the study of the distribution of platelet-sized particles over a wide range of hematocrit, that the basic profile is reproducible to within 15%, and that the non-uniform profile is not a result of events at the tube entrance.

Complaint review procedures of state licensing boards.

In the highly litigious society in which we practice, situations all too frequently arise in which a dentist and a patient disagree. The disagreement may be as minor as a misunderstanding regarding fees charged for services rendered, or as substantial as that resulting from an injury secondary to dental treatment. Regardless of the exact nature of the incident, it nonetheless may result in the filing of a complaint by the aggrieved patient with the state board of dentistry against the treating clinician. This article explains the process leading to the resolution of a complaint.

Asymptomatic carriage of toxigenic Clostridium difficile by hospitalized patients.

Asymptomatic carriage of Clostridium difficile is common in hospitals, but the risk for transmission by carriers is unclear. In this point prevalence culture survey of asymptomatic hospitalized patients, 18 of 149 (12%) were carriers of toxigenic C. difficile. By comparison with C. difficile infection (CDI) patients, the prevalence of skin and/or environmental contamination was significantly lower in asymptomatic carriers (3/18, 17% versus 5/6, 83%; P = 0.007), but carriers outnumbered CDI patients in the hospital by a factor of 3 to 1. These data suggest that asymptomatic carriers have the potential to contribute to C. difficile transmission in hospitals.