Boundary layer drug delivery using a helical catheter

BACKGROUND: A catheter-based approach for local endovascular drug delivery has been developed. The catheter is deployed percutaneously, while the end of the catheter is in the form of a helix that is placed just proximal to the vascular site to be treated. The helices are in contact with the vessel wall. A number of small holes is drilled in the coils of the catheter through which drug is infused, so that the infused drug remains within the blood fluid 'boundary layer' adjacent to the vessel wall. This approach is expected to be highly efficient for administration of antithrombotic and antiproliferative agents that target processes leading to vascular occlusion, heart attacks, and strokes. METHODS: The helical catheter was qualitatively evaluated using optical dye density measurements of Evans blue dye infused using an in vitro steady flow system under a physiologic range of conditions. To further demonstrate the efficiency of the technique, its capacity to inhibit thrombosis was evaluated in a baboon thrombosis model. The catheter was inserted into a femoral arteriovenous shunt (blood flow rate = 100 ml/min) and placed proximal to a segment of highly thrombogenic Dacron vascular graft (4.0 mm i.d.). Integrelin (an inhibitor of platelet glycoprotein IIb/IIIa; doses: 0.25-1.0 microg/min) and hirudin (an antithrombin; doses: 10-100 microg/min) were used to inhibit thrombus formation. RESULTS: Experimental flow visualization studies demonstrated that high concentrations of the infused Evans blue dye were retained near the vessel wall. In the animal experiments, platelet deposition on the Dacron graft surface was reduced by 82-97% (Integrelin) and 68-92% (hirudin) over 1-2 h of blood exposure. The local antithrombotic effects produced were found to be 200-fold and 30-fold more efficient than systemic administration of the same agents. CONCLUSIONS: Local drug infusion using the helical catheter approach can achieve high drug concentration levels at target sites, may avoid systemic effects, and can reduce cost of therapy by reducing total drug requirements.     

Pathogenic mechanisms in the rheumatoid nodule: comparison of proinflammatory cytokine production and cell adhesion molecule expression in rheumatoid nodules and synovial membranes from the same patient

OBJECTIVE: To investigate the production of proinflammatory cytokines and expression of cell adhesion molecules in the rheumatoid nodule. METHODS: Cytokine content (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], and IL-1 receptor antagonist [IL-1Ra]), at the messenger RNA (mRNA) and protein levels, and cell adhesion molecule expression were studied in 16 rheumatoid nodules and 6 synovial membranes. RESULTS: Macrophages in the rheumatoid nodules contained TNFalpha, IL-1beta, and IL-1Ra mRNA and protein, particularly in perivascular cells of the stroma and in the palisading layer. All cell adhesion molecules studied were expressed in both the rheumatoid nodules and synovial membranes, with increased expression of E-selectin in the rheumatoid nodule compared with the synovial membrane, and with the absence of vascular cell adhesion molecule 1 expression on cells of the palisading layer in the rheumatoid nodule. CONCLUSION: The presence of similar proinflammatory cytokines and cell adhesion molecules in the rheumatoid nodule and synovial membrane suggests that similar pathogenic processes result in the chronic inflammation and tissue destruction in these lesions.     

Visualizing the dynamics of T cell activation: intracellular adhesion molecule 1 migrates rapidly to the T cell/B cell interface and acts to sustain calcium levels

T cell recognition typically involves both the engagement of a specific T cell receptor with a peptide/major histocompatibility complex (MHC) and a number of accessory interactions. One of the most important interactions is between the integrin lymphocyte function-associated antigen 1 (LFA-1) on the T cell and intracellular adhesion molecule 1 (ICAM-1) on an antigen-presenting cell. By using fluorescence video microscopy and an ICAM-1 fused to a green fluorescent protein, we find that the elevation of intracellular calcium in the T cell that is characteristic of activation is followed almost immediately by the rapid accumulation of ICAM-1 on a B cell at a tight interface between the two cells. This increased density of ICAM-1 correlates with the sustained elevation of intracellular calcium in the T cell, known to be critical for activation. The use of peptide/MHC complexes and ICAM-1 on a supported lipid bilayer to stimulate T cells also indicates a major role for ICAM-1/LFA-1 in T cell activation but, surprisingly, not for adhesion, as even in the absence of ICAM-1 the morphological changes and adhesive characteristics of an activated T cell are seen in this system. We suggest that T cell antigen receptor-mediated recognition of a very small number of MHC/peptide complexes could trigger LFA-1/ICAM-1 clustering and avidity regulation, thus amplifying and stabilizing the production of second messengers.     

cDNA cloning and functional characterization of the mouse Ca2+-gated K+ channel, mIK1. Roles in regulatory volume decrease and erythroid differentiation

We have cloned from murine erythroleukemia (MEL) cells, thymus, and stomach the cDNA encoding the Ca2+-gated K+ (KCa) channel, mIK1, the mouse homolog of hIK1 (Ishii, T. M., Silvia, C., Hirschberg, B., Bond, C. T., Adelman, J. P., and Maylie, J. (1997) Proc. Natl. Acad. Sci.(U. S. A. 94, 11651-11656). mIK1 mRNA was detected at varied levels in many tissue types. mIK1 KCa channel activity expressed in Xenopus oocytes closely resembled the Kca of red cells (Gardos channel) and MEL cells in its single channel conductance, lack of voltage-sensitivity of activation, inward rectification, and Ca2+ concentration dependence. mIK1 also resembled the erythroid channel in its pharmacological properties, mediating whole cell and unitary currents sensitive to low nM concentrations of both clotrimazole (CLT) and its des-imidazolyl metabolite, 2-chlorophenyl-bisphenyl-methanol, and to low nM concentrations of iodocharybdotoxin. Whereas control oocytes subjected to hypotonic swelling remained swollen, mIK1 expression conferred on oocytes a novel, Ca2+-dependent, CLT-sensitive regulatory volume decrease response. Hypotonic swelling of voltage-clamped mIK1-expressing oocytes increased outward currents that were Ca2+-dependent, CLT-sensitive, and reversed near the K+ equilibrium potential. mIK1 mRNA levels in ES cells increased steadily during erythroid differentiation in culture, in contrast to other KCa mRNAs examined. Low nanomolar concentrations of CLT inhibited proliferation and erythroid differentiation of peripheral blood stem cells in liquid culture.     

CCR5/delta(ccr5) heterozygosity: a selective pressure for the syncytium-inducing human immunodeficiency virus type 1 phenotype. NIAID AIDS Clinical Trials Group Protocol 241 Virology Team

Mechanisms underlying the delay in dominance of syncytium-inducing (SI) phenotype HIV-1 (human immunodeficiency virus type 1) in vivo are unknown. Both random mutational events and selective pressures operative only late in the disease process have been suggested to underlie the shift from CCR5 to alternative coreceptor usage. Among the moderately advanced patients who entered AIDS Clinical Trials Group protocol 241, SI viral phenotype was more common among CCRS/delta(ccr5) heterozygotes (7/7, 100%) than among CCR5/CCR5 homozygotes (29/88, 33%; P < .001, Fisher's exact test). Other characteristics did not differ at study entry by CCR5 genotype, including median CD4 cell counts, plasma RNA levels, and infectious HIV-1 titers in circulating cells. These data indicate that CCR5/delta(ccr5) heterozygosity, which decreases cell-surface levels of CCR5 available to serve as an HIV-1 entry coreceptor, is a selective pressure for evolution of T cell line-tropic viruses that use an alternative coreceptor.     

Mismatch negativity and auditory sensory memory evaluation: a new faster paradigm

A new faster paradigm to measure the duration of auditory sensory memory, as indexed by mismatch negativity (MMN) suppression to stimuli presented at increasing inter-stimulus intervals (ISI), is proposed. Trains of three stimuli were delivered at very short ISI (300 ms). The inter-train interval varied according to the memory probe interval (MPI) tested. Trains started randomly with a deviant or standard stimulus (50% each), with their event-related brain potentials subtracted to obtain the MMN. The new paradigm provided MMNs identical to the conventional one at MPIs of 0.4 and 4.0 s in young subjects, and revealed MMN suppression when the MPI was increased to 5.0 s in older subjects. The new paradigm estimates auditory sensory memory duration in one-third the time of conventional MMN.     

Biomechanical study of sternal closure using rigid fixation techniques in human cadavers

BACKGROUND: We believe rigid plate fixation may be superior to wire fixation in sternal closure, as rigid fixation used in the craniofacial skeleton has shown greater stability, lower postoperative pain, and accelerated bone healing. We hypothesize that sterna fixed with titanium plates are more stable mechanically than sterna fixed with wires. METHODS: The sterna from human cadavers were used in this two-phased study. Phase I compared wires to four-hole titanium straight plates. Phase II compared wires to four-hole titanium custom H plates. The sterna were tested biomechanically using all fixation methods. RESULTS: Phase I showed no statistically significant difference in the stiffness or lateral displacement between the wired and straight plated sterna. Phase II showed a statistically significant greater stiffness (p < 0.05) and less lateral displacement (p < 0.05) in the custom plated sterna over the wired sterna. CONCLUSIONS: Our results showed that custom titanium H plates were superior to wire fixation. Furthermore, our results established the importance of plate configuration in sternal fixation. Our study may have beneficial clinical implications, as decreased motion at the sternotomy site could mean less postoperative pain, a decreased incidence of infection, and accelerated bone healing.     

Ligand-induced endocytosis of the asialoglycoprotein receptor: evidence for heterogeneity in subunit oligomerization

Prostate cancer is the most common form of cancer in older men and the major cause of death from prostate cancer is metastatic disease. The matrix metalloproteinases (MMPs) play a significant role in the growth, invasion and metastasis of many tumors, including those of the prostate. We previously demonstrated that doxycycline, a synthetic tetracycline, inhibits MMPs and cell proliferation and induces apoptosis in several cancer cell lines. We also demonstrated that in an in vivo model of metastatic breast cancer in athymic mice doxycycline inhibits tumor size and regrowth after resection. In the present study, gelatinolytic activity in the human prostate cancer cell line, LNCaP, was suppressed and significant inhibition of cell growth occurred after exposure to 5 or 10 microg/ml of doxycycline, while cell growth was normal in untreated cells. Radioisotope incorporation into proteins was reduced by doxycycline. DNA fragmentation, consistent with apoptosis, was demonstrated in cells treated with doxycycline. These data suggest that doxycycline may have potential utility in the management of prostate cancer.