Browsing by Subject "Guinea Pigs"

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    3D-Printed Microneedles Create Precise Perforations in Human Round Window Membrane in Situ.
    (Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 2020-02) Chiang, Harry; Yu, Michelle; Aksit, Aykut; Wang, Wenbin; Stern-Shavit, Sagit; Kysar, Jeffrey W; Lalwani, Anil K

    Hypothesis

    Three-dimensional (3D)-printed microneedles can create precise holes on the scale of micrometers in the human round window membrane (HRWM).

    Background

    An intact round window membrane is a barrier to delivery of therapeutic and diagnostic agents into the inner ear. Microperforation of the guinea pig round window membrane has been shown to overcome this barrier by enhancing diffusion 35-fold. In humans, the challenge is to design a microneedle that can precisely perforate the thicker HRWM without damage.

    Methods

    Based on the thickness and mechanical properties of the HRWM, two microneedle designs were 3D-printed to perforate the HRWM from fresh frozen temporal bones in situ (n = 18 total perforations), simultaneously measuring force and displacement. Perforations were analyzed using confocal microscopy; microneedles were examined for deformity using scanning electron microscopy.

    Results

    HRWM thickness was determined to be 60.1 ± 14.6 (SD) μm. Microneedles separated the collagen fibers and created slit-shaped perforations with the major axis equal to the microneedle shaft diameter. Microneedles needed to be displaced only minimally after making initial contact with the RWM to create a complete perforation, thus avoiding damage to intracochlear structures. The microneedles were durable and intact after use.

    Conclusion

    3D-printed microneedles can create precise perforations in the HRWM without damaging intracochlear structures. As such, they have many potential applications ranging from aspiration of cochlear fluids using a lumenized needle for diagnosis and creating portals for therapeutic delivery into the inner ear.
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    ItemOpen Access
    Anatomical and Functional Consequences of Microneedle Perforation of Round Window Membrane.
    (Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 2020-02) Yu, Michelle; Arteaga, Daniel N; Aksit, Aykut; Chiang, Harry; Olson, Elizabeth S; Kysar, Jeffrey W; Lalwani, Anil K

    Hypothesis

    Microneedles can create microperforations in the round window membrane (RWM) without causing anatomic or physiologic damage.

    Background

    Reliable delivery of agents into the inner ear for therapeutic and diagnostic purposes remains a challenge. Our novel approach employs microneedles to facilitate intracochlear access via the RWM. This study investigates the anatomical and functional consequences of microneedle perforations in guinea pig RWMs in vivo.

    Methods

    Single three-dimensional-printed, 100 μm diameter microneedles were used to perforate the guinea pig RWM via the postauricular sulcus. Hearing was assessed both before and after microneedle perforation using compound action potential and distortion product otoacoustic emissions. Confocal microscopy was used ex vivo to examine harvested RWMs, measuring the size, shape, and location of perforations and documenting healing at 0 hours (n = 7), 24 hours (n = 6), 48 hours (n = 6), and 1 week (n = 6).

    Results

    Microneedles create precise and accurate perforations measuring 93.1 ± 29.0 μm by 34.5 ± 16.8 μm and produce a high-frequency threshold shift that disappears after 24 hours. Examination of perforations over time demonstrates healing progression over 24 to 48 hours and complete perforation closure by 1 week.

    Conclusion

    Microneedles can create a temporary microperforation in the RWM without causing significant anatomic or physiologic dysfunction. Microneedles have the potential to mediate safe and effective intracochlear access for diagnosis and treatment of inner ear disease.
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    Cartilage mechanics in the guinea pig model of osteoarthritis studied with an osmotic loading method.
    (Osteoarthritis and cartilage, 2004-05) Flahiff, Charlene M; Kraus, Virginia B; Huebner, Janet L; Setton, Lori A
    To determine the material properties of articular cartilage in the Hartley guinea pig model of spontaneous osteoarthritis.Cartilage-bone samples from the medial femoral condyle and tibial plateau of 12 month-old guinea pig knees were subjected to osmotic loading. Site-matched swelling strains and fixed charge density values were used in a triphasic theoretical model for cartilage swelling to determine the modulus of the cartilage solid matrix. The degree of cartilage degeneration was assessed in adjacent tissue sections using a semi-quantitative histological grading scheme.Decreased values for both moduli and surface zone fixed charge density were associated with increasing grades of cartilage degeneration. Decreases in moduli reflect damage to the collagen matrix, which give rise to greater swelling strains.Histological evidence of cartilage degeneration was associated with impaired cartilage mechanics in the aging Hartley guinea pig.
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    Comparative immunogenicity of HIV-1 clade C envelope proteins for prime/boost studies.
    (PLoS One, 2010-08-11) Smith, Douglas H; Winters-Digiacinto, Peggy; Mitiku, Misrach; O'Rourke, Sara; Sinangil, Faruk; Wrin, Terri; Montefiori, David C; Berman, Phillip W
    BACKGROUND: Previous clinical efficacy trials failed to support the continued development of recombinant gp120 (rgp120) as a candidate HIV vaccine. However, the recent RV144 HIV vaccine trial in Thailand showed that a prime/boost immunization strategy involving priming with canarypox vCP1521 followed by boosting with rgp120 could provide significant, although modest, protection from HIV infection. Based on these results, there is renewed interest in the development of rgp120 based antigens for follow up vaccine trials, where this immunization approach can be applied to other cohorts at high risk for HIV infection. Of particular interest are cohorts in Africa, India, and China that are infected with clade C viruses. METHODOLOGY/PRINCIPAL FINDINGS: A panel of 10 clade C rgp120 envelope proteins was expressed in 293 cells, purified by immunoaffinity chromatography, and used to immunize guinea pigs. The resulting sera were collected and analyzed in checkerboard experiments for rgp120 binding, V3 peptide binding, and CD4 blocking activity. Virus neutralization studies were carried out with two different assays and two different panels of clade C viruses. A high degree of cross reactivity against clade C and clade B viruses and viral proteins was observed. Most, but not all of the immunogens tested elicited antibodies that neutralized tier 1 clade B viruses, and some sera neutralized multiple clade C viruses. Immunization with rgp120 from the CN97001 strain of HIV appeared to elicit higher cross neutralizing antibody titers than the other antigens tested. CONCLUSIONS/SIGNIFICANCE: While all of the clade C antigens tested were immunogenic, some were more effective than others in eliciting virus neutralizing antibodies. Neutralization titers did not correlate with rgp120 binding, V3 peptide binding, or CD4 blocking activity. CN97001 rgp120 elicited the highest level of neutralizing antibodies, and should be considered for further HIV vaccine development studies.
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    Novel hybrid action of GABA mediates inhibitory feedback in the mammalian retina.
    (PLoS biology, 2019-04) Grove, James CR; Hirano, Arlene A; de Los Santos, Janira; McHugh, Cyrus F; Purohit, Shashvat; Field, Greg D; Brecha, Nicholas C; Barnes, Steven
    The stream of visual information sent from photoreceptors to second-order bipolar cells is intercepted by laterally interacting horizontal cells that generate feedback to optimize and improve the efficiency of signal transmission. The mechanisms underlying the regulation of graded photoreceptor synaptic output in this nonspiking network have remained elusive. Here, we analyze with patch clamp recording the novel mechanisms by which horizontal cells control pH in the synaptic cleft to modulate photoreceptor neurotransmitter release. First, we show that mammalian horizontal cells respond to their own GABA release and that the results of this autaptic action affect cone voltage-gated Ca2+ channel (CaV channel) gating through changes in pH. As a proof-of-principle, we demonstrate that chemogenetic manipulation of horizontal cells with exogenous anion channel expression mimics GABA-mediated cone CaV channel inhibition. Activation of these GABA receptor anion channels can depolarize horizontal cells and increase cleft acidity via Na+/H+ exchanger (NHE) proton extrusion, which results in inhibition of cone CaV channels. This action is effectively counteracted when horizontal cells are sufficiently hyperpolarized by increased GABA receptor (GABAR)-mediated HCO3- efflux, alkalinizing the cleft and disinhibiting cone CaV channels. This demonstrates how hybrid actions of GABA operate in parallel to effect voltage-dependent pH changes, a novel mechanism for regulating synaptic output.