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Biomedical subjects

David Kent

Publications and source records attributed to David Kent.

6 recordsLinked to original sources
PubMed2006

High-resolution video monitoring of hematopoietic stem cells cultured in single-cell arrays identifies new features of self-renewal.

To search for new indicators of self-renewing hematopoietic stem cells (HSCs), highly purified populations were isolated from adult mouse marrow, micromanipulated into a specially designed microscopic array, and cultured for 4 days in 300 ng/ml Steel factor, 20 ng/ml IL-11, and 1 ng/ml flt3-ligand. During this period, each cell and its progeny were imaged at 3-min intervals by using digital time-lapse photography. Individual clones were then harvested and assayed for HSCs in mice by using a 4-month multilineage repopulation endpoint (>1% contribution to lymphoid and myeloid lineages). In a first experiment, 6 of 14 initial cells (43%) and 17 of 61 clones (28%) had HSC activity, demonstrating that HSC self-renewal divisions had occurred in vitro. Characteristics associated with HSC activity included longer cell-cycle times and the absence of uropodia on a majority of cells within the clone during the final 12 h of culture. Combining these criteria maximized the distinction of clones with HSC activity from those without and identified a subset of 27 of the 61 clones. These 27 clones included all 17 clones that had HSC activity; a detection efficiency of 63% (2.26 times more frequently than in the original group). The utility of these characteristics for discriminating HSC-containing clones was confirmed in two independent experiments where all HSC-containing clones were identified at a similar 2- to 3-fold-greater efficiency. These studies illustrate the potential of this monitoring system to detect new features of proliferating HSCs that are predictive of self-renewal divisions.

Animals↗
PubMed2006

Roadkill attenuates Hedgehog responses through degradation of Cubitus interruptus.

The final step in Hedgehog (Hh) signal transduction is post-translational regulation of the transcription factor, Cubitus interruptus (Ci). Ci resides in the cytoplasm in a latent form, where Hh regulates its processing into a transcriptional repressor or its nuclear access as a transcriptional activator. Levels of latent Ci are controlled by degradation, with different pathways activated in response to different levels of Hh. Here, we describe the roadkill (rdx) gene, which is expressed in response to Hh. The Rdx protein belongs to a conserved family of proteins that serve as substrate adaptors for Cullin3-mediated ubiquitylation. Overexpression of rdx reduced Ci levels and decreased both transcriptional activation and repression mediated by Ci. Loss of rdx allowed excessive accumulation of Ci. rdx manipulation in the eye revealed a novel role for Hh in the organization and survival of pigment and cone cells. These studies identify rdx as a limiting factor in a feedback loop that attenuates Hh responses through reducing levels of Ci. The existence of human orthologs for Rdx raises the possibility that this novel feedback loop also modulates Hh responses in humans.

Alleles↗
PubMed2003

Choroidal neovascularization: a wound healing perspective.

The process of submacular angiogenesis seen in association with a variety of chorioretinal disorders is termed choroidal neovascularization (CNV). It invariably results in significant and permanent vision loss arising from the development of scar tissue formation. At the cellular level, CNV appears to be a component of several key processes that can be broadly referred to as wound healing or tissue repair. Wound healing involves a coordinated cascade of cellular events driven, in the main, by the production of cytokines and which are interpreted by target cells in the context of a continually evolving extracellular matrix (ECM). A similar process occurs in what is clinically termed CNV. Angiogenesis is just one component of this wound healing process. Other key components include inflammation, matrix deposition and remodelling. Thus, in the context of a tissue repair response, viable treatment options for CNV could include therapies other than those that are currently directed at the angiogenic component of this process.

Choroidal Neovascularization↗
PubMed2002

Initial experience using the transconjunctival sutureless vitrectomy system for vitreoretinal surgery.

OBJECTIVE: To describe the initial experience and to evaluate the safety and feasibility of using the 25-gauge Transconjunctival Sutureless Vitrectomy System (TSV) for a variety of vitreoretinal procedures. DESIGN: Retrospective review of a consecutive interventional case series. PARTICIPANTS: Thirty-five eyes of 33 patients, including cases of idiopathic epiretinal membrane (12 cases), retinal detachment (6 cases), macular hole (5 cases), branch retinal vein occlusion (4 cases), retinopathy of prematurity (4 cases), persistent diabetic macular edema (1 case), diabetic vitreous hemorrhage (1 case), retained lens material after cataract extraction (1 case), and Norrie disease (1 case). INTERVENTION: All patients underwent surgery using the 25-gauge TSV. MAIN OUTCOME MEASURES: Intraocular pressure, visual acuity, and postoperative complications. RESULTS: The median preoperative intraocular pressure was 16 mmHg (range, 10-21 mmHg), whereas the median intraocular pressure on the first postoperative day was 12 mmHg (range, 6-28 mmHg). The median intraocular pressure at 1 week and 1 month were both 16 mmHg (range, 10-30 mmHg). Overall, the median preoperative visual acuity was 20/100 (range, 20/30 to hand motions), and the median postoperative visual acuity after a mean follow-up of 14 weeks (range, 1-60 weeks) was 20/60 (range, 20/20-20/150). One eye developed a postoperative retinal detachment. CONCLUSIONS: The 25-gauge TSV seems to be practical and safe for a variety of vitreoretinal procedures. The concept of transconjunctival surgery has the potential to increase the efficiency of a variety of vitreoretinal surgeries and possibly hasten the postoperative recovery and outcomes in several conditions by simplifying the surgical procedure; minimizing surgically induced trauma; and decreasing the convalescence period, the operating time, and the postoperative inflammatory response.

Adult↗
PubMedDate not supplied

Edible mushroom (Agaricus bisporus) lectin inhibits human retinal pigment epithelial cell proliferation in vitro.

The retinal pigment epithelium (RPE) plays a major role in the development of the anomalous retinal scarring response termed proliferative vitreoretinopathy. The present study was undertaken to investigate whether agaricus bisporus lectin inhibited human RPE proliferation in vitro. Fluorescein isothiocyanate-labeled agaricus bisporus lectin was used to study binding of lectin to cultured human RPE. The effect of a 24-hour exposure of agaricus bisporus lectin on RPE proliferation was measured using (methyl-3H)-thymidine incorporation into DNA. Toxicity studies were assessed using morphologic evaluation, trypan blue exclusion, and a cell viability assay. Agaricus bisporus lectin bound to RPE cells and was inhibited by preincubation of lectin with asialomucin. Agaricus bisporus lectin caused a dose-dependent inhibition of RPE proliferation (one-way ANOVA, F = 94.470, p < 0.001) that was partially reversible on removal of the lectin. Compared with controls, cells remained viable and no morphological changes or trypan blue staining was noted in RPE exposed to agaricus bisporus lectin. Human RPE binds agaricus bisporus lectin and inhibits proliferation without apparent cytotoxicity. It therefore merits consideration as a potential antiproliferative agent in the prevention and treatment of proliferative vitreoretinopathy and other nonocular anomalous wound healing processes.

Cell Division↗