Search PubMed⌕ Search

Biomedical subjects

Chris Hall

Publications and source records attributed to Chris Hall.

4 recordsLinked to original sources
PubMed2006

An essential role for zebrafish Fgfrl1 during gill cartilage development.

The vertebrate craniofacial skeleton develops via a complex process involving signaling cascades in all three germ layers. Fibroblast growth factor (FGF) signaling is essential for several steps in pharyngeal arch development. In zebrafish, Fgf3 and Fgf8 in the mesoderm and hindbrain have an early role to pattern the pouch endoderm, influencing craniofacial integrity. Endodermal FGF signaling is required for the differentiation and survival of postmigratory neural crest cells that form the pharyngeal skeleton. We identify a novel role for zebrafish Fgf receptor-like 1a (Fgfrl1a) that is indispensable during gill cartilage development. We show that depletion of Fgfrl1a is sufficient to abolish cartilage derivatives of the ceratobranchials. Using an Fgfrl1a-deficient model, we analyzed expression of genes critical for chondrogenesis in the different compartments of the developing pharyngeal arch. Fgfrl1a-depleted animals demonstrate typical neural crest specification and migration to populate the arch primordia as well as normal pouch segmentation. However, in the absence of Fgfrl1a, larvae fail to express the transcription factor glial cells missing 2 (gcm2), a gene necessary for cartilage and gill filament formation, in the ectodermal lining of the branchial arches. In addition, two transcription factors essential for chondrogenesis, sox9a and runx2b, fail to express within the mesenchymal condensations of the branchial arches. A duplicate zebrafish gene, fgfrl1b, has now been identified. We show that Fgfrl1b is also required for proper formation of all ventral cartilage elements and acts cooperatively with Fgfrl1a during gill cartilage formation.

Amino Acid Sequence↗
PubMed2006

Distraction osteogenesis in irradiated rabbit mandibles with adjunctive hyperbaric oxygen therapy.

PURPOSE: The purpose of this study was to evaluate the effect of hyperbaric oxygen therapy on bone regeneration during distraction of irradiated rabbit mandibles. MATERIALS AND METHODS: Twenty New Zealand white rabbits were randomly sub-divided into 4 groups. Group 1 served as control, group 2 received preoperative radiation therapy, group 3 received pre- and postoperative hyperbaric oxygen (HBO) therapy, and group 4 received preoperative radiation therapy and pre- and postoperative HBO therapy. All rabbits underwent a corticotomy of the left body of the mandible after placement of a distraction device. Distraction, at a rate of 1 mm/day and a rhythm of 1 turn/day, began after a 3-day latency period for 14 days. Thirty days after completion of the distraction protocol, the animals were euthanized, and histomorphometric and radiographic data of the distraction segments were obtained. RESULTS: Histomorphometric analysis of new bone fill was greatest in the non-irradiated groups compared to groups receiving radiation therapy, regardless of HBO therapy (P = .03). Pre-corticotomy bone density measurements showed a significant increase in bone density over time (P = .0007). This resulted in a significant relationship between HBO therapy, radiation therapy, and time (P = .0050). CONCLUSIONS: The results of the study support the use of HBO therapy during distraction osteogenesis. Any additional therapeutic benefit of HBO therapy in irradiated bone would require additional investigation.

Analysis of Variance↗
PubMed2005

Where has all the chlamydia come from? The clinical impact of the introduction of an improved chlamydia test.

At a time of increasing demands on genitourinary (GU) medicine clinics, the introduction of a new nucleic acid test to a GU medicine clinic has the potential to increase the workload due to increased numbers of patients being identified with chlamydia, and a consequent increase in partner notification. In one clinic setting, we found a doubling in the rates of chlamydial infection following the introduction of a new test, but a concomitant reduction in the rates of non-specific genital infection. The improved specificity of the test has made counselling of patients with chlamydia and non-specific infection much easier. An audit has shown that contact-tracing outcomes are significantly better in patients who are diagnosed with chlamydia.

Adolescent↗