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Biomedical subjects

A L David

Publications and source records attributed to A L David.

6 recordsLinked to original sources
PubMed2006

Ultrasound-guided injection and occlusion of the trachea in fetal sheep.

OBJECTIVES: To access the fetal sheep trachea by ultrasound-guided transthoracic injection in order to deliver gene therapy vectors or occlude the trachea with a detachable balloon. METHODS: Fetal sheep were operated on at a mean gestational age of 102 (range, 81-116) days (term = 145 days). Under ultrasound guidance, either a 20-G spinal (for vector delivery) or a 16-G Kellett (for placement of an occlusive balloon) needle was inserted via the fetal thorax into the fetal trachea. RESULTS: Using the 20-G spinal needle the trachea was accessed successfully in 33/36 fetuses, with 97% survival. Failure to inject was related to fetal position and gestational age. Blood vessel damage causing significant morbidity occurred in two fetuses (6%). Tracheal occlusion was achieved by puncturing the trachea with the 16-G needle and advancing an endoluminal balloon in three out of five attempts in a mean time of 17 (range, 16-19) min, with 100% survival. In one case, the balloon became sited within the accessory lobe bronchus and was not inflated. At postmortem examination 21 days later, all balloons remained inflated and occluded the trachea, and the lung-to-body weight ratio and airways morphometric indices were consistent with relative pulmonary hyperplasia in the obstructed lungs. CONCLUSIONS: Ultrasound-guided transthoracic tracheal puncture is a reliable technique in fetal sheep, with low morbidity and mortality. Using this technique, a detachable endotracheal balloon can be placed to provoke pulmonary growth. Advances in needle design and balloon size may improve the success rate.

Animals↗
PubMed2006

Clinically applicable procedure for gene delivery to fetal gut by ultrasound-guided gastric injection: toward prenatal prevention of early-onset intestinal diseases.

Targeting gene therapy vectors to the fetal intestinal tract could provide a novel means toward prevention of the early postnatal intestinal pathology of cystic fibrosis and other conditions, such as congenital enteropathy, that cause intestinal failure. Among these conditions, cystic fibrosis is by far the most common lethal genetic disease. It is caused by a functional absence or deficiency of the cystic fibrosis transmembrane conductance regulator and manifests in the gut as meconium ileus. Prenatal treatment of genetic disease may avoid early-onset tissue damage and immune sensitization, and may target cells that are less accessible in the adult. We investigated gene transfer to the fetal gut, using a minimally invasive injection technique. First-generation replication-deficient adenoviral vectors encoding the beta-galactosidase gene and transduction-enhancing agents were injected into the stomach of early-gestation fetal sheep (n = 8, 60 days of gestation; term, 145 days) under ultrasound guidance. Reporter gene expression was observed 2 days after injection in the villi of the gastrointestinal epithelia after 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining and beta-galactosidase immunohistochemistry of fetal tissues. Expression of beta-galactosidase, as measured by enzyme-linked immunosorbent assay, was enhanced after pretreatment of the fetal gut with sodium caprate, which opens tight junctions, and after adenovirus complexation with DEAE-dextran, which confers a positive charge to the virus. Instillation of the fluorocarbon perflubron after virus delivery resulted in tissue transduction from the fetal stomach to the colon. Using a clinically relevant technique, we have demonstrated widespread gene transfer to the fetal gastrointestinal epithelia.

Adenoviridae↗
PubMed2005

Gene therapy progress and prospects: fetal gene therapy--first proofs of concept--some adverse effects.

Somatic gene delivery in utero is a novel approach to gene therapy for genetic disease based on the hypothesis that prenatal intervention may avoid the development of severe manifestations of early-onset disease, allow targeting of otherwise inaccessible tissues including expanding stem cell populations, induce tolerance against the therapeutic transgenic protein and thereby provide permanent somatic gene correction. This approach is particularly relevant in relation to prenatal screening programmes for severe genetic diseases as it could offer prevention as a third option to families faced with the prenatal diagnosis of a genetically affected child. Most investigations towards in utero gene therapy have been performed on mice and sheep fetuses as model animals for human disease and for the application of clinically relevant intervention techniques such as vector delivery by minimally invasive ultrasound guidance. Other animals such as dogs may serve as particular disease models and primates have to be considered in immediate preparation for clinical trials. Proof of principle for the hypothesis of fetal gene therapy has been provided during the last 2 years in mouse models for Crigler Najjar Disease, Leber's congenital amaurosis, Pompe's disease and haemophilia B showing long-term postnatal therapeutic effects and tolerance of the transgenic protein after in utero gene delivery. However, recently we have also observed a high incidence of liver tumours after in utero application of an early form of third-generation equine infectious anaemia virus vectors with SIN configuration. These findings highlight the need for more investigations into the safety and the ethical aspects of in utero gene therapy as well as for science-based public information on risks and benefits of this preventive gene therapy approach before application in humans can be contemplated.

Animals↗
PubMed2000

Factors influencing postnatal liver function tests.

OBJECTIVE: To investigate liver function tests (LFTs) changes in the puerperium and the influence of specific obstetric events on these changes. DESIGN: A longitudinal observational study. SETTING: West Middlesex University Hospital, Twickenham. POPULATION: Ninety-four women with uncomplicated pregnancy who delivered at term. METHODS: Aspartate transaminase (AST), alanine transaminase (ALT), gamma glutamyl transferase (GGT), total bilirubin (Bilirubin) and alkaline phosphatase (ALP) were measured in early labour and on day 1, day 2, day 5 and day 10 postnatal. MAIN OUTCOME MEASURES: Peak enzyme concentration, time of peak enzyme concentration, the area under the curve for each enzyme and the rate of change of enzyme level from predelivery to peak concentration. RESULTS: All LFTs were affected by delivery (P < 0.001), increasing by 88% (0-500%) on day 2 or day 5 for AST, 147% (0-1140%) on day 5 for ALT and 63% (0-450%) on day 5 or day 10 for GGT. Multiple linear regression showed that caesarean section and opioid administration was associated with a faster rise in AST (P = 0.001, P = 0.033 respectively). The mean peak GGT concentration was 39% higher in women having caesarean section compared with vaginal delivery (P = 0.015). Univariate analysis showed that perineal trauma, use of Entonox, maternal age at delivery and breastfeeding also influenced LFT concentration significantly. CONCLUSION: Liver enzyme levels change significantly in the puerperium and are affected by common obstetric events, particularly caesarean section. This study aids clinical interpretation of postnatal LFTs in women recovering from liver-related illnesses, by facilitating the differentiation of physiological and pathological processes.

Adolescent↗
PubMedDate not supplied

Percutaneous ultrasound-guided injection of the trachea in fetal sheep: a novel technique to target the fetal airways.

OBJECTIVE: To access the fetal airways percutaneously using ultrasound-guided injection of the fetal trachea in sheep. METHODS: Adenoviral gene therapy vectors and transduction-enhancing agents were delivered to the trachea via a needle inserted through the thorax or the neck of late-gestation (0.9 term, n = 3) or mid-gestation (0.5-0.8 term, n = 18) fetal sheep using ultrasound guidance. RESULTS: Injection of the trachea in the fetal thorax was successful in 16 out of 18 fetuses and achieved at the first attempt in 9 fetuses within 12 min [mean 7 min and 31 s +/- (SD) 3 min and 4 s]. Survival was 100%. Injecting the trachea in the neck was less successful. CONCLUSIONS: The fetal trachea of the sheep can be safely accessed by percutaneous ultrasound-guided injection to deliver vectors directly to the fetal airways for gene therapy. It may also enable tracheal occlusion for the antenatal treatment of congenital diaphragmatic hernia without the need for endoscopy or open surgery.

Adenoviridae↗