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Biomedical subjects

M Burton

Publications and source records attributed to M Burton.

At least 37 records · Page 2Linked to original sources
PubMed1999

Coexpression of factor VIII heavy and light chain adeno-associated viral vectors produces biologically active protein.

We are interested in using recombinant adeno-associated viral vectors in the treatment of hemophilia A. Because of the size constraints of recombinant adeno-associated viral vectors, we delivered the heavy and light chains of the human factor 8 (hFVIII) cDNA independently by using two separate vectors. Recombinant AAV vectors were constructed that utilized the human elongation factor 1alpha promoter, a human growth factor polyadenylation signal, and the cDNA sequences encoding either the heavy or light chain of hFVIII. Portal vein injections of each vector alone, a combination of both vectors, or a hFIX control vector were performed in C57BL/6 mice. An ELISA specific for the light chain of hFVIII demonstrated very high levels (2-10 microgram/ml) of protein expression in animals injected with the light chain vector alone or with both vectors. We utilized a chromogenic assay in combination with an antibody specific to hFVIII to determine the amount of biologically active hFVIII in mouse plasma. In animals injected with both the heavy and light chain vectors, greater than physiological levels (200-400 ng/ml) of biologically active hFVIII were produced. This suggests that coexpression of the heavy and light chains of hFVIII may be a feasible approach for treatment of hemophilia A.

Animals↗
PubMed1999

Optimization of retroviral gene transduction of mobilized primitive hematopoietic progenitors by using thrombopoietin, Flt3, and Kit ligands and RetroNectin culture.

We have investigated the ability of several cytokine combinations to improve retrovirus-mediated transduction of human primitive hematopoietic progenitors (PHPs) from mobilized peripheral blood (MPB). Retroviral infection of CD34+ cells was performed by culture on fibronectin fragment CH-296 (RetroNectin, RN), using the truncated human nerve growth factor receptor (NGFR) as the transgene reporter. Transgene expression among progeny of PHPs was assayed by FACS analysis after long-term stromal culture (LTC). Transgene delivery to PHPs was assessed by PCR of individual stromal culture-derived methylcellulose colonies (LTC-CFCs). Compared with interleukin 3 (IL-3), IL-6, and leukemia inhibitory factor (LIF), the combination of thrombopoietin (TPO), Flt3 ligand (FL), and Kit ligand (KL) effected a 73-fold increase in NGFR expression among CD34+ cells (to 14%) and a 14-fold increase in NGFR expression among total cells (to 10%) after LTC. In addition, a 2.4-fold increase in neo gene marking of LTC-CFCs was observed. A preclinical study comparing the effect of high-speed centrifugation ("spinoculation") or culture on RN during exposure to retroviral particles in teflon cell culture bags showed no difference in the efficiency of transduction of PHPs between these two methods.

Antigens, CD34↗
PubMed1999

Long-term correction of canine hemophilia B by gene transfer of blood coagulation factor IX mediated by adeno-associated viral vector.

Hemophilia B is a severe X-linked bleeding diathesis caused by the absence of functional blood coagulation factor IX, and is an excellent candidate for treatment of a genetic disease by gene therapy. Using an adeno-associated viral vector, we demonstrate sustained expression (>17 months) of factor IX in a large-animal model at levels that would have a therapeutic effect in humans (up to 70 ng/ml, adequate to achieve phenotypic correction, in an animal injected with 8.5x10(12) vector particles/kg). The five hemophilia B dogs treated showed stable, vector dose-dependent partial correction of the whole blood clotting time and, at higher doses, of the activated partial thromboplastin time. In contrast to other viral gene delivery systems, this minimally invasive procedure, consisting of a series of percutaneous intramuscular injections at a single timepoint, was not associated with local or systemic toxicity. Efficient gene transfer to muscle was shown by immunofluorescence staining and DNA analysis of biopsied tissue. Immune responses against factor IX were either absent or transient. These data provide strong support for the feasibility of the approach for therapy of human subjects.

Animals↗
PubMed1999

Public-private partnerships: working at the local level to increase the quality and number of medical homes for Medicaid children.

We have described a process in which one state's public health leaders provided a large degree of flexibility at the community level to improve pediatric health care access for children in need. This "room-to-wiggle" allowed program providers to tailor their programs to the specific needs of their communities while remaining faithful to the statewide goals. Among the most promising outcomes of the coordinated efforts to forge public-private partnerships is the continuation of the relationships that developed in the process and the further collaborations they have spawned.

Child↗
PubMed1997

Calbindin and parvalbumin are early markers of non-mitotically regenerating hair cells in the bullfrog vestibular otolith organs.

Earlier studies have demonstrated hair cell regeneration in the absence of cell proliferation, and suggested that supporting cells could phenotypically convert into hair cells following hair cell loss. Because calcium-binding proteins are involved in gene up-regulation, cell growth, and cell differentiation, we wished to determine if these proteins were up-regulated in scar formations and regenerating hair cells following gentamicin treatment. Calbindin and parvalbumin immunolabeling was examined in control or gentamicin-treated (GT) bullfrog saccular and utricular explants cultured for 3 days in amphibian culture medium or amphibian culture medium supplemented with aphidicolin, a blocker of nuclear DNA replication in eukaryotic cells. In control cultures, calbindin and parvalbumin immunolabeled the hair bundles and, less intensely, the cell bodies of mature hair cells. In GT or mitotically-blocked GT (MBGT) cultures, calbindin and parvalbumin immunolabeling was also seen in the hair bundles, cuticular plates, and cell bodies of hair cells with immature hair bundles. Thus, these antigens were useful markers for both normal and regenerating hair cells. Supporting cell immunolabeling was not seen in control cultures nor in the majority of supporting cells in GT cultures. In MBGT cultures, calbindin and parvalbumin immunolabeling was up-regulated in the cytosol of single supporting cells participating in scar formations and in supporting cells with hair cell-like characteristics. These data provide further evidence that non-mitotic hair cell regeneration in cultures can be accomplished by the conversion of supporting cells into hair cells.

Animals↗
PubMed1997

A BRCA1 founder mutation, identified with haplotype analysis, allowing genotype/phenotype determination and predictive testing.

We searched for a founder mutation in a population from one geographic region of Norway with prevalent breast/ovarian cancer families. We sampled 33 breast/ovarian cancer families and determined haplotypes of four markers linked to the BRCA1 region. Of the affected 33 index women, 13 (39.4%) shared one haplotype. In five (15% of total), an identical mutation was indicated by an abnormal truncated protein test (PTT) of exon 11 and shown to represent a 1675delA mutation. In the other index women, PTT of exon 11 showed no abnormality. No other BRCA1 founder mutation of this prevalence is likely because no other haplotype was more frequent in affecteds than in controls. All families with the 1675delA mutation in this geographic region may be considered as part of one large kindred. This allows a genotype-phenotype correlation to be precisely determined and used in genetic counselling for predictive testing within this kindred. Identification of identical haplotypes between unrelated affected individuals may be used to estimate the extent of founder effects for any mapped disease, without knowledge of the specific founder mutation.

Adult↗
PubMed1997

Acute pulmonary oedema complicating laryngospasm.

Pulmonary oedema is an uncommon but important complication of laryngeal spasm which in turn occurs more commonly in ENT practice than in most other surgical specialties. A case is reported and the literature reviewed, with particular reference to the proposed pathophysiological mechanism of this phenomenon.

Acute Disease↗
PubMed1997

The prevalence of cataract in two villages of northern Pakistan with different levels of ultraviolet radiation.

To study the effect of ultraviolet (UV) light on the development of age-related cataract, a community-based cross-sectional study was undertaken in two villages in the mountainous Northern Areas of Pakistan. The relative UV light exposure was calculated by the UK Universities Global Atmospheric Modelling Program using the variables direct sunlight hours per day, latitude and ground reflectivity. A total of 797 subjects (410 men, 387 women) over the age of 40 years from both villages were examined for the presence of cataract. The prevalence of cataract increased with age (p < 0.001) and was significantly higher in women at all ages (p < 0.01). There was no significant difference in the overall prevalence of cataract between the two villages. The male population in each village was subdivided into those who worked predominantly indoors and those who worked predominantly outdoors. All women worked outdoors. There was no significant difference in the prevalence of cataract between the male outdoor workers in the two villages. The indoor workers in the village with higher UV light exposure (Hunza) had a significantly higher cataract prevalence (p < 0.001) than the indoor workers in the village with lower UV light exposure (Nomol). In the village with lower UV light exposure (Nomol), the male outdoor workers had a significantly higher prevalence of cataract than the male indoor workers (p < 0.001). There was no significant difference in the prevalence of cataract between the male indoor and outdoor workers in the village with higher UV light exposure (Hunza). Overall, these results are not strongly supportive of UV light being of major importance in cataractogenesis, but they are consistent with a saturation model of UV light as a risk factor for cataract formation.

Adult↗
PubMed1997

Development of an acute and chronic ecotoxicity assay using lux-marked Rhizobium leguminosarum biovar trifolii.

A soil isolate of Rhizobium leguminosarum bv. trifolii was marked with a lux CDABE gene cassette to enable the expression of bioluminescence. The suitability of the bacterium as a soil pollution biosensor was assessed using acute and chronic assays. Bacterial bioluminescence responded sensitively to the metals studied. The order of sensitivity was found to be Cd > Ni = Zn > Cu for the acute test and Cd > Ni = Zn = Cu for the chronic test. The sensitive response of the biosensor highlighted its potential for use as an indicator of soil pollution.

Biosensing Techniques↗
PubMed1997

The neurological basis of attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a serious disability with long-term consequences. At present the disorder is considered organic in pathology, particularly in regard to central nervous system functioning. This paper reviews research on ADHD. The role of neurochemical stimulation is discussed, and the signs of neurological deficits are explored. Nearly 600,000 young people in the United States receive medication daily for ADHD, and these drugs mimic brain neurotransmitters. The chemical action of these drugs and the cognitive, affective, and behavioral effects are discussed. Side effects and dosage levels are also examined. Basic behavior modification with ADHD children and how these techniques can be combined with effective drug treatment are elaborated.

Attention Deficit Disorder with Hyperactivity↗
PubMed1996

Species differences in 5-HT autoreceptors.

Release of 5-HT in the CNS is under the control of autoreceptors. These autoreceptors fall into two categories: cell body autoreceptors and terminal autoreceptors. The former inhibit 5-HT release through inhibition of cell firing; the latter through direct inhibition of release at the terminal. Cell body (or somatodendritic) autoreceptors belong to the 5-HT1A receptor subtype in all species studied so far. In the rat and mouse, the terminal autoreceptor is known to be a 5-HT1B receptor, whereas in human, pig, rabbit, and guinea pig, the terminal autoreceptor is thought to belong to the 5-HT1D receptor subtype. Until recently, the absence of a potent and selective 5-HT1D receptor antagonist has hindered this classification. We now present data with the novel 5-HT1D receptor antagonist, GR 127935, which demonstrates that in guinea pig cerebral cortex the terminal autoreceptor is a 5-HT1D receptor. In vitro [3H]5-HT release studies demonstrate that 5-HT inhibition of [3H]5-HT release is attenuated by GR 127935. In vivo, using the technique of microdialysis, GR 127935 and the non-selective antagonist methiothepin, when administered down the dialysis probe, potentiate extracellular levels of 5-HT. Both the in vitro and in vivo effects of these compounds are consistent with terminal autoreceptor blockade. However, when GR 127935 and methiothepin were administered systemically, both compounds inhibit extracellular levels of 5-HT. The most plausible explanations for this effect, such as partial agonism or activation of somatodendritic 5-HT1A receptors, are discussed.

Animals↗
PubMed1996

Effects of keratin 14 ablation on the clinical and cellular phenotype in a kindred with recessive epidermolysis bullosa simplex.

We studied a kindred with recessive epidermolysis bullosa simplex in which the affected members lacked expression of the basal cell keratin 14. The patients had severe generalized skin blistering that improved slightly with age. The basal cells of the patients did not express keratin 14 and contained no keratin intermediate filaments. The expression of keratin 5, the obligate copolymer of keratin 14, was slightly reduced. The expression of keratin 15, the alternative basal cell keratin, was increased, suggesting upregulation or stabilization to compensate for the lack of keratin 14. The expression of keratin 16, keratin 17, and keratin 19 in the patient's skin was not different from controls. Immunoelectron microscopy showed a loose network of keratin 5/keratin 15 protofilaments in the basal cells. Keratin 15 filaments did not aggregate into higher order bundles. Sequence analysis of genomic DNA revealed a homozygous mutation in the 3'-acceptor splice site of intron 1 (1840 A-->C) in the affected individuals. This mutation led to the skipping of exon 2 in 24% of the KRT14 transcripts and to the use of a cryptic splice site in 76% of the transcripts. Premature termination codons were generated in all transcripts (codons 175+1 or 175+29), leading to a truncated keratin 14 protein within the helical 1B rod domain. The disorder was associated with circumscribed hyperkeratotic lesions with the histology of epidermolytic hyperkeratosis. The prognosis of keratin 14 ablation is much better in the human than in the mouse.

Adult↗
PubMed1996

Functional characterization of the 5-HT terminal autoreceptor in the guinea-pig brain cortex.

1 In guinea-pig cerebral cortical slices in vitro we have shown that the rank order of potency of 5-hydroxytrptamine (5-HT), 5-carboxamidotryptamine and sumatriptan for inhibition of electrically stimulated [3H]-5-HT release correlates well with published data on their 5-HT1D receptor binding affinities. 2 Both the non-selective 5-HT1D receptor antagonist, methiothepin and the selective 5-HT1D receptor antagonist, N-[4-methoxy-3-(4-methyl-1-piperazinyl]phenyl]-2'-methyl-4'- (5-methyl-1,2,4-oxadiazole-3-yl) [1,1-biphenyl]4-carboxamide (GR127935) increased stimulated [3H]-5-HT release per se and also attenuated agonist-induced inhibition of [3H]-5-HT release. GR127935 (10 nM-100 nM) produced a pA2 of 9.0 against 5-HT, which is consistent with its 5-HT1D receptor binding affinity. 3 From these findings we conclude that, in guinea-pig cerebral cortex, the 5-HT terminal autoreceptor is of the 5-HT1D receptor subtype. However, three observations suggest the presence of multiple terminal autoreceptors: shallow inhibition curves to the agonists; a shallow Schild slope of GR127935 antagonism and differences in the maximal responses to 5-HT between whole cortex and frontal cortex.

Animals↗