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Biomedical subjects

D J Harris

Publications and source records attributed to D J Harris.

At least 19 recordsLinked to original sources
PubMed2003

Phylogeography of the Madeiran endemic lizard Lacerta dugesii inferred from mtDNA sequences.

Partial sequences from two mitochondrial DNA genes, cytochrome b and 12S rRNA, were used to assess the phylogenetic relationships of populations of Lacerta dugesii from the volcanic Atlantic islands of Madeira, the Desertas, Porto Santo, and the Selvagens. All four-island groups are genetically distinguishable and populations within each contain similar degrees of genetic diversity. Molecular clock estimates suggest that the islands were colonized much later after their emergence compared to other Atlantic islands, possibly due to their greater geographical isolation. Mismatch analysis of all populations is consistent with exponential growth, as expected after colonization of empty niches. The Selvagens contain genetic substructuring between the islets.

Animals↗
PubMed2003

Ancient introgression of Lepus timidus mtDNA into L. granatensis and L. europaeus in the Iberian Peninsula.

A 587 bp fragment of cytochrome b sequences from 90 individuals of 15 hare (Lepus) species and two outgroups were phylogenetically analysed and compared to an analysis derived from 474 bp sequences of the nuclear transferrin gene. Mountain hare (Lepus timidus) type mtDNA was observed in L. granatensis and L. europaeus from the Iberian Peninsula, far away from the extant distributional range of L. timidus. In addition to these two hare species, other hare species may also contain mtDNA from L. timidus. This species may have introgressed with other species of Lepus that occur within its present range, or where fossils indicate its historical presence during glacial periods. L. timidus mtDNA is common in the northern part of the L. granatensis range. Finally, we reassessed the phylogenetic relationships of the five European hare species based on both mitochondrial and nuclear DNA sequences.

Animals↗
PubMed2002

Extracorporeal membrane oxygenation for Legionnaires disease: a case report.

A case of Legionella pneumonia, severe adult respiratory distress syndrome (ARDS) and multiple organ failure is described in a patient who required extracorporeal membrane oxygenation (ECMO) prior to transfer to a hospital with ECMO facilities. She eventually made a good recovery, highlighting the potential benefits of ECMO in patients with severe and refractory ARDS.

Journal Article↗
PubMed2001

Identification of a dominant negative homeodomain mutation in Rieger syndrome.

Mutations in the PITX2 bicoid-like homeobox gene cause Rieger syndrome. Rieger syndrome is an autosomal-dominant human disorder characterized by glaucoma as well as dental hypoplasia, mild craniofacial dysmorphism, and umbilical stump abnormalities. PITX2 has also been implicated in the development of multiple organs and left-right asymmetry in the body plan. The PITX2 homeodomain has a lysine at position 50, which has been shown to impart the bicoid-type (TAATCC) DNA binding specificity to other homeodomain proteins. A mutation (K88E), found in a Rieger syndrome patient, changes this lysine to glutamic acid. We were intrigued by the relatively pronounced phenotypic consequences of this K88E mutation. In the initial analyses, the mutant protein appeared to simply be inactive, with essentially no DNA binding and transactivation activities and, unlike the wild type protein, with an inability to synergize with another transcription factor, Pit-1. However, when the K88E DNA was cotransfected with wild type PITX2, analogous to the patient genotype, the K88E mutant suppressed the synergism of wild type PITX2 with Pit-1. In contrast, a different PITX2 homeodomain mutant, T68P, which is also defective in DNA binding, transactivation, and Pit-1 synergism activities, did not suppress the wild type synergism with Pit-1. These results describe the first dominant negative missense mutation in a homeodomain and support a model that may partially explain the phenotypic variation within Rieger syndrome.

Abnormalities, Multiple↗
PubMed2001

Relationships of scincid lizards (Mabuya spp; Reptilia: Scincidae) from the Cape Verde islands based on mitochondrial and nuclear DNA sequences.

Partial DNA sequences from two mitochondrial (mt) and one nuclear gene (cytochrome b, 12S rRNA, and C-mos) were used to estimate the phylogenetic relationships among the six extant species of skinks endemic to the Cape Verde Archipelago. The species form a monophyletic unit, indicating a single colonization of the islands, probably from West Africa. Mabuya vaillanti and M. delalandii are sister taxa, as indicated by morphological characters. Mabuya fogoensis and M. stangeri are closely related, but the former is probably paraphyletic. Mabuya spinalis and M. salensis are also probably paraphyletic. Within species, samples from separate islands always form monophyletic groups. Some colonization events can be hypothesized, which are in line with the age of the islands. C-mos variation is concordant with the topology derived from mtDNA.

Animals↗
PubMed2001

Autosomal dominant inheritance of a negative electroretinogram phenotype in three generations.

PURPOSE: We report an abnormal electroretinogram with a negative configuration in a child who presented with moderate myopia, nystagmus, and visual developmental delay. We investigated the electroretinogram and explored the possibility of a metabotropic glutamate receptor subtype 6 mutation in six family members spanning four generations. METHODS: Case report and family study: Complete eye examinations and Ganzfeld electroretinograms were recorded from the maternal great-grandmother, maternal grandmother, mother, uncle, and sibling of the 7-month-old female proband. The electroretinogram was repeated in the proband at 17 months of age. Dark adaptometry was performed in all adult subjects. Fundus photographs and visual field examinations were administered to the grandmother and mother. The metabotropic glutamate receptor subtype 6 gene was amplified and sequenced in all affected subjects. RESULTS: The proband had a negative electroretinogram and a normal fundus. The maternal grandmother, uncle, and mother had an abnormal electroretinogram identical to the proband yet had no visual complaints. The ophthalmology examinations in the adult subjects were normal, and subsequent examination of the proband at 17 months, 5 years, and 6.5 years of age showed no changes in the fundus or refractive error. Her nystagmus resolved by 5 years of age. Rod threshold and visual fields were normal in the affected adult subjects. No mutation in the metabotropic glutamate receptor subtype 6 gene was found. CONCLUSIONS: In this family, a negative electroretinogram was not associated with decreased rod threshold, visual acuity loss, visual field loss, muscle disease, or metabotropic glutamate receptor subtype 6 mutation. Additional study will be required to understand the nature of the negative electroretinogram phenotype in this family.

Adult↗
PubMed2001

Structure and evolution of the mitochondrial DNA complete control region in the Drosophila subobscura subgroup.

The complete A + T-rich region of mitochondrial DNA (mtDNA) has been cloned and sequenced in the species of the Drosophila subobscura subgroup D. subobscura, D. madeirensis and D. guanche. Comparative analysis of these sequences with others already published has identified new sequence motifs that are conserved in Drosophila and other insects. A putative bi-directional promoter and a stop signal are proposed to be involved in the primary mtDNA strand replication of Drosophila. This region strongly resolves relationships of the species included in a phylogenetic analysis, both for closely related species and also at deeper phylogenetic levels when only the left and central domains are taken into account.

AT Rich Sequence↗
PubMed2001

Partial correction of defective Cl(-) secretion in cystic fibrosis epithelial cells by an analog of squalamine.

Defective cystic fibrosis (CF) transmembrane conductance regulator (CFTR)-mediated Cl(-) transport across the apical membrane of airway epithelial cells is implicated in the pathophysiology of CF lungs. A strategy to compensate for this loss is to augment Cl(-) transport through alternative pathways. We report here that partial correction of this defect could be attained through the incorporation of artificial anion channels into the CF cells. Introduction of GL-172, a synthetic analog of squalamine, into CFT1 cells increased cell membrane halide permeability. Furthermore, when a Cl(-) gradient was generated across polarized monolayers of primary human airway or Fischer rat thyroid cells in an Ussing chamber, addition of GL-172 caused an increase in the equivalent short-circuit current. The magnitude of this change in short-circuit current was ~30% of that attained when CFTR was maximally stimulated with cAMP agonists. Patch-clamp studies showed that addition of GL-172 to CFT1 cells also increased whole cell Cl(-) currents. These currents displayed a linear current-voltage relationship and no time dependence. Additionally, administration of GL-172 to the nasal epithelium of transgenic CF mice induced a hyperpolarization response to perfusion with a low-Cl(-) solution, indicating restoration of Cl(-) secretion. Together, these results demonstrate that in CF airway epithelial cells, administration of GL-172 is capable of partially correcting the defective Cl(-) secretion.

Amiloride↗
PubMed2000

The monophyletic origin of freshwater crayfish estimated from nuclear and mitochondrial DNA sequences.

Despite their widespread use as model organisms, the phylogenetic status of the around 520 species of freshwater crayfish is still in doubt. One hypothesis suggests two distinct origins of freshwater crayfish as indicated by their geographical distribution, with two centres of origin near the two present centres of diversity; one in south-eastern United States and the other in Victoria, Australia. An alternative theory proposes a single (monophyletic) origin of freshwater crayfish. Here we use over 3000 nucleotides from three different gene regions in estimating phylogenetic relationships among freshwater crayfish and related Crustacea. We show clear evidence for monophyly of freshwater crayfish and for the sister-group relationship between crayfish and clawed lobsters. Monophyly of the superfamilies Astacoidea and Parastacoidea is also supported. However, the monophyly of the family Cambaridae is questioned with the genus Cambaroides being associated with the Astacidae.

Animals↗
PubMed2000

Enrollment of women in cardiovascular clinical trials funded by the National Heart, Lung, and Blood Institute.

BACKGROUND: With the recognition that certain aspects of cardiovascular disease are specific to sex, the government has sought to ensure that federally funded clinical research yields adequate high-quality information about heart disease in women. METHODS: We tabulated the numbers of men and women in cardiovascular clinical trials funded by the National Heart, Lung, and Blood Institute (NHLBI) between 1965 and 1998, recording both total numbers and the numbers for each type of cardiovascular disease. We analyzed the data according to the sex-specific prevalence of disease and assessed changes in enrollment over time. We performed a similar analysis after excluding all single-sex trials. RESULTS: A total of 398,801 subjects (215,796 women and 183,005 men) were enrolled in NHLBI-funded studies of cardiovascular disease. The overall enrollment rate for women (54 percent) exceeded the prevalence of cardiovascular disease in women in the general population (49 percent) and increased over time (P=0.002). With single-sex trials excluded, the enrollment rate for women was 38 percent, which did not change significantly over time. In studies of coronary artery disease and hypertension the rates of enrollment of women were similar to or exceeded the prevalence of these disorders in women. The enrollment rate increased significantly over time in studies of coronary artery disease (P<0.001) but not in studies of hypertension or arrhythmia. Women were under-enrolled in studies of heart failure, and the rate of enrollment did not change significantly over time. When single-sex trials were excluded from the analysis of enrollment rates according to the prevalence of disease, the results were similar. There was no change in enrollment rates overtime for any category of disease. CONCLUSIONS: Federal efforts to increase the representation of women in clinical trials have been moderately successful primarily because of the institution of a small number of large, single-sex trials involving coronary artery disease. There has been no change in the sex composition of cohorts in the majority of studies of cardiovascular disease.

Cardiovascular Diseases↗
PubMed2000

Intragenomic variation within ITS1 and ITS2 of freshwater crayfishes (Decapoda: Cambaridae): implications for phylogenetic and microsatellite studies.

Intragenomic variation in ITS1 and ITS2 is known to exit but is widely ignored in phylogenetic studies using these gene regions. The amount of variation in seven crayfish species, including three populations of Orconectes luteus and two of Procambarus clarkii, was assessed by sequencing 3, 5, or 10 clones from the same individuals, for a total of 77 sequences. The ITS1 and ITS2 sequences reported here are some of the longest known, with aligned lengths of 760 and 1,300 bp, respectively. They contain multiple microsatellite insertions, all of which show considerable intragenomic variation in the number of repeat elements. This variation is enough to obscure phylogenetic relationships at the population level, although relationships between species can be estimated. Given the hybridization techniques used to locate microsatellites, multiple-copy regions like ITS1 and ITS2 will be preferentially found if they contain microsatellites, and in these cases the microsatellites will not behave as typical Mendelian markers and could give spurious results.

Animals↗
PubMed2000

Cationic lipid structure and formulation considerations for optimal gene transfection of the lung.

Enhanced gene transduction to the lung using cationic lipids could be attained through optimization of the structure of the lipids and the formulation of the cationic lipid:plasmid DNA (pDNA) complexes. We have expanded on our earlier observation of the importance of the structural orientation of the cationic lipid headgroup. Through the synthesis of a number of matched pairs of cationic lipids differing only in the configuration of their headgroup, we confirmed that those harboring a T-shape headgroup are more active than their linear counterparts, at least when tested in the lungs of BALB/c mice. Additionally, we demonstrated that not only are the structural considerations of these cationic lipids important, but also their protonation state, the free base being invariably more active than its salt counterpart. The salt forms of cationic lipids bound pDNA with greater avidity, which may have affected their subsequent intracellular dissolution and transit of the pDNA to the nucleus. Inclusion of a number of frequently used solutes in the vehicle severely inhibited the gene transfection activity of the cationic lipids. The selection of neutral co-lipids was also an important factor for overall transfection activity of the formulation, with significant gains in transfection activity realized when diphytanoylphosphatidylethanolamine or dilinoleoylphosphatidylethanolamine were used in lieu of dioleoylphosphatidylethanolamine. Finally, we showed that a transacylation reaction could occur between the cationic lipid and neutral co-lipid which reduced the transfection activity of the complexes. It is the hope that as our understanding of the many factors that influence the activity of these cationic lipid:pDNA complexes improves, formulations with much greater potency can be realized for use in the treatment of pulmonary diseases.

Animals↗
PubMed1999

Clinical studies of families with hearing loss attributable to mutations in the connexin 26 gene (GJB2/DFNB1)

OBJECTIVE: This retrospective study describes the phenotype associated with the single most common cause of genetic hearing loss. The frequency of childhood deafness is estimated at 1/500. Half of this hearing loss is genetic and approximately 80% of genetic hearing loss is nonsyndromic and inherited in an autosomal recessive manner. Approximately 50% of childhood nonsyndromic recessive hearing loss is caused by mutations in the connexin 26 (Cx26) gene (GJB2/DFNB1), making it the most common form of autosomal recessive nonsyndromic hearing loss with a carrier rate estimated to be as high as 2.8%. One mutation, 35delG, accounts for approximately 75% to 80% of mutations at this gene. METHODS: Hearing loss was examined in 46 individuals from 24 families who were either homozygous or compound heterozygous for Cx26 mutations. A subset of these individuals were examined for vestibular function, otoacoustic emissions, auditory brainstem response, temporal bone computed tomography, electrocardiography, urinalyses, dysmorphology, and thyroid function. RESULTS: Although all persons had hearing impairment, no consistent audiologic phenotype was observed. Hearing loss varied from mild-moderate to profound, even within the group of families homozygous for the common mutation 35delG, suggesting that other factors modify the phenotypic effects of mutations in Cx26. Furthermore, the hearing loss was observed to be progressive in a number of cases. No associations with inner ear abnormality, thyroid dysfunction, heart conduction defect, urinalyses, dysmorphic features, or retinal abnormality were noted. CONCLUSION: Newborns with confirmed hearing loss should have Cx26 testing. Cx26 testing will help define a group in which approximately 60% will have profound or severe-profound hearing loss and require aggressive language intervention (many of these patients will be candidates for cochlear implants).

Child↗
PubMed1999

ERG phenotype of a dystrophin mutation in heterozygous female carriers of Duchenne muscular dystrophy.

PURPOSE: Mutations in the dystrophin gene result in Duchenne muscular dystrophy (DMD). DMD is associated with an abnormal electroretinogram (ERG) if the mutation disrupts the translation of retinal dystrophin (Dp260). Our aim was to determine if incomplete ERG abnormalities would be associated with heterozygous carriers of dystrophin gene mutations. METHODS: Ganzfeld ERGs were obtained under scotopic and photopic testing conditions from a family which includes the heterozygous maternal grandmother, the heterozygous mother, and her children, two affected boys and dizygotic twin sibs, an unaffected male and heterozygous female. Southern blot analyses were done to characterise the dystrophin mutation. RESULTS: The dystrophin gene was found to contain a deletion encompassing exon 50. The ERGs in the two affected boys were abnormal, consistent with the DMD ERG phenotype. Serial ERGs of the heterozygous females were abnormal; however, they were less severely affected than the DMD boys. The ERG of the female sib showed a greater abnormality than her mother and maternal grandmother. The unaffected twin had a normal ERG. CONCLUSIONS: The ERG shows abnormalities associated with carrier status in this family with a single exon deletion. A large study of confirmed obligate carriers is planned to clarify further the value of the ERG in detecting female heterozygous carriers of dystrophin gene mutations.

Adult↗
PubMed1998

Relationships of lacertid lizards (Reptilia: Lacertidae) estimated from mitochondrial DNA sequences and morphology.

DNA sequences from parts of the 12S, 16S and cytochrome b mitochondrial genes, which totalled 1049 aligned base pairs, were used to estimate the relationships of 49 species of Lacertidae, including representatives of 19 out of the 23 recognized genera and 23 species of the paraphyletic genus Lacerta. These data were used, together with morphological information, to estimate the relationships within the family. Molecular evidence corroborates the monophyletic status of many genera and species groups originally based on morphology. It indicates that Psammodromus forms a clade with Gallotia, which is the sister taxon of all other lacertids. These comprise three units: the primarily Afrotropical armatured group; the largely Oriental Takydromus; and the west Palaearctic Lacerta and its derivatives, Podarcis and Algyroides. Morphology also supports the first three assemblages, but suggests that they are derived from a paraphyletic Lacerta. Within Lacerta and its allies, DNA sequence analysis corroborates the affinity of some members of each of the subgenera Lacerta s. str. and Timon, and of the L. saxicola group. It also supports the relationship of L. monticola, L. bonnali and L. horvathi, and suggests that the L. parva--L. fraasi clade and L. brandli are not related to Psammodromus Gallotia, as morphology indicates, but instead are associated respectively with the L. danfordi and L. saxicola groups. DNA sequence data provide additional evidence that the eastern Arabian 'Lacerta' jayakari and 'L.' cyanura are members of the armatured clade and also sister species. Our analysis supports an origin for present lacertids in west Eurasia. The armatured clade invaded Africa, probably in the mid-Miocene, spreading widely and evolving increasingly xeric-adapted forms, one lineage of which later moved back into the Palaearctic. 'Lacerta' jayakari and 'L.' cyanura are assigned to Omanosaura, Lutz and Mayer 1986. The name Gallotiinae Cano, Baez, Lopez-Jurado & Ortega, 1984 is available for the Gallotia-Psammodromus clade, Eremiainae Shcherbak 1975 for the armatured clade and Lacertinae for Lacerta, Podarcis and Algyroides. Two new subgenera of Lacerta are proposed here: Caucasilacerta for L. saxicola and its allies, and Parvilacerta for L. parva and L. fraasi.

Animals↗
PubMed1998

Rapid speciation, morphological evolution, and adaptation to extreme environments in South African sand lizards (Meroles) as revealed by mitochondrial gene sequences.

Data derived from the morphology of the seven species of South African sand lizards, Meroles (Reptilia, Lacertidae), and their outgroups produce a robust estimate of phylogeny when a maximum parsimony approach is applied. The estimate is fully resolved with little character conflict and internal branches are relatively long. This analysis indicates that Meroles is a true clade that includes the aberrant lacertid long separated as Aporosaura anchietae. The tree is pectinate, its successive external branches representing species with increasing adaptation to desert conditions, especially aeolian sand habitats. This pattern, and the robustness of the tree, support a model of invasion of severe habitats in which successive rounds of speciation, displacement, and adaptation result in spread into extreme ecological situations. To test the robust morphological phylogeny and, indirectly, the model as well, DNA from mitochondrial 12S and 16S ribosomal genes was sequenced and analyzed by both maximum parsimony and maximum likelihood approaches. Trees produced were largely congruent with that derived from morphology, although different from ones resulting from protein electrophoresis. However, in contrast to the internal branches of the morphological tree, those of the DNA maximum likelihood tree are quite short. The DNA data provide some corroboration for the relationships within Meroles based on morphology and consequently for the model as well. The disparity in internal branch lengths between the maximum parsimony morphological and maximum likelihood DNA trees may well indicate that the multiple adaptations to desert conditions arising on the main lineage of Meroles evolved quite rapidly. In this study DNA thus not only corroborates the phylogeny but also provides evidence about another aspect of evolutionary history.

Adaptation, Physiological↗