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D M Hunt

Publications and source records attributed to D M Hunt.

At least 91 records · Page 5Linked to original sources
PubMed1997

Characterisation of the ultraviolet-sensitive opsin gene in the honey bee, Apis mellifera.

The cDNA sequence of the ultraviolet-sensitive opsin in the honey-bee, Apis mellifera, with associated 5' and 3' untranslated regions, is presented. The analysis of genomic structure reveals seven introns in the coding region of the gene, with six at novel positions for an insect opsin gene. The equivalent site to the counterion in vertebrate opsins is occupied by a Tyr residue. This contrasts with the presence of Phe at this site in the ultraviolet-sensitive opsins of Drosophila sps. A comparison of the amino acid sequence within the seven alpha-helical transmembrane regions of insect ultraviolet/blue-sensitive opsins identifies substitution at five sites that involve either replacement of a polar with a non-polar residue, or a change in charge. Such changes are known to result in spectral shifts in vertebrate pigments. Phylogenetic analysis indicates that the ultraviolet-sensitive pigments represent an ancient class of insect opsins.

Amino Acid Sequence↗
PubMed1997

Molecular evolution of the cottoid fish endemic to Lake Baikal deduced from nuclear DNA evidence.

Lake Baikal in Eastern Siberia contains a remarkable flock of 29 species of teleost fishes of the suborder Cottoidei (sculpins, bullheads) that are endemic to the lake and its associated rivers and occupy all depth habitats down to over 1500 m. The species are divided into three families, the Cottidae with 7 species, the Abyssocottidae with 20 species, and the Comephoridae with 2 species. Nucleotide sequences of the rod opsin gene from 12 of these species, plus a non-Baikal marine species, have been used to examine the evolutionary relations and the divergence time of the flock. Phylogenetic trees, generated by neighbor-joining and maximum parsimony, indicate that the unique Comephoridae family with its viviparity and unusual appearance is closely related to the Cottidae and Abyssocottidae, whereas the genus Cottocomephorus, at present placed in the Cottidae, was the first to diverge from the ancestral species and forms a separate lineage. The major adaptation to deep water would appear to be of relatively recent origin, and there is evidence that the ancestral species occupied a shallow-water-marine or brackish habitat. Estimates of antiquity obtained from synonymous substitutions place the origin of the species flock at around 4.9 million years ago.

Animals↗
PubMed1997

Visual pigments and oil droplets from six classes of photoreceptor in the retinas of birds.

Microspectrophotometric examination of the retinal photoreceptors of the budgerigar (shell parakeet), Melopsittacus undulatus (Psittaciformes) and the zebra finch, Taeniopygia guttata (Passeriformes), demonstrate the presence of four, spectrally distinct classes of single cone that contain visual pigments absorbing maximally at about 565, 507, 430-445 and 360-380 nm. The three longer-wave cone classes contain coloured oil droplets acting as long pass filters with cut-offs at about 570, 500-520 and 445 nm, respectively, whereas the ultraviolet-sensitive cones contain a transparent droplet. The two species possess double cones in which both members contain the long-wave-sensitive visual pigment, but only the principal member contains an oil droplet, with cut-off at about 420 nm. A survey of the cones of the pigeon, Columba livia (Columbiformes), confirms the presence of the three longer-wave classes of single cone, but also reveals the presence of a fourth class containing a visual pigment with maximum absorbance at about 409 nm, combined with a transparent droplet. No evidence was found for a fifth, ultraviolet-sensitive receptor. In the chicken, Gallus gallus (Galliformes), the cone class with a transparent droplet contains "chicken violet" with maximum absorbance at about 418 nm. The rods of all four species contain visual pigments that are spectrally similar, with maximum absorbance between about 506 and 509 nm. Noticeably, in any given species, the maximum absorbance of the rods is spectrally very similar to the maximum absorbance of the middle-wavelength-sensitive cone pigments.

Animals↗
PubMed1997

Hierarchical expression of desmosomal cadherins during stratified epithelial morphogenesis in the mouse.

Desmosomes contain two heterogeneous families of specialized cadherins (desmogleins or Dsgs and desmocollins or Dscs), subtypes of which are known to be expressed in tissue-specific and differentiation-dependent patterns in adult epithelial tissues. To examine the temporal and spatial order in which the individual desmosomal cadherins are expressed during stratified epithelial development we have obtained partial cDNA clones of all six murine desmosomal cadherins and have carried out in situ hybridization analysis on E12.5 to E16.5 mouse embryos. The results indicate that the type 2, type 3 and type 1 desmosomal cadherin messages are not obligatorily expressed as pairs during stratified epithelial morphogenesis. Instead the individual genes appear to be transcribed in hierarchical, overlapping temporal and spatial patterns extending from DSG2 to DSC1. DSG2 was the most uniformly expressed message in all E12.5 epithelia, gradually becoming confined to the basal cell layers during epithelial stratification indicating that its transcription was restricted to undifferentiated cells. In contrast, DSC2 message was expressed variably in early epithelia and was strongly upregulated in the suprabasal cell layers during the stratification of wet-surfaced epithelia. DSC3 message was expressed before that of DSG3 in the dental and lingual epithelium where its spatial distribution matched that of DSG2, but after DSG3 in the non-glandular gastric epithelium. DSC3 transcripts became confined to the lower layers of stratifying epithelia but were usually less basally restricted than those of DSG2. Like DSC2, DSG3 mRNA was strongly upregulated in the suprabasal layers of wet-surfaced epithelia as they stratified. Upregulation of DSG1 message was temporally linked to that of DSG3 in all tissues apart from the non-glandular gastric epithelium.

Amino Acid Sequence↗
PubMed1997

Localisation of a gene for dominant cone-rod dystrophy (CORD6) to chromosome 17p.

We have performed genetic linkage analysis on a four generation British family with cone-rod dystrophy. Significant linkage to the disease gene was obtained with eight marker loci situated on chromosome 17p12-p13. A maximum two-point lod score of 5.93 with no recombination was obtained with marker locus D17S1844. Critical recombinants identified with flanking marker loci placed the disease gene between D17S796/D17S938 and D17S954, an interval estimated to be 8 cM in size. This new localisation for autosomal dominant cone-rod dystrophy (CORD6) overlaps with regions attributed previously to Leber's congenital amaurosis, central areolar choroidal dystrophy and dominant cone dystrophy. Given their differences in phenotype, the most plausible explanation would be that these different retinal disorders are caused by mutations in different genes mapping close together within the genome.

Chromosome Mapping↗
PubMed1997

Gene therapy for retinal degeneration.

Inherited retinal degenerations are a group of diseases leading to blindness through progressive loss of vision in many patients. Although with the cloning of more and more disease genes the knowledge on the molecular genetics of these conditions and on the apoptotic pathway as the common disease mechanism is steadily increasing, there is still no cure for those affected. In recent years, new experimental treatments have evolved through the efforts of many investigators and have been explored in animal models. The rationale of the different strategies for developing a treatment based on gene replacement or rescue of the diseased neuronal tissue with growth factors will be outlined and discussed in this paper.

Adenoviridae↗
PubMed1997

Uncemented total hip replacements using the Mecron acetabular cup--a prospective study.

The uncemented threaded cup gained some popularity over the past decade, firstly as a revision and then as a primary procedure. We elected to test the Mecron acetabular threaded cup system as a routine hip replacement. As there was no matched femoral component, we decided to use an uncemented femoral stem of the Ring system of the hip prosthesis. All patients were logged on to the study at the outset although this is not a controlled comparison with another system. Patients were assessed annually for up to 4-years at the time of reporting. There were 104 primary total hip replacements in 99 patients between 1987 and 1991. The mean follow-up for this report was 22.5 months (range 12 to 48 months). The mean age was 76.3 years (range 24 to 88 years) and the female to male sex ratio was 3.3:1. Within the study period, 5 hips required revision, all for acetabular loosening. Patients were assessed by the modified Harris score annually and 60.6% of the cases had an excellent or good short-term result. Poor results were observed in 18.3% of cases. Radiographic studies of the acetabular component were undertaken annually and measured. Migration and tilting of the acetabular cup was observed in all cases. Heterotropic bone formation occurred in 10 patients. As a result of these poor results, the prosthesis was abandoned in 1991. The cohort of patients continues to be followed. Failure of the Mecron acetabular cup in our series was mainly due to tilting and migration and not untwisting.

Acetabulum↗
PubMed1996

Assessment of association of D3 dopamine receptor MscI polymorphism with schizophrenia: analysis of symptom ratings, family history, age at onset, and movement disorders.

Several studies have reported an association between schizophrenia and homozygosity for the MscI restriction site in exon 1 of the D3 dopamine receptor gene, but other studies have failed to find this association. Recent reports have suggested that the association is most salient in male patients with a family history of schizophrenia. We examined this restriction site in a group of schizophrenic patients (n = 84) and in normal controls (n = 77). Patients were subdivided according to demographic and clinical features, particular attention being paid to movement disorders. No significant difference in allelic or genotypic distribution was seen between the two groups. No association was seen between homozygosity and a positive family history, age at onset of illness, clinical subtype, negative symptom score, or movement disorder scores.

Chi-Square Distribution↗
PubMed1996

Human guanylate kinase (GUK1): cDNA sequence, expression and chromosomal localisation.

Guanylate kinase (GK) catalyses the conversion of GMP to GTP as part of the cGMP cycle. In mammalian phototransduction, this cycle is essential for the regeneration of cGMP following its hydrolysis by phosphodiesterase. Mutations in different parts of this signalling cascade lead to retinal degeneration in humans. Protein studies have localized a locus for GK to a region of human chromosome 1 that also contains an autosomal recessive form of retinitis pigmentosa (RP12) and Usher's type 11a (USH2A). We report the sequence of this human GK (GUK1) and a further refinement of its localization to 1q32-41, placing it in the same interval as USH2A.

Amino Acid Sequence↗
PubMed1996

Hemopexin in the human retina: protection of the retina against heme-mediated toxicity.

The existence of the blood-retinal barrier means that proteins that protect the retina from damage by reactive oxygen species must either be made locally or specifically transported across the barrier cells; however, such transepithelial transport does not seem to occur. Among the circulatory proteins that protect against iron-catalyzed production of free radicals are apo-transferrin, which binds ferric iron and has previously been shown to be made by cells of the neural retina (Davis and Hunt, 1993, J. Cell Physiol., 156:280-285), and the extracellular antioxidant, apo-hemopexin, which binds free heme (iron-protoporphyrin IX). Since hemorrhage and heme release can be important contributing factors in retinal disease, evidence of a hemopexin-based retinal protection system was sought. The human retina has been shown to contain apo-hemopexin which is probably synthesized locally since its mRNA can be detected in retinal tissue dissected from human donor eyes. It is likely that the retina contains a mechanism for the degradation of hemopexin-bound heme since the blood-retinal barrier also precludes the exit of heme-hemopexin from the retina. Retinal pigment epithelial cells have been found to bind and internalize heme-hemopexin in a temperature-dependent, saturable, and specific manner, analogous to the receptor-mediated endocytic system of hepatoma cells. Moreover, the binding of heme-hemopexin to the cells stimulates the expression of heme oxygenase-1, metallothionein-1, and ferritin.

Apoproteins↗
PubMed1996

Spectral tuning and molecular evolution of rod visual pigments in the species flock of cottoid fish in Lake Baikal.

Lake Baikal in Eastern Siberia is the deepest and one of the largest and most ancient lakes in the world. However, even in the deepest regions, oxygenation levels do not fall below 75-80% of the surface levels. This has enabled a remarkable flock of largely endemic teleost fish of the sub-order Cottoidei to colonize all depth habitats. We have previously shown that species that occupy progressively deeper habitats show a blue shift in the peak wavelength of absorbance (lambda max) of both their rod and cone visual pigments; for the rod pigments, a number of stepwise shifts occur from about 516 nm in littoral species to about 484 nm in abyssal species. By sequencing the rod opsin gene from 11 species of Baikal cottoids that include representatives from all depth habitats, we have been able to identify four amino acid substitutions that would account for these shifts. The effect of each substitution on lambda max is approximately additive and each corresponds to a particular lineage of evolution.

Amino Acid Sequence↗
PubMed1996

Amplification of stromelysin-3 transcripts from carcinomas of the colon.

Stromelysin-3 has been recently described in association with the stroma of different types of cancer including colorectal carcinomas. This article reports the detection of transcripts for stromelysin-3 (matrix metalloproteinase-11 [MMP-11]) in extracts of tissue from colorectal carcinomas using the technique of reverse transcription-polymerase chain reaction (RT-PCR). In 12 cases of primary colon carcinoma, stromelysin-3 messenger RNA (mRNA) was detected after 25 cycles, whereas this procedure did not reveal stromelysin-3 mRNA expression in one rectal carcinoma micrometastasis to the liver or in normal colon tissue (controls) after 30 cycles of PCR. However, stromelysin-3 mRNA was detected in normal colon specimens after 45 cycles. The high sensitivity of this technique allows application for the investigation of the expression of stromelysin-3 in small amounts of tissue.

Adenocarcinoma↗
PubMed1996

Clinical features of progressive bifocal chorioretinal atrophy: a retinal dystrophy linked to chromosome 6q.

PURPOSE: The gene for progressive bifocal chorioretinal atrophy (PBCRA) has been linked to chromosome 6q, near the genomic assignment for North Carolina macular dystrophy. A study was undertaken to define the clinical features of a large PBCRA pedigree and to determine whether PBCRA and North Carolina macular dystrophy are phenotypically distinct entities. METHODS: Fifteen affected individuals from 1 large family were examined clinically, which included angiography and electrophysiologic studies. RESULTS: The PBCRA is an autosomal dominant chorioretinal dystrophy of early onset characterized by large atrophic macular and nasal retinal lesions, nystagmus, myopia, poor vision, and slow progression. A large atrophic macular lesion and nasal subretinal deposits are evident soon after birth. An atrophic area nasal to the optic nerve head appears in the second decade, which enlarges progressively. Electro-oculographic and electroretinographic studies indicated marked, diffuse abnormalities of rod and cone function. Fluorescein and indocyanine green angiography showed a large circumscribed area of macular choroidal atrophy with staining of deposits in the peripheral retina. In addition to previously documented features, nasal retinal abnormalities from a few weeks of age, marked photopsia in a number of patients, and retinal detachments in three eyes are reported as new features of the disease. CONCLUSIONS: An extended description of PBCRA is presented highlighting that the phenotype is distinct from North Carolina macular dystrophy, although some phenotypic similarities exist between the two conditions. These disorders may be the result of different mutations on the same gene or nearby genes.

Adolescent↗
PubMed1996

X-ray microanalysis of cell elements in normal and cystic fibrosis jejunum: evidence for chloride secretion in villi.

BACKGROUND & AIMS: Cystic fibrosis transmembrane conductance regulator (CFTR) is an adenosine 3',5'-cyclic monophosphate-dependent chloride channel that is defective in cystic fibrosis. The aims of this study were to determine if defective apical chloride secretion in the intestine of patients with cystic fibrosis alters the intracellular electrolyte milieu and to examine the geographical localization of CFTR in the normal intestine. METHODS: The content of intracellular elements was assessed in cryosections using energy-dispersive x-ray microanalysis, and CFTR was identified by immunocytochemistry using commercially available antibodies. RESULTS: Cystic fibrosis jejunum had a significantly lower Na+ content, higher K+ and Cl- content, and higher potassium/phosphorus ratio in both villus and crypt regions. Incubation of normal jejunum with the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (300 mumol/L) resulted in decreased K+ and Cl- content in both crypt and villus regions, indicative of Cl- secretion. CFTR was identified on the surface of normal villus and crypt enterocytes but not in cystic fibrosis samples. CONCLUSIONS: Defective apical chloride channels in cystic fibrosis result in alterations in the intracellular electrolyte milieu. The microanalysis observations and immunocytochemical studies imply a role for villus enterocytes in human intestinal chloride secretion.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Gene transfer into the mouse retina mediated by an adeno-associated viral vector.

Gene transfer to photoreceptor cells may provide a means for arresting the retinal degeneration that is characteristic of many inherited causes of blindness, including retinitis pigmentosa (RP). However, transduction of photoreceptors has to date been inefficient, and further limited by toxicity and immune responses directed against vector-specific proteins. An alternative vector system based on adeno-associated virus (AAV) may obviate these problems, and may be useful for transduction of neuronal cells. In this study we have demonstrated successful transduction of all layers of the neuroretina as well as the retinal pigment epithelium (RPE) following subretinal injection of recombinant AAV particles encoding lac Z. Furthermore, the efficiency of transduction of photoreceptors is significantly higher than that achieved with an equivalent adenoviral vector. This is the first report showing that AAV is capable of transducing photoreceptor cells and supports the use of this vector system for gene therapy of retinal diseases such as RP.

Animals↗
PubMed1995

The rhodopsin-encoding gene of bony fish lacks introns.

A study of the sequences of the rhodopsin-encoding genes (Rh) in eight fish species from two of the major subdivisions of the teleosts reveals that no introns are present in the coding region. This contrasts with the opsin-encoding genes of all other vertebrates where either four or five introns are invariably found. Phylogenetic analysis shows that this intronless teleost Rh is homologous to the intron-containing Rh of amphibia, birds and mammals. Possible mechanisms for intron loss are discussed, including replacement by homologous conversion of Rh with a processed cDNA.

Amphibians↗