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Biomedical subjects

R H Thomas

Publications and source records attributed to R H Thomas.

At least 19 recordsLinked to original sources
PubMed1992

The use of rRNA sequences and fluorescent probes to investigate the phylogenetic positions of the anaerobic ciliate Metopus palaeformis and its archaeobacterial endosymbiont.

The polymerase chain reaction (PCR) was used to amplify small-subunit ribosomal DNA from the anaerobic ciliated protozoon Metopus palaeformis, and from its uncultured endosymbiotic bacteria. This was accomplished directly from total DNA extracted from protozoa without prior isolation or enrichment for symbiont cells. The double-stranded amplification products were precipitated and directly sequenced using the linear PCR reaction. Fluorescent oligonucleotide probes were designed and used in whole-cell hybridizations to provide direct visual evidence that the sequences originated from the host ciliate and from the endosymbiont. Phylogenetic analysis of the Metopus palaeformis sequence consistently placed it as a deep-branching lineage near the root of the ciliate tree. However, the present data were insufficient to resolve the detailed relationship between Blepharisma and Metopus and thus to determine if the heterotrichs are mono- or paraphyletic. Phylogenetic analysis of the symbiont partial sequence clearly demonstrated that it is an archaeobacterium and that it is closely related to, but distinct from, Methanobacterium formicicum.

Animals↗
PubMed1991

The molecular evolution of the alcohol dehydrogenase locus and the phylogeny of Hawaiian Drosophila.

DNA sequences in the alcohol dehydrogenase genes of flies representing the major groups of Hawaiian Drosophila are used to clarify the relationships of these groups, among themselves and with mainland Drosophila. The topology of the tree derived from these sequences agrees with karyotypic and morphological data but disagrees, in part, with the results of an earlier study that used immunological comparisons between variants of a larval hemolymph protein. A time scale, derived from a comparison of closely related Hawaiian Drosophila species, provides divergence-time estimates that are substantially more recent than those obtained from the immunological studies, although they are still within the bounds set by fossil and biogeographical evidence. The two major lineages of Hawaiian Drosophila, the scaptomyzoids and the drosophiloids, are shown to be widely separated from one another. The scaptomyzoids appear to have diverged early in the history of the subgenus Drosophila, greater than 25 Mya. While hundreds of scaptomyzoid species are found in the Hawaiian archipelago, many fewer are found elsewhere around the world, suggesting that they could have originated outside Hawaii. The drosophiloid lineage is strictly endemic to Hawaii and originated little more than 10 Mya, according to the alcohol dehydrogenase molecular clock. Thus, Drosophila apparently inhabited the Hawaiian archipelago (greater than or equal to 5 Myr before the emergence of the oldest existing high island, Kauai, 5 Mya.

Alcohol Dehydrogenase↗
PubMed1990

Breeding structure of natural populations of Drosophila buzzatii: effects of the distribution of larval substrates.

The population structure of several Australian populations of the cactophilic Drosophila buzzatti was investigated, with seasonal samples from two populations analyzed for six polymorphic allozymes. Significant inbreeding throughout the year was detected in both populations, and significant but relatively slight differences in allele frequencies between collections were found in one population. Little significant 2-locus linkage disequilibrium was detected and the variances of linkage disequilibrium coefficients were generally consistent with genetic drift. Individual breeding substrates (rotting cactus cladodes) were collected and the adult flies emerging from them were scored for their allozyme genotypes. The data suggest that approximately ten individuals contribute to the progeny emerging from a rot. The influence of the sizes and distributions of breeding substrates on the maintenance of genetic variation is discussed.

Alleles↗
PubMed1990

Unusual presentation of paraproteinemic corneal infiltrates.

A 76-year-old man with bilateral corneal infiltrates secondary to a monoclonal gammopathy of undetermined significance (MGUS) is described. The corneal changes simulated a remote lattice dystrophy. Although the clinical presentation of corneal opacities secondary to paraproteinemic conditions is somewhat variable, this patient's corneas lacked the common crystalline appearance of immunoglobulin deposits. This patient demonstrates an atypical clinical presentation of corneal infiltration secondary to a paraproteinemia.

Aged↗
PubMed1989

DNA phylogeny of the extinct marsupial wolf.

The phylogenetic affiliation of the extinct marsupial wolf (Thylacinus cynocephalus), which once was widespread in Australia, has been uncertain. On the basis of morphology, some systematists argue that the thylacine was most closely related to an extinct group of South American carnivorous marsupials, the borhyaenids, whereas others consider it to be closer to Australian carnivorous marsupials. Here we use direct sequencing by means of the polymerase chain reaction (PCR) to compare 219 bases of mitochondrial (mt) DNA from museum specimens of the marsupial wolf and representatives of six genera of extant marsupials. In agreement with the results of an antigenic study of albumin, our genetic data suggest that the marsupial wolf was more closely related to other Australian marsupial carnivores than to those of South America. Thus, the marsupial wolf represents an example of convergent morphological evolution to South American carnivorous marsupials as well as to true wolves.

Amino Acid Sequence↗
PubMed1987

The treatment of resistant mosaic plantar warts with aggressive cryotherapy under general anaesthetic.

Twelve patients with treatment-resistant mosaic plantar warts were treated with aggressive cryotherapy under a general anaesthetic. Seven patients (58%) had complete cure, two patients (16%) experienced substantial but incomplete clearing of their warts and the remaining three patients (25%) had no improvement. The procedure was well tolerated and post cryotherapy pain was acceptable to the patients.

Adolescent↗
PubMed1987

Prolonged increase in digital blood flow following iloprost infusion in patients with systemic sclerosis.

Thirteen patients with Raynaud's phenomenon secondary to systemic sclerosis received three 8-hour infusions of a synthetic prostacyclin analogue (Iloprost) on consecutive days and were followed-up over a period of 10 weeks during the winter of 1985/86. Six weeks after infusion, digital peripheral vascular resistance had fallen (P less than 0.05) and dicrotic notch proportion of pulse amplitude increased (P less than 0.05). Digital blood flow and pulse amplitude (measured by photoplethymography) were also increased but did not reach statistical significance. The trend of improvement in these blood flow parameters was still evident after 10 weeks. The number of cutaneous lesions (digital ulcers, etc) fell from 26 lesions before infusion to only 7 lesions by the end of the study, confirming the subjective improvement reported by the patients.

Adult↗
PubMed1987

Acquired immune deficiency syndrome without the recognized risk factors.

We report two cases of acquired immune deficiency syndrome (AIDS), apparently without the usual exposure factors, in whom a temporal association was detected after detailed epidemiological investigation. The index case, a 45 year old housewife, had provided terminal home-nursing care for a 33 year old African man, who died from an undiagnosed encephalitis. At that time she had fissures of the skin of both her hands. Review of post-mortem pathology specimens of the African man allowed a retrospective diagnosis of AIDS with cerebral toxoplasmosis to be made. The type of home-nursing care given by the index case was quite different from that normally provided by health care workers with the training and facilities to prevent the spread of infection.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Polysulfone corneal lenses.

Polysulfone is a thermoplastic compound first synthesized in 1965. A unique characteristic of polysulfone is its high refractive index (1.633), which allows very thin optical lenses to be manufactured. Over the last five years, D. Peter Choyce has surgically implanted over 40 polysulfone lenses into eyes of his patients. Analysis of his data indicates that polysulfone intraocular lenses are capable of correcting large refractive errors. Based on his work, a multicenter study was undertaken to evaluate the safety and efficacy of polysulfone as an intracorneal lens material in laboratory models. Four monkeys, eight baboons, and 24 cats were used as laboratory models; 5.0-mm to 6.0-mm diameter hyperopic (+28.5 diopter) and myopic (-17.0 and -25.5 diopter) lenses were surgically implanted within the corneal stroma in one eye of each of the laboratory models while a sham lamellar dissection was performed in the other eye. One hundred percent (4/4) of monkey eyes, 12.5% (1/8) of baboon eyes, and 70.0% (18/24) of cat eyes maintained clear media by ophthalmoscopic examination at follow-ups ranging from three to six months. Complications included both visually and nonvisually significant interface opacities, lens extrusion, anterior corneal necrosis, refractile particles, and epithelial thinning.

Animals↗
PubMed1986

Fixed drug eruption due to paracetamol.

A patient who developed a fixed drug eruption due to paracetamol is reported. There is only one previous account of this eruption occurring as a consequence of paracetamol therapy.

Acetaminophen↗
PubMed1985

The influence of ranitidine, alone and in combination with clemastine, on histamine-mediated cutaneous weal and flare reactions in human skin.

Significant, (P less than 0.05) inhibition of histamine induced cutaneous weal and flare reactions by ranitidine at 10(-5) M concentration has been demonstrated in a double blind, in vivo study; the results support the evidence for cutaneous H2-histamine receptors provided by previous studies using cimetidine and metiamide. The degree of inhibition of histamine mediated cutaneous reactions achieved by clemastine was increased by the administration of clemastine and ranitidine together, for ranitidine concentrations 10(-5) M (P less than 0.001) and 10(-6) M (P less than 0.05). The magnitude of the inhibitory effect of ranitidine, both administered alone and in combination with clemastine, suggests that in the production of histamine induced cutaneous weal and flare reactions, the contribution afforded by stimulation of cutaneous H2-histamine receptors is only small.

Adult↗
PubMed1985

Plasma or serum from patients with systemic sclerosis alters behaviour of normal erythrocytes.

Incubation of washed normal erythrocytes with fresh or frozen plasma or serum from patients with systemic sclerosis (SS) significantly decreased the filterability of the cells, whereas the incubation of homologous normal serum or plasma with washed erythrocytes did not alter the filterability of these cells. The endothelial cell adherence of normal erythrocytes was increased by 3.5- and 2.6-fold (p less than 0.01) respectively when plasma or serum from patients with SS rather than that from normal controls was added to the incubation medium. Further investigation and isolation of the reactive material(s) present in the serum and plasma of patients with SS, which affect the deformability and endothelial cell adherence of erythrocytes, may be helpful in understanding the pathogenesis of the disease.

Adult↗