Biomedical subjects

T J Robinson

Publications and source records attributed to T J Robinson.

At least 37 records · Page 2Linked to original sources

PubMed2002

Chromosome painting refines the history of genome evolution in hares and rabbits (order Lagomorpha).

Fluorescence in situ hybridization (FISH) was used to define homologous segments among representatives of 7 of the 11 recognized leporid genera. Chromosome painting using 22 rabbit chromosome-specific paints derived from flow-sorted chromosomes revealed that at least 18 fusions and six fissions differentiate the extant karyotypes from the presumed ancestral state (2n = 48). The riverine rabbit, Bunolagus monticularis, has the most derived karyotype, differing from the ancestor by seven fusions and five fissions, followed by Pronolagus rupestris, with four fusions and one fission. These findings are consistent with the proposed Palaeolaginae/Leporinae dichotomy in the lagomorphs. The molecular cytogenetic data allow for a refinement of the structural changes that have shaped genome evolution in this group of mammals and underscore the rapid radiation of the Leporidae suggested by mitochondrial DNA sequence data.

Animals↗

PubMed2002

Monitoring dietary compliance in coeliac disease using red cell distribution width.

Red cell distribution width (RDW) as measured on modern blood analysers is a sensitive marker of nutritional deficiency affecting red blood cell production and maturation. Such deficiencies are common in coeliac disease and it may therefore be possible indirectly to assess response to a gluten-free diet by monitoring the RDW. We measured RDW, iron, B12, folate and endomysial antibodies (EMA) in 46 newly diagnosed coeliac patients at diagnosis and after a gluten-free diet. RDW was elevated in 76% of patients at diagnosis. There was a significant decrease in RDW (17.3% vs 13.8%) after 12 months of diet, corresponding to sero-conversion of EMA and normalisation of serum iron, B12 and folate levels. We conclude that monitoring RDW is a simple indirect means of assessing response to a gluten-free diet in coeliac disease.

Anemia, Iron-Deficiency↗

PubMed2001

Retrieval of four adaptive lineages in duiker antelope: evidence from mitochondrial DNA sequences and fluorescence in situ hybridization.

Independent molecular markers (mitochondrial DNA sequences from two genes and fluorescence in situ hybridization with satellite DNA sequences as hybridization probes) were employed to investigate phylogenetic relationships among duiker antelope. When analyzed singly or taken together, the molecular and cytogenetic data allowed for the delimitation of four adaptive groups: the conservative dwarfs which are basal, a savanna specialist which groups apart from the forest duikers, the giant duikers, and the red duikers. Within the latter, a further subdivision comprising an east African and a west African red duiker clade is evident. The placement of the endangered zebra duiker and Aders' duiker remains problematic. Several of the nomenclatural divisions in current use are questioned by our results. These include the recognition of Philantomba as genus name for the blue and Maxwell's duiker and that Harvey's duiker be relegated to a subspecies of the Natal red duiker. We place our results in a biogeographic context and argue that duiker speciation has been driven predominantly by habitat fragmentation which probably led to the disruption of gene flow between geographic populations.

Animals↗

PubMed2001

Chromosomal evolution in the vlei rat, Otomys irroratus (Muridae: Otomyinae): a compound chromosomal rearrangement separates two major cytogenetic groups.

G- and C-banding delimits two cytogenetic groups within the vlei rat, Otomys irroratus. One has a diploid number of 2n = 24, resulting from a centric fusion of chromosomes 7 and 12 of the O. irroratus standard coupled with a tandem fusion to chromosome 8. The second has a diploid number of 2n = 28, lacks the compound chromosome, and appears to have a far wider geographic distribution within South Africa. Additionally, the two groups differ through the presence of cytotype-specific heterozygous centric fusions and one to three B chromosomes which appear as floating polymorphisms in the 2n = 28 complex.

Animals↗

PubMed2001

Effects of gamma-2-melanocyte-stimulating hormone on protein kinase C activity and expression in spontaneous hypertensive rats (SHR).

Administration of gamma-2-melanocyte stimulating hormone (gamma-2-MSH) to rats increases blood pressure, heart rate and natriuresis by acting through the nervous system and this response is more pronounced in spontaneous hypertensive rat (SHR). The molecular mechanisms underlying these effects are unknown, however, protein kinase C (PKC) activity is higher in SHR tissues and melanocortins are known to activate the phosphoinositide (PI) signaling pathway. In this study, we tested the hypothesis that gamma-2-MSH potentiation of PKC activation is increased in nerve terminals from SHR brain. Synaptosomes were isolated from SHR and age-matched control Wistar Kyoto (WKY) rats and incubated with gamma-2-MSH. Total particulate-fraction associated PKC activity was determined and the expression of individual isozymes analyzed by immunoblotting. Treatment with gamma-2-MSH resulted in an increase in particulate-associated PKC activity in hindbrain synaptosomes that was more prominent in SHR. The levels of membrane-associated PKC-alpha and beta-isozymes were considerably less than for PKC-gamma in these tissues as determined by immunoblotting. The novel PKC isozymes delta and epsilon were detected in total synaptosomes but not in membrane fractions. These data suggest that PKC-gamma is the major presynaptic PKC isozyme and that PKC may be an important mediator for gamma-2-MSH in neural tissues.

Animals↗

PubMed2001

Expression and distribution of protein kinase C isozymes in brain tissue of spontaneous hypertensive rats.

Hypertension activates many endocrine, neuroendocrine and metabolic responses. How hypertension alters these functions remains unknown. Consequently the pathophysiology of hypertension related illnesses are incompletely understood. Protein kinase C (PKC) isoforms play an important role in cellular signal transduction and altered PKC activity has been reported in spontaneous hypertensive rats (SHR). In order to understand the role that PKC plays in hypertension, we hypothesized that PKC activity is significantly expressed in synaptosomal preparations from the brains of SHRs. In addition, the neuroanatomical distribution of this expression was mapped and compared to control animals. The brains were further studied for signs of neuropathology. Total PKC activity was significantly increased in synaptosomal samples isolated from the forebrain, midbrain, and hindbrain of SHR rats. Westem blot analysis identified PKC-alpha, -beta, -gamma, -delta, -epsilon and -zeta in all brain regions. Immunohistochemical analyses indicated that PKC-gamma was localized in cell bodies and processes in many autonomic cardiovascular control regions. These results suggest that PKC may be an important modulator of autonomic blood pressure control.

Animals↗

PubMed2000

Stable methylation patterns in interspecific antelope hybrids and the characterization and localization of a satellite fraction in the Alcelaphini and Hippotragini.

Conflicting data has recently appeared concerning altered methylation patterns in interspecific mammalian hybrids and the potential this may hold for driving karyotypic evolution. We report no detectable methylation difference in the genomic DNA of different interspecific F1 antelope hybrids (family Bovidae) and their parent species using the methylation-sensitive enzyme HpaII and its methylation insensitive isoschizomer MspI. However, both enzymes released a tandemly repeated satellite array. Characterization of the repeat using Southern blotting and a combination of sequencing, fluorescence in-situ hybridization (FISH) and C-banding, shows some similarity in the family of repeats between the hybridizing antelope species groups, and that the satellite is localized in the centromeric C-band positive regions of the chromosomes. Moreover, although there is little meaningful sequence homology with the well characterized bovine 1.715 satellite DNA, there is 86% sequence similarity with the sheep/goat satellite I, suggesting that they are related and are likely to have originated and evolved separately from the bovine unit.

Animals↗

PubMed1999

Cytochrome b phylogeny of the family bovidae: resolution within the alcelaphini, antilopini, neotragini, and tragelaphini.

The family Bovidae is characterized by an incomplete fossil record for the period during which most bovid subfamilies emerged. This, coupled to extensive morphological convergence among species, has given rise to inconsistencies in taxonomic treatments, especially at the tribal and subfamilial levels. In an attempt to clarify some of these issues we analyzed the complete mtDNA cytochrome b gene (1140 bp) from 38 species/subspecies representing at least nine tribes and six subfamilies. Specific emphasis was placed on the evolution of the Alcelaphini (hartebeest and wildebeest), the Tragelaphini (kudu, eland, and close allies), the Antilopini (gazelles), and the Neotragini (dwarf antelope). Saturation plots for the codon positions revealed differences between bovid tribes and this allowed for the exclusion of transitional substitutions that were characterized by multiple hits. There was no significant rate heterogeneity between taxa. By calibrating genetic distance against the fossil record, a transversion-based sequence divergence of 0.22% (+/-0.015%) per million years is proposed for cytochrome b clock calibrations in the Bovidae. All evidence suggests that the Alcelaphini form a monophyletic group; there was no support for the recognition of the Lichtenstein's hartebeest in a separate genus (Sigmoceros), and the acceptance of the previously suggested Alcelaphus is recommended for this species. High bootstrap support was found for a sister taxon relationship between Alcelaphus and Damaliscus, a finding which is in good agreement with allozyme and morphological studies. In the case of the Tragelaphini, the molecular data suggest the inclusion of Taurotragus in the genus Tragelaphus, and no genetic support was found for the generic status of Boocercus. Although associations within the Antilopinae (comprising the tribes Neotragini and Antilopini) could not be unequivocally resolved, there was nonetheless convincing evidence of non-monophyly for the tribe Neotragini, with the Suni antelope (Neotragus moschatus) grouping as a sister taxon to the Impala (Aepyceros melampus, tribe indeterminate, sensu Gentry, 1992) and the Klipspringer (Oreotragus oreotragus) falling within the duiker antelope tribe (Cephalophini).

Animals↗

PubMed1999

Multiple substitutions affect the phylogenetic utility of cytochrome b and 12S rDNA data: examining a rapid radiation in leporid (Lagomorpha) evolution.

Partial sequences of two mitochondrial genes, the 12S ribosomal gene (739 bp) and the cytochrome b gene (672 bp), were analyzed in hopes of reconstructing the evolutionary relationships of 11 leporid species, representative of seven genera. However, partial cytochrome b sequences were of little phylogenetic value in this study. A suite of pairwise comparisons between taxa revealed that at the intergeneric level, the cytochrome b gene is saturated at synonymous coding positions due to multiple substitution events. Furthermore, variation at the nonsynonymous positions is limited, rendering the cytochrome b gene of little phylogenetic value for assessing the relationships between leporid genera. If the cytochrome b data are analyzed without accounting for these two classes of nucleotides (i.e., synonymous and nonsynonymous sites), one may incorrectly conclude that signal exists in the cytochrome b data. The mitochondrial 12S rRNA gene, on the other hand, has not experienced excessive saturation at either stem or loop positions. Phylogenies reconstructed from the 12S rDNA data support hypotheses based on fossil evidence that African rock rabbits (Pronolagus) are outside of the main leporid stock and that leporids experienced a rapid radiation. However, the molecular data suggest that this radiation event occurred in the mid-Miocene several millions of years earlier than the Pleistocene dates suggested by paleontological evidence.

Animals↗

PubMed1999

Mitochondrial DNA population structure of roan and sable antelope: implications for the translocation and conservation of the species.

Mitochondrial DNA (mtDNA) control region sequences were analysed to determine the geographical genetic structure of Hippotragus niger (sable antelope) and H. equinus (roan antelope). Analyses by AMOVA, minimum evolution networks, parsimony, neighbour joining and maximum likelihood show that the roan antelope populations are geographically partitioned and that their phylogeography corresponds well with subspecific boundaries. In sharp contrast, however, our sequence data group all the sable antelope into two well-delineated maternal clades. One comprising specimens from the strictly east African H.n. roosevelti, and a second geographically diverse group which includes H.n. niger (South Africa, Zimbabwe), H.n. variani (Angola), and H.n. Kirkii (Zambia, Malawi). The differences in the genetic population structure suggest that distinct extrinsic and intrinsic factors have shaped the phylogeography of these two closely related antelope species. In the absence of obvious extrinsic barriers to gene flow, we suggest that behavioural differences may be responsible, at least in part, for the contrasting spatial patterns detected among geographical localities. Although our data reflect only the maternal phylogeny of these important game species, they nonetheless suggest that different management strategies should be applied. We recommend that roan antelope be translocated only within the currently defined subspecies boundaries, while in the case of sable antelope, conservation measures should focus on preserving the genetic integrity of the east African and southern African sable populations. Implicit in this is that translocations of animals between populations comprising these two distinct maternal genetic clades should be actively discouraged.

Africa↗

PubMed1999

A comparison of open access endoscopy and hospital-referred endoscopy in a district general hospital.

Open access endoscopy (OAE) is widely used in many hospitals. The aim of this study was to compare the upper gastrointestinal endoscopies referred to as "OGDs" performed under the OAE service and those referred from hospital outpatient clinics (HR) during the initial year in which an OAE service was provided in a district general hospital. A retrospective review of medical records from all patients undergoing OGD during the first year of OAE to identify the waiting time for OGD, the extent of pre-treatment at the time of OGD, the endoscopic findings and the number of endoscopies in which oesophageal or gastric neoplasia was detected. Follow-up endoscopies (n = 41) were excluded. Of 739 OGDs included, 384 (177 male; mean age 48.0 yrs.) were performed under the OAE service, 346 (149 male; mean age 50.7 yrs.) were referred from outpatient clinics and 9 could not be accurately classified. The waiting time was significantly lower in the OAE group compared to the HR group (24.5 v. 29.8 days, p<0.001). Pre-treatment at the time of OGD was significantly more frequent in the OAE group compared to the HR group (295 v. 186, p<0.001). Frequencies of the main endoscopic diagnoses did not differ significantly between the two groups. The OAE service provided faster access to OGD than the HR group and the endoscopic findings were similar in the two groups.

Endoscopy, Digestive System↗

PubMed1998

Pneumonitis secondary to the influenza vaccine.

We report a 58-year-old man who developed respiratory distress and interstitial shadowing on chest X-ray 10 days after receiving the influenza vaccine. He failed to respond to intravenous antibiotics but his clinical condition, hypoxia and chest X-ray changes improved dramatically on oral steroids. The clinical diagnosis was pneumonitis secondary to recent influenza vaccination.

Anti-Inflammatory Agents↗

PubMed1998

Subarachnoid haemorrhage: difficulties in diagnosis and treatment.

Aneurysmal subarachnoid haemorrhage is associated with a uniquely severe headache of acute onset. Classical cases are readily identified as such, although this is not always the case. Four cases who were admitted to a district general hospital within a 3-month period are presented, because they demonstrate a variety of presentations, management options, and outcomes.

Adult↗

PubMed1998

A molecular cytogenetic analysis of X chromosome repatterning in the Bovidae: transpositions, inversions, and phylogenetic inference.

Chromosomal homologies among the X chromosomes of species representative of eight bovid subfamilies and most of the recognized tribes were established using a combination of FISH and conventional G- and C-banding. Our analyses allowed for the delimitation of three X chromosome types represented, respectively, by cattle (Bovinae, tribe Bovini), the tragelaphines (Bovinae, tribe Tragelaphini), and a large assemblage comprising all the remaining subfamilies and their tribes (the Cephalophinae, Hippotraginae, Alcelaphinae, Antilopinae, Aepycerotinae, Peleinae, and Caprinae). The use of the bacterial artificial chromosome probe BAC 101 (which maps to Xp12 in cattle) and an Xp painting probe comprising sequences specific for the short arm of cattle Xp (Xp24-->p12) allowed us to orient this region, which has moved as a conserved euchromatic block during the evolution of the bovid X chromosome. We show that the differences between the three chromosomal types are attributable to a transposition, two inversions, and heterochromatic additions/deletions. A paucity of comparative mapping data precludes the assignment of the sequences contained in cattle Xp to either the presumed conserved (XCR) or the recently added (XAR) region of the eutherian X chromosome, and the reasons for the retention of these sequences as an evolutionarily conserved unit in the intrachromosomal restructuring of the bovid X across lineages remain enigmatic.

Animals↗

PubMed1997

Phylogenetic relationships of cottontails (Sylvilagus, Lagomorpha): congruence of 12S rDNA and cytogenetic data.

The genus Sylvilagus, which comprises the New World cottontail rabbits, contains several commercially important as well as endangered (or threatened) species. Understanding the evolution of this group is pertinent to their management and conservation. The purpose of this study was to examine the evolutionary history of the cottontails using sequence data from the mitochondrial 12S rRNA gene. The 12S data provide a robust phylogeny which was supported under a variety of phylogenetic approaches and transition/transversion (Ti/Tv) weighting schemes. Stem and loop regions of the gene were analyzed separately and two different methods of estimating Ti/Tv ratios were employed. The phylogeny obtained was consistent with available cytogenetic information. The 12S data indicate that separate generic status for the pygmy rabbit, Brachylagus idahoensis, is warranted based on its phylogenetic position and sequence divergence values. Additionally, the taxa which are geographically adjacent are also phylogenetically closely related; for example, the marsh rabbit, S. palustris, and the swamp rabbit, S. aquaticus, are sister taxa, as are the mountain cottontail, S. nuttallii, and desert cottontail, S. audubonii. This finding suggests that recent vicariance events might explain the diversification of several cottontail lineages.

Animals↗

PubMed1997

Genetic population structure in the yellow mongoose, Cynictis penicillata.

Phylogeographic structure was determined for the yellow mongoose, Cynictis penicillata, using mtDNA RFLPs and control region sequences. The RFLP analysis revealed 13 haplotypes which showed weak geographical patterning consistent with a recent range expansion from a refugial population(s). An analysis of molecular variance (AMOVA) revealed no correspondence between mtDNA phylogeography and subspecies delimitation, nor between matrilines and areas characterized by a high incidence of the viverrid-type rabies, of which the yellow mongoose is the principal vector. The lack of structure was also shown by control region sequences although four of the maternal lineages shared a near-perfect 81 bp repeat. We speculate that regional hot spots of the viverrid rabies biotype reflect population density differences in the yellow mongoose that are not underscored by genetic partitioning, at least at the level of resolution provided by our analyses.

Animals↗

PubMed1997

Molecular phylogeny of the springhare, Pedetes capensis, based on mitochondrial DNA sequences.

The phylogenetic position of the Pedetidae, represented by a single species Pedetes capensis, is controversial, reflecting in part the retention of both Hystricomorphous and Sciurognathous characteristics in this rodent. In an attempt to clarify the species evolutionary relationships, mtDNA gene sequences from 10 rodent species (representing seven families) were analyzed using phenetic, parsimony, and maximum-likelihood methods of phylogenetic inference; the rabbit, Oryctolagus cuniculus (Order Lagomorpha), and cow, Bos taurus (Order Artiodactyla), were used as outgroups. Investigation of 714 base pairs of the protein-coding cytochrome b gene indicate strong base bias at the third codon position with significant rate heterogeneity evident between the three structural domains of this gene. Similar analyses conducted on 816 base pairs of the 12S rRNA gene revealed a transversion bias in the loop sections of all taxa. The cytochrome b gene sequences proved useful in resolving associations between closely related species but failed to produce consistent tree topologies at the family level. In contrast, phylogenetic analysis of the 12S rRNA gene resulted in strong support for the clustering of Pedetidae/Heteromyidae/Geomyidae and Muridae in one clade to the exclusion of the Hystricidae/Thryonomyidae and Sciuridae, a finding which is concordant with studies of rodent fetal membranes as well as reproductive and other anatomical features.

Animals↗

PubMed1997

X chromosome evolution in the suni and eland antelope: detection of homologous regions by fluorescence in situ hybridization and G-banding.

Comparative cytogenetics and fluorescence in situ hybridization (FISH) were used to track structural rearrangements in the X chromosomes of two African antelope species, the eland (Taurotragus oryx; tribe Tragelaphini) and the suni (Neotragus moschatus; tribe Neotragini). Using two microdissected cattle chromosome painting probes (one specific for Xp-containing sequences corresponding to Xp24-->p12 of the cattle X, and one specific for Xq-containing sequences corresponding to Xq12-->qter), we show that intrachromosomal rearrangements distinguish the X chromosomes of these species. Furthermore, there is clear evidence that, superimposed on this background of intrachromosomal evolutionary change, the sequences contained in the cattle Xp painting probe appear to have moved as a complete unit during the repatterning of the bovid X. Although we are unable to infer the order of the rearranged chromosomal segments, given the large regions of homology detected by the chromosome paints, we nonetheless believe that this approach (combining conventional and molecular cytogenetic studies on the X chromosome) will prove useful for inferring phylogenetic relationships in the family Bovidae, particularly as more probes become available.

Animals↗