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T J Robinson

Publications and source records attributed to T J Robinson.

At least 19 recordsLinked to original sources
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↗
PubMed1997

Chromosomes of Brants' whistling rat and genome conservation in the Otomyinae revealed by G-banding and fluorescence in situ hybridization.

Conventional G- and C-banding were used to describe the chromosomes of the whistling rat, Parotomys brantsii. This species has a diploid number of 42 chromosomes. C-banding showed that large blocks of pericentromeric heterochromatin or entirely heterochromatic short arms characterize most chromosomes. G-banding and fluorescence in situ hybridization (FISH) incorporating two laboratory mouse chromosome paints were used to compare the genomes of P. brantsii, the bush karoo rat (Otomys unisulcatus; 2n = 28), and the vlei rat (O. irroratus; 2n = 28-31). The FISH results showed that sequences corresponding to mouse chromosome 2 are conserved as a single chromosome in O. irroratus but are found on two separate chromosomes in P. brantsii and O. unisulcatus. In contrast, a mouse chromosome 6 paint showed hybridization to single chromosomes in all three species examined. When taken together, the FISH and cytogenetic results produce two important findings: (1) previously undetected homoeologies between the two Otomys species can be identified and (2) a high proportion of conserved chromosomes exists between P. brantsii and O. unisulcatus. This, in conjunction with previously reported allozyme and immunoblot data, raises serious questions about the validity of the current generic taxonomy of the Otomyinae.

Animals↗
PubMed1996

Mitochondrial DNA differentiation among geographical populations of Pronolagus rupestris, Smith's red rock rabbit (Mammalia: Lagomorpha).

Geographical genetic population structure was determined for an endemic African leporid, Smith's red rock rabbit, Pronolagus rupestris. Restriction fragment length polymorphism analysis of mitochondrial DNA from 55 specimens revealed 32 distinct material lineages for the population sampled. The data show two major genetic assemblages separated by a mean sequence divergence of 7.94 per cent (+/- 1.40 per cent) and provide little support for the continued recognition of most of the described subspecies. The south-eastern assemblage is confined to the mountain ranges comprising the Great Escarpment of South Africa, while the north-western assemblage is not so tightly constrained. With the possible exception of elevation, no readily apparent ecological or topographical barrier could be identified which delimits the two mitochondrial clades. The sequence divergence separating the south-eastern and north western P. rupestris clades is high, and approximates the interspecific sequence divergences detected between P. rupestris and other Pronolagus species. The two P. rupestris clades are parapatric for part of their distribution, and the absence of shared mtDNA lineages is consistent with the hypothesis that the two populations are reproductively isolated from each other. We provisionally interpret this to reflect the presence of two hitherto undetected biological species in what has conventionally been recognized as a single taxon, P. rupestris.

Animals↗
PubMed1996

Chromosomal evolution in duiker antelope (Cephalophinae: Bovidae): karyotype comparisons, fluorescence in situ hybridization, and rampant X chromosome variation.

Fluorescence in situ hybridization (FISH) and conventional banding techniques were used to identify patterns of similarity among the genomes of six species of antelope, subfamily Cephalophinae. The G-banded euchromatic portions of the autosomes were invariable in all species; however, significant modifications of the X chromosomes were detected. Two of the taxa, Cephalophus maxwellii and C. monticola, were characterized by acrocentric X's, while X chromosome morphology varied from submetacentric to metacentric in the remaining species (C. dorsalis, C. natalensis, Sylvicapra grimmia, and C. silvicultor). The short arm of the X was heterochromatic in each species. Total genomic DNAs from these antelope were used as hybridization probes against Cephalophus metaphase chromosomes and resulted in robust fluorescence in the pericentromeric region of each autosome and in the heterochromatic short arm of the X chromosome, indicating complimentarity of DNA sequences in these regions. Conversely, chromosome painting involving genomic DNAs derived from the subfamilies Alcelaphinae (Pygargus dorcas) and Neotraginae (Oreotragus oreotragus) showed a marked absence of hybridization at these sites. Additionally, X chromosome comparisons between the Cephalophinae and Bovinae (represented by Bos taurus) revealed two euchromatic pericentric inversions which had occurred since their common ancestry. There is good G-band homoeology between the inverted cattle chromosome region Xq12 --> q34 and most of the proximal portion of Xq in duikers, as well as between the distal third of the duiker Xq and the cattle Xp. The latter rearrangement was further confirmed by in situ hybridization using a probe containing an insert spanning bands p12 to p14 of the cattle X chromosome.

Animals↗
PubMed1995

Helical CT angiography with multiplanar reformation: techniques and clinical applications.

The technique and potential clinical applications of multiplanar reformation (MPR) of imaging data from helical computed tomography (CT) to display images of the blood vessels in the abdomen and the thorax are described. Helical CT was performed following bolus intravenous contrast material enhancement in patients with suspected tumor involvement of vessels in various regions of the body. The axial images were stacked to form a volume of imaging data from which a plane could be selected to display the desired vascular image in a two-dimensional format. Various techniques were used to change the image plane so that different vessels in different regions of the body could be displayed, including the splanchnic vessels around the pancreas, the portal veins and hepatic artery in the porta hepatis, the renal vessels, and the venae cavae and aorta. Rotation from a coronal or sagittal plane was necessary to display most vessels. The technique is practical and reproducible, but it requires that the operator be knowledgeable about vascular anatomy. Helical CT angiography with MPR has the potential to display vascular images that are similar to angiograms.

Abdomen↗
PubMed1995

Absence of geographic chromosomal variation in the roan and sable antelope and the cytogenetics of a naturally occurring hybrid.

The determination of geographic chromosomal variation in rare or endangered species, or those of special management concern, is important, since geographically defined cytotypes can negatively influence breeding programs involving founders drawn from widely divergent localities. We cytogenetically analyzed specimens of the roan (Hippotragus equinus) and sable antelope (H. niger) collected from widely divergent localities throughout their respective ranges. Each species was characterized by a diploid number of 60 and an invariant karyotype. In contrast to the absence of intraspecific variation, however, the two species differ with respect to centromeric constitutive heterochromatin and numbers of nucleolar organizer regions. These cytogenetic landmarks were subsequently used to verify an anecdotal account of a naturally occurring roan x sable hybrid. The data show that, despite their markedly distinct phenotypes, the roan and sable antelope are nonetheless sufficiently similar genetically to produce viable offspring. Hybridization, although a rare event between these species, is probably partly promoted by behavioral differences which are not always sufficient to prevent mating between them.

Africa↗
PubMed1994

Pathways of nodal metastasis from pelvic tumors: CT demonstration.

Although the normal pathways of lymphatic drainage from the pelvic organs have been well described in the anatomy literature, the pathways of nodal metastasis from individual pelvic neoplasms are not well illustrated in the imaging literature. The authors retrospectively reviewed computed tomographic scans of the abdomen and pelvis in patients with various pelvic neoplasms, including those of the ovary, testis, prostate, cervix, bladder, anorectum, and other sites, to define the pathways of nodal metastasis. In most patients, pathways of nodal metastasis correlated well with the normal lymphatic pathways described in the anatomy literature, including the superficial inguinal pathway; the anterior, lateral, hypogastric, and presacral routes of the pelvic pathway; and the paraaortic pathway. However, there also were various uncommon pathways of nodal metastasis, such as metastasis along the gonadal vessels, mesenteric and mesocolic nodes, posterior iliac crest nodes, and inferior phrenic nodes. Understanding these common and uncommon lymphatic pathways of metastasis will help radiologists detect disease spread from pelvic tumors.

Humans↗
PubMed1994

The effects of stress on lipoproteins and catecholamines in rats.

In order to investigate the effects of transportation stress on metabolic activities, we measured the changes in plasma lipoprotein and catecholamine levels in those rats that had just arrived in our Animal Facility and age-matched rats which had acclimatized in the Facility for at least 21 days. The acclimatized rats were considered as control, and the values from the newly arrived rats was done within 4-6 days of their arrival in the Facility. The cholesterol levels in very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) were higher (71-84%) than the control levels. Also, the stressed animals had higher levels of norepinephrine (4.5-fold) and epinephrine (3-fold) than the control levels. However, dopamine levels was 34-fold lower than that of control. On the basis of the data, we concluded that the change in plasma levels of lipoprotein and catecholamines in response to the transportation stress is significant and may require at least three weeks after the transportation to establish a stable baseline for investigations in which the plasma levels of lipoproteins and catecholamines is a critical factor.

Animals↗
PubMed1993

Somatic cell hybrid mapping on mouse chromosome 11 (MMU11): assignment of markers relative to two breakpoints in band D.

Mouse x rat somatic cell hybrids were generated by fusing mouse cell lines that are heterozygous for reciprocal translocations involving the T42H and T9Ad breakpoints on mouse chromosome 11 (MMU11) to a thymidine kinase-negative (Tk-) rat cell line, RT2Tk-. Selection in HAT medium with geneticin disulfate (G418) resulted in some hybrid clones retaining only one derivative translocation chromosome with that part of MMU11 carrying the Tk-1 locus. Southern blot and PCR analyses of these hybrids were used to map the two breakpoints and 30 markers relative to them. The T42H breakpoint has been localized between Mpo and the Cola-1/Hox-2 cluster of loci and is proximal to the T9Ad breakpoint. The T9Ad breakpoint is proximal to the distal loci Tk-1, Gaa, D11Jkn1, and P4hb. The positions of 14 loci (Hox-2, Cola-1, Rara, Phb, Erba, Rnula-1, D11Pas1, Gfap, D11Mit13, D11Mit11, D11Mit12, Myla, Empb3 and Gh) have been further refined by their localization between the two breakpoints in band D. This study therefore improves the correlation of the genetic and physical maps of MMU11 and extends the known homology between MMU11 and human chromosome 17 (HSA17) by the assignment of three additional HSA17 markers, the profilin gene, Pfn, an anonymous marker, D17s28h, and the Crk oncogene, to above the T42H breakpoint; and the prohibitin gene, Phb, to between the T42H and T9Ad breakpoints in band D on MMU11.

Animals↗
PubMed1993

CT of the mesocolon. Part 1. Anatomic considerations.

To define the anatomy of the mesocolic attachment of the colon as seen on computed tomographic (CT) scans, the authors reviewed CT scans of patients with diseases of the colon and the pancreas and found that disease processes in these areas usually spread along the mesocolon. The plane of the mesocolon can be distinguished from the mesentery of the small bowel by identifying the vessels in the mesocolon that serve as its landmarks. These vessels include the ileocolic vessels and right colic vessels for the ascending mesocolon, the middle colic vessels for the transverse mesocolon, and the inferior mesenteric vein for the sigmoid and descending mesocolon. These vessels can be seen routinely on CT scans of the abdomen and pelvis, and knowledge of the anatomy of the mesocolon can help the radiologist understand and identify the pathways for spread of diseases of the colon and pancreas. Recognition of the anatomy of the mesocolon is also helpful in the identification of the pattern of recurrent disease after treatment.

Cecum↗
PubMed1993

CT of the mesocolon. Part 2. Pathologic considerations.

The anatomy of the mesocolon can be seen on computed tomographic (CT) scans, and its CT anatomy can be described by using the vessels in the mesocolon as anatomic landmarks. Knowledge of this anatomy is the basis to understanding pathologic processes involving the mesocolon. Common pathologic conditions usually occur due to spread of disease between organs to which the mesocolon is attached, primarily the colon and pancreas. The disease may be a malignant lesion, a benign inflammatory process, or, rarely, a primary tumor of the mesocolon; the mode of spread may be via the lymphatic vessels, direct extension, vascular invasion, or vascular involvement. The authors demonstrate various pathologic conditions and modes of spread, as seen on CT scans, with emphasis on disease of the colon and pancreas. The pathway for the spread of disease and its progression in these organs can be predicted in patients with a known disease. More important, identification of abnormalities in the mesocolon leads to careful evaluation of the organs to which the mesocolon is attached.

Colonic Diseases↗
PubMed1993

Autoradiographic demonstration of the distribution of diacylglycerol in the gastric muscularis muscle of Bufo marinus: is diacylglycerol one of the second messengers in the muscularis muscle?

The distribution of 1,2-diacylglycerol (DAG) in the muscularis muscle of Bufo marinus has been determined using autoradiographic techniques. Strips of the muscle from the body of the stomach were fixed in 4% paraformaldehyde/2.5% glutaraldehyde, postfixed, washed and longitudinal sections (15 microns) were cut on a cryotome and placed on gelatinized slides. The sections were then incubated in the presence and absence of agonist, acetylcholine (ACh) 10(-5) M or carbachol (CCh) 10(-5) M plus Li+ (10 mM) in the medium which causes a marked potentiation of agonist-stimulated formation of cytidine diphosphate-DAG (CDP-DAG). The sections were processed through an autoradiographic technique using [3H]-cytidine, which binds to 1,2-diacylglycerol within the tissue to form CDP-DAG. Analysis of the developed tissue slides indicated that the dose of ACh (10(-5) M) which had been predetermined to elicit automaticity of the preparation in vitro increased the density of CDP-DAG grains. When the muscle strips were pretreated with ACh (10(-5) M) and CCh (10(-5) M) in the presence of LiCl (10 mM), the density of the CDP-DAG grains were further enhanced. CDP-DAG grains were localized throughout the muscle fibers. The increase in the density of the grains which was induced by the conditions eliciting automaticity suggest that DAG is one of the second messengers in the manifestation of automaticity of the muscularis muscle of Bufo marinus.

Acetylcholine↗