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R C Thompson

Publications and source records attributed to R C Thompson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Proenkephalin and opioid mu-receptor mRNA expression in ovine hypothalamus across the estrous cycle.

The neural mechanism underlying the preovulatory surge of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) is thought to include reduced opioid inhibition of GnRH secretion (disinhibition). Possible mechanisms for disinhibition include reduced endogenous opioid peptide or receptor mRNA expression. Proenkephalin and opioid mu-receptor mRNA expression were measured by in situ hybridization using 35S-labeled cRNA probes and computer-assisted grain counting in hypothalamic nuclei of ovary-intact ewes (n = 4) killed on day 10 of the luteal phase or 24 or 48 h into the follicular phase. In a second experiment, proenkephalin and mu-receptor mRNA expression were compared in ewes killed on day 10 of the luteal phase or during the preovulatory LH surge. Cells expressing proenkephalin mRNA were more widely distributed in ovine hypothalamus than previously described. In the periventricular nucleus, there was a significant reduction in the grain count per cell and the number of labeled cells during the follicular phase and during the LH surge, as compared to the luteal phase. In the ventromedial hypothalamus, there was a significant reduction in the grain count per cell during the follicular phase and LH surge as compared to the luteal phase, but no change in the number of labeled cells. No differences in proenkephalin mRNA expression were detected in the medial septum, diagonal band of Broca, preoptic area, anterior hypothalamic area or paraventricular nucleus across the estrous cycle. Cells expressing opioid mu-receptor mRNA were also widely distributed. No difference in mu-receptor mRNA expression was detected in the medial septum, diagonal band, medial preoptic area, anterior hypothalamus or bed nucleus of the stria terminalis across the cycle. We conclude that in sheep, proenkephalin gene expression in the periventricular nucleus and ventromedial hypothalamus is reduced during the follicular phase and at the time of the LH surge. This may be part of the neural mechanism underlying the GnRH/LH surge in this species.

Animals↗
PubMed2001

Spontaneous retroclival hematoma presenting as a thunderclap headache. Case report.

An excruciating headache of instantaneous onset, or thunderclap headache, may be caused by a variety of serious disorders, including aneurysmal subarachnoid hemorrhage, cerebral venous sinus thrombosis, pituitary apoplexy, and carotid artery or vertebral artery dissection. The authors describe a patient with this type of headache who was found to have a spontaneous retroclival hematoma. A 49-year-old woman experienced an instantaneous excruciating headache. Results of computerized tomography (CT) scans of the head were normal, but on examination of the cerebrospinal fluid xanthochromia was found. Magnetic resonance (MR) imaging of the cervical spine revealed a retroclival hematoma. Three cerebral angiographic studies did not reveal the source of the hemorrhage and a repeated MR image demonstrated resolution of the hematoma. The patient made an uneventful recovery. Spontaneous retroclival hematoma is an exceedingly rare type of intracranial hemorrhage and may be associated with normal findings on CT scans. Spontaneous retroclival hematoma should be included in the differential diagnosis of thunderclap headache.

Cerebral Angiography↗
PubMed2000

The "chip" as a specific genetic tool.

DNA microarrays are powerful tools for the analysis of the organization and regulation of the brain, in both illness and health. Such messenger RNA expression methods are outgrowths of a marriage between the several genome sequencing projects and a wide variety of physical, chemical, optical, and electronic systems. The advantages of microarray analyses include the ability to study the regulation of several genes or even the entire genome in a single experiment. However, there are substantive issues associated with the use of these tools that need to be considered before drawing conclusions about the genomic regulation of the brain. These issues include the loss of most anatomic (i.e., cellular and circuit) specificity, only fair sensitivity, lack of absolute quantitative data, poor comparability between studies, and high variability in sample values, to mention the most obvious. In this review we point to some of the solutions proposed for these problems and novel techniques and approaches for newer methods. Among these are methods for making arrays more sensitive, including nonarray messenger RNA expression systems. The future of this field and its links to deeper protein and cell biology are both emphasized.

Clinical Laboratory Techniques↗
PubMed2000

Prevalence and genotypic characterisation of Giardia in dairy calves from Western Australia and Western Canada.

In this study, the prevalence of Giardia duodenalis infections was determined in Western Canadian and Western Australian dairy calves. Faecal samples were collected from Holstein calves located on a commercial dairy near Lethbridge, Alta., Canada (N=28) and from calves located on two commercial dairies located near Perth, WA, Australia (N=36). Faecal samples were examined for the presence of Giardia cysts using sucrose gradient centrifugation, followed by immunofluoresence microscopy. DNA was then extracted from Giardia isolates obtained from positive samples. A PCR based method was employed to amplify and sequence a 292bp region of the 16S-rRNA gene. Genetic sequences obtained from Giardia isolates were compared to each other and to previously sequenced isolates. Following a single faecal sample, 58% of Western Australian calves and 57% of Western Canadian calves were positive for Giardia. Geometric mean cyst counts/g of faeces were 839 for Western Australian calves and 3475 for Western Canadian calves, but these values did not differ significantly. Genetic sequences were obtained from 10 calves from Western Canada, while six sequences were obtained from Western Australian calves. Of the Western Canadian isolates, eight aligned with the proposed 'Hoofed livestock' genotype. Of the five isolates obtained from Western Australian calves, four sequences were identical to the 'Hoofed livestock' genotype. Two isolates from the Western Canadian calves and one isolate from the Western Australian calves had the identical genetic sequence to the Genotype (Assemblage) A sequence, a common human genotype. The results of this study demonstrate, for the first time, that Giardia infections occur in Western Australian calves. Also, calves from different geographical locations appear to be primarily infected with a Giardia genotype unique to hoofed livestock. However, calves can shed Giardia cysts potentially infective for humans. Thus, Giardia infections should be considered important to Australian dairy producers, and infections in calves may pose a risk to public health regardless of geographical location.

Animals↗
PubMed2000

Coaggregation of paramagnetic d- and f-block metal ions with a podand-framework amine phenol ligand.

This report covers initial studies in the coaggregation of nickel (Ni2+) and lanthanide (Ln3+) metal ions to form complexes with interesting structural and magnetic properties. The tripodal amine phenol ligand H3tam (1,1,1-tris(((2-hydroxybenzyl)amino)methyl)ethane) is shown to be particularly accommodating with respect to the geometric constraints of both transition and lanthanide metal ions, forming isolable complexes with both of these ion types. In the solid-state structure of [Ni(H2tam)(CH3CN)]PF6.2.5CH3CN.0.5CH3OH (1), the Ni(II) center has a distorted octahedral geometry, with an N3O2 donor set from the [H2tam]- ligand and a coordinated solvent (acetonitrile) occupying the sixth site. The reaction of stoichiometric amounts of H3tam with the Ni(II) ion in the presence of lanthanide(III) ions provides [LnNi2(tam)2]+ cationic complexes which contain coaggregated metal ions. These complexes are isolable and have been characterized by a variety of analytical techniques, with mass spectrometry proving to be particularly diagnostic. The solid-state structures of [LaNi2(tam)2(CH3OH)1/2(CH3CH2OH)1/2(H2O)]ClO4.0.5CH3OH.0.5CH3CH2OH.4H2O (2), [DyNi2(tam)2(CH3OH)(H2O)]ClO4.CH3OH. H2O(6), and [YbNi2(tam)2(H2O)]ClO4.2.58H2O(9) have been determined. Each complex contains two octahedral Ni(II) ions, each of which is encapsulated by the ligand tam3- in an N3O3 coordination sphere; each [Ni(tam)]-unit caps the lanthanide(III) ion via bridging phenoxy oxygen donor atoms. In 2, La3+ is eight-coordinated, while in 6, Dy(III) is seven- (to "weakly eight-") coordinated, and Yb(III) in 9 has a six-coordination environment. The complexes are symmetrically different, 2 possessing C2 symmetry and 6 and 9 having C1 symmetry. Magnetic studies of 2, 6, and 9 indicate that antiferromagnetic exchange coupling between the Ni(II) and Ln(III) ions increases with decreasing ionic radius of Ln(III).

Amines↗
PubMed2000

Evaluation of the feasibility of and results of measuring health-status changes in patients undergoing surgical treatment for skeletal metastases.

The goal of treating patients with skeletal metastases is to decrease pain and improve or maintain physical function. Assessment of the effectiveness of treatment should therefore include evaluation of patient-rated measures of quality of life. The primary objective of the study was to determine the feasibility of studying the effect of surgical treatment of skeletal metastases on quality of life. The secondary objective was to provide data that begin to characterize this effect. The characteristics of patients with skeletal metastases are heterogeneous, patient enrollment in the study may be low, high attrition occurs secondary to death, and well accepted health-status measures (such as the Short Form-36) may be ineffective at detecting changes in health status; therefore, it is difficult to study these patients. High attrition and adjuvant treatment with radiation or chemotherapy made it impractical to draw firm conclusions about the effect of surgical treatment, but a trend toward improvement in selected health-status measures for both physical and mental health was noted. Analysis of patient-rated health-status scores as predictors of survival indicates that improvement in these scores 6 weeks after surgery is associated with an increase in the length of survival following surgery.

Adult↗
PubMed2000

Giardiasis as a re-emerging infectious disease and its zoonotic potential.

The reasons for considering giardiasis as a re-emerging infectious disease are presented, with emphasis on Giardia infections in child care centres, livestock and pets, and the role of zoonotic transmission. However, the aetiology and control of giardiasis is complicated by the genetic and phenotypic variability of Giardia species infective to mammals. Of particular significance has been the uncertainty about host specificity and the question of zoonotic transmission. The recent application of molecular characterisation procedures based on PCR has made an enormous contribution to an understanding of the genetic structure of Giardia populations, and this is reviewed in the context of the zoonotic transmission and molecular epidemiology of Giardia infections.

Adult↗
PubMed2000

The role of companion animals in the emergence of parasitic zoonoses.

Pets offer individuals and the community significant benefits, however cognisance must be taken of the potential for transmission of infectious agents from these animals to humans. The prevalence of many parasites, such as Giardia and Cryptosporidium, has increased over the past few decades while others, such as Toxocara and Ancylostoma, have decreased. These changes could be real, associated with the ready availability of efficacious anthelmintic products or could be artificial due to the type of surveys conducted, the animals surveyed and the diagnostic tests used. Immunocompromised people, in particular, must be aware of the potential risk of acquiring parasitic infections from their pets. However, with the adoption of good hygiene and a thorough knowledge of the transmission of these parasites, immunocompromised people should be able to continue to enjoy the significant benefits of pet ownership. As many owners are not aware of the zoonotic parasites that could be carried by their pets or their mode of transmission, it is concluded that veterinarians need to play a greater role in the education of their clients.

Animals↗
PubMed2000

Cryptosporidium systematics and implications for public health.

There is controversy in the taxonomy of Cryptosporidium parasites and the public health significance of Cryptosporidium isolates from various animals. Recent advances in molecular characterization of Cryptosporidium parasites have allowed the re-examination of species structure of the genus Cryptosporidium. Non-parvum Cryptosporidium spp and new C. parvum genotypes in immunocompromised humans can now be clearly detected. In this article, Lihua Xiao and colleagues summarize the current biological and molecular evidence for different Cryptosporidium spp, and the public health importance of these species and new C. parvum genotypes.

Animals↗
PubMed2000

Nomenclature and genetic groupings of Giardia infecting mammals.

Giardia is a ubiquitous and well-known enteric parasite affecting humans and a range of domestic and wild mammals. It is one of the most common parasites of domestic dogs and dairy cattle and a frequently recognized waterborne pathogen. Giardiasis is considered to be a re-emerging infection because of its association with outbreaks of diarrhoea in child-care centres. Although only a single species has been recognized as causing disease in humans and most other mammals, molecular characterization of morphologically identical isolates from humans and numerous other species of mammals has confirmed the heterogeneity of this parasite and provided a basis for a clearer understanding of the taxonomy and zoonotic potential of Giardia.

Animals↗
PubMed2000

Molecular and phylogenetic analysis of Cryptosporidium muris from various hosts.

Isolates of Cryptosporidium muris and C. serpentis were characterized from different hosts using nucleotide sequence analysis of the rDNA 18S and ITS1 regions, and the heat-shock (HSP-70) gene. Phylogenetic analysis confirmed preliminary evidence that C. muris is not a uniform species. Two distinct genotypes were identified within C. muris; (1) C. muris genotype A; comprising bovine and camel isolates of C. muris from different geographical locations, and (2) C. muris genotype B comprising C. muris isolates from mice, a hamster, a rock hyrax and a camel from the same enclosure. These 2 genotypes may represent separate species but further biological and molecular studies are required for confirmation.

Animals↗
PubMed2000

Intracerebroventricular administration of melanin-concentrating hormone suppresses pulsatile luteinizing hormone release in the female rat.

Melanin-concentrating hormone (MCH) has been reported to be involved in the regulation of feeding behaviour in rats and mice. Because many neuropeptides that influence ingestive behaviour also regulate reproductive function, the present study was designed to determine if central administration of MCH changes pulsatile secretion of luteinizing hormone (LH) in the rats. Wistar-Imamichi strain female rats were ovariectomized and implanted with oestradiol to produce a moderate inhibitory feedback effect on LH release. The effects of i. c.v. injections of MCH on LH release were examined in freely moving animals. Blood samples were collected every 6 min for 3 h through an indwelling cannula. After 1 h of sampling, MCH (0.1, 1 or 10 microg/animal) or vehicle (saline) was injected into the third cerebroventricle. Because MCH is also reported to affect the hypothalamo-pituitary-adrenal (HPA) axis, which in turn, can influence reproductive function, plasma corticosterone concentrations were determined in the same animals at 30-min intervals during the first and last hours and every 12 min during the second hour of the 3-h sampling period. When expressed as per cent changes, mean plasma LH concentrations after MCH administration were significantly lower in the animals injected with all doses of the peptide compared with vehicle-treated animals; LH pulse frequency was significantly lowered by 1 microg of MCH. Per cent changes in mean plasma corticosterone levels were not significantly affected by MCH administration. These results in oestradiol-treated ovariectomized rats indicate that central MCH is capable of inhibiting pulsatile LH secretion. We have previously shown that 48-h fasting suppresses pulsatile LH release in the presence of oestrogen. Take together, these results raise the possibility that MCH could play a role in mediating the suppression of LH secretion during periods of reduced nutrition.

Animals↗
PubMed2000

The binding and distribution of albendazole and its principal metabolites in Giardia duodenalis.

Trophozoites of the protozoan parasite Giardia duodenalis were exposed to various albendazole concentrations for 4 h, washed, fixed and incubated with antibodies raised against albendazole and its two major metabolites albendazole sulphoxide and albendazole sulphone. Tubulin antibodies were also used. A peroxidase- or FITC-conjugated secondary antibody was used to detect the primary antibody with transmission electron microscopy or confocal laser scanning microscopy, respectively. Albendazole, a benzimidazole compound, was detected in the mid-dorsal region of trophozoites, albendazole sulphoxide in the posterior-dorsal region and albendazole sulphone in clusters above the median bodies. Tubulin was recognised in the ventral disk. This is the first indication that G. duodenalis may be capable of metabolising albendazole and the potential path of the metabolised drug traced within the trophozoite. Fluorescence measurements revealed that albendazole sulphoxide binding decreased and albendazole sulphone binding increased with exposure of the trophozoites to increasing albendazole concentration. This indicates that if albendazole was being metabolised by trophozoites, it occurred to a greater extent following exposure to higher albendazole concentrations.

Albendazole↗
PubMed2000

Fractures in large-segment allografts.

Segment skeletal defects that result from resection of a malignant bone neoplasm commonly are reconstructed with large segment allografts. Excellent functional results after these reconstructions and significant complications have been reported. Although it is known that a common complication seen with the use of allografts is allograft fracture, the factors associated with allograft fracture are not entirely clear. In this study, the hypothesis was examined that allograft reconstructions, which use internal fixation devices that penetrate the cortex of the allograft, are associated with an increased risk of fracture. Findings from large segment allograft reconstructions in 74 patients with a minimum followup of 36 months were studied. These 74 patients include 35 patients whose outcomes were reported previously and now have additional followup and 39 patients whose outcomes are being reported for the first time. Thirty-one of the 74 (42%) allografts fractured, and the mean time to fracture was 26 months. When the fixation techniques resulted in cortical penetration of the allograft, fractures occurred in 27 of the 43 (63%) allografts, and when fixation of the graft to the host bone required no cortical penetration, only four of the 31 (13%) allografts fractured. Fractures occurred in 12 of 15 (80%) tibial allografts and in only two of 17 (12%) proximal femoral allografts; however, the anatomic site was not statistically independent of method of fixation because 14 of the 15 tibial grafts had cortical penetration and 15 of the 17 proximal femoral grafts had no cortical penetration. The authors' analysis indicates that internal fixation devices that require cortical penetration are associated with an increased risk of allograft fracture.

Adolescent↗
PubMed2000

Fixation of large segment femoral allografts using plates augmented with cerclage wires.

Results using plates augmented with cerclage wires to stabilize eight large segment femoral allografts are described. Two patients had plates augmented with cerclage wires placed at the time of tumor resection, and six patients had plates augmented with cerclage fixation placed to manage allograft nonunions or fractures. These internal fixation techniques spanned 10 osteotomy sites: two metaphyseal and eight diaphyseal. The goal of operations that involved internal fixation with plates augmented by cerclage fixation was to obtain osseous union. Osseous union was achieved at both metaphyseal osteotomy sites and at one of the diaphyseal osteotomy sites. Internal fixation of large segment allografts with plates that are augmented with cerclage wires yield poor results when osseous union is the goal of treatment.

Adolescent↗
PubMed2000

Neurosurgical and neuroendovascular management of Takayasu's arteritis.

OBJECTIVE: The roles of surgical and endovascular treatments for patients with Takayasu's arteritis are not clear. We report our experience in the neurosurgical and/or neuroendovascular treatment of patients with Takayasu's arteritis who exhibited ischemic neurological symptoms. METHODS: Between 1994 and 1998, seven patients with Takayasu's arteritis and neurological symptoms were treated at the Stanford University Medical Center. All patients were angiographically evaluated and received maximal medical therapy. Cerebral blood flow studies were performed for six patients. Three patients underwent surgical revascularization procedures alone, two underwent combinations of surgical and endovascular procedures, and two underwent endovascular treatment alone. RESULTS: The most common neurological symptoms were dysequilibrium, syncope, and visual disturbances. The characteristic angiographic features of Takayasu's arteritis were identified for all patients. The subclavian arteries and proximal carotid and vertebral arteries were involved in all patients. Two patients exhibited improvement of their symptoms after endovascular treatment alone. There were two deaths after surgery, involving patients with severe global cerebral hypoperfusion. All other surgically treated patients exhibited improvement of their symptoms, with patent grafts, up to 4 years after surgery. Cerebral blood flow improved after treatment. CONCLUSION: Improvement of symptoms can be achieved with surgical revascularization and/or endovascular treatment. Staged revascularization might be better than one-stage bilateral high-flow grafting for patients with severe global hypoperfusion.

Adolescent↗
PubMed2000

Cryptosporidium meleagridis in an Indian ring-necked parrot (Psittacula krameri).

OBJECTIVE: To perform a morphological and genetic characterisation of a Cryptosporidium infection in an Indian ring-necked parrot (Psittacula krameri) and to compare this with C meleagridis from a turkey. DESIGN: Tissue and intestinal sections from an Indian ring-necked parrot were examined microscopically for Cryptosporidium. The organism was also purified from the crop and intestine, the DNA extracted and a portion of the 18S rDNA gene amplified, sequenced and compared with sequence and biological information obtained for C meleagridis from a turkey as well as sequence information for other species of Cryptosporidium. RESULTS: Morphological examination of tissue sections from an Indian ring-necked parrot revealed large numbers of Cryptosporidium oocysts attached to the apical border of enterocytes lining the intestinal tract. Purified Cryptosporidium oocysts measured about 5.1 x 4.5 microns, which conformed morphologically to C meleagridis. The sequence obtained from this isolate was identical to sequence information obtained from a C meleagridis isolate from a turkey. CONCLUSION: Cryptosporidium meleagridis was detected in an Indian ring-necked parrot using morphological and molecular methods. This is the first time that this species of Cryptosporidium has been reported in a non-galliform host and extends the known host range of C meleagridis.

Animals↗