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Biomedical subjects

C Stephen

Publications and source records attributed to C Stephen.

At least 19 recordsLinked to original sources
PubMed2006

Cryptococcus gattii in wildlife of Vancouver Island, British Columbia, Canada.

Although Cryptococcus gattii has emerged as an important pathogen of humans and domestic animals on Vancouver Island, Canada since 1999; its distribution in regional wildlife species is largely unknown. Opportunistic sampling methods were employed to obtain nasal swabs for fungal culture from wild mammal species residing within the coastal Douglas fir biogeoclimatic zone on the southeast coast of the island. Samples were collected from 91 animals representing 14 species. Cryptococcus gattii was isolated from the nasal swabs of two eastern gray squirrels (Sciurus carolinensis) trapped in Duncan, British Columbia. The relative proportion of nasal colonization in wild mammal species is consistent with findings in domestic animals, suggesting that animals may be good indicators of environmental organisms.

Animals↗
PubMed2005

Sub-clinical infection and asymptomatic carriage of Cryptococcus gattii in dogs and cats during an outbreak of cryptococcosis.

Since 1999, Cryptococcus gattii has emerged as an important pathogen of humans and animals in British Columbia, Canada. Nasal swabs and serum samples were collected from dogs and cats residing within the Coastal Douglas Fir biogeoclimatic zone on Vancouver Island, where clinical cases have been reported. Deep and superficial nasal fungal cultures of 280 dogs and 94 cats identified four (4.3%) cats and three (1.1%) dogs with C. gattii serotype B in their nasal cavity. Serum samples collected from 266 dogs and 84 cats identified six (7.1%) cats and two (0.8%) dogs with a positive cryptococcal antigen titer. Overall cats were 4.4 times more likely than dogs to be positive on one or both tests. Identification of sub-clinical infection and nasal colonization is an important step in the characterization of the outbreak of clinical cryptococcosis on Vancouver Island.

Animals↗
PubMed2005

Follow-up study of dogs and cats with asymptomatic Cryptococcus gattii infection or nasal colonization.

The pathogenesis of Cryptococcus spp. infection following nasal colonization is unclear. This article reports follow-up data on a cohort of seven cats and five dogs identified in a previous study as sub-clinically infected with Cryptococcus spp. or colonized by C. gattii. Two cats progressed to clinical disease within four to six months of initial detection of antigenemia and nasal cavity colonization. The ten other animals remained asymptomatic but many were repeatedly positive on cryptococcal antigen testing or nasal fungal culture suggesting protracted infection or colonization. The results indicate that asymptomatically infected animals may clear the organism, remain sub-clinically infected or progress to clinical disease. Factors influencing the transition from exposure to disease require further investigation.

Animals↗
PubMed2002

Implications of agricultural and wildlife policy on management and eradication of bovine tuberculosis and brucellosis in free-ranging wood bison of northern Canada.

Although disease is often an important factor in the population dynamics of wild ungulates, it is largely the threat-both real and perceived-that sylvatic disease reservoirs pose to the health status of commercial livestock or game farm industry that has led governments to establish policy and legislation for disease management, trade, and movement. With respect to bovine tuberculosis and brucellosis in wildlife, policies are largely borrowed from the existing regulatory framework for domestic livestock. In this paper, we review how general policy goals for managing these reportable diseases in domestic livestock have also affected conservation and management of bison in Canada. We argue that there is a need to better integrate conservation biology with agricultural livestock policy to develop management options and better address the unique conservation challenges that diseased free-ranging bison populations present.

Agriculture↗
PubMed2001

Biological significance of a small highly conserved region in the N terminus of the p53 tumour suppressor protein.

The p53 tumour suppressor protein plays a central role in maintaining genomic integrity in eukaryotic cells. The most significant biological function of p53 is to act as a sequence-specific DNA-binding transcription factor, which can induce the expression of a variety of target genes in response to diverse stress stimuli. The p53 protein contains six highly conserved regions, one of which, termed Box I, is located in the N-terminal transactivation domain (amino acid residues 13 and 26). The second half of the Box I region is crucial for the interaction with the basal transcription machinery and is thus required for p53's activity as a transcription factor. The same region also binds to Mdm2. Since p53 is targeted by Mdm2 for ubiquitin-mediated proteasome-dependent degradation, this region is also essential for the regulation of p53's stability in response to stress signals. Although the first half of Box I is highly conserved, its biological function is not clearly defined. The aim of this study was to characterise this conserved region and investigate its role in the biological functions of p53. We have generated short deletions and point mutations within this region and analysed their effect on p53 function and regulation. Biochemical analyses demonstrate that deletion of residues 13 to 16 significantly increases both the transcriptional transactivation and G(2) arrest-inducing activities of murine p53. Residues 13 to 16 appear to function as a regulatory element in p53, modulating p53-dependent transcriptional transactivation and cell-cycle arrest, possibly by affecting the structural stability of the core domain of the protein. In support of this, the deletion was found to induce second-site reversion of the Val135 temperature-sensitive mutant of murine p53.

Amino Acid Sequence↗
PubMed2001

The appropriateness of the current antibiotic empiric therapy based on the bacteria isolated from severely malnourished Jamaican children.

We performed a retrospective audit of antimicrobial sensitivities of bacteria isolated from children admitted with a diagnosis of malnutrition to the Tropical Metabolism Research Unit (TMRU), University of the West Indies, between January 1995 and December 1999. There were 150 admissions for severe malnutrition to the TMRU during this period, which was approximately 50% fewer than in a previous TMRU study done ten years ago, between 1984 and 1989. In the present study, bacteraemia was documented in 10% of 150 severely malnourished children between 1 and 31 months of age. The most common organisms isolated were coagulase-negative Staphylococci, which represented 40% of the total isolates. The micro-organisms grown were most likely to be sensitive to amoxycillin/clavulanic acid. The current TMRU treatment protocol for severe malnutrition recommends use of crystalline penicillin plus gentamicin as empirical antibiotic therapy. This study has provided valuable information suggesting that the current empiric antibiotic therapy may be inappropriate.

Anti-Bacterial Agents↗
PubMed2000

Intestinal parasites of raccoons (Procyon lotor) from southwest British Columbia.

This is the first extensive survey of metazoan parasites (particularly of the roundworm Baylisascaris procyonis) from the intestines of raccoons in British Columbia. The sample collected in 1997-1998 consisted of 82 raccoons that had been sick or had been killed accidentally by automobiles. Fifteen parasite taxa were found: 3 nematodes, 9 digenetic trematodes, 2 acanthocephalans and 1 cestode. Ten of these parasites constitute new host records for raccoons, including 4 digenetic trematodes that have been reported in marine birds and mammals on the Pacific Coast of North America. Baylisascaris procyonis infected 61% of the raccoons with a mean intensity of 27. The high rate of infection indicates a large potential for environmental contamination and, thus, human and animal exposure to infectious eggs. Prevention of larva migrans is discussed, particularly for people in contact with raccoons in wildlife rehabilitation centers.

Animals↗
PubMed1999

[Atherosclerosis--a chronic infectious disease caused by Chlamydia pneumoniae].

Recent investigations allow a controversial but convincing interpretation of the pathogenesis of atherosclerosis (arteriosclerosis). Atherosclerosis can be apparently the result of ultrachronic persistent infection by Chlamydia pneumoniae and not the result of heterogenous risk factors. The main arguments for the chlamydial genesis are: Correlation of coronary heart disease and other atherosclerotic diseases and antibodies against Chlamydia pneumoniae. Chlamydia pneumoniae could be detected with different techniques (PCR, ICC, immunohistology, electromicroscopy, culture) in a high percentage in atheromas from different sites. Three successful international studies with macrolides in coronary heart disease. Target cells of atherosclerosis (endothelia, macrophages, muscle cells) can be infected by Chlamydia pneumoniae in vitro. Provocation of an arteriitis in animal experiments. The reduction of incidence of atherosclerotic diseases since the 1960s, probably due to advanced antibiotic therapy. Elevated acute-phase proteins and other inflammatory signs (CRP, WBC count, fibrinogen) briefly before occurrence of myocardial infarction. There are good arguments for intervention studies in coronary heart disease and other manifestations of atherosclerosis. The relevant antibiotics are licensed for chlamydial infections, cheap and safe. Meticulous records and long-term observation of patients need to be developed, sometimes contrary to interests of the pharmaceutical industry.

Animals↗
PubMed1999

Potential contamination of drinking water with Toxoplasma gondii oocysts.

The world's first documented toxoplasmosis outbreak associated with a municipal water supply was recognized in 1995 in Victoria, British Columbia, Canada. It was hypothesized that domestic cat (Felis catus) or cougar (Felis concolor) faeces contaminated a surface water reservoir with Toxoplasma gondii oocysts. An extensive investigation of the Victoria watershed 1 year following the outbreak documented the presence of an endemic T. gondii cycle involving the animals inhabiting the area. Cats and cougars were observed throughout the watershed. Serological evidence of T. gondii infection was demonstrated among domestic cats living in the Victoria area. Cougars were found to shed T. gondii oocysts. Serological evidence of T. gondii infection in deer mice living in the riparian environments of the watershed suggested that T. gondii oocysts were being shed near the water edge. Contamination of Victoria's water supply with T. gondii oocysts potentially occurred during the study period and future waterborne toxoplasmosis outbreaks in this and other communities are possible.

Animals↗
PubMed1998

Toxoplasma gondii in Vancouver Island cougars (Felis concolor vancouverensis): serology and oocyst shedding.

One of 12 necropsied cougars (Felis concolor vancouverensis) from Vancouver Island, British Columbia, Canada, shed Toxoplasma gondii oocysts confirmed by mouse bioassay. Eleven of the 12 cougars (92%) had antibodies to T. gondii by the modified agglutination test with titers of <1:25 (1 cougar), 1:50 (8 cougars), and 1:500 (3 cougars). One additional cougar fecal sample collected from the Victoria watershed environment also contained T. gondii oocysts. In 1995, the largest reported outbreak of human toxoplasmosis was linked to municipal drinking water in Victoria, British Columbia. This study supports the initial hypothesis at the time of the outbreak that not only domestic cats, but also cougars, pose a risk to Victoria's water supply.

Agglutination Tests↗
PubMed1996

Capture-recapture methods in epidemiological studies.

Medical researchers often are faced with the challenge of estimating the total number of cases in a population based on incomplete samples. Because of a lack of explicit methods for determining if all cases have been counted, indirect methods for estimating the abundance of disease have been developed. Capture-recapture models are an indirect method of estimating population sizes that have been employed in recent epidemiological studies. These methods, derived from techniques developed for studies of animal abundance, estimate the true population size by evaluating the degree of overlap among incomplete lists of cases from existing data sources. Although intuitively appealing, the successful application of these methods is dependent upon a clear understanding of the biology of the disorder involved, the dynamics of the reference population, and the assumption and robustness of the specific models used. Failure to address these issues can lead to inaccurate and sometimes misleading results. This article describes some of the strengths and limitations of recapture techniques and provides the reader with a foundation from which to explore the methods in further detail.

Animals↗
PubMed1996

Descriptive epidemiology of marine anemia in seapen-reared salmon in southern British Columbia.

Marine anemia, also known as plasmacytoid leukemia, is a recently described disease of farmed Pacific salmon in British Columbia. Most of what is known about the disease has been generated through laboratory studies or field investigations of severely affected farms. The goals of this study were to determine the range of the spatial and temporal distribution of naturally occurring marine anemia, identify potential risk factors, and provide an initial description of the impact of the disease on commercial salmon farms in British Columbia. Data were obtained from mail surveys, farm visits, and reviews of clinical and laboratory records. An attempt was made to evaluate negative, as well as mildly, moderately, and severely affected sites. The results showed marine anemia to be widely distributed throughout the major salmon farming regions in British Columbia. The disease was most commonly diagnosed in August and September, when water temperatures were at their seasonal peaks. A wide variety of lineage's and fish sources were associated with the disease. The average mortality rate attributed to marine anemia was 6% (range 2.5% to 11%). The peak occurrence of the disease was associated with a peak in the occurrence of other infectious and inflammatory diseases. The broad demographic distribution of marine anemia, coupled with its endemic nature, indicated that the disease is unlikely to be due to the recent introduction of a new pathogen and that causal factors are widespread in southern British Columbia. It is concluded that the significance of diagnosing marine anemia is not that it is predictive of an impending epidemic of mortality, but that it is an indicator of the general pattern of disease on a farm.

Anemia↗
PubMed1995

Oxidized low-density lipoproteins facilitate leukocyte adhesion to aortic intima without affecting endothelium-dependent relaxation. Role of P-selectin.

Inflammatory cell deposition in atherosclerotic blood vessels has been thought to relate to loss of endothelium-derived nitric oxide (NO). To examine whether cell deposition correlates temporally with the loss of NO activity, rat aortic rings were incubated with buffer, native LDL (n-LDL), oxidized LDL (ox-LDL), or the endothelium-derived relaxing factor synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) for 2 hours, and vascular contractile response to norepinephrine and relaxant response to acetylcholine, thrombin, and calcium ionophore A23,187 were examined. Thereafter, the rings were exposed to biotin-fluorescein isothiocyanate-labeled fluorescent or unlabeled leukocytes for 30 minutes. Cell adhesion was quantitated by fluorescent microscopy as well as by scanning electron microscopy. Incubation with n-LDL or ox-LDL did not affect either the contractile or the relaxant response of rings. However, leukocyte adhesion increased markedly in all ox-LDL-treated rings but not in those treated with n-LDL. Thus, leukocyte adhesion occurred independent of NO activity. In keeping with this concept, pretreatment of rings with the NO precursor L-arginine failed to influence leukocyte adhesion to rings incubated with ox-LDL. Treatment of rings with L-NAME also resulted in adhesion of a large number of leukocytes. Furthermore, all rings treated with ox-LDL or L-NAME demonstrated marked expression of P-selectin leukocyte adhesion molecules, determined by immunohistochemistry. Pretreatment of rings with the P-selectin blocking antibody PB1.3 markedly decreased deposition of leukocytes in rings exposed to ox-LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

DNA tetraploidy in Feulgen-stained bladder washings assessed by image cytometry.

The prognostic utility of DNA cytometry has been demonstrated for irrigation specimens from bladder neoplasms. While the traditional method of measuring the DNA content of cells recovered by bladder irrigation is flow cytometry, image analysis has been applied increasingly, with successful results. In some cases, image analysis has been shown to detect DNA aneuploid populations missed by flow cytometry. The DNA aneuploid population most frequently missed by flow cytometry is in the DNA tetraploid range. The purpose of the present study was to review image cytometry data on bladder washings analyzed at the University of Florida Diagnostic Referral Laboratories during a one-year period, with special emphasis on the subset with DNA tetraploid histograms. Of the 205 cases reviewed, 127 (62%) were DNA diploid, 36 (18%) DNA aneuploid and 42 (20%) DNA tetraploid. Corresponding cytology was negative in 113/127 (89%) of DNA diploid, 3/36 (8%) of DNA aneuploid and 29/42 (69%) of DNA tetraploid cases. Within the DNA tetraploid group, 45% of cases had no clinical (cystoscopic) or pathologic (cytologic and histologic) evidence of neoplasia. None of these patients developed tumors during follow-up. The presence of DNA tetraploidy in cytologically negative cases should be interpreted cautiously.

Aneuploidy↗