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Biomedical subjects

R McLeod

Publications and source records attributed to R McLeod.

At least 55 records · Page 3Linked to original sources
PubMed1998

Reconstructive surgery for pelvic pouches.

Restorative proctocolectomy with ileo-pouch-anal anastomosis has become the elective surgical procedure of choice for most of our patients with ulcerative colitis and for selected patients with familial adenomatous polyposis. This report reviews the results of the outcome of patients who have undergone a more radical reconstructive approach for salvage of the pelvic pouch where multiple local procedures have failed. A group of 24 patients were reviewed (19 females, 5 males). The indication for surgery was ulcerative colitis in 22 patients; 10 of the 24 patients were referred from other centers. The 24 patients underwent a mean of 2.9 local salvage procedures per patient. Of the 19 females within the group, 12 had an anastomotic vaginal fistula. The 24 patients were divided into two groups. The first group consisted of 14 patients whose initial pouch was used once again for revisionary surgery. Group 2 comprised 10 patients whose initial pouch was removed and a redo pouch was constructed. Of the 24 patients, only 2 have had their pouches removed. More than 75% of the patients have had a successful outcome using a reconstructive approach. Four patients still have an ileostomy; of these four, two are awaiting closure of their loop ileostomy. Of 18 patients who were evaluable, 13 were considered to have normal daytime continence, and 17 of 18 were sexually functional. Of the 18 evaluable patients, 15 were satisfied with the outcome. Radical reconstructive surgery can be performed where local procedures to effect pouch salvage have failed, and it should be considered as a first-line management where factors dictate that local procedures might fail. The commitment of the surgeon and the patient to achieving a successful outcome is essential. Severe pouch-specific complications can be managed successfully by surgeons who have a specific interest in pelvic pouch surgery and have considerable experience dealing with complications that arise.

Adolescent↗
PubMed1997

Protection conferred by selenium deficiency against aflatoxin B1 in the rat is associated with the hepatic expression of an aldo-keto reductase and a glutathione S-transferase subunit that metabolize the mycotoxin.

Fischer 344 rats fed on a diet that is deficient in selenium are more resistant to the hepatocarcinogen aflatoxin B1 (AFB1) than those fed on a selenium-sufficient diet. Hepatic cytosol from either selenium-deficient Fischer 344 rats or Hooded Lister rats possesses a marked increase in both reductase activity toward AFB1-dialdehyde and glutathione S-transferase (GST) activity toward AFB(1)-8,9-epoxide than hepatic cytosol from selenium-sufficient rats. The elevation in hepatic AFB1-aldehyde reductase (AFAR) activity in selenium-deficient animals is accompanied by an increase of 11- and 15-fold in the levels of AFAR protein in liver cytosol from Fischer 344 and Hooded Lister rats, respectively. The amount of AFAR protein in selenium-sufficient and -deficient Fischer rats was modulated by treatment with N-acetylcysteine; this antioxidant reduced basal expression of AFAR but did not modulate the relative overexpression of AFAR during selenium deficiency. The enhanced capacity to conjugate glutathione with AFB(1)-8,9-epoxide in selenium-deficient livers from Fischer 344 and Hooded Lister rats is associated with a 5- and 7-fold increase, respectively, in the hepatic levels of the AFB1-metabolizing alpha-class GSTA5 subunit. The elevated levels of AFAR and GSTA5 protein in the selenium-deficient animals coincided with increases in the steady-state levels of their mRNAs. In selenium-deficient Fischer 344 rats, AFAR and GSTA5 were both found to be expressed throughout the centrilobular and midzonal areas of the liver lobule but were essentially absent from periportal hepatocytes. The effect of selenium insufficiency is pleiotropic, and it was also noted that the theta-class GSTT1 is overexpressed 3- and 10-fold in livers of selenium-deficient Hooded Lister and Fischer 344 rats. Inasmuch as GSTT1 is responsible for the metabolic activation of dihaloalkanes, selenium deficiency may increase the susceptibility of rats to mutagens such as dichloromethane.

Acetylcysteine↗
PubMed1997

Chemotherapy for desmoid tumors in association with familial adenomatous polyposis.

PURPOSE: This study was designed to assess the effect of chemotherapy on complex desmoid tumors associated with familial adenomatous polyposis. METHODS: Five patients (3 males, 2 females; age range, 29-45 years) had symptomatic, unresectable intra-abdominal desmoid tumors in association with familial adenomatous polyposis that were unresponsive to conventional medical therapy. Each patient was treated with a cytotoxic chemotherapeutic regimen consisting of doxorubicin and dacarbazine followed by carboplatin and dacarbazine. Response to treatment was assessed by measurement of tumor size using computerized tomography. Follow-up has been for a mean of 22 (range, 10-30) months. RESULTS: One patient has had a complete response, and three patients have had a partial response, with a reduction in tumor volume of at least 50 percent. One patient had a minimum response to treatment and developed a rapid increase in tumor size on cessation of therapy. Complications of treatment included febrile neutropenia, severe epistaxis, and subclavian vein thrombosis. CONCLUSIONS: The cytotoxic chemotherapeutic regimen described is effective in the treatment of selected unresectable desmoid tumors associated with familial adenomatous polyposis and should be considered in symptomatic patients who do not respond to conventional medical therapy.

Adenomatous Polyposis Coli↗
PubMed1997

Eye manifestations of congenital toxoplasmosis.

PURPOSE: To determine the natural history of treated and untreated congenital toxoplasmosis and impact of this infection on vision. METHODS: In this prospective, longitudinal study, 76 newborns were treated with pyrimethamine and sulfadiazine for approximately one year, and 18 individuals not treated during their first year of life entered the study after age 1 year (historical patients). RESULTS: Chorioretinal scars were the most common eye finding in all patients and were most common in the periphery (58% of treated and 82% of historical patients). Macular scars were present in 54% of the treated patients; 41% were bilateral. Macular scars were present in 76% of the historical patients; 23% were bilateral. Visual acuity in the presence of macular lesions ranged from 20/20 to 20/400. Of the patients followed up from the newborn period and treated, 29% had bilateral visual impairment, with visual acuity for the best eye of less than 20/40. Causes for this visual impairment in eyes with quiescent lesions included macular scars, dragging of the macula secondary to a peripheral lesion, retinal detachment, optic atrophy, cataract, amblyopia, and phthisis. There were recurrences in both treated (13%, 7/54) and previously untreated historical patients (44%, 8/18). The total, median, and range of years of follow-up during which recurrences were observed were, for treated patients, 189 years (total), five years (median) and three to ten years (range) and, for historical, untreated patients, 160 years (total), 11 years (median), and three to 24 years (range). New lesions occurred in previously normal retinas and also contiguous to older scars. Active lesions appeared to become quiescent within ten to 14 days after beginning pyrimethamine and sulfadiazine therapy. CONCLUSION: Many children with congenital toxoplasmosis have substantial retinal damage at birth and consequent loss of vision. Nonetheless, vision may be remarkably good in the presence of large macular scars. Active lesions become quiescent with treatment.

Adolescent↗
PubMed1997

Outcome studies in surgical research.

Providers, payers, buyers, and the public at large will continue to demand information regarding the quality of health care service. High quality clinical and functional data on the entire population would not only allow a better understanding of health outcomes after medical or surgical interventions but would also provide information regarding disease burden, the population at risk, and indications for treatment. We currently are dealing with two separate pieces of the puzzle. On the one hand, randomized clinical trials and observational studies continue to provide high quality information regarding small samples of the population. On the other hand, the analysis of large administrative data sets provides a broad overview of health care services and patient outcomes at the population level. To provide meaningful data regarding the quality of health care, we must go beyond morbidity and mortality rates and attempt to measure patient function at the population level.

Clinical Trials as Topic↗
PubMed1996

Eye manifestations of congenital toxoplasmosis.

PURPOSE: To determine the natural history of treated and untreated congenital toxoplasmosis and impact of this infection on vision. METHODS: In this prospective, longitudinal study, 76 newborns were treated with pyrimethamine and sulfadiazine for approximately one year, and 18 individuals not treated during their first year of life entered the study after age 1 year (historical patients). RESULTS: Chorioretinal scars were the most common eye finding in all patients and were most common in the periphery (58% of treated and 82% of historical patients). Macular scars were present in 54% of the treated patients; 41% were bilateral. Macular scars were present in 76% of the historical patients; 23% were bilateral. Visual acuity in the presence of macular lesions ranged from 20/20 to 20/400. Of the patients followed up from the newborn period and treated, 29% had bilateral visual impairment, with visual acuity for the best eye of less than 20/40. Causes for this visual impairment in eyes with quiescent lesions included macular scars, dragging of the macula secondary to a peripheral lesion, retinal detachment, optic atrophy, cataract, amblyopia, and phthisis. There were recurrences in both treated (13%, 7/54) and previously untreated historical patients (44%, 8/18). The total, median, and range of years of follow-up during which recurrences were observed were, for treated patients, 189 years (total), five years (median), and three to ten years (range) and, for historical, untreated patients, 160 years (total), 11 years (median), and three to 24 years (range). New lesions occurred in previously normal retinas and also contiguous to older scars. Active lesions appeared to become quiescent within ten to 14 days after beginning pyrimethamine and sulfadiazine therapy. CONCLUSION: Many children with congenital toxoplasmosis have substantial retinal damage at birth and consequent loss of vision. Nonetheless, vision may be remarkably good in the presence of large macular scars. Active lesions become quiescent with treatment.

Adolescent↗
PubMed1996

The impact of gender on the choice of surgery as a career.

BACKGROUND: The objective of the survey was to examine factors affecting career choice by medical students. METHODS: A questionnaire was distributed to the 245 fourth-year students at the University of Toronto, sampling qualities of importance in specialties, the importance of role models, attitudes toward surgery, and specialty match results. RESULTS: There was a 69% return rate. Males were more likely to choose a surgical career than were females (27% versus 10%, respectively; P = 0.01). Males were more likely to identify technical challenge, earning potential, and prestige (P < 0.01) whereas females were more likely to identify residency conditions, part-time work, and parental leave availability as important qualities in a specialty (P < 0.01). Females were less likely to take surgical electives (P < 0.001) and more likely to identify a lack of role models (P < 0.003). Students agreed that surgeons have rewarding careers (79%) and earn more (64%); however, they do not agree that surgeons enjoy spending time with patients (10%) or have rewarding family lives (5%). CONCLUSIONS: Fewer females than males were found to consider or choose a surgical career, possibly due to differences in qualities of importance in specialties, availability of role models, and exposure through electives.

Adult↗
PubMed1996

Congenital toxoplasmosis transmitted from an immunologically competent mother infected before conception.

Congenital transmission of Toxoplasma gondii from a mother who was apparently immunologically competent and who had toxoplasmic lymphadenitis 2 months before conception is described. Since no T. gondii-specific serological data were available for this mother from the time her lymph node biopsy specimen was obtained, the specimen was studied by polymerase chain reaction (PCR) to determine whether the T. gondii B1 gene was present. The predictive diagnostic value of histologic findings previously considered to be classic signs of T. gondii lymphadenitis also was studied. This was done by correlation of serological tests diagnostic of acute acquired T. gondii infection and presence of characteristic findings in biopsy specimens from persons without known immunocompromise. Both PCR and review of the characteristic features of her lymph node biopsy specimen confirmed the diagnosis of preconceptual infection in the mother. We also discuss two other cases in which apparently immunologically competent mothers with preconceptually acquired infection transmitted this parasite to their fetuses.

Animals↗
PubMed1996

Modulation of the cytochrome P450 system as a mechanism of chemoprotection.

The cytochrome P450-dependent mono-oxygenase system has evolved as one of our primary defences against toxic chemicals present in our environment. This multi-enzyme system functions as an adaptive response to environmental challenge in that exposure to specific toxic agents induces the expression of cytochrome P450 isozymes active in their metabolism. In most cases, such metabolism leads to an increased rate of chemical detoxification, but in certain cases it can also lead to an increased rate of chemical activation to toxic products. The induction of cytochrome P450s leading to cytoprotection is a major mechanism of chemoprotection, and it is well documented that this pathway prevents a large number of toxic reactions. Incredibly, despite the importance of this metabolic pathway, the effects of a wide range of chemoprotective agents with different mechanisms of action on the expression of specific cytochrome P450 isozymes remains poorly understood. In this chapter, we discess the ability of different chemical compounds to modulate cytochrome P450 both at the transcriptional and post-transcriptional levels, in a way which affects its ability to metabolize or detoxify chemical carcinogens.

Animals↗
PubMed1996

Regulation of glutathione S-transferases and aldehyde reductase by chemoprotectors: studies of mechanisms responsible for inducible resistance to aflatoxin B1.

A number of xenobiotics, including the synthetic antioxidant ethoxyquin, inhibit aflatoxin B1 (AFB1)-induced hepatocarcinogenesis in the rat. Two detoxification enzymes that mediate ethoxyquin-induced chemoprotection against AFB1 have been identified by protein purification: a glutathione S-transferase (GST) Yc2 subunit with at least 100-fold greater activity towards AFB1-8,9-epoxide than previously studied transferases, and a unique aldehyde reductase with activity towards the dialdehydic form of AFB1-8,9-dihydrodiol. Molecular cloning has revealed that the Yc2 subunit is a class alpha GST and that the aflatoxin-metabolizing aldehyde reductase (AFAR) is a distant member of the aldo-keto reductase superfamily. Enzyme assay and western blotting have shown that many chemoprotectors, such as ethoxyquin, butylated hydroxyanisole, butylated hydroxytoluene, oltipraz and indole-3-carbinol, that inhibit AFB1-mediated hepatocarcinogenesis induce both GST Yc2 and AFAR. However, western blotting suggests that these enzymes are not always coordinately regulated, as treatment with phenobarbital and beta-naphthoflavone results in differences in the relative increase in hepatic GST Yc2 and AFAR. These findings indicate that GST Yc2 and AFAR represent important resistance mechanisms against AFB1 in the rat. This conclusion is supported by the observation that GST Yc2 and AFAR are overexpressed in rat liver preneoplastic nodules, which display pleiotropic drug resistance.

Aflatoxin B1↗
PubMed1995

Psychological responses to malignant melanoma. An investigation of traumatic stress reactions to life-threatening illness.

A cross-sectional study of 95 individuals with malignant melanoma was conducted to investigate posttraumatic stress responses to a diagnosis of melanoma and to validate the use of the Impact of Event Scale (IES) as a measure of the response to the trauma of life-threatening disease. The diagnosis and progression of malignant disease are likely to present a range of acute and chronic trauma to the individual and the individual's family. The findings suggest that the IES is a reliable and valid measure of this distress, with scores varying according to disease progression and prognostic status of nonmetastatic disease patients. This indicates the importance of clinical attention to the specific symptoms that may best reflect the traumatic impact of life-threatening illness and its progression, and the applicability of posttraumatic stress syndromes in understanding the psychological distress of this clinical population.

Adult↗
PubMed1995

Immunogenetics in the analysis of resistance to intracellular pathogens.

Recent studies have identified genes involved in resistance to intracellular pathogens. Such genes include the murine MHC class I gene, Ld (toxoplasmosis), HLA-BW53, HLA DRB1* 1302-DQ B10s01 and TNF2 (malaria), murine Nramp (toxoplasmosis, leishmaniasis and tuberculosis), gene(s) modulating the T-helper type 1 and type 2 dichotomy (leishmaniasis, leprosy and HIV infection) and the natural killer cell complex (cytomegalovirus infection). There also have been other advances in immunogenetics that have led to a better understanding of resistance to intracellular pathogens. These include effector mechanisms of immune response genes and factors modulating genetic susceptibility. Identification of genes that determine resistance/susceptibility (and their effector mechanisms) has impacted on vaccine development. Immunogenetics has been important in characterizing roles of TCR genes, superantigens, and host genes that play a role in molecular mimicry in disease pathogenesis. In addition, recent work with gene knockout, recombinant inbred or congenic, mutant, consomic, and transgenic mice, positional cloning, mouse/human gene homologies to identify candidate human resistance genes, and the rapid expansion of the gene transcription maps of the human genome, have been important in analysis of resistance to intracellular pathogens.

Animals↗
PubMed1995

Definitive identification of a gene that confers resistance against Toxoplasma cyst burden and encephalitis.

Control of resistance to cyst burden following per-oral infection with Toxoplasma gondii has been mapped previously to a region of mouse chromosome 17 of approximately 140 kb. This region is contiguous with and contains the class I gene, Ld. Resistance to development of toxoplasmic encephalitis has also been reported to be controlled by genes in this region of H-2. TNF-alpha, D and L genes, as well as unidentified genes, are also in this region. The work described here was performed to identify definitively the gene(s) in this 140 kb region that confers resistance to cysts and encephalitis. The study demonstrates that relative resistance to T. gondii organisms and cyst burden in brain, and toxoplasmic encephalitis, 30 days following per-oral T. gondii infection is correlated absolutely with the presence of the Ld gene in inbred, recombinant, mutant and C3H.Ld transgenic mice. Mice with the Ld gene had lower cyst burdens and less encephalitis than those without the Ld gene. Specifically, 30 days after infection mice with the Ld gene had minimal perivascular inflammation and meningeal inflammation and very few Toxoplasma cysts or organisms in immunoperoxidase-stained preparations of their brains. Mice without the Ld gene had a similar pattern of inflammation, but in addition they had collections of inflammatory cells in the brain parenchyma. Free tachyzoites were found within these foci of inflammation and cysts were present in these areas as well as in contiguous areas without inflammatory cells. There were CD4+ and CD8+ T lymphocytes in the areas of inflammation and throughout the brain parenchyma. Mice that were resistant to cysts and encephalitis had little detectable brain cytokine mRNA expression, while mice that were susceptible had elevated levels of mRNA for a wide range of cytokines, consistent with their greater amounts of inflammation. The present work definitively demonstrates that a Ld-restricted response decreases the number of organisms and cysts within the brain and thereby limits toxoplasmic encephalitis and levels of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), IL-6, IL-10, transforming growth factor-beta (TGF-beta), IL-1 alpha, IL1 beta and macrophage inhibiting protein (MIP) mRNA in the brain 30 days after per-oral infection.

Animals↗
PubMed1994

Effects of human class I transgenes on Toxoplasma gondii cyst formation.

MHC class I genes are important in the regulation of cyst number in mice perorally infected with Toxoplasma gondii. Since human MHC class I molecules may be capable of functioning as restriction elements in mice, to determine whether class I genes also control outcome of T. gondii infection for humans, a transgenic mouse model was developed using human class I genes in mice. Human HLA-B27 and Cw3 transgenic mice, with the cyst-susceptible B10 mouse background, were tested for resistance to cyst formation after peroral infection with the Me49 strain of T. gondii. Introduction of the B27 gene into susceptible mice made them even more susceptible to T. gondii brain cyst formation. In contrast, HLA-DB27 transgenic mice that have a substitution of the alpha 3 portion of the human class I molecule with the alpha 3 portion of the mouse Kd molecule had the same number of brain cysts as susceptible B10 control mice when perorally infected. Similarly, HLA-Cw3 transgenic mice had the same number of brain cysts as the susceptible B10 controls. These results indicate that the interaction between CD8 on mouse T cells and the human class I molecule in transgenic mice does not always occur, and sometimes may hinder a normal response. Furthermore, B27 and Cw3 transgenes did not generate resistance to cyst formation in infection by T. gondii.

Animals↗
PubMed1994

Prospective evaluation of early morphological changes in pelvic ileal pouches.

BACKGROUND/AIMS: Little is known about the evolution of morphological changes in pelvic ileal-pouch mucosa. This study evaluates prospectively the sequence of early morphological, histochemical, and phenotypic features in pouch mucosal biopsy specimens. METHODS: Twenty-two patients with pelvic ileal pouches constructed after total colectomy for chronic ulcerative colitis had biopsies performed at the time of ileostomy closure and after 6 weeks and 6 months of pouch function and were evaluated to assess the type and degree of inflammation, villus atrophy, Paneth's cell hyperplasia, mucin histochemical changes, the mucosal proliferative activity using the murine monoclonal antibody 1 (MIB-1), and the expression of the enzyme sucrase-isomaltase. RESULTS: Early changes (6 weeks) were characterized by neutrophilic and eosinophilic inflammation, mild villus atrophy, Paneth's cell hyperplasia, a partial transition to colonic mucin phenotype, and an increased MIB-1 proliferation index. These features remained relatively stable after 6 months, except for a greater degree of mononuclear infiltration, a progressive increase in the degree of eosinophilic inflammation and a new higher steady state level of crypt epithelial kinetics. Expression of sucrase-isomaltase remained stable. CONCLUSIONS: Pelvic ileal pouches develop inflammatory, phenotypic, and kinetic changes early in the course of function but have only a limited potential for colonic type metaplasia. The persistence of these changes is evidence in support of an adaptive response to a new luminal environment.

Adolescent↗