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Biomedical subjects

M Roy

Publications and source records attributed to M Roy.

At least 55 records · Page 3Linked to original sources
PubMed2000

Occurrence of sulfate-reducing bacteria under a wide range of physico-chemical conditions in Au and Cu-Zn mine tailings.

Sulfate-reducing bacteria (SRB) have been observed in mining environments, but their presence has not been linked to specific physico-chemical and mineralogical factors. The present study was undertaken to assess the presence of SRB in several Au and Cu-Zn mine tailings located near Timmins, Ont., Canada, and determine the factors responsible for their presence. Vegetated and non-vegetated mine tailings were sampled for SRB enumeration, pH, Eh, water content, total carbon content and sequential chemical extraction. Results first showed that SRB populations were present at all sites and that their distribution varied with depth. Populations were recovered from neutral pH and slightly anoxic tailings and from highly acidic (pH 2) and oxic tailings. The total carbon content of the tailings was generally low and not related to the presence of vegetation. In addition, the carbon content did not affect SRB population distribution and appeared to be more related to the type of tailings, i.e., oxidized and acidic Cu-Zn tailings contained on average more carbon than Au tailings. Results also indicated that the water content of the tailings varied greatly with depth and was not related to the presence of SRB populations. The sequential chemical extraction showed that the pyrite content of the tailings was lower in Au tailings than in Cu-Zn tailings, and that some oxidized Cu-Zn sites were depleted in pyrite due to microbial and chemical oxidation. Our results indicate that SRB could be cultured from a variety of sites and sample types, and that factors such as pH, Eh, water content and carbon content at the collection sites did not exert control on their presence.

Journal Article↗
PubMed2000

An essential intermediate in the folding of dihydrofolate reductase.

The folding of Escherichia coli dihydrofolate reductase was examined at pH 7.8 and 15 degrees C by using stopped-flow fluorescence and absorbance spectroscopies. The formation of a highly fluorescent intermediate occurs with relaxation times ranging between 142 and 343 msec, whereas stopped-flow absorbance spectroscopy using methotrexate binding assays shows a distinct lag phase during these time frames for the native state. The lag in absorbance kinetics and the lack of fast-track folding events indicate that the formation of this ensemble of intermediates is an obligatory step in the folding reaction.

Bacterial Proteins↗
PubMed2000

Aggregation events occur prior to stable intermediate formation during refolding of interleukin 1beta.

A point mutation, lysine 97 --> isoleucine (K97I), in a surface loop in the beta-sheet protein interleukin 1beta (IL-1beta), exhibits increased levels of inclusion body (IB) formation relative to the wild-type protein (WT) when expressed in Escherichia coli. Despite the common observation that less stable proteins are often found in IBs, K97I is more stable than WT. We examined the folding pathway of the mutant and wild-type proteins at pH 6.5 and 25 degrees C with manual-mixing and stopped-flow optical spectroscopy to determine whether changes in the properties of transiently populated species in vitro correlate with the observation of increased aggregation in vivo. The refolding reactions of the WT and K97I proteins are both described by three exponential processes. Two exponential processes characterize fast events (0.1-1.0 s) in folding while the third exponential process correlates with a slow (70 s) single pathway to and from the native state. The K97I replacement affects the earlier steps in the refolding pathway. Aggregation, absent in the WT refolding reaction, occurs in K97I above a critical protein concentration of 18 microM. This observation is consistent with an initial nucleation step mediating protein aggregation. Stopped-flow kinetic studies of the K97I aggregation process demonstrate that K97I aggregates most rapidly during the earliest refolding times, when unfolded protein conformers remain highly populated and the concentration of folding intermediates is low. Folding and aggregation studies together support a model in which the formation of stable folding intermediates afford protection against further K97I aggregation.

Amino Acid Substitution↗
PubMed2000

Combined laparoscopic and vaginal radical surgery in cervical cancer.

OBJECTIVE: The purpose of our study was to review our experience with laparoscopic staging and vaginal radical surgery in the treatment of early stage cervical cancer. STUDY DESIGN: We reviewed the charts of 102 patients who had a laparoscopic pelvic lymphadenectomy followed by vaginal radical hysterectomy (VRH) or vaginal radical trachelectomy (VRT). RESULTS: Patients' age ranged from 25 to 68 years (median: 36). Squamous and adenocarcinoma histology occurred in 68 and 32%, respectively. Stage Ib1 occurred in 77% of cases and the rest were stage Ia1 (1%), 1a2 (16%), and IIa (6%). Patients were divided into three groups: VRH (57), VRT (34), and node only (NO) (11), when positive nodes were identified on frozen section. Median operative time for VRH and VRT were 270 and 260 min compared to 200 min in the NO group (half also had bilateral paraaortic node dissection, which lengthened the OR time). Hospital stay was shorter in the NO group (2 days). For each group (VRH, VRT, and NO) the median pelvic node count was 27, 26, and 23 and the median paraaortic node count was 3, 4, and 9. Two VRH were converted to an abdominal procedure because of technical difficulties and one VRT was converted to a VRH because of positive endocervical margins. Intraoperative complications related to laparoscopy included two iliac and one epigastric vessel injuries. Complications related to the radical surgeries included three cystostomies, managed vaginally, and a laparotomy for parametrial bleeding after VRT. Postoperative complications occurred in 6% of patients and only one was considered major (an abscess which required surgical drainage). Overall, there were only four recurrences in the vaginal surgery groups and one in the NO group. There were no ureteral or intestinal injuries and there have been no trocar site recurrences. CONCLUSION: Our data show that approaching cervical cancer with a combined laparoscopic and vaginal surgery is feasible. The overall morbidity and complication rate are low and the lymph node count is satisfactory. Staging the nodes laparoscopically first to identify positive nodes is advantageous, particularly since we favor the use of chemoradiation therapy in those cases. The laparoscopic node staging thus avoids an unnecessary laparotomy in patients with positive nodes, reduces morbidity, and allows for early radiation therapy.

Adenocarcinoma↗
PubMed2000

Evaluating contraceptive choice through the method-mix approach. An Indian Council of Medical Research (ICMR) task force study.

The method-mix approach was used to evaluate informed contraceptive choices in the present study. A total of 8,077 potential clients were given a balanced presentation of all available contraceptive methods in the national program, ie, the CuT 200 intrauterine device (IUD), low-dose combined oral pills (OC), condom, and sterilization (female/male) along with a new method, Norplant(R).(1) The majority of women opted for spacing methods; among them, the IUD was preferred by about 60% of clients, followed by condoms (9%), OC (6%), and Norplant (5%). Sterilization, mainly female, was accepted by about 17% of the women making an informed choice. The economic status of couples did not influence the contraceptive choices, as all the methods were offered free of cost in the present study, which is the current practice in the national program. Illiterate women more often accepted sterilization (about 25%) than did literate women (15%). This is because illiterate women had more children; about 30% of illiterate women had three or more children, as opposed to 16.2% of literate women. However, literacy status did not influence the choice of any specific spacing method. The study also revealed that, by encouraging potential clients to make an informed choice, they could override the provider's bias while accepting a particular type of spacing method. This is evident from the observation that Norplant was the first choice of the provider for 35% of the women, whereas only 5% of women preferred and accepted Norplant. The present study stresses an urgent need to promote the practice of informed choices in the national program with a variety of contraceptive options-especially, spacing methods for improving contraceptive prevalence and reproductive health in the country.

Adolescent↗
PubMed2000

Coexisting dysbetalipoproteinemia and familial hypercholesterolemia. Clinical and laboratory observations.

Type III dysbetalipoproteinemia and familial hypercholesterolemia (FH) are two metabolic disorders giving rise to severe disturbances of lipid homeostasis and premature atherosclerosis. Both metabolic abnormalities have a genetic basis and co-occurrence in the same patient has seldom been described. Because of the unique structure of the French Canadian population, there was an opportunity to observe patients with both dysbetalipoproteinemia (E2/2 homozygotes) and FH (N=14) and to compare their clinical data with that of patients with type III (N=75), patients with FH (N0.7 and the presence of beta-VLDL on electrophoresis. Presence of a low density lipoprotein receptor, LDL-R, mutation should be suspected in a type III patient with a LDL-C level above 3.0 mmol/l and a family history of premature CAD. In the group of patients studied, the coexistence of dysbetalipoproteinemia and heterozygous FH does not appear to increase the prevalence of cardiovascular complications above that observed among control type III or control E3/3-FH patients. Thus, the presence of two epsilon2 alleles in these patients affects the expression of the abnormal LDL-R allele and the resulting phenotype substantiates the non additive effects of alleles at these two loci (epistasis).

Adult↗
PubMed2000

Epidemic Bacillus endophthalmitis after cataract surgery II: chronic and recurrent presentation and outcome.

OBJECTIVE: To report the clinical outcome of chronic Bacillus endophthalmitis after cataract surgery. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Five eyes of five patients with late-onset or recurrent inflammation after exposure to bacteria-contaminated viscoelastic material were studied. INTERVENTION: Repeated vitrectomies, wide excision of the remnant posterior capsule, and intravitreal injections of antibiotics in five patients. Eventual explantation of the intraocular lens in four patients. MAIN OUTCOME MEASURES: Final visual acuities and results of microbiologic studies of aqueous and vitreous specimens as well as pathologic studies using hematoxylin-eosin, Gram, and periodic acid-Schiff (PAS) stain of explanted capsular remnants were obtained. RESULTS: Final visual acuity of 20/40 or better was obtained in three patients. Bacillus species were grown from two cases. PAS- and Gram-positive microorganisms were identified in the capsular tissue in three of four patients who had explantation of the intraocular lens. CONCLUSIONS: A chronic form of Bacillus endophthalmitis is described for the first time. The clinical outcome is similar to chronic endophthalmitis caused by other organisms.

Aged↗
PubMed2000

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Journal Article↗
PubMed2000

Quantification of growth factor levels using a simplified method of platelet-rich plasma gel preparation.

PURPOSE: This study compared two methods of preparing platelet-rich plasma (PRP) gel and the levels of PDGF and TGFbeta in each preparation. MATERIALS AND METHODS: Platelet-rich plasma gel was prepared by centrifugation and clotted using the ITA gelling agent (Natrex Technologies Inc, Greenville, NC) or by the addition of thrombin and calcium chloride. The levels of platelet-derived growth factor (PDGF) and transforming growth factor beta (TGFbeta) generated by clot formation were assayed by enzyme-linked immunoassay (ELISA). RESULTS: Both methods of preparation yielded PRP gel in less than 30 minutes. However, the ITA preparation did not require thrombin to achieve adequate gel formation. The levels of PDGF and TGFbeta were similar regardless of which method was used for initiation of clot formation. CONCLUSION: Use of ITA for gel preparation is equivalent to using calcium chloride and thrombin, without the need for special equipment and the risk of coagulopathy.

Blood Coagulation↗
PubMed2000

Association of a balanced chromosomal translocation (4; 12)(q21.3; q15), affective disorder and autism.

This case report describes a set of monozygotic twins with severe intellectual disability, autism and affective disorder with a balanced translocation between chromosomes 4 and 12. Their mother, who carries the same balanced translocation, had severe postnatal depression. The association between autism affective disorder and these chromosome break points has not been reported previously. The implications are discussed.

Adult↗
PubMed2000

Selenium and immunocompetence in patients with head and neck cancer.

This randomized double-blind placebo-controlled study aimed to determine whether oral intake of 200 microg/d of sodium selenite, a dose within the safe and adequate daily intake (50-200 microg/d) recommended by the U.S. Food and Nutrition Board, will abrogate depressed or enhance normal-level immune functions of patients receiving therapy for squamous cell carcinoma of the head and neck. Subjects were given one selenium/placebo tablet/d for 8 wk, beginning on the day of their first treatment for the disease (e.g., surgery, radiation, or surgery and radiation) and their immune functions were monitored. Supplementation with selenium (Se) during therapy resulted in a significantly enhanced cell-mediated immunue responsiveness, as reflected in the ability of the patient's lymphocytes to respond to stimulation with mitogen, to generate cytotoxic lymphocytes, and to destroy tumor cells. The enhanced responsiveness was evident during therapy and following conclusion of therapy. In contrast, patients in the placebo arm of the study showed a decline in immune responsiveness during therapy, which was followed, in some patients, by an enhancement, but the responses of the group remained significantly lower than baseline values. The data also show that at baseline, patients entered in the study had significantly lower plasma Se levels than healthy individuals, and patients in stage I or II of disease had significantly higher plasma selenium levels than patients in stage III or IV of disease.

Adult↗
PubMed2000

[Radical vaginal trachelectomy for invasive cervical cancer].

The use of operative laparoscopy in gynecologic oncology has paved the way to a more conservative approach in radical treatments of some cancers, particularly cervical cancer. After the vaginal approach which shortens the hospital stay and the morbidity of a radical hysterectomy, a new fertility-preserving radical treatment has been proposed : the Radical Vaginal Trachelectomy (RVT). This technique has been used since 1991 in our institution. Until July 1999, 37 patients with early-stage cervical cancer desiring to retain their fertility were treated by a laparoscopic pelvic lymphadenectomy (LPL) and RVT. The median age was 32 (22-42), and 25 were nulliparous. Twelve were FIGO stage Ia2, 22 Ib1, 2 IIa and one Ia1 (VSI+). Most of the tumors were squamous (23), grade I (21), and the lesion was 2cms or less in 35 patients. Median operating time was 275 minutes ( 200 for the last 10 cases), and blood loss 200cc. Complications were mainly due to the LPL (3 arterial injuries) rather than the RVT (one iatrogenic cystotomy and one parametrial bleeding). The mean follow-up is 42 months. Two patients recurred including one who had a small-cell neuroendocrine tumor. Ten patients had a total of 13 pregnancies with 7 live births. One newborn died of E.coli-septicemia. Two patients had early miscarriages and 2 second trimester abortions (17 and 20 weeks). Two patients are still pregnant. LPL-RVT seems to be a good treatment modality for early-stage cervical cancer. It preserves fertility without lowering the chances of survival.

Adult↗
PubMed1999

Detailed analysis of stem I and its 5' and 3' neighbor regions in the trans-acting HDV ribozyme.

To determine the stem I structure of the human hepatitis delta virus (HDV) ribozyme, which is related to the substrate sequence in the trans -acting system, we kinetically studied stem I length and sequences. Stem I extension from 7 to 8 or 9 bp caused a loss of activity and a low amount of active complex with 9 bp in the trans -acting system. In a previous report, we presented cleavage in a 6 bp stem I. The observed reaction rates indicate that the original 7 bp stem I is in the most favorable location for catalytic reaction among the possible 6-8 bp stems. To test base specificity, we replaced the original GC-rich sequence in stem I with AU-rich sequences containing six AU or UA base pairs with the natural +1G.U wobble base pair at the cleavage site. The cis -acting AU-rich molecules demonstrated similar catalytic activity to that of the wild-type. In trans -acting molecules, due to stem I instability, reaction efficiency strongly depended on the concentration of the ribozyme-substrate complex and reaction temperature. Multiple turnover was observed at 37 degreesC, strongly suggesting that stem I has no base specificity and more efficient activity can be expected under multiple turnover conditions by substituting several UA or AU base pairs into stem I. We also studied the substrate damaging sequences linked to both ends of stem I for its development in therapeutic applications and confirmed the functions of the unique structure.

Catalysis↗
PubMed1999

Effect of combined adoptive immunotherapy and radiotherapy on tumor growth.

Advanced squamous cell carcinomas of the head and neck are difficult to control despite optimal surgery, radiotherapy and/or chemotherapy, and the tumors are usually not immunogenic. Because of the anatomic accessibility of the tumors, local adoptive immunotherapy of these tumors is feasible and may interact with radiotherapy to retard tumor growth. It is hypothesized that antigens released from tumor cells injured by radiation may stimulate, in the presence of interleukin-2, an enhanced immunocytodestruction of live tumor cells by adoptively transferred lymphokine activated killer cells and recruited tumor cytotoxic cells. DBA/2 mice were injected subcutaneously with 5 x 10(5) syngeneic squamous cell carcinoma cells in the thigh and the resulting tumors were treated for two weeks with daily peritumoral injections of interleukin-2 (1,000 International Units) or saline, four radiation treatments of 625 cGy each, and four peritumoral injections of 10(7) lymphokine activated killer cells. The results suggested that radiotherapy combined with peritumoral injection of lymphokine activated killer cells and interleukin-2 resulted in a significant reduction (P < 0.01) of tumor size whereas radiation alone, at the same dose, failed to produce a significant effect. Such results may have direct clinical application in enhancing the response of tumors to radiotherapy and in reducing the incidence of tumor recurrence.

Animals↗