Biomedical subjects

C Potvin

Publications and source records attributed to C Potvin.

At least 19 recordsLinked to original sources

PubMed1992

[Quality of life of patients after restorative surgery for cancer of the rectum].

During the last decades surgeons have put a tremendous effort to perform low anterior resection (LAR) as a curative procedure for rectal cancer treated classically by abdomino-perineal resection (APR) and permanent colostomy. A psychological evaluation testing the multi-dimensional concept of quality of life was done in 32 patients (M = 21; F = 11) treated by APR and compared to 28 patients (M = 16; F = 12) treated by LAR. Patients were assessed for quality of life on the following dimensions: physical well-being, psychological well-being, dietary habits, surgical response, social concerns, body image, stress and marital adjustment. Using as covariables social support and time elapsed since surgery, a covariate analysis was used to determine the presence of group ans sex interaction. Patients with LAR had a better body image (p.001), dietary habits (p.003) and tolerance to stress (p.004). Better global quality of life (p.001), physical well being (p.001) and less surgical sequela (p.001) were found with LAR in women only. No significant difference was found on psychological well being, social concerns and marital adjustment in both surgical groups.

Adult↗

PubMed1992

Detection and localization of parathyroid adenomas in patients with hyperparathyroidism using a single radionuclide imaging procedure with technetium-99m-sestamibi (double-phase study)

Dual radionuclide imaging using a combination of 201Tl with either 99mTcO4- or 123I is recognized as a useful procedure in the preoperative localization of parathyroid adenomas. Recently, 99mTc-sestamibi (MIBI) has been introduced for myocardial perfusion imaging as an alternative to 201Tl. The purpose of this prospective study was to evaluate parathyroid scan using early and late imaging following MIBI injection. Twenty-three patients (21 F, 2 M, mean age: 57 yr) with a clinical and biologic diagnosis of hyperparathyroidism were submitted to a MIBI study prior to surgical exploration of the neck. Cervico-thoracic planar imaging (anterior view, 10 min/view) was performed at 15 min and at 2-3 hr after an intravenous injection of 20-25 mCi of MIBI. A positive MIBI scan for parathyroid adenoma was defined as an area of increased focal uptake which persisted on late imaging, contrary to the uptake in the normal thyroid tissue which progressively decreases over time (differential washout). Surgical exploration of the neck, performed between 1 day and 72 days (average: 16 days) after the MIBI study, showed a parathyroid adenoma in 21 patients and hyperplasia in two patients. MIBI scan correctly detected and localized 19/21 adenomas (90%). In conclusion, parathyroid imaging using a single radionuclide with MIBI (early and late study with differential washout analysis) is a promising procedure in the preoperative detection and localization of parathyroid adenomas in patients with primary hyperparathyroidism.

Adenoma↗

PubMed1991

Classification of type-II restriction endonucleases and cloning of non-identical cohesive-end fragments without self-polymerization using nonpalindromic oligodeoxyribonucleotide adapters.

Enzymatic partial filling-in of recessed 3'-end sequences, left after digestion of DNA by the restriction endonucleases (ENases) Sau3A and SalI, with the Klenow fragment of E. coli DNA polymerase I allows the forced ligation of the resulting fragments; this technology is already used for subcloning and for genomic bank construction. To simplify and generalize its utilization, class-II ENases have been arranged into 16 different families according to the composition of the 5'-protruding sequences present after cleavage. Moreover, this system was extended to allow the joining of noncompatible ends by the use of nonpalindromic complementary oligodeoxyribonucleotides (NPCOs) containing two nucleotides protruding at each 5' end. The use of these synthetic adapters maintains all the advantages of the initial gap-filling cloning technique: only one insert can be cloned per vector molecule and no self-ligation or -polymerization can occur with any of the DNA molecules involved. Only 22 such oligodeoxyribonucleotides are needed to generate the 60 NPCO pairs necessary to ligate to each other any member of twelve ENase families when the regeneration of ENase recognition sites is not required.

Base Composition↗

PubMed1991

High-yield method for directional cDNA library construction.

Improvement of a cDNA synthesis procedure using a single stranded (ss) vector primer [Bellemare et al., Gene 52 (1987) 11-19] is reported. This vector (pPBS27), upon linearization with XbaI using an appropriate restriction site-directed fragment, releases a thymidilic tail used to prime cDNA synthesis. DNA polymerase I and RNase H replace the RNA strand and replicate the vector before double-stranded (ds) blunt-end ligation with T4 DNA ligase. More than 10(7) cfu/microgram of vector can be obtained with an efficient transformation protocol using either globin-encoding or 7.5-kb poly(A)-tailed RNA. This improved cloning method is easier, faster and a few hundred times more efficient than the original procedure as it involves ds rather than ss DNA for transformation.

Base Sequence↗

PubMed1991

Cloning, sequencing, and expression in Escherichia coli of a Streptococcus faecalis autolysin.

A Streptococcus faecalis genomic bank was obtained by partial digestion with MboI and cloning into the SalI restriction site of pTZ18R. Screening of about 60,000 Escherichia coli transformants for cell wall lysis activity was done by exposing recombinant colonies grown on medium containing lyophilized Micrococcus lysodeikticus cells to chloroform and toluene vapors in order to release proteins. Because this procedure provoked cell death, colonies could not be used directly for transformant recovery; however, recovery was achieved by partial purification of plasmid DNA from active colonies on the agar plate and transformation of E. coli competent cells. About 60 recombinants were found. One of them (pSH6500) codes for a lytic enzyme active against S. faecalis and M. lysodeikticus cell walls. A shorter clone (pSH4000) was obtained by deleting an EcoRI fragment from the 6.5-kb original insert, leaving a 4-kb EcoRI-MboI insert; this subclone expressed the same lytic activity. Sequencing of a portion of pSH4000 revealed a unique open reading frame of 2,013 nucleotides coding for a 641-amino-acid (74-kDa) polypeptide and containing four 204-nucleotide direct repeats.

Amino Acid Sequence↗

PubMed1990

An assessment of the risk of neoplasia in long-term ileal reservoirs using the DMH rodent model.

This study was undertaken to determine if the construction of an ileal reservoir induces mucosal changes that can potentiate the effect of a chemical carcinogen (1,2-dimethylhydrazine) on ileal mucosa. Animals were divided into three groups: 1) sham operation (n = 19), 2) total colectomy with ileorectal anastomosis (n = 20), 3) total colectomy with an ileal reservoir made of terminal ileum sutured to the rectum (n = 20). An adaptation period of 12 weeks was allowed to promote fecal stasis and the histologic changes before exposure to weekly subcutaneous injections of DMH (25 mg/kg) for 16 weeks. Sodium butyrate was added to the diet as a tumor promotor. All animals were sacrificed one month later. Fecal stasis, along with enlargement, occurred in all the reservoirs (mean dimensions, 74 X 58 X 43 mm). Their mean volume was 88 +/- 14 ml. The histologic changes in the ileal reservoirs were: chronic inflammation (14/20), villous atrophy (14/20), and atrophy of the glands (8/20). In group 3, five carcinomas were seen. There were three in the duodenum and two in the reservoirs. In contrast, 21 carcinomas were detected in the control groups. There were 17 in the colon, 3 in the jejunum, and 1 in the ileum. No significant difference in the number of carcinomas was seen in the ileum with and without reservoir. Although it is possible to induce carcinomas in ileal reservoirs, the incidence remained significantly less than in the colon. In conclusion, the histologic changes induced by the construction of an ileal reservoir do not increase the risk of malignant transformation in the DMH model for intestinal carcinogenesis.

1,2-Dimethylhydrazine↗

PubMed1988

Cloning, sequencing and expression of a Bacillus bacteriolytic enzyme in Escherichia coli.

Several hundred bacterial isolates were screened for bacteriolytic activity by growing them on agar medium containing autoclaved, lyophilized Micrococcus lysodeikticus cells as the substrate. A Bacillus sp. producing the largest lytic zone was selected. A genomic bank of this selected bacterium was constructed in the multi-functional vector pTZ18R, with partial SauIIIA DNA fragments inserted at the SalI restriction site. Screening of 800 colonies of this bank for cell lysis gave 5 recombinants exhibiting lytic activity, as detected by analysis of extracts of sonicated Escherichia coli cells on denaturing polyacrylamide gels containing autoclaved, lyophilized M. lysodeikticus cells as the substrate. One clone (pBH2500), expressed in E. coli strain NM522, was found to code for a lytic enzyme corresponding, in molecular weight, to the 27 kDa Bacillus sp. hydrolase. This clone with an insertion of 2.5 kb was then subcloned as a 929 bp EcoRI-SauIIIA fragment in pTZ18R (pBH929) and showed higher cell lytic activity. A unique open reading frame for a protein of 251 amino acids, followed by a putative terminator sequence, was found after a consensus ribosome binding site. A putative leader sequence was identified in the first 37 amino acids. One truncated subclone (pBH703), corresponding to 196 out of 251 residues from the protein N-terminal end, still possessed lytic activity.

Amino Acid Sequence↗

PubMed1988

Androgen regulation of canine prostatic arginine esterase mRNA using cloned cDNA.

Canine prostatic arginine esterase complementary DNA has been cloned in pPBS27, a new cloning vector. The relative abundance of androgen-regulated mRNA in intact dog prostate was reflected by the finding that a high proportion of the clones in the cDNA library hybridized strongly by plaque or colony hybridization with a poly(A)+ RNA probe from intact dog prostate but not with a poly(A)+ RNA probe from castrated dog prostate. One clone carrying a 400 base pairs cDNA insert was selected for further studies. Translation of the hybrid-selected RNA in a cell-free system resulted in the production of a 31 kDa peptide immunoprecipitable by antibodies against arginine esterase. This identification was confirmed by partial sequence analysis of the cDNA revealing an encoding protein with high homology to known kallikreins. Northern blot analysis of poly(A)+ and total RNA showed that arginine esterase mRNA had an approximate size of 1.0 kb which corresponded to a major androgen-regulated RNA species that could be observed after denaturing agarose gel electrophoresis of prostatic poly(A)+ RNA from intact dogs. Dot-blot analysis showed that dogs which had been castrated 3 weeks before had more than 100-fold lower arginine esterase mRNA level than intact dogs or castrated dogs treated with Depo-testosterone.

Amino Acid Sequence↗

PubMed1987

Use of a phage vector for rapid synthesis and cloning of single-stranded cDNA.

We have developed a technique for synthesis of single stranded complementary DNA (ss cDNA) using specifically designed phage ssDNA as vector primer. This vector (pPBS27) was constructed by introducing a poly(dT) tail adjacent to the XbaI site of pTZ18R, which can exist either as a plasmid in Escherichia coli or as a ssDNA phage. The pPBS27 phage vector is linearized with XbaI using a restriction-site-directed fragment and used to anneal a mixture of poly(A) + RNA for cDNA synthesis by reverse transcriptase. The RNA is then hydrolysed with NaOH and a poly(dG) tail added to the 3' end of the vector-cDNA with terminal transferase. The linear hybrid ssDNA is then closed by annealing with a 15-mer site-directed fragment oligodeoxynucleotide molecule and ligated with T4 DNA ligase. Almost 10(5) E. coli transformants per microgram of vector primer can be obtained in two days.

Base Sequence↗

PubMed1986

Chemical DNA sequencing in the opposite direction to the dideoxy chain termination method, using a single preparation of M13 single-stranded DNA.

A strategy has been developed allowing the use of a single preparation of single-stranded DNA clones for chemical DNA sequencing in the opposite direction to the classical dideoxy chain termination method. Oligonucleotide complementary to the 5'-end of the multipurpose cloning sequence, with the proper restriction enzyme, is used to cleave specifically the molecules to expose a unique 5'-end, upstream to the inserted DNA, for the kinase labeling reaction. No further treatments are necessary before Maxam-Gilbert chemical sequencing reactions.

Base Sequence↗

PubMed1985

Malignant myoepithelioma (myoepithelial carcinoma) of the breast: an ultrastructural and immunocytochemical study.

This report describes the light (LM) and electron microscopic (EM) features and the results of an indirect immunofluorescence study (IF), the latter using monoclonal and monospecific antibodies to cytoskeletal proteins, of a malignant, invasive and metastatic breast myoepithelioma. A 53-year-old female underwent mastectomy for a large necrotic mammary tumor that had invaded the overlying skin. By LM, the neoplasm was composed of interlacing bundles of large, elongated and interspersed stellate cells with acidophilic cytoplasm. The neoplastic cells displayed a moderate degree of anaplasia, high mitotic activity, and strong tendency for necrosis. Stromal desmoplasia was marked, especially toward the center of the neoplasm. By IF, the tumor cells revealed bright cytoplasmic fluorescence with antibodies to actin, prekeratin, and cytokeratin. A few scattered spindle cells, which stained with the anti-vimentin and anti-actin anti-bodies, most likely represented stromal myofibroblasts. The anti-desmin reaction was negative. By EM, the neoplasm was composed of variably differentiated, elongated and stellate myoepithelial cells connected by desmosomes, enveloped by remnants of basal lamina, and containing pinocytotic vesicles, a well-developed rough endoplasmic reticulum, large Golgi areas, aggregates of intermediate filaments that were often arranged in dense curvilinear bundles (tonofilaments), and bundles of microfilaments with fusiform, dense bodies. The combined LM, EM, and IF study of this mammary tumor establishes its myoepithelial origin and, thus, identifies it as myoepithelial carcinoma distinct from other spindle cell breast tumors. This neoplasms was locally invasive and cytologically malignant; moreover, its malignancy was further confirmed by the development of lung and pleural metastases.

Actins↗

PubMed1979

Prognostic value of pre-treatment lymphocyte count and T cell levels in localized bronchogenic carcinoma.

In the patient with clinically localized bronchogenic carcinoma, the pre-treatment peripheral blood lymphocyte count and the thymus-dependent lymphocyte (T cell) level correlated with the prognosis of the tumor histology was either squamous cell, oat cell, or undifferentiated carcinoma. Patients whose pre-treatment lymphocyte count was less than 1,000/ml or whose T cell level was less than 750/ml either died or developed distant metastases by nine months after treatment of their localized tumor. By contrast, 55% of patients whose pre-treatment T cell level was greater than 750/ml were alive and without evidence of metastases nine months after treatment (P less than 0.02). Analysis of survival of these patients by the life-table method through the first post-treatment year further demonstrates the prognostic value of a low pre-treatment lymphocyte count or T cell level. The pre-treatment lymphocyte count and T cell level in patients with adenocarcinoma did not correlate with prognosis.

Adult↗

PubMed1978

Host immunocompetence in genitourinary cancer: relation to tumor stage and prognosis.

We used delayed hypersensitivity skin testing, in vitro lymphocyte blastogenesis, and lymphocyte surface markers to examine the relationships among host immunologic competence, tumor type, tumor stage, prognosis, and the effects of cancer treatments in patients with genitourinary cancer. We found correlations between host immune competence and both tumor stage and prognosis among patients with bladder cancer, renal cell cancer, and those with advanced prostate cancer not receiving endocrine therapy, but not among patients with prostate cancer receiving endocrine therapy. Radiation and chemotherapy suppressed T-lymphocyte levels, but a chemotherapy-induced tumor remission resulted in a rebound of T-cell counts to above normal levels. In tissue sections of bladder cancers, regions of mononuclear infiltration were virtually devoid of cells with complement receptors or receptors for cytophilic antibody, which suggested that lymphocytes infiltrating bladder cancers are predominantly T-lymphocytes.

Dinitrochlorobenzene↗

PubMed1977

Thymosin reconstitution of T cell deficits in vitro in cancer patients.

Thymosin, a soluble extract of fetal calf thymus, has increased cellular immunity in children with thymic deficiency. Prior to therapy, an increase in thymus-dependent lymphocyte (T cell) levels in vitro after incubation with thymosin correlated with a rise in peripheral blood T cell levels and improvement in other parameters of cellular immunity. These correlations constituted the basis for a study of the effects of thymosin on T cell levels in vitro in cancer patients. Groups studied were 350 untreated patients with local-regional solid malignancies, 157 patients cured of these tumors, 340 patients studied at 523 intervals during radiation therapy, 80 patients receiving chemotherapy for disseminated solid malignancies, and 427 normal volunteers. Although there were significant differences among the groups in mean leukocyte, lymphocyte and T cell levels, among those with low T cell levels in each group there was a significant inverse relation between T cell levels after incubation with thymosin in vitro and initial T cell levels, with the exception of patients receiving chemotherapy. In patients receiving chemotherapy, T cell levels increased independently of initial T cell levels. These in vitro observations are consistent with evidence that a major effect of thymosin is maturation of T cell precursors; however, the effect is that of reconstitution at low T cell levels, and not of elevation to levels significantly above normal. The results provide a rationale for clinical trials with thymosin to maintain immune competence during radiation therapy and chemotherapy, and for a two-phase approach to immunotherapy of cancer utilizing thymosin for reconstitution of cellular defects followed by administration of agents that potentiate cellular immunity.

Adolescent↗

PubMed1977

Effect of thymosin in vitro on T cell levels during radiation therapy: correlations with radiation portal and initial T cell levels.

The effect of thymosin in vitro on percent T cells was determined in 388 blood specimens from patients with head and neck, mediastinal, and pelvic malignancies during radiation therapy, in 94 untreated patients with these malignancies, and 277 normal adults. Changes in percent T cell levels after incubation of lymphocytes with thymosin did not correlate with tumor histology or cumulative radiation dose, but in all groups correlated with radiation portal and initial T cell levels. T cell levels increased by a similar increment in normals and in the untreated patients. During irradiation, the mean levels after incubation with thymosin did not change in patients with head and neck and pelvic malignancies, but in patients with mediastinal malignancies the levels increased significantly more than in normals. For a given T cell level, the increase in patients with mediastinal malignancies was greater than in patients with pelvic malignancies, and as a group was greater than in patients with head and neck malignancies. The results can be explained by an increase in circulating thymosin-responsive lymphocytes during mediastinal irradiation due to suppression of a function of the thymus important for maturation of these cells, and a decrease in these cells during pelvic irradiation due to a deleterious effect on precursors in pelvic bone marrow. The results thus provide a rationale for clinical trials to assess the efficacy of thymosin in averting declines of T cell levels in patients receiving mediastinal irradiation.

Adolescent↗

PubMed1976

In vitro lymphocyte reactivity and T cell levels in patients with melanoma: correlations with clinical and pathological stage.

In vitro lymphocyte reactivity (LR) to phytohemagglutinin (PHA) and peripheral blood thymus-dependent lymphocyte (T cell) levels were determined in 42 tumor-bearing patients with clinically operable melanoma and were compared to 41 age-matched normal controls. Patients with tumors clinically confined to the primary site (Stage I) as a group had normal immune reactivity and T cell levels, and those with regional metastases by clinical assessment (Stage II) had relatively impaired LR and T cell levels. In six of 24 patients with clinical Stage II tumors, widespread metastases (Stage III) subsequently were found. The severe immune defects in this group with occult disseminated melanoma accounted for the impaired LR and low T cell levels in the group with clinical Stage II tumors. Although overlapping levels of LR and T cells in the patients with pathological Stage II and III tumors prevent use of the data as a determinant of tumor extent in individual patients, the results show that these in vitro assays define a relation between cellular immunocompetence and tumor burden in patients with melanoma.

Adult↗

PubMed1975

Multiple primary malignant neoplasms. A search for an immunogenetic basis.

The occurrence of multiple primary malignant neoplasms in single individuals is well documented. Although many hypotheses have been advanced to explain this occurrence, there has been no study to determine if a presumed "increased susceptibility to cancer" has an immunogenetic basis. We evaluated the cellular immunity and histocompatibility antigens of 42 patients who had had from two to four multiple primary malignant neoplasms. We failed to demonstrate a preexisting impairment of immunocompetence or abnormal HL-A antigen frequencies in these patients. The occurrence of multiple primary malignant neoplasms in related tissues, eg, lung/larynx/oral cavity, and the occurrence of successive primary malignant neoplasms at a time interval consistent with the patient's being cured of preceding malignant neoplasms suggest that multiple primary malignant neoplasms result from repetitive induction by the same or similar etiologic factors in patients who are cured after treatment of the first malignant neoplasm.

Adult↗

PubMed1975

Prolonged depression of cellular immunity in cured laryngopharyngeal cancer patients treated with radiation therapy.

Immune competence was evaluated in cured patients who had been treated by irradiation for carcinoma of the laryngopharynx, and compared with that of similar patients treated by surgery alone, and normal controls. Cellular immunity was determined by quantitation of in vitro phytohemagglutinin (PHA)-induced lymphocyte reactivity and peripheral blood thymus-dependent lymphocyte (T cell) levels. Humoral immunity was assessed by measurement of serum immunoglobulin levels and by the effect of serum on in vitro normal lymphocyte reactivity to PHA. In 21 patients who were studied for 4-23 years (mean 8.4) after surgical treatment alone for laryngopharyngeal carcinoma, neither cellular nor humoral immunity differed from that of 44 controls. In contrast, 14 patients who had been irradiated and subsequently cured for 4-15 years (mean 9.0) prior to evaluation displayed significantly impaired cellular immune competence when compared to normals and patients treated by surgery alone. Since previous determinations of the effects of radiation therapy have been in patients who received irratiation to the thymic region or large area of bone marrow, this study indicates that radiation therapy for cancer administered via portals that encompass a minimal area of the immune system may be associated with prolonged impairment of cellular immunity.

Humans↗