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Biomedical subjects

C Potvin

Publications and source records attributed to C Potvin.

At least 37 records · Page 2Linked to original sources
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

Effect of Leaf Detachment on Chlorophyll Fluorescence during Chilling Experiments.

The effect of leaf detachment on chlorophyll fluorescence was analyzed for Zea mays, Cucumis sativus, Phaseolus vulgaris, and Echinochloa crus-galli. Results clearly indicate that detachment hastens the decrease in chlorophyll fluorescence during the course of chilling experiments. For maize and bean, the activity of photosystem II of chloroplasts isolated from detached leaves is lower than that of chloroplasts isolated from attached leaves. There are also large differences in ionic loss between detached and attached leaves of barnyard grass which could correlate with changes in leaf water status. The detached leaves lost some 50% of their total ionic content. Finally, detachment alters the ranking of the species with regard to their chilling tolerance.

Journal Article↗
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↗
PubMed1984

Effects of Temperature and CO(2) Enrichment on Carbon Translocation of Plants of the C(4) Grass Species Echinochloa crus-galli (L.) Beauv. from Cool and Warm Environments.

Plants of Echinochloa crus-galli from Québec and Mississippi were grown under two thermoperiods (28 degrees C/22 degrees C, 21 degrees C/15 degrees C) and two atmospheric CO(2) concentrations (350 and 675 microliters per liter) to examine possible differential responses of northern and southern populations of this C(4) grass species. Translocation was monitored using radioactive tracing with short-lived (11)C. CO(2) enrichment induced a decrease in the size of the export pool in plants of both populations. Other parameters did not strongly respond to elevated CO(2). Low temperature reduced translocation drastically for plants from Mississippi in normal CO(2) concentration, but this reduction was ameliorated at high CO(2). Overall, plants from Québec had a higher (11)C activity in leaf phloem and a higher percentage of (11)C exported, whereas these northern plants had lower turnover time and smaller pool size than plants from the southern population.

Journal Article↗
PubMed1984

Intra-arterial infusion chemotherapy in rectal cancer.

Chemotherapy by intra-arterial infusion, using mitomycin C and 5-fluorouracil, was administered to six patients with cancer of the rectum. In three patients who presented initially with an inoperable rectal tumour, medication was infused through the inferior mesenteric artery. Tumour regression was documented in all three, allowing subsequent resection in two. Of three other patients with locally recurrent rectal cancer, none showed tumour regression after infusion, but two experienced substantial relief of perineal pain, with improvement in the quality of life. Unexpected complications occurred in the form of a reversible ischemic colitis in two patients and an arterioenteric fistula in a third.

Aged↗
PubMed1981

Early gastric cancer at the Hôtel-Dieu de Montréal: a 30-year review.

Early gastric cancer is usually defined as a lesion involving the mucosa alone or the mucosa and submucosa, regardless of whether lymph-node metastases are present. Between 1948 and 1978, 1295 gastric cancers were diagnosed at the Hôtel-Dieu de Montréal. Of these, 65 (5%) were early gastric cancers. Sixty of the 64 patients underwent gastric resection for cure. The other four cancers were found incidentally at autopsy. One patient (1.7%) died following operation. Ten patients were followed up for less than 5 years and therefore were excluded from survival analysis, as were 6 patients who died of unrelated causes. Forty-one of 43 patients survived, free of disease, for more than 5 years following operation, a survival rate of 95.3%. The annual yield of early gastric cancers has remained relatively constants since 1948, even with a decreasing number of gastric cancers treated at the hospital. The advent of fiberoptic endoscopy significantly (P less than 0.005) increased the number of early gastric cancers detected. Further improvements will depend on a more vigorous approach to endoscopy, especially in high-risk patients. A refined radiologic technique, including double-contrast roentgenography after a barium meal, was diagnostic in all patients who underwent operation in this study.

Female↗
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↗
PubMed1975

Thymus-dependent lymphocyte levels in bronchogenic carcinoma: correlations with histology, clinical stage, and clinical course after surgical treatment.

The in vitro spontaneous lymphocyte rosette (T cell) assay was used to determine cellular immunologic competence in 112 patients with bronchogenic carcinoma. Among preoperative patients with localized tumors. T cell levels were significantly lower than in 237 normal controls. With advanced stages of disease, T cell levels declined progressively among patients with squamous cell carcinoma, oat cell carcinoma, and undifferentiated carcinoma, but not among patients with adenocarcinoma. Squamous carcinoma patients considered cured had persisting low T cell levels, but cured adenocarcinoma patients had normal levels. Serial determinations that showed a fall in T cell levels preceded the development of clinically evident metastases by an average of 2.5 months. Postoperative patients with rising T cell levels have remained clinically free of disease. The data indicate that T cell levels correlate with extent of tumor and clinical course of patients with bronchogenic carcinoma. The assay may, therefore, provide a rational basis for the selection of patients who are at high risk for the development of recurrence after surgical resection and who may benefit from the early institution of adjunctive therapy.

Adenocarcinoma↗
PubMed1975

Identification of complement-receptor lymphocytes (B cells) in lymph nodes and tumor infiltrates.

To monitor the distribution of lymphocyte sub-populations infiltrating tumors, a simplified modification of standard techniques was developed to identify the complement-receptor B lymphocytes in frozen tissue sections. This technique is based on binding of antibody-coated bovine erythrocytes by B lymphocytes in the presence of sub-hemolytic concentrations of mouse complement. B lymphocytes can be identified in frozen tissue sections by adherent sensitized bovine erythrocytes. The specificity of the technique for B lymphocytes was established by 1) absence of spontaneous rosette formation with bovine erythrocytes by human T lymphocytes, 2) specific binding of bovine erythrocyte-antibody-complement complexes to B cell regions of normal lymph nodes and spleen and 3) binding of erythrocyte-antibody-complement to a high proportion of chronic lymphocytic leukemia (a B cell leukemia) lymphocytes. Five transitional carcinomas studied had regions of mononuclear infiltration that were virtually devoid of complement-receptor lymphocytes. The results suggest that lymphocytes infiltrating bladder carcinomas may be predominantly T lymphocytes.

Animals↗
PubMed1975

The immunobiology of skin cancer.

The immunobiology of skin cancer was studied with thymus-dependent lymphocyte (T cell) levels (an in vitro measure of cellular immunity), with lymphocytic infiltration (LI) of the tumor (an in vivo measure of host-tumor relationship), and with HL-A typing (a genetic measure of histocompatibility). The T cell levels in preoperative patients with squamous (SCC) and basal (BCC) cell carcinoma were significantly lower than in the non-cancer control population (normals). The T cell levels were significantly lower in patients with large tumors than in those with small tumors. The T cell levels remained significantly low in patients cured of large tumors, but were normal in those cured of small tumors. Patients with Bowen's disease not only had T cell levels significantly lower than normal (as a group), but there was also a significant increase in the number of patients who had T cell levels less than two standard deviations below the normal mean. This may signify that they have a greater risk of developing a second kind of malignancy elsewhere. There was a direct correlation between the degree of lymphocytic infiltration (LI) of the tumor, the tumor size, and the T cell level. Small, well-localized tumors had a marked LI and high T cell levels--while the large, deeply invasive tumors had a minimal, or absent, LI and low T cell levels. The presence of HL-A antigens 1 and 8 correlated both with a tendency toward large tumors and with low T cell levels. This may represent the association of a human immune response gene with the human histocompatibility locus. Possibilities for the application of these findings in the clinical management of skin cancer are discussed.

Adult↗