PubMed Health⌕ Search

Biomedical subjects

H Kahn

Publications and source records attributed to H Kahn.

At least 19 recordsLinked to original sources
PubMed1995

The Henrietta Banting Breast Centre database: a model for clinical research utilizing a hospital-based inception cohort.

The cohort study design has been used successfully in clinical cancer research. Cohorts, however, are valuable only if they produce results which are valid and generalizable. Some hospital-based inception cohorts satisfy both these requirements and may thus be useful research tools. The development of one such hospital-based cohort, the Henrietta Banting Breast Centre database, is described. This cohort is composed of 1097 women diagnosed with primary breast cancer at Women's College Hospital, Toronto, from January 1977 through December 1986. Details of diagnostic procedures, pathology, treatment, dates and sites of recurrence, and date of death are available on 96% of women. By comparison with published series and with the Ontario Cancer Registry, we have demonstrated validity and generalizability. A major advantage is the ready availability of paraffin tissue blocks on virtually all cases, facilitating analyses of the prognostic importance of specific biologic variables and immunocytochemical hormone assays. Other completed studies and future uses of the cohort are described.

Breast Neoplasms↗
PubMed1995

Chemical and physical evaluations of commercial dicalcium phosphates as sources of phosphorus in animal nutrition.

Seven samples of commercial dicalcium phosphate, expected to contain variable amounts of monocalcium phosphate, from five established producers in Brazil and two in the United States, were evaluated and compared with a purified grade calcium phosphate dibasic dihydrate used as a reference standard. All samples were submitted to a wide range of tests at seven laboratories. Each determination was performed at least at two different laboratories, except for moisture, insoluble residue, loss on ignition, and x-ray diffraction assays, obtained from one single laboratory. All phosphate samples studied were in compliance with the manufacturer's levels of guarantee, except for three samples that were slightly out of specification (Ca, P, and F). Particle size patterns were variable, allowing for a classification of two products as "coarse", three as "fine", and three as "irregular". Phosphorus solubility in 2% citric acid ranged from 85.9 to 97.6%, pH from 3.2 to 6.1, and apparent density from 572 to 967 g/L. Atomic absorption or plasma emission spectrometry concentrations (average parts per million) for Al (3,200), As (10), B (14), Ba (165), Bi (< .1), Cd (6), Cr (57), Co (11), Cu (28), Fe (7,515), Hg (< .2), Mg (11,300), Mn (367), Mo (6), Ni (25), Pb (17), Se (< .5), Sb (1.3), Th (19), U (51), V (134), W (< 5), and Zn (152) were safe for all phosphates as compared to NRC standards. X-ray diffraction detected CaCO3 and impurities for all commercial samples, dolomite for three phosphates. Monocalcium phosphate was found in four samples. Aluminum salts present were identified as the low solubility, low toxicity silicates, and phosphates.

Animal Feed↗
PubMed1993

Multiple hamartoma syndrome with osteosarcoma.

Multiple hamartoma syndrome, also known as Cowden's disease, is a rare genodermatosis with characteristic mucocutaneous lesions associated with multiple internal abnormalities. We describe a patient having classic dermatologic manifestations of Cowden's disease and multiple neoplasia including follicular adenocarcinoma of the thyroid gland with lung metastasis, intraductal breast carcinoma within a fibroadenoma, and an osteosarcoma. To our knowledge, this is the first reported case of an osteosarcoma in Cowden's disease.

Adult↗
PubMed1992

A comparison of all-subset Cox and accelerated failure time models with Cox step-wise regression for node-positive breast cancer.

Clinical studies usually employ Cox step-wise regression for multivariate investigations of prognostic factors. However, commercial packages now allow the consideration of accelerated failure time models (exponential, Weibull, log logistic, and log normal), if the underlying Cox assumption of proportional hazards is inappropriate. All-subset regressions are feasible for all these models. We studied a group of 378 node positive primary breast cancer patients accrued at the Henrietta Banting Breast Centre of Women's College Hospital, University of Toronto, between January 1, 1977, and December 31, 1986. 85% of these patients had complete prognostic factor data for multivariate analysis, and 96% of the patients were followed to 1990. There was evidence of marked departures from the proportional hazards assumption with two prognostic factors, number of positive nodes and adjuvant systemic therapy. The data strongly supported the log normal model. The all-subset regressions indicated that three models were similarly good. The variables 1) number of positive nodes, 2) tumour size, and 3) adjuvant systemic therapy were included in all three models along with one of three biochemical receptor variables 1) ER, 2) combined receptor (ER- PgR-; ER+PgR-; ER- PgR+; ER+PgR+; or 3) PgR. Better multivariate modeling was achieved by using quantitative prognostic factors, a check for appropriate underlying model-type, and all-subset variable selection. All-subset regressions should be considered for routine use with the many new prognostic factors currently under evaluation; it is very possible that there may not be a single model that is substantially better than others with the same number of variables.

Adult↗
PubMed1992

Peripancreatic lymph node gastrinoma in a patient with Zollinger-Ellison syndrome.

The case of a patient who had Zollinger-Ellison syndrome caused by a primary peripancreatic lymph node gastrinoma is presented. Accompanying diffuse pancreatic islet cell hyperplasia, a well-documented occurrence in hypergastrinemia, was present. A perforated esophageal ulcer in a Barrett's esophagus led to right-sided necrotizing pleuritis, septicemia, and death. The diffuse parathyroid hyperplasia also noted in the patient is thought to be secondary to chronic hypertensive renal failure rather than MEN-I syndrome.

Aged↗
PubMed1991

Human immunodeficiency virus-associated Hodgkin's disease. Clinicopathologic studies of 24 cases and preponderance of mixed cellularity type characterized by the occurrence of fibrohistiocytoid stromal cells.

Hodgkin's disease (HD) was diagnosed in 24 patients who were either seropositive for human immunodeficiency virus (HIV) (21) or members of a high-risk group (three), but had not developed acquired immune deficiency syndrome (AIDS). Clinical presentation of the disease was characterized by constitutional symptoms in all, especially fever (23/24) and disseminated disease (22/24) at diagnosis. Mediastinal adenopathy was rare. Bone marrow involvement was particularly frequent (12/24), and a positive bone marrow biopsy preceded lymph node biopsy in 5 of the 12. Histopathologic features of these tumors included an increased number of nonlymphoid stromal cells, i.e., histiocytic and/or fibroblastoid. In some tumors these fibrohistiocytoid stromal cells were arranged in bundles, but distinct nodule with birefringent collagen band formation was not observed. Twenty-two patients were treated, most with combination chemotherapy; one was untreated; one, unknown. Sixteen, including the one untreated, died with disease at 3 to 25 months; one died of an unrelated cause; four were alive at 3 to 24 months; three were lost to follow-up. Frequent bone marrow involvement at presentation suggests the usefulness of the bone marrow biopsy for diagnosis in subjects at risk, especially when they present with spiking fever of unknown origin. Contrary to most previous series, virtually all of our cases were of mixed cellularity type, characterized by increased fibrohistiocytoid stromal cells in place of depleting lymphocytes. The classic nodular sclerosing feature with birefringent collagen band formation was not observed. In conclusion, HIV-associated HD was characterized by advanced stage with fever at presentation, preponderance of mixed cellularity histologic type with increased fibrohistiocytoid stromal cells, and poor outcome. Hodgkin's disease in AIDS patients presents an intriguing biological model to study the role of stromal histiocytes in immunodeficient patients.

Adult↗
PubMed1991

Acute biologic response to excimer versus thermal laser angioplasty in experimental atherosclerosis.

Vascular injury and platelet accumulation after balloon angioplasty are two potentially important triggers of the process of restenosis that may be minimized by the use of laser energy to ablate atherosclerotic plaque. The type of laser most suitable to achieve these goals remains unknown. Accordingly, angiographic and histologic studies and quantitative platelet deposition analysis were performed on 27 atherosclerotic rabbit iliac arteries randomized to treatment with excimer laser or thermal laser angioplasty. Excimer laser angioplasty was achieved with 35 to 40 mJ/mm2 of 308 nm xenon chloride irradiation delivered through a 4.5F catheter made of 13 concentrically arranged 200 microns fiber optics, at a repetition rate of 25 to 30 Hz and a pulse duration of 135 ns; thermal laser angioplasty was achieved with a 1.7 mm metal probe heated with 10 W of continuous wave argon laser energy. The baseline and post-laser luminal diameters of excimer laser-treated vessels (0.92 +/- 0.28 and 1.56 +/- 0.48 mm, respectively) were similar to those observed in thermal laser-treated vessels (1.05 +/- 0.44 and 1.61 +/- 0.41 mm, respectively). Perforation occurred in 4 (29%) of 14 thermal laser-treated arteries and in 0 of 13 excimer laser-treated arteries (p = 0.04); spasm was observed in only 1 thermal laser-treated vessel. On the basis of a quantitative histologic grading scheme (damage scores of 0 to 4), greater degrees of injury were measured in thermal versus excimer laser-treated vessels (2.4 +/- 1.0 versus 1.3 +/- 0.4, p = 0.009).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

Hepatocellular carcinoma in a long-term survivor of intrahepatic biliary duct hypoplasia.

We describe the development of hepatocellular carcinoma (HCC) in a 46-yr-old woman with intrahepatic biliary duct hypoplasia. Her underlying liver disease was quiescent for many years until a dramatic rise in serum bilirubin was seen. Orthotopic liver transplantation was performed, and a large tumor was found during surgery. A bile-producing HCC was identified, infiltrating about 50% of an otherwise noncirrhotic liver which had a paucity of intrahepatic ducts. The findings of HCC in this long-term survivor of intrahepatic biliary duct hypoplasia indicates HCC may occur in patients with long-standing disease.

Bile Ducts, Intrahepatic↗
PubMed1991

Immunoglobulin-related amyloidosis presenting as recurrent isolated lymph node involvement.

Up to 37% of cases of generalized primary and secondary amyloidosis demonstrate lymph node involvement. Lymph node involvement as the presenting feature of generalized amyloidosis is uncommon. Isolated lymph node amyloidosis (that is, with no extranodal amyloidosis) is exceedingly rare; review of the literature reveals only two reported cases. A case of recurrent isolated lymph node amyloidosis is presented, with review of the literature.

Amyloidosis↗
PubMed1991

Poorly differentiated skin tumors. Beyond hematoxylin-and-eosin staining.

Although many tumors may be diagnosed by light microscopy alone, a few require further investigation. Selective use of antibodies by immunohistochemical techniques solves most diagnostic problems. The explosive discovery of many new antibodies often raises more questions than it answers, and electron microscopy still plays a significant role when used judiciously. It is important to recognize that every new antibody must be adequately assessed in the clinical situation and that its specificity, or lack thereof, is appreciated by both clinician and pathologist. With every new antibody, we increase our knowledge of basic disease processes. In the future, antibodies will be part of the pathologist's armamentarium for predicting disease outcomes. Not only will the cell of origin be identified but proliferation rates and production of various factors that influence metastatic potential will be delineated.

Humans↗
PubMed1990

Coronary excimer laser angioplasty: reduced complications and indium-111 platelet accumulation compared with thermal laser angioplasty.

The relative safety and thrombogenicity of pulsed excimer and thermal laser angioplasty systems were compared in 20 normal coronary artery segments in a total of seven pigs. Using similar over the wire catheter systems and laser delivery periods of 3 to 5 s, thermal laser angioplasty was achieved with a 1.3 mm metal probe heated with 10 W of continuous argon laser energy and excimer laser angioplasty was performed with a 4.5F excimer laser catheter consisting of 13 concentrically arranged 200 microns fiber optics delivering 35 to 40 mJ/mm2 of xenon chloride (308 nm) excimer laser irradiation at a repetition rate of 25 to 30 Hz and a pulse duration of 120 ns. On angiography, the incidence of vessel perforation (1 in 10 versus 3 in 10) and abrupt vessel closure (0 in 10 versus 2 in 10) was less with excimer compared with thermal laser angioplasty. Macroscopically, there was a greater incidence of mural and occlusive thrombus formation after thermal laser than after pulsed excimer laser angioplasty. Histologic examination confirmed that this thrombogenicity was associated with greater charring and coagulation necrosis of the media. Quantitative indium-111-labeled platelet deposition was significantly increased after thermal laser angioplasty (median 87.2 x 10(6)/cm length) compared with excimer-treated (0.4 x 10(6)/cm length) or control (1.2 x 10(6)cm length) segments (p less than 0.001). Thus, excimer laser angioplasty was found to result in fewer complications and, as a consequence, less thrombosis and platelet accumulation than did thermal laser angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1989

Vocational education and students with learning disabilities.

This inquiry focuses on the status of nearly 500 students with learning disabilities in 17 state-operated regional vocational-technical schools in a northeastern state. The inquiry addressed four primary concerns: patterns of assessment, career choice, school marks, and attendance. The data indicate that a variety of instruments were used in the assessment process and that the overall grade equivalent levels of attainment ranged between fifth- and seventh-grade levels. Children defined as learning disabled participated in a large number of vocational trade specialties and some 50% or more had school marks indicating that they were passing in these areas. Attendance was high. Many children with learning disabilities successfully perform in competitive vocational education programs designed to produce proficiency at the level of journey person.

Adolescent↗
PubMed1986

Role of immunohistochemistry in the diagnosis of undifferentiated tumors involving the skin.

Twenty undifferentiated skin tumors were examined by immunostaining in an attempt to achieve more precise identification. Light microscopy yielded only a differential diagnosis, whereas immunostaining of formalin-fixed, paraffin-embedded tissue sections with a panel of antibodies to intermediate filaments and other cell components led to a definitive diagnosis. Four cytokeratin-positive epithelial tumors were subtyped into squamous cell carcinomas and adenocarcinomas with the use of antibodies to different cytokeratin polypeptides. Fifteen vimentin-positive tumors were subdivided into malignant melanomas with the use of antibody to S-100 protein, lymphomas with the use of antibody to immunoglobulin, and mesenchymal tumors (angiosarcomas, atypical fibroxanthomas, dermatofibrosarcoma protuberans, and meningiomas) with the use of antibody to S-100 protein, factor VIII, and lysozyme. One desmin-positive tumor was diagnosed as a leiomyosarcoma of the skin. A scheme is presented for using immunohistochemistry to facilitate the diagnosis of undifferentiated tumors involving the skin.

Antibodies↗