Biomedical subjects

H K Tan

Publications and source records attributed to H K Tan.

69 records · Page 4Linked to original sources

PubMed1978

The bone marrow examination in breast cancer: diagnostic considerations and clinical usefulness.

Bone marrow examinations were performed on 116 women with primary and metastatic breast cancer and were correlated with the clinical status of the patient and other specific diagnostic modalities. The relative diagnostic efficacy of the marrow biopsy, aspirate smear and clot section was examined, as was the value of serial marrow examinations. A marrow positive for tumor was found in 40% of those with metastatic disease, 55% with positive x-rays, 56% with positive bone scans, but only 4% (1/24) with both scan and x-ray normal. Routine hematologic parameters were of limited usefulness in predicting the finding of a positive marrow. The biopsy was superior to the smear and clot section but aspirated material also had to be analyzed to maximize diagnostic yield. When analyzed qualitatively, i.e., positive or negative for tumor, serial marrow examinations were not useful in assessing the efficacy of antitumor treatment. The potential usefulness of bone marrow examination in patients with breast cancer is discussed.

Biopsy, Needle↗

PubMed1978

Demonstration of the outer surface of freeze-etched normal human platelets: correlation with buoyant density.

The external surface of the normal human platelet shows clusters of spherical particles in a reticular pattern with smooth and regular surface membrane in adjacent areas. Labelling with cationic ferritin demonstrates a diffuse distribution of ferritin particles which stop at the fracture face of the intramembranous surface. The intramembranous surface is not labelled. Previously discrepant observations on the plasma membrane surface are probably due to different techniques of platelet preparation for freeze-etch electron microscopy. Density-dependent platelet sub-populations do not differ with respect to the ultrastructural features of their external surface and intramembranous portions of the plasma membrane. Based upon the relationship between platelet density and age, it appears that the ultrastructure of the normal platelet plasma membrane does not change with in vivo ageing.

Blood Platelets↗

PubMed1977

Human factor VIII: morphometric analysis of purified material in solution.

Study of purified human factor VIII in buffer by freeze-etch electron microscopy reveals rounded, rod-shaped particles measuring 22 by 42 nanometers. When thrombin was added to purified normal factor VIII, there was a rapid loss of rod-shaped particles during the first 15 minutes of incubation at 37 degrees C. Purified plasma from two patients with severe hemophilia contained spherical particles measuring 10 to 50 nanometers in diameter, with no evidence of significant numbers of rod-shaped forms. Negatively stained and unstained air-dried samples of factor VIII corroborate the relative shape and size differences between normal and hemophiliac material.

Blood Coagulation Factors↗

PubMed1977

Diagnosis of acute leukemia. Variability of morphologic criteria.

The diagnosis of acute leukemia depends on the morphologic appearance of Romanowsky-stained blast cells. Three commonly used and accepted criteria for distinguishing among blast cells of different acute leukemias are (1) nuclear chromatin pattern, (2) appearance of nucleoli, and (3) nuclear-cytoplasmic ratio. It is sometimes assumed that Romanowsky stains do not differ in their abilities to demonstrate characteristic features of blast cells. In the present study six different Romanowsky stains were applied to smears from a single bone marrow aspirate from each of 22 patients with acute leukemia. Marked, stain-dependent variation in the appearances of the same blast cell population was repeatedly observed for all modalities except nuclear-cytoplasmic ratio. The authors caution against generalizations regarding morphology and suggest that the exact stain employed is a significant variable in morphologic studies.

Adolescent↗

PubMed1977

Erythrocyte membrane plaques from rats with magnesium deficiency.

This study investigated the anemia of dietary magnesium deficiency in inbred Fisher white rats using freeze-fracture electron microscopy. The plasma membranes of erythrocytes from animals receiving two different magnesium-deficient and control diets were observed at weekly or biweekly intervals for 6 wk. The earliest changes were small plaques on the external surface (ES) and fracture face (PF) of erythrocyte plasma membranes, which occurred after 2 wk of either magnesium-deficient diet. These plaques persisted and increased in size with progressive magnesium deficiency. When fully developed, the plaques consisted of round or oval elevations approximately 30-50 nm in diameter outlined by a narrow raised border. The surface of the plaques was smooth and devoid of intramembranous particles. Incubation of erythrocytes from magnesium-deficient rats in a physiologic solution containing 2 meq/liter magnesium for 1 hr at 37degrees C did not alter the appearance of the plaques. Erythrocytes from control rats, obtained during the same time periods, showed no plaques. Thus, a deficiency of magnesium in rats altered erythrocyte membrane structure.

Animals↗

PubMed1976

Ultrastructure and light microscope appearance of Blastocystis hominis in a patient with enteric disease.

The patient reported had a fulminant, refractory diarrhea of unknown etiology producing about 81 of diarrheal fluid daily which required continuously large volumes of intravenous fluid therapy. No protozoon other than Blastocystis hominis was present. Bacterial counts were very low in the fecal material because of continuous antibiotic therapy. Blastocystis hominis was present in large numbers, averaging for a 5-day period, 8.3 X 10(6)/ml of diarrheal fluid. Treatment with metronidazole for 12 days had no effect on either the diarrhea or the numbers of B. hominis present. The patient died from aspiration pneumonia without a firm diagnosis of his underlying disease. Identification of an unusual form of B. hominis seen only in diarrheal fluid was confirmed through cultivation, specific fluorescent antibody staining, as well as by transmission electron microscopy and light microscopy using hematoxylin staining and Nomarski interference contrast. The most significant result of this study is the description of ultrastructure of the in vivo trophozoite form of B. hominis. The persistence of certain morphologic features of the in vivo and in vitro forms of B. hominis is described. In vivo, B. hominis has a larger nucleus than in vitro, more prominent, well structured nucleoli, and hundreds of mitochondria with numerous delicate saccular cristae in a clear electron-lucent matrix and complex internal structure. Many cytoplasmic vesicles lined with ribosomes are present. The in vivo structure differs from the granular culture form of B. hominis, which has a smaller nucleus (nuclei), no distinct nucleoli, mitochondria characterized by a uniform structureless electron dense matrix, and few cytoplasmic, ribosome-lined vesicles. A feature retained in both in vivo and in vitro B. hominis is a distinct crescentic band of nuclear chromatin.

Diarrhea↗

PubMed1976

Immunoblastic lymphadenopathy. Evolution into a malignant lymphoma with plasmacytoid features.

In the patient described progressive lymphadenopathy, splenomegaly and interstitial pulmonary disease developed two months after the development of immunoblastic lymphadenopathy. Light microscopic examination of a lymph node biopsy specimen suggested a diagnosis of immunoblastic sarcoma. Evolution of this malignant lymphoma into a leukemic phase allowed detailed studies of the malignant cells by electron microscopy, cytochemical staining and immunologic technics. Evidence is presented that this is a case of malignant lymphoma with plasmacytoid and not lymphoid features. Review of the literature on immunoblastic sarcoma suggests that light microscopy and clinical setting are not sufficient to define a homogeneous clinicopathologic disease.

Adult↗

PubMed1974