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Biomedical subjects

G C Yang

Publications and source records attributed to G C Yang.

At least 73 records · Page 4Linked to original sources
PubMed1975

Stabilization and clarification of sections mounted on formvar-coated slot grids by deliberate irradiation in the electron beam.

Epon-Araldite sections supported on Formvar-coated slot grids can be stabilized by exposing the area of interest in the column of the electron microscope to irradiation of 0-5C/cm-2. With this procedure one can obtain electron micrographs of high quality, without drift or distortion, from any part of the open slot area. After treatment the support film is not only stable and transparent but robust enough to permit repeated removal and replacement of the specimen in the microscope column. We illustrate the method with a series of electron micrographs with initial magnifications ranging from x300 to x500,000 to show the quality of image that can be achieved. The effect of the irradiation on tissue architecture is checked by resectioning the irradiated sections. We recommend this method of local irradiation of sections for investigations using low or intermediate magnifications for the wide field it permits, for the durability it confers on the specimen and for its convenience.

Cell Membrane↗
PubMed1974

Effect of Ca2+ on morphology and division of Yersinia pestis.

Wild-type cells of Yersinia pestis are known to exhibit a nutritional requirement for physiological levels of Ca(2+) ( approximately 2.5 mM) at 37 but not 26 C. Upon shift of Ca(2+)-deficient cultures from 26 (permissive condition) to 37 C (restrictive condition), bacterial mass quadrupled as the organisms doubled in number and then became elongated to about twice their normal size. As shown in thin sections, the resulting static cells contained axial filaments which differed from the typical irregularly lobate nucleoids of normal yersiniae grown under the permissive condition. Following prolonged cultivation under the restrictive condition (12 h), the organisms generally exhibited apparent degenerative changes, including separation or infolding of the cell wall and cytoplasmic membrane, degeneration of deoxyribonucleic acid, and appearance of vacuoles within the cytoplasm. At this time, the cells were unable to reinitiate cell division at 37 C upon addition of Ca(2+) but divided in partial synchrony after return to 26 C. This observation indicated that, at 37 C, continuous exposure to Ca(2+) is necessary for yersiniae to maintain normal morphology and the ability to divide.

Bacteriological Techniques↗
PubMed1972

Specificity, induction, and absorption of pesticin.

Irradiation of pesticinogenic (Pst(+)) cells of Yersinia pestis with ultraviolet light resulted in a five- to eightfold increase in titer of intracellular pesticin. Extracellular activity in irradiated or control cultures never approached that found within the bacteria. Upon chromatography of crude extracts of Pst(+) cells on columns of diethylaminoethyl-cellulose, Sephadex G200, and calcium hydroxyapatite, fractions were recovered which inhibited the growth of indicator cells of Escherichia coli, Y. pseudotuberculosis, Y. enterocolitica, and Pst(-)Y. pestis. By means of these methods, in conjuntion with fractional precipitation with ammonium sulfate, the antibacterial activity was purified to homogeneity (as judged by disc gel electrophoresis and analysis by double diffusion in agar). The relative sensitivity of each cell type was constant and not affected by the state of purification. These findings indicate that the pesticin molecule alone accounts for lethality. Cells of E. coli and Y. pseudotuberculosis were about 100 and 10 times more sensitive to pesticin, respectively, than were those of Pst(-)Y. pestis. Activity directed against sensitive cells of these three species was enhanced by 0.1% ethylenediaminetetraacetate (EDTA) and completely inhibited by 0.01 m hemin or 0.001 m Fe(3+). The response of Y. enterocolitica to pesticin was variable in the presence of EDTA and was not influenced by Fe(3+). Attempts to detect common surface structures responsible for absorption of pesticin by the four cell types were not successful.

Absorption↗
PubMed1971

Effect of ca on the synthesis of deoxyribonucleic Acid in virulent and avirulent yersinia.

Virulent and potentially virulent cells of Yersinia (Pasteurella) pestis produce virulence or V and W antigens (VW(+)) but remain static at 37 C during aeration in enriched Ca(2+)-deficient media containing 0.02 m Mg(2+). In this environment, which simulates mammalian intracellular fluid, VW(+) cells possessed a functional cytoplasmic membrane as judged by concentration of (14)C-isoleucine, release of (32)P, and consumption of oxygen at rates comparable to those of dividing cells cultivated with Ca(2+). Furthermore, rates of protein and ribonucleic acid synthesis were essentially identical in dividing and static VW(+) cells and in mutant VW(-) organisms. However, the rate of deoxyribonucleic acid (DNA) synthesis in static cells was about 10% of that observed in dividing organisms. Accordingly, bacteriostasis of VW(+) cells in the simulated intracellular environment is evidently caused by reactions directly associated with cessation of DNA synthesis rather than by alterations in the regulatory capacity of the cytoplasmic membrane.

Journal Article↗
PubMedDate not supplied

Topographies of extracytoplasmic compartments in developing chick tendon fibroblasts.

The complex topography of the fibroblast leading to the formation of extracellular compartments is demonstrated in the native three-dimensional state in cryofractured chick embryo tendon at different stages of development. Tendon collagen fibrils, fibril bundles, and macroaggregates are intimately associated with these extracytoplasmic domains. The localization of fibrils within narrow channels, bundles within peripheral compartments, and the coalescence of bundles into macroaggregates within larger extracytoplasmic compartments is illustrated at different stages of development. Changing patterns of matrix organization are apparent as morphogenesis proceeds. Our interpretation is that collagen fibrils, oriented along the tendon axis, appear in extracytoplasmic channels defined by the fibroblast which are added at the periphery of the cell until a row of fibrils outlines the cellular border at Day 10. By Day 14, cytoplasmic processes have partitioned the fibrils into groups and then into round bundles. New fibrils are continually added to the fibril bundles through fusion of the extracytoplasmic channels. As the bundles grow larger, the cell boundaries between the bundles retract and bundles begin to coalesce into macroaggregates. The fibroblast becomes attenuated, bundle-forming compartments disappear as processes retract, bundles coalesce, and macroaggregates predominate by Day 17. This work is consistent with the model proposed for the compartmentalization of the extracellular space by the fibroblast, providing distinct microenvironments where collagen fibrillogenesis and matrix morphogenesis occur under close cellular regulation.

Animals↗
PubMedDate not supplied

Aflatoxin and Reye's syndrome: a study of livers from deceased cases.

In order to reinvestigate a strong reported association, we attempted to identify aflatoxin in the livers of 12 children who presumably died of Reye's Syndrome and in the liver of one child who died accidentally. Aflatoxins were detected, but not confirmed in only one of the liver specimens (limits of detection 20 ppt). In addition, the microscopic appearance of the livers was reviewed. Although most of the cases fit the clinical definition of Reye's Syndrome, the microscopic appearance of the liver was varied. We conclude that aflatoxin is not regularly recoverable from cases of Reye's Syndrome at a high rate, and question the proposed etiologic relationship. We confirm the varied appearance of the liver late in the course of Reye's Syndrome; however, microvesicular fat was present in most cases.

Aflatoxins↗
PubMedDate not supplied

A low-power, "architectural," clue to the follicular variant of papillary thyroid adenocarcinoma in aspiration biopsy.

OBJECTIVE: To search for low-power, or "architectural," clues to the diagnosis of the follicular variant of papillary thyroid adenocarcinoma (FVP) in Diff-Quik-stained aspiration biopsy smears in order to aid in the rapid diagnosis of FVP, especially as a complement to frozen sections. STUDY DESIGN: The smears of 23 cases, each with tissue-proven FVP, were compared to those of 23 cases of classic papillary thyroid adenocarcinoma (PTA), 23 cases of tissue-proven follicular neoplasms (FN) (i.e., adenoma or well-differentiated adenocarcinoma) and 23 samples of colloid nodules (CN). The low-power (10x) features of the four groups were studied and compared. RESULTS: Our study showed that FVP exhibited monolayered cellular sheets with branched, irregular contours, which can be distinguished from the uniform microfollicles with smooth contours formed in FN and the large, round or oval monolayered sheets of follicular cells found in CN. FVP shared all of the features of classic PTA except for the larger, complex sheets of epithelial cells and psammoma bodies found in the latter. CONCLUSION: The branched sheets of epithelial cells evident during low-power examination of Diff-Quick-stained smears of thyroid aspirates are a ready first clue to the rapid diagnosis of FVP. The diagnosis can be confirmed by subsequent careful evaluation of nuclei in Papanicolaou-stained smears and sections of tissue.

Adenocarcinoma, Papillary↗
PubMedDate not supplied

Application of Ultrafast Papanicolaou stain to body fluid cytology.

OBJECTIVE: To investigate the applicability of the Ultrafast Papanicolaou stain to the cytology of fluids and to compare it with other methods. STUDY DESIGN: Over a 30-month period, 528 unfixed fluids (462 serous effusions, 48 pelvic washings, 16 cyst fluids and 2 bile duct drain fluids) were mixed thoroughly and centrifuged. Two Swedish-style air-dried smears were made and stained with Diff-Quik (Mercedes Medical, Inc., Sarasota, Florida, U.S.A.) and Ultrafast Papanicolaou stain (Richard Allan Scientific, Kalamazoo, Michigan, U.S.A.), and the remaining sediment was fixed in CytoRich Red (TriPath Imaging, Inc., Burlington, North Carolina, U.S.A.), centrifuged onto a 17.5-mm circle with a Hettich cytocentrifuge and stained by the Papanicolaou method. RESULTS: For the 115 malignant fluids, Ultrafast Papanicolaou stain was the preferred method in the 94 non-hematopoietic malignant fluids, Diff-Quik was the preferred method in the 9 hematopoietic malignancies, and CytoRich Red was the preferred preparation in 8 bloody effusions containing rare cancer cells and 4 malignant pelvic washings. The diagnostic turnaround time of smears stained by Ultrafast Papanicolaou stain was < 15 minutes, fast enough for intraoperative consultations. CONCLUSION: It seems that Ultrafast Papanicolaou stain improves the resolution of cytoplasmic and nuclear details of nonhematopoietic cells in body fluids. However, to detect cancer in all types of fluids, Diff-Quik and CytoRich preparations are also required. We now examine three slides per fluid sample, one slide by each of the three techniques.

Ascitic Fluid↗
PubMedDate not supplied

Epithelial-myoepithelial carcinoma of the parotid. A case of ductal-predominant presentation with cytologic, histologic and ultrastructural correlations.

BACKGROUND: The cytologic features of the usual type of epithelial-myoepithelial carcinoma (EMC) of the parotid, with myoepithelial cell predominance, is well described in the cytology literature. In contrast, the cytologic features of ductal-predominant-type EMC has not yet been reported. CASE: An 82-year-old male presented with a 2.7-cm parotid mass of two years' duration. Fine needle aspiration smears stained with Diff-Quik showed cohesive tissue fragments outlined by metachromatic fibrils scattered in abundant, smooth, bluish background material. Ultrafast Papanicolaou stain revealed sharply outlined, large ductal cells with smooth, round to oval nuclei, prominent nucleoli and abundant vacuolated cytoplasm; the cells were arranged tridimensionally in occasional follicles that contained thick secretions. Neoplastic myoepithelial cells were occasionally seen at the periphery of tissue fragments, most commonly hidden underneath the neoplastic ductal epithelium at a slightly different focal plane; the cells had small, oval, dark nuclei and inconspicuous cell borders. The nuclear area and cell size of the neoplastic ductal cells was two and three times, respectively, that of neoplastic myoepithelial cells. CONCLUSION: EMC, depending on the ratio of ductal to myoepithelial cell components, has different cytologic presentations. This case illustrates the ductal-predominant presentation of EMC.

Aged↗
PubMedDate not supplied

Multilocular thymic cyst with follicular lymphoid hyperplasia in a male infected with HIV. A case report with fine needle aspiration cytology.

BACKGROUND: Multilocular thymic cyst with follicular lymphoid hyperplasia is a rare complication in HIV-infected patients, causing pseudotumorous enlargement of the anterior mediastinum. There have been six reported cases, all with only histologic findings. This paper reports another such case and includes perhaps the first cytologic findings on this rare entity. CASE: A 35-year-old, HIV-infected male intravenous drug abuser, who complained of worsening central chest discomfort and pain on deep inspiration, was found to have a large, septated anterior mediastinal mass. Computed tomography-guided fine needle aspiration biopsy was performed. The cytologic presentation mimicked that of thymoma, with cystic degeneration and a dual population of epithelial cells and lymphocytes as well as large aggregates of "epithelial" cells intermixed with lymphocytes in a background of macrophages and cyst fluid. Histologic examination of the resected mass revealed a multilocular thymic cyst with follicular lymphoid hyperplasia. HIV-1 core protein p24 was localized immunohistochemically in the dendritic follicular cells of the germinal centers. In retrospect, the quantity of epithelium derived from the cyst lining was too scanty for thymoma, and the presence of plasma cells and lymphohistiocytic aggregates suggested follicular lymphoid hyperplasia. CONCLUSION: Multilocular thymic cyst with follicular lymphoid hyperplasia should be considered in the differential diagnosis of an anterior mediastinal mass in HIV-infected patients after lymphoma and tuberculosis.

Adult↗
PubMedDate not supplied

Compact cell blocks. Use for body fluids, fine needle aspirations and endometrial brush biopsies.

OBJECTIVE: To obtain an ideal cell block wherein the maximal number of cells are displayed within the smallest area on the block surface. STUDY DESIGN: Cyto-Rich Red (AutoCyte, Inc., Elon College, North Carolina, U.S.A.) is added to fresh cellular sediment in a centrifuge tube at a ratio of 1:1. After two minutes, three to four drops of plasma and topical thrombin (5,000 U/10 mL) is added. The tube is then gently agitated for two minutes, until a gelatinous clot is obtained. The clot is then slid onto a lens tissue on top of paper towels. The lens tissue is folded once over the clot. By gently squeezing the excess fluid from it through the lens tissue into the paper towels, the clot is transformed into a flat, compact, densely cellular aggregate, which is painted with mercurochrome prior to fixation in formaldehyde. RESULTS: From each of the 495 cases, including 250 body cavity fluids, 170 fine needle aspirates and 75 endometrial brush biopsies, processed with the above protocol, there was a compact cell block containing packed cells or tissue fragments in a clean background devoid of red blood cells. CONCLUSION: The compact cell block is about 10-20% the size of a conventional cell block, yet more cells are on display, thus reducing the need for deeper cuts and screening time while increasing the efficiency of cytodiagnosis. The compact cell block technique is particularly helpful for endometrial brush biopsies.

Biopsy↗
PubMedDate not supplied

Uncommon tumors of the salivary gland in fine needle aspiration biopsies. A surgeon's perspective.

OBJECTIVE: To determine the utilization of fine needle aspiration (FNA) biopsy in guiding the surgeon in the management of patients with parotid masses and to study the cytohistologic correlations of rare parotid tumors. STUDY DESIGN: FNA biopsies and parotidectomies performed by a head-and-neck surgeon over an approximate three-year period were analyzed. Cytologic features of rare salivary gland tumors were also studied and correlated with their histology. RESULTS: In an acinic cell carcinoma in a 15-year-old female whose smears were stained with Diff-Quik, novel negative images of crystals were found intracytoplasmically and extracellularly, corresponding to the crystallized, membrane-bound, exocrine, secretory substance ultrastructurally. A truly malignant mixed tumor from a 73-year-old female showed capsular invasion in the primary site that later metastasized to the lung with both epithelial and mesenchymal components. The tumor cells did not exhibit nuclear atypia except for fine cytoplasmic vacuoles in the Diff-Quik-stained smears. Basal cell adenoma, membranous (dermal analogue) type, from an 87-year-old female had an interesting geographic pattern on smears. CONCLUSION: Within three years, a total of 70 FNAs were performed. Of those cases, 46 had surgery. Preoperative FNAs of the salivary gland lesions were utilized by the surgeon in guiding treatment options for large, fixed masses as well as masses < 1 cm, in elderly and acquired immunodeficiency syndrome patients.

Adolescent↗
PubMedDate not supplied

Combined use of the "scratch and smear" sampling technique and Ultrafast Papanicolaou stain for intraoperative cytology.

OBJECTIVE: To assess the applicability of Ultrafast Papanicolaou stain (UFP), a 90-second, high-resolution stain incorporating the air-dried rehydration technique, to intraoperative cytology in surgical pathology laboratories. STUDY DESIGN: Two hundred sixty-two randomly selected surgical specimens for intraoperative consultations were included in the study. Each specimen was first conventionally prepared by touch imprinting, wet fixation in alcohol and staining by hematoxylin and eosin (H&E); the remaining specimens were then sampled by the "scratch and smear" technique and subjected to the UFP staining protocol. RESULTS: The combined use of the scratch and smear sampling technique and UFP staining was superior to the conventional methods of touch imprinting and H&E staining in every case because of the following features: (1) intact tissue fragments composed of both epithelial and stromal elements rather than epithelial cells only, (2) polychromasia rather than bichromasia, (3) sharper nuclear and cytoplasmic details, (4) histologic criteria applicable to thick tissue fragments due to transparency and flatness and (5) clear background devoid of red blood cells and eosin. CONCLUSION: The combined use of the "scratch and smear" sampling technique and UFP enhances intraoperative cytology.

Cytological Techniques↗
PubMedDate not supplied

Presacral myelolipoma. Report of a case with fine needle aspiration cytology and immunohistochemical and histochemical studies.

The cytomorphologic features of a case of the rare presacral myelolipoma, diagnosed by computed tomography (CT)-guided percutaneous fine needle aspiration (FNA) biopsy, are presented. It occurred in a 40-year-old man on prolonged steroid therapy for bronchial asthma. On the air-dried, Diff-Quik-stained smear, hematopoietic cells of all lineages and fragments of collapsed stroma were seen in a background of fat droplets. Megakaryocytic, myelocytic and eosinophilic lineages were further demonstrated by Factor VIII immunostain, chloroacetate esterase and LUNA-E histochemical stain, respectively. The reticulum stain of the resected tumor demonstrated that the hematopoietic cells and fat were supported by numerous reticulum fibers of varying thickness; that accounted for the collapsed stroma in the aspirated material. Presacral myelolipoma, occurring predominantly in female adults and presenting secondarily as a space-occupying lesion, is best regarded as encapsulated, heterotopic bone marrow supported by a network of reticulum fibers; it has a characteristic image on CT scan and can be diagnosed by FNA.

Adult↗
PubMedDate not supplied

Mixed small cell/large cell carcinoma of the lung. Report of a case with cytologic features and ultrastructural correlation.

BACKGROUND: Mixed small cell/large cell carcinoma of the lung, a chemotherapy- and radiation-resistant subtype of small cell lung cancer, constitutes 4-6% of small cell lung cancer but has been described rarely in the cytopathology literature. CASE: A 64-year-old man presented with a left hilar mass. A concurrent transbronchial biopsy and postbiopsy bronchial washing were performed. The latter presented as loosely cohesive cells, scattered singly, in small clusters, in monolayer sheets and in a perivascular arrangement. The tumor exhibited a wide spectrum of cytomorphology: small cells with pyknotic nuclei and scanty cytoplasm were admixed with larger cells with vesicular nuclei, prominent nucleoli and abundant cytoplasm. Nuclear shape included oval, spindle and peg. Nuclear size was also highly variable. The tumor was retrieved from the transbronchial biopsy and processed for ultrastructural study. CONCLUSION: Based on cytologic-ultrastructural correlations. the seemingly "mixed" morphology may have resulted from the rapid degeneration of a single clone of tumor cells: the viable tumor cells were the "large" cells, and the dying cells were the "small" cells. A novel ultrastructural observation is that the perivascular tumor cells developed peculiar, fingerlike cytoplasmic processes abutting an undulating basement membrane along the thin-walled blood vessel.

Carcinoma, Large Cell↗
PubMedDate not supplied

Rapid assessment of Diff-Quik-stained pancreatic aspirates. A retrospective study of 40 intraoperative fine needle aspiration consultations, with measurement of nuclear size of look-alike small tissue fragments by image analysis.

Pancreatic cytomorphology based on Papanicolaou-stained smears has been studied extensively; however, studies on Diff-Quik-stained pancreatic smears are rather limited. Air-dried, Diff-Quik-stained smears lack crisp nuclear details, the cells are flattened on the slides, and the nuclei appear large and hyperchromatic. Between January 1988 and June 1992, 40 cases of intraoperative pancreatic fine needle aspirates were assessed by Diff-Quik stain. The objective of this study was to find practical clues applicable to the rapid and accurate assessment of Diff-Quik-stained pancreatic aspirates for intraoperative consultations. All cases were reviewed and correlated with histopathology. In particular, three cases that proved to be adenocarcinoma on subsequent frozen section but were not so diagnosed during intraoperative fine needle aspiration evaluation were analyzed. The nuclear sizes of small tissue fragments with overlapping nuclei, including three cases of normal pancreatic acini (mean diameter, 0.98, 1.17 and 1.04 x RBCs; coefficient of variation, 0.53, 0.83 and 0.62 x RBCs), 2 cases of islet cell tumor (mean diameter, 1.19 and 1.32 x RBCs; coefficient of variation, 1.88 and 1.4 x RBCs) and 3 cases of adenocarcinoma (mean diameter, 1.55, 1.86 and 1.72 x RBCs; coefficient of variation, 1.5, 1.7 and 1.9 x RBCs) were obtained with an image analyzer. The adjacent RBCs served as internal size controls. In Diff-Quik-stained, air-dried smears we relied on the accurate identification of pancreatic acini, which had the same size as the adjacent RBCs. Islet cell tumors had slightly larger nuclei, which were much more variable in size. The nuclei of adenocarcinoma were much larger than the surrounding RBCs and also showed marked variation in size. The composition of the pancreatic aspirate is important: ductal epithelium predominates in ductal carcinoma, and acini predominate in pancreatitis.

Adult↗