PubMed Health⌕ Search

Biomedical subjects

L T Yam

Publications and source records attributed to L T Yam.

At least 19 recordsLinked to original sources
PubMed1996

Localization of tartrate-resistant acid phosphatase in human placenta.

Tartrate-resistant acid phosphatase is an inducible marker of cell differentiation and activation expressed by specialized cells of macrophage lineage and some activated lymphocytes. Clinically, this phosphatase is a diagnostic marker for hairy cell leukaemia and osteoclast activity. The cDNA for this enzyme has been cloned from a placental expression library, yet the cell(s) expressing the enzyme protein has not been determined with certainty. Our laboratories have developed a monoclonal antibody, 9C5, suitable for immunohistochemical localization of tartrate-resistant acid phosphatase in paraffin sections. The purpose of this study was to use antibody 9C5 to identify cells expressing tartrate-resistant acid phosphatase in sections of paraffin-embedded, normal, full-term placenta and to determine if those cells expressed other macrophage markers including CD68 (PG-M1 antibody), LN5, lysozyme, alpha 1-antitrypsin and alpha 1-antichymotrypsin. Histochemical localization of activity in frozen sections was compared with immunohistochemical localization in paraffin sections of the same tissue specimens. The activity and antigenicity of this enzyme were detected in decidual cells, syncytiotrophoblast, and some macrophages distributed throughout maternal and embryonic tissues, but not in neutrophils. Unlike other tissues previously examined, placenta contains significant numbers of the phosphate-positive cells that are not of macrophage origin.

Acid Phosphatase↗
PubMed1996

Epitope enhancement for immunohistochemical demonstration of tartrate-resistant acid phosphatase.

We have developed a monoclonal antibody (9C5) for immunohistochemical localization of tartrate-resistant acid phosphatase (TRAcP). This antibody reacts with a denatured epitope of TRAcP and requires enhancement methods to promote antigenicity in paraffin-embedded tissues. We used this antibody to systematically examine proteolytic digestion and heat denaturation conditions for epitope enhancement in both paraffin sections and fixed smears. The goal was to increase the sensitivity of the immunohistochemical stain for TRAcP. Optimal conditions for proteolytic digestion were established. Denaturation in a conventional boiling water bath was compared to microwave irradiation in several commonly used solutions. Immunohistochemistry was compared directly to TRAcP cytochemistry in fixed smears from hairy cell leukemia specimens to gauge the level of sensitivity of our improved method. Attempts were made to "retrieve" the 9C5 epitope from overfixed tissues and aged smears. Maximal immunoreactivity of TRAcP was achieved by microwave irradiation in a citrate or Tris buffer of pH 6.0-8.0 without the need for a subsequent protease digestion step. With this method of epitope enhancement, immunohistochemistry with antibody 9C5 was as sensitive as direct cytochemical staining of TRAcP activity. However, once a tissue specimen had been overfixed or a smear stored for a year or more, the 9C5 epitope was no longer retrievable. The key element in epitope enhancement for 9C5 immunohistochemistry is heat denaturation of the target epitope. Immunohistochemistry of TRAcP in paraffin sections would be a great asset to the study of specialized forms of the monocyte/macrophage lineage and to the process of macrophage activation. It would also provide another means for more precise evaluation of residual disease in bone marrow of patients treated for hairy cell leukemia.

Acid Phosphatase↗
PubMed1995

Hairy cell identification by immunohistochemistry of tartrate-resistant acid phosphatase.

Tartrate-resistant acid phosphatase (TRAcP) has been an indispensible marker for hairy cell leukemia (HCL) for over two decades. However, the traditional TRAcP cytochemical stain cannot be performed effectively on sections of paraffin-embedded tissues that are important resources for histopathologic evaluation in diagnosis and treatment of HCL. Wide variation in expression of TRAcP activity by hairy cells (HCs) within and among patients is an interesting biologic phenomenon that has not been explained and can cause some diagnostic uncertainty as well. To solve the problem of staining TRAcP in paraffin sections and to begin to address the questions of variable TRAcP expression in HCL, we developed a monoclonal antibody to TRAcP, 9C5, for immunohistochemical identification of HCs. In smears of blood and bone marrow, immunocytochemistry of TRAcP using 9C5 was as specific but slightly less sensitive than direct cytochemical staining of enzymatic activity. In paraffin sections of spleen and bone marrow from HCL patients, immunohistochemistry with 9C5 stained the HCs with high sensitivity and specificity and clearly showed the characteristic diffuse infiltration by HCs. Other cells noted to stain strongly with 9C5 were occasional macrophages in bone marrow smears and osteoclasts and occasional tissue macrophages in paraffin sections. These are cells known to express abundant TRAcP activity. Immunohistochemistry with anti-TRAcP monoclonal antibody 9C5 may have utility as an added option in the diagnosis of HCL, as a means to evaluate residual disease in HCL patients undergoing new treatments, and as a way to address questions regarding variable expression of TRAcP activity by HCs within and among patients with HCL. Also, 9C5 has potential as a reagent for the immunoassay of bone-derived serum TRAcP in patients with certain bone diseases and cancers with bone metastasis.

Acid Phosphatase↗
PubMed1995

Immunohistochemical detection of tartrate-resistant acid phosphatase in non-hematopoietic human tissues.

Immunohistochemical studies were done on formalin-fixed, paraffin-embedded tissues to evaluate the specificity of a newly developed monoclonal antibody (9C5) against tartrate-resistant acid phosphatase. Sections from 195 specimens were examined, which included 33 types of tissues/organs. These tissues included normal, inflammatory, and neoplastic processes. Neoplastic tissues from 14 patients with hairy cell leukemia served as positive controls. Epitope enhancement was accomplished either by microwave irradiation in citrate buffer or by boiling in water followed by trypsin digestion. Tissues were reacted with monoclonal antibody 9C5 and stained with either the avidin-biotin peroxidase method or the alkaline phosphatase anti-alkaline phosphatase method. The hairy cells of all cases of hairy cell leukemia reacted positively with 9C5. Other positively stained cells included osteoclasts, activated macrophages and giant cells. Immunohistochemical studies with 9C5, when interpreted within the context of the specificity of this antibody, are useful for the diagnosis and assessment of treatment results for hairy cell leukemia. Monoclonal antibody 9C5 also may be useful as a marker for osteoclasts and the activated macrophages and for the diagnosis of disorders involved by these cells.

Acid Phosphatase↗
PubMed1994

Cytochemistry and immunochemistry in hematologic diagnoses.

With new understanding in the biology of hematologic diseases and the rapid progress in their treatment, it is essential to diagnose and classify the various hematologic diseases with great precision. In recent years, the cell type-specific markers have been used successfully in cell identification for more precise diagnosis and classification of neoplastic diseases. The cytochemical method for cell identification is simple and is most useful for disorders of granulocytes, monocytes/histiocytes, hairy cells, and mast cells. The immunochemical methods are particularly useful in identifying the cell types, the clonality, and the maturation of cells in the lymphoid disorders. They are also helpful in the diagnosis of disorders of the erythroid and megakaryocytic cells, as well as nonhematopoietic neoplasms with marrow involvement.

Acute Disease↗
PubMed1993

Fine-needle aspiration of histiocytic necrotizing lymphadenitis (Kikuchi's disease).

Fine-needle aspiration (FNA) of the lymph node was done in five patients with histiocytic necrotizing lymphadenitis (Kikuchi's disease). In four patients, the aspirates were found to have many small and large atypical lymphocytes, some reactive, phagocytic histiocytes, and intense extracellular debris. Neutrophils, plasma cells, or multinucleated giant cells were not seen. These cytologic findings were considered diagnostic for Kikuchi's disease. In one patient, the aspirate did not show significant histiocytosis or tissue necrosis and was considered nondiagnostic. In patients with both typical clinical features and characteristic cytologic findings in the lymph node aspirates, FNA of the lymph node alone will suffice for diagnosis. In those patients with typical clinical features but nondiagnostic findings in the FNA aspirates, the diagnosis of Kikuchi's disease may have to be established either on repeated nodal FNA or on lymph node biopsy.

Adolescent↗
PubMed1993

Myelodysplastic syndrome: diagnostic implications of cytochemical and immunocytochemical studies.

Cytochemical and immunocytochemical studies were performed on bone marrow aspirates from 96 cases of primary myelodysplastic syndrome (MDS), 11 cases of secondary MDS, 22 cases of non-MDS hematologic disorders, and 10 cases of nondiagnostic, apparently normal marrow specimens to determine the practicality and utility of these stains for diagnosing MDS. Cytochemical studies included iron stain, periodic acid-Schiff (PAS), peroxidase, butyrate esterase, chloroacetate esterase, and double esterase stains. Immunocytochemical staining was done with monoclonal antibody HP1-1D, which recognizes the glycoprotein IIb/IIIa complex in megakaryocytes. The iron stain remained most helpful in identifying abnormal ringed sideroblasts, a feature of dyserythropoiesis, and thus in supporting the diagnosis of MDS. The PAS stain was helpful, if positive, in identifying patients with MDS; however, when it was negative, this stain did not help distinguish MDS from non-MDS hematologic disorders. The immunocytochemical stain with HP1-1D monoclonal antibody was also helpful in identifying atypical micromegakaryocytes, indicative of dysmegakaryopoiesis. Other cytochemical abnormalities were infrequently observed and were less specific for the diagnosis of MDS. The combination of two stains--for example, PAS and iron stain or PAS and double esterase--was helpful, however, in excluding MDS, inasmuch as neither the miscellaneous nor the control group stained positively with these combinations.

Bone Marrow↗
PubMed1992

Heterogeneity of hairy cell tartrate-resistant acid phosphatase.

The human nonerythrocytic acid phosphatases (AcP) are composed of seven distinct activity bands in nondenaturing polyacrylamide gel electrophoresis (PAGE) when stained using either 1-naphthyl phosphate or naphthol ASBI phosphate as substrate. They are numbered 0, 1, 2, 3, 3b, 4, and 5 according to their increasing mobility toward the cathode in acidic conditions. Of these, only the most cationic "band 5" is tartrate resistant (TRAcP). When naphthol ASBI phosphate is used as substrate, AcP activity can also be stained in situ. In the presence of tartrate, activity remains strong in the hairy cells (HC) of hairy cell leukemia (HCL). Thus, the TRAcP stain has remained a reliable marker for HC. To investigate the function of TRAcP in HC, we purified two isoforms of TRAcP from HCL spleen tissue and found them to have similar substrate specificities and inhibitor sensitivities. In this report, we describe in detail the methods for TRAcP purification and compare some of the structural properties of the two isoforms to reinforce the concept that human TRAcP is a heterogeneous group of related enzymes. Band 5 represented only 15-20% of the total TRAcP extracted from HCL spleen. The remaining 80% of TRAcP hydrolyzed p-nitrophenyl phosphate but not naphthol ASBI phosphate and was not detectable in acidic, nondenaturing PAGE gels. Band 5 was solubilized from tissue using 500 mmol/L NaCl after previous extraction with 0.5% (v/v) NP-40 removed most other AcP and TRAcP activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1992

Protein-tyrosine phosphatase activity of hairy cell tartrate-resistant acid phosphatase.

Tartrate-resistant acid phosphatase (TRAcP) is a reliable cytochemical marker for the diagnosis of hairy cell leukemia (HCL). The enzyme has been the subject of much biochemical investigation yet its function in the hairy cells (HC) is still unknown. Two TRAcPs have been purified from HCL spleen tissues by a series of chromatographic separations. The two enzymes, provisionally called peak 1 and peak 2, had specific activities of greater than 600 U/mg and 800 U/mg respectively when p-nitrophenyl phosphate (p-NPP) was used as substrate and had Km values in the range of 1 to 5 mM p-NPP. The two TRAcPs had the same substrate specificities and inhibitor sensitivities, therefore could be isoforms of the same enzyme. Their pH optima were between 5 and 6 for all substrates tested including the phosphotyrosine-containing peptide, Raytide, which was still hydrolyzed efficiently at neutral pH. Neither phosphoserine nor phosphoserine-containing casein were hydrolyzed by either enzyme. The TRAcPs of HC may thus be capable of functioning as protein-tyrosine phosphatases (PTP). High activity of a PTP could regulate the activities of protein-tyrosine kinases and thereby influence the growth and differentiation of the hairy cells.

Acid Phosphatase↗
PubMed1991

Hemopoietic inhibition in hairy cell leukemia.

Leukopenia, thrombocytopenia, and anemia are important features of hairy cell leukemia (HCL). They are generally considered to be due to hypersplenism and to inadequate production by bone marrow which is heavily infiltrated by the neoplastic hairy cells (HC). However, the cytopenias may also be caused by hemopoietic inhibition by cytokines derived from the mononuclear cells (MNC) of HCL. We studied the MNC of HCL with an in vitro assay for granulocyte-macrophage progenitors (CFU-GM) to search for this hemopoietic inhibitor(s) and to determine the cell source and mechanism of its production/release. We found that MNC conditioned media from 7 of 9 HCL cases exerted substantial inhibitory effect (23% to 66%) on normal marrow cells. Peak inhibitory activity was obtained in media conditioned with 10(6) MNC/ml for 90 minutes to 24 hours. Both HC and lymphocytes could release inhibitor(s) through mutually synergistic cell interactions. HC alone were inactive and lymphocytes alone were only weakly active. Mixtures of conditioned media of HC and of lymphocytes were not synergistic. The lymphocytes responsible for the inhibition were present in preparations depleted of cells bearing the cluster designation 4 antigen (CD4+) and B cells and were most likely the CD8+ T-cells. In one patient so examined, a partial reversal of inhibition was achieved by treating MNC-CM with antibodies to tumor necrosis factor (TNF)-alpha suggesting that TNF-alpha was at least partly involved in the inhibition of CFU-GM. This mechanism of cytokine release may be operative in vivo to account for the cytopenias in HCL and, if so, could alter the concept of hypersplenism in this disease.

Granulocytes↗
PubMed1991

Coexistence of testicular carcinoma and hairy cell leukemia.

The coexistence of two relatively rare disorders in 1 patient often induces speculation about possible cause and effect of these disorders. The suitable therapeutic regimen for both diseases and roentgenologic manifestations are described.

Humans↗
PubMed1990

Comparison of tartrate resistant acid phosphatase in a giant cell bone tumor and a spleen infiltrated with hairy cells.

Acid phosphatase (E.C.3.1.3.2) in a giant cell bone tumor and a spleen infiltrated with hairy cells was extracted by citrate buffer and then by 0.3 mol/L NaCl. The cationic acid phosphatase in the crude extract was isolated by CM-cellulose chromatography, and further separated by high pressure liquid chromatography. The majority of the tartrate resistant acid phosphatase in the hairy cell spleen was unabsorbed on CM-cellulose and was insensitive to iron. A much larger portion of the acid phosphatase in the bone tumor, than in the spleen, was cationic and was eluted from the column by 0.8 mol/L NaCl. The cationic acid phosphatase was further separated into consecutive peaks of acid phosphatases with different sensitivity to iron. A major portion of acid phosphatase in the giant cell bone tumor was enhanced by iron, while the amounts of iron-enhanced and iron-insensitive acid phosphatase were about the same in the spleen. The differences of the phosphatases in these two types of pathologic specimens indicate the occurrence of two types of enzymes with different biological significance.

Acid Phosphatase↗
PubMed1990

The detection of Epstein-Barr virus in hairy cell leukemia cells by in situ hybridization.

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of several B-cell lymphoid proliferations. Because patients with hairy cell leukemia (HCL) have a high incidence of seropositivity for EBV antigens, we studied the cells of HCL for evidence of EBV infection using in situ hybridization techniques. EBV mRNA was detected in the tumor cells in four of six cases using a radiolabeled RNA probe. Confirmatory serologic data were available in three cases in which the viral DNA was detected and in one negative case. Our results suggest that EBV infection may have a pathogenetic role in this disorder.

Adult↗
PubMed1989

Improved immunohistochemical detection of prostatic acid phosphatase by a monoclonal antibody.

A monoclonal antibody with high affinity to acid phosphatase isoenzyme 2 (Ab-AcP2) was selected to examine its binding to different normal and tumor tissues using the indirect immunohistochemical method. Both mature prostatic epithelial cells in the prostate and the highly dedifferentiated prostatic cancer cells in the bone marrow showed strong binding to the antibody. Among nonprostatic tissues, only bone marrow, breast, and kidney showed trace staining in some specimens. The specificity of Ab-AcP2 was much better than that of the polyclonal antibody to acid phospatase previously reported. When the antibody to the prostate-specific antigen (Ab-PSA) was used, weak background staining was often encountered, and weak to moderate stains were seen in the prostatic stroma, bone marrow, lung, skin, and melanoma.

Acid Phosphatase↗
PubMed1989

Diagnostic significance of levamisole-resistant alkaline phosphatase in cytochemistry and immunocytochemistry.

The authors have used two immunoalkaline phosphatase methods to study nonhematopoietic tumor tissues of four patients, one each with alveolar cell carcinoma of the lung, renal cell carcinoma, gastric adenocarcinoma, and colon carcinoma. They found, regardless of specific antibodies used, definite enzyme activity in the tumor cells of these four patients. Although it was possible to determine that the tumor cells were epithelial in origin because of their intense staining with antibodies to epithelial cell antigens, control slides labeled with nonimmune mouse ascites also contained cells with definite enzyme activity. In two of these cases, unlabeled smears were stained for alkaline phosphatase and showed that the tumor cells contained endogenous levamisole-resistant enzyme activity. This endogenous enzyme activity is not demonstrable in either the benign cells of these cases or the benign or malignant cells of other control cases. The findings suggest that the immunoalkaline phosphatase methods also have their inherent endogenous enzymic problems. They also suggest that cytochemical demonstration of levamisole-resistant alkaline phosphatase may be a useful cell marker for the identification of tumor cells in serous effusions.

Alkaline Phosphatase↗
PubMed1989

Assessment of a method for immunochemical detection of antigen on nitrocellulose membranes.

Immunoblotting techniques are widely used for detection of antigen immobilized on nitrocellulose membranes. There are many immunolabeling methods and staining methods available to disclose the presence of antigen in such techniques. Five common staining methods each for alkaline phosphatase and horseradish peroxidase were examined. The staining methods with the highest sensitivity and the lowest background were selected for studies comparing five immunological labeling methods using human IgG as a model antigen. Results were evaluated on the basis of the least amount of detectable antigen and background staining. The most sensitive dot-blot method was then tested for its applicability to Western blots. For both dot-blots and Western blots, the immunoalkaline phosphatase methods are more sensitive than the corresponding immunoperoxidase methods. The use of biotinylated secondary antibodies and an avidin-enzyme conjugate is recommended. Disclosure of alkaline phosphate is best achieved with naphthol AS phosphate as substrate and fast blue BB as chromogen. Peroxidase is best stained using H2O2 and diaminobenzidine (DAB). Potential endogenous enzyme activities are demonstrable by blotting methods but can be inhibited by including levamisole in the disclosure reaction medium for calf intestinal alkaline phosphatase indicators, or by incubation of blots with sodium azide and hydrogen peroxide before immunolabeling when using horseradish peroxidase indicators.

Alkaline Phosphatase↗
PubMed1988

Significance of systemic mast cell disease with associated hematologic disorders.

A clinical and hematopathologic review of 66 patients with systemic mast cell disease (SMCD) was undertaken to investigate the frequency and the clinical significance of associated hematologic disorders. Twenty-two patients were found to have a second hematologic disorder, 19 of which involved the myeloid cells (ten dysmyelopoietic syndromes, five myeloproliferative disorders, three acute nonlymphocytic leukemias, and one chronic neutropenia), and three of which involved the lymphoid cells (three malignant lymphomas). A chromosome analysis of the bone marrow revealed abnormalities characteristic of neoplastic myeloid disorders in four patients. Five-year survival for patients with hematologic disorders was 28% compared with 61% for other SMCD patients (P = 0.004). Patients with hematologic disorders differed significantly from other SMCD patients in that they were about 7 years older (P = 0.039), and they presented more commonly with anemia (P less than 0.001) and constitutional symptoms (P = 0.007). These patients also had less frequent skin symptoms (P = 0.003) and urticaria pigmentosa (P = 0.018). By definition, patients with hematologic disorders had a greater percent of hematopoiesis (P less than 0.001) and decreased fat cells (P = 0.011) on bone marrow biopsies. A multivariate model demonstrated that the following independent variables were associated with the presence of hematologic disorders: low hemoglobin (P = 0.001), the absence of hepatomegaly (P = 0.016), high leukocyte count (P = 0.021), and the presence of pathologic fractures (P = 0.051). The frequent coexistence of SMCD with dysplastic and neoplastic disorders of myeloid cells is consistent with the concept that SMCD itself is a disorder of myeloid cells and that the mast cell may be myeloid in origin.

Adult↗