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P Tsang

Publications and source records attributed to P Tsang.

At least 19 recordsLinked to original sources
PubMed2006

Clonal T-large granular lymphocyte proliferation in solid organ transplant recipients.

Large granular lymphocytic (LGL) leukemia is a rare disorder, usually caused by clonal proliferation of CD3+ CD57+ T-LGL cells. T-cell clonality is confirmed by rearrangements of the T-cell receptor (TCR) gene. Characteristic features of T-LGL leukemia include neutropenia, anemia, and constitutional symptoms such as fatigue. Many solid organ transplant recipients experience similar symptoms and have neutropenia and anemia often attributed to immunosuppressive therapy. The purpose of this study was to determine the prevalence of T-LGL proliferation in solid organ transplant recipients and demonstrate its association with leukopenia and anemia. Twenty-three cardiac and renal transplant patients were evaluated by peripheral smear examination, flow cytometry, and TCR gene rearrangement study by polymerase chain reaction. Ten of 14 (71%) cardiac transplant patients and 4 of 9 (44%) renal transplant patients, without evidence of either allograft rejection or a viral syndrome, were found to have clonal expansion of T-LGL cells. Constitutional symptoms were present in 30% of these patients. Anemia of <10 g/dL was seen in 75% of renal transplant and 10% of cardiac transplant patients. None of these patients had significant neutropenia defined as absolute neutrophil count of 1500 mu/L. Most of the patients did not require any specific therapeutic intervention. Although TCR gene rearrangement is considered a hallmark of T-LGL leukemia, we believe that this monoclonality is not a true form of posttransplant lymphoproliferative disorder. Constant antigenic stimulus from the allograft may be the underlying etiology of clonal expansion and may contribute to cytopenias and fatigue seen in transplant patients.

Anemia↗
PubMed2001

Low incidence of HPV DNA in sera of pretreatment cervical cancer patients.

OBJECTIVE: The aim of this study was to investigate the feasibility of using DNA in the circulation as a diagnostic tool for cervical cancer. METHODS: We used PCR followed by Southern hybridization to detect human papillomavirus (HPV) DNA in serum samples taken from patients of cervical cancer before treatment. RESULTS: A total of 60 samples were analyzed. In a set of 40 samples, without knowledge of the HPV DNA status in the corresponding cervical carcinomas, we could detect 8 (20%) positive samples, of which 7 (17.5%) were HPV 16 and 1 (2.5%) was HPV 18. In another set of 20 samples, known to be HPV 16 infected in the corresponding cervical carcinomas, we detected only 4 (20%) HPV-16-positive samples. The occurrence of HPV DNA in sera of cervical cancer patients seems sporadic. CONCLUSION: The low incidence indicates that serum HPV DNA has limited application in the diagnosis of cervical cancer.

Blotting, Southern↗
PubMed2000

The binding of a glycoprotein 120 V3 loop peptide to HIV-1 neutralizing antibodies. Structural implications.

The structural and antigenic properties of a peptide ("CRK") derived from the V3 loop of HIV-1 gp120 protein were studied using NMR and SPR techniques. The sequence of CRK corresponds to the central portion of the V3 loop containing the highly conserved "GPGR" residue sequence. Although the biological significance of this conserved sequence is unknown, the adoption of conserved secondary structure (type II beta-turn) in this region has been proposed. The tendency of CRK (while free or conjugated to protein), to adopt such structure and the influence of such structure upon CRK antigenicity were investigated by NMR and SPR, respectively. Regardless of conjugation, CRK is conformationally averaged in solution but a weak tendency of the CRK "GPGR" residues to adopt a beta-turn conformation was observed after conjugation. The influence of GPGR structure upon CRK antigenicity was investigated by measuring the affinities of two cognate antibodies: "5023A" and "5025A," for CRK, protein-conjugated CRK and gp120 protein. Each antibody bound to all the antigens with nearly the same affinity. From these data, it appears that: (a) antibody binding most likely involves an induced fit of the peptide and (b) the gp120 V3 loop is probably conformationally heterogeneous. Since 5023A and 5025A are HIV-1 neutralizing antibodies, neutralization in these cases appears to be independent of adopted GPGR beta-turn structure.

Antibodies, Viral↗
PubMed1999

A distinctive composite lymphoma consisting of clonally related mantle cell lymphoma and follicle center cell lymphoma.

Although follicle center cell lymphoma and mantle cell lymphoma are both B cell non-Hodgkin's lymphomas (NHL), they are regarded as separate entities with distinct clinical, morphological, immunophenotypic and molecular characteristics. To our knowledge, the coexistence of these 2 lymphomas in the same patient has never been reported. We describe a 70-year-old woman with a long-standing history of follicle center cell lymphoma, cytological grade I, who subsequently developed a composite lymphoma consisting of well-demarcated foci of persistent follicle center cell lymphoma surrounded by mantle cell lymphoma. This morphological interpretation was supported by the presence of both bcl-1 and bcl-2 gene rearrangements, which are molecular genetic hallmarks of mantle cell lymphoma and follicle center cell lymphoma, respectively. Polymerase chain reaction (PCR) analysis for rearranged immunoglobulin heavy chain (IgH) genes showed a dominant band identical in size in microdissected tumor cells of the follicle center cell and mantle cell lymphomas. Cloning and sequence analysis of the PCR products revealed a common clone-specific IgH gene rearrangement in these 2 lymphomas. These findings suggest that this composite lymphoma represents the unusual evolution of a malignant B-cell clone that resulted in the development of 2 morphologically distinct but clonally related B-cell NHLs. These findings also show the importance of integrating morphological, immunophenotypic, and molecular data to enhance our understanding of the complex pathogenic interrelationships in lymphomagenesis.

Aged↗
PubMed1999

Biopsy diagnosis of colitis: possibilities and pitfalls.

The histopathologic diagnosis of inflammation is common in colorectal biopsies but is of limited value, if not further specified. We reviewed 280 endoscopic colorectal biopsy specimens for nonneoplastic disease from 100 consecutive patients in order to assess (a) the frequency of inflammation in excess of the physiologic infiltrate, (b) the frequency with which the cause of the inflammation could be specified, and (c) the interobserver variability in diagnosing inflammation. Based on the reviewers' impression, each case was classified into one of three categories: (I) normal or nonspecific change, (II) nonspecific inflammation, and (III) inflammation suggestive or diagnostic of specific cause. Inflammation was diagnosed in 68% of cases. The majority of these cases (75%) showed features typically associated with specific types of colitis, including Crohn's disease (n = 16), ulcerative colitis (n = 13), inflammatory bowel disease not otherwise specified (n = 5), infectious colitis (n = 6), ischemic colitis (n = 4), solitary rectal ulcer syndrome (n = 3), radiation colitis (n = 2), and lymphocytic colitis (n = 2). Interobserver variability was greatest in biopsy specimens interpreted by the reviewers as normal or showing nonspecific changes, most of which had been diagnosed as mild inflammation by the original pathologists. Etiologic classification of colitis was lacking in 59% of the cases interpreted by the reviewers as suggestive or diagnostic of a specific cause. We conclude that (a) the majority of colorectal biopsy specimens from patients with nonneoplastic disease in this series show inflammation, (b) the majority of such cases allow a specific cause of colitis to be suggested or firmly diagnosed, and (c) pathologists tend to overdiagnose the physiologic inflammatory infiltrate as evidence of colitis and underdiagnose specific etiologic types of colitis.

Adult↗
PubMed1998

Additional mimics of mucinous mammary carcinoma: fibroepithelial lesions.

To determine the origin and nature of mucinlike material in fine-needle aspiration (FNA) smears of the breast in noncancerous breast lesions, we studied breast FNA smears from four patients. All smears contained epithelial cells floating in a mucinlike background, which raised suspicion for mucinous (colloid) carcinoma. Mucicarmine stain was performed on one smear from each case. Subsequent tissue biopsy specimens were studied using mucicarmine, periodic acid-Schiff with and without diastase, and alcian blue stains at pH 2.7 and 0.9 on selected tissue sections. Correlation of the cytologic and histologic findings of each lesion was performed. The mucinlike background in all four FNA smears stained strongly with mucicarmine. Corresponding biopsy specimens revealed pseudoangiomatous hyperplasia in the first case, fibroadenoma and atypical ductal hyperplasia in the second, benign phyllodes tumor in the third, and fibroadenoma in the fourth. Each lesion in cases 1 to 3 was associated closely with fibrocystic changes. In case 4, cystic changes were located within the fibroadenoma. On tissue sections of all four cases, the cyst contents and 10% to 50% of normal lobule and duct contents stained with mucicarmine, indicating that the cyst contents were the most probable source of mucin in the FNA smears. The presence of pools of mucicarmine-positive material in FNA smears of the breast is not an exclusive feature of mucinous carcinoma; mucicarmine-positive mucin can arise from benign cystic changes as well as from normal lobules and ducts.

Adenocarcinoma, Mucinous↗
PubMed1996

Some practical aspects of double-resonance techniques in solution-state NMR studies of high-molecular-weight systems.

This paper addresses some of the practical issues associated with solution NMR investigations of high-molecular-weight ( > 20 kDa) biomolecules and their complexes. The experimental example of a high-molecular-weight system used here is a 52 kDa Fab/peptide complex. Theoretical as well as experimental aspects of solution NMR techniques employed to study such larger systems are discussed. Specific topics covered include hardware considerations, solvent suppression, and the relative efficiencies of various isotope-edited NMR techniques. Typical NOE methods used to derive structural information on these higher-molecular-weight systems and the scope of structural detail achievable are also examined.

Antibodies, Monoclonal↗
PubMed1996

Oral condyloma acuminatum associated with human papillomavirus and p53 overexpression mimicking cyclosporine effect in a transplant patient.

A case of human papillomavirus-associated condyloma acuminatum in the oral cavity, presumed to be fulminant cyclosporine-induced gingival hyperplasia, is reported in a 55-year-old cardiac transplant patient. Approximately 47 months following the transplant, the patient developed severe hyperplasia of the uvula and oral mucosa, resulting in difficulty swallowing. The histopathologic features of the lesion were typical of those of condyloma acuminatum. In situ hybridization of the paraffin-embedded material revealed infection with human papillomavirus types 6/11. This case lends further support to the putative role of long-term cellular immunosuppression in the development of human papillomavirus-associated squamous lesions. In addition, positive staining for p53 protein raises the possibility of concomitant p53 involvement in the pathogenesis of this oral lesion.

Condylomata Acuminata↗
PubMed1996

Molecular characterization of primary mediastinal B cell lymphoma.

Primary mediastinal B cell lymphoma (PMBL) is a diffuse large B cell lymphoma (DLCL) postulated to arise from noncirculating thymic B lymphocytes. Because of its distinctive clinical and morphological features and putative unique cellular origin, PMBL is generally considered a distinct clinicopathological entity. Little is known, however, about the molecular characteristics of PMBL. Therefore, we analyzed 16 PMBLs for molecular alterations involving the bcl-1, bcl-2, bcl-6, c-myc, H-ras, K-ras, N-ras, and p53 genes and for Epstein-Barr virus infection, which are commonly involved in lymphoid neoplasia. Employing a combination of Southern blotting and/or polymerase chain reaction and single-strand conformation polymorphism assays, we detected genetic alterations in 7 of the 16 (44%) PMBLs. Whereas the bcl-6 gene is rearranged in up to 45% of DLCLs, rearrangement of the bcl-6 gene was detected in only 1 of these 16 (6%) PMBLS. Point mutations of the 5' noncoding region of the c-myc gene were demonstrated in 3 other cases (19%), although c-myc gene rearrangements were not seen by Southern blotting. Missense point mutations of the p53 gene were identified in 3 additional PMBLs (19%). Alterations of the bcl-1, bcl-2, or ras genes and evidence of Epstein-Barr virus infection were not observed. In conclusion, a variety of molecular lesions occur in PMBLs and may be involved in their pathogenesis. This molecular genetic pattern bears little resemblance to that known for other B cell malignancies, including DLCL. In particular, the infrequent occurrence of bcl-6 gene rearrangement in PMBLs distinguishes them from other DLCLs of B cell origin, suggesting that PMBLs do not represent a distinct subtype of DLCL.

Adolescent↗
PubMed1995

A novel L23-related gene 40 kb downstream of the imprinted H19 gene is biallelically expressed in mid-fetal and adult human tissues.

The closely linked IGF2 and H19 genes on human chromosome 11p15.5 are monoallelically expressed as a result of genomic imprinting and show altered expression in Wilms' tumors (WTs). To map regional imprinting we have sought to isolate additional human genes close to IGF2/H19 and to characterize their allelic expression patterns. Here we report a novel gene, provisionally named L23MRP [L23 (mitochondrial)-related protein], which is oriented 'tail-to-tail' with H19 and is transcribed to within 40 kb of the last H19 exon. L23MRP is expressed biallelically in many mid-fetal and adult human tissues. This gene is also expressed at normal levels in WTs which have lost expression of H19 either via loss of the maternal chromosome 11p15.5 or via an epigenetic pathway involving site-specific DNA hypermethylation. These data indicate that, at least in post-embryonic stages, L23MRP is functionally insulated from the IGF2/H19 imprinted domain.

Adult↗
PubMed1994

Gastrointestinal disease in the immunocompromised patient.

Gastrointestinal (GI) disease is frequent in all types of immunocompromised patients but occurs with greatest frequency in patients with acquired immunodeficiency syndrome (AIDS). Thus, much of this review deals with human immunodeficiency virus (HIV)-related GI diseases. Gastrointestinal diseases in other immunocompromised patients are compared with those in patients with AIDS. Conditions unique to transplant recipients, such as graft-versus-host disease (GVHD) and posttransplant lymphoproliferative disorders (PTLDs), are discussed separately. We have divided these GI diseases into four main categories: (1) HIV-related inflammatory conditions other than opportunistic infections (HIV-related enteropathy, proctocolitis, and CD8 lymphocytosis); (2) inflammatory conditions unrelated to HIV or opportunistic infections (neutropenic enterocolitis, regional enteritislike enteropathy, and GVHD); (3) opportunistic infections (illnesses caused by herpesvirus, cytomegalovirus, and miscellaneous other viruses; Mycobacterium, Candida, Histoplasma, Cryptococcus, Cryptosporidium, Microsporida, Isospora, Leishmania, Toxoplasma and Strongyloides organisms as well as Pneumocystitis carinii; and (4) neoplasias (Kaposi's sarcoma [KS], AIDS-related non-Hodgkin's lymphoma [NHL], HIV-related Hodgkin's disease [HD], PTLDs, and miscellaneous neoplasms). The prevalence, pathogenesis, clinical manifestations, gross pathological findings, and microscopic features of each disease entity are discussed.

AIDS-Related Opportunistic Infections↗