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Biomedical subjects

A E Walts

Publications and source records attributed to A E Walts.

At least 37 records · Page 2Linked to original sources
PubMed1989

Computerized interactive morphometry. An expert system for the diagnosis of lymphoid-rich effusions.

The authors present experimental techniques for the diagnosis of malignant lymphoma and benign lymphocytosis in lymphoid-rich effusions with the use of an inexpensive microcomputer-based video system for computerized interactive morphometry (CIM). Lymphoid cells were randomly selected by a trained observer from real-time images of Papanicolaou-fixed and -stained cytospin smears prepared from pleural, peritoneal, or pericardial effusions. The lymphoid cells were classified by the instrument, based on the size and shape of their nuclear profiles. The morphometric data collected by the instrument were interpreted by a simple rule-based expert system that classified the smears as benign or malignant. One hundred four cases, including 28 malignant lymphomas, 63 benign lymphocytoses, 8 chronic lymphocytic leukemias, and 5 cases with incomplete immunopathologic data, were studied retrospectively. Sixty-three of these effusions had been stained to detect light chain monoclonality. Ninety-one effusions were correctly classified by the expert system. There were four potential false negative diagnoses and one potential false positive diagnosis by the CIM system. Eight effusions from patients with chronic lymphocytic leukemia (CLL) were consistently classified as benign. Although the author's series of patients with a history of CLL is small, their results suggest that CIM is unsuitable for the diagnosis of malignancy in these effusions. If only those effusions from patients with a history of CLL are excluded, the predictive value of a diagnosis of malignant lymphoma was 96.5%, whereas the predictive value of a diagnosis of benign lymphocytosis was 94.0%.

Algorithms↗
PubMed1988

Cytodiagnosis of malignant melanoma. Immunoperoxidase staining with HMB-45 antibody as an aid to diagnosis.

The specificity and sensitivity of HMB-45, an antimelanoma monoclonal antibody, was evaluated in cytologic specimens from extracutaneous melanomas. Melanoma cells in 23 of 25 (92%) cases stained with this antibody. Staining was intense and diffuse in 22 of these melanomas and focal in 1. Amelanotic tumors and tumors with scanty pigment were included. Neither degree of pigmentation, site of primary, cytologic characteristics of tumor, nor source of specimen predicted the immunostaining pattern. Cytopreparations containing benign (6 cases) and malignant (16 cases) cells with which melanoma may be confused constituted the nonmelanoma group. None of the 22 cases in this group stained. Undifferentiated carcinomas, adenocarcinomas, large cell lymphomas, sarcomas, mesothelial hyperplasias, and a benign nerve sheath tumor were included. Effusions, fine-needle aspirates, bronchial material, and imprints were studied. All smears had been fixed and stained by Papanicolaou's method before immunostaining. Excellent cytomorphologic characteristics were preserved, and immunostaining was not affected. HMB-45 antibody is a highly specific and sensitive marker for malignant melanoma in cytologic material.

Antibodies, Monoclonal↗
PubMed1988

Involucrin.

Explore the source record for details and available documents.

Epithelium↗
PubMed1987

Chorismate aminations: partial purification of Escherichia coli PABA synthase and mechanistic comparison with anthranilate synthase.

Chorismate is converted by regiospecific amination/aromatization sequences to o-aminobenzoate and p-aminobenzoate (PABA) by anthranilate synthase (AS) and PABA synthase (PABS), respectively. We report here the first partial purification of the large subunit of Escherichia coli PABA synthase, previously reported to be quantitatively inactivated in purification attempts. The subunit encoded by the pabB gene was overexpressed from a T7 promoter and purified 9-fold to 25-30% homogeneity. The pabB subunit appears unusually sensitive to inactivation by glycerol so this cosolvent is contraindicated. The Km for chorismate is 42 microM in the ammonia-dependent conversion to PABA, and we estimate a turnover number of 2.6 min-1. A variety of chorismate analogues have been prepared and examined. Of these compounds, cycloheptadienyl analogue 11 has been found to be the most potent inhibitor of Serratia marcescens anthranilate synthase (Ki = 30 microM for an RS mixture) and of the E. coli pabB subunit of PABA synthase (Ki = 226 microM). Modifications in the substituents at C-3 [enolpyruyl ether, (R)- or (S)-lactyl ether, glycolyl ether] or C-4 (O-methyl) of chorismate lead to alternate substrates. The Vmax values for (R)- and (S)-lactyl ethers are down 10-20-fold for each enzyme, and V/K analyses show the (S)-lactyl chorismate analogue to be preferred by 12/1 over (R)-lactyl for anthranilate synthase while a 3/1 preference was observed for (R)-/(S)-lactyl analogues by PABA synthase. The glycolyl ether analogue of chorismate shows 15% Vmax vs. chorismate for anthranilate synthase but is actually a faster substrate (140%) than chorismate with PABA synthase, suggesting the elimination/aromatization step from an aminocyclohexadienyl species may be rate limiting with AS but not with PABS. Indeed, studies with (R)-lactyl analogue 14 and anthranilate synthase led to accumulation of an intermediate, isolable by high-performance liquid chromatography and characterized by NMR and UV-visible spectroscopy as 6-amino-5-[(1-carboxyethyl)oxy]-1,3-cyclohexadiene-1-carboxylic acid (17). This is the anticipated intermediate predicted by our previous work with conversion of synthetic trans-6-amino-5-[(1-carboxyethenyl)oxy]-1,3-cyclohexadiene-1-carbo xylic acid (2) to anthranilate by the enzyme. Compound 17 is quantitatively converted to anthranilate on reincubation with enzyme, but at a 1.3-10-fold lower Vmax than starting lactyl substrate 14 under the conditions investigated; the basis for this kinetic variation is not yet determined.

Anthranilate Synthase↗
PubMed1987

Epithelial membrane antigen in the cytodiagnosis of effusions and aspirates: immunocytochemical and ultrastructural localization in benign and malignant cells.

Immunoreactivity for epithelial membrane antigen (EMA) was evaluated in exfoliated benign and malignant cells using immunoperoxidase and immunogold techniques. In addition, protein A-colloidal gold was used for ultrastructural localization of EMA. Our results suggest that EMA is useful in distinguishing adenocarcinoma cells (strongly positive) from reactive mesothelial cells (negative or weakly positive), lymphoid cells (negative), and a variety of nonepithelial neoplasms (negative) with which they may be confused. Exfoliated cells from two mesotheliomas were also strongly positive for EMA. Ultrastructurally, EMA was distributed in a dense, even, linear pattern along the cell membrane and microvillous surface processes of adenocarcinoma cells. A similar but sparse distribution pattern was observed in reactive mesothelial cells. These observations reflect the increased sensitivity and higher resolution of the immunogold technique.

Adenocarcinoma↗
PubMed1987

Thrombosed, ruptured atheromatous plaques in saphenous vein coronary artery bypass grafts: ten years' experience.

During the past decade the number of patients undergoing saphenous vein coronary artery bypass grafting (CABG) has increased worldwide. With a rate of late graft occlusion approximating 4% each year, the number of patients at risk for late graft occlusion continues to increase. Whereas in 1976 only 0.8% of the CABGs performed at our institution were reoperations for occluded grafts, by 1985 repeat procedures comprised 12.4% of the CABGs performed. Excised, occluded saphenous vein grafts from 52 of 119 (44%) of these patients showed thrombosis superimposed on ruptured atheromatous plaques. Ten autopsy patients showed similar lesions in their occluded grafts. The lesion was present in grafts excised as early as 3 years and as late as 14 years after bypass surgery; most occurred 5 to 10 years after implantation. Neither age at first bypass, sex, nor coronary artery bypassed permitted prediction of the occurrence of the lesion. Thrombosed, ruptured atheromatous plaque is a common, clinically significant mechanism of late graft occlusion. It is associated with recurrent symptoms that necessitate repeat revascularization and may result in death. The lesion may also be amenable to thrombolytic therapy, angioplasty, or both.

Acute Disease↗
PubMed1986

Bacterial organomercurial lyase: overproduction, isolation, and characterization.

Organomercurial lyase mediates the first of two steps in the microbial detoxification of organomercurial salts. This enzyme encoded on the plasmid R831 obtained from Escherichia coli J53-1 has been overproduced to the level of 3% of the soluble cell protein in E. coli by a construction using the T7 promoter. The enzyme has been purified to homogeneity in quantity in three steps. It is a monomer of Mr 22,400 with no detectable cofactors or metal ions. It catalyzes the protonolysis of the C-Hg bond in a wide range of organomercurial salts (primary, secondary, tertiary, alkyl, vinyl, allyl, and aryl) to the hydrocarbon and mercuric ion with turnover rates in the range of 1-240 min-1.

Amino Acid Sequence↗
PubMed1986

Mechanistic studies of a protonolytic organomercurial cleaving enzyme: bacterial organomercurial lyase.

Mechanistic studies of the protonolytic carbon-mercury bond cleavage by organomercurial lyase from Escherichia coli (R831) suggest that the reaction proceeds via an SE2 pathway. Studies with stereochemically defined substrates cis-2-butenyl-2-mercuric chloride (1) and endo-norbornyl-2-mercuric bromide (2) reveal that a high degree of configurational retention occurs during the bond cleavage, while studies with exo-3-acetoxynortricyclyl-5-mercuric bromide (3) and cis-exo-2-acetoxy-bicyclo[2.2.1]hept-5-enyl-3-mercuric bromide (4) show that the protonolysis proceeds without accompanying skeletal rearrangement. Kinetic data for the enzymatic reactions of cis-2-butenyl-2-mercuric chloride (1) and trans-1-propenyl-1-mercuric chloride (6) indicate that these substrates show enhanced reaction rates of ca. 10-200-fold over alkylvinylmercurials and unsubstituted vinylmercurials, suggesting that the olefinic methyl substituent may stabilize an intermediate bearing some positive charge. Enzymatic reaction of 2-butenyl-1-mercuric bromide (5) yields a 72/23/5 mixture of 1-butene/trans-2-butene/cis-2-butene, indicative of intervening SE2' cleavage. The observation of significant solvent deuterium isotope effects at pH 7.4 of Vmax (H2O)/Vmax(D2O) = 2.1 for cis-2-butenyl-2-mercuric chloride (1) turnover and Vmax(H2O)/Vmax(D2O) = 4.9 for ethylmercuric chloride turnover provides additional support for a kinetically important proton delivery. Finally, the stoichiometric formation of butene and Hg(II) from 1 and methane and Hg(II) from methylmercuric chloride eliminates the possibility of an SN1 solvolytic mechanism. As the first well-characterized enzymatic reaction of an organometallic substrate and the first example of an enzyme-mediated SE2 reaction the organomercurial lyase catalyzed carbon-mercury bond cleavage provides an arena for investigating novel enzyme structure-function relationships.

Deuterium↗
PubMed1985

Involucrin, a marker of squamous and urothelial differentiation. An immunohistochemical study on its distribution in normal and neoplastic tissues.

Involucrin is a soluble protein precursor of the cross-linked envelope present in the submembranous zone of human stratum corneum, and subsequently demonstrated in stratified squamous epithelia. The immunoperoxidase technique was used to assess the distribution of involucrin in 107 normal and 318 abnormal tissues. With few exceptions, involucrin was restricted to squamous epithelia, urothelium, some skin appendages and thymic Hassall's corpuscles. In normal squamous epithelium and normal urothelium, staining was most intense in the superficial layers where it was concentrated at the cell periphery and gradually decreased toward the basal layer. This orderly staining pattern was maintained in benign squamous and urothelial lesions and in grade I papillary urothelial carcinomas. Higher grade papillary urothelial carcinomas, infiltrating urothelial and squamous carcinomas, and in situ urothelial and squamous carcinomas demonstrated abnormal staining patterns for involucrin that are described. Foci of squamous differentiation in adenocarcinomas and other epithelial malignancies stained intensely for involucrin. Brenner tumours of the ovary and Walthard rests of the fallopian tube, lesions of uncertain histogenesis but possibly urothelial-related, also stained for involucrin. Results of this study suggest that involucrin is a sensitive and specific marker for squamous and urothelial differentiation, staining patterns for involucrin may be helpful in distinguishing benign from malignant urothelial and squamous lesions, and presence of involucrin may be helpful in determining the histogenesis of selected lesions.

Carcinoma in Situ↗
PubMed1985

Chromogranin as a marker of neuroendocrine cells in cytologic material--an immunocytochemical study.

Cytologic material, including fine-needle aspirations, bronchial brushings, body cavity fluids, and tissue imprints from 39 neuroendocrine and 26 nonneuroendocrine tumors, was stained for chromogranin by the immunoperoxidase technic. Our results suggest that chromogranin is useful in identifying primary as well as metastatic neuroendocrine lesions from a variety of body sites. All lymphoid proliferations and carcinomas, including small-cell anaplastic carcinomas of the lung (oat-cell carcinomas), were negative. Chromogranin appears to be a useful marker in diagnostic cytology. This technic can be applied to routinely prepared cytologic material.

Bronchial Neoplasms↗
PubMed1984

Keratins of different molecular weight in exfoliated mesothelial and adenocarcinoma cells--an aid to cell identification.

Keratin profiles of exfoliated mesothelial and adenocarcinoma cells were determined using antisera to different molecular weight keratins (45, 46, 55, 63 kdaltons) and the immunoperoxidase technic. Most metastatic adenocarcinomas in effusions stained for low (45, 46 kdaltons) and intermediate (55 kdaltons) molecular weight keratins but were negative for 63 kdalton keratin. In contrast, most reactive and malignant mesothelial cells in effusions stained strongly for 63 kdalton keratin and keratins of lower molecular weight. This is the first report of high molecular weight (greater than 60 kdaltons) keratin in exfoliated cells of nonepidermal origin. Differences in staining for 63 kdalton keratin between mesothelial and adenocarcinoma cells may help to distinguish these cells in effusions.

Adenocarcinoma↗
PubMed1983

Keratin and carcinoembryonic antigen in exfoliated mesothelial and malignant cells: an immunoperoxidase study.

Immunoperoxidase technics were used to identify keratin and carcinoembryonic antigen (CEA) in exfoliated cells of fine-needle aspirates and body cavity fluids. Staining was evaluated in cytocentrifuge preparations from 27 malignant and 30 benign cytologic specimens. Most reactive mesothelial cell preparations were strongly positive for keratin and negative or only weakly positive for CEA. Diffuse, peripheral, and perinuclear concentration of staining for keratin was noted in exfoliated reactive mesothelial cells. Positive staining for keratin, predominantly diffuse, was noted in exfoliated cells from 56% of the adenocarcinomas. Sixty-nine per cent of adenocarcinoma preparations were strongly positive for CEA. These findings suggest that keratin proteins are not restricted to squamous cells and that keratin staining does not permit distinction between adenocarcinoma and mesothelial cells in cytologic specimens. Staining for CEA and keratin was compared in cytocentrifuge preparations and histologic sections of 12 adenocarcinomas and 7 lymphomas. In some adenocarcinomas, staining was detected only in cytologic preparations. Possible explanations for these differences are discussed. Variable staining for keratin was observed among exfoliated reactive mesothelial cells, possibly identifying different mesothelial cell populations. All reactive and neoplastic lymphoid cells were negative for keratin and CEA in cytologic and histologic preparations. Immunoperoxidase technics can be applied to rehydrated Papanicolaou-fixed and Papanicolaou-stained cytologic preparations with excellent preservation of cytologic detail.

Adenocarcinoma↗