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Biomedical subjects

R Silber

Publications and source records attributed to R Silber.

At least 73 records · Page 4Linked to original sources
PubMed1985

A reappraisal of leukocyte dehydroascorbate reductase.

Dehydroascorbate reductase (glutathione:dehydroascorbate oxidoreductase, EC 1.8.5.1) activity was determined in human leukocyte homogenates using a direct spectrophotometric assay. Despite previous studies, using a less sensitive coupled assay, which reported that this enzyme was present in leukocytes, we found that neither neutrophil nor chronic lymphocytic leukemia lymphocyte extracts had detectable activity. Furthermore, when the product was quantitated by HPLC, protein-dependent generation could not be demonstrated. Mixing experiments with a partially purified enzyme preparation from spinach leaves provided no evidence for the presence of an inhibitor in neutrophil homogenates. These findings suggest that in human leukocytes, dehydroascorbate reduction does not occur enzymatically.

Chromatography, High Pressure Liquid↗
PubMed1985

Vasculitic leg ulcers in chronic myelogenous leukemia.

Recurrent bilateral leg ulcers developed in two patients receiving hydroxyurea therapy during the chronic phase of chronic myelogenous leukemia. The ulcers were extremely painful and were associated with extensive edema and vasculitic papules. A small-vessel vasculitis with degeneration of collagen and ulceration was seen on biopsy. The ulcers did not respond to treatment with steroids or low-dose cyclophosphamide but gradually healed with local measures. The possible pathogenesis of ulcers in chronic myelogenous leukemia is discussed.

Aged↗
PubMed1985

Amelioration of lytic abnormalities of paroxysmal nocturnal hemoglobinuria with decay-accelerating factor.

Purified decay-accelerating factor (DAF), from the stroma of normal human erythrocytes, was incorporated into the membranes of erythrocytes of patients with paroxysmal nocturnal hemoglobinuria (PNH), and its effect on the complement sensitivity of the cells was investigated. Reconstitution with exogenous DAF restored the ability of the affected PNH cells to resist assembly of the homologous C3 convertase, C4b2a, on their surfaces, and decreased the susceptibility of the cells to lysis in acidified serum. Conversely, treatment of normal erythrocytes with monoclonal or polyclonal anti-DAF antibodies abrogated the capacity of the normal cells to circumvent C4b2a assembly and rendered the cells sensitive to acid lysis. These findings show that the previously reported association of DAF deficiency with PNH is causally related to the lytic abnormalities of the cells and clarify the molecular basis for restriction of autologous convertase formation on normal human erythrocytes.

Acids↗
PubMed1985

Medical care and mortality: racial differences in preventable deaths.

We analyzed deaths of blacks and whites in Alameda County, California where previous studies have documented consistent racial inequalities in health services. We classified each death during 1978 as due to preventable and manageable conditions or as "non-preventable" according to lists compiled by the Working Group on Preventable and Manageable Diseases chaired by Dr. David Rutstein. The total death rate for blacks 0-65 years of age exceeded that of whites by 58 percent (p less than .01). Rates of death due to preventable and manageable conditions for persons aged 0-65 years were 77 percent higher for blacks than for whites (p less than .01). More than one-third of the excess total death rate of blacks relative to whites could be explained by the excess of potentially preventable deaths. Our findings suggest that inequalities in health services reinforce broader social inequalities and are in part responsible for disparities in health status. Improvements in the health and longevity of blacks and other oppressed groups might be achieved by improved access to existing medical, public health, and other preventive measures.

Adolescent↗
PubMed1985

Chronic lymphocytic leukemia.

Chronic lymphocytic leukemia is a neoplasm characterized by the accumulation of monoclonal lymphocytes in blood, bone marrow, and other tissues. Staging of the disease is based on lymphoid mass and the presence of anemia or thrombocytopenia, with prognosis also related to the pattern of bone-marrow involvement, chromosomal abnormalities, and surface membrane phenotype. Transformation to a diffuse large-cell lymphoma or to prolymphocytic leukemia may occur as a terminal event. A number of biochemical and surface membrane abnormalities that may suggest approaches for future clinical investigations have been described.

Aged↗
PubMed1985

Effects of new N-alkyl analogues of adriamycin on in vitro survival and cell cycle progression of L1210 cells.

The effects of N-benzyladriamycin-14-valerate (AD198) and N,N-dimethyladriamycin-14-valerate (AD199), two novel lipophilic N-alkyl derivatives of Adriamycin (ADR), on cell growth and cell cycle distribution were investigated in L1210 cells grown in suspension. Following a 1-h exposure to the drug levels selected, growth inhibition was noticeable in all cultures for most or all of the observation period of 96 h. With flow cytometry, an asynchronous cell population was measured with respect to cellular DNA, RNA, and light scatter (size) properties following a 1-h incubation with the various ADR analogues. In addition, flow cytometric techniques were utilized to determine whether drug treatment altered the sensitivity of DNA in situ to acid-induced denaturation or to binding by small DNA-intercalating dyes. Unlike the parent compound ADR or its DNA-nonbinding derivative N-trifluoroacetyladriamycin-14-O-hemiadipate (AD143), the N-alkyl derivatives AD198 and AD199 only slightly affected L1210 cell cycle traverse over the first 5 h posttreatment. However, by 24 h, AD199 (0.62 micrograms/ml) caused an S- and G2 + M-phase accumulation which became more dramatic at 48 and 72 h. AD198 (3.27 micrograms/ml) also caused an accumulation of cells predominantly in G2 + M phase at longer culture times (48 to 96 h). The two half-substituted congeners N-benzyladriamycin (AD288) and N,N-dimethyladriamycin (AD280) affected L1210 cell cycle traverse over a similar time scale at concentrations of 12.3 and 4.17 micrograms/ml, respectively. AD280 blocked cells in G1 and G2 + M whereas AD288 caused predominantly a G2 + M accumulation. While neither ADR nor AD143 interfered appreciably with binding and fluorescence of the intercalating dye acridine orange, all of the N-alkyl analogues tested reduced the fluorescence signal of acridine orange-stained L1210 cells by 26 to 60%. This effect lasted, with decreasing intensity, for at least 48 h following a 1-h exposure to the drugs. In addition, while ADR appeared to stabilize DNA in situ against acid-induced denaturation, all N-alkyl derivatives, to varying degrees, tended to increase DNA denaturability. Thus alkylation at the glycoside amine combined with the lipophilic 14-valerate side chain function accounts for several new biochemical and biological properties of AD198 and AD199, relative to ADR.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Relationship of dehydroascorbic acid transport to cell lineage in lymphocytes from normal subjects and patients with chronic lymphocytic leukemia.

Dehydroascorbic acid is the principal form for the cellular uptake by blood cells of vitamin C. Since previous studies from this laboratory had shown a higher content of ascorbic acid and dehydroascorbic acid (DHA) in chronic lymphocytic leukemia (CLL) lymphocytes when compared to their normal counterparts, DHA uptake was characterized using these cells. The affinities of CLL and normal lymphocytes for DHA uptake were similar, as demonstrated by the Km values of 3.7 and 3.5 mM, respectively. Differences were found in other kinetic constants of DHA uptake. The Vmax for normal lymphocytes, 634 mumol/liter cell H2O/min, was approximately twice that of CLL cells, 392 mumol/liter cell H2O/min. In addition, the initial velocity and the maximal DHA uptake by normal lymphocytes were greater than that of CLL lymphocytes. These differences were not simply a reflection of lymphocyte subsets since CLL B-cells demonstrated lower uptake rates than did normal B-cells whereas CLL T-cells were similar to their normal counterparts. The alterations appear to be specific for the leukemic B-cell since they were not shared by neoplastic cells from two patients with T-cell CLL. When analyzed in light of the 3-fold greater cellular DHA and ascorbic acid content in B-cell CLL as compared to normal lymphocytes, these kinetic parameters support the occurrence of a concentration-dependent transport system for DHA. We conclude that the DHA uptake properties of CLL lymphocytes of B-cell origin serves to distinguish this lineage from T-cell CLL or normal lymphocytes.

Ascorbic Acid↗
PubMed1984

Two mechanisms of adriamycin-DNA interaction in L1210 cells.

Among the effects exerted by adriamycin (ADR), interaction with DNA is closely related to cytotoxicity. The interaction results in the formation of protein-associated DNA single-strand breaks (PA-SSB) and, at drug levels greater than or equal to 2.8 X 10(-6) M, also in "direct" (nonenzymatic) DNA single-strand breaks (D-SSB). To characterize the two types of DNA lesions, euoxic mouse leukemia L1210 cells were treated with various antioxidant agents in the presence of 2.8 X 10(-6), X 10(-5), or X 10(-4) M concentrations of ADR. The enzymes superoxide dismutase (200 micrograms/ml) or catalase (250 micrograms/ml), the OH' scavengers dimethyl sulfoxide (70 mM) or ethanol (70 mM), and an inhibitor of superoxide production, 2-deoxy-glucose (1 and 10 mM), reduced the frequency of D-SSB to 18.3 to 68.2% of its level in ADR-treated controls, while the frequency of PA-SSB remained unchanged. These observations seem to indicate that ADR-mediated free radicals cause discernible DNA damage in euoxic cells only at very high drug concentrations, greater than the peak plasma level achievable clinically following i.v. bolus. At lower ADR levels, relevant to clinical use, another type of interaction between the drug and DNA prevails, which apparently does not involve a free-radical mechanism.

Animals↗
PubMed1984

Patient transfers: medical practice as social triage.

We studied 458 consecutive patient transfers from 14 private hospitals to a public hospital emergency room during a six-month period. The transferred patients were predominantly male, young, and uninsured, and included large numbers of minority group members. We established criteria to identify patients at high risk for adverse effects of transfer and reviewed the clinical records of the 103 patients meeting these criteria. We judged that transfer resulted in substandard care for 33 of these patients, either because they were at risk for life-threatening complications in transit or because urgently needed diagnosis or therapy was delayed. In the community studied, transfer is a common and potentially dangerous medical intervention which appears to reinforce racial and class inequalities of access to medical care.

Adult↗
PubMed1984

Decreased 5'-nucleotidase activity in a T lymphocyte subpopulation from patients with B cell chronic lymphocytic leukemia.

The activity of the ectoenzyme 5'-nucleotidase (5'N) was determined in the T lymphocyte subpopulations from patients with chronic lymphocytic leukemia (CLL). 5'N could be detected only in the T cells from patients whose B cells also had enzyme activity. The specific activity of CLL T4 cells was 0.17 +/- 0.02 micron/h/mg protein, similar to that of normal T4 cells, which was 0.13 +/- 0.08 micron/h/mg. The CLL T8 cells, however, had a significantly lower 5'N activity (0.17 +/- 0.02 micron/h/mg) than normal T8 cells (0.41 +/- 0.11 micron/h/mg) (P = .003). Normal null cells had very low activity, while much higher levels were found in the null cells of CLL patients whose B cells had activity. These findings document a difference in activity of an enzyme between the T8 cell population of patients with CLL and that of normal subjects.

5'-Nucleotidase↗
PubMed1984

Chronic lymphocytic leukemia lymphocytes: membrane anomalies and H2O2 vulnerability.

This paper reviews selected biochemical and functional studies characterizing B lymphocytes from patients with chronic lymphocytic leukemia. When compared to B lymphocytes from the circulation of normal subjects, a number of differences are noted. Functionally, the CLL B lymphocyte is impaired in mitogen response, cap formation following attachment of multivalent ligands, and the density of surface immunoglobulins. It also differs from normal in the content of the ectoenzyme 5' nucleotidase, which is often decreased, and the concentration of ascorbic and dehydroascorbic acid, which are markedly elevated in these cells. The level of tocopherol is decreased. CLL and normal B lymphocytes are more vulnerable than T lymphocytes to the toxic effect of H2O2. This sensitivity is Ca2+ dependent and inhibited by nanomolar concentrations of nonsteroidal antiinflammatory agents. These studies identify the human B lymphocyte as a cell that should be a suitable target for selective killing by H2O2.

B-Lymphocytes↗
PubMed1984

Anomalous function of vimentin in chronic lymphocytic leukemia lymphocytes.

Chronic lymphocytic leukemia (CLL) lymphocytes manifest anomalous motility and cap formation. Since these processes involve cytoskeletal proteins, vimentin from intermediate filaments of normal and CLL lymphocytes was investigated using hetero- and monoclonal antisera. The antisera reacted predominantly with a 60-kD polypeptide, following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of total lymphocyte proteins. When lymphocytes were stained by indirect immunofluorescence, normal lymphocytes demonstrated well defined cytoplasmic fibrils that capped spontaneously after contact with a glass surface and incubation at 37 degrees C. This capping was dependent on energy and intact microfilaments. Lymphocytes from patients with CLL showed several patterns. In one group, the initial staining was weak, and few capped cells were present after incubation. Lymphocytes from other patients had either normal or aberrantly organized fibrils in which capping was diminished. In another group, a fibrillar pattern with normal or increased capping was seen. In total, 47% +/- 5.1% (mean +/- SE) of normal lymphocytes capped after a 1-hr incubation at 37 degrees C (n = 12) compared to 21% +/- 5.1% for CLL lymphocytes (n = 20, p less than 0.002). Purified subpopulations of normal B and T cells did not differ from unfractionated normal lymphocyte populations. These results demonstrate an anomalous vimentin capping response in CLL lymphocytes. They also show that the arrangement of vimentin in these cells differs from that of normal lymphocytes.

Antibodies, Monoclonal↗
PubMed1984

How to achieve total gastric sympathectomy.

Experimental examinations on acute, stress induced gastric ulcers have shown the outstanding role of the sympathetic innervation in the pathogenesis of this ischemic disease. As reduction of sympathetic tonus resulted in a significant prophylaxis against "stress ulcers", further experimental work was done to achieve total but selective gastric sympathectomy. In a histomorphological study in dogs (Method: Hillarp and Falck in the modification of Heene ) the effects of three different surgical procedures on gastric sympathetic denervation were investigated: 1. Selective proximal vagotomy (= SPV, 8 dogs) 2. SPV and periarterial denervation of the main gastric arteries with severance of the gastrolineal ligament (= PASD , 8 dogs) 3. PASD alone (7 dogs) Selective proximal vagotomy resulted in a sympathetic denervation of major parts of the right site of the fundus and corpus. Following selective proximal vagotomy with periarterial denervation ( PASD ) there was a complete sympathetic denervation of the entire stomach. Only a minimal area of resting sympathetic innervation was observed on the esophago-cardial border when periarterial denervation ( PASD ) was performed alone.

Animals↗
PubMed1984

Reduced tocopherol content of B cells from patients with chronic lymphocytic leukemia.

The tocopherol content of lymphocytes, erythrocytes, and plasma from patients with chronic lymphocytic leukemia (CLL), hairy cell leukemia (HCL), and normal subjects was measured by a sensitive high performance liquid chromatographic method. Lymphocytes from patients with CLL had lower values of tocopherol (1.7 +/- 1.0 micrograms/10(9) cells) than lymphocytes from normal subjects (3.8 +/- 0.7 micrograms/10(9) cells). Mononuclear cells from patients with HCL had an increased tocopherol content of 6.2 +/- 1.0 micrograms/10(9) cells. Subfractionation of the lymphocytes from patients with CLL into T- and B-cell subgroups showed that the tocopherol content of T cells was the same as in normal subjects (4.1 +/- 0.5 micrograms/10(9) cells versus 3.5 +/- 1.2), but that the tocopherol content of the B cells was markedly reduced compared to normals (2.6 +/- 1.0 versus 6.0 +/- 1.3).

B-Lymphocytes↗
PubMed1984

Human B lymphocytes show greater susceptibility to H2O2 toxicity than T lymphocytes.

Lymphocytes from patients with chronic lymphocytic leukemia (CLL) and from normal subjects were incubated with a glucose-glucose oxidase hydrogen peroxide (H2O2) generating system to study the effect of oxidant stress on these cells. Within 4 hr, 90% of normal but only 21% of CLL lymphocytes remained viable. When normal and CLL preparations enriched in B or T cells were exposed to H2O2, B lymphocytes from both groups were highly susceptible to oxidative damage while T lymphocytes were relatively resistant. The H2O2 scavenger catalase prevented the cytotoxicity. The present work identifies the human B lymphocyte as a cell that should be a suitable target for selective killing by H2O2-generating systems.

B-Lymphocytes↗
PubMed1983

A specific high-performance liquid chromatography assay for dehydroascorbic acid shows an increased content in CLL lymphocytes.

A method for the assay of dehydroascorbic acid using high-performance liquid chromatography with uv detection is described. The dehydroascorbic acid is separated from ascorbic acid and reduced with dithiothreitol, and is then quantitated as ascorbic acid following rechromatography. Since as little as 22 pmol can be detected, sensitivity is at least 40-fold greater than that of other currently available procedures. This method was used to measure the level of dehydroascorbic acid in normal and chronic lymphocytic leukemia lymphocytes. A significantly higher concentration of dehydroascorbic acid was found in leukemic (21.80 +/- 3.55 nmol/10(8) cells, mean +/- SE) than in normal lymphocytes (9.32 +/- 1.15 nmol/10(8) cells) (P less than 0.03). Analysis of extracts from normal B cell lymphocytes revealed comparable dehydroascorbic acid levels to unfractionated lymphocytes, indicating that the elevated level in chronic lymphocytic leukemia was not simply a reflection of the increased percentage of B lymphocytes in this disorder. These studies illustrate that the technique can be used to measure the dehydroascorbic acid content from sources where only scanty material is available or low levels are found.

Ascorbic Acid↗
PubMed1983

Simultaneous occurrence of mycosis fungoides and Hodgkin disease: clinical and histologic correlations in three cases with ultrastructural studies in two.

We present three patients who manifested both Hodgkin disease and mycosis fungoides. Ages ranged from 39 to 66 and two were male. Skin lesions were present from 3 to 40 years before the diagnosis of Hodgkin disease. In all cases, mycosis fungoides was confirmed histologically by skin biopsy; the clinical course of the mycosis fungoides was indolent in all cases. Hodgkin disease was confirmed histologically in three, and confirmed by electron microscopy in two. All three patients responded to appropriate treatment for Hodgkin disease and are alive and well at the present time.

Adult↗