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Biomedical subjects

A Malkin

Publications and source records attributed to A Malkin.

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

Solving the problem of antibody interference in commercial "sandwich"-type immunoassays of carcinoembryonic antigen.

We evaluated the effect of human anti-murine antibodies (HAMA) on apparent concentrations of carcinoembryonic antigen (CEA) as measured in serum with commercial enzyme immunoassay (EIA) kits manufactured by Abbot ("two-step" double monoclonal antibody assay), Roche, and Hybritech (room-temperature protocol). In sera from patients given parenteral murine monoclonal antibody for experimental diagnostic and immunotherapy studies, HAMA titers were determined with Immunomedics' "ImmuSTRIP HAMA-EIA" kit reagents. "True" CEA titers were established by using the ImmuCEA/MA-EIA and heat-extraction to destroy HAMA before assay for CEA. The concordance of the ImmuCEA/MA assay with the Abbott and Roche CEA EIAs was established with sera from normal individuals and from patients who had not received parenteral injections of murine monoclonal antibody. At high (100 mg/L) concentrations of HAMA, false-positive results were observed with all three kits. The Hybritech and Roche assays were more sensitive to interference by HAMA than was the Abbott CEA-EIA, false-positive results being observed at HAMA concentrations between 1 and 10 mg/L. Similar sensitivity of the three kits to interference by primate anti-MAb sera was demonstrated. Use of primate anti-MAb sera to create controls with HAMA activity and of analyte is recommended to evaluate MAb assays for potential HAMA interference and for use to devise methods to eliminate HAMA interference.

Animals↗
PubMed1988

The effect of nonviral liver damage on the T-lymphocyte helper/suppressor ratio.

In the present investigation an attempt was made to ascertain whether nonviral liver impairment in rats affects the THelper/TSuppressor ratio. Two hepatotoxic agents were used: (i) galactosamine (GA), which causes a drug-induced hepatitis-like damage, and (ii) orotic acid (OA), which induces fatty changes. Since these two substances act as antidotes to one another they were administered to rats either separately or simultaneously. GA caused severe liver damage documented by a 104-, 48-, and 1.6- fold rise in the plasma concentrations of ALT, AST, and ALP and by multiple foci of hepatocyte necrosis. This was followed by a drop in TH/TS ratio from 2.25 observed in the controls to 0.89 in the GA-treated rats. All of these phenomena were prevented by concurrent administration of GA and OA. OA alone did not show an effect on the liver with respect to changes in plasma enzyme concentrations and by light microscopic analysis. However, OA caused a drop in the TH/TS ratio from 2.25 to 1.55. Neither GA nor OA produced a change in TH/TS ratios in in vitro experiments.

Animals↗
PubMed1988

Effect of ethanol extract of cancer patients' serum on the vulnerability of lymphocytes to cortisol.

We have shown previously that cortisol-sensitive lymphocytes (thymocytes) have a much lower capacity than cortisol-resistant cells to catabolize cortisol. We have also shown that sera of cancer patients (CPS) possess ethanol-extractable substance(s) which can inhibit the catabolism of cortisol by lymphocytes (CCL). Recently, we noted that unsaturated fatty acids can both inhibit CCL and modulate the sensitivity of lymphocytes to cortisol. In the present study, we attempt to identify the compounds responsible for CCL inhibition and to demonstrate that inhibition of CCL may make cortisol-resistant lymphocytes vulnerable to the steroid. The enzymes DNase, RNase, pronase and lipase were added to ethanol extracts of serum as a first step in our efforts to identify the nature of the inhibitors of CCL. Only lipase had an effect on the inhibition. In fact, lipase enhanced the inhibition of CCL. This finding correlates with our previous observations that unsaturated fatty acids are potent inhibitors of CCL. Examining the effect of ethanol extracts of CPS and normal serum on the vulnerability of lymphocytes to cortisol, we noted that ethanol extracts of normal serum had no significant killing effect, whereas an ethanol extract of CPS makes lymphocytes more sensitive to cortisol. Since the adsorbance of free fatty acids of CPS by defatted albumin reduced but did not eliminate the capacity of the serum to inhibit CCL, we assume that other compounds besides free fatty acids might also be involved in CCL inhibition and modulation of the sensitivity of lymphocytes to cortisol.

Deoxyribonucleases↗
PubMed1988

An enzyme immunoassay for carcinoembryonic antigen which employs simultaneous incubation of specimen with solid phase and enzyme-conjugated antibodies.

The Abbott CEA-EIA Monoclonal One-Step procedure was evaluated and compared to the Abbott CEA-EIA Monoclonal, a two-step assay. The reproducibility, sensitivity, recovery and dilution linearity were similar for both assays. Excellent correlations were found between the carcinoembryonic antigen (CEA) values obtained with these assays for healthy donors (n = 261, r = 0.951), patients with benign diseases (n = 171, r = 0.994) and cancer patients (n = 585, r = 0.997). In serial monitoring studies, one-step CEA values paralleled the CEA values determined with the two-step assay regardless of the type of cancer. The advantages of the one-step CEA assay over the two-step assay include significant reduction in both attended and total assay times, reduced sample volume, dry antibody-coated beads, color-coded reagents and an extended range for the standard curve. These test improvements were achieved without affecting the reproducibility, sensitivity and accuracy of the CEA measurement.

Antibodies, Monoclonal↗
PubMed1987

The effect of linoleic acid on the sensitivity of human lymphocytes to cortisol and their capacity to catabolize the steroid.

We have shown previously that cortisol-sensitive lymphocytes (thymocytes) have a much lower capacity than cortisol-resistant cells to catabolize cortisol. In the present study, we attempt to demonstrate that inhibition of cortisol catabolism may make cortisol-resistant lymphocytes vulnerable to the steroid. Linoleic acid, which has the capacity to inhibit the catabolism of cortisol by lymphocytes, was used for this purpose. By using various concentrations of linoleic acid (20-60 micrograms/mL) we showed an inverse linear relationship between linoleic acid concentration and the rate of cortisol catabolism by lymphocytes. During this experiment which took 17 h the viability of cells did not change significantly (minimum viability 95%), even at the highest concentration of linoleic acid. Keeping the metabolism of cortisol at a level of 40% of that obtained by the control, by adding linoleic acid to lymphocyte cultures (50 micrograms/mL) and measuring the viability of the cells for a period of 3 days in the presence or absence of cortisol, we were able to show a rise in the death rate of the cells which started after 24 h of incubation owing to the presence of the steroid.

Humans↗
PubMed1987

Imaging studies and the prognostic value of serum calcitonin in staging small-cell lung cancer.

The controversial prognostic significance of serum calcitonin in small-cell lung cancer (SCC) prompted this retrospective study relating serum levels to (1) stage of disease [limited disease (LD) vs. extensive disease (ED)], (2) imaging studies of metastases to bone, liver, and brain, and (3) survival. Of the 127 previously untreated patients with SCC presenting from 1979 to 1984, calcitonin levels could be compared to the stage of the disease in 69 patients (25 LD and 44 ED) and to various staging procedures including 99mTc methylene diphosphonate bone scans (63 patients), 99mTc sulfur colloid liver-spleen scans (64 patients), computed tomography of the head (63 patients) and serum calcium (61 patients). 71% (49/69) of patients had elevated calcitonin of whom 65% (32/49) had ED. 29% (20/69) had normal levels of whom 60% (12/20) had ED. 40% (18/45) of patients with raised calcitonin had liver metastases. 100% (19/19) with normal calcitonin had no liver involvement. Two patients with hypercalcemia and increased calcitonin had extensive bony metastases. The survival experiences of patients with normal and elevated serum calcitonin levels were analyzed. No significant differences were found within each stage or in the group overall. The positive correlation of serum calcitonin to liver metastases was statistically significant. No such relationship could be demonstrated with stage of disease, bone metastases, brain metastases, or survival.

Calcitonin↗
PubMed1987

Effect of a non-viral fraction of acquired immunodeficiency syndrome plasma on the vulnerability of lymphocytes to cortisol.

We have observed previously that the rate of cortisol catabolism by lymphocytes (CCL) was indicative of the vulnerability of these cells to cortisol. We attempted to ascertain whether cortisol-sensitive lymphocytes (e.g. thymocytes) metabolize cortisol at a different rate from cortisol-resistant cells and whether lymphocytes in which cortisol catabolism is inhibited become cortisol sensitive. The work was facilitated by the observation that an ethanol extract plasma from patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) had the capacity to inhibit CCL. The capacity of thymocytes to metabolize cortisol was found to be 11 times lower than that of peripheral lymphocytes. Inhibition of CCL with an ethanol extract of plasma from AIDS/ARC patients made the cells vulnerable to cortisol, causing them to die at a rate seven times greater than that of control samples. It is suggested that these findings may have important implications with regard to the nature of lymphocyte depletion in AIDS/ARC patients or in people at risk of developing the syndrome.

AIDS-Related Complex↗
PubMed1986

Activation of thyroid adenyl cyclase by antisera to thyroid plasma membrane preparations: effects of IgG and non-IgG antiserum components.

We have previously shown that IgG isolated from rabbit antibovine thyroid plasma membrane (anti-BTPM) antibodies exhibits properties similar to long acting thyroid stimulator (LATS) and HTS-lg in that it activates thyroid adenyl cyclase. In order to test whether another immunoglobulin class, eg, IgM, of anti-BTPM antiserum can also stimulate the bovine thyroid adenyl cyclase system, protein molecules of the antiserum were separated into different molecular sizes by gel filtration chromatography on Sephadex G-200. It was observed that the low molecular weight fraction, consisting predominantly of albumin, was inactive in stimulating adenyl cyclase of the thyroid gland. In contrast, both IgM-enriched and IgG-enriched fractions of the immune serum were fully active. Furthermore, the thyroid-stimulating activity of the IgM-enriched fraction can only be inhibited by anti-IgM and that of the IgG-enriched fraction by anti-IgG. Our data suggest that IgM, in addition to IgG, may also have LATS or LATS-like activities in terms of activating adenyl cyclase of the thyroid gland.

Adenylyl Cyclases↗
PubMed1986

Alteration of lymphocyte reactivities by thyroid hormones.

The effects of thyroid hormones (L-T4, L-T3 and rT3) on the proliferative response of rabbit peripheral blood lymphocytes to T-cell mitogens, PHA and Con A, and B cell specific goat anti-rabbit light chain antibodies (Anti-L) were investigated. It was observed that L-T4 potentiated the lymphocyte response to mitogens and Anti-L in a dose-dependent manner: 10(-9) M and 10(-8) M had no effect while 10(-7)-10(-5) M significantly enhanced the lymphocyte response. L-T3 (10(-11)-10(-8) M) had no effect on the lymphocyte response to PHA and Con A. At 10(-7) M, L-T3 inhibited the response to PHA but not Con A. L-T3 (10(-11)-10(-7) M) suppressed the lymphocyte response to Anti-L. The suppression was directly proportional to the L-T3 concentration. rT3 (10(-11)-10(-7) M) inhibited the proliferative response to PHA and Anti-L in a dose-related manner. Its effect on the lymphocyte response to Con A was stimulatory at 10(-11) M but inhibitory at higher concentrations (10(-8) and 10(-7) M). rT3 suppressed the enhancement by L-T4 of the lymphocyte response to the mitogens and Anti-L. The degree of suppression was proportional to its concentration. This data indicated that thyroid hormones can alter the reactivities of lymphocytes. The direction and magnitude of the alteration appear to depend on the concentration of a specific thyroid hormone encountered by the responding cells.

Adjuvants, Immunologic↗
PubMed1986

Effect of glucose, NADH and NADPH on cortisol metabolism by mononuclear cells.

Mononuclear cell preparations are capable of metabolizing cortisol to three metabolites which lack the immunosuppressive effect of their precursor. In the present study we noted a linear correlation, up to a point, between glucose concentration and the rate of human mononuclear cell cortisol metabolism in vitro. The mechanism by which glucose exerts its effect was investigated further. We observed that: the effect of glucose on mononuclear cell cortisol metabolism was not influenced by insulin; NADPH and NADH enhanced cortisol metabolism by disrupted cells, irrespective of whether the homogenates were dialysed or not; lactate and ATP inhibited mononuclear cell cortisol metabolism and almost all the glucose used was converted to lactate. It is concluded that mononuclear cell cortisol metabolism can depend on both nucleotides.

Adenosine Triphosphate↗
PubMed1986

Role and mechanism of action of tamoxifen in premenopausal women with metastatic breast carcinoma.

Tamoxifen was evaluated as initial hormone therapy for metastatic breast cancer in 85 premenopausal patients. Tamoxifen responders continued on tamoxifen, while tamoxifen failures and initial responders who later progressed were to receive ovarian ablation next. Of 74 evaluable patients, 5 had complete responses (CR) and 15 had partial responses (PR) while 12 remained stable (ST), giving response rates of 27% (CR + PR) or 43% (CR + PR + ST). Of the 23 patients who initially responded (CR + PR + ST) to tamoxifen but then progressed and received ovarian ablation alone, 15 are assessable. Nine (60%) responded (CR + PR + ST) to ovarian ablation. Sixteen patients who failed tamoxifen had ovarian ablation alone, and of 14 assessable patients 2 had ST while 12 progressed. Thus response to tamoxifen strongly predicted response to ovarian ablation (P = 0.021). Serial follicle stimulating hormone, prolactin, and estradiol levels suggested that tamoxifen does not act by induction of a "medical ovariectomy" or by alteration of prolactin levels in premenopausal patients.

Breast Neoplasms↗
PubMed1986

Sera of patients with cancer or cirrhosis and of newborns exhibiting inhibitory effects on the metabolism of cortisol by lymphocytes.

The effect was examined of ethanol extracts of normal sera (NS), cancer patients' sera (CPS), cirrhosis patients' sera (CirPS), and umbilical cord sera (UCS) on cortisol metabolism by lymphocytes (CML). All the ethanol extracts of these sera showed an inhibitory effect on CML. The most significant inhibition was obtained with CPS and CirPS followed by UCS. A significant inhibition of NS was obtained after doubling their equivalent volume.

Ethanol↗
PubMed1986

Clinical correlations of carcinoembryonic antigen in post-operative patients with epithelial ovarian cancer.

Plasma CEA as a tumor marker was studied in 681 postoperative patients with invasive epithelial cancer of the ovary. The sensitivity of a single CEA value was low in correlating with tumor burden, relapse status or in predicting subsequent relapse. The false negative rate was high. Serial samples were helpful in predicting relapse in a small number of patients where the value was persistently high. CEA showed greater sensitivity and prognostic value in patients with the mucinous tumor subtype, than other histologies. A clinically useful role for CEA is likely to be restricted to small subsets of patients, such as those with mucinous tumors where CEA may have a complementary role with other markers. A change in assay method during the course of the study resulted in a weakening of the value of CEA as a tumor marker.

Analysis of Variance↗
PubMed1986

3,5,3'-Triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) synthesis in rats hosting the R3230AC mammary tumour.

Generation of T3 and rT3 from T4 was studied in R3230AC mammary tumours grown in Fischer 344 rats as well as in the liver and kidney of these tumour-bearing hosts. The primary objective of this study was to determine if reversion of T3 to rT3 synthesis occurs in this experimental tumour model and in organs remote from the tumour site. Tumours, hepatic and renal homogenates were analyzed 14-16 days following tumour implantation for 5- and 5'-iodothyronine deiodinase activity using thyroxine as substrate. It was observed that similar to the liver and kidney, the mammary tumour was capable of generating both T3 and rT3 from T4; renal synthesis of T3 was significantly greater than that of rT3 in tumour hosts and controls. In contrast, there was no significant difference between T3 and rT3 synthesis in the tumour itself and the livers of normal and tumour-bearing animals. Hepatic and renal T3 synthesis were greater in the tumour-bearing than in the normal rats; no difference in the hepatic and renal rT3 synthesis was observed between the tumour-bearing and the normal animals. Despite the fact that serum T3 was significantly lower in the tumour-bearing than in the normal rats, no difference in the serum rT3 level was observed between the two groups of animals. Our data demonstrate that in this particular animal model there is no evidence of dedifferentiation of iodothyronine deiodinase activity either within the tumour or in remote tissues.

Adenocarcinoma↗
PubMed1985

A qualitative agar gel immunoprecipitin (IP) test for detection of fecal occult human hemoglobin.

A versatile, qualitative, agarose gel immunoprecipitation (IP) test for the detection of fecal occult hemoglobin (Hb) was developed to provide a more accurate method for the detection of occult blood in stool. This test allowed detection of 0.2 mg human hemoglobin/g of stool after a 2-h incubation. In addition, a specimen application device which can accommodate a variety of specimens was developed for this test. A study of 252 clinical stool specimens revealed a close correlation in the results obtained at three separate laboratories. The IP test identified blood in 11 out of 24 specimens collected from patients with colorectal carcinoma as compared to 4 of 24 specimens positive with a guaiac-based Hemoccult II test. The simplicity of immunoprecipitation coupled with the high sensitivity and specificity of this technique suggests that this new test would be a very useful and effective means with which to screen for occult blood in stool.

Adult↗