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Biomedical subjects

E Cohen

Publications and source records attributed to E Cohen.

At least 325 records · Page 18Linked to original sources
PubMed1982

Participation of ornithine decarboxylase in early stages of tomato fruit development.

The apparent association of ornithine decarboxylase (ODC) with rapid cell proliferation in developing tomato (Lycopersicon esculentum Mill. cv. Pearson ms-35) fruits has been previously described. Further evidence is provided by the use of two ODC inhibitors, alpha-difluoromethylornithine (alpha-DFMO) and alpha-methylornithine (alpha-MO). Fruit development was inhibited by these inhibitors if applied during the period of intensive cell division. When applied in vitro, the two inhibitors were shown to inhibit the activity of ODC but not that of arginine decarboxylase (ADC). When applied in vivo, alpha-DFMO, a catalytic irreversible inhibitor, caused 97.1% reduction of ODC activity in the dialyzed extract from the treated ovaries, while it had no effect on ADC. On the other hand, alpha-MO, a reversible inhibitor, did not reduce the activity of these two enzymes in the dialyzed extracts when applied in vivo. The dialysis procedure probably removed alpha-MO from the enzyme fraction. Putrescine, the product of both ODC and ADC, alleviated the inhibition of fruit development but did not restore ODC activity to the control level. These results suggest that in the young developing tomato fruit, ODC is the enzyme responsible for the synthesis of putrescine, which is essential for the early stages of fruit development. The reduced activity of ODC elicited by putrescine suggests a mechanism of feedback regulation by enzyme repression or release of an ODC anti-enzyme.

Journal Article↗
PubMed1982

Ornithine decarboxylase and arginine decarboxylase activities in meristematic tissues of tomato and potato plants.

Ornithine decarboxylase and arginine decarboxylase activities were measured in roots and buds of tomato (Lycopersicon esculentum Mill. cv. Pearson ms-35) and potato (Solanum tuberosum cv. Desire) plants. In both tomato and potato, the activity of ornithine decarboxylase was the highest at the root tip, decreasing proximally. The same was true for potato buds. In vegetative buds of tomato, the highest activity was found in the youngest leaves. The older the leaf, the lower was orithine decarboxylase activity. Arginine decarboxylase, on the other hand, did not display a similar gradient. These findings are in accordance with the suggestion that in tomato and potato elevated ornithine decarboxylase activity is associated with intense mitotic activity.

Journal Article↗
PubMed1982

Effects of source leukocyte collection on the immune system.

This study was initiated in order to assess any immunologic effects that source leukocyte concentrate collection might have on double-bag plasmapheresis donors. Previous studies have shown that surveillance parameters, such as T versus non-T lymphocyte subpopulations, showed no abnormal values in donors with as many as 500 visits over a 12-year period. The present study demonstrates that the frequency and the total number of leukocyte donations do not effect the lymphocyte subpopulations and functions observed. No significant changes were noted for specific and nonspecific stimulation, natural killer (NK) cell activity, lymphocyte surface markers and a variety of functional parameters. For example, the apheresis donors manifested no differences in NK cell activity, human leukocyte interferon production, IgG synthesis by B cells and percent suppression of both IgG synthesis and mixed lymphocyte cultures, when compared to non-apheresed donors.

Blood Donors↗
PubMed1982

[Comparative results of hip resection and coaptation for septic arthritis. Apropos of 36 cases].

The Girdlestone procedure was performed in 36 cases of septic arthritis of the hip, most of which arose following operation. In 21 instances, the greater trochanter was inserted into the acetabulum and the hips were fixed by external fixators. In 15 instances a standard operation was performed followed by traction. The results were better after simple procedures; there was less pain and more mobility but the hip was more unstable. It is concluded that the simple procedure is preferable especially when it is planned to perform a further arthroplasty later.

Adult↗
PubMed1982

In vitro chitin synthesis in an insect: formation and structure of microfibrils.

Chitin microfibril synthesis in Tribolium castaneum chitin synthetase (CS) assays results in the formation of a considerable precipitate. Such precipitate does not appear in the absence of the CS substrate (uridine diphospho N-acetyl-D-glucosamine) or in the presence of polyoxin-D, a potent CS inhibitor. Diflubenzuron which blocks in vivo chitin synthesis in insects has no effect on the precipitate formation at a relatively high concentration (3 x 10(-4) M). Electron microscopic examination of the CS product reveals a network of long, parallel oriented microfibrils. The microfibrils vary in thickness from 10 to 80 nm. Thinner elements merge to form larger and thicker microfibrils which are packed in distinct bundles. Particles associated with the microfibrils are largely spheroidal and range from about 50 to 250 nm in diameter. Coiled fibroid structures enclosed inside particles were observed. Similar coiled structures or extended fibroids attached to the outside (shell) of particles were also found. The nature of the particles and their possible role in chitin synthesis and fibrillogenesis in insects are discussed.

Animals↗
PubMed1982

A comparative study on the specificity of Androctonus australis (Saharan scorpion) and Limulus polyphemus (horseshoe crab) agglutinins.

The specificities of Limulus polyphemus and Androctonus australis sera were compared by agglutination and agglutination-inhibition micromethods with human untreated and enzyme-treated peripheral blood cells (erythrocytes, normal lymphocytes and chronic lymphocytic leukemia lymphocytes). Androctonus sera give higher titers than Limulus sera with erythrocytes and lymphocytes. Both sera show more avidity for leukemic than for normal lymphocytes. Limulus sera fail to agglutinate neuraminidase-treated cells but Androctonus sera react with untreated and neuraminidase-treated erythrocytes at the same degree. Sialyl-lactose is the best inhibitor for Androctonus sera, followed by N-acetylneuraminic and N-glycolylneuraminic acids, glucuronic and galacturonic acids, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. The amounts of inhibitor required depend upon the particular cell and enzyme treatment: agglutination of neuraminidase-treated erythrocytes by Androctonus is inhibited by lower concentrations of the same compounds that inhibit untreated erythrocytes agglutination. Results suggest that although Limulus and Androctonus have specificity for sialic acid containing compounds, on the cell surface, the Limulus receptors might be different from Androctonus receptors.

Agglutination↗
PubMed1981

Comparison of thrombelastography with common coagulation tests.

Thrombelastography, although proven as a useful research tool has not been evaluated for its clinical utility against common coagulation laboratory tests. In this study we compare the thrombelastographic measurements with six common tests (the hematocrit, platelet count, fibrinogen, prothrombin time, activated thromboplastin time and fibrin split products). For such comparisons, two samples of subjects were selected, 141 normal volunteers and 121 patients with cancer. The data was subjected to various statistical techniques such as correlation, ANOVA, canonical and discriminant analysis to measure the extent of the correlations between the two sets of variables and their relative strength to detect blood clotting abnormalities. The results indicate that, although there is a strong relationship between the thrombelastographic variables and these common laboratory tests, the thrombelastographic variables contain additional information on the hemostatic process.

Blood Coagulation Disorders↗
PubMed1981

Acetylcholinesterase activity in an Aedes aegypti cell line.

Considerable acetylcholinesterase (AChE) activity was detected in an Aedes aegypti established cell line. The enzyme is blocked by 10(-6) M eserine sulfate, displays excess substrate inhibition and slowly hydrolyzes butyrylthiocholine. A 2-fold stimulation of AChE activity was shown after 2 days exposure to 3 x 10(-7) M beta-ecdysone. AChE activity found in the fresh medium is the contribution of the fetal calf serum portion. A direct relationship between levels of serum and the AChE activity in the cultured cells was demonstrated.

Acetylcholinesterase↗
PubMed1981

Successful tumour immunotherapy with cimetidine in mice.

Cimetidine significantly slowed metastatic development and prolonged survival in tumour-bearing mice, in association with inactivation of suppressor cells. Pharmacological blockade of the suppressor cell system may represent a new strategy for successful immunotherapy of human neoplasia.

Animals↗
PubMed1981

Cell surface labeling of embryonic neural retina cells exposed to low temperature, energy inhibitors, cytochalasin B and colchicin.

Large blebs devoid of receptors for hemocyanin-labeled concanavalin A appear on neural retina cells from 8-day chick embryos exposed to low temperature or to potassium cyanide or 2,4(alpha)-dinitrophenol at room temperature. Labeling with mixed antibodies against a crude retina membrane preparation and with goat anti-rabbit-hemocyanin conjugate showed the same results. Determination of cell ATP content indicated a drop in ATP concentration after exposure to low temperature or to respiration inhibitors. Disruption of microtubules by colchicin inhibited the formation of 'naked' large blebs, whereas cytochalasin B had no such inhibitory effect.

2,4-Dinitrophenol↗
PubMed1981

A quantitative determination for the detection of immunoglobulin (IgG) on the surface of platelets.

A sensitive method for the quantitation of IgG on platelets had not been demonstrated until 1975, when Dixon, Rosse, and Ebbert described a quantitative antiglobulin consumption test useful in detecting platelet associated IgG (N Engl J Med 292:230, 1975). A modification of that technique has rendered the assay reproducible and removed the need for daily repetition of a standard IgG titration curve for quantitation. This modification utilizes 1-ethyl-3-3(dimethylaminopropyl)carbodiimide HCl (ECDI) (Sigma, E-7750), in place of chromic chloride, as a coupling agent for attaching IgG (Miles 64-145) to sheep cells (SRC), used as indicator cells. The ECDI consistently couples IgG to SRC and does not subject the SRC to sporadic spontaneous lysis, as does chromic chloride. This modification permits the detection of IgG on platelets (Direct Test), or in sera (Indirect Test) by incubation of a washed platelet pool with sera in vitro, and testing as in the Direct Test. Normal values of 0.01-1.56 and 0.14-1.6 femtograms (F) per platelet have been obtained for the Direct and Indirect Tests, respectively. In six cases of suspected ITP, values ranged 12.0-221.0 F and 2.9-37.6 F for the Direct and Indirect Tests, respectively. In conclusion, in disease states or other abnormal situations, quantities of IgG can be detected that are not usually present on the platelets of normal subjects.

Blood Platelets↗