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Biomedical subjects

N Cohen

Publications and source records attributed to N Cohen.

At least 379 records · Page 21Linked to original sources
PubMed1976

Biological effects of the enhanced excretion of zinc after calcium diethylenetriaminepentaacetate chelation therapy.

An enhanced, uncompensated excretion of zinc may be responsible for unwanted side-effects that could develop after prolonged chelation therapy with calcium diethylenetriaminepentaacetate (Ca-DTPA). As a preliminary means of defining "potential toxicity" within this hypothesis, the "normal" concentration range of Zn++ excreted in the urine of three adult female baboons was measured on a daily basis; changes in urinary Zn++ excretion were then quantitated as a function of the injection time and dose of the chelating agent Na3(Ca-DTPA) originally administered to enhance the excretion of 241Am from the body. In addition, the inhibitory action of the chelator compound on the activity of a specific metalloenzyme system, erythrocytic aminolevulinic acid dehydratase (ALAD), which requires Zn++ as a co-factor, has been determined as a measure of a specific biological effect. It was found that whenever the concentration of Zn++ in urine was above 2 mug/ml (or greater than approximately four times the "normal" urinary excretion level), the activity of ALAD dropped below 250 nmol PBG/ml RBC/hr or approximately one-half the mean "normal" activity value for this primate species.

Animals↗
PubMed1976

Folic acid absorption in regional enteritis.

The authors have investigated intestinal absorption of folic acid by jejunal perfusion with a triple lumen tube in five subjects with regional enteritis. The subjects' intestinal disabilities ranged from terminal ileitis to short bowel syndrome. Two had steatorrhea and two had low serum folate levels. Absorption of pteroylglutamic acid was normal in all five. This suggests that folic acid deficiency, common in this disorder, is largely caused by malnutrition, not malabsorption.

Adult↗
PubMed1975

Dinoflagellate ribosomal RNA; an evolutionary relic?

The apparent molecular weights of the rRNA subunits of the dinoflagellate Peridinium cinctum fa. westii were determined by polyacrylamide gel electrophoresis to obtain an indication of its evolutionary status. The apparent molecular weights of the Peridinium light and heavy rRNA subunits were 0.7 and 1.23 X 10(6) respectively. The light rRNA is therefore typically eukaryotic but the heavy rRNA has a significantly lower MW than previously reported for higher eukaryotes which range from 1.3 to 1.75 X 10(6) depending on their evolutionary position. Thus by this criterion Peridinium is similar to red algae and may represent a eukaryotic stage, lower than fungi or green plants.

Biological Evolution↗
PubMed1975

Phylogeny of functional humoral transplantation immunity: comparative studies in amphibians and rodents.

Remarkably comparable observations from parallel experiments in salamanders and mice utilizing three related model systems (implant-induced immunomanipulation; passive transfer; and putative B cell suppression) argue directly that functional humoral transplantation immunity is highly developed at the phylogenetic level of Amphibia and that it plays a major role in regulating graft survival in these species (Fig. 4). Although it is still conjectural whether such humoral immunity and weak H-antigens evolved concurrently, the argument that enhancing atibodies evolved exclusively in viviparous species to protect the fetus from potential rejection by the maternal immune system no longer seems tenable (1).

Animals↗
PubMed1975

Effect of parenteral acetazolamide on intestinal absorption of salt and water in man.

Acetazolamide was administered intravenously during jejunal perfusion of isotonic saline in six subjects. Bicarbonate was present in very low concentration intraluminally and there was net bicarbonate secretion during control and acetazolamide perfusions. Acetazolamide significantly inhibited sodium chloride, and water absorption. As this occurred in the absence of an effect on net bicarbonate secretion, it may have been due to an action other than carbonic anhydrase inhibition.

Acetazolamide↗
PubMed1975

The influence of histocompatibility and antithymocyte serum on the ability of alloantigenic pretreatment to prolong the survival of mouse skin grafts.

Test skin allografts enjoy prolonged survival when alloantigenic pretreatment (implants of small fragments of liver or kidney on the host's kidney cortex) is separated from test grafting by 9 days and donor and host strains differ only at the relatively weak H-3 + H-13 histocompatibility barrier (Baldwin and Cohen 1971, 1974). However, test skin grafts are rejected in an accelerated fashion when this protocol is followed but the donor strains differ at stronger non-H-2 barriers. In 2 such strain combinations in which control first-set grafts are rejected acutely, varying the implant-to-test graft interval, using F-1 mice as implant donors, or varying the sex of the donors and hosts, all failed to prolong test graft SURVIVAL. However, survival of some test grafts was significantly greater following a combined host treatment of alloimplanatation and ATS than it was following either procedure alone. This synergism suggests that across stronger H-barriers, alloantigenic pretreatment does elicit an immunosuppressive component whose effective presence is normally masked by thymus-dependent cell-mediated immunity.

Animals↗