Expression of {beta}-galactoside {alpha}2,6-sialyltransferase does not alter the susceptibility of human colon cancer cells to NK-mediated cell lysis

The extent of processing of N-linked oligosaccharides and thesialylation of the target cell membranes has been positivelycorrelated with resistance to lysis mediated by NK cells, buta conclusive evidence has never been reached. Colon cancer tissuesexpress an increased activity of ß-ga-lactoside     

Iron supplementation moderates but does not cure the Belgrade anemia

Belgrade rats inherit microcytic, hypochromic anemia as an autosomalrecessive trait (gene symbol b). Erythrocytes and tissue are iron deficientin the face of elevated TIBC (total iron binding capacity) and percent ironsaturation; iron injections increased the number of erythrocytes but theirappearance remained abnormal. We have investigated iron supplements toimprove husbandry of b/b rats and to learn more about the underlying defectand its tissue distribution. Weekly IM (intramuscular) injections ofiron–dextran (Imferon at 30 mg kg) improved the anemia but did not alter thered cell morphology. Certain diets also improved the health of b/b rats whencompared to standard rat chows by the criteria of weight, survival toadulthood, hematology and reproduction. The critical nutritional factorturned out to be iron bioavailability, with ferrous iron added to the dietimproving the health of Belgrade rats without affecting the underlyingerythroid defect. Tissue iron measurements after dietary or parenteralsupplementation confirmed the iron deficient status of untreated b/b rats andestablished that dietary ferrous iron partially relieved this deficiency,with injections leading to greater amounts of tissue iron. Serum iron andTIBC were also found to be elevated in untreated b/b rats, with dietarysupplementation decreasing but not eliminating the elevation in TIBC. Thesestudies indicate that iron supplements can improve the health of b/b ratswithout altering the underlying defect and also suggest that the mutationcould alter iron uptake in the GI (gastrointestinal) tract.     

A comparison of some pharmacological actions of prostaglandin E1, 6-oxo-PGE1 and PGI2

Some pharmacological actions of prostaglandin E1 (PGE1), 6-oxo-PGE1 and PGI2 have been studied. 6-oxo-PGE1 and PGE1 relaxed guinea-pig tracheal muscle in vitro and increased nasal patency in normal volunteers and in subjects with vasomotor rhinitis whereas PGI2 produced opposite effects. All three compounds produced bronchodilatation in the anaesthetised guinea-pig and relaxed human respiratory tract muscle in vitro. PGI2 was several times more potent than either 6-oxo-PGE1 or PGE1 against ADP-induced aggregation of human and baboon platelets in vitro. Intravenous 6-oxo-PGE1 in the baboon caused an ex vivo inhibition of platelet aggregation, but the EC50 was 7.7 times that of PGI2. As a vasodepressor in the baboon 6-oxo-PGE1 and PGI2 were equipotent. Thus with the exception of the vasodepressor effect, the actions of 6-oxo-PGE1 qualitatively and quantitatively resembled those of the structurally related PGE1 rather than those of PGI2.     

Formation of trichothecenes by Fusarium solani var. coeruleum and Fusarium sambucinum in potatoes.

Fusarium solani var. coeruleum can form deoxynivalenol in potato tubers and in liquid medium, although concentrations observed in the rot were highly variable; acetyldeoxynivalenol and HT-2 toxin were detected in 1 to 3 tubers only (of 57). Trichothecenes were also detected in a very few (3 of 20) cultures of Fusarium sambucinum in potato tubers.     

A male-specific DNA probe detects heterochromatin sequences in a familial Yq- chromosome.

Using a recombinant DNA probe, we have demonstrated the presence of residual 3.4-kilobase (kb) repeat sequences in a family with a Yq- chromosome. The heterochromatin of this Y variant was not readily detectable with conventional chromosome-banding techniques. These data suggest that the breakpoint of the deletion occurs at the heterochromatin region proximal to the euchromatin/heterochromatin junction.     

Differential uptake of liposomes varying in size and lipid composition by parenchymal and kupffer cells of mouse liver

Using liposomes differing in size and lipid composition, we have studied the uptake characteristics of the liver parenchymal and Kupffer cells. Desferal labeled with iron-59 was chosen as a radiomarker for the liposomal content, because Desferal in its free form does not cross cellular membranes. At various time intervals after an intravenous injection of liposomes into mice, the liver was perfused with collagenase, and the cells were separated in a Percoll gradient. It was found that large multilamellar liposomes (diameter of about 0.5 μm) were mainly taken up by the Kupffer cells. For these large liposomes, the rate of uptake by Kupffer cells was rapid, with maximum uptake at around 2 hours after liposome injection. Unexpectedly, small unilamellar liposomes (diameter of about 0.08 μm) were less effectively taken up by Kupffer cells, and the rate of uptake was slow, with a maximum uptake at about 10 hours after liposome injection. In contrast, parenchymal cells were more effective in taking up small liposomes and the uptake of large liposomes was negligible. In addition, liposomes made with a galactolipid as part of the lipid constituents appeared to have higher affinity to parenchymal cells than liposomes made without the galactolipid. These findings should be of importance in designing suitable liposomes for drug targeting.     

Partitioning of electrostatic and conformational contributions in the redox reactions of modified cytochromes c

The reduction of acetylated, fully succinylated and dicarboxymethyl horse cytochromes c by the radicals CH₃CH(OH), CO₂, O₂, and e⁻_aq′ and the oxidation of the reduced cytochrome c derivatives by Fe(CN)³⁻₆ were studied using the pulse radiolysis technique. Many of the reactions were also examined as a function of ionic strength. By obtaining rate constants for the reactions of differently charged small molecules redox agents with the differently charged cytochrome c derivatives at both zero ionic strength and infinite ionic strength, electrostatic and conformational contributions to the electron transfer mechanism were effectively partitioned from each other in some cases. In regard to cytochrome c electron transfer mechanism, the results, especially those for which conformational influences predominate, are supportive of the electron being transferred in the heme edge region.     

Spin-label studies of membrane-associated denatured hemoglobin in normal and sickle cells

A maleimide spin label (N-(1-oxyl-2,2,5,5-tetramethylpyrrolidinyl)-maleimide) was reacted with oxyhemoglobin-free cell stromata of normal and sickle cells. The EPR spectrum of spin-labeled red cell membranes showed that the spin labels are attached to at least two different binding sites. There was a major signal, A, which characterized a strongly immobilized environment and a minor signal, B, which characterized a weakly immobilized environment. Quantitative EPR measurements using equal amounts of Hb AA and Hb SS red blood cells demonstrated that Hb SS red cell membranes had an approximately four times higher EPR signal intensity than Hb AA red cell membranes ((7.98 ± 1.14) · 10⁵ and (2.2 ± 1.2) · 10⁵ spin labels/cell, respectively). Moreover, the ratio of signal intensities A and B are different in these cells. Comparative spectrophotometric studies of membrane-associated denatured hemoglobins of Hb AA and Hb SS red cell membranes suggested that the EPR signal A is derived from spin labels attached to membrane-associated denatured hemoglobin, while signal B is mainly from spin labels attached to membrane-associated denatured hemoglobin, while signal B is mainly from spin labels attached to membranes. The combination of EPR spectrum of Hb AA membranes pretreated with N-ethyl-maleimide and that of spin-labeled precipitated hemoglobin further strengthened this conclusion.     

In vitro differentiation of B lymphocytes from pre-B cells.

Adult bone marrow contains both B lymphocytes and their immediate precursors, pre-B cells. These two cells differ in size and can be separated by velocity sedimentation; B cells are enriched in the subpopulation of cells sedimenting at between 2.0 and 3.5 mm/hr and pre-B cells in the subpopulation between 5.0 and 7.0 mm/hr. Incubation of pre-B cells in vitro for 4 or 5 days leads to their differentiation into functional B lymphocytes. The transition form pre-B to B appears to occur in two steps. The first step gives mitogen responsive B cells with an intermediate sedimentation velocity and the second step produces typical small, slowly sedimenting B cells. Pre-B cells can be quantified by using a limiting dilution assay and occur at a frequency of 1/60 in the subpopulation of rapidly sedimenting bone marrow cells.