Rat strain differences in response to dark pulse triggering of paradoxical sleep

Previous studies of inbred rats have shown that Brown Norway (BN) rats had more daily paradoxical sleep (PS) than Lewis (L) rats, while F1 progeny had intermediate amounts, suggesting codominant or polygenic transmission. Amount of PS and the induction of PS episodes may be under separate genetic control. Earlier work had shown that five-minute exposures to cage lights-off every half-hour can trigger PS in outbred albino strains. To explore the genetic controls for PS induction, PS triggering by dark pulse stimulation was examined in L and BN rats. L rats showed a five-fold increase in PS during dark pulse stimulation. Although, as in the earlier study, BN rats had more total daily PS than L rats, they exhibited no dark pulse triggering of PS. Thus L and BN rats show significant strain differences in two independent parameters of PS, and may be a useful model for studying genetic and neurologic factors which regulate PS.

O6-methylguanine-DNA methyltransferase activity and sensitivity to N-methyl-N'-nitro-nitrosoguanidine during human T-lymphocyte differentiation

The activity of O6-methylguanine-DNA methyltransferase (MT) was assayed in various human lymphoid cell populations. It was found that during T-cell differentiation the activity of MT increased from 7000 MT molecules in thymocytes to 31,000 MT molecules in mature T-lymphocytes. The number of MT molecules also increased 2- to 3-fold in the course of the cell division cycle but the specific activity of MT did not change significantly. T-cell tumors and T-cell lines contained a higher number of MT molecules (70,000-125,000 molecules/cell) compared to normal T-lymphocytes. The sensitivities of various lymphoid cells to the DNA methylating agent N-methyl-N'-nitro-N-nitrosoguanidine correlated well with MT activities observed in cell extracts.

Characterization of mouse lymphoma cells with altered nucleoside transport

A mutant clone (NT-1) of a T-cell lymphoma was selected for its ability to grow in HAT medium (hypoxanthine, aminopterin and thymidine) in the presence of the nucleoside transport inhibitor P-nitrobenzyl-6-mercaptoinosine (NBMI). NT-1 cells contain half the number of NBMI binding sites present on the parental S49 cells and are partially able to transport nucleosides in the presence of the transport inhibitor (NBMI). These observations suggest that the mutant cells are heterozygous for nucleoside transport proteins and contain two types of transport proteins: the first protein can both bind and is inhibited by NBMI similar to the wild type phenotype, and the second is an altered protein. The altered transport protein apparently lost its NBMI binding sites without a parallel loss of nucleoside transport ability suggesting that the nucleoside transported sites are separate from the binding sites of the transport inhibitor.

Mineral contents of selected pre-prepared food sampled in a hospital food service line

Twenty-four pre-prepared foods sampled as served at the VA hospital in Tacoma, Washington, were analyzed for contents of nine minerals (sodium, potassium, magnesium, calcium, iron, copper, zinc, manganese, and phosphorus). Samples were taken at three different times during the menu cycle. There were significant differences among the three monthly sampling times for nearly all minerals. Variation by month was partly attributed to varying proportions of food components in mixed food samples received in the food service line and to different manufacturers, food lots, and sources of raw materials. Two prepared foods labeled "low-sodium" contained 36 to 43 percent as much sodium as the comparable "regular" foods.

Recognition of lysozyme by lymphocyte subsets

Extensive studies with antisera from a variety of animals have failed to detect any cross-reactivity between egg white lysozyme and its reduced, S-carboxymethylated (CM-) derivative. In contrast, a number of studies addressing the specificity of T lymphocytes have revealed that these two forms of lysozyme cross-react rather extensively at that level. Preliminary attempts to eliminate this latter cross-reactivity by further denaturation and/or chemical modification have so far proven unsuccessful. In a second line of experimentation the response to CM-lysozyme of mice which are genetically unresponsive to native lysozyme was assessed and found deficient. The implications of these findings are discussed.

Immune plasma-dependent cytotoxicity of immune and non-immune peripheral lymphoid cells for target cells coated with bacterial outer unit membrane

The development of a model system for use in the study of lymphoid cell cytotoxicity to bacterial membrane antigens was attempted. In this system 51 Cr-labelled chicken red blood target cells were coated with pieces of the outer unit membrane of leptospirae rather than with soluble antigens. Using the model system to study dog peripheral immune lymphoid cell cytotoxicity to coated target cells we found that both immune and non-immune lymphocytes are antibody dependent for the expression of their cytotoxicity. It was also found that the unit membrane preparation from leptospirae can serve as a good antigenic stimulant to immune dog lymphoid cells as measured by increased [3H]thymidine uptake.