Donald H. Ford

THE UPTAKE OF DL-LYSINE-H3 INTO THE NERVOUS SYSTEM AS COMPARED WITH OTHER TISSUES IN EUTHYROID AND DYSTHYROIDAL MALE RATS,

Abstract : In two separate experiments it was shown that DLLysine-H3 uptake is lower in hyperthyroid rats and higher in hypothyroid animals than normal. This is believed to be largely due to metabolic considerations which effect the turnover rate of amino acids in brain and tissue proteins rather than being related to an increase or decrease in the synthesis of the total amount of protein. It was observed that the brain reacted to variations in thyroid state of the animal in a manner comparable to other tissues. A method is described whereby one can study the uptake of lysine and presumably other amino acids into nerve cells. With lysine, enough labeled amino acid entered the cells to permit chromatographic identification of the injected material as well as quantitative counting by liquid scintillation procedures. Uptake of lysine into the ventral horn motor neurons of the spinal cord was 25 to 30 times higher than was observed in the ventral horn tissue as a whole. Thus, the total uptake in a region of mixed nerve cells, supporting tissues and nerve fibers reflects only the uptake in a heterogenous tissue where a relatively high concentration of amino acid uptake by nerve cells is camouflaged by the relatively low uptake in vascular and glial tissue. (Author)

Localization of methadone in fetal rat eye by the immunofluorescence technic.

Abstract The eyes of 28 adult methadone tolerant rats and of 56 rat neonates delivered from an additional nine methadone tolerant mothers were examined by the fluorescent antibody technic using specific methadone antiserum. Positive retinal fluorescence was seen in 32% of the neonates but was not observed in any of the adults. These findings suggest that the retinal cells of neonatal rats are still sufficiently undifferentiated so as to retain the fundamentally neural ability to bind opiates.

The effect of multiple exposure to high pressure oxygen on the accumulation of [3H]lysine into spinal cord grey matter, retina and various types of neurons

Abstract Male Wistar strain rats were subjected to repeated exposures to oxygen at high pressure (OHP) at 3 atm absolute for 1 hr each day for 10 days. They were then injected with [3H] dl -lysine while in the awakened state through indwelling intravenous cannulas and compared with appropriate controls in relation to [3H]lysine accumulation in plasma, retina, spinal cord grey matter, Purkinje cells, ventral horn motor neurons and in dorsal root ganglia and supraoptic neurons. Accumulation of lysine into blocks of tissue was depressed in retina, whole dorsal root ganglia and spinal cord grey matter, but not in Purkinje cells or ventral horn motor neurons. Accumulation was depressed in cells of the dorsal root ganglia, but elevated in the cells of the supraoptic nucleus. These variations would seem to represent regional differences in response to OHP.

[131I]Triiodothyronine transport into rat cerebral cortex slices☆

Abstract As a result of a previous investigation where X-irradiation depressed T 3 accumulation into the rat CNS in a manner which suggested an effect on an enzyme transport system for the hormone, this series of experiments was initiated to determine if there might be any specific evidence for active transport of the hormone into tissue. All the results obtained on increased T 3 accumulation into cortex slices with increasing periods of incubation, the effects of altering substrate concentration or of changing pH could as well be said to relate to active as to the commonly accepted passive mode of transport. However, the inhibition of hormone uptake in the presence of CN − , ouabain and 2,4-DNP suggested an energy-dependent system in which ATP and cytochrome oxidase are involved. Further, the dependence of hormone accumulation in brain slices on Na + is comparable to that observed for amino-acids, which are known to be actively transported. Finally, the slight inhibition of T 3 accumulation in the presence of tyrosine or when slices were incubated in an unoxygenated media or at 0°C strongly suggest that at least a part of the accumulation of [ 131 ]T 3 into rat cerebral cortex slices in vitro is activity mediated. Anatomical studies on incubated rat cerebral cortex slices indicate that marked structural changes in neurons occur very quickly with disruption of membranes occurring after 60 min incubation. Thus, if transport mechanisms are to be studied by such in vitro procedures, they should be limited to the shorter periods (30 min) wherein the neuronal cell membranes remain intact.

HORMONAL PROTECTION OF RATS BREATHING OXYGEN AT HIGH PRESSURE1,2

Sex differences in susceptibility to high pressure oxygen (OHP)‐induced convulsions were observed in mature rats. Male rats convulsed significantly earlier than did females. After adrenalectomy, seizures disappeared in most females and some male rats. The number of adrenalectomized male rats which resisted OHP‐induced convulsions increased from 40 % to 91 % when they were treated with estradiol subcutaneously. Rats which do not convulse during the exposure to OHP eventually develop pulmonary edema and congestion and die. Strain variations in respect to susceptibility to oxygen poisoning and the contreversal nature of OHP and electroshock‐induced convulsions in response to steroid hormones are discussed.