The mode of morphine uptake into brain slices

Teller, David N.; Guzman, T. De; Lajtha, Ábel

doi:10.1016/0006-8993(74)90809-9

Cited by 18 publications

(2 citation statements)

References 16 publications

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“…The hydrolysates were then taken up in a small amount of water and put on the amino acid analyser. One part of the tyrosine peak from the analyser was used for the determination of the amount of tyrosine with ninhydrin and another for the determination of radioactivity in a scintillation spectrometer (Teller et al, 1974). The changes in the specific radioactivity (d.p.m./pmol) of proteinbound tyrosine in relation to the average specific radioactivity of free tyrosine in brain in each time interval were used to estimate metabolic rates.…”

Section: Measurement Of Incorporation Of ['4c]tyrosinementioning

confidence: 99%

Turnover of myelin proteins in mouse brain in vivo

Lajtha¹,

Tóth²,

Fujimoto³

et al. 1977

Biochemical Journal

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The incorporation of tyrosine into proteins was measured after the subcutaneous implantation of a pellet of [14C]tyrosine in mice. This method keeps the specific radioactivity of free tyrosine fairly constant and makes it possible to follow incorporation up to a 10-day period. At the end of 10 days most of the protein-bound tyrosine was replaced (i.e. most protein turned over) in lung, liver, heart, kidney and spleen; about half was replaced in brain, one-quarter in muscle. The rate of protein turnover in myelin was approx. 40% of that of whole brain proteins; at 10 days one-fifth of the myelin proteins were replaced. All protein components of myelin measured were in a dynamic state; incorporation decreased in the following order, Wolfgram greater than DM-20 greater than basic greater than proteolipid proteins. The incorporation of tyrosine into each protein fraction was greater in the 0-5-day than in the 5-10-day period, indicating heterogeneity of metabolic rates. The results show that after myelination at least a portion of each protein component of myelin is undergoing significant metabolic turnover. In the adult, myelin components are not stable, but turnover is heterogeneous, and each protein may be compartmentalized. Turnover can be influenced by a variety of factors.

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Section: Measurement Of Incorporation Of ['4c]tyrosinementioning

confidence: 99%

Turnover of myelin proteins in mouse brain in vivo

Lajtha¹,

Tóth²,

Fujimoto³

et al. 1977

Biochemical Journal

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“…The final tissue pellet was dissolved in 5 ml of 0.2N NaOH. The protein content ofthis solution was determined (Lowry, Rosehrough, Farr, and Randall, 1951), and its radioactivity was measured in a scintillation counter (Teller, DeGuzman, and Lajtha, 1974). The lysine content in the feeding medium was determined in an amino-acid analyzer.…”

Section: Methodsmentioning

confidence: 99%

The effect of amino acids on protein metabolism as measured in long‐term experiments in immature brain explants

et al. 1978

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In a study of a system suitable for investigating long-term effects on brain protein metabolism, we measured amino-acid incorpration into isolated immature brain explants incubated under sterile conditions up to ten days. Measurements of changes in total proteins, total DNA, cell number during the experiments, and 14C-thymidine incorporation measurements indicated no significant net growth; new cell formation was below 5% in a 5-day period; therefore, amino-acid incorporation was mainly due to protein turnover. The rate of incorporation in our immature brain preparation was similar to that of the adult brain in vivo: by ten days about one-half of the tissue protein turned over. The label incorporated was released in subsequent incubations with cold amino acids. Such release occurred in all subcellular fractions examined. Incorporation was fairly stable; at temperatures below 30 degrees C it rapidly declined, but it was not affected when phenylalanine or the branched chain amino acids (leucine, isoleucine, valine) were elevated in the incubation medium. Brief exposure to low amino-acid media had no effect; longer exposure resulted in tissue damage. Our model system indicates that overall brain protein turnover is not sensitive to such variations in the level of most amino acids, which may occur under various conditions. Protein metabolism of the nervous system occurs at a high rate. A recent long-term labeling method (Lajtha, Latzkovits, and Toth, 1976) gave a best fit to incorporation curves by assuming two compartments for adult brain proteins, one of which (about 6%) has a half-life of 15 hr and the other (94%) has a half-life of ten days. The disappearance of protein-bound label with time under conditions in which all proteins were previously labeled indicated that most, possibly all, proteins in brain are in a dynamic state (Lajtha and Toth, 1966). Incorporation of amino acids was found in all proteins and structures that have been studied to date; myelin proteins previously thought less active are also metabolized at a significant rate (Sabri, Bone, and Davison, 1974; Lajtha, Toth, Fujimoto, and Agrawal, 1977). We have fairly extensive information available in addition to turnover studies about the mechanisms of protein synthesis in brain (Roberts, 1971); protein breakdown was also studied in some detail (Marks and Lajtha, 1971). In contrast to our knowledge about protein metabolism under physiological equilibrium conditions, our information about alterations during functional demands or pathological conditions is scanty. Although a significant amount of work has been reported, largely because of technical difficulties the results are difficult to interpret unequivocally. The present report represents our effort to address some of the obstacles: to develop a system in which influences on long-term incorporation can be studied...

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Cerebral uptake of nicotine and of amino acids

Sershen

Lajtha

1979

J of Neuroscience Research

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Nicotine is among the compounds that enter the brain very rapidly (blood-flow-limited). It also leaves the brain rapidly; by five minutes, 90% exits, an exit somewhat slower than that of water. In spite of rapid exit, brain levels remain higher than levels in blood over a wide range of blood concentrations. Nicotine enters the fetal circulation from the maternal blood; it enters fetal brain but to a smaller extent than adult brain. Nicotine entry is different from that of amino acid: No interaction of amino acid transport and nicotine could be detected. Most close analogs have no effect on nicotine uptake, but at higher concentrations nicotine uptake is saturable. Nicotine and morphine mutually inhibit each other's uptake. The results suggest an uptake compartment (lipid space) for nicotine shared by morphine.

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The mode of morphine uptake into brain slices

Cited by 18 publications

References 16 publications

Turnover of myelin proteins in mouse brain in vivo

Turnover of myelin proteins in mouse brain in vivo

The effect of amino acids on protein metabolism as measured in long‐term experiments in immature brain explants

Cerebral uptake of nicotine and of amino acids

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