Changes in catecholamine excretion after short-term tyrosine ingestion in normally fed human subjects

The effects of ingesting the aromatic amino acid L-tyrosine on excretion of unconjugated catecholamines (dopamine, norepinephrine, and epinephrine) and tyrosine were studied. (Tyrosine is the circulating precursor for the catecholamines, but only a small fraction of the tyrosine in the body is utilized for catecholamine synthesis.) In 10 of 11 normal volunteer subjects, ingestion of 100 mg/kg tyrosine (in three divided doses, preceding each meal, between 8 AM and 5 PM) for 1 day increased the 24-h excretions of total catecholamines by 25%. Only 0.42% of the tyrosine dose was excreted unchanged, but this was sufficient to increase urinary tyrosine by 138%. Both tyrosine and catecholamine excretions varied diurnally; 60% or more of the total output occurred during the day. Since urinary catecholamines reflect molecules synthesized outside the central nervous system, these findings indicate that tyrosine administration can accelerate catecholamine synthesis in the human sympathoadrenal system, probably by enhancing saturation of tyrosine hydroxylase. Therefore, tyrosine may be useful therapeutically in diseases characterized by peripheral catecholamine deficiencies.

[Daily rhythms of melatonin in pineal, serum and urine of rats (author's transl)]

The levels of melatonin in urine, serum, and pineals were determined in rats during the light/dark cycle. Previous to the radioimmunoassay, melatonin was isolated using a new ascending chromatographic method with programmed multiple development. The daily excretion of melatonin and its serum levels showed a characteristic rhythm, night samples containing several times more melatonin than those of the light period. The pineal content of melatonin of animals killed at different intervals also showed a similar day/night rhythm. The chromatographic method used gave a perfect separation of melatonin from other materials which could interfere in the assay. The mobility of material detected by RIA was identical to that of authentic melatonin chromatographed concurrently.

Tyrosine loading enhances catecholamine excretion by rats

Tyrosine administration to rats causes dose-related increases in urinary catecholamine levels without reducing tissue catecholamines. Pretreatment with carbidopa, a peripheral inhibitor of aromatic-L-amino acid decarboxylase, reduces basal urinary catecholamine levels and blocks of urinary catecholamine increases caused by tyrosine administration or cold exposure. DOPA excretion, which is usually undetectable by our methods, becomes significant after carbidopa, and rises a further four-fold when rats are also given tyrosine. These observations suggest that tyrosine availability can affect both catecholamine synthesis in and release from the sympathoadrenal apparatus.

Alkylating nucleosides 1. Synthesis and cytostatic activity of N-glycosyl(halomethyl)-1,2,3-triazoles. A new type of alkylating agent

1,3-Dipolar cycloaddition of benzyl azide or peracetylated glucopyranosyl azides to propargyl halides or 1,4-dihalobutynes yielded 1-benzyl- or 1-glycosyl(halomethyl)-1,2,3-triazoles. Alkylating chloromethyl- bromomethyl- and iodomethyl-1,2,3-triazoles were also obtained from the corresponding hydroxymethyl derivatives by treatment with (C6H5)3P/CCl4, (C6H5O)3P/Br2, and (C6H5O)3P/I2, respectively. 1-Benzyl-4-(fluoromethyl)-1,2,3-triazole was obtained from 1-benzyl-4-(bromomethyl)-1,2,3-triazole by treatment with KF and 18-crown-6. Chloromethyl-, bromomethyl-, and iodomethyl-1,2,3-triazole derivatives inhibited the "in vitro" growth of HeLa cells. Some of these compounds increased the life span of mice bearing tumors.

Lactate dehydrogenase isoenzymes of the hypothalamus, limbic structures, and the anterior pituitary during the estrous cycle

Lactate dehydrogenase (LDH) and its isoenzyme (ISO) pattern were measured in the hypothalamus (HYP), amygdala (AMYG), hippocampus (HIP), cerebral cortex and anterior pituitary (PIT) of adult female rats sacrificed at different estrous cycle phases. The HYP, the AMYG and the PIT showed their maximal LDH values at proestrus and the lowest at diestrus. Those of the HIP showed the opposite pattern. The study of the ISO distribution pattern indicated that the cyclic variations of pituitary LDH activity were mainly due to changes of the ISO rich in A subunits, while in the B type they remained constant. By contrast, the cyclic changes of total LDH activity of all the brain structures studied were due to well balanced variations of both A and B subunits.

Antiandrogenic effects of the pineal gland and melatonin in castrated and intact prepubertal male rats

In castrated prepubertal rats, pinealectomy enhanced the testosterone-induced growth response of the seminal vesicles and melatonin inhibited this effect in a dose-related manner. In entire animals, the serum concentration of LH was increased after pinealectomy with no significant changes in other parameters. Administration of melatonin to intact, pinealectomized rats did not affect the serum concentrations of LH or testosterone but caused a dose-related decrease in the weight of the seminal vesicles. The highest dose of melatonin tested reduced the weight of the ventral prostate gland and the uptake of radioactivity by both the ventral prostate gland and the testes after injection of [5-3H]uridine. It is suggested that the pineal gland and melatonin may exert an antagonistic effect on the biological activity of androgens administered to castrated rats and that melatonin can reduce the growth of the accessory sex organs of intact, pinealectomized rats, in spite of a high concentration of LH in the serum. The well-known inhibitory influence of systemically administered melatonin on the accessory sex organs in male rats may be due to its antagonistic effect at a peripheral level.

Increase in pituitary levels of luteinizing hormone and follicle-stimulating hormone after pinealectomy in both intact and castrated male rats

Twenty-eight-day-old male Wistar rats were pinealectomized and/or castrated. Animals were killed 26 days later and anterior pituitaries were dissected out, weighed, and their content of LH and FSH measured by RIA. Pinealectomized rats showed higher body weights than sham-operated animals, which suggests an inhibitory influence of the pineal on growth. The weights of pituitaries were increased by both pinealectomy and castration. However, in pinealectomized rats, but not in castrated, the elevated pituitary weights seemed to be due to the high body weights of those animals. The pituitary content and concentration of LH and the content of FSH were increased by pinealectomy in both intact and castrated rats. This finding may suggest that the pineal gland exerts an inhibitory action on the hypothalamic-pituitary axis that seems to be independent of the testicular function.

Melatonin secretion decreases during the proestrous stage of the rat estrous cycle

Urine was collected from rats during 12 consecutive daily dark periods and assayed for melatonin and norepinephrine; the phase of the vaginal estrous cycle associated with each urine sample was determined from daily vaginal smears. The proestrous phase of the estrous cycle was consistently associated with significant reductions in the excretions of both compounds. The level of melatonin in any urine sample tended to vary as a function of its norepinephrine content; however, the slope of the curve relating these two compounds in metestrous-diestrous samples differed from that for proestrous-estrous specimens. This difference suggests that factors other than the catecholamine (e.g., gonadal hormones) also affect melatonin secretion. Oophorectomy elevated the melatonin concentration of serum but not that of the pineal; this rise was suppressed by the administration of estrogen plus progesterone. The fate of circulating melatonin (as indicated by the proportion of an exogenous dose excreted into the urine) was not affected by the state of the estrous cycle.

Study of penicillin antibodies by fluorescence polarization and immunodiffusion

1. Antibodies prepared in the rabbit to penicilloyl-rabbit serum albumin or to penicilloyl-bovine serum albumin were demonstrated by immunodiffusion and absorption methods to be apparently directed exclusively against the penicilloyl moiety. The antibodies could precipitate heavily substituted penicilloyl polylysine, as well as each other, with "reactions of identity". All could mutually deplete detectable antibodies by cross-absorption. 2. Small haptens containing both fluorescein and the penicilloyl group were synthesized. They were also capable of completely absorbing the antipenicilloyl antibodies from rabbit antiserum, as evidenced by immunodiffusion tests. The haptens were used in fluorescence polarization tests with gamma globulin from normal and immunized rabbits, and from normal and allergic humans. The rabbit antipenicilloyl gamma globulins in concentrations as low as 5 to 10 microg of protein/ml could significantly increase the polarization of the haptens. Normal gamma globulin had no effect at the highest concentrations tested, 1200 microg/ml. In all tests, rabbit and human antibody reacted similarly. 3. Fluorescence polarization titration curves for both human and rabbit antipenicilloyl gamma globulins were analyzed by computer and the antibody concentrations, avidities, and heterogeneity constants were determined. For the human antibody, the latter two values were 3.0 x 10(7)M(-1) and 0.78, while for the rabbit, they were 8.7 x 10(6)M(-1) and 0.71. The data were employed to estimate the limit of sensitivity of fluorescence polarization for detecting antipenicilloyl antibodies. Under the conditions employed, this value was roughly 0.4 microg antibody/ml. 4. When the whole rabbit sera were tested for penicilloyl antibodies by fluorescence polarization, both normal (preimmune) and immune sera revealed striking and equivalent increases in polarization with the penicilloyl haptens. This non-specific binding was shown to be due at least in part to serum albumin. Indications were obtained that it might be significantly reduced by increasing the pH or the salt concentration of the medium, or by addition of certain anions.