Elevated Monoamine Levels in the Cerebral Hemispheres of Microencephlic Rats Treated Prenatally with Methylazoxymethanol or Cytosine Arabinoside

Abstract: Methylazoxymethanol (MAM) injection to rats on day 15 of gestation caused a significant rise in monoamine concentrations (1.6, 2.0, and 2.8 times the control value for serotonin, norepinephrine, and dopamine, respectively) accompanying a decrease in the brain weight and DNA content in the cerebral hemispheres of the offspring at 3 months of age; in the brain stem, these changes were much smaller. Similar change of monoamine concentrations was observed in cytosine arabinoside-induced microencephaly. The decrease of DNA content and the elevation of monoamine levels were lower with MAM injection on day 15, 13, or 17 of gestation (in that order). Serotonin content of the MAM-treated cerebral hemispheres was already 50% higher than the control immediately after birth. The activity of tryptophan hydroxylase in the MAM-treated cerebrum was 1.6 times the control value, with no change in the brain stem, while the concentration of tryptophan in the brain and plasma was equal to the control value, suggesting an important role played by this enzyme in the elevation of serotonin content. Although the marked decrease of DNA content in the cerebral hemispheres of MAM-treated rats indicates a loss of cerebral cells due to prenatal MAM poisoning, the kind of cells destroyed remain to be studied. That the remaining neurons, axons, and oligodendroglia were intact was suggested by the normal activity of CNPase.     

Effects of Dietary Amino Acids on Brain Amino Acids and Transmitter Amines in Rats with a Portacaval Shunt

The etiologic relationship between disturbances in metabolism of amino acids and amines and hepatic coma was investigated by examining the effects of diets containing various mixtures of amino acids on brain amine metabolism in rats with a portacaval shunt, using a method for simultaneous analysis of amino acids and amines. Rats with a portacaval shunt were fed on four different amino acid compositions with increased amounts of various amino acids suspected to be etiologically related to hepatic coma, such as methionine, phenylalanine, tyrosine, and tryptophan. The animals were killed 4 weeks after operation. During the experimental period, these animals did not become comatose, but exhibited various behavioral abnormalities. Marked increase in the plasma and brain levels of the augmented amino acids, especially methionine and tyrosine, were observed in rats with a portacaval shunt. Brain noradrenaline, dopamine, and serotonin levels were significantly decreased when the brain tyrosine level was increased. These results indicate that in rats with a portacaval shunt the dietary levels of amino acids greatly influence the brain levels of both amino acids and transmitter amines.     

The Biosynthesis of Transfer Ribonucleic Acid in the Developing Rat Brain and in Cultured Glial Cells

Abstract: The biosynthesis of tRNA was investigated in cultured astroglial cells and the 3-day-old rat brain in vivo. In the culture system astrocytes were grown for 19 days and were then exposed to [³H]guanosine for 1.5–7.5 h; 3-day-old rats were injected with [³H]guanosine and were killed 5–45 min later. [³H]tRNA was extracted, partially purified, and hydrolyzed to yield [³H]-guanine and [³H]methyl guanines. The latter were separated from the former by high performance liquid chromatography and their radioactivity determined as a function of the time of exposure to [³H]guanosine. The findings indicate that labeling of astrocyte tRNA continued for 7.5 h and was maximal, relative to total RNA labeling, at 3 h, while in the immature brain tRNAs were maximally labeled at 20 min after [³H]guanosine administration. The labeling pattern of the individual methyl guanines differed considerably between astrocyte and brain tRNAs. Thus, [³H]1-methylguanine represented up to 35% of the total [³H]methyl guanine radioactivity in astrocyte [³H]tRNA, while it became only negligibly labeled in brain [³H]tRNA. Conversely, brain [³H]tRNA contained more [³H]N²-methylguanine than did astrocyte [³H]tRNA. Approximately equal proportions of [³H]7-methylguanine were found in the [³H]tRNAs of both neural systems. The [³H]methylguanine composition of brain [³H]tRNA was followed through several stages of tRNA purification, including benzoylated DEAE-cellulose and reverse phase chromatography (RPC-5), and differences were found between the [³H]methylguanine composition of RPC-5 fractions containing, respectively, tRNA^lys and tRNA^phe. The overall results of this study suggest that developing brain cells biosynthesize their particular complement of tRNAs actively and in a cell-specific manner, as attested by the significant differences in the labeling rates of their methylated guanines. The notion is advanced that cell-specific tRNA modifications may be a prerequisite for the successful synthesis of cell-specific neural proteins.     

Repair of damage by ultraviolet radiation in xeroderma pigmentosum cell strains of complementation groups E and F

The xeroderma pigmentosum fibroblast strains XP2RO, complementation group E, and XP23OS, group F, were compared with normal human primary fibroblasts with regard to repair of damage induced by 254-nm UV. In XP2RO cells, repair DNA synthesis, measured by autoradiography (unscheduled DNA synthesis = UDS), was about 50% of the value found in normal human cells. In these cells also the removal of UV-induced sites recognized by a specific UV-endonuclease proceeds at a reduced rate. By having BUdR incorporated into the repaired regions, followed by the induction of breaks in these patches by 313-nm UV, it was shown that the reduced repair synthesis is not caused by a shorter length of the repair regions in XP2RO, but is solely due to a reduction in the number of sites removed by excision repair. In XP23OS a discrepancy was observed between the level of UDS, which was about 10% of the normal value, and other repair-dependent properties such as UV survival, host-cell reactivation and removal of UV-endonuclease-susceptible sites, which were less reduced than could be expected from the UDS level. However, when UDS was followed over a longer period than the 2 or 3 h normally used in UDS analysis, it appeared that in XP23OS cells, the rate of UDS remained constant whereas the rate decreased in normal control cells. Consequently, the residual level of UDS varies with the period over which it is studied.     

Ein neues germacran-8.12-olid und neue diterpene aus Polymnia canadensis

The aerial parts of P. canadensis afforded a new germacran-8,12-olide and several diterpenic acids. The stereochemistry of the lactone could be established only by careful ¹H NMR investigations of the corresponding pyrazolines formed by addition of diazomethane, while the natural compound and its acetate only show very uncharacteristic NMR spectra. The diterpenes all belong to the rare isokaurene type. The chemotaxonomic aspects are discussed briefly.     

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Genetically uniform burley tobacco (Nicotiana tabacum) was grown under field and various controlled-environment conditions to determine whether environment influenced epicuticular alkane, fatty acid, and fatty-alcohol composition of the leaves. Quantity and quality of alkanes, fatty acids, and fatty alcohols were greatly influenced by environmental conditions. Highest light intensity did not result in the largest total long aliphatic carbon-chain production. Generally, long photoperiod and cool temperature were associated with highest long aliphatic carbon-chain production on a leaf area basis. Quantity of the individual alkane, fatty acid, or fatty alcohol classes present under the different growth conditions varied in relation to the leaf metabolic status and not leaf size.     

Organic acids from the anaerobic decomposition of Agropyron repens rhizomes

Phytotoxicity originating from the anaerobic decomposition of couch grass rhizomes has been studied. Short chain aliphatic (acetic, propionic and butyric) acids appear to be mainly responsible but hexanoic, succinic, phenylacetic, cinnamic, p-coumaric, 4-hydroxyphenylpropionic and 3,4-dihydroxyphenylpropionic acids are also present in the phytotoxic solutions formed during the decomposition.     

Chemically defined serum-free media for the cultivation of primary cells and their susceptibility to viruses

Summary Chemically defined media SFRE-199-1 for the growth and SFRE-199-2 for the maintenance of primary baboon kidney (Bak) cell cultures were formulated by supplementing medium M199 with insulin, sodium pyruvate, zinc sulfate, and increasing arginine-HCl, cysteine, cystine,l-glutamine,l-glutamic acid, glycine, histidine, tyrosine, and glucose to maximally active nontoxic concentrations. For prolonged maintenance of the cells, physiological pH control, and blocking of excessive lactic acid accumulation in the spent medium of the cell cultures, it was necessary to supplement the medium containing Earle's balanced salts withd-(+) galactose. The cells grew and were maintained equally well on glass or polystyrene surfaces. Selenium, when added to growth medium or substituted for insulin and zinc sulfate, did not stimulate cell growth. Electron microscopy showed that numerous dense particles, approximately 250 to 400 ? in diameter, with the appearance of glycogen, were found throughout the cytoplasm in the cells grown in SFRE-199-1 and maintained in SFRE-199-2. Echovirus types 1 to 3, poliovirus types 1 to 3, coxsackievirus types B2, B4, B5,Herpesvirus hominis type 1, simian herpesvirusH. simiae and SA8, and simian adenovirus SV34 when titrated in primary Bak cells and grown and maintained in SFRE-199-1 and 2, respectively, developed titers comparable to those obtained in conventionally grown and maintained cells. This study was supported in part by National Institute of Health Grant RR00361 and World Health Organization Grant V4/181/38. This laboratory serves as the NIH/WHO Collaborating Center for Reference and Research in Simian Viruses.     

Nature of amino acid substitutions in homologous proteins during evolution

Replacement substitutions of mitochondrial cytochrome $\text{c}$ and α- and β-chains of haemoglobin have been studied by considering the structural similarity among amino acid residues at the secondary and tertiary structural levels. Secondary structural similarity explains ～70% while tertiary structural similarity explains ～50% of observed replacements for most of the cases. These structural similarities could not account for all the replacement substitutions. The study was extended to consider the composition of codons, and the chemical nature and polarity of the replacing and replaced residues. These also could not individually account for all the affected replacements. In general, no property of amino acid residues is conserved for substitutions occurring at any single position during evolution of proteins.