Maternal vitamin A restriction alters biochemical development of the brain in rats.

The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 micrograms retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats.     

Inhibition by tetanus and botulinum A toxin of the release of [3H]noradrenaline and [3H]GABA from rat brain homogenate

Summary Rat brain homogenate was preloaded with [³H]noradrenaline or [³H]GABA and stimulated with high K⁺. Tetanus toxin and botulinum A neurotoxin partially prevent the evoked [³H]noradrenaline release in the same range of toxin concentrations starting below 10^–10M. In contrast, release of -amino butyric acid (GABA) is much more sensitive to tetanus than to botulinum A toxin.     

Expression of the mutant gene for L-gulono-γ-lactone oxidase in scurvy-prone rats

A mutant strain of Wistar rats with L-gulono--lactone oxidase deficiency has recently been established. To investigate this deficiency by DNA and RNA blot hybridization analyses, a fragment of a previously cloned cDNA encoding rat L-gulono--lactone oxidase was used as a probe. When genomic DNA of the mutant rat was digested with several restriction enzymes, the probe hybridized to fragments of the same sizes as those produced from DNA of normal rats. Poly(A)⁺RNA from the liver of the mutant rat was found to contain an L-gulono--lactone oxidase-specific mRNA of a normal size at a comparable level to that of normal rats. An in vitro translation experiment revealed that the mRNA programmed the synthesis of an enzyme protein which had the same molecular weight as that of the translational product of the normal mRNA, although the amount synthesized was markedly reduced as compared with that synthesized with the normal mRNA. In accordance with this observation, a very low but definite degree of L-gulono--lactone oxidase activity was detected in the microsomes of the mutant rat by a newly developed, highly sensitive method.Acknowledgments. The authors thank Dr Susumu Makino, Shionogi Research Laboratories, Shionogi & Co., Ltd, Japan, for his kind donation of normal (ODS- +/+) and ODS (ODS-od/od) rats. This work was supported in part by Grant-in-Aid (59570103) for Scientific Research from the Ministry of Education, Science and Culture of Japan.     

Effect of tingenone,a quinonoid triterpene,on growth and macromolecule biosynthesis inTrypanosoma cruzi

Summary Tingenone and horminone, two natural quinonoid substances, inhibited the in vitro growth ofTrypanosoma cruzi, 30 M drug concentration producing total inhibition of growth. Tingenone inhibited total uptake and incorporation of [³H]thymidine, [³H]uridine, L-[³H]leucine into parasite macromolecules. Other quinonoids assayed were either less effective (abruquinone A) or even quite inactive (visminone B and ferruginin B). Investigation of several mechanisms for the cytotoxic action of tingenone pointed to the interaction with DNA as the most likely factor involved. Tingenone also inhibited the growth ofCrithidia fasciculata, but the drug was significantly less active on this organism than onT. cruzi.This work was supported by grants of UNDP/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseases, Organization of American States (Multinational Programme of Biochemistry) and Programa Nacional de Enfermedades Endémicas (SECYT), República Argentina. A preliminary account was given at the Workshop on Oxidative Damage and Related Enzymes, Frascatti (Italy), 1983.     

A2 adenosine receptors in human glomerular mesangial cells

A₂ adenosine receptors were characterized in human glomerular mesangial cells using [³H] 5-N-ethylcarboxamidoadenosine (NECA) as a tracer. There was a single group of receptor sites with a K_D of 184 nM, and a number of sites of 317 fmol/mg of cell protein. Adenosine agonists increased 5-nucleotidase activity via A₂ receptor stimulation. The specific A₂ agonist-NECA, at 0.1 and 1 m, was a potent inhibitor of DNA synthesis.     

Phospholipase C activation via a GTP-binding protein in tumoral islet cells stimulated by carbamylcholine

Summary Carbamylcholine and GTP act synergistically in stimulating the production of [³H]inositol-1-phosphate by digitonized tumoral islet cells (RINm5F line) prelabeled with myo-[2-³H(N)]inositol. The response to these two agents is similar to that evoked by GTPS. These findings suggest that a GTP-binding regulatory protein couples the occupancy of muscarinic receptors to activation of phospholipase C in pancreatic islet cells.This work was supported by grants from the Belgian Foundation for Scientific Medical Research.     

Glucose-evoked recovery of hepatic thyroxine 5′-deiodinase independent of de novo protein synthesis in fasted rat

Summary The glucose-evoked recovery of Type I thyroxine 5-deiodinase activity in the hepatic microsomes of fasted rat was not inhibited by either cycloheximide, puromycin or actinomycin D during 3 h after glucose feeding; however, [³H]-leucine uptake by the liver or the hepatic microsomal fraction was significantly inhibited by cycloheximide and puromycin but not by actinomycin D. These results indicate that the glucose-evoked recovery of deiodinase activity may be independent of de novo protein synthesis.     

Effects of a new cholecystokinin antagonist (GE 410) on the smooth muscle of the guinea pig ileum

Summary Suc-Tyr-(SE)-Met-Gly-Trp-Met-Asp--phenethylamide (GE 410) competitively antagonized the contractions of smooth muscle strips from guinea pig ileum (pA₂=7.6, n=0.95) induced by cholecystokinin-octapeptide (CCK8). GE 410 inhibited the electrically-induced cholinergically mediated contractile responses and the [³H]ACh release in the ileum, as well as the CCK-stimulated electrical contractile responses and the [³H]ACh release in the cholinergic nerve terminals. The results suggest the existence of CCK-receptors not only in the smooth muscles but also on the neurons.     

Phenytoin-induced DNA synthesis and inositol 1,4,5-triphosphate formation in L-929 fibroblasts

Summary Culture of L-929 fibroblasts in the presence of phenytoin (2.5–5.0 g/ml) increased DNA synthesis, as indicated by increased [³H]thymidine uptake, while a higher dose (20 g/ml) inhibited DNA synthesis. In like manner, a low dose of phenytoin (5.0 g/ml) was effective in increasing inositol 1,4,5-trisphosphate formation while a higher dose (10 g/ml) tended to inhibit this activity. These data suggest that the formation of inositol phosphate second messengers may play a role in phenytoin-induced fibroblast proliferation and connective tissue growth.     

Decrease in [3H]ouabain binding sites in heart and brain from spontaneously hypertensive rats

Summary A decrease in the number of binding sites (B_max) for [³H]ouabain was observed in the heart (37%) and the brain (22%) of spontaneously hypertensive rats (SHR) when compared with age-matched control Wistar Kyoto rats. No variation was detected in the affinity constant (K_D).     

Plasma and hepatic antioxidant control and vitamin A nutritional status

Twenty-seven rats were divided into three groups and fed on diets containing 0.3, 6 or 60 RE (retinol equivalent) retinyl palmitate/g food. After 7 weeks, hepatic vitamin A uptake was found to be more efficient in vitamin A-deficient rats than in rats given adequate vitamin A. We showed that during the metabolic adaptation of the animals to the level of vitamin A in the diet, extensive modifications occur in the antioxidant defences of the organism. In parallel with the increase in the level of vitamin A, the decrease in the level of -tocopherol in the plasma can bring about a greater susceptibility of the lipoproteins to oxidative stress. Similarly, the decrease in the hepatic -tocopherol level and in glutathione peroxidase activity leads to the weakening of the liver's antioxidant defences.     

Epidermal growth factor stimulates proliferation of rat hepatoma cells producing α-fetoprotein

Summary Epidermal growth factor stimulated both [³H]thymidine uptake and proliferation of rat AH66 hepatoma cells. However, the increase in cell number was not accompanied by a proportional increase in the levels of -fetoprotein of the culture media. The effects of EGF on the cell proliferation were antagonized by N⁶, O²-dibutyryl cAMP.     

Transport,verteilung und Metabolismus von3H-und14C-markiertem DDT in graviden mäusen unter hungerbelastung

Summary After i.p. application of 1, 0,5 and 0,1 mg p,p' DDT, labelled with³H or¹⁴C, to pregnant mice in different stages of pregnancy, the same level of radioactivity was found in the fetal and maternal blood. Starvation for 2 days caused a significant increase of residues, especially in the liver. Residue levels of DDT and its metabolities DDE, DDD, DCB and (DDOH+DDA) are found in fetal and maternal blood, brain liver and fat.     

Bombesin promotes pancreatic growth in suckling rats

Summary The pancreatic growth promoting effect of long term administration of bombesin was investigated in suckling rats. The authors showed that bombesin given in 10 g/kg b.wt doses s.c. every 8 h for 10 days from the day of parturition stimulated pancreatic growth: it increased pancreatic weight, protein and DNA content, trypsin and amylase activity and trypsin/DNA ratio. Conclusion: Bombesin is an effective stimulator of pancreatic growth in suckling rats.     

Labelling of steroids in axillary sweat after administration of3H-Δ5-pregnenolone and14C-progesterone to a healthy man

Résumé L'administration intraveineuse du prégnène-3-ol-20-one[7-³H]- ⁵ avec le progestérone[4-¹⁴C] à un homme sain amena la sécrétion d'autant de radioactivité dans la sueur des aiselles que dans la plupart du reste du corps. Le prégnénolone- ⁵, l'androstène-3,17-dione- ⁴ et le déhydroépiandrostérone furent les principaux stéroïdes marqués identifiés comme partant des deux sources de sueur.

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Acknowledgments. The author expresses grateful thanks to the subject (A.C.) who subjected himself to this experiment, and to Mr. D. A. A.Wilson for his technical assistance.     

Brain factor fromGalleria mellonella (Lepidoptera) stimulating silk gland activity

Brain extracts from day 1–4 last instar larvae ofGalleria mellonella (Lepidoptera) stimulate RNA synthesis in cultured silk glands from day 3 last instar larvae. When the fibroin-synthesizing posterior parts of silk glands were incubated for 3 h in vitro in the presence of brain extract (0.1 brain equivalent), [³H]-uridine incorporation into RNA was stimulated more than twofold. The stimulating effect of brain extract showed a dose response relationship. It is suggested that the heat-resistant and protease-sensitive brain factor is a peptide.     

Changes in placental permeability to corticosterone and estradiol-17β toward the end of gestation in the rat

Summary Radioactivity in the fetal plasma 1 h after maternal injection of¹⁴C-4-corticosterone or¹⁴C-4-estradiol-17 on day 21 of gestation was markedly higher than that 1 h after injection on day 22. Radioactivity in the maternal plasma was not different on these 2 days. The results suggest that the placental permeability to steroids from the mother to the fetus declines toward the end of gestation in the rat.Acknowledgment. We are indebted to Professor Tatsuo Imori (Department of Veterinary Surgery, College of Agriculture, University of Osaka Prefecture) for his valuable suggestions during the course of this study.     

Alternariol,a dibenzopyrone mycotoxin ofAlternaria spp., is a new photosensitizing and DNA cross-linking agent

Summary The mycotoxin alternariol (3,4,5-trihydroxy-6-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4-dihydroxy-5-methoxy-6-methyldibenzo [a] pyrone) is phototoxic toEscherichia coli in the presence of near UV light (320–400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant ofE. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.Acknowledgment. Dr Albert Stoessl (Agriculture Canada, London, Ontario, Canada) generously provided a mixture of alternariol and alternariol monomethyl ether, and made many helpful suggestions. Dr Ashwood-Smith (University of Victoria, Victoria, British Columbia, Canada) kindly supplied the microorganisms through Dr G.H.N. Towers (University of British Columbia, Vancouver). We gratefully acknowledge the gifts. It is a pleasure to acknowledge the able assistance of Mr S. Tallevi.     

Arousal-induced increase of cortical [K+] in unrestrained rats

Summary Changes of extracellular concentration of brain potassium [K⁺]_e were studied in lightly anesthetized unrestrained rats with ion-selective K⁺-microelectrodes introduced into the cerebral cortex with a head-mounted microdrive system. Nociceptive stimuli elicited EEG arousal lasting for 47 sec on the average which was accompanied by an increase of [K⁺]_e from 3.0 mM to 3.31 ± 0.04 mM.Acknowledgment. I wish to express my sincere gratitude to Dr. Bure from the Institute of Physiology, Czechoslovak Academy of Sciences, for his kind help in the preparation of this article.     

K252a: A new blocker of the cell-cycle at G1 phase in a human hepatoma cell line

The administration of 200 nM K252a to HuH7 suppressed the proliferation of the cells almost completely. The uptake of [³H]thymidine was inhibited, and flow cytometry revealed only one peak at 2C on day 3 after treatment with 100 nM K252a. The expression of proto-oncogene c-myc was not reduced. Despite the blockage at G1, both the size of the cells and the amount of cell protein had increased by 4 times by day 3 after treatment with K252a, while the cells secreted albumin and -fetoprotein into the medium as usual. These results show that K252a can increase the cell size of HuH7 without losing its function by blocking the cell cycle at G1 phase.