Effects of Salicylate on Virus-Infected Tobacco Plants

Salicylate watered onto the soil of tobacco plants in pots reduced the antigen accumulation and local lesion growth of tobacco necrosis virus mechanically inoculated on the leaves. It also retarded the growth of the necrotic centres of lesions and, in parallel, inhibited ethylene production from infected leaves. However, the therapeutic index of salicylate was very small and the chemical had to be applied in advance of, or at the same time as virus inoculation to give good levels of resistance. The number of lesions and their rate of appearance were not affected by salicylate. In addition, it did not induce resistance against multiplication, systemic spread or symptom severity in tobacco plants inoculated with a necrotic strain of potato virus Y. These findings suggest that salicylate is not likely to prove useful as polyvalent chemotherapeutic agent.     

Protease activities in non-embryogenic and embryogenic carrot cell strains during callus growth and embryo formation

Embryogenic and non-embryogenic cell strains of Daucus carota L. were examined for their protease activity using a wide range of chromogenic synthetic peptides as substrates. High arginine-specific activity was present in all strains, but no protease activity "specific" for embryogenic or non-embryogenic strains could be detected with the substrates tested. The specific protease activity was 5–10 times higher in the non-embryogenic as compared to the embryogenic strain for most tested substrates, and this difference was not due to release of proteases in the latter. All strains showed a decrease in protease activity when cultured in media without 2,4-dichlorophenoxyacetic acid, but the embryos had high protease activity in comparison with the nondifferentiated cell aggregates. In the latter aggregates, hydrolyzing activity towards three of the substrates (H-D-Phe-Pip-Arg- p -nitroanilide, Suc-Ala-Pro-Phe- p -nitro-anilide and Bz-Phe-Val-Arg- p -nitroanilide) was absent, whereas the embryos were able to hydrolyze them.     

Differential Effects of Bromocriptine on Dopamine and Acetylcholine Release Modulatory Receptors

Rabbit neostriatal slices were prelabeled with [3H]dopamine (DA) and [14C]choline and then superfused. The electrical stimulation-evoked release of DA and of acetylcholine (ACh) was abolished by 0.33 microM tetrodotoxin and by low calcium concentrations (0.13 mM). Bromocriptine, a selective D2-DA receptor agonist, inhibited in a concentration-dependent manner the evoked overflow of DA and ACh, without affecting the basal efflux of both transmitters. The effects of bromocriptine were antagonized by sulpiride, a specific antagonist of D2-DA receptors. With stimulation at 0.3 Hz and 120 pulses, bromocriptine was eight times more potent in inhibiting the evoked overflow of DA (IC50: 11 nM) than that of ACh (IC50: 83 nM). Stimulations at 3 Hz and 360 pulses markedly reduced the potency of bromocriptine in inhibiting DA and ACh release, and diminished its selectivity for presynaptic receptors. These results indicate that DA receptors that modulate the release of DA and ACh are of the D2 subtype. The greater potency of bromocriptine at pre- than at postsynaptic sites suggests that these receptors may be different in quantity and/or quality [D2-alpha (presynaptic) versus D2-beta (postsynaptic)]. Finally, marked differences in the potency and efficacy of DA agonist actions on DA and ACh release modulatory receptors are obtained, depending on the parameters of stimulation used.     

Vasoactive intestinal peptide (VIP) binding to solubilized material from rat liver plasma membranes

A non-ionic detergent such as Lubrol-PX extracts in soluble form the VIP-binding structures of rat liver plasma membranes. Detergent-solubitized proteins bind specifically [¹²⁵I]VIP and the complex tracer-protein is identified by the use of Sepharose 6B columns. The interaction is only possible in the absence of detergent (below 0.001%) and is inhibited by native peptide. A molecular weight of about 80,000 was estimated for VIP-binding proteins by reference to a series of globular markers of proteins. Binding to VIP soluble proteins is specific and dependent on time as studied by the Hummel and Dreyer (Biochim. Biophys. Acta 63:530–532, 1962) assay.     

Ontogenetical development of the chick and duck subcommissural organ

Summary The ontogenetical development of the subcommissural organ (SCO) was investigated in chick embryos collected daily from the 1st to the 21st day of incubation. Some duck embryos, and adult chickens and ducks were also studied. Immunocytochemistry using an anti-Reissner's fiber (RF) serum as the primary antibody was the principal method used.In the chick embryos the events occurring at different days of incubation were: day 3 morphologically undifferentiated cells in the dorsal diencephalon displayed immunoreactive material (IRM); days 4 to 6 immunoreactive cells proliferated, formed a multilayered structure and developed processes which traversed the growing posterior commissure and ended at the brain surface; day 7 i) blood vessels penetrated the SCO, ii) scarce hypendymal cells appeared, iii) the first signs of ventricular release of IRM were noticed, iv) appearance of IRM bound to cells of the floor of the Sylvius aqueduct; day 7 to 10 the number of apical granules and amount of extracellular IRM increased progressively; day 11 RF was observed along the Sylvian aqueduct; day 12 RF was present in the lumbar spinal cord; day 13 IRM on the aqueductal floor disappeared; days 10 to 21 i) hypendymal cells proliferated, developed processes and migrated dorsally, ii) ependymal processes elongated and their endings covered the external limiting membrane. In adult specimens the ependymal cells lacked basal processes and the external membrane was contacted by hypendymal cells. The duck SCO appears to follow a similar pattern of development.Supported by Grant I/60 935 from the Stiftung Volkswagenwerk, Federal Republic of Germany, and Grant RS-82-18 from the Dirección de Investigaciones, Universidad Austral de Chile. M.H. was recipient of a personal grant from JNO (29-5-54), which is gratefully acknowledged     

Production of Methyl Ketones from Secondary Alcohols by Cell Suspensions of C2 to C4n-Alkane-Grown Bacteria

Nineteen new C₂ to C₄n-alkane-grown cultures were isolated from lake water from Warinanco Park, Linden, N.J., and from lake and soil samples from Bayway Refinery, Linden, N.J. Fifteen known liquid alkane-utilizing cultures were also found to be able to grow on C₂ to C₄n-alkanes. Cell suspensions of these C₂ to C₄n-alkane-grown bacteria oxidized 2-alcohols (2-propanol, 2-butanol, 2-pentanol, and 2-hexanol) to their corresponding methyl ketones. The product methyl ketones accumulated extracellularly. Cells grown on 1-propanol or 2-propanol oxidized both primary and secondary alcohols. In addition, the activity for production of methyl ketones from secondary alcohols was found in cells grown on either alkanes, alcohols, or alkylamines, indicating that the enzyme(s) responsible for this reaction is constitutive. The optimum conditions for in vivo methyl ketone formation from secondary alcohols were compared among selected strains: Brevibacterium sp. strain CRL56, Nocardia paraffinica ATCC 21198, and Pseudomonas fluorescens NRRL B-1244. The rates for the oxidation of secondary alcohols were linear for the first 3 h of incubation. Among secondary alcohols, 2-propanol and 2-butanol were oxidized at the highest rate. A pH around 8.0 to 9.0 was found to be the optimum for acetone or 2-butanone formation from 2-alcohols. The temperature optimum for the production of acetone or 2-butanone from 2-propanol or 2-butanol was rather high at 60°C, indicating that the enzyme involved in the reaction is relatively thermally stable. Metal-chelating agents inhibit the production of methyl ketones, suggesting the involvement of a metal(s) in the oxidation of secondary alcohols. Secondary alcohol dehydrogenase activity was found in the cell-free soluble fraction; this activity requires a cofactor, specifically NAD. Propane monooxygenase activity was also found in the cell-free soluble fraction. It is a nonspecific enzyme catalyzing both terminal and subterminal oxidation of n-alkanes.     

Standardization of Radiorenography in Dehydrated and Rehydrated Primates Under Laboratory Conditions

Radiorenography with ^99mTo-labelled diethylenctriaminepcntacetic acid ([^99mTc]-DTPA) was performed on chacma baboons (Papio ursinus) and vervet monkeys (Cereopithecus pygerythus) to establish the effects of various states of hydration on the data obtained from the DTPA-renogram. The renogram parameters, which can be related to certain aspects of kidney function, varied significantly with the degree of hydration. It is therefore imperative for clinically directed animal research projects on the urinary system to standardise the experimental procedure for radiorenography. A dehydration of 6 h followed by an hour IU rehydration period using 200 ml of a 0.9% NaCI solution on baboons under thiopentone sodium anaesthetic, was found to be the most suitable procedure for radiorenographic investigations in this primate model.     

Dosage Compensation of Genes on the Left and Right Arms of the X Chromosome of DROSOPHILA PSEUDOOBSCURA and DROSOPHILA WILLISTONI

We have investigated the occurrence of dosage compensation in D. willistoni and D. pseudoobscura, two species whose X chromosome is metacentric with one arm homologous to the X and the other homologous to the left arm of chromosome 3 of D. melanogaster. Crude extracts were assayed for isocitrate dehydrogenase (XR), glucose-6-phosphate dehydrogenase (XL?), 6-phosphogluconate dehydrogenase (XL?), and α-glycerophosphate dehydrogenase (chromosome 2) in D. willistoni, and for esterase-5 (XR), glucose-6-phosphate dehydrogenase (XL?), 6-phosphogluconate dehydrogenase (XL?) and amylase (chromosome 3) in D. pseudoobscura. Our results indicate that a mechanism for dosage compensation is operative in both arms of the X chromosome of these two species.