Regulation of DOPA Decarboxylase Activity in Brain of Living Rat

Abstract: To test the hypothesis that l -DOPA decarboxylase (DDC) is a regulated enzyme in the synthesis of dopamine (DA), we developed a model of the cerebral uptake and metabolism of [³H]DOPA. The unidirectional blood-brain clearance of [³H]DOPA ( K ^D₁) was 0.049 ml g⁻¹ min⁻¹. The relative DDC activity ( k ^D₃) was 0.26 min⁻¹ in striatum, 0.04 min⁻¹ in hypothalamus, and 0.02 min⁻¹ in hippocampus. In striatum, 3,4-[³H]dihydroxyphenylacetic acid ([³H]DOPAC) was formed from [³H]DA with a rate constant of 0.013 min⁻¹, [³H]homovanillic acid ([³H]HVA) was formed from [³H]DOPAC at a rate constant of 0.020 min⁻¹, and [³H]HVA was eliminated from brain at a rate constant of 0.037 min⁻¹. Together, these rate constants predicted the ratios of endogenous DOPAC and HVA to DA in rat striatum. Pargyline, an inhibitor of DA catabolism, substantially reduced the contrast between striatum and cortex, in comparison with the contrast seen in autoradiograms of control rats. At 30 min and at 4 h after pargyline, k ^D₃ was reduced by 50% in striatum and olfactory tubercle but was unaffected in hypothalamus, indicating that DDC activity is reduced in specific brain regions after monoamine oxidase inhibition. Thus, DDC activity may be a regulated step in the synthesis of DA.     

Bud proliferation and plant regeneration in liquid-cultured philodendron treated with ancymidol and paclobutrazol

Philodendron plants propagated in liquid shake or bioreactor cultures proliferated profusely in the presence of paclobutrazol (PAC) and to a lesser extent in the presence of ancymidol (ANC). The growth retardants inhibited leaf development and induced the formation of bud clusters. Short transient treatments with low concentrations (1.7–3.4 M) of the growth retardants limited leaf growth and proliferation to a lesser extent than higher concentrations (6.8–17 M). The growth retardants had a carryover dwarfing effect in the semi-solid hardening medium, which was more pronounced at the higher concentrations or prolonged exposure periods. Regenerated plants resumed normal growth 3–6 weeks after transplanting. Treatment with growth retardants may become a useful method in the prevention of abnormal leaf growth in large-scale liquid cultures, as well as in enhancing bud proliferation.     

Salicylate as an in vivo free radical trap: studies on ischemic insult to the rat intestine.

Ischemia of rat intestine was induced in vivo by occlusion of the superior mesenteric artery (SMA) for 15 min. Sodium salicylate, 100 mg/kg, given IP, 30 min prior to the ischemic event served as a specific trap for hydroxyl radicals. Portions of the bowel were sequentially isolated and removed--2 min prior to ischemia, 2 min prior to declamping of the SMA, and 10 min following reperfusion. The bowel segments were homogenized in 3% TCA. The homogenate was centrifuged and filtrated through a 0.22 mu filter. The hydroxylation products of salicylate, dihydroxybenzoic acid (DHBA) derivatives, were isolated, identified, and quantified by HPLC coupled with electrochemical detection (ECD). The level of 2,5-DHBA (M +/- SE, ng/g tissue) in the preischemic bowel (N = 21) was 241.8 +/- 10.0. In the ischemic specimen the level of 2,5-DHBA increased significantly to 313.3 +/- 15.5 (p = 0.0129), and remained unchanged in the reperfusion period (322.8 +/- 15.5). The histological examination correlated well with these levels: mild villi damage in the ischemic period with no further exacerbation during the reperfusion period. This study in an in vivo animal model of intestinal ischemia-reperfusion provides direct evidence for the involvement of free radicals during the ischemic insult.     

Physiological and enzymatic properties of a thymidine-requiring Pediococcus cerevisiae mutant.

We describe the isolation and characterization of a Pediococcus cerevisiae thymidine-requiring mutant and its thymidine-independent revertant. The mutant strain lacked thymidylate synthetase activity and had an absolute requirement for low concentrations (2 micrograms/ml) of thymidine in addition to a requirement for N-5-formyl tetrahydrofolic acid (folinate). Even at high concentrations (up to 500 micrograms/ml), thymine could not replace thymidine. In contrast to its wild-type parent, which grows only on folinate, the thymidine-requiring mutant (Thy- Fol+) was able to take up and grow on picogram quantities of unreduced folic acid. When both strains were grown on folinate, the Thy- Fol+ strain was at least 10(3)-fold more resistant to the folic acid analogs aminopterin and methotrexate than the wild-type strain. On the other hand, when grown on folic acid, the Thy- Fol+ strain was as sensitive to the folic acid analogs as the Thy+ Fol+ strain and was 10(2)-fold more sensitive than the wild-type strain grown on folinate. The thymidine-independent revertant (Thy+ Fol+) regained the wild-type level of thymidylate synthetase activity, but maintained the ability to take up and grow on unreduced folic acid like its Thy- Fol+ parent.     

Chloride-dependent restoration of coupling by oligomycin in rat liver mitochondria.

In rat liver mitochondria suspended in KC1 medium, oligomycin interfered with the effect of uncouplers on energy conservation. It antagonized the effect of uncouplers that are weak acids (2,4-dinitrophenol etc.), but enhanced that of the lipid-penetrating cation NN-dimethyl-N'N'-dibenzylammonium. Oligomycin caused none of the above effects when Br- or NO-/3 was substituted for C1- as the major anionic species in the assay medium. The concentration of oligomycin that exerted the above-mentioned effects was lower than that necessary for the inhibition of energy transfer, but was in the range that induced C1- permeation through the cristae membrane. The possible connexion between the effect of oligomycin on C1- permeation and its interference with the action of uncouplers is discussed.     

Field test of an automated radio‐telemetry system: tracking local space use of aerial insectivores

Documenting local space use of birds that move rapidly, but are too small to carry GPS tags, such as swallows and swifts, can be challenging. For these species, tracking methods such as manual radio‐telemetry and visual observation are either inadequate or labor‐ and time‐intensive. Another option is use of an automated telemetry system, but equipment for such systems can be costly when many receivers are used. Our objective, therefore, was to determine if an automated radio‐telemetry system, consisting of just two receivers, could provide an alternative to manual tracking for gathering data on local space use of six individuals of three species of aerial insectivores, including one Cliff Swallow (Petrochelidon pyrrhonota), one Eastern Phoebe (Sayornis phoebe), and four Barn Swallows (Hirundo rustica). We established automated radio‐telemetry systems at three sites near the city of Peterborough in eastern Ontario, Canada, from May to August 2015. We evaluated the location error of our two‐receiver system using data from moving and stationary test transmitters at known locations, and used telemetry data from the aerial insectivores as a test of the system's ability to track rapidly moving birds under field conditions. Median location error was ~250 m for automated telemetry test locations after filtering. More than 90% of estimated locations had large location errors and were removed from analysis, including all locations > 1 km from receiver stations. Our automated telemetry receivers recorded 17,634 detections of the six radio‐tagged birds. However, filtering removed an average of 89% of bird location estimates, leaving only the Cliff Swallow with enough locations for analysis of space use. Our results demonstrate that a minimal automated radio‐telemetry system can be used to assess local space use by small, highly mobile birds, but the resolution of the data collected using only two receiver stations was coarse and had a limited range. To improve both location accuracy and increase the percentage of usable location estimates collected, we suggest that, in future studies, investigators use receivers that simultaneously record signals detected by all antennas, and use of a minimum of three receiver stations with more antennas at each station.     

Elicitation of phenylpropanoids in maqui (Aristotelia chilensis [Mol.] Stuntz) plants micropropagated in photomixotrophic temporary immersion bioreactors (TIBs)

Plant Cell, Tissue and Organ Culture (PCTOC) - A biotechnological system for the production of plants biomass and phenylpropanoids of maqui was developed in photomixotrophic TIBs. The in vitro...     

Growth and Yield Response of Upland Rice to Application of Plant Growth-Promoting Rhizobacteria

Journal of Plant Growth Regulation - This study evaluated the effects of plant growth-promoting rhizobacteria (PGPR) isolates in enhancing upland rice growth and yield. Bacteria were isolated,...     

General descriptions of the dermis structure of a juvenile whale shark Rhincodon typus from the Gulf of California

The aim of this study is to provide preliminary observations on the microanatomy of Rhincodon typus skin using histology and electron microscopy analyses. Skin biopsies were obtained from a deceased juvenile male shark (548 cm total length) stranded in La Paz, Mexico, during February 2018. The results of this study evidenced the basic structure of the dermal denticles in the epidermis of the trunk of the shark, as well as the composition of the connective tissue in the hypodermis. Histological images of the hypodermis showed a high concentration of collagen fibres, formed by a large number of fine and wavy fibres of compact shape and little intercellular substance.