Oxygen activation during the interaction between MPTP metabolites and synthetic neuromelanin--an ESR-spin trapping, optical, and oxidase electrode study

Oxidase electrode measurements as well as optical and electron spin resonance spectroscopic data have shown that synthetic neuromelanin oxidizes the neurotoxin metabolite 1-methyl-4-phenyl-2,3-dihydropyridinium in a dose-dependent manner forming 1-methyl-4-phenylpyridinium and hydrogen peroxide. Hydroxyl radicals are formed in this reaction which is promoted by iron chelates. In contrast, neither 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine nor 1-methyl-4-phenylpyridinium reacts with synthetic neuromelanin in a similar fashion. The mechanism of selective toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in pigmented neuronal cells is discussed in the light of these findings.     

Prazosin treatment during the effector stage of disease suppresses experimental autoimmune encephalomyelitis in the Lewis rat

As part of a study on the role of vasoactive amines in experimental autoimmune encephalomyelitis (EAE), we have found that treatment beginning 7 days post-inoculation (dpi) with the specific alpha 1-adrenoceptor antagonist prazosin can significantly suppress clinical signs of disease in the Lewis rat. In this paper we have addressed the effect of treatment with prazosin commencing at varying times in the disease process. The results show that treatment during the early inductive stage (1 to 6 dpi) has no effect on the clinical course of the disease, whereas treatment commencing at the time of onset of early clinical signs (10 to 16 dpi) still significantly suppresses EAE. Leakage of serum proteins into the central nervous system (CNS) and histologic expression of EAE are also suppressed. Prazosin had no effect on lymphocyte responses to mitogen or antigen as determined by lymphocyte transformation tests when lymphocytes were exposed to prazosin in vitro, and the responses of lymphocytes from prazosin-treated animals were similar to those from saline-treated animals. These results support the hypothesis that prazosin suppresses EAE through a direct vascular effect although they do not preclude an immunologic component to its mechanism of action.     

Calcium uptake by isolated rat intestinal cells

Intestinal cells were isolated by a combination of mechanical and enzymatic means, and their calcium uptake was assayed by a rapid filtration procedure. Calcium uptake was a time- and concentration-dependent process that was markedly elevated at 25 and 37°C, as compared to 0°C. Cells isolated from rat duodenum exhibited higher uptakes than cells from jejunum, which in turn took up more calcium than cells from the ileurn. Duodenal cells from vitamin D-deficient animals took up less calcium than cells from vitamin D-replete cells. In vivo vitamin D repletion with 1,25-dihydroxyvitamin D₃ raised calcium uptake by duodenal cells from treated animals toward that of cells from replete rats. Furthermore, calcium uptake by duodenal cells from vitamin D-deficient animals approximated that of ileal cells from replete rats. These findings with isolated cells parallel prior findings of tissue calcium transport and suggest that cellular calcium uptake may be related to the saturable component of intestinal calcium absorption. Isolated intestinal cells may therefore constitute one experimental model for the study of transcellular calcium transport.     

STYLE ABSCISSION IN THE CITRON (CITRUS MEDICA L.) AND OTHER CITRUS SPECIES: MORPHOLOGY,PHYSIOLOGY, AND CHEMICAL CONTROL WITH PICLORAM

Style abscission was studied in detail in citrons (Citrus medica L.) and other citrus varieties. The course of style abscission was followed under orchard conditions and also in an “explant” system consisting of pistils implanted in an agar-sucrose medium and maintained at 25 C in a humid chamber. Morphological and anatomical observations carried out with the explant system revealed a prominent swelling of cell layers proximal to the separation layer prior to abscission. Tests with explants from flowers of different developmental stages showed that before the end of anthesis only the ovaries are capable of performing abscission while style abscission is possible only at a later stage, presumably after fertilization had occurred. Ethylene was able to induce ovary abscission at later stages but could not induce earlier style abscission. Picloram (4, amino-3,5,6-trichloropicolinic acid) increased the percentage of style persistence in citron varieties which naturally tend to retain their styles. Picloram also induced style persistence in Valencia oranges and Eureka lemons, which naturally show 100 % style abscission. Hormonal determinations showed that the style had higher levels of auxin than the ovary but also higher levels of inhibitors, which increased towards the time of style abscission.     

Thiamine-induced Formation of the Monopyrrole Moiety of Prodigiosin

Thiamine stimulates the production of a red pigment, which is chromatographically and spectrophotometrically identical to prodigiosin, by growing cultures of Serratia marcescens mutant 9-3-3. This mutant is blocked in the formation of 2-methyl-3-amylpyrrole (MAP), the monopyrrole moiety of prodigiosin, but accumulates 4-methoxy-2,2,'-bipyrrole-5-carboxaldehyde (MBC) and can couple this compound with MAP to form prodigiosin. Addition of thiamine caused production of MAP, and as little as 0.02 mg of thiamine per ml in a peptone-glycerol medium stimulated production of measurable amounts of prodigiosin. Phosphate salts and another type of peptone decreased the thiamine-induced formation of prodigiosin; yeast extract and glycerol enhanced the formation of this substance. Thiamine also enhanced production of prodigiosin by wild-type strain Nima of S. marcescens. The thiamine antagonists, oxythiamine and pyrithiamine, inhibited thiamine-induced production of MAP and of prodigiosin by the mutant strain 9-3-3, formation of prodigiosin by the wild-type strain Nima, and production of MAP by another mutant, strain WF. The pyrimidine moiety of thiamine was only 10% as effective as the vitamin; the thiazole moiety, only 4%; and the two moieties together, 25%. Various other vitamins tested did not stimulate formation of prodigiosin by strain 9-3-3. Thiamine did not stimulate production of prodigiosin by a single-step mutant that showed the same phenotypic block in prodigiosin biosynthesis as strain 9-3-3. This is not surprising since strain 9-3-3 originated as a result of two mutational events. One event may involve thiamine directly, and the other may involve the biosynthesis of MAP. Thiamine is probably involved in the regulation of the biosynthesis of MAP, because the vitamin or inhibitory antagonists must be added during the early phases of growth in order to be effective.