Prostaglandin synthesis by the cochlea of the guinea pig. Influence of aspirin, gentamicin, and acoustic stimulation

This study describes the synthesis of prostaglandins (PGs) by the vascular structures of the inner ear (lateral wall = stria vascularis and spiral ligament) in vitro. The main PGs produced were PGI2, PGF2 alpha and PGE2. PGI2 and PGF2 alpha were also found in the perilymph. A 350 mg/kg ip injection of aspirin decreased PG synthesis by the lateral wall and PG levels in perilymph. This effect was reversed after 3 days. Gentamicin (10(-9) to 10(-5) M) decreased significantly and reversibly PG synthesis in vitro, as did 100 mg/kg ip injection. Acoustic stimulation increased ex vivo PGI2 and PGE2 synthesis without modifying PG levels in perilymph. Results suggest that PGs could be one humoral mediator of the cochlear microcirculation homeostasis, and, possibly, of the circulatory disturbances reported after acoustic stimulation. The decreased PG synthesis after gentamicin treatment could account for the angiotoxic component observed in aminoglycoside ototoxicity.     

The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles

Transport of reduced glutathione (GSH) was studied in isolated rat liver canalicular membrane vesicles by a rapid filtration technique. The membrane vesicles exhibit uptake of [2-3H]glycine--labeled GSH into an osmotically reactive intravesicular space. Although the canalicular membrane vesicles possess gamma-glutamyltransferase and aminopeptidase M, enzymes that hydrolyze glutathione into component amino acids, inactivation of the vesicle-associated transferase by affinity labeling with L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125) had no effect on the initial rate of GSH transport. Chemical analysis revealed that intact GSH accounted for most of vesicle-associated radioactivity. The initial rate of transport followed saturation kinetics with respect to GSH concentration; an apparent Km of 0.33 mM and V of 1.47 nmol/mg protein in 20 s were calculated. These results indicate that transport of GSH across the canalicular membranes is a carrier-mediated process. Replacement of NaCl in the transport medium by KCl, LiCl or choline chloride had no effect on the transport activity of the vesicles. The rate of GSH uptake by the vesicles was enhanced by valinomycin-induced K+-diffusion potential (vesicle inside-positive) and was inhibited by probenecid, indicating that GSH transport across the canalicular membranes is electrogenic and involves the transfer of negative charge. The transport of GSH was inhibited by oxidized glutathione or S-benzyl-glutathione. This transport system in canalicular plasma membranes may function in biliary secretion of GSH and its derivatives which are synthesized in hepatocytes by oxidative processes or glutathione S-transferase.     

Comparison of the localization of nucleic acid synthesis during bud formation on leaf fragments and on intact undetached leaves ofBegonia rex Putz.

The budding capacity ofBegonia rex leaf fragments is well known; that of undetached leaves has been shown by us only recently after treating the leaves with 6γγ DMAAP. Benzyladenine is as effective as 6γγ DMAAP in stimulating budding. Lower temperatures (17°, 22–12°, 12°) are also capable of inducing bud formation but only after a small cut has been made in a main vein of the undetached leaf. Root formation can also be provoked on undetached leaves which have a cut in the main leaf vein by higher temperatures (24–22°) or by an IAA treatment. Differences in the first stages of bud formation on leaf fragments and on undetached leaves are observed using histochemical and histoautoradiographic techniques.     

Expression of O-glycans during enterocytic differentiation of HT-29 cells

The expression of O- and N-glycan chains during the enterocytic differentiation of HT-29 cells was followed using L-[63H]-fucose and D-[6-3H]-glucosamine radiolabeling. Whatever the cell population, i.e., differentiated or undifferentiated, the incorporation of radiolabeled sugars into glycoproteins was similar. However, differences among these two cell populations were noted when the ratio [3H]-glucosamine/[3H]-galactosamine and the sensitivity of glycopeptides to mild alkaline treatment were followed. From these data, we could conclude that there is a shift in the high molecular weight glycopeptides during the differentiation of HT-29 cells meaning an increase of O-linked glycopeptides correlated with a decrease of N-linked forms.     

Occurrence of Shiga-like toxin-producing Escherichia coli in retail fresh seafood, beef, lamb, pork, and poultry from grocery stores in Seattle, Washington.

Fresh meat, poultry, and seafood purchased from Seattle area grocery stores were investigated for the presence of Shiga-like toxin-producing Escherichia coli by using DNA probes for Shiga-like toxin (SLT) genes I and II. Of the 294 food samples tested, 17% had colonies with sequence homology to SLT I and/or SLT II genes.     

New Isopropyl Chromone and Flavanone Glucoside Compounds from the Leaves of Syzygium cerasiforme (Blume) Merr. & L.M.Perry and Their Inhibition of Nitric Oxide Production

A new isopropyl chromone ( 1 ) and a new flavanone glucoside ( 2 ) together with eleven known compounds ( 3–13 ) were isolated from the leaves of Syzygium cerasiforme (Blume) Merr. & L.M.Perry. Their structures were elucidated as 5,7-dihydroxy-2-isopropyl-6,8-dimethyl-4H-chromen-4-one ( 1 ), 5,7-dihydroxyflavanone 7-O-β-D-(6′′-O-galloylglucopyranoside) ( 2 ), strobopinin ( 3 ), demethoxymatteucinol ( 4 ), pinocembrin-7-O-β-D-glucopyranoside ( 5 ), (2S)-hydroxynaringenin-7-O-β-D-glucopyranoside ( 6 ), afzelin ( 7 ), quercetin ( 8 ), kaplanin ( 9 ), endoperoxide G3 ( 10 ), grasshopper ( 11 ), vomifoliol ( 12 ), litseagermacrane ( 13 ) by the analysis of HR-ESI-MS, NMR, and CD spectral data. Compounds 1 , 2 , 5 , 6 and 10 inhibited NO production on LPS-activated RAW264.7 cells with IC₅₀ values of 12.28±1.15, 8.52±1.62, 7.68±0.87, 9.67±0.57, and 6.69±0.34 μM, respectively, while the IC₅₀ values of the other compounds ranging from 33.38±0.78 to 86.51±2.98 μM, compared to that of the positive control, N^G-monomethyl-L-arginine acetate (L-NMMA) with an IC₅₀ value of 32.50±1.00 μM.     

Conditions used with a continuous cultivation system to screen for d-hydantoinase-producing microorganisms

The continuous cultivation technique has been used to screen for microorganisms producing d-hydantoinase, a biocatalyst involved in the production of optically active amino acids. Pseudomonas putida strain DSM 84 was used as a model hydantoinase producer to establish selective culture conditions through the addition of various pyrimidines, dihydropyrimidines, hydantoins and 5-monosubstituted hydantoins. Thymine induced more activity than all cyclic amides tested. Addition of thymine as a non-metabolised inducer at a concentration of 0.05 g l^–1 in a continuous culture of P. putida stimulated hydantoinase production up to 80 times the basal level. Using continuous culture conditions established with the model strain, a different strain of P. putida having hydantoinase activity was isolated from commercial mixed cultures of microorganisms. DNA fingerprinting revealed that this new isolate was distinct from strain DSM 84. When used as a probe, the d-hydantoinase gene of strain DSM 84 hybridized with the DNA of the new P. putida isolate.     

Pituitary response of prepuberal lambs to oestradiol-17 beta.

In two experiments 48 prepuberal Merino ewe lambs were injected with oestradiol-17 beta (E2) or saline to study the effect of E2 on their plasma LH levels and on oestrus and ovulation. In the three groups which received 30 (experiment I), 50 and 30 (experiment II) microgram E2 respectively, 27 out of 28 lambs showed an LH response, the corresponding mean LH peaks being 64.3 +/0 22.5, 153.6 +/-33.4 and 91.7 +/- 16.9 ng/ml at mean intervals of 11.1, 11.2 and 10.5 h, respectively, after injection. None of the 20 lambs in the control groups had an LH level higher than 18 ng/ml 12 h after injection. In the three E2 groups, 41.7, 62.5 and 37.5% of animals showed oestrus within 26 h of injection while in the control groups only one animal showed oestrus. Of 13 animals showing oestrus in the E2 groups, 11 failed to ovulate. The mean pre-injection plasma FSH level in experiment I was 102.7 ng/ml, and in four 5--7-month-old lambs over several weeks uas 155.3 ng/ml. Despite these high pre-injection levels of FSH, it appears that the follicles were unable to respond to the LH peak which followed the E2 injection.     

HETEROGENEITY OF HISTAMINE Hi-RECEPTORS: SPECIES VARIATIONS IN [3H]MEPYRAMINE BINDING OF BRAIN MEMBRANES

[³H]Mepyramine binds with high affinity to membranes from brain of human, rat, guinea-pig, rabbit and mouse with drug specificity indicating an association with histamine H₁receptors. Considerable species differences occur in the affinity of [³H]mepyramine, with guinea-pig and human having 34 times greater affinity than rat, mouse or rabbit. The greater affinity of [³H]mepyramine in guinea-pig than in rat is attributable both to faster association and slower dissociation rates in guinea-pig. Species differences in affinity for H₁ receptor sites occur for some antihistamines but not for others. Some tricyclic antidepressant and neuroleptic drugs are extremely potent inhibitors of [³H]mepyramine binding, exceeding in potency any H₁ antihistamines examined. The tricyclic antidepressant doxepin and the neuroleptic clozapine are the most potent of all drugs examined in competing for [³H]mepyramine binding. The regional distribution of specific [³H]mepyramine binding differs considerably in the various species examined.