Evidence for Distinct 5-Hydroxytryptamine2 Binding Site Subtypes in Cortical Membrane Preparations

5-Hydroxytryptamine (5-HT) displays a sixfold higher affinity for 5-HT2 binding sites labeled by [3H]ketanserin in rat (IC50 = 200 +/- 40 nM) and human (IC50 = 190 +/- 50 nM) cortex than for 5-HT2 sites in bovine cortex (IC50 = 1,200 +/- 130 nM). The Hill slopes of the 5-HT competition curves are 0.67 +/- 0.04 in rat, 0.69 +/- 0.08 in human, and 0.96 +/- 0.02 in bovine cortex. Scatchard analysis of (+/-)-[3H]4-bromo-2,5-dimethoxyamphetamine ([3H]DOB) binding in the rat indicates a population of binding sites with a KD of 0.38 +/- 0.04 nM and a Bmax of 1.5 +/- 0.05 pmol/g tissue. In contrast, specific [3H]DOB binding cannot be detected in bovine cortical membranes. These data indicate that species variations exist in 5-HT2 binding site subtypes and that [3H]ketanserin appears to label a homogeneous population of 5-HT2 binding site subtypes in bovine cortex.     

Modified, large-scale purification of the cytochrome o complex (bo-type oxidase) of Escherichia coli yields a two heme/one copper terminal oxidase with high specific activity.

The cytochrome o complex is a bo-type ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli. This complex has a close structural and functional relationship with the eukaryotic and prokaryotic aa3-type cytochrome c oxidases. The specific activity, subunit composition, and metal content of the purified cytochrome o complex are not consistent for different preparative protocols reported in the literature. This paper presents a relatively simple preparation of the enzyme starting with a strain of Escherichia coli which overproduces the oxidase. The pure enzyme contains four subunits by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Partial amino acid sequence data confirm the identities of subunit I, II, and III from the SDS-PAGE analysis as the cyoB, cyoA, and cyoC gene products, respectively. A slight modification of the purification protocol yields an oxidase preparation that contains a possible fifth subunit which may be the cyoE gene product. The pure four-subunit enzyme contains 2 equivs of iron but only 1 equiv of copper. There is no electron paramagnetic resonance detectable copper in the purified enzyme. Hence, the equivalent of CuA of the aa3-type cytochrome c oxidases is absent in this quinol oxidase. There is also no zinc in the purified quinol oxidase. Finally, monoclonal antibodies are reported that interact with subunit II. One of these monoclonals inhibits the quinol oxidase activity of the detergent-solubilized, purified oxidase. Hence, although subunit II does not contain CuA and does not interact with cytochrome c, it still must have an important function in the bo-type ubiquinol oxidase.     

Establishment of anaerobic,reducing conditions in lake sediment after deposition of acidic,aerobic sediment by a major storm

Hurricane Danny resulted in the rapid deposition of 10cm of oxidized, acidic sediment in the Contrary Creek arm of Lake Anna, Virginia. Several biological and geochemical parameters were monitored with time to ascertain how long it took the newly-deposited lake sediments to attain the anaerobic, circumneutral, actively sulfate-reducing state normally observed in this portion of the lake. The sediment platinum-electrode potential dropped from 350 mV to 100 mV within the first week after the storm. The pH of the pore water increased from 4.5 to 5.8 within three weeks, and titratable alkalinity was detected within two weeks and three weeks at 3 cm and 1 cm depths, respectively. Accumulation of reduced products of sulfate reduction (acid volatile sulfide) began by three to four weeks after the storm event. Both methanogens and sulfate reducers were present in high and approximately equal numbers in the freshly deposited material. The rapid neutralization of the acidity in the fresh sediment prior to the onset of sulfate reduction suggests that reactions other than sulfate reduction caused the initial increase in pH and alkalinity in this system.     

Preparation of lipid emulsions by pressure extrusion

Lipid emulsions consisting of a surface monolayer of phospholipid enclosing a core of neutral lipids have been prepared by repeated extrusion through polycarbonate filters of defined pore size. Particle size, as measured by photon correlation spectroscopy, decreases on successive passes through a 100 nm filter, reaching a near constant value (130-150 nm) after 4 passes. A corresponding decrease in the standard deviation of the particle size distribution occurs during this process. The recovery of lipids, especially of cholesterol and cholesterol ester, is improved if the emulsion is sonicated before extrusion through filters. [31P]-NMR and fluorescence techniques are used to confirm that the resulting structures are emulsions rather than lipid bilayers.     

Transformed plants with elevated levels of chloroplastic SOD are not more resistant to superoxide toxicity

The petunia nuclear gene which encodes the chloroplast isozyme of superoxide dismutase, SOD-1, has been fused with an efficient rbcS promoter fragment and 3 flanking region and introduced into tobacco and tomato cells. Transformed plants carrying this chimeric gene have up to 50-fold the levels of SOD-1 which occur in wild-type plants. However, tobacco plants with 30-to 50-fold the normal SOD-1 activity do not exhibit resistance to the light-activated herbicide paraquat. Similarly, tomato plants with 2-to 4-fold increases in SOD-1 do not exhibit tolerance to photoinhibitory conditions known to increase superoxide levels (high light, low temperatures and low CO₂ concentrations). Our data indicate that increasing the chloroplastic SOD level in a plant cell is not sufficient to reduce the toxicity of superoxide.     

Selective effect of zinc compared to other divalent metals on L-triiodothyronine binding to rat c-erbA alpha and beta proteins

The effects of zinc and other divalent metals on the [125I]T3 binding to rat c-erbA alpha and beta recombinant proteins were assessed. The addition of ZnCl2 caused a reversible and dose-dependent inhibition of [125I]T3 binding to rc-erbA beta proteins with half maximum inhibition occurring at 50-100 microM, but no significant effect on [125I]T3 binding to rc-erbA alpha under the same assay conditions. Scatchard analysis revealed a decrease in [125I]T3 binding capacity to beta protein without marked change in Kd values in presence of zinc. Moreover, significant inhibitions of [125I]T3 binding to both alpha and beta proteins were observed in the presence of 100 microM of either MnCl2, CdCl2 or CuCl2, but not MgCl2. Thus, the selective effect of zinc compared to other divalent metals to inhibit T3 binding to rc-erbA beta, but not alpha, proteins was documented and suggest a possible regulatory role for zinc in modulating the intracellular action of thyroid hormone.     

Multiple fruiting of the edible mushroomCoprinus cinereus from explants of the stipe

Summary Carpophores were developed on defined medium from explants of stipes produced in the dark using an expansionless mutant (no. 190) ofCoprinus cinereus. Explants taken from stipes within 24 h of formation developed multiple fruit within 3–12 days without formation of mycelia. Fruiting levels were affected by stipe age (24 h), medium composition, explant size, and polarity of the explant on fruiting medium. This method offers a new tool for developmental studies and may also be of use to commercial mushroom growers.     

Papillary carcinoma of thyroid: classical and variants

Papillary carcinoma, the commonest primary cancer of thyroid, exhibits a broad morphological spectrum. In this review, the clinicopathological features of papillary carcinoma, classical and its variants (follicular, solid, cribriform, variant with exuberant nodular fasciitis-like stroma, encapsulated, diffuse sclerosing, diffuse follicular, tall cell, columnar cell, oxyphil cell, "dedifferentiated", occult, latent and microcarcinoma) are summarized.     

Eight small subunits of Euglena ribulose 1-5 bisphosphate carboxylase/oxygenase are translated from a large mRNA as a polyprotein.

The small subunit (SSU) of ribulose 1-5 bisphosphate carboxylase/oxygenase is a 15 kd protein in Euglena gracilis. The protein is synthesized as a 130 kd precursor as shown by immunoprecipitation of in vitro translation products and confirmed by immunoprecipitation of in vivo pulse-labeled Euglena proteins. From the published SSU amino acid sequence, an oligonucleotide was synthesized that specifically hybridizes to a large mRNA whose length (approximately 4.3 kb) is consistent with the precursor size. The complete nucleotide sequence of the SSU mRNA was obtained by sequencing a cDNA clone from a lambda gt11 library and completed by direct mRNA sequencing. We report for the first time the complete sequence of a large mRNA and show that it encodes eight consecutive SSU mature molecules. The deduced precursor amino acid sequence shows that the amino terminus of the first SSU molecule is preceded by a 134 amino acid peptide which is cleaved during the maturation process. This long transit peptide exhibits features characteristic of signal peptides involved in the secretion of proteins through the endoplasmic reticulum. This is in agreement with the idea that the third (outer) membrane of the Euglena chloroplast envelope is of endoplasmic reticulum origin.     

Free amino acid levels and the regulation of nitrate uptake in maize cell suspension cultures

The ability of individual amino acids to regulate nitrate uptakeand induction was studied in a Zea mays embryo cell line grownin suspension culture. The maize cells exhibited a marked preferencefor absorbing amino acids over nitrate when both were presentin culture medium. The addition of an individual amino acid(2 mM glutamine, glycine, aspartic acid, or arginine) to theculture medium with 1 mM nitrate completely inhibited nitrateuptake and resulted in a cycle of low levels of nitrate influxfollowed by efflux to the growth medium. Glutamine was readilyabsorbed by the cells and was particularly effective in supportingoptimum cell growth in the absence of an inorganic nitrogensource as compared to the three other amino acids evaluated.However, neither glutamine nor any of the remaining 19 proteinaceousamino acids appeared to be solely responsible for regulationof nitrate uptake and induction. The ability of amino acidsto regulate nitrate uptake and assimilation appears to be morerelated to their overall levels in the cell rather than to anaccumulation of a specific amino acid. Key words: Amino acids, nitrate uptake, maize, regulation, cell suspension culture