Chromium oxalate: A new spin label broadening agent for use with thylakoids

Potassium tris(oxalato)chromate(III) trihydrate (chromium oxalate) has been shown to be a more useful broadening agent than potassium ferricyanide for the spin label 2,2,6,6-tetramethylpiperidine-N-oxy-4-amine (Tempamine) in thylakoid suspensions. Our data show that chromium oxalate is less permeable than ferricyanide, does not inhibit thylakoid electron transport or photophosphorylation, and is not photoreduced by thylakoids.     

SYNAPTIC VESICLES ISOLATED FROM RAT HEART: l-[3H]NOREPINEPHRINE UPTAKE PROPERTIES1

A fraction containing synaptic vesicles was isolated from rat heart by differential centrifugation, and the uptake of l-[³H]norepinephrine was studied in vitro., Uptake was highly dependent upon time and temperature, and was linear for 6 min at 30° or 4 min at 37°C. About 80% of the measured uptake required both ATP and Mg²⁺ and was inhibited by nanomolar concentrations of reserpine; no inhibition was obtained with cocaine. These properties are characteristic of storage vesicle uptake as opposed to synaptic membrane uptake. Uptake of norepinephrine was saturable and displayed a single K_m value of 2 μM. The uptake was completely stereospecific, as unlabeled dl-norepinephrine was less than half as effective as unlabeled l-norepinephrine in reducing uptake of l-[³H]norepinephrine. Norepinephrine uptake could be inhibited by various phenethylamines and indoleamines following the rank order: reserpine > harmaline > 5-hydroxytryptamine > dopamine > norepinephrine. The vesicle preparation also incorporated [³H]5-hydroxytryptamine and [³H]dopamine. 5-Hydroxytryptamine uptake displayed a K_m of 0.5 μM and a maximal uptake equivalent to that seen with norepineph-rine; dopamine uptake followed complex kinetics. Administration of reserpine in vivo or destruction of sympathetic neurons by long-term guanethidine treatment both eliminated the ability of the preparation to take up norepinephrine. Synaptic vesicles of cardiac sympathetic neurons thus resemble vesicles prepared from other central and peripheral catecholaminergic tissues; this method may be used readily to examine drug effects on rat heart synaptic vesicle function.     

Grain size,sucrose level and starch accumulation in developing rice grain

Five rices (Oryza sativa L.) differing in final grain size were studied at the midmilky stage to determine if any factor could be identified which might limit rate of starch accumulation. Only UDP glucose pyrophosphorylase activity increased with increasing grain size. Detached rice panicles incubated in liquid medium containing 1% sucrose and 0.1% glutamine, in addition to minerals and vitamins, produced grains similar to those on intact plants. Sucrose level (0–1.5%) in the medium determined the extent of dry matter and starch accumulation and influenced physiological development of the ripening grains. Chemical and enzymic composition of the grain were similar to previously reported levels in grains of intact panicles analysed at regular intervals after anthesis. Addition of 3-P glycerate or K⁺ to the medium did not improve dry matter accumulation in the developing grain.     

DIASTOLIC OPENING OF THE AORTIC VALVE (AV) IN A CASE OF AORTIC INSUFFICIENCY DUE TO AV FENESTRATION

A patient with severe aortic insufficiency due to fenestration of the non-coronary aortic valve leaflet is described. A preoperative echocardiogram demonstrated early closure of the mitral valve and early diastolic separation of the aortic valve leaflets. These findings disappeared after partial surgical correction and subsequent hemodynamic improvement. Premature opening of the aortic valve is common in severe aortic insufficiency.     

Novel shuttle plasmid vehicles for Escherichia-Streptococcus transgeneric cloning

A novel plasmid vector that is able to replicate both in Escherichia coli and in Streptococcus sanguis is described. This 9.2-kb plasmid, designated pVA856, carries Cm^r, Tc^r and Em^r determinants that are expressed in E. coli. Only the Em^r determinant is expressed in S. sanguis. Both the Cm^r and the Tc^r of pVA856 may be insertionally inactivated. This plasmid affords several different cleavage-ligation strategies for cloning in E. coli followed by subsequent introduction of chimeras in to S. sanguis. In addition, we have modified a previously described E. coli-S. sanguis shuttle plasmid [pVA838; Macrina et al., Gene 19 (1982) 345–353], so that it is unable to replicate in S. sanguis. The utility of such a plasmid for cloning and selecting sequences enabling autonomous replication in S. sanguis is demonstrated.     

Zinc levels in zinc-stabilized insulin are inhibitory to the growth of cells in vitro

Summary Adult human prostatic epithelium was cultured in a defined medium consisting of RPMI 1640 supplemented with transferrin, insulin, epidermal growth factor, dexamethasone, and vitamin A. In the presence of insulin, stabilized with zinc, maximum epithelial multiplication was obtained at an insulin concentration of 0.03 to 0.1 U/ml, corresponding to a zinc concentration of 1.4×10⁻⁷ M. At higher insulin concentrations, growth stimulation declined. Zinc-free insulin, on the other hand, stimulated cell multiplication with an optimum concentration of 0.3 to 1.0 U/ml. At this concentration the maximum growth was twice that obtained with zinc-stabilized insulin. Results demonstrate that growth inhibition caused by zinc limits the concentration of zinc-stabilized insulin, which can be used in serum-free, defined culture media. This work was supported by the Division of Cancer Cause and Prevention, National Cancer Institute, DHHS Grant No. CA-28279 to Webber.     

Tradescantia-micronucleus (Trad-MCN) bioassay on clastogenicity of wastewater and in situ monitoring.

The Tradescantia-micronucleus (Trad-MCN) bioassay was used to determine the clastogenicity of wastewater samples collected from the Arena canal which contains effluent from the industrial district Benito Juarez of the city of Queretaro, Mexico. Fifteen wastewater samples which were collected, in most cases, at bi-weekly intervals beginning in September 1986 through February 1988, after a 3-fold dilution were used to treat Tradescantia plant cuttings. The clastogenicity expressed in terms of micronucleus frequencies of treated groups (30 h of treatment without recovery time) was significantly (0.01) higher than that of the tapwater control groups. The Trad-MCN bioassay was also used for in situ monitoring of air pollutants for the clastogenicity at 3 sites near the industrial and residential areas (Flores Magon, Conalep and Bellas Artes) of the city of Queretaro. Fourteen monitoring trips were made to each of the 3 sites at monthly intervals beginning in May 1988 through June 1990. Seasonal variation of micronucleus frequencies was exhibited with the peak clastogenicities shown in May and June 1988, June 1989 and April 1990 at the three sites. Micronucleus frequencies of all the exposed groups at the Conalep site, a predominantly industrial area, were markedly higher than that of the laboratory control groups throughout the 2-year period.