Occurrence,localization, and possible significance of an ornithine-containing lipid in Paracoccus denitrificans

A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium.Non standard abbreviations TLC thin-layer chromatography - Tris-HCl tris(hydroxymethyl)aminomethane hydrochloride - TMS trimethylsilyl - TFA triluoroacetyl - NPPN ninhydrin-positive, phosphorus-negative - ECL equivalent chain length     

The rates of sediment-water exchange of oxygen and sediment bioturbation in Lough Neagh,Northern Ireland

Oxygen is transported 30 mm into the sediment at an 8 m depth site in eutrophic Lough Neagh by the irrigational activities of the benthic fauna. Faunal activity also mixes the upper 20 mm of sediment. Sediment oxygen uptake rate, redox potential-depth profile and the chlorophylla concentration were measured in the upper sediment layers from February to November 1979. Chlorophylla input to the sediment, following the Spring phytoplankton maximum, remained in the 0–1 cm sediment layer but did cause the redox potential profile to change from one with potentials around 400 mV in the upper 50 mm to one with a strong gradient over the 0–30 mm region. The start of benthic faunal activity in May caused the chlorophylla to be mixed into the 1–2 cm layer and also caused oxygen to be transported into the sediment at a rate sufficient to change the redox potential back to its initial state. The biodiffusion coefficient for solids in the upper 20 mm was estimated to be 6 × 10⁻⁸ cm² s⁻¹. Oxygen transport in the pore, waters of the upper sediment layers was considered to be best described as advection, caused by the irrigational activities of the benthic fauna.     

Developmental patterns of ornithine decarboxylase activity in organogenesis phase rat embryos in culture and in utero

Summary Ornithine decarboxylase activity was measured during organogenesis in rat embryos grown in utero and whole rat conceptuses maintained in an in vitro culture system. Ornithine decarboxylase levels in vivo showed a distinct peak at embryonic age 10.5 d. Despite identical morphology, protein content, crown rump length and numbers of somites cultured embryos displayed a different developmental pattern and possessed less than half the ODC activity of that in vivo. The data suggest that the normal embryonic programming of ODC activity is significantly altered by the culture environment and that further biochemical comparisons of embryos growing in utero and in vitro may be required to evaluate properly the applicability of this technique to detailed studies of teratogenesis and developmental biology. This work was supported by NIH-5-507-RR5359-17 and a 1980 Research Starter Grant from the Pharmaceutical Manufacturers Association Foundation.     

Some electrophysiological consequences of electrogenic sodium and potassium transport in cardiac muscle: a theoretical study

A previous paper described a kinetic model for electrogenic sodium-potassium transport in cardiac muscle, combining a thermodynamically-constrained transport model with simple passive permeabilities for sodium and potassium to generate a cardiac action potential (Chapman, Kootsey & Johnson, 1979). The present paper explores the extent to which this simplest of active-passive transport models can account (without further modification) for the electrophysiological behavior of cardiac muscle. The long term (several minutes) changes in the duration of the action potential observed following a change in stimulation rate are predicted by the model through a shift in the steady-state current-voltage relationship caused by small changes in inside ion concentrations. The diastolic hyperpolarization observed following an increase in rate is also predicted, including the linear relationship between the maximum diastolic depolarization and the rate of stimulation. Varying the outside potassium concentration in the model produces changes in the rest potential and current-voltage relationship similar to published data. Deviations from ideal potassium electrode behavior occur at both high and low concentrations because of effects on the pump. The model not only predicts the observed shift of the current-voltage curve in the depolarizing direction with increasing [K⁺]₀, but also the crossing of the curve in normal [K ⁺]₀ without having to assume a variation in g_K. Anoxia was introduced into the model by changing the concentrations of ATP and ADP, thereby enabling the model to account for the rapid diastolic depolarization observed in myocardial ischemia.     

Morphological and functional specializations of the shell, musculature and pallial glands in the Lithophaginae (Mollusca: Bivalvia)

The structure of the pallial glands in limestone and coral boring species of Lithophaga (Bivalvia: Lithophaginae) is examined and related to evolutionary trends in habitat specialization. Boring glands of all species occur in the middle mantle fold but display a progressive degree of complexity from simple epithelial to ducted sub-epithelial structures coinciding with increasing specialization of habitat from natural limestone to species specific live coral dwellers. The size of this gland is relatively reduced anteriorly and along the entire length of the mantle in live coral borers.