Characterization of membrane lipids of a general fatty acid auxotrophic bacterium by electron spin resonance spectroscopy and differential scanning calorimetry

Lipids in the plasma membrane of the general fatty acid auxotroph Butyrivibrio S2 pack as a bilayer that is characterized by a high order and high motional anisotropy and a low membrane fluidity compared to mammalian plasma membranes. Lipid packing as determined by the electron spin resonance (ESR) order parameter and membrane fluidity as measured by ESR correlation times are, however, comparable to those of other bacterial membranes. Membranes of the organism grown with saturated fatty acids of well-defined hydrocarbon chain length undergo a broad reversible endothermic phase transition, the peak temperature of which is well below the growth temperature; the end-point temperature of this thermal transition approximately coincides with the minimum temperature supporting significant growth of the organism. The lipid phase transition is also reflected in the temperature dependence of various ESR parameters, whereby the transition temperature thus derived is higher than the peak temperature of the endothermic transition but still lower than the growth temperature. ESR and calorimetry evidence taken together suggest that the endothermic transition is a gel to liquid-crystal transition and that, at the growth temperature, the plasma membrane of Butyrivibrio S2 is in the liquid-crystalline state. Similar values were measured for the order parameter of cell membranes of Butyrivibrio S2 regardless of whether the organism was grown on myristic, palmitic, or stearic acid. Butyrivibrio S2 has a mechanism enabling it to maintain membrane packing and fluidity at a fairly constant level.(ABSTRACT TRUNCATED AT 250 WORDS)     

New view of the surface projections of Chlamydia trachomatis.

Two kinds of surface specializations of chlamydiae have been described: hemispheric projections and spikelike rods. We undertook the present studies to demonstrate chlamydial ultrastructure in greater detail in conventional thin-sectioned specimens. Chlamydia trachomatis (LGV strain L2/434/Bu), cultured for 40 h in L929 mouse fibroblasts, was fixed in glutaraldehyde-acrolein, p-formaldehyde-glutaraldehyde, or glutaraldehyde-osmium tetroxide mixtures, postfixed in osmium tetroxide, stained in uranyl acetate, dehydrated in ethanols, and embedded in Epon. By the use of fixatives that penetrate and fix rapidly, chlamydial outer and plasma membranes were clearly revealed. Our results indicate that the hemispheric projections are specializations of the plasma membrane of elementary bodies. The spikelike projections are found in intermediate forms, originate beneath depressions of the plasma membrane, and extend through the periplasmic space and outer membrane to end with pointed tips. Improved preservation of chlamydiae provides a new, informative view of their complex structure. Significant interactions between chlamydiae and host cells might be influenced by the surface structures shown in this study.     

A probability matrix for the identification of vibrios

A probability matrix for computer-assisted identification of vibrios has been constructed, based on the API 20E system. Data were gathered from 173 strains representing 31 taxa of vibrios and related organisms, from a variety of sources. The matrix was tested internally by four statistical programs. Program OVERMAT tested the separation and program MOSTTYP the discretion and homogeneity of the taxa. Most of the taxa were satisfactory but a few were less so; reasons for this are discussed. Program CHARSEP and program DIACHAR tested the separation and diagnostic values, respectively, of the characters used. The overall test error was 4.5%. The matrix was assessed externally by its performance in the identification of vibrio-like strains isolated from freshwater. Of 243 wild strains, 79.4% were identified with ten taxa, with a Willcox score of greater than or equal to 0.99.     

Evidence for [D-Ala2,D-Leu5]Enkephalin-Induced Supersensitivity to 5-Hydroxytryptamine in a Neurotumor × Brain Hybrid Cell Line (NCB-20)

A neuroblastoma X Chinese hamster embryonic brain explant hybrid cell line (NCB-20) expressed 5-hydroxytryptamine (5-HT1) receptors, linked to adenylate cyclase, which closely resembled 5-HT1 receptors previously characterized in central nervous tissue. However, the affinity of the receptors for 5-HT was only 150 nM compared to 5 nM in membranes prepared from cerebral cortex. The elevation of cyclic AMP levels in NCB-20 cells produced by 5-HT was found additive to that produced by cholera toxin but synergistic with that produced by either prostaglandin E1 (PGE1) or forskolin, suggesting that these latter two agents elevate cyclic AMP levels by a different mechanism than 5-HT. The elevation of cyclic AMP levels by either 5-HT or PGE1 was reversed by [D-Ala2,D-Leu5]enkephalin (DADLE), morphine, clonidine, and 3,4-dihydroxyphenylethylamine (dopamine) on a short (30 min) time scale. However, continued exposure to DADLE resulted in loss of the initial inhibitory effects of DADLE after 6 h and return of cyclic AMP levels to that seen with either 5-HT or PGE1 alone. When the DADLE exposure time was increased to 48 h, 5-HT produced a further twofold increase in cyclic AMP levels, but there was no increase in the responsiveness of the cells to PGE1 unless naloxone was added 1 h prior to treatment with PGE1. Scatchard analysis showed that the increased potency of 5-HT resulted from an increase in receptor affinity for 5-HT (from a KD of 150 +/- 20 nM to one of 20 +/- 7 nM), with a reduction in the number of apparent binding sites. The 5-HT supersensitivity observed in NCB-20 cells may be a good model for neurotransmitter interactions that produce desensitization or facilitation in the intact nervous system.     

Thyroidectomy results in termination of photorefractoriness in starlings (Sturnus vulgaris) kept in long daylengths

Four groups of 10 male starlings were transferred from short daylengths (8 h light/day) to long daylengths (18 h light/day), which caused the tests to develop rapidly to maximum size and then to decrease to minimal size as birds became photorefractory. Birds were surgically thyroidectomized at 8, 16 or 28 weeks. A fourth group was left intact. Testicular volume and plasma FSH and prolactin concentrations were measured. After 42 weeks all birds were castrated and plasma FSH was measured during the next 6 weeks. Testicular growth began in all thyroidectomized birds between 4 and 8 weeks after thyroidectomy. By 42 weeks, the testes of all thyroidectomized birds were large, whereas those of intact birds were still of minimal size. Plasma FSH concentrations remained low in all birds and plasma prolactin values, originally elevated by long daylengths, decreased at a similar rate in thyroidectomized and intact birds. After castration at 42 weeks, plasma FSH values increased rapidly in all thyroidectomized birds but remained low in non-thyroidectomized birds. The results demonstrate that thyroidectomy of photorefractory starlings does not induce immediate testicular growth but may initiate a process which eventually terminates photorefractoriness in a way similar to that caused by return to short daylengths.     

Enhanced depressor effect of muscimol in the DOCA/NaCl hypertensive rat: evidence for altered GABAergic activity in brain

To elucidate the role of the central gamma-aminobutyric acid (GABA) system in the maintenance of deoxycorticosterone (DOCA)NaCl hypertension, the responses of mean arterial pressure (MAP), plasma norepinephrine (NE), and epinephrine (EP) to intracerebroventricular (ICV) administration of muscimol, a GABA agonist, and the responses of MAP to bicuculline, a GABA antagonist, and to clonidine, an alpha 2-adrenoceptor agonist known to lower blood pressure by inhibiting sympathetic tone, were examined in conscious, unrestrained 4 week DOCA/NaCl hypertensive rats and age-matched uninephrectomized control rats. Muscimol (50-1000 ng/300 g, ICV) caused dose-dependent decreases in MAP which were greater in DOCA/NaCl rats than in controls. Basal plasma NE and EP were significantly higher in DOCA/NaCl rats than in controls. Muscimol (1000 ng/300 g, ICV) induced decreases in plasma EP which were greater in DOCA/NaCl rats than in controls without changing NE levels in either group. Bicuculline (3 micrograms/300 g, ICV) caused increases in MAP which were the same in both groups. The depressor response to clonidine (5 micrograms/300 g) was greater in DOCA/NaCl rats than in controls. These results suggest that the activity of the central GABAergic system is altered in the rat with established DOCA/NaCl hypertension and that the alteration in central GABAergic function may be related to the increased sympathoadrenal activity and the maintenance of hypertension in this model.     

Effects of ribavirin and adenine arabinoside on tobacco mosaic virus in Nicotiana tabacum L. var Xanthi tissue cultures

Although both ribavirin (1--ribofuranosyl-1,2,4-triazole-3carboxamide) and adenine arabinoside inhibited the multiplication of tobacco mosaic virus (TMV) in mechanically inoculated leaf tissues, neither chemical inhibited virus multiplication in unorganized tobacco callus after in vitro inoculation. The adenine deaminase inhibitor, pentostatin, did not increase the activity of adenine arabinoside in cultured cells. Several different developmental conditions and media did not increase the ability of either chemical to eradicate the virus from tobacco tissue cultures. However, the virus was eradicated from TMV-infected callus when grown in the presence of combinations of ribavirin and adenine arabinoside in shoot inducing medium.     

Production of citric acid from sugars present in wood hemicellulose usingAspergillus niger andSaccharomycopsis lipolytica

Summary One strain each of the fungus,Aspergillus niger, and the yeast,Saccharomycopsis lipolytica, were investigated for their ability to produce citric acid from the sugars present in hemicellulose hydrolysates.S. lipolytica produced citric acid as efficiently from mannose as from glucose, but failed to assimilate xylose, arabinose or galactose.A. niger readily assimilated mannose, xylose and arabinose, and produced citric acid from these sugars although the yields were lower than from glucose. A possible inhibitory effect of arabinose on citric acid production from other sugars was observed usingA. niger.     

Hypoxic induction of Ca2+-dependent action potentials in small pulmonary arteries of the cat

Small pulmonary arteries (less than 300 micron) from cats were mounted in myographs to record mechanical and electrical responses to hypoxia. When these preparations were exposed to a PO2 of 30-50 Torr after equilibration at 300 Torr they consistently developed active force, which increased or decreased in amplitude as [Ca2+] was raised or lowered, respectively, and was blocked on addition of verapamil. Intracellular electrical recording with glass microelectrodes demonstrated membrane depolarization and action potential generation when PO2 was lowered. Steady-state voltage vs. applied current curves obtained before and during hypoxia showed a significant reduction in input resistance. The relationship between membrane potential and extracellular K+ was not different during hypoxia compared with control, suggesting that there were not marked changes in K+ permeability under this condition. In the presence of verapamil to block Ca2+ inward current the hypoxia-induced action potentials were abolished concomitant with partial membrane repolarization. The results of these studies suggest that in certain isolated pulmonary arteries hypoxia induces contraction by a mechanism involving an increased Ca2+ conductance. These data suggest that the sensor involved in hypoxic pulmonary vasoconstriction may lie within the vessel wall and somehow mediates changes in smooth muscle ionic conductances.