Evidence for triacylglycerol synthesis in the lumen of microsomes via a lipolysis-esterification pathway involving carnitine acyltransferases

In this study a pathway for the synthesis of triacylglycerol (TAG) within the lumen of the endoplasmic reticulum has been identified, using microsomes that had been preconditioned by depleting their endogenous substrates and then fusing them with biotinylated phosphatidylserine liposomes containing CoASH and Mg(2+). Incubating these fused microsomes with tri[(3)H] oleoylglycerol and [(14)C]oleoyl-CoA yielded microsome-associated triacylglycerol, which resisted extensive washing and had a [(3)H]:[(14)C] ratio close to 2:1. The data suggest that the precursor tri[(3)H]oleoylglycerol was hydrolyzed by microsomal lipase to membrane-bound di[(3)H]oleoylglycerol and subsequently re-esterified with luminal [(14)C]oleoyl-CoA. The accumulation of TAG within the microsomes, even when overt diacylglycerol acyltransferase (DGAT I) was inactive, is consistent with the existence of a latent diacylglycerol acyltransferase (DGAT II) within the microsomal lumen. Moreover, because luminal synthesis of TAG was carnitine-dependent and markedly reduced by glybenclamide, a potent carnitine acyltransferase inhibitor, microsomal carnitine acyltransferase appears to be essential for trafficking the [(14)C]oleoyl-CoA into the microsomal lumen for subsequent incorporation into newly synthesized TAG. This study thus provides the first direct demonstration of an enzymatic process leading to the synthesis of luminal triacylglycerol, which is a major component of very low density lipoproteins.     

Spontaneous neural activity is required for the establishment and maintenance of the olfactory sensory map

We have developed a genetic approach to examine the role of spontaneous activity and synaptic release in the establishment and maintenance of an olfactory sensory map. Conditional expression of tetanus toxin light chain, a molecule that inhibits synaptic release, does not perturb targeting during development, but neurons that express this molecule in a competitive environment fail to maintain appropriate synaptic connections and disappear. Overexpression of the inward rectifying potassium channel, Kir2.1, diminishes the excitability of sensory neurons and more severely disrupts the formation of an olfactory map. These studies suggest that spontaneous neural activity is required for the establishment and maintenance of the precise connectivity inherent in an olfactory sensory map.     

Inhaled nebulized nitrite is a hypoxia-sensitive NO-dependent selective pulmonary vasodilator

The blood anion nitrite contributes to hypoxic vasodilation through a heme-based, nitric oxide (NO)-generating reaction with deoxyhemoglobin and potentially other heme proteins. We hypothesized that this biochemical reaction could be harnessed for the treatment of neonatal pulmonary hypertension, an NO-deficient state characterized by pulmonary vasoconstriction, right-to-left shunt pathophysiology and systemic hypoxemia. To test this, we delivered inhaled sodium nitrite by aerosol to newborn lambs with hypoxic and normoxic pulmonary hypertension. Inhaled nitrite elicited a rapid and sustained reduction ( approximately 65%) in hypoxia-induced pulmonary hypertension, with a magnitude approaching that of the effects of 20 p.p.m. NO gas inhalation. This reduction was associated with the immediate appearance of NO in expiratory gas. Pulmonary vasodilation elicited by aerosolized nitrite was deoxyhemoglobin- and pH-dependent and was associated with increased blood levels of iron-nitrosyl-hemoglobin. Notably, from a therapeutic standpoint, short-term delivery of nitrite dissolved in saline through nebulization produced selective, sustained pulmonary vasodilation with no clinically significant increase in blood methemoglobin levels. These data support the concept that nitrite is a vasodilator acting through conversion to NO, a process coupled to hemoglobin deoxygenation and protonation, and evince a new, simple and inexpensive potential therapy for neonatal pulmonary hypertension.     

Cutting edge: bacterial lipoprotein induces endotoxin-independent tolerance to septic shock

Tolerance to bacterial cell wall components is an adaptive host response. Endotoxin/LPS tolerance is characterized by a survival advantage against subsequent lethal LPS challenge. However, it is uncertain whether LPS tolerance can afford protection against other septic challenges. In this study, we show that tolerance induced by bacterial lipoprotein (BLP) protects mice against not only BLP-induced lethality, but also LPS-, live bacteria-, and polymicrobial sepsis-induced lethality. In contrast, LPS tolerance offers no survival benefit against the latter two challenges. Furthermore, induction of BLP tolerance results in overexpression of complement receptor type 3 and FcgammaIII/IIR on neutrophils (polymorphonuclear neutrophils) and peritoneal macrophages, with increased bacterial recognition and bactericidal activity, whereas LPS-tolerized mice exhibit an impaired ability to ingest and to kill bacteria. These results indicate that BLP tolerance is a novel adaptive host response associated with a unique protective effect during septic shock.     

Driving plasticity in human adult motor cortex is associated with improved motor function after brain injury

Changes in somatosensory input can remodel human cortical motor organization, yet the input characteristics that promote reorganization and their functional significance have not been explored. Here we show with transcranial magnetic stimulation that sensory-driven reorganization of human motor cortex is highly dependent upon the frequency, intensity, and duration of stimulus applied. Those patterns of input associated with enhanced excitability (5 Hz, 75% maximal tolerated intensity for 10 min) induce stronger cortical activation to fMRI. When applied to acutely dysphagic stroke patients, swallowing corticobulbar excitability is increased mainly in the undamaged hemisphere, being strongly correlated with an improvement in swallowing function. Thus, input to the human adult brain can be programmed to promote beneficial changes in neuroplasticity and function after cerebral injury.     

Salinity tolerance and antioxidant status in cotton cultures

This investigation focuses upon cell growth and antioxidant status in cultured cells of cotton (Gossypium herbaceum) cvs. Dhumad (salt-tolerant, TOL), H-14 (medium salt-tolerant, MED), and RAhs-2 (salt-sensitive, SEN) exposed to saline stress (50-200 mM NaCl). Mean (+/- SEM) callus fresh weight (f.wt.) and dry weight (d.wt.) gains were significantly (p <.05) greater on Murashige and Skoog (MS) [1]-based medium with 50 mM NaCl for the TOL cv. (62% and 16%, respectively) over NaCl-free controls (2020 +/- 45 and 166 +/- 4 mg, respectively); comparable differences were not observed for the MED cv. A significant (p <.05) decrease in mean f.wt. occurred with the SEN cv. exposed to 50 mM NaCl. For all cvs., there were (p <.05) reductions in mean f.wts. in medium with >or=100 mM NaCl. At 200 mM NaCl, mean f.wt. decreases were 52% (TOL), 89% (MED), and 91% (SEN), respectively. A strong correlation existed between antioxidant status and growth of cells with NaCl. Superoxide dismutase and glutathione reductase activities increased with increasing salinity in the TOL cv. to maximum values of 26.3 +/- 1.1 U mg(-1) protein and 1.05 +/- 0.01 AB(340 nm) min(-1) mg(-1) protein, respectively, at 150 mM NaCl; for the MED and SEN cvs., there were no changes in activities of these enzymes between control and salt treatments. Catalase activity decreased progressively with increasing salt concentration in all cvs. except for SEN with 100 mM NaCl, where mean catalase activity (1.75 +/- 0.04 AB(240 nm) min(-1) mg(-1) protein) was greater (p <.05) than control (1.13 +/- 0.08). Overall, cultured cotton cells provide an experimental system for investigating the role of antioxidants in salt tolerance at the cellular level.     

The genetics of glycosylation in Gram-negative bacteria

In recent years there has been a dramatic increase in reports of glycosylation of proteins in various Gram-negative systems including Neisseria meningitidis, Neisseria gonorrhoeae, Campylobacter jejuni, Pseudomonas aeruginosa, Escherichia coli, Caulobacter crescentus, Aeromonas caviae and Helicobacter pylori. Although this growing list contains many important pathogens (reviewed by Benz and Schmidt [Mol. Microbiol. 45 (2002) 267-276]) and the glycosylations are found on proteins important in pathogenesis such as pili, adhesins and flagella the precise role(s) of the glycosylation of these proteins remains to be determined. Furthermore, the details of the glycosylation biosynthetic process have not been determined in any of these systems. The definition of the precise role of glycosylation and the mechanism of biosynthesis will be facilitated by a detailed understanding of the genes involved.     

Novel approaches for regulating gas supply to plant systems <Emphasis Type="Italic">in vitro</Emphasis>: Application and benefits of artificial gas carriers

Summary The composition of the gaseous environment within tissue culture vessels is a critical factor in determining in vitro plant growth and morphogenic responsiveness. Consequently, the provision of an adequate and sustainable oxygen supply for cultured plant cells (including isolated protoplasts), tissues and organs is a crucial prerequisite for optimization and regulation of such cultural responses. During the past decade, research has focused on improving growth and development using artificial gas carriers based on inert perfluorocarbon (PFC) liquids and hemoglobin (Hb) solution. Supplementation of culture media with such artificial oxygen carriers has demonstrated beneficial effects of increased and sustainable cellular mitotic division and subsequent biomass production in a diverse range of plant species, during both short- and longer-term culture. Studies have targeted systems where oxygen availability is actually or potentially a major growth-limiting factor. Undoubtedly, gas carrier-facilitated improvements in regulating the supply of respiratory gases to cultured cells, tissues and organs will have increasingly important biotechnological and practical implications in the context of plant micropropagation, somatic hybridization, transgenic plant production, and secondary product biosynthesis.