Regulation of 5-lipoxygenase activity in mononuclear phagocytes: characterization of an endogenous cytosolic inhibitor

The proinflammatory leukotrienes (LT) play important roles in host defense and disease states. However, no endogenous mechanisms to downregulate 5-lipoxygenase (5-LO), the enzyme catalyzing LT synthesis, have been described. We observed that the cytosolic fraction of rat alveolar macrophages (AMs) and peritoneal macrophages (PMs), and of peripheral blood monocytes (PBMs) contain substantial amounts of 5-LO protein, but little detectable 5-LO activity. We therefore examined these mononuclear phagocyte (MNP) cytosolic fractions for inhibitory activity against 5-LO. MNP cytosol dose-dependently reduced the 5-LO activity in neutrophil (PMN) cytosol and AM membrane. Furthermore, MNP cytosol dose-dependently prolonged the lag phase of soybean lipoxygenase (LO) without affecting the rate of product formation. This effect was overcome by subsequent addition of 13(S)-hydroperoxy-9-cis-11-trans-octadecadienoic acid (13-HpOD), suggesting that the active factor scavenges hydroperoxides. Inactivation by boiling and roteinase K suggest that is a protein. We speculate that this cytosolic factor(s) may serve as an endogenous means for the down-regulation of 5-LO in macrophages.     

Effect of low dose UVB irradiation on the migratory properties and functional capacities of human skin dendritic cells

We recently described the 'spontaneous' migration of skin dendritic cells out of human split skin during culture. Since newly infiltrating cells from the circulation are excluded, this in vitro model is very suitable for studying the effect of UVB irradiation on the migratory properties, phenotype and functional capacities of skin cells. In the present study, we show that UVB irradiation of the skin before the culture period results in a significantly lower number of migrated cells that could be obtained compared with untreated skin. Relatively more dendritic cells of the population that migrated from UVB-irradiated skin were of dermal origin, as indicated by a higher percentage of CD1b+ cells. These data imply that UVB irradiation inhibits migration, especially of the epidermal Langerhans cells. Ultrastructural analysis of the irradiated skin revealed that the UVB dose used did not cause any directly visible damage to the cells. However, the cell population that had migrated from UVB-irradiated skin showed a significantly lower capacity to stimulate allogeneic T cells. This was not due to a lower expression of MHC class II on these cells. The percentage of cells expressing B7.1, B7.2 and LFA-3 was decreased in the population migrated from irradiated skin. The possible mechanism underlying the UVB-induced suppression is discussed.     

Multiple anterograde tracing, combining Phaseolus vulgaris leucoagglutinin with rhodamine- and biotin-conjugated dextran amine

The simultaneous use of different neuroanatomical anterograde tracers provides a potentially powerful method to study the convergence of afferent systems in a particular brain area. However, a simple routine procedure to apply multiple anterograde tracers in conjunction with their simultaneous visualization is still missing. We report an easy and straightforward application of three sensitive anterograde tracers: Phaseolus vulgaris leucoagglutinin (PHA-L), rhodamine-conjugated dextran amine (RDA) and biotin-conjugated dextran amine (BDA). These tracers can be visualized simultaneously and permanently through a triple-staining procedure with nickel-enhanced diaminobenzidine (DAB-Ni), DAB and 1-naphthol/Azur B as chromogens. Our test model comprised the projections from the nucleus reuniens thalami and entorhinal cortex. Both projection systems show a high degree of overlap in their terminal fields in the hippocampus. Two tracers were injected in the left and right entorhinal cortex, respectively; a third tracer was injected in the nucleus reuniens. This combination of injections provided a good opportunity to compare the three tracers in one and the same animal. PHA-L, RDA and BDA, injected in either of the injection sites, turned out to be equally sensitive and revealed the morphology of the involved projection systems in great detail. The triple-staining protocol yielded an excellent, simultaneous detectability of the three tracers with a remarkably low background level. Thus, the combination of the anterograde tracers PHA-L, RDA and BDA, in conjunction with the triple-staining procedure, offers a very attractive approach for neuroanatomical research.     

Detection of soluble interleukin-2 receptor in the serum of patients with non-Hodgkin''s lymphoma

Falls are the most common type of injury among the elderly, and the source of both functional and psychological morbidity. The aim of this study was to validate the Elderly Fall Screening Test (EFST). In a community primary-care clinic, the members 60 years or older who were functionally independent were screened. Of the 568 elderly persons who met these criteria, 361 were interviewed once and 283 persons were re-interviewed a year later. The EFST, a five-item test, was used to divide participants into low- and high-risk groups. Concurrent criterion validity was assessed by physical examinations conducted by physicians who were blind as to the risk designation. Using data from the follow-up interview, predictive validity was assessed on both fall-related and general health measures. Based on the results of the EFST, 28% of the respondents were designated as being at high risk for falls (i.e. having a score of two or more risk items). The results of physicians' examinations corroborated the screening test results in 75% of the cases, with 83% sensitivity and 69% specificity. In the follow-up interview, the high-risk group, as compared to the low-risk group, was more likely to have high scores on EFST, a fall in the past month or year, frequent near falls, and an injurious fall. Those with high EFST scores were more likely to report four or more sick days in the past six months, a hospitalization in the past year, poor self-rated health, a decline in health in the past 6 months, and symptoms of depression. The EFST has both criterion and predictive validity. It can be useful in community-based prevention programmes with functionally independent elderly people.     

Gastric spiral bacteria and intramuscular sarcocysts in African lions from Namibia

Addition of glucose to Saccharomyces cerevisiae inactivates the maltose transporter. The general consensus is that this inactivation, called catabolite inactivation, is one of the control mechanisms developed by this organism to use glucose preferentially whenever it is available. Using nitrogen-starved cells (resting cells), it has been shown that glucose triggers endocytosis and degradation of the transporter in the vacuole. We now show that maltose itself triggers inactivation and degradation of its own transporter as efficiently as glucose. This fact, and the observation that glucose inactivates a variety of plasma membrane proteins including glucose transporters themselves, suggests that catabolite inactivation of the maltose transporter in nitrogen-starved cells is not a control mechanism specifically directed to ensure a preferential use of glucose. It is proposed that, in this metabolic condition, inactivation of the maltose transporter might be due to the stimulation of the general protein turnover that follows nitrogen starvation.     

Synthesis of the four isomers of 4-aminopyrrolidine-2,4-dicarboxylate: identification of a potent, highly selective, and systemically-active agonist for metabotropic glutamate receptors negatively coupled to adenylate cyclase

The four isomers of 4-aminopyrrolidine-2,4-dicarboxylate (APDC) were prepared and evaluated for their effects at glutamate receptors in vitro. (2R,4R)-APDC (2a), an aza analog of the nonselective mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate (1S,3R)-ACPD, 1), was found to possess relatively high affinity for metabotropic glutamate receptors (mGluRs) (ACPD-sensitive [3H]glutamate binding IC50 = 6.49 +/- 1.21 microM) with no effects on radioligand binding to NMDA, AMPA, or kainate receptors up to 100 microM. None of the other APDC isomers showed significant mGluR binding affinity, indicating that this interaction is highly stereospecific. Both 1 and 2a were effective in decreasing forskolin-stimulated cAMP formation in the adult rat cerebral cortex (EC50 = 8.17 +/- 2.21 microM for 1; EC50 = 14.51 +/- 5.54 microM for 2a); however, while 1 was also effective in stimulating basal tritiated inositol monophosphate production in the neonatal rat cerebral cortex (EC50 = 27.7 +/- 5.2 microM), 2a (up to 100 microM) was ineffective in stimulating phosphoinositide hydrolysis in this tissue preparation, further supporting our previous observations that 2a is a highly selective agonist for mGluRs negatively coupled to adenylate cyclase. Microelectrophoretic application of either 1 or 2a to intact rat spinal neurons produced an augmentation of AMPA-induced excitation (95 +/- 10% increase for 1, 52 +/- 6% increase for 2a). Intracerebral injection of 1 (400 nmol) produced characteristic limbic seizures in mice which are not mimicked by 2a (200-1600 nmol, ic). However, the limbic seizures induced by 1 were blocked by systemically administered 2a in a dose-dependent manner (EC50 = 271 mg/kg, ip). It is concluded that (2R,4R)-APDC (2a) is a highly selective, systemically-active agonist of mGluRs negatively coupled to adenylate cyclase and that selective activation of these receptors in vivo can result in anticonvulsant effects.