Central Interleukin-1ß Suppresses the Nocturnal Secretion of Melatonin.

In vertebrates, numerous processes occur in a rhythmic manner. The hormonal signal reliably reflecting the environmental light conditions is melatonin. Nocturnal melatonin secretion patterns could be disturbed in pathophysiological states, including inflammation, Alzheimer's disease, and depression. All of these states share common elements in their aetiology, including the overexpression of interleukin- (IL-) 1ß in the central nervous system. Therefore, the present study was designed to determine the effect of the central injection of exogenous IL-1ß on melatonin release and on the expression of the enzymes of the melatonin biosynthetic pathway in the pineal gland of ewe. It was found that intracerebroventricular injections of IL-1ß (50 µg/animal) suppressed (P < 0.05) nocturnal melatonin secretion in sheep regardless of the photoperiod. This may have resulted from decreased (P < 0.05) synthesis of the melatonin intermediate serotonin, which may have resulted, at least partially, from a reduced expression of tryptophan hydroxylase. IL-1ß also inhibited (P < 0.05) the expression of the melatonin rhythm enzyme arylalkylamine-N-acetyltransferase and hydroxyindole-O-methyltransferase. However, the ability of IL-1ß to affect the expression of these enzymes was dependent upon the photoperiod. Our study may shed new light on the role of central IL-1ß in the aetiology of disruptions in melatonin secretion.

Interleukin-1 ß Modulates Melatonin Secretion in Ovine Pineal Gland: Ex Vivo Study.

The study was designed to determine the effect of proinflammatory cytokine, interleukin- (IL-) 1ß, on melatonin release and expression enzymes essential for this hormone synthesis: arylalkylamine-N-acetyltransferase (AA-NAT) and hydroxyindole-O-methyltransferase (HIOMT) in ovine pineal gland, taking into account the immune status of animals before sacrificing. Ewes were injected by lipopolysaccharide (LPS; 400 ng/kg) or saline, two hours after sunset during short day period (December). Animals were euthanized three hours after the injection. Next, the pineal glands were collected and divided into four explants. The explants were incubated with (1) medium 199 (control explants), (2) norepinephrine (NE; 10 µM), (3) IL-1ß (75 pg/mL), or (4) NE + IL-1ß. It was found that IL-1ß abolished (P < 0.05) NE-induced increase in melatonin release. Treatment with IL-1ß also reduced (P < 0.05) expression of AA-NAT enzyme compared to NE-treated explants. There was no effect of NE or IL-1ß treatment on gene expression of HIOMT; however, the pineal fragments isolated from LPS-treated animals were characterized by elevated (P < 0.05) expression of HIOMT mRNA and protein compared to the explants from saline-treated ewes. Our study proves that IL-1ß suppresses melatonin secretion and its action seems to be targeted on the reduction of pineal AA-NAT protein expression.

TrkA-expressing trigeminal sensory neurons display both neurochemical and structural plasticity despite a loss of p75NTR function: responses to normal and elevated levels of nerve growth factor.

In neural crest-derived sensory ganglia, approximately half of the neuronal population expresses the transmembrane trkA receptor that is required for neuronal binding of target-derived nerve growth factor (NGF). These same neurons also express the p75 neurotrophin receptor (NTR) that increases the affinity of trkA for NGF. Depleting p75NTR expression reduces both the survival of trkA-positive sensory neurons and their afferent innervation of peripheral targets. In this investigation, we assessed the neurochemical and structural plasticity of trigeminal sensory neurons in p75NTR-deficient mice in response to either normal or elevated levels of NGF during postnatal development and into adulthood. Although p75NTR-deficient mice have 30% fewer trigeminal neurons, levels of trkA mRNA expression are modestly elevated in these mutant mice as compared to control mice. The density of central afferent axons and local levels of NGF are, however, comparable between mutant and control animals. Thus, despite the survival of fewer trigeminal neurons, neither ganglionic levels of trkA mRNA expression nor the density of central afferent projections are depleted in p75NTR-deficient mice. In response to elevated levels of NGF protein, transgenic mice with and without p75NTR expression display both increased levels of trkA mRNA expression and a greater density of trigeminal central afferent axons as compared to control mice. These data further reveal that an absence of p75NTR function in trigeminal sensory neurons does not diminish their capacity for NGF-dependent plasticity, namely trkA mRNA expression and collateral growth of central afferent axons.

Absence of p75(NTR) expression reduces nerve growth factor immunolocalization in cholinergic septal neurons.

Septal axons provide a cholinergic innervation to the nerve growth factor (NGF)-producing neurons of the mammalian hippocampus. These cholinergic septal afferents are capable of responding to target-derived NGF because they possess trkA and p75(NTR), the two transmembrane receptors that bind NGF and activate ligand-mediated intracellular signaling. To assess the relative importance of p75(NTR) expression for the responsiveness of cholinergic septal neurons to hippocampally derived NGF, we used three lines of mutant and/or transgenic mice: p75(-/-) mice (having two mutated alleles of the p75(NTR) gene), NGF/p75(+/+) mice (transgenic animals overexpressing NGF within central glial cells and having two normal alleles of the p75(NTR) gene), and NGF/p75(-/-) mice (NGF transgenic animals having two mutated alleles of the p75(NTR) gene). BALB/c and C57B1/6 mice (background strains for the mutant and transgenic lines of mice) were used as controls. Both lines of NGF transgenic mice possess elevated levels of NGF protein in the hippocampus and septal region, irrespective of p75(NTR) expression. BALB/c and C57Bl/6 mice display comparably lower levels of NGF protein in both tissues. Despite differing levels of NGF protein, the ratios of hippocampal to septal NGF levels are similar among BALB/c, C57B1/6, and NGF/p75(+/+) mice. Both p75(-/-) and NGF/p75(-/-) mice, on the other hand, have markedly elevated ratios of NGF protein between these two tissues. The lack of p75(NTR) expression also results in a pronounced absence of NGF immunoreactivity in cholinergic septal neurons of p75(-/-) and NGF/p75(-/-) mice. BALB/c, C57B1/6, and NGF/p75(+/+) mice, on the other hand, display NGF immunoreactivity that appears as discrete granules scattered through the cytoplasm of cholinergic septal neurons. Elevated levels of NGF in the hippocampus and septal region coincide with hypertrophy of cholinergic septal neurons of NGF/p75(+/+) mice but not of NGF/p75(-/-) mice. Levels of choline acetyltransferase (ChAT) enzyme activity are, however, elevated in the septal region and hippocampus of both NGF/p75(+/+) and NGF/p75(-/-) mice, compared with control mice. These data indicate that an absence of functional p75(NTR) expression disrupts the normal cellular immunolocalization of NGF by cholinergic septal neurons but does not affect the ability of these neurons to respond to elevated levels of NGF, as determined by ChAT activity.

Enhanced neurotrophin-induced axon growth in myelinated portions of the CNS in mice lacking the p75 neurotrophin receptor.

Axonal growth in the adult mammalian CNS is limited because of inhibitory influences of the glial environment and/or a lack of growth-promoting molecules. Here, we investigate whether supplementation of nerve growth factor (NGF) to the CNS during postnatal development and into adulthood can support the growth of sympathetic axons within myelinated portions of the maturing brain. We have also asked whether p75(NTR) plays a role in this NGF-induced axon growth. To address these questions we used two lines of transgenic mice overexpressing NGF centrally, with or without functional expression of p75(NTR) (NGF/p75(+/+) and NGF/p75(-/-) mice, respectively). Sympathetic axons invade the myelinated portions of the cerebellum, beginning shortly before the second week of postnatal life, in both lines of NGF transgenic mice. Despite the presence of central myelin, these sympathetic axons continue to sprout and increase in density between postnatal days 14 and 100, resulting in a dense plexus of sympathetic fibers within this myelinated environment. Surprisingly, the growth response of sympathetic fibers into the cerebellar white matter of NGF/p75(-/-) mice is enhanced, such that both the density and extent of axon ingrowth are increased, compared with age-matched NGF/p75(+/+) mice. These dissimilar growth responses cannot be attributed to differences in cerebellar levels of NGF protein or sympathetic neuron numbers between NGF/p75(+/+) and NGF/p75(-/-) mice. Our data provide evidence demonstrating that growth factors are capable of overcoming the inhibitory influences of central myelin in the adult CNS and that neutralization of the p75(NTR) may further enhance this growth response.

Absence of the p75 neurotrophin receptor alters the pattern of sympathosensory sprouting in the trigeminal ganglia of mice overexpressing nerve growth factor.

Sympathetic axons invade the trigeminal ganglia of mice overexpressing nerve growth factor (NGF) (NGF/p75(+/+) mice) and surround sensory neurons having intense NGF immunolabeling; the growth of these axons appears to be directional and specific (). In this investigation, we provide new insight into the neurochemical features and receptor requirements of this sympathosensory sprouting. Using double-antigen immunohistochemistry, we demonstrate that virtually all (98%) trigeminal neurons that exhibit a sympathetic plexus are trk tyrosine kinase receptor (trkA)-positive. In addition, the majority (86%) of those neurons enveloped by sympathetic fibers is also calcitonin gene-related peptide (CGRP)-positive; a smaller number of plexuses (14%) surrounded other somata lacking this neuropeptide. Our results show that sympathosensory interactions form primarily between noradrenergic sympathetic efferents and the trkA/CGRP-expressing sensory somata. To assess the contribution of the p75 neurotrophin receptor (p75(NTR)) in sympathosensory sprouting, a hybrid strain of mice was used that overexpresses NGF but lacks p75(NTR) expression (NGF/p75(-/-) mice). The trigeminal ganglia of NGF/p75(-/-) mice, like those of NGF/p75(+/+) mice, have increased levels of NGF protein and display a concomitant ingrowth of sympathetic axons. In contrast to the precise pattern of sprouting seen in the ganglia of NGF/p75(+/+) mice, sympathetic axons course randomly throughout the ganglionic neuropil of NGF/p75(-/-) mice, forming few perineuronal plexuses. Our results indicate that p75(NTR) is not required to initiate or sustain the growth of sympathetic axons into the NGF-rich trigeminal ganglia but rather plays a role in regulating the directional patterns of axon growth.

Stimulation of erythrocyte membrane Mg(2+)-ATPase activity by glutathione S-conjugates.

Pig erythrocyte membrane Mg2+-ATPase activity was stimulated by various glutathione S-conjugates. For alkyl S-conjugates, the Km for the stimulation was lower, the more hydrophobic was the conjugate. 2,4-Dinitrophenyl-S-(N-acetyl)cysteine also stimulated the Mg2+-ATPase activity, suggesting a low specificity of the ¿glutathione S-conjugate pump¿. The Km values for the stimulation by 2,4-dinitrophenyl conjugates were lower than predictable on the basis of hydrophobicity which indicates a high affinity of the transporter for these conjugates.

Survey of the esophagus during the upper gastrointestinal examination in 500 patients.

Of 500 patients referred for an examination of the upper gastrointestinal tract, 15% were found to have radiographic evidence of esophageal disease. A cursory esophageal survey appears to be insufficient. Thorough evaluation should consist of a minimal multiphasic approach involving double- and single-contrast radiography, fluoroscopic studies of motility, and a mucosal relief study.

The minimum effective dose of glucagon in upper gastrointestinal radiography.

The effect of small intravenous doses (0.025 and 0.05 mg) of glucagon was evaluated in 22 patients. All 12 patients given 0.05 mg demonstrated by hypotonicity of the stomach and duodenum at 1 min and beginning return of peristalsis at 2 1/2 min. Subsequently, 100 patients with radiographically normal upper gastrointestinal examinations who received 0.05 mg of glucagon intravenously were compared to 100 patients with normal examinations without it. Comparison was made to determine the effect of glucagon on gastric mucosal coating and distention of the stomach and duodenum. In all areas of the stomach, mucosal coating was significantly improved in the glucagon group. There was also increased distention of the distal antrum, duodenal bulb, and duodenal loop. No adverse effects were reported. Because of the short duration of action of glucagon, the examination needs to be coordinated and done rapidly. The routine use of a small dose of glucagon increased the performance time slightly with small additional cost but was compensated for by the increased diagnostic quality of the examination.